Biomedical subjects
Publications and source records attributed to L Martini.
A 30 year-old man presented with progressive left peroneal nerve palsy. At surgery, an intraneural cystic tumour was found in the common peroneal nerve. Pathological examination showed that the tumour was of synovial origin.
It has been demonstrated that exposure of the hamster to a short photoperiod (light on less than 12 h/day) induces an increased sensitivity of the hypothalamic-pituitary axis to the feedback effect of testosterone. It was consequently felt of interest to investigate whether the photoperiod might act by increasing the formation of estrogens in the CNS and/or in the anterior pituitary. The aromatase activity was studied utilizing a sensitive in vitro assay that measures the amount of 3H2O formed during the conversion of [1 beta-3H]androstenedione to estrone. First of all it has been investigated whether the aromatizing enzymes, previously found in the hypothalamus, were present also in the cerebral cortex and in the anterior pituitary; secondly, the kinetic parameters of the enzyme were determined; finally, the possible variation of the central aromatase activity in hamsters exposed to a long or to a short photoperiod was investigated. The results obtained indicate that both in the hypothalamus and in the cerebral cortex the aromatization of androstenedione is linear with respect to time of incubation and tissue concentration; moreover, in the two structures, the enzyme demonstrated a similar Michaelis-Menten constant (0.03 and 0.08 microM respectively). From a quantitative point of view, the hypothalamus seems to possess an aromatizing activity higher than that of the cerebral cortex. Exposure of the hamsters to a short photostimulation for 60 days resulted in a significant regression of the reproductive system (decreased testicular weight and serum LH levels) and in a decrease of the aromatase activity of the hypothalamus. There was no effect of the photoperiod on the aromatase of the cerebral cortex. Since androgens are known to stimulate the aromatase, the present data might be tentatively interpreted by suggesting that the variation in the formation of estrogens during the short photoperiod might be the consequence of the decreased serum testosterone levels typical of the hamster in the quiescent gonadal period.
The present experiments were performed in order to analyze whether the administration of estrogens (single injection of 500 micrograms of estradiol benzoate s.c.) to neonatal male rats might modify the weight of the ventral prostate and the epididymis as well as the metabolism of testosterone in these two organs. The metabolism of testosterone was evaluated in vitro using 14C-radiolabelled testosterone as the substrate. The metabolites dihydrotestosterone (DHT), 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol), 5 alpha-androstane-3 beta,17 beta-diol (3 beta-diol), androstenedione, 5 alpha-androstane-3,17-dione (5-A-dione) and 3 alpha-hydroxy-5 alpha-androstane-17-one (androsterone) were quantified. After neonatal estrogen administration animals were killed on days 22 and 90 of age. The following changes were observed: (1) the body weight, the weight of the testes and of the ventral prostate were lower than in controls on both day 22 and 90; (2) the weight of the epididymides was higher than in controls on day 22 and lower on day 90; (3) in the ventral prostate the in vitro formation of DHT was lower and that of the diols was higher than in control tissue on day 22 of age; (4) the in vitro formation of alpha-reduced metabolites of the 17-keto series (5 alpha-A-dione + androsterone) was higher in ventral prostate of treated animals than in that of controls on day 22; (5) in treated animals, no formation of DHT in the caput epididymis was observed at day 22. On the contrary, at the same age the formation of androstenedione was higher than in controls; on day 90 of age the formation of DHT, androstenedione and the 5 alpha-reduced metabolites of the 17-keto series was identical in caput epididymis of the treated animals and of the controls, while the formation of the diols was higher in the treated than in the controls. The data indicate that neonatal estrogenization may induce important changes in testosterone metabolism in the prostates and in the epididymides of the rat.
Several experiments have been performed in order to analyze whether physiological or experimental changes of the endocrine environment might modify the binding characteristics of brain mu and kappa opioid receptors in the brain of the female and male rat. (a) In a first series of experiments, it has been observed that in the whole brain of regularly cycling female rats the number of mu receptors shows variation during the different phases of the estrous cycle. In particular a significant increase of the number of mu receptors has been observed in the morning of proestrus and in the afternoon of estrus. (b) In a second series of experiments, it has been shown that the administration of estrogens brings about a significant increase in the number of mu receptors in the hippocampus and in the thalamus of ovariectomized rats, while the administration of a regime including estrogen and progesterone induces a significant decrease of the number of mu receptors in the hypothalamus and in the corpus striatum. These data seem to indicate that hypothalamic mu receptors may be involved in the positive but not in the negative feedback control of LH secretion. (c) In a third series of experiments, it has been found that the number of mu receptors in the whole brain of 15- and 22-month-old male rats and in the hypothalamus of 22-month-old male rats is significantly lower than in the same tissues of young animals; moreover, the administration to old animals of testosterone does not modify the number of hypothalamic mu opioid receptors, indicating that the decline of brain mu receptors in old animals is not the consequence of the physiological decline of testosterone secretion but probably represents an autonomous phenomenon. (d) In a fourth series of experiments, it was shown that, in young male rats, the concentration of kappa receptors is extremely variable in different regions of the brain. The highest concentrations have been found in the hypothalamus and in the striatum; also in the mesencephalon and in the amygdala kappa receptors are present in rather elevated quantities; lower concentrations have been found in the thalamus, the frontal poles, the hippocampus and in the anterior and posterior cerebral cortex. These experiments have shown in addition that the process of aging induces an increase of the number of kappa receptors in the amygdala and in the thalamus; no age-linked modifications were observed in the other structures examined.(ABSTRACT TRUNCATED AT 400 WORDS)
The experiments to be described have been designed in order to: (a) provide new information on the concentrations of opioid kappa receptors in different regions of the brain of the male rats; and (b) to analyze whether the density of brain kappa receptors might be modified by the process of aging. The concentration of kappa receptors was investigated in the hypothalamus, amygdala, mesencephalon, corpus striatum, hippocampus, thalamus, frontal poles, anterior and posterior cortex collected from male rats of 2 and 19 months of age. 3H-bremazocine (BRZ) was used as the ligand of kappa receptors, after protection of mu and delta receptors respectively with dihydromorphine and d-ala-d-leu-enkephalin. The results obtained show that: (1) in young male rats, the number of kappa opioid receptors is different in the various brain areas examined: the hypothalamus and the striatum have a concentration of kappa binding sites which is significantly higher than that found in the mesencephalon and in the amygdala; much lower concentrations of kappa binding sites have been found in the thalamus, the frontal poles, the hippocampus, the anterior and posterior cerebral cortex. (2) Aging exerts little influence on the number of kappa receptors in the majority of the brain structures considered. However in the amygdala and in the thalamus the number of kappa receptors was increased in old animals. To the authors' knowledge, the data here presented are the first ones which suggest that age may increase rather than decrease the number of neurotransmitter receptors in the brain.
The 5 alpha-reductase, the enzyme which converts testosterone into its major "active" metabolite (dihydrotestosterone, DHT), has been found to be present in high concentration in brain structures particularly rich of myelin (white matter structures), as well as in myelin membranes. Previous ontogenetic observations seem to indicate that, during the process of myelinogenesis, the enzyme might be synthesized in the oligodendrocytes, and subsequently incorporated into the myelin membranes. It is well established that postnatal malnutrition produces a decreased formation of myelin, when starvation is performed from birth until to the 2nd or 3rd week of life; on the contrary food deprivation does not produce any significant effect on myelin accumulation when performed after the 14th day of life. The present experiments have been performed in the rat in order to study the effects of postnatal undernutrition (from birth to the 19th day of life: long malnutrition; and from the 14th to the 19th day of life: short malnutrition) on the 5 alpha-reductase activity present in the following brain structures: cerebral cortex, hypothalamus, corpus callosum, pyramidal tract, as well as in isolated myelin membranes. Undernourished animals have been killed at 20 days of age. Normally nourished animals served as controls. Long undernutrition induced a statistically significant decrease of the formation of DHT in the corpus callosum and in the pyramidal tract vs controls. On the contrary, the nutritional deficiency did not decrease the 5 alpha-reductase activity in the cerebral cortex and in the hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)
It is known that the neural mechanisms which control PRL and gonadotropin secretion are different in male and female rats. The present experiments have been designed in order to analyze: 1) whether sexual differences exist in the responses of PRL and LH to the opioid antagonist naloxone; and 2) the mechanisms underlying these possible differences. To this purpose the responses of PRL and LH to the sc injection of either saline (0.5 ml) or naloxone (2.5 mg/kg) have been tested in the following four groups of animals: 1) normal male rats; 2) normal female rats; 3) female rats treated on the second day of life with 1.25 mg testosterone (androgenized female rats); and 4) male rats orchidectomized 2 days postnatally (demasculinized male rats). The naloxone challenge has been provided when the animals were 16, 26, and 60 days old; the animals were killed in the afternoon 20 min after treatment. The results obtained have shown that the acute injection of naloxone significantly decreases serum levels of PRL in normal males and in androgenized females at all ages considered. On the contrary, the opioid antagonist was always ineffective in normal females and in neonatally castrated males. The treatment of male rats with naloxone was without any effect on LH release before puberty (at 16 and 26 days of age), but induced a significant increase of serum LH titers after sexual maturation (60 days). In normal females, naloxone brought about a significant increase of serum LH only at 16 and 60 days (animals in estrus), but not at 26 days. Treatment with naloxone did not exert any significant effect on LH release in androgenized females and in deandrogenized males of any age. The present data suggest that, in the rat a sexual difference exists in the opiatergic control of PRL secretion; apparently, the central opioid systems which regulate PRL secretion develop towards a male pattern because of the presence of androgens in the neonatal period. On the contrary neonatal androgens do not seem to exert any important effect in directing the organization of the opiatergic mechanisms controlling LH release.
The intraprostatic concentrations of testosterone (T) and dihydrotestosterone (DHT) have been measured in only a few men. We measured, in prostatic tissue obtained at surgery from seven men with benign prostatic hyperplasia, the effects of 3-month treatment with a long-acting GnRH agonist on 1) the intraprostatic concentrations of T, DHT, and 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol); 2) prostatic 5 alpha-reductase activity; and 3) the prostatic content of androgen receptors (AR). Plasma T, DHT, and 3 alpha-diol levels also were measured. Prostatic tissue samples obtained at surgery from a group of untreated men with benign prostatic hyperplasia also were studied. The mean DHT and 3 alpha-diol concentrations in the prostatic tissue of the treated men were about 10% of those in untreated men (n = 19; P less than 0.01 for DHT and P less than 0.05 for 3 alpha-diol), and the mean intraprostatic T concentration in the treated men was about 25% of that in the control group (0.10 greater than P greater than 0.05). The mean in vitro formation of DHT by the prostatic tissue of the treated men was about 50% lower (P less than 0.05) than that by prostatic tissue of the untreated men (n = 9). The mean cytosolic AR content in the prostatic tissue of the treated men was significantly higher (P less than 0.05), whereas the mean nuclear content of both salt-extractable and salt-resistant AR was significantly lower (P less than 0.05) than that in the prostatic tissue of the untreated men (n = 8). The mean plasma T levels in treated men decreased from 4.77 +/- 1.79 (SD) ng/mL (16.5 +/- 6.2 nmol/L) to 0.27 +/- 0.42 ng/mL (0.9 +/- 1.5 nmol/L) after 1 month of therapy and remained in the castrate range thereafter. We conclude that pharmacological castration resulting from 3-month treatment with a long-acting GnRH agonist decreases the intraprostatic T concentration to about one fourth and those of DHT and 3 alpha-diol to about one tenth of the levels in untreated men. Thus, GnRH agonist treatment may not completely abolish intraprostatic androgen concentrations in metastatic prostatic cancer patients. The decrease in prostatic 5 alpha-reductase activity as well as the decrease in nuclear receptors are probably secondary to the decrease in plasma T concentrations.
In the central nervous system of the rat, the 5 alpha-reductase, the enzyme which converts testosterone into dihydrotestosterone, appears to be concentrated in the white matter and in particular to be associated with myelin. In order to verify whether a temporal correlation might exist between the formation of myelin membranes and the variations of the 5 alpha-reductase activity observed in the brain, the enzymatic activity was studied in the cerebral cortex and in the hypothalamus of male rat in the age range of 3-60 days, in myelin purified from animals of 15-60 days of life and in oligodendrocytes (i.e. in the cells responsible for the formation of the myelin) isolated from the brain of adult and very young rats (7th day of life, when the myelination process is not yet initiated). The results show that the formation of 5 alpha-androstane-17 beta-ol-3-one (DHT) in the cerebral cortex and in the hypothalamus has a peak activity in the first two weeks of life, before the beginning of the myelination process; purified myelin has an enzymatic activity always much higher than that present in the cerebral cortex and in the hypothalamus and shows a peak in the formation of DHT in the first period of myelinogenesis, on the third week of life. Finally the oligodendrocytes of young rats possess a much higher ability to convert testosterone into the 5 alpha-reduced metabolites than the oligodendrocytes of adult animals. A possible involvement of this enzyme in the myelin function may be hypothesized.
Previous results obtained in this laboratory indicate that in the rat brain the 5 alpha-reductase, the enzymatic activity involved in metabolizing testosterone into 5 alpha-androstan-17 beta-ol-3-one (dihydrotestosterone), is particularly concentrated in the white matter. In the present experiments, this enzymatic activity was studied in the following white matter structures, which were microdissected using the punch technique of Palkovits: anterior commissure (CA), fornix (FX), habenulo-interpeduncular tract (HP), corpus callosum (CC), stria medullaris (SM), optic chiasm (CO), fimbria of the hippocampus (FI), cerebral peduncle (PC), pontine fibers (FP), cerebellar medulla (CMD) and corticospinal tract (TCS). Moreover brain myelin was isolated and purified by sucrose density gradient ultracentrifugation. The results obtained confirm that, in the rat brain, the enzymes involved in testosterone 5 alpha-reduction are preferentially localized in the white matter. However, clearcut differences in the metabolic activity exist between the different structures examined so far. DHT formation increases rostro-caudally, so that the highest activity has been recorded in the white matter structures punched at the level of pons (FP), medulla oblungata (TCS) and cerebellum (CMD). The high metabolic activity associated with the white matter structures appears to be linked to the presence of myelin, since the specific activity of the enzyme is particularly elevated in purified preparations of myelin sheaths.
Aging exerts profound influences on the function of the hypothalamic-pituitary-testicular-axis. This work has been performed in order to verify whether, in male rats, the decreased secretion of LH and testosterone (T) occurring in old animals is reflected by modifications of luteinizing hormone-releasing hormone (LHRH) receptors at the level of the anterior pituitary and of the testes. To this purpose, the affinity constant (Ka) and the maximal binding capacity (Bmax) for the LHRH analog [D-Ser(tBu)6]des-Gly10-LHRH-N-ethylamide were evaluated, by means of a receptor binding assay, in membrane preparations derived from the anterior pituitary and testicular Leydig cells of male rats of 3 and 19 months of age. Serum levels of LH and T were measured by specific RIAs. The results obtained show that, in aged male rats, the concentration of pituitary LHRH receptors is significantly lower than that found in young animals. On the other hand, the concentration of LHRH binding sites is significantly increased on the membranes of Leydig cells of old rats. In no instance the Ka for the LHRH analog is significantly affected. Serum levels of LH and T are significantly lower in old than in young male rats. In conclusion, these results suggest that the reduced secretion of LH in old male rats may be linked, at least partially, to a decrease of the number of pituitary LHRH receptors. The impaired production of testosterone occurring in aged rats is accompanied by a significant increase of the number of testicular LHRH receptors, indicating that also the intratesticular mechanisms controlling testosterone release undergo significant alterations with aging.
Experiments have been designed in order to analyze whether the binding capability of mu opioid receptors in the brain of the male rat is modified by age. In a first experiment, the number of receptors (Bmax) and the constant of affinity (Ka) for the mu ligand 3H-dihydromorphine (3H-DHM) have been measured in the whole brain of male rats of 2, 15 and 22 months of age. In a second experiment the Bmax and the Ka for 3H-DHM have been evaluated in the hypothalamus of male rats of 2 and 22 months of age. In this experiment it was also investigated whether the administration of exogenous testosterone modifies the number and/or the affinity of the hypothalamic mu receptors. Serum levels of LH, FSH, prolactin and testosterone have been measured by specific RIAs. The results obtained show that: serum testosterone levels are significantly decreased in aged rats, while serum LH and FSH show only a small decline; serum prolactin is higher in old than in young animals; the number of mu receptors in the whole brain of 15 and 22 month old animals and in the hypothalamus of 22 month old rats is significantly lower than in the same tissues of young animals; the administration to old animals of testosterone, in doses able to bring back towards normal serum levels of testosterone, induces a decrease of LH and FSH, but has no effect on serum prolactin titers. Testosterone administration does not modify the number of hypothalamic mu opioid receptors, indicating that the decline of brain mu receptors in old animals is not the consequence of the physiological decline of testosterone secretion; in no instance the Ka for the mu ligand is significantly affected.
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In the brain of several animal species testosterone is converted into a series of 5-alpha-reduced metabolites, and especially into 17-beta-hydroxy-5-alpha-androstan-3-one (DHT), by the action of the enzyme 5-alpha-reductase. The formation of DHT has never been evaluated in the white matter structures of the brain, which are composed mainly of myelinated axons. The experiments here described were performed in order to study, in the rat and the mouse, the DHT forming activity of several white matter structures, in comparison with that of the cerebral cortex and of the hypothalamus. Two sampling techniques were used in the rat: microdissection under a stereo-microscope from frozen brain sections of fragments of corpus callosum, optic chiasm and cerebral cortex; fresh tissue macrodissection of subcortical white matter, cerebral cortex and hypothalamus. Only macrodissection was used in the mice. The data show that, independently from the sampling technique used, there are considerable quantitative differences in the distribution pattern of the 5-alpha-reductase activity within different brain structures. Both in the rat and in the mouse, the enzyme appears to be present in higher concentrations in the white matter structures, than in the cerebral cortex and in the hypothalamus. The present results clearly show that the subcortical white matter and the corpus callosum are at least three times as potent as the cerebral cortex in converting testosterone into DHT. An even higher 5-alpha-reductase activity has been found in the optic chiasm. Further work is needed in order to understand the possible physiological role of DHT formation in the white matter structures.
It is becoming increasingly clear that the effects of the opioids and their synthetic analogs on anterior pituitary function largely depend on the steroid milieu present in the animal at time of drug administration. However, it is still unclear whether gonadal steroids regulate the opioid-modulated mechanisms by affecting the number of opiate receptors in the brain. To further investigate these issues, the effects of opiate agonists and antagonists on LH, FSH and prolactin (Prl) secretion have been studied in: (a) normal and castrated male rats, and (b) normally cycling female rats. The binding characteristics of the brain subclass of mu opiate receptors have been analyzed in the same group of experimental animals; this type of receptors seems to be particularly involved in the control of gonadotropin and Prl release. When injected intraventricularly into normal male rats, morphine (200 micrograms/rat) induced in a significant elevation of serum LH levels at 10 and 20 min. In long-term castrated animals the administration of the drug significantly reduced LH secretion at 40 and 60 min after the injection, the inhibition lasted up to 180 min. Morphine, when given intraventricularly to normal males, induced a conspicuous and significant elevation of serum Prl levels at 10, 20, 40 and 60 min after treatment. However, when the drug was administered to castrated rats, it did not significantly affect Prl release at any time interval considered. Morphine intraventricular injections did not modify serum FSH levels either in normal or in castrated male rats. The concentration of mu opiate receptors was found to be similar when measured in the whole brain of normal and orchidectomized rats. In adult cycling female rats, s.c. injections of naloxone (2.5 mg/kg) stimulated LH release in every phase of the estrous cycle; the magnitude of the responses was highly variable, being particularly elevated at 16.00 h of the day of proestrous and at 10.00, 12.00 and 14.00 h of the day of estrous. Conversely, LH response to naloxone was totally obliterated at 18.00 and 20.00 h of the day of proestrous, when the preovulatory LH surge was found to occur. The concentration of brain opiate receptors of the mu type showed significant variations during the different phases of the estrous cycle, with higher levels at 12.00 h of the day of proestrous and at 18.00 h of the day of estrous.(ABSTRACT TRUNCATED AT 400 WORDS)
It is known that the metabolism of testosterone in the brain and in the anterior pituitary is different in mammalian and in photoperiodic avian species. In many mammalian species, testosterone is mainly metabolized to 5-alpha-reduced compounds (e.g. 17-beta-hydroxy-5-alpha-androstan- 3-one, 5 alpha-DHT and 3-alpha,17-beta-dihydroxy-5-alpha-androstane, 5-alpha,3-alpha-diol) and, to a smaller extent, to 4-androstene-3,17-dione (androstenedione), while in birds, androstenedione is the main testosterone metabolite and the conversion to the 5-alpha-reduced compounds is quantitatively negligible. In avian species, testosterone is also converted to 5-beta-reduced steroids (mainly 17-beta-hydroxy-5-beta-androstan-3-one, 5-beta-DHT and 3-alpha,17-beta-dihydroxy-5-beta-androstane, 5-beta,3-alpha-diol), and there is also evidence that in these species testosterone metabolism in the central structures may be influenced by the photoperiod. Since the hamster is a mammal whose reproductive cycle is controlled by day length, it has been analyzed whether: (a) the central structures of the hamster (cerebral cortex, hypothalamus and anterior pituitary) metabolize testosterone in vitro following a mammalian (5-alpha-reduced derivatives) or an avian (androstenedione and 5-beta-reduced compounds) pattern; and (b) the metabolism of testosterone in the same structures may be modified by the exposure to different photoperiods (LD 14:10 or LD 8:16). The present data indicate that no one of the hamster structures examined produces the 5-beta-reduced derivatives. Moreover, the formation of the 5 alpha-DHT is quantitatively low, and is not affected by the photoperiod. In contrast, androstenedione is formed in quite high yields and the exposure of the animals to 60 days of short photostimulation increases the formation of this steroid in the pituitary gland, but not in the brain structures. From these data, it appears that the central structures of the hamster metabolize testosterone with a pattern which is intermediate between that of birds and mammals.
The present experiments have been performed in order to analyse whether the binding characteristics of brain opioid receptors of the mu type vary during the different phases of the oestrous cycle in the female rat. To this purpose different groups of females with a regular 4-day oestrous cycle were killed by decapitation in different phases of their oestrous cycle, i.e. at 10.00 and 16.00 h of the first and second day of dioestrus, at 10.00, 12.00, 14.00, 16.00 18.00 and 20.00 of the day of pro-oestrus, and at 10.00, 12.00 14.00, 16.00 and 18.00 of the day of oestrus. The total brains, after discarding the cerebellum, were homogenized and crude membrane preparations were obtained. On these preparations the maximal binding capacity (Bmax, index of the number of receptors) and the constant of affinity (Ka) for dihydromorphine, a typical ligand of mu opioid receptors were evaluated. Serum concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin were measured by specific radioimmunoassays in order to exactly ascertain the different phases of the oestrous cycle. The results obtained show that the number of mu opioid receptors in the whole brain presents significant changes during the different phases of the oestrous cycle. In particular, an increase in the concentration of these receptors was observed at 12.00 h of the day of pro-oestrus and at 18.00 h of the day of oestrus; these fluctuations of the number of mu receptors were not accompanied by any change of their affinity for the ligand.(ABSTRACT TRUNCATED AT 250 WORDS)
The present study reports the effects exerted by 4-hydroxy-4-androstene-3,17-dione (4-OH-A) on the in vitro metabolism of labelled testosterone, dihydrotestosterone (DHT) and androstenedione (delta-4-A) in the prostate of adult male rats and in human benign prostatic hypertrophic (BPH) tissue. It has been found that 4-OH-A decreases the formation of DHT and of the diols. When testosterone is used as the substrate, the presence in the medium of 4-OH-A enhances the formation of delta-4-A and of 5-alpha-androstanedione (5-alpha-A); 4-OH-A does not inhibit the conversion of labelled DHT into the diols. Also, the transformation of labelled delta-4-A into 5-alpha-A is not modified by 4-OH-A. On the basis of these findings, it is suggested that 4-OH-A might represent a potential new agent for the prevention and/or treatment of human BPH.