Biomedical subjects
Publications and source records attributed to D W Johnson.
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A unique and characteristic bacteriocine-like inhibitor elaborated by M-type 4, T-pattern 4, group-A streptococci was isolated and partially purified. This inhibitor was found to be produced optimally in Todd-Hewitt broth; after extraction and concentration, was shown to be protein in nature, and to have a m.w. of c. 8000. It was extremely heat stable and acid tolerant, but was quickly inactivated in alkaline conditions. It could be demonstrated in cell-bound form, but 99.5% was found in culture supernates. It was specifically adsorbed by viable sensitive cells, and its mode of action was bacteristatic.
This study investigated the acoustic reflex, which uses the ventro-medial brain-stem system, to determine laterality superiority with respect to age, sex, dominance for handedness, and their various interactions, 54 normal children and 21 normal adults were evaluated. No major effects for age, sex or handedness for the reflex were found, but the right ear appeared slightly more sensitive to broad-band white noise stimuli than the left, regardless of handedness. An age-handedness effect was also present which suggested that left-handed children mature differently from right-handed children in the acoustic reflex. Data on adults were inconclusive as to whether this maturity effect carried over into adulthood. The findings suggest that there was a laterality effect for the acoustic reflex using the ventro-medial brain-stem, which was thus brain-stem related rather than cortex-level related.
Incubation of bovine peripheral blood monocytes with bovine viral diarrhea virus (either Singer or NY-1 strain) caused a consistent, statistically significant decrease in their random locomotion (no chemoattractant) and chemotaxis towards a chemotactic lymphokine. Chemotaxis was determined by a modification of the Boyden method. Incubation of bovine viral diarrhea virus with mononuclear cells depressed chemotaxis by a mean of 56% (P less than 0.0005). Heat-killed virus had no effect on monocyte motility. Data suggest that bovine viral diarrhea virus can rapidly suppress monocyte functions in vitro, but by unknown mechanisms, not by killing cells.
Exogenously added prostaglandin E1 or E2 inhibited the blastogenic response of Mycobacterium bovis-sensitized bovine peripheral blood lymphocytes stimulated with concanavalin A, phytohemagglutinin, or M. bovis purified protein derivative as measured by [3H]thymidine uptake. The kinetics of the response showed that prostaglandins must be added to lymphocyte cultures within hours after mitogen or antigen addition to achieve maximum suppression of [3H]thymidine uptake. Addition of prostaglandins 24 h after the addition of mitogens or antigens resulted in considerably less suppression, supporting a hypothesis that prostaglandins initiate an early series of events which ultimately control lymphocyte blastogenesis rather than directly inhibit deoxyribonucleic acid synthesis.
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Organochlorine residues of TDE, DDE, and PCBs as high as 1.96, 2.79, and 28.74 microgram/kg, respectively, have been found in sediments of American Falls Reservoir, Idaho. Residues of TDE, DDE, and dieldrin in the flesh of sport fish were as high as 52.3, 67.2, and 160.4 microgram/kg, respectively. Maximum organochlorine residue levels found in sucker taken in the commercial fishery were 1.1 mg PCBs/kg, 781.7 microgram TDE/kg, and 82.1 microgram DDE/kg.
A study on cell-mediated immune responses in cattle with different exposure experiences to Brucella abortus was conducted by an in vitro lymphocyte stimulation assay. The purpose of this study was to determine how soon the cell-mediated immune responses would be detected following experimental exposure to B. abortus and to study the cell-mediated immune trend following experimental and natural exposure of cattle to B. abortus. The first positive cell-mediated immune responses occurred one to two weeks after experimental inoculation with living B. abortus strain 2308. The cell-mediated immune responses in these animals appeared at least one week before the appearance of of B. abortus serum agglutinating antibodies. Animals which were naturally infected with B. abortus biotypes 1 and 2 demonstrated positive cell-mediated immune responses throughout the study.
Cell-mediated immune (CMI) responses in cattle vaccinated with Brucella abortus strain 19 vaccine during calfhood were studied by an in vitro lymphocyte stimulation assay. Cattle were grouped in six groups according to the age after vaccination, and CMI responses of these groups, as well as of individual animals, were compared. Lymphocytes were prepared from peripheral blood of these cattle by the Ficoll-diatrizoate technique. Lymphocytes were then cultured with B abortus-soluble antigen. Culture results were assayed for [3H]thymidine incorporation into DNA by liquid scintillation spectrometry. On a group basis, B abortus-soluble antigen induced lymphocyte stimulation responses in lymphocytes from all the groups, except the sixth group which contained animals that had been vaccinated the longest time (18 to 24 months before this experiment). Animals that had been vaccinated for 3 to 6 months had the highest lymphocyte stimulation response. Seroagglutination tests were conducted simultaneously with the lymphocyte stimulation test, but there was no apparent correlation between the concentrations of humoral antibodies and the CMI responses as measured by in vitro specific lymphocyte stimulation. The lymphocyte stimulation test exhibited significantly higher specificity (P less than 0.005) than the serologic tests.
Cell-mediated immune responses in cattle adult-vaccinated with Brucella abortus strain 19, cattle infected with B abortus field strain, and nonexposed cattle were studied by an in vitro lumphocyte-stimulation test (LST). Lymphocytes were prepared from peripheral bovine blood by the Ficoll-diatrizoate technique, and results were assayed for [3H]thymidine incorporation into DNA by liquid scintillation spectrometry. Serotests and bacteriologic isolation attempts were conducted simultaneously with LST. Lymphocytes from cattle infected with field strains had significantly (P = 0.01) higher specific lymphocyte-stimulation inexposed controls. The LST, the serum standard-tube agglutination test (STT), the Rivanol (RIV) test, and the complement-fixation (CF) test correctly classified cattle from which field strains and strain 19 of B abortus were isolated. The LST was negative in cattle vaccinated with B abortus strain 19 (nonshedding), but the three serotests had many false-positive reactions. The CF test had the least false-positive reaction, followed by the RIV test, and the STT was the least specific. Well before the three serotests became positive, the LST was positive in samples from some cattle during the incubation period of the infection. There was little or no correlation between cell-mediated immune responses (as measured by LST) and serum antibody responses (as measured by STT, RIV test, and CF test) in vaccinated but culture-negative cattle and in some nonvaccinated cattle during the incubation period.
This is a statistical study of the 1976 location, by region and state, of the active civilian dentists of the United States in relation to the dental schools from which they graduated. The focus of the study is a master matrix table which shows state-by-state distribution of the graduates of each dental school and, conversely, where each state obtained its dentists, by individual dental school of graduation. Comparisons are made with similar data from several studies since the early 1950s, certain relationships and trends are identified, and a few projections are made to 1990. The study provides detailed information useful to organizations and individuals studying dental manpower and who are planning dental educational facilities and programs. A most important aid in such planning is information not only on the location but also on the sources of present dentist manpower.
The rosette-forming capacity of bovine peripheral blood lymphocytes (PBL) was determined with dextran and 2-aminoethylisothiouronium bromide (AET)-treated sheep erythrocytes (SRBC). Both dextran and AET-enhanced rosette formation; however, AET-treated SRBC detected a larger percentage of rosette-forming cells and thus was used in this study. The specificity of rosette formation by bovine thymus-derived (T) lymphocytes was shown by (1) demonstration of rosettes and surface-membrane immunoglobulins sIg) on different cells in PBL and nylon-wool fractionated lymphocyte populations and (2) rosette formation by a large percentage (83--90%) of thymocytes from three bovine foetuses and two 14-month-old heifers. A procedure was also developed to identify bovine monocytes by latex phagocytosis and 10--30% latex-ingesting cells were detected in PBL preparations isolated by Ficoll-Hypaque flotation. The frequency of sIg-bearing latex-ingesting, and sIg-bearing latex non-ingesting cells in bovine peripheral blood was also determined. These procedures were utilized to determine the distribution of T and bone-marrow derived (B) lymphocytes in peripheral blood of normal and lymphocytotic cattle. PBL from twenty normal cattle contained approximately 63% T and 11% B (sIg+ latex non-ingesting) lymphocytes. In peripheral blood of three cattle with persistent lymphocytosis, a prodromal stage of bovine leukaemia, the percentage of B cells was elevated approximately to 59% whereas T lymphocytes decreased to 35%, thus providing additional evidence that persistent lymphocytosis is a B-cell disease.
The ontogeny of lymphocyte subpopulations and monocytes was studied in developing bovine foetuses. Fifty-four bovine foetuses ranging in age from 3 to 9 months of gestation were collected and examined for the presence of thymus-derived (T lymphocytes), bone marrow-derived (B lymphocytes) and phagocytic (macrophage) cells from thymus, spleen and peripheral blood. Detection of the cells expressing T lymphocyte surface markers was done using a modified sheep red blood cell rosette assay. Lymphocytes bearing surface immunoglobulin (sIg) were detected by staining with a fluoresceinated rabbit antibody prepared against bovine IgG. The procedure used for detecting monocytes was a latex bead phagocytic assay. In the thymus, the percentage of T lymphocytes was relatively constant throughout gestation at approximately 60-70%, with B lymphocytes remaining at about 1%, whereas the phagocytic cells showed an increase from 1% at 3 months to approximately 8% at term. The spleen showed an increasing percentage of T lymphocytes, from 11% at 3 months to over 40% at term, whereas the percentage of B lymphocytes remained consistent at about 2-3% from 3 months until term. The percentage of monocytes increases from 1% at 3 months to over 20% at 9 months. Peripheral blood T lymphocytes increased steadily from approximately 1% at 3 months to 45% at term. B lymphocyte levels remained low, about 1%, throughout gestation, whereas monocytes increased from 1% at 3 months to 5% at 9 months.
B-lymphocytes from 7 normal cattle and from 3 persistent lymphocytotic, 6 lymphosarcomatosus, and 3 bovine leukemia virus-infected animals with diverse defects in humoral immunity were examined for their capacity to undergo terminal differentiation in vitro. Pokeweek mitogen-stimulated cells from normal and leukemic cattle were stimulated to synthesize and secrete immunoglobulins, and these were detected by radial immunodiffusion. Lymphocytes from normal cattle synthesized more IgM than those from persistent lymphocytotic-, lymphosarcomatous-, and bovine leukemia virus-infected cattle. Leukemic cattle have a higher percentage of cells containing intracytoplasmic immunoglobulins; most cells are believed to contain IgG. The serum IgM in normal cattle is significantly (P less than 0.05) higher than that in leukemic cattle. The results indicate that there is an abnormality either in synthesis or secretion of IgM or in abnormal catabolism of Ig from leukemic B-lymphocytes.