[Respiratory diseases in sheep due to Mycoplasma ovipneumoniae]

Mycoplasma ovipneumoniae was isolated from sheep and lambs affected with a respiratory disease. It was established that the pneumonic disease caused by this organism was a severe one, with high mortality rate in young lambs. Adult sheep and older lambs remained chronically affected. Susceptibility varied, depending on the breed of the animals, some imported animals running a more severe course of the disease than the local ones. The disease was artificially induced in lambs at the joint infection with M. ovipneumoniae and P. haemolytica. The morphologic changes in the lungs consisted in a prevailing proliferation of the septal cells and polynuclear cells in the alveoli, an interseptal histiocyte proliferation, and a serous leukocyte infiltration.

Spin-labelling of DNA with hydrazine mustard spin label (HMSL)

1. The hydrazine mustard spin label (HMSL), recently synthesized in our laboratory (Raikova, 1977) was used for spin-labelling of DNA. 2. It alkylates both double- and single-stranded DNAs. 3. The reaction of HMSL with DNA was studied with respect to the kinetics of alkylation, dependence on salt concentration and base specificity. 4. It was found that HMSL is a base-specific reagent, alkylating preferentially guanine. According to their ability to bind HMSL, the four deoxyribonucleotides are ordered in the following way: G greater than A greater than C greater than T. 5. The EPR spectra obtained strongly depended on the secondary structure of the spin-labelled DNA: unlike the immobilized spectra of the double-stranded DNAs (2AZZ = 44.8G), the EPR spectra of single-stranded DNAs were non-immobilized (2AZZ = 32.8 G). 6. When sheared double-stranded DNA was spin-labelled, the parameters of the EPR spectrum depended also on the GC content of DNA.

[Biorhythm changes in DNA synthesis in hepatocytes exposed to organophosphates and strontium-89]

The authors irradiated albino rats with I microc/gr strontium89 with previously modelled liver injury by FOS (Agria 1050). A temporary inhibition of the methodical activity was established as well as aberrant mitoses and strongly manifested polyploidity of the hepatic cells. Those phenomena faded quickly (within 8 days), with the exception of polyploidity, which as a sign of physiological regeneration the authors admit to be adaptive reaction directed to the restoration of the functional level of the liver on account of the hepatocytes preserved. Prior to the onset of tissue regeneration, the cellular one should be terminated, due to which, the mytotic activity was highly inhibited on the 3rd day of the irradiation, the DNA-synthesis cycle being lengthened and mainly on account of tgi, i.e. during the reparative biosynthesis the cell is incapable/of developing in the mitotic phase. After the presynthetic period is over the hepatocytes rapidly overcome the inhibition, tgi is considerably shortened and from presynthesis they almost immediately enter the period of mitosis. That requires an additional protein synthesis, manifested by the changes in serum protein. S and G1 proved to be most sensitive to DNA-synthesis blocking. The presynthetic period is essentially lengthened due to lesions of the cellular structures, synthesizing substances, necessary for entering S - i.e. the hepatocytes pass T, equal to the inhibition between G1 and S, its duration being proportional to the degree of the lesion of the organ.

[Allergic skin reaction in infectious rhinotracheitis and infectious pustular vulvovaginitis in cattle]

Through a skin-allergic reaction were subjected to a study cattle of different ages (calves-sucklings, growing calves and grown up calves), originating from 4 different from the epizootic point of view cow-farms--one latent focus, two foci with an apparent infection and one cow-farm in good health conditions. On the healthy cow-farm the skin-allergic reaction and the virus neutralizing reaction were not marked. On the farms affected with latent infection and with manifestation of abortions with cows, the skin-allergic reaction with calves till the age of 3 months was negative, whereas the virus neutralizing reaction was usually positive; with the calves at the age of about 6 months the skin-allergic reaction began slightly to become positive. The virus neutralizing reaction was also positive. With the grown up animals both reactions were positive. In the development of recently brought clinical infection among the calves, without affecting their mothers, both reactions were negative with newly born calves, whereas from the second month onward, they began to become positive.

"Maturation" of DNA duplexes

Reassociation of typical single-copy DNAs, like E. coli DNA, even when performed at relatively low temperatures, results in the formation of perfect duplexes with thermal stability very close to that of the native DNA. In contrast, duplexes of mouse repeated DNA as well as duplexes of Streptomyces DNA prepared under the same conditions, show a low thermal stability and undergo post-reassociation changes upon prolonged incubation. These changes, called "maturation" of the DNA duplexes, result in increasing of their thermal stability. Some of the factors affecting the rate of "maturation" are studied. The implication of the "maturation" process in reassociation analysis and in characterization of the heterogeneity of DNA is discussed.

Characterization of a new strain of leptospira isolated from surface water in India

A new strain of Leptospira, isolated from surface water in India, is studied and classified. It shows, in the biological tests, a behaviour like that of saprophytic leptospirae; further serovar it represents a new serovar which we named poona.