Population pharmacokinetics of sirolimus in kidney transplant patients

OBJECTIVE: To characterize the dose-related pharmacokinetics of the immunosuppressant agent sirolimus (formerly rapamycin) in kidney transplant patients by use of two-stage and nonlinear mixed-effect model population methods. METHODS: Patients (n = 36) from three centers (Germany, the United Kingdom, and Sweden) who received steady-state oral doses of cyclosporine (ciclosporin) were assessed after single oral administration of sirolimus at doses of 3, 5, 10, and 15 mg/m2. Plasma and whole blood sirolimus samples were analyzed by a high-performance liquid chromatographic/mass spectrophotometric method. Simultaneous fitting used biexponential functions with intercept/slope or clearance/volume terms, as well as first-order absorption (ka) and a lag-time. RESULTS: The nonlinear mixed-effect model method (P-Pharm) provided a better characterization of sirolimus kinetics, especially for the absorption and distribution phases where fewer data were available per patient. Sirolimus distribution between whole blood and plasma was concentration-independent, with a mean blood/plasma ratio (coefficient of variation) of 30.9 (48.5%). Elimination was not influenced by dose, as shown by estimates of the terminal half-life of 63 hours (27.5%) and apparent oral blood clearance of 8.9 L/hr (38.2%). Sirolimus distribution parameters were influenced by body weight and surface area. Sirolimus was rapidly absorbed, as shown by the absorption lag-time of 0.27 hour (35.1%), and ka of 2.77 hr-1 (48.4%). The concomitant administration of sirolimus and cyclosporine did not reveal any pharmacokinetic interactions. CONCLUSION: This report provides an initial population pharmacokinetics of sirolimus in kidney transplant recipients receiving cyclosporine concurrently. Sirolimus blood and plasma pharmacokinetics were biexponential and linear for doses from 3 to 15 mg/m2. No pharmacokinetic interaction was found between sirolimus and cyclosporine.     

Variations in uterine innervation during the estrous cycle in rat

Uterine innervation undergoes profound remodeling during puberty, pregnancy, and after parturition. However, the extent to which uterine innervation may change during the estrous cycle is uncertain. The objective of the present study was to determine whether nerve fiber density of the uterine horn is altered during the estrous cycle and, if so, which subpopulations are affected. Immunostaining for the pan-neuronal marker protein gene product (PGP) 9.5 revealed fibers within the vascular zone, myometrium, and endometrium, with greater density in the ovarian and cervical regions than in the middle. In most structures, nerve density was reduced during estrus. This could not be accounted for by increased target volume, as the reduction in longitudinal muscle innervation persisted after correction for changes in target size. Immunostaining for vasoactive intestinal polypeptide-immunoreactive parasympathetic nerves revealed fibers associated predominantly with the vascular zone and circular muscle within the cervical region. No cyclical variation was detected. Calcitonin gene-related peptide-immunoreactive nerves were present within all structures, and density was highest at the ovarian end. These fibers also did not vary significantly through estrous. Dopamine beta-hydroxylase-immunoreactive sympathetic nerves innervated all structures, with greater density in the ovarian end. These fibers were reduced substantially during estrus, but the decline was also significant in proestrus, thus preceding that detected by using the pan-neuronal marker. We conclude that the estrous cycle in rat is accompanied by structural remodeling of sympathetic nerves by way of retraction or degeneration of terminal fibers during estrus. The structural loss of the terminal axon apparently is preceded by depletion of catecholamine-synthesizing enzyme.     

A local circuit approach to understanding integration of long-range inputs in primary visual cortex

Integration of inputs by cortical neurons provides the basis for the complex information processing performed in the cerebral cortex. Here, we have examined how primary visual cortical neurons integrate classical and nonclassical receptive field inputs. The effect of nonclassical receptive field stimuli and, correspondingly, of long-range intracortical inputs is known to be context-dependent: the same long-range stimulus can either facilitate or suppress responses, depending on the level of local activation. By constructing a large-scale model of primary visual cortex, we demonstrate that this effect can be understood in terms of the local cortical circuitry. Each receptive field position contributes both excitatory and inhibitory inputs; however, the inhibitory inputs have greater influence when overall receptive field drive is greater. This mechanism also explains contrast-dependent modulations within the classical receptive field, which similarly switch between excitatory and inhibitory. In order to simplify analysis and to explain the fundamental mechanisms of the model, self-contained modules that capture nonlinear local circuit interactions are constructed. This work supports the notion that receptive field integration is the result of local processing within small groups of neurons rather than in single neurons.     

Oligopeptidase B-dependent signaling mediates host cell invasion by Trypanosoma cruzi

Mammalian cell invasion by the intracellular protozoan parasite Trypanosoma cruzi is mediated by recruitment and fusion of host cell lysosomes, an unusual process that has been proposed to be dependent on the ability of parasites to trigger intracellular free calcium concentration ([Ca2+]i) transients in host cells. Previous work implicated the T.cruzi serine hydrolase oligopeptidase B in the generation of Ca2+-signaling activity in parasite extracts. Here we show that deletion of the gene encoding oligopeptidase B results in a marked defect in host cell invasion and in the establishment of infections in mice. The invasion defect is associated with the inability of oligopeptidase B null mutant trypomastigotes to mobilize Ca2+ from thapsigargin-sensitive stores in mammalian cells. Exogenous recombinant oligopeptidase B reconstitutes the oligopeptidase B-dependent Ca2+ signaling activity in null mutant parasite extracts, demonstrating that this enzyme is responsible for the generation of a signaling agonist for mammalian cells.     

Comparison of the effectiveness of various comprehensive treatments for locally advanced breast cancer

OBJECTIVE: Auditory testing is not routinely performed within 4-6 weeks after stapedotomy, because hearing acuity is thought to be transiently depressed. In rare circumstances, postsurgical auditory and vestibular complaints may lead one to test hearing soon after stapedotomy. The early postoperative effects of carbon dioxide (CO2) and potassium titanyl phosphate (KTP) lasers, which now are routinely used to perform stapedotomies, have not been reported. The purpose of this report is to present normative data for auditory thresholds measured within 2 weeks of laser stapedotomy. STUDY DESIGN: The study design was a prospective, unblinded study. SETTING: The study was conducted at three academic medical centers. PATIENTS: Thirty-six subjects undergoing 38 stapedotomies for otosclerosis by 5 surgeons participated. MAIN OUTCOME MEASURES: Behavioral audiometry was performed using standard techniques beginning before surgery and continuing through > 1 year after surgery. RESULTS: The CO2 laser was used in 26 stapedotomies and the KTP laser was used in 12. Nine cases were revision procedures. Bone conduction pure-tone averages and speech discrimination scores did not worsen during the early postoperative period. Bone conduction at 250 and 4,000 Hz dropped slightly within the first 2 weeks (-4.3 and -6.7 dB) but recovered thereafter. Bone conduction at 1,000 Hz actually improved within the first week after surgery (+6.2 dB, p = 0.021). Significant improvements in air conduction thresholds (and air-bone gap) were seen at the second week and late audiometry. The results for CO2 and KTP laser-treated groups were not significantly different. CONCLUSIONS: Cochlear function is not significantly depressed in the early postoperative period after laser (CO2 or KTP) stapedotomy.     

Clinical, neurophysiological and hemodynamic effects of a new nondepolarizing myorelaxant mivacurium in heart surgery patients]

Thirty patients aged 23 to 65 years with ASA class III operated on the heart under total intravenous anesthesia were examined after the Good Clinical Practice protocol. Mivacurium in bolus dose of 0.2 mg/kg was injected for intubation of the trachea; neuromuscular blocking (NMB) was maintained by a repeated injection of the drug in a dose of 0.15 mg/kg, after which it was infused at a rate of 1 to 10 micrograms/kg/min. Accelerometric control of neuromuscular conduction was carried out by the Organon (Belgium) TOF-Guard device. Central and peripheral hemodynamics was monitored. Side effects of the drug were recorded. Bolus injection of mivacurium in a dose of 0.2 mg/kg caused T1 suppression (90%) after 2.6 +/- 0.7 min. Maximal (97.7 +/- 4.5%) suppression was observed after 4.17 +/- 2.5 min. The conditions of intubation of the trachea after 3.9 +/- 1.8 min in the presence of 78 to 100% T1 suppression (97.7 +/- 4.5%) were considered excellent or good in 96.6% of cases. Clinically and neurophysiologically sufficient muscle relaxation after the first injection of the drug persisted for 27.7 +/- 7.3 min. Minimal rate of infusion for maintaining the NMB at 95 +/- 4% level of T1 suppression was 6.3 +/- 1.7 micrograms/kg/min. Bolus injection of mivacurium in a dose of 0.2 mg/kg for 60 sec involved a 1-3-min drop of the mean arterial pressure by 10.5% and a 10.3% decrease of heart rate. Repeated bolus injection of the drug in a dose of 0.15 mg/kg and its infusion did not change the peripheral and central hemodynamics. The most typical side effect of the drug in a dose of 0.2 mg/kg is short-term reversible reddening of the skin of the face and neck, observed in 20% of patients. The results permit us to consider mivacurium as an effective, safe, and controllable agent, which can be used in cardiosurgical patients.     

The P300 component of the auditory evoked potential in the posttraumatic vegetative state

The dynamic studies of P300 component of the acoustic evoked potential were conducted in 12 patients in posttraumatic state of the autonomic system. The amplitude and time parameters of P300 were analyzed, its spatial distribution over the cortex, and features of generation. The obtained results were compared with the normative data. Significant changes in P300 in comparison with the normal characteristics were revealed in patients with the absence of conscious mental activity. These changes were maximally expressed when the state of patients was irreversible. In case of patients' outcome from the studied state the amplitude-temporal and topographic response characteristics tended to normalization but did not reach it completely. The obtained results allow us to consider the P300 component as one of the most informative indices in consciousness recovery after severe brain injury.     

A program system interpreting recording of long-latency evoked potentials

An algorithm and a personal computer program for automatic distinguishing between EEC records containing evoked and no potentials, based on the detected invariants reflecting experts' experience in evoked potential analysis have been developed. The efficiency of the programme (its high accuracy and speed, low volume) has been demonstrated in the system for automatic determination of the hearing level by long-latent evoked potentials. It is easily modifiable to identify evoked potentials from other modalities (visual, somatosensory ones) in the systems using the traditional and/or up-to-date computerized EEC equipment.     

Constitutive activation of photoreceptor guanylate cyclase by Y99C mutant of GCAP-1. Possible role in causing human autosomal dominant cone degeneration

Photoreceptor membrane guanylate cyclases (RetGC) are regulated by calcium-binding proteins, GCAP-1 and GCAP-2. At Ca2+ concentrations below 100 nM, characteristic of light-adapted photoreceptors, guanylate cyclase-activating protein (GCAPs) activate RetGC, and at free Ca2+ concentrations above 500 nM, characteristic of dark-adapted photoreceptors, GCAPs inhibit RetGC. A mutation, Y99C, in human GCAP-1 was recently found to be linked to autosomal dominant cone dystrophy in a British family (Payne, A. M., Downes, S. M., Bessant, D. A. R., Taylor, R., Holder, G. E., Warren, M. J., Bird, A. C., and Bhattachraya, S. S. (1998) Hum. Mol. Genet. 7, 273-277). We produced recombinant Y99C GCAP-1 mutant and tested its ability to activate RetGC in vitro at various free Ca2+ concentrations. The Y99C mutation does not decrease the ability of GCAP-1 to activate RetGC. However, RetGC stimulated by the Y99C GCAP-1 remains active even at Ca2+ concentration above 1 microM. Hence, the cyclase becomes constitutively active within the whole physiologically relevant range of free Ca2+ concentrations. We have also found that the Y99C GCAP-1 can activate RetGC even in the presence of Ca2+-loaded nonmutant GCAPs. This is consistent with the fact that cone degeneration was dominant in human patients who carried such mutation (Payne, A. M., Downes, S. M., Bessant, D. A. R. , Taylor, R., Holder, G. E., Warren, M. J., Bird, A. C., and Bhattachraya, S. S. (1998) Hum. Mol. Genet. 7, 273-277). A similar mutation, Y104C, in GCAP-2 results in a different phenotype. This mutation apparently does not affect Ca2+ sensitivity of GCAP-2. Instead, the Y104C GCAP-2 stimulates RetGC less efficiently than the wild-type GCAP-2. Our data indicate that cone degeneration associated with the Y99C mutation in GCAP-1 can be a result of constitutive activation of cGMP synthesis.