Biomedical subjects

J G Morris

Publications and source records attributed to J G Morris.

At least 19 recordsLinked to original sources

PubMed2006

Increasing dietary crude protein does not increase the essential amino acid requirements of kittens.

Essential amino acid (EAA) requirements of omnivores and herbivores (e.g. chicks, lambs, pigs and rats) are directly related to the concentration of dietary crude protein (CP). When an EAA is limiting in the diet, addition of a mixture of EAA lacking the limiting one (which increases dietary CP) results in a decrease in food intake and weight gain. This interaction has been referred to as an AA imbalance and has not been studied in depth in strict carnivores. The objectives of these experiments were to examine the effects on growing kittens (2-week periods) of the addition to diets of a mixture of AA lacking the limiting one. The control diets were at the requirement of the respective limiting EAA (or about 85% of the 1986 National Research Council requirement). In experiment 1, with the dietary EAAs at the minimally determined requirements, the concentration of the essential or dispensable amino acids was increased to determine if CP or an EAA was limiting. Results of growth rates (n = 12) and plasma AA concentrations indicated that tryptophan was limiting, but increased body weight gain also occurred when the concentration of CP was increased as dispensable amino acids without additional tryptophan. Experiment 1 was repeated in experiment 2 using a crossover design. Again, when tryptophan was limiting additional concentrations of dispensable AAs increased body weight gain. This response is the opposite of that in herbivores and omnivores. Experiment 3 consisted of 10 separate crossover trials, one for each of the 10 EAA and examined the effect of two concentrations of dietary CP (200 and 300 g CP/kg diet) on body weight gain of kittens (n = 8) offered diets limiting in each respective EAA. Body weight gain was numerically greater when diets contained 300 g CP/kg than 200 g CP/kg for eight of 10 EAAs (p < 0.05 for only isoleucine and threonine) when each amino acid was limiting. This response is the reverse of that which occurs in chicks, lambs, pigs and rats when an EAA is limiting and dietary CP lacking the limiting EAA is increased. These results indicate that the EAA requirements of kittens are not positively correlated with dietary CP concentrations.

Amino Acids, Essential↗

PubMed2006

Excess dietary cystine intensifies the adverse effect of a methionine deficiency in the cat.

Foot pad dermatitis has been observed in turkeys, puppies and kittens fed diets deficient in methionine. Excess cystine aggravated the lesions and decreased body weight gain in puppies and turkeys. The objective of this study was to determine whether methionine deficiency induced perioral and foot pad lesions in kittens and whether excess cystine exacerbated the lesions. Eighteen kittens were divided into three groups and offered one of three diets: diet 1, low-methionine, low-cystine (LMLC; 1.6 g methionine and 1.6 g cystine/kg diet); diet 2, low-methionine, high-cystine (HMHC; 1.6 methionine and 15 g cystine/kg diet); diet 3, high-methionine, high-cystine (HMHC; 15 g methionine and 15 g cystine/kg diet). Kittens in the LMLC group lost body weight, whereas those in the LMHC group maintained their body weight and those in the HMHC group gained weight. Plasma methionine concentrations were significantly higher (p < 0.001) for the HMHC group than for the LMLC and LMHC groups. Plasma cyst(e)ine (sum of cysteine and cystine) concentrations were different (p < 0.001) among all the three groups. Two kittens given the LMLC diet developed mild perioral lesions. All kittens receiving the LMHC diet developed foot pad lesions and severe perioral lesions. Histopathological changes observed in perioral biopsy specimens were similar to those described in protein deficiency. In conclusion, the results showed that a diet severely deficient in methionine causes perioral lesions in kittens, and that addition of excess cystine to the diet aggravates the perioral lesions and also causes foot pad lesions.

Animal Feed↗

PubMed2005

Muscle metabolism, temperature, and function during prolonged, intermittent, high-intensity running in air temperatures of 33 degrees and 17 degrees C.

Nine unacclimatized university sportsmen performed a prolonged, intermittent, high-intensity shuttle running test in hot (HT) (33 degrees C, dry bulb temperature, approximately 28 %, relative humidity) and moderate (MT) (17 degrees C, 63 %) environmental conditions. Subjects performed 60 m of walking, a 15-m sprint, 60 m of cruising ( approximately 85 % V.O (2max)), and 60 m of jogging ( approximately 45 %V.O (2max)) for 14.8 +/- 0.1 min followed by a 3-min rest, repeated until volitional exhaustion. The hot trial was performed first followed, 14 days later, by the moderate trial. During exercise subjects drank water ad libitum. Subjects ran almost twice as far in the moderate as in the hot trial (HT 11216 +/- 1411, MT 21644 +/- 1629, m, p < 0.01), and the decline in average 15-m sprint performance was greater in the heat (HT, 0.17 +/- 0.05, MT, 0.09 +/- 0.03, s, p < 0.05). Average heart rates, blood lactate and glucose, and plasma adrenaline and noradrenaline concentrations were greater in the HT (main effect trial, p < 0.01), as were serum cortisol concentration (main effect trial p < 0.05, n = 5) and muscle temperature (HT exhaustion vs. same time point in MT, 40.2 +/- 0.3 vs. 39.3 +/- 0.2, degrees C, p < 0.01). Peak torque during knee flexion and extension was not different pre-and post-exercise in the HT. Muscle glycogen utilization tended to be greater in the heat (HT 193.2 +/- 19.5, MT 143.8 +/- 23.9, mmol . kg dry wt (-1), p = 0.055, n = 8). In 7 out of the 8 subjects the increase in utilization was between 19 and just over 200 % greater in the HT. Glycogen remaining in the muscle at exhaustion was greater in the hot than moderate trial (HT 207.4 +/- 34.3, MT 126.5 +/- 46.8, mmol . kg dry wt (-1), p < 0.01, n = 8). Rectal temperature (T (rec)) was higher in the HT at exhaustion than at the same point in time in the moderate trial (HT, 39.60 +/- 0.15 vs. MT 38.75 +/- 0.10, degrees C, interaction trial-time, p < 0.01). There was a very strong negative relationship between rate of rise in T (rec) and distance completed in the HT (HT r = - 0.90, p < 0.01, MT r = - 0.76, p < 0.05). Thus, the earlier onset of exhaustion during prolonged intermittent shuttle running in the heat is associated with hyperthermia. However, while muscle glycogen utilization may be elevated by heat stress, low whole muscle glycogen concentrations would not seem to be the cause of this earlier exhaustion.

Adult↗

PubMed2005

Localizing the X-linked orange colour phenotype using feline resource families.

Many genes influencing mammalian coat colours are well conserved. While genes responsible for pelage phenotypes in one species provide strong evidence for a candidate gene in a different species, the X-linked orange phenotype of the domestic cat is unique within mammals. The orange locus (O) undergoes X-inactivation, producing females that express both wildtype black (wt) and orange (variant) phenotypes when heterozygous (tortoiseshell). The orange locus has not yet been localized on the X chromosome. Tortoiseshell male cats have been identified but have been shown to be sex chromosome trisomies (XXY). To localize the cat orange locus, 10 feline-derived X-linked microsatellites were analysed in two extended cat pedigrees consisting of 79 and 55 individuals, respectively, segregating for the orange phenotype. Linkage analyses excluded close association of orange in the vicinity of the nine informative X-linked microsatellites. One marker was not polymorphic within either family. Several markers suggested exclusion (Z < -2.0) at distances of 7.5-33 cM. Exclusion analyses suggested a possible location for orange a 14 cM region near Xcen. Recombination distances of markers in the segregating feline pedigrees were reduced as compared with the feline interspecies backcross family. Thus, the presented pedigrees may be useful as reference families for the domestic cat because more accurate recombination rates for domestic cats can be determined.

Animals↗

PubMed2004

Animal growth promoters: to ban or not to ban? A risk assessment approach.

The use of antibiotics for animal growth promotion has been controversial because of the potential transfer of antibiotic resistance from animals to humans. Such transfer could have severe public health implications in that treatment failures could result. We have followed a risk assessment approach to evaluate policy options for the streptogramin-class of antibiotics: virginiamycin, an animal growth promoter, and quinupristin/dalfopristin, a antibiotic used in humans. Under the assumption that resistance transfer is possible, models project a wide range of outcomes depending mainly on the basic reproductive number (R(0)) that determines the potential for person-to-person transmission. Counter-intuitively, the benefits of a ban on virginiamycin were highest for intermediate values of R(0), and lower for extremely high or low values of R(0).

Animal Husbandry↗

PubMed2004

Lysine requirement of kittens given purified diets for maximal growth.

Three experiments were conducted using a total of 15 male and 15 female weaned specific pathogen-free kittens given amino acid-based purified diets containing varying concentrations of lysine (from 4.0 to 11.3 g/kg diet) in a Latin square design of 10 day periods. In experiment 1, the predicted lysine requirement was 7.7 g/kg diet, and in experiments 2 and 3, maximal weight gain occurred at 8.0 g lysine/kg diet. In experiment 3, nitrogen balance was not different for kittens given diets containing 8.0 and 9.0 g lysine/kg. These experiments support a requirement of 8.0 g lysine (free base)/kg diet, in a diet with a calculated metabolizable energy value of 4.7 kcal/g.

Animal Feed↗

PubMed2004

Do cats need arachidonic acid in the diet for reproduction?

A brief review of the status of arachidonic acid as an essential dietary nutrient for cats is presented. The reproductive performance of male and female cats given a purified diet containing only partially hydrogenated vegetable oil as the fat source from weaning was investigated. Male kittens did not require a supplemental source of arachidonate for normal body weight gain and successful reproduction. Female kittens given the same diet also appeared to grow normally, came into oestrus and conceived, but produced only a limited number of viable litters. Subsequent supplementation of these queens with arachidonic acid did not result in the birth of viable kittens. It is suggested that completion of a normal pregnancy by queens given a diet based on partially hydrogenated oil for protracted periods may require fatty acids in addition to arachidonate.

Animals↗

PubMed2003

Assessing risks for a pre-emergent pathogen: virginiamycin use and the emergence of streptogramin resistance in Enterococcus faecium.

Vancomycin-resistant enterococci (VRE) are an important cause of hospital-acquired infections and an emerging infectious disease. VRE infections were resistant to standard antibiotics until quinupristin/dalfopristin (QD), a streptogramin antibiotic, was approved in 1999 for the treatment of vancomycin-resistant Enterococcus faecium infections in people. After that decision, the practice of using virginiamycin in agriculture for animal growth promotion came under intense scrutiny. Virginiamycin, another streptogramin, threatens the efficacy of QD in medicine because streptogramin resistance in enterococci associated with food animals may be transferred to E faecium in hospitalised patients. Policy makers face an unavoidable conundrum when assessing risks for pre-emergent pathogens; good policies that prevent or delay adverse outcomes may leave little evidence that they had an effect. To provide a sound basis for policy, we have reviewed the epidemiology of E faecium and streptogramin resistance and present qualitative results from mathematical models. These models are based on simple assumptions consistent with evidence, and they establish reasonable expectations about the population-genetic and population-dynamic processes underlying the emergence of streptogramin-resistant E faecium (SREF). Using the model, we have identified critical aspects of SREF emergence. We conclude that the emergence of SREF is likely to be the result of an interaction between QD use in medicine and the long-term use of virginiamycin for animal growth promotion. Virginiamycin use has created a credible threat to the efficacy of QD by increasing the mobility and frequency of high-level resistance genes. The potential effects are greatest for intermediate rates of human-to-human transmission (R0 approximately equal 1).

Anti-Bacterial Agents↗

PubMed2003

Teratogenic effects of chronic ingestion of high levels of vitamin A in cats.

High concentrations of retinoids occur in some commercial cat food formulations as a result of the use of animal liver as an ingredient. Our objective was to study the teratogenic potential of dietary vitamin A in cats. We investigated the incidence of birth defects in kittens of queens given diets with retinyl acetate concentrations of 6000, 306000, or 606000 retinol equivalents (RE)/kg diet (control, 306K, or 606K groups, respectively) for approximately 3 years [1 RE=1 micro g retinol=3.3 International Units (IU)]. Each group comprised 12-15 age-matched, nulliparous domestic short-haired queens that were exposed to toms. There were a total of 396 kittens born in 97 litters. Pregnancy rate, number of kittens per gestation and gestations per year were not significantly different among treatment groups. A total of 2, 5 and 11 malformed kittens occurred in the control, 306K and 606K groups, respectively. Malformations included cleft palate, cranioschisis, foreshortened mandible, stenotic colon, enlarged heart and agenesis of the spinal cord and small intestine, which are typical foetal defects consistent with ingestion of excess retinoids in other species. This study demonstrated that a concentration of 306000 RE/kg diet has a potential for causing birth defects in the kittens.

Abnormalities, Drug-Induced↗

PubMed2003

Determination of the selenium requirement in kittens.

The purpose of this study was to determine the selenium (Se) requirement in kittens. Thirty-six specific-pathogen-free kittens (9.8 weeks old) were utilized in a randomized complete block design to determine the Se requirement in cats with gender and weight used as blocking criteria. Kittens were fed a low Se (0.02 mg/kg Se) torula yeast-based diet for 5 weeks (pre-test) after which an amino acid-based diet (0.027 mg Se/kg diet) was fed for 8 weeks (experimental period). Six levels of Se (0, 0.05, 0.075, 0.10, 0.20 and 0.30 mg Se/kg diet) as Na2SeO3 were added to the diet and were used to construct a response curve. Response variables included Se concentrations and Se-dependent glutathione peroxidase activities (GSHpx) in plasma and red blood cells (RBC) as well as plasma total T3 (TT3) and total T4 (TT4). No significant changes in food intake, weight gain or clinical signs of Se deficiency were noted. Estimates of the kitten's Se requirement (i.e. breakpoints) were determined for RBC and plasma GSHpx (0.12 and 0.15 mg Se/kg diet, respectively), but no definitive breakpoint was determined for plasma Se. Plasma TT3 increased linearly, whereas plasma TT4 and the ratio of TT4 : TT3 decreased in a quadratic fashion to dietary Se concentration. The requirement estimate determined in this study (0.15 mg Se/kg) for kittens is in close agreement with other species. As pet foods for cats contain a high proportion of animal protein with a Se bioavailability of 30%, it is recommended that commercial diets for cats contain 0.5 mg Se/kg DM.

Animals↗

PubMed2002

A low-selenium diet increases thyroxine and decreases 3,5,3'triiodothyronine in the plasma of kittens.

The effect of a low-selenium diet on thyroid hormone metabolism was investigated in growing kittens. Twelve specific-pathogen-free kittens with ages ranging from 16 to 18 weeks were divided into two groups of equal number with equal sex distribution in each group. One group was fed a yeast-based low-selenium diet (0.02 mg Se/kg diet) while the other group was fed the same diet supplemented with Na2SeO3 at 0.4 mg Se/kg diet for 8 weeks. Food intake, body weight and body weight gain were not affected by the low-Se diet during the study period. However, kittens given the low-Se diet had significantly reduced plasma selenium concentration and glutathione peroxidase activity. Plasma total thyroxine (T4) increased and total 3,5,3'triiodothyronine (T3) decreased significantly in kittens fed the low-Se diet at the end of the study. These results suggest that type I deiodinase in cats is a selenoprotein- or a selenium-dependent enzyme.

Animals↗

PubMed2002

Cats discriminate between cholecalciferol and ergocalciferol.

A comparison was made of the ability of ergocalciferol and cholecalciferol to elevate plasma concentrations of vitamin D and 25-hydroxyvitamin D in cats. Cholecalciferol, given as an oral bolus in oil, resulted in a rapid elevation of plasma concentration of cholecalciferol followed by a rapid decline. In contrast, 25-hydroxyvitamin D concentration in plasma increased until day 3 after administration and remained elevated for a further 5 days. When 337 microg of both cholecalciferol and ergocalciferol in oil were given as an oral bolus to 10 cats, the peak plasma concentrations of cholecalciferol and ergocalciferol occurred at 8 or 12 h after administration. Peak concentrations of cholecalciferol were over twice those of ergocalciferol (570 +/- 80 vs. 264 +/- 42 nmol/l). The area under the curve 0-169 h for cholecalciferol was also more than twice that for ergocalciferol. When ergocalciferol and cholecalciferol were administered in a parenteral oil-based emulsion, higher concentrations of 25-hydroxyvitamin D3 than 25-hydroxyvitamin D2 were maintained in plasma. When both vitamins were included in the diet in the nutritional range, plasma concentrations of 25-hydroxyvitamin D2 were 0.68 of those of 25-hydroxyvitamin D3. Discrimination against ergocalciferol by cats appears to result from differences in affinity of the binding protein for the metabolites of the two forms of vitamin D. These results indicate that cats discriminate against ergocalciferol, and use it with an efficiency of 0.7 of that of cholecalciferol to maintain plasma 25-hydroxyvitamin D concentration.

Administration, Oral↗

PubMed2001

Gastrointestinal and respiratory tract symptoms following brief environmental exposure to aerosols during a pfiesteria-related fish kill.

An outbreak of illness with flulike symptoms among state workers responding to a Pfiesteria bloom that resulted in fish death and distress on the Chicamacomico River on Maryland's Eastern Shore was investigated. Using case-control methodology, seven workers present at the Chicamacomico were compared to seven occupationally matched controls not present. Participants completed questionnaires assessing their exposures to water and their symptom histories and were assessed with a standard neuropsychological test battery. Three months later, the same questionnaires and neuropsychological tests were repeated. Three of the seven exposed workers cited minimal direct contact with water and four cited none. During the event, four developed burning eyes or nares and six developed a headache or sore throat. Six developed crampy abdominal pain, nausea, or diarrhea within 4 h of their exposure. In contrast, the only aforementioned symptom reported by controls was headache in two individuals. Acute and follow-up neuropsychological tests showed no consistent pattern of deficiency among the exposed. In conclusion, a flulike clinical illness was observed following exposure to a Pfiesteria-related fish kill, possibly as a result of inhalation of toxic aerosols.

Abdominal Pain↗

PubMed2001

Lesion of thalamic centromedian--parafascicular complex after chronic deep brain stimulation.

A patient with PD who exhibited disabling tremor and prominent dyskinesia underwent deep brain stimulation (DBS) of the left thalamic ventral intermediate nucleus. The electrode migrated and was replaced but with suboptimal clinical response. Two years later, postmortem analysis found the second electrode tip had entered the thalamic centromedian-parafascicular complex. There was a small thalamotomy and cell loss exceeding that found in PD. Thalamic damage may occur in association with DBS for PD.

Chronic Disease↗

PubMed2001

Serotype distribution of Salmonella isolates from food animals after slaughter differs from that of isolates found in humans.

If raw meat and poultry are the primary point of entry for Salmonella species into human populations, a correlation might be expected between the serotype distribution of Salmonella species isolated from animals at the time of slaughter and that of isolates found in humans. For 1990-1996, sufficient national data were available to permit such a comparison. A mathematical model was developed to predict serotype distributions of Salmonella isolates among humans on the basis of animal data. There was a significant mismatch between the serotype distributions among humans predicted by the model and those actually observed. This mismatch raises questions about the validity of the "standard" assumptions about Salmonella transmission on which the model was based-namely, that raw animal products are the primary source for human salmonellosis, that the risk of transmission to humans is equal for all food product categories, and that all Salmonella serotypes have an equal ability to cause human illness.

Abattoirs↗

PubMed2001

Corticobasal syndrome with tau pathology.

Six cases with a clinical corticobasal syndrome (progressive asymmetric apraxia and parkinsonism unresponsive to levodopa) and tau pathology were selected from 97 brain donors with parkinsonism. Postmortem volumetric measures of regional brain atrophy (compared with age/sex-matched controls) were correlated with clinical features and the degree of underlying cortical and subcortical histopathology. At death, no significant asymmetry of pathology was detected. All cases had prominent bilateral atrophy of the precentral gyrus (reduced by 22-54%) with other cortical regions variably affected. Subcortical atrophy was less severe and variable. Two cases demonstrated widespread atrophy of basal ganglia structures (44-60% atrophy of the internal globus pallidus) and substantial subcortical pathology consistent with a diagnosis of progressive supranuclear palsy (PSP). The remaining four cases had typical pathology of corticobasal degeneration. In all cases, neuronal loss and gliosis corresponded with subcortical atrophy, while the density of cortical swollen neurons correlated with cortical volume loss. Atrophy of the internal globus pallidus was associated with postural instability, while widespread basal ganglia histopathology was found in cases with gaze palsy. This study confirms the involvement of the precentral gyrus in the corticobasal syndrome and highlights the variable underlying pathology in these patients.

Aged↗

PubMed2001

Kinetics of taurine depletion and repletion in plasma, serum, whole blood and skeletal muscle in cats.

The relationship between taurine concentrations of plasma, whole blood, serum and skeletal muscle during taurine depletion and repletion was investigated in cats, to identify the most useful indicators of taurine status. Sixteen cats were fed a purified diet containing either 0 or 0.15 g/kg taurine for 5 months. Treatments were then reversed and the taurine concentration was measured during repletion and depletion phases. Plasma taurine exhibited the fastest rate (slow component) of depletion (t 1/2 = 4.8 wk), followed by serum (5.3 wk), whole blood (6.2 wk), and skeletal muscle (11.2 wk). Whole blood taurine was the first to replete at a rate of 0.74 wk to 1/2 maximal repletion, followed by serum (2.1 wk), skeletal muscle (3.5 wk), and plasma (3.5 wk). Whole blood more closely reflected skeletal muscle taurine concentrations than plasma during depletion, while plasma taurine concentrations appear to be the most valuable predictor of skeletal muscle taurine concentrations during repletion. This study suggests that the best clinical method to evaluate the taurine status of the cat is the determination and interpretation of both plasma and whole blood taurine concentrations.

Animals↗

PubMed2001

Effect of low levels of dietary tyrosine on the hair colour of cats.

Experiments were conducted to investigate the basis for the change in hair colour of black cats to reddish-brown. Black cats were given purified diets based on gelatin, casein plus lactalbumin, or crystalline amino acids as protein sources. Diets that caused the colour of hair to change to reddish-brown were associated with a reduction in melanin in hair (observed by direct microscopic examination), a decreased total melanin concentration and low concentrations of tyrosine in plasma. Reddish hair coat was induced in black kittens born to queens given a tyrosine-deficient diet during pregnancy. Black hair colour was maintained or restored by diets containing a high concentration of tyrosine or phenylalanine. Current dietary recommendations for dietary tyrosine and phenylalanine for cats are below those required to support maximal melanin synthesis in black cats. The requirement appears to be greater than a combination of 4.5 g tyrosine plus 12 g phenylalanine/kg diet but less than 24 g phenylalanine alone/kg diet.

Amino Acids↗