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Biomedical subjects

R Khan

Publications and source records attributed to R Khan.

At least 91 records · Page 5Linked to original sources
PubMed1989

Clinical and experimental mycotic corneal ulcer caused by Aspergillus fumigatus and the effect of oral ketoconazole in the treatment.

Aspergillus fumigatus was isolated from a case of keratomycosis. The patient, a 12-year-old boy presented with large corneal ulcer with hypopyon. The direct microscopic examination of scrapings revealed hyaline, septate mycelium. In vitro some antimycotics (amphotericin B,5-fluorocytosine, oxiconazole, amorolfine and ketoconazole) were tested against A. fumigatus by agar dilution method. Ketoconazole with minimum inhibitory concentration of 30 micrograms/ml after 11 days of incubation was most effective against A. fumigatus. Experimental corneal ulcer was produced by injecting intralamellary spore suspension (2.5 x 10(6) c.f.u.) into the right eyes of previously immunosuppressed albino and black wild types of rabbits. The extent of ocular infection was graded up to 32 days. Histopathologic examination showed infiltration and large destruction of corneal stroma. Oral ketoconazole therapy exhibited partial response followed by relapse. The black type of rabbit appeared more suitable as an animal model for mycotic keratitis.

Administration, Oral↗
PubMed1989

The suppression of iron release from activated myoglobin by physiological electron donors and by desferrioxamine.

Interactions between ferrimyoglobin and hydrogen peroxide have been postulated to lead to the formation of activated ferryl myoglobin. In such systems hydroxyl radical formation has also been demonstrated by its ability to degrade deoxyribose subsequent to the release of iron from the porphyrin ring of the myoglobin. We have investigated the potential for ferrylmyoglobin formation and for iron release from ferrylmyoglobin exposed to hydrogen peroxide; the modulation of the stability of the haem group by membranes and in the presence of desferrioxamine and ascorbate have also been assessed. The results show that iron release from ferrimyoglobin activated by hydrogen peroxide is suppressed in the presence of membranes, apparently by the reduction of the ferryl myoglobin species, and lipid peroxidation occurs. In the presence of desferrioxamine, formation of the ferrylmyoglobin species is suppressed by the electron donating properties of the trihydroxamate moiety, which also functions as a chain-breaking antioxidant when added to peroxidising membranes. The physiological antioxidant ascorbate not only suppresses the formation of the ferryl myoglobin species under the conditions described here, but also reduces the myoglobin iron to the iron II state.

Ascorbic Acid↗
PubMed1988

Human methylated DNA-binding protein. Determinants of a pBR322 recognition site.

Methylated DNA-binding protein (MDBP) from human placenta has a high affinity for a site in pBR322 (pB site 1) when that site is methylated at its CpG dinucleotides. Dimethyl sulfate interference analysis and experiments with ligands prepared by oligonucleotide-directed mutagenesis indicate that 15 contiguous base pairs, 14 of which exhibit hyphenated dyad symmetry, influence MDBP binding to pB site 1. These 14 base pairs, 5'-RTMGYCAMGG(M/T)GAY-3' (M, 5-methylcytosine), suffice for recognition by MDBP as demonstrated with a double-stranded, MpG-containing oligonucleotide used as a free ligand or cloned into M13mp19 and subsequently methylated. Seven single-site mutations at different positions of this 14-base pair region largely eliminated binding, and several others increased binding up to 2-fold when compared to the nonmutant, triply methylated sequence. However, MDBP recognizes a site in hemimethylated M13mp19 replicative form DNA, which was homology to pB site 1 at only 10 of 14 base pairs, and all four of these different base pairs are equivalent to transversions. Based upon the above data, a mixed oligonucleotide probe was constructed that contains variants of pB site 1 which should be recognized by MDBP. This 14-base probe hybridizes under stringent conditions to a number of discrete fragments in restriction digests of human DNA. this suggests that there are multiple pB site 1-related sequences in human DNA that might, when methylated, bind MDBP in vivo.

Amino Acid Sequence↗
PubMed1988

Methylated DNA-binding protein is present in various mammalian cell types.

A DNA-binding protein from human placenta, methylated DNA-binding protein (MDBP), binds to certain DNA sequences only when they contain 5-methylcytosine (m5C) residues at specific positions. We found a very similar DNA-binding activity in nuclear extracts of rat tissues, calf thymus, human embryonal carcinoma cells, HeLa cells, and mouse LTK cells. Like human placental MDBP, the analogous DNA-binding proteins from the above mammalian cell lines formed a number of different low-electrophoretic-mobility complexes with a 14-bp MDBP-specific oligonucleotide duplex. All of these complexes exhibited the same DNA methylation specificity and DNA sequence specificity. From the extracts of rat and calf tissues, oligonucleotide protein complexes formed that also had the same specificity as human placental MDBP although they had a higher electrophoretic mobility probably due to digestion by proteases in the nuclear extracts. Although MDBP activity was found in various mammalian cell types, it was not detected in extracts of cultured mosquito cells and so may be associated only with cells with vertebrate-type DNA methylation.

5-Methylcytosine↗
PubMed1986

Methylated DNA-binding protein from human placenta recognizes specific methylated sites on several prokaryotic DNAs.

Methylated DNA-binding protein (MDBP) from human placenta recognizes specific DNA sequences containing 5-methylcytosine (m5C) residues. Comparisons of binding of various prokaryotic DNAs to MDBP indicate that m5CpG is present in the recognition sites for this protein but is only part of the recognition sequence. Specific binding to MDBP was observed for bacteriophage XP12 DNA, which naturally contains approximately 1/3 of its residues as m5C, and for Micrococcus luteus DNA, M13mp8 replicative form (RF) DNA, and pBR322 when these three DNAs were methylated at CpG sites by human DNA methyltransferase. Five DNA regions binding to MDBP have been localized by DNase I footprinting or restriction mapping in methylated pBR322 and M13mp8 RF DNAs. A comparison of their sequences reveals a common 5'-m5CGRm5CG-3' element or closely related sequence in which one of the m5C residues may be replaced by a T. In addition to this motif, one upstream and one downstream m5CpG as well as other common residues over an approximately 20-bp long region may be recognized by MDBP.

Base Sequence↗
PubMed1985

Renal oncocytoma. A report of 3 cases.

Three cases of renal oncocytoma are presented; all were in women and involved the lower pole of the kidney. The patients presented with renal masses, but haematuria was not a feature. Unexplained monocytosis was found in 2 cases. Ultrasound investigations and intravenous pyelography gave non-specific results and the diagnoses were made on the basis of the histopathological findings.

Adenoma↗
PubMed1985

The radiographic appearance of arterial sheath kinking.

A case of arterial sheath kinking is reported. Radiographically, sheath kinking has some features which mimic sheath fracture. The radiographic appearance of sheath kinking is, however, distinctive and clearly separable from sheath fracture, the hallmark of which is extravasation of contrast at the fracture site.

Angioplasty, Balloon↗
PubMed1985

Changed learning curve for percutaneous transluminal coronary angioplasty. Implication for the future treatment of coronary artery disease.

As with all skilled techniques, there is a learning curve for percutaneous coronary angioplasty. This curve has been well described in the literature and it is generally quoted that an initial success rate of 70 to 75 percent in reaching and crossing lesions is to be expected during the first 20 cases. However, the introduction of the steerable or guidewire-directed dilation catheter has altered the learning curve. After an initial experience of six nonsteerable percutaneous transluminal coronary angioplasty procedures, 20 consecutive steerable percutaneous transluminal coronary angioplasty procedures were performed without a single failure to reach or cross a lesion. These 20 consecutive steerable coronary angioplasty procedures included eight single left anterior descending lesions, two double (lesions located in series) left anterior descending lesions, six single right coronary lesions, one double (lesions located in series) right coronary lesion, and three single circumflex lesions. It is concluded that the introduction of the steerable system for percutaneous transluminal coronary angioplasty has shifted the learning curve, and that skilled and experienced coronary angiographers beginning a coronary angioplasty program can expect an initial success rate in reaching and crossing obstructive coronary lesions far in excess of the figures quoted in the literature. This may have significant implication for the ultimate availability of percutaneous transluminal coronary angioplasty to patients with coronary artery disease.

Adult↗
PubMed1985

Surgical management of synchronous coronary artery disease and multiple aortic stenosis: a case report with brief review of the literature.

One-stage surgery was successfully performed in a 44-year-old hypertensive man with uncontrolled angina, multiple coarctations of the thoracic and abdominal aorta, and a previous subtotal gastrectomy. There was a gradient of 120 mm Hg between the thoracic and abdominal aorta. A graft was placed retroperitoneally from the infrarenal aorta to the ascending aorta and was followed by a coronary artery bypass graft. Twenty-four months postoperatively, the patient was free of angina, and his hypertension was easily controlled.

Journal Article↗
PubMed1985

Use of a diode array detector in investigation of neonatal organic aciduria.

We investigated the use of a diode array detector in conjunction with isocratic cation-exchange liquid chromatography for detection of organic acids in urine. The spectra and retention times of abnormal peaks found on chromatography of urine from patients with methylmalonic aciduria, maple syrup urine disease, and lactic aciduria were recorded and compared with those obtained for group of pure organic acids. Our results show that diode array detection helps considerably in tentatively identifying peaks appearing on an abnormal chromatogram while awaiting confirmation by mass spectrometry.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

Nonrandom occurrence of single-vessel coronary artery disease.

The location of obstructive coronary artery lesions in single-vessel disease is nonrandom. The circumflex coronary artery is protected relative to the right coronary artery. This may have important implications regarding the causation of coronary obstructive lesions.

Coronary Angiography↗
PubMed1983

Catheter separation during coronary angiography.

Complete fracture and separation of a right coronary Judkins catheter during coronary angiography is presented. The possible mechanism underlying the separation and retrieval of the catheter fragment is described.

Angiography↗
PubMed1983

Aortico-right ventricular shunt following aortic valve replacement.

A 58-year-old man developed cardiac decompensation following aortic valve replacement as a result of an aortico-right ventricular fistula. Serial hemodynamic and electrocardiographic changes are presented. Attention is drawn to this rare complication as a cause of hemodynamic deterioration following aortic valve surgery.

Aortic Diseases↗
PubMed1981

HLA antigens in Asian Indians: HLA-D-DR relationships.

Fifty-nine Asian Indians were typed for HLA-A, B, D, and DR antigens. Peculiar to the population that we have tested was the absence of HLA-A25, B13, B14, DR1, DW1, LD13 (a DR1-associated HLA-D allele), and LD12 (a DR4-associated HLA-D allele). Certain haplotypes that exhibit high frequencies in Caucasians (such as A2-BW50, AW24-B18, B8-DR3, BW44-DR7, B18-DR5) or in Blacks (such as A29-B7) also show significant delta in Asian Indians. The HLA-D-DR associations previously described in European and North American Caucasians were also found in Asian Indians. Additionally, however, Asian Indians exhibited two new HLA-D antigens, one associated with DR5 and the other with DRw6. The genetic distance between Asian Indians and Caucasians, Blacks, or Mongoloids is of the same order of magnitude.

Alleles↗
PubMed1981

HLA-D-DR relationships: PLT studies of HLA-D specificities associated with DR1, DR2, and DR4.

The primed lymphocyte test (PLT) detects gene products of the HLA-D-DR region which activate the secondary (memory) response of MLC stimulated T cells. In the present study attempts were made to determine whether different HLA-D alleles associated with the same DR, such as DR1, 2, and 4 can be discriminated by PLT typing. PLTs were generated by using, as responders and primary MLC stimulators, HLA-D different HTCs which shared all DR groups (major DR, supertypic MT and second locus MB) or only the MT or MB groups. As secondary stimulators, lymphocytes from an HLA-D selected panel of 72 individuals were used. PLTs raised in DR identical responder-primary stimulator combinations were able to discriminate between the different HLA-D antigens associated with the same DR. In contrast, when priming was performed in combinations differing for the major DR group, the restimulation response was highly associated with the DR specificity of the primary stimulator, regardless of whether or not this was compatible with the responding HTC for the MT or MB groups. This data indicate that the specificity of primed lymphocytes largely depends on the combinations used for priming and that the memory response can be activated by both HLA-D and DR antigens. The dissociation of HLA-D from DR by PLT typing might provide a useful tool for further analysis of this HLA region.

Epitopes↗