Subcellular localization of the magnetosome protein MamC in the marine magnetotactic bacterium Magnetococcus marinus strain MC-1 using immunoelectron microscopy.

Magnetotactic bacteria are a diverse group of prokaryotes that biomineralize intracellular magnetosomes, composed of magnetic (Fe3O4) crystals each enveloped by a lipid bilayer membrane that contains proteins not found in other parts of the cell. Although partial roles of some of these magnetosome proteins have been determined, the roles of most have not been completely elucidated, particularly in how they regulate the biomineralization process. While studies on the localization of these proteins have been focused solely on Magnetospirillum species, the goal of the present study was to determine, for the first time, the localization of the most abundant putative magnetosome membrane protein, MamC, in Magnetococcus marinus strain MC-1. MamC was expressed in Escherichia coli and purified. Monoclonal antibodies were produced against MamC and immunogold labeling TEM was used to localize MamC in thin sections of cells of M. marinus. Results show that MamC is located only in the magnetosome membrane of Mc. marinus. Based on our findings and the abundance of this protein, it seems likely that it is important in magnetosome biomineralization and might be used in controlling the characteristics of synthetic nanomagnetite.

Inhibition of nucleolar protein nucleolin by electroporation with anti-nucleolin antibodies results in an increase of the nucleolar size.

Electroporation of exponentially growing human larynx epidermoid carcinoma cells (HEp-2) with a serum against nucleolin, one of the most abundant non-histone nuclear proteins, has shown, 24 h after electroporation, a significant increase in the size of the nucleolus of these cells compared with normal HEp-2 cells (non-electroporated) and electroporated HEp-2 cells in the absence of anti-nucleolin serum (P < 0.01). Image analysis evaluation of the different nucleolar components proved a major contribution of the dense fibrillar component to the total nucleolar size in cells electroporated with anti-nucleolin antibodies, more than that corresponding to the dense fibrillar component in cells from any of the control groups (P < 0.01), indicating that the reported increase in nucleolar size was due to a marked enlargement of the dense fibrillar regions. These results, in agreement with previous biochemical and molecular biology studies, suggest a pivotal role for nucleolin in pre-rRNA processing and constitute morphological evidence supporting this role. Following nucleolin inhibition, impaired pre-rRNA processing might result in an accumulation of this molecular species in the dense fibrillar component of the nucleolus, where pre-rRNA is first present.

Localization of nitric oxide synthase in the adult rat brain.

The distribution of the immunoreactivity to nitric oxide synthase has been examined from rostral to caudal areas of the rat central nervous system using light microscopy. Endogenous nitric oxide synthase was located using a specific polyclonal antiserum, produced against affinity purified nitric oxide synthase from whole rat brain, following the avidin-biotin peroxidase procedure. Immunoreactive cell bodies and processes showed a widespread distribution in the brain. In the telencephalon, immunoreactive structures were distributed in all areas of the cerebral cortex, the ventral endopiriform nucleus and claustrum, the main and accessory olfactory bulb, the anterior and posterior olfactory nuclei, the precommisural hippocampus, the taenia tecta, the nucleus accumbens, the stria terminalis, the caudate putamen, the olfactory tubercle and islands of Calleja, septum, globus pallidus and substantia innominata, hippocampus and amygdala. In the diencephalon, the immunoreactivity was largely found in both the hypothalamus and thalamus. In the hypothalamus, immunoreactive cell bodies were characteristically located in the perivascular-neurosecretory systems and mamillary bodies. In addition, immunoreactive nerve fibres were detected in the median eminence of the infundibular stem. The mesencephalon showed nitric oxide synthase immunoreactivity in the ventral tegmental area, the interpeduncular nucleus, the rostral linear nucleus of the raphe and the dorsal raphe nucleus. Immunoreactive structures were also found in the nuclei of the central grey, the peripeduncular nucleus and substantia nigra pars lateralis, the geniculate nucleus and in the superior and inferior colliculi. The pons displayed immunoreactive structures principally in the pedunculopontine and laterodorsal tegmental nuclei, the ventral tegmental nucleus, the reticulotegmental pontine nucleus, the parabrachial nucleus and locus coeruleus. In the medulla oblongata, immunoreactive neurons and processes were detected in the principal sensory trigeminal nucleus, the trapezoid body, the raphe magnus, the pontine reticular nuclei, the supragenual nucleus, the prepositus hypoglossal nucleus, the medial and spinal vestibular nuclei, the dorsal cochlear nucleus, the medullary reticular field, the nucleus of the solitary tract, the gracile and cuneate nuclei, the dorsal nucleus of the vagus nerve and the oral, interpolar and caudal parts of the spinal trigeminal nucleus. In the cerebellum, the stellate and basket cells showed immunoreactivity, which was also seen in the basket terminal fibres of the Purkinje cell layer. Isolated immunoreactive Purkinje cells were found in the vermis and parafloccular regions of the cerebellum. In the granular layer of the cerebellum, the granular cells and glomeruli were also immunoreactive. Numerous positive varicose nerve fibres and occasional neurons were also found in the lateral and interposed cerebellar nuclei.(ABSTRACT TRUNCATED AT 400 WORDS)

Quantitative alterations after long-term alcohol administration in the dorsal lateral geniculate nucleus (dLGN) in the rabbit (Oryctolagus cuniculus).

The effects of chronic excessive alcohol ingestion on the central nervous system were studied in neurons of the dorsal lateral geniculate nucleus (dLGN) in the rabbit (Oryctolagus cuniculus). In this nucleus, neuron density and other morphometric parameters such as the somatic volume of the cells have been investigated both under normal conditions and under alcohol intoxication. Special attention was given to the possibility that positive somatic heteropycnosis may be a sign of imminent cell death. In addition, the percentage volumes occupied by normal neuronal soma and by affected cells were determined. Continuous alcohol treatment for 6 months reduced the size of certain types of neurons, the alteration being specially intense in areas with an abundance of larger neurons. In these areas more intense signs of somatic heteropycnosis also appeared. We discuss the relationship between the condition of the inhibitory neurons (GABAergic interneurons), the distribution of these in the lower zone of the nucleus, and their greater resistance to the influence of alcohol. This type of stereological analysis is intended to provide a better interpretation of the different degrees of the effects of alcohol, and to give more detailed information about changes at cellular level, both for comparative purposes with other situations and to shed light on the alterations caused by alcoholism.

Morphological changes induced by colchicine in the chick optic cup in early stages of development. A stereological study.

In this study chick embryo optic cups at HH stage 13 of development were analyzed under normal conditions and after inoculation with colchicine for 1, 2, 4, and 8 h. Several changes were seen after these periods of treatment: 1) modifications of the structure, with thicker regions in the cup and a general decrease in the total volume according to the duration of exposure to the drug (about 4 times less than normal, 5,035 x 10(3) microns 3 vs 1,334 x 10(3) microns 3 after 8 h of treatment); 2) enlargement of the ventricular cavity and its closure, due to failure of approximation of retinal and pigmentary layers; 3) failure of lens development, with delay and impairment of pit formation and deformation of all structures; lens volume was less than normal (about 4 times less, 2,148 x 10(3) microns 3 vs 658 x 10(3) microns 3 after 8 h of treatment); 4) a general segregation of the cells making up the structure, principally in the more active proliferating zones. The local alterations found are described.

Increased sensory neuropeptides in nodular prurigo: a quantitative immunohistochemical analysis.

Seven patients with nodular prurigo, five patients with lichenified eczema and seven control volunteers were studied immunohistochemically using antisera to the pan-neuronal marker protein gene product 9.5 (PGP), and the neuropeptides calcitonin gene-related peptide (CGRP), substance P (SP), tyrosine hydroxylase (TH), vasoactive intestinal polypeptide (VIP) and the C-flanking region of neuropeptide Y (C-PON). PGP-, CGRP- and SP-immunoreactivities were also evaluated using image analysis quantification, and the data compared by statistical analysis. No significant changes were noted in the lichenified skin of patients with chronic eczema, compared with the control groups. In contrast, a significant increase in PGP immunoreactive nerve fibers was seen in lesional skin of all nodular prurigo cases studied, when compared with non-lesional skin from the same patient or from control subjects (P < 0.001). In one case massive neural hyperplasia was also identified. Staining for CGRP and SP showed a large increase of immunoreactive nerves in lesional skin of nodular prurigo patients, which closely paralleled that of PGP. Staining with VIP, C-PON and TH was similar in both lesional and non-lesional skin. These results indicate that neural changes in nodular prurigo are associated with an increase of sensory neuropeptides, which could be related to the intense pruritus which accompanies nodular prurigo. The absence of significant changes in lichenified skin suggests that the increase in CGRP- and SP-immunoreactive nerve fibres is a characteristic feature of nodular prurigo and may be important in its pathogenesis.

Stereological study of the synaptic profiles belonging to interneurons in the dorsal lateral geniculate nucleus of the rabbit.

This study is concerned with some characteristics of the interneurons belonging to the dLGN (dorsal Lateral Geniculate Nucleus) of the rabbit. The work deals with the distribution of such cells in the alpha E sector of the nucleus and their F1 and F2 presynaptic contacts. The F1 and the F2 profiles are present in all three of the alpha E zones studied. The F1 profiles are significantly more numerous in the upper zone (57 +/- 2 profiles per 10(4) microns2 of section) and the middle zone (59 +/- 3 profiles per 10(4) microns2 of section) than in the lower one (41 +/- 2 profiles per 10(4) microns2 of section). The F2 profiles are more abundant in the alpha E sector than the F1 ones are, particularly in the lower zone, where F2 profiles (104 +/- 4 profiles per 10(4) microns2 of section) are not only significantly more numerous than F1 profiles but also more abundant than the F2 profiles in the middle zone (84 +/- 3 profiles per 10(4) microns2 of section) and upper zone (88 +/- 2 profiles per 10(4) microns2 of section). These results and their comments reveal diverse density of the element distribution from the dorsal to the ventral part of the alpha E sector as well as the possible relationship or independence from the extranuclear afferent inputs.

Morphometry and frequency of afferent synaptic terminals in the rabbit dorsal-lateral geniculate nucleus.

Morphological and morphometric features of the retinal synaptic terminals (RLP) and cortical synaptic terminals (RSD) were analyzed in the alpha E sector of the rabbit dorsal-lateral geniculate nucleus (dLGN). A methodological approach was selected which allowed us to determine volume of the neuropil and elsewhere record variations in the size and distribution of the two types of terminals found in the three zones (superior, middle, and inferior) from up to down into which the alpha E sector of the dLGN was divided. After obtaining an isotropic, uniform, and pseudorandom (IUR) sample, the terminals were examined on the basis of a set of morphometric parameters. An analysis of these data showed the retinal terminals (RLP) to be more numerous and to occupy a greater total area of the neuropil in the dorsal (superior) zone of the nucleus, whereas the number and total area occupied by cortical terminals (RSD) did not vary in the superior, middle, and inferior zones. Upon comparing the two types of terminals, the RLP were larger and more widely distributed, the greatest differences between the two appearing in the dorsal (superior) zone of the dLGN.

Cytoarchitecture of the dorsal lateral geniculate nucleus in the rabbit.

The cytoarchitecture and morphometry of the neurons in the alpha E sector of the dorsal lateral geniculate nucleus of the rabbit have been studied. The preparation techniques used were those of Golgi-Adams and Klüver-Barrera. Our method was to subdivide the alpha E sector into three zones (superior, medial and inferior) and then to cut each zone along the horizontal, transverse and saggital planes in order to obtain precise measurements and descriptions of the neurons whatever their orientation. Differences exist in both the size and distribution of neurons in the inferior zone of the alpha E sector compared to the other two.

Stereological study on the mode of optic cup expansion and the accumulation of mitoses in the early stages of chick embryo development.

The present study was designed to contribute to our understanding of the factors that take part in the developmental transformation of the optic vesicle into the optic cup. The expansion and formation of this structure are dependent upon factors such as cellular proliferation, the space or zone occupied by the growing optic cup, and environmental influences. Our investigation in the chick embryo analyzes the relationship between retinal thickness and ventricular mitotic density. This relationship is shown in the study as PEI (proliferation-expansion index). That index varies in the superior, medial and inferior regions of the retina when the zones of the same stage are compared, as well as in the comparisons of values between the 13-14 stage and the 17-18 stage. These differences indicate a different behavior of the cells constituting the retinal regions. Also discussed is the influence of the retinal fissure on the morphological changes observed during optic cup development.