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Biomedical subjects

G Dörner

Publications and source records attributed to G Dörner.

At least 55 records · Page 3Linked to original sources
PubMed1989

The value of cw-Doppler ultrasonography and DSA in the diagnosis of extra- and intracranial stenosis--a comparison with intraoperative findings.

The use of cw-Doppler sonography and digital subtraction angiography (DSA) for diagnosis of cerebro-vascular insufficiency (CVI) was evaluated in a retrospective study. 113 findings obtained by DSA and 315 findings obtained by cw-Doppler sonography were compared to the corresponding intraoperative finding. Furthermore, we examined the incidence of accompanying intracranial stenoses of the carotid artery. The impact of these stenoses on the CVI stage was analyzed by means of 200 transcranial Doppler sonographic studies. Cw-Doppler sonography (sensitivity: 95%) was clearly superior to DSA (sensitivity: 70%) for diagnosis of high grade and subtotal stenoses of the internal carotid artery (ICA). Sensitivity of both methods was insufficient for diagnosis of low grade stenoses (cw-Doppler: 50%, DSA 25%). Analysis of 200 transcranial Doppler sonographic studies did not reveal pathologic changes of intracranial vessels in 67% of all cases. This finding did not depend on the condition of the extracranial vessels and did also not depend on the CVI stage. Additionally, there was no correlation between the incidence and degree of intracranial stenoses and the CVI stage or the degree of stenosis of the ICA. These results support the view that Doppler sonography is the method of choice for diagnosis of high grade stenoses of the carotid artery. The use of DSA is limited to cases in which kinking or occlusion is suspected. Additional intracranial changes did not correlate with the CVI stage.

Angiography↗
PubMed1989

The influence of sex hormones on the development of sex-specific cholesterol serum levels in rats.

1. The development of sex-specific cholesterol serum levels (under a fat-enriched diet) depends on the sex hormone status during the postpuberal activation phase. 2. The efficiency of postpuberal sex hormones seems to be influenced by the presence of definite sex hormone levels during the prepuberal/puberal maturation phase. 3. An influence of the perinatal sex-specific brain differentiation on the development of sex-typical cholesterol biosynthesis as reported by Carlson et al. was not demonstrable, possibly because of our special diet regimes (fat-enriched diet).

Animals↗
PubMed1988

Neuroendocrine response to estrogen and brain differentiation in heterosexuals, homosexuals, and transsexuals.

Since 1964, we have found positive estrogen feedback to be a relatively sex-specific reaction of the hypothalamo-hypophyseal system in rats as well as in human beings. It is dependent on the estrogen-convertible androgen level during sexual brain differentiation and also on estrogen priming in adulthood. The lower the estrogen-convertible androgen or primary estrogen level during brain differentiation, the higher the evocability of a positive estrogen action on LH secretion in later life. In clinical studies, we induced a positive estrogen feedback luteinizing hormone secretion in most intact homosexual men, in clear-cut contrast to intact heterosexual or bisexual men. In addition, the evocability of a positive estrogen feedback was also demonstrable in most homosexual male-to-female transsexuals in significant contrast to hetero-or bisexual male-to-female transsexuals. The following relations have been found between sex hormone levels during brain differentiation and sex-specific responses in adulthood: (i) Estrogens, which are mostly converted from androgens, are responsible for the sex-specific organization of gonadotropin secretion and hence the evocability of a positive estrogen feedback in later life; (ii) both estrogens and androgens, occurring during brain differentiation, predetermine sexual orientation, and (iii) androgens, without conversion to estrogens, are responsible for the sex-specific organization of gender role behavior. Furthermore, the organization periods for sex-specific gonadotropin secretion, sexual orientation, and gender role behavior are not identical but overlapping. Thus, combinations as well as dissociations between deviation of the neuroendocrine organization of sex-specific gonadotropin secretion, sexual orientation, and gender role behavior may occur.

Brain↗
PubMed1988

The effect of an acute maternal stress on beta-endorphin and growth hormone releasing factor in the rat fetus.

Pregnant rats were injected with saline or L-tyrosine methylester HCl (200 mg/kg) and subjected to an acute forced immobilization stress on day 20 of gestation. At 10, 30, 60, and 120 minutes after the onset of stress, their fetuses were dissected out, and the contents of hypothalamic and pituitary immunoreactive beta-endorphin (IR-beta-EP) and hypothalamic immunoreactive growth hormone-releasing factor (IR-GRF) were determined by specific radioimmunoassays. The maternal stress arose a significant decrease of hypothalamic IR-beta-EP at 30 minutes, while pituitary IR-beta-EP slightly elevated at 30 minutes, then declined at 60 minutes. Hypothalamic IR-GRF showed a gradual increase during the maternal stress. Tyrosine supplementation tended to attenuate stress-induced changes in hypothalamic and pituitary IR-beta-EP, but the response of hypothalamic IR-GRF was less modified by tyrosine. These results showed the functional changes in fetal central beta-EP and GRF under maternal stress in the late gestational life, and suggested that catecholaminergic regulations participate, at least in part, in the fetal neuroendocrine response to maternal stress.

Animals↗
PubMed1988

Sexual endocrinology and terminology in sexology.

Sexual endocrinology has contributed decisively to the development of sexology. Effects of most recent findings in neuroendocrine research on the development of terminology in sexology, sex therapy and sex legislation are discussed.

Endocrinology↗
PubMed1988

Effect of medial preoptic oestradiol implants on hypothalamic beta-endorphin concentration.

Twenty-four-day-old immature and cyclic female rats in metoestrus were ovariectomized and bilaterally implanted with oestradiol benzoate (OB) and cholesterol at a ratio of 1:360 or with cholesterol alone in the medial preoptic area (MPOA), or, for control, the hypothalamic dorsomedial nucleus. Estimation of beta-endorphin immunoreactivity in the ventromedial-arcuate-median eminence region at 6 and 3 days after implantation, respectively, revealed a significantly higher concentration in rats implanted with OB in the MPOA as compared to those implanted with cholesterol. OB implants placed in the dorsomedial nuclei were ineffective in this regard. The hypothesis is put forward that inhibition of hypothalamic beta-endorphin release as probably resulting from the implantation of OB in the MPOA may be related to desensitization of the negative oestrogen feedback that is induced by similar preoptic oestrogen implantation.

Animals↗
PubMed1988

Teratogenetic maternofoetal transmission and prevention of diabetes susceptibility.

Gestational diabetes and impaired glucose tolerance in pregnancy were found to be important teratogenetic risk factors for the development of diabetes in the offspring. Mechanisms of action and prevention of maternofetal transmission of teratogenetic susceptibility to diabetes are presented. Gestational diabetes induced in the F0 generation produced the following effects in the F1 and/or F2 generation: Early postnatal hyperinsulinaemia, decreased noradrenaline and serotonin and increased endorphin concentrations in specific brain regions, permanent hypoplasia of the hypothalamic ventromedial nuclei, decreased insulin responsiveness to glucose, impaired glucose tolerance and increased diabetes susceptibility.

Animals↗
PubMed1988

Partial compensation of sexual receptivity deficits in female rats with bilateral lesions of the hypothalamic ventromedial nucleus by transplants of fetal mediobasal hypothalamic tissue.

Bilateral aspiration as well as bilateral electrolytic lesions of the hypothalamic ventromedial nucleus (VMN) in ovariectomized, adult female rats treated with testosterone or estrogen resulted in a long-lasting decrease of sexual receptivity. Fetal mediobasal hypothalamic (MBH) tissue was grafted successfully to the site of VMN lesions. The following presuppositions for a sufficient rate of long-term survival of the grafts could be defined: (1) careful lesioning and minimalizing of damage to the surrounding tissues, (2) high vitality of the donor fetuses, (3) delay of transplantation after lesioning, and (4) testosterone treatment of the recipient animals at an early stage of graft development. In rats with surviving MBH grafts the receptivity deficits resulting from bilateral aspiration of the VMN were compensated partially.

Animals↗
PubMed1988

Sex-specific postnatal development of negative oestrogen feedback in rats.

Experiments were performed in immature and adult male and female rats to study the postnatal development of the negative oestrogen feedback in males and to investigate the mechanisms underlying this development. The following results were obtained: 1. Immature male and neonatally androgenized female rats were less responsive to the LH-inhibiting effect of oestradiol benzoate (OB) than untreated females. In contrast, long-term castrated adult males and females with the androgen-induced persistent oestrus syndrome were distinctively more sensitive than cyclic females to the negative feedback action of oestrogen. 2. The low oestrogen sensitivity in prepubertal males is probably caused by the testicular androgen secretion during the perinatal critical differentiation phase, because after neonatal castration, the LH response to OB injected at 21 days of age did not differ between both sexes. 3. As opposed to the peripubertal desensitization to the negative feedback action of testosterone, the sensitivity to the inhibitory effect of oestrogen on LH secretion did not decrease in males at the time of puberty. 4. Whereas former studies have shown that implantation of OB in the medial preoptic area results in significant reduction of the oestrogen sensitivity in female rats, medial preoptic implants containing oestradiol, testosterone or 5 alpha-dihydrotestosterone did not diminish the LH-suppressing effect of s.c. injected OB in males. The results suggest that 1. a marked sex difference exists in the postnatal development of the negative oestrogen feedback in rats. 2. Higher oestrogen sensitivity in adult male as compared to adult female rats may depend, at least partly, on prepubertal and cyclic desensitization of the negative oestrogen feedback in females and more or less constant sensitivity in males from infancy to adulthood. 3. In males the oestrogen sensitivity seems to be settled for long by the testicular androgen secretion during the perinatal critical differentiation phase. 4. The prepubertal increase of gonadotrophin secretion necessary for the induction of male puberty may mainly be caused by diminution of the gonadotrophin-inhibiting effect of androgens and by the decline of testicular release of inhibin. 5. The oestrogen-induced desensitization of the negative oestrogen feedback mediated by the medial preoptic area is probably a sex-specific mechanism that is only operative in female rats.

Aging↗
PubMed1988

Impairment of sexual behaviour in female rats with impaired glucose tolerance due to streptozotocin treatment of their maternal grandmothers.

A decreased receptive sexual behaviour was found in female F2-offspring of Streptozotocin-treated maternal grandmothers. These F2-offspring are characterized by decreased glucose tolerance and increased diabetes susceptibility, their metabolic situation being comparable to that of Type II prediabetes. The observed phenomena were associated with permanent hypoplasia of the hypothalamic ventromedial nucleus (HVN). It is hypothesized that there could be a causal relationship between these morphological changes in the HVN and impaired sexual behaviour in female prediabetic rats.

Animals↗
PubMed1988

Diminished oestrogen sensitivity and increased ovulation rate in adult female rats after prepubertal treatment with oestrogen or pimozide.

Immature female rats were implanted with oestradiol benzoate or cholesterol in the medial preoptic area at different ages, and the inhibition of the ovariectomy-induced increase of LH secretion by s.c. injected oestradiol was investigated. Medial preoptic oestrogen implants reduced the inhibition of LH secretion in 4-week-old rats, but not in younger animals. Elevation of the circulating oestrogen concentration or suppression of the central nervous dopamine activity by daily injections of oestradiol and pimozide, respectively, from Day 26 to the day of vaginal opening, i.e. during the time when the mechanism of the oestrogen-induced desensitization of the negative oestrogen feedback matures, resulted in considerable diminution of the LH-inhibiting effect of oestradiol in ovariectomized adult females. In intact cyclic rats, both prepubertal treatments led to a significant increase of the average number of eggs per ovulation that was mainly caused by reduction of the number of animals with a low ovulation rate.

Animals↗
PubMed1988

[The place of 67Ga scintigraphy in the primary diagnosis and follow-up evaluation of opportunistic pneumonia in patients with AIDS].

Opportunistic pneumonias are a life-threatening complication in patients with AIDS. Early diagnosis and therapy is necessary to improve prognosis. This study was designed to assess the value of 67Ga scintigraphy in the primary detection and follow-up of these special pneumonias. 67Ga scintigraphy was performed in 40 patients: 10 normal controls and 30 HIV-positive patients with AIDS or AIDS-related complex (ARC). 67Ga scan results were compared with current chest radiographs and the results of pathogen detection. The evaluation of positive scans was based on a quantification of the pulmonary uptake, expressed as a pulmonary/soft-tissue uptake ratio. Only 8/30 patients had a normal scan, 22/30 showed diffuse (13/22) or focal (9/22) increases of pulmonary uptake. In 7/8 patients with normal scans the chest radiograph was negative as well. The one patient with negative scan but positive chest radiograph had pulmonary Kaposi's sarcoma. In 11/22 patients the 67Ga scan and chest radiograph were positive simultaneously. In the other 11/22 patients with positive scans chest radiographs were initially negative but showed pathology in 5 cases within 1-2 weeks. The reason for positive scans in most cases was an opportunistic lung infection; other forms of pneumonia were only observed in two cases. The defined uptake ratio demonstrated to be a highly sensitive parameter for monitoring pneumonia and the effects of therapy in follow-up studies. In conclusion, quantitative 67Ga scintigraphy proved to be a reliable and highly sensitive method for primary detection and follow-up of opportunistic pneumonias in patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Sexual differentiation of gonadotrophin secretion, sexual orientation and gender role behavior.

The positive estrogen feedback was found to be a relatively sex-specific reaction of the hypothalamo-hypophyseal system in rats as well as in human beings. It is dependent--most of all--on the estrogen convertible androgen level during sexual brain differentiation, but also on an estrogen priming effect in adulthood. The lower the estrogen convertible androgen or primary estrogen level during brain differentiation, the higher is the evocability of a positive estrogen action on LH secretion in later life. In clinical studies, we were able to induce a positive estrogen feedback on LH secretion in most intact homosexual men in clear-cut contrast to intact hetero- or bisexual men. These findings were strongly confirmed by Gladue and associates. In addition, the evocability of a positive estrogen feedback was also demonstrable in most homosexual male-to-female transsexuals in significant contrast to hetero- or bisexual male-to-female transsexuals. These findings suggest that homosexual males possess, at least in part, a predominantly female-differentiated brain, which may be caused by a low estrogen convertible androgen level during brain organization. Recently, the following relations were found between sex hormone levels during brain differentiation and sex-specific responses in adulthood: (1) estrogens--which are mostly converted, however, from androgens--are responsible for the sex-specific organization of gonadotrophin secretion and hence the evocability of a positive estrogen feedback in later life; (2) estrogens and androgens, occurring during brain differentiation, predetermine synergistically sexual orientation and (3) androgens--without conversion to estrogens--are responsible for the sex-specific organization of gender role behaviour in later life. Furthermore, the organization periods for sex-specific gonadotrophin secretion, sexual orientation and gender role behaviour are not identical but overlapping. Thus, combinations as well as dissociations between deviations of the neuroendocrine organization of sex-specific gonadotrophin secretion, sexual orientation and gender role behaviour are conceivable. Most recently, female-type sexual orientation could be converted to male-type sexual orientation in adult rats by administration of the dopamine agonist and serotonin antagonist lisuride.

Androgens↗
PubMed1987

Familial diabetes aggregation in type I diabetics: gestational diabetes an apparent risk factor for increased diabetes susceptibility in the offspring.

A significantly decreased familial diabetes aggregation on the maternal side of insulin-dependent diabetic children born between 1974 and 1984 as compared to those born between 1960 and 1973 was observed. This phenomenon was explained by an increased prevention of hyperglycaemia during pregnancy since 1974, particularly of gestational diabetes in women with familial diabetes aggregation. A highly significant predominance of Type II diabetes was found in great-grandmothers of infantile-onset diabetics on the maternal side as compared to the paternal side. This finding may suggest that gestational diabetes, which can represent a risk factor for diabetes transmission on the maternal side, is often followed by "extragestational" type II diabetes in higher age. This conclusion is supported by the data of familial diabetes aggregation obtained in insulin-dependent infantile- or juvenile-onset diabetics, when familial diabetes aggregation was ascertained as late as at least 20 years after birth of the diabetics. In this case, a significant predominance of familial diabetes aggregation in first- and second-degree relatives, particularly in grandmothers, was found on the maternal side as compared to the paternal side. All these findings are consistent with a teratogenetic effect of gestational diabetes on diabetes susceptibility in the offspring, which can be prevented by avoiding hyperglycaemia in pregnant women and hyperinsulinism in foetuses.

Adolescent↗
PubMed1987

Effects of neonatal intracerebral implantation of sex steroids on sexual behaviour, social play behaviour and gonadotrophin secretion.

Female rats were intracerebrally implanted with testosterone propionate (TP) or 5 alpha-dihydrotestosterone (DHT) on the 3rd day of life. After both treatments, prepuberal social play behaviour was significantly enhanced as compared to control females and did not differ from that recorded in males. In contrast, intracerebral implantation of oestradiol benzoate (OB) at the same day of age had no effect on the frequency with which females engaged in social play. DHT, which is not aromatizable to oestrogen, showed a significant male-type organizational effect also on sexual orientation but not on the organization of gonadotrophin secretion pattern and hence on ovarian weight. On the other hand, OB displayed in a dose-dependent manner a significant male-type organizational effect on gonadotrophin secretion resulting in an anovulatory syndrome with significantly decreased ovarian weights due to failure of corpus luteum formation as well as on male-type sexual orientation. The results suggest that different sex hormones (oestrogens and/or androgens) are responsible for the sex-specific brain differentiation of gonadotrophin secretion, sexual orientation and gender role behaviour.

Animals↗
PubMed1987

Influence of the medial preoptic dopaminergic activity on the efficiency of the negative estrogen feedback in prepubertal and cyclic female rats.

Immature and adult female rats were bilaterally implanted in the medial preoptic area (MPOA) or hypothalamic ventromedial-arcuate region (VMAR) with the dopamine (DA) antagonist, pimozide, or the DA agonist, apomorphine, and the sensitivity to the LH-inhibiting effect of a subcutaneous injection of estradiol benzoate (EB), the onset of puberty and ovarian cyclicity were investigated. Diminution of the inhibitory effect of EB on LH secretion was recorded in ovariectomized immature and adult females implanted in the MPOA with pimozide. This response was not obtained in rats implanted in the VMAR. In contrast, medial preoptic, but not intrahypothalamic, implantation of agar pellets containing apomorphine resulted in enhanced sensitivity to estrogen both prepubertally and during the ovarian cycle. The sensitizing effect of apomorphine was completely prevented in prepubertal rats by pretreatment with EB for 6 days. Bilateral implantation of pimozide-agar pellets in the MPOA of 28-day-old intact females induced significant advancement of the onset of puberty, whereas sexual maturation was not affected by daily subcutaneous injections of the DA antagonist from day 28 till the day of vaginal opening. In adult 4-day-cyclic rats fitted with guide cannulae, the forthcoming ovulation was delayed for about 7 days as compared to the controls implanted with agar if apomorphine was placed in the MPOA from the morning of metestrus to the morning of diestrus. Similar implants located in the VMAR were ineffective in this regard. The results suggest that: (1) low DA activity in the MPOA reduces and high activity enhances the sensitivity of the negative estrogen feedback in immature and adult female rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Retardation of preovulatory desensitization to negative oestrogen feedback: mechanism of the effect of progesterone in 5-day cyclic rats.

Recent studies have shown that oestrogen can induce desensitization to its own gonadotrophin-inhibiting effect in female rats by an action on the medial preoptic area (MPOA). Probably as a consequence of this action, sensitivity to the negative oestrogen feedback declines markedly between metoestrus and dioestrus of the 4-day ovarian cycle. To study this desensitization process in 5-day cyclic rats, females exhibiting regular 5-day vaginal cyclicity were ovariectomized on consecutive days of the cycle, injected with oestradiol benzoate (OB) or oil on the day of ovariectomy and autopsied 24 h after the injection. Estimation of the serum concentration of LH revealed that desensitization to negative oestrogen feedback occurred only between day 2 of dioestrus and pro-oestrus, i.e. 2 days later than in females with a 4-day cycle. In the latter animals, an injection of progesterone in metoestrus or early dioestrus, which induced lengthening of the ovarian cycle for 1 day, delayed the onset of desensitization to a degree similar to that found in spontaneously 5-day cyclic rats. In acutely ovariectomized females, progesterone implants placed in the MPOA, but not those located in the mediobasal hypothalamus, increased the LH-inhibiting effect of low doses of OB. The results suggest that the prolonged secretion of progesterone recorded in 5-day cyclic rats retards follicle maturation and delays the forthcoming ovulation by acting, at least partly, on the MPOA and antagonizing the desensitizing effect of oestrogen. In this way, inhibition of gonadotrophin secretion by oestrogen is enhanced and the increase in tonic LH secretion necessary for the completion of follicle maturation is retarded.

Animals↗