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Biomedical subjects

G N Rowland

Publications and source records attributed to G N Rowland.

At least 37 records · Page 2Linked to original sources
PubMed1986

Excess dietary vitamin A in the growing chick: effect of fat source and vitamin D.

Studies were conducted to determine the nutritional interrelationship between different fat sources, vitamin D3 (vit D) and excess dietary vitamin A (vit A) in the growing chick. Birds tolerated as much as 30 times the recommended level of vit A without compromising performance or skeletal development as measured by bone ash. The response to excess dietary vit A was not influenced by the type of dietary lipid (corn oil, tallow, or poultry oil). No nutritional interaction between vit A (1,500, 15,000, or 45,000 IU/kg) and vit D (100 or 1000 ICU/kg) was detected as measured by growth, bone ash, growth hormone, incidence of tibial dyschondroplasia (TD), or rickets. Serum alkaline phosphatase activity, however, was significantly affected by vit A, vit D, and age of the chicks. The higher vit D level significantly enhanced growth, bone ash, and reduced incidence of rickets, although it had no effect on incidence of TD.

Aging↗
PubMed1985

Free chondral fragment involving the lateral trochlear ridge of the talus in a dog.

A saucer-shaped defect involving the lateral trochlear ridge of the talus and a radiopaque joint fragment were evident on radiographs of the left tarsus in a 6-month-old Rottweiler. Surgical treatment involved removal of the joint fragment and debridement of the defect. Histologic interpretation of the specimen was a chondral fragment. It is important to realize the possibility of a lesion in the location described, as this may be an additional site for osteochondrosis dissecans of the canine tarsus.

Animals↗
PubMed1985

Cyclopiazonic acid mycotoxicosis in the dog.

The subacute toxic effects of cyclopiazonic acid (CPA; given orally) were characterized in the dog (CPA was purified from cultures of Aspergillus flavus). Four groups of dogs were given CPA in gelatin capsules for 90 days at the following dosage levels: 0.05, 0.25, 0.5, and 1.0 mg/kg of body weight; a 5th group was used as controls. All dogs administered the 0.5 and 1.0 mg of CPA/kg dosages and 1 dog given the 0.25 mg of CPA/kg dosage died or were humanely killed before the scheduled termination of the study. Clinical signs of intoxication appeared 2 to 44 days after dosing was started and consisted of anorexia and, in 1 to 2 days, vomiting, diarrhea, pyrexia, dehydration, weight loss, and CNS depression. Grossly, the entire alimentary tract had diffuse hyperemia with focal areas of hemorrhage and ulceration. Other lesions were renal infarcts, necrotizing epididymitis, and ulcerative dermatitis. Microscopic lesions included ulceration, necrosis, vasculitis, lymphoid necrosis, karyomegaly in several organs, and decreased mitotic activity in intestinal crypt epithelium. Ulcerative and necrotic lesions were usually associated with vascular lesions. Clinical pathologic changes were leukocytosis, neutrophilia, lymphopenia, monocytosis, and increased serum alkaline phosphatase activity.

Adrenal Glands↗
PubMed1985

Evaluation of Key's hypothesis in the feline tibia: an experimental model for augmented bone healing studies.

Key's hypothesis states that a segmental long bone defect 1.5 times the diaphyseal diameter exceeds the regenerative capacity of bone in skeletally mature dogs and results in nonunion. This hypothesis was evaluated in 5 adult cats with rigidly fixated segmental tibial ostectomies ranging from 1.25 to 1.52 times the diaphyseal diameter. Clinical, radiographic, and histologic data were obtained over a 12-week period. Healing was classified as mature bony union, clinical union, delayed union, or nonunion. Absence of a consolidating callus and instability after removal of fixation devices was found for all cats at 12 weeks. Scant formation of new bone within the gap was histologically evident for only 1 cat. In the remaining 4 cats, fibrous tissue and striated muscle predominated within the gap, and independent healing of the proximal and distal cut ends of the bone were observed. The occurrence of 4 nonunions and 1 equivocally delayed union indicated that Key's hypothesis overestimates the regenerative capacity of bone in the cat. Failure of this experimental model to produce clinical union within 12 weeks demonstrated that this model is a valid method of investigating augmented bone healing techniques that promote union within this period in the cat.

Animals↗
PubMed1984

Radiographic, macroscopic, and microscopic changes in growth plates of calves raised on hard flooring.

The effect of flooring on the development of physeal and metaphyseal lesions of the limbs was studied in 1- to 5-month-old dairy calves. Calves were allotted to 2 groups. Group I was housed on a clay floor throughout the study and group II was housed on metal slats until weaned and then on concrete. Radiographs of the right thoracic limb of the animals were made 7 times during the experimental period and of the right thoracic and pelvic limbs at necropsy. Selected sections of the physeal regions of the distal part of the radius, metacarpus, metatarsus, and rib were examined microscopically. The physes of the limbs in the 2 groups had eosinophilic streaks and patches which originated in the germinal zone and were associated with blood vessels. These foci varied from small streaks parallel to the chondrocyte columns to multiple horizontal branching patches in which cleft formation and necrosis interrupted the physis, resulting in osseous bridging. Remnants of necrotic cartilage or cartilage containing hypertrophied chondrocytes were located in the metaphysis adjacent to the areas of physeal disruption. Multiple undulations of the physes with variations in thickness and orientation of the chondrocyte columns occurred in the physes of all limbs examined. These areas did not interrupt the physis and were not associated with metaphyseal lesions. The ribs in both groups had focal areas of failure of endochondral ossification characterized by elongation of the hypertrophied zone, accumulation of fibrin and hemorrhage in the zone of provisional calcification, and retention of cartilage within the metaphysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1981

Effect of Rush pins on the distal femoral growth plate of young dogs.

Rush pins were placed in the distal portion of the left femur in 15 young (4 months old) mongrel dogs. Microscopic evaluation of the growth plate showed closure beginning 1 month after the pins were implanted and complete closure occurring a month earlier than in the control (right) femur. The left femurs had a mean decrease in length of 22 mm compared with the length of the control femurs at the time of growth plate closure. When the Rush pins were removed 1 month after implantation, the growth plate regained normal microscopic appearance and difference in femur lengths (left vs right) did not occur. Tibial length did not change relative to femur length. Recommendations are made about the use of Rush pins in young dogs.

Animals↗
PubMed1980

Magnesium toxicity: bone lesions.

Broiler chicks fed corn-soy rations supplemented with toxic levels of magnesium from one day of age grew poorly, developed diarrhea, and exhibited characteristic skeletal abnormalities. Tibiae from magnesium intoxicated chicks were shortened, thickened, and bowed. Percent tibial ash was greatly reduced. Upon microscopic examination, the bone lesion appeared rachitic as evidenced by widened and lengthened growth plates, excessive osteoid seams on endochandral bone, and osteoid or bone capped metaphyseal blood vessels with very few associated osteoblasts. Tibial calcium to phosphorus mass ratios decreased while tibial magnesium to phosphorus mass ratios increased concomitantly with increased dietary magnesium. Calcium and phosphorus homeostasis was possibly affected as evidenced by a general decrease in size and cellularity of parathyroid glands and a general increase in size and cellularity of ultimobranchial glands.

Animals↗
PubMed1978

Hypercalcemia secondary to chronic renal failure in the dog: a report of four cases.

Hypercalcemia occurred in 4 dogs with renal failure. Primary causes of hypercalcemia previously described in the dog (primary hyperparathyroidism, pseudohyperparathyroidism, vitamin D toxicosis) were not identified. Increased concentrations of circulating immunoreactive parathormone were found in 2 dogs, and thyroparathyroidectomy of 1 dog resulted in decreased serum concentrations of that hormone as well as of calcium. The latter observations indicated that hypercalcemia was related to increased parathormone activity, but the possibility of other homeostatic imbalances was not excluded. It was concluded that renal failure should be considered as a primary cause of hypercalcemia, along with other causes previously identified.

Animals↗
PubMedDate not supplied

Replacement of the medial collateral ligament with polypropylene mesh or a polyester suture in dogs.

The medial collateral ligament of one stifle in 20 adult dogs was excised and replaced with polypropylene mesh or a polyester suture. After 26 weeks, the fibrous tissue-prosthesis composites were evaluated clinically, morphologically, and biomechanically. Clinical lameness was not significantly different after 10 days. The polypropylene mesh reconstructions consistently had more fibrous tissue and greater collagenous ingrowth than the polyester suture reconstructions. There were four complications related to fixation of the polypropylene mesh prosthesis and one to the polyester suture. The polypropylene mesh reconstructions had greater stability and were biomechanically more similar to the natural ligaments than the polyester suture reconstructions. Although the results with polypropylene mesh were favorable, more challenging biomechanical testing and alternative anchoring techniques are required before polypropylene mesh can be recommended as a collateral ligament replacement in dogs.

Animals↗
PubMedDate not supplied

The effect of trans-stifle external skeletal fixation and hyaluronic acid therapy on articular cartilage in the dog.

Transarticular external skeletal (TES) fixators were applied unilaterally to the stifle joints of 10 young adult dogs. After 4 weeks, the fixators were removed from all dogs. Two dogs were not allowed a remobilization period, whereas 8 dogs were provided with 4 additional weeks of weight-bearing activity in a kennel run. Four dogs were given high-molecular weight hyaluronic acid by intra-articular injection weekly during the remobilization period. Clinical gait evaluations and range of motion were determined during the remobilization period. Articular cartilage samples from both stifle joints of all dogs were evaluated histologically and histochemically. No significant differences in gait scores or range of motion were noted between treated and untreated dogs. Articular cartilage proteoglycan content was reduced after 4 weeks of trans-stifle external skeletal fixation as determined by loss of alcian blue (AB) histochemical staining. Improved homogeneity of histochemical staining was observed after remobilization. However, remobilization was associated with histological damage to the surface and tangential layers of articular cartilage. Remobilization combined with hyaluronic acid (HA) therapy improved histochemical staining and reduced structural damage to articular cartilage when compared with remobilization alone.

Animals↗