Mechanical measures during maximal velocity knee extension exercise and their relation to fibre composition of the human vastus lateralis muscle

A method for measuring the maximal velocity of knee extension exercise is described using a very light lever arm. Instrumentation of the lever arm with a potentiometer and accelerometer also allows for the measurement of peak acceleration, time to peak acceleration, the average rate of development of acceleration (jerk) and peak torque. With this apparatus and surface electromyography, electromechanical delay (EMD) was also determined. This apparatus was tested using 17 female and 10 male subjects, and the measures obtained were related to the percentage of fast twitch fibres (% FT) and the relative area of fast twitch fibres (% FTA) in the vastus lateralis determined from duplicate muscle biopsy samples. Peak velocity of unloaded knee extension averaged 12.1 +/- 1.2 and 12.2 +/- 1.7 rad.s-1 for females and males, respectively, and were not significantly different. As well, peak acceleration, time to peak acceleration jerk and EMD values were not significantly different between the female and male subjects, but the mean peak torque for the female subjects (73.5 +/- 14.7 N.m) was significantly lower than that for the males (98.4 +/- 31.5 N.m). Peak acceleration was significantly correlated with %FT (r = 0.40, P = 0.04) for the total subject population. None of the other measures was significantly related to either %FT or %FTA for the male and female subjects or the combined population of subjects.     

Heterogeneity of a murine B cell lymphoma. Isolation and characterization of idiotypic variants

mAb directed toward the idiotype of the 38C13 murine B cell lymphoma can be used to treat and cure a high percentage of mice challenged previously with an otherwise lethal dose of tumor cells. Tumors developing in animals despite antibody therapy were examined by immunofluorescence and found to demonstrate either loss of surface Ig, or expression of an altered idiotype that no longer bound the antibody used for treatment. Further immunofluorescence analysis of the variant tumors revealed individual patterns of cross-reactivity with anti-38C13 idiotype mAb other than that used for therapy. The variant tumor cells were fused to myeloma cells and hybrids were isolated which secreted large quantities of the altered idiotype proteins. Polyclonal antibodies and mAb prepared against the mutant proteins demonstrated cross-reactivity with the original 38C13 protein and its other variants. But the variants and wild type cells could be distinguished from each other by their patterns of reactivity with the panels of anti-idiotype antibodies. Differences in apparent m.w. were demonstrated in the L chains of each of the mutant proteins. Southern blot analysis of the H chain locus of these mutants established that they were all clonally related; however, the L chain loci were grossly different. Thus, rare cells with alteration in their Ig L chain genes and expressed proteins can give rise to idiotype variants in this B cell tumor.     

Trimethyloxonium modification of single batrachotoxin-activated sodium channels in planar bilayers. Changes in unit conductance and in block by saxitoxin and calcium

Single batrachotoxin-activated sodium channels from rat brain were modified by trimethyloxonium (TMO) after incorporation in planar lipid bilayers. TMO modification eliminated saxitoxin (STX) sensitivity, reduced the single channel conductance by 37%, and reduced calcium block of inward sodium currents. These effects always occurred concomitantly, in an all-or-none fashion. Calcium and STX protected sodium channels from TMO modification with potencies similar to their affinities for block. Calcium inhibited STX binding to rat brain membrane vesicles and relieved toxin block of channels in bilayers, apparently by competing with STX for the toxin binding site. These results suggest that toxins, permeant cations, and blocking cations can interact with a common site on the sodium channel near the extracellular surface. It is likely that permeant cations transiently bind to this superficial site, as the first of several steps in passing inward through the channel.     

Ex vivo elimination of neoplastic T-cells from human marrow using an anti-Mr 41,000 protein immunotoxin: potentiation by ASTA Z 7557

ASTA Z 7557 potentiated the ex vivo efficiency of a T-cell directed immunotoxin containing pokeweed antiviral protein (PAP). We used an immunotoxin of pan-T monoclonal antibody 3-A1 directed against p41 antigen expressed both on normal and leukemic T-cells. Treatment with 3A1-PAP in combination with ASTA Z 7557 produced 7-8 logs elimination of target lymphoblastic leukemia cells. Our data suggest that this new strategy shows potential for more effective ex vivo marrow purging in autologous marrow transplantation for acute lymphoblastic leukemia.     

Anti-T cell immunotoxins containing pokeweed anti-viral protein: potential purging agents for human autologous bone marrow transplantation

The ex vivo anti-leukemic efficacy and stem cell toxicity of two different T cell directed immunotoxins containing pokeweed antiviral protein (PAP) were studied by clonal assays. 5E9-11-PAP, an immunotoxin directed against human transferrin receptors, elicited a maximum leukemic cell kill of 3.9 logs. However, it was also toxic against normal pluripotent stem cells, and therefore is not a clinically useful purgative reagent. PAP conjugated to 3-A1, a monoclonal antibody directed against CD7 (T, p41), was more effective against leukemic T cells than 5E9-11-PAP and eliminated a maximum of 4.8 log of cells. 3A1-PAP was only slightly toxic to pluripotent stem cells: 13% of CFU-GEMM were lost after treatment with 3000 ng of 3A1-PAP/ml, a concentration that eliminated 99.96% of contaminating leukemic T cells from a 200-fold excess of normal bone marrow. Cryopreservation of treated cells by conventional methods did not affect the extreme selectivity and potency of 3A1-PAP. Incubation of 3A1-PAP with peripheral blood mononuclear cells resulted in the complete inhibition of phytohemagglutinin-induced mitogenic response, illustrating the possibility of using this immunotoxin as a potent anti-T cell reagent for prophylaxis against graft vs host disease in allogeneic BMT as well.     

Solubilization of an Adenosine Uptake Site in Brain

Procedures are described for the solubilization of adenosine uptake sites in guinea pig and rat brain tissue. Using [3H]nitrobenzylthioinosine [( 3H]NBI) the solubilized site is characterized both kinetically and pharmacologically. The binding is dependent on protein concentration and is saturable, reversible, specific, and high affinity in nature. The KD and Bmax of guinea pig extracts are 0.13 +/- 0.02 nM and 133 +/- 18 fmol/mg protein, respectively, with linear Scatchard plots obtained routinely. Similar kinetic parameters are observed in rat brain. Adenosine uptake inhibitors are the most potent inhibitors of [3H]NBI binding with the following order of potency, dilazep greater than hexobendine greater than dipyridamole. Adenosine receptor ligands are much less potent inhibitors of binding, and caffeine is without effect. The solubilized adenosine uptake site is, therefore, shown to have virtually identical properties to the native membrane site. The binding of the adenosine A1 receptor agonist [3H]cyclohexyladenosine [( 3H]CHA) to the solubilized brain extract was also studied and compared with that of [3H]NBI. In contrast to the [3H]NBI binding site [3H]CHA binds to two apparent populations of adenosine receptor, a high-affinity site with a KD of 0.32 +/- 0.06 nM and a Bmax of 105 +/- 30 fmol/mg protein and a lower-affinity site with a KD of 5.50 +/- 0.52 nM and Bmax of 300 +/- 55 fmol/mg protein. The pharmacology of the [3H]CHA binding site is consistent with that of the adenosine receptor and quite distinct from that of the uptake [( 3H]NBI binding) site. Therefore, we show that the adenosine uptake site can be solubilized and that it retains both its binding and pharmacologic properties in the solubilized state.     

Simultaneous potentiation and fatigue in quadriceps after a 60-second maximal voluntary isometric contraction

Potential mechanisms of fatigue (metabolic factors) and potentiation (phosphate incorporation by myosin phosphorylatable light chains) were investigated during recovery from a 60-s maximal voluntary isometric contraction (MVC) in the quadriceps muscle of 12 subjects. On separate days before and for 2 h after the 60-s MVC, either a 1-s MVC or electrically stimulated contractions were used as indexes to test muscle performance. Torque at the end of the 60-s MVC was 57% of the initial level, whereas torques from a 1-s MVC and 50-Hz stimulation were most depressed in the immediate recovery period. At this time, muscle biopsy analyses revealed significant decreases in ATP and phosphocreatine and a 19-fold increase in muscle lactate. Conversely, isometric twitch torque and torque from a 10-Hz stimulus were the least depressed of six contractile indexes and demonstrated potentiation of 25 and 34%, respectively, by 4 min of recovery (P less than 0.05). At this time, muscle lactate concentration was still 16 times greater than at rest. An increased phosphate content of the myosin phosphorylatable light chains (P less than 0.05) was also evident both immediately and 4 min after the 60-s MVC. We conclude that the 60-s MVC produced marked force decreases likely due to metabolic displacement, while the limited decline in the twitch and 10-Hz torques and their significant potentiation suggested that myosin phosphorylation may provide a mechanism to enhance contractile force under conditions of submaximal activation during fatigue.     

Exercise and blood lymphocyte subset responses: intensity, duration, and subject fitness effects

This study examined the effect of exercise intensity and duration on the percent blood lymphocytes in men of low [LF; maximal O2 uptake (VO2max) less than 50 ml.kg-1.min-1 and sedentary], moderate (MF; VO2max = 50-60 ml.kg-1.min-1 and recreationally active), and high (HF; VO2max greater than 60 ml.kg-1.min-1 and recent training history) fitness. Thirty healthy adult men (aged 20-31 yr) participated in four randomly ordered cycle ergometer rides: ride 1 (65% VO2max, 30 min), ride 2 (30% VO2max, 60 min), ride 3 (75% VO2max, 60 min), and ride 4 (65% VO2max, 120 min). Blood samples were drawn at various times before and after the exercise sessions. Lymphocyte subsets were determined by flow cytometry using monoclonal antibodies for total T (CD3+), T-helper (CD4+), and T-suppressor (CD8+) lymphocytes and for a subset of cells expressing a natural killer (NK) cell antigen (Leu7+). Plasma catecholamines were assayed to determine exercise stress. There were sharp reductions (P less than 0.01) in the percentage of pan-T and T-helper lymphocytes immediately after exercise across all fitness levels; the magnitude of this reduction was greatest after the highest intensity (ride 3) or longest duration (ride 4) work. In contrast, the absolute number of T and T-helper cells tended to increase after exercise and significantly so in the HF subjects (P less than 0.005). There was no significant effect of exercise or subject fitness category on the percentage of T-suppressor lymphocytes, although the absolute numbers of this subset increased significantly after exercise in LF subjects. Marked increases (P less than 0.01) in the percentage of NK cells occurred immediately after exercise at all intensities and durations tested; numerical increases in total NK cells were significant in all fitness groups after the highest intensity work (ride 3; P less than 0.005). Irrespective of whether the changes were expressed as percentage or total numbers, recovery to base line occurred at 30 min after exercise. The results suggest that the exercise effect on blood lymphocyte subset percentages in men is transient and occurs across all fitness levels. Concomitant changes in plasma catecholamine concentrations are only weakly associated with these lymphocyte subset percentage responses to exercise. Furthermore, this study shows that the exercise-induced changes in lymphocyte percentages do not consistently reflect changes in the absolute numbers of cells.     

Relative apparent synapomorphy analysis (RASA). I: The statistical measurement of phylogenetic signal

We have developed a new approach to the measurement of phylogenetic signal in character state matrices called relative apparent synapomorphy analysis (RASA). RASA provides a deterministic, statistical measure of natural cladistic hierarchy (phylogenetic signal) in character state matrices. The method works by determining whether a measure of the rate of increase of cladistic similarity among pairs of taxa as a function of phenetic similarity is greater than a null equiprobable rate of increase. Our investigation of the utility and limitations of RASA using simulated and bacteriophage T7 data sets indicates that the method has numerous advantages over existing measures of signal. A first advantage is computational efficiency. A second advantage is that RASA employs known methods of statistical inference, providing measurable sensitivity and power. The performance of RASA is examined under various conditions of branching evolution as the number of characters, character states per character, and mutations per branch length are varied. RASA appears to provide an unbiased and reliable measure of phylogenetic signal, and the general approach promises to be useful in the development of new techniques that should increase the rigor and reliability of phylogenetic estimates.      

Energetic constraints and foraging efficiency

Previous research considers foraging options that differ interms of their gross rate of gain b and rate of energy expenditurec. This research argues that maximizing efficiency b/c willmaximize net energetic gain when there is an upper limit onthe amount of energy that can be assimilated. This analysisdoes not include the expenditure during the time for which theanimal is unable to forage because of this constraint. Whenthis expenditure is included, maximizing efficiency is no longeroptimal. Instead the best feeding option is the one with thehighest value of b/(c – c₁), where c, is the metabolicrate when the animal is not foraging.