Although cell differentiation usually involves synthesis of new proteins, little is known about the role of protein degradation. In eukaryotes, conjugation to ubiquitin polymers often targets a ...protein for destruction. This process is regulated by deubiquitinating enzymes, which can disassemble ubiquitin polymers or ubiquitin-substrate conjugates. We find that a deubiquitinating enzyme, UbpA, is required for Dictyostelium development.ubpA cells have normal protein profiles on gels, grow normally, and show normal responses to starvation such as differentiation and secretion of conditioned medium factor. However,ubpA cells have defective aggregation, chemotaxis, cAMP relay, and cell adhesion. These defects result from low expression of cAMP pulse-induced genes such as those encoding the cAR1 cAMP receptor, phosphodiesterase, and the gp80 adhesion protein. Treatment of ubpA cells with pulses of exogenous cAMP allows them to aggregate and express these genes like wild-type cells, but they still fail to develop fruiting bodies. Unlike wild type, ubpAcells accumulate ubiquitin-containing species that comigrate with ubiquitin polymers, suggesting a defect in polyubiquitin metabolism. UbpA has sequence similarity with yeast Ubp14, which disassembles free ubiquitin chains. Yeast ubp14 cells have a defect in proteolysis, due to excess ubiquitin chains competing for substrate binding to proteasomes. Cross-species complementation and enzyme specificity assays indicate that UbpA and Ubp14 are functional homologs. We suggest that specific developmental transitions in Dictyostelium require the degradation of specific proteins and that this process in turn requires the disassembly of polyubiquitin chains by UbpA.
To evaluate the effect of extreme altitude on cardiac function in normal young men, electrocardiograms were recorded at rest and during maximal exercise at several simulated altitudes up to the ...equivalent of the summit of Mt. Everest (240 torr or 8,848 m). The subjects spent 40 days in a hypobaric chamber as the pressure was gradually reduced to simulate an ascent. Changes in the resting electrocardiogram were evident at 483 torr (3,660 m) and were more marked at 282 torr (7,620 m) and 240 torr (8,848 m). They consisted of an increase in resting heart rate from 63 +/- 5 to a maximum of 89 +/- 8 beats/min; increase in P-wave amplitude in inferior leads; right-axis shift in the frontal plane; increased S/R ratio in the left precordial leads; and increased T negativity in V1 and V2. No significant arrhythmias or conduction defects were observed. Most changes reverted to normal within 12 hours of return to sea level, with the exception of the frontal-plane axis and T-wave alterations. Maximal cycle ergometer exercise at 282 torr (7,620 m) and 240 torr (8,848 m) resulted in a heart rate of 138 +/- 7 and 119 +/- 6 beats/min at the 2 altitudes, respectively. No ST depression or T-wave changes suggestive of ischemia occurred despite a mean arterial oxygen saturation of 49% and a mean pH of 8 during peak exercise. Occasional ventricular premature beats were observed during exercise in 2 subjects.
Examined (a) differences in physiological response of Type A and Type B individuals to conditions that varied in both controllability and consistency of controllability over an aversive stimulus and ...(b) whether Type A relative to Type B individuals use more denial and/or projection in cognitively coping with arousing situations as well as whether they differ in being preoccupied in such situations. 96 male undergraduates were randomly assigned to 1 of 4 conditions: no control over shock, consistent control over shock, intermittent control over shock, and low stress. Type A and B behaviors were assessed with the Activity scale of the Thurstone Temperament Schedule. Results indicated that relative to Type B Ss, Type A's manifested (a) greater pulse rates and systolic and diastolic blood pressure in the consistent control condition, (b) greater systolic blood pressure in the no-control condition, and (c) greater diastolic blood pressure in the intermittent control condition. Type A's also used more denial and projection across the 3 high-stress conditions but did not differ in how preoccupied they were as compared to Type B's. (39 ref)
Examined (a) whether Type A (coronary-prone) individuals respond with more psychophysiological arousal to threat to self-esteem than to threat of shock, (b) whether differences between Type A and ...Type B individuals in psychophysiological responses are greater under high than low stress, and (c) whether Type A and Type B individuals differ in how they cognitively cope with stress. 84 male college students participated. Results indicate that Type A Ss manifested higher pulse rates across all conditions and greater systolic and diastolic blood pressures in response to threat to self-esteem than did Type B Ss. Type A Ss also employed more suppression in response to both threat to self-esteem and threat of shock and employed more denial in response to threat to self-esteem than did Type B Ss. Implications regarding the means by which Type A behavior increases the risk of premature heart disease are discussed. (25 ref)
Cerebrovascular accidents (CVA) or strokes are now the third leading cause of death in the United States. Many who suffer strokes are admitted to rehabilitation centers in order to receive therapy to ...help rebuild and recovery function. Nutrition plays a significant role in rehabilitation patient outcomes, and is an essential part of comprehensive care. The purpose of this study is to determine if nutrition and diet consistency are directly and independently associated with changes in the Functional Independence Measure (FIM) scores in stroke patients in an acute rehabilitation unit. This study was a retrospective secondary analysis review of medical chart records, and included a total of 84 patients. Patients were divided into groups based on their admission diet: Regular, Dysphagia Advanced, Dysphagia Mechanically Altered, Dysphagia Pureed, and Nutrition Support. Measurements included admission and discharge Total, Motor, and Cognitive FIM scores; BMI, albumin and prealbumin; age, sex, and race. Patients did show a significant improvement in their FIM scores during their stay, with patients on Regular diets having the highest FIM scores. Patients who were more debilitated and had lower FIM scores were usually in one of the altered texture diet groups, or on nutrition support. Prealbumin and BMI were also the highest in patients who had high FIM scores. Patients who were admitted on an altered diet also tended to advance in their diets, which show improvement in overall function. It is crucial to continue to improve nutrition administration to this population to help prevent morbidity and mortality. Proper nutrition in the acute phase of stroke can lay the essential groundwork for recovery.
Eight male volunteers had rest and exercise measurement to determine the mechanisms of oxygen transport during a 40-day chamber decompression simulating high-altitude exposure equivalent to the ...summit of Mt Everest. Five subjects completing the study decreased their maximum oxygen uptake by 72%. During maximal or near-maximal exercise, arterial PCO2 fell as low as 8 mm Hg, defending the alveolar PO2 and confirming marked hyperventilation. Alveolar-arterial diffusion did not improve and V/Q worsened. Cardiac function was unimpaired. Circulatory oxygen transport resembled that at sea level. The decrease in mixed venous PO2 was not enough to preserve fractional oxygen utilization "on the summit." The PO2 gradients from atmosphere to alveolus, alveolus to arterial blood, arterial to venous blood, and from venous (capillary) blood to mitochondria all decreased. However, hyperventilation appeared to be the primary adaptation that defended the maximum oxygen uptake.
A field study was conducted to determine if high dosages and multiple applications of insecticidal baits could be used to increase mortality of rangeland grasshoppers. Twenty-four rangeland plots in ...western North Dakota were treated with either single applications of 2% (AI) carbaryl bran bait at 1.68, 3.36, or 5.04 kg/ha; double applications of carbaryl bran bait at 1.68 kg/ha for each application; triple applications of the bait at 1.68 kg/ha; or left untreated. Densities of all grasshopper species were estimated before treatments and 2, 4, and 7 days after treatments. The insecticidal bait treatments caused significant reductions (57-100%) in densities of Aulocara elliotti Thomas, Melanoplus sanguinipes (F.), Camnula pellucida Scudder, and Ageneotettix deorum (Scudder), but had no significant effect on Aeropedellus clavatus (Thomas) or Melanoplus bivittatus (Say). A single application of the insecticidal bait at 5.04 kg/ha caused significantly greater mortality of A. elliotti (82%) than single applications of the other dosages. Dosage had no consistent effect on densities of M. sanguinipes, C. pellucida, A. deorum, or all species combined, after 2 days. Multiple applications of the insecticidal baits caused additional 32-52% reductions in densities of total grasshoppers after each successive application, indicating that the quantity of bait can affect grasshopper mortality. However, final mortality of total grasshoppers after 7 days was not affected by high dosages or multiple applications of the insecticidal baits, indicating that multiple and high dosages of insecticidal baits had no real advantage over single applications at 1.68 kg/ha.
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