PubMed Health⌕ Search

Biomedical subjects

H Greene

Publications and source records attributed to H Greene.

At least 19 recordsLinked to original sources
PubMed2001

Changes in the structure of xyloglucan during cell elongation.

Xyloglucans were isolated by sequential extraction of the cell walls of pea (Pisum sativum L. cv. Alaska) with a xyloglucan-specific endoglucanase and KOH. The xyloglucan content and xyloglucan-oligosaccharide composition were determined for fractions obtained from the elongating and non-elongating segments of pea stems grown in the light and in darkness. The results were consistent with the hypothesis that regulated growth of the cell wall depends on xyloglucan metabolism. Furthermore, the characterization of xyloglucan extracted from leaves of light-grown pea plants indicates that xyloglucan metabolism is tissue specific. Changes in xyloglucan subunit structure observed in elongating stems are consistent with the in muro realization of a metabolic pathway that was previously proposed solely on the basis of the in vitro activities of plant glycosyl hydrolases.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2000

Plasma and urine riboflavin during riboflavin-free nutrition in very-low-birth-weight infants.

BACKGROUND: Very-low-birth-weight (VLBW; birth weight <1500 g) infants receive enteral and parenteral nutriture that provides greater daily riboflavin (vitamin B2) than does term infant nutriture, and elevated plasma riboflavin develops in these infants after birth. The purpose of this study was to measure plasma and urine riboflavin concentrations in VLBW infants during riboflavin-free nutrition. Our hypothesis was that elevated plasma riboflavin develops in VLBW infants because of high daily intake and immature renal riboflavin elimination. METHODS: Eighteen clinically healthy VLBW infants received parenteral nutrition and preterm infant formula during the first postnatal month. On postnatal days 10 and 28, the infants received specially prepared riboflavin-free enteral and parenteral nutrition for the 24-hour study period. Serial collections of plasma were made at time 0 and at 12 and 24 hours. Urine was collected continuously for the 24-hour period in 4-hour aliquots. Samples were analyzed for riboflavin concentration. RESULTS: During the 24-hour riboflavin-free study period on postnatal day 10, plasma riboflavin decreased 56% from 185 +/- 37 ng/mL (mean +/- SEM), and urine riboflavin decreased 75% from 3112 +/- 960 mg/mL. Similarly, on postnatal day 28, plasma riboflavin decreased 79% from 184 +/- 32 ng/mL, and urine riboflavin concentration decreased 91% from 5092 +/- 743 ng/mL during the 24-hour riboflavin-free study period. Riboflavin half-life (t(1/2)) was 18.5 hours on postnatal day 10 and decreased 48% by postnatal day 28. Riboflavin elimination was 145.1 +/- 20.6 mg/kg per day on postnatal day 10 and increased 40% by postnatal day 28. CONCLUSION: The VLBW infants who received parenteral nutrition and preterm infant formula had elevated plasma riboflavin on postnatal days 10 and 28. Plasma riboflavin t(1,2) was shorter and renal riboflavin elimination was greater on postnatal day 28 than on postnatal day 10. Plasma riboflavin was normal after 24 hours of riboflavin-free nutrition. The pattern of plasma and urine riboflavin in VLBW infants suggests a lower daily intake would maintain plasma riboflavin close to normal.

Aging↗
PubMed1999

Arsenic binding proteins from human lymphoblastoid cells.

Arsenic is a ubiquitous contaminant of drinking water and food. The mechanisms of the toxic action of inorganic arsenic are unknown. We report the isolation of proteins having a high affinity for arsenic in the +3 oxidation state that are induced by arsenite (AsIII) in human lymphoblastoid cells. The arsenic-binding proteins were isolated using a p-aminophenylarsine oxide affinity column. At least four proteins of 50, 42, 38.5 and 19.5 kDa were isolated by elution with 10 or 100 mM 2-mercaptoethanol. Two proteins were tentatively identified as tubulin and actin on the basis of their molecular weights and previously reported affinity for the arsenic column. The identities of the remaining proteins are unknown. Heme oxygenase 1 was induced by AsIII but did not bind to the arsenic affinity column. We conclude that AsIII induces multiple proteins that have variable affinities for arsenic in the +3 state as judged by the concentration of 2-mercaptoethanol required for their elution. The arsenic binding motif of these proteins may involve three thiol groups arranged 3-6 A apart by the tertiary structure of the protein as suggested by others. These proteins may serve as high affinity binding sites for AsIII and may be involved in the biological action of AsIII.

Actins↗
PubMed1999

(-)-Hydroxycitric acid does not affect energy expenditure and substrate oxidation in adult males in a post-absorptive state.

OBJECTIVE: (-)-Hydroxycitric acid ((-)-HCA) is available as a herbal supplement, and promoted as a weight loss agent. It is hypothesized that (-)-HCA can increase fat oxidation by inhibiting citrate lyase, an enzyme which plays a crucial role in energy metabolism during de novo lipogenesis. The indirect inhibition of the cytosolic pool of citrate by (-)-HCA and the subsequent reduction in acetyl coenzyme A and oxaloacetate alters steps in the citric acid cycle that promote fat oxidation. The objective of this study was to determine the effect of (-)-HCA on marker substrates of altered metabolism, as well as on respiratory quotient (RQ) and energy expenditure (EE) in humans, following an overnight fast and during a bout of exercise. HYPOTHESIS OF STUDY: We hypothesized that supplementation with (-)-HCA would result in an increase in fat oxidation and metabolic rate, reflected by an increase in beta-hydroxybutyrate and EE and/or a decrease in RQ. Furthermore, during moderately intense exercise, we hypothesized that (-)-HCA supplementation would increase the rate of lactate conversion to glucose in the liver, with a subsequent reduction of circulating lactate and an elevation of circulating ketone bodies due to the increased partial oxidation of fatty acids (FA) in mitochondria. Studies have examined the fat regulating action of (-)-HCA on steps of the citric acid cycle in rodents showing reductions in body weight and food intake. No studies have investigated the effects of (-)-HCA supplementation in conjunction with a typical daily dietary composition (that is approx 30-35% fat) on metabolic processes which could influence body weight regulation in humans. DESIGN: This was a double blind, placebo controlled, randomized, crossover study involving three days of (-)-HCA (3.0 g/d) or placebo supplementation. The effects of (-)-HCA supplementation on metabolic parameters with or without moderately intense exercise was studied over four laboratory visits. SUBJECTS: Sedentary adult male subjects (n = 10, age: 22-38 y, body mass index (BMI) 22.4-37.6 kg/m2). MEASUREMENTS: Two of the four visits involved no exercise (Protocol A) with and without (-)-HCA treatment, while the remaining two visits included a moderately intense exercise bout (Protocol B; 30 min at 40% maximal aerobic fitness (VO2max) and 15 min at 60% VO2max) with and without (-)-HCA treatment. EE (by indirect calorimetry) and RQ were measured for 150 min following an overnight fast. Blood samples were collected for the determination of glucose, insulin, glucagon, lactate, and beta-hydroxybutyrate concentrations. RESULTS: In a fasted state and following 3 d of (-)-HCA treatment, RQ was not significantly lowered during rest (Protocol A) nor during exercise (Protocol B) compared with the placebo treatment. Treatment with (-)-HCA did not affect EE, either during rest or during moderately intense exercise. Furthermore, the blood substrates measured were not significantly different between treatment groups under the fasting conditions of this study. CONCLUSION: These results do not support the hypothesis that (-)-HCA alters the short-term rate of fat oxidation in the fasting state during rest or moderate exercise, with doses likely to be achieved in humans while subjects maintain a typical Western diet (approx 30-35% total calories as fat).

Adipose Tissue↗
PubMed1998

Human lymphocyte heme oxygenase 1 as a response biomarker to inorganic arsenic.

We propose the use of human lymphocyte heme oxygenase 1 (HO1) as a biomarker of response to environmental arsenic exposure. We report the induction of HO1 in human lymphoblastoid cells (LBs) by arsenite in a dose-related manner. HO1 was identified by SDS-PAGE from its molecular weight and from its detection by Western blotting with anti-HO1. HO1 levels in LBs treated with arsenite increased by de novo synthesis as demonstrated by incorporation of 35S-methionine and by inhibition of HO1 synthesis by actinomycin D. The amount of HO1 in LBs was estimated by quantifying Western blots. HO1 was also induced by 10 microM cadmium or mercuric chloride. We suggest that circulating lymphocyte HO1 levels may be useful in assessing the biological activity of arsenic exposure in vivo under properly controlled conditions of simultaneous urinalysis for arsenic, cadmium, and mercury.

Arsenic↗
PubMed1993

Lipid accumulation and body fat distribution is influenced by type of dietary fat fed to rats.

The amount of fat in the diet is known to influence body weight and body composition, but it is not clear whether dietary fat composition can affect body composition independently. We studied the effects of six months of feeding diets containing lard (L), corn oil (CO), fish oil (FO) or medium chain triglycerides (MCT) on body weight and body composition in adult male Wistar rats. Although FO fats ate slightly less total energy than the other groups, there were no differences among groups in body weight at any time during the study. However, body composition, the composition of depot triglyceride, body fat distribution and insulin resistance were all influenced by the type of fat in the diet. FO rats had less total body fat, less intra-abdominal fat, and less insulin resistance than all other groups. Although some of these metabolic effects may have been secondary to a slightly lower energy intake, we believe these data demonstrate the potential impact which dietary fat composition can have on metabolism and body weight regulation.

Adipose Tissue↗
PubMed1991

Sexing of human clavicles using length and circumference measurements.

Measurement of clavicular length and circumference, and computation of clavicular robustness and length-circumference product from 724 autopsied adults of known age, sex, and body length between the ages of 15 and 96 years produced useful sex-predictive values. This predominantly North American white population contained 560 males and 164 females with intact, nondeformed clavicles. Clavicle length and circumference and particularly their product have been found useful in sexing, but robustness as a single trait has not. Despite a significant overlap of male and female values, the use of single cutoff values allowed correct sex assignment of up to 93% of the entire study population, including 94% of males and 89% of females. The ratios of body length to clavicle circumference and to clavicle length are on average greater in women than in men. The former ratio yields male predictive values greater than 95% for those individuals with ratios falling below the cutoff value of 43, whereas the latter ratio is a relatively poor sex predictor.

Adolescent↗
PubMed1988

Increased urinary methylmalonic acid excretion in breast-fed infants of vegetarian mothers and identification of an acceptable dietary source of vitamin B-12.

Increased urinary methylmalonic acid (UMMA) concentrations might indicate vitamin B-12 deficiency. Our study tested the hypothesis that elevated UMMA in breast-fed infants is associated with decreased maternal serum B-12 concentrations. UMMA concentrations were measured in 17 vegetarian mothers and their infants and in six infants of nonvegetarian mothers. Serum vitamin B-12 concentrations were determined in all mothers. Range of UMMA for vegetarian infants (3-924 mcg/mg [2.6-790.9 mumol/mmol] creatinine) was much broader than that for omnivorous infants (2-25 mcg/mg [1.7-21.4 mumol/mmol] creatinine). Maternal UMMA and serum vitamin B-12 were negatively correlated (r = -0.700, p = 0.003). Infant UMMA concentrations correlated positively with maternal UMMA concentrations (r = 0.686, p = 0.003) and inversely with maternal serum vitamin B-12 concentrations (r = -0.681, p less than 0.001). In three infants with high UMMA concentrations, vitamin B-12 treatment (oral B-12, vitamin B-12 injection, or a modification of maternal diet within the vegetarian philosophy) led to an abrupt decrease of UMMA.

Adult↗
PubMed1986

Vasopressin antagonist analogs modified at position 7.

Vasopressin antagonist analogs having alanine or glycine at position 7 were essentially equipotent with analogs with proline, N-methylalanine or sarcosine at position 7. This demonstrates that the conformational constraint imposed by an N-alkyl residue at position 7 is not necessary for binding of antagonist to the receptor, the exact opposite of what is seen in agonists. This suggests that antagonists bind to the receptor in a manner which is very different from that of agonists.

Animals↗
PubMed1982

Surgical implications of chronic pancreatitis.

Surgical experience with 9 patients with chronic pancreatitis is reviewed. Vague, atypical abdominal pain and obstructive jaundice were the most common form of presentation. Serum amylase was elevated in less than half the patients. Ultrasound, ERCP, and operative cholangiopancreatography were the most helpful studies. Ampullary or intrapancreatic obstruction were the main indications for operation, and, when relieved, resulted in resolution of symptoms for an average followup of 4.4 yr. Patients with familial and recurrent bouts of pancreatitis should be studied with ERCP to determine if an anatomic lesion is present.

Adolescent↗
PubMed1981

A controlled comparison of continuous versus intermittent feeding in the treatment of infants with intestinal disease.

We compared two feeding regimens, continuous intragastric feedings and intermittent oral feeding, in nine infants with protracted diarrhea and malnutrition and two infants with surgically created short bowel. Continuous nasogastric feeding caused significant increases in enteral balance of the major nutrients, whereas intermittent feedings resulted in negative or only slightly positive enteral balance. The improvements in enteral balance from intermittent to continuous feeding in infants with diarrhea were as follows: Fat from 13 +/- 0.8 to 22 +/- 2.0 gm/24 hours; nitrogen from 0.63 +/- 0.2 to 1.7 +/- 0.2 gm/24 hours; calcium from -63 +/- 20 to 145 +/- 4 mg/24 hours; zinc from -0.57 +/- 0.2 to 1.3 +/- 0.2 mg/24 hours; and copper from -0.09 +/- 0.03 to 0.21 +/- 0.02 mg/24 hours. There was also a significant increase in body weight during the continuous feeding (168 +/- 16 gm/72 hours) as compared to the intermittent feeding (-171 +/- 26 gm/72 hours). Similar improvements in enteral balance were seen in the two infants with short bowel. These findings document that improved enteral balance can be achieved with continuous feeding in infants with bowel disease.

Body Weight↗
PubMed1981

Regression of hepatic adenomas in type Ia glycogen storage disease with dietary therapy.

Individuals with type Ia glycogen storage disease (glucose-6-phosphatase deficiency) frequently develop hepatic adenomas. Potential complications involving these adenomas include malignant transformation and hemorrhage. Five of 9 patients with this disease had evidence of hepatic filling defects on radionucleotide liver scan when first evaluated at our hospital. Dietary therapy aimed at preventing hypoglycemia was begun in 7 of the 9 patients. Prevention of hypoglycemia resulted in the correction of all of the metabolic abnormalities (lactic acidosis, hyperlipidemia, hyperuricemia, and growth retardation). Treatment also corrected the marked elevation in plasma glucagon concentrations. A disappearance of the hepatic lesions occurred in 2 of the treated patients, and a marked reduction in size of the adenoma occurred in the third patient. The hepatic filling defects remained present in the two untreated patients. None of the affected patients receiving dietary therapy have developed hepatic adenomas. One of these patients is now 22 yr old and has received dietary therapy for 7 yr. Early dietary therapy seems to be effective in preventing development of adenomas as well as inducing their resolution.

Adenoma↗
PubMed1980

Reye's syndrome in three siblings. Association with type A influenza infection.

Reye's syndrome occurred simultaneously in three siblings. All had characteristic changes in liver histology ascertained by light and electron microscopy. The two patients with the most severe disease also had serum that caused marked stimulation of mitochondrial state 4 respiration in vitro. Histocompatibility locus antigen typing showed that no unique haplotypes were shared by all three children. There was no evidence of exposure to aflatoxins, pesticides, or other substances that have been previously postulated to be associated with Reye's syndrome. Influenza A/Brazil/11/78-like virus was isolated from one patient, and all three patients had a fourfold or greater rise in hemagglutination-inhibiting antibody to H1N1 influenza virus.

Antigens, Viral↗