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Biomedical subjects

R K Chandra

Publications and source records attributed to R K Chandra.

287 records · Page 16Linked to original sources
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Immune responses in parasitic diseases. Part B: mechanisms.

A number of host defenses provide variable resistance against parasites. From the biological point of view, invading parasites must not eliminate the susceptible host population; therefore, antiparasite immunity plays an essential role in limiting the invasion and proliferation of parasites. Several differences exist between immune responses to parasites and immune responses to other microorganisms. Effector mechanisms include T lymphocyte-mediated inflammatory granuloma formation and encapsulation involving the deposition of fibrous tissue. In some instances, passive immunity can be transferred by serum antibodies. Antibodies may act via complement fixation, granulocyte adhesion, opsonization, inhibition of invasion, or mast cell degranulation. Of the nonspecific factors, macrophage activation, natural killer cells, and serum factors other than antibodies are critical in the battle against parasites. The net result of these immune responses may be antiparasitic, proparasitic, of no consequence to either host or parasite, or harmful to the host.

Animals↗
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Golan memorial lecture. Nutritional regulation of immunity and infection: from epidemiology to phenomenology to clinical practice.

Malnutrition is the most common cause of acquired immune dysfunction worldwide. Nutritional deficiencies, excesses, and imbalances influence specific components of the immune system. The severity of immunological impairment depends upon the extent and nature of undernutrition, the presence of infection, and the age of onset of nutritional deprivation. Profound immunological changes occur in children with marasmus and kwashiorkor as well as in deficiencies of vitamins A, E, B6, folate, zinc, iron, copper, and selenium. On the other hand, obesity and excessive intake of several vitamins, minerals, cholesterol, and polyunsaturated fatty acids also impair immunocompetence. These epidemiological observations and immunological phenomena are of practical significance in clinical practice.

Humans↗
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Nutritional modulation of intestinal mucosal immunity.

Protein-energy malnutrition results in an increased risk of gastrointestinal infection. This can be attributed in part to impaired immune responses. Cell-mediated immunity is decreased as judged by reduced number and function of thymus-dependent lymphocytes, impaired delayed cutaneous hypersensitivity reactions, and decreased production of lymphokines. Concentration of secretory IgA is reduced and there are fewer intraepithelial lymphocytes. Antibody responses following viral vaccine administration are reduced and there is decrease in natural killer cell activity. In addition, the number of bacteria binding to epithelial cells is increased. These changes are observed also in certain selected nutrient deficiencies, such as that of vitamin A. It is suggested that impaired systemic and mucosal immunity contributes to the increased frequency and severity of intestinal infections seen in undernourished individuals.

Animals↗
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[Effect of the diet on the nutritional status of ballerinas: immunologic markers].

UNLABELLED: Athletes have special nutritional needs that will vary with sex, age, body composition and most importantly by the type, intensity, frequency and duration of the physical exercise. However the diet of certain groups of athletes such as ballet dancers is inadequate due to overly restrictive habits as a consequence of their obsession with losing or maintaining a low body weight that reflects an aesthetic preference for thinness. Physical exercise implies energy expenditure and thus, an increase in the energy intake is required to avoid possible situations of malnutrition. Both a negative energy balance and physical exertion have been shown to induce immunological changes which have been implicated as a possible explanation for increased susceptibility to illness and infections. OBJECTIVE: To find out the influence of a restricted energy intake on the immune system of 14 ballet dancers (20-25 h/w) in comparison with a control sedentary group (n = 23) by evaluating dietetic, anthropometric and some immunological parameters. RESULTS: Ballet dancers consumed a hypocaloric diet (mean: 1555 kcal), the energy intake being significantly lower than in the control group. None of both groups showed a similar calorie profile to the recommended intake for Spanish population, especially fat percentage was higher than it should. Regarding weight, ideal body weight and BMI values, no significant differences were shown between both groups. However, all the skinfolds thickness and the sum of skinfolds were significantly lower in ballet dancers than in controls. Leukocytes, lymphocytes and all lymphocyte subset counts were lower in ballet dancers in comparison with controls. CONCLUSIONS: In view of these results, ballet dancers may suffer from an impaired nutritional status, determined by a depletion of anthropometric and immunological parameters. The nutritional requirements for this population should be increased in order to compensate their high-energy expenditure, avoid a negative energy balance and lessen the nutritional damage.

Adolescent↗
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Enriched feeding formula and immune responses and outcome after Listeria monocytogenes challenge in mice.

Immunocompromised malnourished patients are at high risk of developing serious opportunistic infection. This study examined the effect of feeding a special nutrient-enriched formula (Immun-Aid) on immune responses and mortality in mice challenged with Listeria monocytogenes. Two protocols were followed. In the first protocol, the animals were challenged with microorganisms when the experimental formula was introduced as the sole source of their nutrition. There was no significant effect on total T-lymphocyte number, but the proportion of helper T cells increased by day 7, resulting in a higher helper/suppressor (H/S) T lymphocyte ratio as well. Response to the mitogen phytohemagglutinin (PHA) was slightly higher on day 3 but came down and was comparable with that of control animals by day 7. Natural killer cell activity was slightly higher on day 7. Other immunologic parameters were unchanged. There was no significant difference in mortality between the two groups. In the second protocol, the animals were fed the experimental diet for 7 days before the infectious challenge. There was a slight increase in the total number of T lymphocytes on day 7. The numbers of helper and suppressor T lymphocytes were unchanged, but H/S was slightly higher on day 3 in the experimental group. Response to PHA was again higher on day 3 but plateaued on day 7. Natural killer cell activity was not altered. Mortality after infectious challenge was slightly but significantly decreased in the group of animals fed the enriched special formula. These results indicate a slight enhancement of selected parameters of immunity in mice fed the specially enriched formula and show that prior feeding with this formula for several days may partly protect against infectious challenge, resulting in reduced mortality.

Animals↗
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Nutrition and immunity: I. Basic considerations. II. Practical applications.

Nutrition, immunity and infection are intricately linked to one another. Nutritional deficiencies and excesses influence various components of the immune system. Early studies investigating the association between nutrition and immunity focused on generalized protein-energy malnutrition, particularly in children in developing countries. The extent of immunological impairment depends not only on the severity of malnutrition but on the presence of infection and on the age of onset of nutritional deprivation, among other factors. In industrialized nations, immune function has been shown to be comprised in many malnourished hospitalized patients, small-for-gestational-age infants and the elderly. Obesity also may adversely influence immune function. Imbalances of single nutrients are relatively uncommon in humans and investigations of protein and amino acids and specific vitamins, minerals and trace elements generally are carried out in experimental animals. Deficiencies of protein and some amino acids, as well as vitamins A, E, B6 and folate, and trace minerals are associated with reduced immunocompetence. In contrast, excessive intake of fat, in particular polyunsaturated fatty acids, iron and vitamin E are immunosuppressive. Knowledge regarding nutritional regulation of immunity is leading to many practical applications.

Humans↗
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Zinc and immunity.

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Animals↗
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Growth comparison of breast-fed and formula-fed infants.

Growth during infancy was analyzed using data from a study in which groups of infants were fed breast-milk or one of three formulas: Good Start, Isomil, or Similac. After adjustments for size at birth and parental stature, growth was within the normal range for all feeding groups and there were few significant differences in growth between those fed different formulas. There was, however, some evidence that Similac was associated with larger gains in weight and that those fed breast-milk or Isomil had lower weights at ages older than two months. Additionally, at six months, recumbent length tended to be smaller in the Isomil group of boys and in both the Isomil and Similac groups of girls and larger in the Good Start groups of boys and girls.

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