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Biomedical subjects

E Lee

Publications and source records attributed to E Lee.

At least 307 records · Page 17Linked to original sources
PubMed1992

Catalytic subunits of Aplysia neuronal cAMP-dependent protein kinase with two different N termini.

Previously, two forms of cAMP-dependent protein kinase catalytic subunit generated by mutually exclusive use of two internal exon cassettes (A1 and A2) were demonstrated in Aplysia neurons. Here, it is shown that there also exist catalytic subunits with alternative N termini derived from two exons, N1 and N2, expressed in combination with either of the internal cassettes. Processed transcripts including N1 or N2 sequences are of about equal abundance in the nervous system, arise through alternative promoter use, and encode catalytically active polypeptides. The N2 amino acid sequence is 21 residues longer than the N1 sequence and is homologous to the nonmyristoylated N terminus of the TPK1 gene product, a yeast catalytic subunit homolog. These data support the view that cAMP-dependent protein kinase activity in Aplysia neurons is produced by a complex array of regulatory and catalytic subunits that generate multiple holoenzymes with a spectrum of properties.

Amino Acid Sequence↗
PubMed1992

The G226A mutant of Gs alpha highlights the requirement for dissociation of G protein subunits.

Adenylylcyclase cannot be activated by hormones or guanine nucleotide analogs in membranes from cells that express the G226A mutant form Gs alpha instead of the wild-type protein. The mutant Gs alpha protein appears incapable of undergoing the conformational change necessary for guanine nucleotide-induced dissociation of the G protein alpha subunit from the beta gamma subunit complex (Miller, R.T., Masters, S.B., Sullivan, K.A., Beiderman, B., and Bourne, H.R. (1988) Nature 334, 712-715). G226A Gs alpha was synthesized in Escherichia coli, purified, and characterized. Examination of the kinetics of dissociation of guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) suggests that G226A Gs alpha is incapable of assuming the conformation necessary for high affinity binding of Mg2+ to the alpha subunit-GTP gamma S complex. Associated changes include the failure of Mg2+ and GTP gamma S to confer resistance to tryptic proteolysis upon the protein, to enhance intrinsic tryptophan fluorescence, or to cause dissociation of alpha from beta gamma. However, the GTPase activity of the mutant protein is near normal (at high Mg2+ concentrations), and the protein is capable of activating adenylylcyclase. A similar defect is present in G49V Gs alpha. Failure of G protein subunit dissociation appears to be the explanation for the phenotypic properties of cells that express G226A Gs alpha, and this mutation thus highlights the crucial nature of this reaction as a component of G protein action.

Adenylyl Cyclases↗
PubMed1992

Importance of gastric acid in gastric ulcer formation in rabbits with antibody-induced prostaglandin deficiency.

The role of gastric acid in the development of gastroduodenal ulcers in prostaglandin-deficient conditions is unclear. In the current study, the effect of the proton pump inhibitor omeprazole on the formation of gastric ulcers was examined in a previously validated rabbit model of antibody-induced prostaglandin deficiency. Intragastric administration of 20 mg/kg omeprazole every 12 hours caused a profound suppression of gastric acidity (i.e., pH above 5 continuously). This same dose of omeprazole significantly reduced gastric ulcer formation induced by passive immunization with 6-keto-prostaglandin F1 alpha antibodies. It is concluded from these observations that gastric acid plays a critical role in the formation of gastric ulcers in rabbits with antibody-induced prostaglandin deficiency.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Subepithelial collagen table thickness in colon specimens from patients with microscopic colitis and collagenous colitis.

Microscopic colitis and collagenous colitis are similar conditions that are differentiated by the presence or absence of subepithelial collagen table thickening. To better understand the relationship between these two disorders and the role of collagen table thickening in the pathogenesis of diarrhea, colonic mucosal biopsy specimens from 24 patients with microscopic or collagenous colitis and 9 control subjects were analyzed using a computer-assisted morphometric method to evaluate the average thickness of the subepithelial collagen table. The collagen table thickness in colitis patients taken together formed a multimodal rather than a unimodal distribution. There was no tendency for collagen table thickening to increase with age or with duration of symptoms. In general, the types and distribution of inflammatory cells were similar in patients with normal and thickened collagen tables. Stool weight correlated with lamina propria cellularity but not with collagen table thickening. The multimodal distribution of collagen table thickening and the lack of correlation with age, duration of symptoms, or inflammation suggest that microscopic colitis and collagenous colitis are discrete conditions, although the inflammatory changes in the two conditions are similar. Moreover, because stool weight correlates with lamina propria cellularity but not with collagen table thickening, diarrhea probably is caused by the inflammatory changes and not by collagen table thickening per se.

Adult↗
PubMed1992

Direct sequence analysis of amplified dengue virus genomic RNA from cultured cells, mosquitoes and mouse brain.

A method is described for direct sequence analysis of selected regions of dengue virus genomic RNA in infected tissues. Using specific primers, total high-molecular-weight infected-cell RNA is reverse transcribed to single-stranded (ss) complementary DNA, amplified using the polymerase chain reaction (PCR) and sequenced using ssDNA obtained after lambda exonuclease digestion of one strand of the PCR product (R.G. Higuchi and H. Ochman, Nucleic Acids Research, 17, 5865, 1989). Sequence data for the envelope protein gene of two dengue-3 virus isolates were obtained using RNA from small numbers (10(5)) of cultured mosquito or monkey kidney cells, from one mg of infected mouse brain and from 1/300th of an infected Toxorhynchites amboinensis mosquito. Independent determinations showed that errors occurring during reverse transcription or PCR were not represented to a significant degree in the sequence of the amplified DNA. The method does not depend on extensive passaging of virus or large-scale growth to generate material for sequencing and therefore provides a means of obtaining sequence data for unadapted dengue virus isolates.

Aedes↗
PubMed1992

Analysis of phospholipid metabolism in murine keratinocytes transformed by the v-ras oncogene: relationship of phosphatidylinositol turnover and cytokine stimulation to the transformed phenotype.

Introduction of a v-rasHa oncogene into cultured mouse keratinocytes by transduction with a defective retrovirus is sufficient to transform keratinocytes to the benign phenotype. Transduced keratinocytes overexpress TGF alpha and hyperproliferate in culture medium with 0.05 mM Ca2+. Whereas normal keratinocytes respond to elevated medium Ca2+ by cessation of proliferation and induction of terminal differentiation, v-rasHa keratinocytes are not induced to differentiate by Ca2+. We now demonstrate that v-rasHa keratinocytes have elevated basal levels of phosphatidylinositol, inositol phosphates and diacylglycerols in 0.05 mM Ca2+ medium. Basal turnover of phosphatidylcholine is not altered by the rasHa oncogene. The generation of inositol phosphates is even further stimulated in v-rasHa cells by an increase in extracellular Ca2+ or by exposure to aluminum fluoride. Thus, the v-rasHa gene product does not stimulate the inositol phospholipid pathway maximally and additional phosphatidylinositol is available for turnover in response to inducers of phospholipase C activity. TGF alpha and medium conditioned by v-rasHa keratinocytes, both of which stimulate proliferation of normal cells in 0.05 mM Ca2+, transiently increased phosphatidylinositol turnover in normal keratinocytes but did not inhibit Ca(2+)-induced terminal differentiation. In contrast, sustained elevation in basal phosphatidylinositol metabolism was produced by aluminum fluoride. Combined exposure to aluminum fluoride and exogenous TGF alpha caused hyperproliferation, resistance to Ca(2+)-induced differentiation and morphological changes identical to those of v-rasHa keratinocytes. These results provide a link between the biological consequences of v-rasHa gene expression and biochemical changes which are known to alter the keratinocyte phenotype.

Aluminum↗
PubMed1992

Tumor necrosis factor in alcohol enhanced endotoxin liver injury.

Endotoxin administration causes liver injury. Patients with alcoholic liver disease frequently have portal vein and systemic endotoxemia, and some investigators have suggested that endotoxin plays an etiologic role in alcoholic liver injury. Many of the metabolic effects of endotoxin are mediated by the cytokine tumor necrosis factor (TNF). It was the purpose of this study to determine whether TNF plays a role in ethanol-enhanced endotoxin liver injury. Rats were fed either a diet in which 36% of the calories were from ethanol or an isocaloric control diet. After 6 weeks, groups of 10 rats were intravenously injected with either saline, 1 mg/kg endotoxin, or 30 micrograms/kg of a prostaglandin E1 (PGE1) analogue + 1 mg/kg endotoxin 24 hr prior to sacrifice. Ethanol/endotoxin-treated rats had significantly higher liver enzyme levels (ALT: 1064 +/- 355 IU/liter, AST: 2024 +/- 515 IU/liter) compared with isocaloric/endotoxin controls (ALT: 237 +/- 54 IU/liter, AST: 602 +/- 80 IU/liter). Ethanol/endotoxin rats also had significantly higher peak serum TNF concentrations (992 +/- 200 units/ml) compared with isocaloric/endotoxin controls (344 +/- 96 units/ml). Pretreatment of ethanol/endotoxin rats with PGE1 caused significant attenuation of liver injury (ALT: 267 +/- 64 IU/liter, AST: 612 +/- 77 IU/liter) and a diminished serum TNF response. In contrast to chronic ethanol administration, acute gavage with 2 mg/kg ethanol (30% w/v) followed by intravenous injection of 2 mg/kg endotoxin produced significantly lower peak serum TNF concentrations (401 +/- 76 units/ml) than gavage with distilled water (1152 +/- 208 units/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Alprostadil↗
PubMed1992

Nerve growth factor-induced derepression of peripherin gene expression is associated with alterations in proteins binding to a negative regulatory element.

The peripherin gene, which encodes a neuronal-specific intermediate filament protein, is transcriptionally induced with a late time course when nerve growth factor (NGF) stimulates PC12 cells to differentiate into neurons. We have studied its transcriptional regulation in order to better understand the neuronal-specific end steps of the signal transduction pathway of NGF. By 5' deletion mapping of the peripherin promoter, we have localized two positive regulatory elements necessary for full induction by NGF: a distal positive element and a proximal constitutive element within 111 bp of the transcriptional start site. In addition, there is a negative regulatory element (NRE; -179 to -111), the deletion of which results in elevated basal expression of the gene. Methylation interference footprinting of the NRE defined a unique sequence, GGCAGGGCGCC, as the binding site for proteins present in nuclear extracts from both undifferentiated and differentiated PC12 cells. However, DNA mobility shift assays using an oligonucleotide probe containing the footprinted sequence demonstrate a prominent retarded complex in extracts from undifferentiated PC12 cells which migrates with slower mobility than do the complexes produced by using differentiated PC12 cell extract. Transfection experiments using peripherin-chloramphenicol acetyltransferase constructs in which the footprinted sequence has been mutated confirm that the NRE has a functional, though not exclusive, role in repressing peripherin expression in undifferentiated and nonneuronal cells. We propose a two-step model of activation of peripherin by NGF in which dissociation of a repressor from the protein complex at the NRE, coupled with a positive signal from the distal positive element, results in depression of the gene.

Animals↗
PubMed1992

Aspirin-induced acute gastric mucosal injury is a neutrophil-dependent process in rats.

Aspirin, one of the most widely used drugs in the world, consistently produces gastric mucosal injury, but the pathogenic mechanisms are incompletely understood. The present study was designed to determine the role of neutrophils in aspirin-induced acute gastric mucosal injury. Gastric mucosal lesions induced by acidified aspirin (300 mg/kg) were completely prevented in rats that had been rendered profoundly neutropenic by anti-neutrophil serum. Aspirin-induced acute gastric mucosal lesions were also significantly, albeit incompletely, reduced in rats that had been rendered moderately neutropenic by methotrexate. Moreover, in the methotrexate-induced neutropenia model, the neutropenia-associated mucosal protection against aspirin-induced injury could be reversed by leucovorin rescue. Aspirin caused a marked and statistically significant reduction in gastric mucosal 6-ketoprostaglandin F1 alpha synthesis, but no significant changes in gastric mucosal leukotriene synthesis. Thus no gastric mucosal lesions were observed in profoundly neutropenic rats that were treated with aspirin, despite the marked inhibition of prostaglandin synthesis. These findings demonstrate that aspirin-induced acute gastric mucosal injury is a neutrophil-dependent process.

Acute Disease↗
PubMed1992

Betamethasone-induced resistance to neuromuscular blockade: a comparison of atracurium and vecuronium in vitro.

Steroids induce resistance to neuromuscular blocking drugs. Betamethasone-induced resistance to vecuronium has been demonstrated in vitro, and a presynaptic site of interaction has been suggested. This study investigated whether atracurium is similarly affected. Rat phrenic nerve-hemidiaphragm preparations were bathed in a physiologic solution, and one-half were exposed to betamethasone (1 mumol/L). Dose responses were recorded for atracurium (8-13 mumol/L) and vecuronium (2-12 mumol/L) for control and betamethasone-treated preparations. In comparison to control, the betamethasone groups had significantly less depression of muscle contraction force at all concentrations of atracurium (P = 0.0004) and vecuronium (P = 0.002). The calculated ED50 (50% depression of muscle contraction force, expressed as mean +/- SEM) for atracurium was 8.83 +/- 0.62 mumol/L for controls and 11.19 +/- 0.54 mumol/L for betamethasone-treated preparations. The calculated ED50 for vecuronium was 4.72 +/- 0.41 mumol/L for controls and 6.84 +/- 0.66 mumol/L for betamethasone-treated preparations. Betamethasone therefore increased the ED50 for atracurium by 27% and vecuronium by 45%; however, the magnitudes of these differences were not significant (P = 0.74) between the neuromuscular blocking agents. These results indicate that betamethasone-induced resistance to nondepolarizing neuromuscular blockade affects both atracurium and vecuronium to similar degrees in vitro.

Animals↗
PubMed1992

Stereoselective conjugation of a uricosuric diuretic with glutathione by glutathione transferase 3-3.

1. The activity of glutathione (GSH) transferases in rat liver cytosol was inhibited by the (-) enantiomer of a uricosuric diuretic (6,7-dichloro-5[N,N-dimethylsulphamoyl]-2,3-dihydrobenzofuran-2-ca rboxylic acid, DBCA) in a concentration-dependent manner. Although the DBCA (+) enantiomer inhibited the activity of liver cytosol GSH transferases, it was less effective. 2. Among four purified GSH transferase isozymes obtained from rat liver cytosol, isozyme 3-3 showed stereoselective interactions with the enantiomers of DBCA. This isozyme most actively and preferentially catalysed the transfer of GSH to DBCA (-) enantiomer.

Animals↗
PubMed1992

Gastric and duodenal mucosal prostaglandin concentrations in gastric or duodenal ulcer disease: relationships with demographics, environmental, and histological factors, including Helicobacter pylori.

We measured gastric and duodenal mucosal prostaglandin concentrations in 69 patients with active or inactive duodenal or gastric ulcer disease and 26 non-ulcer controls. Each underwent endoscopy enabling us to obtain multiple biopsies from the gastric body and antrum and from the duodenal bulb and postbulbar duodenum for measurement of mucosal prostaglandin concentrations, as well as a single biopsy from each region for mucosal histology. Using a multivariate linear regression model, we found that neither gastric nor duodenal ulcer disease significantly affected gastric or duodenal mucosal prostaglandin concentrations. Mucosal prostaglandin concentrations were similar at the edge of the ulcer and in the adjacent non-ulcerated mucosa. Neither gender symptoms, smoking, use of H2-receptor antagonists, disease activity, nor Helicobacter pylori infection had an independent effect on mucosal prostaglandins in any region. Gastritis in the body of the stomach was associated with significantly higher prostaglandins, while older age was associated with significantly lower gastric and duodenal prostaglandins. Gastroduodenal mucosal prostaglandins are thus not altered in patients with active or inactive peptic ulcer disease, even when multiple demographic and histologic variables are taken into consideration.

Age Factors↗
PubMed1992

Adjunctive desipramine in the treatment of cocaine abusing schizophrenics.

Because schizophrenic patients have a lifetime prevalence rate for cocaine abuse between 15 and 50 percent, the use of adjunctive pharmacotherapy should be considered in cocaine-abuse treatment programs. This 12-week, open-label outpatient study compares 12 cocaine-abusing schizophrenic patients treated with desipramine (DMI) 100 to 150 mg and antipsychotic agents to 15 patients treated with only antipsychotic agents (no DMI). All 27 patients participated in a Dual Diagnosis Relapse Prevention (DDRP) program, which integrates traditional substance-abuse relapse prevention and psychiatric social skills training. The DMI group was more likely to complete the study (83% vs. 60%, odds ratio = 3.3, NS) and had fewer cocaine-positive urines during the last 6 weeks (20% vs. 50%, odds ratio = 4.0, p < .01). In the context of a specialized dual diagnosis treatment program, patients receiving DMI substantially decreased cocaine usage and had improved psychiatric symptoms.

Adult↗
PubMed1992

Effect of aging on gastric and duodenal mucosal prostaglandin concentrations in humans.

The effect of aging on gastric and duodenal mucosal prostaglandins has not been reported. Gastric and duodenal mucosal prostaglandin concentrations were measured in 46 healthy adults, 35 of whom were relatively young (21-40 years old) and 11 of whom were considerably more elderly (aged 52-72 years). Mucosal biopsy specimens were obtained endoscopically from the fundus, antrum, duodenal bulb, and postbulbar duodenum, and extracts were assayed for prostaglandin F2 alpha and E2 concentrations by radioimmunoassay. Older age was associated with significantly lower fundic, antral, and post-bulbar duodenal prostaglandin concentrations. A second experiment was performed in 20 additional subjects (9 younger, 11 older) to determine whether lower mucosal concentrations in older subjects were reproducible and, if so, whether reduced gastric mucosal prostaglandins would have a physiological counterpart, namely increased gastric acid secretion. As in the original experiment, fundic, antral, and postbulbar mucosal prostaglandin levels were significantly lower in older subjects than in younger subjects. Mean basal acid output was significantly higher in older than younger subjects (9.8 +/- 2.5 vs. 4.8 +/- 1.6 mmol/h). It is concluded that gastric and duodenal prostaglandin concentrations decline with aging in humans and that the decline in fundic mucosal prostaglandins is associated with an increase in gastric acid secretion.

Adult↗