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Biomedical subjects

J S Nielsen

Publications and source records attributed to J S Nielsen.

At least 19 recordsLinked to original sources
PubMed2002

Muscle fibre type, efficiency, and mechanical optima affect freely chosen pedal rate during cycling.

UNLABELLED: This study investigated the variation in freely chosen pedal rate between subjects and its possible dependence on percentage myosin heavy chain I (%MHC I) in m. vastus lateralis, maximum leg strength and power, as well as efficiency. Additionally, the hypothesis was tested that a positive correlation exists between percentage MHC I and efficiency at pre-set pedal rates but not at freely chosen pedal rate. Twenty males performed cycling at low and high submaximal power output ( approximately 40 and 70% of the power output at which maximum oxygen uptake (VO(2max)) was attained at 80 r.p.m.) with freely chosen and pre-set pedal rates (61, 88, and 115 r.p.m.). Percentage MHC I as well as leg strength and power were determined. Freely chosen pedal rate varied considerably between subjects: 56-88 r.p.m. at low and 61-102 r.p.m. at high submaximal power output. This variation was only partly explained by percentage MHC I (21-97%) as well as by leg strength and power. Interestingly, %MHC I correlated significantly with the pedal rate at which maximum peak crank power occurred (r = -0.81). As hypothesized, %MHC I and efficiency were unrelated at freely chosen pedal rate, which was in contrast to a significant correlation found at pre-set pedal rates (r = 0.61 and r = 0.57 at low and high power output, respectively). CONCLUSIONS: Subjects with high percentage MHC I chose high pedal rates close to the pedal rates at which maximum peak crank power occurred, while subjects with low percentage MHC I tended to choose lower pedal rates, favouring high efficiency. Nevertheless, the considerable variation in freely chosen pedal rate between subjects was neither fully accounted for by percentage MHC I nor by leg strength and power. Previously recognized relationships between percentage Type I ( approximately %MHC I) and efficiency as well as between pedal rate and efficiency were confirmed for pre-set pedal rates, but for freely chosen pedal rate, these variables were unrelated.

Adolescent↗
PubMed2001

Low-current, vertical blowup in a stored laser-cooled ion beam.

Using a novel technique for real-time transverse beam profile diagnostics of a stored ion beam, we have observed the transverse size of a stored laser-cooled ion beam. Earlier we observed that the density of the beam is independent of the beam current. At very low currents, we observe an abrupt change in this behavior: The vertical beam size increases suddenly by about an order of magnitude. This observation implies a sudden change in the indirect vertical cooling mediated by intrabeam scattering. Our results have serious implications for the ultimate beam quality attainable by laser cooling.

Journal Article↗
PubMed2001

Effects of high extracellular [K+] and adrenaline on force development, relaxation and membrane potential in cardiac muscle from freshwater turtle and rainbow trout.

Increases in extracellular K(+) concentrations reduced the twitch force amplitude of heart muscle from the freshwater turtle (Trachemys scripta elegans) and rainbow trout (Oncorhynchus mykiss). Adrenaline augmented twitch force amplitude and reduced the relative influence of [K(+)]. In the absence of adrenaline, high [K(+)] had less effect in reducing twitch force in turtle than in trout, whereas the reverse was true in the presence of adrenaline. Under anoxic conditions, twitch force was lower in 10 mmol l(-1) than in 2.5 mmol l(-1) K(+) in both preparations, but adrenaline removed this difference. A further analysis of turtle myocardium showed that action potential duration was shorter and resting potential more positive in high [K(+)] than in low [K(+)]. Adrenaline restored the duration of the action potential, but did not affect the depolarisation, which may attenuate Na(+)/Ca(2+) exchange, participating in excitation/contraction coupling. The contractile responses in the presence of adrenaline were, however, similar in both high and low K(+) concentrations when increases in extracellular Ca(2+) were applied to increase the demand on excitation/contraction coupling. The possibilities that adrenaline counteracts the effects of high [K(+)] via the sarcoplasmic reticulum or sarcolemmal Na(+)/K(+)-ATPase were examined by inhibiting the sarcoplasmic reticulum with ryanodine (10 micromol l(-1)) or Na(+)/K(+)-ATPase with ouabain (0.25 or 3 mmol l(-)). No evidence to support either of these possibilities was found. Adrenaline did not protect all aspects of excitation/contraction coupling because the maximal frequency giving regular twitches was lower at 10 mmol l(-1) K(+) than at 2.5 mmol l(-1) K(+).

Action Potentials↗
PubMed2000

Cloning and expression of cytochrome P450 enzymes catalyzing the conversion of tyrosine to p-hydroxyphenylacetaldoxime in the biosynthesis of cyanogenic glucosides in Triglochin maritima.

Two cDNA clones encoding cytochrome P450 enzymes belonging to the CYP79 family have been isolated from Triglochin maritima. The two proteins show 94% sequence identity and have been designated CYP79E1 and CYP79E2. Heterologous expression of the native and the truncated forms of the two clones in Escherichia coli demonstrated that both encode multifunctional N-hydroxylases catalyzing the conversion of tyrosine to p-hydroxyphenylacetaldoxime in the biosynthesis of the two cyanogenic glucosides taxiphyllin and triglochinin in T. maritima. This renders CYP79E functionally identical to CYP79A1 from Sorghum bicolor, and unambiguously demonstrates that cyanogenic glucoside biosynthesis in T. maritima and S. bicolor is catalyzed by analogous enzyme systems with p-hydroxyphenylacetaldoxime as a free intermediate. This is in contrast to earlier reports stipulating p-hydroxyphenylacetonitrile as the only free intermediate in T. maritima. L-3,4-Dihydroxyphenyl[3-(14)C]Ala (DOPA) was not metabolized by CYP79E1, indicating that hydroxylation of the phenol ring at the meta position, as required for triglochinin formation, takes place at a later stage. In S. bicolor, CYP71E1 catalyzes the subsequent conversion of p-hydroxyphenylacetaldoxime to p-hydroxymandelonitrile. When CYP79E1 from T. maritima was reconstituted with CYP71E1 and NADPH-cytochrome P450 oxidoreductase from S. bicolor, efficient conversion of tyrosine to p-hydroxymandelonitrile was observed.

Amino Acid Sequence↗
PubMed1999

The T-superfamily of conotoxins.

We report the discovery and initial characterization of the T-superfamily of conotoxins. Eight different T-superfamily peptides from five Conus species were identified; they share a consensus signal sequence, and a conserved arrangement of cysteine residues (- -CC- -CC-). T-superfamily peptides were found expressed in venom ducts of all major feeding types of Conus; the results suggest that the T-superfamily will be a large and diverse group of peptides, widely distributed in the 500 different Conus species. These peptides are likely to be functionally diverse; although the peptides are small (11-17 amino acids), their sequences are strikingly divergent, with different peptides of the superfamily exhibiting varying extents of post-translational modification. Of the three peptides tested for in vivo biological activity, only one was active on mice but all three had effects on fish. The peptides that have been extensively characterized are as follows: p5a, GCCPKQMRCCTL*; tx5a, gammaCCgammaDGW(+)CCT( section sign)AAO; and au5a, FCCPFIRYCCW (where gamma = gamma-carboxyglutamate, W(+) = bromotryptophan, O = hydroxyproline, T( section sign) = glycosylated threonine, and * = COOH-terminal amidation). We also demonstrate that the precursor of tx5a contains a functional gamma-carboxylation recognition signal in the -1 to -20 propeptide region, consistent with the presence of gamma-carboxyglutamate residues in this peptide.

Amino Acid Sequence↗
PubMed1999

Biosynthesis of cyanogenic glucosides in Triglochin maritima and the involvement of cytochrome P450 enzymes.

The biosynthesis of the two cyanogenic glucosides, taxiphyllin and triglochinin, in Triglochin maritima (seaside arrow grass) has been studied using undialyzed microsomal preparations from flowers and fruits. Tyrosine was converted to p-hydroxymandelonitrile with V(max) and K(m) values of 36 nmol mg(-1) g(-1) fresh weight and 0.14 mM, respectively. p-Hydroxyphenylacetaldoxime and p-hydroxyphenylacetonitrile accumulated as intermediates in the reaction mixtures. Using radiolabeled tyrosine as substrate, the radiolabel was easily trapped in p-hydroxyphenylacetaldoxime and p-hydroxyphenylacetonitrile when these were added as unlabeled compounds. p-Hydroxyphenylacetaldoxime was the only product obtained using microsomes prepared from green leaves or dialyzed microsomes prepared from flowers and fruits. These data contrast earlier reports (Hösel and Nahrstedt, Arch. Biochem. Biophys. 203, 753-757, 1980; and Cutler et al., J. Biol. Chem. 256, 4253-4258, 1981) where p-hydroxyphenylacetaldoxime was found not to accumulate. All steps in the conversion of tyrosine to p-hydroxymandelonitrile were found to be catalyzed by cytochrome P450 enzymes as documented by photoreversible carbon monoxide inhibition, inhibition by antibodies toward NADPH-cytochrome P450 oxidoreductase, and by cytochrome P450 inhibitors. We hypothesize that cyanogenic glucoside synthesis in T. maritima is catalyzed by multifunctional cytochrome P450 enzymes similar to CYP79A1 and CYP71E1 in Sorghum bicolor except that the homolog to CYP71E1 in T. maritima exhibits a less tight binding of p-hydroxyphenylacetonitrile, thus permitting the release of this intermediate and its conversion into triglochinin.

Adipates↗
PubMed1999

Recurrence of uterine intravenous leiomyomatosis with intracardiac extension. Diagnostic considerations and surgical removal.

A 28-year-old woman (gravida 2, para 2) was admitted 20 months after a hysterectomy because of fibromyoma. The hysterectomy specimen had shown intravenous leiomyomatosis. The patient presented with unspecific abdominal symptoms, serologic signs of hepatic and renal failure and clinical right-sided heart failure. Progression despite treatment with a gonadotropin-releasing hormone analogue promoted transferral to the present centre. Abdominal ultrasonography, phlebography and transoesophageal echocardiography showed a left pelvic mass and a seemingly free-floating tumour extending from the left main iliac vein via the inferior caval vein to the right ventricle. During a combined cardiac and distal caval approach using extracorporeal circulation, a 45 cm massive leiomyoma was removed successfully. Seven weeks later the left pelvic tumour was removed radically together with left oophorectomy. At control 12 months later the patient was well and without any remaining symptoms.

Adult↗
PubMed1996

[Acute porphyria and multiple organ failure during treatment with lamotrigine].

A 38-year-old female suffered from an acute porphyric attack, multi-organ failure and disseminated intravascular coagulation (DIC) within two weeks of starting lamotrigine, a new antiepileptic drug. The porphyric attack was characterized by excess urinary excretion of aminolevulinic acid (ALA), porphobilinogen (PBG) and coproporphyrin III, a pattern similar to that seen in hereditary coproporphyria, however the diagnostic criteria for this specific porphyria were not fulfilled. We suggest that the observed clinical picture represents a rare adverse reaction to lamotrigine.

Adult↗
PubMed1994

[Endocarditis--clinical picture of native valve infection].

In a population of 930,000 inhabitants all records of native valve infective endocarditis diagnosed in the decade 1980-89 were reviewed. One hundred and thirty-two cases were found, of whom 23 were not diagnosed until postmortem. Median prehospital duration of symptoms was 20 days (range 0-180) and median in-hospital diagnostic delay five days (range 0-54). Known cardiac disease was found in 42%, possible portal of entry in 33%, but in 36% no predisposing factors were found. During the clinical course 55% experienced cardiac failure and 17% embolic episodes. Surgery was required in 19 patients. Of 111 culture positive cases, streptococci were found in 61 and staphylococci in 45 cases. Overall mortality was 33% with a mortality of clinically diagnosed cases of 18%. Native valve endocarditis is thus associated with a significant mortality in part due to significant diagnostic delays and a large number of post-mortem diagnosed cases. Only by securing a high level of alertness towards endocarditis can we expect a reduced mortality.

Adult↗
PubMed1992

[Incapacitating angina pectoris treated with electric stimulation of the spinal cord].

Thirty patients who had severe incapacitating angina pectoris which had not reacted to the conventional therapeutic measures and which required massive daily opioid consumption were treated with electrical spinal cord stimulation (SCS) by means of a completely implantable stimulation system. The therapeutic effect was good in 87% of the patients who experienced considerably reduced frequency of attacks and markedly reduced opioid consumption (p less than 0.00005). Nine of the patients could reduce opioid consumption and 14 out of 27 could cease their otherwise daily opioid consumption. In four patients, the therapeutic effect was unsatisfactory. In the first 22 patients in whom a unipolar electrode was introduced, displacement of the electrode and subsequent reoperation was a frequent problem. This problem disappeared after change to multipolar electrodes as slight changes in placing of the electrode could easily be compensated for via the external programming equipment. This investigation reveals that SCS is a good therapeutic alternative for this selected patient category.

Aged↗
PubMed1992

Bronchogenic metastasis to the gingiva.

We report a rare case of a bronchogenic adenocarcinoma metastatic to the lower gingiva as the first clinical sign of metastatic disease. The following safe approach is recommended: a tumor in the oral cavity should be regarded as malignant or as a metastasis until the hypothesis can be abandoned.

Adenocarcinoma↗
PubMed1992

Native valve infective endocarditis in the general population: a 10-year survey of the clinical picture during the 1980s.

In a population of 930,000 inhabitants all records of native valve infective endocarditis diagnosed in the decade 1980-89 were reviewed. Using strict case definitions 132 clinically well-defined or post-mortem diagnosed cases were found. Included were cases referred to the local department of cardiology, as well as cases treated in non-specialized departments. Of 132 cases found 23 were only diagnosed post mortem. The male/female ratio was 71/61. The median prehospital duration of symptoms was 20 days (range 0-180 days) and the median in-hospital diagnostic delay was 5 days (range 0-54 days). Known cardiac disease was found in 42% of cases, a possible portal of entry was found in 33%, but in 36% there were no predisposing factors. Remarkably, only two patients had known rheumatic heart disease and none had a known dental focus. During the clinical course 55% experienced cardiac failure and 17% embolic episodes. In 19 patients surgery was required. Of 111 culture-positive cases streptococci were found in 61 and staphylococci in 45 cases. Echocardiography was performed in 95 cases with echocardiographic signs of endocarditis in 65 patients. Overall mortality was 33% with a mortality in clinically diagnosed cases of 18%. Of 14 cases needing immediate surgical intervention, two died.

Adolescent↗
PubMed1992

EDTA treatment of intermittent claudication--a double-blind, placebo-controlled study.

A double-blind, randomized multicentre study was undertaken to evaluate the possible effect of chelation treatment with ethylenediamine-tetraacetic acid (EDTA) in patients with severe intermittent claudication. A total of 153 patients received 20 intravenous infusions of either 3 g Na2EDTA or placebo during a period of 5-9 weeks. Vitamin, mineral and trace element supplements were administered orally. The changes observed in the pain-free and maximal walking distances, measured on a treadmill, were similar in the two groups. During the 3-month (n = 149) and 6-month (n = 123) follow-up period, no long-term therapeutic effect of EDTA could be demonstrated. The ankle-brachial blood pressure index remained unchanged throughout the study period. This study failed to demonstrate any effect of EDTA chelation treatment in intermittent claudication.

Aged↗
PubMed1992

Hereditary peromelia in Mohair goats.

The occurrence of a new congenital defect of the appendicular skeleton in Mohair goats is described. The malformation is peromelia and occurs in a familiar pattern. The defect seems to have an autosomal recessive mode of inheritance with variation in the expressivity of the genotype. The pathological abnormalities were described in 8 cases, all characterized by agenesia of the phalanges and parts of the metacarpus or metatarsus affecting one or more limbs. In some cases additional skeletal defects were found. Furthermore, 5 cases were reported by the owners with a description of the limb affected and 1 case was examined clinically. Predisposition for pelvic limbs to be affected was observed. The defect, which does not seem to have been described in goats previously, is phenotypically similar to and possibly also genetically homologous to a defect described in sheep.

Animals↗
PubMed1991

[Residual metastases from testicular cancer. CT as a diagnostic and strategic adjuvant].

Forty-nine young males with advanced testicular cancer treated between March 1982 and June 1989 comprised a 49/588 (8%) subgroup with distant metastases to the retroperitoneum, mediastinum and lungs, and required mandatory surgery on basis of the risk for reactivation of "slumbering" malignant components in tumor tissue temporarily inactivated by chemotherapy and/or radiotherapy. Preoperative CAT-scan was carried out with the intention of mapping regional pathology related to the size, number, burden of the tumor tissue, and the occasional and prognostic ominous invasion of the great vessels. Regarding radical surgery, the positive predictive value of CAT-scan was found to be 33/34 (97%). The negative predictive value was 5/15 (33%) and was interpreted as an expression of the radiologist's cautious assessment. 14/49 (29%) died before March 1990. Poor prognosis was related to invasion of major vessels and was found in 14 patients of whom eight died. It seems established that CAT-scan presents an extremely valuable preoperative investigation when it comes to planning of surgical strategy in a patient population with testicular cancer metastases with difficult access.

Adolescent↗