Inference for a discretized stochastic logistic differential equation and its application to biological growth.

In this paper, we present a method to adjust a stochastic logistic differential equation (SLDE) to a set of highly sparse real data. We assume that the SLDE have two unknown parameters to be estimated. We calculate the Maximum Likelihood Estimator (MLE) to estimate the intrinsic growth rate. We prove that the MLE is strongly consistent and asymptotically normal. For estimating the diffusion parameter, the quadratic variation of the data is used. We validate our method with several types of simulated data. For more realistic cases in which we observe discretizations of the solution, we use diffusion bridges and the stochastic expectation-maximization algorithm to estimate the parameters. Furthermore, when we observe only one point for each path for a given number of trajectories we were still able to estimate the parameters of the SLDE. As far as we know, this is the first attempt to fit stochastic differential equations (SDEs) to these types of data. Finally, we apply our method to real data coming from fishery. The proposed adjustment method can be applied to other examples of SDEs and is highly applicable in several areas of science, especially in situations of sparse data.

Glenoid track «off-track¼ as a risk factor for recurrence of anterior glenohumeral instability in postoperative patients / El encarrilamiento glenoideo off-track como factor de riesgo de recidiva de inestabilidad glenohumeral en pacientes postoperados

Abstract: Introduction: Glenoid track is used to assess the engagement of Hill-Sachs lesions. The objective of this study was to identify if off-track glenoid track was a risk factor for recurrence of anterior glenohumeral instability in postoperative patients with arthroscopic anterior labrum repair. Material and methods: Sixty patients with glenohumeral instability who underwent arthroscopic repair of the anterior labrum were studied. Study group (patients with recurrence of postoperative dislocation) and control (no dislocation). Radiographic measurements were made on magnetic resonance imaging and computed tomography. Measurements of glenoid diameter, glenoid bone loss, as well as the presence and size of Hill-Sachs lesions were obtained. Later they were classified as «on-track¼ or «off-track¼. Results: Seven (11.67%) patients suffered recurrence, of which six (10%) were carriers of an off-track injury and 1 (1.67%) on-Track. 53 (88.33%) patients did not experience recurrence, of which 11 (18.33%) were carriers of an off-track injury and 42 (70%) on track. A 23.47 increased risk of recurrence of instability was interpreted in patients with «off-track¼ lesions compared to patients with «On track¼ lesions. Conclusions: Off-track injuries were a risk factor for recurrence of instability in patients who underwent Bankart-type arthroscopic repair. This allows us to recommend that the presence of lesions be routinely studied and classified as «on-track¼ or «off-track¼ to provide a better therapeutic approach.

Resumen: Introducción: El encarrilamiento glenoideo se emplea para valorar el enganche de lesiones Hill-Sachs. El objetivo de este estudio fue identificar si el encarrilamiento glenoideo off-track fue un factor de riesgo de recidiva de inestabilidad glenohumeral anterior en pacientes postoperados de reparación de labrum anterior por vía artroscópica. Material y métodos: Se estudiaron 60 pacientes sometidos a reparación artroscópica del labrum anterior. Grupo de estudio (pacientes con recidiva de luxación postoperatoria) y control (sin luxación). Las mediciones radiográficas se realizaron en resonancia magnética y en tomografía axial computarizada. Se obtuvieron mediciones del diámetro glenoideo, pérdida ósea glenoidea así como la presencia y tamaño de lesiones de Hill-Sachs. Posteriormente se clasificaron como on-track u off-track. Resultados: Siete (11.67%) pacientes sufrieron recidiva, de los cuales seis (10%) eran portadores de lesión off-track y uno (1.67%) on-track. 53 (88.33%) pacientes sin recidiva, de los cuales 11 (18.33%) eran portadores de lesión off-track y 42 (70%) on-track. Se interpretó un aumento de riesgo de recidiva de inestabilidad de 23.47 en los pacientes portadores de lesión de tipo off-track en comparación con los pacientes portadores de lesiones on-track. Conclusiones: Las lesiones off-track fueron un factor de riesgo de recidiva de inestabilidad en los pacientes a quienes se realizó reparación artroscópica tipo Bankart, lo cual nos permite recomendar que de forma rutinaria se estudie la presencia de lesiones y clasificarlas como on-track u off-track para brindar un mejor abordaje terapéutico.

Glenoid track ''off-track'' as a risk factor for recurrence of anterior glenohumeral instability in postoperative patients.

INTRODUCTION: Glenoid track is used to assess the engagement of Hill-Sachs lesions. The objective of this study was to identify if off-track glenoid track was a risk factor for recurrence of anterior glenohumeral instability in postoperative patients with arthroscopic anterior labrum repair. MATERIAL AND METHODS: Sixty patients with glenohumeral instability who underwent arthroscopic repair of the anterior labrum were studied. Study group (patients with recurrence of postoperative dislocation) and control (no dislocation). Radiographic measurements were made on magnetic resonance imaging and computed tomography. Measurements of glenoid diameter, glenoid bone loss, as well as the presence and size of Hill-Sachs lesions were obtained. Later they were classified as "on-track" or "off-track". RESULTS: Seven (11.67%) patients suffered recurrence, of which six (10%) were carriers of an off-track injury and 1 (1.67%) on-Track. 53 (88.33%) patients did not experience recurrence, of which 11 (18.33%) were carriers of an off-track injury and 42 (70%) on track. A 23.47 increased risk of recurrence of instability was interpreted in patients with "off-track" lesions compared to patients with "On track" lesions. CONCLUSIONS: Off-track injuries were a risk factor for recurrence of instability in patients who underwent Bankart-type arthroscopic repair. This allows us to recommend that the presence of lesions be routinely studied and classified as "on-track" or "off-track" to provide a better therapeutic approach.

INTRODUCCIÓN: El encarrilamiento glenoideo se emplea para valorar el enganche de lesiones Hill-Sachs. El objetivo de este estudio fue identificar si el encarrilamiento glenoideo. MATERIAL Y MÉTODOS: off-track fue un factor de riesgo de recidiva de inestabilidad glenohumeral anterior en pacientes postoperados de reparación de labrum anterior por vía artroscópica. Se estudiaron 60 pacientes sometidos a reparación artroscópica del labrum anterior. Grupo de estudio (pacientes con recidiva de luxación postoperatoria) y control (sin luxación). Las mediciones radiográficas se realizaron en resonancia magnética y en tomografía axial computarizada. Se obtuvieron mediciones del diámetro glenoideo, pérdida ósea glenoidea así como la presencia y tamaño de lesiones de Hill-Sachs. Posteriormente se clasificaron como. RESULTADOS: on-track u off-track. Siete (11.67%) pacientes sufrieron recidiva, de los cuales seis (10%) eran portadores de lesión. CONCLUSIONES: off-track y uno (1.67%) on-track. 53 (88.33%) pacientes sin recidiva, de los cuales 11 (18.33%) eran portadores de lesión off-track y 42 (70%) on-track. Se interpretó un aumento de riesgo de recidiva de inestabilidad de 23.47 en los pacientes portadores de lesión de tipo off-track en comparación con los pacientes portadores de lesiones on-track. Las lesiones.

Effects of Ultrasonic Disintegrates from Epimastigote Biomass of Trypanosoma cruzi Albarrada Strain (Mexico) on the Development of L5178Y Solid Malignant Transplanted Tumors in Male BALB/c Mice.

We studied in vivo antitumor effect of epimastigote form detritus of Trypanosoma cruzi, Mexican Albarrada strain, on L5178Y malignant tumor in BALB/c mice. The antitumor effect of ultrasonic detritus of the parasite was confirmed by shrinkage of the tumor and changed size of its symplastic necroses.

Blood flow rate and energy charge in the isolated perfused canine liver.

Background. Liver viability depends on blood flow rate, which varies among isolated perfused livers used in different studies. We aimed to identify the minimal blood flow capable of keeping the energy charge compatible with liver viability. Materials and methods. Isolated canine livers were assigned to different groups (n = 4) with blood flow rates of 0.5 (Group I), 1.0 (Group II), and 1.5 ml/g/min (Group III). Blood gases, hematocrit, and glucose were measured over 180 min. Nucleotides, serum osmolarity, and electrolytes were also measured. Morphological changes were recorded at the end of each experiment. Results. Acid-base balance was better in livers from Group III. Electrolytes, osmolarity, hematocrit, and glucose showed no differences. Higher energy charges correlated with higher blood flow rates. On histopathology, there was evidence of more hydrostatic pressure-related changes in Group III, with no difference in necrosis or inflammatory-related alterations. Conclusions. (1) Energy charge correlates strongly with blood flow rate. (2) A rate of 1.5 ml/g/min allows for a better electrolyte, osmolarity, and acid-base balance. (3) Morphological analysis is not a sensitive predictor of organ viability as assessed by energetic potential. (4) The minimal blood flow rate required to attain an energy charge above 0.75 is 1.33 ml/g/min.

Mechanisms involved in the cardiovascular alterations immediately after spinal cord injury.

The early cardiovascular effects resulting from an acute spinal cord injury (SCI) produced by a contusion procedure at T5-T6 were evaluated in anaesthetized rats. The mean arterial pressure (MAP) and heart rate (HR) were measured during one hour after the injury. A marked decrease in MAP and HR was observed immediately after injury, followed by an abrupt increase in MAP. These changes were observed between 3 and 9 min and the basal values were recovered after 20 min. Fall in the MAP and HR and increase in MAP induced by SCI were abolished by atropine. The interruption of the parasympathetic outflow by vagotomy also significantly diminished the fall and increase in MAP and the fall in HR. Likewise, pre-treatment with nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) completely abolished the effects produced by SCI. These data suggest that after SCI the decrement in MAP and HR was probably due to acetylcholine release from parasympathetic fibers and NO from endothelial source probably by a cholinergic stimulation. Additionally, the MAP increase observed was probably due to a reflex compensatory vasoconstriction.

A model of suture-induced urolithiasis with urographic control in the bladder of the rat.

The characteristics of a model of urolithiasis in the bladder of male Wistar rats were evaluated. Two techniques were compared: one knot of suture material through the bladder wall, or 15-throw knots inside the bladder. Rats were randomly assigned to one of six groups, according to the technique and suture material used (polyester, silk, or chromic catgut). An excretory urogram was performed at days 30, 60, and 90. At the moment of positive radiographic diagnosis, animals were sacrificed and stones were obtained. All rats were sacrificed at day 90 regardless of the x-ray results. Variables evaluated were average days to a positive urogram, average weight of all uroliths, and percentage of animals developing urolithiasis throughout the study. There were no statistical differences between groups for the average weight of stones, which ranged from 0.008 to 1.502 g for individual cases. All three materials were more lithogenic with the 15-throw knot inside technique. No significant differences were detected for lithogenesis criteria between suture materials. X-ray dispersion spectroscopy evidenced calcium phosphate composition of two stones from chromic catgut, and magnesium phosphate composition of two stones from chromic catgut, two from silk, and two from polyester. Neo-epithelization over the suture was confirmed microscopically in bladders with the one-throw technique. We conclude that (1) this is an effective model of urolithiasis, with predictability in time, composition, and amount of stone formation; (2) the presence of more suture material inside the bladder is more lithogenic; and (3) excretory urograms are highly sensitive and specific for the noninvasive diagnosis of bladder urolithiasis.

Early changes in nitric oxide synthase activity in atrial intramural arteries following experimental spinal cord injury in rats.

Previously, we have shown that immediately after an experimental spinal cord injury (SCI) in anaesthetized rats, there is a large fall in mean arterial pressure (MAP) and heart rate (HR), followed by an abrupt increase in MAP. To evaluate the participation of nitric oxide (NO), we evaluated the activity of nitric oxide synthase (NOS) using Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry in sections of atria at several post-injury time-intervals. Staining increased at 3 min, reached a maximum at 9 min and diminished 30 min after injury. Pretreatment with atropine prevented changes in MAP, HR and NADPH-d staining suggesting that such modifications result from an increased vagal stimulation. In conclusion, the NOS activity is transiently elevated in the atrial intramural arteries of rats subjected to an SCI.

The protective action of amlodipine on cardiac negative inotropism caused by prolonged incubation in vitro.

The mechanism of the antihypertensive action of the 1,4-dihydropyridine Ca2+ antagonist amlodipine was studied in isolated ventricular strips and aortic rings from Wistar rats after oral treatment with amlodipine 15 mg/kg/day for one week. The contractions evoked by electrical stimulation of isolated strips from right ventricles pretreated with amlodipine (5 nM) were unaffected during the first hour after mounting, but they decreased in magnitude after prolonged incubation (4 hr). However, the decrease in response of these preparations after prolonged incubation was less than that observed in strips prepared from untreated rats. A negative inotropic effect of amlodipine was observed at concentrations higher than 300 nM. In the presence of lower concentrations of amlodipine (5 nM-30 nM) after prolonged incubation, the contractions of ventricular strips were significantly more sustained than in the absence of amlodipine. Likewise, the decrease in contractility evoked by increasing the stimulation frequency from 1 to 3 Hz was reduced in amlodipine treated rats. The recovery of contractility was improved when stimulation frequency was returned to 1 Hz. On the other hand, when rat ventricular strips pretreated with amlodipine (5 nM) were exposed to isoprenaline (3 microM), the contractions evoked by isoprenaline were enhanced. The isoprenaline effect was not altered with 300 nM amlodipine, but with 3 microM became weak and was significantly lower than in strips treated with isoprenaline alone. In addition, treatment with amlodipine produced a marked decrease in the contractions evoked by 100 mM KCl solution in isolated aortic rings when compared to untreated rats. This inhibition was produced in a time-dependent manner with an IC50 equal to 30 and 3 nM after 2 and 45 min of contraction, respectively. Ex vivo results show that amlodipine treatment decreased aortic contractility without producing a negative inotropic effect although there was an occupation of cardiac Ca2+ channels. These results suggest that a protective effect of amlodipine on cardiac negative inotropism is produced by prolonged incubation in vitro.

Diferencias entre los efectos del indorrenato y otros agonistas 5-HT1A en la aorta de conejo / Action of indorenate and other 5-HT1A agonists in rabbit aorta

El objeto de este estudio fue determinar si en forma similar a lo que sucede con la buspirona, la ipsapirona y el 8-hidroxi-2(di-N-propilamino) tetralin (8-OH-DPAT), los receptores adrenérgicos-Ó1 están relacionados con las respuestas producidas por el indorrenato en anillos de aorta de conejo. Excepto la ipsapirona, todos los agonistas 5-HT1A mencionados contrajeron los anillos. La contracción ocasionada por buspirona y 8-OH-DPAT se bloqueó con prazosina (antagonista Ó1-adrenérgico), mientras que el efecto del indorrenato no se inhibió con dicho antagonista, pero sí con ritanserina (antagonista 5-HT2). Por otra parte, la buspirona, la ipsapirona y el 8-OH-DPAT, pero no el indorrenato, relajaron anillos precontraídos con metoxamina (agonista Ó1-adrenérgico). Ninguno de los agonistas relajó preparaciones precontraídas con serotonina, acetilcolina o KCl. Los resultados indican que la buspirona y el 8-OH-DPAT son agonistas parciales de los receptores Ó1 ya que indujeron contracción, que se bloqueó con prazosina, y relajaron solamente anillos precontraídos con metoxamina. La ipsapirona se conportó como un antagonista adrenérgico-Ó1 ya que presentó el efecto relajante pero no el contráctil. Finalmente, no se encontró evidencia de que el indorrenato mostrara afinidad por receptores adrenérgicos-Ó1. La contracción inducida por este agonista, aparentemente es mediada por receptores 5-HT2 ya que se inhibió con ritanserina

[Differences between the effects of indorenate and other 5-HT1A agonists on the rabbit aorta]. / Diferencias entre los efectos del indorrenato y otros agonistas 5-HT1A en la aorta de conejo.

The aim of this study was to determine if like buspirone, ipsapirone and 8-hydroxy-2(di-N-propylamino)tetralin (8-OH-DPAT), the alpha 1-adrenoceptors are involved in the responses elicited by indorenate in rabbit aorta. Exception made of ipsapirone, all the 5-HT1A agonists above mentioned contracted aortic rings. The contraction elicited by buspirone and 8-OH-DPAT was blocked with prazosin (alpha 1-adrenergic antagonist), whereas the effect of indorenate was unaffected with this blocker but it was inhibited with ritanserin (5-HT2 antagonist). On the other hand, buspirone, ipsapirone and 8-OH-DPAT but not indorenate relaxed arteries precontracted with methoxamine (alpha 1-adrenergic agonist) and none of the agonists relaxed preparations precontracted with acetylcholine or KCl. The results indicate that buspirone and 8-OH-DPAT are partial alpha 1-adrenoceptor agonists since they elicited contractions which are blocked with prazosin and relaxed only rings precontracted with methoxamine. Ipsapirone behaved as an alpha 1-adrenoceptor antagonist since it showed the relaxant but not the contractile effect. Finally, we found no evidence that indorenate has afinity for alpha 1-adrenoceptors. Contraction elicited by this agonist seems to be mediated by 5-HT2 receptors, inasmuch it was blocked with ritanserin.