Commitment, differentiation, and diversification of avian cardiac progenitor cells.
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Animals↗
Biomedical subjects
M Gannon
Publications and source records attributed to M Gannon.
Diversification of cardiomyogenic cell lineages in vitro.
The ability of undifferentiated cardiogenic mesoderm to generate diversified myogenic phenotypes was assayed in a minimal culture system. During cardiogenesis in vivo, the anterior and posterior segments of the avian heart have distinct patterns of contractile protein gene expression when they first differentiate. To assess the potential of undifferentiated cardiogenic tissue to diversify into distinct anterior and posterior lineages prior to heart formation, cardiogenic mesoderm and endoderm were removed together from the embryo at Hamburger and Hamilton stages 4-8. Explants from each of these stages differentiated in defined medium as indicated by the expression of muscle-specific genes. However, the ability to express the atrial-specific myosin heavy chain (AMHC) mRNA was confined to posterior cardiac progenitors. Diversification was not dependent on anterior endoderm, suggesting that inductive interactions between the mesoderm and endoderm are not necessary to maintain diversified cardiac lineages after stage 4. The diversified potential of explanted cardiogenic tissue was altered with retinoic acid treatment, resulting in the activation of AMHC1 gene expression in the anterior progenitors. Anterior cardiogenic cells removed from the embryo at stage 8, when the heart begins to differentiate in vivo, are not susceptible to the alteration of diversified phenotype by retinoic acid treatment. Therefore, the potential to form distinct cardiomyogenic cell lineages is present in the anterior lateral plate mesoderm soon after gastrulation and the maturation of these lineages in a positionally dependent manner is maintained in a simple defined culture system in vitro.
Animals↗
A survey of new long-stay hospital patients in an Irish health board area.
OBJECTIVES: The aims of this study were to determine the number and rate of accumulation of new long-stay hospital patients in one of Ireland's eight health board areas, to describe their demographic and clinical features, and to assess their needs in relation to possible community placement. METHODS: Demographic and clinical information was obtained on all patients over age 17 who had been continuously hospitalized in area hospitals for more than one year and less than six years on the census day of March 1, 1992. The Community Placement Questionnaire was used to rate the patients' social functioning, problem behavior, physical disability, social contact, and needs for accommodation and day care. RESULTS: The survey identified 175 new long-stay patients, mainly middle aged to elderly. Schizophrenia was the most common psychiatric diagnosis. The bed occupancy rate for these patients was 14 per 100,000 population, and the annual accumulation rate was 2.3 per 100,000 population. CONCLUSIONS: New long-stay patients were chronically ill with significant psychiatric and social disabilities. Involuntary patients were overrepresented in the group. Two-thirds could be placed in the community if facilities were available and had sufficiently high staffing levels.
Activities of Daily Living↗
Initiation of cardiac differentiation occurs in the absence of anterior endoderm.
Anterior endoderm has been proposed to be a specific inducer of cardiac differentiation in vertebrates (reviewed in Jacobson and Sater, Development 104, 341-359, 1988). The ability of cardiogenic mesoderm to differentiate in a minimal culture system was examined using cardiac-specific gene expression as an assay. Anterior lateral plate mesoderm was explanted from chick embryos with and without associated endoderm at developmental stages from just after gastrulation (stage 4; Hamburger and Hamilton, J. Morph. 88, 49-67, 1951) to just prior to contraction (stage 9). At all stages examined, cardiogenic mesoderm expressed a profile of cardiac-specific mRNAs after two days in minimal medium independent of the presence of endoderm. Our studies indicate that endoderm is necessary for the generation of stable sarcomeric protein expression, organized myofibrils and beating tissue from stage 4-6. Subsequent to this stage, an interaction with anterior endoderm is no longer required. Examination of cardia bifida embryos from which anterior endoderm had been unilaterally removed also showed a stage-dependent effect of endoderm on beating, while cardiac gene expression and heart morphogenesis were unaffected. These results demonstrate that anterior endoderm does not induce or maintain cardiac gene expression, nor is it required for terminal differentiation. Endoderm does appear to be necessary for a short period of time between initiation of cardiac gene expression and the onset of contraction.
Animals↗
Manganese (Mn) transport across the rat blood-brain barrier: saturable and transferrin-dependent transport mechanisms.
Using a single capillary pass technique, the transport of manganese (Mn) across the rat blood-brain barrier (BBB) was characterized. Initial rate measurements (15 s) of Mn2+ [0-1000 microM] accumulation in rat brains clearly indicated saturation kinetics by both 1/v vs. 1/s plots, and plots of v vs. [s]. Common carotid injection of freshly mixed Mn2+ with transferrin at a 1:10 molar ratio did not result in a significant change in the initial rate of Mn brain levels compared with injection of Mn2+ alone. However, when Mn2+ was incubated at 25 degrees C in the presence of transferrin at a 1:10 ratio for up to 5 days prior to common carotid injection, the initial rate of Mn uptake by brain was incubation-time-dependent, increasing linearly with prolonged incubations. These findings suggest that the saturable component of divalent Mn transport into brain represents but one of the transport mechanisms for Mn across the BBB. A second transport system for Mn may occur by a transferrin-conjugated Mn transport system.
Animals↗
Methylmercury-induced alterations in excitatory amino acid transport in rat primary astrocyte cultures.
To determine whether methylmercury (MeHg) has the potential to interfere with homeostatic functions in neonatal rat cortical primary astrocyte cultures, the effects of MeHg on the uptake and efflux of both L-glutamate and D-aspartate were examined. Uptake of both of these excitatory amino acids (EAAs) was significantly (P < 0.05) reduced in the presence of MeHg concentrations as low as 10(-5) M. Efflux of both glutamate and aspartate from preloaded astrocytes was also increased by MeHg in a dose- and time-dependent fashion. Since in our earlier studies we had found that MeHg causes dose-dependent astrocytic swelling, which could have been the mechanism of the increased efflux, we examined whether blockage of conductive ion fluxes, which have been implicated in astrocytic swelling, could reverse the MeHg-induced increase in L-glutamate and D-aspartate efflux. Three compounds which inhibit the hypotonic-media-induced efflux of EAA, 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS), L-644,711 (a derivative of ethacrynic acid) and furosemide were tested at their maximal concentrations for their ability to reverse MeHg-induced EAA efflux. Only furosemide (5 mM) could sustain the reversal for the entire 120 min duration of the efflux measurement. Since hypotonic-media swelling-induced release of EAAs is inhibited by these anion inhibitors (in the following rank order: L-644,711 > SITS > furosemide), we conclude that different mechanisms account for EAA release from primary astrocyte cultures during MeHg exposure as compared to hypotonic media-induced efflux.
4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗
Beta-naphthoflavone induction of a cytochrome P-450 arachidonic acid epoxygenase in chick embryo liver distinct from the aryl hydrocarbon hydroxylase and from phenobarbital-induced arachidonate epoxygenase.
Cytochrome P-450-mediated arachidonic acid metabolism in chick embryo liver microsomes was increased by both Ah receptor-dependent (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and beta-naphthoflavone) and independent (phenobarbital) P-450 inducers. Arachidonic acid epoxides and monohydroxyeicosatetraenoic acids were increased 9-12-fold. omega-1-OH arachidonic acid was also significantly increased by TCDD and beta-naphthoflavone while omega-OH arachidonic acid, the main metabolite in uninduced livers, was decreased by all three agents. The P-450s catalyzing the enhanced arachidonate metabolism in beta-naphthoflavone- and phenobarbital-treated liver were investigated in reconstituted systems containing wholly or partially purified P-450s. beta-Naphthoflavone induced formation of a 55-kDa P-450 selective for arachidonate metabolism and for epoxygenation in particular. This P-450 was purified (beta NFAA). It was found to be distinct from a 54.5-kDa beta-naphthoflavone-induced P-450 catalyzing aryl hydrocarbon hydroxylase and 7-ethoxyresorufin deethylase (designated NF1). Mean turnover numbers for arachidonate epoxygenase, aryl hydrocarbon hydroxylase, and 7-ethoxyresorufin deethylase were 11.2, 0.56, and 0.04, respectively, for reconstituted beta NFAA and 0.33, 11.8, and 2.4 for NF1. beta NFAA and NF1 also differed in chromatography elution characteristics and N-terminal amino acid sequences. Both were low spin, with carbon monoxide binding peaks at 448 nm. The phenobarbital-induced arachidonate epoxygenation was catalyzed by P-450 fractions containing the main 48- and 49-kDa phenobarbital-induced P-450s; fractions in which the 49-kDa P-450 predominated were the most active. Turnover numbers for arachidonic acid epoxygenation were not correlated with those for aminopyrine demethylation or 7-ethoxycoumarin deethylation for P-450s from phenobarbital-treated livers or with aryl hydrocarbon hydroxylase, 7-ethoxyresorufin deethylase, or 7-ethoxycoumarin deethylase for P-450s from beta-naphthoflavone-treated livers. Also, different P-450s catalyzed the epoxygenation and the omega-hydroxylation of arachidonic acid in both beta-naphthoflavone- and phenobarbital-treated livers. The findings support a physiologic role for P-450-induced arachidonate metabolism and provide a basis for a possible link between TCDD's induction of P-450 and alterations of cellular homeostasis.
Amino Acid Sequence↗
Interactions of trimethyl tin (TMT) with rat primary astrocyte cultures: altered uptake and efflux of rubidium, L-glutamate and D-aspartate.
Studies were undertaken to assess the effects of trimethyl tin (TMT) on metabolic functions in primary neonatal rat cultured astrocytes. Concentrations as low as 10(-5) M TMT significantly inhibited the initial rate (1 min) of uptake of 86RbCl, used as a tracer for K+. TMT also markedly inhibited the initial rate (1 min) of Na(+)-dependent uptake of L-[3H]glutamate and D-[3H]aspartate, and stimulated the release of intracellular 86Rb+, -[3H]glutamate and D-[3H]aspartate in a dose-dependent fashion. These observations support the hypothesis that the astrocyte plasma membrane is potentially an important target for TMT's toxic effect and specifically that small concentrations of this organometal can inhibit the ability of astrocytes to maintain a transmembrane K+ gradient. This would be expected to compromise the ability of astrocytes to control extracellular K+ either by spatial buffering or active uptake, and exacerbate on-going swelling. Increased levels of glutamate and aspartate in the extracellular fluid upon release from astrocytes may play an important role in TMT neurotoxicity.
Animals↗
Transforming growth factor-beta 1 acts cooperatively with sodium n-butyrate to induce differentiation of normal human keratinocytes.
Growth factors with established biological activity toward cultured normal human epidermal keratinocytes (NHEKs) (e.g., transforming growth factor-beta, TGF-beta; retinoic acid, RA) initiate programmed changes in cellular maturation which differ with regard to the specific differentiation pathway (normal or abnormal) analyzed. Sodium butyrate (NaB) initiates one form of epidermal differentiation leading to enhanced cornified envelope (CE) formation which involves abrogation of the normally inhibitory effect of RA on NHEK maturation. NaB also induces TGF-beta mRNA in the maturing suprabasal compartment, suggesting that TGF-beta may play a role in NaB-initiated NHEK differentiation. Treatment with TGF-beta 1 alone, however, only marginally increased (by twofold) the number of detergent-resistant CEs compared to control NHEKs and did not alter the prevalence of fully mature enucleated CEs. TGF-beta 1 was quite effective in inducing significant levels of CE expression when used simultaneously with suboptimal concentrations of NaB. The cooperative action of suboptimal NaB and TGF-beta 1 generated numbers of CEs which, in fact, exceeded the incidence of mature CEs formed in response to optimal levels of NaB alone. Neutralizing antibodies to TGF-beta, moreover, effectively reduced the incidence of CE formation in cultures treated with optimal NaB concentrations, further implicating endogenous TGF-beta activity in the NaB-initiated NHEK differentiation model. It is suggested, therefore, that within the NaB-induced pathway of NHEK differentiation, TGF-beta can positively modulate expression of the differentiated phenotype but alone is insufficient for generation of mature CEs.
Butyrates↗
Manganese uptake and efflux in cultured rat astrocytes.
Astrocytes play a central role in manganese (Mn) regulation in the CNS. Using primary astrocyte cultures from neonatal rat brains, these studies demonstrate a specific high-affinity transport system for Mn2+. Saturation kinetics are clearly indicated by both 1/v versus 1/s plots (Km = 0.30 +/- 0.03 microM; Vmax = 0.30 +/- 0.02 nmol/mg of protein/min) and plots of v versus [s]. Several divalent cations (Co2+, Zn2+, and Pb2+) failed to inhibit the initial rate of 54Mn2+ uptake. In contrast, extracellular Ca2+ at 10 microM decreased 54Mn2+ uptake. Exchange with extracellular Mn2+ was not obligatory for the efflux of 54Mn2+ into extracellular medium because efflux occurred into Mn(2+)-free extracellular medium, but efflux of 54Mn2+ was enhanced when astrocytes were equilibrated in the presence of unlabeled Mn2+. Efflux of 54Mn2+ was biphasic with both a rapid and a slow component. Efflux was most rapid during the first 10 min of incubation, with 27.5 +/- 2.2% of 54Mn2+ transported extracellularly, and 37.2 +/- 1.2% of preloaded 54Mn2+ was retained by the astrocytes at 120 min. These studies show, for the first time, that mammalian astrocytes can transport Mn via a specific transport system.
Animals↗
Arachidonic acid metabolism by dioxin-induced cytochrome P-450: a new hypothesis on the role of P-450 in dioxin toxicity.
Dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD) is a highly potent inducer of cytochrome P-450. The role of the induced P-450 in TCDD toxicity has been obscure as P-450 neither detoxifies TCDD nor activates it to genotoxic or cytotoxic metabolites. We show, using a chick embryo model, that TCDD causes major increases in the NADPH dependent metabolism of arachidonic acid (AA), a predominant cell membrane fatty acid, that it does so with extremely high potency (ED50, 6.3 pmol per egg) and that this metabolism is catalyzed by TCDD-induced cytochrome P-450 species. Thus, TCDD treatment increased by six to ten fold the P-450 mediated hepatic microsomal metabolism of AA to epoxides and monohydroxyeicosatetraenoic acids, products whose diverse biological activities suggest links to TCDD's toxic effects. In contrast only x and x-1 hydroxy AA, inactive products, were significantly formed by the controls. These findings open a new perspective on how P-450 induction could be related to the diverse toxic effects of TCDD. They lead to the novel hypothesis that TCDD-induced cytochrome P-450 metabolizes an endogenous fatty acid to reactive products that in turn mediate or modulate varied manifestations of TCDD toxicity.
Animals↗
Cutaneous Mycobacterium malmoense infection in an immunocompromised patient.
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Female↗
Hepatitis B in psychiatric institutions.
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Hepatitis B↗
Which children fail hearing tests?
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Child↗
High-dose naltrexone therapy and dietary counseling for obesity.
There is considerable evidence that antagonism of the endogenous opioids will suppress food intake in a variety of animal species. The authors report a double-blind, placebo-controlled trial of the long-acting, orally active narcotic antagonist naltrexone in the promotion of weight loss in obese male subjects who were also undergoing dietary counseling for weight reduction. Subjects received medication (naltrexone, 300 mg/day or placebo) for 8 weeks following an initial 2-week single-blind placebo phase. The results failed to demonstrate an advantage for the active drug. However, the naltrexone was associated with hepatotoxicity when used at this dosage in this population.
Adult↗
The effect of naloxone on nocturnal food intake in female and male rats.
Previous studies have shown that estradiol and progesterone can alter the response of female rats to naloxone. For example, ovariectomized rats receiving estradiol were found to be less sensitive to the anorexic effect of naloxone than ovariectomized rats receiving oil (vehicle) or progesterone. In the present paper, we evaluated the effect of naloxone on nocturnal food intake in female rats during each stage of the estrous cycle to determine whether changing levels of gonadal hormones in intact female rats would affect their response to naloxone. To evaluate the role testosterone might play in modulating the male rat's feeding response to naloxone we studied the effect of peripherally administered naloxone (0.1, 1.0 and 10 mg/kg) on nocturnal food intake of intact, castrate and castrate + testosterone propionate male rats. During late metestrus, diestrus and proestrus, female rats decreased nocturnal food intake following the administration of naloxone (1.0 and 10 mg/kg) SC (p less than 0.05). During estrus, female rats failed to decrease food intake following any of the doses of naloxone administered. The male rat's response to naloxone does not appear to be altered by the presence or absence of testosterone. Thus, the level of estradiol and progesterone at different stages of the estrous cycle may affect the female rat's response to the satiety effect of naloxone.
Animals↗