Aortic valve replacement 13 years following Bentall procedure

Aortic valve dysfunction secondary to leaflet degeneration of porcine bioprosthesis incorporated in a conduit poses a challenge to the surgeon. An adult male required repeat aortic valve replacement 13 years following insertion of an intraoperatively constructed conduit composed of a Carpentier-Edwards bioprosthesis and Dacron tube graft. At surgery, the extremely difficult situation was easily resolved by excising the degenerated leaflets and inserting a St. Jude aortic valve within the frame of the bioprosthesis. The patient has remained Class I during the 3-year follow-up period, enjoying normal aortic valve function.

Effects of glucose on insulin secretion, glucokinase activity, and transgene expression in transgenic mouse islets containing an upstream glucokinase promoter-human growth hormone fusion gene

We have analyzed in organ culture the effects of glucose on glucose-induced insulin secretion, glucokinase (GK) activity, and human growth hormone (hGH) expression in pancreatic islets from transgenic mice containing an upstream GK promoter-hGH fusion gene. Freshly isolated islets from these mice had a normal insulin secretory response to glucose but showed subtle defects after culture in low or high glucose for 4 days that may have been due to the accumulation of hGH in the culture media. Islets cultured from both normal and transgenic mice had approximately a fourfold induction of GK activity in response to an increased concentration of glucose in the culture media, whereas no such change in total islet hGH production was observed. Immunocytochemical localization of hGH in islets cultured in 3 mM glucose showed a pattern similar to that in freshly isolated islets. However, after culture in 30 mM glucose, hGH immunostaining became strikingly more heterogeneous. We conclude 1) that GK-hGH transgene expression does not appear to adversely affect glucose-stimulated insulin secretion in vivo or in freshly isolated islets, 2) that glucose does not induce transgene expression, thus providing additional evidence against an effect of glucose on GK gene transcription in the islet, and 3) that glucose stimulates the co-release of hGH with insulin, thereby enhancing the heterogeneous staining pattern seen among pancreatic beta-cells.

Selectivity in aortic root reconstruction

Anatomical variations in aortic root pathology, including combinations of dissection, aneurysmal dilatation, annuloaortic ectasia, and valve disease, defy standardized repair and mandate application of various surgical reconstructions. To examine these techniques, and their influence on morbidity and mortality, we reviewed 53 consecutive patients undergoing aortic root procedures. Thirty-two patients underwent total root reconstruction. Of these, 21 underwent Bentall procedures, 9 had a modification thereof, and 2 underwent a Cabrol reconstruction. Less extensive pathology was corrected in 21 patients with a partial root reconstruction. These included aortic valve replacement (AVR) and a separate tube graft in 14 patients, AVR and primary aortic repair +/- wrapping in 4 individuals, and AVR and patch aortic root enlargement in 3 patients. Mean age was 53.2 years (range 20 to 79). Nearly 20% had undergone previous cardiac surgery and 7.5% were emergencies. Early mortality was 4%. Complications included dysrhythmias (48%), myocardial infarction (4%), stroke (4%), pneumonia (14%), and pancreatitis (2%). There were no reoperations for bleeding. Three late complications, one pseudoaneurysm and two perivalvular leaks, were successfully repaired. Late deaths (13.7%) were caused by congestive heart failure (3), myocardial infarction (MI) (1), cancer (1), stroke (1), and accidental fall (1). Kaplan-Meier analysis reveals 1-, 5-, and 10-year survivals of 98%, 81%, and 66%. Survival and mortality data did not differ between groups, and except for the incidence of atrial dysrhythmias, complication rates also were not significantly different. This series illustrates the need for and the successful application of a selective approach to aortic root reconstruction.

Mitral valve replacement through the aortic root

This report discusses the case histories of two patients who had had previous cardiac operations and required extensive reoperations including mitral valve replacement. In both patients the replacement of the mitral valve was performed through the aortic root. This rare approach to the mitral valve, conducted with remarkable facility in these patients, encourages more liberal use of transaortic mitral valve operations in selected patients.

Extended aortic valvuloplasty for recurrent valvular stenosis and regurgitation in children

Recurrent significant aortic valvular stenosis or regurgitation, or both, after balloon or open valvotomy in pediatric patients often necessitates aortic valve replacement. In an attempt to preserve the aortic valve, we performed extended aortic valvuloplasty in 21 children with recurrent aortic valve stenosis or regurgitation from January 1989 to March 1993. Previous related procedures were one open aortic valvotomy or more (n = 15), balloon valvotomy (n = 4), balloon valvotomy after surgical valvotomy (n = 1), and repair of iatrogenic valve tear (n = 1). Mean age at the time of the extended aortic valvuloplasty was 6 +/- 3.4 years. Mean pressure gradient across the aortic valve was 56 +/- 12 torr. Regurgitation was moderate (grade 2 to 3) in nine and severe (grade 4) in 12 patients. Extended aortic valvuloplasty techniques consisted of thinning of valve leaflets (n = 15), augmentation of scarred and retracted leaflets with autologous pericardium (n = 11), resuspension of the augmented leaflet (n = 14), release of the rudimentary commissure from the aortic wall (n = 5), extension of the valvotomy incision into the aortic wall on both sides of the commissure (n = 20), patch repair of the sinus of Valsalva perforation (n = 1), reapproximation of tears (n = 5), and narrowing of the ventriculoaortic junction (n = 2). No operative deaths occurred. The postoperative mean pressure gradient, assessed by most recent Doppler echocardiography or cardiac catheterization at a follow-up of 18 +/- 6 months, was 19 +/- 6 torr (p < 0.01 versus the preoperative gradient). Aortic regurgitation was absent in 13, mild in 6, and moderate-to-severe, necessitating subsequent aortic valve replacement, in 2. This short-term experience indicates that extended aortic valvuloplasty is a safe and effective surgical approach that minimizes the need for aortic valve replacement in children with significant recurrent aortic valve stenosis or regurgitation.

Dacron aorta

During the span of 6 years a 67-year-old woman underwent four consecutive major aortic operations, ultimately replacing her entire thoracoabdominal aorta with the exception of a tiny segment from which the left subclavian artery originated. The relatively uneventful postoperative course with each operation (one emergency and three elective procedures) and her current satisfactory condition at age 73 years have been attributed to her physical and mental fortitude, excellent anesthesia, superb postoperative care, and the chronic nature of her segmental aortic lesions caused by arteriosclerosis.

Mitral and aortic annular enlargement for insertion of adequate size prosthetic valves

Mitral and aortic valve rings were radically enlarged in a 70-year-old white female presenting with unusually tiny and severely stenotic rheumatic mitral and aortic valve disease. A common aorto-left atrial incision created by cutting across the two valves made it possible to implant adequate size St. Jude valves. The resulting defect in the roof of the left atrium and the aortic root were closed with a generous patch of polytetrafluoroethylene (PTFE). The center of the patch and the unattached segments of the two prostheses were incorporated with interrupted horizontal mattress sutures.

1980: descending aortic aneurysmectomy without adjuncts to avoid ischemia. 1993 update

Encouraged by reports on the safety of simple aortic cross-clamping for resection of descending aortic aneurysm, we began utilizing this technique more liberally in 1976. This study was undertaken to examine the results of operation in 36 patients, equally divided into two distinct groups. In Group 1, either extracorporeal circulation or indwelling temporary shunts were employed during the period of aortic occlusion. In Group 2, simple aortic cross-clamping was utilized to manage the lesion. No adjuncts were used to avoid ischemia in the latter group. The only 2 early deaths and two instances of paraplegia occurred in Group 1. In general, there were fewer complications in Group 2, with approximately two-thirds of the patients experiencing an uneventful postoperative course. These differences are considered important since the two groups were similar in respect to the extent and nature of the lesions and other factors contributing to operative risk.

Differential effects of advanced age on neurologic and cardiac risks of coronary artery operations

Two thousand patients undergoing coronary artery bypass grafting with cardiopulmonary bypass were prospectively studied to compare the influence of age on the incidence of neurologic, cardiac, and other complications. Postoperative neurologic events were found in 56 (2.8%) patients, with an incidence in patients > or = 75 years (8.9%) more than twice that of patients 65 to 74 (3.6%) and nine times larger than in patients < 65 (0.9%). Cardiac complications did not differ between age groups except for low cardiac output state, which occurred 1.7 times more frequently in patients > or = 75 years compared with those < 65. Patients with postoperative neurologic events had a ninefold increase in mortality--35.7% versus 4.0%. Logistic regression analysis demonstrate the most important predictors of a postoperative neurologic event to be age, preoperative neurologic abnormality, recent myocardial infarction, and duration of cardiopulmonary bypass. The risk of neurologic complications increases disproportionately to the risk of cardiac complications in the elderly undergoing coronary artery bypass grafting with cardiopulmonary bypass. Despite neurologic improvement (32 of 56 patients), a postoperative neurologic event was second only to low cardiac output state as the postoperative complication most highly associated with in-hospital death. These results are important for decisions regarding selection of candidates for coronary artery bypass grafting and for prediction of surgical outcome.

Expression and function of GLUT-1 and GLUT-2 glucose transporter isoforms in cells of cultured rat pancreatic islets

We have previously investigated glucose induction of glucokinase, glucose usage and insulin release in isolated cultured rat pancreatic islets (Liang, Y., Najafit, H., Smith, R. M., Zimmerman, E. C., Magnuson, M. A., Tal, M., and Mastchinsky, F. M. (1992) Diabetes (1992) 41, 792-806). Here we studied the expression and function of GLUT-1 and GLUT-2 glucose transporter isoforms, using the same system, i.e. isolated pancreatic rat islets immediately after isolation or cultured in the presence of 3 or 30 mM glucose for as long as 10 days. We found by immunofluorescence microscopy and Western and Northern blot analysis of islet extracts that GLUT-1 expression was induced in islet beta-cells in tissue culture both with low or high glucose present. The induction of GLUT-1 was specific to beta-cells but was not present in all beta-cells and was not detected in alpha-cells. GLUT-2 expression was also specific for beta-cells and was not observed in all beta-cells. Some beta-cells in culture coexpressed GLUT-1 and GLUT-2. The expression of the two glucose transporters was regulated in the opposite direction in response to glucose concentration in the culture medium. GLUT-1 was more effectively induced when glucose was low, and GLUT-2 expression was more pronounced when glucose was high in the culture media. Another difference between the two glucose transporters was that GLUT-2 expression was increased while GLUT-1 expression was decreased as culturing continued as long as 7 days. Thus, after 7 days of culture GLUT-2 expression in beta-cells was nearly the same at low and high glucose, whereas GLUT-1 was practically absent no matter what the glucose level was. In attempts to correlate GLUT-1 and GLUT-2 expression to beta-cell function glucose uptake and glucose-stimulated insulin release in fresh and cultured islets were measured. In freshly isolated islet glucose uptake was estimated to be 100-fold in excess of actual glucose use. Glucose uptake was reduced by 7-day culture to about one-third of that observed in freshly isolated islets no matter what the glucose concentration of the culture media. We conclude that in the present experimental system GLUT-1 and GLUT-2 expression and function are not closely associated with glucose usage rates or the secretory function of beta-cells.

Morbidity and duration of ICU stay after cardiac surgery. A model for preoperative risk assessment

Although risk factors for mortality after cardiac surgery have been identified, there is no widely applicable method for readily determining risk of postoperative morbidity based on preoperative severity of illness. The goal of this study was to develop a model for stratifying the risk of serious morbidity after adult cardiac surgery using readily available and objective clinical data. After univariate analysis of risk factors in 3,156 operations, 11 variables were identified as important predictors by logistic regression (LR) analysis and used to construct an additive model to calculate the probability of serious morbidity. Reliable correlation was found between a simplified additive model for clinical use and the LR model. The clinical and logistic models were then tested prospectively in 394 patients and demonstrated a pattern of increasing morbidity with ascending scores similar to that predicted by the reference group. Increasing clinical risk score was also associated with a greater frequency of individual complications as well as prolongation of ICU stay. This study demonstrates that it is feasible to design a simple method to stratify the risk of serious morbidity after adult cardiac surgery. With further prospective multicenter refinement and testing, such a model is likely to be useful for adjusting severity of illness when reporting outcome statistics as well as planning resource utilization.

Concordant glucose induction of glucokinase, glucose usage, and glucose-stimulated insulin release in pancreatic islets maintained in organ culture

Using cultured islets as the experimental system, this study established dosage-response and time-dependency curves of the inductive glucose effect on glucose-stimulated insulin release, glucose usage, and glucokinase activity. Glucose-stimulated insulin release in islets cultured for 1, 2, or 7 days was increased as a function of glucose concentration in the culture medium and as a function of time. Glucose usage in the cultured islets showed a close relationship with glucose concentration in the culture medium at both 2 and 7 days of culture. Glucokinase activity increased in islets cultured for 1, 2, or 7 days as a function of increasing glucose concentrations in the culture medium and as a function of time. The V(max) of glucokinase in islets cultured for 7 days in medium containing 30 mM glucose was twice the value of freshly isolated islets and was almost fivefold higher than that in islets cultured for 7 days in 3 mM glucose. The glucose induction of glucose-stimulated insulin release, of glucose usage, and of glucokinase activity were tightly correlated. The biochemical mechanisms of glucose induction of islet glucokinase were further studied. Immunoblotting with an antibody against C-terminal peptide of glucokinase showed that densities of a 52,000-kD protein band from tissue extracts of islets cultured for 7 days in 3, 12, and 30 mM glucose were 25, 44, and 270% compared with that of extract from freshly isolated islets (100%). RNA blot analysis of glucokinase mRNA demonstrated virtually the same levels in fresh islets and islets after 7 days of culture in 3 or 30 mM glucose. The adaptive response of glucokinase to glucose appears therefore to be occurring at a translational or posttranslational site in cultured islets. These data greatly strengthen the concept that glucose is the regulator that induces the activity of glucokinase, which in turn determines the rate change of glucose usage as well as glucose-stimulated insulin release from beta-cells. Thus, the hypothesis that glucokinase is the glucose sensor of beta-cells is strengthened further.

Identification of glucose response proteins in two biological models of beta-cell adaptation to chronic high glucose exposure

High resolution 2-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with computerized analysis of gel images was used to search for proteins whose biosynthesis was induced or repressed in pancreatic islet cells chronically exposed to high glucose in an in situ and a tissue culture model of islet cell adaptation to excessive fuel load. The in situ model involved a 4-day intravenous infusion of either 50% glucose or 0.45% saline solution, followed by islet isolation, [35S]methionine labeling at 3 and 18 mM glucose for both groups, and protein analysis by 2-dimensional SDS-PAGE. The tissue culture model involved a 7-day culture of isolated rat islets in RPMI 1640 with 10% fetal calf serum containing either 3 or 30 mM glucose, followed by radiolabeling and 2-dimensional PAGE of proteins as in the in situ model. A small fraction of about 1.5% of the approximately 2000 identifiable proteins can be characterized as adaptive proteins. Of these altogether 58 proteins in the two models, 5 proteins were demonstrable in both models and two of these (proteins 1526 and 7622) are particularly noteworthy. Protein 1526 (Mr 57,000; pI 5.09) showed the same response pattern in both models and its expression was most enhanced when islets from chronically glucose-infused animals or those cultured for 7 days at 30 mM were radiolabeled at 18 mM glucose. Protein 7622 (Mr 68,000; pI 6.50) (also known as GSP-65; Collins, H.W., Buettger, C., and Matschinsky, F.M. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 5494-5498) showed a different labeling pattern in the two models: stimulation of [35S]methionine incorporation by 18 mM glucose both in control and experimental islets from the infusion study, but lack of such stimulation of radiolabeling in islets cultured for 7 days at 30 mM glucose in contrast to islets cultured at 3 mM. The experimental strategy and the methodology are evaluated and the significance of the results is discussed. Potentials of the approach and plans for future experiments are considered.

Effects of alternate RNA splicing on glucokinase isoform activities in the pancreatic islet, liver, and pituitary

Different glucokinase isoforms are produced by tissue-specific alternative RNA splicing in the liver and pancreatic islet, the only tissues in which glucokinase activity has been detected. To determine whether differences in protein structure brought about by alternative RNA splicing have an effect on glucose phosphorylating activity, we expressed cDNAs encoding four different hepatic and islet glucokinase isoforms and determined the Km and Vmax of each. When the glucokinase B1 and L1 isoforms were expressed in eukaryotic cells, both high Km glucose phosphorylating activity and immunoreactive protein were detected. However, when the glucokinase B2 and L2 isoforms were expressed, both of which differ by deletion of 17 amino acids in a region between the putative glucose and ATP-binding domains, no high Km glucose phosphorylating activity and much less immunoreactive protein were detected. When the glucokinase B1 and B2 isoforms were expressed in Escherichia coli as fusion proteins with glutathione S-transferase, affinity-purified B1 fusion protein was able to phosphorylate glucose whereas the B2 fusion protein was not, thus indicating that the lack of glucose phosphorylating activity from both the B2 and L2 isoforms is due to lack of intrinsic activity in addition to accumulation of less protein. The Km values of the B1 and L1 isoforms, which differ from each other by 15 amino acids at the NH2 terminus, were similar, but the Vmax of the B1 isoform was 2.8-fold higher than that of the L1 isoform. Mutagenesis of the first two potential initiation codons in the glucokinase B1 cDNA from ATG to GTC (methionine to valine) indicated that the first ATG was crucial for activity and is, therefore, the likely translation initiation codon. Messenger RNAs encoding both the B2 and L2 isoforms of glucokinase were detected in islet and liver by polymerase chain reaction amplification of total cDNA, indicating that mRNAs utilizing this weak alternate splice acceptor site in the fourth exon are normally present in both the liver and islet but as minor components. A regulatory role for weak alternate splice acceptor and donor sites in the glucokinase gene was suggested by examining the expression of the gene in the pituitary and in AtT-20 cells. Interestingly, although glucokinase mRNAs of appropriate sizes were detected in both the AtT-20 cells and rat pituitaries, neither exhibited any detectable high Km glucose phosphorylating activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Glucose regulates glucokinase activity in cultured islets from rat pancreas

In this study, we have used isolated pancreatic islets cultured for 7 days in 3 or 30 mM glucose to explore whether glucokinase is induced or activated by high glucose concentrations and has related enzyme activity to glucose-stimulated insulin release. Islets cultured in low glucose medium or low glucose medium plus 350 ng/ml insulin did not respond to high glucose stimulation. Islets cultured in medium containing high glucose concentrations showed a high rate of basal insulin secretion when perifused with 5 mM glucose, and the insulin release was greatly augmented in a biphasic secretion profile when the glucose concentration was raised to 16 mM. Islet glucokinase and hexokinase activities were determined by a sensitive and specific fluorometric method. Glucokinase activity was reduced to approximately 50% in islets cultured in low glucose medium with or without insulin present compared to results with fresh islets. However, islets cultured in 30 mM glucose showed that glucokinase activity was elevated to 236% compared to results with fresh islets. It is concluded that (a) glucose is the physiological regulator of glucokinase in the islet of Langerhans and that (b) the activity of glucokinase plays a crucial role in glucose-induced insulin secretion.

Inferior vena cava interruption with the Hunter-Sessions balloon: eighteen years' experience in 191 cases

Over a period of 18 years, 191 consecutive patients had interruption of the inferior vena cava with the Hunter-Sessions balloon for complications of deep venous thrombosis and pulmonary embolism. Causes of deep venous thrombosis and pulmonary embolism included the postoperative state (33%), cancer (32%), and stroke (11%). There were 93 females and 98 males; ages ranged from 17 to 90 years (average, 57 years). Indications for placement of the Hunter-Sessions balloon were as follows: contraindication to anticoagulants (33%), anticoagulant complications (24%), pulmonary embolism despite anticoagulants (45%), and others including inferior vena cava thrombus (12%). Sixty-eight percent had clinical phlebitis and 36% had positive venography results. Pulmonary embolism had occurred in 165 patients (86%). It was diagnosed by ventilation-perfusion scanning (75%), angiography (23%), or on clinical grounds (2%) in patients with confirmed deep venous thrombosis. At the time of the procedure 52% were in significant cardiopulmonary distress, and 10% were intubated and on respirators. Transjugular placement was done in 188 patients, and transfemoral placement was performed in three. All All tolerated inferior vena cava interruption. Thirty patients (15%) died while in the hospital an average of 21 days after balloon placement, which was unrelated to the deaths. Follow-up was 45 months. Ninety-four patients are dead, 95 are alive, and the status of two patients is unknown. Twenty-nine of 64 patients (45%) who died after they left the hospital died of cancer. At last follow-up, 75% of patients had legs free of edema and 25% had need for elastic stockings. No malfunction or migration has occurred with the device. No patient had a pulmonary embolism while in the hospital after insertion of the Hunter-Sessions balloon, and no patient died of pulmonary embolism. Late minor pulmonary embolism occurred in three patients.

Selective activation of Ca2+ influx by extracellular ATP in a pancreatic beta-cell line (HIT)

The action of exogenous ATP on cytoplasmic free Ca2+ ([Ca2+]i) was studied in insulin secreting cells using fura-2. Stimulation of clonal pancreatic beta-cells (HIT) with ATP (range 2-20 microM) evoked a sustained elevation in [Ca2+]i. ATP selectively promoted Ca2+ influx and not Ca2+ mobilization since (1) the effect required external Ca1+ and (2) was observed in cells in which internal stores were depleted with ionomycin (3) the rate of Mn2+ influx, measured as the quenching of the fura-2 signal, was accelerated by ATP. The action of ATP was unaffected by the voltage-sensitive Ca2+ channel blockers nifedipine and verapamil as well as by a depolarizing concentration of K+. The effect on [Ca2+]i was highly specific for ATP since AMP, ADP, adenosine 5'-[gamma-thio]triphosphate, adenosine 5'-[beta, gamma-methylene]triphosphate, GTP and adenosine were ineffective. In normal pancreatic islet cells, both exogenous ATP (range 0.2-2 microM) and ADP induced a transient Ca2+ elevation that did not require external Ca2+. The nucleotide specificity of the effect on [Ca2+]i suggests that ATP activates P2 gamma purinergic receptors in normal beta-cells. Thus, ATP evokes a Ca2+ signal in clonal HIT cells and normal islet cells by different transducing systems involving distinct purinoreceptors. A novel mechanism for increasing [Ca2+]i by extracellular ATP is reported in HIT cells, since the nucleotide specificity and the selective activation of Ca2+ influx without mobilization of internal Ca2+ stores cannot be explained by mechanisms already described in other cell systems.

Coronary artery bypass surgery in patients less than 40 years of age

Coronary bypass patients less than 40 years of age were identified and compared with a control group previously studied at our hospital. In patients less than 40 years, the average age was 35 years. Men comprised 90.1 percent of group 1, and 83.4 percent of group 2. Operative mortality was 2.89 percent for group 1 and 2.1 percent for group 2. Patients less than 40 years were more likely to have positive family history (46.3 percent vs 21.94 percent), elevated cholesterol levels (25.62 vs 11.36 percent), and be smokers (59.09 vs 39.9 percent). Group 1 patients were less likely to have diabetes (4.54 vs 13.37 percent) or hypertension (18.18 vs 31.43 percent). The percentage of late deaths was much higher for younger patients. Postoperative angina and the need for reoperation was higher in group 1.

Control of glucose metabolism in pancreatic beta-cells by glucokinase, hexokinase, and phosphofructokinase. Model study with cell lines derived from beta-cells

Glucose usage by soluble fractions of cell extracts from two insulin-producing cell lines, RINm5F and HIT, was investigated. Analysis of enzyme activities indicated that glucose phosphorylation and phosphofructokinase are likely to be the rate-limiting steps of glycolysis in both RINm5F and HIT cell extracts. RINm5F extracts, which lack glucokinase, exhibited relatively flat concentration-dependency curves of glucose usage and showed substantial inhibition of hexokinase. HIT cell extracts, which contain glucokinase but lack hexokinase, exhibited sigmoidal concentration-dependency curves of glucose usage, reflecting almost fully expressed glucokinase activity. A reconstituted system prepared from RINm5F and HIT cell extracts exhibited a composite concentration-dependency curve of glucose usage and showed substantial inhibition of hexokinase and almost fully expressed glucokinase. However, conditions that activate phosphofructokinase, such as addition of ammonium sulfate or fructose 2,6-bisphosphate or alkalization, removed the inhibition of hexokinase without noticeably affecting the glucokinase component of usage. Results obtained with a reconstituted system containing RINm5F cell extract and purified glucokinase were consistent with these findings. The data presented here indicate that this reconstituted cell-free system serves as a valid model for the study of aspects of glycolytic control in the islet. This model illustrates the preeminent role of glucokinase in the control of glycolysis, consistent with its glucose-sensor function in the islet. In addition, these studies help to define the contribution of phosphofructokinase to the control of glycolysis and the mechanism whereby changes in phosphofructokinase activity could modulate, via changes in the glucose 6-phosphate concentration, the activity of hexokinase and hence the net glycolytic flux.

Postperfusion coronary stenosis

A patient is described who had left main coronary artery stenosis four months after aortic valve replacement. He was seen with unstable angina, and subsequent catheterization revealed stenosis of a previously normal left main coronary artery. The diagnosis, treatment, and means of prevention are discussed.