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T Hasan

Publications and source records attributed to T Hasan.

116 records · Page 7Linked to original sources
PubMed1983

Reversed-phase high-performance liquid chromatography of Escherichia coli ribosomal proteins. Characteristics of the separation of a complex protein mixture.

We have previously reported the application of reversed-phase high-performance liquid chromatography (RP-HPLC) to the separation of Escherichia coli ribosomal proteins (A. R. Kerlavage, L. Kahan and B. S. Cooperman, Anal. Biochem., 123 (1982) 342-348; A. R. Kerlavage, T. Hasan and B. S. Cooperman, J. Biol. Chem., in press). In the present studies RP-HPLC is shown to yield much greater resolution of these proteins than does size-exclusion HPLC. In addition, we report on various aspects of RP-HPLC of ribosomal proteins including column capacity, resolution, reproducibility, recovery, separation of irreversibly denatured protein, and analysis of affinity-labeled ribosomal protein. The capacity of analytical columns was found to range from several micrograms to several milligrams with minimal loss in resolution and highly reproducible retention values. Recovery varied from protein to protein and ranged from 27% to 91%, with an average total protein recovery of 70%. The partitioning of several proteins between two peaks was shown to be due to irreversible denaturation of a small fraction. Finally, the utility of RP-HPLC in the study of the ribosome was demonstrated by analyses of [3H]puromycin-labeled ribosomal proteins, and the demonstration that labeling slightly alters protein elution.

Bacterial Proteins↗
PubMed1983

Reverse phase high performance liquid chromatography of Escherichia coli ribosomal proteins: standardization of 70 S, 50 S, and 30 S protein chromatograms.

We recently described the use of reverse phase high performance liquid chromatography for the separation of the proteins of the 30 S subunit of Escherichia coli ribosomes (Kerlavage, A. R., Kahan, L., and Cooperman, B. S. (1982) Anal. Biochem. 123, 342-348). In the present studies we report improvements in the technique and its extension to the separation of the proteins of the 50 S subunit and of 70 S ribosomes. Using an octadecasilyl silica column and a trifluoroacetic acid/acetonitrile solvent system, the 21 proteins of the 30 S subunit have been resolved into 17 peaks, the 33 proteins of the 50 S subunit into 22 peaks, and the 53 proteins of the 70 S ribosome into 31 peaks. The proteins present in each peak have been identified by polyacrylamide gel electrophoresis, by comparison with previously standardized chromatograms, and by calibration with authentic samples of purified proteins. All of the known ribosomal proteins have been identified on the chromatograms with the exception of L31 and its variant, L31'. Three protein peaks, not corresponding to known ribosomal proteins, have been observed in preparations from the total protein from 50 S subunits and 70 S ribosomes, but the significance of these peaks is unclear. The reverse phase high performance liquid chromatography technique has the potential for purifying all ribosomal proteins, as demonstrated by the increase in resolution we obtain when a peak isolated under standard gradient conditions and containing several proteins is reapplied to the column and eluted with a shallower gradient. Its utility in preparing proteins for functional studies is demonstrated by a reconstitution of active 30 S particles using 30 S proteins prepared by reverse phase high performance liquid chromatography.

Chromatography, High Pressure Liquid↗
PubMed1983

Erythroderma: a follow-up of fifty cases.

Fifty consecutive cases of erythroderma were studied. The mean onset age was 61 years, and thirty-three of the fifty were male. As a causative factor, a preexisting dermatosis was identified in twenty-one cases, topical sensitization to drugs in six cases, reaction to internal drugs in five cases, and mycosis fungoides in two cases. In sixteen cases a causative factor could not be disclosed. A follow-up survey of the patients at a mean of 6 years after the start of the erythroderma indicated that seventeen patients had cleared completely, twelve patients had less symptoms than initially, and six suffered from undiminished erythroderma. Ten patients had died from causes unrelated to the erythroderma. It is concluded that the underlying causes for erythroderma have remained rather unchanged during several decades, and that the majority of present-day erythroderma patients can expect a favorable prognosis.

Adult↗
PubMedDate not supplied

Mechanisms of action of photodynamic therapy with verteporfin for the treatment of age-related macular degeneration.

Age-related macular degeneration, especially the neovascular form of the disease, is the leading cause of blindness in elderly people in developed countries. Thermal photocoagulation is still the preferred treatment for choroidal neovascularization that does not involve the fovea, but it is suitable for only a small number of patients and it can lead to immediate loss of visual acuity. Photodynamic therapy with use of photochemical light activation of verteporfin as a photosensitizer (verteporfin therapy) has been shown to be effective in treating vascularized tumors, and its potential to treat other conditions involving neovascularization has also been suggested. Preclinical and clinical studies have indicated that verteporfin therapy can be used to treat choroidal neovascularization secondary to age-related macular degeneration effectively and safely. Selective occlusion of choroidal neovasculature by this therapy causes minimal damage to the neurosensory retina and, therefore, does not induce loss of visual acuity. This benefit allows verteporfin therapy to be used in the large proportion of patients who are not eligible for treatment by laser photocoagulation. The mechanistic aspects of the mode of action of light-activated verteporfin are described in this review.

Animals↗
PubMedDate not supplied

Vitamin D and prostate cancer.

Our recent epidemiological study (Ahonen et al., Cancer Causes Control 11(2000) (847-852)) suggests that vitamin D deficiency may increase the risk of initiation and progression of prostate cancer. The nested case-control study was based on a 13-year follow-up of about 19000 middle-aged men free of clinically verified prostate cancer. More than one-half of the serum samples had 25OH-vitamin D (25-VD) levels below 50 nmol/l, suggesting VD deficiency. Prostate cancer risk was highest among the group of younger men (40-51 years) with low serum 25-VD, whereas low serum 25-VD appeared not to increase the risk of prostate cancer in older men (>51 years). This suggests that VD has a protective role against prostate cancer only before the andropause, when serum androgen concentrations are higher. The lowest 25-VD concentrations in the younger men were associated with more aggressive prostate cancer. Furthermore, the high 25-VD levels delayed the appearance of clinically verified prostate cancer by 1.8 years. Since these results suggest that vitamin D has a protective role against prostate cancer, we tried to determine whether full spectrum lighting (FSL) during working hours could increase serum 25-VD concentrations. After 1-month exposure, there was no significant increase in the serum 25-VD level, although there was a bias towards slightly increasing values in the test group as opposed to decreasing values in controls. There was no significant change in the skin urocanic acid production. The possibility to use FSL in cancer prevention is discussed. In order to clarify the mechanism of VD action on cell proliferation and differentiation, we performed studies with the rat and human prostates as well prostate cancer cell lines. It is possible that 25-VD may have a direct role in the host anticancer defence activity, but the metabolism of vitamin D in the prostate may also play an important role in its action. We raised antibodies against human 1alpha-hydroxylase and 24-hydroxylase. Our preliminary results suggest that vitamin D is actively metabolised in the prostate. Vitamin D appears to upregulate androgen receptor expression, whereas androgens seem to upregulate vitamin D receptor (VDR). This may at least partially explain the androgen dependence of VD action. VD alone or administered with androgen causes a suppression of epithelial cell proliferation. VD can activate mitogen-activated kinases, erk-1 and erk-2, within minutes and p38 within hours. Also, auto/paracrine regulation might be involved, since keratinocyte growth factor (mRNA and protein) was clearly induced by VD. Based on these studies, a putative model for VD action on cell proliferation and differentiation is presented.

Adult↗
PubMedDate not supplied

Structural considerations in the metabolism of nitriles to cyanide in vivo.

In order to investigate structure-activity relationships that influence metabolism of nitriles to CN-, thiocyanate was measured, as an index of CN- release, in urine of rats given equimolar doses of nitriles. Significantly more SCN- was excreted after po than after ip administration of saturated (C2-C5) nitriles, but SCN- excretion was the same after both routes for n-hexanenitrile. Among saturated nitriles, SCN- excretion was maximal for the C3 and C4 compounds, propionitrile, n-butyronitrile, and isobutyronitrile, after both po and ip administration. SCN- excretion was not elevated after administration of the tertiary nitrile trimethylacetonitrile. Administration (po) of the unsaturated nitriles acrylonitrile, crotonitrile, and 3-butenenitrile yielded 37%, 5.6%, and 29% of the dose as SCN-, whereas after ip injection 4.5%, 4.6%, and 18% of the doses were excreted as SCN-, respectively. After iv injection of acrylonitrile, urinary SCN- content was not elevated, whereas 45% of an iv dose of the saturated analog propionitrile was excreted as SCN-. These results suggest that length of the carbon chain, presence of substituents at the alpha-carbon, position of double bonds, and, for some compounds, route of administration, are important factors influencing the release of CN- from nitriles.

Animals↗