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Biomedical subjects

S A Bustamante

Publications and source records attributed to S A Bustamante.

At least 19 recordsLinked to original sources
PubMed1996

Inducible nitric oxide synthase and the regulation of central vessel caliber in the fetal rat.

BACKGROUND: The purpose of this study was to evaluate the possibility that inducible nitric oxide synthase (iNOS) regulates the fetal circulation. METHODS AND RESULTS: Positive evidence for iNOS gene expression was noted in heart central vessels and placenta of untreated rat fetuses. Rats in the last week of pregnancy were treated for 5 days with L-NG-(1-Iminoethyl)lysine (L-NIL), a selective inhibitor of iNOS, at 1, 10, and 100 micrograms/mL in the drinking water. To raise NO levels, lipopolysaccharide (LPS) 30 micrograms/kg was given by intraperitoneal injection, and sodium nitroprusside (SNP) was placed in mini-osmotic pumps to deliver 10 micrograms/kg per minute. Control animals were undisturbed. On day 21 of gestation, dams were anesthetized and fetuses were delivered by cesarean section and rapidly frozen in isopentane chilled in liquid nitrogen. Frozen sections (10 microns) were used to reconstruct a computer-generated three-dimensional image of the great vessels and ductus arteriosus. Significant constriction of the great vessels and ductus arteriosus was observed with L-NIL, whereas both LPS and SNP dilated these vessels. The vasorelaxant effect of LPS was blocked by L-NIL. NO release from placental explants was 633 +/- 41 nmol/L under basal conditions, increasing to 4.0 +/- 0.4 mumol/L with LPS administration, although placental iNOS message and protein levels were unchanged. CONCLUSIONS: We suggest that nitric oxide, generated by iNOS, plays a significant role in control of major vessel and ductus arteriosus caliber in the rat fetus. In regard to the nitrergic regulation of the circulation, the fetus is clearly different from the adult.

Animals↗
PubMed1994

Dietary nucleotides: effects on the gastrointestinal system in swine.

Nucleotides in the intestinal lumen may decrease the inflammatory response to ischemia-reperfusion. In a newborn-swine model, we showed that perfusion of the intestinal lumen with nucleotides in concentrations similar to those in human milk induced hyperemia. The levels of hypoxanthine (and xanthine) were not increased in the presence of nucleotides during ischemia-reperfusion, and the number of leukocytes accumulated in the intestine was reduced in the presence of nucleotides. Furthermore, nucleotides may have decreased protein leak and the production of nitric oxide during ischemia. These effects are not changed significantly in the presence of an adenosine antagonist. We interpreted our results to indicate that the protective effects of nucleotides in the intestinal lumen are not due to adenosine alone.

Adenosine↗
PubMed1993

Nitric oxide release in response to gut injury.

We evaluated nitric oxide release in several models of intestinal inflammation through luminal nitrite concentrations. In anesthetized rabbits, piglets, and guinea pigs, luminal lavages were collected from loops of normal or injured small intestine. Lavages were analyzed spectrophotometrically for nitrite (Griess reagent) and protein. Myeloperoxidase (MPO) content of intestinal segments was used as an index of granulocyte infiltration and intestinal inflammation. Acute ileal inflammation was induced by luminal acetic acid + casein in rabbits and luminal deoxycholate in neonatal piglets and adult rabbits. Chronic ileitis was induced in guinea pigs by intraluminal trinitrobenzenesulfonic acid. In each model nitrite levels in ileal lavages were significantly greater than control loops/animals. Increased luminal protein and intestinal MPO activity paralleled the changes in nitrite levels. To determine whether nitric oxide production influenced mucosal repair, segments of ileum were perfused with the L-arginine antagonist NG-nitro-L-arginine methyl ester (L-NAME, 10 mg/ml) after acute acetic acid + casein exposure. L-NAME administration reversed the decline in epithelial permeability characteristic of epithelial restitution, causing an increase in epithelial permeability which was readily reversible. These results suggest that nitrite production is a useful index of gut injury and that nitric oxide may contribute to the functional repair of the epithelial barrier under acute conditions.

Animals↗
PubMed1990

Age-related changes in sucrase and lactase activity in the small intestine of 3- and 10-week-old obese mice (C57BL/6Jobob).

The relationship between obesity and the digestion of carbohydrates is poorly understood. Data in humans have provided conflicting results. Studies using the obese mouse (C57BL/6Jobob) suggest that obesity is associated with increased activity of intestinal alpha-disaccharidases. To evaluate the developmental pattern of these enzyme activities in obesity, we determined the activity of sucrase and lactase in the small intestine of genetically obese mice (C57BL/6Jobob) and lean littermates at 3 and 10 weeks of age. Sucrase and lactase activities were measured on intestinal homogenates from segments of the small intestine in mice maintained on standard laboratory diets during the postweaning period. Results were expressed as specific activity and total activity per intestinal segment. Obese mice did not differ from lean littermates in body weight at 3 weeks of age, but exhibited increased protein content in the proximal small intestine. Sucrase specific activity was significantly higher in the obese mice at 3 weeks of age in all intestinal segments. Sucrase total activity showed a similar pattern. At 10 weeks of age, body weights of obese mice were substantially greater than the lean littermates. Sucrase specific and total activities were also greater in the obese mice at 10 weeks of age. Lactase specific activity, however, was similar in both obese and lean mice at both ages studied. Lactase total activity was greater in the obese mice, consistent with their greater intestinal mass. These observations demonstrate that changes in the intestinal sucrase activity of the obese mouse precede the development of excessive body weight.

Age Factors↗
PubMed1989

A swine model for studying intestinal circulation of the newborn.

We describe a newborn swine model to study intestinal hemodynamics of developing mammals. The preparation is designed to allow measurement of perfusion pressure and blood flow in an isolated segment of ileum under controlled conditions. Piglets in this study had a mean blood pressure of 65 +/- 14 (SD) mm Hg and mean intestinal blood flow of 80 +/- 20 (SD) ml/100 g/min at an average age and weight of 6.1 +/- 3 (SD) days and 1,718 +/- 427 (SD) g (n = 21). Experiments were performed to evaluate the effects of common physiologic perturbations: (a) Increased venous pressure caused a decrease in blood flow proportional to the lower perfusion pressure, but the relative change in vascular resistance was greater than the blood flow change. This effect, suggestive of a myogenic response, was significantly greater at a venous pressure increase of 20 cm of water over baseline compared with an increase of 10 cm water. (b) Gradual decrease in mesenteric artery blood pressure by clamping resulted in proportional decreases in blood flow. The calculated peripheral vascular resistance remained constant at blood pressure greater than 50 mm Hg and then increased as blood pressure decreased. (c) Stimulation of periarterial, postganglionic nerves surrounding the mesenteric artery produced a characteristic initial vasoconstriction followed by "autoregulatory escape." Frequency response tests using trains of stimulation of 6 ms and 12 V demonstrated responses starting at 2 Hz and maximal at 16 Hz. We suggest that this model should be applicable to a number of physiologic studies including assessment of water and nutrient flux in the intestine concomitant to changes in the circulation.

Animals↗
PubMed1989

Evidence for an intramural nervous control of epithelial cell migration in the small intestine of the rat.

The migration of epithelial cells along the crypt-villus axis in the small intestine of the rat was followed by labelling epithelial cells during mitosis with [3H]thymidine given i.v. Using two different techniques (autoradiography and determination of tissue radioactivity) it was demonstrated that 6-9 h after giving the tracer the labelled cells had migrated longer in intestinal segments exposed to cholera toxin than in control segments. This effect of cholera toxin was abolished by giving hexamethonium. We have earlier shown that cholera toxin induces fluid secretion to a large extent by activating the enteric nervous system and we conclude from the present observations that cholera toxin in a similar fashion exerts a trophic effect on the intestinal epithelium via intramural nervous reflexes. The importance of co-release of several neurotransmitters in explaining the trophic effect is tentatively discussed.

Animals↗
PubMed1989

Evidence for a countercurrent exchanger in the intestinal villi of suckling swine.

The possible existence of a countercurrent exchanger (multiplier) in the intestinal villi of suckling swine was investigated with three different methods: (1) Comparing venous appearance of oxygen and red cells in the mesenteric vein after close i.a. injection of a blood sample equilibrated with pure oxygen and containing methaemoglobinaemic red cells. (2) Determining sodium (micrograms) over protein (mg) ratios along villi. (3) Estimating tissue osmolality in the villus tissue from measurements of freezing-point depression. It was observed that oxygen appeared earlier than red cells in the mesenteric vein after i.a. injection. Furthermore, both the chemical measurements of sodium/protein ratios in the villi and the estimations of tissue osmolality indicate that there exists a gradient of osmolalities along the villus length, the villus tip being hyperosmolar as compared to the villus base. We conclude that a countercurrent exchanger (multiplier) exists in the villi of suckling swine. Its possible pathophysiological significance is discussed.

Animals↗
PubMed1989

Use of a transparent adhesive dressing in very low birthweight infants.

The present study was designed to test the safety and efficacy of a transparent adhesive dressing (TAD) to decrease transepidermal water loss (TEWL) in very low birthweight (VLBW) infants. Thirteen infants with birthweights of 770-1,450 g were randomly assigned to either routine care (n = 7) or TAD (n = 6). There were no differences between the groups with regard to weight at birth, length, head circumference, skinfold thickness measures, and fluid balance at any time during the study period. Electric current used by the radiant warmer operated in the servo-control mode was measured using a clamp-type AC ammeter connected to a single channel recorder. The TAD group used an average of 112 +/- 3.9 watts (n = 30 observation periods), the control group 133 +/- 5.5 (n = 34 observation periods), P = less than .01. TEWL measured by an evaporimeter in four infants of each group was significantly higher in the control group than it was in the TAD group in the area where the skin was covered.

Adhesives↗
PubMed1989

Hemodynamics during increased intraluminal pressure in the ileum of suckling swine.

Studies of intestinal hemodynamics during increased abdominal and intraluminal pressure in adult animals (canine and feline) have shown that blood flow is practically unchanged at pressures up to 35-40 mm Hg. In the young animal, however, decreased total intestinal blood flow has been shown at pressures of 15 mm Hg or greater. To help characterize the effect of intraluminal pressure on intestinal circulation, we have studied pressure-flow relationships in an isolated loop of terminal ileum in piglets 2-14 days of age (mean, 6.1 +/- 3.7 SD, n = 14) with a mean weight of 1,745 +/- 345 SD. Intraluminal pressure was increased from 0-50 cm of water pressure in 10-cm steps of two min' duration. Blood flow was reduced with every increase in intraluminal pressure and significantly reduced at pressures of 20 cm of water or more. The calculated peripheral vascular resistance increased with every increment of intraluminal pressure. Analysis of the relationship of arterial blood pressure to changes in blood flow suggests that blood flow reductions are greater in animals with lower blood pressure at every level of intraluminal pressure studied. Increased intraluminal pressure could be a mechanism of intestinal mucosal ischemia in the newborn, particularly affecting those with low arterial blood pressure.

Animals↗
PubMed1987

Growth of premature infants fed formulas with 10%, 30%, or 50% medium-chain triglycerides.

Questions regarding fat deposition and hormonal control of lipogenesis in infants fed formulas containing medium-chain triglycerides have been raised by studies in animals. To compare growth, clinical observations, and laboratory measures of infants fed the same basic isocaloric formulas with 10%, 30%, or 50% of the total fat as medium-chain triglycerides, we studied longitudinally for the first four weeks of life 22 infants who weighed 1000 to 1750 g. We found no differences in weight or skin-fold thickness between the groups. There were no clinical characteristics to distinguish one group from another. Two-hour postprandial levels of insulin and glucagon showed no differences one week to ten days after the start of the formula diet. The skin-fold thickness of all infants studied continued to increase after birth, regardless of weight loss. The increase in skin-fold thickness was comparable with the increase expected in the fetus in utero, but not significantly greater. The weight curve was parallel to the fetal weight curve but was lower, due to the first-week loss that possibly reflected a loss of body water, as suggested by the dynamic skin-fold thickness curve.

Humans↗
PubMed1986

Dietary regulation of intestinal glucohydrolases in adult rats: comparison of the effect of solid and liquid diets containing glucose polymers, starch, or sucrose.

For 1 wk, 3-mo-old male rats were fed a low-starch (5 cal%), high-fat (73 cal%, corn oil) diet followed by a high-glucose-polymer (70 cal%), low-fat (7 cal%, corn oil) or a middle-glucose-polymer (40 cal%), middle-fat (37 cal%, corn oil) diet. Other animals were fed similar diets but with starch or sucrose instead of the glucose polymers. Rats were sacrificed 2 or 7 days later. Food intake, body weight changes, and protein content per intestinal segment were similar in all groups. Increased carbohydrate intake evoked an increase of sucrase, maltase, glucoamylase, and lactase activity in both the jejunum and ileum. Effect of glucose polymers on glucohydrolase was similar in animals fed commercial liquid-soy-based infant formulas containing sucrose, glucose polymers, or both. Results support using glucose polymers as replacements for sucrose or starch when digestion impairment of those sugars is suspected or when a formula of lower osmolality is indicated.

Animals↗
PubMed1983

Body weight, static and dynamic skinfold thickness in small premature infants during the first month of life.

The growth of prematurely born infants is different from the growth of fetuses of the same age remaining in utero. This is in part due to changes in body composition that occur after birth. In search for a practical and reliable method to assess the growth of small prematures, we analyzed data obtained in two anthropometric studies that included 180 premature infants of 750-1750 g weight at birth, and we studied the relationships between weight, static skinfold thickness (SSFT) and dynamic skinfold thickness (delta SFT, i.e. the percentage of change in skinfold thickness between 15 and 60 s after application of the Harpenden caliper). The results show that the SSFT increases steadily after birth in spite of a significant decrease in weight and delta SFT. Whether it contains fat or not, the fold of the skin is increasing in thickness at a time when by weight alone, one would have considered that there was no growth. The nutritional implication of this finding remains to be studied. Serial correlations of measures obtained at each period indicate that weight and SSFT have a good correlation to same measures in subsequent weeks (P less than 0.01). delta SFT, however, showed only a weak correlation (P = 0.05). The delta SFT follows the general pattern of known changes in total body water, but it is not accurate enough to determine changes in individual infants; further studies are thus needed to find a practical method to evaluate changes of body composition and its relevance in the measurement of growth of premature infants.

Body Composition↗
PubMed1978

Fetal hydantoin syndrome in triplets. A unique experiment of nature.

Birth defects associated with phenytoin and phenobarbital taken during pregnancy include craniofacial and limb deformities. These anomalies were found in various degrees of severity in triplets born to a mother taking phenobarbital and phenytoin for an epileptic disorder, giving us a unique opportunity to recognize different manifestations of the hydantoin syndrome in infants that presumably were exposed to the same level of the drugs. These infants were trizygotic and their clinical manifestations varied widely, suggesting the possibility that genetic background may play a significant role in the susceptibility of the fetus to phenytoin and phenobarbital during pregnancy.

Abnormalities, Drug-Induced↗