Effects of hyperthermia and hypothermia on oxygen extraction by tissues during hypovolemia

As systemic delivery of O2 (QO2 = QT X CaO2) is reduced during progressive hemorrhage, the O2 extraction ratio [(CaO2 - CVO2)/CaO2] increases until a critical delivery is reached below which O2 uptake (VO2) becomes limited by delivery (O2 supply dependence). When tissue metabolic activity and O2 demand are increased or reduced, the critical QO2 required to maintain VO2 should rise or fall accordingly, unless other changes in the distribution of a limited QO2 precipitate the onset of O2 supply dependence at a different critical extraction ratio. We compared the critical QO2 and critical extraction ratio in 23 normothermic (38 degrees C), hyperthermic (41 degrees C), or hypothermic (34 decrees C) dogs during stepwise reduction in delivery produced by bleeding, as arterial O2 content was maintained. Dogs were anesthetized, paralyzed, and mechanically ventilated. Hypothermia reduced whole-body VO2 by 31%, whereas hyperthermia increased VO2 by 20%. The critical QO2 was significantly reduced during hypothermia (5.6 +/- 0.95 ml.min-1.kg-1) (P less than 0.05) and increased during hyperthermia (8.9 +/- 1.1) (P approximately equal to 0.06) compared with normothermic controls (7.4 +/- 1.2). The extraction ratio at the onset of supply dependency was significantly increased in hyperthermia (0.76 +/- 0.05) compared with hypothermia (0.65 +/- 0.10) (P less than 0.05), and the normothermic critical extraction was 0.71 +/- 0.1. These results suggest that higher body temperatures are associated with an improved ability to maintain a VO2 independent of QO2, since a higher fraction of the delivered O2 can be extracted before the onset of O2 supply dependence, relative to lower body temperatures.

Systemic and intestinal limits of O2 extraction in the dog

When systemic delivery of O2 (QO2 = QT X CaO2, where QT is cardiac output and CaO2 is arterial O2 content) is reduced by bleeding, the systemic O2 extraction ratio [ER = (CaO2 - CVO2)/CaO2, where CVO2 is venous O2 content] increases until a critical limit is reached below which O2 uptake (VO2) becomes limited by O2 delivery. During hypovolemia, reflex increases in mesenteric arterial tone may preferentially reduce gut blood flow so that the onset of O2 supply dependence occurs in the gut before other regions. We compared the critical O2 delivery (QO2c) and critical extraction ratio (ERc) of whole body and an isolated segment (30-50 g) of small bowel in seven anesthetized paralyzed dogs ventilated with room air. Systemic QO2 was reduced in stages by controlled hemorrhage as arterial O2 content was maintained, and systemic and gut VO2 and QO2 were measured at each stage. Body QO2c was 7.9 +/- 1.9 ml X kg-1 X min-1 (ERc = 0.69 +/- 0.12), whereas gut O2 supply dependency occurred when gut QO2 was 34.3 +/- 11.3 ml X min-1 X kg gut wt-1 (ERc = 0.63 +/- 0.09). O2 supply dependency in the gut occurred at a higher systemic QO2 (9.7 +/- 2.7) than whole-body QO2c (P less than 0.05). The extraction ratio at the final stage (maximal ER) was less in the gut (0.80 +/- 0.05) than whole body (0.87 +/- 0.06). Thus during reductions in systemic QO2, gut VO2 was maintained by increases in gut extraction of O2.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer modeling of the reaction between antigen and heterogeneous antibody in fixed antigen excess: a new method for measuring antibody affinity

Antigen-antibody binding experiments were performed by choosing antigen excess starting conditions and then diluting both the 125I-BSA antigen and anti-BSA proportionately so that the ratio between the reactants remained constant. The fraction antigen bound was measured at each dilution. Binding data were analyzed by computer using non-linear least squares regression to determine the affinity and affinity distribution of different antisera. Early anti-BSA was found to have a unimodal distribution with a binding constant in the range of 10(6)M-1. Intermediate anti-BSA had a bimodal distribution: 1/3 high affinity (1.0 X 10(9] and 2/3 low affinity (3.4 X 10(6)M-1). Late and hyperimmune rabbit BSA antibodies had unimodal affinity distributions with binding constants varying between 1.7 and 2.9 X 10(10)M-1. Antibody affinity can be readily determined by computer analysis of binding curves obtained in constant antigen excess conditions.

Neurogenic hyperacute ascites in mice

Four groups of mice were subjected to controlled fatal head trauma and then evaluated for the presence of ascites (neurogenic hyperacute ascites, NHA). The animals died virtually instantaneously and without evidence of maintained pain or suffering. The volume of ascites was determined in one group of animals. Two of the traumatized groups were pretreated, one with the beta-blocker propranolol and the other with the alpha-blocker phentolamine. A fifth, non-traumatized, group which was killed with either inhalation served as a control group. Two more groups of non-traumatized mice were administered either the alpha-adrenergic agonist methoxamine hydrochloride or the beta-agonist isoethrane mesylate before killing by ether inhalation, and then evaluated for ascites. Transudative ascitic fluid was found in 87-100% of untreated traumatized mice and in no control animals. Pretreatment with phentolamine had no effect on the prevalence of ascites. Pretreatment with propranolol produced a significant decrease in the prevalence of ascites compared with trauma alone (P less than 0.001). Isoethrane (beta-agonist) administration caused ascites in 100% of the treated animals. Methoxamine (alpha-agonist) administration did not cause ascites. A previously undescribed consequence of acute brain trauma is described (NHA) which appears to be mediated by beta-sympathetic activity of central origin. NHA is inhibited by beta-blockade and can be simulated with beta-agonist administration.

Pulmonary arteriovenous malformations: a critical update

Although first reported 90 yr ago, the natural history of pulmonary arteriovenous malformations (PAVM) is still incompletely understood. We review historical perspectives and pathologic classification of this rare disease and identify etiologic factors and clinical features in the 450 reported cases. The many different diagnostic modalities currently available are described, and a logical sequence of investigations is suggested. Pulmonary angiography remains mandatory prior to definitive treatment. The available evidence strongly suggests that morbidity and mortality in untreated PAVM exceeds that associated with either surgical resection or embolic occlusion. Thus, definitive treatment should be offered in all cases, with the possible exception of asymptomatic patients with small lesions who have no evidence of Osler-Weber-Rendu disease. Embolotherapy is now the treatment of choice in institutions with the necessary expertise and facilities, notwithstanding the absence of long-term follow-up for patients treated this way. It is suggested that increased documentation of long-term morbidity and mortality in both treated and untreated patients with PAVM will lead to greater understanding and more effective management of this enigmatic condition.

Microcomputer simulation of antigen-antibody binding at a fixed antigen/antibody ratio

Computer simulation techniques were used to define the theoretical nature of the reaction of antigen with antibody at a constant degree of antigen excess. The simulation studies show that binding curves obtained under these conditions have unique features which are determined by antibody affinity, affinity heterogeneity and the concentrations of antigen and antibody. When analyzed by non-linear least squares regression these curves can be used to determine the affinity of antibody in homogeneous and heterogeneous systems.

Pulmonary vascular tone is increased by a voltage-dependent calcium channel potentiator

The mechanism of hypoxia-induced pulmonary vasoconstriction remains unknown. To explore the possible dependence of the hypoxic response on voltage-activated calcium (Ca2+) channels, the effects of BAY K 8644 (BAY), a voltage-dependent Ca2+ channel potentiator, were observed on the pulmonary vascular response to hypoxia of both the intact anesthetized dog and the perfused isolated rat lung. In six rat lungs given BAY (1 X 10(-6)M), hypoxia increased mean pulmonary arterial pressure (Ppa) to 30.5 +/- 1.7 (SEM) Torr compared with 14.8 +/- 1.2 Torr for six untreated rat lungs (P less than 0.01). After nifedipine, the maximum Ppa during hypoxia fell 14.1 +/- 2.4 Torr from the previous hypoxic challenge in the BAY-stimulated rats (P less than 0.01). BAY (1.2 X 10(-7) mol/kg) given during normoxia in seven dogs increased pulmonary vascular resistance 2.5 +/- 0.3 to 5.0 +/- 1.2 Torr X 1(-1) X min (P less than 0.05), and systemic vascular resistance 55 +/- 4.9 to 126 +/- 20.7 Torr X 1(-1) X min (P less than 0.05). Systemic mean arterial pressure rose 68 Torr, whereas Ppa remained unchanged. Administration of BAY during hypoxia produced an increase in Ppa: 28 +/- 1.5 to 33 +/- 1.9 Torr (P less than 0.05). Thus BAY, a Ca2+ channel potentiator, enhances the hypoxic pulmonary response in vitro and in vivo. This, together with the effect of nifedipine on BAY potentiation, suggests that increased Ca2+ channel activity may be important in the mechanism of hypoxic pulmonary vasoconstriction.

Legionella pneumophila pericarditis without pneumonia

To our knowledge, Legionella pericarditis has been reported only four times in the literature and only once without pneumonia. We report the second case of nonpneumonic Legionella pericarditis in a man who eventually required pericardiectomy for constriction. Since Legionella endocarditis, myocarditis, and pericarditis have all been documented by culture or direct fluorescent antibody staining, it is important to be aware of the possibility of cardiac legionellosis.

Analysis of historical variables, risk factors and the resting electrocardiogram as an aid in the clinical diagnosis of recurrent chest pain

A prospective study on 184 consecutive patients presenting with the chief complaint of recurrent chest pain (RP) for diagnostic coronary arteriography (CA) was conducted utilizing a simple questionnaire of historical, physical and electrocardiographic variables. A linear logistic regression analysis yielded a final data set of 13 variables. Concurrently, staff cardiologists who obtained the questionnaire data through direct questioning rendered a clinical diagnosis of either angina (coronary artery disease [CAD]) or noncardiac chest pain. Utilization of the regression analysis increased diagnostic accuracy from 69 to 86% (p less than 0.0003); sensitivity from 83 to 88% (NS) and specificity from 49 to 84% (p less than 0.0001). The best predictive variables for the presence or absence of obstructive CAD documented by CA were in order of decreasing value: age, electrocardiogram, pain aggravated by sex, sex (gender), pain aggravated by movement, diabetes mellitus, pain described as prickling, pain described as burning, pain relieved by rest, pain with radiation to both arms, associated nausea, associated dyspnea, and a history of a lipid disorder. Four variables were predictive of normal coronary anatomy (NCA), pain aggravated by movement, prickling, nausea, and dyspnea. Although this set of predictor variables may not apply equally well to all populations of cardiac patients, the availability and relative simplicity of the program allow for adding or deleting variables and thus provide for considerable potential in the diagnostic assessment of RP. An inexpensive pocket computer can utilize the coefficients generated by the logistic regression program to calculate the probability of CAD as the cause of RP.

Computer simulation of plasma exchange therapy in autoimmune disease

Computer simulation of plasma exchange in autoimmune disease shows that a single treatment may reduce the amount of antibody bound to antigen by as much as 60-80%. The reduction is greatest when autoantibody is of low affinity and there is an excess of antibody compared to antigen.

Theoretical analysis of the Farr antibody assay with a computer model: importance of antigen concentration and antibody affinity

The Farr assay for antibody was analyzed theoretically in order to determine the maximum sensitivity of the assay, the quantitative relationship between actual antibody concentration and antibody estimates by the Farr technique, and the relationship between antibody affinity and the Farr avidity index. Analysis shows that sensitivity is limited by the antigen concentration when large amounts of antigen are used in the assay. Sensitivity at low antigen concentrations is maximal and varies with the affinity of the antibody studied. Antibody titers obtained by the Farr technique using low antigen concentrations vary with antibody affinity as well as antibody concentration. Titers measured at high antigen concentration are less affected by affinity and correlate better with antibody concentration. Antibody measurements expressed as Antigen Binding Capacity reflect antibody concentration only when the antigen concentration used in the assay exceeds a value equal to ten times the reciprocal of the antibody affinity constant. The Farr avidity index correlates with antibody affinity over a narrow affinity range. Different ranges of affinity can be examined by changing the antigen concentrations.

A rapid method for the determination of antibody affinity

A rapid method for estimating antibody affinity is described. To perform the assay fixed amounts of radiolabeled antigen and antibody are mixed in different total reaction volumes. The fraction of antigen bound to antibody is measured in aliquots from each reaction volume by the ammonium sulfate precipitation technique. Affinity constants can be estimated from these data graphically or by means of a microcomputer. This method is much quicker and easier to perform than traditional techniques for estimating antibody affinity.

Nonvolumetric assessment of ventricular function by two-dimensional echocardiography in patients with coronary artery disease

Left ventricular ejection fraction (EF) was prospectively predicted by nonvolumetric parameters obtained by M-mode and two-dimensional (2DE) echocardiography in 55 patients with angiographically proven coronary artery disease. In particular, the mitral E-point to septum separation (EPSS) could predict the angiographic ejection fraction (EF) according to the formula %EF = 74 - 2 (EPSS) with a correlation of 0.81 and a standard error of the estimate (SEE) of 12%. An EPSS of greater than 10 mm predicted ventricular dysfunction with a sensitivity of 0.81 and a specificity of 0.93. A Wall Motion Score (WMS), obtained by summing segmental wall motion assessed as normal = 4, hypokinetic = 3, akinetic = 2, dyskinetic = 1, for each of seven segments and dividing by seven (the number of segments evaluated), also correlated with the angiographic EF (r = .76). An abnormal WMS was found to be less than 3.3 and together with an EPSS greater than 10 mm, these parameters had a sensitivity of 0.90, a specificity of 0.92, and predictive value of 0.90 for ventricular dysfunction, as evidenced by an EF of less than 0.51. We conclude that the EPSS has a great a predictive value for the EF as the more vigorous quantitative volumetric echocardiographic estimates. Together with the WMS, these parameters are of considerable clinical value in detecting ventricular dysfunction.

Hematologic findings in Southeast Asian immigrants with particular reference to hemoglobin E

Recent immigrants from Southeast Asia were screened for hematologic abnormalities using a multichannel cell counter (Coulter S), peripheral smear, free erythrocyte protoporphyrin (FEP), isoelectric focusing, and a qualitative screen for glucose-6-phosphate dehydrogenase deficiency. Hematologic abnormalities were further defined by hemoglobin electrophoresis, globin electrophoresis, HbA2 levels, and HbF levels. Of the 189 adults studied, 68 (36 percent) were hematologically abnormal, including 28 hemoglobin E (HbE) heterozygotes, six HbE homozygotes, 14 with alpha-thalassemia minor, and 10 with presumptive iron deficiency. Of the 54 people with microcytic (MCV less than 80fl) red blood cells (RBC), 52 had evidence of HbE or thalassemia and two had iron deficiency alone; five had both iron deficiency and a hemoglobinopathy. Homozygosity for HbE results in an asymptomatic condition similar to thalassemia minor with microcytic RBC, large numbers of target cells, normal or slightly reduced hematocrit and greater than 90 percent HbE. People heterozygous for HbE are asymptomatic and have hematologic findings similar to thalassemia minor with slightly reduced or low normal MCV and 25 to 35 percent HbE.

Free erythrocyte protoporphyrin (FEP) II. The FEP test is clinically useful in classifying microcytic RBC disorders in adults

Microcytic red blood cells (RBC) are commonly encountered in clinical medicine and are caused by disorders of heme synthesis [usually iron deficiency anemia (IDA) or anemia of chronic disease (ACD)] or disorders of globin synthesis (usually thalassemia syndromes or HbE). Using the clinical history and standard laboratory tests (hematocrit, per cent saturation of transferrin (% sat), serum ferritin, Hb electrophoresis, HBA2, and HbF) we classified 198 adults with microcytic RBC as follows: 48 IDA, 11 probable IDA, 11 iron-deficient erythropoiesis without anemia, 13 ACD, 42 alpha-thalassemia trait, 35 probable alpha-thalassemia trait, 20 beta-thalassemia trait, and 15 unclassified. In addition, we demonstrated that the FEP test reliably (83-90% of the time, depending on FEP methodology) classifies microcytic RBC states into disorders of heme synthesis vs. disorders of globin synthesis. Because of reliability and ease of measurement, we recommend the hematofluorometer FEP as the first step in the clinical laboratory evaluation of microcytic RBC disorders in both adults and children.

Free erythrocyte protoporphyrin (FEP) I. Normal values for adults and evaluation of the hematofluorometer

Since the early 1970s, measurement of free erythrocyte protoporphyrin (FEP) (by microextraction or by hematofluorometer) has been widely used to screen for lead poisoning and to evaluate microcytic red blood cell (RBC) disorders in children. However, published information on normal values for FEP, performance of the hematofluorometer, and usefulness of FEP in classifying microcytic RBC disorders in adults is scant. In an adult population with normal hematocrit and MCV and normal values for serum ferritin, blood lead level, and serum bilirubin, we obtained normal hematofluorometer FEP levels of less than 30 micrograms/dL for men, and less than 40 micrograms/dL levels for women. We have evaluated a hematofluorometer against a standard microextraction procedure and feel that the hematofluorometer is superior for clinical laboratories if elevated FEPs are confirmed by retesting with washed RBC. In the second part of this paper we demonstrate the usefulness of the FEP in classifying microcytic RBC disorders in adults.

Brief prophylaxis with doxycycline for the prevention of traveler's diarrhea

A prospective, randomized double-blind trial of doxycycline prophylaxis for traveler's diarrhea was conducted on 145 volunteers during a 2.5-day visit to Mexico. Traveler's diarrhea occurred in 15 (21%) of the placebo group and in 3 (4%) of the doxycycline group (p = 0.002). There was no rebound increase in the incidence of acute diarrhea after departure from the high risk area in the doxycycline-treated group. A variety of bacterial pathogens were isolated from individuals symptomatic with traveler's diarrhea. Nausea alone (8%) or nausea with vomiting (4%) occurred in the doxycycline-treated group only and were the only side effects observed (p = 0.003). We conclude that doxycycline is safe and efficacious for the prophylaxis of traveler's diarrhea for short-term exposure in a high risk area.

Coronary artery disease and ventricular function in angina

Coronary arteriograms and left ventriculograms of 500 patients with coronary artery disease and angina pectoris were correlated with respect to coronary arterial pattern and left ventricular dyssynergy. We found that the severity of left ventricular dyssynergy was not altered by coronary arterial pattern. The concept of dividing the left ventricle into anterior and posterior zones was validated. Patients with anterior dyssynergy alone or combined anterior and posterior dyssynergy had comparably more severe coronary artery disease in the anterior region than did patients with normal left ventriculograms or posterior dyssynergy alone. Patients with posterior dyssynergy alone or combined anterior anterior and posterior dyssynergy had comparably more severe coronary artery disease in the posterior region than did patients with normal left ventriculograms or anterior dyssynergy alone. Lesions of greater than 90% reduction of coronary arterial luminal diameter best correlated with motion abnormalities of the left ventricular wall.

Immune suppression of erythropoiesis in transient erythroblastopenia of childhood

Serum and IgG from four children with transient erythroblastopenia of childhood (TEC) was tested to see what effect it would have on development of erythroid colonies from bone marrow mononuclear cells. Serum and IgG specimens obtained at the time of diagnosis uniformly suppressed erythroid colony development from CFU-E. Washed bone marrow mononuclear cells from a child with TEC failed to grow in the presence of his own serum, but grew normally in the presence of isologous serum. Serum specimens obtained from patients after recovery from TEC had no effect on erythroid colony development. The anemia of TEC appears to be due to transient immune suppression of erythroid colony development.

Distribution and severity of coronary artery disease in 500 patients with angina pectoris

The distribution and severity of coronary disease in 500 patients with angina pectoris and at least one area of 50% or greater reduction of luminal diameter in a major coronary artery were compared with respect to patients' age and coronary arterial pattern. The coronary arterial patterns were separated into right (360 patients), mixed (89 patients), and left (51 patients) systems, depending upon the blood supply to the inferior surface of the left ventricle. The following relationships were noted: 1) In patients with angina pectoris, the distribution and severity of coronary artery disease is similar from the third to eighth decade. 2) Coronary arterial stenoses of 50-70% of greater reduction of luminal diameter involve most frequently the proximal portion of the major vessels. Coronary artery disease is multivessel in nature in 80% of cases. In single vessel disease the left anterior descending artery is involved most frequently. 3) The left main coronary artery is moderately to severely obstructed less frequently in individuals with left (2%) as compared to right (8%) and mixed (10%) systems. Otherwise, the distribution of coronary artery disease is similar in right, mixed, and left systems. 4) Coronary artery disease is a diffuse rather than a focal process. As demonstrated by coronary arteriography, patients with coronary artery disease have smaller vessels throughout the arterial tree as compared with individuals free of evident coronary atherosclerosis.

Binding of alkali metal ions by cyclic polyethers: significance in ion transport processes

Values for the formation constant (log K), the change in enthalpy (triangle upH degrees ), and the change in entropy (triangle upS degrees ) have been determined for the interaction of lithium, sodium, potassium, rubidium, and cesium ions with the two isomers of the cyclic polyether, 2,5,8,15,18,21-hexaoxatricyclo[20.4.0.0(9,14)] hexacosane. The stability order of these metal ions with either isomer is identical to the permeability order for these same metal ions with the structurally related antibiotics, valinomycin and monactin.