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Biomedical subjects

A Bollen

Publications and source records attributed to A Bollen.

197 records · Page 11Linked to original sources
PubMedDate not supplied

Secretion of glycosylated human recombinant haptoglobin in baculovirus-infected insect cells.

Human haptoglobin (Hp alpha 2 beta) was synthesized in insect cells using the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV) as an expression vector. Viruses carrying the proHp alpha 2 beta cDNA, either fused or non fused to viral polyhedrin DNA sequences, expressed intracellularly low levels of unglycosylated and non maturated haptoglobin. On the contrary, recombinant viruses containing the preproHp alpha 2 beta cDNA directed the expression of high levels of prohaptoglobin. To a large extent, the uncleaved product was found in the culture medium as a glycosylated molecule. Despite the lack of maturation into subunits, the secreted recombinant prohaptoglobin was able to bind hemoglobin in vitro, although less efficiently than plasma-derived haptoglobin.

Amino Acid Sequence↗
PubMedDate not supplied

Total DNA synthesis and cloning in Escherichia coli of a gene coding for the human growth hormone releasing factor.

A DNA containing a sequence coding for the human growth hormone releasing factor (hGRF) has been obtained by enzymatic assembly of chemically synthesized DNA fragments. The synthetic gene consists of a 140 base-pair fragment containing initiation and termination signals for translation and appropriate protruding ends for cloning into a newly constructed plasmid vector (pULB1219). Eleven oligodeoxyribonucleotides, from 14 to 31 bases in length, sharing pairwise stretches of complementary regions of at least 13 bases were prepared by phosphotriester solid-phase synthesis. The DNA sequence was designed to take into account the optimal use of E. coli codons. Oligomers were annealed in one step and assembled by ligation. The DNA fragment of the expected size (140 bp) was recovered and cloned into the pULB1219 vector. The expected sequence was confirmed by DNA sequencing.

Amino Acid Sequence↗
PubMedDate not supplied

A multi-institutional retrospective study of intracranial ependymoma in children: identification of risk factors.

PURPOSE: The goal of this multi-institutional retrospective study of children with intracranial ependymoma was to identify risk factors associated with unfavorable overall survival (OS) and event-free survival (EFS). PATIENTS AND METHODS: Clinical data, including demographics, tumor location, spread, histology, details of surgery, radiation treatment, and chemotherapy were collected. Clinical characteristics and univariate and multivariate analyses of risk factors for OS and EFS are presented. RESULTS: Eleven U.S. institutions contributed 83 patients treated from 1987 to 1991. The OS at 5 and 7 years was 57% and 46%, and EFS at 5 and 7 years was 42% and 33%. Patients 3 years of age or younger differed from the older group by more common infratentorial location, less common gross total resection (GTR), and postoperative use of chemotherapy rather than radiation. This younger group of patients had worse survival (P < 0.01) than the older age group. Other than young age, less than GTR and World Health Organization (WHO) II grade 3 histology were significant adverse risk factors for EFS in univariate and multivariate analyses. OS shared the same adverse risk factors except for histology in multivariate analysis, which was only of borderline significance (P = 0.05). Progression at the original tumor location, present in 89% of patients, was the major pattern of tumor recurrence. Adjuvant chemotherapy in the group older than 3 years or craniospinal radiation in M0 patients did not significantly change EFS. CONCLUSIONS: Adverse outcome in childhood intracranial ependymoma is related to age (3 years or younger), histology (grade 3), and degree of surgical resection (less than GTR). New approaches, particularly for local tumor control in younger patients, are needed to improve survival.

Brain Neoplasms↗
PubMedDate not supplied

Pharmacological and functional characterisation of the wild-type and site-directed mutants of the human H1 histamine receptor stably expressed in CHO cells.

A cDNA clone for the human histamine H1 receptor was isolated from a lung cDNA library and stably expressed in CHO cells. The recombinant receptor protein present in the cell membranes, displayed the functional and binding characteristics of histamine H1 receptors. Mutation of Ser155 to Ala in the fourth transmembrane domain did not significantly change the affinity of the receptor for histamine and H1 antagonists. However, mutation of the fifth transmembrane Asn198 to Ala resulted in a dramatic decrease of the affinity for histamine binding, and for the histamine-induced polyphosphoinositides breakdown, whereas the affinity towards antagonists was not significantly modified. In addition, mutation of another fifth transmembrane amino acid, Thr194 to Ala also diminished, but to a lesser extent, the affinity for histamine. These data led us to propose a molecular model for histamine interaction with the human H1 receptor. In this model, the amide moiety of Asn198 and the hydroxyl group of Thr194 are involved in hydrogen bonding with the nitrogen atoms of the imidazole ring of histamine. Moreover, mutation of Thr194 to Ala demonstrated that this residue is responsible for the discrimination between enantiomers of cetirizine.

Amino Acid Sequence↗
PubMedDate not supplied

[Mutagenesis of the human histamine H1 receptor and design of new antihistamine agents].

The binding cavity of histamine and histamine antagonists is explored using site directed mutagenesis of the human histamine H1 receptor and the amino acids involved in ligand binding are identified. Whereas Asp107 and Phe199 are important for both agonists and antagonists, two additional amino acids (Asn198 and Trp103) are required for efficient histamine binding. The binding site of antagonists is best defined as resulting from a strong ionic bond to Asp107, an orthogonal interaction between one of the aromatic rings with Phe199, and probably a hydrophobic interaction between the second aromatic ring and the lipophilic amino acids of the upper part of TMIV and TMV. This is consistent with structure-activity data of most described antagonists.

Amino Acid Sequence↗