[Neuropsychology of event-based prospective memory]. / Neuropsicologia de la memoria prospectiva basada en el evento.

INTRODUCTION: Prospective memory is the capacity to remember actions that are to be performed in the future. Different studies from experimental neuropsychology attempt to unravel the neurocognitive processes underlying event-based prospective memory, that is, delayed actions that take place in a predetermined context, which would play the role of an external cue and would therefore contribute to successful intentional recall. DEVELOPMENT: Taking the dynamism and flexibility of multiprocess theory as a reference, the main findings have highlighted the fact that prospective memory is influenced by, among other factors, the type of cue. Thus, when the cue is focal, the person tends to rely on spontaneous retrieval. In contrast, when the cue is not focal, there is usually a tendency towards monitoring. In parallel to this, studies in experimental neuropsychology have determined that the anterior prefrontal cortex and the dorsal frontoparietal network would participate in the cue monitoring processes. Conversely, the ventral frontoparietal network would intervene in automatic retrieval processes. Moreover, the role of the parietal lobe and the medial temporal lobe in prospective tasks is discussed. CONCLUSION: This study defends the idea that both processing pathways (monitored and spontaneous) favour success in recalling the event-based intentional action. It must nevertheless be borne in mind that the moment a person decides to set one type of processing (or another) in motion it is influenced by the type of cue.

TITLE: Neuropsicologia de la memoria prospectiva basada en el evento.Introduccion. La memoria prospectiva es la capacidad para recordar las acciones que se han de ejecutar en el futuro. Diferentes investigaciones provenientes de la neuropsicologia experimental intentan dilucidar los procesos neurocognitivos subyacentes a la memoria prospectiva basada en el evento, esto es, las acciones demoradas que tienen lugar en un contexto predeterminado, el cual asumiria el papel de clave externa y, por tanto, contribuiria al exito en el recuerdo intencional. Desarrollo. Tomando como referencia el dinamismo y la flexibilidad de la teoria multiproceso, los principales hallazgos han subrayado que el recuerdo prospectivo esta influido, entre otros factores, por el tipo de clave. Asi, cuando la señal es focal, la persona tiende a confiar en los procesos de recuperacion espontanea. Por otro lado, cuando la señal es no focal, suele haber una tendencia a la monitorizacion. De forma paralela, los estudios en neuropsicologia experimental han distinguido que la corteza prefrontal anterior y la red frontoparietal dorsal participarian en los procesos de monitorizacion de la señal. Por otro lado, la red frontoparietal ventral intervendria en los procesos de recuperacion automatica. Se discute ademas el papel del lobulo parietal y el lobulo temporal medial en las tareas prospectivas. Conclusion. El presente trabajo aboga por que las dos vias de procesamiento (monitorizado y espontaneo) favorecen el exito en el recuerdo de la accion intencional basada en el evento. No obstante, conviene tener muy en cuenta que el momento en el que la persona decide poner en marcha un tipo de procesamiento (u otro) esta influido por el tipo de señal.

A novel monoclonal antibody-based enzyme-linked immunosorbent assay to determine luteinizing hormone in bovine plasma.

The development of a novel enzyme-linked immunosorbent assay (ELISA) for determining luteinizing hormone (LH) in bovine plasma is described. Anti-bovine LH (bLH) monoclonal antibodies (mAbs) were produced and characterized. One mAb recognizing the bLH ß subunit was used for immunoaffinity purification of substantial amounts of biologically active bLH from pituitary glands. The purified bLH in combination with 2 anti-bLH ß subunit mAbs was used to develop a sandwich ELISA, which satisfied all the criteria required to investigate LH secretory patterns in the bovine species. The ELISA standard curve was linear over the range 0.05 to 2.5 ng/mL, and the assay proved suitable for measuring bLH in plasma without any prior treatment of samples. Cross-reactivity and recovery tests confirmed the specificity of the method. The intra- and inter-assay coefficients of variation ranged between 3.41% and 9.40%, and 9.29% and 15.84%, respectively. The analytical specificity of the method was validated in vivo by provocative tests for LH in heifers, using the LH releasing peptide gonadotropin-releasing hormone. In conclusion, the adoption of mAbs for this ELISA for coating the wells and labeling, combined with the easy one-step production of reference bLH, ensures long-term continuity in large-scale measurements of LH in the bovine species.

Digit loss due to Demodex spp. infestation in a dog: clinical and pathological features.

Here we describe a rare clinical manifestation of canine pododemodicosis. A dog was presented with pedal erythema, scaling, crusting, severe edema and digit loss. The following diseases were taken into account for the differential diagnosis: pododemodicosis, lethal acrodermatitis, zinc responsive dermatosis and pemphigus foliaceus. Results from skin biopsies revealed the presence of Demodex spp. of mites in the follicular infundibula and a severe inflammatory process (pododemodicosis). Upon the acaricidal treatment, the patient exhibited favorable signs of clinical improvement.

Agarose cell block technique as a complementary method in the diagnosis of fungal osteomyelitis in a dog.

A 7-year-old Labrador Retriever female dog presenting left forelimb lameness for one day was admitted to the Veterinary Hospital (UNESP-Botucatu) for clinical evaluation. Several tests, including blood and image analysis, microbiological culture and cytology of lytic areas of affected bone were made in order to establish a diagnosis. Serum biochemical profile revealed increased levels of liver enzymes, plasma globulin, creatine kinase (CK) and calcium. Hemogram revealed anemia and leukocytosis; left humerus image analysis revealed an osteolytic lesion and cytology revealed a suppurative periostitis. Differential diagnosis was a nonspecific infectious inflammatory process or osteosarcoma. Since it was not possible to achieve a definitive diagnosis and there was a highly suspicious for an infectious agent, an agarose cell block of the bone marrow fine-needle aspiration was made. The cytological examination of cell block presented similar findings as described previously. However, additional stains including periodic acid-Schiff (PAS) were positive for fungal hyphae, which rendered a diagnosis of fungal osteomyelitis due to Aspergillus spp. This case report illustrates an uncommon cause of osteomyelitis for breed that was diagnosed by an underused method in veterinary medicine.

Pulmonary maturation in canine foetuses from early pregnancy to parturition.

Development of the foetal respiratory system includes both pulmonary growth and maturation. In human medicine, a higher incidence of respiratory distress is reported in newborn males. This study aimed to identify different phases of canine foetal lung maturation throughout pregnancy, to determine the stage of pregnancy in which surfactant production begins and to compare pulmonary development of male and female foetuses. Pregnant bitches (34) were subjected to elective ovariohysterectomy and allocated into four groups, according to the stage of pregnancy: 30-40 days of pregnancy (n = 10), 41-50 days (n = 10), 51-60 days (n = 10) and bitches in the first stage of parturition (n = 4). Foetal lungs were histologically processed and evaluated by optical microscopy. The pseudoglandular phase was identified between the 35th day and 46th day of gestation; the onset of canalicular and saccular periods was observed, respectively, from the 48th day and 60th day of pregnancy. Lungs from foetuses at term were in the saccular phase; thus, the development into the alveolar period occurs in the neonatal period. The histological analyses revealed that respiratory tract development is centrifugal, from upper to lower airways. Therefore, it is possible to identify distinct development periods in different portions of the same organ. In conclusion, the saccular phase of lung development begins around 57 and 60 days of pregnancy, the period in which surfactant production is believed to occur. Male and female foetuses present similar pulmonary development from early pregnancy until parturition.

Electrophysiological response to dialysis: the role of dialysate potassium content and profiling.

UNLABELLED: The task of dialysis therapy is, amongst other things, to remove excess potassium (K+) from the body. The need to achieve an adequate K+ removal with the risk of cardiac arrhythmias due to sudden intra-extracellular K+ gradient advises the distribution of the removal throughout the dialysis session instead of just in the first half. The aim of the study was to investigate the electrical behavior of two different K+ removal rates on myocardial cells (risk of arrhythmia and ECG alterations). Constant acetate-free biofiltration (AFB) and profiled K+ (decreasing during the treatment) AFB (AFBK) were used in a patient sample to understand, first of all, the effect on premature ventricular contraction (PVC) and on repolarization indices [QT dispersion (QTd) and principal component analysis (PCA)]. The study was divided into two phases: phase 1 was a pilot study to evaluate K+ kinetics and to test the effect on the electrophysiological response of the two procedures. The second phase was set up as an extended cross-over multicenter trial in patient subsets prone to arrhythmias during dialysis. Phase 1: PVC increased during both AFB and AFBK but less in the latter in the middle of dialysis (298 in AFB vs. 200 in AFBK). The PVC/h in a subset of arrhythmic patients was 404 +/- 145 in AFB and 309 +/- 116 in AFBK (p = 0.0028). QT interval (QTc) prolongation was less pronounced in AFBK than in AFB. Phase 2: The PVC again increased in both AFB and AFBK but less in the latter mid-way through dialysis (79 +/- 19 AFB vs. 53 +/- 13 AFBK). Moreover, in the most arrhythmic patients the benefit accruing from the smooth K+ removal rate was more pronounced (103 +/- 19 in AFB vs. 78 +/- 13 in AFBK). CONCLUSION: It is not the K+ dialysis removal alone that can be destabilizing from an electrophysiological standpoint, but rather its removal dynamics. This is all the more evident in patients with arrhythmias who benefit from the K+ profiling during their dialysis treatment.

[Acetate free biofiltration (AFB) and ionic dialysance]. / AFB e dialysance ionica.

Among various methods and models to evaluate the dialysis dose, the on-line measure of ionic dialysance gives good results. Compared to measured KT/V, ionic dialysance does not require blood sampling and, consequently, it reduces the risks and the costs. Functional evaluations during acetate free biofiltration (AFB treatments) confirm the usefulness of the on-line continuous measure by biosensors, especially when they are integrated in the dialysis machinery.

Physical methods for preventing deep vein thrombosis in stroke.

BACKGROUND: Deep vein thrombosis (DVT) and resulting pulmonary embolism (PE) are uncommon but important complications of stroke. There is good evidence that anticoagulants can reduce the risk of DVT and PE after stroke, but this benefit is offset by a small but definite risk of serious haemorrhages. Physical methods to prevent DVT and PE (such as compression stockings applied to the legs) are not associated with any bleeding risk and are effective in some categories of medical and surgical patients. We sought to assess their effects in stroke patients. OBJECTIVES: To assess the effectiveness and safety of physical methods of preventing the onset of deep vein thrombosis and fatal or non fatal pulmonary embolism in patients with recent stroke. SEARCH STRATEGY: We searched the Cochrane Stroke Group trials register (last searched June 2003). In addition we searched the following electronic bibliographic databases: Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 2, 2003), MEDLINE (1966 to June 2003), EMBASE (1980 to June 2003) and CINAHL (1982 to June 2003). The reference lists of all relevant papers were screened for additional trials. SELECTION CRITERIA: Unconfounded randomised controlled trials comparing physical methods for the prevention of DVT with control, in which prophylaxis was started within seven days of the onset of stroke. DATA COLLECTION AND ANALYSIS: Two reviewers independently searched for relevant trials and three others independently checked the results. MAIN RESULTS: We identified two small trials which included 123 patients. In one trial of 97 patients, compression stockings were associated with a non significant trend towards a reduction in DVT detected by Doppler ultrasound. In one trial of 26 patients, an intermittent pneumatic compression device was not associated with a significant reduction in DVT detected by 125-I-fibrinogen scanning. Overall, physical methods were not associated with a significant reduction in DVT during the treatment period in survivors (Odds ratio (OR) 0.54, 95% Confidence Interval (CI) 0.18 to 1.57) or death (OR 1.54, 95% CI 0.5 to 4.77). REVIEWERS' CONCLUSIONS: There is insufficient evidence from randomised trials to support the routine use of physical methods for preventing DVT in acute stroke.

Polychlorinated biphenyls in colostral milk and visual function at 12 months of life.

BACKGROUND AND AIMS: Environmental contaminants such as persistent organic chlorines and heavy metals, which are supplied to the foetus by transplacental transfer and to breastfed infants by the milk, may impair cognitive functions. Long-chain polyunsaturated fatty acids, which are known to enhance development during foetal life and early infancy, may counteract the toxic effect of environmental contaminants. In this study, we have investigated whether polychlorinated biphenyls (PCBs) impair early development of vision, and whether such impairment can be modulated by essential long-chain polyunsaturated fatty acids. MATERIAL: Healthy term infants born in Milan and its surroundings, and who were exclusively breastfed for at least 4 mo, were prospectively examined up to the age of 12 mo. METHODS: Samples from colostrums, the first 2 d after delivery, and of mature breast-milk after 1 and 3 mo were collected. The samples were analyzed for PCB 105, 118, 138, 153, 156 and 180 and for DDT and DDE. In all infants, the plasma levels of the long-chain polyunsaturated fatty acids (LC-PUFAs), C18:2 n-6, C18:3 n-3, C20:4 n-6, C20:5 n-3 and C22:6 n-3 were analysed within the first three postnatal days. The PCB levels in colostral milk, as well as of LC-PUFAs in plasma, were considered to mirror perinatal supply. Visual function was evaluated by P100 with latency evoked potentials (VEPs) at 12 mo of age. Statistical analysis was based on simple and partial correlation coefficients (p < 0.05). RESULTS: On bivariate analysis, wave latency VEP at 15 min was significantly related to the colostral levels of DDT, DDE and all examined PCBs except PCB 105 (with correlation coefficient r = 0.401 to 0.618), whereas P100 wave latency VEP at 60 min was related to DDT (r = 0.513) and PCB 180 (r = 0.504). Infant plasma levels of C22:6 n-3 were inversely associated with P100 wave latency at 60 min (r = -0.418) and at 1Hz-2J (r = -0.466). After controlling for C22:6 n-3, the partial correlation coefficient of P100 wave latency VEP at 15 min to the colostral level of PCB 180 was 0.403 (p = 0.07). CONCLUSION: Within the population of this study, a weak relation was found between impaired visual function at 12 mo of age of healthy infants and the levels of PCBs, DDT and DDE in colostral milk. The effect of impairment was no longer evident after controlling for the plasma level of LC-PUFAs as found in the infant a few days after birth.

Earlier smoking habits are associated with higher serum lipids and lower milk fat and polyunsaturated fatty acid content in the first 6 months of lactation.

OBJECTIVE: To investigate the relation between maternal smoking habits, plasma lipids and milk fatty acid (FA) content and composition. DESIGN: Breastfeeding mothers who gave birth to healthy, full-term infants were recruited. Mothers were interviewed on smoking habits, being defined smokers (S) when usually smoking at least five cigarettes per day before pregnancy. SETTING: Department of Pediatrics, San Paolo Hospital, Milan, Italy. SUBJECTS: In total, 92 mothers: 61 non-S (NS) and 31 S. INTERVENTIONS: Pooled hindmilk was collected at the first raise of milk (colostrum stage), 1, 3 and 6 months, and total lipid (TL) content and fatty acid (FA) composition were evaluated. Maternal dietary habits were assessed by a food-frequency questionnaire. Two subsamples (16 NS, 6 S) were investigated after delivery and at 3 months for serum lipids and FA status. At 6 months after delivery, the number of mothers still breastfeeding decreased to 30. Variables were compared using nonparametric tests. RESULTS: In smoking mothers serum levels of triglycerides, cholesterol and low-density lipoproteins were higher, while those of high-density lipoproteins were lower. TL content in breast milk was similar in the two groups just after delivery but higher in milk from NS at 1 month. TL content and FA absolute amounts of linoleic, arachidonic, alpha-linolenic and docosahexaenoic (DHA) acid in breast milk were lower in S vs NS 1 month after delivery. Also 3 months after delivery, the breast milk of smoking mothers contained less DHA than the breast milk of nonsmoking mothers. CONCLUSIONS: Maternal cigarette smoking in early pregnancy is associated with higher plasma lipid levels and lower milk TL and DHA content in the first months of lactation.

Physical methods for preventing deep vein thrombosis in stroke.

BACKGROUND: Deep vein thrombosis (DVT) and resulting pulmonary embolism (PE) are uncommon but important complications of stroke. There is good evidence that anticoagulants can reduce the risk of DVT and PE after stroke, but this benefit is offset by a small but definite risk of serious haemorrhages. Physical methods to prevent DVT and PE (such as compression stockings applied to the legs) are not associated with any bleeding risk and are effective in some categories of medical and surgical patients. We sought to assess their effects in stroke patients. OBJECTIVES: To assess the effectiveness and safety of physical methods of preventing the onset of deep vein thrombosis and fatal or non fatal pulmonary embolism in patients with recent stroke. SEARCH STRATEGY: We searched the Cochrane Stroke Group Trials Register (last searched October 2001). In addition we searched the following electronic bibliographic databases: Cochrane Controlled Trials Register (1999, Issue 3), MEDLINE (1966- Jan 2001), EMBASE (1980- Jan 2001) and CINAHL (1982-May 1999). The reference lists of all relevant papers were screened for additional trials. SELECTION CRITERIA: All completed randomised unconfounded trials or controlled clinical trials comparing physical methods in patients allocated to receive physical methods, applied within one week of onset of stroke, with patients allocated to no physical methods. DATA COLLECTION AND ANALYSIS: Two reviewers independently searched for relevant trials and three others independently checked the results. MAIN RESULTS: We identified two small trials which included 123 patients. In one trial of 97 patients, compression stockings were associated with a non significant trend towards a reduction in DVT detected by Doppler ultrasound. In one trial of 26 patients, an intermittent pneumatic compression device was not associated with a significant reduction in DVT detected by 125-I-fibrinogen scanning. Overall, physical methods were not associated with a significant reduction in DVT (Odds ratio 0.59, 95%.CI 0.24-1.48) or death (Odds ratio 5.06, 95% CI 0.96-26.78). REVIEWER'S CONCLUSIONS: There is insufficient evidence from randomised trials to support the routine use of physical methods for preventing DVT in acute stroke.

Growth pattern of breastfed and nonbreastfed infants with atopic dermatitis in the first year of life.

OBJECTIVE: The growth of infants with atopic dermatitis (AD) has been poorly investigated based on the early type of feeding. The aim of this study was to assess the growth pattern of AD infants during the first 12 months of life in comparison to healthy infants, according to the early type of feeding (breastfed or nonbreastfed). METHODS: Fifty-five term AD infants (36 breastfed and 19 nonbreastfed) and 114 term healthy infants (58 breastfed and 56 nonbreastfed) were evaluated by standardized growth indices (z scores; National Center for Health Statistics-World Health Organization data) through the first 12 months of life. RESULTS: No difference was found between AD and healthy groups at birth. In AD infants, weight (WA) and length (LA) z scores decreased with age and were significantly lower, compared with healthy infants from the second month of age onward. The difference of mean z scores between AD and healthy infants at 12 months of age was -.69 (95% confidence interval [CI]: -1.00 to -.38) for WA and -.67 (95% CI: -.98 to -.36) for LA. The growth pattern of AD infants was not influenced by the early type of feeding, whereas in the 6- to 12-month period, the delay in growth was more pronounced in patients with more severe dermatitis. CONCLUSIONS: In the first year of life, AD infants show a progressive impairment in growth irrespective of the early type of feeding. The severity of disease may be an independent factor negatively influencing growth.

Growth patterns of breast fed and formula fed infants in the first 12 months of life: an Italian study.

AIM: To compare the growth patterns of breast fed and formula fed Italian infants in the first 12 months of life using World Health Organisation (WHO) reference data. METHODS: The growth patterns of 73 breast fed infants (36 male, 37 female) and 65 formula fed infants (35 male, 30 female) were compared. Solid foods were introduced with the same weaning schedules from the 5th month in both groups. The weight for age (WA), length for age (LA), and weight for length (WL) z scores (National Center for Health Statistics-WHO data) were calculated at birth, 1, 2, 3, 4, 6, 9, and 12 months. RESULTS: Breast fed infants had the highest z scores (WA, WL) at birth. Breast fed groups had significantly higher growth indices at 1 month (WA, LA), 2 months (WA) and 3 months (WA, LA) of age. Compared to breast fed groups, formula fed infants showed significantly higher WA z score changes in the 1-2, 2-3, 3-4, and 4-6 month intervals. LA z score changes were higher for breast fed infants at 0-1 month and for the formula fed infants at 4-6 months. In the 6-12 month interval growth indices progressively increased for the formula fed infants and declined for infants breast fed for longer (12 months). The 0-12 month changes in WA, LA, and WL z scores were positive for formula fed infants and negative for the 12 month breast fed group. Nevertheless, the 12 month breast fed group showed an absolute WA z score just below 0 (mean (SEM) -0.04 (0.26)) at 12 months. CONCLUSION: The growth pattern of breast fed and formula fed Italian infants differs in the first 12 months of life. This questions the validity of current reference values for monitoring the growth of breast fed infants. Growth indices in breast fed groups, high at birth and closer than expected to the reference at 12 months, may reflect differences in genetic factors, intrauterine conditions, or both.

High-order behaviour in learning gate networks with lateral inhibition.

In this work we present a neural network model incorporating activity-dependent presynaptic facilitation with multidimensional inputs. The processing unit used is based on a slightly simplified version of the Learning Gate Model proposed by Ciaccia et al. (1992). The network topology integrates a well-known biological neural circuit with a lateral inhibition connection subnet. By means of simulation experiments, we show that the proposed networks exhibit basic and high-order features of associative learning. In particular, overshadowing and blocking are reproduced in the presence of both noise-free and noisy inputs. The role of noise in the development of high-order learning capabilities is also discussed.

Analytic solution of the Variable-Volume Double-Pool urea kinetics model applied to parameter estimation in hemodialysis.

An analytic solution of the Variable-Volume Double-Pool urea kinetics model and its application to the estimation of clinically relevant parameters of the patient-machine system, are presented. These include the urea distribution volume and generation rate and the mean dialyzer clearance. The estimation of these parameters is based on the assumption of constant values for the diffusion coefficient between the two pools and the intra-extracellular volume ratio. Results obtained by computer simulations show that the effect of a +/- 50% variation of these parameters influences the estimates less than standard measurement errors. Starting from these results, four methods to in vivo estimate the urea distribution volume and generation rate from blood samples are compared. Two methods are based on the analytic solution of the double-pool model using seven samples (reference method) or three samples (new clinical method). The remaining methods are based on urea mass-balance and are largely used in the clinical practice. These last techniques differ from each other for the blood sample taken at the end of the treatment or 30 min later. The results obtained from hemofiltration sessions show that the urea generation rate is accurately estimated by all methods. The total distribution volume is still accurately estimated by the new clinical method while it is systematically underestimated by the urea mass-balance when the blood sample at the end of dialysis is used. Instead, a high overcompensation results using the blood sample taken 30 min after the end of dialysis. Finally, the new clinical method also provides reliable estimates for the dialyzer clearance starting from only three blood samples all taken during dialysis.

Estimation of beta-cell sensitivity from intravenous glucose tolerance test C-peptide data. Knowledge of the kinetics avoids errors in modeling the secretion.

Parametric models of insulin secretion are used to measure indexes of beta-cell function from plasma C-peptide concentration during an intravenous glucose tolerance test (IVGTT). Since the models have been usually assessed against plasma C-peptide data, both secretory and kinetic parameters need to be simultaneously estimated. However, undesired compensations between the two sets of parameters may arise. In this study, in order to evaluate IVGTT insulin secretion models, we have analyzed IVGTT data from seven normal subjects for whom individual C-peptide kinetics were known from a separate experiment. Three different beta-cell models have been examined: the minimal model M1 (Diabetes 37:223-231, 1988); a variation of a published model, M2 (Math Biosci 27:319-332, 1975); and a new one, M3. A two-compartment model was used to describe C-peptide kinetics. The results suggest the inadequacy of M1 since kinetic parameter estimates were consistently biased versus the known individual values, and systematic errors were present in the prediction of C-peptide data when kinetic parameters were fixed to the known individual values. M2 performs better than M1 since it reproduces C-peptide data satisfactorily when the individually known description of the kinetics is adopted. M3 retains the second-phase description of M2 but improves the description of first-phase release. M3 is thus proposed to reconstruct the insulin secretion time course and to estimate parameters of first- and second-phase sensitivity to glucose. We also show the robustness of M3, i.e., standard values of C-peptide kinetic parameters can be used when individual values are not available without a loss of accuracy in the estimated secretion parameters. Finally, the shortcomings of using a simplified single-compartment description of C-peptide kinetics are discussed.

On-line estimation and prediction of urea kinetics during hemodialysis: a simulation approach.

A new method for the on-line estimation of urea kinetic parameters from blood urea concentration (BUN) continuously measured during a dialysis session is proposed. The method, based on the variable-volume double-pool model, is evaluated through a simulation approach in order to easily consider a large set of well-controlled test conditions. The model is characterized by six parameters, knowledge of which enables early prediction of the end dialysis urea concentration and the dose of dialysis. The sensitivity of the model predicted BUN with respect to the parameters was first analyzed to investigate which can be reliably estimated from blood urea measurements taken at a suitable rate. This analysis showed that the model predicted BUN is highly sensitive to the initial blood urea concentration and to the dialyzer clearance, normalized with respect to the total initial distribution volume, while it is scarcely influenced by the normalized ultrafiltration and urea generation rates. The new on-line estimation technique keeps these two last parameters constant and takes advantage of an original analytic solution of the second order urea kinetics. The results of the estimation process on realistic simulated data showed that the proposed method provides early and reliable estimates of the normalized clearance and of the end dialysis concentration. The transcellular mass transfer coefficient and the intra-extra cellular volume ratio can also be estimated, although with less accuracy. Moreover, it was shown that the use of the single-pool model, instead of the double-pool one, provides systematic errors on the estimates.