Showing papers on "Low protein published in 1977"

Effect of protein A on staphylococcal opsonization.

Abstract: To study the effect of wall protein A on bacterial opsonization, phagocytosis of 10 strains of Staphylococcus aureus with high and low protein A contents was measured. Those strains that contained the highest concentrations of protein A were phagocytized by human neutrophils at a slower rate than strains with little or no protein A when normal human serum and purified immunoglobulin G (IgG) were used as opsonic sources. When IgG-deficient serum was used as an source, however, protein A-rich strains were phagocytized more rapidly than protein A-deficient strains. Extracellular (purified) protein A decrease the opsonic activity of all sera tested including IgG-deficient serum. It is proposed that when IgG is not present in the opsonic medium, cell wall protein A is capable of activating complement at the bacterial surface and thereby opsonization is promoted.

Structural study of spectrin from human erythrocyte membranes.

Abstract: Human erythrocyte spectrin prepared from fresh blood is a mixture of different association states. Depending on the manner of preparation, the two-chain dimer or the tetramer predominates. These forms are not in rapid thermodynamic equilibrium. The molecular weight of the dimer by sedimentation and diffusion and by light scattering is about 5 X 10(5). The frictional properties indicate a low or moderate asymmetry (axial ratio in the range 2-10), and from the angular dependence of light scattering intensity an upper limit of about 80 A can be set for the radius of gyration. The tetramer similarly has a moderate asymmetry. Electron microscopy reveals that the dimer is a compact, slightly elongated molecule, and that the tetramer probably consists of two parallel dimers. On increasing the concentration of solutions containing spectrin dimers, oligomers are formed, which are not rapidly dissociated on dilution. At very low protein concentrations (below about 0.05 mg/mL) there is evidence of the onset of a rapid dissociation equilibrium between dimers and single chains. Other physical properties of the spectrin have been measured. The size and shape of the spectrin molecule would seem to rule out any major physical resemblance to myosin.

Kidney Function in Calcium and Phosphate Metabolism

Abstract: Publisher Summary This chapter discusses the kidney function in calcium and phosphate metabolism. Production of urine is the most conspicuous expression of kidney function but not the most significant always. The amount of phosphate excreted per day is equal to the amount of phosphate adsorbed from the diet. The average diet contains about 1500 mg phosphate per day, and the average 24-hour renal excretion of phosphate is about 600 mg. Variations in intake and urinary output are closely related. The most common cause of a low phosphate excretion rate is a phosphate-poor diet—such as low protein or low calcium diets—or administration of aluminum hydroxyde gels, which bind phosphate in the gut. Phosphate reabsorption is decreased in primary and secondary hyperparathyroidism and increased in hypoparathyroidism. A chronic high phosphate intake produces a steady state with reduced tubular reabsorption of phosphate, reduced calcium excretion, normocalcemia or slight hypocalcemia, increased immunoreactive parathyroid hormone serum level, and parathyroid hyperplasia. Chronic renal failure with decreased glomerular filtration rate is associated with bone disease.

Biochemical characteristics of different forms of protein-energy malnutrition: an experimental model using young rats.

Abstract: I In three separate experiments, four groups of five to eight young male rats were fed either (i) a high-protein diet, for which the net dietary protein:total metabolizable energy ratio (NDp:E) was 0-1 (HP diet); or (ii) a low-protein diet, for which NDp:E was 0-04 (LP diet) In both these groups, food intake was ad lib In group (iii) the HP diet was given in an amount approximately equal to that taken by the LP group fed ad lib (HP-restricted) In group (iv) rats were fasted for 48 h after receiving the HP diet (HP-fasted) Each experiment lasted 4 weeks 2 In the LP and HP-restricted groups, food intake was about 50% of that of the HP rats, while body-weight, after 4 weeks on diet was about 35% and 55% of that of HP rats, for LP and HP-restricted respectively Both groups of malnourished rats gained some weight during the experiment 3 Measurements of oral glucose tolerance and plasma insulin levels were made in the fourth week LP and HP-restricted rats both showed low fasting insulin levels and low insulin to glucose ratios during the glucose tolerance tests; the LP rats were more seriously affected 4 At the end of the fourth week the rats were killed and blood, liver and gastrocnemius muscle were analysed LP rats showed specifically and consistently low values for haemoglobin and plasma protein concentration, and low activities of hepatic glucose-6-phosphatase (EC 3-1-3-9) and of alanine aminotransferase (EC 2612) in liver and muscle The activity of hepatic aspartate aminotransferase (EC 2611) was, if anything, increased The plasma amino acid concentrations and ratios showed a specific fall in branched-chain amino acids Liver fat concentration was consistently elevated The HP-restricted rats had normal values for haemoglobin, plasma protein andliver fat, and near-normal values for plasma amino acids Hepatic alanine aminotransferase showed increased activity compared with HP rats, but muscle alanine aminotransferase showed reduced activity The HP-fasted rats had increased haemoglobin, plasma protein and liver fat concentration, and very low liver glycogen concentrations Hepatic alanine aminotransferase activity was elevated Plasma alanine concentration was specifically reduced 5 The results are consistent with suppression of gluconeogenesis, liver dysfunction and essential amino acid deprivation in LP rats These biochemical changes found in rats on a low intake of a diet of low protein and high carbohydrate value are similar to those found in kwashiorkor An equally low intake of a diet of good protein value (HP-restricted) led to marginally better growth, accompanied by biochemical signs of increased gluconeogenesis, analogous to those reported for nutritional marasmus This nutritional state was not biochemically identical with that of acute fasting 6 The results are discussed in terms of the consistency of the rat model, and its contribution to understanding biochemical changes found in infant malnutrition

Excretion in mammals: role of the renal pelvis in the modification of the urinary concentration and composition.

Abstract: The mammalian renal pelvis has previously been regarded as having no physiological function other than that of a receptacle for the urine before it moves through the ureter. It has long been known that the renal pelvis in mammals shows elaborate extensions that bring the urine in intimate contact with outer and inner medullary tissue. The epithelium covering these areas is of a type that indicates that transport of solutes and water can take place across it. Physiological studies have shown that urea and water readily move across the renal papillary epithelium. The pronounced ability of ruminants to conserve urea when placed on a low protein diet coincides with a highly developed renal pelvis with specialized fornices and secondary pouches. It is suggested that urea conservation in low protein animals takes place partly in the renal pelvic extensions where urea is returned to the blood. A hypothesis is also proposed for the concentrating mechanism in which recycling of urea from the pelvic urine across the papillary epithelium plays an important role.

Flexibility of myosin rod, light meromyosin, and myosin subfragment-2 in solution

Abstract: Myosin rod was prepared by papain proteolysis of myosin. The components of rod, light meromyosin (LMM) and subfragment-2 (S-2), were prepared by proteolysis of myosin and rod, respectively, using trypsin treated with tosylphenylalanine chloromethyl ketone. S-2, thus prepared, was of greater molecular weight than obtained previously, so that the combined molecular weights of LMM and S-2 were equal to that of rod, and S-2 contained virtually all of the region of the rod susceptible to trypsin. Electro-optical measurements were made on the three fragments in 2 mM sodium pyrophosphate, pH 9.3 at 3 degrees, over a large range of protein concentrations. Analysis of the relaxation of birefringence, at low protein concentration where there was no aggregation, showed that LMM (relaxation time 13.1 micros) behaves as a rigid cylinder. Rod (relaxation time 41.2 micros) and S-2 (relaxation time 6.0 micros) had relaxation rates that were too fast for rigid molecules of their dimensions, and therefore are not straight rods. This implies that myosin rod is flexible in the S-2 portion, presumably in the region susceptible to proteolysis. The implications of rod flexibility for the mechanism of muscle contraction are discussed.

Principles for the use of non-protein nitrogen and bypass proteins in diets of ruminants.

Abstract: The apparent inefficiency of ruminants compared with monogastric animals in utilising protein rich feeds has been used as an argument to emphasise the importance of monogastric animals in preference to ruminants for meat production. Recent studies however (see Preston & Willis, 1970 ; flrskov, Fraser, McDonald & Smart, 1974 ; Kempton & Leng, J-976 ), have indicated that with correct balancing of digestible nutrients, ruminants given feed of apparently variable quality can grow at rates much greater than those generally reported ($rskov, 1976). These results have been achieved with approximately 50 70% of the usual recommended requirements for protein in a diet. Ruminants are therefore potentially highly efficient users of protein feeds under a variety of agricultural situations, including the utilization of low protein by-products of agro-industries.

The Effect of Dietary Lysine Level on the Energy and Nitrogen Balance of the Dark-Eyed Junco

Abstract: Our knowledge of dietary requirements of passerine birds is severely limited, but it has been found (Martin 1968) that Tree Sparrows (Spixellu arborea) can maintain positive weight, nitrogen balance, and energy balance when fed an 8.7% protein diet which supplies 4,060 calories per gram. Diets with approximately the same caloric content, but lower protein contents (2.5% and 4.9%) are not adequate for maintenance; one of higher protein content (16.9%) results in wastage of protein. Low protein diets (about 9%) also have been found to be adequate for maintenance in House Sparrows (Passer domesticus) (Martin, unpubl. data). Nevertheless, standard poultry diets that have been fed to passerine birds in bioenergetic studies in recent years usually contained 14-16% protein with combustible energy contents of about 4,000 Cal/g (Kendeigh 1949, Seibert 1949, Zimmerman 1965, Brenner 1966, Brooks 196S, Helms 1968, Kontogiannis 1968). Although the essential amino acid requirements have been studied extensively in commercially important fowl (NRC 1966), they have not been investigated in passerine birds. The purpose of our study was to investigate the maintenance energy and nitrogen balance of the Dark-eyed Junco (Junco hyemalis) when fed amino acid-supplemented 8% protein wheat diets. We chose the requirement for lysine for study because lysine is often a major limiting amino acid in Gramineae seeds (Block and Weiss 1956, Orr and Watt 1957), and such seeds are the predominant winter food of the junco and many other granivorous passerines (Martin et al. 1951).

Low molecular weight organic acids in the urine of the newborn

Abstract: The urinary excretion of seven selected low molecular weight organic acids in normal neonates was measured by gas chromatography. First and third to fourth day of life excretion of the following compounds was significantly unchanged: 3-OH-butyric acid (less than 13 mumol/mmol creatinine), succinic acid (approx. 43 mumol/mmol creatinine), adipic acid (approx. 12 mumol/mmol creatinine), 2-OH-glutaric acid (approx. 23 mumol/mmol creatinine), 3-OH-3-Me-glutaric acid (approx. 25 mumol/mmol creatinine) and citric acid (approx. 115 mumol/mmol creatinine). The excretion of 4-OH-phenyl-acetic acid increased during the first four days of life (from less than 8 mumol/mmol creatinine to approx. 20 mumol/mmol creatinine). It is postulated that urinary orgainc acid excretion in the neonate, which is clearly different from the adult urinary pattern, is a reflection of the specific neonatal metabolic situation, including a high fatty acid utilisation and a low protein catabolism.

Wheat Protein Premiums and Price Differentials

Abstract: supply shifter for a product is the price of its closest substitute. Frequently, the substitute is a different quality, grade, or brand of the same commodity. (Tomek and Robinson provide a useful discussion on price differences, pp. 134-43.) These differences cannot be examined in empirical work where aggregate functions rather than separate, closely related functions are estimated. The research reported in this note investigates the relationships between different qualities of a commodity, adding to the sparse body of empirical work on this topic. A Lancaster "product characteristics" approach is used in differentiating classes of wheat by their protein content characteristic.1 The specific objective is to generate a simple statistical model for analyzing the effect of changes in available supplies of wheat of various protein content on their relative prices. Prediction rather than complete behavioral understanding is the goal. Historically, high protein wheats have been relatively scarce, bringing a higher price than lower protein wheats. The price differential is commonly called a "protein premium." The amount of premium for wheats of various protein content varies in response to changing supplies of, and demand for, the protein component of wheat. Demand for high protein wheat is derived from the demand for bread. The demand for low protein wheat is derived from the demand for biscuits, cakes and pastries, and livestock products.2 Occasionally, little or no premium is paid for protein. This occurred, for example, during several months in 1972, 1973, and 1974, a period when U.S. exports soared. Earlier research to investigate a possible negative impact of exports on protein premia found that supply factors were associated with much of the variability in the premia (Ryan and Bale, p. 31). Accordingly, this note focuses on the role of supply factors on relative price movements. Protein is regarded as the differentiating characteristic in wheat. Since the object of this note is to estimate price variations, two price dependent functions of wheats of two different protein contents are specified. The quantity supplied of each commodity is assumed to be predetermined. No short-run supply response is possible because productio and carry-in stocks are determined in the previous time period. Only one demand shifter is explicitly specified for each function-the quantity of the major competing wheat. From the two price dependent functions, one function is formed for estimation, equation (1). The dependent variable is a ratio of the prices of the wheats. The price ratio defines protein premium rather than the more usual definition of price differences (Hyslop). We prefer a price ratio, since it avoids the need to deflate prices. The ratio can, of course, be converted to an absolute difference at any given level of either price:

Relationship between composition, stability and rheological properties of raw comminuted meat batters

Abstract: The rheological constants for sausage meat batters of varying composition were determined using a tube viscometer. Values for shear stress as a function of the rate of shear were fitted to the power law model of a fluid having a yield stress. Seven formulations were tested varying in composition from 20–60% fat, 30–60% water, and 9–18% protein, from mixtures of boneless beef, beef plates and flanks, and pork back fat. An eighth batter chopped from 100% pork back fat was also evaluated. Values for the power law coefficient ranged from 140–8,580 (in dyne-set/cm2 units), the power law exponent ranged from 0.104–0.722, (dimensionless) and the yield stress ranged from 0–278 (dynes/cm2). The formulations having high fat and low protein contents had lower values for the coefficient, and higher values for the exponent, in spite of their lower water contents compared to the rest of the batters. Among the formulations, there appears to be no direct relationship between the magnitude of the rheological constants and the stability measured as the amount of fat and water released during heating. However, in two of the formulations having exactly the same fat, water, and protein contents but made up of different proportions of the meats used, the more stable formulation showed a higher value for the coefficient and a lower value for the exponent when compared to the unstable formulation.

Growth in White-Tailed Deer Fawns Fed Varying Energy and Constant Protein

Abstract: In the fall a 40 percent restriction in energy intake caused a 76 percent reduction in body fat deposition but no significant decrease in body weight or protein deposition (P > 0.05). As energy intake was restricted, urine nitrogen increased suggesting use of dietary protein for energy. J. WILDL. MANAGE. 41(3):506-510 One major determinant of size of whitetailed deer populations, especially in Northern ranges, is winter survival of fawns. Undernutrition often is evident. Thompson et al. (1973) estimated the maintenance metabolizable energy (ME) requirement of fawns in October to be 166 kcal per kilogram metabolic body weight (WO.75). Subsequently, Holter et al. (1977) found a corresponding value of 162 in yearlings in May through October. Although energy usually is the most critical factor in deer nutrition, the work of Murphy and Coates (1966) suggested that low protein content in foods may account for low productivity and suboptimal growth. Smith et al. (1975), studying fawns in September through December, found optimum body protein deposition when daily intake of digestible nitrogen was about 3 g/kgWo.75; diet dry matter contained 2.5 kcal ME/g. However, reduction in protein deposition (growth) was not great when digestible nitrogen intake was reduced to approximately 2 g/kgW075 because urinary nitrogen loss declined markedly. Yet little is known about the energy needs of deer, especially that needed above maintenance for productive functions, and the amount of deprivation that can be tolerated without seriously affecting growth and body size. The objective of this study was to observe in weaned fawns the effect on growth and body composition of a diet offered in increme ts below ad libitum intake. Daily protein intake was held constant. The authors gratefully acknowledge technical support of H. A. Davis, B. Mueller, T. Kenna, and E. Poff.

Whole-body albumin mass and distribution in rats fed on low-protein diets

Abstract: 1 From 5 weeks of age, control and experimental rats were given diets containing 210 and 31 g protein/kg respectively, and killed for analysis at 0, 2, 5, 8, 12 and 20 d after the start of the experiment At these times estimates were made of plasma albumin concentration, plasma volume and total vascular and extravascular albumin mass 2 Plasma albumin concentrations were significantly lower in the experimental animals when compared to controls at 8, 12 and 20 d but plasma volumes (ml/kg body-weight) tended to be greater in the former animals Total vascular albumin mass (g/kg body-weight) was significantly less in experimental animals compared to controls at 8 and 20 d, but was significantly reduced below values at 0 d only at 20 d 3 extravascular albumin mass (g/kg body-weight) was significantly lower in experimental animals in comparison with controls at 2, 5, 8, 12 and 20 d and significantly reduced below values at 0 d at 5, 8, 12, and 20 d 4 Whole-body albumin mass was significantly reduced at 5, 8, 12 and 20 d when compared both with controls killed at the same time and animals killed at 0 d Measurement of the ratio, extravascular albumin mass: vascular albumin mass indicated a significant redistribution of whole-body albumin mass at 5 and 20 d and mean values for this ratio were always lower in experimental animals than in controls 5 It was concluded that measurement of plasma albumin concentration does not indicate the true extent of whole-body albumin losses in protein deficiency since total vascular albumin mass is, to some extent, maintained at the expense of extravascular albumin mass

Energy and protein intake in elderly patients in an orthopedic surgical ward.

Abstract: A study was made during a 3-month period of the food intake of all patients older than 60 years, who were admitted to a ward of acute orthopedic surgery. This amounted to 31 women and 15 men, whose average age was 74 years. Each patient's diet was studied for 16 days on an average. The mean daily energy intake was 1 163+/-341 kcal (4 868 +/- 1 427 kJ) for women and 1 558+/-539 kcal (6 521+/-2 856 kJ) for men. 44 of 46 patients received fewer calories than is recommended for healthy persons the same age, and 25 of 46 patients consumed less calories per day than the basal metabolism. The mean daily protein intake was 0.7+/-0.3 g/kg/day for both men and women. 28 of the patients received less than 0.8 g/kg/day which is the amount of protein recommended healthy adults and none of our patients received 1.5 g protein/kg/day, the protein intake recommended patients in hospital. The low protein intake was due to a poor intake of energy as well as a high consumption of refreshing drinks and titbits, both a little nourishment.

Energy requirements for the synthesis of body proteins during growth as determined in model experiments in rats. 2. Studies with dietary casein and wheat gluten used unsupplemented or supplemented with methionine or lysine

Abstract: Rats were used in 7 trials each comprising 9 animals (197 total metabolism trials carried out at an environmental temperature of 30 degree). The animals received casein, casein+methionine, wheat gluten, wheat gluten+lysine as protein sources and were investigated for their nitrogen and energy turnover. The rations fed contained between 10% and 27% protein. Supplementation of the natural proteins with synthetic amino acids positively influenced the growth rate and the rate of N retention. The feeding of wheat gluten as sole protein source induced an absolute depression of the food and energy intake. The rates of tetention of protein and fat energy per animal/day showed opposing trends, in dependence upon the protein levels in the rations. It was found in the trials with casein that the proteins yielded 25%, or 18% of the total energy retention if the rats received low protein rations while the percentage of protein energy retention increased to 49-53%, if the rations contained high protein levels. The rats utilized between 67% and 84% of the metabolizable energy for the turnover of body energy. A negative correlation was found between the levels of energy utilization and protein intake. The energy demends for protein retention were calculated (mean of all trials) to be 1.67 kcal of metabolizable energy while those for fat retention amounted to 1.15 kcal. The energy demands for protein retention were not found to be dependent on the type of protein source used. The maintenance requirements of the rats were 102 kcal of metabolizable energy per kg LM0,75.

Relation of protein nutrition to the reduction of red blood cells induced by physical training.

Abstract: Sports anemia induced by tennis training or exercising on a bicycle ergometer was studied in healthy male students. Since the anemia has been attributed to an increased susceptibility of red blood cells to lysis during exercise and influence by the nutritional status of the individuals has been suggested, the relation of sports anemia to the nutritional conditions of the subjects and to osmotic fragility of red cells were studied in groups by controlling protein levels in diets. Anemia was most pronounced and the recovery from it was most prolonged in subjects with low protein diets, while it was least pronounced and the recovery was most rapid in subjects with high protein diets. The extent of increase in osmotic fragility of red cells was highest in subjects with low protein diets, and lowest in subjects with high protein diets. The erythropoietic responses to the exercise were different among the dietary groups; i.e., an early increase in blood reticulocytes in subjects with high protein diets and a late increase in subjects with low protein diets were observed during the course of training. From above observations, we conclude that the extent of anemia is closely related to protein intake from the diets and that it is one of adaptive processes of individuals to stenuous physical training rather than an exaggeration of the physiological process of erythrocyte destruction.

Diet, DDT, and the toxicity of drugs and chemicals.

Abstract: The toxic and carcinogenic effects of many compounds depend on their activation to reactive molecules in the cytochrome P-450 system of the endoplasmic reticulum of cells. Changes in dietary input alter P-450 levels in different tissues and so alter toxicity. In this way, low protein diets protect against carbon tetrachloride poisoning. Fats, proteins, and nonnutrients such as flavones, antioxidants, and contaminants like DDT all affect P-450 levels. The activated molecules may be diverted from their target sites by inactivation processes, such as epoxide hydratase or glutathione trappin. This is also under nutritional control. Low protein diets render animals sensitive to acetaminophen by reducing glutathione levels. In the sequence of events leading from initial contact of toxin with organism to eventual cell injury or neoplasm, nutritional factors are of import at every stage. Assessments of the toxicity of chemicals that do not take into account the nutritional variable in man are likely to be incorrect.

The impact of contamination by organochlorine insecticides on poultry nutrition and feeding.

Abstract: Nutrient interactions with organochlorine insecticides have been described primarily for vitamin A and protein. Storage of liver vitamin A is reduced by DDT and dieldrin. Low protein diets protect rats from heptachlor toxicity, whereas the toxicity of DDT, dieldrin and lindane is reduced by increasing the quantity and quality of diet protein intake. Biological performance of poultry is adversely affected by 50 to 500 ppm of most of these compounds. Hatchability of eggs and survival of chicks from hens fed insecticides are usually the most sensitive parameters of toxicity. Higher levels of DDT decrease thyroid activity. While several insecticides reduce egg shell thickness in wild birds, such changes are not observed in poultry. Extensive low level contamination of poultry tissues and eggs results from the organochlorine insecticides, with the exception of methoxychlor where tissue residues are not a problem. Tissue and egg accumulation of residues is related to dose but quantitatively different for each organochlorine compound. Tissue withdrawal and excretion takes place slowly and most of the compounds are metabolized by liver hydroxylating enzymes to various derivatives that are also stored in the body. In one case (heptachlor epoxide), the oxidation product is more toxic than the body. In one case (heptachlor epoxide), the oxidation product is more toxic than the parent compound.

Periodic hyperammonemia, hyperlysinemia, and homocitrullinuria associated with decreased argininosuccinate synthetase and arginase activities.

Abstract: Summary: An 18-year-old mentally and physically retarded male with periodic hyperammonemia is described. Levels of lysine and citrulline in his serum and those of blood ammonia were elevated and daily excretions of homocitrulline in his urine were strikingly high on an ordinary diet. With a decrease in protein intake to 1.5 g/kg body weight/day, only urinary homocitrulline excretion remained about 10 times higher than the normal values whereas the other amino acids in his serum and urine appeared to he within the normal range. After an oral load of lysine on a normal protein intake, several abnormal findings were observed. That is, clinically he had episodes of irritability, vomiting, and coma caused by ammonia intoxication. Biochemically, levels of citrulline and arginine in his serum and the urinary homocitrulline excretion rate continued to increase and arginase in the blood cells was markedly depressed. Blood cell arginase, which showed lower activity than that of control subjects, particularly on a normal protein intake, was extremely inhibited by lysine in the in vitro experiment. The citrulline tolerance curve after the load of L-citrulline was found to be normal on a low protein intake. Lysine:NAD-oxidoreductase activity in the liver was near the lower limits of the control values. The activity of argininosuccinate synthetase (ArgSS) was reduced to 22% of the control values. Arginase activity was also reduced. Speculation: Hyperlysinemia, hypercitrullinemia, and massive homocitrullinuria found in our patient may he due to a partial defect of ArgSS, which has affinity for both citrulline and homocitrulline. We speculate that impairment of ammonia disposal participates in the deficiency of ArgSS as well as arginase.

The influence of dietary protein insufficiency on the murine thymus. Evidence for an intrathymic pool of progenitor cells capable of thymus regeneration after severe atrophy.

Abstract: Low protein diets initiated at wearning in Balb/c mice cause a rapid and profound reduction in thymus weight and cellularity. Thymus weight falls to less than that of involuted thymus of adult mice and remains depressed for as long as diets are fed. Although most peripheral T cell functions do not appear to be depressed, suppressor cell activity was not as vigorous in deprived animals despite the presence of functional suppressor populations. Thymus growth was reinitiated promptly when high protein diets were fed to deprived animals. Thymus regeneration appeared to be due to both a resident population of stem cells which persisted in the thymus through the period of deprivation and a second, probably bone-marrow derived, population of stem cells. It is suggested that in normal mice the synchronized growth of the first population produces the characteristic innate growth pattern of the thymus. This is superimposed on the growth of the second population which continuously seeds the thymus and is constantly replaced. Protein deprivation severely restricts the growth of the first and second population, but both maintain their capacity for growth during long periods of protein restriction.

Infection of weanling pigs with known numbers of Ascaris suum fourth stage larvae.

Abstract: Nineteen weanling pigs were each infected per os with 200 fourth stage Ascaris serum larvae and were fed either a low protein or a high protein diet for 8 weeks. Worms expelled during the 8 weeks were recovered and all worms remaining in the gastrointestinal tract at slaughter were collected. Fifty-four percent of all worms were recovered at slaughter. Ten of the 19 animals maintained an infection for 8 weeks; the other 9 showed no signs of A. suum infection. A total of 377 worms were recovered. Average worm burdens were 37.7 worms per pig, 50.8 worms per low protein pig, and 30.8 worms per high protein pig. Times of and possible causes for expulsion are discussed. Procedure for infection of pigs is discussed in detail and possible improvements in technique are suggested.