Search PubMed⌕ Search

Biomedical subjects

A Lombardo

Publications and source records attributed to A Lombardo.

At least 91 records · Page 5Linked to original sources
PubMed1981

Influence of age and sex on five human plasma lysosomal enzymes assayed by automated procedures.

Automated fluorimetric procedures for the assay of five lysosomal glycohydrolases-beta-N-acetylglucosaminidase; beta-galactosidase; beta-glucuronidase; alpha-mannosidase; alpha-fucosidase-in human plasma were set up. A Carlo Erba autoanalyser CLA 1500, provided with a sampler refrigerating unit and connected with a recording Turner Mod 111 fluorimeter was employed. The automated procedures, under the established optimal conditions, proved to be highly accurate and reproducible. Using the automated assay procedures the effect of sex and age on the plasma levels of the same enzymes was studied. 1273 randomly selected health subjects were studied. No sex differences were observed for all the enzymes studied with the exception of beta-glucuronidase which displayed higher values (about 30%) in males from 25 to 60 years. The developmental profiles of all enzymes in females and males were similar and characterised by: (a) absolute maximum level in the umbilical cord blood; (b) absolute minimum level at 10-14 years; (c) decrease to a second minimum occurring around 35 years (not displayed by beta-galactosidase and by beta-glucuronidase in males); (e) slow further increase up to the elderly level which was then maintained till the oldest age examined, 74 years.

Acetylglucosaminidase↗
PubMed1980

Enzymes of lysosomal origin in human plasma and serum: assay conditions and parameters influencing the assay.

The condition for maximal activity (pH, buffer, saturating substrate concentration, range of linear relationships between enzyme activity versus incubation time, and versus enzyme concentration) in the fluorimetric assay of several glycohydrolases of lysosomal origin in human plasma and serum have been established. The following enzymes were studied: alpha-galactosidase, beta-galactosidase, beta-N-acetylglucosaminidase, beta-glucosidase, beta-glucuronidase, alpha-mannosidase, alpha-fucosidase. All examined enzymes turned out to be more or less unstable upon storage at 37 degrees C, 4 degrees c, and -20 degrees C in both serum and plasma. The only exceptions were beta-glucuronidase, which was stable in plasma and serum, and alpha-fucosidase which was stable only in plasma. Generally the degree of instability was greater in serum than in plasma. The levels of some enzymes (alpha-galactosidase, beta-galactosidase, beta-N-acetyl glucosaminidase, beta=glucuronidase) were markedly higher in serum than in plasma; conversely the levels of the same enzymes in "platelet free" serum equalled those in plasma. This stresses the necessity to use freshly prepared plasma for lysosomal glycohydrolase assay. Under the procedural conditions recommended for the assay the methods for the determination of lysosomal glycohydrolases in plasma appeared to be simple, sensitive and reproducible.

Acetylglucosaminidase↗
PubMed1979

Optimal conditions for the assay of fibroblast neuraminidase with different natural substrates.

A method for the assay of neuraminidase in human cultured fibroblasts has been worked out. The substrates, all naturally occurring, were: sialyloligosaccharides (alpha(2 lead to 3)sialyllactose, alpha(2 leads to 6)sialyllactose, disialyllactose), sialylglycoplipids (disialogangliosides GD1a and GD1b), sialylglycoproteins and sialylglycopeptides (ovine submaxillary glycoprotein and its pronase-glycopeptides). The method was based on the determination of the enzymically liberated N-acetylneuraminic acid (NeuAc) by a chromatographic-colorimetric microprocedure. The enzyme acted on sialyloligosaccharides and, in the presence of Triton X-100, on gangliosides, while it did not appreciably affect sialylglycoproteins and sialylglycopeptides. The optimum pH was 4.0 for all tested substrates; the Km values were higher for sialyloligosaccharides (about 10(-3) M), lower for gangliosides (about 10(-4) M); the apparent maximum velocity was higher with alpha(2 leads to 3)sialyllactose (400 mU/mg protein); the reaction rate was linear with time for up to 2 h, and with up to 0.6 mg of enzymic protein. The assay method proved to be sufficiently sensitive (3-4 nmol liberated NeuAc), simple, and reproducible (mean activity on pooled fibroblasts with alpha(2 leads to 3)sialyllactose: 400 mU +/- 6 S.E.).

Cells, Cultured↗
PubMed1978

Studies on brain cytosol neuraminidase. II. Extractability, solubility and intraneuronal distribution of the enzyme in pig brain.

The origin and properties of cytosolic neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18) from pig brain were studied. 1. The brain extracts containing the cytosol derived from neuronal bodies and glial cells carry 0.69 munits neuraminidase/g fresh tissue. The behaviour of neuraminidase during extraction closely paralleled that of authentic cytosolic enzyme, lactate dehydrogenase; whereas, it differed from that of the lysosomal enzymes, beta-hexosaminidase and beta-galactosidase, also found in the extracts. 2. Nerve endings from either crude or purified preparations, when treated by hypoosmotic shock, released neuraminidase activity up to a maximum of 1.25 munits/g fresh tissue. The behaviour of releasable neuraminidase was always identical to that of lactate dehydrogenase and very similar to that of ATPase and acetylcholinesterase. Typical lysosomal enzymes, however, such as beta-galactosidase and beta-hexosaminidase, behaved differently under the same conditions. This neuraminidase activity is thought to be derived from the cytosol of nerve endings. 3. The specific activity of neuraminidase in nerve-ending cytosol is 15--20 times that in neuronal body and glial cell cytosol. Some properties (pH, Km value, V/t relationship) of the cytosolic enzymes of different origin are similar; others (stability on standing at 4 degrees C; resistance to freezing and thawing) are different. Hypoionic solutions caused both cytosolic neuraminidases to slowly precipitate and to assume a stable insoluble form which was still active.

Animals↗