IN VIVO EFFECTS OF CARDIOTROPHIN-1

Cardiotrophin-1 (CT-1) is a recently discovered cytokine that was isolated based on its ability to induce cardiac myocyte hypertrophy in vitro. In this study, the effects of chronic administration of CT-1 to mice (0.5 or 2 μg by intraperitoneal injection, twice a day for 14 days) were determined. A dose-dependent increase in both the heart weight and ventricular weight to body ratios was observed in the treated groups. The body weights of the animals were unaffected. These results indicate that CT-1 can induce cardiac hypertrophy in vivo. CT-1 was not specific for the heart, however. It stimulated the growth of the liver, kidney, and spleen, and caused atrophy of the thymus. CT-1 administration also increased the platelet counts by 70%, with no change in mean platelet volume. Red blood cell counts were increased in the treated animals, and there was a concomitant increase in haemoglobin concentration. Thus, CT-1 has a broad spectrum of biological activities in vivo. This observation is consistent with previous in-vitro findings showing that the mRNA for CT-1 is expressed in several tissues, and that CT-1 can function through binding to the leukaemia inhibitory factor (LIF) receptor and signalling through the gp130 pathway.     

GROWTH OF HETEROSIGMA CARTERAE (RAPHIDOPHYCEAE) ON NITRATE AND AMMONIUM AT THREE PHOTON FLUX DENSITIES: EVIDENCE FOR N STRESS IN NITRATE-GROWING CELLS

The marine alga Heterosigma carterae Hulburt (Raphidophyta) was grown in N-limiting batch cultures using either nitrate or ammonium as the N source, at photon flux densities (PFDs) of 50, 200, and 350 μmol·m^-2·s^-1 in a 12:12 h LD cycle. Carbon content could be estimated from biovolume (μg C = 0.278 × nL; R = 0.98) but not reliably from pigment content. During exponential growth, ammonium-grown cells (in comparison with nitrate-grown cells at the same PFD) attained higher growth rates by at least 20%, contained more N, and had a lower C:N ratio, higher concentrations of intracellular free amino acids, and higher ratios of glutamine: glutamate (Gln: Glu) and asparagine: aspartate (Asn:Asp). Growth was nearly light-saturated on ammonium at 200 μmol·m^-2·s^-1 (cell-specific growth rate of 1.2 d^-1) but probably not saturated in nitrate-grown cells at 350 μmol·m^-2·s^-1. PFD did not affect Gln: Glu or Asn: Asp for a given N source. These results indicate that the nitrate-growing cells were more N-stressed than those using ammonium (which in contrast were relatively C-stressed) and that this organism would show an enhanced competitive advantage against other species when supplied with a transient supply of ammonium rather than nitrate .     

Monitoring trichloroethylene mineralization by Pseudomonas cepacia G4 PR1

To analyze the extent of mineralization of trichloroethylene (TCE) without disturbing an actively growing biofilm, a minimal growth medium was formulated that reduces the concentration of chloride ions to the extent that the chloride ions generated from TCE mineralization may be detected with a chloride-ion-specific electrode. By substituting chloride salts with phosphates and nitrates, a chloride-free minimal medium was produced that yields a specific growth rate for Pseudomonas cepacia G4 PR1 which was 93% of that in chloride-ion-containing minimal medium. Furthermore, TCE degradation by resting cell suspensions was similar in both media (85% of 75 M TCE degraded in 6 h), and complete mineralization of TCE was slightly superior in the chloride-free minimal medium (77% compared to 60% of 75 M TCE mineralized in 6 h). In addition, indole-containing, minimal-medium agar plates were developed to indicate the presence of the TCE-degrading enzyme toluene ortho-monooxygenase (fire-engine-red colonies) as well as to distinguish this enzyme from other TCE-degrading enzymes (toluene dioxygenase and toluene para-monooxygenase).     

Studies on the capacity of the cellulase of the anaerobic rumen fungus Piromonas communis P to degrade hydrogen bond-ordered cellulose

The anaerobic rumen fungus Piromonas communis, when cultured on cotton fibre as the carbon source, produces an extracellular cellulase that is capable of solubilizing crystalline hydrogen-bond-ordered cellulose, in the form of the cotton fibre, at a rate that is greater than that of any other cellulases reported in the literature hitherto. The cell-free culture fluid is also very rich in xylan-degrading enzymes. The activity towards crystalline cellulose resides in a high-molecular-mass (approximately 700–1000 kDa) component (so-called crystalline-cellulose-solubilizing component, CCSC) that comprises endo (1 4)--D-gluconase (carboxymethylcellulase), -D-glucosidase and another enzyme that appears to be important for the breakdown of hydrogen-bond-ordered cellulose. The CCSC is associated with only a small amount of the endo-(1 4)--D-glucanase (1.9%), -D-glucosidase (0.7%) and protein (0.5%) found in the crude cell-free cellulase preparation. The CCSC, unlike the bulk of the endo-(1 4)--D-glucanase and -D-glucosidase, is very strongly absorbed on the microcrystalline cellulose, Avicel.     

The summer zooplankton community at South Georgia: biomass,vertical migration and grazing

Zooplankton abundance and biomass were determined during January 1990 at two stations to the north-west of South Georgia using a Longhurst Hardy Plankton Recorder (LHPR). At both shelf and oceanic station sites, zooplankton biomass, (excluding Euphausia superba), was found to be ca. 13 g dry mass m^–2. Copepods and small euphausiids dominated the catches. These estimates are over 4 times higher than values generally reported for the Southern Ocean and may reflect firstly, the high productivity of the study area, secondly, the time of year, summer, when biomass for many species is maximal, and thirdly, the high sampling efficiency of the LHPR. Principal components analysis disclosed similarities and differences between adjacent depth strata in terms of abundance, biomass and species composition. At both stations most variability occurred in the mixed layer (0–60 m) and thermocline (60–120 m) with depth horizons below this being more homogeneous. Diel migrations were observed for most taxa with abundance increasing in the mixed layer at night. At the oceanic station, species and higher taxa belonging to the mesopelagic community were generally well spread throughout this domain and, with the exception of Pleuromamma robusta and Metridia curticauda, showed little evidence of migration. The grazing impact of the epipelagic community (copepods and small euphausiids) was estimated to remove 3–4% of the microbial standing stock day^–1 and a conservative 25% and 56% of daily primary production at the oceanic and shelf stations respectively.     

The effect of kainate on protein kinase C,GABA, and the uptake of serotonin in the rabbit retina in vivo

The purpose of this study was to investigate the effect of kainate on protein kinase C (PKC), -aminobutyrate (GABA) and serotonin uptake in the rabbit retina. Kainate when injected into the vitreous humour produces a change in the GABA immunoreactivity within 6 hours. After 3 days, remnants of the normal GABA immunoreactivity still persist and additionally astrocyte and microglia-like elements stain positively for GABA. After 7 days exposure to kainate none of the normal GABA immunoreactivity is apparent, instead a number of round-shaped elements which may be reactive astrocytes and/or microglia stain positively for GABA. During these stages kainate does not affect the PKC immunoreactivity associated with the on-bipolar cells. Six hours following kainate treatment the ability of certain GABA amacrine cells to take up exogenous serotonin is unaffected. After three days only a few of these cells can still take up exogenous serotonin and then not avidly. After seven days the GABA/serotonin amacrine cells cannot take up exogenous serotonin suggesting that all of these neurons are irreversibly damaged. One hour after treatment with kainate both calcium-dependent and-independent PKC species are translocated from the cytosolic to membrane compartments. After 5 hours and 7 days there was also evidence from the enzyme assay experiments that kainate caused the calcium-dependent and-independent PKC enzymes to be translocated but because the total enzyme activity was reduced due perhaps to down-regulation of the enzyme this was difficult to assess precisely. However, the electrophoresis/blotting experiments of tissues exposed for 5 hours (but not one hour) to kainate established clearly that , , and PKC are translocated from cytosolic and membrane compartments.     

A general-purpose system for characterizing medically important bacteria to genus level

A computer program and accompanying data matrix have been prepared for bacteria of medical interest, to assist the assignment of an unidentified bacterium to the most likely genus. The results on a set of relatively simple tests are entered. The program prints the more likely genera, followed by a list of diagnostic tables in Cowan & Steel (1974) and Buchanan & Gibbons (1974). Where available, identification matrices for further computer-assisted study, are presented. This program may be of particular help in laboratories where a wide range of bacteria have to be identified.     

Clinical implications of developments in in vitro fertilisation.

During February 1979 to December 1983, 831 infertile couples were treated by in vitro fertilisation and embryo transfer. The problems they faced included deciding on the number of oocytes to be collected at laparoscopy, the numbers to be donated or fertilised, the numbers of embryos to be transferred and frozen, and whether abnormal embryos should be used for research or discarded. The 831 patients received a total of 1530 treatment cycles. Of the 763 patients for whom complete data were available, 136 (17.8%) became pregnant. The rate of pregnancy, however, increased dramatically from 7.4% when only one embryo was transferred to 21.1% and 28.1% when two and three embryos were transferred, respectively. The chance of multiple pregnancy also increased with the number of embryos transferred, but the risk (2% for twins) was far outweighed by the relatively poor result after transferring a single embryo. Out of 40 embryos freeze-thawed, 23 survived thawing and were transferred; of these, 4 (17%) resulted in pregnancy. Thirty four transfers of donor oocyte embryos also resulted in four pregnancies (12%), but two of these ended in abortion. Neither microscopy nor any other available test can determine the potential of an oocyte to result in pregnancy, so that discarding oocytes that may look abnormal simply reduces the chances of conception--both for the patient and for any prospective recipient of donor oocyte embryos. In any case, abnormal embryos tend to die when growth is allowed to continue in vitro. Probably all oocytes harvested from a patient should be inseminated and the utilisation of the embryos decided once the number developed is known.