Na+-K+-ATPase in rat skeletal muscle: content, isoform, and activity characteristics.

The purpose of this study was to investigate the hypothesis that muscle Na+-K+-ATPase activity is directly related to Na+-K+-ATPase content and the content of the alpha2-catalytic isoform in muscles of different fiber-type composition. To investigate this hypothesis, tissue was sampled from soleus (Sol), red gastrocnemius (RG), white gastrocnemius (WG), and extensor digitorum longus (EDL) muscles at rest from 38 male Wistar rats weighing 413 +/- 6.0 g (mean +/- SE). Na+-K+-ATPase activity was determined in homogenates (Hom) and isolated crude membranes (CM) by the regenerating ouabain-inhibitable hydrolytic activity assay (ATPase) and the 3-O-methylfluorescein K+-stimulated phosphatase (3-O-MFPase) assay in vitro. In addition, Na+-K+-ATPase content (Bmax) and the distribution of alpha1-, alpha2-, beta1-, and beta2-isoforms were determined by [3H]ouabain binding and Western blot, respectively. For the ATPase assay, differences (P < 0.05) in enzyme activity between muscles were observed in Hom (EDL > WG) and in CM (Sol > EDL = WG). For the 3-O-MFPase assay, differences (P < 0.05) were also found for Hom (Sol > RG = EDL > WG) and CM (Sol = WG > RG). For Bmax, differences in the order of RG = EDL > Sol = WG (P < 0.05) were observed. Isoform distribution was similar between Hom and CM and indicated in CM, a greater density (P < 0.05) of alpha1 in Sol than WG and EDL (P < 0.05), but more equal distribution of alpha2 between muscles. The beta1 was greater (P < 0.05) in Sol and RG, and the beta2 was greater in EDL and WG (P < 0.05). Over all muscles, the correlation (r) between Hom 3-O-MFPase and Bmax was 0.45 (P < 0.05) and between Hom alpha2 and Bmax, 0.59 (P < 0.05). The alpha1 distribution correlated to Hom 3-O-MFPase (r = 0.79, P < 0.05) CM ATPase (r = 0.69, P < 0.005) and CM 3-O-MFPase activity (r = 0.32, P < 0.05). The alpha2 distribution was not correlated with any of the Na+-K+-ATPase activity measurements. The results indicate generally poor relationships between activity and total pump content and alpha2 isoform content of the Na+-K+-ATPase. Several factors, including the type of preparation and the type of assay, appear important in this regard.     

Relative stability of human respiration during progressive hypoxia

We have systematically studied the relationship between the relative stability (R) of respiration and the loop gain (LG) of the CO2 control system in 15 healthy awake adult males during progressive hypoxia. R was measured by the ventilatory oscillations after brief (less than 10 s) CO2 challenges. Control theory suggests that such oscillations are completely governed by LG. A significant positive correlation was found between R and LG (r = 0.74, P less than 0.01, n = 85). A minimal mathematical model of respiratory control was used to predict R as a function of LG. Serial correlation analysis (r = 0.09, P greater than 0.1) of the residuals indicated statistical agreement between predictions and observations. The mean residual (0.011) was not significantly different from zero (P greater than 0.1). Also, as the model predicted, sustained periodic breathing (PB) occurred whenever the estimated LG was greater than unity. The mean LG breathing room air was 0.51 and for the 13 epochs of PB was 1.17 (range 0.71-1.65). It is concluded that PB is a quantitative extension of the relative stability continuum and corresponds to unstable operation of the CO2 control system. Furthermore, relative stability can be quantitatively predicted for each subject by a minimal mathematical model.     

Serum transferrin as a marker of bone growth in boys: correlation with serum alkaline phosphatase activity, plasma insulin-like growth factor 1 and rate of growth in height

Transferrin (TF) has a growth promoting activity in cell culture. The aim of this work was to study possible relationships between serum TF, alkaline phosphatase activity (ALP), plasma insulin-like growth factor 1 (IGF-1) levels and rate of height increase in boys. 149 boys aged 13-15 yrs were studied. TF levels were measured using turbidimetric method. The serum levels of ALP could be used as a biochemical marker for bone formation. Significant correlation was found between serum TF levels and ALP levels (r = 0.31, P less than 0.0005). The TF levels are higher in iron-deficiency anemia. The hemoglobin (Hb) and serum ferritin were measured in all boys. Thirty-one of 149 boys had no iron-deficiency anemia (Hb 14.0 g/dl and serum ferritin 23 ng/ml). The rate of growth in height was estimated over a 5 month period. In these boys, the rate of growth in height was significantly correlated with serum TF levels (r = 0.37; P less than 0.05). A significant correlation was found between serum TF levels and plasma IGF-1 levels (r = 0.45; P less than 0.05). These data indicate that serum TF levels may be a marker of skeletal growth in normal boys.     

Blood selenium and glutathione peroxidase activity of populations in New Zealand, Oregon, and South Dakota

The relationship of whole blood selenium (Se) to glutathione peroxidase (GPX) activity was examined for individuals in New Zealand, Oregon, and South Dakota who represented, respectively, populations with exposure to low, medium, and high amounts of Se. The mean (respective) blood Se levels were 60, 200, and 400 ng/ml. Intergroup differences in blood Se levels were highly significant (P less than 0.001). GPX assays were performed using two variations of an enzyme-coupled procedure to assess the equivalence of the two methods. Despite a fourfold difference in absolute activities measured by these methods, the GPX activities were highly correlated (r = .86) between procedures. Average blood GPX activity was significantly lower (P less than 0.001) for the New Zealand group compared with the other two groups, but there was no difference in GPX activities between the Oregon and South Dakota groups. Linear regression of GPX vs. Se values within each group indicated a significant correlation of these parameters only in the New Zealand group (r = .46, P less than 0.01). Comparison of these parameters for combined data from all three groups also showed a significant positive correlation (r = .60, P less than 0.001). A saturation model (In GPX = k1 + k2 (Se)-1)) fits the combined data better (r = .80, P less than 0.01) than does direct comparison of the two parameters. These results suggest that GPX activity is an appropriate indicator of human Se status only in populations with below normal exposure to Se, as activity of this enzyme is saturated at relatively low levels.     

Sex differences in abdominal, gluteal, and thigh LPL activity

Lipoprotein lipase (LPL) activity is necessary for adipocytes to take up triglycerides from the circulation, and regional differences in LPL activity could help determine regional fat storage. LPL activity has been reported to increase as a function of fat cell size, but this issue has not been extensively evaluated in different depots comparing sexes. Our objective was to determine whether sex alters the relationship between LPL activity and fat cell size. Subcutaneous adipose tissue biopsies were taken from the abdomen and thigh after an overnight fast and 1 h after a meal in 65 females (BMI 25.4 +/- 0.8, means +/- SE) and 41 males (BMI 23.7 +/- 0.3); gluteal adipose samples were obtained in 47 of the females and 27 of the males. Fat cell size was greater in females than males in thigh (P < 0.005) and gluteal (P < 0.05) regions but not in the abdomen. There was a relationship between fasting LPL activity/fat cell and fat cell size in females (abdomen r2 = 0.52, P < 0.0001; gluteal r2 = 0.23, P < 0.005; thigh r2 = 0.19, P < 0.005). In males, this relationship was seen only in the abdomen (r2 = 0.51, P < 0.0001) and thigh (r2 = 0.17, P < 0.05). Males and females had a significantly different relationship in the thigh only in the fasted state. Similar results were found in the fed state, although the strength of the relationship decreased in the abdominal regions for females only. This suggests fundamental differences in the regulation of triglyceride uptake between males and females and adipose regions.     

Effects of exercise and conditioning on clotting and fibrinolytic activity in men

Sixty healthy men in three physical fitness categories (sedentary, on no organized fitness program; joggers, running 5-15 miles/wk; and marathoners, running greater than 50 miles/wk) were evaluated for changes in blood clotting and fibrinolytic activity before and after maximum exercise on a treadmill according to the Bruce protocol. The rate of blood clotting, as measured by prothrombin times, partial thromboplastin times and thrombin times, was accelerated by exercise (all P less than 0.005). The ability of euglobulin clots and plasma clots to lyse incorporated 125I-fibrin, termed 125I-euglobulin clot lysis (IEL) and 125I-plasma clot lysis (IPCL), were used as indexes of fibrinolytic activity. Marathoners had greater increases in fibrinolytic activity with exercise (76% compared with 63% for joggers and 55% for sedentary subjects by IEL; 427% compared with 418% for joggers and 309% for sedentary subjects by IPCL; all P less than 0.05). Fibrin degradation products increased with exercise (P less than 0.005 for the total group of 60 subjects). The absolute concentrations of alpha 2-plasmin inhibitor, alpha 2-macroglobulin, and antithrombin III increased with exercise (all P less than 0.005), but when concentrations were corrected for acute shifts of plasma water during exercise, the quantity of these inhibitors actually decreased (all P less than 0.005). The changes in clotting assays with exercise were not significantly correlated with changes in whole blood lactate, blood pyruvate, or rectal temperatures. Fibrinolytic assays before and after exercise correlated poorly to moderately with blood lactates (IEL: r = 0.441 and r = 0.425, respectively; IPCL: r = 0.294 and r = 0.544, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Kinetic model for carbon partitioning in Solanum tuberosum tubers stored at 2 degrees C and the mechanism for low temperature stress-induced accumulation of reducing sugars

Exposure to low but nonfreezing temperatures induces the breakdown of starch and the accumulation of sucrose, glucose and fructose in potato tubers, a complex phenomenon known as low-temperature sweetening (LTS). A kinetic model for the degradation of starch to sucrose, fructose, glucose, hexose phosphates and carbon dioxide in 2 degrees C-stored mature Solanum tuberosum cv. Norchip (LTS-sensitive) and Solanum tuberosum seedlling ND860-2 (LTS-tolerant) tubers is presented in this work. Analysis of sugar accumulation data in tubers grown in 1993 and 1994 showed no significant differences in the rates of conversion of starch to hexose phosphates and hexose phosphates to sucrose for both cultivars (P > 0.05). The rate constant corresponding to invertase activity was 2.3 day(-1) for Norchip tubers and 1.1 day(-1) for ND860-2 tubers grown in 1993 (P < or = 0.05); however, no significant differences were observed in invertase activity for 1994-grown tubers (P > 0.05). The accumulation of the reducing sugars fructose and glucose was found to be dependent on the relative difference in rate constants corresponding to invertase activity and glycolytic/respiratory capacity. This difference was 3-4 fold greater for Norchip in 1993, and 4-6 fold greater for Norchip in 1994, than for ND860-2 (P < or = 0.05). Results from the analysis also suggest that the amount of available starch for degradation was greater in Norchip tubers than ND860-2 tubers (P < or = 0.05). Our analysis suggests that tubers with decreased invertase activity coupled to increased glycolytic/respiratory capacity should be more tolerant to low-temperature stress.     

Significant correlations between atmospheric spectra according to Baumer and the in vitro incorporation of [3H]thymidine into the nuclear DNA of C6-glioma cells

Significant correlations between certain spectra of atmospherics (spherics) according to Baumer (a.t.B), i.e. naturally occurring electro-magnetic impulses in the range of 4-50 kHz, and several diseases or biological parameters have been published earlier. Now we show that there exists a highly significant negative correlation (r = -0.61, P greater than 0.004) between the occurrence of 28 kHz impulses (a.t.B.) and the in vitro incorporation of thymidine into the nuclear DNA of C6-glioma cells. The positive correlation with the 10 kHz impulses (a.t.B) (r = 0.39), however, is statistically not significant (P greater than 0.055).     

Heterozygotes for cystic fibrosis: models for study of airway and autonomic reactivity

Airway reactivity to cold air and methacholine, alpha-adrenergic and cholinergic reactivity measured as pupillary responses to phenylephrine and carbachol, respectively, and beta-adrenergic reactivity assessed by lymphocyte adenosine 3',5'-cyclic monophosphate (cAMP) response to isoproterenol were compared in 108 parents of patients with cystic fibrosis (CF) and 133 healthy adult controls. No differences were found between CF parents and controls in airway response to cold air or methacholine or in lymphocyte cAMP response to isoproterenol. Significant differences were found, however, in the response of the pupils to both phenylephrine and carbachol. Heterozygotes for CF have more reactive pupils; i.e., they require smaller doses of agonist for a 10% change in pupil size. In control subjects, the response of the pupils to phenylephrine and carbachol is highly correlated (r = 0.45, P less than 0.001), whereas in CF heterozygotes, the correlation is not significantly different from zero (r = -0.02). In controls, the pupil response to carbachol has a significant negative correlation with cold air response (r = 0.39, P less than 0.05), indicating that those whose pupils were most sensitive to carbachol had the greatest airway reactivity to cold air, but in CF heterozygotes the correlation is not significant (r = 0.10). A significant correlation exists between lymphocyte cAMP response and airway cold air response in CF heterozygotes (r = -0.32, P less than 0.05) (those whose beta-adrenergic responsiveness is low have greater airway reactivity), but not in controls. The CF parents with the most reactive airways tend to have lower beta-adrenergic responses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Progesterone, 17-OH-progesterone, androstenedione and testosterone plasma levels in spermatic venous blood of normal men and varicocele patients

Progesterone (P), 17-OH-progesterone (17-OH-P), Androstenedione (delta 4) and testosterone (T) plasma levels were measured in spermatic venous blood of twenty-nine varicocele patients (V) and in twelve normal subjects (N). Our data reveal a significant decrease of the mean testosterone in the spermatic blood of varicocele patients with respect to normal controls: (N = 1708.7 +/- 223.8 (SEM) nmol/l, n = 10. V = 1190.9 +/- 101.1 (SEM) nmol/l, n = 29. P less than 0.03). An inverse correlation has been observed between the age of varicocele patients and 17-OH-P (n = 29. y = -33.38x + 1384.70, r = -0.59, P less than 0.01) and delta 4 values (n = 23, y = -1.62x + 85.65, r = -0.49, P less than 0.05). The 17-OH-P/delta 4 ratio appears significantly augmented in varicocele patients with respect to normal controls (n = 4.80 +/- 0.86 (SEM), n = 12. V = 9.65 +/- 1.21 (SEM), n = 23.0.02 greater than P greater than 0.01). This indicates a deficiency in varicocele patients of 17-20 lyase activity. The positive correlation between the P/17-OH-P ratio and age of varicocele patients (n = 28, y = 0.007 x -0.090, r = 0.45, P less than 0.03) suggests a progressive impairment of 17-alpha-hydroxylase in such patients as they grow relatively older. These data demonstrated that the reduced spermatic levels of testosterone in varicoceles are due to the enzymatic impairment of testosterone biosynthesis, concerning firstly 17-20 lyase activity and secondly 17-alpha-hydroxylase activity. The latter enzymatic impairment is age related as is seen from the significant increase of the P/17-OH-P ratio in older patients.     

Effect of simultaneous variation of weight, density, temperature and O2 concentration on rainbow trout (Oncorhynchus mykiss) body composition.

The simultaneous effect of weight, initial density (kg/m3, temperature and O2 concentration on rainbow trout body composition (fat, protein, moisture and ash) has been studied. In 3 successive experimental phases fish were kept in different lots of varying initial weight (178-372 g), initial density (7.2-38.8 kg/m3) and temperature (15-20 degrees C). Simple correlations were statistically significant for weight vs fat (r = 0.56; P less than 0.001) and moisture (r = -0.57; P less than 0.001); temperature vs fat (r = 0.73; P less than 0.001) moisture (r = -0.73; P less than 0.001) and ash (r = -0.26; P less than 0.02); and O2 concentration vs fat (r = 0.22; P less than 0.05). Multivariant equations for the different compounds were obtained. Only fat and moisture percentages showed significant differences (rm = 0.75; P less than 0.00005); an inverse relation existing between them (r = -0.94; P less than 0.001). Temperature is the factor which has the strongest influence on fat and moisture when it varies simultaneously with weight, initial density and O2 concentration, which is shown by its equation coefficients (P less than 0.00005).     

Plasma accumulation of hypoxanthine, uric acid and creatine kinase following exhausting runs of differing durations in man

During exhausting exercise adenylate kinase in the muscle cells is activated and a degradation of adenosine 5'-diphosphate occurs. Consequently, degradation products of adenosine 5'-monophosphate including hypoxanthine and uric acid, accumulate in plasma. The aim of this study was to compare the concentration changes of hypoxanthine and uric acid in plasma following running of varying duration and intensity. In addition, plasma creatine kinase activity was measured to assess the possible relationship between metabolic stress and protein release. Four groups of competitive male runners ran 100 m (n = 7), 800 m (n = 11), 5000 m (n = 7) and 42,000 m (n = 7), respectively, at an exhausting pace. Subsequent to the 100 m event (mean running time 11 s) plasma concentrations of hypoxanthine and uric acid increased by 364% and 36% respectively (P less than 0.05), indicating a very high rate of adenine nucleotide degradation during the event. Following the 800-m event (mean running time 125 s), hypoxanthine and uric acid concentrations had increased by 1598% and 66%, respectively (P less than 0.05). Both the events of longer duration, 5000 m and 42,000 m, also caused a significant increase in plasma concentration of hypoxanthine (742% and 237% respectively, P less than 0.05) and plasma uric acid (54% and 34% respectively, P less than 0.05). Plasma activities of creatine kinase were significantly increased at 24 h only following the 5000 m and 42,000 m events (64% and 1186% respectively, P less than 0.05). Changes in plasma creatine kinase activity showed no correlation with changes in plasma concentration of either hypoxanthine or uric acid for the 5000 m and 42,000 m events (r = 0.00-0.45, P greater than 0.05).     

Characterization and Partial Purification of AIM: A Plasma Protein That Induces Rat Cerebral Type 2 Astroglia from Bipotential Glial Progenitors

Studies on glial cultures have demonstrated that fetal bovine serum contains a factor that induces bipotential glial precursors known as oligodendrocyte-type 2 astrocyte (O-2A) progenitors to become type 2 astroglia rather than oligodendroglia. The goal of this research project was to characterize and purify this factor, which we refer to as the astroglia-inducing molecule (AIM). Using cultures enriched in O-2A progenitors, we determined that AIM is present in human and bovine sera and that fetal bovine serum qualified as the best serum for purifying AIM. AIM is heat and trypsin labile and may be a plasma glycoprotein. A 240-fold enriched AIM preparation was produced by applying an ammonium sulfate precipitate of fetal bovine serum to heparin and then lentil lectin-agarose, followed by gel filtration chromatography. In crude preparations, AIM activity migrated at 50 kDa by gel filtration. With enrichment, activity was seen at several molecular masses, all of which were approximate multiples of 50 kDa. Treatment with 6 M guanidine hydrochloride generated an AIM with a molecular mass between 12 and 18 kDa, a result suggesting that AIM aggregates. On a preparative isoelectric focusing gel, AIM activity most frequently migrated between pH values of 3 and 4; however, proteins with isoelectric points of greater than 9 or at 6 also had activity in several experiments. These data suggest that either multiple AIMs exist or that a single AIM exists that associates with other proteins. Immunofluorescence for ganglioside GD3 and glial fibrillary acidic protein confirmed that AIM preparations induce type 2 astroglia from O-2A progenitors and suggests that AIM has little effect on type 1 astroglia. Because none of the known growth factors that have been tested to date mimics its effects. AIM may be a novel differentiation factor.     

A systems model of training responses and its relationship to hormonal responses in elite weight-lifters

A systems model, providing an estimation of fatigue and fitness levels was applied to a 1-year training period of six elite weight-lifters. The model parameters were individually determined by fitting the predicted performance (calculated as the difference between fitness and fatigue) to the actual one. The purpose of this study was to validate the systems model by comparing the estimated levels of fatigue and fitness with biological parameters external to the model calculation. The predicted and the actual performances were significantly correlated in each subject. The calculated fitness and fatigue levels were related to serum testosterone concentration, testosterone: cortisol and testosterone: sex hormone binding globulin ratios. The best results were obtained by the comparison between fitness and testosterone levels, which varied in parallel in each subject. In two subjects this correlation was significant (r = 0.91, P less than 0.05, and r = 0.92, P less than 0.01). The fitness changes calculated in each subject between the 15th and the 51st weeks of training were significantly correlated with the changes in serum testosterone concentration measured in the same period (r = 0.99, P less than 0.001). For the whole group testosterone and fitness variations were also significantly intercorrelated (r = 0.73, P less than 0.001). Correlations, less homogeneous and less significant, were calculated also for other hormones and ratios. These results suggest that (1) the relationships between training and performance can be described by the systems model, (2) the estimated index of fitness has a physiological meaning. The fatigue index remains to be clarified.     

Volume of ankle dorsiflexors and plantar flexors determined with stereological techniques.

The validity of the methods used for determination of muscle mass has not been evaluated previously. We determined muscle mass by estimating muscle volume with assumption-free stereological techniques applied to magnetic resonance imaging (MRI) in 18 healthy untrained subjects (6 women, 12 men) aged 41 yr (29-64 yr; median, range). Muscle mass was also estimated by measuring leg circumference and cross-sectional muscle areas (CSA) from MRIs at three predetermined levels. Power [peak torque (PT)] of the ankle dorsiflexors and plantar flexors was estimated by using isokinetic dynamometry. Dorsiflexor volume (r2 = 0.76, P < 5 x 10(-6)) and CSA (r2 = 0.73, P < 5 x 10(-5)) were related to PT, whereas circumference was not (r2 = 0.17, not significant). Correspondingly, a relationship to plantar PT was established for plantar flexor volume (r2 = 0.69, P < 5 x 10(-5)) and CSA (r2 = 0.46, P < 5 x 10(-3)) but not leg circumference (r2 = 0.15, not significant). SDs of the residuals were smaller for the relationship between dorsiflexor PT and volume than between PT and CSA (0.42 vs. 0.45) for plantar flexors (1.5 vs. 2.0). By using the Cavalieri method, six MRI sections and 15 min of point counting are sufficient to obtain a valid estimate of the volume of the muscles of the lower leg.     

Determinants of insulin-stimulated glucose disposal in middle-aged, premenopausal women

Controversy exists regarding the relative importance of adiposity, physical fitness, and physical activity in the regulation of insulin-stimulated glucose disposal. To address this issue, we measured insulin-stimulated glucose disposal [mg. kg fat-free mass (FFM)(-1). min(-1); oxidative and nonoxidative components] in 45 nondiabetic, nonobese, premenopausal women (mean +/- SD; 47 +/- 3 yr) by use of hyperinsulinemic euglycemic clamp (40 mU. m(-2). min(-1)) and [6,6-2H2]glucose dilution techniques. We also measured body composition, abdominal fat distribution, thigh muscle fat content, maximal oxygen consumption (VO2 max), and physical activity energy expenditure ((2)H(2)(18)O kinetics) as possible correlates of glucose disposal. VO2 max was the strongest correlate of glucose disposal (r = 0.63, P < 0.01), whereas whole body and abdominal adiposity showed modest associations (range of r values from -0.32 to -0.46, P < 0.05 to P < 0.01). A similar pattern of correlations was observed for nonoxidative glucose disposal. None of the variables measured correlated with oxidative glucose disposal. The relationship of VO2 max to glucose disposal persisted after statistical control for FFM, percent body fat, and intra-abdominal fat (r = 0.40, P < 0.01). In contrast, correlations of total and regional adiposity measures to insulin sensitivity were no longer significant after statistical adjustment for VO2 max. VO2 max was the only variable to enter stepwise regression models as a significant predictor of total and nonoxidative glucose disposal. Our results highlight the importance of VO2 max as a determinant of glucose disposal and suggest that it may be a stronger determinant of variation in glucose disposal than total and regional adiposity in nonobese, nondiabetic, premenopausal women.     

A new method for body fat evaluation, body adiposity index, is useful in women with familial partial lipodystrophy

BMI is a widely used method to evaluate adiposity. However, it has several limitations, particularly an inability to differentiate lean from fat mass. A new method, body adiposity index (BAI), has been recently proposed as a new measurement capable to determine fat excess better than BMI. The aim of this study was to investigate BAI as a mean to evaluate adiposity in a group of women with familial partial lipodystrophy (FPLD) and compare it with BMI. Thirteen women with FLPD Dunnigan type (FPLD2) and 13 healthy volunteers matched by age and BMI were studied. Body fat content and distribution were analyzed by dual X-ray absorptiometry (DXA). Plasma leptin was also measured. BAI was significantly lower in FPLD2 in comparison to control group (24.6 ± 1.5 vs. 30.4 ± 4.3; P < 0.001) and presented a more significant correlation with total fat (%) (r = 0.71; P < 0.001) and fat Mass (g) (r = 0.80; P < 0.001) than BMI (r = 0.27; P = 0.17 for total fat and r = 0.52; P = 0.006 for fat mass). There was a correlation between leptin and BAI (r = 0.57; P = 0.01), [corrected] but not between leptin and BMI. In conclusion, BAI was able to catch differences in adiposity in a sample of FPLD2 patients. It also correlated better with leptin levels than BMI. Therefore, we provide further evidence that BAI may become a more reliable indicator of fat mass content than the currently available measurements.     

Circadian rhythm in the membrane of circulating human blood cells: microviscosity and number of benzodiazepine binding sites. A search for regulation by plasma ions, nucleosides, proteins or hormones

Circadian rhythms in both the number of peripheral type binding sites for benzodiazepines in platelet membranes and the microviscosity of the erythrocyte membrane were demonstrated in 7 healthy men. Neither variable appeared to be linked to each other, or regulated by the plasma concentrations of total or free cortisol, testosterone, potassium, magnesium, calcium, cAMP, cGMP or proteins or by the erythrocytic concentration of magnesium or potassium or by the plasma cAMP:cGMP ratio or by the ratio of intra-erythrocyte:plasma concentrations of potassium or magnesium. A highly significant negative correlation was found between the microviscosity of the erythrocyte membrane and the activity of the membrane-bound enzyme, methyltransferase I. Such a correlation was validated both on raw data and on 24 hr-means (r = 0.84; P less than 0.01). A circadian rhythm in the activity of this enzyme was also demonstrated. Moreover, a highly significant correlation was also found between plasma transcortin concentration (TRC) and microviscosity (r = 0.50, P less than 0.01), and between TRC and methyltransferase I activity (r = 0.61, P less than 0.01). Such findings may constitute clues towards the understanding of the regulation of the circadian rhythm in the fluidity of the red blood cell membrane in man and guide future steps with regard to the role of this rhythm upon the availability of drug binding sites at the cell surface.     

In vitro primary satellite cell growth and differentiation within litters of pigs

Postnatal muscle growth is dependent on satellite cell (SC) proliferation, differentiation and fusion to increase the DNA content of existing muscle fibres and thereby the capacity to synthesize protein. The purpose of the present study was to examine the ability of isolated SCs from low, medium and high weaning weight litter mates of pigs to proliferate and differentiate, and to affect protein synthesis and degradation after fusion into myotubes. At 6 weeks of age, SCs from the lowest weight (LW), medium weight (MW) and highest weight (HW) female pigs within eight litters were isolated. Thereby, eight cultures of SCs were established for each of the three weight groups within litter, representing three groups of SCs from pigs exhibiting differences in postnatal muscle growth performance. Proliferation was estimated as the number of viable cells at different time points after seeding. SC differentiation was evaluated by measuring the activity of the muscle-specific enzyme, creatine phosphokinase, and protein synthesis and degradation were measured by incorporation and release of 3H-tyrosine, respectively. A tendency towards a difference in proliferation between SC cultures was found (P = 0.09). This was evident as the number of viable cells at day 3 was lower in cultures from LW pigs than from HW (P < 0.05) and MW (P < 0.01) pigs. Differentiation was significantly different between cultures (P < 0.05). There was a significant difference between LW and MW cultures at 72 h (P < 0.05), and a tendency towards a difference between LW and HW cultures at 45 h (P = 0.07). Protein synthesis per μg protein or per μg DNA did not differ among SC cultures from LW, MW and HW pigs. Neither did protein degradation rate differ significantly among SC cultures from LW, MW and HW pigs. Overall, the results show that SCs from LW pigs seem to proliferate and differentiate at a slower rate than SCs from MW and HW pigs. The results found in this study show no difference in the ability of SCs to affect protein synthesis or degradation between SCs from litter mates exhibiting different growth rates in vivo.     

Plasma phospholipid transfer protein activity in patients with low HDL and cardiovascular disease treated with simvastatin and niacin

Plasma phospholipid transfer protein (PLTP) is an important modulator of high-density lipoprotein (HDL) metabolism, regulating its particle size, composition, and mass. In patients with low HDL and cardiovascular disease (CVD), plasma PLTP activity is positively correlated with the concentration of HDL particles containing apo A-I but not apo A-II (Lp(A-1)). We recently completed a study to determine the effect of simvastatin and niacin (S-N) therapy on disease progression/regression in these patients, and found that this therapy selectively increased Lp(A-I). To determine if PLTP was also increased with this drug therapy, we measured the PLTP activity in the plasma of 30 of these patients obtained at baseline and after 12 months of therapy, and compared the changes to a similar group of 31 patients who received placebo for the drugs. No significant increase in PLTP activity was observed in either group of patients. However, changes in apo A-I and A-II between these two time points were correlated with the corresponding change in PLTP activity. The correlation coefficients were r=0.57 (P=0.001) and r=0.43 (P=0.02) for apo A-I, and r=0.54 (P=0.002) and r=0.41 (P=0.02) for apo A-II in the placebo and S-N group, respectively. At baseline, PLTP activity correlated positively with the percent of plasma apo A-I associated with Lp(A-I) (r=0.38, P=0.04) and the amounts of apo A-I in these particles (r=0.43, P=0.02). These relationships persisted in patients who took placebo for 12 months (r=0.46, P=0.009 and r=0.37, P=0.04, respectively), but was attenuated in those treated with S-N. These data indicate that S-N-induced increase in Lp(A-I) was PLTP-independent. It also confirms our previous observation that an interrelationship exists between PLTP and apo-specific HDL particle subclasses in CVD patients with low HDL, and that this relationship is altered by drug intervention.