RESUMO
L-N-Acetylhistidine crystallizes from aqueous solution as the monohydrate. The crystals are triclinic, space group P1, with two formula units per cell. The structural solution was accomplished by direct methods. The two independent molecules have very different conformations, one open and one closed. These two conformations are compared with those found in other histidine structures.
Assuntos
Cristalografia , Histidina , AcetatosRESUMO
This paper discusses an application of a random network with a variable number of links and traps to the elimination of drug molecules from the body by the liver. The nodes and links represent the transport vessels, and the traps represent liver cells with metabolic enzymes that eliminate drug molecules. By varying the number and configuration of links and nodes, different disease states of the liver related to vascular damage have been simulated, and the effects on the rate of elimination of a drug have been investigated. Results of numerical simulations show the prevalence of exponential decay curves with rates that depend on the concentration of links. In the case of fractal lattices at the percolation threshold, we find that the decay of the concentration is described by exponential functions for high trap concentrations but transitions to stretched exponential behavior at low trap concentrations.
Assuntos
Hepatócitos/fisiologia , Hepatopatias/metabolismo , Fígado/metabolismo , Modelos Biológicos , Preparações Farmacêuticas/metabolismo , Farmacocinética , Transdução de Sinais/fisiologia , Animais , Simulação por Computador , Humanos , Cinética , Taxa de Depuração Metabólica , Modelos EstatísticosRESUMO
We further investigate, both analytically and numerically, the properties of the fractal two-compartment model introduced by Fuite [J. Fuite, R. Marsh, and J. Tuszynski, Phys. Rev. E 66, 021904 (2002)]. Specifically, we look at the effects of the fractal exponent of the elimination rate coefficient on the long-time behavior of the pharmacokinetic clearance tail. For small exponent values, the tail exhibits exponential behavior, while for larger values, there is a transition to a power law. The theory is applied to seven data sets simulating drugs taken from the pharmacological literature.
Assuntos
Fractais , Modelos Biológicos , Farmacocinética , Simulação por Computador , Cinética , Taxa de Depuração Metabólica , Fatores de TempoRESUMO
BACKGROUND: Although morphologic, radiographic, and manometric features of achalasia have been well defined, it has not been established by careful retrospective analysis whether achalasia is a progressive disorder resulting in complete decompensation. STUDY DESIGN: To verify the hypothesis that achalasia is a progressive disease, we retrospectively investigated manometric, radiographic, and symptomatic data in patients with achalasia. Sixty-three patients (36 women and 27 men) with a median age of 44 years (range 11 to 79 years) were evaluated. The duration of symptoms ranged from 1 to 442 months, with a median of 48 months. Patients were divided into four groups according to the duration of symptoms: 36 patients with less than 5 years, 11 with 5 to 10 years, 9 with 10 to 15 years, and 7 with 15 years or more. RESULTS: Contraction pressures of the esophageal body decreased significantly at every level when the duration of symptoms increased (p < 0.04). The percentage of simultaneous waves in the esophageal body rose as the duration of symptoms increased. All waves were synchronous in every patient who had had symptoms for more than 15 years. The maximal width of the esophageal body measured on esophagram became greater with an increase in the duration of symptoms, but this measurement did not reach statistical significance (p = 0.063). The tortuosity of the esophagus, measured by the maximal angle of the esophageal axis, was significantly greater in patients with a longer duration of symptoms (p < 0.02). The type of symptoms was not associated with the duration of symptoms. CONCLUSIONS: Achalasia is a progressive disease, as verified by manometric and radiographic findings. The classification of esophageal motor function expressed by amplitude of contraction pressure and angle of tortuosity is objective and useful. Classification of achalasia by duration of symptoms may be important in treatment selection and effectiveness.
Assuntos
Acalasia Esofágica/diagnóstico , Manometria , Radiografia , Adolescente , Adulto , Idoso , Sulfato de Bário , Criança , Meios de Contraste , Transtornos de Deglutição/etiologia , Acalasia Esofágica/fisiopatologia , Acalasia Esofágica/cirurgia , Esôfago/fisiopatologia , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Resultado do TratamentoRESUMO
Technical controversies abound regarding the surgical treatment of achalasia. To determine the value of a concomitant antireflux procedure, the best antireflux procedure, the correct length for gastric myotomy, the optimal surgical approach (thoracic or abdominal), and the equivalency of minimally invasive surgery, a literature review was carried out. The review is based on 23 articles on open transabdominal or transthoracic myotomy, 14 articles on laparoscopic myotomy, and four articles on thoracoscopic myotomy. Postoperative results of traditional open thoracic or transabdominal myotomy as determined by symptomatology were better with fundoplication than without fundoplication. The incidence of postoperative reflux as proved by pH monitoring was high in patients who had an open transabdominal myotomy without fundoplication. The type of antireflux procedure used and the length of gastric myotomy had little effect on results. The results of transthoracic Heller myotomy do not require a concomitant fundoplication. Laparoscopic and thoracoscopic myotomy had excellent results at short-term follow-up. A fundoplication must be added if the myotomy is performed transabdominally. A randomized prospective study is required to determine the best fundoplication and the extent of gastric myotomy. Although minimally invasive surgery for achalasia has excellent initial results, longer follow-up in a larger population of patients is needed.
Assuntos
Acalasia Esofágica/cirurgia , Procedimentos Cirúrgicos do Sistema Digestório/métodos , Humanos , Procedimentos Cirúrgicos Minimamente Invasivos/métodosRESUMO
The purpose of this study was to measure the length of the esophagus and assess its relationship to sex, weight, age, height, and various esophageal disorders. A retrospective analysis was undertaken of 617 esophageal manometric studies, which included 51 normal control subjects (27 males and 24 females) and 566 patients (297 males and 269 females) with esophageal disorders (50 with achalasia, 6 with diffuse esophageal spasm, 64 with strictures, 38 with nutcracker esophagus, 398 with gastroesophageal reflux disease [GERD] with positive 24-hour pH monitoring, and 66 with possible GERD but negative 24-hour pH monitoring). Manometry was performed in all of them by the station pull-through technique. The length of the esophagus was defined as the distance between the proximal end of the upper esophageal sphincter and the distal end of the lower esophageal sphincter. In the control group the mean (+/- standard deviation) length of the esophagus was 28.3 +/- 2.41 cm. In patients with esophageal disorders the mean length of the esophagus was 28.0 +/- 2.87 cm. Length of the esophagus is related to height but not to weight, sex, age, diffuse esophageal spasm, or nutcracker esophagus. Achalasia is associated with a longer esophagus, and GERD is associated with a shorter esophagus. Stricture is associated with a shorter esophagus, but this is in part due to the association between stricture and GERD. Patients with possible GERD but negative 24-hour pH monitoring have an esophageal length similar to that of GERD patients with positive 24-hour pH monitoring. Patients with GERD and stricture formation showed esophageal shortening in shorter patients. Achalasia, GERD, and GERD with stricture formation influence esophageal length. GERD-related strictures shorten the esophagus more significantly in short patients.
Assuntos
Doenças do Esôfago/fisiopatologia , Esôfago/patologia , Adulto , Feminino , Humanos , Masculino , Manometria , Pessoa de Meia-Idade , Estudos RetrospectivosRESUMO
BACKGROUND: Laparoscopic vagotomy represents a new and less invasive treatment for peptic ulcer disease, but the problem of postvagotomy dysphagia has not been solved. The aim of this study was to determine the etiologic factors related to long-term laparoscopic postvagotomy dysphagia. METHODS: Two female and 11 male patients with a mean age of 48.5 years who underwent laparoscopic vagotomy were investigated retrospectively. Preoperative diagnosis included duodenal ulcer resistant to medical treatment, gastric hypersecretion, gastric outlet obstruction, cholelithiasis, and gastroesophageal reflux disease (GERD). Ten patients underwent laparoscopic highly selective vagotomy, and three patients had laparoscopic truncal vagotomy with gastrojejunostomy or pyloroplasty. Nine of these patients had a Nissen fundoplication in conjunction with the vagotomy. RESULTS: The median long-term follow-up period was 47 months. Two patients complained of severe dysphagia, one of moderate dysphagia, and two of mild dysphagia. Neither type of vagotomy nor an additional fundoplication was correlated with the severity of postoperative long-term dysphagia. Severity of postoperative dysphagia was associated with severity of preoperative dysphagia (r = 0.752, p = 0.003) but not with heartburn (r = 0.358, p = 0.531) or regurgitation (r = 0.024, p = 0.938). The cause of preoperative dysphagia varied; however, all of these patients had GERD and consequent esophageal lesions. CONCLUSION: Preexisting dysphagia appears to play an integral role in persistent postoperative dysphagia. Care must be taken to construct a loose fundoplication in patients with dysphagia.
Assuntos
Transtornos de Deglutição/etiologia , Laparoscopia/efeitos adversos , Vagotomia/efeitos adversos , Colelitíase/cirurgia , Transtornos de Deglutição/diagnóstico , Diagnóstico Diferencial , Úlcera Duodenal/cirurgia , Feminino , Obstrução da Saída Gástrica/cirurgia , Refluxo Gastroesofágico/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Índice de Gravidade de Doença , Inquéritos e QuestionáriosRESUMO
AIM: To determine the usefulness of endoscopically-delivered small intestinal submucosa (SIS) as a scaffold in enhancing the lower oesophageal sphincter (LOS) pressures. METHODS: Six dogs were endoscopically injected--four with the SIS and two with its glycerin carrier. Manometry was performed prior to injection and every four weeks post-op. RESULTS: Adequate and site correct injections were made in four dogs. In one dog, significant augmentation of pressures were obtained at four weeks. None had significant changes in pressure at eight weeks, differences in length at either four or eight weeks or significant differences in the thickness of the examined layers. Four of the six had capillary cushions on pathological examination. The dog injected with the carrier had a loose and disorganise collection, while the others were well organised. CONCLUSION: SIS is a biologically compatible material. Lack of an animal model for gastro-oesophageal reflux disease (GORD) makes determining the ability of injections of SIS to combat reflux problematic.
Assuntos
Junção Esofagogástrica/cirurgia , Refluxo Gastroesofágico/terapia , Mucosa Intestinal/transplante , Animais , Cães , Endoscopia , ManometriaRESUMO
The Social Security Administration is responsible for administering assistance programs not only to needy citizens but also to lawfully admitted aliens who require such aid. It therefore is interested in the economic situation of all the Nation's inhabitants, including refugees. This article examines the status of one such group--the Indochinese refugees who came to this country following the fall of the South Vietnamese government in 1975. A series of sample surveys, commissioned by the Department of Health, Education, and Welfare, reveals that most members of the original group of 130,000 Indochinese had achieved a large measure of economic self-sufficiency by the end of 1978. In the fall of that year, however, a new wave of Indochinese refugees began emigrating to the United States. The latecomers--who now outnumber the original group--are generally poorer, less well educated, and less acclimated to urban living than were their predecessors. Such characteristics suggest higher future resettlement costs, which could well be exacerbated by the propensity of ethnic groups to cluster in a few areas.
Assuntos
Asiático , Refugiados , Previdência Social , Adolescente , Adulto , Fatores Etários , Idoso , Camboja/etnologia , Criança , Emprego/tendências , Características da Família , Feminino , Humanos , Renda , Laos/etnologia , Masculino , Pessoa de Meia-Idade , Fatores Socioeconômicos , Estados Unidos , Vietnã/etnologiaRESUMO
The Social Security Administration (SSA) recently released two publications dealing with the economic situation of persons aged 55 and older in 1978. These reports--Income & Resources of the Aged, 1978 (a chartbook containing 17 charts and brief explanatory paragraphs) and Income of the Population 55 and Over, 1978 (a staff paper containing 43 tables and supporting text)--are the most recent in a series of analyses of the aged population begun by SSA 40 years ago. By means of selected findings, tabulations, tables, and charts, this article presents a sampling of the information available in the two publications. The reports reveal that the aged as a group are no longer disproportionately poor compared with the adult population as a whole, and that the 1978 income of most elderly units had kept pace with inflation since 1976, the next most recent survey year.
Assuntos
Idoso , Renda , Fatores Etários , Demografia , Feminino , Humanos , Masculino , Casamento , Pessoa de Meia-Idade , Pobreza , Previdência Social , Estados UnidosRESUMO
In March 1979, 10.4 million persons were receiving Aid to Families With Dependent Children (AFDC). Nearly 70 percent of these recipients were children and most of the remainder were mothers. At that time, most AFDC families had only one or two children, were headed by women, and lived in a metropolitan area. Comparison with earlier surveys reveals that the number of children and other recipients per household has been declining in recent years, that the proportion of blacks on the rolls has diminished slightly, and that AFDC parents are younger and better educated than they used to be.
Assuntos
Ajuda a Famílias com Filhos Dependentes , Adolescente , Adulto , Fatores Etários , Criança , Pré-Escolar , Escolaridade , Emprego , Feminino , Humanos , Renda , Masculino , Pais , Fatores Sexuais , Estados UnidosAssuntos
Aminoácidos , Peptídeos , Arginina , Computadores , Cristalografia , Histidina , Pirrolidinas , Triptofano , Difração de Raios XRESUMO
Pharmacokinetic models play a crucial role in analyzing and assessing the results of in vitro and in vivo studies. In this review, comparative analysis of pharmacokinetic models under homogeneous and heterogeneous conditions is performed, placing special focus on the role of fractal theory. The concept of fractals provides a new perspective from which processes occurring in heterogeneous, confined, or poorly mixed environments can be modeled. Following a brief theoretical overview, the applicability of fractals in characterizing anatomical structures and physiological processes as well as the transport and reaction of drugs within the body is discussed. There is significant evidence that drug absorption, distribution, metabolism, and excretion are often anomalous, that is to say their behavior deviates from classical theory, and possible reasons and appropriate models are considered.
Assuntos
Química Farmacêutica/métodos , Avaliação Pré-Clínica de Medicamentos , Fractais , Farmacocinética , Tecnologia Farmacêutica/métodos , Animais , Difusão , Dimerização , Desenho de Fármacos , Humanos , Cinética , Modelos Biológicos , Modelos Químicos , Modelos Estatísticos , Modelos TeóricosRESUMO
The structure of this compound, originally described in space group C2/c [Averbuch-Pouchot & Durif (1987). Acta Cryst. C43, 1653-1655] is properly described as rhombohedral, space group R3c, with a = 12.355 (4) A, a = 51.01 (2) degrees, Z = 2. (Hexagonal cell: a = 10.640 (4), c = 32.16 (2) A, Z = 6). Revised coordinates are given.
Assuntos
Telúrio , Cristalografia , Estrutura Molecular , Fosfatos , Potássio , SódioRESUMO
The structure of this compound [Olszak, Stepien, Wajsman, Grabowski, Glinka & Lecocq (1987). Acta Cryst. C43, 2169-2171], which contains a 13-membered heterocyclic ring, was described as triclinic, space group P1, with a = 12.756 (3), b = 9.950 (3), c = 13.566 (3) A, alpha = 90.49 (1), beta = 118.04 (1), gamma = 90.04 (1) degrees, Z = 2. It should be described as monoclinic, space group C2/c, with a' = 23.947 (6), b' = 12.756 (3), c' = 9.950 (3) A, beta' = 90.57 (3) degrees, Z = 4. The C2/c coordinates are given. The molecule lies on an exact, rather than an approximate, twofold axis.
Assuntos
Compostos Heterocíclicos , Cristalografia/métodos , Conformação MolecularRESUMO
Revised structures are reported for 19 crystalline compounds, based on space groups of higher symmetry than originally reported. In four cases the Laue symmetry is changed, one from 1 to 2/m and three from 2/m to mmm; in the remaining fifteen a center of symmetry has been added. For eight of these latter compounds we have obtained F values and carried out least-squares refinements in the centrosymmetric space groups, with more satisfactory results than originally reported.
Assuntos
Cristalografia , Guanidinas , Compostos OrganometálicosRESUMO
The space group for the entry under the reference codes FEBMUU and FEBMUU01 in the Cambridge Structural Database (1992) should be further corrected to space group C2/c rather than P1 (FEBMUU) or C2 (FEBMUU01).
RESUMO
From a search of the October 2000 release of the Cambridge Structural Database we find coordinate data for approximately 1500 entries under space group No. 5: C2 or, occasionally, A2, I2 or B112. Software designed to detect cases of missed higher symmetry identified 144 entries for detailed inspection. Of these, 50 should, we believe, be revised to space groups of higher symmetry. The most common revision is to space group C2/m, which entails adding a center of inversion and usually results in important changes in bond lengths and angles.