Interaction of purified bovine brain A1-adenosine receptors with guanine nucleotide-binding proteins of human platelet membranes following reconstitution

A1-adenosine receptors and associated guanine nucleotide-binding proteins (G proteins) have been co-purified from bovine cerebral cortex by agonist affinity chromatography [J. Biol. Chem. 264:14853-14859 (1989)]. In this study we have reconstituted purified bovine brain A1 receptors into human platelet membranes that contain A2- but no detectable A1-adenosine receptors. The recovery of reconstituted receptors was assessed from the binding of the antagonist radioligand [125I]3-(4-amino-3-iodo)phenethyl-1-propyl-8-cyclopentyl-xanthine and ranged from 32 to 84%. Coupling of reconstituted A1 receptors to platelet G proteins was evaluated by measurement of the high affinity binding of an agonist radioligand, 125I-aminobenzyladenosine, to receptor-G protein complexes and by stereospecific photoaffinity labeling of a 35,000-Da receptor polypeptide with the agonist photoaffinity label 125I-azidobenzyladenosine. Fifty percent of receptors reconstituted into platelet membranes bound agonists with high affinity, indicative of coupling to platelet G proteins. Reconstituted A1 receptors bound various ligands with affinities characteristic of A1 receptors of bovine brain. Although platelets contain both pertussis toxin-sensitive and -insensitive G proteins, reconstituted high affinity agonist binding was almost completely abolished by treatment of platelet membranes with guanosine 5'-3-O-(thio)triphosphate, pertussis toxin, N-ethylmaleimide, or heparin. Following reconstitution, A1 receptors could be resolubilized in complexes with platelet G proteins. The data suggest that marked species differences in the binding affinity of ligands to adenosine receptors result from differences in the receptors rather than membrane structure or G proteins and, further, that A1 receptors couple selectively and tightly to pertussis toxin-sensitive G proteins.     

Effect of the external donors on the polymerization of 4-methyl-1-pentene with high activity MgCl2/TiCl4 catalytic system

In order to find out correlations between the structure of an external donor and the obtained polymer, the effects of different external donors on the activity and stereospecificity of the MgCl₂/TiCl₄ catalytic system in the bulk polymerization of 4-methyl-1-pentene (4MP) were carefully studied. Different silane compounds of the structure R_nSi(OR')_4-n (where: n = 1–3, R = alkyl/phenyl, R = alkyl) and Al(i-Bu)₃ (TIBA) were used as external donors and cocatalyst, respectively. The effect of the donor/TIBA mole ratio on the activity and stereospecificity of the catalytic system was studied. Some major effects were observed for the three different external donors, namely, Me₃Si(OMe), Me₂Si(OMe)₂, and Me₃Si(OBu)₃, in the 4MP polymerization process. It was observed that the effect of the external silane donor on the polymerization strongly depends upon the size of the alkoxy and hydrocarbon (alkyl/phenyl) groups which are attached to the silicon atom. A selective deactivation of the non-stereospecific centers, as well as a transformation of the non-stereospecific into isospecific centers, is assumed to occur. On the basis of the obtained results and literature data available for the propene polymerization, the concept of structural conformity between the ligand-surrounded active center and the monomer molecule was carried forward.     

The effect of midazolam on median nerve somatosensory evoked potentials

Objective. To quantify the effect of an induction dose of midazolam on median nerve somatosensory evoked potentials.Methods. We studied 10 patients undergoing lumbar spine surgery. After an induction dose of intravenous midazolam was given, MNEPs were collected for ten minutes. After ten minutes the patients were intubated and their anesthetic was supplemented with 0.5% isoflurane, narcotic, and N₂O.Results. We found a clinically significant decrease in amplitude and an insignificant delay in latency.Conclusion. When midazolam is used as an anesthetic induction agent, a decrease in amplitude can be expected.     

Relationship between the existing caries status, plaque S. mutans and Cariostat caries activity test in children

An attempt was made in this study to find out the sensitivity and specificity of a caries activity test, CARIOSTAT and its relationship to the existing caries status and the plaque S. mutans level. The test proved to be highly sensitive and specific with significant relationship to the S.mutans count in the dental plaque. There also was a significant relationship between both the cultured microorganisms on MSB agar and the plaque in the Cariostat medium.     

Small bowel necrosis associated with early postoperative jejunal tube feeding in a trauma patient

Several investigators have reported the association of small bowel ischemia and necrosis with needle catheter jejunostomy. We report a case of small bowel necrosis with continuous jejunal tube feeding and review the pathogenesis implicated in feeding-induced bowel necrosis.     

Can Smart Pens Help Improve Diabetes Management?

Smart pen technology has evolved over the past decade with new features such as Bluetooth connectivity, bolus dose calculators, and integration with mobile apps and continuous glucose monitors. While similar in appearance to a traditional insulin pen, smart pens have the ability to record and store data of insulin injections. These devices have the potential to transform diabetes management for clinicians, and patients with type 1 and type 2 diabetes on insulin therapy by improving adherence, glycemic control, and addressing barriers to diabetes management. Smart pens can also highlight the relationship between insulin, food, and physical activity, and provide insight into optimizing insulin regimens. Education of clinicians and patients, and more clinical studies showing the benefits of smart pens and cost-effectiveness, are needed.