Rowett Research Institute

About: Rowett Research Institute is a based out in . It is known for research contribution in the topics: Rumen & Population. The organization has 2986 authors who have published 4459 publications receiving 239472 citations.

Some factors controlling food intake by zinc-deficient rats.

Abstract: 1. Male hooded Lister rats given a diet containing 40 mg zinc/kg were described as Zn-adequate. Other rats were subsequently given diets containing less than 1 mg Zn/kg. After a period of approximately 5 d these animals ceased to grow and were described as Zn-deficient.2. Zn-deficient rats offered ad lib. a Zn-deficient diet containing 200 g egg albumen/kg ate only 55% of the weight eaten by Zn-adequate rats given a similar diet supplemented with Zn. The intake of the deficient rats increased when the metabolizable energy content of the diet was decreased and also when the environmental temperature was lowered.3. Zn-deficient rats offered Zn-deficient diets containing 200 g egg albumen/kg showed a high day-to-day variability of intake. When the albumen content was raised to 400 g/kg, neither the mean food intake of the rats nor the variability of food intake changed, but with diets containing only 50 g albumen/kg the quantity eaten increased and the variability of food intake decreased. Results obtained when the low-protein diet was supplemented with essential and non-essential amino acids indicated that increased variability of intake was associated with the essential amino acid content of the diet. The effect on variability of intake was greatest when the supplements contained methionine, phenylalanine, threonine and tryptophan; addition of this group of amino acids to a Zn-supplemented, low-protein diet produced the largest increase in the growth rate of Zn-adequate rats.4. When the food intake of the rats was examined for periods of 2 h throughtout the day, the Zn-deficient rats were found to eat on fewer occasions than the control rats. However, in those periods when the Zn-deficient rats did eat, the quantities eaten in 2 h showed the same distribution of weights as did those for the Zn-adequate rats.5. There were significant relationships between food intake and plasma Zn concentration; the most significant was the negative correlation between food intake in 24 h and plasma Zn concentration at the end of the 24 h period.6. Zn deficiency resulted in a failure of growth in the young rat and therefore in a reduction in its rate of energy expenditure but did not appear to cause directly a loss of appetite. It is suggested that cyclical patterns of food intake associated with Zn deficiency in young rats resulted from the slow but effective control of food intake by the energy balance of the animals.

High and low carbohydrate and fat intakes: limits imposed by appetite and palatability and their implications for energy balance.

Abstract: This report examines several issues concerning the effects of dietary fats and carbohydrates (CHOs) on body weight and the limits set on the intake of these nutrients by factors influencing appetite control: (i) the physiological relationship between feeding behaviour (FB) and body weight; (ii) the distribution of nutrients in Western foods and the implications this may have for FB; (iii) the contribution of nutrients in the diet, to total EI under both extreme and typical Western conditions; (iv) the known effects that fats, CHOs and dietary energy density (ED) exert on appetite and energy balance (EB); (v) the potential role of sensory factors in promoting or limiting fat, CHO and energy intakes (EI) in modern human populations Population studies and large surveys have identified individuals with wide ranges of fat and CHO intakes. Intakes of fat can vary from an average of 180 g/day to 25 g/day in a representative sample. But on individual days fat intake can rise to well over 200 g according to a selection of high fat foods. In a single meal, people can consume an amount of fat greater than the population daily average. From this analysis it can be deduced that the appetite control mechanism will permit the consumption of large amounts of fat (if an abundance of high fat foods exist in the food supply). Except for specific physiological circumstances (e.g. endurance explorers) where there is an urgent need for EIs, in the face of decreasing body weight, it is unlikely that the body will generate a specific drive for fat. Because CHO foods have a lower ED than fat foods (on average) and because of their greater satiating capacity, the free intake of high CHO foods is likely to be self-limiting (at lower EIs than those generated by fatty foods). This does not mean that excess EIs are impossible when people feed ad libitum on high CHO diets.

Glycosidases in mammalian sperm and seminal plasma.

Abstract: PREVIOUS investigations of animal glycosidases have shown that certain enzymes of this group occur in a state of particularly high activity in reproductive organs; for example, β-glucuronidase in the preputial glands of the female rat1, and β-N-acetyl-glucosaminidase and α-mannosidase in the epididymis of the male rat2. Preliminary results indicated high α-mannosidase, and relatively low β-N-acetylglucosaminidase, activity in rat epididymal sperm, whereas the high activity of both enzymes in bull semen was largely confined to the seminal plasma (Conchie, J., and Levvy, G. A., unpublished work). It was the object of the present investigation to extend the study of these enzymes to the sperm, seminal plasma and male accessory secretions of other animals, and also to compare the activity of the three glycosidases mentioned with that of other similar enzymes, namely, β-mannosidase, α- and β-glucosidase, α- and β-galactosidase, β-xylosidase and α-N-acetylglucosaminidase. The substrates used were phenolphthalein glucuronide and the phenol and o- or p-nitrophenol derivatives of other glycosides3. Results are expressed in units, defined as micrograms of aglycone (phenolphthalein, phenol and o- or p-nitrophenol, respectively) liberated under suitable conditions2,3 by 1 ml. semen or accessory gland secretion in 1 hr. at 37° C. Results for sperm are calculated on the original volume of semen. The species investigated include the ram, bull, boar, stallion, rabbit, dog and man.

Molecular cloning of genes from Ruminococcus flavefaciens encoding xylanase and beta(1-3,1-4)glucanase activities.

Abstract: Clones expressing activity against xylan or beta(1-3,1-4)glucan (lichenan) were isolated from a library of Ruminococcus flavefaciens 17 DNA made in bacteriophage lambda EMBL3. Hybridization analyses indicated the recovery of four separate genes encoding xylanases that showed no detectable associated carboxylmethylcellulase activity. One of these genes was associated with clones that also expressed beta(1-3,1-4)glucanase and beta-xylosidase activities.