Experimental histoplasmosis in mice treated with anti-murine interferon-gamma antibody and in interferon-gamma gene knockout mice

Histoplasma capsulatum is an important fungal pathogen in immunocompromised hosts, including AIDS patients. Experimental evidence suggests interferon-gamma (IFN) plays a role in host defense against H. capsulatum. In these studies we sought to demonstrate the importance of IFN in innate resistance to systemic histoplasmosis. The possible exacerbation of infection in BALB/c mice was assessed by administering 200 microg of hamster anti-IFN antibody prior to infection with H. capsulatum (2 x 10(6) yeasts, i.v.) and by comparing the severity of infection between BALB/c IFN gene knockout mice (GKO) and congenic control animals. In two separate studies, we found that anti-IFN treatment caused a dramatic loss of resistance to lethal infection and resulted in earlier mortality of IFN-depleted animals compared with normal IgG or no treatment (P<0.001). GKO mice were significantly (P<0.001) more susceptible to lethal infection than were control animals, and histological studies corroborated this. These studies clearly demonstrate that IFN is a vital part of the host's innate resistance to systemic infection with H. capsulatum and provide an additional rationale for studying IFN as an immunomodulatory therapeutic for the treatment of this disease.     

Prepubertal growth in children with long-term parenteral nutrition

In children who depend on long-term parenteral nutrition (PN), a major goal is to obtain optimal growth. The aim of this retrospective study was to analyze growth in children on long-term cyclic nocturnal home PN, over at least 8 years before puberty. Nine boys and 7 girls were studied. Their mean age at the time of study was 11 years with a mean PN duration of 10.5 (8.6-16.4) years. Diseases were short bowel syndrome (5), intractable diarrhea (4), chronic intestinal pseudo-obstruction (4) and long segment Hirschsprung's disease (3). In each child, periods of at least 2 years were analyzed: either periods of regular growth (R: height gain >50th percentile), or slow growth (S: height gain < or =25th percentile). Results were expressed as mean +/- SD. Comparisons were performed using either Student's test for unpaired data or Wilcoxon's test for paired data. PN provided a mean of 224 +/- 80 mg nitrogen/kg/day and 43 +/- 14 kcal/kg/day equivalent to 50% of recommended supplies. At the time of study, the population presented with weight (W) = -0.7 +/- 0.8 SD and height (H) = -1.5 +/- 1.3 SD. The difference between W and expected W for H (W/H) was significant (p < 0.002). W/H ratio was 105 +/- 11%. For the total PN duration, weight gain was +0.2 +/- 1.5 SD and height loss was -0.75 +/- 1.4 SD. An excess weight gain occurred in parallel with the deflection of height gain. Of the 16 children, regular prepubertal growth was achieved in 4 only. The other 12 showed alternate periods of R and S. In 8 of them, 26.5 years of R and 33.5 years of S were compared, each child being his own control. PN nitrogen and energy supplies were significantly higher during R periods than during S periods. In the absence of any disease or treatment explaining the failure to thrive, inadequate PN supplies, especially in terms of nitrogen supply, are thought to be responsible for a negative nitrogen balance and slowed growth. In case of any deflection away from the individual growth curve, it is recommended to adjust the PN supply early, especially nitrogen supply.     

Selenium in total parenteral nutrition

In clinical practice, selenium deficiency may arise under conditions of chronic malnutrition and especially after long-term total parenteral nutrition (TPN). In infants receiving long-term TPN, we observed plasma selenium levels as low as those previously reported in Chinese children with Keshan disease. Low plasma selenium levels were also usually associated with very low activities of glutathione peroxidase. Although clinical symptoms of selenium deficiency did not occur in our patients, several cases have been described in the literature, indicating the need for supplementation in TPN. In order to derive at the appropriate dosage, it is proposed to correlate it with the total protein supply. According to our present knowledge, .5–1.0 μg selenium/g of protein appears to be adequate to keep patients in Se balance. For Se repletion of body stores, this dosage has been increased up to 3 μg of Se/g of protein. Advantages and disadvantages of selenite and of selenomethionine as possible supplemental forms of Se for TPN solutions are discussed.     

Prolactin evokes lactational transmission of larvae in mice infected with Toxocara canis

We investigated the trans-lactational maternal–neonatal transmission of Toxocara canis larvae in mice, with particular interest in the role of prolactin in their migration to the mammary gland. Two female mice were infected with 300 T. canis eggs soon after delivery of 27 offspring. After 1 week of breast-feeding, seven larvae were recovered from 4 of 13 offspring. After 2 weeks of lactation, 101 larvae were recovered from all the remaining offspring. Daily prolactin administration (5 μg) was performed 2 weeks before T. canis infection and continued until 2 weeks after infection in six non-pregnant female mice, which resulted in larval accumulation in the mammary gland. Furthermore, prolactin administration in female mice that had been infected with T. canis 4 weeks prior to prolactin treatment induced migration of larvae into the mammary gland. These findings suggest that prolactin is a promoting factor contributing to lactational transmission of T. canis larvae in mice.     

Studies with a safflower oil emulsion in total parenteral nutrition.

The prevention of essential fatty acid deficiency and the provision of adequate amounts of energy are two major concerns in total parenteral nutrition. Since earlier preparations of fat emulsion used to supplement the usual regimen of hypertonic glucose and amino acids have widely varying clinical acceptability, a new product, a safflower oil emulsion available in two concentrations (Liposyn), was evaluated. In four clinical trials the emulsion was used as a supplement to total parenteral nutrition. In five surgical patients 500 ml of the 10% emulsion infused every third day prevented or corrected essential fatty acid deficiency; however, in some cases in infusion every other day may be necessary. In 40 patients in severe catabolic states the emulsion provided 30% to 50% of the energy required daily: 10 patients received the 10% emulsion for 14 to 42 days, 9 patients received each emulsion in turn for 7 days, and 21 patient received the 20% emulsion for 14 to 28 days. All the patients survived and tolerated the lipid well; no adverse clinical effects were attributable to the lipid infusions. Transient mild, apparently clinically insignificant abnormalities in the results of one or more liver function tests and eosinophilia were observed in some patients. Thus, the safflower oil emulsion, at both concentrations, was safe and effective as a source of 30% to 50% of the energy required daily by seriously ill patients.     

History of parenteral nutrition in pediatrics with emphasis on amino acids

Central venous total parenteral nutrition (TPN) has proved to be a valuable and often life-saving measure in selected newborn infants with surgically repairable, major anomalies of the gastrointestinal tract and infants with chronic intractable diarrhea. However, in infants of low--and especially very low--birth weight, the TPN regimen that was so successful in older infants was frequently associated with severe risks of hyperglycemia. An alternative approach that has proved to be the most satisfactory relies on the fact that the energy expenditure of a premature infant, nursing in a thermally neutral environment, rarely exceeds 50 kcal/kg, a level that can be safely and effectively maintained. With respect to the development of parenteral amino acid solutions, three generations of such mixtures can now be identified. The first of these was represented by the protein hydrolysates. With the advent of technology for the production of pure L-amino acids, a second generation of crystalline mixtures was developed. Evaluation of these revealed that extrapolation from data on oral nutrition was often unsatisfactory for the adequate formulation of such mixtures. The direct study of the parenterally nourished patient led to the third generation of special purpose amino acid solutions such as those targeted for patients with renal failure, liver failure, or trauma or for the promotion of anabolism. It seems likely that development of other solutions will follow the trend of relying on accurate definition of a given metabolic disorder and the perfection of a specific solution to correct it.     

Lipid emulsions for parenteral nutrition in critical illness

Critical illness is a life-threatening multisystem process that can result in significant morbidity and mortality. In most patients, critical illness is preceded by a physiological deterioration, characterized by a catabolic state and intense metabolic changes, resulting in malnutrition and impaired immune functions. In this context, parenteral lipid emulsions may modulate inflammatory and immune reactions, depending on their fatty acid composition. These effects appear to be based on complex modifications in the composition and structure of cell membranes, through eicosanoid and cytokine synthesis and by modulation of gene expression. The pathophysiological mechanisms underlying these fatty acid-induced immune function alterations in critical ill patients are however complex and partially understood. Indeed, despite a very abundant literature, experimental and clinical data remain contradictory. The optimization of lipid emulsion composition thus represents a major challenge for clinical medicine, to adequately modulate the inflammatory pathways. In the present review, we first address the metabolic response to aggression, the effects of parenteral lipid emulsions on inflammation and immunity, and finally the controversial place of these lipid emulsions during critical illness. The analysis furthermore highlights the pathophysiological mechanisms underlying the differential effects of lipid emulsions and their potential for improving the handling of critically ill patients.     

Selenium depletion in patients on home parenteral nutrition

Severe selenium (Se) depletion was found in nine patients receiving long-term home parenteral nutrition because of short bowel syndrome. Plasma Se ranged from 0–0.51 (median 0.21 μmol/L) and erythrocyte Se ranged from 0.7–2.6 (median 1.8 μmol/gHgb), which was significantly lower than in the controls. Glutathione peroxidase (GSHPx) in plasma and erythrocytes was also decreased. After bolus injections with 200 μg Se/d in the form of sodium selenite for 4 mo, followed by 100 μg/d for 8 mo, plasma Se increased to values slightly but significantly higher than in the controls. Erythrocyte Se reached normal levels in most of the patients after 4 mo substitution, but it remained lower than in the controls. Following Se supplementation, plasma and erythrocyte GSHPx did not differ between patients and controls. These data suggest that all patients receiving long-term parenteral nutrition because of short bowel syndrome should receive at least 100 μg sodium selenite/d when given as bolus injections to avoid Se depletion.