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T O Fox

Publications and source records attributed to T O Fox.

At least 37 records · Page 2Linked to original sources
PubMed1982

Resolution of two fractions of androgen receptor from mouse kidney.

Putative androgen receptors from mouse kidney were separated and re-chromatographed on DNA-cellulose columns. With either [3H]-dihydrotestosterone or [3H]-testosterone as ligands, two major fractions of androgen receptors were obtained in both elutions from DNA-cellulose columns; these eluted, respectively, at 140-150 mM NaCl (lower-salt) and 180-190 mM NaCl (higher-salt). Therefore, the two major peaks detectable with extracts of mouse kidney result from differences that are intrinsic to the receptor complexes rather than heterogeneity of the DNA-cellulose matrix. These findings are discussed in relation to two forms of androgen receptors that exist in a different proportion in extracts of brain and in relation to other steroid receptors.

Animals↗
PubMed1981

Androgen and estrogen receptors in embryonic and neonatal rat brain.

We provide biochemical evidence that specific androgen- and estrogen-binding macromolecules are present in rat hypothalamus-preoptic area throughout the "critical period' of brain sexual differentiation. Macromolecules with the properties of putative androgen and estrogen receptors are present in cytosolic extracts of embryonic neonatal, prepubertal rat hypothalamus-preoptic area and other brain regions. Both the androgen and estrogen receptors in perinatal rat brain are qualitatively similar to those in adult brain by virtue of their high affinity and limited capacity for hormone, specificity of hormone-binding, ability to adhere to DNA, differential behavior during DNA-cellulose affinity chromatography, behavior during velocity sedimentation, and tissue specificity. As early as 7 days before birth, both androgen and estrogen receptors are detectable in hypothalamus-preoptic area and other brain regions. Both receptors are more abundant in the hypothalamus-preoptic area relative to other regions. The concentrations of both receptors in hypothalamus-preoptic area increases as a function of age, although the relative rate of appearance of each receptor is distinctive: estrogen receptor concentrations increase approximately 6-fold during the last week of gestation, approximately adult-like levels at birth; androgen receptor concentrations increase slightly during late gestation, gradually rising to adult-like levels a few weeks after birth. The ontogeny profiles of both receptors from rat hypothalamus-preoptic area are compared with those from mouse. The presence of sex hormone receptors in perinatal rodent brain is discussed in the context of the hormonal milieu of perinatal rodent brain, and its effects on sexual differentiation of neural organization. The coincident appearance of receptors and post-mitotic neurons in prenatal rodent brain may indicate that sex hormones effect the early differentiation of these neurons.

Aging↗
PubMed1981

A DNA-binding fraction of mouse kidney 3-ketosteroid reductase: comparison with androgen receptors.

Since approximately 1% of 3-ketosteroid reductase (which metabolizes dihydrotestosterone (17 beta-hydroxyl-5 alpha-androstan-3-one] to 5 alpha-androstane-3 alpha, 17 beta-diol or 5 alpha-androstane-3 beta, 17 beta-diol) from mouse kidney cytosol adheres to DNA under conditions that allow virtually complete androgen receptor binding, these two DNA-binding activities were compared in cytosol extracts of mouse kidney and hypothalamus-preoptic area. This DNA-binding fractions of 3-ketosteroid reductase was distinguished from androgen receptor in several ways: (1) its pattern of elution from DNA-cellulose with steps of increasing NaCl concentration differed from that for receptors from wild-type kidney; (2) it was influenced differently by the mutation Tfm, both in level and in DNA-cellulose elution pattern; (3) in mouse kidney cytosol it was relatively stable at moderate (25 degrees C) temperatures which rapidly inactivated ligand-free androgen receptors in the same cytosols; (4) the DNA-binding was not proportional to androgen receptor levels between two wild-type tissues, the hypothalamus-preoptic area and kidney. By these criteria, a simple relationship of androgen receptors and a DNA-binding fraction of 3-ketosteroid reductase activity is unlikely.

3-Hydroxysteroid Dehydrogenases↗
PubMed1981

Isoelectric focusing of androgen receptors from wild-type and Tfm mouse kidneys.

Putative androgen receptors from wild-type mice and the androgen-resistant mutant with testicular feminization (Tfm) were analyzed sequentially by DNA-cellulose chromatography, isoelectric focusing, and sucrose density gradient sedimentation. Wild-type kidney receptors labeled with [3H]testosterone or [3H]dihydrotestosterone were partially purified by single step elution from DNA-cellulose. For these eluates, two isoelectric focusing peaks were obtained, with approximate pI values of 5 (pH 4.9 +/- 0.16; n = 10) and 6 (pH 5.7 +/- 0.09; n = 10), respectively. In isoelectric focusing of Tfm mice eluates, a single step DNA-cellulose eluate appeared predominantly at pH 7-8. The complete complement (10-15% of the wild-type level) of Tfm receptors elutes only as a higher salt form in DNA-cellulose chromatography, while the wild-type yields both lower salt and higher salt forms. Accordingly, for comparison to Tfm mice, we examined separated DNA-cellulose peaks of wild-type mice by isoelectric focusing. For isoelectric focusing, as for differential DNA-cellulose chromatography, the ratio of the two wild-type peaks differed when [3H]testosterone and [3H]dihydrotestosterone were used as the bound ligand, with [3H]testosterone favoring the pH 6 peak and the lower salt eluting peak. As predicted from this correlation, when the lower salt fraction was focused, a peak was still detected at pH 6, with less radioactivity at pH 5. However, when subjected to isoelectric focusing, the higher salt fraction appeared predominantly at pH 7-8. Thus, a characteristic pattern was obtained during isoelectric focusing for both the higher salt eluting fraction of wild-type mouse androgen receptor and the single step, complete eluate of the Tfm mouse.

Animals↗
PubMed1980

Release of immunoreactive somatostatin from hypothalamic cells in culture: inhibition by gamma-aminobutyric acid.

Primary cultures of dispersed hypothalamic cells were prepared from embryonic rats to study the release of immunoreactive somatostatin. The immunoreactive somatostatin content of these cultures increased during the first 2 weeks after plating and was readily measurable for several weeks thereafter; this material was characterized by gel permeation and reverse-phase chromatography. Depolarization of the cells with 60 mM K+ or with veratridine resulted in a calcium-dependent release of immunoreactive somatostatin which cochromatographed with synthetic somatostatin on reverse-phase chromatography. Tetrodotoxin blocked the veratridine-evoked release. However, even in the absence of exogenous stimuli, immunoreactive somatostatin was released by the cells into the medium. More than 70% of this tonic release was found to be calcium dependent and to be inhibited by tetrodotoxin, indicating that spontaneous electrical activity in the cultures leads to a release of immunoreactive somatostatin. gamma-Aminobutyric acid inhibited the tonic release of immunoreactive somatostatin and this was reversed by bicuculline. These findings support the hypothesis that gamma-aminobutyric acid inhibits somatostatin release in vivo.

Animals↗
PubMed1979

Carrier protein effects on DNA-cellulose chromatography of putative steroid receptors.

In the absence of carrier proteins, putative androgen receptors elute from DNA-cellulose in the range of 120 to 190 mM NaCl. However, in the presence of lysozyme, most of the receptor elutes in the range of 200 to 230 mM NaCl. This is the same range in which the lysozyme itself, a basic protein, elutes after being chromatographed in the same manner. Moreover, at low ionic strength, lysozyme also increases the sedimentation velocity of both androgen and estrogen receptors. In contrast, bovine serum albumin neither adheres to DNA-cellulose nor alters the sedimentation properties of these proteins. The lysozyme effects can account for some discrepancies reported in the literature. Thus, for qualitative elution studies, the use of lysozyme as a carrier protein is not advised, although its direct interaction with receptors might facilitate quantitative fractionation.

Animals↗
PubMed1979

Embryonic rodent brain contains estrogen receptors.

Estradiol-binding proteins with the properties of putative estrogen receptors are present in cytosol extracts of embryonic mouse hypothalamus and other brain regions. These embryonic estrogen receptors are adultlike in their high affinity and limited capacity for estradiol, sensitivity to diethylstilbestrol, ability to adhere to DNA, and behavior during DNA-cellulose affinity chromatography. As early as 4 days before birth, mouse hypothalamus has approximately 40 percent of the adult concentration of hypothalamic estrogen receptors with these properties. These observations raise the possibility that embryonic rodent brain has the biochemical potential to respond to sex hormones and that the critical period of brain sexual differentiation could be initiated prenatally.

Age Factors↗
PubMed1979

Estrogen-binding proteins in the oviduct of the turtle, Chrysemys picta: evidence for a receptor species.

Estradiol-binding proteins in the reproductive tract of the turtle, Chrysemys picta, were characterized. Cytosol was prepared from the oviducts of mature female turtles, and estradiol binding was measured using charcoal adsorption and glycerol density gradient centrifugation. A sex steroid-binding protein (SBP) similar to that found in turtle plasma was demonstrated in oviduct cytosol. The characteristics of this SBP-like binding were as follows: Ka = 10(8) M-1; capacity, 10(-12) mol/mg protein; and sedimentation coefficient, 6--7S in low salt gradients. The SBP-like protein binds testosterone and progesterone as well as 17 beta-estradiol but does not bind diethylstilbestrol. No receptor-like binding activity could be demonstrated using these techniques. Explant culture and DNA cellulose affinity chromatography were used to remove the SBP-like material before assay of [3H]estradiol binding. Using these techniques, a high affinity (Ka = 10(9) M-1), low capacity (n = 10(-14) mol/mg cytosol protein) estradiol receptor was demonstrated. The putative turtle receptor exhibits steroid specificity and sedimentation profiles (6S and 8S in low salt, 4S and 5S in high salt) comparable to those of estrogen receptors in mammalian species. These results suggest a certain degree of physiochemical similarity between putative estrogen receptors in mammalian and turtle reproductive tracts.

Animals↗
PubMed1978

Selective complexing of the "nuclear" 5S estradiol receptor by a serum component, 5S-CA.

A component present in several sera interacts selectively with the 5S "nuclear" form of estradiol receptor but not with the 4S "cytosol" form. This component is therefore referred to as "5S-complexing activity (5S-CA)." This selective interaction occurs with 5S receptor from mouse, calf, or rat. In addition, 5S-CA recognizes the nuclear form of the receptor from hypothalamic as well as uterine tissue Thus, 5S-CA indicates a general similarity in the chemical nature of 5S nuclear receptors prepared from several sources. Using 5S-CA as a chemical probe for the nuclear form of the estradiol receptor, I have shown the chemical as well as physical similarity of 5S receptors prepared in vivo (by injection of [3H]estradiol and subsequent isolation from nuclear/myofibrillar extracts) and in vitro (by labeling of cytoplasmic extracts and subsequent chromatography on columns of DNA-cellulose). These results indicate a distinctive chemical property of nuclear 5S forms of estradiol receptor. The data are interpreted with regard to models for 5S receptor formation. 5S-CA was found in sera from animals immunized against various antigens. The importance of testing for 5S-CA in antisera directed against steroid derivatives, steroid receptors, and other steroid-binding proteins is discussed.

Animals↗
PubMed1977

Estradiol and testosterone binding in normal and mutant mouse cerebellum: biochemical and cellular specificity.

Estradiol and testosterone binding macromolecules are demonstrated in normal mouse cerebellum. Identity of the estradiol binder as the 'receptor' is provided by its binding to DNA-cellulose, which does not occur for other estradiol binding proteins. The androgen binder is identified as 'receptor' by its specific deficiency (85% reduced) in the androgen-insensitive mutant mouse, testicular feminization (Tfm). The relative amounts of these two components are reversed in cerebellum compared to hypothalamus-preoptic area. Neurological mouse mutants, which lack specified neurons, are examined to test for the cells in which these hormone binding proteins are located. Experiments with Purkinje cell degeneration (pcd), weaver (wv) and staggerer (sg), suggest that the majority of these receptors are present in granule cells.

Animals↗
PubMed1975

Androgen- and estrogen-binding macromolecules in developing mouse brain: biochemical and genetic evidence.

Androgen- and estrogen-binding macromolecules from the hypothalamus plus preoptic area of 3- to 4-week-old mice have been detected and partially characterized. These components bind the respective hormones with high affinity (saturating at 4-8 nM) and sediment with rates typical of presumed steroid receptors (4.0-4.5 S in 0.15 M NaCl, 5.0-7.5 S without salt). A 90-95% reduction in androgen binding found in the androgen-insensitivity mutant mouse, testicular feminization (Tfm), provides a genetic control for the specificity of binding. This reduced androgen binding with Tfm/Y mutants and blocking experiments with non-radioactive estradiol [estra-1,3,5(10)-triene-3,17beta-diol] and testosterone (17beta-hydroxy-4-androsten-3-one) indicate the existence of at least two binding components: one with high affinity only for estradiol, the other with affinity for both androgens and estrogen. Based on these properties, a receptor mechanism that detects relative concentrations of androgens and estrogens is proposed.

Animals↗