Biomedical subjects

B Hostetler

Publications and source records attributed to B Hostetler.

3 recordsLinked to original sources

PubMed1992

Canalization failure of the müllerian tract.

A patient is described with canalization failure of the müllerian system. This patient presented with primary amenorrhea and absence of the vagina. At the time of laparotomy, a uterus of normal size and shape was found with two small areas of canalization. This syndrome, associated with absence of the vagina, appears to result from a defect occurring later in development than does classical müllerian aplasia. Pathological examination of the patient's uterus supports the tenant that canalization begins after fusion and at various places along the line of fusion.

Adolescent↗

PubMed1985

Intestinal membrane lipid composition and fluidity during development in the rat.

We have characterized microvillus membrane (MVM) lipid composition and derived estimates of membrane fluidity using fluorescence polarization [with 1,6-diphenyl-1,3,5-hexatriene (DPH) as the probe] in MVM from the jejunum and ileum of suckling (day 14-20) and mature postweaning (day 28-49) rats. The anisotropic values are lower (i.e., increased fluidity) in MVM from jejunum and ileum of suckling rats compared with values from MVM of mature rats, suggesting a more disordered molecular environment in MVMs of suckling animals, although the ileal MVM was relatively less fluid than jejunal membranes in both groups. Anisotropic determinations in protein-free MVM liposomes demonstrate that protein-lipid interactions are major determinants of fluidity estimates. Arrhenius plots of DPH anisotropies in MVM and MVM liposomes indicate a thermotropic lipid-phase transition at 23 degrees C in mature rat jejunum and ileum; however, no clear transition point was observed in 14- to 20-day animals. In addition, both the jejunal and ileal MVM in suckling animals contained greater amounts of total lipid, cholesterol, and phospholipid per milligram protein than did mature MVM preparations. Membrane phospholipid composition changed with age, with a decrease in sphingomyelin and an increase in phosphatidylcholine in the jejunum of the postweaning animal and with similar weight ratios of saturated to unsaturated fatty acids in both age groups. The data demonstrate that the small intestinal MVM manifests both age-dependent and regional proximal-distal differences in lipid composition and biophysical properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1984

Lipid composition and membrane fluidity in the small intestine of the developing rabbit.

Characteristics of small intestinal microvillus membrane lipid composition and associated lipid fluidity were studied throughout postnatal development in the rabbit. Microvillus membranes from jejunal and ileal epithelia were isolated in high purity from 14 days to adulthood. Significant jejunal-ileal differences in microvillus membrane cholesterol to phospholipid molar ratios were observed at all ages. Despite a relatively constant cholesterol content (as percentage of total lipids) both regionally and at all ages, marked increases in the microvillus membrane cholesterol to phospholipid ratio were observed after weaning in both jejunum (14 days = 0.56, adult = 0.83) and ileum (14 days = 0.66, adult = 0.98). Further age-related changes in microvillus membrane lipid composition were characterized by a significant reduction in the weight ratio of saturated to unsaturated fatty acids in jejunum and ileum and by the emergence, in the mature animal, of a jejunal-ileal difference in total lipid content (jejunum = 1.21 mg/mg protein, ileum = 1.01 mg/mg protein). Changes in microvillus membrane lipid fluidity estimated by fluorescence polarization spectrometry directly paralleled changes in the cholesterol to phospholipid molar ratio. Fluorescence anisotropy of jejunal and ileal microvillus membranes increased during the weaning period, suggesting decreased membrane fluidity. At all ages, ileal membranes were relatively less fluid than jejunal microvillus membrane. Studies of protein-free microvillus membrane liposomes, prepared from extracted membrane lipid, confirmed a major lipid-dependent thermotropic transition point at approximately 23 degrees C in adult jejunal and approximately 25 degrees C in adult ileal enterocyte membranes, although no clear transition point was observed in suckling microvillus membrane. These combined data suggested that significant alterations in the microvillus membrane lipid composition and its physical-chemical properties occur during postnatal development in both jejunal and ileal rabbit small intestinal microvillus membrane. It is proposed that membrane lipid-dependent structural characteristics may be directly related to the maturation of enterocyte transport function.

Aging↗