Efficacy of bilateral pallidotomy

Unilateral pallidotomy is a safe and effective treatment for medically refractory bradykinetic Parkinson's disease, especially in those patients with levodopa-induced dyskinesia and severe on-off fluctuations. The efficacy of bilateral pallidotomy is less certain. The authors completed 11 of 12 attempted bilateral pallidotomies among 150 patients undergoing pallidotomy at New York University. In all but one patient, the pallidotomies were separated by at least 9 months. Patients were selected for bilateral pallidotomy if they exhibited bilateral rigidity, bradykinesia, or levodopa-induced dyskinesia prior to treatment or if they exhibited disease progression contralateral to their previously treated side. The Unified Parkinson's Disease Rating Scale (UPDRS) and timed upper-extremity tasks of the Core Assessment Protocol for Intracerebral Transplantation (CAPIT) were administered to all 12 patients in the "off" state (12 hours without receiving medications) preoperatively and again at 6 and 12 months after each procedure. The median UPDRS and contralateral CAPIT scores improved 60% following the initial procedure (p = 0.008, Wilcoxon rank sums test). The second pallidotomy generated only an additional 10% improvement in the UPDRS and CAPIT scores ipsilateral to the original procedure (p = 0.05). Worsened speech was observed in two cases. In the 12th case, total speech arrest was noted during test stimulation. Speech returned within minutes after stimulation was halted. Lesioning was not performed. These results indicate that bilateral pallidotomy has a narrow therapeutic window. Motor improvement ipsilateral to the first lesion leaves little room for further improvement from the second lesion and the risk of speech deficit is greatly enhanced. Chronic pallidal stimulation contralateral to a previously successful pallidotomy may prove to be a safer alternative for the subset of patients who require bilateral procedures.

Parallel compensatory and pathological events associated with tau pathology in middle aged individuals with Down syndrome

Aged individuals with Down syndrome (DS) develop senile plaques and neurofibrillary tangles consistent with Alzheimer disease (AD). Prior to or in parallel with AD pathology, compensatory growth responses may occur. Immunohistochemistry and confocal microscopy studies in the hippocampus from 15 individuals ranging in age from 5 months to 67 years compared markers of normal and abnormal tau accumulation (phosphorylated tau [AT8, MC-1], tau-1, N-terminal tau) with the extent and location of neuronal growth marker immunoreactivity (BDNF, GAP-43, MAP-2). In middle age (30-40 years), prior to entorhinal neuron loss, the earliest tau accumulation occurred in the outer molecular layer (OML), which was consistent with both pathological and compensatory fetal tau expression. These events were followed at a later age, associated with entorhinal neuron loss, by an increase in GAP-43. Hilar neurons exhibiting a sprouting morphology were also noted. Age-dependent observations in the DS brain in the current study parallel hippocampal compensatory responses described in entorhinal cortex lesion studies in rodents. Thus, compensatory growth responses may occur in DS prior to extensive AD pathology and may be one mechanism underlying observations in PET studies of hypermetabolism in the entorhinal cortex of individuals with DS.

Management of age-related macular degeneration

With the increase in life expectancy across the world, the magnitude of blindness due to age-related macular degeneration (AMD) is expected to rise. Exudative form is the major cause of visual loss from AMD. Several treatment options are available for this form of the disease. However, all treatment strategies aim at preservation of residual vision rather than regaining the lost vision. Two well-proven strategies are laser photocoagulation and photodynamic therapy. Other viable options are submacular surgery, transpupillary thermotherapy and pharmacological modalities like angiostatic-steroids. Oral anti-oxidants and zinc appear to be beneficial in preventing disease progression in early cases. Further research is on to explore more efficient treatments and to prove the safety and efficacy of large number of emerging newer treatment options.

The effect of plants on the degradation and toxicity of petroleum contaminants in soil: a field assessment

A field project located at the US Naval Base at Port Hueneme, California was designed to evaluate changes in contaminant concentrations and toxicity during phytoremediation. Vegetated plots were established in petroleum (diesel and heavy oil) contaminated soil and were evaluated over a two-year period. Plant species were chosen based on initial germination studies and included native California grasses. The toxicity of the impacted soil in vegetated and unvegetated plots was evaluated using Microtox, earthworm, and seed germination assays. The reduction of toxicity was affected more by contaminant aging than the establishment of plants. However, total petroleum hydrocarbon concentrations were lower by the end of the study in the vegetated plots when compared to the unvegetated soil. Although phytoremediation is an effective approach for cleaning-up of petroleum contaminated soil, a long-term management plan is required for significant reductions in contaminant concentrations.

Risk period for developing osteonecrosis of the femoral head in patients on steroid treatment

Patients who require long-term steroid use are at risk for the development of osteonecrosis. However, the risk period for developing osteonecrosis of the femoral head has not yet been defined. The authors attempted to determine the onset of osteonecrosis of the femoral head following steroid treatment. Medical record data of patients with steroid-related osteonecrosis of the femoral head from four university hospitals were reviewed. Information was collected regarding the duration and dose of steroid use for patients who were diagnosed at the early stage by magnetic resonance imaging (MRI) without positive findings on plain radiographs (Association Research Circulation Osseous stage I osteonecrosis). Twenty-two patients were diagnosed at Association Research Circulation Osseous stage I. There were eight male and 14 female patients ranging in age from 17 to 60 years (mean 33). The total dose of steroid, which was used until the time of detection of osteonecrosis by MRI, ranged from 1800 to 15 505 mg prednisolone or its equivalent (mean 5928 mg). The period from the start of steroid treatment to the diagnosis by MRI ranged from 1 month to 16 months (mean 5.3 months). Twenty-one of 22 patients were diagnosed within 12 months of the initiation of steroid treatment. The duration of steroid treatment within this period ranged from 1 month to 12 months (mean 4.5 months). There may be a risk period of 12 months for developing femoral head osteonecrosis in patients receiving long-term steroid treatment. Close observation and more aggressive screening are recommended within the first year of long-term steroid treatment to prevent advanced osteonecrosis of the femoral head.

A cost-effectiveness evaluation of amlodipine usage in patients with coronary artery disease in Sweden

The objective of this analysis was to calculate the cost-effectiveness of amlodipine therapy in patients with coronary artery disease in Sweden. It is hypothesised that treatment with amlodipine will have an impact on overall cardiovascular disease treatment costs, resulting in a positive cost-effectiveness profile. A Markov cohort simulation model was constructed to simulate event-related and procedure-related health economic outcomes of coronary artery disease populations on amlodipine versus those on placebo. Patient level data from the Prospective Evaluation of the Vascular Effects of Norvasc Trial was used to populate the model. The total number of adverse cardiovascular clinical outcomes experienced over a three-year period was lower for patient on amlodipine than for those on placebo. The rate of hospitalisation per patient due to angina, coronary artery bypass graft, percutaneous transluminal coronary angioplasty, congestive heart failure, and myocardial infarction in the placebo cohort was 64.7%, while the rate in the amlodipine cohort was 46.9%. The cost per patient was Swedish kroner (SEK)26,600 for amlodipine patients and SEK27,400 for placebo patients. The use of amlodipine resulted in improved clinical outcomes as well as a slight savings in cost over a three-year period.

Hypoxia-induced regulation of MAPK phosphatase-1 as identified by subtractive suppression hybridization and cDNA microarray analysis

Subtractive suppression hybridization was used to generate a cDNA library enriched in cDNA sequences corresponding to mRNA species that are specifically up-regulated by hypoxia (6 h, 1% O(2)) in the oxygen-responsive pheochromocytoma cell line. The dual specificity protein-tyrosine phosphatase MAPK phosphatase-1 (MKP-1) was highly represented in this library. Clones were arrayed on glass slides to create a hypoxia-specific cDNA microarray chip. Microarray, northern blot, and western blot analyses confirmed that MKP-1 mRNA and protein levels were up-regulated by hypoxia by approximately 8-fold. The magnitude of the effect of hypoxia on MKP-1 was approximately equal to that induced by KCl depolarization and much larger than the effects of either epidermal growth factor or nerve growth factor on MKP-1 mRNA levels. In contrast to the calcium-dependent induction of MKP-1 by KCl depolarization, the effect of hypoxia on MKP-1 persisted under calcium-free conditions. Cobalt and deferoxamine also increased MKP-1 mRNA levels, suggesting that hypoxia-inducible factor proteins may play a role in the regulation of MKP-1 by hypoxia. Pretreatment of cells with SB203580, which inhibits p38 kinase activity, significantly reduced the hypoxia-induced increase in MKP-1 RNA levels. Thus, hypoxia robustly increases MKP-1 levels, at least in part through a p38 kinase-mediated mechanism.

Crystal structure and mechanism of catalysis of a pyrazinamidase from Pyrococcus horikoshii

Bacterial pyrazinamidase (PZAase)/nicotinamidase converts pyrazinamide (PZA) to ammonia and pyrazinoic acid, which is active against Mycobacterium tuberculosis. Loss of PZAase activity is the major mechanism of pyrazinamide-resistance by M. tuberculosis. We have determined the crystal structure of the gene product of Pyrococcus horikoshii 999 (PH999), a PZAase, and its complex with zinc ion by X-ray crystallography. The overall fold of PH999 is similar to that of N-carbamoylsarcosine amidohydrolase (CSHase) of Arthrobacter sp. and YcaC of Escherichia coli, a protein with unknown physiological function. The active site of PH999 was identified by structural features that are also present in the active sites of CSHase and YcaC: a triad (D10, K94, and C133) and a cis-peptide (between V128 and A129). Surprisingly, a metal ion-binding site was revealed in the active site and subsequently confirmed by crystal structure of PH999 in complex with Zn(2+). The roles of the triad, cis-peptide, and metal ion in the catalysis are proposed. Because of extensive homology between PH999 and PZAase of M. tuberculosis (37% sequence identity), the structure of PH999 provides a structural basis for understanding PZA-resistance by M. tuberculosis harboring PZAase mutations.

Expression of slow skeletal troponin I in adult transgenic mouse heart muscle reduces the force decline observed during acidic conditions

1. Acidosis in cardiac muscle is associated with a decrease in developed force. We hypothesized that slow skeletal troponin I (ssTnI), which is expressed in neonatal hearts, is responsible for the observed decreased response to acidic conditions. To test this hypothesis directly, we used adult transgenic (TG) mice that express ssTnI in the heart. Cardiac TnI (cTnI) was completely replaced by ssTnI either with a FLAG epitope introduced into the N-terminus (TG-ssTnI) or without the epitope (TG-ssTnI) in these mice. TG mice that express cTnI were also generated as a control TG line (TG-cTnI). Non-transgenic (NTG) littermates were used as controls. 2. We measured the force-calcium relationship in all four groups at pH 7.0 and pH 6.5 in detergent-extracted fibre bundles prepared from left ventricular papillary muscles. The force-calcium relationship was identical in fibre bundles from NTG and TG-cTnI mouse hearts, therefore NTG mice served as controls for TG-ssTnIand TG-ssTnI mice. Compared to NTG controls, the force generated by fibre bundles from TG mice expressing ssTnI was more sensitive to Ca(2+). The shift in EC(50) (the concentration of Ca(2+) at which half-maximal force is generated) caused by acidic pH was significantly smaller in fibre bundles isolated from TG hearts compared to those from NTG hearts. However, there was no difference in the force-calcium relationship between hearts from the TG-ssTnIand TG-ssTnI groups. 3. We also isolated papillary muscles from the right ventricle of NTG and TG mouse hearts expressing ssTnI and measured isometric force at extracellular pH 7.33 and pH 6.75. At acidic pH, after an initial decline, twitch force recovered to 60 +/- 3 % (n = 7) in NTG papillary muscles, 98 +/- 2 % (n = 5) in muscles from TG-ssTnIand 96 +/- 3 % (n = 7) in muscles from TG-ssTnI hearts. Our results indicate that TnI isoform composition plays a crucial role in the determination of myocardial force sensitivity to acidosis.

A streamlined process to phenotypically profile heterologous cDNAs in parallel using yeast cell-based assays

To meet the demands of developing lead drugs for the profusion of human genes being sequenced as part of the human genome project, we developed a high-throughput assay construction method in yeast. A set of optimized techniques allows us to rapidly transfer large numbers of heterologous cDNAs from nonyeast plasmids into yeast expression vectors. These high- or low-copy yeast expression plasmids are then converted quickly into integration-competent vectors for phenotypic profiling of the heterologous gene products. The process was validated first by testing proteins of diverse function, such as p38, poly(ADP-ribose) polymerase-1, and PI 3-kinase, by making active-site mutations and using existing small molecule inhibitors of these proteins. For less well-characterized genes, a novel random mutagenesis scheme was developed that allows a combination selection/screen for mutations that retain full-length expression and yet reverse a growth phenotype in yeast. A broad range of proteins in different functional classes has been profiled, with an average yield for growth interference phenotypes of approximately 30%. The ease of manipulation of the yeast genome affords us the opportunity to approach drug discovery and exploratory biology on a genomic scale and shortens assay development time significantly.

Significance of lymphoscintigraphic mapping with Tc-99m human serum albumin and tin colloid in sentinel lymph node biopsy in breast cancer

Sentinel lymph node biopsy (SLNB) in breast cancer is considered in order to spare node-negative patients from axillary lymph node dissection. To assess the clinical significance of lymphoscintigraphic mapping in SLNB, we analyzed the lymphatic drain to the sentinel lymph nodes (SLNs) in terms of the pattern and direction of the hot spot. Twenty-three breast cancer patients were enrolled for SLNB. Before surgery, lymphoscintigraphic mapping of SLN was performed using Tc-99m human serum albumin (HSA) and tin colloids, and the hot spot was marked. The Tc-99m HSA and tin colloids were subcutaneously injected above the tumor and peritumor sites, respectively, and lymphoscintigraphic scanning was monitored every 5 to 10 min, for up to 2 h after injection. The SLN was identified using a combination of a blue dye, indigocalmine, and a gamma probe during surgery. The hot spot pattern and direction of the lymphatic drains were evaluated in 21 of 23 cases. Two cases did not have a hot spot. Single, double, and multiple hot spots were observed in 12 cases (52.1%), 8 cases (34.7%), and 1 case (4.3%), respectively. The positions of the hot spots were: axillary (n=17, 80.9%), axillary and sternal (n=3, 14.2%), and phrenic (n=1, 4.7%). The sensitivity and specificity rates in SLNB were 66.6% and 100%, respectively, and the overall predictive rate was 85.7%. Lymphoscintigraphy produced false negatives in three cases (33.3%), including one on the phrenic side. Lymphoscintigraphic mapping with Tc-99m HSA and tin colloids is useful for determining the SLN, and avoiding a false negative. The pattern and direction of the lymphatic drain to the SLN in scintigraphy need to be considered for the elimination of axillary lymph node dissection in node-negative patients with breast cancer.

A pitfall in the survival benefit of adjuvant chemotherapy for node- and hormone receptor-positive patients with breast cancer: the paradoxical role of Bcl-2 oncoprotein (review)

The survival benefit of adjuvant chemotherapy in node-positive patients with breast cancer compared with surgery alone has been established. The survival benefit differs considerably between hormone receptor-positive and -negative patients, and it is believed that the effectiveness of adjuvant chemotherapy can be increased by hormonal therapy with tamoxifen. In the present review, we discuss the rationale behind the effectiveness of combination treatment with anticancer drugs and tamoxifen in terms of the paradoxical role of Bcl-2 in apoptosis in breast cancer. The survival benefit between receptor-positive and -negative patients was assessed using previous reports of randomized controlled studies for postoperative adjuvant chemotherapy in node-positive breast cancer. Tamoxifen induces the anti-apoptotic gene, Bcl-2, by its effect on estradiol (E2), via an E2-response element in the promotor region of Bcl-2. The efficicacy of chemoendocrine therapy was assessed in terms of the influence of tamoxifen on the effect of anticancer drugs. Adjuvant chemotherapy, including anthracycline and non-anthracycline based regimens, has an overall survival benefit in node-positive breast cancer, with a 23.5% reduction in the annual odds of recurrence and a 15% reduction in mortality (P<0.00001). A comparison of the reduction of the relative risk indicates that the survival benefit in receptor-negative patients is superior to that in receptor-positive patients by approximately 3-fold. Further, in contrast to receptor-negative patients, there is no additional benefit from paclitaxel over doxorubicin and cyclophosphamide (AC) in receptor-positive patients. The possible reasons that the chemotherapy benefit in receptor-positive patients is small and marginal are the following: i) concurrent treatment or pretreatment with tamoxifen can increase plasma E2 levels in premenopausal patients, thereby inducing Bcl-2 in residual cancer cells, which might decrease drug-sensitivity in combination with chemotherapy; ii) induction of Bcl-2 might be involved predominantly in the resistance to taxanes, the cytotoxic action of which targets Bcl-2. Co-treatment or pretreatment with tamoxifen for adjuvant therapy might decrease the efficacy of anticancer drugs, an effect that is mediated by induction of Bcl-2, especially in premenopausal patients with node-positive breast cancer. Treatment with anticancer drugs should be followed by treatment with tamoxifen to produce a survival benefit from combination therapy in receptor-positive patients.

[Current status and future perspectives on chemotherapy in patients with gastric cancer: can the clinical data from Japan lead to a standard international therapy?]

From a meta-analysis of clinical studies in Japan and the West, although no survival benefit for stage I gastric cancer was observed in patients who received postoperative adjuvant chemotherapy, the survival benefit for patients with stage II and III disease was small and marginal effect, respectively, since the odds ratios were between 0.80 and 0.82 with a 95% confidence interval of less than 1.0. Anticancer drugs used for combination therapy included mitomycin C, anthracyclines, alkylating agents, and 5-fluorouracil. Increased long-term survival and the prevention of peritoneal recurrence were found in some patients who received combination therapy with mitomycin C, 5-fluorouracil, and nonspecific immunomodulators such as PSK and OK-432. Regarding chemotherapy for advanced and recurrent cases, administration of biochemical modulators such as low-dose FP and the new dehydropyrimidine dehydrogenase inhibitory fluoropyrimidine agent S 1 resulted in increased response rates, improved quality of life, and prolongation of survival. The development of rigorous trials and personalized chemotherapy with molecular targeting are needed to achieve further survival benefit for patients with gastric cancer.

[A new therapeutic approach to advanced and recurrent gastric cancer by TS-1]

In the present study, we demonstrate the treatment results of TS-1 on 22 gastric carcinoma patients (15 far advanced and 7 recurrent patients) from June 1999 to December 2000. TS-1 was administered at 75 mg/m2/day, twice daily per body for 28 days followed by a 14-day interval (1 cycle). Successful treatment was obtained in from 1 to 11 cycles, and we obtained 9 (47.4%) partial responses (PR), 7 stable disease (NC) and progressive disease (PD) among 19 evaluable patients. PR was obtained in 7 (58.3%) out of 12 primary lesions of the stomach. We also obtained 1 CR of liver metastasis and 4 PR of 9 distant lymph node metastases (44.4%). Moreover, malignant ascites disappeared in 4 (57.1%) out of 7 cases and PR was obtained in 3 (50%) out of 6 measurable cases of peritoneal disease. In addition, two patients had hydronephrosis which improved after 1 cycle of TS-1 treatment. The adverse effects observed were grade 3 bone marrow suppression in three cases, severe diarrhea in one case, one case of liver dysfunction and a few cases of nausea and vomiting. These results indicate that the oral tegafur compound, TS-1, is a new therapeutic tools for advanced and recurrent gastric carcinomas, especially peritoneal disease.

An analysis of relapsed breast cancer in patients previously treated with breast conserving surgery

BACKGROUND

Recent advances in breast surgery have focused on breast conserving surgery in combination with radiotherapy. In the present study, we examine by retrospective analysis 105 patients with breast cancer who received breast conserving surgery for factors influencing disease free survival.

METHODS

The analysis was performed on 105 patients with breast cancer who received breast conserving surgery in our department, including 38 patients without radiotherapy and 67 patients treated with radiotherapy. The disease-free survival of the patients was analyzed using the Kaplan-Meier method. The relapsed patients were assessed by examining pathological features and gene expression by immunohistochemical staining.

RESULTS

There was no significant difference in the disease free survival at 5 years between patients without radiotherapy (89.6%) and with radiotherapy (94.5%). Relapse after breast conserving surgery was found in 6 patients including 4 patients without radiotherapy and 2 patients with radiotherapy. Local relapse and bone metastasis were found in 4 (3.8%) and 2 patients, respectively. Among the 4 local relapses, 1 patient had received radiotherapy and 3 patients had not. There was no significant difference between the type of relapse in terms of lymph node metastasis, hormone receptor, nuclear grade and intraductal component, but more vessel invasion was observed in the 2 cases with bone metastasis. The overexpression of apoptosis and angiogenesis genes such as p53, Bax, Bcl-XL, Bcl-2 and VEGF was not common in the relapsed patients, whereas the overexpression of drug resistance genes, either P-gp or MRP1, was found in the all patients.

CONCLUSIONS

Although radiotherapy may reduce the incidence of local relapse and increase disease free survival after breast conserving surgery, the development of an effective adjuvant chemotherapy based on drug resistance markers, is also required.

Actual colonoscopy: what are the risks of perforation?

Recent studies have suggested that virtual colonoscopy (VC) and actual colonoscopy (AC) have similar efficacy for detection of polyps >6 mm. However, procedural risks with emerging technology such as VC need to be assessed before widespread implementation. We propose to demonstrate complication rates after AC that can be used for a comparative benchmark in VC. From 1994 to 1999 all patients undergoing AC who sustained perforation that required operation were analyzed for the mortality and complications. There were 26,162 consecutive colonoscopies that required 21 operations for perforation. Of these 16,948 (65%) colonoscopies were diagnostic and 9,214 (35%) were therapeutic with 11 (0.06%) and 10 (0.11%) operations respectively. Overall risk for colonoscopic perforation that requires operation was one in 1,246 (one in 1,541 for diagnostic and one in 921 for therapeutic). Five perforations were oversewn, 15 were resected (five with stoma), and one was drained. One patient died. There were two reoperations. Mortality was 0.006 per cent (one in 16,948) for diagnostic and zero for therapeutic colonoscopy. Overall risk for perforation that requires operation or mortality after AC is low. Virtual colonoscopists who propose screening and subsequent therapeutic interventions need to report high volume without complications as the perforation rate requiring operation was one in 1,246.

Pharmacokinetic and biochemical analysis in the treatment of weekly paclitaxel in relapsed breast cancer

The mechanism(s) by which weekly paclitaxel exerted more therapeutic efficacy than the triweekly schedule in relapsed breast cancer is still unclear. To assess the rationale in therapeutic efficacy of weekly paclitaxel in relapsed breast cancer, pharmacokinetic and biochemical analyses were examined in terms of the mean peak plasma concentration at 0 min (Cmax), 30 min, and 24 h after finishing the infusion, and the extracellular domain of HER-2 in response to the treatment with paclitaxel. Twenty-five patients treated with weekly 1 h infusion of paclitaxel in the dose range from 40 mg/m(2) to 80 mg/m(2) were studied. Eleven patients responded to the treatment including 4 cases of complete response (CR) and 7 cases of partial response (PR), while 14 patients did not respond including 12 cases of no change (NC) and 2 cases of progressive disease (PD). The plasma concentration of paclitaxel and extracellular domain of HER-2 in the patients were measured by high-pressure liquid chromatography and enzyme immunoassay, respectively. The peak concentration (Cmax) and the other peaks at 30 min and 24 h in 10 patients including 3 cases of 40 mg/m(2), 3 cases of 60 mg/m(2) and 4 cases of 80 mg/m(2) in the weekly paclitaxel were compared in proportion to the increase of dose escalation, and compared to their tumor response. Further, the plasma levels of extracellular domain of HER-2 in 17 patients treated with the weekly paclitaxel were measured, and also compared to their tumor response. The mean Cmax treated with 40 mg/m(2), 60 mg/m(2) and 80 mg/m(2) in the weekly paclitaxel was 1.94, 2.18 and 1.54 microM, respectively. The dose escalation of paclitaxel and the dose intensity were not correlated with the increase of plasma concentration of paclitaxel nor with the tumor response. In contrast, the plasma level of extracellular domain of HER-2 in responders was higher than that of non-responders in the weekly paclitaxel regimen(p=0.0512, Mann-Whitney's U-test). These results suggest that tumor response to the weekly 1 h infusion of paclitaxel was not associated with the plasma concentration and the dose intensity, rather the plasma level of extracellular domain of HER-2 protein may be a predictor of tumor response in the treatment of weekly paclitaxel in relapsed breast cancer.

Chemical denaturation and elevated folding temperatures are required for wild-type activity and stability of recombinant Methanococcus jannaschii 20S proteasome

The 20S proteasome from the extreme thermophile Methanococcus jannaschii (Mj) was purified and sequenced to facilitate production of the recombinant proteasome in E. coli. The recombinant proteasome remained in solution at a purity level of 80-85% (according to SDS PAGE) following incubation of cell lysates at 70 degrees C. Temperature-activity profiles indicated that the temperature optima of the wild-type and recombinant enzymes differed substantially, with optimal activities occurring at 119 degrees C and 95 degrees C, respectively. To ameliorate this discrepancy, two recombinant enzyme preparations were produced, each of which included denaturation of the proteasome by 4 M urea followed by high-temperature (85 degrees C) dialysis. The wild-type temperature optimum was restored, but only if proteasome subunits were denatured and refolded prior to assembly (a preparation designated as alpha & beta). In contrast, when proteasome assembly preceded denaturation (designated alpha + beta) the optimum temperature was raised to a lesser degree. Moreover, the alpha & beta and alpha + beta preparations had apparent thermal half-lives at 114 degrees C of 54.2 and 26.2 min, respectively, and the thermostability of the less stable enzyme was more sensitive to a reduction in pH. Attainment of wild-type activity and stability thus required the proper folding of both the alpha- and beta-subunits prior to proteasome assembly. Consistent with this behavior, dual-scanning calorimetry (DSC) measurements revealed differences in the reassembly efficiency of the two proteasome preparations. The ability to produce structural conformers with dramatically different thermal optima and thermostabilities may facilitate the determination of molecular forces and structural motifs responsible for enzyme thermostablity and high-temperature activity.

Resident training and endoscopic hospital privileging

Laparoscopic techniques were originally confined to female sterilization. As both instrumentation and methodology improved, gynecological endoscopy was applied to more complex processes, including salpingostomy or salpingectomy for ectopic pregnancy, and ovarian cystectomy or oophorectomy for benign conditions. Now, the laparoscopic treatment of adhesions, endometriosis and hysterectomy is almost commonplace. More sophisticated endoscopic procedures include the management of pelvic floor disease, incontinence and malignancies. However, at least two problems have become readily apparent: (i) there is often limited basic laparoscopic and hysteroscopic teaching during residency and fellowship training; and (ii) there is no standard by which to privilege or train physicians who may not have had any significant endoscopic training during residency. In this article we describe current learning theories and identify goals and specific objectives for residents in implementing a successful training program. We also discuss the mechanisms by which to privilege attending staff for gynecological procedures and the important clinical outcomes that can be improved. Finally, we raise concerns about creating algorithms by which to renew clinical privileges in endoscopic procedures.

Effect of inhibitors of cysteine and serine proteases in anticancer drug-induced apoptosis in gastric cancer cells

Activation of proteases can play an important role in apoptotic cell death induced by anticancer drugs. To assess involvement of activation of cysteine and serine proteases in anticancer drug-induced apoptosis, we tested effect of inhibitors of cysteine and serine proteases on sensitivity to anticancer drugs in MKN45 gastric cancer cells. Cytotoxic effect by adriamycin (ADM), SN-38 (active form of irrinotecan) and cisplatin (CDDP) was significantly prevented by cotreatment with Z-Val-Ala-Asp-fluoromethylketone (Z-VAD-fmk) (p<0.01), a pancaspase inhibitor compared with drug alone using MTT assay. In contrast, cotreatment with N-acetyl-Tyr-Val-Ala-Asp aldehyde (AC-YVAD-CHO), a caspase 1 inhibitor did not prevent any cytotoxic effect of these drugs. Cotreatment of N-acetyl-Asp-Glu-Val-Asp aldehyde (AC-DEVD-CHO), a caspase 3 inhibitor prevented cytotoxic effect of VP-16 and SN-38 (p<0.01). Prevention of these cytotoxic effects by caspase inhibitors was not dose-dependent. Cotreatment of N-tosyl-L-lysyl chloromethylketone (TLCK), a serine protease inhibitor significantly prevented cytotoxic effect of ADM, SN-38, 5-fluorouracil (5-FU) and CDDP in a slight dose-dependent manner (p<0.01) except for etoposide (VP-16) and docetaxel (TXT), while an other serine protease inhibitor, N-tosyl-L-phenylalanyl chloromethylketone (TPCK) did not prevent any anticancer drug-induced cytotoxic effect. These effects were associated with prevention of internucleosomal DNA ladder formation in apoptosis. Further, protease inhibitors did not block induction of cytochrome c, that can explain the partial effect of prevention by anticancer-induced cell death. These results suggest that anticancer drug-induced cytotoxic effect is mediated by activation of serine protease (caspase-independent) as well as caspase-dependent pathway leading to apoptotic cell death, and that protease-independent pathway may also be involved in apoptotic pathways. The involvement of protease in signal transduction pathways may differ in cytotoxic action of drugs in gastric cancer cells.

BeF(3)(-) acts as a phosphate analog in proteins phosphorylated on aspartate: structure of a BeF(3)(-) complex with phosphoserine phosphatase

Protein phosphoaspartate bonds play a variety of roles. In response regulator proteins of two-component signal transduction systems, phosphorylation of an aspartate residue is coupled to a change from an inactive to an active conformation. In phosphatases and mutases of the haloacid dehalogenase (HAD) superfamily, phosphoaspartate serves as an intermediate in phosphotransfer reactions, and in P-type ATPases, also members of the HAD family, it serves in the conversion of chemical energy to ion gradients. In each case, lability of the phosphoaspartate linkage has hampered a detailed study of the phosphorylated form. For response regulators, this difficulty was recently overcome with a phosphate analog, BeF(3)(-), which yields persistent complexes with the active site aspartate of their receiver domains. We now extend the application of this analog to a HAD superfamily member by solving at 1.5-A resolution the x-ray crystal structure of the complex of BeF(3)(-) with phosphoserine phosphatase (PSP) from Methanococcus jannaschii. The structure is comparable to that of a phosphoenzyme intermediate: BeF(3)(-) is bound to Asp-11 with the tetrahedral geometry of a phosphoryl group, is coordinated to Mg(2+), and is bound to residues surrounding the active site that are conserved in the HAD superfamily. Comparison of the active sites of BeF(3)(-) x PSP and BeF(3)(-) x CeY, a receiver domain/response regulator, reveals striking similarities that provide insights into the function not only of PSP but also of P-type ATPases. Our results indicate that use of BeF(3)(-) for structural studies of proteins that form phosphoaspartate linkages will extend well beyond response regulators.