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1.
Ann Surg Oncol ; 2022 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-35307803

RESUMO

BACKGROUND: Patients with T4 colon adenocarcinomas have an increased risk of peritoneal metastases (PM) but the histopathologic risk factors for its development are not well-described. OBJECTIVE: The purpose of this study was to determine factors associated with PM, time to recurrence, and survival after recurrence among patients with T4 colon cancer. PATIENTS AND METHODS: Patients with pathologic T4 colon cancer who underwent curative resection from 2005 to 2017 were identified from a prospectively maintained institutional database and classified by recurrence pattern: (a) none - 68.8%; (b) peritoneal only - 7.9%; (c) peritoneal and extraperitoneal - 9.9%; and (d) extraperitoneal only - 13.2%. Associations between PM development and patient, primary tumor, and treatment factors were assessed. RESULTS: Overall, 151 patients were analyzed, with a median follow-up of 66.2 months; 27 patients (18%) developed PM (Groups B and C) and 20 (13%) patients recurred at non-peritoneal sites only (Group D). Median time to developing metastases was shorter for Groups B and C compared with Group D (B and C: 13.7 months; D: 46.7 months; p = 0.022). Tumor deposits (TDs) and nodal stage were associated with PM (p < 0.05), and TDs (p = 0.048) and LVI (p = 0.015) were associated with additional extraperitoneal recurrence. Eleven (41%) patients with PM underwent salvage surgery, and median survival after recurrence was associated with the ability to undergo cytoreduction (risk ratio 0.20, confidence interval 0.06-0.70). CONCLUSION: PM risk after resection of T4 colon cancer is independently associated with factors related to lymphatic spread, such as N stage and TDs. Well-selected patients can undergo cytoreduction with long-term survival. These findings support frequent postoperative surveillance and aggressive early intervention, including cytoreduction.

2.
BMC Vet Res ; 15(1): 117, 2019 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-30992015

RESUMO

BACKGROUND: Porcine deltacoronavirus (PDCoV) is a novel coronavirus that can cause diarrhea in nursing piglets. This study was aimed to investigate the roles of host differentially expressed genes on metabolic pathways in PDCoV infections. RESULTS: Twenty thousand six hundred seventy-four differentially expressed mRNAs were identified in 5-day-old piglets responded to PDCoV experimental infections. Many of these genes were correlated to the basic metabolism, such as the peroxisome proliferator-activated receptor (PPAR) signaling pathway which plays a critical role in digestion. At the same time, in the PPAR pathway genes of fatty acid-binding protein (FABP) family members were observed with remarkably differential expressions. The differential expressed genes were associated with appetite decrease and weight loss of PDCoV- affected piglets. DISCUSSION: Fatty acid-binding protein 1 (FABP1) and fatty acid-binding protein 3 (FABP3) were found to be regulated by PDCoV. These two genes not only mediate fatty acid transportation to different cell organelles such as mitochondria, peroxisome, endoplasmic reticulum and nucleus, but also modulate fatty acid metabolism and storage as a signaling molecule outside the cell. Therefore, it can be preliminarily concluded that PPAR differential expression caused by PDCoV was mostly associated with weight loss and death from emaciation. CONCLUSIONS: The host differentially expressed genes were associated with infection response, metabolism signaling and organismal systems signaling pathways. The genes of FABP family members in the PPAR signaling pathway were the most highly altered and played important roles in metabolism. Alteration of these genes were most likely the reason of weight loss and other clinical symptoms. Our results provided new insights into the metabolic mechanisms and pathogenesis of PDCoV infection. METHODS: Animal experiment, Determination of viral growth by real-time RT-PCR, Histopathology, Immunohistochemical staining, Microarray analysis.


Assuntos
Animais Recém-Nascidos/virologia , Infecções por Coronavirus/veterinária , Coronavirus , Doenças dos Suínos/virologia , Animais , Animais Recém-Nascidos/metabolismo , Infecções por Coronavirus/metabolismo , Infecções por Coronavirus/virologia , Intestino Delgado/metabolismo , Intestino Delgado/patologia , Intestino Delgado/virologia , Jejuno/metabolismo , Jejuno/patologia , Jejuno/virologia , Redes e Vias Metabólicas/genética , Análise de Sequência com Séries de Oligonucleotídeos/veterinária , Reação em Cadeia da Polimerase em Tempo Real/veterinária , Suínos , Doenças dos Suínos/metabolismo , Transcriptoma
4.
Osteoporos Int ; 27(4): 1493-1505, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26556739

RESUMO

UNLABELLED: The inhibitory effects of glucocorticoids (GCs) on bone marrow stromal stem cell (BMSC) proliferation and osteoblastic differentiation are an important pathway through which GCs decrease bone formation. We found that microRNA-34a-5p was a critical player in dexamethasone (Dex)-inhibited BMSC proliferation and osteogenic differentiation. MicroRNA-34a-5p might be used as a therapeutic target for GC-impaired bone formation. INTRODUCTION: The inhibitory effects of glucocorticoids (GCs) on bone marrow stromal stem cell (BMSC) proliferation and osteoblastic differentiation are an important pathway through which GCs decrease bone formation. The mechanisms of this process are still not completely understood. Recent studies implicated an important role of microRNAs in GC-mediated responses in various cellular processes, including cell proliferation and differentiation. Therefore, we hypothesized that these regulatory molecules might be implicated in the process of GC-decreased BMSC proliferation and osteoblastic differentiation. METHODS: Western blot, quantitative real-time PCR, and cell proliferation and osteoblastic differentiation assays were employed to investigate the role of microRNAs in GC-inhibited BMSC proliferation and osteoblastic differentiation. RESULTS: We found that microRNA-34a-5p was reciprocally regulated by Dex during the process of BMSC proliferation and osteoblastic differentiation. Furthermore, we confirmed that microRNA-34a-5p was a critical player in Dex-inhibited BMSC proliferation and osteogenic differentiation. Mechanistic studies showed that Dex inhibited BMSC proliferation by microRNA-34a-5p targeting cell cycle factors, including CDK4, CDK6, and Cyclin D1. Furthermore, downregulation of microRNA-34a-5p by Dex leads to Notch signaling activation, resulting in inhibition of BMSC osteogenic differentiation. CONCLUSIONS: These results showed that microRNA-34a-5p, a crucial regulator for BMSC proliferation and osteogenic differentiation, might be used as a therapeutic target for GC-impaired bone formation.


Assuntos
Glucocorticoides/farmacologia , Células-Tronco Mesenquimais/efeitos dos fármacos , MicroRNAs/genética , Osteogênese/efeitos dos fármacos , Animais , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/genética , Proliferação de Células/efeitos dos fármacos , Proliferação de Células/genética , Células Cultivadas , Dexametasona/farmacologia , Relação Dose-Resposta a Droga , Regulação da Expressão Gênica/efeitos dos fármacos , Masculino , Células-Tronco Mesenquimais/citologia , Camundongos Endogâmicos C57BL , Terapia de Alvo Molecular/métodos , Osteoblastos/citologia , Osteoblastos/efeitos dos fármacos , Osteogênese/genética
6.
Zhonghua Liu Xing Bing Xue Za Zhi ; 42(5): 846-852, 2021 May 10.
Artigo em Zh | MEDLINE | ID: mdl-34814477

RESUMO

Objective: To investigate health status and calculate health life expectancy (HE) of residents in Shanghai, analyze health related factors and provided foundation of health policy. Methods: A multi-stage stratified random sampling was used to obtain self-reported health survey in Shanghai. WHO questionnaire was used to evaluate the health quality of life which was designed for the world health survey, Sullivan's method was used to calculate HE. Results: The self-assessment disability measure for adults over 18 years old in Shanghai was 0.25, higher for women (0.28) than for men (0.23). LE was 65.76 years for adults over 18 years old, higher for women (68.22) than for men (63.39). HE for adults over 18 years old was 47.99 years old, higher for men (49.05) than women (47.14). HE's proportion in LE gradually decreases with age. It accounts for 72.97% in the 18 years old and 39.00% in the 85 years old. Conclusions: The health of adult male in Shanghai is higher than that of female, and the proportion of HE loss of elderly is higher than young people. It is necessary to focus on the aging problem and strengthen the long-term care and health support system for the elderly. Improve the prevention and control of major diseases such as chronic diseases,which affect the quality of life expectancy seriously. Promotes the health level and quality of life in Shanghai.


Assuntos
Pessoas com Deficiência , Expectativa de Vida , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , China/epidemiologia , Feminino , Nível de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Qualidade de Vida
7.
Oncotarget ; 12(11): 1037-1045, 2021 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-34084278

RESUMO

BACKGROUND: The clinical utility of a blood-based biomarker in squamous cell carcinoma of the anus (SCCA) is unknown. We analyzed carcinoembryonic antigen (CEA), a commonly employed assay for patients with colorectal adenocarcinoma, as a serum biomarker for patients with biopsy-proven SCCA. MATERIALS AND METHODS: Medical records from 219 patients with biopsy-proven SCCA at the University of Texas MD Anderson Cancer Center were reviewed under an IRB-approved protocol from 2013 to 2020 to assess for correlations between CEA levels and corresponding clinical and pathologic characteristics. RESULTS: The mean CEA among subgroups by clinical status at the time of presentation to our institution was highest among those patients with metastatic SCCA to visceral organs (M-V, 20.7 ng/mL), however this finding was not statistically significant by ANOVA (p = .74). By clinical subgroup, the percentage of patients with an abnormally elevated CEA was highest in those patients with metastatic disease to lymph nodes (M-L, 41.2%) followed by recurrent/unresectable SCCA (36.8%), and metastatic SCCA to visceral organs (M-V, 35.2%), and was statistically significant between groups (Fisher's exact test p = .02). Using RECIST criteria for tumor progression and disease response, the mean change in CEA for patients with progression was an increase in 19 ng/mL, compared to a change of -7.3 ng/mL in those with disease response (p = .004). We likewise assessed whether CEA levels were associated with survival outcomes for all patients with metastatic SCCA, and found no correlation between CEA and likelihood for survival in a ROC analysis (multivariate, age-adjusted analysis for CEA cutoff of 8, HR = 1.01, 95% CI 0.52-1.96). CONCLUSIONS: Despite interesting patterns of abnormally high CEA in SCCA patients with advanced disease, and correlation of increased CEA with disease progression (and conversely decreased CEA with disease response), CEA is not associated with survival outcomes in SCCA, and is not a clinically relevant biomarker in this disease.

8.
Cancers (Basel) ; 12(7)2020 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-32640573

RESUMO

Standard treatment for locally advanced rectal cancer (LARC) is neoadjuvant chemoradiotherapy (NACRT), followed by surgical resection. However, >70% of patients do not achieve a complete pathological response and have higher rates of relapse and death. There are no validated pre- or on-treatment factors that predict response to NACRT besides tumour stage and size. We characterised the response of 33 LARC patients to NACRT, collected tumour samples from patients prior to, during and after NACRT, and performed whole exome, transcriptome and high-depth targeted sequencing. The pre-treatment LARC genome was not predictive of response to NACRT. However, in line with the increasing recognition of microbial influence in cancer, RNA analysis of pre-treatment tumours suggested a greater abundance of Fusobacteria in intermediate and poor responders. In addition, we investigated tumour heterogeneity and evolution in response to NACRT. While matched pre-treatment, on-treatment and post-treatment tumours revealed minimal genome evolution overall, we identified cases in which microsatellite instability developed or was selected for during NACRT. Recent research has suggested a role for adaptive mutability to targeted therapy in colorectal cancer cells. We provide preliminary evidence of selection for mismatch repair deficiency in response to NACRT. Furthermore, pre-NACRT genomic landscapes do not predict treatment response but pre-NACRT microbiome characteristics may be informative.

9.
Transbound Emerg Dis ; 66(5): 2180-2183, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31207129

RESUMO

A new highly virulent swine acute diarrhoea syndrome coronavirus (SADS-CoV) emerged in Guangdong province in 2017 followed by fatal diarrhoea that involved the death of 24,693 piglets. And yet from May 2017 to January 2019, there were no new SADS cases arising in pig herds in Guangdong. In this study, we reported the recent diarrhoea outbreak of SADS-CoV in Southern China on February 2019. Intestinal samples collected from diarrhoeal piglets were detected for common swine virus and confirmed that SADS-CoV was responsible for the diarrhoea case. Meanwhile, serological investigation of sows' sera implied that SADS-CoV has existed in the farm and PEDV antibody may not directly contribute to the amplification of SADS-CoV. Homology and phylogenetic analysis of the whole genome showed that the re-emerging SADS-CoV strain shared high sequence identities with existing SADS-CoV strains and all strains clustered together in Alpha coronavirus. All in all, the report herein emphasized the re-emerging of SADS-CoV and highlights continuous monitoring for this virus.


Assuntos
Alphacoronavirus/fisiologia , Infecções por Coronavirus/veterinária , Surtos de Doenças/veterinária , Doenças dos Suínos/epidemiologia , Alphacoronavirus/genética , Animais , China/epidemiologia , Infecções por Coronavirus/epidemiologia , Infecções por Coronavirus/virologia , Diarreia/epidemiologia , Diarreia/veterinária , Diarreia/virologia , Filogenia , Suínos , Doenças dos Suínos/virologia
10.
Vaccine ; 36(16): 2181-2192, 2018 04 12.
Artigo em Inglês | MEDLINE | ID: mdl-29544689

RESUMO

Human papilloma virus (HPV)-associated cancer is a significant global health burden and despite the presence of viral transforming antigens within neoplastic cells, therapeutic vaccinations are ineffective for advanced disease. HPV positive TC1 cells are susceptible to viral oncolysis by MG1-E6E7, a custom designed oncolytic Maraba virus. Epitope mapping of mice vaccinated with MG1-E6E7 enabled the rational design of synthetic long peptide (SLP) vaccines against HPV16 and HPV18 antigens. SLPs were able to induce specific CD8+ immune responses and the magnitude of these responses significantly increased when boosted by MG1-E6E7. Logically designed vaccination induced multi-functional CD8+ T cells and provided complete sterilising immunity of mice challenged with TC1 cells. In mice bearing large HPV-positive tumours, SLP vaccination combined with MG1-E6E7 was able to clear tumours in 60% of mice and these mice were completely protected against a long term aggressive re-challenge with the TC1 tumour model. Combining conventional SLPs with the multi-functional oncolytic MG1-E6E7 represents a promising approach against advanced HPV positive neoplasia.


Assuntos
Vacinas Anticâncer/imunologia , Imunoterapia , Neoplasias/etiologia , Neoplasias/terapia , Terapia Viral Oncolítica , Vírus Oncolíticos/genética , Infecções por Papillomavirus/complicações , Vacinas de Subunidades Antigênicas/imunologia , Sequência de Aminoácidos , Animais , Antígenos Virais/imunologia , Vacinas Anticâncer/administração & dosagem , Linhagem Celular , Terapia Combinada , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos , Mapeamento de Epitopos , Epitopos/imunologia , Feminino , Humanos , Imunização , Camundongos , Neoplasias/patologia , Terapia Viral Oncolítica/métodos , Papillomaviridae/imunologia , Infecções por Papillomavirus/imunologia , Infecções por Papillomavirus/virologia , Vacinas de Subunidades Antigênicas/administração & dosagem , Vacinas de Subunidades Antigênicas/química , Ensaios Antitumorais Modelo de Xenoenxerto
11.
J Inherit Metab Dis ; 30(2): 265, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17323145

RESUMO

Leigh syndrome is the most common mitochondrial disorder in children characterized by necrotic lesions in the central nervous system. Both mitochondrial DNA (mtDNA) and nuclear DNA defects in the mitochondrial respiratory chain can lead to this disease. To characterize the clinical and genetic traits of Leigh or Leigh-like syndrome patients in China, 124 unrelated cases were collected between 1992 and 2005. Seventy-seven cases (62.1%) met the typical criteria of Leigh syndrome, including symmetrical bilateral abnormal signals in the basal ganglia, thalamus and brain stem, etc. Other cases (37.9%) belonged to Leigh-like syndrome with atypical clinical or radiological manifestations. Late-onset patients accounted for 20.2%, which is more than previously reported. Movement disorder was the most common symptoms in our patients. Thirty-two patients (25.8%) were confirmed to carry mutant genes. Among them, six cases (4.8%) have been demonstrated to have point mutations in mitochondrial DNA. Two separate patients were detected to have mutations on A8344G and A3243G. The T8993G point mutation was identified in one patient and T8993C in one other patient. SURF1 mutations associated with cytochrome-c oxidase deficiency were identified in 25 patients (20.2%). Four unreported variations have been identified in SURF1 gene from three patients. G604C was found in 22 patients. Only one patient had C214T mutation in the pyruvate dehydrogenase E1alpha subunit gene. In the remaining 92 patients (74.2%), a specific molecular dysfunction or underlying metabolic abnormality could not be identified.


Assuntos
Povo Asiático , Doença de Leigh/complicações , Doença de Leigh/genética , Mutação , Adolescente , Idade de Início , Povo Asiático/genética , Encéfalo/diagnóstico por imagem , Encéfalo/patologia , Criança , Pré-Escolar , Deficiência de Citocromo-c Oxidase/genética , DNA Mitocondrial/genética , Feminino , Variação Genética , Humanos , Lactente , Recém-Nascido , Doença de Leigh/diagnóstico , Doença de Leigh/epidemiologia , Imageamento por Ressonância Magnética , Masculino , Proteínas de Membrana/genética , Proteínas Mitocondriais/genética , Transtornos dos Movimentos/etiologia , Mutação Puntual , Piruvato Desidrogenase (Lipoamida)/genética , Tomografia Computadorizada por Raios X
12.
Mol Cell Biol ; 16(1): 115-20, 1996 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-8524287

RESUMO

The RNA polymerase II of Saccharomyces cerevisiae exists in holoenzyme forms containing a complex, known as the mediator, associated with the carboxyl-terminal domain. The mediator includes several SRB proteins and is required for transcriptional activation. Previous work showed that a cyclin-dependent kinase-cyclin pair encoded by SSN3 and SSN8, two members of the SSN suppressor family, are identical to two SRB proteins in the mediator. Here we have identified the remaining SSN genes by cloning and genetic analysis. SSN2 and SSN5 are identical to SRB9 and SRB8, respectively, which encode additional components of the mediator. Genetic evidence implicates the SSN genes in transcriptional repression. Thus, these identities provide genetic insight into mediator and carboxyl-terminal domain function, strongly suggesting a role in mediating transcriptional repression as well as activation. We also show that SSN4 and SSN7 are the same as SIN4 and ROX3, respectively, raising the possibility that these genes also encode mediator proteins.


Assuntos
Proteínas Fúngicas/genética , Genes Fúngicos , RNA Polimerase II/metabolismo , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , Primers do DNA/genética , DNA Fúngico/genética , Proteínas Fúngicas/metabolismo , Complexo Mediador , Dados de Sequência Molecular , Mutação , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Supressão Genética , Transativadores/genética , Transativadores/metabolismo
13.
Chinese Pharmacological Bulletin ; (12): 1066-1071, 2022.
Artigo em Zh | WPRIM | ID: wpr-1014064

RESUMO

Aim To observe the proteetive effect of meseneephalie astrocyte-de rived neurotrophic faetor (MANF) on intestinal epithelial eells under endoplas- mic reticulum stress (EH stress).Methods Normal human intestinal epithelial cell line FHs74Int was stimulated with EH stress inducers, tunicmycin (TM) and TNF-cx, then the expression of endogenous MANF was observed.The recombinant plasmids MANF-GFP and GFP were transfected into FHs74Int cells individually, the transfection efficiency was observed by fluorescence j j microscopy, and the effect of MANF on EH stress was observed by Western blot.The effect of MANF on the proliferation of intestinal epithelial cells stimulated by TM was detected via CCK-8 assay.The effect of MANF on apoptosis after EH stress was detected by Western blot and flow cytometry.Results EH stress could induce the expression of endogenous MANE in intestinal epithelial cells.Overexpression of MANE significantly inhibited the expression of the EH stress-related proteins, Bip and CHOP, and promoted the proliferation of intestinal epithelial cells.At the same time, it could reduce the production of the proapoptotic proteins cleaved-c a spa se-3 and Bax, increase the expression of the antiapoptotic protein Bcl-2, and inhibit the proportion of early and late apoptosis of intestinal epithelial cells.Conclusions MANF plays a protective role in inhibiting EH stress in intestinal epithelial cells by promoting cell proliferation and reducing apoptosis.

14.
J Mol Biol ; 202(4): 865-84, 1988 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-3172241

RESUMO

We present a new method for predicting the secondary structure of globular proteins based on non-linear neural network models. Network models learn from existing protein structures how to predict the secondary structure of local sequences of amino acids. The average success rate of our method on a testing set of proteins non-homologous with the corresponding training set was 64.3% on three types of secondary structure (alpha-helix, beta-sheet, and coil), with correlation coefficients of C alpha = 0.41, C beta = 0.31 and Ccoil = 0.41. These quality indices are all higher than those of previous methods. The prediction accuracy for the first 25 residues of the N-terminal sequence was significantly better. We conclude from computational experiments on real and artificial structures that no method based solely on local information in the protein sequence is likely to produce significantly better results for non-homologous proteins. The performance of our method of homologous proteins is much better than for non-homologous proteins, but is not as good as simply assuming that homologous sequences have identical structures.


Assuntos
Simulação por Computador , Modelos Biológicos , Conformação Proteica , Sequência de Aminoácidos , Animais , Inteligência Artificial , Métodos
15.
Protein Sci ; 3(10): 1770-8, 1994 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-7849595

RESUMO

Huperzine A, a potential agent for therapy in Alzheimer's disease and for prophylaxis of organophosphate toxicity, has recently been characterized as a reversible inhibitor of cholinesterases. To examine the specificity of this novel compound in more detail, we have examined the interaction of the 2 stereoisomers of Huperzine A with cholinesterases and site-specific mutants that detail the involvement of specific amino acid residues. Inhibition of fetal bovine serum acetylcholinesterase by (-)-Huperzine A was 35-fold more potent than (+)-Huperzine A, with KI values of 6.2 nM and 210 nM, respectively. In addition, (-)-Huperzine A was 88-fold more potent in inhibiting Torpedo acetylcholinesterase than (+)-Huperzine A, with KI values of 0.25 microM and 22 microM, respectively. Far larger KI values that did not differ between the 2 stereoisomers were observed with horse and human serum butyrylcholinesterases. Mammalian acetylcholinesterase, Torpedo acetylcholinesterase, and mammalian butyrylcholinesterase can be distinguished by the amino acid Tyr, Phe, or Ala in the 330 position, respectively. Studies with mouse acetylcholinesterase mutants, Tyr 337 (330) Phe and Tyr 337 (330) Ala yielded a difference in reactivity that closely mimicked the native enzymes. In contrast, mutation of the conserved Glu 199 residue to Gln in Torpedo acetylcholinesterase produced only a 3-fold increase in KI value for the binding of Huperzine A.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Aminoácidos/análise , Inibidores da Colinesterase/metabolismo , Colinesterases/química , Colinesterases/metabolismo , Sesquiterpenos/metabolismo , Acetilcolinesterase/química , Acetilcolinesterase/metabolismo , Alcaloides , Aminoácidos/metabolismo , Animais , Sítios de Ligação , Butirilcolinesterase/química , Butirilcolinesterase/metabolismo , Inibidores da Colinesterase/farmacologia , Eletroquímica , Humanos , Ligação de Hidrogênio , Cinética , Camundongos , Modelos Moleculares , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Sesquiterpenos/química , Sesquiterpenos/farmacologia , Estereoisomerismo , Termodinâmica , Torpedo
16.
FEBS Lett ; 336(2): 263-6, 1993 Dec 27.
Artigo em Inglês | MEDLINE | ID: mdl-8262242

RESUMO

Molecular modeling (GEMM 7.3) and molecular mechanics calculations (YETI V 5.3) using the X-ray coordinates for acetylcholinesterase (AChE) from Torpedo californica indicate electrostatic stabilization by the active site, Glu-199, of the developing positive charge on the incipient carbonium ion in the dealkylation in the adducts of AChE with PSCR and PSCS diastereomers of 2-(3,3-dimethylbutyl) methylphosphonofluoridate (soman). His-440 is indispensable as a general acid catalyst of C-O bond breaking in the dealkylation reaction and that of bond breaking to the Ser gamma-O in reactivation. This demand for catalysis seems to be satisfied for the reactivation of enzyme from the PSCS diastereomer of soman, but not from the P(S)C(R) diastereomer.


Assuntos
Acetilcolinesterase/metabolismo , Inibidores da Colinesterase/farmacologia , Soman/farmacologia , Acetilcolinesterase/química , Sequência de Aminoácidos , Animais , Sítios de Ligação , Modelos Moleculares , Dados de Sequência Molecular , Conformação Proteica , Torpedo , Difração de Raios X
17.
FEBS Lett ; 349(1): 60-4, 1994 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-8045303

RESUMO

The channels connecting the active site of acetylcholinesterase (AChE) to the protein exterior were mapped by computational techniques in order to find potential exit routes for charged reaction products. 3.9% of the total volume of the AChE monomer is hollow space and over 50% of the void is located in the center; it is partitioned into three chambers, a deep entry channel, below it a wide channel located in a slightly positive region of AChE and ideally suitable for the exit of negatively charged fragments and a small chamber above Trp84 and Met83. The latter serve as gates for the departure of the positively charged choline product of the hydrolysis of acetylcholine into the small cavity. An efficient product clearance is a prerequisite to a very low energy pathway for the irreversible hydrolysis of acetylcholine.


Assuntos
Acetilcolinesterase/metabolismo , Acetatos/metabolismo , Acetilcolina/metabolismo , Animais , Sítios de Ligação , Transporte Biológico , Colina/metabolismo , Simulação por Computador , Hidrólise , Modelos Moleculares , Conformação Proteica , Torpedo
18.
Vision Res ; 40(21): 2999-3016, 2000.
Artigo em Inglês | MEDLINE | ID: mdl-11000397

RESUMO

Westheimer and Levi [(1987) Vision Research, 27, 1361-1368] found that when a few isolated features are viewed foveally, the perceived depth of a feature depends not only on its own disparity but also on those of its neighbors. The nature of this interaction is a function of the lateral separation between the features: When the distance is small the features appear to attract each other in depth but the interaction becomes repulsive at larger distances. Here we introduce a two-dimensional extension of our recent stereo model based on the physiological studies of Ohzawa, DeAngelis and Freeman [(1990) Science, 249, 1037-1041] and demonstrate through analyses and simulations that these observations can be naturally explained without introducing ad hoc assumptions about the connectivity between disparity-tuned units. In particular, our model can explain the distance-dependent attraction/repulsion phenomena in both the vertical-line configuration used by Westheimer [(1986) Journal for Neurophysiology, 370, 619-629], and the horizontal-line-and-point configuration used by Westheimer and Levi. Thus, the psychophysically observed disparity interaction may be viewed as a direct consequence of the known physiological organization of the binocular receptive fields. We also find that the transition distance at which the disparity interaction between features changes from attraction to repulsion is largely determined by the preferred spatial frequency and orientation distributions of the cells used in the disparity computation. This result may explain the observed variations of the transition distance among different subjects in the psychophysical experiments. Finally, our model can also reproduce the observed effect on the perceived disparity when the disparity magnitude of the neighboring features is changed.


Assuntos
Percepção de Distância/fisiologia , Ilusões Ópticas/fisiologia , Disparidade Visual/fisiologia , Simulação por Computador , Visão Binocular/fisiologia
19.
Vision Res ; 37(13): 1811-27, 1997 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-9274767

RESUMO

We previously proposed a physiologically realistic model for stereo vision based on the quantitative binocular receptive field profiles mapped by Freeman and coworkers. Here we present several new results about the model that shed light on the physiological processes involved in disparity computation. First, we show that our model can be extended to a much more general class of receptive field profiles than the commonly used Gabor functions. Second, we demonstrate that there is, however, an advantage of using the Gabor filters: similar to our perception, the stereo algorithm with the Gabor filters has a small bias towards zero disparity. Third, we prove that the complex cells as described by Freeman et al. compute disparity by effectively summing up two related cross products between the band-pass filtered left and right retinal image patches. This operation is related to cross-correlation but it overcomes some major problems with the standard correlator. Fourth, we demonstrate that as few as two complex cells at each spatial location are sufficient for a reasonable estimation of binocular disparity. Fifth, we find that our model can be significantly improved by considering the fact that complex cell receptive field are, on average, larger than those of simple cells. This fact is incorporated into the model by averaging over several quadrature pairs of simple cells with nearby and overlapping receptive fields to construct a model complex cell. The disparity tuning curve of the resulting complex cell is much more reliable than the constructed from a single quadrature pair of simple cells used previously, and the computed disparity maps for random dot stereograms with the new algorithm are very similar to human perception, with sharp transitions at disparity boundaries. Finally, we show that under most circumstances our algorithm works equally well with either of the two well-known receptive field models in the literature.


Assuntos
Percepção de Profundidade/fisiologia , Modelos Neurológicos , Disparidade Visual/fisiologia , Córtex Visual/fisiologia , Algoritmos , Sinais (Psicologia) , Humanos , Psicofísica
20.
Vision Res ; 39(13): 2205-11, 1999 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10343802

RESUMO

The motion of an object can be described by a single velocity vector, or equivalently, by direction and speed separately. Similarly, our ability to see subtle differences in the motion of two objects could be constrained by either a velocity-based sensory response, or separate sensory responses to direction and speed. To distinguish between these possibilities we investigated whether direction discrimination and speed discrimination were differentially affected by changes in the axis-of-motion. Psychophysical data from 12 naive observers indicated that direction discrimination depended on axis-of-motion, but speed discrimination did not. The difference suggests that a velocity-based sensory response is not the limiting factor on the two tasks. Instead, the results imply that the sensory response which constrains speed discrimination is at least partially independent from the sensory response which constrains direction discrimination.


Assuntos
Limiar Diferencial/fisiologia , Percepção de Movimento/fisiologia , Humanos , Psicofísica , Fatores de Tempo
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