On the dynamics of bursting systems

The dynamics of three-variable models of bursting are studied. It is shown that under certain conditions, the dynamics on the attractor can be essentially reduced to two dimensions. The salient dynamics on the attractor can thus be completely described by the return map of a section which is a logistic interval map. Two specific bursting models from the literature are shown to fit in the general framework which is developed. Bifurcation of the full system for one case in investigated and the dynamical behavior on the attractor is shown to depend on the position of a certain nullcline.

Right lower lobectomy for pulmonary infarction before orthotopic heart transplantation

A 39-year-old potential heart transplant recipient had a right lower lobe infiltrate and on pulmonary angiography was found to have an embolous to the common basilar artery. This was successfully managed by a right lower lobectomy, after aggressive medical management failed. The patient was treated postoperatively with antibiotics and subsequently underwent orthotopic heart transplantation. At 1 year after transplant the patient has no evidence of cardiac or pulmonary insufficiency.

Decreased platelet number and function and increased fibrinolysis contribute to postoperative bleeding in cardiopulmonary bypass patients

We simultaneously evaluated platelet and fibrinolytic parameters to assess their individual and combined contributions to postoperative blood loss in cardiopulmonary (CP) bypass patients. Platelet count, platelet aggregability, hematocrit, plasminogen (PLG) concentration, alpha 2-antiplasmin (AP) concentration, free protease activity (fPA), and antithrombin-III (AT-III) were measured in nine patients undergoing surgery using cardiopulmonary bypass. Chest tube drainage was used as the measure of postoperative blood loss. Hematocrit, platelet count, PLG, AP, and AT-III all decreased during CP bypass, with PLG and AT-III decreasing much more than dilution. During CP bypass, platelet aggregability to ADP did not change significantly from pre-bypass, but aggregability to arachidonic acid (AA) decreased significantly. Following protamine administration there was a large increase (83%) in fPA, the platelet count showed a further drop (from 61% to 50% of pre-bypass levels), and platelet aggregability decreased significantly (from 95% to 34% of pre-bypass levels for ADP, and from 55% to 11.9% for AA). Chest tube drainage during the first four postoperative hours correlated positively (p less than 0.05) with the combination of increase in free protease activity and decrease in platelet count. The total chest tube drainage correlated significantly with the combination of decrease in platelet count and the decrease in platelet aggregability. These combinations of changes correlated significantly with postoperative blood loss whereas the individual changes did not.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological observations from feeding heated corn oil and heated peanut oil to rats

Five groups of male weanling rats were provided purified diets containing 15% by weight of either fresh or laboratory-heated corn oil (FCO, HCO) or fresh, laboratory-heated, or commercial pressure deep-fry peanut oil (FPO, HPO, PPO). Total weight gain, feed consumption, and feed efficiency were consistently greater for the FCO, FPO, and PPO groups. Although relative heart weights were unaffected, the HCO and HPO produced elevated liver and kidney weights. The dietary fats had no effect on the hematological status of the animals or the proportions of cells comprising the total leukocytes of the blood. Physical, chemical, and microscopic evaluation of the urine detected no pathologic conditions. Rats fed diets containing HCO or HPO demonstrated toxicity of thermally oxidized fats by the appearance of diarrhea, dermatitis, seborrhea, and hair loss. Histological examinations revealed injury of the thymus by all fat samples except the FCO; the liver was damaged by the HCO, HPO, and PPO, and the testes and epididymides by HPO and PPO. In the latter case there was complete cessation of spermatogenesis.

Calcium-accentuated ischemic damage during reperfusion: the time course of the reperfusion injury in the isolated working rat heart model

The purpose of this study was to determine the time course of calcium-induced postischemic reperfusion injury to the myocardium, using an initial short-term calcium-enriched reperfusion solution. The isolated rat heart model was subjected to 30 min of normothermic potassium cardioplegia-induced ischemic arrest. Control hearts received normal calcium Krebs-Henseliet buffer (KHB) reperfusion. Experimental hearts were challenged with 10 min of calcium-enriched (KHB) reperfusion starting at 0, 1, 2, 5, 15, and 30 min after the beginning of reperfusion. Aortic flow recovery 60 min after reperfusion was used to determine functional recovery. Control hearts recovered 82 +/- 3% of preischemic aortic flow. Hearts which received calcium challenge at 0 and 1 min after the start of reperfusion recovered 43 +/- 4 and 69 +/- 3% of preischemic aortic flow, respectively (P less than 0.01 and P less than 0.05, respectively). Hearts which received calcium challenge 2, 5, 15, and 30 min after reperfusion recovered 75 +/- 2, 80 +/- 2, 85 +/- 2, and 83 +/- 2% of preischemic aortic flow, respectively. Our results indicate that the postischemic myocardium is very susceptible to calcium-accentuated ischemic damage during the initial period of reperfusion. The postischemic heart, however, quickly recovers its ability to withstand a calcium challenge. Five minutes after the start of reperfusion the heart is not influenced by calcium challenge.

Spontaneous oscillations in two 2-component cells coupled by diffusion

Mathematical examples are presented of oscillators with two variables which do not oscillate in isolation, but which do oscillate stably when coupled with a twin via diffusion. Two examples are presented, the Lefever-Prigogine Brusselator and a system used to model glycolytic oscillations. The mathematical method is not the usual bifurcation theory, but rather a type of singular perturbation theory combined with bifurcation theory. For both examples, it is shown that all stationary solutions are unstable for appropriate parameter settings. In the case of the Brusselator, it is further shown that there exist limit cycles; i.e. stable oscillations, in this parameter range. A numerical example is presented.

Terminal magnesium cardioplegia: protective effect in the isolated rat heart model using calcium accentuated ischemic damage

We have developed a modified isolated working rat heart model to study the effect of potassium and magnesium cardioplegia given just prior to reperfusion, "terminal cardioplegia," on preservation of aortic flow following a standard ischemic insult. The model incorporates a short-term calcium challenge at the beginning of reperfusion to accentuate ischemic injury. All hearts were given initial potassium cardioplegia and subjected to 30 min of normothermic ischemia. Terminal cardioplegia was given for the 2 min prior to reperfusion. Calcium-challenged hearts were reperfused initially with calcium-enriched reperfusate and then switched to standard reperfusate. Aortic flow prior to and 60 min after ischemia was used to determine functional protection. Hearts recovered 82 +/- 3% of preischemic aortic flow when reperfused with normocalcemic reperfusate. When the initial reperfusate was enriched with calcium, aortic flow was only 43 +/- 4% of control. Hearts given terminal magnesium cardioplegia and then challenged with calcium-enriched reperfusate recovered 79 +/- 4% of control aortic flow. Hearts given terminal potassium cardioplegia recovered only 53 +/- 5% of control aortic flow when challenged with calcium-enriched initial reperfusate. Our results indicate that the recovery of aortic flow is significantly reduced by short-term postischemic calcium challenge. This damage is blocked by terminal magnesium cardioplegia, but not by terminal potassium cardioplegia.

Chylothorax review

Chylous leakage from the thoracic duct into the pleural space may occur after any type of thoracic surgery; however, there are few reports of this condition after coronary artery bypass grafting. A case of chylothorax after combined coronary bypass and mitral valve replacement is reported to illustrate a discussion of its pathologic basis, diagnosis and management.

Long-term experience with nadolol in treatment of hypertension and angina pectoris

Two-hundred ninety-one patients with hypertension and 313 patients with angina pectoris were enrolled and treated with nadolol for up to 2 years. The efficacy of nadolol in hypertension and angina was maintained over the 2-year period. Discontinuation because of an adverse reaction occurred with 8.3% of the hypertensive patients and 8.6% of the angina patients. The observed reactions were typical of those which occur with beta-blocking drugs. Serum creatinine levels fell significantly (p less than 0.05) after 12 months of treatment for both the angina and hypertensive patients. After 24 months of treatment the serum creatinine levels had decreased 20% from baseline (p less than 0.001). Blood urea nitrogen levels fell in the angina patients after 12 months of treatment but not in the hypertensive patients. Nadolol is safe and effective for the long-term treatment of both hypertension and angina. Renal function, as measured by serum creatinine levels, improved with long-term treatment.

Inhibition of chemiluminescence in human neutrophils by dapsone

Dapsone at doses of 0.5 to 5.0 micrograms/ml was found to produce a dose-dependent inhibition of opsonized zymosan-induced human polymorphonuclear leukocyte (PMN) chemiluminescence (CL) in vitro. Simultaneous exposure of PMN to dapsone and zymosan was as effective in reducing CL as preincubation of PMN with dapsone. Preincubation of PMN with dapsone followed by washing, resulted in the loss of dapsone-mediated CL inhibition, indicating that dapsone did not permanently alter the CL-generating mechanism and that the drug had to be present to inhibit CL. Dapsone did not absorb light at the wavelength of CL and was not toxic to PMN at concentrations tested. Sodium azide, an inhibitor of myeloperoxidase-mediated CL inhibited PMN CL to the same degree as dapsone. When incubated together with PMN, dapsone and azide did not produce an additive inhibition of CL. These data suggest that inhibition of myeloperoxidase may be the mechanism by which dapsone inhibits PMN CL.

Captopril in the treatment of scleroderma renal crisis

Scleroderma is a disease of unknown cause characterized by interstitial fibrosis and vascular lesions in many organ systems. Renal failure, often associated with malignant hypertension, may ensue as a life-threatening component of this disorder. Activation of the renin-angiotensin-aldosterone system has been hypothesized as a cause of this complication. Captopril has been used in 23 patients with this condition. Of this group, 20 (87%) responded favorably with a decrease of the supine diastolic BP to less than 90 mm Hg and a reduction in the serum creatinine level in 14 patients. During long-term therapy (median, 29 months), 11 of the 23 patients continued to have a good clinical response while receiving captopril. Six patients died and six patients were alive after captopril therapy was discontinued. These data suggest that captopril is beneficial in the treatment of scleroderma renal crisis.

Stapled esophagogastric anastomosis

In a consecutive, nonrandomized series of 92 patients, esophagogastric anastomosis was performed with a suture technique in 32 patients and with a stapler in 60 patients. Only one anastomotic leak occurred in each group. Stricture later formed in three sutured anastomoses and in eight of the stapled anastomoses. A review of published reports shows anastomotic leak in 3.5 percent of the patients with stapled anastomoses. In patients with sutured anastomoses, leak occurred in approximately 10 percent. The improved results with the stapler do not alter the necessity for meticulous attention to technical detail.

Enzymatic hydrolysis in vitro of thermally oxidized sunflower oil

The hydrolysis of thermally oxidized sunflower oil by pancreatic lipase was studied in relation to chemical changes in the acylglycerols. Four classes of compounds (monomers, dimers, trimers and polymers) formed from the acylglycerols were separated from the heated oils by column chromatography on silica gel, and further verified by thin layer chromatography. Each fraction, after analyses for generaly properties, was subjected to a time course study of hydrolysis by pancreatic lipase over a 30-min period. After 70 hr of heating, the amount of hydrolysis for the acylglycerol dimers was only about half that of the monomers, and that for the trimers was, in turn, about one-third that of the monomers. The polymers were the least hydrolyzed and showed no further reaction after 5 min. The reduction in enzymatic hydrolysis of isolated fractions from the thermally oxidized oils indicates structural differences, related to formation of polar compounds and polymerization products. Adverse effects on animals from feeding these materials can be attributed partly to inhibition of hydrolysis resulting in less available energy.

Enzymatic hydrolysis of fractionated products from oils thermally oxidized in the laboratory

Enzymatic hydrolysis of the acylglycerol products obtained from thermally oxidized vegetable oils was studied. Corn, sunflower and soybean oils were heated in the laboratory at 180 C for 50, 70 and 100 hr with aeration and directly fractionated by silicic acid column chromatography. By successive elution with 20%, then 60% isopropyl ether in n-hexane, and diethyl ether, the thermally oxidized oils were separated into three fractions: the nonpolar fraction (monomeric compounds), slightly polar fraction (dimeric compounds), and polar fraction comprising oligomeric compounds. Enzymatic hydrolysis with pancreatic lipase showed that the monomers were hydrolyzed as rapidly as the corresponding unheated oils, the dimers much more slowly, and the oligomeric compounds barely at all. Overall, the hydrolysis of the dimers was less than 23% of that for the monomers, with small differences among the oils. Longer heating periods resulted in greater reductions in hydrolysis of the dimeric compounds. These results suggest that the degree of enzymatic hydrolysis of the fractionated acylglycerol compounds is related to differences in the thermal oxidative deterioration, and amounts of polar compounds in the products.

Dysrhythmias caused by histamine release in guinea pig and human hearts

Histamine is released into the systemic circulation during anaphylaxis, by drugs and by surgical procedures. Studies in animal models have conclusively demonstrated that released cardiac histamine is a major mediator of arrhythmias that occur during anaphylaxis and following the administration of histamine-releasing drugs. Several lines of evidence suggest a similar arrhythmogenic role for cardiac histamine in humans: (1) The human heart is rich in histamine; (2) cardiac histamine can be readily released from human heart in vitro by therapeutic concentrations of drugs; (3) histamine has potent arrhythmogenic effects on the human heart in vitro. Arrhythmogenic effects of histamine include enhancement of normal automaticity, induction of abnormal automaticity, induction of triggered tachyarrhythmias, depression of atrioventricular conduction, and increase in the vulnerability of the ventricles to fibrillation. A combination of H1 and H2 antihistamines is needed to block the arrhythmogenic effects of histamine. Certain arrhythmogenic effects of histamine (e.g. induction of slow responses and delayed afterdepolarizations) can also be blocked by drugs which inhibit the influx of cations through slow channels. In contrast, the commonly-used drug digitalis potentiates the arrhythmogenic effects of histamine. We propose that histamine release produced by drugs and surgical procedures may be an overlooked factor in fatal cardiac arrhythmias. Experimental studies suggest that selective pharmacological methods can be developed to block the arrhythmogenic effects of histamine.

Influence of dose level and methionine intake on the effects of linamarin administration to rats

Rats were fed a semipurified diet providing 10% casein supplemented with methionine for 2 wk, at which time some animals received the same diet without the methionine for 4 d. Animals that received linamarin were given a single oral dose containing 500 or 250 mg per kilogram of body weight. At the higher linamarin dose all animals died within 5 h after dosing. Biochemical and physiological changes observed in these rats included severe metabolic acidosis, decreased cytochrome oxidase activities, atrial fibrillation, and decreased respiratory rates. In general, the cardiac adenosinetriphosphatase enzymes were inhibited by linamarin. None of these changes were moderated by dietary methionine supplementation. At the lower linamarin dose dietary supplementation with methionine appeared to reduce incidences of clinical toxicity signs and fatalities. No methionine effect was observed in the other biochemical and physiological measurements in rats given this amount of linamarin. The results suggest that dietary supplementation with methionine provided some protection against the toxicity of the lower level of linamarin administered.

Cytotoxicity of thermally oxidized fats

The effects of oxidized fat components (free fatty acids from the distillable nonurea adductable fraction) isolated from heated corn oil or heated olive oil on the morphology and growth of heart cells in primary culture were investigated. The free fatty acid fractions isolated from the fresh fats served as controls. Different concentrations of the fat fractions (20, 60, and 100 micrograms/ml) were added to the medium in the form of an emulsion with bovine serum albumin (Fraction V, poor in unesterified fatty acids). In the cell cultures treated with heated fats, intracellular lipid accumulation, increased cytoplasmic vacuolization, mitotic aberrations, pyknotic cells, and decreased mitosis were observed and were more pronounced in the case of the heated olive oil. These cytotoxic effects increased with higher concentrations of heated fats in the medium. The fresh fats also produced intracellular lipid accumulation, reductions in mitosis, and changes in the nucleus and cytoplasm, at the higher levels. These effects were greater in fresh olive oil-treated cultures. These observations indicate that oxidized fat components interfere physically or biochemically with normal cell functions resulting in pathological changes.

Chemical and biological properties related to toxicity of heated fats

Heating of fats brings about measurable changes in their chemical and physical characteristics. Heat is applied in processing for food manufacture, such as during hydrogenation of oils with a catalyst, and in frying for meal preparation. Partially hydrogenated products generally contain substantial quantities of geometric and positional isomers of the original unsaturated fatty acids. During deep-fat frying, when the fat is used repeatedly, oxidative and thermal effects result in the formation of many volatile and nonvolatile products, some of which are potentially toxic, depending on the level of intake. Because of concern about the types of changes that take place in fats during oxidative and thermal deterioration and the effects the derivatives could have on the consumer, many chemical and biological studies have been carried out. Experimental findings indicate that any potential danger to the consumer is relative to the severity of the overall treatment of the fat. In some studies we evaluated biological effects on rats of trans fatty acid in the diet and of concentrates of fatty acid derivatives produced in thermally oxidized fats. trans-Octadecenoic acid changed the concentrations of the phospholipid classes in the liver lipids, and interfered with conversion of the essential n - 6 series of fatty acids to higher members. Compared to oleic acid, elaidic acid was preferentially incorporated into the phospholipids instead of the triacylglycerols and was also concentrated in the lipoprotein fractions. Administration of non-urea-adductable concentrates from thermally oxidized fats produced cellular damage in hearts, livers, and kidneys of the animals. Since even practical processing and frying conditions can produce some nutritionally undesirable products, a concerted effort should be made to minimize substantial accumulation of these in our dietary fats.

Effects of vitamin E and ascorbyl palmitate on cultured myocardial cells exposed to oxidized fats

Primary cultures of rat heart cells were used as a model system to study the influence of two antioxidants, vitamin E and ascorbyl palmitate, on biological effects of thermally oxidized fat. The free fatty acid fraction of the distillable non-urea-adductable fraction of heated corn oil (HCO) was used as the test lipid; the free fatty acid fraction of fresh corn oil was the control. HCO (100 microgram/ml medium) depressed the mitotic index, induced excessive lipid accumulation, and increased the number of pyknotic nuclei in the cells. Addition of extra vitamin E (10 microgram/ml medium) reduced the toxicity of HCO by counteracting these changes. In comparison, ascorbyl palmitate (10 microgram/ml medium) in the presence of HCO was beneficial in that it produced only a slight increase in the mitotic index. HCO treatment also resulted in reduced levels of linoleic and arachidonic acids in the phospholipid fractions of the cells, and addition of vitamin E or ascorbyl palmitate increased the level of arachidonic acid. The triacylglycerol fraction of HCO-treated cells showed markedly reduced linoleic acid and increased arachidonic acid. These changes were unaffected by the antioxidant treatments. Vitamin E counteracted the adverse effects of HCO treatment on the rat heart cells. Ascorbyl palmitate only was as efficient as vitamin E in elevating the concentration of arachidonic acid at the membrane level in the presence of HCO.

Lung abscess and empyema of the thorax

Empyema is best managed by the physician familiar with the indications and principals of the various procedures used in the treatment of empyema of the thorax. The objective of each modality used to treat empyema is to drain the pleura cavity and to allow full expansion of the lung. If the infected material can be removed and the visceral and parietal pleural approximated, the body will heal the pleural infection. The procedure chosen to treat empyema greatly depends upon the phase of maturation of the empyema when treatment is begun.