Paul Hsu

Role of Inhibition in Respiratory Pattern Generation

Postsynaptic inhibition is a key element of neural circuits underlying behavior, with 20–50% of all mammalian (nongranule) neurons considered inhibitory. For rhythmic movements in mammals, e.g., walking, swimming, suckling, chewing, and breathing, inhibition is often hypothesized to play an essential rhythmogenic role. Here we study the role of fast synaptic inhibitory neurotransmission in the generation of breathing pattern by blocking GABAA and glycine receptors in the preBötzinger complex (preBötC), a site essential for generation of normal breathing pattern, and in the neighboring Bötzinger complex (BötC). The breathing rhythm continued following this blockade, but the lung inflation-induced Breuer–Hering inspiratory inhibitory reflex was suppressed. The antagonists were efficacious, as this blockade abolished the profound effects of the exogenously applied GABAA receptor agonist muscimol or glycine, either of which under control conditions stopped breathing in vagus-intact or vagotomized, anesthetized, spontaneously breathing adult rats. In vagotomized rats, GABAAergic and glycinergic antagonists had little, if any, effect on rhythm. The effect in vagus-intact rats was to slow the rhythm to a pace equivalent to that seen after suppression of the aforementioned Breuer–Hering inflation reflex. We conclude that postsynaptic inhibition within the preBötC and BötC is not essential for generation of normal respiratory rhythm in intact mammals. We suggest the primary role of inhibition is in shaping the pattern of respiratory motor output, assuring its stability, and in mediating reflex or volitional apnea, but not in the generation of rhythm per se.

Latino physician supply in California: sources, locations, and projections.

Purpose To determine the number of Latino physicians in California, identify the schools and countries where they were educated, determine the percentage located in Latino areas, and project the supply of Latino physicians to 2020. Method From a 1999 list of 74,345 licensed physicians, the authors identified Latino U.S. medical graduates (USMGs) by “heavily Hispanic” surnames and Latino international medical graduates (IMGs) by country and school of graduation. The 1999 license addresses of all physicians in Los Angeles County were analyzed against 1998 Latino-population data by zip code. A baseline projection of the supply of Latino physicians was based on the ten-year (1986 to 1995) average annual production of Latino physicians educated in California, out of state, and in Latin America. A worst-case projection assumed the continuation of recent trends: a 32% decrease in California-educated Latino USMGs, a 19% decrease in out-of-state Latino USMGs, and a reduction of Latino IMGs to five per year. Results In 1999, 3,578 Latino physicians comprised 4.8% of all Californian physicians. In contrast, Latinos made up 30.4% of the states population. Latino physicians were more likely than non-Latinos to have addresses in a heavily Latino zip code. In the baseline projection, while the overall supply of Latino physicians will increase by nearly 30% by 2020, that growth will be dwarfed by the 74% growth in the Latino population over the same time. In the worst-case projection, the actual number of Latino physicians will decrease from the 1999 figure of 3,578 to 3,448 by 2020, while the Latino population continues to grow. Conclusions (1) The Latino USMG supply must be markedly increased in the number of first-year matriculants in both California and out-of-state schools. (2) The issue of Latino IMGs requires special attention, and may provide a temporary solution to the Latino physician shortfall. (3) Non-Latino physicians need to be prepared to be culturally effective with a large and growing Latino patient population.

An expert system based preventive medicine examination adviser.

Periodic preventive medicine examinations generally rely on a standardized approach. In addition, they are often performed by physicians with only limited training in preventive medicine. Evaluation of a corporate-based program led to the prototype development of an artificial intelligence (AI)-based expert system to collect information from employees and make very specific recommendations for primary practitioners. Unique features include the customizing of questions for each subject and the selection of information to be acquired, both based on answers to previous questions. Recommendations are highly person specific and fall into four categories: laboratory testing, primary physician testing, counseling, and referral. The AI approach allows for easy updating of recommendations in order to meet changes in local preventive resources and national recommendations.