[Clinical results in arthroscopic rotator cuff repair with the modified Mason-Allen technique]. / Resultados clínicos en la reparación artroscópica de manguito rotador con la técnica de Mason-Allen modificada.

INTRODUCTION: rotator cuff tears are one of the most common shoulder injuries. The treatment of choice is arthroscopic repair with the use of anchors. The modified Mason-Allen technique, which combines the benefits of suture bridge and mattress sutures, has shown satisfactory results. This study aims to report and analyze the clinical results using these suture techniques in rotator cuff tears. RESULTS: preoperative mean active flexion 126o, 169o at three months, 175o at 12 months (p < 0.0001), active abduction 98o, 159o at three months and 167o at 12 months (p < 0.0001), internal rotation preoperative value 4.4 ± 3, at three months 7.1 ± 1.7 (p < 0.05) and 12 months 7.6 ± 1.1 (p < 0.001). Constant score 45.76 ± 16.35 (p < 0.0001) at three months 87.27 ± 10.94 and 12 months 91.30 ± 6.00. SSV 41.30 ± 20.89, three months 81.43 ± 18.31 and 12 months 94.37 ± 6.90 (p = 0.0001). Initial mean VAS 6.6 ± 1.6 and 12 months 0.63 ± 1.02 (p < 0.0001). CONCLUSION: in rotator cuff tears, using a single row with the modified Mason-Allen technique is a recommended and replicable option with satisfactory results and statistically significant clinical improvement at three and 12 months post-surgery.

INTRODUCCIÓN: la lesión del manguito de los rotadores es una de las lesiones más comunes del hombro. El tratamiento por elección es la reparación artroscópica con uso de anclas. La técnica Mason-Allen modificada, que integra los beneficios de las suturas puente y colchonero, ha demostrado resultados satisfactorios. El propósito de este estudio es reportar y analizar los resultados clínicos del uso de dicha sutura en rupturas del manguito de los rotadores. RESULTADOS: flexión activa media 126o inicial, 169o a tres meses, 175o a 12 meses (p < 0.0001), abducción activa 98o, tres meses 159o y 167o a 12 meses (p < 0.0001), rotación interna valor prequirúrgico 4.4 ± 3, a los tres meses 7.1 ± 1.7 (p < 0.05) y 12 meses 7.6 ± 1.1 (p < 0.001). Constant Score 45.76 ± 16.35 con un valor de p < 0.0001, a tres meses 87.27 ± 10.94 y 12 meses 91.30 ± 6.00. SSV 41.30 ± 20.89, tres meses 81.43 ± 18.31 y 12 meses 94.37 ± 6.90 (p = 0.0001). EVA media inicial 6.6 ± 1.6 y 12 meses 0.63 ± 1.02 (p < 0.0001). CONCLUSIÓN: en rupturas del manguito de los rotadores, el uso de hilera simple con técnica Mason-Allen modificada es una opción recomendada y replicable con resultados satisfactorios y mejoría clínica estadísticamente significativa a los tres y 12 meses postquirúrgicos.

Applying Data Science methods and tools to unveil healthcare use of lung cancer patients in a teaching hospital in Spain.

PURPOSE: Our primary goal was to study the use of outpatient attendances by lung cancer patients in Hospital Universitario Puerta de Hierro Majadahonda (HUPHM), Spain, by leveraging our Electronic Patient Record (EPR) and structured clinical registry of lung cancer cases as well as assessing current Data Science methods and tools. METHODS/PATIENTS: We applied the Cross-Industry Standard Process for Data Mining (CRISP-DM) to integrate and analyze activity data extracted from the EPR (9.3 million records) and clinical data of lung cancer patients from a previous registry that was curated into a new, structured database based on REDCap. We have described and quantified factors with an influence in outpatient care use from univariate and multivariate points of view (through Poisson and negative binomial regression). RESULTS: Three cycles of CRISP-DM were performed resulting in a curated database of 522 lung cancer patients with 133 variables which generated 43,197 outpatient visits and tests, 1538 ER visits and 753 inpatient admissions. Stage and ECOG-PS at diagnosis and Charlson Comorbidity Index were major contributors to healthcare use. We also found that the patients' pattern of healthcare use (even before diagnosis), the existence of a history of cancer in first-grade relatives, smoking habits, or even age at diagnosis, could play a relevant role. CONCLUSIONS: Integrating activity data from EPR and clinical structured data from lung cancer patients and applying CRISP-DM has allowed us to describe healthcare use in connection with clinical variables that could be used to plan resources and improve quality of care.

[Conversion of arthrodesis to total hip replacement in Mexico. Case report]. / Conversión de artrodesis a prótesis total de cadera en México. Reporte de un caso.

Since 1900, hip fusion was considered a definitive treatment, being the method of choice for osteoarthritis (OA) of the hip in young patients, and others as infections or sequelae of childhood illnesses, although today it has been migrated to the use of prostheses with non-cemented implants. Currently orthopedic management of osteoarthritis in the hip of the young patient has changed dramatically in part derived from the consequences of long-term arthrodesis in adjacent joints, so we present this case where we perform the conversion to total hip arthroplasty.

Desde 1900, la artrodesis de cadera se consideraba como un tratamiento definitivo, siendo el método de elección para la osteoartritis (OA) de cadera en pacientes jóvenes y otros padecimientos como infecciones o secuelas de enfermedades infantiles, aunque hoy día se ha migrado al uso de prótesis con implantes no cementados. Actualmente, el manejo ortopédico de la osteoartritis en la cadera del paciente joven ha cambiado de forma impresionante, en parte derivado de las consecuencias de la artrodesis a largo plazo en las articulaciones vecinas, por ello presentamos este caso en el que se realiza la conversión a una artroplastía total de cadera (ATC).

[Localized pigmented vellonodular sunovitis, cause of knee hemarthrosis]. / Sinovitis vellonodular pigmentada localizada, causa de hemartrosis en rodilla.

The pigmented vellonodular sinovitis (PVNS) is benign neoplasm with synovial proliferation and hemosiderin deposit, characterized by large compromising joints, especially the knee. At present, two variants of clinics, the diffuse form (PVNSD) and the localized (PVNSL) are described. Arthroscopic synovectomy and radiosynoviorthesis (RSO) is the treatment that has shown the best functional results. Nuclear magnetic resonance is an appropriate method for conducting the diagnosis of PVNSL.

La sinovitis vellonodular pigmentada (SVP) es una neoplasia benigna con proliferación sinovial y depósito de hemosiderina, se caracteriza por comprometer grandes articulaciones, en especial la rodilla. En la actualidad se describen dos variantes clínicas, la forma difusa (SVPD) y la localizada (SVPL). La sinovectomía artroscópica y sinovectomía por radiación conforman el tratamiento que ha demostrado mejores resultados funcionales. La resonancia magnética nuclear es un método adecuado para establecer el diagnóstico de la SVPL.

Interfacial properties of binary mixtures of square-well molecules from Monte Carlo simulation.

We determine the interfacial properties of mixtures of spherical square-well molecules from direct simulation of the vapor-liquid interface. We consider mixtures with the same molecular size and intermolecular potential range but different dispersive energy parameter values. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of mixtures of square-well molecules. In particular, we determine the pressuretensor using the mechanical (virial) route and the vapor-liquid interfacial tension evaluated using the Irving-Kirkwood method. In addition to the pressuretensor and the surface tension, we also obtain density profiles, coexistence densities, and interfacial thickness as functions of pressure, at a given temperature. This work can be considered as the extension of our previous work [F. J. Martínez-Ruiz and F. J. Blas, Mol. Phys. 113, 1217 (2015)] to deal with mixtures of spherical molecules that interact through a discontinuous intermolecular potential. According to our results, the main effect of increasing the ratio between the dispersive energy parameters of the mixture, ϵ22/ϵ11, is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative maximum in the density profiles of the more volatile component at the interface. This maximum is related with adsorption or accumulation of these molecules at the interface, since there are stronger attractive interactions between these molecules in comparison with the rest of intermolecular interactions. Also, the interfacial thickness decreases and the surface tension increases as ϵ22/ϵ11 is larger, a direct consequence of the increasing of the cohesive energy of the system.

[Hip osteosynthesis with IM nail: lateral decubitus without fracture table]. / Osteosíntesis de cadera con clavo centromedular: posición en decúbito lateral, sin mesa de fracturas.

BACKGROUND: Hip fractures have increased in the last decades, mainly in elderly patients with osteoporosis. The incidence becomes in some countries up to 250 thousand new cases per year, generating millions for health systems costs, so it should be considered a public health problem. They are treated in supine position, with a fracture table, through a lateral approach. However, it is important to know that there are other techniques, which can dispense a table of fractures and in a different position. MATERIAL AND METHODS: Show a surgical technique for the treatment of transtrochanteric fractures of hip in lateral decubitus, without a fracture tab le and define its advantages and precise indications. RESULTS: Eight patients, five women (62.5%) and three men (37.5%). Bleeding average 115 cc and average surgical time of 67 minutes. A patient with detachment of the system that ended in Girdlestone. No neurological complications or early infection was documented. CONCLUSIONS: The reduction and fixation of transtrochanteric hip fractures with intramedullary nail without fracture tab le and in lateral decubitus is feasible and with a low level of associated complications.

ANTECEDENTES: Las fracturas de cadera han aumentado en las últimas décadas, principalmente en pacientes mayores con osteoporosis. La incidencia llega a ser en algunos países de hasta 250 mil casos nuevos por año, generando costos millonarios para los sistemas de salud, por lo que se debe de considerar como un problema de salud pública. Los pacientes se tratan, de manera tradicional, en posición decúbito supino, con mesa de fracturas, a través de un abordaje lateral. Sin embargo, es importante saber que existen otras técnicas que pueden prescindir de una mesa de fracturas y en una posición diferente. MATERIAL Y MÉTODOS: Mostrar una técnica quirúrgica para el tratamiento de las fracturas transtrocantéricas de cadera en decúbito lateral, sin necesidad de mesa de fracturas y definir sus ventajas e indicaciones precisas. RESULTADOS: Ocho pacientes, cinco mujeres (62.5%) y tres hombres (37.5%). Sangrado promedio de 115 mL y tiempo quirúrgico promedio de 67 minutos. Un paciente con desanclaje del sistema terminó en Girdlestone. No se documentó ninguna complicación neurológica ni infección temprana. CONCLUSIONES: La reducción y fijación de fracturas transtrocantéricas de cadera con clavo centromedular sin mesa de fracturas y en decúbito lateral es factible y con un nivel bajo de complicaciones asociadas.

Liquid-liquid interfacial properties of a symmetrical Lennard-Jones binary mixture.

We determine the interfacial properties of a symmetrical binary mixture of equal-sized spherical Lennard-Jones molecules, σ11 = σ22, with the same dispersive energy between like species, ϵ11 = ϵ22, but different dispersive energies between unlike species low enough to induce phase separation. We use the extensions of the improved version of the inhomogeneous long-range corrections of Janec̆ek [J. Phys. Chem. B 110, 6264 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] and Martínez-Ruiz et al. [J. Chem. Phys. 141, 184701 (2014)], to deal with the interaction energy and microscopic components of the pressure tensor. We perform Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of the symmetrical mixture with different cut-off distances rc and in combination with the inhomogeneous long-range corrections. The pressure tensor is obtained using the mechanical (virial) and thermodynamic route. The liquid-liquid interfacial tension is also evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the test-area methodology. This allows to check the validity of the recent extensions presented to deal with the contributions due to long-range corrections for intermolecular energy and pressure tensor in the case of binary mixtures that exhibit liquid-liquid immiscibility. In addition to the pressure tensor and the surface tension, we also obtain density profiles and coexistence densities and compositions as functions of pressure, at a given temperature. According to our results, the main effect of increasing the cut-off distance rc is to sharpen the liquid-liquid interface and to increase the width of the biphasic coexistence region. Particularly interesting is the presence of a relative minimum in the total density profiles of the symmetrical mixture. This minimum is related with a desorption of the molecules at the interface, a direct consequence of a combination of the weak dispersive interactions between unlike species of the symmetrical binary mixture, and the presence of an interfacial region separating the two immiscible liquid phases in coexistence.

Role of bacteria in marine barite precipitation: a case study using Mediterranean seawater.

Marine bacteria isolated from natural seawater were used to test their capacity to promote barite precipitation under laboratory conditions. Seawater samples were collected in the western and eastern Mediterranean at 250 m and 200 m depths, respectively, since marine barite formation is thought to occur in the upper water column. The results indicate that Pseudoalteromonas sp., Idiomarina sp. and Alteromonas sp. actually precipitate barite under experimental conditions. Barite precipitates show typical characteristics of microbial precipitation in terms of size, morphology and composition. Initially, a P-rich phase precipitates and subsequently evolves to barite crystals with low P contents. Under laboratory conditions barite formation correlates with extracellular polymeric substances (EPS) production. Barite precipitates are particularly abundant in cultures where EPS production is similarly abundant. Our results further support the idea that bacteria may provide appropriate microenvironments for mineral precipitation in the water column. Therefore, bacterial production in the past ocean should be considered when using Ba proxies for paleoproductivity reconstructions.

Effect of dispersive long-range corrections to the pressure tensor: the vapour-liquid interfacial properties of the Lennard-Jones system revisited.

We propose an extension of the improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 110, 6264-6269 (2006)], presented recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2009)] to account for the intermolecular potential energy of spherical, rigid, and flexible molecular systems, to deal with the contributions to the microscopic components of the pressure tensor due to the dispersive long-range corrections. We have performed Monte Carlo simulations in the canonical ensemble to obtain the interfacial properties of spherical Lennard-Jones molecules with different cutoff distances, r(c) = 2.5, 3, 4, and 5σ. In addition, we have also considered cutoff distances r(c) = 2.5 and 3σ in combination with the inhomogeneous long-range corrections proposed in this work. The normal and tangential microscopic components of the pressure tensor are obtained using the mechanical or virial route in combination with the recipe of Irving and Kirkwood, while the macroscopic components are calculated using the Volume Perturbation thermodynamic route proposed by de Miguel and Jackson [J. Chem. Phys. 125, 164109 (2006)]. The vapour-liquid interfacial tension is evaluated using three different procedures, the Irving-Kirkwood method, the difference between the macroscopic components of the pressure tensor, and the Test-Area methodology. In addition to the pressure tensor and the surface tension, we also obtain density profiles, coexistence densities, vapour pressure, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the cutoff distance and the long-range corrections on these properties. According to our results, the main effect of increasing the cutoff distance (at fixed temperature) is to sharpen the vapour-liquid interface, to decrease the vapour pressure, and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases, the width of the tangential microscopic component of the pressure tensor profile increases, and the surface tension increases as the cutoff distance is larger. We have also checked the effect of the impulsive contribution to the pressure due to the discontinuity of the intermolecular interaction potential when it is cut. If this contribution is not accounted for in the calculation of the microscopic components of the pressure tensor, incorrect values of both components as well as a wrong structure along the vapour-liquid interface are obtained.

Effect of molecular flexibility of Lennard-Jones chains on vapor-liquid interfacial properties.

We have determined the interfacial properties of short fully flexible chains formed from tangentially bonded Lennard-Jones monomeric units from direct simulation of the vapor-liquid interface. The results obtained are compared with those corresponding to rigid-linear chains formed from the same chain length, previously determined in the literature [F. J. Blas, A. I. M.-V. Bravo, J. M. Míguez, M. M. Piñeiro, and L. G. MacDowell, J. Chem. Phys. 137, 084706 (2012)]. The full long-range tails of the potential are accounted for by means of an improved version of the inhomogeneous long-range corrections of Janecek [J. Phys. Chem. B 129, 6264 (2006)] proposed recently by MacDowell and Blas [J. Chem. Phys. 131, 074705 (2008)] valid for spherical as well as for rigid and flexible molecular systems. Three different model systems comprising of 3, 5, and 6 monomers per molecule are considered. The simulations are performed in the canonical ensemble, and the vapor-liquid interfacial tension is evaluated using the test-area method. In addition to the surface tension, we also obtained density profiles, coexistence densities, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the chain length and rigidity on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. Comparison between predictions for fully flexible and rigid-linear chains, formed by the same number of monomeric units, indicates that the main effects of increasing the flexibility, i.e., passing from a rigid-linear to a fully flexible chain, are: (a) to decrease the difference between the liquid and vapor densities; (b) to decrease the critical temperature and to increase the critical density; (c) to smooth the density profiles along the interfacial region; (d) to increase the interfacial thickness; and (e) to decrease the vapor-liquid surface tension.

Higher prevalence of meticillin-resistant Staphylococcus aureus among dental students.

In order to test the hypothesis that more dental students are meticillin-resistant Staphylococcus aureus (MRSA) carriers than non-dental students, 100 dental students with five to six years of exposure to patients and 81 non-dental students were tested for nasal and pharyngeal MRSA carriage by polymerase chain reaction. All 181 students were clinically healthy and none had taken antibiotics. Significantly more dental students (20/100) carried MRSA than non-dental students (5/81) (odds ratio: 4.04; 95% confidence interval: 1.6-12.6; P = 0.0033). Also, more dental students' mobile phones (8/100) carried MRSA. All MRSA isolates were distinguished by pulsed-field gel electrophoresis from epidemiologically significant strains. The results suggest that dental students are occupationally exposed to MRSA.

Anthropogenic impact and lead pollution throughout the Holocene in Southern Iberia.

Present day lead pollution is an environmental hazard of global proportions. A correct determination of natural lead levels is very important in order to evaluate anthropogenic lead contributions. In this paper, the anthropogenic signature of early metallurgy in Southern Iberia during the Holocene, more specifically during the Late Prehistory, was assessed by mean of a multiproxy approach: comparison of atmospheric lead pollution, fire regimes, deforestation, mass sediment transport, and archeological data. Although the onset of metallurgy in Southern Iberia is a matter of controversy, here we show the oldest lead pollution record from Western Europe in a continuous paleoenvironmental sequence, which suggests clear lead pollution caused by metallurgical activities since ~3900 cal BP (Early Bronze Age). This lead pollution was especially important during Late Bronze and Early Iron ages. At the same time, since ~4000 cal BP, an increase in fire activity is observed in this area, which is also coupled with deforestation and increased erosion rates. This study also shows that the lead pollution record locally reached near present-day values many times in the past, suggesting intensive use and manipulation of lead during those periods in this area.

Universal scaling behaviour of surface tension of molecular chains.

We use and extend the universal relationship recently proposed by Galliero [G. Galliero, J. Chem. Phys. 133, 074705 (2010)], based on a combination of the corresponding-states principle of Guggenheim [E. A. Guggenheim, J. Chem. Phys. 13, 253 (1945)] and the parachor approach of Macleod [J. Macleod, Trans. Faraday Soc. 19, 38 (1923)], to predict the vapour-liquid surface tension of fully flexible chainlike Lennard-Jones molecules. In the original study of Galliero, the reduced surface tension of short-chain molecules formed by up to five monomers is expressed as a unique function of the difference between the liquid and vapour coexistence densities. In this work, we extend the applicability of the recipe and demonstrate that it is also valid for predicting the surface tension of two different chainlike molecular models, namely, linear tangent chains that interact through the Lennard-Jones intermolecular potential and fully flexible chains formed by spherical segments interacting through the square-well potential. Computer simulation data for vapour-liquid surface tension of fully flexible and rigid linear Lennard-Jones, and fluid flexible square-well chains is taken from our previous works. Our results indicate that the universal scaling relationship is able to correlate short- and long-chain molecules with different degrees of flexibility and interacting through different intermolecular potentials.

Removal of primary tumor improves survival in metastatic breast cancer. Does timing of surgery influence outcomes?

BACKGROUND: Resection of intact primary tumor is controversial in metastatic breast cancer patients. The aim of this study is to review the impact of surgical resection of primary tumor on overall survival and to assess the role of timing of surgery on survival rates. METHODS: 208 patients with metastatic breast cancer diagnosed between 1982 and 2005 in the Hospital Clinico of Valencia (Spain) were analysed. Exclusion criteria were age >80, PS 3-4, Charlson score 3 or follow-up < 90 days. 123 of these underwent surgery and 85 did not. In order to assess the role of timing, the "surgery" cohort was divided into two sub-groups: "before" (n = 78) or "after" (n = 45) diagnosis of disseminated disease. RESULTS: In the surgery group, patients underwent mastectomy with axillary dissection (82.9%), without axillary dissection (8.9%) and conservative surgery (8.1%). After a median follow-up of 29.68 months, median OS in the "surgery" and the "non-surgery" groups were, 40.4 and 24.3 months. Removal of the primary tumor therefore had a significant positive impact on survival rates (p < 0.001). Benefits of surgery were observed mainly in patients with visceral disease (p = 0.005); no statistical differences were found in those with bone disease (p = 0.79). Univariate analysis for overall survival (OS) identified surgery, performance status, clinical T stage, hormone receptors and number and type of metastases as variables that impacted on survival. In the multivariate test, only resection of primary tumor and estrogen receptors maintained statistical significance, surgery having a protective effect with an HR 0.52 (95% CI 0.35-0.77). No differences in survival were found between the two sub-groups according to the timing of surgery: "before" vs "after"(p = 0.996). CONCLUSIONS: Resection of primary tumor should be considered not only as a palliative or preventive strategy but also as an approach that possibly contributes to the control of the disease in selected patients.

Impact of a mammography screening programme on the breast cancer population of the Region of Valencia (Spain)

OBJECTIVE: Randomised clinical trials with a control arm of non-screened patients are nowadays ethically impossible. The aim of this study was to establish the impact of mammography screening on a non-selected population. PATIENTS AND METHODS: Between January 1993 and December 2002, 3662 patients were included, 2313 in the screened group and 1349 in the unscreened group. RESULTS: 55.3% of the screened patients were diagnosed in stage I vs. 26.1% in the non-screened group. The proportion of stage III-IV was 4.6% and 19.8% for the screened and unscreened groups respectively (p<0.001). 48.8% in the screening group were submitted to mastectomy vs. 66.4% of the unscreened patients (p<0.001). Overall survival was superior for the prevalent cases in the screening group, with a relative risk of 0.49, and was not significant for the incident cases. CONCLUSIONS: Diagnosis of breast cancer in the mammography screening programme of the Region of Valencia significantly increases conservative surgery rates and suggests an improvement in survival in prevalent cases. The increased rate of early stages in these patients could be the main reason of this benefit (AU)

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[Sciatic nerve block with 1% mepivacaine for foot surgery: posterior versus lateral approach to the popliteal fossa]. / Estudio comparativo del bloqueo del nervio ciático en el hueco poplíteo por abordaje posterior frente al abordaje lateral con mepivacaína al 1% para cirugía del pie.

AIMS: To compare the efficacy and feasibility of the sciatic nerve block performed using either a posterior or a lateral approach to the popliteal fossa, taking into consideration patient comfort during puncture and postoperative analgesia. PATIENTS AND METHODS: Sixty patients scheduled for foot surgery were randomly assigned to 2 groups: a posterior approach was used in performing the sciatic nerve block in 1 group (n = 30) and a lateral approach was in the other group (n = 30). The local anesthetic employed was mepivacaine 1%. RESULTS: Duration of sensory block was used significantly longer with the lateral approach (5.4 hours, range 3.3-8 hours) than with the posterior approach (4.4 hours, range 1.5-7 hours) (P < 0.001). Time to onset of the block was significantly shorter with the lateral approach (10 minutes, range 5-25 minutes) than with the posterior approach (17 minutes, range 4-45 minutes) (P < 0.01). Quality of the blockade was similar with both approaches. CONCLUSIONS: The lateral approach to the block of the sciatic nerve in the popliteal fossa provides analgesia comparable to that obtained with the posterior approach, with a faster onset and longer postoperative duration.

Effect of environmental temperature on tissue lead accumulation in mice repeatedly treated with lead acetate.

The effect of environmental temperature on lead accumulation in tissues of mice repeatedly treated with lead acetate (2 mg/kg per day and 5 mg/kg per day) for 3 or 6 weeks was studied. In blood, kidney and liver, the amount of lead accumulated after 3 weeks of treatment was markedly higher in animals exposed to 22 degrees C than those maintained at 35 degrees C. Conversely, when the treatment was extended to 6 weeks, lead concentrations in the liver and kidney were equal or higher respectively, in the mice exposed to 35 degrees C. In the brain, lead concentration was lower than that found in kidney and liver and it was independent of dose and ambient temperature of lead being higher at 35 degrees C than at 22 degrees C. These results demonstrate that environmental temperature influences the amount of lead accumulated in some rodent tissues, and that the duration of the treatment modifies the effect produced by temperature, suggesting that the changes elicited during the period of acclimation to the hot environment could be responsible for these findings.