Search PubMed⌕ Search

Biomedical subjects

P J Markwell

Publications and source records attributed to P J Markwell.

At least 19 recordsLinked to original sources
PubMed2005

Multivariate analysis of risk factors for feline hyperthyroidism in New Zealand.

AIM: To search for putative risk factors for feline hyperthyroidism in New Zealand, using a case-control study. METHODS: A questionnaire-based case-control study involving the owners of 375 cats in New Zealand (125 hyperthyroid cats, 125 randomly selected control cats, and 125 age- and sex-matched control cats) was conducted to examine associations between potential risk factors and occurrence of feline hyperthyroidism. Data were collected between December 1996 and February 1998, relative to cat and owner demography and medical history, cats' indoor and outdoor environments, and cats' diets. A range of statistical techniques was employed to analyse the data, including descriptive analyses, univariate logistic regression for each variable and multivariate stepwise forward logistic regression. RESULTS: Multivariate analysis revealed that affected cats were more likely to be female (odds ratio (OR)=3.3; 95% confidence interval (CI)=1.2-9.0) and older than unaffected random control cats. Purebred cats were at a much lower risk of being diagnosed as hyperthyroid than were domestic short- and long-haired cats (OR=0.01; 95% CI=0.001-0.20). If more than one cat was present in a household, hyperthyroidism was less likely to be identified (OR=0.15; 95% CI=0.05-0.44) compared with single-cat households. Hyperthyroid cats were 6.6 times more likely (95% CI=1.8-23.9) to be reported to sleep predominantly on the floor than control cats. Cats whose bedding was regularly treated with anti-flea products appeared to be at a considerably higher risk for hyperthyroidism (OR=57.6; 95% CI=3.8-->200); and, to a lesser extent, so were cats living in households where fly sprays were reported to be used regularly (OR=3.3; 95% CI=1.2-9.3). The interaction between drinking water from puddles and regular use of organic garden fertilisers, such as compost or animal manure, was associated with a 5.3-fold (95% CI=1.1-25.6) increase in the risk of cats being diagnosed with the disease. Hyperthyroid cats were twice as likely (95% CI=0.3-12.9) to have eaten at least half of their daily food requirements as canned commercial cat food compared with unaffected cats. Cats exposed to a variety of flavours of canned cat food were more likely to be diagnosed with hyperthyroidism than were those fed only one flavour (OR=3.8; 95% CI=1.5-9.6). The presence of dental disorders was associated with a 5.5-fold increase in the risk of being diagnosed as hyperthyroid and this association was independent of the cat's age (95% CI=1.7-17.5). CONCLUSIONS: The results of this study support and extend those in several earlier reports and show that cats in New Zealand are, in many respects, similar to cats in Europe and North America in terms of their susceptibility to hyperthyroidism. The finding that female cats are predisposed to hyperthyroidism is at variance with most previously published work. It remains unclear which, if any, of the identified disease associations are causal, so further studies of this increasingly prevalent feline endocrinopathy are warranted.

Animals↗
PubMed2003

Effect of dietary moisture and sodium content on urine composition and calcium oxalate relative supersaturation in healthy miniature schnauzers and labrador retrievers.

The aim of this series of studies was to evaluate two possible feeding strategies as methods for reducing the risk of calcium oxalate (CaOx) formation in two breeds of healthy dog. The studies compared the effect of dietary moisture (Study 1) and dietary sodium (Na), (Study 2) on urine composition of labrador retrievers (LR) and miniature schnauzers (MS). A nutritionally complete dry dog food was fed to 16 dogs (eight LR, eight MS; Study 1) and 15 dogs (seven LR, eight MS; Study 2) for 24 days (Study 1), or 36 days (Study 2). The dogs were fed the diet alone (7% moisture, 0.06 g Na/100 kcal), or supplemented with deionised water to 73% moisture (Study 1), or dietary Na, to deliver 0.20 or 0.30 g Na per 100 kcal (Study 2). Urine pH, volume, specific gravity, and concentrations of 12 analytes were measured for each dog. Urinary relative supersaturations (RSS) with CaOx were calculated from these values. The effects of supplemental Na or water were established using t tests (Study 1) or analysis of variance, and multiple range tests (least significant difference) (Study 2); P<0.05 was considered significant. Increasing dietary moisture significantly increased total moisture intake (P=0.001), and reduced urine specific gravity (P=0.003), urinary oxalate concentration (P=0.04), and CaOx relative supersaturation (P=0.04) in the MS. Urinary parameters remained unchanged in the LR, indicating that feeding a high moisture diet may reduce the risk of CaOx formation in high-risk breeds. Increasing dietary Na led to production of urine with a significantly lower CaOx RSS in both breeds, indicating that sodium supplementation to dry diet formats may reduce the risk of CaOx formation. These feeding strategies should be considered when evaluating methods for preventing CaOx formation within high-risk groups.

Animal Feed↗
PubMed2003

The relative effects of supplemental dietary calcium and oxalate on urine composition and calcium oxalate relative supersaturation in healthy adult dogs.

The aim of this study was to establish the relative effects of dietary calcium and oxalate (in the form of oxalic acid) on the composition of urine produced by healthy adult Cairn Terriers and Miniature Schnauzers. A nutritionally complete dry dog food was fed to 7 dogs (4 Cairn terriers and 3 Miniature schnauzers) for 24 weeks. The dogs were fed the diet alone, or supplemented with six different combinations of dietary calcium (as carbonate and sulphate) and oxalate (as oxalic acid) commonly found in dry commercially prepared dog foods. Urine pH, volume, specific gravity, and concentrations of 12 analytes were measured for each dog; urinary relative supersaturation (RSS) with calcium oxalate (CaOx) was calculated from these values. The effects of supplemental calcium and oxalate were established using two-way analysis of variance and multiple range tests (least significant difference); P<0.05 was considered significant. The lowest level of dietary calcium and oxalate resulted in the lowest CaOx RSS. The high calcium, low oxalate diet resulted in the highest CaOx RSS, a low calcium diet with increased dietary oxalate also tended to increase CaOx RSS although results were highly variable. Urinary calcium concentration increased significantly with dietary calcium; urinary oxalate increased, although inconsistently, with dietary oxalic acid only when dietary calcium was low. Measures to reduce both calcium and oxalate should be considered when implementing dietary changes to reduce the risk of calcium oxalate formation in dogs. A reduction in dietary calcium without a concomitant decrease in dietary oxalate may increase the risk of CaOx crystallisation in susceptible dogs.

Animals↗
PubMed2003

Assessment of acid-base status of cats with naturally occurring chronic renal failure.

Metabolic acidosis is reported to be a common complication of feline chronic renal failure (CRF) but acid-base status of feline patients with this disease is rarely assessed by general practitioners. A cross-sectional study involving 59 cases of naturally occurring feline CRF was conducted to determine the prevalence of acid-base disturbances. Cases were categorised on the basis of their plasma creatinine concentrations as mild, moderate or severe. A group of 27 clinically healthy, age-matched cats was assessed for comparison. A low venous blood pH (<7.270) was found in 10 of the 19 severe cases (52.6 per cent), three of the 20 moderate cases (15 per cent) and none of the 20 mild cases. Acidaemia was associated with an increased anion gap contributed to by both low plasma bicarbonate and low chloride ion concentrations. Biochemical analysis of urine samples showed urine pH to decrease with increasing severity of renal failure. Urinary loss of bicarbonate was not associated with the occurrence of acidaemia and there was a tendency for urinary ammonium ion excretion to decrease as the severity of renal failure increased. Cats with naturally occurring CRF do not show plasma biochemical evidence of acid-base disturbances until the disease is advanced.

Acidosis↗
PubMed2003

Acid-base balance of cats with chronic renal failure: effect of deterioration in renal function.

In a previous cross-sectional study of feline chronic renal failure (CRF), metabolic acidosis was identified in 52.6 per cent of animals with severe renal failure (plasma creatinine concentration >400 micromol/litre). The aim of this longitudinal study was to determine whether metabolic acidosis preceded or accompanied a deterioration in renal function in cats with CRF. Data were analysed from 55 cats with CRF that had been followed longitudinally for at least four months. Twenty-one cases showed deterioration in renal function over the period of the study, as evidenced by significant rises in their plasma creatinine concentrations and decreases in bodyweight. In five of the 21 cases, acidaemia accompanied the deterioration in renal function. Only one of these cats had evidence of metabolic acidosis before renal function deterioration. One other case developed metabolic acidosis without a rise in plasma creatinine concentration. These data suggest that biochemical evidence of metabolic acidosis does not generally occur until late in the course of feline CRF.

Acidosis↗
PubMed2002

Influence of a high fibre diet on glycaemic control and quality of life in dogs with diabetes mellitus.

A study was undertaken to evaluate a high fibre diet used in the management of 10 dogs with naturally occurring insulin-dependent diabetes mellitus. Following baseline measurements of health and glycaemic control, the dogs were fed a canned diet containing a blend of insoluble and soluble dietary fibres and were monitored during the ensuing four months. Switching to the high fibre diet was associated with significantly lower mean 24-hour and postprandial plasma glucose concentrations, which were maintained over the study period. The high fibre diet was also associated with significant reductions in plasma concentrations of fructosamine, glycated haemoglobin, free glycerol and cholesterol, and there were significant improvements in dog activity and demeanour. Bodyweight declined during the fourth month of feeding the diet, which is likely to have resulted from underfeeding relative to increased activity. The results indicate that a high fibre diet can significantly improve glycaemic control and quality of life in dogs with diabetes mellitus.

Animals↗
PubMed2001

Evaluation of selected-protein-source diets for management of dogs with adverse reactions to foods.

OBJECTIVE: To evaluate 3 commercially available selected-protein-source diets as maintenance diets in dogs with pruritus caused by adverse food reactions. DESIGN: Randomized crossover trial. ANIMALS: 40 dogs > 6 months of age with pruritus caused by adverse reactions to foods. PROCEDURE: Diagnosis was confirmed by use of diet elimination and provocation studies. Subsequently, dogs were fed 3 commercial diets for 3 weeks each in a randomized, blinded, crossover trial. Dogs were evaluated for pruritus, vomiting, diarrhea, and flatulence. RESULTS: Pruritus recurred in 52.5% of dogs fed a chicken-rice diet, 47.5% of dogs fed a catfish-rice diet, and 85% of dogs fed a venison-rice diet. Overall 95% of the dogs could be managed successfully with at least 1 of the 3 diets. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that commercially available limited-allergen diets with selected protein sources may be appropriate for long-term management of pruritus caused by adverse food reactions. Testing of various protein sources is usually required.

Animal Feed↗
PubMed2001

Feline hypertension: clinical findings and response to antihypertensive treatment in 30 cases.

Systolic hypertension was diagnosed in 30 cats. At diagnosis, 16 of those were found to be in chronic renal failure only, while five were azotaemic and either receiving treatment for hyperthyroidism (four cases) or were untreated hyperthyroid cases (one case). Two cases were untreated hyperthyroid cases with no evidence of azotaemia and the remaining seven cases had no definitive diagnosis of the underlying cause of their hypertension. The successful treatment used for the majority of cases was amlodipine, which lowered systolic blood pressure from 202.5+/-16.8 to 153.2+/-21.6 mmHg (mean+/-SD; n=29) within the first 50 days. Each case was followed for at least three months, or to the end of its natural life, and each cat was re-examined every six to eight weeks. Systolic blood pressure was kept below a target value of 165 mmHg in 58 per cent of cases treated for three months or longer. At the time of writing, 19 of the cases had died or been euthanased with a median treatment time of 203 days, one case was lost to follow-up and 10 cases were still alive, nine of which had been treated for six months or more. Amlodipine can be used for long-term control of feline systemic hypertension.

Amlodipine↗
PubMed2001

Comparison of urine composition of healthy Labrador retrievers and miniature schnauzers.

OBJECTIVE: To compare urine composition in Labrador Retrievers (LR) and Miniature Schnauzers (MS) fed the same dog food. ANIMALS: 8 healthy LR (mean [+/- SD] age, 3.1+/-1.7 years) and 8 healthy MS (mean age, 3.7+/-1.3 years). PROCEDURE: A nutritionally complete dry dog food was fed to the dogs for 24 days. Urinary pH, volume, specific gravity, frequency of urination, and urinary concentrations of 12 analytes were measured for each dog; urinary relative supersaturation (RSS) with calcium oxalate and brushite (calcium hydrogen phosphate dihydrate) were calculated from these values. RESULTS: MS urinated significantly less often and had a lower urine volume (ml/kg of body weight per d) and a significantly higher urine pH, compared with LR. Urinary calcium concentration and brushite RSS were significantly higher in the urine of MS. As a result of a high calorie requirement, primarily as a result of high surface area to volume ratio, MS had significantly higher intake (per kg body weight) of dietary minerals, compared with LR. CONCLUSIONS AND CLINICAL RELEVANCE: Differences in urine composition exist between breeds fed the same diet, some of which, including lower urine volume, higher calcium concentration, and higher brushite RSS, may contribute to the high prevalence of calcium oxalate uroliths observed in MS. Differences between breeds should be considered when evaluating strategies for controlling calcium oxalate stone formation.

Animals↗
PubMed2001

Influence of age and sex on plasma lipid and lipoprotein concentrations and associated enzyme activities in cats.

OBJECTIVE: To determine effects of age and sex on plasma lipid and lipoprotein metabolism in cats. ANIMALS: 33 kittens and 16 adolescent, 23 adult, and 10 senior cats. PROCEDURE: Plasma concentrations of cholesterol, triglyceride, and lipoprotein-cholesterol and activities of lipoprotein lipase, hepatic lipase, and lecithin:cholesterol acyl transferase (LCAT) were measured and compared within and among groups. RESULTS: Plasma cholesterol and triglyceride concentrations were significantly higher in 5- and 7-week-old kittens, compared with the same kittens after weaning and cats in the other age groups. Cholesterol concentration was significantly less in 20-week-old kittens, compared with adolescent and adult cats. Lipid and lipoprotein-cholesterol concentrations were not significantly different among the adolescent, adult, and senior groups, nor did sex influence lipid and lipoprotein-cholesterol concentrations in these groups. Activities of lipoprotein and hepatic lipases were significantly less in senior cats, compared with the other groups. Activity of LCAT was highest in 20-week-old kittens and was greater in sexually intact adult and adolescent females, compared with their male counterparts. After castration, activities of hepatic lipase and LCAT significantly decreased in adolescent male cats. CONCLUSIONS AND CLINICAL RELEVANCE: The upper limits of reference ranges for plasma cholesterol and triglyceride concentrations should be increased for kittens < 8 weeks of age. Low cholesterol concentrations in adolescent cats likely reflect high tissue demands for growth and steroidogenesis. Decrease in lipoprotein and hepatic lipase activity in senior cats could predispose this age group to hypertriglyceridemia, particularly in insulin-resistant cats or those fed a high fat diet.

Age Factors↗
PubMed2000

Survival of cats with naturally occurring chronic renal failure: effect of dietary management.

Fifty cats with naturally occurring stable chronic renal failure (CRF) were entered into a prospective study on the effect of feeding a veterinary diet restricted in phosphorus and protein with or without an intestinal phosphate binding agent on their survival from initial diagnosis. Twenty-nine cats accepted the veterinary diet, whereas compliance (due to limited intake by the cats or owner resistance to diet change) was not achieved in the remaining 21. At diagnosis, both groups of cats were matched in terms of age, bodyweight, plasma creatinine, phosphate, potassium and parathyroid hormone (PTH) concentrations, packed cell volume and urine specific gravity. Feeding the veterinary diet was associated with a reduction in plasma phosphate and urea concentrations and prevented the increase in plasma PTH concentrations seen in cats not receiving the diet. Cats fed the veterinary diet survived for longer when compared with those that were not (median survival times of 633 versus 264 days). These data suggest that feeding a diet specifically formulated to meet the needs of cats with CRF, together with phosphate binding drugs if required, controls hyperphosphataemia and secondary renal hyperparathyroidism, and is associated with an increased survival time.

Animals↗
PubMed2000

Effects of dietary potassium citrate supplementation on urine pH and urinary relative supersaturation of calcium oxalate and struvite in healthy dogs.

OBJECTIVE: To assess the effect of dietary potassium citrate supplementation on the urinary pH, relative supersaturation of calcium oxalate and struvite (defined as the activity product/solubility product of the substance), and concentrations of magnesium, ammonium, phosphate, citrate, calcium, and oxalate in dogs. ANIMALS: 12 healthy adult dogs. PROCEDURE: Canned dog food was fed to dogs for 37 days. Dogs were randomly allocated to 3 groups and fed test diets for a period of 8 days. Study periods were separated by 6-day intervals. During each study period the dogs were fed either standard diet solus (control) or standard diet plus 1 of 2 types of potassium citrate supplements (150 mg potassium citrate/kg of body weight/d) twice daily. Urinary pH, volume and specific gravity, relative supersaturation of calcium oxalate and struvite, and concentrations of magnesium, ammonium, phosphate, calcium, oxalate, and citrate were assessed for each treatment. RESULTS: Mean urine pH was not significantly affected by dietary potassium citrate supplementation, although urine pH did increase by 0.2 pH units with supplementation. Diets containing potassium citrate maintained a higher urine pH for a longer part of the day than control diet. Three Miniature Schnauzers had a significantly lower urinary relative calcium oxalate supersaturation when fed a diet supplemented with potassium citrate, compared with control diet. CONCLUSIONS AND CLINICAL RELEVANCE: Dietary potassium citrate supplementation has limited effects on urinary variables in most healthy dogs, although supplementation results in maintenance of a higher urine pH later in the day. Consequently, if supplementation is introduced, dogs should be fed twice daily and potassium citrate should be given with both meals or with the evening meal only.

Animals↗
PubMed1999

Clinical evaluation of commercially available urinary acidification diets in the management of idiopathic cystitis in cats.

OBJECTIVE: To compare recurrence of signs of lower urinary tract disease (LUTD) in cats with idiopathic cystitis that were fed the dry or canned formulation of a commercial diet designed to result in production of an acidic urine. DESIGN: Prospective trial. ANIMALS: 54 client-owned cats with idiopathic cystitis that was diagnosed on the basis of a history of abnormal micturition, abnormal results on urinalysis, radiography, or cystoscopy, and lack of an alternative diagnosis. PROCEDURE: Cats were assigned to be fed the canned or dry formulation of the diet. Reevaluations conducted at 2 and 16 weeks, and at 6 and 12 months included a physical examination, CBC and serum biochemical analysis (except week 2), blood gas analysis, and urinalysis. Regular telephone contacts were also made. The study was discontinued after 12 months or if signs of LUTD recurred. RESULTS: Signs of LUTD did not recur in 16 of 18 cats fed the canned diet, and 17 of 28 cats fed the dry diet (chi 2, P < 0.05). Seven cats were reevaluated at recurrence. Owners of remaining cats in which signs of LUTD recurred declined to have their pets reexamined. A different problem (bacterial urinary tract infection) was identified in only 1 cat on reevaluation. Eight cats were lost to follow-up evaluation. CLINICAL IMPLICATIONS: Feeding this commercial canned urinary acidifying diet may reduce the proportion of cats with idiopathic cystitis that will have recurrence of signs of LUTD within a 12-month period.

Animal Feed↗
PubMed1999

Effect of dietary phosphate restriction on renal secondary hyperparathyroidism in the cat.

Twenty-three cats with stable chronic renal failure (CRF) were examined in a prospective study of the effects of feeding a veterinary diet restricted in phosphorus and protein with or without an intestinal phosphate binding agent (aluminium hydroxide) on plasma phosphate and parathyroid hormone (PTH) concentrations. Fifteen cats accepted the veterinary diet; compliance was not achieved in the remaining eight (due to limited intake by the cats or owner resistance to diet change). Feeding the veterinary diet was associated with a significant fall in plasma phosphate and PTH concentrations by five months, with only two cats requiring aluminium hydroxide therapy. The maximum decrease in plasma PTH concentration was not associated with a significant change in plasma 1,25 dihydroxycholecalciferol concentration. Euparathyroidism was achieved in eight cats. Conversely, in cats with CRF fed proprietary diets over the same time period, mean plasma PTH concentrations did not change significantly; indeed, in seven of the eight cats, PTH concentrations increased. Dietary therapy alone or in combination with intestinal phosphate binders does reduce PTH concentrations in cats with CRF and, when effective control of phosphate intake is achieved, plasma PTH can be normalised.

Aluminum Hydroxide↗
PubMed1998

The effect of diet on lower urinary tract diseases in cats.

Because dietary ingredients and feeding patterns influence the volume, pH and solute concentration of urine, diet can contribute to the etiology, management or prevention of recurrence of some causes of lower urinary tract disease. Most research assessing the effect of diet has focused on the latter two aspects, primarily because of interest in struvite urolithiasis. Manipulation of urine pH through dietary means has proven an effective tool for the management and prevention of struvite urolithiasis; acidification of urine, however, may be a risk factor for calcium oxalate urolithiasis, which now appears to occur with approximately equal frequency in cats. Prediction of urine pH from dietary analysis would thus be a valuable tool, but considerable further research is required before this can be achieved with commercial canned foods. With the growing importance of urolith types other than struvite, alternatives to the measurement of urine pH are required to assess critically the likely beneficial (or detrimental) effects of manipulation of nutrient profile. Measurement of urinary saturation may permit the development and fine tuning of nutrient profiles aimed at controlling lower urinary tract diseases in cats that are associated with a range of different mineral types. The majority of cats with signs of lower urinary tract disease do not, however, have urolithiasis; indeed, no specific cause can be established in most of these cats. Recent observations suggest that recurrence rates of signs in cats classified as having idiopathic lower urinary tract disease may be more than halved if affected animals are maintained on high, rather than low moisture content diets. J. Nutr. 2753S-2757S, 1998

Animals↗