Hans Ditrich

Afferent portal venous system in the mesonephros and metanephros of chick embryos: development and degeneration.

In the chick embryo, both mesonephros and metanephros have a renal portal system. The classical literature gives uncertain answers about the development and degeneration of the meso‐ and metanephric portal venous system. Some mesonephric vessels present angiogenic processes to colonize the metanephros, while others show signs of degeneration and disappear together with the mesonephros. The adult avian kidney has a conspicuously placed valve, the renal portal valve. The development of this functionally important renal portal valve has not yet been studied in detail.

Heat‐producing organ of the swordfish (Xiphias gladius): A modified eye muscle

In swordfish (Xiphias gladius), the dorsal rectus muscle of the eye (M. rectus dorsalis) is partly differentiated for heat production similar to brown adipocytes. Other parts of the dorsal rectus show a typical muscular structure. This modified muscle and its anatomical relationships to neighboring organs were investigated using macroscopic dissections, light and transmission electron microscopy, nuclear magnetic resonance tomography, and scanning electron microscopy of vascular corrosion casts. The ophthalmic artery off the efferent pseudobranchial artery supplies the dorsal rectus muscle. The ophthalmic artery branches in a brush‐like manner as it enters the origin of the muscle. In this region, numerous arterioles and venules are arranged in parallel, suggesting a countercurrent heat exchange mechanism. Thermogenic cells, morphologically similar to brown adipocytes, surround small vascular branches in the middle of the muscle. Muscular cells also extend into this area. The vessels then divide into a tree‐like pattern, forming an extensively capillarized area near the surface of the muscle at the basisphenoid bone. The basisphenoid is reduced to a thin connective tissue layer in this area, hence facilitating thermal transfer between the blood in the muscle and the brain base. The Tela lymph‐adiposa surrounds the brain with large masses of fat. Additionally, voluminous masses of periocular fat provide thermal insulation lateral to the lateral rectus muscle of the eye. It is suggested that this system for raising the temperature of areas of the brain a few degrees above ambient temperature allows an optically oriented predator such as the swordfish to respond to optical input in cold water more efficiently. J. Morphol. 234:89–96, 1997.

Renal vasculature and uriniferous tubules in the common iguana

The pattern of vascular supply and the histology of uriniferous tubules of the kidney in the common iguana were studied by light microscopy of semithin sections and by scanning electron microscopy of microcorrosion casts. The corrosion casts showed a strongly developed renal portal system that forms an extensive capillary network throughout the kidney. Glomeruli are numerous and have a capillary pattern consisting of three to six loose coils of capillaries intercalated between afferent and efferent arterioles. Glomeruli are ovoid in shape and relatively small (mean diameter of the casts: 67 ± 19 μm in short axis and 79 ± 18 μm in long axis). Each glomerulus has a single afferent arteriole and efferent arteriole. The length and volume of the glomerular capillaries per unit volume of renal corpuscle are 0.0029 ± 0.0008 μm/μm3 and 0.321 ± 0.077, respectively. A short neck segment consisting of low epithelial cells is interposed between Bowmans capsule and the proximal tubule. A close association between the distal tubule and the glomerular hilus can be interpreted as a juxtaglomerular apparatus.

Brain macrophages in cerebellar cell cultures

Brain macrophages were studied in dispersed monolayer cultures of post-natal mouse cerebella. The phagocytotic activity, binding of immunoglobulins, presence and characteristics of nucleoside diphosphatases as well as argentophilia and lipid distribution were tested, with results similar to those for brain macrophages in vivo and for other macrophages in vitro. The macrophages in the cultures showed four different forms with continuous transition from one form to the following and subsequent cell death. No signs of proliferation of this cell type was found. Dynamic investigations showed repelling of neuronal growth cones by certain macrophages, resulting in the formation of areas devoid of neuronal and glial processes around the macrophages. An in vitro model for these cells, described by other authors as being important in post-natal reshaping of the brain, is presented and investigated in this study.

The vascular structure of the kidney of the neotenous axolotl and its metamorphosed counterpart

The renal vascular and glomerular structures of the kidney of neotenous and experimentally metamorphosed axolotls (Ambystoma mexicanum: Amphibia, Urodela) are investigated using light, transmission electron, and scanning electron microscopy of critical‐point dried specimens and vascular corrosion casts. The blood vascular system of the kidney in the axolotl is generally similar to that in other urodeles. The glomeruli are comparatively large and distincly ovoid (mean size 267 × 201 μm). Glomerular endothelial nuclei frequently bulge into the vascular lumen. Whereas the lamina rara externa and the lamina densa are quite uniform in diameter, the lamina rara interna shows a very irregular thickness with frequent interposed cellular processes. In the thyroxine‐metamorphosed animals, the glomerular surface decreased by a factor of approximately 36%; this was mainly due to the reduction of the glomerular diameter in the direction from vascular to urinary pole. No significant degeneration or new formation of renal tubules was observed during or after metamorphosis. A notable relative decrease in renal volume (approx. 57%) in the metamorphosed forms can be attributed mainly to a reduction in interstitial volume.

Anatomy and use of the caudal spines in the aggressive behaviour of a surgeonfish (Osteichthyes: Acanthuridae)

We examined the anatomy of the lateral caudal spines of Acanthurus leucosternon and their use during intraspecific agonistic interactions. A. leucosternon can actively and independently erect its spines to a maximum of 80° from the sagittal plane through contraction of an epaxial erector muscle which does not directly insert on any part of the spine but in the cutis caudally of its anchoring basal plate. Maintenance of erection of the spine is achieved through the mechanical support of a prominent lateral apophysis of the 22nd vertebra. When presented with a model of a conspecific inside their territory both male and female A. leucosternon engaged in escalating aggressive activities and performed tailbeats with erected spines that lacerated the model. A similar escalation to the point of tissue damaging tailbeats could be elicited by introducing live fish to an aquarium containing a conspecific resident. Field and laboratory observations of A. leucosternon revealed that non‐experimental agonistic interact...

Scanning electron microscopy of vascular corrosion casts of the glomeruli of two species of turtles

Scanning electron micrographs of microcorrosion casts of the renal vascular system of Pseudemys scripta and Testudo hermanni show fairly well‐developed, round glomeruli in the former (mean diameter of casts: 83.1 μm) and fewer but bigger, ovoid glomeruli (mean diameter of casts: 111.1 μm/131.6 μm) in the more arid‐adapted. T. hermanni. Furthermore, the intrarenal development of the pertiubular capillary system differs in these two species. These relatively minor morphological differences correlate well with the major differences in the ecology of these species, as well as with physiological data on urine composition from the literature.

Endothelial nuclear bulging: Morphological evidence for an intraglomerular perfusion regulating mechanism in the axolotl

Kidneys of the Axolotl (Ambystoma mexicanum: Urodela, Amphibia) have been investigated by light and electron microscopy as well as microvascular corrosion casting. Numerous glomerular endothelial nuclei bulge into the glomerular capillary lumen. It is concluded that these cells virtually stop the blood-flow in the respective vessel by blockage of erythrocyte passage. A proposal for an intraglomerular regulation mechanism of capillary perfusion (and thus filtration) by endothelial isometric contraction in the Axolotl is made on the basis of morphological methods.

The transmission of the Black Death to western Europe: a critical review of the existing evidence

In 1347 the Black Death was introduced from the north-eastern coast of the Black Sea and the Sea of Asov towards southern and western Europe, where it then spread dramatically. A report by the Italian chronicler Gabriel de Mussis of the siege of Caffa (1345–47) is often credited as describing an early deployment of a “biological weapon”, thus triggering the “Black Death” in western Europe. He reports that Mongol troops threw plague victims into the city with catapults, thus contaminating the inhabitants. However, re-evaluation of historical, biological and epidemiological data indicates that the spread of the disease was probably an inevitable consequence of the intense trade relations along the coasts of the Black Sea and the Mediterranean. Therefore, the alleged catapulting of infected corpses would rather have been a marginal contribution to the diffusion of the disease (if it took place at all). The infection was subsequently spread by refugee ships via ports at Constantinople and along the Mediterranean trading routes and harbours towards Genoa, Marseille and Venice, thus initiating the Plague in Europe. The further propagation of the disease inland is still a matter of controversial discussions. However, epidemiological data indicate that the most essential animal vector for further distribution of the plague in central and northern Europe was probably the human louse (Pediculus humanis), instead of the oriental (or tropical) rat flea (Xenopsylla cheopis).

SEM-EDS Micro-Analytical Data from Enamel Samples of Cellini's Salt Cellar “Saliera”

Benvenuto Cellini’s salt cellar – the “Saliera” – was stolen from the Viennese Museum of Fine Arts (Kunsthistorisches Museum Wien – KHM) in 2003. This masterpiece of the Italian Renaissance was made between 1540 and 1543 and is unique in its kind. Although priceless, the assurance value has been estimated to 50 million Euros. Several hundreds of confession and blackmail letters were received in the days following the theft. Police investigators thus faced the problem to decide which traces to follow and which letters should be excluded from further investigation as hoaxes or coming from copycats.