Acid hydrolase and cytochrome oxidase activities in nitrosourea induced tumors of the nervous system

Activity of lysosomal exoglycosidases in human gliomas

There is a lot of data suggesting that modifications of cell glycoconjugates may be important in progression of cancer. In the present work we studied activities of lysosomal exoglycosidases: beta-hexosaminidase and its isoenzymes A and B, beta-galactosidase and alpha-mannosidase, in human gliomas. Enzyme activity was determined spectrophotometrically based on the release of p-nitrophenol from p-nitrophenyl-derivative of appropriate sugars. The activities of the exoglycosidases tested were significantly higher in malignant glial tumors than in control tissue (normal brain tissue) and non-glial tumors. The highest activities of exoglycosidases were observed in high-grade gliomas, and a positive correlation of enzyme activities and degree of malignancy was noted. Our results suggest that lysosomal exoglycosidases may participate in the progression and dynamical development of glial tumors.

Characterization of N-nitrosourea-induced tumors of the nervous system; their prospective value for studies of neurocarcinogenesis and brain tumor therapy

Two decades of research with resorptive neurocarcinogens firmly established the high potency of methyl and ethylnitrosourea (MNU and ENU) as neurocarcinogens, particularly in rats. There are significant differences in susceptibility to these agents among species. There are also differences among age groups. Fetuses are between 50 to 100 times more susceptible than adult rats. One single iv inoculation of 20-50 mg/kg ENU into pregnant rats may produce neurogenic tumors in 100% of the offspring. The tumors produced by these compounds have been well characterized morphologically, biologically, biochemically and histochemically. Tumors produced by both compounds are mostly gliomas and neurinomas (Schwannomas), however, clear differences exist between ENU and MNU produced neoplasms. Transplacental exposure to ENU generally results in a high number of anaplastic neurinomas and mostly differentiated gliomas (astrocytomas, oligodendrogliomas or mixed gliomas). In contrast, multiple exposures of adult rats to MNU result in a moderate number of mostly differentiated neurinomas and a high number of anaplastic gliomas. Tumors usually start out as well differentiated oligodendrogliomas or astrocytomas. As they grow larger, they become more mixed and anaplastic. In contrast to spontaneous gliomas in old rats, MNU and ENU-induced astrocytomas can be readily identified with well established biomarkers such as the S100 protein and particularly GFAP (glial fibrillary acidic protein). Neurinomas are also strongly positive for S100 protein. No reliable markers exist for oligodendrogliomas. Neurogenic tumors induced by MNU or ENU, as well as derived cell lines and clones from such tumors, have been successfully used as models for neurocarcinogenesis and therapeutic screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Mono- and diacylglycerol lipases in spinal cord of lean and obese Zucker rats

1. Genetically obese Zucker rats (fa/fa) contain 2-3 times higher activities mono- and diacylglycerol lipases in their spinal cords than their lean littermates. 2. When rats were exercised (1 hr daily, 5 days/week) on a treadmill for 6 months, there was a decrease of about 30% (P less than 0.05) in the activities of mono- and diacylglycerol lipases in lean rats but not in obese animals. 3. High activities of lipases in Zucker obese rats may be related to the elevated levels of beta-endorphin present in these animals. 4. The activities of arylsulfatase, beta-N-acetylhexosaminidase and alkaline phosphatase, tested to check the stability of spinal cord extracts, were similar in lean and obese rat spinal cords.

Experimental brain tumors and edema in rats. II. Tumor edema

Experimentally induced brain tumors in rats with the morphological characteristics of low differentiated gliomas were investigated with special consideration of the distribution of extravasated serum proteins within the tumor itself. Protein extravasation across tumor vessels occurs by pinocytotic vesicles which enclose serum proteins at the luminal surface of the endothelial cells. These vesicles move to the abluminal cell surface where proteins are released after fusion between vesicles and the cell membrane. Serum proteins then spread through the extracellular space from where they are taken up in tumor cells by pinocytosis. They are then transmitted to and digested by lysosomes in which acid phosphatase activity could be demonstrated. Tracer studies (human serum albumin, horseradish peroxidase) revealed that proteins reach the lysosomes 15 min after systemic application. The cellular content of tracers is variable even when systemic circulation has lasted 120 min.

Lysosomal isozyme patterns in ethylnitrosourea-induced brain tumors

Isozyme patterns for five acid hydrolases, acid phosphatase (AP), aryl-sulfate (AS), beta-glucuronidase (beta-Glu), N-acetylglucosaminidase (NAG) and beta-galactosidase (beta-Gal), were studied in isolated lysosomes from ethylnitrosourea (ENU)-induced gliomas and compared with normal and newborn rat brains. With polyacrylamide gel electrophoresis (PAGE), AP was separated into three bands, acidic (A), intermediate (B) and basic (C). In tumors and newborn brains there was a decrease in A and C but a significant increase in B. For NAG the acidic form was elevated by 9-19% in tumors, while newborn brains showed a 19% decrease. Even though the band intensities of beta-Glu in tumors and newborn brains were increased, the relative distribution remained similar to normal brain. With isoelectric focusing, five hydrolases were separated into four to five distinct forms. In ENU-induced gliomas the intensities of all peaks were considerably increased, but in most cases the number of isozymes remained the same. In tumors the isoelectric points were shifted towards the acidic side and smaller peaks in the basic regions merged into more acidic peaks. This effect was especially evident for AP and Gal. In the cases of AS, beta-Glu and NAG, consistently more activity was associated with acidic peaks than with the basic ones. Our data indicates that there is a significant increase in acidic forms of some of the lysosomal hydrolases studied in ENU-induced brain tumors.

Experimental brain tumors and edema in rats. I. Histology and cytology of tumors

In this study an experimental intracerebral tumor has been investigated with special consideration of structures, which may be involved in edema production and/or resolution. For this purpose a cloned tumor cell line (RG1 2.2) has been injected stereotactically into the brain of BD-IX rats. The tumor has some characteristics in common with low differentiated oligodendroglioma in men. A honeycomb architecture may be seen in the center of the tumor. It is built up by rounded or elongated cells, which can be impregnated in parts. In the central area, cells exhibit a voluminous digestive apparatus, composed of dictyosomes, vesicles, and some vacuoles with a membranaceous or homogeneous content. Tumor cells in the periphery show large processes and a small digestive apparatus. The sinusoidal tumor vessels are composed of an endothelium with many vesicles but no openings.