Acid DNase Activity Research Articles

A subcellular localization of the gene product of the DNase-1 locus in Drosophila melanogaster

A study was undertaken to determine the subcellular location of DNase-1, a major acid deoxyribonuclease in Drosophila melanogaster. Embryonic tissue used in these experiments was derived from a wild type strain and from a strain homozygous at the DNase-1 locus (3–61.8) for the null activity allele, DNase-1 n324. The majority of total acid DNase and DNase-1 activity is found in the small particulate fraction of tissue homogenates fractionated by differential centrifugation. The activity exhibits latency in these extracts indicating that it is membrane delimited. DNase-1 activity also co-equilibrates in sucrose density gradients with acid phosphatase activity which, in D. melanogaster, is known to be lysosomal. These results suggest that DNase-1 is localized largely within the lysosomes of embryonic tissue. Functional implications of a lysosomal location for DNase-1 are discussed.

Changes in intracellular activities of lysosomal enzymes in tissues of rats during aging

A comparison of results obtained from studies of the intracellular fractions of the tissues of liver, brain and heart of “young” (1–2 months), “old” (24–27 months) and “senile” (34–37 months) rats showed that the ratios of three enzymes, acid phosphatase, β- N-acetylglucosaminidase and acid RNase of the liver and heart were very similar and their activities decreased with age. On the other hand, the protein content in the supernatant of the liver, and acid DNase activities in the supernatant of the brain increased significantly with age. When the 24–27 month and 34–37 month old rats were compared, the ratios of the total activities of liver β- N-glucosaminidase and brain acid DNase in the supernatant and the specific activity of brain β- N-glucosaminidase in the microsomal fraction increased significantly.

Induction of the deficient acid DNAse activity in mouse interfollicular epidermis by croton oil as a possible tumor promoting mechanism.

Histochemical activity of acid DNAse, intensity of nucleic acid staining and histological alterations in mouse interfollicular epidermis (I.F.E.) were investigated after a single dose or after chronic topical administration of two hyperplastic agents, of which one (croton oil) was a potent tumor promotor, and the other one (podophyllin) did not promote skin carcinogenesis. Podophyllin induced intense uniform I.F.E. hyperplasia without any proliferation of poorly differentiated basal cells, without increased nucleic acid staining and without any appreciably decreased acid DNAse activity. On the other hand, croton oil (as well as TPA) produced almost immediate, distinct hyperplasia of poorly differentiated basal cells with increased intensity in the staining of both nucleic acids and nearly complete deficiency in acid DNAse activity. Similar histochemical and histological patterns were observed at the sites of wounding hyperplasia in untreated control mice. Such wounding hyperplasia was thought also to be a tumor promoting factor. It was suggested that the decrease in acid DNAse activity which occurred almost immediately after administration of potent tumor promoters and which could not be induced by a hyperplastic agent without tumor promoting action may have a particular importance in the mechanisms of tumor promotion.

Studies on the synthesis and degradation of DNA in developing and old chick cerebellum.

The levels of DNA, RNA, protein and acid and alkaline DNase were studied in developing and old chick cerebellum. The in vitro synthesis of DNA, by both chick cerebrum and cerebellum was also studied, by following the incorporation of [3H]thymidine into DNA. It was observed that the increase in DNA content of chick cerebellum continued well beyond adult stages of life span. Maximal DNA synthesis, as judged by the [3H]thymidine incorporation, was noticed during the early embryonic development but decreased with advancement of age. There was, however, another peak of activity, although smaller, at about 9 months of age. Both cerebrum and cerebellum showed similar patterns. The highest specific activity of acid DNase was also found during the early period of cerebellar development, that is at a time when rapid cellular proliferation was occurring. The activity steadily declined with the aging and in 2-year-old cerebellum very little activity could be detected. Alkaline DNase, on the other hand, not only exhibited high activity during the early development but also remained at a significant level even in old cerebellum. It is concluded that acid DNase shows a positive correlation to the early embryonic DNA synthesis but not to the cell increase occurring in old age.

Histochemical correlation between glycogen, nucleic acids and nucleases in pre-neoplastic and neoplastic lesions of rat liver after short-term administration of N-nitrosomorpholine

After 7 weeks of oral administration of the carcinogen N-nitrosomorpholine (12 mg NNM ad 100 ml of drinking water) to male rats, marked hepatocellular changes were found predominantly in the centers of the lobules. These were loss of glycogen, disorganisation of the basophilic bodies and, sometimes, loss of cytoplasmic basophilia or pyroninophilia, necrotic cells and increase in the activity of acid DNAse and RNAse. These centrilobular alterations were reversible after withdrawal of the carcinogen. They are, therefore, attributed to the nonspecific-toxic effect of the carcinogen. In peripheral and midzonal regions of the lobules basically different cellular changes appeared which were unimportant during the phase of intoxication, but became prominent after cessation of the carcinogenic treatment. These lesions were: excessive storage of glycogen, displacement of basophilic bodies and an increase in cytoplasmic acidophilia. The hepatocytes showing these cytoplasmic changes initially formed foci. Neoplastic nodules and frank hepatocellular carcinomas developed later. During these later stages of the experiment both the foci and the nodules consisted of 4 main types of altered hepatocytes: 1) "clear" glycogen storage cells, 2) acidophilic cells, 3) vacuolated (fat storing) cells, 4) basophilic (pyroninophilic) cells poor in, or free from, glycogen. The larger nodules and carcinomas contained predominantly basophilic cells. The activity of nucleases, especially that of acid DNAse, decreased in small foci which as a rule developed later than the foci of glycogen storage. In most cells of neoplastic nodules and carcinomas the activity of these enzymes disappeared, but it reappeared in necrotic cells. The progressive alterations in the activity of the nucleases seemed to be related to the phenotypic expression of malignancy and could be a sign of a fundamental metabolic change taking place during a relatively late step in the malignant transformation.

Changes in the levels of DNA, RNA, protein and DNases in developing and old chick brain.

Abstract—The levels of DNA, RNA, protein and activities of acid and alkaline DNases in developing and old chicken brain were studied. A rapid increase in DNA content was found in the embryonic brain until just prior to hatching. Thereafter, with a transient plateau around the day of hatching, the DNA continued to increase but at a very slow rate. Two‐year‐old brain was found to have a markedly higher level of DNA as compared to the 10th day postnatal value. RNA showed a steady increase up to the 20th day of embryonic life. Protein levels showed a gradual increase throughout the period studied. Both acid and alkaline DNases exhibited maximum activity during embryonic life, i.e. at a time when rapid cellular proliferation was occurring. With advancing age, the acid DNase activity showed a marked decline thus exhibiting no correlation to the high level of DNA found in the old brain. The alkaline DNase activity, however, was still at a significant level in the 2‐year‐old brain.

DEOXYRIBONUCLEASES IN DEVELOPING AND ADULT RAT CEREBELLUM: TRANSIENT AND LONG DURATION ACTIONS OF METHYLAZOXYMETHANOL

Abstract—Acid and alkaline DNase activities were determined in postnatal and adult rat cerebellum. Normal animals were compared with those injected with 10 mg/kg methylazoxymethanol acetate using varying schedules after birth in order to induce transient damage to proliferating cell populations. In all animals studied, both immature and adult, methylazoxymethanol caused an increase in acidic and decrease in alkaline DNase activity. These effects were not specific to the dividing populations and occurred in nonmitotic cells as well. When injections were given to young adults, these effects appeared irreversible and persisted up to 3 months after birth.

Gastric carcinogenesis in rat induced by methylnitrosourea (MNU). Morphology, and histochemistry of nucleases.

27 squamous cell carcinomas of the forestomach, 2 adenocarcinomas of the glandular stomach and very numerous preneoplastic lesions of the mucosa in both parts of the stomach were induced after chronic oral administration of MNU in Wistar R rats. Single transplacental administration of MNU did not produce any gastric tumor, however preneoplastic alterations were detected in the forestomach of 42 animals and in the glandular stomach in 25 animals out of 51 examined, showing histologic patterns like those found in rats after chronic oral MNU administration. The pre- and neoplastic alterations in the forestomach demonstrated a distinct decrease of acid and alkaline DNase and RNase activity as compared with the normal forestomach. The last mentioned observation and our previously published results suggest that the deficiency of nucleases precedes or facilitates carcinogenesis.

Influence of aflatoxin B 1 and aflatoxin B 2 on rat liver lysosomal acid deoxyribonuclease

The in vitro effects of aflatoxins B 1 and B 2 were studied on the permeability of isolated rat liver lysosomes. Only aflatoxin B 1 altered the lysosomal membrane with the consequent release of lysosomal enzymes. The results of the in vivo experiment with aflatoxin B 1 show that the specific activity of acid DNase in liver lysosomes was markedly decreased in the rats dosed aflatoxin B 1 while the specific activity of the cytoplasmic acid DNase, or nonsedimentable acid DNase, was dramatically increased. The results are discussed in relation to a hypothesis concerning the role of lysosomes in carcinogenesis.

Acid deoxyribonuclease activity in developing human foetal brain

The presence of acid deoxyribonuclease activity in developing human foetal brain has been shown. The specific activity of this enzyme, either in whole brain or in cerebrum, was highest upto 20 weeks of gestational age but gradually decreased by full term. In the cerebellum, however, the activity increased with the advancement of gestation and maximum specific activity was found at full term. This pattern of changes in the acid DNase activity correlates well with the already observed rates of DNA synthesis in these regions of developing human foetal brain. This interesting relationship appears to exist in developing rat brain as well.

Effect of aflatoxin on rat liver lysosomes.

The effect of aflatoxin on the activities of 5 rat liver lysosomal enzymes (acid deoxyribonuclease, arylsulfatases A and B, β-glucuronidase, β-glucosidase and β-galactosidase) has been investigated in vivo and in vitro . Three hours after the administration of aflatoxin, activities of most of the enzymes increased significantly reaching maximal levels at 48 hr. The activity of acid DNase increased the most (276 per cent of the control level). At the same period (48 hr) the activity of the soluble lysosomal enzymes greatly increased. Aflatoxin had a labilizing effect on lysosomal membranes, causing the release of lysosomal enzymes into the supernatant. The data are discussed in connection with the biochemical mechanism of aflatoxin intoxication.

A histochemical study of alkaline and acid nuclease activity in the human brain compared to the incidence of malignant tumours

Alkaline and acid DNase and RNase activities were investigated histochemically in human brain. Intense activity of alkaline nucleases was found mainly in the choroid plexus and ependymal epithelium as well as in the leptomeninges. Acid nuclease activity was strongest in all nerve cells. The glial cells demonstrated very weak activity of both acid and alkaline nucleases. Comparison of these results with the incidence of human brain malignant tumours has indicated that low nuclease activity in normal brain cells coincides with the high incidence of malignant tumours deriving from these cells and vice versa. These observations and the results of similar investigations in the rat CNS and in the digestive tube of the rat and man suggest that low nuclease activity in normal cells could be considered to be a factor which may predispose to malignant trans-formation.

Correlation of nucleolytic activities with the stage of growth of the silkworm

From the tissues of the silkworm several nucleolytic enzymes were detected. Among these, acid ribonuclease (RNase) and alkaline nuclease were dominant. The optimal pH values for these are 5·3 and 10·3, respectively. An acid deoxyribonuclease (DNase), optimally active at pH 5, was also found in the tissues of the insect. Changes of activity were investigated of the acid RNase and the alkaline nuclease through the whole life cycle of the silkworm. The former remains very active during each step of development. By contrast, the latter exists at higher levels only during the feeding period, and then drops abruptly to an almost undetectable level at the initiation of spinning. The acid DNase activity showed a peak 3 days after pupation. The acid RNase and DNase showed a wide distribution in the tissues of the silkworm, whereas the alkaline nuclease is restricted to the gut juice and to the gut.

Nucleases activity in different segments of the human digestive tube compared to the incidence of carcinomas (histochemical study).

The alkaline and acid DNase and RNase activity was histochemically investigated in biopsies from the human digestive tube. Activity of these enzymes in the mucosal epithelium in different segments of the digestive tube was compared to the statistical incidence of malignant tumors deriving from this tissue (carcinomas). It was found that the alkaline and acid nucleases activity was very intense in small intestine precisely in this segment where the incidence of carcinomas was low, whereas the low activity of these enzymes in the stomach and large intestine corresponded to the high incidence of carcinomas. This observation confirmed our previously elaborated hypothesis, according to which the low activity of nucleases in normal tissues appeared to be a predisposing factor for malignant transformation. It could be also supposed that the nucleases constitute some kind of double barrier mechanism protecting the genetical stability of the cell against foreign nucleic acid incorporation or production; alkaline nucleases being an extracellular and acid nucleases an intracellular barrier.

Age variations of acid deoxyribonuclease activity in mouse liver nuclei.

THERE are at least two endonucleases in mouse liver. One of these, probably identical to the enzyme in rat liver described by Curtis et al.1,2, at an optimum pH of 7, hydrolyses RNA and DNA denatured by heat, preferentially to native DNA (personal data). The other is an acid deoxyribonuclease (DNase), the partial purification and properties of which have been described elsewhere3. These properties are very similar to those of the acid DNases extracted from several organs of higher mammals4. Although these acid DNases are widely distributed, their role in the cell is still unknown. A relationship may exist between the activity of these enzymes and the replication of DNA5. We have investigated variations in acid DNase activity in mice of different ages. A nuclear fraction and a cytoplasmic fraction containing the mitochondria and lysosomes were isolated from liver cells. The nuclear activity is high at 24–48 h and decreases markedly during the first month of life, while the activity of the cyboplasmic fraction remains constant.

Deoxyribonucleases from rat brain.

Abstract—Two distinctly different DNases were isolated from rat brain and could be separated easily by ammonium sulphate fractionation. One of the DNases acts optimally at pH 5.0 hydrolysing preferentially native DNA and requiring an optimal Mg2+ concentration of about 0.03 m. The other DNase has its optimal pH between 7.4 and 8.9, acts preferentially on heat‐denatured DNA and requires a lower Mg2+ concentration, the optimum being 1 × 10−4m.Cerebellum from adult rat brain has a lower acid DNase activity and higher alkaline DNase activity, and therefore has a higher ratio of alkaline DNase to acid DNase than the other areas of brain studied. This unique activity ratio in cerebellum of adult rat brain was not observed in infant rat brain.

Abscopal Effects of X-Irradiation on Mouse Bone Marrow

X-Irradiation of the rest of the body with the spleen shielded has been observed to cause reduction in cell number and increase in acid deoxyribonuclease (DNase) activity per average remaining cell in the protected spleen (1). The mechanism of this of X-irradiation remains unclear. Shift in cell population probably plays a role but is not likely to account for the entire phenomenon. Whereas loss of cells low in DNase, leaving behind a population high in DNase, could account for an increase in DNase content per average remaining cell, it could not account for the transitory increase in total DNase activity observed. The short life of active radicals makes it improbable that the circulation of such products of X-irradiation could mediate the indirect effects. However, other breakdown products which might have a toxic effect on the spleen could mediate the effect. It would be expected that such a mechanism would be influenced by the volume of tissue irradiated and possibly also by the X-irradiation sensitivity of the irradiated organs. Finally, the possibility that irradiation of endocrine organs might produce the distant effects was also considered (1). It is the purpose of this paper to report on experiments designed to detect local and abscopal effects of X-irradiation on bone marrow. Since bone marrow cells are very radiosensitive, the abscopal effect might be expected to be a function of the volume of bone marrow irradiated, whether the mechanism involved primarily shift in cell population (interchange between irradiated and protected marrow sites) or toxic effects. Beyond the lethal dose for the cells low in DNase activity in the irradiated tissue, approximately 800 r (2), increase in radiation dose would not be expected to produce increase in acid DNase activity per average remaining cell.

The Effect of Whole-Body X-Irradiation on the Distribution of Acid Deoxyribonuclease and β-Galactosidase in Subcellular Fractions of Rat Spleen

The distribution of acid DNase activity in spleen subcellular fractions of rats given 700 r of whole-body x irradiation was determined 16 and 64 hours postirradiation and compared to that in pair-fed controls. In the controls, the percentage distribution in nuclei, mitochondria, microsomes, and supernatant fraction was 25.8%, 30.6%, 10.7%, and 32.5%, respectively. Sixteen hours after irradiation this had changed to 15.9%, 26.9%, 13.1%, and 44.2% for the same fractions, respectively. There was no further significant change at 64 hours. Considerable increases in specific acid DNase activity were measured in the homogenate and all fractions 16 hours postirradiation; smaller changes were observed at 64 hours. At 16 hours postirradiation, evidence was obtained for a small net increase (14.5%) in total spleen DNase activity, compared to that in controls, and it was suggested that this increase might be caused by either increased enzyme synthesis or increased susceptibility of spleen lysosomes from irradiated animals to breakage during isolation and assay. In spleen of control animals, 67% of the BETA -galactosidase activity was found in the supernatant fraction, and 700 r of whole-body x irradiation did not significantly alter the distribution of this enzyme in subcellular fractions at either 16 or 64 hoursmore » postirradiation.« less

Relation entre l'activité de la desoxyribonuclease acide et la croissance chez le rat

The activity of acid deoxyribonuclease and the mitotic indexes have been determined in the liver, spleen, kidneys and brain of rats killed 1 hr, 1, 2, 6, 21 and 49 days after birth. The activity of the enzyme expressed per mg DNA, i.e. per cell, is lower in the most actively dividing tissue (spleen). When expressed per mg protein, however, the specific activity of acid DNAase is always highest in the spleen and lowest in the brain, as is also the case for the mitotic indexes. In regenerating liver, the activity of acid DNase markedly increases at the 18th hr post-operation, at a time when no mitosis and no DNA synthesis are observed. A correlation between acid DNAase activity and rate of growth definitely exists in a homogeneous population of synchronized cells, but is not so unequivocal when one compares different organs exhibiting different rates of growth.

Acid Deoxyribonuclease and Acid Phosphatase Activities in Regenerating Rat Liver after Whole-Body X-Irradiation

Acid DNase and acid phosphatase activity were determined in regenerating livers of normal and irradiated rats. in normal rats, hepatectomy brings about an increase of acid DNase between 12 and 18 hours postoperation. The possible role of this increase in the mitotic cycle is discussed. Fifteen per cent of acid DNase and acid phosphatase activity is present in supernatant fraction of homogenates of normal and regenerating livers. This percentage is not changed in nonregenerating livers by irradiation by 700 r. In regenerating livers, however, irradiation with 700 r increases the percentage of free enzyme activity (from 15 to 30%) when it is given 10 minutes or 12 hours after hepatectomy. Irradiation 24 hours after hepatectomy no longer solubilizes the enzyme activities.