Steroid hormone target cells in the periventricular brain: relationship to peptide hormone producing cells.

Steroid hormone concentrating cells in hypothalamic and extrahypothalamic regions are reviewed and the topographic relationship to the periventricular brain and the ventricular recess organs is discussed. Steroid hormone target cells in the brain are considered feedback sites and production sites of polypeptide hormones. The anatomical distribution of estrogen, androgen and progestin target neurons, as defined by autoradiography, is compared with the localization of antibodies to luteinizing hormone-releasing hormone and somatostatin in perikarya of neurons, as characterized by immunocytochemistry. Around the optic recess of the third ventricle in the lamina terminalis and the preoptic nucleus as well as in the periventricular nucleus of the hypothalamus, the steroid hormone target neurons and the assumed polypeptide hormone producing neurons occupy corresponding sites.     

Drag reduction by Acinetobacter calcoaceticus BD4

The encapsulated bacterium Acinetobacter calcoaceticus BD4 at a density of 3.6 X 10(9) cells per ml reduced the friction of turbulent water in a narrow pipe by 55%. This drag reduction was due to the tightly bound polysaccharide capsules (0.4 mg per ml) of culture. Capsule-deficient mutants of BD4 failed to reduce drag. The cell-bound polysaccharide demonstrated a threefold-higher drag-reducing activity than the polymer which was free in solution.     

A computational study of systemic hydration in vocal fold collision

Mechanical stresses develop within vocal fold (VF) soft tissues due to phonation-associated vibration and collision. These stresses in turn affect the hydration of VF tissue and thus influence voice health. In this paper, high-fidelity numerical computations are described, taking into account fully 3D geometry, realistic tissue and air properties, and high-amplitude vibration and collision. A segregated solver approach is employed, using sophisticated commercial solvers for both the VF tissue and glottal airflow domains. The tissue viscoelastic properties were derived from a biphasic formulation. Two cases were considered, whereby the tissue viscoelastic properties corresponded to two different volume fractions of the fluid phase of the VF tissue. For each case, hydrostatic stresses occurring as a result of vibration and collision were investigated. Assuming the VF tissue to be poroelastic, interstitial fluid movement within VF tissue was estimated from the hydrostatic stress gradient. Computed measures of overall VF dynamics (peak airflow velocity, magnitude of VF deformation, frequency of vibration and contact pressure) were well within the range of experimentally observed values. The VF motion leading to mechanical stresses within the VFs and their effect on the interstitial fluid flux is detailed. It is found that average deformation and vibration of VFs tend to increase the state of hydration of the VF tissue, whereas VF collision works to reduce hydration.     

1,25-Dihydroxyvitamin D3 stimulated increase of 7,8-didehydrocholesterol levels in rat skin

A convenient, accurate assay was developed for determining skin cholesta-5,7-dien-3 beta-ol (7,8-didehydrocholesterol) concentrations. Ultraviolet spectrophotometry provided quantitation of the sterol from rat skins following saponification and chromatography on Lipidex and high-performance liquid chromatography. Correction for recoveries was accomplished by using 7,8-didehydro[3 alpha-3H]cholesterol as an internal standard. Chronic dosing of vitamin D-deficient rats with 1,25-dihydroxyvitamin D3 caused a 4-fold increase in skin 7-dehydrocholesterol content. This rise was not the result of changes in food consumption, body weight, or plasma calcium. Cholesterol concentrations were not significantly elevated although some of the other nonsaponifiable lipid components found in the high-performance liquid chromatogram appeared to be increased by the treatment. These results suggest that the vitamin D hormone 1,25-(OH)2D3 may exert a positive feedback regulation on the production of vitamin D3 in skin.     

Novel antipeptide antibodies to the human glucocorticoid receptor: recognition of multiple receptor forms in vitro and distinct localization of cytoplasmic and nuclear receptors.

We have synthesized two peptides that correspond to unique regions of the amino-terminus of the human glucocorticoid receptor (GR). Peptides representing amino acids 245-259 and 346-367 (designated 59 and 57, respectively) were chosen on the basis of hydrophobicity/hydrophilicity ratios as well as overall proline content. These peptides were then used as antigens to produce epitope-specific antibodies that recognize and interact with human GR in a variety of physical states. Antiserum directed against each peptide recognizes denatured, [3H] dexamethasone mesylate-labeled GR as well as unliganded receptor on Western blots. In contrast to other antipeptide GR antibodies, these antibodies recognize and form stable complexes with unactivated and molybdate-stabilized forms of the GR, indicating that neither epitope is occluded when the receptor exists in an oligomeric state. Activated, 4S DNA-binding forms of the receptor are also recognized by both antibodies. The interaction of antibodies 59 and 57 with human GR in various states is highly specific based on the observation that preincubation of either antiserum with the appropriate peptide completely precludes the recognition of receptor by antibody. Titration analysis of antisera reveals that an increase in the antibody concentration cause discrete increases in the sedimentation coefficient of GR on sucrose gradients. These shifts occur under high salt conditions and are consistent with the formation of multiple stable antibody-receptor complexes. Interestingly, neither antibody interferes with the ability of the GR to be activated into a DNA-binding form or with the ability of the activated GR to interact with DNA cellulose. Consistent with these observations, both antibodies recognize and form stable complexes with GR when the receptor is associated with DNA fragments that contain specific glucocorticoid-responsive elements. Thus, both antibodies appear to recognize all known forms of the human GR protein. Using immunohistochemical techniques to visualize GR in HeLa S3 cells as well as in Chinese hamster ovary cells that stably express transfected human GR, a cytoplasmic location for receptor is observed in the absence of ligand. In contrast, immunoreactive GR is predominantly nuclear after hormone treatment, further supporting a role for nuclear translocation in GR function.     

Are estrogen receptors cytoplasmic or nuclear? Some immunocytochemical and biochemical studies

The subcellular localization of estradiol receptor (ER) has been examined using various experimental approaches. Immunocytochemical studies using the monoclonal antibody JS 34/32, raised against calf uterine cytosolic ER, yielded only equivocal results. In general, cells and tissues pretreated with estradiol showed positive immunostaining in the nuclei whereas those not exposed to the steroid did not show any staining. Nuclear translocation of ER was examined in intact MCF-7 cells using compounds which are known to influence receptor activation. When MCF-7 cells were exposed to molybdate (20 mM), nuclear translocation was completely inhibited while dithiothreitol (20 mM), dibutyryl cAMP (1 microM) and dibutyryl cGMP (1 microM) increased the translocation 2-3-fold. Phenol red, at the range of concentrations generally used in tissue culture media, also increased translocation. The physiological validity of such translocation was examined using cellular progesterone receptor (PR) synthesis as a specific parameter. When MCF-7 cells were grown in media containing phenol red for 48 h, the PR synthesis increased significantly. We further examined whether cytoskeletal proteins are involved in the translocation of ER. Colchicine, an inhibitor of microtubule assembly, inhibited translocation of ER in MCF-7 cells at 1-10 microM. PR synthesis was also inhibited by colchicine in a dose-dependent manner. It may be concluded from these and other published data that ER may not be located at all times in a single subcellular compartment but may rather exist in a dynamic equilibrium between the plasma membrane, cytoplasm and nucleus.