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1.
Int J Legal Med ; 133(6): 1949-1955, 2019 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-31410546

RESUMEN

The main criterion of dental age assessment in living adolescents and young adults is the evaluation of third molars' mineralization. Concerning forensic age assessment after the completion of third molars' mineralization, apposition of secondary dentine and narrowing of the periodontal membrane as seen as decreasing radiolucent areas in the radiographs for mandibular third molars have already been described as regressive features. The present study examines the combination of both these features for the purpose of age assessment in regression analyses after rescaling the data to make it on the interval scale. To this end, a total of 1245 orthopantomograms was evaluated, taken from 606 females and 639 males in the age group of 15-40 years. The apposition of secondary dentine and narrowing of the periodontal membrane as seen as decreasing radiolucent areas in the radiographs were determined for the lower third molars. The correlation of the features with the chronological age was assessed by means of rescaled regression analyses. Furthermore, regression formulas for age assessment were established. The values of the standard error of estimate ranged between 3.55 and 4.52 years. In general, the rescaled regression of the examined features appears to be suited for forensic age assessment. A limitation of the present study is the comparatively low number of evaluable teeth in the examined age group. Due to an incomplete development or a lack of the mandibular third molars, only a mere half of the respective teeth could be included in the statistical analysis.


Asunto(s)
Determinación de la Edad por los Dientes/métodos , Tercer Molar/diagnóstico por imagen , Tercer Molar/crecimiento & desarrollo , Análisis de Regresión , Adolescente , Adulto , Dentina Secundaria/diagnóstico por imagen , Femenino , Humanos , Masculino , Ligamento Periodontal/diagnóstico por imagen , Ligamento Periodontal/crecimiento & desarrollo , Radiografía Panorámica , Estudios Retrospectivos , Calcificación de Dientes , Raíz del Diente/diagnóstico por imagen , Raíz del Diente/crecimiento & desarrollo , Adulto Joven
2.
Eur J Vasc Endovasc Surg ; 56(6): 874-879, 2018 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-30172665

RESUMEN

OBJECTIVE: Iliac vein compression syndrome can cause severe leg symptoms. In clinical practice, it remains a challenge to differentiate which compression is clinically relevant. The aim of the current study was to assess the general treatment indications and the prevalence of angiographic signs of iliac vein compression in a group of healthy participants. METHODS: This was a prospective cohort study. A total of 20 healthy volunteers (median age 21, range 20-22 years) were recruited through advertisement and underwent angiography of the iliac veins. When no compression signs were present, a balloon occlusion was performed. Additionally, a 10 item survey regarding indications for venous stenting was developed and sent to 30 vascular specialists treating patients with deep venous obstruction. RESULTS: In 16 (80%) participants, at least two signs indicative of May-Thurner compression were seen. In three (15%) subjects, narrowing of the common iliac vein without collaterals was shown and one (5%) did not show any signs of obstruction. In 23 (70%) of the survey responders, collaterals were found to be the most typical sign indicative of significant venous obstruction. An angiographic sign of >50% compression was found to be an indication to stent in 55% of responders. CONCLUSION: This study demonstrates a remarkably high percentage of generally accepted signs of significant iliac vein obstruction (May-Thurner compression) on venography in healthy young subjects. Diagnosis of true iliac vein obstruction remains a major challenge, which mostly leans on improvement of clinical symptoms rather than imaging findings. Treating the patient rather than the image seems to be a valid principle all the more.


Asunto(s)
Síndrome de May-Thurner/diagnóstico por imagen , Flebografía/métodos , Circulación Colateral , Femenino , Humanos , Vena Ilíaca , Masculino , Síndrome de May-Thurner/fisiopatología , Estudios Prospectivos , Adulto Joven
3.
Int J Legal Med ; 131(2): 579-584, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-27924404

RESUMEN

To improve the accuracy of forensic age estimation where there is no legal basis for carrying out x-ray examinations, it would be useful to establish non-x-ray imaging techniques. The objective of this study was to provide reference data for the magnetic resonance imaging-based evaluation of the ossification stage of the distal radius. Furthermore, we tested a new criterion of the maturity of the distal radial epiphysis for determining whether an individual has completed the age of 18. We investigated 668 MRI scans of the distal radial epiphysis from 333 female and 335 male subjects ranging in age from 12 to 24. To determine the ossification stage, we used the clavicular ossification staging systems described by Schmeling et al. and Kellinghaus et al. Ossification stage IV as described by Schmeling et al. was divided into two sub-stages, IVa and IVb, depending on whether or not it was possible to identify a triple-banded meta-epiphyseal zone of calcification. All study subjects were able to be assigned to an ossification stage without ambiguity. We present statistics relating to the distribution of ossification stages divided by sex. The age of the youngest female subject assessed as ossification stage IVb was 16.8, the age of the youngest male subject 18.6. The youngest age at which female subjects were assessed as ossification stage V was 22.3; for male subjects it was 23.1. Further independent studies should be carried out to determine whether ossification stage IVb can indeed be used to reliably determine whether a male subject has completed the age of 18.


Asunto(s)
Determinación de la Edad por el Esqueleto/métodos , Epífisis/crecimiento & desarrollo , Osteogénesis , Radio (Anatomía)/crecimiento & desarrollo , Adolescente , Niño , Epífisis/diagnóstico por imagen , Femenino , Antropología Forense , Humanos , Imagen por Resonancia Magnética , Masculino , Radio (Anatomía)/diagnóstico por imagen , Adulto Joven
4.
Int J Legal Med ; 131(2): 569-577, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-27909868

RESUMEN

There is a need for dental age estimation methods after completion of the third molar mineralization. Degenerative dental characteristics appear to be suitable for forensic age diagnostics beyond the 18th year of life. In 2012, Olze et al. investigated the criteria studied by Gustafson using orthopantomograms. The objective of this study was to prove the applicability and reliability of this method with a large cohort and a wide age range, including older individuals. For this purpose, 2346 orthopantomograms of 1167 female and 1179 male Germans aged 15 to 70 years were reviewed. The characteristics of secondary dentin formation, cementum apposition, periodontal recession and attrition were evaluated in all the mandibular premolars. The correlation of the individual characteristics with the chronological age was examined by means of a stepwise multiple regression analysis, in which the chronological age formed the dependent variable. Following those results, R 2 values amounted to 0.73 to 0.8; the standard error of estimate was 6.8 to 8.2 years. Fundamentally, the recommendation for conducting age estimations in the living by these methods can be shared. The values for the quality of the regression are, however, not precise enough for a reliable age estimation around regular retirement date ages. More precise regression formulae for the age group of 15 to 40 years of life are separately presented in this study. Further research should investigate the influence of ethnicity, dietary habits and modern health care on the degenerative characteristics in question.


Asunto(s)
Determinación de la Edad por los Dientes/métodos , Tercer Molar/crecimiento & desarrollo , Calcificación de Dientes , Adolescente , Adulto , Anciano , Cementogénesis , Cemento Dental/diagnóstico por imagen , Dentina Secundaria/diagnóstico por imagen , Dentina Secundaria/crecimiento & desarrollo , Femenino , Recesión Gingival/diagnóstico por imagen , Humanos , Masculino , Persona de Mediana Edad , Tercer Molar/diagnóstico por imagen , Radiografía Panorámica , Análisis de Regresión , Atrición Dental/diagnóstico por imagen , Adulto Joven
5.
Ann Vasc Surg ; 45: 269.e5-269.e9, 2017 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-28739465

RESUMEN

Caval aneurysms are very rare but potentially lethal. Discussion about the need for treatment rises on individual basis. Based on the underlying etiology, a well-considered treatment plan should be made. Possible complications for invasive treatment and conservative management should be carefully weighed against each other. We present a patient with a caval aneurysm due to an arteriovenous fistula which we treated with endovascular embolization. Six months after treatment the patient is asymptomatic and the aneurysm size is decreased.


Asunto(s)
Aneurisma/terapia , Fístula Arteriovenosa/complicaciones , Embolización Terapéutica/métodos , Procedimientos Endovasculares/métodos , Arteria Renal/anomalías , Vena Cava Inferior/anomalías , Aneurisma/diagnóstico por imagen , Aneurisma/etiología , Fístula Arteriovenosa/diagnóstico por imagen , Angiografía por Tomografía Computarizada , Femenino , Humanos , Angiografía por Resonancia Magnética , Persona de Mediana Edad , Flebografía/métodos , Arteria Renal/diagnóstico por imagen , Resultado del Tratamiento , Ultrasonografía Doppler Dúplex , Vena Cava Inferior/diagnóstico por imagen
6.
Sci Justice ; 57(4): 257-261, 2017 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-28606331

RESUMEN

Eruption and mineralization of third molars are the main criteria for dental age estimation in living adolescents. As the validation of completion of the 18th year of life appears not to be possible with the forensically necessary probability even if all the third molars of a person are completely mineralized, degenerative dental characteristics might be used for this purpose. In previous publications by Olze et al. (2010a,b) the radiographic visibility of the periodontal ligament and the root pulp in lower third molars were suggested as methods for this purpose. The aim of this study was to validate these characteristics in a large study population with a wide age range. In a material of 2346 orthopantomograms of 1167 female and 1179 male Germans aged from 15 to 70years the radiographic visibility of the root pulp in the lower third molars with completed mineralization were studied according to stage classifications proposed by Olze et al. (2010a,b). 1541 orthopantomograms of 705 females and 836 males with a sufficient quality of the radiograph showed at least one third molar. The suitability of the studied characteristics for age estimation in living individuals could be confirmed. Males and females presenting stage 1 of both characteristics were older than 18years of life. Males and females presenting stage 2 of both characteristics were older than 21years of life. The high number of missing third molars in the studied age group (46-60%) must be considered as a limitation of the methods. In further studies the influence of ethnicity, dietary habits and modern dental health care on the characteristics in question should be investigated.


Asunto(s)
Determinación de la Edad por los Dientes/métodos , Pulpa Dental/diagnóstico por imagen , Tercer Molar/diagnóstico por imagen , Ligamento Periodontal/diagnóstico por imagen , Raíz del Diente/diagnóstico por imagen , Adolescente , Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Radiografía Panorámica , Adulto Joven
7.
Sci Justice ; 55(2): 139-44, 2015 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-25754000

RESUMEN

Alongside a variety of clinical and forensic issues, age determination in living persons also plays a decisive role in the field of professional sport. Only methods of determining skeletal age which do not expose individuals to ionizing radiation are suitable for this purpose. The present study examines whether MRI diagnosis of the distal radial epiphysis can be utilised to monitor internationally relevant age limits in professional football. The wrist area of 152 male footballers aged 18 to 22 years belonging to regional clubs was prospectively examined using MRI. The ossification stage of the distal radial epiphysis was subsequently determined on the basis of established criteria used in determining the maturity of the medial clavicular epiphysis. For the first time, we ascertained evidence of an increase in the prevalence of the phenomenon of threefold linear stratification (hypointense line, hyperintense line, and hypointense line) in the representation of the fused epiphyseal plate of the radius using magnetic resonance imaging with increasing chronological age. Within our study population, test persons with an ossified epiphyseal plate without any verifiable epiphyseal scar were not represented. The presumably high minimum age of entry into this final stage of development (>22 years) must be verified in the course of further studies. According to the results of the present study, the fused epiphyseal plate of the distal radius provides potential maturation criteria which appear suitable for reliable monitoring of all relevant age limits in international football with the aid of magnetic resonance imaging.


Asunto(s)
Determinación de la Edad por el Esqueleto/métodos , Imagen por Resonancia Magnética , Osteogénesis , Radio (Anatomía)/anatomía & histología , Adolescente , Adulto , Epífisis/anatomía & histología , Antropología Forense , Humanos , Masculino , Estudios Prospectivos , Fútbol , Adulto Joven
9.
J Vasc Surg Venous Lymphat Disord ; 8(1): 89-94, 2020 01.
Artículo en Inglés | MEDLINE | ID: mdl-31653533

RESUMEN

OBJECTIVE: Surgical desobliteration or endophlebectomy of the common femoral vein during deep venous recanalization with complementary polytetrafluoroethylene (PTFE) arteriovenous fistula (AVF), may lead to higher rates of surgical site infection (SSI). It has been reported that closed incisional negative pressure wound therapy (cINPT) may decrease SSI rates after different surgical procedures. The aim of this study was to determine the potential effect of cINPT on the SSI rate of femoral endophlebectomy with a complimentary PTFE AVF. METHODS: Patients with recanalization of the femoral-iliac veins and femoral endophlebectomy with a complementary PTFE AVF and postoperative cINPT were identified. SSI, patency, and complication rates were analyzed. RESULTS: This study included 65 patients with a mean age of 41 ± 14 years. The mean procedure time was 240 ± 11.9 minutes. Primary patency rate was 69.2% and secondary patency rate was 78.4%. SSI classified as Szilagyi I, II, and III occurred in 7.6% (n = 5), 3% (n = 2), and 7.6% (n = 5), respectively, with an overall SSI rate of 18.2%. Surgical wound revision with the application of a vacuum pump was required in 10.7% (n = 7). A multivariate analysis showed that the duration of the surgical procedure (P = .003) as well as lymphatic fistulas (P = .044) to have a significant impact on the SSI rate. CONCLUSIONS: Endophlebectomy with complementary PTFE AVF of the femoral vein is related to an increased rate of lymphatic leakage and SSI. Lymphatic fistula and the duration of surgery could be assessed as relevant influencing factors of SSI. Application of cINPT in this surgical setting may reduce the SSI rate. Despite this potential improvement, SSI rates still limit the clinical success of a deep venous recanalization.


Asunto(s)
Derivación Arteriovenosa Quirúrgica/instrumentación , Implantación de Prótesis Vascular/instrumentación , Prótesis Vascular , Vena Femoral/cirugía , Terapia de Presión Negativa para Heridas , Politetrafluoroetileno , Infección de la Herida Quirúrgica/prevención & control , Adulto , Derivación Arteriovenosa Quirúrgica/efectos adversos , Implantación de Prótesis Vascular/efectos adversos , Femenino , Vena Femoral/diagnóstico por imagen , Vena Femoral/fisiopatología , Alemania , Humanos , Masculino , Persona de Mediana Edad , Terapia de Presión Negativa para Heridas/efectos adversos , Diseño de Prótesis , Factores Protectores , Estudios Retrospectivos , Medición de Riesgo , Factores de Riesgo , Infección de la Herida Quirúrgica/diagnóstico , Infección de la Herida Quirúrgica/microbiología , Factores de Tiempo , Resultado del Tratamiento , Grado de Desobstrucción Vascular
10.
Ned Tijdschr Geneeskd ; 1632019 07 05.
Artículo en Holandés | MEDLINE | ID: mdl-31283116

RESUMEN

A 46-year-old woman presents to her general practitioner with a painless swelling of her right index finger, which developed spontaneously one year ago and is slowly growing since. Histopathological investigation shows a superficial acralfibromyxoma: a rare benign soft tissue tumour that occurs mostly on the digits and predominantly in men at a mean age at diagnosis of 48 years. Complete excision is important to prevent local recurrence.


Asunto(s)
Angiofibroma/diagnóstico , Angiofibroma/cirugía , Dedos/patología , Neoplasias de los Tejidos Blandos/diagnóstico , Neoplasias de los Tejidos Blandos/cirugía , Femenino , Humanos , Persona de Mediana Edad , Recurrencia Local de Neoplasia/prevención & control
11.
J Vasc Surg Venous Lymphat Disord ; 6(3): 321-329, 2018 05.
Artículo en Inglés | MEDLINE | ID: mdl-29396156

RESUMEN

OBJECTIVE: Minimally invasive interventions by recanalization, percutaneous transluminal angioplasty, and stenting in post-thrombotic syndrome (PTS) obstructions and iliac vein compression syndrome (IVCS) have shown good results. Until recently, no dedicated venous stents were available, and stent-related issues accounted for a decrease in patency scores. The introduction of dedicated stents with more flexibility and higher radial forces could result in higher patency scores. This study focused on the outcomes of patients treated by a dedicated sinus-Venous stent (OptiMed GmbH, Ettlingen, Germany). Patency rates and clinical evaluation are described for both PTS and IVCS patients. METHODS: A total of 200 patients treated at a tertiary university referral center were analyzed. A percutaneous procedure was performed in 103 (51%) PTS patients and 48 (24%) IVCS patients. In 49 (25%) patients, a hybrid procedure was executed. Patency rates and complications were analyzed by duplex ultrasound. Clinical improvement was scored by Venous Clinical Severity Score, Villalta scale, and venous claudication rates. RESULTS: The mean age was 43.2 ± 14.5 (17-81) years, and 66% were female. Mean Villalta score decreased from 10.5 ± 4.2 (3-24) to 5.3 ± 3.8 (0-14) at the latest follow-up (P < .001). Venous Clinical Severity Score decreased by a total of 3 points (P < .001). At baseline, venous claudication was present in 132 patients, which subsided in 115 (87%). Overall patency scores revealed a primary patency of 68%, assisted primary patency of 83%, and secondary patency of 90% with a median follow-up of 12 (11-12) months. Of all included patients, 122 (61%) did not have a complication during follow-up; the most frequent complications were in-stent restenosis (n = 23) and occlusion (n = 25) of the stented tract. CONCLUSIONS: Short-term clinical results using the sinus-Venous stent are comparable to previous research. Loss of stent patency due to stent-related issues like kinking or tapering is hardly ever seen in this short-term follow-up.


Asunto(s)
Síndrome de May-Thurner/terapia , Síndrome Postrombótico/terapia , Stents , Grado de Desobstrucción Vascular/fisiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Angioplastia/efectos adversos , Angioplastia/instrumentación , Angioplastia/métodos , Femenino , Estudios de Seguimiento , Humanos , Claudicación Intermitente/etiología , Estimación de Kaplan-Meier , Masculino , Síndrome de May-Thurner/diagnóstico por imagen , Síndrome de May-Thurner/fisiopatología , Persona de Mediana Edad , Flebografía , Síndrome Postrombótico/diagnóstico por imagen , Síndrome Postrombótico/fisiopatología , Diseño de Prótesis , Falla de Prótesis , Recurrencia , Índice de Severidad de la Enfermedad , Stents/efectos adversos , Resultado del Tratamiento , Adulto Joven
12.
J Vasc Surg Venous Lymphat Disord ; 4(4): 426-33, 2016 10.
Artículo en Inglés | MEDLINE | ID: mdl-27638997

RESUMEN

OBJECTIVE: Chronic deep venous obstruction can cause a significant loss of quality of life, although it can be treated successfully by stenting. A clear referral pattern for additional imaging is warranted in patients with lower limb complaints. The aim of this study was to determine the value of clinically visible abdominal wall collateral veins in the diagnosis of a potentially treatable deep venous obstruction. METHODS: A total of 295 patients referred for evaluation at a tertiary venous clinic with a collateral vein on the abdominal wall or pubic bone, visible on physical examination, were retrospectively analyzed and compared with a randomly selected control group of 365 patients without such a collateral vein. Duplex ultrasound, magnetic resonance venography, computed tomography venography, and conventional venography were used to determine the presence or absence of deep venous obstruction. RESULTS: Mean age of the group with a positive collateral was 43.5 ± 13.7 (6-76) years compared with 44.7 ± 14.2 (16-89) years in the control group. In the collateral group, 66.1% were female compared with 63.3% in the control group. Sensitivity of the abdominal wall collateral vein for any obstruction at the level of the groin or more proximal was 53% (95% confidence interval [CI], 48-57); specificity, 86% (95% CI, 79-91); positive predictive value, 93% (95% CI, 90-96); and negative predictive value, 32% (95% CI, 28-37). Sensitivity was 68% (95% CI, 62-73) for higher degrees of post-thrombotic obstruction and 27% (95% CI, 19-36) in iliac vein compression. CONCLUSIONS: A collateral vein on the abdominal wall or across the pubic bone in patients with complaints of the lower limb has an excellent positive predictive value for deep venous obstructive disease at the level of the groin or higher. Such collateral veins should therefore not be removed, and symptomatic patients could be offered further diagnostics and treatment.


Asunto(s)
Vena Ilíaca/patología , Enfermedades Vasculares/diagnóstico por imagen , Vena Cava Inferior/patología , Adolescente , Adulto , Anciano , Niño , Constricción Patológica/diagnóstico por imagen , Femenino , Humanos , Masculino , Persona de Mediana Edad , Flebografía , Estudios Retrospectivos , Adulto Joven
13.
J Pharm Sci ; 84(7): 884-8, 1995 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-7562442

RESUMEN

The products of recrystallization of tenoxicam (4-hydroxy-2-methyl-N-2-pyridinyl-2H-thieno[2,3-e]-1,2-thiazine-3- carboxamide 1,1-dioxide) from ethanol and acetonitrile were investigated by thermogravimetric analysis, differential scanning calorimetry, and X-ray diffraction. Recrystallization from ethanol yielded a polymorph designated 1, and recrystallization from acetonitrile gave a solvate 2 with 1:1 stoichiometry. The structures of 1 and 2 were determined by single-crystal X-ray methods. Polymorph 1 is triclinic, space group P1, with Z = 4; solvate 2 is monoclinic, space group P2(1)/n, with Z = 4. In both crystal structures, the tenoxicam molecule exists in the zwitterionic form, adopting a planar conformation that is stabilized by two intramolecular hydrogen bonds (N(+)-H...O and N-H...O-). Tenoxicam molecules associate by N(+)-H...O and C-H...N hydrogen bonding in both crystal structures. Desolvation of 2 yields a polymorph of tenoxicam that is different from polymorph 1. A study of the kinetics of the desolvation of 2 by dynamic thermogravimetry yielded estimates of the activation energy in the range 69-72 kJ.mol-1. From a comparison of experimental and simulated X-ray powder diffraction patterns, neither 1 nor 2 undergoes a polymorphic transition upon grinding. X-ray patterns based on the single-crystal X-ray data for 1 and 2 are presented as reliable references for their identification.


Asunto(s)
Antiinflamatorios no Esteroideos/química , Estructura Molecular , Piroxicam/análogos & derivados , Termogravimetría , Acetonitrilos/química , Etanol/química , Piroxicam/química , Temperatura , Rayos X
14.
Ned Tijdschr Geneeskd ; 157(24): A6161, 2013.
Artículo en Holandés | MEDLINE | ID: mdl-23759181

RESUMEN

BACKGROUND: In most patients, infection with a non-typhoid Salmonella species usually results in self-limiting gastroenteritis. Severe complications such as bacteraemia and extra-abdominal infections are most often attributed to typhoid subspecies like S. typhi and S. paratyphi. In this article, we present the case of a healthy patient with non-typhoid salmonellosis who nevertheless developed severe complications. CASE DESCRIPTION: A 63-year-old man with an unremarkable medical history presented at the emergency department with abdominal complaints suggestive of gastroenteritis. Cultures of faeces and blood yielded S. typhimurium. The infection was complicated by many intra-abdominal abscesses, abdominal sepsis and an intestinal perforation requiring multiple interventions. The patient has been symptom-free for half a year now. CONCLUSION: Severe complications related to infection with non-typhoid S. typhimurium are rare. The incidence of salmonellosis has risen over the past few years, however; the risk of severe complications has therefore also increased.


Asunto(s)
Perforación Intestinal/diagnóstico , Infecciones por Salmonella/complicaciones , Infecciones por Salmonella/diagnóstico , Salmonella typhimurium/aislamiento & purificación , Absceso Abdominal/diagnóstico , Absceso Abdominal/microbiología , Bacteriemia/diagnóstico , Bacteriemia/microbiología , Diagnóstico Diferencial , Humanos , Perforación Intestinal/microbiología , Masculino , Persona de Mediana Edad , Intoxicación Alimentaria por Salmonella/complicaciones , Intoxicación Alimentaria por Salmonella/diagnóstico
15.
Phys Rev E Stat Nonlin Soft Matter Phys ; 85(4 Pt 1): 041133, 2012 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-22680444

RESUMEN

Nonequilibrium steady states of Markov processes give rise to nontrivial cyclic probability fluxes. Cycle decompositions of the steady state offer an effective description of such fluxes. Here we present an iterative cycle decomposition exhibiting a natural dynamics on the space of cycles that satisfies detailed balance. Expectation values of observables can be expressed as cycle "averages," resembling the cycle representation of expectation values in dynamical systems. We illustrate our approach in terms of an analogy to a simple model of mass transit dynamics. Symmetries are reflected in our approach by a reduction of the minimal number of cycles needed in the decomposition. These features are demonstrated by discussing a variant of an asymmetric exclusion process. Intriguingly, a continuous change of dominant flow paths in the network results in a change of the structure of cycles as well as in discontinuous jumps in cycle weights.


Asunto(s)
Cadenas de Markov , Modelos Teóricos , Reología/métodos , Simulación por Computador
16.
J Membr Biol ; 157(2): 117-26, 1997 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-9151653

RESUMEN

We here report on studies on the frog skin epithelium to identify the nature of its excretory H+ pump by comparing transport studies, using inhibitors highly specific for V-ATPases, with results from immunocytochemistry using V-ATPase-directed antibodies. Bafilomycin A1 (10 microM) blocked H+ excretion (69 +/- 8% inhibition) and therefore Na+ absorption (61 +/- 17% inhibition after 60 min application, n = 6) in open-circuited skins bathed on their apical side with a 1 mm Na2SO4 solution, "low-Na+ conditions" under which H+ and Na+ fluxes are coupled 1:1. The electrogenic outward H+ current measured in absence of Na+ transport (in the presence of 50 microM amiloride) was also blocked by 10 microM bafilomycin A1 or 5 microM concanamycin A. In contrast, no effects were found on the large and dominant Na+ transport (short-circuit current), which develops with apical solutions containing 115 mm Na+ ("high-Na+ conditions"), demonstrating a specific action on H+ transport. In immunocytochemistry, V-ATPase-like immunoreactivity to the monoclonal antibody E11 directed to the 31-kDa subunit E of the bovine renal V-ATPase was localized only in mitochondria-rich cells (i) in their apical region which corresponds to apical plasma membrane infoldings, and (ii) intracellularly in their neck region and apically around the nucleus. In membrane extracts of the isolated frog skin epithelium, the selectivity of the antibody binding was tested with immunoblots. The antibody labeled exclusively a band of about 31 kDa, very likely the corresponding subunit E of the frog V-ATPase. Our investigations now deliver conclusive evidence that H+ excretion is mediated by a V-ATPase being the electrogenic H+ pump in frog skin.


Asunto(s)
Macrólidos , Bombas de Protones/metabolismo , ATPasas de Translocación de Protón/metabolismo , Piel/enzimología , ATPasas de Translocación de Protón Vacuolares , Animales , Antibacterianos/farmacología , Anticuerpos Monoclonales , Inhibidores Enzimáticos/farmacología , Epitelio/efectos de los fármacos , Epitelio/enzimología , Inmunohistoquímica , Técnicas In Vitro , Bombas de Protones/efectos de los fármacos , ATPasas de Translocación de Protón/antagonistas & inhibidores , ATPasas de Translocación de Protón/inmunología , Rana esculenta , Piel/citología , Piel/efectos de los fármacos , ATPasa Intercambiadora de Sodio-Potasio/efectos de los fármacos , ATPasa Intercambiadora de Sodio-Potasio/metabolismo
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