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- Author or Editor: James G. Morris x
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Abstract
Objective—To determine whether ingestion of 63 times the recommended amount of vitamin D3 (cholecalciferol) results in renal calcification or damage in cats.
Animals—20 four-month-old kittens, 17 queens, and 20 kittens born to these queens.
Procedure—4-month-old kittens and queens were given a purified diet with 846 μg of cholecalciferol/kg of diet (high vitamin D3 diet) or 118 μg of cholecalciferol/ kg of diet (control diet) for 18 months. Kittens born to queens were weaned onto the same diet given to dams.
Results—There were no apparent adverse effects of the high vitamin D3 diet. Plasma cholecalciferol and 25-hydroxycholecalciferol (25-OHD3) concentrations of queens and 4-month-old kittens given the high vitamin D3 diet significantly increased with time. At 6 months, plasma cholecalciferol concentrations in these kittens and queens were 140.0 ± 7.3 nmol/L and 423.6 ± 26.6 nmol/L, respectively (10 times initial values). Corresponding 25-OHD3 concentration in queens was 587.5 ± 59.4 nmol/L (2.5-fold increase over initial values). At 3 months of age, kittens born to queens given the high vitamin D3 diet had an increase in serum BUN and calcium concentrations and a decrease in RBC and serum total protein, albumin, and hemoglobin concentrations. By 18 months, these kittens had an increase in plasma cholecalciferol (276.0 ± 22.2 nmol/L) and 25-OHD3 (1,071.9 ± 115.3 nmol/L) concentrations. However, all indices of renal function and the appearance of renal tissue on histologic evaluation were normal.
Conclusions and Clinical Relevance—These results indicate that cats are resistant to cholecalciferol toxicosis when the diet is otherwise complete and balanced. (Am J Vet Res 2001;62:1500–1506)
Abstract
Objective—To determine the neurologic effects of reduced intake of phenylalanine and tyrosine in black-haired cats.
Animals—53 specific pathogen-free black domestic shorthair cats.
Procedure—Cats were fed purified diets containing various concentrations of phenylalanine and tyrosine for ≤ 9 months. Blood samples were obtained every 2 months for evaluation of serum aromatic amino acid concentrations. Cats were monitored for changes in hair color and neurologic or behavioral abnormalities. Three cats with neurologic deficits underwent clinical and electrophysiologic investigation; muscle and nerve biopsy specimens were also obtained from these cats.
Results—After 6 months, neurologic and behavioral abnormalities including vocalization and abnormal posture and gait were observed in cats that had received diets containing < 16 g of total aromatic amino acid/kg of diet. Electrophysiologic data and results of microscopic examination of muscle and nerve biopsy specimens from 3 cats with neurologic signs were consistent with sensory neuropathy with primary axonal degeneration. Changes in hair color were detected in cats from all groups receiving < 16 g of phenylalanine plus tyrosine/kg of diet.
Conclusions and Clinical Relevance—Findings suggested that chronic dietary restriction of phenylalanine and tyrosine in cats may result in a predominantly sensory neuropathy. In cats, the long-term nutritional requirement for phenylalanine and tyrosine appears to be greater for normal neurologic function than that required in short-term growth experiments. Official present-day recommendations for dietary phenylalanine and tyrosine in cats may be insufficient to support normal long-term neurologic function. ( Am J Vet Res 2004;65:671–680)
Abstract
Objective—To characterize the radiosensitivity and capacity for sublethal damage repair (SLDR) of radiation-induced injury in 4 canine osteosarcoma cell lines.
Sample Population—4 canine osteosarcoma cell lines (HMPOS, POS, COS 31, and D17).
Procedures—A clonogenic colony-forming assay was used to evaluate the cell lines' intrinsic radiosensitivities and SLDR capacities. Dose-response curves for the cell lines were generated by fitting the surviving fractions after radiation doses of 0 (control cells), 1, 2, 3, 6, and 9 Gy to a linear quadratic model. To evaluate SLDR, cell lines were exposed to 2 doses of 3 Gy (split-dose experiments) at an interval of 0 (single 6-Gy dose), 2, 4, 6, or 24 hours, after which the surviving fractions were assessed.
Results—Mean surviving fraction did not differ significantly among the 4 cell lines at the radiation doses tested. Mean surviving fraction at 2 Gy was high (0.62), and the α/β ratios (predictor of tissue sensitivity to radiation therapy) for the cell lines were low (mean ratio, 3.47). The split-dose experiments revealed a 2.8- to 3.9-fold increase in cell survival when the radiation doses were applied at an interval of 24 hours, compared with cell survival after radiation doses were applied consecutively (0-hour interval).
Conclusions and Clinical Relevance—Results indicated that these canine osteosarcoma cell lines are fairly radioresistant; α/β ratios were similar to those of nonneoplastic, lateresponding tissues. Future clinical investigations should involve increasing the fraction size in a manner that maximizes tumor killing without adverse effects on the nonneoplastic surrounding tissues.
