The Membrane Lipid Cholesterol Modulates Anesthetic Actions on a Human Brain Ion Channel

Background: Molecular theories of general anesthesia often are divided into two categories: (l) Anesthetics may bind specifically to proteins, such as ionic channels, and alter their function directly, and (2) anesthetics may alter the functions of integral membrane proteins indirectly through modification of the physical properties of the membrane. Recent studies have provided evidence that anesthetics can bind to proteins and modify their function directly, bringing into question the role of the membrane in anesthetic interactions. To reexamine the role of membrane lipids in anesthetic interactions, an experimental approach was used in which the membrane lipid composition could be systematically altered and the impact on anesthetic interactions with potential targets examined.

Methods: Sodium channels from human brain cortex were incorporated into planar lipid bilayers with increasing cholesterol content. The anesthetic suppression of these channels by pentobarbital was quantitatively examined by single channel measurements under voltage-clamp conditions.

Results: Changes in cholesterol content had no effect on measured channel properties in the absence of anesthetic. In the presence of pentobarbital, however, cholesterol inhibited anesthetic suppression of channel ionic currents, with 1.9% (weight/weight, corresponding to 3.5 mol%) cholesterol decreasing anesthetic suppression of sodium channels by half.     

Involvement of ADAM10 in axonal outgrowth and myelination of the peripheral nerve

The disintegrin and metalloproteinase 10 (ADAM10) is a membrane‐anchored metalloproteinase with both proteolytic and disintegrin characteristics. Here, we investigate the expression, regulation, and functional role of ADAM10 in axonal outgrowth and myelination of the peripheral nerve. Expression pattern analysis of 11 ADAM family members in co‐cultures of rat dorsal root ganglia (DRG) neurons and Schwann cells (SCs) demonstrated the most pronounced mRNA expression for ADAM10. In further studies, ADAM10 was found to be consistently upregulated in DRG‐SC co‐cultures before the induction of myelination. Neurons as well as SCs widely expressed ADAM10 at the protein level. In neurons, the expression of ADAM10 was exclusively limited to the axons before the induction of myelination. Inhibition of ADAM10 activity by the hydroxamate‐based inhibitors GI254023X and GW280264X resulted in a significant decrease in the mean axonal length. These data suggest that ADAM10 represents a prerequisite for myelination, although its activity is not required during the process of myelination itself as demonstrated by expression analysis of myelin protein zero (P0) and Sudan black staining. Hence, during the process of myelin formation, ADAM10 is highly upregulated and appears to be critically involved in axonal outgrowth that is a requirement for myelination in the peripheral nerve. © 2009 Wiley‐Liss, Inc.     

Sonographic evaluation of gallbladder kinetics: in vitro and in vivo comparison of different methods to assess gallbladder emptying.

In an in vitro study, 10 gallbladders of adult pigs and 6 gallbladders of lambs, all removed immediately after slaughtering, were stimulated in a water bath by electric means to induce active contraction. Gallbladder emptying was followed by ultrasonography employing five measurement procedures: (1) gallbladder width, (2) longitudinal planimetry, (3) transverse planimetry, (4) ellipsoid method, and (5) sum of cylinders method. In an in vivo investigation, gallbladder emptying of 30 volunteers (12 healthy subjects, 18 diabetics) was evaluated in the same way after ingestion of a fatty meal. Gallbladder width was found to be unsuitable to estimate the decrease in gallbladder volume due to a nonlinear relation of the parameters. Longitudinal planimetry tended to be less valid than transverse planimetry in assessing gallbladder volume reduction. The most valid estimation of gallbladder volume decreases was obtained by the two three-dimensional procedures. However, in neither in vitro nor in vivo could a significant difference between the sum of cylinders method and the ellipsoid method in determining relative volume reduction be established. We conclude that a three-dimensional measurement procedure should be used for valid assessments of gallbladder motility. However, according to our data there is no advantage in using the time-consuming sum of cylinders method compared to the simple ellipsoid method.     

Does Additional Doxorubicin Chemotherapy Improve Outcome in Patients with Hepatocellular Carcinoma Treated by Liver Transplantation?

The aim of this prospective randomized study was to determine whether additional doxorubicin chemotherapy improves outcome in patients with hepatocellular carcinoma (HCCA) treated by liver transplantation. Stratification parameters were tumor stage (UICC I-IVa), gender, age 50 years, α-fetoprotein 20 ng/mL, cirrhosis and HbsAg status. For pre-operative chemotherapy doxorubicin (15 mg/m²) was given biweekly, intra-operative chemotherapy was a single dose administered before surgical manipulation. Post-operative chemotherapy from day 10 was as given preoperatively for a total dosage of 300 mg/m². Outcome parameters were overall survival (OS) and disease-free survival. Of the 75 consecutive patients who received liver transplantation for treatment of HCCA, 62 patients were enrolled. Thirty-four patients were randomized in the chemotherapy group; 28 patients were in the control group and transplanted only. OS rates at 5 years were 38% in the chemotherapy group and 40% in the control group, disease-free survival rates at 5 years 43% and 53%, respectively. Tumor stage and vascular invasion were identified as independent risk factors for recurrence of disease. Doxorubicin chemotherapy did not improve organ survival and disease-free survival in patients undergoing liver transplantation for HCCA.     

The role of nuclear medicine in oncology

Nuclear Medicine offers screening methods for oncology such as bone and bone marrow scintigraphy. During the last two decades, special procedures have gained widespread application. This paper is centered around the “tumor-specific” radiopharmaceuticals. In patients with thyroid cancer, I-131 still plays a significant role. Ga-67 still has its indications in lymphoma, while in other diseases Tl-201 cloride is now the agent of choice. Especially in thyroid cancer, Tl-201 has proved to be a reliable tumor imaging radiopharmaceutical. More recently, Tc-99m MIBI was introduced for tumor imaging. Tc-99m HMPAO may also be used for tumor scintigraphy, especially in brain lesions. In addition, I-123 IMP has successfully been used for imaging malignant melanoma. Another promising field of tumor diagnosis is receptor imaging. In neuroblastoma and malignant pheochromocytoma, I-131/123 mIBG is the radiopharmaceutical of choice and may be considered as a receptor imaging agent also. First clinical results with In-111 octreotide show potentials as somatostatine-receptor radiopharmaceutical in insulinoma, islet cell carcinoma, medullary and lung cancer, while I-123 estradiol needs some improvement until it may be recommended as diagnostic tool in breast cancer. Since 1978, radiolabeled poly- or monoclonal tumor antibodies and their fragments have gained widespread application. Especially the Tc-99m 225.28S melanoma antibody, I-131 or Tc-99m CEA and In-111/I-131 labeled OC-125 antibodies have proven to be of clinical significance in melanoma, colorectal and ovarian cancer.     

Cellular kinetics of prednimustine versus chlorambucil plus prednisolone in vitro

Summary Intracellular concentrations of prednimustine (PM), chlorambucil (CLB), phenylacetic acid mustard (PAAM) and prednisolone (P) were measured in different experimental tumor cell lines that had been incubated with either PM or CLB+P. For intracellular analytical determination, we modified a high-pressure liquid chromatographic method for the detection of these substances in plasma. Intact PM could be detected in the intracellular compartment of the incubated tumor cells. PM-incubated cells from PM-injected rats exhibited a higher intracellular concentration-time integral (PAAM) and longer concentration-time profiles for drugs with alkylating capacity than did cells exposed to the CLB+P mixture or to CLB. PAAM was not detectable after incubation of cells with PM, whereas in CLB-incubated cells the AUC of PAAM exceeded that of the parent drug CLB. Our in vitro results therefore favour the concept of a facilitated intracellular uptake and an increased antiproliferative effect for PM versus CLB and CLB+P.Dedicated to Prof. Dr. H. J. Dengler on the occasion of his 65th birthday. This study was supported by the Ministry of Science and Research of Nordrhein-Westfalen     

Quantification of oxidative DNA modifications in mitochondria

Specific repair endonucleases were used to quantify oxidativemodifications in mitochondrial DNA (mtDNA) from rat liver andfrom porcine liver and kidney by means of a relaxation assay.In rat liver mitochondria the number of modifications sensitiveto formamidopyrimidine-DNA glycosylase (FPG protein), whichinclude 8-hydroxyguanine (8-oxo-7, 8-dihydro-guanine) residues,was only 0.8±0.2 per 10⁵ base pairs (bp). Even lowervalues were observed in porcine kidney (0.5±0.3 per 10⁵bp) and liver (0.4±0.2 per 10⁵ bp). The numbers of sitesof base loss (AP sites) sensitive to T4 endonuclease V and of5,6-dihydropyrimidines sensitive to endonuclease III were lessthan 0.2 per 10⁵ bp in all cases. The data provide evidencethat the steady-state levels of oxidative mtDNA modificationsare low under physiological conditions, either because reactiveoxygen species generated in the mitochondria are instantly inactivatedor because of efficient DNA repair processes inside mitochondria.