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1.
J S Afr Vet Assoc ; 93(2): 139-143, 2022 Nov.
Article in English | MEDLINE | ID: mdl-35934911

ABSTRACT

Under stressful conditions, black rhinoceroses that are sub-clinical carriers of Babesia bicornis can succumb to babesiosis. After 16 days in captivity, a five-year-old female black rhino captured for relocation presented with inappetence, abdominal discomfort and constipation. After chemical immobilisation, dry faecal balls were removed from the rectum, peripheral blood smears were made and blood collected into EDTA tubes. She was treated prophylactically for colic with flunixin meglumine, penicillin and doramectin. Piroplasms were seen on fixed and stained peripheral blood smears. Overnight she developed severe haemoglobinuria, a sign consistent with babesiosis. Subsequently, DNA extracted from a blood specimen reacted with the B. bicornis probe on Reverse Line Blot (RLB) assay, confirming the diagnosis of babesiosis. Specific treatment consisted of 14 ml imidocarb dipropionate (dosage 2.4 mg/kg) administered intramuscularly by pole syringe. Fifteen days later the patient was still moderately anaemic, with the red blood cell (RBC) count, haematocrit and haemoglobin concentration within normal ranges but on microscopic examination there was a marked RBC macrocytosis and polychromasia indicative of a regenerative anaemia. DNA extracted from blood collected at that time did not react with the B. bicornis probe on RLB assay, indicating that treatment with imidocarb had been effective. Once the patient's appetite improved, she started gaining weight. After 82 days in captivity and 65 days after babesiosis had been diagnosed, she was released at the site where she had been captured.


Subject(s)
Babesia , Babesiosis , Female , Animals , Babesiosis/drug therapy , Perissodactyla , DNA
2.
Eur Arch Paediatr Dent ; 23(3): 355-364, 2022 Jun.
Article in English | MEDLINE | ID: mdl-34767190

ABSTRACT

PURPOSE: Anterior open bite is defined by the lack of incisal contact between the teeth in centric relation. The aim of this study was to determine the prevalence of anterior open in children and adolescents. METHODS: This systematic review included a search in the databases: PubMed, Scopus, Web of Science, LILACS, Google Scholar, and ProQuest. The acronym PECOS was considered: (P) children and adolescents, (E) presence of anterior open bite, (C) not applicable, (O) prevalence, and (S) observational studies. The risk of bias assessment was carried out using the Joanna Briggs Institute Critical Appraisal Checklist for Studies Reporting Prevalence Data. The prevalence meta-analyses were performed using MedCalc® software. The certainty of the evidence was determined with the GRADE approach. RESULTS: 26 studies were included. Eleven studies were judged at low, seven at moderate, and eight at high risk of bias. The overall prevalence of anterior open bite was 16.52% (95% CI 12.34-21.17) in children and adolescents. The prevalence was 19.38% (95% CI 13.77-25.69) in South America. The prevalence of anterior open bite was 22.67% (95% CI 16.56-29.43) among females and 16.99% (95% CI 11.77-22.94) among males. The prevalence of anterior open bite was 18.84% (95% CI 13.88-24.38) in the primary dentition, and 14.26% (95% CI 7.67-22.46) in the mixed dentition. The overall certainty of the evidence was very low. CONCLUSION: The overall prevalence of anterior open bite was 16.52% in children and adolescents aged 2-16 years. Giving the limitations of a prevalence meta-analysis, the extrapolation of the results should be cautious. REGISTRATION NUMBER: CRD42020183162, 10 July 2020.


Subject(s)
Open Bite , Adolescent , Child , Dentition, Mixed , Female , Humans , Male , Open Bite/epidemiology , Prevalence
5.
Plant Biol (Stuttg) ; 14(4): 666-74, 2012 Jul.
Article in English | MEDLINE | ID: mdl-22288430

ABSTRACT

The non-invasive leaf patch clamp pressure (LPCP) probe measures the attenuated pressure of a leaf patch, P(p) , in response to an externally applied magnetic force. P(p) is inversely coupled with leaf turgor pressure, P(c) , i.e. at high P(c) values the P(p) values are small and at low P(c) values the P(p) values are high. This relationship between P(c) and P(p) could also be verified for 2-m tall olive trees under laboratory conditions using the cell turgor pressure probe. When the laboratory plants were subjected to severe water stress (P(c) dropped below ca. 50 kPa), P(p) curves show reverse diurnal changes, i.e. during the light regime (high transpiration) a minimum P(p) value, and during darkness a peak P(p) value is recorded. This reversal of the P(p) curves was completely reversible. Upon watering, the original diurnal P(p) changes were re-established within 2-3 days. Olive trees in the field showed a similar turnover of the shape of the P(p) curves upon drought, despite pronounced fluctuations in microclimate. The reversal of the P(p) curves is most likely due to accumulation of air in the leaves. This assumption was supported with cross-sections through leaves subjected to prolonged drought. In contrast to well-watered leaves, microscopic inspection of leaves exhibiting inverse diurnal P(p) curves revealed large air-filled areas in parenchyma tissue. Significantly larger amounts of air could also be extracted from water-stressed leaves than from well-watered leaves using the cell turgor pressure probe. Furthermore, theoretical analysis of the experimental P(p) curves shows that the propagation of pressure through the nearly turgorless leaf must be exclusively dictated by air. Equations are derived that provide valuable information about the water status of olive leaves close to zero P(c) .


Subject(s)
Olea/physiology , Plant Leaves/physiology , Water/physiology , Dehydration , Light , Patch-Clamp Techniques , Plant Transpiration , Pressure
7.
J Physiol Pharmacol ; 61(4): 443-9, 2010 Aug.
Article in English | MEDLINE | ID: mdl-20814072

ABSTRACT

Ghrelin is a hormone mainly produced in the stomach and its first discovered action was connected with regulating growth hormone secretion. It was found that ghrelin injection increases growth hormone release and that this action is dose-dependent. Ghrelin may influence growth hormone secretion both by central and peripheral action. Ghrelin acts via its receptors named growth hormone secretagogue receptors (GHSR). Ghrelin receptors were found in almost all tissues including the central nervous system. Besides influence on growth hormone secretion, ghrelin also regulates food intake and energy metabolism centrally as well as peripherally. In our study, active ghrelin and growth hormone levels in serum were measured. We also investigated gene expression of proghrelin, growth hormone releasing hormone (GHRH) and growth hormone receptor (GH-R) in the hypothalamus and the active form of ghrelin receptor (GHSR-1a) in hypothalamus and pituitary. Expression of growth hormone and growth hormone releasing hormone receptor (GHRH-R) in the pituitary were also measured. The results of our study indicate that active ghrelin and growth hormone levels in serum increased during pregnancy. Expression of ghrelin in hypothalamus and its receptor also increased in hypothalamus and pituitary during pregnancy. We also observed that growth hormone gene expression rose in pituitary, while its receptor mRNA level in hypothalamus decreased. Additionally, growth hormone expression in placenta decreased during pregnancy. Moreover, GHRH in hypothalamus and its receptor in pituitary showed reduced levels during pregnancy. Our results may indicate that ghrelin is a important factor influencing growth hormone release during pregnancy.


Subject(s)
Ghrelin/physiology , Growth Hormone/metabolism , Hypothalamo-Hypophyseal System/metabolism , Pregnancy/metabolism , Animals , Down-Regulation/physiology , Female , Ghrelin/biosynthesis , Growth Hormone/biosynthesis , Growth Hormone/genetics , Hypothalamo-Hypophyseal System/physiology , RNA, Messenger/antagonists & inhibitors , RNA, Messenger/biosynthesis , RNA, Messenger/metabolism , Rats , Rats, Wistar , Receptors, Somatotropin/antagonists & inhibitors , Receptors, Somatotropin/biosynthesis , Receptors, Somatotropin/genetics , Up-Regulation/physiology
8.
Plant Biol (Stuttg) ; 12(3): 424-36, 2010 May 01.
Article in English | MEDLINE | ID: mdl-20522178

ABSTRACT

Turgor pressure provides a sensitive indicator for irrigation scheduling. Leaf turgor pressure of Musa acuminate was measured by using the so-called leaf patch clamp pressure probe, i.e. by application of an external, magnetically generated and constantly retained clamp pressure to a leaf patch and determination of the attenuated output pressure P(p) that is highly correlated with the turgor pressure. Real-time recording of P(p) values was made using wireless telemetric transmitters, which send the data to a receiver base station where data are logged and transferred to a GPRS modem linked to an Internet server. Probes functioned over several months under field and laboratory conditions without damage to the leaf patch. Measurements showed that the magnetic-based probe could monitor very sensitively changes in turgor pressure induced by changes in microclimate (temperature, relative humidity, irradiation and wind) and irrigation. Irrigation effects could clearly be distinguished from environmental effects. Interestingly, oscillations in stomatal aperture, which occurred frequently below turgor pressures of 100 kPa towards noon at high transpiration or at high wind speed, were reflected in the P(p) values. The period of pressure oscillations was comparable with the period of oscillations in transpiration and photosynthesis. Multiple probe readings on individual leaves and/or on several leaves over the entire height of the plants further emphasised the great impact of this non-invasive turgor pressure sensor system for elucidating the dynamics of short- and long-distance water transport in higher plants.


Subject(s)
Musa/physiology , Plant Leaves/physiology , Plant Transpiration , Pressure , Environment , Photoperiod , Photosynthesis , Water/physiology
9.
Plant Biol (Stuttg) ; 11(5): 701-12, 2009 Sep.
Article in English | MEDLINE | ID: mdl-19689778

ABSTRACT

An advanced non-invasive, field-suitable and inexpensive leaf patch clamp pressure probe for online-monitoring of the water relations of intact leaves is described. The probe measures the attenuated output patch clamp pressure, P(p), of a clamped leaf in response to an externally applied input pressure, P(clamp). P(clamp) is generated magnetically. P(p) is sensed by a pressure sensor integrated into the magnetic clamp. The magnitude of P(p) depends on the transfer function, T(f), of the leaf cells. T(f) consists of a turgor pressure-independent (related to the compression of the cuticle, cell walls and other structural elements) and a turgor pressure-dependent term. T(f) is dimensionless and assumes values between 0 and 1. Theory shows that T(f) is a power function of cell turgor pressure P(c). Concomitant P(p) and P(c) measurements on grapevines confirmed the relationship between T(f) and P(c). P(p) peaked if P(c) approached zero and assumed low values if P(c) reached maximum values. The novel probe was successfully tested on leaves of irrigated and non-irrigated grapevines under field conditions. Data show that slight changes in the microclimate and/or water supply (by irrigation or rain) are reflected very sensitively in P(p).


Subject(s)
Ecology/instrumentation , Plant Leaves/physiology , Pressure , Vitis/physiology , Water/physiology , Botany/instrumentation , Models, Biological , Patch-Clamp Techniques
10.
Am Nat ; 174(1): E23-39, 2009 Jul.
Article in English | MEDLINE | ID: mdl-19426110

ABSTRACT

A change in the environmental conditions across space-for example, altitude or latitude-can cause significant changes in the density of a vegetation type and, consequently, in spatial connectivity. We use spatially explicit simulations to study the transition from connected to fragmented vegetation. A static (gradient percolation) model is compared to dynamic (gradient contact process) models. Connectivity is characterized from the perspective of various species that use this vegetation type for habitat and differ in dispersal or migration range, that is, "step length" across the landscape. The boundary of connected vegetation delineated by a particular step length is termed the " hull edge." We found that for every step length and for every gradient, the hull edge is a fractal with dimension 7/4. The result is the same for different spatial models, suggesting that there are universal laws in ecotone geometry. To demonstrate that the model is applicable to real data, a hull edge of fractal dimension 7/4 is shown on a satellite image of a piñon-juniper woodland on a hillside. We propose to use the hull edge to define the boundary of a vegetation type unambiguously. This offers a new tool for detecting a shift of the boundary due to a climate change.


Subject(s)
Ecosystem , Environment , Climate , Geography , Juniperus , Models, Biological , New Mexico
11.
Plant Biol (Stuttg) ; 11(3): 307-27, 2009 May.
Article in English | MEDLINE | ID: mdl-19470103

ABSTRACT

The continuity of the xylem water columns was studied on 17- to 23-m tall birch trees (trunk diameter about 23 cm; first branching above 10 m) all year round. Fifty-one trees were felled, and 5-cm thick slices or 2-m long boles were taken at regular, relatively short intervals over the entire height of the trees. The filling status of the vessels was determined by (i) xylem sap extraction from trunk and branch pieces (using the gas bubble-based jet-discharge method and centrifugation) and from trunk boles (using gravity discharge); (ii) (1)H nuclear magnetic resonance imaging of slice pieces; (iii) infusion experiments (dye, (86)Rb(+), D(2)O) on intact trees and cut branches; and (iv) xylem pressure measurements. This broad array of techniques disclosed no evidence for continuous water-filled columns, as postulated by the Cohesion-Tension theory, for root to apex directed mass transport. Except in early spring (during the xylem refilling phase) and after extremely heavy rainfall during the vegetation period, cohesive/mobile water was found predominantly at intermediate heights of the trunks but not at the base or towards the top of the tree. Similar results were obtained for branches. Furthermore, upper branches generally contained more cohesive/mobile water than lower branches. The results suggest that water lifting occurs by short-distance (capillary, osmotic and/or transpiration-bound) tension gradients as well as by mobilisation of water in the parenchymatic tissues and the heartwood, and by moisture uptake through lenticels.


Subject(s)
Betula/physiology , Plant Transpiration/physiology , Trees/physiology , Water/physiology , Xylem/physiology , Biological Transport/physiology , Plant Roots/physiology , Plant Stems/physiology
12.
Hematol Oncol ; 27(3): 154-9, 2009 Sep.
Article in English | MEDLINE | ID: mdl-19274614

ABSTRACT

Mantle cell lymphoma (MCL) has a poor prognosis with often short and incomplete remissions. We aimed to test the efficacy and tolerability of gemcitabine in treating MCL. Gemcitabine was given in doses of 1000 mg/m(2) as a 30 min infusion on days 1 and 8 of each 3 week cycle for a maximum of nine cycles. Eighteen patients with a median age of 70 years were recruited. MCL was newly diagnosed in half of patients and relapsed in the remainder. Fifteen patients had Ann Arbor stage IV. The best-recorded responses were 1 CR (complete remission), 4 PRs (partial responses), 8 SDs (stable diseases) and 4 PDs (diseases progression). The response rate (RR) (CR + PR) was 5 (28%; 95% confidence interval: 7.1, 48.5). The patient achieving a CR had stage IV disease. Most haematological adverse events occurred during the first chemotherapy cycle. Three patients developed non-haematological serious adverse events: dyspnea, glomerular microangiopathy with haemolytic uremic syndrome (HUS) and hyperglycaemia. The median time-to-progression and treatment response duration (TRD) was 8.0 (95% confidence interval: 5.5, 9.3) and 10.6 (95% confidence interval: 5.5, 10.9) months, respectively. We conclude that Gemcitabine is well tolerated, moderately active and can induce disease stabilization in patients with MCL.


Subject(s)
Antimetabolites, Antineoplastic/adverse effects , Antimetabolites, Antineoplastic/therapeutic use , Deoxycytidine/analogs & derivatives , Lymphoma, Mantle-Cell/drug therapy , Aged , Deoxycytidine/adverse effects , Deoxycytidine/therapeutic use , Disease Progression , Female , Humans , Lymphoma, Mantle-Cell/pathology , Male , Middle Aged , Recurrence , Remission Induction , Gemcitabine
13.
Protoplasma ; 235(1-4): 101-5, 2009 Mar.
Article in English | MEDLINE | ID: mdl-19145400

ABSTRACT

Investigation of 67 gymnosperm and angiosperm species belonging to 25 orders shows that epistomatal mucilage plugs are a widespread phenomenon. Measurements of the leaf water status by using the leaf patch clamp pressure technique suggest that the mucilage plugs are involved in moisture uptake and buffering leaf cells against complete turgor pressure loss at low humidity.


Subject(s)
Adaptation, Physiological , Plant Leaves/physiology , Plant Physiological Phenomena , Plant Transpiration/physiology , Phylogeny , Plant Leaves/cytology , Water , Xylem/physiology
14.
Vet Microbiol ; 135(1-2): 142-6, 2009 Mar 16.
Article in English | MEDLINE | ID: mdl-18945556

ABSTRACT

Ocular infections by chlamydiae are associated with ocular disease manifestations such as conjunctivitis and keratitis in humans and animals. Limited evidence exists that members of the order Chlamydiales can also cause ocular disease in sheep. In the current study, the prevalence of chlamydiae in the eyes of sheep was investigated by using PCR methods. Data obtained in sheep by broad-range 16S rRNA order Chlamydiales-specific PCR were compared to the prevalence of antibodies against chlamydiae detected by a competitive enzyme-linked immunosorbent assay (cELISA). Flocks tested included a clinically healthy flock and two flocks suffering from ocular disease and with histories of Ovine Enzootic Abortion (OEA). PCR detected DNA of Chlamydophila (Cp.) abortus and Cp. pecorum in the eyes of both healthy and sick animals but also identified Chlamydia (C.) suis and a variety of uncultured chlamydia-like organisms. Good correlation was found between the presence of Cp. abortus DNA in sheep conjunctival samples and seropositivity detected by cELISA. Despite these findings, no association was found between the presence of chlamydial DNA in the sheep conjunctival samples and the onset of clinical disease. These results suggest that the biodiversity of chlamydiae in the eyes of sheep is greater than that previously thought. Further investigations are needed to determine whether a causal relationship between infection by chlamydiae and ocular disease exists in these animals.


Subject(s)
Chlamydia Infections/veterinary , Eye Infections, Bacterial/veterinary , Sheep Diseases/microbiology , Animals , Chlamydia Infections/microbiology , Enzyme-Linked Immunosorbent Assay/veterinary , Eye Infections, Bacterial/microbiology , Female , Polymerase Chain Reaction/veterinary , Serologic Tests/veterinary , Sheep
15.
Plant Biol (Stuttg) ; 10(5): 604-23, 2008 Sep.
Article in English | MEDLINE | ID: mdl-18761499

ABSTRACT

Seasonal variations in osmolality and components of xylem sap in tall birch trees were determined using several techniques. Xylem sap was extracted from branch and trunk sections of 58 trees using the very rapid gas bubble-based jet-discharge method. The 5-cm long wood pieces were taken at short intervals over the entire tree height. The data show that large biphasic osmolality gradients temporarily exist within the conducting xylem conduits during leaf emergence (up to 272 mosmol x kg(-1) at the apex). These gradients (arising mainly from glucose and fructose) were clearly held within the xylem conduit as demonstrated by (1)H NMR imaging of intact twigs. Refilling experiments with benzene, sucrose infusion, electron and light microscopy, as well as (1)H NMR chemical shift microimaging provided evidence that the xylem of birch represents a compartment confined by solute-reflecting barriers (radial: lipid linings/lipid bodies; axial: presumably air-filled spaces). These features allow transformation of osmolality gradients into osmotic pressure gradients. Refilling of the xylem occurs by a dual mechanism: from the base (by root pressure) and from the top (by hydrostatic pressure generated by xylem-bound osmotic pressure). The generation of osmotic pressure gradients was accompanied by bleeding. Bleeding could be observed at a height of up to 21 m. Bleeding rates measured at a given height decreased exponentially with time. Evidence is presented that the driving force for bleeding is the weight of the static water columns above the bleeding point. The pressure exerted by the water columns and the bleeding volume depend on the water-filling status of (communicating) vessels.


Subject(s)
Betula/physiology , Plant Roots/physiology , Trees/physiology , Water/physiology , Xylem/physiology , Carbohydrate Metabolism , Electrolytes/metabolism , Magnetic Resonance Spectroscopy , Osmolar Concentration , Osmotic Pressure , Seasons
16.
Virchows Arch ; 453(5): 473-84, 2008 Nov.
Article in English | MEDLINE | ID: mdl-18807072

ABSTRACT

APC, a tumor suppressor gene in the Wnt pathway, stabilizes beta-catenin and controls cell growth. Mutation of APC or beta-catenin leads to nuclear accumulation of beta-catenin and transcription of cyclin D1/cyclin A. Pulmonary artery sarcoma (PAS) were studied by morphologic, immunohistochemical, and molecular genetic methods of the Wnt pathway. Eighteen cases were included: mean age 52 years, primary intraluminal location with typical clinical presentation. PAS were classified as epithelioid (n = 4) or malignant fibrous histiocytoma (MFH; spindled/pleomorphic, n = 4), myxofibrosarcoma (n = 8), and one each hemangiopericytoma-like or malignant inflammatory myofibroblastic tumor-like. The tumor cells demonstrated vimentin, focal actins, and rare focal desmin positivity. All but one were grade 2 or 3 by FNCLCC grading. Alteration in chromosome 5q21 (APC) was found in 4/14 PAS by LOH, mostly epithelioid-type; an MFH-type case demonstrated microsatellite instability (MSI) and nuclear beta-catenin. Cyclin D1 was expressed in seven tumors, all myxofibrosarcoma-type. No mutations were detected in APC or beta-catenin. In summary, PAS are predominantly intermediate grade myxofibrosarcoma in middle-aged males, and fatal in two-thirds of patients. Despite myofibroblastic phenotype, APC/beta-catenin pathway changes are rare. Cyclin D1, only expressed in the myxofibrosarcoma-type, is likely transcribed via factors other than beta-catenin.


Subject(s)
Adenomatous Polyposis Coli Protein/metabolism , Pulmonary Artery/pathology , Sarcoma/classification , Signal Transduction/physiology , Tunica Intima/pathology , Vascular Neoplasms/classification , beta Catenin/metabolism , Adenomatous Polyposis Coli Protein/genetics , Adult , Aged , Cyclin A/metabolism , Cyclin D1/metabolism , Female , Humans , Loss of Heterozygosity/genetics , Male , Middle Aged , Pulmonary Artery/metabolism , Retrospective Studies , Sarcoma/genetics , Sarcoma/pathology , Sequence Analysis, DNA , Tunica Intima/metabolism , Vascular Neoplasms/genetics , Vascular Neoplasms/pathology , beta Catenin/genetics
17.
J Exp Bot ; 59(11): 3157-67, 2008.
Article in English | MEDLINE | ID: mdl-18689442

ABSTRACT

A high-precision pressure probe is described which allows non-invasive online-monitoring of the water relations of intact leaves. Real-time recording of the leaf water status occurred by data transfer to an Internet server. The leaf patch clamp pressure probe measures the attenuated pressure, P(p), of a leaf patch in response to a constant clamp pressure, P(clamp). P(p) is sensed by a miniaturized silicone pressure sensor integrated into the device. The magnitude of P(p) is dictated by the transfer function of the leaf, T(f), which is a function of leaf patch volume and ultimately of cell turgor pressure, P(c), as shown theoretically. The power function T(f)=f(P(c)) theoretically derived was experimentally confirmed by concomitant P(p) and P(c) measurements on intact leaflets of the liana Tetrastigma voinierianum under greenhouse conditions. Simultaneous P(p) recordings on leaflets up to 10 m height above ground demonstrated that changes in T(f) induced by P(c) changes due to changes of microclimate and/or of the irrigation regime were sensitively reflected in corresponding changes of P(p). Analysis of the data show that transpirational water loss during the morning hours was associated with a transient rise in turgor pressure gradients within the leaflets. Subsequent recovery of turgescence during the afternoon was much faster than the preceding transpiration-induced water loss if the plants were well irrigated. Our data show the enormous potential of the leaf patch clamp pressure probe for leaf water studies including unravelling of the hydraulic communication between neighbouring leaves and over long distances within tall plants (trees).


Subject(s)
Agriculture/instrumentation , Plant Leaves/chemistry , Plant Physiological Phenomena , Water/analysis , Circadian Rhythm , Computers , Osmotic Pressure , Patch-Clamp Techniques
18.
Biochem Biophys Res Commun ; 369(4): 1022-6, 2008 May 16.
Article in English | MEDLINE | ID: mdl-18331832

ABSTRACT

Functional Channelrhodopsin-2 (ChR2) overexpression of about 10(4)channels/mum(2) in the plasma membrane of HEK293 cells was studied by patch-clamp and freeze-fracture electron microscopy. Simultaneous electrorotation measurements revealed that ChR2 expression was accompanied by a marked increase of the area-specific membrane capacitance (C(m)). The C(m) increase apparently resulted partly from an enlargement of the size and/or number of microvilli. This is suggested by a relatively large C(m) of 1.15+/-0.08 microF/cm(2) in ChR2-expressing cells measured under isotonic conditions. This value was much higher than that of the control HEK293 cells (0.79+/-0.02 microF/cm(2)). However, even after complete loss of microvilli under strong hypoosmolar conditions (100 mOsm), the ChR2-expressing cells still exhibited a significantly larger C(m) (0.85+/-0.07 microF/cm(2)) as compared to non-expressing control cells (0.70+/-0.03 microF/cm(2)). Therefore, a second mechanism of capacitance increase may involve changes in the membrane permittivity and/or thickness due to the embedded ChR2 proteins.


Subject(s)
Bacteriorhodopsins/metabolism , Cell Membrane/physiology , Electric Capacitance , Membrane Proteins/metabolism , Bacteriorhodopsins/genetics , Cell Line , Cell Membrane/ultrastructure , Freeze Fracturing , Humans , Membrane Proteins/genetics , Microscopy, Electron , Patch-Clamp Techniques
19.
J Membr Biol ; 221(2): 107-21, 2008 Jan.
Article in English | MEDLINE | ID: mdl-18197354

ABSTRACT

Interactions of structurally dissimilar anionic compounds with the plasma membrane of HEK293 cells were analyzed by patch clamp and electrorotation. The combined approach provides complementary information on the lipophilicity, preferential affinity of the anions to the inner/outer membrane leaflet, adsorption depth and transmembrane mobility. The anionic species studied here included the well-known lipophilic anions dipicrylamine (DPA(-)), tetraphenylborate (TPB(-)) and [W(2)(CO)(10)(S(2)CH)](-), the putative lipophilic anion B(CF(3))(4)(-) and three new heterocyclic W(CO)(5) derivatives. All tested anions partitioned strongly into the cell membrane, as indicated by the capacitance increase in patch-clamped cells. The capacitance increment exhibited a bell-shaped dependence on membrane voltage. The midpoint potentials of the maximum capacitance increment were negative, indicating the exclusion of lipophilic anions from the outer membrane leaflet. The adsorption depth of the large organic anions DPA(-), TPB(-) and B(CF(3))(4)(-) increased and that of W(CO)(5) derivatives decreased with increasing concentration of mobile charges. In agreement with the patch-clamp data, electrorotation of cells treated with DPA(-) and W(CO)(5) derivatives revealed a large dispersion of membrane capacitance in the kilohertz to megahertz range due to the translocation of mobile charges. In contrast, in the presence of TPB(-) and B(CF(3))(4)(-) no mobile charges could be detected by electrorotation, despite their strong membrane adsorption. Our data suggest that the presence of oxygen atoms in the outer molecular shell is an important factor for the fast translocation ability of lipophilic anions.


Subject(s)
Anions/chemistry , Cell Membrane/physiology , Electric Capacitance , Picrates/metabolism , Tetraphenylborate/metabolism , Animals , Cell Line , Female , Humans , Hydrophobic and Hydrophilic Interactions , Jurkat Cells , Organometallic Compounds/metabolism , Patch-Clamp Techniques , Rotation , Xenopus laevis
20.
Oncogene ; 27(6): 732-40, 2008 Jan 31.
Article in English | MEDLINE | ID: mdl-17653085

ABSTRACT

Therapy resistance represents a major problem for disease management in oncology. Histone deacetylase inhibitors (HDACi) have been shown to modulate the cell cycle, to induce apoptosis and to sensitize cancer cells for other chemotherapeutics. Our study shows that the HDACi valproic acid (VPA) and the ribonucleotide reductase inhibitor hydroxyurea (HU) potentiate the pro-apoptotic effects of each other towards several cancer cell lines. This correlates with the HU-induced degradation of the cyclin-dependent kinase inhibitors (CDKI) p21 and p27, mediated by the proteasome or caspase-3. Moreover, we found that caspase-3 activation is required for VPA-induced apoptosis. Remarkably, p21 and p27 can confer resistance against VPA and HU. Both CDKI interact with caspase-3 and compete with other caspase-3 substrates. Hence, p21 and p27 may contribute to chemotherapy resistance as apoptosis inhibitors. Since the biological effects of VPA and HU could be achieved at concentrations used in current treatment protocols, the combined application of these compounds might be considered as a potential strategy for cancer treatment.


Subject(s)
Apoptosis , Cell Cycle/drug effects , Enzyme Inhibitors/pharmacology , Histone Deacetylase Inhibitors , Hydroxyurea/pharmacology , Ribonucleotide Reductases/pharmacology , Caspase 3/metabolism , Caspase Inhibitors , Cell Line, Tumor , Cyclin-Dependent Kinase Inhibitor p21/metabolism , Cyclin-Dependent Kinase Inhibitor p27/metabolism , Humans , Melanoma/enzymology , Valproic Acid/pharmacology
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