Post-mortem pulmonary tuberculosis: comparison of available diagnostic methods

Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a serious public health threat with the World Health Organisation (WHO) reporting 5.8 million cases and 1.3 million deaths in the year 2020 due to TB. TB can be diagnosed by imaging, histopathological and bacteriological methods with culture remaining the gold standard. This study was performed to look at the sensitivity and specificity of post-mortem computed tomography (PMCT) imaging when compared to culture in diagnosing pulmonary tuberculosis. This was a retrospective comparative study looking at post mortem cases where lung tissue samples sent for TB culture at Hospital Kuala Lumpur were compared against PMCT imaging. Exclusion criteria included contaminated samples, decomposed cases, immunocompromised subjects and those below 18 years of age. Subjects included 80 medico-legal autopsy cases at the National Institute of Forensic Medicine, Hospital Kuala Lumpur, Malaysia who had whole body PMCT done in accordance with the Institute's protocol and tissue samples sent for bacteriology culture for tuberculosis. PMCT findings were positively associated with acid-fast organisms in 23.5 out of 33 cases (71.2%). Our study also showed that PMCT had a sensitivity of 71.3% and specificity of 54.3% (95% CI: 39.5-68.4) in diagnosing TB based on the protocol set in this study. This study showed that there was relatively good agreement between radiological PMCT findings and bacterial culture, suggesting that radiological examination is a relatively reliable tool for preliminary screening and possible diagnosis of TB prior to a postmortem examination which would be beneficial in reducing the risk of transmission of TB to health workers during autopsy.

Novel frameshift variant in the PCNT gene associated with Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II and small kidneys

Background

Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II is an autosomal recessive condition encompassing a heterogeneous group of disorders characterized by symmetrical growth retardation leading to dwarfism, microcephaly, and a range of multiple medical complications including neurovascular diseases. Biallelic pathogenic variants in the pericentrin gene (PCNT) have been implicated in its pathogenesis.

Case presentation

We performed whole-exome sequencing to ascertain the diagnosis of a 2 year and 6 months old boy who presented with severe failure to thrive, microcephaly, and facial gestalt suggestive of MOPD Type II which included features such as retrognathia, small ears, prominent nasal root with a large nose, microdontia, sparse scalp hair, bilateral fifth finger clinodactyly. He had a small ostium secundum atrial septal defect and bilaterally small kidneys. Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II was confirmed based on a pathogenic compound heterozygous frameshift variant in the PCNT gene c.5059_5060delAA | p. Asn1687fs (novel variant) and c.9535dup (p. Val3179fs). His parents were found to be heterozygous carriers for the variants.

Conclusion

We report a novel frameshift variant in the PCNT gene and a previously unreported phenotype for Microcephalic Osteodysplastic Primordial Dwarfism (MOPD) Type II.

Air pollution interventions and respiratory health: a systematic review

BACKGROUND: Indoor and ambient air pollution exposure is a major risk to respiratory health worldwide, particularly in low- and middle-income countries (LMICs). Interventional trials have mainly focused on alternatives to cooking stoves, with mixed results. Beyond cooking, additional sources of particulate matter also contribute to the burden of air pollution exposure. This review explores evidence from current randomised controlled trials (RCTs) on the clinical effectiveness of interventions to reduce particulate matter in LMICs.METHODS: Twelve databases and the grey literature (e.g., Government reports and policy papers) were searched. Eligible studies were RCTs conducted in LMICs aiming to reduce particulate exposure from any source and reporting on at least one clinical respiratory outcome (respiratory symptoms, lung function or clinical diagnoses). Data from relevant studies were systematically extracted, the risk of bias assessed and narrative synthesis provided.RESULTS: Of the 14 included studies, 12 tested 'improved' cookstoves, most using biomass, but solar and bioethanol cookers were also included. One trial used solar lamps and another was an integrated intervention incorporating behavioural and environmental components for the treatment and prevention of chronic obstructive pulmonary disease. Of the six studies reporting child pneumonia outcomes, none demonstrated significant benefit in intention-to-treat analysis. Ten studies reported respiratory symptom outcomes with some improvements seen, but self-reporting made these outcomes highly vulnerable to bias. Substantial inter-study clinical and methodological heterogeneity precluded calculation of pooled effect estimates.CONCLUSION: Evidence from the RCTs performed to date suggests that individual household-level interventions for air pollution exposure reduction have limited benefits for respiratory health. More comprehensive approaches to air pollution exposure reduction must be developed so their potential health benefits can be assessed.

Novel variant in NSDHL gene associated with CHILD syndrome and syndactyly- a case report

Background

Congenital hemidysplasia with ichthyosiform erythroderma and limb defects also known as CHILD syndrome is an X-linked dominant, male lethal genodermatosis with a prevalence of 1 in 100,000 live births. Mutations in NSDHL gene located at Xq28 potentially impair the function of NAD(P) H steroid dehydrogenase-like protein and is responsible for its pathogenesis.

Case presentation

The proband was a 9-month-old twin (T2) girl with a healthy twin sister (T1) of Sri Lankan origin born to non-consanguineous parents. She presented with right sided continuous icthyosiform erythroderma and ipsilateral limb defects and congenital hemidysplasia since birth. Notably the child had ipsilateral hand hypoplasia and syndactyly. There were other visceral abnormalities. We performed whole exome sequencing and found a novel heterozygous variant (NSDHL, c.713C > A, p.Thr238Asn).

Conclusion

We report a novel missense variant in the NSDHL gene that resides in a highly-conserved region. This variant affects the NAD(P) H steroid dehydrogenase-like protein function via reduction in the number of active sites resulting in the CHILD syndrome phenotype and syndactyly.

Methanol related death in National Institute of Forensic Medicine, Hospital Kuala Lumpur: A case series

INTRODUCTION

Methanol is a widely available chemical with a range of uses including as solvent, as a fuel, in chemical synthesis and anti-freeze preparations. Most of the cases are accidental exposures to drinking beverages contaminated with methanol.

MATERIALS AND METHODS

In mid-September 2018, there was a single outbreak of methanol poisoning in Malaysia especially involving the state of Federal Territory Kuala Lumpur and Selangor. There were 33 reported deaths suspected due to methanol poisoning in this current outbreak where 11 of them were brought in to the Institute of Forensic Medicine (NIFM), Kuala Lumpur. The last outbreak was in the year 2013 with 29 deaths reported out of 44 cases.

RESULTS

There were 3 cases (27.2%) died in hospital and the remaining 8 cases (72.8%) were found dead at home and were later brought in dead to the hospital. A full autopsy was carried out for each case. Autopsy findings, as well as lab results pertaining to cases that survived and directly brought in dead, were of a different spectrum.

CONCLUSION

Methanol related deaths are almost always as a result of greed. The running truism is 'methanol poisoning is a result of deliberate addition/adulteration with industrial methanol'. Prevention of the illegal production of methanol and methylated spirits should be established to curb this matter in the future.

Kerosene lighting contributes to household air pollution in rural Uganda

The literature on the contribution of kerosene lighting to indoor air particulate concentrations is sparse. In rural Uganda, kitchens are almost universally located outside the main home, and kerosene is often used for lighting. In this study, we obtained longitudinal measures of particulate matter 2.5 microns or smaller in size (PM_2.5 ) from living rooms and kitchens of 88 households in rural Uganda. Linear mixed-effects models with a random intercept for household were used to test the hypotheses that primary reported lighting source and kitchen location (indoor vs outdoor) are associated with PM_2.5 levels. During initial testing, households reported using the following sources of lighting: open-wick kerosene (19.3%), hurricane kerosene (45.5%), battery-powered (33.0%), and solar (1.1%) lamps. During follow-up testing, these proportions changed to 29.5%, 35.2%, 18.2%, and 9.1%, respectively. Average ambient, living room, and kitchen PM_2.5 levels were 20.2, 35.2, and 270.0 μg/m³ . Living rooms using open-wick kerosene lamps had the highest PM_2.5 levels (55.3 μg/m³ ) compared to those using solar lighting (19.4 μg/m³ ; open wick vs solar, P=.01); 27.6% of homes using open-wick kerosene lamps met World Health Organization indoor air quality standards compared to 75.0% in homes using solar lighting.

What is the clinical significance of pulmonary hypertension in acute respiratory distress syndrome? A review

Elevated pulmonary arterial pressures appear to be a prominent feature of the acute respiratory distress syndrome (ARDS). Current clinical guidelines for the management of ARDS do not specifically address treatment of pulmonary hypertension or associated right ventricular dysfunction because the clinical significance of this entity remains unclear. Interpretation of elevated pulmonary arterial pressures, pulmonary vascular resistance, and transpulmonary gradient as well as signs of right ventricular dysfunction is confounded by the effects of positive pressure ventilation. There does not appear to be a consistent relationship between the diagnosis of pulmonary hypertension or right ventricular failure and mortality in patients with ARDS, but it is unclear if right ventricular failure contributes to the mortality risk per se or if the underlying cause of pulmonary hypertension, including intravascular micro and macro thrombosis, are simply markers for systemic dysregulation of coagulation and fibrinolysis that may lead to multiorgan failure in ARDS. While studies of pulmonary vasodilator therapies have not shown a mortality benefit in ARDS, such trials have targeted improved oxygenation rather than improved pulmonary hemodynamics so that the possible contribution of improved right ventricular function to better outcomes has not been directly tested in large trials. Future studies are needed to determine if treatment of pulmonary hypertension and associated right ventricular dysfunction will affect mortality in patients with ARDS.

An updated meta-analysis to understand the variable efficacy of drotrecogin alfa (activated) in severe sepsis and septic shock

BACKGROUND

Significant debate continues over the efficacy of drotrecogin alpha activated (DAA) in sepsis. This updated meta-analysis provides an updated summary effect estimate and explores the reasons for outcome heterogeneity in placebo-controlled randomized clinical trials of DAA on 28-day all-cause mortality in patients with severe sepsis or septic shock.

METHODS

Computer searches of MEDLINE, EMBASE, the Cochrane Library, ClinicalTrials.gov, published abstracts from major intensive care meetings and examination of reference lists were used to identify five placebo-controlled randomized clinical trials with 7260 patients. The primary endpoint was 28-day all-cause mortality. Secondary outcomes were 28-day incidence of severe bleeding and intracranial hemorrhage.

RESULTS

DAA was not associated with improved 28-day all-cause mortality in patients with severe sepsis or septic shock (pooled relative risk (RR) of 0.97 [95% CI 0.83-1.14]), and is associated with an increase in serious bleeding. The significant heterogeneity in the pooled RR for 28-day mortality (I2 value of 59.4%, χ2 P-value 0.043) is no longer present with exclusion of the post-study amendment portion of PROWESS (I2 value of 0%, χ2 P-value 0.44 without PROWESS post-amendment). Using meta-regression, the best ranked predictor of outcome heterogeneity was baseline mortality in the placebo arm, which was among the highest in PROWESS.

CONCLUSION

DAA is not associated with improved survival in patients with severe sepsis or septic shock. Further studies should be done to determine whether changes in supportive therapy for sepsis explain the variable efficacy of DAA in randomized controlled clinical trials observed over time.

Screening of dystrophin gene deletions in Malaysian patients with Duchenne muscular dystrophy

Duchenne Muscular Dystrophy (DMD) is an X-linked recessive genetic disorder characterized by rapidly progressive muscle weakness. The disease is caused by deletion, duplication or point mutation of the dystrophin gene, located on the X chromosome (Xp21). Deletion accounts for 60% of the mutations within the 79 exons of the dystrophin gene. Seven exons (43, 44, 45, 46, 49, 50, and 51) were found to be most commonly deleted among the Asian patients. To detect the frequency of deletion of these 7 exons in Malaysian DMD patients, we carried out a molecular genetic analysis in 20 Malaysian DMD patients. The mean age of initial presentation was 60 months (SD 32 months, range 5-120 months). Fourteen patients were found to have deletion of at least one of the seven exons. The remaining six patients did not show any deletion on the tested exons. Deletions of exons 49, 50 and 51 were the most frequent (71.43%) and appear to be the hot spots in our cohort of patients.

Colon epithelial cell death in 2,4,6-trinitrobenzenesulfonic acid-induced colitis is associated with increased inducible nitric-oxide synthase expression and peroxynitrite production

Peroxynitrite, derived from the reaction of nitric oxide (NO(.)) with superoxide (O(2)), is a potent nitrating and oxidizing agent that can induce apoptosis in a variety of different cell types. In the present study, we investigated the possible role of peroxynitrite as a mediator of colon epithelial cell death in rat colitis. Rat colon inflammation was induced by intracolonic administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) and rats were sacrificed 24 h after TNBS administration. Expression of inducible nitric-oxide synthase (iNOS) was detected by reverse transcription-polymerase chain reaction and immunohistochemistry. The enzymatic activities of Ca(2+)-independent iNOS and Ca(2+)-dependent constitutive nitric-oxide synthase were determined biochemically. Evidence of peroxynitrite-mediated cell injury was detected by immunostaining of nitrotyrosine. Apoptosis was examined by in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and DNA gel electrophoresis. To evaluate the specific contribution of peroxynitrite to the observed cell injury, a selective iNOS inhibitor, L-N(G)-[1-iminoethyl]lysine (L-NIL), was administered after TNBS induction. Morphological examination and analysis of TUNEL/cytokeratin double immunofluorescence revealed significant apoptosis in mucosal epithelial cells. Nitrotyrosine was colocalized with TUNEL, strongly demonstrating the association of peroxynitrite with the apoptotic death of colon epithelial cells. The administration of L-NIL reduced iNOS activity in 24-h lesions by 92% and also significantly attenuated both nitrotyrosine staining and apoptotic cell counts in the colon epithelium. These results strongly suggest that local elevated level of peroxynitrite produced from increased iNOS expression and activity is a major contributor to colon epithelial apoptosis during colon inflammation.

Pattern of cytokine and adhesion molecule mRNA in hapten-induced relapsing colon inflammation in the rat

We examined the mRNA expression of cytokines, chemokines, integrins, and selectins in colon lesions of rat colitis with a semi-quantitative RT-PCR assay. Rat colitis was induced by trinitrobenzene sulfonic acid (TNBS) in 50% ethanol. Within 24 h, an acute inflammation occurred with hyperemia, edema, necrosis and an intense infiltration of granulocytes in the mucosa. The lesion proceeded into a T-lymphocyte/monocyte-driven chronic inflammation for two weeks and healed in 6 weeks. An acute inflammation recurred at the same site when the recovered animals were systemically injected with TNBS. We isolated RNA from colon tissue at 24 h, 1, 2, 4, 6 weeks after TNBS treatment and from the relapsed animals. The mRNA for cytokines IL-1beta, IL-6, IL-10 and the chemokines CINC, MIP-1alpha, MCP-1 were significantly (P < 0.05) elevated and persisted for 2 weeks, decreased in 6 weeks and increased again during relapse. IFN-gamma mRNA stayed at control levels initially, but increased dramatically in the second weeks of chronic inflammation as well as in relapse. The mRNA levels of adhesion molecules, ICAM-1, VCAM-1, the mucosal homing integrin beta7 as well as P- and E-selectin were greatly enhanced between 1 and 3 weeks. The data showed that the chronically inflamed tissue expresses a time-dependent changing pattern of TH1 cytokines and adhesion molecules that maintain the infiltration and activation of inflammatory cells and tissue injury.

Mechanism and signal transduction of 14 (R), 15 (S)-epoxyeicosatrienoic acid (14,15-EET) binding in guinea pig monocytes

14(R), 15(S)-epoxyeicosatrienoic acid (14,15-EET) is a cytochrome P-450 monooxygenase (epoxygenase) metabolite of arachidonic acid (AA). In this study, we have identified a population of specific high affinity binding sites for 14,15-EET in the guinea pig mononuclear (GPM) cells. The results of competition studies showed that 14(R), 15(S)-EET was an effective competing ligand with a Ki of 226.3 nM followed by 11(R), 12(S)-EET, 14(S), 15(R)-EET, 14,15 thia(S)-ET, and 14,15-aza(N)-ET. The binding was sensitive to various protease treatments suggesting that the binding site is protein in nature. Cholera toxin (CT) and dibutyryl cAMP attenuated 14,15-EET binding in GPM cells. Mean binding site density (Bmax), decreased 32.0% and 19.1% by the pretreatment with cholera toxin (200 micrograms/ml) and dibutyryl cAMP (100 nM), respectively, without changing the dissociation constant. A specific protein kinase A (PKA) inhibitor, H-89, but not the PKC inhibitor K252a reversed the down regulation of 14,15-EET receptor binding caused by dibutyryl cAMP in GPM cells. Thus, the results sug-gest that the specific binding site of 14,15-EET in GPM cells be associated with a receptor that could be down regulated through an increase in intracellular cAMP and activation of a PKA signal trans-duction. We propose that the signal transduction mechanism begins with the binding of 14,15-EET to its receptor that leads to increase intracellular cAMP levels and the activation of PKA, and finally, with the down regulation of 14,15-EET receptor binding.

Role of endogenous nitric oxide in TNF-alpha and IL-1beta generation in hepatic ischemia-repefusion

In the present study, we examined the role of nitric oxide (NO) in early-response cytokine production by using a rat model of hepatic ischemia-reperfusion (HI/R). The left and median lobes of the liver were subjected to 30 min of ischemia, followed by 4 h of reperfusion. Group I and II rats were sham-operated controls that received saline (vehicle) or N(W)-nitro-L-arginine methylester (L-NAME) (10 mg/kg, iv); group III and IV rats were subjected to HI/R and received vehicle or L-NAME (10 mg/kg, iv, 10 min before reperfusion), respectively. Administration of L-NAME to rats subjected to I/R resulted in a fourfold decrease in plasma NO levels, accompanied by a marked increase of plasma alanine aminotransferase (ALT) activity relative to group III. These changes in group IV were associated with elevation of superoxide generation in ischemic liver lobes by 2.1-fold and circulating leukocyte number by 1.42-fold, compared with group III. Normalized for expression of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) messenger ribonucleic acid (mRNA), expression of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) mRNA in ischemic liver of group IV was augmented by 207% and 175% compared with Group III. The expression of (iNOS) mRNA was also increased (223%) relative to group III. Moreover, in group IV, plasma TNF-alpha levels at 4 h of reperfusion and IL-1beta levels at 90 min and 4 h of reperfusion were significantly increased compared with group III. No statistically significant changes were observed between groups I and II in plasma ALT activity, plasma NO levels, circulating leukocyte counts, superoxide generation in the ischemic lobes of liver, and plasma TNF-a and IL-1beta concentrations. The observed enhancement of I/R injury by L-NAME is consistent with the hypothesis that endogenous NO down-regulates TNF-alpha and IL1beta generation, thereby decreasing HI/R injury.

Role of interferon-gamma in lung inflammation following cecal ligation and puncture in rats

Interferon-gamma (IFN-gamma) has been implicated in the mortality of animal models of endotoxemia. On the other hand, the specific role of IFN-gamma in the development of organ inflammation in a model of polymicrobial sepsis has not been elucidated. In this study, we hypothesized that IFN-gamma plays an important role in lung inflammation after cecal ligation and puncture (CLP). To verify this hypothesis, lung tissue was removed 5 h after CLP or from sham controls. The mRNA expression (by RT-PCR) of IFN-gamma was increased in lung homogenates of CLP rats compared to sham controls. Using immunohistochemistry, we show for the first time the increased presence of IFN-gamma staining cells in the lung following CLP. Only very small amounts of positive staining for IFN-gamma was observed in lungs of sham controls. The presence of IFN-gamma in the lung 5 h after CLP correlated with a twofold increases in lung superoxide generation and MPO activity (index of neutrophil sequestration). Plasma and lung nitrite levels (breakdown product of nitric oxide) were also significantly increased in CLP rats. IFN-gamma antibody (1.2 mg/kg, i.v.) administered immediately after CLP significantly decreased lung superoxide levels to levels similar to the sham controls without affecting MPO activity, or lung or plasma nitrite levels. These results provide evidence that IFN-gamma may contribute to lung inflammation 5 h following CLP via increased production of superoxide.

A comprehensive method to scan for point mutations of the glucose 6 phosphate dehydrogenase gene

We have developed a fast and comprehensive method to scan for point mutations in a gene on X chromosome. A target region of the gene is first amplified. Then, using the amplified product as a template, PCR is carried out with multiple short-length forward primers arrayed in tandem in the scanned region, and a common reverse primer. The absence of amplified product defines the site of a mutation within a narrow region of the primer recognition site. To evaluate our method, point mutations in exon 12 of the human glucose-6-phosphate dehydrogenase (G6PD) gene were used as a model system. Out of 12 Singaporean G6PD-deficient patients, 6 cases were shown by the method to have a nucleotide change in this exon. Sequence analysis confirmed the presence of a nucleotide change in the region identified by our scanning. Thus, our method is accurate in localizing mutations within a narrow region, and allows large numbers of samples to be handled simultaneously.

Post-receptor signal transduction and regulation of 14(R),15(S)-epoxyeicosatrienoic acid (14,15-EET) binding in U-937 cells

14(R),15(S)-epoxyeicosatrienoic acid (14,15-EET), a cytochrome P-450 monooxygenase (epoxygenase) metabolite of arachidonic acid has been reported to induce adhesion of a monocyte cell line (U-937) to cultured endothelial cells. In this study, we identified a population of specific, high affinity binding sites for 14(R),15(S)-EET in U-937 cell surface with Kd of 13.84 +/- 2.58 nM and Bmax of 3.54 +/- 0.28 pmol/10(6) cells. The specific binding of [3H]-14,15-EET on U-937 cells is more effectively displaced by 14(R),15(S)-EET than the 14(S),15(R)-isomer thus indicating stereospecificity. The binding was sensitive to various protease treatments suggesting the binding site is protein in nature. 14,15-EET binding in U937 cells is attenuated by cholera toxin (CT) and dibutyryl cAMP. Mean binding site density (Bmax) decreased 31.61% and 34.8% by the pretreatment with cholera toxin (200 micrograms/ml) and dibutyryl cAMP (300 nM), respectively, without affecting the dissociation constant. Under similar conditions, pertussis toxin (20-200 ng/ml) was less effective as compared to CT and dibutyryl cAMP. The down regulation of 14,15-EET binding caused by dibutyryl cAMP in U-937 cell was reversed by a specific protein kinase A (PKA) inhibitor, H-89, but not by the PKC inhibitor K252a. Thus, the results suggest that the specific binding site of 14,15-EET in U-937 cells is associated with a receptor that could be down regulated through an increase in intracellular cAMP and activation of a PKA signal transduction mechanism. We propose that the signal transduction mechanism of 14,15-EET begins with the binding of the receptor, which leads to the increase of intracellular cAMP levels and the activation of PKA, and finally with the down regulation of 14,15-EET receptor binding.

Detection of low numbers of neuroblastoma cells in vitro

Neuroblastoma is a tumour derived from the sympathoadrenal progenitors of the neural crest. It is one of the most malignant solid tumours in childhood with an annual incidence of 9.4 per 10(6) children under 15 years of age. Recent studies suggest that immunocytological detection of neuroblastoma cells in bone marrow and circulating neuroblasts during treatment may predict clinical outcome and correlate with tumour relapse. The present methods of diagnosing metastasis in neuroblastoma include histological, biochemical and immunohistological analysis. Morphological distinction between tumour cells and primitive lymphoblasts in bone marrow is often difficult, and these methods may also not always be sensitive enough for early detection of the residual and minimally circulating tumor cells. A sensitive assay for detection of such residual cells using two tissue-specific markers, NFM and SYN, by reverse transcriptase-polymerase chain reaction (RT-PCR) is reported here. Analysis of the specificity of this assay in three neuroblastoma cell lines, namely IMR 32, SK-N-SH and SY5Y showed positive expression while control peripheral blood mononuclear cells (HL 60) were negative. In reconstituted cell spiking tests, this method has the ability to detect 1-10(3) neuroblastoma cell in 10(7) normal peripheral blood mononuclear cells (PBMC), as shown by serial dilution and limiting dilution. The NFM marker was found to be a more sensitive marker. The specificity and sensitivity of this technique makes it suitable for future application in detection of minimally disseminated tumour cells in neuroblastoma patients.

Molecular studies of loss of heterozygosity in retinoblastoma

Retinoblastoma (Rb) is a paediatric intraocular tumour in which predisposition can be inherited. Cases of Rb tumours can be divided into three types: familial cases, sporadic bilateral cases and sporadic unilateral cases. Familial and sporadic bilateral cases are usually categorised as hereditary while sporadic unilateral cases as non-hereditary. In both familial and non-familial forms of Rb, loss of heterozygosity of the Rb locus has been reported although its frequency in tumours has not so far been accurately determined. The cloning of the gene responsible for retinoblastoma (Rb1) has facilitated DNA studies and genetic counselling of patients. We have examined forty-five cases of retinoblastoma at five intragenic sites of the Rb1 locus, namely intron 1/BamH1, intron 17/Xba1, intron 24/TthIII1, intron 25/Dra1 and Rb1.20 VNTR. Thirty-six out of the forty-five cases (80%) were informative for these markers. Comparison of results between genomic DNA from peripheral blood and from tumours revealed that loss of heterozygosity of alleles could be detected in 50% of cases studied in which tumour samples were available. Investigation of parental origin of retained alleles showed that in all these cases, the paternal alleles were preferentially retained. The analysis of the genetic origin of mutations predisposing to retinoblastoma can facilitate new approaches for identifying recessive mutant genes that lead to cancer as well as to provide a conceptual basis for accurate prenatal predictions of cancer predisposition.

Molecular diagnosis of Duchenne muscular dystrophy in Singapore

Duchenne muscular dystrophy (DMD) is a common lethal sex-linked recessive disorder. Seventy percent of the cases are inherited and 30% are due to mutations. The mainstay of prevention is detection of female carriers and antenatal diagnosis of affected foetuses. Before the era of molecular diagnosis, DMD has been clinically defined. Serum creatine kinase (CK) has also been used to screen women at risk for carrier status. With the isolation and sequencing of the DMD gene at Xp21 and the identification of the DMD gene-product dystrophin, DNA technology can be applied for the diagnosis of the affected, for the detection of carriers and in antenatal diagnosis. The multiplex polymerase chain reaction (PCR) technique offers a rapid and simple screening method for deletions of the gene. We were able to detect partial deletions which account for 58.3% of gene defects in our patients. This direct demonstration of the gene defect that causes DMD gives a 100% assurance of accuracy and specificity of the diagnosis. Linkage analysis is especially useful for prenatal diagnosis and carrier detection in the remaining 41.7% of families without detectable deletions or duplications. This approach however is indirect and is dependent on information on genotypes from affected males and key family members. With the availability of increasingly more restriction fragment length polymorphisms (RFLPs), it has become practical to use the haplotype method for accurate carrier detection and prenatal diagnosis.

Antithrombotic effects of peroxynitrite: inhibition and reversal of aggregation in human platelets

The inhibition of platelet aggregation by peroxynitrite, a reactive oxygen species derived from the interaction of nitric oxide (NO) and superoxide, was examined in platelet-rich plasma. In this report, we have used a preparation of peroxynitrite that was free of H2O2 and MnO2. As such, peroxynitrite dose-dependently (50-200 microM) inhibited aggregation of human platelets stimulated by ADP (5 microM), collagen (0.5 microgram), thrombin (0.5U/microL) and U46619 (1 microM). In addition, peroxynitrite reversed platelet aggregation induced by collagen, ADP, and thrombin. Peroxynitrite, preincubated with platelet-poor plasma or albumin (7%) for 30 min, did not alter the inhibition of platelet aggregation. This suggested that the inhibitory action of peroxynitrite may be due to nitrosylation of proteins, which by themselves possess activity, rather than conversion to NO or NO donors. Furthermore, we show that peroxynitrite increased the cGMP level only at 200 microM concentrations, further suggesting that the action of peroxynitrite was not completely due to its conversion to NO or NO donors.

Molecular characterization of beta-thalassaemia in Singaporean Chinese: application to prenatal diagnosis

Sixty-five beta-thalassaemia genes from 14 unrelated Chinese beta-thalassaemia major patients and 37 Chinese beta-carriers were analysed by allele-specific oligonucleotide (ASO) hybridization after DNA amplification by the polymerase chain reaction (PCR). Six mutations were studied and are represented by 49.2% of codon 41-42, 30.8% of IVSII #654, 6.2% of 17 beta, 3.1% of IVSI #5 (G-->C) and 1.5% of -28 TATA box. The complete mutations responsible for beta-thalassaemia major in 13 of our 14 affected families were identified. For these families prenatal diagnosis at 10 weeks gestation using DNA amplification and ASO hybridization will replace the globin chain biosynthesis technique at 19 weeks gestation. Using ASO analysis, our results indicate that 5 oligo-probes (41-42, II-#654, 17 beta, IVSI-#5 and -28) allow determination of beta-thalassaemia mutations in 59/65 (90.8%) of the Singaporean Chinese studied.

Deletion analysis of DMD/BMD children in Singapore using multiplex polymerase chain reaction (PCR) technique

Twenty-three children suffering from Duchenne/Becker muscular dystrophy (DMD/BMD) in Singapore were analysed using the multiplex polymerase chain reaction (PCR) technique. Deletions were found in 14 cases. One rare case of total deletion of all nine exons was observed. This is the first DMD/BMD deletion analysis on South East Asian children. This technique for screening deletions was informative in 61 per cent of the local cases and would be useful for rapid diagnosis of deletion cases of DMD/BMD.

Pathogenesis of Duchenne muscular dystrophy: the calcium hypothesis revisited

Rapid advances in the molecular genetics of Duchenne muscular dystrophy (DMD) and the discovery and localization of the gene product dystrophin has brought new hope that successful treatment for this disease may not be too far away. Dystrophin has been postulated to have a mechanical function, helping to resist stress associated with muscle contraction. The presence of dystrophin in low concentrations in muscle cells, its expression in nervous tissue and the observation that hypercontraction of the sarcomeres precedes membrane rupture make the hypothesis unlikely. On the basis of an analogy with a cytoskeletal protein ankyrin, which is associated with the sodium/potassium adenosine triphosphatase (ATPase) in the kidney, it is possible that dystrophin deficiency leads initially to an increased but inefficient calcium-ATPase activity, which pumps calcium out of the cell. Partial failure of the pump would result in intracellular accumulation of calcium, hypercontractions of the sarcomeres, rupture of the cell membrane, massive influx of calcium and cell necrosis.

Depolymerization of heparin by complexed ferrous ions

Treatment of porcine heparin with the ferrous-EDTA complex and ascorbic acid for 24 h at 37 degrees C results in the degradation of most of the glycosaminoglycan to smaller fragments. About 65% of the products comprise oligosaccharides composed of less than 30 sugar units. The extent of depolymerization is decreased significantly if ascorbate or EDTA is not included in the reaction mixture. Gel filtration of the reaction products yielded fractions with narrow chain length ranges. The sulfate content of the fractions and their electrophoretic mobilities on cellulose acetate indicate that the components have equivalent charge densities. Depolymerization products with 20 or more sugar units retain significant anticoagulant potencies as measured by their effect in accelerating the neutralization of factor Xa by antithrombin.

Deletional types of alpha-thalassaemia in central Java

The frequency of deletional alpha-thalassaemia in a Javanese population sample (n = 103) was investigated at three restriction sites of the alpha-globin gene (BamHI, BglII and RsaI). The overall gene frequency of alpha+ deletional thalassaemia was found to be very low (0.03). Leftward (-alpha 4.2) and rightward (-alpha 3.7) deletions and triplicated genes were present in equal frequency (0.015 and 0.005, respectively).

Prenatal diagnosis of alpha- and beta-thalassaemias in Singapore--current status

Prenatal diagnosis was performed in 31 pregnancies where the fetuses were at risk for either homozygous alpha(0) - or beta-thalassaemia. First-trimester prenatal diagnosis by DNA analysis using chorionic villi was carried out for 17 pregnancies at risk for homozygous alpha (0)-thalassaemia. The alpha-globin genes in fetal DNA were detected by gene mapping using restriction endonuclease mapping and hybridization with cloned alpha-globin probe. Homozygous alpha (0)-thalassaemia was detected in four fetuses and the results were subsequently confirmed by electrophoresis of the cord blood where only Hb Barts was detected. Prenatal diagnosis for beta-thalassaemia was carried out by globin chain biosynthesis using fetal blood at 18-20 weeks' gestation. Using carboxymethyl (CM) sepharose chromatography, homozygous beta-thalassaemia was predicted in six pregnancies, and one fetus carried Hb E-beta thalassaemia. The seven pregnancies were terminated and globin chain analysis using cord blood confirmed the prenatal diagnoses. The remaining seven fetuses were diagnosed as either normal or beta-thalassaemia carriers. Using DNA analysis and globin chain biosynthesis for prenatal diagnosis of homozygous alpha(0)- and beta-thalassaemia, a 100% correlation was achieved with fetuses predicted to possess the homozygous condition.

Comparison of two methods for bacteriocin typing of Serratia marcescens

Two methods of bacteriocin susceptibility typing for Serratia marcescens were compared. A total of 80 epidemiologically unrelated isolates from patients in a single hospital were typed by the cross-streaking method and the mitomycin C-induced (spotting) method. The cross-streaking method was found to be more discriminatory than the spotting method. Using the cross-streaking method, it was possible to differentiate 50 bacteriocin groups out of the 80 isolates, whereas only 31 groups could be obtained with the spotting method. The reproducibility and percentage typability of the cross-streaking method (82.5 and 93.75%, respectively) were found to be as good as, if not better than, those of the spotting method (78.75 and 90.0%, respectively). Other factors, such as lower economic cost, technical simplicity, and the relative ease in the scoring of results, indicate a preference for the cross-streaking method. The findings of this study support the choice of the cross-streaking method for the bacteriocin typing of S. marcescens in epidemiological studies.

Hemagglutinin activity in Nereis coelomic fluid

1. Nereis coelomic fluid agglutinates rat, mouse, chicken, guinea pig and rhesus monkey erythrocytes (RBC). 2. Lipid fractions of the particulate matter from coelomic fluid are hemagglutinins exhibiting different activity inhibition profiles with complex polysaccharides. 3. The high mol. wt hemagglutinin from coelomic fluid supernatant is not a protein and is inhibited by bovine submaxillary mucin (BSM), thyroglobulin, transferrin and their asialo derivatives. 4. Coelomic fluid supernatant has a population of low mol. wt protein hemagglutinins inhibited by BSM, fetuin, antiserum to coelomic fluid and some mannan preparations. 5. Hemagglutination by lipids characterized by RBC specificity and specificity for inhibition by carbohydrate is noteworthy and may be significant in studies of cellular interactions and immunity in invertebrates.