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Biomedical subjects

M I Khan

Publications and source records attributed to M I Khan.

At least 109 records · Page 6Linked to original sources
PubMed1985

Arrangement of subunits in peanut lectin. Rotation function and chemical cross-linking studies.

X-ray intensity data from the native orthorhombic crystals of peanut lectin have been collected using oscillation photography. Rotation function studies using data up to a resolution of 4.5 A indicate that the four subunits in the molecule, which constitute the asymmetric unit in the crystals, are related to one another by three mutually perpendicular noncrystallographic 2-fold axes. Chemical cross-linking experiments in solution followed by sodium dodecyl sulfate gel electrophoresis, carried out in parallel, suggest that there is more than one type of intersubunit approach in the molecule. Rotation function and cross-linking studies thus show that the tetrameric molecule of peanut lectin is a dimer of a dimer. The two monomers in a dimer are related by a 2-fold axis. The two dimers are in turn related by another 2-fold axis perpendicular to the one that relates the two monomers in the dimer, endowing the molecule with 222 (D2) symmetry.

Cross-Linking Reagents↗
PubMed1985

Beta-blocker toxicity--the role of glucagon. Report of 2 cases.

We describe 2 cases of acute overdosage with beta-adrenergic receptor blocking agents. Both patients presented with profound bradycardia and cardiogenic shock. The effectiveness of intravenous glucagon administration is demonstrated in the first case. We suggest that glucagon should be used more readily in cases of circulatory failure due to beta-blocker poisoning than has hitherto been the case.

Adult↗
PubMed1985

Micrognathia, obstructive sleep apnoea and cor pulmonale--a case for tracheostomy.

A patient with congenital micrognathia, hypersomnia and severe pulmonary hypertension which resulted in sudden death during sleep is described. Hypersomnolence is a well-recognized manifestation of the pickwickian syndrome. A less recognized but similar disorder may affect patients with congenital or acquired micrognathia. The pathogenesis of this syndrome and obstructive sleep apnoea are reviewed. Tracheostomy timeously performed may be life-saving and the value of early resort to this apparently drastic procedure in a high-risk patient is emphasized.

Adolescent↗
PubMed1984

Chemical modification studies on Abrus agglutinin. Involvement of tryptophan residues in sugar binding.

The galactose-binding lectin from the seeds of the jequirity plant (Abrus precatorius) was subjected to various chemical modifications in order to detect the amino acid residues involved in its binding activity. Modification of lysine, tyrosine, arginine, histidine, glutamic acid and aspartic acid residues did not affect the carbohydrate-binding activity of the agglutinin. However, modification of tryptophan residues carried out in native and denaturing conditions with N-bromosuccinimide and 2-hydroxy-5-nitrobenzyl bromide led to a complete loss of its carbohydrate-binding activity. Under denaturing conditions 30 tryptophan residues/molecule were modified by both reagents, whereas only 16 and 18 residues/molecule were available for modification by N-bromosuccinimide and 2-hydroxy-5-nitrobenzyl bromide respectively under native conditions. The relative loss in haemagglutinating activity after the modification of tryptophan residues indicates that two residues/molecule are required for the carbohydrate-binding activity of the agglutinin. A partial protection was observed in the presence of saturating concentrations of lactose (0.15 M). The decrease in fluorescence intensity of Abrus agglutinin on modification of tryptophan residues is linear in the absence of lactose and shows a biphasic pattern in the presence of lactose, indicating that tryptophan residues go from a similar to a different molecular environment on saccharide binding. The secondary structure of the protein remains practically unchanged upon modification of tryptophan residues, as indicated by c.d. and immunodiffusion studies, confirming that the loss in activity is due to modification only.

Arginine↗
PubMed1984

Complete recovery after profound acidosis (pH 6.49).

We describe an infant with profound acidosis caused by chronic therapeutic salicylate poisoning. The confirmed arterial blood pH of 6.49 must be close to the limit of tolerable acidity and is the lowest such value in our experience. Full recovery was made.

Acidosis↗
PubMed1983

Sporotrichosis arthritis. A case presentation and review of the literature.

Mimicry by fungal infection of other chronic bone and joint diseases may easily result in a tardy diagnosis with subsequent needless surgery or permanent damage to the joint and its function. A case of sporotrichosis arthritis involving both wrists and knee joints is described. Diagnostic pitfalls and therapeutic dilemmas are outlined. The literature on this apparently 'rare' form of arthritis is reviewed.

Amphotericin B↗
PubMed1983

The recurrence of intracranial meningiomas after surgical treatment.

A study of 114 surgically treated patients with intracranial meningiomas was carried out to evaluate factors influencing recurrence. The data of the initial surgery extended over a 24-year period from January, 1956, to December, 1979. The patients ranged in age from 1 1/2 years to 82 years. Seventy-one (62.3%) were females and 43 (37.7%) were males. The surgical procedure was graded according to Simpson's classification from 1 to 5 (Grade 1 = complete excision, Grade 5 = simple decompression). In this series, 33 procedures (28.9%) were Grade 1, 55 (48.2%) were Grade 2, seven (6.1%) were Grade 3, 18 (15.8%) were Grade 4, and one (0.9%) was Grade 5. There were eight (7%) postoperative deaths. Approximately 60% of the tumors were located in the sphenoid wing (23.7%), convexity (21.1%), and parasagittally (14.9%). Histological diagnosis in 96% of the patients was transitional (42.1%), syncytial (34.2%), and fibroblastic (20.2%) meningiomas. Eight (7%) patients received postoperative radiotherapy. There was evidence of recurrence in 22 patients (19.3%). Twenty-one underwent a second surgical procedure. Using survival analysis, it was determined that 80% of the patients were free of recurrence 5 years after the initial surgery, and approximately 50% showed no recurrence 20 years after the initial surgery. Only the grade of the initial surgery had a statistically significant influence on recurrence. Sex of patients, site and histology of the tumor, and postoperative radiotherapy had no statistically significant influence on recurrence. Angioblastic and malignant meningiomas were rare (only four cases), and recurred relatively quickly.

Adolescent↗
PubMed1982

Chemical modification studies on Ricinus communis (Castor Bean) agglutinin.

Ricinus communis agglutinin was subjected to various chemical treatments and the effect on its hemagglutinating and saccharide-binding properties was studied. Acetylation, succinylation and citraconylation led to a complete loss in the activity of the agglutinin, whereas reductive methylation had no effect on the activity, showing that charged amino groups were involved in the hemagglutinating and saccharide-binding activity of Ricinus agglutinin. Modification of tryptophyl, arginyl and carboxyl-group-containing residues did not lead to any loss in the activity of the agglutinin. Acetylation of tyrosyl groups with N-acetylimidazole strongly reduced the hemagglutinating and saccharide-binding property of Ricinus agglutinin. The loss in activity was restored on deacetylation of the tyrosyl groups. Modification of tyrosyl residues also led to a change in the immunological properties of the agglutinin. The initial rate of modification of tyrosyl and amino groups and the concomitant loss of activity was reduced in the presence of lactose.

2-Hydroxy-5-nitrobenzyl Bromide↗
PubMed1982

Survey of tuberculous infection in schoolchildren in Bahrain.

A tuberculin survey was carried out on young schoolchildren in Bahrain and the results are compared with those of a previous survey. In 1969, with the co-operation of the World Health Organisation, a sample tuberculin survey was carried out on all age groups; it was found that 55 of the 897 children 6-7 years of age showed positive reactions (6.1%). In 1981, 12 years later, this same age group was surveyed again. A total of 6151 children was tested, of whom 86 were positive reactors (1.4%). This decline in the rate of tuberculous infection, by 12% a year, is highly significant (P much less than 0.001). The survey also shows a significantly higher rate of tuberculin positive reactors amongst immigrant children than amongst native Bahrainis.

Bahrain↗
PubMed1982

Clinical - radiological correlates in intracerebral hematomas due to aneurysmal rupture.

In this series of intracerebral hematomas from aneurysmal rupture, gathered from several neurosurgical services, certain morphological features were studied in detail. Patients with very large hematomas tended to have poor neurological grades on admission to hospital and their immediate discharge outlook was correspondingly poor. Ruptured middle cerebral and pericallosal artery aneurysms were relatively common causes of intracerebral hematomas. Patients with temporal lobe hematoma did relatively well; those with parietal hematoma did poorly. The larger the hematoma the less chance there was of developing cerebral vasospasm but the more likely was pre-operative brain herniation. The survival was more closely linked to size and location of the hematoma than to the location of aneurysm or the degree of midline shift.

Cerebral Hemorrhage↗
PubMed1981

Fluorimetric studies of the binding of Momordica charantia (bitter gourd) lectin with ligands.

The association constants for the binding of a series of ligands with a galactose-specific lectin from Momordica charantia (bitter gourd) has been determined through the ligand-induced quenching of protein fluorescence. Analysis of the iodide quenching suggested that there is a slight increase in the accessibility of tryptophan residues of the lectin on binding lactose.

Carbohydrates↗
PubMed1981

Fluorescence polarization as a tool to study lectin-sugar interaction. An investigation of the binding of 4-methylumbelliferyl beta-D-galactopyranoside to Abrus precatorious agglutinin.

Polarization of ligand fluorescence was used to study the binding of 4-methylumbelliferyl beta-D-galactopyranoside (MeUmb-Galp) to Abrus precatorious agglutinin. The binding of the fluorescent sugar to the lectin led to considerable polarization of the MeUmb-Galp fluorescence, which was also quenched by about 30% on binding to the lectin. The binding of the fluorescent sugar was carbohydrate-specific, as evidenced by inhibition of both fluorescence polarization and quenching when lectin was preincubated with lactose. The association constant as determined by fluorescence polarization is 1.42 x 10(4) M-1 at 25 degrees C and is in excellent agreement with those determined by fluorescence quenching (Ka = 1.51 x 10(4) M-1) and equilibrium dialysis (Ka = 1.62 x 10(4) M-1) at 25 degrees C. The numbers of binding sites as determined by fluorescence polarization, quenching and equilibrium dialysis agree very well with one another, n being equal to 2.0 +/- 0.05. The consistency between the association constant value determined by fluorescence polarization, quenching and equilibrium dialysis shows the validity of this approach to study lectin-sugar interaction.

Binding Sites↗
PubMed1981

Pasteurella multocida subdural empyema: a case report.

The first case of Pasteurella Multocida subdural empyema is reported. This was secondary to hematogenous spread from the pharynx to a chronic subdural hematoma. Positive cultures were obtained from the primary source, the blood and the subdural space. The patient was discharged with no neurological deficit following surgical drainage and parenteral antibiotics. The incidence, predisposing factors, clinical features, bacteriology, diagnostic procedures, treatment and mortality of subdural empyema are briefly discussed.

Brain Abscess↗