Modulation of N-type Ca2+ currents by A1-adenosine receptor activation in male rat pelvic ganglion neurons

Modulation of voltage-activated Ca2+ channels by adenosine was investigated in male rat major pelvic ganglion (MPG) neurons by using the whole-cell variant of the patch-clamp technique. Adenosine inhibited high voltage-activated (HVA) Ca2+ currents in a concentration-dependent manner with an EC50 of 313 nM and a maximal inhibition of 36%, respectively. Inhibition of HVA Ca2+ currents in adrenergic and cholinergic MPG neurons was similar. Adenosine did not modulate T-type Ca2+ channels present in adrenergic MPG neurons. Reverse transcription-polymerase chain reaction analysis indicated that MPG neurons express mRNAs encoding A1 and A2a receptors. Ca2+ current inhibition by adenosine was mimicked by N6-cyclopentyladenosine, an A1-selective agonist (EC50 = 63 nM) and prevented by 100 nM 8-cyclopentyl-1,3-dipropylxanthine, an A1-selective antagonist. Conversely, CGS 21680, an A2a-selective agonist, displayed a relatively low potency (EC50 = 2200 nM) for inhibiting Ca2+ currents. The action of adenosine was significantly attenuated by 2 mM guanosine-5'-thiodiphosphate or 500 ng/ml pertussis toxin. The voltage dependence of adenosine-induced current inhibition was evident by 1) a bell-shaped profile between the current inhibition and test potentials, 2) kinetic slowing in the presence of agonist, and 3) relief of the current inhibition by a conditioning prepulse to +80 mV. Finally, 1 microM omega-conotoxin GVIA occluded adenosine-induced current inhibition. Taken together, we concluded that adenosine inhibits N-type Ca2+ currents by activation of A1 receptors via a voltage-dependent and PTX-sensitive pathway in rat MPG neurons. Our data may explain how adenosine acts as an inhibitory modulator of ganglionic and neuromuscular transmission in the pelvic plexus.

Ifosfamide nephrotoxicity in pediatric cancer patients

The renal functions in pediatric cancer patients who received ifosfamide (IFO) treatment were evaluated and the risk factors related to IFO nephrotoxicity were determined. The medical records of all children treated with IFO were reviewed, and 62 with normal renal function before IFO treatment were selected. Nephrotoxicity was diagnosed by measuring urine beta2-microglobulin and glucose, and serum phosphate, bicarbonate, and creatinine. Forty-eight (77.4%) had a history of previous cisplatin treatment. Nephrotoxicity was detected in 20 patients (32.3%). beta2-Microglobulinuria was observed in all 20, hypophosphatemia in 10 (16.1%), hypocarbia in 2 (3.2%), glucosuria in 5 (8.1%), and decreased creatinine clearance in 7 (11.3%). The cumulative dose of IFO and a history of previous cisplatin therapy were related to nephrotoxicity. Among the 20 patients with nephrotoxicity, the median cumulative dose of IFO in patients with a low (<500 mg/m2) and high (>500 mg/m2) cumulative dose of previous cisplatin was 80 g/m2 (73-102 g/m2) and 45 g/m2 (11-76 g/m2), respectively. Most of the nephrotoxicity persisted after cessation of IFO treatment. In conclusion, close monitoring of IFO nephrotoxicity should be started earlier in patients with high-dose cisplatin pretreatment. Tubular proteinuria, as indicated by beta2-microglobulinuria, was the most-sensitive marker for IFO nephrotoxicity. Long-term follow-up study for reversibility of IFO nephrotoxicity is in progress.

VIP receptors as molecular targets of breast cancer: implications for targeted imaging and drug delivery

Receptors for vasoactive intestinal peptide (VIP-R) are overexpressed in human breast cancer. This phenomenon may have important diagnostic and therapeutic implications because carrier systems loaded with imaging or therapeutic agents, and with surface ligands to VIP-R could potentially be actively targeted to breast cancer. Previously, we have prepared sterically stabilized liposomes (SSL) with VIP non-covalently associated on their surface. However, these liposomes were not able to actively target to breast cancer in rats in situ, most probably due to dissociation of non-covalently associated VIP from SSL. Hence, there is a need to conjugate VIP covalently to SSL. This study aims to begin to address this issue and to test the targeting ability of VIP-SSL to n-methyl nitrosourea (MNU)-induced rat breast cancer in vitro. First, VIP was conjugated to DSPE-PEG(3400)-NHS [1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-n-[poly(ethylene glycol)]-N-hydroxy succinamide, PEG M(w) 3400] under mild conditions to obtain a predominantly 1:1 conjugate of VIP and DSPE-PEG(3400) (DSPE-PEG(3400)-VIP), as evidenced by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Next, DSPE-PEG(3400)-VIP was inserted into preformed fluorescent cholesterol (BODIPY-Chol) labeled SSL by incubation at 37 degrees C. To test breast cancer targeting ability in vitro, these VIP-SSL were subsequently incubated with MNU-induced rat breast cancer tissue sections. The results showed that when compared to fluorescent SSL without VIP or non-covalently attached VIP, significantly more VIP-SSL were attached to rat breast cancer tissues indicating that SSL with covalently attached VIP can be actively targeted to rat breast cancer tissues. This targeted carrier system is currently being explored for functional imaging and targeted chemotherapy of breast cancer.

Inducible macrolide resistance in Corynebacterium jeikeium

Corynebacterium jeikeium is an opportunistic pathogen primarily of immunocompromised (neutropenic) patients. Broad-spectrum resistance to antimicrobial agents is a common feature of C. jeikeium clinical isolates. We studied the profiles of susceptibility of 20 clinical strains of C. jeikeium to a range of antimicrobial agents. The strains were separated into two groups depending on the susceptibility to erythromycin (ERY), with one group (17 strains) representing resistant organisms (MIC > 128 microg/ml) and the second group (3 strains) representing susceptible organisms (MIC < or = 0.25 microg/ml). The ERY resistance crossed to other members of the macrolide-lincosamide-streptogramin B (MLSb) group. Furthermore, this resistance was inducible with MLSb agents but not non-MLSb agents. Expression of ERY resistance was linked to the presence of an allele of the class X erm genes, erm(X)cj, with >93% identity to other erm genes of this class. Our evidence indicates that erm(X)cj is integrated within the chromosome, which contrasts with previous reports for the plasmid-associated erm(X) genes found in C. diphtheriae and C. xerosis. In 40% of C. jeikeium strains, erm(X)cj is present within the transposon, Tn5432. However, in the remaining strains, the components of Tn5432 (i.e., the erm and transposase genes) have separated within the chromosome. The rearrangement of Tn5432 leads to the possibility that the other drug resistance genes have become included in a new composite transposon bound by the IS1249 elements.

Phase, compositional, and morphological changes of human dentin after Nd:YAG laser treatment

Although techniques for repairing root fracture have been proposed, the prognosis is generally poor. If the fusion of a root fracture by laser is possible, it will offer an alternative to extraction. Our group has attempted to use lasers to fuse a low melting-point bioactive glass to fractured dentin. This report is focused on the phase, compositional, and morphological changes observed by means of X-ray diffractometer, Fourier transforming infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy in human dentin after exposure to Nd:YAG laser. The irradiation energies were from 150 mJ/ pulse-10 pps-4 s to 150 mJ/pulse-30 pps-4 s. After exposure to Nd:YAG laser, dentin showed four peaks on the X-ray diffractometer that corresponding to a-tricalcium phosphate (TCP) and beta-TCP at 20 = 30.78 degrees/34.21 degrees and 32.47 degrees/33.05 degrees, respectively. The peaks of a-TCP and beta-TCP gradually increased in intensity with the elevation of irradiation energy. In Fourier transforming infrared analysis, two absorption bands at 2200 cm(-1) and 2015 cm(-1) could be traced on dentin treated by Nd:YAG laser with the irradiation energies beyond 150 mJ/pulse-10 pps-4 s. The energy dispersive X-ray results showed that the calcium/phosphorus ratios of the irradiated area proportionally increased with the elevation of irradiation energy. The laser energies of 150 mJ/ pulse-30 pps-4 s and 150 mJ/pulse-20 pps-4 s could result in the a-TCP formation and collagen breakdown. However, the formation of glass-like melted substances without a-TCP at the irradiated site was induced by the energy output of 150 mJ/ pulse-10 pps-4 s. Scanning electron micrographs also revealed that the laser energy of 150 mJ/ pulse-10 pps-4 s was sufficient to prompt melting and recrystallization of dentin crystals without cracking. Therefore, we suggest that the irradiation energy of Nd:YAG laser used to fuse a low melting-point bioactive glass to dentin is 150 mJ/ pulse-10 pps-4 s.

Nucleophilic substitution at the imidoyl carbon atom: intermediate mechanistic and reactivity behavior between carbonyl and vinyl carbon substitution

Gas-phase nucleophilic substitution reactions at the imidoyl carbon have been investigated using chloride exchanges, Cl- + RY=CHCl right harpoon over left harpoon RY=CHCl + Cl- with Y = N and R = F, H or CH3, at the MP2, B3LYP and G2(+) levels using the MP2/6-311+G geometries. The results are compared with those for the vinyl (Y = CH) and carbonyl (Y = O) carbon substitution. The mechanism and reactivity of substitution at the imidoyl carbon are intermediate between those of carbonyl (SNpi) and vinyl carbon (SNsigma) substitution, which is directly related to the electronegativity of Y, CH < N < O. The prediction of competitive SNsigma with SNpi path for the imidoyl chloride is consistent with the S(N)1-like mechanism proposed for reactions in solution. The important factors in favor of an in-plane concerted SN2 (SNsigma) over an out-of-plane pi-attack (SNpi) path are (i) lower proximate sigma-sigma* charge-transfer energies (DeltaECT), (ii) stronger electrostatic stabilization (DeltaENCT), and (iii) larger lobe size on C(alpha) for the sigma*- than pi*-LUMO despite the higher sigma* than pi* level. The electron correlation energy effects at the MP2 level are overestimated for the relatively delocalized structure (S(N)pi TS) but are underestimated for the localized structure (SNsigma TS) so that the MP2 energies lead to a wrong prediction of preferred reaction path for the vinyl chloride. The DFT at the B3LYP level predicts correct reaction pathways but overestimates the electron correlation effects.

Characterization of primary pure cholesterol hepatolithiasis: cholangioscopic and selective cholangiographic findings

BACKGROUND

Primary pure cholesterol hepatolithiasis has been described recently. The aim of this study was to analyze its clinical and radiologic features, focusing on the cholangioscopic and selective cholangiographic findings.

METHODS

Primary pure cholesterol hepatolithiasis was identified in 3% (6 of 172) of patients who were treated with cholangioscopic stone removal for primary hepatolithiasis during the study period from 1995 to 1999. These 6 consecutive patients (M/F 5:1, mean age 40 years) were enrolled in the study. They underwent abdominal US, CT, endoscopic retrograde cholangiography (ERC), and percutaneous transhepatic cholangioscopy (PTCS). After confirming that the stones were of the cholesterol type, cholangioscopic stone removal via the percutaneous transhepatic route was performed. For the prevention of recurrence, ursodeoxycholic acid (10 mg/kg/day) was prescribed during follow-up.

RESULTS

US demonstrated high echogenicity with strong shadowing in dilated peripheral ducts, whereas CT failed to demonstrate any intraductal abnormal density or calcification except localized duct dilatation. PTCS demonstrated multiple, white to yellowish stones that were morphologically readily distinguishable from brown pigment intrahepatic stones. In all patients, selective cholangiography disclosed the ductal abnormalities, which could not be delineated by ERC in 4 patients. Complete stone removal by PTCS was achieved in 5 of 6 patients. During follow-up (12 to 49 months, mean 22 months), they were asymptomatic and stone recurrence was not detected by US.

CONCLUSIONS

Primary pure cholesterol hepatolithiasis is distinguishable from the more common brown pigment hepatolithiasis by its cholangioscopic and selective cholangiographic characteristics.

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts

BACKGROUND AND OBJECTIVE

The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair.

STUDY DESIGN/MATERIALS AND METHODS

Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining.

RESULTS

The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality.

CONCLUSION

Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.

Human leiomyoma smooth muscle cells show increased expression of transforming growth factor-beta 3 (TGF beta 3) and altered responses to the antiproliferative effects of TGF beta

Transforming growth factor-betas (TGF betas) are multifunctional peptides that regulate growth and differentiation in a variety of cells. The goals of this study were to compare expression of the TGF beta isoforms in normal myometrium and benign leiomyoma tumors of the uterus and to examine the effects of TGF betas on cell proliferation and collagen production by these cells in vitro. Myometrium and leiomyoma tissues were obtained from patients undergoing elective hysterectomies. Tissues were processed for ribonucleic acid (RNA) and were also established as primary cell cultures. Northern blot analysis showed that the levels of TGF beta 1 messenger RNAs (mRNAs) were similar between leiomyoma and myometrium, whereas leiomyoma showed 5-fold higher levels of expression of TGF beta 3 mRNA than autologous myometrium. Expression of TGF beta 3 protein detected by immunohistochemistry was much more intense in leiomyoma tissues than in corresponding myometrium. Levels of both TGF beta 1 and TGF beta 3 increased with increasing cell density for leiomyoma and myometrium smooth muscle cells cultured in vitro. Effects of TGF beta 1 and TGF beta 3 on cell proliferation were assessed by measuring changes in DNA synthesis with the tritiated thymidine incorporation assay. The doses of TGF betas tested were 0, 0.1, 1.0, and 10.0 ng/mL. All three doses of TGF beta 1 and TGF beta 3 inhibited DNA synthesis in myometrium smooth muscle cells by 31--54%. Concomitant treatment with an immunoneutralizing antibody to TGF beta 1--3 reversed this inhibitory effect. In contrast, TGF beta 1 had no effect on leiomyoma smooth muscle cells, whereas TGF beta 3 increased DNA synthesis by leiomyoma cells. Combined treatment with the immunoneutralizing antibody prevented this increase. Treatment of leiomyoma and myometrial cells with the TGF beta immunoneutralizing antibody for 24 h caused a 45--60% reduction in collagen type I and type III mRNA levels, suggesting that endogenous TGF betas are important for collagen production. These results support the hypothesis that alterations in the TGF beta system produce loss of sensitivity to the antiproliferative effects of TGF beta, and increased expression of TGF beta 3 may contribute to the growth of these tumors.

Octamer binding protein-1 is involved in inhibition of inducible nitric oxide synthase expression by exogenous nitric oxide in murine liver cells

Nitric oxide (NO) has diverse effects on immune responses and hepatic functions. In BNL CL.2 cells, the murine embryonic liver cells, inducible nitric oxide synthase (iNOS) mRNA expression appeared after 3 h of treatment with IFN-gamma and LPS. Interestingly, mRNA and protein expression of iNOS was down-regulated by sodium nitroprusside (SNP) and diethylamine dinitric oxide in a time- and dose-dependent manner, but not by H2O2. TNF-alpha gene expression was also dramatically reduced by SNP, but IL-6 gene expression was inhibited much less. IFN-gamma and LPS-induced chloramphenicol acetyltransferase activity of iNOS promoter constructs was inhibited by SNP. Electrophoretic mobility shift assay showed that SNP inhibited IFN-gamma plus LPS-induced Oct-1 binding activity, and the inhibition was reversed by DTT. Mutation in the Oct-1 site completely abolished iNOS promoter activity. In addition, supershift assay and Southwestern analysis demonstrated that the Oct-1 binding activity was inhibited by SNP. Taken together, these results indicate that NO suppresses IFN-gamma plus LPS-induced iNOS expression, and that Oct-1 is an important element in this process.

Beta-poly(L-malate) production by non-growing microplasmodia of Physarum polycephalum. Effects of metabolic intermediates and inhibitors

The production of beta-poly(L-malate) (PMLA) by non-growing microplasmodia of Physarum polycephalum was investigated. Growth was minimal in culture medium devoid of nitrogen source, but PMLA production occurred at a substantial rate. The addition of metabolic intermediates, malate, fumarate, succinate, and oxaloacetate, and the omission of hematin showed considerable growth inhibition in the presence of the nitrogen source, while PMLA production per unit biomass increased significantly. The results indicated that PMLA production was dissociated from biomass production under these conditions. The stimulating effect of carbonate on PMLA production was independent on growth. Cultivation in the absence of the nitrogen source and hematin or in the presence of the metabolites may be a useful technique for efficient PMLA production at a minimum of biomass production.

The amino-terminal domain of the B subunit of vacuolar H+-ATPase contains a filamentous actin binding site

Vacuolar H(+)-ATPase (V-ATPase) binds actin filaments with high affinity (K(d) = 55 nm; Lee, B. S., Gluck, S. L., and Holliday, L. S. (1999) J. Biol. Chem. 274, 29164-29171). We have proposed that this interaction is an important mechanism controlling transport of V-ATPase from the cytoplasm to the plasma membrane of osteoclasts. Here we show that both the B1 (kidney) and B2 (brain) isoforms of the B subunit of V-ATPase contain a microfilament binding site in their amino-terminal domain. In pelleting assays containing actin filaments and partially disrupted V-ATPase, B subunits were found in greater abundance in actin pellets than were other V-ATPase subunits, suggesting that the B subunit contained an F-actin binding site. In overlay assays, biotinylated actin filaments also bound to the B subunit. A fusion protein containing the amino-terminal half of B1 subunit bound actin filaments tightly, but fusion proteins containing the carboxyl-terminal half of B1 subunit, or the full-length E subunit, did not bind F-actin. Fusion proteins containing the amino-terminal 106 amino acids of the B1 isoform or the amino-terminal 112 amino acids of the B2 isoform bound filamentous actin with K(d) values of 130 and 190 nm, respectively, and approached saturation at 1 mol of fusion protein/mol of filamentous actin. The B1 and B2 amino-terminal fusion proteins competed with V-ATPase for binding to filamentous actin. In summary, binding sites for F-actin are present in the amino-terminal domains of both isoforms of the B subunit, and likely are responsible for the interaction between V-ATPase and actin filaments in vivo.

Inhibition of natural killer cell-mediated cytotoxicity by Kaposi's sarcoma-associated herpesvirus K5 protein

Kaposi's sarcoma-associated herpesvirus (KSHV) K3 and K5 proteins dramatically downregulate MHC class I molecules. However, although MHC class I downregulation may protect KSHV-infected cells from cytotoxic T lymphocyte recognition, these cells become potential targets for natural killer (NK) cell-mediated lysis. We now show that K5 also downregulates ICAM-1 and B7-2, which are ligands for NK cell-mediated cytotoxicity receptors. As a consequence, K5 expression drastically inhibits NK cell-mediated cytotoxicity. Conversely, de novo expression of B7-2 and ICAM-1 resensitizes the K5-expressing cells to NK cell-mediated cytotoxicity. This is a novel viral immune evasion strategy where KSHV K5 achieves immune avoidance by downregulation of cellular ligands for NK cell-mediated cytotoxicity receptors.

Syntheses and binding affinities of 6-nitroquipazine analogues for serotonin transporter. Part 1

6-Nitroquipazine has been known as one of the most potent and selective inhibitors of serotonin transporter in vitro and in vivo. Nine derivatives of 6-nitroquipazine were synthesized and tested for their potential abilities to displace [3H]citalopram binding to the rat cortical membranes.

Synthesis of tetrakis(multifluoro-4-pyridyl)porphin derivatives as acetylcholinesterase inhibitors

New tetrakis(multifluoro-4-pyridyl)porphin derivatives (2-4) and water soluble porphyrin (5) were synthesized to investigate their interactions with acetylcholinesterase from electric eel. These compounds have been found to be the potent reversible inhibitors of the enzyme with Ki values of microM range. In addition, porphyrin (5) showed broad spectrum of anticancer activities.

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: thermal behavior and phase transformation of human tooth enamel and dentin after irradiation by CO2 laser

Acute trauma or trauma associated with occlusal disharmony can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. The responses of soft tissues to lasers of different wavelengths are fairly well known, but the reactions of hard tissues are still to be understood. The purpose of this research was to study the feasibility of using a medium energy continuous-wave CO(2) laser and a low melting-point bioactive glass to fuse or bridge tooth fractures. The present report is focused on the first part of the research, the analysis of changes in laser-irradiated human tooth enamel/dentin by means of X-ray diffractometer (XRD), Fourier-transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). After CO(2) laser irradiation, there were no marked changes in the X-ray diffraction pattern of the enamel when compared to that before laser treatment. However, a small peak belonging to alpha-TCP appeared at the position of 2theta=30.78 degrees C. After being treated with CO(2) laser, the dentin showed much sharper peaks on the diffraction patterns because of grain growth and better crystallinity. alpha-TCP and beta-TCP were identified after laser treatment. In the FTIR analysis, an HPO(4)(-2) absorption band was noted before laser treatment disappeared after the irradiation. No significant change in the absorption band of HPO(4)(-2) was found on the FTIR curves of enamel after laser treatment. The results of DTA/TGA indicated that loss of water and organic materials occurred in both enamel and dentin after laser treatment. Under SEM, melting and resolidification occurred in both enamel and dentin by medium energy of CO(2) laser. This implies that using a continuous-wave CO(2) laser of medium energy density to fuse a low melting-point bioactive glass to the enamel/dentin is possible. We believe these phase changes and thermal data can make a useful guide for future studies on the thermal interaction and bridging mechanism between the bioactive glass and enamel/dentin under CO(2) laser irradiation.

Downregulation of major histocompatibility complex class I molecules by Kaposi's sarcoma-associated herpesvirus K3 and K5 proteins

The T-cell-mediated immune response plays a central role in the defense against intracellular pathogens. To avoid this immune response, viruses have evolved elaborate mechanisms that target and modulate many different aspects of the host's immune system. A target common to many of these viruses is the major histocompatibility complex (MHC) class I molecules. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes K3 and K5 zinc finger membrane proteins which remove MHC class I molecules from the cell surface. K3 and K5 exhibit 40% amino acid identity to each other and localize primarily near the plasma membrane. While K3 and K5 dramatically downregulated class I molecules, they displayed different specificities in downregulation of HLA allotypes. K5 significantly downregulated HLA-A and -B and downregulated HLA-C only weakly, but not HLA-E, whereas K3 downregulated all four HLA allotypes. This selective downregulation of HLA allotypes by K5 was partly due to differences in amino acid sequences in their transmembrane regions. Biochemical analyses demonstrated that while K3 and K5 did not affect expression and intracellular transport of class I molecules, their expression induced rapid endocytosis of the molecules. These results demonstrate that KSHV has evolved a novel immune evasion mechanism by harboring similar but distinct genes, K3 and K5, which target MHC class I molecules in different ways.

Sarcoplasmic reticulum Ca(2+)ATPase and cell contraction in developing rabbit heart

The purpose of the present study was to determine whether age-related changes in the expression and function of the cardiac isoform of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) play a role in SR Ca(2+)release and cell contraction. SERCA2a protein levels and subcellular localization were compared between fetal, neonatal, juvenile and adult New Zealand White rabbits. Studies of SERCA function in isolated myocytes were performed in situ by examining the rate of reloading of the SR Ca(2+)stores following caffeine-induced depletion. We found that significant quantities of SERCA2a were present early in immature heart and that SERCA2a expression reached adult levels within 15-30 days after birth. Furthermore, SERCA2a protein is present as a series of transverse striations within the cell as early as 1 day of age. In contrast to previous studies of SERCA in vitro, the SERCA protein function in situ was found to be comparable between neonatal and adult myocytes in maintaining SR Ca(2+)stores. These results indicate that the paucity of SR Ca(2+)release in immature ventricular cardiac myocytes is not the result of immaturity in SERCA2a expression.