An unexpected life in nutrition

In this biographical article, I describe the evolution of my career in nutrition from an early period as an animal nutritionist interested in amino acid metabolism and genetic variation in nutrient requirements to an involvement in human nutrition and international public health. The career changes were in some respects a mirror of the evolution of nutritional science in my lifetime. I spent my entire career at Cornell University in what I think of as three distinct phases. As a researcher and teacher in the Poultry Science Department, I was able to do research in animal nutrition and witness the rapid industrialization of the production of poultry meat and eggs, helped by the findings of the era of nutrient discovery in nutritional science. Later I had the opportunity to lead the reorganization of human nutrition at Cornell during a period when research in nutritional science turned away from identifying new nutrients and became increasingly concerned with the roles of diet and chronic disease. During this period my research focus evolved as I became interested in aspects of international nutrition problems, particularly the influence of parasitic infections on child health and nutrition. I also became involved nationally in nutrition issues through participation in organizations such as the National Nutrition Consortium, the Food and Nutrition Board, and National Institutes of Health study sections at a time of great ferment in nutrition about the relationship of dietary patterns to health. Finally, I became provost of Cornell University and involved in the administration of a major research university. I describe my career in the context of my origins and early education springing from life on a sustainable family farm in rural Illinois.

Maternal income-generating activities, child care, and child nutrition in Mali

BACKGROUND

Women in sub-Saharan Africa play a key role in household food security. The income-generating activities of mothers are postulated to be related to the nutritional status of children.

OBJECTIVE

The objective of the study was to examine whether maternal income-generating activities, maternal food production, and child care were determinants of the nutritional status of children in rural West Africa. The study hypotheses were that maternal income-generating activities and maternal food production are positively associated with children's dietary intake and anthropometry, and that maternal income-generating activities are not associated with child care.

METHODS

Data were collected from a cross-sectional sample of mother-child pairs on maternal time use, child anthropometry, maternal food production, dietary intake, parasitic infection, and household, maternal, and child determinants of child nutritional status. The children were 12 to 36 months of age and included breastfed and nonbreastfed children. Food intake was assessed by the 24-hour recall method. The data were analyzed by multivariate regression and controlled for confounding variables.

RESULTS

Time spent by the mother in income-generating activities was negatively associated with children's animal protein intake and height-for-age (p < .05). Maternal cash crop production was positively associated with children's weight-for-height, whereas maternal staple food production was negatively associated with energy intake from non-breastmilk foods (p < .05). The negative relationships observed for children's animal protein intake and children's height-for-age were not mediated by any child-care variable. Maternal supervision of feeding was a positive predictor of children's animal protein intake. Giardia infection was negatively related to children's weight gain (p < .05).

CONCLUSIONS

Own-account cash crop farming by mothers benefits children's nutrition. Maternal income-generating activities in the context of extended families, sibling caretaking, and prolonged breastfeeding do not adversely affect child care.

Intermittent iron supplementation regimens are able to maintain safe maternal hemoglobin concentrations during pregnancy in Venezuela

Daily iron supplementation programs for pregnant women recommend amounts of iron that are considered by some to be excessive, and either lower-dose or less frequent iron supplementation regimens have been proposed. A randomized, placebo-controlled study was performed to assess and compare the relative effectiveness of a weekly (WS) or twice weekly (TW) iron supplementation schedule in maintaining or achieving hemoglobin (Hb) levels at term considered to carry minimal maternal and fetal risk (90-130 g/L). Pregnant women (n = 116) at wk 10-30 of gestation (63 WS and 53 TW) were enrolled in the study (52 in WS and 44 TW completed the study). Women were randomly allocated to receive a 120-mg oral dose of iron as ferrous sulfate and 0.5 mg of folic acid weekly (n = 52) or 60 mg iron and 0.25 mg folic acid and a placebo twice weekly (n = 44). Hb, hematocrit, serum ferritin, and transferrin saturation were estimated at baseline and at 36-39 wk of gestation. Baseline dietary data and the presence and intensity of intestinal helminthic infections were assessed. The duration of supplementation was 14 +/- 4 wk and the median level of adherence was 60.5%. Hb concentrations improved in women following the TW regimen and in women following WS who had low baseline Hb levels. About 89% of WS women and 95% of TW women maintained Hb levels at term (between 90 g/L and 130 g/L), a range associated with optimal pregnancy outcomes. One woman in the TW group exhibited higher Hb levels that potentially carried perinatal risk (>130 g/L). Intermittent iron and folic acid supplementation may be a valid strategy when used as a preventive intervention in prenatal care settings.

Nutritional impact of intestinal helminthiasis during the human life cycle

Poor people in developing countries endure the burden of disease caused by four common species of soil-transmitted nematode that inhabit the gastrointestinal tract. Disease accompanying these infections is manifested mainly as nutritional disturbance, with the differing infections having their deleterious effects at different phases during the human life cycle. Reduced food intake, impaired digestion, malabsorption, and poor growth rate are frequently observed in children suffering from ascariasis and trichuriasis. Poor iron status and iron deficiency anemia are the hallmarks of hookworm disease. The course and outcome of pregnancy, growth, and development during childhood and the extent of worker productivity are diminished during hookworm disease. Less is known about the impact of these infections in children under 2 years of age. The severity of disease caused by soil-transmitted nematodes has consistently been found to depend on the number of worms present per person. Cost-effective measures based on highly efficacious anthelminthic drugs are now available to reduce and control disease caused by these infections.

What is the research base for the use of dietary supplements?

The market for dietary supplements in the USA was estimated as about 11.8 billion dollars in 1997 with a growth rate of 10-14% projected in the next 3 years. Data from the Food and Drug Administration collected in 1995 indicate that over 55% of adults surveyed used some type of dietary supplement. The marketing of dietary supplements in the USA has been essentially deregulated by the passage of the Dietary Supplement Health and Education Act of 1994 (DSHEA). This legislation defined dietary supplements, made manufacturers responsible for the safety of supplements and allowed certain statements of nutrition support to be made on supplement labels. The US Congress in passing the DSHEA indicated that supplements should be available on the market so that consumers could make decisions about their use for themselves and their families. Unfortunately, information about the research base for supplement claims is not readily accessible to health professionals and consumers. There is a need for authoritative reviews of the data underlying supplement claims to assist public health professionals in their role of providing advice to the public about dietary supplements.

Serum retinol concentrations in children are affected by food sources of beta-carotene, fat intake, and anthelmintic drug treatment

The provision of vitamin A in food sources of beta-carotene is an alternative to the distribution of high-dose capsules. To examine factors that may influence the success of food-based programs, a study was carried out in Sumatra, Indonesia, of the effect of food sources of beta-carotene, extra dietary fat, and Ascaris lumbricoides infection on serum retinol concentrations in children. Meals and snacks with various amounts of beta-carotene and fat were fed at midday to children 3-6 y of age for 3 wk. Some groups of children were dewormed with the anthelmintic levamisole before the feeding period, whereas others remained infected. Results showed that the incorporation of beta-carotene sources (mainly in the form of red sweet potatoes) into the meal significantly increased serum retinol concentrations. The greatest rise in serum retinol occurred when meals contained added beta-carotene sources and added fat and the children were dewormed. Adding more fat to the meal and deworming the children caused a rise in serum retinol similar to that seen when feeding additional beta-carotene sources. Moreover, the effects of fat and deworming together were additive to the effects of additional beta-carotene sources. When the meal contained additional beta-carotene sources, added fat caused a further improvement in serum retinol concentrations but only if A. lumbricoides infection was low. These studies indicated that food-based interventions in vitamin A-deficient areas might be successful and that other interventions such as increasing dietary fat concentrations and anthelmintic treatment should be considered along with increasing consumption of beta-carotene-rich food.

Atwater initiative in food consumption

Trained as an agricultural chemist by the great German scientists of that time, Atwater applied this knowledge to understanding what people ate and the factors that effected food selection. He addressed many of the questions that are still important today. He wanted to use knowledge of food composition to help people make sound food choices within their economic constraints. In carrying out the first true dietary studies in the United States, he recognized many of the important criteria for such studies that impact on the accuracy and precision of the resulting data. Today, we still struggle with ways to improve the accuracy of food consumption studies while at the same time increasing the utility of the data for many users.

Dietary level of maize oil affects growth and lipid composition of Walker 256 carcinosarcoma

Walker 256 carcinosarcoma cells (1 x 10(4)) were injected into the right thigh muscle of Sprague-Dawley rats (125 g) consuming isoenergetic (200 g fat/kg) diets containing 20, 100 and 200 g maize oil/kg and 180, 100 or 0 g hydrogenated lard/kg respectively. Ten rats from each dietary regimen were killed every 4th day. Tumours grew rapidly from day 0 to day 8 post-transplant regardless of dietary regimen. However, after 8 d more tumours regressed and there were fewer deaths in animals fed on 200 g maize oil/kg compared with animals fed on 20 or 100 g maize oil/kg. Linoleic acid (LA) levels were higher in phospholipids (PL) of growing tumours than in regressing tumours whereas arachidonic acid levels in PL were lower in growing tumours indicating a possible alteration in the desaturation and elongation of LA. Serum prostaglandin E2 levels were slightly lower in rats with regressing tumours than in rats with growing tumours.

Human nutrition needs and parasitic infections

The series of articles that follow in this volume deals with specific aspects of how parasites might influence nutrient utilization by their human hosts. To put these aspects of parasitic disease in context, this contribution is intended to provide an overview of human nutritional needs and to introduce concepts of how nutritional consequences of parasitic infection might be viewed. Although parasitic diseases are often considered to be those caused by protozoa and helminths, the principles considered here can be applied to any infectious agent, including bacteria and viruses.

Haemoglobin concentrations and concomitant infections of hookworm and Trichuris trichiura in Panamanian primary schoolchildren

The blood haemoglobin concentrations and intestinal helminth infections were surveyed in 658 children aged between 6 and 12 years attending 4 primary schools in Coclé Province, Panama, in November 1987. 147 (22.3%) of the children were judged to have haemoglobin concentrations indicative of iron-deficiency anaemia. Blood haemoglobin concentrations were significantly lower in children with heavier Trichuris trichiura infections (> 5000 eggs/g) (P = 0.014), and in children with dual infections of both hookworm and T. trichiura (P = 0.005). Children with concomitant T. trichiura and hookworm infections were also significantly more likely to have blood haemoglobin levels indicative of anaemia than children who were uninfected or had single infections with either of these helminths (P < 0.005). In a longitudinal study involving 171 children selected from the original 658, blood haemoglobin concentrations were measured again in November 1988. Children who were considered to show an improvement in both hookworm and T. trichiura infections over this 12 month period showed a significantly greater increase in blood haemoglobin concentrations than children who had remained uninfected with either of these helminths throughout the study period (P < 0.05).

Interactions between vitamin A deficiency and Plasmodium berghei infection in the rat

It has been claimed that vitamin A deficiency increases the severity of malarial infection in rats. We measured parasitemia, mortality, serum retinol, liver retinol, spleen weight, and degree of xerophthalmia in vitamin A-deficient rats (A-), pair-fed control rats (A+PF), and ad libitum-fed control rats (A+AL) infected with Plasmodium berghei, a rodent malarial parasite. In experiments 1 and 2 vitamin A deprivation began at weaning. Parasitemia and mortality among mildly deficient (expt. 1, mean serum retinol 19 micrograms/dl) or acutely deficient rats (expt. 2, mean serum retinol less than 5 micrograms/dl) infected with P. berghei were not significantly different from those of infected A+AL or A+PF rats. Furthermore, when the mildly deficient rats were given a second, larger dose of P. berghei, all demonstrated complete immunity to the parasite. However, when vitamin A was withdrawn midway through pregnancy (expt. 3), the A- rats experienced significantly higher parasitemia and mortality during infection with P. berghei. Malaria caused a significant decrease in the serum retinol but not liver retinol of the A+PF and A+AL rats. Among the acutely deficient rats, xerophthalmia was significantly more prevalent and more severe among those infected with malaria than among those not infected with malaria. Malaria and vitamin A deficiency acted synergistically to increase spleen weight, and this interaction was highly significant. In these experiments, vitamin A deficiency decreased the rats' ability to recover from malaria, but only when the deficiency began early in life, was very severe, and the rats were young when infected.(ABSTRACT TRUNCATED AT 250 WORDS)

Soil-transmitted helminth infections in school children from Cocle Province, Republic of Panama

A survey was carried out to determine values for the prevalence and intensity of infection of intestinal helminths in children living in Cocle Province, Republic of Panama. The data set consisted of the results of microscopic examinations (modified Kato Katz technique) of stool samples collected in November 1987 from 661 children attending primary schools in 4 communities in the province. The overall prevalences of Ascaris lumbricoides, hookworm and Trichuris trichiura infections were found to be 18.2, 12.0 and 27.5% respectively. There were significant differences between the infection prevalence values for children attending the different schools, but not with respect to age or sex. Positive associations were detected between particular pairs of infections and these were most evident when Trichuris trichiura was involved. The data revealed evidence of a positive association between siblings at one school only for each helminth infection. There was extreme variation in the values for intensity of infection (20-126180 epg for A. lumbricoides). Highly significant, and unexplained, differences were observed in the intensity of A. lumbricoides infection by primary school; this finding did not apply to hookworm or T. trichiura. The analysis also revealed that children heavily infected with A. lumbricoides were also likely to be heavily infected with T. trichiura. Comparisons with the results of surveys carried out in Cocle Province in 1926 and 1974 indicate that these infections are declining in this region of Panama.

The effect of iron therapy on malarial infection in Papua New Guinean schoolchildren

The effect of iron therapy on malarial infection was investigated in Papua New Guinea, where malaria is endemic. Prepubescent schoolchildren with hemoglobin levels of 8-12 g/dl were randomly assigned to receive either 200 mg ferrous sulfate or a placebo twice daily for 16 weeks. Iron status and malarial infection were assessed at baseline, after 6 and 16 weeks of therapy, and 8 weeks after therapy was discontinued. Iron status was significantly improved by the treatment. The treatment did not significantly affect parasite rate, parasite density, or levels of anti-malarial IgG. No changes in spleen size were observed in either group. Furthermore, there was no significant difference between the groups in reported episodes of suspected malaria during the therapy. These results suggest that, in malaria endemic areas, oral treatment for iron deficiency can be carried out in semi-immune or immune schoolchildren without adverse consequences.

Intestinal helminthiases in relation to the socioeconomic environment of Panamanian children

A cross-sectional investigation was made into ascariasis and nutritional status in Panamanian preschool children from October 1983 to July 1984. Within this framework, an analysis was undertaken of possible relationships between a range of intestinal helminthiases and the socioeconomic status of the participants. Attention was paid to caregiver's education, parental occupation, family earnings, quality of housing and sanitation in the assessment of socioeconomic status. On this basis, strong associations were established between the socioeconomic status of the children and infection with Ascaris lumbricoides, Trichuris trichiura and hookworm. In general, the prevalence of single and multiple helminth infections was significantly higher in children living in housing made of wood or bamboo than in those living in housing made of concrete blocks. The same pattern applied to levels of sanitation. Ascaris lumbricoides occurred more frequently in children of mothers with the least formal education and in children living in relatively crowded conditions. Evidence was also obtained to indicate that the intensity of the intestinal helminth infections was greater in the children from the poorer environment. Since children from poorer socioeconomic conditions might be more exposed to infective stages than those from a better environment, the possible role of socioeconomic factors in contributing to the predisposition of some individuals to harbour large worm burdens of intestinal helminths was briefly discussed.

Contributions of ascariasis to poor nutritional status in children from Chiriqui Province, Republic of Panama

Relationships between ascariasis and lactose digestion and between ascariasis and food transit time from mouth to caecum were investigated in young children from Chiriqui Province, Republic of Panama. The breath hydrogen method was used in both studies. Ascaris-infected children showed a significantly poorer degree of lactose digestion following a test oral load than uninfected children. Recovery of the capacity of the children to digest lactose was still not fully complete for at least 3 weeks following anthelmintic treatment. On average, the mouth-to-caecum transit time was similar in infected and uninfected children, but among the Ascaris-infected children the transit time tended to be shorter in relation to the intensity of infection. Evidence from a cross-sectional survey indicated that ascariasis was significantly associated with reduced plasma vitamin A and carotenoid concentrations. This relationship remained after controlling for a range of socio-economic variables. Ascaris-infected children were frequently found to have lower haematocrits and blood haemoglobin concentrations than uninfected children, but these relationships could not be attributed to ascariasis alone.

Ascaris lumbricoides infection in pre-school children from Chiriqui Province, Panama

An epidemiological survey of intestinal parasitic infections was conducted in a sample of 203 children aged 3-5 years from a semi-urban and a rural community in Chiriqui, Panama, in 1983-4. On the basis of stool examinations, the prevalences of Ascaris lumbricoides, Trichuris trichiura, hookworm, Giardia intestinalis, Entamoeba spp. and Strongyloides stercoralis were found to be 27, 34, 14, 15, 5 and 4% respectively. The results from children from the two communities were compared. Polyparasitism occurred significantly more often in rural than semi-urban children. Following anthelmintic treatment with levamisole, the numbers of A. lumbricoides passed/child were recorded and the frequency distribution of the parasite was observed to be highly aggregated with a variance to mean ratio of 10.2. For A. lumbricoides, relationships between worm burden, worm biomass and egg production were investigated. In the data analysis, an attempt was made to explore the influence of numbers of male worms on egg production. The results are compared with those obtained during other recent studies on the epidemiology of A. lumbricoides infection in other countries.

Kidney clearance of D- and L-tryptophan by rats

Renal clearances of D-tryptophan and of L-tryptophan by rats were compared. Both D- and L-tryptophan were reabsorbed by the rat kidney tubules very efficiently. Compared to the rapid excretion of D-tryptophan by the chick, the good retention of this isomer by the rat kidney might be responsible for its efficient utilization by rats.

Iron deficiency protects inbred mice against infection with Plasmodium chabaudi

Plasmodium chabaudi infections of NFR/N mice made anemic by dietary iron deficiency produced mortalities of 25% (male) and 7% (female) compared with 100% in iron-sufficient controls. When iron-deficient mice convalescing from the primary infection were returned to the normal diet, 100% experienced recrudescent parasitemia. No recrudescence occurred in mice maintained on the iron-deficient diet.

Influences in child growth associated with poverty in the 1970's: an examination of HANESI and HANESII, cross-sectional US national surveys

This research examines associations between various measures of child growth (height, weight, triceps skinfold thickness, subscapular skinfold thickness), dietary variables, and poverty status in a sample of 13,750 black and white children aged 1 to 17 yr. The data used in this survey were collected in the National Health and Nutrition Examination Surveys I and II (HANESI, 1971-1975, and HANESII, 1976-1980). In general, lower mean values for all the growth measures examined were found in children living below the defined poverty threshold in comparison with those above the poverty threshold. The magnitude of these poverty-associated differences tended to decrease between the times of the HANESI and HANESII surveys, though not sufficiently to be statistically significant. These differences in growth were not consistently associated with differences in dietary intake of energy between poverty groups or surveys.

The influence of diet on the regression of the Walker carcinosarcoma 256 in rats

Regression of the Walker carcinosarcoma 256 has been observed in rats inoculated with 10(4) viable tumor cells. The regression was found to be affected by dietary composition. Tumors in rats fed a commercial laboratory diet (CLD) regressed after a 9-day initial growth period while tumors in rats fed a purified diet high in free fatty acids continued to grow. Diets with 20% corn oil promoted tumor regression, but rats fed diets containing 20% free fatty acids from corn oil had tumors that continued to grow. The nonsaponifiable fraction (NSF) of corn oil appeared to promote tumor regression when this fraction was added to diets containing corn oil fatty acids. At the end of the experiment (14 days), the tumors of rats fed a free fatty acid diet weighed 13-17 g. The tumors of rats fed CLD, corn oil diet and the corn oil free fatty acid diet plus the NSF of corn oil weighed 1-5 g. These results indicate that something in the NSF of corn oil was associated with the regression of the tumor. However, the nature of the dietary components promoting tumor regression, and the host response to those components, have not been determined.

Effects of diets deficient in glucose and glucose precursors on the growth of the Walker carcinosarcoma 256 in rats

The effects of carbohydrate-deficient diets on the growth of the Walker carcinosarcoma 256 in rats and on the carcinostatic action of the glucose analogue 2-deoxyglucose were studied. All diets contained 13.0% casein with glucose levels as indicated and the balance of calories present as corn oil free fatty acids. The growth of the tumor was directly related to the glucose level in such diets; after 16 days rats fed 0.0, 1.5 and 4.5% glucose had tumors weighing 7.0, 11.1 and 13.3 g, respectively. The decrease in tumor weight was related to dietary glucose level rather than the anorexia produced by the diets low in glucose, as shown by the fact that tumors in rats fed 4.5% glucose were larger than rats fed 1.5% glucose even when the rats fed 4.5% glucose were pair-fed to the levels consumed by those fed 1.5% glucose. 2-Deoxyglucose (0.2%) also caused a reduction in tumor growth in a manner independent from the anorexia produced by its presence in the diet. This carcinostatic effect was potentiated by low glucose levels in the diets in the rats fed 4.5% glucose plus 0.2% 2-deoxyglucose had proportionally greater reductions in tumor weights due to the glucose analogue than did rats fed 20% glucose plus 0.2% 2-deoxyglucose.

Mucosal surface lesions in young protein-deficient pigs infected with Ascaris suum (Nematoda)

The morphology of the mucosal surface of samples from the small intestine of young protein-deficient pigs was examined by scanning electron microscopy. Three pigs had been infected with Ascaris suum for at least 58 days while 1 had remained uninfected; all pigs were housed and maintained under the same conditions, at the same time. The tissue samples collected at post mortem examination from pigs which contained A. suum showed varying degrees of villous atrophy and fusion. In addition, unusual small craters and as yet unidentified objects were observed at the surfaces of the enterocytes of Ascaris-infected pigs. These changes in mucosal morphology were not seen in the tissue taken from the uninfected pig. The possible association between the mucosal lesions and lactose maldigestion in young, protein-deficient pigs infected with A. suum is discussed.

Some experimental approaches to the study of nutrition and parasitic infection

Two experimental models to examine the relationship between host nutrition and parasitic infection are considered. Moniliformis dubius, an acanthocephalan parasite of the laboratory rat, is dependent on the type and amount of host dietary carbohydrate for growth and reproduction. Starch, glucose, fructose, and mannose in host diets support parasite growth and development, but much lower dietary amounts of starch, fructose, and mannose are needed compared to free glucose. The pig-Ascaris suum relationship is considered as a model for human ascariasis. Experimental Ascaris infections in pigs resulted in reduced growth, reduced food intake, lowered biological value of dietary protein, and reduced intestinal lactase activity and lactose tolerance. These results are similar in some respects to reported effects of Ascaris infection in humans.

Lactose maldigestion in Ascaris-infected preschool children

Two studies were conducted to investigate the contribution of Ascaris lumbricoides to lactose maldigestion in preschool children in two different communities in Panama where milk is available as a source of nutrients and the prevalence of Ascaris is known to be high. Both Ascaris-infected and uninfected children were given a standard lactose load and lactose absorption was studied by measuring the rise in plasma glucose in study 1 and by determination of breath hydrogen concentrations at regular intervals after ingestion of the test dose in study 2. All children were tested before anthelmintic treatment with levamisole and 3 wk after therapy. The mean rise in blood glucose from infected (n = 13) children 40 min after the ingestion of lactose was about half of that of the controls (n = 21). After deworming, lactose digestion improved in previously infected children. In study 2, significant differences in breath hydrogen concentrations postmilk ingestion were observed between the Ascaris-infected (n = 47) and the uninfected children (n = 35) before treatment. There was a substantial reduction of breath hydrogen after milk ingestion in the previously infected children after therapy. No differences were observed in breath hydrogen content of the uninfected children during the pre- and posttreatment phases of the study in the lactose tolerance test. These studies provide evidence that infection with Ascaris lumbricoides impairs lactose digestion in preschool children.

Rat-dietary fructose and the intestinal distribution and growth of Moniliformis (Acanthocephala)

The numbers, distribution in the small intestine, sexual development and growth (dry weight) of 5-week-old Moniliformis dubius (Acanthocephala) were investigated experimentally in adult, female CFHB rats fed on theoretically isoenergetic diets containing known amounts of fructose in combination with either maize-oil fatty acids or maize oil and two concentrations of casein. There was no obvious development of M. dubius when there was no fructose in the host's diet. In contrast, estimated consumption by the host of as little as about 2 g of fructose during the 5-week infection period was accompanied by marked sexual dimorphism and weight gain in most of the M. dubius present. The dry weights of M. dubius of both sexes were positively correlated with fructose concentrations ranging from 0 to 2.5% (w/w) in the diets containing fatty acids. Significant, but not substantial, increases in M. dubius dry weight were observed as the dietary fructose concentration was raised to 12% (w/w). Similar trends were observed when the fructose was offered to the infected rats with maize oil, but in general, fructose added to the fatty-acid based diets supported most M. dubius growth. Differences in the distribution pattern of the worms in rats fed on the fatty-acid or maize-oil based diets were observed and their possible significance is discussed.

Branched-chain amino acid aminotransferase activity in the tissues of lake trout

The enzyme branched-chain amino acid aminotransferase (BCAT) was found in five tissues of fingerling lake trout, Salvelinus namaycush, (listed in order of decreasing tissue specific activity): posterior kidney, skeletal muscle, gill, liver, and anterior kidney. This pattern is consistent with that found in other animals. The results of this study seem to indicate that BCAT in the liver of lake trout has a higher specific activity than that of the rat and that the specific activity is higher in both the liver and skeletal muscle than it is in these organs of the chick.

Arginine uptake by chick kidney mitochondria

Arginine uptake by kidney mitochondria in two strains of chicks of high (HA) and low (LA) requirement of dietary arginine was studied by using an ion-exchange method. Dietary factors influencing uptake of arginine were also investigated. The results indicate that arginine uptake by kidney mitochondria of HA chicks was significantly higher than the LA chicks when arginine-deficient diet or diet with excess lysine was fed. The arginine uptake by kidney mitochondria reflects the kidney arginase activity. Both arginase activity and arginine uptake inversely correlated with growth rate of the two strains of chicks. However, the dietary factors that affect kidney mitochondria arginase activity are not completely parallel to the uptake of arginine by kidney mitochondria. A system that facilitates entry of arginine into kidney mitochondrial membrane is suggested.

Effect of energy restriction on total heat production, basal metabolic rate, and specific dynamic action of food in rats

Man and experimental animals are able to adapt to restricted levels of energy intake mainly by a reduction in basal metabolic rate (BMR) while the effects of energy restriction on the specific dynamic action (SDA) of food and the spontaneous activity are less well established. In this study, growing rats were fed ad libitum or restricted amounts of diet during 28-31 days. Then total heat production (THP) and BMR during 22 hours, as well as SDA of a test meal, were measured on individual rats by indirect calorimetry. After the calorimeter study rats were kept in metabolic cages for 6 days after which they were killed and analyzed for total body composition. The energy balance of the rats over the last 7 days of the study was calculated from changes in body composition and measurements of food intake during this period. During the calorimeter experiment an indirect estimation of the spontaneous activity of the rat was made. Results showed that THP, BMR and SDA of restricted rats were significantly lower than for ad libitum-fed rats. From body composition measurements, rats restricted in food intake before the calorimetry study were found to mobilize more protein and less fat compared to rats fed ad libitum until the calorimetry and body composition studies were carried out. No difference in spontaneous activity was observed between the two dietary treatments.

The growth of Moniliformis (Acanthocephala) in rats fed on various monosaccharides and disaccharides

Aspects of the course of infection, growth and reproductive activity of Moniliformis were studied in adult male and female rats fed on isoenergetic purified diets containing various sugars. When rats were infected and fed on experimental diets containing either 3% glucose or 3% galactose for 5 weeks, very little growth of worms and no signs of reproduction were observed. In contrast, Moniliformis grew well and showed many signs of normal reproduction when the rats were fed on diets containing either 3% fructose or 3% mannose. The ability of the worms to grow and reproduce was not lost by maintaining them first for 5 weeks in rats fed on diets containing 3% glucose and 3% galactose. When the diets of such rats were changed to ones containing 3% starch and 3% fructose, respectively, for a further 5 weeks, the worms grew and normal reproduction occurred. Similar experiments were carried out in which groups of infected rats were fed for 5 weeks on diets containing gradually increasing amounts of glucose (6-36%). It was not until the rats were fed on diets containing 24% glucose that the mean dry mass of the worms approached that of worms from rats fed on the diet containing 3% fructose; no host diet was found to be as effective a supporter of worm growth as 3% mannose. Under no circumstances, not even when the host's diet contained 36%, was galactose found to be a suitable sugar for supporting the growth and reproduction of Moniliformis. Results consistent with those recorded for worms from rats fed on the diets containing monosaccharides were obtained when infected rats were fed for 5 weeks on diets containing 3% of various disaccharides. Considerable growth and reproduction of Moniliformis occurred when sucrose was included in the host's diet, but not when lactose, maltose or trehalose was present. Several of these observations may be related to the fact that different sugars are absorbed at different rates from the intestinal tract. It is suggested that all of a given sugar, when present in the diet at a low concentration, may be removed rapidly from the anterior part of the small intestine with the result that none will be available to the parasites. Significant amounts, however, of those sugars that are absorbed more slowly may reach the region of the intestine in which the parasite normally lives.

Purification and biochemical characterization of an inhibitor of DNA synthesis produced by an Epstein-Barr virus-transformed B cell line

An inhibitory factor, which has been shown to suppress the uptake of 125I-iododeoxyuridine by both lymphoid and nonlymphoid cells, was isolated from the supernatant of an Epstein-Barr virus- (EBV) transformed B cell line (1605L) established from a cotton-topped marmoset. Purification of the inhibitor, which was produced in serum-free medium by crowded cultures of the 1605L cells, was achieved by DEAE-cellulose chromatography followed by preparative polyacrylamide gel electrophoresis. The apparent m.w. of the 1605L factor was determined to be 65,000 to 70,000 by SDS-polyacrylamide gel electrophoresis. The inhibitor was sensitive to digestion by trypsin and chymotrypsin but not RNase or DNase, indicating that it was protein in nature. Exposure of the 1605L factor to 56 degrees C for 1/2 hr or pH 2 for 48 hr at 4 degrees C destroyed its inhibitory activity. The biochemical characteristics and activity of the 1605L inhibitor distinguish it from Type I interferon and several other soluble immunologic mediators known to be produced by lymphoid cell lines.

Purification and biochemical characterization of an inhibitor of DNA synthesis produced by an Epstein-Barr virus-transformed B cell line

An inhibitory factor, which has been shown to suppress the uptake of 125I-iododeoxyuridine by both lymphoid and nonlymphoid cells, was isolated from the supernatant of an Epstein-Barr virus- (EBV) transformed B cell line (1605L) established from a cotton-topped marmoset. Purification of the inhibitor, which was produced in serum-free medium by crowded cultures of the 1605L cells, was achieved by DEAE-cellulose chromatography followed by preparative polyacrylamide gel electrophoresis. The apparent m.w. of the 1605L factor was determined to be 65,000 to 70,000 by SDS-polyacrylamide gel electrophoresis. The inhibitor was sensitive to digestion by trypsin and chymotrypsin but not RNase or DNase, indicating that it was protein in nature. Exposure of the 1605L factor to 56 degrees C for 1/2 hr or pH 2 for 48 hr at 4 degrees C destroyed its inhibitory activity. The biochemical characteristics and activity of the 1605L inhibitor distinguish it from Type I interferon and several other soluble immunologic mediators known to be produced by lymphoid cell lines.

Response of rats fed diets low in glucose and glucose precursors to low levels of glucose, starch and chemically modified starch

Several levels of glucose or starches were added to a basal diet that was free of available carbohydrate and low in carbohydrate precursors and fed to male, weanling rats. Rats fed such diets were highly responsive to dietary carbohydrate in growth rate, blood glucose levels and blood ketone bodies. There were no significant differences in the activities of pancreatic amylase, liver glucokinase, glucose-6-phosphatase and fructose-1,6-diphosphatase when dietary carbohydrate varied from 1.5 to 6% of the diet. Under these feeding conditions, a minimum of 6% by weight or 5.8% of the dietary calories has to be provided by carbohydrate to allow the rat an optimum rate of growth. Such diets that are low in glucose precursors were employed as an assay system for glucose availability from chemically cross-bonded starches with various degrees of phosphate crosslinkage. The data showed that introducing low levels of phosphate crosslinkages into the starch had little effect on the glucose availability from the starch.

Relationships between Ascaris infection and growth of malnourished preschool children in Kenya

A longitudinal study in Ascaris-infected and noninfected children was conducted in two Kenyan villages. Anthropometric, clinical, and stool exams were performed three times at 14-week intervals. All children received an anthelmintic drug (levamisole) at the second examination. In the 14 weeks before deworming, children with Ascaris (n = 61) did not differ from controls (n = 125) in percentage expected weight gain. In the 14 weeks after deworming, previously infected children showed higher percentage expected weight gain than controls. Before deworming, there was a statistically significant (P less than 0.0005) decrease in triceps skinfold thickness in Ascaris-infected children versus controls. After deworming, skinfold increased significantly (P less than 0.0005) in previously infected children versus controls. Multiple regression analysis showed that Ascaris infection was by far the most important variable of those studied explaining decrease in skinfold thickness before and increase after deworming. It appears that even light Ascaris infections might adversely influence nutritional status, and deworming might enhance growth.