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Biomedical subjects

B Mai

Publications and source records attributed to B Mai.

28 records · Page 2Linked to original sources
PubMed1994

Isolation of a granulocyte inhibitory protein from uraemic patients with homology of beta 2-microglobulin.

Increased incidence of infection in uraemic patients is mainly caused by granulocyte dysfunction. Recently we discovered a granulocyte inhibitory protein (GIP I) in the ultrafiltrate of haemodialysis patients, that inhibits four fundamental functions of polymorphonuclear leukocytes (PMNLs). We now report on the isolation of a further polypeptide in end-stage renal disease patient ultrafiltrate using a polyamide filter with biological activity inhibiting healthy PMNL function in vitro. This protein (GIP II) has a molecular weight of about 9500 Da. In-vitro nanomolar concentrations inhibit PMNL O2- production and glucose uptake stimulated by phorbol-myristate-acetate (PMA), but not by formyl-methionyl-leucyl-phenylalanine (FMLP). In-vitro studies were performed to compare the effects of GIP I and GIP II on several PMNL functions. In contrast to GIP II, GIP I inhibits only FMLP-, but not PMA-stimulated PMNL glucose uptake. The NH2 terminal amino acid sequence (21 amino acids) of GIP II shows homology to beta 2-microglobulin. Commercially available intact beta 2-microglobulin had no effect on PMNL glucose uptake and O2- production. The beta 2-microglobulin homologue protein isolated from plasma ultrafiltrates of uraemic patients cross-reacts with three different commercially available assays for intact beta 2-microglobulin. Therefore, beta 2-microglobulin levels measured in the plasma ultrafiltrates of regular haemodialysis patients are overestimated with contribution of an uncertain amount of the beta 2-microglobulin homologue protein (GIP II).

Amino Acid Sequence↗
PubMed1993

Identification of a protein from Saccharomyces cerevisiae with E2F-like DNA-binding and transactivating properties.

The promoter of the human proto-oncogene MYC has been the first cellular target shown to be subject to regulation by the E2F transcription factor. E2F also has binding sites in other promoters regulated by cell proliferation and during the cell cycle. We have analyzed Saccharomyces cerevisiae for the presence of an E2F-analogous protein. GAL1-based promoter constructs carrying the E2F binding site of the MYC or the adenovirus E2 promoter showed transcriptional activity in yeast cells. A DNA-binding factor, designated YE2F, binds specifically to the E2F consensus sequence and was partially purified from yeast extracts. YE2F showed identical contact points within the MYC binding site as authentic E2F protein from mammalian cells. The results suggest that the existence of an E2F-like protein in the yeast S. cerevisiae.

Amino Acid Sequence↗
PubMed1993

Normalization of enhanced neutrophil cytosolic free calcium of hemodialysis patients by 1,25-dihydroxyvitamin D3 or calcium channel blocker.

Patients undergoing regular hemodialysis treatment display elevated intracellular free calcium and impaired glucose uptake in polymorphonuclear leukocytes (PMNLs) in the presence of enhanced serum parathyroid hormone (PTH) levels. Normalization of intracellular calcium can be achieved by different therapeutic interventions acting by different mechanisms. Effective oral 1,25-dihydroxyvitamin D3 therapy (0.5-1.0 microgram/day) normalizes PMNL cytosolic calcium via suppression of PTH levels. Hemodialysis patients treated orally with the calcium channel blocker nitrendipine (20-40 mg/day) normalizes calcium without affecting serum PTH levels. Both therapeutic interventions improved glucose uptake and displayed no synergistic effect.

Blood Glucose↗
PubMed1992

Effect of hemodialysis on intracellular calcium in human polymorphonuclear neutrophils.

Hemodialysis (HD) leads to neutrophil activation depending on the membrane material used. Calcium plays a major role in PMN function and metabolism. A rise of cytosolic free calcium [Ca2+]i is an important intracellular messenger for neutrophils. In this study we measured intracellular resting Ca2+ and the chemotactic peptide FMLP-stimulated intracellular Ca2+ during HD using membranes made of polysulfone and polymethylmethacrylate (PMMA). Also, we investigated the effect of continuous infusion of nifedipine in a dose of 18 micrograms/kg/h during HD with PMMA. Only HD with PMMA causes an increase of both resting and FMLP-stimulated [Ca2+]i after 30 min of starting HD. Polysulfone did not affect [Ca2+]i. Continuous infusion of nifedipine during HD with PMMA completely inhibited these changes of [Ca2+]i. Although the existence of voltage-sensitive calcium channels has not been proved, the present data provide further indirect evidence either for the existence of calcium channels or for a mechanism of action that is independent of antagonism.

Calcium↗
PubMed1991

A novel divergently transcribed human histone H2A/H2B gene pair.

A genomic clone containing a novel closely linked human histone H2A/H2B gene pair has been isolated and sequenced along with extensive 5' and 3' flanking regions. Both genes are devoid of introns and code for core histone proteins. The nucleotide sequences are 84% and 87% homologous to the coding regions of a human genomic H2A and H2B gene, respectively. A comparison of the nucleotide-derived amino acid sequences shows that the histone H2A protein corresponds to the human H2A.1 subtype, whereas the H2B histone gene predicts an H2B protein sequence which is almost identical to the histone H2B.2 variant from human and bovine obtained by direct protein sequencing. The 3' flanking regions contain previously identified conserved sequence elements thought to be involved in transcription termination and processing of replication-dependent histone gene poly(A)- mRNAs. Primer extension analyses of the histone mRNAs encoded within this clone demonstrate that both genes are divergently transcribed from a 313 bp intergene promoter region. The spatial arrangement and orientation of two TATA-boxes, four CAAT-boxes, and one H2B-box within this region suggests that the linked genes share common promoter elements for transcriptional regulation.

Amino Acid Sequence↗
PubMed1985

Unresponsiveness to experimental allergic encephalomyelitis in Lewis rats pretreated with complete Freund's adjuvant.

A single injection of complete Freund's adjuvant blended with aluminum hydroxide gel (ALU-CFA) was successfully used to prevent clinical as well as histologic experimental allergic encephalomyelitis (EAE) in Lewis rats for more than 330 days. Adjuvant preparations with Mycobacterium tuberculosis were more potent than those with Mycobacterium butyricum. Neither the removal of the ALU-CFA inoculum nor a splenectomy 1 month after immunization arrested the adjuvant induced unresponsiveness. However cyclophosphamide restored responsiveness in more than half of the treated animals when applied 2 days before the encephalitogenic challenge at a dose of 20 mg/kg. Passive EAE was not prevented by the ALU-CFA pretreatment. The disease was induced by the transfer of 4 X 10(6) T lymphocytes of a cell line reactive against myelin basic protein. This indicates that the adjuvant prevents EAE at the inductive rather than at the effector phase of the autoimmune response.

Age Factors↗
PubMed1980

The influence of testosterone on the alkaline proteolytic activity in rat skeletal muscle.

The effects of testectomy and subsequent administration of testosterone propionate on the activity of the alkaline proteinases in rat skeletal muscle were investigated. Castration of the mature rat was followed by a short-term delay in protein accretion in skeletal muscle tissue as measured by the protein/DNA ratio and was paralleled by a 2-3-fold increase in specific activity of the alkaline proteinase(s). This increase of proteolytic activity was equally significant when expressed relative to microgram DNA. Although the gain in body weight was significantly lower in the castrated rats, nevertheless the protein/DNA ratio in muscle after 6 weeks approximated the values of sham-operated control rats without normalization of the proteolytic activity. Treatment of the castrated rats with testosterone propionate resulted in restoring normal levels of previously elevated levels of alkaline proteolytic activity in muscle tissue. The normalization of enzyme activity as well as protein accretion in muscle was dose-dependent. Treatment of the rats with a low dose (0.1 mg/day) of testosterone propionate failed to restore the proteolytic activity, but led to a small increase of th protein/DNA ratio as well as to a progressive increase in body weight. These data indicate a regulatory role of testosterone in the adaptive behaviour of the alkaline proteolytic system in rat skeletal muscle.

Animals↗