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Biomedical subjects

M I Malik

Publications and source records attributed to M I Malik.

10 recordsLinked to original sources
PubMed2000

A preliminary gene map for the Van der Woude syndrome critical region derived from 900 kb of genomic sequence at 1q32-q41.

Van der Woude syndrome (VWS) is a common form of syndromic cleft lip and palate and accounts for approximately 2% of all cleft lip and palate cases. Distinguishing characteristics include cleft lip with or without cleft palate, isolated cleft palate, bilateral lip pits, hypodontia, normal intelligence, and an autosomal-dominant mode of transmission with a high degree of penetrance. Previously, the VWS locus was mapped to a 1.6-cM region in 1q32-q41 between D1S491 and D1S205, and a 4.4-Mb contig of YAC clones of this region was constructed. In the current investigation, gene-based and anonymous STSs were developed from the existing physical map and were then used to construct a contig of sequence-ready bacterial clones across the entire VWS critical region. All STSs and BAC clones were shared with the Sanger Centre, which developed a contig of PAC clones over the same region. A subset of 11 clones from both contigs was selected for high-throughput sequence analysis across the approximately 1.1-Mb region; all but two of these clones have been sequenced completely. Over 900 kb of genomic sequence, including the 350-kb VWS critical region, were analyzed and revealed novel polymorphisms, including an 8-kb deletion/insertion, and revealed 4 known genes, 11 novel genes, 9 putative genes, and 3 psuedogenes. The positional candidates LAMB3, G0S2, HIRF6, and HSD11 were excluded as the VWS gene by mutation analysis. A preliminary gene map for the VWS critical region is as follows: [see text] 41-TEL. The data provided here will help lead to the identification of the VWS gene, and this study provides a model for how laboratories that have a regional interest in the human genome can contribute to the sequencing efforts of the entire human genome.

Animals↗
PubMed1997

Characterization of the humoral immune response in heparin-induced thrombocytopenia.

Recent reports indicate that antibodies associated with heparin-induced thrombocytopenia and thrombosis (HITP) are specific for complexes formed between heparin and the heparin-binding, platelet alpha granule protein, platelet factor 4 (PF4). As with other disorders mediated by immune complexes (IC), the characteristics of the involved immunoglobulins could affect the ability of IC to cause symptoms. We therefore studied the class, subclass, and potency of antibodies specific for heparin:PF4 complexes formed by two groups of patients: one with severe thrombocytopenia, with or without thrombosis, and a positive serotonin release assay (SRA) (Group 1) and another with mild or absent thrombocytopenia, absence of thrombosis, and a negative SRA despite having formed antibodies reactive with heparin:PF4 complexes (Group 2). IgG antibodies were more common in the Group 1 patients (100%) than in Group 2 (46%), whereas IgM antibodies were more common in Group 2 (81%) than in Group 1 (42%) (P = 0.009). About half of each group formed IgA antibodies. In each group, the IgG antibodies were predominantly IgG1 (82%); 42% were IgG3. Only one IgG2 antibody was identified in a total of 52 antibody formers. Antibodies of the IgG class were consistently of higher titer in Group 1 patients than in Group 2 patients (P < 0.001). Recent reports suggest that the H131 form of the Fc gammaRII receptor, which binds preferentially to IgG2 Fc, is found with greater than expected frequency in patients with HITP. Identification of only one IgG2 antibody among 38 antibodies of the IgG class argues against a unique role for antibodies of this subclass in the pathogenesis of HITP. The finding that titers of antibodies in Group 1 patients were a significantly higher titer than in Group 2 patients suggests that development of the full-blown HITP syndrome may require the formation of antibodies of unusually high titer.

Aged↗
PubMed1997

Increased urinary excretion of 3-hydroxyisovaleric acid and decreased urinary excretion of biotin are sensitive early indicators of decreased biotin status in experimental biotin deficiency.

To assess the utility of various indicators of biotin status, marginal biotin deficiency was induced experimentally in normal adults. Ten subjects consumed a diet that contained enough avidin to bind seven times more biotin than that in the diet. Blood and 24-h urine samples were collected before the diet began and twice weekly thereafter for 20 d. The urinary excretion and serum concentration of biotin and its two principal inactive metabolites bisnorbiotin and biotin sulfoxide were determined after HPLC separation with an avidin-binding assay. The urinary concentration of 3-hydroxyisovaleric acid, an indicator of reduced activity of a biotin-dependent enzyme, was quantitated by gas chromatography-mass spectrometry. The urinary excretion of 3-hydroxyisovaleric acid increased significantly (P < 0.0001). For all subjects, the urinary excretion of both biotin and bisnorbiotin decreased significantly (P < 0.0001 for each). In contrast, the mean serum concentration of biotin did not decrease significantly (P = 0.06). These data provide evidence that the urinary excretion of 3-hydroxyisovaleric acid and the urinary excretion of biotin are early and sensitive indicators of biotin deficiency and that the serum concentration of biotin is not.

Adult↗
PubMed1992

Distribution of biotin in human plasma: most of the biotin is not bound to protein.

Estimates of the plasma concentration of biotin differ considerably. Variation in detectability of biotin bound covalently to protein is one potential source of disagreement. In this study we determined the amount of biotin covalently bound to plasma protein. First, greater than 99% of free and reversibly bound biotin was removed by dialysis; then greater than 90% of covalently bound biotin was released by acid hydrolysis. For plasma samples from 11 normal adults, the ratio of covalently bound biotin to free biotin was 0.15 +/- 0.09 (mean +/- SD). Taking into account the additional biotin that is reversibly bound to protein, this study provides evidence that approximately 12% of total biotin in plasma is covalently bound, 7% is reversibly bound, and 81% is free. We conclude that covalently bound biotin cannot account for the reported sixfold increase in biotin detected after acid hydrolysis. We speculate that the reported increase was an artifact caused by substances produced during acid hydrolysis of plasma.

Adult↗
PubMed1992

A case of percutaneous industrial methanol toxicity.

Methanol (CH3OH) is a chemical feedstock of increasing importance as well as a commonly used solvent. In the early 1980s methanol production was introduced at a new petrochemical complex in the Saudi port of Jubail. A case is presented of a consultant supervising tank cleaning prior to methanol loading. He wore positive pressure breathing apparatus but no protective clothing. After 2-3 hours working in the confined space of the tank, he worked on deck and continued to wear his methanol-soaked clothing which eventually dried out. Visual symptoms of acute methanol toxicity presented some 8 hours after exposure. The appropriate treatment (with ethanol provided by the ship bond) was carried out in hospital and the individual recovered completely. Most reported cases of methanol toxicity are social in origin, arising from ingestion. This particular case, though unusual, does present some interesting lessons.

Adult↗
PubMed1990

Syringomyelia presenting as cricopharyngeal pseudostricture.

A 14-year-old boy was referred for evaluation of a cervical esophageal "stricture" diagnosed by upper gastrointestinal radiograph, which had been performed for evaluation of dysphagia and dysphonia of several months' duration. Neurological examination revealed several cranial nerve abnormalities and hyperreflexia, raising the suspicion of a cervicomedullary junction lesion. However, computed tomography of the head, neck, and spine was completely normal. Findings on the swallowing videofluoroscopy were interpreted as consistent with a stricture (a "tight constriction distal to the pyriform sinus"). However, no evidence for this was found by either esophagoscopy or esophageal manometry, which revealed a low-pressure cervical esophageal sphincter. Neurologic evaluation was pursued with magnetic resonance imaging, which revealed a large syrinx extending from C2 to T2 segments. We report this case to point out the importance of considering neurologic disease in the differential diagnosis of "stricture" of the cervical esophagus.

Adolescent↗
PubMed1986

T-cell chronic lymphocytic leukemia with pure red cell aplasia: laboratory demonstration of persistent leukemia in spite of apparent complete clinical remission.

A 40-year-old woman presented with splenomegaly, macrocytic anemia, and red cell aplasia. Although lymphocytosis was absent in the peripheral blood, large atypical lymphoid aggregates were present in the bone marrow. Splenectomy resulted in partial remission of red cell aplasia, but a gradual increase in the number of peripheral blood lymphocytes followed during the next 36 months. Flow cytometric analysis demonstrated that the majority of these peripheral blood lymphocytes had suppressor, natural killer T-cell phenotype. No other treatment was given until red cell hypoplasia worsened 42 months after initial presentation. Repeat bone marrow evaluation again demonstrated severe erythroid hypoplasia and large abnormal lymphocytic infiltrates. Cyclophosphamide given for 8 months resulted in complete resolution of the red cell aplasia and complete clinical remission of CLL. However, flow cytometric analysis revealed persistent increase in bone marrow T-cells, and bone marrow co-culture studies demonstrated residual ability of peripheral blood mononuclear cells to inhibit erythropoiesis in vitro, suggesting that residual, clinically undetectable leukemia persists in spite of complete clinical remission.

Adult↗
PubMed1984

Cardiopulmonary bypass for patients with previously documented heparin-induced platelet aggregation.

Heparin-dependent intravascular coagulation is a widely recognized syndrome in which heparin acts as a hapten for an antiplatelet antibody and causes accelerated intravascular thrombosis and thrombocytopenia that may culminate in organ loss, hemorrhagic diathesis, and even death. Diagnosis is made in vitro by observing heparin-stimulated aggregation of normal platelets suspended in the patient's platelet-poor plasma. Treatment consists of cessation of heparin and use of antiaggregating agents with or without warfarin sodium. Management of patients with prior heparin-dependent intravascular coagulation who require cardiopulmonary bypass has not been reported. We now have successfully managed three such patients and herein present guidelines for management. Each patient was undergoing heparin therapy and manifested hallmark heparin tachyphylaxis, thrombocytopenia, and increased thrombotic symptoms (further venous thrombosis after cardiac catheterization in two cases and exacerbation of unstable angina in the other). In vitro aggregation studies were abnormal. Heparin was stopped, and antiaggregative therapy was begun with good response in each instance. In vitro studies were done serially until the antiplatelet antibody reaction had vanished (usually 4 to 8 weeks), and coronary revascularization was then conducted with full heparinization. Further heparin exposure postoperatively was avoided. There was no perioperative evidence of intravascular thrombosis or bleeding diathesis, and in vitro heparin-dependent aggregation did not recur. We conclude that patients with previously documented heparin-dependent intravascular coagulation can safely sustain the massive heparin rechallenge of cardiopulmonary bypass, provided that in vitro aggregation has ceased and rechallenge therapy is not prolonged.

Aged↗