Changes in the ribosome content, principal microsomal protein composition, and secretory character of mammary epithelial rough endoplasmic reticulum during differentiation. Evidence that messenger RNAs specific for milk proteins are incorporated into rough endoplasmic reticulum formed de novo after parturition

The equilibrium density distribution, protein composition, and secretory character of mouse mammary epithelial rough microsomes have been determined during differentiation. The density range exhibited by the rough microsomes broadens during mammary development; rough microsomes within the 1.25-1.29 g/ml density range appear soon after conception and then within the 1.30-1.34 range after the onset of lactation. The appearance of these denser microsomes represents the progressive increase of the average ribosome content of the rough endoplasmic reticulum (ER) during gestation and lactation. Fractionation of rough microsomal proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals that two proteins, having molecular weights of 57,000 and 76,000, occur to a significant extent only during lactation and are then most prominent in the very dense rough microsomes of the 1.30-1.34 range. Nascent polypeptide chains discharged (by incubation with puromycin) from 17-days lactation rough microsomes in either the 1.21-1.29 or 1.30-1.34 density range are distributed equally between the intra- and extravesicular compartments. Whereas 36% of the chains are discharged intravesicularly from 1-day lactation rough microsomes in the 1.30-1.34 range, only 25% are so discharged from those in the 1.21-1.29 range. The results indicate (a) that there is no correlation between the relative levels in lactation rough microsomes of the two microsomal proteins which become prominent during lactation and the extent of secretory activity and (b) that for a short period after parturition the rough ER elements bearing high surface densities of ribosomes have a greater proportion of ribosomes synthesizing milk proteins than the rough ER elements with moderate ribosome densities.

The experimental production of gastric ulcers by induced muscle spasm

A new technique is described for the experimental production of gastric ulcers in dogs. It depends on producing an intermittent but severe localized increase in the contractility of the stomach by means of electrodes implanted in the gastric muscle. A suitable stimulator is attached to the animal's back. Following some early technical, failures an adequate stimulus was applied for 2–3 weeks in 16 animals. In 13 cases macroscopic lesions developed in the stimulated area, varying from frank perforation to superficial erosions. Confirmation by barium meal examinations and histology is provided.

It is suggested that the responsible mechanism may be a localized ischaemia, due to the increased muscle spasm, predisposing to the necrosis and ulceration of the mucosa followed by the more superficial layers of the stomach wall.

Emergency oesophageal transection in uncontrolled variceal haemorrhage

The results of emergency oesophageal transection are described. The overall operative mortality-rate was 45 per cent. There were no operative deaths in the patients with extrahepatic obstruction and normal liver function. The operative mortality-rate for the patients with cirrhosis was 53 per cent, or a salvage rate of 47 per cent if one considers that this is a highly selected group of patients (albeit negatively)–patients with impaired liver function who had not responded to intensive medical treatment and who were still bleeding at the time of surgery.

Potential pathogens in the environment: Klebsiella pneumoniae, a taxonomic and ecological enigma

A nitrogen-deficient medium and m-Endo agar were employed in the isolation of members of the tribe Klebsielleae from surfaces of vegetables and seeds. With m-Endo agar at an incubation temperature of 37 C, nearly 50% of the vegetables and seven out of seven seed samples yielded organisms which biochemically and serologically were identified as Klebsiella pneumoniae, Viable counts were generally in the range of 10(3) cells per g of vegetable peel or seed. Organisms classified as K. pneumoniae exhibited seven different IMViC patterns, with the --++, ++++, and -+++ patterns most common. Seven of the eleven K. pneumoniae serotypes encountered have previously been isolated from human urinary tract and other infections. Fifty percent of the 40 K. pneumoniae examined exhibited positive acetylene-reducing activity, i.e., they possessed the capability for fixing N(2). Vegetables containing K. pneumoniae may constitute a potential reservoir for human nosocomial genitourinary or other infections.

Induction of the ara operon of Escherichia coli B-r

The inducer specificity and kinetics of induction of the ara operon were examined in Escherichia coli B/r. A difference in the kinetics of induction was found between our B/r strains and the K-12 strain previously described by Schleif. The roles of active transport and metabolism of inducer, and of cell density, in induction were studied. d-Fucose and beta-methyl-l-arabinoside were competitive inhibitors of induction. No inducer of the wild-type strain other than l-arabinose was found. However, a procedure for selecting mutants with altered inducer affinity or specificity was developed. The properties of one such mutant (inducible by d-fucose) are described.

A simple infrared spectrum retrieval system

The retrieval of an unknown spectrum from a medium-sized collection (up to 10,000) of infrared curves has been studied and a system based on a film feature card using microfilm storage developed. Tests of alternative methods of coding resulted in the choice of the six most intense absorption peaks in defined areas of the spectrum. Correct identification within 1–2 min is achieved in over 95% of searches. The system is compact, easy to operate, relatively inexpensive and easily perused.