Exogenous gangliosides increase the release of brain-derived neurotrophic factor

Gangliosides are lipophilic compounds found in cell plasma membranes throughout the brain that play a role in neuronal plasticity and regeneration. Indeed, absence or abnormal accumulation of gangliosides has been shown to lead to neurological disorders. Experimental data have shown that exogenous gangliosides exhibit properties similar to the neurotrophins, a family of neurotrophic factors that are important in the survival and maintenance of neurons and prevention of neurological diseases. Brain-derived neurotrophic factor (BDNF) is the most abundant of the neurotrophins. This work was done to reveal the neurotrophic mechanism of exogenous gangliosides. In particular, we examined whether gangliosides promote the release of BDNF. Rat hippocampal neurons or human neuroblastoma cells were transduced with a recombinant adenovirus expressing BDNF-flag to facilitate detection of BDNF. Release of BDNF was then determined by Western blot analysis and a two-site immunoassay of culture medium. The depolarizing agent KCl was used as a comparison. In hippocampal neurons, both GM1 ganglioside and KCl evoked within minutes the release of mature BDNF. In human cells, GM1 and other gangliosides released both mature BDNF and pro-BDNF. The effect of gangliosides was structure-dependent. In fact, GT1b preferentially released mature BDNF whereas GM1 released both mature and pro-BDNF. Ceramide and sphingosine did not modify the release of BDNF. This work provides additional experimental evidence that exogenous gangliosides can be used to enhance the neurotrophic factor environment and promote neuronal survival in neurological diseases. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.

Activity-dependent alpha-cleavage of nectin-1 is mediated by a disintegrin and metalloprotease 10 (ADAM10)

Nectin-1 is known to undergo ectodomain shedding by alpha-secretase and subsequent proteolytic processing by gamma-secretase. How secretase-mediated cleavage of nectin-1 is regulated in neuronal cells and how nectin-1 cleavage affects synaptic adhesion is poorly understood. We have investigated alpha-and gamma-secretase-mediated processing of nectin-1 in primary cortical neurons and identified which protease acts as a alpha-secretase. We report here that NMDA receptor activation, but not stimulation of AMPA or metabotropic glutamate receptors, resulted in robust alpha- and gamma-secretase cleavage of nectin-1 in mature cortical neurons. Cleavage of nectin-1 required influx of Ca(2+) through the NMDA receptor, and activation of calmodulin, but was not dependent on calcium/calmodulin-dependent protein kinase II (CaMKII) activation. We found that ADAM10 is the major secretase responsible for nectin-1 ectodomain cleavage in neurons and the brain. These observations suggest that alpha- and gamma-secretase processing of nectin-1 is a Ca(2+)/calmodulin-regulated event that occurs under conditions of activity-dependent synaptic plasticity and ADAM10 and gamma-secretase are responsible for these cleavage events.

Matrix metalloproteinase-dependent shedding of intercellular adhesion molecule-5 occurs with long-term potentiation

Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that can be released or activated in a neuronal activity dependent manner. Although pathologically elevated levels of MMPs may be synaptotoxic, physiologically appropriate levels of MMPs may instead enhance synaptic transmission. MMP inhibitors can block long term potentiation (LTP), and at least one family member can affect an increase in the volume of dendritic spines. While the mechanism by which MMPs affect these changes is not completely understood, one possibility is that the cleavage of specific synaptic cell adhesion molecules plays a role. In the present study, we have examined the ability of neuronal activity to stimulate rapid MMP dependent shedding of the intercellular adhesion molecule-5 (ICAM-5), a synaptic adhesion molecule that is thought to inhibit the maturation and enlargement of dendritic spines. Since such cleavage would likely occur within minutes if it were relevant to a process such as LTP, we focused on post stimulus time points of 30 min or less. We show that NMDA can stimulate rapid shedding of ICAM-5 from cortical neurons in dissociated cell cultures and that such shedding is diminished by pretreatment of cultures with inhibitors that target MMP-3 and -9, proteases thought to influence synaptic plasticity. Additional studies suggest that MMP mediated cleavage of ICAM-5 occurs at amino acid 780, so that the major portion of the ectodomain is released. Since reductions in ICAM-5 have been linked to changes in dendritic spine morphology that are associated with LTP, we also examined the possibility that MMP dependent ICAM-5 shedding occurs following high frequency tetanic stimulation of murine hippocampal slices. Results show that the shedding of ICAM-5 occurs in association with LTP, and that both LTP and the associated ICAM-5 shedding are reduced when slices are pretreated with an MMP inhibitor. Together, these findings suggest that neuronal activity is linked to the shedding of a molecule that may inhibit dendritic spine enlargement and that MMPs can affect this change. While further studies will be necessary to determine the extent to which cleavage of ICAM-5 in particular contributes to MMP dependent LTP, our data support an emerging body of literature suggesting that MMPs are critical mediators of synaptic plasticity.

Effects of herpes simplex virus amplicon transduction on murine dendritic cells

The herpes simplex virus (HSV)-based amplicon is a versatile vaccine platform that has been preclinically vetted as a gene-based immunotherapeutic for cancer, HIV, and neurodegenerative disorders. Although it is well known that injection of dendritic cells (DCs) transduced ex vivo with helper virus-free HSV amplicon vectors expressing disease-relevant antigens induces antigen-specific immune responses, the cellular receptor(s) by which the amplicon virion gains entry into DCs, as well as the effects that viral vector transduction impinges on the physiological status of these cells, is less understood. Herein, we examine the effects of amplicon transduction on mouse bone marrow-derived DCs. We demonstrate that HSV-1 cellular receptors HveC and HveA are expressed on the cell surface of murine DCs, and that HSV amplicons transduce DCs at high efficiency (>90%) with minimal effects on cell viability. Transduction of dendritic cells with amplicons induces a transient DC maturation phenotype as represented by self-limited upregulation of MHCII and CD11c markers. Mature DCs are less sensitive to HSV amplicon transduction than immature DCs regarding DC-related surface marker maintenance. From this and our previous work, we conclude that HSV amplicons transduce DCs efficiently, but impart differential and transient physiological effects on mature and immature DC pools, which will facilitate fine-tuning of this vaccination platform and further exploit its potential in immunotherapy.

Percutaneous transcatheter aortic valve replacement: first transapical implant in Asia

Percutaneous transcatheter implantation of the aortic valve has been demonstrated as an alternative to open heart surgery in high-risk patients with symptomatic severe aortic stenosis (AS) who are not suitable for open surgery. The majority of these new devices are delivered via the transfemoral approach. However, due to the current size of delivery sheaths, the small and tortuous iliofemoral anatomy makes this approach challenging. The transapical approach provides a viable option for this patient subgroup. The first-in-Asia transcatheter aortic valve implantation via the transapical route is described. A 79-year-old Chinese woman with symptomatic severe AS and peripheral arterial disease, who was at high surgical risk, was successfully treated, and had good functional and haemodynamic results at the three-month follow-up.

Viral vectors for neurotrophic factor delivery: a gene therapy approach for neurodegenerative diseases of the CNS

The clinical manifestation of most diseases of the central nervous system results from neuronal dysfunction or loss. Diseases such as stroke, epilepsy and neurodegeneration (e.g. Alzheimer's disease and Parkinson's disease) share common cellular and molecular mechanisms (e.g. oxidative stress, endoplasmic reticulum stress, mitochondrial dysfunction) that contribute to the loss of neuronal function. Neurotrophic factors (NTFs) are secreted proteins that regulate multiple aspects of neuronal development including neuronal maintenance, survival, axonal growth and synaptic plasticity. These properties of NTFs make them likely candidates for preventing neurodegeneration and promoting neuroregeneration. One approach to delivering NTFs to diseased cells is through viral vector-mediated gene delivery. Viral vectors are now routinely used as tools for studying gene function as well as developing gene-based therapies for a variety of diseases. Currently, many clinical trials using viral vectors in the nervous system are underway or completed, and seven of these trials involve NTFs for neurodegeneration. In this review, we discuss viral vector-mediated gene transfer of NTFs to treat neurodegenerative diseases of the central nervous system.

High SUV uptake on FDG-PET/CT predicts for an aggressive B-cell lymphoma in a prospective study of primary FDG-PET/CT staging in lymphoma

BACKGROUND

Data assessing the role of positron emission tomography (PET)/computed tomography (CT) imaging in lymphoma staging is still being accumulated and current staging is based primarily on CT. This study aims to compare the value of PET/CT over conventional CT and bone marrow biopsy (BMB) in the initial evaluation of patients with lymphoma.

METHODS

Data on 122 patients with PET/CT scans as part of their initial staging were prospectively collected and reviewed. All patients had complete staging, including BMB.

RESULTS

Among the 122 patients, 101 had non-Hodgkin's lymphoma (NHL) and 21 had Hodgkin's lymphoma (HL). Compared with conventional CT, PET/CT upstaged 21 (17%) cases [B-cell non-Hodgkin's lymphoma (B-NHL), 12; T-cell non-Hodgkin's lymphoma (T-NHL), 3; HL, 6]. Of significance, in 13 patients with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG)-avid splenic lesions, four had normal CT findings. A maximum FDG uptake of >10 standardized uptake value (SUV) seems to significantly correlate with an aggressive B-cell lineage (odds ratio 2.47, 95% confidence interval 2.23-2.70). Overall, PET scan was concordant with BMB results in 108 (89%) and discordant in 14 (11%) cases. In HL, our data show that PET scan and marrow results agreed in 19 of the cases (90%), being concordantly negative in 18 cases and concordantly positive in one, giving a negative predictive value (NPV) of 100%, sensitivity of 100% and specificity of 90%. Of note, all 13 with early-stage HL had negative PET/CT scan and BMB. In NHL, all 17 cases of T-NHL had concordant PET and BMB results. In patients with aggressive B-NHL, BMB and PET/CT agreed in 58 patients (92%) and disagreed in five (8%), while the corresponding rates in indolent B-cell lymphoma were 14 (67%) and seven patients (33%), respectively. All seven were falsely negative.

CONCLUSIONS

PET/CT upstages 17% of cases and detects occult splenic involvement. This may have potential therapeutic and prognostic implications. SUV >10 may predict for an aggressive histology. Except for indolent B-NHL, our data show that PET scans have a good overall NPV in excluding lymphomatous bone marrow involvement. This is particularly true of early-stage HL, suggesting that BMB may be safely omitted in this group.

Percutaneous transcatheter aortic valve replacement: first transfemoral implant in Asia

Surgical aortic valve replacement (AVR) is the standard of care for patients with symptomatic severe aortic stenosis (AS), providing relief of symptoms and prolonging survival. However, many patients are either denied or not offered surgery due to high surgical risk or non-operability for open AVR. The technology of percutaneous aortic valve implantation emerged in 2002, and has since evolved rapidly with satisfactory results. Currently, almost all the procedures are performed predominantly in Europe and North America. The first-in-Asia percutaneous transcatheter aortic valve implantation via the transfemoral route is described. A 77-year-old man with symptomatic severe AS and at high surgical risk was successfully treated, with sustained clinical improvement and satisfactory haemodynamic results at 30-day follow-up.

Lipid-altering efficacy of ezetimibe/simvastatin 10/40 mg compared with doubling the statin dose in patients admitted to the hospital for a recent coronary event: the INFORCE study

BACKGROUND

The aim of this study was to investigate the efficacy and safety profile of switching to ezetimibe/simvastatin (Eze/Simva) 10/40 mg compared with doubling the statin dose upon discharge in patients taking a statin and admitted to the hospital for the investigation of a coronary event.

DESIGN

This phase IV, multi-centre, randomised, open-label, active-controlled, parallel group study enrolled 424 patients (aged >/= 18 years) hospitalised for an acute coronary event and taking a stable dose of a statin (>/= 6 weeks) that could be doubled per the product label. Upon discharge from the hospital, patients were stratified by their statin dose/potency (high, medium and low) and randomised 1 : 1 to doubling of the statin dose (n = 211) or Eze/Simva 10/40 mg (n = 213) for 12 weeks. The primary efficacy variable was the absolute low-density lipoprotein cholesterol (LDL-C) value (mmol/l) at study end-point.

RESULTS

Mean baseline LDL-C for the two treatment groups were 2.48 and 2.31 mmol/l for the Eze/Simva and statin groups respectively. At study end-point, least squares mean LDL-C values were 1.74 mmol/l in the Eze/Simva group and 2.22 mmol/l in the statin group resulting in a significant between-group difference of -0.49 mmol/l (p </= 0.001). Eze/Simva 10/40 mg also produced significantly lower total cholesterol (-0.49 mmol/l), non-high-density lipoprotein cholesterol [(non-HDL-C); -0.53 mmol/l] and apolipoprotein B (-0.14 mmol/l) values compared with doubling the statin dose (p </= 0.001 for all). Both treatments produced similar effects on triglycerides, C-reactive protein and HDL-C; the between treatment group differences were not significant (p >/= 0.160). Significantly more patients achieved LDL-C levels < 2.5 (< 100 mg/dl; 86% vs. 72%), < 2.0 (< 77 mg/dl; 70% vs. 42%) and < 1.8 mmol/l (< 70 mg/dl; 60% vs. 31%) with Eze/Simva than statin (all p </= 0.001). Eze/Simva was generally well tolerated, with a safety profile similar to statin. There were no differences in the incidences of liver transaminases >/= 3 x upper limit of normal (ULN) or creatine kinase >/= 10 x ULN between the groups.

CONCLUSIONS

In patients taking a statin and admitted to the hospital for investigation of a coronary event, treatment with Eze/Simva 10/40 mg for 12 weeks produced greater improvements in lipids with a similar safety profile compared with doubling of the statin dose.

Temporal and spatial localization of nectin-1 and l-afadin during synaptogenesis in hippocampal neurons

Nectins are cell adhesion molecules that, together with the intracellular binding partner afadin, mediate adhesion and signaling at a variety of intercellular junctions. In this work we studied the distribution of nectin-1 and afadin during hippocampal synapse formation using cultured primary hippocampal neurons. Nectin-1 and afadin cluster at developing synapses between hippocampal neurons. These nectin-afadin clusters uniformly colocalize with N-cadherin-catenin pairs, suggesting that formation of developing synapses involves participation of both bimolecular systems. Nectin-1 is initially expressed at excitatory and inhibitory synapses but is progressively lost at inhibitory synapses during their maturation. Treatment of neurons with actin depolymerizing agents disrupts the synaptically localized nectin-1 and afadin cluster at an early stage and elicits nectin-1 ectodomain shedding. These data indicate that the synaptic localization of nectin-1 and l-afadin are F-actin-dependent and that the shedding of nectin-1 is a mechanism contributing to synaptic plasticity.

Clinical features and outcome of emergency percutaneous intervention of left main coronary artery occlusion in acute myocardial infarction

INTRODUCTION

Acute myocardial infarction (AMI) due to left main coronary artery (LMCA) occlusion carries a grave prognosis. Large series reporting on the outcome of emergency revascularisation (percutaneous or surgical) of acute LMCA occlusion have been scarce. We seek to identify, in our local population, the clinical presentation and outcome of this group of patients.

METHODS

From January 2000 to December 2005, a total of 1,539 patients underwent primary percutaneous coronary angioplasty for AMI in our institution. 11 patients (0.8 percent) underwent percutaneous intervention to the LMCA. These patients became the subjects of our study. Data on demography, clinical features and outcome was collected from all in-hospital and clinical notes. One sub-investigator, who was blinded to the study outcome, assessed the angiographical features.

RESULTS

The overall inpatient mortality was 82 percent (9 out of 11). Nine out of 11 patients presented with cardiogenic shock. All patients presented with shock died during the hospital stay. All patients required intra-aortic balloon counter pulsation insertion. Of the two patients who survived till discharge, one had angioplasty followed by bypass surgery. The remaining one had angioplasty and stenting to the left main artery. Both survivors have been doing well without further major adverse cardiac event after an average of 64 months of follow-up.

CONCLUSION

Percutaneous revascularisation of acute LMCA occlusion is feasible and the best outcome is seen in stable patients. Prognosis is still poor in patients with unfavourable clinical features.

Effect of left ventricular shape alteration on contractility and function

We have investigated the effect of left ventricular (LV) shape on contractility and ejection function. In this study, a new contractility index is developed in terms of the wall stress (sigma*, normalized with respect to LV pressure) by means of an LV ellipsoidal model. Using cine-ventriculography data, the LV ellipsoidal model (LVEM) major (B) and minor axes (A) are derived for the entire cardiac cycle. Thereafter, a new contractility index (CONT1) is derived as dsigma*/dt, incorporating the LV ellipsoidal shape factor. Also, another contractility index (CONT2) was developed in terms of the generated sigma* at the start of ejection phase, and maximized with respect to B/Ashape parameter, to obtain the optimal value of B/Aover the physiological ranges of the ratio of myocardial volume and LV volume. The in vivovalue of B/Aat the start of ejection is compared with this optimal value, and the LV contractility is evaluated in terms of the proximity of the in vivo B/Ato the optimal B/A. The results indicate that a non-optimal less-ellipsoidal shape (or more spherical) is associated with decreased contractility (and poor systolic function) of the LV, associated with a failing heart.

Electrocardiographical case. Beware of this ECG in patients presenting with cardiogenic shock

A 64-year-old Chinese man presented to the Accident and Emergency Department with chest pain and was found to be in cardiogenic shock. The electrocardiogram (ECG) showed features of acute myocardial infarction due to left main coronary artery occlusion,which had no ST elevation in precordial leads. Emergency coronary angiogram revealed left main coronary artery complete occlusion. Percutaneous intervention of the left main coronary artery was carried out. The epidemiology and clinical features of a left main occlusion were briefly described, and ECG features of a left main occlusion were discussed.

Proteolytic processing of proNGF is necessary for mature NGF regulated secretion from neurons

Nerve growth factor mediates neuronal survival, synaptogenesis, and synaptic remodeling. We utilized primary hippocampal cultures to investigate the intrinsic motifs of proNGF that might contribute to its processing and subsequent allocation to a regulated versus constitutive secretory pathway. The addition of a carboxypeptidase E motif to proNGF did not alter the secretion of NGF. However, mutagenesis of proNGF proteolytic processing sites had significant effects on the final NGF product and its secretion. The furin recognition site (R118-S-K-R121) is essential for the proper processing of proNGF to its 13.5kDa mature product and mutating the furin site exposed an alternative processing site resulting in an intermediate NGF product of approximately 22kDa. Finally, inhibiting the processing of proNGF abolished regulated secretion of the resulting NGF product. These experiments demonstrate that hippocampal neurons harbor multiple pathways to process proNGF of which the furin consensus sequence is the preferred processing site.

Recurrence after Successful Percutaneous Endoscopic Lumbar Discectomy

The purpose of this study is to investigate the risk factors for recurrence after successful percutaneous endoscopic lumbar discectomy (PELD). Recently, PELD has become the most common surgical technique. However, there are only a few studies on the factors causing the reappearance of the symptoms. Between January 2002 and December 2004, 42 patients with recurrent disc herniation after successful PELD were classified as a recurrent group and 42 patients who underwent PELD with a satisfactory result were randomly selected for a non-recurrent group. For all the patients, we analyzed the medical records and radiological studies retrospectively. The patients' mean age was 47.4 years (range: 18-76) in the recurrent group, while the mean age of the non-recurrent group was 34.4 years (range: 17-66) (p=0.001). The body mass index was 24.9 in the recurrent group and 22.9 in the non-recurrent group (p=0.006). On the radiological studies, the protrusion (p=0.013) and the presence of Modic change (p=0.003) were more frequent in the recurrent group. For the successful PELD, it is desirable for the surgeon to consider the above risk factors carefully.

Association analysis of endothelial nitric oxide synthase gene polymorphism with primary hypertension in a Singapore population

Vascular endothelial cells produce nitric oxide (NO), which contributes to the regulation of blood pressure and regional blood flow. Endothelial nitric oxide synthase (eNOS) gene polymorphisms are associated with coronary artery disease, but their linkage with primary hypertension is controversial. A total of 103 individuals with primary hypertension and 104 normotensive control subjects were studied in Singapore. The specific genotypes for G894T missense variant in exon 7, variable number tandem repeats (VNTR) in intron 4 (eNOS 4A/B/C) and T-786C in the promoter were isolated using allele-specific gene amplification and restriction fragment length polymorphism to examine the association of genotype and allelic frequency in both groups. Logistic regression analysis was also used to detect the association between genotypes and hypertension. Five genotypes of intron 4 VNTR (AA, AB, BB, AC and BC) were observed. Intron 4 B/B genotype was significantly associated with the hypertension group (P = 0.035), but disequilibrium of G894T and T-786C was absent between the two groups (P = 0.419 and P = 0.227), respectively. The overall distribution of allelic frequency differed significantly between the two groups, with four-repeat allele (4A) of intron 4 more frequent in the normotensive group than the hypertensive group (P = 0.019). Logistic regression analysis showed that intron 4 B/B genotype was significantly associated with systolic blood pressure of individuals with body mass index greater than 25 kg/m2 (P = 0.04). In conclusion, the eNOS 4 B/B genotype is a genetic susceptibility factor for primary hypertension in a Singapore population.

Inter‐ and intralaboratory variation of in vitro diffusion cell measurements: An international multicenter study using quasi‐standardized methods and materials

In vitro measurements of skin absorption are an increasingly important aspect of regulatory studies, product support claims, and formulation screening. However, such measurements are significantly affected by skin variability. The purpose of this study was to determine inter- and intralaboratory variation in diffusion cell measurements caused by factors other than skin. This was attained through the use of an artificial (silicone rubber) rate-limiting membrane and the provision of materials including a standard penetrant, methyl paraben (MP), and a minimally prescriptive protocol to each of the 18 participating laboratories. "Standardized" calculations of MP flux were determined from the data submitted by each laboratory by applying a predefined mathematical model. This was deemed necessary to eliminate any interlaboratory variation caused by different methods of flux calculations. Average fluxes of MP calculated and reported by each laboratory (60 +/- 27 microg cm(-2) h(-1), n = 25, range 27-101) were in agreement with the standardized calculations of MP flux (60 +/- 21 microg cm(-2) h(-1), range 19-120). The coefficient of variation between laboratories was approximately 35% and was manifest as a fourfold difference between the lowest and highest average flux values and a sixfold difference between the lowest and highest individual flux values. Intralaboratory variation was lower, averaging 10% for five individuals using the same equipment within a single laboratory. Further studies should be performed to clarify the exact components responsible for nonskin-related variability in diffusion cell measurements. It is clear that further developments of in vitro methodologies for measuring skin absorption are required.

Can patients with early-stage diffuse large B-cell lymphoma be treated without bone marrow biopsy?

BACKGROUND

Data on the incidence of bone marrow (BM) involvement in early-stage diffuse large B-cell lymphoma (DLBCL) are lacking. Although BM biopsy is a safe procedure, it is often poorly tolerated. This analysis aims to assess the incidence of BM involvement and to identify parameters predicting BM involvement in early-stage DLBCL.

PATIENTS AND METHODS

One hundred and ninety-two patients with radiological stages 1 and 2 disease were analysed. The data collected were age, sex, presence of B symptoms, white blood cell (WBC) count, platelet count, haemoglobin (Hb), serum lactate dehydrogenase level, serum beta(2)-microglobulin level, presence of extranodal disease, and the presence of bulky disease (defined as >7 cm).

RESULTS

Overall incidence of BM involvement was 3.6%. Hb < 10 g/dl (P=0.02), WBC count < 4 x 10(9)/l (P=0.007) and bulky disease (P=0.06) were found to be predictive of BM involvement. Among the 120 patients without any of these three factors, only one patient had BM involvement (0.83%; 95% confidence interval 0.02% to 4.6%). The absence of all three factors gave a negative predictive value of 99.2%. Overall 3-year survival for patients without all three risk factors was 80%.

CONCLUSIONS

BM biopsy may be safely omitted in selected patients with early-stage DLBCL.

Posterior mediastinal paraganglioma with bilateral adrenal pheochromocytoma

Paraganglioma and adrenal pheochromocytoma are tumors of common origin arising from chromaffin cells. However, it is extremely rare to find mediastinal paraganglioma simultaneously with bilateral adrenal pheochromocytoma. We report a 53-year-old man who was diagnosed with posterior mediastinal paraganglioma and bilateral adrenal pheochromocytoma and who underwent successful excision of the posterior mediastinal mass and bilateral total adrenalectomy.

Neurotrophin secretory pathways and synaptic plasticity

Neurotrophins and synaptic activity work in conjunction during the process of synaptic plasticity. Both are required to stabilize new synaptic structures and the loss of either can lead to cognitive impairments, as new information cannot be stored efficiently or later recalled. Neurotrophins are becoming recognized as mediators of activity-dependent plasticity. The synthesis and release of neurotrophins follow neurosecretory pathways. They are synthesized as immature, pro-neurotrophin molecules, processed, and then mature forms are secreted. These then activate distinct signal tranduction pathways that modify the synapse. High frequency stimulation is known to induce long-term potentiation (LTP) and synaptic enhancement, however, the stability of these changes requires a bi-directional communication between the pre- and post-synaptic terminals and neurotrophins can function in such a capacity. The NGFXAT somatic mosaic murine model demonstrated how neurotrophin and active learning induces a robust synaptic reorganization. Synaptic dysfunction decreases efficient neurotransmission or neurotrophin production and then precedes overt neurodegeneration. The study of synaptic dysfunction and neurotrophin actions with respect to activity will lead to future therapeutic interventions of age-related dementias.

CPT-11 and cisplatin in the treatment of advanced gastric cancer in Asians

There is no standard chemotherapy for advanced gastric cancer. A combination of CPT-11 and cisplatin was evaluated for response and toxicity in Asians. 38 patients with histologically proven stage IV gastric/gastroesophageal junction adenocarcinoma were treated with CPT-11 50 mg/m2 and cisplatin 30 mg/m2 weekly for 3 weeks. Each cycle was repeated every 28 days. The median number of cycles was 1.66 (range 0.33-4.33). Dose delay was needed in 11 (29%) patients and dose reductions in 19 (50%) patients. The overall response rate was 42%. There was no complete response. Grade 3 and 4 hematological toxicity was 26%. Grade 3 or 4 diarrhea was not common. Median time to progression for all patients was 15 weeks. Median duration of survival of all patients was 42 weeks. Patients with better performance status and no prior chemotherapy did better. CPT-11 and cisplatin is a useful regimen with significant but manageable toxicity that can be administered without a central venous catheter.

Turbulent drag reduction and degradation of DNA

Turbulent drag reduction induced by lambda-DNA is studied. The double-stranded DNA is found to be a good drag reducer when compared with the other normal linear polymers. However, this drag reducing power disappears when the DNA denatures to form two single-strand molecules. Mechanical degradation of DNA is also different from that of the normal linear-chain polymers: DNA is always cut in half by the turbulence. Our results suggest that the mechanism for turbulent degradation of DNA is different from that of the normal flexible long-chain polymers.

Rheumatic heart diseases in pregnancy

Acute rheumatic fever and rheumatic valvular disease remain prevalent in many parts of the world, and are probably the most common cause of heart disease in pregnancy. Mitral stenosis is the most frequently encountered rheumatic valvular lesion. A variety of pregnancy-associated cardiovascular changes often exacerbate the signs and symptoms of valvular lesions. Pregnancy should not be allowed to proceed, if possible, in patients with uncorrected severe valvular lesions or mechanical heart valves requiring anticoagulation, as maternal and fetal morbidity and mortality are high. For those with milder disease, pregnancy is best undertaken after the valvular lesion has been rectified or stabilised. Recent advances in the management of valvular disease include the use of beta-blockers for patients with mitral stenosis, vasodilators in those with aortic and mitral regurgitation, and percutaneous balloon valvuloplasty for mitral and aortic stenosis. Application of these therapies in the pregnant patient is as yet unclear, and management decision needs to be individualized, weighing the risk and benefit to ensure maternal survival and to promote fetal well-being.