Biomedical subjects

D Che

Publications and source records attributed to D Che.

44 records · Page 3Linked to original sources

PubMed1996

Chromophore reorientations in the early photolysis intermediates of bacteriorhodopsin.

The photoselection-induced time-resolved linear dichroism of a bacteriorhodopsin suspension of purple membrane from 350 to 750 nm is measured by a new pseudo-null measurement technique. In combination with time-resolved absorption measurements, these linear dichroism measurements are used to determine the reorientation of the retinal chromophore of bacteriorhodopsin from 50 ns to 50 microseconds after photolysis. This time range covers the times when the K photointermediate decays to form L, as well as the early times during the formation of the M intermediate in the photocycle. An analysis of the photoselection-induced linear dichroism measured directly, along with the absorbance changes polarized parallel to the linearly polarized excitation, shows that the anisotropy is invariant over this time period, implying that the photolyzed chromophore rotates less than 8 degrees C with respect to unphotolyzed chromophores during this part of the photocycle.

Anisotropy↗

PubMed1995

Nanosecond optical rotatory dispersion spectroscopy: application to photolyzed hemoglobin-CO kinetics.

A standard technique for static optical rotatory dispersion (ORD) measurements is adapted to the measurement of ORD changes on a nanosecond (ns) time scale, giving approximately a million-fold improvement in time-resolution over conventional instrumentation. The technique described here is similar in principle to a technique recently developed for ns time-resolved circular dichroism (TRCD) spectroscopy, although the time-resolved optical rotatory dispersion (TRORD) technique requires fewer optical components. As with static ORD, TRORD measurements may be interpreted by empirical comparisons or may be transformed, via the Kramers-Kronig relations, to more easily interpreted TRCD spectra. TRORD can offer experimental advantages over TRCD in studying kinetic processes effecting changes in the chiral structures of biological molecules. In particular, the wider dispersion of ORD bands compared with the corresponding CD bands means that ORD information may often be obtained outside of absorption bands, a signal-to-noise advantage for multichannel measurements. Demonstration of the technique by its application to ns TRORD and the transform-calculated TRCD of carboxy-hemoglobin (Hb-CO) after laser photolysis is presented.

Biophysical Phenomena↗

PubMed1995

[Effects of hypoxia on the expression of platelet-derived growth factor (PDGF) gene and PDGF-B chain protein in porcine pulmonary artery endothelial cells].

Northern blot, slot blot hybridization and quantitative immunocytochemistry analyses were used to study the effects of hypoxia on the expression of PDGF gene and PDGF-B chain protein in cultured pulmonary artery endothelial cells (PAEC). Hypoxia (3% oxygen) significantly increased PDGF-B chain mRNA in PAEC, whereas mRNA level of PDGF-A chain was not increased significantly in comparison with normoxic control (21% oxygen). PDGF-B chain immunoreactivity on PAEC exposed to hypoxia was markedly stronger than that of normoxic PAEC and PDGF-B China immunoreaction. was found in cytoplasm and perinuclear region of the hypoxic PAEC, however, only in the nuclear region of normoxic PAEC. Increased expression of PDGF-B chain protein roughly paralleling that of PDGF-B mRNA was also observed. These results suggest that hypoxia may stimulate the expression of PDGF-B chain by PAEC in vivo and PDGF may play an important role in the vascular remodeling of hypoxic pulmonary hypertension.

Animals↗

PubMed1995

[The relationship of intraacinar pulmonary arterial structural remodelling with pulmonary hypertension].

Pulmonary hypertension (PHT) was induced in rats by a single subcutaneous injection of monocrotaline (MCT). Light and electron microscopy, immunohistochemistry and morphometry were applied to investigate the different pathological changes of the intraacinar pulmonary arteries (IAPA) and their relationship with PHT. The results showed that pulmonary function was related to the morphological structure and indicated that the remodelling in the IAPA structure was the pathological basis of PHT. The results further suggested that the proliferation and myoid differentiation of the pericyte play an important role in the muscularization of the nonmuscular pulmonary artery in IAPA.

Animals↗

PubMed1995

Effects of hypoxic endothelial cell conditioned medium on proliferation and collagen synthesis of smooth muscle cells and inhibitory effects of radix salviae miltiorrhizae.

The effects of hypoxic endothelial cell conditioned medium (HECCM) on proliferation and collagen synthesis of cultured porcine pulmonary arterial smooth muscle cells (PASMCs) were studied by 3H-thymidine (3H-TdR) and 3H-proline incorporations, image analysis for determination of DNA content and colorimetric assay using MTT, and the inhibitory effects of radix salviae miltiorrhizae (RSM) on them were also investigated. The results showed that HECCM could induce enhancement of the enzymatic activity of mitochondria, increase of the nucleic DNA content and increases of the 3H-TdR and 3H-proline incorporation in PASMCs. The 3H-proline incorporation in PASMCs cultured in HECCM was 1.83 times as much as that cultured in normoxic endothelial cell conditioned medium (NECCM). Compared with the control, Chinese herb medicine RSM could inhibit the proliferation of PASMCs cultured in HECCM and decrease the 3H-proline incorporation in PASMCs cultured in both HECCM and NECCM (P < 0.001). However, RSM had no effects on the nucleic DNA content and 3H-TdR incorporation into DNA of PASMCs cultured in NECCM. It suggests that hypoxia may stimulate the endothelia to synthesize and secrete some cytokines which can stimulate the proliferation and the synthesis of collagen of PASMCs and RSM can inhibit this process.

Animals↗

PubMed1995

[Effects of hypoxia on the phenotype of porcine pulmonary arterial smooth muscle cells in vitro].

The effects of hypoxia on phenotype modulation of pulmonary artery smooth muscle cells (PASMC) was observed using cell culture and morphometry analysis. The results showed that the number of diploid cells and alpha-sm-actin of the hypoxic endothelial cell condition medium group (HECCM) was lower and the myofibrils were even less than that of the normal endothelial cell condition medium group (NECCM). On the contrary, the volume density of rough endothelial reticulum (RER) and mitochondria of the HECCM group were higher than that of the NECCM group. However, under hypoxic condition for 24 hours, the phenotype of cultured PASMCs remained unchanged. It suggests that the HECCM can induce phenotype modulation of PASMCs, may be mediated by the pulmonary artery endothelial cells (PAECs) which can secrete some cytokines affecting the PASMCs.

Animals↗

PubMed1994

Nanosecond absorption study of kinetics associated with carbon monoxide rebinding to hemoglobin S and hemoglobin C following ligand photolysis.

The absorption spectra of photolysis intermediates of the CO complex of hemoglobin S and hemoglobin C, in the tetramer form, have been measured between 10 ns and 200 ms after excitation. These data were analyzed using singular value decomposition (SVD) and global analysis to determine kinetic lifetimes associated with various processes involved in CO recombination. The results of this analysis show that, in the tetramer (non-aggregated) form, hemoglobin S and hemoglobin C exhibit the same kinetics associated with CO recombination as hemoglobin A.

Absorption↗

PubMedDate not supplied

[Tinea capitis: sample surveys among school doctors and dermatologists in the Paris suburbs].

BACKGROUND: Subsequent to detection of several cases of anthropophilic tinea capitis, we wanted to know whether the legal decree requiring eviction from school and an epidemiology survey in the children community or the family is implemented properly. METHODS: Two sample surveys were carried out among 50 school doctors from the Hauts-de-Seine department and 110 dermatologists working the Paris suburbs. RESULTS: Eviction from school was rare and not based on the type of dermatophytes (anthropophilic or zoophilic agent). Likewise, epidemiology survey was neglected, often being solely clinical for other family members. Systematic sampling in the children community or in the family was very exceptional. DISCUSSION: Despite the rise in the number of cases of anthropophilic tinea capitis in Paris suburbs, the decree is not often implemented. Dermatologists would appear to be responsible for this situation, especially in case of M. langeronii, which is very contagious in nursery school.

Child↗