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Biomedical subjects

R James

Publications and source records attributed to R James.

At least 163 records · Page 9Linked to original sources
PubMed1994

Identification of membrane-bound CR1 (CD35) in human urine: evidence for its release by glomerular podocytes.

Complement receptor 1 (CR1) is present on erythrocytes (E-CR1), various leucocytes, and renal glomerular epithelial cells (podocytes). In addition, plasma contains a soluble form of CR1 (sCR1). By using a specific ELISA, CR1 was detected in the urine (uCR1) of normal individuals (excretion rate in 12 subjects, 3.12 +/- 1.15 micrograms/24 h). Contrary to sCR1, uCR1 was pelleted by centrifugation at 200,000 g for 60 min. Analysis by sucrose density gradient ultracentrifugation showed that uCR1 was sedimenting in fractions larger than 19 S, whereas sCR1 was found as expected in fractions smaller than 19 S. The addition of detergents reduced the apparent size of uCR1 to that of sCR1. After gel filtration on Sephacryl-300 of normal urine, the fractions containing uCR1 were found to be enriched in cholesterol and phospholipids. The membrane-association of uCR1 was demonstrated by analyzing immunoaffinity purified uCR1 by electron microscopy which revealed membrane-bound vesicles. The apparent molecular mass of uCR1 was 15 kD larger than E-CR1 and sCR1 when assessed by SDS-PAGE and immunoblotting. This difference in size could not be explained on the basis of glycosylation only, since pretreatment with N-glycosidase F reduced the size of all forms of CR1; however, the difference in regular molecular mass was not abrogated. The structural alleles described for E-CR1 were also found for uCR1. The urine of patients who had undergone renal transplantation contained alleles of uCR1 which were discordant with E-CR1 in 7 of 11 individuals, indicating that uCR1 originated from the kidney. uCR1 was shown to bind C3b-coated immune complexes, suggesting that the function of CR1 was not destroyed in urine. A decrease in uCR1 excretion was observed in 3 of 10 patients with systemic lupus erythematosus, corresponding to the three who had severe proliferative nephritis, and in three of three patients with focal sclerosis, but not in six other patients with proteinuria. Taken together, these data suggest that glomerular podocytes release CR1-coated vesicles into the urine. The function of this release remains to be defined, but it may be used as a marker for podocyte injury.

Adult↗
PubMed1994

Tandem overproduction and characterisation of the nuclease domain of colicin E9 and its cognate inhibitor protein Im9.

We report the overproduction of the non-specific endonuclease domain of the bacterial toxin colicin E9 and its preliminary characterisation in vitro. The enzymatic colicins (61 kDa) are normally released from producing cells in a complex with their cognate inhibitors, known as the immunity proteins (9.5 kDa). Tryptic digestion of the purified ColE9 complex was found to generate two major components, a monomer derived from the N-terminal and central regions of the toxin and a heterodimer comprising the catalytically active C-terminal domain of the colicin bound to its intact immunity protein, Im9. N-terminal amino acid sequencing, in conjunction with electrospray mass spectrometry, shows that preparations of the DNase domain isolated by this method are heterogeneous, thus making subsequent mechanistic and structural analysis difficult. This problem was circumvented by selectively overexpressing the C-terminal 15-kDa nuclease domain of colicin E9 in tandem with its cognate inhibitor in Escherichia coli. This tandem overexpression strategy allowed high-level production of a 25-kDa protein complex comprising the C-terminal DNase domain of colicin E9 tightly bound to its specific inhibitor Im9, thus masking the anticipated toxicity of the nuclease. The DNase domain was then separated from Im9 under denaturing conditions, refolded by removal of the denaturant and the renatured protein shown to possess both endonuclease and Im9 binding activity. These results describe a novel method for the overproduction of a nuclease in bacteria by co-expressing its specific inhibitor and lay the foundations for a full mechanistic, biophysical and structural characterization of the isolated DNase domain of the colicin E9 toxin.

Amino Acid Sequence↗
PubMed1994

Hereditary motor and sensory neuropathy with myelin outfolding: clinical, genetic and neuropathological study of three cases.

We describe 3 patients affected by a congenital motor and sensory neuropathy with excessive myelin outfoldings (MOs). Clinical and electrophysiological features supported the diagnosis of hereditary motor and sensory neuropathy (HMSN). The genetic study failed to demonstrate either the duplication in chromosome 17p11.2 or the mutations at exons 1 and 2 of the myelin protein gene, PMP-22, recently observed in HMSN type Ia, and suggested an autosomal recessive (AR) inheritance. Sural nerve biopsy revealed a demyelinating process with prominent hypertrophic changes and excessive MOs formation. The percentage of MOs was significantly higher than in 3 age-matched HMSN Ia patients. MOs were morphologically and morphometrically different from tomacular-like thickenings of myelin. Myelin thickness was significantly lower than in the three HMSN Ia controls and linear regression showed a thinner myelin related to axon diameter. The reported cases demonstrate that HMSN with MOs is a well defined variant of HMSN and that a primary defect in the myelination process may be proposed as a possible pathogenic mechanism.

Adolescent↗
PubMed1994

Hemodynamic and renal effects of dopexamine and dobutamine in patients with reduced cardiac output following coronary artery bypass grafting.

OBJECTIVE: Dopexamine hydrochloride is a novel synthetic adrenergic agonist that combines the renal effects of dopamine with the hemodynamic effects of dobutatmine. Our study is designed to compare the hemodynamic, diuretic, and natriuretic effects of dopexamine and dobutamine in patients with reduced cardiac index following heart surgery. DESIGN: Prospectively randomized, blinded study. SETTING: Operating room and intensive care unit of a large, urban, academic medical center. PATIENTS: Twenty-eight patients undergoing elective coronary artery bypass grafting (CABG) with preoperative ejection fraction of at least 40 percent gave informed consent. The study group consisted of the ten patients who had a cardiac index < or = 2.5 L/min/m2 (while receiving no inotropic medication) immediately after separation from cardiopulmonary bypass. INTERVENTIONS AND MEASUREMENTS: Study patients were randomly given a starting dose of either 5 micrograms/kg/min of dobutamine (n = 5) or 2 micrograms/kg/min of dopexamine (n = 5). During the initial 30 min following separation from bypass, dosages were titrated incrementally to maintain cardiac index > or = 3.0/L/min/m2. Further titrations of the drug were done only if cardiac index fell below 3.0 L/min/m2 or if sustained tachycardia occurred during the 24-h study period. Data were collected at 5- and 10-min intervals for the first 30 min after separation from bypass, hourly for the next 8 h, then every 2 h for the remainder of the study period. RESULTS: Both drugs increased cardiac index by more than 50 percent over baseline (dobutamine 2.2 +/- 0.1 to 3.5 +/- 0.2 [p < 0.05]; dopexamine, 2.3 +/- 0.1 to 3.5 +/- 0.1 [p < 0.05] L/min/m2). The mean dose required to maintain cardiac index > or = 3.0L/min/m2 was 1.5 micrograms/kg/min for dopexamine and 3.5 micrograms/kg/min for dobutamine. There were no significant differences in either urinary output or net sodium excretion in the dopexamine group compared with the dobutamine group, and tachycardia (heart rate > 120 beats/min) was more common in the dopexamine group. CONCLUSIONS: Our study demonstrates that dopexamine produces hemodynamic, diuretic, and natriuretic effects similar to dobutamine in patients with reduced cardiac index following CABG.

Adrenergic beta-Antagonists↗
PubMed1993

Isolation and characterization of the murine homeobox gene Cdx-1. Regulation of expression in intestinal epithelial cells.

The murine homeobox gene Cdx-1 is postulated to play an important role in the process of cellular commitment in the intestinal epithelium based upon its graded, tissue-specific expression pattern in the adult animal. We have isolated and sequenced both cDNA and genomic clones in order to understand how this expression pattern is regulated and to determine the amino acid sequence of the encoded protein. Our studies show that the Cdx-1 gene contains 3 exons and 2 introns and encodes a 268-amino acid protein which is translated from a 1.7-1.8-kilobase mRNA. Transcription of the Cdx-1 gene initiates some 30 base pairs downstream from a typical TATA box which, together with the 5' end of the gene, is located within a CpG island. Transient transfection experiments have shown three regions which regulate Cdx-1 gene expression. These include a typical silencer element at -589 to -380, an element at -887 to -1040 which blocks the effect of the silencer and a positive element at -47 to +66; the only one which shows epithelial cell specificity. Using gel shift and footprinting assays we have detected proteins in nuclear extracts prepared from colonic epithelial cells which bind to the silencer element. These initial results suggest that Cdx-1 gene expression is regulated by multiple positive and negative transcription factors.

Amino Acid Sequence↗
PubMed1993

[Comparison of 2 cholesterol synthesis inhibitors (simvastatin and pravastatin)].

Inhibitors of cholesterol synthesis (HMG-CoA reductase) are the most effective cholesterol-lowering drugs. Comparison of several studies in the literature suggests that simvastatin is approximately twice as effective as pravastatin on a milligram basis. These results are confirmed by the present study, which compares treatment with simvastatin (10 mg/d) with pravastatin (20 mg/d) in the same hypercholesterolemic patients (n = 17). The reduction in LDL cholesterol is the same with twice the dose of pravastatin as with simvastatin (26 +/- 3% vs 27 +/- 2% respectively). The reductions in atherogenic ratios, total cholesterol, HDL cholesterol and ApoB/ApoA1 are similar. Undesirable effects are rare and comparable. The differences between the two inhibitors appear to be on the molecular level, in tissue selectively and regarding in vivo efficacy.

Anticholesteremic Agents↗
PubMed1993

Topical timolol maleate might adversely affect serum lipoproteins.

Conflicting observations have been reported about the effects of topically administered timolol maleate on serum lipoproteins. We therefore considered this issue in a series of eight glaucoma patients receiving timolol maleate. Cholesterol and triglycerides were measured in plasma and in low-density lipoproteins (LDL), and high-density lipoproteins (HDL), both before and following three months of treatment. Following the treatment, the mean atherogenic index was increased from 2.72 to 3.38 (p = 0.012). This suggests that the atherogenic index should be determined before and during timolol maleate treatment in high-risk cardiovascular patients.

Administration, Topical↗
PubMed1993

Insemination and population density in Entobdella soleae, a monogenean skin parasite of the common sole, Solea solea.

Immature specimens of the monogenean skin parasite Entobdella soleae, experimentally isolated from other individuals, fail to self-inseminate when maturity is reached and self-insemination has not been recognized during many hours spent observing living parasites. E. soleae lives on the lower surface of its flatfish host, the common sole (Solea solea), in relatively small numbers, most commonly 1, 2 or 3 adults per fish, but in spite of the low density and extensive habitat, freshly collected wild parasites were found to be inseminated. If it is assumed that E. soleae is unable to self-inseminate in the wild, then it seems likely that single isolated parasites on wild soles have lost their partners as a result of death or transfer to another host and that parasites have an efficient way of locating a mating partner. Mathematical modelling indicates that random locomotion with searching movements of the body would lead to mating contacts between 2 individuals on a small sole within the reproductive life-time of the parasites, but is unlikely to maximize reproductive output because it cannot ensure that mating will occur soon after sexual maturity is achieved. It is suggested that pheromonal attraction may ensure early meetings and that the thin stagnant layer of sea water between the lower surface of the relatively inactive sole and the sea bottom is an ideal environment for the operation of such a system and may account for the preference of adult E. soleae for the host's lower surface.

Animals↗
PubMed1993

Human islet isolation--a prospective randomized comparison of pancreatic vascular perfusion with hyperosmolar citrate or University of Wisconsin solution.

University of Wisconsin solution has become the most commonly used vascular perfusate during multiorgan donation world-wide. In the UK however, hyperosmolar citrate remains in common use. The purpose of this prospective randomized study was to compare the effect of systemic perfusion with UW or HOC on subsequent islet yield and purification for pancreata with short cold ischemic times. Seven pancreata were randomized to each group, with the donor age, pancreas weight, and period of cold ischemia being similar in both. Perfusion with UW was shown to inhibit collagenase digestion, and a higher concentration of this enzyme was needed to achieve comparable numbers of islets with good separation of exocrine and islet tissue after a similar period of digestion. There were no differences in the number, size, purity, or viability of islets between the two groups. In conclusion, UW solution offers no benefits over HOC for pancreata with short cold ischemic times, and because of its expense and need to use greater amounts of collagenase enzyme, we continue to use HOC.

Adenosine↗
PubMed1993

Evaluation of the West Australian School Development in Health Education Project.

In December 1990, the National Centre for Research into the Prevention of Drug Abuse was invited to evaluate the School Development in Health Education Project (SDHE), a national program tested in Western Australia (WA) in 1991. A formative evaluation indicated the project was moderately successful in achieving the objectives in the operational plan. Schools involved reported the project was successful, and they agreed to continue health planning meetings during 1992. The evaluation also indicated that while most schools achieved macro-level change, they achieved little at the micro level. A significant outcome for SDHE WA was the successful application for three-year funding to continue and expand the project as the West Australian School Health program (WASH). Recommendations generated from the SDHE evaluation produced a shift in emphasis for the WASH program from the "action research" orientation of the national program to more content-based professional development. This study highlights the important role formative evaluation can play in developing and refining health education programs.

Adolescent↗
PubMed1993

Community-based cholesterol screening and education to prevent heart disease: five-year results of the North Coast Cholesterol Check Campaign.

A cardiovascular disease screening and education campaign was conducted throughout the North Coast Region of New South Wales from 1987 to 1991. Objectives were: to screen 20 per cent of the adult population for blood cholesterol and other heart disease risk factors; to raise awareness of the risks associated with a high-fat diet; to provide nutrition counselling and referral advice for those with elevated cholesterol; and to monitor these participants' cholesterol levels with a follow-up test at three months. During the five years, 42,869 individuals or 18 per cent of North Coast adults participated, with some overrepresentation of women aged 40 to 60 years. Initially, 65 per cent of participants had elevated cholesterol levels (> or = 5.5 mmol/L) and 46 per cent were overweight (body mass index over 25). A three-month retest was offered to all participants with elevated cholesterol, of whom 53 per cent attended. Participants who received nutrition counselling generally reported dietary changes which were reflected in significant cholesterol and weight reductions. Of participants who attended retest, 63 to 87 per cent had reduced cholesterol levels and 57 to 71 per cent reduced weight. A stratified random sample of participants was retested at one and three years. Reductions in cholesterol were well maintained for one year but showed signs of relapse after three years. There was a tendency for initially lower cholesterol levels to increase over a three-year period. Contributing factors included aging, regression to the mean and complacency. Maintenance may be enhanced by regular reinforcement of nutrition changes and development of more supportive environments.

Adult↗
PubMed1993

Five open reading frames upstream of the dnaK gene of E. coli.

The nucleotide sequence of 3.17 kb of DNA upstream of the dnaK gene of E. coli was determined. Analysis of the sequence indicated the presence of five open reading frames (ORFs), two of which are coded on one strand and three on the other. ORFs 3 and 4 appear to constitute an operon. One of the ORFs (htgA) is preceded by a -10 promoter sequence which is identical to that of the dnaK sigma 32 P1 promoter, and thus suggests that htgA could be a heat-shock gene. ORF4 and htgA overlap each other on opposite strands of DNA, this would offer some interesting regulatory possibilities.

Amino Acid Sequence↗