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Biomedical subjects

R Young

Publications and source records attributed to R Young.

At least 199 records · Page 11Linked to original sources
PubMed1989

Preparation of antibodies against xanthine oxidase from human milk.

1. Human xanthine oxidase [XO; EC 1.2.3.2.] was isolated by a non-proteolytic method from fresh human milk. Final purification of the protein was achieved by hydroxyapatite chromatography. Most (less than 95%) of the enzyme was released in the 0.40 M phosphate fraction at pH 6.8. 2. The specific activity of this preparation was found to be 0.047 microM min-1 mg-1 with xanthine as substrate. 3. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE) separated two subunits, each with a mol. wt approximately 122 kDa. 4. On non-denaturing acrylamide gels both of these subunits exhibited oxidase-like activity with xanthine as substrate in the presence of nitroblue tetrazolium and molecular oxygen. 5. Immunoconjugates of XO were prepared by the keyhole limpet hemocyanin (KLH)- and glutaraldehyde-crosslinking techniques. 6. Polyclonal antibodies to XO were raised by i.m. injection of these conjugates into female New Zealand rabbits. 7. Western blot analysis using the semi-dry technique was employed to confirm the specificity of the antibody.

Animals↗
PubMed1989

Quantitative whole-body autoradiographic determination of tacrine tissue distribution in rats following intravenous or oral dose.

Tacrine (1,2,3,4-tetrahydro-9-acridinamine) has been employed in diverse clinical situations but has recently been of considerable interest for the treatment of cognitive deficits associated with senile dementia (Alzheimer's disease). The present studies examined tissue distribution of radiolabeled tacrine by quantitative whole-body autoradiography. Tacrine radioequivalents were widely distributed to tissue following iv or peroral dose, with an apparently prolonged absorption phase following po dose. The presence of high levels of activity in kidneys and ureters indicates a major role for urinary excretion, but there is also evidence for biliary excretion and direct secretion of compound or metabolites into the intestinal lumen. Tacrine was rapidly taken up into the brain and demonstrated regional localization to cortex, hippocampus, thalamus, and striatum. Although the inhibition of acetylcholinesterase by tacrine is well documented, regional uptake in brain did not correlate consistently with distribution of the enzyme, supporting suggestions by others that the alleged action of tacrine in treatment of senile dementia may be by mechanisms other than cholinesterase inhibition.

Administration, Oral↗
PubMed1989

Study of DNA polymorphisms of the apolipoprotein AI-CIII-AIV gene cluster in patients with peripheral arterial disease.

1. We have determined the frequency of DNA polymorphisms of the human apolipoprotein AI-CIII-AIV gene cluster, detected with XmnI, PstI, and PvuII, in a group of patients with peripheral arterial disease. 2. Of the patients, 81 had no evidence of disease in the coronary and carotid arteries, 73 had coronary artery disease but no evidence of carotid artery disease, 25 patients had carotid artery disease but no evidence of coronary artery disease, and 38 had both coronary and carotid artery disease. 3. Levels of triacylglycerol, cholesterol, apolipoprotein B and apolipoprotein AI were not significantly different between the four patient groups. 4. The frequencies of the alleles for the apolipoprotein AI-CIII-AIV polymorphisms, detected with XmnI, PstI and PvuII, did not differ significantly in the patient groups when compared with a sample of clinically well normolipidaemic individuals also from a London population. 5. All five patients with the XmnI genotype we designate X2X2 had high levels of cholesterol, apolipoprotein B and apolipoprotein AI. 6. Patients with the rare VB2 allele of the apolipoprotein CIII-AIV restriction fragment length polymorphism had lower levels of cholesterol, acylglycerol and significantly lower levels of serum apolipoprotein. 7. Our observations suggest that variation in the apolipoprotein AI-CIII-AIV gene cluster may not be contributing significantly to the development of peripheral arterial disease, but variation associated with some of the restriction fragment length polymorphisms may be involved in determining levels of cholesterol- and apolipoprotein-B-containing lipoproteins.

Adult↗
PubMed1989

Long-term culture and fine specificity of human cytotoxic T-lymphocyte clones reactive with human immunodeficiency virus type 1.

The definition of human immunodeficiency virus type 1 (HIV-1) immunogenic epitopes is central to the rational design of AIDS vaccine strategies. In this study, we have generated seven HIV-1 reverse transcriptase-specific cytotoxic T-lymphocyte (CTL) clones from the peripheral blood of two seropositive subjects. Epitopes recognized by these CTL clones were identified by using target cells infected with recombinant HIV-1-vaccinia virus vectors expressing truncated reverse transcriptase proteins and further defined by using target cells incubated with overlapping 25-amino acid synthetic reverse transcriptase peptides. Five different CTL epitopes were identified, and in each case recognition was restricted by class I human leukocyte antigens (HLA). Clones maintained specific cytolytic function in continuous culture for up to 11 months, requiring only periodic restimulation with a CD3-specific monoclonal antibody. These results indicate that HIV-1-specific, major histocompatibility class I-restricted CTL recognize multiple epitopes of a single viral gene product in conjunction with different host HLA antigens. In addition, they demonstrate that human virus-specific CTL can be grown in long-term culture without the need for reexposure to viral antigen.

Cell Line↗
PubMed1989

Cloning and characterization of a hemolysin gene from Actinobacillus (Haemophilus) pleuropneumoniae.

Neutralizing antisera to the leukotoxin secreted by Pasteurella haemolytica neutralized the hemolysin of Actinobacillus pleuropneumoniae and recognized a 110-kD antigen in cell-free culture supernatants from this organism. A series of nine overlapping recombinant phage clones carrying the gene for this 110-kD antigen were identified using affinity-purified anti-hemolysin antibody and a DNA probe containing sequences from the P. haemolytica lktCA genes. Eight of the nine clones expressed a 110-kD protein recognized by both anti-leukotoxin and anti-hemolysin antisera. The remaining clone expressed a truncated 80-kD antigen which was also recognized by both antisera. Sequence analysis of a region of the cloned DNA revealed two open reading frames encoding proteins with predicted masses of 18.5 and 102.5 kD. These genes, which we designate appC and appA, respectively, are similar in sequence to the hlyCA genes of Escherichia coli and the lktCA genes of P. haemolytica. Hemolytic activity could be detected in lysates of E. coli harboring plasmids containing the appCa genes.

Actinobacillus↗
PubMed1989

Detection of cyclic 1,N2-propanodeoxyguanosine adducts in DNA of rats treated with N-nitrosopyrrolidine and mice treated with crotonaldehyde.

Cyclic 1,N2-propanodeoxyguanosine adducts are formed in vitro in DNA treated with alpha-acetoxy-N-nitrosopyrrolidine or its metabolite, crotonaldehyde. However, the in vivo formation of these cyclic adducts in DNA has not been demonstrated due to the lack of a sensitive detection method. In this study, a 32P-postlabeling method specific for the detection of 1,N2-propanodeoxyguanosine adducts was developed by using the corresponding 3'-monophosphates as standards. This method was validated by using DNA modified in vitro. It was then applied for the in vivo experiments in which hepatic DNA of rats treated with N-nitosopyrrolidine (NPYR) (total dose, 1.0 mmol) in drinking water or skin DNA of Sencar mice treated topically with crotonaldehyde (1.4 mmol) was isolated and subjected to 32P-postlabeling analysis. 1,N2-Propanodeoxyguanosine adducts were detected in these DNA samples. The minimal levels of adducts from liver DNA and skin DNA detected were estimated to be approximately 0.06 and approximately 0.24 mumol/mol guanine respectively. Interestingly, a background adduct spot chromatographically indistinguishable from the 1,N2-cyclic adducts was observed in the liver DNA of untreated rats. However, no such background adduct was detected in skin DNA of mice. This method demonstrated for the first time the in vivo formation of the cyclic 1,N2-propanodeoxyguanosine adducts.

Adenosine Triphosphate↗
PubMed1989

Amonabactin, a novel tryptophan- or phenylalanine-containing phenolate siderophore in Aeromonas hydrophila.

Aeromonas hydrophila 495A2 excreted two forms of amonabactin, a new phenolate siderophore composed of 2,3-dihydroxybenzoic acid, lysine, glycine, and either tryptophan (amonabactin T) or phenylalanine (amonabactin P). Supplementing cultures with L-tryptophan (0.3 mM) caused exclusive synthesis of amonabactin T, whereas supplements of L-phenylalanine (0.3 to 30 mM) gave predominant production of amonabactin P. The two forms of amonabactin were separately purified by a combination of production and polyamide column chromatographic methods. Both forms were biologically active, stimulating growth in iron-deficient medium of an amonabactin-negative mutant. Of 43 additional siderophore-producing isolates of the Aeromonas species that were tested, 76% (19 of 25) of the A. hydrophila isolates were amonabactin positive, whereas only 19% (3 of 16) of the A. sobria isolates and all (3 of 3) of the A. caviae isolates produced amonabactin, suggesting a predominant synthesis of amonabactin in certain Aeromonas species.

Aeromonas↗
PubMed1989

Growth hormone treatment reduces total body fat accumulation in Zucker obese rats.

Lean and obese Zucker rats were injected daily intraperitoneally with high doses (5-10 mg/kg) of human growth hormone (GH) for 3 weeks. In the obese rats after GH treatment, carcass lipid was decreased by 50 percent, and bone weight increased to levels of lean controls. During the last two weeks of GH treatment, food intake was increased in lean rats and not significantly affected in obese rats. Loss of body weight in obese animals was masked by water retention. Serum insulin concentrations were doubled in obese animals but unchanged in lean phenotypes after GH treatment. Hepatic fatty acid oxidation in obese animals was stimulated 5-fold by treatment, while hepatic lipid synthesis was stimulated 2-fold and adipose lipid synthesis was reduced 3-fold. These results suggest that growth hormone induces a partitioning of nutrients in obese rats which results in less lipid accumulation.

Adipose Tissue↗
PubMed1989

[Sarmiento function fracture treatment of the tibia].

Sarmiento's functional brace treatment of tibial bone fractures is introduced and discussed. After fixation with a plaster cast and extension, the injured limb is fitted into a synthetic brace until complete bony union is achieved. Our four years of experience with 73 patients and the distribution of age, sex, localization, and cause are presented, as are the reexamination results. The possible complications and their treatment are demonstrated. The results justify extensive use of this method.

Adolescent↗
PubMed1988

Dominance in lambda S mutations and evidence for translational control.

Phenotypic analysis of a collection of point mutations in the lysis gene S of bacteriophage lambda indicates that many of the S alleles exhibit at least partially dominant character, suggesting that the S gene product (gpS) must oligomerize to achieve its lethal membrane effect. Moreover, mutations found 5' to the coding sequence also show a dominant character and appear to define a site, designated sdi (structure directed initiation) where mRNA secondary structure controls the choice of initiation codons. We propose that formation of the sdi structure occludes the consensus Shine-Dalgarno sequence and results in initiation at the Met3 codon, generating a lethal 105 residue polypeptide. The model predicts that, in the absence of the sdi stem-and-loop, initiation occurs at the Met1 codon, generating a 107 residue polypeptide, which is a non-lethal inhibitor of lysis. In support of the model, alteration of the first codon was achieved using site-directed mutagenesis, resulting in an S allele that is more lethal and induces lysis significantly sooner than the wild-type.

Amino Acid Sequence↗
PubMed1988

DNA polymorphisms of the gene for apolipoprotein B in patients with peripheral arterial disease.

We have determined the frequency of DNA polymorphisms of the gene for human apolipoprotein B, detected with XbaI and EcoRI, in 205 patients with documented peripheral arterial disease. Of the patients, 78 have no evidence of disease in the coronary and carotid arteries, 64 have coexisting coronary artery disease but no evidence of carotid artery disease, 26 patients have coexisting carotid artery disease but no evidence of coronary artery disease, and 37 have coexisting coronary and carotid artery disease. Levels of triglycerides, cholesterol and apolipoprotein B were measured for each patient, and RFLP frequency was determined in all the patients. Lipid, lipoprotein and apolipoprotein levels were not significantly different between the different patient groups. Compared with a sample from the clinically well London population, the frequency of the R2 allele of the polymorphism detected with EcoRI, and the frequency of the X1 allele of the XbaI polymorphism was significantly higher in the patient group. The frequency of these alleles was not significantly different in the different patient groups. In patients with only peripheral arterial disease, individuals with the XbaI genotype X1X1 have the lowest and those with the genotype X2X2 have the highest mean levels of serum cholesterol. However, in all other patient groups this trend was reversed (X1X1 highest and X2X2 lowest). Our observations suggest that variation at the apo B locus is one of the factors involved in predisposing an individual to develop arterial disease but does not determine where in the arterial system the disease develops.

Adult↗
PubMed1988

Chlorphentermine may produce dual stimulus effects: a preliminary investigation.

1. Rats were trained to discriminate injections of either (+)-amphetamine (0.75 mg/kg) or (+/-)-fenfluramine (1.5 mg/kg) from saline in a two-lever drug discrimination task. 2. After stable discrimination performances were attained in each group, stimulus generalization studies were conducted with amphetamine, fenfluramine, and chlorphentermine. 3. Stimulus generalization (substitution) did not occur between amphetamine and fenfluramine when either drug was used as the training stimulus. 4. In contrast, both the amphetamine stimulus and the fenfluramine stimulus generalized completely to chlorphentermine. 5. Taken together, the results suggest that chlorphentermine may be capable of producing dual stimulus effects in animals.

Animals↗
PubMed1988

Pyrido[2,1-b]quinazolinecarboxamide derivatives as platelet activating factor antagonists.

A series of N-[(heteroaryl)alkyl]pyrido[2,1-b]quinazolines were evaluated for their ability to inhibit the binding of radiolabeled platelet activating factor (PAF) to its receptor on dog platelets. The most potent compounds in this series were found to be pyrido[2,1-b]quinazoline-8-carboxamides possessing a four- or six-carbon chain between the carboxamide nitrogen atom and a 3-pyridinyl or 5-pyrimidinyl moiety. Since earlier metabolism studies with pyridoquinazolinecarboxamides suggest that the carboxamide moiety is labile to hydrolysis in vivo, attempts were made to find isosteric replacements for this group. The substitutions examined led to a loss of activity; however, insertion of a methyl group on the carbon atom alpha to the carboxamide nitrogen led to an enantioselective enhancement of potency. (R)-2-(1-Methylethyl)-N-[1-methyl-4-(3-pyridinyl)butyl]-11-oxo-11H- pyrido[2,1-b]quinazoline-8-carboxamide (34) was more potent than the corresponding S enantiomer in the PAF binding assay and was also shown to be more resistant to degradation by amidases present in whole liver homogenates obtained from guinea pig, dog, and squirrel monkey. The corresponding rac-2-(1-methylethyl)-N-[1-methyl-4-(3-pyridinyl)butyl]-11-oxo-11H- pyrido[2,1-b]quinazoline-8-carboxamide (33) was found to inhibit transient PAF-induced thrombocytopenia and decreases in blood pressure in guinea pigs after intravenous or oral administration and to have a duration of action of greater than 5 h after an oral dose of 200 mg/kg. Compound 33 thus represents the prototype of a new class of orally active PAF antagonists.

Animals↗
PubMed1988

Conservative management of abdominal gunshot wound in a pregnant woman.

An abdominal gunshot wound in pregnancy warrants prompt surgical exploration but does not mandate uterine evacuation. Despite an entry and exit bullet wound to the uterus an apparent desire for pregnancy termination, a conservative approach was adopted with primary repair of the uterus, in conjunction with surgical repair of associated injuries.

Abdominal Injuries↗
PubMed1988

Participation of volunteer faculty members in education research projects.

Physicians in private practice who are also volunteer clinical faculty members are a recognized resource for teaching and patient care at teaching hospitals. Clinical faculty members have seldom been included in education research despite the frequent complaint from community practitioners that the results from studies at teaching hospitals are not applicable to community practice. The authors report on a study involving volunteer clinical faculty members in a randomized education trial to improve patients' everyday functioning. Seventy-six clinical faculty physicians in office practice of internal medicine participated. At the end of the study the physician participants were asked to complete an evaluation questionnaire concerning the appropriateness of clinical faculty members' participation in such research projects. Ninety-five percent said the experiment was appropriate, and 88 percent would participate again.

Activities of Daily Living↗
PubMed1988

Evaluation of the interaction of phi X174 gene products E and K in E-mediated lysis of Escherichia coli.

Gene K of bacteriophage phi X174 was cloned, and its gene product was localized in the cell envelope of Escherichia coli. Compared with the sole expression of the phi X174 lysis gene E, the simultaneous expression of the K and E genes had no effect on scheduling of cell lysis. Therefore, a direct interaction of proteins E and K could be excluded. In contrast, phi X174 infection of a host carrying a plasmid expressing gene K resulted in a delayed lysis and an apparent increase in phage titer.

Bacteriophage phi X 174↗
PubMed1988

In vivo microscopy of the cerebral microcirculation using neonatal allografts in hamsters.

Studies were performed to characterize the morphology and vascular reactivity of the allografted cerebral microcirculation. Cerebral cortical tissue was allografted into the cheek pouch of the hamster so that cerebral parenchymal vessels could be studied. The vascular morphology was characterized by a large number of looping vessels. The ultrastructural examination indicated viable cerebral tissue containing typical vessels, that is, "tight" junctions, not like those of the cheek pouch. Also, the microvasculature was impermeable to 150, 70, and 20 kDa fluorescein isothiocyanate dextrans. Angiotensin II and norepinephrine caused constriction of the cerebral vessels whereas adenosine caused dilation. Isoproterenol did not affect cerebral arterioles; however, it dilated cheek pouch arterioles. Thus, this preparation provides a satisfactory model for studying the living cerebral microcirculation.

Adenosine↗