Effect of pregnancy on renal graft function and maternal survival in renal transplant recipients.
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Creatinine↗
Biomedical subjects
P K Tan
Publications and source records attributed to P K Tan.
Pregnancy after renal transplantation: experience in Singapore General Hospital.
INTRODUCTION: Renal transplantation offers the best hope for those women with end-stage renal disease who wish to have children. However, pregnancy after renal transplantation is associated with increased maternal and fetal morbidity. The aim of this retrospective study was to review the outcome of pregnancy in renal transplant patients in Singapore General Hospital. MATERIALS AND METHODS: Forty-two pregnancies, occurring between December 1986 and December 2000, in 25 out of 141 renal transplant women in their reproductive age group (18 to 45 years old) were identified from our high-risk pregnancy record and retrospectively analysed. RESULTS: Thirteen (31%) pregnancies were unsuccessful; 10 abortions, 2 ectopic pregnancies and 1 stillbirth. The remaining 29(69%) successful pregnancies were complicated by maternal anaemia (65.5%), superimposed hypertension (44.8%), premature rupture of membranes (27.6%), urinary (17.2%) and lower genital tract (13.8%) infections, abnormal glucose tolerance test (13.8%), premature delivery (44.8%), low-birth-weight babies (44.8%), small-for-gestational-age babies (20.7%) and intrauterine growth restriction (20.7%). There were no documented cases of multiple pregnancies, congenital anomalies or deterioration of renal function. The outcome of pregnancy was not statistically influenced by preconception renal function and transplant-conception interval. CONCLUSIONS: Successful pregnancy is possible in women after renal transplantation. Such pregnancy is often associated with increased maternal and fetal complications and should be managed by a multidisciplinary approach in a tertiary centre. The function and survival of renal allograft was not adversely affected by pregnancy.
Abortion, Spontaneous↗
An acidic motif retains vesicular monoamine transporter 2 on large dense core vesicles.
The release of biogenic amines from large dense core vesicles (LDCVs) depends on localization of the vesicular monoamine transporter VMAT2 to LDCVs. We now find that a cluster of acidic residues including two serines phosphorylated by casein kinase 2 is required for the localization of VMAT2 to LDCVs. Deletion of the acidic cluster promotes the removal of VMAT2 from LDCVs during their maturation. The motif thus acts as a signal for retention on LDCVs. In addition, replacement of the serines by glutamate to mimic phosphorylation promotes the removal of VMAT2 from LDCVs, whereas replacement by alanine to prevent phosphorylation decreases removal. Phosphorylation of the acidic cluster thus appears to reduce the localization of VMAT2 to LDCVs by inactivating a retention mechanism.
Amino Acid Motifs↗
A phosphorylation site regulates sorting of the vesicular acetylcholine transporter to dense core vesicles.
Vesicular transport proteins package classical neurotransmitters for regulated exocytotic release, and localize to at least two distinct types of secretory vesicles. In PC12 cells, the vesicular acetylcholine transporter (VAChT) localizes preferentially to synaptic-like microvesicles (SLMVs), whereas the closely related vesicular monoamine transporters (VMATs) localize preferentially to large dense core vesicles (LDCVs). VAChT and the VMATs contain COOH-terminal, cytoplasmic dileucine motifs required for internalization from the plasma membrane. We now show that VAChT undergoes regulated phosphorylation by protein kinase C on a serine (Ser-480) five residues upstream of the dileucine motif. Replacement of Ser-480 by glutamate, to mimic the phosphorylation event, increases the localization of VAChT to LDCVs. Conversely, the VMATs contain two glutamates upstream of their dileucine-like motif, and replacement of these residues by alanine conversely reduces sorting to LDCVs. The results provide some of the first information about sequences involved in sorting to LDCVs. Since the location of the transporters determines which vesicles store classical neurotransmitters, a change in VAChT trafficking due to phosphorylation may also influence the mode of transmitter release.
Amino Acid Substitution↗
A leucine-based motif mediates the endocytosis of vesicular monoamine and acetylcholine transporters.
Specific transport proteins mediate the packaging of neurotransmitters into secretory vesicles and consequently require targeting to the appropriate intracellular compartment. To identify residues in the neuron-specific vesicular monoamine transporter (VMAT2) responsible for endocytosis, we examined the effect of amino (NH2-) and carboxyl (COOH-)-terminal mutations on steady state distribution and internalization. Deletion of a critical COOH-terminal domain sequence (AKEEKMAIL) results in accumulation of VMAT2 at the plasma membrane and a 50% reduction in endocytosis. Site-directed mutagenesis shows that replacement of the isoleucine-leucine pair within this sequence by alanine-alanine alone reduces endocytosis by 50% relative to wild type VMAT2. Furthermore, the KEEKMAIL sequence functions as an internalization signal when transferred to the plasma membrane protein Tac, and the mutation of the isoleucine-leucine pair also abolishes internalization of this protein. The closely related vesicular acetylcholine transporter (VAChT) contains a similar di-leucine sequence within the cytoplasmic COOH-terminal domain that when mutated results in accumulation of VAChT at the plasma membrane. The VAChT di-leucine sequence also confers internalization when appended to two other proteins and in one of these chimeras, conversion of the di-leucine sequence to di-alanine reduces the internalization rate by 50%. Both VMAT2 and VAChT thus use leucine-based signals for efficient endocytosis and as such are the first synaptic vesicle proteins known to use this motif for trafficking.
Acetylcholine↗
Neurotransmitter release from semi-intact synaptosomes.
We have developed a secretion assay composed of semi-intact synaptosomes from which transmitter release is optimally evoked by micromolar Ca2+ in the presence of cytosol. Transmitter release from this preparation reconstitutes known characteristics of regulated exocytosis and is accompanied by a marked decrease in synaptic vesicles. The assay is useful in characterizing the components known to be involved in transmitter release, and should also facilitate the identification of additional factors that are important for this process.
Animals↗
Ureteroscopic lithoclast lithotripsy: a cost-effective option.
Seventy-four consecutive cases of ureteral stones listed for ureteroscopic lithotripsy were studied prospectively. In all cases, the Wolf 7.5F or 9F ureteroscope was used in conjunction with the Swiss Lithoclast system. Dormia baskets were employed on four occasions to prevent forward propulsion of fragments. Ureteroscopic access to the stones was successful in 70 patients (95%). Lithoclast lithotripsy was successfully applied in 68 patients (92%), with complete fragmentation noted in 62 patients (91%), one requiring two sessions. The 6-week stone-free rate was 96% for these patients. Five patients with partial fragmentation had successful adjuvant SWL. The overall successful fragmentation rate was thus 84% (62 of 74) and 91% (67 of 74) in combination with adjuvant SWL. Cost analysis indicated a three-fold advantage for the Lithoclast over Candela lasertripsy. Ureteroscopic Lithoclast lithotripsy is a cost-effective treatment modality for ureteral stones.
Adult↗
Haematuria clinic--a preliminary audit and considerations for a one-stop assessment centre.
AIM: To audit and study the practicality of an integrated Haematuria Clinic as a one-stop assessment centre for the investigations of patients presenting with haematuria. METHODS: A weekly clinic was organised to facilitate consultation, intravenous urogram and flexible cystoscopy for patients with haematuria. A protocol was set up and data on symptoms, types of haematuria, results of the investigations and outcomes were collected. RESULTS: About half of all the patients seen in this clinic were found to harbour urological lesions; of which urolithiasis (20.4%) and urological malignancies (14.2%) were the most common lesions identified. Transitional cell carcinoma of the bladder was the most common malignancy diagnosed (8%). Significantly, 2 of 9 (22.2%) bladder cancers were found on cystoscopy and missed on the cystogram phase of the intravenous urogram. Ten urological lesions would have been missed if cystoscopies were not performed. Conversely, in 14 patients, cystoscopy could be avoided because their intravenous urograms identified lesions sufficiently to allow for definitive treatment. CONCLUSIONS: The need and types of investigation for patients with haematuria are evolving. We recommend intravenous urogram and flexible cystoscopy as the standard investigations and caution against ignoring microscopic haematuria. These assessments can be organised into an integrated clinic improving deliverance of clinical care; which may result in better patient compliance for investigations and earlier detection and treatment of urological lesions presenting as haematuria.
Adult↗
Traumatic dislocation of the testes.
Dislocation of the testes is an uncommon sequela of trauma. In contemporary times, it is usually associated with motorcycle accidents. We present 2 cases of unilateral traumatic testicular dislocation and 1 case of bilateral dislocation, all involving motorcyclists. Spontaneous reduction is rare. Early reduction is recommended because of histological changes seen in dislocated testes. Surgical reduction is often required. The significance of this condition must be emphasised to doctors managing trauma patients and early urological consultation obtained.
Accidents, Traffic↗
Suppressors of YCK-encoded yeast casein kinase 1 deficiency define the four subunits of a novel clathrin AP-like complex.
In Saccharomyces cerevisiae, the redundant YCK1 and YCK2 genes (Yeast Casein Kinase 1) are required for viability. We describe here the molecular analysis of four mutations that eliminate the requirement for Yck activity. These mutations alter proteins that resemble the four subunits of clathrin adaptors (APs), with highest sequence similarity to those of the recently identified AP-3 complex. The four yeast subunits are associated in a high-molecular-weight complex. These proteins have no essential function and are not redundant for function with other yeast AP-related proteins. Combination of suppressor mutations with a clathrin heavy chain mutation (chc1-ts) confers no synthetic growth defects. However, a yck(ts) mutation shows a strong synthetic growth defect with chc1-ts. Moreover, endocytosis of Ste3p is dramatically decreased in yck(ts) cells and is partially restored by the AP suppressor mutations. These results suggest that vesicle trafficking at the plasma membrane requires the activity of Yck protein kinases, and that the new AP-related complex may participate in this process.
Adaptor Proteins, Vesicular Transport↗
Leptomeningeal metastasis with urological presentation.
The incidence of clinical leptomeningeal metastases from non-neurologic solid tumour is generally increasing as a result of better survival of systemic cancer with chemotherapy. Their presentation varies according to the neurological involvement. A case of leptomeningeal metastasis from an unknown primary source presenting with urinary incontinence as the sole complaint is reported. While urinary incontinence is common in the community and is often functional, neurogenic causes must also be considered. Urodynamic study and electrophysiological assessment are useful investigations in the exclusion of a neurogenic cause. An MRI of the spine will be required to define any anatomic lesion.
Adenocarcinoma↗
Duodeno-ureteric fistula secondary to chronic duodenal ulceration.
Renoalimentary fistulae are rare. When they occur, they are usually between the right renal pelvis and the duodenum. The primary pathology often resides in the kidney, and nephrectomy is often necessary in the management of such fistulae. We describe a case of an elderly man who presented with non-specific abdominal pains. He had a history of peptic ulcer which was treated with H2 antagonist. He was well for the past few years until recently when he experienced upper abdominal pains. Subsequent investigations showed a duodeno-ureteric fistula secondary to a chronic duodenal ulcer. The kidney was normal. Polya gastrectomy was performed and the patient recovered with complete resolution of his symptoms.
Chronic Disease↗
Liver injury model in mice induced by a cellular immunologic mechanism--delayed-type hypersensitivity-induced liver injury to picryl chloride and phenotype of effector cell.
Liver injury was induced in BALB/c mice by local delayed-type hypersensitivity (DTH) to picryl chloride (PC1). Distinct changes of biochemical parameters were observed including the elevation of serum alanine and aspartate aminotransferases, increase of liver lipid peroxides, as well as decrease of serum alkaline phosphatase. Damage was confirmed by histopathological findings such as hepatocellular necrosis, granulocyte infiltration, and fatty degeneration. The liver injury was passively transferred into naive syngeneic mice by infusing spleen cells from immune mice. The capacity of the splenocytes to induce liver injury in recipient mice was almost completely abolished by pretreatment of the cells with anti-Thy 1.2 or anti-CD4, but not anti-CD8 antibody. These findings suggest that the production of liver injury by a local DTH mechanism is possible and the subpopulation of T cells, Thy-1.2+, L3T4+, and Lyt-2- cells, is at least one of the effector cells that mediate the injury.
Animals↗
The sequence NPFXD defines a new class of endocytosis signal in Saccharomyces cerevisiae.
The yeast membrane protein Kex2p uses a tyrosine-containing motif within the cytoplasmic domain for localization to a late Golgi compartment. Because Golgi membrane proteins mislocalized to the plasma membrane in yeast can undergo endocytosis, we examined whether the Golgi localization sequence or other sequences in the Kex2p cytoplasmic domain mediate endocytosis. To assess endocytic function, the Kex2p cytoplasmic domain was fused to an endocytosis-defective form of the alpha-factor receptor. Ste2p. Like intact Ste2p, the chimeric protein, Stex22p, undergoes rapid endocytosis that is dependent on clathrin and End3p. Uptake of Stex22p does not require the Kex2p Golgi localization motif. Instead, the sequence NPFSD, located 37 amino acids from the COOH terminus, is essential for Stex22p endocytosis. Internalization was abolished when the N, P, or F residues were converted to alanine and severely impaired upon conversion of D to A. NPFSD restored uptake when added to the COOH terminus of an endocytosis-defective Ste2p chimera lacking lysine-based endocytosis signals present in wild-type Ste2p. An NPF sequence is present in the cytoplasmic domain of the a-factor receptor, Ste3p. Mutation of this sequence prevented pheromone-stimulated endocytosis of a truncated form of Ste3p. Our results identify NPFSD as a clathrin-dependent endocytosis signal that is distinct from the aromatic amino acid-containing Golgi localization motif and lysine-based, ubiquitin-dependent endocytosis signals in yeast.
Amino Acid Sequence↗
Primary amyloidosis of the bladder: a case report.
An otherwise healthy elderly lady who presented with gross haematuria was found to have a papillary lesion in her bladder. Histological examination of the lesion showed amyloid deposits. Investigations for systemic amyloidosis were all negative. Primary amyloidosis of the bladder is a rare clinicopathological condition with only 57 documented cases in the medical literature. It often mimics bladder carcinoma in presentation and cystoscopic appearance. Amyloid deposits in the bladder may be primary (organ-limited amyloidosis) or part of systemic amyloidosis. Exclusion of systemic amyloidosis is important for management and prognosis. Localised primary lesions are best treated with transurethral resection and recurrences are uncommon. Diffuse involvement of the bladder is difficult to manage and may require urinary diversion. We report the first case of primary amyloidosis of the bladder in Singapore.
Amyloidosis↗
Malaria: an audit of 56 cases admitted to a hospital.
A 2-year prospective audit on the profile and outcome of malaria cases admitted to a general hospital was performed. Fifty-six cases were seen from January 1991 to December 1992, 52 of which were due to monoinfections with Plasmodium vivax. The main presenting complaints were fever, chills, sweats, myalgia, dry cough and headache. A significant percentage had anaemia (64.3%), thrombocytopaenia (57.1%), hyponatraemia (42.9%), and liver dysfunction (44.7%). Diagnosis rests on the demonstration of parasites in stained peripheral blood smears. None of the patients developed major complications. A high index of suspicion of malaria must be maintained in the medical evaluation of all patients and in particular, of returning travellers.
Adolescent↗
Saccharomyces cerevisiae Apl2p, a homologue of the mammalian clathrin AP beta subunit, plays a role in clathrin-dependent Golgi functions.
Clathrin-coated vesicles mediate selective intracellular protein traffic from the plasma membrane and the trans-Golgi network. At these sites, clathrin-associated protein (AP) complexes have been implicated in both clathrin coat assembly and collection of cargo into nascent vesicles. We have found a gene on yeast chromosome XI that encodes a homologue of the mammalian AP beta subunits. Disruptions of this gene, APl2, and a previously identified beta homologue, APl1, have been engineered in cells expressing wild-type (CHC1) or temperature sensitive (chc1-ts) alleles of the clathrin heavy chain gene. APl1 or APl2 disruptions (apl1 delta or apl2 delta) yield no discernable phenotypes in CHC1 strains, indicating that the Apl proteins are not essential for clathrin function. However, the apl2 delta, but not the apl1 delta, allele enhances the growth and alpha-factor pheromone maturation defects of chc1-ts cells. Disruption of APl2 also partially suppresses the vacuolar sorting defect that occurs in chc1-ts cells immediately after imposition of the non-permissive temperature. These Golgi-specific effects of apl2 delta in chc1-ts cells provide evidence that Apl2p is a component of an AP complex that interacts with clathrin at the Golgi apparatus.
Adaptor Proteins, Vesicular Transport↗
Extracorporeal shock wave lithotripsy monotherapy for selected staghorn stones.
OBJECTIVE: To define a subgroup of staghorn stones that is amenable to extracorporeal shockwave lithotripsy (ESWL) monotherapy and review the need for prophylactic ureteric stents. METHODS: Fifty-eight renal units with staghorn calculi in 56 patients (30 males and 26 females) were treated by ESWL monotherapy on the EDAP LT-01 lithotripter. The stones were grouped as complete staghorn (11, 19%), partial staghorn (34, 59%) and borderline staghorn (13, 22%). Results of treatment were analysed in relation to subgroup and calyceal dilatation. Post-treatment complications were studied and the influence of prophylactic ureteric stents examined. RESULTS: The average number of ESWL sessions was 3.1 (range: 1 to 8). The mean follow-up period was 13 months. Stone-free rate at 10 months was 52%. When clinically insignificant residual fragments less than 4mm were included, the overall clearance rate was 75%. Favourable factors influencing treatment outcome included smaller stone burden, peripheral distribution of stone mass and absence of pelvicalyceal dilatation. The overall complication rate was 39% with urosepsis being the commonest. Complications were related to stone burden. More than half of the renal units with complete staghorn stones developed one or more complications. Auxiliary procedures were required in 18% of the renal units. Twenty of 39 renal units with a stone burden (sum of length and width) greater than 50mm had pretreatment ureteric stenting using the double-J (DJ) siliastic stent. A urosepsis rate of 50% was noted in those with ureteric stents compared to 26% in those not stented. The stents did not offer any advantage in preventing post-treatment obstruction by fragments. Six of 7 renal units with post-treatment obstruction had in-situ stents. CONCLUSIONS: ESWL monotherapy is suitable for selected staghorn stones. Prophylactic ureteric stents do not offer any advantage and may predispose to urosepsis.
Adult↗