Identification of seven novel HLA class I alleles in New Zealand.

Seven new HLA class I alleles have been identified in the New Zealand population in the process of routine HLA typing and they are described here. Unusual bead positivity in Luminex typing identified potential new alleles in a bone marrow registry donor (B*40:285) and two HIV patients prior to abacavir prescription (B*14:02:09, B*41:29). In addition, four new class I alleles were identified through class I sequencing-based typing (SBT) outside of exons 2 and 3. One mutation was identified in exon 4 (new allele C*12:125) and three have been found in exon 5, an exon rarely sequenced. Two stem cell transplant recipients (B*07:02:45, C*03:279) had novel mutations in exon 5 and one was found in exon 5 of a potentially matched unrelated donor from DKMS, previously thought to be B*40:02:01 (B*40:303).

The internal quaternary ammonium receptor site of Shaker potassium channels.

Quaternary ammonium (QA) compounds inhibit K+ conductance by entering and occluding the open pore of voltage-activated K+ channels. We characterized the effects of a series of alkyl-triethylammonium blockers on the Shaker K+ channel and tested them on a series of site-directed mutants of the channel protein in order to define the structural features of the binding sites. We found that mutations in two regions of the channel protein, the pore (P) region and the last transmembrane sequence (S6), appear to alter QA binding, not through their effects on gating but perhaps through direct effects on the binding site. Several mutations in the P region affect tetraethylammonium binding but have minimal effects on longer blockers, suggesting that the hydrophobic tail contributes to binding in a nonadditive fashion. Binding of the longer blockers can be affected by varying the hydrophobicity of 1 residue within S6 by site-specific substitution, in a manner consistent with a direct hydrophobic interaction between the side chain at this site and the alkyl chains of the blocker.

Prevalence and significance of white-coat hypertension and masked hypertension in type 2 diabetics.

OBJECTIVES: To explore the prevalence of various categories of hypertension in diabetic patients, and assess any corresponding associations with end-organ complications. DESIGN: Cross-sectional study. SETTING: Tertiary centre of a regional hospital in Hong Kong. PATIENTS: All ambulatory type 2 diabetic patients attending our clinics from January 2002 to November 2004 were invited to participate in the protocol. RESULTS: A total of 133 diabetic patients were included; 82 had normal clinic blood pressures, 15 (18%) of whom had masked hypertension, the remaining 67 (82%) had 'normotension'. The remaining 51 patients had high clinic blood pressures, of whom 28 (55%) had white-coat hypertension and 23 (45%) had sustained hypertension. Urinary albumin excretion rate was higher in patients with masked hypertension (10 mg/day; range, 7-580 mg/day) and sustained hypertension (7 mg/day; 7-3360 mg/day) in comparison to those with white-coat hypertension (7 mg/day; 7-109 mg/day) or 'normotension' (7 mg/day; 7-181 mg/day) [P<0.01]. Likewise, the prevalence of albuminuria was significantly higher in patients with masked hypertension (40%) and sustained hypertension (26%) than in those with 'normotension' (6%) and white-coat hypertension (11%) [P<0.01]. The prevalence of left ventricular hypertrophy was significantly higher in subjects with masked hypertension (38%) and sustained hypertension (26%) compared to patients with 'normotension' (8%) or white-coat hypertension (11%) [P<0.01]. Left ventricular diastolic dysfunction was more prevalent in patients with masked hypertension (46%), sustained hypertension (48%), and white-coat hypertension (43%) in comparison to subjects with 'normotension' (18%) [P=0.01]. CONCLUSION: Masked hypertension is associated with a higher prevalence of albuminuria, left ventricular diastolic dysfunction, and hypertrophy. White-coat hypertension carries a more benign prognosis than sustained hypertension and masked hypertension. Our cross-sectional study supports the recommendation to performing ambulatory blood pressure measurements in type 2 diabetic patients.

Use of lithium in the treatment of thyrotoxicosis.

OBJECTIVES: To evaluate the efficacy and safety of lithium in the treatment of thyrotoxicosis, and to study the dose and serum levels at which therapeutic response occurs. DESIGN: Retrospective study. SETTING: Thyroid clinic of a regional hospital in Hong Kong. PATIENTS: Thirteen patients with thyrotoxicosis pending therapy with radioiodine or surgery, in whom thionamides were contra-indicated due to adverse reactions or failure of treatment. MAIN OUTCOME MEASURES: Free thyroxine levels, time to euthyroidism, and side-effects of lithium. RESULTS: A satisfactory response, defined as a fall by 40% or more in free thyroxine levels and clinical improvement, was achieved in eight patients within 1 to 2 weeks of lithium therapy. In four others, response occurred in 3 to 5 weeks. Response was slow and inadequate in one patient due to 'escape'. The median dosage of lithium was 750 mg daily, with a range of 500 to 1500 mg daily. The median serum lithium level was 0.63 mmol/L. Lithium toxicity was observed in one patient. CONCLUSIONS: A relatively low dose of lithium offers a safe and effective alternative means of controlling thyrotoxicosis in patients who cannot tolerate or do not respond to thionamides.

The role of Langerhans cells and keratinocytes in epidermal immunity.

The immunology of the epidermis has received considerable study over recent years. After the antigen-presenting capacity of epidermal Langerhans cells was confirmed, subsequent studies suggested that keratinocytes could modulate certain immunologic events through production of a cytokine, epidermal cell-derived thymocyte-activating factor (ETAF). Most recently, a murine epidermal cell population, the dendritic Thy-1-positive cell, has been shown to possess natural killer-cell-like activity. In this review, the biology of these cell types are discussed. A discussion of allergic contact hypersensitivity and its alteration by ultraviolet light is used to illustrate some of the complex control mechanisms that continue to be the subject of ongoing study.

Medullary thyroid carcinoma in Hong Kong Chinese patients.

OBJECTIVE: To study the clinical parameters and treatment outcome of medullary thyroid carcinoma in Hong Kong Chinese patients. DESIGN: Retrospective study. SETTING: Regional oncology unit, Hong Kong. PATIENTS: Patients with medullary thyroid carcinoma who were identified among 1656 patients with thyroid malignancies seen in a single institute in Hong Kong from January 1960 to June 2003. MAIN OUTCOME MEASURES: Ten-year cause-specific survival, locoregional failure-free survival, and distant metastasis failure-free survival. RESULTS: Twenty-two (1.3%) patients with medullary thyroid carcinoma were identified. The mean age at diagnosis was 43.7 (standard deviation, 16.5) years. The sex ratio was 1:1. The 10-year cause-specific survival, locoregional failure-free survival, and distant metastasis failure-free survival were 75.4%, 82.0%, and 62.4%, respectively. Lymph node metastasis was present in seven (31.8%) patients at diagnosis. Distant metastasis developed in nine (40.9%) patients: lung, 3 (13.6%); bone, 5 (22.7%); liver, 2 (9.1%); mediastinum, 4 (18.2%). Seven (31.8%) patients died of distant metastasis. Mediastinal (n=3) and bone metastases (n=3) were important causes of death. Genetic study confirmed multiple endocrine neoplasia type 2A in 3 (25.0%) of 12 patients who all had bilateral and multifocal diseases. Younger age (<45 years) was associated with better survival, better locoregional control, and less distant metastasis. Patients with pT1N0 disease (n=3) had an excellent prognosis: all were disease-free following total thyroidectomy. Among eight patients who received external radiation therapy, seven achieved good locoregional control. In seven patients with lymph node metastasis, external radiation therapy gave 100% (4/4) locoregional control compared with 33.3% (1/3) in those without external radiation therapy. Chemotherapy using dacarbazine and 5-fluorouracil was tried in three patients with poor response. CONCLUSIONS: Early stage (T1N0) medullary thyroid carcinoma is associated with a very good prognosis. Postoperative external radiation therapy can achieve good locoregional control in patients with lymph node metastasis or locally advanced disease.

Combined orbital irradiation and systemic steroids compared with systemic steroids alone in the management of moderate-to-severe Graves' ophthalmopathy: a preliminary study.

OBJECTIVE: To assess the efficacy and safety of combined orbital irradiation and systemic steroids in the management of moderate-to-severe Graves' ophthalmopathy. DESIGN: Single-blind randomised prospective study. SETTING: Regional hospital, Hong Kong. PATIENTS: Sixteen patients with active moderate-to-severe Graves' ophthalmopathy who were randomly assigned to steroid therapy (ST group) or combination therapy of orbital irradiation and systemic steroids (SRT group) between June 2000 and June 2003. MAIN OUTCOME MEASURES: NOSPECS scoring system, total eye score, subjective eye score, and extra-ocular muscle thickness as determined by either computed tomographic or magnetic resonance imaging scans. RESULTS: The study was completed by 15 of 16 patients. Both groups experienced improvement in total eye score, soft tissue swelling, ocular motility, visual acuity, and subjective eye score at 52-week follow-up. Total eye score improved earlier in the SRT group, achieving statistical significance (P<0.05) at as early as 4 weeks of follow-up. Improvement in ocular parameters was greater and led to a significantly greater reduction in total eye score than in the ST group at weeks 16, 24, and 52. Maximum extra-ocular muscle thickness was significantly reduced in the SRT group only. No change was observed in proptosis in either group. No serious adverse effect was observed with the addition of orbital irradiation to steroid therapy. CONCLUSION: A combination of orbital irradiation and systemic steroids is well tolerated and more effective than steroids alone in the treatment of active moderate-to-severe Graves' ophthalmopathy. It achieves greater and more rapid improvement in soft tissue swelling, ocular motility, and visual acuity.

Physical and biological properties of cationic triesters of phosphatidylcholine.

The properties of a new class of phospholipids, alkyl phosphocholine triesters, are described. These compounds were prepared from phosphatidylcholines through substitution of the phosphate oxygen by reaction with alkyl trifluoromethylsulfonates. Their unusual behavior is ascribed to their net positive charge and absence of intermolecular hydrogen bonding. The O-ethyl, unsaturated derivatives hydrated to generate large, unilamellar liposomes. The phase transition temperature of the saturated derivatives is very similar to that of the precursor phosphatidylcholine and quite insensitive to ionic strength. The dissociation of single molecules from bilayers is unusually facile, as revealed by the surface activity of aqueous liposome dispersions. Vesicles of cationic phospholipids fused with vesicles of anionic lipids. Liquid crystalline cationic phospholipids such as 1, 2-dioleoyl-sn-glycero-3-ethylphosphocholine triflate formed normal lipid bilayers in aqueous phases that interacted with short, linear DNA and supercoiled plasmid DNA to form a sandwich-structured complex in which bilayers were separated by strands of DNA. DNA in a 1:1 (mol) complex with cationic lipid was shielded from the aqueous phase, but was released by neutralizing the cationic charge with anionic lipid. DNA-lipid complexes transfected DNA into cells very effectively. Transfection efficiency depended upon the form of the lipid dispersion used to generate DNA-lipid complexes; in the case of the O-ethyl derivative described here, large vesicle preparations in the liquid crystalline phase were most effective.

Epidermal Langerhans cell density and contact sensitivity in young and aged BALB/c mice.

The loss of tissue and organ function with age may depend on the inability of old cells to carry out specialized functions. Like other systems in the body, the immune system deteriorates with age. Over the past 10 years it has become clear that the skin can play an active role in immunological processes. In this report we evaluated changes in murine cutaneous immunity with age. Studies in humans had shown a decreased Langerhans cell density with age, but it is difficult to control for the effect of ultraviolet light in human studies. Since ultraviolet light has a significant effect on Langerhans cells, we chose to evaluate the effect of age on Langerhans cell density using inbred mice not exposed to ultraviolet light. Cutaneous immunity was examined phenotypically by studying Langerhans cell density and functionally by studying allergic contact sensitivity. Langerhans cell density was assessed in epidermal sheets prepared from ear skin of mice and examined by ATPase histochemistry and fluoresceinated anti-Ia staining. With both methods, aged (18 months old) mice had approximately two-thirds the number of Langerhans cells that young (10-12 weeks old) animals did. Allergic contact sensitivity response to trinitrochlorobenzene (TNCB) was compared between aged and young animals. Although the aged animals demonstrated increased variability in their responsiveness, there was no overall difference in this example of cutaneous immunoreactivity between the two age groups.

Simultaneous in situ detection of IgE receptors and cytoplasmic granules in murine cutaneous mast cells.

A method is described for the simultaneous in situ detection of surface receptors and cytoplasmic granules in mast cells of frozen sections of mouse skin. Surface IgE receptors are detected after saturation of the receptors with a murine monoclonal antibody of IgE isotype. The latter is subsequently detected by monospecific rabbit anti-mouse IgE (purified on protein A-Sepharose) followed by FITC-conjugated goat anti-rabbit IgG. Cytoplasmic granules are localized by staining with TRITC-avidin conjugate. Normal cutaneous mast cells show green surface fluorescence and red intracellular granules. The method is specific for mast cells; other cells with Fc receptors for IgE are not seen. This method should be useful in the study of situations in which mast cells may have become degranulated.

O-ethylphosphatidylcholine: A metabolizable cationic phospholipid which is a serum-compatible DNA transfection agent.

1,2-dioleoyl-sn-glycero-3-ethylphosphocholine was prepared in a one-step reaction from phosphatidylcholine by reaction with ethyl trifluoromethanesulfonate. This and related O-alkyl phosphatidylcholines constitute the first chemically stable triesters of biological lipid structures and the first cationic derivatives of phospholipids consisting entirely of biological metabolites linked with ester bonds. The complex of cationic phospholipid and plasmid DNA transfected cells with high efficiency. Maximum efficiency of transfection was obtained with complexes in which the positive charge was a few percent in excess over the negative charge. Modest stimulation of transfection of common cell lines was obtained by continuous culture in the presence of 10% serum. Incubation of the phospholipid complex for at least 2 h at 37 degrees C in nearly pure serum had no deleterious effects on transfection efficiency. The lipid has low toxicity; BHK cells tolerated amounts of 2 mg/2 x 10(6) cells at concentrations of 1 mg/mL. The lipid is biodegradable; it was hydrolyzed by phospholipase A(2) in vitro and was metabolized with a half-life of a few days in cells in culture. The synthetic route to cationic phospholipids is well suited to the preparation of derivatives that are tailor-made to have a wide variety of different properties.

A Chinese family with familial dysalbuminaemic hyperthyroxinaemia.

We report the results of biochemical and genetic studies in a Chinese family with familial dysalbuminaemic hyperthyroxinaemia. Total thyroxine levels were 1.2 to 1.7 times the upper limit of the reference range and free thyroxine levels were 1.2 to 1.6 times the upper reference limit. Concentrations of thyroid-stimulating hormone (thyrotropin) and free tri-iodothyronine were normal in all family members tested. Overall, thyroid function tests showed high total thyroxine levels in five males and two females over two generations in the family. The diagnosis of familial dysalbuminaemic hyperthyroxinaemia was confirmed by the detection of a guanine to adenine missense mutation in the second nucleotide of codon 218 of the gene encoding human serum albumin, showing that the mutation in this family is the same as that previously found in Caucasian populations.

A case of giant malignant phaeochromocytoma.

Malignant phaeochromocytoma is defined as the presence of tumour deposits at sites that are normally devoid of chromaffin cells. We report on a 63-year-old man who had a giant malignant phaeochromocytoma of the right adrenal gland that encased the inferior vena cava. The urinary excretion rates of catecholamines and their metabolites were normal, except for normetanephrine, which was excreted at a higher rate than normal. The tumour was surgically unresectable by laparotomy. Postoperatively, the patient was given a 4-month trial of subcutaneous octreotide and intravenous meta-iodobenzylguanidine I 131. Occult lung secondary tumours were first detected by meta-iodobenzylguanidine scintigraphy after 2 years, and the patient died of bone and lung metastases 1 year later. Because phaeochromocytoma is rare, local experience in managing this disease is limited. This report alerts physicians of the methods of diagnosing and managing surgically unresectable malignant phaeochromocytoma.

A patient with an increased troponin level without evidence of ischaemic cardiac injury.

A 74-year-old man was admitted for chest infection with acute exacerbation of chronic obstructive pulmonary disease. He was incidentally found to have an increased serum level of cardiac troponin I, despite the absence of symptoms and electrocardiographic evidence of ischaemic heart disease. Troponin I became undetectable after the serum was treated with polyethylene glycol, which removed any interfering antibodies. Serum cardiac troponin T was also undetectable after this treatment. Interference of the cardiac troponin I assay by heterophilic antibodies was thus confirmed. Because of the possibility of false-positive results due to immunoassay interference, clinicians should be alerted whenever laboratory findings are incompatible with the clinical picture, and should be ready to perform additional laboratory tests.

Primary hyperparathyroidism in Hong Kong: an analysis of 44 cases.

Primary hyperparathyroidism is increasingly being diagnosed subsequent to the detection of hypercalcaemia using multichannel auto-analyser screening. This paper provides a local picture of the clinical presentation and management of primary hyperparathyroidism. A retrospective review was conducted of 44 patients with primary hyperparathyroidism who were treated at the Queen Elizabeth Hospital between January 1987 and July 1996. Twenty-five (56.8%) of the patients were asymptomatic. Only three (6.8%) patients gave radiograms that had features indicating primary hyperparathyroidism; seven (15.9%) had renal stones. The patients underwent one or more of the following localisation procedures: computerised tomography, ultrasonography, thallium-technetium subtraction scanning, and technetium Tc 99m sestamibi scanning. The latter method was the most sensitive (64.3%). Ten adenomas that could not be localised by any of these procedures were successfully removed during surgery. Surgery was successful in 94.4% of cases and surgical outcome was comparable to that reported in the literature.

Use of the low-dose corticotropin stimulation test for the diagnosis of secondary adrenocortical insufficiency.

OBJECTIVE: To assess the clinical utility and safety of the low-dose corticotropin stimulation test in the diagnosis of secondary adrenocortical insufficiency. DESIGN: Prospective study. SETTING: Regional hospital, Hong Kong. PARTICIPANTS: Seventy-two Chinese patients with suspected secondary adrenocortical insufficiency. MAIN OUTCOME MEASURE: Serum cortisol response during the low-dose corticotropin stimulation test, using the insulin tolerance test as the gold standard. RESULTS: The 30-minute cortisol level during the low-dose corticotropin stimulation test was most closely correlated (r=0.79) with the peak cortisol level achieved during the insulin tolerance test. The optimum sensitivity and specificity of the low-dose corticotropin stimulation test were obtained at a cut-off value of 550 nmol/L or more for the 30-minute cortisol level. Using the insulin tolerance test as the gold standard for comparison, the low-dose corticotropin stimulation test had a sensitivity of 97%, a specificity of 78%, a positive predictive value of 81%, and a negative predictive value of 97% at this cut-off value. The positive likelihood ratio was 4.4 and the negative likelihood ratio 0.04. CONCLUSION: The low-dose corticotropin stimulation test, using the cortisol response at 30 minutes after synacthen 1 microg is a safe, convenient, and sensitive method for screening abnormalities of the hypothalamic-pituitary-adrenocortical axis in Chinese patients suspected of having secondary adrenocortical insufficiency.

Consensus statement on iodine deficiency disorders in Hong Kong.

This article reviews the available data on the study of iodine deficiency disorders in Hong Kong and to discuss the approach towards preventing such disorders in Hong Kong. The importance of iodine and iodine deficiency disorders is described, and the available data on the dietary iodine intake and urinary iodine concentration in different populations of Hong Kong are summarised and discussed. Dietary iodine insufficiency among pregnant women in Hong Kong is associated with maternal goitrogenesis and hypothyroxinaemia as well as neonatal hypothyroidism. Borderline iodine deficiency exists in the expectant mothers in Hong Kong. Women of reproductive age, and pregnant and lactating women should be made aware and educated to have an adequate iodine intake, such as iodised salt, as an interim measure. A steering group involving all stakeholders should be formed to advise on the strategy of ensuring adequate iodine intake, including universal iodisation of salt in Hong Kong. Continuous surveillance of iodine status in the Hong Kong population is necessary.

Tetraethylammonium blockade distinguishes two inactivation mechanisms in voltage-activated K+ channels.

Voltage-activated K+ channels are a family of closely related membrane proteins that differ in their gating behavior, conductance, and pharmacology. A prominent and physiologically important difference among K+ channels is their rate of inactivation. Inactivation rates range from milliseconds to seconds, and K+ channels with different inactivation properties have very different effects on signal integration and repetitive firing properties of neurons. The cloned Shaker B (H4) potassium channel is an example of a K+ channel that inactivates in a few milliseconds. Recent experiments have shown that removal of an N-terminal region of the Shaker protein by site-directed deletion practically abolishes this fast inactivation, but the modified channel does still inactivate during a prolonged depolarization lasting many seconds. Here we report that this remnant inactivation must occur by a distinct mechanism from the rapid inactivation of the wild-type Shaker channel. Like the inactivation of another K+ channel [Grissmer, S. & Calahan, M. (1989) Biophys. J. 55, 203-206], this slow inactivation is retarded by the application of a channel blocker, tetraethylammonium, to the extracellular side of the channel. By contrast, the fast inactivation of the wild-type Shaker channel is sensitive only to intracellular application of tetraethylammonium. Intracellular tetraethylammonium slows down the fast inactivation process, as though it competes with the binding of the inactivation particle.

Cutaneous mast cell depletion and recovery in murine graft-vs-host disease.

Mast cells as studied by light microscopy with metachromatic staining, have been noted to "disappear" from the skin of mice with chronic graft-vs-host disease (GVHD) produced across minor histocompatibility barriers. This mast cell disappearance is accompanied by ultrastructural evidence of loss of granule contents. In this study, we followed cutaneous mast cells in chronic GVHD over 9 mo by three methods: Light microscopy of toluidine blue-stained sections showed that mast cells not seen at day 42 reappeared between days 94 and 125, were supramaximal at days 146 and 164, and returned to normal levels at days 195 and 280. Double immunofluorescent staining of mast cells for the presence of surface IgE receptors and cytoplasmic granules (avidin) revealed IgE receptor-bearing cells that lacked avidin-binding granules at the time when mast cells were not apparent on light microscopy. By electron microscopy, reappearing mast cells have the morphology of immature dermal mast cells. Ultrastructural abnormalities of mast cells persist some 150 days after GVHD induction. The possible relationship of these mast cell changes to the development of dermal fibrosis in chronic GVHD is discussed.