Mu-opioid-receptor-mediated inhibition of the N-type calcium-channel current.

The predominant consequences of mu-opioid-receptor activation are depression of both neuronal activity and transmitter release. Mu-Opioid agonists have previously been observed to increase a potassium conductance and to inhibit adenylate cyclase. We now report that activation of mu-opioid receptors directly decreases the N-type calcium-channel current in a differentiated, human neuroblastoma cell line (SH-SY5Y). The coupling between the mu-opioid receptor and the calcium channel involves a pertussis toxin-sensitive G protein and is independent of changes in adenylate cyclase activity. The inhibition of the calcium-channel current is voltage dependent because it is largely overcome by strong membrane depolarization. It is not associated with changes in the kinetics of current inactivation. Therefore, the mu-receptor belongs to the superfamily of G-protein-coupled, inhibitory neurotransmitter receptors which modulate the activity of calcium and potassium channels and adenylate cyclase.     

Regulation of Escherichia coli secA mRNA translation by a secretion-responsive element.

The Escherichia coli secA gene, whose translation is responsive to the proficiency of protein export within the cell, is the second gene in a three-gene operon and is flanked by gene X and mutT. By using gene fusion and oligonucleotide-directed mutagenesis techniques, we have localized this translationally regulated site to a region at the end of gene X and the beginning of secA. This region has been shown to bind SecA protein in vitro. These studies open the way for a direct investigation of the mechanism of secA regulation and its coupling to the protein secretion capability of the cell.     

Genes newly identified as regulated by glucocorticoids in murine thymocytes

Glucocorticoids induce dramatic biochemical and morphological changes in lymphocytes through an unknown process that requires RNA and protein synthesis. In order to identify genes involved in this response, we previously isolated 11 cDNA clones from the murine WEHI-7TG thymoma cell line that correspond to mRNAs induced by glucocorticoids. We now report the isolation of two new cDNA clones whose gene expression is regulated by glucocorticoids in WEHI-7TG cells. We further characterize the two new cDNA clones, as well as those described previously, by examining the response of each of the corresponding mRNAs to glucocorticoids in murine thymocytes. With the exception of two, all cDNAs correspond to genes that are induced by glucocorticoids in murine thymocytes within 4 h of treatment. We previously identified two of the cDNAs as the mouse VL30 retrovirus-like element and the mouse homolog of chondroitin sulfate proteoglycan core protein. We have now identified four additional cDNA clones that correspond to the genes for calmodulin, mitochondrial phosphate carrier protein, immunoglobulin (Ig)-related glycoprotein (GP-70), and the 70 kilodalton autoantigen for Lupus and Graves diseases. Two other cDNA clones represent previously undescribed genes: one shares a high similarity to known sequences for the family of G-protein-coupled receptors and the other to a human placental-specific protein, PP11. Another cDNA appears to contain sequences for an unknown gene and the remnants of a mouse transposon. ETn. The remaining clones represent new, unidentified genes induced by glucocorticoids in murine thymocytes and in the WEHI-7TG cell line.     

The origin of postembryonic neuroblasts in the ventral nerve cord of Drosophila melanogaster

Embryonic and postembryonic neuroblasts in the thoracic ventral nerve cord of Drosophila melanogaster have the same origin. We have traced the development of threefold-labelled single precursor cells from the early gastrula stage to late larval stages. The technique allows in the same individual monitoring of progeny cells at embryonic stages (in vivo) and differentially staining embryonic and postembryonic progeny within the resulting neural clone at late postembryonic stages. The analysis reveals that postembryonic cells always appear together with embryonic cells in one clone. Furthermore, BrdU labelling suggests that the embryonic neuroblast itself rather than one of its progeny resumes proliferation as a postembryonic neuroblast. A second type of clone consists of embryonic progeny only.     

Phylogenetic relationships among four members of Stizostedion (Percidae) determined by mitochondrial DNA and allozyme analyses

Phylogenetic relationships among four Stizostedion species were examined using mitochondrial DNA (mtDNA) and allozyme analyses. Twenty-six allozyme loci were scored, and mtDNA variation was examined using 24 restriction endonucleases, yielding 48–57 restriction sites among the species. Genetic distance analyses show that the two North American species ( S. canadense and S. vitreum ) cluster in one group, while the two European species ( S. hciopercu and S. vogense ) form a second group. Nei's genetic distance between these two groups was 0.7 ± 0.2 for allozymes, while the corresponding mtDNA sequence divergence was 14.8 ± 2.0%, suggesting that these two groups diverged approximately 10 million years ago. Thus, these data are consistent with the hypothesis that Stizostedion colonized North America during the Pliocene.     

Structure and biological activity of crustacean gastrointestinal peptides identified with antibodies to gastrin/cholecystokinin.

Four gastrin/cholecystokinin-like peptides (G/CCK) which cross-react with a specific C-terminal gastrin/CCK antiserum have been isolated from the stomach of the marine crustacean Nephrops norvegicus. The molecular weight of the four peptides was estimated between 1000 and 2000 Da by molecular sieving. By radioimmunoassay, the cross-reactivity of these peptides with human gastrin 17-I was found to be around 0.03%. Pure peptidic fractions were recovered after four successive steps of HPLC. Amino-acid analysis suggested a similarity between the four peptides identified which may belong to a new family. A limited homology between the C-terminus of one Nephrops peptide and vertebrate G/CCK was found after sequencing. Two of the peptides exhibited secretagogue effects on crustacean isolated midgut glands. The Nephrops peptides, although structurally distinct from the vertebrate G/CCKs, appear to serve similar biological functions in crustaceans.     

Pyridostigmine enhances even if it does not normalize the growth hormone responses to growth hormone-releasing hormone in patients with Cushing's disease.

Subjects with Cushing's disease have diminished growth hormone (GH) response to growth hormone-releasing hormone (GHRH). The aim of our study was to investigate the underlying mechanism of this diminished GH response in these patients using pyridostigmine (PD), an acetylcholinesterase inhibitor, which is reported to increase GH secretion by reducing somatostatin tone. Eight subjects with untreated Cushing's disease (caused by a pituitary adenoma) and 6 control subjects received GHRH 100 micrograms in 1 ml of saline, as intravenous bolus injection 60 min after (1) placebo (2 tablets, p.o.) or (2) PD (120 mg, p.o.). After GHRH plus placebo, the GH peak (mean +/- SEM) was significantly lower in subjects with Cushing's disease (2.4 +/- 0.5 micrograms/l) compared to control subjects (25.1 +/- 1.8 micrograms/l, p less than 0.05). After GHRH plus PD, the GH peak was significantly enhanced both in subjects with Cushing's disease (7.1 +/- 2.3 micrograms/l, p less than 0.05) and in control subjects (42.3 +/- 4.3 micrograms/l, p less than 0.05). In patients with Cushing's disease, the GH response to GHRH plus PD was lower with respect to the GH response to GHRH alone in normal subjects. We conclude that hypercortisolism may cause a decrease in central cholinergic tone which is in turn hypothesized to be responsible of an enhanced somatostatin release from the hypothalamus. However, other metabolic or central nervous system alterations may act synergistically with hypercortisolism in causing GH inhibition in patients with Cushing's disease.     

Maternal serum alpha-fetoprotein screening activities of state health agencies: a survey.

Maternal serum alpha-fetoprotein (MSAFP) screening has been demonstrated to be cost-effective on a population basis and is becoming standard practice. The American Society of Human Genetics has twice published policy statements to define the essential elements of a quality screening program. The present study reviewed the impact of these policy statements on state public-health agencies with respect to regulation or provision of MSAFP screening in their jurisdictions. With a few exceptions, states have not elected to play a major role in provision or regulation of this test. There is need to address issues of funding, standards, and data collection in a collaborative effort, if policy statements on genetic services are to be translated into effective state population screening.     

In Situ Analysis of Na,K-ATPase α1- and α3-Isoform mRNAs in Aging Rat Hippocampus

Abstract: Age-related changes in the expression of Na,K-ATPase α1- and α3-isoform mRNAs were analyzed by in situ hybridization in the Fischer-344 rat hippocampus. Quantification of signal density with cRNA probes in rat hippocampus at 3 months of age showed (a) α1 content is 1.5 times higher in granule than in pyramidal cell layers, whereas α3 content shows the opposite ratio and (b) α3 label is found in large clusters related to mossy cells and basket cells and in medium clusters corresponding to interneurons within the dendritic fields of CA1–3. In the 24-month-old rats as compared with the young animals, the α1 signal is increased more than sevenfold in the dendritic fields and is not significantly changed in perikaryal layers. The α3 signal is reduced about threefold ( p < 0.0001, ANOVA, n = 6) in perikaryal layers, is almost completely absent over the interneurons, basket cells, and mossy cells, and is not significantly changed in dendritic fields. These data indicate age-related, cell- and isoform-specific alterations in pretranslational regulation of Na,K-ATPase α isoforms. The striking changes in the dendritic fields, mossy cells, and GABAergic basket cells and interneurons may constitute early and sensitive markers for age-related alterations in hippocampal function, before cell loss.