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Biomedical subjects

K Y Fong

Publications and source records attributed to K Y Fong.

At least 19 recordsLinked to original sources
PubMed1992

Homozygous hereditary C3 deficiency due to a partial gene deletion.

The molecular mechanism of C3 deficiency in an Afrikaans patient with recurrent pyogenic infections was studied. Restriction enzyme analysis showed a gene deletion of 800 base pairs (bp) mapping to the alpha chain of C3. Amplification of genomic DNA, using the PCR, demonstrated that the deletion included exons 22 and 23 of the C3 gene. Truncated mRNA was shown in an Epstein-Barr virus-transformed B-cell line by PCR amplification of first-strand cDNA. A consequence of this deletion was that the RNA transcribed 3' to the deletion was out of frame, resulting in formation of a stop codon 19 bp downstream from the deletion. The molecular basis of the deletion was compatible with homologous recombination between two Alu sequences located in introns 21 and 23. An unrelated nonconsanguineous relative and two of a sample of 174 Afrikaans-speaking individuals were heterozygous carriers of the same gene deletion. The wide prevalence of this null allele in this population is probably due to the effects of a small founder population. The presence of this deletion in the C3 gene is not compatible with production of any functional C3, supporting the idea that study of such patients offers a valid model for understanding physiological activities of C3 in vivo in humans.

Base Sequence↗
PubMed1992

Anticardiolipin antibodies, haemolytic anaemia and thrombocytopenia in systemic lupus erythematosus.

Anticardiolipin antibody (ACA) levels were determined in 17 Asian female SLE patients with autoimmune haemolytic anaemia (AIHA) and 29 Asian female SLE inpatients without AIHA (control patients). Both IgG and IgM isotypes were measured by ELISA. Elevated IgM APA titres (greater than 5 SD of normal health controls) were seen in 11 (64.7%) of 17 AIHA patients and six (20.7%) of 29 control patients (P less than 0.01). There was no significant difference in IgG ACA titres between the two groups. Thrombocytopenia was present in 11 (64.7%) of the AIHA patients and nine (31%) of the control patients (P less than 0.05). None of the control SLE patients with thrombocytopenia had raised IgM ACA levels and only one had an elevated IgG ACA titre. Autoimmune haemolytic anaemia occurring in the context of SLE frequently associated with the concomitant presence of thrombocytopenia (Evan's syndrome) and with the presence of ACA.

Anemia, Hemolytic, Autoimmune↗
PubMed1992

Treatment of idiopathic hemifacial spasm with botulinum toxin.

Twelve patients with idiopathic hemifacial spasm received treatment with botulinum toxin A over a period of 18 months. Of 76 treatments given, most (94.7%) led to successful relief of eyelid spasms and all treatments were successful for perioral and lower facial muscle spasms. An average dose of 9.3 units of toxin per session was given to produce a mean interval of relief of 10.8 weeks. Blepharoptosis was the only ocular side effect; it was mild, reversible and occurred in 2 patients. However, lower facial palsy was frequent (9 patients); it was mild to moderate in severity but only partially reversible in 8 patients. Dosage for lower facial muscles should therefore be reduced.

Adult↗
PubMed1992

Vascular pseudoparkinsonism.

Vascular pseudoparkinsonism may be confused with idiopathic Parkinson's disease. Patients may be unnecessarily treated with anti-parkinsonian drugs while their underlying vascular disease is ignored. We investigated 250 parkinsonian patients seen in our Movement Disorders Clinic for a possible vascular etiology. After excluding those with a known secondary cause such as drug-induced parkinsonism, progressive supranuclear palsy, multiple system atrophy and hyperparathyroidism, brain computed tomography and/or magnetic resonance imaging were performed on those who showed poor or no response to levodopa. In those with an ischemic lesion demonstrated on neuroimaging, anti-parkinsonian drugs were stopped and the patients were reassessed. Eleven patients (4.4%) had ischemic brain lesions accounting for their parkinsonism. All were initially diagnosed as Parkinson's disease because of the prominence of bradykinesia and rigidity. Gait disturbance was also common, but resting tremor was distinctly absent. Three anatomical patterns with different prognosis were identified. Three patients with basal ganglia lacunar infarct recovered spontaneously, three with frontal lobe infarcts remained static and five with periventricular and deep subcortical white matter lesions had progressive deterioration. Autopsy in one patient confirmed bilateral frontal lobe watershed infarcts and the absence of brain stem Lewy bodies. Parkinsonian patients with poor or no response to levodopa therapy should be investigated for a vascular etiology.

Aged↗
PubMed1992

Treatment of acute cerebral hemorrhage with intravenous glycerol. A double-blind, placebo-controlled, randomized trial.

BACKGROUND AND PURPOSE: Hitherto, treatment of acute cerebral hemorrhage with intravenous glycerol has not been evaluated in rigorous clinical studies with sufficient patient numbers. METHODS: We undertook a double-blind, stratified and randomized, placebo-controlled clinical trial. Only patients with a first stroke admitted to the hospital within 24 hours after onset of symptoms were recruited, provided computed tomography confirmed hemorrhage and informed consent was obtained. After stratification into alert, semicoma, and coma subgroups using the Glasgow Coma Scale, 107 patients received active treatment (500 ml of 10% glycerol in saline by intravenous infusion over 4 hours on 6 consecutive days) and 109 were given corresponding saline treatment. Using a variety of objective scoring systems, patients were followed up for up to 6 months. RESULTS: At follow-up, all measures of outcome in the treated and control groups were very similar. At 6 months, respective mortality rates were 37 of 107 and 33 of 109. Corresponding mean +/- SD improvements in Scandinavian Stroke Study Group scores were 8.35 +/- 16.9 versus 11.55 +/- 15.6 (long-term) and 0.64 +/- 7.3 versus 2.40 +/- 6.9 (prognostic), and improvements in the Barthel Index ratings were 10.72 +/- 24.7 versus 13.95 +/- 23.3, respectively. Glasgow Coma Scale score improvements in the survivors were 0.81 +/- 1.5 and 1.16 +/- 1.7 in the treated and control groups, respectively. Hemolysis (generally subclinical) was the only adverse effect of glycerol noted. CONCLUSIONS: In the absence of any clinically or statistically significant difference in outcome between the treated and control groups, this trial provides no justification for glycerol therapy following acute cerebral hemorrhage.

Acute Disease↗
PubMed1992

Postinfectious myelitis, encephalitis and encephalomyelitis.

Six cases of post-infectious encephalomyelitis are described. A preceding non-specific viral-like illness occurred 4 to 20 days before the onset of the neurological deficits. The clinical syndromes included transverse myelitis, focal encephalitis and encephalomyelitis (each in one case) and diffuse encephalitis in 3. Magnetic resonance imaging appeared to be the investigation of choice. High dose corticosteroids were given to 4 patients who recovered partially or fully. The patient with focal encephalitis had a spontaneous and complete recovery. The remaining patient with diffuse encephalitis died 3 days after the onset; autopsy showed prominent lymphocytic perivascular cuffing in the white matter and lymphocytic infiltration of the meninges.

Adrenal Cortex Hormones↗
PubMed1992

The antiphospholipid syndrome.

The antiphospholipid syndrome (APS) describes an entity characterised by recurrent thrombosis, recurrent spontaneous abortions, thrombocytopenia, and elevated levels of antiphospholipid antibodies (IgG or IgM). The clinical features of APS include manifestations of thrombosis and/or cell damage. There is usually an associated underlying connective tissue disorder. The primary antiphospholipid syndrome refers to the presence of these clinical features without evidence of an associated autoimmune disorder. Detection of these antibodies include the lupus anticoagulant test, VDRL test and assays for anticardiolipin antibodies. Overlapping populations of these antibodies are detected by various immunologic tests. Management is based on the use of immunosuppressives, platelet inhibitors and anticoagulants.

Antiphospholipid Syndrome↗
PubMed1990

Molecular basis of polymorphisms of human complement component C3.

C3 exhibits two common allotypic variants that may be separated by gel electrophoresis and are called C3 fast (C3 F) and C3 slow (C3 S). C3 F, the less common variant, occurs at appreciable frequencies only in Caucasoid populations (gene frequency = 0.20). An increased prevalence of the C3 F allele has been reported in patients with partial lipodystrophy, IgA nephropathy, and Indian childhood hepatic cirrhosis. Studies of the genomic organization of the human C3 gene led to the identification of a single change (C to G) between C3 S and C3 F at nucleotide 364 in exon 3. This leads, at the translation level, to the substitution of an arginine residue (positively charged) in C3 S for a glycine residue (neutral) in C3 F. This substitution results in a polymorphic restriction site for the enzyme HhaI. The resulting restriction fragment length polymorphism (RFLP) was investigated using genomic DNA, amplified using the polymerase chain reaction; there was absolute concordance between the genomic polymorphism and the distribution of C3 S and C3 F in 50 normal subjects. The molecular basis of a second structural polymorphism, defined by the monoclonal antibody HAV 4-1, was also characterized. The polymorphic determinant was identified at codon 314 in the exon 9 of the beta chain where a leucine residue (HAV 4-1+) is substituted for a proline residue (HAV 4-1-). Identification of the amino acid sequences of these polymorphic variants will facilitate characterization of possible functional differences between different allotypes of C3. Three RFLPs (BamHI, EcoRI, and SstI) were located to introns in the C3 gene. There was no allelic association between these three RFLPs, or between the RFLPs and the C3 F/S polymorphic site. Genetic equilibration of these polymorphisms has occurred within a gene of 41 kb.

Antibodies, Monoclonal↗
PubMed1990

Genomic organization of human complement component C3.

Six overlapping clones, spanning the entire C3 gene and the 5' flanking region, were isolated from two genomic lambda libraries. Thirty exons, covering the complete beta chain and part of the alpha chain as far as the C3d region, were analyzed. The full exon-intron organization of the gene was deduced by combining our data with the reported organization of the alpha' chain (Barnum et al., 1989, J. Biol. Chem. 264: 8471-8474). The complete gene is 41 kb and consists of 41 exons. The C3 beta chain spans 13 kb from exon 1 to exon 16. Exon 16 encodes both alpha and beta chains. The alpha chain is 28 kb and contains 26 exons, including exon 16. The 5' flanking region was sequenced up to 514 bases upstream from the ATG start site. The major transcription initiation site was mapped to an adenine residue 61 bases upstream from the signal peptide by primer extension analysis of poly(A)+ mRNA from hepatocytes and U937 cells. The TATA box motif was assigned at position -85. Several putative binding sites for transcription factors were found in the 5' flanking region, suggesting possible pathways for the regulation of the C3 gene.

Base Sequence↗
PubMed1990

Molecular basis of hereditary C3 deficiency.

Hereditary deficiency of complement component C3 in a 10-yr-old boy was studied. C3 could not be detected by RIA of serum from the patient. Segregation of C3 S and C3 F allotypes within the family confirmed the presence of a null gene for C3, for which the patient was homozygous. 30 exons have been characterized, spanning the entire beta chain of C3 and the alpha chain as far as the C3d region. Sequence analysis of the exons derived from the C3 null gene showed no abnormalities in the coding sequences. A GT-AT mutation at the 5' donor splice site of the intervening sequence 18 was found in the C3 null gene. Exons 17-21 were amplified by the polymerase chain reaction (PCR) from first-strand cDNA synthesized from mRNA obtained from peripheral blood monocytes stimulated with LPS. This revealed a 61-bp deletion in exon 18, resulting from splicing of a cryptic 5' donor splice site in exon 18 with the normal 3' splice site in exon 19. This deletion leads to a disturbance of the reading frame of the mRNA with a stop codon 17 bp downstream from the abnormal splice in exon 18. His parents had both the normal and abnormal C3 mRNA and were shown to be heterozygous for this mutation by sequence analysis of genomic DNA amplified by PCR. Similar splice mutants have previously been reported in the beta-globin, phenylalanine hydroxylase, and porphobilinogen deaminase genes. This mutation is sufficient to cause the deficiency of C3 in the patient.

Base Sequence↗
PubMed1989

Clinical efficacy of sulbactam/ampicillin in the treatment of moderately severe bacterial infections.

20 patients with moderately severe bacterial infections were studied to determine the clinical efficacy and safety of parenteral sulbactam/ampicillin. There were 9 female and 11 male patients. Their mean age was 51 years. 8 patients had pneumonia, 5 urinary tract infection, 4 cellulitis of the leg and 3 had pustular tonsillitis. 85% of patients had resolution of fever and symptoms within 48 hours of commencing treatment. 95% had successful treatment outcome. The organisms isolated included E. Coli, Klebsiella sp, Branhamella catarrhalis and Bacillus species. In 2 patients, the organisms isolated demonstrated in-vitro ampicillin resistance. However, they recovered fully with sulbactam/ampicillin therapy. No adverse side-effects were reported and dosage adjustment was not required in the elderly.

Adult↗
PubMed1989

Antinuclear antibodies in systemic lupus erythematosus.

Autoantibodies to the three extractable nuclear antigens (ENA), Anti-SSA (Ro), Anti-Sm, Anti-RNP and antinuclear antibodies were determined in 150 patients with SLE. Seventy patients (46.7%) had Anti-SSA (Ro), 40 (26.7%) Anti-Sm and 25 (16.7%) Anti-RNP antibodies. Ninety four percent patients had a positive Fluorescent anti-nuclear antibody (FANA) test. The commonest FANA pattern is the speckled pattern. Subclinical keratoconjunctivitis sicca (KCS) was present in 60% patients. No correlation could be demonstrated between the presence of ENA autoantibodies and the clinical features of patients.

Adolescent↗
PubMed1988

Pulmonary haemorrhage, pulmonary infarction, and the lupus anticoagulant.

A patient with systemic lupus erythematosus developed pulmonary haemorrhage and pulmonary infarction as rare initial manifestations of her disease. The latter was associated with the presence of the circulating lupus anticoagulant. She recovered with pulse doses of methylprednisolone and plasmapheresis. Anticoagulants were not administered.

Adolescent↗