Objective—To determine whether ingestion of 63
times the recommended amount of vitamin D3 (cholecalciferol)
results in renal calcification or damage in
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)
Objective—To determine the neurologic effects of
reduced intake of phenylalanine and tyrosine in black-haired
Animals—53 specific pathogen-free black domestic
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
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)
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.