Modeling and simulation of bone mineral density in Japanese osteoporosis patients treated with zoledronic acid using tartrate-resistant acid phosphatase 5b, a bone resorption marker.

Annual intravenous administration of zoledronic acid is used in the treatment of osteoporosis. A mathematical model was developed to predict bone mineral density up to 2 years after two annual doses of zoledronic acid from the early values of a bone resorption marker in osteoporosis patients. INTRODUCTION: The measurement of bone mineral density (BMD) has been used as a surrogate marker instead of the observation of incident fractures to detect the efficacy of treatment. However, this method requires a long time to obtain significant changes. On the other hand, bone resorption markers respond to bone resorption inhibitors within a few weeks. Therefore, the aim of this study was to develop a mathematical model predicting long-term BMD after two annual doses of zoledronic acid (ZOL) using the early response of a bone resorption marker in osteoporosis patients. METHODS: The model was constructed using 3410 tartrate-resistant acid phosphatase 5b (TRACP-5b) serum concentrations and 1146 lumbar spine (L2-L4) BMD values from 306 patients with primary osteoporosis. A mathematical model was developed to describe the time-dependent profiles of TRACP-5b and BMD. RESULTS: The percentage changes from baseline of the BMD (%BMD) at up to 2 years were predicted from patients' baseline BMD and baseline and 12-week TRACP-5b values by the model obtained. The simulated 90% prediction interval almost covered the observed %BMD distribution at each time point, and the predictions were comparable to the observed %BMD. CONCLUSIONS: This is the first model to predict BMD for up to 2 years following two annual doses of ZOL using patients' background characteristics and the early response of TRACP-5b. This model allows us to inform patients at the initial stage of ZOL treatment of their predicted response to treatment.

S-1 as adjuvant chemotherapy for stage III colon cancer: a randomized phase III study (ACTS-CC trial).

BACKGROUND: S-1 is an oral fluoropyrimidine whose antitumor effects have been demonstrated in treating various gastrointestinal cancers, including metastatic colon cancer, when administered as monotherapy or in combination chemotherapy. We conducted a randomized phase III study investigating the efficacy of S-1 as adjuvant chemotherapy for colon cancer by evaluating its noninferiority to tegafur-uracil plus leucovorin (UFT/LV). PATIENTS AND METHODS: Patients aged 20-80 years with curatively resected stage III colon cancer were randomly assigned to receive S-1 (80-120 mg/day on days 1-28 every 42 days; four courses) or UFT/LV (UFT: 300-600 mg/day and LV: 75 mg/day on days 1-28 every 35 days; five courses). The primary end point was disease-free survival (DFS) at 3 years. RESULTS: A total of 1518 patients (758 and 760 in the S-1 and UFT/LV group, respectively) were included in the full analysis set. The 3-year DFS rate was 75.5% and 72.5% in the S-1 and UFT/LV group, respectively. The stratified hazard ratio for DFS in the S-1 group compared with the UFT/LV group was 0.85 (95% confidence interval: 0.70-1.03), demonstrating the noninferiority of S-1 (noninferiority stratified log-rank test, P < 0.001). In the subgroup analysis, no significant interactions were identified between the major baseline characteristics and the treatment groups. CONCLUSION: Adjuvant chemotherapy using S-1 for stage III colon cancer was confirmed to be noninferior in DFS compared with UFT/LV. S-1 could be a new treatment option as adjuvant chemotherapy for colon cancer. CLINICALTRIALSGOV: NCT00660894.

Evaluation of the quality of life of lupus erythematosus patients with cutaneous lesions in Japan.

The quality of life (QOL) of lupus erythematosus (LE) patients with skin manifestations is impaired, but little is known about Japanese patients. We assessed whether the skin symptoms in LE are associated with the QOL using the Japanese versions of the Skindex-29 and Cutaneous Lupus Erythematosus Disease Area and Severity Index (CLASI). In all, 54 LE patients with cutaneous lesions completed the Japanese version of the Skindex-29, and physicians assessed the severity of their eruptions using the CLASI before and after treatment. The QOL of the LE patients was better after the therapeutic intervention using the Skindex-29 questionnaire. We tested several factors for an independent association with the QOL. A significant risk factor for a poor QOL was a female gender in "Functioning" before treatment. In addition, a poor QOL tended to be correlated with a female gender in "Emotions" and older current age in "Symptoms" before treatment, and with a longer duration of SLE in "Functioning" after treatment. In the CLASI analysis, skin manifestation activity in the acute phase correlated with a poor emotional and functional QOL rather than a symptomatic QOL. To the best of our knowledge, this is the first report evaluating the QOL of Japanese LE patients, despite the small cohort.

Nitrate-dependent ferrous iron oxidation by anaerobic ammonium oxidation (anammox) bacteria.

We examined nitrate-dependent Fe(2+) oxidation mediated by anaerobic ammonium oxidation (anammox) bacteria. Enrichment cultures of "Candidatus Brocadia sinica" anaerobically oxidized Fe(2+) and reduced NO3(-) to nitrogen gas at rates of 3.7 ± 0.2 and 1.3 ± 0.1 (mean ± standard deviation [SD]) nmol mg protein(-1) min(-1), respectively (37°C and pH 7.3). This nitrate reduction rate is an order of magnitude lower than the anammox activity of "Ca. Brocadia sinica" (10 to 75 nmol NH4(+) mg protein(-1) min(-1)). A (15)N tracer experiment demonstrated that coupling of nitrate-dependent Fe(2+) oxidation and the anammox reaction was responsible for producing nitrogen gas from NO3(-) by "Ca. Brocadia sinica." The activities of nitrate-dependent Fe(2+) oxidation were dependent on temperature and pH, and the highest activities were seen at temperatures of 30 to 45°C and pHs ranging from 5.9 to 9.8. The mean half-saturation constant for NO3(-) ± SD of "Ca. Brocadia sinica" was determined to be 51 ± 21 µM. Nitrate-dependent Fe(2+) oxidation was further demonstrated by another anammox bacterium, "Candidatus Scalindua sp.," whose rates of Fe(2+) oxidation and NO3(-) reduction were 4.7 ± 0.59 and 1.45 ± 0.05 nmol mg protein(-1) min(-1), respectively (20°C and pH 7.3). Co-occurrence of nitrate-dependent Fe(2+) oxidation and the anammox reaction decreased the molar ratios of consumed NO2(-) to consumed NH4(+) (ΔNO2(-)/ΔNH4(+)) and produced NO3(-) to consumed NH4(+) (ΔNO3(-)/ΔNH4(+)). These reactions are preferable to the application of anammox processes for wastewater treatment.

Modulation in concentrative nucleoside transporters-mediated intestinal absorption of mizoribine, an immunosuppressive agent, in lipopolysaccharide-treated rats.

The characteristics of intestinal absorption of mizoribine and cephalexin, that are mediated by concentrative nucleoside transporters (CNTs) and PEPT1, respectively, was examined in lipopolysaccharide (LPS)-treated rats. LPS treatment is known to modify the expression of some transporters and induce cholestasis. At 24 h after the LPS treatment, averaged concentrations of IL-6 and total bile acids in plasma were 15-fold and 2-fold that in untreated control rats, respectively, and bile flow rate decreased by 40% of control, indicating the induction of inflammatory and cholestatic states. The oral bioavailability, estimated by urinary excretion percentage of unchanged form, of mizoribine in LPS-treated rats was 1.5-fold higher than that in control rats, whereas the bioavailability of cephalexin remained unchanged. When mizoribine and cephalexin were administered into in-situ jejunum loops, there were no differences in the absorption rates between control and LPS-treated rats. These results indicated that the functional expression of CNT1, CNT2, and PEPT1 were not modulated by LPS treatment. When mizoribine (a CNT1/CNT2 substrate) and gemcitabin (a CNT1 substrate) were administered as a solution dissolved in bile into the intestinal loop, their absorption rates decreased significantly. In contrast, the absorption rate of ribavirin (a CNT2 substrate) remained unchanged. In conclusion, LPS treatment exerted no significant effect on the expression of CNT1 and CNT2 in the intestine. Bile was found to suppress the CNT1-mediated intestinal absorption of mizoribine and gemcitabin. The increased oral bioavailability of mizoribine in LPS-treated rats could be ascribed to the less amount of bile or bile acids in the intestine under cholestatic state of rats.

Growth pattern in the muscular layer reflects the biological behaviour of colorectal cancer.

OBJECTIVE: To determine the clinical value of evaluating the cancer morphology in muscularis propria (MP) for colorectal cancer (CRC) patients. METHOD: A total of 994 patients with advanced CRC were reviewed in terms of two distinctive growth patterns in the MP: (i) horizontal spread between the circular and longitudinal muscle layers (H-spread) and (ii) 'streaming' spread between the muscle bundles of the circular muscle layer (S-spread). RESULTS: The incidence of H-spread (n = 153) and S-spread (n = 150) showed a positive correlation with tumour-node-metastasis (TNM) stage and both exerted a negative impact on postoperative survival. Adverse morphology in the MP (H-spread and/or S-spread) was consistent with a high grade of vascular invasion and budding in the extramural layer, as also with unfavourable fibrotic stromas in the reactive fibrous zone; the 5-year survival rate in patients with such features was 64.2%, which was lower than that in those without (86.5%, P < 0.0001). Multivariate analysis demonstrated that adverse morphology was an independent prognostic determinant, along with T- and N -stage. As the mode of H-spread, perineural invasion in the myenteric plexus was found to be predominant over lymphatic spread on the basis of S100 and CD34 immunostaining, but neural cell adhesion molecule expression, whether on cancer cells or on neural cells, was not significant for this growth pattern. CONCLUSION: A particular group of CRCs ingeniously utilizes the thin space between muscle fascicles for development in the MP. Although the biological mechanism remains unknown, this distinctive growth pattern could be a useful indicator to identify CRC patients at high risk of recurrence.

The central respiratory chemoreceptor: where is it located?-Invited article.

We review previous reports on the localization of the central chemoreceptor focusing on our studies that used various experimental techniques including lesioning (brainstem transection and removal of pia mater), analyses of neuronal responses to CO(2) by electrophysiological and optical recording, mapping of CO(2)-excitable neurons by c-fos immunohistochemistry and local acidic stimulation. Among these experimental techniques, voltage imaging with calculation of cross correlation coefficients between the respiratory output activity and each pixel, i.e., correlation coefficient imaging technique, enabled us to effectively analyze imaging data without empirical signal processing. The reviewed studies have indicated that the most superficial layer of the rostral ventral medulla, i.e., the surface portions of the nucleus retrotrapezoideus/parafacial respiratory group, nucleus parapyramidal superficialis and nucleus raphe pallidus, is important in central chemoreception. We suggest that one of the major respiratory rhythm generators, i.e., the preBötzinger complex, is not chemosensitive in itself or rather inhibited by CO(2). Based on our detailed analysis of c-fos immunohistochemistry, we propose a cell-vessel architecture model for the central respiratory chemoreceptor. Primary chemoreceptor cells are mainly located beneath large surface vessels within the marginal glial layer of the ventral medulla, and surround fine penetrating vessels that branch from a large surface vessel. Respiratory neurons in the rostral portion of the ventral respiratory group could be intrinsically chemosensitive, but their role in chemoreception might be secondary. Definitive identification of chemosensitive sites and chemoreceptor cells needs further studies.

Anatomical architecture and responses to acidosis of a novel respiratory neuron group in the high cervical spinal cord (HCRG) of the neonatal rat.

It has been postulated that there exists a neuronal mechanism that generates respiratory rhythm and modulates respiratory output pattern in the high cervical spinal cord. Recently, we have found a novel respiratory neuron group in the ventral portion of the high cervical spinal cord, and named it the high cervical spinal cord respiratory group (HCRG). In the present study, we analyzed the detailed anatomical architecture of the HCRG region by double immunostaining of the region using a neuron-specific marker (NeuN) and a marker for motoneurons (ChAT) in the neonatal rat. We found a large number of small NeuN-positive cells without ChAT-immunoreactivity, which were considered interneurons. We also found two and three clusters of motoneurons in the ventral portion of the ventral horn at C1 and C2 levels, respectively. Next, we examined responses of HCRG neurons to respiratory and metabolic acidosis in vitro by voltage-imaging together with cross correlation techniques, i.e., by correlation coefficient imaging, in order to understand the functional role of HCRG neurons. Both respiratory and metabolic acidosis caused the same pattern of changes in their spatiotemporal activation profiles, and the respiratory-related area was enlarged in the HCRG region. After acidosis was introduced, preinspiratory phase-dominant activity was recruited in a number of pixels, and more remarkably inspiratory phase-dominant activity was recruited in a large number of pixels. We suggest that the HCRG composes a local respiratory neuronal network consisting of interneurons and motoneurons and plays an important role in respiratory augmentation in response to acidosis.

Nomograms predicting survival and recurrence in colonic cancer in the era of complete mesocolic excision.

Background: More extensive lymphadenectomy may improve survival after resection of colonic cancer. Nomograms were created predicting overall survival and recurrence for patients who undergo D2-D3 lymph node dissection, and their validity determined. Methods: This was a multicentre study of patients with colonic cancer who underwent resection with D2-D3 lymph node dissection in Japan. Inclusion criteria included R0 resection. A training cohort of patients operated on from 2007 to 2008 was analysed to construct prognostic models predicting survival and recurrence. Discrimination and calibration were performed using an external validation cohort from the Japanese colorectal cancer registry (procedures in 2005-2006). Results: The training cohort consisted of 2746 patients. Predictors of survival were: age (hazard ratio (HR) 1·04), female sex (HR 0·71), depth of tumour invasion (HR 1·15, 1·22, 2·96 and 3·14 for T2, T3, T4a and T4b respectively versus T1), lymphatic invasion (HR 1·11, 1·15 and 2·95 for ly1, ly2 and ly3 versus ly0), preoperative carcinoembryonic antigen (CEA) level (HR 1·21, 1·59 and 1·99 for 5·1-10·0, 10·1-20·0 and 20·1 and over versus 0-5·0 ng/ml), number of metastatic lymph nodes (HR 1·07), number of lymph nodes examined (HR 0·98) and extent of lymphadenectomy (HR 0·23, 0·13 and 0·11 for D1, D2 and D3 versus D0). Predictors of recurrence were: female sex (HR 0·82), macroscopic type (HR 3·82, 4·56, 6·66, 7·74 and 3·22 for types I, II, III, IV and V versus type 0), depth of invasion (HR 1·25, 2·66, 5·32 and 6·43 for T2, T3, T4a and T4b versus T1), venous invasion (HR 1·43, 3·05 and 4·79 for v1, v2 and v3 versus v0), preoperative CEA level (HR 1·39, 1·43, 1·56 and 1·85 for 5·1-10·0, 10·1-20·0, 20·1-40·0 and 40·1 or more versus 0-5 ng/ml), number of metastatic lymph nodes (HR 1·07) and number of lymph nodes examined (HR 0·98). The validation cohort comprised 4446 patients. The internal and external validated Harrell's C-index values for the nomogram predicting survival were 0·75 and 0·74 respectively. Corresponding values for recurrence were 0·78 and 0·75. Conclusion: These nomograms could predict survival and recurrence after curative resection of colonic cancer.

Hayabusa2 arrives at the carbonaceous asteroid 162173 Ryugu-A spinning top-shaped rubble pile.

The Hayabusa2 spacecraft arrived at the near-Earth carbonaceous asteroid 162173 Ryugu in 2018. We present Hayabusa2 observations of Ryugu's shape, mass, and geomorphology. Ryugu has an oblate "spinning top" shape, with a prominent circular equatorial ridge. Its bulk density, 1.19 ± 0.02 grams per cubic centimeter, indicates a high-porosity (>50%) interior. Large surface boulders suggest a rubble-pile structure. Surface slope analysis shows Ryugu's shape may have been produced from having once spun at twice the current rate. Coupled with the observed global material homogeneity, this suggests that Ryugu was reshaped by centrifugally induced deformation during a period of rapid rotation. From these remote-sensing investigations, we identified a suitable sample collection site on the equatorial ridge.

Cellular basis of vasospasm: role of small diameter arteries and voltage-dependent Ca2+ channels.

Constriction of small (100-200 microm) diameter cerebral arteries in response to increased intravascular pressure plays an important role in the regulation of cerebral blood flow. In arteries from healthy animals, these pressure-induced constrictions arise from depolarization of arterial smooth muscle leading to enhanced activity of L-type voltage-dependent calcium channels. Recently, we have observed that pressure-induced constrictions are greatly enhanced in cerebral arteries obtained from a rabbit model of subarachnoid hemorrhage (SAH) due to the emergence of R-type voltage-dependent calcium channels in arterial myocytes. Enhanced pressure-induced constrictions and the resulting decrease in cerebral blood may contribute to the development of neurological deficits in SAH patients following cerebral aneurysm rupture. This work supports the concept that small diameter arteries represent important targets for current treatment modalities (e.g. Hypertensive, Hypervolemic, Hemodilution "triple H" therapy) used in SAH patients. Further, we propose targeting R-type calcium channels, encoded by the gene Ca(v)2.3, as a novel therapeutic strategy in the treatment of SAH-induced cerebral vasospasm.

Acute and chronic effects of oxyhemoglobin on voltage-dependent ion channels in cerebral arteries.

Voltage-dependent potassium (Kv) and calcium (VDCC) channels play an important role in the regulation of membrane potential and intracellular calcium concentration in cerebral artery myocytes. Recent evidence suggests VDCC activity is increased and Kv channel activity is decreased in cerebral arteries following subarachnoid hemorrhage (SAH), promoting enhanced constriction. We have examined the impact of the blood component oxyhemoglobin on Kv and VDCC function in small (100-200 microm) diameter cerebral arteries. Acute (10 min) exposure of oxyhemoglobin caused cerebral artery constriction and Kv current suppression that was abolished by tyrosine kinase inhibitors and a Kv channel blocker. Although short-term oxyhemoglobin application did not directly alter VDCC activity, five-day exposure to oxyhemoglobin was associated with enhanced expression of voltage-dependent calcium channels. This work suggests that acute and chronic effects of oxyhemoglobin act synergistically to promote membrane depolarization and increased VDCC activity in cerebral arteries. These actions of oxyhemoglobin may contribute to the development of cerebral vasospasm following aneurysmal subarachnoid hemorrhage.

cDNA microarray analysis of cancer associated gene expression profiles in malignant peripheral nerve sheath tumours.

BACKGROUND: Malignant peripheral nerve sheath tumour (MPNST) is a highly aggressive malignancy that arises within peripheral nerves, and is associated with poor prognosis. Little is known about the underlying biology of MPNST, especially the mechanisms involved in cell proliferation, invasion, or escape from apoptosis. AIMS: To identify genes differentially expressed in MPNST compared with benign tumours, such as neurofibromas and schwannomas, by means of cDNA microarray analysis. METHODS: Six MPNST cases and five benign cases (three schwannomas and two neurofibromas) were analysed. RESULTS: Six genes (keratin 18, survivin, tenascin C, adenosine deaminase, collagen type VIa3, and collagen type VIIa1) were significantly upregulated in MPNST, whereas one gene, insulin-like growth factor binding protein 6, was downregulated in MPNST. Survivin and tenascin C expression was validated by reverse transcription polymerase chain reaction. Immunohistochemistry confirmed upregulation of survivin in MPNST at the protein level in six of eight cases compared with benign tumours. Tenascin C was also expressed at the invasive front and tumorous stroma in all MPNST cases. MPNST cells expressed tenascin C in four of nine cases. CONCLUSIONS: Survivin and tenascin C may be associated with the malignant potential of MPNST and could be considered as potential therapeutic targets.

Crystal structure of the E166A mutant of extended-spectrum beta-lactamase Toho-1 at 1.8 A resolution.

Bacterial resistance to beta-lactams is mainly due to the production of beta-lactamase. Especially through the production of extended-spectrum beta-lactamases (ESBLs), bacteria have acquired resistance not only to penicillins, but also to expanded-spectrum cephems. Here, we describe the crystal structure of the E166A mutant of class A beta-lactamase Toho-1 at 1.8 A resolution, the first reported tertiary structure of an ESBL. Instead of the wild-type enzyme, a mutant Toho-1, in which Glu166 was replaced with alanine, was used for this study, because of the strong tendency of the wild-type enzyme to form twinned crystals. The overall structure of Toho-1 is similar to the crystal structures of non-ESBLs, with no pronounced backbone rearrangement of the framework. However, there are some notable local changes. First, a difference in the disposition of an arginine residue, which is at position 244 in non-ESBLs but at position 276 in Toho-1 and other ESBLs, was revealed and the role of this arginine residue is discussed. Moreover, changes in the hydrogen-bonding pattern and in the formation of the hydrophobic core were also observed near the Omega loop. In particular, the lack of hydrogen bonds in the vicinity of the Omega loop could be a cause of the extended substrate specificity of Toho-1. Through the generation of a model for the enzyme-substrate complex, a conformational change of Toho-1 occurring on complex formation is discussed based on the active-site cleft structure and the substrate profile.

Enzyme immunoassay of human chorionic gonadotropin employing beta-galactosidase as label.

An enzyme-linked immunoassay was applied to the determination of hCG, a glycoprotein hormone usually assayed by RIA. For this purpose, an enzyme hormone conjugate was prepared by reacting hCG with beta-D-galactosidase (beta-Gal.) of E. coli in the presence of N-(m-maleimidobenzoyloxy) succinimide (MBS) as coupling reagent. The conjugate, after purification by affinity and gel chromatographies, was shown to exhibit sufficient enzyme activity and immunoactivity. The immunoassay of hCG was performed by the double antibody method and, using this assay, 0.4-250 mIU/ml hCG were detectable. This was about 10 times as sensitive as the RIA. Difficulty was experienced when this method was utilized for the determination of hCG in plasma samples from patients. Since the presence of the plasma may have affected this assay method, the following improvements were made: 1) the same volume of hormone-free plasma was added to the standard solutions of hCG, and 2) the volume of plasma sample was 10 microliter. The performance and validity of this assay were comparable to the RIA using [125I]hCG as tracer. The dose-response curves of both assay have the same slope and there was no significant difference between the values (correlation coefficient, Y = 0.96X + 1.53).

A survey of a functional amino acid of class C beta-lactamase corresponding to Glu166 of class A beta-lactamases.

The class C beta-lactamase of Citrobacter freundii GN346 is a typical cephalosporinase comprising 361 amino acids. The aspartic acid at position 217 and glutamic acid at position 219 in this beta-lactamase were, respectively, previously shown not to be the counterpart of Glu166 (ABL166) in class A beta-lactamases, even though sequence alignment of class A and C enzymes strongly suggested this possibility [(1990) FEBS Lett. 264, 211-214; (1990) J. Bacteriol. 172, 4348-4351]. We tried again to assign candidates for the counterpart of Glu166 through sequence alignment based on other criteria, the glutamic acids at positions 195 and 205 in the class C beta-lactamase being selected. To investigate this possibility, these two glutamic acids were changed to glutamine, lysine or alanine, respectively. All the mutant enzymes showed more than 50% of the activity of the wild-type enzyme, indicating that the possibility was ruled out. These results strongly suggested the possibility that the class C beta-lactamase lacks a functional acidic residue corresponding to Glu166 in class A enzymes.

Oligomannose-coated liposomes as an adjuvant for the induction of cell-mediated immunity.

The effect of the coating of ovalbumin-reconstituted liposomes with various oligosaccharides on their immunogenicity was investigated in mice. The coating of liposomes with oligomannose or yeast mannan drastically enhanced their ability to induce an ovalbumin-specific delayed-type footpad swelling response with a peak at 24 to 48 h post-challenge. Among various oligosaccharides tested, only those with mannose residue at the nonreducing termini manifested the activity when applied to liposomes. Since such oligosaccharides are ubiquitously found in the body, these results suggested the usefulness of oligomannose-coated liposomes as a safe adjuvant for the induction of cell-mediated immunity.

Synovial sarcoma of the prostate with t(X;18)(p11.2;q11.2).

A case of monophasic synovial sarcoma of the prostate in a 37-year-old man is reported. Histologically, the tumor was chiefly composed of uniform spindle and oval cells, which often formed interlacing fascicles resembling those of fibrosarcoma. In some areas, the compact fascicles of tumor cells alternated with hypocellular myxoid tissue bearing a superficial resemblance to peripheral nerve sheath tumors, whereas small portions of the tumor showed a pericytomatous pattern consisting of polygonal cells arranged around dilated, thin-walled blood vessels. By immunohistochemistry, vimentin was detected in most cells, and a focal reactivity for epithelial membrane antigen was also observed. The tumor cells, however, were negative for keratin, S-100 protein, neuron-specific enolase, CD34, desmin, muscle-specific actin, and alpha-smooth muscle actin. Cytogenetic analysis and fluorescence in situ hybridization (FISH) using the cultured tumor cells demonstrated a translocation t(X;18)(p11.2;q11.2), an aberration specific for synovial sarcoma. To the authors' knowledge, this is the first report of a primary prostatic synovial sarcoma confirmed by cytogenetic analysis.

Modeling study on a hydrolytic mechanism of class A beta-lactamases.

Comparison of the hydrogen-bond networks at the active site in the crystallographic structures reported for class A beta-lactamases revealed an importance of a switch of the hydrogen-bond network for the catalytic process. Taking account of the conformational mobility of the Lys73 residue, we have constructed putative complex models for beta-lactam antibiotics and the enzymes in the multistep hydrolysis which consists of a Michaelis complex, an acyl-enzyme, and a tetrahedral oxyanion for deacylation. In the acylation, the C3 carboxylate of penicillin derivatives would participate in activation of the Ser130 hydroxyl group and then the oxyanion of the Ser130 residue would deprotonate the ammonium group of the Lys73 residue which will act as a general base for activation of the Ser70 residue. In the deacylation, the deacylating water molecule would be accommodated during a conformational change of the acyl moiety without a structural change of the active-site residues and the unprotonated N4 atom of the penicillins would act as a general base to activate the water molecule. This catalytic process provided a new account for the stability of the acyl-enzyme complexes. This substrate-assisted mechanism would also be extended to a hydrolytic mechanism of class C enzymes.