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Biomedical subjects

B C Polak

Publications and source records attributed to B C Polak.

12 recordsLinked to original sources
PubMed1992

von Willebrand factor and early diabetic retinopathy: no evidence for a relationship in patients with type 1 (insulin-dependent) diabetes mellitus and normal urinary albumin excretion.

High plasma levels of von Willebrand factor, an indicator of endothelial cell dysfunction, have been reported in both diabetic retinopathy and nephropathy. It is unclear, however, whether von Willebrand factor is related to diabetic retinopathy in the absence of diabetic nephropathy. The relationship between retinal status and plasma von Willebrand factor concentration was investigated in a cohort of 17 patients with Type 1 (insulin-dependent) diabetes mellitus who were followed-up for a median of 42 months. The patients were examined three times. They were selected for having had normal urinary albumin excretion and no evidence of retinopathy (on fundoscopy) at the first and second examination. They were then divided into two groups, according to absence (Group A; n = 9) or presence (Group B; n = 8) of retinopathy on fundoscopy or fluorescein angiography at the third examination. Urinary albumin excretion remained normal in all patients. Plasma von Willebrand factor levels were similar in both groups: (median) 128 vs 123%, 164 vs 132% and 159 vs 130% (first, second and third examination, respectively). Median changes in plasma von Willebrand factor were also similar: +7 vs +9% and +5 vs +1% (first-second and second-third examination). Patients in whom the plasma von Willebrand factor concentration increased had higher systolic blood pressure at the third examination (150 +/- 30 vs 130 +/- 12 mmHg, p = 0.02) when compared to those in whom plasma von Willebrand factor did not increase, but were of similar age and had similar diabetes duration, retinal status, diastolic blood pressure, glycated haemoglobin and serum cholesterol concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1992

Transient decrease of secretory IgA in tears during rigid gas permeable contact lens wear.

Decreased humoral defense mechanisms may be involved in the occurrence of keratic ulcerations after contact lens wear. To investigate the effect of contact lens wear on tear protein composition a prospective study was performed whereby tears were collected with Schirmer papers from 42 healthy individuals, before and at varying times after contact lens wear. Tear proteins were quantitated using HPLC analysis. Analysis of tear fluid by HPLC is a rapid and simple technique to detect the major tear proteins. Four separate peaks containing respectively IgA, lactoferrin, TSPA and lysozyme can easily be identified. The results show that the mean relative level of secretory IgA in the collected tear samples decreased significantly after the first months of contact lens wear but was not significantly altered after one year. The decrease in IgA was accompanied by a significant increase in the relative amount of lysozyme, whereas the levels of lactoferrin and TSPA remained the same. Certain individuals showed a marked decrease in their tear secretory IgA levels after wearing the lenses for more than one year. Future studies will clarify whether such individuals are at higher risk to develop corneal complications.

Adolescent↗
PubMed1990

Deep corneal stromal opacities in long-term contact lens wear.

In 32 patients with long-term contact lens wear (up to 19 years), deep whitish opacities directly adjacent to Descemet's membrane were seen in the central part of the cornea. These opacities were seen in soft hydroxyethylmethacrylate (HEMA) as well as in hard (polymethylmethacrylate, PMMA) contact lens wear. These conditions could reduce visual acuity. When contact lens wear was discontinued or when the HEMA or PMMA lenses were replaced by gas-permeable rigid lenses, the lesions gradually diminished and resolved completely in most patients. One possible cause of these opacities is an allergic reaction to thimerosal. Another possible cause is chronic anoxia of the corneal stroma and endothelium. Endothelial cell density was not abnormal, but there was a marked polymegethism of the endothelium as a sign of endothelial stress.

Adult↗
PubMed1977

Macular lesions in Alport's disease.

In three male patients with Alport's disease, two of them successfully treated by kidney transplantation, ophthalmoscopy revealed bilaterally densely packed whitish-yellow lesions around, and to some extent in, the macular area. These spots, superficially located in the retina, have not been previosly desribed in Alport's disease.

Adolescent↗
PubMed1977

Electro-rentinal abnormalities in heterozygotes of renal-retinal dysplasia.

The relatives of two patients with medullary cystic disease associated with retinitis pigmentosa were studied. A new case was found in one of these families, and consanguinity of the parents was established in another. Conventional fundoscopic examination of relatives without renal disease did not show retinal abnormalities, but electro-ophthalmologic investigation demonstrated retinal dysfunction in three relatives, including two of the four parents who may be considered obligatory heterozygotes under the assumption of autosomal recessive inheritance of this syndrome. Less severe electro-ophthalmological abnormalities were observed in the other two parents. It is considered highly probable that all three patients are homozygous for a mutant gene causing both the renal and the retinal abnormalities. The results of this study support the view that medullary cystic disease associated with retinitis pigmentosa is transmitted as an autosomal recessive trait, in contrast to the dominant form, which is reported not to be associated with eye abnormalities. With respect to genetic couseling and donation of kidneys by relatives, it is important to establish the mode of inheritance of cystic medullary disease in a given family. Electro-ophthalmologic examination should therefore be included in the examination of families in which medullary cystic disease occurs.

Adolescent↗