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Biomedical subjects

B Tennant

Publications and source records attributed to B Tennant.

At least 37 records · Page 2Linked to original sources
PubMed1996

Antiviral activity of a conjugate of adenine-9-beta-D-arabinofuranoside 5'-monophosphate and a 9 kDa fragment of arabinogalactan.

An arabinogalactan conjugate containing a 9 kDa fragment of arabinogalactan and adenine-9-beta-D-arabinofuranoside 5'-monophosphate (araAMP), denoted AG(9 kDa)-araAMP, has been synthesized and characterized. In 2.2.15 (human hepatoblastoma) cells, the attachment of araAMP to AG(9 kDa), a ligand of the asialoglycoprotein receptor, decreased the effective concentration for inhibiting extracellular hepatitis B virus (HBV) production by 90% (EC90) from 17 to 0.9 microM adenine arabinoside (araA) equivalents, and increased the cytotoxic concentration (CC50) from 188 to > 17 300 microM araA equivalents. Hence, the selectivity index (CC50/EC90) of araA was improved from 11 (188/17) to > 19200 (17 300/0.9) by conjugation with the 9 kDa fragment of arabinogalactan. AG(9 kDa)-araAMP did not affect the production of viral RNA or viral proteins. In the woodchuck hepatitis model, AG(9 kDa)-araAMP inhibited woodchuck hepatitis virus (WHV) DNA replication at a dose of 0.3 mg of araA equivalents per kg; in this case, AG(9 kDa)-araAMP was 20-30 times more potent than was unconjugated araA. AG(9 kDa)-araAMP was effective by intramuscular or subcutaneous administration. The reduction in HBV DNA levels obtained in 2.2.15 cells and of WHV DNA levels in woodchucks was sustained after treatment with AG(9 kDa)-araAMP ceased. In both cases, viral DNA gradually returned to pre-treatment levels.

Animals↗
PubMed1996

Collection of seasonally spermatozoa-rich semen by electroejaculation of laboratory woodchucks (Marmota monax), with and without removal of bulbourethral glands.

Male woodchucks were subjected to electroejaculation during the early- or mid-breeding season by a commercial stimulator and rectal probe (1.3 x 13 cm, with longitudinal electrode strips on one side) with electrodes oriented ventrally. A study of the voltage and stimulation parameters at a probe depth of 4 to 9 cm suggested that a series of 15 to 75 3-sec pulses of 3 to 6 V each could result in ejaculation and collection of semen. Pulses of only 1 to 2 V frequently caused erection but not ejaculation. Trials conducted on 12 bulbourethral (Cowper's) gland-intact males (n = 18 trials) versus six males from which Cowper's glands had been surgically removed (n = 18 trials) identified these glands as the source of urethral plugs in 77% of ejaculates from the gland-intact males and presumably the source of copulation plugs obtained from the vagina of female woodchucks. The fluid portion of ejaculates from both groups contained few or no spermatozoa. An additional 32 trials were conducted on 12 gland-intact males and eight males without Cowper's glands. These trials included 16 shallow (5 to 8 cm) versus 16 deep (10 to 13 cm) placements of the tip of the rectal probe in each group of males. In gland-intact males the stimulation of sacral (shallow) elements routinely resulted in the emission of large (200 to 300 microl) urethral plugs and fluid volume of 40 to 400 microl, containing few or no spermatozoa. In males without Cowper's glands the sacral stimulation typically produced volumes of 60 to 350 microl of noncoagulating liquid without urethral plugs, containing few or no spermatozoa. Lumbar (deep) stimulation in both groups of males usually resulted in fluid ejaculates, with 60% containing numerous spermatozoa (typically, 0.5 to 3 x 10(6)/ejaculate). Lumbar stimulation usually produced urethral plugs of little (50 to 100 microl) or no volume in gland-intact males and no urethral plugs in males without Cowper's glands. Ejaculates did not coagulate during handling or storage for 4 to 24 h. Serial lumbar stimulation of six males at 2- to 3-week intervals resulted in few spermatozoa, except for a 4- to 8-week period during which > or =0.25 x 10(6) spermatozoa/ejaculate and peaks of 5.3 +/- 2.4 x 10(6) spermatozoa/ejaculate were obtained. The results suggest that electroejaculation can be used to obtain spermatozoa-containing liquid that might be useful for semen evaluation or artificial insemination in laboratory woodchucks, that Cowper's glands are the source of urethral plugs in the ejaculates of this species, and that the fertile period of the male breeding season is limited to 4 to 8 weeks.

Animals↗
PubMed1993

New enzyme immunoassays for the serologic detection of woodchuck hepatitis virus infection.

The woodchuck and the woodchuck hepatitis virus (WHV) have been used as a model of hepatitis B virus infection and its disease sequelas. Serologic responses to WHV infection have been described in previous reports from this laboratory by using virus-specific radioimmunoassays (RIAs) for WHV surface antigen, antibody to WHV core antigen, and antibody to WHsAg. In this study, we developed and evaluated new enzyme immunoassays (EIAs) for these WHV serologic markers. Relative to the established RIAs, the EIAs were either improved or comparable in their sensitivity and specificity, and in their utility for monitoring experimental WHV infection and classifying woodchucks into serological diagnostic categories. These EIA systems are amenable to the quantitative titration of antibodies and quantitation of WHV antigens in serum, and ultimately should allow improved resolution of virologic and humoral immune responses of woodchucks to WHV infection.

Animals↗
PubMed1993

Alteration of growth, advancement of puberty, and season-appropriate circannual breeding during 28 months of photoperiod reversal in woodchucks (Marmota monax).

In woodchucks (Marmota monax), as in other marmotine rodents, endogenous circannual metabolic and reproductive cycles persist and free-run at intervals of 10-12 mo for up to 4 yr in a neutral photoperiod of 12L:12D. The annual metabolic cycle is not altered by exposure to constant long days or short days for several months. In the wild, changes in food intake cause body weight to peak in late summer and reach nadirs in early spring, and there is a single annual breeding season in late winter. To determine whether normal changes in photoperiod entrain the endogenous circannual cycle, aspects of reproduction, food intake, and body weight were studied for 28 mo in eight groups of woodchucks housed in light-controlled rooms. These included four groups of 7-10 males and four groups of 7-10 females exposed to automated and continuous daily changes in photoperiod. The imposed changes in photoperiod resembled native Northern Hemisphere (boreal) changes or Southern Hemisphere (austral) changes in photoperiod. The treatments started at the summer solstice shortly after capture as 2.5-mo-old juveniles or 14.5-mo-old yearling adults. In austral vs. boreal woodchucks, started as juveniles, annual increases in testosterone and testis descent at 5, 14, and 23 mo of study were advanced by 2, 5, and 6 mo, respectively. Annual increases in progesterone at 7, 16, and 25 mo of study were advanced by 4, 5, and 6 mo, respectively. The older woodchucks were significantly but less dramatically affected by austral photoperiod for the first 6 mo of study, and by 8-12 mo were advanced the same as the younger animals. At 16-17 and 26-27 mo of photoperiod reversal, 16 austral females had normal pregnancy rates (78%) and produced normal-sized litters (4.3 +/- 0.2) that were advanced by 5 and 6 mo, respectively, relative to those of boreal controls. Body weights in austral vs. boreal juveniles were reduced at 3-5 mo of study but not in older woodchucks. At 1 and then 2 yr of austral lighting, peaks in body weight were advanced by 4 and then 5 mo relative to boreal controls in young animals, and by 2 and then 5 mo in older animals. Between 1 and 2 yr of austral lighting in both age groups the nadirs in food intake (45 g per day) were about 16-25% of peak food intake 6-8 mo earlier, as in boreals, but advanced by 5-6 mo relative to boreals.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Induction and enhancement of feline infectious peritonitis by canine coronavirus.

Preexisting antibody to feline infectious peritonitis virus (FIPV) causes acceleration and enhancement of disease on subsequent infection of cats with FIPV. Other workers have shown that canine coronavirus (CCV) can infect cats subclinically, but have found no evidence of enhancement of, or protection against, subsequent FIPV infection. With various isolates of CCV, we determined that 1 strain of CCV can induce transient mild diarrhea in cats and, furthermore, that previous infection with CCV causes acceleration and enhancement of subsequent infection with FIPV. In addition, sequential inoculation of cats with another strain of CCV caused lesions indistinguishable from those of FIP, without exposure at any time to FIPV.

Animals↗
PubMed1990

Endocrine correlates of hibernation-independent gonadal recrudescence and the limited late-winter breeding season in woodchucks, Marmota monax.

Woodchucks (Marmota monax) normally experience gonadal recrudescence towards the end of a 4-5 month hibernation, emerge in late winter, immediately breed in a short 3-week breeding season, and have regressed gonads before the next hibernation. Our studies of wild and captive animals show that fertile females give birth to single litters after a 32-day gestation and their breeding season is terminated by a reactivation of the corpora lutea of pregnancy for 1-3 months immediately postpartum. In nonbred females the breeding season is likewise terminated by spontaneous luteinization of the ovaries for 1-3 months shortly after the vernal equinox. Tests regress and testosterone declines during and after the breeding season. Circannual reproductive cycles persist in the absence of hibernation and are shortened to 9-10 months after 3-5 years of a 12L:12D photoperiod. Unique aspects of this species that merit endocrine investigation include descent/retraction of testes, transient luteolysis at parturition, superactivation of postpartum corpora lutea, regulation of the pituitary-gonadal axis by an annual endogenous metabolic cycle entrained to the annual change in photoperiod, and the hormonal basis of hibernation.

Animal Husbandry↗
PubMed1984

Serum progesterone profiles and corpora lutea of pregnant, postpartum, barren and isolated females in a laboratory colony of woodchucks (Marmota monax).

Female woodchucks, greater than or equal to 1 year old (n = 10) or recently weaned locally in the wild at 42 degrees N (n = 10), were maintained indoors in standard laboratory animal facilities from one summer solstice to the next except for those killed after 11 months of study. Available ambient light was supplemented with a 12L: 12D incandescent light schedule. Food and water were provided ad libitum, except for a 63-day period when feeding and supplemental lighting were discontinued, starting at the winter solstice . Temperatures fluctuated with outdoor temperatures greater than or equal to 4 degrees C. During the winter, females within each age class (adult vs. subadult ) were housed with (n = 5) or without (n = 5) a male cagemate , and scored for hibernation at variable intervals. Blood samples for serum progesterone assay were collected at intervals of 1-4 weeks. Birth of litters occurred in 2 of 5 adults (March 19, April 2) and in 0 of 5 subadults . Neither the incidence nor frequency of hibernation were correlated to the occurrence of pregnancy or to the extent or timing of elevations in progesterone in barren or isolated females. Serum progesterone was elevated during the 31-day gestation and for 1-2 months postpartum in the 2 fertile colonized animals and in 7 others captured pregnant during the same breeding season and which gave birth April 12-24. Postpartum animals had progesterone levels equal or above those near midgestation and had 3.1 +/- 0.2-mm diameter corpora lutea which numbered 2.5 +/- 0.3 per ovary.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Corpora lutea of pregnancy and elevated serum progesterone during pregnancy and postpartum anestrus in woodchucks (Marmota monax).

Serum samples (n = 62) were collected from wild-caught woodchucks (n = 45) that were nonpregnant (n = 3), pregnant (n = 25) or postpartum (n = 34) when bled at the time of capture and/or necropsy, or following maintenance and observation for variable periods of time. Progesterone concentrations were determined by radioimmunoassay and related to the actual or estimated time from parturition which occurs at 31 days postcoitum in this species. Mean serum progesterone levels during the initial, middle and last third of pregnancy were 6.5 +/- 1.7, 22.5 +/- 3.7 and 16.8 +/- 3.2 ng/ml, respectively. Postpartum progesterone levels were elevated above basal values (less than or equal to 0.3 ng/ml) in both lactating and nonlactating animals for 2-3 months postpartum and were not consistently basal until more than 90 days postpartum. Mean progesterone levels at less than 30, 30-60, 61-90, and greater than 90 days postpartum were 25.1 +/- 6.2, 60.6 +/- 18.5, 22.8 +/- 8.7 and 0.4 +/- 0.2 ng/ml, respectively, and those at 30-60 days postpartum were greater than those at midpregnancy (P less than 0.05). Mean corpus luteum diameters were also greater (P less than 0.05) postpartum (2.9 +/- 0.3 mm) than during pregnancy (1.5 +/- 0.3 mm). The correlation between placental scars and ipsilateral corpora lutea indicated that the corpora lutea observed postpartum were the corpora lutea of the recent pregnancy. The termination of each uterine horn in a separate external cervical os precluded the occurrence of transcornual migration.(ABSTRACT TRUNCATED AT 250 WORDS)

Amenorrhea↗
PubMed1982

Paradoxic hypercalcemia and hypophosphatemia associated with chronic renal failure in horses.

Chronic renal failure associated with hypercalcemia and hypophosphatemia was diagnosed in 6 horses. The renal lesions in 5 of the horses were classified as chronic glomerulonephritis and in the sixth, as chronic interstitial nephritis/pyelonephritis. There was no evidence of primary hyperparathyroidism or pseudohyperparathyroidism, thus suggesting that hypercalcemia associated with advanced renal failure in horses is related to a unique role of the equine kidney in calcium homeostasis.

Animals↗
PubMed1982

Six cases of squamous cell carcinoma of the stomach of the horse.

Six cases of squamous cell carcinoma of the stomach in horses seen at the New York State College of Veterinary Medicine are compared with 15 similar cases reported previously. Clinical signs included anorexia in all cases, emaciation, fever, anaemia and/or palpable abdominal masses in 3, colic in 2 and dysphagia in one case. Haematological studies revealed normochromic, normocytic anaemia in 3 and absolute neutrophilia in 5 cases. Peritoneal fluid analysis was performed in 4 cases and revealed slightly to moderately elevated total protein concentrations in 3 and a markedly elevated number of white blood cells in 2 cases. Exploratory laparotomy, performed in 3 cases, was essential for a definitive diagnosis. The data presented here suggest that squamous cell carcinoma of the equine stomach may be increasing in frequency and demonstrate the need for prospective epidemiological studies.

Animals↗
PubMed1981

Acute hemolytic anemia, methemoglobinemia, and heinz body formation associated with ingestion of red maple leaves by horses.

From June 1975 through June 1979, acute hemolytic anemia developed in 11 horses from 7 New York farms. Of the 7 horses that died, 6 had methemoglobinemia. In the 4 horses that recovered, methemoglobinemia was not observed. but Heinz body formation was seen in 3 of the 4. On 2 of the premises involved, frank methemoglobinemia was observed concurrently with Heinz body formation, suggesting a relationship between the pathogenesis of methemoglobinemia and Heinz body formation in the hemolytic process. In addition to the 11 cases described, 22 clinically similar cases were reported to us during the period of this investigation by practicing veterinarians from New York, Pennsylvania, and the New England states. All 33 cases of hemolytic anemia occurred between June and October of each year, and affected horses had access to outside paddocks or fields containing a variety of native grasses, weeds, and trees. On 2 farms, hemolytic anemia developed after the horses were observed browsing fallen branches of red maple trees (Acer rubrum). Red maple leaves and bark were obtained from 1 of these farms, and approximately 1 kg of a leaf and bark mixture was fed to each of 2 ponies. Within 48 hours, both ponies became ill. The syndrome was indistinguishable from that observed in clinical patients and was characterized by methemoglobinemia and intravascular hemolysis. The ponies died 5 and 6 days after which time the packed cell volumes were 6% and 7% respectively. It was concluded that many cases of hemolytic anemia in horses in northeastern states may be related to ingestion of leaves or bark from red maple trees. The studies did not, however, define the factors that predispose to poisoning and did not exclude the possibility that other environmental toxins may have been involved.

Acute Disease↗