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Biomedical subjects

S L Chew

Publications and source records attributed to S L Chew.

70 records · Page 4Linked to original sources
PubMed1994

Parvovirus infection causing red cell aplasia and leukopenia in rheumatoid arthritis.

A case of acute parvovirus B19 infection causing fever, anaemia, leukopenia, and red cell aplasia, in a patient with chronic rheumatoid arthritis is described. The patient had received low doses of corticosteroids for several years, and a small dose of methotrexate recently. There was no evidence of haemolytic anaemia, iron deficiency or drug toxicity. Recovery was associated with the development of antibodies against parvovirus B19, and clearance of viraemia as detected by the polymerase chain reaction. Possible mechanisms for the development of leukopenia are discussed, but there was no evidence for haemophagocytosis.

Arthritis, Rheumatoid↗
PubMed1994

Bilateral phaeochromocytomas in von Hippel-Lindau disease: diagnosis by adrenal vein sampling and catecholamine assay.

Three unrelated patients with von Hippel-Lindau disease had phaeochromocytomas diagnosed as a result of screening in their third decade. All had raised 24-h urinary noradrenaline levels and obvious unilateral adrenal tumours on ultrasound scanning and computed tomography. The contralateral adrenal appeared either normal or equivocally abnormal using the same imaging techniques. Radiolabelled meta-iodo-benzylguanidine uptake and enhanced T2-weighted magnetic resonance signals confirmed the ipsilateral lesion, but showed no abnormality in the contralateral adrenal. Nevertheless, venous sampling demonstrated abnormally elevated noradrenaline:adrenaline ratios (normal < 1) in blood draining both adrenals in all three patients. All underwent bilateral adrenalectomy: histological examination confirmed bilateral phaeochromocytomas in all three patients, with the smaller adrenal showing tumours between 3 and 11 mm in diameter. A fourth patient with von Hippel-Lindau disease was also evaluated because of a left 'suprarenal' mass discovered by ultrasound scanning. Urinary and plasma catecholamines were normal. Computed tomography showed a normal right adrenal, with a left para-aortic mass lying superior to the left adrenal. Magnetic resonance scanning showed an enhanced T2 signal from the mass, which also showed positive uptake with radiolabelled mIBG. At operation, a non-secretory left para-aortic paraganglioma was found. Venous sampling suggested that the left adrenal was normal, and this was confirmed on histology. Venous sampling for catecholamine assays is effective in locating small bilateral phaeochromocytomas and defining a normal adrenal gland, and can be useful in preventing unnecessary or repeat operations in patients with non Hippel-Lindau disease.

Adrenal Gland Neoplasms↗
PubMed1993

Urinary enzymes in acute renal failure.

Intestinal-type alkaline phosphatase (IAP) has been localized to the S3 segment of the renal tubule in previous studies, a site believed to be particularly vulnerable to toxic and ischaemic damage. During a 17-month period a pilot study of the value of urinary enzyme measurements (IAP and tissue non-specific alkaline phosphatase--TNAP, using monoclonal antibody-based immunoassays, and N-acetyl-beta-glucosaminidase--NAG, using colorimetric assay) in 50 prospectively followed cases of acute renal failure (ARF) was performed. Urinary enzymes were measured at initial evaluation ('start'), and then each day for 14 days, with the highest enzyme value ('peak') also used for analysis. Patients were divided into prerenal (n = 16), renal (n = 28), postrenal (n = 6) categories according to standard criteria. Of the renal ARF patients 23 of 28 had acute tubular necrosis (ATN), 3 of 28 acute interstitial nephritis (AIN), and 2 of 28 acute glomerulonephritis (AGN); 18 of 50 had a fatal outcome and 1 of 50 was dialysis-dependent at discharge ('poor' prognosis group), while 31 of 50 survived hospital without becoming dialysis-dependent ('good' prognosis group). Median enzyme concentration were increased in 'poor' compared to 'good' prognosis patients: start IAP 3.2 versus 2.2 U/g creat (NS), start NAG 48.6 versus 13.7 (P < 0.01), start TNAP 3.5 versus 0.9 (P < 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylglucosaminidase↗
PubMed1993

Intranasal caffeine and amphetamine causing stroke.

A 37 year-old man with an ischaemic stroke after the nasal use of amphetamine and caffeine is reported. Transient arterial hypertension due to these agents may have been the mediator of the stroke. Mitral annular calcification was the only other abnormality found, and was thought not to play an important role in this patient. There was no evidence of a primary or secondary hypercoagulable state. Stroke due to nasal use of these agents appears not to have been previously reported (Medline literature search 1983-1993).

Administration, Intranasal↗
PubMed1992

Are antiphospholipid antibodies clinically relevant in dialysis patients?

A cohort of 60 stable dialysis patients (56 haemodialysis, 4 continuous ambulatory peritoneal dialysis) was followed for 1 year to determine the relationship between anticardiolipin (aCL) antibodies and lupus anticoagulant (LA), and clinical events. The outcome measures were death, arterial, venous, and fistula thromboses, and fistula repairs. At baseline 15% had antibodies (5/60 IgG aCL, 3/60 LA, and 1/60 had both); 15 patients had a history of arterial thrombosis (1 patient was aCL positive), seven venous thrombosis (1 patient LA positive), 10 fistula thromboses (1 aCL positive); and 21 had a history of fistula repairs (4 aCL positive). Renal diagnosis, age (66.78 versus 59.67 years) and duration of dialysis (38.11 versus 45.25 months) were similar in patients with and without aCL antibodies or LA. Only the sex ratio showed a female predominance in the aCL- or LA-positive patients compared to the negative patients (3M:6F versus 36M:15F), but this was not significant (P = 0.07). After 1 year there were 10 deaths (1 LA positive), 12 thrombotic events in eight patients (none aCL or LA positive), and nine fistula repairs in seven patients (1 aCL-positive patient). We are unable to show higher rates of death, thrombotic event, or fistula repair in dialysis patients with aCL antibodies or LA followed up for 1 year in one centre. The clinical importance of antiphospholipid antibodies in dialysis patients is uncertain.

Adult↗
PubMed1992

Protein kinase C in normal human epidermal keratinocytes during proliferation and calcium-induced differentiation.

Recent evidence has implicated protein kinase C (PKC) in the etiology of hyperproliferative diseases such as psoriasis and non-melanoma skin cancer. In this study, PKC activity, immunoreactive protein, and phorbol ester-binding kinetics were examined in primary cultures of normal human epidermal keratinocytes (NHEK) in order to elucidate the relationship between PKC and NHEK proliferation and differentiation. NHEK were maintained in a proliferative phase in serum-free low-calcium (0.15 mM) medium, and then were exposed to high calcium (1.6 mM) in order to stimulate growth arrest and differentiation. Staurosporine was inhibitory to Ca(++)-induced differentiation. Scatchard analysis of phorbol binding indicated that exposure to high calcium for 24 h increased the number of binding sites (Bmax) by fivefold. In correlation with the ligand-binding results, PKC activity was extremely low in proliferating (low-calcium) NHEK compared to differentiating cells (high calcium). When assayed after 24, 48, and 72 h, high calcium induced tenfold or greater increases in Ca++/phospholipid-dependent phosphotransferase activity. Immunoblot analysis of NHEK PKC using antibodies directed against the hinge region of PKC alpha/beta also indicated that exposure to high calcium resulted in higher levels of immunoreactive protein. Therefore, PKC in NHEK appears to be upregulated under conditions of Ca(++)-induced growth arrest and differentiation. In addition, NHEK and other human skin cell particulate fractions contain a protein of approximately 116 kDa that is highly immunoreactive to an antibody to PKC alpha/beta, which coelutes from DEAE-sephacel under the same buffer conditions as the 80-kDa PKC.

Adult↗
PubMed1992

Erythropoietin resistance due to vitamin B12 deficiency. Case report and retrospective analysis of B12 levels after erythropoietin treatment.

We describe the first reported case of resistance to human recombinant erythropoietin (rhEPO) treatment caused by vitamin B12 deficiency in a chronic hemodialysis patient. Despite a normal B12 level before rhEPO treatment, resistant anemia together with a low B12 level and a megaloblastic bone marrow developed after only 8 months of rhEPO. There was a rapid reticulocyte response to B12 supplements, and transfusion requirements dropped from 2 units monthly to nothing. Atrophic gastritis was diagnosed through endoscopy and biopsy. Because of the fall in B12 level after 8 months of rhEPO treatment, we analyzed the results of routinely measured B12 levels in 30 hemodialysis patients treated with rhEPO, and found the mean B12 levels to be unchanged before and after rhEPO treatment. Although we found screening for B12 deficiency of little benefit, any patient with rhEPO resistance should have B12 levels tested, given the potentially serious extra-hematological effects of B12 deficiency.

Aged↗
PubMed1991

Visceral leishmaniasis in an adult with HIV infection.

We present the first case of visceral leishmaniasis (VL) in a Spanish patient with HIV infection living in Belgium. After four weeks of stibogluconate and zidovudine treatment, the initially low CD4 count improved, and the splenomegaly regressed. VL is becoming frequently reported in association with HIV infection, especially in countries where leishmaniasis is endemic. The apparent effect of VL on the CD4 count may cause problems in the staging of HIV infections.

Adult↗
PubMed1990

Lack of platelet response to collagen associated with an autoantibody against glycoprotein Ia: a novel cause of acquired qualitative platelet dysfunction.

Platelets from a patient with an acquired hemorrhagic disorder had a severely impaired response to collagen, whereas platelet aggregation to other agonists and coagulations tests were normal. No abnormalities of the patient's platelet membrane glycoproteins (GP) were seen. Treatment of the patient with immunosuppressive agents temporarily improved both the bleeding tendency and the collagen responsiveness of the platelets. An IgG was found to be present in the plasma, directed against a protein comigrating with GPIa, and coadsorbing with GPIa to insoluble collagen fibers in a Mg2+(-)dependent manner. Furthermore, GPIa was recognized by the patient's antibody when affinity-purified GPIa-IIa was used as antigen. Finally, the GPIa-IIa complex was immunoprecipitated from a platelet lysate by patient's plasma. In addition, purified platelet specific IgG's from the patient inhibited aggregation of normal platelets induced by collagen or by wheat germ agglutinin. We conclude that the lack of response to collagen of the patient's platelets may well be due to the presence of an autoantibody against GPIa.

Adult↗
PubMed1986

Intelligibility of vowels sung by a countertenor.

Ten American English vowels were sung in a /b/-vowel-/d/ consonantal context by a professional countertenor in full voice (at F0 = 130, 165, 220, 260, and 330 Hz) and in head voice (at F0 = 220, 260, 330, 440, and 520 Hz). Four identification tests were prepared using the entire syllable or the center 200-ms portion of either the full-voice tokens or the head-voice tokens. Listeners attempted to identify each vowel by circling the appropriate word on their answer sheets. Errors were more frequent when the vowels were sung at higher F0. In addition, removal of the consonantal context markedly increased identification errors for both the head-voice and full-voice conditions. Back vowels were misidentified significantly more often than front vowels. For equal F0 values, listeners were significantly more accurate in identifying the head-voice stimuli. Acoustical analysis suggests that the difference of intelligibility between head and full voice may have been due to the head voice having more energy in the first harmonic than the full voice.

Humans↗
PubMed1985

Morpheus revisited.

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Administration, Oral↗