Michael F. Tarttelin

FELININE : A URINARY AMINO ACID OF FELIDAE

Felinine (2-amino-7-hydroxy-5,5-dimethyl-4-thiaheptanoic acid) has been identified in the urine of several members of the Felidae family including the cat (Felis catus). Rates of excretion of 95 mg/day have been recorded for entire male cats with entire female cats excreting around 19 mg/day. These high excretion rates in entire male cats may have a significant effect on the daily sulphur amino acid requirement. The isoamyl moiety of felinine seems to originate from the same isoprenoid pool as used for the synthesis of cholesterol in the cat. The sulphur in the felinine molecule appears to originate from cysteine, although some contradictory evidence exists. The site of synthesis and the method of transportation in the blood remain largely unknown. The biological significance of felinine to the animal is still a matter for speculation, but its function as a precursor to a pheromone seems likely. Recently, an accurate chemical assay for felinine has been developed that will allow investigation of felinine in different tissues and excretions and from a wider range of mammals.

Iodine content of commercially-prepared cat foods

Twenty-eight varieties of commercially-available cat food (23 canned, 5 dried) were analysed for iodine. The iodine concentration varied from less than 0.37 micromol/kg to 41.8 pmol/kg, wet weight (less than 1.48 micromol/kg to 167 micromol/kg, dry weight). Excessive or insufficient iodine intake or wide swings in iodine intake over prolonged periods may contribute to thyroid disorders in cats.

Some effects of ovariectomy and estrogen replacement on body composition in the rat

Sprague-Dawley rats were ovariectomized (OvX) at 3 ages, day 2 (D2), week 4 (W4) and week 7 (W7); a group of OvX W7 rats were treated daily with estrogen (OB;2 micrograms for 2 or 5 weeks from 10 weeks of age). Rats were slaughtered at 4 ages, weeks 7, 9, 12 and 15, for the chemical analysis of carcass and skin. Chemical compositions were analysed as % wet weight and as component weights by two-way analysis of variance. Component weights were also analysed by allometry, regressing against nose-anal length. Ovariectomy increased overall body weight without causing obesity. The weight gain of the OvX rat was mainly a true growth response but OvX affected body proportions so that at a given body length the OvX rat had a larger skin and carcass than controls. Ovariectomy at the earliest age (D2) produced the smallest response in body weight and body length but produced the greatest fat redistribution towards the skin and away from the carcass; there was no net change in whole body fat levels following OvX. Long-term daily OB treatment increased fat reserves but slowed the growth of other body components, including the axial skeleton. Whereas OvX redistributed components between skin and carcass, OB treatment reversed this process.

Twenty-four hour feline excretion patterns in entire and castrated cats

The purpose of this study was to determine the 24 h urinary excretion of a sulphur containing amino acid called felinine in entire and castrated cats of both sexes. Entire male cats excreted (mean ± SEM) 122 ± 23.6 mmol of felinine per kg bodyweight per day with castrated males, entire females and spayed females excreting 41 ± 8.4, 36 ± 7.3 and 20 ± 3.8 mmol, respectively. There was an overall significant differences between entire males and of felinine excreted in 24 h [F(3, 24) = 11.8, p < 0.0001] with there being significant differences between entire males and castrated males (p < 0.001) and castrated males and spayed females (p < 0.05). There was no difference in excretion between entire and spayed females. Urine volumes were not significantly different for the 24 h period. The differences in excretion levels were caused by different concentrations of felinine in the urine with entire male cats excreting (mean ± SEM) 2.0 ± 0.55 g of felinine per litre of urine. The data obtained in the present study support the concept that felinine, which has been found in Felidae species only, may be testosterone dependent. Felinine may be involved in territorial marking.

Serum free thyroxine levels in cats maintained on diets relatively high or low in iodine.

Excessive or deficient intake of iodine may play a role in the development of goitre and hyperthyroidism in cats. Previous investigations have shown that the serum free thyroxine level of cats is affected by brief administration of food high or low in iodine content. We have now measured serum free thyroxine levels in groups of cats fed relatively high or low iodine diets for much longer periods (5 months). In contrast to our earlier findings, the chronic ingestion of relatively high or low iodine diets did not lead to statistically significant differences in serum free thyroxine levels. The results of the present investigations show that the cat is able to maintain normal levels of thyroid hormone despite prolonged high or low iodine diets. It may be that the adaptive mechanisms that are called into play during chronic high or low iodine intake lead to thyroid disease, particularly in certain predisposed individuals.

Relationship between plasma testosterone and urinary felinine in the growing kitten.

Felinine, a unique amino acid the functions of which are not well understood, is found in large quantities in male cat urine. Our study ran for 13 calendar months and involved taking monthly samples of blood and urine from 10 male and 10 female kittens starting at 6 months of age and measuring urinary felinine and plasma testosterone concentrations. Felinine was detectable at 6 months of age in all cats (range, mean +/- SEM, nmol/mL, 13.8-801.1, 432.3+/-112.2, males and 34.3-393.0, 140.4+/-45.0 females). In entire males, felinine showed a biphasic pattern, peaking (2550 nmol/mL) between 11-13 months of age toward the end of the attainment of puberty then falling to a low (1048 nmol/mL) at 15 months of age then climbing to a peak (3661 nmol/mL) at 17 months of age. Natural plasma testosterone levels in entire males showed a similar biphasic pattern peaking (6.8 pmol/mL) at 12 months of age, falling (1.3 pmol/mL) at 15 months, and finally rising again (12.6 pmol/ml) at 16 months of age. Castration of half the male cats induced a parallel fall in both testosterone and felinine that was reversed following testosterone supplementation. Urinary felinine levels in entire females rose slowly throughout the study and reached 795 nmol/mL at 18 months of age compared to the level of 365 nmol/mL reached by the spayed females: these levels were not significantly different when expressed as felinine/creatinine ratios. We could not detect testosterone in either entire or spayed females and so concluded that felinine was unrelated to testosterone in these groups. There was strong evidence that plasma testosterone levels are positively correlated with urinary felinine levels in male cats. The control of felinine might be sex-linked and may be part of a pheromonal signaling process of the male cat.

SEASONAL HAIR GROWTH IN THE ADULT DOMESTIC CAT (FELIS CATUS)

Determination of amino acid requirements by the factorial method requires an estimate of the amount of amino acids required for the replacement of hair. Hair growth rates in a total of 39 adult male and female domestic short-haired cats were determined throughout the year using the mid-side patch technique. The ratio of hair on the mid-side area to total hair on the body was also determined to allow conversion of mid-side hair growth rates to hair growth rates over the entire body. The mid-side hair growth rate showed a sinusoidal pattern throughout the year, similar to that found for day length and daily mean air temperature, with a maximum hair growth rate of 289 μg/cm2/day in summer and a minimum hair growth rate of 62 μg/cm2/day in winter. The peak hair growth rate for the female cats was reached earlier than that for the male cats. Sine-functions describing day length, minimum and maximum daily air temperatures and daily hair growth rates are presented. Adult domestic short-haired cats were found to grow 32.7 g of hair per kg body weight per year. Monthly amounts of hair growth per unit of body weight and body surface area are calculated.

The amino acid composition of cat (Felis catus) hair

The amino acid composition of cat hair was determined by conventional 24-h acid hydrolysis and non-linear least-squares extrapolation to time zero of the amino acid composition data from a series of hydrolysis intervals. Twenty-five individual samples of cat hair, consisting of four colours, were also analysed (24-h hydrolysis) to determine if there was an effect of hair colour on amino acid composition. Amino acids were determined following HCl hydrolysis (6 mol/l) with cysteine and methionine determined by performic acid oxidation of the sample prior to hydrolysis. There was no significant (P > 0·05) effect of hair colour on the amino acid composition of cat hair. The non-linear compartmental model used to determine the amino acid composition of cat hair took into account the simultaneously occurring processes of hydrolysis and degradation of amino acids over time. The amino acids cysteic acid, methionine-sulphone, threonine and serine exhibited high loss rates during 6 molll HCl hydrolysis while the peptide bonds involving valine and leucine were slowly hydrolysed. Amino acid nitrogen accounted for 0·94 of the total nitrogen in cat hair when determined by conventional 24-h hydrolysis and 0·99 of the total nitrogen when the compartmental model was applied. The average nitrogen proportion in cat hair protein was found to be 0·175. The amino acid composition of cat hair protein is comparable with that of dog, horse, sheep and human hair although the proline content of cat hair protein appears to be lower than that in the other species.

An accurate method for the preparation and analysis of the composition of animal tissue

Abstract A method for the routine preparation and analysis of the components of animal tissues is described. Tissues are reduced to a finely divided homogeneous dry state by autoclaving, homogenizing, freeze-drying and then further grinding in a high speed rotary grinder. Fat is analysed by a chloroform:methanol:water solvent partition method which is less expensive, quicker, safer and more accurate than traditional methods using petroleum ether. Estimates of precision gave an average within assay coefficient of variation of 0.56% for four-replicate recoveries of pure lipid. Ash is estimated by muffle furnace firing. Protein can be accurately calculated from estimates of dry matter, fat and ash obviating the nitrogen estimation method of Kjeldahl.

The ventromedial nucleus of the hypothalamus of sheep (Ovis aries) and the effects on food and water intake following its electrolytic destruction.

A description is presented of the ventromedial nucleus of the hypothalamus (VMN) of sheep following study of paraffin-embedded material stained with a Nissl and a myelin stain. The VMN is related to most structures in the ventrobasal hypothalamus and is ellipsoidally shaped with its poles tilted both medially and anteriorly. Three kinds of neurons can be distinguished under the high power of the light microscope, and other cellular variants are probably the three basic types seen in different orientations. The commonest neuron had bipolar processes and a basophilic line structure apparently curving over the surface of the nucleus. The food and water intake of four sheep with discrete destruction of the VMN is described and compared with sheep with anterior hypothalamic lesions and controls. Discrete destruction of the VMN was without effect on food and water intake. The conclusion is reached that more lateral and ventrolateral areas of the tuberal hypothalamus might be involved in satiety regulation in the sheep.