The Power-law Formalism as a Tool for Modeling Hormonal Systems

Modeling a hormone system requires a number of simplifying assumptions. Often, the final conceptual model incorporates a number of aggregated processes that have no correspondence with a single enzyme-catalyzed reaction. In such cases, it is discussible using models based on classical biochemical kinetics rate laws that are valid only under specific conditions. The power-law formalism provides an alternative framework for building up a mathematical model in such cases. The resulting model is a set of ordinary differential equations with a special structure that allows efficient symbolic and numerical analysis of the system's properties. In these equations, the underlying rate-laws of each of the component processes are represented by a power-law that is an exact representation of the actual rate-law at the operating point. The particular form of these equations allows representation of a wide range of kinetic features without changing the basic power-law form. Moreover, its parameters have an immediate interpretation as apparent kinetic-orders and rate-constants. This is especially helpful for incorporating both quantitative and qualitative information in the process of model definition. This is particularly useful when detailed kinetic information concerning system's components is not available. In this paper we show the utility of the power-law approach in this context by deriving an illustrative model of a complex physiological system: the hypothalamus-anterior pituitary-thyroid network. First, we derive a conceptual model that incorporates the key features of this system. Then, we derive an S-system model, one of the preferred variants within the power-law formalism, and we show its utility in exploring the system properties. The model qualitatively reproduces the response of normal, hyperthyroid, and hypothyroid patients to a clinical test involving a thyrotropin releasing hormone injection. Finally, we illustrate the utility of this modeling strategy for studying the system's response to different dynamic patterns of regulatory signals, and for exploring how altered dynamic patterns of stimulatory signals can cause pathological states

A Quantitative method for the characterization of lytic metastases of the bone from radiographic images

The aim of our study was to assess the diagnostic usefulness of the gray level parameters to distinguish osteolytic lesions using radiological images. Materials and Methods: A retrospective study was carried out. A total of 76 skeletal radiographs of osteolytic metastases and 67 radiographs of multiple myeloma were used. The cases were classified into nonflat (MM1 and OL1) and flat bones (MM2 and OL2). These radiological images were analyzed by using a computerized method. The parameters calculated were mean, standard deviation, and coefficient of variation (MGL, SDGL, and CVGL) based on gray level histogram analysis of a region-of-interest.Diagnostic utility was quantified bymeasurement of parameters on osteolyticmetastases andmultiplemyeloma, yielding quantification of area under the receiver operating characteristic (ROC) curve (AUC). Results: Flat bone groups (MM2 and OL2) showed significant differences in mean values of MGL ( = 0.048) and SDGL ( = 0.003). Their corresponding values of AUC were 0.758 for MGL and 0.883 for SDGL in flat bones. In nonflat bones these gray level parameters do not show diagnostic ability. Conclusion: The gray level parametersMGL and SDGL show a good discriminatory diagnostic ability to distinguish between multiple myeloma and lytic metastases in flat bones

Metodología de preparación y presentación de trabajos científicos en medicina

Podeu consultar la versió en català a: http://hdl.handle.net/2445/1701[eng] This paper describes the implementation of a free election grade in the Campus of Bellvitge, University of Barcelona in which the aims are to elaborate and preparate a scientific work by the second cycle students of Medicine.[spa] Este artículo describe la implementación de una asignatura de libre elección en el Campus de Bellvitge, Universidad de Barcelona, cuyos objetivos son elaborar y preparar un trabajo científico por alumnos de segundo ciclo de Medicina

Biologia i control de l'envelliment

Les millores de les condicions sanitàries i els avenços de la medicina han anat acompanyats d'una progressiva i notable disminució de la mortalitat no relacionada amb l'envelliment, mentre el procés de l'envelliment s'ha mantingut pràcticament invariable. Així, l'envelliment ha anat adquirint un paper cada vegada mes primordial amb relació a la mortalitat i la morbiditat, i s'ha convertit en un dels problemes claus de la medicina. Des d'aquesta perspectiva, pot ésser útil analitzar i comparar l'envelliment a diferents nivells d'organització, valorar-lo des d'un punt de vista evolutiu, analitzar les teories sobre les causes de l'envelliment i les possibilitats de modificar-lo o controlar-lo

Criobiologia i hivernació

Reproducció digital del document publicat en format paperLa criobiologia, aplicació del fred als organismes vius i a d'altres components biològics, s'ha desenvolupat en els darrers anys de manera molt important. En l'actua­litat s'utilitza en camps molt diversos: conservació d'ali­ments, tècniques de fecundació artificial, trasplanta­ment d'òrgans, cirurgia cardíaca, hematologia, etc. El fred actua alentint o aturant les reaccions químiques i, consegüentment, els processos biològics. Un efecte del fred és, doncs, alentir o aturar el temps biològic. Algunes especies animals presenten durant l'hivern un estat d'hivernació natural, caracteritzat per una dismi­nució de la seva temperatura corporal, que s'acompa­nya d'una forta disminució del metabolisme, de les necessitats energètiques i de totes les funcions de l'organisme; en el cas d'alguns amfibis arriba a l'arrest cardíac, circulatori i respiratori reversibles. Per analo­gia, el terme hivernació artificial s'aplica a les situa­cions de hipotèrmia induida

Ewing sarcoma of the rib: respiratory tract infection as initial symptoms in a 14-year-old boy. Functional medical imaging findings

Ewing sarcoma or primitive neuroectodermal tumor (PNET) of bone is the second most common pediatric malignant bone tumor. The median age at diagnosis is 15 years and there is a male predilection of 1.5/1. The authors present the case of a 14-year-old boy with Ewing sarcoma situated on the left ninth rib which was being investigated for respiratory tract infection. Pleurisy is the most common misdiagnosis. Our case illustrates the importance of recognizing exceptional features when interpreting FDG PET or scintigraphy to prevent the misinterpretation of metastases as other etiologies, such as infection

Osteolytic metastasis detected in a patient with lung carcinoma by F18-FDG PET

We present a 53-year-old man with a vocal cord paralysis observed as a primary manifestation of lung carcinoma. Tc-99m MDP whole body bone scan was performed and resulted in a normal scintiscan. The bone scan did not reveal any suspicious foci of uptake. The possibility of bone metastasis was taken into consideration. A whole body F18-FDG-PET scan showed intense uptake in the left upper lung corresponding to the primary tumor. A bronchial biopsy confirmed infiltration by small cell lung carcinoma (SCLC). SCLC is composed of poorly differentiated, rapidly growing cells with diseases usually occurring centrally rather than peripherally. It metastasizes early. The whole-body F18-FDG-PET scan clearly demonstrated a focus of increased uptake in the second lumbar vertebral body suspicious for osteolytic metastasis. A lytic bone metastasis was confirmed by MRI. The patient then received therapy and underwent follow up abdominal CT. The scan showed blastic changes in the L2 vertebra suggesting response to treatment

Breastfeeding and Immunohistochemical Expression of ki-67, p53 and BCL2 in Infiltrating Lobular Breast Carcinoma

Background/Aim: Invasive lobular breast carcinoma is the second most common type of breast cancer after invasive ductal carcinoma. According to the American Cancer Society, more than 180,000 women in the United States find out they have invasive breast cancer each year. Personal history of breast cancer and certain changes in the breast are correlated with an increased breast cancer risk. The aim of this work was to analyze breastfeeding in patients with infil- trating lobular breast carcinoma, in relation with: 1) clinicopathological parameters, 2) hor- monal receptors and 3) tissue-based tumor markers. Materials and Methods: The study included 80 women with ILC, 46 of which had breastfeed their children. Analyzed parameters were: age, tumor size, axillary lymph node (N), distant metastasis (M), histologi- cal grade (HG), estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), Ki-67, p53 and BCL2. Results : ILC of non-lactating women showed a larger (p = 0.009), lymph node involvement (p = 0.051) and distant metastasis (p = 0.060). They were also more proliferative tumors mea- sured by Ki-67 (p = 0.053). Breastfeeding history did not influence the subsequent behavior of the tumor regardless of histological subtype. Conclusion: Lactation seems to influence the biological characteristics of ILC defining a subgroup with more tumor size, axillary lymph node involvement, distant metastasis and higher prolifera- tion measured by ki-67 expression

Osteolytic metastasis detected by F18-FDG PET in a patient with lung carcinoma (WP)

This case is described in part in the paragraph of lung carcinoma (chapter 16): Àngel González-Sistal, Alicia Baltasar Sánchez, Michel Herranz Carnero and Álvaro Ruibal Morell (2011). Advances in Medical Imaging Applied to Bone Metastases, Medical Imaging, Dr. Okechukwu Felix Erondu (Ed.), ISBN: 978-953-307-774-1. http://dx.doi.org/10.5772/28519 - http://hdl.handle.net/2445/21498We present a 53-year-old man with a vocal cord paralysis observed as a primary manifestation of lung carcinoma. Tc-99m MDP whole body bone scan were performed and resulted a normal scintiscan. The bone scan does not revealed suspicious foci of uptake. The possibility of bone metastasis was taken into consideration. A whole body F18-FDG-PET scan showed intense uptake in the left upper lung corresponding to the primary tumor. A bronchial biopsy confirmed infiltration by small cell lung carcinoma (SCLC). SCLC is composed of poorly differentiated, rapidly growing cells with disease usually occurring centrally rather than peripherally. It metastasizes early. The whole-body F18-FDG-PET scan clearly demonstrated a focus of increased uptake in the second lumbar vertebral body suspicious for osteolytic metastasis. A lytic bone metastasis was confirmed by MRI. The patient then received therapy and underwent follow up abdominal CT. The scan showed blastic changes in the L2 vertebra suggesting response to treatment