H. G. Hartwig

Neurone und zentralnervöse Verbindungen des Pinealorgans der Anuren

SummaryThe problem of interneurons appears to be very important for the functional interpretation of the chromatic and achromatic responses of pineal sense organs. Previous results seemed to indicate a bineuronal chain in the pineal organ (epiphysis cerebri) ofRana temporaria andRana esculenta. Precise images of pineal receptors, neurons and their connexions were obtained in the present studies using methylene-blue and Golgi methods. A limited number of interneurons probably exist in theepiphysis ofR. temporaria andR. esculenta: the images of these scattered neurons were observed to differ from the classical bipolar, horizontal and amacrine cells of the amphibian retina. The pineal tract of R. temporaria andR. esculenta is formed by the axons of large multipolar and smaller scarcely ramified nerve cells. The central projection of this pinealo-fugal (afferent) pathway is of great functional interest. After complete surgical interruption of the pineal tract degenerating nerve fibers were traced in Nauta (Fink-Heimer) preparations. Degenerating fibers were observed within and beneath the posterior commissure, in the pretectal region and in the nuclear areas of the “periventricular gray”. The subependymal layer and the basal aminergic nuclei of the frog mesencephalon were always free of degenerating fibers. The anatomical connexion of the pineal tract described in this paper could serve as a basis for some light-dependent (phototactic) reflexes. Further investigations concerned with the central projections of the pineal tract are in progress.ZusammenfassungDas Problem der Zwischenneurone nimmt bei der Deutung der chromatischen und achromatischen Antworten der pinealen Sinnesorgane eine Schlüsselstellung ein. Frühere Ergebnisse schienen darauf hinzuweisen, daß der nervöse Apparat des Pinealorgans (Epiphysis cerebri) vonRana temporaria undRana esculenta bineuronal organisiert ist. Mit modifizierten Methylenblau- und Golgi-Methoden gelang es jetzt, die nervösen Strukturen der pinealen Rezeptoren und Nervenzellen präziser darzustellen. Das neurohistologische Bild der Epiphysis cerebri enthält auch Nervenzellen, die an Zwischenneurone denken lassen. Diese diffus verstreuten kleinen Elemente unterscheiden sich von den klassischen Typen der retinalen Bipolar-, Horizontal- und Amakrinzellen. Der Tractus pinealis vonR. temporaria undR. esculenta wird von Axonen großer multipolarer und kleiner, wenig verzweigter Ganglienzellen gebildet. Die zentrale Projektion dieser pinealofugalen (afferenten) Bahn ist von großem funktionellem Interesse. Nach vollständiger Unterbrechung des Tr. pinealis finden sich degenerierende Faserelemente innerhalb und am unteren Rand der Comm. posterior, in der Area praetectalis und in den Kernarealen des sog. „Zentralen Graus“. Keine degenerierenden Tractusfasern sind in der subependymalen Schicht und in den aminergen Kerngebieten des Mesencephalon zu beobachten. Die beschriebenen Verbindungen des Tr. pinealis könnten die anatomische Basis einiger lichtabhängiger (phototaktischer) Reflexe darstellen. Weitere Untersuchungen über die zentralnervöse Projektion des Tr. pinealis sind im Gang.

Monoaminergic tracts of the diencephalon and innervation of the pars intermedia in Rana temporaria

SummaryWith the fluorescence technique of Falck-Hillarp two monoaminergic tracts having independent nuclear sources, and extending towards the hypophysis, were identified in the diencephalon of Rana temporaria. The nature of the fluorophore in the diencephalic nuclei which give rise to the tracts, and also that of the nerve fibers innervating the pars intermedia (PI), were analyzed microspectrofluorimetrically.The first tract, the preoptic recess organ (PRO)-hypophysial tract, arises from the neurons of the PRO, traverses the preoptic region, ascends towards the dorsal chiasmatic area, curves down and extends posteriorly along the mid-ventral region of the tuber cinereum towards the median eminence. Apparently this pathway has no contact with either the paraventricular organ (PVO) or the nucleus infundibularis dorsalis (NID). The second pathway, the paraventricular organ (PVO)-hypophysial tract, arises mainly from the PVO of each side, traverses the tuber cinereum and converges posteriorly to join the PRO-hypophysial tract at the hind end of the tuber cinereum. Participation of the NID neurons in the formation of this tract could not be excluded. It is argued that the PVO-hypophysial tract, but not the PRO-hypophysial tract which runs along the mid-ventral region of the tuber cinereum, may be responsible for transportation of the monoamines from the PVO/NID to the pars intermedia.Microspectrofluorimetric study indicated that the PRO neurons contain only dopamine, whereas two types of neuronal fluorophores were observed in the PVO and NID. Many perikarya in both these nuclear sites possess dopamine, while some contain 5-hydroxytryptamine (5HT) and/or 5-hydroxytryptophane (5HTP). An analysis of the fluorescent nerve fibers in the PI revealed a double innervation. The first category includes dopaminergic fibers, whereas the second type seems to be adrenergic or noradrenergic in nature.On leave from the Department of Zoology, Nagpur University, Nagpur, India.

Electron microscopic evidence for a retinohypothalamic projection to the suprachiasmatic nucleus of Passer domesticus

SummaryThe possibility of a direct retinohypothalamic projection was reinvestigated in Passer domesticus by electron microscopy following left unilateral retinectomy. To avoid misinterpretation of non-specific degeneration, the course of degenerative changes was observed at intervals of 6, 12, 24, 48 and 96 hours after operation. Of the hypothalamic areas examined in only one, the contralateral suprachiasmatic nucleus, was it possible to identify reliable indications of secondary anterograde degeneration comparable to those observed in the contralateral optic tectum. Single dark profiles within the supraoptic nucleus and the basal infundibular (tuberal) nucleus showed neither internal changes in structure nor an increase in number per unit area in retinectomized birds. Since photoperiodically induced gonadal growth occurs in totally blinded birds the functional significance of the retinohypothalamic projection to the suprachiasmatic nucleus is open to discussion.

Noradrenergic innervation of the median eminence. Microspectrofluorimetric and pharmacological study in the duck, Anas platyrhynchos.

SummaryThe median eminence of duck, following freeze-drying and formaldehyde treatment (method of Falck-Hillarp), revealed within the subependymal layer of the internal zone a plexus of green fluorescent nerve fibers that encircled scattered neurons which apparently belong to the basal infundibular (tuberal) nucleus. Scarce fluorescent structures accompanied by a diffuse weak fluorescent reaction were seen in the reticular and palisade layers of the external zone. Fluorescent sympathetic fibers surrounded primary portal vessels in the perivascular space. Microspectrofluorimetric analysis revealed the presence of catecholamines in all fibers measured. After HCl treatment, the modifications of the excitation spectra indicated that the fibers in the subependymal layer of the inner median eminence contained noradrenaline. Dopaminergic fibers were not found in this region. The fluorescent contents of noradrenergic fibers was depleted by reserpine. After inhibition of dopamine-β-hydroxylase by FLA 63, some dopamine could be demonstrated in these noradrenergic fibers. After three successive intraventricular injections of 6-OH-dopamine their fluorescent contents disappeared. However, three months after this treatment some green fluorescent fibers were again seen in this location.

Secretory parvocellular neurons in the rostral hypothalamus and in the tuberal complex of Passer domesticus

SummaryNumerous secretory perikarya were found in the suprachiasmatic, medial preoptio and anterior hypothalamic nuclei of Passer domesticus. The secretory granules of these parvocellular neurons fall into the following ranges: 1000 Å; 1300–1500 Å; 1800–2000 Å. The specialized parvocellular neurons of the rostral hypothalamus form unit-like clusters. They are embedded in a neuropil rich in synaptic structures. Many presynaptic terminals contain dense-core vesicles < 1000 Å in diameter. Thus far there is no evidence as to whether the secretory neurons of the anterior hypothalamus project into the median eminence or into other hypothalamic or extrahypothalamic regions. Secretory neurons were also observed in the dorsal portion of the tuberal complex and in the premammillary area.

The regeneration of the monoaminergic system in the cerebral ganglion of the earthworm, Allolobophora caliginosa

SummaryThe regeneration of monoaminergic neurons in the cerebral (supraesophageal) ganglion of the earthworm, Allolobophora caliginosa, was studied by the fluorescence method of Falck-Hillarp 3, 4, 5, and 6 weeks after extirpation of the ganglion. The monoamine fluorophores in control and regenerating cerebral ganglia were estimated by microspectrofluorimetric analysis. In the control animals catecholaminergic (noradrenergic, dopaminergic) and indolaminergic (5-HT/5-HTP) neurons were observed. Four weeks after the removal of the cerebral ganglia, two types of monoamine-containing neurons reappeared. Microspectrofluorimetrically dopaminergic and indolaminergic perikarya were identified. Reconstructions from serial sections and counts of the regenerated fluorescent cells showed no further increase in the number of these cells between the 5th and 6th postoperative weeks. In the 5- and 6-week groups the intrinsic and afferent aminergic pathways of the cerebral ganglion were reestablished.

Rasterelektronenmikroskopische Beobachtungen an pinealen Sinneszellen der Forelle,Salmo gairdneri (Teleostei)

SummaryThe outer segments of pineal photoreceptor cells ofSalmo gairdneri were investigated with the scanning electron microscope. The scanning electron micrographs showed three different types of outer segments. These results are discussed with respect to the ultrastructural concepts of Rüdeberg (1969) and Bergmann (1971). Scanning electron microscopy permits better anatomical classification of pineal photoreceptor cells according to the form of their outer segments.ZusammenfassungIm rasterelektronenmikroskopischen Bild des Pinealorgans vonSalmo gairdneri kann man drei verschiedene Außengliedtypen der Photorezeptoren unterscheiden. Diese Ergebnisse werden im Hinblick auf die Ultrastrukturkonzepte von Rüdeberg (1969) und Bergmann (1971) diskutiert. Rasterelektronenmikroskopische Studien erleichtern die anatomische Klassifizierung von pinealen Sinneszellen aufgrund ihrer Außengliedform.

Karyometrische Untersuchungen am Nucleus suprachiasmaticus geblendeter Ratten

SummaryIntraocular injection of labeled amino acids results, in different mammals, in an accumulation of radioactive material not only in the primary optic centers but also within the hypothalamic suprachiasmatic nucleus (Moore et al., 1972; Hendrickson et al., 1972; Moore, 1973). This finding argues in favour of a direct connection between the retina and the secretory suprachiasmatic nucleus although silver techniques do not show such a pathway. In male Wistar rats the nuclear diameter of the suprachiasmatic neurons decreases significantly 6 days after bilateral experimental ablation of the retina. These results indicate an alteration in activity of the suprachiasmatic neurons in blinded rats.ZusammenfassungRadioaktiv markierte Aminosäuren werden bei Säugetieren nach intraokulärer Injektion nicht nur zu den primären optischen Kerngebieten, sondern auch in den Nucleus suprachiasmaticus des Hypothalamus transportiert (Moore und Lenn, 1972; Hendrickson, Wagoner und Cowan, 1972; Moore, 1973). Dieser Befund macht eine direkte Verknüpfung zwischen der Netzhaut und dem sekretorisch aktiven Nucleus suprachiasmaticus wahrscheinlich, obwohl mit Silbertechniken eine solche Verbindung nicht sicher nachgewiesen werden konnte. Karyometrische Studien am Nucleus suprachiasmaticus männlicher Wistar-Ratten zeigen 6 Tage nach beidseitiger Blendung eine signifikante Abnahme der Zellkerndurchmesser. Dieses Ergebnis spricht für eine Aktivitätsänderung der Neurone im Nucleus suprachiasmaticus geblendeter Ratten.

Aminergic systems in pulmonate gastropod molluscs

SummaryHistochemical fluorescence (Falck-Hillarp) and microspectro-fluorometric (MSF) methods were used to characterize different types of catecholamine-containing cellular elements located in the reproductive system of fresh-water snails (Bulinus truncatus, Planorbarius corneus) and land snails [Archachatina marginata, Helix (Cryptomphalus) aspersa]. Transverse sections through the genital tract display a common structural pattern of tubular differentiations: (1) an internal epithelium bordering the lumen and containing variable numbers of monoaminergic cells; (2) an enveloping sheath of connective and muscular tissue containing fine nerve fibers in the form of a network that exhibits a variable degree of density.MSF determinations showed that the formaldehyde-induced fluorophores of the intraepithelial aminergic cells belong to the following classes: (1) the DOPA/dopamine group in the duct of the albumen gland of B. truncatus and the carrefour of A. marginata; and (2) the norepinephrine/epinephrine group in the duct of the albumen gland and in the oviduct sac of P. corneus. In the reproductive systems of B. truncatus and P. corneus (duct of the albumen gland, oviduct sac, vagina), A. marginata and H. aspersa (duct of the fertilization pocket, origin of the receptaculum seminis, carrefour), the MSF analysis revealed norepinephrine/epinephrine-containing intramural nerve fibers. On the other hand, the small neurons in the vagina of B. truncatus belong to the DOPA/dopamine group.

Distribution patterns of formaldehyde-induced fluorescence of hypothalamic monoamines.

SummaryIn a circumscribed area of the preoptic periventricular nucleus of a male rat, formaldehyde-induced monoamine fluorophores modified by treatment with HCl vapors were investigated microfluorometrically (measurement of excitation peak ratio 370∶320 nm) in all fluorescent terminals and preterminals. Microfluorometric recordings of an individual fluorescent structure were performed without UV irradiation of neighboring fluorophores. Recorded data were sampled and corrected by a microcomputer (WangPCS II). 19 neuronal processes (axons) contained noradrenaline fluorophores; 11 contained dopamine fluorophores; 6 exhibited uncharacteristic excitation peak ratios; and in 9 recordings technical problems did not allow identification of the fluorophore content.