Biomedical subjects

I A Shibley

Publications and source records attributed to I A Shibley.

14 recordsLinked to original sources

PubMed2001

Differential expression of glucose transporters during chick embryogenesis.

The patterns of Glut1 and Glut3 glucose transporter protein and mRNA expression were assessed during embryogenesis of chicken brain and skeletal muscle, Glut4 protein levels were also evaluated in skeletal muscle and heart, and Glut1 was examined in the developing heart and liver. Glut1 protein expression was detectable throughout brain ontogeny but was highest during early development. Glut1 mRNA levels in the brain remained very high throughout development. Glut3 protein was highest very early and very late and mRNA was highest during the last half of development. In embryonic skeletal muscle, the levels of Glut1 and Glut3 proteins and mRNA were highest very early, and declined severely by mid-development. Glut1 protein and mRNA in the heart also peaked early and then decreased steadily. Although Glut1 mRNA levels were consistently high in the embryonic liver, Glut1 protein expression was not detected. These results suggest that (1) Glut1 is developmentally regulated in chick brain, skeletal muscle, and heart, (2) Glut1 mRNA is present in liver but does not appear to be translated, (3) Glut3 in brain increases developmentally but is virtually absent in muscle, and (4) Glut4 protein and mRNA appear to be absent from chick heart and skeletal muscle.

Animals↗

PubMed1999

Ethanol-induced decrease of developmental PKC isoform expression in the embryonic chick brain.

Prenatal ethanol exposure can cause a number of physiological deficits known as fetal alcohol syndrome (FAS). Because protein kinase C (PKC) regulates the cell cycle and has been linked to growth, we examined the effect of ethanol on PKC isoform expression in a developing chick brain. Ethanol exposure causes decreased head weight in chickens at day 5 in a dose-dependent manner and a decreased brain weight at days 7 and 10 at an ethanol concentration of 1.0 g/kg. Antibodies specific for PKC-alpha, beta, gamma, delta, epsilon, iota, lambda, mu and zeta were used to examine ethanol's effect on PKC expression in the growth-suppressed brain at days 5, 7 and 10 of development. Only four of the PKC isoforms tested are expressed in the chick brain prior to day 10: alpha, gamma, epsilon, and iota. PKC-alpha, gamma, and epsilon are developmentally increased during the time period studied. Ethanol causes a decreased expression of PKC-alpha on days 5, 7 and 10 and a decreased expression of PKC-gamma on days 7 and 10. Ethanol causes a decreased expression of PKC-epsilon only on day 7. PKC-iota expression is unchanged over the developmental times studied and ethanol exposure has no effect on PKC-iota expression. These data suggest that only specific PKC isoforms are developmentally expressed in the embryonic chick brain and that ethanol may inhibit the expression of those PKC isoforms that are developmentally regulated.

Animals↗

PubMed1999

Increased intracellular localization of brain GLUT-1 transporter in response to ethanol during chick embryogenesis.

Fetal exposure to ethanol is associated with growth retardation of the developing central nervous system. We have previously described a chick model to study the molecular mechanism of ethanol effects on glucose metabolism in ovo. Total membrane fractions were prepared from day 4, day 5, and day 7 chick embryos exposed in ovo to ethanol or to vehicle. By Western blotting analysis, ethanol exposure caused a mean 7- to 10-fold increase in total GLUT-1 and a 2-fold increase in total GLUT-3. However, glucose uptake by ethanol-treated cells increased by only 10%. Analysis of isolated plasma (PM) and intracellular (IM) membranes from day 5 cranial tissue revealed a mean 25% decrease in GLUT-1 in the PM and a 66% increase in the IM in the ethanol group vs. control. The amount of PM GLUT-3 was unchanged but that of IM GLUT-3 was significantly decreased. The data suggest that GLUT-3 cell surface expression may be resistant to the suppressive effects of ethanol in the developing brain of ethanol-treated embryos. The overall increase in GLUT-1 may reflect a deregulation of the transporter induced by ethanol exposure. The increased IM localization and decreased amount of PM GLUT-1 may be a mechanism used by the ethanol-treated cell to maintain normal glucose uptake despite the overall increased level of the transporter.

Animals↗

PubMed1997

Changes in brain glucose levels and glucose transporter protein isoforms in alcohol- or nicotine-treated chick embryos.

Suppression of fetal brain growth during pregnancy as the result of maternal smoking or alcohol consumption leads to significant problems for the offspring as well as for the society who must care for these individuals. Chronic maternal intake of cigarette smoke is frequently observed in humans and studies using animal models suggest that in utero nicotine exposure is an important component of the growth suppression that results. Similarly, maternal consumption of alcohol (ethanol) has a profound, negative effect on fetal growth. The developing fetal central nervous system (CNS) is sensitive to the growth inhibitory effect of nicotine or alcohol and morphological as well as functional CNS deficits may result from fetal exposure. Using an embryonic chick model which minimizes drug-induced changes in maternal nutrition and behavior, the studies presented here indicate that nicotine or alcohol exposure during early embryonic development inhibits brain growth to a degree comparable to that seen in the rest of the organism, i.e., there was no 'brain sparing' in this model. Glucose content per milligram tissue was markedly decreased in brains of the nicotine-treated embryos but was not significantly different in the alcohol-exposed embryos. Western blots of fetal brain glucose transporter protein isoforms showed no change in the Glut 3 transporter content in the growth suppressed brains compared to vehicle-treated brains. The Glut 1 55 kilodalton (kd) isoform protein content was significantly decreased in the nicotine-treated brains but unchanged in the ethanol-treated brains, while the reverse was true for the Glut 1 45 kd isoform. Thus, the changes in the 55 kd isoform protein content were correlated with tissue glucose levels in the ethanol- and nicotine-treated embryos.

Analysis of Variance↗

PubMed1997

Ethanol differentially affects metabolic and mitotic processes in chick embryonic cells.

Our laboratory has been investigating the mechanisms by which ethanol-induced growth inhibition occurs in a developing embryo, and our studies have focused on disruption of cellular signaling pathways. Previous work on ethanol-induced changes in signaling systems that regulate ornithine decarboxylase activity indicated that the pathways containing protein kinase A, protein kinase C (PKC), and insulin-dependent tyrosine kinase were important for the control of ornithine decarboxylase in chick embryonic cells. Herein, we report ethanol's effect on the regulation of glucose uptake and thymidine uptake by these same kinase pathways. A pronounced increase in glucose uptake was associated with PKC downregulation in both vehicle- and ethanol-exposed cells, with the larger increase occurring in ethanol-exposed cells. An increase in thymidine uptake was associated with an activation of all three kinases, as well as with downregulation of PKC. Because previous work on signaling pathways has looked for changes in the insulin signaling pathway, the work herein focuses on the signaling pathways involving protein kinase A and PKC. cAMP levels were increased by ethanol treatment, but the increase was relatively small. Analysis of changes in PKC activity induced by ethanol exposure showed a significant suppression of PKC activity in the ethanol-treated cells and suggested that, overall, ethanol treatment affects the regulation of glucose uptake in embryonic cells predominantly by PKC downregulation.

Animals↗

PubMed1995

Ethanol's effect on tissue polyamines and ornithine decarboxylase activity: a concise review.

An extraordinarily diverse literature describes the cellular/tissue systems in which the molecular effects of both acute and chronic alcohol exposure seem to be mediated by changes in polyamine levels and/or ornithine decarboxylase (ODC) activity. The single unifying factor that links most of these studies is that they all, in some way, involve tissues that are undergoing relatively rapid cell division. Non-dividing cells expressing the NMDA receptor are a notable exception in that ethanol and the polyamines seem to act via discrete regions of that receptor. Under most cellular conditions, ODC activity is a reflection of the relative tissue polyamine content, and an increase in ODC activity and polyamine content seems to be one of the early events in the progression of quiescent cells toward cell division. Thus, it is not surprising that ethanol, which has been widely reported to delay cell division, should be found to interact with the ODC/polyamine pathway. Perhaps the most unique aspect of these studies is the fact that, with rare exception, both acute and chronic ethanol exposure have been found to slow growth and to lower tissue polyamine (putrescine) content. Furthermore, in most studies, the ethanol-induced suppression of cell division could be overcome by the administration of exogenous putrescine. These data suggest that the ethanol-induced suppression of cell division resulted from the loss of putrescine. In addition, because the cells were able to respond to the exogenous putrescine, the studies suggest that the signaling pathway remained intact beyond the polyamine synthesis step.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Drinking↗

PubMed1995

Insulin signaling in chick embryos exposed to alcohol.

Although insulin is known to be an important generator of regulatory signals during fetal growth and development, neither the immediate nor long-term effects of alcohol (ethanol) on insulin action are well understood. In the rat, fetal exposure to alcohol has been shown to be correlated with a subsequent abnormal response to a glucose load in the neonate and adult. Further, fetal hypoplasia secondary to maternal alcohol consumption is correlated with decreased placental glucose transport and with a lowering of the glucose levels in fetal tissues. However, the fetal effects of alcohol cannot be completely overcome by glucose/caloric supplementation, suggesting that factors other than glucose transport are involved. Using an embryonic chick model that negates the factors of maternal/placental metabolism and transport, the current study found that fetal alcohol exposure markedly increased insulin binding in developing tissue, but had little effect on the binding of the insulin-like growth factors. Competitive binding experiments revealed a marked increase in insulin receptor numbers, but no change in binding affinity as a result of the alcohol exposure. Basal uptake of 2-deoxyglucose by fetal tissue was lowered by alcohol exposure, but incubation with exogenous porcine insulin (1 x 10(-7) M) resulted in a significant increase in glucose uptake by the alcohol-exposed embryos. The increases in insulin binding and in insulin-dependent glucose uptake notwithstanding, exogenous insulin could not induce normal levels of ornithine decarboxylase activity in embryonic cells previously exposed to alcohol.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1995

Signaling pathways regulating ornithine decarboxylase activity in the embryonic chicken.

The pathways regulating ornithine decarboxylase (ODC) activity in the chick embryo were studied to determine which kinase-signaling pathways regulate ODC activity levels during development. Insulin-dependent tyrosine kinase, protein kinase C and cAMP-dependent protein kinase were activated by the addition of insulin, tetradecanoylphorbol-12,13-acetate, and forskolin, respectively. All three drugs increased ODC activity and forskolin combined with insulin increased ODC activity above the increase caused by either drug alone. These results suggest that all three signaling pathways regulate ODC activity during development and that common intermediates exist among the pathways downstream of the kinases.

Animals↗

PubMed1994

Biochemical changes, early brain growth suppression and impaired detour learning in nicotine-treated chicks.

Fetal growth suppression associated with chronic maternal intake of cigarette smoke is frequently observed in humans and studies using animal models suggest that in utero nicotine exposure is an important component of this growth suppression. The developing fetal central nervous system (CNS) is sensitive to the growth inhibitory effect of nicotine and morphological as well as functional CNS deficits may result from fetal nicotine exposure. The studies presented here show that nicotine exposure during early embryonic development ultimately inhibits the ability of 7-11 day old chicks to learn a detour task. The brain growth suppression caused by nicotine is paralleled by a failure of the early embryo brain to express the normal developmental increase in ornithine decarboxylase (ODC) activity. This biochemical change may be germane to the mechanism of nicotine-induced growth inhibition and/or nicotine-induced behavioral changes because the appropriate expression of ODC activity is essential to normal growth and differentiation in the fetal CNS. In the chick embryo, nicotine exposure alters several important signaling pathways that regulate ODC expression. For example, nicotine exposure lowers embryonic brain glucose levels and causes significant decreases in whole brain cyclic adenosine 3',5'-monophosphate (cyclic AMP) levels and in cyclic AMP binding proteins (protein kinase-A regulatory activity). Also, in cultured chick cells, nicotine inhibits the ability of a potent mitogen (insulin) to induce ODC activity, but, paradoxically, in ovo nicotine exposure increased insulin binding and stimulated insulin receptor autophosphorylation in brain membranes.

Animals↗

PubMed1993

Deoxyguanosine-resistant leukemia L1210 cells. Loss of specific deoxyribonucleoside kinase activity.

A mouse leukemia L1210 cell line was selected for resistance to deoxyguanosine. The deoxyguanosine-resistant cells (dGuo-R) were 126-fold less sensitive to deoxyguanosine than the wild-type cells. The IC50 values for araC and araG were increased, but only 10-12-fold in the dGuo-R cells when compared with the wild-type cells. The dGuo-R cell line showed an increased level of resistance to 2-fluoro-2'-deoxyadenosine and 2-fluoroadenine arabinoside (11-14-fold), but essentially no increase in resistance to deoxyadenosine or adenine arabinoside. Deoxyribonucleoside kinase activity was decreased only slightly (19%) when deoxycytidine was utilized as substrate; when cytosine arabinoside or deoxyguanosine was used as the substrate, the kinase activity in the extracts from the dGuo-R cells was only 10% of the enzyme activity in the extracts from the wild-type cells. The determination of the kinetic parameters, Km and Vmax, indicated that there were marked decreases in the Vmax values for deoxyguanosine and cytosine arabinoside as substrates, but not for deoxycytidine as substrate; the Km values for deoxycytidine and cytosine arabinoside were increased in the extracts from the dGuo-R cells. By use of high-performance liquid chromatography, the kinase activities in the extracts from the wild-type and resistant cells could be resolved. There was the specific loss of kinase activity toward cytosine arabinoside and deoxyguanosine as substrates. These data indicate that the dGuo-R cells have decreased levels of a specific deoxyribonucleoside kinase activity.

Animals↗

PubMedDate not supplied

Sodium ion-dependent (N-methylamino)-alpha-isobutyric [correction of isobutryic] acid uptake by embryonic chick cells exposed to ethanol in ovo:response to the stimulation/downregulation of protein kinases.

Amino acid uptake, critical for embryonic development, was studied in cultured chick cells isolated from 5-day-old chick embryos that had received treatment in ovo with either vehicle (sterile chick Ringer's solution) or vehicle plus ethanol (1.5 g/kg). Upon being placed in culture, the cells were grown in the absence of ethanol per se. The uptake of (N-methylamino)-alpha-isobutyric [correction of isobutryic] acid (AIB) was used to estimate amino acid uptake via system A, a Na+-dependent system that transports short-chain amino acids. The uptake of AIB in cultured chick embryo cells in response to the stimulation/downregulation of three protein kinases [tyrosine kinase, cyclic AMP-dependent kinase A (PKA) and protein kinase C (PKC)] was determined. Acute activation of PKC by treatment of the cells with a phorbol ester (TPA) inhibited Na+-dependent AIB uptake. Conversely, treatment of the cells with TPA for 24 h, to downregulate PKC activity, significantly increased AIB uptake. The data suggest that in these cells, PKC plays an important role in the regulation of amino acid uptake via system A. Activation of PKA via treatment of the cells with forskolin, an adenylyl cyclase activator, had little effect on AIB uptake in cells from vehicle-treated embryos and only a slight depressing effect on uptake by cells from ethanol-treated embryos. Insulin and insulin-like growth factor-1 (IGF-1) both stimulated AIB uptake, but the higher concentrations of insulin necessary to increase uptake to a level comparable to that of IGF-1 stimulation suggested that insulin could be acting through the IGF-1 receptor. Thus, while AIB uptake by cells of in ovo ethanol-treated embryos was significantly increased by treatment with either insulin or IGF-1, IGF-1 appeared to be the more physiologically important compound in the chick embryo. Overall, there was a consistent trend for cells isolated from in ovo ethanol-treated embryos to have higher levels of AIB uptake relative to cells isolated from vehicle-treated embryos, regardless of the in vitro treatment.

Animals↗

PubMedDate not supplied

Teratogenicity of ethanol in different chicken strains.

This study investigated the teratogenicity of ethanol in several different strains of chickens. The chick embryo provides a useful model for studying the fetal alcohol syndrome. Two broad classifications of chicks, each containing many strains, are commercially available for use: broilers and layers. Teratogenicity of ethanol in broilers and layers was studied by examining three different parameters: embryo weight, ratio of torso weight to head weight, and embryo viability. Broilers and layers experienced similar ethanol-induced reductions in embryo weight, Broiler embryos experienced a preferential ethanol-induced suppression of head growth. Differences in viability between different strains were found, but no clear pattern between broilers or layers could be determined, possibly due to environmental conditions. The data presented here suggest that the strain of chick and the handling of the eggs are important considerations when studying the teratogenicity of ethanol. An ethanol dose-response test should be periodically performed as a check on environmental conditions affecting the eggs--conditions that are beyond the control of the researcher.

Animals↗

PubMedDate not supplied

Experimental models used to measure direct and indirect ethanol teratogenicity.

The teratogenic effects of ethanol have been widely studied in a variety of experimental models. In humans, ethanol teratogenicity results from both direct and indirect effects. This paper reviews the differences between direct and indirect effects of ethanol on the developing fetus. Experimental paradigms are discussed that attempt to differentiate between direct and indirect effects. For the purpose of this review, direct effects of ethanol are caused by ethanol interacting with the fetal cell. Indirect effects of ethanol teratogenicity are defined as any perturbation of the developing fetus resulting from ethanol exposure but not caused by ethanol's interacting with the fetal cell. Indirect effects of ethanol teratogenicity include: ethanol-induced maternal undernutrition; ethanol-induced placental dysfunction and acetaldehyde teratogenicity.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Metabolic and mitotic changes associated with the fetal alcohol syndrome.

In the USA, fetal alcohol syndrome (FAS) is the leading known cause of mental retardation. FAS is estimated to affect 4000 infants yearly in the USA with an additional 7000 children suffering various forms of fetal alcohol effects in the absence of the full syndrome. A comparable incidence would be expected in other industrialized countries, but essentially no data are available from either developing or third world countries. An understanding of the biochemical causes of FAS has been slow to develop, but progress has been made toward a molecular causation theory of FAS. This paper summarizes much of the current work as to the effects of fetal ethanol exposure on mitotic and metabolic parameters as well as ethanol's effect on the cellular signalling pathways thought to regulate these processes. Based upon these studies, it is apparent that exposure of embryonic tissue to ethanol results in decreased growth and that alcohol adversely affects a multitude of cellular functions critical for the growth of the developing organism, including inhibition of protein and DNA synthesis. In addition, ethanol alters the uptake of critical nutrients such as glucose and amino acids and causes changes in several kinase-mediated signal transduction pathways that regulate these biochemical processes.

Central Nervous System Depressants↗