Cardioprotective Efficacy of Verapamil and Mibefradil in Young UM-X7.1 Cardiomyopathic Hamsters

Summary. Since calcium overload and increased in T-type calcium channel activity have been observed in the cardiomyopathic (CM) hamster, we hypothesized that mibefradil (Ro 40-5967), a new T- and L-type calcium channel blocker, may exert significant cardioprotection in the early phase of the disease. Young (30-day-old) CM hamsters of the UM-X7.1 subline were treated with mibefradil or verapamil for 4 to 6 weeks. Mibefradil doses were in the range of 0.5 to 8 mg/kg/day while verapamil was given at a dose of 5–10 mg/kg/day, both drugs being injected twice daily (sc and ip alternatively). At the end of the treatment period, myocardial and skeletal muscle (tongue) were harvested and processed for assessment of necrotic changes and calcification. In hearts from control CM hamsters, numerous necrotic and calcified foci were observed. These myocardial necrosis markers were not attenuated by mibefradil in the dose range studied whereas verapamil significantly reduced their severity. The dystrophic process in skeletal muscle (tongue) was not inhibited by mibefradil or verapamil. These results suggest that mechanisms other than inhibition of T- and L-type calcium channels are related to the cardioprotection observed in the presence of verapamil. A specific action on the sarcoplasmic reticulum (ryanodine-sensitive calcium channel) or the mitochondria may explain the efficacy of phenylalkylamines (verapamil) in this condition.     

Prolonged hypercapnia-evoked cerebral hyperemia via K(+) channel- and prostaglandin E(2)-dependent endothelial nitric oxide synthase induction

Mechanisms for secondary sustained increase in cerebral blood flow (CBF) during prolonged hypercapnia are unknown. We show that induction of endothelial NO synthase (eNOS) by an increase in prostaglandins (PGs) contributes to the secondary CBF increase during hypercapnic acidosis. Ventilation of pigs with 6% CO(2) (PaCO(2 approximately)65 mm Hg; pH approximately 7.2) caused a approximately 2.5-fold increase in CBF at 30 minutes, which declined to basal values at 3 hours and gradually rose again at 6 and 8 hours; the latter increase was associated with PG elevation, nitrite formation, eNOS mRNA expression, and in situ NO synthase (NOS) reactivity (NADPH-diaphorase staining). Subjecting free-floating brain sections to acidotic conditions increased eNOS expression, the time course of which was similar to that of CBF increase. Treatment of pigs with the cyclooxygenase inhibitor diclofenac or the NOS inhibitor Nomega-nitro-L-arginine blunted the initial rise and prevented the secondary CBF increase during hypercapnic acidosis; neuronal NOS blockers 1-(2-trifluoromethylphenyl) imidazole and 3-bromo-7-nitroindazole were ineffective. Diclofenac abolished the hypercapnia-induced rise in cerebrovascular nitrite production, eNOS mRNA expression, and NADPH-diaphorase reactivity. Acidosis (pH approximately 7.15, PCO(2 approximately )40 mm Hg; 6 hours) produced similar increases in prostaglandin E(2) (PGE(2)) and eNOS mRNA levels in isolated brain microvessels and in NADPH-diaphorase reactivity of brain microvasculature; these changes were prevented by diclofenac, by the receptor-operated Ca(2+) channel blocker SK&F96365, and by the K(ATP) channel blocker glybenclamide. Acidosis increased Ca(2+) transients in brain endothelial cells, which were blocked by glybenclamide and SK&F96365 but not by diclofenac. Increased PG-related eNOS mRNA and NO-dependent vasorelaxation to substance P was detected as well in rat brain exposed to 6 hours of hypercapnia. PGE(2) was the only major prostanoid that modulated brain eNOS expression during acidosis. Thus, in prolonged hypercapnic acidosis, the secondary CBF rise is closely associated with induction of eNOS expression; this seems to be mediated by PGE(2) generated by a K(ATP) and Ca(2+) channel-dependent process.     

Binding assay for thyrotropin receptor autoantibodies using the recombinant receptor protein.

We have characterized a transfected Chinese hamster ovary cell line, JP09, which expresses high levels of the human TSH receptor (TSH-R). Based on a theoretical biological activity for TSH of 40 IU/mg, JP09 has approximately 90,000 receptors per cell, having a dissociation constant of 1.64 x 10(3) mU/L or 1.47 x 10(-9) mol/L. We have used JP09 to prepare solubilized TSH-Rs which have formed the basis of a binding assay for thyroid-binding inhibiting immunoglobulins in unfractionated sera. We have compared the JP09 assay with the TRAK assay (which is based on solubilized porcine TSH-R) and found a highly positive correlation between the two assays, r = 0.83 P < 0.0001, in 55 sera from patients with autoimmune thyroid disease. JP09 can be adapted to growth in suspension culture, permitting large scale production. The tracer in the assay is bovine [125I]TSH; surprisingly, despite the use of a hTSH-R, hTSH had no effect on the binding of the tracer up to 10(3) mU/L and only a minor effect at 10(4) mU/L.     

Yellow-nail syndrome. Review of the literature apropos of 2 cases associated with cancer

Two cases of "yellow-nail syndrome" are reported: in the first, nail changes began eight months after the diagnosis of a breast cancer; in the second, yellow dystrophic nails were associated with hypertrophic osteoarthropathy due to pleuro-pulmonary metastatic lesions. Clinical features are described: characteristic nail changes, lymphoedema, pleural effusions, and, often bronchopulmonary infections and sinusitis. Various combinations are seen, and the time between the development of the different manifestations may vary from several months to many years. Among associated diseases, immunological changes and malignancy are emphasized. The pathogenesis remains obscure. Accurate part taken by lymphoedema, immunological changes, is unknown, and the relationships between "yellow-nail syndrome" and malignancy are still uncertain.     

Thiocyanate induces cell necrosis and fibrosis in selenium- and iodine-deficient rat thyroids: a potential experimental model for myxedematous endemic cretinism in central Africa

Thyroid destruction leading to endemic myxoedematous cretinism is highly prevalent in central Africa, where iodine (I) and selenium (SE) deficiencies as well as thiocyanate (SCN) overload are combined. All three factors have been studied experimentally in the etiology of the disease, but they have never been studied in combination. In a model using rats, we have previously shown that combining I and SE deficiencies increases the sensitivity of the thyroid to necrosis after iodide overload, an event unlikely to occur in the African situation. To develop a model that would more closely fit with the epidemiological findings, we have determined whether an SCN overload would also result in thyroid necrosis as does the I overload. The combination of the three factors increased by 3.5 times the amount of necrotic cells, from 5.5 +/- 0.3% in the I-SE+ thyroids to 18.9 +/- 1.6% in the I-SE-SCN-overloaded ones. Methimazole administration prevented the SCN-induced necrosis. SE- thyroids evolved to fibrosis, whereas SE+ thyroids did not. TGFbeta was prominent in macrophages present in SE- glands. Thyroid destruction in central Africa might therefore originate from the interaction of three factors: I and SE deficiencies by increasing H(2)O(2) accumulation, SE deficiency by decreasing cell defense and promoting fibrosis, and SCN overload by triggering follicular cell necrosis.     

Glucagon-like peptide-1 receptor agonists as neuroprotective agents for ischemic stroke: a systematic scoping review

Stroke mortality and morbidity is expected to rise. Despite considerable recent advances within acute ischemic stroke treatment, scope remains for development of widely applicable neuroprotective agents. Glucagon-like peptide-1 receptor agonists (GLP-1RAs), originally licensed for the management of Type 2 Diabetes Mellitus, have demonstrated pre-clinical neuroprotective efficacy in a range of neurodegenerative conditions. This systematic scoping review reports the pre-clinical basis of GLP-1RAs as neuroprotective agents in acute ischemic stroke and their translation into clinical trials. We included 35 pre-clinical studies, 11 retrospective database studies, 7 cardiovascular outcome trials and 4 prospective clinical studies. Pre-clinical neuroprotection was demonstrated in normoglycemic models when administration was delayed by up to 24 h following stroke induction. Outcomes included reduced infarct volume, apoptosis, oxidative stress and inflammation alongside increased neurogenesis, angiogenesis and cerebral blood flow. Improved neurological function and a trend towards increased survival were also reported. Cardiovascular outcomes trials reported a significant reduction in stroke incidence with semaglutide and dulaglutide. Retrospective database studies show a trend towards neuroprotection. Prospective interventional clinical trials are on-going, but initial indicators of safety and tolerability are favourable. Ultimately, we propose that repurposing GLP-1RAs is potentially advantageous but appropriately designed trials are needed to determine clinical efficacy and cost-effectiveness.     

Storage of platelet concentrates using ion exchange resin charged with dibasic phosphate.

Platelet concentrates were prepared at twice the normal concentration and stored at room temperature for 7 days in either standard bags (controls) or bags to which 1 or 2 g of Amberlite resin beads charged with dibasic phosphate had been added. The resin beads served as a buffer system by providing a "slow release" form of phosphate ions as well as by binding CO2 produced during platelet metabolism. Control platelets demonstrated rapid falls in pH, ATP content, morphology score, and thrombin-induced nucleotide release after 24 hr of storage with a fall in pH to less than 6.0 by day 3. Profound ultrastructural changes and a rise in pO2, suggesting loss of platelet viability, accompanied these changes. In contrast, the resin-stored platelets remained near normal after 24 hr of storage, with preservation of discoid morphology, 95% of ATP levels, excellent ultrastructural appearance, and evidence of continued oxygen consumption after 3 days of storage. Even after 7 days of storage, ATP levels remained greater than 50% of baseline and ultrastructurally intact platelets were seen. In the 1-g resin bags the pH remained at baseline levels (6.9-7.0), while there was a rise in pH in the 2-g resin bags. These results demonstrate the beneficial effects of maintaining a higher pH during platelet storage and provide a new approach to studying the metabolic changes that occur during longer term storage.