A small-conductance charybdotoxin-sensitive,apamin-resistant Ca2+-activated K+ channel in aortic smooth muscle cells (A7r5 line and primary culture)

A small conductance K⁺ channel was identified in smooth muscle cells of the rat aortic cell line A7r5 and also in rat aortic smooth muscle cells in primary culture, using conventional single-channel recording techniques. The single-channel conductance shows no rectification, either in the range –70 to +40 mV under asymmetrical conditions (9.1 pS), or in the range –100 to +50 mV in symmetrical 150 mM K⁺ (37 pS). Channel activity is reversibly inhibited by extracellular application of charybdotoxin, with a concentration of 8 nM producing half-maximal inhibition. It is unaffected by apamin or scyllatoxin. Channel activity depends on the presence of free Ca²⁺ on the cytosolic face of the membrane, with an activation zone between 0.1 and 1 M. This small-conductance, charybdotoxin-sensitive, Ca²⁺-regulated K⁺ channel is activated by vasoconstrictors such as vasopressin and endothelin.     

Intracellular calcium ions activate a low-conductance chloride channel in smooth-muscle cells isolated from human mesenteric artery

Calcium-activated chloride currents were studied by the patch-clamp technique in vascular smooth muscle cells (VSMC) isolated from human mesenteric arteries. Bath application of 20 mM caffeine caused the cell membrane to depolarize by a calcium-activated inward current that peaked to –654±230 pA (holding potential –50 mV). Cell-attached, at the same time inwardly directed single-channel currents were detected with an amplitude of –0.22 pA. In open-cell-attached patches channel activity was triggered by elevating [Ca²⁺]_i to 10 M. At –60 mV the mean amplitude of the current was –0.24 pA and the mean open time of the channels was 28 ms. Plotting the amplitude of the current versus the test potential yielded a single-channel conductance of 2.8±0.5 pS. The currents disappeared when [Cl^–] was reduced from 150 mM to 5 mM at the cytosolic side of the inside-out patch at a holding potential of -60 mV (calculated reversal potential –58 mV) suggesting that the calcium-activated current was a chloride current. This suggests that, in human mesenteric VSMC, elevation of [Ca²⁺]_i activates a low-conductance chloride channel, which may mediate the agonist-induced depolarization of the cell membrane.     

Molecular diagnosis of a vascular prosthesis infection, due to Propionibacterium acnes, by amplification and sequencing of 16S rDNA

We describe a case of indolent vascular prosthesis infection due to Propionibacterium acnes. The microorganism was identified only by amplification and sequencing of 16S rDNA, while standard cultures remained negative. This observation underscores the usefulness of molecular techniques for the diagnosis of infection caused by fastidious microorganisms.     

Effect of the heparinoid pentosan polysulphate (SP 54) on the functional properties of cultured bovine aortic endothelial cells

Summary The effect of the heparinoid, pentosan polysulphate (PP) on the proliferative behaviour of cultured bovine endothelial cells (EC) was examined. In addition, the toxicity of the drug towards EC, its influence on prostacyclin production and release, and on cell-associated plasminogen activator activity was determined. At a concentration of 10 g/ml in the culture medium, PP exerted a growth promoting effect on EC. Increased cell numbers were accompanied by increased ³H-thymidine incorporation into cellular DNA compared with controls, however, final density of the cells was not affected. In contrast, at doses of 1 mg/ml the growth of EC was substantially slowed down. This finding did not reflect cell injury as shown by an unaltered release of ⁵¹Cr from the cells. Incubation of PP with EC had no influence on the prostacyclin release from the cells neither on the accumulation of the metabolite in the culture fluid over 24 hours nor on the releasing capacity upon stimulation with arachidonic acid. PP increased the cell-associated plasminogen activator activity in growing cells and counteracted in cultures at final density the inhibitory effect of serum on the intracellular plasminogenactivator activity. Our results suggest that stimulation of the fibrinolytic activity of the endothelium and a growth promoting effect for endothelial cells that may lead to faster coverage of small lesions could contribute to the antithrombotic potency of pentosan polysulphate in vivo.     

Dexamethasone suppression and multiple hormonal responses (TSH,prolactin and growth hormone) to TRH in some psychiatric disorders

Summary Baseline and TRH-induced changes of thyroid stimulating hormone (TSH), prolactin (PRL), and growth hormone (GH) were measured in 15 healthy control subjects and 63 psychiatric inpatients with DSM-III diagnoses of major depression (n = 19), schizophrenic disorder (n = 20), alcohol dependence (n = 10), and adjustment disorder (n = 14); baseline and postdexamethasone cortisol (CS) were also determined 3–6 days after the TRH-challenge. All patients and controls were women of similar mean age, weight, height, and they were free from interfering illness or drugs.Baseline TSH and PRL were lower in depression, TRH-induced TSH and PRL responses were lower in the whole patient group, but most markedly in depression and alcohol dependence. Postdexamethasone CS was significantly higher in depression, schizophrenia and alcohol dependence. Basal GH did not differentiate the subgroups; TRH-induced pathological GH responses were sometimes found in the patient groups. The differences were most marked quantitatively in major depression: a multivariate analysis of variance showed that TSH, postdexamethasone CS and PRL were the most important variables in separating patients from controls. A discriminant function derived from these variables classified all controls and 18 of 19 depressed patients correctly; however, 25 of the 44 other patients were also classified with depression.It was confirmed that psychiatric patients show significantly more endocrine disturbances than controls, and this was seen not only in major depression but also in at least three other conditions. Further work is needed to identify other neuroendocrine patterns more specific to depressive disorder.     

Beta-2-adrenoceptor agonists as inhibitors of lung vascular permeability to radiolabelled transferrin in the adult respiratory distress syndrome in man

Increased lung vascular permeability leading to increased plasma protein extravasation and accumulation (PPA) is a characteristic feature of acute lung injury. Using a previously described technique, PPA was monitored in the lungs of patients with the adult respiratory distress syndrome (ARDS) — an extreme example of acute lung injury in man. An external radiation probe detector was used to monitor the pulmonary accumulation of the plasma protein transferrin radiolabelled in-vivo with ^113mIn. Ten patients with ARDS exhibiting increased PPA indices (>1.0x10^-3/min) were given an intravenous infusion of terbutaline (7 g/kg) over 30 min. Of the four patients in whom the post-drug PPA indices remained within the ARDS range, none survived, whilst five of the six patients in whom the post-drug PPA indices were reduced to below 1.0x10^-3/min survived. PPA indices prior to the administration of terbutaline were not significantly different between the survivor (n=5) and non-survivor (n=5) groups. There was a significant decrease in the PPA indices following terbutaline in survivors (p<0.01) but not in non-survivors. Thus beta-2-agonists in therapeutic doses can inhibit increased lung vascular permeability in man. These findings may have prognostic and therapeutic implication for beta-2-agonists in ARDS.     

Short-termin vivo stability of endothelial-lined polyester elastomer and polytetrafluoroethylene grafts

A fibronectin substrate will significantly enhance the strength of endothelial cell attachment on grafts constructed of polyester elastomer (PE) and polytetrafluoroethylene (e-PTFE). This experiment was undertaken to determine the short-termin vivo stability of endothellum on these fibronectin coated surfaces. Eight mongrel dogs underwent bilateral carotid artery replacement with both graft materlals. All grafts were inoculated with 2,000 cells/mm² using cultured autogenous venous endothelium labelled with Indium-111-oxine. The Indium-111 label in the grafts was measured immediately prior to implantation, after 1 hour ofin vivo perfusion, and at explantation after 24 hours. The percentage of inoculated cells attached to the grafts before perfusion was simillar for both materials, 93.3±3.0% versus 92.2±7.2%, for PE and e-PTFE respectively. All grafts were patent at one hour after implantation. PE grafts were found to have 93.8±3.9 % of the attached cells present at one hour while e-PTFE grafts had only 54.5 ± 10.8 % remaining, p<.001. After 24 hours, 5/8 (62.5%) e-PTFE grafts and 2/8 (25.0 %) PE grafts remained patent, p=.13. Of the patent grafts however, endothelial cell retention was still superior on the PE grafts with 78.0±0.6% of the attached cells remaining compared to only 24.5±6.1% on e-PTFE, p<.001. Occluded PE grafts had fewer cells remaining at 24 hours than patent ones, 78.0±0.6% versus 31.1±32.8%, respectively, p=.13. Histologically, patent PE grafts demonstrated nearly confluent endothelial monolayers while e-PTFE had patches of endothelial cells surrounded by, a platelet-fibrin carpet. We conclude that short-term patency appears to be determined by the extent of endothelial retention on PE but not e-PTFE.     

Use of VA ECMO and percutaneous palliation of ductal dependent coarctation in a neonate with trisomy 21 and COVID-19 pneumonia

We present a case of a neonate with trisomy 21, ductal-dependent aortic coarctation, and severe respiratory failure secondary to coronavirus disease 2019 (COVID-19) pneumonia. The neonate was managed with venoarterial extracorporeal membrane oxygenation (VA ECMO), palliative stenting of the coarctation, and a vascular plug occlusion of a large patent ductus arteriosus. The patient was successfully weaned off extracorporeal membrane oxygenation (ECMO). The patient is currently awaiting a definitive surgical repair in the near future.