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Biomedical subjects

M Lindberg

Publications and source records attributed to M Lindberg.

At least 199 records · Page 11Linked to original sources
PubMed1979

Determination of apomorphine in plasma and brain tissue by ion-pair extraction and liquid chromatography.

Apomorphine is extracted from plasma or tissue homogenate with ethyl acetate. After back-extraction into hydrochloric acid, the apomorphine is extracted as an ion pair with 3,5-di-tert.-butyl-2-hydroxybenzene sulphonate into a small volume of methylene chloride and the solution is injected into the chromatographic column. Apomorphine is separated on microporous silica with a mixture of aqueous perchloric acid, methanol and methylene chloride as the mobile phase. With absorbance measurement of the eluent at 254 nm the method permits the determination of 15 pmol of apomorphine in 1 ml of plasma or in a rat brain. The coefficient of variation was 4% at the 100 pmol level.

Animals↗
PubMed1979

Biologically active luteinizing hormone (LH) in plasma. V. A re-analysis of the differences in the ratio of biological to immunological LH activities during the menstrual cycle.

The relationship between the biological and immunological activities of human luteinizing hormone (hLH) in plasma collected from female subjects was examined. The biological activity was measured by an in vitro bioassay and the immunological activity by an hLH radioimmunoassay (RIA), using improved reagents, such as the 1st IRP for human pituitary LH for immunoassay (code No. 68/40) as standard, a subunit-free biologically active iodinated hLH preparation as tracer and an anti-hLH serum of relatively high specificity. Similar profiles of biological (B) and immunological (I) activity were obtained in the plasma samples collected daily throughout 40 menstrual cycles (5 cycles from each of 8 subjects). However, the B/I ratios were significantly lower during the period of LH surge (P less than 0.001) than throughout the remainder of the cycle. The within- and between-assay variation in B/I ratios was investigated by the simultaneous assay of biological and immunological activities in plasma pools obtained by combining equal aliquots of plasma from each daily sample of the menstrual cycle from each of 5 cycles of each of 4 subjects. The analysis of these 20 pools revealed highly significant individual differences in B/I ratios, ranging from 0.81 to 1.33. The coefficient of variation was 20% between-subjects and 5% within-subjects. There was no seasonal variation in B/I ratios. That the individual differences in plasma B/I ratios were not attributable to the procedure of pooling was ascertained by the simultaneous assay of both activities in parellel in daily plasma samples and in the pools formed from these samples from three complete cycles. Thus the analysis of the differences in B/I ratios obtained throughout the menstrua- cycle revealed three major sources of variation. The first occurs in the form of generally elevated (higher than unity) B/I ratios, the second consists of a significant drop in B/I ratios during the midcycle LH surge, and the third source is represented by the significant between-subject differences. It is concluded that the first source is attributable to the relatively higher levels of "impurity" (i.e. biologically inactive, immunologically active material) in the standard preparation compared to those present in plasma of biologically inactive, immunologically active material of unknown composition and origin. If so, the latter source limits the quantitative significance of the RIA procedures employed. It is suggested that these three sources of variation account for most of the differences in B/I ratios for plasma lLH reported in the literature.

Adult↗
PubMed1978

Effects of streptomycin and novobiocin on Staphylococcus aureus gene expression.

Streptomycin and novobiocin induced production of protein A and inhibited production of alpha- and beta-hemolysins in mutants of Staphylococcus aureus strains RN450 and RN1 resistant to these antibiotics. Streptomycin, but not novobiocin, also inhibited propagation of bacteriophages of serological group B, whereas phages of group A were unaffected. Streptomycin had to be present at adsorption of the phage, and 10 mM CACL2 reversed the inhibitory effect. Lysogenization and competence induction occurred in the presence of streptomycin, suggesting that some early phage genes were expressed.

Bacterial Proteins↗
PubMed1975

Preparation of analogues of ATP, ADP and AMP suitable for binding to matrices and the enzymic interconversion of ATP and ADP in solid phase.

Alkylation of ATP with iodoacetic acid at pH 6.5 yielded 1-carboxymethyl-ATP which, after alkaline rearrangement, gave N-6-carboxymethyl-ATP. Condensation of this analogue with 1,6-diaminohexane in the presence of a water-soluble carbodiimide generated N-6-[(6-aminohexyl)carbamoylmethyl]-ATP in an overall yield of 40% based on the parent nucleotide ATP. The coenzymic activities of both N-6-adenine-substituted derivatives of ATP were tested with three kinases. Both derivatives showed coenzymic function against hexokinase with the "long" derivative having highest activity (95%) relative to unsubstituted ATP. Their activities towards the other two kinases tested was negligible except with the "long" analogue against glycerokinase (20%). The latter ATP analogue, when bound to Sepharose through its terminal amino group, could be dephosphorylated to the corresponding ADP analogue with soluble hexokinase yielding glucose 6-phosphate in an enzymic "solidphase" fashion. The Sepharose-bound ADP formed could subsequently be phosphorylated back to ATP using soluble acetate kinase. Sepharose-ATP preparations were also used in preliminary affinity chromatography studies using citrate synthase. Alkylation of ADP following the above procedure yielded the corresponding ADP analogue, N-6-[(6-aminohexyl)carbamoylmethyl]-ADP in an overall yield of 40%. Alkylation of AMP yielded the corresponding N-6-[(6-aminohexyl)carbamoylmethyl]-AMP in an overall yield of 45%.

Adenosine Diphosphate↗
PubMed1975

Thymineless bacteriophage induction in Staphylococcus aureus. I. High-frequency transduction with lysates containing a bacteriophage related to bacteriophage phi 11.

A thymine-requiring mutant of Staphylococcus aureus, strain 8325 (PI258)thy, undergoes prophage induction and lysis after thymine starvation. Four different phages were isolated from the lysate in low titers, among which was a phage designated phi 14, which differs from phage phi 11 in its immunity locus. The thymineless induced lysates of strain 8325(PI258)thy transduce the penicillinase plasmid at high frequency (10(-1), whereas transduction of chromosomal markers is inefficient. A plasmic-cured derivative of strain 8325(PI258)thy is also lysed by thymine starvation and be used for high-frequency transduction of other plasmids. Reconstitution of a strain of S. aureus that responds to thymine starvation was only partially successful, but this system can effectively be used to transduce plasmids or plasmid derivatives.

Drug Resistance, Microbial↗
PubMed1975

Thymineless bacteriophage induction in Staphylococcus aureus. II. Specific transduction of constitutive and inducible erythromycin resistance.

Specific transduction of inducible (eroA) and constitutive (eroB) erythromycin resistance is mediated by thymineless induced lysates from derivatives of Staphylococcus aureus strain 8325(N)thy. Both loci can coexist in the same cell but segregate by transduction or transformation. The gene(s) is probably integrated in the recipient chromosome and excised at thymine starvation.

Chromosomes, Bacterial↗
PubMed1974

Factors affecting competence for transformation in Staphylococcus aureus.

A chemically defined medium has been developed for isolation of amino acid-requiring mutants of Staphylococcus aureus strain 8325, and for use as a selective medium in transformation assays. Variables affecting transformation of both plasmid and chromosomal markers have been studied. The optimal pH and temperature for transformation are 6.75 to 7.0 and 30 C, respectively. Ca ions are required for transformation, and only cells lysogenic for the phage phi11 can be transformed. Superinfection of competent cells with phi11 does not increase the transformation frequency. Maximal number of transformants is obtained after 20 min of contact between cells and deoxyribonucleic acid. The transformation frequencies for the plasmid marker erythromycin resistance (ero) and the chromosomal markers trp, thy, and cyt are of the same order of magnitude, whereas the frequency for the chromosomal marker tyr is approximately one order of magnitude lower.

Barium↗
PubMed1973

Competence for transfection in Staphylococcus aureus.

Lysogenicity with phage P11 is a requirement for competence in the presence of calcium ions in Staphylococcus aureus 8325N. The wild-type strain 8325N, lysogenic for the phages P11, P12, and P13, is also competent, but strain 8325-4, a nonlysogenic derivative of strain 8325N, as well as strains 8325-4 (P12) and 8325-4 (P13) could not develop competence. Preincubation of strain 8325-4 with culture filtrates from a competent strain can induce competence, but rabbit anti-P11 serum can neutralize the competence factor. Superinfection of competent strain 8325-4 (P11) with phage P11 at high multiplicities increases the transfection frequency. Uptake of deoxyribonucleic acid by competent cells is dependent on calcium ion concentration, pH, and temperature. Inhibition of energy metabolism or protein synthesis before and during incubation with deoxyribonucleic acid affects the binding and uptake. The ability to develop competence during bacterial growth differs between the wild-type strain (8325N) and a nuclease-deficient mutant (8325N nuc). The wild-type strain has a narrow competence maximum in the early exponential growth phase where no extracellular nuclease activity is produced. The nuc strain shows in addition competence maxima later in the exponential growth phase.

Animals↗
PubMed1973

Plasmid-specific transformation in Staphylococcus aureus.

Transformation of Staphylococcus aureus cells with circular duplex deoxyribonucleic acid prepared from plasmid-carrying strains by alkali denaturation and selective renaturation or by dye-buoyant density centrifugation is reported. In all of the transformants tested, the transformed markers became established as autonomous plasmids that were biologically and physically indistinguishable from those carried by the donor strains. Transformation with bulk deoxyribonucleic acid from a strain carrying the penicillinase plasmid, PI(258), gave rise to transformants in which the erythromycin locus, the only plasmid marker transformed, was shown to be integrated into the host chromosome.

Cadmium↗
PubMed1973

Isolation and characterization of two protease-producing mutants from Staphylococcus aureus.

Two mutants with increased protease production were isolated after nitrosoguanidine treatment of Staphylococcus aureus 8325N. The wild type produces low amounts of extracellular proteolytic activity. The enzyme was inducible and could only be detected if casein or preferably skim milk powder was used as inducer. The optimal pH, salt concentration, and media for enzyme production were determined. The mutants differed from the wild type in several phenotypic characters. The pattern of extracellular deoxyribonuclease and alkaline phosphatase differed between the mutants and the wild type. Several carbohydrates such as lactose, galactose, and mannitol were not utilized by the mutants, probably owing to a block in the uptake. Glucose could, however, be utilized by the mutants. Reversion frequency to wild type with regard to carbohydrate utilization was spontaneously high, and all revertants regained the parental pattern irrespective of the carbohydrate used for selection. The results suggest that a single locus may control the excretion of extracellular enzymes and carbohydrate uptake in S. aureus.

Alkaline Phosphatase↗
PubMed1972

Transfection of Staphylococcus aureus with bacteriophage deoxyribonucleic acid.

Staphylococcus aureus cells of strain 8325 (N) are competent for phage deoxyribonucleic acid (DNA) when harvested in the early exponential growth phase. Phenotypic expression of the competence requires divalent cations, and calcium ions are most effective. Treatment of phage DNA with deoxyribonuclease completely destroys infectivity and heat-denaturated DNA is not infectious. The highest frequency of transfection is around 10(4) plaque-forming units per mug of DNA.

Calcium↗