Hypericin prolongs action potential duration in hippocampal neurons by acting on K+ channels

BACKGROUND AND PURPOSE

Synaptic deficiency is generally accepted to be involved in major depression, and accordingly classic antidepressants exert their effects through enhancing synaptic efficiency. Hypericin is one of the major active constituents of extracts of St. John's Wort (Hypericum perforatum L.) with antidepressive actions, but little is known about its therapeutic mechanisms. Our aim was to explore whether hypericin has a modulatory effect on neuronal action potential (AP) duration by acting on voltage-gated ion channels.

EXPERIMENTAL APPROACH

We used voltage-clamp and current-clamp techniques in a whole-cell configuration to study primary cultures of neonatal rat hippocampal neurones. We measured the effects of extracellularly applied hypericin on AP duration as well as on voltage-gated Na(+), I(A) and I(K) currents.

KEY RESULTS

Extracellularly applied hypericin dose-dependently increased AP duration but barely affected its amplitude. Further analysis revealed that hypericin inhibited both transient I(A) and delayed rectifier I(K) potassium currents. In contrast, hypericin exerted no significant effect on both Na(+) peak current and its decay kinetics.

CONCLUSIONS AND IMPLICATIONS

Extracellularly applied hypericin increased AP duration, which might be ascribed to its effect on I(A) and I(K) currents. As a small increase in AP duration could lead to a dramatic increase in synaptic efficiency, our results imply that hypericin might exert its antidepressant effects by enhancing presynaptic efficiency.

The human apoE7 and apoE4 transgenic mice models

To scrutinize the disorders caused by human mutant apoE7/apoE4, human apoE4 and E7 transgenic mice were established with microinjection technique to examine molecular genetic phenomena in vivo. The integration and expression of h-apoE mutant genes in transgenic mice were determined with Southern blot, Northern blot and ELISA. The current studies indicated that the transgenes and the phenotypes regarding expression of transgenes could be transmitted stably in transgenic lines. The levels of serum lipid in transgenic mice showed the characteristics of hyperlipidemia. Besides, behavior tests demonstrated the degeneration of learning and memory in transgenic mice. Short life span was observed in 2 transgenic lines. After fed with high lipid food high serum lipid was found both in normal and transgenic mice, but their mechanism regulating lipid metabolism was different. It was also verified that the human apoE mutants located at either N-terminal or C-terminal had the same pathogenesis regarding disorders of lipid metabolism in murine.

A mathematical model of presynaptic dopamine homeostasis: implications for schizophrenia

Several lines of evidence implicate altered dopamine neurotransmission in schizophrenia. Current drugs for schizophrenia focus on postsynaptic sites of the dopamine signaling pathways, but do not target presynaptic dopamine metabolism. We have begun to develop a mathematical model of dopamine homeostasis, which will aid our understanding of how genetic, environmental, and pharmacological factors alter the functioning of the presynaptic dopamine neuron. Formulated within the modeling framework of BIOCHEMICAL SYSTEMS THEORY, the mathematical model integrates relevant metabolites, enzymes, transporters, and regulators involved in the control of the biochemical environment within the dopamine neuron. In this report we use the model to assess several components and factors that affect the dopamine neuron and have been implicated in schizophrenia. These include the enzymes COMT, MAO, and TH, different dopamine transporters, as well as administration of amphetamine or cocaine. We also investigate scenarios that could increase (or decrease) dopamine neurotransmission and thus exacerbate (or alleviate) symptoms of schizophrenia. Our results indicate that the model predicts the effects of various factors related to schizophrenia on the homeostasis of the presynaptic dopamine neuron rather well. Upon further refinements and testing, the model has the potential of serving as a tool for screening novel therapeutics aimed at altering presynaptic dopamine function and thereby potentially ameliorating some of the symptomology of schizophrenia.

Steps of modeling complex biological systems

A disease like schizophrenia results from the malfunctioning of a complex, multi-faceted biological system. As a consequence, the root causes of such a disease and the trajectories from health toward the disease are very difficult to comprehend with simple cause-and-effect reasoning. Similarly, reductionistic investigations are crucial for the discovery of specific disease mechanisms, but they are not sufficient for comprehensive assessments and explanations. A promising option for advancing the field is the utilization of mathematical models that can quantitatively account for hundreds of components and their interactions and thus have the potential of truly explaining complex diseases. While the potential of mathematical models is quite evident in principle, their practical implementation is a daunting task. On the one hand, many distinctly different approaches are possible. For instance, in the case of schizophrenia, models could focus on neurological aspects, physiological features, or the biochemical malfunctioning within some cell complexes in the brain, and each model would ultimately be very different. On the other hand, it seems that there are no rules or recommendations that guide the development of a new mathematical model from scratch. We discuss here that, even though mathematical models in biology and medicine may ultimately have a very different appearance, their development can be structured as a sequence of generic steps. Major drivers for many of the details of model development are the goals and objectives of the modeling task and the availability and quality of data that can be used for model design and validation.

Nonlinear Cerenkov radiation in nonlinear photonic crystal waveguides

We study nonlinear Cerenkov radiation generated from a nonlinear photonic crystal waveguide where the nonlinear susceptibility tensor is modulated by the ferroelectric domain. Nonlinear polarization driven by an incident light field may emit coherently harmonic waves at new frequencies along the direction of Cerenkov angles. Multiple radiation spots with different azimuth angles are simultaneously exhibited from such a hexagonally poled waveguide. A scattering involved nonlinear Cerenkov arc is also observed for the first time. Cerenkov radiation associated with quasi-phase matching leads to these novel nonlinear phenomena.

Microdissection-based high-resolution genomic array analysis of two patients with cytogenetically identical interstitial deletions of chromosome 1q but distinct clinical phenotypes

We describe two boys with cytogenetically identical interstitial deletions in the q42.11-q42.13 region of the long arm of chromosome 1 detected by high-resolution G-banding analysis. These children share some phenotypic features but also exhibit distinct morphologic differences. We further characterized the deletions using a new technical strategy--microdissection-based high-resolution genomic array (MHGA) analysis--to define the breakpoints, genomic sizes, and gene contents of the deletions. This showed that the patients had distinguishable deletions that were adjacent but did not overlap, thus explaining the observed phenotypic differences. These results were surprising because we expected at least some degree of overlap to explain the features that were shared. MHGA can quickly give precise and detailed information about any rearrangement in the genome using as little material as a single cell. This novel strategy provides unique advantages for both clinical diagnosis and genomic research.

Regulatory effect of sulphatides on BKCa channels

BACKGROUND AND PURPOSE

Sulphatides are sulphated glycosphingolipids expressed on the surface of many cell types, particularly neurones. Changes in sulphatide species or content have been associated with epilepsy and Alzheimer's disease. As the large conductance, calcium sensitive K(+) channel (BK(Ca)) are modulated by membrane lipids, the aim of the study was to explore possible effects of sulphatides on BK(Ca) channels.

EXPERIMENTAL APPROACH

Using patch-clamp techniques, we studied effects of exogenous sulphatides on BK(Ca) channels expressed in Chinese hamster ovary cells.

KEY RESULTS

Sulphatides reversibly increased the whole-cell current and the single channel open probability of BK(Ca) channels dose-dependently. The EC(50) value on the channel at +10 mV was 1.6 microM and the Hill coefficient was 2.5. In inside-out patches, sulphatides increased the single channel open probability from both intra- and extra-cellular faces of the membrane, but more effectively with external application. Furthermore, activation of the channels by sulphatides was independent of intracellular Ca(2+) concentration. Sulphatides also shifted the activation curve of the channels to less positive membrane potentials. Mutant BK(Ca) channels lacking a 59 aminoacid region important for amphipath activation (STREX) were less activated by the sulphatides.

CONCLUSIONS AND IMPLICATIONS

Sulphatides are novel activators of BK(Ca) channels, independent of intracellular Ca(2+) or other signalling molecules but partly dependent on the STREX sequence of the channel protein. As changes of sulphatide content are associated with neuronal dysfunction, as in epilepsy and Alzheimer's disease, our results imply that these effects of sulphatides may play important pathophysiological roles in regulation of BK(Ca) channels.

Glomerular injury is exacerbated in diabetic integrin α1-null mice

Excessive glomerular collagen IV and reactive oxygen species (ROS) production are key factors in the development of diabetic nephropathy. Integrin alpha1beta1, the major collagen IV receptor, dowregulates collagen IV and ROS production, suggesting this integrin might determine the severity of diabetic nephropathy. To test this possibility, wild-type and integrin alpha1-null mice were rendered diabetic with streptozotocin (STZ) (100 mg/kg single intraperitoneal injection), after which glomerular filtration rate (GFR), glomerular collagen deposition, and glomerular basement membrane (GBM) thickening were evaluated. In addition, ROS and collagen IV production by mesangial cells as well as their proliferation was measured in vitro. Diabetic alpha1-null mice developed worse renal disease than diabetic wild-type mice. A significant increase in GFR was evident in the alpha1-null mice at 6 weeks after the STZ injection; it started to decrease by week 24 and reached levels of non-diabetic mice by week 36. In contrast, GFR only increased in wild-type mice at week 12 and its elevation persisted throughout the study. Diabetic mutant mice also showed increased glomerular deposition of collagen IV and GBM thickening compared to diabetic wild-type mice. Primary alpha1-null mesangial cells exposed to high glucose produced more ROS than wild-type cells, which led to decreased proliferation and increased collagen IV synthesis, thus mimicking the in vivo finding. In conclusion, this study suggests that lack of integrin alpha1beta1 exacerbates the glomerular injury in a mouse model of diabetes by modulating GFR, ROS production, cell proliferation, and collagen deposition.

Potential effects of tetrodotoxin exposure to human glial cells postulated using microarray approach

Sodium channels play an important role in many neurological disorders and also in prostate cancer. Tetrodotoxin (TTX), a blocker of voltage-gated sodium channels has been chiefly used as a molecular probe for the study and characterization of these channels. The regulation of gene expression in response for the exposure of TTX to glial cells which are reported to be involved in neurodegenerative process is poorly understood. Therefore, the present study aims to develop a repository of genes and map it on a few pivotal neurodegenerative pathways to speculate the effect of TTX. Using Affymetrix GeneChip (HG-U133A), we have selected a subset of 692 differentially expressed genes, several of which are-cullin 4A (CUL4A), ubiquitin carrier protein (E2-EPF), proteasome (prosome, macropain) subunit, beta type, 8 (large multifunctional protease 7) (PSMB8), protein tyrosine phosphatase type IVA (PTP4A1), intercellular adhesion molecule 1 (ICAM1), prostaglandin-endoperoxide synthase 2 (PTGS2), and caspase 1 (CASP1). These genes, which facilitate some of the neurodegenerative pathways, such as ubiquitin, proteasome, inflammation and kinases, were identified to be up- or down-regulated for the TTX treatment. Thus, the selected genes were further examined on ubiquitin-proteasome mediated inflammatory responses pathway as ample evidence for the role of glial cell-mediated inflammation in the neurodegenerative process are available. In summary, our result provides a basic understanding of the differentially expressed genes along with one of the possible pathway which may have been modulated by the exposure of TTX.

Additive Effects of Leflunomide and Tacrolimus in Prevention of Islet Xenograft Rejection

Leflunomide is a low molecular weight immunosuppressive drug which inhibits the enzymes dehydroorotate dehydrogenase and protein tyrosine kinase, both of which are important components in the immune response. As the mechanisms of action of leflunomide and tacrolimus are different, we postulated an additive or synergistic effect of the two drugs and investigated the effects of leflunomide alone, or in combination with a suboptimal dose of tacrolimus, on xenogeneic islet transplantation in a rat-to-mouse model. A total of 1200-1500 rat islets were transplanted under the left kidney capsule of streptozotocin-induced diabetic BALB/c mice. The median survival time (MST) of the untreated group was 6 days. Leflunomide at 5, 10 and 20 mg/kg/d administrated for 10 days significantly prolonged MST to 10, 16 and 20 days. A dose of tacrolimus (2 mg/kg/d) was associated with a graft survival of 9 (range 6-12) days; most grafts rejected during ongoing therapy. When tacrolimus (2 mg/kg/d) was combined with leflunomide (10 mg/kg/d), the survival time of the islet xenografts was increased further to 22 days, significantly longer than with leflunomide or tacrolimus alone. In summary, our findings demonstrate that leflunomide prolonged xenogeneic islet graft survival, and that its immunosuppressive effect was improved when combined with tacrolimus.

Characterization of a Functionally Expressed Stretch-activated BKca Channel Cloned from Chick Ventricular Myocytes

We have characterized electrophysiological and pharmacological properties of a stretch-activated BKca channel (SAKcaC) that was cloned from cultured chick ventricular myocytes (CCVM) and expressed in chinese hamster ovary cells (CHO) using the patch-clamp technique. Our results indicate that the cloned SAKcaC keeps most of the key properties of the native SAKcaC in CCVM, such as conductance, ion selectivity, pressure-, voltage- and Ca(2+)-dependencies. However, there was a slight difference between these channels in the effects of channel blockers, charybdotoxin (CTX) and gadolinium (Gd(3+)). The native SAKcaC was blocked in an all-or-none fashion characterized as the slow blockade, whereas the conductance of the cloned SAKcaC was gradually decreased with the blockers' concentration, without noticeable blocking noise. As the involvement of some auxiliary components was suspected in this difference, we cloned a BK beta-subunit from CCVM and coexpressed it with the cloned SAKcaC in CHO cells to examine its effects on the SAKcaC. Although the pharmacological properties of the cloned SAKcaC turned out to be very similar to the native one by the coexpression, it also significantly altered the key characteristics of SAKcaC, such as voltage- and Ca(2+)-dependencies. Therefore we concluded that the native SAKca in CCVM does not interact with the corresponding endogenous beta-subunit. The difference in pharmacological properties between the expressed SAKcaC in CHO and the native one in CCVM suggests that the native SAKca in CCVM is modulated by unknown auxiliary components.

[Experimental study on induction of apoptosis of leukemic cells by Boswellia carterii Birdw extractive]

The purpose of the study was to investigate the apoptosis of leukemic cells induced by Boswellia Carterii Birdw(BCB). The target leukemia cell line HL60 and bone marrow leukemic cells from 30 acute non-lymphocytic leukemic(ANLL) patients (3 M1 11 M2a 10 M3 1 M4a 5 M5b) were studied. Apoptosis was detected by morphological observation, DNA electrophoresis, percentage of DNA fragmentation test and flow cytometric cell cycle analysis. It is concluded that BCB can induce apoptosis in ANLL cells and HL60 cells.

[Study of calcitonin gene methylation in chronic myeloid leukemia by using Hpa II-PCR]

To investigate the role of calcitonin(CT) gene hypermethylation in the transformation from the initial chronic phase to blast crisis of chronic myeloid leukemia, 31 CML patients were studied by using Hpa II-PCR. The results showed that the 10.52%(2/19) chronic phase, 71.4%(5/7) accelerated phase and 80.0%(4/5) blast crisis of patients had CT gene hypermethylation and that the increased methylation of the CT gene were related with the disease progression. The reports indicated that the hypermethylation of CT gene might be a useful marker for predicting the evolution of CML and selecting chronic phase patients for BMT.

[Measurement of soluble Fas in patients with hematological malignancy]

We measured serum levels of soluble Fas(sFas) in 68 patients with hematological malignancy by using sandwich ELISA and detected bone marrow mononuclear cell membrane Fas(mFas) positive cells in 46 patients with acute leukemias by immunohistochemical technic. It was found that sFas levels were significantly higher in acute lymphoblastic leukemia(ALL) patients(median 10.48 +/- 5.89 ng.ml-1) and non-Hodgkin's lymphoma(NHL) patients(median 18.26 +/- 16.47 ng.ml-1) than those in healthy donors (median 0.92 +/- 0.88 ng.ml-1) (P < 0.05). Elevated sFas levels were correlated with the disease stage and progress, but not with other clinical parameters. According to the follow-up of five ALL patients, their serum sFas levels decreased after complete remissions. We conclude that sFas has prognostic value and is an effective clinical parameter with ALL or NHL patients. In addition, sFas levels in the sera of acute non-lymphoblastic leukemia patients were also found to be unchanged compared with those in the normal control.

Cyclooxygenase-2 selective inhibitors and the kidney

Cyclooxygenases (COX) are the target of non-steroidal anti-inflammatory drugs (NSAIDs) which exert their therapeutic effect by blocking COX's capacity to metabolize arachidonate to a series of biologically active fatty acids, designated prostaglandins. NSAID use is associated with two major tonicities: gastrointestinal bleeding and renal dysfunction. In the setting of significant physiologic stress, renal function becomes dependent upon prostaglandins and NSAID use may be associated with acute deterioration of renal function, including development of sodium retention, edema, hypertension, hyperkalemia, and or papillary necrosis. Two isoforms, COX1 and COX2, have been identified. They are products of distinct genes and their expression is under different regulatory control. Both COX1 and COX2 are highly expressed in the kidney and both are inhibited by conventional NSAIDs. Accumulating data using recently developed selective COX2 inhibitors suggest that while these agents spare the gastrointestinal tract they have similar renal effects as non-selective NSAIDs. Therefore, caution should be taken when prescribing selective COX2 inhibitor to patients, especially to patients with predisposed physiologic stress.

Phosphorylation of human N-myristoyltransferase by N-myristoylated SRC family tyrosine kinase members

N-Myristoyltransferase (NMT) is an essential eukaryotic enzyme that catalyzes the cotranslational and/or posttranslational transfer of myristate to the amino terminal glycine residue of a number of important proteins especially the non-receptor tyrosine kinases whose activity is important for tumorigenesis. Human NMT was found to be phosphorylated by non-receptor tyrosine kinase family members of Lyn, Fyn and Lck and dephosphorylated by the Ca(2+)/calmodulin-dependent protein phosphatase, calcineurin. Deletion of 149 amino acids from the N-terminal end resulted in the absence of phosphorylation suggesting that the phosphorylation sites are located in the N-terminal end of NMT. Furthermore, a site-directed mutagenesis study indicated that substitution of tyrosine 100 with phenylalanine served NMT as a poor substrate for the Lyn kinase. A synthetic peptide corresponding to the amino-terminal region encompassing tyrosine 100 of NMT served as a good substrate for the Lyn and Fyn kinases. Our studies also indicated that NMT was found to interact with Lyn through its N-terminal end in a phosphorylation-dependent manner. This is the first study demonstrating the cross-talk between NMT and their myristoylated protein substrates in signaling pathways.

[A century of developmental history of laparoscopic surgery]

Till the year 2001, the development of laparoscopic surgery will have gone through a total of one hundred years. Laparoscopic surgery has made a great progress during the last more than a decade. In retrospect its history, the development of laparoscopic surgery underwent three main eras, viz. diagnostic laparoscopy, operative laparoscopy and the modern laparoscopy era. Although the laparoscopic technology started rather late in China, it develops very quickly. Along with the development of high -- tech, laparoscopic surgery will have a promising future.

[Isolation and study of one novel full-length gene related to human glioma]

OBJECTIVES

To obtain differentially expressed genes related to human glioma using cDNA microarray and make a preliminary study of one novel full-length gene.

METHODS

Total RNA was extracted from human glioma tissues and normal brain tissues, and mRNA was used to make probes. After hybridization and washing procedure, the results of hybridization were scanned using computer system. One gene named 507E08 clone was subsequently analyzed by northern blotting, in situ hybridization, bioinformatics and radiation hybridization.

RESULTS

Fifteen differentially expressed novel genes related to human glioma were obtained through four times of hybridization and scanning. Northern blotting and in situ hybridization confirmed that 507E08 clone was lowly expressed in normal human brain tissue and over-expressed in human glioma tissue. BLASTn and BLASTx analysis showed that the clone 507E08 was a novel full-length gene with the length of 2002 bp. This gene, called human ribosomal protein 14.22 gene, codes 203 amino acids and is located on chromosome 14 between D14S1066 Marker and D14S265 Marker.

CONCLUSION

cDNA microarray technology can be successfully applied to identify differentially expressed genes with small amount of specimen, high quality, high speed, and high sensitivity. The novel full-length human ribosomal protein 14.22 gene may correlate with formation of human glioma.

[Cloning and phylogenetic analysis of hepatitis-associated TT virus subgenome]

Polymerase chain reaction (PCR) was utilized for the DNA amplification from transfusion transmitted virus (TTV) positive serum samples. Five TTV DNA fragments, overlapped about 90% of the genome, were amplified by long template PCR for the generation of TTV subgenome. Recombinant plasmids were obtained by directly inserting PCR products into pT-Adv vector, and DNA sequence analyses showed they were TTV DNA fragments. By using specific restriction enzymes, five TTV DNA fragments were ligated into a TTV DNA subgenome clone and named as TTV021. TTV021 has been deposited in GenBank database with the accession number AF254410. The results of computer analyses showed that TTV021, 3472 nt long, contains two open reading frames (ORF1, 785 aa; ORF2, 146 aa). Identity alignments between TTV021 and other TTV isolates indicated several high conserved regions existed. Phylogenetic analysis of 356 nt from TTV021 suggested that the isolate has close evolutionary relationship with CHN1 (type 1a), but has far relation with other TTV isolates.