Cytogenetic analysis of 15 retinoblastomas developed in children having no constitutional chromosome 13 deletion has been carried out. In tumor cells, no deletion or loss of chromosome 13 was revealed. The specific marker chromosome i(6p) described in our previous publications has been found in 9 tumors. Besides, in two cases, trisomy of short arm of chromosome 6 was present. Other non-random changes (trisomy 1q, monosomy 16 and loss of one of the sex chromosomes) were not specific for retinoblastomas, because they were described in literature for some other tumors as well. The possible significance for genesis of retinoblastomas of dose multiplication of the genes located in the 6p is discussed.

The paper is concerned with the analysis of expression of myc, myb, fos, ras and sis oncogenes in 11 gastric tumors of different histological patterns, 5 histologically-unaltered areas adjacent to tumor and in stomach tumor metastases into lymph nodes. A high frequency of myc, ras and fos oncogene expression was registered in all the types of tissue examined without any apparent signs of tissue specificity. The study failed to detect sis oncogene transcripts. The myb oncogene, generally dormant in solid tumors, was expressed in 2 gastric tumor metastases.

Genomic DNA of intact colonic mucosa obtained from a female patient suffering colonic cancer revealed amplified nucleotide sequences (multiple copies) related to viral myc oncogene. The study failed to detect amplification in tumor. Causation and pathways of the event are discussed.

Preparations of DNA isolated from malignant melanoma (Ja heterotransplant), neuroblastoma (L-AN-1 cell line) and breast cancer (SK-BR-3 cell line) induced a high incidence of transformation of recipient NIH 3T3 cells in two consecutive cycles of transfection. Transformed NIH 3T3 cells appeared to be highly tumorigenic in newborn BALB/c mice. The analysis of DNA samples isolated from primary and secondary NIH 3T3 transformants identified Alu-repetitive DNA sequences of human genome as well as additional sequences homologous to ras-family oncogene. Transforming c-Ha-ras I gene was identified for the first time in NIH 3T3 cells transformed by preparations of DNA isolated from human malignant melanoma, neuroblastoma and breast cancer.

Recent data on the genome structure of transforming retroviruses and their cellular counterparts has been reviewed. Retroviruses are divided in several groups according to their oncogenic potential. Comparison of oncogenes and their protein products for most abundant transforming viruses are presented. Probable mechanisms of capture of cellular proto-oncogenes by retroviruses and the hypothesis of existence of endogenous transforming viruses are discussed. General features of cellular proto-oncogenes and possible ways of their activation resulting in neoplastic transformation are discussed. Some unresolved problems of retroviral carcinogenesis, in particular, the problem of existence of unidentified "X"-genes in retroviral genomes and involvement of constitutional viral genes in carcinogenesis are mentioned.

Multistage carcinogenesis is the process of development of neoplastic changes, including the successive stages of initiation and promotion which occur in a strict order. This process is subject to the application of a similarly strict sequence of exo-and/or endogenous carcinogenic factors, either of which alone is incapable of tumor induction. Initiation includes the phases of metabolic activation, interaction of reactive metabolites with DNA and fixation of induced lesion. It is the stage of development of such primary mutation lesions of genotype of target-cells as the irreversible transition of these cells to an "initiated" status (predisposition to transformation). Promotion is the stage of quantitative and quantitative-qualitative changes including secondary epigenomic reversible lesions of the phenotype (gene expression) of initiated cells. This process culminates in irreversible transformation of cells.

The authors describe 4 families whose members showed myeloproliferative diseases. In one of the families, polycythemia vera (PV) was seen in twin brother and sister, in the other one, chronic myeloleukemia (CML) afflicted both daughter and mother, and in the two remaining families PV and CML afflicted two brothers and mother and daughter, respectively. It was established that neutrophil phosphatase activity was lowered not only in the afflicted brother but also in healthy members of the third family. Based on the reported and their own data the authors arrive at the conclusion that familial myeloproliferative diseases occur in rare cases. In all the cases of familial myeloproliferative diseases, the transmission of the illness by heredity was discovered to be impossible. It was also ascertained that transmitted by heredity are only those cell deficiencies of the tissues that later on will be afflicted by leukemia or will develop immunodeficiency manifested by increased mutation of the myelopoietic cells (DNA repair deficiencies) or by inability to eliminate the leukemic cells.

Data from literature and author's own experiments concerning conditions of the endogenous MuMTV genome expression and its influence on the organism are reviewed. Some findings on the expression in women of antigens related to the MuMTV antigens and antibodies to them are analyzed.

Morphometric studies using the Integral instrumentation complex and the ICP--II pulsed cytophotometer assays of DNA in lung tumor cells of various histological patterns were conducted to obviate difficulties involved in establishing differential cytologic diagnosis of small cell undifferentiated lung cancer. It was shown that morphometric and pulsed cytophotometric measurements may offer considerable advantage when used in conjunction with other procedures of differential diagnosis with a view to improving diagnosis of various forms of lung tumors and small cell undifferentiated lung cancer, in particular.

The principal problems in molecular and genetic immunology to be resolved are the structure of Ig-genes and the regulation of their expression. The isolation of mRNA for light and heavy Ig-chains would be a first step along this line. A combination of two approaches may be the best strategy in mRNA preparation. Affinity purification allows one to obtain pure mRNA in a one-step procedure whereas immunoprecipitation makes it possible to prepare mRNAs for both heavy and light immunoglobulin chains in considerable amounts. In the series of experiments, conditions for synthesis of long and short cDNA chains were elaborated and the clone containing the fragment of kappa-chain gene was isolated and characterized. This clone was used as a probe for hybridization with genomic DNA from myeloma and hybridoma cells. It was shown that both allelic genes on homologous chromosomes were rearranged in myeloma MOPC21 cells. The original cell line of hybridoma PTF02 contains the embryonic gene as well as the differentiated genes. However, only differentiated genes can be detected in a similar experiment conducted with the same hybridoma after passage on mice. In conclusion, the coordination of homologous and heterologous chromosome expression in B cells in discussed in terms of the feed-back control.