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Biomedical subjects

J L van Delft

Publications and source records attributed to J L van Delft.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effects of microwave-induced hyperthermia on the anterior segment of healthy rabbit eyes.

Hyperthermia was induced in nine healthy rabbit eyes by means of a microwave 2450 MHz stripline applicator. The anterior segment of each eye was heated to a fixed temperature of between 42 degrees C and 46 degrees C for 30 min. The temperature distribution in the eye was calculated using a thermal model and the actual boundary temperatures and microwave intensity were measured. The effects of treatment were evaluated by daily macroscopic examination, fluorescein angiography and fluorophotometry, as well as by histology. Histological examination of changes induced by this hyperthermic delivery system revealed a sharp transition at 44 degrees-45 degrees C from no permanent damage to the anterior chamber at lower temperatures to serious damage such as local necrosis, pigment disruption and local cataract at high temperatures. A sharp transition in the same temperature range was observed in vivo in the fluorescein leakage of the iris vessels by comparative fluorescein angiography and by anterior segment fluorophotometry.

Animals↗
PubMed1989

In vivo ultrasound backscattering estimation for tumour diagnosis: an animal study.

In this study the efficacy of a quantitative analysis of backscattered ultrasound for the differential diagnosis of intraocular tumours is tested. The data acquisition was performed with an on-line acquisition and processing system for in vivo work. The backscattering spectra were corrected for the beam effects (diffraction and focussing). The measurements were taken from an animal model (rabbit) in which a Greene's amelanotic melanoma was implanted in the anterior chamber of the eye. The special histologic arrangement of this tumour makes it optimally suited to an assessment of the correlation between histology and backscattering cross section. Various backscattering models were considered theoretically and the choice for a practical testing was motivated on the properties of the observed backscattering spectra. We conclude that the backscattering model based on an "inhomogeneous continuum" with a cylindrical Gaussian autocorrelation function fits the data optimally. The relatively low correlation of the backscattering cross-sections to histology cannot yet be fully explained. The range of acoustic scatterer sizes, however, corresponds quite well to the dimension of observed and quantified histologic structures.

Animals↗
PubMed1989

Effect of indomethacin and prednisolone on the disruption of the blood-aqueous barrier after hyperthermia on the rabbit eye by focused ultrasound.

In 24 rabbits both eyes were treated in the perilimbic area with hyperthermia by focussed ultrasound at a frequency of 4.65 MHz. The intra-ocular pressure (IOP) decreased significantly in all eyes. The effect of pre-treatment with indomethacin and prednisolone on the inflammatory response induced by the insonification was assessed by determination of protein in the aqueous humour 2 h after ultrasound treatment. Local pre-treatment with indomethacin but not with prednisolone was followed by less increase in protein concentration of the aqueous humour as compared to placebo-treated controls. The IOP was not influenced significantly by the drug pre-treatments.

Animals↗
PubMed1989

The effects of ultrasonically induced hyperthermia on experimental tumors in the rabbit eye.

Greene's melanomas, implanted in the anterior chamber of 31 eyes of 19 Dutch rabbits, were treated with hyperthermia induced by high intensity focused ultrasound (HIFU). The percentage necrosis 24 hr after treatment (N) as a function of steady-state intratumor temperature (T) could be described with N(T) = -181.5 + 4.7T (P less than 0.05). The most frequent side effect was a local hemorrhagic keratitis. The acoustic absorption coefficient and thermal conductivity of the tumor tissue were 0.08 cm-1 X MHz-1 at 36 degrees C and 0.011 W, cm-1 X degrees C-1, respectively. With these parameters a simple thermal model was established that enabled us to predict the ultrasonic intensity needed to reach a desired intratumor temperature.

Animals↗
PubMed1988

Specific receptor sites for PAF in iris and ciliary body of the rabbit eye.

The existence of specific binding sites by using tritiated 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (3H-PAF) was investigated on iris and ciliary body tissue of pigmented rabbit eyes. The binding was saturable, specific, time-dependent and reversible. Scatchard's analysis indicated the presence of two types of binding sites with a Kd1 4.90 +/- 0.47 nM, a Kd2 11.60 +/- 0.33 nM, a Bmax1 3.17 +/- 0.50 pmol/mg protein and a Bmax2 12.45 +/- 2.30 pmol/mg protein for iris tissue, and a Kd1 5.71 +/- 0.09 nM, a K2d 24.40 +/- 0.91 nM, a Bmax1 3.41 +/- 1.00 pmol/mg protein and a Bmax2 16.60 +/- 0.51 pmol/mg protein for ciliary body. The binding was fully displaced by unlabelled PAF in both iris and ciliary body preparations, and partially inhibited by the PAF antagonist BN 52021 in iris tissue.

Animals↗
PubMed1987

Comparison of the effects of corticosteroids and indomethacin on the response of the blood-aqueous barrier to injury.

Aqueous protein content was estimated as a measure of the integrity of the blood-aqueous barrier after paracentesis or argon laser photo-coagulation of the iris in rabbits. Corticosteroid pretreatment topically or by subconjunctival or intramuscular injection exerted only a moderate inhibitory effect on the breakdown of the blood-aqueous barrier. Instillation of 0.1% indomethacin however, strongly inhibited the response in both models. The results are indicative of the potential usefulness of topical administration of prostaglandin synthetase inhibitors in the treatment of non-infectious inflammatory diseases.

Adrenal Cortex Hormones↗
PubMed1986

Topical application of 5-fluorouracil in premalignant lesions of cornea, conjunctiva and eyelid.

Local application of 5-Fluorouracil was practised on 5 patients. In 3 patients with multiple premalignant oculo-cutaneous lesions, two of whom had also premalignant epibulbar lesions, local 5% 5-Fu cream and/or 1% 5-Fu eyedrops were applied. In 2 other patients who had only premalignant lesions on the cornea and conjunctiva, 1% 5-Fu eyedrops were used only. In animal experiments 1% 5-Fu was not found to cause any damage to normal corneal and conjunctival epithelium. The frequency of the applications and the duration of the treatment were dependent on the location and extent of the lesions. Except for easily treatable lesions, caused by the separation of the tumour epithelium, no complications of local 5-Fu treatment were seen. The visual acuity improved in all 4 patients in whom the cornea was affected. In these premalignant conditions the diagnosis and assessment of the therapy were based on exfoliative cytology and biopsies.

Aged↗
PubMed1986

Enzyme activities in the rabbit cornea during immunogenic keratitis.

In rabbits inflammation of the cornea was induced by intrastromal injection of horse serum. Between 2 and 4 weeks after injection, infiltration of the cornea with leukocytes and neovascularization could be observed. During this period, the rabbits were killed and their corneas analyzed for protein, alkaline phosphatase, acid phosphatase, N-acetyl-beta-D-glucosaminidase, and lactate dehydrogenase. The enzyme activities in the inflamed corneal stroma reflect the high lysosomal activity, which probably originates from the leukocytes. The enzyme activities in the epithelium indicate that the tissue is abnormal and undergoing repair processes.

Acetylglucosaminidase↗
PubMed1986

Scintimetric detection of choroidal malignant melanoma with [123I]-5-iodo-2-thiouracil.

[123I]-5-iodo-2-thiouracil (123I-ITU) was evaluated as a radiopharmaceutical for tumor detection in 10 patients with proven choroidal melanoma. Uptake of 123I-ITU was measured with a specially designed single eye probe collimator, 24 h after administration of 123I-ITU. Increased uptake in the tumor-bearing eye as compared to the fellow nontumor bearing eye was found in 7 out of 10 cases when the probe was located 3.5 cm in front of the eye (p less than 0.01). By using a double pinhole collimator tests were positive in 3 out of 10 123I-ITU studies only. Tests with 123I-ITU were compared with 67Ga tests in the same patients. The 67Ga tests with the single eye probe collimator were positive in 6 out 10 cases when the probe was located 6 cm in front of the eye. With the double pinhole collimator tests were positive in 7 out of 10 67Ga studies. It is concluded that 123I-labeled thiouracil is at least as useful as a radiopharmaceutical for ocular melanoma diagnosis as 67Ga-citrate, provided measurements are performed with a single eye probe.

Choroid Neoplasms↗
PubMed1986

Effect of indomethacin on immunogenic keratitis.

The effect of topically administrated indomethacin was studied in rabbits on an experimentally provoked inflammatory keratitis. Intrastromal injection with horse serum induced in the cornea a ring-shaped infiltration with leukocytes and neovascularization. Indomethacin was given as eye drops three times daily during the experiment. In the indomethacin treated eyes leukocyte infiltration was prolonged but not the concomitant neovascularization. The potentiation of the leukocyte response may be due to a facilitation of chemotactic lipoxygenase products.

Animals↗
PubMed1985

Hematoporphyrin derivative photoradiation treatment of experimental malignant melanoma in the anterior chamber of the rabbit.

The effects of Hematoporphyrin Derivative Photoradiation Therapy (HpD-PRT) on Greene's amelanotic melanoma implanted into the anterior chamber of rabbits have been examined by biomicroscopy, fluorescein angiography and histopathology. The tumors were irradiated 24 hours after injection of HpD when both the porphyrin concentration and the porphyrin ratio tumor/iris were highest. Blanching and shrinkage of tumors were the first signs of tumor destruction. Fluorescein angiography as soon as 20 minutes after irradiation found non-perfusion of blood vessels at the tumor surface. Histopathological observation of vessel wall destruction is in agreement with this finding. Subtotal tumor necrosis was demonstrated in 12 out of 13 experiments. Necrosis was complete in only one experiment. Clusters of viable tumor cells were found when shielded behind pigment, at the tumor periphery and around some blood vessels. Lens damage was observed after irradiation when the iris pigment epithelium was disorganized by the tumor. The iris contained high concentrations of porphyrin and PRT resulted in depigmentation, non-perfusion of the capillary bed, damage to larger iris vessels and finally atrophy. Light intensity measurements were performed in vivo during PRT. The average effective attenuation coefficient at 630 nm was 0.56 mm-1 at the beginning of irradiation and 0.87 nm-1 at the end. Results indicate that as a treatment HpD-PRT in itself might be insufficient but may prove to be an effective modality in combination with other tumor destructive therapies.

Animals↗
PubMed1983

Inhibitors of prostaglandin synthesis and the cornea.

Low doses of indomethacin were applied topically to rabbit eyes in an experimental model of immunologically provoked inflammatory keratitis. Leucocyte infiltration was potentiated but not the concomitant neovascularization.

Animals↗
PubMed1983

Irrigation with mercury chloride and sodium hypochlorite to prevent local recurrence after excision of conjunctival melanoma. An experimental study.

Two chemical agents, sodium hypochlorite 0.5% (Dakin's solution) and mercury chloride 0.1%, capable of killing seeded tumour cells, were used for washing the cornea and conjunctiva of rabbits. Both agents produced considerable superficial lesions in the cornea and conjunctiva after irrigation for 3 and 5 min, but these were restored to normal after 2 weeks.

Animals↗
PubMed1983

Drug prevention of blood-aqueous barrier disruption.

In order to evaluate the anti-inflammatory effect of non-steroidal compounds on the eye, we tested them in rabbits using the inhibitory effect on paracentesis-induced disruption of the blood-aqueous barrier. Protein and--after intravenous-injection--fluorescein were determined in punctates of aqueous humor. Indomethacin, flurbiprofen and diclofenac in a 0.01% solution showed a marked inhibitory effect, which lasted for 24 h. Addition of polysorbate to eye drugs diminished the inhibitory effect.

Animals↗
PubMed1983

Comparison between in vivo and in vitro fluorophotometry in the rabbit eye.

In order to evaluate the reliability of a new commercial computer fluorophotometer (Fluorotron Master) for in vivo measurements, the distribution of fluorescein concentration in 10 rabbit eyes was measured in vivo as well as in vitro. In all but 1 eye the results for parts measured in vitro were within 27% in agreement with those for corresponding parts measured in vivo.

Animals↗
PubMed1981

The effect of indomethacin on the anterior segment of the eye after paracentesis.

The prostaglandin-inhibiting effect of Indomethacin (IN) was studied in rabbits, using paracentesis as a stimulus and rise in aqueous protein and fluorescein concentration after intravenous fluorescein injection as parameters. In eye pre-treated with IN eyedrops the rise in fluorescein and protein concentration in the secondary aqueous was less than the control eyes; the rise in the control eyes was less than in the eye of rabbits not treated with IN. There was good correlation between the rise in protein and the rise in fluorescein concentration in the secondary aqueous. The four different 0.5% IN suspensions used showed different PG-inhibiting activity, attributed to the difference in physiochemical composition.

Animals↗