A screening method for determining nitrofuran drug residues in animal tissues

A method was developed for measuring low levels of total nitrofurans in animal tissues and milk. The antimicrobial nitrofurans (5 or more products) used in agriculture are extracted from tissue with aqueous acid in the presence of ethyl acetate. After centrifugation and evaporation, the organic residue is washed with hexane and the nitrofurans are hydrolyzed to 5-nitrofuraldehyde in aqueous acid at 70 degrees C. The hydrolysis product is extracted with benzene and measured by gas-liquid chromatography with electron capture detection. Recoveries of nitrofurazone and furazolidone from fortified poultry and swine tissues at the levels of 0.5 and 0.1 ppm are 75 and 65%, respectively. This procedure can be used to detect the total nitrofuran content of as little as 10 ppb muscle tissues and milk, 100 ppb liver, and 50 ppb fat with no interference from related veterinary nitrodrugs.

Studies on synthesis of 1,2-cis-D-galactosides with partially benzylated intermediates

The 1-bromides of p-nitrobenzoylated 2-O-benzyl- (1) and 2,3- (8) and 2,6-di-O-benzyl-D-galactose (14) and 2-O-benzyl-D-glucose (20) were treated under Koenigs-Knorr conditions with 6-(trifluoroacetamido)-1-hexanol. Examination of the products by p.m.r. spectroscopy, g.l.c., and mass spectrometry revealed that, whereas the major product derived from 14 was the pyranoside (19), the glycosides derived from both 1 and 8 were mainly furanosides. The corresponding glycoside from 20 was entirely the pyranoside (23).

Polyacrylamide gels copolymerized with active esters. A new medium for affinity systems

A new and versatile method for linking biologically active ligands to a polyacrylamide matrix is reported. Active esters of acrylic acid (N-succinimicyl acrylate and N-phthalimidyl acrylate) were synthesized, then copolymerized with acrylamide and N,N'-methylenebisacrylamide. Displacement of the active ester in the gel thus formed by various ligands containing aliphatic amino groups resulted in the formation of stable amid bonds between the ligands and the polyacrylamide gel. The affinity gel thus prepared has the following advantages: (i) resistance to chemical and microbiological degradation, (ii) ease of control of ligand level and higher levels of ligand possible, (iii) ease of control of porosity, and (iv) total displacement of the active ester under suitable conditions. Efficacy of this system was tested by preparation of 6-aminohexyl 2-acetamido-2-deoxy-beta-D-glucopyranoside derivative polyacrylamide gel by the described method. It was found to be more effective for purification of wheat germ agglutinin than the previously published affinity chromatography systems and the wheat germ hemagglutinin was obtained in crystalline form. In addition, partial resolution of isolectins was obtained from the affinity gel witha pH gradient.

Echocardiographic and electrocardiographic criteria for diagnosing left atrial enlargement

Electrocardiographic criteria for left atrial enlargement (LAE) were evaluated in a group of 100 patients with a wide spectrum of cardiovascular diseases and compared with the echocardiographic measurement of left atrial dimension (LAD). Data analysis showed a high degree of correlation between the echocardiographic measurement of LAD and the EKG criteria for LAE. The magnitude of the P terminal force in lead V1 was the most specific of the EKG criteria evaluated, while the P/P-R segment ratio was least specific. Concordance between the two methods of measuring left atrial size increased when multiple positive EKG criteria were present.

Radiosensitization of a human cell line lacking repair replication

A human cell line has been isolated that is deficient in X-ray-induced repair replication. The slope of the radiation survival curve is greater in the presence of the anthracycline antibiotic, adriamycin. The results suggest that radiosensitization by DNA-binding drugs is more probably related to DNA strand breakage phenomena than to the polymerase step of excision-repair.

Adhesion of cultured fibroblasts to insoluble analogues of cell-surface carbohydrates

Animal cells are coated with complex carbohydrates. Insoluble analogues of these substances were prepared by coupling monosaccharides to Sephadex beads (crosslinked dextran), and the interactions between these derivatives and three established cell lines were studied. A virally transformed fibroblast, simian virus 40-transformed 3T3 cells, adhered to the beads derivatized with D-galactose, but did not adhere to the corresponding beads derivatized with D-glucose or N-acetyl-D-glucosamine. Cells that adhered to the galactose-beads appeared to initiate a nucleation process in that they became more adhesive towards the cells in suspension, leading to the formation of large aggregates containing both cells and galactose-beads. The results suggest that specific carbohydrates are involved in the processes of cell recognition or cell adhesion, or both.

Calcium ions and the cardiotonic action of glucagon (calcium fluxes-myocardial function-asystole-membrane transport-cat)

The positive inotropic action of glucagon on the cat heart is dependent upon the extracellular Ca concentration. The inotropic effect is proportionately greater, the lower the concentration of Ca in the perfusate (above zero, at which glucagon is without significant effect). Nevertheless, Ca influx (as measured with (45)Ca) into the myocardium is not demonstrably influenced by glucagon, except at 0.09 mM Ca, where the interpretation of the effect is complicated by the fact that there is mechanical asystole at that Ca concentration in the absence of glucagon, while excitation-contraction coupling still occurs when the hormone is added. The possibility is suggested that glucagon may influence intracellular movement of Ca, even when its transmembrane movement is affected only slightly.

Influx of calcium into rabbit myocardium in relation to its ionic environment

In the first 150 seconds after contracture of rabbit myocardium has been induced by shifting from perfusion with zero [Ca(2+)] and low [K(+)] to solutions with normal levels of those cations, there is a large influx of Ca(2+) as measured both by isotopic tracer flux and by total tissue [Ca]. Tracer studies indicate that the influx is 90 per cent complete in 90 seconds. Contracture due to substitution of either Li(+) or K(+) for Na(+) in perfusion fluids is also associated with an increased influx, but of lesser magnitude. The latter types of contracture are reversible while the former is not. It seems probable that the irreversible contracture is induced by the large Ca(2+) influx.