Trafficking of preassembled opioid mu-delta heterooligomer-Gz signaling complexes to the plasma membrane: coregulation by agonists

The cellular site of formation, Galpha-coupling preference, and agonist regulation of mu-delta opioid receptor (OR) heterooligomers were studied. Bioluminescence resonance energy transfer (BRET) showed that mu-deltaOR heterooligomers, composed of preformed mu and delta homooligomers, interacted constitutively in the endoplasmic reticulum (ER) with Galpha-proteins forming heteromeric signaling complexes before being targeted to the plasma membrane. Compared to muOR homooligomers, the mu-delta heterooligomers showed higher affinity and efficiency of interaction for Gz over Gi, indicating a switch in G-protein preference. Treatment with DAMGO or deltorphin II led to coregulated internalization of both receptors, whereas DPDPE and DSLET had no effect on mu-delta internalization. Staggered expression resulted in non-interacting mu and delta receptors, even though both receptors were colocalized at the cell surface. Agonists failed to induce BRET between staggered receptors, and resulted in internalization solely of the receptor targeted by agonist. Thus, mu-deltaOR heterooligomers form and preferentially associate with Gz to generate a signaling complex in the ER, and have a distinct agonist-internalization profile compared to either mu or delta homooligomers.     

Influence of calcium on proliferation and phenotype alteration of cardiomyocyte in vitro

An accelerated weight gain is noted in the heart of Ca-deficient, hypertensive chick embryos maintained in a shell-less culture in vitro. We previously observed that the Ca handling property of cardiomyocytes isolated from the shell-less embryo is altered, i.e., faster Ca uptake, suggesting a requirement for adequate Ca supply and/or proper Ca handling in embryonic cardiac development. In this study, we have examined the function of Ca on cardiomyocytes by analyzing the effects of (1) various Ca concentration in the culture medium (NCa, 1.8 mmol/L; HCa, 2.8 mmol/L; LCa, 0.9 mmol/L), and (2) various modulators of Ca handling on cell proliferation and phenotype regulation in chick embryonic cardiomyocytes. The analytical parameters included cell number, DNA content, expression of cell cycle–specific and cardiomyocyte-specific proteins, and creatine phosphokinase (CPK) and lactate dehydrogenase (LDH) enzyme activities. Cell number and total DNA were significantly larger (P < 0.01) in LCa cultures compared with those in NCa. The level of LDH was elevated (P < 0.01), but that of CPK was lowered in LCa. Expression of the G1-S–specific protein PCNA was raised, but that of the contractile proteins myosin and tropomyosin was substantially suppressed in LCa; in HCa, the cells did not proliferate as well, whereas the level of contractile proteins was higher. Thapsigargin, a sarcoplasmic reticulum (SR)-specific, Ca-ATPase inhibitor, simulated the effects of LCa by enhancing cell proliferation and lowering the expression of tropomyosin. These results suggest that culturing in low Ca concentration and inhibition of SR Ca pumping enhance myocardial cell proliferation and suppress sarcomeric protein expression, perhaps by inducing cellular de-differentiation. The in vitro effects of medium Ca concentration and Ca handling modulators on cardiomyocytes also suggest that the in vivo cardiomegaly of the SL embryos is a direct result of Ca-deficiency, and that Ca is important in the phenotype regulation of cardiomyocytes. J. Cell. Physiol. 177:289–298, 1998. © 1998 Wiley-Liss, Inc.     

Host plants mixture and fitness of Kolla paulula: with an evaluation of the application of Weibull function

The xylem‐feeding leafhopper Kolla paulula (Walker), a vector of Pierce's disease, occurs primarily on weeds in and around fruit and ornamental crop orchards in Taiwan. Because our preliminary studies showed that K. paulula performed poorly when reared on pilose beggarticks (Bidens pilosa L. var. radiata) (PB) or trilobate wedelia (Wedelia triloba (L.)) (TW) alone, we collected the life table data of K. paulula reared on a mixture of both host plants to determine the effect at the population level. During their lifespan, 95.6% of feeding time was spent on the major host plant (PB) and only 4.4% on the minor host plant (TW). The intrinsic rate of increase (r), finite rate of increase (λ), net reproduction rate (R₀) and mean generation time (T) of K. paulula were 0.0487, 1.0500 day^?1, 35.86 offspring and 73.4 days, respectively. Because more than 95% of the insects have been observed feeding on both plants, this would indicate that the minor host plant may play an important role in the fitness of K. paulula regardless of the short feeding time. We calculated the percentage contribution to the population parameters made by females that had fed on both PB and TW and compared these with the values obtained for offspring of females that had fed solely on PB. We also evaluated the usefulness of applying the Weibull distribution in demographic studies. We demonstrated that when there is a higher mortality in specific life stages, the fitted Weibull distribution would be inaccurate in describing the survival curve and that application of the fitted curve to the calculation of life expectancy or other statistics would result in significant discrepancy to the actual curve.     

Human palatine tonsil: a new potential tissue source of multipotent mesenchymal progenitor cells

Introduction  

Mesenchymal progenitor cells (MPCs) are multipotent progenitor cells in adult tissues, for example, bone marrow (BM). Current challenges of clinical application of BM-derived MPCs include donor site morbidity and pain as well as low cell yields associated with an age-related decrease in cell number and differentiation potential, underscoring the need to identify alternative sources of MPCs. Recently, MPC sources have diversified; examples include adipose, placenta, umbilicus, trabecular bone, cartilage, and synovial tissue. In the present work, we report the presence of MPCs in human tonsillar tissue.     

Accumulation of sesquiterpenes and polysaccharides in cells of zedoary (Curcuma zedoaria Roscoe) cultured in a 10 L bioreactor

We developed a cell suspension culture system for zedoary (Curcuma zedoaria Roscoe), using 100 g fresh weight inoculum in a batch culture. The maximum cell biomass of 68.46 g/L fresh weight was obtained after 14 days of culture in a 10 L bioreactor with a pitch-blade impeller maintained at an agitation speed of 150 rpm and an aeration rate of 2.5 L/min. The accumulation of sesquiterpenes and polysaccharide in zedoary cells from 2 to 18 days was measured by HPLC and a phenol-sulfuric acid assay, respectively. The total polysaccharide concentration increased between 2 to 10 days of culture and reached a maximum value of 6.55%. HPLC revealed several eluted peaks of sesquiterpenes, which increased in amplitude from days 2 to 10. Furthermore, our results indicated that biotransformation occurred in the cell suspension, transforming certain sesquiterpenes into other types during culture.