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Biomedical subjects

F Wilhelm

Publications and source records attributed to F Wilhelm.

At least 37 records · Page 2Linked to original sources
PubMed2001

[Investigations on the cornea donation at the Martin-Luther-University Halle-Wittenberg].

AIM: We analysed the number of the potential cornea donors of the Martin-Luther-University, Halle-Wittenberg over a four-years period, 1995 to 1998 in relationships to the number of the actual donors. PATIENTS AND METHODS: We retrospectively reviewed the data of 2545 patients who died at the hospitals of the Martin-Luther-University, Halle-Wittenberg over a four-years period, from January 1995 to December 1998. The medical records of the patients were inspected and contraindications for cornea donation examined. The patients who were younger than 12 months were omitted in our analysis. The patients with at least one contraindication were excluded as potential cornea donors. Additionally we registered the actual cornea donors of the hospitals of the Martin-Luther-University, Halle-Wittenberg between 1995 to 1998. RESULTS: The mean age of the died patients was 60 years. Because of contraindications 597 patients (23.5 %) were excluded from the cornea donation. An acute sepsis with 25.1 % as well as leukemias and lymphomas with 24.8 % matched about half of the exclusion criteria. In the period of investigation we counted 1948 potential cornea donors. In the hospitals of the Martin-Luther-University, Halle-Wittenberg only 57 (2.9 % of potential donors) actual cornea donors have been registered. CONCLUSIONS: The possible leading causes for the large discrepancy between the number of the potential and actual donors are: (1) the imperfect identification of potential donors, (2) the donor family have not been asked and (3) the denial of consent by the potential donors family.

Adolescent↗
PubMed2001

In vitro corneal permeation of unoprostone isopropyl (UI) and its metabolism in the isolated pig eye.

The corneal permeability, hydrolysis, and metabolism of unoprostone isopropyl (UI), a docosanoid, were examined in isolated porcine ocular tissues. The apparent permeability coefficient (Papp) of the esterified prodrug and of the acid metabolite were determined in a modified Valia-Chien permeation chamber and quantified by high performance liquid chromatography. Enzymatic hydrolysis and subsequent metabolism were examined in isolated tissue homogenates. The prodrug (ester form) was found to permeate the isolated intact porcine cornea with a Papp of 9.47 x 10(-7) cm/sec. Only the acid metabolite could be detected in the receiver chamber, indicating the requirement of hydrolysis for permeation. The acid metabolite could not permeate the intact cornea but was able to cross an epithelium-denuded cornea with a Papp of 1.22 x 10(-6) cm/sec. Enzymatic hydrolysis of UI was confined to the isolated intact cornea and epithelium, indicating that the esterase activity was localized in the corneal epithelium. Incubations with different porcine ocular tissues, conjunctiva, iris-ciliary body, trabeculum, as well as aqueous humor, did not reveal other metabolites. These findings demonstrate that the ocular penetration of UI is dependent on its uptake into the epithelium and subsequent hydrolysis prior to its penetration into the anterior chamber, a very common pathway for ophthalmic drugs. In the pig eye, unoprostone does not appear to be further metabolized.

Acetylcholinesterase↗
PubMed2000

Layer-resolved magnetic moments in Ni/Pt multilayers

The magnetic moments in Ni/Pt multilayers are thoroughly studied by combining experimental and ab initio theoretical techniques. SQUID magnetometry probes the samples' magnetizations. X-ray magnetic circular dichroism separates the contribution of Ni and Pt and provides a layer-resolved magnetic moment profile for the whole system. The results are compared to band-structure calculations. Induced Pt magnetic moments localized mostly at the interface are revealed. No magnetically "dead" Ni layers are found. The magnetization per Ni volume is slightly enhanced compared to bulk NiPt alloys.

Journal Article↗
PubMed1999

[Difficulties of fungus detection in corneal culture medium].

UNLABELLED: It is not always possible to prevent the growth of microorganisms in organ culture for cornea preservation, despite many prophylactic measures. It is especially difficult to prove the presence of fungi in the cultural medium. MATERIALS AND METHODS: A culture medium was examined for sterility after 8 days' storage of cornea in organ culture. To prove the presence of fungi a culture of Sabouraud 2% glucose-agar was prepared and its growth examined by light microscopy. RESULTS: After 8 days of preservation we noticed a color change in the cultural medium and suspected contamination with fungi. Coagulase-negative Staphylococci could be cultivated from the conjunctival smear obtained before preparation of the cornea only. Routine screening of microbiological contamination did not show any results. We were able to identify an Aspergillus species only after preparing a special culture. The conjunctival smear as well as the cultural medium of the other eye of the same donor showed no contamination. CONCLUSIONS: In spite of the fact that microbiological contamination can be seen macroscopically, it is difficult to prove the presence of a specific microorganism and even more so when dealing with fungus. Especially in these cases the incubation of the cornea in media might have an advantage because contamination can be suspected by just looking at the medium. By excluding these preparations from transplantation we can possibly prevent infections, even when routine examinations show negative results.

Aspergillus↗
PubMed1999

[Examination of resistance of the lens capsule against the waterjet].

BACKGROUND: Although cataract surgery is highly developed today, there are still problems such as secondary cataract. In polishing the posterior capsule lens, epithelial cells often remain, causing secondary cataracts. Additionally, there are the problems of tissue heating and endothelial cell loss during phacoemulsification by ultrasound. This could be another field for improvement of cataract surgery by using the waterjet. METHODS: After removing the cornea of freshly enucleated porcine bulbs, we used the water jet from 4 to 12 bar. The hit angel on the capsule varied between 45 degrees and 90 degrees. RESULTS: Rupture of the posterior capsule occurred at a mean of 8.5 bar using the jet at 45 degrees and a mean of 8.6 bar using the jet at 90 degrees. CONCLUSION: The waterjet pressure should not be over 4 bar during polishing of the posterior capsule.

Animals↗
PubMed1998

[Potential of the water jet in cataract surgery].

UNLABELLED: Though cataract surgery is highly developed today, there are still problems such as endothelial cell loss after surgery and the occurrence of aftercataract. To reduce these complications we looked for techniques with a high degree of safety and precision. We found the water jet, an instrument already well established in liver surgery. We tested the possibility of improving the results of cataract surgery using the water jet method. METHODS: We performed cataract surgery--phacoemulsifikation and polishing of the capsule--on freshly enucleated porcine bulbs using water jet and by conventional procedures. By scanning electron microscope examination we compared the results. Additionally we emulsified human lens nuclei obtained by extracapsular cataract extraction using the water jet. RESULTS: The epithelial cells and lens fragments on the capsule were considerably reduced after the water jet procedure. CONCLUSION: The results show the possibility of improvement of cataract surgery by using the water jet. Further studies are necessary to adapt this technique to routine surgery in humans.

Animals↗
PubMed1998

[Cutting edges after automatic lamellar keratotomy].

BACKGROUND: In order to perform an automatic lamellar keratotomy microkeratomes are used, which differ from each other in several technical details. This study was done to examine, whether there are characteristics of the cutting edge, typical of each device, and whether there are some correlations between the cutting quality and technical parameters. METHODS: In Germany seven different keratomes are used today. We performed the procedure of automatic lamellar keratotomy by using each of them on 8 fresh enucleated pig eyes and we examined the corneal tissue by means of scanning electron microscopy. The cutting edges were judged by their smoothness and sharpness. RESULTS: A dominantly smooth cutting edge was found on the corneas cut by the MKM-System, the Universal Keratome and the BK-Microkeratome Set, while the Automatic Corneal Shaper, the Microtech-Mikrokeratom, the Rotor-Keratom and the Schwind-Mikrokeratom mostly produced a saw-toothed edge. CONCLUSIONS: The quality of the cutting edge may be influenced by the relationship of the speed of the pass and the rate of blade oscillation/rotation. Therefore it seems that a lower feed during one oscillation/rotation results in a more smooth pattern of the cutting edge.

Animals↗
PubMed1995

A multicenter trial of low dose gallium nitrate in patients with advanced Paget's disease of bone.

Gallium nitrate is a potent antiresorptive drug that has been extensively tested in patients with accelerated bone turnover. We have evaluated the effects of this new agent in a pilot multicenter trial of 49 patients with advanced Paget's disease of bone. Patients were randomized to receive 0.05, 0.25, or 0.5 mg/kg.day gallium nitrate administered by sc injection in two 14-day cycles. Serum alkaline phosphatase, fasting 2-h urinary hydroxyproline and N- telopeptide collagen cross-links excretion, and quality of life were assessed every 2 weeks for 12 weeks. The group mean alkaline phosphatase activity at baseline was 854 +/- 100 (+/- SEM) IU/L. The mean changes from baseline to week 12 in serum alkaline phosphatase were +0.5%, -24%, and -31%, respectively, for the three doses tested. The differences for each of the higher dose levels (0.25 and 0.5 mg/kg.day) was statistically significant (P < or = 0.05), and nearly half of the patients treated with the 0.5 mg/kg.day dose achieved a 50% or more reduction in enzyme activity. The nadir value in hydroxyproline excretion occurred at 10 weeks, with mean changes of +9%, -10%, and -17% for the 0.05, 0.25, and 0.5 mg/kg.day doses, respectively; the difference was significant only at the 0.5 mg/kg.day level (P < 0.01). Urinary collagen cross-link excretion showed a significant decrease at the 0.25 and 0.5 mg/kg.day doses. We also observed a definite, but nonsignificant, trend for improved quality of life in patients treated at the highest drug dose. Minor discomfort at the injection site was frequently reported, but did not lead to interruption of therapy. Our results in these patients who had received moderate to extensive prior therapies with other drugs show that cyclical, low dose, sc administration of gallium nitrate is safe and effective for treating patients with advanced Paget's disease of bone.

Adult↗
PubMed1995

[Differential value of various vital stains of corneal endothelium].

Specular microscopy shows the integrity of the endothelial cell pattern, and vital staining methods allow the evaluation of endothelial viability. Dyes commonly used such as trypan blue enter the cells passively through the disturbed membrane. The uptake of fluorescein diacetate (FDA) is an active process. To compare the efficiency of the two methods we performed double stainings and examined the results. Pig cornea endothelium was stained by both trypan blue and FDA and vital and non-vital cells were compared. More non-vital cells were stained by FDA than by trypan blue, indicating that cells with membranes that are not permeable by trypan blue cannot metabolize FDA. This fact is important where estimating the endothelial viability of donor corneas.

Animals↗
PubMed1993

[Duration of fluorescein diacetate in corneal endothelium].

Fluorescein diacetate (FDA) is a suitable substance for vital staining of corneal endothelium. Uptake and metabolism is an active process. This means that a fluorescing cell must be functionally intact. The duration of endothelial fluorescence is limited and should be tested in an experimental study. Cultured endothelial cells (calf aorta endothelial cells) were stained by FDA and the loss of fluorescence time registered. We tested corneal buttons in the same way. The cultured endothelial cells showed no fluorescence after 2 h and the corneal buttons after 40-50 min. The fluorescence of FDA-stained endothelial cells decreases both in cultured cells and in whole corneal buttons, but this is not a sign of loss of endothelial viability. This fact must be taken into consideration when interpreting the results of FDA staining.

Animals↗
PubMed1989

Experiences with a new corneal suction trephine.

The importance of exact trephining for successful keratoplasty is well known. We employ a new suction trephine, thus obtaining exact and sharp cutting margines which are examined by scanning electron microscopy (SEM). The first observed clinical results in 25 cases are good.

Cornea↗
PubMed1987

[Ultrasonic detection of gallstone ileus].

A woman of 60 years of age with acute abdominal pain, vomiting, constipation and radiological signs of small bowel obstruction was subjected to sonographic examination. Careful examination of the entire abdomen demonstrated a hyperechoic object within the distended terminal ileum with an intensive acoustic shadow. The gallbladder was not visible. This strongly suggested gallstone ileus, especially since the patient had a history of gallbladder disease. She was treated immediately by enterotomy and extraction of a noncalcified obstructing stone. The value of ultrasound in detecting gallstones causing small bowel obstruction is discussed.

Cholelithiasis↗