An autosomal gene assignment in a marsupial: The gene for LDH-A is on chromosome 5 of the red kangaroo,Macropus rufus

A number of somatic cell hybrids between red kangaroo (Macropus rufus) and mouse cells, which lose marsupial chromosomes, were found to express the kangaroo form of LDH-A. Concordance between the expression of marsupial LDH-A and the presence of chromosome 5 in the hybrid cells and selected subclones enabled the gene for LDH-A to be assigned to this chromosome. This is the first autosomal gene assignment in a marsupial and should prove important for chromosome mapping in the red kangaroo and in many other species of marsupials.     

Analysis of development and growth in a mutant of Physarum polycephalum with defective cytokinesis

Cultures of amoebae of the mutant strain ATS23 isolated from strain CLd of Physarum polycephalum contain multinucleate cells and cells with increased nuclear DNA content. Plasmodia derived from ATS23 clones show abnormal morphology and defective sporulation. All abnormalities are enhanced by high incubation temperature (31 °C). Genetic analysis suggested that all the abnormalities were caused by a single mutation, denoted hts-23. The kinetics of plasmodium formation were followed in cultures of apogamic amoebae carrying hts-23 and hts⁺ (wild type) respectively. Results indicated that, relative to wild type, hts-23 did not increase the rate of plasmodium formation. There was evidence that, in both mutant and wild-type strains, commitment to plasmodium development occurred in uninucleate cells. Analysis of cell pedigrees by time-lapse cinematography indicated that the primary abnormal event in cultures of hts-23 amoebae was failure of cytokinesis; an apparently complete cleavage furrow was formed but cell separation failed, resulting in a binucleate cell. This event occurred randomly in pedigrees in which the majority of divisions were completed normally; its frequency increased during incubation at 31 °C. All other abnormalities in hts-23 amoebal cultures could be attributed to this primary event, assuming that DNA synthesis continued in the absence of cytokinesis and that the binucleate cells underwent the amoebal type of “open” mitosis, allowing the possibility of spindle fusion. This implies that the acquisition of “closed” mitosis is an essential early step in plasmodium development.     

Diel variations of selected physico-chemical parameters in Lake Kissimmee,Florida

Every two months, diel depth profiles were made of dissolved oxygen, pH, temperature and conductivity at two stations in Lake Kissimmee, Florida, from July 1974 through June 1975. Results suggest that stratification does not occur in the large (137 km²), shallow (mean depth 2.5 m) lake, though steep vertical gradients in these parameters may develop. The data also suggest that when these gradients do occur, they rapidly degenerate at night or under slight wind stress. Since many Florida lakes are relatively shallow (mean depth < 5 m) and topography offers little obstruction to wind action, it is believed that the holomictic condition observed in Lake Kissimmee may be typical of the state's lakes, particularly those in the central portion of the peninsula.     

A yellow polysaccharide-producing bacterium with unusual characteristics

Summary A polysaccharide-producing Gram-negative bacterium was isolated from a sample of hay. It grew best on nitrate-containing media with sucrose as carbon source; the colony form was highly unusual. No polysaccharide was formed on glucose. A spontaneous mutant producing the same polysaccharide on both sucrose- and glucose-containing media was isolated. The polysaccharide has been characterized as an acid heteropolymer containing D-galacturonic acid, D-glucose, D-galactose and D-mannose in the approximate molar ratio 1:1:3:1, together with about 2 mol of acetate. The polysaccharide in aqueous solution was highly viscous with pseudoplastic characteristics.     

Silver staining of the lampbrush chromosomes ofTriturus cristatus carnifex

Lampbrush chromosomes fromTriturus cristatus carnifex were stained using the ammoniacal silver staining (AgAS) technique. Many of the recognized marker structures proved to be silver positive, plus between six and fifteen lateral loop pairs. None of the stained loop pairs corresponded to known sites of the nucleolus organizers, although the extrachromosomal nucleoli were silver positive. The ammoniacal silver staining technique does not demonstrate the specificity for active ribosomal cistrons in lampbrush chromosomes that it does in a wide variety of mammalian mitotic chromosomes.     

The response of development rate to temperature in the univoltine cranefly,Tipula subnodicornis Zetterstedt

Summary The cranefly, Tipula subnodicornis, emerges as an adult in the spring and has an annual life-cycle in the British Isles. This is maintained partly through the presence of a winter diapause but the response of development rate to temperature also acts to preserve the timing of the cycle. During development under constant temperature conditions in the laboratory the optimum temperature (taken as the temperature which promoted the most rapid development) dropped from 25°C, or above, in the egg stage to below 20°C in the late larval stages. It is suggested that at the warmer, southern limits of the geographical range rapid early development may be compensated by a retardation in late larval growth. In addition, the response of growth rate to change in temperature was small in the fourth, final, instar and resulted in low Q ₁₀ values; 2.4 between 7° and 10°C, 1.5 between 10° and 15°C and 0.9 between 15° and 20°C. As the fourth instar comprises the greater part of the growth period, this has the effect of minimising the effect of temperature differences which are the result of differences of latitude or altitude. Even at optimum temperatures the growth period was prolonged and larvae in the field do not reach maximum weight, and the photosensitive stage, until late autum when short daylength promotes diapause. Subsequent development in the spring, before pupation and during the pupal period, showed a reversion to the higher Q ₁₀ figures of the early stages in development.The development of final instar Tipula subnodicornis larvae is contrasted with that of Tipula melanoceros. Tipula melanoceros emerges as an adult in September and it is likely that it has an egg diapause. Consequently larval development is confined to a short period between April and late July and growth must be rapid during this period. Under constant temperature conditions in the laboratory the growth of final instar larvae showed a marked contrast to that of Tipula subnodicornis in that the response to temperature was large and remained positive over a wider temperature range.     

The enzymic degradation of lipids resulting from physical disruption of cucumber (Cucumis sativus) fruit

Homogenization of fresh tissue from cucumber fruits results in a loss of endogenous lipid catalysed by acyl hydrolase enzymes. Deacylation of lipids is not accompanied by accumulation of free fatty acids. The levels of both saturated (mainly palmitic) and polyunsaturated (linoleic and linolenic) fatty acids in the lipids are reduced. Losses of the major acyl lipid constituents of cucumber (triacylglycerols and phospholipids) are mainly responsible for the observed hydrolysis. Triacylglycerol acyl hydrolase (lipase), phospholipase D and polar lipid acyl hydrolase enzyme activities were demonstrated. It is suggested that hydrolytic attack on endogenous lipids is the initial event on disruption of cucumber tissue, in the formation of lipid degradation products, amongst which are the volatile carbonyl compounds responsible for the characteristic flavour of cucumber.     

Prophage Induction in Escherichia coli (Lambda) by N-Nitrosamines

Carcinogenic N-nitrosamines were tested for their ability to induce λ in a lysogenic strain of Escherichia coli K-12 (58-161 F⁺). Dimethylnitrosamine, di-n-propylnitrosamine, methyl-n-propylnitrosamine, and N-nitrosopiperidine were shown to be inducers of prophage.