A proton magnetic resonance study of ligand exchange on Pentakis(N,N-diethylacetamide)dioxouranium(VI)

Pentakis(N,N-diethylacetamide)dioxouranium(VI) bisperchlorate, [UO2(AcNEt2)5] has been isolated. Proton N.M.R. spectroscopy shows that, in the presence of excess free ligand, [UO2- AcNEt2)5]2+ is the greatly predominant dioxouranium(V1) species in both CD2Cl2 and CD3CN solutions. The rate of ligand exchange is independent of free ligand concentration as shown by the rate law exchange rate = 5k1[UO2(AcNEt2)52+]where in CD2Cl2 solution k1(265 K) = 54.8 � 8.3 s-1, ΔH.‡ = 68.3 � 1.2 kJ mol-1 and ΔS‡ = 47.1 � 4.6 JK-1 mol-1. Somewhat different values for these parameters are obtained in CD3CN solution. These data are compared with similar data for other dioxouranium(VI) systems, and mechanistic comparisons are made.

Mediastinoscopic removal of a superior mediastinal foreign body

A metallic mediastinal foreign body, which eroded into the esophagus and resulted in a mediastinal abscess, was removed through the mediastinoscope. Tubes for drainage and irrigation were easily inserted after the pus had been entirely drained. Satisfactory low-risk treatment was accomplished without the need for major surgical intervention.

Recent experience with tuberculous pericarditis

Twelve patients with tuberculous pericarditis were found among 1,194 patients with tuberculosis treated at the University of Texas Medical Branch over a 10-year period, an incidence of 1%. Surgical treatment was undertaken in 4 patients, and the rest were treated medically. The surgically treated patients had no major complications, and none of them died. In the medically treated group, however, 1 patient died, 1 had an anaerobic empyema, and 1 experienced respiratory arrest. In addition, the average hospital stay was 33 days less in the surgically treated group. Early surgical intervention should be carried out in patients with tuberculous pericarditis who do not respond promptly to adequate antituberculosis chemotherapy.

Suppression of a demand pacemaker in the presence of redundant transvenous right ventricular leads

A ventricular inhibited demand cardiac pacemaker was inhibited in the presence of intimate contact between the active temporary bipolar electrode ring and a retained inactive permanent bipolar electrode tip. Electromagnetic interference effects, lack of insulation, lead breaks, and loose connections were all ruled out as the cause of pacemaker suppression.

Delayed recurrent massive thromboembolism through a vena caval clip after pulmonary embolectomy

A case of recurrent massive pulmonary embolization through a modified Miles' clip two weeks after successful emergency pulmonary embolectomy is reported. Vena caval ligation is probably a safer alternative in these critically ill patients.

Subclavian steal syndrome: an update

The clinical findings in this series of 22 cases of subclavian steal syndrome showed a predominance of men (13:9), a mean age of 51 years, and a predominance of left subclavian artery obstruction. There was a blood pressure differential of more than 20 mm Hg and diminished pulses ipsilaterally in most. Main indications for surgical repair were transient neurologic symptoms. Twenty-one of our patients had surgical repair of the subclavian steal syndrome; six had concomitant carotid artery surgery. The most common surgical procedure performed consisted of a carotid subclavian bypass graft. One patient had only carotid revascularization; 19 patients have had good long-term results. One patient, with tetralogy, died and three had complications. The asymptomatic or mildly symptomatic patient may be given a trial of medical treatment. Symptomatic patients can have extrathoracic bypass with a very low risk. Surgery is indicated if significant associated carotid lesions are present.

Intrapleural instillation of quinacrine for treatment of recurrent spontaneous pneumothorax

We used intrapleural instillation of quinacrine hydrochloride in 20 patients (Group A) with recurrent spontaneous pneumothorax (one bilateral) and compared their clinical course with 19 patients who underwent thoracotomy and scarification or pleurectomy (Group B) and 63 patients treated by tube thoracostomy alone (Group C). In Group A, there was one complication of treatment, a pneumothorax immediately following tube removal, which necessitated repeat tube thoracostomy, and there was one late ipsilateral recurrence 2 years after treatment. These 20 patients with 21 recurrent spontaneous pneumothoraces treated with intrapleurally administered quinacrine have been followed for from 6 months to more than 4 years with only one late recurrence on the treated side. Eight patients in Group B had postoperative complications: 2 patients who had had pleurectomy required reoperation for postoperative bleeding; lobar pneumonia developed in 3; 1 had lack of total expansion of the lung; an intrathoracic hematoma developed in 1; and an ipsilateral pneumothorax necessitating tube thoracostomy developed in 1. In Group C, the rate of recurrence of pneumothorax was 23% during the first year following treatment. Intrapleural instillation of quinacrine is a simple, low-risk, reliable, and effective treatment for recurrent spontaneous pneumothorax, and is equally as effective as thoracotomy and scarification.

Human pulmonary dirofilariasis presenting as a solitary pulmonary nodule

A case of human pulmonary dirofilariasis had positive serologic testing postoperatively. Increased awareness of this entity as a cause of solitary pulmonary nodules may lead to preoperative serologic and intradermal testing, and to the possibility of arriving at a preoperative diagnosis.

Myocardial stimulation impedance: the effects of electrode, physiological, and stimulus variables

With exposed metal at the electrode tissue interface (8 mm2, 28 mm2, 57 mm2), myocardial threshold stimulation impedance increased as pulse duration was lengthened, with left ventricular intramyocardial stimulation, and with the smaller surface area electrode. An 0.5 mm2 differential-current-density electrode, which eliminated direct metal-to-tissue contact at the electrode-myocardial interface, was associated with notably higher impedances than each of the three metal tip electrodes and did not show increasing impedance levels with changes in pulse duration, confirming the minimization of polarization energy losses with this device. The majority of electrode, electrode tissue interface, and myocardial variables that are characterized by high threshold stimulation impedance are associated with low threshold energy requirements for pacing and reduced pacemaker power source drain. No accurate information about sensing impedances can be derived from current knowledge of pacing impedance.

A Proton Magnetic Resonance Study of Ligand Exchange on the Pentakis (N-formylpyrrolidine)dioxouranium (VI) Ion

Pentakis(N-formylpyrrolidine)dioxouranium(VI) perchlorate, [UO2(fpr)5] (ClO4)2, has been isolated from solution. In the presence of excess free fpr the greatly predominant species in CD2Cl2 solutions is [UO2(fpr)5]2+, as shown by 1H N.M.R. spectroscopy, and fpr exchange is characterized by a two term rate law: exchange rate = 5(k1+ k2[fpr])[UO2(fpr)52+] It is found that k1(220 K) = 42�6�0�5 s-1, ΔH‡ = 30�7�1�4 kJ mol-1 and ΔS‡ = -71�6�6�3 J K-1 mol-1, and k2(220 K) = 369�20 dm3 mol-1 s-1, ΔH‡ = 30�5�1�0 kJ mol-1 and ΔS‡ = -54�9�5�0 J K-1 mol-1. The mechanistic implications of these data are discussed.

Epidemiological evidence for causal relationship between Epstein-Barr virus and Burkitt's lymphoma from Ugandan prospective study

Results from a prospective sero-epidemiological study initiated in Uganda in 1971 indicate that children with high antibody titres to Epstein-Barr virus structural antigens are at high risk of developing Burkitt's lymphoma. These findings strongly support a causal relationship between the Epstein-Barr virus and Burkitt's lymphoma but suggest that the oncogenic potential of the virus is realised only in exceptional circumstances.

Symptomatic deep venous thrombosis of the arm associated with permanent transvenous pacing electrodes

From October 1970 to May 1977, a total of 212 pacemakers were implanted at the Milton S. Hershey Medical Center of Pennsylvania State University, Hershey. During this period, we encountered five patients with symptomatic thrombosis of the subclavian vein, a rate for this complication of approximately 2 percent. Although this complication was reported only rarely prior to 1976, we believe that symptomatic subclavian thrombosis after insertion of a transvenous pacemaker electrode occurs more frequently than previously suspected. The etiology, pathogenesis, and treatment of this interesting condition are discussed.

19F nuclear magnetic resonance studies of the interaction of inhibitors with chymotrypsin. N-Acetyl derivatives of fluorophenylalanines

Binding parameters, ΔB and KI, for the three competitive inhibitors N- acetyl-o-fluoro-D-phenyl-alanine, N-acetyl-m-fluoro-D-phenylalanine and N-acetyl-p-fluoro-D-phenylalanine have been determined by Fourier- transform 19F n.m.r, techniques. Association between the enzyme aromatic binding site and the three inhibitors appears to result in greater immobilization of the aromatic rings than is the case for the analogous N-trifluoroacetyl compounds. A balance between the enzyme-inhibitor interactions at the aromatic and amido binding sites is believed to be responsible for the observed effects. The relationship between KI and KS values of inhibitors obtained from kinetic data and KI values obtained by N.M.R. methods is discussed.

Space-time clustering of Burkitt's lymphoma in the West Nile district of Uganda: 1961-1975

Epidemiological data relating to all 202 patients diagnosed with Burkitt's Lymphoma (BL) in the West Nile District of Uganda in the period 1961 to 1975 have been reviewed and analysed. Statistically significant evidence of space-time clustering of cases, first reported for the period 1961-65, was also present during 1972-73, but not during other periods. The patients involved in such clusters were found to be older than other patients (P less than 0.001). The average annual incidence of BL in the District was 2.45 x 10(-5) and overall there was no change in the incidence during the study period. However, there were statistically significant changes in incidence in different counties, which could not be explained as case-ascertainment artifacts. One sib pair of patients with BL was found and the series also included 7 instances of BL in two cousins. It is suggested that study of variation in the intensity and type of malarial infestation in different areas at different times may help explain the epidemiological findings and suggest what, if any, aspects of this infection are critical for inducing BL.

Carbon-13 N.M.R. chemical shifts and rotational barriers of ortho-substituted N,N-dimethylbenzamides

The barriers to rotation about the carbon-nitrogen bond and the carbon- 13 N.M.R. chemical shifts of a series of 2-substituted N,N- dimethylbenzamides have been measured. The substituent effects have been examined by a multi-substituent parameter method incorporating a steric effect parameter. The barriers to rotation are subject to a large steric effect, whilst the carbon-13 chemical shifts of the carbonyl group and the methyl groups are dominated by the resonance effect.

Similarity of clinical and laboratory results obtained with microporous teflon membrane oxygenator and bubble-film hybrid oxygenator

For 80 elective clinical cardiopulmonary bypasses we alternately used either a commercial microporous Teflon membrane oxygenator or a commercial hybrid bubble-film oxygenator. Setup time was a little longer with the membrane unit (20 minutes), but priming volume (2,250 ml) was the same. No problems were encountered with the hybrid oxygenator. However, despite our monitoring of additional variables, including shim and inlet pressure and recirculation flow, gas exchange abnormalities were encountered in 5 patients on whom the membrane oxygenator was used; in 4 of these cases the abnormalities were encountered prior to our recognition of the potential for occasional internal shunting with this device. There were no hospital deaths. When the two groups, matched except for oxygenator selection, were compared, there were no significant differences clinically or hematologically. For cardiopulmonary bypass of 2 hours or less, both oxygenators studied are definite improvements over previous silicone membrane and high-gas-flow bubble oxygenators. However, lower cost and reduced complexity favor the hybrid oxygenator.

Carbon-13 N.M.R. chemical shifts and rotational barriers of para-substituted N,N-dimethylbenzamides

The carbon-13 N.M.R. chemical shifts for a series of para-substituted N,N-dimethylbenzamides have been measured. The substituent induced 13C shifts have been examined by a dual substituent parameter (DSP) method using Hammett-type constants. The barriers to rotation have also been correlated with Hammett-type constants by the DSP method and related to 13C substituent induced shifts. Substituent effects of the bromomethyl, dibromomethyl and tribromomethyl groups have been examined by using the chemical shift and rotational barrier probes.