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Biomedical subjects

T David

Publications and source records attributed to T David.

At least 91 records · Page 5Linked to original sources
PubMed1995

In vivo inhibition of lens regrowth by fibroblast growth factor 2-saporin.

PURPOSE: To investigate the ability of fibroblast growth factor (FGF) 2-saporin to prevent lens regrowth in the rabbit. METHODS: Chemically conjugated and genetically fused FGF2-saporin (made in Escherichia coli) were used. Extracapsular extraction of the lens was performed on the rabbit, and the cytotoxin either was injected directly into the capsule bag or was administered by FGF2-saporin-coated, heparin surface-modified (HSM) polymethylmethacrylate intraocular lenses. The potential of the conjugate was checked by slit lamp evaluation of capsular opacification and by measuring crystallin synthesis. Toxin diffusion and sites of toxin binding were assessed by immunohistochemistry. Possible toxicity was determined by histologic analysis of ocular tissues. RESULTS: FGF2-saporin effectively inhibited lens regrowth when it was injected directly into the capsular bag. However, high concentration of the toxin induced transient corneal edema and loss of pigment in the iris. Intraocular lenses coated with FGF2-saporin reduced lens regrowth and crystallin synthesis without any detectable clinical side effect. After implantation, FGF2-saporin was shown to have bound to the capsules and, to a lesser extent, to the iris; no histologic damage was found on ocular tissues as a result of implantation of drug-loaded HSM intraocular lenses. CONCLUSIONS: Chemically conjugated (FGF2-SAP) and genetically fused FGF2-saporin (rFGF2-SAP) bound to HSM intraocular lenses can prevent lens regrowth in the rabbit.

Animals↗
PubMed1995

[Characteristics of corneal topography in candidates for surgery for myopia].

INTRODUCTION: Videokeratography analyses the corneal anterior topography. It is necessary in refractive surgery to estimate the anatomical effect of the surgery and to eliminate early Keratoconus. METHODOLOGY: Corneal anterior topography was studied on 70 consecutive patients (140 eyes) candidates for low myopia surgery (-1 to -6); 87 eyes were wearing regularly contact lenses. With the topographic analysis machine of EYESYS compagny, keratometry (Km) at 3 mm, astigmatism (delta K) at 3 mm, I-S value at 3 mm and 5 mm according to Rabinowitz method were measured in each eye. RESULTS: The average keratometry was 43.50 +/- 1.87 D. The average astigmatism was 0.909 +/- 0.75 D. 51 eyes presented an asymmetric corneal and among them 32 ware contact lenses regularly; 8 eyes out of 140 (6%) presented the association of an high central Keratometry value (> or = 47 D) and corneal asymmetry (I-S > 0.5 value). COMMENTS: The incidence of Keratoconus is higher in a candidate population for refractive surgery by self-selection. Its frequency is difficult to evaluate accurately because of the present limits for the diagnostic measures. In this population, it seems to represent about 6%. CONCLUSION: The videokeratography before refractive surgery is necessary to reveal corneal anterior topography abnormalities and to eliminate early Keratoconus.

Astigmatism↗
PubMed1994

[The clinical course of surgically managed para-articular femoral fractures in geriatric surgery].

246 patients (average 82.4 years) with proximal femur fractures treated with bipolar endoprosthesis, sliding lag screw or Ender nailing, related to the fracture type were analysed in a retrospective study. Pre-existing diseases, duration of operation, postoperative complications, transfusions, hospital stay, mobility achieved and mortality were noted. In result we found a high multimorbidity related to the age, the highest requirement of transfusions in patients undergoing Ender nailing, a long period to achieve postoperative mobility, a long hospital stay and increasing mortality with average age and average hospital stay.

Aged↗
PubMed1994

A new method to evaluate cardiovascular response in anesthetized rats. Hypertension after variable intensity, brief electrical stimuli.

To establish and standardize a nociceptive response in anesthetized rats, the hypertensive responses to defined electrical and mechanical stimuli were studied. Rats (n = 7) were given etomidate, 3.8 mg/kg/hr intravenously (i.v.) 2 hr following carotid artery and jugular vein cannulation. At 15 min after beginning the infusion, four types of noxious stimuli were administered sequentially at 1-min intervals (14 stimuli total): Type 1: Square electrical waves, 125 cps, 1.6 msec, 2-sec train duration, varying current from 0.4 to 12 mA (11 stimuli); Type 2: A single 10-mA electrical stimulus, 5-sec train duration; Type 3: Tail clamping; and, Type 4: Skin incision. After each stimulus, maximum change in systolic blood pressure (delta SBP) was measured. delta SBP after the most intense stimuli was as follows: Type 1 (12 mA, 2 sec), 32.1 +/- 2.14 mmHg; Type 2 (10 mA 5 sec), 42.9 +/- 2.4 mmHg; Type 3 (tail-clamping), 34.3 +/- 3.3 mmHg; Type 4 (skin incision), 14.2 +/- 2.8 mmHg. For the multiple Type-2 stimuli, a relationship between current and delta SBP was present. The authors believe that characterized graded electrical stimulation will allow a more quantitative evaluation of the hypertensive response to noxious stimuli in etomidate anesthetized rats, as compared to observing a single response to a single stimulus. The characterization of the electrical stimulation by amplitude, frequency, and wave form makes research work on nociception under anesthesia easily reproducible.

Anesthesia↗
PubMed1994

Preliminary experience with the Toronto SPV stentless porcine bioprosthesis for aortic valve replacement.

From November 1992 to March 1993 fourteen patients received the Toronto SPV stentless porcine xenograft as aortic valve replacement. Median age was 56 years (range 32-70 years). 7 patients were male and 7 female. Implanted valve sizes ranged from 23 mm to 29 mm, the majority of patients received valves with 27 and 29 mm tissue diameter. A learning process was evident by aortic crossclamp time decreasing with experience. No valve-related mortality or morbidity occurred. Postoperatively echocardiography showed near normal valve performance in most patients. The longevity of the valve, however, still has to be established. Meanwhile we continue the implant of stentless bioprostheses as aortic valve substitutes in selected patients.

Adult↗
PubMed1994

Basic fibroblast growth factor modulates corneal wound healing after excimer laser keratomileusis in rabbits.

We have previously demonstrated beneficial effects of basic fibroblast growth factor (bFGF) on corneal epithelial healing in different in vivo models. In the present study, we investigated the influence on epithelial and stromal healing of topical bFGF after excimer laser keratomileusis in a rabbit model. The corneas of 24 New Zealand white rabbits were deepithelialized (7-mm diameter) and subsequently received identical deep stromal laser ablations (depth, 50 microns; 6 D; diameter, 5 mm). The animals were randomly assigned to one of four treatment groups: PBS (control); bFGF at 500 ng/application; dexamethasone 0.1%, and bFGF+dexamethasone (n = 12 eyes/group). All treatments were given four times daily; with bFGF being given until complete epithelial healing and dexamethasone and PBS, until 3 months postsurgery. Wound surface regression on time was determined by means of computer-assisted image analysis of fluorescein-stained corneas. Corneal opacity was scored using slit-lamp observation and graded following a previously established scoring system. As compared with the other three treatment groups, a highly significant acceleration in the rate of epithelial wound healing was found after bFGF application for 2-3 days only (P < 0.001). A combined therapy (bFGF+steroid) had no effect on the healing rate. As compared with control values, the peak scores for subepithelial haze were significantly lower in eyes that had received bFGF; the regression on time of the haze in the growth factor group paralleled that in eyes receiving continuous steroid treatment. These results demonstrate for the first time the efficiency of a growth factor in modulating the wound-healing response after excimer laser photoablation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Biphasic effect of the mitotoxin bFGF-saporin on bovine lens epithelial cell growth: effect of cell density and extracellular matrix.

We have studied the effect of a specific FGF receptor suicide antagonist on the growth of bovine epithelial cells (BEL cells) in culture. This basic fibroblast growth factor-saporin conjugate (bFGF-SAP) has a biphasic effect on bovine lens epithelial cells (BEL cells). Whereas 0.01 nM and 0.1 nM bFGF-SAP stimulate BEL cells proliferation, 1 nM and 10 nM bFGF-SAP have the predicted toxic effects on BEL cell growth. The toxicity of bFGF-SAP is observed 2 to 3 days after the initial treatment and depends on cell density. Accordingly, the sensitivity of confluent cells to bFGF-SAP is reduced compared to sparse cells. A time course analysis reveals that bFGF-SAP is effective after a short exposure to cells and that its effects are not increased with longer treatments. Cell growth on bFGF-SAP pretreated extracellular matrix (ECM) or posterior lens capsule (PLC) is also affected. Basic FGF-SAP has been shown to bind to the extracellular material, allowing a modulation of lens cells migration and survival by a single treatment in vitro. This finding raises the possibility of its use in vivo to prevent capsules invasion by lens cells after cataract surgery.

Animals↗
PubMed1992

Analysis of regurgitant jets in natural and bio-prosthetic heart valves.

Artificial bio-prosthetic heart valves are prone to fatigue tearing, having a 50% failure rate in ten years. Tears in valves give rise to pulsing reverse flow back through the valve. This is termed regurgitant flow and the resultant jet of blood a regurgitant jet. The regurgitant volume of the jet during the pulsing cycle gives a measure of the severity of the valve defect and clinical significance. Hence, it is important for the cardiologists to be able to quantify this volume. Although the velocity of the regurgitant jet can be determined using Doppler ultrasound, the dimensions of the heart valve lesion cannot be measured directly; hence, the volumetric flow rate cannot be quantified accurately. At present the severity of the regurgitant jet is assessed qualitatively from the intrusion of the jet into the cardiac chamber. In the present study, classical mathematical theories of turbulent jets have been used to describe the velocity distributions for the types of jets expected in defective heart valves and these distributions have been verified experimentally. One of these models has been developed to enable the regurgitant volumetric flow through an axisymmetric orifice of unknown radius to be calculated from the velocity distribution of the jet. This relationship may be used in conjunction with ultrasound techniques to quantify the regurgitant volume within defective artificial heart valve implants. The present study shows that there is a significant difference in the velocity distributions in jets emanating from axisymmetric and high aspect ratio slots.(ABSTRACT TRUNCATED AT 250 WORDS)

Bioprosthesis↗
PubMed1991

Images of 16S ribosomal RNA by scanning tunnelling microscopy.

We report the use of scanning tunnelling microscopy (STM) to study surface topographies of complex nucleic acid structures. From low-resolution STM images of uncoated 16S ribosomal RNA, we demonstrate the possibility of determining several objective parameters (molecular mass and radius of gyration) in order to characterize and identify the molecules observed. These parameters were compared with values obtained by other physical methods and the radius of gyration was found to be the most reliable. At high resolution, it was possible to measure the main dimensions of selected V-form particles more precisely than with electron microscopy. Images of the more compact form have been also obtained that show different domains in the macromolecular structure.

Escherichia coli↗
PubMed1991

[Neuropsychological sequelae in children treated for brain tumor].

Treatment modalities of childhood brain tumors are associated with adverse neuropsychologic sequelae that may be manifested years after therapy. Based on recent published studies, the authors review the etiological factors, the symptoms and the evolutive features of these disorders and their management.

Brain Neoplasms↗
PubMed1990

[Nanophthalmos with uveal effusion].

A typical case of nanophthalmos with uveal effusion syndrome is reported. Clinical, pathological and therapeutic aspects of uveal effusion syndrome are discussed. A surgical treatment consisting of lamellar sclerectomies is proposed.

Adult↗
PubMed1989

Rheology of bovine bone marrow.

The viscosity of bovine bone marrow was measured using samples taken from proximal and distal sites of five radii. The viscosity was found to be independent of shear rate and temperature above 37 degrees C (distal samples) and 42 degrees C (proximal samples). The viscosity of all samples fell to a lower limit of 0.04 Pas above these temperatures, irrespective of the treatments used. Below them the measured viscosity of the proximal marrow was some ten times that of the distal marrow at 35 degrees C and some 15 times that of the distal marrow at 30 degrees C. Below 30 degrees C the proximal marrow solidified. Distal marrow remained liquid to below 20 degrees C.

Animals↗
PubMed1989

[Orthopedic treatment of regular dorsal and dorsolumbar hyperkyphosis. New principles of active correction].

The orthopaedic treatment of hyper-kyphosis should not be unique. If the principles of treatment are different in relation with the thoracic or thoraco-lumbar localisation of the apex of the deformity, it is necessary to distinguish for the middle thoracic curve two types of patients: these in whom the kyphosis and the lordosis are balanced (the cast must diminish the lumbar lordosis and the imbalanced posterior types with a great kyphotic curve and a short compensatory lordosis which is important not to be diminish by the treatment. The principles of plaster casting are described in the two types; emphasizing on the unlucky aspect of the sternal support in the middle thoracic kyphosis and in the necessity of the thoracic modification if we wish to obtain a good result. The active expiratory reeducation is capital before and during the treatment.

Casts, Surgical↗
PubMed1988

[Lamellar keratoplasty with the Barraquer microkeratome. Preliminary clinical study apropos of 7 cases].

The authors report the results of a preliminary clinical study about lamellar keratoplasty performed with the Barraquer microkeratome. Seven eyes were operated on by this technique, with good functional and anatomical results. Nevertheless, some problems remain. An accurate diameter of the resected button, concerning both the donor and recipient corneas cannot be exactly predicted. There may also exist some irregularities at the edges of the resection. For these reasons, a good incorporation of the donor cornea into the recipient bed may be difficult. These are the main problems with this technique, which facilitates an improved visual prognosis of lamellar keratoplasty.

Adolescent↗
PubMed1988

Colour flow imaging in severe mitral and aortic regurgitation.

Several criteria have been proposed for the grading of severe aortic and mitral regurgitation by colour flow imaging. To evaluate the sensitivity of these criteria, colour flow imaging was performed in 21 patients with isolated severe mitral regurgitation and 11 patients with isolated severe aortic regurgitation prior to clinically indicated valvular surgery. In the colour flow imaging assessment of mitral regurgitation the criterion of the maximum distance of mitral regurgitant jet from mitral orifice greater than 4.5 cm was 95% sensitive (range 4.4 to 8.4 cm). Maximum ratio of mitral regurgitant jet area to left atrial area greater than 40% was 86% sensitive (range 32 to 84%) and maximum mitral regurgitant jet area greater than 6 cm2 was 100% sensitive (range 8.1 to 35.7 cm2) in the detection of severe mitral regurgitation. For aortic regurgitation, the criterion of height of regurgitant jet to height of left ventricular outflow tract greater than 65% in the parasternal long axis view was 100% sensitive (range 71 to 100%), whereas the ratio of area of regurgitant jet to area of left ventricular outflow tract greater than 60% in the short axis view was only 36% sensitive (range 8 to 74%) in the detection of severe aortic regurgitation requiring surgery. It is concluded that the most sensitive colour flow imaging criteria for severe mitral regurgitation is an absolute mitral jet area greater than 8 cm2; and for severe aortic regurgitation, ratio of height of regurgitant jet to height of left ventricular outflow tract greater than 65%.

Adult↗