Heterotopic transplantation of cryopreserved tracheae in a rat model.

INTRODUCTION: The successful use of cryopreserved tracheal allografts in canine models suggests their use in humans. The grade of genetic difference, the mechanism of revascularisation and the method of cryopreservation are not clearly defined. The purpose of our study was to investigate the rejection of tracheal transplants in a standardised heterotopic rat model using different forms of cryopreservation. METHODS: Tracheae from Brown Norway rats were implanted into the omentum from Brown Norway rats or Lewis rats. We transplanted fresh isografts or allografts and pretreated isografts or allografts. Cryopreservation was performed in a medium containing 10% dimethyl sulphoxide at -80 degrees C for 28 days (I) or -196 degrees C for 84 days (II) or without medium at -80 degrees C for 28 days (III). The transplants were excised after 7 and 21 days, respectively. RESULTS: Histological examinations revealed normal structure and function of isografts after 21 days. In the cryopreserved isograft, the epithelium had disappeared and the tracheal lumen was partially obstructed by a non-compact fibrous tissue. In the fresh allografts, the epithelium was replaced by aggressive fibrous tissue, infiltrating the membranous part of the trachea and occluding the tracheal lumen. The cartilage was vital without any sign of rejection. In the cryopreserved allografts, the tracheal lumen was obstructed by dense fibrous tissue with an inflammatory reaction. The cartilage of cryopreserved allografts (II) and (III) had lost the nuclei corresponding to non-vital tissue. Only in the cryopreserved allografts (I) did we find nodular regeneration at the edges of the cartilaginous bow. CONCLUSIONS: The heterotopic transplantation model allows the study of the mechanisms leading to tracheal obstruction. Cryopreservation was found to have no clear advantage in reducing transplant immunogenicity. Cryopreservation leads to significant damage to the cartilage, the intensity of which is dependent on the mode of cryopreservation.     

Correlation between sperm penetration into the human zona pellucida and in vitro fertilization rates

Summary.  Sperm penetration into the zona pellucida of unfertilized oocytes, and its correlation with in vitro fertilization rates of the sibling oocytes, were assessed. This was performed in order to evaluate the prediction rate of the sperm penetration test into the zona pellucida. Unfertilized oocytes ( n =1872) from 371 cycles were pipetted through a microcapillary, and the remaining sperm cells penetrating the zona pellucida were counted. The mean (±SD) number of spermatozoa that penetrated the zona pellucida of unfertilized oocytes was 12.9±16.37. A significant correlation was found between the fertilization rate and the mean number of spermatozoa that penetrated into the zona pellucida of the unfertilized sibling oocytes (r = 0.48; P < 0.001), or the percent of unpenetrated zonae pellucidae in a cohort (r= —0.43; P < 0.001). However, a distinct variation in the number of spermatozoa that penetrated into the zona pellucida was detected. A step-wise regression analysis proved the number of spermatozoa penetrating the zona pellucida to be more predictive for fertilization rates than the variable of percent of unpenetrated zonae pellucidae. The results imply that although there is interdependence between penetration into the zona pellucida and fertilization rate, the predictive value of sperm penetration test for prognosis and future management after the first in vitro fertilization attempt, is limited.     

Biocompatibility pattern of a bicarbonate/lactate-buffered peritoneal dialysis fluid in APD: a prospective, randomized study.

BACKGROUND: In chronic ambulatory peritoneal dialysis, bicarbonate-buffered fluids, with their neutral pH and less advanced glycosylation end-products (AGE) and glucose degradation products (GDP), have better biocompatibility than conventional peritoneal dialysis (PD) solutions. That difference may be more beneficial in automated peritoneal dialysis (APD), due to its more frequent exchanges and longer contact times with fresh dialysate. We performed a prospective, randomized study in APD patients to compare the biocompatibility of conventional and bicarbonate/lactate-buffered PD fluids. METHODS: We randomized 14 APD patients to have APD with either conventional or bicarbonate/lactate-based fluids. After 6 months, both groups changed to the other solution. The overall observation period was 12 months. After 1 and 5 months and again after 7 and 11 months, phagocytotic and respiratory burst capacities of effluent peritoneal macrophages were determined. Plasma interleukin (IL)-6 and C-reactive protein (CRP) as well as effluent IL-6, CRP, transforming growth factor (TGF)-beta 1, AGE and CA125 concentrations were measured. Inflow pain was quantified using a patient questionnaire. RESULTS: Respiratory burst capacity remained unchanged and phagocytotic activity increased significantly during APD (P<0.001) with the bicarbonate/lactate fluid. Effluent IL-6 release was significantly lower than with the lactate fluid (P<0.05). While in the effluent TGF-beta 1 was unaffected, AGE concentration was lower after bicarbonate/lactate treatment (P<0.05). Effluent CA125 concentration, an indicator of mesothelial cell integrity, was higher (P<0.05) in neutral effluents. Finally, patients' inflow pain diminished (P = 0.05) when using the neutral fluid. CONCLUSIONS: The use of a neutral PD fluid in APD improved patients' inflow pain as well as biocompatibility parameters reflecting enhanced phagocytotic activity of peritoneal macrophages, reduced constitutive inflammatory stimulation (IL-6), reduced AGE accumulation in the peritoneal cavity and better preservation of the mesothelial cell integrity. From the biocompatibility point of view, a neutral fluid with low GDP content can be recommended as the primary choice for APD.     

The automatic implantable cardioverter-defibrillator. Clinical experience, complications, and follow-up in 25 patients

Twenty-five patients with recurrent ventricular tachyarrhythmias underwent implantation of an automatic implantable cardioverter-defibrillator. The mean length of follow-up was 11.9 +/- 10.8 months. Before the implantation, the patients had survived one or more cardiac arrests (mean, 1.7; range, 1 to 4) and episodes of syncope (mean, 2.2; range, 2 to 3) and had received 6.0 +/- 1.0 antiarrhythmic drug trials. The in-hospital complications included death (two patients), reoperation (one patient), intraoperative myocardial infarction (one patient), sensing-failure (one patient), infection (five patients), and pocket seroma (two patients). The posthospital complications included device failure (four patients), device deactivation (one patient), and inappropriate discharge (two patients). The device discharged appropriately in seven patients due to sustained ventricular tachycardia. During electrophysiologic measurements, the energy requirement for successful cardioversion-defibrillation was related to the type of ventricular arrhythmia induced (monomorphic or pleomorphic ventricular tachycardia or fibrillation). Ventricular tachycardia acceleration occurred in ten patients (40%). No significant changes were found in the size of the electrograms or in the cardioversion threshold during early and late follow-up measurements. Life table analysis showed a 12-month survival rate of 86% and an arrhythmic death survival rate of 100%. We confirm the improved rate of survival in this high-risk group of patients, despite significant complications.     

Bacterial hydrogen peroxide contributes to cerebral hyperemia during early stages of experimental pneumococcal meningitis.

Alterations of blood flow contribute to major clinical complications in invasive infections such as sepsis and bacterial meningitis. As a unique feature streptococci -- in particular, Streptococcus pneumoniae, the most frequent pathogen in bacterial meningitis -- release hydrogen peroxide (H(2)O(2)) because of the absence of functional catalase. In a 6 h rat model of experimental meningitis, we studied the impact of bacterial H(2)O(2) production on regional cerebral blood flow (rCBF) and intracranial pressure (ICP). Compared to wild-type D39 pneumococci, the increase of rCBF was diminished in meningitis induced by the H(2)O(2) defective SpxB(-) mutant (maximum increase, 135% +/- 17% versus 217% +/- 23% of the individual baseline; P<0.01) or after treatment of D39-induced meningitis with H(2)O(2)-degrading catalase or with tetraethylammonium (TEA), a blocker of calcium-sensitive potassium channels, which mediate H(2)O(2)-induced vasodilation. Catalase did not significantly reduce the remaining rCBF increase caused by SpxB(-), supporting the predominant role of bacterial H(2)O(2). We conclude that in addition to host-sided mediators, bacterial-derived H(2)O(2) acts as a potent vasodilator, which accounts for a certain proportion of the early cerebral hyperperfusion in pneumococcal meningitis.     

Numerical representations in primates.

Research has demonstrated that human infants and nonhuman primates have a rudimentary numerical system that enables them to count objects or events. More recently, however, studies using a preferential looking paradigm have suggested that preverbal human infants are capable of simple arithmetical operations, such as adding and subtracting a small number of visually presented objects. These findings implicate a relatively sophisticated representational system in the absence of language. To explore the evolutionary origins of this capacity, we present data from an experiment with wild rhesus monkeys (Macaca mulatta) that methodologically mirrors those conducted on human infants. Results suggest that rhesus monkeys detect additive and subtractive changes in the number of objects present in their visual field. Given the methodological and empirical similarities, it appears that nonhuman primates such as rhesus monkeys may also have access to arithmetical representations, although alternative explanations must be considered for both primate species.     

Dependence of Genotoxicity of Benzo[a]pyrene Suspensions in Mutatox Test on Dissolved Concentration and S9 Addition

The Mutatox test is a novel genotoxicity test measuring the ability of a test chemical to restore the luminescent state in dark mutants ofVibrio fischeri.Chemicals can be tested with or without rat hepatic S9 enzymes for metabolic activity, so that promutagenic agents can be detected as well. In theMicrobics Mutatox Manual(1993, Microbics Corp., Carlsbad, CA), benzo[a]pyrene is recommended as positive control for S9 medium at a nominal concentration of 10 mg/liter with 2% DMSO as carrier solvent. The concentration of benzo[a]pyrene dissolved in this test suspension without addition of S9 was determined by GC–MS. It was significantly lower than the nominal concentration and did not reveal a genotoxic effect in the Mutatox test with S9. The analytical concentration of benzo[a]pyrene in the supernatant of the test suspension in S9 medium was significantly higher and induced the luminescence of bacteria. Therefore, S9 microsomes seem, apart from metabolizing benzo[a]pyrene to its genotoxic epoxide, to increase transfer of benzo[a]pyrene intoV. fischeriin such a way that the genotoxic effect is produced. This suggests that sparingly soluble compounds might have different ecotoxicological effects as suspensions than as solutions. Therefore, the possible uptake of suspended particles by organisms without being completely dissolved before should be considered in ecotoxicological tests.     

Seizure Disorders: The Changes With Age

Summary: Age has a profound influence on our approach to the convulsive disorders. Age is a variable which is an important determinant for risk factors for epilepsy. Age, as a surrogate of brain maturation, is a determinant of the specific characteristics of the seizure disorder in those with epilepsy, and age-related changes in these manifestations can be identified. Age is a determinant for the occurrence of acute symptomatic seizures in several types of metabolic or central nervous system insults. Age is a determinant for prognosis, whether one considers remission, medication withdrawal in those entering remission, relapse following prolonged remission, or mortality. Last, age per se seems to be a risk factor for epilepsy independent of other factors. This seems particularly true for partial seizures.