Gas-liquid chromatographic analysis of cyasin in cycad flour

A method for the quantitative determination of cycasin from cycad flour by gas-liquid chromatography is described. The flour is extracted with 70% ethanol and the residue from the dried extract is directly trimethylsilylated. Androsterone was found to be an excellent internal standard. The average content of cycasin from ten separate analyses of one lot of flour was $\text{0.429 gm}\text{100 gm}$. The method is rapid, sensitive, and not hindered by contaminating compounds.     

Characterization and Stability of Ribosomes from Mesophilic and Thermophilic Bacteria

Ribosomes were isolated from three mesophilic and three thermophilic strains of Bacillus. The ribosomes consisted of about 55% protein and 45% ribonucleic acid. Average ratios for the absorbance at 260/235 and 260/280 mmu were 1.77 and 1.92 for the mesophiles and 1.63 and 1.84 for the thermophiles. Ultracentrifugation revealed mainly components with sedimentation coefficients of about 30, 50, 70, 100, and 120S. All the preparations were shown to contain a ribonuclease which, in the presence of ethylenediaminetetraacetic acid, led to ribosome breakdown as measured by the increase in acid-soluble nucleotides. The stability of the ribosomes from the thermophiles was consistently greater than that of the ribosomes from the mesophiles. After 5 hr at 37 C, the breakdown was about 80% for the ribosomes from the mesophiles and 55 to 70% for those from the thermophiles. At 60 C, the ribosomes from the mesophiles were broken down slightly more and at a faster rate than those from the thermophiles. At temperatures above 60 C, the breakdown was again more pronounced for the ribosomes from the mesophiles.     

Role of the epithelium in airway smooth muscle responses to relaxant agonists.

We studied the role of the guinea pig tracheal epithelium in modulating tracheal smooth muscle responses to the relaxant agonists albuterol, sodium nitroprusside, and theophylline. We used an in vitro preparation that allowed separation of the fluids bathing the luminal (internal) and serosal (external) surfaces of the trachea, and bronchodilators were administered to either surface of carbachol-contracted tracheae. All three drugs produced dose-dependent relaxation. However, albuterol and nitroprusside were less potent (concentration that produced half-maximal effect increased by 100- and 32-fold, respectively) when given to the epithelial side with the epithelium intact compared with the epithelium denuded or compared with serosal administration with the epithelium intact. These differences were not observed for theophylline, where smooth muscle responses were independent of either the side of stimulation or of the presence or absence of the epithelium. Direct measurements of the diffusion of theophylline across the tracheal wall in the presence or absence of epithelium showed that after 5 h of incubation with a fixed luminal concentration of theophylline, only 1.7% had diffused across the tracheal wall with the epithelium intact. This increased to only approximately 3.3% when the epithelium was denuded. These results suggest that the epithelial is a relatively weak barrier for lipophilic agents but has a major role as a diffusion barrier to hydrophilic substances.     

绕茧蜂属寄生于云杉四眼小蠹成虫的—新种记述并附本属世界种检索表(膜翅目:茧蜂科)

绕茧蜂属Ropalophorus Curtis,1837是茧蜂科中的一个小属,迄今世界上仅记载有2种。一种为R.clavicornis(Wesmael),1835,分布于欧州及日本,寄生于云杉八齿小蠹Ips typographus及I.amitinus成虫体内;另一种为R.wisconsinensis Shenefelt,1960,仅分布于美国,由于该种是用诱捕器捕到的,因此,其奇主不详,但有可能为I.pini(Shenefelt,1960)。     

Lumenal hydrolysis of menhaden and rapeseed oils and their fatty acid methyl and ethyl esters in the rat

Simple alkyl (ethyl) esters of polyunsaturated fish oil fatty acids have been proposed as dietary supplements, but their relative efficiency of digestion and absorption have not been determined. Using stomach tubes, we gave rats menhaden or rapeseed oils, or the corresponding methyl and ethyl esters, and determined by chromatographic methods the lipid classes and molecular species recovered from the lumen of the jejunum during the first 1 to 2.5 h of digestion. Hydrolysis of menhaden oil resulted in a preferential retention of a high proportion of the polyunsaturated long chain acids in the sn-2-monoacylglycerols and in the residual triacyglycerols, while digestion of rapeseed oil led to a preferential release of free long chain monounsaturated fatty acids. In contrast, hydrolysis of the alkyl (methyl and ethyl) esters of the fatty acids of either menhaden or rapeseed oil resulted in a composition of free fatty acids which was much more representative of the original esters. It was therefore concluded that the differential lumenal liberation of the long chain and polyunsaturated (three or more double bonds) fatty acids from fish and rapeseed oil is largely due to their characteristic distribution between the primary and secondary positions in the glycerol molecule, and to a much lesser extent to a chain length discrimination by pancreatic lipase. This study also shows that the methyl and ethyl esters are hydrolyzed about 4 times more slowly than the corresponding triacylglycerols, which is sufficient to maintain a saturated micellar solution of fatty acids in the intestinal lumen during absorption.     

Isolation and chromosomal localization of the human En-2 gene

By low stringency hybridization we have isolated from a human cosmid genomic library sequences homologous with a probe from the Drosophila engrailed gene. Partial nucleotide sequence analysis shows a consensus splice acceptor site followed by an open reading frame (ORF) that can encode 104 amino acids; the first 94 amino acids have 71% identity with the Drosophila engrailed protein. The shared region contains a homeo domain and is within the region of engrailed shared with the Drosophila invected gene and the mouse En-1 and En-2 genes. At the amino acid level, the human sequence is 85% identical with the mouse En-1 gene and 100% identical with the mouse En-2 gene. Hybridization against a panel of human-hamster somatic cell hybrids maps this human En-2 gene to chromosome 7, and regional mapping by in situ hybridization to human chromosomes localizes it to region 7q36 at the end of the long arm.