Homologous interference of lymphocytic choriomeningitis virus: detection and measurement of interference focus-forming units

Lymphocytic choriomeninigitis (LCM) virus defective interfering (DI) particles form foci of protected cells in a monolayer under an agarose-containing overlay medium. Foci originate from one cell dually infected with at least 1 interference focus-forming unit and infectious virus. As a result, an interfering factor is produced and released which interacts with neighboring cells, thereby protecting them against cytopathic lysis by challenge virus. The property of individual LCM virus DI particles to induce countable foci has been made the basis of quantitative assay that is comparable in every respect to the plaque assay of infectious virus and is much more sensitive and probably more accurate than other procedures used to measure LCM virus DI particles. LCM virus was passaged, undiluted, 10 times in cell cultures. When yields were analyzed as to concentrations of PFU and interference focus-forming units, both entities were found to fluctuate with the pattern expected from theoretical considerations.

Histochemical observations of the folate metabolism in the human principal gastric glands

By means of two original histochemical methods, the folate metabolism was investigated in the gastric glands proper. The presence of a high concentration of folic acid and dihydrofolate reductase in the parietal cells suggests a straight metabolic interrelation between the intrinsic factor, vitamin B12 and folate in these gland cells.

[Results of intermittent treatment with antitubercular agents in cavernous pulmonary tuberculosis in adults]

The effectiveness of the intermittent treatment (2/7) with Rifampicin + Etambutol, administered over periods of 3 to 24 months, was tested in a log of 229 out-patients suffering from tuberculosis (bacilli carriers). Negativation of the cultures was obtained in 88.4% of the cases, most of the failures being recorded in the aged patients from rural areas, suffering from various other associated diseases and in those who did not cooperate. As these patients raise particular problems concerning the therapeutical attitude, the authors consider they should be admitted to hospital, at least during the critical periods of the disease.

Comparative study of the gamma-radiation-induced changes in the tissular levels of acyclic and cyclic adenosine phosphates

Periodical measurement of total adenosine phosphates and cAMP in liver, intestinal mucosa and brain carried out in rats after irradiation with either 500 rads or 750 rads generally revealed high intratissular levels of these compounds, suggesting both a stimulated cellular synthesis and an abnormal redistribution in different tissues. The most interesting findings were those regarding the brain considering their close relationships with the clinical evolution of the animals and other previously described biochemical observations.

[Treatment of duodenal ulcer with chemical sclerosis of the gastric mucosa. Preliminary results]

On the basis of experimental studies and of the results obtained, the authors have applied over the last two years, sclerosis of the gastric mucosa with fresh, sterile solution of hypertonic (66%) glucose in 25 patients with duodenal ulcers and cellular and vagal hyperacidity resistant to medical therapy. Mucosclerosis was associated with gastric drainage in 14 patients with duodenal ulcer complicated by stenosis or hemmorhage. Sclerosis of the gastric mucosa is a physiological intervention because it achieves the sclero-atrophy of the acid-secreting glands and vago-sympatic denervation in the gastric territory, while the storage function of the stomach is maintained. It was not followed by extra-gastric disturbances or antro-pyloric distonia. It is easy to perform from the technical viewpoint and has a high degree of fiability, providing constantly satisfactory clinical, functional and metabolic results. Chemical values of basal secretion have decreased in a constant manner but in 9 patients the values of induced acidity showed inconstant decreases. Gastro-antro-pyloro-duodenal transit was good and all operated patients have gained weight. No diarrhea, dumping or peptic recidives were noted.

Diversity of lymphocytic choriomeningitis virus: variation due to replication of the virus in the mouse

Depending on passage history, strain WE infectious LCM virus either damages L cells more or less severely or leaves them morphologically intact. Correspondingly, the plaques which are formed on L cell monolayers are of different appearance, ranging from intensely turbid to clear. Multiplication of LCM virus in certain mouse organs profoundly affects plaque characteristics. The brain, for instance, favours lytic variants while the spleen supports the replication of virus which forms turbid plaques. This statement holds if virus taken from organs of persistently infected mice or virus passaged from mouse to mouse is analysed and is true also if the initial preparation contains virus forming predominantly either clear or turbid plaques on L cell monolayers. Selection is not rapid and not absolute. It may take months of multiplication before a final state is reached, and even then the number of characteristic plaques is usually in great excess of the rest but never reaches 100%. Cloning procedures may alter the proportions, but with our experimental conditions no plaque has ever been isolated which would retain its characteristics upon passage. Differences of plaque type morphology were not reflected in differences of pathogenic properties, and both clear and turbid variants caused persistent infection if used to infect newborn mice and led to disease with signs of neurological involvement and death if inoculated intracerebrally into adult animals.

Use of iodinated organic compounds for the density gradient centrifugation of viruses

Use of Urografin and Conray for the equilibrium centrifugation of viruses is described. These pharmaceuticals, which consist of iodinated arylic compounds, reach densities of 1.6 g/cm3 and have low intrinsic viscosities. Poliovirus, Newcastle disease virus, and lymphocytic choriomeningitis virus were centrifuged to equilibrium in gradients made of these substances. Viral infectivities were not measurably affected, which is especially noteworthy in the case of the very labile lymphocytic choriomeningitis virus. Buoyant densities were found to be significantly lower than densities obtained with gradients made of CsCl and sucrose.

The in situ localization of folic acid

A histochemical azo-coupling method for localizing folic acid in situ is described. Cat and rat liver, kidney, bone marrow and brain were found to be rich in folic acid; stomach, intestine, salivary glands, and blood contained less. Folic acid was localized in the cytoplasm of tissues having a very active metabolism, but in the nucleus of highly specialized cells such as neurons.

LCM virus infection of cells in vitro

Most mammalian cells cultivated in vitro can be infected with lymphocytic choriomeningitis (LCM) virus. In addition to infectious virus, the cells produce antigenic material that fixes complement in the presence of antibody and is precipitated by antiserum. Intracellular antigen can also be demonstrated by the immunofluorescence procedure. When infected cells are viewed with the electron microscope, viral structures are seen either budding from or in association with the cell membranes. Immunoelectron microscopy, immunofluorescence, and cytotoxicity tests reveal virus-specific antigens on the surface of intact cells. Virus multiplication may be succeeded by cytolysis. Two LCM virus-specific antigens (or antigenic groups) can at present be distinguished. One corresponds to the infectious virus; the other is the complement-fixing "soluble" antigen. This extractable complement-fixing activity is produced by infected cells and is also a structural component of the infectious virus. It is not represented on the surface of either the virion or the infected cell. The cytolytic potential of LCM virus varies and is dependent on its previous passage history. Cytolytic and "attenuated" variants are able to initiate persistent infection of Mus musculus.Together with infectious virus, particles are produced that temporarily protect cells against standard virus. They appear to be by-products of virus multiplication, not in the sense of deletion mutants but of virus structures insufficiently equipped for their own active or passive replication, though capable of interfering with infectious virus. No evidence has been found for the generation of "defective interfering" particles, though their presence has not yet been excluded.