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1.
Musculoskelet Surg ; 107(4): 413-421, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37273144

RESUMO

PURPOSE: The management of overriding distal forearm fractures is still controversial. This study aimed to evaluate the efficacy of immediate closed reduction and cast immobilization (CRCI) at the emergency department (ED) using equimolar nitrous oxide (eN2O2) as conscious sedation, and without the use fluoroscopic assistance. METHODS: Sixty patients with overriding distal forearm fracture were included in the study. All procedures were performed in the ED without fluoroscopic assistance. Antero-posterior and lateral wrist radiographs were taken after CRCI. Follow-up radiographs were taken 7 and 15 days post-reduction, and at cast removal to evaluate callus formation. Depending on the radiological outcome, two groups of patients could be identified: Group 1 (satisfactory reduction and maintenance of alignment) and Group 2 (poor reduction or secondary displacement requiring further manipulation and surgical fixation). Group 2 was additionally divided into Group 2A (poor reduction) and Group 2B (secondary displacement). Pain was assessed using Numeric Pain Intensity (NPI) score, while functional outcome was measured according to Quick DASH questionnaire. RESULTS: Mean age at the time of injury was 9.2 ± 2.4 years (range, 5-14). Twenty-three (38%) patients were aged between 4 and 9 years old, 20 (33%) patients between 9 and 11, 11 (18%) patients between 11 and 13, and 6 (10%) patients between 13 and 14. The mean follow-up time was 45.6 ± 12 months (range, 24-63). Satisfactory reduction with maintenance of alignment was achieved in 30 (50%) patients (Group 1). Re-reduction was performed in the remaining 30 (50%) patients (Group 2) due to poor reduction (Group 2A) or secondary displacement (Group 2B). No complications related to the administration of eN2O were recorded. No statistically significant difference could be identified between the three groups for any clinical variable (Quick DASH and NPI). CONCLUSION: Overriding distal forearm fractures may be safely treated with CRCI at ED using eN2O2 as conscious sedation. However, fluoroscopic assistance during CRCI might significantly improve the quality of reduction thus avoiding further treatment as the lack of relaxed muscle can restrain reduction.


Assuntos
Fraturas do Rádio , Fraturas do Punho , Humanos , Pré-Escolar , Criança , Adolescente , Fraturas do Rádio/terapia , Fraturas do Rádio/cirurgia , Óxido Nitroso , Punho , Sedação Consciente , Moldes Cirúrgicos , Resultado do Tratamento
2.
Malays Orthop J ; 16(3): 113-119, 2022 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-36589369

RESUMO

Introduction: Many surgical approaches have been described for hip hemiarthroplasty (HHA) treating femur neck fractures (FNFs). Direct lateral approach (DLA) is one of the most used. Today, the direct anterior approach (DAA) has become very attractive, but it seems to involve more intra-operative fractures. Our main endpoint was to demonstrate that the DAA may be a valid alternative comparing to the DLA. Materials and methods: Patients affected by FNFs and treated with HHA between the years 2016 and 2020 were studied. We divided the treatment of the fractures according to the surgical approach. The analysis was focused on perioperative complications and radiological outcomes. Results: There were a total of 166 patients. The DLA group included patients with an average age of 83.5 years and the DAA group of 83 years. We found similar surgical times (DLA 67 min vs DAA 61 min; p = 0,55), number of transfusions (DLA 3/person vs DAA 4/person; p = 0,91), perioperative complications (fractures: DLA 0 vs DAA 0 - dislocations: DLA 2,50% vs DAA 0) and functional outcomes (HHS: DLA 83 points vs DAA 87 points; p = 0,71). There were no statistical differences comparing diaphyseal filling (Canal Fill Index at the proximal third: DLA 0,79 vs DAA 0,78; p= 0,24), bone loss (Paprosky I: DLA 96,25% vs DAA 91,86%; p = 0,47) and prevalence of heterotopic ossification (Broker low degree: DLA 93,75% vs 95, 34%; p = 0,87). Conclusion: Analysing perioperative complications and studying post-operative radiographic evolution, our results suggest that the DAA is a valid alternative to the DLA in HHA treating FNFs.

3.
Artigo em Inglês | WPRIM (Pacífico Ocidental) | ID: wpr-962218

RESUMO

@#Introduction: Many surgical approaches have been described for hip hemiarthroplasty (HHA) treating femur neck fractures (FNFs). Direct lateral approach (DLA) is one of the most used. Today, the direct anterior approach (DAA) has become very attractive, but it seems to involve more intra-operative fractures. Our main endpoint was to demonstrate that the DAA may be a valid alternative comparing to the DLA. Materials and methods: Patients affected by FNFs and treated with HHA between the years 2016 and 2020 were studied. We divided the treatment of the fractures according to the surgical approach. The analysis was focused on perioperative complications and radiological outcomes. Results: There were a total of 166 patients. The DLA group included patients with an average age of 83.5 years and the DAA group of 83 years. We found similar surgical times (DLA 67 min vs DAA 61 min; p = 0,55), number of transfusions (DLA 3/person vs DAA 4/person; p = 0,91), perioperative complications (fractures: DLA 0 vs DAA 0 – dislocations: DLA 2,50% vs DAA 0) and functional outcomes (HHS: DLA 83 points vs DAA 87 points; p = 0,71). There were no statistical differences comparing diaphyseal filling (Canal Fill Index at the proximal third: DLA 0,79 vs DAA 0,78; p= 0,24), bone loss (Paprosky I: DLA 96,25% vs DAA 91,86%; p = 0,47) and prevalence of heterotopic ossification (Broker low degree: DLA 93,75% vs 95, 34%; p = 0,87). Conclusion: Analysing perioperative complications and studying post-operative radiographic evolution, our results suggest that the DAA is a valid alternative to the DLA in HHA treating FNFs.

4.
Musculoskelet Surg ; 103(1): 23-30, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30311075

RESUMO

The main objective of this paper is to review the current literature on treatment of tibial and femur fractures in children and adolescents guided by body weight in patients weighing 50 kg (110 lb) or more. A secondary aim of this mini-review was to determine, as per literature review, whether weight > 50 kg (110 lb) is an identifiable factor associated with increased complication rate. A search of the PubMed/MEDLINE, EMBASE and Cochrane Database of Systematic Reviews databases from 1954 to September 2017 was performed to identify papers related to pediatric tibia and femur fractures in children weighing more than 50 kg (110 lb). Abstracts were screened, and relevant full-text articles were retrieved for further review. Reference sections of identified papers were also screened to identify further literature. All levels of evidence were included. Overall, seven full-text articles dealing with pediatric tibia or femur fractures in patients weighing more than 50 kg (110 lb), and one article reporting on both femur and tibia fractures in this patients' population, have been identified (n = 8 full-text article included). The articles reviewed a total of 679 children. In particular, 48/438 femur shaft fractures (mean weight: 51.7 kg or 113.9 lb) and 91/241 tibia fractures (mean weight: 53.3 kg or 117.5 lb) met the inclusion criteria. The overall rate of complications was 27.9%. In particular, the rate of complication was 51.7 and 29.6% in children with femur and tibia fracture weighing more than 50 kg (110 lb), respectively (p < 0.05). Elastic stable intramedullary nailing (ESIN) has become the treatment of choice for displaced tibia and femur shaft fractures in children between six and 12-15 years of age. Unstable fracture pattern, higher age and higher weight have been reported as potential risk factors associated with poor outcomes in children and adolescents treated with ESIN for displaced long bone fractures of the lower extremity, in particular femur shaft fractures. Despite these findings, data reporting exclusively on ESIN-treated long bone fractures in children weighing 50 kg (110 lb) or more remain scant.


Assuntos
Peso Corporal , Fraturas do Fêmur/cirurgia , Fixação Intramedular de Fraturas/métodos , Fraturas da Tíbia/cirurgia , Adolescente , Criança , Fraturas do Fêmur/complicações , Humanos , Obesidade/complicações , Fraturas da Tíbia/complicações , Resultado do Tratamento
5.
Radiol Med ; 114(3): 358-69, 2009 Apr.
Artigo em Inglês, Italiano | MEDLINE | ID: mdl-19381764

RESUMO

PURPOSE: The aim of this study was to correlate left main (LM) coronary artery dimensions with the presence of atherosclerosis by multidetector-row computed tomography (MDCT) coronary angiography (CA) and to assess coronary atherosclerotic plaques with a semiquantitative method. MATERIALS AND METHODS: Sixty-two consecutive patients (41 men, mean age 60+/-11) with suspected coronary artery disease underwent 64-MDCT coronary angiography. LM dimensions (length, ostial and bifurcation diameters), quantitative [location, Hounsfield unit (HU) attenuation] and qualitative (composition, shape) analysis of plaques within the LM were performed. All patients underwent conventional CA. RESULTS: Thirty patients (mean age 55+/-10) without plaques in the LM presented the following average dimensions: length 10.6+/-6.1 mm, ostial diameter 5.5+/-0.7 mm, bifurcation diameter 4.9+/-0.9 mm. LM plaques (n=36) were detected in 32 patients (mean age 64+/-10) with the following LM average dimensions: length 11.3+/-4.0 mm, ostial diameter 6.0+/-1.2 mm and bifurcation diameter 6.0+/-1.2 mm. Plaques were calcified (40%, mean attenuation 742+/-191 HU), mixed (43%, mean attenuation 387+/-94 HU) or noncalcified (17%, mean attenuation 56+/-14 HU) and were frequently eccentric (77%). Age was significantly different in the two groups (p<0.05). LM diameters of patients with plaques were improved (p<0.05). A moderate correlation was found between the LM bifurcation diameter and the corresponding plaque area (r=0.56). Significant conventional CA lesions of the LM were present in just three patients (5%). CONCLUSIONS: Increased LM diameters are associated with the presence of atherosclerosis. MDCT CA indicates relevant features of LM atherosclerotic burden, as rupture and subsequent thrombosis of vulnerable plaques may develop from lesions characterised as nonsignificant at conventional CA.


Assuntos
Angiografia Coronária , Doença da Artéria Coronariana/diagnóstico por imagem , Tomografia Computadorizada por Raios X , Angiografia Coronária/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada por Raios X/métodos
6.
Radiol Med ; 113(5): 644-57, 2008 Aug.
Artigo em Inglês, Italiano | MEDLINE | ID: mdl-18594764

RESUMO

PURPOSE: The aim of our study was to assess the influence of heart rate on the selection of the optimal reconstruction window with 40-slice multidetector-row computed tomography (40-MDCT) coronary angiography. MATERIALS AND METHODS: We studied 170 patients (114 men, age 60+/-11.3 years) with suspected or known coronary artery disease with 40-MDCT coronary angiography. Patients [mean heart rate (HR) 62.9+/-9.3 bpm, range 42-94 bpm] were clustered in two groups (group A: HR 65 bpm). Multiphase reconstruction data sets were obtained with a retrospective electrocardiogram (ECG)-gated 40-MDCT coronary angiography scan from 0% to 95% every 5% of the R-R interval. Two radiologists in consensus evaluated the best data sets for diagnostic purposes. RESULTS: In group A, the optimal reconstruction windows were at 70% (55/110, 71/110 and 69/110 for the right coronary artery, left anterior descending and the left circumflex, respectively) and 75% (26/110, 28/110 and 28/110, respectively) of the R-R interval. In group B, a wide range of reconstruction windows were employed, both in the end-systolic phase at 40% (32/60, 18/60 and 17/60, for the right coronary artery, left anterior descending and circumflex, respectively) and diastolic phases at 70% (12/60, 22/60 and 19/60, respectively). Six scans were excluded due to severe respiratory artefacts. CONCLUSIONS: Optimal position of the image reconstruction window relative to the cardiac cycle is significantly influenced by the heart rate during scanning. Diastolic reconstruction phases often allowed an optimal assessment in group A. Reconstruction phases from 30% to 45% are advisable for higher heart rates.


Assuntos
Angiografia Coronária , Frequência Cardíaca , Processamento de Imagem Assistida por Computador , Tomografia Computadorizada por Raios X , Adulto , Idoso , Idoso de 80 Anos ou mais , Artefatos , Angiografia Coronária/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade
7.
Heart ; 94(7): 848-54, 2008 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17881474

RESUMO

OBJECTIVE: To evaluate the performance of dual source CT coronary angiography (DSCT-CA) in the detection of in-stent restenosis (>or=50% luminal narrowing) in symptomatic patients referred for conventional angiography (CA). DESIGN/ PATIENTS: 100 patients (78 males, age 62 (SD 10)) with chest pain were prospectively evaluated after coronary stenting. DSCT-CA was performed before CA. SETTING: Many patients undergo coronary artery stenting; availability of a non-invasive modality to detect in-stent restenosis would be desirable. RESULTS: Average heart rate (HR) was 67 (SD 12) (range 46-106) bpm. There were 178 stented lesions. The interval between stenting and inclusion in the study was 35 (SD 41) (range 3-140) months. 39/100 (39%) patients had angiographically proven restenosis. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of DSCT-CA, calculated in all stents, were 94%, 92%, 77% and 98%, respectively. Diagnostic performance at HR <70 bpm (n = 69; mean 58 bpm) was similar to that at HR >or=70 bpm (n = 31; mean 78 bpm); diagnostic performance in single stents (n = 95) was similar to that in overlapping stents and bifurcations (n = 83). In stents >or=3.5 mm (n = 78), sensitivity, specificity, PPV, NPV were 100%; in 3 mm stents (n = 59), sensitivity and NPV were 100%, specificity 97%, PPV 91%; in stents or=3.5 mm was significantly higher than in stents

Assuntos
Reestenose Coronária/diagnóstico por imagem , Oclusão de Enxerto Vascular/diagnóstico por imagem , Stents , Idoso , Angina Pectoris/diagnóstico por imagem , Angiografia Coronária/métodos , Métodos Epidemiológicos , Feminino , Frequência Cardíaca , Humanos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Pessoa de Meia-Idade , Seleção de Pacientes , Tomografia Computadorizada por Raios X/métodos
8.
Radiol Med ; 112(8): 1117-31, 2007 Dec.
Artigo em Inglês, Italiano | MEDLINE | ID: mdl-18080097

RESUMO

PURPOSE: This paper aims to provide the tools for a complete anatomical evaluation of the coronary tree using 64-slice computed tomography (CT) and evaluate the prevalence of anatomical variants and anomalies in a population of 202 consecutive patients. MATERIALS AND METHODS: Two hundred and two patients with suspected coronary artery disease underwent 64-slice CT with a standard protocol. Two observers working in consensus evaluated and collected the data regarding anatomical variants and anomalies of the coronary vessels. RESULTS: In the 202 consecutive patients, the prevalence of anatomical variants was: left dominant circulation (7%), absent left main (5%), presence of intermediate branch (17%), aortic origin of conus branch (13%) and circumflex origin of sinus node branch (15%). Coronary anomalies (origin and course, intrinsic and termination) showed an overall prevalence of 25%. CONCLUSIONS: CT is the ideal method for the three-dimensional evaluation of the coronary tree. Anatomical variants and anomalies of the coronary arteries are quite common and should be known and recognised promptly by the operators.


Assuntos
Anomalias dos Vasos Coronários/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Angiografia Coronária , Doença das Coronárias/diagnóstico por imagem , Anomalias dos Vasos Coronários/epidemiologia , Feminino , Humanos , Imageamento Tridimensional , Masculino , Pessoa de Meia-Idade , Prevalência , Interpretação de Imagem Radiográfica Assistida por Computador
9.
Radiol Med ; 112(7): 969-81, 2007 Oct.
Artigo em Inglês, Italiano | MEDLINE | ID: mdl-17952682

RESUMO

PURPOSE: Our aim was to evaluate the diagnostic accuracy of 64-slice computed tomography coronary angiography (MSCT-CA) for detecting significant stenosis (>or=50% lumen reduction) in a population of patients at low to intermediate risk. MATERIALS AND METHODS: We studied 72 patients (38 men, 34 women, mean age 53.9+/-8.0 years) with atypical or typical chest pain and stratified in the low-to intermediate risk category. MSCT-CA (Sensation 64 Cardiac, Siemens, Germany) was performed after IV administration of 100 ml of iodinated contrast material (Iomeprol 400 mgI/ml, Bracco, Italy). Two observers, blinded to the results of conventional coronary angiography (CAG), assessed the MSCT-CA scans in consensus. Diagnostic accuracy for detecting significant stenosis was calculated. RESULTS: CAG demonstrated the absence of significant disease in 70.1% of patients (51/72). No patient was excluded from MSCT-CA. There were 37 significant lesions on 1,098 available coronary segments. Sensitivity, specificity and positive and negative predictive value of MSCT-CA for detecting significant coronary artery on a per-segment basis were 100%, 98.6%, 71.2% and 100%, respectively. All patients with at least one significant lesion were correctly identified by MSCT-CA. MSCT-CA scored 15 false positives on a per-segment base, which affected only marginally the per-patient performance (only one false positive). CONCLUSIONS: We concluded that 64-slice CT-CA is a diagnostic modality with high sensitivity and negative predictive value in patients at low to intermediate risk.


Assuntos
Angiografia Coronária/métodos , Doença das Coronárias/diagnóstico por imagem , Tomografia Computadorizada Espiral/métodos , Algoritmos , Dor no Peito , Meios de Contraste , Estenose Coronária/diagnóstico por imagem , Interpretação Estatística de Dados , Eletrocardiografia , Feminino , Humanos , Iopamidol/análogos & derivados , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Fatores de Risco , Sensibilidade e Especificidade , Função Ventricular Esquerda
10.
Radiol Med ; 112(7): 937-48, 2007 Oct.
Artigo em Inglês, Italiano | MEDLINE | ID: mdl-17952684

RESUMO

PURPOSE: The aim of the study was to investigate the prevalence of the noncardiac collateral findings during multislice computed tomography coronary angiography (MSCT-CA). MATERIALS AND METHODS: Six hundred and seventy patients undergoing MSCT-CA with 16-slice and 64-slice CT scanners for suspected atherosclerotic disease of the coronary arteries were retrospectively reviewed. All data sets obtained with a large field of view (FOV) were analysed by two radiologists using standard mediastinal and lung window settings. Collateral findings were divided according to clinical importance into nonsignificant, remarkable and compulsory to be investigated. RESULTS: Eighty-five percent of patients revealed coronary artery disease (CAD). Only 138/670 (20.6%) were without any additional finding. An additional 1,234 findings were recorded: nonsignificant 332 (26.9%), mild 821 (66.53%), compulsory for study 81 (6.56%). A total of 81 patients (12.08%) had significant noncardiac pathology requiring clinical or radiological follow-up. Among these, newly discovered pathologies were revealed in two patients (2.46%). CONCLUSIONS: A significant number of noncardiac findings might have been missed in MSCT-CA scans; the appropriate approach should be as a team trained in cardiology and radiology.


Assuntos
Angiografia Coronária/métodos , Doença das Coronárias/diagnóstico por imagem , Radiografia Abdominal , Radiografia Torácica , Tomografia Computadorizada Espiral/métodos , Idoso , Interpretação Estatística de Dados , Eletrocardiografia , Feminino , Seguimentos , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Sensibilidade e Especificidade , Fatores de Tempo
11.
Radiol Med ; 112(5): 637-59, 2007 Aug.
Artigo em Inglês, Italiano | MEDLINE | ID: mdl-17653628

RESUMO

The goal of this article is to illustrate the main invasive and noninvasive diagnostic modalities to image the vulnerable coronary plaque, which is responsible for acute coronary syndrome. The main epidemiologic and histological issues are briefly discussed in order to provide an adequate background. Comprehensive coronary atherosclerosis imaging should involve visualization of the entire coronary artery tree and plaque characterization, including three-dimensional morphology, relationship with the lumen, composition, vascular remodelling and presence of inflammation. No single technique provides such a comprehensive description, and no available modality extensively identifies the vulnerable plaque. In particular, we describe multislice computed tomography, which at present seems to be the most promising noninvasive tool for an exhaustive image-based quantification of coronary atherosclerosis.


Assuntos
Doença da Artéria Coronariana/diagnóstico , Diagnóstico por Imagem , Meios de Contraste , Doença da Artéria Coronariana/epidemiologia , Doença da Artéria Coronariana/fisiopatologia , Diagnóstico Diferencial , Humanos , Imageamento Tridimensional , Valor Preditivo dos Testes , Fatores de Risco , Ruptura Espontânea , Sensibilidade e Especificidade
15.
Chir Ital ; 36(6): 1046-64, 1984 Dec.
Artigo em Italiano | MEDLINE | ID: mdl-6400077

RESUMO

Acute cholecystitis is a non-rare disease, the incidence of which was increasing in the last years parallel to biliary lithiasis, which in 90% of cases is the first cause of such pathology. From the anatomopathological standpoint, we distinguish three types of acute cholecystitis: catarrhal, suppurative and gangrenous. The most frequently remarked symptom is ache at right hypochondrium. Only in 30% of cases cholecyst can be palpated, in form of ovoid mass; typical is the positiveness of Murphy's manoeuvre; constant is fever, but not subicterus. The introduction of new methods of ascertainment, exempt from any risks, simple to be performed and remarkably careful, made the diagnostics of acute cholecystites easier: parietal cholecystotomography, hepato-biliary scintigraphy, echotomography (first approach investigation), computerized axial tomography and laparoscopy almost always succeed in dispelling doubts. By using more than one of these investigations, a diagnostic accuracy, touching on 100%, can be reached. The differential diagnosis should be placed with: peptic ulcer, acute pancreatitis, acute appendicitis, gonococcus perihepatitis, virus hepatitis, acute pyelonephritis, right basal pneumonia. The complications an acute cholecystitis can occur are: perforation (localized, in free peritoneum or in a hollow organ), choleperitonaeum, necrosis of hepatic parenchyma, acute pancreatitis. Due to the possible arising of such complications, the mortality unfortunately is not indifferent (5%), especially in patients already weakened by other chronic diseases. Still discussed is the question as to when performing operation. In fact, there are three trends: intervention in immediate emergency, in postponed emergency, or in remote time (preceded by a medical treatment). The Authors prefer the intervention in postponed emergency, as, in their experience, they remarked the poor effectiveness of the delay medical treatment, also involving a greater difficulty in the technical execution of the intervention and a longer stay in hospital. From 1973 up to 1983, 241 cases of acute cholecystitis (158 women and 83 men) were hospitalized at the First Aid Surgical Centre of the Catania University. Eight patients refused the surgical intervention. The remaining 233 underwent, depending upon the seriousness of the affection, the associated diseases and the different reactiveness to the medical treatment, operation: in immediate emergency (26.1%); in postponed emergency (67.8%; in remote time (6.1%). The mortality was 2.2%, with the lowest percentage in the second group.


Assuntos
Colecistite , Doença Aguda , Adulto , Idoso , Colecistite/complicações , Colecistite/diagnóstico , Colecistite/etiologia , Colecistite/patologia , Colecistite/terapia , Colelitíase/complicações , Diagnóstico Diferencial , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Prognóstico , Tomografia Computadorizada por Raios X , Ultrassonografia
18.
Experientia ; 31(8): 914-5, 1975 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-169142

RESUMO

In Neurospora cells growing in various media, the specific activity of cytochrome oxidase increases very markedly during early exponential growth, reaching a maximum after 4-5 duplication times, then it slowly declines.


Assuntos
Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Neurospora crassa/enzimologia , Neurospora/enzimologia , Divisão Celular , Glucose/metabolismo , Neurospora crassa/crescimento & desenvolvimento
19.
Biosystems ; 7(1): 183-8, 1975 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-1156669

RESUMO

The assumption that prompted the studies reported in this paper was that the unsatisfactory state of our knowledge on the regulation of cellular growth might derive from the reductionistic approach used to investigate it. Thus an analysis of cellular growth which applied concepts derived from systems dynamics was undertaken. First of all a dynamic model of cellular growth has been constructed. It has the following features: the levels of DNA, ribosomes and proteins are the defining levels; cellular growth is expressed by a close loop in which the level of ribosomes per genome and, indirectly, the level of proteins per genome are stabilized around goal values by the action of negative feed backs. The validity of the model has been tested by its ability to predict the growth kinetics of a real system (exponentially growing Neurospora cells). The simulated growth has been found to reproduce with great accuracy that of Neurospora cells. A slightly modified model, which takes into consideration also the degradation of ribosomes and of proteins, is shown to predict with accuracy the dynamics of growth of both growing and resting fibroblasts. These latter results suggest that the rates of macromolecular turnovers play a central role in the control of proliferation of mammalian cells: the condition of zero growth seems to be achieved when the rate of synthesis and the rate of degradation of proteins are the same. The possibility is discussed that the model indicates a unifying hypothesis of the mode of action of growth controlling conditions (hormones, growth factors, contact inhibition).


Assuntos
Divisão Celular , Linhagem Celular , Células/metabolismo , DNA/metabolismo , Replicação do DNA , Matemática , Modelos Biológicos , Biossíntese de Proteínas , Proteínas/metabolismo , Ribossomos/metabolismo , Transcrição Gênica
20.
J Biol Chem ; 250(12): 4381-8, 1975 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-124730

RESUMO

The levels of ribosomes, tRNA molecules, and total protein per genome in Neurospora mycelia have been determined in eight different conditions of exponential growth. By increasing the rate of growth the number of ribosomes per genome increases dramatically while the level of total protein remains almost unchanged and the level of tRNA increases only slightly. The rates of synthesis of each of the macromolecules have been estimated. Increasing the rate of growth (mu) up to 0.5, the ratio between the rates of synthesis of tRNA and rRNA decreases reaching a constant value. The equations that best describe the dependence of the rate of synthesis of the macromolecules on the rate of growth (mu) have been determined. The rate of rRNA synthesis (rr), expressed as nucleotides polymerized, min- minus 1 per genome, is given by the equation: rr equals 6.51 times 10-7 mu-2-19. The rate of protein synthesis (rp), expressed as amino acids polymerized, min- minus 1 per genome is given by the following relationship: rp equals -1.43 times 10-7 + 3.43 times 10-8 mu. The equation describing the tRNA synthesis (rt) expressed as nucleotides, min- minus 1 per genome is rt equals 6.45 times 10-5 times exp 2.30 mu; however, more accurate determinations appear to be required for a firmer assignment of this latter equation. The significance of these equations for the studies on the regulation of rRNA and protein synthesis is discussed. For instance the rate of rRNA synthesis may set the limit for the maximal growth rate attainable by a cell, as the maximal rate of rRNA synthesis that may take place in a given cell is limited by the degree of redundancy of the rRNA genes.


Assuntos
Proteínas Fúngicas/metabolismo , Neurospora crassa/metabolismo , Neurospora/metabolismo , RNA Ribossômico/metabolismo , RNA de Transferência/metabolismo , Acetatos/farmacologia , Divisão Celular , DNA/biossíntese , Etanol/farmacologia , Proteínas Fúngicas/biossíntese , Glucose/farmacologia , Glicerol/farmacologia , Cinética , Matemática , Neurospora crassa/efeitos dos fármacos , RNA Ribossômico/biossíntese , RNA de Transferência/biossíntese , Ribossomos/metabolismo , Fatores de Tempo
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