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Biomedical subjects

R White

Publications and source records attributed to R White.

At least 667 records · Page 37Linked to original sources
PubMed1984

An SEM study of posts cemented with an unfilled resin.

Post preparations in two groups of endodontically treated anterior teeth were completed. In Group I, the preparation was rinsed with 2 ml of 5.25% NaOCL. In Group II, the preparation was rinsed with 1 ml of 17% EDTA, followed by 1 ml of 5.25% NaOCl. A plastic post was fitted and cemented with an unfilled resin. After polymerization, the teeth were decalcified in 5% nitric acid. The decalcified structured was dissolved away with 5.25% NaOCl, leaving a model of the cemented post. This was examined by SEM to determine the extent of resin penetration into the dentinal tubules. In Group I, most of the post was smooth, and there was penetration only in small, random areas. In Group II, there was penetration into the tubules the full length and circumference of the post. Such penetration provides a very strong mechanical lock that enhances the tensile strength of the cemented post. Removing the smeared layer and then cementing a post with a Bis-GMA resin results in greatly increased tensile strength, even with shorter posts.

Bisphenol A-Glycidyl Methacrylate↗
PubMed1984

A locus on chromosome 11p with multiple restriction site polymorphisms.

We have discovered and characterized a new polymorphic locus on chromosome 11p, D11S12, defined by an arbitrary genomic DNA segment cloned in the plasmid pADJ762. Four different polymorphic restriction sites with minor allele frequencies greater than 5% are revealed by Southern hybridization of this probe and its derivatives to digests of human DNAs. These include two MspI sites, a TaqI site, and a BclI site. The frequencies of the common haplotypes at this locus have been determined in a Utah population. Significant linkage disequilibrium has been demonstrated to exist between some pairs of polymorphic sites. A molecular map of this region has been determined, and the polymorphic sites have been localized. Comparison of physical separation with degree of linkage disequilibrium reveals an interesting case where an MspI site and a TaqI site that are separated by 6.8 kilobases (kb) show a greater degree of disequilibrium with each other than they do with two polymorphic sites located between them. One of the two interior sites is a BclI site that is approximately 0.2 kb away from the TaqI site but shows the same degree of disequilibrium with the TaqI site as with the MspI site 6.7 kb away. Although there is significant linkage disequilibrium at this locus, there are four major haplotypes with frequencies of 5% or greater, and the polymorphic information content (PIC) of this locus is .64.

Alleles↗
PubMed1984

Isolation and regional localization of DNA segments revealing polymorphic loci from human chromosome 13.

A recombinant DNA library enriched for portions of human chromosome 13 has been constructed from a hamster-human somatic cell hybrid that contained human chromosomes 13, 12, and 6p. A total of 733 phages were identified that contain human DNA inserts, and 46 single-copy subfragments have been derived and used as probes on Southern transfers of genomic DNA isolated from unrelated individuals. From this set, nine fragments revealing polymorphic loci (RFLP) in Msp I- or Taq I-digested DNA have been identified, of which three are polymorphic with both enzymes. Six of these probes have been shown to segregate concordantly with human chromosome 13 in a somatic cell hybrid mapping panel, and the RFLPs at these loci have been shown to behave as codominant Mendelian alleles. Additionally, hybridization to DNA isolated from cells containing various deletions of chromosome 13 has allowed regional localization. This recombinant DNA library will be useful in the study of retinoblastoma as well as in the study of the mechanisms responsible for abnormalities of this autosome.

Animals↗
PubMed1984

EMG biofeedback-controlled exercise in chronic arthritic knee pain.

Reinstitution of a regular exercise program for patients with chronic arthritic knee pain can be extremely important, given the overall medical and psychosocial status of the patient. A 60-year-old man with intense pain in his right knee was targeted for an exercise intervention program. Before treatment, the patient's symptoms included near absence of vastus medialis muscle, subpatellar crepitation, and other signs of atrophy. The patient had 17 exercise sessions of 15 minutes each using an ergometer. During these sessions, the patient was given audio feedback to train him to use the vastus medialis as the predominant knee extensor while minimizing use of the vastus lateralis. As treatment progressed, pain was markedly lessened, the vastus medialis increased to normal size, and crepitation was less than in prior exams. A portable home biofeedback device was used to help maintain the appropriate exercise response. Importantly, the patient reported an increase in positive mood as he was able to ambulate without pain.

Arthritis↗
PubMed1983

Developmental changes in DNA methylation around prostatic steroid-binding protein genes.

The state of DNA methylation around prostatic steroid-binding protein genes has been investigated at CCGG sites by using the restriction enzymes MspI and HpaII. In the ventral prostate, these sites change from being completely methylated around the C1, C2, and one of two C3 genes in 10-day-old animals to being unmethylated in 28-day-old animals. The second C3 gene is always methylated and probably transcriptionally inactive, and all four genes are hypermethylated in other tissues. Hormone withdrawal from mature animals results in methylation of approximately 50% of CCGG sites in the ventral prostate which correlates with an increase in the number of stromal cells relative to epithelial cells. This suggests that the state of DNA methylation in epithelial cells, where prostatic steroid-binding protein is expressed, is unchanged. Thus, the inverse correlation between gene expression and DNA methylation is valid during development but probably not during subsequent hormone withdrawal.

Aging↗
PubMed1983

Autoradiographic localization of estradiol- and progesterone-concentrating neurons in the isolated rhesus monkey hypothalamus.

Progesterone- and estradiol-concentrating neurons were autoradiographically localized in the in situ, vascularly isolated, rhesus monkey hypothalamus. Estradiol-concentrating neurons were dispersed throughout the hypothalamus, their density being greatest in the medial preoptic (MPOA) and medial basal hypothalamic nuclei (viz. dorsomedial, ventromedial (VMH) and infundibular nuclei). In contrast, progesterone-concentrating neurons were less densely localized in the medial preoptic, ventromedial (medial division) and infundibular nuclei. There was a virtual absence of progestin-concentrating cells in the anterior and posterior hypothalamic zones. This localization of cells was not attributed to the perfusion pattern of the isolated hypothalamus since a complete distribution of injected microspheres was found throughout the hypothalamus. The results of these studies indicate that a possible division between estradiol- and progesterone-concentrating neurons exists within the MPOA-medial basal hypothalamic nuclei of the rhesus monkey.

Animals↗
PubMed1983

Prostatic steroid-binding protein. Isolation and characterization of C3 genes.

Prostatic steroid-binding protein, whose expression is stimulated by androgens, consists of two subunits, one containing the polypeptides C1 and C3 and the other containing the polypeptides C2 and C3. We have isolated and sequenced cDNA clones specific for C3 mRNA and used them to isolate and characterize genomic clones for two C3 genes. Both genes are 3.2 kilobases with identical exon/intron arrangements, which is similar to the organization of the C1 and C2 genes, suggesting that they may have arisen by duplications of an ancestral gene. Finally, homologous human genes have not been detected.

Amino Acid Sequence↗
PubMed1983

Pluralism, professionalism and politics in nursing.

This paper describes the pluralist nature of the nursing society and highlights the different and often conflicting objectives of the several interest groups. In the second section the paper describes how the Royal College of Nursing dealt with these difficulties during the years 1948-61. The paper ends with a discussion of the present and future position in policy making with particular reference to the position of the Rcn as the nurses' professional organisation.

Education, Nursing↗
PubMed1983

Astrocyte cell lineage. II. Mouse fibrous astrocytes and reactive astrocytes in cultures have vimentin- and GFP-containing intermediate filaments.

When cells from mouse neopallium are grown in colony cultures for 10-12 days, small cells with many processes, resembling normal fibrous astrocytes, form on top of the astrocyte precursor cells independently of the presence of dBcAMP in the culture medium. These cells are distinctly different from the much larger, previously described reactive astrocytes which also form in colony cultures and whose maturation is greatly enhanced by the presence of dBcAMP in the culture medium. Immunofluorescence studies showed that both vimentin-containing and glial filament protein (GFP)-containing intermediate filaments (IF) are present in the small normal fibrous astrocytes as well as in the larger reactive astrocytes. The vimentin-containing IF are assembled first in astrocyte precursor cells, whereas GFP-containing IF are assembled later toward the final stages of astrocyte differentiation both in vivo and in vitro. Thus in respect to the expression of the two types of IF, astrocyte differentiation in vitro closely resembles that in vivo. Parallel studies by electron microscopy showed that the vimentin-positive but GFP-negative astrocyte precursor cells contain single IF or small groups of IF, whereas in the more differentiated normal fibrous astrocytes and reactive astrocytes which are also GFP-positive, additional IF arranged in large bundles are present.

Animals↗
PubMed1983

Prenatal diagnosis by ultrasonography of genitourinary abnormalities.

Prenatal ultrasound has resulted in the earlier recognition of genitourinary-related abnormalities. This is a review for urologists of the normal developmental anatomy, physiology, and ultrasound characteristics of representative urogenital abnormalities with guidelines for diagnostic or therapeutic intervention.

Ascites↗
PubMed1983

Mouse killing in rats induced by lesions of the medial hypothalamus or medial accumbens: short-term preoperative exposure to a mouse does not suppress the killing.

Rats were either exposed or not exposed to a mouse in their living cage for a 48-hr period. At the end of this time a bilateral lesion was made in the medial accumbens region or in the medial hypothalamus. When tested 2 days postoperatively, the killing frequency among rats that had been exposed to mice preoperatively was not significantly lower than that of rats that were not preoperatively exposed. The ineffectiveness of preoperative experience in suppressing the mouse killing induced by medial accumbens and medial hypothalamic lesions is similar to that found previously with dorsal-median raphe lesions and olfactory bulb lesions and is in contrast to the ease with which preoperative experience prevents mouse killing induced by septal lesions and serotonergic lesions induced by 5,7-dihydroxytryptamine.

Aggression↗
PubMed1983

False dopa reaction in studies of mammalian tyrosinase: some characteristics and precautions.

In cytochemical studies of B16 melanoma cells with the dopa reaction for tyrosinase, a false positive result that can easily be confused with authentic reactions has been observed. A preliminary characterization of this false reaction in comparison to authentic reactions with respect to stereospecificity, morphological characteristics, and subcellular localization has been conducted. Modifications of the classic dopa method have been devised that minimize occurrence of the false reaction.

Animals↗
PubMed1983

Effect of healing on small internal diameter arterial graft compliance.

Porosity is an essential component for long term function of small internal diameter synthetic vascular prostheses. Theoretically, porosity is required for healing by providing a scaffold for ingrowth of periprosthetic tissues. Porosity may be required for transfer of fluids and ions in prostheses even if tissue ingrowth does not occur. Increased permeability of vascular grafts has been shown to enhance tissue incorporation. Implants with pore sizes greater than 10 microns but less than 45 microns become ingrown with fibrohistiocytic tissue and capillaries. Implants with pore sizes greater than 45 microns are ingrown with organized fibrous tissue and minimal histiocytic response. The phenomenon of differential ingrowth may have important functional significance. Prostheses which heal with organized fibrous tissue have the potential for long term contracture, strangulation of vascularity and calcification. Fibrohistiocytic tissue has low mechanical strength and does not appear to contract or calcify. Elastomeric microporous vascular prostheses which are minimally ingrown or ingrown with fibrohistiocytic tissue maintain compliance after months of implantation. This study was designated to determine the effects of healing on the compliance of small internal diameter vascular replacements and to correlate the compliance to patency rates.

Animals↗
PubMed1983

Thrombogenicity and the interaction of proteins, platelets and white cells.

Radioactive labeled protein and platelet studies suggest that an ideal vascular surface absorbs albumin and prevents platelet adherence and aggregation. This study examines the interaction of serum and plasma proteins, white cells, and platelets in the thrombotic response to small internal diameter vascular prostheses. Thirty-seven replamineform silicone rubber vascular prostheses, 4 mm internal diameter and 6 cm length, had 5% aspirin and 5% theophylline by weight dispersed in a luminal coating (D); the remaining 37 control (C) prostheses had an identical silicone rubber coating without drugs. Scanning electron and darkfield microscopy confirmed similar surface topography in C and D grafts. One C and one D graft were studied in parallel using a modified canine arteriovenous fistula. Consistently, D prosthesis had increased bleeding through the graft wall. The 7 serum and 8 plasma experiments demonstrated greater accumulation on the D prostheses, the greatest deposition occurring within the first 30 minutes. In 8 platelet experiments, D grafts accumulated more radioactivity at both the 5 and 30 minute intervals. Six mononuclear and 8 PMN experiments had less accumulation on the D grafts at 15 minutes and no consistent difference at 60 minutes. Elution of C and D Grafts demonstrated significant drug levels in only the D grafts at the beginning of the experiments and after 15 minutes of exposure of blood. We conclude: (1) aspirin and theophylline have an effect on the initial interaction of plasma proteins, platelets and white cells in the thrombogenic response, (2) the effect diminishes as time released drug levels decrease.

Animals↗
PubMed1983

Chromosomal assignments of three random RFLP loci defined by base-pair changes in MspI sites.

Three cloned single copy sequences isolated from a random partial plasmid library of human EcoRI-HindIII restriction fragments detect MspI site polymorphisms in human DNA. Since at least two of them have allele frequencies that make them suitable for family linkage studies, we have determined their chromosomal localizations. DNA samples extracted from a panel of 31 Chinese hamster x human somatic cell hybrids, that were derived from six different human donors, were analyzed for the presence of human EcoRI or HindIII fragments hybridizing with the three probes. The results were correlated with the human chromosome contents of the hybrids. Concordancy was observed for clone pMS 1-14 (preliminary locus designation DOSLC3) and human chromosome 15, for clone pMS 1-27 (DOSLC2) and chromosome 20, and for clone pMS 1-37 (DOSLC1) and chromosome 3. Two independent hybrids had retained only the long arm of chromosome 3 and did not hybridize with this probe. Therefore, we assign this locus (now termed D3S3) to the short arm of chromosome 3.

Animals↗