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D Brown

Publications and source records attributed to D Brown.

At least 811 records · Page 45Linked to original sources
PubMed1989

Modulation of ras expression by anti-sense, nonionic deoxyoligonucleotide analogs.

Anti-ras oligodeoxyribonucleoside methylphosphonates (ONMP's) complementary to the initiation codon region have been synthesized to explore their efficacy and specificity on ras-p21 translation. ONMP (IC-0) precisely complementing the first initial 11 nucleotides of the Balb-ras initiation codon region acts in a dose-dependent manner to inhibit p21 translation by a rabbit reticulocyte lysate. At 100 microM, IC-0 inhibits the cell-free translation of p21 close to completion. The two control oligomers containing one or two nucleotide mismatches were significantly less effective than IC-0 at the equivalent concentration. In living cells, a perfectly matched ONMP directed against the initiation codon region inhibited Ha-ras p21 expression by 90% at a concentration of 50 microM.

Animals↗
PubMed1988

Problem points.

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Humans↗
PubMed1988

Mevalonate deprivation leads to aneuploidy in Chinese hamster ovary cells.

After exposure to compactin, the competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, 22% of CHO-K1 cells contained abnormally high numbers of chromosomes. In two populations of cells selected for compactin resistance 31 and 33% of the cells contain more than 22 chromosomes. Some cell lines isolated from these populations have the wild type chromosome number of 20-21, while others have a broad distribution of chromosome number, often with a mean around 36-40. Finally, Chinese hamster ovary cells that are mutant for 3-hydroxy-3-methylglutaryl-CoA reductase and therefore auxotrophic for mevalonate were starved for that compound. This treatment also increased the number of cells containing extra chromosomes. These results indicate that interruption of the cellular supply of mevalonate results in abnormal chromosome number.

Aneuploidy↗
PubMed1988

Solution conformations of DNAs containing binding sites of the catabolite gene activator protein and lac repressor protein: characterization by Raman spectroscopy.

Raman spectra from three subfragments of the Escherichia coli lactose promoter region were obtained in 0.1 M NaCl. The three DNAs are 21, 40, and 62 bp in length. The 21 and 62 bp DNAs contain the binding site for the catabolite gene activator protein (CAP). The 40 bp DNA contains the binding site for the lac repressor. A quantitative analysis of Raman band characteristics indicates an overall B-type conformation for these gene regulatory sites. Bands which correspond to A-family (807 cm-1) and B-family (834 cm-1) deoxyribose phosphate vibrations have the same intensities as bands found in heterogeneous DNAs. The spectra of the 21 bp CAP site have, however, a small band at 867 cm-1 and several other small differences similar to some characteristics observed in C-DNA spectra. Several dG nucleosides in the CAP site appear to be altered from the conventional C2'-endo/anti conformation. At 45 degrees C, well below the melting region of these DNAs, small changes occur in the spectra of the 40 bp lac repressor site which are not observed in the other DNAs. A weak band occurs at 705 cm-1, and intensity changes are observed at 497, 682, and 792 cm-1. The changes suggest that the conformations of several dG nucleosides are altered and that a small region may exist with characteristics of an A-family backbone. This conformational change at 45 degrees C coincides with previous NMR observations indicating an enhanced imino proton exchange rate at a GTG sequence within the lac operator site.

Binding Sites↗
PubMed1988

Endosomes from kidney collecting tubule cells contain the vasopressin-sensitive water channel.

The mechanism by which vasopressin rapidly and dramatically increases the water permeability of target epithelial cell membranes is thought to involve a cycle of exo- and endocytosis during which vesicles carrying 'water channels' are successively inserted into, and removed from the apical plasma membrane of epithelial cells. Clusters of intramembranous particles, visible by freeze-fracture electron microscopy and presumed to represent water channels, appear on apical membranes in parallel with increased transepithelial water flow. In the collecting duct, these clusters are located in clathrin-coated pits which are subsequently internalized. There has been no direct evidence, however, that subcellular membranes in vasopressin-sensitive epithelia contain functional water channels. In this report, we have used fluorophores that are sensitive to volume and do not pass through membranes to label and to measure directly the osmotic water permeability of endocytosed vesicles isolated from renal papilla. We present direct evidence that vasopressin induces the appearance of a population of endocytic vesicles whose limiting membranes contain water channels.

Animals↗
PubMed1988

Dental amalgam.

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Biology↗
PubMed1988

An H+-ATPase in opposite plasma membrane domains in kidney epithelial cell subpopulations.

Vectorial solute transport by epithelia requires the polarized insertion of transport proteins into apical or basolateral plasmalemmal domains. In the specialized intercalated cells of the kidney collecting duct, the selective placement of an apical plasma membrane proton-pumping ATPase (H+-ATPase) and of a basolateral membrane anion-exchange protein results in transepithelial proton secretion. It is currently believed that amino-acid sequences of membrane proteins contain critical signalling regions involved in sorting these proteins to specific membrane domains. Recently, it was proposed that intercalated cells can reverse their direction of proton secretion under different acid-base conditions by redirecting proton pumps from apical to basolateral membranes, and anion exchangers from basolateral to apical membranes. But others have found that antibodies raised against the red cell anion-exchange protein (Band 3) only labelled intercalated cells at the basolateral plasma membrane, providing evidence against the model of polarity reversal. In this report, we have examined directly the distribution of proton pumps in kidney intercalated cells using specific polyclonal antibodies against subunits of a bovine kidney medullary H+-ATPase. We find that some cortical collecting duct intercalated cells have apical plasma membrane proton pumps, whereas others have basolateral pumps. This is the first direct demonstration of neighbouring epithelial cells maintaining opposite polarities of a transport protein. Thus, either subtle structural differences exist between proton pumps located at opposite poles of the cell, or factors other than protein sequence determine the polarity of H+-ATPase insertion.

Animals↗
PubMed1988

Junctional complexes and cell polarity in the urinary tubule.

In this review, we demonstrate how differentiated membrane domains can be detected in epithelial cells using conventional light and electron microscopy, freeze-fracture electron microscopy and the immuno- and cytochemical detection of membrane components. Using specific examples from the kidney, we show how the polarized insertion of these components into either apical or basolateral plasma membrane regions on either side of the tight junction barrier is related to specific functions of principal and intercalated cells in the collecting duct. In addition, distinct basal and lateral membrane domains have been revealed in some cells that are maintained in the absence of a tight junctional barrier in the plane of the membrane. This suggests that other factors, possibly related to cytoskeletal elements, may be involved in the functional segregation of these membrane areas. We propose that epithelial cell plasma membranes should be subdivided into apical, lateral and basal regions, and that the term "basolateral" may be an oversimplification.

Animals↗
PubMed1988

Automated histochemical analysis of cell populations in the intact follicle-associated epithelium of the mouse Peyer's patch.

A new technique of quantitative histochemistry has been developed to study the cellular composition of the follicle-associated epithelium of the mouse Peyer's patch. This technique involves applying naphthol AS-BI phosphate to the surface of intact tissue where it is hydrolysed by alkaline phosphatase present in the luminal membrane of the epithelial cells. Naphthol AS-BI produced by this reaction is then coupled to Fast Red TR diazonium salt at the site of hydrolysis. M cells present in the epithelium contain little alkaline phosphatase activity and, therefore, remain white. Treatment with Alcian Blue is finally used to label goblet cells. Subsequent quantitative analysis of alkaline phosphatase-rich cells is carried out by scanning microdensitometry. Using this technique it is possible to detect two populations of alkaline phosphatase-containing cells in mice reared in a normal animal house environment. These results are discussed in relation to possible interactions taking place between enteric antigens and the gut-associated lymphoid tissue which could reduce the ability of follicle-associated enterocytes to express alkaline phosphatase.

Alkaline Phosphatase↗
PubMed1988

Patient acceptance of prefilled disposable vaginal applicator.

Patient acceptance of a new, compact, prefilled disposable vaginal applicator was tested in an open study in which 2% butoconazole cream was used for the treatment of vulvovaginal candidiasis. Twenty nonpregnant patients with clinical signs and symptoms of candidiasis and microscopic identification of Candida in wet smear were treated for 3 days and then asked to rate the convenience of and their acceptance of the prefilled vaginal applicator. No adverse events were reported. All of the patients readily accepted the idea of a prefilled applicator and judged the shape and surface of the test applicator to be comfortable and the applicator to be easily inserted. Patients judged this applicator to be the most convenient and least messy when compared with other commercially available, reusable, or prefilled disposable applicators.

Administration, Intravaginal↗
PubMed1988

Nucleotide sequence of RNA segment 7 and the predicted amino sequence of M1 and M2 proteins of FPV/Weybridge (H7N7) and WSN (H1N1) influenza viruses.

Since the gene products (M1 and M2) of influenza virus RNA segment 7 have been implicated in host range restriction, sensitivity to the drug amantadine, virus yield in chicken embryos as well as in virus assembly and morphology, we have determined the nucleotide sequence of this RNA segment for an avian [A/FPV/Weybridge (H7N7)] and a human [A/WSN/33 (H1N1)] virus and compared it to that of the other influenza A virus strains. The results show that all ten strains of influenza A virus contain an identical number of nucleotides (1027 bases) in RNA segment 7 and an identical number of amino acids in M1 (252 aa) and M2 (97 aa) proteins. The observed amino acid changes are conservative in nature suggesting the requirement of a critical structure of both proteins in virus assembly. Furthermore, the presence of some consistent amino acid substitutions among different human and avian strains also supports the possible existence of host range and drug resistance determinants in M1 and M2 proteins.

Amino Acid Sequence↗
PubMed1988

Comparative toxicity of cisplatin, carboplatin (CBDCA) and iproplatin (CHIP) in combination with cyclophosphamide in patients with advanced epithelial ovarian cancer.

Sixty patients with FIGO stage IIb, IIc, III and IV ovarian cancer were entered into a randomized Phase III study of cyclophosphamide 600 mg/m2 with cisplatin 100 mg/m2, iproplatin 240 mg/m2 or carboplatin 300 mg/m2. Dose modifications were made according to renal function and myelotoxicity. The arms containing carboplatin (CBDCA) and iproplatin (CHIP) were not shown to be significantly different from the cisplatin containing arm with regard to response rate, duration of response and survival. Subjective toxicity showed that cisplatin and cyclophosphamide therapy was associated with more nausea and vomiting (P = 0.0005). The duration of vomiting showed a significant increase with successive courses of chemotherapy for the cisplatin containing arm only (P less than 0.003). The cyclophosphamide/CHIP combination caused significantly more diarrhoea (P less than 0.0006). Alopecia was more severe (P less than 0.02), and neurotoxicity was more common, in patients who received cyclophosphamide and cisplatin (paraesthesiae P = 0.0007, tinnitus P less than 0.00005, deafness P = 0.0018). All three combinations caused cumulative toxicity on haemoglobin (Hb) (P less than 0.001 for each treatment), leukocyte count (WCC) (P less than 0.0005 for each treatment), and platelet count (P less than 0.0005 for each treatment). The degree of fall in Hb for each course of therapy was greater in the cisplatin containing arm compared with the CHIP and CBDCA arms which were not significantly different from each other (P = 0.0005). For WCC the cisplatin/cyclophosphamide regimen was significantly less toxic than CHIP/cyclophosphamide, with CBDCA/cyclophosphamide falling between the two and not being significantly different from either (P = 0.0005). The CHIP containing arm caused more thrombocytopenia than the other arms which were of equal toxicity (P less than 0.0005). Serum creatinine showed a gradual significant overall rise with each course of cisplatin/cyclophosphamide therapy (P less than 0.0005), whereas the CBDCA arm showed no change and the CHIP arm showed a small fall in serum creatinine after most courses of therapy. This study showed that CHIP or CBDCA in combination with cyclophosphamide was less toxic than cisplatin/cyclophosphamide therapy with regard to alopecia, degree and duration of nausea and vomiting, renal toxicity, neurotoxicity and anaemia. The CHIP/cyclophosphamide regimen caused more thrombocytopenia and diarrhoea. The CHIP and CBDCA containing arms caused more leukopenia than the cisplatin containing regimen. Either iproplatin or carboplatin would be an acceptable alternative to cisplatin in chemotherapy regimens, and would result in reduced toxicity.

Aged↗