Synaptic organization of the glomerulus in the main olfactory bulb: Compartments of the glomerulus and heterogeneity of the periglomerular cells

According to the combinatorial receptor and glomerular codes for odors, the fine tuning of the output level from each glomerulus is assumed to be important for information processing in the olfactory system, which may be regulated by numerous elements, such as olfactory nerves (ONs), periglomerular (PG) cells, centrifugal nerves and even various interneurons, such as granule cells, making synapses outside the glomeruli. Recently, structural and physiological analyses at the cellular level started to reveal that the neuronal organization of the olfactory bulb may be more complex than previously thought. In the present paper, we describe the following six points of the structural organization of the glomerulus, revealed by confocal laser scanning microscopy and electron microscopy analyses of rats, mice and other mammals: (i) the chemical heterogeneity of PG cells; (ii) compartmental organization of the glomerulus, with each glomerulus consisting of two compartments, the ON zone and the non-ON zone; (iii) the heterogeneity of PG cells in terms of their structural and synaptic features, whereby type 1 PG cells send their intraglomerular dendrites into both the ON and non-ON zones and type 2 PG cells send their intraglomerular dendrites only into the non-ON zone, thus receiving either few synapses from the ON terminals, if present, or none at all; (iv) the spatial relationship of mitral/tufted cell dendritic processes with ON terminals and PG cell dendrites; (v) complex neuronal interactions via chemical synapses and gap junctions in the glomerulus; and (vi) comparative aspects of the organization of the main olfactory bulb.     

Blastocyst development in co-culture: development and morphological aspects

A retrospective study was undertaken to determine if initialculture conditions and embryo quality had an effect on subsequentblastocyst development in co-culture for cryopreservation. Theapparent effects of freeze–thawing on blastocysts at theultrastructure level were also observed. On day 3 of culture,embryos were categorized into two groups based on their morphologicalattributes. Results suggest that the initial culture environmentof embryos up to day 3 (5- to 8-cell stage) did not affect thesubsequent rate of blastocyst formation in co-culture. However,the initial embryo quality had an impact on blastocyst formationand quality. On day 5.5, 90% (60/67) of the optimal qualityembryos (six to eight blastomeres with minimal or no fragmentationon day 3) had attained the blastocyst stage, which was greater(P < 0.01) than the 55% (31/56) observed with the sub-optimalembryos (five to eight blastomeres with 30–50% fragmentationon day 3). Furthermore, 66% (44/67) of embryos initially gradedas optimal were suitable for cryopreservation, which was greater(P < 0.01) than attained with embryos of lesser quality (22/56;39%). At the ultrastructural level, the polarized distributionof plasma membrane microvilli was retained, as was the integrityof the nuclear membrane following thawing.co-culture     

The olfactory glomerulus: a cortical module with specific functions

The axons of many olfactory receptor cells converge on an individual glomerulus in the olfactory bulb, where they make contacts with the distal dendrites of mitral and tufted cells. Each glomerulus is targeted by olfactory receptor neurons expressing a single type of olfactory receptor protein. The glomerulus provides a unique model in which the function of a cortical module can be unambiguously established. Here we review the increasing evidence that a key functional operation of the glomerulus is to act as a signal-to-noise enhancing device in the processing of sensory input and that this function is critical across vertebrate and invertebrate species for the ability to detect specific odor stimuli within “noisy” odor environments and to carry out discriminations between odor molecules that are structurally closely related.     

Specializations of a pheromonal glomerulus in the Drosophila olfactory system

Insect pheromonal glomeruli are thought to track the fine spatiotemporal features of one or a few odorants to aid conspecific localization. However, it is not clear whether they function differently from generalist glomeruli, which respond to many odorants. In this study, we test how DA1, a model pheromonal glomerulus in the fruit fly, represents the spatial and temporal properties of its input, compared with other glomeruli. We combine calcium imaging and electrical stimulation in an isolated brain preparation for a simultaneous, unbiased comparison of the functional organization of many glomeruli. In contrast to what is found in other glomeruli, we find that ipsilateral and contralateral stimuli elicit distinct spatial patterns of activity within DA1. DA1's output shows a greater preference for ipsilateral stimuli in males than in females. DA1 experiences greater and more rapid inhibition than other glomeruli, allowing it to report slight interantennal delays in stimulus onset in a "winner-take-all" manner. DA1's ability to encode spatiotemporal input features distinguishes it from other glomeruli in the fruit fly antennal lobe but relates it to pheromonal glomeruli in other insect species. We propose that DA1 is specialized to help the fly localize and orient with respect to pheromone sources.     

On the organization of olfactory and vomeronasal cortices

Classically, the olfactory and vomeronasal pathways are thought to run in parallel non-overlapping axes in the forebrain subserving different functions. The olfactory and vomeronasal epithelia project to the main and accessory olfactory bulbs (primary projections), which in turn project to different areas of the telencephalon in a non-topographic fashion (secondary projections) and so on (tertiary projections). New data indicate that projections arising from the main and accessory olfactory bulbs converge widely in the rostral basal telencephalon. In contrast, in the vomeronasal system, cloning two classes of vomeronasal receptors (V1R and V2R) has led to the distinction of two anatomically and functionally independent pathways that reach some common, but also some different, targets in the amygdala. Tertiary projections from the olfactory and vomeronasal amygdalae are directed to the ventral striatum, which thus becomes a site for processing and potential convergence of chemosensory stimuli. Functional data indicate that the olfactory and vomeronasal systems are able to detect and process volatiles (presumptive olfactory cues) as well as pheromones in both epithelia and bulbs. Collectively, these data indicate that the anatomical and functional distinction between the olfactory and vomeronasal systems should be re-evaluated. Specifically, the recipient cortex should be reorganized to include olfactory, vomeronasal (convergent and V1R and V2R specific areas) and mixed (olfactory and vomeronasal) chemosensory cortices. This new perspective could help to unravel olfactory and vomeronasal interactions in behavioral paradigms.     

Liver-associated large granular lymphocytes: morphological and functional aspects

Large granular lymphocytes (LGLs) differ from other lymphocytes in their recirculation pattern and are distributed preferentially in nonlymphoid organs such as the liver and lung. The liver-associated LGLs adhere strongly to the sinusoidal endothelium and show a natural killer (NK) cytotoxicity against incoming metastatic tumor cells; this reaction occurs very rapidly because, in contrast to the immune response, it does not require complex processes in the lymphoid tissue. They have been extensively studied morphologically in terms of pit cells. LGLs have two characteristic cell organelles which participate in the NK cytolysis, i. e., dense granules and rod-cored vesicles. The former are lysosomes derived from multivesicular bodies and contain pore-forming proteins. The latter are the secretory vesicles exclusively seen in LGLs and are markedly increased in number when the NK function is augmented by biological response modifiers. These two structures are believed to be exocytosed in the space between LGL and the conjugated tumor cell. The microenvironment of the liver sinusoids, which includes Kupffer cells, endothelial cells and other lymphocytes, is considered to regulate the function of the liver-associated LGLs. Liver-associated LGLs, as well as Kupffer cells, are intrinsically involved in the defense system of the liver under various physiological and pathological conditions.     

Replacement of the ureter by an ileal loop. Quantitative aspects of long-term morphological alterations in minipigs.

In minipigs 1 ureter was replaced by a loop of the terminal ileum and the contralateral kidney removed. After 2.5 to 3 years the morphology of the replaced ureter was compared with the normal ileum. Independent of the 3 different operative techniques used, in about half of the pigs there was loss or flattening of the villi. In the other pigs the morphometrically determined number of intraepithelial lymphocytes, the cell density in the lamina propria and the length of the villi did not differ significantly compared with the normal ileum. There was no increase in goblet cells in the crypts. The transitional epithelium covered only a short distance at the anastomotic junctions. Peyer''s patches of normal age-related size were found in the replaced ureter. Despite the long-term contact with urine instead of gut contents, in many pigs a normal amount of lymphocytes remained in the "ileal ureter".     

New morphological and biochemical aspects of atherosclerosis

According to morphological and biochemical findings, disturbances of metabolism (turnover) and function of smooth muscle cells and proteoglycans/GAG are decisive for the development of early and progressive atherosclerotic changes. The feedback dependencies between the smooth muscle cells and the components of the extracellular substance demonstrated, permit to call primary target points of atherogenic injuries of al constituents of this regulating circle system. If the increased turnovers of the arterial components do not return to a normal equilibrium, the result is hyperplasia of the cellular and intercellular constituents. The early atherosclerotic lesions can progress or relapse. In late and regressive lesions, the cell content as well as the anabolic and esp. the catabolic processes decrease. There result scars rich in collagen fibres and poorer in cells, ground substance, and elastin. The healing of atherosclerotic lesions can take place in any stage, the later the more difficult and insufficient. Disturbances of the fat metabolism, the own synthesis, and the intake of substances by smooth muscle and hematogenic cells are secondary sequels of the primary early atherosclerotic alterations and might be regarded as metabolic lesion of the smooth muscle cells. Other secondary and tertiary processes (calcification, fibrous degeneration, esp. of elastin) support the hypothesis that the early atherosclerotic lesions and their progress may finally start and perpetuate a metabolic insufficiency of the arterial wall.     

Osteogenesis imperfecta: morphological, histochemical and biochemical aspects. Modifications induced by (+)-catechin.

Two patients affected with two different forms of Osteogenesis Imperfecta were examined in order to study collagen and glycosaminoglycans (GAGs) in skin and iliac crest cartilage. A sharp decrease of the galactosamine to glucosamine ratio due to a reduced content of chondroitin sulfate was evidenced in both patients. Moreover the structure of proteoglycans appeared altered, this being more evident in the severe form of the disease. Morphological examination in light and electron microscopy of cartilage of the less severely diseased patient showed that GAGs in the extracellular matrix did not present regular connection with collagen fibers. Chondrocytes, elongated and disorderly scattered, showed large lipidic inclusions and, on histochemical basis, were devoid of UDPG dehydrogenase activity. Treatment with (+)-catechin produced an improvement, in both patients, of the biochemical pattern of collagen and GAGs. Similarly a shift of the cellular activity and of the matrix morphology towards normality was observed in the investigated cartilage of the less severely affected patient.     

Lytic growth of human herpesvirus 8: morphological aspects

The human herpesvirus 8 (HHV-8), also known as Kaposi's sarcoma-associated herpesvirus, is a gamma herpesvirus associated with AIDS-related body cavity-based lymphomas (BCBL), also called primary effusion lymphomas (PEL). These are a rare form of non-Hodgkin lymphomas in which HHV-8 is present, often associated with Epstein-Barr virus (EBV) infection. HHV-8 is also present in a latent state or in a state of low-level persistence in different primary effusion lymphoma-derived cell lines, such BCBL-1 cells, that lack EBV infection. This cell line was induced to produce mature virions by treatment with 12- O -tetradecanoyl phorbol-13-acetate (TPA) and the characteristic ultrastructural features of HHV-8 lytic replication were identified and compared to those of the other members of Herpesviridae family.