Thymic stromal cell specialization and the T-cell receptor repertoire

Ten years ago, we proposed a model for thymus function in which thymic epithelial cells are primarily responsible for imprinting major histocompatibility complex (MHC)-restricted specificity, and bone marrow-derived macrophages or dendritic cells are responsible for the induction of self-tolerance. Since then, transgenic and knockout models have allowed for a dissection of thymic stromal components in vivo, leading to a new understanding of their specialized functions. We have determined that with regard to class II-restricted CD4 T-cell development, two distinct subsets of thymic epithelium help shape the repertoire: Cortical epithelium appears solely responsible for positive selection, whereas a fucose-bearing subset of medullary epithelium is specialized for negative selection. This absolute separation of positive and negative selection into two distinct spatial and temporal compartments leads to a much simpler view of the process of repertoire selection. Finally, a novel view of the function of the thymic medulla is discussed.     

Enhanced period-peak analysis of electro-encephalograms using a fast sinc function

In an effort to reduce the memory space and processing time required by fast Fourier transforms, enhanced period-peak detection is investigated. The method is based on a combination of Fourier transforms and period-peak detection. The signal is considered as a train of truncated sinusoidal functions. Each truncated sinusoidal function is limited by two successive local extrema. The Fourier transform of the truncated sinusoidal function is a sinc function. The summation of these sinc functions yields an approximate frequency spectrum of the signal.     

Electron Microscopic Studies on IgA Nephropathy

We carried out electron microscopic studies on renal tissues from 9 patients with IgA nephropathy. Electron dense deposits were present in the mesangial area in all cases, subendothelial deposits in 4, and subepithelial deposits in only one. In basement membrane, segmental swelling and rarefaction of basement membrane substance were observed. In some cases the degenerated basement membrane substance protruded through the dilated endothelial fenestration into capillary lumina. Focal splitting, attenuation, mouse eaten appearance, and herniation of basement membrane were seen in a high incidence. Mesangial cells possessed well developed rough endoplasmic reticulums and polysomes. In the peripheral areas of mesangial cell cytoplasm, there was accumulation of electron dense substance and this was occasionally continuously present in the mesangial matrix. There was segmental swelling of endothelial cell cytoplasm, resulting in loss of fenestration. Epithelial cells had well developed rough endoplasmic reticulums and polysomes. Segmental foot process fusion was seen, and these processes, regardless of fusion, became electron denser in the area close to the basement membrane. Multivesiculated bodies were present in all cases in the epithelial cells and in 7 cases in the endothelial cells. Spherical microparticles were present in 3 cases in the urinary space or between the basement membrane and the epithelial cells.     

Elektrokardiographische Beobachtungen Über den Ablauf Einer Akuten Myokarditis Nach Grippe

Zusammenfassung Bei einem 21 jähr. Studenten, der zur Zeit einer Grippeepidemie eine Influenza durchgemacht hatte, traten 2 Wochen darauf zuerst kompletter Block mit Ohnmachtsanfällen, später nach Wiederherstellung der normalen Schlagfolge Störungen der Reizbildung und insbesondere der Reizausbreitung sowohl im Vorhof als auch in besonders ausgedehntem Maße innerhalb der Kammer auf, die auf eine diffuse Erkrankung des spezifischen Muskelsystems hinwiesen. Gleichzeitig bestanden Oppressionsgefühl auf der Brust, Mattigkeit, vorübergehend geringe Temperatursteigerungen. Alle diese Symptome werden als Grippe-Myokarditis gedeutet. Besonders wertvoll für die Erkennung dieses und ähnlicher Krankheitsbilder erweist sich die elektrokardiographische Untersuchung, die auch beim Fehlen anderer auf die Myokardaffektion bezüglichen Symptome, insbesondere auch von Arhythmien, durch den Nachweis von Störungen der Erregungsausbreitung in Vorhof oder Kammer Aufklärung über das Bestehen eines pathologischen Prozesses im Myokard zu geben vermag. Die frühzeitige Erkennung dieses Krankheitszustandes ist aber mit Rücksicht auf die notwendigen prophylaktischen Maßnahmen von großer Wichtigkeit.     

Action of the SP2–11 and SP3–11 fragments of substance P on rat peritoneal mast cells

The ability of the SP fragments SP_2–11 and SP_3–11 to release histamine from rat peritoneal mast cells has been compared with that of the whole peptide. SP_1–11 was found to be about 3.4 times more active than SP_2–11 and about 10.4 times more active than SP_3–11. The substance P antagonist [D-Pro⁴, D-Trp^7,9,10] SP_4–11 was equally effective at antagonizing the histamine releasing action of SP_1–11, SP_2–11 and SP_3–11. Benzalkonium chloride was found to be a competitive antagonist of SP and SP_3–11: the dissociation constants for the benzalkonium chloride-receptor interaction being about the same when either SP_1–11 or SP_3–11 was used as the agonist.     

A critique of impedance measurements in cardiac tissue

The specific impedance of cardiac tissue cannot be measured directly. Instead, the investigator obtains voltage and current measurements and places them into a model of the tissue's structure to infer the impedances of elements of the model. If the model fails to describe major aspects of the real tissue, the results may be worthless, although possibly self-consistent. In the literature of impedance measurement in cardiac tissue, only rarely is the model explicitly described; more commonly, the tissue model is adopted implicitly when equations giving the impedance in terms of voltage and current measurements are adopted. This paper examines the series of models that have been used in specific impedance measurements of cardiac tissue and shows how the same or similar measurements can accurately describe tissue impedivity or can lead to significant errors when inadequate models such as isotropic and anisotropic monodomains (although a part of work of historical merit) are used.     

Zur Kenntnis der Akuten Infektiösen Myokarditis

Zusammenfassung Es wird über zwei beobachtete Fälle von akuter Myokarditis berichtet, welche im Verlaufe bzw. im Anschlusse an eine akute Infektionskrankheit auftraten, bei denen die elektrokardiographisch festgestellten Störungen des Rhythmus und des Erregungsablaufes für die Stellung der Diagnose von großem Werte waren. In beiden Fällen trat nach einer kurzen Krankheitsdauer völlige Erholung ein.     

Changes in the retino-fugal pathways following cortical and tectal lesions in neonatal and adult rats

Summary Several months after unilateral removal of the striate cortex or superior colliculus, or both, in infant and adult rats the retinal projections were studied autoradiographically. The retinal projection areas in adult-operated animals were not different from those of unoperated controls, but aberrant pathways were found in the infant group. Following removal of striate cortex there was a small aberrant pathway to the lateral posterior nucleus of the thalamus (LP) and possibly to the pretectum. After removal of the superior colliculus there was a conspicuous aberrant projection to LP, which was even more prominent after combined removal of striate cortex and superior colliculus. The results support the proposal that when the normal field of termination is damaged, either directly by a tectal lesion or indirectly by a cortical lesion, axons grow and innervate LP, which has been partly deafferented by the lesion and which consequently possesses vacant synaptic space. Although the different consequences of early and late lesions may indicate that only infantile damaged terminals can redistribute themselves an alternative is that in infants many axons have not yet reached their normal terminal sites at the time of operation and that only those axons have the ability to continue growing and to form an aberrant pathways. The role of the aberrant pathway in vision is unknown.     

Time course and effective sites for inhibition from midbrain periaqueductal gray of spinal dorsal horn neuronal responses to cutaneous stimuli in the cat

Summary Inhibition of spinal dorsal horn neuronal responses to noxious (50 °C) skin heating by stimulation of the midbrain periaqueductal gray (PAG) was quantitatively investigated in cats anesthetized with sodium pentobarbital and nitrous oxide. Systematic variation of the interval between onset of PAG stimulation (PAGS) and onset of noxious skin heating revealed that a marked reduction of spinal unit heat-evoked discharges occured immediately upon onset of PAGS, and ceased immediately at offset of PAGS with a post-stimulation excitatory rebound. Stimulation at sites in both ventral and dorsal PAG produced inhibition, the strength of which increased sometimes in a linear manner with increasing strength of PAGS. Thresholds for the generation of descending inhibition were higher in dorsal than ventral PAG. PAGS also inhibited spinal unit responses to non-noxious skin stimulation (brushing of hairs). Descending inhibition from PAG is considered as a possible mechanism for analgesia produced by stimulation of PAG and other brainstem structures.The work was supported by a grant from the Deutsche Forschungsgemeinschaft (Zi 110)