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Biomedical subjects

J B Jackson

Publications and source records attributed to J B Jackson.

At least 145 records · Page 8Linked to original sources
PubMed1990

Human immunodeficiency virus type 1 detected in all seropositive symptomatic and asymptomatic individuals.

Between February 1987 and October 1988, peripheral mononuclear blood cells (PBMC) from 409 adult individuals antibody positive by Western (immuno-)blot for human immunodeficiency virus type 1 (HIV-1) (56 acquired immunodeficiency syndrome [AIDS] patients, 88 patients with AIDS-related complex, and 265 asymptomatic individuals) were consecutively cultured for HIV-1 or tested for the presence of HIV-1 DNA sequences by a polymerase chain reaction assay (PCR). We isolated HIV-1 or detected HIV-1 DNA sequences from the PBMC of all 409 HIV-1 antibody-positive individuals. None of 131 healthy HIV-1 antibody-negative individuals were HIV-1 culture positive, nor were HIV-1 DNA sequences detected by PCR in the blood specimens of 43 seronegative individuals. In addition, HIV-1 PCR and HIV-1 culture were compared in testing the PBMC of 59 HIV-1 antibody-positive and 20 HIV-1 antibody-negative hemophiliacs. Both methods were found to have sensitivities and specificities of at least 97 and 100%, respectively. In contrast, the sensitivities of serum HIV-1 antigen testing in AIDS patients and asymptomatic seropositive patients were 42 and 17%, respectively. Our ability to directly demonstrate HIV-1 infection in all HIV-1 antibody-positive individuals provides definitive support that HIV-1 antibody positivity is associated with present HIV-1 infection. Moreover, the sensitivities and specificities of PCR and culture for the detection of HIV-1 appear to be equivalent, and both methods are superior to testing for HIV-1 antigen in serum for the direct detection of HIV-1.

AIDS-Related Complex↗
PubMed1990

Human immunodeficiency virus type 1 antigen and culture assays.

Commercial enzyme immunoassays have recently been developed for the detection and quantitation of human immunodeficiency virus type 1 (HIV-1) viral proteins in blood and other body fluids of infected patients. At the same time, culture assays for HIV-1 have become more rapid, sensitive, and specific for HIV-1 isolation from the blood of infected patients. Both of these assays have clinical utility in the diagnosis, prognosis, and monitoring of HIV-1 infection in certain patients.

Antiviral Agents↗
PubMed1989

Electron transport pathways to nitrous oxide in Rhodobacter species.

1. Electron transport components involved in nitrous oxide reduction in several strains of Rhodobacter capsulatus and in the denitrifying strain of Rhodobacter sphaeroides (f. sp. denitrificans) have been investigated. Detailed titrations with antimycin A and myxothiazol, inhibitors of the cytochrome bc1 complex, show that part of the electron flow to nitrous oxide passes through this complex. The sensitivity to myxothiazol varies between strains and growth conditions of R. capsulatus; the higher rates of nitrous oxide reduction correlate with the higher sensitivities. Partial inhibition of the nitrous oxide reductase enzyme with azide decreased the sensitivity to myxothiazol of the strains that had the highest nitrous oxide reductase activity. 2. Inhibition of nitrous oxide reduction in cells of R. capsulatus by myxothiazol could be restored under dark conditions by addition of N,N,N',N'-tetramethyl-p-phenylene diamine. The highest activities observed after addition of this electron carrier were found in the strains that had the highest sensitivity to myxothiazol, consistent with the premise that this inhibitor is more effective at the higher flux rates to nitrous oxide. 3. Addition of nitrous oxide to cells of R. capsulatus strain N22DNAR+ under darkness caused oxidation of both b- and c-type cytochromes. The oxidation of b cytochromes was less pronounced in the presence of myxothiazol, consistent with a role for the cytochrome bc1 complex in the electron pathway to nitrous oxide. Ferricyanide, in the absence of myxothiazol, caused a similar extent of oxidation of b cytochromes, but a greater oxidation of c-type, suggesting that there was a pool of c-type cytochrome that was not oxidisable by nitrous oxide. The time course showed that both the b- and c-type cytochromes were oxidised within a few seconds of the addition of nitrous oxide. During the following seconds there was a partial re-reduction of the cytochromes such that after approximately 1 min a lower steady-state of oxidation was attained and this persisted until the nitrous oxide was exhausted. 4. A mutant, MTCBC1, of R. capsulatus that specifically lacked a functional cytochrome bc1 complex reduced nitrous oxide, albeit at 30% of the rate shown by the parent strain MT1131. A reduced minus nitrous-oxide-oxidised difference spectrum for MTCBC1 in the absence of myxothiazol was similar to the corresponding difference spectrum observed for strain N22DNAR+ in the presence of myxothiazol. It is suggested that these difference spectra identify the cytochrome components, including a b-type, involved in a pathway that is alternative to, and independent of, the cytochrome bc1 complex.(ABSTRACT TRUNCATED AT 400 WORDS)

Anaerobiosis↗
PubMed1989

The coupling between protonmotive force and the NAD(P)+ transhydrogenase in chromatophores from photosynthetic bacteria.

1. The activity of NAD(P)+ transhydrogenase in chromatophores of Rhodobacter capsulatus relaxed from a high rate during illumination to a lower rate after darkening with a half-time of approximately 100 ms. 2. The dissipative ionic current flowing across the chromatophore membrane was increased in the presence of transhydrogenase substrates. This is attributed to proton current through the transhydrogenase enzyme. Subject to the assumption that transhydrogenase does not conduct in the absence of nucleotide substrates, the ratio of protons translocated across the membrane per hydride ion transferred was 0.4 +/- 0.5. Within the error and uncertainities in the calibration procedure, this ratio may be consistent with a stoichiometry of one but higher values seem unlikely. The ratio of hydride ion transferred in the transhydrogenase to electrons transferred through the cyclic electron transport system was approximately 0.2. 3. The Kappm values for the transhydrogenase substrates were determined for chromatophores in illuminated and darkened suspensions over a range of pH. These values are discussed in relation to the equivalent parameters reported for mitochondria transhydrogenase [Rydstrom, J. (1977) Biochim. Biophys. Acta 255, 9641-9646] and were used to calculate the concentrations of substrates which effectively saturate the enzyme. 4. At substrate concentrations which were in excess of 8 X Kappm the dependence of transhydrogenase rate on the value of the membrane potential (zero pH gradient) was determined at pH 6.3, 6.9, 7.6 and 9.0. The relation was similar at pH 6.9 and 7.6. At alkaline pH the apparent threshold in the relation became more prominent as it was shifted to slightly higher values of membrane potential. At acid pH a shift in the opposite direction diminished the apparent threshold and saturation at high membrane potential became more dominant. We use these data in an attempt to discriminate between two models of energy transduction: (a) the driving force exerted by the membrane potential is mediated by a pH gradient formed through the operation of a proton well in the transhydrogenase; (b) the membrane potential increases a rate constant for charge translocation through transhydrogenase by decreasing the effective height of the Eyring barrier for charge transfer across the membrane through the enzyme. The second model leads to a more simple description than the first of the pH dependence of transhydrogenase rate on membrane potential.4+ transhydrogenase activity in chromatopho

Bacteria↗
PubMed1989

Performance characteristics of serologic tests for human immunodeficiency virus type 1 (HIV-1) antibody among Minnesota blood donors. Public health and clinical implications.

STUDY OBJECTIVE: To evaluate performance characteristics of sequential enzyme immunoassay (EIA) and Western blot human immunodeficiency virus type 1 (HIV-1) antibody testing in a low-risk population. DESIGN: Three-year prospective study of a selected sample from a community-based population. SETTING: Two blood collection facilities in Minnesota. POPULATION: Minnesota blood donors. RESULTS: During the study period, 630,190 units of blood (donations) from an estimated 290,110 Minnesota-resident donors were screened for HIV-1 antibody. Seventeen Minnesota-resident donors were identified as positive for HIV-1 antibody. Sixteen donors were available for follow-up HIV-1 culture: all were culture positive. The other donor, who was not available for follow-up culture, was likely infected with HIV-1 based on a history of high-risk behavior and positive serologic findings for hepatitis B surface antigen. Using 95% binomial confidence intervals, performance characteristics for sequential EIA and Western blot HIV-1 antibody serology were as follows: false-positive rate by number of donations, 0% to 0.0006%; specificity by number of donations, 99.9994% to 100%; predictive value of a positive test, 81% to 100%. CONCLUSIONS: In this low-risk population, the false-positive rate of serologic tests for HIV-1 antibody, using HIV-1 culture as the definitive standard for infection status, was extremely low and test specificity was extremely high.

AIDS Serodiagnosis↗
PubMed1989

Comparison of two serum HIV antigen assays for selection of asymptomatic antigenemic individuals into clinical trials.

The detection and recruitment of HIV antigen-positive asymptomatic individuals for clinical trials is important. Two commercial enzyme-linked immunosorbent assays (ELISA) for the detection and quantitation of human immunodeficiency virus (HIV) antigens were evaluated for sensitivity by testing serum samples from 155 asymptomatic HIV Western blot positive individuals. The Abbott HIV antigen ELISA detected HIV antigen in the serum of 17 (11.0%) of 155 patients compared with 18 (11.6%) of 155 by the Coulter HIV antigen ELISA. In serial twofold dilution experiments, there was no significant difference in sensitivity between these two assays in the detection of HIV serum antigen. However, both assays are limited in their ability to detect HIV antigen in most asymptomatic HIV-infected patients. This low detection rate should be taken into account in the design of clinical trials involving asymptomatic infected patients.

Adolescent↗
PubMed1989

Assessment of potential for cancer control by Golden State Medical Association physicians.

To gather data on which to base the design of an intervention program to decrease cancer mortality in the black population of California, physician members of the Golden State Medical Association were surveyed to determine their current practices relating to early cancer detection and cancer prevention. Respondents' estimates of the proportions of their patients in various categories indicated that at least 60% to 70% of their patients were potential subjects for intensive early cancer detection and cancer prevention efforts. Thirty-four percent of respondents reported that they were performing early cancer detection examinations on all their patients. On the average, respondents estimated that about 70% of their patients (more than 80% of patients of primary care physicians) were receiving either routine check-ups or specific early cancer detection examinations. Patient education about various aspects of cancer and cancer prevention emerged as the most readily attainable means to reduce cancer mortality in blacks. It was most frequently mentioned both as something that physicians could do to help achieve this goal and as an outside resource physicians would find useful in their practices. Its lack was cited as the greatest barrier to early cancer detection and cancer prevention in the black population.

Adult↗
PubMed1988

Hemophiliacs with HIV antibody are actively infected.

Cultures of peripheral blood mononuclear cells for human immunodeficiency virus type 1 (HIV-1) and assays for the p24 antigen were performed for a group of 75 unselected hemophiliacs to determine whether patients positive for HIV-1 antibody are actively infected rather than immunized by viral proteins in non-heat-treated factor VIII or IX concentrates. Fifty-six (75%) of the 75 hemophiliacs were antibody positive and 55 (98%) of the 56 with antibodies also had positive cultures. The one culture-negative individual had detectable HIV-1 proviral DNA sequences in three separate samples of peripheral blood mononuclear cell DNA, as detected by a polymerase chain reaction assay. Detection of serum p24 antigen and the time to development of a positive culture were significantly more frequent and shorter, respectively, in symptomatic vs asymptomatic patients. None of the 19 hemophiliacs negative for HIV-1 antibody had positive cultures, detectable p24 serum antigen, or symptoms of HIV-1 infection. Moreover, latent HIV-1 infection was not detected in 16 female sexual partners of hemophiliacs positive for HIV-1 antibody using Western blot testing, assays for p24 antigen, HIV-1 cultures, and polymerase chain reaction assays, despite repeated unprotected sexual exposure. We conclude that antibody-positive hemophiliacs have been actively infected by HIV-1 and that a long period of latent HIV-1 infection prior to overt seroconversion is unlikely.

Adolescent↗
PubMed1988

Evaluation of two commercial tests for human immunodeficiency virus antigens in culture supernatant fluid.

Two commercial enzyme-linked immunosorbent assays (EIAs) for human immunodeficiency virus (HIV) antigens were evaluated for sensitivity and reproducibility by use of supernatant fluid from cell cultures of peripheral mononuclear cells of 18 patients with acquired immunodeficiency syndrome (AIDS) and 12 asymptomatic HIV antibody-positive patients. Both commercial assays detected HIV antigen in all cultures by day 21; however, the Abbott HIV antigen EIA (Abbott Laboratories, North Chicago, IL) detected HIV antigen three to seven days earlier in 15 of 48 cultures (31%), on the same day in 32 cultures (67%), and three days later in 1 culture (2%) when compared with the DuPont HIV antigen EIA (DuPont Laboratories, Wilmington, DE). In serial twofold dilution experiments, the Abbott HIV Ag EIA was found to have at least a twofold to eightfold increased sensitivity over the DuPont assay. Repeat testing of 15 initially positive supernatant fluids by both assays revealed that 13 of 15 and 12 of 15 were consistently positive by the Abbott and DuPont assays, respectively. The authors conclude that the Abbott EIA demonstrated better performance in this study than the DuPont EIA for detection of HIV in cell culture because of its shorter time-to-positivity and greater sensitivity.

Antigens, Viral↗
PubMed1988

Practical diagnostic testing for human immunodeficiency virus.

Since the discovery of human immunodeficiency virus (HIV) as the causative agent of acquired immunodeficiency syndrome in 1983, there has been a proliferation of diagnostic tests. These assays can be used to detect the presence of HIV antibody, HIV antigen, HIV ribonucleic and deoxyribonucleic acids, and HIV reverse transcriptase. Enzyme-linked immunosorbent assays, Western blot, radioimmunoprecipitation assays, indirect immunofluorescence assays, reverse transcriptase assays, and several molecular hybridization techniques are currently available. Enzyme-linked immunosorbent, Western blot, and indirect immunofluorescence assays for HIV antibody are very sensitive, specific, and adaptable to most laboratories. An enzyme-linked immunosorbent assay for HIV antigen is also readily adaptable to most laboratories and will be commercially available soon. While the other assays are more tedious, they are valuable confirmatory tests and are suitable for reference laboratories. The biohazards of performing HIV testing can be minimized with proper biosafety measures.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Rapid and sensitive viral culture method for human immunodeficiency virus type 1.

Peripheral blood mononuclear cells from 142 consecutive patients with antibodies to human immunodeficiency virus type 1 (HIV-1) were cultured for HIV-1. All 72 patients with symptoms of HIV-1 infection were culture positive, as were 69 of 70 asymptomatic patients. Of the 142 patients, 132 (93%) were culture positive within 10 days after initiation of the culture.

AIDS-Related Complex↗
PubMed1985

Nitrous oxide reduction by members of the family Rhodospirillaceae and the nitrous oxide reductase of Rhodopseudomonas capsulata.

After growth in the absence of nitrogenous oxides under anaerobic phototrophic conditions, several strains of Rhodopseudomonas capsulata were shown to possess a nitrous oxide reductase activity. The enzyme responsible for this activity had a periplasmic location and resembled a nitrous oxide reductase purified from Pseudomonas perfectomarinus. Electron flow to nitrous oxide reductase was coupled to generation of a membrane potential and inhibited by rotenone but not antimycin. It is suggested that electron flow to nitrous oxide reductase branches at the level of ubiquinone from the previously characterized electron transfer components of R. capsulata. This pathway of electron transport could include cytochrome c', a component hitherto without a recognized function. R. capsulata grew under dark anaerobic conditions in the presence of malate as carbon source and nitrous oxide as electron acceptor. This confirms that nitrous oxide respiration is linked to ATP synthesis. Phototrophically and anaerobically grown cultures of nondenitrifying strains of Rhodopseudomonas sphaeroides, Rhodopseudomonas palustris, and Rhodospirillum rubrum also possessed nitrous oxide reductase activity.

Acetylene↗
PubMed1985

A survey of retired dentists in the United States. Council on Dental Practice.

This paper reports on the results of a national survey of retired dentists carried out in the winter and spring of 1984. More than eight in ten of the respondents were general practitioners. Most retirees are between the ages of 60 and 69, married, and report their overall health at retirement to be excellent or good. As do retired scientists, dentists find intrinsic gratification in the work role, but apparently accept retirement as part of the life cycle. Retired dentists have income substantially greater than retirees in general. As is the case for the greater majority of older Americans, Social Security provides an important income support for respondent dentists. However, the primary source of retirement income for dentists comes from savings and investments. One of three retired dentists reports net worth in 1984 as between $200-$499,999. Retired dentists are well adjusted to retirement. Overall, most dentists report high satisfaction with retirement to date. Additional leisure time for hobbies, flexibility in owning one's time, and social activities with family and friends seem the main contributors to this satisfaction. Investment planning, health assessment, enthusiasm for outside interests, and personal preparation for retirement with a spouse are reported as important in retirement planning. Retirement is not a satisfying experience for all dentists. Some do report experiencing uselessness and depression. A still smaller proportion report feelings of loneliness and inadequacy. As is the case for older people in general, solitary activities including reading, watching television, and gardening are important for retired dentists. Most older people attempt to retain activity patterns and preferences developed earlier in life.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1984

Changes in membrane ionic conductance, but not changes in slip, can account for the non-linear dependence of the electrochemical proton gradient upon the electron-transport rate in chromatophores.

Decrease in the rate of cyclic electron transport (JE) measured from the absorbance changes associated with reaction centre bacteriochlorophyll led to a less than proportionate decrease in the membrane potential (delta psi) measured by electrochromism. In principle this result can be explained either by a delta psi-dependent slip in the H+/e- coupling ratio (nE) or by a delta psi-dependent change in the membrane ionic conductance. Simultaneous measurement of the membrane ionic current (JDIS) did not reveal any significant changes in the H+/e- ratio (JDIS/JE) and showed that conductance changes (JDIS/delta psi) account quantitatively for the curved dependence of delta psi on JE. Simultaneous recordings of JDIS and the extravesicular pH from cresol-red absorbance changes, suggest that protons are the main current-carrying species across the chromatophore membrane at high values of delta psi in the presence and absence of Fo-ATPase inhibitor. At reduced delta psi the flux of other ions outweighs the hydrogen ion current.

Absorption↗