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Biomedical subjects

H Bender

Publications and source records attributed to H Bender.

At least 73 records · Page 4Linked to original sources
PubMed1994

Cerebrospinal fluid variables in clinically normal foals from birth to 42 days of age.

To determine the effects of age on each analyte, CSF variables were evaluated in healthy foals from birth through 42 days of age. Cerebrospinal fluid was collected from 14 clinically normal, naturally delivered cross-bred foals and was analyzed for glucose, sodium, potassium, magnesium, and total protein concentrations, total and differential WBC counts, RBC count, and lactate dehydrogenase, aspartate transaminase, and creatine kinase activities. Samples were collected in 3 foals < 48 hours old, and at 11 to 14 days of age in 4 foals, 21 to 22 days of age in 3 foals, and 31 to 42 days of age in 4 foals. Each foal was tested only once, to avoid any effects of CSF sample collection on subsequent analysis. Regression analysis confirmed age-related effects on CSF glucose, protein, and magnesium concentrations, but did not indicate an effect of age on CSF sodium and potassium concentrations or cell counts. Results indicate that CSF glucose concentration decreases with age; foals < 2 days old had the highest CSF glucose values, 98.8 +/- 12.0 mg/dl (mean +/- 1 SD). In foals 10 to 14 days old, CSF glucose concentration was 67.3 +/- 12.0 mg/dl, was 65.3 +/- 4.5 mg/dl in foals 21 to 22 days old, was 70.0 +/- 5.4 mg/dl in foals 31 to 42 days old, and was 51.1 +/- 2.5 mg/dl in adults.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1992

Catalytic center of cyclodextrin glycosyltransferase derived from X-ray structure analysis combined with site-directed mutagenesis.

An X-ray structure analysis of a crystal of mutant Asp229----Ala of cyclodextrin glycosyltransferase from Bacillus circulans (Ec 2.4.1.19) that had been shortly exposed to beta-cyclodextrin showed density corresponding to a maltose bound at the catalytic center. The crystal structure was refined to an R-factor of 18.7% at 2.5-A resolution. The catalytic center is defined by homology with the structurally known alpha-amylases and by the observation that mutants Asp229----Ala and Asp328----Ala are almost inactive. By model building, the density-defined maltose was extended to a full beta-cyclodextrin, which then indicated the general locations of seven subsites for glucosyl units. The catalytically competent residues Asp229, Glu257, and Asp328 are at the reducing end of the density-defined maltose. In the unligated wild-type structure, Glu257 and Asp328 form a 2.6-A hydrogen bond between their carboxylates in an arrangement that resembles those of the catalytically competent carboxylates in acid proteases. Presumably, the first catalytic step is an attack of the proton between Glu257 and Asp328 on the oxygen of the glycosidic bond.

Bacillus↗
PubMed1992

Immunotherapy of human glioma xenografts with unlabeled, 131I-, or 125I-labeled monoclonal antibody 425 to epidermal growth factor receptor.

Monoclonal antibody (mAb) 425 (IgG2a) binds to the external domain of the epidermal growth factor receptor. This determinant is highly expressed by human glioma tissues but rarely by normal brain tissues, and is absent on peripheral blood lymphocytes and bone marrow cells. The mAb exerts variable cytotoxic effects against cultured human glioma cells in conjunction with human and murine effector cells. Inhibition of growth of s.c. glioma xenografts in nude mice by the mAb may be mediated by murine macrophages or may be related to the capacity of the mAb to antagonize growth stimulation of glioma cells by epidermal growth factor. In approaches to radioimmunotherapy of human glioma with mAb 425, the 125I-labeled mAb 425 exhibited more significant antitumor effects than the 131I-labeled mAb both in vitro and in vivo in xenotransplanted nude mice. These differences may be due to enhanced nuclear damage caused by 125I-labeled versus 131I-labeled fragments following their internalization into the glioma cells. Our studies provide the rationale for immunotherapy of glioma patients with either unlabeled or 125I-labeled anti-epidermal growth factor receptor mAb 425.

Animals↗
PubMed1992

Enhancement of epidermal growth factor receptor expression on glioma cells by recombinant tumor necrosis factor alpha.

Recombinant tumor necrosis factor alpha (rTNF alpha; optimal dose 1000 U/ml) significantly increased the density of epidermal growth factor receptor (EGF-R) in three of four glioma cell lines in culture as determined by binding analysis of anti-EGF-R monoclonal antibody (mAb) 425. Since enhancement of EGF-R expression by rTNF-alpha was inhibited when cells were treated with the protein synthesis inhibitor cycloheximide, the effects of rTNF alpha may be protein-synthesis-dependent. The dose of rTNF alpha that was optimal for up-regulation of EGF-R on glioma cells did not inhibit the growth of these cells. 125I-labeled mAb 425 lysed glioma cells in culture following its internalization into the cells. After glioma cells had been treated with rTNF alpha, the growth-inhibitory effects of the mAb were significantly enhanced, probably a reflection of the increase in EGF-R density on the tumor cell surfaces. The rTNF alpha effects were specific to the EGF-R and did not affect unrelated glioma-associated antigens. In our previous clinical trials, 125I-labeled mAb 425 showed immunotherapeutic effects in glioma patients. The present study provides the basis for considerations of combined immunotherapy of glioma patients with 125I-labeled mAb 425 and rTNF alpha.

Antibodies, Monoclonal↗
PubMed1992

Malignant astrocytomas treated with iodine-125 labeled monoclonal antibody 425 against epidermal growth factor receptor: a phase II trial.

Twenty-five patients with primary presentation of malignant astrocytoma, astrocytoma with anaplastic foci, and glioblastoma multiforme were treated with surgical resection and definitive radiation therapy followed by intravenous or intra-arterial administration of Iodine-125 labeled monoclonal antibody-425, which binds specifically to human epidermal growth factor receptor. The patients presented with primary untreated disease, positive contrast enhanced computed tomography scans of the brain, and compatible clinical symptoms. In this Phase II clinical trial, the patients had surgical debulking or biopsy followed by definitively administered external beam radiation therapy and one or multiple doses (35 to 90 mCi per infusion) of radiolabeled antibody. The total cumulative doses ranged from 40 to 224 mCi. The administrations of the radiolabeled antibody were performed in most cases 4-6 weeks following completion of the primary surgery and radiation therapy. Ten patients had astrocytoma with anaplastic foci and 15 had glioblastoma multiforme. No significant life-threatening toxicities were observed during this trial. At 1 year 60% of the patients with astrocytoma with anaplastic foci or glioblastoma multiforme are alive. The median survival for both groups was 15.6 months.

Actuarial Analysis↗
PubMed1992

Immunoluminometric assay of chromogranin A in serum with commercially available reagents.

Chromogranin A (Cg A) is a useful marker of neuroendocrine neoplasia in humans. Here we describe an immunoluminometric assay (ILMA) for measuring Cg A in serum, with use of a new tube as a solid phase. The new tube has a large surface area and is coated with a polyclonal antibody. Optimized coating conditions provide a high IgG adsorption to the polystyrene wall. Serum is added to the coated tube and incubated for 2 h or overnight. After washing the tubes, acridinium ester-labeled monoclonal antibody against Cg A is added and incubation is continued for 2 h. The tubes are washed again and the bound luminescence is measured. The assay is very sensitive (detection limit 1 microgram/L, if 25 microL of serum is used), is specific for human Cg A, and offers a wide dynamic range (1-1000 micrograms/L). The range in healthy humans is 10-53 micrograms/L (median 30 micrograms/L). The correlation of serum Cg A to creatinine and parathyroid hormone is described. We also report the influence of intravenous calcium injection on Cg A concentrations in serum.

Antibodies, Monoclonal↗
PubMed1991

Branched saccharides formed by the action of His-modified cyclodextrin glycosyltransferase from Klebsiella pneumoniae M 5 al on starch.

Digestion of potato starch with His-modified alpha-cyclodextrin glycosyltransferase from Klebsiella pneumoniae M 5 al yielded branched tetra- to nona-saccharides, as revealed by debranching with pullulanase. Maltose and maltotriose stubs preponderated together with small proportions of D-glucose stubs. The branched saccharides accounted for approximately 1.2% of the starch.

Carbohydrate Sequence↗
PubMed1991

On the role of histidine residues in cyclodextrin glycosyltransferase: chemical modification with diethyl pyrocarbonate.

Ethoxyformylation with diethyl pyrocarbonate of approximately 1.5 His residues per molecule of enzyme reduced the cyclising activity of both the alpha-cyclodextrin glycosyltransferase from Klebsiella pneumoniae strain M 5 al and the beta-cyclodextrin glycosyltransferase from Bacillus circulans strain 8 by greater than 90%. Pre-incubation with substrate protected the enzymes from ethoxyformylation. Digestion of starch by the modified enzymes resulted in a delayed formation of cyclodextrins (cyclomalto-oligosaccharides, CDs), but a marked increase in the production of reducing saccharides. Similarly, coupling of alpha CD and maltose and successive disproportionation yielded mainly glucose and malto-oligosaccharides. The results are discussed in the context of the role of conserved His residues for binding of substrate and the transfer reactions.

Amino Acid Sequence↗
PubMed1990

Studies of the mechanism of the cyclisation reaction catalysed by the wildtype and a truncated alpha-cyclodextrin glycosyltransferase from Klebsiella pneumoniae strain M 5 al, and the beta-cyclodextrin glycosyltransferase from Bacillus circulans strain 8.

The actions of the wildtype and a truncated alpha-cyclodextrin glycosyltransferase from Klebsiella pneumoniae strain M 5 al on malto-oligosaccharides showed no significant differences, and there was marked dependence of the kinetic parameters on the chain lengths of the substrate. The action of the beta-cyclodextrin glycosyltransferase from Bacillus circulans was less dependent on the chain length of the substrate, but Vmax of the initial cyclisation with the longer malto-oligosaccharides was only 28% of that determined for the enzyme of K. pneumoniae. The rate parameters suggested that the active site of each enzyme spans nine glucosyl residues, and that the catalytic sites are situated between subsites three and four for the K. pneumoniae enzymes and between subsites two and three for the B. circulans enzyme. The molecular binding affinities and the affinities of the 9th subsite were calculated from the rate parameters. The primary and tertiary structures of alpha-amylases and cyclodextrin glycosyltransferases are compared in the context of the reaction mechanism of the latter enzymes.

Bacillus↗
PubMed1990

Vagally induced release of gastrin, somatostatin and bombesin-like immunoreactivity from perfused rat stomach. Effect of stimulation frequency and cholinergic mechanisms.

The isolated stomach of rats was vascularly perfused to measure the secretion of gastrin, somatostatin (SLI) and bombesin-like immunoreactivity (BLI). The gastric lumen was perfused with saline pH 7 or pH 2, and electrical vagal stimulation was performed with 1 ms, 10 V and 2, 5 or 10 Hz, respectively. Atropine was added in concentrations of 10(-9) or 10(-7) M to evaluate the role of cholinergic mechanisms. In control experiments, vagal stimulation during luminal pH 2 elicited a significant increase of BLI secretion only at 10 Hz but not at 2 and 5 Hz. Somatostatin release was inhibited independent of the stimulation frequency employed. Gastrin secretion at 2 Hz was twice the secretion rates observed at 5 and 10 Hz, respectively. At luminal pH 7 BLI rose significantly at 5 and 10 Hz. SLI secretion was decreased by all frequencies. Gastrin secretion at 2 and 5 Hz was twice as high as during stimulation with 10 Hz. Atropine at doses of 10(-9), 10(-8), 10(-7) and 10(-6) M had no effect on basal secretion of BLI, SLI and gastrin. At luminal pH 2, atropine increased dose-dependently the BLI response at 2 and 5 but not at 10 Hz. The decrease of SLI during 2 and 5 Hz but not 10 Hz was abolished by atropine 10(-9) M. SLI was reversed to stimulation during atropine 10(-7) M at all frequencies. The rise of gastrin at 2 Hz was reduced by 50%. At luminal pH 7, atropine had comparable effects with a few differences: the BLI response at 10 Hz was augmented and the gastrin response to 2 and 5 Hz was reduced. In conclusion the present data demonstrate a frequency and pH-dependent stimulation of BLI and gastrin release. The stimulation of BLI is predominantly due to atropine-insensitive mechanisms while muscarinic cholinergic mechanisms exert an inhibitory effect on BLI release during lower stimulation frequencies (2 and 5 Hz) independent of the intragastric pH and also during higher frequencies at neutral pH. Both, atropine sensitive and insensitive mechanisms are activated frequency dependent. The atropine-sensitive cholinergic mechanisms but not the noncholinergic mechanisms involved in regulation of G-cell function are pH and frequency dependent. Somatostatin is regulated largely independent of stimulation frequency and pH by at least two pathways involving cholinergic mechanisms of different sensitivity to atropine. These data suggest a highly differentiated regulation of BLI, gastrin and SLI secretion and the interaction between these systems awaits further elucidation.

Animals↗
PubMed1990

Molecular cloning, nucleotide sequence and expression in Escherichia coli of the beta-cyclodextrin glycosyltransferase gene from Bacillus circulans strain no. 8.

The beta-cyclodextrin glycosyltransferase (beta-CGTase) gene was isolated from a lambda-library prepared from Bacillus circulans strain no. 8. It was subcloned into plasmid pTZ and expressed by its endogenous regulatory sequences in Escherichia coli JM 103. The structural gene was sequenced and showed an open reading frame for a polypeptide of 718 amino acid residues. The recombinant beta-CGTase had the same enzymatic properties as the extracellular CGTase (684 amino acid residues, corresponding to a mol. wt. of 74416) produced by B. circulans strain no. 8. The amino acid sequence showed the highest homology (74.6% identical amino acids) with the CGTase of B. circulans strain F-2, which had been erroneously described as an amylase. The homology with the enzyme from the alkalophilic Bacillus sp. strain no. 1011 was 71.4%. The amino acid sequence derived will be used for elucidating the three-dimensional structure of the enzyme.

Amino Acid Sequence↗
PubMed1990

Prophylactic administration of histamine1 and histamine2 receptor blockers in the prevention of protamine-related haemodynamic effects.

We studied the effects of the prophylactic administration of histamine1 and histamine2 receptor blockers on haemodynamic changes, including systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MBP), central venous pressure (CVP), and heart rate (HR, beats.min-1) before and after the administration of protamine in two groups of patients having coronary artery bypass graft surgery. Group I patients received no histamine blockers, whereas patients in Group II were treated prophylactically with both H1 (diphenhydramine) and H2 (cimetidine) receptor blockers. The mean SBP, DBP, MBP, CVP, and HR before (and after) administration of protamine in group I patients were 114 +/- 16 (90 +/- 16) mmHg, 64 +/- 11 (51 +/- 8) mmHg, 81 +/- 11 (65 +/- 10) mmHg, 10 +/- 3 (11 +/- 7) mmHg, and 92 +/- 10 (87 +/- 13) before (and after) protamine administration. Group II patients had mean SBP, DBP, MBP, CVP, and HR of 113 +/- 19 (113 +/- 17) mmHg, 61 +/- 12 (62 +/- 11) mmHg, 79 +/- 15 (80 +/- 13) mmHg, 9 +/- 3 (9 +/- 2) mmHg, and 88 +/- 6 (86 +/- 4) before (and after) protamine administration. Our data show that only in Group I patients who did not receive histamine receptor blockers, were there significant haemodynamic changes following protamine administration (P less than 0.05). We conclude that the prophylactic administration of histamine receptor blockers prevents some of the adverse haemodynamic effects associated with protamine administration.

Aged↗
PubMed1990

Engineering a heavy atom derivative for the X-ray structure analysis of cyclodextrin glycosyltransferase.

Based on a preliminary structural model of cyclodextrin glycosyltransferase from Bacillus circulans (EC 2.4.1.19), Ser428 and Ser475 of the enzyme were mutated to cysteines in order to produce suitable heavy atom derivatives. Mutant Ser475----Cys could not be expressed as protein. Mutant Ser428----Cys was expressed in Escherichia coli and purified. It crystallized isomorphously and gave rise to a mercury derivative that improved the electron density map. The structural results show that the new mercury-binding site is in a pocket at the protein surface.

Bacillus↗
PubMed1990

Substance P, acetylcholinesterase, and beta-endorphin levels in the plasma and pericardial fluid of patients with and without angina pectoris.

We measured substance P-like immunoreactivity (SPLI), beta-endorphin-like immunoreactivity (BELI), acetylcholinesterase activity, and total protein content in pericardial fluid and plasma of patients with angina pectoris and patients with no angina pectoris. SPLI and BELI levels, acetylcholinesterase activity, and total protein content were determined by radioimmunoassay, a colorimetric method, and by the method of Lowry et al. (J Biol Chem 1951; 193:265-75), respectively. In the pericardial fluid, patients with angina had SPLI, BELI, acetylcholinesterase, and total protein values of 1.69 +/- 0.23 fmol/mg protein, 0.16 +/- 0.13 fmol/mg protein, 0.06 +/- 0.02 units, and 25.7 +/- 3.2 mg/ml, respectively. Patients with no angina had SPLI, BELI, acetylcholinesterase, and total protein values of 0.93 +/- 0.17 fmol/mg protein, 0.19 +/- 0.10 fmol/mg protein, 0.16 +/- 0.02 units, and 44.6 +/- 5.3 mg/ml, respectively. SPLI levels were significantly higher (p less than 0.03), and acetylcholinesterase (less than 0.002) and total protein content (less than 0.004) were significantly lower in the pericardial fluid of patients with angina when compared with those of patients with no angina. BELI levels were not significantly different between the two groups. In the plasma, no significant differences were found in SPLI, BELI, acetylcholinesterase, and total protein values between the two groups of patients. Patients with angina had SPLI, BELI, acetylcholinesterase, and total protein values of 0.47 +/- 0.26 fmol/mg protein, 0.06 +/- 0.06 fmol/mg protein, 0.29 +/- 0.15 units, and 68.2 +/- 8.7 mg/ml, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1989

Three-dimensional structure of cyclodextrin glycosyltransferase from Bacillus circulans at 3.4 A resolution.

Cyclodextrin glycosyltransferase (EC 2.4.1.19) from Bacillus circulans has been purified, crystallized and analyzed by X-ray diffraction. The enzyme is monomeric. SDS/polyacrylamide gel electrophoresis gave an Mr of 73,600(+/- 1000), corresponding to 670(+/- 10) amino acid residues. The structure of the crystalline enzyme has been elucidated at a resolution of 3.4 A, using multiple isomorphous replacement and solvent flattening for phase determination. The resulting electron density map allowed tracing of the polypeptide chain; 664 residue positions have been assigned. The chain fold has been subdivided into five domains. The N-terminal domain forms a (beta alpha)8-barrel, which contains the second domain of about 55 residues as an insert after the third beta-strand. The three remaining domains form almost exclusively beta-pleated sheet structures and consist of about 90, 80 and 95 residues. The chain fold of the three N-terminal domains of 492 residues resembles closely the two known structures of alpha-amylases. This geometric similarity corresponds to the observed amino acid sequence homology. On the basis of the sequence homology with alpha-amylases, the active center can be located. The fourth domain has an immunoglobulin fold and is far away from the active center, while the fifth domain participates in the formation of the broad depression at the active center. Accordingly, the cyclodextrin glycosyltransferase chain fold can be considered as an alpha-amylase chain fold with two additional domains.

Crystallography↗