In this study, we examined the usefulness of arterial blood gas variables, as changed by the hypoxic stimulus, in discerning various experimentally-induced conditions of diaphragm weakness in anesthetized cats. We defined three experimental situations (models): (i) intact muscle, statistical Class I, (ii) four degrees of muscle dysfunction (after sequential diaphragm denervation), Classes II-V, and (iii) entirely paralyzed muscle, Class VI. Responses to a hypoxic stimulus in the above-mentioned conditions were evaluated by using the methods of the pattern recognition theory. We found that before the hypoxic stimulus, with partial but of different severity denervation of the diaphragm, the k-nearest neighbor classifier (k-NN) assigned 100% of the classified cases to Class II (one phrenic nerve rootlet cut). In contrast, during hypoxia only 67% of cases were assigned to Class II, the remaining being spread throughout other classes of muscle weakness. When one limits the procedure to the extreme classes: Class I (intact diaphragm) and Class VI (totally denervated diaphragm), the k-NN picks out 33% and 50% cases of bilateral diaphragm paralysis before and during hypoxia, respectively. We conclude that any remaining innervations of the diaphragm ensure the functionally optimal level of lung ventilation that may waver when hypoxia develops.
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Two new Sarcocystis species found in muscle fibres of the diaphragm of a hippopotamus in South Africa are described by light and electron microscopy. Sarcocystis hippopotami sp. n. forms macrocysts (4-10 x 0.66-1.10 mm) with a parasite-induced encapsulation of the host muscle fibre in which the plasma membrane of the latter remains unaltered. The sarcocyst wall represents a new ultrastructural type, characterized by thumb-like villar protrusions with a compact central bundle of microtubules in the core. The bradyzoites (15.6 x 2.2 µm) are straight and slender. Sarcocystis africana sp. n. forms round microcysts (diameter 0.5-0.7 mm) representing a new type of the cyst wall ultrastructure which is characterized by irregularly semicircular or rectangular villar protrusions with granular and fibrillar content. The bradyzoites (9.5 x 3.1 µm) are straight and plump.
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