Biomedical subjects

J Nielsen

Publications and source records attributed to J Nielsen.

At least 199 records · Page 11Linked to original sources

PubMed1997

Purification and characterization of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine synthetase from Penicillium chrysogenum.

delta-(L-alpha-Aminoadipyl)-L-cysteinyl-D-valine synthetase (ACVS) from Penicillium chrysogenum was purified to homogeneity by a combination of (NH4)2SO4 precipitation, protamine sulphate treatment, ion-exchange chromatography, gel filtration and hydrophobic interaction chromatography. The molecular mass of ACVS was estimated with native gradient gel electrophoresis and SDS/PAGE. The native enzyme consisted of a single polymer chain with an estimated molecular mass of 470 kDa. The denatured enzyme had an estimated molecular mass of 440 kDa. The influence of different reaction parameters such as substrates, cofactors and pH on the activity of the purified ACVS was investigated. The Km values for the three precursor substrates L-alpha-aminoadipic acid, L-cysteine and L-valine were determined as 45, 80 and 80 microM respectively, and the optimal assay concentration of ATP was found to be 5 mM (with 20 mM MgCl2). The dimer of the reaction product bis-delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (bisACV) gave feedback inhibition of the purified ACVS; the inhibition parameter KbisACV was determined as 1.4 mM. Furthermore dithiothreitol was shown to inhibit the purified ACVS. From the addition of a glucose pulse to a steady-state glucose-limited continuous culture of P. chrysogenum it was found that there is glucose repression of the synthesis of ACVS and that there must be a constant turnover of ACVS owing to synthesis and degradation.

2-Aminoadipic Acid↗

PubMed1997

A novel compound, 1,1-dimethyl-5(1-hydroxypropyl)-4,6,7-trimethylindan, is an effective inhibitor of the tet(K) gene-encoded metal-tetracycline/H+ antiporter of Staphylococcus aureus.

A novel indan derivative, 1,1-dimethyl-5-(1-hydroxypropyl)-4,6,7-trimethylindan (Ro 07-3149), was found to be a strong inhibitor of the tet(K) gene-encoded tetracycline/H+ antiporter of Staphylococcus aureus. One micromole of this compound per mg membrane protein was enough for complete inhibition of the Tet(K)-mediated tetracycline transport and tetracycline-coupled proton transport, without the energy state of the membrane being affected. The mode of inhibition was non-competitive. Although this compound caused membrane de-energization at a high concentration, the IC50 value for de-energization (7.3 micromol/mg membrane protein) was about 17 times and 33 times higher than the values for Tet(K)-mediated proton/tetracycline antiport and [3H]tetracycline transport, respectively, indicating that the inhibitory action of Ro 07-3149 is not due to the uncoupling effect of the inhibitor.

Antiporters↗

PubMed1997

Distinct repression of translation by wortmannin and rapamycin.

The role of phosphatidylinositol 3-kinase and FK506-binding protein rapamycin-associated protein (FRAP) in translational control has been examined by treating RD-rhabdomyosarcoma cells with wortmannin and rapamycin and studying the effects on cell-growth, translation initiation, and protein synthesis. Whereas wortmannin and rapamycin exhibit subtle effects on global translation, examination of individual mRNAs in sucrose gradients and of individual proteins in two-dimensional polyacrylamide gels reveals that wortmannin and rapamycin exhibit distinct effects on the translation of individual mRNAs. Wortmannin represses the synthesis of a third of cellular proteins, whereas rapamycin affects a subset of these proteins. Since ribosomal protein S6 was rapidly dephosphorylated following wortmannin and rapamycin treatment, and the phosphorylation status of the eukaryotic initiation factor 4E was unchanged, our data imply that the p70 signalling pathway has at least one branch-point upstream of FRAP leading to an additional route of translational control.

Androstadienes↗

PubMed1997

Evidence suggesting a transcortical pathway from cutaneous foot afferents to tibialis anterior motoneurones in man.

1. Stimulation of the superficial peroneal or the sural nerve (3 shocks, 3 ms interval, 1 ms duration, 2.5 x perception threshold) evoked a reflex activation of the tibialis anterior muscle at a latency of approximately 70-95 ms in all of nine healthy human subjects. Stimulation of the medial plantar nerve only rarely produced similar effects. The possibility that a transcortical pathway contributes to these late reflex responses was investigated by combining the cutaneous stimulations and a transcranial magnetic stimulation of the contralateral motor cortex. 2. A significant facilitation of short-latency peaks in the post-stimulus time histogram of single tibialis anterior motor units evoked by the transcortical magnetic stimulation was observed in eight out of nine subjects following stimulation of the superficial peroneal or sural nerves at the latency of the long-latency reflex. In contrast such a facilitation was only rarely seen when the medial plantar nerve was stimulated. 3. With the same timing for the stimuli, the superficial peroneal and sural nerve stimulations also produced a significant increase in the short-latency, presumed monosynaptic, facilitation of the tibialis anterior H reflex produced by the brain stimulation. 4. Similar facilitatory effects of the cutaneous stimuli could not be demonstrated when the magnetic stimulation of the cortex was replaced with electrical stimulation, implying that cortical excitability is affected by a conditioning cutaneous stimulation. 5. It is suggested that the long-latency reflexes in the tibialis anterior muscle evoked by activation of cutaneous afferents from the human foot are, at least partly, mediated by a transcortical pathway.

Adult↗

PubMed1997

Structure and function of the dihydropteroate synthase from Staphylococcus aureus.

The gene encoding the dihydropteroate synthase of staphylococcus aureus has been cloned, sequenced and expressed in Escherichia coli. The protein has been purified for biochemical characterization and X-ray crystallographic studies. The enzyme is a dimer in solution, has a steady state kinetic mechanism that suggests random binding of the two substrates and half-site reactivity. The crystal structure of apo-enzyme and a binary complex with the substrate analogue hydroxymethylpterin pyrophosphate were determined at 2.2 A and 2.4 A resolution, respectively. The enzyme belongs to the group of "TIM-barrel" proteins and crystallizes as a non-crystallographic dimer. Only one molecule of the substrate analogue bound per dimer in the crystal. Sequencing of nine sulfonamide-resistant clinical isolates has shown that as many as 14 residues could be involved in resistance development. The residues are distributed over the surface of the protein, which defies a simple interpretation of their roles in resistance. Nevertheless, the three-dimensional structure of the substrate analogue binary complex could give important insight into the molecular mechanism of this enzyme.

Amino Acid Sequence↗

PubMed1997

Metabolic control analysis of biochemical pathways based on a thermokinetic description of reaction rates.

Metabolic control analysis is a powerful technique for the evaluation of flux control within biochemical pathways. Its foundation is the elasticity coefficients and the flux control coefficients (FCCs). On the basis of a thermokinetic description of reaction rates it is here shown that the elasticity coefficients can be calculated directly from the pool levels of metabolites at steady state. The only requirement is that one thermodynamic parameter be known, namely the reaction affinity at the intercept of the tangent in the inflection point of the curve of reaction rate against reaction affinity. This parameter can often be determined from experiments in vitro. The methodology is applicable only to the analysis of simple two-step pathways, but in many cases larger pathways can be lumped into two overall conversions. In cases where this cannot be done it is necessary to apply an extension of the thermokinetic description of reaction rates to include the influence of effectors. Here the reaction rate is written as a linear function of the logarithm of the metabolite concentrations. With this type of rate function it is shown that the approach of Delgado and Liao [Biochem. J. (1992) 282, 919-927] can be much more widely applied, although it was originally based on linearized kinetics. The methodology of determining elasticity coefficients directly from pool levels is illustrated with an analysis of the first two steps of the biosynthetic pathway of penicillin. The results compare well with previous findings based on a kinetic analysis.

Algorithms↗

PubMed1997

Colorectal function in patients with spinal cord lesions.

PURPOSE: This study was designed to describe the frequency and severity of colorectal problems among patients with spinal cord lesions and to determine whether these problems are associated with age, gender, time since the lesion, and level and severity of the lesion. PATIENTS AND METHODS: A detailed questionnaire describing colorectal and bladder function was sent to all 589 members of The Danish Paraplegic Association; 424 responded (72 percent). RESULTS: Only 19 percent felt a normal desire to defecate, whereas the remaining patients felt no desire to defecate (38 percent) or a combination of abdominal discomfort (37 percent) and headache, physical uneasiness, and perspiration (25 percent). Digital stimulation of the anal canal before defecation or digital evacuation of the rectum was used regularly by 65 percent of patients. Fecal incontinence was experienced by 75 percent of patients; however, most patients only had a few episodes of fecal incontinence each month (15 percent) or each year (56 percent). Overall, 39 percent of patients reported that colorectal dysfunction caused some or major restrictions on social activities or on their quality of life, and 30 percent regarded colorectal complaints to be worse than both bladder and sexual dysfunction. The severity of most symptoms was significantly correlated with the severity of the lesion, and the self-reported impact on social activities or quality of life was significantly more severe among women than men. CONCLUSION: Colorectal dysfunction is very common among spinal cord-injured patients, often causing restriction on social activities and quality of life. Therefore, these problems deserve more attention in the treatment of spinal cord-injured patients.

Adolescent↗

PubMed1997

Detection of antibodies against porcine parvovirus nonstructural protein NS1 may distinguish between vaccinated and infected pigs.

The humoral antibody response against the nonstructural protein NS1 and the structural protein VP2 of porcine parvovirus (PPV) was evaluated by immuno-peroxidase test (IPT) and enzyme linked immuno sorbent assay (ELISA) using recombinant PPV antigens. The coding sequence for NS1 and VP2 was inserted into the baculovirus. Autographa californica nuclear polyhedrosis virus (AcNPV) genome resulting in two recombinant baculoviruses AcNPV-NS1 and AcNPV-VP2, respectively. Sf9 cells (Spodoptora frugidiperda) inoculated with AcNPV-NS1 producing recombinant nonstructural protein (rNS1) and AcNPV-VP2 producing recombinant virion protein (rVP2) were used in IPT and ELISA to analyse serum antibodies. Pigs vaccinated with an inactivated whole virus vaccine and experimentally infected pigs were studied. Significant titers against rVP2 were obtained in both vaccinated and infected pigs. Specific antibodies against rNS1 could only be detected in infected pigs and NS1 may in this way allow the specific detection of infected animals. Analysis of serum samples collected up to 18 days post infection (p.i.) from four pigs experimentally infected with PPV showed that antibodies against rNS1 and rVP2 could in all cases be detected on day 9 p.i. Two individual pigs were inoculated twice with PPV and the antibody response was followed 89 days after second inoculation. Serum antibodies against both rVP2 and rNS1 could be detected for this period of time.

Animals↗

PubMed1997

Examination of virus shedding in semen from vaccinated and from previously infected boars after experimental challenge with porcine reproductive and respiratory syndrome virus.

Danish artificial insemination (AI) centres house several boars antibody positive to porcine reproductive and respiratory syndrome virus as well as PRRSV-naive boars which may become acutely infected. The risk of transmission of PRRSV by semen may therefore constitute a serious problem to the Danish pig industry. The use of a vaccination-program may be a way to avoid or reduce the problem. This study evaluates the use of two vaccines: One live, attenuated vaccine and one inactivated vaccine. A pronounced reduction in viremia and shedding of virus in semen was demonstrated by use of the live vaccine compared to the non-vaccinated control animals. In contrast, no changes in onset, level and duration of viremia and shedding of virus in semen were observed using the inactivated vaccine. Neither viremia nor seminal shedding of virus was detected in previously PRRSV-infected, PRRSV-antibody positive boars after challenge with a Danish field strain of PRRSV.

Animals↗

PubMed1997

Hematological and immunological parameters of 4 1/2-month old pigs infected with PRRS virus.

4 1/2-month old SPF pigs were experimentally infected with PRRS virus. Blood samples were collected with regular intervals up to day 35 post inoculation (PI). Serum was used for PRRS virus isolation and antibody detection and stabilized blood for total leucocyte counts, differential counts and characterization of lymphocyte subpopulations by flow cytometry analysis using monoclonal antibodies specific for porcine CD2, CD4 and CD8. After an initial viremic period of 1-7 days duration for individual pigs, PRRS virus was intermittently detected in pigs up to day 18 PI. All pigs had developed antibodies against PRRS virus by day 14 PI. Total blood leucocyte counts and lymphocyte counts were significantly decreased for a few days shortly after infection, but had returned to pre-infection levels on day 8-10 PI. A major change in the distribution of lymphocyte subpopulations was observed on day 3 PI, where the percentages of CD2+, CD4+ and CD8+ cells were significantly decreased. However, the percentages of these lymphocyte subsets quickly returned to approximately pre-infection values. The observed changes of the parameters examined do not indicate long-term systemic immunosuppression of the infected pigs.

Animals↗

PubMed1997

Evaluation of a blocking Elisa for screening of antibodies against porcine reproductive and respiratory syndrome (PRRS) virus.

A blocking Elisa was developed for the detection of antibodies against PRRS virus with a view to satisfying the need for examination of blood samples on a large scale. The test was evaluated in comparison with an indirect Elisa and the immunoperoxidase monolayer assay. The blocking Elisa was sensitive and specific. It had a higher capacity and was cheaper to perform than the immunoperoxidase monolayer assay and the indirect Elisa. It was comparable to the immunoperoxidase monolayer assay and better than the indirect Elisa in detecting antibodies formed early after infection, and it was superior to both the immunoperoxidase monolayer assay and the indirect Elisa in detecting antibodies at a late stage of infection.

Animals↗

PubMed1997

New developments in low-bit rate videotelephony for people who are deaf.

This study was designed to evaluate the picture quality requirements for three visual communication modes: speechreading, fingerspelling, and sign language. Video recordings of everyday spoken, fingerspelled, and signed sentences were made, and some recordings were processed using a computer simulation of the IBIDEM technology: a videophone based on a novel type of visual sensor. This retina-like sensor, implemented in the camera, has a high resolution in the central part and a degrading resolution in the peripheral part of the picture. Two independent variables were examined: frame rate (10 and 15 frames per second) and spatial resolution (6000 and 8000 pixels per frame). Twenty-four people who were prelingually deaf participated, 8 in each communication mode. The results showed a marked effect of frame rate on speechreading. Fingerspelling and sign language were not affected by frame rate, and spatial resolution had no effect on any of the three communication modes.

Adolescent↗

PubMed1997

Relationship between follicular fluid steroids and tissue renin concentrations and secretion rates in bovine ovaries.

The relationship between follicular fluid concentrations of oestradiol (E2) and progesterone (P4), and follicular wall tissue renin concentrations and in-vitro secretion rates was investigated. The follicular fluid concentrations of prorenin correlated negatively with oestradiol and the E2/P4 ratio, and positively with progesterone in accordance with earlier findings. The high concentrations of active renin and prorenin in the follicular wall tissue, and the secretion rates of both active renin and prorenin all correlated positively with oestradiol and the E2/P4 ratio, but negatively with progesterone. These findings suggest that atretic follicles have higher follicular fluid renin concentrations but lower tissue renin concentrations and in-vitro secretion rates than healthy non-atretic follicles. The high follicular fluid prorenin concentrations in atretic follicles are most likely caused by a high prorenin secretion rate earlier in the oestrus cycle. The existence of relationships between the follicular fluid steroids and the follicular wall concentrations and secretion rates of active renin and prorenin indicates an interaction between the reninangiotensin system and steroidogenesis, but it may also reflect regulation by common factors, such as gonadotropins.

Animals↗

PubMed1997

Spatial summation of heat induced pain within and between dermatomes.

The aim was to study spatial summation within and between ipsi- and contralateral dermatomes at different painful temperatures. For heat stimulation we used a computer controlled thermofoil based thermode. The thermode area could be varied in five discrete steps from 3.14 to 15.70 cm2. When we applied the stimuli within a dermatome, the mean heat pain threshold decreased significantly from 45.6 to 43.5 degrees C as the area was increased from minimum (3.14 cm2) to maximum (15.70 cm2). When the areas were increased involving different dermatomes (both ipsi- or contralateral), we found similar decreases in pain threshold. Spatial summation was also found within and between dermatomes at supra-threshold temperatures (46, 48, 50 degrees C). The study shows that spatial summation of pain is most likely a mechanism acting across segments and is existing from pain threshold to tolerance.

Adult↗

PubMed1997

Silencing MIG1 in Saccharomyces cerevisiae: effects of antisense MIG1 expression and MIG1 gene disruption.

Silencing of MIG1, a transcription factor imposing carbon catabolite repression on invertase, was attempted, either by disrupting the gene or by expressing antisense copies of the gene. The performance of the recombinant strains in bioreactor batch cultivations on sucrose, in the presence of glucose, was compared with that of the wild-type strain under the same conditions. In the delta migI strain, the rate of sucrose utilization was independent (10 mmol/g/h) of the glucose concentration. During the cultivations with the wild-type strain and the antisense strains, two distinct phases were observed. The rates of sucrose hydrolysis were < 1 mmol/g/h and 9 to 10 mmol/g/h in the first and second phases, respectively. Entry into the second cultivation phase was characterized by a decline in glucose concentration below 12 mmol/liter. As expected, disruption of MIG1 resulted in a relief of glucose repression. However, silencing of MIG1 expression was not achieved by expressing antisense MIG1, even though antisense MIG1 RNA was sufficiently stable to be detected. In the wild-type and delta migI strains, the specific growth rate was 0.32 to 0.33 h-1, whereas it was lower in the antisense strains, 0.25 to 0.30 h-1.

Base Sequence↗

PubMed1997

Chronic respiratory symptoms, skin test results, and lung function as predictors of peak flow variability.

We examined how chronic respiratory symptoms, reported in a questionnaire, and results of skin prick tests and spirometry predicted variability in peak expiratory flow (PEF) among 6-12-yr-old children (n = 1,854). After characterization with skin tests and spirometry, children were followed for 2-3 mo during the winter of 1993-1994. Peak expiratory flow was measured daily in the morning and evenings. Children with asthmatic symptoms (wheeze and/or attacks of shortness of breath with wheeze in the past 12 mo and/or ever doctor diagnosed asthma) had a greater variation in PEF than children with dry nocturnal cough as their only chronic respiratory symptom. Similarly, doctor-diagnosed asthma was associated with a greater variation in PEF, also among children with asthmatic symptoms. Peak flow variability increased with an increasing number of symptoms reported in the questionnaire. Atopy, positive skin test reactions to house dust mite and cat and lowered level (as % of predicted) in FEV1 and in MMEF were also associated with an increased variation in PEF. All the differences were observed in both diurnal and day-to-day variation in PEF. In conclusion, chronic respiratory symptoms reported in a questionnaire, spirometric lung function and skin prick test results among asthmatic children predicted variation in PEF measured during a 2-3 mo follow-up. The difference in morning PEF coefficient of variation (CV) between children with asthmatic symptoms and children with cough only was somewhat bigger in girls than in boys. The effect of atopy on morning PEF CV was somewhat bigger in young than in older children.

Animals↗

PubMed1996

[Nasal catheters versus Hudson face mask in oxygen therapy].

Thirty-two females, ASA class I, scheduled for termination of pregnancy before the 13th week participated in the study. After induction of anaesthesia, a soft plastic catheter was inserted in the oropharynx and the patients were postoperatively monitored with a capnograph, which sampled in- and expired air from the catheter. In a randomized cross-over design the patients received oxygen therapy by the Hudson face-mask and a nasal cannula. Humidified and heated oxygen was given in both cases, using a flow of 15 litres per minute. The nasal cannula resulted in a significantly higher expired end-tidal O2-fraction (FETO2) compared to the Hudson mask. During the nasal cannula period the respiratory rate was significantly lower than during the face mask period. The end-tidal CO2 pressure (PETCO2) remained constant.

Abortion, Induced↗

PubMed1996

[Continuous monitoring of end-tidal CO2-tension in non-intubated patients].

We describe and evaluate a method for continuously monitoring end-tidal CO2 (PETCO2) in non-intubated, spontaneously breathing patients. In 18 ASA I patients scheduled for minor surgery a 3.3 mm (10 CH) soft plastic catheter was preoperatively inserted through one nostril placing the tip at the level of the epiglottis. In the recovery room a capnograph was connected to the catheter for monitoring PETCO2. We found no significant differences between arterial carbon dioxide tension (PaCO2) and PETCO2 obtained by the catheter (0.2 +/- 2.2 mmHg) or obtained by a maximal expiration through a mouthpiece (-0.8 +/- 2.8 mmHg). We tested the possibility of mixing expired air with supplementary oxygen via the other nostril at a flowrate of 15 litres min-1, and found no significant difference in PETCO2 with or without flow (0.0 +/- 0.9 mmHg). Values are mean +/- SD. In conclusion we find that this method allows accurate monitoring of PETCO2 in non-intubated, spontaneously breathing patients even at supplementary oxygen flow-rates of up to 15 litres min-1.

Abortion, Induced↗