Metabolic activity of the human ventromedial nucleus neurons in relation to sex and ageing

The ventromedial nucleus (VMN) in animals is involved in a number of sexually dimorphic behaviors, including reproduction, and is a well-documented target for sex steroids. In rats and in lizards, it is also characterized by the presence of structural sexual dimorphisms. In the present study, we determined whether the metabolic activity of human ventromedial nucleus neurons was sex- or age-related. The size of the immunocytochemically defined Golgi apparatus (GA) and cell profiles were determined as measures for neuronal metabolic activity in 12 male and 16 female control brains sub-divided into four groups with the dividing line being the age of 50. It appeared that the size of the GA relative to cell size was 34% larger in young women (<50 years old) than in young men and was 25% larger in elderly men (> or = 50 years old) than in young men. In addition, the GA/cell size ratio correlated significantly with age in men and not in women. Our data suggest that androgens play an inhibitory role with respect to the metabolic activity of the human VMN neurons.

The role of calcium signaling in early axonal and dendritic morphogenesis of rat cerebral cortex neurons under non-stimulated growth conditions

The effects of depolarizing stimuli on neurite outgrowth have been shown to depend on an influx of extracellular calcium. However, the role of calcium under non-stimulated growth conditions is less well established. Here we investigated the contribution of calcium signaling to early neuronal morphogenesis of rat cerebral cortex neurons at three levels by blocking L-type voltage sensitive calcium channels, by depleting intracellular calcium or by blocking myosin light chain kinase. Detailed quantitative morphological analysis of neurons treated for 1 day revealed that depletion of intracellular calcium strongly decreased the density of filopodia, arrested axonal outgrowth and strongly decreased dendritic branching. Preventing calcium influx through L-type voltage sensitive calcium channels and blocking of myosin light chain kinase activity selectively decreased dendritic branching. Our observations support an essential role for basal intracellular calcium levels in axonal elongation. Furthermore, under non-stimulated conditions calcium entry through L-type voltage sensitive calcium channels and myosin light chain kinase play an important role in dendritic branching.

Decreased hippocampal metabolic activity in Alzheimer patients is not reflected in the immunoreactivity of cytochrome oxidase subunits

In the present study we have compared histochemically determined cytochrome oxidase activity with the levels of immunocytochemically stained cytochrome oxidase subunits (CO II and CO IV) and ATP synthase in the human hippocampus in relation with Alzheimer's disease. Cytochrome oxidase activity was significantly reduced in all hippocampal areas of Alzheimer patients. The protein levels of subunits II and IV were not different between control subjects and Alzheimer patients. Additionally, it was observed that the active cytochrome oxidase is evenly distributed over both cell bodies and neuropil, while a relatively large pool of inactive enzyme or precursors is limited to the neuronal somata. Further, in Alzheimer patients the CO IV immunoreactivity decreased with age, whereas in control subjects it increased with age. Our results suggest that the assembly of cytochrome oxidase or the processing of its subunits may be impaired.

Male-to-female transsexuals have female neuron numbers in a limbic nucleus

Transsexuals experience themselves as being of the opposite sex, despite having the biological characteristics of one sex. A crucial question resulting from a previous brain study in male-to-female transsexuals was whether the reported difference according to gender identity in the central part of the bed nucleus of the stria terminalis (BSTc) was based on a neuronal difference in the BSTc itself or just a reflection of a difference in vasoactive intestinal polypeptide innervation from the amygdala, which was used as a marker. Therefore, we determined in 42 subjects the number of somatostatin-expressing neurons in the BSTc in relation to sex, sexual orientation, gender identity, and past or present hormonal status. Regardless of sexual orientation, men had almost twice as many somatostatin neurons as women (P < 0.006). The number of neurons in the BSTc of male-to-female transsexuals was similar to that of the females (P = 0.83). In contrast, the neuron number of a female-to-male transsexual was found to be in the male range. Hormone treatment or sex hormone level variations in adulthood did not seem to have influenced BSTc neuron numbers. The present findings of somatostatin neuronal sex differences in the BSTc and its sex reversal in the transsexual brain clearly support the paradigm that in transsexuals sexual differentiation of the brain and genitals may go into opposite directions and point to a neurobiological basis of gender identity disorder.

Double immunolabeling of neuropeptides in the human hypothalamus as analyzed by confocal laser scanning fluorescence microscopy

The main goal of this study was to develop a better light microscopic procedure for quantitative study of the cellular co-localization of neuropeptides in adult human brain tissue. To reach this goal, we opted for a method (proved to be optimal on rat brain) in which sections were double immunolabeled with two different fluorophore-conjugated secondary antibodies and analyzed with a confocal laser scanning fluorescence microscope. One of our main problems faced was a strong autofluorescence of the sections, mainly caused by lipofuscin granules normally present in adult human brain tissue, which made any analysis of specific fluorescence impossible. This problem could be solved by staining the sections after immunolabeling with the dye Sudan Black B, which completely blocked this autofluorescence. The complete optimized procedure that we eventually developed can be summarized as follows. After a relatively short fixation time (6-14 days) in 4% freshly depolymerized paraformaldehyde, the resected brain tissue can best be stored in a 30% sucrose solution supplemented with 0.05% NaN3 at 4C. Stored under these conditions, cryosections from the tissue still reveal good histology and allow successful immunocytochemical staining after a period of 6 months. Double immunolabeling is done by incubating cryo- or paraffin sections in a mixture of two primary antibodies directed against the targeted antigens, followed by incubation with two different fluorophore-conjugated secondary antibodies. Amplification with a biotinylated secondary antibody followed by fluorophore-conjugated streptavidin is possible. Finally, the sections are stained with Sudan Black B, mounted in plain 80% Tris-buffered glycerol, and studied by confocal laser scanning fluorescence microscopy. Sections processed in this way are well suited for qualitative and quantitative analyses of co-localized neuropeptides in human brain tissue.

Lack of association between depression and loss of neurons in the locus coeruleus in Alzheimer disease

BACKGROUND

Depression, one of the most frequent psychiatric disturbances in Alzheimer disease (AD), is proposed to have its neurobiological basis in neuron loss in the noradrenergic locus coeruleus, although this is not the case in idiopathic depression.

METHODS

We performed image analyzer-assisted morphometry of the locus coeruleus in 6 depressed, 6 transiently depressed, and 6 nondepressed patients with AD and in 8 control subjects, emphasizing longitudinal psychiatric evaluations and matching for the clinical and neuropathological severity of dementia.

RESULTS

The mean (+/-SD) number of pigmented neurons in the locus coeruleus in controls (11 607+/-946) was higher than in patients with AD, regardless of being depressed (5165+/-928; P=.001), transiently depressed (5647+/-1163; P=.003), or nondepressed (3717+/-661; P=.001). No significant difference was found in the number of pigmented neurons between patients with AD who were depressed, transiently depressed, and nondepressed. Patients who had depression at the onset of AD had a higher pigmented neuron number than other patients with AD.

CONCLUSIONS

We confirmed the loss of pigmented neurons in the locus coeruleus of patients with AD; however, no supplementary loss of pigmented neurons in the locus coeruleus was found in patients with depression and AD. This finding resembles the situation in idiopathic depression, but is in contrast with earlier studies on depression in AD.

Depolarization stimulates lamellipodia formation and axonal but not dendritic branching in cultured rat cerebral cortex neurons

Electric activity is known to have profound effects on growth cone morphology and neurite outgrowth, but the nature of the response varies strongly between neurons derived from different species or brain areas. To establish the role of electric activity in neurite outgrowth and neuronal morphogenesis of rat cerebral cortex neurons, cultured neurons were depolarized for up to 72 h and quantitatively analyzed for changes in axonal and dendritic morphology. Depolarization with 25 mM potassium chloride induced a rapid increase in lamellipodia in almost all growth cones and along both axons and dendrites. Lamellipodia formation was dependent on an influx of extracellular calcium through L-type voltage-sensitive calcium channels. Prolonged depolarization for 24 h induced an increase in total axonal length, mainly due to an increase in branching. After three days of depolarization axonal outgrowth was largely the same as in control neurons, suggesting accommodation of the growth cones to chronic depolarization. Dendrites showed very little change during the first three days in culture, and dendritic length or branching were not affected by depolarization. Thus, in early cerebral cortex neurons depolarization specifically stimulates axonal outgrowth through increased branching. This increase in branching may be a consequence of the earlier increase in lamellipodia formation. In contrast, early dendrites seem to be unable to translate the increase in lamellipodia into changes in outgrowth or branching. This difference between axons and dendrites could be due to differences in the stabilization of the tubulin cytoskeleton.

Evidence from confocal fluorescence microscopy for a dense, reciprocal innervation between AVP-, somatostatin-, VIP/PHI-, GRP-, and VIP/PHI/GRP-immunoreactive neurons in the rat suprachiasmatic nucleus

The rat suprachiasmatic nucleus (SCN) consists of several classes of neurons which can be identified by their transmitter content. Knowledge of putative interaction between these different cell types is essential in order to understand the possibilities of information processing within the SCN. The aim of the present study was therefore to obtain more information about the mutual innervation between the main cell classes in the rat SCN, viz. those containing the neuropeptides arginine vasopressin (AVP), vasoactive intestinal peptide (VIP), peptide histidine isoleucine (PHI), gastrin-releasing peptide (GRP) and somatostatin respectively. For this purpose, vibratome sections were double-immunolabelled for seven different peptide combinations and subsequently analysed by high-resolution confocal laser scanning fluorescence microscopy. Attention was focused on axosomatic appositions, the occurrence and frequency of which were quantitatively estimated. Our analysis of double-immunolabelled sections demonstrated that some of the VIP- and some of the GRP-immunoreactive nerve cells and endings showed colocalization. Assuming, on the basis of literature data, that VIP and PHI are always colocalized at the cellular level, the five main cell classes in the SCN appeared to be interconnected, at least axosomatically, in the following reciprocal way: AVP <--> VIP/PHI, AVP <--> GRP, AVP <--> somatostatin, somatostatin <--> VIP/PHI, somatostatin <--> GRP, VIP/PHI <--> GRP, VIP/PHI/GRP <--> GRP, VIP/PHI/GRP <--> VIP/ PHI. In addition to this heterologous axosomatic innervation, these cell groups also showed substantial homologous innervation. Supported by electron microscope data from the literature showing the existence of axodendritic synapses for some of these peptide combinations, our findings strongly suggest that the rat SCN comprises a complex synaptic network with strong interactive capabilities, which is probably a requisite for its biological clock function.

Quantitative estimation of estrogen and androgen receptor-immunoreactive cells in the forebrain of neonatally estrogen-deprived male rats

Using quantitative immunocytochemical procedures, the total number of estrogen and androgen receptors was estimated in a large number of hypothalamic and limbic nuclei of male rats, in which brain estrogen formation was inhibited neonatally by treatment with the aromatase inhibitor 1,4,6-androstatriene-3,17-dione. The highest densities of estrogen receptor immunoreactivity were observed in the periventricular preoptic area and the medial preoptic area. Neonatally estrogen-deprived males showed a higher estrogen receptor immunoreactivity than control males in the periventricular preoptic area and the ventrolateral portion of the ventromedial nucleus of the hypothalamus, i.e. those brain areas in which sex differences have been reported, with female rats showing a greater estrogen binding capacity than male rats. The highest densities of androgen receptor immunoreactivity were found in the septohypothalamic nucleus, the medial preoptic area, the posterior division of the bed nucleus of the stria terminalis and the posterodorsal division of the medial amygdaloid nucleus. No significant differences in distribution or total numbers of androgen receptors were found between neonatally estrogen-deprived males and control males. These findings suggest that neonatal estrogens, derived from the neural aromatization of testosterone, are involved in the sexual differentiation of the estrogen receptor system in the periventricular preoptic area and the ventromedial hypothalamus. The role of neonatal estrogens in the development of the forebrain androgen receptor system is less clear.

Unchanged amounts of vasopressin mRNA in the supraoptic and paraventricular nucleus during aging and in Alzheimer's disease

The paraventricular (PVN) and supraoptic nucleus (SON) demonstrate a striking stability with respect to cell numbers during aging and Alzheimer's disease (AD). Vasopressin (AVP) neurons even become activated during aging as judged from several parameters for neuronal activity, such as increased AVP plasma levels, enlarged nucleolar as well as cell size and an increased size of the Golgi apparatus in AVP-neurons. The activation possibly occurs as compensation for an age-related loss of AVP-receptors in the kidney. As a specific marker for AVP synthesis, we used quantitative in situ hybridization and estimated total amounts of AVP-mRNA in the entire SON and PVN of 14 control subjects and 14 AD patients that were matched for age, fixation time, postmortem delay and storage time of the tissue in paraffin. Following quantification, no differences were observed in total amounts of AVP-mRNA in the SON or PVN between young and old controls or between young and old AD patients, nor between the entire group of controls and AD patients. A significant negative correlation was found between the volume of the AVP-mRNA signal in the AD SON and age while the total amount of mRNA remained the same. This suggests a redistribution of cells or cell compartments in aging. A significant positive relation in both SON and PVN of AD patients was found between storage time of the paraffin-embedded tissue and the total amount of AVP-mRNA. A significant positive relation was present in the PVN, but not SON between pH of the cerebrospinal fluid, which is a marker for agonal state and the total amount of AVP mRNA. The present unchanged AVP-mRNA levels in SON and PVN confirm earlier observations on the stability of cell numbers in these nuclei in aging and AD. Although on the basis of other parameters, AVP-mRNA upregulation was expected, gradual, chronic stimulation over prolonged periods of time may, possibly, induce alternative mechanisms of regulation such as changes in translatability or in mRNA stability.

Modulatory role of catecholamines in the transsynaptic expression of c-fos in the rat medial prefrontal cortex induced by disinhibition of the mediodorsal thalamus: a study employing microdialysis and immunohistochemistry

We studied the interaction of catecholaminergic and thalamic afferents of the medial prefrontal cortex (PFC) by analyzing the effects of catecholamine depletion on thalamus-induced c-fos expression in the PFC of freely moving rats. Thalamic projections to the PFC were pharmacologically activated by perfusing the GABA-A receptor antagonist bicuculline (0.03 mM or 0.1 mM) through a dialysis probe implanted into the mediodorsal thalamic nucleus. Bicuculline perfusion induced Fos-like immunoreactivity in the thalamic projection areas, including the PFC, and in the thalamic nuclei surrounding the dialysis probe. 6-Hydroxydopamine lesions of the ventral tegmental area causing a 70-80% depletion of catecholamines in the PFC did not influence the increase in the number of Fos-like immunoreactive nuclei in the prefrontal cortex in response to thalamic stimulation. However, densitometric image analysis revealed that the intensity of Fos-like immunoreactivity in the PFC of lesioned rats perfused with 0.1 mM bicuculline was higher than in correspondingly treated controls. The behavioral activity to bicuculline perfusion, an increase of non-ambulatory activity (0.03 mM) followed by locomotion and rearing (0.1 mM), was not changed in 6-hydroxydopamine-lesioned rats. It is suggested that the thalamically induced c-fos response is directly mediated by excitatory, presumably glutamatergic, transmission and not indirectly by an activation of catecholaminergic afferents of the PFC. The increase in the intensity of Fos-like immunostaining in strongly stimulated, catecholamine-depleted rats suggests that catecholamines modulate the degree to which thalamic activity can activate the PFC of awake animals.

Differences in colocalization between Fos and PHI, GRP, VIP and VP in neurons of the rat suprachiasmatic nucleus after a light stimulus during the phase delay versus the phase advance period of the night

Two groups of four rats each received a 15-minute light stimulus during the first part of the night (ZT14) and the second part (ZT19), respectively. After 45-60 minutes, the animals were killed by perfusion fixation. Adjacent Vibratome sections through the suprachiasmatic nucleus (SCN) were double-immunostained for the presence of peptide histidine isoleucine (PHI), gastrin releasing peptide (GRP) or vasoactive intestinal peptide (VIP) with Fos by using fluorophore-conjugated secondary antibodies. A few sections were triple-immunostained for PHI, GRP or VIP with vasopressin (VP) and Fos. Sections were analyzed with a confocal laser scanning microscope. It turned out that the ZT19 light stimulus induced 4.2 times more nuclear profiles in the SCN immunoreactive for Fos than the light stimulus given at ZT14. The SCN of control animals did not show any Fos immunoreactivity. After the ZT14 light stimulus, approximately 33% of the Fos profiles showed colocalization with a perikaryal profile immunoreactive for PHI, GRP or VIP, whereas at ZT19, this percentage had doubled to approximately 65%. After the light stimulus at ZT14, the relatively low Fos induction was numerically and proportionally most prominent in the PHI-immunoreactive perikarya. As compared with ZT14, the increase of Fos after the ZT19 light stimulus was most pronounced in the GRP-immunoreactive perikarya (21x) followed by VIP (15x) and PHI (5x). This outcome suggests that at least three different cell groups characterized by, respectively, PHI alone, GRP, and VIP fully or partly colocalized with PHI, play a prominent role during light-induced phase shifts: the PHI neurons during light-induced phase delays, the GRP and VIP/(PHI) neurons during light-induced phase advances.

In situ hybridization for vasopressin mRNA in the human supraoptic and paraventricular nucleus; quantitative aspects of formalin-fixed paraffin-embedded tissue sections as compared to cryostat sections

In order to study the suitability of formalin-fixed paraffin-embedded brain tissue for vasopressin (AVP)-mRNA detection, we used symmetric halves of 5 human hypothalami. In every case, one half was formalin fixed for 10-35 days and paraffin embedded while the other half was frozen rapidly. Following in situ hybridization (ISH) histochemistry on systematically obtained sections of the supraoptic (SON) and paraventricular nucleus (PVN) of both halves, total amounts of AVP-mRNA in these nuclei were estimated using densitometry of film autoradiographs. Total amounts of radioactivity were found to vary considerably between patients and amounted to 1297 +/- 302 arbitrary units (AU) (PVN) (mean +/- SEM) and 2539 +/- 346 (SON) for the cryostat sections and 868 +/- 94 (PVN) and 1259 +/- 126 (SON) for the paraffin tissue. Variations introduced by the method itself yielded a coefficient of variation of only 0.19. Furthermore, a non-significant negative trend with postmortem delay was found in cryostat tissue, but not in paraffin sections. No effect of fixation time was observed in the paraffin tissue. Both ways of tissue treatment have specific advantages and disadvantages that may be different for other probes or other brain areas. For ISH of a highly abundant mRNA like AVP in a very heterogeneous brain area such as the human hypothalamus, formalin-fixed paraffin-embedded tissue sections can be used for quantitative analysis of entire brain nuclei because of the small variation in this tissue, the remarkably good signal recovery (some 75% as compared to cryostat sections) and its practical advantages with regards to anatomical orientation, storage and sampling of the tissue.

In situ hybridization for vasopressin mRNA in the human supraoptic and paraventricular nucleus; quantitative aspects of formalin-fixed paraffin-embedded tissue sections as compared to cryostat sections

In order to study the suitability of formalin-fixed paraffin-embedded brain tissue for vasopressin (AVP)-mRNA detection, we used symmetric halves of 5 human hypothalami. In every case, one half was formalin fixed for 10-35 days and paraffin embedded while the other half was frozen rapidly. Following in situ hybridization (ISH) histochemistry on systematically obtained sections of the supraoptic (SON) and paraventricular nucleus (PVN) of both halves, total amounts of AVP-mRNA in these nuclei were estimated using densitometry of film autoradiographs. Total amounts of radioactivity were found to vary considerably between patients and amounted to 1297 +/- 302 arbitrary units (AU) (PVN) (mean +/- SEM) and 2539 +/- 346 (SON) for the cryostat sections and 868 +/- 94 (PVN) and 1259 +/- 126 (SON) for the paraffin tissue. Variations introduced by the method itself yielded a coefficient of variation of only 0.19. Furthermore, a non-significant negative trend with postmortem delay was found in cryostat tissue, but not in paraffin sections. No effect of fixation time was observed in the paraffin tissue. Both ways of tissue treatment have specific advantages and disadvantages that may be different for other probes or other brain areas. For ISH of a highly abundant mRNA like AVP in a very heterogeneous brain area such as the human hypothalamus, formalin-fixed paraffin-embedded tissue sections can be used for quantitative analysis of entire brain nuclei because of the small variation in this tissue, the remarkably good signal recovery (some 75% as compared to cryostat sections) and its practical advantages with regards to anatomical orientation, storage and sampling of the tissue.

Image analyser-assisted morphometry of the locus coeruleus in Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis

Several observations suggest that neuronal shrinkage rather than cell death is the major phenomenon in neurodegenerative diseases. In order to make this distinction, smaller cells should also be included in cell counts. Also, morphometric determination of total cell numbers of brain structures is required. Morphometry was performed on the locus coeruleus using a newly developed method to delineate this nucleus from five patients who had died with Alzheimer's disease, five with Parkinson's disease, five with amyotrophic lateral sclerosis and from five control subjects who had died from causes that would not have affected the locus coeruleus. The length and volume of the locus coeruleus and its total number of large pigmented neurons, small unpigmented neurons and glial cells were determined. Since reliable delineation of the boundaries of the locus coeruleus is a requirement for the determination of total cell numbers, an image analyser-assisted procedure was developed. In Alzheimer's disease we found an 82% decrease in the number of large pigmented neurons and a 39% decrease of small unpigmented neurons. In Parkinson's disease, we found a 39% decrease of large pigmented neurons but also a 44% (though not significant) increase of small unpigmented neurons, which is indicative of a shift from large pigmented neurons to small unpigmented neurons in Parkinson's disease. The large pigmented/small unpigmented neuron number ratio was greatly and significantly reduced in Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. These findings support the hypothesis that the decrease of large pigmented neurons of the locus coeruleus in some neurodegenerative diseases is not entirely due to cell death, but rather to cell shrinkage and a loss of phenotype. This hypothesis may have consequences for the development of therapeutic strategies since atrophied cells can be activated. On the other hand our data confirm that, at least in Alzheimer's disease, large pigmented neurons do also undergo cell death.

Activation of vasopressin neurons in aging and Alzheimer's disease

The supraoptic (SON) and paraventricular nuclei (PVN) of the human hypothalamus are production sites of vasopressin (AVP) and oxytocin (OXT). Although the hypothalamus is affected in Alzheimer's disease (AD), previous work has not only shown that in these two nuclei no neurons are lost, neither during aging nor in AD, but that the number of AVP-expressing neurons and their nucleolar size had even increased with age. These observations indicated that the peptide synthesis of the AVP neurons was activated in the oldest age-groups. Recently published, qualitative observations, using the area of the Golgi Apparatus (GA) as a sensitive parameter for neurosecretory activity, confirmed the activation of SON and PVN neurons with age in human; however, in this report the neurons were not identified according to their neuropeptide content. In the present quantitative study we determined whether the AVP neurons were indeed activated as a result of the aging process in controls and AD patients. We applied a polyclonal antiserum directed against the medial cisternae of the GA on formalin-fixed, paraffin-embedded tissue sections taken from the dorsolateral SON (dl-SON) of 10 controls and 10 AD patients, and performed our measurements in this area that is known to be predominantly occupied (90-95%) by AVP neurons. In addition, the sparse OXT cells present in the area of study, were excluded from the measurements on the basis of alternative sections stained for OXT. In the dl-SON, the area occupied by the GA and the cellular profile area per patient were quaNtified by means of image analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

The monoclonal antibody Alz-50, used to reveal cytoskeletal changes in Alzheimer's disease, also reacts with a large subpopulation of somatostatin neurons in the normal human hypothalamus and adjoining areas

The monoclonal antibody Alz-50 is directed against Alzheimer's disease-related modified tau proteins and reveals cytoskeletal changes, i.e. neurofibrillary tangles and dystrophic neurites. The present study shows that, in the hypothalamus of non-demented control subjects, this same antibody gives a distinctive staining pattern of a subpopulation of somatostatin neurons and beaded fibres. Furthermore, Alz-50 occasionally recognizes somatostatin-containing cell bodies and dystrophic neurite-like fibers in the (neuritic) senile plaques of AD patients. These observations have direct consequences for the interpretation of Alz-50 staining in diagnostic usage and for the assessment of Alzheimer's disease-like changes induced by beta-amyloid in experimental animal brains. On dot spotting, Alz-50 was found to bind to a number of fragments from the somatostatin precursor, of which somatostatin 15-28 stained best. Preadsorption of Alz-50 by somatostatin 15-28, as well as other specificity tests, failed, however, to provide any clue to the nature of the unknown compound(s) stained in the control hypothalamus.

Kindling induces time-dependent and regional specific changes in the [3H]muscimol binding in the rat hippocampus: a quantitative autoradiographic study

To investigate possible changes in the GABAA receptor agonist site in the CA1 area and fascia dentata of rats kindled by stimulation of Schaffer collaterals, a quantitative autoradiographic study of the [3H]muscimol binding was carried out. Two kindled groups were studied, at 24 h (fully kindled stage) and at 28 days (long-term stage) after the last class V seizure. Several concentrations of [3H]muscimol were tested in the range of the high/intermediate (5-40 nM) and low-affinity (60-100 nM) binding sites. In the fully kindled group, the binding over the complete range of tested [3H]muscimol concentrations was significantly increased by 30-50% in the fascia dentata, while the binding was significantly decreased by 10-25% in the CA1 area. The high/intermediate-affinity binding was still significantly increased by 20-30% in the fascia dentata 28 days after the last seizure. In this long-term group there was still a significant decrease of 10-18% of the low-affinity binding in the CA1 area. These results show that kindling epileptogenesis induces long-lasting changes in the GABAA receptor agonist binding sites that are region specific. We hypothesize that the changes encountered at the fully kindled stage, i.e. increased binding in the fascia dentata and decreased binding in the CA1 area, may underly the electrophysiologically observed increased paired-pulse depression of field potentials in the former and the decreased paired-pulse depression in the latter area [Kamphuis et al. (1992) Neurosci. Lett. 141, 101-105; Kamphuis et al. (1988) Brain Res. 440, 205-215; Zhao and Leung (1991) Brain Res. 564, 220-229; Zhao and Leung (1992) Brain Res. 582, 163-167]. We conclude that the observed changes may not only contribute to the induction of kindling epileptogenesis but may also play a role in the maintenance of the kindled state.

Decreased neuronal activity in the nucleus basalis of Meynert in Alzheimer's disease as suggested by the size of the Golgi apparatus

In order to study changes in neuronal activity in the nucleus basalis of Meynert in aging and Alzheimer's disease, we applied a polyclonal antibody directed against the Golgi apparatus on formalin-fixed, paraffin-embedded material. Subsequently, an image analysis system was used to measure the size of the Golgi apparatus in (i) all nucleus basalis neurons and also separately in (ii) the remaining large cells (perikaryonal diameter > 30 microns). A significant reduction of 49% in the size of the Golgi apparatus was found in the entire population of nucleus basalis neurons in Alzheimer's disease. Furthermore, although there was no significant decrease in the size of the persisting large neurons in the nucleus basalis of Meynert, a significantly decreased size of the Golgi apparatus was found in these neurons in Alzheimer's disease. These results suggest that the overall activity of nucleus basalis neurons is severely decreased in Alzheimer's disease. Furthermore, these data support the idea that atrophy and decreased activity are the main phenomena in the nucleus basalis in Alzheimer's disease; they also indicate that the size of the Golgi apparatus is a sensitive parameter to follow this process.

Characterization of opioid binding sites in the neural and intermediate lobe of the rat pituitary gland by quantitative receptor autoradiography

Previous studies have suggested an involvement of enkephalins in regulation of oxytocin (OXT) and vasopressin (AVP) release, which seems to disagree with the very low affinities of Met- and Leu-enkephalin for the kappa opioid receptor. As opioid receptors in the neural lobe exclusively exist of kappa receptors, we studied the binding characteristics of larger pro-enkephalin derived peptides for opioid binding sites in the neural lobe by means of light microscopic receptor autoradiography. In addition, the pharmacological characteristics of opioid binding sites in the neural lobe were compared with those in other parts of the pituitary. In the neural as well as the intermediate lobe both high and low affinity 3H-bremazocine binding sites were present. Binding to these sites was completely displaceable by both naloxone and nor-binaltorphimine suggesting that these sites represent kappa opioid receptors. Also with regard to selectivity and affinity characteristics to other ligands, opioid binding sites in the neural and intermediate lobe were quite similar. In the anterior lobe a very low level of bremazocine binding was present, which could not be displaced by nor-binaltorphimine. Displacement studies with pro-enkephalin and pro-dynorphin derived peptides showed that both groups of peptides could bind to opioid binding sites in the neural and intermediate lobe. Especially the relatively large pro-dynorphin and pro-enkephalin derived peptides, such as dynorphin 1-17 and BAM22, appeared to be very potent ligands for these opioid binding sites and were much more potent than smaller fragments, such as dynorphin 1-8, and Met- and Leu-enkephalin. These results contradict the existence of a mismatch in the neural (and intermediate) lobe with regard to the local type of opioid peptides and receptors present.

An improved immunocytochemical staining method for large semi-thin plastic epon sections: application to GABA in rat cerebral cortex

We describe here a procedure that significantly enhances the intensity and method-specificity of immunocytochemical staining in large mounted semi-thin plastic Epon sections. The procedure was developed for the detection of the neurotransmitter gamma-aminobutyric acid (GABA) in rat brain tissue fixed with glutaraldehyde, but it may also be helpful in unmasking other antigens under different conditions. In addition to some practical suggestions for improving the reproducibility of the staining procedure, we demonstrate that the crucial step in the procedure is pre-treatment of the deplasticized sections with proteinase-K before exposure to the first antibody. This leads to a high morphological resolution and an excellent immunocytochemical signal.

Distribution and activity of glutamine synthase and carbamoylphosphate synthase upon enlargement of the liver lobule by repeated partial hepatectomies

Glutamine synthase and carbamoylphosphate synthase show a strikingly heterogeneous and fully complementary distribution in the rat liver. In the human liver, however, there is a midlobular zone where both enzymes are absent. The diameter of the human liver lobule is approximately twice the size of the rat lobule. To investigate whether lobule size is a major determinant for the expression patterns of glutamine synthase and carbamoylphosphate synthase, Wistar strain rats were partially hepatectomized 3 times, at weekly or monthly intervals. Due to hepatic regeneration the cross-sectional area of the liver lobules increased twofold. However, a midlobular zone which lacked expression of both glutamine synthase and carbamoylphosphate synthase did not develop in these livers, thus showing that lobular size is not a major determinant for the distribution patterns of glutamine and carbamoylphosphate synthase. The twofold increase in the cross-sectional area of the liver lobule was associated with a similar reduction in the relative number of glutamine synthase-positive cells and in the enzyme content of the liver, indicating that the regeneration process does not affect the pericentral pattern of glutamine synthase expression. After regeneration was complete, the glutamine synthase content in the liver was restored to its original value, demonstrating a twofold increase in the cellular concentration of glutamine synthase-positive hepatocytes. An increase in the diameter of the liver lobule was only seen after the first partial hepatectomy. Liver growth following subsequent partial hepatectomies can be explained by an increase in the length of the liver lobule and/or by splitting of liver lobules. The zonal distribution of DNA replication, which is characteristic of the first partial hepatectomy, is lost after repeated partial hepatectomies. Furthermore, evidence was obtained that the signal for inducing DNA synthesis may originate at the level of single liver units.

Differential lateral septal vasopressin innervation in aggressive and nonaggressive male mice

The vasopressinergic (VP) projection from the bed nucleus of the stria terminalis (BNST) to the lateral septum (LS) is sexually dimorphic and dependent of androgens at adult and neonatal age. We studied the relation between testosterone (T) and VP in male mice, which were genetically selected for their differences in aggression level. Aggressive males, characterized by a short attack latency (SAL), have a higher production capacity of T at adult age compared to males with a long attack latency (LAL). Neonatally, however, a higher T production occurs in the nonaggressive LAL males than in SAL males. In the present study we showed a more dense VP-immunoreactive (VP-ir) innervation in the LS and a higher VP-ir neuron density in the BNST of LAL males as compared to SAL males. The described differences may be the consequence of a differential neonatal androgen effect on the organization of the forebrain vasopressinergic network.

Fc-mediated nonspecific staining of the porcine brain with rabbit antisera in immunocytochemistry is prevented by pre-incubation of the sera with proteins A and G

Nonspecific staining was detected in immunocytochemical procedures on the porcine hypothalamus with rabbit antisera, irrespective of the antigen specificity of the sera, in magnocellular neurons of the paraventricular (PVN) and supraoptic nuclei (SON), and in the vasopressin- and oxytocin-containing nucleus (VON). The present study was designed to test the hypothesis that this staining is mediated by the Fc portion of rabbit immunoglobulins. Rabbit antisera against neuropeptides localized predominantly outside the PVN, SON, and VON were employed in combination with different detection methods. The intensity of the nonspecific staining varied depending on the antiserum and persisted after pre-absorption of the antisera with their homologous peptides. Nonspecific staining and antigen-specific staining were differentially affected by the method of tissue fixation. The nonspecific staining could be prevented by preincubation of the antisera with proteins A and G, which left the antigen-specific staining intact, whereas additional preabsorption with homologous peptide abolished all staining. These observations suggest that the Fc region of IgGs is indeed involved in the nonspecific staining. On press-blots of homogenates from SON tissue subjected to isoelectric focusing, one band in the low-pH region was found with all antisera. Pre-incubation of the antisera with protein A abolished the staining of this band but did not affect staining of antigen-specific bands. Pre-incubation with proteins A and G is proposed as a routine control to check for nonspecific staining mediated by the Fc region of IgGs in immunocytochemical procedures, particularly those that employ rabbit sera in porcine brain.

Increased vasopressin immunoreactivity in the rat brain after a postmortem interval of 6 hours

Enhanced immunocytochemical staining of vasopressin-containing neurons was observed after incubation of rat brain slices in Ringer medium for 6 h at room temperature, as compared to brain tissue fixed immediately after death. Hypothalamic vasopressin neurons in the supraoptic nucleus, the paraventricular nucleus and the suprachiasmatic nucleus stained more intensely after a postmortem interval of 6 h. Extrahypothalamic vasopressin neurons (VP) in the bed nucleus of the stria terminalis, the medial amygdala and the locus coeruleus proved to be stained as well. Extrahypothalamic VP neurons in the locus coeruleus could, until now, only be visualized after in vivo pretreatment with colchicine. In addition, staining was observed at two new sites, the dorsal raphe nucleus and the lateral septum. Staining of VP was corroborated by application of different antibodies directed against the intact vasopressin molecule as well as by antibodies directed against the other parts of the vasopressin precursor molecule, i.e. neurophysin and glycopeptide. The specificity of the VP-staining was validated by using pre-immune serum and using Brattleboro rat brain tissue, resulting in a negative staining in both cases. Furthermore, homogenated punches of the suprachiasmatic nucleus were submitted to iso-electric focussing on polyacrylamide gel, followed by press blotting and subsequent immunocytochemical staining for vasopressin. Iso-electric foccussing enabled us to characterize and quantify peptides in the suprachiasmatic nucleus. The vasopressin content increased 6 h postmortem, while c-terminal glycopeptide and neurophysin levels remained stable. Similar results were observed in the suprachiasmatic nucleus from decapitated rats whose brains were left intact in the skull for 6 h at room temperature.

Vasopressinergic neurons in the magnocellular nuclei of the human basal forebrain

Vasopressinergic structures were examined within the magnocellular nuclei of the human basal forebrain. Vasopressinergic neurons were found in all parts of the diagonal band nucleus, and less frequently in the anteromedial subnucleus of the basal nucleus (Meynert). They belong to the group of large multipolar neurons, previously defined as type I neurons, characterized by fine lipofuscin granules widely spread within the soma. Species differences exist in the topographic arrangement of vasopressinergic structures.

Immunochemical detection of peptides and proteins on press-blots after direct tissue gel isoelectric focusing

A sensitive method is described for the detection of tissue peptides and proteins. They are separated by tissue isoelectric focusing using thin large-pore polyacrylamide gels, containing detergent and dimethylformamide, and are fixed with either glutaraldehyde or formaldehyde in gelatin-coated nitrocellulose membranes using press-blotting. The fixed peptide and protein antigens are visualized by immunoperoxidase staining. The spectrum of fixed tissue constituents may also be used to test antiserum reactivity and specificity in immunocytochemical staining procedures. Isoelectric focusing of 2 microL homogenates of the neurointermediate lobe of the pituitary allowed the immunodetection of peptides and proteins of various sizes and the determination of isoelectric points. However, direct application onto gels of small pieces of frozen tissue sections, sliced in a cryostat, appeared to be more efficient. By direct tissue isoelectric focusing of brain tissue, peptides were effectively eluted and separated from sections up to 100 microns thickness. This allowed the detection of small peptides with a detection limit of approximately 10 pg/section.

Development of the dopaminergic innervation in the prefrontal cortex of the rat

The pre- and postnatal development of the dopaminergic innervation in the prefrontal cortex (PFC) of the rat is described from embryonic day 14 through postnatal day 90. By embryonic day 15 the dopamine (DA)-containing fibers reach the anlage of the lateral neocortex; 2 days later the first fibers have reached the subplate of the future prefrontal cortex. The process of entering the cortical plate starts just before birth. Prenatally, some dopaminergic fibers can be observed in the marginal zone of both the lateral and the medial wall of the hemisphere. Within 48 hours after birth a large number of dopaminergic fibers can be observed in the marginal zone, i.e., the future layer I, in some subareas of the PFC. A transient appearance of DA-positive fibers is noticed in the late embryonic and early postnatal periods especially in the marginal zone and possibly in the superficial layers of the pregenual cingulate cortex. Changes in the morphology of DA fibers at P4 suggest that the actual DA innervation starts at this age. From postnatal day 6 the different subareas of the PFC can be recognized according to the characteristics of the topographical distribution of the dopaminergic fibers. Until postnatal day 60 the density of the dopaminergic fibers continues to increase. No difference in density and topography was observed between postnatal days 60 and 90.

Mesotocin and vasotocin in the brain of the lizard Gekko gecko. An immunocytochemical study

The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.

Press-blotting on gelatin-coated nitrocellulose membranes. A method for sensitive quantitative immunodetection of peptides after gel isoelectric focusing

A method is presented for the fixation of peptides in nitrocellulose membranes after isoelectric focusing on thin polyacrylamide gels. Focusing gels are covered with gelatin-coated nitrocellulose membrane. Using glutaraldehyde, focused peptides are covalently fixed onto this membrane. Fixed peptides are stained using the peroxidase-anti-peroxidase method and the immunoreaction is quantified by rendering the membrane transparent and measuring the optical density of the precipitated chromogen in each band. The effect of pore size and gelatin content of the membrane, glutaraldehyde concentration and fixation time on fixation efficiency and immunostaining has been investigated. Gelatin coating considerably increases the efficiency of glutaraldehyde fixation of peptides and greatly enhances antibody-binding. Consequently, sensitive quantitative immunodetection is possible and, depending on the antiserum, peptides are readily detected in quantities down to 10 pg.

Effects of neonatal thermal lesioning of the mesocortical dopaminergic projection on the development of the rat prefrontal cortex

The role of dopamine (DA) in the development of the prefrontal cortex (PFC) was investigated by depleting the dopaminergic innervation of the PFC. A new stereotaxic procedure made it possible to produce small lesions in 1-day-old rats confined to the A10 group of dopaminergic cell bodies in the ventral tegmentum, from which the dopaminergic projection to the PFC originates. The variety in the lesions revealed a clear topographical organization of the efferent connections of the ventral tegmental area (VTA) to the prefrontal cortex. As far as we know from the literature the data presented in this study are a first direct indication of a neurotrophic role for dopamine in the development of the prefrontal cortex. When the prefrontal cortex was depleted of the dopaminergic innervation from birth on, by lesioning the cells of origin on postnatal day 1, the cortical thickness in the medial PFC was reduced by about 6%. Although coagulative lesions in the ventral tegmentum cause also a depletion of cortical serotonin, cortical reduction seems to be rather the result of the absence of dopamine during its development. This is indicated by the absence of a significant cortical thickness reduction in the dysgranular part of the first somatosensory cortex, which receives a serotonergic but no dopaminergic innervation.

Seasonal variation in vasopressin innervation in the brain of the European hamster (Cricetus cricetus)

Using immunocytochemistry, vasopressin innervation was determined in the brain of the European hamster (Cricetus cricetus) during different seasons. It was found that the spring period coincides with a dense vasopressin innervation in many brain regions in the male hamster, and lower vasopressin fibre density in some brain regions in the female hamster. In autumn just before hibernation an almost complete disappearance of vasopressin innervation is noted in those brain regions that are sexually dimorphically innervated in spring. These results suggest that vasopressin activity in certain areas of the brain might be required for some seasonal functions to find expression.

The vasopressin and oxytocin neurons in the human supraoptic and paraventricular nucleus; changes with aging and in senile dementia

The neuropeptides vasopressin (AVP) and oxytocin (OXT) are supposed to be involved not only in peripheral functions (e.g. diuresis, labour and lactation) but also in central processes that are frequently disturbed during aging and senile dementia (e.g. fluid and electrolyte homeostasis and cognitive functions). A concomitant decrease in activity of the hypothalamo-neurohypophyseal system (HNS) with aging has been postulated in the literature, but has not yet been established. In order to investigate possible age-related changes in the human HNS, immunocytochemically identified AVP and OXT neurons in the paraventricular and supraoptic nucleus (PVN and SON) were analysed morphometrically in subjects from 10 to 93 years of age, including patients with senile dementia of the Alzheimer type (SDAT). Cell size was used as a parameter for peptide production. Mean profile area of OXT cells did not show any significant changes with increasing age. Mean profile area of AVP cells, however, showed an initial decrease up to the sixth decade of life, after which a gradual increase was observed. Size of AVP and OXT cell nuclei did not change significantly with aging. Observations in brains from patients with SDAT were within the range for their age group. The present results do not support degeneration or diminished function of the HNS in senescence or SDAT, as generally presumed in the literature, but suggest an activation of AVP cells after 80 years of age. The activation of AVP cells in senescence is in accordance with previous findings in the aged Wistar rat.

Immunocytochemical localization of vasopressin-binding sites in the rat kidney

The rat kidney and brain are major target organs for vasopressin (VP). A procedure was developed for immunocytochemical staining of VP and its binding sites in the kidney. This procedure involved preincubation of kidney sections with the ligand, followed by immunocytochemical detection of VP. The staining in renal tubules from Wistar rats was enhanced by preincubation of tissue sections with increasing concentrations of VP (6-6000 nmol/l). Staining was present in the epithelium of distal convolutions and collecting ducts (medullary and cortical portions) and more pronounced in the apical zone of the tubular epithelium. With high concentrations of VP in the preincubation, staining was also obtained in the thick ascending limb of the loop of Henle. There was no staining under any circumstances in proximal tubules. In the kidney of the Brattleboro rat homozygous for hypothalamic diabetes insipidus (DI) which congenitally lacks VP but responds to the peptide, exactly the same staining pattern was observed after preincubation with VP, but the maximal staining was less intense. The VP binding to the DI rat kidney, after 2 weeks treatment with VP (using Accurel implants), reached levels seen in the Wistar kidney after in-vitro preincubation with high doses of VP.

The dopaminergic innervation of the supraoptic and paraventricular nucleus. A light and electron microscopical study

An antiserum that has been raised against glutaraldehyde-conjugated dopamine was used to demonstrate specifically dopamine in the rat hypothalamus. This dopamine antiserum permitted an optimal fixation with glutaraldehyde and therefore enabled the simultaneous light and electron microscopic immunocytochemical localization of dopamine. It was demonstrated that the paraventricular and supraoptic nuclei of the hypothalamus were innervated by thin dopaminergic fibers, in contrast to the suprachiasmatic nucleus, which hardly received any dopaminergic input. Ultrastructural observations revealed that the dopamine fibers terminated synaptically on the magnocellular neurons and their processes. It is concluded that the present results may explain the effect of centrally injected dopamine on vasopressin and oxytocin release. In the dopamine-containing terminals the reaction product was frequently observed in 90 nm dense core vesicles and around clear vesicles.

Quantification of antiserum reactivity in immunocytochemistry. Two new methods for measuring peroxidase activity on antigen-coupled beads incubated according to an immunocytoperoxidase method

Antigens covalently coupled to agarose beads provide a matrix for an economical, sensitive, and quantitative immunocytochemical detection of antiserum bindings potencies. Despite some very powerful features (e.g., the ability to control the outcome of a solid phase adsorption on the same matrix), the use of this technique is not very widespread when compared with the other enzyme-linked immunosorbent assay (ELISA) techniques. The main reason for this is the necessity for rather laborious measurements of the immunocytochemical tracer on individual beads. A description of two new methods for the batch measurement of the peroxidase activity on immunoperoxidase incubated antigen-coupled beads is presented. The first method involves the measurement of the diaminobenzidine (DAB) extinction from a large number of beads with a scanning microspectrophotometer. In the second method, during the peroxidase reaction, the beads are incubated with o-phenyldiamine (OPD), which is soluble both in the reduced and oxidized form, whereby absorbance measurements of the supernatant of the beads in a normal spectrophotometer are possible. The sensitivity and the quantitative relation between bound first antibody and absorbance are compared for both methods. From the two immunoperoxidase procedures used (the three step peroxidase-antiperoxidase and the two-step peroxidase conjugate procedure) only the latter met the conditions for a quantitative (first) antibody assay.

First demonstration of highly specific and sensitive antibodies against dopamine

Dopamine was coupled to bovine serum albumin (BSA) with glutaraldehyde, precautions were taken in order to preserve the catechol ring. After injection of this immunogen into rabbits, anti-dopamine antibodies were obtained and tested using radioimmunochemical binding studies and adsorption to catecholamine covered sepharose beads. A good correlation was found between the results of the different test systems, allowing us to visualize dopamine specifically in glutaraldehyde-fixed rat brains.

Fixation and immunoperoxidase staining of oligopeptides after isoelectric focusing in thin polyacrylamide slab gels

In this paper a new method for immunological detection of small peptides after isoelectric focusing in thin (200 micron) polyacrylamide slab gels is presented. The peptides are immobilized immediately after focusing by pressing a sheet of glutaraldehyde-impregnated filter paper onto the gel. By this procedure, the gel adheres to the paper and this press-blot can be stained using immunoperoxidase staining procedures. Using the two-step peroxidase conjugate and the three-step peroxidase-antiperoxidase method, several oligopeptides could be visualized after focusing. The detection limit of this method appears to be in the nanogram range.

Immunohistochemical detection of O6-ethyldeoxyguanosine in the rat brain after in vivo applications of N-ethyl-N-nitrosourea

An immunohistochemical procedure was developed which allows the localization of the DNA lesion O6-ethyldeoxyguanosine (O6-EtdGuo) within tissues and organs. The method permits the detection of 24,000 residues of O6-EtdGuo per diploid nucleus. We have used this procedure to localize N-ethyl-N-nitrosourea (ENU)-induced O6-EtdGuo in the rat brain. Shortly after a single injection of ENU, we observed O6-EtdGuo in most or all of the rat brain nuclei. After repeated injections of small doses of ENU, with intervals of 1 or 2 weeks between the injections and between the last injection and sacrifice, we could demonstrate O6-EtdGuo only in part of the rat brain nuclei. Oligodendrocytes, granular neurons and endothelial cells, and part of the pyramidal neurons and astrocytes had accumulated O6-EtdGuo, while in all other cells this lesion was not detectable after repeated injections of small doses of ENU. We found no obvious correlation between the putative sensitivity of rat brain cells to tumor induction and the accumulation of O6-EtdGuo in their DNA.

Enkephalin immunoreactivity in synaptoid elements on glial cells in the rat neural lobe

Opioid peptides were localized in fibres of the rat neural lobe using various immunocytochemical methods at the light- and electron-microscopical level. Leu-enkephalin immunoreactivity was present in beaded fibres distributed throughout the neural lobe. These fibres surround the neurohypophyseal glial cells (pituicytes) and make synaptoid contacts upon their soma and processes. The reaction product was localized both in dense-core vesicles of about 100 nm in diameter and diffusely spread over the cytoplasm. No arguments in support of the co-existence of enkephalins and the neurohypophyseal hormones vasopressin and oxytocin in the same terminal were found. It is suggested that pituicytes might mediate the inhibitory effect of opiod peptides on vasopressin and oxytocin release from the neural lobe.

The distribution of vasotocin and isotocin in the brain of the rainbow trout

The distribution of vasotocin and isotocin in the brain of the rainbow trout Salmo gairdneri was investigated by the unlabeled antibody enzyme method, by using purified antisera against arginine vasotocin and isotocin. In the preoptic nucleus no clear differences were observed in the distribution of vasotocin- and isotocin-containing cells. Vasotocin and isotocin innervation was found in most brain regions, though in general isotocin fibers were much more abundant. The area dorsalis pars medialis of the telencephalon, the saccus dorsalis, and the basal part of the nucleus recessus posterioris were found to be innervated by vasotocin and scarcely by isotocin fibers. In the nucleus habenularis, the nucleus recessus lobus lateralis, the nucleus preglomerulosus pars medialis, and the tectum mesencephali isotocin fibers prevailed. These findings in the trout brain are compared with the vasopressin and oxytocin innervation of the rat brain.

Differentiation of muscle fiber types in the teleost Brachydanio rerio, the zebrafish. Posthatching development

The trunk musculature of adult zebrafishes contains three major fiber types: adult red, intermediate, and white; and two minor populations: red muscle rim and scattered intermediate fibers. In this paper, the post hatching development of these muscle fiber types was studied by means of immunohistochemistry, using anti-myosin sera. Just hatched larvae contain two muscle fiber populations: embryonic red and white, which give rise to the red muscle rim and the intermediate fibers respectively. Adult red fibers arise post hatching as a new separate population with distinct myosin properties. The differentiation of these fiber types occurs within the first four weeks after fertilization, when the adult pattern of peripheral axon bundles has become established. Differences in the muscle fiber type composition between the midbody and the tail myotomes become apparent in two month old fries. The number of scattered intermediate fibers increases from rostral to caudal, the opposite holds for the red muscle rim fibers. The red and intermediate area is triangular in the midbody; in the tail part it is stretched out along the lateral surface of the myotomes. These changes are considered as adaptations to improve the efficiency of the swimming performance.

Effects of immobilization and partial denervation on the differentiation of muscle fiber types in the Zebrafish, Brachydanio rerio

In this study we tested the effects of immobilization and of spinal cord lesion on the differentiation of muscle fiber types in the myotomal muscle of the zebrafish. We found that the differentiation of embryonic red and white muscle fibers occurs in immobilized as well as in denervated myotomes of zebrafish embryos. Intermediate and adult red muscle fibers are not formed in denervated myotomes of larvae. Adult zebrafishes with spinal cord lesions in the anal region show abnormal undulating movements in the rostral part of the body. This change in muscle activity correlates with an increase in the number of intermediate scattered fibers. We conclude that direct contact with spinal cord motorneurons is not necessary for the differentiation of embryonic red and white fibers. The differentiation of intermediate muscle fibers is under extrinsic control. The factors that determine the formation of adult red fibers are not yet clear.

Calculation and registration of the same motor unit action potential

In order to increase insight into the electrical phenomena of active motor units, a computer simulation model has been developed. With this model motor unit action potentials (MUAPs) have been calculated. The model has been based on the superposition of the muscle fibre potentials of the fibres of one motor unit. For verification, calculated MUAPs have been compared with the matching recorded MUAPs. During experiments one motor unit was stimulated and the MUAP of this unit was measured with intramuscular wire electrodes. After the experiments the positions of the activated fibres of this unit and of the electrodes were determined by means of histochemical techniques. Other parameters were derived from other experiments or the literature. Using the obtained set of parameters in the model MUAPs were calculated. These MUAPs were compared with the measured MUAPs. From this comparison it has been concluded that the model predicts the MUAP to an appreciable degree. The results clearly show the dominating effect of muscle fibres in close vicinity of the electrode and the important effect of the activation moment of those fibres on the shape of the MUAP.

Myofibrillar differences among mammalian skeletal muscle fibres at the ultrastructural level. A comparison of immunocytochemical and morphometrical parameters

In the light microscope two types (I, II) of skeletal muscle fibres can be distinguished with antibodies against myosin isozymes. At the ultrastructural level a difference in Z-line width has led to muscle fibre classification. In this study we distinguish at the ultrastructural level between type I and type II fibres of the M. soleus and M. plantaris of adult mice using ultracryosections with immuno-ferritin and antisera against myosin isozymes. Muscle fibres of the M. plantaris are identified as type II fibres and the fibres of the M. soleus are divided in type I and type II fibres. In the immunologically identified fibres the filament overlap in the Z-line was measured. The type II fibres of the M. plantaris have narrow Z-lines, whereas type I and type II fibres of the M. soleus have wide Z-lines. We conclude that a classification of fibres based on Z-line width differs from the type I/type II classification. The antimyosin antibodies react exclusively with the A-band. In serial sections the myosin isozymes can be identified unambiguously. This is a prerequisite for further studies of myosin isozyme distribution in "mixed" muscle fibres.

An immune histochemical and enzymic characterization of the muscle fibres in myotomal muscle of the teleost Brachydanio rerio, Hamilton-Buchanan

The myotomal muscles of teleosts have a complex internal structure. For a better understanding of the functional anatomy of these muscles we analysed the myofibrillar properties of the myotomal muscle fibres in a small teleost: Brachydanio rerio, the zebrafish. By immune histochemical techniques we discerned 4 types of muscle fibres: red lateral fibres, red muscle rim (RMR) fibres, intermediate fibres and white fibres, each with a distinct type of heavy chain myosin. In addition we discerned 2 populations of muscle fibres in which the myofibrils contain mixtures of white and intermediate heavy chain myosin. The immune histochemical classification correlates well with an enzyme histochemical classification of the muscle fibres. In order to find out whether the immune and enzyme histochemical differences correlate with differences in dynamic properties of the muscle fibres, we analysed the ATP-ase activity of glycerinated muscle fibres. 3 of the 5 muscle fibre types which are discriminated by immune histochemical methods could thus be analysed. Differences in histochemical reactions coincide with differences in ATP-ase activities of the glycerinated muscle fibres. 2 classes of muscle fibres were homogeneous as to the ATP-ase activity of their muscle fibres. The 3rd class, the white fibres, could be divided in 2 populations with slightly different ATP-ase activities. The results indicate that the myotomal muscle fibre population is much more heterogeneous than has been considered thusfar. This heterogeneity may allow an almost continuous range of contraction speeds in the myotomal muscle.

Quantitative succinate-dehydrogenase histochemistry. III. Variations in histochemical succinatedehydrogenase activity in different cross-sections of the same muscle fibre

The variation in histochemical SDH-activity at different levels in the same muscle fibre was determined in muscle fibre cross-sections both by visual classification and quantitative determination of the formazan-deposits. This work resulted in a confirmation of the earlier micro-biochemical studies of Spamer AND Pette (1977, 1979) and Lowrey et al. (1978) that the activity of enzymes of the citric acid cycle is not homogeneously distributed in a muscle fibre over its entire length. In addition it is shown that the observed variations in histochemical SDH-activity strongly interfere with the visual muscle fibre typing. Some of the possible causes for these variations in histochemical SDH-activity (section-thickness, presence of the motor-endplate) and the implications of these findings for the relation between histochemical characteristics and functional properties of the muscle fibres are briefly discussed.