Serum and Cerebrospinal Fluid Pharmacokinetics of Intravenous and Oral Lamivudine in Human Immunodeficiency Virus-Infected Children

We studied the pharmacokinetics of intravenously and orally administered lamivudine at six dose levels ranging from 0.5 to 10 mg/kg of body weight in 52 children with human immunodeficiency virus infection. A two-compartment model with first-order elimination from the central compartment was simultaneously fitted to the serum drug concentration-time data obtained after intravenous and oral administration. The maximal concentration at the end of the 1-h intravenous infusion and the area under the concentration-time curve after oral and intravenous administration increased proportionally with the dose. The mean clearance of lamivudine (± standard deviation) in the children was 0.53 ± 0.19 liter/kg/h (229 ± 77 ml/min/m² of body surface area), and the mean half-lives at the distribution and elimination phases were 0.23 ± 0.18 and 2.2 ± 2.1 h, respectively. Clearance was age dependent when normalized to body weight but age independent when normalized to body surface area. Lamivudine was rapidly absorbed after oral administration, and 66% ± 25% of the oral dose was absorbed. Serum lamivudine concentrations were maintained above 1 μM for ≥8 h of 24 h on the twice daily oral dosing schedule with doses of ≥2 mg/kg. The cerebrospinal fluid drug concentration measured 2 to 4 h after the dose was 12% (range, 0 to 46%) of the simultaneously measured serum drug concentration. A limited-sampling strategy was developed to estimate the area under the concentration-time curve for concentrations in serum at 2 and 6 h.     

Syntheses of Novel Pyridazinomorphinans by Inverse Electron Demand Cycloaddition and their Binding to μ and κ Receptors

A number of novel pyridazinomorphinans have been synthesized by the inverse electron demand Diels-Alder reaction of various 3,6-disubstituted 1,2,4,5-tetrazines with enamines derived from dihydrocodeinone and with codeinone. Reduction of some of the pyridazinomorphinans did not furnish the expected pyrroloepoxymorphinans; in all cases investigated reductive cleavage of the epoxybridge was observed to yield dihydropyridazino- or pyrrolomorphinans. The structures of all new compounds were assigned by the spectral data, that of the cycloadduct of codeinone was additionally verified by X-ray crystallography. Compounds 5a, 8, 11a , and 16 have been evaluated for their affinity at μ and κ opioid receptors in radioligand binding assays. Their ability to inhibit [³H]DAMGO binding at μ and [³H]U 69.593 binding at κ receptors, respectively as compared to codeine has been found to be lower.     

Affective and physiological responses to environmental noises and music.

Research suggests that respiratory patterns may reflect general dimensions of emotional response. In this study, we investigated the relationships between judgments of affective valence (pleasantness) and arousal and respiratory responses to acoustic stimuli. Sixteen environmental noises and 16 musical fragments of 30 s duration were presented to 31 participants, while respiration, skin conductance level and heart rate were recorded. Judgments of valence and arousal were registered using the 9-point Self-Assessment Manikin. For noises, breathing accelerated and minute ventilation augmented with decreases in pleasantness for low-arousal stimuli and with increases in arousal for positive stimuli. For music, breathing accelerated and minute ventilation augmented with increases both in rated valence and arousal. Skin conductance level increased with arousal ratings for music but not for noises, whereas mean heart rate increased with rated arousal for noises but not for music. Although both noises and music are sound-vibrations, differences in the relationships between affective judgments and physiological responses were found suggesting differences in the processing of the two types of acoustic stimuli.     

Vasopressin-induced taurine efflux from rat pituicytes: a potential negative feedback for hormone secretion

Previous work on the whole neurohypophysis has shown that hypotonic conditions increase release of taurine from neurohypophysial astrocytes (pituicytes). The present work confirms that taurine is present in cultured pituicytes, and that its specific release increases in response to a hypotonic shock. We next show that vasopressin (VP) and oxytocin (OT) also specifically release taurine from pituicytes. With an EC₅₀ of ∼2 n m , VP is much more potent than OT, and the effects of both hormones are blocked by SR 49059, a V_1a receptor antagonist. This pharmacological profile matches the one for VP- and OT-evoked calcium signals in pituicytes, consistent with the fact that VP-induced taurine efflux is blocked by BAPTA-AM. However, BAPTA-AM also blocks the taurine efflux induced by a 270 mosmol l⁻¹ challenge, which per se does not evoke any calcium signal, suggesting a permissive role for calcium in this case. Nevertheless, the fact that structurally unrelated calcium-mobilizing agents and ionomycin are able to induce taurine efflux suggests that calcium may also play a signalling role in this event. It is widely accepted that in hypotonic conditions taurine exits cells through anionic channels. Antagonism by the chloride channel inhibitors 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB) suggests the same pathway for VP-induced taurine efflux, which is also blocked in hypertonic conditions (330 mosmol l⁻¹). Moreover, it is likely that the osmosensitivity of the taurine channel is up-regulated by calcium. These results, together with our in situ experiments showing stimulation of taurine release by endogenous VP, strengthen the concept of a glial control of neurohormone output.     

Localization of self antigen: implications for antigen presentation and induction of tolerance

The fifth component of complement (C5) is a self antigen expressed in serum of normal mice at a concentration of about 50 μg/ml. We have previously shown that C5 is constitutively processed and presented by antigen-presenting cells (APC) in normal mice to induce and maintain complete tolerance in major histocompatibility complex (MHC) class II-restricted T cells. This report addresses the question of whether C5 presentation involves exogenous antigen which has been internalized for processing or whether intracellular, biosynthesized C5 is being presented with MHC class II. Macrophages were found to synthesize, but not secrete C5 in bone marrow chimeras made from irradiated C5-deficient [C5(?)] hosts reconstituted with C5-sufficient [C5(+)] bone marrow [C5(+) ← C5(?)]. In these mice, macrophages are the only source of C5. [C5(+) ← C5(?)] chimeras are not tolerant of C5 and generate C5-specific T and B cell responses upon immunization indistinguishable from those of C5(-) mice. Macrophages from [C5(+) ← C5(-)] chimeras are unable to activate C5-specific T cell hybrids in vitro unlike macrophages from a C5(?) strain that has matured in a C5-expressing environment [C5(?) ← C5(+) chimeras]. This shows that under physiological conditions in vivo intracellular C5 does not get access to the class II presentation pathway and thus, does not induce tolerance in class II-restricted T cells.     

In vitro negative selection of αβ T cell receptor transgenic thymocytes by conditionally immortalized thymic cortical epithelial cell lines and dendritic cells

We have established conditionally immortalized thymic cortical epithelial cell lines from transgenic mice carrying a temperature-sensitive SV40 large Tantigen. One of these cell lines expresses cortical markers and produces IL-1α, IL-6, IL-7, and TGF-β1. These cells express class I major histocompatibility complex (MHC) constitutively and class II MHC upon induction with IFN-μ. The cells appear to have a normal class I antigen presenting pathway since messages for both peptide transporter genes (TAP1, TAP2) were detected. The ability of these cortical epithelial cells to present peptide antigen was compared to that of thymic dendritic cells. In suspension culture with αβ Tcell receptor (TcR) transgenic thymocytes, these epithelial cells and dendritic cells (pre-pulsed with peptide cognate for the transgenic TcR) caused down-regulation of CD4, CD8, and TcR in an antigen dose-dependent and MHC-restricted manner. CD4^dullCD8^dull cells were taken as evidence for negative selection because these cells contained apoptotic DNA. Concentration of peptide required for negative selection of thymocytes was similar between dendritic cells and cortical epithelial cells. In contrast, αβ transgenic spleen cells were activated only by dendritic cells but not by cortical epithelial cells.     

DNA ploidy and cell-cycle analysis in pancreatic and ampullary carcinoma: flow cytometric study of formalin-fixed paraffin-embedded tissue

Summary The cellular DNA content of formalin-fixed, paraffin-embedded specimens from 47 ductal adenocarcinomas of the pancreas and 5 adenocarcinomas of the ampulla of Vater was analysed using flow cytometry. Ploidy and the fraction of cells in the S and G2M phases were determined and correlated with tumour stage and grade as well as patients' survival. Cell populations with aneuploid DNA content were observed in 15% of the tumours. The S + G2M fractions ranged between 1% and 10%. Compared to non-neoplastic tissue of the pancreas the S + G2M fraction was significantly higher in the carcinomas. Cox regression analysis revealed the S + G₂M fraction as an independent prognostic factor (p< 0.05). Ploidy was of no prognostic value for survival, but correlated weakly with tumour stage and tumour grade. All patients without lymph node metastases at time of surgery had diploid tumours. Aneuploidy was restricted to tumours in advanced stages and tended to be more frequent in high-grade tumours.     

Association analysis of a polymorphism in the G‐protein stimulatory α subunit in patients with major depression*

Growing evidence suggests that G‐proteins may be involved in pathogenesis and treatment of affective disorders. Several studies have reported altered levels and/or activities of stimulatory G‐proteins in depression. The aim of this study was to investigate whether a polymorphism in the stimulatory α subunit of G‐proteins (T/C point mutation in exon 5; ATT → ATC at codon 131) is associated with major depression or response to antidepressant treatment. Therefore, we performed a case‐control association study with 212 depressive patients and 137 healthy, unrelated controls. There was no evidence for an association between the investigated polymorphism in the Gα_s gene and major depression, as well as to treatment response. The results of our study are in concordance with recently published findings which do not support the hypothesis that the gene for the stimulatory α subunit of G‐proteins is a major susceptibility factor in the pathophysiology of major depression. © 2002 Wiley‐Liss, Inc.     

Repositioning accuracy of fractionated stereotactic irradiation: assessment of isocentre alignment for different dental fixations by using sequential CT scanning.

BACKGROUND AND PURPOSE: To quantify the accuracy and reproducibility of patient repositioning in fractionated stereotactic conformal radiotherapy (SCRT) using dental fixations in conjunction with a stereotactic head mask. PATIENTS AND METHODS: One hundred and fourteen verification CT scans were performed on 57 patients in order to check set-up alignment. The first scan was done immediately after the first treatment. Twelve patients were checked for alignment accuracy with weekly CT scans over a period of 3-6 weeks, all others had 1-2 scans. Two different dental fixations were used in combination with a non-invasive mask system: an upper jaw support (35 patients) and a customised bite-block (17 patients). Five patients were treated with no additional fixation. Co-registration to the planning CT was used to assess alignment of the isocentre to the reference markers. Additionally, the intra-operator variability of image co-registration was assessed. RESULTS: There was a significant improvement of the overall alignment in using the bite-block instead of the upper jaw support (P<0.001). The mean deviation was for the bite-block 2.2+/-1.1 mm (1 SD), for the upper jaw support 3.3+/-1.8 mm and 3.7+/-2.8 mm for the mask alone. Overall isocentre deviations independent of the method of fixation were 2.8 mm (1.7 mm, 1 SD). Displacements in CC direction were significantly less for the bite-block compared to the upper jaw support (P=0.03). The addition of an upper jaw support significantly reduced lateral rotations compared to the mask system alone (P=0.03). The intra-operator variability of image co-registration was 1.59+/-0.49 mm (1 SD). CONCLUSION: The reproducibility of patient positioning using a re-locatable head mask system combined with a bite-block is within the reported range for similar devices and is preferable to a simple upper jaw support. In order to further reduce the margin for the planning target volume an intra-oral dental fixation is recommended.