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.     

Steroid hormone responsiveness of a family of closely related mouse proviral elements

Regulation of the mouse sex-limited protein (Slp) gene is unusual in that hormone response is conferred by the 5′ LTR of an upstream inserted provirus, dubbed the imposon (imp1). In a search for additional genes whose regulation has been affected by retrotransposition events, we isolated two partial proviral elements by stringent screening of a mouse genomic library. One clone (imp2) contained a portion of the envelope gene and a 3′ LTR that was nearly identical to the 3′ LTR of imp1; this similarity extended to insertion into a B1 repetitive element. The second proviral clone (imp3) contained a 5′ LTR and associated coding sequences, but lacked its 3′ LTR; the LTR of imp3 differed by 12% from the imp1 sequence. To assess potential hormone response, proviral enhancer regions cloned into reporter vectors were tested in transfection. The imp2 enhancer was similar in behavior to imp1, conferring both androgen and glucocorticoid induction in one fragment context and an androgen-specific response in another. In contrast, the imp3 enhancer allowed high expression in the absence of hormone and was less responsive to steroids in general and androgen in particular. These three proviral elements define a small family of steroid responsive proviruses in the mouse genome, and at least one member has had a lasting impact on an endogenous gene's regulation. Received: 29 April 1997 / Accepted: 14 July 1997     

Mycoplasma pneumoniae Pneumonia—Experience at a Referral Center

Mycoplasma pneumoniae pneumonia is usually a benign illness, and respiratory complications and extrapulmonary manifestations occur rarely. In this series, patients admitted to a referral hospital with this disorder had unusual symptoms, signs and findings on chest roentgenograms and laboratory studies. Pneumonia was often severe and extrapulmonary manifestations were frequent, resulting in prolonged hospital stays and illnesses. Although this extreme end of the spectrum of disease caused by M pneumoniae is not representative of this type of pneumonia as seen in outpatients, it is important to realize that patients admitted to hospital with severe, complicated pneumonia frequently have unusual manifestations of a common disease.     

Blood chemistry of the common marmoset (Callithrix jacchus) maintained in an indoor-outdoor environment: Primate comparisons

Blood chemistry values were collected over a three-year period from at least 10 colony-born and 24 wild-born apparently normal common marmosets. BUN, SGOT, creatinine, calcium, phosphorus, alkaline phosphatase, protein, albumin, cholesterol, triglycerides, uric and glucose values were determined. A statistical comparison of baseline values was made between wild-born, colony-born, male and female marmosets. Also the same comparison was made between common marmosets and cotton-top tamarins, white lipped tamarins and human subjects.     

The effect of cycloheximide on Euglena gracilis phenylalanyl-tRNA synthetases

The effect of cycloheximide on the chloroplastic, cytoplasmic and mitochondrial phenylalanyltransferRNA synthetases of Euglena gracilis was studied by growing both logarithmic and stationary phase cultures in the presence of the antibiotic. Enzyme activity was measured relative to untreated control cultures. At very low concentrations of cycloheximide (1 g/ml), all three log phase enzymes showed an increase in activity of 40–50%. At slightly higher concentrations (2.5 g/ml), the phenylalanyl-tRNA synthetase activities were comparable to those of the control cultures. At a cycloheximide concentration of 5g/ml the enzyme activities from stationary phase cultures showed only very slight decreases (5–20%). The cytoplasmic and mitochondrial enzymes behaved similarly in log phase cultures at this concentration. However, the chloroplastic phenylalanyl-tRNA synthetase from log phase cultures treated with 5g/ml cycloheximide showed a marked decrease in activity (70%). A further increase in antibiotic concentration to 10g/ml resulted in significant losses of activity of all three enzymes, from both growth stages. The implications of the data with regard to identification of the site(s) of chloroplast enzyme synthesis are discussed.     

Evaluation of a new modified pediatric bubble oxygenator

A comparison was made of the S-070 Pediatric Bubble Oxygenator, which was unreliable above flow rates of approximately 1.5 L/min, with a modified S-070A, which proved to be extremely efficient to flow rates of 2.5 L/min.     

Steroid hormone receptor studies in melanoma model systems

The Transplantable B-16 melanotic melanoma carried in syngeneic C57B1/6J female mice and the Syrian hamster melanoma cell line, RPMI 3460, were utilized to determine whether steroid-hormone receptors are present in animal melanomas. In the B-16 melanoma, a cytoplasmic-estrogen receptor is detectable, but there is no evidence for androgen or progestin receptors. Some tumors contain a glucocorticoid-binding macromolecule. Sucrosedensity gradient centrifugation of cytosol after incubation with [³H]-estradiol revealed an 8S peak that was suppressed by excess radioinert diethylstilbesterol. Binding varied from 5–35 fmoles per mg cytosol protein. Scatchard analysis of [³H]-estradiol binding in cytosol yielded a single class of high-affinity binding sites; the dissociation constant is 6 × 10^?10 M. The receptor molecule is shown to be estrogen-specific by ligand competition assays. In contrast to B-16 melanoma, no estrogen, androgen, or progestin receptor can be found in the Syrian hamster melanoma cell line. However, a substantial level of specific binding is observed using [³H]-dexamethasone. Sucrose-gradient centrifugation of cytosol from this cell line after incubation with [³H]-dexamethasone revealed a 7S peak that was suppressed by excess radioinert dexamethasone. Scatchard analysis indicated a single class of high affinity sites with a dissociation constant of 2 × 10^?9 M. Binding levels from 70–610 fmoles per mg cytosol protein were observed. The Syrian hamster melanoma cells also exhibit a biological response to glucocorticoids: Dexamethasone causes both an inhibition of growth and a decrease in final-cell density in these cells.     

Modulation of autonomic neurotransmission by PGD2: Comparison with effects of other prostaglandins in anesthetized cats

Experiments with anesthetized cats were done to study possible roles of different prostaglandins (PGs) in modulating sympathetic neuroeffector transmission. We recorded contractions of the nictitating membrane (n.m.), blood flow in the carotid artery, heart rate and blood pressure, both under control conditions and while stimulating the cut cervical sympathetic nerve. Intra-carotid arterial injection (i.a.) of PGD₂ depressed sympathetic transmission to the n.m. without depressing the effects of exogenous norepinephrine (NE). In contrast, PGE₂ enhanced the effects of nerve transmission or exogenous NE on the stimulated n.m. PGI₂ had similar but shorter effects to PGE₂. PGF_2α or a stable PGH₂ analog, contracted the n.m. smooth muscle with no detected effect on nerve transmission. Carotid blood flow was increased by PGD₂, PGE₂ and PGI₂. PGD₂ and PGI₂ caused bradycardia that could be blocked by atropine. This ability of PGD₂ to modulate autonomic nerve activity is of particular interest because of recent reports that nerve tissue synthesizes PGD₂.     

Modification of cell membrane in variants of chinese hamster cells resistant to abrin

Stable and heritable variants of Chinese hamster ovary (CHO) cells which are resistant to different levels (0.1, 1.0 and 10 μg/ml) of the toxin abrin have been isolated and characterized. The frequency of resistant colonies to abrin was increased with the concentration of a chemical mutagen. There was no effect of cell density or cross-feeding on the recovery of variants. In experiments using fluorescein-labeled abrin and ricin which bind to terminal (non-sialylated) galactose residues of cell-surface oligosaccharides, parental cells exhibited strong binding toward both toxins, whereas no fluorescence was observed in the resistant clones. A fluorescein-conjugated lectin, BS II, which is specific for terminal N-acetyl- -glucosaminyl residues, did not interact with the parental cells, but did with the resistant clones. This suggests that on the surface of resistant cells the number of terminal galactosyl residues of oligosaccharide chains in glycoproteins was reduced, exposing the penultimate N-acetyl- -glucosaminyl residues. The number of available endogenous acceptor sites for galactosyl transferase in the abrin-resistant clones was directly proportional to the degree of resistance. In the presence of great excess of exogenous acceptor, the rates of galactosyl transfer were similar in all the abrin-resistant cell types tested, with levels ranging from 1.4 to 1.7 times parental cell values. Studies with tetraploid cell hybrids reveal that resistance was a recessive trait. Fluctuation analysis showed that abrin resistance occurred in CHO cell populations at a rate of 4−7 × 10⁻⁸/cell/generation. The system may serve as a new marker for quantitative mutagenesis studies.