Biomedical subjects

X Wang

Publications and source records attributed to X Wang.

At least 487 records · Page 27Linked to original sources

PubMed2001

Pancreatitis-associated protein-I mRNA expression in mouse pancreas is upregulated by lipopolysaccharide independent of cerulein-pancreatitis.

BACKGROUND AND AIMS: It is well known that endotoxemia, which is caused by a bacterial infection, can exacerbate acute pancreatitis, whereas pancreatitis-associated protein (PAP) has the ability to induce bacterial aggregation. Pancreatitis-associated protein is supposed to protect the tissue from infection during inflammation. In order to clarify the relationship between PAP mRNA expression and endotoxemia during acute pancreatitis, the kinetic patterns of PAP-I mRNA in mouse pancreas treated with either cerulein or lipopolysaccharide (LPS) or both were investigated in this study. METHODS AND RESULTS: The administration of LPS (5 mg/kg) intraperitoneally resulted in a dramatic upregulation of PAP-I mRNA expression, increasing 18.61-fold to a maximum at 12 h, then decreasing, but still sustaining at a high level and reaching baseline on day five. These changes were accompanied by the upregulation of tumor necrosis factor (TNF)-alpha, interleukin-1beta (IL-1beta), interleukin 6 (IL-6) and interferon gamma (IFNgamma) mRNA expressions in the pancreas, but not by marked alterations of serum amylase, lactic dehydrogenase (LDH) and histology. Cerulein also increased PAP-I mRNA expression. However, the combination of cerulein and LPS was not able to enhance PAP-I mRNA expression further, although more prominent pancreatitis based on significant changes of serum amylase, LDH and histology were observed. CONCLUSION: These results suggest that PAP-I mRNA might be modulated by endotoxemia, independent of cerulein-pancreatitis. There were no strong correlations between PAP-I mRNA expression and the severity of pancreatitis.

Acute Disease↗

PubMed2001

Gastrointestinal stromal tumors: clinicopathological study of Chinese cases.

In the present study, we reviewed 73 Chinese cases of gastrointestinal stromal tumor (GIST), and analyzed factors in evaluating malignant potential, in particular focusing on Ki-67 index and p53 expression to determine whether these can be used as prognostic indicators in GIST. The p53 positive rate was 50.7% and it was significantly higher in malignant (25/35; 71.43%) than in benign cases (13/38; 34.21%). A Ki-67 labeling index of >10% was also significantly different between malignant (23/35; 65.71%) and benign cases (14/38; 36.84%). In the cases in which the patient died, 15/21 and 14/21 cases showed expression of p53 and Ki-67, respectively; both had a higher expression than in surviving cases. Comparing the cases positive for both Ki-67 and p53 with those positive for Ki-67 or p53 alone, and those negative for both Ki-67 and p53, the latter demonstrated the best prognosis. The study also indicated that the malignant potential of GIST is correlated with the mitotic index (> or =1/10 high-power fields; HPF), tumor size (> or =5 cm), high cellularity, tumor invasive growth, tumor location, tumor hemorrhage and tumor necrosis.

Adolescent↗

PubMed2001

Ganglioside modulates ligand binding to the epidermal growth factor receptor.

Whereas previous investigations have shown that pharmacologic addition of gangliosides inhibits keratinocyte proliferation by downregulating epidermal growth factor receptor phosphorylation, the underlying biochemical basis and physiologic relevance are unknown. Using Scatchard and displacement plots, we have shown that supplemental purified gangliosides decrease the binding of (125)I-labeled epidermal growth factor to keratinocyte-derived SCC12 cells. Conversely, SCC12 cells transfected with sialidase and thus depleted of gangliosides show increased ligand binding to the epidermal growth factor receptor, which is consistent with their increased proliferation in response to epidermal growth factor and transforming growth factor-alpha, and increased phosphorylation of the epidermal growth factor receptor, and downstream signal transduction pathway components. The mechanism of the altered binding appears to involve primarily decreased numbers of available receptors within the intact membrane, but not altered receptor protein expression. These studies provide evidence that the effect of gangliosides on keratinocyte proliferation results, at least in part, from the direct binding of ganglioside to the receptor and disruption of the receptor-ligand interaction. Manipulation of membrane ganglioside content may be a powerful new means to alter epidermal growth factor receptor-dependent cell proliferation.

DNA, Complementary↗

PubMed2001

Inhibition of the phosphatidylinositol 3-kinase pathway contributes to HT29 and Caco-2 intestinal cell differentiation.

BACKGROUND & AIMS: Phosphatidylinositol 3-kinase (PI3K), an important mediator of intracellular signal transduction, has been shown to affect proliferation, differentiation, and apoptosis in a number of cells; the role of PI3K in intestinal cell differentiation is not known. METHODS: The effect of PI3K inhibition on enterocyte-like differentiation of the human colon cancer cells, HT29 and Caco-2, was assessed using complementary approaches (i.e., chemical inhibition with wortmannin, transfection with a dominant negative p85 mutant, or overexpression of the tumor suppressor gene phosphatase and tensin homologue deleted on chromosome 10 [PTEN]). Brush-border enzyme (intestinal alkaline phosphatase [IAP] and sucrase) activities, IAP messenger RNA levels, and IAP promoter induction were measured. RESULTS: The PI3K inhibitor, wortmannin, in combination with sodium butyrate, synergistically induced IAP and sucrase enzyme activities and IAP messenger RNA levels in a time- and dose-dependent fashion. Consistent with these results, cotransfection using the dominant negative mutant of p85 (Deltap85) induced IAP promoter activity. Moreover, overexpression of PTEN, which antagonizes PI3K, significantly augmented the induction of IAP enzyme activity in HT29 and Caco-2 cells treated with sodium butyrate and in spontaneously differentiated Caco-2 cells. CONCLUSIONS: Our results show that inhibition of PI3K significantly enhances enterocyte-like differentiation of HT29 and Caco-2 cells. Taken together, our findings suggest a contributory role for the PI3K/PTEN pathway in intestinal cell differentiation.

Alkaline Phosphatase↗

PubMed2001

Earlier expression of the transcription factor HFH-11B diminishes induction of p21(CIP1/WAF1) levels and accelerates mouse hepatocyte entry into S-phase following carbon tetrachloride liver injury.

Partial hepatectomy (PH) or toxic liver injury induces the proliferation of terminally differentiated hepatic cells to regenerate the original size of the adult liver. Previous PH liver regeneration studies showed that premature transgenic expression of the Forkhead Box M1b (FoxM1b, HFH-11B) transcription factor accelerated hepatocyte entry into DNA replication (S-phase). In this study, we used carbon tetrachloride (CCl(4)) liver injury to induce a different type of mouse liver regeneration and show that premature hepatic HFH-11B levels also accelerate the onset of hepatocyte S-phase in this injury model. Unlike PH liver regeneration, earlier hepatocyte proliferation after CCl(4) liver injury is correlated with diminished transgenic hepatic levels of p21(CIP1/WAF1) at the G1/S transition of the cell cycle. Differential hybridization of cDNA arrays and RNase protection studies determined that CCl(4) regenerating liver of transgenic mice displayed early stimulated expression of the S-phase promoting cyclin D1 and cyclin E and sustained levels of Cdc25a phosphatase genes. Compared with previous PH liver regeneration studies, our data suggest that premature expression of HFH-11B activates distinct S-phase promotion pathways in the CCl(4) liver injury model. Although proliferating transgenic hepatocytes induced by either PH or CCl(4) liver injury displayed early expression of identical M-phase cyclin genes (cyclin B1, B2, A2, and F), only CCl(4) regenerating transgenic liver exhibited earlier expression of the M-phase promoting Cdc25b. These studies suggest that CCl(4) injury of transgenic liver not only uses the same mechanisms as PH to mediate accelerated hepatocyte entry into mitosis, but also promotes M-phase entry by stimulating Cdc25b expression.

Animals↗

PubMed2001

Secretion of annexin V from cultured cells requires a signal peptide.

Annexin V is an intracellular protein that lacks a hydrophobic signal peptide. However, there are several studies reporting the extracellular presence of annexin V. In this study, we designed transgenes of annexin V with or without an attached secretory signal peptide and investigated the secretion of the transgene products in COS-7 cells. The signal peptide, targeted annexin V to the endoplasmic reticulum (ER), the Golgi and culture media of transfected cells. In contrast, without the signal peptide, annexin V was present only in the cytoplasm and was not detected in the medium. To confirm our results we also evaluated the presence of extracellular annexin V in two cultured cell lines: BeWo, a choriocarcinoma cell model of placental trophoblasts, and human umbilical vein endothelial cells (HUVEC). Our results showed that annexin V was immunolocalized on the surfaces of both cells but could not be detected in the culture medium of either cell type. Our results suggest that the secretion of annexin V required the recombinant addition of a hydrophobic signal peptide and that the limited quantities of endogenous cell surface annexin V on BeWo and HUVEC cells is most likely derived from adjacent damaged cells.

Animals↗

PubMed2001

Decreased expression of high-molecular-weight calmodulin-binding protein and its correlation with apoptosis in ischemia-reperfused rat heart.

A cardiac high-molecular-weight calmodulin-binding protein (HMWCaMBP) was previously identified as a homologue of the calpain inhibitor, calpastatin. In the present study, we investigated the expression of HMWCaMBP and calpains in rat heart after ischemia and reperfusion. Western blot analysis of normal rat heart extract with a polyclonal antibody raised against bovine HMWCaMBP indicated a prominent immunoreactive band of 140kDa. Both the expression and the activity of HMWCaMBP were decreased by ischemia reperfusion. Immunohistochemical studies showed strong-to-moderate HMWCaMBP immunoreactivity in normal heart and poor immunoreactivity in ischemia-reperfused heart muscle. However, the expression of micro-calpain and m-calpain in ischemia-reperfused heart was increased as compared to normal heart. The calpain inhibitory activity of ischemia-reperfused heart tissues was significantly lower as compared to normal heart tissues. The pre-ischemic and post-ischemic perfusion of hearts with a cell-permeable calpain inhibitor suppressed the increase in calpain expression but increased the HMWCaMBP expression. In-vitro HMWCaMBP was proteolyzed by micro-calpain and m-calpain. We also measured apoptosis in normal and ischemia-reperfused tissues. An increase in the number of apoptotic bodies was observed with increased duration of ischemia and reperfusion. Bcl-2 expression did not change in any of the groups, whereas Bax expression increased with ischemia-reperfusion and correlated well with the degree of apoptosis. Our findings suggest that HMWCaMBP may sequester calpains from its substrates in the normal myocardium, but it is susceptible to proteolysis by calpains during ischemia-reperfusion. Thus, decreased expression of HMWCaMBP may play an important role in myocardial injury.

Animals↗

PubMed2001

Role of placental tissues in the intrauterine transmission of hepatitis B virus.

OBJECTIVE: The purpose of this study was to determine the mechanism of intrauterine transmission of hepatitis B virus. STUDY DESIGN: Placental tissues from 158 pregnant women who tested positive for hepatitis B surface antigen were examined for hepatitis B virus markers, Fc gamma receptors, and hepatitis B surface antigen-anti-hepatitis B surface antigen in different layers of cells. RESULTS: It was shown that the hepatitis B virus infection rate among different layers of placental cells gradually decreased from the maternal side to the fetal side. Furthermore, the closer the infected cell layer was to the fetal side, the higher the risk of intrauterine hepatitis B virus infection. Fc gamma receptors were found on cells of both hepatitis B surface antigen positive and negative placentas; Fc gamma receptors III were found on trophoblastic cells and villous mesenchymal cells, and Fc gamma receptors II were found on only villous mesenchymal cells. Hepatitis B surface antigen-antibodies to hepatitis B surface antigen was detected in the cytoplasm and on the membrane of trophoblastic cells and villous mesenchymal cells in 2 hepatitis B surface antigen-positive placentas. CONCLUSION: The results support the hypothesis that intrauterine hepatitis B virus transmission could be caused through "cellular transfer" in the placenta. One of the means of cellular transfer could be through Fc gamma receptor III-mediated entry of hepatitis B surface antigen-antibodies to hepatitis B surface antigen into cells.

Adolescent↗

PubMed2001

Ovulation in the tree shrew (Tupaia belangeri) induced by gonadotrophins.

The induction of ovulation by exogenous gonadotrophins is an important approach for recovering oocytes used for studies on the reproductive biology of some mammals. In the present study, pregnant mare serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) were used to induce ovulation in the tree shrew (Tupaia belangeri) using the following regimens. Groups A1-A3, multiple injections of PMSG (30-60 IU) followed by a single dose of hCG (30-60 IU); B1, combination of a single injection of PMSG (60 IU) with a single dose of hCG (60 IU); E1, combination of a single injection of PMSG (60 IU) with a single dose of hCG (30 IU) plus PMSG (30 IU); and administration of either PMSG (C1 and C2) or hCG (D1). The ovulation rate of animals producing oocytes with either first polar body or distinct perivitelline space, and the mean number of oocytes per animal were considered the most important criteria in each regimen. The most effective induction of ovulation was achieved in groups B1 and E1, with ovulation rates of 4/4 and 4/4, respectively, and mean numbers of ovulated oocytes per animal of 3.25 +/- 0.48 and 4.00 +/- 0.71 respectively. No ovulation was observed in the control group or in group D1. Therefore, regimes B1 and E1 were considered as the simplest and most effective for the induction of ovulation in the tree shrew.

Animals↗

PubMed2001

Effects of Panax quinquefolius L. on brainstem neuronal activities: comparison between Wisconsin-cultivated and Illinois-cultivated roots.

Brainstem neurons receiving subdiaphragmatic vagal inputs were recorded in an in vitro neonatal rat brainstem-gastric preparation. Aqueous extracts of American ginseng root (Panax quinquefolius L.) from Wisconsin and Illinois were applied to the gastric compartment or the brainstem compartment of the bath chamber to evaluate the peripheral gut or central brain effects of the extracts on brainstem unitary activity. After P. quinquefolius extract application to the gastric or brainstem compartment, a concentration-related inhibition in neuronal discharge frequency in brainstem unitary activity was observed, suggesting that P. quinquefolius plays an important role in regulating the digestive process and modulating the brain function in the rat. In this study, pharmacological effects of Wisconsin-cultivated P. quinquefolius and Illinois-cultivated P. quinquefolius were compared. Our results showed that Illinois-cultivated P. quinquefolius possesses a significantly stronger peripheral gastric as well as central brain modulating effect on brainstem neuronal activity. Data from our high performance liquid chromatography ginsenoside analysis suggest that this increase in inhibitory effects by Illinois-cultivated P. quinquefolius may be due to its different ginsenoside profile.

Animals↗

PubMed2001

Effects of inhibition of PAF, ICAM-1 and PECAM-1 on gut barrier failure caused by intestinal ischemia and reperfusion.

BACKGROUND: The role of cell adhesion molecules and transmigration of PMNs through the endothelial barrier is probably essential in intestinal ischemia and reperfusion (I/R)-induced gut barrier dysfunction. Although cytokines are released in I/R, it is unclear whether cytokines directly increase permeability or if this phenomenon requires both expression of cell adhesion molecules and PMN adhesion-activation. Endothelial barrier dysfunction plays an important role in the pathogenesis of multiple organ dysfunction syndrome, inducing gut barrier failure, but the mechanisms are not fully understood. The purpose of this study was to evaluate the potential therapeutic value of inhibition of platelet activating factor (PAF), intercellular adhesion molecule-1 (ICAM-1), and platelet endothelial cell adhesion molecule-1 (PECAM-1) in gut barrier dysfunction induced by intestinal I/R. METHODS: A PAF antagonist (lexipafant, BB-882) and monoclonal antibodies against rat ICAM-1 (anti-ICAM-1-MAb) and PECAM-1 (anti-PECAM-1-MAb) were used in a model of gut barrier dysfunction caused by intestinal ischemia for 40 min and concomitant reperfusion for 12 h in the rat, and endothelial permeability, myeloperoxidase activity, interleukin-1beta and protease inhibitor levels were evaluated. RESULTS: The endothelial permeability and tissue leukocyte recruitment in the distal small intestine significantly increased in rats with I/R treated with saline. Proteolytic activity in plasma was evident by low levels of the three measured plasma protease inhibitors. These changes were, to different degrees, reduced by treatment with lexipafant, anti-ICAM-1-MAb, or anti-PECAM-1-MAb. Alterations in systemic levels of interleukin-1beta paralleled the changes found in gut barrier permeability and leukocyte trapping. CONCLUSIONS: Our results suggest that treatment with the PAF inhibitor lexipafant and monoclonal antibodies against ICAM-1 or, seemingly most efficient, PECAM-1 reduces the severity of I/R-associated intestinal dysfunction, associated with a decrease in systemic concentrations of IL-1beta local leukocyte recruitment, and partly restoring plasma protease inhibitor levels.

Animals↗

PubMed2001

Reawakening the dragon: changing patterns of opiate use in Asia, with particular emphasis on China's Yunnan province.

Asian countries adjacent to the Golden Triangle and their neighbors have witnessed an evolution in "drug abuse" from traditional opium smoking to heroin eating, smoking, and finally heroin injection. A recent study of 630 heroin users was conducted in China's Yunnan Province, located close to the Golden Triangle. Data collected between August 1997 and February 1998 indicate injecting heroin users, in comparison to noninjectors, were more likely to have used drugs for a longer period of time, and to use drugs more frequently everyday. Other major differences existed between urban and rural subjects, especially highlighting differences between men and women. Women comprised a much higher proportion of urban subjects than rural subjects. Rural injectors were much more likely to be male, but urban injectors were almost evenly split between men and women. The emerging epidemic of heroin use in China and the continuing substance abuse problem in the United States provide an opportunity for collaborative research of mutual benefit.

Acquired Immunodeficiency Syndrome↗

PubMed2001

Enteral compared with parenteral nutrition: a meta-analysis.

BACKGROUND: The difference in outcomes in patients is unclear when 2 types of enteral nutrition, ie, tube feeding and conventional oral diets with intravenous dextrose (standard care), are compared with parenteral nutrition. OBJECTIVE: We reviewed systematically and aggregated statistically the results of prospective randomized clinical trials (PRCTs) to examine the relations among the nutrition interventions, complications, and mortality rates. DESIGN: We conducted a MEDLINE search for PRCTs comparing the effects of enteral and parenteral nutrition in adults. Two different people abstracted data for the method and outcomes separately. We used fixed-effects meta-analysis technique to combine the relative risks (RRs) of the outcomes of infection, nutrition support complications, other complications, and mortality. RESULTS: Twenty-seven studies in 1828 patients met the study criteria. Aggregated results showed a significantly lower RR of infection with tube feeding (0.64; 95% CI: 0.54, 0.76) and standard care (0.77; 95% CI: 0.65, 0.91). A priori hypotheses showed a lower RR of infection with tube feeding than with parenteral nutrition, regardless of nutritional status, presence of cancer, year of study publication, or quality of the study method. In studies in which participants had high rates of protein-energy malnutrition, there was a significantly higher risk of mortality (3.0; 95% CI: 10.9, 8.56) and a trend toward a higher risk of infection with standard care than with parenteral nutrition (1.17; 95% CI: 0.88, 1.56). CONCLUSIONS: Tube feeding and standard care are associated with a lower risk of infection than is parenteral nutrition; however, mortality is higher and the risk of infection tends to be higher with standard care than with parenteral nutrition in malnourished populations.

Enteral Nutrition↗

PubMed2001

Bayesian analysis of case control polygenic etiology studies with missing data.

Many genetic studies are based on analysing multiple DNA regions of cases and controls. Usually each is tested separately for association with disease. However, some diseases may require interacting polymorphisms at several regions, and most disease susceptibility is polygenic. In this paper, we develop new methods for determining combinations of polymorphisms that affect the risk of disease. For example, two different genes might produce normal proteins, but these proteins improperly function when they occur together. We consider a Bayesian approach to analyse studies where DNA data from cases and controls have been analysed for polymorphisms at multiple regions and a polygenic etiology is suspected. The method of Gibbs sampling is used to incorporate data from individuals who have not had every region analysed at the DNA sequence or amino acid level. The Gibbs sampling algorithm alternatively generates a sample from the posterior distribution of the sequence of combinations of polymorphisms in cases and controls and then uses this sample to impute the data that are missing. After convergence the algorithm is used to generate a sample from the posterior distribution for the probability of each combination in order to identify groups of polymorphisms that best discriminate cases from controls. We apply the methods to a genetic study of type I diabetes. The protein encoded by the TAP2 gene is important in T cell function, and thus may affect the development of autoimmune diseases such as insulin dependent diabetes mellitus (IDDM). We determine pairs of polymorphisms of genetic fragments in the coding regions of linked HLA genes that may impact the risk of IDDM.

Journal Article↗

PubMed2001

Up-regulation of TRPM-2, MMP-7 and ID-1 during sex hormone-induced prostate carcinogenesis in the Noble rat.

Prostate cancer is the most frequently diagnosed malignancy in the Western world and changes in the ratio of testosterone and estrogens with advancing age is one of the potential risk factors in the development of this disease. However, the molecular mechanisms associated with hormone imbalance in prostate carcinogenesis are poorly understood. In this study we induced a high incidence of prostate hyperplasia, dysplasia and adenocarcinoma in the Noble rat using a combination of testosterone and estradiol-17beta. Using this animal model, we studied the gene expression profile during sex hormone-induced prostate carcinogenesis using a cDNA array technique; the results were further confirmed by RT-PCR, western blotting and immunohistochemical analyses. We found up-regulation of TRPM-2 (testosterone-repressed prostatic message-2), MMP-7 (matrix metalloproteinase-7) and Id-1 (inhibitor of differentiation or DNA binding) during development of sex hormone-induced prostate cancer. Increased expression of TRPM-2 and MMP-7 was observed in both premalignant and malignant tissues after sex hormone treatment, indicating their role in the early stages of hormone response and prostate cancer development. In contrast, Id-1 was expressed at relatively low levels in all premalignant samples but increased in malignant cells, suggesting its potential roles as a biomarker for prostate cancer cells. Furthermore, expression of Id-1 appeared to be stronger in poorly differentiated lesions than in well-differentiated carcinomas, suggesting that the levels of Id-1 expression may be correlated with the malignancy of tumors. Our results provide the first evidence of up-regulation of TRPM-2, MMP-7 and Id-1 during sex hormone-induced prostate carcinogenesis and strongly suggest their association with the development of prostate cancer.

Adenocarcinoma↗

PubMed2001

Map position and expression of the genes in the 38 region of Drosophila.

With the completion of the Drosophila genome sequence, an important next step is to extract its biological information by systematic functional analysis of genes. We have produced a high-resolution genetic map of cytological region 38 of Drosophila using 41 deficiency stocks that provide a total of 54 breakpoints within the region. Of a total of 45 independent P-element lines that mapped by in situ hybridization to the region, 14 targeted 7 complementation groups within the 38 region. Additional EMS, X-ray, and spontaneous mutations define a total of 17 complementation groups. Because these two pools partially overlap, the completed analysis revealed 21 distinct complementation groups defined by point mutations. Seven additional functions were defined by trans-heterozygous combinations of deficiencies, resulting in a total of 28 distinct functions. We further produced a developmental expression profile for the 760 kb from 38B to 38E. Of 135 transcription units predicted by GENSCAN, 22 have at least partial homology to mobile genetic elements such as transposons and retroviruses and 17 correspond to previously characterized genes. We analyzed the developmental expression pattern of the remaining genes using poly(A)(+) RNA from ovaries, early and late embryos, larvae, males, and females. We discuss the correlation between GENSCAN predictions and experimentally confirmed transcription units, the high number of male-specific transcripts, and the alignment of the genetic and physical maps in cytological region 38.

Animals↗

PubMed2001

Auxin- and abscisic acid-dependent osmoregulation in protoplasts of Phaseolus vulgaris pulvini.

Protoplasts isolated from the laminar pulvinus of Phaseolus vulgaris and bathed in a medium containing KCl as the major salt were found to swell in response to IAA and to shrink in response to ABA. The protoplasts of flexor cells and those of extensor cells responded similarly. The results indicate that the cellular content of osmotic solutes is enhanced by IAA and reduced by ABA. The IAA-induced swelling was abolished when either the K(+) or the Cl(-) of the bathing medium was replaced by an impermeant ion or when the medium was adjusted to neutral pH (instead of pH 6). The response was inhibited by vanadate. It is concluded that the swelling is caused by enhanced influxes of K(+) and Cl(-), which probably occur through K(+) channels and Cl(-)/H(+) symporters, respectively. The ABA-induced shrinking was inhibited by 5-nitro-2-(3-phenylpropylamino)-benzoic acid, an anion-channel inhibitor, suggesting that it is caused by Cl(-) efflux through anion channels and charge-balancing K(+) efflux through outward-rectifying K(+) channels. It appears that the two plant hormones act on pulvinar motor cells to regulate their turgor pressure, as they do in stomatal guard cells. The findings are discussed in relation to the pulvinar movements induced by environmental stimuli.

Abscisic Acid↗

PubMed2001

Blue-light-dependent osmoregulation in protoplasts of Phaseolus vulgaris Pulvini.

Blue light was found to induce shrinkage of the protoplasts isolated from first-leaf lamina pulvini of 18-day-old Phaseolus vulgaris. The response was transient following pulse stimulation, while it was sustainable during continuous stimulation. No apparent difference was found between flexor and extensor protoplasts. Protoplasts of the petiolar segment located close to the pulvinus showed no detectable response. In the plants used, the pulvinus was fully matured and the petiole was ceasing its elongation growth. When younger, 12-day-old, plants were used, however, the petiolar protoplasts did respond to blue light. The pulse-induced response was similar to that in pulvinar protoplasts, although the response to continuous stimulation was transient and differed from that in pulvinar protoplasts. No shrinkage was induced in pulvinar protoplasts when the far-red-light-absorbing form of phytochrome was absent for a period before blue-light stimulation, indicating that the blue-light responsiveness is strictly controlled by phytochrome. Inhibitors of anion channels and H(+)-ATPase abolished the shrinking response, supporting the view that protoplasts shrink by extruding ions. The response of pulvinar protoplasts is probably involved in the blue-light-induced, turgor-based movement of pulvini. The blue-light responding system in pulvini is suggested to have evolved from that functioning in other growing organs.

Adaptation, Physiological↗