Chromosomal assignment of amplified genes in hydroxyurea-resistant hamster cells

We have shown previously that cDNAs for the M1 and M2 subunits of ribonucleotide reductase, ornithine decarboxylase (ODC), and p5-8, a 55,000-Dalton protein, hybridize to amplified genomic sequences in a highly hydroxyurea-resistant hamster cell line. We have extended these observations to include two additional, independently isolated, hydroxyurea-resistant cell lines: SC8, a single-step hamster ovary cell line, and KH450, a multistep human myeloid leukemic cell line, have also undergone genomic amplification for sequences homologous to ODC and p5-8 cDNAs. However, neither SC8 nor KH450 contains amplified genomic sequences homologous to an M1 cDNA probe. A panel of mouse-hamster somatic cell hybrids was used to map sequences homologous to M1, M2, ODC, and 5-8 cDNAs in the hamster genome. The M2, ODC, and p5-8 cDNAs hybridized to DNA fragments that segregated with hamster chromosome 7. In contrast, M1 cDNA hybridized to DNA fragments that segregated with hamster chromosome 3. These data suggest that the genes RRM2, (M2), ODC, and p5-8, but not RRMI (M1), are linked and may have been co-amplified in the selection of the hydroxyurea-resistant hamster and human cell lines.     

Effect of etmozin on thrombocyte aggregation capacity

It was shown in in vitro experiments that etmozin at a concentration of 100 micrograms/ml significantly suppressed (by 21%) platelet aggregation induced by ADP, but it had no effect on platelet aggregation induced by arachidonic acid. In in vivo experiments etmozin was found to cause a marked suppression of tendon collagen-induced platelet aggregation in the doses 2-5 mg/kg having antiarrhythmic activity. Under suppressed platelet aggregation induced by indomethacin, the prostaglandin biosynthesis blocker etmozin displayed no antiaggregation effect. It is suggested that etmozin effects on ADP release from platelets play the main role in the mechanism of its antiaggregation action.     

The role of arctic zooplankton in biogeochemical cycles: respiration and excretion of ammonia and phosphate during summer

The study of the structural and functional properties of key components of polar marine ecosystems has received increased attention in order to better understand the ecological consequences of future sea temperature rise and seasonal ice retraction. Owing to this purpose, during the ATOS-Arctic cruise, held in July 2007 in the framework of the 2007–2008 International Polar Year, we studied the respiratory carbon demand of mesozooplankton as well as their contribution to the regeneration of inorganic nitrogen and phosphorus (NH₄-N and PO₄-P) via excretion. The studied area comprised several stations along a latitudinal gradient in the East Greenland current, plus a network of stations NW of the Svalbard islands. The specific respiratory carbon losses and phosphorus (PO₄-P) excretion rates were similar or slightly higher than some reports for Arctic mesozooplankton, but the nitrogen (NH₄-N) excretion rates were higher by a factor of 3 when compared with previous data sets. The mesozooplankton respiratory losses were equivalent to 23% of primary production, and at turn zooplankton contributed by excretion to more than 50% of the N and P required by phytoplankton. Although C:N, C:P and N:P metabolic atomic quotients almost coincided with the average Redfield’s stoichiometric ratios, the low C:N values when compared to previous reports suggested a predominance of protein-related metabolic substrates. The potential consequences of changes observed in the C:N, N:P and C:P metabolic ratios of mesozooplankton for Arctic marine ecosystems are discussed.     

Two types of eye movements during electrical stimulation of the rostral and caudal parts of the medial frontal "oculomotor" area in cats

The character of eye movements during electrical stimulation of the medial wall of the brain beneath the cruciate sulcus and of the inferior wall of the cruciate sulcus itself in the frontal cortex was investigated in waking cats. Stimulation of this part of the brain evoked two types of eye movements: unidirectional concomitant saccades, whose direction and amplitude were independent of the original position of the eyes in the orbits, and saccades into the central position (so-called centering saccades). Unidirectional saccades appeared in response to stimulation of the caudal part of the investigated zone, centering saccades in response to stimulation of its rostral part. Analysis of the directions and amplitudes of unidirectional saccades suggested the retinotopic organization of the caudal zone. Systematic changes in the magnitude and direction of vertical saccades during stimulation of the deep parts of the cruciate sulcus indicated previsely the projection of the vertical meridian of the retina. Reappearance of vertical saccades evoked by stimulation of certain parts of the medial wall of the brain suggests the existence of more than one retinotopically organized zone in this region. Inconstancy of stereotaxic coordinates of the oculomotor area, studied in different animals, was noted.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 761–766, November–December, 1984.     

Two-dimensional gel analysis of swine histocompatibility antigens

Miniature swine MHC antigens from three inbred herds were examined by two-dimensional gel electrophoresis. These antigens were found to constitute a series of complex glycoproteins displaying haplotype-specific patterns that allowed the distinction of both class I and class II molecules among the three haplotypes. Selected outbred pig antisera reacted with a subset of class I antigens, suggesting the presence of at least two distinct molecular species among these antigens. Similarly, alloantisera reacting with mouse Ia antigens and a monoclonal anti-human DR were shown to immunoprecipitate a subset of class II molecules. Examination of the cells from two recombinant haplotypes demonstrated that both independent recombinational events took place between the class I and class II genes.     

Use of fibre-optic endoscopes in studies of gastric digestion in carnivorous vertebrates

1. Two methods of assessing gastric digestion rates of three prey types fed to Sooty albatrosses Phoebetria fusca were compared: removal of stomach contents, using a water-flushing stomach pump (a technique used commonly in diet studies), and inspection using a fibre-optic gastroscope (a previously unused technique). 2. The stomach pump yielded quantitative information, but proved stressful and resulted in incomplete recovery of meals ingested 3-6 hr before pumping. Gastric morphology of the animals studied and digestion state of their stomach contents may influence the effectiveness of this technique. 3. Inspection using the gastroscope yielded qualitative information only but permitted serial inspection of the same animal, and was less stressful than the stomach pump. Times for total evacuation of the stomach were 6-12 hr less when estimated using the gastroscope than when using the stomach pump. 4. The specifications of endoscopes relevant to their use by biologists are given. 5. Previous non-medical biological uses of endoscopes are given. Potential uses include underwater observations, sampling of digestive juices and stomach linings for enzyme analyses, observations of ingested prey, and assessment of parasite infestation.