Human glyceraldehyde-3-phosphate dehydrogenase: mRNA levels and enzyme activity in developing muscle.

Analysis of human glyceraldehyde-3-phosphate dehydrogenase mRNA revealed that levels in adult skeletal muscle are 12-fold greater per microgram of polyadenylated RNA than in fetal skeletal muscle, whereas in cardiac muscle RNA levels were about equal in fetal and adult tissue. The mRNA levels correlate well with glyceraldehyde 3-phosphate dehydrogenase enzyme activities. There was no evidence for fetus- or tissue-specific forms.     

Tissue abscission and wound healing in the operculum of Pomatoceros lamarckii Quatrefages (Polychaeta: Serpulidae)

Following opercular amputation in Pomatoceros lamarckii Quatrefages, wound healing is initiated from a predetermined point on the peduncle. The events of abscission, cell migration and cuticle deposition during wound healing have been studied by light and electron microscopy. Abscission occurs at a predetermined point on the peduncle indicated by specialized epidermal cells, the easy break-point cells (EBP). Following detachment of tissues distal to the EBP cells, the resultant wound is plugged by a knot of coelomocytes which provide a substratum over which epidermal cells migrate to seal and restore the epidermis. During their migration, the epidermal cells undergo differentiation and deposit a new cuticle. Cuticle formation is initiated by the deposition of a finely filamentous matrix. The fine filaments subsequently coalesce to form thicker fibrils which become aggregated into layers of orthogonally-arranged fibril bundles. The mechanisms involved in abscission, cell migration and cuticle deposition during wound healing of the opercular filament are discussed.     

Thermoregulation and metabolism in the smallest African gerbil, Gerbillus pusillus

The effect of temperature on thermoregulation, metabolism, evaporative water loss and thermal conductance was studied in Gerbillus pusillus . Its resting body temperature (TB) was 34·6°C, approximately 5°C higher than the mean ambient temperature (TA) encountered in its burrow. As TA increased above 34°C, its ability to lose heat to the environment decreased. It overcame this problem by tolerating increases in TB to a non-lethal maximum of 41°C, whilst also eliminating increasing quantities of obligate heat by pulmocutaneous evaporation and conduction.
Metabolic rate was 41% lower than that predicted from Kleiber's (1975) allometric equation. This confers a considerable saving in energy in an environment where food is often scarce, whilst simultaneously reducing heat production and the degree of gaseous exchange in the already oxygen-poor and carbon dioxide-rich environment encountered in the plugged burrows of its natural milieu.
Gerbillus pusillus , therefore, does not maintain strict homeothermy and utilizes a labile TB and reduced metabolic rate as an adaptive mechanism for survival in the arid zones of tropical Africa.     

Population fluctuations, reproduction and survival in the Striped fieldmouse Rhabdomys pumilio on the Cape Flats, South Africa

A wild population of Striped fieldmice was studied for a continuous period of five years in an area of alien Acacio bush about 24 km from Cape Town, South Africa. Mice were live-trapped, marked by toe-clipping and released on a 60-station grid, and also kill-trapped in a separate area. Marked annual fluctuations in the population size were correlated with a 6–8 month summer breeding season. There were also marked inter-annual differences in peak population size. The age of sexual maturity of females was determined from the first pregnancy which occurred at 6–7 weeks old; and of males from the presence of visible spermatozoa in the vas deferens which occurred at about 11 weeks old. Litter size was affected by both the age and the body mass of the female. It appeared that mean survival from birth was only approximately 1.5 months and that survival from first capture was about 1.9–2.5 months. This high mortality appeared to be the major reason for the sharp seasonal fluctuations in population size and may also have been responsible for the interannual differences since marked changes in survival were recorded between some years.     

Plasma esterase polymorphism in the Bank vole, Clethrionomys glareolus, in Britain

Three hundred and eighty-three Clethrionomys glareolus from 20 localities in England, Wales and Scotland were typed for plasma esterase and a genetic polymorphism was discovered. The esterase was named Es-1. Breeding tests suggested that three alleles were segregating: Es-1^o when homozygous results in complete absence of enzyme activity. The active alleles Es-1^f and Es-1^s code for enzyme variants which migrate more rapidly and less rapidly, respectively, under starch gel electrophoresis. Of these active alleles, Es-1^f is morc common in the north of Britain and Es-1⁸ in the south. A 23-month field study on two areas at Wicken Fen, Cambridgeshire, suggested that animals possessing Es-1^s survived less well at high population densities, perhaps through their being more likely to emigrate.     

Selective protection of in vitro synthesized cDNA against nucleases by incorporation of phosphorothioate-analogues.

The conditions for the stepwise synthesis of single- (ss) and double-stranded (ds) cDNA using thio-analogues instead of dNTPs are described in this paper. RNA of paramyxovirus Sendai (strain 6/94) serves as template in these experiments. The increased resistance of this alpha S-modified cDNA against several nucleases, like S1-Nuclease, DNase I, Exonuclease III, snake venom Phosphodiesterase (PDE) and the combination of DNase I and PDE is demonstrated.     

Structure of viral DNA in a rat cell line transformed by the cloned EcoRI-C fragment of adenovirus 12.

A DNA segment carrying viral DNA was cloned from a rat cell line transformed by the cloned EcoRI-C fragment (0 to 16.4 map units) of human adenovirus type 12(Ad12), and the viral sequence in the clone was analysed. The cloned segment contained the region from nucleotide positions 118 to 3520 of the Ad12 genome in the middle. No unique structure was found at the viral and non-viral DNA junctions. When examined the transforming activity, the conserved viral sequence was able to transform rat 3Y1 cells efficiently. Southern blotting analysis of the viral sequence in five re-transformed cell lines showed that the viral sequence was inserted at different sites of cellular DNA. These results indicate that (I) the Ad12 DNA moiety from the enhancer-promoter region of the E1A gene to the end of the E1B gene contains enough information for efficient transformation of the rat cell, and (II) integration of the viral sequence at unique cellular sites is not prerequisite for transformation.     

Structure of the human alpha 1-acid glycoprotein gene: sequence homology with other human acute phase protein genes.

We have determined the sequence coding for human alpha 1-acid glycoprotein from two independently isolated cDNA clones and a genomic clone. The aminoacid sequences deduced from the three clones, deriving from three different individuals, are identical. Southern blot analysis on human DNA indicates that there are at least two genes coding for alpha 1-AGP. We propose that alpha 1-AGP found in plasma is a mixture of the products of these two different genes. This is the simpler explanation for the heterogeneity in the aminoacid composition in purified alpha 1-AGP observed by Schmid et al. (1). DNA sequence comparison with cDNA clones coding for human alpha 1-antitrypsin and haptoglobin shows a conserved sequence within the 5' untranslated region which may play a role in the acute phase response.     

Direct-acting mutagenicity of N4-aminocytidine derivatives bearing alkyl groups at the hydrazino nitrogens.

To investigate the mechanism of N4-aminocytidine-induced mutagenesis, N'-alkyl-N4-aminocytidines and N4-alkyl-N4-aminocytidines were prepared and their mutagenicity on bacteria were assayed. N'-Methyl-N4-aminocytidine, N'-(2-hydroxyethyl)-N4-aminocytidine and N',N'-dimethyl-N4-aminocytidine showed direct-acting mutagenicity on S. typhimurium TA100 and E. coli WP2 uvrA, tester strains that are sensitive to base-pair substitutions. In contrast, N4-methyl-N4-aminocytidine, N4-(2-hydroxyethyl)-N4-aminocytidine and N4,N'-dimethyl-N4-aminocytidine were not mutagenic on these bacteria. Since N'-methyl-N4-aminocytidine does not form hydrazones, the possibility that N4-aminocytidine causes mutation due to its reactivity with carbonyl compounds has been excluded. Furthermore, the fact that only those alkyl N4-aminocytidines having a hydrogen on the nitrogen at position 4 are mutagenic is consistent with the previously proposed mechanism in which the tautomerization between the amino and the imino forms of N4-aminocytosine allowing an ambiguous base pairing is the cause of the mutagenesis.