Biomedical subjects

T Bek

Publications and source records attributed to T Bek.

63 records · Page 4Linked to original sources

PubMed1991

Cotton-wool spots and retinal light sensitivity in diabetic retinopathy.

In 14 eyes of 14 patients with diabetic retinopathy the light sensitivity of retinal cotton-wool spots was studied by computerised perimetry, and the visual field data were accurately correlated with the corresponding morphology as seen on fundus photographs and fluorescein angiograms. In 12 of the eyes the examinations were repeated within one year in order to follow changes in retinal light sensitivity during the evolution of the lesions. Retinal cotton-wool spots were in all eyes associated with localised non-arcuate scotomata in the visual field. In four eyes the cotton-wool spots disappeared within three months of the first examination, and in two of these cases the corresponding scotomata disappeared together with the morphological lesions. In eight eyes the cotton-wool spots (and the corresponding scotomata) had not resolved one year after the first examination. The mean blood pressure showed no significant difference between the patients in whom the lesions resolved within three months and the patients in whom the lesions persisted longer.

Diabetic Retinopathy↗

PubMed1990

Accurate superimposition of perimetry data onto fundus photographs.

A technique for accurate superimposition of computerized perimetry data onto the corresponding retinal locations seen on fundus photographs was developed. The technique was designed to take into account: 1) that the photographic field of view of the fundus camera varies with ametropia-dependent camera focusing 2) possible distortion by the fundus camera, and 3) that corrective lenses employed during perimetry magnify or minify the visual field. The technique allowed an overlay of perimetry data of the central 60 degrees of the visual field onto fundus photographs with an accuracy of 0.5 degree. The correlation of localized retinal morphology to localized retinal function was therefore limited by the spatial resolution of the computerized perimetry, which was 2.5 degrees in the Dicon AP-2500 perimeter employed for this study. The theoretical assumptions of the technique were confirmed by comparing visual field records to fundus photographs from patients with morphologically well-defined non-functioning lesions in the retina.

Diabetic Retinopathy↗

PubMed1990

Coexistence of localized scotomata and neovascularizations in proliferative diabetic retinopathy.

Fifteen eyes of 15 patients with proliferative diabetic retinopathy within the central 60 degrees of the eye fundus were examined with computerized perimetry, and the visual field data were accurately correlated with the corresponding morphology as seen on fundus photographs and fluorescein angiograms. In 12 out of 13 eyes with neovascularizations outside the optic disc area an absolute scotoma could be correlated with a retinal area distal from the neocascularization, and in one case no scotoma was found in this area. The localized scotomata corresponded in 8 cases to non-perfusion areas as seen on fluorescein angiograms, whereas in 5 cases no pathological morphology was detected in these areas. Seven eyes which had neovascularizations at the optic disc showed the same pattern, but with visual field loss of more pronounced degree. Furthermore, other scotomata which not corresponded to any pathological fundus morphology occurred at approx. 30 degrees eccentricity in the visual field. The findings are discussed in relation to the current hypothesis about the initiation and development of neovascularizations in proliferative diabetic retinopathy.

Diabetic Retinopathy↗

PubMed1990

Localised blood-retinal barrier leakage and retinal light sensitivity in diabetic retinopathy.

Twenty patients with insulin dependent diabetes mellitus were selected on the basis of morphological signs of blood-retinal barrier leakage--namely, hard exudates seen on fundus photographs and/or localised leakage of fluorescein seen on fluorescein angiograms. Computerised perimetry was carried out in visual field areas that corresponded to the morphological lesions, and the visual field data were accurately correlated with the morphology as seen on fundus photographs and fluorescein angiograms. In addition, in seven of the patients who represented the range of leakage among the patients studied, the blood-retinal barrier leakage was quantitated by vitreous fluorophotometry. In 16 cases normal light sensitivity was found in retinal areas showing localised leakage as studied on fluorescein angiograms. In four cases with pronounced maculopathy, where scotomata occurred, there was no topographical correlation between the scotomata and barrier leakage. Furthermore hard exudates often, but not consistently, caused localised scotomata when arranged in dense conglomerates. The permeability values correlated with angiographically observed hyperfluorescence in the macular area. On the basis of the techniques employed in the present study it seems that breakdown of the blood-retinal barrier is an earlier event than disturbance of neurosensory function in the development of diabetic retinopathy. However, the findings give no evidence of a causal relationship between barrier leakage and damage to sensory cell function.

Blood-Retinal Barrier↗

PubMed1990

Effect of one year continuous subcutaneous infusion of a somatostatin analogue, octreotide, on early retinopathy, metabolic control and thyroid function in Type I (insulin-dependent) diabetes mellitus.

Growth hormone is assumed to be involved in the development of diabetic retinopathy. In a randomized study we evaluated the possible effects of one year treatment with a somatostatin (SRIH) analogue, octreotide, on early retinopathy and on metabolism in Type I (insulin-dependent) diabetes mellitus. Eleven patients were allocated to treatment with a continuous sc infusion of 400 micrograms octreotide per day and 9 served as controls. Only 7 patients from each group completed the study. Three octreotide-treated patients left the study owing to severe diarrhea. The subjects were evaluated at entry, after 2, 6 and 12 months treatment, and 2 months after withdrawal. Octreotide induced a decrease in GH secretion, expressed as the area under the 24 h serum GH profiles (p less than 0.05), and of the serum levels of IGF-I (p less than 0.05). The entire decline in GH levels occurred during the daytime, whereas the nocturnal levels were unaffected. Retinopathy, as assessed by determination of the blood retina barrier permeability, by colour fundus photography, and flurescein angiography was unchanged in both groups. Apart from a decline in insulin requirements, octreotide had no major effect on glycemic control, but induced a mild transient pituitary hypothyroidism, not clinically relevant. We conclude that treatment with octreotide for one year has modest effects on GH, IGF-I, and glucose metabolism, but has no significant effect on early retinopathy in Type I (insulin-dependent) diabetes.

Adult↗

PubMed1989

The influence of stimulus size on perimetric detection of small scotomata.

The influence of perimetric stimulus size on the detection of small scotomata was examined, and the blind spot was used as a paradigm of a small scotoma. A customized point pattern for perimetry was created on a Humphrey field analyzer. The point pattern had a density of 1.4 degrees and was arranged in a grid in the area of the blind spot. Four normal persons were tested with full-threshold strategy in the points of this grid using Goldmann stimulus sizes ranging from I to V. The delimitation of the blind spot was found to depend strongly on stimulus size. For small stimulus sizes, the blind spot could be delimited as an absolute scotoma with almost sharp borders. However, with larger spot sizes a relative scotoma zone gradually developed, extending centrally from the borders of the blind spot. The central absolute scotoma component of the blind spot totally disappeared for the largest stimulus sizes. We could establish that some of these larger stimuli would be projected totally within the optic nerve head, if perfect imaging through the refractive media of the eye, was assumed. We interpret our findings to be a result of light scattering in the refractive media of the eye, causing a blur to appear around the image of the light stimulus at the retinal plane. We conclude that perimetric resolution power is highly dependent on stimulus size. The smallest stimulus size possible should be used when dense stimulus patterns are used for perimetric detection of small scotomata.

Adult↗

PubMed1985

VIP and PHI in cat neurons: co-localization but variable tissue content possible due to differential processing.

The concentrations of vasoactive intestinal polypeptide (VIP) and the peptide with NH2- terminal histidine and COOH-terminal isoleucine (PHI) in various peripheral tissues and some areas in the CNS of the cat were compared with their immunohistochemical localization. The VIP levels in the gastrointestinal tract were 3 to 6 times higher than PHI levels. Much (up to 10-fold) higher VIP than PHI levels were also observed in the genitourinary tract as well as in the lung and heart. In the neurohypophysis, however, the VIP/PHI ratio was close to 1. Gel-permeation chromatography revealed that VIP- and PHI-immunoreactivity (IR) in the intestine, pancreas and brain consisted of three larger molecular forms in addition to the 'standard' peptides. These larger forms which had overlapping elution positions may represent prepro-VIP/PHI forms. The immunohistochemical analysis revealed that VIP- and PHI-IR was present in the same ganglion cells in the intestine, pancreas, uterus and sympathetic ganglia. Furthermore, the terminal networks for these two peptides were very similar in the periphery. In the median eminence of the hypothalamus and in the posterior lobe of the pituitary, considerably more nerves were PHI- than VIP-IR. This observation was in parallel to a low VIP/PHI ratio. In conclusion, VIP and PHI seem to co-exist in most neuronal systems. Although the ratio of VIP and PHI on the precursor gene is 1:1, differences in posttranslational processing may create a considerably higher content of VIP than PHI in most terminal areas.

Amino Acid Sequence↗

PubMedDate not supplied

The effect of galanin, CGRP and ANP on spontaneous smooth muscle activity of rat uterus.

In the present study the effect of the newly isolated peptides galanin, calcitonin gene-related peptide (CGRP) and atrial natriuretic peptide (ANP) was examined on spontaneous uterine smooth muscle activity on the rat in vitro. Galanin showed a slight and insignificant stimulatory effect on the amplitude, while both CGRP and ANP were found to be potent inhibitors of the uterine smooth muscle contractions. In connection with the recent demonstration of galanin and CGRP nerves in the genital tract, these pharmacological findings suggest that the peptides may participate in the control of nervous control of uterine muscular activity, although the exact physiological roles remain to be clarified.

Animals↗

PubMedDate not supplied

The prognostic value of post-treatment retinopathy after panretinal photocoagulation for proliferative diabetic retinopathy in type 1 diabetes.

PURPOSE: To study the prognostic value of post-treatment retinopathy after panretinal laser photocoagulation for proliferative diabetic retinopathy in type 1 diabetes mellitus. Proliferative diabetic retinopathy is treated with panretinal photocoagulation, which significantly reduces the risk of visual loss from this complication. However, no parameters are presently known that can be used to define an optimal control interval after the initial panretinal photocoagulation treatment that ensures enhancement of the treatment in cases where this is needed. METHODS: In this retrospective cohort study, 85 eyes from 56 type 1 diabetic patients were identified who had been subjected to panretinal photocoagulation for proliferative diabetic retinopathy before 1990. The patients were divided into two groups: Group 1 had four or fewer microaneurysms only at the first post-treatment examination whereas Group 2 had more retinopathy. RESULTS: At the first photographic examination after treatment the eyes in Group 1 had a significantly lower visual acuity (VA) (mean =0.23, range: 0.01-1.00) than the patients in Group 2 (mean=0.48, range: 0.01-1.6). During the follow-up period the VA was further reduced in Group 2 but not in Group 1. Three eyes out of six in Group 1 had improvement of VA from below to above 0.1, whereas 6 eyes out of 12 in Group 2 experienced progression of retinopathy with a consequent worsening of VA to below 0.1 after a mean of 10.8 years (range: 6.8-15.9) after treatment. CONCLUSIONS: The severity of post-treatment retinopathy can be used to assess the need for enhancing photocoagulation of proliferative diabetic retinopathy in type 1 diabetes. The interval between post-treatment examinations can be increased to several years when the initial treatment has reduced retinopathy to a minimal level.

Adult↗