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Biomedical subjects

M R Bleavins

Publications and source records attributed to M R Bleavins.

At least 37 records · Page 2Linked to original sources
PubMed1995

Cynomolgus monkeys (Macaca fascicularis) in preclinical immune function safety testing: development of a delayed-type hypersensitivity procedure.

A delayed-type hypersensitivity (DTH) test commonly used for humans was adapted for use with cynomolgus monkeys (Macaca fascicularis). Pilot experiments showed naive animals had poor response rates and inconsistent reactivity to the antigens. In an exploratory phase, it was determined that monkeys could be experimentally sensitized by immunization with commercially available antigens. Animals were then sensitized with various concentrations of diphtheria and tetanus toxoids, Candida, and Trichophyton in the dose-response phase. Antigens were injected intradermally (i.d.) 3 times over a 7-day period and monkeys were tested 14 days after the last injection. Responses were measured 24, 48, and 72 h post-challenge, with skin biopsies taken from two animals per group at the 24 h interval. Optimal concentrations were 1.2 Lf diphtheria, 6 Lf tetanus, 1000 PNU Candida, and 1000 PNU Trichophyton. These concentrations produced the best balance between DTH responses, homogeneity of dermal mononuclear cell infiltrate and lowest frequency of undesirable skin reactions. Positive responses were seen at 24 and 48 h post-challenge and were waning by 72 h. DTH responses were inhibited by topical corticosteroids. The final phase of these studies assessed whether sensitization of naive animals could be achieved using subcutaneous (s.c.) administration of the optimal antigen concentrations. Comparable responses to i.d. sensitization were obtained and skin sores did not develop at injection sites. These studies show that the DTH test adapted to monkeys was reproducible, minimally invasive, did not require sacrifice of the test animal, allowed repeated measurements and paralleled the reactions observed in humans.

Animals↗
PubMed1995

Subacute toxicity of a purine nucleoside phosphorylase inhibitor in rats.

Rats received daily oral doses of 15, 50, 150, or 200 mg/kg CI-1000 for 4 weeks. Doses were selected based on findings from a 2-week range-finding study where doses of 250 and 500 mg/kg resulted in mortality. In the 4-week study, females given 200 mg/kg were sacrificed during Week 2 due to poor condition. Serum creatinine and urea nitrogen increased 2- to 2.5-fold in females given 200 mg/kg. Dose-related increases in urine volume, urinary protein excretion, and osmolar excretion occurred in both sexes beginning at 50 mg/kg. Kidney weights increased 9-40% in both sexes at > or = 50 mg/kg; histopathologic changes were confined to the 150 and 200 mg/kg groups. At Week 4, T-suppressor/cytotoxic lymphocytes were reduced 43% and T-helper/inducer lymphocytes were reduced 22% in males given 200 mg/kg. In females, T-suppressor/cytotoxic lymphocytes were significantly decreased (approximately 40%) at 50 and 150 mg/kg, with no significant effects on T-helper/inducer lymphocyte populations. At Week 8, following 4 weeks without treatment, T-lymphocyte subpopulations were similar in control and drug-treated groups. B-lymphocyte counts and percentages were increased at Weeks 4 and 8 in males receiving 150 or 200 mg/kg. Thymic weights decreased at Week 4 at doses of 150 and 200 mg/kg. Plasma CI-1000 levels were higher in females than in males at all doses except 15 mg/kg; Cmax and AUC values were largely dose proportional in both sexes. In summary, CI-1000 was well-tolerated at doses of 15, 50, and 150 mg/kg with no adverse effects occurring at 15 mg/kg. Drug-induced changes in the kidney were mild and reversible. Immunomodulatory effects were noted at doses of 50 mg/kg or higher.

Adjuvants, Immunologic↗
PubMed1995

Effects of cyclosporine A on ozone-induced pulmonary lesion formation: pharmacologic elimination of the T-lymphocyte regulatory response.

To assess the involvement of T-lymphocytes in ozone-induced lung damage, CD-1 mice were exposed to air or 0.7 ppm ozone (1.37 mg O3/m3 air) in the presence and absence of the immunosuppressive drug cyclosporine A (CSA). Mice were thus divided into four treatment groups for both the 4 and 14 day exposure times: 1) AIR + VEH, 2) AIR + CSA, 3) O3 + VEH, and 4) O3 + CSA. Thy-1.2 positive cells (T-lymphocytes) per pulmonary lesion were determined and quantitative histomorphometric analysis of lesion volume was performed. By Day 14, the number of T-lymphocytes per lesion in O3 + VEH (vehicle) animals had increased to approximately 3.5 times that seen at Day 4. At 4 and 14 days of O3 + CSA treatment, the number of T cells per lesion was half that seen in O3 + VEH mice. At Day 4, lesion size and appearance were comparable in O3 + VEH and O3 + CSA animals, while at Day 14, O3 + CSA treatment resulted in larger and more cellular lesions that contained a greater proportion of polymorphonuclear cells, and the lesions extended further into the lung periphery. Inflammatory cells were observed in areas of epithelial cell proliferation and in alveolar spaces distal to the small airway terminus. After 14 days, lesion volume was approximately twice as great following O3 + CSA administration than with O3 treatment alone. These results are consistent with effects seen in another model of immunosuppression, the nude mouse, and they implicate a regulatory role for T-lymphocytes in the response to ozone.

Animals↗
PubMed1993

Cell cycle dependent distribution of proliferating cell nuclear antigen/cyclin and cdc2-kinase in mouse T-lymphoma cells.

The aim of the present study was to investigate bromodeoxyuridine (BrdU) uptake and coordinated distribution of proliferating cell nuclear antigen (PCNA) and p34-cdc2-kinase, two important proteins involved in cell cycle regulation and progression. Flow cytometric analysis of marker proteins in freshly plated mouse T-lymphoma cells (Yac-1 cells), using fluorescein isothiocyanate (FITC)-labeled specific antibodies, showed PCNA distributed throughout the cell cycle with increased intensity in S-phase. PCNA is essential for cells to cycle through S-phase and its synthesis is initiated during late G1-phase before incorporation of BrdU and remains high during active DNA replication. The intensity of PCNA fluorescence increases with the duration of incubation after plating. The cdc2-kinase was detectable in all phases of the cell cycle and the G2-M-phase appears to have the maximum concentrations. The cell cycle analysis of high dose colcemid (2 micrograms/ml) treated Yac-1 cells showed an aneuploid or hypodiploid population. Although the G2-M-phase seems to be the dominating population in aneuploid cells, the concentrations of cdc2-kinase were variable in this phase of cell cycle. The colcemid treatment at 25 ng/ml arrested 96% of cells in S-phase and G2-M-phase, but PCNA expression was evident in a portion of the cell population in G2-M-phase. Although cells blocked in M-phase seem to have high levels of cdc2-kinase, colcemid renders them inactive. From these data, it appears that the down regulation and/or inactivation of cdc2-kinase could be responsible for the colcemid arrest of cells in M-phase.

Animals↗
PubMed1993

Flow cytometric characterization of lymphocyte subpopulations in the cynomolgus monkey (Macaca fascicularis).

Characterization of immune cell subpopulations in the cynomolgus monkey was performed using a direct immunofluorescence technique adaptable for routine and repeated monitoring. This whole blood procedure is faster and requires less volume than conventional density gradient isolation methods. Low intra- and inter-animal variations were seen in hematology parameters and in CD4, CD8, and CD20 lymphocyte subtypes. CD4 values were 28% of lymphocytes in males and 30% in females. Fifty-six percent were CD8+ in males and 54% in females. CD4:CD8 ratios were approximately 0.5 in both sexes. This proportion is the reverse of that observed in humans, but appears normal for the cynomolgus. Consistent with values reported for humans, approximately 12% of cynomolgus peripheral blood lymphocytes were CD20+. Greater than 95% of the lymphocytes present in blood were identified as CD4, CD8, or CD20 positive.

Animals↗
PubMed1991

Alpha 2u-globulin nephropathy without nephrocarcinogenesis in male Wistar rats administered 1-(aminomethyl)cyclohexaneacetic acid.

Alpha 2u-Globulin (alpha 2u) nephropathy is a male rat-specific condition caused by a diverse group of xenobiotics. Features of this nephropathy include hyaline droplet accumulation in proximal tubules, tubular epithelial necrosis and regeneration, exacerbation of spontaneous renal disease, and induction of renal epithelial tumors. Nephrocarcinogenicity of compounds that cause this nephropathy may be a consequence of increased proximal tubular proliferation resulting from cell injury. These studies document alpha 2u nephropathy without primary renal epithelial tumors in male Wistar rats administered 1-(aminomethyl)cyclohexaneacetic acid (gabapentin), a therapeutic agent with antiepileptic/anticonvulsant properties. In a series of preclinical studies gabapentin was administered to rats at the following doses and durations: 50 and 2000 mg/kg for 2 weeks; 250, 1000, 2000, and 3000 mg/kg for 13 weeks; 250, 1000, and 2000 mg/kg for 52 and 104 weeks. Renal effects were evaluated by biochemical, immunocytochemical, histopathologic, and ultrastructural techniques. Reversible increases in size and distribution of hyaline droplets within proximal tubular epithelium occurred through 1 year of treatment at a severity that was dose-dependent. In males given 2000 mg/kg, alpha 2u accumulation, degeneration, and necrosis of the P2 segment and intraluminal cellular casts were seen after 2 days of treatment. In the 2-week study, the size and number of phagolysosomes containing alpha 2u and the renal tissue alpha 2u increased with increasing dose and time. By Day 7, polymorphic crystalline inclusions were abundant in phagolysosomes of 2000 mg/kg males. In subchronic and chronic studies, spontaneous glomerulonephrosis was exacerbated in males given 2000 mg/kg, and, interestingly, no drug-related effect on renal tumor incidence was observed. To the best of our knowledge, this is the first documentation of the absence of nephrocarcinogenic effect in male rats treated for up to 104 weeks with a compound that causes acute and chronic lesions of alpha 2u nephropathy.

Acetates↗
PubMed1991

Effects of CI-949, a novel antiallergy compound, on host resistance in mice.

The effect of CI-949, a novel inhibitor of allergic mediator release, on immune function was assessed with holistic mouse models of immunocompetence. Resistance to the bacterial pathogens Listeria monocytogenes and Streptococcus pneumoniae and the B16F10 melanoma cell line was used to evaluate the potential of CI-949 to affect immune function. CI-949 treatment of female B6C3F1 mice increased pulmonary tumor burden at 100 mg/kg/day in the B16F10 melanoma model, with a no effect level of at least 50 mg/kg/day. A correlation was seen between decreased clearance of the B16F10 cells and increased tumor burden. However, CI-949 produced this effect only at the maximum tolerated dose. No effect of the drug was seen in the S. pneumoniae model. Host resistance to L. monocytogenes was increased after CI-949 administration, with the no adverse effect level in this model being at least equivalent to the top dose of 100 mg/kg/day. Therefore, the immune system does not appear to be adversely affected or to be a specific target for CI-949 even at an overtly toxic dose.

Animals↗
PubMed1991

Effects of CI-949, a novel antiallergy agent, on immune function of male Fischer 344 rats.

CI-949 is an orally effective inhibitor of allergic mediator release as measured with in vitro and animal models. To assess the effects of CI-949 on immune function, male Fischer 344 rats were evaluated for splenic T- and B-lymphocyte populations, antibody-forming cell response to sheep red blood cells (sRBC), concanavalin A- and pokeweed mitogen-induced lymphocyte proliferation, Natural Killer cell activity and reticuloendothelial system clearance of sRBC. CI-949 was administered by gavage to rats at 25, 50 and 100 mg/kg/day for 14 consecutive days. A vehicle control and two positive controls (cyclosporine A and cyclophosphamide) were run concurrently. CI-949 at 100 mg/kg/day decreased body weight gain and was lethal to 5 of 40 rats. The deaths occurred between days 5 and 12 of study. This overtly toxic dose did not alter splenic cellularity or change the percentages of T- and B-lymphocyte subpopulations. Additionally, CI-949 did not inhibit lymphocyte proliferation or hinder clearance of sRBC by the reticuloendothelial system. Antibody-forming cell response after immunization showed a dose-related increase in the number of immunoglobulin M secreting cells. Based on the results of these assays, the immune system does not appear to be adversely affected by CI-949 even at high doses.

Animals↗
PubMed1990

An immunofluorescence study of T and B lymphocytes in ozone-induced pulmonary lesions in the mouse.

Ozone is a photochemical oxidant which reacts with a variety of biological molecules. In experimental animals the toxicity of ozone results from damage to cells in the lung and is associated with the process of reactive repair and an influx of inflammatory cells. In this work we used an indirect immunofluorescence technique to study the effect of ozone on T and B lymphocytes with special reference to their presence in ozone-induced pulmonary lesions. BALB/c mice were exposed to ozone at a concentration of 0.7 ppm for 20 hr per day, 7 days per week, for 4 or 14 days. Control mice were housed in comparable chambers lacking ozone. Frozen sections of lung were prepared and stained for the surface markers Thy-1.2 (T lymphocyte) and sIgM (B lymphocyte). These experiments showed that T lymphocytes infiltrate the lung lesions during ozone inhalation, and increase their presence as ozone exposure continues. They were present in the centroacinar region and tended to occur in clusters within the ozone-induced lesions. In contrast, the infiltration of B lymphocytes was virtually nonexistent with few or no sIgM positive cells present in the lesions after either 4 or 14 days of exposure to ozone. These results show that T lymphocytes occur within the sites of ozone-induced damage and support that this cell type plays a role in the reactive host response to ozone inhalation.

Animals↗
PubMed1984

Effects of dietary hexachlorobenzene exposure on regional brain biogenic amine concentrations in mink and European ferrets.

In the initial trial, adult mink and ferrets were administered hexachlorobenzene (HCB) via the feed at concentrations of 1, 5, or 25 ppm for 47 wk. Animals receiving 125 and 625 ppm HCB in the diet died before termination of the experiment, with female ferrets at the 125 ppm level displaying abnormal aggressiveness and hyperexcitability just prior to death. Hypothalamic serotonin (5-HT) was significantly elevated at all dose levels in mink, and cerebellar 5-HT was significantly elevated at 1 ppm in the ferret. Regional brain biogenic amine concentrations were also determined in the offspring of the female mink that were administered 1 and 5 ppm HCB. Hypothalamic dopamine (DA) concentrations were significantly depressed by 1 and 5 ppm in these kits. In a second study, adult male and female ferrets were administered 250 or 500 ppm HCB via the diet for 7 wk. Two animals at the 250-ppm level and 3 animals at the 500-ppm level died before termination of the experiment without showing behavioral changes. Of the remaining animals, 3 ferrets at 250 ppm and 1 ferret at 500 ppm showed slight aggressiveness and hyperexcitability during the last week of the experiment. Concentrations of 5-HT were significantly elevated at 500 ppm in the cerebral hemispheres and at 250 ppm in the midbrain of male ferrets, while in the females, 5-HT was elevated in the cerebral hemispheres at 250 ppm and in the hypothalamus at both 250 and 500 ppm. Norepinephrine (NE) concentrations were significantly elevated in the cerebellum of males exposed to 250 and 500 ppm, as were NE concentrations in the midbrain. HCB at 500 ppm caused a significant increase in medullary NE, while 250 ppm caused an increase in hypothalamic NE in males. The only change in regional brain dopamine (DA) concentrations occurred at 500 ppm HCB in the midbrain of males, where there was a significant elevation of this neurotransmitter.

Aggression↗
PubMed1983

Effects of excessive dietary zinc on the intrauterine and postnatal development of mink.

Dietary exposure to 1000 ppm of supplemental Zn did not result in grossly observable Zn toxicity or Zn-induced Cu deficiency in adult mink. These same concentrations did, however, produce achromatrichia, alopecia, lymphopenia and a reduced rate of growth in the offspring produced by the Zn-treated females. These mink kits also exhibited profound immunosuppression. The in vitro blastogenic response of peripheral blood lymphocytes to concanavalin A was significantly (P less than 0.001) lower in kits born to Zn-treated dams than the response of those born to control dams. The depressed immunoresponsiveness was not a permanent defect since a normal lymphocyte response was seen approximately 14 weeks after weaning and being placed on an unsupplemented basal diet. The impaired lymphocyte reactivity is believed to be the result of altered DNA synthesis in these cells and/or an inhibition of macrophage functions necessary for normal response to the mitogen concanavalin A.

Age Factors↗