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Biomedical subjects

C Long

Publications and source records attributed to C Long.

At least 19 recordsLinked to original sources
PubMed2006

Outcome of parastomal hernia repair with and without midline laparotomy.

BACKGROUND: Surgical options for parastomal hernia (PSH) repair are primary fascial, mesh repair, and relocation with or without midline laparotomy. Overall, recurrence rates are higher after fascial repairs than after relocation. However, stoma relocation may require a midline laparotomy with higher associated morbidity. The aim of this study was to assess the outcome of PSH repair with relocation with or without a midline laparotomy. METHODS: All patients who underwent PSH repair with relocation were identified from a clinical database. Data were collected by retrospective review of medical records including patient demographics, presenting symptoms, predisposing factors, type of surgery, postoperative complications, recurrence, and follow-up. Patients were divided into two subgroups, with or without a midline laparotomy. In patients without a laparotomy, the stoma was intraperitoneally mobilized, passed behind the abdominal wall, and delivered and matured through a premarked stoma site, across the midline. RESULTS: Between 1992 and 2001, a total of 27 patients underwent PSH repair with relocation of the stoma to the opposite side of the abdominal wall. Of these, the operation was performed without a midline laparotomy in 11 patients (41%). There were no significant differences in age, gender, body mass index, and the duration of hernia between the non-laparotomy and laparotomy groups. Prior abdominal surgery was recorded for 3 patients in the group without a laparotomy and for 9 patients in the group with a laparotomy (p=NS). Although not quantified, patients in the non-laparotomy group were less likely to have significant intraabdominal adhesions. Conversely, patients in the laparotomy group had more advanced adhesions. The operative time was longer in the group with a laparotomy than in the group without [96.8 (50-220) minutes vs. 123.9 (45-360) minutes; (p=NS)], and the mean hospital stay was significantly less in patients without vs. with a laparotomy [5.5 (SD=1.6) days vs. 9.5 (SD=3.8) days, respectively; (p<0.05)]. There was only one recurrence in the group without a laparotomy compared to 3 in the group with a laparotomy. The mean follow-up periods were 36.8 and 56.6 months in the groups without and with a laparotomy, respectively. The postoperative complications included wound infection that occurred in 3 patients in each group. CONCLUSIONS: PSH repair with relocation without laparotomy was associated with a significantly shorter hospital stay, possibly due to the lack of a midline abdominal wound. It may not be feasible in patients with significant intraabdominal adhesions.

Aged↗
PubMed2006

Variable precision registration via wavelets: optimal spatial scales for inter-subject registration of functional MRI.

The detection of significantly activated brain regions in multi-subject functional magnetic resonance imaging (fMRI) studies almost invariably entails the coregistration of individual subjects' data in a standard space. Here, we investigate how sensitivity to detect loci of generic activation in such studies may be conditioned by the precision of anatomical registration. We describe a novel algorithm, implemented in the wavelet domain, for inhomogeneous deformation of individual images to match a template. The algorithm matches anatomical features in a coarse-to-fine fashion, first minimising a cost function in terms of relatively coarse spatial features and then proceeding iteratively to match the images in terms of progressively more detailed anatomical features. Applying the method to data acquired from two groups of 12 healthy volunteers (with mean age 27 and 70 years, respectively), during performance of a paired associate learning task, we show that geometrical overlap between template and individual images is monotonically improved, compared to an affine transform, by additional inhomogeneous deformations informed by more detailed features. Likewise, sensitivity to detect activated voxels can be substantially improved, by a factor of 4 or more, if wavelet-mediated deformations informed by medium-sized anatomical features are applied in addition to a preliminary affine transform. However, sensitivity to detect activated voxels was reduced by "over-registering" data or matching anatomical features at the finest scales of the wavelet transform. The benefits of variable precision registration are particularly salient for data acquired in older subjects, which showed evidence of greater inter-subject anatomic variability and generally required more extensive local deformation to achieve a satisfactory match to the template image. We conclude that major benefits in sensitivity to detect functional activation in multi-subject fMRI studies can be attained with an inhomogeneous deformation applied over appropriate spatial scales.

Adult↗
PubMed2006

Effect of stealthy liposomal topotecan plus amlodipine on the multidrug-resistant leukaemia cells in vitro and xenograft in mice.

BACKGROUND: Multidrug resistance (MDR) is a major obstacle to successful cancer chemotherapy as the over-expressed MDR protein acts as an efflux pump, which leads to a reduction in the uptake of the anticancer agent by tumour cells. We combined topotecan and amlodipine together into the stealthy liposomes, in which amlodipine was applied as a MDR reversing agent to overcome the resistance. MATERIALS AND METHODS: Cytotoxicity, apoptosis and the signalling pathway assays were performed on human chronic myelogenous leukaemia K562, promyelocytic leukaemia HL-60 and MDR HL-60 cells, respectively. Pharmacokinetics and antitumour activity studies were performed on normal Kunming mice and female BALB/c nude mice with MDR HL-60 xenografts, respectively. RESULTS: Topotecan alone was effective in inhibiting the growth of non-resistant leukaemia cells, K562 and HL-60 cells but not the growth of MDR HL-60 cells. The resistance of topotecan in MDR HL-60 cells was potently reversed by the addition of amlodipine. Moreover, amlodipine enhanced the apoptosis-inducing effect of topotecan synergistically. Apoptosis was through activating caspases in a cascade: first, the initiator caspase 8 and then effectors caspase 3/7 (total activity of caspases 3 and 7) were activated. Being encapsulated into the stealthy liposomes with an acidic internal medium, topotecan existed dominantly in an active lactone species, which was reversibly changed from an inactive carboxylate form via a pH-dependent reaction. After administration of stealthy liposomes to mice, the blood exposure of the lactone form was evidently increased and extended. The antitumour effects in the MDR HL-60 xenografted tumour were stealthy liposomal topotecan (SLT) plus amlodipine > SLT > un-encapsulated topotecan > blank control. CONCLUSIONS: The enhanced antitumour activity in the MDR HL-60 cells by the SLT plus amlodipine could be owing to multiple reasons: (a) synergistic apoptosis inducing effect, (b) reversing MDR by amlodipine and (c) increasing the availability of active lactone of topotecan by the stealthy liposomes. The apoptosis induced by amlodipine is through caspase 8 and then the 3/7 signalling pathway.

Amlodipine↗
PubMed2006

Effect of cold blood cardioplegia enriched with potassium-magnesium aspartate during coronary artery bypass grafting.

AIM: The aim of this investigation is to evaluate the effect of enriched with potassium-magnesium aspartate cold-blood cardioplegia on early reperfusion injury and postoperative arrhythmias in patients with ischemic heart disease undergoing coronary artery bypass grafting (CABG), using measurements of cardiac troponin I (CTnI), hemodynamic indexes and clinical parameters. METHODS: Forty patients with three-vessel coronary artery disease (CAD) and stable angina, receiving first-time elective CABG, were randomly divided into 2 groups: patients in control group (C group n=20) received routine institutional cold blood cardioplegia (4 degrees C) concentration of Mg2+4 mmol/L, Ca2+1.2 mmol/L and K+ 24mmol/L during myocardial arrest. Patients in P group (n=20) received modified cold blood cardioplegia enriched with potassium-magnesium aspartate and maintained concentration of Mg2+10 mmol/L, Ca2+1.2 mmol/L and K+20mmol/L in the final blood cardioplegia solution. Clinical outcomes were observed during operation and postoperatively. Serial venous blood samples for CTnI were obtained before induction, after cardiopulmonary bypass (CPB), and postoperative 6, 24, and 72 hours. Hemodynamic indexes were obtained before and after bypass by the radial catheter and Swan-Ganz catheter. RESULTS: In both groups, there were no differences regarding preoperative parameters. There were no cardiac related deaths in either group. The time required to achieve cardioplegic arrest after cardioplegia administration was significantly shorter in P group (47.5+/-16.3 s) than in C group (62.5+/-17.6 s) (P<0.01). The number of patients showing a return to spontaneous rhythm after clamp off was significantly greater in P group (n=20, 100%) than in C group (n=14, 70%) (P<0.01). Eight patients in C group had atrial fibrillation (AF) compared with two patients in P group (P<0.05) in the early of postoperative period. The level of CTnI increased 6 hours and 12 hours postoperatively, and there was a significant difference between groups (P<0.05). P group also shortened the time of postoperative mechanical ventilation (P<0.05) after surgery. CONCLUSIONS: Cold blood cardioplegia enriched with potassium-magnesium aspartate is beneficial on reducing reperfusion injury.

Aged↗
PubMed2005

Modulation of cellular response to cisplatin by a novel inhibitor of DNA polymerase beta.

DNA polymerase beta (Pol beta) is an error-prone enzyme whose up-regulation has been shown to be a genetic instability enhancer as well as a contributor to cisplatin resistance in tumor cells. In this work, we describe the isolation of new Pol beta inhibitors after high throughput screening of 8448 semipurified natural extracts. In vitro, the selected molecules affect specifically Pol beta-mediated DNA synthesis compared with replicative extracts from cell nuclei. One of them, masticadienonic acid (MA), is particularly attractive because it perturbs neither the activity of the purified replicative Pol delta nor that of nuclear HeLa cell extracts. With an IC50 value of 8 microM, MA is the most potent of the Pol beta inhibitors found so far. Docking simulation revealed that this molecule could substitute for single-strand DNA in the binding site of Pol beta by binding Lys35, Lys68, and Lys60, which are the main residues involved in the interaction Pol beta/single-strand DNA. Selected inhibitors also affect the Pol beta-mediated translesion synthesis (TLS) across cisplatin adducts; MA was still the most efficient. Therefore, masticadienonic acid sensitized the cisplatin-resistant 2008C13*5.25 human tumor cells. Our data suggest that molecules such as masticadienonic acid could be suitable in conjunction with cisplatin to enhance anticancer treatments.

Animals↗
PubMed2004

Two brothers with trichiasis, entropion and corneal scarring, sensorineural hearing loss, progressive thinning of scalp hair, mild learning difficulties and distinct facial features. A new syndrome?

Two brothers with very similar phenotypes involving trichiasis (misdirected lashes), entropion with corneal abrasions, strabismus, progressive thinning of the scalp hair, sensorineural hearing impairment, mild learning difficulties, and inguinal hernias are described. They have similar, distinctive facial features with deep-set eyes, a high nasal bridge and a short philtrum. Both brothers are carriers of a maternally inherited apparently balanced translocation of chromosomes 11 and 18: 46,XY, t(11;18)(p13;q21)mat. However, this is thought to be coincidental, since their younger brother also carries this translocation and is phenotypically normal. Although they have many features that are found in the ectodermal dysplasia syndromes, their combination of features is distinct and has to our knowledge not been previously reported.

Adolescent↗
PubMed2003

Dopaminergic drug effects on physiological connectivity in a human cortico-striato-thalamic system.

Cortico-striato-thalamic (CST) systems are anatomical substrates for many motor and executive functions and are implicated in diverse neuropsychiatric disorders. Electrophysiological studies in rats, monkeys and patients with Parkinson's disease have shown that power and coherence of low frequency oscillations in CST systems can be profoundly modulated by dopaminergic drugs. We combined functional MRI with correlational and path analyses to investigate functional and effective connectivity, respectively, of a prefronto-striato-thalamic system activated by object location learning in healthy elderly human subjects (n = 23; mean age = 72 years). Participants were scanned in a repeated measures, randomized, placebo-controlled design to measure modulation of physiological connectivity between CST regions following treatment with drugs which served both to decrease (sulpiride) and increase (methylphenidate) dopaminergic transmission, as well as non-dopaminergic treatments (diazepam and scopolamine) to examine non-specific effects. Functional connectivity of caudate nucleus was modulated specifically by dopaminergic drugs, with opposing effects of sulpiride and methylphenidate. The more salient effect of sulpiride was to increase functional connectivity between caudate and both thalamus and ventral midbrain. A path diagram based on prior knowledge of unidirectional anatomical projections between CST components was fitted satisfactorily to the observed inter-regional covariance matrix. The effect of sulpiride was defined more specifically in the context of this model as increased strength of effective connection from ventral midbrain to caudate nucleus. In short, we have demonstrated enhanced functional and effective connectivity of human caudate nucleus following sulpiride treatment, which is compatible both with the anatomy of ascending dopaminergic projections and with electrophysiological studies indicating abnormal coherent oscillations of CST neurons in parkinsonian states.

Aged↗
PubMed2003

Neurons in the periaqueductal gray are critically involved in the neuronal network for audiogenic seizures during ethanol withdrawal.

The periaqueductal gray (PAG) is implicated in the network subserving audiogenic seizures (AGS). AGS are seen during ethanol withdrawal (ETX), and the present study examined effects of focal NMDA receptor blockade in PAG during ETX and PAG neuronal firing changes associated with ETX. Bilateral cannulae or microwire electrodes were chronically implanted into PAG. Ethanol was administered intragastrically at 8-h intervals for 4 days, resulting in AGS susceptibility during ETX. Microinjection of a competitive NMDA receptor antagonist, DL-2-amino-7-phosphonoheptanoic acid (AP7) (2 and 5 but not 1 nmol/side), into the PAG suppressed AGS, in part, reversibly. In microwire experiments spontaneous and acoustically evoked PAG neuronal responses in behaving rats were reduced significantly 1 h after initial administration of ethanol. During ETX, when the animals were susceptible to AGS, significant increases in spontaneous and acoustically evoked PAG neuronal firing occurred. PAG neurons exhibited burst firing 2-4 s prior to the tonic-clonic phase of AGS and tonic repetitive firing during this seizure phase, which ceased during post-ictal depression. Increased NMDA receptor function in PAG may be important to the aberrant PAG neuronal firing in AGS, since previous studies observed upregulation of NMDA receptors during ETX, and the present study observed that focal microinjection of a NMDA antagonist into PAG blocked AGS.

2-Amino-5-phosphonovalerate↗
PubMed2001

Neurons in the deep layers of superior colliculus are a requisite component of the neuronal network for seizures during ethanol withdrawal.

Ethanol withdrawal (ETX) in ethanol-dependent animals and humans often results in seizure susceptibility. The deep layers of superior colliculus (DLSC) are proposed to be involved in the neuronal networks of several types of seizures. In rodents, ETX results in susceptibility to audiogenic seizures (AGS), and the DLSC are implicated as a critical component of the seizure network in a genetic form of AGS. Ethanol inhibits NMDA receptors, and the binding at these receptors is increased during ETX in certain brain regions. Therefore, the effect of focal microinjection into DLSC of a competitive NMDA receptor antagonist, DL-2-amino-7-phosphonoheptanoic acid (AP7) on ETX seizures was examined. AP7 (2 and 5 nmol/side) microinjected bilaterally into DLSC suppressed AGS, supporting a critical role of the DLSC in the AGS network during ETX. DLSC neuronal firing changes in behaving rats were subsequently examined, using chronically implanted microwire electrodes. Acoustically-evoked DLSC firing was significantly suppressed during ethanol intoxication and during ETX. However, DLSC neurons began firing tonically 1-2 s before the onset of the wild running behavior of AGS. Acoustically-evoked DLSC firing was suppressed during post-ictal depression with recovery beginning as the righting reflex returned. These data support a requisite role of the DLSC in AGS during ETX. These neuronal firing changes suggest an important role of DLSC neurons in generation of the wild running phase of AGS during ETX, which may be a general pathophysiological mechanism and a critical event in the initiation of wild running, since a similar pattern was seen previously in a genetic form of AGS.

Acoustic Stimulation↗
PubMed2001

Clustered mutations in HIV-1 gag are consistently required for escape from HLA-B27-restricted cytotoxic T lymphocyte responses.

The immune response to HIV-1 in patients who carry human histocompatibility leukocyte antigen (HLA)-B27 is characterized by an immunodominant response to an epitope in p24 gag (amino acids 263-272, KRWIILGLNK). Substitution of lysine (K) or glycine (G) for arginine (R) at HIV-1 gag residue 264 (R264K and R264G) results in epitopes that bind to HLA-B27 poorly. We have detected a R264K mutation in four patients carrying HLA-B27. In three of these patients the mutation occurred late, coinciding with disease progression. In another it occurred within 1 yr of infection and was associated with a virus of syncytium-inducing phenotype. In each case, R264K was tightly associated with a leucine to methionine change at residue 268. After the loss of the cytotoxic T lymphocyte (CTL) response to this epitope and in the presence of high viral load, reversion to wild-type sequence was observed. In a fifth patient, a R264G mutation was detected when HIV-1 disease progressed. Its occurrence was associated with a glutamic acid to aspartic acid mutation at residue 260. Phylogenetic analyses indicated that these substitutions emerged under natural selection rather than by genetic drift or linkage. Outgrowth of CTL escape viruses required high viral loads and additional, possibly compensatory, mutations in the gag protein.

Arginine↗
PubMed2001

Pilot trial of interleukin-2 with granulocyte colony-stimulating factor for the mobilization of progenitor cells in advanced breast cancer patients undergoing high-dose chemotherapy: expansion of immune effectors within the stem-cell graft and post-stem-cell infusion.

PURPOSE: To evaluate whether administration of interleukin-2 (IL-2) with granulocyte colony-stimulating factor (G-CSF) improves mobilization of immune effector cells into the stem-cell graft of patients undergoing high-dose chemotherapy and autografting. PATIENTS AND METHODS: We performed a trial of stem-cell mobilization with IL-2 and G-CSF in advanced breast cancer patients receiving high-dose chemotherapy with cyclophosphamide, thiotepa, and carboplatin and stem cells followed by IL-2. The trial defined immune, hematologic, and clinical effects of IL-2 in this setting. RESULTS: Of 32 patients enrolled, nine received G-CSF alone for mobilization. Twenty-one of 23 patients mobilized with IL-2 plus G-CSF had stem cells collected with more mononuclear cells than those receiving G-CSF (19.3 v 10.4 x 10(8)/kg; P =.006), but fewer CD34(+) progenitor cells (6.9 v 22.0 x 10(6)/kg; P =.049). The IL-2 plus G-CSF-mobilized patients had greater numbers of activated T (CD3(+)/CD25(+)) cells (P =.009), natural killer (NK; CD56(+)) cells (P =.007), and activated NK (CD56 bright(+)) cells (P: =.039) than those patients mobilized with G-CSF. NK (P =.042) and lymphokine-activated killer (LAK) (P =.016) activity was increased in those mobilized with IL-2 + G-CSF, whereas G-CSF-mobilized patients had a decline in cytolytic activity. In the third week posttransplantation, immune reconstitution was superior in those mobilized with IL-2 plus G-CSF based on greater numbers of activated T cells (P =.003), activated NK cells (P =.04), and greater LAK activity (P =.003). The 16 of 21 IL-2 + G-CSF-mobilized patients with adequate numbers of stem cells (> 1.5 x 10(6) CD34(+) cells/kg) collected engrafted rapidly posttransplantation. CONCLUSION: The results demonstrate that G-CSF + IL-2 can enhance the number and function of antitumor effector cells in a mobilized autograft without impairing the hematologic engraftment, provided that CD34 cell counts are more than 1.5 x 10(6) cells/kg. Mobilization of CD34(+) stem cells does seem to be adversely affected. In those mobilized with IL-2 and G-CSF, post-stem-cell immune reconstitution of antitumor immune effector cells was enhanced.

Adult↗
PubMed2001

Colored noise and computational inference in neurophysiological (fMRI) time series analysis: resampling methods in time and wavelet domains.

Even in the absence of an experimental effect, functional magnetic resonance imaging (fMRI) time series generally demonstrate serial dependence. This colored noise or endogenous autocorrelation typically has disproportionate spectral power at low frequencies, i.e., its spectrum is (1/f)-like. Various pre-whitening and pre-coloring strategies have been proposed to make valid inference on standardised test statistics estimated by time series regression in this context of residually autocorrelated errors. Here we introduce a new method based on random permutation after orthogonal transformation of the observed time series to the wavelet domain. This scheme exploits the general whitening or decorrelating property of the discrete wavelet transform and is implemented using a Daubechies wavelet with four vanishing moments to ensure exchangeability of wavelet coefficients within each scale of decomposition. For (1/f)-like or fractal noises, e.g., realisations of fractional Brownian motion (fBm) parameterised by Hurst exponent 0 < H < 1, this resampling algorithm exactly preserves wavelet-based estimates of the second order stochastic properties of the (possibly nonstationary) time series. Performance of the method is assessed empirically using (1/f)-like noise simulated by multiple physical relaxation processes, and experimental fMRI data. Nominal type 1 error control in brain activation mapping is demonstrated by analysis of 13 images acquired under null or resting conditions. Compared to autoregressive pre-whitening methods for computational inference, a key advantage of wavelet resampling seems to be its robustness in activation mapping of experimental fMRI data acquired at 3 Tesla field strength. We conclude that wavelet resampling may be a generally useful method for inference on naturally complex time series.

Artifacts↗
PubMed2001

Audiogenic seizure susceptibility is induced by termination of continuous infusion of gamma-aminobutyric acid or an N-methyl-D-aspartic acid Antagonist into the inferior colliculus.

The inferior colliculus (IC) is strongly implicated in seizure initiation in a genetic form of audiogenic seizures (AGS) and in AGS observed during ethanol withdrawal (ETX). Ethanol is known to block the actions of excitatory amino acids (EAA) and enhance the actions of gamma-aminobutyric acid (GABA) in several brain areas, including the IC. The present study investigated the effects on susceptibility to AGS following withdrawal from continuous blockade of N-methyl-D-aspartic acid (NMDA) receptors or continuous activation of GABA receptors in the IC. This involved infusion of GABA (1 M) or a competitive NMDA antagonist, DL-2-amino-7-phosphonoheptanoic acid (AP7, 1 mM), at 0.25 microl/h for 7 days using an Alzet osmotic minipump. Following abrupt termination of the infusion, AGS susceptibility began at 30 min. The incidence of AGS was 38.9 and 56.3% following GABA and AP7 withdrawal, respectively. The AGS behaviors observed during withdrawal, which included wild running and bouncing clonus, were very similar to those evoked by acoustic stimuli during ETX. AGS susceptibility lasted for several hours and in 13% of animals persisted for up to 6 months. The current results support diminished GABAergic and elevated glutamatergic function in the IC as the critical mechanisms and sites for AGS initiation. The present study, coupled with previous evidence that chronic ethanol exposure reduced GABA-mediated inhibition and enhanced EAA-mediated excitation, suggests that these amino acid receptor-mediated alterations in the IC are key elements in initiating AGS during ethanol withdrawal.

2-Amino-5-phosphonovalerate↗
PubMed2001

Endotoxin and cytokines alter contractile protein expression in cardiac myocytes in vivo.

Release of bacterial endotoxin and cytokines induce cardiac failure during sepsis. We investigated the direct effects of E. coli endotoxin (lipopolysaccharide, LPS) and cytokines induced by LPS on the cardiac myocyte gene program. For in vivo-experiments adult Wistar rats were given 600 microg/day LPS i.v. for 24 h or 7 days. In addition, cultured adult rat cardiac myocytes were treated with LPS, interleukin-1beta (IL-1beta), tumour necrosis factor-alpha (TNFalpha), interferon-gamma (IFNgamma) or IL-6 for 24 h. mRNA expression was evaluated for cardiac-alpha-actin (cAct), skeletal-alpha-actin (skAct), beta- and alpha-myosin heavy chain (MHC). LPS induced betaMHC-mRNA 3.6-fold and repressed alphaMHC 2.7-fold and cAct 2.5-fold after 24 h in vivo. Up-regulation of betaMHC (3-fold) and repression of cAct (2.5-fold) were still observed after 7 days LPS infusion, whereas alphaMHC-mRNA levels had returned to normal. At the protein level, increased expression of betaMHC by LPS treatment occurred already after 24 h and was maintained thereafter. LPS had no influence on skAct-mRNA. Similar changes in contractile protein mRNA expression were observed in LPS-treated cardiomyocytes in culture, whereas the tested cytokines either activated (IL-1beta, IFNgamma) or repressed (TNFalpha, IL-6) both MHC-isoforms and cAct. In conclusion, LPS and proinflammatory cytokines induce changes in contractile protein expression that may contribute to the acute heart failure observed during endotoxaemia.

Actins↗
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

Light-dependent osmoregulation in pea stem protoplasts. photoreceptors, tissue specificity, ion relationships, and physiological implications.

Light-induced changes in the volume of protoplasts bathed in a medium of constant osmolarity are useful indications of light-dependent cellular osmoregulation. With this in mind, we investigated the effect of light on the volume of protoplasts isolated from the elongating stems of pea (Pisum sativum) seedlings raised under red light. The protoplasts were isolated separately from epidermal peels and the remaining peeled stems. Under continuous red light, the protoplasts of peeled stems swelled steadily, but those of epidermal peels maintained a constant volume. Experiments employing far-red light and phytochrome-deficient mutants revealed that the observed swelling is a light-induced response mediated mainly by phytochromes A and B with a little greater contribution by phytochrome A. Protoplasts of epidermal peels and peeled stems shrank transiently in response to a pulse of blue light. The blue light responsiveness in this shrinking response, which itself is probably mediated by cryptochrome, is under the strict control of phytochromes A and B with equal contributions by these phytochromes. We suggest that the swelling response participates in the maintenance of high tissue tension of elongating stems and that the shrinking response is involved in stem growth inhibition. Other findings include the following: The swelling is caused by uptake of K+ and Cl-. The presence of Ca2+ in the bathing medium is required for phytochrome signaling in the swelling response, but not in the response establishing blue light responsiveness. Phytochrome A mediates the two responses in a totally red/far-red light reversible manner, as does phytochrome B.

Calcium↗
PubMed2001

Pentacarbonyl(4-phenylpyridine)tungsten(0) and pentacarbonyl(2-phenylpyridine)chromium(0).

In pentacarbonyl(4-phenylpyridine)tungsten(0), [W(C(11)H(9)N)(CO)(5)], the molecules have mm site symmetry and the pyridine ligand, with m symmetry, is completely planar. In pentacarbonyl(2-phenylpyridine)chromium(0), [Cr(C(11)H(9)N)(CO)(5)], the molecules are in general positions and the phenyl and pyridine rings of the ligand are twisted by 67.7 (3) degrees with respect to one another by rotation about the C-C bond joining them. In both compounds, the axial M-C(carbonyl) bond trans to the M-N(ligand) bond is significantly shorter than the equatorial M-C(carbonyl) bonds.

Journal Article↗