Effect of lacidipine on ischaemic and reperfused isolated rabbit hearts

Lacidipine is a new developed dihydropyridine calcium-antagonist, showing a slow onset and long lasting-selective activity.To assess whether the administration of lacidipine protects the myocardium in a dose-dependent manner against ischaemia and reperfusion, isolated rabbit heart were infused with three different concentrations of lacidipine: 10^–10; 10^–9; 10^–8 M. Diastolic and developed pressures were monitored; coronary effluent was collected and assayed for CPK activity and for noradrenaline concentration; mitochondria were harvested and assayed for respiratory activity, ATP production and calcium content and tissue concentration of ATP, creatine phosphate (CP) and calcium were determined. Occurrence of oxidative stress during ischaemia and reperfusion was also monitored in terms of tissue content and release of reduced (GSH) and oxidized (GSSG) glutatione. Treatment with lacidipine at 10^–10 and 10^–9 M had no effects on the hearts when perfused under aerobic condition, whilst the higher dose reduced developed pressure of 36%. The ischaemic-induced deterioration of mitochondrial function was attenuated. On reperfusion treated hearts recovered better than the untreated hearts with respect to left ventricular performance, replenishment of ATP and CP stores and mitochondrial function. The reperfusion-induced tissue and mitochondrial calcium overload, release of CPK and of noradrenaline and oxidative stress were also significantly reduced. The effects of lacidipine were dose-dependent. The lower concentration (10^–10 M) failed to modify ischaemic and reperfusion damage. The dose of 10^–9 M was cardioprotective, but the best effect was found at 10^–8 M.It is concluded that lacidipine infusion provides a dose dependent protection of the heart against ischaemia and reperfusion. Because this protection occurred also at 10^–9 M, in the absence of negative inotropic effect during normoxia and of a coronary dilatory effect during ischaemia, it cannot be attributed to an energy sparing effect or to improvement of oxygen delivery. From our data we can envisage two other major mechanism:-1) membrane protection-2) reduction of oxygen toxicity. The ATP sparing effect occurring at 10^–8 M is likely to be responsable for the further protection.     

Occurrence of oxidative stress during myocardial reperfusion

Reperfusion, without doubt, is the most effective way to treat the ischaemic myocardium. Late reperfusion may however cause further damage. Myocardial production of oxygen free radicals above the neutralizing capacity of the myocytes is an important cause of this reperfusion damage. There is evidence that prolonged ischaemia reduces the naturally occurring defence mechanisms of the heart against oxygen free radicals, particularly mitochondrial manganese superoxide dismutase, and intracellular pool of reduced glutathione. Consequently, reperfusion results in a severe oxidative damage, as evidenced by tissue accumulation and release of oxidized glutathione.An oxygen free radical-mediated impairment of mechanical function also occurs during reperfusion of human heart. In fact we observed during surgical reperfusion of coronary artery disease (CAD) patients, a prolonged and sustained release of oxidized glutathione;the degree of oxidative stress was inversely correlated with recovery of mechanical and haemodynamic function. These findings represent the rationale for therapeutic interventions which increase the cellular antioxidant capacities and improve the efficacy of myocardial reperfusion.     

Inhibition in vitro of yeast DNA polymerase I activity by beta-blockers

The activity of DNA polymerase I from Saccharomyces cerevisiae is inhibited, in a dose-dependent fashion, by the oncogenic beta-blocker 1-(2-nitro-3-methyl-phenoxy)-3-tert-butylamino-propan-2-ol (ZAMI 1305) and by the non-oncogenic beta-blockers 1-(2-nitro-5-methyl-phenoxy)-3-tert-butylamino-propan-2-ol (ZAMI 1327), atenolol, and propranolol, the latter having the highest inhibiting activity. The inhibition is due to an interaction of the beta-blockers with the free enzyme and with the enzyme-DNA complex. The degree of inhibition is directly related to the hydrophobicity of the aromatic moiety and to the length and hydrophilicity of the aliphatic chain of the inhibitor. No relation seems to exist between the in vitro inhibition of yeast DNA polymerase I by beta-blockers and their oncogenic activity.     

Injection molded thermoplastic starch/natural rubber/clay nanocomposites: Morphology and mechanical properties

Unmodified and modified natural rubber latex (uNRL and mNRL) were used to prepare thermoplastic starch/natural rubber/montmorillonite type clay (TPS/NR/Na⁺-MMT) nanocomposites by twin-screw extrusion. After being dried, the nanocomposites were injection molded to produce test specimens. Scanning electron micrographs of fractured samples revealed that chemical modification of NRL enhanced the interfacial adhesion between NR and TPS; improving their dispersion. X-ray diffraction (XRD) showed that the nanocomposites exhibited partially intercalated/exfoliated structures. Surprisingly, transmission electron microscopy (TEM) showed that clay nanoparticles were preferentially intercalated into the rubber phase. Elastic modulus and tensile strength of TPS/NR blends were dramatically improved from 1.5 to 43 MPa and from 0.03 to 1.5 MPa, respectively, as a result of rubber modification. Properties of blends were almost unaffected by the dispersion of the clay except for the TPS/mNR blend loading 2% MMT. This was attributed to the exfoliation of the MMT.     

Efficient regeneration and antioxidant potential in regenerated tissues of <Emphasis Type="Italic">Piper nigrum</Emphasis> L.

The organogenic potential and antioxidant potential (1, 1-diphenyl-2-picrylhydrazyl-scavenging activity) of the medicinal plant Piper nigrum L. (black pepper) were investigated. Callus induction and shoot regeneration were induced from leaf explants of potted plants cultured on MS medium supplemented with different plant growth regulators. The best callogenic response was observed on explants cultured for 30 days on MS medium supplemented with either 0.5 or 1.5 mg l⁻¹ 6-benzyladenine (BA) + 1.0 mg l⁻¹ α-naphthaleneacetic acid. Subsequent transfer of the callogenic explants onto MS medium supplemented with 1.5 mg l⁻¹ BA + 1.0 mg l⁻¹ gibberellic acid (GA₃) achieved 85% shoot organogenesis after 30 days of culture. The maximum number (7.2) of shoots/explant was recorded for explants cultured in MS medium supplemented with 1.0 mg l⁻¹ BA. Following the transfer of shoots to an elongation medium, the longest shoots (5.4 cm) were observed on MS medium supplemented with 1.0 mg l⁻¹ BA + 1.0 mg l⁻¹ GA₃. The elongated shoots were rooted on MS medium supplemented with different concentrations of indole butyric acid. An assay of the antioxidant potential of the in vitro-grown tissues revealed that the antioxidant activity of the regenerated shoots was significantly higher than that of callus and the regenerated plantlets.     

PVA-gel (Lentikats®) as an effective matrix for yeast strain immobilization aimed at heterologous protein production

Three different yeast strains, namely Saccharomyces cerevisiae mnn1mnn9, Kluyveromyces lactis JA6/GAA and Zygosaccharomyces bailii [pZ₃klIL-1β], were entrapped in polyvinyl alcohol (PVA) gel particles, obtained following the commercially available immobilization kit named Lentikat^®. After immobilization in the PVA-gel particles, yeast cells remained viable: colonization of the gel matrix reached up 100 mg d.w. of cells cm⁻³ gel for all the strains examined.Lentikats^® of K. lactis JA6/GAA and Z. bailii [pZ₃klIL-1β] showed to be suitable for the continuous production of glucoamylase and interleukin 1β, respectively, when employed under non-selective conditions. They were of easy handiness and showed excellent mechanical properties during prolonged operation in stirred tank reactors.     

Human osteoclast-poor osteopetrosis with hypogammaglobulinemia due to TNFRSF11A (RANK) mutations

Autosomal-Recessive Osteopetrosis (ARO) comprises a heterogeneous group of bone diseases for which mutations in five genes are known as causative. Most ARO are classified as osteoclast-rich, but recently a subset of osteoclast-poor ARO has been recognized as due to a defect in TNFSF11 (also called RANKL or TRANCE, coding for the RANKL protein), a master gene driving osteoclast differentiation along the RANKL-RANK axis. RANKL and RANK (coded for by the TNFRSF11A gene) also play a role in the immune system, which raises the possibility that defects in this pathway might cause osteopetrosis with immunodeficiency. From a large series of ARO patients we selected a Turkish consanguineous family with two siblings affected by ARO and hypogammaglobulinemia with no defects in known osteopetrosis genes. Sequencing of genes involved in the RANKL downstream pathway identified a homozygous mutation in the TNFRSF11A gene in both siblings. Their monocytes failed to differentiate in vitro into osteoclasts upon exposure to M-CSF and RANKL, in keeping with an osteoclast-intrinsic defect. Immunological analysis showed that their hypogammaglobulinemia was associated with impairment in immunoglobulin-secreting B cells. Investigation of other patients revealed a defect in both TNFRSF11A alleles in six additional, unrelated families. Our results indicate that TNFRSF11A mutations can cause a clinical condition in which severe ARO is associated with an immunoglobulin-production defect.     

Effects of microwaves (900 MHz) on the cochlear receptor: exposure systems and preliminary results

The purpose of this paper is to present the experimental device and the work in progress performed in search for objective organic correlation of damage to hearing, examining possible acoustic otofunctional effects on the cochlear epithelium of the rat due to exposure to microwaves (900 MHz). Two experiments using male Sprague-Dawley rats were carried out with a far-field exposure in a cubic chamber. No statistically significant evidence was obtained at both specific absorption rate (SAR) values. The exposure system and the diagnostic apparatus are extremely useful to investigate a potential effect on the auditory system: however, with the parameters applied in these experiments, no evidence was observed. Received: 16 March 1999 / Accepted: 1 March 2000