Parallel end-butt coupling for optical integrated circuits

The method of parallel end-butt coupling has been used to couple GaAs laser diodes to Ta (2)O(5) thin film waveguides. Theoretical caluclations predict that a coupling efficiency into the lowest order waveguide mode of 90% is achievable if the thicknesses of the waveguide (t(g)) and the laser light emitting layer (t(L)) are equal. Experimentally, efficiencies as high as 45.1% have been measured for laser and waveguide combinations with t(g)/t(L) = 0.34. The tolerance to misalignment of the laser and waveguide has been theoretically and experimentally evaluated.

Vibrio cholerae infection and immunity in mice

Lyophilized cultures of V. cholerae 569B slowly lose their virulence for neonatal and adult mice during long term storage. Following a single passage in orally infected 6-day old mice, a highly virulent strain (designated 569B/MP) was isolated. This organism causes rapidly fatal intestinal infections in 6-day old mice; large numbers can be isolated in pure culture from the intestinal fluid. Freezing and storage at -60 degrees of dead animal provides a simple means of maintaining the high virulence of the culture over a period of at least 9 months. This strain produces choleracic symptoms and death in approx. 50% of adult mice following oral infection. Large numbers of viable organisms may also be isolated from the small intestine over a period of at least 40 h. These criteria have been used as a basis for assessing protection against cholera infection induced by immunization with living or heat-killed V. cholerae given orally or intraperitoneally.

Rupture of major vessels after radiation

Rupture of irradiated large vessels is an uncommon complication which tends to occur in carotid, aorta, and femoral arteries, in decreasing order of incidence. It particularly affects men subjected to surgery and radiotherapy for epidermoid carcinomas in oropharynx, esophagus, or genitalia. Contrary to some opinion, radiation is not the most significant cause; this "spontaneous" arterial rupture can occur without radiation. The perforation is not associated with tumor invasion of arterial wall, as has been claimed. Surgical complications, especially necrosis of skin flaps, infection, and fistulas are most important etiologically. Only 2 of the 11 instances that we describe appear to have been caused mainly by radiation. The perforation is usually fatal, but several patients, including 3 of our series (2 carotid, 1 femoral), have been saved by hospital personnel aware of this complication. To prevent it, prolonged exposure or infection of arteries, whether irradiated or not, should be avoided.

Use of cornmeal bolus as an aid in obtaining cranial four-vessel angiograms

In cranial angiography it has always been difficult to visualize extracranial vessels of the cervico-thoracic region, upon one radiograph, by using the same exposure factors for both regions. For this reason, we experimented and found that by applying a dry cornmeal bolus on specific areas of the neck a technically superior radiograph of these regions can be achieved. This bolus simulated added soft tissue to the cervical region. The density of the cervical region is now similar to that of the upper thoracic. As a result, factors set for one exposure will adequately penetrate both areas.

Antigenic cross-reaction between mouse intestine and a member of the autochthonous microflora

Antigenic cross-reaction has been demonstrated between homogenates of intestine taken from fetal mice and suspensions of a Bacteriodes species isolated from the large intestines of normal adult mice. This observation provides an explanation for the lack of immunological response observed in mice after antigenic stimulation with this member of the normal autochthonous intestinal flora of these animals.

Localization of bacteria in the gastrointestinal tract: a possible explanation of intestinal spirochaetosis

The large intestine of rats and dogs was examined by light and electron microscopy. In both species localization of bacteria in specific areas of the tissue was observed. Fusiform bacteria mixed with spirochaetes were seen at the opening of the crypts into the large bowel. However, at the base of the crypts homogeneous populations of spiral organisms were found; some crypts contained Borrelia-type spirochaetes, whereas others contained spiral bacteria with other morphology. Very few spiral bacteria, including those of the spirillum type, were seen in the lumen of the large intestine. Experiments in rats showed that mucosa-associated spiral organisms appeared in large numbers in the stools when diarrhea was induced with magnesium sulfate. These observations were taken as a basis for explaining intestinal spirochaetosis of dogs and other animals, a syndrome which has been frequently described and which, until now, has been considered to reflect pathogenicity of these organisms.

Immunological response of mice to members of the autochthonous intestinal microflora

Based on agglutination, complement fixation, bactericidal, and opsonization tests, it is evident that suspensions of a Bacteroides sp. isolated from the mouse intestine and given by parenteral routes do not initiate antibody formation in mice. Rats also respond poorly to the antigenic stimulus. In contrast, suspensions of other bacterial species isolated from the rodent intestine are highly immunogenic. Furthermore, high titers of antibody are produced in rabbits, guinea pigs, and sheep after parenteral injection of the Bacteroides suspensions. Marked differences in the absolute and relative numbers of Bacteroides in the intestinal contents of rodents and the latter three animal species have been demonstrated. It is proposed that the immunological unresponsiveness of rodents to this organism is related to its existence as a member of the autochthonous microflora in these animals.

Changes in the mouse intestinal microflora during weaning: role of volatile fatty acids

The influence of volatile fatty acids on the ecology of the bacterial flora of the mouse intestinal tract has been studied in three situations where large fluctuations in the composition of the microflora have been observed. Young mice were shown to ingest solid food particles when 11 days old; this correlated with the appearance of strictly anaerobic fusiform bacilli in the intestinal lumen and a 10,000-fold decrease in numbers of coliform bacilli. Over the same period, volatile fatty acids were shown by gas-liquid chromatography to appear in the intestinal content. It is suggested that the fusiform bacilli are responsible for the presence of the volatile acids (especially butyric acid) which exert an inhibitory effect on the coliform bacteria, resulting in the decline in numbers. When germ-free mice are placed in a specific pathogen-free mouse colony, changes in the intestinal flora occurred which were similar to those observed in the young mice approaching weaning. Once again, the decline in the coliform population correlated with the appearance of significant levels of butyric acid in the large intestine. In a further series of experiments, mice were fed penicillin and levels of the intestinal fatty acids were measured. The antibiotic eliminated the anaerobic fusiforms from the intestine, resulting in the disappearance of significant levels of butyric acid and a million-fold increase in the numbers of coliform bacilli.

The mouse intestinal microflora with emphasis on the strict anaerobes

The various components of the intestinal microflora in the mouse become established according to a definite time sequence; the strict anaerobes are the last groups of bacteria to reach their maximum population levels, 14-16 days after birth. The multiplication of these strict anaerobes in the mouse intestine seems to depend upon the prior multiplication of other bacterial species, and coincides with the ingestion of food other than maternal milk. These two conditioning factors may correspond to the establishment of a suitably reduced Eh potential and to the provision of certain metabolites. Once established, the strict anaerobes constitute by far the largest percentage of the total intestinal microflora; most of them are associated in a viable form with the mucosa. In normal animals they persist at very high levels throughout the life span. However, their populations can be drastically reduced by dietary manipulation of the animal, by administration of vancomycin, or by certain disease processes of the intestine. The strict anaerobic bacteria seem to play an important, and perhaps essential role in the maintenance of the anatomic structures and physiological functions of the intestine. They also seem to hold in check several species of intestinal bacteria, in particular the coliform bacilli.