Cooperative unit size in the gel-liquid crystalline phase transition of dipalmitoyl phosphatidylcholine-water multilayers: an estimate from Raman spectroscopy.

The temperature dependence of the Raman spectral transitions assigned to the acyl chain C-C stretching modes of dipalmitoyl phosphatidylcholine was determined for the gel, phase transition and liquid crystalline states of the lipid multilayers. The van't Hoff enthalpy differences delta HVH between trans and gauche rotational isomers were obtained from the Raman spectral data for the temperature region characteristic of each bilayer state. An average size for the cooperative unit undergoing the chain melting process during the phase transition was estimated from the ratio of the appropriate van't Hoff enthalpy to an adjusted calorimetric enthalpy.

Safety and efficacy of central intravenous bolus administration of adenosine for termination of supraventricular tachycardia.

OBJECTIVES: This study was done to quantify the dosing differences between central and peripheral adenosine administration for treatment of supraventricular tachycardia. BACKGROUND: Earlier studies that evaluated the safety and efficacy of adenosine primarily utilized a peripheral site of administration. Although it has been recommended that lower doses should be given centrally, dosing recommendations have not been provided. METHODS: Thirty adults with supraventricular tachycardia underwent invasive electrophysiologic study and were treated with central and peripheral intravenous administration of adenosine. Peripheral injections were administered through a venous catheter in an upper extremity and central infusions were accomplished by means of a catheter positioned in or near the right atrium. The site of administration was randomized and each subject received adenosine by both routes. Adenosine was administered every minute in increasing increments of 3, 6, 9 and 12 mg until the tachycardia terminated. Peripheral responses were compared with those obtained centrally. RESULTS: The minimal effective peripheral dose was distributed among the four doses: Tachycardia was terminated in 11 patients with 3 mg (37%), in 10 (33%) with 6 mg, in 4 (13%) with 9 mg and in 5 (17%) with 12 mg. In contrast, after central administration, 23 episodes of tachycardia (77%) were terminated with 3 mg, 6 (20%) with 6 mg and 1 (3%) with 9 mg; none required 12 mg. Lower doses of adenosine were more effective after central than after peripheral administration, with 63% of the subjects requiring a lesser dose. There was no difference between the two routes of drug administration in the incidence of side effects or transient arrhythmias at the time of tachycardia termination. CONCLUSIONS: Adenosine can be safely given centrally for termination of supraventricular tachycardia. The initial dose should be 3 mg.

Left main coronary artery reconstruction after radiation therapy.

We report the case of a patient with radiation-induced left main coronary stenosis in whom an internal mammary artery bypass graft failed a 5 years and necessitated direct left main reconstruction.

The initial manifestations of acute myocardinal infarction.

A review of 132 consecutive patients 65 years of age and older who had a myocardial infarction showed that two-thirds of them experienced pain at onset. Pain was the only symptom leading to bedside diagnosis in one-fourth of the patients. Pain at onset combined with sudden or increased dyspnea was present in one-fifth of the patients and pain associated with other symptoms in one-sixth. Dyspnea unaccompanied by pain heralded onset of infarction in one-fifth of the patients, and in almost 7 percent, onset was marked only by other symptoms. Cerebral symptoms dominated onset in one-tenth of the patients. Preexisting coronary heart disease, hypertension, or diabetes was not predictive of painless infarction. To avoid pitfalls and facilitate bedside diagnosis of infarction, physicians should be aware of the different clinical presentations of painless infarction in the aged, which occurred in over one-third of the patients in this cohort. They also should suspect the possibility of myocardial infarction in any patient in whom symptoms are not clear, even when they are mild and unobtrusive. Questioning of the elderly patient, his family, or others around him as early as possible after the onset of an acute attack is likely to elicit a history of pain, which may lead to the correct diagnosis.

Stroke: incidence and risk factors.

The incidence of stroke was estimated prospectively in a total population of 2,502 persons over age 65 who resided in homes for the aged. The incidence in persons born in Asian and African countries was close to that in persons born in European countries. No sex differential was found in either ethnic group, and there was no significant increase in the incidence of stroke with advancing age in either sex. In the European population, prior heart disease was the strongest risk-increasing factor, ranking ahead of hypertension. Diabetes mellitus was not associated with a higher risk of stroke among the women; the findings for the men were inconclusive. In the Afro-Asian population, the risk of stroke was related to heart disease and diabetes mellitus but was not associated with blood pressure. Total serum cholesterol or relative weight was not associated with stroke in either group. The early establishment of programs for the control of hypertension and stroke appears most desirable.

[Visits to emergency rooms and hospital ownership categories].

Trends in emergency room (ER) visits in Israeli general hospitals were analyzed and differences were found according to category of hospital ownership, Data for 1986-90 were gathered from 23 hospitals which included 90% of the country's acute care beds. An upward trend in ER visits in the 1970's and early 1980's ended in 1987. Despite a 7% increase in population during 1987-90, total ER visits decreased by 4%. In Jerusalem's public hospitals ER visits decreased by 13%, in government and government-municipal hospitals by 7%, while in Kupat Holim Clalit hospitals there was a 2% increase. The proportion of ER visits resulting in hospital admissions also varied by hospital ownership and also among individual hospitals within any given ownership category. Factors which might influence ER visits include size and composition of populations, development of alternative sources of care in the communities, price of services, changes in hospital admission policies, nature of the competition between hospitals, supply of physicians, and the use of ER's for primary care.

[Ocular injuries from seashore racketball].

A 3-year prospective study revealed 39 hospitalized cases of ocular injuries from seashore racketball sports. Most were children and young adults and most had internal injuries of the globe. Over a third had retinal edema, 2 eyes were blinded, and at least 4 are subject to serious future complications.

Hydrocarbon trans-gauche isomerization in phospholipid bilayer gel assemblies.

The vibrational Raman spectra of dimyristoyl (DMPC)-, dipalmitoyl (DPPC)-, and distearoylphosphatidycholine (DSPC)-water bilayer system were used to probe lipid hydrocarbon chain trans-gauch isomerization dynamics below the gel-liquid crystalline phase transition temperature. In addition to the 1090-1085 cm-1 vibrational transitions, which appear with increasing temperatures and are characteristic of gauche conformers within the acyl chains, a new feature arises in all three bilayer systems at approximately 1122 cm-1. This carbon-carbon stretching mode is associated with the formation of the gauche bond rotation of the terminal methyl group oriented toward the center of the bilayer. Estimates of the enthalpy differences (deltaH) between hydrocarbon chains in an all-trans conformation and chain configurations containing gauche forms may be made from peak height intensities of vibrational features associated with the appropriate rotational isomers. For the DMPC-H2O, DPPC-H2O, and DSPC-H2O assemblies, the Raman data yield enthalpy differences of 2.9 +/- 0.6, 3.4 +/- 0.5, and 9.9 +/- 1.2 kcal/mol, respectively. These values are interpreted to reflect approximately two gauche bonds per lipid molecule for the DMPC-H2O and the DPPC-H2O gels and six gauche bonds per molecule for the DSPC-H2O gels.