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PubMed1997

Design and Synthesis of Transition State Analogs for Induction of Hydride Transfer Catalytic Antibodies.

Alcohol dehydrogenases and related aldehyde reductase enzymes catalyze the oxidation of alcohols to aldehydes and the simultaneous reduction of a nicotinamide derivative (NAD(+) or NADP(+)) to the corresponding 1,4-dihydronicotinamide. Herein we report the design and synthesis of a stable transition state analog for this hydride transfer process. Compound 1 is a rigid [3.2.2] bicyclic structure containing 3-piperidone oxime as a mimic for 1,4-dihydronicotinamide. The piperidone is held in the boat conformation corresponding to the transition state by a three-atom lactam bridge between N(1) and C(4). The oxime function mimics the carboxamide group in nicotinamide. The lactam nitrogen serves as an attachment point for the alkyl group of the alcohol substrate, and the amide oxygen atom mimics its hydroxyl group. Compound 1 was prepared in 10 steps from N-benzylpiperidone, functionalized with substrate and cofactor recognition elements into transition state analogs 2 and 3 and conjugated to carrier proteins for immunization. These novel analogs open the way for the exploration of the dehydrogenase reaction using catalytic antibodies.

Journal Article↗

PubMed2004

Gesture-speech combinations as a transition to multiword utterances.

This study was designed to determine if certain types of gesture-speech combinations act as transitional phenomena preceding production of 2-word utterances. Ten normally developing children with a mean age of 15 months at the beginning of the study participated in this research. The children were sampled longitudinally at monthly intervals as they approached the onset of early multiword utterances. Temporally synchronized gesture-speech combinations were analyzed over a 6-month period to describe whether they encoded 1 semantic element (pointing to a car and saying "car") or 2 semantic elements (pointing to a car and saying "big"). These gesture-speech combinations were examined in terms of their onset in relation to early multiword combinations. It was found that there was a significant increase in gesture-speech combinations encoding 2 semantic elements during the 6-month period and that the onset of these combinations preceded or co-occurred with the 1st productions of multiword utterances. This finding, coupled with prior studies on smaller numbers of participants, suggests that gesture-speech combinations encoding 2 elements may be a transitional element between single-word communication and the onset of multiword combinations.

Analysis of Variance↗

PubMed2006

Quantum-classical modeling of nonlinear pulse propagation in a dissolved two-photon active chromophore.

In the present work we outline the implications of a quantum-classical approach for modeling two-photon absorption of organic chromophores in solution. The approach joins many-photon absorption dynamic simulations with quantum chemical first principles calculations of corresponding excitation energies and transition matrix elements. Among a number of conclusions of the study, we highlight three: (i) The use of either short- or long-pulse excitation is demonstrated to switch the absorptive capacity of the nonlinear medium owing to enhancement of the nonlinear stepwise processes; (ii) The two-photon cross section strongly depends on the way in which the dephasing rate decays when the laser frequency is tuned off-resonant with the corresponding molecular transition; (iii) The results of the pulse propagation simulations based on electronic structure data obtained with a new Coulomb attenuated functional is shown to be in much better agreement with the experimental results than those based on data received with traditional density functionals.

Absorption↗

PubMed1994

[Neoadjuvant and adjuvant chemotherapy of bladder cancer].

Conventional treatments such as surgery and radiotherapy for deeply invasive, clinically non-metastatic bladder cancer are associated with cure in less than 30% of cases. This has led to the search for new approaches to therapy. Based on the excellent results with combination chemotherapy such as M-VAC in patients with advanced disease, neoadjuvant or adjuvant chemotherapy has been advocated to improve survival. Twenty patients with primary invasive bladder cancer who underwent radical cystectomy received postoperative adjuvant chemotherapy using a CAP (cyclophosphamide, doxorubicin and cisplatin) or modified M-VAC (methotrexate, vinblastine, pirarubicin and cisplatin) regimen. Sixteen of the patients were treated with CAP and four with the modified M-VAC. Of the 20 patients, 17 had transitional cell carcinoma with or without non-transitional cell elements. All of the patients had tumors with a histological grade of G2 (six cases) or G3 (14 cases). As for lymph node metastasis, there were 10 N0 cases, three N1 cases, six N2 cases, and one N3 case. The five-year survival rate of these 20 patients was 65.9%, while that of 49 patients not administered any adjuvant chemotherapy was 29.9%. Regarding toxicity, both adjuvant chemotherapy regimens in this study were generally well tolerated. The most common toxic effects were gastrointestinal symptoms, alopecia and myelosuppression. Twenty other patients with invasive transitional cell carcinoma of the bladder received two or three cycles of neoadjuvant chemotherapy using the modified M-VAC or MEC (methotrexate, epirubicin and cisplatin) regimen prior to radical cystectomy or partial cystectomy. Of 19 evaluable patients who received neoadjuvant chemotherapy, a complete response was observed in two (10%), a partial response in 11 (55%), and no change in six (30%). The overall response rate was 65%. The five-year survival rate of 20 patients who received neoadjuvant chemotherapy was 74.2%. Regarding toxicity, one patient died of a bowel complication after surgery, and the complication was suggested to be drug-induced.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed1988

Neoadjuvant M-VAC (methotrexate, vinblastine, doxorubicin and cisplatin) for extravesical urinary tract tumors.

A total of 11 patients with stage T2-4N0M0 extravesical tumors (prostate, prostatic urethra, urethra and ureter) received 1 to 4 cycles of neoadjuvant methotrexate, vinblastine, doxorubicin and cisplatin. Of 10 evaluable patients 4 (40 per cent) had downstaging to T0 disease with a clinical complete remission observed in 3 of 5 (60 per cent) with transitional cell tumors of the prostate and prostatic urethra. Four patients with urethral tumors of mixed or nontransitional histology failed to achieve a complete remission. The disease was staged pathologically in 4 patients: 1 had a partial remission and 3 had progression (all 4 had residual disease). Because therapy with methotrexate, vinblastine, doxorubicin and cisplatin induced only significant tumor regression of transitional cell elements of extravesical tumors and because it was ineffective against mixed histological tumors and in preventing new stage Tis lesions, surgical resection of such lesions is required.

Aged↗

PubMed2005

Geochemistry of trace elements in paddy (rice) soils of Sri Lanka--implications for iodine deficiency disorders (IDD).

Iodine Deficiency Disorders (IDD) are a common health problem prevalent in the wet zone of Sri Lanka with a prevalence of >25% of the population. In comparison, in the dry zone of Sri Lanka IDD occurs in <10% of the population. Seventy soil samples from 14 villages selected on the basis of the incidence of goitre, were collected and analysed for 13 trace elements using ICP-MS. In order to identify any prevailing differences in antecedent chemical environments, soil samples from each pre-selected village were classified into three groups in terms of their geographical location. Among the elements investigated, the total soil concentrations of Rb, Sr, Ba, Mn and Co are lower in the wet zone of Kalutara. In contrast, total soil Rb, Sr, Ba and Mn contents are higher in the dry zone of Anuradhapura. Further soil total Mo and Nb levels are relatively similar in all pre-selected study locations. The high endemic goitre regions (IDD >25% of the population) show low levels of Rb, Sr, Ba, and Mn and higher levels of V, Cr, Co, Ni, Cu, Zn and Pb as compared with moderate and non-goitre areas. Factor analysis was used to exploit the correlation structure present in data and yielded three groups in all cases. This indicated that most transition group elements and iodine are associated with the Mn phase in the low IDD areas whereas iodine shows a high affinity for the organic phase in high IDD regions. The variable distribution of trace elements, therefore, must be due to differences in mobility and capacity for incorporation into the structure of secondary minerals or organic phases.

Deficiency Diseases↗

PubMed1994

Adjuvant and neoadjuvant chemotherapy for invasive bladder cancer.

A total of 20 patients with primary invasive bladder cancer who underwent radical cystectomy received postoperative adjuvant chemotherapy using a CAP (cyclophosphamide, doxorubicin, and cisplatin) or modified M-VAC (methotrexate, vinblastine, pirarubicin, and cisplatin) regimen. In all, 16 of the patients were treated with CAP and 4 received the modified M-VAC regimen. Of the 20 patients, 17 had transitional-cell carcinoma with or without non-transitional-cell elements. All of the patients had tumors with a histological grade of G2 (6 cases) or G3 (14 cases). As for lymph-node metastasis, there were ten N0 cases, three N1 cases, six N2 cases, and one N3 case. Adjuvant chemotherapy was usually commenced 2 weeks after the surgery and was given every 3-4 weeks for two or three cycles. The 5-year survival rate of these 20 patients was 65.9%, whereas that of 49 patients who did not receive any adjuvant chemotherapy was 30.2%. Regarding toxicity, both of the adjuvant chemotherapy regimens used in this study were generally well tolerated. The most common toxic effects were gastrointestinal symptoms, alopecia, and myelosuppression. Another 19 patients with invasive transitional-cell carcinoma of the bladder received 2 or 3 cycles of neoadjuvant chemotherapy using the modified M-VAC or MEC (methotrexate, epirubicin, and cisplatin) regimen. Of 18 pathologically evaluable patients who underwent radical cystectomy or partial cystectomy, the stage was pT0 in 3 cases (17%), pTis in 3 (17%), pT1 in 3 (17%), and pT2 or higher in 9 (50%). The 4-year survival rate of 18 patients who received neoadjuvant chemotherapy was 71.5%. Regarding toxicity, one patient died of a bowel complication after surgery, and the complication was suggested to be drug-induced.

Adenocarcinoma↗

PubMed2004

Reactions under autogenic pressure at elevated temperature (RAPET) of various alkoxides: formation of metals/metal oxides-carbon core-shell structures.

The RAPET reaction at 700 degrees C, of different alkoxides (Ti, V, and Si) led to three different nanocomposites. Carbon is the element common to all three structures. Carbon was found as the core in the decomposition of TEOS, as the shell in the decomposition of VO(OEt)3 and embedded in, or mixed completely with, TiO2 in the decomposition of Ti(OiPr)4. This novel method using only metallic alkoxide precursor, in the absence of catalyst, leads in a one-step process to core-shell structures.

Carbon↗

PubMed1988

Neoadjuvant M-VAC (methotrexate, vinblastine, doxorubicin and cisplatin) effect on the primary bladder lesion.

Of 50 patients with bladder cancer given 1 to 5 cycles of neoadjuvant methotrexate, vinblastine, doxorubicin and cisplatin in a pilot phase I and II study 63 per cent of 41 with pure transitional cell stage T2-4 lesions responded. While significant downstaging occurred by transurethral resection of the bladder in 70 per cent and by cytology in 60 per cent of the patients, the final T response rate by all noninvasive clinical staging procedures, including sonography and computerized tomography, revealed complete remission in 24 per cent and partial remission in 39 per cent. Of 30 patients who underwent pathological staging 33 per cent achieved stage P0 and 17 per cent stage Tis disease or P less than T. Despite extensive re-evaluation by transurethral resection of the bladder and other noninvasive staging procedures, a clinical staging error (T versus P) of 38 per cent was observed. Of the other 9 patients 4 with mixed nontransitional cell histological findings at presentation never achieved complete remission, although 3 had resolution of all transitional cell elements and 5 (10 per cent) were inevaluable. The toxicity of the regimen was generally acceptable but 6 per cent of the patients required hospitalization for neutropenic fever. While this active regimen can clinically (T) and pathologically (P) induce downstaging in a significant number of patients with primary bladder tumors, this pilot study has raised serious questions concerning the design of future nonrandomized and randomized neoadjuvant studies.

Adult↗

PubMedDate not supplied

[Primary adenocarcinoma of the bladder].

A clinicohistopathological study of 12 cases of primary adenocarcinoma of the bladder diagnosed over an 11 year period is presented. Six of these were pure adenocarcinomas, while the remainder consisted of 2 adenocarcinoma with transitional malignant elements, 2 adenosquamous carcinomas and 2 mesonephric adenocarcinomas. The biological behaviour of these neoplasms was particularly aggressive: in none of the cases was the neoplasm limited to the bladder epithelium, but was generally seen to have infiltrated the muscular wall. Leaving aside the specific treatment carried out, the prognosis was in all patients poor and a complete clinical recovery was achieved for just 2 subjects. Except for one case, death was always directly attributable to bladder cancer, but as a result of obstructive and inflammatory diseases relating to the size and the degree of local infiltration of the tumor rather than metastatic spread.

Adenocarcinoma↗

PubMed2006

In-vitro biological evaluation of some ONS and NS donor Schiff's bases and their metal complexes.

Complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) with the Schiff bases salicylidene-o-aminothiophenol (H2L) and thiophene-o-carboxaldeneaniline (SB) have been synthesized and characterized by elemental analyses, magnetic measurements, thermogravimetric analyses as well as infrared spectra and reflectance spectra. The nature of the bonding has been discussed on the basis of IR spectral data. Magnetic susceptibility measurements and electronic spectral data suggest a six-coordinated octahedral structure for these complexes. The complexes of Mn(II), Co(II), Ni(II), Cu(II) are paramagnetic, while Zn(II) and Cd(II) are diamagnetic in nature. The complexes were tested for their antimicrobial activities against Salmonella typhi, Escherichia coli and Serratia marcescens using the "Disc Diffusion Method". The results are compared with the standard drug (tetracycline) and show moderate activity.

Anti-Infective Agents↗

PubMed2002

Large-area synthesis of carbon nanofibres at room temperature.

Carbon nanotubes, first identified by Iijima, require for their production a source of elemental carbon and a transfer of energy that is specific to the type of source and the growth environment. Methods developed so far involve arc discharge, and vaporization using laser, pyrolysis and chemical vapour deposition of hydrocarbons. Here, we show growth of carbon nanofibres from radio-frequency plasma-enhanced chemical vapour deposition at room temperature, which was made possible by substituting the thermal energy requirements for the growth with plasma decomposition of methane on the Ni catalyst. Electron microscopy analysis provides evidence for a 'tip' growth model, with the Ni catalyst particle attached to the tip of the nanofibre. Energy-filtered imaging shows the Ni catalyst has a surface layer rich in carbon, consistent with the formation of a eutectic Ni-C droplet as a nucleation site for the carbon nanofibres, so that the carbon diffuses across the surface. The reduced distortion of the catalyst particles at low temperatures leads to a more uniform growth of the carbon nanofibres over large areas. The lower growth temperature allows for the removal of the silicon dioxide barrier layer associated with catalytic growth, and should allow in situ growth of nanofibres on relatively large areas of temperature-sensitive substrates, such as plastics, organics and even paper.

Diffusion↗

PubMed2005

Metal to insulator transitions in clusters.

The strict criterion for metallicity, a finite density of states (DOS) at the Fermi energy (E(F)), cannot be applied to clusters because energy levels are always discrete in a system of finite size. We propose an alternative definition whereby clusters can be considered metallic when the gap between occupied and unoccupied states at E(F) is consistently smaller than or equal to the Kubo band gap delta. We use the experimental findings of photoelectron spectroscopy of anionic clusters to analyze band gaps of various cluster families. Monovalent clusters (alkali and noble metals) grossly follow the shell structure pattern, producing band gaps smaller than delta for most cluster sizes, with some exceptional sizes exhibiting electronic shell closure or symmetry-induced band gaps. Among the bivalent metals, only mercury shows consistent band gap closure with increasing cluster size, that is a simple insulator-metal transition. Other bivalent elements such as Zn and Mg exhibit a much more complicated behavior. We also briefly discuss complex cluster families such as aluminum and transition metals.

Aluminum↗

PubMed2000

Visible-light detoxification and charge generation by transition metal chloride modified titania.

Amorphous microporous metal oxides of titanium (AMM-Ti) modified with chlorides of PtIV, IrIV, RhIII, AuIII, PdII, CoII, and NiII have been prepared by the sol-gel method and characterized by various surface analytical methods. These hybrid AMM-Ti powders are catalysts for the photodegradation of 4-chlorophenol (4-CP) in aqueous solution when illuminated with visible (lambda > or = 400 or 455 nm) or UV (lambda > or = 335 nm) light. The initial rate depends on the dopant level and is highest at 3.0% Pt in the case of PtIV/AMM-Ti. When employed in a photoelectrochemical cell, the activity spectrum of the photocurrent extends downward to about 600 nm, as does the photodegradation of 4-CP. It is suggested that the metal salt acts as a redox-active chromophore, transmitting the photogenerated charges to the amorphous matrix.

Catalysis↗

PubMed1979

Ultrastructure of a primary fibrosarcoma of the human thyroid gland.

A primary fibrosarcoma of the thyroid occurring in a patient with a nodular goiter is described. Light microscopy showed interwoven bundles of spindle cells admixed with plump ovoid cells, and foci of multinucleated giant cells. Remnants of distorted thyroid follicles were found only at the periphery of the tumor. "Transitional" epithelial elements were not discernible but the tumor resembled an anaplastic giant cell carcinoma. Multiple blocks studied by electron microscopy, however, revealed that the tumor cells, including the giant cells, have the ultrastructure features of a fibroblast.

Aged↗

PubMed2001

Studies on the mechanism of metal-catalyzed hydrogen transfer from alcohols to ketones.

The mechanism of metal-catalyzed hydrogen transfer from alcohols to ketones has been studied. Hydrogen transfer (H-transfer) from (S)-alpha-deutero-alpha-phenylethanol ((S)-1) to acetophenone was used as a probe to distinguish between selective carbon-to-carbon H-transfer and nonselective transfer involving both oxygen-to-carbon and carbon-to-carbon H-transfer. The progress of the reaction was monitored by the decreasing enantiomeric excess of (S)-1. After complete racemization, the alcohol was analyzed for its deuterium content in the alpha-position, which is a measure of the degree of selectivity in the H-transfer. A number of different rhodium, iridium, and ruthenium complexes (in total 21 complexes) were investigated by using this probe. For all rhodium complexes a high degree of retention of deuterium at alpha-carbon (95-98%) was observed. Also most iridium complexes showed a high degree of retention of deuterium. However, the results for the ruthenium complexes show that there are two types of catalysts: one that gives a high degree of deuterium retention at alpha-carbon and another that gives about half of the deuterium content at alpha-carbon (37-40%). Two different mechanisms are proposed for transition-metal-catalyzed hydrogen transfer, one via a monohydride (giving a high D content) and another via a dihydride (giving about half of D content). As comparison non-transition-metal-catalyzed hydrogen transfer was studied with the same probe. Aluminum- and samarium-catalyzed racemization of (S)-1 gave 75-80% retention of deuterium in the alpha-position of the alcohol, and involvement of an electron transfer pathway was suggested to account for the loss of deuterium.

Alcohols↗

PubMed2002

Control of polymer topology by chain-walking catalysts.

Chain-walking catalysts are demonstrated to control the branching topology of polyethylene by tuning the competition between monomer insertion and chain isomerization (walking). The topology of the polyethylene was controlled from linear with moderate branching to hyperbranched to dendritic. Although overall branching number and distribution of short chain branching are relatively constant, the topology of the polyethylene changes from linear polyethylene with moderate branches at high ethylene pressures to a dendritic polyethylene at low pressures. This provides a straightforward one-pot process for making polymers with a full range of tunable topologies.

Catalysis↗

PubMed2001

Imido Analogues of Common Oxo Anions: A New Episode in the Chemistry of Cluster Compounds.

Oxo anions of p- and d-block elements, for example, SiO(4)(4-), PO(4)(3-), SO(4)(2-), and CrO(4)(2-), are commonly encountered species. The full or partial replacement of the oxo ligands by isoelectronic imido (NR) groups generates homoleptic polyimido anions of the type [E(NR)(x)](z-) or heteroleptic imidooxo anions with the general formula [O(y)E(NR)(x-y)](z-) (where E=main group element or transition metal). The alkali metal derivatives of this new class of anions form ternary or quaternary cluster systems, respectively. The structures of these clusters can be rationalized in terms of the self-assembly of fundamental building blocks. An understanding of the factors that control this process may allow the design of functional materials with specific properties. In addition, these anions are attracting attention as multidentate ligands with unique electronic and stereochemical properties that may engender novel metal-centered chemistry.

Journal Article↗