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Biomedical subjects

W R Summer

Publications and source records attributed to W R Summer.

125 records · Page 7Linked to original sources
PubMed1979

Postpartum acute myocardial infarction: a rare occurrence of uncertain etiology.

Two women who had an acute myocardial infarction during the early postpartum period are described, and the findings in nine other women previously reported on are summarized. Attention is called to the atypical nature of ischemic heart disease and myocardial infarction in these patients when compared with myocardial infarction during pregnancy and with ischemic heart disease in men. Postpartum infarcts most often occur in women in their 20s during their first pregnancy, frequently a pregnancy complicated by the preeclampsia-eclampsia syndrome, and are associated with a high mortality rate. In one of our patients and one patient previously reported on, the results of coronary arteriography were normal, suggesting that coronary arterial thromboembolism or spasm was a cause of the infarction. Because postpartum myocardial infarction may be unrelated to atherosclerotic narrowing, detailed angiographic studies in such patients appear warranted. These cases indicate the variety and complexity of ischemic heart disease in women.

Adult↗
PubMed1979

Effects of spontaneous respiration on canine left ventricular function.

The purpose of this study was to determine the mechanism of the decrease in left ventricular stroke volume during spontaneous inspiration. We determined the transmural pressures of the left heart by measuring left atrial and diastolic left ventricular pressures relative to esophageal pressure. We estimated the directional changes in end-systolic and end-diastolic volumes of the left ventricle by determining the transit time of sound transmission between two ultrasonic crystals facing each other across the minor axis of the left ventricle. Left ventricular stroke volume decreased with spontaneous inspiratory effort as pleural pressure fell, regardless of whether lung volume increased or remained constant. The stroke volume was decreased during the fall in pleural pressure because of an increase in end-systolic volume with an essentially unchanged diastolic volume. Thus, the decrease in stroke volume was due to a decrease in ejection, rather than a decrease in filling of the left ventricle. We believe that left ventricular ejection was impeded by the fall in pressure around the heart relative to the pressure in the aorta. In spite of the essentially constant diastolic volume, diastolic left ventricular transmural pressure rose, suggesting that spontaneous inspiration decreases the diastolic compliance of the left ventricle. The change in diastolic compliance contributed to the decrease in stroke volume but was not the primary cause.

Animals↗
PubMed1979

Comparison of Xe-133 washout and single-breath imaging for the detection of ventilation abnormalities.

The Xe-133 ventilation studies of 115 patients were analyzed to determine the relative abilities of the single-breath and washout phases to detect regional ventilation abnormalities. All Xe-133 images were obtained in the posterior projection before 6-view perfusion studies with Tc-99m human albumin microspheres. There were 275 regions with matching V-P abnormalities in the patients. The washout portion of the study detected 258 of these regions (94%) and the single breath detected 175 (64%) (p less than 0.01). The discrepancies were confined to regions with nonsegmental perfusion defects, where the single breath detected 139 matches and the washout 216. The discrimination ratio between normal areas and areas of obstructive lung disease improved from 2 to 1 after 1 min washout to 30 to 1 after 5 min. The late phases of Xe-133 washout are useful in detecting ventilation abnormalities, especially those associated with nonsegmental perfusion defects.

Adolescent↗
PubMed1977

Role of the parasympathetic system in antigen-induced bronchospasm.

Human subjects, sensitive to ragweed, inhaled aerosols of increasing concentrations of ragweed pollen extract in the presence and absence of pretreatment with inhaled atropine. The cumulative dose of antigen required for a 35% decrease in airways conductance was termed PD35. Atropine, 1.2 or 5 mg, increased airways conductance before antigenic challenge but did not alter signigicantly the PD35 for ragweed extract, although these doses of atropine inhibited airways responses to inhaled methacholine chloride and citric acid. We conclude that the cholinergic nervous system plays a modulating role in bronchomotor tone and responses to irritants, but that parasympathetic reflexes are not invariably a major component of human bronchial responses to inhaled allergen.

Airway Resistance↗
PubMed1977

The effect of atropine on acute antigen-mediated airway constriction in subjects with allergic asthma.

Exposure to antigen by inhalation challenge may produce airway constriction in patients with allergic asthma. To examine the role of reflex bronchoconstriction mediated by the vagus nerve in the antigen-induced airway response, we compared the responses of 6 asthmatic volunteers to inhaled ragweed antigen alone and to antigen given after pretreatment with atropine sulfate, a parasympathetic blocking agent. We found significant increases in airway resistance, limitation of parasympathetic blocking agent. We found significant increases in airway resistance, limitation of forced expiratory flow, increases in lung volumes, and alterations in the distribution of inspired gas after antigen was given. When subjects were pretreated with atropine, we found a mean increase in the 1-sec forced expired volume of 0.380 liter (P less than 0.025) and a mean increase in specific airway conductance of 0.067 sec-1-cm H2O-1 (P less than 0.005). Atropine pretreatment did not prevent the responses to antigen in our subjects. After atropine pretreatment subjects began the antigen challenge with better pulmonary function and at a given antigen dose maintained a better level of function compared to when antigen was given alone. Differences in the absolute level of pulmonary function between the two challenges became smaller with the administration of larger antigen doses. We conclude that reflex bronchospasm involving postganglionic efferent parasympathetic nerve pathways is not a major component of the response to inhaled antigen in human allergic asthma.

Adult↗
PubMed1977

Lung disease in reformed drug addicts: diagnostic and physiologic correlations.

Pulmonary morphologic alterations secondary alterations secondary to intravenous drug abuse have been previously identified by histopathologic study of autopsy and biopsy material. Recent investigative efforts have been directed toward defining functional abnormalities that would allow for early clinical diagnosis. For this reason, 12 asymptomatic addicts were studied with roentgenography, spirometry, single breath diffusing capacity (DLco), 99Tc perfusion and 133 Xe ventilation scanning. Nine of the twelve were heavy cigarette smokers. None reported historical evidence of chronic bronchitis or right-sided endocarditis. The DLco was the only significant routine pulmonary function abnormality (p less than .001) observed in these patients. The DLco was significantly reduced even after correction for smoking habits (p less than .001). The decrease in DLco correlated with the number of perfusion defects detected by 99Tc scanning (r = -.560). There was no correlation between DLco and the number of defects on the 133Xe ventilation scan, age, pack-years smoked, or other routine pulmonary function tests. Further, there was no correlation between the number of perfusion and the number of ventilation defects. The data suggest that the decrease in DLco found in these addicts is the result of reduction of the pulmonary capillary bed secondary to vascular or interstitial granulomatosis.

Adult↗
PubMed1976

Thallium 201 myocardial imaging in patients with pulmonary hypertension.

The appearance of the right ventricular myocardium on thallium 201 myocardial perfusion images was evaluated in patients with chronic pulmonary hypertension and compared to patients without pulmonary hypertension. Four groups of patients were studied: 1) eight normals, 2) five patients with angiographically documented coronary artery disease and normal pulmonary artery pressures, 3) ten patients with moderate to severe pulmonary parenchymal or vascular disease and documented pulmonary hypertension and 4) eight patients with chronic left ventricular dysfunction and pulmonary hypertension discovered during cardiac catheterization. The right ventricular free wall was visualized on the thallium 201 myocardial perfusion image in only one of eight normals (group 1) and in only one of the five patients with coronary artery disease (group 2) and measured 0.5 cm and 0.9 cm in thickness, respectively. In patients with documented pulmonary hypertension the right ventricle was visualized on low contrast thallium 201 myocardial perfusion image in all patients. The apparent right ventricular free wall thickness measured from the ungated thallium 201 myocardial perfusion images was 1.7 +/- 0.3 cm in group 3 and 1.5 +/- 0.2 cm in group 4. Right ventricular hypertrophy was detected by electrocardiography in only five of ten patients in group 3 and only one of eight patients in group 4. Thallium 201 myocardial perfusion imaging appears to be a useful technique for assessing the effects of chronic pulmonary hypertension on the right ventricular myocardium.

Chronic Disease↗
PubMed1976

Severe viral pneumonia in young adults.

Three patients with primary group-A influenzal pneumonia had diffuse pulmonary infiltrates, arterial oxygen tensions (PaO2) less than 50 mm Hg while breathing oxygen at 1 atm (fractional concentration of oxygen in the inspired gas (FIo2) equals 1.0), and right-to-left pulmonary shunts greater than 45 percent of total pulmonary blood flow. At an FIo2 of 1.0, end-expiratory pressure (EEP) was added in increments of 2 to 5 cm H2O every 30 to 60 minutes until the PaO2 was above 200 mm Hg and right-to-left shunting had fallen to less than 25 percent. The FIo2 was then lowered to 0.5. Using this systematic approach, all three patients required an FIo2 of 1.0 for less than 12 hours, minimizing the risk of oxygen toxicity. Two of the three patients did not require mechanical ventilation and breathed spontaneously while on continuous positive airway pressure (CPAP), and one of them tolerated an EEP of 31 cm H2O. Two patients survived, and one died of a neurologic complication of cardiopulmonary arrest, despite clearing on the chest x-ray film and improved gas exchange. Therapy with CPAP can be safely used in adults and has practical as well as theoretic benefits over continuous positive-pressure ventilation.

Adult↗
PubMed1975

Bronchoprovocation: effect on priming and desensitization phenomenon in the lung.

Priming, or increased sensitivity to antigen, has not been demonstrated in the lung and could play a role in asthmatic symptomatology during seasonal pollen exposure. It is also an important consideration in the design of any experimental protocol requiring serial bronchoprovocations with antigen. Thirteen patients with a history of asthma symptoms during the pollen season and a positive skin test to ragweed extract were selected. Patients were given bronchial challenge out of season on 4 successive days with stepwise inhalations of antigen, and airways conductance was monitored in the body plethysmograph. Antigen dose-response curves were drawn, and the cumulative dose required for a 35% reduction in specific airway conductance was calculated and designated Provocation Dose (PD35). No regular trend toward either priming or desensitization was noted. The daily changes in antigen sensitivity did not correlate with daily variation of baseline pulmonary function. To determine if there was any priming due to natural exposure to pollen, 9 patients were brought back and rechallenged during the pollen season with no significant increase in bronchial sensitivity to ragweed extract. The PD35 method provides figures useful for comparing dose-response curves and shows a one-log variation from day to day. Any evaluation by bronchial challenge of antigen sensitivity or drug efficacy must take into account such variation.

Aerosols↗
PubMed1975

Response of patients with chronic obstructive lung disease to the regular administration of nebulized isoproterenol. A double-blind crossover study.

The effect of the regular use of neublized isoproterenol in 14 patients with symptomatic chronic obstructive lung disease (COLD) was evaluated in a double-blind crossover 16-week study. FEV1, FVC and SGaw were measured before and 45 minutes after bronchodilator therapy every two weeks, while arterial blood gases were measured every eight weeks, before and 45 minutes after bronchodilator therapy. When the patients were considered as a group, there was no significant difference in mean symptom scores or objective pulmonary functions during the drug and placebo periods. Four patients had significantly higher (p less than .05) and two patients significantly lower mean values for at least one of the pulmonary function tests during the isoproterenol period. The patient who is most likely to benefit from isoproterenol on a regular basis appears to have the following characteristics; (1) consistent improvement in pulmonary function tests 45 minutes after use of nebulized bronchodilator; (2) moderate rather than severe COLD; and (3) a relatively normal DLCO.

Aerosols↗
PubMedDate not supplied

Endothelin produces systemic vasodilation independent of the state of consciousness.

The effects of endothelin, ET-1, on pulmonary and systemic hemodynamics were studied in the open chest dog and changes in systemic arterial pressure in dogs under conscious and anesthetized states were compared. Rapid intravenous (IV) bolus injections of ET-1, 100-1,000 nanograms/kg, significantly decreased systemic arterial pressure, and significantly decreased systemic vascular resistance whereas left atrial pressure and pulmonary vascular resistance were not altered. Reductions in systemic arterial pressure in response to bolus injection of ET-1, 100 and 300 nanograms/kg IV, during conscious state and during anesthesia were similar, respectively. The present data suggest that ET-1 dilates the systemic vascular bed independent of the animal's state of consciousness. The present data also suggest that when compared to the systemic vascular bed, the pulmonary vascular bed is less responsive to bolus administration of ET-1.

Anesthesia, General↗
PubMedDate not supplied

Ethanol relaxes pulmonary artery by release of prostaglandin and nitric oxide.

Acute-intake of ethanol is associated with vasodilation of vascular smooth muscle (VSM). Relaxation of VSM is dependent, in part, on the actions of nitric oxide (NO) and prostaglandin (PG) produced by endothelial cells (EC) lining the VSM. We examined the effects of endothelium rubbing and inhibition of EC synthesis of NO and PG on ethanol-induced relaxation of bovine pulmonary artery (BPA) and pulmonary vein (BPV) in vitro. Rings of isolated BPA and BPV were mounted in muscle chambers for the isometric recording of force development. Blood vessels were precontracted with an EC50 concentration of the thromboxane receptor mimetic U46619. Ethanol (0.01, 0.02, 0.04, 0.08, 0.16, 0.32, 0.64, and 1.28% (w/v) produced concentration-dependent relaxation of BPA and BPV. Ethanol-induced relaxation was attenuated in BPA with rubbed EC and by the NO synthase inhibitors, L-NG monomethylarginine (LNMMA, 50 microM) and L-nitroarginine (NOLA, 10 microM), and the prostaglandin cyclooxygenase inhibitor, ibuprofen (10 microM). In contrast, ethanol-induced relaxation of BPV was not affected by endothelium rubbing or by NOLA or LNMMA, but was partially attenuated by ibuprofen. Nitric oxide was measured with the chemiluminescence technique. Ethanol increased the content of NO released under basal conditions by the BPA but did not effect basal NO release from BPV. However, ethanol enhanced bradykinin-induced release of NO from BPA and BPV and, at low concentrations, augmented bradykinin-induced relaxation of both BPA and BPV.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Escherichia coli-induced inhibition of endothelium-dependent relaxation and gene expression and release of nitric oxide is attenuated by chronic alcohol ingestion.

We examined the effect of chronic administration of ETOH on Escherichia coli-mediated suppression of relaxation and nitric oxide (NO) production by the rat thoracic aorta (RTA) and gene expression for constitutive NO synthase (cNOS) by the adrenal gland. Chronic alcoholic rats ("alcoholic") were fed a diet containing ETOH as 36% of the caloric intake for 8-10 weeks. Nonalcoholic control rats ("control") were fed an isocaloric equivalent diet containing 36% dextrin. Alcoholic rats were given an injection of approximately approximately 10(10) live E. coli through a dorsal SC catheter 24 and 19 h before experimentation ("alcoholic-septic"), and control rats were treated in an identical manner ("septic"). The next day the rats were anesthetized with ketamine-xylazine (0.1 ml/100 g rat) and rings of RTA were mounted in muscle chambers for isometric recording of force development. Rings of RTA were precontracted with an EC50 concentration of phenylephrine, and relaxation to acetylcholine (ACh), A23187, and nitroglycerin were obtained. A23187- and ACh-induced relaxation was attenuated in RTA obtained from septic rats, whereas the relaxation to nitroglycerin was slightly enhanced. Chronic administration of ETOH attenuated the effects of E. coli on endothelium-dependent relaxation in alcoholic-septic rats. NO was measured with ozone chemiluminescence. Basal and stimulated NO production was attenuated in RTA obtained from septic rats and unaffected in RTA obtained from alcoholic or alcoholic-septic rats. cNOS was unmeasurable in adrenals from septic rats. ETOH increased mRNA for cNOS, an effect amplified in alcoholic-septic rats. Thus, E. coli inhibits endothelium-dependent relaxation and NO production, and ETOH attenuates these effects of E. coli on the endothelium-NO system, possibly by upregulating gene expression for cNOS.

Acetylcholine↗
PubMedDate not supplied

Ethanol suppresses LPS-induced mRNA for nitric oxide synthase II in alveolar macrophages in vivo and in vitro.

Alcohol abuse increases the incidence and severity of opportunistic lung infections and pneumonias. Inducible nitric oxide (NO) synthase (iNOS II) and NO may be a pivotal system in the intracellular bactericidal activity of macrophages. We tested the hypothesis that acute administration of ethanol (ETOH) suppressed Escherichia coli endotoxin lipopolysaccharide (LPS) mediated upregulation of the iNOS II system in the lung of the rat, in vivo. We also tested the effect of ETOH on alveolar macrophage (AM) production of free NO using microelectrodes. Male Sprague-Dawley rats were given ETOH (5.5 g/kg, IP) 30 min. before giving intratracheal sterile phosphate buffered saline solution (PBS, 0.5 ml) or LPS (1 mg/kg in a total volume of 0.5 ml PBS). The isolated lungs were subjected to bronchoalveolar lavage (BAL) 3.5 hr. later. Aliquots of the BAL fluid were assayed for tumor necrosis factor alpha TNF alpha and reactive nitrogen intermediates (nitrate and nitrite) (RNI) with chemiluminescence. Aliquots of AM were incubated 1 hr ex vivo for spontaneous production of RNI or frozen and assayed for iNOS II mRNA with competitor exchange reverse transcriptase polymerase chain reaction (cERT-PCR). The lung was homogenized and assayed for RNI. LPS increased BAL fluid TNF alpha and RNI, lung RNI, and the spontaneous production of RNI by AM, ex vivo. These effects were inhibited by in vivo administration of inhibitors of iNOS II. LPS increased iNOS mRNA in AM. This was unaffected by iNOS inhibitors. ETOH suppressed LPS-induced BAL fluid TNF, iNOS mRNA and RNI production by AM and the lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMedDate not supplied

A new controllable suction catheter for blind cannulation of the main stem bronchi.

A new controllable suction catheter is described which was used for blind cannulation of the main stem bronchi. Cannulation of the right main stem bronchus was successful in 24 of 25 attempts (96%). Cannulation of the left main stem bronchus was successful in 22 of 25 attempts (88%). The use of a controllable tip suction catheter increases the rate of successful cannulation of the left main stem bronchus compared to previous reports in the literature.

Bronchi↗