Hypertrophy of rat plantaris muscle fibers after voluntary running with increasing loads

There have been no systematic comparisons ofskeletal muscle adaptations in response to voluntary wheel runningunder controlled loading conditions. To accomplish this, a voluntaryrunning wheel for rats and mice was developed in which a known load canbe controlled and monitored electronically. Five-week-old maleSprague-Dawley rats (10 rats/group) were assigned randomly to either a1) sedentary control group(Control); 2) voluntary exercisedwith no load (Run-No-Load) group; or3) voluntary exercised withadditional load (Run-Load) group for 8 wk. The load for the Run-Loadgroup was progressively increased to reach ~60% of body weightduring the last week of training. The proportions of fast glycolytic(FG), fast oxidative glycolytic (FOG), or slow oxidative (SO) fibers inthe plantaris were similar in all groups. The absolute and relativeplantaris weights were greater in the Run-Load group compared with theControl and Run-No-Load groups. The mean fiber cross-sectional areas of FG, FOG, and SO fibers were 20, 25, and 15% greater in the Run-Load than in Control rats. In addition, these fiber types were 16, 21, and12% larger in Run-Load than in Run-No-Load rats. The muscle weightsand mean cross-sectional areas of each fiber type were highlycorrelated with the average running distances and total work performedin the Run-Load, but not the Run-No-Load, group. The slope of therelationship between fiber size and running distance and total workperformed was significant for each fiber type but was higher for FG andFOG fibers compared with SO fibers. These data show that the load on arat running voluntarily can determine the magnitude of a hypertrophicresponse and the population of motor units that are recruited toperform at a given loading condition.

     

Stereospecificity of hydrogen transfer by pyridine nucleotide-dependent enoyl reductases in fatty acid synthesis: Studies with enzymes obtained from developing castor bean seeds and Chlorella vulgaris

The mechanism of hydrogen incorporation into fatty acids wasinvestigated with fatty acid synthetase systems from developingcastor bean seeds and Chlorella vulgaris. Fatty acids synthesizedin the presence of D₂O or stereospecifically deuterium-labeledNADPH or NADH were isolated and analyzed by mass spectrometryto examine the localization of deuterium atoms in the molecule.The stereospecificities of ß-ketoacyl-acyl carrierprotein (ACP) reductase and enoyl-ACP reductase for reducedpyridine nucleotide were determined with acetoacetyl-ACP andcrotonyl-ACP as substrates. The products were also analyzedby gas chromatography-mass spectrometry. The following resultswere obtained:

1. ß-Ketoacyl-ACP reductases from both castor bean seedsand C. vulgaris used the B-side hydrogen of NADPH.
2. Enoyl-ACPreductase from C. vulgaris required NADH for the activity.
3. Enoyl-ACPreductase from castor bean seeds used the A-side hydrogenofNADPH, whereas that from C. vulgaris used the B-side hydrogenof NADH.
4. When stearate was synthesized with the crude fattyacid synthetasefraction from castor bean seeds, hydrogen atomsfrom water werefound on the even-numbered methylene carbonatoms (two hydrogenatoms per carbon atom) and some were foundon the odd-numberedmethylene carbon atoms. Hydrogen atoms fromthe B-side of NADPHwere found on the odd-numbered methylenecarbon atoms (one hydrogenatom per carbon atom). Hydrogen atomsfrom the A-side of NADPHwere also found on the odd-numberedmethylene carbon atoms,but the number of incorporated hydrogenatoms was less thanexpected.

(Received October 17, 1979; )     

Organics in chimneys and water samples from deep-sea hydrothermal systems: implications for sub-vent biosphere.

Searching for life in extreme terrestrial environments can be a model of that for extraterrestrial life. Submarine hydrothermal system is one of promising sites for the frontier of life on the earth. Here seawater and vent chimnies were collected from deep-sea hydrothermal vents at Suiyo Seamount, Izu-bonin arc, Pacific Ocean as a part of Archaean Park Project. Pure seawater sample of 300 degrees C (purity>97%) could be collected. Dissolved and total hydrolyzable amino acids were determined by ion-exchange HPLC, and their enantiomeric ratio was measured by reversed-phase HPLC for the first time. Glycine and serine were two most abundant amino acids, followed by other proteinous amino acids such as alanine, glutamic acid and aspartic acid. Non-proteinous amino acids were detected as minor constituents. Most of the amino acids detected were of the L-form. Thus amino acids of abiotic origin were quite minor, and most of the amino acids detected were formed biologically. These results, together with analytical results of the vent chimney samples, suggest that there is active microbial activities near the hydrothermal systems.     

Neurochemical and histological analysis of motor dysfunction observed in rats with methylnitrosourea-induced experimental cerebellar hypoplasia

Histological and neurochemical changes related to motor dysfunction observed in rats after neonatal treatment with nitrosoureas were examined. Neonatal rats received subcutaneous injections of methylnitrosourea (MNU: 0.125 mmol/kg, s.c.) or ethylnitrosourea (ENU: 0.25 mmol/kg, s.c.) daily at 4,5,6 and 7 days post partum, a period of cerebellar granule cell, stellate cell and basket cell formation. At 14 days and 45 days after birth, MNU-treated rats displayed a lowering in motor coordination skills measured by tests of retainment ability on a rod of 26 mm diameter, chinningclimbing ability on parallel rods or retainment ability on a rotating rod. Histological examination at 14 days after birth showed a cerebellar hypoplasia with reduced cellularity of the internal granule cell layer and a disperse disposition of Purkinje cells in the granule cell layer. Cerebellar growth and cerebellar content and concentration of DNA were remarkably reduced in the MNU-treated rat. The degree of the reduction in cerebellar content of glutamic acid paralleled the degree of the cerebellar hypoplasia at 14 and 45 days after birth. In contrast, the concentrations of gamma-aminobutyric acid, acetylcholine, 5-hydroxytryptamine and norepinephrine were significantly increased by MNU treatment. ENU treatment control did not exert any significant changes in the neurotransmitters and motor coordination. These results suggest that the motor dysfunctions observed in MNU treated rats are induced by unbalanced output activities from Purkinje cells to motor neurons.     

Comparative studies on the extractability of collagen from aortas of stroke-prone spontaneously hypertensive and normotensive rats.

The molecular states of collagen in the aortas of age-matched stroke-prone spontaneously hypertensive (SHRSP) and normotensive Wistar Kyoto rats (WKY) were studied by analyzing its extractability under defined conditions. The monomeric and oligomeric collagen extractable with 0.5 M acetic acid/6 M urea from aortic homogenates of 9-month-old SHRSP and WKY comprised approx. 0.6 and 2.0%, respectively, of the total collagen. On incubation of the acetic acid/urea-extracted residues with pepsin at 4 degrees C, the levels of the collagen alpha 1(I) and alpha 2(I) chains solubilized from the SHRSP residues were both less than 50% of those from the WKY residues. When the residues were incubated with pepsin at 15 or 25 degrees C, the differences became smaller. When the acetic acid/urea residues were hydrolyzed with cyanogen bromide, nearly identical peptide maps were obtained for SHRSP and WKY. The aortas from 2-month-old SHRSP and WKY contained much larger proportions of acid/urea-extractable collagen than those of the older rats (8.2 and 13% of the respective total collagen). The levels of the alpha 1(I) and alpha 2(I) chains solubilizable from the respective residues by pepsin at 4 degrees C were similar to each other. These results indicate that aortic collagen fibrils in SHRSP are stiffened more prominently than those in WKY.     

Electrical properties of squid axon membrane. II. Effect of partial degradation by phospholipase A and pronase on electrical characteristics

Passive electrical characteristics of perfused squid axon membrane are investigated. In a previous publication, we reported that the capacitance of intact squid axon membrane is partly frequency dependent. We extended the same measurement to perfused axons. We found that the electrical characteristics of perfused axon membrane are essentially the same as those of intact axons. In this work, we investigated the effects of phospholipase A and pronase on the membrane capacitance. Phospholipase A is known to block the sodium activation and pronase to eliminate the sodium inactivation. Phospholipase A is found to increase the frequency dependent as well as the frequency independent capacitances. Our tentative conclusion is that this enzyme perturbs the lipid structure and decreases its thickness. Pronase is found to increase the frequency dependent capacitance slightly while the capacitance of the lipid layer remains unaltered. Although voltage clamp data indicate that the pronase disrupts the excitatory mechanism extensively, this enzyme has relatively little effect on the overall membrane capacitance.     

Membrane capacity of squid giant axon during hyper- and depolarizations

Summary The change in membrane capacitance and conductance of squid giant axons during hyper- and depolarizations was investigated. The measurements of capacitance and conductance were performed using an admittance bridge with resting, hyperpolarized and depolarized membranes. The duration of DC pulses is 20–40 msec and is long enough to permit the admittance measurements between 1 and 50 kHz. The amplitudes of DC pulses were varied between 0 and 40mV for both depolarization and hyperpolarization. Within these limited experimental conditions, we found a substantial increase in membrane capacitance with depolarization and a decrease with hyperpolarization. Our results indicate that the change in membrane capacitance will increase further if low frequencies are used with larger depolarizing pulses. The change in membrane capacitance is frequency dependent and it increases with decreasing frequencies. The analyses based on an equivalent circuit (vide infra) gives rise to a time constant of active membrane capacitance close to that of sodium currents. This result indicates that the observed capacitance changes may arise from sodium channels. A brief discussion is given on the nature of frequency-dependent membrane capacitance of nerve axons.     

Elucidating functions of DP1 and DP2 subunits from the Thermococcus kodakarensis family D DNA polymerase

Extremophiles - DNA polymerase D (PolD), originally discovered in Pyrococcus furiosus, has no sequence homology with any other DNA polymerase family. Genes encoding PolD are found in most of...