Middle cerebral artery blood velocity,arterial diameter and muscle sympathetic nerve activity during post-exercise muscle ischaemia

During exercise the transcranial Doppler determined mean blood velocity (V_mean) increases in the middle cerebral artery (MCA) and reflects cerebral blood flow when the diameter at the site of investigation remains constant. Sympathetic activation could induce MCA vasoconstriction and in turn elevate V_mean at an unchanged cerebral blood flow. In 12 volunteers we evaluated whether V_mean relates to muscle sympathetic nerve activity (MSNA) in the peroneal nerve during rhythmic handgrip and post-exercise muscle ischaemia (PEMI). The luminal diameter of the dorsalis pedis artery (AD) was taken to reflect the MSNA influence on a peripheral artery. Rhythmic handgrip increased heart rate (HR) from 74 ± 20 to 92 ± 21 beats min^?1 and mean arterial pressure (MAP) from 87 ± 7 to 105 ± 9 mmHg (mean ± SD; P < 0.05). During PEMI, HR returned to pre-exercise levels while MAP remained elevated (101 ± 9 mmHg). During handgrip contralateral MCA V_mean increased from 65 ± 10 to 75 ± 13 cm s^?1 and this was more than on the ipsilateral side (from 63 ± 10 to 68 ± 10 cm s^?1; P < 0.05). On both sides of the brain V_mean returned to baseline during PEMI. MSNA did not increase significantly during handgrip (from 56 ± 24 to 116 ± 39 units) but the elevation became statistically significant during PEMI (135 ± 86 units, P < 0.05), while AD did not change. Taken together, during exercise and PEMI, V_mean changed independent of an elevation of MSNA by more than 140% and the dorsalis pedis artery diameter was stable. The results provide no evidence for a vasoconstrictive influence of sympathetic nerve activity on medium size arteries of the limbs and the brain during rhythmic handgrip and post-exercise muscle ischaemia.     

Comparison of gas exchange data using the Aquatrainer® system and the facemask with Cosmed K4b2 during exercise in healthy subjects

The aim of this study was to determine the level of agreement between the new Aquatrainer^® system and the facemask in the assessment of submaximal and maximal cardiopulmonary responses during exercise performed on ergocycle. Twenty-six physically active healthy subjects (mean age: 41 ± 14 years) performed a submaximal constant work test followed by maximal incremental exercise test on ergocycle, one with cardiopulmonary responses measured using the Cosmed K4b2 facemask, the other using the Cosmed K4b2 Aquatrainer^®. Using the Aquatrainer^®, the gas exchange variables at 100 W were significantly lower for VO₂ (1,483 ± 203 vs. 1,876 ± 204 ml min^?1, P < 0.0001), VCO₂ (1,442 ± 263 vs. 1,749 ± 231 ml min^-1, P < 0.0001), VE (38 ± 5 vs. 44 ± 6 l min^?1, P < 0.0001), and VT (1.92 ± 0.47 vs. 2.18 ± 0.41 l, P < 0.0001) relative to facemask. The bias ±95% limits of agreement (LOA) for VO₂ was 393 ± 507 ml min^?1 for the submaximal constant work test at 100 W and 495 ± 727 ml min^?1 for VO_2max. At maximal intensity, cardiopulmonary responses measured with the Aquatrainer^® system were significantly lower for: VO₂ (2,799 ± 751 vs. 3,294 ± 821 ml min^?1, P < 0.0001), VCO₂ (3,426 ± 836 vs. 3,641 ± 946 ml min^?1, P = 0.012), VE (98 ± 21 vs. 108 ± 26 l min^?1, P = 0.0009) relative to facemask. A non-constant measurement error [interaction effect: (facemask or aquatrainer) × power] was noted from 60 to 270 W for VO₂ (ml min^?1), VCO₂ (ml min^?1), ventilation (l min^?1) (P < 0.0001) and VT (l, P = 0.0001). Additional studies are required to detect the main sources of error that could be physical and/or physiological in nature. Due to the significant measurement error, the new Aquatrainer^® system should be used with extreme caution in filed testing conditions of swimmers.     

Frequencies of hprt mutant lymphocytes in smokers,non-smokers,and former smokers

Previous work with the autoradiographic mutant lymphocyte assay has provided information about the time-course of development of hprt mutations and the persistence of detectable mutant cells in human subjects following therapeutic exposures to genotoxic agents. These early studies also revealed elevations in frequencies of mutant cells in pretreatment blood samples from patients who were current tobacco smokers, but no information was available on former smokers. In the present study, blood samples were obtained from 21 healthy former tobacco smokers who had quit smoking at least 1 year before sampling, 42 subjects who had never smoked, and 23 tobacco smokers. Plasma from all samples was tested for cotinine, a metabolite of nicotine. Current smokers were categorized as heavy smokers (≥10 cigarettes per day, cotinine ≥90 ng/ml plasma) and light smokers (<10/day, cotinine < 90 ng/ml). Lymphocytes from the blood samples were isolated, cryopreserved, and later thawed and assayed with the autoradiographic hprt assay. The 21 former tobacco smokers had a mean variant (mutant) frequency (Vf ± standard error) of 1.97 (±0.13) per million evaluatable cells. The Vf of 42 subjects who had never smoked was 1.74 (±0.13) × 10^-6, not significantly different from the former smokers. The smokers had Vfs of 8.09 (±0.78) × 10^-6 for 18 heavy smokers and 5.22 (±1.02) × 10^-6 for five light smokers. The two categories of smokers had frequencies of mutant cells significantly different from each other, and each was significantly higher than non-smokers and former smokers (P < 0.05). Vfs were significantly correlated with both cotinine concentrations and the number of cigarettes smoked per day, P < 0.001. This study demonstrates the sensitivity of the autoradiographic hprt assay for detecting mutagenic effects related to chronic low-level exposures to genotoxins, and indicates that this assay is more likely to detect the effects of recent rather than past exposures. Environ. Mol. Mutagen. 30:131–138, 1997. © 1997 Wiley-Liss, Inc.     

Effect of endurance training on muscle microvascular filtration capacity and vascular bed morphometry in the elderly

Aim: Exercise training is a strong stimulus for vascular remodelling and could restore age‐induced vascular alterations. The purpose of the study was to test the hypothesis that an increase in vascular bed filtration capacity would corroborate microvascular adaptation with training. Methods: We quantified (1) microvascularization from vastus lateralis muscle biopsy to measure the capillary to fibre interface (LC/PF) and (2) the microvascular filtration capacity (K_f) in lower limbs through a venous congestion plethysmography procedure. Twelve healthy older subjects (74 ± 4 years) were submitted to a 14‐week training programme during which lower‐limbs were trained for endurance exercise. Results: The training programme induced a significant increase in the aerobic exercise capacity of lower limbs (+11%Vo _2peak; P < 0.05; +28% Citrate Synthase Activity; P < 0.01). K_f was largely increased (4.3 ± 0.9 10^?3 mL min^?1 mmHg^?1 100 mL^?1 post‐training vs. 2.4 ± 0.8 pre‐training, mean ± SD; P < 0.05) and microvascularization developed as shown by the rise in LC/PF (0.29 ± 0.06 post‐ vs. 0.23 ± 0.06 pre‐training; P < 0.05). Furthermore, K_f and LC/PF were correlated (r = 0.65, P < 0.05). Conclusion: These results demonstrated the microvascular adaptation to endurance training in the elderly. The increase in K_f with endurance training was probably related to a greater surface of exchange with an increased microvessel/fibre interface area. We conclude that measurement of the microvascular filtration rate reflects the change in the muscle exchange area and is influenced by exercise training.     

System Issues: Mutagenic response of the endogenous hprt gene and lacl transgene in benzo[a]pyrene-treated Big Blue™ B6C3F1 mice

Big Blue™ (BB) and generic B6C3F1 mice were given one to three i.p. injections of 50 mg/kg benzo[a]pyrene (B[a]P) in DMSO every other day to achieve cumulative doses of 50 to 150 mg/kg. Three weeks after treatment, the mutation frequency at the endogenous hprt gene and lacl transgene was measured in splenic T cells. Generic mice given 50, 100, and 150 mg/kg B[a]P displayed induced hprt⁻ frequencies (observed hprt⁻ frequency minus control frequency) of 5.5 ± 1.0, 11 ± 2.0, and 19 ± 2.6 × 10⁻⁶, respectively (average ± SEM). In contrast, BB mice given 50 and 150 mg/kg B[a]P displayed induced hprt⁻ frequencies of 0.9 ± 0.6 and 9.1 ± 1.5 × 10⁻⁶. ³²P postlabelling revealed that the lower hprt response in BB mice correlated with lower amounts of BP-DNA adducts in spleen, liver, and lung 24 hours offer B[a]P exposure. Western blot analysis of liver samples from B[a]P-treated mice suggests that the reduced adducts load in turn may be due to lower P450 1A1 levels in BB mice. The frequency of induced, nonsectored blue plaques (observed blue plaque frequency minus control frequency) in BB mice receiving 50 and 150 mg/kg B[a]P was 41 ± 9 and 134 ± 10 × 10⁻⁶ (15- to 40-fold higher than the induced hprt− frequency in the same treated animals). Sectored plaques were observed in both control and B[a]P groups but their frequency showed no relationship to dose (sectored frequency in all groups was approximately 20 × 10⁻⁶). To test whether persistent DNA adducts in the packaged lambda vector were contributing to the observed blue plaque frequency, purified λ-LIZ DNA was treated in vitro with B[a]P diol epoxide (BPDE), packaged, and plated on E. coli lawn cells. Treatment with BPDE did not produce significant increases in homogeneous blue plaques, suggesting that the majority of mutants obtained from B[a]P-treated BB mice occurred in vivo. These results indicate that B[a]P exposure produces many more mutations at the lacl transgene than at the endogenous hprt locus. © 1996 Wiley-Liss, Inc.     

Middle cerebral artery blood velocity during exercise with β‐1 adrenergic and unilateral stellate ganglion blockade in humans

A reduced ability to increase cardiac output (CO) during exercise limits blood flow by vasoconstriction even in active skeletal muscle. Such a flow limitation may also take place in the brain as an increase in the transcranial Doppler determined middle cerebral artery blood velocity (MCA V_mean) is attenuated during cycling with β‐1 adrenergic blockade and in patients with heart insufficiency. We studied whether sympathetic blockade at the level of the neck (0.1% lidocain; 8 mL; n=8) affects the attenuated exercise – MCA V_mean following cardio‐selective β‐1 adrenergic blockade (0.15 mg kg^?1 metoprolol i.v.) during cycling. Cardiac output determined by indocyanine green dye dilution, heart rate (HR), mean arterial pressure (MAP) and MCA V_mean were obtained during moderate intensity cycling before and after pharmacological intervention. During control cycling the right and left MCA V_mean increased to the same extent (11.4 ± 1.9 vs. 11.1 ± 1.9 cm s^?1). With the pharmacological intervention the exercise CO (10 ± 1 vs. 12 ± 1 L min^?1; n=5), HR (115 ± 4 vs. 134 ± 4 beats min^?1) and ΔMCA V_mean (8.7 ± 2.2 vs. 11.4 ± 1.9 cm s^?1) were reduced, and MAP was increased (100 ± 5 vs. 86 ± 2 mmHg; P < 0.05). However, sympathetic blockade at the level of the neck eliminated the β‐1 blockade induced attenuation in ΔMCA V_mean (10.2 ± 2.5 cm s^?1). These results indicate that a reduced ability to increase CO during exercise limits blood flow to a vital organ like the brain and that this flow limitation is likely to be by way of the sympathetic nervous system.     

A new T-lymphocyte cloning assay for detection of in vivo mutations in the human hypoxanthine-guanine phosphoribosyltransferase gene

The X-linked hypoxonthine-guanine phosphoribosyltransferase (hprt) gene is a target of analyses of in vivo mutation frequencies in circulating T-lymphocytes. We established a novel, accessory cell-free cloning method of T-lymphocytes with a hprt mutation by a combined use of recombinant interleukin-2, conditioned medium from activating T-lymphocytes and culture plates coated with anti-CD3 monoclonal antibody. Using the method, we examined mutation frequencies of the hprt gene in T-lymphocytes from six healthy individuals, nine patients with colon cancer including two patients from different families with hereditary nonpolyposis colon cancer and six cancer-free relatives of the patients. In six healthy individuals, the mean cloning efficiency and mutation frequency (MF) of the hprt gene in T-lymphocytes were 0.51 ± 0.28 and 9.4 ± 7.5 × 10⁻⁶, respectively. These data were similar to the reported values. The mean MFs in the nine colon cancer patients (10.6 ± 7.3 × 10⁻⁶) were not significantly different from those of the 12 cancer-free individuals (11.6 ± 9.4 × 10⁻⁶). The correlation between mutation frequencies and age of the individuals was significant regardless of the presence or absence of cancers. The single-strand conformation polymorphism analyses of nested RT-PCR products of hprt mRNA were done in 33 mutant clones from five members of a family of which MF values were high. All the analyzed mutant clones show a genetic aberration in the coding region of the hprt gene. At least 28 of 33 mutants were independent. Our method provides a new versatile tool for in vivo analysis for mutations of the hprt gene. Environ. Mol. Mutagen. 30:31–39, 1997 © 1997 Wiley-Liss, Inc.     

Altered basal and adenosine-mediated protein flux from coronary arterioles isolated from exercise-trained pigs

Solute flux per unit surface area and concentration gradient, (J_S/SΔC), was quantified in arterioles isolated from hearts of sedentary (SED) and exercise-trained (EX) female Yucatan Miniature Swine. Apparent permeability (P_S) was assessed from measures of J_S/SΔC for two proteins, α-lactalbumin (α-lact) and porcine serum albumin (PSA), under basal conditions and following 5 min suffusion with 10^?5M adenosine (ADO). Both proteins were labelled with the fluorescent dye tetramethyl rhodamine isothiocyanate. Basal P_s to α-lact differed with exercise training ((P^α-lact_s)_SED=5.2±1.8 (median±median absolute deviation (MAD), n=9 pigs) versus (P^α-lact_s)_EX=7.4±1.1×10^?7 cm s^?1, n=9, P<0.05). For the larger protein PSA, basal P_s did not change with training ((P^PSA_s)_SED=5.0±1.6, N=11 vs. (P^PSA_s)_EX=4.1±1.2×10^?7 cm s^?1, N=11). Suffusion of the arterioles (33±4 μm diameter, n=18 vessels) from SED hearts (n=14) with 10^?5M ADO decreased P^α-lact_s 15±8% relative to control and was without effect on P^PSA_s. By contrast, in arterioles (39±4 μm diameter, n=22 vessels) from EX hearts (n=14), ADO increased P^α-lact_s and P^PSA_s by 32 and 65% respectively, indicating that receptor-mediated changes in permeability were also sensitive to exercise training. These data demonstrate that, for coronary arterioles, permeability to macromolecules adapts to exercise training. The adaptive mechanisms may involve more than one structural component of the vessel wall as the changes in permeability were size-dependent.     

Water permeability of the mammalian cochlea: functional features of an aquaporin-facilitated water shunt at the perilymph–endolymph barrier

The cochlear duct epithelium (CDE) constitutes a tight barrier that effectively separates the inner ear fluids, endolymph and perilymph, thereby maintaining distinct ionic and osmotic gradients that are essential for auditory function. However, in vivo experiments have demonstrated that the CDE allows for rapid water exchange between fluid compartments. The molecular mechanism governing water permeation across the CDE remains elusive. We computationally determined the diffusional (P _D) and osmotic (P _f) water permeability coefficients for the mammalian CDE based on in silico simulations of cochlear water dynamics integrating previously derived in vivo experimental data on fluid flow with expression sites of molecular water channels (aquaporins, AQPs). The P _D of the entire CDE (P _D?=?8.18?×?10^?5 cm s^?1) and its individual partitions including Reissner's membrane (P _D?=?12.06?×?10^?5 cm s^?1) and the organ of Corti (P _D?=?10.2?×?10^?5 cm s^?1) were similar to other epithelia with AQP-facilitated water permeation. The P _f of the CDE (P _f?=?6.15?×?10^?4 cm s^?1) was also in the range of other epithelia while an exceptionally high P _f was determined for an epithelial subdomain of outer sulcus cells in the cochlear apex co-expressing AQP4 and AQP5 (OSCs; P _f?=?156.90?×?10^?3 cm s^?1). The P _f/P _D ratios of the CDE (P _f/P _D?=?7.52) and OSCs (P _f/P _D?=?242.02) indicate an aqueous pore-facilitated water exchange and reveal a high-transfer region or “water shunt” in the cochlear apex. This “water shunt” explains experimentally determined phenomena of endolymphatic longitudinal flow towards the cochlear apex. The water permeability coefficients of the CDE emphasise the physiological and pathophysiological relevance of water dynamics in the cochlea in particular for endolymphatic hydrops and Ménière's disease.     

Low total haemoglobin mass, blood volume and aerobic capacity in men with type 1 diabetes

Blood O₂ carrying capacity affects aerobic capacity (VO_2max). Patients with type 1 diabetes have a risk for anaemia along with renal impairment, and they often have low VO_2max. We investigated whether total haemoglobin mass (tHb-mass) and blood volume (BV) differ in men with type 1 diabetes (T1D, n = 12) presently without complications and in healthy men (CON, n = 23) (age-, anthropometry-, physical activity-matched), to seek an explanation for low VO_2max. We determined tHb-mass, BV, haemoglobin concentration ([Hb]), and VO_2max in T1D and CON. With similar (mean ± SD) [Hb] (144 vs. 145 g l^?1), T1D had lower tHb-mass (10.1 ± 1.4 vs. 11.0 ± 1.1 g kg^?1, P < 0.05), BV (76.8 ± 9.5 vs. 83.5 ± 8.3 ml kg^?1, P < 0.05) and VO_2max (35.4 ± 4.8 vs. 44.9 ± 7.5 ml kg^?1 min^?1, P < 0.001) than CON. VO_2max correlated with tHb-mass and BV both in T1D (r = 0.71, P < 0.01 and 0.67, P < 0.05, respectively) and CON (r = 0.54, P < 0.01 and 0.66, P < 0.001, respectively), but not with [Hb]. Linear regression slopes were shallower in T1D than CON both between VO_2max and tHb-mass (2.4 and 3.6 ml kg^?1 min^?1 vs. g kg^?1, respectively) and VO_2max and BV (0.3 and 0.6 ml kg^?1 min^?1 vs. g kg^?1, respectively), indicating that T1D were unable to reach similar VO_2max than CON at a given tHb-mass and BV. In conclusion, low tHb-mass and BV partly explained low VO_2max in T1D and may provide early and more sensitive markers of blood O₂ carrying capacity than [Hb] alone.     

Fibrinolytic markers and vasodilatory capacity following acute exercise among men of differing training status

We evaluated the effect of differing physical activity patterns on fibrinolysis and vasodilatory capacity using a cross-sectional design with 16 endurance-trained (ET) (mean ± SE) (28 ± 6 years), 14 resistance-trained (RT) (28 ± 7 years), and 10 untrained (UT) (26 ± 7 years) men. t-PA and PAI-1 activity and t-PA antigen were measured before and after a maximal treadmill test (VO_2peak). Vasodilatory capacity was assessed using strain-gauge plethysmography on the forearm following reactive hyperemia (RH) before and after the treadmill test. The ET group had a smaller body mass index (BMI) (22.8 ± 0.5 ET, 26.4 ± 0.4 RT, 25.1 ± 0.8 UT kg m⁻²) (P < 0.05) and a greater VO_2peak (57 ± 1 ET, 42 ± 2 RT, 45 ± 2 UT mL min⁻¹ kg⁻¹) (P < 0.05). Peak vasodilatory capacity (29.7 ± 2 ET, 32.0 ± 2 RT, 27.4 ± 2 UT mL min⁻¹ 100 mL of tissue) was similar between groups before and after exercise. Area under the curve for forearm blood flow was greater following acute exercise (212 vs. 122, P < 0.05), again with no differences between groups. t-PA activity and antigen increased following maximal exercise in all groups (P < 0.0001), with no group differences. PAI-1 activity decreased the least in RT after exercise (70% decrease vs. 86% ET and 82% UT; P < 0.05). The change in t-PA activity with exercise was not related to exercise-induced change in overall vasodilatory capacity. These findings demonstrate that in healthy young men different physical activity patterns do not appear to impact the exercise-induced changes in fibrinolysis or vasodilatory capacity.     

Quantitative MRI in murine radiation‐induced rectocolitis: comparison with histopathological inflammation score

Murine radiation‐induced rectocolitis is considered to be a relevant animal model of gastrointestinal inflammation. The purpose of our study was to compare quantitative MRI and histopathological features in this gastrointestinal inflammation model. Radiation rectocolitis was induced by localized single‐dose radiation (27 Gy) in Sprague‐Dawley rats. T₂‐weighted, T₁‐weighted and diffusion‐weighted MRI was performed at 7 T in 16 rats between 2 and 4 weeks after irradiation and in 10 control rats. Rats were sacrificed and the histopathological inflammation score of the colorectal samples was assessed. The irradiated rats showed significant increase in colorectal wall thickness (2.1 ± 0.3 mm versus 0.8 ± 0.3 mm in control rats, P < 0.0001), normalized T₂ signal intensity (4 ± 0.8 versus 2 ± 0.4 AU, P < 0.0001), normalized T₁ signal intensity (1.4 ± 0.1 versus 1.1 ± 0.2 AU, P = 0.0009) and apparent and pure diffusion coefficients (ADC and D) (2.06 × 10^?3 ± 0.34 versus 1.51 × 10^?3 ± 0.23 mm²/s, P = 0.0004, and 1.97 × 10^?3 ± 0.43 mm²/s versus 1.48 × 10^?3 ± 0.29 mm²/s, P = 0.008, respectively). Colorectal wall thickness (r = 0.84, P < 0.0001), normalized T₂ signal intensity (r = 0.85, P < 0.0001) and ADC (r = 0.80, P < 0.0001) were strongly correlated with the histopathological inflammation score, whereas normalized T₁ signal intensity and D were moderately correlated (r = 0.64, P = 0.0006, and r = 0.65, P = 0.0003, respectively). High‐field MRI features of single‐dose radiation‐induced rectocolitis in rats differ significantly from those of control rats. Quantitative MRI characteristics, especially wall thickness, normalized T₂ signal intensity, ADC and D, are potential markers of the histopathological inflammation score.     

Lowered microvascular vessel wall oxygen consumption augments tissue pO<Subscript>2</Subscript> during PgE1-induced vasodilation

Continuous infusion of intravenous prostaglandin E1 (PgE1, 2.5 μg/kg/min) was used to determine how vasodilation affects oxygen consumption of the microvascular wall and tissue pO₂ in the hamster window chamber model. While systemic measurements (mean arterial pressure and heart rate) and central blood gas measurements were not affected, PgE1 treatment caused arteriolar (64.6 ± 25.1 μm) and venular diameter (71.9 ± 29.5 μm) to rise to 1.15 ± 0.21 and 1.06 ± 0.19, respectively, relative to baseline. Arteriolar (3.2 × 10⁻² ± 4.3 × 10⁻² nl/s) and venular flow (7.8 × 10⁻³ ± 1.1 × 10⁻²/s) increased to 1.65 ± 0.93 and 1.32 ± 0.72 relative to baseline. Interstitial tissue pO₂ was increased significantly from baseline (21 ± 8 to 28 ± 7 mmHg; P < 0.001). The arteriolar vessel wall gradient, a measure of oxygen consumption by the microvascular wall decreased from 20 ± 6 to 16 ± 3 mmHg (P < 0.001). The arteriolar vessel wall gradient, a measure of oxygen consumption by the vascular wall, decreased from 20 ± 6 to 16 ± 3 mmHg (P < 0.001). This reduction reflects a 20% decrease in oxygen consumption by the vessel wall and up to 50% when cylindrical geometry is considered. The venular vessel wall gradient decreased from 12 ± 4 to 9 ± 4 mmHg (P < 0.001). Thus PgE1-mediated vasodilation has a positive microvascular effect: enhancement of tissue perfusion by increasing flow and then augmentation of tissue oxygenation by reducing oxygen consumption by the microvascular wall.     

A Genome‐Wide Search for Type 2 Diabetes Susceptibility Genes in an Extended Arab Family

Twenty percent of people aged 20 to 79 have type 2 diabetes (T2D) in the United Arab Emirates (UAE). Genome‐wide association studies (GWAS) to identify genes for T2D have not been reported for Arab countries. We performed a discovery GWAS in an extended UAE family (N = 178; 66 diabetic; 112 healthy) genotyped on the Illumina Human 660 Quad Beadchip, with independent replication of top hits in 116 cases and 199 controls. Power to achieve genome‐wide significance (commonly P = 5 × 10^?8) was therefore limited. Nevertheless, transmission disequilibrium testing in FBAT identified top hits at Chromosome 4p12‐p13 (KCTD8: rs4407541, P = 9.70 × 10^?6; GABRB1: rs10517178/rs1372491, P = 4.19 × 10^?6) and 14q13 (PRKD1: rs10144903, 3.92 × 10^?6), supported by analysis using a linear mixed model approximation in GenABEL (4p12‐p13 GABRG1/GABRA2: rs7662743, P_adj‐agesex = 2.06 × 10^?5; KCTD8: rs4407541, P_adj‐agesex = 1.42 × 10^?4; GABRB1: rs10517178/rs1372491, P_adj‐agesex = 0.027; 14q13 PRKD1: rs10144903, P_adj‐agesex = 6.95 × 10^?5). SNPs across GABRG1/GABRA2 did not replicate, whereas more proximal SNPs rs7679715 (P_adj‐agesex = 0.030) and rs2055942 (P_adj‐agesex = 0.022) at COX7B2/GABRA4 did, in addition to a trend distally at KCTD8 (rs4695718: P_adj‐agesex = 0.096). Modelling of discovery and replication data support independent signals at GABRA4 (rs2055942: P_{adj‐agesex‐combined} = 3 × 10^?4) and at KCTD8 (rs4695718: P_{adj‐agesex‐combined} = 2 × 10^?4). Replication was observed for PRKD1 rs1953722 (proxy for rs10144903; P_adj‐agesex = 0.031; P_{adj‐agesex‐combined} = 2 × 10^?4). These genes may provide important functional leads in understanding disease pathogenesis in this population.     

Serial effects of high-resistance and prolonged endurance training on Na+–K+ pump concentration and enzymatic activities in human vastus lateralis

The purpose of this study was to compare two contrasting training models, namely high-resistance training and prolonged submaximal training on the expression of Na⁺–K+ ATPase and changes in the potential of pathways involved in energy production in human vastus lateralis. The high-resistance training group (VO _2peak = 45.3 ± 1.9 mL kg^?1 min^?1, mean ± SE, n = 9) performed three sets of six to eight repetitions maximal, each of squats, leg presses and leg extensions, three times per week for 12 weeks, while the prolonged submaximal training group (VO _2peak = 44.4 ± 6.6 mL kg^?1 min^?1, n = 7) cycled 5–6 times per week for 2 h day^?1 at 68% VO _2peak for 11 weeks. In the HRT group, Na⁺–K⁺ ATPase (pmol g^?1 wet wt), measured with the ³H-ouabain binding technique, showed no change from 0 (289 ± 22) to 4 weeks (283 ± 15), increased (P < 0.05) by 16% at 7 weeks and remained stable until 12 weeks (319 ± 19). For prolonged submaximal training, a 22% increase (P < 0.05) was observed from 0 (278 ± 31) until 3 weeks (339 ± 29) with no further changes observed at either 9 weeks (345 ± 25) or 11 weeks (359 ± 34). In contrast to high-resistance training, where a 15% increase (P < 0.05) was observed, only in the maximal activity of phosphorylase, prolonged submaximal training resulted in increases in malate dehydrogenase, β-hydroxyl-CoA dehydrogenase, hexokinase and phosphofructokinase. In contrast to high-resistance training which failed to result in an increase in VO _2peak, prolonged submaximal training increased VO _2peak by ≈15%. Only for prolonged exercise training was a relationship observed for VO _2peak and Na⁺–K⁺-ATPase (r = 0.59; P < 0.05). Correlations between VO _2peak and mitochondrial enzyme activities were not significant (P > 0.05) for either training programme. It is concluded that although both training programmes stimulate an up-regulation in Na⁺–K⁺ ATPase concentration, only the prolonged submaximal training programme enhances the potential for β-oxidation, oxidative phosphorylation and glucose phosphorylation.     

Enhanced cerebral CO2 reactivity during strenuous exercise in man

Light and moderate exercise elevates the regional cerebral blood flow by ~20% as determined by ultrasound Doppler sonography (middle cerebral artery mean flow velocity; MCA V _mean). However, strenuous exercise, especially in the heat, appears to reduce MCA V _mean more than can be accounted for by the reduction in the arterial CO₂ tension (P _aCO₂). This study evaluated whether the apparently large reduction in MCA V _mean at the end of exhaustive exercise relates to an enhanced cerebrovascular CO₂ reactivity. The CO₂ reactivity was evaluated in six young healthy male subjects by the administration of CO₂ as well as by voluntary hypo- and hyperventilation at rest and during exercise with and without hyperthermia. At rest, P _aCO₂ was 5.1±0.2 kPa (mean ± SEM) and MCA V _mean 50.7±3.8 cm s⁻¹ and the relationship between MCA V _mean and P _aCO₂ was linear (double-log slope 1.1±0.1). However, the relationship became curvilinear during exercise (slope 1.8±0.1; P<0.01 vs. rest) and during exercise with hyperthermia (slope 2.3±0.3; P<0.05 vs. control exercise). Accordingly, the cerebral CO₂ reactivity increased from 30.5±2.7% kPa⁻¹ at rest to 61.4±10.1% kPa⁻¹ during exercise with hyperthermia (P<0.05). At exhaustion P _aCO₂ decreased 1.1±0.2 kPa during exercise with hyperthermia, which, with the determined cerebral CO₂ reactivity, accounted for the 28±10% decrease in MCA V _mean. The results suggest that during exercise changes in cerebral blood flow are dominated by the arterial carbon dioxide tension.     

Human Fetal/Neonatal Suppressor Activity: Relation Between OKT Phenotypes and Sensitivity to Prostaglandin E2 in Maternal and Neonatal Lymphocytes

ABSTRACT: T lymphocytes from human fetuses and newborns strongly and spontaneously suppress various adult cell functions (i.e. T-cell proliferation, B-cell differentiation, and Ig synthesis). The precise phenotype of the suppressor cell is controversial. In this investigation we use cord T-cell subsets negatively selected by the panning technique or by complement-mediated lysis using the monoclonal antibodies OKT4 and OKT8. Cord T cells deprived of the OKT4⁺ subpopulation exerted only a marginal suppressor activity (12 ± 7 as compared to 73 ± 4% of unfractionated T cells) on the proliferation of maternal cells in our PHA-stimulated co-culture assay using sex chromosomes as markers for dividing cord (male) and maternal cells. The suppressive effect was direct, i.e. not mediated by induction of maternal OKT8⁺ suppressor effector cells. Cord and maternal T-cell subsets were also tested for their sensitivity to exogenous prostaglandin E₂ (PGE₂) at doses varying between 1.4 × 10^?5 and 1.4 × 10^?9 M. Both maternal OKT4^? and OKT8^? T-cell subsets were highly sensitive to suppression by PGE₂. In contrast, cord OKT8^? T cells were essentially nonsensitive at all doses of PGE₂ used, whereas cord OKT4^? T cells were significantly suppressed at four out of five concentrations tested (1.4 × 10^?6 through 1.4 × 10^?9). Our results suggest a direct correlation between the phenotypes of the cord-suppressor and maternal-target T cells and their sensitivity to PGE₂.     

Affinity of the interaction between Fcgamma receptor type III (FcγRIII) and monomeric human IgG subclasses. Role of FcγRIII glycosylation

Binding of the Fc region of IgG antibodies to low affinity Fcγ receptors (FcγR) triggers important effector functions in the immune system. The type IIIb FcγR (FcγRIIIb or CD16) is a heavily glycosylated protein anchored to the membrane of neutrophils by a glycosylphosphatidylinositol link. This receptor contributes to cell activation by IgG immune complexes. To better understand the nature of the ligand-receptor association, we have studied the affinity and kinetics of the interaction between human IgG subclasses and two soluble forms of FcγRIIIb (sFcγRIIIb or sCD16) corresponding to the 188 N-terminal amino acids of the extracellular region of the receptor, a glycosylated one made in eucaryotic cells (euc.sCD16) and a non-glycosylated one (proc.sCD16) made in Escherichia coli. Experiments using a BIAcore^TM instrument, to measure protein binding in real time, showed that monomeric human IgG1 and IgG3, but not IgG2, IgG4, IgA and divalent antigen-binding fragments (F(ab′)₂) of IgG1, bound to immobilized euc.sCD16 with an affinity constant (K_A) of 1.3 ± 0.6 × 10⁶ M^?1 and 2.6 ± 0.4 × 10⁵ M^?1, respectively. The affinity constant of proc.sCD16 for human IgG1 was in the same range (1.1 ± 0.2 × 10⁶ M^?1), whereas that for human IgG3 was twofold higher (4.2 ± 0.4 × 10⁵ M^?1). The specificity of the non-glycosylated receptor for human IgG subclasses bound to Sepharose was IgG1 > IgG3 ? IgG4 ? IgG2. Thus, the extracellular polypeptide of FcγRIIIb dictates the interaction of the receptor with IgG subclasses although glycosylation plays an inhibitory role in the interaction with human IgG3.     

The influence of PaO2, pH and SaO2 on maximal oxygen uptake

Influence of arterial oxygen pressure (P_aO₂) and pH on haemoglobin saturation (S_aO₂) and in turn on O₂ uptake (VO ₂) was evaluated during ergometer rowing (156, 276 and 376 W; VO _2max, 5.0 L min^?1; n = 11). During low intensity exercise, neither pH nor S_aO₂ were affected significantly. In response to the higher work intensities, ventilations (V_E) of 129 ± 10 and 155 ± 8 L min^?1 enhanced the end tidal PO₂ (P_ETO₂) to the same extent (117 ± 2 mmHg), but P_aO₂ became reduced (from 102 ± 2 to 78 ± 2 and 81 ± 3 mmHg, respectively). As pH decreased during maximal exercise (7.14 ± 0.02 vs. 7.30 ± 0.02), S_aO₂ also became lower (92.9 ± 0.7 vs. 95.1 ± 0.1%) and arterial O₂ content (C_aO₂) was 202 ± 3 mL L^?1. An inspired O₂ fraction (F_IO₂) of 0.30 (n = 8) did not affect V_E, but increased P_ETO₂ and P_aO₂ to 175 ± 4 and 164 ± 5 mmHg and the P_ETO₂–P_aO₂ difference was reduced (21 ± 4 vs. 36 ± 4 mmHg). pH did not change when compared with normoxia and S_aO₂ remained within 1% of the level at rest in hyperoxia (99 ± 0.1%). Thus, C_aO₂ and VO _2max increased to 212 ± 3 mL L^?1 and 5.7 ± 0.2 L min^?1, respectively. The reduced P_aO₂ became of importance for S_aO₂ when a low pH inhibited the affinity of O₂ to haemoglobin. An increased F_IO₂ reduced the gradient over the alveolar-arterial membrane, maintained haemoglobin saturation despite the reduction in pH and resulted in increases of the arterial oxygen content and uptake.     

Specificity of training velocity and training load on gains in isokinetic knee joint strength

The present study investigated the effects of three different strength training regimes on the isokinetic strength profile of the knee extensors (quadriceps, Q) and flexors (hamstrings, H) and if increases in isokinetic strength were accompanied by an enhanced performance during a more complex leg movement, the soccer kick. Twenty-two elite soccer players performed 12 weeks of strength training (three times per week) at either high resistance (HR group: 4 sets, 8 reps, 8RM loading), low resistance (LR group: 4 sets, 24 reps, 24RM loading), loaded kicking movements (LK group: 4 sets, 16 reps, 16RM loading) while one group served as controls (CO group). Isokinetic concentric and eccentric moment of force was obtained (KinCom) as peak moment (M_peak) and moment at 50° knee flexion (M₅₀) at angular velocities of 30, 120, 240° s^-1. Isokinetic knee joint strength was unchanged in groups LR, LK, CO. However, after the HR strength training, concentric M_peak (±SD) increased (P<0.01) at 30° s^-1 (Q, 258±37 to 297±57 Nm; H, 122±22 to 140±21 Nm). Furthermore, eccentric M_peak increased at 30, 120 and 240° s^-1 (Q, 274±60 to 345±57 Nm (P<0.01), 291±56 to 309±49 Nm and 275±43 to 293±36 Nm (P<0.05), respectively; H, 143±32 to 158±25 Nm, 152±39 to 169±31 Nm and 148±27 to 163±19 Nm (P<0.05)). Corresponding increases (P<0.05) were observed for M₅₀. The H/Q ratio calculated as eccentric hamstring strength divided by concentric quadriceps strength (H_ecc/Q_con, representative for knee extension) at 240° s^-1 increased (P<0.05) from 107 to 118% (based on M_peak) and from 90 to 105% (M₅₀). Kicking performance estimated by maximal ball flight velocity was unaffected by any of the strength training regimes investigated. In conclusion, only heavy-resistance strength training induced increases in isokinetic muscle strength in the absence of learning effects. Concentric strength gains were observed at the actual velocity of training, while eccentric strength gains were found over the entire range of velocities examined. The capacity of the hamstring muscles for providing stability to the knee joint during fast extension was augmented as a result of the heavy-resistance strength training. Strength training should be integrated with other types of training involving the actual movement pattern in order to increase the performance within more complex movement patterns.