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Biomedical subjects

G Richard

Publications and source records attributed to G Richard.

At least 127 records · Page 7Linked to original sources
PubMed1996

Trichorhinophalangeal syndrome type III.

Trichorhinophalangeal syndrome (TRPS) type III is a newly defined clinical entity. This symptom complex is inherited as an autosomal dominant trait and clinically characterized by growth retardation, craniofacial abnormalities, severe brachydactyly and sparse hair. In addition, absence of mental retardation and cartilaginous exostoses are required for the diagnosis of TRPS III. To further delineate this newly recognized entity, we report on a patient from a Turkish family segregating TRPS III in 7 family members. The patient had a very short stature (147 cm, < 3rd standard deviation), a thin upper lip and a prominent lower lip, a pear-shaped nose, stubby fingers and toes with cone-shaped epiphyses and sparse scalp hair. Scanning electron microscopy findings and results of energy-dispersive X-ray microanalysis are presented in such a patient for the first time.

Abnormalities, Multiple↗
PubMed1996

Correlation of prenatal renal pelvic anteroposterior diameter with outcome in infancy.

PURPOSE: We attempted to correlate prenatal renal pelvic anteroposterior diameter with outcome in infancy. MATERIAL AND METHODS: Between May 1992 and March 1994 we identified 27 cases of fetal hydronephrosis in which renal pelvic anteroposterior diameter was 4 mm. or greater before 33 weeks of gestation and 7 mm. or greater at or after 33 weeks of gestation. RESULTS: Hydronephrosis was bilateral in 18 fetuses and unilateral in 9. Shortly after birth radiological assessment revealed vesicoureteral reflux in 6 neonates, ureteropelvic junction obstruction in 6, extrarenal pelves in 3 and persistent nonobstructive hydronephrosis in 4. Radiological evaluation was normal in 8 newborns. CONCLUSIONS: When these screening criteria for hydronephrosis are met prenatally a complete radiological assessment should be done following birth.

Analysis of Variance↗
PubMed1996

[In vitro study of the bacteriostatic and bactericidal activity of meropenem against strains of Pseudomonas aeruginosa multiresistant to antibiotics].

Meropenem is a new dehydropeptidase stable carbapenem which has an in vitro bacteriostatic activity superior to imipenem against Pseudomonas aeruginosa. Minimal inhibitory concentrations of meropenem (MEM) and imipenem (IPM) were determined on twelve strains: two were genetically characterized reference strains and ten isolated from patients. Killing curves were performed for MEM used at 1,2 and 4 fold the MIC and 32 mg/l; survivors were counted at baseline and after 5 and 24 hours of incubation by spiral plating. Five strains were susceptible to MEM and IPM; five were intermediate and two resistant to MEM; these seven strains were resistant to IPM. A weak bactericidal effect was obtained after 5 h at each concentration. Only one strain achieved a 3 log 10 reduction after 5 h at 2 x MIC. A regrowth of all the strains tested was observed after 24 h.

Dose-Response Relationship, Drug↗
PubMed1996

Influence of vascular endothelial growth factor on bovine corneal endothelial cells in a wound-healing model.

In this study we determined the influence of vascular endothelial growth factor (VEGF) on bovine corneal endothelial cell proliferation and wound healing. Proliferation was determined by measurement of DNA replication as well as by counting of the number of cells present after a defined growth period. In a wound-healing model, reproducible cell-free areas were created within monolayers of cultured bovine corneal endothelial cells and the migration of the cells into these areas was analyzed. The DNA replication and cell proliferation of bovine corneal endothelial cells were not influenced by VEGF. In contrast, in the wound-healing model, VEGF supplementation at concentrations of 1 and 10 ng/ml increased the cell density of the wounded area by 20% and 50%, respectively, as compared with the cell density of wounds left untreated by VEGF. Furthermore, no increase in DNA replication was found in cells involved in wound healing. Our results demonstrate that healing of bovine corneal endothelial cell layers after wounding is predominantly performed by cell migration rather than by proliferation. This migration can be stimulated by the addition of exogenous VEGF.

Animals↗
PubMed1996

Structural failure of pyrolytic carbon heart valves.

Pyrolite carbon has been used for the manufacture of mechanical heart valve prostheses for the past 25 years. In general, pyrolytic carbon mechanical heart valves have provided adequate physiological function and satisfactory structural performance. Although rare in occurrence, incidents of valve failure due to fracture of one or more components have been reported. These reports of failure are reviewed and a few representative examples are examined in detail in order to determine the characteristic failure mechanism. Understanding the underlying factors responsible for causing these failures provides a solid basis for improved design and manufacture of future mechanical heart valve prostheses.

Biocompatible Materials↗
PubMed1996

Differences in proliferation and migration of corneal endothelial cells [correction of epithelial cells] after cell transplantation in vitro.

For regular function the human cornea requires an intact endothelial cell layer with a sufficiently high cell density. One approach used to compensate endothelial cell loss is transplantation of cultured corneal endothelial cells. Using a previously described transplantation protocol, we observed topographic differences after transplantation of cultured human corneal endothelial cells to recipient corneas previously denuded of their own endothelium. The results presented in this paper suggest different interactions of the transplanted endothelial cells with the central or the peripheral part of the corneal matrix, respectively. Furthermore, cells isolated from the center of a human cornea differ from those isolated from the periphery in terms of their mitogenic capacity. The significance of these observations for corneal endothelial cell transplantation is discussed.

Animals↗
PubMed1996

Detection of endotoxin in media from sterile corneal organ cultures.

Lipopolysaccharides (LPS) are elements of the cell wall of gram-negative bacteria. They are also called endotoxins and are known to stimulate various inflammatory reactions by interaction with cytokines and macrophages. Additionally, they may have a direct effect on other cells. As contamination of sterile organ-culture media with bacterial substances may influence the donor-tissue prognosis, we investigated a series of culture media drawn from organ culture for the presence of endotoxin. A total of 341 samples of sterile organ-culture media from 3 different cornea banks using either organ culture or the refrigerated-storage technique were tested for endotoxin. The assay was performed using the Limulus amebocyte-lysate test. A level of endotoxin above the background threshold was found in 99/341 (29%) culture media. The incidence of endotoxin ranged from 14% up to 50%, depending on the cornea bank and culture system used. Endotoxin detected in sterile corneal organ cultures probably derives from nonreplicating bacterial postmortem donor-tissue contamination. The presence of endotoxin-positive cultures varied between the eye banks but was not related to a given storage method. As endotoxin may directly influence graft viability or trigger inflammatory host responses, these findings may have significance for the clinical results of corneal grafting.

Cornea↗
PubMed1995

Keratin 13 point mutation underlies the hereditary mucosal epithelial disorder white sponge nevus.

Although pathogenic keratin mutations have been well characterized in inherited epidermal disorders, analogous defects in keratins expressed in non-epidermal epithelia have yet to be described. White sponge nevus (WSN) is a rare autosomal dominant disorder of non-cornifying squamous epithelial differentiation that presents clinically as bilateral white, soft, thick plaques of the oral mucosa. Less frequently the mucous membranes of the nose, esophagus, genitalia and rectum are involved. Histopathological features, including epithelial thickening, parakeratosis, extensive vacuolization of the suprabasal keratinocytes and compact aggregates of keratin intermediate filaments (KIF) in the upper spinous layers, resemble those found in epidermal disorders due to keratin defects. We analysed a multigenerational family with WSN and found cosegregation of the disease with the keratin gene cluster on chromosome 17. We identified a missense mutation in one allele of keratin 13 that leads to proline substitution for a conserved leucine. The mutation occurred within the conserved 1A region of the helical rod domain, which is critical for KIF stability and is the site of most pathogenic keratin mutations. This mutation enlarges the spectrum of keratins with disease-causing defects to include mucosally expressed keratin 13, and extends the known keratin diseases to disorders of non-cornifying stratified squamous epithelia.

Amino Acid Sequence↗
PubMed1995

[Transplantation of retinal components].

BACKGROUND: The objective of recent animal experimental studies is to substitute destroyed or degenerated retina and to improve visual function by transplanting retinal components. Mature or immature retinal components were transplanted into the subretinal space of different animal species. METHODS: Embryonic and non-embryonic retina components of different animals or of humans are used as grafts. They are transplanted to adult host animals. There is the possibility of utilizing a posterior transscleral approach or a vitreoretinal approach. The latter offers a better visual control. Transplantation of retinal pigment epithelium could rescue photoreceptors in adult rats with inherited or age-related macular degeneration. RESULTS: After the transplantation it was possible to measure significantly higher visual evoked potentials in the transplanted eye than in the untreated fellow eye. Additionally, an almost normal pupillary reflex was identified. As it is not possible to adequately determine visual acuity in rodents, it is necessary to examine, as to whether visual improvement is also evident in primates. CONCLUSION: The eye is an immunologically privileged location for transplants because of retinal autoantigenic specific immunosuppression that protects the transplant from immunologic rejection. Many questions regarding operation technique, gaining of transplantation tissue and immunoreaction are to be answered before the use is possible on humans. The counseling of the patients and the informational policies towards the media should be correspondingly retentive.

Evoked Potentials, Visual↗
PubMed1995

Hailey-Hailey disease maps to a 5 cM interval on chromosome 3q21-q24.

Hailey-Hailey disease (HHD) is a rare autosomal dominant genodermatosis characterized by disturbed keratinocyte adhesion. The disease has recently been mapped to a 14 cM region on chromosome 3q. We have further refined the location of the HHD gene by linkage analysis in six HHD families from Germany and Italy using 11 polymorphic microsatellite markers and found no evidence for genetic heterogeneity. We observed complete cosegregation between HHD and marker D3S1587, with a maximal lod score of 4.54. Detailed haplotype analyses allowed us to narrow the interval containing the HHD locus to 5 cM, flanked by D3S1589 and D3S1290.

Chromosome Mapping↗
PubMed1995

An interlaboratory comparison of the FDA protocol for the evaluation of cavitation potential of mechanical heart valves.

Five laboratories carried out measurements of cavitation threshold for a common set of six mechanical prosthetic heart valves, two each from three different manufacturers. This study was intended to evaluate to what extent FDA's current guidance for cavitation testing would lead to consistent results in a variety of laboratory settings and to seek areas for improvement in the recommended test protocol. The inter-laboratory study protocol specified: (1) characterization of the test fluid by oxygen content and electrical conductivity, (2) location and frequency response of pressure sensors, (3) determination of ventricular and atrial pressures (P) and loading rates (dP/dt) averaged over the time period of valve closure and over the time periods of 1 ms, 5 ms, and 20 ms prior to video visualization. The protocol did not specify: (1) the fluid pumping equipment to be used to generate cavitation, (2) the pump or fluid parameters adjusted to raise or lower the loading rate, (3) the equipment, technique, or sensitivity used to visualize cavitation, and (4) a specific definition of the threshold for cavitation. Results from the five laboratories are reported. Significant differences in results were observed in dP/dt and in the pressure difference across the valves during closure at cavitation threshold. Specific differences in test systems included a wide range of ventricular compliance and single valved versus double valved test systems. Three single valve systems with compliant ventricles produced results in reasonable agreement with one another. Further similarity in test equipment should be specified to assure adequate interlaboratory reliability for cavitation testing. Areas needing better specification include the design of the valve mount, the design of the cavitation generators, and qualitative criteria for detection of threshold cavitation.

Biocompatible Materials↗
PubMed1994

[The prognosis of arterial occlusions of the eye].

Central retinal artery occlusion is caused by embolism or changes in blood rheology and viscosity. In the past, different concepts of treatment were introduced. Main princip is to improve microcirculation by increasing the pressure of perfusion, the diameter of retinal vessels or decreasing blood viscosity. Success of therapy depends on the age of artery occlusion and the rate of persisting retinal perfusion. The different concepts of therapy and their results are discussed.

Combined Modality Therapy↗
PubMed1994

Comparison of two techniques for measurement of in vitro killing kinetics of five antibiotics against Pseudomonas aeruginosa.

The in vitro activity of ticarcillin, imipenem, gentamicin, amikacin and ciprofloxacin against six Pseudomonas aeruginosa isolates was evaluated by two time-killing curve methods: the conventional broth technique, and another method previously described which employs a transfer filter membrane. The patterns of the killing curves obtained over a 5 h period with the two techniques were similar. In contrast to the results obtained for beta-lactam agents, the reduction of inoculum was great and increased with the concentration for aminoglycosides and ciprofloxacin. After 5 h, regrowth of the six strains tested was observed in broth with all antibiotics, whereas a bactericidal effect was observed over 24 h with the filter membrane method. Further studies are warranted to determine the reasons for this difference.

Amikacin↗
PubMed1994

Fine mapping of the Darier's disease locus on chromosome 12q.

Darier's disease (DD) is an autosomal dominant genodermatosis characterized by epidermal acantholysis and dyskeratosis. We have performed genetic linkage studies in 10 families with DD (34 affected) by analyzing 14 polymorphic microsatellite markers. Our results confirm recent reports mapping the DD gene to chromosome 12q23-q24.1. Haplotype analysis of recombinant chromosomes in our families, along with previously reported data, narrow the location of the DD gene to a 5 cM interval flanked by the loci D12S354 and D12S84/D12S105. This localization allowed exclusion of two known genes, PLA2A and PAH, as candidate loci for DD. Three other gene loci (PPP1C, PMCH, PMCA1), mapping in 12q21-q24, remain potential candidates.

Adolescent↗
PubMed1994

Hydrodynamic performance of Carbomedics valves in double valve replacement.

Most patients undergoing double valve replacements have reduced myocardial capacity. However, little is known about the influence of valve sizes on myocardial energy consumption in double valve replacement. This study was designed to supply hydrodynamic data for the proper selection of sizes in double valve replacement. A mock loop system was used to measure the energy consumption of CarboMedics valves at conditions resembling rest (5 L/min) and moderate exercise (9 L/min). All combinations of aortic valves size #21 to #27 with mitral prosthesis sizes #25 to #29 were tested separately. Larger size aortic prostheses revealed remarkably less energy consumption up to size #27. Under high flow (9 L/min) this effect was more pronounced. In contrast, mitral valve prosthesis sizes #25 to #29 had similar hydrodynamic data. At low flow conditions (5 L/min) no significant benefit was found with the use of a larger mitral valve. Only a reduction of less than 10 percent of total energy consumption could be achieved with the use of a mitral valve larger than #25 at 9 L/min flow. In conclusion there is no hydrodynamic reason for using a valve larger than #25 in the mitral position for patients who exercise moderately. Continuous reduction of cardiac work can be expected with the use of the largest possible aortic prosthesis up to size #27 at rest and at moderate exercise.

Aortic Valve↗