Search PubMed⌕ Search

Biomedical subjects

H W Clark

Publications and source records attributed to H W Clark.

At least 37 records · Page 2Linked to original sources
PubMed1988

Detection of mycoplasmal antigens in immune complexes from rheumatoid arthritis synovial fluids.

This study was directed towards the detection of suspected antigenic microbial fragments in the immune complex (IC) fraction from chronic inflammatory disorders of the delayed type allergy. Mycoplasmas as the microbial prototype and joint fluids from the rheumatoid host were investigated. Protein-A affinity chromatography was used to isolate the immunoglobulin complex (IgG-IC) in six synovial fluids obtained from rheumatoid arthritis patients. The IgG-IC was digested with pepsin to further purify and obtain F(ab)2 complexes with greater specificity. The F(ab)2 complexes were dissociated and electrophoresed by SDS-PAGE and analyzed by immunoblotting using affinity purified rabbit antisera to six reference strains of human mycoplasmas. The presence of trace amount of mycoplasma antigens in the immune complex fractions was indicated by specific banding with antisera to M. pneumoniae, M. arthritidis, M. hominis, M. fermantans, and M. salivarium in one or more of the six synovial fluid fractions. The ELISA and immunoblot assays of seroconversion in rabbits immunized with the synovial fluid fractions also indicated the presence of mycoplasmal antigens.

Antigen-Antibody Complex↗
PubMed1987

In vitro effect of alpha-interferon on mononuclear cells of normal and autoimmune patients.

The effect of lymphoblastoid interferon (IFN-alpha) on cell-mediated and humoral immunity was studied in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). The base-line natural killer (NK) and antibody dependent cytotoxic cell (ADCC) activity was higher than normal in individuals with RA. The NK and ADCC activities were tested after IFN-alpha pretreatment and the augmentation of NK and ADCC activity was less in these patients than in normals. Lymphoblastoid IFN inhibited antigen induced T-cell proliferation in SLE to a lesser extent than in normal individuals. Finally, the addition of lymphoblastoid IFN was also less effective at suppressing in vitro polyclonal antibody formation by mononuclear cells from patients with SLE than from normals, with enhancement observed in some patients at the lower IFN-alpha concentrations tested.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1985

Medium-dependent properties of mycoplasmas.

Without a cell wall, the morphology, growth rate, and composition of mycoplasmas are culture media-dependent with variable properties best described as environmentally related. The adaptation of mycoplasmas to either a tissue cell or cell-free culture media, with dependency upon specific animal or plant products for survival, has led to investigations of their human host-related properties. The influence of culture media on the antibiotic sensitivities of mycoplasmas was measured by use of three different broths in two different assay systems. The variable results indicate that the inhibition of mycoplasma protein synthesis or growth may also be host-tissue dependent. The addition of noninhibitory penicillins to different culture media was found to affect the composition and antigenicity of some mycoplasmas. Using the complement fixation test, we found some human sera that were more reactive than rabbit antisera to mycoplasmas cultured in human synovial broth or in myelin-enriched broth. Mycoplasmas cultured in human lung broth and pig lung broth had media-dependent antigenicity. The antigenicity and the growth of mycoplasmas were found to depend on the proteolytic enzymes used to provide the essential peptides in tissue broths. The media-affected mycoplasmas indicate the presence of species-, strain-, and tissue-specific antigen sites that may determine immunopathogenicity in the genetically susceptible host.

Adaptation, Physiological↗
PubMed1983

Defective serum chemotactic capacity in rheumatoid arthritis.

Polymorphonuclear leukocytes (PMN) chemotaxis and serum chemoattractant ability were studied in patients with rheumatoid arthritis (RA) employing the agarose plate technique. No statistically significant differences were observed in random migration of unstimulated cells compared to the controls. Moreover, there were no statistically significant differences between the chemotactic migration of control and patient cells in response to a number of non-treated sera. The chemotactic responsiveness of normal PMN cells to treated rheumatoid serum was significantly less than that observed using treated control serum with Escherichia coli lipopolysaccharide. The possible explanation for this abnormality may be due to the presence of chemotactic inhibitors in some RA serum. No correlation was detected between chemoattractant activity of rheumatoid arthritis serum, circulating immune complexes or rheumatoid factor. There were no statistically significant differences in the adhesiveness of RA-PMNs compared to normal PMNs.

Antigen-Antibody Complex↗
PubMed1982

Inhibition of polymorphonuclear leukocyte migration by sera of patients with rheumatoid arthritis.

The migration of peripheral polymorphonclear leukocytes (PMN) of patients with rheumatoid arthritis (RA) and normal controls was studied using autologous sera and homologous rheumatoid positive and negative sera. A significant inhibition of cells from RA patients was observed using autologous or homologous rheumatoid sera in contrast to patients' PMN exposed to control sera in which no significant migration inhibition was detected. Negative results were observed when rheumatoid sera were used with PMN from normal controls. No correlation was found between the degree of PMN migration inhibition and the titer of rheumatoid factor. The results of these studies indicate that mononuclear cells in rheumatoid patients have varying degrees of sensitization to certain factor(s) in rheumatoid sera.

Arthritis, Rheumatoid↗
PubMed1982

Studies of phagocytic cell function in rheumatoid arthritis. I. Phagocytic and metabolic activities of neutrophils.

The polymorphonuclear cells (PMN's) of 20 patients with rheumatoid arthritis (RA) were analyzed for endocytic ability and metabolic capacity and were compared to those from a healthy control group over short intervals. The results of these studies indicate that the phagocytic activity (PA) and the nitroblue tetrazolium (NBT) dye reduction were significantly decreased in RA patients after 30 minutes of incubation. The rheumatoid patients showed a higher percentage of band cells and hypersegmented nuclei of their peripheral blood PMN's (PB-PMN's). No correlation was found between neutrophil functions and other parameters of the rheumatoid disease activity.

Adult↗
PubMed1982

Studies of phagocytic functions in rheumatoid arthritis. II. Effects of serum factors on phagocytic and metabolic activities of neutrophils.

A previous article has shown a diminished phagocytic and intracellular metabolic activity of the polymorphonuclear cells (PMN's) from patients with rheumatoid arthritis (RA). No correlation was found between PMN's functions with either clinical or laboratory expression of disease activity. In the present study the effects of rheumatoid sera on PMN's functions were investigated and the results revealed significant inhibition of phagocytic activity (PA) and nitroblue tetrazolium (NBT) dye reduction capacity of cells from RA as well as from a normal (N) control group. The number of PMN's showing aggregated latex particles on their surfaces was significantly higher in RA patient groups in the presence of rheumatoid sera. PMN's from N and RA groups were lysed in the presence of rheumatoid sera, with more significant destruction of RA-PMN's. No correlation was found between the PMN's function and the amount of circulating immune complexes (CIC's) or rheumatoid factor (RF). Significantly lower concentration of complement (C4) levels and higher IgA mean values were observed in the patient group compared to the standard values. The mechanism(s) underlying the impaired PA and NBT reduction may be due to defective intrinsic cell function as well as the extra cellular effects of blocking or lytic factors present in rheumatoid sera.

Antigen-Antibody Complex↗
PubMed1981

Evaluation of lymphocyte populations and their mitogenic activity in relation to serum copper and immunoglobulin levels in rheumatoid arthritis.

Purified mononuclear cells from the peripheral blood and sera from 30 patients with active rheumatoid arthritis (RA) were compared to the control or standard values in respect to the total number of B (EA) and T (E) rosette forming lymphocytes, their responsiveness to phytohemagglutinin (PHA) and pokeweed (PWM) mitogen, and serum immunoglobulins, (C3) complement and copper levels. The RA patients had significantly lower values for EA cells, PWM stimulation index, hemoglobin and hematocrit. Significantly higher values for serum copper and sedimentation rates were found. Relatively higher values for IgG, M, A and C3 were found in RA patients with lower values for E cells.

Adult↗
PubMed1980

Why psychiatry is a low-paid medical specialty.

The authors examine the effect of economic forces on the income of psychiatrists and compare the economic position of psychiatry with that of the rest of medicine. Since 1970 the income of psychiatrists has been losing ground compared with that of other medical specialists, although recent data suggest a possible improvement in the economic position of psychiatry. The authors believe that psychiatrists' incomes are important as a sign of the value of psychiatric care and as one measure of the economics of practice, that is, the incentives related to the distribution of scarce technology and labor in the service delivery system.

Humans↗
PubMed1965

Sedimentation counting and morphology of Mycoplasma.

Clark, Harold W. (The George Washington University School of Medicine, Washington, D.C.). Sedimentation counting and morphology of Mycoplasma. J. Bacteriol. 90:1373-1386. 1965.-The sedimentation technique for counting viral particles was applied to the quantitation and morphological identification of Mycoplasma in broth cultures. Mycoplasma, apparently in their native form, firmly adhered to the surface, when sedimented on glass cover slips or onto electron microscope grids. The sedimented cover slip preparations stained with crystal violet could be readily counted in the light microscope. The cultures sedimented onto electron microscope grids were readily counted at low magnification and provided excellent preparations for morphological examination at higher magnifications. It was found that air-dried Mycoplasma particles were enlarged considerably because of excessive flattening. Fixation of sedimented Mycoplasma particles in diluted OsO(4) prior to air drying yielded a more realistic morphology, with various sizes and shapes in the stages of the growth cycle exhibited. A new technique of differentially staining Mycoplasma colonies on agar plates was developed to facilitate the quantitation of viable colony-forming units for comparison with total counts. The use of plastic or Parafilm gaskets for dry mounting was developed to facilitate the handling and examination of the stained cover slip preparations. The results of this investigation indicated that the growth cycle of some Mycoplasma species includes a stage of hexadic fission with the cleavage of minimal reproductive units (less than 100 mmu) containing a limited deoxyribonucleic acid genetic coding molecule (approximately 4 x 10(6)).

Bacteriological Techniques↗
PubMed1963

IDENTIFICATION OF MYCOPLASMATACEAE BY THE FLUORESCENT ANTIBODY METHOD.

Clark, Harold W. (The George Washington University, Washington, D.C.), Jack S. Bailey, Richard C. Fowler, and Thomas McP. Brown. Identification of Mycoplasmataceae by the fluorescent antibody method. J. Bacteriol. 85:111-118. 1963.-The conditions of the fluorescent antibody reactions were studied in relation to their application to Mycoplasmataceae or pleuropneumonia-like organisms (PPLO). Mycoplasma hominis type 1 and 2 antigens and their homologous antisera were used to determine the activity and specificity of these and other strains. Fluorescein isothiocyanate conjugated antiserum globulin preparations were used in both the direct and indirect fluorescent antibody methods. A direct tube technique was used for the detection and measurement of growth in broth cultures by the addition of conjugated antiserum. The specific fluorescent staining and recognition of hot water fixed M. hominis colonies was presented as a suitable identification standard. The antigenic activity was found to remain in the insoluble residue after exposure of M. hominis strains to sonic vibration (9 kc) for 30 min and centrifugation. Brief 2-min exposures of tissue cells to vibration (9 kc) caused the disruption of tissues, with the release of viable and "bound" nonwashable strains that reacted specifically with fluorescent antibody. It is proposed to apply both the sonic vibration and the fluorescent antibody techniques for the identification of Mycoplasmataceae in human tissues.

Journal Article↗
PubMed1961

Antigenic properties of pleuropneumonia-like organisms from tissue cell cultures and the human genital area.

Bailey, Jack S. (George Washington University, Washington, D. C.), Harold W. Clark, William R. Felts, Richard C. Fowler, and Thomas McP. Brown. Antigenic properties of pleuropneumonia-like organisms from tissue cell cultures and the human genital area. J. Bacteriol. 82:542-547. 1961.-Antigens were prepared from several tissue culture and human genital strains of pleuropneumonia-like organisms (PPLO) by a method utilizing continuous agitation of the incubating cultures. Antisera were produced in rabbits by intravenous injection of suspensions of these organisms standardized turbidimetrically. The antigenic properties of the selected strains were compared by agglutination techniques supplemented by a test based upon the inhibition of growth of PPLO by specific antisera.The majority of tissue culture strains of PPLO studied, including contaminants from several HeLa cell lines, appeared to be antigenically similar to the human type 1 strains. However, one strain (Sp-1) from a HeLa cell line was found to be related to the human type 2 PPLO.

Cell Line↗
PubMedDate not supplied

When to begin smoking cessation in substance abusers.

During the past several years, there has been an increasing recognition and acceptance that the use of tobacco products often produces nicotine dependence and nicotine addiction. Despite this, the substance abuse treatment community has been slow to promote smoking cessation for patients who are in substance abuse treatment for another addiction. Dogma, although starting to change, persists that cigarette smoking pales in comparison to other addictions and should not be addressed at the time of initial treatment for another addiction. The limited research to date, which will be reviewed in this article, does not support this dogma. In addition, patients presenting for substance abuse treatment report high interest in stopping smoking, including interest in stopping when they initially present for substance abuse treatment.

Alcoholism↗
PubMedDate not supplied

An open trial of low dose buprenorphine in treating methadone withdrawal.

Buprenorphine (BPN) is a prescription analgesic with mixed opioid agonist and antagonist properties. This pilot study conducted detailed case studies with 15 methadone dependent patients. The study sought to determine whether repeated low doses (0.15 to 0.3 mg) of sublingual BPN would relieve opioid withdrawal symptoms. Subjects developed mild to moderate withdrawal symptoms within 26 to 31 hours of methadone discontinuation. Once in withdrawal, the subjects received 0.15 mg of BPN sublingually. A second dose of 0.15 mg was administered in an hour, and a 0.30 mg dose in 2 hours, if the subject obtained no relief of withdrawal symptoms. In 6 subjects a low dose of 0.15 to 0.30 mg sublingual BPN resulted in the disappearance of subjective and objective withdrawal symptoms within 10 minutes to 2.5 hours. Four others had brief, partial relief of symptoms. Five subjects failed to experience any relief of withdrawal symptoms after a total of 0.6 mg BPN administered over 3 hours. One nonresponder suffered what appeared to be a severe precipitated withdrawal reaction similar to that which can be produced in addicts by a naloxone challenge. The 4 Caucasian responders required 1 to 2 hours to respond to BPN, whereas the 2 African-American responders required only 10 to 20 minutes. Low (analgesic) doses of BPN were sufficient to treat all methadone withdrawal symptoms in 6 of 15 subjects. There may be ethnic differences in response to BPN. Low dose BPN may play a role in carefully monitored heroin detoxification treatment.

Adult↗