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Biomedical subjects

B Holmquist

Publications and source records attributed to B Holmquist.

At least 73 records · Page 4Linked to original sources
PubMed1986

Kininase II of human seminal fluid: kinetics and inhibition.

The activity of kininase II in crude human sperm was measured continuously by measuring the hydrolysis of a blocked tripeptide 3-(2-furylacryloyl)-L- phenylalanyl-glycyl-glycine (1 mmol/l). Mean seminal plasma activity was 335 +/- 61 U/g protein; the Km was 0.7 mmol/l; pH optimum was 8.8 in a 50 mmol/l HEPES buffer and the chloride optimum was 300 mmol/l. This male genital tract enzyme is inhibited by several kininase II inhibitors. Captopril (SQ 14225) showed IC50 = 1.6 X 10(-8) mol/l, with a competitive pattern (Ki = 7.3 X 10(-9)). 3-(Mercaptomethyl)-oxo-piperidineacetic acid showed the same kind of inhibition with an IC50 = 1.8 X 10(-6) mol/l (Ki = 6.8 X 10(-7) mol/l). Enalapril diacid was the most potent inhibitor and had an IC50 of 4.1 X 10(-9) mol/l and showed a mixed competitive and non-competitive inhibition (Ki = 10(-9) mol/Ki' = 9.5 X 10(-10) mol/l). These in vitro inhibition data suggest that, in vivo, such drugs may effect the function of kininase II in the male reproductive system. The observed 50% inhibition constants are comparable to those observed in lung enzyme suggesting similar kinetic properties.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

Extracellular fluid proteins of goldfish brain: evidence for the presence of proteases and esterases.

Preparations of enriched fractions of extracellular fluid (ECF) proteins from goldfish brain were found to contain protease(s) and esterase(s). The N-substituted furanacryloyl (FA) peptides FA-Phe-Gly-Gly and FA-Phe-OMe were used as model substrates for determining protease and esterase activity, respectively, in a spectrophotometric assay. Studies of the profile of substrate specificity and identification of the types of compounds that were effective as inhibitors showed that these ECF enzymes have some distinctive properties. GSH, but not GSSG, and EDTA inhibited the protease(s) without influencing the esterase(s), whereas L-1-tosylamide-2-phenylethylchloromethyl ketone blocked both protease and esterase activities of ECF. Most of the protease and esterase properties of ECF could be bound to concanavalin A-Sepharose affinity chromatographic columns in association with ependymin--a brain extracellular protein. These observations indicate that ECF may contain a metalloprotease(s) and raise the possibility that the ependymins might be a substrate for these ECF enzymes.

Animals↗
PubMed1986

Effects of methylene chloride on body and organ weight and plasma butyrylcholinesterase activity in mice.

Exposure to methylene chloride produced a time and concentration related increase in liver weight. The effect was more prominent in female mice than in male. The activity of plasma butyrylcholinesterase (BuChE) increased even more than the liver weight at corresponding exposures, but only in the males. Fatty infiltration was noticeable after exposure to 75 p.p.m. and was more prominent in the females than in the males. Thirty to 60 days of continuous exposure were required to reach stable maxima. Intermittent exposure was less effective than continuous exposure in producing the effects. Most effects were fully reversible after exposure for both 30 and 90 days if the animals were transferred to a solvent-free environment. However, after exposure for 90 days, BuChE activity in the males did not return to normal within 30 days but after 90 and 120 days free from exposure only slight if any effects on BuChE activity remained.

Animals↗
PubMed1986

Cardiovascular complications of estrogen therapy for nondisseminated prostatic carcinoma. A preliminary report from a randomized multicenter study.

In a prospective multicenter study, 244 men with highly or moderately differentiated prostatic cancer in stage I, II or III (VACURG) were consecutively randomized to three groups of treatment: Group A (77 patients) received polyestradiol phosphate (Estradurin, Leo) 80 mg i.m. every fourth week + ethinyl estradiol (Etivex, Leo) 150 micrograms daily, group B (72 patients) estramustine phosphate (Estracyt, Leo) 280 mg twice daily, and group C (76 patients) no therapy. Only men without current or previous other malignancy and without cardiovascular disease were admitted to the study. After 4 1/2 years 125 of the 244 patients had left the study, 9 because of cancer progression (stage IV, VACURG). The most serious complications were cardiovascular, including ischemic heart disease, cardiac decompensation, cerebral ischemia and venous thromboembolism, which occurred in 24 patients from group A and 9 from group B as compared to only one patient in group C. The subgroup superficial or deep venous thrombosis comprised 11 group A and 2 group B patients. Estrogens (E + e) offered as palliative treatment to patients with non-generalized prostatic carcinoma is burdened with a high incidence of serious cardiovascular complications.

Aged↗
PubMed1985

Structural relationships among class I isozymes of human liver alcohol dehydrogenase.

The alpha subunit of human liver alcohol dehydrogenase has been submitted to structural analysis. Together with earlier work on the beta and gamma subunits, the results allow conclusions on the relationship of all known forms of the class I type of the enzyme. Two segments of the alpha subunit were determined; one was also reinvestigated in the beta and gamma subunits. The results establish 11 residue replacements among class I subunits in the segments analyzed and show that the alpha, beta, and gamma protein chains each are structurally distinct in the active site regions, where replacements affect positions influencing coenzyme binding (position 47; Gly in alpha, Arg in beta and gamma) and substrate specificity (position 48; Thr in alpha and beta, Ser in gamma). Residue 128, previously not detected in beta and gamma subunits, corresponds to a position of another isozyme difference (Arg in beta and gamma, Ser in alpha). The many amino acid replacements in alcohol dehydrogenases even at their active sites illustrate that in judgements of enzyme functions absolute importance of single residues should not be overemphasized. Available data suggest that alpha and gamma are the more dissimilar forms within the family of the three class I subunits that have resulted from two gene duplications. The class distinction of alcohol dehydrogenases previously suggested from enzymatic, electrophoretic, and immunological properties therefore also holds true in relation to their structures.

Alcohol Dehydrogenase↗
PubMed1985

Spectral and kinetic studies of metal-substituted Aeromonas aminopeptidase: nonidentical, interacting metal-binding sites.

Apoenzyme prepared by removal of the 2 mol of Zn2+/mol from Aeromonas aminopeptidase is inactive. Addition of Zn2+ reactivates it completely, and reconstitution with Co2+, Ni2+, or Cu2+ results in a 5.0-, 9.8-, and 10-fold more active enzyme than native aminopeptidase, respectively. Equilibrium dialysis and spectral titration experiments with Co2+ confirm the stoichiometry of 2 mol of metal/mol. The addition of only 1 mol of metal/mol completely restores activity characteristic of the particular metal. Interaction between the two sites, however, causes hyperactivation; thus, addition of 1 mol of Zn2+/mol subsequent to 1 mol of Co2+, Ni2+, or Cu2+ per mole increases activity 3.2-, 42-, or 59-fold, respectively. The cobalt absorption spectrum has a peak of 527 nm with a molar absorptivity of 53 M-1 cm-1 for 1 mol of cobalt/mol, which increases to 82 M-1 cm-1 for a second cobalt atom and is unchanged by further addition of Co2+. Circular dichroic (CD) and magnetic CD spectra indicate that the first Co2+ binding site is tetrahedral-like and that the second is octahedral-like. Stoichiometric quantities of 1-butylboronic acid, a transition-state analogue inhibitor of the enzyme [Baker, J. O., & Prescott, J. M. (1983) Biochemistry 22, 5322], profoundly affects absorption, CD, and MCD spectra, but n-valeramide, a substrate analogue inhibitor, has no effect. These findings suggest that the tetrahedral-like site is catalytic and the other octahedral-like site is regulatory or structural.

Aeromonas↗
PubMed1985

Narcan inhibition of human liver alcohol dehydrogenase.

Narcan, the pharmaceutical agent for the administration of naloxone, has been reported to antagonize ethanol intoxication. In addition to naloxone, Narcan contains the antioxidant esters methyl- and propylparaben. Pure naloxone and these two esters were examined for their capacity to inhibit ethanol oxidation by purified isozymes of human liver alcohol dehydrogenase (ADH). Naloxone (400 micromolar) fails completely to inactivate any of the three ADH isozyme classes. In contrast, methyl- and propylparaben, and some related esters, competitively inhibit the oxidation of ethanol and reduction of acetaldehyde by all isozymes examined. The reported effects of Narcan on ethanol-intoxicated animals or cells cannot be attributed to the action of naloxone.

Alcohol Dehydrogenase↗
PubMed1985

Effects of organic solvents on motor activity in mice.

Groups of male mice were exposed via inhalation to methylene chloride, perchloroethylene, toluene, trichloroethylene or 1,1,1-trichloroethane. The exposures were started at 2300 h. Generation of vapor was stopped after 1 h. Motor activity of the animals during the exposures was measured with a Doppler radar. Several concentrations of each solvent were tested. Concentrations could be found for all solvents at which they initially increased the motor activity. When the generation of vapor was terminated and the concentration started to decline, a new phase of changes in motor activity was induced. At this phase, motor activity was in most cases influence in the opposite direction to that at the beginning of the exposure. Trichloroethylene concentrations could be found which gave no increase in activity at the start of exposure but a prominent decrease at termination. The lowest concentration at which effects could be seen was different for the different solvents. Perchloroethylene was more and 1,1,1-trichloroethane less potent than the other solvents in inducing motor activity. The time pattern of the motor activity alterations was specific for each solvent. Both the concentration and the rate of the concentration increase were responsible for the effects on motor activity. The differences between the solvents probably reflect differences in their site of action, their distribution and their biotransformation.

Administration, Intranasal↗
PubMed1985

chi-ADH is the sole alcohol dehydrogenase isozyme of mammalian brains: implications and inferences.

Class III (chi) is the only alcohol dehydrogenase (ADH) in human, equine, bovine, simian, canine, and rodent brain and is the first to be identified, purified, and characterized from the brain of humans or other vertebrates. Like the corresponding isozymes from human placenta and liver, the chi-ADH isozymes purified from mammalian brain are neither inhibited by nor do they bind to immobilized pyrazole, and they oxidize ethanol only very poorly (Km greater than 2.5 M). Indeed, it would be incorrect to classify them as "ethanol dehydrogenases." They contain 4 g.atom of zinc/mol, bind 2 moles of NAD, and readily oxidize long-chain aliphatic and aromatic primary alcohols. These findings appear to exclude the possibilities that ADH protects the brain of these vertebrates against ethanol or its metabolic products and that the brain can generate energy for cerebral function from ADH-monitored ethanol metabolism. Thus chi-ADH must serve a totally different but as yet unknown role. The failure to detect any ethanol dehydrogenase activity in brain creates an intellectual dilemma only if it is assumed that such an enzyme has evolved and developed as a protective mechanism for ethanol detoxification in that organ, as has been assumed. Tissue and substrate specificities of ADH isozymes are likely to give new insight regarding their physiological roles.

Alcohol Dehydrogenase↗
PubMed1985

Effects of solvent exposure on testosterone levels and butyrylcholinesterase activity in mice.

In female and male mice the effect of exposure to trichloroethylene (TCE) seen at the lowest concentration is an increase in liver weight. The activity of plasma butyrylcholinesterase (BuChE) increases even more than the liver weight at corresponding concentrations, but only in the males. Depletion of testosterone through castration or destruction of the pituitary gland or hypothalamus, are the only other ways to experimentally induce corresponding increases in BuChE. Plasma BuChE activity increase was found to be a common reaction after exposure to TCE, perchloroethylene, chloroform, methylene chloride and carbon tetrachloride and also after exposure to ethanol. Other solvents such as toluene, xylene, benzene and 1,1,1-trichloroethane had little or no effect on BuChE activity. Normal and castrated male mice were continuously exposed for one month to 150 p.p.m. TCE. The increase in BuChE activity after the exposure was of the same magnitude as the increase seen after castration. BuChE activity in castrated males was not further increased by TCE exposure. Administration of testosterone with osmotic minipumps for 13 days almost restored the normal testosterone and BuChE levels in castrates. The effect of TCE exposure on BuChE activity in these animals was the same as on normal males. Testosterone levels were not influenced by the TCE exposure in normal males or in castrates given testosterone. No sex hormone binding globulins (SHBG) could be detected in the mice. BuChE activity changes induced through solvent exposure are therefore neither directly nor indirectly (through SHBG) due to effects on testosterone. The results from these animal experiments do not support the epidemiological findings of decreased testosterone levels in humans exposed to solvents.

Animals↗
PubMed1984

Physical and enzymatic properties of a class II alcohol dehydrogenase isozyme of human liver: pi-ADH.

Homogeneous class II alcohol dehydrogenase (pi-ADH) has been isolated from human liver homogenates by chromatography on DE-52 cellulose, 4-[3-[N-(6-amino-caproyl)amino]propyl]pyrazole-Sepharose, SP-Sephadex C-50, and agarose-hexane-AMP, yielding an enzyme that has a significantly higher specific activity and is markedly more stable than that isolated by an earlier procedure. pi-ADH is composed of two identical 40 000-dalton subunits, contains 4 mol of zinc/dimer, and is readily inhibited by metal-chelating agents. The purified enzyme binds two molecules of coenzyme per dimer, exhibits an absorption maximum at 280 nm, epsilon 280 = 57 000, and exhibits an isoelectric point of 8.6. The class II isozyme catalyzes the oxidation of a variety of alcohols with Km values ranging from 7 microM to 560 mM and with kcat values from 32 min-1 to 600 min-1 and demonstrates a preference for hydrophobic substrates. The kcat/Km ratio for ethanol oxidation exhibits a pH maximum at 10.4.

Alcohol Dehydrogenase↗
PubMed1984

Human liver alcohol dehydrogenase. 1. The primary structure of the beta 1 beta 1 isoenzyme.

Determination of the amino acid sequence of the beta 1 subunit from the class I (pyrazole-sensitive) human liver alcohol dehydrogenase isoenzyme beta 1 beta 1 revealed a 373-residue structure differing at 48 positions (including a gap) from that of the subunit of the well studied horse liver alcohol dehydrogenase EE isoenzyme. The structure deduced is compatible with known differences in composition, ultraviolet absorbance, electrophoretic mobility and catalytic properties between the horse and human enzymes. All zinc-liganding residues of the horse E subunit are strictly conserved in the human beta 1 subunit, despite an earlier report of a mutation involving Cys-46. This residue therefore remains conserved in all known alcohol dehydrogenase structures. However, the total cysteine content of the beta 1 structure is raised from 14 in the subunit of the horse enzyme to 15 by a Tyr----Cys exchange. Most exchanges are on the surface of the molecule and of a well conserved nature. Substitutions close to the catalytic centre are of interest to explain the altered substrate specificity and different catalytic activity of the beta 1 homodimer. Functionally, a Ser----Thr exchange at position 48 appears to be of special importance, since Thr-48 in beta 1 instead of Ser-48 in the horse enzyme can restrict available space. Four other substitutions also line the active-site pocket, and appear to constitute partly compensated exchanges.

Alcohol Dehydrogenase↗
PubMed1984

Physical and enzymatic properties of a class III isozyme of human liver alcohol dehydrogenase: chi-ADH.

chi-Alcohol dehydrogenase (chi-ADH), a class III isozyme characterized by its anodic electrophoretic mobility and lack of inhibition by 4-methylpyrazole, has been isolated from human liver and purified to homogeneity in a reducing medium. chi-ADH resembles other human liver ADH isozymes of classes I and II with respect to its molecular weight, dimeric structure, stoichiometry of zinc and NADH binding, and pH optima for the oxidation of alcohols. This homodimer exhibits subtle differences in its absorption spectrum and amino acid composition relative to those of other human isozymes but differs markedly from their specificity toward alcohols and aldehydes. chi-ADH oxidizes ethanol very poorly. The reaction is bimolecular, and an apparent Km cannot be discerned up to 2.3 M ethanol. The enzyme is inactive toward methanol, ethylene glycol, digitoxigenin, digoxigenin, and gitoxigenin , but alcohols with carbon chain lengths greater than four are oxidized rapidly with Km values decreasing with increasing carbon chain length. Taken jointly, the composition, structure, and enzymatic properties of the ADH isozymes purified and studied so far strongly imply that their metabolic roles, yet to be discovered, will give a new perspective to ethanol metabolism and pathology.

Alcohol Dehydrogenase↗
PubMed1984

Affinity chromatographic purification of angiotensin converting enzyme.

The compounds N-[1 (S)-carboxy-5-amino-pentyl]-L-phenylalanylglycine and N-[1 (S)-carboxy-5-aminopentyl]-DL-alanyl-L-proline were synthesized and explored as potential ligands for the affinity chromatography of angiotensin converting enzyme (dipeptidyl carboxypeptidase, EC 3.4.15.1) (ACE), a membrane-bound zinc metalloprotease. The N-alkylated Ala-Pro derivative has an apparent Ki less than 1 nM (at pH 7.5, 0.50 M NaCl) while the Phe-Gly derivative is a much less potent competitive inhibitor with an apparent Ki = 0.20 microM under the same conditions and thus more suitable for use as an affinity ligand. Immobilization of these compounds via a 28-A spacer to agarose yields resins with binding capacities of greater than 7 mg of enzyme/mL of resin, while spacers of 22 A or less result in binding capacities at least 350 times smaller. Immobilized N-[1 (S)-carboxy-5-amino-pentyl]-L-Phe-Gly is superior to the Ala-Pro derivative because elution can be affected by raising the pH to 8.9 with 98% yields compared with only 20% from the latter. Thus, a three-step process involving detergent extraction, concentration by ammonium sulfate precipitation, and affinity chromatography on the resin-immobilized Phe-Gly derivative provides 30 mg of homogeneous ACE from 640 g of rabbit lung tissue. An ACE-like metalloprotease has also been isolated from testicular tissue by this same technique.

Animals↗
PubMed1984

Treatment of prostatitis in the rat.

A spontaneous, nonacute, age-dependent prostatitis was found in a high incidence in the lateral prostatic lobes of Lewis rats. Such rats were treated with methylprednisolone, indometacin , testosterone, hexyloxyphenylproprionate , polyestradiol phosphate, various antibiotics, or were caged together with female rats. The effect of the different treatment modalities was evaluated microscopically by blind observation of the degree of inflammatory reaction in the lateral prostate. Methylprednisolone and the testosterone ester caused a reduction of the inflammatory reactions and so did caging with female rats. The similarity of the rat prostatitis to the human condition may suggest the possibility of using corticosteroids or androgens for the treatment of patients with nonacute prostatitis.

Adrenal Cortex Hormones↗
PubMed1984

Pitfalls in the interpretation of long-term inhalation experiments.

Age- and weight-matched groups of mice were enclosed in airtight chambers and exposed to clean, filtered air for 1 month. At the end of the exposure period, body, liver and spleen weights and plasma butyrylcholinesterase (BuChE) activity were measured. More than twice as many significant differences in these parameters occurred compared with the expected results if only random differences existed between the groups. Thus, isolation of animal groups for extended periods of time in inhalation experiments alone may lead to differences in various biological parameters. When testing the effects of unknown substances such differences may be mistaken for reactions to the test agent, which actually may have no effect.

Animals↗