Electron-microscopic cytochemistry of the catecholaminergic innervation of ACTH-containing neurons in the rat hypothalamic arcuate nucleus

The synaptic relationship between catecholamine terminals and adrenocorticotropic hormone (ACTH)-containing neurons in the arcuate nucleus (AN) of the rat hypothalamus was investigated by electron microscopy, using ACTH immunocytochemistry combined with autoradiography after 3H-dopamine (3H-DA) injection or 5-hydroxydopamine (5-OHDA) uptake in the same tissue section. ACTH-like (ACTH-LI) immunoreactive nerve cell bodies and fibers received synaptic inputs by axon terminals labeled with 3H-DA or 5-OHDA in the AN. This suggests that catecholaminergic neurons, at least DA- and 5-OHDA-containing neurons, may play an important role in the regulation of ACTH secretion or other functions of ACTH neurons via synapses in the AN of the rat hypothalamus.     

Electron-microscopic study of monotreme neuroglia.

Glia cells were examined in the brains of a mature platypus and an immature echidna. In the echidna a few dark, organelle-rich glia cells were encountered. The lighter glia cells had resemblances with the single type of glia cell encountered in the brain of the platypus. These cells were characterised by highly homogeneous areas of nuclear chromatin and light cytoplasm containing dark, finely granular condensations which frequently surrounded Golgi membranes. Microtubules were present within the cytoplasm but neither filaments nor glycogen-like particles were encountered. It was concluded that the cells described conformed to the types of neither astrocytes nor oligodendrocytes as encountered in metatherian and eutherian mammals. Among their functional capacities such cells presumably include, either in the immature or mature forms, the roles of both astrocytes and oligodendrocytes.     

Volumetric studies on the red nucleus of the rat at different ages.

The postnatal development of the red nucleus in albino rat was quantitatively studied. Planimetric studies on stained paraffin sections of the midbrain showed that the red nucleus has a rounded contour with tapering ends and a broad centre. The volume of the red nucleus revealed an increase from birth, to reach its maximum at the age of 3 months, then declines until the age of 2 years. However, the size does not regain its newly born value. On the other hand, the number of cells remains constant during the entire life span of the animal.     

Electron-microscopic study of the rat masseter muscle following injection of lidocaine

The ultrastructure of rat masseter muscle was examined at 15 min, 1 and 6 h, and 1 and 2 days following a single injection of 2% lidocaine. Lesions developed within 15 min. The plasma membrane was disrupted and invaginated. The nuclei were pyknotic and the mitochondria appeared swollen. The myofibrils separated and became disoriented. By 1 and 6 h, these changes were severe. By 1 day, the macrophages appeared in damaged myofibers. The presence of a few presumptive myoblasts signaled the onset of regeneration. By 2 days, presumptive myoblasts formed within the basement membrane. The basal lamina proved most resistant to injury. Regeneration of masseter muscle following the damage produced by lidocaine appeared discontinuous in nature. The singly nucleated presumptive myoblasts seemed to arise within the lesions.     

Medico-genetic study of the population of Kostroma Province. I. The population burden of hereditary pathology

Data on the prevalence of hereditary diseases in five regions of the Kostroma province were obtained and analysed. It was shown that the ascertainment was close to the truncate selection for the rural population and to the single selection for the urban population. Segregational analysis proved the rightness of the material subdivision, according to the type of inheritance. The load of hereditary diseases (for the registered forms) in the population was: 0.78 +/- 0.08 X 10(-3) for autosomal dominant, 0.75 +/- 0.08 X 10(-3) for autosomal-recessive and 0.54 +/- 0.1 X 10(-3) for X-linked recessive disorders. The dynamics of the load of hereditary diseases in the populations with different structure is discussed.     

Electron-microscopic immunocytochemistry of neuropeptide Y immunoreactive innervation of vasopressin neurons in the paraventricular nucleus of the rat hypothalamus

The neuropeptide Y (NPY) immunoreactive synaptic input to neurons containing neurophysin II (NP II), the carrier protein of vasopressin (VP), was observed in the paraventricular nucleus (PVN) of the rat hypothalamus by double-labeling immunocytochemistry combining the preembedding peroxidase-antiperoxidase (PAP) method with the postembedding immunogold staining method at the electron-microscopic level. NPY-like immunoreactivities were detected by the PAP method in the dense granular vesicles (70-100 nm in diameter) in the immunoreactive presynaptic axon terminals. NP II-like immunoreactive large neurosecretory granules labeled with gold particles were found in the neurons receiving synaptic input of the NPY-like immunoreactive terminals. This suggests that NPY may be a neurotransmitter or neuromodulator and that NPY neurons may, through synaptic contacts, regulate the secretion of VP neurons.     

Ultrastructural study on the meiotic prophase nucleus of rat oocytes.

Rat oocytes in the meiotic prophase are studied by means of classical techniques of electron microscopy, preferential staining methods for DNA and RNA and specific enzymatic hydrolysis. The axial cores in leptotene and the lateral arms in the pachytene synaptonemal complex are composed by fibrils that keep a positive contrast after the application of the ethylenediaminetetraacetic acid staining method. They disappear with RNAse treatment, which reveals the presence of chromatin fibrils in the zone occupied by the cores. Preferential staining for DNA corroborates this evidence. Medial arm and lateral-medial fibrils are formed by ribonucleoproteic filaments that form bridges between pairing homologues in the zygotene. In the advanced pachytene stage, the RNA becomes scarce in these structures. No DNA can be detected either in the lateral-medial fibrils or in the medial arm. During diplotene the synaptonemal complex loses its individually and the synaptic space becomes wider and irregular. At the same time, loss of chromatin and a large increase of RNA-containing particles occur. These processes lead to the typical interphasic arrangement of nuclear components seen in the dictyate stage.     

Electrophysiological properties of neurons of the red nucleus in rat brain slices

In experiments on rat brain slices, we carried out intracellular recording from neurons of the red nucleus (RN). Passive electrical properties of these neurons (input resistance, membrane time constant) were evaluated. We detected voltage-dependent rebound depolarization and time dependent inward rectification when passing hyperpolarizing pulses of current through the cell. Injections of depolarizing currents caused rhythmical firing of the neurons; the frequency of these firings depends upon the strength of injected current. Rhythmical firings were also characterized by rapid frequency adaptation when currents of different frequency were injected. Stimulation of regions of slices presumably corresponding to the decussion of the brachium conjunctivum mainly evoked EPSPs with a "fast" rise time in RN neurons. This suggests activation of synaptic input from the cerebellar nucleus interpositus. Stimulation of this same region sometimes evoked EPSP-IPSP mixtures and "pure" IPSPs in RN neurons.L. A. Orbeli Institute of Physiology, Armenian Academy of Sciences, Erevan. Translated from Neirofiziologiya, Vol. 23, No. 5, pp. 607–616, September–October, 1991.     

Electron-microscopic immunohistochemical study of the localization of immunoglobulin G in the choroid plexus of the rat

Summary The localization of autologous antiperoxidase immunoglobulin G (IgG) was studied in the choroid plexus of Lewis rats immunized against horseradish peroxidase (HRP). This experiment was performed to study the permeability of the choroid plexus to intravascular IgG. It was shown that autologous IgG was present in the extravascular spaces. The transendothelial transfer appeared to occur mainly via the fenestrations and some interendothelial junctions. No transfer of IgG at the level of epithelial cells toward the cerebrospinal fluid was demonstrated. Interstitial spaces in contact with the connective-tissue cells of the choroid stroma were strongly labeled. The significance of these spaces remains hypothetical and raises the question of the fate of IgG from the interstitial space.This work has been partly supported by Crédits Recherche Universitaire, Paris-val de Marne.     

Electron-microscopic study of silver staining of nucleoli in growing oocytes of rat ovaries

The nucleoli of dictyate-stage growing oocytes in rat ovaries were examined both with routine electron microscopy and electron microscopy after silver nitrate and ammoniacal silver nitrate (Ag-AS) staining. The nucleoli of the unilaminar follicular oocytes consist of twisted strands of dense fibrillar components, aggregates of granular components, and small fibrillar centers. After Ag-AS staining, silver grains are numerous on the dense fibrillar strands, fewer on the fibrillar centers, and very sporadic on the granular aggregates. The same stainability of three nucleolar components with the Ag-AS method was also confirmed in the nucleoli segregated by actinomycin D. During the transition of growing oocytes from bilaminar to plurilaminar follicle stage, the nucleolar dense fibrillar strands gradually conglomerate and are transformed into large and compact spherules. The stainability of dense fibrillar components with the Ag-AS method was lost along with this nucleolar transformation. These results may provide some new clues on the functional significance of Ag-AS-positive proteins in the nucleoli.