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Biomedical subjects

R Morrison

Publications and source records attributed to R Morrison.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effect of cell swelling on membrane and cytoplasmic distribution of pICln.

pICln is found ubiquitously in mammalian cells and is postulated to play a critical role in cell volume regulation. Mutagenesis studies led to the proposal that pICln is a swelling-activated anion channel. However, recent studies in Madin-Darby canine kidney cells and endothelial cells have shown that the protein is localized primarily to the cytoplasm. It has therefore been postulated that activation involves reversible translocation of pICln from the cytoplasm and insertion into the plasma membrane. We tested this hypothesis using several different approaches. Fractionation of C6 glioma cells into plasma membrane- and cytoplasm-containing fractions demonstrated that approximately 90% of the recovered pICln was confined to the cytosol. Swelling had no effect on the relative amount of protein present in the plasma membrane fraction. Immunofluorescence microscopy revealed that pICln is localized primarily, if not exclusively, to the cytoplasm of swollen and nonswollen cells. Similarly, transfection of cells with a green fluorescent protein-labeled pICln construct failed to reveal any membrane localization of the protein. These findings do not support the hypothesis that pICln is a volume regulatory anion channel activated by swelling-induced membrane insertion.

Animals↗
PubMed1997

Characterization of volume-sensitive organic osmolyte efflux and anion current in Xenopus oocytes.

Cell swelling activates an outwardly rectifying anion current in numerous mammalian cell types. An extensive body of evidence indicates that the channel responsible for this current is the major pathway for volume regulatory organic osmolyte loss. Cell swelling also activates an outwardly rectifying anion current in Xenopus oocytes. Unlike mammalian cells, oocytes allow the direct study of both swelling-activated anion current and organic osmolyte efflux under nearly identical experimental conditions. We therefore exploited the unique properties of oocytes in order to examine further the relationship between anion channel activity and swelling-activated organic osmolyte transport. Swelling-activated anion current and organic osmolyte efflux were studied in parallel in batches of oocytes obtained from single frogs. The magnitude of swelling-activated anion current and organic osmolyte efflux exhibited a positive linear correlation. In addition, the two processes had similar pharmacological characteristics and activation, rundown and reactivation kinetics. The present study provides further strong support for the concept that the channel responsible for swelling-activated Cl- efflux and the outwardly rectifying anion conductance is also the major pathway by which organic osmolytes are lost from vertebrate cells during regulatory volume decrease.

Animals↗
PubMed1997

The novel chemokine mob-1: involvement in adult respiratory distress syndrome.

BACKGROUND: Using differential display reverse transcriptase-polymerase chain reaction we have recently identified mob-1, the novel rat homologue of the human alpha-chemokine IP-10, as a highly inducible gene in adult respiratory distress syndrome (ARDS) lungs. The present study aimed to further implicate mob-1 in the pathogenesis of ARDS. METHODS: Pulmonary mob-1 mRNA up-regulation was confirmed by Northern blot analysis in three different rat models of ARDS-like lung injury and localized to pulmonary macrophages by using in situ hybridization. Also, Escherichia coli-derived recombinant mob-1 (rmob-1) was tested for its properties in relationship to lung injury. RESULTS: In vivo, intratracheal injection of rmob-1 (50 micrograms/rat) induced pulmonary leukosequestration (myeloperoxidase +93% +/- 8% versus control, p < 0.05) with preferential accumulation of neutrophils in bronchoalveolar lavage fluid (36.0% +/- 1.0% versus 0.1% +/- 0.1% in controls, p < 0.01). In vitro, transwell migration studies demonstrated chemotactic activity of rmob-1 (50 to 100 ng/ml) toward human monocytes (+151% +/- 34% versus rmob-1 vehicle, p < 0.01) and only weak chemotaxis for human neutrophils (+15% +/- 0% versus rmob-1 vehicle, p < 0.01). Utilizing a rat aortic ring model ex vivo, rmob-1 at 100 ng/ml exerted a very potent inhibitory effect on angiogenesis (-78.7% +/- 6.3% versus rmob-1 vehicle, p < 0.01), a major component of the resolution phase of ARDS. CONCLUSIONS: Taken together, these data support the involvement of mob-1 in the pathogenic mechanisms of ARDS possibly through chemotaclic actions on inflammatory cells and modulation of angiogenesis in the recovery phase of the disease.

Animals↗
PubMed1994

Osmoregulatory changes in myo-inositol content and Na+/myo-inositol cotransport in rat cortical astrocytes.

Exposure of cortical astrocytes to 325, 350, or 390 mosM culture media for 48 h caused a 1.4-, 2.1-, and 3.5-fold increase, respectively, in cellular content of the compatible osmolyte myo-inositol. Elevated myo-inositol levels accounted for approximately 56-100% of the solute needed by the cells for complete volume regulation under hypertonic conditions. Myo-inositol accumulation was associated with 4-5-fold (peak rate) and 1.8-2-fold (steady-state rate) increases in the rate of Na(+)-dependent myo-inositol uptake when cells were acclimated to 390 mosM culture medium for 12 h or 24-96 h, respectively. When medium osmolality was elevated by 25 mosM, peak and steady-state increases in myo-inositol uptake of 1.7-fold and 1.3-fold, respectively, were observed. Exposure to 390 mosM medium for 12-48 h induced a 3-8-fold increase in cotransporter mRNA levels suggesting that the increase in myo-inositol uptake is brought about by increased cotransporter gene expression. Abrupt return of hypertonic cells to an isotonic medium induced a rapid increase in myo-inositol efflux and a return of cotransporter mRNA to control values in < 2 h. In contrast, the cotransporter remained fully activated at hypertonic levels for 16 h. Between 16-24 h after the transfer, the rate of myo-inositol uptake returned to control values. The remarkable sensitivity of the cotransporter to hypertonic stress indicates that upregulation of myo-inositol transport in glial cells is likely to occur in a variety of disease states that cause an elevation of plasma osmolality. Slow downregulation of the cotransporter may be responsible in part for the slow loss of myo-inositol and cerebral edema that occurs with too rapid correction of chronic plasma hypertonicity.

Animals↗
PubMed1994

A cladistic analysis of the evolutionary relationships of the members of the tyrosinase gene family using sequence data.

Recently, DNA sequence data have been published on tyrosinase and tyrosinase-related proteins (TRPs) in a wide variety of vertebrates ranging from Rana to Homo. These proteins are in turn members of a larger family of binuclear copper-binding proteins, which all contain two highly conserved copper-binding domains. This gene family also includes tyrosinases from fungi and bacteria as well as arthropodan and molluscan hemocyanins. Parsimony-based alignment and tree construction algorithms (Malign, v1.85 and PAUP, 3.1.1) were used to analyze the diversification of both the evolutionarily conserved copper-binding domains in copper-binding proteins in general as well as the diversification of the vertebrate tyrosinase gene family more specifically. These analyses show that the diversification of the vertebrate tyrosinase gene family minimally predates the diversification of vertebrates. Vertebrate tyrosinases proper first diverged from an ancestral tyrosinase-related protein (TRP) that then subsequently diverged to form tyrosinase-related protein-1s (TRP-1s) and tyrosinase-related protein-2s (TRP-2s).

Algorithms↗
PubMed1994

The volume-sensitive organic osmolyte-anion channel VSOAC is regulated by nonhydrolytic ATP binding.

Efflux of intracellular organic osmolytes to the external medium is a ubiquitous response to cell swelling. Accumulating evidence indicates that volume regulatory loss of structurally unrelated organic osmolytes from cells is mediated by a relatively nonselective volume-sensitive anion channel. In C6 cells, we have termed this channel VSOAC for volume-sensitive organic osmolyte-anion channel. Swelling-induced activation of VSOAC required the presence of ATP or nonhydrolyzable ATP analogues [adenosine 5'-O-(3-thiotriphosphate), adenylylmethyl-enediphosphonate (AMP-PCP), or 5'-adenylylimidodiphosphate] in the patch pipette. Sustained activation of VSOAC also required ATP. Channel rundown was observed when cellular ATP levels were lowered by intracellular dialysis with the patch pipette solution. Rundown was prevented by the ATP analogue AMP-PCP. Passive swelling-induced myo-[3H]inositol and [3H]taurine efflux was blocked by metabolic inhibitors that decreased cellular ATP levels. Titration of cellular ATP levels with azide demonstrated that the apparent dissociation constant (Kd) for ATP of both myo-inositol and taurine efflux was approximately 1.7 mM. The high Kd for ATP indicates that cellular metabolic state plays an important role in modulating organic osmolyte loss. Regulation of VSOAC activity by ATP prevents depletion of metabolically expensive organic osmolytes when cellular energy production is reduced. In addition, ATP-dependent regulation provides essential feedback to minimize the loss of energy-producing carbon sources such as pyruvate, short-chain fatty acids, ketone bodies, and amino acids, which readily permeate this channel.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Mechanism and regulation of swelling-activated inositol efflux in brain glial cells.

Rat C6 glioma cells chronically acclimated to hypertonic media accumulate large quantities of inositol. When returned to isotonic conditions, the cells swell and lose inositol slowly via a four- to fivefold increase in the rate of passive inositol efflux. The inositol efflux pathway is a Na(+)-independent transport mechanism with low affinity for inositol and is inhibited by quinidine, quinine, various anion transport blockers, and cis-unsaturated fatty acids. Ionomycin-induced elevation of intracellular Ca2+ (Ca2+i) had no effect on basal or swelling-induced inositol efflux. Inositol efflux was not inhibited by chelation of Ca2+i with 1,2-bis(2-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid. In addition, Ca2+i measured with fura 2 did not change during cell swelling, indicating that increases in Ca2+i do not regulate inositol efflux. Exposure of C6 cells to 20 nM phorbol 12-myristate 13-acetate, 0.5 mM adenosine 3',5'-cyclic monophosphate (cAMP), or 50 microM forskolin had no effect on basal inositol efflux but stimulated swelling-induced inositol loss by 2.6-, 2.2-, and 3.4-fold, respectively. Exposure to the protein kinase inhibitors 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine or staurosporine or downregulation of protein kinase C (PKC) activity, however, had no inhibitory effect on inositol efflux, and cellular cAMP levels were not altered by cell swelling. Taken together, these results indicate that stimulation of PKC and protein kinase A modulates the activity of the efflux pathway but is not required for swelling-induced activation. Ketoconazole, cinnamyl-3,4-dihydroxy-alpha-cyanocinnamate, and gossypol, inhibitors of lipoxygenase enzymes, blocked both basal and swelling-induced inositol efflux, suggesting indirectly that lipoxygenase metabolites may be responsible for swelling-induced activation of the efflux mechanism. The characteristics of inositol efflux in C6 cells are similar to those described for volume regulatory sorbitol and taurine efflux in a number of cell types, suggesting the existence of a common transport mechanism.

Animals↗
PubMed1993

Basic fibroblast growth factor (bFGF) acts intracellularly to cause the transdifferentiation of avian neural crest-derived Schwann cell precursors into melanocytes.

We previously found that cultured neural crest-derived cells from embryonic quail peripheral nerves, which consist mostly of Schwann cell precursors, gave rise to melanocytes following treatment with basic fibroblast growth factor (bFGF) or 12-O-tetradecanoyl phorbol-13-acetate (TPA). Here, we show that antisense deoxyoligonucleotides targeted against two regions of the bFGF mRNA transcript blocked this TPA-induced transdifferentiation of Schwann cell precursors. Neither sense nor scrambled antisense control oligonucleotides had any effect in this regard. TPA increased bFGF protein expression in cell lysates but not in conditioned media from these cultures, and this expression was localized to the nucleus and cytoplasm. Furthermore, bFGF-neutralizing antibodies and inositol-hexakisphosphate (InsP6) both inhibited pigmentation caused by exogenous bFGF, but had no affect on TPA-induced melanogenesis, suggesting that bFGF is not released by these cells. These data indicate that bFGF is necessary for the TPA-induced transdifferentiation of Schwann cell precursors into melanocytes and that bFGF acts via an intracrine mechanism.

Animals↗
PubMed1993

Medication non-compliance.

Medication non-compliance is a perplexing, pervasive and poorly understood problem. Historically, the medical community viewed it as an act of defiance. But in recent years nurses have challenged that position, instead seeing non-compliance as behavior that can be intentional or unintentional; detrimental or, on occasion, beneficial.

Drug Therapy↗
PubMed1992

Multiple molecular weight forms of basic fibroblast growth factor are developmentally regulated in the central nervous system.

Basic fibroblast growth factor (bFGF) is a heparin-binding protein implicated in the differentiation, proliferation, and maintenance of cells in the central nervous system (CNS). It is not clear how bFGF achieves this multiplicity of effects. Multiple molecular weight forms of bFGF have recently been identified, however, and each form may have distinct activities during CNS development. We have examined the pattern of bFGF expression during CNS development using protein immunoblot and RNA blot analyses. RNA blot analysis detected a major bFGF transcript of 3.7 kb in embryonic and adult rat brain; however, this message decreased in abundance during development. Three bFGF protein forms were identified on immunoblots of adult rat brain extract with approximate molecular weights of 18, 21, and 22 kDa. Embryonic rat brain extracts also contained the 18- and 21-kDa bFGF protein forms, but lacked the 22-kDa form. Expression of the 22-kDa form was first detected in the neonate and then steadily increased to adult levels by 1 month of age. Immunoblots of adult human brain extracts also showed the presence of three bFGF protein forms with approximate molecular weights of 18, 22, and 24 kDa. In human second trimester fetal brain extracts, only the 18-kDa bFGF protein was detected. Comparison of bFGF proteins in developing rat spinal cord, cerebellum, and cortex demonstrated that distinct patterns of bFGF protein forms exist in different regions of the CNS. Therefore, the expression of individual bFGF protein forms is regulated in the CNS with regard to both developmental stage and location. These data support the idea that different forms of bFGF may be associated with specific developmental events during the maturation and organization of the nervous system.

Amino Acid Sequence↗
PubMed1992

A chromosomal reciprocal translocation (1q+; 14q-) in a boar siring reduced litter sizes.

In our initial cytogenetic surveillance of boars one of 15 was found to be hypoprolific. It averaged 7.1 piglets per litter in over 51 monospermic matings with sows which, with other boars averaged 10.8 piglets per litter. Cytogenetic evaluations revealed only the hypoprolific boar to have an abnormal karyotype, namely {38XY, t(1;14) (q2.12, q2.2)}. This represents a new type of 1;14 reciprocal translocation, and also the first report of a reciprocal translocation for swine in the United States.

Journal Article↗
PubMed1992

Volume regulation during recovery from chronic hypertonicity in brain glial cells.

Rat C6 glial cells undergo rapid regulatory volume increase (5-10 min) via electrolyte uptake when exposed to a hypertonic medium. With chronic exposure to hypertonicity (greater than 8 h), accumulated electrolyte is replaced partly by inositol. Inositol accumulation is brought about by upregulation of Na(+)-dependent inositol transport. When C6 cells acclimated chronically to hypertonic NaCl medium were returned to isotonic conditions, inositol levels dropped slowly from 478 nmol/mg protein towards control values (117 nmol/mg protein) in 18-24 h. Inositol loss occurred in part by efflux to the external medium via a pathway distinct from the uptake mechanism. Laser light-scattering measurements demonstrated that regulatory volume decrease (RVD) is slow under these experimental conditions. In contrast, cells exposed acutely to hypertonicity swell and then undergo a rapid and nearly complete RVD when returned to isotonic medium. These results suggest that slow inositol loss is rate limiting for RVD during recovery from chronic hypertonic stress. The slow inositol loss and RVD may be due to slow turnover of the efflux mechanism and/or slow downregulation of the hypertonically stimulated inositol uptake pathway.

Animals↗
PubMed1992

Drug analysis of biological samples. A survey of validation approaches in chromatography in the UK pharmaceutical industry.

1. The results of a survey on validation of analytical chromatographic methods are reported. The survey was carried out in 1990 within most of the principal British Pharmaceutical Companies. 2. A general method of validation is established from the collated results. 3. A comparison is made with existing reports from international meetings.

Chemistry, Pharmaceutical↗