Basal Tumor Cell Isolation and Patient-Derived Xenograft Engraftment Identify High-Risk Clinical Bladder Cancers

Strategies to identify tumors at highest risk for treatment failure are currently under investigation for patients with bladder cancer. We demonstrate that flow cytometric detection of poorly differentiated basal tumor cells (BTCs), as defined by the co-expression of CD90, CD44 and CD49f, directly from patients with early stage tumors (T1-T2 and N0) and patient-derived xenograft (PDX) engraftment in locally advanced tumors (T3-T4 or N+) predict poor prognosis in patients with bladder cancer. Comparative transcriptomic analysis of bladder tumor cells isolated from PDXs indicates unique patterns of gene expression during bladder tumor cell differentiation. We found cell division cycle 25C (CDC25C) overexpression in poorly differentiated BTCs and determined that CDC25C expression predicts adverse survival independent of standard clinical and pathologic features in bladder cancer patients. Taken together, our findings support the utility of BTCs and bladder cancer PDX models in the discovery of novel molecular targets and predictive biomarkers for personalizing oncology care for patients.

Oncogenic CXCL10 signalling drives metastasis development and poor clinical outcome

Background:

The CXCL10/CXCR3 signalling mediates paracrine interactions between tumour and stromal cells that govern leukocyte trafficking and angiogenesis. Emerging data implicate noncanonical CXCL10/CXCR3 signalling in tumourigenesis and metastasis. However, little is known regarding the role for autocrine CXCL10/CXCR3 signalling in regulating the metastatic potential of individual tumour clones.

Methods:

We performed transcriptomic and cytokine profiling to characterise the functions of CXCL10 and CXCR3 in tumour cells with different metastatic abilities. We modulated the expression of the CXCL10/CXCR3 pathway using shRNA-mediated silencing in both in vitro and in vivo models of B16F1 melanoma. In addition, we examined the expression of CXCL10 and CXCR3 and their associations with clinical outcomes in clinical data sets derived from over 670 patients with melanoma and colon and renal cell carcinomas.

Results:

We identified a critical role for autocrine CXCL10/CXCR3 signalling in promoting tumour cell growth, motility and metastasis. Analysis of publicly available clinical data sets demonstrated that coexpression of CXCL10 and CXCR3 predicted an increased metastatic potential and was associated with early metastatic disease progression and poor overall survival.

Conclusion:

These findings support the potential for CXCL10/CXCR3 coexpression as a predictor of metastatic recurrence and point towards a role for targeting of this oncogenic axis in the treatment of metastatic disease.

Dose-dependent and independent temporal patterns of gene responses to ionizing radiation in normal and tumor cells and tumor xenografts

U87 cells derived from human malignant gliomas and growtharrested human embryonic lung (HEL) fibroblasts were examined with respect to their response to ionizing radiation by profiling their RNAs. In the first series of experiments, cells grown in vitro were harvested and the RNAs were extracted 5 h after exposure to 1, 3, or 10 Gy. In the second series of experiments the U87 tumors were implanted in nude mice and subjected to the same doses of irradiation. The xenografts were harvested at 1, 5, or 24 h after irradiation and subjected to the same analyses. We observed and report on (i) cell-type common and cell-type specific responses, (ii) genes induced at low levels of irradiation but not at higher doses, (iii) temporal patterns of gene response in U87 xenografts that varied depending on radiation dose and temporal patterns of response that were similar at all doses tested, (iv) significantly higher up-regulation of cells in xenografts than in in vitro cultures, and (v) genes highly up-regulated by radiation. The responding genes could be grouped into nine functional clusters. The representation of the nine clusters was to some extent dependent on dose and time after irradiation. The results suggest that clinical outcome of ionizing radiation treatment may benefit significantly by taking into account both cell-type and radiation-dose specificity of cellular responses.

Angiostatin effects on endothelial cells mediated by ceramide and RhoA

Angiostatin is a cleavage product of plasminogen that has anti-angiogenic properties. We investigated whether the effects of angiostatin on endothelial cells are mediated by ceramide, a lipid implicated in endothelial cell signaling. Our results demonstrate that angiostatin produces a transient increase in ceramide that correlates with actin stress fiber reorganization, detachment and death. DNA array expression analysis performed on ceramide-treated human endothelial cells demonstrated induction of certain genes involved in cytoskeleton organization. Specifically, we report that treatment with angiostatin or ceramide results in the activation of RhoA, an important effector of cytoskeletal structure. We also show that treatment of endothelial cells with the antioxidant N-acetylcysteine abrogates morphological changes and cytotoxic effects of treatment with angiostatin or ceramide. These findings support a model in which angiostatin induces a transient rise in ceramide, RhoA activation and free radical production.

Quantitative analysis of DNA array autoradiographs

DNA arrays and chips are powerful new tools for gene expression profiling. Current arrays contain hundreds or thousands of probes and large scale sequencing and screening projects will likely lead to the creation of global genomic arrays. DNA arrays and chips will be key in understanding how genes respond to specific changes of environment and will also greatly assist in drug discovery and molecular diagnostics. To facilitate widespread realization of the quantitative potential of this approach, we have designed procedures and software which facilitate analysis of autoradiography films with accuracy comparable to phosphorimaging devices. Algorithms designed for analysis of DNA array autoradiographs incorporate 3-D peak fitting of features on films and estimation of local backgrounds. This software has a flexible grid geometry and can be applied to different types of DNA arrays, including custom arrays.

LINE L1 retrotransposable element is targeted during the initial stages of apoptotic DNA fragmentation

Using a directional cloning strategy, DNA sequence information was obtained corresponding to the site of early radiation-induced apoptotic DNA fragmentation within the human lymphoblastoid cell line TK6. Data were obtained from 88 distinct clones comprising approximately 65 kbp of sequenced material. Analysis of all cloned material showed that sequences in the 10 bp immediately adjacent to the cleavage sites were enriched in short oligoT tracts. The proportion of repetitive DNA within the entire cloned material was found to be within the normal range. However the distribution of Alu and LINE repetitive DNA were biased to positions at or adjacent to the apoptotic cleavage site. In particular, a non-random distribution of five cleavage sites was found clustered within the second ORF of the LINE L1 that partially overlapped with two binding sites for the nuclear matrix-associated protein SATB1. Three other clones, containing alpha satellite elements, were also linked to a DNA matrix binding function. These data indicate that the site of chromatin loop formation at the nuclear matrix may be a specific target for early DNA fragmentation events during apoptosis.

Accumulation of specific RNAs encoding transcriptional factors and stress response proteins against a background of severe depletion of cellular RNAs in cells infected with herpes simplex virus 1

Herpes simplex virus 1 encodes several functions to preclude the shutoff of host response to infection, including degradation of mRNA immediately after infection. To determine whether any cellular mRNAs accumulate in infected cells against a background of severe loss of host RNA, we hybridized cDNAs derived from three different cell lines infected with wild type and a mutant virus to a DNA array containing probes for 588 human genes representing different functional groups. The results were that (i) infected cells accumulated at levels above those of mock-infected cells, a small number of transcripts representing transcriptional factors that could regulate gene expression both positively and negatively, and one stress response protein (GADD45), (ii) the amount and nature of the accumulated transcripts showed limited variability depending on the cell and virus, and (iii) at least some of the proteins encoded by the accumulated transcripts could benefit either the virus or the host.

Abortive apoptosis as an initiator of chromosomal translocations

Apoptosis is a well-recognized regulator of a cell populations size and structure. Irreversible stages of apoptosis lead to activation of different enzymatic cascades, changes in cell morphology and DNA fragmentation. However, little is known about nuclear events which accompany the initial stages of apoptosis. These events are connected with introduction of limited amounts of double strand breaks into genomic DNA, some of which may be subsequently rejoined. We hypothesize here that the initial stages of apoptotic DNA fragmentation may be reversible and connected with the initiation of recombinational events and certain chromosomal translocations. The factors influencing apoptosis reversibility and cell survival after delivery of apoptotic stimuli may provide new insights into mechanisms of lymphocyte development and tumorigenesis.

Mycoplasma infection can sensitize host cells to apoptosis through contribution of apoptotic-like endonuclease(s)

Mycoplasma infection may lead to various pathologies in a broad range of hosts. It has been shown that Mycoplasma may trigger cell death in cell cultures; however, the mechanism remains unknown. In the present paper we show that Mycoplasma infection of different lymphocyte and epithelial tumour cell lines leads to the inhibition of proliferation, and increased cell death, accompanied by DNA fragmentation and the morphological features of apoptosis. We also showed that this infection leads to an increased sensitivity of cells to various inducers of apoptosis targeting different signalling pathways. Finally, we show that increased apoptosis is associated with overexpression of an endonuclease produced by Mycoplasma. This endonuclease is recovered in the nuclear fraction of host cells, introduces mostly DSB and is active at neutral pH in the presence of divalent cations. Activation of this endonuclease is connected with limited proteolysis, which may be reproduced in vitro by snake venom serine proteinase.

Association between DNA cleavage during apoptosis and regions of chromatin replication

We have addressed the association between the site of DNA cleavage during apoptosis and DNA replication. DNA double strand breaks were introduced into chromatin containing pulse labeled nascent DNA by the induction of apoptosis or autocleavage of isolated nuclei. The location of these breaks in relation to nascent DNA were revealed by Bal31 exonuclease digestion at the cut sites. Our data show that Bal31 accessible cut sites are directly linked to regions enriched in nascent DNA. We suggest that these regions coincide with the termini of replication domains, possibly linked by strong DNA-matrix interactions with biophysically defined topological structures of 0.5-1.3 Mbp in size. The 50 kbp fragments that are commonly observed as products of apoptosis are also enriched in nascent DNA within internal regions but not at their termini. It is proposed that these fragments contain a subset of replicon DNA that is excised during apoptosis through recognition of their weak attachment to the nuclear matrix within the replication domain.

Mechanisms of induction of apoptotic DNA fragmentation

PURPOSE

Despite its common use as an indicator of apoptosis, little is known about the mechanisms controlling apoptotic DNA fragmentation in irradiated cells. This review discusses the pathways of chromatin fragmentation, and the role of both nucleases and chromatin structure in this process.

DEFINITIONS

DNA fragmentation linked to apoptosis is a combination of cleavage events excising both large DNA fragments within the range 0.4-1.0 Mbp and 50 kbp followed by random cuts within internucleosomal regions (i.e. DNA laddering). The first two cleavage steps can be detected in virtually all apoptotic cells, but DNA laddering is not ubiquitously observed. Endonucleases that mediate this cleavage of chromatin may be classified by substrate specificity, mode of DNA cleavage and their cofactor requirements.

CONCLUSIONS

Three major pathways of DNA fragmentation are proposed and discussed: (1) upregulation of endonucleases, (2) their intranuclear/intracellular redistribution and (3) primary changes of chromatin structure.

Multiple forms of endonuclease activity linked with radiation induced apoptosis in C4-1 cervical carcinoma cells

Irradiation of C4-1 cervical carcinoma cells induced apoptosis, as determined by their morphology and the presence of oligonucleosomal DNA fragmentation, with the formation of 5'- P and 3'-OH termini. Extracts of nuclear proteins from both control and irradiated cells possessed similar metallodependent endonucleolytic activity which cleaved target plasmid DNA with the same specificity as that found in apoptotic cells. Fractionation of the nuclear extracts revealed that the predominant endonuclease activity of unirradiated cells was a protein of approximately 40 kDa. After irradiation, the predominant activity was found to be associated with a 70 kDa fraction, with a reduction in the 40 kDa form. The activity of each endonuclease was found to be Ca2+ and Mg2+ dependent. It is proposed that the changes in molecular weight observed for these enzymes may be linked to the final step in apoptosis execution, irreversible chromatin fragmentation, and thus offer a potentially novel target for manipulating the effector pathway of apoptosis in these cells.

Topologically constrained domains of supercoiled DNA in eukaryotic cells

The size of supercoiled, topologically constrained DNA domains within the squamous carcinoma cell line SQ-20B were determined by direct comparison with a panel of irradiated supercoiled plasmid DNAs. Loss of supercoiling in plasmids was determined by gel electrophoresis and in cells by nucleoid flow cytometry. Comparison of dose-response data for plasmid relaxation with that obtained from SQ-20B cells enabled a direct estimation of supercoil target size in these cells. Plasmids pUCD9P (3.9 kbp), pXT-1 (10.1 kbp), pdBPV-MMT-neo (14.6 kbp), pRK290 (20.0 kbp), and R6K (38 kbp) were used and analyzed under the same exposure conditions as nucleoid DNA. Two sizes of topologically closed domains were found in nucleoids of 0.51+/-0.17Mbp and 1.34+/-0.3 Mbp. In an attempt to relate these large-scale organizations of DNA with function, cells were exposed to the DNA topoisomerase II inhibitor, VP16 and the G1/S cell cycle blocking agent mimosine. A 1 h exposure to VP16 was effective in reducing DNA synthesis which was associated with a parallel increase in nucleoid supercoiling. Addition of the G1 > S inhibitor mimosine enhanced both responses. It is concluded that chromosomes and interphase nuclei are organized into at least two sizes of topologically constrained domains of DNA which may have functional relevance to the control and execution of DNA synthesis.

An inducible lymphocyte nuclear Ca2+/Mg(2+)-dependent endonuclease associated with apoptosis

Apoptotic cell death is typically accompanied by internucleosomal chromatin fragmentation. Although a number of candidate enzymes have been proposed, there is as yet no direct evidence for the involvement of any particular endonuclease in this process. Here we demonstrate the existence of an endonuclease(s) that is up-regulated during apoptotic T cell death. The endonuclease(s) is located in the nucleus, and its activity is increased up to eightfold by a variety of stimuli or conditions that induce apoptosis in T cell hybridomas and thymocytes. Treatments that prevent TCR-mediated apoptosis, such as cyclosporin A or concomitant administration of glucocorticoids, also prevent the induction of enzyme activity. The endonuclease activity is associated with three molecular forms, designated A, B, and C, with apparent M(r) of 49K, 47K, and 45K, respectively, and constitutes the major endonuclease activity in T hybridoma cells. From A exists in resting cells, and its activity is increased threefold after the induction of apoptosis. Forms B and C are absent in resting cells and are induced up to 20-fold after stimuli that lead to apoptosis. All three forms are Ca2+/Mg2+ dependent and are inhibited by Zn2+. This enzyme(s) introduces double strand breaks and single strand nicks into supercoiled plasmid DNA, demonstrating the mode of DNA fragmentation characteristic of products of apoptotic chromatin degradation. The enzyme(s) produces DNA fragments with 5'-P and 3'-OH terminals, also consistent with apoptotic chromatin degradation. Finally, enzyme solubilized from cells activated to die cleaves chromatin in nuclei isolated from unstimulated T hybridoma cells, yielding the classic DNA ladder. Because of its biologic properties, we named this enzyme(s) inducible lymphocyte Ca2+/Mg(2+)-dependent endonuclease, or ILCME. Because inducible lymphocyte Ca2+/Mg(2+)-dependent endonuclease possesses the key features predicted for an apoptosis-specific enzyme, it is a new candidate for an enzyme(s) that participates in DNA cleavage in apoptotic T cells.

An inducible lymphocyte nuclear Ca2+/Mg(2+)-dependent endonuclease associated with apoptosis

Apoptotic cell death is typically accompanied by internucleosomal chromatin fragmentation. Although a number of candidate enzymes have been proposed, there is as yet no direct evidence for the involvement of any particular endonuclease in this process. Here we demonstrate the existence of an endonuclease(s) that is up-regulated during apoptotic T cell death. The endonuclease(s) is located in the nucleus, and its activity is increased up to eightfold by a variety of stimuli or conditions that induce apoptosis in T cell hybridomas and thymocytes. Treatments that prevent TCR-mediated apoptosis, such as cyclosporin A or concomitant administration of glucocorticoids, also prevent the induction of enzyme activity. The endonuclease activity is associated with three molecular forms, designated A, B, and C, with apparent M(r) of 49K, 47K, and 45K, respectively, and constitutes the major endonuclease activity in T hybridoma cells. From A exists in resting cells, and its activity is increased threefold after the induction of apoptosis. Forms B and C are absent in resting cells and are induced up to 20-fold after stimuli that lead to apoptosis. All three forms are Ca2+/Mg2+ dependent and are inhibited by Zn2+. This enzyme(s) introduces double strand breaks and single strand nicks into supercoiled plasmid DNA, demonstrating the mode of DNA fragmentation characteristic of products of apoptotic chromatin degradation. The enzyme(s) produces DNA fragments with 5'-P and 3'-OH terminals, also consistent with apoptotic chromatin degradation. Finally, enzyme solubilized from cells activated to die cleaves chromatin in nuclei isolated from unstimulated T hybridoma cells, yielding the classic DNA ladder. Because of its biologic properties, we named this enzyme(s) inducible lymphocyte Ca2+/Mg(2+)-dependent endonuclease, or ILCME. Because inducible lymphocyte Ca2+/Mg(2+)-dependent endonuclease possesses the key features predicted for an apoptosis-specific enzyme, it is a new candidate for an enzyme(s) that participates in DNA cleavage in apoptotic T cells.

[Comparative characteristics of some parameters of the cell nucleus in the series myeloma-hybridoma-lymphocyte]

A comparative study of several parameters of the cell nuclei of hybridoma MLC-1c and its parent cells--myeloma X-63.Ag8.653 and spleen lymphocytes of Balb/c mice, has been carried out. The results of cytogenetic studies suggest that although the hybridoma and myeloma cell lines used in this study are rather stable, they contain some proportion of the altered chromosomal material. Two-dimensional electrophoresis performed according to O'Farrell revealed that the similarity between the relative presentation and reciprocal location of the nuclear proteins expressed by the myeloma and the hybridoma was greater than that between these cell lines and lymphocytes. Probing of the chromatin structure by micrococcal nuclease showed no significant differences in the degree of nuclease resistance of chromatin between myeloma, hybridoma and lymphoid cells. A comparative study of the Ca/Mg-dependent endonuclease activity of the nuclei in situ and in nuclear extracts demonstrated that whereas its content in lymphocytes was rather high, in myeloma and hybridoma it was practically absent. At the same time, cell nucleus extracts of the myeloma and the hybridoma contained high amounts of DNA-binding proteins which were undetectable in mouse spleen lymphocytes.

Internucleosomal chromatin degradation in myeloma and B-hybridoma cell cultures

The activity of Ca/Mg-dependent endonuclease (CME) is strongly inhibited in myeloma X-63.Ag8.653 and B-hybridoma MLC-1c as compared with mouse splenocytes. Nevertheless, pronounced internucleosomal chromatin degradation occurs in both cell lines during long-term cultivation without passing. In isolated cell nuclei of X-63 the activation of CME, which precedes chromatin fragmentation in vivo and loss of cell viability, is revealed. The time-course of CME activation is opposite to cell proliferation and is not accompanied by alterations in enzyme quantity. The results suggest that cell death of X-63 and MLC-1c occurs via apoptosis, and involves the mechanisms controlling the activation and/or interaction of CME with chromatin.

Intermolecular homologies of human interferon-alpha

Human interferon-alpha 2 (IFN) was analyzed by homology search computer program with the use of protein primary structures data bases. Results indicate that four domains with heightened ability to form homology pairs with different proteins exist in the IFN molecule. These domains occupy regions 35-56, 72-85, 97-110 and 124-136, mainly between the alpha-helical cylinders on the tertiary structure models. Additionally, results show in IFN structure the presence of amino-acid motifs that create the opportunity for this cytokine to influence directly the processes of DNA functioning in cell nuclei.

[Changes in Ca, Mg-dependent endonuclease of DNA in isolated nuclei of human lymphocytes in lymphoproliferative diseases]

Ca, Mg-dependent endonuclease is one of the main DNAses of lymphocyte chromatin. It's activity is known to increase in the immune response and to decrease in spontaneous and experimental CLL. These observations became a basis for analysis of possible clinical meaning of it's enzymatic activity assay. Donors' peripheral blood lymphocytes being tested, normal level of endonucleolysis for men and children was defined. Except that patients with different clinical forms of lymphoproliferative diseases such as chronic lympholeukemia, non-Hodgkin lymphomas, Hodgkin's disease were observed. The results showed that Ca, Mg-dependent endonucleolysis activity was decreased in comparison to donors' one. Ca, Mg-dependent endonucleolysis activity was the same in the group of patients with non-malignant pathology and in donors' one. Successful treatment and remission state of our patients was associated with alteration of the Ca, Mg-dependent endonucleolysis activity to normal level as well as immunological parameters. That is why the activity of Ca, Mg-dependent endonucleolysis is suggested to be a new criterion of immune state and lymphocyte malignant transformation.

Early postirradiation chromatin degradation in thymocytes

The decrease in the average DNA size in thymocytes starts soon after in vivo irradiation and at approximately 45 min reaches a plateau, thereafter showing only minor changes up to 3 h. This fall in extent of chromatin cleavage coincides with the accumulation of 1.0-1.5 kb DNA fragments. Double-strand breaks generated by endonucleases are not randomly distributed along DNA but clustered in such a way that they give rise to fragments of 1-5 nucleosomes in size. Cycloheximide treatment partially inhibits nuclease activity in nuclear extracts isolated from thymus of irradiated mice. This suggest that DNA fragmentation is an early event in programmed death of thymocytes mediated by irradiation. The data indicate that it requires protein synthesis and that it precedes release of polydeoxyribonucleotides.

[DNA recombination in vitro initiated by Ca/Mg-dependent endonuclease from cell nuclei of human splenocytes]

The system of DNA recombination in vitro was constructed. It comprises two plasmids, the derivatives of pBR322 deleted in the genes for tetracycline resistance, and the recombinogenic extract of the thymus lymphocytes nuclei of mice. The system permits to study the effect of proteins and factors on the efficiency of recombination resulting in reconstruction of the tetracycline resistance gene. Double-strand cuts in one of the deleted plasmids were necessary for recombination. Double-strand cuts by Ca/Mg-dependent endonuclease of the human spleen lymphocytes nuclei were more efficient as compared with the ones of DNAase I, restriction endonucleases PaeI and SalI in the initiation of recombination. The possible role of Ca/Mg-dependent endonuclease in recombination in vivo is discussed.

[Characteristics of the effect of Ca/Mg-dependent endonuclease from cell nuclei of human lymphocytes on J kappa-cluster of immunoglobulin genes]

The cleavage of the murine J kappa-segments by purified Ca/Mg-dependent endonuclease was studied. The enzyme was shown to cleave specifically the J kappa-segments introducing the double strand breaks in 5'-regions of the J kappa-genes. The number of thus generated discreet fragments does not change during incubation. Specificity of the enzyme is not changed by substitution of Ca/Mg for Mn. The enzyme activity is inhibited by 0.1 M NaCl as well as its specificity. Comparison of the enzyme with the known nuclease activities that cleave specifically the J kappa-segments demonstrated that the activities of the latter are determined by Ca/Mg-dependent endonuclease. The results suggest the possible participation of Ca/Mg-dependent endonuclease in Ig-genes recombination.

[Isolation and analysis of Ca/Mg-dependent endonuclease from cell nuclei of human splenocytes]

A scheme for the isolation of Ca,Mg-dependent endonuclease from human spleen lymphocyte nuclei has been developed. The isolation procedure resulted in protein preparations (Mr = 57 kD) possessing an enzymatic activity and stable upon storage for over a period of one year. The enzyme is an endonuclease which predominantly cleaves double-stranded DNA by a mixed single- and double-hit mechanism with the formation of 5'-phosphate and 3'-OH terminal groups. Its maximal activation is induced by Ca2+ plus Mg2+. The enzyme is also active in the presence of Mn2+, Ca2+, Mg2+ and Zn2+ and is inhibited by Co2+. NaCl and KCl (0.15-0.2 M) and p-chloromercuribenzoate (1 mM) also inhibit the enzyme. ATP has no activating effect.

[Use of monoclonal antibodies in comparative studies of Ca, Mg-dependent endonuclease in cell nuclei]

Eight hybridoma cell lines derived from fusion between myeloma X-63 and mouse splenocytes were found to secrete monoclonal antibodies against Ca/Mg-dependent endonuclease of human spleen cell nuclei. Two of them, termed N and S, were used in comparative research of enzymes from different organs and species of animals. The data obtained show that N and S antibodies recognize different antigenic determinants of the enzyme molecule. Cross-reactions of antibodies with different antigens having similar antigenic determinants, exist in Ca/Mg-endonuclease of such species as man, mouse, rat and cattle. The evolutionary conservatism of this enzyme is suggested. The data show that the existence of tissue-specific (thymus-specific and spleen-specific) isoforms of Ca/Mg-endonuclease of cell nuclei is possible.

[Radionuclide method of determining the proteolytic activity of the stomach contents (clinical studies)]

The authors described clinical testing of a new tubeless radionuclide rapid method for measuring gastric content proteolytic activity (GCPA) using a protein (gelatin) capsule filled with a radiopharmaceutical (RP). The solution time of a capsule with a radiotracer determined by its clearance, corresponded to GCPA measured after Mett's method. The testing has shown that the above method is physiological, causes no complications and unpleasant sensations in patients, is simple to perform, and can be recommended for a wide clinical use in gastroenterology.

[New radionuclide method of determining the proteolytic activity of the stomach contents (experimental studies)]

A possibility of the use of a radionuclide tubeless rapid method for measuring gastric content proteolytic activity (GCPA) with the help of a protein (gelatin) RP containing capsule was demonstrated in experiments in vitro. There was correlation between the time of dissolution of RP containing capsules and GCPA determined after Mett's method. Reference time intervals were established for normal, raised and lowered proteolytic activity. The method was shown to be physiological, simple and time-saving.

[Dynamics of the endo-DNAase activity of cell nuclei of mouse thymus and spleen lymphocytes during the immune response]

Endo-DNAse (mostly Ca/Mg-dependent endonuclease) activity was studied in extracts of lymphocyte cellular nuclei from the spleen and thymus of mice upon their immunization with sheep red blood cells. Endo-DNAses were detected by their action on super-stranded DNA pBR 322. It has been established that endo-DNAse activity considerably changes in the course of immune response. The changes start in the early (induction) phase of immune response, are characterized by certain regularities and are distinct in thymus and spleen lymphocytes. It is assumed that endo-DNAses of lymphocyte cellular nuclei are involved in antigen-dependent lymphocyte differentiation.

[Ca/Mg-dependent endonuclease as a probe for detecting chromatin changes in lymphocytes in chronic lymphoid leukemia]

Chromatin fragmentation of bovine peripheral blood lymphocytes from normal animals and the ones suffering from chronic lympholeucosis (CLL) by DNase I, micrococcal nuclease and purified Ca/Mg-dependent endonuclease from nuclei of human splenocytes was studied. The lymphocytes chromatin from CLL animals was shown to be more resistant to nucleases, than the one from normal animals. It was found that difference between fragmentation of chromatin samples from normal and CLL bovines was more dramatic when Ca/Mg- dependent endonuclease was used versus traditionally exploited DNase I and micrococcal nuclease. The data suggest that purified Ca/Mg-dependent endonuclease can be a useful enzymatic probe for detection of lymphocytes chromatin changes during CLL.

[Changes in central hemodynamics in chronic liver diseases (radiocardiologic study)]

Some indices of central hemodynamics: cardiac and systolic indices, specific peripheral resistance and circulating plasma and blood volumes were studied in 136 patients with chronic liver diseases using radionuclide cardiography. I. Three hemodynamic types of blood circulation (hyper-, eu- and hypokinetic) were defined in patients with chronic liver diseases as well as in healthy persons. II. In liver cirrhosis and ascites the number of patients with the hyperkinetic type of circulation increased significantly, mainly at the expense of patients with hypervolemia. III. A significant decrease in circulating plasma and blood volumes was noted in patients with liver cirrhosis complicated by ascites, with the hypokinetic type of circulation. It should be borne in mind in administration of diuretics to such patients. The above results suggested that different types of circulation in patients with chronic liver diseases were formed under the influence of the disease against a background of existing constitutionally and genetically determined hemodynamic heterogeneity.

[Computer analysis of chromatin fragmentation with nucleases]

Computerizing of the densitograms of chromatin hydrolysate DNA is offered. It is based on searching for gaussoids depicting the peaks of individual oligomers so that the resultant curve corresponded to the experimental curve to a high enough accuracy. The method suggested was used to study the time course of mononucleosome and oligomer accumulation during chromatin fragmentation with endogenous nuclease. Comparison of the experimental data to a model calculated for break down of 500-nucleosome chromatin fragments demonstrates that in chromatin, the release of mono-, di- and trinucleosomes is shifted towards nucleosomes during break down induced by endogenous nuclease.

[Quantitative determination of DNA in gels]

The parameters affecting the determination of the amount of DNA in gels have been studied. The conditions have been offered for photographing gels, for the development of the negatives, choosing the time of exposition and DNA amounts providing for the work in the linear area of the characteristic curve.

[Nucleases from Brevibacterium ammoniagenes differing in their effects on chromatin]

A method of isolation of three different, partially purified deoxyribonucleases from the cells of Brevibacterium ammoniagenes is descrirbed. The enzyme preparations were activated by various bivalent metal ions: 50mM MgCl2 (I), 5 mM CaCl2+5 mM MgCl2 (II), 10 mM CaCl2 (III), and had different pH optima -- 8.8 (I), 7.2 (II) and 8.2 (III). In the isolated nuclei of rat brain the first and third fractions split chromatin at the internucleosomal sites with a formation of nucleosomes -- structural subunits of chromatin. The second fraction exhibited no structural specificity for chromatin. A possible use of the enzymes for the analysis of chromatin structure is discussed.