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Biomedical subjects

W McArthur

Publications and source records attributed to W McArthur.

10 recordsLinked to original sources
PubMed1996

Oral diseases, mycology and periodontal microbiology of HIV-1-infected women.

HIV-1 infection is increasing more rapidly among heterosexual women. Relatively limited information is available on HIV-related oral pathoses in these individuals. To gain insight into the type and occurrence of oral lesions in this population, 25 HIV-1 infected women including asymptomatic, symptomatic and AIDS patients were examined clinically and sampled for detection of oral yeast and characterization of their subgingival microbial flora. Sixty percent of the subjects were African-American, with 80% infected via heterosexual contact. Oral candidiasis was the most common nonperiodontal oral lesion, observed in 44% of the patients. Oral yeast was cultured from all women with candidiasis and 76% of the total subjects. Oral hairy leukoplakia was clinically diagnosed in 16% of the subjects. Clinically mild to moderate gingivitis and periodontitis were observed in 84% and 52% of the patients, respectively. Candidiasis and the presence of cultivable yeast were observed in patients with low, intermediate, and high CD4+ T lymphocyte numbers. Plaque samples were collected from each subject and enumerated by predominant cultivable methods, selective media and microscopy. No differences were detected in the microflora associated with seropositive women with existing periodontitis relative to those without periodontitis or to seronegative women with periodontitis. Candidiasis was the most notable oral clinical manifestation in the HIV-1-infected women and may be a useful clinical indicator of early immune dysfunction mediated by HIV-1.

AIDS-Related Opportunistic Infections↗
PubMed1988

Effect of mouth rinsing with two polyvinylpyrrolidone-iodine mixtures on iodine absorption and thyroid function.

A prospective study was conducted to investigate the effect of long term therapy with two iodine-containing mouth rinses on thyroid function. Two groups of subjects were treated daily for 6 months with either a 5% polyvinylpyrrolidone (PVPI)-1.5% H2O2 mixture (Perimed) or a 5% PVPI-water mixture. Thyroid function studies, serum iodine concentrations, and urinary iodine excretion were measured before treatment, at 6-week intervals during the 6-month treatment period, and 3 weeks after the last treatment. There was evidence of significant iodine absorption (elevated serum total iodine and inorganic iodide concentrations and urinary iodine excretion) from daily use of both Perimed and the PVPI-water mixture. Serum T3 and T4 concentrations and the free T4 index did not change. There was a small significant rise in serum TSH concentrations during mouth rinse therapy, but all values remained within the normal range. This small increase in serum TSH is a normal adaptive response to the antithyroid effect of increased iodine intake and accounts for the maintenance of normal serum T4 and T3 concentrations. While daily use of these iodine-containing mouth rinses does result in significant iodine absorption, there is no evidence for the development of thyroid dysfunction during a 6-month course of therapy.

Absorption↗
PubMed1983

Characterization of a lymphokine produced by human T cells which inhibits collagen synthesis.

Human lymphocytes, isolated from peripheral blood, were cultured for 48 hr in a defined medium containing 10 mg/ml bovine serum albumin and phytohemagglutinin. A lymphokine which inhibits collagen synthesis by cultured human dermal fibroblasts was purified from the lymphocyte incubation medium by successive steps of ammonium sulfate precipitation, gel filtration chromatography, and isoelectric focusing. Good recovery of this collagen synthesis inhibitory factor (CSIF) was obtained and a factor with an approximate molecular weight of 55,000 and a pI of 6.2 was isolated. The purification of the factor should permit further studies on its mechanism of action.

Chromatography, Gel↗
PubMed1983

Implant experience with unipolar polyurethane pacing leads.

A total of 905 unipolar polyurethane pacing leads have been implanted by the first author's group, between April 1978 and February 1982, with a mean implant of 1.4 years. Twelve leads were explanted and analyzed. Eleven of the explanted leads exhibited some degree of surface damage or "frosting." Of the 11, five atrial (Medtronic 6991 U) and one ventricular (Medtronic 6971) lead suffered complete insulation failure. One lead was completely free from surface damage. Clinically, insulation failure presented as muscle stimulation and/or battery depletion. Surface damage appears to be due to an environmental stress cracking (ESC) mechanism. ESC requires both a surface active agent from the hostile biological environment, and stress in excess of a threshold value. The minor surface damage or "frosting" of the eleven explanted leads was typically 10 to 15 microns deep on leads implanted about one year, although one device (15 months) had 30 micron cracks. No lead failures in this series were attributed to this shallow cracking mechanism. The severe cracking of the six Medtronic leads leading to insulin failure was thought to be due to the unusually high tensile stresses imposed by manufacturing processes and ligatures. The incidence of failure was 7% (5/74) for the Medtronic 6991 U and 0.2% (1/454) for the Medtronic 6971. Medtronic lead manufacturing processes have been modified to reduce the high residual tensile stresses and a fixation sleeve has been added to reduce ligature stress.

Arrhythmias, Cardiac↗
PubMed1980

Bone solubilization by mononuclear cells.

Mononuclear cells derived from chicken peripheral blood or from thioglycollate-induced mouse peritoneal exudates were found to cause calcium release from devitalized homologous bone in vitro. These mononuclear cells with osteolytic activity were adherent to plastic surfaces and were identified as being macrophages by cell surface markers and histochemical staining. Other mononuclear cells such as chicken thymocytes, nonadherent peripheral blood mononuclear cells, and chick embryo fibroblasts did not cause bone dissolution. In parallel with the active solubilization of bone mineral, 14C-label was also released from devitalized calvaria prelabeled with 14C-proline. Macrophages, inactivated by repeated freezing and thawing as well as those cultured in the presence of iodoacetate, did not solubilize bone in vitro. The degree of bone solubilization was directly related to the numbers of macrophages per culture as well as the duration of the culture period. Powdered devitalized homologous bone was used in most experiments, but macrophages were also able to solubilize bone material in vitro from devitalized calvaria and bone slabs. The addition of Escherichia coli lipopolysaccharide to cultures of bone and macrophages significantly increased the levels of calcium released from bone. The addition of parathyroid hormone and calcitonin had no effect on macrophage-mediated bone dissolution. These results suggest that viable macrophages have osteolytic activity and that this activity is modulated by an inflammatory mediator, endotoxin.

Animals↗
PubMed1979

Inhibition of collagen synthesis by mononuclear cell supernates.

Mononuclear cell infiltration and alteration in the connective tissues are prominent features of the inflammatory response in a number of diseases. To determine whether mononuclear cell products can modulate collagen synthesis, human peripheral mononuclear cells from normal donors were isolated by Ficoll-Hypaque gradient centrifugation and then incubated for 48 h with or without phytohemagglutinin. Confluent cultures of normal, human skin fibroblasts were incubated with [14C]proline and various amounts of dialyzed supernates from the mononuclear cell cultures. Labeled, newly synthesized collagen was estimated by [14C]hydroxyproline analysis, collagenase digestion, and chromatography on Agarose A-5m in sodium dodecyl sulfate. The total incorporation of [14C]proline was not significantly affected by addition of the mononuclear cell supernates, but as much as 90% decrease in the synthesis by the fibroblasts of labeled collagen was found relative to controls. Supernates from the phytohemagglutinin-stimulated cultures were more active than those from nonstimulated cells. These results suggest that mononuclear cells can synthesize a factor(s) which can selectively inhibit collagen synthesis.

Ascorbic Acid↗
PubMed1979

The porous endocardial electrode.

The permanent endocardial electrode has exhibited the problems of dislodgement, excessive threshold rises and loss of sensing. These failure modes are addressed with a new electrode incorporating a porous body of Pt-Ir fibers with a fiber diameter of 20 micrometers and an overall density of 10%. Porous electrodes have the advantages of utilizing the electrode interior both for tissue ingrowth to improve anchoring and for electrolyte penetration which improves R wave amplitude and reduces polarization losses. A series of 20 porous electrodes was compared with 17 solid electrodes of similar dimension. Electrodes were implanted in dogs in the apex of the right ventricle, and were subsequently followed up to 210 days. Comparison of the electrode data revealed that the porous electrodes had a 40% reduction in chronic voltage thresholds and had an overall dislodgement rate of 10%, compared to 53% for the solid electrodes. Histological examination revealed tissue ingrowth throughout the electrode interior and a fibrotic capsule about half the thickness of the solid electrodes. R wave stability was enhanced with the porous electrode due to improved anchoring, reduction in slew rate changes and less R wave attenuation. Assuming results are translatable to humans, the porous electrode will provide a greater pacing safety margin when used with a standard demand pacemaker, or improved longevity with the same safety margin as solid electrodes if used with a programmable pacemaker. The incidence of dislodgement and sensing failure will also be diminished with the porous electrode.

Animals↗
PubMedDate not supplied

Physiological and electrical characteristics of the porous endocardial electrode.

The principal complications in pacemaker therapy involve electrode-tissue instability. A new porous electrode has been devised that allows tissue ingrowth into the electrode interior, improving electrode biocompatibility and resulting in reduced dislodgment incidence, lower pacing thresholds, and improved sensing. Electrode porosity reduces polarization impedance permitting small-electrode design for both improved pacing longevity and optimal sensing function.

Connective Tissue↗