Pancreatic microcirculation in the monkey with special reference to the blood drainage system of langerhans islets: Light and scanning electron microscopic study

The microcirculation of the pancreas in 20 monkeys (Macaca mulatta) was further studied by scanning electron microscopy (SEM) of vascular corrosion casts and light microscopy (LM) of Chinese ink-injected/cleared tissues. The results revealed that 91% of islets observed received arterial blood from the terminal branches of the intralobular arteries—the afferent arterioles, and 9% received no arterial blood, being entirely supplied by the efferent vessels of the intermediate or large islets. Some islets received blood from the translobular afferent arterioles of the adjacent lobule. Two patterns of islet drainage channels with different features in the monkey were demonstrated in our study. These patterns might be termed as continuous or convergent portal vessels. All islets possessed continuous portal vessels, 7–8 μm in diameter, which ran a short distance (∼100 μm) and then drained into the peri-islet acinar region, forming a typical continuous insulo-acinar portal system. About 21% of the islets possessed one or two convergent portal vessels, occasionally more. This was first observed in the monkey. These vessels were relatively long and/or thick and drained into different regions: (1) the acinar region far from the islet in the lobule, forming a convergent insulo-acinar portal system, (2) crossed the interlobular septum into an adjacent lobule where sometimes no islet existed and then drained into the exocrine acinar region, forming a translobular convergent insulo-acinar portal system, (3) drained into an adjacent small islet through the insulo-insular drainage vessels—one part of the drainage system of the islets. Translobular vascular anastomoses observed between the microcirculation of pancreatic lobules in the monkey formed a new arrangement of pancreatic microcirculation—translobular pancreatic microcirculation. The functional and clinical significance of the pancreatic portal circulation and translobular circulation is discussed in this report. © 1996 Wiley-Liss, Inc.     

Three-dimensional cytoarchitecture of rat pulmonary venous walls: a light and scanning electron microscopic study

 The three-dimensional architecture of the rat pulmonary veins was studied by light microscopy (LM) and scanning electron microscopy (SEM). For LM, the left lungs were fixed with formalin, sectioned and immunostained with an anti-α-smooth muscle actin (α-SMA) antibody in addition to conventional staining. For SEM, the specimens were fixed with glutaraldehyde and immersed in 30% KOH solution for 8 min followed by treatment of collagenase solution for more than 5 h. By LM, the smooth muscle cells stained with anti-α-SMA showed discontinuous, periodical thickenings of circular bundles in the wall of the venules, but they became thin and continuous in the larger vessels (or veins) that had a cardiac muscle layer on the outside. Under SEM, the smooth muscle cells formed circular-oriented bundles at constant intervals along the venules less than 100 μm in diameter. These bundles had circumferential constrictions in the lumen. The cardiac muscle cells, which appeared in large pulmonary veins of more than 100 μm, ran in a circular or oblique direction and completely surrounded the vessel wall outside of the thin continuous layer of smooth muscle cells. The muscle arrangements were considered to play a significant role in the return blood flow in rat pulmonary veins. Accepted: 15 June 1998     

The cholinergic innervation of the rat substantia nigra: a light and electron microscopic immunohistochemical study

Summary Putative cholinergic axons and synaptic endings were demonstrated in the substantia nigra (SN) of the rat by light and electron microscopy on the basis of the localization of choline acetyltransferase (ChAT) immunoreactivity. The distribution of ChAT immunoreactivity in the SN as demonstrated by light microscopy revealed a modest network of ChAT-immunoreactive beaded axons in the SNc, in comparison to a relatively sparse distribution in the SNr. These axonal profiles were most dense in the middle of the rostral-caudal extent of the SNc and appeared to be concentrated in the middle third of the medial-lateral extent. By electron microscopy, unmyelinated, small diameter (0.25 m) ChAT-immuno-reactive axons were observed interspersed among numerous other non-immunoreactive axons in the SNc. ChAT-immunoreactive synaptic endings were observed in juxtaposition to small caliber (0.5 m) non-immunoreactive dendrites, and contained numerous spheroidal synaptic vesicles and occasional mitochondria. Synaptic contact zones were characterized by an accumulation of synaptic vesicles along the presynaptic membrane, and a prominent postsynaptic densification producing an asymmetrical pre-/postsynaptic membrane profile typical of excitatory synapses. These findings provide direct evidence for a cholinergic innervation of the SN, and suggest that this input may have an excitatory effect on neuronal elements in the SNc.     

The possible protective effect of N-acetyl-L-cysteine and folic acid in combination against aspartame-induced cerebral cortex neurotoxicity in adult male rats: a light and transmission electron microscopic study

The purpose of this study is to investigate structural and ultrastructural alterations in the rat’s brain cerebral cortex after aspartame (ASP) treatment and to evaluate the possible ameliorating role of N-acetyl-L-cysteine (NAC) and folic acid (FA). Forty adult rats were divided into four equal groups: Group I, received appropriate vehicle only and served as control. Group II, received oral doses of both NAC (600 mg/kg body weight (b.w.)) and FA (12 mg/kg b.w.) daily for 42 days. Group III, received oral doses of ASP (500 mg/kg b.w.) daily for 42 days. Group IV, received both NAC and FA, concurrently with ASP at the same doses, route and period of administration of the previous groups. Histological examination of the cerebral cortex of ASP-treated rats showed severe degenerative changes, especially in the nerve cells. Some of these cells appeared shrunken, irregular in shape, while the others appeared swollen and were surrounded by pericellular halos. Immunohistochemical and morphometric study of ASP-treated group revealed a weak B-cell lymphoma-2 (Bcl-2) immunoexpression in the cytoplasm of many cells, while intense positive immunoreaction for glial fibrillary acidic protein (GFAP) was observed in the cytoplasm and processes of astrocytes compared to control group with statistically significant difference (p < 0.001). Light microscopic results were confirmed by ultrastructural findings. However, NAC and FA in combination had an obvious protective effect against ASP-induced injury in the rat’s cerebral cortex. In conclusion, these results suggested that NAC combined with FA can ameliorate the toxic effect of ASP on the rat’s cerebral cortex.     

Organization of projections from the principal sensory trigeminal nucleus to the hypoglossal nucleus in the rat: an experimental light and electron microscopic study with axonal tracer techniques

Summary The organization of projections from the principal sensory trigeminal nucleus (PSN) to the hypoglossal nucleus (XII) in the rat was investigated at the light and electron microscopic level with retrograde and anterograde axonal tracer techniques. Microiontophoretic injection of horseradish peroxidase (HRP) into XII resulted in retrograde labeling of neurons confined to the dorsal one-third of the PSN. Labeled neurons were found bilaterally, although a clear preponderance for ipsilateral distribution was evident. Most labeled neurons were found in the medial one-third and caudal two-thirds of the PSN. Labeled neurons were large (30–50 m), round-to-pear shaped multipolar cells with dendrites oriented primarily in the mediolateral direction. At the electron microscopic level, HRP reaction product was found throughout the cytoplasm of soma and processes of PSN projection neurons. The ultrastructural characteristics of these cells included a round, centrally placed nucleus and invaginated nuclear envelope, sparse Nissl bodies, numerous free ribosomes, mitochondria, lysosomes and Golgi complexes. Three to four main stem dendrites gradually tapered from the cell body and numerous synaptic terminals impinged upon soma and dendrites of labeled PSN neurons. Microiontophoretic injection of tritiated amino acids or HRP into the dorsal one-third of the PSN resulted in moderately dense terminal labeling in XII bilaterally, although mainly ipsilaterally. Terminal labeling was found diffusely throughout all regions of XII. Fibers descended the brainstem in the dorsolateral reticular formation and entered XII ventrolaterally. At the electron microscopic level, boutons containing HRP reaction product were found to synapse on dendritic processes in XII. Labeled boutons were characterized by clear, spherical vesicles and an asymmetrical postsynaptic density. The significance of these results are discussed in relation to oro-lingual motor behavior.Abbreviations used in Figures Am Nucleus ambiguus - Ax Axon - Den Dendrite - dlRF dorsolateral reticular formation - G Golgi apparatus - IO Inferior olive - ITR Intertrigeminal region - IV Fourth ventricle - Lf Lipofuscin - LRN Lateral reticular nucleus - mRF Medial reticular formation - mPB Medial parabrachial nucleus - MV Motor trigeminal nucleus - MVN Medial vestibular nucleus - Nu Nucleus - PSN Principal sensory trigeminal nucleus - Py Pyramid - R Ribosomes - RF Reticular formation - SC Subnucleus caudalis - SI Subnucleus interpolaris - SO Subnucleus oralis - SOL Solitary tract nucleus - STR Supratrigeminal region - T Terminal - TB Trapezoid body - VII Facial nucleus - VIIn Facial nerve - X Dorsal vagal nucleus - XII Hypoglossal nucleus     

Age-related alterations in the lacrimal gland of adult albino rat: A light and electron microscopic study

BackgroundAge related changes in the lacrimal gland are associated with alterations in the structural organization and functional response in the gland of diverse mammalian species. Dry eye syndrome is one of the most common ocular problems in the world especially in old age. It results when the lacrimal gland fails to secrete proteins and fluid in sufficient quantity or appropriate composition.Aim of the workThe present study is designed to demonstrate the influence of aging on the structure of the lacrimal gland of albino rat and to provide a morphological basis to explain the pathogenesis of the dry eye syndrome with ageing. It also aims to carry out a comparative analysis of age-dependent changes in male and female rats and to address how the lacrimal gland ages in each sex.Material and MethodsEighty albino rats were used in this study. The animals were divided into two age groups, young adult and senile. Tear secretion was measured using a modified Schirmer test. Corneal impression cytology of the anesthetized rats was done. The glands were subjected to gross morphologic examination, microscopic examination using H&E, PAS, Masson's trichrome and Giemsa stains. Electron microscopic examination was done in addition to quantitative histomorphometric estimations included acinar density, ductal count and mast cell count.ResultsLight microscopic examination of the lacimal glands of the senile rats revealed different pathological changes. These included acinar, ductal as well as stromal changes. Electron microscope examination of the lacrimal gland of the senile group showed a decrease in the electron dense secretory vesicles, mitochondrial swelling and lipofuscin-like inclusions were frequently seen in the cytoplasm of acinar cells in senile rats.ConclusionThe structural changes in the lacrimal glands of senile rats were associated with reduction in tear secretion as well as alterations in corneal epithelium. Gender difference in lacrimal gland structure was recorded.     

Immunocytochemical localization of glutamic acid decarboxylase and substance P in the lateral cervical nucleus: a light and electron microscopic study in the cat

Using immunocytochemical technique, the light and electron microscopic localization of substance P and glutamic acid decarboxylase (GAD) immunoreactivity in the feline lateral cervical nucleus (LCN) has been investigated. A dense substance P labeling, confined mainly to boutons contacting dendritic profiles, was demonstrated in the ventromedial part of the LCN. GAD-positive boutons, frequently in contact with cell bodies, were found scattered throughout the nucleus. The results suggest that gamma-aminobutyric acid is an inhibitory transmitter in the LCN. The role of the substance P is unclear. Its distribution, however, supports the concept of a separate function of the ventromedial part of the LCN.     

Blood vascular beds of rat adrenal and accessory adrenal glands, with special reference to the corticomedullary portal system: a further scanning electron microscopic study of corrosion casts and tissue specimens

Blood vascular casts of the rat adrenal glands were observed with a scanning electron microscope. The cortical capillary plexus drains, through the corticomedullary venous radicles, into the subcortical veins continuous with the medullary collecting veins. The medullary capillary plexus drains into the corticomedullary venous radicles, subcortical veins and medullary collecting veins. No portal vessel was noted between the cortical and medullary capillaries. These findings indicate that the cortical blood rich in glucocorticoids preferentially and continuously flows into the corticomedullary venous radicles, subcortical veins and medullary collecting veins all three of which are fenestrated in type, and also suggest that the vascular route from the cortical capillaries to the medullary collecting veins functions as a substitute for the portal system, controlling the biosynthesis of catecholamines in the adrenal medulla. The vascular bed of the accessory adrenal gland (extra-adrenal cortical or chromaffin body) is sometimes annexed to that of the adrenal gland. On rare occasions, the vascular beds of the extra-adrenal cortical and chromaffin bodies fuse with each other. Additional scanning of tissue samples confirmed the direct drainage of cortical capillaries into the medullary veins and also the endothelial fenestrations of these capillaries and veins.     

Light and electron microscopic study of omental milky spots in New Zealand Black mice, with special reference to the extramedullary hematopoiesis

Omental milky spots are especially large and numerous in New Zealand Black (NZB) mice, which are known to develop spontaneous autoimmune diseases. We investigated omental milky spots in NZB mice by light and electron microscopy. The milky spots were composed of abundant lymphocytes/plasma cells with macrophages, neutrophils, eosinophils, megakaryocytes, and various stromal cells. In addition, clustered neutrophils in various maturation stages with occasional mitotic figures were frequently present in the milky spots: apparent neutrophilic myelopoiesis was present. The presence of megakaryocytes was sporadic. Considering the giant size of megakaryocytes, their direct migration into the milky spots from the bone marrow or spleen seems improbable. Thus, the presence of megakaryocytes was interpreted as probable megakaryopoiesis. Erythroblasts were not contained in the milky spots. These findings seem to indicate that the milky spots in NZB mice represent a special type of lymphoid tissue with active neutrophilic myelopoiesis and probable megakaryopoiesis. Reticulum cells in the milky spots in NZB mice had well-developed dense bodies consisting of clustered parallel tubules that showed a hexagonal array. However, the biological significance of these cells remains unknown.     

Organization of the fibrous connective tissue of the fallopian tubes in fertile and climacteric periods: a scanning electron microscopic and stereologic study

The extracellular matrix (ECM) of the fallopian tubes is subject to several changes due to hormonal influences and aging. However, there is a lack of studies regarding its arrangement in older women. We aimed to analyze the organization of ECMcomponents, including collagen and elastic fibers, in the fallopian tube’s ampulla from young and old women by means of scanning electron microscopical and stereological methods. Twenty-one samples were analyzed: 12 from female cadavers in a fertile age (G1) and 9 from the climacteric period (G2). Masson’s trichrome stain was used to observe collagen and smooth muscle, while Weigert’s Fuchsin-Resorcin was employed to observe elastic fibers. Statistical analysis was performed by the Wilcoxon-Mann-Whitney test with the aid ofthe R^© software. The tissue was also fixed for scanning electron microscopic analysis in a modified Karnovsky solution and the three-dimensional organization of fibrous connective tissue was observed and compared. Statistically significant differences (P < 0.01) were found in all stereologic comparisons of the extracellular matrix between the groups, which revealed a higher volumetric density of the fibrous tissue in the climacteric group. Scanning electron microscopy showed degenerative alterations of extracellular matrix. According to our results, aging caused significant changes to the elements of the extracellular matrix and the smooth muscle of the fallopian tubes.     

Argentaffin endocrine carcinoma (carcinoid) of the pancreas with concomitant breast metastasis: an immunohistochemical and electron microscopic study

A pancreatic carcinoid tumor that metastasized to the breast is reported. The breast tumor was originally diagnosed as adenocarcinoma of the breast. Silver impregnation revealed the presence of argentaffin cytoplasmic granules. Immunocytochemical studies demonstrated immunoreactivity for serotonin but not for lactalbumin, a marker for breast epithelial cells. These features, together with the electron microscopic observation of pleomorphic secretory granules, permitted recognition of the tumor as metastatic carcinoid. This report illustrates the importance of the combined histochemical, immunocytochemical, and electron microscopic studies of breast tumors with a carcinoid pattern.     

A light and electron microscopic analysis of the convergent insular cortical and amygdaloid projections to the posterior lateral hypothalamus in the rat, with special reference to cardiovascular function

The synaptic organization between and among the insular cortex (IC) axons, central amygdaloid nucleus (ACe) axons and posterolateral hypothalamus (PLH) neurons was investigated in the rat using double anterograde tracing and anterograde tracing combined with postembedding immunogold analysis. After ipsilateral injections of biotinylated dextran amine (BDA) into the IC and Phaseolus vulgaris-leucoagglutinin (PHA-L) into the ACe, the conspicuous overlapping distribution of BDA-labeled axon terminals and PHA-L-labeled axon terminals was found in the PLH region just medial to the subthalamic nucleus ipsilateral to the injection sites. At the electron microscopic level, approximately two-thirds of the IC terminals made synapses with small-sized dendrites and the rest did with dendritic spines of the PLH neurons, whereas about 79%, 16% and 5% of the ACe terminals established synapses with small- to medium-sized dendrites, somata, and dendritic spines, respectively, of the PLH neurons. In addition, the IC axon terminals contained densely packed round clear vesicles and their synapses were of asymmetrical type. On the other hand, most of the ACe terminals contained not only pleomorphic clear vesicles but also dense-cored vesicles and their synapses were of symmetrical type although some ACe terminals contained densely packed round clear vesicles and formed asymmetrical synapses. Most of the postsynaptic elements received synaptic inputs from the IC or ACe terminals, and some of single postsynaptic elements received convergent synaptic inputs from both sets of terminals. Furthermore, almost all the ACe terminals were revealed to be immunoreactive for gamma-aminobutyric acid (GABA), by using the anterograde BDA tracing technique combined with immunohistochemistry for GABA. The present data suggest that single PLH neurons are under the excitatory influence of the IC and/or inhibitory influence of the ACe in the circuitry involved in the regulation of cardiovascular functions.     

Glycogen-rich clear cell carcinoma of the breast: a solid variant with mucus. A light microscopic, immunohistochemical and ultrastructural study of a case

The light microscopic, immunohistochemical and ultrastructural features of a clear cell carcinoma of the breast have been studied. Both intraductal and invasive components were found. Histochemistry showed large amounts of intracytoplasmic glycogen and sparse neutral mucin in the tumour. The tumour cells were stained by antisera to carcinoembryonic antigen, keratin and epithelial membrane antigen, but not by antisera to alpha-lactalbumin, desmin or vimentin. Ultrastructurally, the epithelial derivation of the tumour was confirmed. Only a few intracytoplasmic lumina were demonstrated. The tumour was classified as a mucin-containing variant of glycogen-rich, clear cell carcinoma of the breast.     

Carcinoma of the breast with metaplasia to chondrosarcoma: a light and electron microscopic study

Two carcinomas of the breast containing large areas of sarcomatous tissue were studied by light and electron microscopy. In one of these, the sarcomatous element was frankly cartilaginous and in the other, predominantly myxoid but with small cartilaginous-looking foci. By light microscopy, a highly suggestive metaplastic transition could be traced from cells within the epithelial nests to those within the sarcomatous lobules. Ultrastructurally, cells in the former region showed epithelial characteristics and those in the latter region, mesenchymal and/or cartilaginous features. The carcinomatous cells contained desmosomes and formed intercellular spaces lined by microvilli; a few cells showed prominent profiles of rough endoplasmic reticulum. In the first case, the cells in the immediate vicinity of the epithelial nests and those in the fully developed cartilaginous regions showed a progressive dilatation of their endoplasmic reticulum to form large sac-like structures filled with a finely granular and floccular material. The intercellular matrix was electron lucent and contained scattered dense particles, fibrillo-granular material and collagen fibres. Condensation of this material at some distance from the cell resulted in the formation of lacunae. In the second case, the cells in the myxoid areas also showed prominent dilatation of endoplasmic reticulum.     

Microcirculation of the rat pancreas, with special reference to the insulo-acinar portal and insulo-venous drainage systems: a further scanning electron microscope study of corrosion casts.

Microcirculation in rat pancreas was studied by scanning electron microscopy of resin vascular casts and by light microscopy of India ink-injected and sectioned tissue samples. In the scanning survey of the casts, islets larger than 30 microns in diameter counted no less than 400 in the adult rat pancreas. They were located either in the exocrine lobules (intralobular islets, counting 210 or more), or in the interlobular tissue spaces and along the secretory ducts (extralobular islets, 190 or more). Every islet received arterial blood via one or more proper arterioles. These afferent vessels first divided in the peripheral zone of the islet consisting of A and D cells and later extended deeper to form a capillary network in the islet core consisting of B cells. Blood originating from this capillary network left the islet via efferent vessels. This microvascular pattern may favor the regulation by A and D cells over the secretory activity of B cells. The intralobular islets gave their efferent vessels to the capillary bed of the exocrine tissue of the lobule, thus forming an insulo-acinar portal system. When the lobule was relatively small in size, superfluent blood was led directly to veins via insulo-venous drainage vessels. The intralobular islets sometimes issued one or more long translobular portal vessels reaching adjacent lobules. The extralobular islets issued either insulovenous vessels draining to interlobular veins, or extralobular insulo-acinar portal vessels supplying adjacent lobules.     

Kappa opioid receptors are expressed by interneurons in the CA1 area of the rat hippocampus: a correlated light and electron microscopic immunocytochemical study

A local GABA-system is known to have a mediatory function between several afferents and the principal cells of the hippocampus. This study examines the distribution and fine structure of kappa opioid receptor-immunoreactive elements in the CA1 subfield and reveals some new aspects concerning the structural basis of opioid-GABA interaction in the rat hippocampal formation. Kappa receptors were visualized immunocytochemically with a previously produced and characterized monoclonal antibody, the mAb KA8 (Maderspach, K., Németh, K., Simon, J., Benyhe, S., Szûcs, M., Wollemann, M., 1991. A monoclonal antibody recognizing kappa-, but not mu- and delta-opioid receptors. J. Neurochem. 56, 1897–1904). The antibody selectively recognizes the kappa opioid receptor with preference to the kappa₂ subtype. Neuronal cell bodies, proximal dendrites and occasionally glial processes surrounding neuronal perikarya were labelled in the CA1 area. The immunopositive cells were present mainly in the stratum oriens, followed by the stratum pyramidale in a rostrocaudally increasing number. Their shape was fusiform, or multipolar. Occasionally kappa receptor-immunoreactive boutons surrounding weakly immunopositive somata were also observed. Electron microscopy of immunopositive neurons showed that the DAB labelling was intensive in the perinuclear cytoplasm. The widths and electron densities of the postsynaptic densities of some axosomatic synapses were remarkably increased. Similar increase of postsynaptic densities were observable at some axodendritic and axospinous synapses. On the basis of their location and fine structural properties the labelled cells are suggested to be GABAergic inhibitory interneurons, probably belonging to the somatostatinergic sub-population. The axons of these inhibitory interneurons are known to arborize in the stratum lacunosum-moleculare where the entorhinal afferents terminate. A modulatory effect of opioids on the entorhinal input, mediated by somatostatinergic interneurons is suggested