Chicken arachnoid granulations: a new model for cerebrospinal fluid absorption in man.

Cerebrospinal fluid (CSF) absorption was investigated chicken and rat using infusion tests into the cisterna magna. Data were analysed according to a mathematical model by Johnson et al. Results in rat predicted a predominant lymphatic mechanism, which was confirmed by rapid outflow of X-ray contrast media into the olfactoric mucosa. In contrast, dynamics measurements suggested CSF drainage via arachnoid granulations in chicken. CSF spaces along the optic nerve were contrasted radiographically resulting in venous drainage. Electron microscopically, villus-like structures were found at the distal optic nerve connecting the subarachnoid space with accompanying veins, resembling human arachnoid granulations. We hypothesize that CSF absorption through arachnoid villi in microsmatic chicken reflects the situation in man very well.

Breakdown of the meningeal barrier surrounding the intraorbital optic nerve after experimental subarachnoid hemorrhage.

PURPOSE: The intraorbital optic nerve sheath meninges contain a perineural subarachnoid space lined by meningeal cell layers and intercellular fibrous tissue. We sought to determine whether functional or structural characteristics, or both, of the optic nerve sheath are influenced by the increased intracranial pressure after the rupture of cerebral aneurysms. METHODS: We infused the great cisterns of cats with either x-ray contrast medium or autologous blood. The cisternal infusions were done under the experimental condition of a sudden 2.5-minute increase in intracranial pressure similar to that recorded after the rupture of cerebral aneurysms in humans. RESULTS: Digital subtraction radiographs of the optic nerves taken during the cisternal infusion of contrast medium at the start showed the opacification of the optic nerve subarachnoid space. After 2 minutes, the contrast medium leaked into the orbit, indicating the breakdown of the meningeal fluid barrier. Ultrastructural investigation of the optic nerve sheath after high-pressure cisternal infusions showed the arachnoid cell layers scattered. The flattened arachnoid cells displayed mainly intracellular and some intercellular, porelike openings. After infusion of blood into the great cistern, erythrocytes were found within porelike openings of the arachnoid cells. CONCLUSIONS: The meningeal fluid barrier of the optic nerve sheath can be destroyed by pressure changes associated with subarachnoid hemorrhage. This disruption might be regarded as a natural optic nerve sheath fenestration that allows outflow of cerebrospinal fluid into the orbit to protect the optic nerve from increased intracranial pressure after aneurysmal rupture.

Ultrasound anatomy: a practical teaching system in human gross anatomy.

Cross-sectional imaging such as CT and ultrasound have rapidly developed a central role in diagnostic medicine. However, cross-sectional anatomy has lagged behind in its incorporation into medical school education, often leaving students without even a basic understanding of these images. At Hannover Medical School, we have successfully combined hands-on ultrasound workshops performed by medical students on other students with our anatomy course. This interactive component of our anatomy courses improves our students' understanding of clinical anatomy and introduces them to ultrasound imaging.

Lymph heart musculature in birds.

Development and innervation of the lymph heart musculature of chicken, emu, rhea, and duck was studied by electron microscopy at post-hatch ages from 3 days to adulthood. Development of innervation was monitored by acetylcholinesterase staining. Horseradish peroxidase was used to determine the extent of the transverse tubule network. Chickens were unusual among these birds in that lymph heart myocytes had already undergone a definitive differentiation and degeneration by 3 days. In ducks and ratite birds, lymph heart myocytes more slowly but progressively differentiate a cytomorphology that does not conform in all characteristics to cardiac or skeletal muscle and even resembles in some aspects, smooth muscle. Myofibrils become the dominant cytoplasmic structure, transverse tubules form "internal couplings" with agranular reticulum cisternae, and "external couplings" are formed between myocytes at myomyal junctions. The myomyal junctions also contain AChE-positive reaction product and some subplasmalemmal vesicles that lack a dense core. The lymph heart myocardium of ducks of 2 weeks demonstrated mitotic figures. In adult ducks the myosatellite cell numbers diminish and a characteristic pattern of myocyte degeneration appears. In juvenile ducks and ratites some myocytes differentiate to conductile cells, much as the conductile myocytes and myofibers of the blood heart. The lymph heart innervation is described, and the role of nerve in differentiation and maintenance of myocyte morphology in the lymph heart is discussed.

The bursa cloacae (Fabricii) of Struthioniforms in comparison with the bursa of other birds.

The late embryonic and postembryonic genesis of the bursa cloacae (Fabricii) of struthioniforms and other birds is described and discussed. The bursa of ostrich and emu is a wall organ of the caudal cloacal chamber. The bursa of rhea is, like the bursa of Gallus, a cranial appendix of the proctodeum. Lobuli bursales of struthioniforms are composed of a peripheral pars lymphoepithelialis (PLE) and a central pars lymphoreticularis (PLR). By contrast, lobuli bursales of Gallus are composed of a peripheral PLR and a central PLE. The fine structure of the bursa of struthioniforms is described. Other than in Gallus, the apical cell association of the PLE of struthioniforms shows secretory granules. This study thus far does not answer in detail the question of how the imprinting mechanism of the B-lymphocytes operates. It is assumed that they are imprinted in the PLE. Postcapillary venules in the PLR are responsible for the transport of B-lymphocytes. Hormonal bursectomies have been made to get information about the involution of the bursa of struthioniforms. In these species, involution means a gradual metaplasia while in Gallus it means a complete degeneration of the bursa.

Detection of antibody in transparent fluid of semen and in serum after inoculation of Newcastle disease vaccines by different routes.

Cocks were immunized with live and inactivated Newcastle disease virus (ND) vaccines by different routes. Haemagglutination-inhibiting (HI) antibody activity could be detected in transparent fluid of semen (TF) of these birds except after intracloacal application of an inactivated ND vaccine. Although a comparative study of the HI antibody course in both serum and TF showed similarities after primary and secondary vaccinations, morphological studies of the TF-producing organ suggest the development of local immunity.

A morphological study of antibody transport in the transparent fluid flowing form the lymph-folds of the copulatory organ into the cloacal lumen of the cock (Gallus domesticus).

The lymph of the copulatory organ of the cock is produced mainly in the lymphobulbus phalli. The lymph fluid passes the secretory duct with its branching lymph capillaries and discharges into the lymph-fold. From here, it is released into the interstitial tissue through gaps of the lymph capillaries but also through the intercellular spaces between the endothelial cells of the lymph capillaries. A minor portion of the lymph is produced also in the lymph-fold from where it is transported in the interstitial tissue either by transfer vesicles of the circulatory blood capillaries or by pores and fenestrae of the transudatory blood capillaries. During the erection of the copulatory organ the lymph is pressed through the intercellular spaces of the epithelial covering the lymph-fold which is cylindrical and multistratified in shape. From here, it reaches the cloacal lumen in the form of transparent fluid (TF). TF was collected by different methods. It contains immunoglobulins which arise from plasma cells of the lymph-fold. Juxtaluminally, the lymph passage takes place via zonulae pseudooccludentes. The epithelial covering secretes a mucoid substance which is added to the TF prior to its following the spermatic phase as the final fraction of the ejaculate. Plasma cells and lymphocytes migrate along the lymph flow in the intercellular spaces of the epithelial covering of the lymph-fold. After an experimental application of antigen the sub- and intraepithelial cells and lymphocytes increase in number with their portion of active cells exceeding the less active ones. The increase coincides with the increase in antibodies detected in the TF where they may cause a local immunisation.