ASTROGLIAL UPTAKE IS MODULATED BY EXTRACELLULAR K +

Primary cultures of rat brain astrocytes were used to examine the uptake of the glucose analogue, 2-deoxy- d -glucose (2-DOG). 2-DOG competes with glucose for uptake, indicating that both are transported by the same carrier system. Extracellular K + at 11.9 mM increased the uptake of 2-DOG at 2-DOG concentrations greater than 100 ΜM. Uptake. appears Na + -dependent only at high concentrations of 2-DOG. This suggests that the extracellular concentrations of Na + and K + may regulate the astrocytic uptake of 2-DOG.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65513/1/j.1471-4159.1979.tb05224.x.pd

ATPase activity in glial cells and in neuronal perikarya of rat cerebral cortex during early postnatal development 1

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65822/1/j.1471-4159.1972.tb01365.x.pd

THE EARLY POST-NATAL DEVELOPMENT OF THE NEURONAL LYSOSOME 1

The hydrolysis of p -nitrophenyl-2-acetamido-2-deoxy-Β-d-gluco-(I) and Β-d-galacto-pyranoside (II) and of p -nitrophenyl-Α-d-mannopyranoside (III) by neuronal cell bodies and glial cells isolated from the cerebral cortex of 18-day-old or adult rats was found to be equally efficient, with relative ratios of hydrolysis for I, II and III of approximately 10:1:0.5 in both cell types and at both ages. Homogenates of the neuronal cell bodies obtained from cerebral cortices of 3-, 8-, 12-, 18- and 32-day-old rats were subjected to differential centrifugation and the subcellular localization of N -acetyl-Β-d-glucosaminidase (EC 3.2.1.30) hydrolysing (I)] was compared to that of the mitochondrial marker, succinate-INT- oxidoreductase (EC 1.3.99.1). A fraction in which N -acetyl-Β-d-glucosaminidase exhibited maximal specific activity could be isolated at all ages, an observation indicating that the potential for active hydrolytic performance is incorporated into the neuronal lysosome very early post-natally. The specific activities of N -acetyl-Β-d-glucosaminidase and succinate- INT-oxidoreductase reached their respective maxima at widely different times postnatally: at 10–12 days for the mitochondrial enzyme and at about 18 days for the glycosidase, a difference suggesting that in the cortical neuron lysosomes and mitochondria develop out of step. The mitochondrial, lysosomal and microsomal fractions obtained by differential centrifugation were subjected to equilibrium density centrifugation and the presence of two populations of N -acetyl-Β-d-glucosaminidase-bearing particles was demonstrated. Although their presence was readily apparent in the neurons from 8- and 12-day old brains, it was difficult to discern their presence in the neurons from the 3- and the 18-day-old brains. In 8-day-old brains gradient fractions obtained from neurons containing N -acetyl-Β-d-glucosaminidase of a specific activity up to 8-fold higher than that of the enzyme in the original neuronal homogenate were examined by electron microscopy and the concentration of numerous lysosomes and derivative bodies in these fractions was verified. Our present study demonstrates the capability of the immature and developing neuron to tightly couple the pace of its degradative processes to that of its highly efficient and highly selective synthetic activities.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66318/1/j.1471-4159.1972.tb01312.x.pd

Lysosomal N-acetyl-[beta]-D-glucosaminidase: interneuronal differences in activity and molecular forms

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/21768/1/0000162.pd

Rapid assay of spermidine synthase activity by high-performance liquid chromatography

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24196/1/0000455.pd

CEREBROSIDE GALACTOSIDASE: A METHOD FOR DETERMINATION AND A COMPARISON WITH OTHER LYSOSOMAL ENZYMES IN DEVELOPING RAT BRAIN 1

(1) A method is described for assaying brain for cerebroside galactosidase activity. The enzyme was liberated by sonication and addition of sodium taurocholate, then by digestion with pancreatic enzymes. It was further purified by precipitation at pH 3. The enzyme was then incubated with an emulsion of galactose-labelled cerebroside in taurocholate and oleate at pH 4·5, and the liberated galactose was determined by scintillation counting. (2) The content of cerebroside galactosidase in rat brain at various ages has been determined. The enzyme was present before cerebroside appears in noticeable amounts (4 days) and the amount rose considerably during the period of active cerebroside deposition and myelination. The amount then remained at a high concentration even in the adult. (3) Comparison with other lysosomal brain enzymes was made in the age study. Nitrophenyl galactoside hydrolase also increased during myelination but levelled off earlier; its activity paralleled the amount of ganglioside. Nitrophenyl glucoside hydrolase started at a lower level and decreased with age. Sulphatase activity rose during myelination, then decreased somewhat after 15 days. Ceramidase followed a pattern similar to that of nitrophenyl galactoside hydrolase; it is suggested that both of these enzymes reflect ganglioside metabolism. (4) The relative amounts of brain enzymes in different states were determined as a function of age in the case of cerebrosidase, nitrophenyl galactoside hydrolase and sulphatase. The proportion found in the high speed supernatant fraction was low but increased after myelination. The proportion that could be ‘solubilized’ by sonication decreased after myelination but the values differed greatly for the three enzymes. This treatment solubilized one-seventh of the cerebrosidase, half the nitrophenyl galactosidase and three-quarters of the sulphatase.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66425/1/j.1471-4159.1969.tb06849.x.pd

Glial and neuronal localization of cerebroside-metabolizing enzymes

Glial and neuronal cell preparations were made from young rat cerebrum and assayed for 3 enzymes involved in sphingolipid metabolism. A galactosyltransferase which makes galactocerebroside, a primary component of myelin, was found in all cell types examined, at fairly similar levels of activity. The same distribution of activities was found for the [beta]-galactosidase which hydrolyzes galactocerebroside. It is suggested that the very low levels of galactocerebroside found in neurons are the result of an inability of neurons to form the lipoidal cerebroside precursor, hydroxy ceramide, or a cerebroside-binding protein.The glucosyltransferase which makes glucocerebroside, an intermediate in ganglioside biosynthesis, was found only in neurons. This may be a new marker enzyme for neurons, in contrast to other brain cells. Since gangliosides are found in non-neuronal membranes, it appears likely that they (or some intermediate in biosynthesis) are transferred from neurons.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34120/1/0000404.pd

Effect of methionine sulfoximine on methylation of guanine residues in astroglial transfer ribonucleic acids

Culture-grown astrocytes derived from 3-day-old rat brain were incubated in the presence of [ 3 H]guanosine and of the convulsant agent l -methionine- dl -sulfoximine (MSO). The resulting [ 3 H]tRNA was purified from control and MSO-exposed cells at several time points during the incubation and was hydrolyzed to [ 3 H]guanine and four [ 3 H]methyl guanines which were separated by high pressure liquid chromatography. Three of the four [ 3 H]methyl guanines were more highly labeled in the [ 3 H]tRNA of the MSO-exposed cells, relative to that of the control cells throughout the entire incubation period. The findings extend to cultured astrocytes, the stimulatory effect of MSO on the methylation of neural tRNA guanines, previouly observed both in vitro using [ 14 C] S -adenosyl- l -methionine and in vivo using [ methyl 3 -H] l -methionine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45427/1/11064_2004_Article_BF00964832.pd

Ameloblastic neoplasia spectrum : a cross-sectional study of MMPS expression and proliferative activity

Objective. To compare the proliferation and the expression of matrix metalloproteinases (MMPs; MMP-2 and MMP-9) in solid and unicystic ameloblastomas with ameloblastic carcinomas. Study Design.Five cases of ameloblastic carcinoma (AC), 18 cases of solid ameloblastoma (SA), and seven of unicystic ameloblastoma (UA) were selected. The immunohistochemical expression of MMPs was assessed by the percentage of positive tumor cells and stained stroma. The mean argyrophilic nucleolar organizer region (AgNOR) and the percentage of cells with more than one AgNOR per nucleus were evaluated. Results. Statistically significant higher mean AgNOR was observed in AC than in SA and UA. MMP-2 was expressed similarly in tumor and stroma among groups. MMP-9 was higher in the stroma of SA than that of UA (P = .0484). Conclusions. The cell proliferation was related to the greater aggressiveness of AC. High expression of MMP-2 and MMP-9 in all lesions highlighted the importance of these enzymes in the biology of ameloblastic tumors