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Biomedical subjects

R Holmes

Publications and source records attributed to R Holmes.

At least 163 records · Page 9Linked to original sources
PubMed1977

Subcellular localization of enterokinase in human duodenal mucosa.

1. Specimens of human duodenal mucosa were obtained at duodenotomy. Superficial mucosal scrapings were homogenized in isotonic sucrose solution and fractionated by differential centrifugation. The distribution of organelles among the subcellular fractions was monitored by assay of suitable marker enzymes. 2. Enterokinase was recovered predominantly in the nuclear+brush-border fraction and 80% of the total activity was found to be particulate; approximately 20% of the enzyme was present in the soluble fraction, compared with 1% of the brush-border markers sucrase and alkaline phosphatase. 3. The brush-border-containing fraction was subfractionated by treatment with hypertonic Tris followed by differential and density gradient centrifugation. Enterokinase was distributed among the subfractions in parallel with brush-border markers and was concentrated in a subfraction which was highly enriched in microvillous membranes. 4. It was concluded that enterokinase is localized primarily to the microvillous membrane of the epithelial cell brush border in man, but that in addition a proportion of the enzyme may be present in a soluble or easily released form in the duodenal mucosa.

Duodenum↗
PubMed1975

Prospective comparative study of variable dosage and variable frequency regimens for administration of gentamicin.

In patients with impaired renal function, careful adjustment of gentamicin dosage is required to achieve therapeutic yet nontoxic concentrations. Two regimens that differ in pharmacodynamic characteristics have been recommended for this purpose: prolonging the intervals between administration of equal doses (variable frequency regimen [VFR]) or administering a loading dose followed at the usual intervals by reduced maintenance doses (variable dosage regimen [VDR]). These regimens were compared in a prospective, randomized study of 20 seriously ill hospitalized patients, 10 on VFR and 10 on VDR. Wide variability in peak serum levels of gentamicin was observed both between patients and in individual patients after separate injections of the same dosage. As predicted by the design of these regimens, the trough serum levels of gentamicin correlated significantly with the serum creatinine concentrations in patients on the VDR but not in patients on the VFR. A gentamicin trough level of >/=4 mug/ml was the only variable among those tested that correlated significantly with development or progression of renal insufficiency during treatment with gentamicin, but such trough levels were observed frequently on both regimens. Whereas this study does not permit a direct comparison of the therapeutic efficacy of VDR and VFR, no difference in the risk of nephrotoxicity with these regimens was observed.

Clinical Trials as Topic↗
PubMed1969

Cholesterol requirement of primary diploid human fibroblasts.

Primary cultures of fibroblast-like cells were obtained from skin and articular cartilage of human donors in the age bracket of 1 to 15 years. For growth these cultures required 1 mg/liter of cholesterol added to Medium A2 plus acetyl choline, Na pyruvate, and D-galactosamine HCl (APG) containing 10% lipoprotein-free human serum. Established cell lines did not require cholesterol for growth. Eagle's medium could be used in place of Medium A2 plus APG with the same results. Desmosterol could replace cholesterol but lansterol or 7 dehydrocholesterol could not. Other cholesterol precursors were tested and found to be inactive. With the proviso that cholesterol precursors entered the cell and had to be converted to cholesterol to function, it was concluded that the particular primaries studied lacked a functional enzyme system to reduce the double bond at carbon 7.

Adolescent↗
PubMed1967

Preparation from human serum of an alpha-one protein which induces the immediate growth of unadapted cells in vitro.

An alpha-one protein is separated from human serum on a microbead column. This nondialyzable protein induces the immediate growth of unadapted cells placed in chemically defined Medium A2 + APG. HeLa, conjunctiva and human heart cells, which stop growing if the protein is removed, continue to grow only if the protein is returned or the cells are permitted to adapt to the defined medium. A 90-120 day period is required for adaptation. The spreading and growth of fully adapted cells is also stimulated by the addition of the protein. As little as 0.4 microg per ml of medium is effective. The protein analyzed by paper, starch, and discontinuous acrylamide gel electrophoresis appears to be a single component. The protein is periodate-Schiff positive and readily binds small molecules which are removed, without loss of biological activity, by precipitating the protein in 50% saturated ammonium sulfate. The protein is adsorbed on the microbead column as a complex with the beta lipoprotein fraction of human serum; it cannot be separated from bovine or equinesera by this method; and it is not identical with fetuin. Its biological response is not duplicated by insulin, carbamyl phosphate, putrescine, or linoleic acid.

Alpha-Globulins↗
PubMedDate not supplied

Gluten-sensitive enteropathy in Irish setter dogs: characterisation of jejunal microvillar membrane proteins by two-dimensional electrophoresis.

This study investigated whether gluten-sensitive enteropathy (GSE) in Irish setter dogs was associated with underlying structural abnormalities of microvillar membrane proteins. Jejunal biopsies taken from eight-month-old GSE-affected dogs reared on a normal, gluten-containing diet exhibited partial villous atrophy and contained more intra-epithelial lymphocytes than controls. The morphological abnormalities were reversed by feeding a gluten-free diet for five months and the changes were accompanied by an increase in the mucosal activity of the microvillar hydrolases, particularly aminopeptidase N and dipeptidyl aminopeptidase IV, which reverted to pre-treatment levels after a gluten challenge. Two-dimensional electrophoresis of microvillar membrane proteins isolated from GSE-affected dogs revealed an essentially normal protein map that was comparable to controls. The exception was an intense 85 kDa protein spot that diminished when the affected dogs were fed a gluten-free diet and re-intensified after a gluten challenge.

Alkaline Phosphatase↗