1. Patterns of respiratory neuronal activity were examined in pentobarbitone anesthetized adult cats in a circumscribed area of the ventrolateral medulla, which has previously been defined as the pre-Bötzinger complex (pre-BOTC) from electrophysiological and morphological criteria in the brain stem-spinal cord preparation of the neonatal rat. The pre-BOTC has been proposed to play a critical role in respiratory rhythm generation in mammals, but electrophysiological properties of the region have not been thoroughly characterized in the adult brain stem in vivo. 2. From intra- and extracellular recordings, we verified the existence of a well-defined zone with a distinct profile of neuronal activity between the rostral Bötzinger complex containing expiratory neurons and the more caudal medullary pool of inspiratory neurons of the ventral respiratory group (VRG) in the para-ambigual region. This zone corresponds to the pre-BOTC. It was characterized by a concentration of the various types of respiratory neurons, particularly those proposed to be involved in respiratory phase transitions, including neurons discharging immediately before the onset of inspiratory phase activity (pre-inspiratory neurons), early-inspiratory, and postinspiratory neurons. The majority of these neurons were presumed interneurons because they were not antidromically activated by spinal cord or cranial nerve stimulation. 3. The locus of the pre-BOTC corresponded histologically to the rostral part of the nucleus ambiguus and ventrolateral reticular formation. It was located caudal to the retrofacial nucleus and rostral to the lateral reticular nucleus, extending 3.0-3.5 mm rostral to the obex, and 3.2-4.0 mm lateral from the midline. This location was homologous to that established in the neonatal rat. 4. Pre-inspiratory neurons (pre-I neurons) were specifically found in the pre-BOTC. Intracellular recordings from these neurons revealed two types of activity patterns. Type 1 of pre-I neurons exhibited a steady membrane depolarization during expiration and a steep membrane depolarization with a high-frequency burst of action-potential discharge during the phase transition from expiration to inspiration. This was followed by a decline of depolarization and spike discharge during the remainder of the inspiratory phase. A second type of pre-I neurons exhibited a secondary graded membrane depolarization and burst discharge during the late-inspiratory period. 5. Synaptic events were examined in other respiratory neurons during the 40-160 ms preceding the onset of phrenic nerve activity when pre-I neurons exhibited peak spike discharge. Early-inspiratory, throughout-respiratory, and postinspiratory neurons were disinhibited during this period, whereas stage-2 expiratory neurons exhibited a decrease in spike activity and repolarization.(ABSTRACT TRUNCATED AT 400 WORDS)
An in vitro brain stem-spinal cord preparation from last trimester (E13-E21) fetal rats, which generates rhythmic respiratory and locomotor patterns, is described. These coordinated motor patterns emerge at stages E17-E18. Synchronous rhythmic motor activity, not clearly characterized as respiratory or locomotor, can occur as early as E13. With this preparation, it is now possible to study the ontogenesis of circuits and cellular mechanisms underlying these critical movements.
\s=b\ Desmoplastic (neurotrophic) melanoma is a histologic variant of cutaneous melanoma that has a distinct clinical behavior. To better understand this behavior and to treat the disease more effectively, the medical records of 16 patients treated for this disease over a 12-year period were reviewed. Thirteen patients had head and neck lesions, the ear being a common site. The average thickness of the lesions was 5.75 mm. Six (46.2%) of 13 patients had local recurrence of disease. Only two patients (15.4%) developed regional node metastases. None of the patients with clinically NO desmoplastic melanoma were found to have positive nodes after elective neck dissection, regardless of the thickness of the primary lesion. Wide excision of the primary lesion with frozen section control of surgical margins and careful examination for the presence of perineural invasion is important in determining the extent of surgical resection.
The autopsies of 13 male homosexuals with acquired immune deficiency syndrome (AIDS) were reviewed. All patients had laboratory evidence of cellular immune dysfunction. The most common diagnoses made were disseminated cytomegalovirus infection in 12 patients and Kaposi's sarcoma in 10. All patients infected with cytomegalovirus had pulmonary compromise. The adrenal glands and gastrointestinal tract also were involved often by cytomegalovirus. Cytomegalovirus infection of organs uncommonly affected such as heart, meninges, cerebrum, and peripheral nerves was documented in two patients. Skin most frequently was involved by Kaposi's sarcoma, followed by gastrointestinal tract and lymph nodes. Two patients had visceral and/or nodal Kaposi's sarcoma with no skin compromise. Other important diagnoses were Pneumocystis carinii pneumonia, cryptosporidiosis, fungal infections, toxoplasmosis, and brain lymphoma. The cause of death was due to one or more infections in most patients. Kaposi's sarcoma did not contribute substantially to the cause of death, except in one patient with massive multifocal and multiorgan involvement.
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