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L D Weaver

Publications and source records attributed to L D Weaver.

34 records · Page 2Linked to original sources
PubMed1990

Interleukin-2-induced lymphoproliferative responses.

Interleukin-2 (IL-2) is capable of both stimulating an in vitro lymphoproliferative response and augmenting non-major-histocompatibility-complex-(MHC)-restricted cytotoxicity. However, there are conflicting reports about the phenotypes of responding cells. In the present studies, we determined phenotypes of Ficoll/Hypaque-separated peripheral blood mononuclear cells stimulated with 50, 100 or 1000 U/ml IL-2; analyses were performed after 1, 3 and 5 weeks. With all concentrations, there was a progressive increase in CD3+ cells: after 3-5 weeks more than 90% of the cells reacted with this antibody. However, the proportions of CD4+ and CD8+ cells proved to be a function of the IL-2 concentration. Cultures containing 50 U/ml or 100 U/ml favored the expansion of the CD4+ subset. By contrast, in cultures stimulated with 1000 U/ml. CD8+ cells predominated. At baseline, CD8+ cells comprised 28 +/- 2%; after 3 weeks, this value increased to 51 +/- 5%. In addition, the proportion of CD56+ (Leu19, NKH-1) cells depended on the amount of IL-2. At 50 U/ml, there was no appreciable change in CD56+ cells. However, at 1000 U/ml, CD56+ cells increased from 17 +/- 1% (day 0) to 39 +/- 4% (3 weeks). This increase was primarily due to an expansion of the CD3+ CD56+ subset (non-NMC restricted cytotoxic T cells). By contrast, natural killer (NK) cells, as measured by the CD16 antibody, steadily declined at all IL-2 concentrations.

Antibodies, Monoclonal↗
PubMed1989

Effect on pregnancy rate of nonestrus insemination in previously inseminated dairy cows.

Lactating dairy cows (n = 157) designated for slaughter under the 1986 U.S. Dairy Termination Program were utilized in two trials to determine the effects of a second insemination on fertility. Cows that had been previously inseminated at estrus were inseminated again at 12-24 d later, when not in estrus. Cows that were reinseminated into the uterine body had significantly lower pregnancy rates (4% vs 40.6% for controls). Differences in pregnancy rates when the reinsemination was performed in the mid-cervical region were not significant (34.8% vs 50% for controls). Based upon these studies, intrauterine insemination of cows displaying questionable signs of estrus should be avoided in previously inseminated cows.

Journal Article↗
PubMed1989

Defective T cell colony formation and IL-2 receptor expression in HIV-infected homosexuals: relationship between functional abnormalities and CD4 cell numbers.

HIV infection is known to induce a progressive T helper/inducer (CD4) lymphopenia and to impair the functional activities of residual cells. The present studies examined the relationship between the CD4 cell count and three functional assays: T cell colony formation in semisolid media, the capacity of PHA-stimulated cells to express IL-2 receptors, and their ability to synthesize and secrete IL-2. Cells from antibody-positive homosexuals with normal numbers of CD4 cells (greater than 700/microliters) showed defective reactivity in two assays, colony growth, and IL-2 receptor expression. These defects became progressively more pronounced in homosexuals with moderate (400-700 cells/microliters) and severe (less than 400/microliters) reductions in assays for IL-2 production by PHA-stimulated lymphocytes. Mixing experiments suggest that cells from HIV-infected men nonspecifically inhibit the colony growth of normal cells; this abnormality could be reversed by addition of exogenous IL-2. These data suggest that defective colony growth and reduced IL-2 expression are functional abnormalities directly resulting from HIV infection. Furthermore, these changes can precede the CD4 lymphopenia induced by this viral infection.

Antibodies, Monoclonal↗
PubMed1988

Economic modeling of the use of gonadotropin-releasing hormone at insemination to improve fertility in dairy cows.

Economic and sensitivity analysis methods were used to evaluate financial returns from use of gonadotropin-releasing hormone (GnRH) at the time of insemination to enhance fertility of dairy cows. A computer spread sheet was used to determine the best service(s) for GnRH treatment, the increase in conception rate required for economic benefit from treatment, and how profits from GnRH treatment are affected by drug cost, herd reproductive efficiency, and production costs. Financial returns increased from use of GnRH at insemination under most herd conditions. Herds with conception rates less than or equal to 45% benefited from GnRH treatment at any 1 or 2 inseminations. Herds with conception rates greater than or equal to 60% benefited from GnRH treatment only at second or later services. Selection of second and/or third insemination as the GnRH treatment service usually resulted in the greatest total return. The enhancement of fertility necessary to achieve the break-even point with GnRH treatment at third service was 2% for low- and 5% for high-conception-rate herds. Base-line herd conception rates, estrus detection efficiency, replacement costs, value of excess days not pregnant, and cost of treatment had the greatest effect on returns from treatment. Herds with high conception rates and low replacement costs were likely to realize the least benefit from GnRH treatment at insemination. On the basis of our findings, we concluded that GnRH treatment at insemination is a profitable procedure under most herd conditions. Optimal treatment regimens for specific herds may best be determined by using herd performance and management data for calculating returns.

Animals↗
PubMed1988

Duration of preventive antibiotic administration for open extremity fractures.

The necessary duration of antibiotic administration after open fracture has not been established. In a double-blind prospective trial we randomized 248 patients with open fractures to receive one or five days of cefonicid sodium therapy or five days of cefamandole nafate therapy as part of the initial treatment. Rates of fracture-associated infections in the three groups were ten (13%) of 79, ten (12%) of 85, and 11 (13%) of 84, respectively. The 95% confidence limit for the difference in infection rates between the one-day group and the combined five-day groups was 0% to 8.3%. The actual difference was 0.2%. A brief course of antibiotic administration is not inferior to a prolonged course of antibiotics for prevention of postoperative fracture-site infections.

Adult↗
PubMed1988

Pathological and toxicological studies of calves fed a high concentration cotton seed meal diet.

Feeding a high concentration of cotton seed meal to young calves resulted in death with lesions compatible with gossypol toxicity. Calves were fed two different commercially prepared rations. Free gossypol concentrations in different lots of the 17% protein ration varied from 250 to 380 ppm, and the 13% protein ration varied from 40 to 240 ppm. Serum sorbitol dehydrogenase elevation was the most consistent clinical pathological finding. The mean serum sorbitol dehydrogenase concentrations for moribund, hospitalized, and clinically healthy calves were 277, 34, and 45 units/liter. The mean for sorbitol dehydrogenase concentration for healthy calves not fed cotton seed meal was 18 units/liter. Gross lesions included severe effusion of a high protein content fluid into the body cavities of most calves, edema of the mesentery, and hepatomegaly. The most consistent histological lesion was severe centrilobular hepatic necrosis. Elevated levels of liver gossypol were demonstrated. The mean liver gossypol concentration for three calves was 41.7 micrograms/g on a wet weight basis.

Animal Feed↗
PubMed1988

Identifying features, performance, and limitations of dairy ration formulation software: a comparison of three ration formulation programs.

A method for evaluating and selecting dairy ration formulation software for microcomputers is presented. Information obtained from a survey of practicing nutritionists and from interviews with computer programmers was used to identify users' needs, desired features, and patterns of use. A benchmark problem consisting of 15 activities frequently required in designing dairy rations was developed to evaluate ease of use, ease of learning, and software performance. Ease of use was measured by counting keystrokes and recording time required by a user familiar with these ration formulation programs to complete the benchmark problem. Ease of learning was measured as the amount of help and time needed by users unfamiliar with this software to complete the benchmark problem. Software performance was measured by speed of formulation, ration costs, ingredients and amounts selected, and nutrient content of rations. Evaluation of three commercially available software applications was made using the method developed.

Animal Feed↗
PubMed1988

Defective T-cell colony formation and IL-2 receptor expression at all stages of HIV infection.

The T-cell colony assay is a highly sensitive measure of immunological dysfunction. The present study evaluated this in vitro response in asymptomatic HIV-infected homosexuals, those with chronic adenopathy as their only clinical manifestation and patients with either ARC or AIDS. The mean colony count in antibody-positive asymptomatic individuals was significantly reduced when compared to either heterosexual controls or antibody-negative homosexuals. Furthermore, there were no differences in the responses of these antibody-positive individuals and those with chronic lymphadenopathy as their only clinical manifestation. By contrast, patients with AIDS or ARC showed a profound defect; this suggests that the colony assay can detect a functional gradient across the spectrum of HIV infections. Colony growth was correlated with the absolute number of T-helper cells and the ability of PHA-stimulated lymphocytes to express IL-2 receptors; no correlation was found with the number of suppressor/cytotoxic cells or in vitro production of IL-2. Recent HIV seroconverters had normal colony counts but impaired ability to express IL-2 receptors. These data suggest a sequential loss of T-cell function as a result of HIV infection; the earliest manifestations are impaired expression of IL-2 receptors and reduced proliferative responses, as measured in the colony assay.

AIDS-Related Complex↗
PubMed1987

Effects of nutrition on reproduction in dairy cows.

It is clear that nutrition is closely related to reproduction in the dairy cow. In addition to classic nutrient deficiency and excess, dry cow body condition and postpartum energy balance have a major impact on fertility. Dry cow rations must be designed to prevent milk fever, dystocia, retained placenta, other calving problems, and metritis. Most importantly, milk yield and reproductive performance should be regularly monitored to detect nutritionally associated health and performance changes that precede impairment of reproductive function.

Animal Nutritional Physiological Phenomena↗
PubMed1986

Treatment of Streptococcus agalactiae mastitis in dairy cows: comparative efficacies of two antibiotic preparations and factors associated with successful treatment.

A commercially available, penicillin-novobiocin, intramammary infusion product and a solution of procaine penicillin G (1.2 X 10(6) IU) in 10 ml of sterile saline solution were evaluated for their comparative efficacies against Streptococcus agalactiae mastitis in 3 California dairy herds. After composite milk samples from each cow in each herd were bacteriologically cultured, cows infected with S agalactiae (n = 228) were assigned randomly to 2 treatment groups. Milk samples were reevaluated bacteriologically 21 to 25 days after treatment. Both preparations were highly effective against S agalactiae in first-lactation cows and in cows scored negative or trace by use of the California Mastitis Test. Efficacy was significantly decreased in cows with California Mastitis Test scores of 1, 2, or 3. Herd and treatment were associated significantly with treatment success or failure. Most treatment failures were in one herd in cows that were given procaine penicillin G in sterile saline solution. Milk production and lactation stage were not associated with success or failure of treatment.

Animals↗
PubMed1986

Factors affecting embryo transfer success in recipient heifers under field conditions.

Recipient age at transfer (less than 525 d old or more than 525 d old), season (fall, winter, spring, summer), method of synchronization (natural or induced), and transfer technique (surgical or nonsurgical transfer) were associated with success of embryo transfer in a log-linear analysis. In a separate analysis, no significant association was found between success of transfer and transfer to the left or right uterine horn. Summer had the lowest proportion of successful transfers (58.9%). Pregnancy rates were 83% using the surgical transfer method and 68% with transcervical transfers. Proportion of pregnancies following a second transfer was not different from the proportion after first transfers. Success of embryo transfer was highest if recipients were greater than 525 d old and if transfers were performed surgically in spring following synchronization of recipients with cloprostenol, an analog of prostaglandin F2 alpha. Probability of success was lowest for transfers to young, prostaglandin-synchronized recipients, performed nonsurgically in summer.

Animals↗
PubMed1986

Comparisons of 12-tetradecanoylphorbol-13-acetate (TPA) and PHA as mitogens in the T-lymphocyte colony assay.

12-O-tetradecanoylphorbol-13-acetate (TPA) has multiple effects on the capacity of human T-lymphocytes to form colonies in soft agar. This compound is directly mitogenic for T-lymphocytes; the optimal concentration (100 ng/ml) stimulates an average of 2862 +/- 583 colonies/7.5 X 10(5) cells plated. Furthermore, TPA can act synergistically with PHA to induce a greater number of colonies than can either mitogen alone. Sephadex G10 nonadherent (NA) cells can be directly stimulated by TPA; by contrast, these isolated T cells do not respond to PHA alone. These data indicate that the phorbol ester is able to provide an inductive signal for T cells, allowing them to respond to the plant lectin. Using T-cell subsets isolated by monoclonal antibodies and complement cytotoxicity, PHA is able to induce colony growth of T4 cells; T8 cells fail to respond unless cocultured with exogenous IL-2. TPA can directly stimulate colony formation by both subsets. In cultures stimulated with either TPA or PHA, approximately equal numbers of colonies are generated in the presence of IL-2, suggesting that T4 and T8 cells have similar proliferative capabilities. Phenotypic studies of cells contained in colonies showed differences between the two mitogens. With PHA, more than 98% are both T11 and T3 positive; by contrast, approximately one-third of the cells stimulated by TPA are T11 +, T3-.

Cell Separation↗
PubMed1985

Defective in vitro T cell colony formation in the acquired immunodeficiency syndrome.

Depressed T cell immunity is a universal characteristic of the acquired immunodeficiency syndrome (AIDS). In the present study, 25 patients with AIDS and opportunistic infections, 22 individuals with AIDS-related complex (ARC, or chronic lymphadenopathy syndrome), and 20 healthy homosexuals were evaluated by means of the T cell colony assay. Forty-seven healthy heterosexual controls showed an average of 3964 +/- 319 colonies/7.5 X 10(5) cells, with a range of 880 to 9340. The mean in the 20 healthy homosexuals (3173 +/- 483) did not differ significantly from the controls; in this group, only three patients had values less than 1000 colonies/plate. By contrast, all AIDS patients and 14 ARC patients had colony counts less than 1000. The mean value for the AIDS patients was only 24 +/- 15 (p less than 0.0005 compared with either controls or healthy homosexuals); values in the ARC group were intermediate (1180 +/- 360). The addition of interleukin 2 to the plates promoted correction of the proliferative abnormality in ARC patients. This interleukin increased colony scores in the AIDS group, but the mean value was still significantly less than controls. Comparison indicated that the colony assay is a more sensitive indicator for detecting proliferative abnormalities than responses to PHA, Con A, or pokeweed mitogen in suspension cultures.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Inhibition of human lymphoproliferative responses and altered lymphocyte membrane phenotype by succinylacetone.

Succinylacetone (SA) proved to be a potent inhibitor of in vitro lymphoproliferative responses. This compound (3.0 mM) reduced the incorporation of 3HTdr by > 90% in mononuclear cell cultures stimulated with PHA, anti-CD3, IL-2 or phorbol dibutyrate-Ca2+ ionomycin. Furthermore, SA caused profound reduction in isotope uptake even if added to 3-day PHA-stimulated cultures as late as 6 h prior to harvest. Cells exposed to SA prior to mitogenic challenge and washed were not impaired in their proliferative activities. The addition of hematin to SA-containing cultures did not reverse the proliferative block. Phenotypic studies of stimulated cells suggested that SA does not preferentially affect one functional group of lymphocytes. However, it appeared that SA may act selectively to inhibit expression of transferrin receptors (CD71), a T-cell activation antigen. These data suggest that SA acts as a noncytotoxic immune inhibitor; this activity may be mediated, in part, by blocking cell activation and subsequent progress through the mitotic cycle.

Animals↗