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Biomedical subjects

K Lindgren

Publications and source records attributed to K Lindgren.

At least 19 recordsLinked to original sources
PubMed1996

Recombinant human bile salt-stimulated lipase: an example of defective O-glycosylation of a protein produced in milk of transgenic mice.

The expression of recombinant human bile salt-stimulated lipase (bssl) was targeted to the lactating mammary gland of transgenic mice. Expression of recombinant genes comprising bsslcDNA, or alternatively genomic bssl DNA, under control of regulatory elements derived from the murine whey acidic protein (wap) gene was achieved and evaluated. Constructs containing genomic bssl sequences mediated high levels (0.5-1 mg ml-1) of recombinant human BSSL in the milk. The recombinant BSSL produced was purified, biochemically characterized and compared to native BSSL and recombinant BSSL produced in mouse C127 and hamster CHO cells. Recombinant BSSL derived from transgenic mice showed a different migration and distribution after SDS-PAGE electrophoresis, lower apparent molecular mass on size-exclusion chromatography and no detectable interactions with a panel of lectins. These results indicate a significantly lower degree of O-glycosylation of recombinant BSSL in milk from transgenic mice than was found for the native enzyme or recombinant CHO- or C127 cell-produced BSSL. Despite these differences, mouse-milk-derived recombinant BSSL exhibited similar lipase activity, the same stability to low pH and similar sensitivity to elevated temperatures as the native enzyme. The observation that mouse-C127-cell-produced recombinant BSSL is heavily O-glycosylated makes species-related restrictions less attractive as an explanation for the reduced O-glycosylation.

Animals↗
PubMed1996

Maternal-fetal conflict: court-ordered cesarean section.

Advances in prenatal care have created areas of conflict between the pregnant woman and her fetus. Court orders mandating cesarean section have denied to pregnant women rights that are accorded to all other competent adults in the United States. The caregiver-patient relationship can become adversarial in such situations. Nurses participating in the decision-making process when judicial involvement is being considered must be informed about the issues.

Adult↗
PubMed1995

Differences in the glycosylation of recombinant and native human milk bile salt-stimulated lipase revealed by peptide mapping.

The milk of some mammals contains a bile salt-stimulated lipase (BSSL). Human milk BSSL is heavily glycosylated (30-40% carbohydrate) and present at a concentration of approximately 100-200 mg/l, thereby being one of the most abundant human whey proteins. BSSL has been shown to have an important role in the uptake of energy from human milk. The risk of HIV contamination has restricted the use of banked human milk for nutritional purposes. This has evoked an interest in the production of a recombinant form of the protein for supplementation of formula. We have produced BSSL in mouse C127 and hamster CHO cells, and used chromatographic methods for the characterization of the products. This study was focused on study of the glycosylation of the protein by using peptide mapping and isolation of glycosylated fragments. The results show how human BSSLs from different sources differ both in extent of glycosylation, in glycan heterogeneity, and in lectin binding.

Animals↗
PubMed1995

The genetic basis of the circadian clock: identification of frq and FRQ as clock components in Neurospora.

Genetic approaches to the identification of clock components have succeeded in two model systems, Neurospora and Drosophila. In each organism, genes identified through screens for clock-affecting mutations (frq in Neurospora, per in Drosophila) have subsequently been shown to have characteristics of central clock components: (1) mutations in each gene can affect period length and temperature compensation, two canonical characteristics of circadian systems; (2) each gene regulates the timing of its own transcription in a circadian manner; and (3) in the case of frq, constitutively elevated expression will set the phase of the clock on release into normal conditions. Despite clear genetic and molecular similarities, however, the two genes are neither molecular nor temporal homologues. The timing of peak expression is distinct in the two genes, frq expression peaking after dawn and per expression peaking near midnight. Also, although expression of per from a constitutive promoter can rescue rhythmicity in a fly lacking the gene, constitutive expression of frq will not rescue rhythmicity in Neurospora frq-null strains, and in fact causes arrhythmicity when expressed in a wild-type strain. These data suggest that frq is and/or encodes a state variable of the circadian oscillator. Recent molecular genetic analyses of frq have shed light on the origin of temperature compensation and strongly suggest that this property is built into the oscillatory feedback loop rather than appended to it. It seems plausible that clocks are adjusted and reset through adjustments in central clock components such as frq, and, by extension, per.

Animals↗
PubMed1995

The lateralized processing of affect in emotionally labile extraverts and introverts: central and autonomic effects.

The purpose of the present study was to better understand both the lateralized hemispheric processing of emotion and the differential neural processing of arousal in extraverts and introverts. We preselected right-handed male and female extraverts and introverts who were high in emotional lability. Each subject was exposed to two positive and two negative emotional stimuli under each of three counterbalanced conditions, including affective, cognitive, and neutral, while EEG and electrodermal activity (EDA) were recorded. Results showed that introverts are more aroused and that extraversion interacts with gender to produce differentiated patterns of lateralized neural activity. In addition, affective conditions produced higher levels of arousal than did cognitive or neutral conditions, particularly in the left hemisphere and under negative as opposed to positive stimuli. Finally, the hemispherically differentiated processing of positive and negative stimuli was affected by the contextual conditions under which they were experienced.

Adolescent↗
PubMed1992

Effects of habitual caffeine use and acute ingestion: testing a biobehavioral model.

A recently proposed model of the biobehavioral effects of caffeine suggests that acute ingestion impacts physiology and behavior differentially depending on the level of habitual usage of the drug. Acute ingestion and habitual usage are particularly expected to affect arousal and attentional processes. Subjects in the present study were preselected for high and low habitual caffeine use, given caffeine or a placebo, exposed to white noise or no white noise, and asked to perform on several tasks. Included were an arousal/habituation task (pure tones), reaction time, paired associates, anagrams, and vigilance. Electrodermal activity and performance were recorded. As predicted, virtually all effects were on the arousal/habituation and attentional (vigilance) tasks. Both acute ingestion and habitual use increased tonic EDA, and chronic use also reduced phasic responding, especially in the presence of a strong habituating stimulus. Both acute and habitual use also liberalized the vigilance response criterion, in that subjects risked more false alarms in order to attain more hits. In addition, habitual use increased sensitivity and reduced accuracy, and acute ingestion increased vigilance response time in the presence of white noise. Overall, the model was partially supported by these early results, though considerable further research is needed.

Adult↗
PubMed1992

Lipid A in Helicobacter pylori.

Free lipid A of Helicobacter pylori was characterized with regard to chemical composition, reactivity with anti-lipid A antibodies, and activity in a Limulus lysate assay. The predominant fatty acids of H. pylori lipid A were 3-OH-18:0, 18:0, 3-OH-16:0, 16:0, and 14:0. Hexosamine was present in amounts similar to those in Campylobacter jejuni or Salmonella typhimurium lipid A. The lipopolysaccharide of H. pylori contained 2-keto-3-deoxyoctonic acid, a common constituent of enterobacterial and C. jejuni lipopolysaccharides. In the enzyme-linked immunosorbent assay, the doses of lipid A required to inhibit anti-lipid A by 50% (EI50 values) by absorption of the immune (rabbit) serum were 7.9, 1.2, and 1.4 micrograms of O-deacylated lipid A's from H. pylori, C. jejuni, and S. typhimurium per ml, respectively. The lower reactivity of H. pylori lipid A compared with those of the other two lipid A preparations (as shown by the higher EI50 value) was underscored by the use of a murine monoclonal anti-lipid A antibody in the inhibition assay. An EI50 value was not obtained at the concentrations tested for H. pylori lipid A; the corresponding figures for C. jejuni and S. typhimurium lipid A's were 13 and 14 micrograms/ml, respectively. No inhibition was obtained with H. pylori lipopolysaccharide, which showed a low-molecular-weight profile on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The activity of H. pylori lipid A in the Limulus assay was approximately 71 and 650 times lower than those of C. jejuni and S. typhimurium lipid A's, respectively. These findings suggest that lipid A is an integral part of the outer cell wall of H. pylori. The lower reactivity of H. pylori lipid A with anti-lipid A antibodies and in the Limulus assay compared with that of C. jejuni or S. typhimurium lipid A may be explained by a different composition of the fatty acids, especially the 3-hydroxy fatty acids, and a possible deviating phosphorylation pattern.

Animals↗
PubMed1991

Endotoxin shedding by enterobacteria: free and cell-bound endotoxin differ in Limulus activity.

The endotoxin activities of gram-negative bacteria and their lipopolysaccharides (LPS) have been quantitated by a chromogenic Limulus amocbocyte lysate (CLAL) assay. When bacterial cell exposing various cell surface structures were compared, the highest Limulus activities were found in R strains of Escherichia coli and Salmonella typhimurium mutants. E. coli with K antigens did not differ from K-negative strains. By measuring beta-hydroxymyristic acid (3-OH tetradecanoic acid, beta-OHC14:0), it was possible to compare the CLAL activities of LPS bound to bacterial cells, LPS shed into the culture medium, and purified LPS. After 16 h of growth, the cell-free culture supernatants of three E. coli O1K1 strains and S. typhimurium showed CLAL activities 14.3 to 20.3 times higher than did the corresponding bacterial cell suspensions in relation to their beta-OHC14:0 contents. Four other E. coli strains (O serotypes O14, O24, and O75) and the S. typhimurium 395 R mutants MR5 and MR6 showed CLAL values 2.8 to 7.9 times higher in their culture supernatants. LPS of E. coli O1K1 and S. typhimurium had lower CLAL activities than the culture supernatants (1/10 and 1/4, respectively). Although the beta-OHC14:0 concentrations of the culture supernatants were approximately half those of the corresponding bacterial cells, all had CLAL values that were 2 to 21 times higher. The bacterial cell suspension, culture supernatant, and purified LPS of S. typhimurium MS were compared by CLAL assay and a quantitative enzyme-linked immunosorbent assay based on monoclonal antibodies to the O5 antigen. Endotoxin shed into the culture medium was the most CLAL-active form of LPS, while purified LPS was the most antigen-active form. The results emphasize the importance of appropriate standards when quantifying endotoxin in various states. In conclusion, E. coli and S. typhimurium bacteria shed significant amounts of endotoxin into the surrounding medium during growth. This form of LPS is more CLAL active than the cell-bound or purified LPS.

Animals↗
PubMed1988

Seasonal, geographic and individual variation of okadaic acid content in cultivated mussels in Sweden.

In Western Europe the dinoflagellate toxin, okadaic acid (OA) has been the main cause of diarrheic shellfish poisoning (DSP). Chemical determination of OA in mussels by homogenization of the hepatopancreas, extraction, purification, reaction with 9-anthryldiazomethane (ADAM), HPLC-separation, and fluorometric quantification has been used for weekly monitoring of mussel growing farms and to control harvested mussels. Within a week, substantial rises (from 0.41 to 5.4 micrograms OA/g hepatopancreas) as well as great reductions (from 7.2 to 1.8 micrograms/g hepatopancreas) were recorded. The rapid rise implies that weekly sampling is not sufficient to ensure that mussels are free from toxic levels of OA. The rapid decrease reveals that efficient toxin clearance mechanisms exist in the mussels. Substantial OA clearance occurs also at low temperatures (1.4-3 degrees C). Within a mussel growing site the OA concentrations could differ considerably between adjacent mussels (0.63 and 4.2 micrograms OA/g hepatop.) and even more between mussels grown at different depths along the same rope (0.63 and 10 micrograms OA/g hepatop.). These data emphasize the importance of sampling in studies on DST in mussels. Great differences between the different mussel growing sites were also observed. These data have been discussed with respect to the spread of the toxin by the sea, and the possibilities of reducing the exposure of the mussels to the toxic algae.

Animals↗
PubMed1986

Plasma carnitine and renal-carnitine clearance during pregnancy.

This study assessed the time course of decrease in plasma carnitine during pregnancy and compared the renal clearance of carnitine during late pregnancy with nonpregnant women. As early as the 8th wk of pregnancy, the mean (+/- SD) value of total plasma-carnitine concentration in 19 women was significantly decreased from 39.0 +/- 6.3 to 32.8 +/- 4.6 mumol/l and the values continued to fall to 17.3 mumol/l by the 36th wk. The pattern was due to a fall in free-carnitine level; acylcarnitine remained unchanged. In 12 other women examined during late pregnancy, the renal clearance of acylcarnitine was significantly higher than in nonpregnant women, 53.9 +/- 29.4 versus 13.3 +/- 3.0 ml/min, in contrast to free carnitine, 3.5 +/- 2.8 versus 2.8 +/- 1.9 ml/min. Urinary excretion of carnitine (expressed per mol creatinine) did not differ between the two groups. Pregnant women showed sustained excretion of carnitine in the presence of low plasma-carnitine concentrations.

Adult↗
PubMed1986

Gas-liquid chromatographic method for determining urinary estriol, with 6 alpha-hydroxyestriol as internal standard.

I describe a chromatographic procedure for quantification of urinary estriol in late pregnancy, with 6 alpha-hydroxyestriol used as internal standard. The hydrolyzed sample is successively passed through a Bond Elut C18 column and a DEAE-Sephadex column. The estrogens are then completely resolved as silyl ethers on a packed gas-liquid chromatographic (GLC) column in isothermal mode. Analytical recoveries of conjugated estriol ranged between 96 and 102%. Between-day precision (CV) was 4.4% at a mean concentration of 85.1 mumol/L. Specificity was assessed by comparing results obtained with a capillary GLC column.

Chromatography, Gas↗
PubMed1986

Spectrophotometry of carnitine in biological fluids and tissue with a Cobas Bio centrifugal analyzer.

A spectrophotometric method for carnitine has been adapted to the Cobas Bio centrifugal analyzer. The addition of carnitine to a system containing carnitine acetyltransferase (EC 2.3.1.7) and acetyl-CoA gives rise to the formation of CoA. The system is coupled to 5,5'-dithiobis(2-nitrobenzoate) (DTNB). Assay response varied linearly with concentration of carnitine over a wide concentration range. The total CV was 5.5% for a carnitine concentration in serum of 58.0 mumol/L. Analytical recovery of carnitine added to a serum sample was 93%. No interference was found in icteric, not grossly hemolyzed, lipemic, or uremic sera. Comparison with a radioenzymatic method showed that results correlated well (r greater than 0.965) but the present method gave values proportionally greater by 10 to 25% for samples of plasma, dialysis fluid, urine, and muscle tissue. Advantages over the original spectrophotometric assays involving DTNB include low reagent costs, rapidity, simplicity, and reproducibility. However, this modification is not as sensitive and probably not as specific as the radioenzymatic methods.

Acetylcarnitine↗
PubMed1986

Determination of vanillylmandelic acid with ion-pair chromatography and fluorescence detection.

We describe a chromatographic procedure for sensitive (2.0 mumol/L), specific quantification of vanillylmandelic acid (VMA) in urine with iso-VMA as an internal standard. After rapid extraction from urine, the VMA is determined by isocratic reversed-phase ion-pair chromatography on a bonded C8 column and detection of the native fluorescence on excitation at 285 nm. The fluorescence signal is quite dependent on the pH of the mobile phase. Results by the method vary linearly with VMA concentration up to 320 mumol/L and correlate well (r = 0.9880) with those obtained by conventional ultraviolet spectrophotometry. The mean 24-h excretion of VMA from 29 healthy volunteers was 21.4 (SD 5.4) mumol.

Adolescent↗