Given an abstract, generate a keyword (a noun phrase) that best describes the focus or contribution of the paper. Such keywords can be directly from the given abstract or outside it.

Ex Input:
Abstract: The accessory optic system (AOS), which was described as early as 1870 by Gudden, constitutes a distinct midbrain visual pathway in all classes of vertebrates. In non-primate mammals, retinal fibres of this system project to a set of three nuclei: the dorsal (DTN), the lateral (LTN) and the medial (MTN) terminal nuclei. Whereas all AOS cells respond to the slow motion of large visual stimuli, the neurons are tuned to complementary directions of movement: horizontal temporo-nasal direction for the DTN, vertical up and down for the LTN and vertical down for the MTN. It has thus been suggested that these nuclei establish a system of retinal coordinates for the detection of whole field motion. As the AOS provides direct and indirect pathways to both oculomotor and vestibular structures, each of these nuclei is thought to be an essential link in the co-ordination of eye and head movements in relation to movement within the visual-field. One problem for the generalization of this theory is that the medial terminal nucleus has never been found in primates. In this report we establish both the existence of this nucleus and its afferent input from the retina in all major groups of primates (prosimians, New and Old World monkeys and apes), indicating a common anatomical plan of organization of the AOS in mammals.

Ex Output:
Animal

Ex Input:
Abstract: To study respiratory muscle interaction in patients with occlusive apnea, diaphragmatic electromyogram (EMGdi) and gastric, pleural, and transdiaphragmatic pressures (Pga, Ppl, and Pdi, respectively) were studied in seven patients during non-rapid-eye-movement (NREM) sleep. Diaphragmatic force output, as assessed by Pdi, followed the periodic changes in EMGdi but during the occlusive phase the increase in Pdi was more than the increase in EMGdi. This increase in Pdi was essentially due to an increase in Ppl, since Pga and EMGdi had a linear relationship (r = 0.98, P less than 0.001) that did not change during the occlusive and ventilatory phases. Abdominal muscle recruitment evident in Pga and abdominal motion tracings during the occlusive phase when paradoxical rib cage motion was observed suggested that this increase in diaphragmatic efficiency was likely due to a change in diaphragmatic length-tension characteristics. These results demonstrate that, in patients with occlusive apneas, the diaphragm is the predominant respiratory muscle during NREM sleep and that its function is supported by abdominal muscle recruitment.

Ex Output:
Abdominal Wall

Ex Input:
Abstract: T lymphocytes differentiate and mature in the thymus. It is here that thymocytes with reactivities to self antigens are eliminated and those with specificities to 'altered' self-major histocompatibility complex (MHC) gene products are positively selected. The selections are presumably carried out on the basis of their T-cell antigen receptors (TcR). The genes of the alpha- and beta-chain T-cell antigen receptors have been cloned. A third T-cell specific gene capable of undergoing somatic rearrangement has also been identified; the role of this third gene is not known. An order of expression of gamma, beta, then alpha is found during T-cell ontogeny. But although alpha- and beta-chain messages are often functional, gamma transcripts are rarely functional in thymocytes or mature T cells. To define the sequential order of expression of these genes further and to continue the search for a possible role for the TcR gamma gene products, we investigated the expression of 'functional' alpha-, beta- and gamma-chain transcripts in young athymic mice. These mice express an undetectable amount (less than one in 8 X 10(5) spleen messages) of 'full-length' alpha- and beta-chain T-cell receptor transcripts, but an increased level of expression of 'full-length' gamma chain messages. Nucleotide sequence analysis of four gamma complementary DNAs show that all four gamma transcripts sequenced are functional. These findings suggest that gamma gene products may be important in a prethymic or extrathymic pathway and may represent a second type of T-cell recognition, possibly in a lineage in which alpha and beta genes are not used.

Ex Output:
Aging