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Biomedical subjects

G Richard

Publications and source records attributed to G Richard.

At least 145 records · Page 8Linked to original sources
PubMed1994

Cavitation threshold ranking and erosion characteristics of bileaflet heart valve prostheses.

In vitro testing was approached using two methods in specially designed cavitation testers. Each method tested production model bileaflet valves with the sewing cuffs removed. First level testing evaluated the visual cavitation thresholds of size 25, 27, and 29 CarboMedics (CPHV), Saint Jude Medical (SJM) and Duromedics (original design prior to 1990 revision) valves using high-speed videographic methods to observe and record the presence of cavitation bubbles generated by each valve upon closure. Visual cavitation thresholds were also determined for size 29 Sorin and Jyros valves. The visual cavitation threshold dP/dt value was 2,500 mmHg/sec for the size 25 SJM and CPHV and 1,600 mmHg/sec for the size 25 Duromedics valve. Second level testing assessed the erosion resistance of size 25 CPHV, SJM, and Duromedics valves cycled at identical drive conditions. Upon visual inspection, damage to the Duromedics valves appeared to be much more severe than on either the CPHV or the SJM valve. Erosion damage observed on the CPHV appeared to be identical to that observed on the SJM valve. All Duromedics valves tested were of the original design (prior to the 1990 revision) and the effects of the sewing cuffs on the cavitation threshold and erosion were not evaluated in this investigation.

Heart Valve Prosthesis↗
PubMed1993

Voltage-dependent potassium currents in cultured human retinal pigment epithelial cells.

Membrane currents in primary cultures of human retinal pigment epithelial cells were studied using the whole-cell configuration of the patch-clamp technique. Two types of voltage-dependent whole-cell currents were observed. First, a time- and voltage-dependent outward current, which was activated by depolarizing the cell to potentials more positive than -30mV, was sensitive to Ba2+ (10mM), 4-aminopyridine (10mM) and TEA+ (30mM). Tail-current analysis indicated that the current was mainly carried by K(+)-ions. Second, hyperpolarization of the cell to potentials more negative than -70mV led to a time- and voltage-dependent inward current which was blocked by Ba2+ (10mM) and 4-aminopyridine (10mM), but not by TEA+ (30mM). In summary, human retinal pigment epithelial cells in primary culture express currents which indicate the presence of a delayed rectifier K(+)-channel and an inward rectifier K(+)-channel.

4-Aminopyridine↗
PubMed1993

Retinopathy of prematurity--current diagnosis and management.

Despite advances in ophthalmological care of premature infants, retinopathy of prematurity (ROP) remains a still unsolved problem for paediatricians as well as ophthalmologists. A survey of the current literature concerning drug therapy and surgical management as related to the different stages of ROP is given. The classification system for ROP according to the International Committee is presented as well as our screening policy in relation to the literature. The effectiveness in preventing severe cases of ROP and the toxicity of vitamin E supplementation in high-risk premature infants is still disputed and no recommendations can be given. Cryotherapy is recommended in symmetric cases of stage 3 + ROP. Nevertheless, quite a number of eyes still progress to more severe stages of ROP. Scleral buckling procedures and vitrectomy may lead to anatomical success in a few cases of retinal detachment, however, the visual outcome of such an operation is usually very poor despite reattachment of the central retina.

Cryosurgery↗
PubMed1993

Synergy of cefotaxime and fosfomycin against penicillin-resistant pneumococci.

The killing kinetics of cefotaxime and fosfomycin, alone and in combination, against seven clinical isolates of penicillin-resistant pneumococci were studied. The antibiotics were tested at 1 x, 2 x and 4 x the MIC for each individual isolate. The results showed a synergic interaction of the two antibiotics for three of the seven strains. This strategy may be useful clinically.

Cefotaxime↗
PubMed1993

A case of acute megakaryocytic leukemia with hematogones.

A case of an infant male with Down's syndrome, pancytopenia, and a relative lymphocytosis is presented. A bone marrow aspirate and crushed marrow biopsy were evaluated by microscopy and flow cytometry. A population of immature lymphoid cells positive for CD10 (CALLA) and CD19 (Leu 12) was initially interpreted as suggestive of an acute lymphoblastic leukemia (ALL). However, a second bone marrow biopsy revealed morphologic features consistent with acute megakaryocytic leukemia (AMKL) with fibrosis. This diagnosis was supported by the flow cytometric study showing increased myeloid and megakaryocytic antigen-positive cells in the bone marrow and peripheral blood obtained after chemotherapy for ALL. This report presents evidence that the original lymphoid population represented hematogones, which were preferentially aspirated due to marrow fibrosis. There are no previous reports of hematogones identified at the presentation of an acute leukemia. It also emphasizes that the presence of hematogones with the resultant marker findings can be misleading. The diagnosis of ALL in pediatric patients should not be based solely on the presence of increased CD10-positive cells.

Biopsy↗
PubMed1993

[Retinoids in therapy of granuloma anulare disseminatum].

We report on four patients with granuloma annulare disseminatum successfully treated with etretinate as basic medication. In two cases there was complete remission after treatment with initial doses of up to 0.9 mg/kg body weight etretinate. One patient did not respond to etretinate alone but the condition was cured when Re-PUVA therapy was administered in addition. In another patient, with widespread granuloma annulare, primary treatment with Re-PUVA was instigated, followed by low-dose monotherapy with etretinate. According to these findings, we propose a three-stage regimen of therapy. After checking that the indications are appropriate, we first initiate monotherapy with etretinate and switch to a low-dose treatment over a longer period on response. If there is no response we switch to the second stage, i.e. Re-PUVA therapy; the third is then etretinate monotherapy to prevent relapse.

Aged↗
PubMed1993

[Hailey-Hailey disease. Early detection of heterozygotes by an ultraviolet provocation tests--clinical relevance of the method].

An UV provocative test to identify genotypical carriers of Hailey-Hailey disease was developed, and performed on 30 non-affected family members of 8 families. The test revealed that 10 individuals were genotypical carriers without clinical signs. We checked the reliability of the UV provocative test during a 3-year follow-up period (family register method). In 50% of the carriers identified by the UV provocative test the first clinical manifestations of Hailey-Hailey disease developed in this period. All individuals with negative UV provocative test results remained clinically healthy. Up to now our results with the UV provocative test have been verified by the clinical development in 80% of cases. The UV provocative test is a practicable and reliable method of determining genotypical carriers of Hailey-Hailey disease.

Adult↗
PubMed1993

[Keratosis follicularis spinulosa decalvans. Therapy with isotretinoin and etretinate in the inflammatory stage].

Keratosis follicularis spinulosa decalvans (KFSD) is a rare X-linked disorder of keratinization of the hair follicle associated with corneal dystrophy. The clinical picture is characterized by solid follicular hyperkeratosis, especially on the exposed skin, sparse eyebrows/eyelashes, follicular scaling and scarring alopecia of the scalp, dry skin and ocular symptoms with keratitis and photophobia. We describe the three stages of the disease: onset, inflammation and partial remission and the treatment appropriate in each. Two patients in the inflammatory stage of KFSD, with recurrent deep, fibrosing folliculitis and perifolliculitis followed by spreading and scarring alopecia on the scalp, responded to oral therapy with retinoids. In both cases there was a distinct and lasting remission of the inflammation and stabilization of the spreading alopecia after treatment with etretinate (Tigason), up to 0.8 mg/kg body weight, or isotretinoin (Roaccutan), 0.5 mg/kg body weight, for 12 weeks. The follicular spinulous hyperkeratosis became softer, but persisted. Thus, oral therapy with retinoids appears helpful in the inflammatory stage of KFSD, even though there is little improvement in the follicular hyperkeratosis.

Administration, Oral↗
PubMed1993

Intralesional alpha interferon. Cost-effective therapy for vulvar vestibulitis syndrome.

The cost-effectiveness of two treatment strategies for vulvar vestibulitis syndrome (VVS) was compared. Our prospective study consisted of 55 patients with human papillomavirus (HPV)- and non-HPV-associated VVS of at least 6 months' duration treated with intralesional recombinant alpha interferon injections, followed by surgery for nonresponders and responders compared with a hypothetical model of surgery alone. The setting was a private-practice multispecialty center for vulvovaginal disorders. Improvement was defined by patients' subjective evaluation of change in the level of introital dyspareunia and the ability to have sexual relations and objective evidence of change in the degree of erythema and tenderness to touch within the vestibule. Statistical analyses of the overall probability of improvement, overall costs and the cost per patient treated were done. Twenty-seven (49%) of 55 patients treated with alpha interferon had substantial or partial improvement. Of the 28 (51%) who did not improve following alpha interferon, 19 elected to have surgery. Surgery resulted in substantial improvement in 84% of the patients and partial improvement in 11%. Statistical analysis comparing the group treated with alpha interferon (some of whom went to surgery with the hypothetical model of surgical treatment alone) showed significant cost-saving in the group first treated with alpha interferon. At the level of effectiveness achieved in this study, intralesional alpha interferon as a first choice in the treatment of VVS is cost-effective.

Adult↗
PubMed1992

[Success of retinal surgery comparing phakic and pseudophakic eyes with reference to preoperative findings and the kind of lens implant].

We analyzed retrospectively 597 eyes over a minimum follow-up of 6 months and compared the results of pseudophakic eyes with phakic eyes. The repair of pseudophakic retinal detachment is more difficult than the surgery in aphakic retinal detachment. Pseudophakic retinal detachment had a more advanced retinal detachment and PVR-stages at the time of diagnosis. Localisation of the tear was more complicated and the surgery was more invasive than in phakic eyes. In 61.2% the repair was for pseudophakic eyes with posterior chamber lens 78%, with anterior chamber lens 81.8% and for iris-fixated IOL's 75%. Compared to this, the anatomic reattachment rate in phakic eyes was 94.8%. The pseudophakic group had less favorable visual results.

Follow-Up Studies↗
PubMed1992

[Bacteriostatic activity and killing curves of eight antibiotics against seven strains of penicillin G-resistant pneumococci].

Increasing resistance to multiple antimicrobial agents including penicillins is a current problem with Streptococcus pneumoniae. Seven cases of severe infection due to penicillin G-resistant pneumococci were seen in two teaching hospitals in Paris (France) during the first half of 1991; six of the strains were recovered from pulmonary secretions (protected brush specimens) and one from cerebrospinal fluid (CSF). The bacteriostatic activity and killing curves of eight antimicrobials against these seven strains were studied. Antimicrobial agents tested included penicillin G (PEN), amoxicillin (AMX), cefotaxime (CTX), imipenem (IPM), rifampin (RIF), vancomycin (VAN), fosfomycin (FOS), and erythromycin (ERO). MICs were determined using the agar dilution method. Killing curves were obtained using a liquid medium inoculated with 10(5) to 10(6) CFU/ml and subjected to continuous agitation; survivors were counted at baseline and after 1, 3 and 5 hours incubation. MICs of each antimicrobial (mg/l) for the seven strains were in the following ranges: PEN: 0.5-2, AMX: 0.5-2; CTX: 0.125-1; IPM: 0.03-0.25; RIF: 0.12-0.25; VAN: 0.25-1; FOS: 16; ERO: 0.06 greater than 4. Overall, bactericidal activity was greatest with vancomycin, followed by imipenem, then amoxicillin. The cefotaxime-fosfomycin combination proved synergistic and exhibited bactericidal activity (2MIC + 2MIC) for three of the seven strains. This study demonstrated the value of the cefotaxime-fosfomycin combination. Both these antimicrobials seem appropriate for the treatment of meningitis caused by penicillin G-resistant pneumococci provided their dosage is adjusted to achieve adequate drug levels in the cerebrospinal fluid.

Amoxicillin↗
PubMed1991

Safety signal withdrawal: a behavioural paradigm sensitive to both "anxiolytic" and "anxiogenic" drugs under identical experimental conditions.

A new method involving the blockade of operant behaviour induced by the withdrawal of a conditioned signal for safety without presentation of a punishment signal has been developed for studying drugs with anxiolytic or anxiogenic properties. For this purpose, rats were trained under two alternating components of a multiple schedule of reinforcement FR8 (food)/FR1 (food) + RR 50% (shocks randomly delivered with 50 +/- 15% of the presses). The nonpunished and punished periods were signalled by one cue light above the right lever (safety signal) or the left lever (punishment signal), respectively. On the test session (safety signal withdrawal), the safety signal was turned off at the end of the first nonpunished period, but the punishment signal was not presented (every press was food rewarded and no shocks were delivered). During this period (4 min), rats exhibited a strong blockade of responding that lessened over time. This suppression seemed not to be caused by intervening events such as novelty, temporal conditioning, schedule of food delivery or ambiguity of the signal presented. The behavioural blockade induced by withdrawal of the safety signal was reduced by benzodiazepines: diazepam (0.5-4 mg/kg), chlordiazepoxide (4-8 mg/kg), nitrazepam (0.25-2 mg/kg), alprazolam (0.25-1 mg/kg), and partial agonists at benzodiazepine receptors: bretazenil (0.125-8 mg/kg) and ZK 91296 (32-64 mg/kg). Various 5-HT-related drugs also lessened the behavioural blockade:pCPA (3 x 150 mg/kg) and the 5-HT1A receptor agonists, buspirone (0.25-2 mg/kg), gepirone (0.25-1 mg/kg) but not 8-OH-DPAT. Compounds that may cause anxiety in humans further enhanced the blockade of lever pressing induced by the safety signal withdrawal at doses that did not modify baseline responding: d-amphetamine (0.125-0.5 mg/kg), caffeine (16 mg/kg) and picrotoxin (1 mg/kg). FG 7142 (8 mg/kg) and CGS 8216 (2-8 mg/kg) decreased responding during both components of the session. Therefore, the present paradigm seems sensitive to both "anxiolytic" and "anxiogenic" effects of drugs under identical procedural conditions.

Animals↗
PubMed1991

Acquired ocular toxoplasmosis. A fluorescein angiography study.

A 31-year-old man exhibited a bilateral deterioration of vision over the course of 1 week. The right fundus showed the picture of a central vein occlusion, and the left of a disseminated choroiditis. Indirect immunofluorescent testing indicated a titer of 1:2048 for toxoplasmosis. Fluorescein angiography revealed a hitherto unique picture of isolated choroidal occlusions but neither a central vein occlusion nor a disseminated choroiditis. Using only specific antitoxoplasmotic therapy, the patient regained full visual acuity on both sides. The original findings and the results of a 14-year follow-up are presented.

Adult↗
PubMed1991

Injector for highly viscous silicone oil.

A syringe device for the injection and evacuation of highly viscous silicone oil was developed. The problem of removing the air interfering with these manoeuvres was solved by providing special outlets in the plunger and handle of a conventional glass syringe. A slightly modified commercial motor perfusor was chosen to power this device, which has proved to be good and fail-safe in more than 100 cases.

Air↗
PubMed1991

Peritonitis in children on chronic peritoneal dialysis: analysis at 10 years.

Peritoneal dialysis is the major form of renal replacement therapy for children awaiting renal transplantation. Peritonitis is the major associated morbidity. We retrospectively identified the pathogens, co-morbid factors and outcome of peritonitis in children on peritoneal dialysis from 1980-1989. Seventy-three children, mean age 12.4 years, received 1,234 patient months of chronic peritoneal dialysis. Twenty-four patients (33%) remained peritonitis free until their dialysis catheters were removed after transplantation. Forty-nine children (67%) developed 219 episodes of peritonitis. Peritoneal fluid cultures were positive in 169 episodes (77%). Of the pathogens identified, 73% were gram positive cocci, 22% gram negative rods, 3% were fungus, and 2% other organisms. The incidence of peritonitis was one episode per 5.6 months. Over a 10 year period: 1) 67% of children on peritoneal dialysis developed peritonitis; 2) gram positive cocci accounted for most episodes; 3) the incidence in children was higher than that reported for adults; 4) there were no deaths attributable to peritonitis.

Child↗
PubMed1991

[Therapy of retinal detachment in Coats' disease].

Coats disease, an idiopathic condition of unknown etiology, includes teleangiectatic and aneurysmatic retinal vessels in association with massive subretinal exudation. Progression to retinal detachment caused by prolonged subretinal exudation means a poor prognosis. Retinal detachment surgery had always been controversial. Twelve patients (aged 7 to 48 years) with retinal detachment and Coats' disease were treated by various operations (cryotherapy, 4X; episcleral buckle, 2X; vitrectomy and gastamponade, 3X; vitrectomy and silicone-oiltamponade, 2X). One case (cryotherapy and cerclage) failed and went on to retinal detachment. In the other 11 cases the retinal was reattached successfully. However, peripheral, small areas remained detached, caused by persistent deposits of subretinal exudation. This means that the underlying Coats' disease is still active and must be treated by laser coagulation. It must also be monitored carefully, to keep an eye on the preretinal vitreous activities leading to detachment.

Adolescent↗
PubMed1991

Investigations on diathermy for anterior capsulotomy.

Diathermy is an approved instrument for intraocular surgery. The authors studied the effects and possible side effects of the first clinical application of a straight bipolar high-frequency probe used to cut the anterior capsule in extracapsular cataract exfraction (ECCE) with a continuous movement. In 25 patients with intumescent or mature cataractous lenses, on which capsulorhexis is difficult to perform, the anterior capsule was cut and a round capsulotomy of the desired diameter obtained. Simultaneously, intraocular temperature was measured for the first time in vivo inside the anterior chamber with a microtemperature probe during the operation. With the technique described, it reached a maximum of 33.4 degrees C (the maximum ranged from 32.8 degrees C-33.4 degrees C). There was no abnormal loss of corneal endothelial cells in the 12-month postoperative follow-up. In addition, electrolysis could not be verified experimentally.

Aged↗