The central vessel of the renal countercurrent bundles of two marine elasmobranchs--dogfish (Scyliorhinus caniculus) and skate (Raja erinacea)--as revealed by light and electron microscopy with computer-assisted reconstruction.

The renal countercurrent bundles of elasmobranch fish were studied by light and electron microscopy. The kidneys of the lesser spotted dogfish, Scyliorhinus caniculus Blainville, and the little skate, Raja erinacea Mitchill, were investigated. Three-dimensional reconstruction with computer assistance revealed the spatial association of the renal tubular segments and their relationships to each other, as well as to the microvasculature. Regular association between structures was assessed by quantification of contact points on histological sections. The bundles contain a hairpin loop of neck segment and the beginning of the proximal tubule, PIa. The limbs of this loop closely adhere to each other, and a second loop (the early distal tubule) coils around the first loop at the tip of the bundle. The collecting tubule runs between the two loops, and merges with the collecting duct inside the end portion of the bundle. A single lymph capillary-like vessel originates from a few blind-ended rami at the tip of the bundle and runs in close contact with the collecting tubule along the entire bundle. This central vessel merges via several side branches with the venous sinusoid capillaries of the peritubular blood circulation. Thereby the central vessel provides a channel for convective flow of NaCl-rich fluid unidirectionally to the venous portal system of the mesial tissue zone of the kidney. By the close spatial arrangement of the collecting tubule and the central vessel countercurrent exchange of urea from the collecting tubule urine to the fluid in the central vessel is feasible. Thus, the spatial organisation of renal tubular segments and the central vessel is considered to represent the morphological correlate to urea retention by the kidney of Elasmobranchii.

Expression of the CD15 epitope in the human magnocellular basal forebrain system.

The distribution of the carbohydrate epitope 3-fucosyl-N-acetyl-lactosamine (CD15) has been immunocytochemically evaluated in coronal paraffin sections through the magnocellular basal forebrain system--the nucleus basalis of Meynert, the nucleus of the diagonal band of Broca and the medial septal nucleus--of 202 human brains. The brains derived from differently aged controls (n = 54) and from patients suffering from organic brain diseases (n = 129) or psychiatric disorders (n = 19). In 30 cases dementia was clinically diagnosed. CD15 first appeared around birth when it became localized on singular astrocytes. The astrocyte number and process density steadily increased, and at approximately 12 years the typical adult-type pattern was acquired. Considerable variations in the expression patterns were noted with regard to the astrocyte number, the intensity in immunostaining and the process relations of CD15-positive astrocytes with the magnocellular neurons. In the light of these variations, and of conflicting additional changes in other areas of most diseased brains, it was difficult to correlate different intensities and patterns to specific diseases. The results, however, provide evidence for an increase in CD15 expression and in process network density of astrocytes in the lateral part of the nucleus basalis of Meynert in cases of Huntington's disease.

Evidence for subdivisions in the human suprachiasmatic nucleus.

The human suprachiasmatic nucleus was analysed by immunohistochemical demonstration of various substances in combination with 3-dimensional computerized reconstruction and video overlay facilities. In the human, the suprachiasmatic nucleus is not as compact as in the rodent. Its boundaries are not easily delineated using conventional stains, and it shows no obvious cytoarchitectonic structure. However, based on its chemoarchitecture, the human suprachiasmatic nucleus can be apportioned into five major subdivisions: Dorsal, comprising a crescent shaped mass of densely packed neurophysin/vasopressin-neurons as well as neurotensin-neurons, and also containing 3-fucosyl-N-acetyl-lactosamine (FAL)-positive neurons in its medial part. Central, occupying the core of the nucleus and consisting precisely of a region devoid of neurophysin/vasopressin neurons but demarcated by calbindin, synaptophysin, and a circumscribed cluster of vasoactive intestinal polypeptide-neurons and containing neurotensin neurons as well. Anteroventrally this division also contains some intermingled neurons positive for neurotensin, neuropeptide Y, somatostatin, and FAL. Ventral, extending from the anterior extreme of the preoptic recess caudolaterally to a field between the optic chiasm and the anteroventral margin of the supraoptic nucleus. This subdivision is specified by synaptophysin, calbindin, and substance P immunoreactivity and is almost free of glial fibrillary acidic protein. From its rostral portion, fibers immunoreactive for calbindin, vasoactive intestinal polypeptide, synaptophysin, and substance P protrude deeply into the optic chiasm. Medial, comprising a thin band between the subependymal zone and the dorsal subdivision, containing scattered somatostatin neurons. External, extending as a band around the dorsal and lateral borders of the nucleus, containing astrocytes expressing the FAL-epitope and scattered neurophysin/vasopressin and neurotensin neurons. These findings indicate that the human suprachiasmatic nucleus contains well-defined subdivisions with different, chemically specific, connections and provides a basis for comparing these subdivisions with the structure and function of subdivisions previously described for the suprachiasmatic nucleus in experimental animals. In addition, the findings strengthen the concept that the human suprachiasmatic nucleus generates and expresses circadian rhythms in a manner similar to that documented for the suprachiasmatic nucleus in experimental animals, and suggest that different subdivisions may subserve specific functional roles.

Formation of a morphologically complex system by peroxidase-positive lysosomal elements in human monocytes.

Computer-aided three-dimensional reconstruction of serial ultrathin sections revealed that freshly prepared monocytes from human blood contained endogenous peroxidase (PO) not only in cytoplasmic granules, but also in long contorted tubules and in complex elements, which consisted of both tubular and granular components. The various PO-positive elements formed an intricate system, which was separate from all other cytoplasmic structures, including the endoplasmic reticulum and the Golgi apparatus. Because the PO-positive elements in monocytes are known to be primary lysosomes, which are involved in host defense mechanisms, we suggest that the antimicrobial functions of human blood monocytes are exerted by functionally and morphologically diverse subcompartments of a complex system rather than by separate uniform granules.

[Quantitative determination of the vascular volume of the cat carotid body under normoxia, hyperoxia, hypoxia and hypercapnia (author's transl)]. / Quantitative Erfassung des Gefässvolumens des Glomus caroticum der Katze unter den Bedingungen der Normoxie, Hyperoxie, Hypoxie und Hyperkapnie.

The ratio vascular volume to total volume was quantitatively analyzed in the cat's carotid body in dependence on the oxygen content of respired air and arterial pO2, respectively. Under hypoxia the vascular volume was 50% higher than under hyperoxia. This connection was ascertained after both perfusion fixation and immersion fixation.