Academic literature on the topic 'Chorda dorsalis'

AbstractTwo new species of the genus Carcharodiscus are described from southeastern Spain. Carcharodiscus procerus sp. n. is characterised by: a very slender (a = 52 - 62) body 1.67 - 2.17 mm long, lip region offset by constriction and 17 - 18 μm diam., anterior portion of the cheilostome 12 - 13× 7.0- 7.5 μm with abundant denticles on its walls, odontostyle 10 - 12 μm long or ca 66% of the lip region diam., presence of a dorsal cell chord behind the cardia, female genital system amphidelphic, vulva longitudinal and somewhat posterior (V = 52 - 58), presence of cuticular irregularities near the vulva area, tail rounded conoid (22 - 28 μm; c = 70 - 83; c′ = 1.0 - 1.2), and male unknown. Carcharodiscus olearum sp. n. is distinguished by its very slender (a = 51 - 55) and long (L = 2.36 2.79 mm) body, lip region offset by deep constriction and 22 - 27 μm in diam., anterior portion of the cheilostome 16.5- 18.0 × 8.0- 9.5 μm with abundant denticles on its walls, odontostyle 16.0- 17.5 μm long or 0.7 to 0.8 times the lip region in diam., presence of a dorsal cell chord behind the cardia, female genital system amphidelphic, vulva longitudinal and somewhat posterior (V = 50 - 58), tail rounded conoid (25 - 28 μm; c = 89 - 99; c′ = 0.8- 0.9), and male unknown. Carcharolaimus eximius is transferred to Carcharodiscus. A list of the species of the genus and key to their identification are also provided.

Sprague-Dawley rats are amongst the most widely used animals in biomedical research and malignant lymphoma has long been known to be a frequent neoplasm in these animals. A 9-month-old male control Sprague-Dawley rat from a toxicity study showed gelatinous material in the cranial cavity and dark, thickened cerebral meninges at necropsy. At microscopic evaluation of the temporal bone, neoplastic lymphocytes were seen invading several structures of the middle ear. The neoplastic cells appeared to extend from the marrow of the temporal bone, covered the dorsal part of the tympanic cavity wall, and surrounded and infiltrated the base of the tensor tympani muscle as well as the chorda tympani branch of the facial nerve. The lymphoma was generalized; neoplastic lymphocytes were also noted in numerous other tissues. Literature regarding neoplasms of the middle and inner ear in animals is scarce and, to our knowledge, this is the first report of a lymphoma involving the middle ear of a rat.

Among 703 professional pianists with medical problems in their hands seen by the author between 1981 and 2000, there were 27 patients who had interosseous muscle pain (23 women, 4 men; mean age, 30 yrs). The main symptom was dorsal hand pain during piano performance, especially when striking the keys with each finger rounded, mainly in the scale technique. Tenderness was noted in the deep part of the dorsal hand in the interosseous muscles, but not along or around the finger extensors. Patients sometimes complained of muscle weakness on abduction of the index, ring, and/or little fingers when performing octaves or chords on the piano keyboard. Resisted abduction and adduction testing of the fingers reproduced the pain which they experienced during or after performance. Pain occurred in the right hand in 10, left hand in 5, and bilaterally in 12. The pain was localized in the 4th and 5th interossei in 15 patients, in the 3rd and 4th in 14 patients; in the 2nd and 3rd in 11 patients; and in the 1st and 2nd in 1 patient.

The validity of the Antarctic species of the “Oikopleura gaussica group” (O. gaussica, O. valdiviae, O. drygalskii, and O. weddelli) is discussed. The characteristics of new material from South Georgia and the Bellingshausen Sea are compared with the original descriptions. We examined 495 specimens at different stages of maturity and concluded that the characters used to differentiate these species of Oikopleura have not enough weight to justify their separation. The morphological variations found were ascribed either to intraspecific variability and/or to the different degree of maturity of the specimens examined of a single species, Oikopleura gaussica. The main taxonomic characters for the identification of this species are: the particular way in which the flat triangular gonads surround the intestinal ball like a sheath, the equal size of the two lobes of the stomach, the oesophagus entering the postero-dorsal edge of the rounded left lobe of the stomach, the presence of oval and some times lobate oral glands, and the variable number of subchordal cells (4 to 14) arranged in a single row on the right (ventral) side of the chorda.