Site-specific mutations in a loop region of the C-terminal domain of the large subunit of ribulose bisphosphate carboxylase/oxygenase that influence substrate partitioning

Amino acids composing a flexible loop (loop 6) of the eight-stranded barrel domain of the L-subunit of Synechococcus ribulose bisphosphate carboxylase/oxygenase (EC 4.1.1.39) involved in reaction intermediate stabilization have been modified by site-specific mutagenesis. Changes at positions both distant and within the active site affect overall catalysis and substrate partitioning. Most significantly, replacement of the active site Lys (Lys-334) with Arg at the apex of the loop almost completely suppressed the carboxylase activity of the enzyme relative to oxygenation, with only a modest reduction in overall catalysis. Val-331 and Thr-342, more distant from the active site but with interacting side chains, were changed to larger and smaller residues with differential effects on both turnover and substrate partitioning. Substitution of the loop with the sequence found in more efficient carboxylases only increased partitioning marginally when accompanied by alterations in the C-terminal tail of the L-subunit that interacts with the loop. Generally, modifications to the loop composition also affected enediol formation, the first step of catalysis, suggesting that the geometry and hence flexibility of this segment affect more than just stabilization of the intermediates immediately following reaction with CO2 or O2.     

Fluoxetine for hypochondriacal patients without major depression

Hypochondriasis without concomitant depression is often considered to be unresponsive to pharmacotherapy. Given marked similarities between hypochondriasis and obsessive-compulsive disorder, we decided to conduct an open trial of high-dose fluoxetine for patients with DSM-III-R hypochondriasis who did not meet criteria for major depression. Ten of 16 patients were much improved at the end of 12 weeks. A comparison of baseline and week 12 scores by the use of a paired-samples t-test revealed a statistically significant reduction in hypochondriacal concerns, as measured by the Heightened Illness Concern Clinical Global Impression Severity scale, the Whiteley Index of Hypochondriasis, and the Heightened Illness Concern Questionnaire. These results suggest that fluoxetine may be a useful therapy for hypochondriacal patients without marked depressive features--a group previously considered to be treatment refractory.     

Progressive frontal dysfunction

A number of causes of progressive mental impairment show a preponderance of frontal lobe symptoms. It is proposed that these disorders can be subdivided into primary and secondary frontal dementias, based on the symptomatology and the site of major pathological disruption. An anatomical explanation, based on variations in cortical and subcortical influences, aids in understanding the clinical differences.     

Preliminary experience with transluminal laser-induced intrahepatic portacaval shunts

This article outlines the objectives for a resident rotation on a pediatric emergency medicine service that is geographically separate from adult-oriented facilities. In this setting, pediatric emergency department care is considered an off service. However, these objectives incorporate key pediatric knowledge and techniques in a practical format for emergency medicine trainees who have no separate pediatric emergency department experience. The content of the pediatric emergency department educational exposure can be attained in a concentrated 2-month exposure at a pediatric facility or extracted throughout the course of multiple pediatric encounters at a general emergency department. These objectives are a part of a continuing series on the goals and objectives to direct emergency medicine resident training on off-service rotations.     

Evaluation of an intervention program for the control of an outbreak of shigellosis among institutionalized persons

After control measures were initiated to stop an outbreak of shigellosis in an institution for the developmentally disabled, there was a sharp decline in the number of cases of Shigella sonnei infection. Among ill residents, those treated with antibiotics had shorter mean duration of diarrhea (2.4 vs. 4.5 days, P < .01) and were less likely to have stool cultures positive for shigellae 2-4 weeks after onset of diarrhea (0/25 vs. 5/19; relative risk [RR] = undefined; P = .02). The attack rate was higher in villages where segregation of ill residents was not practiced (46/73 vs. 53/155; RR = 1.8; 95% confidence limits [CL], 1.4, 2.4). In individual housing units where ill residents were not segregated (preintervention), a correlation was found between mean duration of diarrhea and unit attack rates (r = .88; 95% CL, 0.29, 0.99). A study of all 305 residents 10 weeks after the intervention began revealed no positive stool cultures.     

Collateral ventilation and pulmonary arterial smooth muscle in the coati

Collateral ventilation can participate in ventilation-perfusion regulation by shifting normoxic gas into hypoxic lung regions. In species lacking collateral pathways, such as cattle and swine, ventilation-perfusion balance must rely heavily on hypoxic vasoconstriction, which may explain why their muscular pulmonary arteries are much thicker than those of other animal species. The presence of these unusually muscular vessels in turn may account for the vigorous pressor response to acute hypoxia in these species. The only other species known to lack collateral ventilation is the coati. To determine whether coatis fit the pulmonary circulatory pattern of cattle and swine, we measured pulmonary arterial wall dimensions and pulmonary vascular responsiveness to acute airway hypoxia in 11 adult coatis. Hypoxia caused impressive pulmonary arterial hypertension [normoxia = 17 +/- 1 (SE) Torr, hypoxia = 40 +/- 2 Torr, cardiac output unchanged]. The medial thickness of muscular pulmonary arteries (50-300 microns) was 17.1 +/- 1.8% (SD) of external diameter, a thickness unprecedented in normotensive adult mammals. We conclude that coatis fit the pattern of other species lacking collateral ventilation, since they have thick-walled pulmonary arteries and a vigorous pressor response to hypoxia.     

Isolation of human polymorphonuclear leukocyte elastase by chromatography on immobilized benzamidine

Recent evidence suggests that polymorphonuclear leukocyte (PMN) elastase causes tissue injury in a variety of diseases. Current methods of purification of elastase involve several steps which result in a low yield. We report a simple purification method. PMN (10(9) in 4 ml of 0.05 M Tris, pH 7.8, containing 0.2% Triton X-100 were disrupted and homogenized by freezing and thawing followed by sonication. After centrifugation at 100,000 g for 20 min, enzyme was extracted from the pellet with 2.5 ml of 0.05 M Tris/1M NaCl (pH 7.8). The centrifugation-extraction cycle was repeated 3 times. Elastase from 10(8) PMN was then purified using a 1 ml Protease Inhibitor Affinity-Filter prepared by binding benzamidine to silica. Enzyme activity was determined by cleavage of the synthetic substrate N-Suc-(Ala)3-pNa. SDS-PAGE demonstrated 2 polypeptides, molecular masses of 29 and 27 kD with amino acid composition and partial N-terminal sequence (Ile-Val-Gly-Gly-Arg-Arg-Ala-Arg-Pro-His-Ala-Trp-Pro-) identical with those previously reported for elastase. We obtained 50 micrograms elastase (34-fold purification) with specific activity of 52 U/mg/min from 10(8) PMN. This represents a much greater recovery (23% yield) than is achieved by other methods. This method is simple, highly reproducible, and can be performed within a 2-day period.     

Public health surveillance for chronic conditions: a scientific basis for decisions

In this paper we investigate the important contribution of multiple public health surveillance systems to policy in chronic disease control and prevention. We show that, typically, surveillance for chronic diseases relies on multiple data sources, often created for another purpose. We also define the concept of burden for chronic conditions based on data from multiple sources. An example from a state illustrates a model for combining data for use in policy development. These applications illustrate the central role of statistical methods in ensuring the appropriate use of data from multiple surveillance systems.