Developing high intensity ultrasonic cleaning (HIUC) for post-processing additively manufactured metal components

The high energy phenomenon of cavitation bubble collapses has enabled numerous applications, including cleaning. In ultrasonic cleaning, cavitation intensity is typically lower than in other applications, such as sonochemistry and material processing. However, there has been an emerging application in intense cleaning of metal additively manufactured (AM) components. The presence of partially melted powders on AM surfaces is undesirable, contributing to high surface roughness and posing contamination risks during usage. We designed a high-intensity cavitation cleaning process that has significantly higher inertial cavitation intensity - i.e., erosion potential - than a conventional ultrasonic cleaning tank. Through acoustic signal characterisation, we showed that placing transducer sets on four sides of the tank could effectively focus and generate high-amplitude pressure waves directed towards the central region. Strong subharmonic signals indicate intensely inertial cavitation throughout the tank. Cavitation intensities were measured at various locations to understand the wave transmission characteristics and distribution patterns. Our results show that the cavitation intensity distribution is highly dependent on the height position. Finally, we demonstrated that the high intensity ultrasonic cleaning (HIUC) process could remove partially melted powders from an AM surface - which was not possible through conventional ultrasonic cleaning. HIUC could lead to higher cleaning efficiency and enhanced AM specimen cleanliness.

Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of Nsp14 RNA cap methyltransferase

The COVID-19 pandemic has presented itself as one of the most critical public health challenges of the century, with SARS-CoV-2 being the third member of the Coronaviridae family to cause a fatal disease in humans. There is currently only one antiviral compound, remdesivir, that can be used for the treatment of COVID-19. To identify additional potential therapeutics, we investigated the enzymatic proteins encoded in the SARS-CoV-2 genome. In this study, we focussed on the viral RNA cap methyltransferases, which play key roles in enabling viral protein translation and facilitating viral escape from the immune system. We expressed and purified both the guanine-N7 methyltransferase nsp14, and the nsp16 2'-O-methyltransferase with its activating cofactor, nsp10. We performed an in vitro high-throughput screen for inhibitors of nsp14 using a custom compound library of over 5000 pharmaceutical compounds that have previously been characterised in either clinical or basic research. We identified four compounds as potential inhibitors of nsp14, all of which also showed antiviral capacity in a cell-based model of SARS-CoV-2 infection. Three of the four compounds also exhibited synergistic effects on viral replication with remdesivir.

Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of Nsp5 main protease

The coronavirus 2019 (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), spread around the world with unprecedented health and socio-economic effects for the global population. While different vaccines are now being made available, very few antiviral drugs have been approved. The main viral protease (nsp5) of SARS-CoV-2 provides an excellent target for antivirals, due to its essential and conserved function in the viral replication cycle. We have expressed, purified and developed assays for nsp5 protease activity. We screened the nsp5 protease against a custom chemical library of over 5000 characterised pharmaceuticals. We identified calpain inhibitor I and three different peptidyl fluoromethylketones (FMK) as inhibitors of nsp5 activity in vitro, with IC50 values in the low micromolar range. By altering the sequence of our peptidomimetic FMK inhibitors to better mimic the substrate sequence of nsp5, we generated an inhibitor with a subnanomolar IC50. Calpain inhibitor I inhibited viral infection in monkey-derived Vero E6 cells, with an EC50 in the low micromolar range. The most potent and commercially available peptidyl-FMK compound inhibited viral growth in Vero E6 cells to some extent, while our custom peptidyl FMK inhibitor offered a marked antiviral improvement.

Identifying SARS-CoV-2 antiviral compounds by screening for small molecule inhibitors of Nsp3 papain-like protease

The COVID-19 pandemic has emerged as the biggest life-threatening disease of this century. Whilst vaccination should provide a long-term solution, this is pitted against the constant threat of mutations in the virus rendering the current vaccines less effective. Consequently, small molecule antiviral agents would be extremely useful to complement the vaccination program. The causative agent of COVID-19 is a novel coronavirus, SARS-CoV-2, which encodes at least nine enzymatic activities that all have drug targeting potential. The papain-like protease (PLpro) contained in the nsp3 protein generates viral non-structural proteins from a polyprotein precursor, and cleaves ubiquitin and ISG protein conjugates. Here we describe the expression and purification of PLpro. We developed a protease assay that was used to screen a custom compound library from which we identified dihydrotanshinone I and Ro 08-2750 as compounds that inhibit PLpro in protease and isopeptidase assays and also inhibit viral replication in cell culture-based assays.

From the 20th to the 21st century: the first 100 years of paediatrics in Singapore

In Singapore, paediatrics as a separate discipline was started in 1921 at Singapore General Hospital (SGH). From Mistri Wing to Alexandra Hospital (AH) and Tan Tock Seng Hospital (TTSH), paediatrics was started at National University Hospital (NUH) and the Children’s Hospital at KK Women’s and Children’s Hospital (KKH) from 1997. After World War II, neonatology started in KKH, followed by Toa Payoh Hospital (TPH), AH, NUH and SGH. Neonates from TPH and AH were moved to KKH in 1990. Our pioneering giants include Dr Gopal Haridas, Professors Wong Hock Boon (First Paediatrics Professor), Tan Cheng Lim and Tan Kim Leong. Paediatrics in Singapore is resplendent with many achievements. Prof Wong identified the relationship of hyperbilirubinaemia/kernicterus with glucose-6-phosphate dehydrogenase (G6PD) deficiency and initiated G6PD deficiency screening. This has saved many lives and improved the overall health of children in Singapore. 100 years on, we stand firmly on the shoulders of our pioneering clinician giants as we face the paediatric millennial health needs of this new century.

Homologous Lympho-Epithelial Kazal-type Inhibitor Domains Delay Blood Coagulation by Inhibiting Factor X and XI with Differential Specificity

Despite being initially identified in the blood filtrate, LEKTI is a 15-domain Kazal-type inhibitor mostly known in the regulation of skin desquamation. In the current study, screening of serine proteases in blood coagulation cascade showed that LEKTI domain 4 has inhibitory activity toward only FXIa, whereas LEKTI domain 6 inhibits both FXIa and FXaB (bovine FXa). Nuclear magnetic resonance structural and dynamic experiments plus molecular dynamics simulation revealed that LEKTI domain 4 has enhanced backbone flexibility at the reactive-site loop. A model of the LEKTI-protease complex revealed that FXaB has a narrower S4 pocket compared with FXIa and hence prefers only small side-chain residues at the P4 position, such as Ala in LEKTI domain 6. Mutational studies combined with a molecular complex model suggest that both a more flexible reactive-site loop and a bulky residue at the P4 position make LEKTI domain 4 a weaker but highly selective inhibitor of FXIa.

A comparison of intrauterine hemopoietic cell transplantation and lentiviral gene transfer for the correction of severe β-thalassemia in a HbbTh3/+ murine model

Major hemoglobinopathies place tremendous strain on global resources. Intrauterine hemopoietic cell transplantation (IUHCT) and gene transfer (IUGT) can potentially reduce perinatal morbidities with greater efficacy than postnatal therapy alone. We performed both procedures in the thalassemic HbbTh3/+ mouse. Intraperitoneal delivery of co-isogenic cells at embryonic days13-14 produced dose-dependent chimerism. High-dose adult bone marrow (BM) cells maintained 0.2-3.1% chimerism over ~24 weeks and treated heterozygotes (HET) demonstrated higher chimerism than wild-type (WT) pups (1.6% vs. 0.7%). Fetalliver (FL) cells produced higher chimerism than BM when transplanted at thesame doses, maintaining 1.8-2.4% chimerism over ~32 weeks. We boosted transplanted mice postnatally with BM cells after busulfan conditioning. Engraftment was maintained at >1% only in chimeras. IUHCT-treated nonchimeras and non-IUHCT mice showed microchimerism or no chimerism. Improved engraftment was observed with a higher initial chimerism, in HET mice and with the addition of fludarabine. Chimeric HET mice expressed 2.2-15.1% engraftment with eventual decline at 24 weeks (vs. <1% in nonchimeras) and demonstrated improved hematological indices and smaller spleens compared with untreated HETmice. Intravenous delivery of GLOBE lentiviral-vector expressing human β-globin (HBB) resulted in a vector concentration of 0.001-0.6 copies/cell. Most hematological indices were higher in treated than untreated HET mice, including hemoglobin and mean corpuscular volume, but were still lower than in WT. Therefore, direct IUGT and IUHCT strategies can be used to achieve hematological improvement but require further dose optimization. IUHCT will be useful combined with postnatal transplantation to further enhance engraftment.

The architecture of the OmpC-MlaA complex sheds light on the maintenance of outer membrane lipid asymmetry in Escherichia coli

A distinctive feature of the Gram-negative bacterial cell envelope is the asymmetric outer membrane (OM), where lipopolysaccharides and phospholipids (PLs) reside in the outer and inner leaflets, respectively. This unique lipid asymmetry renders the OM impermeable to external insults, including antibiotics and bile salts. In Escherichia coli, the complex comprising osmoporin OmpC and the OM lipoprotein MlaA is believed to maintain lipid asymmetry by removing mislocalized PLs from the outer leaflet of the OM. How this complex performs this function is unknown. Here, we defined the molecular architecture of the OmpC-MlaA complex to gain insights into its role in PL transport. Using in vivo photo-cross-linking and molecular dynamics simulations, we established that MlaA interacts extensively with OmpC and is located entirely within the lipid bilayer. In addition, MlaA forms a hydrophilic channel, likely enabling PL translocation across the OM. We further showed that flexibility in a hairpin loop adjacent to the channel is critical in modulating MlaA activity. Finally, we demonstrated that OmpC plays a functional role in maintaining OM lipid asymmetry together with MlaA. Our work offers glimpses into how the OmpC-MlaA complex transports PLs across the OM and has important implications for future antibacterial drug development.

Structural basis for the bacterial membrane insertion of dermcidin peptide, DCD-1L

Human dermcidin (DCD) is an antimicrobial peptide secreted constitutively by sweat glands. The anionic derivative, DCD-1L, comprises of the N-terminal 47 residues of DCD and one additional leucine residue. A previous NMR structure of DCD-1L in 50% TFE showed a partial helical conformation, and its crystal structure in the presence of Zn²⁺ outlined a hexameric linear α-helical bundle. Three different models to describe membrane insertion were proposed but no conclusion was drawn. In the current study, the NMR structure of DCD-1L in SDS micelles showed an "L-shaped" molecule with three fully formed α-helices connected by flexible turns. Formation of these helices in DCD-1L in the presence of POPG vesicles suggests that the acidic C-terminal region of DCD-1L can suppress the binding of DCD-1L to POPG vesicles at basic but not acidic pH. Mutation of charged residues on the N-terminal and C-terminal regions of DCD-1L cause differences in POPG binding, suggesting distinct functional roles for these two regions. Charged residues from these two regions are also found to differentially affect Zn²⁺ coordination and aggregation of DCD-1L in the absence or presence of SDS, as monitored by 1D NMR. Our data agrees with one of the three models proposed.

Vitamin D levels in 87 Asian patients with cutaneous lupus erythematosus: a case-control study

BACKGROUND

Cutaneous lupus erythematosus (CLE) is an autoimmune disease, often exacerbated by sun exposure. Patients are encouraged to avoid sun exposure, therefore predisposing them to vitamin D deficiency.

AIM

To investigate the prevalence of and risk factors for vitamin D deficiency in patients with CLE.

METHODS

Total serum 25-hydroxy vitamin D (25(OH)D) was measured in 87 consecutive patients with CLE and in 79 controls. Clinical characteristics, disease severity, medications used and lifestyle factors were analysed and compared to determine risk factors for inadequate (25(OH)D), defined as a serum (25(OH)D) level of < 20 μg/L.

RESULTS

We found that 51% (n = 44) of the patients with CLE had 25(OH)D levels of < 20 μg/L compared with 73% (n = 58) of the controls (P < 0.01). No significant differences in (25(OH)D) levels were found between cases and controls with regard to age, sex, ethnicity, smoking, sun exposure, sunblock use or vitamin D supplementation. Treatment with antimalarials showed a statistically significant association with lower vitamin D levels.

CONCLUSION

Low levels of vitamin D were found in both patients with CLE and controls. Despite being on vitamin D supplementation and living in an equatorial location, our Asian patients with CLE still had low levels of vitamin D. It is therefore important to ensure adequate vitamin D supplementation in patients with CLE, especially for those who are on antimalarial therapy.

Structure of AcrH-AopB Chaperone-Translocator Complex Reveals a Role for Membrane Hairpins in Type III Secretion System Translocon Assembly

Type III secretion systems (T3SSs) are adopted by pathogenic bacteria for the transport of effector proteins into host cells through the translocon pore composed of major and minor translocator proteins. Both translocators require a dedicated chaperone for solubility. Despite tremendous efforts in the past, structural information regarding the chaperone-translocator complex and the topology of the translocon pore have remained elusive. Here, we report the crystal structure of the major translocator, AopB, from Aeromonas hydrophila AH-1 in complex with its chaperone, AcrH. Overall, the structure revealed unique interactions between the various interfaces of AopB and AcrH, with the N-terminal "molecular anchor" of AopB crossing into the "N-terminal arm" of AcrH. AopB adopts a novel fold, and its transmembrane regions form two pairs of helical hairpins. From these structural studies and associated cellular assays, we deduced the topology of the assembled T3SS translocon; both termini remain extracellular after membrane insertion.

Recombinase and translesion DNA polymerase decrease the speed of replication fork progression during the DNA damage response in Escherichia coli cells

The SOS response is a DNA damage response pathway that serves as a general safeguard of genome integrity in bacteria. Extensive studies of the SOS response in Escherichia coli have contributed to establishing the key concepts of cellular responses to DNA damage. However, how the SOS response impacts on the dynamics of DNA replication fork movement remains unknown. We found that inducing the SOS response decreases the mean speed of individual replication forks by 30–50% in E. coli cells, leading to a 20–30% reduction in overall DNA synthesis. dinB and recA belong to a group of genes that are upregulated during the SOS response, and encode the highly conserved proteins DinB (also known as DNA polymerase IV) and RecA, which, respectively, specializes in translesion DNA synthesis and functions as the central recombination protein. Both genes were independently responsible for the SOS-dependent slowdown of replication fork progression. Furthermore, fork speed was reduced when each gene was ectopically expressed in SOS-uninduced cells to the levels at which they are expressed in SOS-induced cells. These results clearly indicate that the increased expression of dinB and recA performs a novel role in restraining the progression of an unperturbed replication fork during the SOS response.

A single-molecule approach to DNA replication in Escherichia coli cells demonstrated that DNA polymerase III is a major determinant of fork speed

The replisome catalyses DNA synthesis at a DNA replication fork. The molecular behaviour of the individual replisomes, and therefore the dynamics of replication fork movements, in growing Escherichia coli cells remains unknown. DNA combing enables a single-molecule approach to measuring the speed of replication fork progression in cells pulse-labelled with thymidine analogues. We constructed a new thymidine-requiring strain, eCOMB (E. coli for combing), that rapidly and sufficiently incorporates the analogues into newly synthesized DNA chains for the DNA-combing method. In combing experiments with eCOMB, we found the speed of most replication forks in the cells to be within the narrow range of 550-750 nt s(-1) and the average speed to be 653 ± 9 nt s(-1) (± SEM). We also found the average speed of the replication fork to be only 264 ± 9 nt s(-1) in a dnaE173-eCOMB strain producing a mutant-type of the replicative DNA polymerase III (Pol III) with a chain elongation rate (300 nt s(-1) ) much lower than that of the wild-type Pol III (900 nt s(-1) ). This indicates that the speed of chain elongation by Pol III is a major determinant of replication fork speed in E. coli cells.

Crystal structure of Der f 7, a dust mite allergen from Dermatophagoides farinae

BACKGROUND

Der f 7 is the group 7 allergen from the dust mite Dermatophagoides farinae, homologous to the major allergen Der p 7 from D. pteronyssinus. Monoclonal antibody that bind to residues Leu48 and Phe50 was found to inhibit IgE binding to residue Asp159, which is important for the cross-reactivity between Der f 7 and Der p 7.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we report the crystal structure of Der f 7 that shows an elongated and curved molecule consisting of two anti-parallel β-sheets--one 4-stranded and the other 5-stranded--that wrap around a long C-terminal helix. The overall fold of Der f 7 is similar to Der p 7 but key difference was found in the β1-β2 loop region. In Der f 7, Leu48 and Phe50 are in close proximity to Asp159, explaining why monoclonal antibody binding to Leu48 and Phe50 can inhibit IgE binding to Asp159. Both Der f 7 and Der p 7 bind weakly to polymyxin B via a similar binding site that is formed by the N-terminal helix, the 4-stranded β-sheet and the C-terminal helix. The thermal stability of Der f 7 is significantly lower than that of Der p 7, and the stabilities of both allergens are highly depend on pH.

CONCLUSION/SIGNIFICANCE

Der f 7 is homologous to Der p 7 in terms of the amino acid sequence and overall 3D structure but with significant differences in the region proximal to the IgE epitope and in thermal stability. The crystal structure of Der f 7 provides a basis for studying the function and allergenicity of this group of allergens.

NMR structure and IgE epitopes of Blo t 21, a major dust mite allergen from Blomia tropicalis

Blo t 21 is a paralogue of the group 5 allergen, Blo t 5, a major allergen from the dust mite Blomia tropicalis. Blo t 21 has moderate sequence identity (40.7%) to Blo t 5 and low to moderate cross-reactivity to Blo t 5. In B. tropicalis, the most prevalent and allergenic allergens are in the order of Blo t 21, Blo t 5, and Blo t 7. Here, we determined the NMR solution structure of Blo t 21, which represents the first structure of the group 21 dust mite allergen. The structure of Blo t 21 closely resembles the structures of Blo t 5 and Der p 5, comprising three anti-parallel α-helices arranged in a helical bundle. Using site-directed mutagenesis and specific IgE binding ELISA, Blo t 21 was found to contain both conserved and unique charged IgE epitope residues at the L2 loop region and on helix α3. Cross-inhibition assays confirmed that Blo t 21 has a low to moderate cross-reactivity with Blo t 5 and Der p 5 and represents a novel group of major allergen in B. tropicalis. In addition to group 5 allergens, Blo t 21 has also a low to moderate cross-reactivity with group 21 allergens from Dermatophagoides mites, confirming that B. tropicalis is a major and distinct source of dust mite allergens.

Evaluation of carbon-based nanosorbents synthesised by ethylene decomposition on stainless steel substrates as potential sequestrating materials for nickel ions in aqueous solution

The present work covers the preparation of carbon-based nanosorbents by ethylene decomposition on stainless steel mesh without the use of external catalyst for the treatment of water containing nickel ions (Ni2+). The reaction temperature was varied from 650 to 850 degrees C, while reaction time and ethylene to nitrogen flow ratio were maintained at 30 min and 1:1 cm3/min, respectively. Results show that nanosorbents synthesised at a reaction temperature of 650 degrees C had the smallest average diameter (75 nm), largest BET surface area (68.95 m2/g) and least amount of impurity (0.98 wt.% Fe). A series of batch-sorption tests were performed to evaluate the effects of initial pH, initial metal concentration and contact time on Ni2+ removal by the nanosorbents. The equilibrium data fitted well to Freundlich isotherm. The kinetic data were best correlated to a pseudo second-order model indicating that the process was of chemisorption type. Further analysis by the Boyd kinetic model revealed that boundary layer diffusion was the controlling step. This primary study suggests that the prepared material with Freundlich constants compared well with those in the literature, is a promising sorbent for the sequestration of Ni2+ in aqueous solutions.

Cloning, expression, purification, crystallization and preliminary X-ray diffraction studies of a major group 7 allergen, Der f 7, from the dust mite Dermatophagoides farinae

Der f 7 is a major group 7 allergen from the dust mite Dermatophagoides farinae that shows 86% sequence identity to the homologous allergen Der p 7 from D. pteronyssinus. Der f 7 was successfully overexpressed in an Escherichia coli expression system and purified to homogeneity using Ni-NTA affinity and size-exclusion column chromatography. SeMet-labelled Der f 7 was crystallized by the hanging-drop vapour-diffusion method using a reservoir solution consisting of 0.1 M bis-tris pH 7.4 and 28% polyethylene glycol monomethyl ether 2000 at 293 K. X-ray diffraction data were collected to 2.24 Å resolution using synchrotron radiation. The crystals belonged to the orthorhombic system, space group P2(1)2(1)2(1), with unit-cell parameters a = 50.19, b = 58.67, c = 123.81 Å. Based on the estimated Matthews coefficient (2.16 Å(3) Da(-1)), two molecules of Der f 7 could be present in the asymmetric unit of the crystal lattice.

Sidewall oxide effects on spin-torque- and magnetic-field-induced reversal characteristics of thin-film nanomagnets

The successful operation of spin-based data storage devices depends on thermally stable magnetic bits. At the same time, the data-processing speeds required by today's technology necessitate ultrafast switching in storage devices. Achieving both thermal stability and fast switching requires controlling the effective damping in magnetic nanoparticles. By carrying out a surface chemical analysis, we show that through exposure to ambient oxygen during processing, a nanomagnet can develop an antiferromagnetic sidewall oxide layer that has detrimental effects, which include a reduction in the thermal stability at room temperature and anomalously high magnetic damping at low temperatures. The in situ deposition of a thin Al metal layer, oxidized to completion in air, greatly reduces or eliminates these problems. This implies that the effective damping and the thermal stability of a nanomagnet can be tuned, leading to a variety of potential applications in spintronic devices such as spin-torque oscillators and patterned media.

Optimising management in Turner syndrome: from infancy to adult transfer

Turner syndrome can be defined as loss or abnormality of the second X chromosome in at least one cell line in a phenotypic female. The condition occurs in approximately 1 in every 2000 live female births,(1) so that in the UK the prevalence for any year of life is in the region of 200 girls. The condition is much more common in utero, it being estimated that 1-2% of all conceptuses are affected, of whom only 1% will survive to term.

Angiotensin-I converting enzyme insertion/deletion polymorphism and its association with diabetic nephropathy: a meta-analysis of studies reported between 1994 and 2004 and comprising 14,727 subjects

AIMS/HYPOTHESIS

The ACE insertion/deletion polymorphism has been examined for association with diabetic nephropathy over the past decade with conflicting results. To clarify this situation, we conducted a comprehensive meta-analysis encompassing all relevant studies that were published between 1994 and 2004 and investigated this potential genetic association.

METHODS

A total of 14,727 subjects from 47 studies was included in this meta-analysis. Cases (n=8,663) were type 1 or 2 diabetic subjects with incipient (microalbuminuria) or advanced diabetic nephropathy (proteinuria, chronic renal failure, end-stage renal disease). Control subjects (n=6,064) were predominantly normoalbuminuric.

RESULTS

No obvious publication bias was detected. Using a minimal-case definition based on incipient diabetic nephropathy, subjects with the II genotype had a 22% lower risk of diabetic nephropathy than carriers of the D allele (pooled odds ratio [OR]=0.78, 95% CI=0.69-0.88). While there was a reduced risk of diabetic nephropathy associated with the II genotype among Caucasians with either type 1 or type 2 diabetes, the association was most marked among type 2 diabetic Asians (Chinese, Japanese, Koreans) (OR=0.65, 95% CI=0. 51-0.83). This OR is significantly different from the OR of 0.90 (95% CI= 0.78-1.04) that was obtained for type 2 diabetic Caucasians (p=0.019). Using a stricter case definition based on advanced diabetic nephropathy, a comparable risk reduction of 24-32% was observed among the three subgroups, although statistical significance was reached only among Asians.

CONCLUSIONS/INTERPRETATION

The results of our meta-analysis support a genetic association of the ACE Ins/Del polymorphism with diabetic nephropathy. These findings may have implications for the management of diabetic nephropathy using ACE inhibitors especially among type 2 diabetic Asians.

A randomized trial of amifostine as a cytoprotectant for patients receiving myeloablative therapy for allogeneic hematopoietic stem cell transplantation

We initiated a randomized study of amifostine (the organic thiophosphate formerly known as WR-2721) given to patients during myeloablative conditioning therapy for allogeneic bone marrow transplantation. Amifostine was given at a dose of 1000 mg/day of conditioning and was well tolerated if attention was given to serum calcium levels, blood pressure and antiemetics. Since August 1998, 60 patients (30 on each arm) have completed the study. There was no significant difference in the days to neutrophil or platelet engraftment in either arm of the study. Significantly, the duration of grade I-IV mucositis was decreased in the group that received amifostine (P=0.02). Also grade III or IV infections (P=0.008), duration of antibiotic therapy (P=0.03) and duration of fever (P=0.04) were significantly reduced with amifostine. However, there were no differences in the incidence of grade III or IV mucositis, liver toxicity or renal toxicity. There were also no differences in early mortality, relapse and long-term survival. We conclude that amifostine, while reducing the duration of mucositis and infections (possibly through some preservation of gut mucosal integrity), has a modest effect in allogeneic bone marrow transplants given the multiplicity of factors influencing organ toxicity and survival in this setting.

Variation in mortality and intraventricular haemorrhage in occupants of Pacific Rim nurseries

OBJECTIVE

A network of neonatal intensive care units in Pacific Rim countries was formed to compare infant risk factors, clinical practices, and outcomes for very low birthweight infants.

METHODOLOGY

A multicentre, prospective study compared outcomes for infants born smaller than 1501 g or at less than 31 weeks gestation.

RESULTS

Gestational age-specific survival and incidence of intracranial haemorrhage varied for infants born in these nurseries. We found differences in infant risk factors among the nurseries. There were also significant differences in the use of antenatal steroids, but similar rates for Caesarean section and surfactant treatment. The factor most predictive of neonatal death and severe intracranial abnormality was an elevated Clinical Risk Index for Babies (CRIB) score. Antenatal steroid treatment (>24 h prior to delivery) was associated with improved survival and decreased incidence of severe intracranial abnormalities. Antenatal steroid treatment for less than 24 h prior to delivery was not associated with improved survival. Caesarean delivery was associated with improved survival, but showed no benefit regarding the incidence of severe intracranial abnormality.

CONCLUSIONS

Our Pacific Rim nursery network found differences in neonatal outcomes that correlated best with measures of neonatal risk at birth, antenatal steroid treatment, and Caesarean delivery. These data emphasize the importance of obstetric care to improve postnatal outcomes in premature infants, and highlight the usefulness of CRIB scores in these patients.

Ureaplasma urealyticum and its association with chronic lung disease in Asian neonates

OBJECTIVE

The aim of the present prospective cohort study was to evaluate the relationship between lower respiratory tract colonization with Ureaplasma urealyticum and development of chronic lung disease (CLD) in a high-risk neonatal population.

METHODS

Prospective cohort study of preterm infants with a birthweight < 1,500 g needing mechanical ventilation within 24 h of birth in a tertiary care neonatal unit. Endotracheal aspirates from these infants were cultured within 24 h for U. urealyticum and the rate of colonization was determined. The primary outcome measure was the incidence of CLD at 28 days of life.

RESULTS

Of the 41 infants studied, 10 (24%) infants were colonized with U. urealyticum. The colonization rate was higher in babies < 1,000 g compared with babies weighing 1,000-1,500 g (P = 0.04). There was no significant difference between the colonized and non-colonized groups with regard to the antenatal use of steroids, maternal prolonged rupture of membranes, gestational age, birthweight, sex, respiratory distress syndrome, use of surfactant, patent ductus arteriosus and gastrooesophageal reflux. Of the 37 survivors, 20 (54%) developed CLD; eight infants (88.5%) in the colonized group developed CLD compared with 12 infants (42.8%) in the non-colonized group (P = 0.01).

CONCLUSIONS

Neonates colonized with U. urealyticum were twice as likely to have CLD than non-colonized babies (relative risk 2.01; 95% confidence interval 1.27-3.37). These data suggest a significant association between colonization with U. urealyticum and CLD in infants weighing < 1,500 g.

Perinatal drug abuse in KK Women's and Children's Hospital

No local figures are available in Singapore on the incidence of perinatal drug abuse and its effect on the foetus and the neonate. The objectives of this study were to determine the incidence of perinatal drug abuse and neonatal abstinence syndrome; to identify a maternal profile at high risk for substance abuse and to document the presenting features and treatment of infants with neonatal abstinence syndrome. Out of 14,690 births during the period January 1994 to December 1996, 38 (0.25%) had evidence of perinatal drug abuse. The study revealed that a high-risk maternal profile for drug abuse comprised of single mothers (52%); history of smoking (52%); no antenatal care (37%) and belonging to the Malay ethnic group (82%); and younger maternal age. Self-reporting was uncommon, occurring only in 8% and in 40% of cases, there was no known history of maternal drug addiction. The drug abused in all cases was heroin. Human immunodeficiency virus (HIV) screening was done only in a minority (21%) of the mothers and it was negative in all. Eighteen (47%) infants had evidence of neonatal abstinence syndrome with neurological manifestations being the commonest. Urine toxicology screening was positive in 26% of cases and had only 70% sensitivity and 41% positive predictive value. On follow up, default rate was high with 42% babies not attending follow up at the outpatient clinic. In conclusion, there is a need to maintain a high index of suspicion of substance abuse in those with high-risk maternal profile and their neonates should be closely watched for features of neonatal abstinence syndrome. Alternative methods of toxicology screening apart from urine need to be evaluated in order to improve the drug detection rate.

Blood pressure standards for very low birthweight infants during the first day of life

Blood pressures during the first day of life were measured prospectively in 61 very low birthweight infants using umbilical or peripheral arterial lines. Video recordings of real time waveforms were reviewed. Blood pressure correlated linearly with birthweight and gestation. Comparison with available standards showed that infants weighing under 800 g had lower acceptable mean arterial pressure (MAP). The lower limits of MAP for infants between 26 to 32 weeks of gestation were numerically similar to the gestational ages.

Persistence of anti-hypertensive effect after missed dose of perindopril

AIMS

To assess the persistence of the antihypertensive effect of the ACE-inhibitor perindopril after one missed dose.

METHODS

After a placebo run-in period, 10 hypertensive patients were started on perindopril 4 mg once daily in the morning, increased to 8 mg once daily after 4 weeks if office diastolic BP >85 mmHg. 24 h BP monitoring was performed at the end of the placebo run-in period and during active treatment in week 9 and 10 on either active treatment or a placebo-day using a double-blind, randomized, cross-over design.

RESULTS

Office BP decreased from 155+/-3/100+/-2 mmHg at the end of placebo to 139+/-3/89+/-2 mmHg (P<0.05 vs placebo) after 8 weeks of active treatment. After 2 months of active treatment, 24 h ABP showed significant decreases in day BP by -11+/-1/-7+/-1 mmHg and in night BP by -11+/-2/-7+/-1 mmHg while on active treatment. During the placebo-day, daytime BP showed decreases by -10+/-1/-5+/-1 and night BP by -8+/-2/-6+/-1 mmHg (NS vs active treatment day).

CONCLUSIONS

Perindopril 4-8 mg day-1 causes a persistent decrease in BP during the 24 h dosing interval, which is mostly maintained over the 24-48 h after dosing.

Parainfluenza type 3 viral outbreak in a neonatal nursery

An outbreak of parainfluenza virus type 3 infection that occurred in a special neonatal care unit is described. Birth weights of affected infants ranged from 1860 to 2080 g and gestational ages were between 28 and 32 weeks. Three infants presented with recurrent episodes of apnoea associated with oxygen desaturations on postnatal ages of 16 days, 26 days and 66 days respectively; upper respiratory tract infection symptoms such as coryza were absent in them. Two older infants who had oxygen dependent bronchopulmonary dysplasia presented with worsening of the respiratory status due to bronchiolitis at 5 and 6 months of age respectively. All infants required supplemental oxygen and assisted ventilatory support and there were no deaths. Parainfluenza virus type 3 was identified by direct antigen detection in 3 cases and was isolated in the other two. The outbreak was controlled by isolating the infected infants, use of gowns and strict hand washing. Nonporous surfaces contaminated with parainfluenza virus type 3 were cleansed with water and detergent. Viral respiratory infections should be considered in the differential diagnosis when growing premature infants present with recurrent apnoeic episodes and they may be severe enough to require assisted ventilatory support. The source of the outbreak was possibly a medical officer and a medical student who had an upper respiratory tract infection prior to the outbreak in the nursery. Medical and nursing staff with viral respiratory infections should avoid working in the nurseries until they are well.

Group B Streptococcal septicaemia/meningitis in neonates in a Singapore teaching hospital

Our aims were to establish the incidence and clinical characteristics of early and late onset Group B Streptococcal (GBS) septicaemia in neonates in our hospital over a period of 1 year. Routine screening for maternal GBS was not standard practice in the hospital. GBS was isolated from high vaginal swabs (HVS) obtained antenatally or postnatally for risk factors as determined by the obstetrician or neonatologist in charge. Data obtained were analyzed separately and these did not form part of the study. By a system of clinical case review and follow-up, mail, telephone and home visits, the outcome of all 15,062 livebirths in the hospital over a 1-year period were verified and reported. Our results show a low incidence of GBS infection in neonates in the hospital: early onset disease was 0.265 per 1,000 livebirths and late onset a quarter of that. The majority of our cases of early onset GBS disease were in premature infants. Because of our low incidence, prophylaxis schedules would have to ensure an acceptably smaller number of mothers exposed to antibiotics over and above the current level and the cooperation of our obstetricians. We have devised a schedule incorporating a current PROM (prelabour premature rupture of membranes) protocol which would result in only an additional 2.2% of mothers requiring prophylactic antibiotics.

Congenital candidiasis: varied presentations

Congenital candidiasis, especially the disseminated disease, is very uncommon but has been reported in very low birth weight infants. Five cases of congenital candidiasis, two with cutaneous type and three with systemic type, are described. All cases were symptomatic within the first 24 hours of life and none of them had significant risk factors such as the presence of foreign body in the maternal genital tract. Cutaneous candidiasis presented as extensive erythematous rash with infiltrative plaques in one and as bullous lesions in the other. Three infants who had disseminated candidiasis presented with extreme leukemoid reaction, severe hyperglycemia, and skin mottling with some patchy areas resembling first-degree burns, respectively. One infant had meningitis and the autopsy of another who died revealed several microabscesses containing Candida spores in the liver and lungs. The urine microscopy obtained by suprapubic bladder aspiration was found to be a good diagnostic marker of systemic invasion. The purpose of this report is to highlight the importance of recognizing candida as a possible pathogen in a critically ill neonate even though the clinical presentation may be nonspecific and varied. The presence of characteristic skin lesions of Candida species within 24 hours of life is an important clue to the possible diagnosis of congenital candidal infection. Even though very high mortality has been reported in congenital disseminated candidiasis, early recognition and treatment could give a favorable outcome.

Efficacy and tolerability of doxazosin versus enalapril in the treatment of patients with mild-to-moderate hypertension

The effects of 4 weeks of treatment with doxazosin or enalapril on diastolic blood pressure (DBP) and plasma lipid levels were studied in 160 patients 18 to 50 years old with mild-to-moderate hypertension. Comparing baseline measurements with measurements taken after 4 weeks, DBP was significantly reduced by 6.8 +/- 7.4 (mean +/- SD) mm Hg and 12.0 +/- 7.1 mm Hg in the doxazosin and enalapril groups, respectively. Systolic blood pressure was significantly decreased from baseline to end of treatment in both groups. There were no significant changes in heart rate from baseline to end of treatment in the doxazosin group, but there was a statistically significant decrease in heart rate in the enalapril group. High-density lipoprotein cholesterol increased statistically significantly in the doxazosin group but not in the enalapril group. A decrease in triglycerides was statistically significant with respect to the doxazosin group and was close to significance for the enalapril group. Forty-nine (62%) patients in the doxazosin group and 43 (54%) patients in the enalapril group reported at least one adverse event. Significant reductions in DBP after 4 weeks of treatment were achieved by both drugs, each taken once daily. This reduction was more pronounced in the enalapril group 24 hours postdose, with a mean final daily dose of 2.8 mg of doxazosin and 12.6 mg of enalapril. However, even relatively short-term treatment with low-dose doxazosin showed a more favorable effect on lipids than did enalapril.

Is 'herbal health tonic' safe in pregnancy; fetal alcohol syndrome revisited

So called 'Herbal Health Tonics' are freely available in the market. This has been promoted by the manufacturers for the following symptoms: poor appetite, gastroenteric weakness, poor blood circulation, chills, fatigue, weak constitution and weakness after disease. We report a case of suspected fetal alcohol syndrome (FAS). A baby boy of 3,700 g born to a 29-year-old Chinese mother at 41 weeks' gestation was found to have features consistent with FAS. On follow up at 3 years of age, both motor and mental milestones as well as speech and language were delayed suggesting the possibility of FAS. There was a history of maternal ingestion of 'Herbal Health Tonic' (which contained 14% alcohol) daily for the first 2 months of the antenatal period. She denied exposure to alcohol or any other drugs. The authors would like to highlight the risk of such 'Herbal Health Tonics' in pregnancy and their probable deleterious effects on the growing fetus. We feel that it is extremely important to look into the traditional practices among pregnant women in Singapore and in other parts of the world where there are similar practices, otherwise more cases like these could occur in future.

The 'TRAP' sequence--life threatening consequences to the pump twin

The acardius foetal malformation is a rare abnormality occurring in monozygotic multiple pregnancies. This is a case report of a pair of twins with the "twin reversed arterial perfusion (TRAP)" sequence and its complications. The recipient twin was born acardius acephalus. The pump twin had problems of prematurity, disseminated intravascular coagulation, sclerema and right ventricular hypertrophy. On follow-up at seven months he has failure to thrive, spastic quadriplegia and developmental delay. An awareness of the TRAP sequence may lead to better antenatal diagnosis and optimal management of the twin pregnancy.

An outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit in Singapore: a 20-month study of clinical characteristics and control

Methicillin resistant Staphylococcus aureus (MRSA) is a major infection control problem in many countries. There have been many reports of outbreaks in neonatal nurseries including, in our part of the world, Australia, Hong Kong and Malaysia. A recent outbreak of MRSA in the neonatal intensive care unit in the Kandang Kerbau Hospital, Singapore, presented us with the opportunity to study the clinical characteristics of the outbreak and the effects of infection control measures. Neonates admitted to the neonatal intensive care unit were studied over a 20-month period. They were all screened for nasal colonisation on admission and weekly thereafter. Infections were documented. Over this period there were altogether 2,576 admissions of which 85 infants had nasal colonisation with MRSA (3.3%) and 28 developed infections (1%). Although the majority of infants colonised by MRSA suffered no ill effects, 3 had septicaemia and 2 had septicaemia with osteomyelitis. There were no deaths. Standard infection control measures with barrier nursing and the use of mupirocin nasal ointment were ineffective, and control was achieved only after strict cohorting together with the use of mupirocin was instituted. This was done without additional costs to the department and without additional nurses or doctors.

A survey of postoperative wound infections in obstetrics and gynaecology--the Kandang Kerbau Hospital experience

Postoperative wound infection is of great importance to both the surgeon and patient. This study covers 6,639 major operations in Kandang Kerbau Hospital, Singapore over a 12-month period. The overall wound infection rate was 2.26%. The highest wound infection rate occurred in hysterectomies and the lowest in laparoscopies. There was a good correlation between monthly caesarean wound infection rate and number of caesarean sections. Staphylococcus aureus was the most common organism isolated. The wound infection rate was also higher in crowded wards and among some surgeons. After distribution of the survey results, we noted a decrease in wound infection rate for some surgeons and a changing pattern in the use of antibiotics. A further study of other risk factors was encouraged.

Acute glomerulonephritis--changing patterns in Singapore children

This study compared the pattern of acute glomerulonephritis (AGN), a disease known to be influenced by socioeconomic and environmental factors, in children 12 years and under, for the years 1971 and 1985. All children admitted to the four major paediatric departments with haematuria and at least two of the following (oedema, hypertension or oliguria) had an initial diagnosis of AGN. A sample population from one unit from 1980 to 1984 showed that over 70% of these children had evidence of a post-streptococcal aetiology. In 1971, 411 children were admitted with AGN, as compared with only 58 in 1985. The age-sex-race standardized rates for 1971 and 1985 were 0.632 and 0.023/1,000 children 12 years and under, respectively (P less than 0.001). The mean age of presentation was lower in 1971. Over this period, Singapore saw a threefold rise in the gross national product, accompanied by rapid urbanization. On analysis of the housing pattern, only 31% of the children lived in high-rise apartments in 1971, in contrast with 86% in 1985 (P less than 0.001). The majority of non-apartment dwellers had homes in rural districts. From an epidemiological perspective, factors which could have led to the highly significant decline in prevalence of AGN in Singapore children included improvement in the socioeconomic status and health care system, and urbanization of the country.

Reliability of the Dinamap non-invasive monitor in the measurement of blood pressure of ill Asian newborns

Four hundred thirty-one paired sets of readings of systolic and diastolic blood pressure and 438 paired sets of readings of mean arterial BP from 49 ill newborns, including 21 very low birth weight infants, were analyzed for the extent and pattern of agreement and the linear relationship between the Dinamap oscillometric monitor and the direct intraarterial blood pressure readings. Agreement between the two methods was measured by the intraclass correlation, whereas the linear relationship was assessed by the product-moment correlation. The intraclass correlations for systolic, diastolic and mean blood pressures were 0.696, 0.766, and 0.781, respectively. The product-moment correlations for systolic, diastolic and mean blood pressures were 0.706, 0.768, and 0.786, respectively. BP measurements by the Dinamap monitor showed reasonably close agreement to those obtained by the intraarterial mean arterial pressure ranges above 40 mmHg. For mean arterial pressure of 40 mmHg and lower, BP readings by the Dinamap monitor tended to be higher than those obtained by the intraarterial method. These findings appeared to be consistent regardless of the birth weight of the newborn.

Neonatology in Singapore

A short account of the history of Neonatology in Singapore is given. Current practice and results of management of neonates are highlighted and future directions for neonatology in Singapore outlined. Brief mention is made of 2 common controversies in neonatal practice.

Kawasaki disease--the Singapore experience

50 children with Kawasaki disease were seen between September 1983 to March 1988. Their ages ranged from 3 months to 10 years with a mean age of 25 months. Male to Female ratio was 2.3 to 1. The diagnosis of Kawasaki disease was made between the fourth to fifteenth day of illness. Marked thrombocytosis, raised erythrocyte sedimentation rate, leucocytosis, mild anemia and sterile pyuria were common features. All patients had a normal ECG and chest X-ray. 2D echocardiogram was done in the sub-acute phase of the illness in every patient. Sixteen patients (32%) had coronary artery dilatation. Thirteen of these had serial 2D echocardiograms done over a period of more than one year. Twelve had echocardiographic resolution of the coronary lesion within 18 months of follow up. Patients with coronary artery dilatation were significantly younger. All had full clinical recovery with aspirin therapy. Kawasaki disease afflicts mostly young children and can present as a diagnostic problem. Coronary artery involvement is common, and except for age, it is not predictable by any clinical or laboratory parameter. Serial echocardiographic examinations are necessary in the management of these patients.

HLA-DR antigens in Chinese children with insulin-dependent diabetes mellitus

We studied the distribution of HLA-DR and MT1, MT2, MT3 genotypes in 23 Chinese children with insulin-dependent diabetes mellitus (IDDM). The frequency of DR3 was 48% in IDDM children compared to 14% of normal controls (corrected p = 0.0098, RR = 5.70). The frequency of DR4 was not increased. These differences when compared with the results of Western populations may contribute to the relative rarity of IDDM among Chinese children.

HLA-system in Chinese children with insulin-dependent diabetes mellitus: a strong association with DR3

We studied the distribution of HLA-A, B, and DR and MT1, MT2, MT3 genotypes in all 20 Chinese children with insulin-dependent diabetes mellitus (IDDM) attending the four government pediatric units in Singapore. We found an increase in HLA BW22 but the corrected probability value was not statistically significant. AW33 and B17 were observed in 50% and 55% of IDDM children, respectively, compared with 11% and 13% of normal controls, respectively. The values for AW33 were as follows: corrected P = 0.00094 and relative risk (RR) = 8.17; for B17 they were corrected P = 0.001 and RR = 7.55. In addition, the frequency of DR3 was 50% in IDDM children compared with 14% of normal controls (corrected P = 0.0019, RR = 6.20). AW33, B17, and DR3 are in linkage disequilibrium in our normal Chinese population. All ten patients who were positive for DR3 also had B17. The frequency of DR4 was not increased, and there were no protection IDDM related antigens found. These differences compared with the results in Western populations may contribute to the relative rarity of IDDM among Chinese children.

Five years' experience with aortocoronary bypass grafting

During a 5-year period (Apr. 14, 1970 to Apr. 14, 1975) 930 patients underwent aortocoronary bypass grafting; the procedure was done as an emergency in 141. Of the entire group 3.3% died at operation, 1.6% died in hospital and 5.8% died later; of the patients undergoing emergency grafting 12.1% died at operation and 5.7% died later. From a detailed analysis of the first 600 patients it was found that both operative and late mortality were clearly related to two factors: severe left ventricular dysfunction at the time of operation and inadequate surgical treatment because of insertion of insufficient numbers of grafts or because of poor blood flow through the grafts.

The synthesis of Benzo[4,5]cyclohepta[1,2,3-de]naphthalene

Muller et al have recently reported a synthesis of benzo[4,5] cyclohepta[1,2,3-de]naphthalene by a dehydrogenation reaction. Some investigations into alternative routes to this compound are now reported. One of these succeeded in giving a compound identical with that described by the previous workers.