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D Brown

Publications and source records attributed to D Brown.

At least 847 records · Page 47Linked to original sources
PubMed1987

Nonclathrin-coated vesicles are involved in endocytosis in kidney collecting duct intercalated cells.

Intercalated cells of the kidney collecting duct are able to modify the structure of their apical plasma membrane in response to different physiological conditions. It has been proposed that this process involves the transfer of membrane components (including a proton-pumping ATPase) to and from the apical membrane by a specialized population of tubulovesicles that are found in the apical cytoplasm of these cells. These vesicles have a prominent cytoplasmic coat of regularly arranged dense studs that we have recently shown to be immunocytochemically and morphologically distinct from clathrin. In this study, we have examined the function of these vesicles by using horseradish peroxidase as a tracer of endocytosis at the light and electron microscopic levels. Following the intravenous injection of rats with the tracer, we found a massive labeling of the tubulovesicle compartment of intercalated cells, providing direct evidence that these nonclathrin-coated vesicles are involved in endocytotic events in this cell type. This novel membrane coating material could contain the cytoplasmic domains of molecules transported to and from the plasma membrane by these vesicles (e.g., and H+ ATPase) or it could be a molecule that is involved in vesicle function, by analogy with clathrin.

Animals↗
PubMed1987

Differences in glycocalyx composition between cells of the cortical thick ascending limb of Henle and the macula densa revealed by lectin-gold cytochemistry.

The glycocalyx composition of cells from the macula densa and the cortical thick ascending limb of Henle was examined in rabbit kidney by means of the lectin-gold technique. A quantitative evaluation at the ultrastructural level showed that macula densa cells had a considerably greater affinity for Helix pomatia lectin than adjacent cells of the thick ascending limb. Wheat germ lectin and concanavalin A bound equally well to both cell types. This difference in plasma membrane glycocalyx composition may be an important aspect of the functional differentiation of cell types in this specialized nephron segment.

Animals↗
PubMed1987

Precommitment states induced during HL-60 myeloid differentiation: possible similarities of retinoic acid- and DMSO-induced early events.

The possible relationship of the pathways by which two inducers, retinoic acid and DMSO, cause myeloid differentiation of HL-60 promyelocytic leukemia cells was studied. HL-60 cells were first exposed to retinoic acid and then washed free of it. As reported previously, this brief exposure results in no subsequent G0 growth arrest or phenotypic differentiation. When these cells were subsequently exposed to DMSO, onset of G1/0 growth arrest but not phenotypic differentiation occurred within 24 h. Since in these cells retinoic acid or DMSO normally requires 48 h of continuous exposure for onset of significant G0 growth arrest and phenotypic differentiation, it appears that retinoic acid and DMSO induce similar early cellular events needed for subsequent G0 growth arrest but not for phenotypic differentiation. While onset of growth arrest and differentiation occur together when the cells are exposed for 48 h to retinoic acid, the present results indicate that their occurrence can be uncoupled by this split dosage to inducers. The results are discussed in terms of a previously hypothesized model of cellular response to the inducers.

Cell Cycle↗
PubMed1987

Control of HL-60 monocytic differentiation. Different pathways and uncoupled expression of differentiation markers.

Control of expression of the terminally differentiated phenotype was studied using the human promyelocytic leukemia cell line HL-60. Three known inducers of HL-60 monocytic differentiation were compared: 1,25-dihydroxy vitamin D3, tetradecanoylphorbol acetate (TPA), and sodium butyrate. At concentrations where all three inducers resulted in similar courses of G1/0-specific growth arrest, the kinetics of appearance of certain differentiation markers typically characteristic of mature monocytic cells was determined. The markers were inducible oxidative metabolism, non-specific esterase activity, and the cell surface determinants Mo1, My4, and Mo2. The results indicate that: Regulation of the expression of these markers during induced monocytic differentiation is not controlled in common. The three monocytic inducers do not induce the same metabolic cascade leading to differentiation. Similar states of differentiation could thus be reached by different pathways apparently due to the fact that control of expression of different differentiation markers was not tightly coupled.

Antigens, Surface↗
PubMed1987

Effects of colorants in the aquatic environment.

Modern colorants use a variety of chromophoric groups which in turn, may carry a wide range of substituents, both to influence the color, and to provide the required properties for dyeing particular substrates. Thus, there are many thousands of different substances used as commercial colorants. Further, the introduction of new structures to meet particular demands for shade and application is still in an area of major innovative activity. However, in general, individual products have a relatively low sales volume and the strategy which has been developed to assess the effect of dyestuffs (water-soluble, or water-dispersible, colorants) in the environment must necessarily be different from that appropriate for, say, pesticides. The paper discusses this strategy and shows how a "base set" package of data, the concept of which was developed by the colorant industry some years ahead of the "6th Amendment" Directive, may be used to assess the possible effects of a specific dyestuff when discharged in an aqueous effluent. As a second part of the strategy, the paper addresses more general questions relating to the ultimate fate of dyestuffs when discharged in aqueous effluents and in particular considers their most likely environmental distribution, their potential for bioaccumulation, and their biodegradability.

Animals↗
PubMed1987

Expression of the macrolide-lincosamide-streptogramin-B-resistance methylase gene, ermE, from Streptomyces erythraeus in Escherichia coli results in N6-monomethylation and N6,N6-dimethylation of ribosomal RNA.

The ermE gene was cloned from Streptomyces erythraeus into Escherichia coli on a series of plasmids. When transcribed from the lac promoter, ermE conferred high-level resistance to erythromycin and other macrolide-lincosamide-streptogramin-B (MLS) antibiotics. A methylase activity capable of N6-mono- and N6,N6-dimethylation of adenine residues in E. coli rRNA was detected in extracts of MLS-resistant cells. In addition, rRNA extracted from MLS-resistant E. coli contained N6-mono- and N6,N6-dimethylated adenine residues.

Adenine↗
PubMed1987

Advances in the application of biochemical tests to diseases of the liver and biliary tract: their role in diagnosis, prognosis, and the elucidation of pathogenetic mechanisms.

Despite the biochemical complexity of the liver, few laboratory tests provide discriminatory diagnostic information in patients with hepatobiliary disease. Recent efforts have concentrated upon tests which assess the function of the liver, the severity of the disease state, and underlying pathological processes. Bile Acids: The emergence of facile technology and widespread application has brought the realization that these assays are not as sensitive in detecting liver disease as previously believed, although the cholate/chenate ratio may be useful in distinguishing cholestasis from chronic liver disease. The presence of unusual bile acids in serum or urine may be helpful in some cases. Drug Metabolism: A number of tests provide good evidence about liver function, hepatic blood flow and portal shunting, but the aminopyrine breath tests is the most useful, giving prognostic information in acetaminophen overdose and alcoholic liver disease. The antipyrine half-life identifies surgical cases at risk from poor hepatic function. Proteins and Immunochemical Tests: Interest has developed in plasma proteins such as prealbumin and retinol-binding protein to monitor hepatic protein synthetic function. Secretory IgA is more elevated in biliary tract disease, unlike the native protein which is increased principally in cirrhosis. Type III procollagen can be measured in serum, and correlates with the activity of collagen synthesis and the degree of fibrosis in biopsy samples. Reye's Syndrome: Biochemical tests play an essential role in diagnosis of this recently discovered disease. These will be presented and discussed.

Bile Acids and Salts↗
PubMed1987

In vitro and in vivo tumour localisation with a monoclonal antibody directed against a membrane antigen on the human hepatocellular carcinoma cell line PLC/PRF/5.

A monoclonal antibody, designated K-PLC1, has been produced to a tumour-associated antigen on the cell membrane of the PLC/PRF/5 cell line. Using an indirect immunofluorescence technique this antibody produced membrane staining of three hepatocellular carcinoma (HCC) cell lines and it has positively stained 10 of 11 human HCC biopsy specimens. In vitro, 125I-labelled K-PLC1 binds specifically to PLC/PRF/5 cells, as shown by competitive inhibition experiments. Tumours derived from the PLC/PRF/5 cell line were grown in nude mice and groups of tumour-bearing animals were injected with either [125I]K-PLC1 or [125I]mouse IgG, and then killed at 1, 4 or 7 days post injection. Bound radioactivity was counted in a variety of solid organs. Tumour:liver ratios for K-PLC1 were greater than those for mouse IgG at each time point, the differences being greatest on day 4 (ratio K-PLC1 4.4 +/- 0.93, ratio mouse IgG 1.53 +/- 0.60, mean +/- SD, P less than 0.05). The amount of [125I]K-PLC1 bound was greater in the tumour than in any other solid organ, the differences again being maximal on day four. Blood pool radioactivity however remained high throughout the study period. We conclude that anti-HCC monoclonal antibodies may be of value as immunodiagnostic and immunotherapeutic agents in human HCC.

Animals↗
PubMed1987

Assessment of four enzyme immunoassay kits for serum beta-hCG screening.

This pilot study evaluates four qualitative serum beta-human chorionic gonadotropin (beta-hCG) enzyme immunoassay kits for both routine pregnancy testing and screening for ectopic pregnancy. We found that the Tandem-E HCG assay had the lowest limit of detection, and longest turnaround time. Tandem ICON HCG assay had the shortest turnaround time. The Vis-Con II was the most economical batch test. The Quest assay kit was both fast and simple and had the lowest cost for stat testing.

Chorionic Gonadotropin↗
PubMed1987

Structure of the novel membrane-coating material in proton-secreting epithelial cells and identification as an H+ATPase.

Specialized proton-secreting cells known collectively as mitochondria-rich cells are found in a variety of transporting epithelia, including the kidney collecting duct (intercalated cells) and toad and turtle urinary bladders. These cells contain a population of characteristic tubulovesicles that are believed to be involved in the shuttling of proton pumps (H+ATPase) to and from the plasma membrane. These transporting vesicles have a dense, studlike material coating the cytoplasmic face of their limiting membranes and similar studs are also found beneath parts of the plasma membrane. We have recently shown that this membrane coat does not contain clathrin. The present study was performed to determine the structure of this coat in rapidly frozen and freeze-dried tissue, and to determine whether the coat contains a major membrane protein transported by these vesicles, a proton pumping H+ATPase. The structure of the coat was examined in proton-secreting, mitochondria-rich cells from toad urinary bladder epithelium by rapidly freezing portions of apical membrane and associated cytoplasm that were sheared away from the remainder of the cell using polylysine-coated coverslips. Regions of the underside of these apical membranes as large as 0.2 micron2 were decorated by studlike projections that were arranged into regular hexagonal arrays. Individual studs had a diameter of 9.5 nm and appeared to be composed of multiple subunits arranged around a central depression, possibly representing a channel. The studs had a density of approximately 16,800 per micron2 of membrane. Similar arrays of studs were also found on vesicles trapped in the residual band of cytoplasm that remained attached to the underside of the plasma membrane, but none were seen in adjacent granular cells. To determine whether these arrays of studs contained H+ATPase molecules, we examined a preparation of affinity-purified bovine medullary H+ATPase, using the same technique, after incorporation of the protein eluted from a monoclonal antibody affinity column into phospholipid liposomes. The affinity-purified protein was shown to be capable of ATP-dependent acidification. In such preparations, large paracrystalline arrays of studs identical in appearance to those seen in situ were found. The dimensions of the studs as well as the number per square micrometer of membrane were identical to those of toad bladder mitochondria-rich cells: 9.5 nm in diameter, 16,770 per micron2 of membrane.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

1987 Volvo award in clinical sciences. The perception of back pain and the role of psychophysical tests of lifting capacity.

In order to study the predictive value of pre-employment screening tests, a volunteer population of 1,741 men and 1,150 women was questioned about their experience of low-back pain (LBP) and their perception of physical exertion at work. They undertook a battery of tests, including psychophysical assessments of lifting capacity, and they were followed up by postal questionnaire after 1 year. The response rate was 88.7%. The psychophysical tests have proved to be simple and inexpensive to administer; in good hands, they are repeatable. Although psychophysical lifting capacity was less in those with previous LBP, the psychophysical strength tests were poor predictors of future LBP. But when the previous history of LBP was known, then the test results significantly enhanced the prediction.

Adult↗