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Biomedical subjects

A P Knight

Publications and source records attributed to A P Knight.

At least 19 recordsLinked to original sources
PubMed2000

Adaptation of pregnant ewes to an exclusive onion diet.

A diet consisting entirely of cull onions fed to pregnant ewes produced Heinz body hemolytic anemia in all sheep after 21 d. After 28 d of daily consumption of 20 kg of onions/ewe, the anemia stabilized, and for the remaining 74 d the packed cell volume increased in the majority of sheep, although it did not return to normal. Compared to control ewes fed an alfalfa and grain diet, the onion-fed ewes had comparable body condition scores and fleece weights. There was no significant difference (alpha = 0.05) in pregnancy or lambing rate, number of lambs born/ewe exposed, or number of lambs born/ewe lambing. Greater numbers of sulfate-reducing bacteria (Desulfovibrio spp) and more ruminal hydrogen sulfide were present in onion-fed sheep compared to controls. Although an average 27% reduction in packed cell volume and Heinz body anemia developed in the onion-fed ewes, on the basis of this study it appears that pregnant ewes may be fed a pure onion diet with minimal detrimental effects. This adaptation to a pure onion diet is in part likely due to the apparent ability of the sheep's rumen to quickly develop a population of sulfate-reducing bacteria that decrease the toxicity of onion disulfides.

Adaptation, Physiological↗
PubMed1999

Analysis of toxic norditerpenoid alkaloids in Delphinium species by electrospray, atmospheric pressure chemical ionization, and sequential tandem mass spectrometry.

A rapid electrospray mass spectrometry method was developed for screening larkspur (Delphinium spp.) plant material for toxic norditerpenoid alkaloids. The method was calibrated using two standard alkaloids, methyllycaconitine (1) and deltaline (2), with a recovery of 92% from spiked samples and relative standard deviations of 6.0% and 8.1% for the two alkaloids, respectively. Thirty-three samples of plains larkspur, Delphinium geyeri, were analyzed. Methyllycaconitine (1) concentration was 0.27% +/- 0.08% during a 1-month period in 1997 establishing the relative risk of poisoning from the plant to be low. The method was also applied to the trace analysis (<1 ppm) of 1 in serum samples from sheep dosed different levels of the alkaloid. Electrospray ionization combined with sequential tandem mass spectrometry and HPLC coupled to atmospheric pressure chemical ionization (APCI) mass spectrometry were used to detect and tentatively identify three new norditerpenoid alkaloids from Delphinium nuttallianum [bearline (6), 14-acetylbearline (7), 16-deacetylgeyerline (8)]. The tentative structure of the new alkaloids was predicted from the tandem mass spectra fragmentation patterns and assigning the substitution pattern for methoxy and acetyl groups at the C-14 and C-16 carbons.

Alkaloids↗
PubMed1998

Dietary calcium, protein, and phosphorus are related to bone mineral density and content in young women.

BACKGROUND: Dietary factors have been implicated in modifying bone health, although the results remain controversial, particularly in young women. OBJECTIVE: The objective of the study was to determine relations of selected dietary factors and anthropometric measurements to bone mineral density (BMD) of the spine, femoral neck, trochanter, Ward's triangle, radius, and total body and the bone mineral content (BMC) of the spine, radius, and total body. DESIGN: The study was a cross-sectional analysis of 215 women aged 18-31 y. RESULTS: Weight, height, and lean mass were correlated with bone mineral measures at every site (r = 0.17-0.78). Postmenarcheal age (years since onset of menses) was positively correlated with total-body BMD and BMC, radius BMD and BMC, and spine BMC, and negatively correlated with Ward's triangle BMD. Radius BMD was correlated with protein, calcium, and phosphorus intakes, and spine BMD and BMC were correlated with energy, protein, calcium, and phosphorus intakes. These correlations remained significant when postmenarcheal age, lean mass, and fat mass were controlled. A pattern emerged in multiple regression analyses that showed a complex relation among calcium, protein or phosphorus, and the calcium-protein or calcium-phosphorus ratio and spine or total-body BMC and BMD. All 3 variables (calcium, protein or phosphorus, and calcium-protein or calcium-phosphorus ratio) were required in the model for significance. CONCLUSIONS: Anthropometric measures were predictors of bone mass. A single ratio of calcium to phosphorus or protein did not optimize bone mass across the range of calcium intakes.

Adolescent↗
PubMed1996

Rattlesnake venom poisoning in horses: 32 cases (1973-1993).

OBJECTIVE: To determine the clinical manifestations, morbidity, mortality, and treatment methods for rattlesnake venom poisoning in horses. DESIGN: Retrospective analysis of medical records. ANIMALS: 27 horses with acute venom poisoning attributable to prairie rattlesnakes, and 5 with chronic problems subsequent to a rattlesnake bite. RESULTS: Most horses were bitten on or near the muzzle while on pasture, resulting in head swelling, dyspnea, and epistaxis. Additional manifestations of acute poisoning included fever, tachycardia, tachypnea, cardiac arrhythmia, hemolytic anemia, thrombocytopenia, hemorrhage, thrombosis of venipuncture sites, colic, diarrhea, and prehensile and masticatory dysfunction. Chronic problems included cardiac disease, pneumonia, laminitis, pharyngeal paralysis, and wound complications. The most common chronic problem was cardiac disease. The most commonly used treatments were antibiotics, nonsteroidal anti-inflammatory drugs, tetanus prophylaxis, and airway support. Mortality in the 27 acutely affected horses was 18.5%; the overall mortality was 25%. CLINICAL IMPLICATIONS: Horses bitten by prairie rattle-snakes may develop multiple, often severe, acute or chronic manifestations of poisoning involving various organ systems. Thorough clinical evaluation, effective treatment, supportive care, and close observation are indicated in horses with rattlesnake venom poisoning.

Animals↗
PubMed1995

Tropane alkaloids and toxicity of Convolvulus arvensis.

Horses in a few, localized northern Colorado pastures exhibited weight loss and colic. At post mortem, intestinal fibrosis and vascular sclerosis of the small intestine was identified. The pastures where the affected horses grazed were overrun by field bindweed (Convolvulus arvensis). Bindweed from the pasture was found to contain the tropane alkaloids tropine, pseudotropine, and tropinone and the pyrrolidine alkaloids cuscohygrine and hygrine. Laboratory mice readily ate C. arvensis and exhibited a variety of abnormal clinical signs depending on the amount eaten. Similar alkaloids have been found in other Convolvulus species and cuscohygrine and calystegines (polyhydroxytropanes) have been previously reported from C. arvensis roots. This is the first report of simple tropane alkaloids in C. arvensis, a world wide problem weed. Pseudotropine, the major alkaloid, is known to affect motility and might represent a causative agent for the observed cases of equine intestinal fibrosis.

Animals↗
PubMed1995

Toxicity of field bindweed (Convolvulus arvensis) to mice.

The effects of feeding high and low doses of field bindweed (Convolvulus arvensis) to mice were investigated. Bindweed contains several alkaloids, including pseudotropine, and lesser amounts of tropine, tropinone, and meso-cuscohygrine. Mice fed bindweed exclusively died or were euthanized after 4-7 d and had severe hepatic necrosis and gastritis with ulceration or erosions. Mice fed low doses of bindweed along with standard laboratory mouse diet for 6 or 8 w had no clinical disease or gross lesions on necropsy examination but did have histologic lesions of mild multifocal hepatitis and gastritis.

Acetone↗
PubMed1994

Llama cardiology.

Auscultatory, ECG, and echocardiographic data have been presented for healthy llamas. The literature, however, contains little information on the incidence of congenital and acquired heart disease in the llama. Data compiled from the medical records at CSU-VTH and the VMDB provide an indication of the types of cardiac disease to be found in llamas in North America. A wide variety of congenital cardiac defects are found in llamas, the most prevalent defect of which is VSD. Llamas tend to do well with this defect but are unlikely to be useful pack animals. Acquired heart disease primarily involved inflammatory processes of the pericardium, endocardium, epicardium, and myocardium, and pericardial effusion without documented inflammatory disease. Although not every cardiac murmur necessitates a complete cardiac work-up, every effort should be made to compile accurate medical histories and physical findings related to the cardiac disease in llamas in order to advance our knowledge of these disorders. There also is a need to use available technologies to better define cardiac abnormalities in the llama and accurately report these findings in the literature before cardiology of llamas is fully understood.

Animals↗
PubMed1990

Antimicrobial therapy for rams with Brucella ovis infection of the urogenital tract.

Rams shedding Brucella ovis in semen but without palpable abnormalities of the epididymides were treated with long-acting oxytetracycline for 15 days and dihydrostreptomycin for 7 days (n = 9) or conventional oxytetracycline and dihydrostreptomycin (n = 9) for 7 days. Nine rams were not treated. More treated rams were considered to have satisfactory breeding soundness examination results at posttreatment weeks 3, 7, 12, and 19. Nontreated rams continued to shed B ovis in semen. After treatment, B ovis was not recovered from 78% of rams given long-acting oxytetracycline and dihydrostreptomycin or from 89% of rams given conventional oxytetracycline and dihydrostreptomycin. At week 21, all rams were euthanatized, and specimens of the testes and epididymides were bacteriologically cultured for B ovis. Brucella ovis was not recovered from the testes of rams or from the epididymides from rams not shedding the organism in the semen. In one treated ram, B ovis was recovered from the semen but not from other tissues. All rams remained ELISA-positive, with the exception of 2 treated rams that ceased shedding B ovis in semen immediately after treatment was started; both these rams became ELISA-negative on the last examination at week 19.

Animals↗
PubMed1990

Pharmacokinetics of phenylbutazone given intravenously or orally in mature Holstein bulls.

Six mature Holstein bulls were each given 10 mg of phenylbutazone (PBZ)/kg of body weight, PO. Of the 6 bulls, 3 were given 10 mg of PBZ/kg by rapid IV administration 4 weeks later. Plasma concentration-vs-time data were analyzed, using nonlinear regression modeling (sum of exponential functions). The harmonic mean of the biologic half-life of PBZ was 62.6 +/- 12.9 hours after oral administration and 61.6 +/- 7.2 hours after IV administration. The mean residence time was 94.61 +/- 8.44 hours and 90.49 +/- 8.93 hours for oral and IV administration, respectively. The mean total body clearance was 0.0015 +/- 0.0003 L/h/kg, with the mean apparent volume of distribution 0.134 +/- 0.021 L/kg. Mean bioavailability was 73 +/- 2% after oral administration. Phenylbutazone was adequately absorbed from the gastrointestinal tract in bulls. The apparent volume of distribution was small, indicating that PBZ distributed mainly into plasma and extracellular fluid. The total body clearance was also small, which accounted for the long half-life of PBZ in bulls.

Administration, Oral↗
PubMed1990

Pharmacokinetics of phenylbutazone in mature Holstein bulls: steady-state kinetics after multiple oral dosing.

Six mature Holstein bulls were given an 8-day course of phenylbutazone (PBZ) orally (loading dose, 12 mg of PBZ/kg of body weight and 7 maintenance doses of 6 mg of PBZ/kg, q 24 h). Plasma concentration-vs-time data were analyzed, using nonlinear regression modeling. The harmonic mean +/- pseudo-SD of the biologic half-life of PBZ was 61.8 +/- 12.8 hours. The arithmetic mean +/- SEM of the total body clearance and apparent volume of distribution were 0.0021 +/- 0.0001 L/h/kg and 0.201 +/- 0.009 L/kg, respectively. The predicted mean minimal plasma concentration of PBZ with this dosage regimen was 75.06 +/- 4.05 micrograms/ml. The predicted minimal plasma drug concentration was compared with the observed minimal plasma drug concentration in another group of bulls treated with PBZ for at least 60 days. Sixteen mature Holstein bulls were given approximately 6 mg of PBZ/kg, PO, daily for various musculoskeletal disorders. The mean observed minimal plasma concentration of PBZ in the 16 bulls was 76.10 +/- 2.04 micrograms/ml, whereas the mean predicted minimal plasma concentration was 74.69 +/- 3.10 micrograms/ml. Dosages of 4 to 6 mg of PBZ/kg, q 24 h, or 10 to 14 mg of PBZ/kg, q 48 h, provided therapeutic plasma concentrations of PBZ with minimal steady-state concentrations between 50 and 70 micrograms/ml.

Administration, Oral↗
PubMed1989

Blindness and sexual dimorphism associated with vitamin A deficiency in feedlot cattle.

Clinical, ophthalmoscopic, and histopathologic findings of vitamin A deficiency in a group of 535 feedlot cattle are described. Liver vitamin A content and results of histologic examination of ocular and osseous (optic canal) tissue confirmed the diagnosis. Blindness was the only clinical sign observed. Even though the steers and heifers in this feedlot were approximately the same age and were fed the same ration for an equal period, none of the heifers had overt clinical signs of hypovitaminosis A. Production of vitamin A by the bovine corpus luteum may account for the sexual dimorphism observed in vitamin A-deficient cattle.

Animals↗
PubMed1987

Serum neutralizing antibody titers in dairy cattle administered an inactivated vesicular stomatitis virus vaccine.

Two doses of a formalin-killed, cell culture-derived vesicular stomatitis virus (vsv)-New Jersey serotype vaccine were administered intramuscularly, 30 days apart, to all lactating and nonlactating cows in a 350-cow dairy herd. Serum specimens were obtained serially from 96 cows before vaccination and at 30, 52 and 80 days after vaccination and from 24 of these cows 175 days after vaccination. Serum neutralizing antibody titers to vsv-New Jersey serotype were determined from serum-dilution, plaque-reduction tests. Serum neutralizing antibody titers also were determined during the same period for 67 nonvaccinated heifers in the herd. Peak group geometric mean serum neutralizing antibody titers of 1:530.46 +/- 1.14 (group geometric mean titer log10, 2.725 +/- 0.055) developed 21 days after the second vaccination, but decreased to a low value of 1:65.36 +/- 1.38 (group geometric mean titer log10, 1.815 +/- 0.142) by 175 days after vaccination. The nonvaccinated group had no detectable antibody titer to vsv-New Jersey serotype throughout the study. All serum specimens from the vaccinates and controls were negative for heterologous reactivity to vsv-Indiana serotype.

Animals↗
PubMed1987

Three primary neoplasms in a goat: hepatocellular carcinoma, phaeochromocytoma and leiomyoma.

A ten-year-old male nubian goat with no previous medical history was found recumbent. Clinical examination revealed an underweight, dehydrated, very depressed and unresponsive animal. At necropsy, the liver contained multiple, well-demarcated hepatocellular carcinomas. The right adrenal gland contained a solitary phaeochromocytoma. Multiple leiomyomas were present within the urinary bladder. The three primary neoplasms reported in this goat have been reported separately in other species; their simultaneous occurrence in one animal is uncommon.

Adrenal Gland Neoplasms↗
PubMed1986

Metabolic changes due to experimentally induced rupture of the bovine urinary bladder.

Metabolic changes were studied in the serum, saliva and peritoneal fluid of 5 healthy yearling feedlot steers after experimentally induced urinary bladder rupture. There were statistically significant decreases in serum, saliva and peritoneal fluid sodium and chloride values and significant increases in serum, saliva and peritoneal fluid urea nitrogen, creatinine and phosphorus values. Serum calcium, pH, bicarbonate, and base excess decreased significantly. Potassium did not change significantly in serum but did increase significantly in the saliva. The hemogram and peritoneal fluid analysis failed to provide clinicopathologic evidence of peritonitis. The average time of death or euthanasia after bladder rupture was 13.6 days with a range of 8-21 days. No single biochemical parameter could be identified which would allow prediction of the approaching time of death or duration of the disease process. There was no peritonitis at necropsy indicating that urine was not irritating to the bovine peritoneal cavity. Extracellular replacement fluid with or without sodium bicarbonate supplementation appeared to be the fluid of choice for correction of fluid and electrolyte imbalances in steers with ruptured urinary bladders. The ratio between serum and peritoneal fluid creatinine concentrations appears to be valuable for the clinical diagnosis of ruptured urinary bladders in steers.

Animals↗
PubMed1984

Malignant melanoma in a goat.

Malignant melanoma was identified in a crossbred goat. It involved the coronary band area and the medial claw of the right hindfoot, which was removed surgically. The goat was reexamined 1 month after tumor removal and found to have widespread metastases with concurrent neurologic signs.

Animals↗