Stiff muscle fibers in calf muscles of patients with cerebral palsy lead to high passive muscle stiffness

Cerebral palsy (CP), caused by an injury to the developing brain, can lead to alterations in muscle function. Subsequently, increased muscle stiffness and decreased joint range of motion are often seen in patients with CP. We examined mechanical and biochemical properties of the gastrocnemius and soleus muscles, which are involved in equinus muscle contracture. Passive mechanical testing of single muscle fibers from gastrocnemius and soleus muscle of patients with CP undergoing surgery for equinus deformity showed a significant increase in fiber stiffness (p < 0.01). Bundles of fibers that included their surrounding connective tissues showed no stiffness difference (p = 0.28).). When in vivo sarcomere lengths were measured and fiber and bundle stiffness compared at these lengths, both fibers and bundles of patients with CP were predicted to be much stiffer in vivo compared to typically developing (TD) individuals. Interestingly, differences in fiber and bundle stiffness were not explained by typical biochemical measures such as titin molecular weight (a giant protein thought to impact fiber stiffness) or collagen content (a proxy for extracellular matrix amount). We suggest that the passive mechanical properties of fibers and bundles are thus poorly understood. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 32:1667–1674, 2014.     

Architectural design of the pelvic floor is consistent with muscle functional subspecialization

Introduction and hypothesis

Skeletal muscle architecture is the strongest predictor of a muscle’s functional capacity. The purpose of this study was to define the architectural properties of the deep muscles of the female pelvic floor (PFMs) to elucidate their structure–function relationships.

Methods

PFMs coccygeus (C), iliococcygeus (IC), and pubovisceral (PV) were harvested en bloc from ten fixed human cadavers (mean age 85 years, range 55–102). Fundamental architectural parameters of skeletal muscles [physiological cross-sectional area (PCSA), normalized fiber length, and sarcomere length (L_s)] were determined using validated methods. PCSA predicts muscle-force production, and normalized fiber length is related to muscle excursion. These parameters were compared using repeated measures analysis of variance (ANOVA) with post hoc t tests, as appropriate. Significance was set to α?=?0.05.

Results

PFMs were thinner than expected based on data reported from imaging studies and in vivo palpation. Significant differences in fiber length were observed across PFMs: C?=?5.29?±?0.32 cm, IC?=?7.55?±?0.46 cm, PV?=?10.45?±?0.67 cm (p?<?0.001). Average L_s of all PFMs was short relative to the optimal L_s of 2.7 μm of other human skeletal muscles: C?=?2.05?±?0.02 μm, IC?=?2.02?±?0.02 μm, PC/PR?=?2.07?±?0.01 μm (p?=?<0.001 compared with 2.7 μm; p?=?0.15 between PFMs, power?=?0.46). Average PCSA was very small compared with other human muscles, with no significant difference between individual PFMs: C?=?0.71?±?0.06 cm², IC?=?0.63?±?0.04 cm², PV?=?0.59?±?0.05 cm² (p?=?0.21, power?=?0.27). Overall, C had shortest fibers, making it a good stabilizer. PV demonstrated the longest fibers, suggesting that it functions to produce large excursions.

Conclusions

PFM design shows individual muscles demonstrating differential architecture, corresponding to specialized function in the pelvic floor.     

Age-related alterations in female obturator internus muscle

Introduction and Hypothesis

Pelvic floor muscle rehabilitation is a widely utilized, but often challenging therapy for pelvic floor disorders, which are prevalent in older women. Regimens involving the use of appendicular muscles, such as the obturator internus (OI), have been developed for strengthening of the levator ani muscle (LAM). However, changes that lead to potential dysfunction of these alternative targets in older women are not well known. We hypothesized that aging negatively impacts OI architecture, the main determinant of muscle function, and intramuscular extracellular matrix (ECM), paralleling age-related alterations in LAM.

Methods

OI and LAM were procured from three groups of female cadaveric donors (five per group): younger (20?–?40 years), middle-aged (41?–?60 years), and older (≥60 years). Architectural predictors of the excursional (fiber length, L _f), force-generating (physiological cross-sectional area, PCSA) and sarcomere length (L _s) capacity of the muscles, and ECM collagen content (measure of fibrosis) were determined using validated methods. The data were analyzed using one-way ANOVA and Tukey’s post-hoc test with a significance level of 0.05, and linear regression.

Results

The mean ages of the donors in the three groups were 31.2?±?2.3 years, 47.6?±?1.2 years, and 74.6?±?4.2 years (P?<?0.005). The groups did not differ with respect to parity or body mass index (P?>?0.5). OI L _f and L _s were not affected by aging. Age >60 years was associated with a substantial decrease in OI PCSA and increased collagen content (P?<?0.05). Reductions in OI and LAM force-generating capacities with age were highly correlated (r ²?=?0.9).

Conclusions

Our findings of age-related decreases in predicted OI force production and fibrosis suggest that these alterations should be taken into consideration, when designing pelvic floor fitness programs for older women.

     

Structure–function relationship of the human external anal sphincter

Introduction and hypothesis

Obstetrical external anal sphincter (EAS) injury and subsequent dysfunction are leading risk factors for female fecal incontinence (FI). Limited knowledge of the EAS structure–function relationship hinders treatment optimization. We directly measured functionally relevant intrinsic parameters of human EAS and tested whether vaginal delivery alters the EAS structure–function relationship.

Methods

Major predictors of in vivo EAS function were compared between specimens procured from vaginally nulliparous (VN, n = 5) and vaginally parous (VP, n = 7) cadaveric donors: operational sarcomere length (L_s), which dictates force–length relationship; physiological cross-sectional area (PCSA), which determines isometric force-generating capacity; fiber length (L_fn), responsible for muscle excursion and contractile velocity; and muscle stiffness. Data were analyzed using unpaired and paired t tests, α < 0.05. Results are presented as mean ± SEM.

Results

The VN and VP (median parity 3) groups were similar in age and BMI. No gross anatomical defects were identified. EAS L_s (2.36 ± 0.05 μm) was shorter than the optimal L_so (2.7 μm), at which contractile force is maximal, P = 0.0001. Stiffness was lower at L_s than L_so (5.4 ± 14 kPa/μm vs 35.3 ± 12 kPa/μm, P < 0.0001). This structural design allows active and passive tension to increase with EAS stretching. EAS relatively long L_fn (106 ± 24.8 mm) permits rapid contraction without decreased force, whereas intermediate PCSA (1.3 ± 0.3 cm²) is conducive to maintaining resting tone. All parameters were similar between groups.

Conclusions

This first direct examination of human EAS underscores how EAS intrinsic design matches its intended function. Knowledge of the EAS structure–function relationship is important for understanding the pathogenesis of FI and the optimization of treatments for EAS dysfunction.

     

The effects of botulinum toxin injection frequency on calf muscle growth in young children with spastic cerebral palsy: a 12-month prospective study

Purpose

This study was a 12-month prospective investigation of changes in the medial gastrocnemius (MG) muscle morphology in children aged 2–5 years with spastic cerebral palsy (CP) who had received no previous intramuscular injections of botulinum neurotoxin type-A (BoNT-A) and were randomised to receive either single or multiple (three) BoNT-A injections to the gastrocsoleus. MG morphological changes were compared to age-matched typically developing (TD) peers.

Methods

Thirteen children with spastic CP with a mean age of 45 (15) months and 18 TD children with a mean age of 48 (14) months participated in the study. The principal outcome measures were MG muscle volume, fascicle length, pennation angle and physiological cross-sectional area (PCSA), which were obtained using 2D and 3D ultrasound.

Results

The single and multiple injection frequency groups significantly increased MG muscle volume at 12 months relative to the baseline by 13 and 15 %, respectively. There were no significant differences in the MG muscle volume 28.5 (12.3) versus 30.3 (3.8) ml, fascicle length 48.0 (10.4) versus 44.8 (1.2) mm or PCSA 7.0 (1.2) versus 6.6 (1.7) cm² between the single and multiple injection groups, respectively, at 12 months follow-up. The change in MG muscle volume in the single and multiple injection groups was significantly lower than the TD peers by 66 and 60 %, respectively.

Interpretation

In young children with spastic CP, naive to BoNT-A treatment, MG muscle growth over 12 months does not appear to be influenced by intramuscular BoNT-A injection frequency. However, MG muscle growth in the spastic CP groups was significantly lower than the age-matched TD peers. It is unclear whether this is an effect of intramuscular BoNT-A injections or reduced growth rates in children with spastic CP in general. Controlled investigations and longitudinal studies with multiple measurement time points are required in order to determine the influence of BoNT-A treatment on muscle physiological and mechanical growth factors in young children with spastic CP.     

Ischemia Increases the Twitch Latent Period in the Soleus and Extensor Carpi Radialis Longus Muscles from Adult Rats

Complete ischemia and reperfusion effects on twitch force (∫(F·t)), twitch latent period (TLP), maximal rate of rise of twitch tension (δF/δt)_max, and twitch maximum relaxation rate (TMRR) were assessed. We divided 36 adult rats into four groups; two control groups (n = 9), a group undergoing 1 hour of ischemia followed by 1 hour of reperfusion (n = 9), and one group exposed to 2 hours of ischemia followed by 1 hour of reperfusion (n = 9). We have induced twitch contractions every 10 minutes in the soleus and the extensor carpi radialis longus (ECRL). Twitch contractions were recorded and then analyzed for ∫(F·t), TLP, (δF/δt)_max, and TMRR. During 1 hour and 40 minutes of ischemia, TLP increased to 179 ± 24% (p < 0.05) in the soleus and to 184 ± 16% (p < 0.05) in the ECRL, an effect that was partially recovered during 1 hour of reperfusion. This increase started after 20 minutes of ischemia in the soleus and after 40 minutes of ischemia in the ECRL. The increase was faster in the ECRL and peaked at the same time for both muscular groups. ∫(F·t) and (δF/δt)_max decreased during 1 hour of ischemia to 46 ± 7% (p < 0.05) in the soleus and to 40 ± 7% (p < 0.05) in the ECRL. TMRR decreased during 1 hour of ischemia to 39 ± 5% (p < 0.05) in the soleus and to 54 ± 8% (p < 0.05) in the ECRL. During 1 hour of reperfusion all of them recovered close to control values.     

Passive mechanical properties of rat abdominal wall muscles suggest an important role of the extracellular connective tissue matrix

Abdominal wall muscles have a unique morphology suggesting a complex role in generating and transferring force to the spinal column. Studying passive mechanical properties of these muscles may provide insights into their ability to transfer force among structures. Biopsies from rectus abdominis (RA), external oblique (EO), internal oblique (IO), and transverse abdominis (TrA) were harvested from male Sprague–Dawley rats, and single muscle fibers and fiber bundles (4–8 fibers ensheathed in their connective tissue matrix) were isolated and mechanically stretched in a passive state. Slack sarcomere lengths were measured and elastic moduli were calculated from stress–strain data. Titin molecular mass was also measured from single muscle fibers. No significant differences were found among the four abdominal wall muscles in terms of slack sarcomere length or elastic modulus. Interestingly, across all four muscles, slack sarcomere lengths were quite long in individual muscle fibers (>2.4 µm), and demonstrated a significantly longer slack length in comparison to fiber bundles (p < 0.0001). Also, the extracellular connective tissue matrix provided a stiffening effect and enhanced the resistance to lengthening at long muscle lengths. Titin molecular mass was significantly less in TrA compared to each of the other three muscles (p < 0.0009), but this difference did not correspond to hypothesized differences in stiffness. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1321–1326, 2012     

Reduced loading due to spinal-cord injury at birth results in “slender” bones: a case study

Introduction The present case study compared bone density, bone geometry and muscle cross-sectional area (CSA) in a male who sustained spinal-cord injury (SCI) at birth (from here called SCI-B) with two matched controls without SCI, and also with four individuals with SCI of similar level and injury completeness but sustained at age 15 or greater. Methods All subjects with SCI were at least 3 years post-injury and had experienced motor incomplete lesions at the cervical level. Computed tomography was used to measure volumetric bone density, indices of bone strength [CSA and maximum, minimum and polar area moments of inertia (I _max, I _min, I _pol)] and muscle CSA at the tibia (66% of tibia length, measured proximally from the distal end). Results Lower leg muscle CSA of SCI-B was 63±6% of values in non-SCI controls, and 72±12% of values in other males with SCI. In SCI-B, bone CSA was roughly half (52±4%) that of non-SCI controls and 73±16% of bone CSA values in other males with SCI. The magnitudes of the area moment of inertia variables (I _max, I _min, and I _pol) in SCI-B were ~25% of control values. Further, the moment of inertia variables in SCI-B were 27–54% of values obtained in other males with SCI, indicating that experiencing SCI in the early stages of life has a remarkable impact on bone shape. Interestingly, tibia bone density did not appear to be affected; the average difference in bone density between SCI-B and non-SCI controls was −1.2±0.7%. The bone densities of other males with SCI were 4–19% lower than in SCI-B. Conclusions Muscle atrophy and bone loss are commonly reported consequences of SCI. This case reveals that important changes in bone geometry occur after SCI, and that mechanical loading during growth plays a vital role in the development of bone size and shape.     

Effect of the SK/IK channel modulator 4,5-dichloro-1,3-diethyl-1,3-dihydro-benzoimidazol-2-one (NS4591) on contractile force in rat, pig and human detrusor smooth muscle

What’s known on the subject? and What does the study add? Increased urinary bladder detrusor smooth muscle phasic contractility has been suggested to be associated with idiopathic bladder overactivity. Small conductance Ca2⁺‐activated K⁺ (SK 1–3) channels have attracted considerable interest as putative target for new therapeutic strategy for treating overactive bladder. These channels play an important role in regulating the function and activity of urinary bladder smooth muscle (UBSM), and the loss of SK channel function has been shown to increase UBSM excitability and contractility. However, it is not known whether activation of SK channels has the converse effect of reducing UBSM excitability and contractility. In this paper, we investigated this possibility in the rat, pig and human UBSM by using the novel SK channel opener NS4591. These studies demonstrate that the SK channel modulator NS4591 has a potential role as a pharmacological tool to study the involvement of SK (and IK) channels in mammals and rodents urinary bladder. NS4591 may have therapeutic potential for treatment of detrusor overactivity.

OBJECTIVE

• ? To investigate the importance of small (SK)‐ and intermediate (IK)‐conductance Ca2⁺‐activated K⁺ channels on bladder function, by studying the effects of 4,5‐dichloro‐1,3‐diethyl‐1,3‐dihydro‐benzoimidazol‐2‐one (NS4591), a new modulator of SK/IK channels, on contractions induced by electrical field stimulation (EFS) and carbachol in rat, pig and human detrusor.

PATIENTS AND METHODS

• ? Detrusor biopsies were obtained from rats, pigs and male patients undergoing cystectomy because of bladder cancer.
• ? Force was recorded using myographs.
• ? Intracellular free Ca²⁺ was measured in myocytes using microfluorimetry.

RESULTS

• ? In rat bladder rings subjected to EFS, cumulative addition of NS4591 (0.1–30 µM) decreased force by 82 ± 2.9% (n = 6).This effect was reduced by 64 ± 5.2% in the presence of 0.3 µM apamin, a specific inhibitor of SK channels. Apamin increased the force evoked by EFS significantly: force was increased by 14.2 ± 3.4% (n = 5) and 10.1 ± 2.6% (n = 7) in pig and human detrusor strips, respectively (P = 0.04 and P = 0.02).
• ? The cumulative addition of NS4591 (0.3–30 µM) significantly reduced the amplitude of carbachol‐induced rhythmic oscillations by 62.0 ± 12.0% (n = 12) and the minimum force between oscillations by 30 ± 5% (n = 9) in pig detrusor strips (P < 0.005). In the presence of 10 µM NS4591, carbachol (1 µM) induced rhythmic contractions with an amplitude and normalized mean power frequency (nmeanPF) of 8.4 ± 5.1% and 0.11 ± 0.06 mN root mean square (rms) Hz (n = 12), respectively, vs. 21 ± 3.4% and 0.17 ± 0.04 mN rms Hz in control strips (n = 13). Apamin induced 6‐ and 11‐fold increases in amplitude and nmeanPF vs. 1.3‐ and 2‐fold increases in control strips.
• ? In human detrusor strips (n = 15), the cumulative addition of NS4591 (1–30 µM) significantly reduced the amplitude by 69 ± 11%, the nmeanPF by 78 ± 6% and the minimum force between carbachol‐induced oscillations by 59 ± 5% (P < 0.008). The addition of apamin (0.3 µM) before application of 1 µM carbachol abolished the effects of NS4591 on amplitude and partially abolished its effect on nmeanPF by 41 ± 7%, vs. a 78 ± 6% reduction in the absence of apamin (n = 8).
• ? In spontaneously active detrusor preparations, NS4591 reduced or abolished contractions.
• ? Furthermore, NS4591 (10 µM) decreased the carbachol‐induced increase in the fura‐2 ratio by 43 ± 3% compared with control (n = 12) (P < 0.03).

CONCLUSIONS

• ? The SK/IK channel modulator NS4591 inhibits EFS‐ and carbachol‐induced contractions in rat, pig and human detrusor muscle.
• ? NS4591 may have therapeutic potential for treatment of detrusor overactivity.

     

Comparison of metabolism of vitamins D2 and D3 in children with nutritional rickets

Children with calcium‐deficiency rickets may have increased vitamin D requirements and respond differently to vitamin D₂ and vitamin D₃. Our objective was to compare the metabolism of vitamins D₂ and D₃ in rachitic and control children. We administered an oral single dose of vitamin D₂ or D₃ of 1.25 mg to 49 Nigerian children—28 with active rickets and 21 healthy controls. The primary outcome measure was the incremental change in vitamin D metabolites. Baseline serum 25‐hydroxyvitamin D [25(OH)D] concentrations ranged from 7 to 24 and 15 to 34 ng/mL in rachitic and control children, respectively (p < .001), whereas baseline 1,25‐dihydroxyvitamin D [1,25(OH)₂D] values (mean ± SD) were 224 ± 72 and 121 ± 34 pg/mL, respectively (p < .001), and baseline 24,25‐dihydroxyvitamin D [24,25(OH)₂D] values were 1.13 ± 0.59 and 4.03 ± 1.33 ng/mL, respectively (p < .001). The peak increment in 25(OH)D was on day 3 and was similar with vitamins D₂ and D₃ in children with rickets (29 ± 17 and 25 ± 11 ng/mL, respectively) and in control children (33 ± 13 and 31 ± 16 ng/mL, respectively). 1,25(OH)₂D rose significantly (p < .001) and similarly (p = .18) on day 3 by 166 ± 80 and 209 ± 83 pg/mL after vitamin D₂ and D₃ administration, respectively, in children with rickets. By contrast, control children had no significant increase in 1,25(OH)₂D (19 ± 28 and 16 ± 38 pg/mL after vitamin D₂ and D₃ administration, respectively). We conclude that in the short term, vitamins D₂ and D₃ similarly increase serum 25(OH)D concentrations in rachitic and healthy children. A marked increase in 1,25(OH)₂D in response to vitamin D distinguishes children with putative dietary calcium‐deficiency rickets from healthy children, consistent with increased vitamin D requirements in children with calcium‐deficiency rickets. © 2010 American Society for Bone and Mineral Research     

Density and Fat Fraction of the Psoas,Paraspinal, and Oblique Muscle Groups Are Associated With Lumbar Vertebral Bone Mineral Density in a Multi-Ethnic Community-Living Population: The Multi-Ethnic Study of Atherosclerosis

Low vertebral bone mass is a major risk factor for vertebral compression fractures. Although sarcopenia has been shown to be associated with low bone mineral density (BMD), it is not known whether trunk musculature is directly associated with lumbar BMD, and whether exercise modifies this association. Using data from the Multi-Ethnic Study of Atherosclerosis (MESA), we sought to determine the association of muscle density and fat fraction of the psoas, paraspinal, and oblique muscle groups with L₃ lumbar volumetric BMD, and whether these associations were modified by exercise. We obtained L₃ vBMD measurements, and fat and muscle measurements (in Hounsfield units [HU]) from abdominal computed tomography (CT) scans spanning the L₂–L₄ intervertebral disc spaces. Muscle density was defined as the mean HU value for a muscle group area. Fat fraction was calculated as the mean HU value for the muscle group fat area/total muscle group area (cm²). Exercise data were self-reported (MET-minute/week). We utilized multivariable linear regression to evaluate these associations, stratified by gender, and adjusting for demographics, body mass index (BMI), smoking status, impaired fasting glucose, and corticosteroid and anti-resorptive medication use. Among 1923 MESA participants, mean ± standard deviation (SD) age was 62 ± 10 years, 49% were female, 40% white, 21% black, 26% Hispanic/Latino, and 13% Chinese. In fully adjusted analysis, for every 1-SD higher psoas fat fraction, there was a 3.19-SD lower L₃ vBMD in men and 4.3-SD lower L₃ vBMD in women (p < 0.001). For every 1-SD higher psoas density, there was a 0.2-SD higher L₃ vBMD (p < 0.001) in men and 0.19-SD higher L₃ vBMD (p < 0.001) in women. Findings were similar for paraspinal and oblique muscles. Intentional exercise did not modify these associations. In men and women, trunk muscle density was positively associated with higher lumbar BMD, suggesting a local association. Future studies are warranted to determine the temporality of this association. © 2022 American Society for Bone and Mineral Research (ASBMR).     

Peak CKMB and cTnT accurately estimates myocardial infarct size after reperfusion

Objectives. To find the time-to-peak for creatine kinase MB_mass (CKMB) and cardiac troponin T (cTnT) after acute reperfusion, to compare peak and cumulative values to estimate infarct size (IS), and to evaluate clinical routine sampling for assessment of IS. Design. Acute primary percutaneous coronary intervention (PCI) was performed in 38 patients with first-time myocardial infarction. In 21 patients, CKMB and cTnT were acquired before PCI and at 1.5, 3, 6, 12, 18, 24, and 48 hours thereafter. In 17 patients, clinical routine samples were acquired at arrival, and at 10 and 20 h. IS was assessed by delayed contrast-enhanced MRI (DE-MRI). Results. Time-to-peak was 7.6±3.6 h for CKMB and 8.1±3.4 h for cTnT. Peak values correlated strongly to cumulative values (r_s=0.97–0.98) as well as to DE-MRI (r_s=0.8–0.82). Clinical routine sampling showed lower r_s values (0.47–0.60). Conclusions. Peak values are likely captured if CKMB and cTnT are acquired at 3, 6, and 12 h after acute PCI. These peak values can be used to estimate myocardial infarct size after acute PCI.     

Oxytocin-loaded sustained-release hydrogel graft provides accelerated bone formation: An experimental rat study

Restoration of the lost bone volume is one of the most deliberate issues in dentistry. Sustained-release microspherical oxytocin hormone in a poloxamer hydrogel scaffold combined with a mixture of β-tricalcium phosphate and hydroxyapatite (CP) may serve as a suitable bone graft. The aim of this study was to design and test a novel thermosensitive hydrogel graft incorporating oxytocin-loaded poly(d , l -lactide-co-glycolide) (PLGA) sustained-release microspheres and CP. Thermosensitive poloxamer hydrogel containing CP (HCP graft) was prepared as a base and combined with hollow microspheres (HCPM) and oxytocin-loaded microspheres (HCPOM). Eighty Wistar rats were used for testing the grafts and a control group in 8-mm-diameter critical-sized calvarial defects (CSD); (n = 20). Bone healing at the 4th and 8th weeks was evaluated by histological, histomorphometric, and radiological (micro-computed tomography [µCT]) analyses. The results were analyzed by two-way analysis of variance (P < .05). Oxytocin-loaded PLGA microspheres prepared by the solvent displacement method yielded a high encapsulation efficiency of 89.5% and a slow drug release. Incorporation of the microspheres into the hydrogel graft slowed the release rate down and the release completed within 32 days. HCPOM revealed the highest new bone formation (26.45% ± 6.65% and 30.76% ± 4.37% at the 4th and 8th weeks, respectively; P < .0001) while HCPM and HCP groups revealed a bone formation of around 10% (P > .05). µCT findings of HCPOM group showed the highest mean bone mineral density values (42.21 ± 5.14 and 46.94 ± 3.30 g/cm³ for the 4th and 8th weeks, respectively; P < .0027). The proposed oxytocin-loaded sustained-release PLGA microspheres containing thermosensitive hydrogel graft (HCPOM) provide an accelerated bone regeneration in the rat calvaria.     

Tacrine does not alter the potency of succinylcholine in the rat

Purpose

Tacrine is a cholinesterase inhibitor used to manage Alzheimer’s dementia. Giveniv, it prolongs succinylcholine blockade in humans but the effects of chronic oral tacrine are not known.

Methods

Groups of adult rats were given 2.5 mg · kg^?1 tacrine (chronic groups) or 1 ml saline (control) twice daily by gavage for one, two, four or eight weeks. An additional (acute) group received 2.5 mg · kg^?1 tacrineiv. Twelve to 18 hr after the last gavage of tacrine or saline, and ~20 min afteriv tacrine, cumulative dose-response curves of succinylcholine were determined in the tibialis and soleus muscles in anaesthetized, ventilated rats during monitoring of evoked twitch response to indirect (nerve) train-of-four stimulation.

Results

The ED₅₀ and ED₉₅ of succinylcholine in control rats were (mean ± SD) 204 ± 41 and 382 ± 96 μg · kg^?1 respectively, in the tibialis muscle, and 280 ± 52 and 629 ± 168 μg · kg^?1 in the soleus muscle (P < 0.05 between muscles). In the acute and chronic tacrine groups, the mean ED₅₀ and ED₉₅ ranged from 166–197 and 277–396 μg · kg^?1, respectively, in the tibialis muscle, and 248–333 and 546–667 μg · kg^?1, in the soleus muscle. Dose responses did not differ among acute and chronic tacrine groups and the control group.

Conclusion

Chronic oral tacrine does not alter muscle response to succinylcholine in the rat. This may not apply to Alzheimer patients receiving chronic tacrine since the interaction between acute tacrine and succinylcholine in the rat differs from that in humans.     

BILATERAL NEPHRECTOMY DELAYS GASTRIC EMPTYING OF A LIQUID MEAL IN AWAKE RATS

Aims: This study evaluates the effect of bilateral nephrectomy on the gastric emptying of a liquid meal. Methods: Male rats were submitted under anesthesia to cervical vessels cannulation and bilateral lumbar incision, followed or not by nephrectomy. Next day, they were gavage fed (1.5 mL) with phenol red (0.5 gmL^?1) in 5% glucose solution and sacrificed 0, 10, 20, 30 or 45 min later. A blood sample was obtained for biochemical analysis while gastric dye retention was determined by spectrophotometry. Data (mean ± SEM) were compared by ANOVA and Student–Newman–Keuls tests. Results: Gastric emptying values from nephrectomy group at 10, 20, 30 and 45 min were lower (P<0.05) than those of sham-operated animals (22.0 ± 4.0 vs. 38.9 ± 6.1%, 34.1 ± 1.4 vs. 66.9 ± 1.3%, 45.5 ± 6.1 vs. 64.9 ± 5.4% and 59.7 ± 2.4 vs. 81.5 ± 4.0%, respectively). Mean arterial pressure, blood volume, serum osmolarity, urea, creatinine and potassium values were higher (P < 0.05) in nephrectomy group than in sham-operated animals (143.3 ± 2.7 vs. 100.5 ± 4.1 mmHg, 15.7 ± 0.9 vs. 8.9 ± 1.1 mL 100 g^?1, 344.0 ± 10.8 vs. 299.4 ± 1.3 mOsm KgH₂O^?1, 344.0 ± 33.7 vs. 47.0 ± 2.8 mg dL^?1, 3.6 ± 0.3 vs. 1.1 ± 0.1 mg dL^?1, 6.4 ± 0.7 vs. 3.7 ± 0.2 mEq L^?1, respectively). The plasmatic Na⁺ values did not change (139.3 ± 2.0 in sham-operation vs. 123.0 ± 7.5 mEq L^?1 in nephrectomy). Conclusion: Acute loss of kidney function markedly delays the gastric emptying rates, which could be involved in gastrointestinal dysmotility complaints seen after renal failure.     

Bone density and structure in long-term survivors of pediatric allogeneic hematopoietic stem cell transplantation

Children requiring allogeneic hematopoietic stem cell transplantation (alloHSCT) have multiple risk factors for impaired bone accrual. The impact of alloHSCT on volumetric bone mineral density (vBMD) and cortical structure has not been addressed. Tibia peripheral quantitative computed tomography (pQCT) scans were obtained in 55 alloHSCT recipients, ages 5 to 26 years, a median of 7 (range, 3–16) years after alloHSCT. pQCT outcomes were converted to sex‐ and race‐ specific Z‐scores relative to age based on reference data in >700 concurrent healthy participants. Cortical section modulus (Zp; a summary measure of cortical bone structure and strength), and muscle and fat area Z‐scores were further adjusted for tibia length for age Z‐scores. AlloHSCT survivors had lower height Z‐scores (?1.21 ± 1.25 versus 0.23 ± 0.92; p < 0.001), versus reference participants; BMI Z‐scores did not differ. AlloHSCT survivors had lower trabecular vBMD (?1.05; 95% confidence interval [CI], ?1.33 to ?0.78; p < 0.001), cortical Zp (?0.63; 95% CI, ?0.91 to ?0.35; p < 0.001), and muscle (?1.01; 95% CI, ?1.30 to ?0.72; p < 0.001) Z‐scores and greater fat (0.82; 95% CI, 0.54–1.11; p < 0.001) Z‐scores, versus reference participants. Adjustment for muscle deficits eliminated Zp deficits in alloHSCT. Total body irradiation (TBI) was associated with lower trabecular vBMD (?1.30 ± 1.40 versus ?0.49 ± 0.88; p = 0.01) and muscle (?1.34 ± 1.42 versus ?0.34 ± 0.87; p < 0.01) Z‐scores. Growth hormone deficiency (GHD) was associated with lower Zp Z‐scores (?1.64 ± 2.47 versus ?0.28 ± 1.24; p = 0.05); however, muscle differences were not significant (?1.69 ± 1.84 versus ?0.78 ± 1.01; p = 0.09). History of graft versus host disease was not associated with pQCT outcomes. In summary, alloHSCT was associated with significant deficits in trabecular vBMD, cortical geometry, and muscle area years after transplantation. TBI and GHD were significant risk factors for musculoskeletal deficits. Future studies are needed to determine the metabolic and fracture implications of these deficits, and to identify therapies to improve bone accrual following alloHSCT during childhood. © 2012 American Society for Bone and Mineral Research.     

Accuracy and limitations of continuous oesophageal aortic blood flow measurement during general anaesthesia for children: comparison with transcutaneous echography-Doppler

Background: Because it is noninvasive and easy to use, oesophageal Doppler ultrasonography appears to be a worthwhile alternative for continuous assessment of cardiac output measurement during anaesthesia. A new oesophageal Doppler‐echography device (Dynemo 3000?, Sometec, Paris, France) can simultaneously determine aortic diameter and aortic blood flow at the same anatomical level (DE_eso). The purpose of this study was to assess the accuracy and the potential limitations of this device during general anaesthesia among 20 children, using transcutaneous Doppler‐echocardiography for comparison (DE_tra). Methods: The reproducibility of paired measurements of mean aortic blood flow velocity (MAFV), aortic diameter (ØAo) and aortic blood flow (ABF) was analysed with both methods. Second, haemodynamic values were measured simultaneously in a blinded manner by both methods before and after surgery. Results: The percent change (%Δ) in MAFV and ABF was calculated with both methods for each child. The age and weight of children included in this study was 8.3 ± 2.5 years and 27 ± 8 kg, respectively. Intraoperator reproducibility of MAFV_tra, ABF_tra, MAFV_eso and ABF_eso, was 5.0 ± 4.1%, 7.0 ± 5.6%, 20.1 ± 17.5% and 22.0 ± 16.6%, respectively. ABF_tra was significantly linked to ABF_eso (R=0.55, P < 0.01). Bias ± SD of ABF measurements between both methods was 2.2 ± 1.1 l · min^?1. %ΔABF_tra was significantly linked to %ΔABF_eso (R=0.62, P < 0.01). The bias ± SD inherent to %ΔABF measurements with both methods was ?0.02 ± 18%. Conclusions: These results suggest that this new oesophageal Doppler method is unsuitable to measure accurately absolute CO values and relative CO changes in children during anaesthesia.     

Albumin dialysis without anticoagulation in high-risk patients: an observational study

Severe liver failure causes coagulopathy and high bleeding risk. Albumin dialysis with Molecular Adsorbent Recirculating System (MARS) (Gambro, Lund, Sweden) is useful for treatment. However, anticoagulation during its use is of uncertain value. We omitted heparin‐saline priming and intradialytic heparin and examined its effects. Albumin dialysis was performed in critically ill patients with intermittent circuit saline flushes (2664 ± 2420 mL per treatment). A total of 12 patients (M : F = 10:2; age 49 ± 9 years) were thus treated: 6 for fulminant hepatic failure and 6 for acute‐on‐chronic liver failure. The overall hospitalization duration was 31 ± 30 days. A total of 44 treatment sessions were performed (average 8 ± 7 sessions per patient). Prescribed versus achieved MARS duration were 13 ± 3 versus 11 ± 4 h, P < 0.05. Twenty‐three percent (10/44) of MARS sessions clotted, 11% (5/44) of treatments were electively terminated, and 2% (1/44) developed vascular catheter occlusion. Spontaneous bleeding occurred in 9% (4/44). Pre‐ versus post‐MARS systemic and blood circuit transmembrane pressures (mm Hg), and albumin dialysate afferent and efferent pressures were all stable. Coagulation indices were (pre‐ vs. post‐MARS): (i) prothrombin time (seconds): 36 ± 30 versus 42 ± 33, P = 0.143; (ii) activated partial thromboplastin time (seconds): 78 ± 43 versus 88 ± 45, P = 0.117; and (iii) platelet count (×10³/µL): 87 ± 40 versus 76 ± 48, P = 0.004. Systemic blood solute concentrations pre‐ versus post‐MARS were: (i) serum urea (mg/dL): 22.4 ± 19.6 versus 14.0 ± 8.4, P < 0.05; (ii) serum creatinine (mg/dL): 2.8 ± 2.3 versus 1.9 ± 1.5, P < 0.05; (iii) total bilirubin (mg/dL): 29.5 ± 8.8 versus 20.5 ± 5.1, P < 0.05; and (iv) plasma ammonia (µg/dL): 186 ± 85 versus 129 ± 66, P < 0.05. Anticoagulant‐free albumin dialysis remained effective despite frequent circuit clotting. This led to significant exacerbation of thrombocytopenia although bleeding risk remained low.     

Vertebral Mineral Density Measured by Dual‐energy X‐ray Absorptiometry (DEXA) in a Group of Healthy Italian Boxer Dogs

We studied the feasibility of using dual‐energy X‐ray absorptiometry (DEXA) to obtain reference bone density values in relation to age, gender and body weight in growing and young adult Italian boxer dogs. The study was performed on eight animals (three males and five females) at 7, 12 and 18 months of age. Animals were carefully examined and blood samples were collected from each dog to detect any sign of metabolic and/or endocrine disease. Each subject underwent radiographs to evaluate growth of the spine and hip. One female was not considered in the statistical model because of the development of grade 4 spondylosis deformans during the study period. All animals were serially scanned using DEXA; the region of interest was the whole spine T₁₂‐L₂, while the subregions of interest were the four vertebrae (T₁₂‐T₁₃‐L₁‐L₂) within the scanned spine. Statistical analysis was performed separately for each region of interest. Age had the strongest relationship with bone density (P < 0.001). Gender effect on spinal mineral density was not significant while vertebral site effect was highly significant. Average bone mineral density (BMD) ± SD for the whole spine trait was 0.862 ± 0.108g/cm² while average BMD ± SD for subregions of interest ranged from 0.836 ± 0.141 g/cm² for T₁₂ to 0.928 ± 0.119g/cm² for L₂. Estimated reference BMD values at 7, 12 and 18 months of age for each vertebral site in males and females are provided.