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Biomedical subjects

A Morgan

Publications and source records attributed to A Morgan.

At least 109 records · Page 6Linked to original sources
PubMed1995

Ca2+ and secretory-vesicle dynamics.

Exocytosis in neurones and neuroendocrine cells is triggered by an increase in the cytosolic concentration of Ca2+, and is followed by endocytotic membrane retrieval. Electrophysiological studies have characterized the nature of the Ca2+ signal that is required for exocytosis, and have defined the Ca(2+)-dependent steps in exocytotic and endocytotic vesicle cycling. In parallel, biochemical approaches have led to the discovery of a range of proteins that appears to function in synaptic- and secretory-vesicle dynamics. The nature of the Ca(2+)-binding proteins, and how they interact with the identified components of the exocytotic and endocytotic machinery, remain key unresolved issues. However, it is apparent that exocytosis involves multiple Ca(2+)-binding proteins with different affinities, and that the Ca2+ sensor involved in the final membrane-fusion step has different affinities for Ca2+ in synapses and neuroendocrine cells.

Animals↗
PubMed1995

Preliminary data from investigations of the in vivo biopersistence of three experimental glass fibres of varying chemical composition.

The durability of three experimental glass fibres (X7753, X7484, and X7779) was investigated in vivo. These fibres had in vitro dissolution rates of 600, 150, and 2 ng cm-2 hour-1, respectively. Three groups of female Fischer-344 rats were intratracheally instilled with a 1.2 mg suspension of one of each of the fibre types. All fibres had previously been neutron activated, to produce radioactive 24Na within the glass, which served as a radiotracer. At 2 days post instillation (PI) about 1 x 10(6) glass fibres were within the pulmonary region of the lung. Animals were killed at various time points from 2 to 360 days PI. Fibres were recovered from the animal lungs by hypochlorite digestion. The retention and morphometry of these fibres was investigated, and preliminary results are presented. After 360 days in the lung, the number of X7753 and X7484 fibres fell respectively to 10% and 50% of those present at 2 days PI. There was no detectable reduction in the number of X7779 fibres in the lung over this period. Morphometric analyses demonstrated a 53% and 22% reduction in the mean length of the X7753 and X7484 fibres, after 360 days in the lung. Reduction in diameter was apparent after only 28 days for the these fibre types. No change in the mean size of the X7779 fibres was observed during the study. The fibre morphometry data suggested that short fibres dissolved at a slower rate than long fibres. In general the in vivo fibre retention and morphometry data reflected the measured in vitro dissolution rate.

Animals↗
PubMed1995

Is NSF a fusion protein?

N-ethylmaleimide-sensitive fusion protein (NSF) is an ATPase required for vesicular transport throughout the constitutive secretory and endocytic pathways. Recently, NSF has also been implicated in regulated exocytosis in synapses--based on SNAP-mediated binding in vitro to a complex of neurotoxin substrates (termed 'SNAREs'). This work has generated an hypothesis in which the interaction of SNAREs (SNAP receptors) on the vesicle membrane with those on the target membrane forms a docking complex to which SNAPs bind, thus allowing NSF to bind and elicit membrane fusion. However, current evidence supports an earlier, pre-fusion role for NSF. We speculate that this role may be as a molecular chaperone for the membrane docking/fusion machinery.

Journal Article↗
PubMed1995

Is early separation anxiety a specific precursor of panic disorder-agoraphobia? A community study.

The present study aimed to examine memories of early separation anxiety symptoms in a community sample of women at heightened risk to neurotic disorder. The chief finding was that subjects with a lifetime history of panic disorder-agoraphobia (PD-Ag) returned statistically higher scores on a retrospective measure of early separation anxiety compared to subjects with either generalized anxiety or other phobic disorders, a result which was not accounted for by differences in neuroticism or General Health Questionnaire scores. Although limited by its retrospective design and the problem of co-morbidity in subclassifying the anxiety disorders, the present study does provide added support for the hypothesis--endorsed by DSM-III-R--that there is a developmental link between early separation anxiety and panic disorder.

Adult↗
PubMed1995

Distinct effects of alpha-SNAP, 14-3-3 proteins, and calmodulin on priming and triggering of regulated exocytosis.

We have used stage-specific assays for MgATP-dependent priming and for Ca(2+)-activated triggering in the absence of free MgATP to examine the effects of alpha-SNAP, 14-3-3 proteins and calmodulin on regulated exocytosis in permeabilized adrenal chromaffin cells. All three proteins lead to a Ca(2+)-dependent increase in catecholamine secretion. Both alpha-SNAP and 14-3-3 proteins stimulated in a priming but not in a triggering assay. In contrast, calmodulin was stimulatory in triggering but not priming. The effects of alpha-SNAP and 14-3-3 proteins were likely to be due to distinct mechanisms of action since they differed in Ca(2+)-dependency, time course and extent of stimulation and their effects were additive. alpha-SNAP and 14-3-3 proteins did not appear to exert their priming action through changes in synthesis of phosphatidylinositol (4,5) bisphosphate. The data show that these three proteins have distinct stage-specific actions on exocytosis and indicate that alpha-SNAP acts in an early MgATP-requiring stage and not in the late Ca(2+)-triggered steps immediately prior to membrane fusion as previously suggested.

14-3-3 Proteins↗
PubMed1995

The N-terminal end of the CH2 domain of chimeric human IgG1 anti-HLA-DR is necessary for C1q, Fc gamma RI and Fc gamma RIII binding.

We have found that amino acid residues necessary for C1q and Fc gamma R binding of human IgG1 are located in the N-terminal region of the CH2 domain, residues 231-238, using a matched set of engineered antibodies based on the anti-HLA-DR antibody L243. Changing the leucine 235 in the CH2 region of IgG3 and IgG4 to glutamic acid was already known to abolish Fc gamma RI binding. We have confirmed this for IgG1 and also found a concomitant abolition of human complement lysis with retention of Fc gamma RIII-mediated function. Changing the glycine at 237 to alanine of IgG1 also abolished Fc gamma RI binding and reduced human complement lysis and Fc gamma RIII-mediated function. Exchanging the whole region 233-236 with the sequence found in human IgG2, abolished Fc gamma RI binding and human complement lysis and reduced Fc gamma RIII-mediated function of IgG1. In contrast, a change in the previously described C1q-binding motif, from lysine at 320 to alanine, had no effect on IgG1-mediated complement lysis.

Amino Acids↗
PubMed1995

Exocytosis.

Exocytosis is the fusion of secretory vesicles with the plasma membrane and results in the discharge of vesicle content into the extracellular space and the incorporation of new proteins and lipids into the plasma membrane. Exocytosis can be constitutive (all cells) or regulated (specialized cells such as neurons, endocrine and exocrine cells). Regulated exocytosis is usually, but not always, triggered by an increase in the cytosolic free Ca2+ concentration. In neurons and endocrine cells, a small proportion of regulated secretory vesicles are ready to fuse with the plasma membrane in response to cell stimulation, but the majority are kept in reserve for subsequent stimulation by linkage to a filamentous network of synapsins (in neurons) or actin (in endocrine cells). Regulated exocytosis varies greatly in kinetics and Ca2+ dependency between cell types. It is likely that several different Ca(2+)-binding proteins are involved in regulated exocytosis, with synaptotagmin apparently essential for fast exocytosis at synapses. GTP-binding proteins of both the monomeric and heterotrimeric forms are involved in exocytosis, although their precise role is unclear. Intense current interest focuses on the idea that the molecular mechanism of vesicle docking and fusion is conserved from yeast to mammalian brain. The SNARE hypothesis postulates that vesicle SNAREs (synaptobrevin and homologues) mediate docking by binding to target SNAREs (syntaxin/SNAP-25 and homologues), whereupon SNAPs and NSF bind to elicit membrane fusion.

Animals↗
PubMed1994

The ATPase activity of N-ethylmaleimide-sensitive fusion protein (NSF) is regulated by soluble NSF attachment proteins.

N-Ethylmaleimide-sensitive fusion protein (NSF) is an ATPase required in multiple stages of the secretory and endocytic pathways. NSF requires other proteins for its action in vesicular transport including the soluble NSF attachment proteins (SNAPs), which act to bind NSF to integral membrane proteins. We have investigated the ATPase activity of NSF and its modulation by alpha- and gamma-SNAPs using His6-tagged recombinant proteins. His6-NSF possessed ATPase activity, which was enhanced in a dose-dependent manner by immobilized (i.e. plastic-adsorbed) but not soluble His6-tagged SNAPs. NSF displayed complex enzyme kinetics consistent with the possession of two ATPase domains with different affinities for ATP. SNAPs apparently enhanced NSF ATPase activity primarily by decreasing the Km of its low affinity site 100-fold. In vivo this effect would be predicted to sensitize the low affinity site to physiological ATP concentrations. Thus SNAPs could act as a molecular switch by "turning on" the normally dormant low affinity ATPase site of NSF.

Adenosine Triphosphatases↗
PubMed1994

Characterization of 14-3-3 proteins in adrenal chromaffin cells and demonstration of isoform-specific phospholipid binding.

Isoform-specific antisera were used to examine which 14-3-3 isoforms were present in bovine adrenal chromaffin cells. The eta, tau and sigma isoforms were not detectable, and the epsilon isoform was present at only low levels. 14-3-3 isoforms were readily detected with antisera against the beta, gamma and zeta isoforms. The latter isoforms were found to leak from digitonin-permeabilized chromaffin cells, as expected for cytosolic proteins, but a proportion of each isoform was retained. In subcellular fractionation studies isoforms recognized by the beta and zeta antisera were found in the cytosol and Triton-insoluble cytoskeletal fractions, while the gamma isoform was found in cytosol and also in microsomal and chromaffin granule membrane fractions. The gamma 14-3-3 protein associated with granule membranes was partially removed by a high-salt/carbonate wash, and the membranes could bind further gamma from cytosol or from a purified brain 14-3-3 protein mixture. The binding of gamma 14-3-3 was not Ca(2+)-dependent, nor was it affected by phorbol ester, GTP analogues or cyclic AMP. Using pure phospholipid vesicles it was found that gamma and also epsilon 14-3-3 proteins bound directly to phospholipids. Little binding of brain beta, eta or zeta to phospholipid vesicles was detected. Brain 14-3-3 proteins were also able to aggregate phospholipid vesicles. Recombinant 14-3-3 isoforms (tau and the Xenopus protein) were able to stimulate Ca(2+)-dependent exocytosis in digitonin-permeabilized chromaffin cells. The Xenopus proteins lacks part of the extreme N-terminus, indicating that this domain is not essential for function in exocytosis.

14-3-3 Proteins↗
PubMed1994

Differential effect of isotype on efficacy of anti-tumor necrosis factor alpha chimeric antibodies in experimental septic shock.

Immune complexes containing human gamma (g)1 or murine g2a antibodies generate secondary effector mechanisms via Fc receptor binding or complement activation, whereas those containing human g4 or murine g1 antibodies generally do not. Therefore, isotype selection of therapeutic antibodies may have important clinical consequences. In a rabbit model of human tumor necrosis factor (rhuTNF)-induced pyrexia, a murine/human chimeric g4 anti-human TNF-alpha monoclonal antibody (mAb) (cCB0011) showed a dose-dependent inhibition of pyrexia, whereas a g1 isotype variant of the same mAb gave a marked pyrexia that was seen at all doses indicative of an immune complex-mediated response. To investigate whether isotype difference could influence mAb efficacy in pathological disease states, hamster/murine chimeric g1 and g2a anti-murine TNF-alpha mAbs (TN3g1, TN3g2a) were studied in experimental shock in mice and rats. In lipopolysaccharide-induced shock in mice, treatment with TN3g1 mAb at 30 and 3 mg/kg resulted in 90% survival by 72 h (p < or = 0.004), and prolonged survival to 45 h (p < or = 0.05), respectively, compared with 100% mortality by 27 h in controls. In contrast, a g2a isotype variant of the same mAb (30 mg/kg) resulted in only 10% survival by 72 h (p < or = 0.05). In a neutropenic sepsis model in rats there was greater survival in animals receiving the g1 isotype of TN3 compared with g2a isotype variant (70 vs. 27%; p < or = 0.005) with 100% mortality in the controls. These differences were not due to the pharmacokinetic profiles of the mAbs. In models of experimental shock antibody isotype can affect outcome with inactive isotypes (human g4 and murine g1) being more efficacious than active isotypes (human g1 and murine g2a).

Animals↗
PubMed1994

Early recognition of neonatal abdominal wall necrotizing fasciitis.

Necrotizing fasciitis (NF) of the abdominal wall occurring in newborns is associated with a 50% mortality rate. Improved survival requires early diagnosis followed by aggressive surgical débridement. During a 10-year period, we treated 7 infants who developed NF. During the same period, 32 infants were admitted with omphalitis that did not progress to NF. The patients with omphalitis and those with NF were compared. Tachycardia, abnormal white blood cell counts, induration, and violaceous skin discoloration were seen exclusively in the NF patients. Polymicrobial infections were documented in 28% of the omphalitis patients and 86% of the NF patients. All omphalitis patients survived, whereas 5 of 7 (71%) NF patients died. Adjuvant hyperbaric oxygen therapy was used for 4 infants with NF, 2 of whom survived (50%). NF is a highly morbid disease, that can be distinguished from other infant abdominal wall infections by the skin changes, white blood cell counts, heart rate, and microbiologic results. Prompt diagnosis of NF improves survival when combined with aggressive surgical débridement.

Abdominal Muscles↗
PubMed1994

Does parent training with young noncompliant children have long-term effects?

The current study was a long-term follow-up (approx. 14 yr following treatment) of 26 late adolescents/young adults (17 yr and older) who had participated in parent training with their mothers when they were young (2-7 yr old) noncompliant children. Parent training, consisting of teaching mothers to use attends and rewards for appropriate behavior, clear commands and time-out, had reduced deviant behavior and increased compliance immediately following treatment. At this follow-up, these individuals were compared to a matched community sample on various measures of delinquency, emotional adjustment, academic progress and relationship with parents. No differences emerged between the two groups on any of the measures, suggesting that noncompliant children who participated in parent training during their early years are functioning as well as nonclinic individuals as they move into adulthood.

Adult↗
PubMed1994

Duplex scan surveillance of infrainguinal prosthetic bypass grafts.

PURPOSE: Surveillance protocols of infrainguinal vein bypass grafts have almost universal acceptance. To date corresponding studies of prosthetic grafts have not been carried out. We have performed a prospective 4-year duplex scan follow-up on polytetrafluoroethylene grafts to assess the usefulness of a surveillance program of prosthetic bypass grafts in preventing graft failure. METHODS: Over 4 years 69 infrainguinal polytetrafluoroethylene grafts in 56 patients were studied at six monthly intervals by our vascular laboratory. Full duplex scan mapping of the grafts and inflow and outflow arteries and standard ankle pressure measurements were performed. A midgraft peak flow velocity was also measured. RESULTS: Over 4 years 27 (39.1%) grafts occluded without any predictive changes in the preceding duplex scan examination. Of the 42 (60.9%) grafts that remained patent, only four developed stenoses (three at the proximal anastomosis and one at the distal anastomosis) that were amenable to intervention. Changes in ankle pressures or midgraft flow velocity did not predict failure. CONCLUSIONS: The low yield of remediable disease does not justify the cost of duplex scan surveillance of infrainguinal prosthetic bypass grafts.

Aged↗
PubMed1994

Antiprogesterone (RU486) effects on metalloproteinase inhibitor activity in human and rat granulosa cells.

OBJECTIVE: To determine if granulosa cells are a source of metalloproteinase inhibitor activity and whether P regulates this activity. DESIGN: Inhibitor activity was measured in media from human and rat granulosa cells cultured with the antiprogesterone mifepristone (RU486). Human granulosa cells were obtained at the time of oocyte retrieval from gonadotropin-stimulated patients after hCG administration. Rat cells were collected from gonadotropin-primed animals before the LH surge. Human and rat cells were cultured for 24 hours in the absence or presence of LH (100 ng/mL or 3.3 nmol/L) and/or RU486 (5 microM or 50 microM). Inhibitor activity and P were measured in the media. SETTING: Reproductive Endocrinology Laboratories, University of Kentucky. RESULTS: Media from human granulosa cells contained metalloproteinase inhibitor activity and the addition of LH did not change this activity. RU486 at 50 microM decreased inhibitor activity in cells cultured in the absence or presence of LH (0.59 +/- 0.12- and 0.24 +/- 0.18-fold change, respectively, versus control cultures; mean +/- SEM). In rat granulosa cells, inhibitor activity increased with LH treatment (1.97 +/- 0.12-fold change). RU486 decreased the activity present in cells cultured in the presence of LH. Progesterone production was stimulated by LH in both human and rat granulosa cells (3.71 +/- 0.90- and 7.18 +/- 0.24-fold change, respectively). In the human cells, RU486 inhibited P production whereas RU486 stimulated P production in the rat cells. CONCLUSIONS: These findings demonstrate for the first time that human granulosa cells are a source of metalloproteinase inhibitor activity. The decrease in granulosa cell-derived inhibitor activity by RU486 suggests that P stimulates inhibitor activity. Thus, P may regulate proteolysis associated with follicular rupture via its ability to stimulate granulosa cell production of metalloproteinase inhibitors. Differences in P production between the human and rat cells may be due to differences in hormonal stimulation regimens (i.e., hCG exposure).

Animals↗
PubMed1994

Modification of flower color in florist's chrysanthemum: production of a white-flowering variety through molecular genetics.

Chimeric chalcone synthase (CHS) constructs were prepared in both anti-sense and sense orientations, and introduced into the chrysanthemum cultivar Moneymaker, along with a T-DNA vector lacking a CHS construct. For both the anti-sense and sense constructs, the majority of the plants produced pink flowers typical of Moneymaker itself. Of 133 sense and 83 anti-sense transgenic individuals 3 of each set produced fully white or very pale pink flowers. No white-flowering transgenic plants were obtained in control transformations. The white flowers were found to accumulate higher levels of chalcone synthase precursors and to have reduced levels of chalcone synthase message. A small-scale field trial was performed to evaluate the stability of the phenotype throughout a series of vegetative propagation steps and during plant growth. The white-flowering trait was maintained well through vegetative propagation; however, during growth of individual white-flowering plants, some pink color was found in some flowers. At one site 2% of the white-flowering plants produced a few pink flowers; at two other sites, as many as 10-12% of the plants produced pale pink flowers.

Acyltransferases↗