James J. Cerda

Total Parenteral Nutrition in the Mouse: Development of a Technique

A method for total parenteral nutrition in the mouse was developed using commercially available supplies and equipment. The mouses inferior vena cava was catheterized and the catheter was exteriorized from the tail. Mice (average body weight 22.5 g) were not tethered but instead were partially restrained by immobilizing the tail to protect the infusion tubing. A solution was formulated to contain 40% dextrose and 4.3% amino acids plus vitamins, electrolytes, and trace elements. It was administered via pump in graded fashion for the first 3 days to allow the mice to adapt, and then at a rate of 8 ml/day thereafter. This volume provided approximately 12 kcal and 54 mg nitrogen per day and was calculated to meet the needs of the mouse fed per os according to guidelines of the National Research Council. During the adaptation period mice lost weight but they were in positive N balance thereafter. At the end of 12 days body weight was not different than at the start, indicating the adequacy of nutrient input. Further, there were no differences in nitrogen balance or body weight in total parenteral nutrition fed mice in comparison with tail-restrained mice given the same solution per os. All mice appeared to tolerate the partial restraint without incidence and showed no untoward side effects. The rationale and validity of this technique is discussed in detail.

Use of Nutritional Supplements in an Ambulatory Elderly Population

The use of nutritional supplements by 3,192 ambulatory elderly participants in a health screening program is described. The 2,009 women used vitamin (45.5 per cent) and mineral (22.4 per cent) products with significantly greater frequencies than did the 1,183 men (34.0 per cent and 15.0 per cent, respectively); chi‐square, P < 0.01. The most commonly used vitamin products were multiple vitamins, multiple vitamins with minerals, vitamin E, and vitamin C; for minerals, the ranking was potassium chloride, calcium salts, and ferrous sulfate. Eighty‐two participants (2.5 per cent) reported the use of four or more supplements. Many older Americans are spending a great deal of money for nutritional supplements, whereas it would seem that the money could be better spent to improve the quality of their diet.

Dietary fiber: fact and fiction.

There have been many conflicting reports about the benefits of dietary fiber. Dietary fiber has been touted to provide remarkable benefits: from the control of functional bowel disease to the prevention of cancer. We have reviewed all prominent studies on the benefits of dietary fiber and examined the nature of their conflicting results. Recommendations for dietary fiber intake are also discussed.

Inhibition of atherosclerosis by dietary pectin in microswine with sustained hypercholesterolemia.

Sustained hypercholesterolemia is a known risk factor for development of atherosclerosis. In animal studies, grapefruit pectin fed concurrently with a high-lipid diet inhibits hypercholesterolemia and atherogenesis. The purpose of the present study was to determine if grapefruit pectin affects cholesterol levels and atherogenesis of animals with established hypercholesterolemia. Microswine were fed an atherogenic diet to establish hypercholesterolemia. Plasma cholesterol levels rose rapidly and for 360 days were sustained at levels 6- to 12-fold the normal level. Then, half the microswine, selected at random, were fed a diet in which 3% grapefruit pectin was substituted for cellulose, and the remaining animals received the original diet. Animals were killed 270 days later, and the extent of atherosclerosis was determined. In animals with established hypercholesterolemia, pectin did not lower their cholesterol levels. However, pectin reduced the extent of atherosclerosis in both the aorta and coronary arteries. The mean surface area covered by atherosclerosis in the aorta was 13.6% in the group that did not receive pectin compared with 5.3% in the group that did receive pectin. The mean coronary artery narrowing was 45% without pectin and 24% with pectin. We conclude that pectin may have a direct beneficial effect on atherosclerosis by a mechanism independent of cholesterol levels.

Unstirred Water Layers in Rabbit Intestine: Effects of Pectin

Abstract Pectins have been shown to affect the absorption of several different nutrients in clinical studies; however, the mechanisms for decreased absorption have not been defined. A possibility not studied with regards to pectin, but previously demonstrated to be important in absorption, is the effect of change in the unstirred water layer. As the unstirred water layer increases in thickness, the rate of absorption decreases for certain nutrients. The effect of pectin on the unstirred water layer in the lumen of rabbit jejunum was examined by previously described techniques. It was observed that: (1) increases in pectin concentration resulted in an increased thickness of the unstirred water layer; (2) for any stir rate, the addition of pectin increased the thickness of the unstirred water layer; and (3) stir rate is inversely related to the thickness of the unstirred water layer. It was concluded from these results that pectin increases the thickness of the unstirred water layer in rabbit jejunum. This mechanism may explain, in part, the reduction of the rate of absorption of certain nutrients seen following pectin ingestion.

Comparison of pteroylpolyglutamate hydrolase (folate conjugase) from porcine and human intestinal brush border membrane

1. A comparative study of pteroylpolygluatamte hydrolase (folate conjugase) of brush border membrane vesicles from human and porcine intestine was conducted. 2. The enrichment of conjugase activity during membrane isolation was 5-fold greater for the human than the pig. 3. Porcine and human conjugases exhibited similar Km values and could completely hydrolyze pteroyltriglutamate (PteGlu3) to PteGlu1 via an exohydrolytic process. 4. Pteroic acid, PteGlu1 and anionic polysaccharides did not inhibit human or porcine conjugase. 5. Apparent mol. wts for detergent-enzyme complexes were 237,000 (pig) and greater than 500,000 (human). 6. These results indicate similar kinetic properties and mode of action but differences in physical behavior between the intestinal brush border folate conjugases of human and pig.

Unstirred water layers in rabbit intestine: effects of guar gum

Guar gum has been shown to affect the absorption of several different nutrients in clinical studies; however, the mechanisms for decreased absorption have not been defined. A possibility not studied with regard to guar gum, but previously demonstrated to be important in absorption, is the effect of change in the unstirred water layer. As the unstirred water layer increases in thickness, the rate of absorption decreases for certain nutrients. The effect of guar gum on the unstirred water layer in the lumen of rabbit jejunum was examined by previously described techniques. It was observed that: increases in guar gum concentration resulted in an increased thickness of the unstirred water layer; for any stir rate, the addition of guar gum increased the thickness of the unstirred water layer; and stir rate is inversely related to the thickness of the unstirred water layer. It was concluded from these results that guar gum increases the thickness of the unstirred water layer in rabbit jejunum. This mechanism may explain, in part, the reduction of the rate of absorption of certain nutrients seen following guar gum ingestion.

Cost Containment Using Cysteine HCl Acidification to Increase Calcium/ Phosphate Solubility in Hyperalimentation Solutions

The purpose of this study was to determine if (1) the calcium/phosphate insoluble product was inversely related to pH [when cysteine HC1 (CH) was added as neonatal supplementation at 0.5 mM/kg/day to hyperalimentation (HAL) solutions] and (2) the potential cost savings to the hospital. The pH of the HAL solutions was adjusted by adding various amounts of CH to the HAL solution. HAL solutions containing 27 mEq of calcium/liter and 30 mEq (15 mM) of phosphate/liter were compounded. Ten-milliliter aliquots were analyzed at 0, 12, 24, and 48 hr. All samples (n = 56) were filtered (0.22 mu), viewed with 7-10,000 X magnification scanning electron microscopy, and qualitatively analyzed with a Philips Energy Dispersive X-Ray Analysis System equipped with a SW9100 Microprocessor. Calcium/phosphate insoluble product was present in the 0-, 12-, 24-, and 48-hr samples from the CH-free solutions. The solutions containing 759 mg (4.17 mM)/liter of CH however, remained free of precipitant. This investigation demonstrated that addition of CH to HAL can foster significant cost containment (projected

Total Parenteral Nutrition in the Mouse: Body Composition and Plasma Chemistries

82,000/yr tangible hospital savings) by the elimination of current calcium/phosphate separation procedures for neonates on parenteral nutrition.

Ultrasonographic demonstration of the pancreatic duct.

Mice that were maintained in energy and nitrogen (N) balance by total parenteral nutrition (TPN) for 12 days were analyzed for changes in organ weight, carcass and liver N and fat, and plasma glucose, urea N, and total protein. The results are compared with two other groups: (1) PO, which consisted of mice that were given the TPN solution per os in amounts equivalent to the TPN group, and (2) AL, which consisted of mice allowed to consume a stock diet ad libitum. In comparison with group AL, the TPN-fed mice had normal liver, kidney, and lung weights but heavier spleens and hearts. Group PO had an increase in liver weight only. Hepatic lipid content declined in group TPN but increased markedly in PO-fed mice. The latter group also demonstrated a 35% increase in carcass fat whereas it was unchanged in the TPN group. No differences were found in plasma urea N and total protein among the groups but plasma glucose increased 2-fold in group PO. It appears that our technique of parenteral feeding in mice maintains fairly normal body composition and plasma chemistries. However, mice drinking the TPN solution (group PO) exhibited the greatest number of alterations. These results are discussed in relation to differences in route of feeding, diet composition, feeding pattern, and the possible influence of circadian rhythms. The dilemma of choosing appropriate control groups in TPN studies is also discussed.