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Biomedical subjects

M Hines

Publications and source records attributed to M Hines.

At least 19 recordsLinked to original sources
PubMed1995

Human behavioral sex differences: a role for gonadal hormones during early development?

Evidence that gonadal hormones during prenatal and neonatal development influence behavior is reviewed. Several theoretical models of hormonal influences, derived from research in other species, are described. These models are evaluated on the basis of data from humans with either normal or abnormal hormonal exposure. It is concluded that the evidence is insufficient to determine which model best explains the data. Sexual differentiation may involve several dimensions, and different models may apply to different behaviors. Gonadal hormones appear to influence development of some human behaviors that show sex differences. The evidence is strongest for childhood play behavior and is relatively strong for sexual orientation and tendencies toward aggression. Also, high levels of hormones do not enhance intelligence, although a minimum level may be needed for optimal development of some cognitive processes. Directions for future research are proposed.

Adolescent↗
PubMed1994

Testosterone has rewarding affective properties in male rats: implications for the biological basis of sexual motivation.

Evidence from mammalian species, including humans, suggests that testosterone (T) enhances motivational aspects of sexual behavior, although the mechanism by which T exerts this effect is unknown. The hypothesis that increases in plasma T have rewarding affective properties was examined. Acute elevations of plasma T were induced in intact male rats by systemic administration of a recently developed testosterone-hydroxypropyl-beta-cyclodextrin inclusion complex that mimics pulsatile release of the hormone. In a conditioned-place-preference paradigm, rats displayed a preference for an environment previously paired with T administration (800 micrograms/kg and 1,200 micrograms/kg) as opposed to an environment paired with saline administration, indicating that T has rewarding affective properties. The findings suggest that T may enhance motivational aspects of mammalian sexual behavior by facilitating acquisition or expression of learned associations between environmental stimuli and sexual activity.

Affect↗
PubMed1994

Androgen and the development of human sex-typical behavior: rough-and-tumble play and sex of preferred playmates in children with congenital adrenal hyperplasia (CAH).

We hypothesized that girls with congenital adrenal hyperplasia (CAH), who experience higher than normal levels of androgens prenatally, would show masculinization of behaviors that show sex differences. Therefore, we examined rough-and-tumble play and sex of preferred playmates in 3-8-year-old children with CAH and in unaffected 3-8-year-old male and female relatives. The hypothesized sex differences in rough-and-tumble play were seen, with unaffected boys showing more rough-and-tumble play than unaffected girls. However, CAH girls were similar to unaffected girls. Additionally, CAH boys showed reduced rough-and-tumble play. In contrast, sex of preferred playmates showed the hypothesized pattern of results. There were sex differences, with unaffected boys preferring boys and unaffected girls preferring girls. In addition, the preferences of girls with CAH were masculinized compared to those of unaffected girls. Results are discussed in terms of possible influences of social, hormonal, and illness factors.

Adrenal Hyperplasia, Congenital↗
PubMed1994

Gender labels and play styles: their relative contribution to children's selection of playmates.

The relative contribution of gender labels and play styles (masculine or feminine) in playmate selection was evaluated in 60 children between the ages of 4 and 8 years using a novel interview measure. In the interview, when targets' gender labels and targets' play styles were presented as independent dimensions, children showed predicted sex differences in preferences for gender labels and for play styles (including toys, rough-and-tumble play, and activity level). However, when targets' gender labels and targets' play styles were presented as competing dimensions, boys of all ages chose female targets with masculine play styles over male targets with feminine play styles. In contrast, younger girls (4-5-year-olds) chose female targets with masculine play styles, whereas older girls (6-8-year-olds) chose male targets with feminine play styles. This suggests possible sex differences in the contribution of gender labels and of play styles in the development of children's preferences for same-sexed playmates.

Age Factors↗
PubMed1992

Sex differences in subregions of the medial nucleus of the amygdala and the bed nucleus of the stria terminalis of the rat.

Sex differences are described in subregions of two nuclei of the rat brain: the medical nucleus of the amygdala (MA) and the bed nucleus of the stria terminalis (BNST). The volume of the posterodorsal region of the medial nucleus of the amygdala (MApd) is approximately 85% greater and the volume of the encapsulated region of the bed nucleus of the stria terminalis (BNSTenc) is approximately 97% greater in males than in females. The MApd and BNSTenc are distinct subregions of the MA and BNST. They exhibit intense uptake of gonadal hormones and are anatomically connected to each other and to other sexually dimorphic nuclei. The MA and BNST in general are involved in regulation of several sexually dimorphic functions, including aggression, sexual behavior, gonadotropin secretion and integration of olfactory information. Precise localization of sex differences in subregions of the MA and BNST, such as the MApd and BNSTenc, may facilitate understanding of the neural basis of such functions.

Amygdala↗
PubMed1992

Effect of androgens on the brain and other organs during development and aging.

Androgens have important biological effects on accessory sexual organs and have a broad range of effects on metabolic processes. Male hormones have been shown to have important organizational and activational effects on morphological, behavioral, and cognitive activity in experimental animals. Sexual dimorphic effects on cognitive and behavioral activities in animals have been linked to androgens during the fetal period. The effects of testosterone on sexual drive are well established in humans, although the threshold for such activity appears to be lower than that required for many of the other and organic effects of testosterone. There are suggestive data to link fetal androgen levels to cognitive and behavioral activities in children and adults, but the behavioral activities may be modified by social and other learning processes. Androgen levels fall in older men at a time when impaired sexual function, osteopenia, and decreased muscle mass can be identified. The relative importance of androgen deficiency in these disorders requires further study, since they are likely to be multifactorial in pathogenesis. Replacement therapy of elderly men who have lowered testosterone levels has been proposed to decrease bone and muscle loss as well as to improve sexual function and general well-being. Careful studies will be required to assess the risk-to-reward ratio of such treatment, since theoretical adverse effects on prostate and cardiovascular diseases may occur. While conservation in management has its virtues, we should be reminded that several decades ago estrogen replacement of postmenopausal women was highly criticized until data supporting its favorable therapeutic ratio were demonstrated.

Aged↗
PubMed1992

Cognition and the corpus callosum: verbal fluency, visuospatial ability, and language lateralization related to midsagittal surface areas of callosal subregions.

Normal volunteers (28 women), 20-45 years old, completed tests of visuospatial ability, verbal fluency, and language lateralization, and the midsagittal surface areas of the splenium, isthmus, midregion, and genu of the corpus callosum were measured from inversion recovery magnetic resonance images. Multivariate statistics were used to analyze patterns of correlations. Verbal fluency correlated positively with the area of the splenium and with the area of a posterior callosal factor defined largely by the splenium. The posterior callosum, particularly the splenium, also correlated negatively with language lateralization. There were no other consistent brain-behavior relationships. These results are relevant to understanding factors involved in the development of cognitive characteristics that show sex differences and to understanding the neural basis of language lateralization and verbal abilities.

Adult↗
PubMed1989

Properties of an excitable dynein model for bend propagation in cilia and flagella.

Murase & Shimizu (1986, J. theor. Biol. 119, 409) introduced an excitable dynein-microtubule system based on a three-state mechanochemical cycle of dynein to demonstrate bend propagation in the absence of a curvature control mechanism. To examine the essential behavior of this class of models in a viscous fluid, we have represented the force generated by the complex dynein mechanochemistry by a formal model consisting of "force" and "activation" functions vs. sliding distance. Since the model has excitable properties with threshold phenomena and hysteresis switching between two opposed subsystems, it closely resembles the more realistic dynein kinetic scheme in its overall properties but is specified by fewer parameters. This model displays both bend initiation and bend propagation when the filaments at the basal end are either fixed or free to slide. A passive region is necessary at one end of the axoneme in order to obtain stable wave propagation; bends propagate towards the end with the passive region. Stable bend propagation is highly sensitive to small perturbations in external force distribution.

Adenosine Triphosphatases↗
PubMed1989

A program for simulation of nerve equations with branching geometries.

A computer program has been developed for simulation of electrical activity in neurons with complex branching morphology, multiple channel types, and inhomogeneous channel distribution. The program is based around an interpreter and screen editor for flexible specification of nerve properties and analysis of simulation results. Efficient simulation of the nerve specification is accomplished with procedure calls to fast, compiled routines for integration of the nerve equations.

Cell Membrane↗
PubMed1989

Two sexually dimorphic cell groups in the human brain.

A quantitative analysis of the volume of 4 cell groups in the preoptic-anterior hypothalamic area (PO-AHA) and of the supraoptic nucleus (SON) of the human brain was performed in 22 age-matched male and female individuals. We suggest the term Interstitial Nuclei of the Anterior Hypothalamus (INAH 1-4) to identify these 4 previously undescribed cell groups in the PO-AHA. While 2 INAH and the SON were not sexually dimorphic, gender-related differences were found in the other 2 cell groups. One nucleus (INAH-3) was 2.8 times larger in the male brain than in the female brain irrespective of age. The other cell group (INAH-2) was twice as large in the male brain, but also appeared to be related in women to circulating steroid hormone levels. Since the PO-AHA influences gonadotropin secretion, maternal behavior, and sexual behavior in several mammalian species, these results suggest that functional sex differences in the hypothalamus may be related to sex differences in neural structure.

Adolescent↗
PubMed1987

Estrogenic contributions to sexual differentiation in the female guinea pig: influences of diethylstilbestrol and tamoxifen on neural, behavioral, and ovarian development.

We administered the synthetic estrogen, diethylstilbestrol (DES), or the antiestrogen, tamoxifen, to pregnant guinea pigs and observed the consequences for sexual differentiation of their female offspring. Hormones were administered during the period when treatment of fetuses with testosterone influences the development of sex-related traits (approximately Days 30 to 65 of gestation). Ovarian function, masculine and feminine sexual behavior, and the structure of a sexually dimorphic neural region in the preoptic area were assessed in adulthood in hormone-exposed animals and in oil-treated and untreated controls. Prenatal exposure to DES dipropionate (DESDP) caused masculinization and defeminization. DESDP-treated females mounted more than control females, both without hormonal stimulation and when given testosterone propionate (TP) as adults. The sexually dimorphic neural region was also masculinized in these females. In regard to defeminization, they showed delayed vaginal opening, impaired progesterone (P) production, an absence of corpora lutea, and impaired lordosis and mounting responses to estradiol benzoate (EB) and P. Prenatal treatment with tamoxifen produced a complicated pattern of results. Tamoxifen-exposed females evidenced less masculine-typical behavior, showing diminished mounting without hormonal stimulation and in response to TP. However, they also showed delayed vaginal opening, enhanced P production, and impaired mounting in response to EB and P. Their lordosis behavior and the volume of the sexually dimorphic neural region were unaffected. These results suggest that estrogens play a substantial role in sexual differentiation in the guinea pig. High levels of estrogen promote masculine-typical development, and unusually low levels may impair some aspects of both masculine-typical and feminine-typical development.

Animals↗
PubMed1986

Spastic pure motor monoparesis.

Pure motor hemiplegia (PMH) is, in most cases, caused by a lacunar infarction. However, pure motor monoparesis (PMM), i.e., isolated motor involvement with spasticity in one limb, has drawn little attention. We studied prospectively 5 patients with PMM and found that it was always due to a mass lesion in the contralateral superficial cerebral hemisphere. Our observation suggests that PMM should not be regarded as simply a variant of PMH.

Aged↗
PubMed1986

Evidence that serotonin is involved in the sexually dimorphic development of the preoptic area in the rat brain.

To investigate the possibility that serotonin plays a role in the sexually dimorphic development of a nucleus in the medial preoptic area of the rat brain, p-chlorophenylalanine, an inhibitor of serotonin biosynthesis, was administered to pregnant dams from day 8 of gestation until parturition. This treatment did not alter plasma steroid levels but increased the volume of the sexually dimorphic nucleus in female neonates to that of control males. Thus, serotonin is implicated as a neurochemical which may be involved in the sexually dimorphic development of the preoptic area.

Animals↗
PubMed1986

Pre- and postnatal influence of an estrogen antagonist and an androgen antagonist on differentiation of the sexually dimorphic nucleus of the preoptic area in male and female rats.

The volume of the sexually dimorphic nucleus in the preoptic area (SDN-POA) of the rat brain is severalfold larger in adult male rats than in adult females. This sex difference in brain structure was previously shown to develop under the influence of androgenic and estrogenic hormones during the perinatal period. We tried to clarify the differential role played by androgens and estrogens during development and differentiation of the SDN-POA by treating male and female rats during an extended pre- and postnatal period either with the estrogen antagonist tamoxifen or with the androgen antagonist cyproterone acetate. Treatment with tamoxifen did not alter serum levels of testosterone in male rats during the perinatal period, but it inhibited development and differentiation of the SDN-POA. Pre- and postnatal treatment of male rats with cyproterone acetate resulted in female phenotypic appearance, but it had no influence on differentiation of the SDN-POA. Perinatal treatment of female rats with tamoxifen resulted in permanent anovulatory sterility, but did not influence SDN-POA differentiation. Treatment of female rats with cyproterone acetate had no influence on SDN-POA differentiation or on the capacity to ovulate. Since pre- and postnatal treatment of male rats with cyproterone acetate is known from previous studies to femenize sexual behavior patterns and to retain the mode for cyclic gonadotropin release, and since the same treatment did not influence differentiation of the SDN-POA in the present study, it may be concluded that the SDN-POA is not directly involved in the control of female sexual behavior and in the control of the gonadotropic hormone release pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Estrogens before birth and development of sex-related reproductive traits in the female guinea pig.

Influences of estrogens on the differentiation of psychosexual traits in the female guinea pig were studied. Pregnant animals were injected intramuscularly with either 1, 2, or 3.3 micrograms estradiol benzoate (EB) or with 1 or 3 micrograms diethylstilbestrol dipropionate (DESDP). Injections were started on the 29th day of pregnancy, given daily for 6 days, and continued every other day until parturition. Female offspring were evaluated for onset of puberty, ovarian function, and lordosis and mounting behavior in adulthood. Prenatal treatment with 3 micrograms DESDP caused delayed puberty, impaired ovarian function, reduced responsiveness of lordosis to EB and P in adulthood (defeminization), augmented mounting in the absence of hormones (masculinization), and reduced responsiveness of mounting to exogenous EB and P in adulthood (defeminization). Prenatal treatment with 1 microgram DESDP produced similar but less pronounced effects. Prenatal treatment with 3.3 micrograms EB also caused a delay in puberty. However, responsiveness of lordosis to EB and P in adulthood was enhanced by treatment with either 1 or 3.3 micrograms EB prenatally. Further, neither mounting in the absence of hormones nor mounting in response to EB and P in adulthood were affected in any measurable way by any prenatal treatment with EB. These results show that estrogens can have masculinizing and defeminizing effects on sexually dimorphic reproductive traits in guinea pigs. The failure of EB to duplicate or parallel the effects of DESDP is not completely understood at this time, but it may indicate that less of the active substance reaches the target tissues following maternal and placental metabolism of EB than of DESDP.

Animals↗
PubMed1985

On the contribution of dynein-like activity to twisting in a three-dimensional sliding filament model.

It has been shown (Hines, M., and J. J. Blum, Biophys.J., 1984, 46:559-565) that passive moment-bearing links do not contribute appreciable twist resistance to an axoneme nor do they cause appreciable twisting in response to internal shear forces. We now examine the contribution of active moment-bearing links such as dynein arms to the generation of twist within an axoneme. The dynein model used causes distal sliding of the adjacent doublet by a force dependent on the angle of attachment of the arms. Attachment of the arms occurs at a specified angle relative to the angle of minimum potential energy. The steady state shape consistent with the forces applied by the attached dyneins is computed. It is shown that the twist generated in an active region is counterclockwise as viewed from tip to base and therefore accumulates at the end of the axoneme. For realistic forces and twist resistances, cumulative twist should not exceed a few degrees.

Adenosine Triphosphatases↗
PubMed1985

Sexually dimorphic regions in the medial preoptic area and the bed nucleus of the stria terminalis of the guinea pig brain: a description and an investigation of their relationship to gonadal steroids in adulthood.

Sexually dimorphic regions are described in two areas of the guinea pig brain: the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BNST). The volume of a darkly staining portion of the MPOA is approximately 4-fold larger in male than in female guinea pigs, and the volume of a darkly staining portion of the BNST is approximately 36% larger in male than in female animals. The sex differences in both of these areas are present in animals that have been gonadectomized as adults as well as in intact animals, suggesting that they result from differences between the sexes in the hormonal environment during early development. Both the MPOA and the BNST bind high levels of gonadal steroids early in life, during the period when functional differentiation occurs. It is possible that dramatic morphological sex differences characterize such steroid-binding areas. Furthermore, these sexually dimorphic areas may form an anatomically and functionally interrelated system. Attention to these possibilities may help elucidate more precisely the neural basis for sexually dimorphic functions, as well as the basic mechanisms underlying sexual differentiation of behavior and the brain.

Animals↗