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C L Baldwin

Publications and source records attributed to C L Baldwin.

65 records · Page 4Linked to original sources
PubMed1985

Cell titration assay for measuring blastogenesis of bovine lymphocytes.

The blastogenic response of bovine peripheral blood lymphocytes to phytohemagglutinin (PHA) and to microbial antigens was measured using a lymphocyte titration assay. Culture conditions, including lymphocyte concentrations, incubation periods and medium formulation, were established which produced linear or nearly linear responses over a range of cell concentrations. These conditions were established by testing lymphocytes from unimmunized cattle and from heifers infected with Brucella abortus with PHA and a B. abortus extract. Four cell concentrations in 2-fold increments were selected for measuring responses to PHA (3.125 X 10(3) to 2.5 X 10(4) cells/well) and to antigens (5.0 X 10(4) to 4.0 X 10(5) cells/well). The strength of response varied among animals and also over time for individual animals, but the titration assay allowed exponential proliferation to be distinguished from decline, which may have been due to overcrowding of microtiter wells, exhaustion of nutrients or induction of regulatory events. This assay provided a more reliable and discriminating method of evaluating lymphocyte proliferation responses than that achieved by single point assays. The displacement of the titration curves could be used to estimate the relative frequency of lymphocytes responding to antigens or mitogens.

Animals↗
PubMed1985

Immune response of cattle to Brucella abortus outer membrane proteins measured by lymphocyte blastogenesis.

Lymphocytes from cattle were tested in a blastogenesis test with outer membrane proteins isolated from smooth strain 2308 and rough strain 45/20 of Brucella abortus. The titration assay developed for measuring blastogenesis to microbial antigens (Baldwin, Antczak and Winter, this issue, pp. 319-333) was used to assess the response to both group 2 (porins) (Douglas et al., 1984) and group 3 proteins (Verstreate et al., 1982). Blastogenesis was evaluated for distinguishing cattle infected with virulent B. abortus strain 2308 from unimmunized cattle, cattle vaccinated with attenuated strain 19, or inoculated with Escherichia coli 0116:H31, known to cause serological cross-reactions with B. abortus (Nielsen et al., 1980). Strain 45/20 porin was the most effective for this purpose and data analyses utilizing the titration assay were better than those relying on a single point assay. When compared with BASA, an antigen preparation used in other studies (Kaneene et al., 1978a), responses to porin provided a more specific index of infection with B. abortus. Reactions to 45/20 porin occurred, however, in some heifers vaccinated as adults with strain 19 or inoculated with E. coli 0116:H31. Furthermore, nonpregnant heifers had negligible or only transient blastogenesis responses to the porin during the first 14 weeks after infection even though they developed strong 0 antibody responses. We do not recommend the blastogenesis test in its present form as a useful adjunct to serological tests, and could allow measurement of cell mediated immune responses relevant to protective immunity.

Animals↗
PubMed1985

Formaldehyde: a comparative evaluation of four monitoring methods.

The performances of four formaldehyde monitoring devices were compared in a series of laboratory and field experiments. The devices evaluated included the DuPont C-60 formaldehyde badge, the SKC impregnated charcoal tube, an impinger/polarographic method and the MDA Lion formaldemeter. The major evaluation parameters included: concentration range, effects of humidity, sample storage, air velocity, accuracy, precision, interferences from methanol, styrene, 1,3-butadiene, sulfur dioxide and dimethylamine. Based on favorable performances in the laboratory and field, each device was useful for monitoring formaldehyde in the industrial work environment; however, these devices were not evaluated for residential exposure assessment. The impinger/polarographic method had a sensitivity of 0.06 ppm, based on a 20-liter air sample volume, and accurately determined the short-term excursion limit (STEL). It was useful for area monitoring but was not very practical for time-weighted average (TWA) personal monitoring measurements. The DuPont badge had a sensitivity of 2.8 ppm-hr and accurately and simply determined TWA exposures. It was not sensitive enough to measure STEL exposures, however, and positive interferences resulted if 1,3-butadiene was present. The SKC impregnated charcoal tube measured both TWA and STEL concentrations and had a sensitivity of 0.06 ppm based on a 25-liter air sample volume. Lightweight and simple to use, the MDA Lion formaldemeter had a sensitivity of 0.2 ppm. It had the advantage of giving an instantaneous reading in the field; however, it must be used with caution because it responded to many interferences. The method of choice depended on the type of sampling required, field conditions encountered during sampling and an understanding of the limitations of each monitoring device.

Air Pollutants, Occupational↗
PubMed1985

Blastogenic response of bovine lymphocytes to Brucella abortus lipopolysaccharide.

Brucella abortus lipopolysaccharide was tested in a blastogenesis assay with unfractionated and nylon wool-separated peripheral blood lymphocytes of Brucella-naive cattle and cattle immunized with B. abortus. Our results indicated that in cattle the lipopolysaccharide of B. abortus is not a B-cell mitogen. In immunized animals it stimulated predominantly nylon wool-adherent cells. The lipopolysaccharide of Escherichia coli O128:B12, in contrast, induced a substantially greater proliferative response in circulating lymphocytes, predominantly those adherent to nylon wool, of the Brucella-naive cattle.

Animals↗
PubMed1984

Evaluation of lymphocyte blastogenesis for diagnosis of bovine brucellosis.

The lymphocyte blastogenesis test (LBT) was evaluated for its usefulness in the diagnosis of bovine brucellosis. Using a cell titration assay which measures the blastogenic response over a range of cell concentrations, peripheral blood lymphocytes (PBL) from various populations of cattle were tested with purified Brucella abortus porin proteins and with Brucella abortus soluble antigen (BASA). Cattle tested included groups infected with virulent B. abortus strain 2308, vaccinated with B. abortus strain 19, infected with Escherichia coli strain 0116:H31 (known to cause serological cross reactions with B., abortus), vaccinated with a bacterin of Staphylococcus aureus, and unimmunized controls. Pregnant heifers vaccinated with strain 19 could generally be distinguished from pregnant animals infected with virulent strain 2308 when LBT responses to porin were analyzed by comparing maximum delta counts per minute (the responses of the cell concentration at which there is the greatest difference between stimulation in the presence of antigen and without antigen). However, a group of nonpregnant heifers infected with strain 2308 either failed to react or reacted in an inconsistent fashion with porin or BASA. The lack of responsiveness in the LBT was accompanied by high concentrations of circulating agglutinins. False positive responses also occurred to porin, although much less frequently than to the crude preparation BASA. The use of nylon wool fractionated PBL did not provide an improved means for distinguishing Brucella infected from uninfected cattle. Based on these findings, we would not recommend the LBT with either of these antigens as a routine method for diagnosis. Lipopolysaccharide was extracted from B. abortus strain 2308 and tested for its role in inducing false positive responses. Although there exist components in B. abortus extracts which are mitogenic for bovine PBL, our data do not support such a function for purified Brucella LPS.

Animals↗
PubMed1982

Outer membrane proteins of Brucella abortus: isolation and characterization.

Outer membrane proteins were derived from one rough and four smooth strains of Brucella abortus by sequential extraction of physically disrupted cells with N-lauroylsarcosinate and dipolar ionic detergent. Extraction of outer membrane proteins was ineffective, however, without predigestion with lysozyme. Three groups of proteins were present and could be separated in their native state by sequential anion-exchange chromatography and gel filtration. Membrane proteins contained substantial quantities of tightly adherent lipopolysaccharide which could be reduced but not eliminated by extraction of cells with trichloroacetic acid before disruption. Group 2 proteins, apparently trimers in their native state, gave rise to 43,000- and 41,000-molecular-weight bands after complete denaturation in sodium dodecyl sulfate. They were antigenically identical among all the strains, showed close resemblance in amino acid composition to each other and a general similarity to OmpF of Escherichia coli, and are proposed to be the porins of B. abortus. Group 3 proteins occurred as 30,000-molecular-weight bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, although additional bands were frequently observed in this region. In none of the strains did group 3 proteins manifest heat-modifiable characteristics. Proteins of different strains bore a high degree of similarity to each other in amino acid composition, except in methionine, isoleucine, tyrosine, and histidine. Differences occurred consistently in amino acid composition between group 2 and 3 proteins, and some of these correspond to differences between OmpF and OmpA. Group 2 and 3 proteins were antigenically distinct from each other, but the principal group 3 antigens were shared among all the strains. Despite the lack of heat modifiability, perhaps influenced by adherent lipopolysaccharide, group 3 proteins are proposed as counterparts to OmpA. Most of the group 1 proteins, minor components, were physically associated with those of group 3 unless in sodium dodecyl sulfate. Group 1 proteins produced a major band at 94,000 and exhibited heat modifiability. No evidence was found of a low-molecular-weight lipoprotein in the outer membrane of B. abortus, but this is not taken to exclude its occurrence.

Amino Acids↗
PubMed1979

Increased spontaneous erythrocyte rosette formation of feline lymphocytes preincubated at 37 degrees C.

Preincubation of feline peripheral blood lymphocytes (PBL) in complete medium at 37 degrees C for up to 24 h resulted in as much as a 5.5-fold increase in the per cent of T cells detectable by spontaneous E rosette formation with guinea pig erythrocytes, as compared to non-preincubated PBL. Under these same conditions, the percent of B cells, detected by EAC rosette formation, remained unchanged. Preincubation with either thymosin or levamisole caused no increase in E rosettes other than that seen with complete medium alone. The preincubation-associated increase in E rosettes was temperature dependent, independent of the source of serum in the preincubation medium, not influenced by the lymphocyte isolation procedure, and not observed when feline thymocytes were tested in place of PBL. No increase in functional activity, assayed by phytomitogen-induced lymphocyte blastogenesis, was observed in preincubated as compared to non-preincubated PBL. These results suggested either a non-specific unmasking, or the differentiation and acquisition, of E receptors by feline PBL during the preincubation procedure.

Animals↗
PubMed1975

Biohazards assessment in large-scale zonal centrifugation.

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both the centrifuge chamber interior and rotor surfaces.

Air Microbiology↗
PubMed1967

Biohazards symbol: development of a biological hazards warning signal.

The need for a symbol to warn of potential infection hazards became apparent during Public Health Service contract work on the development of containment facilities for virus-leukemia research. A program of direct inquiry and a search of the literature revealed that there was no universally used signal and that scientific and safety organizations concurred in the need for one. Criteria for symbol design were established, and final selection was based on "uniqueness" and "memorability." The National Institutes of Health is recommending use of the symbol as a warning of biological hazard.

Accident Prevention↗
PubMedDate not supplied

Monoclonal antibody BLT-1, specific for the bovine homologue of CD5, reacts with the majority of mature T cells, a subpopulation of B cells and stimulates T cell proliferation.

Monoclonal antibody (MAb) BLT-1, an IgG2a with kappa light chains, reacted strongly with 21% of bovine thymocytes, weakly with 15% of thymocytes, with a subpopulation of peripheral blood B cells that also expressed CD20 and with peripheral blood T cells. Practically all of the reactive thymocytes were of a large cell subpopulation. By immunoprecipitation, BLT-1 was shown to recognize a membrane molecule with a molecular mass of 67 kDa. In competitive assays for lymphocyte surface binding, BLT-1 and MAb CC-29 (which had been shown previously to react with bovine CD5) blocked one another, indicating that the epitopes recognized were identical or extensively overlapping. In contrast, another CD-5-reactive MAb, CC-17, did not block BLT-1 reactivity with lymphocytes although the reactivity of CC-17 was blocked by BLT-1, suggesting partial overlap of the epitopes or steric hindrance by BLT-1 but not by CC-17. BLT-1 was able to induce proliferation of bovine lymphocytes in culture alone if monocytes were present or in the absence of monocytes synergized with PMA. The results indicate that BLT-1 recognizes an epitope of the bovine homologue of CD5 and that perturbation of the epitope by MAb binding results in signal transduction to bovine lymphocytes.

Animals↗