Activation of ion transport by combined effects of ionomycin,forskolin and phorbol ester on cultured HT-29cl.19A human colonocytes

The differentiated clone 19A of the HT-29 human colon carcinoma cell line was used as a model to study the intracellular electrophysiological effects of interaction of the cAMP, the protein kinase C (PKC) and the Ca²⁺ pathways, (a) A synergistic effect between ionomycin and forskolin was observed. From intracellular responses it was concluded that the synergistic effect is caused by activation of an apical Cl^– conductance by protein kinase A and a basolateral K⁺ conductance by Ca²⁺. (b) A transient synergistic effect of ionomycin and the phorbol ester phorbol dibutyrate (PDB) was found. The decrease of the response appeared to be due to PKC-dependent inactivation of the basolateral K⁺ conductance. The synergism is caused by PKC-dependent increase of the apical Cl^– conductance and Ca²⁺-dependent increase of the basolateral K⁺ conductance. (c) The effects of carbachol and PDB were not fully additive presumably because of their convergence on PKC activation, (d) Forskolin and PDB, when added in this order, had a less than additive effect. Results of cell-attached patch-clamp studies, presented in the accompanying paper, showed a synergistic effect of forskolin and PDB on non-rectifying small-conductance Cl^– channels. Assuming that these channels are involved in the transepithelial responses it is suggested that forskolin and PDB induce a modulatory, synergistic increase of the apical Cl^– conductance when both pathways are activated simultaneously. (e) The HT-29cl.19A cells differ from T₈₄ cells in that the latter did not respond with an increase of the short-circuit current to addition of phorbol ester. This may be due to a very low expression of PKC.     

Effect of chronic elevation of plasma calcium concentration by PTH or vitamin D3 on blood pressure and hypotensive activity of nifedipine in rats

The influence of a chronically elevated total plasma calcium concentration on blood pressure and heart rate was investigated in conscious normotensive rats. The plasma calcium concentration was elevated by continuous subcutaneous infusion with parathormone (PTH) after parathyreoidectomy, and by oral treatment with vitamin D₃. In both groups an elevated blood pressure was observed at the 1st day of treatment only. Blood pressure was returned to pretreatment values from the second day of treatments onaards. No significant changes in heart rate, due to hypercalcaemia, were observed. In hypercalcaemic rats, the calcium entry inhibitor nifedipine proved more potent in reducing blood pressure than in normocalcaemic control animals. Hydralazine was equipotent in reducing blood pressure in both groups. It is suggested, that the vasoconstrictor effects of a chronically elevated total plasma calcium concentration in conscious rats does not obviously result in a chronically elevated blood pressure, but rather in an enhanced sensitivity of the blood pressure towards calcium entry blockade.     

Do food antigens play a role in the pathogenesis of some cases of human glomerulonephritis?

Circulating immune complexes after a test meal were measured with three methods (PEG precipitation, Clq-ELISA and the indirect granulocyte phagocytosis test) in 10 controls, two symptomless persons with selective IgA deficiency and 14 patients with various types of glomerulonephritis, of which two patients (with idiopathic membranous glomerulopathy and local focal glomerulonephritis) also had selective IgA deficiency. The PEG and Clq-ELISA test did not show significant differences between the groups. In the two symptomless persons with selective IgA deficiency and in the patient with local focal glomerulonephritis and selective IgA deficiency the indirect granulocyte phagocytosis test (IGFT) showed a reproducible increase in IgG, IgM and complement containing immune complexes. In the last patient multiple food antigens were probably responsible for this phenomenon, a rapid amelioration of kidney function could be induced three times by giving an antigen free diet.     

Demonstration of skin-derived antileukoproteinase (skalp) and its target enzyme human leukocyte elastase in squamous cell carcinoma

Skin-derived antileukoproteinase (SKALP), also known as elafin, is a strong and specific inhibitor of elastase and proteinase 3. SKALP is not present in normal epidermis, but is expressed by epidermal keratinocytes under hyperproliferative conditions such as psoriasis, wound healing, and in cell culture. In human epidermal tumours, SKALP is differentially expressed and restricted to tumours with distinct squamous differentiation. We have studied the presence of both SKALP and one of its known target enzymes, leukocyte elastase, in 41 squamous cell carcinomas of the skin. SKALP expression correlated with the degree of differentiation: strong expression was seen in well-differentiated cells and expression was absent in poorly differentiated tumour cells. Most of the squamous cell carcinomas showed elastase-positive cells in the tumour stroma and also within the tumour cell nests. SKALP may interfere with the proteoloytic activity of infiltrating inflammatory cells or with hitherto unknown proteinases from the tumour cells. We hypothesize that in squamous cell carcinoma progressive loss of SKALP expression could facilitate tumour spread.     

The effect of raised pH on pacemaker activity and ionic currents in cardiac purkinje fibers

1. Cardiac Purkinje fibers exposed to alkaline solutions (pH 8 to 9.5) show an increase in rate of diastolic depolarization, eventually resulting in induction of spontaneous activity or an increase of the spontaneous firing rate.
2. The voltage-clamp analysis of the transmembrane currents in pH 9–9.5 shows: i) a shift in the depolarizing direction of the activation (s∞) and time constants (τ _s ) curve of the \(i_{{\text{K}}_{\text{2}} }\) current, ii) a small increase in the maximal value of the fully activated \(i_{{\text{K}}_{\text{2}} }\) current, iii) no significant change of background current in the pacemaker region of membrane potentials.
3. The effect of NH₄Cl was studied as a means to vary intracellular pH. In the presence of Tris buffer the addition of 5 mM NH₄Cl resulted in i) a shift in the depolarizing direction and a decrease in slope of the activation curve of the \(i_{{\text{K}}_{\text{2}} }\) current, ii) a shift in the depolarizing direction of the time-constants curve together with an increase in the maximum value of τ _s , iii) an increase in the maximum value of the fully activated \(i_{{\text{K}}_{\text{2}} }\) current and a depolarizing shift of the reversal potential, similar to the effect of addition of K_c. In the presence of CO₂?HCO₃ buffer the addition of NH₄Cl had no significant effect on the kinetics of the \(i_{{\text{K}}_{\text{2}} }\) current. Since intracellular pH is only affected by NH₄Cl in the presence of Tris buffer, the results suggest that intracellular alkalinization is responsible for the change in \(i_{{\text{K}}_{\text{2}} }\) kinetics.
4. Based on the findings with NH₄Cl it is suggested that perfusion with Tris buffered alkaline solutions not only affects net negative surface charges on the outside but also and to a larger extent increases negative surface charges on the inside of the cell membrane.

     

Elevated plasma levels of the long pentraxin, pentraxin 3, in severe dengue virus infections

C-reactive protein is one of the most widely used indicators of the response of acute-phase proteins. The measurement of C-reactive protein in dengue, however, is clinically not useful, because of marginally elevated levels and absent association with disease severity. The prototypic long pentraxin, pentraxin 3, is an acute phase protein that is structurally related but distinct from C-reactive protein which has proven to correlate with the severity of bacterial infection in critically ill patients. The potential involvement of pentraxin 3 in dengue and its aptitude to predict more severe disease or poor clinical outcome has not been studied previously. We therefore measured pentraxin 3 plasma levels in 44 dengue virus infected patients. Pentraxin 3 levels were strikingly higher when compared to C-reactive protein levels, with highest pentraxin 3 values observed in the first 7 days after the onset of symptoms. Median pentraxin 3 levels at admission and peak levels during follow up were higher in patients suffering from dengue shock syndrome (at admission: 119.3 ng/ml [interquartile range 61.8--188.7], peak values during follow up: 147.9 ng/ml [interquartile range 85.7--204.3]) compared to levels found in patients with dengue fever and dengue hemorrhagic fever (at admission: 59.0 ng/ml [interquartile range 28.6--100.3], P=0.040; peak values during follow up: 80.8 ng/ml [interquartile range 36.1--168.1], P=0.020). Our results indicate that pentraxin 3 seems to be a marker of infection better than C-reactive protein in dengue. The role of pentraxin 3 in the pathogenesis of dengue and its potential as an early prognostic indicator of disease severity needs further assessment.     

Cytoplasmic fatty acid-binding protein facilitates fatty acid utilization by skeletal muscle

The intracellular transport of long-chain fatty acids in muscle cells is facilitated to a great extent by heart-type cytoplasmic fatty acid-binding protein (H-FABP). By virtue of the marked affinity of this 14.5-kDa protein for fatty acids, H-FABP dramatically increases their concentration in the aqueous cytoplasm by non-covalent binding, thereby facilitating both the transition of fatty acids from membranes to the aqueous space and their diffusional transport from membranes (e.g. sarcolemma) to other cellular compartments (e.g. mitochondria). Striking features are the relative abundance of H-FABP in muscle, especially in oxidative muscle fibres, and the modulation of the muscular H-FABP content in concert with the modulation of other proteins and enzymes involved in fatty acid handling and utilization. Newer studies with mice carrying a homozygous or heterozygous deletion of the H-FABP gene show that, in comparison with wild-type mice, hindlimb muscles from heterozygous animals have a markedly lowered (-66%) H-FABP content but unaltered palmitate uptake rate, while in hindlimb muscles from homozygous animals (no H-FABP present) palmitate uptake was reduced by 45%. These findings indicate that H-FABP is present in relative excess and plays a substantial, but merely permissive role in fatty acid uptake by skeletal muscles.     

Effect of biologically active coating on biocompatibility of Nitinol devices designed for the closure of intra-atrial communications

Anti-thrombogenicity and rapid endothelialisation are prerequisites for the use of closure devices of intra-atrial communications in order to reduce the risk of cerebral embolism. The purpose of this study was therefore to assess the effect of bioactive coatings on biocompatibility of Nitinol coils designed for the closure of intra-atrial communications. Nitinol coils (n = 10, each) and flat Nitinol bands (n = 3, each) were treated by basic coating with poly(amino-p-xylylene-co-p-xylylene) and then coated with either heparin, r-hirudin or fibronectin. Anti-thrombogenicity was studied in vitro in a dynamic model with whole blood by partial thromboplastin time (PTT), platelet binding and thrombin generation, respectively, and cytotoxicity by hemolysis. Endothelialisation was studied on Nitinol bands with human umbilical venous endothelial cells (HUVEC) by 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium (MTT) assay and immnuofluorescence analysis of Ki67, vinculin, fibronectin and von Willebrand Factor. Uncoated or coated devices did not influence hemolysis and PTT. r-Hirudin (but not heparin) and fibronectin coating showed lower platelet binding than uncoated Nitinol (p < 0.005, respectively). Heparin and r-hirudin coating reduced thrombin formation (p < 0.05 versus Nitinol, respectively). HUVEC adhesion, proliferation, and matrix formation decreased in the order: fibronectin coating > uncoated Nitinol > r-hirudin coating > heparin coating > basic coating. MTT assay corroborated these findings. In conclusion, r-hirudin and fibronectin coating, by causing no acute cytotoxicity, decreasing thrombogenicity and increasing endothelialisation improve in vitro biocompatibility of Nitinol devices designed for the closure of intra-atrial communications.     

The effect of PEGT/PBT scaffold architecture on oxygen gradients in tissue engineered cartilaginous constructs

Repair of articular cartilage defects using tissue engineered constructs composed of a scaffold and cultured autologous cells holds promise for future treatments. However, nutrient limitation (e.g. oxygen) has been suggested as a cause of the onset of chondrogenesis solely within the peripheral boundaries of larger constructs. In the present study, oxygen gradients were evaluated by microelectrode measurements in two porous polyethylene glycol terephthalate/polybutylene terephthalate (PEGT/PBT) scaffold architectures, a compression-molded and particle-leached sponge (CM) and a 3D-deposited fiber (3DF) scaffold. During the first 14 days in vitro, gradients intensified, after which a gradual decrease of the gradients was observed in vitro. In vivo, however, gradients changed instantly and became less pronounced. Although similar gradients were observed regardless of scaffold type, significantly more cells were present in the center of 3DF constructs after 2 weeks of in vivo culture. Our results stress the importance of a rationally designed scaffold for tissue-engineering applications. Organized structures, such as the 3DF PEGT/PBT polymer scaffolds, offer possibilities for regulation of nutrient supply and, therefore, hold promise for clinical approaches for cartilage repair.