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J Funk

Publications and source records attributed to J Funk.

84 records · Page 5Linked to original sources
PubMed1982

Temperature-induced vertical shift of proteins in membranes.

Thermotropic changes in the transverse order of microsomal membranes isolated from Tetrahymena are revealed by low-angle X-ray diffraction. These are correlated with the lateral order of the membrane lipids by wide-angle X-ray diffraction. Upon lowering the temperature from 28 degrees C to 2 degrees C, the Bragg period of the membrane stack reveals an abrupt increase of approximately 3.1 nm at approximately 19 degrees C, which is reversible upon reheating to 28 degrees C. This is coupled with an alteration in the electron density profile, revealing a shift of mass from the hydrophobic core towards one of the two hydrophilic surfaces. Between 35 degrees C and 0 degrees C, the membrane lipids undergo a broad, thermotropic "two-stage" liquid crystalline in equilibrium crystalline phase separation with a "breakpoint" at approximately 18 degrees C. This breakpoint signals an abrupt lipid redistribution, presumably due to a change in the composition of the two coexisting liquid crystalline and crystalline lipid phases. We conclude: (1) the temperature-induced mass shift reflects a shift in the transverse partition of proteins in membranes; (2) this is triggered by an abrupt lipid redistribution occurring during a broad liquid crystalline in equilibrium crystalline phase separation.

Fatty Acids↗
PubMed1982

Thermotropic 'two-stage' liquid crystalline equilibrium crystalline lipid phase separation in microsomal membranes.

The effect of temperature on native microsomal membrane vesicles isolated from Tetrahymena is investigated by wide angle X-ray diffraction. A 4.2 reflection, typical for lipids in the crystalline state, can be recorded in the temperature range between 0 degree C and 35 degrees C. Quantitative evaluation of this reflection reveals a broad thermotropic 'two-stage' liquid crystalline equilibrium crystalline lipid phase separation with a 'breakpoint' at approx. 18 degrees C. This 'breakpoint' coincides with the emergency of lipid-protein segregations in endomembranes of intact Tetrahymena cells as previously visualized by freeze-etch electron microscopy.

Animals↗
PubMed1981

Evaluation of the electron density profile of the frog rod outer segment disc-membrane in vivo using x-ray diffraction.

The structure of the rod outer segment disc-membrane in vivo was studied by X-ray low-angle scattering. The experiments were made on frogs under narcosis. Diffraction patterns corresponding to a resolution of 1.5 nm could be obtained from the membrane stacks of the rod outer segment discs. For the analysis of the measured diffraction pattern a new special computer procedure was elaborated. Among other generalizations of the theory, it was taken into account that the electron densities in the inter- and intra-disc spaces differ from the mean electron density of the whole stack. The consideration of this possibility, together with an exact experimental measurement of the isotrope background scattering, led to a mathematically unique solution. The calculated electron density profile apparently is a distinct asymmetric bilayer. The electron density of the side of the membrane which is in contact with the disc lumen is higher than the electron density on the side in contact with the cytoplasm. Therefore, a localization of rhodopsin or of other high molecular proteins mainly on the cytoplasmatic edge of the membrane can be excluded for the rod outer segment discs in vivo.

Animals↗
PubMedDate not supplied

[Application of a dynamic pedicle screw system (DYNESYS) for lumbar segmental degenerations - comparison of clinical and radiological results for different indications].

AIM: Evaluation of the efficacy of a dynamic stabilizing system for different indications using medium-term clinical and radiological parameters. METHODS: Out of a total of 70 evaluated patients, 35 showed initial disc degeneration and disc herniation (group 1). In this group, additional nucleotomy was performed. Group 2 included 22 patients with initial osteochondrosis and facet joint osteoarthritis. 13 patients suffered from progressive segment degeneration or degenerative spondylolisthesis (group 3). Clinical evaluation was performed preoperatively, three months postoperatively and at follow-up (33 months). Examinations included subjective and objective measures using the Oswestry Index and VAS as well as radiographs and MRI. RESULTS: Oswestry Index and VAS improved significantly in groups 1 and 2 and remained improved until follow-up. Group 3 showed no significant changes. The evaluation of radiographs and MRI of groups 1 and 2 revealed no progression of the degeneration either at the operated segments or at the adjacent segments. In group 3, 9 cases of progressive degeneration of the operated segments and 3 cases of adjacent segment degeneration were found. Out of 5 implant-associated complications 4 were observed in group 3. CONCLUSION: Dynesys is able to compensate initial morphological changes and to prevent progression of segment degeneration. The system seems not to be indicated for treating marked deformities or if osseous decompression needs to be performed.

Adult↗
PubMedDate not supplied

Chronic postoperative endophthalmitis caused by Propionibacterium acnes.

Persistent intraocular inflammation after cataract surgery with intraocular lens implantation is acquiring importance. Frequently, chronic uveitis or the "toxic lens syndrome" have to be differentiated from bacterial infection. This report describes five cases with chronic postoperative endophthalmitis where the anaerobic bacterium Propionibacterium acnes was found to be the causative organism. Adequate anaerobic culture media and proper sampling from the area around the lens haptics are the most important requirements for the detection of P. acnes.

Cataract Extraction↗
PubMedDate not supplied

Recurrent herpetic keratitis during topical acyclovir application.

Dendritic herpetic keratitis developed in a 49-year-old patient during topical acyclovir treatment. A positive herpes simplex culture was obtained. After acyclovir was replaced by trifluorothymidine and interferon, the dendritic lesion disappeared and herpes simplex culture became negative. Six months later a carcinoma of the larynx was diagnosed. The acyclovir-resistant herpetic keratitis may be associated with the carcinoma because resistant herpes simplex virus strains are predominantly described in patients suffering from immune deficiency.

Acyclovir↗
PubMedDate not supplied

Is the blind spot enlarged in early glaucoma?

PURPOSE: We investigated whether the blind spot is larger in early "preperimetric" glaucoma with already deeply excavated optic discs than in normal persons. METHODS: We examined eight eyes of five patients with definite glaucomatous optic disc cupping but normal visual fields. Ten eyes of five normal healthy volunteers, with normal central excavation, served as controls. With SLO-perimetry we measured the differential light sensitivity 0.5-1.0 degrees outside the disc margins, "within" the center (Goldmann V stimulus) and along the horizontal meridian of the optic discs. Optic disc topography was documented with the Heidelberg Retina Tomograph (HRT). RESULTS: Differential light sensitivities adjacent to the optic discs did not differ in the two groups (normal 8.3dB, early glaucoma 8.4dB). Goldmann IV stimuli presented on the horizontal meridian of optic discs with glaucomatous cupping were seen up to 0.7 degrees centrally (i.e., towards the center) of the disc margin. In the control group this distance was significantly greater (1.3 degrees). The light differential thresholds with stimulus presentation in the disc center (Goldmann V) were significantly higher in the glaucoma group (0+/-2.8dB) than in the normal controls (6.6+/-1.3dB), though disc size was the same in both groups. CONCLUSIONS: Blind spots of normal discs seem to be smaller than those of deeply excavated discs in eyes with early glaucoma, possibly because there is more light scattering by the normal disc surface towards the adjacent functioning retina.

Adaptation, Ocular↗
PubMedDate not supplied

Accuracy of intravenous infusion pumps in continuous renal replacement therapies.

Most extracorporeal continuous renal replacement therapies (CRRT) require inflow pumping of either dialysate, filtrate replacement solution, or both. Outflow of spent dialysate and ultrafiltrate can be accomplished by gravity drainage or pump. Intravenous infusion pumps have been commonly used for these purposes, although little is known about the accuracy of these pumps. To evaluate accuracy of two different types of intravenous infusion pumps used in CRRT, we studied flow rates at nine different pressure variations in three piston type and three linear peristaltic pumps. The results showed that error of either pump was not different for flow rates of 4 and 16 ml/min. Both types of pumps were affected by fluid circuit pressures, although pressure conditions under which error was low were different for each pump type. The linear peristaltic pumps were most accurate under conditions of low pump inlet pressure, whereas piston pumps were most accurate under conditions of low pump pressure gradient (outlet minus inlet) of 0 or -100 mmHg. The magnitude of error outside these conditions was substantial, reaching 12.5% for the linear peristaltic pump when inlet pressure was -100 mmHg and outlet pressure was 100 mmHg. Error may be minimized in the clinical setting by choosing the pump type best suited for the pressure conditions expected for the renal replacement modality in use.

Equipment Design↗
PubMedDate not supplied

Benefit of bicarbonate dialysis during CAVHD.

The effect of bicarbonate dialysate (BD) on acid-base status in six pediatric CAVHD patients was examined during seven episodes of metabolic acidosis. When metabolic acidosis was not corrected with CAVHD, a sterile BD was substituted for either acetate- or lactate-based dialysate. Pre- and post-BD substitution levels of lactate, HCO3, PCO2, anion gap, and pH were recorded, as well as dose of intravenous (i.v.) bicarbonate. Improvements in pH and serum HCO3 were seen in all seven cases. Anion gap decreased in all but one of the patients who were switched from lactate to bicarbonate dialysate, with improvement most marked in those patients with marked elevation of the anion gap. No adverse effect on PCO2 was noted. Lactate dialysate may be less effective when serum lactate levels are high, and may contribute to further elevation of lactate levels and anion gap. These data suggest that bicarbonate dialysate may be preferable to lactate or acetate dialysate in CAVHD patients with persistent metabolic acidosis.

Acid-Base Equilibrium↗