Biomedical subjects
Publications and source records attributed to S L Yu.
Explore the source record for details and available documents.
Pregnancy is a normal physiological state that is characterised by significant adaptive changes, many of which take place in the cardiovascular system. These adaptations are believed to be the cause for the increased incidence in cardiac arrhythmias in pregnancy and particularly, in labour. We report an unusual case of a healthy 32-year-old primigravida who developed profound intrapartum bradycardia which persisted throughout labour. Spontaneous recovery to pre-labour baseline heart rate occurred following spontaneous vaginal delivery. Maternal and foetal statuses remained satisfactory during labour. This case report underscores the importance of recognising that arrhythmias in various forms are common in labour. In the absence of detectable underlying cardiac disease or maternal and foetal compromise, continuation of the labour with a view to vaginal delivery should be the goal.
The protein kinase adenosine monophosphate-activated gamma3-subunit (PRKAG3) gene encodes a muscle-specific isoform of the regulatory gamma-subunit of adenosine monophosphate-activated protein kinase, which plays a key role in regulating energy homeostasis in eucaryotes. It is well known that mutations in the PRKAG3 gene affect high glycogen content in the porcine skeletal muscle and, consequently, meat quality. The genomic structure and sequence of the bovine PRKAG3 were analysed from a Korean cattle BAC clone. The bovine PRKAG3 gene comprises 13 exons and spans approximately 6.8 kb on BTA2. From 5' and 3'-rapid amplification of cDNA ends experiments, the full-length cDNA of bovine PRKAG3 has been identified, encoding a deduced protein of 465 amino acids. Two splice isoforms, generated by the alternative splicing of exon 2, were also identified. Northern blot analysis demonstrated that, similar to other species, the bovine PRKAG3 transcript was only expressed in skeletal muscle. Seven single nucleotide polymorphisms, including two previously identified variants, were detected in four Bos taurus cattle breeds. The bovine PRKAG3 gene described in this study may be involved in muscle-related genetic diseases or meat quality traits in cattle.
INTRODUCTION: Transcatheter uterine artery embolisation (UAE) for the treatment of symptomatic uterine enlargement due to fibroids has been performed in several overseas centres with promising results. We report our experience with UAE in Singapore General Hospital. MATERIALS AND METHODS: Twenty women with symptomatic uterine fibroids who declined surgery were treated by transcatheter UAE. The uterine arteries were selectively catheterised and embolised with polyvinyl alcohol particles. Post-procedure analgesia was administered via a patient-controlled analgesia pump. The patients were followed up at regular intervals clinically and with transabdominal ultrasonography. RESULTS: Transcatheter UAE was performed on all patients with no major complications. Nineteen patients had both uterine arteries embolised while 1 patient had only the right uterine artery embolised on account of hypoplasia of the left uterine artery. The mean hospital stay was 3.5 days (range, 2 to 9). At a mean follow-up of 56 weeks (range, 6 to 168), all patients reported improvements in their presenting symptoms. Objective improvement in terms of reduction of uterine and fibroid sizes was determined on ultrasonography. The median size of the uterine volume decreased from 308 to 187 mL while the median diameter of the largest fibroid reduced from 6.2 to 4.6 cm. The median haemoglobin level increased to 12.7 g/dL from the pre-procedural median of 9.9 g/dL. One patient, who initially responded with a decrease in uterine and dominant fibroid size, became symptomatic (menorrhagia) at 6 months post-embolisation. She underwent a repeat procedure with complete resolution of symptoms. A second patient had recurrence of symptoms at 12 months, but was subsequently lost to follow-up. CONCLUSION: Mid-term results of UAE for the treatment of symptomatic fibroids in our hospital indicate this to be a safe and effective therapeutic option.
INTRODUCTION: Fasting during the month of Ramadan is compulsory in the Muslim faith. Although pregnant women may be exempted, many still choose to fast while others are more careful in practising it. This survey examines the practice of fasting among pregnant Muslim women in Singapore based on the prevalence in relation to factors such as parity, social and economic circumstances. It also analyses the factors that influence the decision to fast and the successful completion of the fast, and examines their knowledge, belief and attitudes on fasting during the holy month of Ramadan. METHODS: This is a retrospective study of all Muslim women who were pregnant and received antenatal care in our hospital during the month of Ramadan from 17 November 2001 to 16 December 2001. A four-page questionnaire was mailed to all eligible subjects in March 2002. RESULTS: Of 202 eligible subjects, 125 responded via mail and 57 via the phone, yielding a response rate of 90 percent. Most women chose to fast during pregnancy, and they do so with adequate support from their spouses and family members. Most of them do not experience any adversities during fasting and even if they do, most were able to overcome them. Most women adopt a positive attitude towards fasting. However, there is a lack of basic religious knowledge among many pregnant women pertaining to the Muslim law of fasting during pregnancy. CONCLUSION: Doctors and health workers need to understand the religious obligations of a Muslim towards fasting during Ramadan. Only through this can a doctor adequately counsel Muslim patients and allow informed decision with regards to fasting. With respect to pregnant women, provisions are allowed for them not to observe fasting.
Explore the source record for details and available documents.
INTRODUCTION: Investigations play a pivotal role in the workup for infertility. The results must be interpreted carefully as these assess dynamic function. Evidence-based guidelines are useful in the selection of appropriate tests. MATERIALS AND METHODS: A review of current evidence-based guidelines for the investigation and management of the infertile couple is undertaken. RESULTS: The main areas that correlate with fecundability are ovulatory function, tubal patency and semen analysis. CONCLUSION: The appropriate selection of investigations based on problem areas identified by history and physical examination would guide the physician in the management of the infertile couple.
Two microbiological sampling techniques, excision and sponge swabbing, were compared by determining counts of aerobic bacteria, coliforms and injured coliforms from 20 de-haired swine carcasses before and after chilling. Excised jowl skin produced significantly greater counts of the three types of bacteria than sponge swabs. Aerobic bacteria, coliforms and injured coliforms recovered by sponge swabbing carcasses before chilling were 11.6%, 0.9% and 11.0% of excised samples, respectively; the corresponding percentages recovered after chilling were 23.9%, 11.1% and 5.0%. Numbers of all bacteria present on the post-chill carcasses were substantially lower than on the pre-chill carcasses. Excision usually produced more countable plates for coliforms and injured coliforms on chilled carcasses than sponge swabbing and therefore, is more suitable in estimating low numbers of faecal bacteria on chilled carcasses. To explore the possible structural bases for these findings, skin samples were inoculated with 10(2)-10(7) cfu cm(-2) faecal bacteria and examined by scanning electron microscopy. Chilled samples showed bacteria and biofilm embedded in superficial crevices, which underlies a possible reason for the lower recovery of bacterial cells by the sponge swabbing. The study indicates that the differences between sampling techniques may be a result of the chilling process of swine carcasses.
The yeast RAD30-encoded DNA polymerase eta (Poleta) bypasses a cis-syn thymine-thymine dimer efficiently and accurately. Human DNA polymerase eta functions similarly in the bypass of this lesion, and mutations in human Poleta result in the cancer prone syndrome, the variant form of xeroderma pigmentosum. UV light, however, also elicits the formation of cis-syn cyclobutane dimers and (6-4) photoproducts at 5'-CC-3' and 5'-TC-3' sites, and in both yeast and human DNA, UV-induced mutations occur primarily by 3' C to T transitions. Genetic studies presented here reveal a role for yeast Poleta in the error-free bypass of cyclobutane dimers and (6-4) photoproducts formed at CC and TC sites. Thus, by preventing UV mutagenesis at a wide spectrum of dipyrimidine sites, Poleta plays a pivotal role in minimizing the incidence of sunlight-induced skin cancers in humans.
Mutations in the human CSB gene cause Cockayne syndrome (CS). In addition to increased photosensitivity, CS patients suffer from severe developmental abnormalities, including growth retardation and mental retardation. Whereas a deficiency in the preferential repair of UV lesions from the transcribed strand accounts for the increased photosensitivity of CS patients, the reason for developmental defects in these individuals has remained unclear. Here we provide in vivo evidence for a role of RAD26, the counterpart of the CSB gene in Saccharomyces cerevisiae, in transcription elongation by RNA polymerase II, and in addition we show that under conditions requiring rapid synthesis of new mRNAs, growth is considerably reduced in cells lacking RAD26. These findings implicate a role for CSB in transcription elongation, and they strongly suggest that impaired transcription elongation is the underlying cause of the developmental problems in CS patients.
OBJECTIVE: This study was to develop computer aided design system of anterior prosthesis, which can improve information communication among doctors, technicians, patients and raise anterior prosthesis cosmetic effect. METHODS: Digital camera was used for image capture; Space field method, neighboring field average method, midst value filter method, and image average method were used for image pre-process; sample teeth were constructed; anterior prosthesis were automatically designed through tooth feature extraction. RESULTS: 86 patients were prosthetically designed through this CAD system with excellent results. CONCLUSION: This system implemented anterior prosthesis CAD rapidly, guided clinical application and promoted information process in the field of prosthetics.
The microscopic classification of embryos, especially unipronuclear embryos, is not very precise. A number of undocumented and unipronuclear embryos were determined to be diploid following karyotyping and fluorescence in situ hybridization (FISH). Accelerated and asynchronous pronuclear dismantling at the time of checking for embryo fertilization accounts for this disparity. Diploid embryos were also observed among tripronuclear embryos. However, not all embryos ascertained as diploid by FISH were karyotypically normal following full karyotype analysis. By taking into account the "background" abnormality rate, the rate of diploid embryo wastage was estimated to be about 40% among undocumented embryos and about 58% in total. A high percentage of misclassification infers an unintended loss of otherwise transferable embryos. Such a discrepancy is particularly important to older women who have fewer embryos. If these are a woman's only embryos, preimplantation genetic diagnosis might be applicable in determining those that are diploid and suitable for transfer. This could potentially reduce the number of wasted embryos and cycles. The present study has also shown that mosaicism is common but it is still unclear whether mosaicism is indicative of embryonic abnormality or is a fairly common phenomenon among healthy embryos. Bipronuclear embryos that present with abnormal or delayed cleavage are often chaotic in their chromosomal constitution. Such embryos should not be transferred.
Oxidative damage to DNA has been proposed to have a role in cancer and ageing. Oxygen-free radicals formed during normal aerobic cellular metabolism attack bases in DNA, and 7, 8-dihydro-8-oxoguanine (8-oxoG) is one of the adducts formed. Eukaryotic replicative DNA polymerases replicate DNA containing 8-oxoG by inserting an adenine opposite the lesion; consequently, 8-oxoG is highly mutagenic and causes G:C to T:A transversions. Genetic studies in yeast have indicated a role for mismatch repair in minimizing the incidence of these mutations. In Saccharomyces cerevisiae, deletion of OGG1, encoding a DNA glycosylase that functions in the removal of 8-oxoG when paired with C, causes an increase in the rate of G:C to T:A transversions. The ogg1Delta msh2Delta double mutant displays a higher rate of CAN1S to can1r forward mutations than the ogg1Delta or msh2Delta single mutants, and this enhanced mutagenesis is primarily due to G:C to T:A transversions. The gene RAD30 of S. cerevisiae encodes a DNA polymerase, Poleta, that efficiently replicates DNA containing a cis-syn thymine-thymine (T-T) dimer by inserting two adenines across from the dimer. In humans, mutations in the yeast RAD30 counterpart, POLH, cause the variant form of xeroderma pigmentosum (XP-V), and XP-V individuals suffer from a high incidence of sunlight-induced skin cancers. Here we show that yeast and human POLeta replicate DNA containing 8-oxoG efficiently and accurately by inserting a cytosine across from the lesion and by proficiently extending from this base pair. Consistent with these biochemical studies, a synergistic increase in the rate of spontaneous mutations occurs in the absence of POLeta in the yeast ogg1Delta mutant. Our results suggest an additional role for Poleta in the prevention of internal cancers in humans that would otherwise result from the mutagenic replication of 8-oxoG in DNA.
Phage AR1 is similar to phage T4 in several essential genes but differs in host range. AR1 infects various isolates of Escherichia coli O157:H7 but does not infect K-12 strains that are commonly infected by T4. We report here the determinants that confer this infection specificity. In T-even phages, gp37 and gp38 are components of the tail fiber that are critical for phage-host interaction. The counterparts in AR1 may be similarly important and, therefore, were characterized. The AR1 gp37 has a sequence that differs totally from those of T2 and T4, except for a short stretch at the N terminus. The gp38 sequence, however, has some conservation between AR1 and T2 but not between AR1 and T4. The sequences that are most closely related to the AR1 gp37 and gp38 are those of phage Ac3 in the T2 family. To identify the AR1-specific receptor, E. coli O157:H7 was mutated by Tn10 insertion and selected for an AR1-resistant phenotype. A mutant so obtained has an insertion occurring at ompC that encodes an outer membrane porin. To confirm the role of OmpC in the AR1 infection, homologous replacement was used to create an ompC disruption mutant (RM). When RM was complemented with OmpC originated from an O157:H7 strain, but not from K-12, its AR1 susceptibility was fully restored. Our results suggest that the host specificity of AR1 is mediated at least in part through the OmpC molecule.
OBJECTIVE: To determine if total nucleated cell counts alone are sufficient for predicting the efficacy of cord blood units for transplant from neonatal umbilical cord blood samples. METHODS: Umbilical cord blood samples were collected from 200 mothers at delivery and the cord blood units processed. The total nucleated cells and CD34+ cells were enumerated and compared for each sample. RESULTS: Despite an apparent linear correlation between total nucleated cell counts and CD34+ cell counts, each group of total nucleated cell counts demonstrated a high degree of variation in CD34+ cell counts and could be as low as 0.1% of total nucleated cell counts. CONCLUSIONS: Large variations in CD34+ cell counts per total nucleated cell count are present for cord blood units from neonatal umbilical cord samples. Hence a CD34+ cell count for each cord blood unit would improve selection of samples for transplant.
Surgical retrieval of spermatozoa for in-vitro fertilisation (IVF) programs for severely oligospermic men has been in use for several years now. In the recent 2 to 3 years, clinicians have begun to move towards non-surgical methods of retrieving sperm in certain selected groups of men. Percutaneous epididymal sperm aspiration (PESA) has had good results in terms of number of sperm obtained, as well as the fertilisation and pregnancy rates. The first reported use of such a technique in Singapore is described.
Vesico-uterine fistula is a very rare complication of lower caesarean section. There has only been two cases seen at the Department of Urology in the past 2 decades. Patients usually present in the early post operative period with the problem of continuous urinary incontinence. On the rare occasion, recurrent urinary tract infection, recurrent gross painless haematuria, or secondary infertility associated with secondary amenorrhoea would be the presenting complaint.
The SGS1 gene of the yeast Saccharomyces cerevisiae encodes a DNA helicase with homology to the human Bloom's syndrome gene BLM and the Werner's syndrome gene WRN. The SRS2 gene of yeast also encodes a DNA helicase. Simultaneous deletion of SGS1 and SRS2 is lethal in yeast. Here, using a conditional mutation of SGS1, it is shown that DNA replication and RNA polymerase I transcription are drastically inhibited in the srs2Delta sgs1-ts strain at the restrictive temperature. Thus, SGS1 and SRS2 function in DNA replication and RNA polymerase I transcription. These functions may contribute to the various defects observed in Werner's and Bloom's syndromes.