Differences in caffeine and paraxanthine metabolism between human and murine CYP1A2

For the characterisation of murine models of CYP1A2 mediated metabolism in humans we compared the metabolism of caffeine and paraxanthine in human liver microsomes (LM) (two samples) and in LM from CYP1A2-null and wild-type mice. Inhibition experiments were carried out with the quinolones norfloxacin and pefloxacin and the substrate, caffeine. Additionally, in vivo pharmacokinetics of paraxanthine was determined in CYP1A2-null and wild-type mice. All LM produced the primary metabolites of caffeine and paraxanthine. In human LM, the main metabolite of caffeine was paraxanthine (K(M) 0.4 and 0.5 mmol L(-1)). In wild-type and CYP1A2-null mice LM, the main caffeine metabolite was 1,3,7-trimethylurate, but formation was not saturable. Apparent K(M) for paraxanthine formation from caffeine in wild-type and CYP1A2-null murine LM were 0.2 and 4.9 mmol L(-1), respectively. The main metabolite of paraxanthine was 1-methylxanthine in human (K(M) 0.13 and 0.2 mmol L(-1)) and in wild-type mice LM (K(M) 0.53 mmol L(-1)). In CYP1A2-null murine LM, the main paraxanthine metabolite was 7-methylxanthine. The quinolones competitively inhibited caffeine metabolism in human but not in wild-type or CYP1A2-null murine LM. No obvious differences were seen for blood pharmacokinetics and urinary metabolite excretion of paraxanthine between CYP1A2-null and wild-type mice. Thus, for paraxanthine, norfloxacin and pefloxacin interaction with CYP1A2 there were clear differences between mice and man. Our results suggest that an interspecies comparison is required for the metabolism of individual xenobiotics interacting with CYP1A2 prior to the use of mice models to predict its toxicity and/or pharmacological activity in man.     

Alterations in membrane-bound and cytoplasmic K-ras protein levels in mouse lung induced by treatment with lovastatin,cholestyramine, or niacin: effects are highly mouse strain dependent

Agents that either increase (cholestyramine, CS) or decrease (lovastatin, Lov) de novo peripheral cholesterol synthesis may increase (CS) or decrease (Lov) ras protein membrane localization by altering protein prenylation, and potentially have pro- or anti-carcinogenic effects. Male A/J, Swiss, and C57/BL6 mice were treated with 2 or 4% CS, 1% dietary niacin, or 25mg/kg of Lov three times per week (Lov-3X) or five times per week (Lov-5X). After 3 weeks, serum cholesterol and triglycerides were determined enzymatically. Membrane and cytoplasmic K-ras proteins in lung were determined by immunoprecipitation followed by western blotting with a K-ras specific antibody. Results confirmed the hypothesis only in isolated instances. A/J mice had a significant 30% increase in cytoplasmic K-ras and a 40% decrease in membrane K-ras from Lov treatment, as predicted. C57/BL6 mice had a significant 77% increase in membrane K-ras, as expected from CS feeding. At variance with the hypothesis, Swiss mice had increased levels (3-28%) of membrane K-ras with all treatments (including Lov), and C57/BL6 mice treated with Lov had a 58-78% increase in cytoplasmic K-ras without any reduction in the levels of membrane K-ras. Niacin, predicted to have no effect on ras membrane localization, decreased cytoplasmic K-ras in A/J mice, increased both membrane and cytoplasmic K-ras in Swiss mice, and had no effect in C57/BL6 mice. Results may have differed from those predicted because of strain-dependent differences in response to the cholesterol-lowering agents. A difference in response among the mouse strains suggests that individual genetic differences may alter the effect of hypocholesterolemic agents on K-ras membrane localization, and potentially the risk of ras-dependent cancer.     

PXR-dependent induction of human CYP3A4 gene expression by organochlorine pesticides

OCP are xenobiotics which display various toxic effects on animal and human health. One of their effects is to bind and activate estrogen receptor alpha (ERalpha). We have previously studied the down-regulation of induced CYP1A1 (cytochrome P450) expression by this class of molecules in mammary carcinoma cells and shown the importance of ERalpha in this process. However, an alternative mechanism was suggested by those experiments in hepatoma cells. In this study, we have performed Northern blot and transient transfection assays in various cell lines and shown that OCP activate human pregnane X receptor (PXR) and subsequent CYP3A4 mRNA expression. This effect is mediated by the distal xenobiotic responsive element modulator of the promoter. The induction of CYP3A4 by OCP was dose-dependent within the 1-10 microM range. The data suggest that chronic exposure to OCP could alter a major metabolite pathway in human liver and putatively modify the pharmacokinetics of drugs and pollutants.     

Differential increases in P2X receptor levels in rat vagal efferent neurones following a vagal nerve section

Extracellular ATP can influence cells via activation of P2X purinoceptors, the distribution of which can be altered in the central and peripheral nervous systems following injury or tissue damage. Here we have investigated the effect of a unilateral section of the cervical vagus nerve on the distribution of P2X(1), P2X(2), P2X(3), P2X(4) and P2X(7) receptor subunit immunoreactivity (R-IR) in the dorsal vagal motor nucleus (DVN) and the nucleus ambiguus (NA) in the medulla oblongata. As early as 2 days, and followed up to 14 days, there was a dramatic ipsilateral increase in P2X(1), P2X(2) and P2X(4)R-IR in the cell soma of vagal efferent neurones in the DVN following the nerve section, but not the NA. There were no changes in P2X(3) and P2X(7)R-IR in either nuclei. To test for possible functional consequences of increased P2X receptor levels, whole-cell patch-clamp recordings were made from DVN cells in brainstem slices 4 days following unilateral vagotomy. Application of ATP revealed large cell-to-cell variance in the current amplitude in neurones from both sectioned and control DVN. However, when ATP responses were compared to those elicited by the nicotinic acetylcholine receptor agonist carbachol, the mean ratio of the peak ATP-evoked current to the peak carbachol-evoked current was significantly larger in DVN neurones ipsilateral to the section. Thus the increase in P2XR levels in DVN cells ipsilateral to a nerve section are likely to reflect an increase in expression of functional P2XRs on the cell surface.     

X-linked motor and sensory neuropathy with pyramidal signs and cerebral white matter lesions

We report two brothers with hereditary motor and sensory neuropathies and pyramidal signs. Electrophysiological evaluation revealed polyneuropathy and involvement of the central motor, somatosensory, and auditory pathways. Brain magnetic resonance imaging studies showed diffuse white matter lesions, and sural nerve biopsy identified a reduction in the large myelinated nerve fibers. The patients' mother and sister exhibited similar, but milder neurologic findings suggesting that the genetic defect may be X-linked; however, a point mutation in the connexin 32 gene was negative.     

Development and Evaluation of a Computer-Animated Tutor for Vocabulary and Language Learning in Children with Autism

Using our theoretical framework of multimodal processing, we developed and evaluated a computer-animated tutor, Baldi, to teach vocabulary and grammar for children with autism. Baldi was implemented in a Language Wizard/Player, which allows easy creation and presentation of a language lesson involving the association of pictures and spoken words. The lesson plan includes both the identification of pictures and the production of spoken words. In Experiment 1, eight children were given initial assessment tests, tutorials, and reassessment tests 30 days following mastery of the vocabulary items. All of the students learned a significant number of new words and grammar. A second within-subject design with six children followed a multiple baseline design and documented that the program was responsible for the learning and generalization of new words. The research indicates that children with autism are capable of learning new language within an automated program centered around a computer-animated agent, multimedia, and active participation and can transfer and use the language in a natural, untrained environment.     

Individual prostate biopsy core embedding facilitates maximal tissue representation

PURPOSE: The probability of detecting small foci of prostate cancer is related to the amount of tissue represented. When multiple prostate biopsy cores are embedded in a single block, less tissue is evaluated because it is difficult to embed all cores in a single plane for optimal tissue representation. A computer simulation of sectioning biopsy cores was devised to examine the total surface area available at various angles of embedding and predict the ability to detect small tumor foci. MATERIALS AND METHODS: The computer simulation of biopsy core was done using commercially available software. Biopsy cores were represented as 3-dimensional cylindrical objects and the cutting blade was represented by a 2-dimensional plane. The intersection of the plane and cylinder represented the cut surface, which varied depending on cylinder angle and position. The simulation program calculates available surface area. RESULTS: Maximal surface area was obtained when the plane was horizontal to the long axis of the core. Any divergence of the cylinder from horizontal decreased the represented area. A single section through a 1 x 15 mm. biopsy core at 0 degrees yielded a surface area of 15 mm(2). The surface area was decreased to 13.3, 9.01 and 4.52 mm(2) at 3, 5 and 10 degrees, respectively. At a small focus of 0.6 mm. there was 100% detection under optimal circumstance, which decreased to 56.2% and 27.9% as the angle increased to 3 and 10 degrees, respectively. CONCLUSIONS: Optimal sectioning, that is maximal surface area, of the core is obtained when a biopsy core is sectioned at a 0-degree angle, that is horizontal to its long axis. It is much more likely when each biopsy core is embedded individually. When multiple cores are embedded together, it is difficult to position all cores in the same plane since cores move to different planes and the cut surface of the cylinders substantially decreases. Thus, for optimal surface representation and cancer detection embedding individual cores is appropriate.     

伴有副肿瘤性天疱疮和肺部异常的局限性Castleman病的临床与病理

目的：分析局限性Castleman病伴有副肿瘤性天疱疮（PNP)和肺浸润的临床、病理和CT表现。方法：4例患者均经手术证实。有完整的临床、实验室、CT影像和病理资料。结果：4例患者临床初诊症状均为PNP,继发性肺部异常包括闭塞性细支气管炎（3例）、多发肺梗塞（1例）和肺脓肿（1例）。CT扫描肿瘤均为单发较大的（直径5－14cm）高强化软组织肿块,病灶位于后腹膜腔3例,前纵隔1例。病理分型,透明血管型3例,中间型1例。PNP于切除肿瘤后2－32周完全消退,而3例闭塞性细支气管炎患者疗效不佳,至今仍有呼吸困难和刺激性咳嗽。结论：PNP和肺部异常为Castlaeman‘s病少见而严重合并症。早期诊断和手术切除肿瘤对患者愈合极为重要。     

计算机辅助立体定向手术定位方法的研究

目的　探讨神经外科立体定向手术的科学性 ,研制计算机辅助神经外科规划系统(CAPN)软件。方法　随机抽取 10 0组立体定向靶点 ,用CAPN系统测定的靶点三维坐标数值与传统的刻度盘测量的靶点数值进行统计学对照分析。临床应用CAPN实施 137例立体定向手术。结果刻度盘目测和CAPN 2种测量方法的靶点数值进行配对t检验的处理结果 :t0 .0 5 ,证明两种方法的结果差异无统计学意义 ,CAPN准确可靠。所有手术均获成功 ,临床效果满意。结论　CAPN对提高神经外科立体定向手术的科学性有积极的作用