Medical Practitioners Act 2007: the increased medical record burden

New medical record keeping obligations are implemented by the Medical Practitioners Act (2007), effective July 2009. This audit, comprising review of 347 medical entries in 257 charts on one day, investigated compliance with the Act together with the general standard of medical record keeping. The Medical Council requirement was absent all but 3 (0.9%) of entries; there was no unique identifier or signature in 28 (8%) and 135 (39%) of entries respectively. The case for change is discussed.

Prevalence and correlates of depression with atypical symptoms in Hong Kong

OBJECTIVE

Previous studies of atypical depression have been conducted in Western communities. There has been no community-based epidemiological study of atypical depression that covers the entire spectrum of bipolar disorders. The aim of the present study was to examine the 12 month prevalence of atypical depression and the differences in demographic and clinical profiles between depressed patients with and without atypical symptoms in the Chinese adult population of Hong Kong.

METHOD

A random sample of 3016 Chinese adults completed a telephone-based structured interview that examined their 12 month prevalence of major depressive episode. Atypical depression was defined as major depressive episode with hypersomnia and increased weight or appetite. Major depressive episode with and without atypical symptoms were compared on sociodemographic variables, number of depressive and manic/hypomanic symptoms, proportion of having lifetime mania/hypomania, suicidality, family psychiatric history, help-seeking behaviour, level of distress and role impairment.

RESULTS

The 12 month prevalence of atypical depression was 1.3%. Compared to non-atypical depression, atypical depression was associated with female gender, soft (subthreshold) bipolar II disorder, family psychiatric history, higher suicidality, more help-seeking from psychiatrists, and more depressive and manic/hypomanic symptoms. There was no difference in levels of distress or impairment.

CONCLUSIONS

Although limited by the lack of detailed information on comorbidity, bipolar family history, and age of onset, the findings support the hypothesis that atypical depression among Chinese people in Hong Kong exhibited prevalence and correlates similar to those found in Western epidemiological and clinical studies. Further research is warranted to examine its association with hypomania and how atypical depression may occupy a nosological position between typical unipolar depression and bipolar spectrum disorders.

A community survey of the twelve-month prevalence and correlates of bipolar spectrum disorder in Hong Kong

BACKGROUND

Recent community and clinical epidemiological studies have indicated that bipolar spectrum disorder (BSD) is a common illness. No community-based epidemiological study of BSD has been conducted in Chinese and other Asian populations.

METHOD

A random sample of 3016 Chinese adults underwent a telephone-based community survey that examined their twelve-month prevalences of BSD, sociodemographic characteristics, level of distress, and role impairment using the Sheehan Disability Scale. Bipolar I disorder (BP-I) and bipolar II disorder (BP-II) were based on DSM-IV criteria. Soft bipolar II disorder (Soft BP-II) fulfilled the DSM-IV criteria of major depressive episode and hypomanic episode except that the hypomanic/manic symptoms lasted two to three days.

RESULTS

The lifetime prevalences of manic episode, hypomanic episode, and soft hypomanic episode were 2.2%, 2.2%, and 10.7% respectively. The twelve-month prevalences of BP-I, BP-II, and Soft BP-II were 1.4%, 0.5%, and 1.8%, respectively. Respondents with BSD were more likely to be female, younger, and single than those without. Impairment and distress associated with depressive symptoms were similar across the three groups of bipolar disorders, but those associated with manic/hypomanic symptoms were more severe among respondents with BP-I than BP-II and Soft BP-II. The number of manic/hypomanic symptoms and depressive symptoms did not differ across the three bipolar groups.

LIMITATION

Structured interview questions based on core DSM-IV mood symptoms might under-estimate hypomania. Detailed sociodemographic information was not available.

CONCLUSION

BSD was common among Chinese people in Hong Kong and exhibited an epidemiological profile comparable to that of western societies.

Diagnosis of 5alpha-reductase 2 deficiency: a local experience

5Alpha-reductase 2 deficiency is an autosomal recessive disorder characterised by lack of masculinisation in XY individuals due to failure to convert testosterone to dihydrotestosterone, the bioactive androgen. Traditionally, the testosterone-to-dihydrotestosterone ratio is used to diagnose this condition but interpreting these results is not always straightforward, thus they may be inconclusive. On the contrary, urinary steroid profiling unambiguously demonstrates a significantly reduced excretion of 5alpha-reduced steroid metabolites compared to their 5beta counterparts. This analytical technique can also simultaneously confirm or rule out other causes of ambiguous genitalia due to steroidogenic defects. Making a DNA-based diagnosis by studying the SRD5A2 gene has become increasingly popular. Here, we report six Chinese patients from different families who were all diagnosed with 5alpha-reductase 2 deficiency based on urinary steroid profile findings and mutational analysis of the SRD5A2 gene. R227Q was the most commonly identified mutation in these patients. Management of sexual development disorders is also discussed.

Concordance between telephone survey classification and face-to-face structured clinical interview in the diagnosis of generalized anxiety disorder in Hong Kong

Telephone surveys of estimating mental disorders have been found to generate comparable findings to large-scale community surveys but the concordance between telephone instruments and clinical interviews is rarely examined. In this study, 100 Chinese respondents who had taken part in a telephone-based population survey of generalized anxiety disorder (GAD) in Hong Kong were administered the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) by clinical interviewers. The discriminability and predictive indicators of the telephone survey instrument were assessed using receiver operating characteristic analysis. Results showed that the telephone survey instrument identified individuals with a positive SCID diagnosis of GAD better than those without. Although its individual questions performed well in identifying the endorsement of the corresponding core SCID criterion of GAD, further studies are needed to find out the optimal combination of questions in the telephone instrument for identifying GAD in community surveys.

Does the pre-operative value of serum CA15-3 correlate with survival in breast cancer?

INTRODUCTION

CA15-3 is a well-known tumour marker for breast cancer. Currently it is not recommended for screening or diagnosis of breast cancer and its main application is in monitoring response to treatment in women with metastatic breast cancer. The aim of this study was to correlate serum CA15-3 at presentation with the stage of disease and overall survival in women with breast cancer in the University Malaya Medical Centre.

METHODS

This is a retrospective study of 437 women who had CA15-3 levels determined at initial presentation of breast cancer to UMMC between Jan 1999 and Oct 2003.

RESULTS

Of those patients who were adequately staged, CA15-3 was found to be elevated (defined as >51 U/ml) in 0% of Stage 1, 7.9% of Stage 2, 36.7% of Stage 3 and 68.6% of Stage 4 cases. In a subset of 331 patients with survival data, patients with normal CA15-3 had a 85% five year overall survival rate compared to 38% in their counterparts with elevation of the tumor marker. The level of elevation was also significantly related to survival; patients with values more than 200 U/ml exhibited only a 28% five year survival. The association of elevated CA15-3 at initial presentation with poor outcome was maintained over univariate and multivariate analyses.

CONCLUSION

Estimation of CA15-3 at presentation of breast cancer is important as it is an independent prognostic indicator and may prompt the physician to investigate for metastases if elevated.

How disease models in static networks can fail to approximate disease in dynamic networks

In the modeling of infectious disease spread within explicit social contact networks, previous studies have predominantly assumed that the effects of shifting social associations within groups are small. These models have utilized static approximations of contact networks. We examine this assumption by modeling disease spread within dynamic networks where associations shift according to individual preference based on three different measures of network centrality. The results of our investigations clearly show that this assumption may not hold in many cases. We demonstrate that these differences in association dynamics do yield significantly different disease outcomes both from each other and also from models using graph-theoretically accurate static network approximations. Further work is therefore needed to explore under which circumstances static models accurately reflect constantly shifting natural populations.

Prevalence of microplastics in Singapore's coastal marine environment

Microplastics have been recently identified as marine pollutants of significant concern due to their persistence, ubiquity and potential to act as vectors for the transfer and exposure of persistent organic pollutants to marine organisms. This study documents, for the first time, the presence and abundance of microplastics (>1.6 microm) in Singapore's coastal environment. An optimized sampling protocol for the collection and analysis of microplastics was developed, and beach sediments and seawater (surface microlayer and subsurface layer) samples were collected from nine different locations around the coastline. Low density microplastics were separated from sediments by flotation and polymer types were identified using Fourier transform infrared (FTIR) spectrometry. Synthetic polymer microplastics identified in beach sediments included polyethylene, polypropylene, polystyrene, nylon, polyvinyl alcohol and acrylonitrile butadiene styrene. Microplastics were detected in samples from four out of seven beach environments, with the greatest quantity found in sediments from two popular beaches in the eastern part of Singapore. Polyethylene, polypropylene and polystyrene microplastics were also found in the surface microlayer (50-60 microm) and subsurface layer (1m) of coastal waters. The presence of microplastics in sediments and seawater is likely due to on-going waste disposal practices from industries and recreational activities, and discharge from shipping.

A two-stage refinement approach for the enhancement of excretory production of an exoglucanase from Escherichia coli

Hyper-expression of a secretory exoglucanase, Exg, encoded by the cex gene of Cellulomonas fimi was previously shown to saturate the SecYEG pathway and result in dramatic cell death of recombinant Escherichia coli (Z.B. Fu, K.L. Ng, T.L. Lam, W.K.R. Wong, Cell death caused by hyper-expression of a secretory exoglucanase in Esherichia coli, Protein Expr. Purif. 42 (2005) 67-77). We propose here that the cell lysate ratio (Pre/Mat RQ) of the unprocessed precursor Exg protein (Pre-Exg) and its processed mature product (Mat-Exg) reflects the capacity of E. coli to secrete Exg. A Pre/Mat RQ of 20/80, designated the "Critical Value," was an important threshold measurement. A rise in the Pre/Mat RQ triggered a mass killing effect. The use of various secretion signal peptides did not improve the viability of cells expressing high levels of Pre-Exg under strong tac promoter control. However, use of the weaker vegG promoter in conjunction with a change in start codon of the spa leader sequence from ATG to TTG in a pM1vegGcexL plasmid construct resulted in a high level (0.9 U ml(-1)) of excreted Exg in shake-flask cultures. This was 50% higher than the best result obtained from plasmid construct lacUV5par8cex, using the lacUV5 promoter and the ompA leader sequence. Variations in the excreted Exg activities were attributable to differences in the Pre/Mat RQ values of the induced cultures harboring pM1vegGcexL and lacUV5par8cex. These values were 18/82 and 10/90, respectively. Employing fed-batch cultivation in two-liter fermentors, an induced JM101(pM1vegGcexL) culture yielded 4.5 U ml(-1) of excreted Exg, which was over six fold greater that previously reported. Our results illustrate the successful application of the Pre/Mat RQ ratio as a guide to the attainment of a maximum level of secreted/excreted Exg.

A Computer Model for Vibrating Conveyors

This paper presents the development of a computer model for predicting the performance of vibrating conveyors with reciprocating, circular or elliptical vibrating excitation. Experimental validation of the computer model for the reciprocating conveyor was carried out. The computer model takes into consideration all the three possible modes of motion (i.e. the throw mode, slide mode and stationary mode) and the transitions from one mode to another. It is based on a single particle mass analysis but using bulk material properties as the input, parameters. The predicted results are presented in non-dimensional plots. An experimental reciprocating vibrating conveyor with variable amplitude and frequency was constructed and tested with padi-rice and wet coal. Agreements between the theoretical and experimental results are good. Contour graphs derived from the non-dimensional plots of the reciprocating vibrating conveyor are also presented for design applications.

Cell death caused by hyper-expression of a secretory exoglucanase in Escherichia coli

Induced expression of a gene fusion between the ompA leader sequence and the Cellulomonas fimi cex gene encoding a secretory exoglucanase, Exg, engineered in the Tac-cassette excretion vector was lethal to Escherichia coli. An exponentially growing culture harboring the recombinant construct suffered slow growth and 99.9% of its cells died within 60-100 min after induction. This abnormality was found to have a close correlation with the rapid increase in the relative amount of the OmpA/Exg fusion precursor (Pre-Exg) compared to its processed product (Mat-Exg). Analysis of subcellular fractions revealed the presence of Pre-Exg in the inner membrane of cultures expressing high levels but not low levels of Pre-Exg. As only Pre-Exg but not Mat-Exg was detectable in the cytoplasm, and Exg was shown by cross-linking experiments to be physically associated with the Sec proteins, it was concluded that secretion and processing of Pre-Exg took place in the SecYEG translocation machinery. The results were in line with the previous speculation that accumulation of unprocessed precursor proteins in the cytoplasmic membrane was detrimental, and supported the idea that cell death was caused by some unusual tie-up of Pre-Exg with the SecYEG translocation machinery, thus imposing an inhibitory effect on the secretion of endogenous secretory proteins. A new model, designated "Saturated Translocation," was proposed to explain the interchangeable lethal and non-lethal properties of Pre-Exg, and to address the possible scenarios that might occur in the course of cell death triggered by secretion of Pre-Exg.

Novel growth hormone receptor mutation in a Chinese patient with Laron syndrome

Laron syndrome, growth hormone (GH) insensitivity syndrome, caused by a mutation of the GH receptor (GHR) gene, is extremely rare in the Chinese population. We report a Chinese girl diagnosed with Laron syndrome at age 1.9 years with height -4.9 SDS, basal GH 344 mIU/ml, IGF-I <12 ng/ml, IGFBP-3 <0.2 mg/ml, and undetectable GHBP. A novel mutation of the GHR, not previously described, was identified at the donor splice site of intron 6.

Application of a slow-release fertilizer for oil bioremediation in beach sediment

A 105-d field experiment was conducted to determine the potential of the slow-release fertilizer, Osmocote (Scotts, Marysville, OH), to stimulate the indigenous microbial biodegradation of petroleum hydrocarbons in an oil-spiked beach sediment on an intertidal foreshore in Singapore. Triplicate microcosms containing 80 kg of weathered sediment, spiked with 5% (w/w) Arabian light crude oil and 1.2% (w/w) Osmocote pellets, were established, together with control microcosms minus Osmocote. Relative to the control, the presence of the Osmocote sustained a significantly higher level of nutrients (NH(4)(+)-N, NO(3)(-)-N, and PO(4)(3-)-P) in the sediment pore water over the duration of the experiment. The metabolic activity of the indigenous microbial biomass, as measured using an intracellular dehydrogenase enzyme assay, was also significantly enhanced over the duration of the experiment in amended sediments. The loss of total recoverable petroleum hydrocarbons (TRPH) and biodegradation of total n-alkanes (C(10)-C(33)), branched alkanes (pristane and phytane), as well as total target polycyclic aromatic hydrocarbons (PAHs) (two- to six-ring), in both the control and Osmocote-amended sediments, followed a first-order biodegradation model. The first-order loss rate of total recoverable petroleum hydrocarbons was 2.57 times greater than that of the control. The hopane-normalized rate constants for total n-alkane, branched alkane, and total target PAH biodegradation in the Osmocote-treated sediments were 3.95-, 5.50-, and 2.45-fold higher than the control, respectively. Overall, the presence of Osmocote was able to significantly enhance and accelerate the biodegradation of aliphatics and PAHs in oil-contaminated sediments under natural field conditions in an intertidal foreshore environment.

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.

Audit of investigations in patients with iron deficiency anaemia

BACKGROUND

Patients with iron deficiency anaemia (IDA) are commonly referred to the gastroenterologists for exclusion of gastrointestinal (GI) pathologies. The British Society of Gastroenterology (BSG) has published a guideline for management of IDA. As recommended by this guideline, all patients should have examinations of both upper and lower GI tract with the exception of pre-menopausal women younger than 45 years old. The primary aim of this audit was to determine how thoroughly patients referred to our unit at the Singapore General Hospital had been investigated. The secondary aim was to determine the yield rate of gastroscopy and lower gastrointestinal investigations (colonoscopy or barium enema) in our patients.

METHODS

We reviewed the case notes of patients who underwent gastroscopy for indication of anaemia between the period from April to December 1999. We classified iron deficiency anaemia as having haemoglobin of lower than reference range with either low ferritin level or iron/ TIBC ratio of less than 10%.

RESULTS

Of a total of 326 patients reviewed, 172 patients (65 men, 109 women) met the inclusion criteria of IDA. The median age for the group was 59 (Range 16 to 88) years old and there were 107 (62.2%) women. There were 31 female patients younger than 45 years old (group A) and 141 patients in group B which included all the males and females older than 45 years old. Due to the method of data retrieval, all of the patients in group A fulfilled the standard set by the BSG guideline in that they all underwent gastroscopy. In this group, few gastrointestinal pathologies were found (one patient with peptic ulcer and two patients with colonic cancer). In terms of finding potential gastrointestinal causes of IDA, the yield rate of gastroscopy and colonoscopy were 3.2% and 13.6% respectively. In group B, 96 patients (68%) underwent upper and lower gastrointestinal investigations. Evaluation with gastroscopy showed peptic ulcer disease in 31 patients (21.7%) and gastric cancer in 9 patients (6.3%). Only 96 patients (68.1%) in group B had lower gastrointestinal investigations. Twenty-six patients were found to have gastrointestinal disorders (12 patients with colon cancer, 10 colonic polyps, one Crohn's disease, one colonic tuberculosis and two haemorrhoids). The yield rate of gastroscopy and colonoscopy were 31.2% and 25% respectively.

CONCLUSION

In this study of patients with confirmed IDA, we found much higher incidence of gastrointestinal disorders in the group of male and postmenopausal women than in the group with premenopausal women. Furthermore, over 30% of patients in this group did not undergo lower gastrointestinal tract investigations as recommended by the BSG guideline. We also found two cases of colonic cancer in the latter group. We would recommend bidirectional endoscopy for postmenopausal women and men with IDA. For premenopausal women, we would recommend similar approach unless there are clinical pointers to dietary iron deficiency or menorrhagia.

Gastrointestinal Cytomegalovirus infection in non-human immunodeficiency virus infected patients

This is a retrospective study of fourteen patients who had proven Cytomegalovirus (CMV) infection of the gastrointestinal tract with no Human Immunodeficiency virus infection. The median age was 60.5 (Range 28 to 81) years. Eight patients were below (Group 1) and six above sixty five years old (Group 2). Areas of gastro-intestinal involvement were: oesophagus (2), stomach (1), colon (10) and multiple sites (1). Seven patients from Group 1 had received immunosuppressive therapy at the time of presentation and one had diabetes mellitus. We found a high prevalence of co-morbidities such as chronic renal failure and diabetes mellitus in Group 2. At median follow up of 13.9 months, there was a mortality rate of 50%. Only four patients were treated with ganciclovir. Our study concludes that the gastrointestinal CMV diseases in young patients were associated with immunosuppression whereas the older patients had chronic renal failure or diabetes.

Severe acute respiratory syndrome in children: experience in a regional hospital in Hong Kong

OBJECTIVE

To report the clinical, laboratory, and radiologic features of children with severe acute respiratory syndrome (SARS) and to examine the difference between the younger and older age groups.

DESIGN

Retrospective descriptive cohort study.

SETTING

A regional hospital in Hong Kong.

PATIENTS

Children younger than 18 yrs with SARS.

RESULTS

Twenty-one children were included, with a mean age of 10.7 +/- 5.1 yrs. Children with SARS presented with fever, nonproductive cough, malaise, chills, headache, myalgia, and loss of appetite. Examination of the chest showed minimal auscultatory findings. Common laboratory findings included lymphopenia, thrombocytopenia, and mild elevations of activated partial thromboplastin time, alanine transaminase, lactic dehydrogenase, and creatine phosphokinase. Bacteriologic and virologic studies were all negative for common pathogens. Unilateral focal opacity was the commonest finding in chest radiography. High-resolution computerized tomography of the thorax was an early diagnostic tool if the chest radiograph was negative. The clinical course was less severe in comparison with adult patients. However, adolescents (age, > or =12 yrs) resembled adults in their clinical features. When compared with the younger age group, the adolescents had significantly higher temperatures, more constitutional upset, and a greater need for steroid treatment. Children younger than 12 yrs seemed less ill but had more coughing. On the whole, the outcome was favorable.

CONCLUSION

Severe acute respiratory syndrome affects children, but the course is less severe. Nevertheless, the disease could have a significant psychosocial impact on children because of the potential seriousness of the disease in their adult family members.

Microwave drying of high strength dental stone: effects on dimensional accuracy

High-strength dental stone is widely used to produce dies for the fabrication of restorations with the lost-wax technique. It is normal to wait at least 24 hours for casts to dry and gain sufficient strength prior to initiating laboratory procedures. This waiting time may be greatly reduced by using microwave drying. This study determined the optimum microwave energy density for preserving working die accuracy of a Type IV high-strength dental stone (Silky Rock; Whipmix). Cylindrical die specimens were fabricated according to manufacturer's instructions and allowed to set for one hour. The specimens were subsequently treated as follows: Group I (Control group)--air dried; Group II--microwaved at 700W for 40 seconds; Group III--microwaved at 490W for 60 seconds. The percentage weight loss of cylindrical specimens (n = 6) and the percentage dimensional change (n = 7) of die specimens in three axes (x, y and z) were determined at 30 minutes, 1 hour and 24 hours after air drying/microwaving. Weight loss was measured using an electronic digital balance, while dimensional changes were assessed using image analysis software. Data was subject to ANOVA/Scheffe's tests at significance level 0.05. No significant difference in percentage weight loss was observed between air drying for 24 hours and microwaved specimens at all time intervals. Although no significant difference in percentage dimensional changes was observed between specimens microwaved at 490W for 60 seconds and specimens air dried for 24 hours, significant changes in x, y and z dimensions were observed after microwaving at 700W for 40 seconds at various time intervals. Microwave radiation at 490W for 60 seconds is recommended for drying Type IV high-strength dental stone. Further investigations are required to determine changes in physical properties associated with the aforementioned microwave power density.

Appendicitis following blunt abdominal trauma

A young boy presented with history of abdominal trauma. History and initial clinical findings suggested a soft tissue injury. Due to increasing abdominal pain and fever, we proceeded with an exploratory laparotomy with a diagnosis of intra-abdominal injury, at which we found a perforated appendix. Appendicitis following blunt abdominal trauma needs high index of suspicion.

Retention modelling of electrostatic and adsorption effects of aliphatic and aromatic carboxylic acids in ion-exclusion chromatography. II. Calculations of adsorption coefficients in unbuffered eluents

Previous models for the retention behaviour of carboxylic acids in ion-exclusion chromatography are applicable only when the degree of ionisation of the analyte is constant over the entire chromatographic peak. When solutions of sulfuric acid are used as eluents, this condition applies only when the eluent concentration is considerably higher than that of the analyte. Since it is common for dilute solutions of sulfuric acid to be used as eluents, a retention model which accounts for unbuffered eluents has been developed. This model also considers the effects on retention of hydrophobic adsorption of the undissociated and dissociated forms of the analyte onto the stationary phase substrate, as well as the effects of organic solvents added to the eluent. The derivation of this model is presented and it has been evaluated using a comprehensive set of retention data obtained using three different sulfonated stationary phases over a range of eluent conditions. The adsorption coefficients calculated from the model are in accordance with expected trends and showed that both the undissociated and dissociated forms of the analyte acids were retained by hydrophobic adsorption effects, although this adsorption was much stronger for the undissociated analytes.

Piezoelectric and pyroelectric properties of PZT/P(VDF-TrFE) composites with constituent phases poled in parallel or antiparallel directions

Composites of lead zirconate titanate (PZT) powder dispersed in a vinylidene fluoride-trifluoroethylene copolymer [P(VDF-TrFE)] matrix have been prepared by compression molding. Three groups of polarized samples have been prepared by poling: only the ceramic phase, the ceramic and polymer phases in parallel directions, and the two phases in antiparallel directions. The measured permittivities of the unpoled composites are consistent with the predictions of the Bruggeman model. The changes in the pyroelectric and piezoelectric coefficients of the poled composites with increasing ceramic volume fraction can be described by modified linear mixture rules. When the ceramic and copolymer phases are poled in the same direction, their pyroelectric activities reinforce while their piezoelectric activities partially cancel. However, when the ceramic and copolymer phases are poled in opposite directions, their piezoelectric activities reinforce while their pyroelectric activities partially cancel.

Pituitary-gonadal axis in male undermasculinisation

AIMS

To study the value of assessing serum concentrations of luteinising hormone (LH), follicle stimulating hormone (FSH), testosterone, and dihydrotestosterone (DHT) in patients with male undermasculinisation not caused by androgen insensitivity.

METHODS

A retrospective study of a register of cases of male undermasculinisation (20 with abnormal testes, eight with 5alpha-reductase deficiency, three with testosterone biosynthetic defects, seven with Drash syndrome, and 210 undiagnosed).

RESULTS

A human chorionic gonadotropin (hCG) stimulation test was performed in 66 of 185 children with male undermasculinisation. In 41 of 66 patients the dose of hCG was either 1000 U or 1500 U on three consecutive days. The rise in testosterone was related to basal serum testosterone and was not significantly different between the two groups. Testosterone:DHT ratio in patients with 5alpha-reductase deficiency was 12.5-72.8. During early infancy, baseline concentrations of LH and FSH were often within normal reference ranges. In patients with abnormal testes, median pre-LHRH (luteinising hormone releasing hormone) concentrations of LH and FSH were 2 and 6.4 U/l, respectively, and post-LHRH concentrations were 21 and 28 U/l. An exaggerated response to LHRH stimulation was observed during mid-childhood in children where the diagnosis was not clear and in all children with abnormal testes.

CONCLUSIONS

The testosterone:DHT ratio following hCG stimulation is more reliable than the basal testosterone:DHT ratio in identifying 5alpha-reductase deficiency. During infancy, the LHRH stimulation test may be more reliable in identifying cases of male undermasculinisation due to abnormal testes than basal gonadotrophin concentrations.

Retention modelling of electrostatic and adsorption effects of aliphatic and aromatic carboxylic acids in ion-exclusion chromatography

The retention mechanism of aliphatic and aromatic carboxylic acids in ion-exclusion chromatography has been investigated with consideration of simultaneous electrostatic repulsion effects and hydrophobic adsorption effects. A mathematical relationship between the retention factor of the analyte and the mobile-phase composition (sulfuric acid concentration and percentage of methanol), the type of analyte (pKa and hydrophobicity) and some physical characteristics of the stationary phase has been derived. Thirteen carboxylic acids (comprising mono- and divalent, aliphatic and aromatic acids) were chosen and used to acquire retention data on three different cation-exchange stationary phases (in which the sulfonate functional groups are bound to polystyrene-divinylbenzene, polymethacrylate or silica) using 14 mobile-phase compositions of varying pH and percent methanol. These retention data were used to derive the parameters necessary to solve the retention model using non-linear regression. In this way, a quantitative measure of the effects of adsorption phenomena on analyte retention were obtained. The model was then used to optimise the separation of nine carboxylic acids.

Effect of dietary macronutrients on food intake, body weight, and tail width in the marsupial S. crassicaudata

The role of dietary fat, as opposed to total energy intake, in the etiology of obesity is controversial. The aim of this study was to determine the effect of macronutrient content, specifically changes in dietary fat on body weight, fat stores, and food intake in S. crassicaudata, a marsupial that stores about 25% of total body fat in its tail. Female animals were divided into three groups (n = 7-9) matched for food intake per gram of body weight. Each group of animals was fed, ad lib an isocaloric diet (1.01 kcal/g), which contained either 10, 20, or 40% of calories from fat. Body weight, food intake, and tail width (an index of body fat stores) were measured daily. Over 21 days, cumulative energy intake was less (p = 0.026) in the 40% fat group compared to the 10% fat group. Despite the differences in food intake, body weight in each group remained stable throughout the study, so that at day 21 there were no differences in the body weights between the three groups. In contrast, tail width increased in the animals who received the 40% fat diet compared to either the 10% (p = 0.016) or 20% (p = 0.001) fat intake groups, whereas there was no significant change in tail width in either of these two groups. These observations indicate that macronutrient composition has a role, independent of total calories in the regulation of food intake and body fat stores, specifically that dietary fat promotes adiposity, independent of total caloric intake.