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K Jensen

Publications and source records attributed to K Jensen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effects of nicotine and mecamylamine-induced withdrawal on extracellular dopamine and acetylcholine in the rat nucleus accumbens.

RATIONALE: Prior research suggests that high levels of acetylcholine (ACh) in the nucleus accumbens (NAc) are associated with aversive states such as morphine withdrawal, but this has not been tested for nicotine withdrawal. OBJECTIVES: The goal was to test the hypothesis that acute nicotine decreases extracellular ACh and increases extracellular dopamine (DA) in the NAc, while withdrawal from nicotine causes an opposite neurochemical imbalance with high extracellular ACh and low DA. METHODS: Rats were prepared with a microdialysis probe in the NAc (primarily the shell region). They received one injection of nicotine (0.5 mg/kg, s.c.) or chronic nicotine (9 mg/kg per day via osmotic minipump). RESULTS: Naive animals receiving acute nicotine showed a mild, significant increase in both ACh (122% of baseline) and DA (124%). After chronic nicotine administration for 7 days, the nicotinic antagonist mecamylamine (1.0 mg/kg, s.c.) precipitated withdrawal with the appearance of somatic signs (teeth chattering and shakes/tremors) and a significant increase in extracellular ACh to 125% of baseline, while extracellular DA decreased to 65%. Control groups receiving saline in place of nicotine or mecamylamine did not show these effects. CONCLUSIONS: Earlier work suggests that the observed release of accumbens ACh and DA in response to acute nicotine administration may be a factor in nicotine-induced suppression of appetite. ACh release during withdrawal, coupled with the decrease in extracellular DA may play a role in the aversive aspects of nicotine withdrawal that contribute to dependency.

Acetylcholine↗
PubMed2001

Influence of body mass on maximal oxygen uptake: effect of sample size.

Basal metabolic rate is scaled to body mass to the power of 0.73, and we evaluated whether a similar scaling applies when the O2 transport capacity of the body is challenged during maximal exercise (i.e. at maximal O2 uptake, VO2max). The allometric relationship between VO2max and body mass (y = a.xb, where y is VO2max and x is body mass) was developed for 967 athletes representing 25 different sports, with up to 157 participants in each sport. With an increasing number of observations, the exponent approached 0.73, while for ventilation the exponent was only 0.55. By using the 0.73 exponent for VO2max, the highest value [mean (SD)] for the males was obtained for the runners and cyclists [234 (16) ml.kg-0.73.min-1], and for the females the highest value was found for the runners [189 (14) ml.kg-0.73.min-1]. For the females, aerobic power was about 80% of the value achieved by the males. Scaling may help both in understanding variation in aerobic power and in defining the physiological limitations of work capacity.

Adolescent↗
PubMed2001

An investigation of the co-evolutionary relationships between onchobothriid tapeworms and their elasmobranch hosts.

There is general consensus that the living elasmobranchs comprise a monophyletic taxon. There is evidence that, among tetraphyllidean tapeworms, the approximately 201 hooked species (Onchobothriidae) may also comprise a monophyletic group. Determinations of host specificity are contingent upon correct specific identifications. Since 1960, over 200 new elasmobranch species and over 100 new onchobothriid species have been described. Some confidence can be placed in host and parasite identifications of recent studies, but specific identifications provided in older literature in many cases are suspect. There is some consensus among published works on the phylogenetic relationships among elasmobranchs. Phylogenetic relationships among onchobothriids remain largely unresolved. Elasmobranchs have been poorly sampled for onchobothriids; records exist for approximately 20% of the 911 species and approximately 44% of the 170 elasmobranch genera. Onchobothriids are remarkably host specific, exhibiting essentially oioxenous specificity for their definitive hosts. Multiple onchobothriid species commonly parasitise the same host species; in some cases these are congeners, in other cases these are members of two different onchobothriid genera. There is substantial incongruence between available host and parasite phylogenies. For example, Acanthobothrium is by far the most ubiquitous onchobothriid genus, parasitising almost all orders of elasmobranchs known to host onchobothriids, yet, there is no evidence of major clades of Acanthobothrium corresponding to postulated major subgroupings of elasmobranchs (e.g. Galea and Squalea or sharks and rays). Potamotrygonocestus appears to be among the most basal onchobothriid groups, yet it parasitises one of the most derived elasmobranch groups (the freshwater stingray genus Potamotrygon). It appears that congeners parasitising the same host species are not necessarily each other's closest relatives. At this point the preliminary and limited available data suggest that, at least in this system, strict host specificity is not necessarily indicative of strict co-evolution. This study was extremely limited by the lack of available robust phylogenies for onchobothriids and elasmobranchs.

Animals↗
PubMed2001

[Measurement of CSF flow in the spinal canal using MRI with an optimized MRI protocol: experimental and clinical studies].

PURPOSE: Measurement of the oscillating CSF flow in the spinal canal (SC) of healthy volunteers and in patients with post-traumatic syringomyelia (PTS) using an optimized MRI protocol as well as to determine whether stenosis induced velocity changes are detectable using MRI. METHODS: In 68 healthy volunteers quantitative studies of CSF flow in the cervical, thoracic, and lumbar regions were performed. First, an optimized sequence was developed and tested in 19 volunteers using four different flow-encoding velocities (4, 8, 12, 16 cm/s). Secondly, the optimized sequence was employed in 49 volunteers to measure the different CSF patterns in the cervical, thoracic, and lumbar spinal canals (CSC, TSC, LSC). Part three of the study, in which patients with PTS are being examined is still underway. We measured the maximum velocity (cm/s), the pixel area (mm2), and the stroke volume (ml/s). Using a flow model the velocities prior to and after compression with 5 different power levels were measured at the stenosis and at a distance of 70 cm. RESULTS: A total of 226 dynamic measurements have been performed--so far 76 in the first part (62 = 81.5% evaluable) and 150 in the second part--using the optimized sequence and optimal flow velocities. A flow-encoding sequence of 12 cm/s was found best in the CSC and one of 6 cm/s in the TSC and LSC. The maximum velocity in the CSC was 0.95 cm/s with the flow being directed caudal and 0.38 cm/s with the flow being directed cranial. In the TSC the values were 4.7 cm/s and 1.65 cm/s and in the LSC 0.96 cm/s and 0.59 cm/s. The highest velocities were found at the TSC, which has the smallest diameter compared to the CSC and LSC. In the 4 patients with PTS, the maximum velocities were between 0.09 cm/s and 0.97 cm/s with the flow being directed cranial and between 0.04 cm/s and 1.03 cm/s with the flow being directed caudal. The stroke volumina in the CSC were between 0.1 and 1.23 ml/s (mean: 0.48 ml/s) and 0.2 and 2.45 ml/s (mean: 0.66 ml/s) in the TSC and in the LSC 0.08 ml/s and 0.67 ml/s (mean: 0.29 ml/s). The results of the flow model studies showed an increase of velocity between 2.06 and 4.94 cm/s (mean: 3.31 cm/s) at the stenosis and 1.1 and 1.33 cm/s (mean: 1.23 cm/s) at a distance of 70 cm. CONCLUSION: Quantitative measurement of the oscillating CSF flow in the entire spinal canal (SC) is possible using an optimized MRI protocol as well as to detect stenosis induced velocity changes. Due to the high interindividual variability in the data of spinal CSF dynamics, further studies are necessary to collect normal data. The detection of movement of CSF in a post-traumatic spinal cord lesion may alter the therapeutic management.

Adult↗
PubMed2001

GHB depresses fast excitatory and inhibitory synaptic transmission via GABA(B) receptors in mouse neocortical neurons.

Gamma-hydroxybutyrate (GHB) is a drug of abuse which induces sedation and euphoria. However, overdoses can severely depress the level of consciousness or can be fatal especially when combined with other substances. Studies have suggested that the GHB-effects are mediated via actions on thalamocortical pathways and local neocortical circuits, although the effect of GHB at the level of single neocortical neurons is not clear. Using whole-cell patch-clamp recordings, we studied the effects of GHB on neocortical neurons in brain slices from 12- to 33-day-old mice. We found that GHB depressed the frequency and amplitude of GABAergic and glutamatergic spontaneous inhibitory and excitatory post-synaptic currents (IPSCs and EPSCs) driven by presynaptic action potential firing, while the amplitude and frequency of Ca(2+) entry-independent miniature IPSCs were not affected. Using minimal stimulation, GHB reduced the probability of release at inhibitory synapses onto neocortical layer 2/3 pyramidal cells. Also, GHB directly hyperpolarized layer 2/3 non-pyramidal cells by up to 11 mV and inhibited action potential firing. All these effects of GHB were mediated via GABA(B)-receptors. In conclusion, GHB activates both pre- and postsynaptic GABA(B)-receptors in neocortical neurons participating in fast synaptic transmission, leading to a powerful depression of neocortical network activity. We propose that GABA(B)-receptor antagonists may be useful in the treatment of acute GHB intoxication.

Action Potentials↗
PubMed2001

Effects of dihydroergotamine on intracranial pressure, cerebral blood flow, and cerebral metabolism in patients undergoing craniotomy for brain tumors.

In a search for a nonsurgical intervention to control intracranial hypertension during craniotomy, the authors studied the effects of dihydroergotamine on mean arterial blood pressure (MABP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), cerebral blood flow (CBF), and cerebral metabolism in patients who underwent craniotomy for supratentorial brain tumors. Twenty patients were randomized to receive either dihydroergotamine 0.25 mg intravenously or placebo as a bolus dose during craniotomy. Anesthesia was induced with thiopental/fentanyl/atracurium, and maintained with isoflurane/N2O/fentanyl at normocapnia. After removal of the bone flap and exposure of intact dura, ICP was measured subdurally and dihydroergotamine/placebo was administered. Intracranial pressure and MABP were measured continuously. Cerebral blood flow (after intravenous administration of 133Xe) and arteriojugular venous difference of oxygen (AVDO2) were measured before, and 30 minutes after, dihydroergotamine/placebo administration. Cerebral metabolic rate of oxygen (CMRO2) was calculated. After administration of dihydroergotamine, a significant increase in MABP from 74 to 87 mm Hg (median) and CPP from 65 to 72 mm Hg (median) were found. Simultaneously to the increase in MABP, a significant increase in ICP from 9.5 to 11.5 mm Hg (median) was disclosed, whereas no significant differences in CBF, AVDO2, or CMRO2 were found. Intracranial pressure was significantly higher after dihydroergotamine than after placebo. In conclusion, no ICP decreasing effect of a bolus dose of dihydroergotamine was found when administered to patients with brain tumors during isoflurane/N2O anesthesia. Corresponding increases in MABP and ICP suggest that abolished cerebral autoregulation might explain why dihydroergotamine was associated with an ICP increase.

Adult↗
PubMed2001

Four new genera and five new species of lecanicephalideans (Cestoda: Lecanicephalidea) from elasmobranchs in the Gulf of California, Mexico.

A total of 53 spiral intestines from 3 species of rays collected in the Gulf of California, Baja, Mexico, was examined for cestodes of the order Lecanicephalidea. Four new genera and 5 new species were discovered as a result of this study. These are Aberrapex senticosus n. gen., n. sp., from Myliobatis californica, Paraberrapex manifestus n. gen., n. sp., from Squatina californica and Healyum harenamica n. gen., n. sp., Healyum pulvis n. sp. and Quadcuspibothrium francisi n. gen., n. sp., from Mobula japanica. Aberrapex n. gen. and Paraberrapex n. gen. can be distinguished from all other lecanicephalidean genera based on the lack of an apical structure (pars apicalis) on their scolex. Aberrapex n. gen. can be distinguished from Paraberrapex n. gen. based on the presence of an external seminal vesicle, a vagina positioned lateral rather than medial in the proglottid, and an ovary that is tetralobed rather than bilobed in cross section. Healyum n. gen. and Quadcuspibothrium n. gen. are unique among lecanicephalidean genera, including Aberrapex n. gen. and Paraberrapex n. gen., in their possession of a trilobed ovary in cross section. Quadcuspibothrium n. gen. can be distinguished from Healyum n. gen. based on its unique shape of the acetabula, which are diamond-shaped. The 2 species of Healyum n. gen. can be distinguished from one another based on the dimensions and the shape of the scolex, the diameter of the suckerlike acetabula, as well as the shape of the spiniform microtriches on the acetabular rims. Discobothrium arrhynchum is transferred to the genus Aberrapex n. gen. and the original description of this species is emended to include details of the vas deferens and the uterine duct and uterus. The microtrich patterns of the 5 new species and Aberrapex arrhynchum n. comb. are described. These are the first records of tapeworms of the Lecanicephalidea from the Gulf of California. Squatina californica and Mobula japanica represent new host records for lecanicephalidean tapeworms. The ordinal diagnosis of the Lecanicephalidea by Euzet (1994) is emended to include these 4 new genera.

Animals↗
PubMed2001

Penicillin as empirical therapy for patients hospitalised with community acquired pneumonia at a Danish hospital.

INTRODUCTION: We report on the outcome of a study of patients hospitalised with community acquired pneumonia (HCAP) at a Danish university hospital. METHODOLOGY: In a retrospective study of 243 consecutive patients with radiographically verified HCAP, data on clinical and laboratory findings and outcome parameters were collected. Three groups were established according to the initial choice of antibiotic(s): penicillin only (n = 160); non-allergic patients starting broader spectrum therapy (n = 54); and patients with suspected penicillin allergy (n = 29). RESULTS: The overall mortality within three months was 12% and the readmission rate within three months was 20%. The three treatment groups were comparable with respect to most demographic and clinical criteria at baseline. No significant differences in outcome between the groups were found: the mortality was 12.5%, 13.0%, and 10.3%, respectively, p = 0.94, and the readmission rate 20.3%, 24.0%, and 14.8%, respectively; p = 0.63. CONCLUSION: Patients treated for community-acquired pneumonia at a Danish university hospital had clinical outcomes fully at height with findings from other countries, and half of the patients were successfully treated with penicillin monotherapy. No differences in clinical outcomes were documented between patients treated empirically with broad-spectrum therapy and penicillin monotherapy. Therefore, penicillin seems to be a reasonable first choice for initial therapy of HCAP in Denmark as in other regions with similar patterns of microbial pathogens and resistance.

Adult↗
PubMed2000

mRNA trans-splicing in the human parasitic cestode Echinococcus multilocularis.

An identical 36-nucleotide exon was identified at the 5' termini of different mRNAs from the cestode Echinococcus multilocularis. We provide evidence that this exon constitutes a new spliced leader (SL) that is obviously trans-spliced to echinococcal pre-mRNAs, donated by a non-polyadenylated, trimethylguanosine-capped SL-RNA of 104 nucleotides. Sequence comparisons indicated that cestode and trematode SLs are likely to be derived from a common ancestor gene. No conservation was, however, observed concerning the spectrum of mRNAs that is trans-spliced in cestodes and trematodes, indicating that trans-splicing of a particular flatworm mRNA is not correlated with the function of the encoded protein. We also show that the echinococcal gene elp, encoding a member of the ezrin/radixin/moesin protein family, is expressed via two alternative transcripts, spliced either cis or trans at an identical splice acceptor site. This was accompanied by the formation of different elp primary transcripts, harboring a complete or a truncated upstream intron, which supports the hypothesis that alternative cis/trans-splicing depends on the presence or absence of an upstream splice donor site. A putative SL gene was also identified on chromosomal DNA of Echinococcus granulosus, indicating widespread utilization of trans-splicing in the genus.

Alternative Splicing↗
PubMed2000

[Arsenic as an environmental problem].

Chronic exposure to arsenic through drinking water is known in different continents. Arsenic compounds from disintegrating rock may be solubilized after reduction by organic material, and harmful concentrations of arsenic may be found in surface water as well as in water from drilled wells. Because of well drilling since the sixties in the Ganges delta numerous millions of people have been exposed to toxic amounts, and hundreds of thousands demonstrate signs of chronic poisoning. A changed water technology and chemical precipitation of arsenic in the drinking water can reduce the size of the problem, but the late sequelae i.e. malignant disease are incalculable. Indications for antidotal treatment of exposed individuals have not yet been outlined.

Antidotes↗
PubMed2000

Regulation of p53 activity in nuclear bodies by a specific PML isoform.

Covalent modification of the promyelocytic leukaemia protein (PML) by SUMO-1 is a prerequisite for the assembly of nuclear bodies (NBs), subnuclear structures disrupted in various human diseases and linked to transcriptional and growth control. Here we demonstrate that p53 is recruited into NBs by a specific PML isoform (PML3) or by coexpression of SUMO-1 and hUbc9. NB targeting depends on the direct association of p53, through its core domain, with a C-terminal region of PML3. The relocalization of p53 into NBs enhances p53 transactivation in a promoter-specific manner and affects cell survival. Our results indicate the existence of a cross-talk between PML- and p53-dependent growth suppression pathways, implying an important role for NBs and their resident proteins as modulators of p53 functions.

Biological Transport, Active↗
PubMed2000

Tetanus-induced asynchronous GABA release in cultured hippocampal neurons.

Asynchronous GABA release was studied in cultured hippocampal neurons using paired whole-cell recordings. Tetanization of the presynaptic GABAergic neuron was accompanied by a train of IPSCs which showed tetanic depression. Asynchronous IPSCs (asIPSCs) also developed during the train and continued for 1.85+/-0.3 s after the stimulation. The threshold frequency for evoking asIPSCs was 10 Hz, while maximal asynchronous activity was achieved at 40 Hz. Perfusion with EGTA-AM blocked asIPSCs. The elevation of [Ca(2+)](i) that accompanies presynaptic action potential firing triggers asynchronous release of GABA vesicles, thereby counteracting tetanic depression of synchronous IPSCs.

2-Amino-5-phosphonovalerate↗
PubMed2000

[Poisonings with the herbicides glyphosate and glyphosate-trimesium].

Generally the herbicide glyphosate is considered harmless to humans. Glyphosate-trimesium is labelled harmful (Xn), whereas glyphosate-isopropylamine carries no warning sign. As cases of serious poisoning have emerged contacts to the Poison Information Centre have been reviewed. The persons exposed were mainly smaller children and adults 20 to 59 years of age. Oral exposure was recorded in 47 persons, inhalation exposure in 24 and topical contact in 42. About one fourth of the exposed persons were asymptomatic. Most of the symptomatic poisonings demonstrated complaints from the mouth, the gastrointestinal tract and the airways. Eleven patients were admitted to hospital. Two died, one of them having ingested the isopropylamine salt, the other the trimesium salt. Death ensued quickly in the latter patient. A similar fate was observed in a child--not included in the present material--who had also ingested the trimesium compound.

Adult↗