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Biomedical subjects

C A Mebus

Publications and source records attributed to C A Mebus.

At least 37 records · Page 2Linked to original sources
PubMed1992

Swine leukocyte antigen and macrophage marker expression on both African swine fever virus-infected and non-infected primary porcine macrophage cultures.

Swine leukocyte antigens (SLA) and a macrophage specific marker were monitored on porcine macrophages cultured with or without macrophage colony stimulatory factor (M-CSF) and on cells infected with African swine fever virus (ASFV). SLA expression was maximal either in the total cell extract or on the cell surface at 3-4 days of culture; after 4 days these values began to decrease. Fluorescence analyses of immunostained macrophages cultured with or without M-CSF indicated a major upward shift in the number of SLA Class I molecules on individual macrophages whereas for SLA Class II both a novel expression of Class II and an upward shift in the number of molecules per cell were evident. Infection of 3-day-old macrophage cultures with three different isolates of ASFV resulted in minor changes in surface expression of SLA Class I, SLA Class II, and macrophage markers. No differences in infection with ASFV was observed whether macrophages were SLA Class II positive or negative, nor was there blocking by anti-SLA Class I or Class II monoclonal antibodies of ASFV infection of cultured macrophages.

African Swine Fever↗
PubMed1992

Methods for assessing rat sperm motility.

Computer-assisted sperm analysis (CASA) systems are becoming more widely used. With this spread of technology come more data from toxicology studies, designed to determine if treatment with putative toxicants affects sperm motion parameters. While these CASA methods provide us with more ways to evaluate toxicity and thus perhaps increase our chances of successfully protecting human health, there is also a greater likelihood that different laboratories will use different methods of collecting data on sperm motility. Different systems used with different methods in different laboratories will inevitably generate data that are difficult to compare. In a prospective attempt to address this issue of comparability and limit the problems, a group of individuals using CASA systems to analyze rat sperm motility convened to discuss methodologic issues, share data, and try to reach a consensus about methods for performing these studies. This article shares those meetings and data in the hope that common methods will enhance interlaboratory comparisons.

Animals↗
PubMed1992

Rift Valley fever virus-induced encephalomyelitis and hepatitis in calves.

Three calves (Nos. 1, 2 = 7 days old; No. 3 = 21 days old) were inoculated subcutaneously with virulent Rift Valley fever (RVF) virus. All calves became viremic and clinically ill, but the two 7-day-old calves were moribund and were euthanatized subsequently on post-inoculation day (PID) 3. Highest viral titers were measured in the serum, with lesser concentrations in the brain, heart, spleen, and liver of these animals. Viral antigens were detected by immunohistochemical analysis only in the livers, where positive staining was localized in coalescing foci of hepatocellular necrosis. The 21-day-old calf appeared to recover after viremia and pyrexia but became lethargic and ataxic and was euthanatized on PID 9. The calf was no longer viremic, and RVF virus was isolated only from the brain. Microscopic examination of the central nervous system revealed diffuse perivascular infiltrates of lymphocytes and macrophages, multifocal meningitis, and focal areas of neuronal necrosis and aggregates of macrophages, lymphocytes, and neutrophils throughout all regions of the brain and cervical spinal cord. There was positive immunohistochemical staining for viral antigens within the cytoplasm of neurons and glial cells throughout the central nervous system. Thus, RVF virus can cause encephalomyelitis in calves, and the specific virologic diagnosis can be made by immunohistochemical localization of viral antigens in formalin-fixed tissues.

Animals↗
PubMed1992

A pathogenesis study of foot-and-mouth disease in cattle, using in situ hybridization.

Eight calves were exposed in an aerosol chamber to nebulized foot-and-mouth disease virus. Two control animals were exposed in a similar manner to cell culture media only. Animals were euthanized at intervals and various tissues examined by in situ hybridization using a biotinylated RNA probe corresponding to a portion of the viral gene coding for the polymerase enzyme. By this technique large amounts of viral nucleic acid were found in coronary band, interdigital cleft and tongue as early as six hours postexposure, indicating a very rapid delivery from the portal of entry to the predilection sites for lesion development. This occurred well before the onset of viremia which by virus isolation was not detectable until 30 hours postexposure. The in situ hybridization signal in these tissues decreased in intensity and extent with time to focally positive areas, occasionally surrounding a vesicle. Other epidermal sites not normally thought of as sites for foot-and-mouth lesion development, such as carpus and eyelid, also had some viral nucleic acid detectable at various time intervals. In the lung by in situ hybridization, alveolar septa had viral nucleic acid early in infection (6-18 h postexposure) while later (36-96 h postexposure), the in situ hybridization signal was prominent in alveolar macrophages.

Animals↗
PubMed1991

Protection against 2-methoxyethanol-induced teratogenesis by serine enantiomers: studies of potential alteration of 2-methoxyethanol pharmacokinetics.

Several simple physiological compounds attenuate the teratogenic effects of 2-methoxyethanol (2-ME) when coadministered with 2-ME to mice. The mechanism of this protective action, however, has not been elucidated. Alteration of the kinetics of 2-ME and its oxidation product 2-methoxyacetic acid (2-MAA), the putative ultimate toxicant, was considered. D-Serine, the most efficacious attenuator, and L-serine (both 16.5 mmol/kg po) were examined for their abilities to mitigate 2-ME teratogenicity and to alter the disposition of an oral or sc bolus dose of 2-ME (3.3 mmol/kg containing 6 microCi 2-[methoxy-14C]ethanol) given to CD-1 mice on Gestation Day 11. L-Serine reduced the incidence of malformed fetuses from greater than or equal to 72% to 26-28%, while only 18 and 9% of fetuses were affected after coadministration of D-serine with sc and po 2-ME, respectively. Changes in the metabolism of orally administered 2-[14C]ME were specific to each enantiomer. D-Serine reduced the amount of 2-methoxy-N-acetylglycine eliminated in the urine to 70-75% of values observed with 2-ME alone, and concurrently increased the amount of urinary 2-MAA. L-Serine induced an initially higher rate of 14CO2 exhalation. Both enantiomers delayed gastrointestinal absorption of 2-ME, and significantly reduced 2-MAA levels in maternal plasma during the first hour after dosing. This resulted in a nonsignificant decrease (10-17%) in total embryonic exposure to 2-MAA. However, when 2-ME was injected sc, maternal plasma 2-ME/2-MAA pharmacokinetics were not affected by serine. In addition, dosing with 2.3 and 1.3 mmol 2-ME/kg sc alone showed that the embryo 2-MAA exposure levels which cause malformations in less than or equal to 35% fetuses were considerably lower than those measured following serine plus 3.3 mmol 2-ME/kg (po or sc). These data infer that serine does not protect against 2-ME-induced teratogenicity by altering 2-ME pharmacokinetics and reducing 2-MAA levels in the embryo.

Animals↗
PubMed1991

Embryo transfer as a means of controlling the transmission of viral infections. XIII. Failure to transmit foot-and-mouth disease virus through the transfer of embryos from viremic donors.

A total of 436 embryos/unfertilized ova was collected from 30 foot-and-mouth disease (FMD) viremic cattle; 106 of these embryos/ova were from eight donors that had FMD virus in their reproductive tracts. The 436 embryos/ova were washed and then either assayed in cell culture or intradermally in steer tongues or transferred to recipients. Foot-and-mouth infectivity was not found to be associated with any of the embryos/ova assayed in cell culture or intradermally. The 149 embryos transferred produced two abortions, five sets of twins born prematurely, and 15 normal calves. All of the recipients and all of the calves remained FMD-seronegative.

Journal Article↗
PubMed1990

Comparison of the effect of various chemical stabilizers and lyophilization cycles on the thermostability of a Vero cell-adapted rinderpest vaccine.

The thermostability of a rinderpest vaccine produced on Vero cells was evaluated using a variety of chemical stabilizers and lyophilization protocols. Three stabilizer preparations and three lyophilization schedules were examined using accelerated stability testing at 37 degrees C. The vaccine preparation exhibiting the greatest stability at 37 degrees C was tested at three additional temperatures, 42, 45 and 56 degrees C, and an Arrhenius plot was constructed from the data. The stability of the reconstituted vaccine produced with the two most efficacious stabilizers was examined using three different diluent preparations. The stabilization method and high Vero cell virus batch titers resulted in a lyophilized vaccine which maintained the minimum required dose of log10 2.5 TCID50 tissue culture infectious dose for more than 20 weeks at 37 degrees C.

Analysis of Variance↗
PubMed1990

The serological response to a thermostable Vero cell-adapted rinderpest vaccine under field conditions in Niger.

A lyophilized thermostable Vero cell-adapted ringerpest vaccine, stabilized with lactalbumin hydrolysate and sucrose, was tested for safety, serological response and suitability for use with an abbreviated cold chain under field conditions in Niger. A total of 480 cattle, 90 goats and 55 sheep of unknown serological status were vaccinated on government ranches and observed for at least 22 days. No untoward effects of the vaccine were detected. The serological response to the vaccine stored at environmental temperatures for 30 to 34 days was determined in 144 previously unvaccinated yearling calves. Seroconversion was demonstrated in 98% of the yearling calves using seroneutralization. The un-refrigerated vaccine retained a titer of 3.69 log10 TCID50 per dose through day 34.

Animals↗
PubMed1990

Isolation of a previously undescribed rickettsia from an aborted bovine fetus.

A previously undescribed obligate intracellular bacterium was isolated from an aborted bovine fetus. The organism was resistant to penicillin, replicated within cytoplasmic vacuoles, exhibited structural characteristics compatible with the rickettsias, and shared antigenic determinants with Cowdria ruminantium.

Abortion, Veterinary↗
PubMed1989

The possible role of one-carbon moieties in 2-methoxyethanol and 2-methoxyacetic acid-induced developmental toxicity.

The ethylene glycol ether, 2-methoxyethanol (2-ME), is rapidly (less than 1 hr) oxidized to 2-methoxyacetic acid (2-MAA). Both agents are selectively embryotoxic and equipotent in causing digit malformations when given to CD-1 mice on gestation Day 11. Previous observations have shown that simple physiological compounds such as formate, acetate, glycine, and glucose ameliorate the embryotoxicity of 2-ME. A common link for all of the attenuating agents may be oxidation pathways involving tetrahydrofolic acid (THF) as a catalyst for one-carbon transfer into purine and pyrimidine bases. In the present study serine at 16.5 mmol/kg, which reacts directly with THF, was as effective as formate in almost completely eliminating digit malformations resulting from treatment with 2-ME. Unlike formate, serine was equally effective against 2-MAA-induced dysmorphogenesis and the attenuating efficacy remained unchanged when serine administration was delayed for up to 8 hr after 2-ME or 2-MAA exposure. The protective effect of sarcosine, which is an intermediate in a pathway leading from choline to glycine and a structural analog of 2-MAA, was also determined. Both concomitant (43, 16.5, or 3.3 mmol/kg) and delayed (16.5 mmol/kg at 6 hr) sarcosine administration resulted in significantly less 2-ME-induced paw dysmorphogenesis. In addition, acetate administration was delayed for increasing intervals after 2-ME to determine the time at which attenuation would no longer occur, and acetate was effective for as long as 12 hr after 2-ME. These results support our hypothesis that 2-MAA, which has a long biological half-life, may interfere with the availability of one-carbon units for incorporation into purine and pyrimidine bases. Alterations in availability of these precursors might be expected to affect DNA and/or RNA synthesis and thereby influence normal cellular proliferation and differentiation in the developing embryo.

Abnormalities, Drug-Induced↗
PubMed1989

Attenuation of 2-methoxyethanol-induced testicular toxicity in the rat by simple physiological compounds.

2-Methoxyethanol (2-ME) is an industrial solvent which is toxic to both male and female reproductive systems of laboratory animals. Earlier data have demonstrated that the developmental toxicity of 2-ME can be attenuated by simple physiological compounds such as serine, acetate, sarcosine, glycine, and D-glucose. The present experiments were designed to evaluate the same compounds for their ability to ameliorate the testicular toxicity that occurs in rats after 2-ME exposure. The extent of testicular damage was assessed by quantitating daily sperm production (DSP) on Day 24 following a single dose of 2-ME (6.6 mmol/kg, 500 mg/kg). Serine completely eliminated 2-ME-induced decreases in DSP, while glucose was without effect. Acetate, sarcosine, and glycine were of similar efficacy resulting in DSP that was significantly greater than that observed in rats which received 2-ME alone. Histopathological studies revealed that 2-ME treatment resulted in stage-specific degeneration of late stage pachytene spermatocytes 24 hr after treatment. No apparent degenerative changes occurred after concurrent treatment with serine. Similarly, serine also prevented the decreased number of spermatids in the lumina of the seminiferous tubules on Day 24 after 2-ME exposure alone. All of the compounds utilized in this study are linked to oxidation pathways involving tetrahydrofolic acid as a catalyst for one-carbon moiety transfer into purine and pyrimidine bases which are necessary precursors for DNA and RNA synthesis. The ability of these compounds to attenuate the testicular toxicity of 2-ME may result from their ability to donate one-carbon units which can be used in purine base biosynthesis. Reduced availability of bases would be expected to affect late stage pachytene spermatocytes which are known to be undergoing rapid RNA synthesis.

Animals↗
PubMed1989

Protection of goats against Caribbean and African heartwater isolates by the Ball 3 heartwater vaccine.

Two groups of castrated male adult goats (three goats/group) were infected intravenously with the Ball 3 vaccine strain of Cowdria ruminantium and treated with long-acting oxytetracycline at the onset of clinical disease 10 days later. Five weeks post-vaccination one group was challenged with a Caribbean isolate (Gardel) and the other group with a West African isolate (Mali) of C. ruminantium. Non-vaccinated controls infected with either the Gardel or Mali isolate died. All of the vaccinated animals challenged with the Gardel strain reacted and survived. The three vaccinated animals challenged with the Mali isolate also reacted and two died of heartwater.

Animals↗
PubMed1989

Virus-specific cellular blastogenesis and interleukin-2 production in swine after recovery from African swine fever.

Animals recovered from viral diseases represent an important model to study the host cellular and humoral immune responses to the etiologic agents. This is particularly important for African swine fever virus (ASFV) infections in which antibodies have little or no virus-neutralizing effect. Pigs surviving experimental infection with the naturally occurring low-virulent, nonhemadsorbing ASFV/NH/P68 (NHV) isolate did, however, exhibit virus-specific T-cell activities, as measured by a variety of assays. A strong virus-induced, antigen-specific blastogenic response was observed only with blood mononuclear cells (BMC) from ASF-recovered swine, whereas cells from recovered and naive swine responded similarly to the mitogens concanavalin A and phytohemagglutinin. The ASFV-induced blastogenesis was dependent on virus dose and on the presence of adherent cells. Blood mononuclear cells cultured with antigenically related hemadsorbing ASFV isolates of different virulence characteristics, the highly virulent L60 isolate and moderately virulent DRII isolate, exhibited a similar magnitude of blastogenesis to cells infected with the low-virulent NHV isolate. Virus-infected cells proved to be an efficient inducer of interleukin-2 (IL-2) activity to cells from recovered swine, but not from naive swine, whereas T-cell-specific lectins induced production of similar amounts of IL-2 activity from cells of naive and recovered swine. Correlated with the appearance of virus-induced IL-2 activity in the culture supernatant was the induction of promiscuous killing in cells exposed to prolonged (7 days) virus stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

African Swine Fever↗
PubMed1988

Moderately virulent African swine fever virus infection: blood cell changes and infective virus distribution among blood components.

Blood samples of pigs infected with a moderately virulent African swine fever virus (ASFV) isolate, obtained from the Dominican Republic (DR-II), were monitored temporally for viremia, infective ASFV association with major blood components, differential changes in blood cell composition, and plasma antibodies to ASFV. After intranasal/oral virus inoculation, pigs underwent acute infection and illness that resolved. Acute illness began on postinoculation day (PID) 4 and continued to PID 11, and pigs were febrile, with maximal infective ASFV titers detected in blood. By PID 11, initial antibody titers to ASFV antigens were detected in plasma. The WBC numbers were maintained near preinoculation counts; however, lymphocyte counts decreased slightly with a compensatory increment in neutrophil and monocyte numbers. From PID 11 to PID 25, rectal temperatures gradually returned to preinoculation values, titers of viremia began to decrease, plasma antibody to ASFV antigens increased to peak titers, and WBC numbers increased slightly. Percentages of lymphocytes returned to preinoculation values, neutrophil percentages decreased to slightly below preinoculation values, monocyte percentages were mildly increased, and eosinophil percentages were unaffected. From PID 25 to PID 46, titers of viremia further decreased, and plasma titers of antibodies to ASFV antigens remained high. In pigs with DR-II viremia (PID 4 to PID 46), most viral infectivity (greater than 95%) was RBC associated. Plasma contained less than 1% infectivity, and less than 0.1% of virus was in the WBC fraction (monocytes, lymphocytes, and granulocytes). After PID 46, viremia was no longer detectable.

Acute Disease↗
PubMed1987

Depression of rat testicular 17-hydroxylase and 17,20-lyase after administration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD).

Toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), such as chloracne, hirsutism, and skin hyperpigmentation, suggest endocrine involvement, however, little is known about the effects of TCDD on steroidogenic organs. It is known that TCDD can cause decreases in testicular heme, testicular microsomal cytochrome P-450, and serum testosterone in the rat. This study was designed to examine the activities of the testicular hemoprotein microsomal cytochrome P-450-dependent enzymes, 17-hydroxylase and 17,20-lyase, following a single, oral dose of either 12.5, 25, or 50 micrograms/kg TCDD. TCDD caused dose- and time-dependent decreases in the activity of the 17-hydroxylase enzyme. Significant decreases were observed at 3, 7 and 14 days at the lowest dose of 12.5 micrograms/kg TCDD. The 17,20-lyase enzyme seemed to be less sensitive to the toxic effects of TCDD with significant decreases in enzyme activity being observed at days 3, 7 and 14 only after treatment with 50 micrograms/kg TCDD. Both microsomal cytochrome P-450 and serum testosterone levels decreased in a dose- and time-dependent manner following 12.5, 25 and 50 micrograms/kg doses of TCDD. These results indicate that decreased testosterone production following treatment with TCDD is related to decreased activities of the testicular microsomal cytochrome P-450-dependent enzymes 17-hydroxylase and 17,20-lyase.

Aldehyde-Lyases↗