Stimulation of gastrin secretion from the perfused rat stomach by somatostatin antiserum

The effect of a high capacity somatostatin antiserum on antral gastrin secretion was examined in an isolated vascularly perfused rat stomach preparation. Infusion of somatostatin antiserum diluted 1:1 and 1:9 with Krebs buffer solution produced significant increases in gastrin secretion throughout the period of infusion. Neither infusion of somatostatin antiserum diluted 1:99 nor infusion of control rabbit serum had any effect on gastrin secretion. The data indicate that antral somatostatin excercises a continous restraint on gastrin secretion in the basal state.     

Critical importance of microsome concentration in mutagenesis assay with V79 Chinese hamster cells.

For optimum mutagensis in V79 Chinese hamster cells, the amount of liver postmitochondrial fraction in the assay was found to be of critical importance, depending on the chemicals being tested. Benzo[a]pyrene (BP) required lower (1-5%) concentrations of the liver 15 000 X g supernatant (S15) from methylcholanthrene pretreated rats for a maximum induction of cytotoxicity and mutagenicity, as determined by 8-azaguanine- and ouabain-resistance. A sharp peak of mutagenicity and cytotoxicity was induced by 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (7,8-diol BP) at a concentration of 1% of the S15 fraction. Little or no response was induced by these compounds with the S15 concentrations of more than 10%. Similarly, aflatoxin B1 induced a sharp peak of mutagenicity and cytotoxicity at a concentration of 2% of the liver S15 fraction from Aroclor-pretreated rats. Under the same condition, non-carcinogenic aflatoxin G2 did not induce cytotoxicity and mutagenicity. Analysis of BP metabolites by high-pressure liquid chromatography indicates that with the 30% S15 fraction, more than 80% of BP was metabolized during the first 15 min, while with the 2% S15 fraction, 7,8-diol BP increased continuously throughout the 120-min incubation period, suggesting a strong metabolic competition to rapidly remove BP and 7,8-diol BP with a high concentration of the S15. In contrast with these compounds, N-nitrosodimethylamine induced mutagenicity and cytotoxicity which increased linearly in proportion to the increasing amount of the S15 fraction from phenobarbitone- and Aroclor-pretreated rats. Various nitrosamines with different lipophilicity were examined at a high (30%) and low (2%) concentration of the S15 fraction from Aroclor-pretreated rats, in which ratios of mutation frequencies at 30% and 2% correlated inversely with lipophilicity of the compound. This result suggests that the lipid solubility of test compounds may be one factor which determines the concentration of post-mitochondrial supernatant for optimum mutagenesis.     

Regulation of growth in larvae of the crab : The effect of cyclic temperatures

Experiments were designed to demonstrate that growth is precisely regulated in crustacean larvae and that cyclic temperatures act as a perturbation on growth regulation. Newly hatched larvae were exposed to either the specific a cyclic temperature, cumulative growth was significantly inhibited. Also, the specific growth rate ( ) of larvae in the cyclic temperature regime was found to oscillate with decreasing amplitude around the of the larvae exposed to constant temperature. This oscillatory pattern has been observed in a wide variety of self-regulating systems. Evidence is presented to demonstrate that this regulatory mechanism also adapts to long-term exposure to cyclic temperatures. These findings increase our understanding of how larvae cope with and adapt to changing environmental temperatures. More significantly, the mechanism could provide a sensitive tool for estimating the effects of specific environmental disturbances on fitness.     

Distributional patterns and an additional species of thePassiflora vitifolia complex: Amazonian species diversity due to edaphically differentiated communities

Field studies in Amazonian Peru show that thePassiflora vitifolia complex, a microcosm of many larger taxa, is concentrated in Amazonia with 4 ecologically separated species. One species is restricted to seasonally inundated forests, a second to non-inundated white sand soils, a third to non-inundated lateritic soils, and the fourth mostly to non-inundated alluvial soils. A new combination is formally proposed to recognize the white sand taxon, previously regarded as a variety, as a distinct species:P. involucrata. The importance of -diversity in maintaining high Amazonian species diversity is emphasized.     

Arthopyrenia endobrya,spec. nov., eine hepaticole Flechte mit intrazellulärem Thallus aus Brasilien

Arthopyrenia endobrya from Southern Brazil is illustrated and described as a new species of lichens. The thallus is composed of filamentous green algae loosely surrounded by fungal hyphae. Both symbionts grow endophytically within the leaf cells of two species ofLejeuneaceae (Hepaticae). The algae and hyphae penetrate the cell walls of the host by means of fine perforations. The ascocarps develop between the leaves and perforate them with their apical region. The classification as a member of the genusArthopyrenia is preliminary.

     

Effects of weaning age on mortality of colony-born Macaca nemestrina

In an effort to determine empirically the proper age for separation of pigtailed macaque (Macaca nemestrina ) infants from their dams in a large domestic breeding colony, we conducted a retrospective survey of 1,592 infants. Survivorship was highest for infants not separated from their dams at all and for those separated within the first four months of life. Survivorship was poor for animals separated during or after the fifth month. Thus, not weaning or weaning early are the most acceptable management strategies in terms of mortality risk. This result is paradoxical with regard to nutritional considerations, but appears to be related to a sensitive period in social development. The relative advantages and disadvantages of various weaning ages are discussed.     

On the yolk sac of the cat

Summary The phase of primitive erythropoiesis in the feline yolk sac lasts from the 14th to the 20th day after mating. The globular nucleated primitive erythroblasts are formed extravascularly to some extent, but they can be clearly distinguished from the endoderm. They do not undergo a denucleation and are still present in the circulating blood on the 45th day. Aging primitive erythroblasts are characterized by a loss of polysomes, by the appearance of long intracytoplasmic electron-lucent channels, and by a nuclear pyknosis which can turn into a karyolysis. Definitive erythropoiesis begins around the 17th day but, even by the 19th day, it is not particularly prominent. It ends around the 45th day. It is almost exclusively intravascular. The distinction of immature primitive erythroblasts from erythroblasts of the definitive series is difficult, because it is based upon only slight differences in the heterochromatinization, in the nuclear-cytoplasmic ratio, and in the organelle content of the cells. In the definitive series, the nuclear divisions follows the law of the rhythmical halving of the nuclear volume. The cells exhibit more clearly identifiable maturation stages here, and the checkerboard nucleus is more distinct. The vascular endothelium is largely attenuated and moderately fenestrated; it lacks a distinct basement membrane. Organelle-rich adventitial cells are found in close apposition.     

Preparation of radioactive iodinated cholylhistamine for use in the radioimmunoassay of cholic acid

A major handicap in the development of simple and accurate radioimmunoassay procedures for bile acids has been the lack of a radioactive standard of high specific activity. To provide such a compound, we first synthesized cholylhistamine using the carbodiimide reaction. The hypothesized structure was confirmed by elemental analysis, thin-layer chromatography, infrared and mass spectral analysis. The cholylhistamine was then iodinated with 125I, using the choloramine-T method. The 125I-cholylhistamine was bound by antisera raised against a cholic acid-bovine serum albumin conjugate. This procedure should prove useful in preparing radioactive conjugates for all of the bile acids.     

Transfer of purified herpes virus thymidine kinase gene to cultured mouse cells.

Treatment of Ltk^?, mouse L cells deficient in thymidine kinase (tk), with Bam I restriction endonuclease cleaved DNA from herpes simplex virus-1 (HSV-1) produced tk⁺ clones with a frequency of 10^?6/2 μg of HSV-1 DNA. Untreated cells or cells treated with Eco RI restriction endonuclease fragments produced no tk+ clones under the same conditions. The thymidine kinase activities of four independently derived clones were characterized by biochemical and serological techniques. By these criteria, the tk activities were found to be identical to HSV-1 tk and different from host wildtype tk. The tk⁺ phenotype was stable over several hundred cell generations, although the rate of reversion to the tk^? phenotype, as judged by cloning efficiency in the presence of bromodeoxyuridine, was high (1–5 × 10^?3). HSV-1 DNA Bam restriction fragments were separated by gel electrophoresis, and virtually all activity, as assayed by transfection, was found to reside in a 3.4 kb fragment. Transformation efficiency with the isolated fragment is 20 fold higher per gene equivalent than with the unfractionated total Bam digest. These results prove the usefulness of transfection assays as a means for the bioassay and isolation of restriction fragments carrying specific genetic information. Cells expressing HSV-1 tk may also provide a useful model system for the detailed analysis of eucaryotic and viral gene regulation.     

The effects of different horticultural practices on the chemical flavour composition of some cabbage cultivars

Variations in the chemical flavour composition of three cultivars of cabbage were determined for plants of different horticultural histories. In some i