Porcine Cardiac Xenograft Valves: Analysis of Survival,Valve Failure,and Explantation

Porcine cardiac xenografts were used for cardiac valve replacement in 1,093 patients. Hospital mortality for aortic valve replacement (AVR) was 3.7%; for mitral valve replacement (MVR), 7.8%; and for AVR + MVR, 4.7%. Total follow-up was 2,036 patient-years; maximum, 7.3 years; and mean, 1.89 years. Actuarial survival (± standard error of the mean) for AVR was 84% ± 2% at 56 months; for MVR, 84% ± 3% at 56 months; and for AVR + MVR, 86% ± 4% at 30 months. Nonfatal thromboembolism occurred in 8 of 1,030 patients (0.78%). Anticoagulation was not routinely employed.Fifty hospital survivors (4.8%) experienced valve dysfunction; 18 of the survivors (1.7%) died; and 32 of the survivors (3.1%) underwent reoperation. The rate of dysfunction increased slowly until the sixth year when an increased rate was observed (p < 0.0001). Patients less than 34 years old had a higher incidence of dysfunction (p < 0.01). Thirty-two hospital survivors (3.1%) underwent explanation of the porcine valve for late dysfunction. Valve dysfunction secondary to endocarditis and paravalvular leak occurred early, while leaflet deterioration or thrombosis was more gradual in onset and was noted later.The porcine valve has functioned well for 1 to 7 years with a low incidence of valve related morbidity and mortality without routine anticoagulation in patients older than 34 years of age.     

Effects of toluene inhalation on brain biogenic amines in the rat

The effects of toluene exposure on the biogenic amine concentrations in the central nervous system were investigated in the rat. Toluene was administered via inhalation to groups of rats at concentrations of 0, l00, 300, or 1000 ppm. After an 8-h continuous exposure, animals were sacrificed and whole brain concentrations of dopamine (DA), norepinephrine (NE), and 5-hydroxytryptamine (5-HT) were determined. The data indicated a significant increase in whole brain concentrations of DA following the 100-ppm exposure. A regional analysis of DA, NE, and 5-HT concentrations in rats exposed to 1000 ppm of toluene for 8-h indicated a significant increase in DA concentration in the striatum. A significant increase in NE concentrations was detected in the medulla and midbrain while 5-HT concentrations were significantly increase in the cerebellum, medulla, and striatum. The results indicate that toluene action results in elevated concentrations of behaviorally significant neuro-transmitters.     

Median Sternotomy T Incision for Thymectomy in Myasthenia Gravis

Controversy exists over the surgical approach for thymectomy for myasthenia gravis. Opinion is divided between transcervical thymectomy and transsternal thymectomy performed through a median sternotomy. A technique that combines the advantages of a small, cosmetic T incision with good visualization through a partial sternotomy is presented. We have utilized this technique in more than 35 patients during the past ten years with excellent results.     

Correlations between phospholipid methylation and neuronal catecholamine transport

A change in the fluidity of biological membranes can be produced by methylation reactions which sequentially transfer methyl groups from phosphatidylethanolamine to phosphatidylcholine. Since the physical properties of membranes may affect the function of membrane-localized transport proteins, the accumulation of norepinephrine (NE) by rat cortical synaptosomes was examined in the presence of S-adenosylhomocysteine (AdoHcy) which inhibits the methylation of phospholipids. A concentration-related decrease in the uptake of [3H]NE was produced by AdoHcy with coincident decreases in the S-adenosylmethionine (AdoMet)-dependent transmethylation of phospholipids in neuronal membranes. A kinetic analysis for the effects of AdoHcy on the neuronal uptake of NE revealed a significant decrease in both the apparent Km and Vmax. Treatment of synaptosomes with adenosine, L-homocysteine thiolactone (HTL), and erythro-9(2-hydroxy-3-nonyl)adenine (EHNA) which leads to the synthesis of intracellular AdoHcy resulted in a decrease in the Vmax with no significant change in the Km. Adenosine or EHNA alone had no effect on NE uptake, but HTL alone significantly inhibited NE uptake. The data suggest that the processes of enzymatic methylation of membrane phospholipids and the transport of norepinephrine may be associated within neuronal membranes. Inhibiting phospholipid methylation reactions can reduce the efficiency of neurotransmitter removal and perhaps indirectly alter synaptic function.     

Comparison of the protective properties of four clinical crystalloid cardioplegic solutions in the rat heart

Although few surgeons dispute the benefits of high-potassium crystalloid cardioplegia, objective comparison of the efficacy of various formulations is difficult in clinical practice. We compared four commonly used cardioplegic solutions in the isolated rat heart (N = 6 for each solution) subjected to 180 minutes of hypothermic (20 degrees C) ischemic arrest with multidose cardioplegia (3 minutes every half-hour). The clinical solutions studied were St. Thomas' Hospital solution, Tyers' solution, lactated Ringer's solution with added potassium, and a balanced saline solution with glucose and potassium. Postischemic recovery of function was expressed as a percentage of preischemic control values. Release of creatine kinase during reperfusion was measured as an additional index of protection. St. Thomas' Hospital solution provided almost complete recovery of all indexes of cardiac function following ischemia including 88.1 +/- 1.6% recovery of aortic flow, compared with poor recovery for the Tyers', lactated Ringer's, and balanced saline solutions (20.6 +/- 6.5%, 12.5 +/- 6.4%, and 9.6 +/- 4.2%, respectively) (p less than 0.001). Spontaneous defibrillation was rapid (less than 1 minute) and complete (100%) in all hearts in the St. Thomas' Hospital solution group, but much less satisfactory with the other formulations. Finally, St. Thomas' Hospital solution had a low postischemic level of creatine kinase leakage, contrasting with significantly higher enzyme release in the other solutions tested (p less than 0.001). Although differences in composition are subtle, all potassium crystalloid cardioplegic solutions are not alike in the myocardial protection they provide. Comparative studies under controlled conditions are important to define which formulation is superior for clinical application.     

Effect of iontophoresis of vasopressin on lateral septal neurons

In rats, arginine-vasopressin (AVP) iontophoretically applied to lateral septal neurons activated by fimbria stimulation produced a decrease in the amplitude of the fimbria-evoked field response and a decrease in the frequency of fimbria-evoked action potentials. A second group of rats, treated with α-methyl-p-tyrosine, showed a significantly smaller decrease in responses after AVP iontophoresis, suggesting an interaction between catecholamines and AVP at the synaptic level.     

The natural history of Meckel's diverticulum and its relation to incidental removal: A study of 202 cases of diseased Meckel's diverticulum found in King County,Washington, over a fifteen year period

To determine the natural history of Meckel's diverticulum, 202 case records of proved disease of Meckel's diverticulum were retrieved, covering a fifteen year period, from all the hospitals of King County, Washington (population, 1,143,800). Using the figure of 2 per cent incidence of Meckel's diverticulum, we calculated that a Meckel's diverticulum has a 4.2 per cent likelihood of causing disease during a lifetime, decreasing to zero with old age. Using previously published mortality and morbidity figures, we calculated that to save one patient's life from the complications of Meckel's diverticulum, it would be necessary to remove approximately 800 asymptomatic Meckel's diverticula. This would be likely to incur a significant amount of postoperative morbidity from postoperative intestinal obstruction and infection. We suggest that the prophylactic removal of Meckel's diverticulum is rarely, if ever, justified.     

Subsensitivity of the norepinephrine receptor-coupled adenylate cyclase system in brain: Effects of Nisoxetine versus fluoxetine

Chronic administration of the norepinephrine (NE) reuptake inhibitor nisoxetine reduced the sensitivity of the NE receptor-coupled adenylate cyclase system in rat cortex. This subsensitivity, unlike that caused by desipramine (DMI), was not related to a reduction in specific β-adrenergic receptor binding. The specific serotonin reuptake inhibitor fluoxetine had no effect on either neurohormonal sensitivity or ³H-dihydroalprenolol binding.