Rat plasma levels of amino acids and related compounds during stress

Forty-one amino acids and related compounds were measured (using an HPLC physiological amino acid analysis procedure fully validated for plasma studies) in rat plasma obtained through an indwelling jugular catheter before, during and following a 30 min period of immobilization. Taurine, phosphoethanolamine, aspartic acid, glutamic acid, alanine, cystine, tyrosine, beta-alanine and ethanolamine were increased during the period of stress; whereas, valine, tryptophan and arginine were decreased. Most of these alterations were restored toward normal during the 30 min of rest following the stress period. However, cystine, ethanolamine and beta-alanine remained significantly elevated, and valine, tryptophan and arginine remained significantly reduced. Serine, isoleucine, leucine and glutamine were not significantly altered during the stress period, but became significantly reduced during the 30 min following the stress period. While the patterns of amino acid alterations were generally consistent from animal to animal, the magnitude of the responses were variable with some rats demonstrating much larger responses than others. These results may implicate amino acids as important markers for stress related pathologies. The individual differences noticed may explain why some individuals show more stress effects than others.     

Characterization of mitoses with sister chromatid differentiation (SCD) and consequences for the analysis of proliferation kinetics and sister chromatid exchanges in asynchronously growing cells

Summary Labeling cells with bromodeoxyuridine (BrdU) permits the differentiation of mitoses of the first, second, and third generation after the addition of BrdU. The term second mitoses is used for those cells which have incorporated BrdU for two-S-phases and which exhibit sister chromatid differentiation (SCD). However, SCD can also be obtained if the cell was in S-phase at the time of BrdU-addition and had already replicated part of its DNA. Such cells with incomplete BrdU-substitution in the first S-phase can only be differentiated from completely substituted ones by the quality of the SCD and are usually also grouped as second mitoses in the evaluation of experiments. Due to the heterogeneity of the evaluated second mitoses, the determination of proliferation delay and the incidence of sister chromatid exchange-induction can depend on the time of chromosome preparation.     

Introduced reindeer and their effects on the vegetation and the epigeic invertebrate fauna of South Georgia (subantarctic)

Summary The introduced reindeer of South Georgia have had a serious impact on the vegetation throughout the range of three populations on the island. Exclosure experiments in areas where the reindeer were introduced have resulted in a dramatic change in the composition of the protected vegetation. Poa flabellata (the major winter food) and Acaena magellanica (a major summer food) have recovered to their former status inside the exclosures, while Deschampsia antarctia and the introduced grass Poa annua tolerate grazing and trampling and have spread over the grazed areas. Festuca contracta and Rostkovia magellanica are not eaten by the reindeer. Trampling has resulted in a high proportion of bare soil and peat in sites freely accessible to reindeer. However, the changes in the vegetation have not had such a significant effect on the associated invertebrate fauna. Thus in grazed and protected areas the faunistic composition is qualitatively similar, although there are quantitative differences, and some of the trends can probably be attributed to the presence of the reindeer. Compared with reindeer-free areas, the abundance of the perimylopid beetle Hydromedion sparsutum (a major primary decomposer) is reduced. The frequency of their egg parasite Notomymar aptenosoma (Hymenoptera, Mymaridae) increases. Consequently the ratio of perimylopoids to mymarids found in pitfall traps shifts from 1:0.01 (ungrazed areas) to 1:0.54 (grazed areas). Also the frequency of sciarids was found to be higher in reindeer areas. The larvae of these probably introduced gnats do not play a role in the natural terrestrial ecosystem of South Georgia, but in reindeer areas they appear to establish larger populations because they are able to live deeper in the soil and in hardened substrates. There is also a shift in the ratio between Collembola (major prey) to spiders from 1:1.3 (ungrazed areas) to 1:0.82 (grazed areas), for animals collected in pitfall traps. This may be a result of the trampling effect of the reindeer.     

Changes in erythropoiesis due to radiation or chemotherapy as studied by flow cytometric determination of peripheral blood reticulocytes

Flow cytometric determination of time dependent changes of numbers of reticulocytes in peripheral blood were investigated as a parameter for changes in erythropoiesis induced by radiation- or chemotherapy. Rats irradiated or treated with drugs (such as e.g. cyclophosphamide 100 mg/kg, vincristin 0.2 mg/kg, or mitomycin C 1.0 mg/kg) showed clear changes in erythropoietic activity. Reticulocyte numbers decreased rapidly until day 3-4 after treatment; this period was followed by a gradual increase and normal control values were seen at day 8-11. Radiation effects of doses as low 0.5 Gy could be detected in such a way. Similar studies were performed with patients with ovarian tumors treated with cis-platinum, a drug that may cause non-immune haemolysis. During prolonged treatment some patients showed increasing numbers of reticulocytes, measured at the first day of each hospitalization period, whereas leucocyte and platelet counts stayed more or less constant. Increasing numbers of reticulocytes generally indicates stimulation of erythropoietic activity of the bone marrow (due to increased blood loss); in this study increasing numbers often preceeded a decrease in hemoglobin values later on. Flow cytometric analysis of reticulocytes is therefore a potentially useful tool to detect changes in erythropoiesis, and considered more sensitive for the early recognition of patients that develop anemia, than hemoglobin measurements only.     

Cytogenetic replication studies with short thymidine pulses in bromodeoxyuridine-substituted chromosomes of different mouse cell lines

Summary In normal diploid fibroblasts of the mouse, 3T3-, SV-3T3-, and Meth A-cells, the chromosome replication patterns were studied by a bromodeoxyuridine (BrdU)-labelling technique. SV-3T3 is a subline of 3T3 transformed by SV 40 and Meth A is a permanent cell line from Balb c transformed by methylcholanthrene. The use of 1 h thymidine pulses permits high resolution of the S-phase after partial synchronization of the cells at G₁/S in an otherwise BrdU-substituted S-phase. It could be shown that the autosomal heterochromatin of the mouse (Mus musculus) starts replication during the early S-phase (R-band replication), continues while R-band chromatin finishes, and still replicates when G-band chromatin starts. The heterochromatin finishes before the majority of G-bands have been replicated. There is no fundamental difference in the course of chromosome replication between the different cell lines studied here. It is concluded that there are no obligate changes in the course of the S-phase linked to the process of transformation.     

Characterization and localization of collagens synthesized by cultured muscle cells stimulated with collagen-inducing factor from embryonic brain extracts

A low molecular weight fraction (Mr = 500-1500) was isolated by membrane and gel filtration from rat embryonic brain extract. This fraction was shown to stimulate collagen production in muscle cultures. Procollagen, intermediate collagenous proteins, and collagens of types I, III, and V were identified by analysis on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and DEAE- and Cm-cellulose chromatography and by selective degradation by pepsin, bacterial collagenase, and cyanogen bromide. Immunofluorescent staining with antisera to collagen types I, III, IV, and V of muscle cultures treated with the collagen-inducing factor revealed a large increase in staining compared to control cultures and a distinct pattern of staining on the surface of the treated myotubes.     

Genetic polymorphism of lactate dehydrogenase isoenzymes in the carp (Cyprinus carpio) apparently due to a “null allele”

As a consequence of polyploidization, the carp is endowed with three genetic loci coding for LDH in most tissues (and additional ones in liver). However, each such duplicated gene may not be functionally essential for the organism and could be eliminated. In a population survey, an electrophoretic polymorphism was detected which may best be interpreted by the assumption of a null allele, which is apparently not subject to selective pressure. Thus this originally duplicated gene would have diverged in the course of evolution without the origin of differences in function, so that one or the other of the genes is dispensable.     

Dielectric properties of hemoglobin and myoglobin. I. Influence of solvent and particle size on the dielectric dispersion

Dielectric dispersion measurements with aqueous solutions of hemoglobin and myoglobin have been performed in the frequency range from 100 kcps to 15 Mcps. The influence of preparation, particle size, and solvent conditions was studied. The results are analyzed in terms of an orientational polarization mechanism.     

CONCENTRIC LAMINATION OF GLIAL PROCESSES IN OLIGODENDROGLIOMAS

Tissues were obtained by open biopsy of a series of human intracranial neoplasms, fixed in Veronal-buffered osmium tetroxide, and embedded in Vestopal-W. In two instances in which specimens were obtained from oligodendrogliomas in regions where the tumor had infiltrated but not entirely destroyed cortical tissues, glial processes were found to be arranged in a highly organized laminar fashion. This feature was not observed in two additional oligodendrogliomas nor in other types of intracerebral neoplasms. Three types of laminar structures were recognized: (a) perikaryal sheaths composed of several layers of overlapping or concentrically orientated glial processes, (b) layers of longitudinally orientated glial processes along the outer aspect of myelinated axons, and (c) small laminated figures composed of several concentrically disposed glial processes. Spirally constituted lamellar systems were not demonstrated. These findings indicate that under certain circumstances glial cells have the capacity to form sheaths and sheath-like structures by concentric lamination of several processes, rather than by spiraling of a single process.