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G Shaw

Publications and source records attributed to G Shaw.

At least 145 records · Page 8Linked to original sources
PubMed1994

Evidence for the essential role of prostaglandins for parturition in a marsupial, Macropus eugenii.

Female tammar wallabies were treated prepartum with the prostaglandin synthase inhibitor indomethacin, with or without the dopamine agonist bromocriptine, to suppress the peripartum pulses of plasma prostaglandin and prolactin. The animals were observed continuously to detect birth, and a series of blood samples taken to define the hormonal profiles before and immediately after parturition. Birth was observed in ten of twelve control animals but not in the six animals treated with indomethacin alone or the six animals treated with indomethacin and bromocriptine. Indomethacin disrupted the normal profile of PGF2 alpha metabolite 13,14-dihydro-15-keto-prostaglandin F2 alpha (PGFM) concentrations, and in the females treated with bromocriptine plus indomethacin the pulse of prolactin normally seen at parturition was completely abolished. Plasma progesterone concentrations fell slowly in treated animals, whereas in control animals they fell steeply immediately after parturition. Postpartum oestrus was delayed or absent in treated and most control animals, suggesting that the frequent blood sampling and disturbances in the peripartum period interfered with these endocrine processes. We conclude that prostaglandin is essential for normal birth. Prolactin, in the apparent absence of a prostaglandin peak, does not induce birth or rapid luteolysis. Prostaglandin release may synchronize the rapid fall in progesterone concentrations associated with birth, but in the absence of this signal, the corpus luteum undergoes a less rapid, autonomous decline.

Animals↗
PubMed1994

Distinct regulatory pathways control neurofilament expression and neurotransmitter synthesis in immortalized serotonergic neurons.

Following infection of dissociated embryonic day 13 rat medullary raphe cells with a retrovirus encoding the temperature-sensitive mutant of SV40 large T-antigen (T-ag), a neuronal cell line, RN46A, was cloned by serial dilution. At 33 degrees C, RN46A cells express nuclear T-ag immunoreactivity and divide with a doubling time of 9 hr. Undifferentiated RN46A cells express low levels of neuron-specific enolase (NSE) and low (NF-L)-and medium (NF-M)- but not high (NF-H)-molecular-weight neurofilament proteins. Under differentiation conditions, RN46A cells cease dividing, take on a neuronal morphology, and express enhanced levels of NSE and all three NF proteins. Elevation of intracellular cAMP levels increases neurofilament protein expression, whereas activators of various other intracellular second messenger systems have no effect. Differentiated RN46A cells express low-affinity nerve growth factor (NGF) receptor (p75NGFR) and are immunoreactive using an antibody that recognizes the carboxy-terminal 13 amino acids of all three trk proteins (pan-trk). Both immunoreactivities could be potentiated by treatment with brain-derived neurotrophic factor (BDNF), NGF, and adrenocorticotropic hormone, fragment 4-10 (ACTH4-10). Differentiated RN46A cells express low levels of tryptophan hydroxylase (TPH) immunoreactivity, which could be enhanced by treatment with ACTH4-10, BDNF, or NGF. Low levels of serotonin immunoreactivity are detected in differentiated RN46A cells, and this was potentiated by differentiating RN46A cells with BDNF for 8 d and 40 mM KCl for days 4-8. HPLC analysis confirmed these immunohistochemical data. RN46A cells should prove useful to elucidate intracellular mechanisms that control neurofilament assembly and 5-HT expression in differentiating raphe neurons.

Animals↗
PubMed1994

A nosocomial outbreak of Mycobacterium tuberculosis.

BACKGROUND: The national incidence of tuberculosis (TB) is increasing, and hospitals are a site of transmission. We investigated a nosocomial outbreak of TB at a 160-bed community hospital in South Carolina that highlights the central role that primary care physicians must play to control this epidemic. METHODS: We reviewed medical records to identify potential source cases. We retrospectively evaluated exposures to suspected source patients and the subsequent tuberculin reactivity of the 38 hospital employees who had a previous negative tuberculin skin test and were assigned to the ward where the outbreak began. We also evaluated the out-of-hospital contacts of TB cases. RESULTS: A review of medical records identified one patient who had died of prostate cancer and chronic cavitary pneumonia but was never in isolation nor evaluated for TB. Ward employees who worked while this patient was hospitalized had an increased risk for skin-test conversion (43% [12 of 28] vs 0% [0 of 9]; relative risk undefined; P = .02). Among employees who worked with this patient, skin-test converters worked more shifts with (median, 10.5 vs 7), dispensed more medication to (median 7 doses vs 1), and wrote more notes on (median 18 vs 5) the index patient than did nonconverters. Five of 12 of the patient's close out-of-hospital contacts had newly recognized positive tuberculin skin tests. Among 20 casual contacts, there were no new skin-test conversions. CONCLUSIONS: A high index of suspicion, prompt isolation and diagnostic testing of potentially infectious hospitalized patients, and a thorough investigation of contacts of patients with TB are needed to prevent TB transmission.

Aged↗
PubMed1993

Expression cloning of a functional glycoprotein ligand for P-selectin.

The initial adhesive interactions between circulating leukocytes and endothelia are mediated, in part, by P-selectin. We now report the expression cloning of a functional ligand for P-selectin from an HL-60 cDNA library. The predicted amino acid sequence reveals a novel mucin-like transmembrane protein. Significant binding of transfected COS cells to P-selectin requires coexpression of both the protein ligand and a fucosyltransferase. This binding is calcium dependent and can be inhibited by a neutralizing monoclonal antibody to P-selectin. Cotransfected COS cells express the ligand as a homodimer of 220 kd. A soluble ligand construct, when coexpressed with fucosyltransferase in COS cells, also mediates P-selectin binding and is immunocrossreactive with the major HL-60 glycoprotein that specifically binds P-selectin.

Amino Acid Sequence↗
PubMed1993

Recombinant bovine heart mitochondrial F1-ATPase inhibitor protein: overproduction in Escherichia coli, purification, and structural studies.

A synthetic gene coding for the inhibitor protein of bovine heart mitochondrial F1 adenosine triphosphatase was designed and cloned in Escherichia coli. Recombinant F1-ATPase inhibitor protein was overproduced in E. coli and secreted to the periplasmic space. Biologically active recombinant F1-ATPase inhibitor protein was recovered from the bacterial cells by osmotic shock and was purified to near homogeneity in a single cation-exchange chromatography step. The recombinant inhibitor protein was shown to inhibit bovine mitochondrial F1-ATPase in a pH-dependent manner, as well as Saccharomyces cerevisiae mitochondrial F1-ATPase. Thorough analysis of the amino acid sequence revealed a potential coiled-coil structure for the C-terminal portion of the protein. Experimental evidence obtained by circular dichroism analyses supports this prediction and suggests F1I to be a highly stable, mainly alpha-helical protein which displays C-terminal alpha-helical coiled-coil intermolecular interaction.

Amino Acid Sequence↗
PubMed1993

Identification of novel pleckstrin homology (PH) domains provides a hypothesis for PH domain function.

Pleckstrin homology (PH) domains are difficult to find in protein sequence databases with widely used computer programs. A simple program developed to overcome this difficulty identified three proteins containing previously unrecognized PH domains; the beta-adrenergic receptor kinase (beta-ARK), the tecA protein kinase and the insulin receptor substrate protein IRS-1. The region of beta-ARK containing the novel PH domain coincides with that previously shown to bind the beta gamma subunits of trimeric G-proteins, suggesting a general hypothesis for PH domain function. PH domains were then found at the N-termini of the tecA homologues Btk and itk. In line with the hypothesis a point mutation in the PH domain of Btk is associated with defects in signal transduction.

Amino Acid Sequence↗
PubMed1993

Rapid identification of proteins.

The amino acid composition, molecular weight, and isoelectric point of a protein can all be easily and economically determined by current electrophoretic techniques. A method which uses such easily obtained data to identify proteins is described. A computer program first corrects for systematic errors in amino acid quantitation and then searches the current sequence database for proteins with amino acid compositions similar to the corrected values, taking into account the reliability of determination of each amino acid. The program also provides the calculated molecular weight, isoelectric point, and name of each candidate, providing three further independent criteria for protein identification. The program is surprisingly sensitive, and the composition data alone, if of good quality, usually suggest the correct protein as a strong candidate if it or a close homologue is present in the database. Further studies show that proteins in the current database have amino acid compositions distinct enough to allow this method to be generally applicable. The method is a quick and cost-effective first step in protein characterization and should become increasingly useful as the number of fully sequenced proteins continues to rise.

Amino Acid Sequence↗
PubMed1993

The topology of the anchor subunit of dimethyl sulfoxide reductase of Escherichia coli.

The terminal electron transfer enzyme Me2SO reductase of Escherichia coli is a heterotrimeric enzyme composed of a membrane extrinsic catalytic dimer (DmsAB) and a membrane intrinsic polytopic anchor subunit (DmsC). The topology of DmsC has been studied using phoA (alkaline phosphatase) and blaM (beta-lactamase) gene fusions. The results of analyzing the properties of proteins produced by the fusions suggests a structure with eight transmembrane helices. Both the amino and carboxyl termini are exposed to the periplasm. The entire DmsC polypeptide is necessary to anchor DmsAB to the membrane as fusions with truncated DmsC were not functional and soluble DmsAB accumulated in the cytoplasm. A dmsC-phoA fusion in the termination codon of dmsC generated a chimeric enzyme with functional Me2SO reductase and alkaline phosphatase activity. Quantitation of the minimal inhibitory concentration of ampicillin for the dmsC-blaM fusions indicated that different transmembrane helices had differing signal sequence activity.

Alkaline Phosphatase↗
PubMed1993

Unusual neurofilament composition in cerebellar unipolar brush neurons.

During antibody screening on sections of rat cerebellum, we noticed a group of small neurons which exhibited unusual staining properties. They were robustly immunopositive for the high molecular weight neurofilament protein, moderately immunostained with antibodies to the low molecular weight neurofilament protein and alpha-internexin, but only faintly immunoreactive (in PAP sections) or essentially immunonegative (in immunofluorescent sections) with all members of a panel of antibodies directed against the middle molecular weight neurofilament protein. Since neurons generally react equally well with phosphate-independent, (antibodies to) low, middle and high molecular weight neurofilament protein, we conclude that middle molecular weight neurofilament protein is present in these cells in an unusually low relative amount. These cells are found in the granular layer and appear concentrated in the flocculus, ventral paraflocculus, and vermis, particularly in the ventral uvula and nodulus (lobules IXd and X). Previous studies performed by Hockfield defined a population of neurons of similar appearance and distribution using the monoclonal antibody Rat-302, which recognized an uncharacterized 160 kDa protein. We show here that the cells described by Hockfield are identical to those we have found and furthermore that the Rat-302 antibody specifically recognizes the dephosphorylated form of the lysine-serine-proline repeated sequences of high molecular weight neurofilament protein. These cells were studied by pre-embedding immunoelectron microscopy. The nucleus is deeply indented and shows little condensed chromatin. The cytoplasm contains scattered microtubules and a larger number of neurofilaments than expected in a small cell. There are numerous large dense core vesicles, an unusual organelle consisting of ringlet subunits, and relatively little granular endoplasmic reticulum. A thin axon and a single stout dendritic trunk emanate from the perikaryon. Although the cell body and the dendritic shaft may form either complex contacts with mossy fibres (resembling those previously termed en marron synapses) or simple symmetric synapses with small boutons containing pleomorphic vesicles, most of the synaptic relations are established on the shafts of brush-like branchlets that form at the tip of the dendrite and enter one or two glomeruli. Each branchlet forms an extraordinarily extensive asymmetric synapse with the mossy fibre rosette and the subsynaptic region shows a microfibrillar web connected to the postsynaptic density. In addition to other organelles, the branchlets contain numerous mitochondria and large dense core vesicles. Short, non-synaptic appendages with few cytoplasmic organelles emanated from the cell body, dendritic shaft and branchlets.(ABSTRACT TRUNCATED AT 400 WORDS)

Acetylcholinesterase↗
PubMed1993

Myenteric plexus neurons have developmentally acquired differences in the medium molecular weight subunit of neurofilament protein.

We have previously shown that neurofilaments in enteric neurons are immunologically distinct from those found in the central nervous system. In particular, one monoclonal antibody to the medium molecular weight neurofilament subunit, called NN18, stained the perikarya of enteric neurons very weakly, if at all, although other medium molecular weight neurofilament subunit antibodies clearly showed the presence of significant amounts of medium molecular weight neurofilament subunit. We have since located the epitope for NN18 in a peptide sequence at the carboxy terminal tail of medium molecular weight neurofilament subunit and have now looked for further neurofilament antibodies that stain the same region. We found two monoclonal antibodies, RMO1 and RMO59, that recognize the same peptide. These antibodies also show much reduced staining in myenteric neurons compared to those in the central nervous system, suggesting that this region of the medium molecular weight neurofilament subunit is specifically modified in certain cells. In the developing enteric nervous system, we found that all the antibodies show strong staining of enteric neurons in the neonatal rat, but that with NN18, RMO1, and RMO59, the staining intensity decreases during further development, and by postnatal day 21 all three demonstrate decreased or absent staining identical to the adult. These results indicate that myenteric neurons, in contrast to the brain, have a developmentally regulated modification in a specific region of the medium molecular weight neurofilament subunit, which may reflect adaptation to structural stress by myenteric neurons.

Alkaline Phosphatase↗
PubMed1993

A yeast SH2 domain.

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Amino Acid Sequence↗
PubMed1993

Demography, nursing and community care: a review of the evidence.

Demography is a most powerful influence upon social policy making. Policy making cannot be divorced from the constitution and the characteristics of the population for which it is intended. This paper commences by identifying and reviewing the most potent of those trends, and then examines the implications, first for the capacity of the community to cope with its dependents and then for the supply of nurses, before illustrating the importance of community nursing to government policies on community care.

Adult↗
PubMed1993

A neurofilament-associated kinase phosphorylates only a subset of sites in the tail of chicken midsize neurofilament protein.

Although neurofilaments are among the most highly phosphorylated proteins extant, relatively little is known about the kinases involved in their phosphorylation. The majority of the phosphates present on the two higher-molecular-mass neurofilament subunits are added to multiply repeated sequence motifs in the tail. We have examined the specificity of a neurofilament-associated kinase (NFAK) partially purified from chicken spinal cord that selectively phosphorylates the middle-molecular-mass neurofilament subunit, NF-M. Two-dimensional phosphopeptide mapping of 32P-labeled NF-M shows that, in vitro, NFAK phosphorylates a subset of peptides phosphorylated in vivo in cultured neurons. The absence of a complete complement of labeled phosphopeptides following in vitro phosphorylation, compared with phosphorylation in vivo, is not due to a lack of availability of phosphorylation sites because the same maps are obtained when enzymatically dephosphorylated NF-M is used as an in vitro substrate. Phosphopeptide maps from in vitro-phosphorylated NF-M and those from a recombinant fusion protein containing only a segment of the tail piece of chicken NF-M reveal identical labeled peptides. The fusion protein lacks a segment containing 17 KXX(S/T)P putative phosphorylation sites contained in the tail of chicken NF-M but contains a segment that includes four KSPs and a KSD site also present in the intact tail. These results suggest (a) that NFAK mediates the phosphorylation of some, but not all, potential phosphorylation sites within the tail of NF-M and (b) that multiple kinases are necessary for complete phosphorylation of the NF-M tail.

Amino Acid Sequence↗
PubMed1993

The tammar wallaby (Macropus eugenii) and the Sprague-Dawley rat: comparative anatomy and physiology of inguinoscrotal testicular descent.

Inguinoscrotal testicular descent in the tammar wallaby (Macropus eugenii) and the Sprague-Dawley rat was studied by macroscopic dissection, histological evaluation and organ culture bioassay. In 3 or 4 d Sprague-Dawley rats (n = 10) the gubernacular tip bulged free from the surrounding tissues, particularly with the application of abdominal pressure. Microscopic examination revealed that only the body of the gubernaculum is connected posteriorly to the pubic region. In contrast, macroscopic dissection of male tammar wallabies (n = 17) revealed a densely adherent distal gubernacular attachment to the inside of the fibrous scrotal bulge while the body of the gubernaculum was less firmly attached. These attachments were present throughout the process of testicular descent, illustrating an important anatomical difference between these species. The gubernaculum from the tammar wallaby pouch young was studied in organ culture with rat calcitonin gene-related peptide for 4 d. Rhythmic gubernacular contractions similar to those documented previously in the rat were not observed. The hypothesis proposed in the rat for the control of inguinoscrotal gubernacular migration via the genitofemoral nerve and its neurotransmitters may not be applicable in marsupial mammals.

Animals↗
PubMed1992

Introduction of intersubunit disulfide bonds in the membrane-distal region of the influenza hemagglutinin abolishes membrane fusion activity.

Influenza virus hemagglutinin (HA) mediates viral entry into cells by a low pH-induced membrane fusion event in endosomes. A number of structural changes occur throughout the length of HA at the pH of fusion. To probe their significance and their necessity for fusion activity, we have prepared a site-directed mutant HA containing novel intersubunit disulfide bonds designed to cross-link covalently the membrane-distal domains of the trimer. These mutations inhibited the low pH-induced conformational changes and prevented HA-mediated membrane fusion; conditions that reduced the novel disulfide bonds restored membrane fusion activity. We conclude that structural rearrangements in the membrane distal region of the HA are required for membrane fusion activity.

Animals↗
PubMed1992

Human T-lymphotropic virus type I-associated myelopathy in patients with the acquired immunodeficiency syndrome.

We describe two cases of serologically confirmed human T-lymphotropic virus type I (HTLV-I)-associated myelopathy involving North American men coinfected by the human immunodeficiency virus type 1. Our first patient suffered from a gradually progressive spastic paraparesis for 10 years prior to presenting with Kaposi's sarcoma, while our second patient developed subacutely progressive spastic paraparesis in the setting of full-blown acquired immunodeficiency syndrome. Autopsy examination of the spinal cords from these two cases revealed widespread axonal loss and demyelination principally involving the lateral columns of case no. 1 and the lateral and anterior columns of case no. 2. Vascular sclerosis and hyalinization were prominent in both cases, but in neither was there a conspicuous inflammatory component. In case no. 2, HTLV-I mRNA was not detected by in situ hybridization, but HTLV-I proviral DNA sequences were detected in this case by polymerase chain reaction. Neither case exhibited multinucleated cell (human immunodeficiency virus type 1) myelitis, vacuolar myelopathy, or evidence of HTLV-II infection by polymerase chain reaction assay.

Acquired Immunodeficiency Syndrome↗