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Biomedical subjects

R K Pullarkat

Publications and source records attributed to R K Pullarkat.

At least 37 records · Page 2Linked to original sources

Bovine brain gray and white matter exhibit differential protein prenyl transferase activity.

Protein farnesyl transferase and geranylgeranyl transferase-I activities were determined in gray and white matter from various regions of bovine brain. Farnesyl transferase activity was 3-8 times greater than geranylgeranyl transferase-I activity. However, farnesyl transferase activity was about 2 times greater in the white matter than in the gray matter in all regions of the brain. Mixing experiments indicated lack of farnesyl transferase activators in white matter. This difference in farnesyl transferase activity may be due to enzyme content and may have implications in brain cell function.

Alkyl and Aryl Transferases↗

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↗

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↗

Hypothesis: prenatal ethanol-induced birth defects and retinoic acid.

A hypothesis is presented to explain the biochemical basis of ethanol-induced birth defects. Prenatal ethanol exposure causes central nervous system and limb abnormalities in humans and in animals. Retinoic acid and didehydroretinoic acid are known to play an important role in the central nervous system and limb developments. Ethanol is known to inhibit the formation of retinoic acid from retinol and deplete hepatic retinoid levels. It is hypothesized that ethanol reduces the levels of retinoic acid in the developing embryo either by inhibiting conversion of retinol to retinoic acid and/or by depleting the level of retinol, thereby causing central nervous system and limb abnormalities.

Alcohol Oxidoreductases↗

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↗

Low molecular weight urinary peptides in ceroid-lipofuscinoses: potential biochemical markers for the juvenile subtype.

Urine from patients with classical and atypical forms of juvenile ceroid-lipofuscinosis (CL) was analyzed for the presence of disease-specific peptides. Two distinct peptide patterns were recognized on lithium dodecyl sulfate polyacrylamide gel electrophoresis in classical juvenile CL patients. Pattern 1 consisted of a single, intensely staining peptide of apparent Mr 2,000, and up to 4 heterogeneous, weakly staining peptides between 2,500 and 6,300 Mr. This peptide pattern was not seen in over 30 samples from patients with other neurodegenerative disorders, nor in normal control individuals. Reduced amounts of the 2,000 Mr peptide were seen in 2 of 3 female heterozygotes whose children had the peptide pattern 1. The presence of large amounts of the 2,000 Mr peptide in urine extracts made patient identification unequivocal. Pattern 2 had 2 to 3 intensely staining peptides of 3,800, 5,000 and 7,000 Mr, a variable number of minor bands, and diffuse staining above 7,000 and below 3,800 Mr. Parents had 2 to 3 weakly staining peptides with molecular weights similar to the major bands seen in the patients. No consistent peptide pattern was seen in 8 patients with atypical CL. Late infantile CL patients had no or very small amounts of low Mr urinary peptides. The urinary components stained well with silver, poorly with Coomassie Blue, and were digested by a nuclease-free protease, as expected for protein. They were distinctly different from the peptides isolated from ovine CL tissues. Amino acid composition analysis showed a predominantly normal spectrum of amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

Brain and liver dolichol in chronic alcoholism: a necropsy study.

Cerebral gray and white matter and liver dolichol levels were measured in postmortem samples from chronic alcoholics and nonalcoholic controls following recent suggestions that dolichol levels may be used as a marker for alcoholism. No significant differences in brain dolichol were found between the control and alcoholic groups. A significant reduction in the liver dolichol was observed in the alcoholic group. This was most marked in those alcoholics with liver disease.

Adult↗

Oligosaccharyl diphosphodolichols in the ceroid-lipofuscinoses.

Autopsy brain samples from patients with late-infantile, juvenile and adult forms of ceroid-lipofuscinosis (CL) and cultured skin fibroblasts from juvenile CL were analyzed for the content of phosphodolichol (P-Dol) related compounds. The levels of P-Dol obtained on treatment with hot dilute acid of the chloroform-methanol (CM 2:1) extract and the chloroform-methanol-water (CMW 1:1:3) extract of the residue were estimated by high performance liquid chromatography. Compared to age-matched control individuals, the levels of P-Dol obtained in both the extracts were increased more than 6.6 times in all the patient samples. Further analysis of the CMW extract indicates that the increased P-Dol is primarily due to oligosaccharyl diphosphodolichol. Cultured skin fibroblasts from the juvenile form of CL show normal level of free dolichol and elevated level of phosphorylated dolichols. Glycoprotein synthesis measured by incorporation of labeled glucosamine show no deficit in the transfer of oligosaccharides from lipids to proteins. A hypothesis is presented to explain the accumulation of oligosaccharyl diphosphodolichol and deficiency of lysosomal proteases in ceroid-lipofuscinosis.

Adolescent↗

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↗

Age-associated increase of free dolichol levels in mice.

Free dolichol levels were determined by high-performance liquid chromatography in liver, brain, heart, lung, testis and kidney of C57 B1/6 mice at 3, 6, 12 and 30 months of age. In all the tissues, free dolichol levels were increased with aging. The largest increase in dolichol was in testis and the smallest increase was in the liver. Among the various tissues, aging testis and kidney showed high levels of free dolichol, and represented more than twice the level of dolichol in brain. The major dolichols among the various tissues were of the 17, 18, 19 and 20 isoprene unit containing types and the proportions were unaffected by aging. Tissues such as brain and testis showed a tendency toward high proportions of longer-chain dolichols , whereas lung and heart showed high proportions of shorter-chain dolichols . This study shows that the age-associated increase in dolichol levels is a general phenomenon and the increases vary widely with tissues.

Aging↗

Accumulation of dolichols in brains of elderly.

Dolichol levels in human brain gray matter increased from 18 micrograms/g in 6-year-old to 263 micrograms/g in 68-year-old human brain gray matter. High performance liquid chromatographic analysis shows dolichols ranging from 14 to 22 isoprene units with 19 isoprene units containing species predominating (approximately 44%). This may be the first report of an appreciable accumulation of a lipid in brains of elderly.

Adolescent↗

Biosynthesis of phosphatidylserine in rat brain microsomes.

1. Rat brian microsomes incorporated L-serine into phosphatidylserine in the presence of 2mM ATP. This reaction was stimulated 2-fold by the addition of phosphatidic acid (0.2 mM) and 5-fold by the addition of nickel (0.5 mM). 2. This phosphatidylserine synthesis was inhibited completely by p-hydroxymercuribenzoate (0.1 mM) and N-ethylmaleimide (1 mM), whereas the Ca2+-dependent phosphatidylserine synthesis was unaffected by these sulfhydryl reagents. 3. The specific activity of the ATP-Ni2+-dependent phosphatidylserine was increased more than 2-fold during active myelination, whereas the Ca2+-dependent system remained unchanged. 4. Preliminary data indicate that pyrophosphatidic acid (p,p'-bis(1,2-diacyl-sn-glycero-3-)pyrophosphate) is the immediate precursor of phosphatidylserine synthesis.

Adenosine Triphosphate↗

Relapsing experimental allergic encephalomyelitis induced with isolated myelin and with myelin basic protein plus myelin lipids.

To test the ability of different spinal cord fractions to reproduce the clinicopathological features of relapsing experimental allergic encephalomyelitis (R-EAE), groups of young guinea pigs were inoculated with: (1) spinal cord myelin; (2) delipidated myelin; (3) reconstituted myelin and (4) MBP plus myelin lipids. The four sets of antigens induced acute EAE in most of the animals tested. During an observation period of 18 months, only one clinical relapse was observed in animals sensitized with myelin and with MBP plus myelin lipids. Extensive CNS demyelination was found in relapsing animals injected with myelin. No demyelinated lesions were observed in non-relapsing animals. By contrast, half of the surviving guinea pigs injected with MBP plus myelin lipids had demyelinated lesions, irrespective of whether they relapsed or not. The inability of the spinal cord myelin fractions to fully reproduce the R-EAE model suggest that other non-myelin antigens may be involved in the pathogenesis of multiple relapses.

Animals↗

Accumulation of ganglioside Gm2 in cerebrospinal fluid of a patient with the variant AB of infantile Gm2 gangliosidosis.

Brain biopsy has been used for the diagnosis of the variant AB of infantile GM2 gangliosidosis. Accumulation of ganglioside GM2 (300 ng of neuraminic acid per milliliter) was observed in the CSF of a patient with this disorder. GM2 was found also in the CSF of a patient with classic Tay-Sachs disease. Normal CSF did not contain any measurable amounts of GM2. In addition, a glycolipid with a mobility, by thin-layer chromatography, similar to that of paragloboside was observed in the CSF of the patient with the variant AB of GM2 gangliosidosis. These findings indicate that the variant AB can be diagnosed by demonstrating accumulation of GM2 in the CSF of patients with normal hexosaminidase activity.

Chromatography, Thin Layer↗

Neuritogenic and chemical properties of guinea pig anterior and posterior root myelin.

In relapsing experimental allergic encephalomyelitis, recurrent demyelination was found in the anterior roots and dorsal root ganglia with minimal involvement of the posterior roots. To determine whether this is an antigen-related phenomenon, the distribution, type and intensity of the lesions in the proximal PNS of guinea pigs immunized with anterior roots or myelin were compared to those of animals immunized with posterior roots or myelin. Homologous anterior roots were less neuritogenic than posterior roots or posterior root myelin. Thin layer chromatography of myelin samples from anterior and posterior roots, dorsal root ganglia and sciatic nerve revealed the presence of a sulfogalactoglycerolipid, tentatively identified as sulfated galactosylglyceride (SGG) in all but the posterior root myelin samples. Although the PNS lesions of relapsing experimental allergic encephalomyelitis appear to recapitulate the regional distribution of SGG, the reason why its presence in anterior roots myelin renders them less neuritogenic is at present not clear.

Animals↗