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Biomedical subjects

M Hamosh

Publications and source records attributed to M Hamosh.

At least 127 records · Page 7Linked to original sources
PubMed1979

Effect of nicotine on the development of fetal and suckling rats.

Nicotine, administered at a dose of 100 micrograms/kg/day from day 14 of gestation, did not affect maternal food intake, weight gain, length of gestation, litter size or fetal development; however, a daily dose of 1 mg/kg led to smaller litter size and higher incidence of stillbirth. Continued maternal administration of nicotine (100 micrograms/kg/day) until 12 days post partum did not affect newborn growth (body weight and length and size of heart and lung) during the first week after birth; during the second week, however, the nicotine-treated group lagged behind the controls. The stomachs of pups of nicotine-treated rats contained less food than those of controls; this difference increased with age, becoming more than 40% at 12 days. We suggest that lower milk production of nicotine-treated rats interferes with the normal development of the offspring during periods of rapid growth.

Animals↗
PubMed1978

Fat digestion in the stomach of premature infants. I. Characteristics of lipase activity.

Lipolytic activity was studied in gastric aspirates of 13 premature infants of birth weight 1,050 to 1,786 gm. All infants received a diet of infant formula fed by gastric tube. Gastric aspirates were collected after irrigating the stomach with 2 to 5 ml sterile saline before regular feeding. Lipolytic activity, tested with doubly labeled 3H glyceryl-14 C tripalmitin substrate, was 55.6 +/- 11.7 n mol/min/ml (range 4.2 to 140). The lipolytic activity had a pH optimum of 5.4 and produced partial glycerides (mono and diglycerides), glycerol, and free fatty acids. Lipolysis was inhibited by bile salts. Our findings show that in premature infants, as in adults, digestion of dietary fat starts in the stomach. Since bile salt concentrations are low in premature infants, the amphiphilic reaction products formed (monoglyceride and FFA) could play a significant role in the stabilization of lipid emulsions.

Digestion↗
PubMed1978

Rat lingual lipase: factors affecting enzyme activity and secretion.

The lingual serous glands of rat tongue secrete a potent lipase that acts in the stomach in which it initiates the digestion of dietary fat. The subcellular localization of the enzyme and factors affecting its activity and secretion were studied in adult male Sprague-Dawley rats. In a fraction rich in secretory granules, 42% of the lipase content of lingual serous glands was recovered after fractionation of homogenates of discontinuous gradients of urografin in 0.3 M sucrose. Lipase secretion was stimulated by isoprenaline: 2 h after isoprenaline administration, the lipase content of lingual serous glands was 73 +/- 5% lower than that of the control group. Accumulation of lipase began 8 h after the injection, reaching 57 +/- 7% of the initial level of the control group after 25 h. Bilateral resection of the glosso-pharyngeal nerves or bilateral sympathectomy led to a 40--50% decrease of enzyme activity in 7 days. Enzyme activity was markedly affected by the fat content of the diet. Feeding a high-fat diet (22% corn oil) for a period of 2 wk led to a 45% increase in the lipase content of lingual serous glands. The exponential rise in the lipase activity of the lingual serous glands immediately after birth could be related to the high-fat content of rat milk. The data suggest that the lingual serous glands are similar to other exocrine glands such as pancreas and parotid gland in the subcellular localization of secretory enzymes and mechanisms of enzyme secretion.

Animals↗
PubMed1978

Metabolic activity of developing rabbit lung.

The uptake and metabolism of [3H]leucine, [U-14C]glucose, and [3H]palmitate were studied in rabbits aged --3, 1, 7, 28, and 90 days up to 1--1.5 years. Although lung composition did not change markedly, there were great differences in lung metabolism between the perinatal period (late fetal and newborn) and later stages of development. Leucine incorporation into lung protein was highest (3.1--3.4 nmol/mg protein/hr) in late fetal and newborn rabbits and decreased rapidly thereafter. Palmitic acid incorporation decreased during the first week after birth from 150 nmol/100 mg/hr to 85 nmol/100 mg/hr at 7 days of age; it increased thereafter to 170 nmol/100 mg/hr at 4 weeks of age and remained at that level throughout the entire period studied. Glucose uptake and lactate production were higher in fetal lungs than in all other age groups. Lipid biosynthesis from glucose was 2--4 times higher in fetal lungs than at all other ages; furthermore, more than 60% of glucose carbon atoms channeled into lipid was incorporated into fatty acids, whereas at all other ages glucose was chiefly a precursor of lipid glycerol.

Animals↗
PubMed1977

The effect of prolactin on the lecithin content of fetal rabbit lung.

1 mg ovine prolactin was injected intramuscularly into rabbit fetuses (24th day of gestation) located in one of the two uterine horns exposed by laparotomy (n = 12). Fetuses in the other uterine horn were injected with an identical volume of vector and served as controls (n = 13). 2 days later the fetuses were removed by a second laparotomy and sacrificed. Analysis of lung tissue composition yielded the following results: (a) the prolactin-treated group of fetuses showed 40% higher total lung phospholipid content (17.0 +/- 0.8 micronmol/g) than the control group (12.2 +/- 0.5 micronmol/g); (b) the prolactin-treated group had a 67% higher lung lecithin content (8.7 +/- 0.8 micronmol/g) than the control group (5.2 +/- 0.4 micronmol/g); (c) dipalmitoyllecithin accounted for 67% of total lung lecithin in the prolactin-treated group and 44% in the control group. These differences were statistically highly significant (P less than 0.001). However, between the prolactin-treated and the control groups, there were no statistically significant differences in body weight and length, lung weight, the ratio of lung weight to body weight, DNA, protein and, water content. These results suggest that prolactin might be a trigger of lung surfactant synthesis in the rabbit fetus.

Animals↗
PubMed1977

Lipolytic activity of human lingual glands (Ebner).

Human tongue preparations contain lipolytic activity similar to that present in human esophageal and gastric aspirates and in serous glands of rat tongue. The activity is present in homogenates of the glandular region (Ebner) beneath the cirumvallate papillae, and in secretions collected from the trough of the papillae. The lipolytic enzyme hydrolyzes long chain triglycerides to partial glycerides (di- and monoglyceride), glycerol, and free fatty acids at pH optimum 5.4. Lipolytic activity, expressed as nanomoles of triglyceride hydrolyzed per minute was in the range of 0 to 500 per gm. of tongue homogenate and 78 to 277 per ml. of aspirate from the vallate papillae. There was a 50% inhibition of the lipolytic activity by 4 mM sodium taurodeoxycholate. Specimens obtained from the region of the vallate papillae were examined by light and electron microscopy. Electron-dense granules similar to secretory granules present in rat Ebner's gland and in serous acini of human submaxillary glands were detected. Our findings suggest that in man, as previously reported in the rat, the lingual serous glands secrete a lipase that acts in the stomach where it initiates the digestion of dietary fat.

Exocrine Glands↗
PubMed1976

Lipoprotein lipase in rat lung. Effect of dexamethasone.

The effect of hormone administration on the activity of lipoprotein lipase in the lung was studied in the rat. The following hormones were administered: dexamethasone, L-thyroxine, estradiol-17beta and progesterone. In addition, lung lipoprotein lipase activity was studied in diabetic and lactating rats. Lipoprotein lipase activity was measured in dried, defatted preparations of rat lung using double labeled ([14C]palmitate, [3H]glycerol) chylomicron triacylglycerol as substrate. Dexamethasone administration caused a rise of 70% in the level of activity of lipoprotein lipase in acetone powders of lung and a 100% increase in the amount of enzyme released during heparin infusion into isolated, perfused lungs. Enzyme activity was higher in lungs of females than of male rats; however; the level of activity was unaffected by estrogen or progesterone administration to either male or ovariectomized rats. Diabetes, hyperthyroidism or lactation did not change lipoprotein lipase activity in the lung. The constant presence of lipoprotein lipase activity in the lung suggests that this organ is able to maintain a steady supply of triacylglycerol-fatty acids under a variety of physiological and pathological conditions. Stimulation of enzyme activity by dexamethasone could lead to increased uptake of triacylglycerol-fatty acids by the lung and may thus be a contributing factor to corticosteroid-induced enhanced surfactant synthesis.

Animals↗
PubMed1975

Lipoprotein lipase in rat lung. The effect of fasting.

We measured lipoprotein lipase activity in dried defatted preparations of rat lung using doubly labeled chylomicron triglyceride as substrate. The enzyme activity was linear for the first hour of incubation at 37 degrees C, had a pH optimum of 8.1 and was completely inhibited by 0.5 M NaC1. Lungs from fed rats hydrolyzed chylomicron triglyceride at a rate of 13.00 mumoles/g per h; the activity rate was unchanged by fasting 8-72 h. Heparin infusion into isolated lungs caused immediate release of lipoprotein lipase to the venous effluent. The activity released was equivalent to about 10% of total lung lipoprotein lipase activity in both fed and fasted rats. Since the ability to remove blood triglyceride is directly related to the level of lipoprotein lipase activity, these findings indicate that the lung is one of the few tissues able to remove efficiently blood triglyceride during fasting.

Animals↗
PubMed1975

The effect of estrogen on the lipoprotein lipase activity of rat adipose tissue.

The effect of 17beta-estradiol or progesterone administration on adipose tissue lipoprotein lipase activity was studied in male and ovariectomized female rats. Lipoprotein lipase activity was measured in acetone-ether-extracted preparations of adipose tissue with doubly labeled (14C-fatty acid, 3H-glyceryl) chylomicron triglyceride as substrate. Administration of 17beta-estradiol to male rats lowered adipose tissue lipoprotein lipase activity from 8.22 plus or minus 1.8 U/g (1 U = 1 mumol triglyceride hydrolyzed per h) to 4.96 plus or minus 0.5 U/g in the treated group. Ovariectomy increased adipose tissue lipoprotein lipase activity from 10.4 plus or minus 1.8 U/g in controls to 22.7 plus or minus 4.3 U/g. 17beta-Estradiol administration to ovariectomized rats cuased a marked fall in adipose tissue lipoprotein lipase activity: 17beta-estradiol (2.5 mug/day) lowered the enzyme activity to 9.00 plus or minus 1.2 U/g, whereas 25 mug/day further decreased lipoprotein lipase activity to 3.2 plus or minus 0.6 U/g. Blood triglyceride levels increased from 0.8 plus or minus 0.05 mumol/ml in ovariectomized rats to 1.4 plus or minus 0.09 mumol/ml in 25 mug/day 17beta-estradiol-treated rats. Progesterone administration did not affect adipose tissue lipoprotein lipase activity in either male or ovariectomized rats. Heart and lung lipoprotein lipase activity was unaffected by hormone treatment. We suggest that the rise in blood triglyceride concentrations, which accompanies high palsma estrogen levels, could be due to the marked inhibition of adipose tissue lipoprotein lipase activity.

Adipose Tissue↗
PubMed1975

Pharyngeal lipase and digestion of dietary triglyceride in man.

Lipolytic activity was studied in esophageal and gastric aspirates obtained with a nasogastric tube from 14 healthy adult subjects. Samples were collected from esophagus, first at 30-35 cm and then at 40-45 cm from the nose, as the subject, after drinking 15-30 ml of a cream-milk mixture, swallowed small amounts of water. The samples from stomach were taken last and usually contained a small amount of cream-milk mixture. Lipolytic activity was assayed using chylomicron, milk, and corn oil triglyceride as substrate. Esophageal and gastric samples both contained lipolytic activity which hydrolyzed long-chain triglyceride to diglyceride, monoglyceride, and FFTA, had a pH optimum of 5.4, and was not affected by either had a pH optimum of 5.4, and was not affected by either 0.5 M NaCl or 4 mM sodium taurodexycholate. The activity, expressed as nanomoles of chylomicron triglyceride hydrolyzed per milliter per minute, ranged from 0 to 145 in upper esophageal, 5 to 303 in lower esophageal, and 50 to 357 in gastric samples. Only a trace of lipolytic activity was found at pH 5.4 in saliva collected from the parotid, submandibular, and sublingual glands, thus excluding those tissues as a source of the activity found in esophageal and gastric aspirates. The findings suggest that in man glands in or near the pharynx secrete a lipase that acts in the stomach to hydrolyze long-chain triglyceride to partial glycerides and FFA. It is proposed this reaction is the first step in the digestion of dietary fat and that the amphiphilic lipids formed by lipolysis facilitate the emulsification of triglyceride in the stomach.

Adult↗
PubMed1973

Lingual lipase and its role in the digestion of dietary lipid.

The serous glands of rat tongue were found to contain a potent lipolytic enzyme which hydrolyzed triglyceride to mostly diglyceride and free fatty acids (FFA) at pH 4.5-5.4. Homogenates of lingual serous glands from adult rats hydrolyzed 40-70 mmol of triglyceride/g per h. The soft palate, anterior oral pharyngeal wall, and lateral oral pharyngeal glands also contained the activity, but at a much lower level. The lipolytic activity was also found in saliva collected through an esophageal cannula and in stomach contents of rats fed a fat-rich meal. The stomach contained very little activity, however, when saliva was excluded. Lipolytic activity was not found in the stomach wall or in the parotid, submandibular, and sublingual glands. The findings suggest that the lingual serous glands secrete a lipase which catalyzes in the stomach the conversion of triglyceride to partial glycerides and FFA. It is proposed that this reaction is the first step in the digestion of dietary lipid.

Animals↗