The cytochemical properties of a guanine-specific synthetic fluorescent analogue of actinomycin D, 7-amino-actinomycin D, have been studied in fixed and living preparations of L cells and polytene chromosomes of salivary glands of Chironomus thummi thummi and Drosophila lummei (Hackman). 7-Amino-actinomycin D has been shown to bind to DNA-containing structures, thereby inducing in them a bright red fluorescence. No specific fluorescence has been found in RNA-containing structures treated with this fluorescent probe. The fluorescence pattern of some regions of polytene chromosomes with a known nucleotide composition was analysed. It has been established that 7-amino-actinomycin D induces a very weak fluorescence in GC-poor chromosome regions of the Drosophila lummei toromere structure. Data indicating a nonlinear dependence between the fluorescence intensity of a stained chromosome region and the GC content in its DNA have been obtained. The influence of DNA nucleotide composition in a chromosome region on the fluorescence of 7-amino-actinomycin D is discussed. In combination with quinacrine staining and the Feulgen fluorescence reaction, treatment with 7-amino-actinomycin D provides useful information about the distribution of GC base pairs in the chromosome region under study.

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The results of the influence of the conditions of keeping Ukrainian red dairy cows on the manifestation of clinical symptoms of damage to the lateral surface of the tibia and the level of reproduction are presented. The study was conducted on the basis of an industrial dairy complex (600 dairy cows with an average productivity of 6050 kg of milk per lactation) as part of agricultural associations in Odessa region. The objects of the study were cows during lactation, which were kept loose in sections with rest boxes (where the floor was a special rubber mat with a thickness of 30 mm). Evaluation (in points) was performed on the clinical manifestation of symptoms of damage to the skin epithelium of the lateral surface of the leg, which was injured by the rubber coating of the stall compared to the level of reproduction (service period, days/%) and the severity of skin pigmentation of the body surface (selection melanism). Clinical, zootechnical, biometric methods were comprehensively applied to realize the purpose of research. Comparison of data (n = 462) visual-clinical assessment of the condition of the skin of the lateral surface of the leg, as an indicator of the adaptability of lactating cows to keep in sections with rubber flooring and the area of pigmented hair of animals of different phenotypes by coat color, showed that cows typical pigmentation, characteristic of red dairy breed (red hair occupied more than 80 % of the body surface), wound lesions of the lower leg are much less common, namely: in comparison with red-spotted animals by 28.41–15.98 %, with mostly white – by 39.03–20.23 %, respectively. Due to the negative impact of open wounds of the skin of the leg on the immunity of lactating cows, it was found that increasing the number of animals with damaged epithelium as a gateway to infection, provokes an increase in the service period in cows with predominantly white or mottled color to 140.97 and 141.07 days, which is higher by 6.74 and 6.84 days, respectively, compared with red animals (P < 0.05).

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SUMMARY -The toromere previously found by other workers in the distal end of the sixth chromosome (microchromosome) of D. limmei was studied using differential staining of Drosophila lummei giant chromosomes. The toromere which was first described as a quinacrine-bright structure appears as a C-positive body. Quantitative cytofluorometric analysis showed highly significant increase in toromeric DNA under low temperature conditions. In situ hybridization of 1 25I nick-translated D. virilis sDNA (all three satellites were included in the sample) with polytene chromosomes of D. lummei larvae cultured at 12° C revealed no label incorporation into toromere region. However in situ hybridization of 3H-RNA complementary to highly repetitious DNA of D. lummei and D. virilis (C 0 t = 10-q0-2 ) with polytene chromosomes of the larvae cultured at 12° C coupled with banding studies enable us to conclude that the toromere probably contains an AT-rich repeated DNA. A well-developed toromere in the sixth chromosome of D. lummei was also demonstrated at normal temperature (25° C) in interspecific hybrids. The role of the toromere structure in the mitotic behavior of microchromosomes and their replication pattern is discussed.