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Biomedical subjects

R Visser

Publications and source records attributed to R Visser.

12 recordsLinked to original sources
PubMed1992

Analysis of the region in between two closely linked patatin genes: class II promoter activity in tuber, root and leaf.

From a potato genomic library a phage lambda clone was isolated that carried nucleotide sequences of two patatin genes, thus demonstrating a close physical linkage between these two members of the patatin gene family. Sequence and restriction analysis showed the genes to be oriented in tandem. The more upstream gene was a pseudogene truncated at the 3' end, whereas the downstream gene was a class II patatin gene. In addition to a 208 bp fragment also present in patatin class I promoters, the region in between both genes contained various direct repeats also found in other patatin genes. To study the promoter activity of this intergenic region, a 2.78 kb fragment was transcriptionally fused to the beta-glucuronidase gene and reintroduced into potato cultivar Bintje. Histochemical analysis revealed expression in the outermost layer of cells of the cortex, in the tuber phellogen, in or around the root vascular system, and also in the abaxial phloem layer of the vascular bundle in leaves.

Amino Acid Sequence↗
PubMed1992

Extended-wear of high oxygen-permeable quantum contact lenses.

This study was performed to investigate the effects of extended-wear of rigid aspherical high gas-permeable contact lenses on the cornea. In the study 32 subjects (62 eyes) were followed over a period of 3 to 24 months. A high gas-permeable contact lens (Dk 92), made of fluoro-silicone-acrylate copolymer, was used. Vision remained constant during the studied period. The corneal thickness decreased significantly (p less than 0.05) during the first six months. Significant changes (p less than 0.05) were found after three months in the corneal curvature, especially in the vertical meridian. No further topographical changes were noted in the period between three and six months of extended-wear. Complications, like acute red eye syndrome and bacterial infections, which may be encountered in soft lens extended-wear, were not noticed. At the end of the study 20 subjects (38 eyes, 61%) were still on extended-wear, 9 subjects (18 eyes, 29%) changed to daily wear and 3 subjects (six eyes, 10%) became unavailable for follow-up. Extended-wear of rigid aspherical high gas-permeable contact lenses may be considered as an acceptable alternative for soft lens extended-wear.

Adult↗
PubMed1992

Sudden unexpected death due to Taxus poisoning. A report of five cases, with review of the literature.

The toxicity of yew (Taxus) has been known since antiquity. However, in the past 31 years, to our knowledge only six cases of Taxus poisoning have been reported in the literature. In the present paper we add five cases. From a forensic point of view, intoxication with Taxus has three important aspects: (i) the clinical presentation, which among other causes should suggest Taxus intoxication; (ii) the fact that the diagnosis may often be easily made by examination of the contents of stomach, duodenum and small bowel and (iii) the widespread availability in the near future of Taxol, an anti-neoplastic drug which is an alkaloid extracted from Taxus. The clinical and autopsy findings are summarized, the diagnostic aspects are discussed and the literature concerning Taxus is reviewed.

Adult↗
PubMed1992

Treatment of ocular surface disorders and dry eyes with high gas-permeable scleral lenses.

Extreme corneal surface disorders and dry-eye conditions cannot be adequately treated with corneal contact lenses. For these cases a scleral lens with a diameter of between 21 and 25 mm could be prescribed. In this study, high oxygen-permeable scleral contact lenses were fitted onto 50 eyes, of which 32 had a deviant corneal topography and 18 had dry-eye syndrome. A significant improvement of visual acuity and good lens tolerance were found. The large lens successfully created a moist atmosphere in front of the cornea with dry-eye circumstances. No signs of oxygen shortage were recorded. In three dry eyes (16.7%) immediate failure in fitting was found, due to lens binding. The new scleral lens provides a physiological condition of the cornea, which allows a revival in the application of such lenses.

Adolescent↗
PubMed1991

Dynamic graciloplasty for treatment of faecal incontinence.

Serious faecal incontinence due to anal sphincter damage should be treated by surgery. Graciloplasty has had limited success because the gracilis is a fast-twitch muscle and fatigues quickly. A favourable outcome in a patient who had dynamic (electrically stimulated) graciloplasty encouraged us to further assess this procedure. Gracilis muscle transposition was done in ten patients with complete anal incontinence due to anal atresia, sphincter damage, or neurogenic causes, and who had had several other unsuccessful treatments. 6 weeks after muscle transposition, intramuscular leads were implanted and connected to an implantable electric stimulator. Eight patients became continent, one patient still has a diverting colostomy, and a fistula developed in the other patient. Anal sphincter pressure improved from 35 mm Hg without stimulation to 62 mm Hg with stimulation at 8 weeks (mean increase 28 mm Hg [95% confidence interval 18, 36], p less than 0.01). Retention time of a phosphate enema increased from 22 to 281 s (mean increase 259 s [82, 436], p less than 0.01). Defaecography showed that the new sphincter was functioning. Defaecation was possible when the stimulator was turned "off" with a magnet. Dynamic graciloplasty can restore continence and it improves quality of life in faecally incontinent patients for whom other treatments have been unsuccessful.

Adult↗
PubMed1991

Gas chromatographic-mass spectrometric analysis of tar compounds formed during pyrolysis of rice husks.

Pyrolysis of agricultural waste to produce fuel gas involves formation of tars as noxious by-products. In this paper the qualitative analysis of tars formed during pyrolysis of rice husks is presented, based on identification by gas chromatography-mass spectrometry and interpolation of retention times on a polyaromatic hydrocarbon index scale. The influence of some reaction parameters on product formation is briefly discussed.

Gas Chromatography-Mass Spectrometry↗
PubMed1991

The problem of participation in the Dutch National Dental Survey.

In 1986 a nationwide dental survey was carried out in the Netherlands. The aims of the study were to assess the prevalence of oral diseases, need and demand for dental care and oral selfcare in the Dutch population aged 15-74 yr. This paper describes the general sampling and analysis procedures to detect selectivity in the participation. Irregular dental attenders seemed to be underrepresented in the final sample. Poststratification was used to overcome this problem of selectivity.

Adolescent↗
PubMed1990

Muscle fiber typing in routinely processed skeletal muscle with monoclonal antibodies.

Muscle fiber typing is conventionally performed using mATPase enzyme histochemistry on cryostat sections. After pre-incubation of sections at pH 4.3, 4.6 and 10.3, based on the pattern of enzyme reactivity, the fibers can be classified in types I, II (subtypes A, AB and B) and the intermediate C (I and II) fibers. We have attempted to perform fiber typing of human psoas muscle by immunohistochemistry, using monoclonal antibodies R11D10 (specific for cardiac and type I skeletal myosin) and MY-32 (specific for fast muscle fibers) on cryostat as well as on paraffin sections. Staining of consecutive cryostat sections showed that type I fibers are R11D10 reactive whereas type II fibers are MY-32 reactive. Subtyping of type II fibers could not be performed by immunohistochemistry. Quantitative analysis of type I and II fibers showed that enzyme histochemical and immunohistochemical analysis are in close agreement.

Antibodies, Monoclonal↗
PubMed1990

The influence of infusion rate on the hemodynamic effects of felodipine.

The hemodynamic effects of the calcium entry blocker felodipine were studied during and after different infusion rates. Eight healthy normotensive volunteers had their individual pharmacokinetics of felodipine determined, and they subsequently entered a double-blind, randomized, crossover study. Individualized infusions of felodipine were given by a computerized infusion pump to reach plasma concentrations of 6 ng/ml (15.6 nmol/L) after 20 minutes, to be sustained for 8 hours (fast infusion) or the same plasma concentration after 8 hours (slow infusion). Control infusions with saline and vehicle were given. Blood pressure, heart rate, ECG conduction times, and baroreceptor sensitivity by the Valsalva test were measured, as well as the plasma concentrations of felodipine. The infusion system used produced the expected plasma concentration-time profiles with higher plasma concentrations after the fast infusion until 8 hours. Both slow and fast infusion increased heart rate (p less than 0.05) and produced a similar decrease in diastolic blood pressure (p less than 0.05). Slow infusion therefore reduced blood pressure more effectively. The tachycardia after the fast infusion was more pronounced during the first hour of the infusion but was indistinguishable from the slow infusion later, when plasma concentrations were still significantly different. Baroreceptor responsiveness was diminished by both felodipine treatments. There was no obvious difference in side effects caused by the two infusion regimes. The initial tachycardia after felodipine can be diminished by a slow rate of administration of the drug with a similar effect on blood pressure.

Adult↗
PubMed1976

The dependence of the blood level of the oxime HS-6 on the severity of organophosphate poisoning.

Atropinised anaesthetised rats were injected i.v. with 4, 6 or 8 X LD50 of the organophosphorous anticholinesterase soman. Subsequent treatment with one dose of HS-6 (100 mg/kg, i.v.) delayed respiratory failure by 1 h or more; a further postponement was obtained when an additional HS-6 infusion was given. At the same infusion rate, HS-6 blood levels after 4 X LD50 soman remained stationary, but rose after the higher soman doses. The rise was greater the higher the soman dose had been. This rapid rise in oxime blood levels after high doses of organophosphate may seriously complicate therapy.

Animals↗