Wrist extensor muscle pathology in lateral epicondylitis.

The morphology of the extensor carpi radialis brevis (ECRB) muscle was investigated in 20 patients with longstanding lateral epicondylitis. Muscle biopsies were obtained from the proximal or distal portion of the ECRB and analysed by enzyme- and immunohistochemical methods. Morphological abnormalities were significantly more frequent in patients than controls and included moth-eaten fibres, fibre necrosis and signs of muscle fibre regeneration as well as higher percentages of the fast-twitch oxidative (type 2A) fibre type. Changes were equally distributed proximally and distally. It is concluded that these changes, directly or indirectly, may reflect the cumulative effect of mechanical and/or metabolic overload and that decreased muscular performance in patients with lateral epicondylitis may be due to both elbow pain and physical damage to the ECRB muscle.     

Neuropeptide tyrosine (NPY): a newly discovered peptide is present in the mammalian respiratory tract.

Neuropeptide tyrosine (NPY), a newly discovered peptide known to modulate blood vessel diameter and smooth muscle tone, has been found in many mammalian organs. Its distribution is similar to that of sympathetic nerve fibres and NPY immunoreactivity has been found in noradrenergic ganglion cells. In a study of the respiratory tract of four mammalian species--man, cat, guinea pig, and rat--NPY immunoreactivity has been localised to nerve fibres. NPY immunoreactive nerve fibres were found in the adventitia of blood vessels and in the airway smooth muscle. Its distribution was strikingly similar to that of sympathetic nerve fibres as demonstrated by dopamine-beta-hydroxylase antibodies. The mean (SD) concentrations of NPY in the guinea pig respiratory tract, as determined by radioimmunoassay of tissue extracts, were: upper trachea 3.3 (0.7), lower trachea 2.0 (0.5), and major bronchus 3.5 (1.1) pmol/g. During developmental studies in man NPY immunoreactive nerve fibres were first observed at 20 weeks' gestation in the trachea, and fibres gradually extended down into the intrapulmonary airways after birth. NPY immunoreactive nerve fibres have a distribution and developmental pattern similar to that of sympathetic nerve fibres in the respiratory tract. The finding of NPY immunoreactivity in nerve fibres in the mammalian respiratory tract adds to the growing number of peptides having potent biological actions found in this organ, and shows that the lung possesses a rich peptidergic system, which may influence pulmonary function.     

Peripheral muscle endurance and the oxidative profile of the quadriceps in patients with COPD

BACKGROUND: Based on previously reported changes in muscle metabolism that could increase susceptibility to fatigue, we speculated that patients with chronic obstructive pulmonary disease (COPD) have reduced quadriceps endurance and that this will be correlated with the proportion of type I muscle fibres and with the activity of oxidative enzymes. METHODS: The endurance of the quadriceps was evaluated during an isometric contraction in 29 patients with COPD (mean (SE) age 65 (1) years; forced expiratory volume in 1 second 37 (3)% predicted) and 18 healthy subjects of similar age. The electrical activity of the quadriceps was recorded during muscle contraction as an objective index of fatigue. The time at which the isometric contraction at 60% of maximal voluntary capacity could no longer be sustained was used to define time to fatigue (Tf). Needle biopsies of the quadriceps were performed in 16 subjects in both groups to evaluate possible relationships between Tf and markers of muscle oxidative metabolism (type I fibre proportion and citrate synthase activity). RESULTS: Tf was lower in patients with COPD than in controls (42 (3) v 80 (7) seconds; mean difference 38 seconds (95% CI 25 to 50), p<0.001). Subjects in both groups had evidence of electrical muscle fatigue at the end of the endurance test. In both groups significant correlations were found between Tf and the proportion of type I fibres and citrate synthase activity. CONCLUSION: Isometric endurance of the quadriceps muscle is reduced in patients with COPD and the muscle oxidative profile is significantly correlated with muscle endurance.     

The morphological sequences in man of de- and reinnervation in free muscle transfer with microneurovascular anastomoses

Muscle biopsies from two patients treated by free gracilis muscle transfer and micro-neurovascular anastomoses for long standing facial palsy due to previous damage to the facial nerve during removal of tumours were examined by histochemistry and electron microscopy. Sequential muscle biopsies of one case taken at various intervals after transferring the muscle permitted the study of events of de- and reinnervation of human skeletal muscle. The changes in the early stages of denervation included atrophy of type 2B fibres. This was followed by progressive atrophy of all fibre types, distortion of the internal structure of the muscle fibres with the incidence of various cytoplasmic inclusions. Massive necrosis of the muscle did not occur. A prominent increase in satellite cells and their maturation to myotubes and new muscle fibres were evident. Reinnervation occurred with the formation of neuromuscular junctions some of them being at preformed sole plates. Fibre type grouping was apparent in addition to other changes such as the occurrence of targetoid hypertrophied muscle fibres. These changes are similar to those described previously during de- and reinnervation studies in experimental animals.     

Vascular plexus is a differentation criterion for muscularis mucosa from muscularis propria in small biopsies and transurethral resection materials of urinary bladder?

Objective: Smooth muscle fibres are found within thesuperficial lamina propria of urinary bladder (Muscularis Mucosa). Thesemuscle fibres of muscularis mucosa should be distinguished from themuscularis propria in cases with urothelial carcinoma, because the depthof infiltration affects prognosis and therapy modalities. The aim of thepresent study was to evaluate whether the presence of vascular plexus isa criterion for muscularis mucosa and to distinguish it from muscularispropria in urinary bladder biopsies and transurethral resectionspecimens. Materials and methods: Hematoxylin-Eosin andMasson-Trichrome stained slides of 54 cases with urothelial carcinomawere reviewed. Results: In all cases (100%), thick walledvessels were observed within the lamina propria of urinary bladder.Smooth muscle layer of lamina propria was seen in 48 of 54 cases(88.8%), and these smooth muscle fibres were co-existed with thickwalled vessels. In invasive urothelial carcinoma; thin smooth musclefibres and thick walled vessels were seen within the lamina propria in22 of 24 cases (91.7%). There were two cases (8.3%)including only vessels in small biopsies of invasive urothelialcarcinoma cases. In cases with non-invasive urothelial carcinoma; musclefibres of muscularis mucosa and vessels were found within the laminapropia in 26 of 30 cases (86.7%). In this group, muscle fibreswere not detected in 4 cases (13.3%). Conclusion:Muscularis mucosa can be detected histologically in urinary bladderbiopsies and TUR materials. We emphasize that the presence of vascularnetwork is a useful criterion to determine muscularis mucosa of urinarybladder, even in the absence of muscle fibres.     

Role of a muscle target organ on the regeneration of motor nerve fibres in long nerve grafts: A synopsis of experimental and clinical data

The importance of the muscle target organ as a promoting factor for nerve fibre regeneration in nerve grafts is still a subject of controversial discussion. In the last few years we published uniform results of experimental series in sheep and rabbits in which we investigated the biology of nerve fibre regeneration in long nerve autografts without connection to a target organ. Surprisingly, we found excellent regeneration of myelinated nerve fibres without the influence of a target organ through the whole length of the nerve graft, with an increase in the number of nerve fibres up to fourfold at the distal end. In the sheep series the additional contact with a muscle target organ for 6 months had a variable effect on the fibre population in the distal end of the nerve graft. The results of our planimetric analyses of nerve biopsies in patients with facial paralysis, who were treated by cross-face nerve grafting and free muscle transplantation, are extremely divergent from the results of our experimental series. Instead of an increase, we found a decrease in number of regenerating nerve fibres arriving at the distal end of the cross-face nerve graft down to 20%. Species-specific differences in the biology of nerve regeneration are discussed, together with their implications for the complex clinical situation of nerve grafting with or without the influence of a target organ. © 1996 Wiley-Liss, Inc.     

Myosin heavy-chain isoform distribution, fibre-type composition and fibre size in skeletal muscle of patients on haemodialysis

OBJECTIVE: Chronic uraemia is associated with abnormalities in skeletal muscles, which can affect their working capacity. It is also well known that the fibre-type composition of skeletal muscles influences endurance, muscle strength and power. In this study we therefore determined the size and distribution of muscle fibres and the myosin heavy-chain (MHC) isoform composition in patients on haemodialysis (HD) in order to establish any differences with values for untrained control subjects. MATERIAL AND METHODS: Muscle biopsies were obtained from the vastus lateralis muscle of 14 non-diabetic patients on HD. The size and distribution of muscle fibres were evaluated using adenosine triphosphate synthase (ATPase) histochemistry, whilst MHC isoform composition was determined in muscle homogenates using sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Values were compared to those for a group of age-, gender- and BMI-matched untrained control subjects. The aerobic work capacity of the patients was also determined. RESULTS: The MHC composition for I, IIA and IIX isoforms was found to be 35.3% +/- 18.2%, 35.9% +/- 7.1% and 28.9% +/- 15.6%, respectively, findings supported by the ATPase histochemically determined fibre-type composition of the vastus lateralis muscle. The mean fibre area of type 1 and 2 fibres was 3283 +/- 873 and 3594 +/- 1483 MICROm2, respectively. The MHC composition and the size of the type 1 fibres of the patients on HD were significantly different from those of the control subjects. CONCLUSIONS: The data demonstrate relatively fewer type 1 and consequently more type 2x fibres, with a corresponding change in MHC isoforms (MHC I and MHC IIX) in the skeletal muscle of patients on HD. Several patients on HD were found to have <15% type 1 (or relative percentage of MHC I) fibres. Such a low percentage of type 1 fibres is very rarely observed in normal untrained subjects. Chronic uraemia more severely affects the composition than the size of fibres.     

Predictors of renal allograft histologic damage progression

The objective of this study was to analyze factors that are involved in the progression of renal allograft damage in the first 6 mo after transplantation. Donor and 6-mo protocol biopsies of 83 patients who received a renal transplant were classified using the Chronic Allograft Damage Index (CADI). Histologic changes were compared and correlated to clinical parameters at transplantation, at 6 mo, and annually over 2 yr. All CADI components increased significantly in the 6-mo posttransplantation period, except chronic vascular changes and the percentage of glomerulosclerosis. Total cholesterol and LDL- cholesterol at the time of biopsy correlated positively with mesangial matrix increase, and HDL cholesterol correlated negatively with vascular intima increase. High BP at biopsy was associated with tubular atrophy. Diastolic BP at biopsy correlated with 6-mo CADI (CADI-6). Patients with diastolic BP > or =85 mmHg at biopsy had a higher difference between CADI score in protocol biopsies and CADI score in donor biopsies (DeltaCADI) and higher creatinine at 1 and 2 yr. CADI in donor biopsies (CADI-0) >1 was more frequently found in older (odds ratio [OR], 1.07; 95% confidence interval [CI], 1.01 to 1.14) and nontraumatic dead donors (OR, 3.89; 95% CI, 1.13 to 13.33). CADI-6 >3 was more frequently found in those with CADI-0 >1 (OR, 3.82; 95% CI, 1.19 to 12.21), older donors (OR, 1.05; 95% CI, 1.01 to 1.10), and number of AB mismatches (OR, 2.36; 95% CI, 1.09 to 5.10). CADI-0, CADI-6, and DeltaCADI correlated significantly with serum creatinine at hospital discharge, at 6 mo, and at 2 yr. DeltaCADI was affected by initial percentage of glomerulosclerosis (OR, 1.10; 95% CI, 1.02 to 1.19) and creatinine at hospital discharge (OR, 1.01; 95% CI, 1.00 to 1.02). Donor-related as well as nonimmunologic factors, such as hypertension and dyslipidemia, are associated with increased risk for renal allograft damage progression.     

A histochemical and immunohistochemical study of the autonomic innervation of the lower urinary tract of the female pig. Is the pig a good model for the human bladder and urethra?

The detrusor muscle, bladder neck, proximal, middle and distal regions of the urethra of the female pig were studied by histochemical and immunohistochemical methods to localize catecholamine-containing, acetylcholinesterase-positive and peptide-containing nerves. The peptides examined included: vasoactive intestinal polypeptide, substance P, somatostatin, [Met]enkephalin, bombesin and gastrin. The greatest density of nerves was found in the smooth muscle of the distal urethra, followed by the bladder neck, middle urethra, and proximal urethra, with the least in the detrusor muscle. The greatest number of nerve fibres stained for acetylcholinesterase, followed by vasoactive intestinal polypeptide- and catecholamine-containing fibres. Substance P-immunoreactive nerve fibres were confined to the bladder neck and distal urethral regions. [Met]enkephalin-and gastrin-immunoreactive nerves were most dense in the distal urethra but absent in detrusor muscle, while somatostatin-immunoreactive nerve fibres were sparsely distributed throughout the lower urinary tract. No nerve fibres showing immunoreactivity to bombesin were found. Catecholamine-containing, acetylcholinesterase-positive, vasoactive intestinal polypeptide-, substance P-, [Met]enkephalin- and gastrin-immunoreactive nerves were also found on the adventitial-medial border of blood vessels in the pig urinary tract. In the intrinsic external urethral sphincter, located in the distal urethra, vasoactive intestinal polypeptide- and gastrin-immunoreactive nerve fibres were found bordering a small number of individual striated muscle fibres, while catecholamine-containing nerves were found predominantly in the connective tissue surrounding the striated muscle fibres. Dense populations of acetylcholinesterase-positive nerve fibres were found associated with the striated muscle fibres, with end plates on some of them. Intramural ganglia, composed of two to 30 neurones, were found in the bladder neck and middle and distal regions of the urethra. In the smooth muscle, and in the vicinity of the striated muscle regions of the intrinsic external urethral sphincter, there were small ganglia, containing two to three neurones, which were vasoactive intestinal polypeptide-, [Met]enkephalin- and somatostatin-immunoreactive. The results are compared to the autonomic innervation of the human bladder and urethra as previously described and it is concluded that the lower urinary tract of the pig is a good model for some features of the lower urinary tract of man, but a poor model for others.     

Red and white muscle fibres in meniscectomy patients. Effects of postoperative physiotherapy.

Clinical examination of the knee joint of 16 meniscectomy patients was performed and muscle biopsies were taken preoperatively and four weeks postoperatively from the vastus medialis of the quadriceps muscle. Corresponding investigations were performed in 15 healthy volunteer controls. One group of the meniscectomy patients was given routine postoperative physiotherapy, the other group intensive physiotherapy. Type I and II muscle fibres were determined from the muscle biopsies of the myosin-ATPase staining method. No difference was observed in the clinical and histochemical findings between the patients given routine and intensive physiotherapy respectively. Compared with the controls, the older patients had clinical quadriceps atrophy preoperatively, but there were no differences in the muscle fibre composition. After meniscectomy the patients developed even more marked quadriceps atrophy, which was more manifest in the patients with a good preoperative muscle status. The surface areas of the type I and II fibres of the operated patients diminished compared with the samples from the healthy volunteer controls. Only in the male patients was the decrease in the type I muscle area considerable. The present data indicate that meniscectomy is accompanied by a marked change in the clinical and histochemical appearance of the quadriceps muscle compared with the muscle status following meniscus injury; the extent of physiotherapy as carried out in the present study did not significantly modify the results.     

A study of the myelinated fibres in the branches of the pelvic plexus

In a 20-year-old human female specimen the nerves to the pelvic organs were dissected and analysed. The gross anatomy of the branches of the pelvic plexus was described. The composition of these nerves was studied and the sizes and distribution of the diameter of a great part of the myelinated nerve fibres were measured and analysed. It was confirmed that the ventral roots S2 and S3 contain many nonmyelinated nerve fibres. There are direct connections between the sacral sympathetic chain and the pelvic plexus. They contain myelinated fibres with sizes as large as 11 μm. There are two different groups of fibres which supply the bladder, one on the dorsal side, mainly nonmyelinated (postganglic sympathetic?), and another group to the lateral side which contains many thin myelinated fibres (parasympathetic preganglionic?). The pelvic plexus and its branches are fixed to the vagina and the rectum. Surgical interventions in this area and perhaps also childbirth can damage the nerve supply to the bladder and the urethra. The functional disturbances of the bladder after such interventions can depend on what group of nerve fibres is most seriously damaged. The large number of thick myelinated fibres which reach the ventro lateral side of the urethra makes it highly probable that these fibres innervate the intrinsic striated urethral musculature. The large number of nonmyelinated nerve fibres in the nerves to the m. levator ani probably innervate smooth muscle tissue which is found in the fasciae of the pelvic floor.     

Hand muscle weakness in long-term vibration exposure

Hand muscle strength was compared between workers regularly exposed to hand-held vibrating tools (n=81) and a non-exposed control group (n=45). Maximal voluntary strengths of hand grip, thumb pinch, thumb palmar abduction and index and little finger abduction were measured. The exposed workers had significantly weaker extrinsic (7%, P<0.01) and intrinsic (19%, P<0.0001) muscles than the controls. Reduced vibration perception was noted in nine vibration-exposed workers who presented with symptoms of hand muscle weakness (P<0.01). Cold intolerance following vibration exposure was found to precede sensorineural and vasospastic symptoms. We therefore postulate that cold intolerance may be a valuable marker for early detection of the adverse effects of vibration. This study emphasizes the need for tests of intrinsic muscle strength in order to evaluate the impairment of hand function observed in vibration-exposed workers.     

Apoptosis in kidney and pancreas allograft biopsies

BACKGROUND: Apoptosis is a particular form of cell death involved in the elimination of somatic cells. In this study, the occurrence of apoptotic cells in kidney and pancreas allograft biopsies was analyzed and correlated with the number of infiltrating macrophages and lymphocytes and granzyme B expression. METHODS: Kidney and pancreas biopsies from patients submitted to simultaneous pancreas-kidney transplantation were classified into three groups: acute rejection, chronic rejection, and transplant cases without evidence of rejection. Formalin-fixed paraffin biopsies were used to identify apoptosis by the terminal deoxynucleotidyl transferase [TdT]-mediated dUTP nick end labeling (TUNEL) method. RESULTS: In normal kidney, only few apoptotic cells were observed. In contrast, in kidney-allograft biopsies, the TUNEL signal was detected in the nuclei of tubular epithelial cells and also in mononuclear cells scattered in the interstitium. In pancreas biopsies, numerous apoptotic cells were detected in acinar cells, in ducts, and occasionally in islets. The number of apoptotic cells in acute pancreas rejection was significantly higher compared with acute rejection of kidney grafts (50+/-14 vs. 21+/-4 cells/mm2; P<0.05). In kidney biopsies, there was a positive correlation between apoptosis and macrophages (r=0.51; P<0.005), and apoptosis versus T lymphocytes (r=0.45; P<0.05). In pancreas biopsies, the number of apoptotic cells correlated only with the number of macrophages (r=0.41; P<0.05). CONCLUSIONS: Apoptosis occurs in kidney and pancreas allograft biopsies, markedly in acute rejection in pancreas biopsies. Although apoptosis may reflect a mechanism of down-regulation of the allograft immune response by eliminating infiltrating cells, the elimination of graft cells may result in graft damage, particularly in pancreas transplantation.     

Skeletal Muscle Fibre Characteristics in Young and Old Bulls and Metabolic Response after a Bullfight

Fibre type composition, activities of enzymes such as citrate synthase (CS), 3‐hydroxyacyl coenzyme A dehydrogenase (HAD), lactate dehydrogenase (LDH), as well as glycogen, lactate and pH levels were analysed in muscle biopsies (m. gluteus medius) obtained after bullfighting from 10 young and 10 old bulls. No changes were seen in fibre type composition between groups, but the older bulls had higher HAD and LDH activities. Low glycogen concentrations and low pH values were found in both groups, but the lactate concentration after bullfighting was higher in the older group of bulls. The histochemical stain for glycogen revealed that type IIB fibres in both young and old bulls contained more glycogen than seen in type IIA and type I fibres. These results show that young and old bulls have similar muscle fibre type composition, but the metabolic capacity differs, with a higher glycolytic capacity and lactate production in older bulls. Furthermore, it seems that the physical and emotional stress in connection with a bullfight causes a marked depletion of glycogen, especially of type I and IIA fibres.     

Mast cells in rapidly progressive glomerulonephritis.

The role of mast cells (MC) in tubulointerstitial damage in glomerulonephritis (GN) is not fully understood. The distribution of MC was compared in renal biopsies from 50 patients with different stages of rapidly progressive GN (RPGN) and in 20 control samples. The immunoreactivity of renal MC with anti-tryptase and anti-chymase antibodies was studied. Interstitial myofibroblasts were stained with anti-alpha-smooth muscle actin (alpha-SMA) antibody, and inflammatory cells were identified by anti-CD3, -CD20, and -CD68 monoclonal antibodies. Positively stained cells were counted, and the relative interstitial and fractional areas of anti-alpha-SMA-stained cells were measured. MC were rarely found in control samples. In contrast, samples showing crescentic GN contained numerous tryptase-positive MC (MC(T)) (43.7+/-4.65 versus 7.14+/-1.3/mm2) and fewer tryptase- and chymase-positive MC (MC(TC)) (13.8+/-1.86 versus 1.89+/-0.86/mm2) in the renal interstitium but never in the glomerulus. Double immunostaining demonstrated the presence of both phenotypes of MC. Accumulation of MC was significantly correlated with the numbers of T lymphocytes (MC(T), r = 0.67) and interstitial macrophages (MC(T), r = 0.455). There was also a significant correlation between the number of MC(T) and the relative interstitial area. The number of MC(TC) was well correlated with the fractional area of alpha-SMA-positive interstitium (r = 0.749) and the percentage of the interstitial fibrotic area (r = 0.598). There was also a significant negative correlation between interstitial MC(TC) accumulation and creatinine clearance (r = 0.661). The density of MC(TC) was higher (1.4-fold) in advanced forms of GN associated with fibrocellular crescents and interstitial fibrosis. These results show the potential involvement of MC in the fibroproliferative process in the renal interstitium of patients with RPGN. The results indicate that these cells constitute part of the overall inflammatory cell accumulation in RPGN.     

Vibration-induced muscle injury. An experimental model and preliminary findings.

The hind paws of rats were subjected to vibration at a frequency of 80 Hz., an acceleration of 32 m./s.2 rms (i.e. ah.w approximately 6.3 m./s.2 rms) for five hours daily during five consecutive days. Morphological, histochemical and immunohistochemical analyses of the soleus, extensor digitorum longus and the plantar muscles in the vibrated limb and the contralateral control limb were performed. No changes were seen in the soleus or extensor digitorum longus muscles but different degrees of degeneration of the muscle fibres were seen in the plantar muscle sections as well as signs of regeneration. No changes were observed in the contralateral unexposed limb. It is concluded that it is not only nervous tissue but also muscle tissue that can be affected by vibration. The changes seem to be confined to muscles close to the vibration exciter.     

Mercury in dental restoration: is there a risk of nephrotoxicity?

BACKGROUND: Concern has been voiced about exposure to mercury (Hg) from dental amalgam fillings, and there is a need to assess whether this leads to signs of nephrotoxicity. METHODS: A total of 101 healthy adults (80 males and 21 females) were included in this study. The population as grouped into those having amalgam fillings (39 males and 10 females) and those without (41 males and 11 females). Hg was determined in blood, urine, hair and nails to assess exposure. Urinary excretion of beta2-microglobulin (beta2M), N-acetyl-beta-D-glucosaminidase (NAG), gamma-glutamyltransferase (gammaGT) and alkaline phosphatase (ALP) were determined as markers of tubular damage. Albuminuria was assayed as an early indicator of glomerular dysfunction. Serum creatinine, beta2M and blood urea nitrogen (BUN) were determined to assess glomerular filtration. RESULTS: Hg levels in blood and urine were significantly higher in persons with dental amalgam than those without; in the dental amalgam group, blood and urine levels of Hg significantly correlated with the number of amalgams. Urinary excretion of NAG, gammaGT and albumin was significantly higher in persons with dental amalgam than those without. In the amalgam group, urinary excretion of NAG and albumin significantly correlated with the number of fillings. Albuminuria significantly correlated with blood and urine Hg. CONCLUSION: From the nephrotoxicity point of view, dental amalgam is an unsuitable filling material, as it may give rise to Hg toxicity. Hg levels in blood and urine are good markers of such toxicity. In these exposure conditions, renal damage is possible and may be assessed by urinary excretions of albumin, NAG, and gamma-GT.     

A comparison of parallel and diverging screw angles in the stability of locked plate constructs

We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20° configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20° divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10° and 20° divergent configurations. In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading.     

A rat model of the post-polio motor unit.

We examined the long-term effects of muscle usage on a rat model of the post-polio motor unit. Isometric tensions, type I and type II muscle fiber areas, the incidence of collateral sprouting, and motor endplate morphology were examined following 1, 3, 6, and 9 months of partial denervation in rat plantaris muscle. Full morphologic and functional stability of the expanded motor units occurred at 6 months post-partial denervation. Fiber hypertrophy was observed, possibly the result of compensatory work hypertrophy due to muscle overuse. Following 9 months of partial denervation and muscle overuse, the twitch and tetanic tensions and type I and type II muscle fiber areas were significantly reduced as compared to sham controls; angulated myofibers and group atrophy also were seen. The percent collateral sprouting, the number of terminal branches per endplate, and the endplate area were all increased, possibly a compensatory response to a decreased synthesis of neurotrophic factor(s) and/or transmitter-related components. These aging-like changes seem to occur earlier in chronically stressed, overenlarged, and overworked motor units.     

Caffeine skinned fiber tension test: application to the diagnosis of susceptibility to malignant hyperthermia]

OBJECTIVE: To assess the reactivity of sarcoplasmic reticulum to caffeine, using the skinned muscle fibre tension test and to compare it with the reference in vitro contracture test in the diagnosis of malignant hyperthermia (HM) susceptibility. STUDY DESIGN: Laboratory investigation. MATERIAL: Muscle biopsies from 63 patients, including 29 classified as susceptible to MH (MHS) and 34 classified as non-susceptible (MHN) according to criteria of the European and the North American MH groups. METHOD: The reactivity to caffeine and halothane of skinned muscle fibres was compared, according to the type of fibres, with the data of the in vitro contracture test. The type of fibres (type I: oxidative, slow; type II: glycolytic, fast) were determined with strontium dose-response curves. RESULTS: The reactivity to caffeine was significantly lower in the MHS group, for both type I and type II skinned fibres. However, in comparison with the data of the in vitro contracture tests, using the ROC curve analysis, the best sensitivity-specificity compromise was 90%-71% and 74%-84% for type I and type II skinned fibres respectively. CONCLUSION: The skinned muscle fibre tension test cannot be used instead of the in vitro contracture test for the diagnostic of MHS. However, it may strengthen the data of the latter.