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Biomedical subjects

J Day

Publications and source records attributed to J Day.

At least 109 records · Page 6Linked to original sources
PubMed1990

Structural alterations in the Bacillus subtilis Spo0A regulatory protein which suppress mutations at several spo0 loci.

Secondary site mutations that restore sporulation to sporulation-defective spo0F or spo0B deletion mutants were found to reside in the spo0A gene. Sequence analysis of 23 such sof mutants showed that the sof mutations fell into six classes of missense codon changes, primarily in the conserved amino-terminal domain of the response regulator Spo0A protein. Changes were observed in codons 12, 14, 60, 92, and 121. The residues affected were predominantly located in the potential turn regions at one end of the amino-terminal conserved domain on the same topological face as the active site aspartate residues. The ability of sof mutations to suppress deficiencies in the transmitter kinases, KinA and KinB, of two-component regulatory systems was tested. All of the sof mutations suppressed the sporulation deficiency of kinA mutants but only two classes among five tested suppressed kinB mutations. sof mutants segregated Spo- colonies at high frequency. Five of these Spo- mutants were found to result from mutations in the spo0A locus that reversed the effect of the sof mutatation. One of these was sequenced and found to have the original sof mutation and a new mutation, sos, at codon 105. The accumulation of sos mutations in sof strains suggested that the sof mutations have a subtle, yet deleterious, effect on the growth of the cell. The results suggested that the sof mutations increase the avidity for or reactivity with transmitter kinases in an allele-specific manner, although in some cases it is possible that the sof mutations obviate the need for phosphorylation to activate the Spo0A protein. An alternative hypothesis is presented in which the sof mutations play the role of bypass mutations for kinases.

Amino Acid Sequence↗
PubMed1989

Lack of tolerance to nicotine-induced dopamine release in the nucleus accumbens.

The extent to which repeated administration produces tolerance to nicotine-induced increases in dopamine transmission in the nucleus accumbens was investigated in rats. In vivo microdialysis was used to sample extracellular dopamine and metabolites after a nicotine challenge (0.35 mg/kg) in (1) naive rats, (2) acutely pretreated rats (1 prior nicotine injection), and (3) chronically pretreated rats (12-15 prior daily nicotine injections, 0.35 mg/kg per injection). Nicotine increased extracellular DA and its metabolites, and these increases were not significantly altered by either acute or chronic prior exposure to the drug. The failure to find evidence of tolerance is compatible with the hypothesis that the mesolimbic dopaminergic system is a substrate for the reinforcing properties of chronically administered nicotine.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1989

Human kallistatin, a new tissue kallikrein-binding protein: purification and characterization.

A new and specific tissue kallikrein-binding protein was identified in mammalian serum and in secreted transformed-cell culture media (Chao et al., Biochem. J. 239: 325-331, 1986). We have designated this kallikrein-binding protein as "kallistatin". Human kallistatin has been purified from serum, using chromatographic steps including DEAE-Sephadex, hydroxylapatite, Cibacron blue-Sepharose, Sephacryl S200, and preparative polyacrylamide gel electrophoresis. The purified kallistatin consists of a single polypeptide chain with an apparent molecular weight of approximately 54 kDa and isoelectric point of approximately 5.0. Kallistatin was eluted as a single peak on reverse-phase HPLC. The purified kallistatin and 125I-labelled human tissue kallikrein form a approximately a 92 kDa SDS- and heat-stable complex. The complex formation is pH dependent and is inhibited by 0.1% (W/V) of deoxycholate or SDS but not by 0.5% (W/V) of Triton X-100, digitonin, Lubrol or CHAPS. A approximately 54 kDa protein was identified in partially purified kallistatin by polyclonal anti-kallistatin antibodies in Western blot analysis and by its binding to 125I-labelled-human tissue kallikrein in ligand blotting. The role of kallistatin in regulating tissue kallikrein activity and metabolism may now be evaluated.

Blotting, Western↗
PubMed1988

Shape changes produced in detergent extracted bovine retinal pigment epithelium when exposed to ATP. A comparison with fibroblasts and smooth muscle cells.

The response of single detergent treated bovine retinal pigment epithelial cells in culture to ATP was measured with an image analyser. The most pronounced contraction was produced by 1.0 mM ATP with most change taking place in the first 10 min. At 1 h the area had decreased by about 33%, perimeter 22% and maximum length 25%. By way of comparison rabbit skin fibroblasts had a decreased area of approximately 40%, perimeter 25% and maximum length 22%. Bovine aortic smooth muscle cells on the other hand decreased in area by 55%, perimeter 40% and maximum length 36%. It is hoped that this assay may be used to evaluate drugs which could counteract contractile events in proliferative vitreoretinopathy.

Adenosine Triphosphate↗
PubMed1987

Whipple's disease confined to the central nervous system.

Progressive hypersomnia, memory disturbance, and vertical ophthalmoplegia developed in a 63-year-old woman. The diagnosis of Whipple's disease of the central nervous system was suggested by her presentation and results of studies using magnetic resonance imaging. Despite a one-month course of antibiotics, active Whipple's disease, localized to the central nervous system, was found at autopsy.

Anti-Infective Agents↗
PubMed1987

Computer-based patient education for older persons with osteoarthritis.

A program of 8 lessons on various aspects of osteoarthritis (OA), its treatment, and patient self-care was prepared on an Apple IIc computer. The courses were then field-tested and evaluated by 72 older (age range 52-88) OA patients in community centers for senior citizens. Statistical analysis of the findings showed significant increases in knowledge and significant self-reported, beneficial behavior changes, including increased exercise, use of heat, and rest. Our findings demonstrate that older persons can use the computer to learn to cope with OA when a thoughtfully planned program is made available in a community setting.

Aged↗
PubMed1986

Isolation, characterization, and preliminary X-ray diffraction data for a serine protease from Penicillium cyclopium.

The major extracellular protein of Penicillium cyclopium has been isolated from its culture media and purified by ammonium sulfate fractionation, gel, and ion-exchange chromatography. We show this secreted protein to be endopeptidase. The molecular weight is approximately 32,000, the pI is 5.0, and the pH optimum using a variety of protein and synthetic substrates is around 7.0. Inhibition studies show that the protease is not inhibited by pepstatin nor by p-chloromercuribenzoic acid, indicating, respectively, that it is not an aspartyl protease nor a thiol protease. Complete inhibition is observed, however, with phenylmethanesulfonyl fluoride. Three crystal forms suitable for high resolution x-ray diffraction studies have been obtained from this purified protease with reflections being observed to well beyond 3.0 A resolution. One form having a needle morphology is of the orthorhombic crystal class and has space group P2(1)2(1)2(1). The unit cell dimensions are a = 41.9 A, b = 43.2 A, and c = 111.5 A with 1 molecule of the protease occurring in the asymmetric unit. The second form grown at pH values less than 6.0 has a plate morphology, is of orthorhombic space group P2(1)2(1)2(1), and has unit cell dimensions a = 59.12 A, b = 62.33 A, and c = 70.62 A. The third form is polyhedral in habit, is also of space group P2(1)2(1)2(1), and appears when the pH of the mother liquor is greater than 7.0. The cell dimensions of this crystal form are a = 57.07 A, b = 58.82 A, c = 70.79 A, and again there is 1 molecule/asymmetric unit. Three-dimensional structural analysis by x-ray diffraction is now underway. All crystal forms are somewhat denser than the norm having mass to volume ratios of 1.58, 2.00, and 1.85 A3/dalton, respectively.

Chromatography, Gel↗
PubMed1986

An experiment regarding crystallization of soluble proteins in the presence of beta-octyl glucoside.

Twenty-one soluble proteins, five tRNAs, and three protein-nucleic acid complexes were studied in a systematic manner with regard to their crystallization behavior from polyethylene glycol and ammonium sulfate solutions in the presence of 0 to 1.5% beta-octyl glucoside. Our observations suggest that this neutral detergent does influence in a very positive way the growth characteristics of the macromolecules included in this experiment. In general, more reproducible and rapid growth was noted with an increased number of large individual crystals at the expense of microcrystals. In several cases, new crystal forms were discovered. Selected x-ray diffraction analyses imply that crystals grown in the presence of beta-octyl glucoside diffract as well or better than those grown in its absence. In addition, a screen of two proteins grown in the presence of 14 different common detergents suggested that a general detergent effect may be beneficial for the growth of crystals of biological macromolecules.

Crystallization↗
PubMed1986

Phagocytosis of latex microspheres by bovine meshwork cells in culture.

The ability of cultured bovine trabecular meshwork cells to phagocytose latex microspheres was studied by electron microscopy. In addition, the incorporation of 125I gamma-globulin-coated microspheres by the meshwork cells was monitored. The cultured cells, on the basis of quantitation by scanning electron microscopy, did not show significant preference between biotic particles (gamma-globulin-coated microspheres) and abiotic particles (uncoated microspheres). Surface microvilli appeared to be involved in the initial stages of phagocytosis; indeed a significant negative correlation was demonstrated between the incidence of microvilli and the commitment to phagocytosis of preconfluent cells. Two weeks postconfluent cells were shown to be significantly less phagocytic than preconfluent cells. The importance of these findings in terms of the behaviour of meshwork cells in vivo is discussed.

Animals↗
PubMed1986

Some effects of phagocytosis on bovine meshwork cells in culture.

In this tissue-culture study, some effects of phagocytosis on the cell were investigated. Third-passage bovine trabecular-meshwork cells were incubated with latex microspheres for periods of up to 60 hr. Cells which had been involved in phagocytosis were found to settle at a faster rate than control cells, but if microspheres were added to the medium of recently settled cells, there was a reduction in their proliferative activity. Incorporation of tritiated proline remained unchanged, whereas uptake of tritiated glucosamine increased with the time period of phagocytosis. The fibronectin scaffold was more extensive and elaborate when cells were pre-incubated with microspheres before settlement. Exposure to a low concentration of microspheres promoted a higher uptake of a second presentation of 125I-labelled microspheres--an effect which was not seen if the original dose was too high.

Animals↗
PubMed1986

Low plasma triglyceride levels in lake dwelling East African tribesmen--a fishy story?

Samples of East African tribesmen from two separate locations were compared with respect to a number of anthropometric, cardiovascular and biochemical variables. The major finding was a large, significant difference in mean triglyceride levels between the groups (0.97 vs. 0.67 mmol/l; p less than 0.001), the mean plasma triglycerides being 31% lower in those for whom fish formed a substantial part of their daily food intake.

Adult↗
PubMed1986

Investigations of cytoskeletal elements in cultured bovine meshwork cells.

An ultrastructural, immunohistochemical, and functional study was conducted on cultured bovine meshwork cells. Particular emphasis was placed on the organization of the cytoskeleton, and the cells were viewed either as whole cells or following detergent extraction. For ultrastructural examination, several modes of viewing were adopted, including a detector situated above the specimens collecting secondary electrons (SE), a detector situated beneath the specimen collecting transmitted electrons (STEM), and conventional transmission electron microscopy at 100 KV (TEM). In whole cell mounts, information was obtained about the organization of the cytoskeleton and its relationship to other cytoplasmic organelles. Extraction procedures removed much of the plasma membrane and most organelles. The nucleus and cytoskeleton remained and stress fibers were prominent. Immunohistochemistry showed that the actin content of the cytoskeleton could be preserved after detergent extraction. Detergent-extracted cells decreased their surface area when exposed to MgATP in a dose-dependent manner. The decrease in surface area was associated with disassembly of cytoskeletal stress fibers and was optimal with 1 mM MgATP. Whether or not the change in surface area could be considered a "contractile event" was discussed.

Actins↗
PubMed1983

The onset of binocular function in human infants.

Visual evoked potentials (VEP) elicited by a dynamic random-dot correlogram were used to assess the development of cortical binocular function in infant subjects. In a group of newborn infants who showed a VEP for a comparable non-binocular stimulus, none showed evidence of binocular function. A further group of infants were tested longitudinally, starting between 35-50 days. The median age for the first evidence of binocular function in this group was 91 days, with individual variation from 54 to at least 105 days.

Aging↗
PubMed1982

Azo reduction of sulphasalazine in healthy volunteers.

1 A comparison of total sulphapyridine saliva concentrations resulting from administration of sulphapyridine and sulphasalazine at equimolar doses has been carried out. It is concluded that the extent of azo reduction of sulphasalazine to release sulphapyridine is complete in healthy volunteers. 2 An ampicillin course of treatment alters the azo reduction of sulphasalazine. The extent of cleavage is reduced by one third on average. There is no change in the rate of absorption of the release sulphapyridine. 3 An ampicillin course of treatment does not alter the disposition of sulphapyridine. The changes noted in acetyl conjugate plasma concentrations are entirely consistent with reduced availability of sulphapyridine.

Ampicillin↗