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Biomedical subjects

J Jonas

Publications and source records attributed to J Jonas.

At least 73 records · Page 4Linked to original sources
PubMed1988

High-resolution 13C NMR study of pressure effects on the main phase transition in L-alpha-dipalmitoyl phosphatidylcholine vesicles.

The effects of pressure on the liquid-crystalline to gel transition in vesicles of L-alpha-dipalmitoyl phosphatidylcholine were investigated by high-resolution proton-decoupled natural-abundance 13C NMR spectroscopy. The linewidths of several 13C resonances, including the choline methyl groups, carbonyl carbons, and choline methylene groups and the palmitoyl methyl groups are reported as a function of pressure at 52.7 degrees C. These preliminary NMR experiments clearly demonstrate that high-pressure, high-resolution proton-decoupled natural-abundance 13C NMR spectra are a promising tool to study the phase-transition behavior and the dynamics of model membrane systems.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

[Unusual aneurysm of the pancreas arcade in occlusion of the celiac trunk].

This is a report about a rare aneurysm of the pancreas arcade--the angiography showing an occlusion of the celiac axis. Using a diagram of the arterial phase of the angiography, the morphology of the collateral circulation between the celiac axis and the superior mesenteric artery is described. The reason the occlusion of the celiac axis formed collateral circulation and the origin of the aneurysm and the therapeutic steps to be taken are discussed.

Aged↗
PubMed1986

[Weather influences on intraocular pressure in patients with chronic glaucoma or ocular hypertension].

From January 1979 to August 1984 intraocular pressure (IOP) was measured on the first Friday of each month under comparable conditions (same instruments, nearly always the same examiner) in a total of 109 patients in whom a primary chronic open-angle glaucoma or ocular hypertension had been diagnosed: The IOP was correlated to the local weather parameters (atmospheric pressure, cloud cover, relative air humidity, mean, maximum and minimum temperature, precipitation, duration of sunshine, mean and maximum wind velocity). In the large number of measurements a significant correlation was found only between IOP and atmospheric pressure: IOP was lower when air pressure was high. There was only a suggestion of a significant correlation between IOP and relative air humidity. However, further statistical analysis revealed that in fact both atmospheric pressure and relative air humidity account for only a negligible part of the variation in IOP values. From a practical point of view, therefore, the IOP of patients with primary chronic open-angle glaucoma or ocular hypertension is not influenced by weather conditions.

Atmospheric Pressure↗
PubMed1985

Cold ischemic arrest: comparison of calcium-free and calcium-containing solutions.

Isolated pumping rat hearts, perfused with reconstituted blood, were studied to compare the effects of 30 minutes of ischemic arrest following calcium-free or normal, calcium-containing cold cardioplegia on recovery of mechanical function, lactate production, myocardial adenosine triphosphate concentration, and release of creatine kinase (CK). As in clinical situations, the volume of the infusate was only three to four times the intracavitary blood volume. Hearts arrested with calcium-free solution showed incomplete recovery of mechanical function, whereas hearts arrested with calcium-containing solution recovered completely. After calcium-free arrest, stroke volume recovered to 76 +/- 29% (standard deviation [SD]) of its prearrest value. Enzyme release (CK) was significantly higher after calcium-free cardioplegia (7.7 +/- 4.6 units [SD]) than after cardioplegia with normal calcium (2.1 +/- 1.6 units [SD]). Since the addition of only 0.025 mmol calcium ions to a liter of calcium-free solution completely prevented its negative effect, it was concluded that calcium-free cardioplegia may cause limited but pronounced damage to myocardial cells, presumably because it removes calcium from the cellular membranes--the so-called calcium paradox. Probably due to residual calcium in blood and extracellular fluid, the damage is not so extensive after calcium-free cardioplegia as to be noticeable in clinical surgical situations. Residual calcium in the heart does not exclude the possibility, however, that a calcium paradox occurs in small scattered areas of the heart.

Adenosine Triphosphate↗
PubMed1983

Cardioplegic arrest in isolated blood-perfused working rat hearts.

An isolated working rat heart model designed for function studies after elective cardiac arrest is described. Before and after a cold ischemic period (induced with St. Thomas' cardioplegic solution) of 30 min, hemodynamic and metabolic variables were assessed in a group of 13 hearts perfused with a modified Krebs-Henseleit solution and in a group of 13 hearts perfused with reconstituted blood. Functional recovery was about 90% in the nonblood-perfusate group and 98% in the blood-perfused group. Functional deterioration in time due to edema formation and limited oxygenation in electrolyte-perfused hearts was found to be of the same magnitude as the function loss ascribed to deleterious effects of cardioplegic arrest. The blood-perfused hearts showed hemodynamic stability during a 75 min continuous working period, and complete recovery of function after 30 min arrest.

Animals↗
PubMedDate not supplied

High pressure 2H nuclear magnetic resonance study of the gel phases of dipalmitoylphosphatidylcholine.

The 2H-NMR lineshapes of dipalmitoylphosphatidylcholine perdeuterated in the acyl chains were studied in a 15% dispersion in water as a function of pressure from 1 bar to 5 kbar over the temperature range from 7 degrees C to 75 degrees C. Increasing pressure in the gel state had the same effect as lowering the temperature: the lineshape gradually changed from a motionally averaged to a rigid lattice type spectrum with much of the intensity in the shoulders at +/- 63 kHz. At very high pressures and low temperatures (7 degrees C, 2.5 kbar; 25 degrees C, 5 kbar) even the methyl portion of the spectrum became a rigid lattice type spectrum at +/- 21 kHz. In addition to the liquid crystalline phase, five gel phases were detected. Using different techniques to determine the phase transitions, a general pressure-temperature phase diagram was constructed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMedDate not supplied

[Corneal endothelial proliferation in anterior synechiae: experimental and clinico-histopathological studies].

Corneal endothelial proliferation over the iris was studied on experimental anterior synechiae in rabbits up to 6 months. Clinico-pathologic studies of 102 post-keratoplasty eyes revealed that only 4 out of 51 anterior synechiae were endothelialized. In contrast all 10 leukomatous+ adhesions found in a series of 132 eyes removed after perforating corneal trauma were endothelialized. The above studies suggest that the most important factor for endothelial proliferation is the availability of suitable substrate. The rate of growth depends on growth factors present in anterior chamber.

Adult↗