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Biomedical subjects

H M Said

Publications and source records attributed to H M Said.

At least 109 records · Page 6Linked to original sources
PubMed1986

Effect of human milk folate binding protein on folate intestinal transport.

The present study examined the effect of human milk folate binding protein (FBP) on the intestinal transport of 5-methyltetrahydrofolate (5-CH3H4PteGlu). This was performed by examining the transport of radiolabeled 5-CH3H4PteGlu bound to FBP using everted sacs of rat intestine. In the jejunum at pH 6, transport of 27 nM bound 5-CH3H4PteGlu was linear with time for 30 min of incubation. Transport of 13 nM bound 5-CH3H4PteGlu was higher in the jejunum than in the ileum at both pH 6 (2.1 +/- 0.3 and 0.36 +/- 0.03 pmol/g wet wt/25 min, respectively) and pH 8 (1.9 +/- 0.3 and 0.32 +/- 0.02 pmol/g wet wt/25 min, respectively). In the jejunum, transport of 13 nM bound 5-CH3H4PteGlu at pH 6 was less than transport of an equimolar concentration of free 5-CH3H4PteGlu (2.1 +/- 0.3 and 5.1 +/- 0.5 pmol/g wet wt/25 min, respectively) but was similar at pH 8 (1.9 +/- 0.3 and 2.47 +/- 0.3 pmol/g wet wt/25 min, respectively). In the ileum transport of bound and free 5-CH3H4PteGlu was similar at pH 6 (0.36 +/- 0.03) and 0.41 +/- 0.06 pmol/g wet wt/25 min, respectively) and pH 8 (0.32 +/- 0.02 and 0.43 +/- 0.1 pmol/g wet wt/25 min, respectively). The transport process of bound 5-CH3H4PteGlu in the jejunum was energy, temperature, and Na+ dependent, but not pH dependent, and was competitively inhibited by sulfasalazine. Ninety-two percent of the transport substrate that appeared in the serosal compartment following incubation with bound 5-CH3H4PteGlu was found to be free (unbound) 5-CH3H4PteGlu. These results show that human milk FBP decreases the rate of transport of 5-CH3H4PteGlu in the jejunum and suggest that FBP-bound 5-CH3H4PteGlu may utilize the same transport system as free 5-CH3H4PteGlu. The results also suggest a role for human milk FBP in regulating the nutritional bioavailability of folate.

Animals↗
PubMed1986

Cystine-rich proteins of human hair: characterization and structure as revealed by reversed-phase and size-exclusion high-performance liquid chromatography.

The human hair cystine-rich proteins have been separated through the combined use of reversed-phase and size-exclusion chromatography into more than fifty components. These have been grouped, based on molecular weight, into six families of closely related members. The families range in molecular weight from less than 6500 for the low-molecular-weight components to more than 67 000 for the high-molecular-weight components, with average intermediate values for the other families of 8000, 11 500, 15 500 and 19 000. The results also suggest an organized structure of the hair matrix proteins. The combined use of reversed-phase and size-exclusion high-performance liquid chromatography in these studies presents an example where the quaternary structure of a multi-component protein can be largely deduced from its chromatographic behaviour.

Amino Acids↗
PubMed1986

Inhibitory effect of bile salts on the enterohepatic circulation of methotrexate in the unanesthetized rat: inhibition of methotrexate intestinal absorption.

The effect of conjugated and unconjugated bile salts on the intestinal absorption of methotrexate (MTX) in the unanesthetized rat was investigated using a recycling perfusion technique. We initially determined the general characteristics of MTX absorption in vivo. Absorption of low (0.5 microM) and high (6 microM) concentrations of MTX was linear with time for 60 min perfusion and occurred at rates of 0.2 and 1.65 nmol/100 cm dry length/min, respectively. Absorption of 0.5 microM MTX was pH-dependent and increased with decreasing perfusate pH. Absorption of MTX involves two processes: (1) a saturable process with a Kt of 0.98 microM, and (2) a nonsaturable diffusion process. The unconjugated deoxycholate and the conjugated taurocholate inhibited the intestinal absorption of 1 microM MTX in a concentration-dependent manner. The inhibitory effect of bile salts was reversible, and was not due to damage to the intestinal mucosa. The structural analogues folic acid and 5-methyltetrahydrofolate and the organic anions rose bengal and sulfobormophthalein were also inhibitory to MTX absorption. This study demonstrates that a variety of organic anions inhibit MTX intestinal absorption. The possible therapeutic importance of this observation is discussed.

Animals↗
PubMed1986

Intestinal transport of zinc and folic acid: a mutual inhibitory effect.

Recent observations suggest an inverse relationship between folic acid intake and zinc nutriture and indicate an interaction between folic acid and zinc at the intestinal level. To define that interaction, we designed in vivo and in vitro transport studies in which folic acid transport in the presence of zinc, as well as zinc transport in the presence of folic acid was examined. These studies show that zinc transport is significantly decreased when folate is present in the intestinal lumen. Similarly folic acid transport is significantly decreased with the presence of zinc. To determine whether this intestinal inhibition is secondary to zinc and folate-forming complexes, charcoal-binding studies were performed. These studies indicate that zinc and folate from complexes at pH 2.0, but that at pH 6.0, these complexes dissolve. Therefore, our studies suggest that under normal physiological conditions a mutual inhibition between folate and zinc exists at the site of intestinal transport.

Animals↗
PubMed1986

Effect of ethanol and other aliphatic alcohols on the intestinal transport of folates.

The effect of ethanol and other aliphatic alcohols on the intestinal transport of 5-methyltetrahydrofolate and folic acid was examined using everted sacs from rat jejunum. Ethanol added to the mucosal medium inhibited the transport of both folate compounds in a parallel manner, and the inhibition increased with increasing ethanol concentration (0.5-10% v/v). Ethanol at 3% v/v in the mucosal medium caused: depression in the pH dependency of the active transport of 5-methyltetrahydrofolate; higher inhibition in the transport of low concentration (0.1 microM) than high concentration (10 microM) of 5-methyltetrahydrofolate, and inhibition in the active accumulation against a concentration gradient of 5-methyltetrahydrofolate and L-leucine. Methanol, propanol and butanol also inhibited the transport of the folate compounds; and in general, the inhibitory effect increased with the increase in the number of carbon atoms in the hydrophobic chain. This study indicates that ethanol and other alcohols inhibit the intestinal transport of folates, that the degree of inhibition is related to the concentration and chain length of the alcohol, that the inhibition is not specific for folates and finally that the mechanism of inhibition is multifactorial.

Alcohols↗
PubMed1986

The effects of metabolic acidosis on jejunal phosphate and glucose transport in weanling rats.

To investigate the effects of metabolic acidosis on jejunal phosphate and glucose absorption, in vivo and in vitro transport studies were performed on weanling rats fed 1.5% NH4Cl for three days and on group pair-fed controls. Both in vivo and in vitro, acidosis significantly depressed phosphate transport without effecting glucose transport. In vitro, the decrease of phosphate transport was due to a depression of sodium-phosphate cotransport, but not of sodium independent phosphate transport. This corresponded to a significant increase of the Km of sodium-phosphate cotransport with no change of the Vmax. Treatment of the acidotic animals with intraperitoneal 1,25 dihydroxycholecalciferol did not restore phosphate transport to control levels. These studies indicate that in weanling rats, metabolic acidosis selectively suppresses jejunal phosphate transport independent of circulating levels of 1,25 dihydroxycholecalciferol.

Acidosis↗
PubMed1986

Effect of epidermal growth factor and artificial feeding in suckling rats.

To evaluate the effects of epidermal growth factor (EGF) in dietary milk, a new method of delivering an artificial (EGF-deficient) formula was developed using 42 rat pups, 1-14 days of age. In a second study the effect of EGF was evaluated in suckling rats from 3-11 days of age: group 1, mother-fed; group 2, mother-fed plus daily injections of EGF (0.1 micrograms/g body weight); group 3, artificial milk fed with added EGF (62 ng/ml); and group 4, artificial milk fed without EGF. Each group consists of nine rats. In group 2 there was premature eye opening and tooth eruption and a significant reduction in body weight and weight of liver, kidney, thyroid, and thymus but an increase in length of the intestine and weights of stomach, pancreas, lung, and adrenal (p less than 0.04), when compared to group 1. Both groups 3 and 4 showed premature tooth eruption and eye opening, and their body weights and most organ weights were similar to group 2; exceptions were a smaller stomach, thyroid, thymus, lung, and adrenal, which were similar to those in group 1. In addition, intestinal length in groups 3 and 4 were similar to the mother-fed EGF-treated pups (group 2). There was no difference in intestinal length between the artificially fed pups, whether or not they received oral EGF. These findings demonstrate a new and effective technique of artificial feeding and suggest that the increase in intestinal length caused by injections of EGF (0.1 micrograms/g body weight) can also be induced by feeding an artificial milk with or without physiologic levels of EGF.

Age Factors↗
PubMed1986

Evaluation of a pediatric multiple vitamin preparation for total parenteral nutrition. II. Blood levels of vitamins A, D, and E.

This study represents the first attempt to evaluate the American Medical Association Nutrition Advisory Group (NAG) recommendations for intravenous vitamin A, D, and E dosages for infants and children. Patients studied included 18 preterm infants (group 1) and 26 term infants and children (group 2A) receiving total parenteral nutrition for 2 to 4 weeks and eight infants and children receiving total parenteral nutrition for 3 to 6 months (group 2B). Term gestation infants and children up to 11 years of age all received the same dosages (those that were recommended by the NAG for children weighing more than 10 kg). Preterm infants received 65% of these doses. In group 1, cord blood alpha-tocopherol levels were less than 0.22 mg/dL in seven preterm infants (reference value = 0.29 +/- 0.04), but mean levels increased to 1.65 +/- 0.17 mg/dL after four days of treatment. Eight infants consistently received additional vitamin E orally (80 to 150 mg daily), and their levels increased to 2.18 +/- 0.26 mg/dL by four days of study and to 3.49 +/- 0.57 mg/dL after 3 weeks. Oral supplementation in the preterm infants appeared to be unnecessary because intravenous vitamins alone maintained levels above 1.1 mg/dL. In group 2, alpha-tocopherol levels were maintained within the reference range. Patients receiving lipid emulsions containing substantial quantities of alpha-tocopherol had significantly higher blood levels than patients receiving lipid emulsions containing little alpha-tocopherol (P less than .01). Mean 25-OH vitamin D levels were maintained above or within the reference range in groups 2A and 2B.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗
PubMed1986

Intestinal surface acid microclimate in vitro and in vivo in the rat.

The presence of the intestinal surface acid microclimate (ISAM) has long been suggested. Controversy, however, still exists as to the existence, general characteristics, and requirements of this microclimate. We examined the existence and distribution of the ISAM along the rat small intestine and colon and determined its general characteristics. The results clearly demonstrate the existence of the ISAM in vitro and in vivo. Glucose and sodium in the incubation medium, as well as normal intracellular metabolism, are essential requirements for the formation and maintenance of the ISAM. We conclude that the ISAM is a normal physiologic phenomenon of the luminal surface of the intestine.

2,4-Dinitrophenol↗
PubMed1986

Intestinal transport of 5-methyltetrahydrofolate in streptozotocin-induced diabetes mellitus in the rat.

The effect of chemically-induced acute diabetes mellitus on the intestinal transport of 5-methyltetrahydrofolate, the predominate dietary form of folate, was examined using an in vivo perfusion technique in unanesthetized restrained rats and the in vitro everted sac technique. Diabetes was induced by an intraperitoneal injection of 70 mg/kg of streptozotocin. Transport experiments were performed 4 days after the induction of diabetes and results were compared to appropriate controls. The amount of 5-methyltetrahydrofolate transported in vivo and in vitro was significantly higher in the diabetic group as compared to controls. The kinetic parameters of the in vitro transport of 5-methyltetrahydrofolate showed an increase in the Vmax value for the diabetic rats as compared to controls (1.52 and 0.80 nmol/g initial tissue wet wt/30 min, respectively) with no change in apparent Kt (1.62 and 1.80 microM, respectively). These observations suggest that the increase in the transport of 5-methyltetrahydrofolate observed in the diabetic rats is due to an increase in the activity and/or the number, but not the affinity, of the transport carriers involved. We conclude that chemically-induced acute diabetes mellitus is associated with an enhancement in folate absorption.

Animals↗
PubMed1985

Reversed-phase high-performance liquid chromatography of some ultra-heterogeneous and covalently-modified proteins from human hair.

A new procedure for the fractionation of the heterogeneous cystine-rich proteins from human hair, utilizing reversed-phase high-performance liquid chromatography, is described. Of these proteins 27 fractions have been collected and analyzed for amino acid composition. There seems to be little correlation between the elution order and the hydrophobicity of the fraction constituents except for the late-eluting fractions. Based on the elution profiles and amino acid contents, these fractions appear to fall into four families. The effects of alkyl chain length, flow-rate and gradient slope, as well as various additives to the organic modifier on the separation have also been investigated. A low flow-rate (0.4 ml/min) and a shallow gradient were essential for the separation of these proteins as was the use of short alkyl chain (C4) or medium alkyl chain (C8) columns. However, with the C4 column reproducibility and recovery were excellent.

Amino Acids↗
PubMed1985

Does aging affect the intestinal transport of riboflavin?

Riboflavin deficiency has been reported in older individuals. The cause of this deficiency is not know but could include a decrease in the intestinal absorptive capacity for riboflavin. Therefore, we examined the intestinal absorption of riboflavin in young (3 month) and old (26 month) rats. We used in vitro jejunal everted sacs. The kinetic parameters of riboflavin absorption disclosed apparent Km of 0.37 and 0.43 microM and Vmax of 37 and 38 pmole/g initial tissue wet wt/20 min in young and old rats, respectively. These data do not demonstrate an aging associated change in the intestinal transport capacity for riboflavin. If these results are extrapolated to man, it would mean that the deficiency of riboflavin found in the elderly is not due to its intestinal malabsorption. Therefore, other mechanisms must be sought to account for the deficiency of riboflavin seen in the elderly.

Aging↗
PubMed1985

Ontogenesis of intestinal transport of 5-methyltetrahydrofolate in the rat.

Developmental aspects of the intestinal transport of 5-methyltetrahydrofolate (5-CH3H4-PteGlu) were studied in suckling (14-day-old), weanling (22-day-old), and adult (90-day-old) rats by use of the intestinal everted-sac technique. Mucosal-to-serosal transport of 0.5 microM 5-CH3H4PteGlu was linear with time for 40-min incubation and occurred at a rate of 0.035, 0.032, and 0.010 nmol X g initial tissue wet wt-1 X min-1 for suckling, weanling, and adult rats, respectively. The transport of 5-CH3H4PteGlu in all age groups was pH dependent (maximal at pH 6) and was higher in the jejunum than in the ileum. In all age groups the transport of 5-CH3H4PteGlu occurred by an active carrier-mediated system. The system was saturable; energy, temperature, and Na dependent; inhibited by structural analogues; and capable of accumulating the substrate against a concentration gradient. Kinetic parameters of the transport process, however, showed some difference. A progressive decrease in Vmax was observed from suckling to weanling to adult rats (5.1, 3.7, and 0.8 nmol X g initial tissue wet wt-1 X 30 min-1, respectively), while apparent Kt was similar (2.2, 1.73, and 1.79 microM, respectively). This study demonstrates that the transport system of 5-CH3H4PteGlu in the rat is fully developed at the suckling age. The results also suggest that the activity and/or the number, but not the affinity, of the transport carriers decrease with maturation.

Animal Population Groups↗
PubMed1985

Impaired intestinal absorption of riboflavin in experimental uremia.

Increased plasma and red blood cell concentrations of riboflavin have been reported in uremia. The possible role of altered intestinal absorption of riboflavin in the genesis of this abnormality is not known. For this reason we examined the intestinal absorption of riboflavin in rats made uremic by subtotal nephrectomy and sham-operated (control) rats in vivo using the recycling perfusion technique and in vitro using the everted-sac technique. Paradoxically, the results showed a significant impairment of intestinal absorption of riboflavin in vivo in uremic rats compared to the control group. However, no significant difference was observed in riboflavin transport in vitro. We conclude that the intestinal absorption of riboflavin is decreased in experimental uremia and cannot account for the reported increase in its plasma and red blood cell concentrations.

Animals↗
PubMed1985

Development maturation of riboflavin intestinal transport in the rat.

The intestinal transport of riboflavin in the immature intestine of the suckling rat (14 day old) and its subsequent maturation in weanling (22 day old) and adult (90 day old) rats were investigated using the intestinal everted sac technique. The mucosal-to-serosal transport of 0.5 microM riboflavin was linear with time for 30-min incubation and occurred at a rate of 4.6, 3.6, and 1.6 pmol/g initial tissue wet wt/min in suckling, weanling, and adult rats, respectively. The transport of 0.5 microM riboflavin was higher in the jejunum than the ileum in all age groups. The transport system of riboflavin in all age groups was saturable, energy-, temperature-, and Na+-dependent. Kinetic parameters of the transport process were different. Apparent Kt of the transport process was the same in suckling and weanling rats (0.12 and 0.11 microM, respectively) but tripled in adult rats (0.35 microM). On the other hand, a progressive decrease in Vmax from 166 to 122 to 54 pmol/g initial tissue wet weight/30 min was observed in the suckling, weanling, and adult rats, respectively. The present study demonstrates that the characteristics of the transport process of riboflavin is similar in suckling, weanling, and adult rats and occurs by an energy-, temperature-, and Na+-dependent carrier-mediated process. However, the affinity and the activity (or the number) of the transport carriers of riboflavin decrease with maturation.

Age Factors↗
PubMed1985

Fetal hydantoin syndrome: inhibition of placental folic acid transport as a potential mechanism for fetal growth retardation in the rat.

Maternal hydantoin ingestion during pregnancy results in a well defined clinical entity termed "fetal hydantoin syndrome". The clinical characteristics of this syndrome includes growth retardation, and congenital anomalies. Because folic acid is essential for protein synthesis and growth, and since hydantoin interferes with intestinal transport of folic acid, we postulated that part of the fetal hydantoin syndrome may be due to inhibition of placental folic acid by maternal hydantoin. Therefore, we studied in vivo placental folate transport in a well-established model for fetal hydantoin syndrome in the rat. Our results indicate that maternal hydantoin ingestion, significantly decreased fetal weight and placental and fetal uptake of folate compared to controls. To determine whether maternal hydantoin ingestion has a generalized or specific effect on placental function, we examined placental and fetal zinc transport in the same model. Our results indicate that zinc transport is not altered by hydantoin ingestion. We conclude that maternal hydantoin ingestion results in fetal growth retardation which may be due in part to inhibition of placental folate transport.

Animals↗