Tissue-dependent loss of phosphofructokinase-M in mice with interrupted activity of the distal promoter: impairment in insulin secretion.

Phosphofructokinase is a key enzyme of glycolysis that exists as homo- and heterotetramers of three subunit isoforms: muscle, liver, and C type. Mice with a disrupting tag inserted near the distal promoter of the phosphofructokinase-M gene showed tissue-dependent differences in loss of that isoform: 99% in brain and 95-98% in islets, but only 50-75% in skeletal muscle and little if any loss in heart. This correlated with the continued presence of proximal transcripts specifically in muscle tissues. These data strongly support the proposed two-promoter system of the gene, with ubiquitous use of the distal promoter and additional use of the proximal promoter selectively in muscle. Interestingly, the mice were glucose intolerant and had somewhat elevated fasting and fed blood glucose levels; however, they did not have an abnormal insulin tolerance test, consistent with the less pronounced loss of phosphofructokinase-M in muscle. Isolated perifused islets showed about 50% decreased glucose-stimulated insulin secretion and reduced amplitude and regularity of secretory oscillations. Oscillations in cytoplasmic free Ca(2+) and the rise in the ATP/ADP ratio appeared normal. Secretory oscillations still occurred in the presence of diazoxide and high KCl, indicating an oscillation mechanism not requiring dynamic Ca(2+) changes. The results suggest the importance of phosphofructokinase-M for insulin secretion, although glucokinase is the overall rate-limiting glucose sensor. Whether the Ca(2+) oscillations and residual insulin oscillations in this mouse model are due to the residual 2-5% phosphofructokinase-M or to other phosphofructokinase isoforms present in islets or involve another metabolic oscillator remains to be determined.

Gender and post-ischemic recovery of hypertrophied rat hearts.

BACKGROUND: Gender influences the cardiac response to prolonged increases in workload, with differences at structural, functional, and molecular levels. However, it is unknown if post-ischemic function or metabolism of female hypertrophied hearts differ from male hypertrophied hearts. Thus, we tested the hypothesis that gender influences post-ischemic function of pressure-overload hypertrophied hearts and determined if the effect of gender on post-ischemic outcome could be explained by differences in metabolism, especially the catabolic fate of glucose. METHODS: Function and metabolism of isolated working hearts from sham-operated and aortic-constricted male and female Sprague-Dawley rats before and after 20 min of no-flow ischemia (N = 17 to 27 per group) were compared. Parallel series of hearts were perfused with Krebs-Henseleit solution containing 5.5 mM [5-3H/U-14C]-glucose, 1.2 mM [1-14C]-palmitate, 0.5 mM [U-14C]-lactate, and 100 mU/L insulin to measure glycolysis and glucose oxidation in one series and oxidation of palmitate and lactate in the second. Statistical analysis was performed using two-way analysis of variance. The sequential rejective Bonferroni procedure was used to correct for multiple comparisons and tests. RESULTS: Female gender negatively influenced post-ischemic function of non-hypertrophied hearts, but did not significantly influence function of hypertrophied hearts after ischemia such that mass-corrected hypertrophied heart function did not differ between genders. Before ischemia, glycolysis was accelerated in hypertrophied hearts, but to a greater extent in males, and did not differ between male and female non-hypertrophied hearts. Glycolysis fell in all groups after ischemia, except in non-hypertrophied female hearts, with the reduction in glycolysis after ischemia being greatest in males. Post-ischemic glycolytic rates were, therefore, similarly accelerated in hypertrophied male and female hearts and higher in female than male non-hypertrophied hearts. Glucose oxidation was lower in female than male hearts and was unaffected by hypertrophy or ischemia. Consequently, non-oxidative catabolism of glucose after ischemia was lowest in male non-hypertrophied hearts and comparably elevated in hypertrophied hearts of both sexes. These differences in non-oxidative glucose catabolism were inversely related to post-ischemic functional recovery. CONCLUSION: Gender does not significantly influence post-ischemic function of hypertrophied hearts, even though female sex is detrimental to post-ischemic function in non-hypertrophied hearts. Differences in glucose catabolism may contribute to hypertrophy-induced and gender-related differences in post-ischemic function.

Adaption of team learning to an introductory graduate pharmacology course.

BACKGROUND: Team-learning experiences within a large group setting have a variety of educational applications. DESCRIPTION: Aspects of the team-learning process were introduced into the endocrine pharmacology unit of an introductory graduate pharmacology course. Each session involved both a faculty lecture and student participation in problem-solving exercises. Curriculum design, small group assignments, instructional materials, small group activities, assessment, student opinions, and cost-benefit considerations were evaluated. EVALUATION: The effects of team-learning strategies on student participation during class, preparation before class, and student perception were examined using a student feedback instrument, instructor perceptions, and comparison of student performances in the unit and the course, as well as personal interviews with students. CONCLUSION: The use of team learning was appreciated by the students and instructor. Students strongly believed that the team-learning component improved the extent and value of their classroom participation and offered insights equaling those of the lecture.

Regular exercise is associated with a protective metabolic phenotype in the rat heart.

Adaptation of myocardial energy substrate utilization may contribute to the cardioprotective effects of regular exercise, a possibility supported by evidence showing that pharmacological metabolic modulation is beneficial to ischemic hearts during reperfusion. Thus we tested the hypothesis that the beneficial effect of regular physical exercise on recovery from ischemia-reperfusion is associated with a protective metabolic phenotype. Function, glycolysis, and oxidation of glucose, lactate, and palmitate were measured in isolated working hearts from sedentary control (C) and treadmill-trained (T: 10 wk, 4 days/wk) female Sprague-Dawley rats submitted to 20 min ischemia and 40 min reperfusion. Training resulted in myocardial hypertrophy (1.65 +/- 0.05 vs. 1.30 +/- 0.03 g heart wet wt, P < 0.001) and improved recovery of function after ischemia by nearly 50% (P < 0.05). Glycolysis was 25-30% lower in T hearts before and after ischemia (P < 0.05), whereas rates of glucose oxidation were 45% higher before ischemia (P < 0.01). As a result, the fraction of glucose oxidized before and after ischemia was, respectively, twofold and 25% greater in T hearts (P < 0.05). Palmitate oxidation was 50-65% greater in T than in C before and after ischemia (P < 0.05), whereas lactate oxidation did not differ between groups. Alteration in content of selected enzymes and proteins, as assessed by immunoblot analysis, could not account for the reduction in glycolysis or increase in glucose and palmitate oxidation observed. Combined with the studies on the beneficial effect of pharmacological modulation of energy metabolism, the present results provide support for a role of metabolic adaptations in protecting the trained heart against ischemia-reperfusion injury.

Teaching pharmacology within a multidisciplinary organ system-based medical curriculum.

We have described how the pharmacology of agents that act on the central nervous system (CNS) and endocrine system were incorporated into a case-based, multidisciplinary, integrated sophomore medical curriculum at Southern Illinois University School of Medicine (SIUSM). Faculty members from the Departments of Pharmacology, Pathology, Internal Medicine, Psychiatry, and Neurology were major participants in the CNS block, and faculty with primary expertise in radiology, epidemiology, and immunology also participated. Integrated sessions involving the entire class were organized around brief patient cases, which were given to the students in advance of the session. During the sessions, each patient case was presented by a physician or pathologist who briefly described symptoms, history, physical findings, differential diagnosis, and the classification of the subtypes of the particular class of disorder. The pathophysiology of the disease was discussed, and the pharmacology of agents to be considered for therapy was presented in the context of the Pharmacology Mental Algorithm, a systematic and rational approach to drug therapy. The session was completed by a clinician who added further clinically relevant information, which was followed by a question-and-answer period involving all faculty participants. The CNS block was presented over a 1-month period and included standardized patients and real patients who consistently exhibited specific disease findings, and these patient-oriented sessions were followed with small group tutorial sessions. Single discipline large-group sessions were also used to present material that is introductory or unique to a particular discipline. Student knowledge was assessed, using integrated evaluations based on case vignettes with multiple-choice questions provided by each discipline. The goal of the examination was to evaluate knowledge base in the discipline areas and its application to clinical problem-solving. A practical evaluation of each student's patient examination skills in CNS was also performed by clinicians. Feedback from the students on the organ system activities was obtained using a questionnaire. Development of these sessions required leadership and a considerable amount of time to organize, improve, and update sessions. The integrated approach largely eliminated the use of conflicting terminology and redundancy of material common with separate presentations on the same subject by different disciplines. The multidisciplinary, case-based sessions were perceived to be instructive, valuable learning experiences, based on formal and informal student and faculty feedback.