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Biomedical subjects

X Zhu

Publications and source records attributed to X Zhu.

At least 703 records · Page 39Linked to original sources
PubMed1993

Effect of gangliosides on diacylglycerol content and molecular species in nerve from diabetic rats.

The effects of ganglioside treatment on 1,2-diacylglycerol content and on molecular species in 1,2-diacylglycerol, phosphatidic acid and total diacylglycerolipids, as well as Na+,K(+)-ATPase activity, were examined in sciatic nerves from streptozotocin-induced diabetic rats. Beginning 2 weeks after induction of diabetes, animals were administered mixed bovine brain gangliosides, AGF1, an inner ester derivative of this mixture, or saline for 5 weeks. The levels of 1,2-diacylglycerol and arachidonoyl-containing molecular species in age-matched non-diabetic animals were not affected by ganglioside treatment. In nerves from saline-treated diabetic animals, 1,2-diacylglycerol levels were not reduced, but both Na+,K(+)-ATPase activity and all arachidonyl-containing species except for 18:0/20:4 1,2-diacylglycerol were significantly decreased. The content of 1,2-diacylglycerol was lowered by 23 and 16% in bovine brain ganglioside and AGF1-treated diabetic animals, respectively, and the quantity of 18:0/20:4 1,2-diacylglycerol was also selectively reduced. Ganglioside administration did not affect the diminished levels of arachidonoyl-containing molecular species in 1,2-diacylglycerol, phosphatidic acid or diacylglycerolipids in nerve from diabetic rats. In the same nerves, bovine brain gangliosides partially and AGF1 completely restored Na+,K(+)-ATPase activity. The results suggest that gangliosides depress the content of total 1,2-diacylglycerol and the quantity of 18:0/20:4 1,2-diacylglycerol, specifically, in diabetic nerve. The possible relationship between the corrective action of gangliosides on Na+,K(+)-ATPase activity and the effect of these substances on 1,2-diacylglycerol molecular species composition and metabolism is discussed.

Animals↗
PubMed1993

Methionine enkephalin-like immunoreactivity, substance P-like immunoreactivity and beta-endorphin-like immunoreactivity post-mortem stability in rat pituitary.

Significant post-mortem changes in peptide concentration occur within the previously unstudied timeframe, i.e. within 1 h, for the proenkephalin A, proopiomelanoccortin, and tachykinin neuropeptidergic systems in the pituitary. These data differ from data obtained in other studies that concluded that peptides are stable for up to 72 h post-mortem. The post-mortem stability of the three neuropeptides, methionine enkephalin, substance P, and beta-endorphin, was studied in the rat pituitary to test the hypothesis that significant post-mortem concentration changes of those three neuropeptides occur in the immediate post-mortem time period.

Animals↗
PubMed1993

Molecular species composition of glycerophospholipids in rat sciatic nerve and its alteration in streptozotocin-induced diabetes.

The molecular species composition of glycerophospholipid classes in nerves of normal and experimentally diabetic rats was determined. sn-1,2-Diacylglycerol (DAG) moieties of purified phospholipids were liberated enzymatically and analyzed as the benzoate derivatives by high-performance liquid chromatography. The most abundant molecular species in phosphatidylinositol (PI) from normal nerve were 18:0/20:4 (54%) and 16:0/18:1 (17%), whereas in phosphatidylcholine (PC), 16:0/18:1 (52%), 16:0/16:0 (12%) and 18:0/18:1 (11%) predominated. In phosphatidylethanolamine and ethanolamine plasmalogen, 18:1/18:1, 16:0/18:1 and 18:0/18:1 comprised more than 60% and 75% of the molecular species, respectively. Phosphatidylserine was characterized by a high content of 18:0/18:1 (38%) and a relative abundance of the 18:1/20:0, 18:1/22:0 and 18:1/24:0 molecular species, which together accounted for over 30% of the total. The molecular species profile of phosphatidic acid did not closely resemble that of any other phospholipids or DAG. In diabetic nerve, the molecular species composition of all diacylphospholipids showed a significant decline in the content of one or more arachidonoyl-containing molecular species. The largest decline occurred in PC and the least in PI. Except in PC, 16:0/20:4 was more depressed than 18:0/20:4. In combination with previous analyses of DAG molecular species which showed a similar decline in the content of arachidonoyl-containing molecular species in nerve from experimentally diabetic rats (Zhu, X. and Eichberg, J. (1990) J. Neurochem. 55, 1087-1090), the results suggest that nerve DAG arises largely, but not entirely, from phosphoinositides and that PC could be a significant precursor, especially in diabetic nerve.

Animals↗
PubMed1993

Molecular characterisation of a human aryl sulfotransferase cDNA.

A full-length aryl sulfotransferase cDNA was isolated from a human liver cDNA library. It was 1155 bp long containing a coding region of 885 basepairs encoding a cytosolic protein (M(r) 34178 Da) of 295 amino acids. This human cDNA shared 80% homology to the rat aryl sulfotransferase cDNA, 58% to the bovine and rat oestrogen sulfotransferase cDNAs, 53% to the rat hydroxysteroid sulfotransferase cDNA and 51% to the human liver dehydroepiandrosterone sulfotransferase cDNA over its whole 885 bp coding region. The deduced amino acid sequence of this human cDNA was 79% homologous to that of the rat aryl sulfotransferase cDNA and the putative common-substrate binding site motif GXXGXXK of the sulfotransferases has been conserved in this human amino acid sequence. At least two sizes of this human aryl sulfotransferase mRNA were detected in the human liver and lung.

Amino Acid Sequence↗
PubMed1993

Structural characterization of the rat insulin-like growth factor binding protein-6 gene.

Recently a family of six distinct insulin-like growth factor binding proteins (IGFBPs) have been identified and the gene structures of the first five (IGFBP-1, -2, -3, -4 and -5) characterized. We now isolated the IGFBP-6 gene from a rat genomic library and determined its organization as well as the DNA sequence at the 5' flanking region of the gene. The rat IGFBP-6 gene spans 5.1 kb of the genomic sequence and contains four exons interrupted by three introns of approximately 2.4, 0.2 and 1.2 kb in length, respectively. Primer extension analysis and ribonuclease protection assay using RNA from rat lung tissues demonstrated two transcriptional start sites located at 85 and 82 nucleotides upstream of the ATG translational initiation codon. The promoter region of the rat IGFBP-6 gene is devoid of a TATA or a CAAT consensus sequence motif, but putative regulatory cis elements, including a Sp1, an estrogen receptor binding site and a retinoic acid responsive element, are present in the promoter region.

Amino Acid Sequence↗
PubMed1993

cDNA expression studies of rat liver aryl sulphotransferase.

A cDNA encoding an isoenzyme of rat liver aryl sulphotransferase was isolated from a rat liver bacteriophage Lambda gt 11 library by the polymerase chain reaction technique. The resulting cDNA was functionally expressed in COS-7 cells and characterised by determining the sulphating capacity of the cells with a range of substrates. The COS-expressed enzyme catalysed the sulphation of both phenol and dopamine with Kms of the same order as those obtained for the high affinity isozyme in rat liver cytosol, while low activity was observed with tyrosine methyl ester. The common food additive vanillin was also a good substrate for sulphate conjugation. The sulphation of vanillin catalysed by the COS-expressed enzyme was consistent with a single enzyme system, in contrast, the kinetics of the reaction catalysed by cytosolic sulphotransferase indicated that vanillin was sulphated by more than one isozyme.

Animals↗
PubMed1993

Cloning of the rat insulin- like growth factor binding protein-5 gene and DNA sequence analysis of its promoter region.

To understand the regulation of the insulin-like growth factor binding protein-5 (IGFBP-5) gene expression, we have cloned the IGFBP-5 gene from rat genomic libraries and determined its genomic organization as well as the DNA sequence at the 5' flanking region of the gene. The rat IGFBP-5 gene spans at least 17 kilobases (kb) of the genome and contains 4 exons interrupted by 3 introns of approximately 10, 0.6 and 0.7 kb, respectively. Southern blot analysis of the rat chromosome DNA revealed a single copy gene for IGFBP-5 in the haploid genome. Primer extension experiments demonstrated a single transcriptional start site located at 772 nucleotides 5' of the ATG translational start codon. In addition to a TATA box and a CAAT box, multiple putative cis-regulatory elements, including an AP-1, an AP-2 and a binding site for progesterone receptor are present in the promoter region. This finding suggests that the IGFBP-5 gene is one of those that are expressed in a tissue-specific manner.

Amino Acid Sequence↗
PubMed1993

A luteinizing hormone receptor with a severely truncated cytoplasmic tail (LHR-ct628) desensitizes to the same degree as the full-length receptor.

The wild type murine luteinizing hormone (mLH) receptor, which in its mature form is predicted to be a protein of 674 amino acids (mLHR), and an artificially mutated form lacking the last 46 amino acids (mLHR-ct628) were stably expressed in murine L cells. Both forms stimulated adenylyl cyclase and underwent rapid desensitization. The mutation removed 1 tyrosine, 2 threonines, and 6 serines from the receptor. The results indicate that none of these potential phosphorylation sites participates in either adenylyl cyclase stimulation or receptor desensitization. Our results with the mLHR-ct628 (carboxyl-terminal amino acid sequence CCKHRAEL) differ from those reported recently for the essentially identically mutated rat LHR that lacks the last 43 amino acids (rLHR-ct631 with carboxyl-terminal amino acid composition CCKRRAELYRR). This 43-amino acid truncation was described to have the effect of preventing hormone-induced desensitization. While the reasons for the discrepant results are not known, our results do not support the proposal for a participatory role of the extreme carboxyl terminus of the receptor in its desensitization.

Adenylyl Cyclases↗
PubMed1993

Mass spectrometric analysis of opioid and tachykinin neuropeptides in non-secreting and ACTH-secreting human pituitary adenomas.

In a study to test the hypothesis that defects in the metabolism of neuropeptides might be a contributing factor to human anterior pituitary tumor formation, the proenkephalin A, proopiomelanocortin (POMC), and tachykinin systems, which produce methionine enkephalin (ME), beta-endorphin (BE), and substance P (SP), respectively, were measured in patients who had a wide variety of pituitary tumors. Mass spectrometry was used to optimize the level of molecular specificity of the ME and BE analytical measurements, and radioimmunoassay was used to measure SP-like immunoreactivity (SP-li). Compared to data obtained from pituitaries from post-mortem controls, the non-secreting tumors contained a significantly lower amount of the POMC neuropeptide, BE. The lower ME level was not significant. However, two adrenocorticotrophic hormone (ACTH)-secreting tumors contained ME, BE, and SP-li amounts that were much higher than both the controls and nonsecreting tumors. These data suggest that a hypometabolism of the POMC precursor may be operating in non-secreting tumors, and that a hypermetabolism of the proenkephalin A, POMC, and tachykinin precursors may be operating in two ACTH-secreting tumors. These data demonstrate that mass spectrometry plays a critical role in the study of human pituitary tumors.

Adenoma↗
PubMed1993

Small subunit rRNA sequence of Enterocytozoon bieneusi and its potential diagnostic role with use of the polymerase chain reaction.

In the past several years, microsporidia have become recognized as another important group of opportunistic infections of immunocompromised patients, especially those with AIDS. Enteric infections with the noncultivatable microsporidian parasite Enterocytozoon bieneusi have been diagnosed from AIDS patients with chronic diarrhea, malabsorption, and wasting. The incidence of infection and mechanism of transmission of these organisms in humans is unknown. Several recent tests for human pathogens have been developed using rRNA genes as diagnostic probes. Using the polymerase chain reaction and conserved regions of the small subunit rRNA (SSU-rRNA) gene, the SSU-rRNA gene of E. bieneusi was successfully cloned and subsequently sequenced. Amplification of E. bieneusi rRNA could be demonstrated from intestinal biopsies from HIV-1-infected patients infected with E. bieneusi but not from intestinal biopsies from noninfected patients. This cloned SSU-rRNA gene was used to develop improved probes for detection of E. bieneusi in tissue of infected patients.

AIDS-Related Opportunistic Infections↗