Stainless steel mouth mirrors.
Explore the source record for details and available documents.
Dental Instruments↗
Biomedical subjects
J M Davis
Publications and source records attributed to J M Davis.
Role of single disulfide in recombinant human tumor necrosis factor-alpha.
Two analogs of tumor necrosis factor-alpha (TNF-alpha) were produced by in vitro site-directed mutagenesis. In these analogs, cysteine residues at positions 69 and 101, which form a disulfide bond, were changed to alanine or leucine. CD spectra showed that the analogs are apparently similar in secondary and tertiary structure to the natural sequence TNF-alpha. In addition, the molecular size of the analogs was identical to that of the natural sequence TNF-alpha as determined by gel filtration. However, fluorescence spectra and quenching indicated that the removal of the disulfide bond alters the local conformation around tryptophan residues. The cytolytic, macrophage activation, and lipogenic activities decreased in the order of the natural sequence TNF-alpha greater than the alanine analog greater than the leucine analog, suggesting that the surface involving the disulfide bond plays a role in these biological functions and the introduced modifications decrease the activity. Differential effect of the modifications was suggested in the antiviral activity, since in this assay only the leucine analog showed significantly lower activity.
Animals↗
Cross-infection through the dental handpiece.
Explore the source record for details and available documents.
Dental Instruments↗
Characterization of recombinant human erythropoietin produced in Chinese hamster ovary cells.
Physicochemical properties of recombinant human erythropoietin were examined. This protein, produced in Chinese hamster ovary cells, showed a conformation apparently identical with the natural product isolated from human urine when examined by circular dichroism, UV absorbance, and fluorescence spectroscopy. Sedimentation equilibrium experiments showed the recombinant erythropoietin preparation to be essentially a single macromolecular component with a molecular weight of 30,400 and a carbohydrate content of 39%. The Stokes radius of recombinant erythropoietin was estimated to be 32 A from gel filtration, much larger than the 20-A radius calculated for a sphere of the observed molecular weight. This difference may be ascribed to the extensive glycosylation. The fluorescence and phosphorescence spectra showed that the luminescent tryptophan(s) is (are) solvent-exposed and can be quenched by I- and acrylamide but not by Cs+. On acid titration, the recombinant erythropoietin showed a conformational transition with a midpoint of pH 4.1. This suggests that the net charges on the protein moiety rather than on the whole molecule play a role in protein structure stability.
Animals↗
Structure of human tumor necrosis factor alpha derived from recombinant DNA.
Recombinant DNA derived tumor necrosis factor alpha, when expressed at a high level in Escherichia coli, appeared in the pellet and soluble fractions of disrupted cells. The protein was purified from the pellet fraction by solubilizing it in urea and reducing agent and was refolded into a buffer without these additives. The structure of the protein was identical with that purified from the soluble fraction without exposure to both reducing and denaturing agents, as demonstrated by circular dichroism, gel filtration, and sulfhydryl titration. As a reflection of the structural similarity, both purified proteins showed identical cytolytic activity on mouse L929 cells. The protein was characterized as an essentially nonhelical and beta-sheet-rich structure and possibly as a noncovalently associating oligomer. Two cysteine residues form an intrapolypeptide disulfide bond.
Chromatography, Gel↗
Recombinant-DNA-derived bovine growth hormone from Escherichia coli. 2. Biochemical, biophysical, immunological and biological comparison with the pituitary hormone.
Bacterially synthesized, recombinant-DNA-derived bovine growth hormone (r-bGH), prepared as described in the preceding paper in this journal, has been characterized in comparison with pituitary bovine growth hormone (pit-bGH). The characterization criteria include sodium dodecyl sulfate/polyacrylamide gel electrophoresis, automated N-terminal sequence analysis, amino acid composition, isoelectric focusing, reverse-phase high-performance liquid chromatography, ultraviolet absorbance, analysis for free protein thiol, sizing by gel filtration, circular dichroism, radioimmunoassay and biological activity in the hypophysectomized rat weight-gain assay. In every respect the r-bGH appears to be virtually identical to pit-bGH.
Amino Acids↗
Decreased beta-adrenergic receptors in the leukocytes of depressed patients.
We studied beta-adrenergic receptor binding, using 125I-cyanopindolol as the ligand, in the leukocyte membranes of depressed patients, schizophrenic patients, and normal control subjects during a drug-free period. We also determined plasma cortisol levels and dexamethasone suppression in these subjects. The maximum number of beta-adrenergic receptor sites (Bmax) was significantly lower in depressed patients than in normal control subjects. Nonsuppressors on the dexamethasone suppression test tended to have a decreased Bmax in comparison to suppressors. There was no significant difference in the Kd between any of the groups. These results indicate that decreased beta-adrenergic receptor responsiveness in the leukocytes of depressed patients is probably due to a decrease in the number of beta-adrenergic receptor sites.
Adult↗
Regression toward the mean: more on the price of beer and the salaries of priests.
Investigators must take great care in studying the temporal association between biological and clinical data. By selecting patients on the basis of deviant levels of a biological parameter, it often is impossible to separate the effect of regression toward the mean from a temporal association of clinical interest. Experimental strategies that focus exclusively on subjects with extreme values are particularly prone to misinterpreting the effects of regression toward the mean as a temporal change in the variable of interest. We cite specific examples of two previous studies of the relationship between the dexamethasone suppression test (DST) and clinical response in depression. Contrary to the conclusions of the investigators, normalization of the DST had no relation to clinical response in the first 5 weeks of treatment. The decrease of post-dexamethasone cortisol levels occurred regardless of clinical response, most likely due to the effect of regression toward the mean.
Antidepressive Agents↗
Cell-surface markers on haemopoietic precursors. Reagents for the isolation and analysis of progenitor cell subpopulations.
Within the last decade, major advances have been made in the analysis of cell-surface marker expression on haemopoietic progenitor cells as a result of the development of multiparameter cell sorting and monoclonal antibody techniques. Although some controversy exists with regard to the actual identification of the stem cell, markers specific for CFU-s and for particular subsets of progenitor cells have not yet been identified. An analysis of cell-surface markers on haemopoietic progenitor cells is complicated by at least three factors. First, it appears that, in mice, the clonal assays do not adequately identify the haemopoietic stem cell. Complete repopulation of all haemopoietic cell compartments in vivo over an extended period of time appears to be the only reliable method for identifying such a cell. Secondly cell-surface marker distribution on haemopoietic progenitors from normal tissues may be indicative of the cycling status of cells. Thus, expression of markers on progenitors from bone marrow or foetal liver which have been perturbed by drugs or viruses may merely reflect a change in their cycling status following drug or viral insult. Thirdly, substantial loss of cells occurs during the purification of particular cell types. For most cell separation procedures, only a minor proportion of the progenitor cells of interest are recovered and these may not be representative of the progenitor population as a whole. During differentiation to mature cells, antigenic determinants present on early progenitor cells may either be progressively lost or amplified. This differential expression of cell-surface molecules has provided a useful tool for the substantial enrichment of haemopoietic subsets, particularly CFU-E and CFU-s. To date, however, most early haemopoietic progenitor cells detected by in vitro CFC assays (day 8 CFC) cannot be completely segregated from one another. The ability to distinguish between such progenitors during the early stages of lineage commitment would provide a more detailed understanding of the relationship between lymphoid precursors, myeloid precursors and stem cells, and would lead to significant advances in developmental biology. Separation of cells at different stages of differentiation within a given lineage would provide an opportunity for studying regulatory mechanisms involved in gene expression in normal cell populations.
Animals↗
Stress hormone response to exercise in elite female distance runners.
Explore the source record for details and available documents.
Adrenocorticotropic Hormone↗
Functions of social workers in a home health agency.
The activities of social workers employed by a public health nursing agency were studied. The data suggested that nurses and social workers collaborate more than prior studies have shown but also suggested that the nurses were selective in their decisions to refer cases to social workers. The study raised questions about the clarity of the agency's expectations of social workers and of nurses.
Community Health Nursing↗
Occupational health and safety in the National Health Service: the present and the future.
Explore the source record for details and available documents.
Humans↗
Synthesis of cytomegalovirus DNA is an antiviral target late in virus growth.
The mechanism of action of 9-(1,3-dihydroxypropoxymethyl)guanine (DHPG) and phosphonoformic acid (PFA) but not 5-fluorouridinedeoxyribose (FUdR), provides selective action against cytomegalovirus (CMV)-coded events and this was used to demonstrate that the synthesis of viral DNA was continuous during the extended phase of virus growth. The synthesis de novo of viral DNA was measured by restriction enzyme analysis after exposure to [32P]orthophosphate and its interruption by DHPG or PFA resulted in a cessation in the extrusion of infective virus from treated cells. The rate of decline in infectivity appeared to correspond to the failure of cells to maintain the synthesis of late proteins once DNA synthesis was blocked. Thus, regulation of late protein synthesis appeared to be linked to synthesis de novo of viral DNA even at late stages in CMV growth. The synthesis of the polyamines spermidine and spermine, considered obligatory for CMV growth, was unaffected by early or late inhibition of viral DNA and this showed that some virus-induced events were unaffected by the restriction on virus growth by DHPG. This provided evidence that polyamine biosynthesis was a target independent of viral DNA synthesis per se, which may be important in future considerations of combined drug therapies.
Acyclovir↗
Conformation and stability of two recombinant human interferon-alpha analogs.
Structural features of a recombinant E. coli derived interferon-alpha analog, interferon consensus1, was studied by circular dichroism and fluorescence spectroscopy. Circular dichroic spectra of the purified protein showed that it has about 70% alpha-helix and a distinct tertiary structure. These structural features are similar to those for a natural interferon-alpha subtype, interferon-alpha 2, indicating that the amino acid substitutions in interferon consensus1 apparently did not alter the protein structure. Another analog, interferon consensus5, which has Ser instead of Cys at residues 1 and 99 but is otherwise identical to interferon consensus1, was prepared to study the role of the disulfide bond between Cys 1 and 99. Circular dichroic and fluorescence spectra indicated similarity in the structure of these two analogs. However, interferon consensus1 was significantly more stable than interferon consensus5 against denaturation. pH unfolding experiments indicated that the former protein is more stable in the transition region by about 1.6 kcal/mol, which was interpreted in terms of the increased free energy of the denatured state due to an extra disulfide bond in interferon consensus1.
Circular Dichroism↗
The New Mexico sealant program: a progress report.
In 1979, the dental health program of the New Mexico Health and Environment Department began a school-based sealant activity. Children in the first, second, third, sixth, and seventh grades in selected New Mexico communities were offered sealants through this sealant activity. During the 1984-85 school year, program staff began seeing several hundred sixth-grade students who had received sealants in either the first, second, or third grade. Tooth- and surface-specific data on the current condition of all the previously sealed occlusal surfaces were collected from all these previous recipients of sealants. During the 1985-86 school year, we found that sixth-grade students who received sealants as first, second, or third graders had 5.6 percent of the occlusal surfaces of their first permanent molars either decayed, missing, or filled. Their classmates who had not previously received sealants had 26.85 percent of the same tooth surfaces either decayed, missing, or filled. During the 1985-86 school year, the complete retention rates for sealants were found to be 67.36 percent after six years, 78.53 percent after five years, and 93.47 percent after one year. The partial retention rates were found to be 10.46 percent after six years, 10.63 percent after five years, and 3.04 percent after one year.
Child↗
Asymptomatic shedding and subsequent transmission of genital herpes simplex virus.
We report the transmission of genital herpes simplex virus (HSV) infection from an asymptomatic woman shedding virus from the cervix to two male sexual partners and further transmission from these two men while their infection was in the prodromal phase. The value of the restriction enzyme analysis of viral deoxyribonucleic acid (DNA) is presented. Guidelines regarding the management of patients who are found to be asymptomatic shedders of HSV are discussed.
Adult↗
Clinical utility of biochemical assays in psychiatry.
Biological abnormalities are found almost consistently in schizophrenia and affective disease. While most remain as research leads, some are sufficiently well studied that they are now or may soon enter in routine medical practice. The dexamethasone test (DST) has been investigated thoroughly enough so it should pass into practice.
Antidepressive Agents↗
Accumulation of deuterium oxide in body fluids after ingestion of D2O-labeled beverages.
A simple low-cost procedure was developed to compare the temporal profiles of deuterium oxide (D2O) accumulation in body fluids after ingestion of D2O-labeled solutions. D2O concentration was measured in plasma and saliva samples taken at various intervals after ingestion of 20 ml of D2O mixed with five solutions differing in carbohydrate and electrolyte concentrations. An infrared spectrometer was used to measure D2O in purified samples obtained after a 48-h incubation period during which the water (D2O and H2O) in the sample was equilibrated with an equal volume of distilled water in a sealed diffusion dish. The procedure yields 100% recoveries of 60-500 ppm D2O with an average precision of 5%. When compared with values for distilled water, D2O accumulation in serial samples of plasma and saliva was slower for ingested solutions containing 40 and 15% glucose and faster for hypotonic saline and a 6% carbohydrate-electrolyte solution. These differences appear to reflect known differences in gastric emptying and intestinal absorption of these beverages. Therefore this technique may provide a useful index of the rate of water uptake from ingested beverages into the body fluids.
Adult↗