Wladimir Ovtscharoff

The role of Willis circle variations during unilateral selective cerebral perfusion: a study of 500 circles

OBJECTIVESnDuring unilateral selective cerebral perfusion (uSCP), with right axillary artery or brachiocephalic trunk cannulation, the brain receives blood only via the right common carotid artery and right vertebral artery (VA). The left hemisphere is perfused mainly through the circle of Willis (CW). However, at least 50% of individuals have some variation in the CW. The aim of the present work was to study the variations in CW and VA that could have an impact on haemodynamics during uSCP.nnnMETHODSnFrom May 2005 to March 2012, a total number of 250 circles obtained via routine dissection for medico-legal reasons were examined. The external diameters of all CW segments and both VAs were measured. From January 2008 to March 2012, a total number of 250 patients subjected to computed tomographic angiography of the CW were also examined.nnnRESULTSnNine evident configurations of the CW that could cause hypoperfusion during uSCP were observed. They were subdivided in to seven types, according to location and the number of major vessels at risk of hypoperfusion. Type IA: hypo/aplasia of left posterior communicating artery (PComA), found in 35.6% of cases; Type IB: hypo/aplasia of anterior communicating artery (AComA), found in 2% of cases; Type IIA: hypo/aplasia of both left PComA and AComA, found in 4.8% of cases; Type IIB: hypo/aplasia of precommunicating (P1) segment of left posterior cerebral artery or right VA, found in 9.2% of cases; Type IIIA: hypo/aplasia of precommunicating (A1) segment of right anterior cerebral artery, found in 6% of cases; Type IIIB: hypo/aplasia of both right VA and AComA, found in 0.2% of cases; Type IV: hypo/aplasia of both right A1 and right VA or both right A1 and left P1, found in 0.8% of cases. All types were present in 58.6% of all examined CWs.nnnCONCLUSIONSnOur results show that CW variations are present in a significant number of patients. Our data support the need for extensive preoperative examination and meticulous intraoperative monitoring of cerebral perfusion during uSCP. Finally, our data support the superiority of bilateral SCP over uSCP, because most of the variations reported do not have haemodynamic significance during bilateral SCP.

Light and electron-microscopic study of leucine enkephalin immunoreactivity in the cat claustrum

The claustrum is a complex telencephalic structure owing to its reciprocal connectivity with most—if not all—cortical areas. However, there is a paucity of data in the literature concerning its histochemical components, including opioid peptide neurotransmitters. The aim of the present study was to examine the morphology, distribution and ultrastructure of leucine-enkephalin-immunoreactive (Leu-enk-ir) neurons and fibers in the dorsal claustrum (DC) of the cat. Seven healthy, adult male and female cats were used in our study. All animals received humane care. They were irreversibly anesthetized and transcardially perfused with fixative. Brains were removed, postfixed, blocked and sectioned. Sections were incubated with polyclonal anti-Leu-enk antibodies using the Avidin–Biotin–Peroxidase Complex method. Leu-enk-ir neurons and fibers were distributed throughout the DC. Some of the neurons were lightly-stained, while others were darkly-stained. Light-microscopically, they varied in shape: oval, fusiform, multipolar and irregular. With regard to size, they were categorized as small (15xa0μm or less in diameter), medium (16–20xa0μm in diameter) and large (21xa0μm or more in diameter). No specific pattern of regional distribution was found. On the electron microscope level, immunoproduct was observed in neurons, dendrites and terminal boutons. Different types of Leu-enk-ir neurons differ in their ultrastructural features, including two types of synaptic boutons. No gender-specific features were observed. In conclusion, it is our hope that our study will serve to contribute to a better understanding of the functional neuroanatomy of the DC in the cat, and that it can be extrapolated and applied to other mammals, including humans.

Structure and Cytochemistry of the Chemical Synapses

Publisher Summary This chapter describes the structure and cytochemistry of chemical synapses. The synapses provide morphologically and functionally specialized contacts for an excitatory and inhibitory action between the nerve cells and between neurons and some non-neuronal cells. Cytochemistry and autoradiography present a link among the morphological, the biochemical and physiological studies. The majority of interneuronal synapses and the neuromuscular junctions in vertebrates are chemical synapses. Structurally, they have three basic components, which are the presynaptic part, the synaptic cleft, and the postsynaptic part. The other organelles and inclusions in the axonal endings probably have no specific role in the synaptic transmission as they are not found in all cases in the presynaptic element. Both cell membranes, which realize the direct conduction of bioelectrical information, the presynaptic and postsynaptic membranes, are highly organized membrane systems, with corresponding structure, cytochemical characteristics, and enzyme equipment. The definite arrangement of the acidic and basic groups on the presynaptic and postsynaptic elements probably plays a determining role in the formation of the synaptic contacts during synaptogenesis.

Neuronal nitric oxide synthase immunopositive neurons in cat claustrum—a light and electron microscopic study

Nitric oxide is a unique neurotransmitter, which participates in many physiological and pathological processes in the organism. Nevertheless there are little data about the neuronal Nitric Oxide Synthase immunoreactive (nNOS-ir) neurons and fibers in the dorsal claustrum (DC) of a cat. In this respect the aims of this study were: (1) to demonstrate nNOS-ir in the neurons and fibers of the DC; (2) to describe their light microscopic morphology and distribution; (3) to investigate and analyze the ultrastructure of the nNOS-ir neurons, fibers and synaptic terminals; (4) to verify whether the nNOS-ir neurons consist a specific subpopulation of claustral neurons; (5) to verify whether the nNOS-ir neurons have a specific pattern of organization throughout the DC. For demonstration of the nNOS-ir the Avidin-Biotin-Peroxidase Complex method was applied. Immunopositive for nNOS neurons and fibers were present in all parts of DC. On the light microscope level nNOS-ir neurons were different in shape and size. According to the latter they were divided into three groups—small (with diameter under 15xa0μm), medium-sized (with diameter from 16 to 20xa0μm) and large (with diameter over 21xa0μm). Some of nNOS-ir neurons were lightly-stained while others were darkly-stained. On the electron microscope level the immunoproduct was observed in neurons, dendrites and terminal boutons. Different types of nNOS-ir neurons differ according to their ultrastructural features. Three types of nNOS-ir synaptic boutons were found. As a conclusion we hope that the present study will contribute to a better understanding of the functioning of the DC in cat and that some of the data presented could be extrapolated to other mammals, including human.

Localization of lectin binding sites on the rat intestinal microvillous membrane

The distribution of peroxidase labeled Asparagus Pea Lectin and Soybean Agglutinin on the rat intestinal microvillous membrane was studied. Controls were carried out to determine the reaction specifity . Some analogy was established between the distribution of the binding sites of both lectins. The reaction product was deposited mainly on the microvillous membrane of the crypt cells and the cells from the lower part of the intestinal villi, and to a lesser extent on the upper part of the latter. Electron dense material was seen on the upper part and chiefly on the tip of the microvilli. From the results of this study and on the basis of data from our previous studies it was proposed, that changes in the carbohydrate content of the microvillous membrane appear during the differentiation and maturation of the intestinal cells.

Concanavalin A binding sites on the intestinal microvillus membrane of rat

Concanavalin A binding sites on the intestinal microvillus membrane have been studied by means of Concanavalin A-horseradish peroxidase method. Several controls were carried out to demonstrate the specifity of this technique. Reaction product on the microvillus membrane of columnar cells on the upper bigger part of intestinal villi was found, while on the intestinal cells from the base of the villi and undifferentiated crypt cells no electron dense material was established. The results of the suggested method were discussed in relation with the literature data.

Topographical distribution and morphology of NADPH-diaphorase-stained neurons in the human claustrum

We studied the topographical distribution and morphological characteristics of NADPH-diaphorase-positive neurons and fibers in the human claustrum. These neurons were seen to be heterogeneously distributed throughout the claustrum. Taking into account the size and shape of stained perikarya as well as dendritic and axonal characteristics, Nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd)-positive neurons were categorized by diameter into three types: large, medium and small. Large neurons ranged from 25 to 35 μm in diameter and typically displayed elliptical or multipolar cell bodies. Medium neurons ranged from 20 to 25 μm in diameter and displayed multipolar, bipolar and irregular cell bodies. Small neurons ranged from 14 to 20 μm in diameter and most often displayed oval or elliptical cell bodies. Based on dendritic characteristics, these neurons were divided into spiny and aspiny subtypes. Our findings reveal two populations of NADPHd-positive neurons in the human claustrum—one comprised of large and medium cells consistent with a projection neuron phenotype, the other represented by small cells resembling the interneuron phenotype as defined by previous Golgi impregnation studies.

Neuronal nitric oxide synthase immunopositive neurons in cat vestibular complex: a light and electron microscopic study

Nitric oxide is a unique neurotransmitter, which participates in many physiological and pathological processes in the organism. Nevertheless, there are little data about the neuronal nitric oxide synthase immunoreactivity (nNOS-ir) in the vestibular complex of a cat. In this respect, the aims of this study were to: (1) demonstrate nNOS-ir in the neurons and fibers, from all major and accessory vestibular nuclei; (2) describe their light microscopic morphology and distribution; (3) investigate and analyze the ultrastructure of the NOS I-immunopositive neurons, fibers, and synaptic boutons. For demonstration of the nNOS-ir, the peroxidase–antiperoxidase–diaminobenzidin method was applied. Immunopositive for nNOS neurons and fibers were present in all major and accessory vestibular nuclei. On the light microscope level, the immunopositive neurons were different in shape and size. According to the latter, they were divided into four groups—small (with diameter less than 15xa0μm), medium-sized (with diameter from 15 to 30xa0μm), large type I (with diameter from 30 to 40xa0μm), and large type II (with diameter greater than 40xa0μm). On the electron microscope level, the immunoproduct was observed in neurons, dendrites, and terminal boutons. According to the ultrastructural features, the neurons were divided into three groups—small (with diameter less than 15xa0μm), medium-sized (with diameter from 15 to 30xa0μm), and large (with diameter greater than 30xa0μm). At least two types of nNOS-ir synaptic boutons were easily distinguished. As a conclusion, we hope that this study will contribute to a better understanding of the functioning of the vestibular complex in cat and that some of the data presented could be extrapolated to other mammals, including human.

Cytochemical localization of adenosine triphosphatase and thiamine pyrophosphatase in the synapses of rat's cerebral cortex

Ultrastructural distribution of adenosine triphosphatase and thiamine pyrophosphatase in synapses of rats cerebral cortex was studied. Adenosine triphosphatase activity in some synaptic vesicles and mitochondria, on pre- and postsynaptic membranes, as well as in the postsynaptic thickening was established. The reaction specificity was proved by means of some controls: various concentrations of ouabain, NaF, NiCl2, cysteine, substrate free medium and non-specific substrates - cocarboxylase and beta-glycerophosphate. At the thiamine pyrophatase reaction, the enzyme positive product was found on the membrane of some clear synaptic vesicles, on the singl sacs of smooth endoplasmic reticulum in the axon terminal, and bouton cell membrane. Substrate free medium, addition of cystein and substitution of orininal substrate with adenosine triphosphate and beta-glycerophosphate as controls were used. The fine structure localization of both enzymes in synaptic structures suggests their important role in the synaptic function.

Postnatal development of neurons expressing NADPH-diaphorase and parvalbumin in the parietal cortex of male and female rats

Expression of the enzyme nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) and the calcium-binding protein parvalbumin was studied in the parietal cortex of male and female rats during postnatal development at 20, 60 and 90 days of age. First, localization of the activity of NADPH-d was combined with the immunohistochemical localization of parvalbumin to facilitate recognition of morphological details and distribution patterns of these two types of cortical neurons. Double staining of neurons for parvalbumin and NADPH-d was never found. Second, it was found that NADPH-d is a simple and proper marker for quantitative studies. Morphometric analysis revealed sexual dimorphism in the density of NADPH-d-positive neurons in 20 days-old prepubertal rats. Females showed higher amounts of NADPH-d-positive neurons than males. No sex-dependent differences were detected in 60 days-old pubertal and 90 days-old postpubertal rats. The present results suggest that sex differences in the number of NADPH-d-positive neurons in the rat parietal cortex may be related to epigenetic effects of gonadal hormones in the early prepubertal period of postnatal development.