The cDNA sequence and chromosomal location of the murine GABAA alpha 1 receptor gene.

The murine GABAA/benzodiazepine (GABAA/BZ) receptor alpha 1 subunit cDNA has been isolated from a BALB/c mouse brain library and sequenced. The cDNA is 2665 nucleotides long with an open reading frame of 455 amino acids. It shows significant homology to the GABAA receptor alpha 1 subunit cDNA sequences of other species. Excluding deletions, the murine GABAA alpha 1 receptor exhibits 96% nucleotide and 100% amino acid sequence homology to the rat alpha 1 receptor cDNA and over 91% nucleotide and 98% amino acid sequence homology to the bovine and human alpha 1 receptor cDNAs in the protein coding region. This murine cDNA was used to locate the alpha 1 receptor subunit gene, Gabra-1, to murine Chromosome 11 between Il-3 and Rel. This assignment extends proximally the segment of mouse Chromosome 11 with known homology to human chromosome 5.     

Proprioceptive regulation of locomotion

Recent investigations of proprioreceptors in the walking systems of cats, insects and crustaceans have identified reflex pathways that regulate the timing of the transition from stance to swing, and control the magnitude of ongoing motoneuronal activity. An important finding in the cat is that during locomotor activity, the influence of feedback from the Golgi tendon organs in extensor muscles onto extensor motoneurons is reversed from inhibition to excitation. The excitatory action of tendon organs during stance ensures that stance is maintained while extensor muscles are loaded, and may regulate the magnitude of extensor activity according to the load carried by the leg. Afferents from primary and secondary spindles in extensor and flexor muscles have also been found to influence the timing of the locomotor rhythm in a functionally relevant manner. Recent studies indicate that reflex reversals and the regulation of timing by multiple proprioceptive systems are also features of walking systems in arthropods.     

The effect of encapsulated fine grain sediment and test morphology on the resistance of planktonic foraminifera to dissolution

The tests of planktonic foraminifera recovered from deep-sea sediment are commonly observed to encapsulate fine grain carbonate sediment within their chambers. In sediment below the lysocline, the interstitial water within the chambers may not be as corrosive as the seawater in contact with the outer surface of the test due to slow continuous dissolution of the encapsulated carbonate. As a consequence, the pore walls of the foram dissolve more slowly than the outer surface of the test.Using published dissolution rate measurements for foraminifera and deep-sea sediment, the effect of diffusional reduction of pore wall dissolution was quantitatively estimated with a one-dimensional model for the steady state condition where diffusional flux out of the foraminifer's pores is balanced by the dissolution flux from the encapsulated fines and pore walls. The diffusional effect is found to principally depend on the structural parametric ratioT_wd_T/f, whereT_w is the wall thickness,d_T the test diameter andf is the test porosity. In the case of adult planktonic foraminifera, the ratio of the pore wall to outer surface dissolution flux is predicted to vary between 60% for the thin-walled porous species and 30% for thick-walled tests.Incorporation of the predicted pore to outer surface flux ratios into the morphologic index equation of Adelseck (1978) results in a very good prediction (73% of the variation) of the solution index of Berger (1975) obtained from ranking species counts from core tops. A simple empirical equation which may be useful for prediction of the resistance of extinct microfossils was found as follows:

$R=\frac{T_w}{\lambda \{1+[A_w/(A_s?A_p)][.74?.27log?(T_w{d}_T/f)]\}}$

is the measured ratio of pore wall area to outer surface of the test, andT_wd_T/f is in units of 10⁴ μm².     

Deoxyribonucleic acid poymerase of BHK-21/C13 cells. Heterogeneity, molecular asymmetry and subcellular distribution of the enzymes.

Nuclear and cytoplasmic fractions were prepared from exponentially-growing BHK-21/C13 cells; DNA polymerase was extracted from them and analysed by gel filtration and sucrose-density-gradient centrifugation. DNA polymerase I is heterogeneous comprising species covering a considerable range of molecular weights. These have been tentatively identified as four subspecies of apparent molecular weights 900000-1000000 (IA), 460000-560000 (IB), 270000-320000 (IC) and 140000-200000 (ID), as assessed by gel filtration through Sepharose 6B. DNA polymerase II has a mol.wt. of 46000 +/- 4000 as assessed by gel filtration on Sepharose 6B, and 48000 +/- 2000 as assessed by gel filtration on Sephadex G-100. Sedimentation analyses on sucrose density gradients showed that the DNA polymerase I species had sedimentation coefficients predominantly in the range 6-8 S. DNA polymerase II had predominantly a sedimentation coefficient of 3.2 S although a component with lower sedimentation coefficient was found. The lack of correlation between the molecular weights derived from gel filtration and the sedimentation coefficients is attributed to molecular asymmetry. DNA polymerase I was found to be associated predominantly with the cytoplasm although certain types of nuclear preparation contained large amounts of it. DNA polymerase II was found to be mostly if not exclusively in nuclear preparations.     

Deoxyribonucleic acid polymerases of Euglena gracilis. Purification and properties of two distinct deoxyribonucleic acid polymerases of high molecular weight.

Two DNA polymerases of high molecular weight, pol A (mol.wt. 190 000) and pol B (mol.wt. 240 ooo), have been purified 6300-fold and 1600-fold respectively from an extramitochondrial supernatant of a bleached strain of Euglena gracilis. They have very similar requirements when assayed with an 'activated'-DNA primer-template [the optimum conditions of pH and ionic (K+ and Mn2+) composition being 7.2, 25 mM and 0.2 mM respectively]. 0.2 mM-Mn2+ was about 1.5-2-fold as effective as 2 mM-Mg2+, owing to substrate activation by deoxyribonucleoside 5'-triphosphates in the presence of Mn2+. Km values for the triphosphates in the absence of activation were about 10(-6)M with Mn2+ and 8 X 10(-6) M with Mg2+ for both enzymes. They were inhibited to the same extent by N-ethylmaleimide, novobiocin and o-phenanthroline, but differed in their chromatographic behaviour on DEAE-cellulose and in their electrophoretic mobilities on polyacrylamide gel. No evidence was found for the existence in these cells of a DNA polymerase of low molecular weight, but there were indications that a third enzyme of high molecular weight might exist.     

Deoxyribonucleic acid-dependent ribonucleic acid polymerases from normal and polyoma-transformed BHK-21/C13 cells.

DNA-dependent RNA polymerase (EC 2.7.7.6) ACTIVITIES FROM NORMAL BHK-21/C13 cells and from BHK-21/C13 cells transformed by polyoma virus (PYY cells) were solubilized and fractionated on columns of DEAE-Sephadex. Various properties of the A and B enzymes from the two types of cell were compared. 1. The yields of polymerase relative to the DNA content of the nuclear preparations are similar for both cell types. 2. The ionic-strength optima of polymerases A and B are 12.5 mM and 100mM with respect to (NH4)2SO4 for both cell types. 3. The Mn2+/Mg2+ activity ratio (measured at the respective optimum for each cation) for polymerase A from BHK-21/C13 cells was 1.48 and for the polymerase A from PYY cells was 0.55. The corresponding ratios for polymerase B were 10.11 for BHK-21/C13 cells and 22.75 for PYY cells. 4. Minor differences in the ability of the A polymerases to transcribe native and denatured DNA templates were observed; such differences were not apparent when the B polymerases were compared. 5. All the polymerases were inhibited completely by actinomycin D and by rifampicin AF/013, but not markedly so by rifampicin. Alpha-amanitin inhibited polymerase B but not polymerase A.     

Deoxycytidylate deaminase. Evidence for a new enzyme in cells infected by the virus of herpes simplex

The activities of dCMP deaminase and DNA polymerase I increased twofold and fivefold in BHK-21/C13 cells after infection by the virus of herpes simplex. The increases were greatly diminished, and under certain conditions prevented, by inclusion of actinomycin D or cycloheximide in the cell-virus system during the infective cycle. The dCMP deaminase purified from infected cells harvested 8h after infection differed from the deaminase purified from non-infected cells inasmuch as (a) it was more resistant to heating at 37 degrees C; (b) the substrate (dCMP) concentration at half-maximum velocity was lower; (c) maximum activation was achieved by a lower concentration of dCTP; (d) it was more resistant to inhibition by dTTP; and (e) it behaved differently when assayed in the presence of a herpes-virus-specific antiserum. The DNA polymerase activity in the infected cells was markedly decreased in the presence of the herpes-virus-specific antiserum.     

Strength and power predictors of sports speed

For many sporting activities, initial speed rather than maximal speed would be considered of greater importance to successful performance. The purpose of this study was to identify the relationship between strength and power and measures of first-step quickness (5-m time), acceleration (10-m time), and maximal speed (30-m time). The maximal strength (3 repetition maximum [3RM]), power (30-kg jump squat, countermovement, and drop jumps), isokinetic strength measures (hamstring and quadriceps peak torques and ratios at 60 degrees .s(-1) and 300 degrees .s(-1)) and 5-m, 10-m, and 30-m sprint times of 26 part-time and full-time professional rugby league players (age 23.2 +/- 3.3 years) were measured. To examine the importance of the strength and power measures on sprint performance, a correlational approach and a comparison between means of the fastest and slowest players was used. The correlations between the 3RM, drop jump, isokinetic strength measures, and the 3 measures of sport speed were nonsignificant. Correlations between the jump squat (height and relative power output) and countermovement jump height and the 3 speed measures were significant (r = -0.43 to -0.66, p < 0.05). The squat and countermovement jump heights as well as squat jump relative power output were the only variables found to be significantly greater in the fast players. It was suggested that improving the power to weight ratio as well as plyometric training involving countermovement and loaded jump-squat training may be more effective for enhancing sport speed in elite players.     

Loss of phylogenetic information in chorion gene families of Bombyx mori gene conversion

The silkmoth chorion has provided a stimulating model for the study of evolution and developmental regulation of gene families. Previous attempts at inferring relationships among chorion sequences have been based on pairwise comparisons of overall similarity, a potentially problematic approach. To remedy this, we identified the alignable regions of low sequence variability and then analyzed this restricted database by parsimony and neighbor-joining methods. At the deepest level, the chorion sequence tree is split into two branches, called "alpha" and "beta." Within each branch, early- and late-expressing genes each constitute monophyletic groups, while the situation with middle-expressing genes remains uncertain. The HcB gene family appears to be the most basal beta-branch group, but this conclusion is qualified because the effect of gene conversion on branching order is unknown. Previous studies by Eickbush and colleagues have strongly suggested that ErA, HcA, and HcB families undergo gene conversion within a gene family, whereas the ErB family does not. The occurrence of conversion correlates with a particular tree structure; namely, branch lengths are much greater at the base of the family than at higher internodes and terminal branches. These observations raise the possibility that chorion gene families are defined by gene conversion events (reticulate evolution) rather than by descent with modification (synapomorphy).