Differential effects of losartan and candesartan on vasoconstrictor responses in the rat

Losartan has been reported to have inhibitory effects on thromboxane (TP) receptor-mediated responses. In the present study, the effects of 2 nonpeptide angiotensin II (AT1) receptor antagonists, losartan and candesartan, on responses to angiotensin II, the thromboxane A2 mimic, U46619, and norepinephrine were investigated and compared in the pulmonary and systemic vascular beds of the intact-chest rat. In this study, intravenous injections of angiotensin II, U46619, and norepinephrine produced dose-related increases in pulmonary and systemic arterial pressure. Losartan and candesartan, in the doses studied, decreased or abolished responses to angiotensin II. Losartan, but not candesartan, and only in a higher dose, produced small, but statistically significant, reductions in pressor responses to U46619 and to norepinephrine in the pulmonary and systemic vascular beds. Furthermore, losartan significantly reduced arachidonic acid-induced platelet aggregation, whereas candesartan had no effect. Pressor responses to angiotensin II were not changed by thromboxane and alpha-adrenergic receptor antagonists, or by cyclooxygenase and NO synthase inhibitors. These results show that losartan and candesartan are potent selective AT1 receptor antagonists in the pulmonary and systemic vascular beds and that losartan can attenuate thromboxane and alpha-adrenergic responses when administered at a high dose, whereas candesartan in the highest dose studied had no effect on responses to U46619 or to norepinephrine. The present data show that the effects of losartan and candesartan on vasoconstrictor responses are different and that pulmonary and systemic pressor responses to angiotensin II are not modulated or mediated by the release of cyclooxygenase products, activation of TP receptors, or the release of NO in the anesthetized rat.     

New bioactive steroidal alkaloids from Buxus hyrcana

Phytochemical studies on the crude methanolic extract of Buxus hyrcana, collected from Iran, resulted in the isolation of two new steroidal alkaloids, (+)-O6-buxafurandiene (1) and (+)-7-deoxy-O6-buxafurandiene (2) along with four known steroidal bases, (+)-benzoylbuxidienine (3), (+)-buxapapillinine (4), (+)-buxaquamarine (5) and (+)-irehine (6). The structures of these new and known compounds were established with the aid of extensive NMR spectroscopic studies. Compounds 1 and 2 belong to the rarely occurring class of Buxus alkaloids having a tetrahydrofuran ring incorporated in their structures. Compounds 1-6 exhibited acetylcholinesterase enzyme inhibitory activity.     

Peroxynitrite does not impair pulmonary and systemic vascular responses.

The effects of peroxynitrite (ONOO-) on vascular responses were investigated in the systemic and hindquarters vascular bed and in the isolated perfused rat lung. Intravenous injections of ONOO- decreased systemic arterial pressure, and injections of ONOO- into the hindquarters decreased perfusion pressure in a dose-related manner. Injections of ONOO- into the lung perfusion circuit increased pulmonary arterial perfusion pressure. Responses to ONOO- were rapid in onset, short in duration, and repeatable without exhibiting tachyphylaxis. Repeated injections of ONOO- did not alter systemic, hindquarters, or pulmonary responses to endothelium-dependent vasodilators or other vasoactive agonists and did not alter the hypoxic pulmonary vasoconstrictor response. Injections of sodium nitrate or nitrite or decomposed ONOO- had little effect on vascular pressures. Pulmonary and hindquarters responses to ONOO- were not altered by a cyclooxygenase inhibitor in a dose that attenuated responses to arachidonic acid. These results demonstrate that ONOO- has significant pulmonary vasoconstrictor, systemic vasodepressor, and vasodilator activity; that short-term repeated exposure does impair vascular responsiveness; and that responses to ONOO- are not dependent on cyclooxygenase product release.     

Glia Maturation Factor Expression in Entorhinal Cortex of Alzheimer’s Disease Brain

Alzheimer’s disease (AD) is characterized by the presence of neuropathological lesions containing amyloid plaques (APs) and hyperphosphorylated Tau containing neurofibrillary tangles (NFTs) and is associated with neuroinflammation and neurodegeneration. Entorhinal cortex (Brodmann’s area 28) is involved in memory associated functions and is one of the first brain areas targeted to form the neuropathological lesions and also severely affected cortical region in AD. Glia maturation factor (GMF), a central nervous system protein and a proinflammatory molecule is known to be up-regulated in the specific areas of AD brain. Our previous immunohistochemical studies using temporal cortex showed that GMF is expressed in the vicinity of APs and NFTs in AD brains. In the present study, we have analyzed the expression of GMF and its association with APs and NFTs in the entorhinal cortex of AD brains by using immunohistochemistry combined with thioflavin-S fluorescence labeling methods. Results showed that GMF immunoreactive glial cells, glial fibrillary acidic protein labeled reactive astrocytes and ionized calcium binding adaptor molecule-1 labeled activated microglia were increased in the entorhinal cortical layers especially at the sites of 6E10 labeled APs and Tau containing NFTs. In conclusion, increased expression of GMF by the glial cells in the entorhinal cortex region, and the co-localization of GMF with APs and NFTs suggest that GMF may play important proinflammatory roles in the pathogenesis of AD.     

Access to Orphan Drugs: A Comprehensive Review of Legislations,Regulations and Policies in 35 Countries

ObjectiveTo review existing regulations and policies utilised by countries to enable patient access to orphan drugs.MethodsA review of the literature (1998 to 2014) was performed to identify relevant, peer-reviewed articles. Using content analysis, we synthesised regulations and policies for access to orphan drugs by type and by country.ResultsFifty seven articles and 35 countries were included in this review. Six broad categories of regulation and policy instruments were identified: national orphan drug policies, orphan drug designation, marketing authorization, incentives, marketing exclusivity, and pricing and reimbursement. The availability of orphan drugs depends on individual country’s legislation and regulations including national orphan drug policies, orphan drug designation, marketing authorization, marketing exclusivity and incentives such as tax credits to ensure research, development and marketing. The majority of countries (27/35) had in place orphan drug legislation. Access to orphan drugs depends on individual country’s pricing and reimbursement policies, which varied widely between countries. High prices and insufficient evidence often limit orphan drugs from meeting the traditional health technology assessment criteria, especially cost-effectiveness, which may influence access.ConclusionsOverall many countries have implemented a combination of legislations, regulations and policies for orphan drugs in the last two decades. While these may enable the availability and access to orphan drugs, there are critical differences between countries in terms of range and types of legislations, regulations and policies implemented. Importantly, China and India, two of the largest countries by population size, both lack national legislation for orphan medicines and rare diseases, which could have substantial negative impacts on their patient populations with rare diseases.     

Changes in the subcellular distribution of brain and heart hexokinase isoenzymes during alloxan diabetes

Changes in the subcellular distribution of hexokinase activity from three brain regions and heart were studied during alloxan induced diabetes. There was an overall decrease in the particulate hexokinase with an increase in the soluble form, after different time intervals of the onset of diabetes. Administration of insulin to the diabetic rats showed a partial counteraction of the enzyme changes. A possible regulation of brain hexokinase by metabolite changes is proposed