Biomedical subjects

T O Fox

Publications and source records attributed to T O Fox.

At least 19 recordsLinked to original sources

PubMed1993

Sex and regional differences in intracellular localization of estrogen receptor immunoreactivity in adult ferret forebrain.

Estrogen receptors were visualized in adult ferret brains using the H222 estrogen receptor antibody and immunocytochemical techniques. H222 immunoreactive (H222ir) cell nuclei were present in many forebrain regions in gonadectomized ferrets of both sexes. In many instances, H222ir cells also had immunoreaction product in their processes. All cells with H222ir processes also contained H222ir nuclei. More H222ir processes were observed in females in the medial and lateral preoptic area/anterior hypothalamus, and at the level of the descending fornix and caudal anterior commissure. Quantitative image analysis confirmed that females had significantly more (approximately 50%) extranuclear H222 immunoreaction product than males in cells in the magnocellular or preoptic subnuclei of the bed nucleus of the stria terminalis. Cells in the principal subnucleus of the bed nucleus of the stria terminalis and ventrolateral septum were notable for the relative paucity of H222ir processes. Sex differences in the intracellular extranuclear distribution of estrogen receptor protein in particular brain regions might contribute to the differential regulation of estrogen-dependent functions in the two sexes.

Animals↗

PubMed1991

Differential hormonal modulation of brain antigens recognized by the AB-2 monoclonal antibody.

The expression of monoclonal antibody AB-2 immunoreactivity is age- and sex-dependent in radial glia of developing rat hypothalamus and is regulated by prenatal exposure to gonadal steroids. In the present study, several proteins were recognized by AB-2 and were distributed selectively in subcellular fractions from neonatal hypothalamus (HYP), remaining forebrain (FB), and brainstem regions. Immunoblots revealed polypeptide bands in 3 major molecular weight classes: one at approximately 195 kDa in the cytosolic compartment; and two doublets at 220 kDa and 340 kDa in both microsomal and crude mitochondrial membrane fractions. The 220 kDa and 340 kDa doublets were also Triton-insoluble, suggesting a cytoskeletal association. The 195 kDa-AB-2-immunoreactive band was present in both Triton-soluble and insoluble fractions. AB-2 also recognized several acidic glycolipids extracted from postnatal rat brain regions on immunoblots following high performance thin layer chromatography. One of the bands from postnatal rat brain extracts migrated similarly to purified bovine brain sulfatide, which was also immunoreactive with AB-2. AB-2 immunoreactivity with proteins, polar lipids, and sulfatide suggests that the epitope is a carbohydrate present in multiple cellular compartments. AB-2 recognized the same molecular bands in males and females. Testosterone treatment selectively decreased the level of the 195 kDa AB-2-immunoreactive polypeptide. The 195 kDa AB-2-immunoreactive polypeptide possibly acts in radial glia in the determination of sexually dimorphic neurons in the preoptic area/hypothalamus.

Animals↗

PubMed1989

Androgen regulation of an antigen expressed in regions of developing brainstem monoaminergic cell groups.

To examine the regulation of brain development by gonadal steroids we are using monoclonal antibodies obtained with neonatal rat brain homogenates as immunogens. One antibody, 3D10, binds selectively in regions of identified monoaminergic neuronal cell groups in the brainstem. Characterization of 3D10 immunoreactivity was carried out using free-floating 50 microns tissue sections from perinatal rats. The strongest reactivity was seen on postnatal day 1 in the locus coeruleus (A6) and in the regions of the A4 (dorsal) and A5 (ventral) noradrenergic cell groups. Immunoreactivity was also seen in the raphe magnus, pallidus and obscuris. Faint immunoreactivity was seen in the more rostral and median raphe nuclei and in the midbrain dopaminergic cell groups of the ventral tegmentum and substantia nigra. The number of 3D10 immunoreactive cells in all groups was greatest perinatally and decreased with age. The number of immunoreactive cells in the A4 region of males decreased at an earlier age than in females. Female offspring treated prenatally with testosterone propionate also had fewer immunoreactive cells in the A4 region at earlier ages, approximating the time course in the male. Thus, changes in the number of 3D10 immunoreactive cells reveal hormonal control of the time course of a developmental process in a selective population of neurons.

Aging↗

PubMed1989

Age-dependent expression of microtubule-associated protein 2 in the ventromedial nucleus of the hypothalamus.

A distinctive developmental pattern of microtubule-associated protein 2 (MAP2) was detected in the ventromedial hypothalamus of rats. A region of more intense MAP2 immunoreactivity in this nucleus was present at birth, became prominent in a ringed appearance by postnatal day 4 and disappeared in the third postnatal week. This period of selective MAP2 expression in particular subcortical regions may signify important functions of MAP2 in the stabilization of developing dendritic structure.

Aging↗

PubMed1989

Sex- and hormone-dependent antigen immunoreactivity in developing rat hypothalamus.

Morphological sex differences in adults can result from differential gonadal steroid exposure during critical perinatal periods. This study describes the use of a monoclonal antibody we have developed to study mechanisms of sexual differentiation of brain structure and function. Used as a marker in immunocytochemistry, antibody AB-2 revealed subsets of cells, including radial glia, transiently during the perinatal period. Peak reactivity in radial glia was on embryonic day 19 in males and on postnatal day 1 in females. On postnatal day 1, AB-2 immunoreactivity in radial glia was 2-fold greater in females than in males. Greater activity was detected in males on one side of the brain than the other (2- to 4-fold, depending on the region). To test the hormone dependence of this sex difference, pregnant rats were injected with testosterone propionate to expose fetal females to androgen on embryonic day 18. This resulted in lower levels of AB-2 immunoreactivity in radial glia of the treated female offspring on postnatal day 1 relative to control females, and the pattern was bilaterally asymmetric, approaching that of males. Thus the difference between sexes in immunoreactivity with AB-2 as a marker was hormone dependent in a predictable manner. Whether this marker is revealing a sex difference in accessibility of antigen by immunocytochemistry or a sex difference in intrinsic antigen levels is not yet resolved. In either case these results support the hypothesis that certain hormone-dependent molecular events occur transiently during development.

Aging↗

PubMed1988

TfmLac: a second isolation of testicular feminization in mice.

TfmLac, a new occurrence of the X-linked mutation testicular feminization, has been isolated in a stock of mice and mapped to the same region as the original TfmH mutation. We compared these two mutants to determine if there are differences in their putative residual androgen receptors or androgen responsiveness. Such differences have been reported for Tfm mutations in humans. We found no evidence for induction of ornithine decarboxylase (ODC) activity in TfmLac despite androgen treatment for up to 3 weeks. This is in agreement with findings for TfmH. Both of these mutants expressed small amounts of androgen binding activity which shared some properties with the normal androgen receptors in mouse kidney. The binding was distinguishable between the two mutants, however, as determined by hormone saturation experiments utilizing DNA-cellulose chromatography. These findings confirm the independence of the two mutations and are consistent with their being allelic: both result in severe deficits of androgen binding and response.

Androgen-Insensitivity Syndrome↗

PubMed1986

Estrogen binding in nuclear and cytosolic extracts from brain and pituitary of middle-aged female rats.

Estrogen binding was compared in brain and pituitary of long-term ovariectomized young and middle-aged (MA) female rats. Binding was quantified in both cytosolic and nuclear extracts to ascertain whether fractions of estrogen binding are altered in MA females. Estrogen binding detected in nuclear extracts from hypothalamus/preoptic area and anterior pituitary of MA females was significantly lower than levels detected in young females. In each case where an age-related decrease in nuclear estrogen binding was observed, an increased number of putative estrogen receptors was detected in the cytosolic extract. Therefore, the age-related decrease in nuclear estrogen binding did not appear to result from a simple decrease in total available cellular estrogen receptors. Rather these results suggest a decrease in the ability of putative estrogen receptors in aging females to remain tightly bound to nuclei after their isolation. The ability of estrogen receptor complexes from aging animals to bind to DNA was evaluated by DNA-cellulose chromatography in order to examine possible quantitative or qualitative differences in estrogen binding proteins with age. The data did not indicate that the properties of estrogen receptors themselves changed with age. It is possible, therefore, that age-related alterations may interfere with the interaction between the estrogen receptor complex and the nucleus.

Aging↗

PubMed1986

Localization of aromatase and 5 alpha-reductase to neuronal and non-neuronal cells in the fetal rat hypothalamus.

Experiments were designed to identify the neural cell type(s) responsible for the aromatization and 5 alpha-reduction of androgens in the rat hypothalamus. Primary cultures of fetal rat hypothalamic cells, which had enhanced neuronal morphology, were treated at various times after plating with kainic acid (KA), a neurotoxic agent which selectively destroys neuronal cells. Neuronal morphology was disrupted in a time (0-6 days)- and dose (10(-4)-10(-2) M)-dependent fashion after KA treatment, with no apparent change in the appearance of the flattened, underlying non-neuronal cells. KA treatment for 4 days decreased aromatization by 94% in a dose-dependent fashion (10(-4)-10(-2) M KA), while 5 alpha-reduction declined by no more than 25%. A 6-day time course with 10(-3) M KA showed a dramatic decline in aromatization and no alteration in 5 alpha-reduction. In control experiments, substance P, a neuronal peptide, declined after KA treatment while the activity of glutamine synthetase, a glial enzyme, did not change. We conclude from these results that aromatase is localized primarily to neuronal cells in the hypothalamus while 5 alpha-reductase is confined primarily to non-neuronal cells.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗

PubMed1986

Sex differences in the shape of the sexually dimorphic nucleus of the preoptic area and suprachiasmatic nucleus of the rat: 3-D computer reconstructions and morphometrics.

Three-dimensional images of nuclei facilitate morphological comparisons between differing animal groups. As revealed by computer-assisted techniques, the greater volume in male rats of the sexually dimorphic nucleus of the preoptic area was not proportional in all directions. The nucleus was more elongated in males than females, indicating a sex-dependent shape. This study also indicated that the volume of the suprachiasmatic nucleus was larger in males.

Animals↗

PubMed1986

Androgen and estrogen receptors in adult zebra finch brain.

Androgens and estrogens have been implicated in the activation of a variety of sexually-dimorphic, hormone-dependent behaviors in the adult zebra finch. In the present report, several biochemical characteristics of two putative sex steroid receptors, androgen- and estrogen-binding activities, were determined by DNA-cellulose chromatography in brain tissues from these birds. High-affinity, limited-capacity receptors for androgens and estrogens were found in cytosolic extracts of telencephalon, diencephalon-mesencephalon, and metencephalon-myelencephalon from adult male and female zebra finches. Androgen-binding activity reproducibly adhered to DNA-cellulose and was eluted within the 110-150 mM NaCl region of a linear salt concentration gradient. Estrogen receptors adhered to DNA-cellulose and exhibited elution maxima between 170 mM and 210 mM NaCl. Collectively these data indicate that brain regions of zebra finches contain steroid receptors that are similar to those found in the brains of other vertebrates and that their biochemical properties are similar in males and females. Quantitatively, males consistently exhibited higher androgen binding than females in both anterior and posterior telencephalic areas. Females treated with estradiol immediately after hatching exhibited adult levels of androgen binding corresponding to those detected in males. Masculinization of the androgen receptor system by early steroid exposure is discussed.

Animals↗

PubMed1986

Differences in the androgen response between two mouse species.

Renal weight and beta-glucuronidase activity are two of several well-characterized androgen-responsive parameters in Mus musculus. A similar sexual dimorphism was not reported for a second mouse species, Mus caroli, however. Since this was not associated with a general absence of androgen action, we considered whether a localized defect in androgen receptors or a difference in renal androgen-responsive endpoints in the two species existed. Only minor differences in the characteristics of renal androgen receptors from the two species were found when they were analyzed by two different methods. These differences were not thought to be sufficient to account for the apparent renal androgen unresponsiveness. No differences were found in androgen receptors from brain. Subsequently, a third renal endpoint, ornithine decarboxylase activity, was found to respond to androgen stimulation in Mus caroli. Control of renal androgen action in these two mouse species thus differs at the level of genetic regulatory elements.

Animals↗

PubMed1986

Growth hormone-secretory patterns in androgen-resistant (testicular feminized) rats.

To investigate the role of androgen receptors in the expression of the male GH-secretory pattern in adult rats, the GH-secretory patterns in androgen-resistant (testicular feminized) rats were compared with their normal male and female littermates. All animals were prepared with intraatrial Silastic catheters and bled every 15 min for 8 h (0800-1600 h). Normal male littermates displayed a characteristic low frequency, high amplitude pattern of GH secretion with bursts of GH occurring every 2.5-3 h and separated by prolonged trough periods where GH values remained low or undetectable (less than 5 ng/ml) for 45-90 min. Normal female littermates showed a characteristic high frequency, low amplitude pattern of GH secretion with pulses of GH occurring every hour. Compared to normal male littermates, females had lower individual GH peak amplitudes and shortened GH-trough periods which contain higher GH levels. GH-secretory profiles displayed by testicular-feminized animals qualitatively and quantitatively resembled those of the normal female littermates. These data suggest that androgen receptors are necessary for the expression of masculine GH-secretory patterns.

Age Factors↗

PubMed1985

Estrogen receptors in the wobbler mouse.

Recent research has raised the interesting possibility that the neurological mutant mouse, wobbler (wr/wr), possesses an estrogen receptor deficit analogous to the androgen receptor deficiency found in androgen-resistant mice with testicular feminization. In the present report we examined estrogen-binding activity in cytosolic extracts of kidney, liver, and brain from wobbler mice, littermate control animals, and C57BL/6J mice, using DNA-cellulose chromatography. Estrogen binding components exhibiting properties of estrogen receptors were present in all tissues examined. Estrogen receptors adhered to DNA, displayed characteristic elution profiles from DNA-cellulose, and showed high affinity and limited capacity for estradiol, in contrast to non-receptor entities which bind estradiol. The qualitative elution patterns for estrogen receptors did not differ among groups within each tissue studied, and were similar to those reported previously in mouse kidney and brain. While estrogen receptors have been shown in mouse liver by other techniques, this is the first demonstration of putative estrogen receptors in mouse liver by DNA-cellulose chromatography. No consistent deficits in estrogen receptor concentration were found in wobblers compared to littermates. Thus, the data do not support the hypothesis that the wobbler mouse is an estrogen receptor-deficient mutant.

Animals↗

PubMed1985

Androgen and estrogen receptors in fetal rhesus monkey brain and anterior pituitary.

In this study, we sought to identify and characterize cytosolic androgen and estrogen receptors in the brain and anterior pituitary gland (AP) of fetal rhesus monkeys using the technique of DNA-cellulose chromatography. Cytosolic extracts were prepared from fetal monkey (days 135-162 of gestation) tissues including hypothalamus-preoptic area/amygdala (HPOA/AMG), cerebral cortex, and AP. Extracts were incubated with [3H]testosterone, [3H]5 alpha-dihydrotestosterone, or [3H] 17 beta-estradiol and applied to DNA-cellulose columns. [3H]Androgen- and [3H]estrogen-binding activities from cytosolic extracts adhered to DNA-cellulose. After elution with a linear salt gradient (10-500 mM NaCl) [3H]androgen-binding activity exhibited elution maxima between 130-150 mM NaCl, while [3H] estrogen-binding activity exhibited elution maxima between 200-220 mM NaCl. These elution patterns were similar in every region examined and were characteristic of putative androgen and estrogen receptors found in other vertebrate species. Additional experiments established the high affinity-low capacity nature of both androgen- and estrogen-binding activities, as well as their inhibition by known competitors of receptor binding. Estimates of binding activity at ligand concentrations that approximated saturation suggested that the concentration (moles specific bound per mg cytosolic protein) of both androgen and estrogen receptor were highest in the AP, intermediate in the HPOA/AMG, and lowest in the cerebral cortex. Comparisons of androgen- and estrogen-binding activities revealed that in the AP, apparent concentrations of the estrogen receptor exceeded those of androgen. Androgen and estrogen receptor concentrations were roughly equivalent in the HPOA/AMG, whereas, in the cerebral cortex, androgen receptor concentration was greater than estrogen. Collectively, these data demonstrate that in the fetal primate brain and AP, distinct androgen and estrogen receptors are present which might mediate the action of gonadal steroids on sexual differentiation.

Amygdala↗

PubMed1985

A genetic variant in the morphology of the medial preoptic area in mice.

Inbred mice of the DBA/2J and C57BL/6J strains are known to differ in physiological and behavioral characteristics that are partially controlled by nuclei in the preoptic area/anterior hypothalamus. We describe a distinguishing nucleus of darkly staining, densely packed cells, which we term the medioventral pars compacta (MVPC), within the medial preoptic nucleus of DBA/2J, but not C57BL/6J mice. The analysis also indicates that this nucleus is nearly 80% larger in volume in females vs males of the DBA/2J strain. The strain difference may be used to define genetic influences on this neuroanatomical and functional property.

Animals↗

PubMed1985

Androgen and estrogen receptors in perinatal ferret brain.

Using DNA-cellulose affinity chromatography and either 3H-labeled dihydrotestosterone, testosterone, or estradiol, we qualitatively and quantitatively analyzed the androgen- and estrogen-binding activities present in four regions of male and female ferret brain at prenatal, early and late neonatal, and adult ages. The cytosolic androgen- and estrogen-binding activities in ferret brain at all ages studied were qualitatively similar in both sexes and in all brain regions and exhibited characteristics which resemble those of androgen and estrogen receptors from other species, including rodents and nonhuman primates. A developmental analysis indicated that high levels of both androgen and estrogen receptors were present in the hypothalamus-preoptic area as early as 5 days before birth. A significant, transient decline in concentrations of estrogen receptors (approximately 5-fold) occurred in anterior hypothalamus-preoptic area and mediobasal hypothalamus at 12 days of age in both males and females; this phenomenon has not been observed in any other species studied to date. The observed ontogeny of androgen receptors correlates with the known ability of testosterone, acting over postnatal days 5 to 20, to cause coital masculinization in ferrets, whereas the observed postnatal dip in estradiol receptor concentrations correlates with the inability of estradiol to cause coital masculinization or defeminization of receptive behavior in this species.

Aging↗

PubMed1983

Androgen and estrogen receptors in adult hamster brain.

Both androgen and estrogen receptors are present in the hypothalamus-preoptic area and remaining "brain' regions of gonadectomized adult male and female hamsters. No quantitative or qualitative sex differences are detectable in either receptor system. According to all biochemical criteria tested, both receptors are qualitatively similar to those present in mouse and rat brain. However, there are striking species differences in both the relative concentration and distribution of both androgen and estrogen receptors in hamster brain compared to mouse and rat brain.

Animals↗

PubMed1983

Residual androgen binding in testicular feminization (TFM).

Most mutants with genetic androgen-resistance possess some level of androgen binding which exhibits properties of receptors. The present studies aim to determine whether the androgen binding activities in mutants are, or are related to, receptors. This binding portion is termed residual androgen receptors. We have examined several androgen-resistance mutants with testicular feminization (TFM). Putative androgen receptors from mice, rats, and humans with TFM have been compared, and at least three different types of residual receptors have been observed. They are discussed in relation to possible receptor defects and to differences in the nature of androgen-resistance associated with each of them.

Androgen-Insensitivity Syndrome↗