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M L Williams

Publications and source records attributed to M L Williams.

At least 145 records · Page 8Linked to original sources
PubMed1990

Serine-palmitoyl transferase activity in cultured human keratinocytes.

Sphingolipids comprise approximately 25% of the stratum corneum lipids and are considered critical constituents of the epidermal permeability barrier. Whether sphingoid base structures are synthesized in the epidermis or whether they are derived from circulating or dermal sources is not known. We report here the initial characterization of serine-palmitoyl transferase (EC 2.3.1.50; SPT), the rate-limiting enzyme in the synthesis of sphingolipids, from cultured human neonatal keratinocytes. Subcellular fractionation studies demonstrated that 79% of the total cellular SPT activity was associated with the microsomes. The specific activity of keratinocyte SPT was 270 +/- 20 pmol/min per mg of microsomal protein, a level significantly higher than activities reported in other tissues. Keratinocyte SPT showed an apparent Km for L-serine of 0.40 (+/- 0.04 mM, with an alkaline pH optimum (8.2 +/- 0.4). Keratinocyte SPT utilizes palmitoyl-CoA preferentially over other saturated or unsaturated acyl-CoA substrates; increasing acyl-CoA chain lengths above C16 by one or two carbons was less detrimental to activity than similar decrements in chain length. Finally, the mechanism-based inhibitors L-cycloserine and beta-chloro-L-alanine, demonstrated potent inhibition of keratinocyte SPT activity, with 50% inhibitory concentrations of approximately 3.0 and 25 microM, respectively. In summary, we have found that cultured human neonatal keratinocytes contain unusually high levels of serine-palmitoyl transferase activity, and that the substrate specificity of keratinocyte SPT may determine the base composition of epidermal sphingolipids.

Acyltransferases↗
PubMed1989

Death of a child as a result of familial hypercholesterolaemia.

A 10-year-old boy died of a myocardial infarction; he had homozygous familial hypercholesterolaemia. Unrecognized tendon xanthomas previously had been removed. His parents and siblings were found to have elevated cholesterol levels. The screening of at-risk children allows the early recognition of hypercholesterolaemia and intervention in the development of atherosclerosis.

Arteriosclerosis↗
PubMed1989

Differentiation of cultured human keratinocytes: effect of culture conditions on lipid composition of normal vs. malignant cells.

Differentiation in keratinocytes can be experimentally modulated by changing the culture conditions. When cultured under conventional, submerged conditions, the extent of cellular differentiation is reduced in the presence of low calcium medium and is enhanced in medium containing physiologic calcium concentrations. Moreover, cultures grown at the air-medium interface or on a dermal substrate, or both, differentiate even further. Herein we report the effect of culture conditions on lipid composition in normal human keratinocytes and three squamous carcinoma cell (SCC) lines that vary in their capacity to differentiate as assessed by cornified envelope formation. Under submerged conditions, the total phospholipid content was lower, triglyceride content higher, and phospholipid:neutral lipid ratio lower in direct correlation to the degree of differentiation in these cultures. When grown at the air-medium interface on de-epidermized dermis, evidence of further morphologic differentiation was found only for well-differentiated SCC cells and normal keratinocytes. Similarly, the phospholipid content remained high in poorly differentiated SCC cells and it decreased modestly in well-differentiated SCC cells and markedly in normal keratinocytes. In all cell lines the triglyceride content was increased and cholesterol content decreased when compared to parallel submerged cultures, but these differences were most pronounced in well-differentiated cell lines. Acylceramides and acylglucosylceramides were found only in normal keratinocytes and only under the most differentiation-enhancing conditions. These studies demonstrate differentiation-related changes in the lipid content of both normal and neoplastic keratinocytes.

Cell Differentiation↗
PubMed1989

Diagnosis of birth asphyxia on the basis of fetal pH, Apgar score, and newborn cerebral dysfunction.

Imprecise diagnosis of birth asphyxia coupled with uncertainties about causal factors for neurologic abnormalities in the newborn have greatly fueled the current litigation crisis in obstetrics. Our goal was to more precisely define birth asphyxia based on fetal condition as measured by umbilical artery blood pH, Apgar scores, and neurologic condition of newborns. We selected for study 2738 patients with singleton pregnancies with cephalic presentations who were delivered of infants at term to avoid complications such as prematurity, which may affect infant outcome independent of birth condition. The basis for study of these particular patients were defined criteria for high risk and an indicated arterial cord pH value. A total of five infants demonstrated cerebral dysfunction as evidenced by seizures during the neonatal period. Infection was linked to seizures in three of these infants; one infant had neonatal asphyxia and only one infant's clinical course could be attributed solely to birth events (uterine rupture). Stratification of umbilical artery blood pH values, Apgar scores, and combinations of these dependent variables in relation to newborn clinical outcomes revealed that infants must be severely depressed at delivery before birth asphyxia can be reliably diagnosed. Such depression includes Apgar scores less than or equal to 3 at 1 and 5 minutes plus umbilical artery pH values less than 7.00.

Acid-Base Equilibrium↗
PubMed1989

Early pregnancy glycosylated hemoglobin, severity of diabetes, and fetal malformations.

Total percent glycosylated hemoglobin (A1a + b + c) was measured before 16 weeks' gestation in 105 insulin-treated diabetic women enrolled for prenatal care at Parkland Memorial Hospital. Seventy-three of the infants were normal, 14 had malformations, and there were 18 spontaneous abortions. The mean glycosylated hemoglobin level for the entire study group was 9.2%, compared with 9.4% for those pregnancies ending in abortion, 8.9% for those resulting in normal infants, and 10.3% when malformations occurred. The mean glycosylated hemoglobin value for women delivered of normal infants was significantly lower than the mean of those with malformed infants. Ten of the 14 malformations occurred in mothers whose early pregnancy values exceeded the mean of the entire study group. There was also an association between malformations and White classification of maternal diabetes since 10 of the 14 fetal anomalies occurred in women assigned to White Classes C, D, F, H, and R. When the distribution of malformations was analyzed according to both glycosylated hemoglobin level and White Class, there was evidence of an interaction to suggest that hyperglycemia increases the relative risk of fetal malformations when associated with maternal diabetes of longer duration and or with vascular complications.

Abortion, Spontaneous↗
PubMed1989

Fatty acid metabolism in human keratinocytes cultivated at an air-medium interface.

Stratum corneum lipids, which provide the mammalian permeability barrier, display a distinctive fatty acid profile with a predominance of long chain, saturated fatty acids. In addition, linoleic acid (18:2) is present in substantial quantities, implying that it is an important structural component. To investigate selectivity of fatty acid incorporation into epidermal lipids, we examined the metabolism of exogenous fatty acids in cultured human keratinocytes, grown at the air-medium interface to enhance differentiation. Keratinocytes were pulsed with [3H] oleic, [14C] stearic, [14C] palmitic, or [14C] linoleic acids; lipids were extracted and fractionated by thin layer chromatography. All fatty acids were taken up and incorporated into complex lipids in a dose-dependent manner that was linear over the first 60 min. These fatty acids were incorporated predominantly into phospholipids and triacylglycerols; their incorporation could be rank ordered: linoleic greater than oleic greater than or equal to palmitic greater than stearic acid. Less than 2% of each fatty acid taken up by keratinocytes was oxidized to CO2; therefore, these differences in utilization cannot be ascribed to differences in rates of beta-oxidation. In pulse-chase studies fatty acids incorporated initially into triacylglycerols, subsequently chased into phospholipids. [14C]Palmitic acid and [14C] acetate were incorporated into sphingolipids more efficiently than the other fatty acids studied. These studies demonstrate that 1) keratinocytes have the ability to incorporate exogenous fatty acids preferentially into complex lipids; 2) triacylglycerols provide a pool of fatty acids for phospholipid synthesis; and 3) palmitate and de novo synthesized fatty acid are preferably utilized for sphingolipid synthesis.

Air↗
PubMed1989

Ichthyosis, deafness, and Hirschsprung's disease.

An infant with congenital ichthyosis and deafness developed Hirschsprung's disease. No evidence of keratitis was present. No previous cases of ichthyosis have been associated with aganglionic megacolon. Although no corneal changes were observed, we believe that the clinical features of ichthyosis and deafness suggest the diagnosis of KID (keratitis, ichthyosis, deafness) syndrome. Whether corneal changes would have occurred is unknown, since the infant died of malnutrition and infectious complications.

Deafness↗
PubMed1989

CHILD syndrome. Phenotypic dichotomy in eicosanoid metabolism and proliferative rates among cultured dermal fibroblasts.

Dermal fibroblasts from a patient with CHILD syndrome (an acronym for congenital hemidysplasia with ichthyosiform erythroderma and limb defects) were obtained and successfully maintained in culture. Fibroblasts from an area of chronically hyperkeratotic skin were compared with fibroblasts from the corresponding contralateral area of normal skin in regard to proliferative activity and to both unstimulated and stimulated generation of PGE2, an eicosanoid with documented effects on both epidermal cell and fibroblast function. Compared with the uninvolved skin fibroblasts, those from involved skin showed (a) a slower rate of proliferation, (b) a cyclical pattern of PGE2 synthesis, and (c) an approximately 20-fold greater synthesis of PGE2 in response to human purified IL-1, a cytokine known to be secreted by epidermal keratinocytes. Furthermore, we were able to demonstrate that the cyclical generation of PGE2 by the involved skin fibroblasts is responsible for their slower rate of growth when compared with the uninvolved skin fibroblasts. These data document a phenotypic dichotomy between the uninvolved and involved skin fibroblasts in CHILD syndrome that may be exploited to increase our understanding of the nature of dermal influences that may affect epidermal growth and differentiation.

Abnormalities, Multiple↗
PubMed1989

Polyclonal proliferation of activated suppressor/cytotoxic T cells with transient depression of natural killer cell function in acute infectious mononucleosis.

In acute infectious mononucleosis large numbers of atypical lymphocytes proliferate in response to B cells infected with Epstein-Barr virus, generally resulting in a self-limited illness. Although both T-cells and NK cells are known to be involved, the precise origin of the large granular lymphocytes in this disorder is incompletely understood. Using two-colour immunofluorescent flow cytometry, we sequentially examined the phenotype of selected T cell and NK cell subsets from nine patients with infectious mononucleosis. In parallel, we determined whether these lymphocytes utilized a restricted repertoire of the T cell receptor gene and also measured their NK activity. Our results show that in acute infectious mononucleosis there was a greater than three-fold increase in T lymphocytes with the phenotype CD2+, CD3+, CD8+ and DR+. A modest increase in Leu7(HNK1)+ and CD4+ T cells was also seen. In addition, there was a three-fold increase in cells coexpressing CD3- and CD16+, the phenotype reported to represent most NK cells. In spite of this latter finding, however, a marked decrease in NK function was found at the time of diagnosis, gradually returning to normal by day 28. Finally, Southern blot analysis of DNA from patient lymphocytes showed polyclonal rearrangements of the T cell receptor beta chain gene. These studies indicate that the proliferation of activated suppressor/cytotoxic T lymphocytes in acute infectious mononucleosis is polyclonal and is associated with transient depression of NK function.

Adolescent↗
PubMed1989

A test of the response deprivation hypothesis in a multiple-response context.

Reinforcement contingencies defined by the response deprivation hypothesis were evaluated in two multiple-response contexts. In one context a high probability response was freely available, and in the other context a low probability response was freely available. In the presence of the low probability, freely available response, a consistent reinforcement effect was evident for all 3 moderately mentally retarded participants; however, in the presence of the high probability response, the reinforcement effect was attenuated. Results were qualitatively consistent with several recent mathematical descriptions of behavior emphasizing the importance of the context in which reinforcement contingencies are introduced.

Adolescent↗
PubMed1988

Continuous subcutaneous insulin infusion during pregnancy.

The development of battery-powered pumps for continuous subcutaneous insulin infusion added new dimensions to control of diabetes during pregnancy. In this report, we describe our experiences with 28 pregnant diabetic women offered participation in an insulin pump program. Fifteen (54%) accepted pump therapy and ten continued usage during their pregnancies. Excluding abortions, eight women continuing pump use are compared to 11 others who declined such therapy and were treated with conventional methods. Although these two groups are small and not strictly comparable, the experiences now reported provide clinical insights into the application of this new technology during pregnancy. Women who successfully used insulin pumps were typically from the private sector and in better glucose control at study entry. The degree of control during pregnancy in women using pumps was not significantly different compared to conventional glucose control methods (mean glucose 120 mg/dl and 142 mg/dl, respectively). Similarly, several indices of pregnancy outcome including length of hospitalization, costs, and perinatal morbidity associated with diabetes were analyzed and no significant differences were observed. We conclude that insulin pumps are not acceptable to all pregnant diabetic women and that such therapy may not necessarily improve pregnancy outcome.

Abortion, Spontaneous↗