Biomedical subjects

R Chaloupka

Publications and source records attributed to R Chaloupka.

10 recordsLinked to original sources

PubMed1999

The effect of hypericin and hypocrellin-A on lipid membranes and membrane potential of 3T3 fibroblasts.

Hypericin (HY) and Hypocrellin-A (HA) photosensitization induce rapid depolarization of plasma membrane in 3T3 cells as revealed by confocal microspectrofluorimetry using diO-C5(3) fluorescent probe. HY and HA are also able to rigidify the lipid membrane of DMPC liposomes as indicated by the decrease of pyrene excimer fluorescence used as a marker of the lipid membrane fluidity. We have also observed a nonspecific inhibition of Na+,K+-ATPase activity due to the HY and HA photosensitization. The described effects are concentration- and light dose-dependent and generally more pronounced for HA than for HY. All these observations suggest that the lipid membranes can play an important role in the photosensitization process induced by HY and HA at the cellular level. It can be hypothesized that for HA and HY the secondary mechanism following type I or type II photosensitization process can be the peroxidation of membrane lipids as well, and thus intracellular membranes seem to be one of the most important targets of these photosensitizers.

3T3 Cells↗

PubMed1999

Complete rotational burst fracture of the third lumbar vertebra managed by posterior surgery. A case report.

STUDY DESIGN: Case report of a young man with rotational burst fracture of the third lumbar vertebra, treated by posterior surgery. OBJECTIVES: To describe the management of a rotational burst fracture of the third lumbar vertebra by posterior surgery consisting of reduction, decompression, fusion, and transpedicular instrumentation. SUMMARY OF BACKGROUND DATA: Surgery is the generally recommended means of managing lumbar burst fractures with neurologic deficit. Some surgeons recommend anterior decompression, fusion, and instrumentation. Posterior surgery with decompression through laminectomy, spongioplasty of the vertebral body, interbody fusion of damaged discs, posterolateral fusion, and transpedicular fixation is also a safe and successful management technique. The combined approach consists of posterior decompression, fusion, transpedicular fixation, and anterior fusion using pelvic autografts. The optimum method of management remains in question. METHOD: An 18-year-old man with complete rotational burst fracture of the third lumbar vertebra was treated by posterior surgery. This surgery consisted of reduction, laminectomy, decompression, structure of dural sac tears, spongioplasty of the vertebral body, interbody fusion of both damaged discs, and the implantation of a transpedicular Socon fixator (Aesculap, Tuttlingen, Germany), including a transverse connector. The case was documented by radiographs and computed tomography scans before surgery and after fixator removal 19 months after surgery. RESULTS: The patient healed solidly with no instrumentation failure. The neurologic deficit Frankel Grade B improved to Frankel Grade D. CONCLUSION: Surgery to manage lumbar burst fracture must include reduction, decompression, restoration and fusion of anterior and posterior elements by using autologous pelvic spongious autografts, and anterior or posterior instrumentation. Posterior surgery including suturing of dural sac tears, fusion of damaged structures, and transpedicular fixation is successful in young patients and patients with good bone quality.

Adolescent↗

PubMed1998

Hypocrellin A photosensitization involves an intracellular pH decrease in 3T3 cells.

The fluorescent pH probe carboxy-seminaphtorhodafluor-1 (C-Snarf-1) has been used for laser microspectro-fluorometric assays of intracellular pH in 3T3 mouse fibroblasts treated with hypocrellin A. These results are compared to those previously obtained with the structurally related hydroxylated polycyclic quinone, hypericin (Sureau et al., J. Am. Chem. Soc. 118, 9484-9487, 1996). A mean local intracellular pH drop of 0.6 units has been observed in the presence of 1 microM hypocrellin A after 90 s of exposure to 0.1 microW of laser irradiation at 514.5 nm. The time evolution of the cytoplasm acidification for hypocrellin A-treated cells is faster than that for cells treated by hypericin. Thus, release of protons from an excited state of hypocrellin A appears to be more efficient than that from hypericin. In addition, the pH dependence of the quenching of C-Snarf-1 fluorescence in 3T3 cells under continuous irradiation has been observed. It is shown here that under continuous illumination, a pH decrease is able to induce a modification of the intracellular binding equilibrium of C-Snarf-1 that results in an increase of C-Snarf-1 fluorescence intensity. This latter observation suggests that the protons generated upon the photoexcitation of hypericin or its analogs may be involved in the production of other photoreactive species. Finally, we suggest that, just as for hypericin, this pH drop may be involved in the antiviral and antitumor activity of hypocrellin A.

3T3 Cells↗

PubMed1997

Measurement of membrane potential in Saccharomyces cerevisiae by the electrochromic probe di-4-ANEPPS: effect of intracellular probe distribution.

Changes in the membrane potential of Saccharomyces cerevisiae were monitored by the electrochromic probe 3-(4-(2-(6-(dibutylamino)-2-naphthyl)-trans- ethenyl)pyridinium)propanesulfonate (di-4-ANEPPS) that should incorporate into the plasma membrane. The probe had suitable spectral characteristics and exhibited an electrochromic shift upon a change in membrane potential but the magnitude of the response increased with time. The presence and properties of the cell wall affected the extent of cell staining. The time dependence of the fluorescent response indicated that the probe was not incorporated solely into the plasma membrane but spread gradually into the whole cell; this was confirmed by confocal microscopy. The probe is therefore suitable for assessing membrane potential changes only over time intervals up to 30 min. Longer monitoring will require either a modified staining protocol or a derivatization of the probe molecule. As found by using the dioctyl derivative di-8-ANEPPS, extending the aliphatic chains of the di-4-ANEPPS molecule does not prevent the dye from penetrating into the cell or liposome interior and, in addition, impairs staining.

Cell Membrane↗

PubMed1990

[The present occurrence of scoliosis and spondylolisthesis].

On the basis of the clinical material of 319 individuals suffering from spondylolysis and spondylolisthesis the authors examined the current occurrence of scoliosis and spondylolisthesis. After eliminating the curves up to 20 degrees and all disruptions of isthmus without slide they found only 18 patients. The slide was on the average 35 per cent (8 per cent to 100 per cent), scoliotic curve 35 degrees (21-71 degrees). The scoliotic curve was idiopathic in 13 cases and once it occurred in case of Marfan syndrome. Only 2 curves were of spastic and 2 of olisthetic type with the maximum of 41 degrees. The analysis has shown that in the selection of more pronounced deformities the number substantially falls of spastic and olisthetic scolioses which are mostly very slight and there prevail idiopathic curves. Operation was performed in one case of idiopathic curve and in one case of Marfan syndrome and in 3 patients suffering from spondylolisthesis.

Adolescent↗

PubMed1988