The sex determination in Ellobius lutescens remains bizarre

Mammalian sex determination and gonad differentiation are the result of a complex interaction of fine-tuned spatial and temporal gene expression with threshold levels of individual genes. The male pathway is initiated by SRY. Some exceptional mammals determine male sex without the SRY gene and even without a Y chromosome. Ellobius lutescens in this report is one example of this "weird" species. We provide key data on the genomic level that there are no coarse differences in the genomes of male and female animals by comparative genomic hybridization. On the gene level we studied the gene Nr5a1 for the orphan nuclear receptor, steroidogenic factor SF-1, a central constituent for gonad differentiation and adrenal gland development. The Ellobius lutescens Nr5a1 gene was mapped to the proximal short arm of chromosome 2 by fluorescence in situ hybridization. In addition, we provide evidence by linkage analysis in two E. lutescens pedigrees that Nr5a1 is not the key male sex-determining gene in Ellobius lutescens.

Protein kinase C isoenzyme: selective expression pattern of protein kinase C-θ during mouse development

Protein kinase C (PKC)-θ, a serine/threonine protein kinase and novel PKC subfamily member, has been recently identified as an essential component of the T cell synapse which activates the NF-kB signaling cascade leading to expression of the IL-2 gene during T cell activation. By RNA in situ hybridization to whole-body embryo sections it is shown that the murine PKCθ is specifically expressed in tissues with hematopoietic and lymphopoietic activity. Expression is also evident in skeletal muscle. A further highly specific expression was observed in the peripheral and central nervous system which is described in detail. Expression in the brain persists up to adult stages.

Exclusion of SOX9 as the testis determining factor in Ellobius lutescens: evidence for another testis determining gene besides SRY and SOX9

In mammals the initiation of testis determination usually depends on the Y-chromosomal gene SRY. A few species, however, escape from this rule with a testis determination that is independent of SRY. The mole vole Ellobius lutescens is one of these species. It is not known how testis determination is initiated in this species but it has been suggested that a gene from the sex determination cascade usually acting downstream of SRY is mutated and has taken over the testis-determining function. At present SOX9 is the only candidate gene for which a testis-determining function in the absence of SRY has been observed. To test the hypothesis that testis differentiation in E. lutescens is initiated by SOX9, segregation analysis of SOX9 alleles was performed in an E. lutescens family. As there is no marker data available in this species we screened both Ellobius SOX9 introns for polymorphisms suitable for segregation studies. A biallelic polymorphism was found in the second intron of the SOX9 gene and analysis of this marker in the Ellobius family revealed an inheritance pattern completely independent of the sex of the animals. Thus, SOX9 can be excluded from being the testis-determining factor in E. lutescens. These results provide evidence for another possibly yet unknown gene besides SRY and SOX9 able to exert testis-determining function.

Developmental profile of Sry transcripts in mouse brain

Transient activation of the gene Sry in the gonadal ridge during a brief period of embryonic development is believed to function as a key signal for sex determination. However, a number of reports suggest that Sry expression is not as restricted in space and time as one would expect if its role was confined to directing male-specific differentiation in the early gonadal anlage. We have previously reported the occurrence of Sry/SRY transcripts in adult murine and human brain. The present communication is concerned with the study of the ontogenetic time course of Sry transcripts in mouse brain as detected by reverse transcription-polymerase chain reaction (RT-PCR). Particular emphasis was placed on the identification of two different forms of Sry mRNA, which can be linear or circular. To this aim, we used specific RT-PCR strategies to distinguish between both. Sry transcripts were found in male brain tissue of all ontogenetic stages investigated. Circular, presumably untranslatable, transcripts were found in embryonic brains of day 11 through 19. In contrast, postnatal Sry transcripts were linear, and thus translatable, and were found in diencephalon, midbrain, and cortex. The change from one transcript form to the other suggests that expression of the Sry gene in mouse brain is developmentally regulated, presumably by a switch in promoter selection. This supports the notion that Sry expression in brain is biologically significant.

Ontogenetic expression and splicing of estrogen receptor-alpha and beta mRNA in the rat midbrain

Several studies have shown that estrogen is important for the differentiation of midbrain dopaminergic neurons. This is supported by the previous demonstration of estrogen synthesis in the perinatal ventral midbrain. The present study attempts to characterize the expression pattern of nuclear estrogen receptors (ER-alpha/beta) mRNAs in the ventral rat midbrain during development. By applying primers specific for the hormone-binding domain, ER-alpha mRNA was detected from embryonic day (E) 14 until postnatal day (P) 20, whereas considerable levels of ER-beta mRNA were found from P3 to P20. In contrast, primers spanning the DNA-binding domain demonstrated the presence of transcripts for ER-alpha as well as ER-beta after birth. These findings indicate that both ERs are expressed in the developing midbrain. The presence of ER-alpha transcripts devoid of the DNA-binding region is discussed in the context of 'non-genomic' estrogen signaling possibly by membrane receptors.

The Y-chromosomal genes SRY and ZFY are transcribed in adult human brain

Sexual differentiation of the brain is thought to be regulated by hormonal signals from the developing male gonad. However, more-recent experimental and clinical data throw some doubt on the general validity of the "classical" steroid hypothesis and suggest that additional intervening factors or mechanisms need to be considered. In particular, it is now envisaged that neurons are capable of acquiring sex-specific properties independently of their hormonal environment. Here we show that two Y-chromosomal genes involved in sex determination of the gonad, SRY and ZFY, are transcribed in hypothalamus, and frontal and temporal cortex of the adult male human brain. These genes are candidates for male-specific transcriptional regulators that could confer upon human brain cells the potential for hormone-independent realization and maintenance of genetic sex.

Birthdates of the tyrosine hydroxylase immunoreactive neurons in the hypothalamus of male and female rats

This study determined the birthdates of the tyrosine hydroxylase-(TH) immunoreactive (IR) neurons in the zona incerta (ZI), periventricular nucleus (PeVN) and arcuate nucleus (AN) of male and female rats. 'Long-survival' [3H]thymidine autoradiography combined with TH immunocytochemistry, the first enzyme of catecholamine synthesis, was used. In males, TH-IR neurons originate in the ZI between embryonic days (E) 12 and 13, while in the PeVN and AN this process is prolonged until E16. The majority of TH-IR neurons became postmitotic at E12 in the ZI, between E12 and E14 in the PeVN and at E15 in the AN. The birthdate of TH-IR neurons was sexually dimorphic with (a) generation of the majority of TH-IR neurons in the ZI in males proceeding that in females, (b) generation of TH-IR neurons in the AN of males delayed as compared to females, and (c) average daily fractions of the newborn TH-IR neurons in each hypothalamic region of females exceeding that seen in males. This sexual dimorphism was observed prior to E16, i.e. before the onset of sex difference in androgen levels, implying a hormone-independent mechanism, determined at the genetic level.

Activation of dopaminergic D1 receptors promotes morphogenesis of developing striatal neurons

The early dopaminergic input from the midbrain may play an important role in the development of the basal ganglia. We therefore investigated whether and how dopamine affects the morphogenesis of striatal target neurons. Dissociated cell cultures of embryonic day 17 rat striatum were raised for seven days. Cells were then incubated with dopamine or various receptor-specific ligands for 1 h. At various times after termination of the treatment, cells were immunostained for growth-associated protein-43. Morphological parameters including numbers of growth cones, length of neurites, number of bifurcations, and neuronal soma size were assessed by means of a computer-based morphometric device. Treatment with dopamine in low concentrations as well as with the D1-like receptor agonist SKF 38393 increased the numbers of growth cones and neurite length and arborization. The morphogenetic effect took several hours to evolve and remained stable for at least 24 h. It could be blocked by the D1-like receptor antagonist SCH 23390 or by cycloheximide but not by pretreatment of the cultures with tetrodotoxin. The D2-like receptor agonist quinpirole had no effect on the morphological parameters and did not contribute to that of SKF 38393. Dopamine and SKF 38393 but not quinpirole also induced an increase in the number of neurons immunoreactive for Fos-like proteins. However, this effect was restricted to growth-associated protein-43-negative neurons. This is the first observation of a positive regulatory effect of D1-like receptors on neuronal morphogenesis. We conclude that the changes reflect true differentiation rather than short-term modulation of cellular properties and that c-fos induction is not an obligatory step in the transduction pathway coupling D1-like receptors to neurite outgrowth. Our results suggest that the differentiation of embryonic striatal neurons is promoted by the dopaminergic nigrostriatal projection through D1-like receptors.

Sex differentiation of rat hippocampal GABAergic neurons

In order to analyse mechanisms of sex differentiation of the hippocampus at the cellular level, the differentiation of hippocampal GABAergic neurons was studied in vitro. Serum-supplemented and serum-free dissociated cell cultures were raised from the hippocampus of embryonic day 17 male and female rat embryos for up to 14 days in vitro. This time period roughly corresponds to the critical phase for sex differentiation of the rat brain as determined in vivo. Serum-free cultures were treated with testosterone and/or 17 beta-oestradiol for the entire culture period. Control cultures from male donors contained twice as many GABA-immunoreactive neurons as those from female donors, while there was no sex difference in overall counts of neurons stained for microtubule-associated protein 5. Measurements of high-affinity uptake of [3H]GABA essentially confirmed this sex difference. The development of the sex difference could not be influenced by long-term treatment with androgen or oestrogen. It is concluded that sex differentiation of a specific subpopulation of hippocampal neurons may take place independently of the environment provided by gonadal steroids and in the absence of extrinsic connections with the hypothalamus or other relays of the limbic circuit.

Pre- and postnatal development of dopaminergic neuron numbers in the male and female mouse midbrain

Quantitative information about dopaminergic neuron numbers in the mesencephalon is needed to assess the significance of physiological cell death in the regulation of the development of this neural system. Therefore, stereological techniques were applied to determine absolute numbers of mesencephalic neurons immunoreactive to tyrosine hydroxylase during the ontogenetic period between embryonic day (E) 13 and postnatal day (P) 90. Male and female CBA/J mice were examined separately. The most rapid development with a 2.5-fold increase of total counts of immunostained cells per midbrain took place in the prenatal period. Beginning at E21, immunostained cells were counted separately in their three main locations, substantia nigra (SN), ventral tegmental area (VTA), and retrorubral field (RRF). Neuron numbers in RRF and VTA reached adult levels perinatally. In contrast, counts of immunostained cells in SN continued to increase postnatally. The only sign of cell loss was a transient decrease in VTA cell numbers (but not in total numbers of immunostained midbrain neurons) between E21 and P14. There were no statistically significant sex differences in cell numbers at any time point investigated. It is concluded that physiological cell death is not a major factor in the developmental regulation of dopaminergic cell numbers in the mouse midbrain.

Genotype-dependent sex differentiation of dopaminergic neurons in primary cultures of embryonic mouse brain

In order to investigate genetic factors that interfere with hormone-mediated sex differentiation of dopaminergic neurons, we raised sex-specific primary cultures from embryonic day 13 diencephalon (D) or mesencephalon (M) of three different strains of mice, NMRI, CBA/J, and BALBc/J. Part of the cultures were maintained for 6 or 13 days in vitro (DIV) in medium containing 17 beta-estradiol or testosterone. The cultures were analyzed for sex differences in numbers of tyrosine hydroxylase-immunoreactive neurons, endogenous dopamine (DA) levels, and specific uptake of [3H]DA. Previous results obtained with cultures of embryonic Sprague-Dawley rats had shown that these parameters develop sex-specific characteristics in the absence of sex differences in hormone environment. Similar steroid-independent sex differences as they occur in the rat were found in M cultures of NMRI but not in CBA and BALBc mice. Long-term sex steroid treatment did not affect any of the above parameters in any strain. It is concluded that cell-autonomous realization of the genetic sex of dopaminergic neurons depends on the genetic background.

Ontogeny of aromatase messenger ribonucleic acid and aromatase activity in the rat midbrain

Estrogen formation catalyzed by neural aromatase is crucial for the sexual differentiation of the brain. Ontogenic expression of aromatase mRNA and aromatase activity were studied in male and female rat midbrains. Aromatase mRNA was transiently expressed in both sexes showing maximum levels on postnatal day (P)2 and being absent on P20 and in adults. Developmental expression of aromatase mRNA preceded that of aromatase activity. These data demonstrate that the capacity for estrogen formation is present during a distinct phase of midbrain development. Our findings suggest an active role for estrogens in the differentiation of midbrain neurons.

Transcription of the Y chromosomal gene, Sry, in adult mouse brain

The Y chromosomal gene Sry encodes a putative transcription factor which appears to serve as a master switch initiating testicular development. Here we show that this gene is transcribed in hypothalamus, midbrain, and testis of adult male but not adult female mice. In contrast to its circular transcripts in adult testis, those in brain are linear and may be translated. We propose that Sry exerts a role in the regulation of sex differentiation of the mammalian nervous system.

Effects of sex and estrogen on tyrosine hydroxylase mRNA in cultured embryonic rat mesencephalon

In order to elucidate cellular events responsible for sex differentiation of the nigro-striatal system, we studied the influence of estrogen on the expression of tyrosine hydroxylase (TH) in sex-specific dissociated cell cultures of embryonic day 14 rat mesencephalon. Cultures were raised in the absence or presence of 17 beta-estradiol (10(-12) M) and hybridized with a [35S]oligonucleotide specific to TH. Cultured cells and tissues were probed for estrogen receptor (ER) transcripts by hemi-nested PCR. More TH mRNA containing cells were present in control cultures from female than from male donors. Estrogen treatment resulted in an up-regulation of TH expression in male cells only and induced a reversal of the sex difference in TH mRNA levels present in early control cultures. ER message was detectable in hypothalamic and uterine tissues but not in mesencephalic tissue or cultured cells. Estrogen exposure failed to induce ER expression in cultured mesencephalic cells. It is concluded that there are sex differences in TH mRNA expression of developing midbrain dopaminergic neurons which are independent of the steroid environment. Estrogen can up-regulate TH mRNA in a sex-specific fashion by modulating signal transduction mechanisms other than the classical nuclear receptor pathway.

Neurotoxicity of dopamine and protective effects of the NMDA receptor antagonist AP-5 differ between male and female dopaminergic neurons

Neurodevelopmental and neurodegenerative disorders related to dopaminergic transmission typically exhibit a sex-specific prevalence. In order to investigate the underlying cellular mechanisms, primary cultures of dissociated embryonic rat midbrain were subject to a 24 h treatment with dopamine in concentrations between 1 and 1000 microM. Dopamine caused a dose-dependent loss of neurons and reduction of neurites immunoreactive to tyrosine hydroxylase with a LD50 of about 100 microM. Application of D1-like or D2-like receptor agonists instead of dopamine did not induce cell loss. Neither D1-like or D2-like receptor antagonists nor the nitric oxide synthase inhibitor N-nitro-L-arginine were capable of blocking dopamine-induced cell death. When tissue from male and female donors was cultured separately, a twofold sex difference was consistently present: (1) Survival rates of female dopaminergic neurons in the presence of LD50 concentrations of dopamine were about twice those of male neurons. (2) The N-methyl-D-aspartate-receptor antagonist AP-5 was capable of rescuing female but not male dopaminergic neurons from dopamine-induced cell death. It is concluded that dopamine neurotoxicity is not mediated by dopamine receptors and is aggravated by glutamate excitotoxicity but not by nitric oxide. The male-specific vulnerability is the first direct evidence that the prevalence of certain neurodevelopmental or neurodegenerative disorders may have a basis in the biology of the single dopaminergic neuron.

Activation of cultured rat hypothalamic dopaminergic neurons by long-term but not short-term treatment with prolactin

Pituitary prolactin (PRL) secretion is inhibited by hypothalamic GABAergic and dopaminergic (DAergic) systems. PRL, in turn, appears to be capable of activating these neurons, thus, providing for a negative feedback regulation. We have recently shown that cultured hypothalamic GABAergic- but not DAergic neurons respond to PRL with a rapid increase in intracellular free calcium. Here, we demonstrate that cultured hypothalamic DAergic neurons can be activated in terms of synthesis of dihydroxyphenylalanine (DOPA) by long-term PRL treatment. Short-term PRL treatment was ineffective. It is concluded that hypothalamic DAergic neurons are indeed capable of responding to PRL. However, their response differs from that of GABAergic neurons with respect to time scale and signal transduction. We suggest that the two types of hypothalamic cells are involved in separate feedback loops that provide for tonic and rapid regulation of pituitary PRL secretion, respectively.

Differentiation of hypothalamic GABAergic neurons in vitro: absence of effects of sex and gonadal steroids

The inhibitory neurotransmitter gamma-aminobutyric acid (GABA) is involved in the control of sexually dimorphic brain functions, such as pituitary secretion and reproductive behavior. Hypothalamic GABAergic systems in vivo exhibit sexually dimorphic functional properties. Sexual dimorphisms in the rat brain are currently thought to be brought about by the organizational influence of gonadal steroids during the perinatal developmental period. The present study is concerned with the question of whether developing hypothalamic GABAergic neurons are primary targets of sex hormones. Since it is impossible to distinguish direct from indirect effects of experimental manipulations of the hormonal environment of the in vivo brain, sex-specific primary cultures raised from embryonic day 14 rat diencephalon and cultured for up to 8 days in vitro (DIV) were used as a model system. Effects of sex steroids were investigated on high affinity uptake of [3H]GABA. GABA transport was already mature at 3 DIV. [3H]GABA uptake was sensitive to inhibition by nipecotic acid and the transmitter was taken up by high affinity transport (Km = 15.2 microM). Immunocytochemical preparations demonstrated extensive networks of GABA-immunoreactive fibers at 8 DIV. Concomitantly with the outgrowth of neurites, there was a marked increase in maximum uptake velocity (Vmax). No differences could be detected regarding cell numbers or uptake kinetics between cultures from male and female donors. Neither cell numbers nor GABA uptake were affected by short- and long-term treatment with estradiol-17 beta or testosterone. It appears that hypothalamic GABAergic neurons in vitro do not develop sex differences in cell numbers or GABA transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Ontogeny of synaptophysin and synaptoporin in the central nervous system: differential expression in striatal neurons and their afferents during development

The expression of the synaptic vesicle antigens synaptophysin (SY) and synaptoporin (SO) was studied in the rat striatum, which contains a nearly homogeneous population of GABAergic neurons. In situ hybridization revealed high levels of SY transcripts in the striatal anlage from embryonic day (E) 14 until birth. In contrast, SO hydridization signals were low, and no immunoreactive cell bodies were detected at these stages of development. At E 14, SY-immunoreactivity was restricted to perikarya. In later prenatal stages of development SY-immunoreactivity appeared in puncta (identified as terminals containing immunostained synaptic vesicles), fibers, thick fiber bundles and 'patches'. In postnatal and adult animals, perikarya of striatal neurons exhibited immunoreaction for SO; ultrastructurally SO antigen was found in the Golgi apparatus and in multivesicular bodies. SO-positive boutons were rare in the striatum. In the neuropil, numerous presynaptic terminals positive for SY were observed. Our data indicate that the expression of synaptic vesicle proteins in GABAergic neurons of the striatum is developmentally regulated. Whereas SY is prevalent during embryonic development, SO is the major synaptic vesicle antigen expressed postnatally by striatal neurons which project to the globus pallidus and the substantia nigra. In contrast synapses of striatal afferents (predominantly from cortex, thalamus and substantia nigra) contain SY.

Uptake and subcellular distribution of azithromycin in human phagocytic cells. Demonstration of the antibiotic in neutrophil polymorphonuclear leucocytes and monocytes by autoradiography and electron microscopy

Azithromycin (CAS 83905-01-5), a new azalide antibiotic, reached high concentrations in alveolar macrophages obtained from patients. Uptake of [14C] azithromycin by macrophages resulted in an intracellular/extracellular concentration ratio of approximately 634 after 90 min incubation. Electron microscopic autoradiography provided visual evidence for the marked uptake and localization of [3H] azithromycin in human neutrophils and monocytes isolated from healthy volunteers. Quantitative analysis of the autoradiographs showed the distribution of azithromycin over the various compartments of the phagocytic cells.

Sex steroids do not alter sex differences in tyrosine hydroxylase activity of dopaminergic neurons in vitro

In order to distinguish the effects of genetic sex from those of sex hormones on the sexual differentiation of dopaminergic neurons, catecholamine synthesis was studied in gender-specific cultures of embryonic day-14 rat diencephalon. In addition to embryos from normal dams, embryos were used whose mothers had been treated with the estrogen antagonist tamoxifen or the testosterone antagonist cyproterone acetate on days 12 and 13 of gestation. Cultures from embryos of untreated dams were fed daily with a medium containing 17 beta-estradiol or testosterone. After 10 days in vitro, cultures were immunostained for tyrosine hydroxylase and the accumulation of dihydroxyphenylalanine (DOPA) was measured in the presence of the DOPA decarboxylase inhibitor NSD 1015. Rates of DOPA synthesis, unlike the numbers of tyrosine hydroxylase-immunoreactive neurons, were markedly higher in female cultures under all experimental conditions. Treatment of dams with antisteroids prior to removal of the embryos had no influence on these results. Treatment of cultures with both steroids decreased DOPA formation in a dose-dependent manner without altering the sex difference. These results suggest that cultured diencephalic dopaminergic neurons develop sex differences in the activity of tyrosine hydroxylase. This sexual dimorphism is initiated independently on the activity of gonadal steroid hormones. Sex hormones exert an additional modulatory influence on the activity of the enzyme but do not abolish or reverse sex differences. Therefore, the concept of a purely epigenetic mode of sexual differentiation of the mammalian brain needs to be broadened to incorporate other mechanisms, such as the cell-autonomous fulfillment of a sex-specific genetic program.

Sex differences of hypothalamic prolactin cells develop independently of the presence of sex steroids

There is evidence for a hypothalamic prolactin (PRL) system that expresses sexually dimorphic traits. The aim of this in vitro study is to gain an insight into the process of sexual differentiation of hypothalamic PRL cells. In particular, we wanted to determine whether sexual differentiation of these cells can occur independently of the surge of gonadal testosterone which, in the male rat embryo, takes place at embryonic day (E) 18 and is commonly believed to start the critical period of sexual differentiation of the brain. Gender-specific cell cultures were prepared from E 14 or E 17 rat diencephalon and raised in the absence of gonadal steroids. After 10 days in vitro, numbers of PRL-immunoreactive (IR) cells and PRL levels were quantified by immunocytochemistry and Western blotting, respectively. Numbers of PRL-IR cells and PRL levels were 2-3 times higher in cultures prepared from female than from male embryos of either age. It is concluded that sexual differentiation of hypothalamic PRL cells starts well before the generally acknowledged onset of the critical period and may proceed independently of the action of gonadal testosterone. Besides gonadal steroids, other mechanisms, such as cell-intrinsic realization of a sex-specific genetic program, may be responsible for initiating the development of sexually dimorphic neuronal phenotypes.

Sex differences in densities of dopaminergic fibers and GABAergic neurons in the prenatal rat striatum

On the basis of observations on dopaminergic neurons developing in gender-specific cultures of embryonic rat mesencephalon, we have hypothesized that as yet unknown sexual dimorphisms might be found in projection areas of dopaminergic neurons. Therefore we searched for possible sex differences in the striatum during the period when massive ingrowth of mesencephalic afferents occurs and the striatal gamma-aminobutyric acid (GABA)ergic neurons differentiate. Male and female rats of embryonic days (E) 16, 18, 20, and 21 were fixed by perfusion through the heart. Vibratome sections were cut from the striatal anlage and sequentially immunostained for GABA by the immunogold-silver technique and tyrosine hydroxylase (TH) by the avidin-biotin-peroxidase method. Ultrathin sections were scanned for numbers of GABA- and TH-immunoreactive (IR) elements. Densities of TH-IR axons as well as of GABA-IR cell body profiles progressed with time. Contacts between TH-IR axons and GABA-IR and immunonegative cells were observed as early as E-16, increasing in numbers toward later stages. Throughout prenatal development, female striata displayed higher densities of both TH-IR axon and GABA-IR cell body profiles than male ones. This is the first report of a distinct anatomical sex difference regarding two major components of a key center of motor control. Prenatal sexual differentiation of the striatum may lead to a sexually dimorphic extrapyramidal circuitry, the existence of which, in the adult, is suggested by experimental and clinical data.

Subcellular distribution and antifungal effects of fluconazole in human phagocytic cells. Demonstration of the antifungal agent in neutrophil polymorphonuclear leucocytes and monocytes by autoradiography and electron micrography

Electron microscopic autoradiography was used to demonstrate the presence of [3H] fluconazole (CAS 86386-73-4) in neutrophils and monocytes isolated from volunteers. Quantitative analysis of the autoradiographs showed significant accumulation of fluconazole in both phagocytic cells. The distribution of fluconazole was equal in the different intracellular compartments such as cytoplasm and nucleus. Fluconazole (20 micrograms/ml) induced ultrastructural changes in Candida albicans cells which had been phagocytized by neutrophils or monocytes (macrophages) in vitro. Particularly, changes in the plasma membrane and in the cytoplasmic structure of the intraphagocytic yeast cells were observed electron microscopically.

Diencephalic GABAergic neurons in vitro respond to prolactin with a rapid increase in intracellular free calcium

In order to analyze the feedback action of prolactin (PRL) on the hypothalamus on the cellular level, we used primary cultures of rat embryonic diencephalon to measure the calcium response of individual neurons to PRL by means of fast fluorescence photometry. The cultures were subsequently stained with antibodies against the neuronal marker MAP-2, glutamic acid decarboxylase (GAD) or tyrosine hydroxylase (TH). PRL caused a rapid rise of intracellular free Ca2+ in a specific type of GABAergic neuron characterized by a spindle-shaped bipolar morphology and immunoreactivity to MAP-2 and GAD but not to TH. It is concluded that a subpopulation of hypothalamic GABAergic but not dopaminergic neurons react to PRL with a rapid increase in intracellular free Ca2+. These data are compatible with the assumption of a rapid negative feedback regulation of the secretion of PRL from the pituitary mediated by tuberoinfundibular GABAergic neurons.

Absence of sex differences in size of the genital ducts of the rat prior to embryonic day 15.5-16.0

Sexual dimorphisms of the rat brain are generally believed to be brought about by the presence of testosterone during a critical period starting at embryonic day (ED) 17/18. In contrast, sex differences of diencephalic and mesencephalic dopaminergic neurons were observed to develop in cell cultures raised from ED 14 rat brains. This was interpreted as evidence indicating that sexual differentiation of certain neural systems may occur independently of gonadal hormones. To substantiate this claim, it was felt necessary to examine the rat embryo for clues to a possible existence of sex differences in hormonal environment prior to ED 17. Morphometry was applied to compare the development of male and female Wolffian and Müllerian ducts, both primary targets of hormones secreted from the male gonad. Diameters of serially cross-sectioned Wolffian and Müllerian ducts were measured in rats of ED 15.0 to ED 16.5. Females had thicker Müllerian ducts from ED 15.5 on. The first step of differentiation in males was the widening of the lumen and a slight increase of the outer diameter of the Wolffian duct at ED 16.0. The size differences of both ducts were most obvious in the vicinity of the lower half of the gonad. Except in Wolffian ducts of ED 16.5, sex differences were absent in the caudal parts of the ducts. It appears that gonadal androgen and Müllerian inhibiting substance do not affect the development of their classical target organs prior to ED 16.0 and ED 15.5, respectively. Furthermore, the first effects are paracrine in nature. There is no evidence for sex differences in systemic androgen environment until ED 16.5.(ABSTRACT TRUNCATED AT 250 WORDS)

[Perineural application of glycerol and phenol-glycerol. Histomorphologic-morphometric study]

In a long-term study the effect of glycerol and phenol-glycerol on rats mandibular nerve was analysed. The substances were applicated perineurally. Nerves treated with glycerol did not show any severe pathological changes. Only the number of desintegrations of myelin seemed to be more pronounced. This, however, was a transitary effect. On the contrary, nerves treated with phenol-glycerol showed the familiar picture of degeneration and regeneration. According to our results it can be stated that the perineural application of glycerol has no toxic and destructive effect on the nerve. Therefore, the perineural glycerol blocking will not cause severe side-effects and the method can be recommended in the therapy of chronic facial pain.

Sexual differentiation of monoaminergic neurons--genetic or epigenetic?

It is currently believed that sexual differentiation of the brain is mediated entirely by the epigenetic action of gonadal steroids during a critical period of development. Ingrid Reisert and Christoph Pilgrim review sexual dimorphisms of monoaminergic systems, which also appear to be generated by sex steroids. However, there are a number of observations that are not explainable by the 'androgen theory of sexual differentiation'. Results obtained from cultures of embryonic rat brain tissue appear to indicate that dopaminergic neurons may develop morphological and functional sex differences in the absence of sex steroids. Hormone-independent and -dependent developmental processes may affect diencephalic and mesencephalic dopaminergic neurons in a regionally diverse fashion. Factors other than sex steroids need to be examined. It is possible that some sexual dimorphisms in the nervous system may develop under primary genetic control.

Cells from embryonic rat striatum cocultured with mesencephalic glia express dopaminergic phenotypes

To study region-specific transmitter phenotype expression, cells of embryonic day 14 (E14) rat neostriatum (ganglionic eminence plus cortical plate) or of the substantia nigra (ventral mesencephalon) were cultured on glial cells either from substantia nigra or neostriatum (E21). By antityrosine hydroxylase immunocytochemistry, immunoblotting of tyrosine hydroxylase protein and quantitation of dopamine and its metabolites by HPLC, dopaminergic cells were revealed in nigral and neostriatal cultures plated on nigral glial cells. No dopaminergic cells were found among neostriatal neurons plated on neostriatal glial cells. It is concluded that glia from substantia nigra but not glia from neostriatum is capable of inducing development or promoting survival of dopaminergic cells.

Dopamine content and metabolism in mesencephalic and diencephalic cell cultures: sex differences and effects of sex steroids

Sexual differentiation of dopaminergic neurons was studied in gender-specific cultures. Dissociated cell cultures were prepared from di- or mesencephalon of gestational day 14 rat embryos and raised in the absence or presence of 17 beta-estradiol or testosterone for up to 13 days in vitro (DIV). Developmental profiles of levels of dopamine (DA) and metabolites as well as capacity for vesicular storage of the transmitter were determined by HPLC. Tyrosine hydroxylase-immunoreactive (TH-IR) neurons were counted. Higher levels of DA were measured in female than in male cultures of both brain regions. In mesencephalic cultures, the differences in DA levels were fully accounted for by sex differences in numbers of TH-IR cells, whereas no sex differences in cell numbers were found in diencephalic cultures. Dihydroxyphenylacetic acid (DOPAC) levels and vesicular storage capacity matured faster in mesencephalic than in diencephalic cultures, but no sex differences were observed. Homovanillic acid (HVA) could not be detected except in 13-DIV mesencephalic cultures. Hormonal treatment did not erase sexual differentiation of dopaminergic neurons. Irrespective of the gender, however, both steroids decreased DA and DOPAC contents in diencephalic cultures but not in mesencephalic cultures. It is proposed that sexual differentiation of dopaminergic systems proceeds in a region-specific fashion and that neurogenesis and development of various parameters of dopaminergic activity may be differentially affected. Sexual differentiation of dopaminergic neurons may be initiated independently of the action of gonadal steroid hormones and may subsequently be modified by differences in hormonal environment.

The influence of genetic sex on sexual differentiation of diencephalic dopaminergic neurons in vitro and in vivo

Soma sizes of embryonic male and female tyrosine hydroxylase-immunoreactive neurons were measured in 3 diencephalic regions in situ and in diencephalic dissociated cell cultures. Male neurons were about 30% larger than female neurons both in vitro and in situ. Treatment of cultures with sex steroids did not affect the sex differences. It is concluded that sexual differentiation of dopaminergic neurons may be under primary genetic control.

Sex-specific schedule in steroid response of rhombencephalic catecholaminergic neurons in vitro

Morphological differentiation of tyrosine hydroxylase-immunoreactive neurons was investigated in dissociated cell cultures of rhombencephalon of male and female day 14 rat embryos grown in the presence or absence of sex steroids. Numbers of cells were counted and morphometrical measurements carried out of soma size and length of tyrosine hydroxylase-immunoreactive neurites (processes). Subtle sex differences in length of stained neurites, which were not yet present after 3 days in vitro, were observed after 6 days in cultures grown in the absence of sex steroids. Female tyrosine hydroxylase-immunoreactive neurites could be traced over longer distances than male ones. Daily treatment of cultures with testosterone or 17 beta-estradiol resulted in an increase of lengths of stained neurites of female neurons after 3 days and of male neurons after 6 days in vitro. Regarding cell numbers or soma size, there were no differences between genders or between controls and hormone-treated cultures. It is concluded that sex steroids promote the outgrowth of neurites from noradrenergic neurons within a gender-specific time frame. It appears that the critical period for developmental effects of sex steroids differs between males and females.

Prenatal development of mesencephalic and diencephalic dopaminergic systems in the male and female rat

Previous results had suggested mesencephalic dopaminergic neurons in cultures of gestational day (GD) 14 rat embryonic brains to be characterized by an early maturation and acquisition of sex-related differences in transmitter uptake. Therefore development of dopaminergic systems was reexamined in the rat in vivo with special emphasis on the prenatal period, mesencephalo-hypothalamic relationships, and possible sex differences. Perfusion-fixed brains of GD 14, 17, 20, 21 and newborn rats were sectioned or processed as whole-mounts and immunostained for tyrosine hydroxylase (TH). Total numbers of mesencephalic TH-immunoreactive cell bodies as assessed by a stereological method rose between GD 14 and 17 and fell again between GD 17 and 21. As early as GD 14, a prominent mesencephalo-hypothalamic projection was observed coming off the medial forebrain bundle and terminating in the retrochiasmatic region. Two additional TH-immunoreactive fiber bundles leaving the medial forebrain bundle, one rostral and one caudal to the former, and terminating in the paraventricular and premammillary region, respectively, were noticed on GD 17. Careful examination of developing TH-immunoreactive neurons in the lower brainstem ascertained that there was no interference from ascending catecholaminergic fibers other than dopaminergic of mesencephalic origin during this early prenatal period. All 3 mesencephalo-hypothalamic projections had largely disappeared by GD 20 and were no longer detectable as distinct fiber bundles thereafter. There were subtle sex differences in numbers and distribution of both mesencephalic and diencephalic TH-immunoreactive neurons present at GD 17, which thus occurred prior to manifestation of other well-known sexual dimorphisms of the rat brain.(ABSTRACT TRUNCATED AT 250 WORDS)

Region- and sex-related differences in maturation of astrocytes in dissociated cell cultures of embryonic rat brain

Previous studies using dissociated cell cultures of fetal rat brain have revealed considerable regional diversity as well as sex steroid-independent sex differences in developmental schedules of dopaminergic neurons. Because these phenomena might be related to glial heterogeneity, cultures of dissociated male and female diencephalon, mesencephalon, and rhombencephalon of gestational day 14 rats were investigated with respect to the development of astrocytic markers. Cultures were incubated for 3-8 days in vitro (DIV) in serum-supplemented or serum-free medium. Vimentin and glial fibrillary acidic protein (GFAP) were quantified by counting of immunolabeled cells and immunoblotting. Vimentin and GFAP content rose from DIV 3 to 6 in all cultures. Regional variation of vimentin content was low, but large differences occurred in amounts of GFAP. GFAP reached high levels in rhombencephalon, especially when supplemented with serum, but remained very low or not detectable in mesencephalon. Simultaneous immunostaining for both cytoskeletal proteins revealed the presence of large numbers of vimentin single-labeled and small numbers of vimentin/GFAP double-labeled cells. Numbers of cells expressing GFAP showed similar regional variations as GFAP contents in both serum-free and serum-supplemented medium. They rose steeply from DIV 3 to 8 in rhomb- and diencephalon but not in mesencephalon. Transiently, female diencephalic cultures contained slightly more GFAP-immunoreactive cells than male cultures. The results thus demonstrate considerable regional heterogeneity of astrocytic maturation. However, neither the regional nor the sex differences show a consistent correlation with previous data on development of dopaminergic and other monoaminergic neurons in vitro. It seems likely that the dependence of neurons on glial environment for realization of an inherent developmental program varies among neuronal phenotypes.

Different developmental potentials of diencephalic and mesencephalic dopaminergic neurons in vitro

Morphological and functional differentiation of dopamine (DA) neurons was compared in dissociated cultures from gestational day 14 rat mesencephalon and diencephalon. Numbers of tyrosine hydroxylase-immunoreactive (TH-IR) neurons relative to all neurons were 4 and 1.7 times higher in mesencephalic than in diencephalic cultures at 6 and 13 days in vitro (DIV), respectively. Morphological maturation of diencephalic DA neurons was retarded in comparison to mesencephalic DA neurons. There were gross differences in soma size and length of processes between the two types of DA neurons, the appearance of which was strongly reminiscent of DA cell types described in vivo. Functional maturation of DA neurons was quantified by measuring uptake and Ca2+-dependent K+-stimulated release of [3H]DA per TH-IR neuron. As early as 6 DIV, DA uptake by mesencephalic DA neurons was saturable, was sensitive to benztropine and reserpine, and could be displaced by unlabeled DA. Twenty to 30% of the radioactivity accumulated could be released upon depolarization within a period of 5 min. At 6 DIV, influx of [3H]DA into diencephalic DA neurons was almost insensitive to benztropine, reserpine and unlabeled DA. Even after 13 DIV, diencephalic DA uptake was characterized by a markedly lower initial velocity, a longer time needed to reach saturation, a lower uptake capacity, and a lower sensitivity to benztropine than mesencephalic DA uptake. The releasable pool was very small and did not increase between DIV 6 and 13. The results demonstrate that mesencephalic DA neurons in vitro differentiate considerably faster than diencephalic DA neurons and gain functional competence very early in brain development. Comparison with data on adult nigrostriatal and hypothalamic DA systems suggests that the in vitro differences reflect a fundamental regional diversity of DA neurons.

Early sexual differentiation of diencephalic dopaminergic neurons of the rat in vitro

Development of dopaminergic neurons was investigated in dissociated cell cultures raised from the diencephalon of male and female rat fetuses from days 14 and 17 of gestation. Striking differences in morphology and function of male and female dopaminergic neurons were observed. Outgrowth of tyrosine hydroxylase-immunoreactive processes initially proceeded at a faster rate in female than in male cultures. Morphological differences disappeared in cultures of gestational day 17. Irrespective of the age of the cultures and of the length of cultivation, the uptake capacity for (3H)dopamine per immunoreactive neuron was twice as high in female than in male cultures. Treatment of the cultures with sex steroids did not influence morphology, numbers or transmitter uptake of tyrosine hydroxylase-immunoreactive neurons. The results suggest that diencephalic dopaminergic systems exhibit a sexual dimorphism that develops unexpectedly early in ontogeny and is independent of the action of gonadal hormones.

Sexual differentiation of mesencephalic neurons in vitro: effects of sex and gonadal hormones

In order to study the influence of gender on the development of transmitter uptake by dopaminergic neurons, dissociated cell cultures were raised separately from male and female midbrains of gestational day 14 rats. It was ascertained by use of specific inhibitors and by autoradiography that the uptake of [3H]dopamine was restricted to neurons immunoreactive for tyrosine hydroxylase and that these neurons have dopaminergic properties. The uptake capacity was higher in male than in female dopaminergic neurons by a factor of 1.5. This sexual dimorphism in dopamine uptake was present in cultures of tissue removed before the perinatal rise of testosterone occurs in males, and was present even in the absence of hormonal additives to the culture medium. It therefore appears to be independent of the presence of gonadal steroids. It occurred likewise in cultures raised with serum-supplemented and serum-free medium, which may indicate that glia are not decisive in generating these differences. In addition, sexual differences were found regarding hormone responsiveness. Whereas testosterone and dihydrotestosterone were ineffective, estradiol was seen to promote dopamine uptake in female but not in male neurons. The results would suggest that mesostriatal and/or mesolimbic dopaminergic systems assume an early role in the development of some sexual dimorphisms of the brain.

Rapid maturation of synaptic functions of prenatal serotoninergic neurons in short-term cultures: absence of sex differences and hormone effects

Serotonin is believed to modulate neuronal differentiation during early stages of brain development. In order to assess basic functional requirements for such a role, it was investigated how early serotoninergic neurons mature with respect to transmitter storage and stimulus-secretion coupling. Dissociated cell cultures were raised from embryonic rat rhombencephalon obtained at gestational day 14 and cultured for 3-8 days, which may roughly correspond to the prenatal period in vivo. Because of a possible involvement of serotonin in processes leading to sexual differentiation of the brain, gender-specific cultures were raised in addition and treated with sex steroids. Sensitivity of [3H]serotonin uptake to fluoxetine could already be observed at 3 days in vitro. Vesicular storage as probed with reserpine and nigericin, and the capability of releasing preaccumulated serotonin in a Ca2+-dependent manner were also present as early as 3 days in vitro. Seven per cent of the pre-accumulated transmitter could be released per minute upon stimulation with 54 mM K+. Immunocytochemical and autoradiographic preparations demonstrated that, after the same short culture period, the neurons had formed large fiber networks. No differences could be detected regarding any of the above parameters between female and male serotonin neurons and between cultures treated with and without estradiol, testosterone and dihydrotestosterone. It is concluded that, in contrast to other neuronal phenotypes, serotoninergic neurons are functionally mature when or shortly after they are taken into culture, i.e. around gestational day 14. The functional competence of prenatal serotonin systems should be a prerequisite for their suspected role in modulating neural development at pre and postsynaptic sites. The present results provide no evidence for the occurrence of a sexual dimorphism of serotonin neurons at this early developmental stage.

Abundant GABAergic innervation of rat posterior pituitary revealed by inhibition of GABA-transaminase

An antibody against gamma-aminobutyric acid (GABA) was used to identify GABAergic elements immunocytochemically in the rat posterior pituitary. In order to increase the intracellular concentration of GABA, rats were treated with the GABA-transaminase inhibitor gamma-vinyl-GABA (GVG). Light-microscopic observations of Vibratome and semithin sections revealed the presence of numerous immunoreactive nerve fibers throughout the neural lobe; the mean number and length of these fibers increased by 90% after GVG treatment. Electron microscopy demonstrated the immunostained axons to be of small diameter. The reaction product was confined to small vesicles. No immunostaining occurred in pituicytes. The richness of the GABAergic innervation of the neural lobe contrasts with previous reports using antibodies against glutamate decarboxylase and supports the idea that GABA participates in the presynaptic control of neurosecretion.

Sex steroids promote neurite growth in mesencephalic tyrosine hydroxylase immunoreactive neurons in vitro

The influence of steroid hormones on the differentiation of catecholaminergic and serotonergic (5-HT) neurons was studied in dissociated cell cultures from embryonic day 14 (E14) rat diencephalon, mesencephalon and metencephalon treated for 6 days with 17 beta-estradiol (E), testosterone (T), 5 alpha-dihydrostestosterone (DHT), progesterone (P), dexamethasone (DEX), or E + T. The effects of these hormones on morphologic differentiation were determined by morphometric measurements of total length of neurites of immunocytochemically identified neurons in culture, which were stained with antisera against tyrosine hydroxylase (TH) or 5-HT. A significant increase in neurite length was observed in cultures of TH-immunoreactive (TH-IR) neurons from the mesencephalon treated with E, T, E + T, but not with P, DHT or DEX. Based on labeling with [3H]dopamine (DA) uptake and competition with specific inhibitors, these mesencephalic TH-IR cells appear to represent DA neurons of the A8-A10 groups (which includes the substantia nigra). No statistically significant effects of these steroids were observed on TH-IR neurons from the diencephalon (assumed to be precursors of the tuberoinfundibular and incertohypothalamic dopaminergic groups). The 5-HT neurons of the raphe nuclei (metencephalon) showed no statistically significant response to steroids. We conclude that during the early fetal period, sex steroids can affect the morphologic differentiation of mesencephalic DA neurons in vitro, indicating that these hormones are capable of selectively influencing the development of a specific population of monoamine neurons during this critical period.

Different developmental schedules of dopaminergic and noradrenergic neurons in dissociation culture of fetal rat midbrain and hindbrain

The development of dopaminergic and noradrenergic neurons in dissociation cultures of mesencephalon and rhombencephalon obtained from 18-day-old rat fetuses was characterized by their capacity to take up and release catecholamines. In both types of cultures, uptake of [3H]dopamine and [3H]noradrenaline was obtained which could be inhibited by reserpine. Autoradiographic studies demonstrated an almost exclusive neuronal localization of the labeled catecholamines. The transmitters could be released by depolarization with K+ in a Ca2+-dependent manner during the entire cultivation period. In contrast, catecholamine uptake by cultures of neocortex was minimal, could not be inhibited by reserpine, and the accumulated radioactivity could not be released upon depolarization. These points provide evidence for an active accumulation of the exogenous transmitters and for the presence of stimulus-secretion coupling in a distinct population of neurons of both brain stem cultures. Striking differences between the two brain stem cultures concerned their sensitivity to desmethylimipramine and benztropine as well as the time course of the development of the uptake capacity. Desmethylimipramine inhibited the uptake of both catecholamines in rhombencephalic, but not in mesencephalic cultures. The reverse was true for benztropine. It is concluded that cultures of rhombencephalon contain predominantly noradrenergic, and those of mesencephalon dopaminergic cells. Comparison of the uptake behaviour suggested that noradrenergic neurons mature considerably later than dopaminergic neurons. The results show that dissociation cultures of mid- and hindbrain, inspite of their heterogeneous composition, can serve as valuable models for the study of development and function of dopaminergic and noradrenergic neurons, respectively.

Quantitative assessment of GABA-uptake sites in the neural lobe by electron-microscopic autoradiography

Distribution of (3H)GABA in the rat neural lobe was investigated 5 min after intracarotid administration using quantitative electron-microscopic autoradiography. Specificity of (3H)GABA-uptake was tested by pretreatment of control animals with nipecotic acid. It was concluded that, apart from a small fraction in the perivascular spaces, radioactivity was present exclusively in pituicytes. The results confirm and quantify earlier in-vitro observations; they are compared with recent immunocytochemical findings that reveal the presence of glutamate-decarboxylase-containing axons in the neural lobe. It is concluded that there may be GABAergic terminals that lack an uptake mechanism for exogenous transmitter. Nevertheless, (3H)GABA autoradiography is useful in demonstrating other functional components of GABAergic systems, i.e., glial cells.

The glial reaction in the course of axon regeneration: a stereological study of the rat hypoglossal nucleus

Both hypoglossal nuclei were examined by electron microscope stereology after unilateral axotomy. The principal aim of this study was a quantitative assessment of the accompanying glial reaction. Volume densities (%) of neuronal and glial perikarya, as well as their processes, were evaluated in terms of volume plus surface densities (mm-1). In addition, specific surfaces (surface to volume ratio) of these neuronal and glial processes were assessed. First, a temporary decrease of dendritic volume density was detected on the ipsilateral side only. Further, the astrocytic reaction displayed differences between stem and lamellar processes. One day after axotomy, a bilateral decrease of volume density, as well as surface density of stem processes, was observed, yet their normal dimensions soon were reestablished. However, a more severe lamellar process reaction was evident. During the first 4 days, a significant increase of volume density and surface density was apparent. In the contralateral hypoglossal nucleus, this glial reaction also occurred but disappeared by day 14, whereas the ipsilateral nucleus continued to display a severe reaction of lamellar processes, only returning to normal status at day 77. In addition, a transient, severe reaction of presumptive microglia was established by employing the volume density and surface density quantitation procedure. Nevertheless, in comparison with the volume and surface contribution of astrocytic processes, the presumed microglial component was minimal. This study indicates a two-step involvement of astrocytes in regenerative repair. Namely, the first phase seems to result in an increase of lamellar processes through reshaping of the stem process.(ABSTRACT TRUNCATED AT 250 WORDS)