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Biomedical subjects

L W Johnson

Publications and source records attributed to L W Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1978

Elevated ejection fractions in patients with the anginal syndrome and normal coronary arteriograms.

The etiology of chest pain in patients with the anginal syndrome and normal coronary arteriograms has not been established. There has been no explanation for the association of electrocardiographic, hemodynamic, and myocardial metabolic abnormalities consistent with myocardial ischemia observed in some patients with this disorder. Historical, clinical, laboratory, and hemodynamic data of 45 patients (24 females, 21 males), mean age 47.5 years, with chest pain and normal coronary arteriograms are reviewed. Left ventriculograms were analyzed utilizing the single-plane cineangiographic measurement of left ventricular volume. Systolic ejection fractions for the 45 patients ranged from 0.66 to 0.91 (mean 0.80 +/- 0.01 SEM). Ventricular volumes determined angiographically revealed mean end-diastolic and end-systolic volumes of 83 +/- 5 ml and 18 +/- 2 ml, respectively. The mean changes in longitudinal and transverse segmental axis shortening that occurred during ventricular systole were 28.8% and 50.7%, respectively. These elevated values for ejection fraction, and reduced measurements of ventricular volumes, indicate that some patients with chest pain and normal coronary arteriograms may have small hearts with hyperdynamic ventricular contraction. These findings suggest that hyperdynamic ventricular contraction may play a causative role in the development of transient, angina-like chest pain in these patients. The etiology of the proposed hyperdynamic ventricle is unknown, but it may be attributable to increased beta-sympathetic stimulation of the myocardium.

Adult↗
PubMed1978

An evaluation of the results of left ventricular aneurysmectomy: use of a simplified method for analysis of the left ventriculogram.

Twenty-three patients underwent left ventricular aneurysmectomy without coronary artery bypass or other surgical procedure. Fourteen patients (Group 1) benefitted from surgery, and nine fared poorly (Group 2), including the four postoperative deaths. Among the 19 survivors, 17 had postoperative catheterizations. Pre- and postoperative left ventriculograms in the right anterior oblique projection were analyzed by planimetry of the aneurysmal and non-aneurysmal areas. This method provided data favorably altered by surgery in the improved patients and unchanged in the others. None of the preoperative ventriculographic measurements effectively separated the postoperative patient groups. The poor results in the Group 2 patients were of heterogeneous origin arising from pre-, peri- and postoperative factors. The more important factors were the largest and smallest aneurysms, surgically induced mitral insufficiency, and progressive coronary artery disease. Thus, the improvement in surgical results from better angiographic preoperative case selection is possible, but limited.

Adult↗
PubMed1977

Determining fetal lung maturity: a sensitive surfactant method.

The presence of fetal lung surfactant in amniotic fluid is indicative that fetal lungs are sufficiently mature for delivery without subsequent respiratory distress. However, current methods for detecting surfactant fail to positively distinguish saturated phosphatidylcholine (primarily dipalmitoyl phosphatidlycholine) from the many similar phosphatidylcholines also present in amniotic fluid. As a result small amounts of this lipid are obscured by the presence of the other lipids and delivery of many patients is delayed unnecessarily. A sensitive method is here described in which extraneous phosphatidylcholines are oxidized while the saturated phosphatidylcholines remain intact for positive determination by thin-layer chromatography. The method is insensitive to contaminating lipids from blood or meconium and provides an unequivocal test for the presence of disaturated phosphatidylcholine in a relatively short time. About one half of the patients tested in whom lecithin/sphingomyelin ratios were 1.4 to 1.7 had this surfactant lipid present in their fluids and presumably could have been delivered immediately.

Amniotic Fluid↗
PubMed1977

Surgical treatment of right ventricular aneurysm: an uncommon procedure.

Most ventricular aneurysms result from transmural myocardial infarction and are located in the left ventricle. Right ventricular aneurysms are unusual, and their origin at times is obscure. A patient with two discrete right ventricular aneurysms is reported. The literature on operative excision of right ventricular aneurysms is reviewed, and the various etiological factors are discussed.

Adolescent↗
PubMed1977

Stress responses of pilots flying high-performance aircraft during aerial combat maneuvers.

In aerial combat maneuvers (ACMs), at Luke AFB, Az, eight pilots flew their two F-15 aircraft against nine pilots in three F-106 aircraft. A total of nine flights, consisting of 23 ACMs, were accomplished in 5 successive days. The degrees of fatigue, stress, and sympathetic activity were quantified using both subjective analyses and the biochemical constituents in the urine of the pilots of the F-15 or F-106. Biochemical indicators, reported per 100 mg creatinine, included: epinephrine, norepinephrine, 17-OHCS, urea, inorganic phosphate, sodium, potassium, and sodium/potassium ratio. The F-106 pilots exerted more relative effort than did the F-15 pilots--effort which appeared to be associated with high-G experience. Both groups of pilots were equally fatigued following ACMs; however, only the fatigue of the F-106 pilots was directly correlated with the length of the ACM. Sympathetic and stress responses during the ACM--similar for both groups of pilots--showed postflight increases of 54% in epinephrine, 19% in norepinephrine, and 20% in 17-OHCS over preflight values, thus suggesting a moderate stress response. Resting levels of these same indicators, for days the pilots did not fly and for pre-ACM values, were similar but higher than control values previously reported for other stressful activities. By late afternoon, postflight values for these indicators had returned to near-preflight levels.

Adult↗
PubMed1976

Identification of Ehrlichia canis in East Africa.

Ehrlichia canis, the causative agent of canine ehrlichiosis or tropical canine pancytopaenia (TCP) has been identified in Kenya. Transmission studies to two dogs resulted in signs of ehrlichiosis including marked thrombocytopaenia, pyrexia, reduction in the packed cell volume and the presence of E canis in peripheral blood mononuclear cells.

Animals↗
PubMed1976

Cine angiographic diagnosis of patent foramen ovale in paradoxical embolism,.

A case of paradoxical embolism is presented in which the antemortem diagnosis was facilitated by a new simple angiographic technique that demonstrated a patent foramen ovale. An additional 14 patients were studied by this technique, and one had a patent foramen ovale. The mechanism of reversal of the normal intraatrial pressure gradient and subsequent right to left shunt through a patent foramen ovale is discussed. This angiographic technique may be readily applied in any diagnostic catheterization laboratory and complements existing methods for detecting patency of the foramen ovale in patients with suspected paradoxidal embolism.

Adult↗
PubMed1976

Follow-up catheterization of patients with myocardial infarction during coronary artery bypass surgery.

Of 197 consecutive patients having aortocoronary bypass grafts over a 30 month period, 38 (19 per cent) had ECG evidence of myocardial infarction. The infarctions occurred more commonly in patients receiving multiple grafts. The infarctions were usually in areas supplied by grafted vessels. The infarctions occurred most often in the inferior wall, even when multiple vessels were grafted. Eleven patients with intraoperative infarction have had repeat postoperative coronary arteriograms. Seven had all grafts patent; three of these patients had hypokinesis of the infarcted wall. Four of the 11 patients had one or more occluded grafts; three of these patients had an area of hypokinesis. We conclude that intraoperative myocardial infarction is a common problem in aortocoronary bypass surgery and is not necessarily caused by graft occlusion.

Angiocardiography↗
PubMed1976

Prophylactic digitalization for coronary artery bypass surgery.

One hundred and twenty patients undergoing aortocoronary bypass procedures were randomly placed into control and digitalized groups. All were initially in normal sinus rhythm and without evidence of congestive heart failure. Supraventricular arrhythmias occurred in 17 of 66 controls and in only three of 54 digitalized patients (P less than 0.01). There was no evidence of digitals toxicity. Based on this evidence we recommend prophylactic digitalization for patients having aortocoronary bypass operations.

Arrhythmias, Cardiac↗
PubMed1976

Effect of cardiac, pulmonary, and vascular disease on one-minute oxygen uptake.

A simplified method for estimation of one-minute oxygen uptake (VO2-1) during treadmill grade walking at vertical power requirements of 250, 750, and 1,000 kg-meters/min was devised, where power=weight (kg) X grade (fractional) X walking speed. All subjects were men. There were 29 controls, 34 subjects with coronary arterial disease (of whom 18 had had myocardial infarction), nine subjects with diffuse pulmonary disease, and four subjects with ischemic vascular disease. Abnormally reduced values for VO2-1 were related to these diseases and, more specifically, to a history of myocardial infarction and (in pulmonary subjects) to reduced single-breath diffusing capacity. Lowest values of VO2-1 for a group were found in ischemic vascular disease. Reduced response of VO2-1 may therefore be caused by central defects of oxygen transport.

Adult↗
PubMed1976

Turnover of erythrocyte protoporphyrin, with special reference to bovine porphyria and iron deficiency anemia.

Available data from human subjects suggests that most of the pools of free protoporphyrin in circulating erythrocytes have T 1/2 values which range from less than 1 hour to approximately 2 weeks. An exception was observed in 2 cows with erythropoietic ("congenital") porphyria. During the several months which followed the simultaneous injection of 14C- and 3H-labelled glycine and ALA, changes in the specific activities of both free- and hemoglobin-protoporphyrin were similar. Since erythropoietic porphyria in the bovine differs from that in the human mainly in the elevated values of free erythrocyte protoporphyrin in the former, it is suggested that this prolonged T 1/2 (equal approximately to the red cell life span) may account for the elevated values seen in the bovine. Variable ratios of red cell/fecal protoporphyrin concentrations reported in other diseases are also believed to be due largely to T 1/2 differences in porphyrin pools. Recorded fluorescence and excitation spectra of blood showed the single fluorescence band of "free" porphyrin in bloods of normal and porphyric cows and of patients with erythropoietic porphyria, protoporphyria, and sideroblastic anemia. The 2 band zinc complex spectrum was found, as expected, in blood of subjects with Pb poisoning and Fe deficiency anemia. T 1/2 values of 1 to 2 weeks were calculated for red cell protoporphyrin from previously published data of patients with Fe deficiency anemia who were treated effectively with iron.

Aminolevulinic Acid↗
PubMed1975

Catalytic properties of phospholipid exchange protein from bovine heart.

A protein which catalyzes the exchange of phosphatidylcholine between membranes has been purified from heart tissue homogenates up to 300-fold by acidic pH precipitation, (NH4)2SO4 precipitation, gel filtration, and ion-exchange chromatography. Binding of the protein to phosphatidylcholine liposomes as measured by Sepharose chromatography was nondetectable. However, isoelectric focusing experiments showed that individual molecules of phosphatidylcholine were transferred from liposomes to the soluble, partially purified protein. Exchange of phospholipid between liposomes and mitochondria was not affected by the presence of moderate amounts of cholesterol in liposomes. A search for competitive inhibitors among moieties similar to phosphatidylcholine failed to show strong binding sites in the hydrophilic part of the substrate. High concentrations of Na+, Ca2+ and Mg2+ impaired the exchange activity.

Animals↗
PubMed1975

Use of phospholipid exchange protein to measure inside-outside transposition in phosphatidylcholine liposomes.

The exchange of phosphatidylcholine between (32P)phosphatidylcholine lipososomes and unlabeled mitochondria was catalyzed by a purified phospholipid exchange protein from bovine heart cytosol. The loss of (23P)phosphatidylcholine from the liposomes appeared to proceed in two stages: with 100 units of phospholipid exchange protein per ml the half-time of the initial stage was about 10 min and that of the final stage 4 days or greater. Agarose-gel chromatography of the liposomes showed an elution compatible with a homofwnwoua pool od amLL single walled vesicles. Treatment of phosphatidyl (14C) choline liposomes with phospholipase D (phosphatidylcholine phosphantidohydrolase) showed that labeled phospholipid removable during the rapid exchange phase was subject to hydrolysis by the phospholipase, but that the labeled phospholipid left after the rapid exchange was completed cound not by hydrolyzed by phospholipase D. It is proposed that the rapidly exchanging phosphatidylcholine constitutes the outer layer of the liposome bilayer. The long half-lives of 4 days or more probably represent the transposition of phosphatidylcholine from the inner to the outer layer of the liposome bilayer.

Animals↗
PubMed1975

Varied manifestations of left atrial myxoma and the relationship of echocardiographic patterns of tumor size.

Four cases of left atrial myxoma with varied clinical manifestations were diagnosed with echocardiographic studies prior to cardiac catheterization and surgery. The unusual clinical features include Raynaud's phenomenon and intermittent claudication. The echocardiographic features of the atrial myxoma appear to be related to tumor size. Systematic echocardiographic evaluation of patients with mitral valvular disease and systemic and cerebral vascular insufficiency will undoubtedly increase the positive diagnostic results in patients with atrial myxomas. Removal of these tumors results in normalization of the echocardiographic pattern.

Adult↗
PubMed1975

Effect of humoral antibodies on the course of Theileria parva infection (East Coast fever) of cattle.

A study was made of the effects of serum and gamma-globulins from vaccinated cattle (donor cattle) given to cattle (principals) exposed to Theileria parva infection (East Coast fever (ECF)). The principals were treated with normal serum, with serum containing high antibody titer against T parva (as evaluated by the indirect fluorescent antibody (IFA) technique), or with globulins prepared from normal and from immune serums. For exposure, the principals were inoculated with standardized suspension of the tick Rhipicephalus appendiculatus containing T parva infective particles. Comparison was made between treatments with normal serum and globulin and treatments with immune serum and globulin, using observations of time lapse after exposure to febrile response (39.5 C), to appearance of T parva macroschizonts, and to death. In addition, hematologic changes were determined. Neither the establishment of infection nor the clinical and hematologic changes in the principals were influenced by their treatment with immune serum or concentrated globulins; all died of ECF. Humoral antibodies did not protect cattle against fatal ECF, nor was enhancement of T parva infection observed.

Animals↗