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Biomedical subjects

G N Morris

Publications and source records attributed to G N Morris.

30 records · Page 2Linked to original sources
PubMed1992

Biochemical studies on the juvenile form of ceroid-lipofuscinosis.

Accumulation of oligosaccharyl diphosphodolichols (oligo-PP-Dol) in brains of patients with various forms of ceroid-lipofuscinoses (CL) is one of the most reproducible biochemical changes known so far. The objective of this study is to understand the biochemical basis of this observation. The biosynthesis of oligo-PP-Dol was studied by the incorporation of labelled glucose from UDP [14C]glucose into oligo-PP-Dol in cultured skin fibroblasts, and showed no changes in the level of synthesis. The level of labelled glucose incorporated into glycoproteins was also unchanged, suggesting that there is no decrease in the oligosaccharide transfer to proteins in this disorder. Since the biosynthesis and utilization of oligo-PP-dol are unaffected, a defect in the catabolism may be the only possibility for the storage of this compound in CL. Since terminal mannose residues are present in the accumulating oligo-PP-Dol, mannosidase activities at pH 4.4 and 6.0 were determined in cultured skin fibroblasts. Both mannosidase activities were unchanged in skin fibroblasts of juvenile CL. Endo-beta-N-acetylglucosaminidase-1 activities were determined in cultured skin fibroblasts using dansylated Man6GlcNAcGlcNAc-Asn as substrate. In three patients, a drastic reduction in the level of the pH 4.5 enzyme was shown, while the neutral pH enzyme activity was unaffected. A deficiency of the endo-beta-N-acetylglucosaminidase-1 will not only explain the accumulation of oligo-PP-Dol but also the known storage of high-mannose glycoproteins.

Carbohydrate Sequence↗
PubMed1991

Dolichol levels during development and ageing of Drosophila melanogaster.

1. Dolichol levels in the fruit fly, Drosophila melanogaster were determined at the larva and pupa stages and in 1, 10, 20 and 30-day-old flies. 2. Free dolichol increased from 1.2 micrograms/g wet weight in the larvae to 14.9 micrograms/g in 30-day-old flies, while total dolichol increased from 3.4 micrograms/g in the larvae to 21.2 micrograms/g at 30-days-old. 3. Dolichol released after saponification is primarily from dolichyl fatty acid ester, which accounts for up to 65% of the total dolichol. 4. The major dolichol homologs, which remain relatively constant throughout development and ageing in D. melanogaster, are C-80, C-85 and C-90, which represent approximately 7%, 60% and 33%, respectively.

Aging↗
PubMed1990

Phosphorylated dolichols in aging.

The age-associated changes in the levels and synthesis of dolichyl phosphate and dolichyl diphosphate derivatives were investigated in brain and liver of 057B1/NNia mice. The total chloroform/methanol (2:1, v/v)-extractable phosphorylated dolichols of brain increased from 1.01 micrograms/g at 3 months to 5.22 micrograms/g at 28 months of age. The long-chain dolichyl diphosphate oligosaccharide (Dol-PP-oligo) levels of brain increased from 0.82 microgram/g in 3 months to 2.8 micrograms/g in 28-month-old animals. However, in liver and in kidney, the levels of these components were unaffected by age. Incorporation of labelled glucose from UDP-glucose into dolichyl phosphate glucose and Dol-PP-oligo in brain microsomes was unaffected by age, whereas, in liver microsomes, the rates of synthesis of both components increased by 50-150%. The increased rate of synthesis and lack of accumulation of Dol-PP-oligo in liver suggest an active utilization and/or catabolism of these glycoprotein precursors. The accumulation of Dol-PP-oligo in aging brain may reflect its decreased utilization for N-glycosylation and/or reduced catabolism.

Aging↗
PubMed1987

A micromethod for the estimation of blood dolichol.

A micromethod for the estimation of dolichol in blood was developed using high performance liquid chromatography. This method can be applied to whole blood or plasma. With detector sensitivity set at 0.005 Absorbance Unit Full Scale, samples as little as 50 microliter are sufficient to carry out the determination. Blood samples from the tail vein of inbred strains of C57 BL/6 NNia-1 mice 3, 6, 12 and 24 mo of age were examined. Blood dolichol levels decreased with age from 163.3 ng/ml at 6 mo to 110.1 ng/ml at 24 mo. The major dolichol homologs were C-85 (10.4%), C-90 (41.6%), C-95 (38.0%) and C-100 (8.1%).

Age Factors↗
PubMed1986

Steroid desmolase synthesis by Eubacterium desmolans and Clostridium cadavaris.

The synthesis of a steroid desmolase was demonstrated in two obligate anaerobes: a new bacterial species, Eubacterium desmolans, isolated from cat fecal flora, and Clostridium cadavaris, recovered from sewage of New York City. The enzyme cleaves the C-17-C-20 bond of corticoids possessing hydroxyl functions at C-17 and C-21. The conversion is quantitative, provided the substrate concentration is less than 100 micrograms/ml and the organisms are in the log phase. The velocity of transformation parallels the bacterial growth curve and in the log phase is higher for E. desmolans than for C. cadavaris. In addition, both organisms synthesize a 20 beta-hydroxysteroid dehydrogenase.

20-Hydroxysteroid Dehydrogenases↗
PubMed1984

Biosynthesis of androgen from cortisol by a species of Clostridium recovered from human fecal flora.

A hitherto unknown species of Clostridium, provisionally designated strain 19, was isolated from the fecal flora of a healthy human adult. This strain synthesizes a constitutive desmolase that cleaves the side chain of cortisol to form 11 beta-hydroxy-4-androstene-3,17-dione. The enzymatic conversion is best demonstrated in supplemented peptone broth and in prereduced brain-heart infusion broth. The fecal concentration of strain 19 is 10(7)-10(8) cells/g. The strain adapts with difficulty to growth on Mueller-Hinton agar and Columbia agar base; colony formation is enhanced by the addition of 5% sheep blood. The organism is sensitive to penicillin G and resistant to tetracycline, chloramphenicol, clindamycin, and erythromycin.

Androstenedione↗
PubMed1984

Mode of action of steroid desmolase and reductases synthesized by Clostridium "scindens" (formerly Clostridium strain 19).

A recently isolated hitherto unknown Clostridium from human feces, designated Clostridium "scindens" (formerly strain 19), synthesizes at least two enzymes active on the side-chain of the steroid molecule and two enzymes active on the hydroxyl groups of the 7-position of bile acids. Steroid desmolase, responsible for side-chain cleavage of corticoids, and 20 alpha-hydroxysteroid dehydrogenase have not been detected in any other bacterial species of the resident colonic flora. Steroid desmolase is Eh-dependent (optimum ca. -130 mV), requires a hydroxy group at C-17, and preferably an alpha-ketol group in the side-chain; an alpha-hydroxy group at C-20 reduces and a beta-hydroxy group at C-20 prevents side-chain cleavage. With suitable substrates, the yield of C-19 steroids is proportional to the bacterial multiplication rate. 20 alpha-Hydroxysteroid dehydrogenase (20 alpha-HSDH) is also Eh-dependent (optimum ca. -300 mV) and reduces the C-20 keto function to an alpha-hydroxy group, regardless of the presence or absence of a hydroxy group at C-17. 7 alpha-Dehydroxylase metabolizes cholic and chenodeoxycholic acid, while 7 beta-hydroxysteroid dehydrogenase acts upon ursodeoxycholic acid. The latter two enzymes are not specific for C. scindens.

Bile Acids and Salts↗
PubMedDate not supplied

The 21-acetylation of corticosteroids by Clostridium sporogenes.

A strain of Clostridium sporogenes, an anaerobic bacterium, isolated from sewage in New York City synthesizes two constitutive enzymes with action on steroid molecules: (i) an enzyme capable of selectively acetylating the 21-hydroxyl function of certain steroids and (ii) the corresponding esterase. Under our experimental conditions the enzymes have a strict structural requirement for 3-keto-4-ene and C-20-keto or 20 alpha-hydroxyl group and convert their respective substrates to a mixture of free and acetylated products.

Acetylation↗