Myeloarchitectonics of the hypothalamic mammillary bodies in the bottle-nosed dolphin

The topography of the main fibrillar bundles realizing the neural connections of the corpora mamillare of the dolphin (Tursiops truncatus) hypothalamus has been studied using sagittal, frontal and horizontal serial sections impregnated with silver nitrate and stained with cresil violet. The dolphin main afferent (fornix, mamillary peduncles) and efferent--mamillary-thalamic, mamillary-tegmental tracts--of the corpora mamillare--have an original topography and dimensions distinctive from those of terrestrial mammals, the human being including.     

Structure of the mammillary bodies of the hypothalamus of the bottlenosed dolphin

In the bottlenosed dolphin (Tursiops truncatus) the hypothalamic corpus mammillaris has been studied using interperpendicular, sagittal, frontal and horizontal serial sections, impregnated in silver and stained with cresil-violet. Comparatively small dimentions of the corpora mammillaria in the bottlenosed dolphin are explained by presence of only two nuclei, medial and lateral. The lateral nucleus is nearly three times as large as the medial one. The size of the neurons in the medial nucleus is on the average two times as large as that of neurons in the lateral nucleus. The density of the neural cells distribution is a little greater in the lateral nucleus. The structure of the bottlenosed dolphin corpora mammillaria is compared with similar structures in other animals and the human being.     

Nuclei of the mammillary bodies and their fiber connections in cattle (Bos taurus var. domesticus). I. Nuclei of the mammillary bodies in cattle]

1. In the present neuroanatomic study the topography and cytoarchitectonic of the nuclei of the mamillary body of cattle are described and quantitative-morphologically investigated in 14 series of brains (6 frontal, 4 sagittal and 4 horizontal series, stained by the methods after Nissl, Klüver and Barrera and after Heidenhain). 2. The medial mamillary nucleus of cattle is with an average volume of 47.7 mm3 the largest nucleus of the mamillary body. It contains about 715,000 cells with a cell density of 15,000 cells/mm3 and can cytoarchitectonically be subdivided into a medial part and a lateral part. 3. The median mamillary nucleus is an unpaired and clearly defined nucleus which accounts with an average volume of 16.9 mm3 for a quarter of the whole volume of the nuclei belonging to the mamillary body, however with 11,000 cells/mm3 it shows a relatively small cell density in comparison with the other mamillary nuclei. 4. The lateral mamillary nuclei of cattle are situated in the rostral third of the mamillary body and account for 5.3 per cent of the whole volume of the nuclei. About 28,000 cells with a cell density of 15,000 cells/mm3 were found in each nucleus.     

Nuclei of the mammillary bodies and their fiber connections in cattle (Bos taurus var. domesticus). 2. Fiber connections of the mammillary bodies in cattle]

1. In the present information the course of fibre pathways which are connected with the mammillary body of the cattle is described in 14 series of brains (6 frontal, 4 sagittal, 4 horizontal series, stained by the combined cell-fibre-method after KLUVER and BARRERA and by the method for myelined fibres after HEIDENHAIN). 2. The mammillary body of cattle is connected with four main fibre systems. These are the fornix and the mamillary peduncle as well as the mamillo-thalamic and the mamillo-tegmental tracts. 3. The fornix system first of all represents a rich myelined fibre connection between the hippocampus and the mamillary body. But also fornix fibres entering the poor-myelined regions of the hypothalamus and the mesencephalon have been demonstrated. 4. The mamillary peduncle ascending from the mesencephalon can be traced to the lateral mamillary nucleus. 5. The mamillo-thalamic tract of cattle has its origin in the mamillary body with the mamillotegmental tract associated to a common principal mamillary tract and passes to the complex of the anterior nucleus of the thalamus, while the mamillo-tegmental tract branching off from it curves into the mesencephalon.     

Comparative characteristics of the capillary bed of the temporal lobe and the mammillary bodies of the hypothalamus in man in relation to age

The data have been obtained on regional differences in structure of the capillary bed in the temporal cortex of the cerebrum (TCC) and in the papillary bodies of the human thalamus (PBHT) during various age periods. The capillary diameter and nuclear volume is greater in perivascular gliocytes of the TCC than in those of the PBHT. With ageing the capillary diameter and hypertrophy of the endotheliocytic nuclei is noted to increase in both areas of the brain.     

Carcinogenesis induced by foreign bodies

This review deals with the contemporary investigations of carcinogenesis induced by foreign bodies. The main attention is given to the interactions of macrophages with an implanted foreign body and their possible role in tumorigenesis.     

Reactive changes in the capillaries of the mammillary bodies of the brains of aging animals

As electron microscopic investigation of the capillary wall in the mammillary bodies has demonstrated, in old animals the number of organells in the endothelial cells decreases; discomplexion and reduction of mitochondrial crists occur, their matrix becomes cleared; myelin-like structures are formed. In pericytes pigment inclusions are accumulating. Noncellular component of the basal layer loses its regular structure and foci of hydratation appear in it. When pharmacological loadings (adrenaline, aminazine) are applied to old animals, distrophic processes in the vascular wall increase; that results in disturbance of permeability, sharp hydratation of the basal layer, edema of the tissue elements around the brain and, hence, in a more prolonged restorative period.     

Two-stage carcinogenesis induced by foreign bodies

Replacement of non-perforated polyvinylchloride films 3.5 months after implantation to CBA mice by perforated polyvinylchloride films or by millipore filters with 0.45 micron pores led to the development of sarcoma at the site of implantation in 37.0 and 21.4% of cases, respectively. The implantation of only perforated films led to the development of sarcoma in 6.9% of cases, while the implantation of filters failed to induce tumour growth. The data obtained show that the latent period of tumour development can be divided into two stages. The first stage occurs in the presence of non-perforated film, while the second stage ensues in the presence of non-cancerogenic films. Complete removal of films 6 months after implantation prevented tumour development. It is suggested that non-perforated films serve as initiating agents, while non-cancerogenic films act as protectors.     

Responses of limbic cortical neurons to stimulation of splanchnic and sciatic nerves and of the mammillary bodies

Spontaneous and evoked unit activity in the anterior limbic cortex in response to stimulation of the splanchnic and sciatic nerves and of the mammillary region of the hypothalamus were recorded extracellularly in acute experiments on cats. The study of heterogeneous transsynaptic influence on limbic cortical neurons showed that in the presence of effective sensory viscerosomatic convergence, weak convergence of influences from the central hypothalamic and peripheral sources took place. Short-latency responses of limbic cortical neurons to stimulation of the mammillary bodies consisted of orthodromic and antidromic responses, evidence of the existence of short two-way connections between the anterior limbic cortex and mammillary nuclei of the hypothalamus.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 11, No. 5, pp. 419–426, September–October, 1979.     

Formation of nerve fibers between organotypic explants of the hippocampus and mammillary bodies of newborn mice]

Nervous fiber bundles formed between the explants during the organotypic cocultivation of the hippocampus and mamillary nuclei of the newborn mouse. Some of the fibers within these bundles were the continuation of axons localized in the alveus of the Ammon's horn. It is suggested that under conditions of cultivation the hippocampal pyramidal neurons deprived of the afferent leads-in from other brain structures are capable of forming the projection efferent connections typical of the intact hippocampus neurons.     

Context and the renewal of conditioned taste aversion: the role of rat dorsal hippocampus examined by electrolytic lesion

An extinguished conditioned response can sometimes be restored. Previous research has shown that this renewal effect depends on the context in which conditioning versus extinction takes place. Here we provide evidence that the dorsal hippocampus is critically involved in the representation of context that underscores the renewal effect. We performed electrolytic lesions in dorsal hippocampus, before or after extinction, in a conditioned taste aversion paradigm with rats. Rats that underwent all conditioning, extinction and testing procedures in the same experimental context showed no renewal during testing in the original context. In contrast, rats that underwent extinction procedures in a different experimental context than the one in which they had acquired the conditioned response, showed a reliable renewal effect during testing in the original context. When electrolytic lesion was performed prior to extinction, the context-dependent renewal effect was disrupted. When electrolytic lesion was undertaken after extinction, we observed a complex pattern of data including the blockage of the conventional renewal effect, and the appearance of an unconventional renewal effect. The implications of these results are discussed with respect to current views on the role of the dorsal hippocampus in processing context information.     

Nitric oxide reduces the thermogenic changes induced by lateral hypothalamic lesion

The experiment described here tests the effect of intracerebroventricular (icv) injection of nitric oxide (NO) precursors, such as L-arginine (L-arg) and nitroprusside (NP), on the thermogenic changes induced by lesion of the lateral hypothalamus (LH). The firing rate of the nerves innervating interscapular brown adipose tissue (IBAT), along with IBAT and colonic temperatures (T_IBAT and T_C) were monitored in urethane-anesthetized male Sprague-Dowley rats lesioned in the LH. These variables were measured before and after and icv injection of 4 μmol L-arg or 400 nmol NP. The same variables were also monitored in: a) lesioned rats with icv administration of saline; b) sham-lesioned animals with icv injection of L-arg or NP; c) sham-lesioned rats with icv injection of saline. The results show that L-arg or NP injection reduces the increases in firing rate, T_IBAT, and T_C induced by LH lesion. These findings suggest that NO plays a key role in the thermogenic changes following LH lesion.