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Biomedical subjects

L S Hurley

Publications and source records attributed to L S Hurley.

At least 19 recordsLinked to original sources
PubMed1991

Longitudinal changes in the mineral composition of mouse milk and the relationship to zinc metabolism of the suckling neonate.

We studied changes in the mineral composition of milk of lactating Swiss-Webster mice and the relationship of those changes to mineral metabolism of suckling mouse pups. Concentrations of Zn, Cu, Mg and Ca were analyzed in maternal and neonatal tissues and in milk; Zn metabolism was studied using 65Zn. Although Cu, Ca and Mg concentrations in milk declined during the first 2 d of lactation, only the concentration of Zn decreased progressively throughout 30 d. Various pup tissues were characterized by developmental changes in concentrations of some elements. Turnover of Zn in neonatal tissues was studied by radiolabeling litters in utero and fostering them at birth to nonradiolabeled lactating dams. The turnover of whole-body 65Zn in suckling mice decreased during development, and, at 20 d of age, the biological half-life of 65Zn in the neonate was approximately the same as for a nonpregnant, nonlactating adult female (20 d). The decreased turnover of 65Zn in lactating dams that characterized progressive lactation and was reflected in the Zn concentration of milk is in agreement with changes in whole-body 65Zn turnover observed for the suckling mouse. These findings demonstrate that the metabolism of the suckling neonate is directly related to longitudinal changes in the composition of maternal milk.

Animals↗
PubMed1991

Mineral status of mice suckling early-, mid- and late-lactating foster dams.

We have demonstrated that the zinc (Zn) concentration of mouse milk declines significantly over the lactation period. Pups radiolabeled in utero with 65Zn were forward-fostered (FF) to nonradiolabeled dams at a later stage of lactation to study the effects of early milk deprivation. Other groups of radiolabeled pups were back-fostered at 5, 10 and 15 days of age to a nonradiolabeled dam who had just given birth; this provided additional colostrum during the suckling period. Litters fostered at birth to an unlabeled dam at d 0 of lactation were used as controls. Weight gain of FF litters decreased and signs of Zn deficiency increased as the foster dam's days of lactation increased. The Zn concentration of kidney, brain and plasma tended to decrease with increasing lactation days of the foster dam. Tibia Zn concentration declined progressively as the lactation days of the foster dam increased, and the concentration of calcium also was lower in all three groups of FF litters than in controls, indicating that bone calcification may have been impaired. Kinetic data proved to be a more sensitive index of Zn status than tissue Zn concentration. The biological half-life of whole-body 65Zn for FF suckling mice increased in a linear fashion with increasing lactation days of the foster dam; whole-body retention of 65Zn for back-fostered litters did not differ from that for controls. Brain, small intestine, kidney muscle, plasma and tibia of pups FF to late-lactating dams seemed to have greater retention of Zn than did controls. Thus, deprivation of early milk impaired growth and development of the mouse neonate despite some ability to conserve Zn.

Animals↗
PubMed1990

Effects of marginal zinc deficiency on microtubule polymerization in the developing rat brain.

One of the possible mechanisms that has been proposed to underlie the deleterious effects of zinc deficiency on brain development is an impairment in the normal formation of the cytoskeletal network. In the current study, in vivo microtubule polymerization was characterized in brain supernatant fluids, from 20-d-old pups whose dams were fed diets containing control (50 micrograms zinc/g) or marginal levels of zinc (10 micrograms zinc/g) throughout pregnancy and lactation. Pup brain and body weights were similar between the groups; however, plasma zinc concentrations were lower (27%) in pups fed the marginal zinc diet than in controls. Tubulin concentrations in 100,000 g brain supernates were similar between the groups; however, tubulin polymerization in the brain supernates was significantly lower in pups fed the marginal zinc diet compared to controls. Primarily, the early events of polymerization were affected; the lag period of the reaction was doubled, and the initial velocity was slower (26%) in supernates from pups fed the marginal zinc diet than in controls. These findings support the idea that some of the negative effects of marginal zinc deficiency on brain development and function may be mediated by an alteration in microtubule formation.

Animals↗
PubMed1979

Evaluation of negative staining technique for determination of CN--insensitive superoxide dismutase activity.

The different forms of superoxide dismutase (superoxide-superoxide oxidoreductase, EC 1.15.11) have been studied, in tissues of rat, mouse and chicken, by the ectrophoresis-nitro blue tetrazolium technique proposed by Beauchamp. Similar enzyme patterns were evident in every tissue. A fast migrating CN--sensitive form of dismutase activity was present in isolated liver mitochondria of each species. Chicken and mouse liver mitochondria, as well as whole homogenate of every tissue of these two species, showed two additional slow-migrating bands of CN--insensitive activity. In contrast, such bands were not detectable in mitochondria isolated from rat liver or in any of the rat tissues analyzed by this technique. Prior to their electrophoretic separation, the samples were analyzed for CN--insensitive superoxide dismutase activity by a spectrophotometric assay; by this assay it was possible to demonstrate and quantitate a CN--insensitive superoxide dismutase activity in every preparation. Two units of CN--insensitive activity were applied to the gels for each sample. These results indicate that the electrophoresis-nitro blue tetrazolium technique is unsuitable for the detection of the rat CN--insensitive form of superoxide dismutase in crude preparations such as whole tissue homogenates or isolated mitochondria.

Animals↗
PubMed1979

Developmental patterns of copper and zinc concentrations in mouse liver and brain: evidence that the gene crinkled (cr) is associated with an abnormality in copper metabolism.

An abnormality in copper metabolism during both the prenatal and postnatal (preweaning) periods was found to be associated with the autosomal recessive gene "crinkled" (cr) in mice. Liver copper concentration was significantly lower in crinkled mice (cr/cr) than in littermate controls (+/?) from 18 days of gestation to 20 days after birth. Crinkled mice older than 20 days of age and liver copper concentrations similar to those of littermate controls. Liver zinc and brain copper and were similar in crinkled and noncrinkled mice at all times tested. In both crinkled and noncrinkled mice, brain copper concentration increased during the suckling period, and liver copper concentration decreased.

Aging↗
PubMed1978

Relationship of dietary zinc to 6-mercaptopurine teratogenesis and DNA metabolism in the rat.

The possible interaction between the level of maternal dietary zinc and the teratogenic activity of 6-mercaptopurine was investigated. Pregnant Sprague-Dawley rats were fed diets containing 9,100 or 1,000 ppm zinc from day zero of pregnancy and were given a single intraperitoneal injection of 6-MP (55mg/kg) on day 11. At term, females in the group fed 1,000 ppm zinc (a high intake) showed less pronounced effects on reproduction and embryogenesis than did those fed 9 ppm (marginally deficient) or 100 ppm (normal) zinc. Embryos examined on day 12 of gestation had similar concentrations of protein and RNA; however, the DNA content was lower and the incorporation of 3H-thymidine was greater in the drug treated groups than in non-drug treated controls. These results indicate that 6-mercaptopurine is acting to alter embryonic DNA metabolism and that high levesl of dietary zinc may ameliorate some of the deleterious effects of this drug on embryonic and maternal toxicity.

Abnormalities, Drug-Induced↗
PubMed1978

Attenuating effect of zinc on abnormal placental morphology in 6-mercaptopurine treated rats.

Pregnant Sprague-Dawley rats were fed diets containing 9 (marginal level), 100 (control level), or 1,000 (very high level) ppm zinc and were given a single intraperitoneal injection of 6-mercaptopurine (6-MP, 55 mg/kg) or an equivalent volume of carboxymethylcellulose on day 11 of gestation. Live young and their placentas were recovered at surgery on day 21 of gestation: they were weighed, measured, and placentas were examined histologically. Placentas from drug treated animals were smaller in diameter and lighter in weight than controls; however, the placentas of animals fed the 1,000 ppm zinc diet were significantly heavier than those of the other drug-treated groups. Histologically, the placentas of the 6-MP treated dams showed a highly disproportionate reduction in the labyrinthine layer with larger, less subdivided maternal sinuses than in controls, reduction of fetal vasculature, vesiculation of trophoblast nuclei, deposition of PAS positive material in the septal wall, and fibrinous degeneration of trophoblast cells. These morphological changes were reduced in placental tissues of drug treated rats given 1,000 ppm of zinc. In contrast, no placental abnormalities were observed in rats not treated with 6-MP.

Abnormalities, Drug-Induced↗
PubMed1978

An interaction between zinc and vitamin A in pregnant and fetal rats.

A possible interaction between zinc and vitamin A metabolism was studied in pregnant rats. Rats were depleted of vitamin A by feeding retinoic acid during growth. At mating, they were fed diets containing 100, 9, or 0.5 microgram/g zinc and were given orally 400, 8, or 0 microgram/kg body weight/day of retinyl palmitate. Low intake of zinc, but not of vitamin A, caused maternal body weight gain, placental weight, and fetal weight all to be low. The number of implantation sites affected and the proportion of fetuses malformed were dependent on intake of both zinc and vitamin A, and there was a significant interaction between these nutrients in regard to both of these parameters. In maternal as well as in fetal animals, plasma and liver zinc concentrations were low in groups fed low levels of zinc, but not in those given low vitamin A. Liver vitamin A values were affected by vitamin A intake but not by dietary zinc concentration. However, plasma vitamin A concentration in both maternal and fetal animals was significantly reduced by low intake of either zinc or vitamin A. There was a significant interaction between these two nutrients in regard to plasma vitamin A. These data indicate an interaction between zinc and vitamin A metabolism possibly at the level of vitamin A mobilization from the liver.

Abnormalities, Drug-Induced↗
PubMed1978

Intestinal absorption of zinc: a role for a zinc-binding ligand in milk.

This study examined the proposal that a low molecular weight, zinc-binding ligand (ZBL) in certain milks is important for zinc absorption in the neonatal period. Ten-day-old rats, in which intestinal ZBL is absent, fed (by stomach intubation) 65Zn-labeled ZBL from rat milk, absorbed significantly more 65Zn than those fed free 65ZnCl2 or bovine milk fractions. ZBL from human milk appeared to have an intermediate effect, possibly due to species specificity. 65Zn was found in the ZBL fraction in intestinal mucosa of 10-day-old rats fed rat or human milk fractions, but not in those fed bovine milk or free 65ZnCl2. In contrast, in 18-day-old rats, which have an endogenous intestinal ZBL, there were no differences in zinc absorption, and any of the labeled milk fractions or free 65Zn caused localization of 65Zn in the ZBL fraction of intestinal mucosa. These results support the hypothesis that the intestinal ZBL plays a role in zinc absorption and that in the neonatal period before its development the milk ZBL is valuable for this function. This mechanism may be important in normal human infants as well as in acrodermatitis enteropathica patients.

Acrodermatitis↗
PubMed1977

Zinc binding: a difference between human and bovine milk.

Gel chromatography indicated that most of the zinc in cow's milk was associated with high-molecular-weight fractions, whereas zinc in human milk was associated with low-molecular-weight fractions. A species difference in zinc-binding ligands may explain why symptoms of the genetic disorder of zinc metabolism, acrodermatitis enteropathica, can be alleviated by feeding human but not cow's milk.

Acrodermatitis↗
PubMed1977

Zinc-binding ligands in milk and intestine: a role in neonatal nutrition?

The hypothesis that a zinc-binding ligand (ZBL) recently discovered in human milk but absent from cow's milk might be related to zinc nutrition in the neonate was investigated. The zinc-binding characteristics of rat milk were examined to determine if the rat was a suitable model. By gel filtration, rat milk was found to contain a ZBL with characteristics similar to those of the ZBL found in human milk. A similar ZBL was identified in the intestinal mucosa of rats 16 days of age and older but was absent in rats from birth to 16 days. These results support the hypothesis that the ZBL of maternal milk may enhance zinc transport in the neonatal period before the development of intestinal mechanisms for zinc absorption.

Aging↗