Wound fluids from saline solution- and Staphylococcus aureus peptidoglycan-inoculated sponges induce expression of matrix metalloproteinase 13 messenger ribonucleic acid by cultured rat fibroblasts

Polyvinyl alcohol sponges inoculated with Staphylococcus aureus peptidoglycan induce an accelerated wound healing response when implanted subcutaneously in rats. S. aureus peptidoglycan leads to a marked increase (50%) in reparative tissue collagen (as measured by hydroxyproline) by 4 days. However, this effect drops by 7 days and by 14 days; hydroxyproline levels are similar in sponges inoculated with S. aureus peptidoglycan or saline solution. These data suggest a very active early remodeling process in S. aureus peptidoglycan sponge reparative tissue. Consistent with this observation, we had found that steady-state levels of matrix metalloproteinase-13 mRNA were higher and persisted longer in S. aureus peptidoglycan sponge reparative tissue than in controls. We hypothesized that S. aureus peptidoglycan might induce a change in reparative tissue fibroblast phenotype or modify the character of the wound fluid. Fibroblasts obtained from saline solution- and S. aureus peptidoglycan-inoculated sponges 4 days after subcutaneous implantation and cultured in Eagle's minimal essential medium supplemented with 10% fetal calf serum were similar with respect to morphologic features, proliferation, and expression of pro alpha1 (I) and alpha1 (III) collagens and tissue inhibitor of metalloproteinase-1 mRNA by Northern blot analysis. Neither cell type expressed matrix metalloproteinase-13 mRNA. No changes in the above parameters were detected when such fibroblasts were cultured for 24 hours in the presence of 0.5 mg of S. aureus peptidoglycan per 10 ml of medium or with fluid obtained from control sponges cultured for 12 hours with phosphate-buffered saline solution. Wound fluids extracted with Eagle's minimal essential medium by homogenization of saline solution- and S. aureus peptidoglycan-inoculated sponges implanted subcutaneously for 12 hours did not affect the proliferation of the fibroblasts. However, the extracts had a profound effect on the cellular expression of tissue inhibitor of metalloproteinase-1, matrix metalloproteinase-13, and pro alpha1 (I) collagen mRNA. Specifically, expression of matrix metalloproteinase-13 mRNA was induced, expression of pro alpha1 (I) collagen mRNA was reduced by 70%, and expression of tissue inhibitor of metalloproteinase-1 mRNA was increased by 150%. These changes were the same irrespective of whether the wound fluid was obtained from saline solution- or S. aureus peptidoglycan-inoculated sponges. Fluid obtained from S. aureus peptidoglycan-inoculated sponges, which contain a greater inflammatory exudate than saline solution-inoculated sponges do, is enriched in matrix metalloproteinase-13 mRNA-inducing activity. The nature of the factor(s) that induces matrix metalloproteinase-13 mRNA expression is not known. However, preliminary data suggest that the matrix metalloproteinase-13-inducing factor(s) is heterogeneous with regard to size and is temperature sensitive and trypsin resistant.

The benefits of laparoscopic antireflux surgery for the treatment of gastroesophageal reflux disease

In the U.S., more then 10% of adults have symptoms of gastroesophageal reflux disease (GERD), which is caused by the combination of incompetent lower esophageal sphincter and sliding hiatal hernia. Most symptoms of this disease are mild and they do not require treatment. However, severe conditions such as esophageal erosion, ulceration, stricture, asthma due to aspiration and chronic respiratory infections require medical or surgical managements. Most patients can be effectively treated with traditional medical management utilizing dietary modification, weight loss, raising the head of the bed, antacids, H2 antagonists and proton pump inhibitors. Recently, though, it has been proven that long-term relief may be achieved more efficiently with antireflux surgery or Laparoscopic Nissen fundoplication. Since 1993, a total of 80 patients with advanced GERD have undergone laparoscopic nissen fundoplication at the United Hospital Center in Clarksburg, W.Va., and the results have been excellent. In addition, the hospital charges for patients having laparoscopic Nissen fundoplication are much less than for those who undergo open procedure and the recuperation time is much shorter.

Disregulation of mitotic checkpoints and regulatory proteins following acute expression of SV40 large T antigen in diploid human cells

SV40 large T antigen (T) inactivates the tumor suppressor proteins p53 and pRb, and can induce cells to enter DNA replication at inappropriate times. We show here that T also compromises three cell cycle checkpoints that regulate the entry into and exit from mitosis. Human diploid fibroblasts infected with a retrovirus expressing T displayed an attenuated radiation-induced mitotic delay, were more susceptible to chemical-induced uncoupling of mitosis from the completion of DNA replication, and were more likely to exit mitosis and rereplicate their DNA when mitotic spindle assembly was inhibited. Consistent with altered mitotic checkpoint control, cells expressing T displayed elevated protein levels and/or associated activities of the mitotic regulatory proteins cyclin A, cyclin B, Cdc25C and p34(cdc2). These changes in mitotic control were evident within 5-10 population doublings after retroviral infection, indicating a direct effect of T expression. Cells acutely infected with the T-expressing retrovirus suffered numerical and structural chromosome aberrations, including increases in aneuploidy, dicentric chromosomes, chromatid exchanges and chromosome breaks and gaps. These findings indicate that T rapidly disrupts mitotic checkpoints that help maintain genomic stability, and suggest mechanisms by which T induces chromosome aberrations and promotes the immortalization and neoplastic transformation of human cells.

Serum responses to the combination of Epstein-Barr virus antigens from both latent and acute phases in nasopharyngeal carcinoma: complementary test of EBNA-1 with EA-D

Elevated serum IgA to antigens of EBV is associated with nasopharyngeal carcinoma (NPC). We have tested 620 NPC sera by ELISA for the presence of antibodies to EBV-encoded DNA binding protein, EBV-specific DNA polymerase, early antigen-diffused (EA-D), EBV nuclear antigen 1 (EBNA-1), EBV-specific thymidine kinase, and BamHI Z fragment EBV replication antigen. Sensitivity of these proteins was in the range of 51.5-79.5% for IgA and 69.4-82.8% for IgG. The complementary use of EBNA-1 with EA-D, however, could increase the sensitivity significantly to 98.1%. Western blot analysis further showed that the combination of EBNA-1 and EA-D is most useful for the detection of NPC. This is the first report of using double biomarkers including EBV gene products from both latent and active infections. The results of this study suggest that EBV in NPC may not be latent alone and that the method may be valuable for the early detection, early treatment, and better survival rate of patients with NPC. Because the application of recombinant EBV protein in ELISA is cost-effective and feasible for mass screening, the method may be of worth for further clinical investigation.

A mitosis-specific phosphorylation of the gap junction protein connexin43 in human vascular cells: biochemical characterization and localization

Western blotting studies revealed that connexin43 (Cx43), one of the major gap junction proteins in human vascular endothelial cells, is posttranslationally modified during mitosis. This mitosis-specific modification results in a Cx43 species that migrates as a single protein band and was designated Cx43(m). Cx43(m) was shown to be the result of additional Ser/Thr phosphorylation as indicated by: (a) the increased gel mobility induced by both alkaline phosphatase and the Ser/ Thr-specific protein phosphatase-2A (PP2A) and (b) the removal of virtually all (32)P(i) from Cx43(m) by PP2A. Immunofluorescent confocal microscopy of mitotic cells revealed that Cx43 is intracellularly located, while in nonmitotic cells Cx43 is located at regions of cell-cell contact. Dye coupling studies revealed that mitotic endothelial cells were uncoupled from each other and from nonmitotic cells. After cytokinesis, sister cells resumed cell coupling independent of de novo protein synthesis. The mitosis-specific phosphorylation of Cx43 correlates with the transient loss of gap junction intercellular communication and redistribution of Cx43, suggesting that a protein kinase that regulates gap junctions is active in M-phase.

Requirement of the DEAD-Box protein ded1p for messenger RNA translation

The DED1 gene, which encodes a putative RNA helicase, has been implicated in nuclear pre-messenger RNA splicing in the yeast Saccharomyces cerevisiae. It is shown here by genetic and biochemical analysis that translation, rather than splicing, is severely impaired in two newly isolated ded1 conditional mutants. Preliminary evidence suggests that the protein Ded1p may be required for the initiation step of translation, as is the distinct DEAD-box protein, eukaryotic initiation factor 4A (eIF4A). The DED1 gene could be functionally replaced by a mouse homolog, PL10, which suggests that the function of Ded1p in translation is evolutionarily conserved.

Dbp3p, a putative RNA helicase in Saccharomyces cerevisiae, is required for efficient pre-rRNA processing predominantly at site A3

In Saccharomyces cerevisiae, ribosomal biogenesis takes place primarily in the nucleolus, in which a single 35S precursor rRNA (pre-rRNA) is first transcribed and sequentially processed into 25S, 5.8S, and 18S mature rRNAs, leading to the formation of the 40S and 60S ribosomal subunits. Although many components involved in this process have been identified, our understanding of this important cellular process remains limited. Here we report that one of the evolutionarily conserved DEAD-box protein genes in yeast, DBP3, is required for optimal ribosomal biogenesis. DBP3 encodes a putative RNA helicase, Dbp3p, of 523 amino acids in length, which bears a highly charged amino terminus consisting of 10 tandem lysine-lysine-X repeats ([KKX] repeats). Disruption of DBP3 is not lethal but yields a slow-growth phenotype. This genetic depletion of Dbp3p results in a deficiency of 60S ribosomal subunits and a delayed synthesis of the mature 25S rRNA, which is caused by a prominent kinetic delay in pre-rRNA processing at site A3 and to a lesser extent at sites A2 and A0. These data suggest that Dbp3p may directly or indirectly facilitate RNase MRP cleavage at site A3. The direct involvement of Dbp3p in ribosomal biogenesis is supported by the finding that Dbp3p is localized predominantly in the nucleolus. In addition, we show that the [KKX] repeats are dispensable for Dbp3p's function in ribosomal biogenesis but are required for its proper localization. The [KKX] repeats thus represent a novel signaling motif for nuclear localization and/or retention.

Mobile cecum syndrome: a report of two cases

Mobile cecum syndrome is characterized by chronic right lower quadrant pain with the evidence of neither appendicitis nor other pathological findings at operation. Two cases of mobile cecum syndrome are reported; both had intermittent right lower quadrant cramping pain for months. One had received appendectomy because of chronic right lower quadrant pain at another hospital about nine months before admission here. The symptoms did not improve postoperatively, and the patient underwent laparotomy under impression of partial intestinal obstruction. The other patient underwent laparotomy under impression of chronic appendicitis. At surgery, both were found to have cecum and ascending colon were not attached to the posterior parietal wall, and cecopexy was performed. They have now been symptom free for one year. Cecopexy appears therefore to be an effective method of treatment of mobile cecum syndrome.

SV40 T antigen increases the expression and activities of p34cdc2, cyclin A, and cyclin B prior to immortalization of human diploid fibroblasts

SV40 T antigen induces karyotype instability soon after it is expressed in human diploid fibroblasts and ultimately promotes cell immortalization and tumorigenesis. Protein levels and activities of mitotic cell cycle proteins have been shown to be elevated in several immortal cell lines relative to their normal parental cells, suggesting a possible role for the aberrant regulation of mitosis in karyotype instability. We show here that IMR-90 human diploid lung fibroblasts expressing the SV40 tumor antigens display increased protein levels and associated enzymatic activities of cyclin A, cyclin B, and p34cdc2 long before crisis and immortalization. These elevations cannot be explained by faster cell growth or altered cell cycle distributions. Increased protein levels were not totally accounted for by elevated levels of the corresponding mRNA, indicating that T antigen modulates expression at least partially by posttranscriptional mechanisms. These results indicate that perturbation of mitotic regulatory proteins precedes crisis, and imply that altered mitotic control is a direct consequence of T antigen expression rather than an outcome of secondary events associated with immortalization.

Purification and characterization of a naturally processed hepatitis B virus peptide recognized by CD8+ cytotoxic T lymphocytes

In vitro studies in patients with hepatitis B virus (HBV) infection have suggested that hepatocytolysis induced by CD8+ cytotoxic T lymphocytes (CTLs) is the most important effector pathway in eliminating infected cells. The recognition is implicated in the endogenously processed HBV antigens in the context of HLA class I molecules presented on the liver cell membrane. However, the naturally occurring HBV peptide antigens have not yet been demonstrated. We report here that a naturally processed peptide antigen P2 was isolated from HLA class I molecules of HBV-infected liver cell membrane. The P2 peptide exhibited the activity of sensitizing target cells for lysis by CD8+ CTLs. The P2 sequence (YVNVNMGLK) purified from liver tissue was in concordance with that encoded by the viral genome for the HBV nucleocapsid antigen or HBcAg 88-96. P2 peptide could also be isolated from the EBV-transformed B cells that were transfected by HBcAg-expressing vector. The P2 epitope, sharing the HLA-A11 binding motifs, was recognized by HLA-A11-restricted CD8+ CTLs. The data provided direct evidence that, in hepatitis B patients, antigenic peptides of HBV were processed by hepatocytes, presented with the class I MHC molecules, and recognized by CD8+ CTLs.

Induction of cyclin A gene expression by homocysteine in vascular smooth muscle cells

Homocysteine is an important and independent risk factor for arteriosclerosis. We showed previously that homocysteine stimulates vascular smooth muscle cell proliferation, a hallmark of arteriosclerosis. We show here that homocysteine and serum increased DNA synthesis synergistically in both human and rat aortic smooth muscle cells (RASMCs). Treatment of quiescent RASMCs with 1 mM homocysteine or 2% calf serum for 36 h increased cyclin A mRNA levels by 8- and 14-fold, respectively, whereas homocysteine plus serum increased cyclin A mRNA levels by 40-fold, indicating a synergistic induction of cyclin A mRNA. Homocysteine did not increase the half-life of cyclin A mRNA (2.9 h), but it did increase the transcriptional rate of the cyclin A gene in nuclear run-on experiments. The positive effect of homocysteine on cyclin A gene transcription was confirmed by our finding that homocysteine increased cyclin A promoter activity and ATF-binding protein levels in RASMCs. Finally, 1 mM homocysteine increased cyclin A protein levels and cyclin A-associated kinase activity by threefold. This homocysteine-induced expression lesions by promoting proliferation of vascular smooth muscle cells.

Effect of enteral and parenteral nutrition on amino acid levels in cancer patients

BACKGROUND

The syndrome of cancer cachexia can have a significant impact on response to therapy as well as on survival in cancer patients. Therapies directed at metabolic perturbations in cachectic patients are dependent on nutritional repletion and maintenance of adequate amino acid substrate levels. This study compares the ability of oral feeding, enteral nutrition, and total parenteral nutrition to alter plasma amino acid levels in cancer patients.

METHODS

Patients with esophageal cancer were stratified by weight loss. Patients with < 20% weight loss were randomized to continue an ad libitum oral diet (group I) or to receive total parenteral nutrition (group II) for 2 weeks; patients with > 20% weight loss were randomized to receive either enteral nutrition (group III) or total parenteral nutrition (group IV) for 2 weeks. Plasma amino acid levels were measured before the study and again after 2 weeks of nutrition support.

RESULTS

Before therapy, there was no difference between the groups in total or essential amino acid levels; however, patients in all groups had significantly lower total amino acid levels compared with those of normal controls. After 2 weeks of treatment, patients in group I and III showed no difference in individual, essential, or total amino acid levels. However, patients in groups II and IV showed significant increases in a number of individual amino acids as well as in essential and total amino acid levels after 2 weeks of TPN.

CONCLUSIONS

Patients with esophageal cancer demonstrated significant alterations in amino acid profiles compared with those of normal controls. Total parenteral nutrition was superior to ad libitum oral feeding and jejunostomy feeding in repleting plasma amino acid levels.

A method of stimulating an immune response with a hapten immobilized on a nitrocellulose membrane

Hapten refers to a chemical compound of small molar mass (typically less than 1000 daltons) that can bind with an antibody, but cannot initiate an immune response by itself unless it is conjugated to a protein carrier of larger molar mass. A novel method to prepare a hapten to generate anti-hapten immunity without covalent conjugation to a carrier was developed. Coating both water-soluble and -insoluble haptens onto a nitrocellulose membrane effectively presented haptens to the system and caused the generation of specific anti-hapten B lymphocytes and antibodies by immunization both in vitro and in vivo. This method has a potential to substitute for conventional hapten carrier conjugation to generate anti-hapten immunity.

Expression of the Epstein-Barr virus DNA polymerase in Escherichia coli for use as antigen for the diagnosis of nasopharyngeal carcinoma

Epstein-Barr virus (EBV) encoded DNA polymerase (POL) was cloned and over-expressed in Escherichia coli. Western blot analysis confirmed the presence of antibody to this POL protein in sera from nasopharyngeal carcinoma (NPC) patients. By Western blot analysis, moderate to high concentration of IgG POL-specific antibodies were present in 43 of 48 NPC sera and only 4 of 48 healthy, seropositive controls. The POL-specific IgG antibodies appear as early as stage I of NPC, suggesting that the recombinant POL protein can be a useful diagnostic marker for early diagnosis of the disease. It was also found that human sera containing high titer of cytomegalovirus (CMV) antibodies or herpes simplex virus type 1 (HSV-1) antibodies did not cross-react with the recombinant EBV POL, despite the homology shared by DNA polymerase proteins of these viruses.

Effect of dl-praeruptorin A on calcium current in ventricular cells of guinea pig

With patch clamp technic (whole cell recording), the effect of dl-praeruptorin A (Pra), an ingredient of Peucedanum praeruptorum Dunn on calcium current (ICa) in the single ventricular cells of guinea pig was studied. Results showed that under Cs/Cs condition, when the holding potential was -40 mV and in the presence of Pra (1, 10, 100 mumol.L-1), ICa was decreased dose-dependently from 2.02 +/- 0.24, 2.00 +/- 0.12, 2.12 +/- 0.33 nA (control) to 1.60 +/- 0.24, 1.32 +/- 0.08, 1.16 +/- 0.43 nA, respectively, and their inhibitory rates were 21%, 33.5%, 45%, respectively. The current-voltage relation curve showed that the reversal potential of ICa was +60 mV; the potential producing peak value of ICa was about 0 mV. The results indicated that Pra had a Ca2+ channel blocking effect.

Effects of 3'-angeloyloxy-4'-acetoxy-3',4'-dihydroseselin on cardiohemodynamics in anesthetized dogs

Cardiohemodynamic effects of 3'-angeloyloxy-4'-acetoxy-3',4'-dihydroseselin (Pd-Ia) isolated from the Chinese medicinal plant Peucedanum praeruptorum Dunn were compared with those of diltiazem (Dil) in anesthetized open-chest dogs. Pd-Ia 3 mg.kg-1 increased coronary blood flow from 25 +/- 11 to 58 +/- 16 ml.min-1 (n = 7, P < 0.01) and decreased mean aortic pressure (MAP) from 13 +/- 2 to 8 +/- 1 kPa (P < 0.01), rate pressure product (RPP) from 1.9 +/- 0.5 to 1.3 +/- 0.3 MPa.bpm (P < 0.05), +dp/dtmax from 246 +/- 56 to 160 +/- 36 kPa.s-1 (P < 0.01) and systemic vascular resistance from 19 +/- 4 to 12 +/- 7 Pa.ml-1.min-1 (P < 0.05), together with an increase in HR. Dil showed effects similar to those of Pd-Ia except for a marked decrease in HR. The effects of Pd-Ia on MAP and RPP were approximately one-tenth as potent as those of Dil. The results demonstrated that Pd-Ia was a Ca2+ channel blocker.

Immune response to a hepatitis C virus nonstructural protein in chronic hepatitis C virus infection

The immune responses to a hepatitis C virus nonstructural protein (T3Ag) overlapping with the C100-3 antigen were examined in three groups of patients with chronic non-A, non-B hepatitis. Group I included 20 cases positive for both anti-C100-3 and the second-generation anti-HCV test (anti-HCV-II): Group II, five cases with anti-C100-3(-)/anti-HCV-II(+); and Group III, seven cases negative for both tests. HCV RNA was detectable in 20 (100%), 4 (80%) and 0 (0%) patients in each group, respectively. Proliferative responses of peripheral blood mononuclear cells to T3Ag were present in 16 (80%), 3 (60%) and 0 (0%) cases in each group, respectively (p < 0.05). Removal of CD8+ T cells from peripheral blood mononuclear cells resulted in a conversion of unresponsiveness to significant proliferation to T3Ag in the remaining cases in groups I and II, but not in group III. This change paralleled the antigen-induced production of interferon-gamma and interleukin-2, but not interleukin-4. The removal also enhanced the T3Ag-stimulated anti-C100-3 antibody production from cultured peripheral blood mononuclear cells in group II patients. These results indicate that the T3Ag-specific type 1 T helper cells play an important role in regulating anti-C100-3 antibody secretion in hepatitis C patients.

Effects of 3'-angeloyloxy-4'-acetoxy-3',4'-dihydroseselin on myocardial dysfunction after a brief ischemia in anesthetized dogs

The effect of a 30-min infusion of 3'-angeloyloxy-4'-acetoxy-3', 4'-dihydroseselin (Pd-Ia), a coumarin isolated from Peucedanum praeruptorum Dunn 0.15 mg.kg-1.min-1 on regional myocardial dysfunction was examined in 16 anesthetized open-chest dogs subjected to a 15-min occlusion of the left anterior descending coronary artery followed by a 3-h reperfusion. Segment lengths of left ventricular wall were measured with an ultrasonic micrometer. The control caused a decrease in the % of segment shortening (SS%) throughout the reperfusion period (n = 8), while Pd-Ia ameliorated segment function immediately after reperfusion and restored the SS% to 41 +/- 51% of the baseline value (n = 8, P < 0.05 vs control) 5 min after reperfusion without any significant changes in cardiohemodynamics. The improvement of myocardial function induced by Pd-Ia was maintained at least 3 h after reperfusion. These findings revealed that Pd-Ia had a cardioprotective action in stunned myocardium.

Effects of a pyranocoumarin compound isolated from a Chinese medicinal plant on ischemic myocardial dysfunction in anesthetized dogs

A pyranocoumarin compound, 3'-angeloyloxy-4'-acetoxy-3',4'-dihydroseselin (Pd-Ia), isolated from Bai-Hua Qian-Hu, a Chinese medicine, is known to possess a Ca2+ channel antagonist action. We examined the effect of Pd-Ia on cardiohemodynamics and regional myocardial dysfunction after transient ischemia in anesthetized open-chest dogs. I.v. injections of Pd-Ia (0.1-3.0 mg/kg, n = 7) significantly and dose dependently increased coronary blood flow and decreased mean aortic pressure, maximal rate of rise in left ventricular pressure, rate pressure product and systemic vascular resistance, together with a slight increase in heart rate. Diltiazem (0.03-1.00 mg/kg, n = 6) showed effects on the cardiohemodynamics similar to those of Pd-Ia, except for a marked decrease in heart rate. The effects of Pd-Ia on mean aortic pressure and rate pressure product were approximately 10 times less potent than those of diltiazem. In the second experiment, the effect of a 30-min infusion of Pd-Ia (0.15 mg/kg/min) or vehicle on regional myocardial dysfunction was examined in 16 anesthetized dogs subjected to a 15-min occlusion of the left anterior descending coronary artery followed by a 3-h reperfusion. Infusion of Pd-Ia was started 15 min before coronary occlusion. The vehicle caused a decrease in percent segment shortening throughout the reperfusion period (n = 8). However, Pd-Ia at the dose that produced no significant changes in cardiohemodynamics resulted in a marked improvement in percent segment shortening of the ischemic and reperfused myocardium (n = 8, P < 0.05 vs. control group).(ABSTRACT TRUNCATED AT 250 WORDS)

Presence of hepatitis B surface antigen (HBsAg)-specific cytotoxic T cells in asymptomatic HBsAg carriers

To investigate whether there is any evidence of an immune stimulation against hepatitis B virus surface antigen (HBsAg) in asymptomatic HBsAg carriers, proliferative and cytotoxic responses to HBsAg were measured in their peripheral blood lymphocytes. Although the majority of asymptomatic carriers had no proliferative response to HBsAg, 3 (25%) of 12 carriers showed significant T cell proliferation against HBsAg. In addition, using HBsAg-expressing autologous lymphoblastoid cell line (LCL) as target cells, HBsAg-specific cytotoxic activity was found in 2 of 3 asymptomatic HBsAg carriers who had a proliferative response against HBsAg. Furthermore, 6 cytotoxic T lymphocyte (CTL) clones were isolated from 1 asymptomatic carrier. The epitope recognized by 2 CTL clones was mapped to the major HBsAg residues 158-172. These CTL clones were able to produce interferon-gamma, tumor necrosis factor-alpha, or granulocyte-macrophage colony-stimulating factor. These findings demonstrate the presence of HBsAg-specific, major histocompatibility complex class I-restricted CTL in asymptomatic HBsAg carriers.

Whole-cell patch clamp measurements and berberine inhibition of hyperpolarization-activated inward current in rabbit sinoatrial node cells

Single rabbit sinoatrial node (SAN) cells were isolated by means of an enzymatic dispersion procedure and used for the whole-cell patch clamp experiment. At a holding potential of -40 mV, a time- and voltage-dependent inward current, I(f), was activated at different hyperpolarization potentials from -60 mV to -110 mV. The current-voltage relation curve showed that I(f) was activated at potential more negative than -40 mV. Five min after treatment by CsCl 2 mmol.L-1-containing Tyrode solution, I(f) was almost completely blocked. At a hyperpolarization potential of -110 mV, I(f) was reduced from 1.7 +/- 0.2 nA of the control to 1.2 +/- 0.4 nA after superfusing with Tyrode solution containing berberine (Ber) 1 mumol.L-1 for 5 min. And it was difficult to wash out this action. Ber also had inhibitory effects on other currents to a certain extent. The results indicate that I(f) is a Cs(+)-sensitive current and that the negative chronotropic effect of Ber may be due to the inhibition of I(f) that functions as an important pacemaking modulator for the spontaneous depolarization of SAN tissue.

Four yeast spliceosomal proteins (PRP5, PRP9, PRP11, and PRP21) interact to promote U2 snRNP binding to pre-mRNA

We have analyzed the functions of several pre-mRNA processing (PRP) proteins in yeast spliceosome formation. Here, we show that PRP5 (a DEAD box helicase-like protein), PRP9, and PRP11 are each required for the U2 snRNP to bind to the pre-spliceosome during spliceosome assembly in vitro. Genetic analyses of their functions suggest that they and another protein, PRP21, act concertedly and/or interact physically with each other and with the stem-loop IIa of U2 snRNA to bind U2 snRNP to the pre-mRNA. Biochemical complementation experiments also indicate that the PRP9 and PRP11 proteins interact. The PRP9 and PRP11 proteins may be functioning similarly in yeast and mammalian cells. The requirement for ATP and the helicase-like PRP5 protein suggests that these factors might promote a conformational change (involving either the U1 or U2 snRNP) that is required for the association of U2 snRNP with the pre-mRNA.