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Biomedical subjects

T Bartsch

Publications and source records attributed to T Bartsch.

At least 19 recordsLinked to original sources
PubMed2003

Precise determination of the 2s(1/2)-2p(1/2) splitting in very heavy lithiumlike ions utilizing dielectronic recombination.

The 2s(1/2)-2p(1/2) energy splittings DeltaE(L) of the lithiumlike ions 19779Au76+, 20882Pb79+, and 23892U89+ have been measured at the Experimental Storage Ring, utilizing low energy dielectronic recombination. The resonance energies in total 41 different 1s(2) 2p(1/2)nl(j(')) (n > or =20) autoionizing Rydberg states populated in the dielectronic capture process have been determined. The 2s(1/2)-->2p(1/2) excitation energies have been obtained by extrapolation of these resonance energies to the associated series limits n--> infinity. The combined analysis of the experimental data for all three ions yields DeltaE(L)=216.134(96) eV for Au76+, 230.650(81) eV for Pb79+, and 280.516(99) eV for U89+.

Journal Article↗
PubMed2003

Increased responses in trigeminocervical nociceptive neurons to cervical input after stimulation of the dura mater.

Pain referral and spread in headache patients may be attributed to a sensitization of central nociceptive neurons with an increased excitability to afferent input. We investigated if noxious dural stimulation evokes sensitization of second-order neurons that leads to an increased responsiveness to stimulation of cervical afferents. Recordings were made from 29 nociceptive neurons in the C2 dorsal horn of the rat that received convergent synaptic input from trigeminal and cervical afferents. Trigeminal afferents of the supratentorial dura mater were activated by mustard oil (MO) and the responses of second-order neurons to stimulation of the greater occipital nerve (GON) were studied before and after dural stimulation. Projection sites to the contralateral thalamus were determined by antidromic stimulation. After dural application with MO, mechanical thresholds of the dura significantly decreased (P < 0.05) and an enlargement of the trigeminal and cervical cutaneous mechanoreceptive fields was observed in 71% of neurons. The responses to noxious mechanical stimulation of deep paraspinal muscles increased after MO application (P < 0.001). Similarly, an increase in the excitability to electrical stimulation of the GON was observed in C-fibre responses (P < 0.001). These results suggest that stimulation of nociceptive afferent C-fibres of the dura mater leads to a sensitization of second-order neurons receiving cervical input. This mechanism might be involved in the referral of pain from trigeminal to cervical structures and might contribute to the clinical phenomena of cervical hypersensitivity in migraine and cluster headache. Understanding this interaction is likely to be pivotal in characterizing the physiology of treatment with manipulations involving cervical input, such as GON injection.

Afferent Pathways↗
PubMed2003

The trigeminocervical complex and migraine: current concepts and synthesis.

Neurones in the trigeminocervical complex are the major relay neurones for nociceptive afferent input from the meninges and cervical structures; therefore, they are the neural substrates of head pain. This review highlights the importance of two basic mechanisms in headache physiology: convergence of nociceptive afferents and sensitization of trigeminocervical neurones. These physiologic findings have clinical correlates such as hypersensitivity and spread and referral of pain frequently seen in patients with primary headache, such as migraine. Special reference is made to the influence of structures from the upper cervical spine in generating and contributing to migraine headaches. The pathophysiology and functional relevance of these basic mechanisms to headaches is discussed in the context of recent experimental findings with regard to pain processing.

Calcium↗
PubMed2002

High Rydberg resonances in dielectronic recombination of pb(79+).

Dielectronic recombination resonances of Pb (79+) associated with 2s(1/2)-->2p(1/2) excitations were measured at the heavy-ion storage ring ESR at GSI. The fine structure of the energetically lowest resonance manifold Pb (78+)(1s(2)2p(1/2)20l(j)) at around 18 eV could partially be resolved, and rate coefficients on an absolute scale were obtained. A comparison of the experimental data with results of a fully relativistic theoretical approach shows that high-angular-momentum components up to j=31/2 significantly contribute to the total resonance strength demonstrating the necessity to revise the widespread notion of negligible high-angular-momentum contributions at least for very highly charged ions.

Journal Article↗
PubMed2002

The ORL-1 (NOP1) receptor ligand nociceptin/orphanin FQ (N/OFQ) inhibits neurogenic dural vasodilatation in the rat.

The effects of the ORL-1 (NOP(1)) receptor ligand nociceptin (N/OFQ) and the nociceptin antagonists [Nphe(1)]N/OFQ-(1-13)-NH(2) (Nphe) and nocistatin (NST) on neurogenic dural vasodilatation (NDV) in the rat dura mater evoked by electrical stimulation of a closed cranial window were studied. The middle meningeal artery was visualised using intravital microscopy, and the vessel diameter analysed using a video dimension analyser. N/OFQ (1, 10, 100 nmol kg(-1); i.v., n=10) significantly and dose-dependently suppressed NDV maximally by 65% (P<0.01). Neither Nphe (100 nmol kg(-1); n=5) nor NST (100 nmol kg(-1); n=4) alone had an effect on NDV (P>0.05). Baseline vessel diameter was not significantly affected by application of N/OFQ, NST or Nphe. Application of the selective N/OFQ antagonist Nphe (10, 100 nmol kg(-1) i.v., n=8) dose-dependently and significantly (P<0.01) reversed the inhibition of NDV induced by application of N/OFQ (10 nmol kg(-1)). NST (10, 100 nmol kg(-1); n=7) failed to reverse the effects elicited by N/OFQ. Application of N/OFQ elicited a dose-dependent transient decrease in arterial blood pressure (P<0.01). Nphe dose-dependently reversed the cardiovascular effects induced by application of N/OFQ (10 nmol kg(-1)) (P<0.01),while NST did not alter the blood pressure reaction elicited by N/OFQ. The results show that N/OFQ inhibits NDV, an effect which is antagonised by Nphe, but not by NST. ORL-1 (NOP(1)) receptors located on trigeminal sensory fibres may be involved in the regulation of dural vessel diameter and hence may play a role in migraine pathophysiology.

Analysis of Variance↗
PubMed2001

Semiclassical quantization by harmonic inversion: comparison of algorithms.

Harmonic inversion techniques have been shown to be a powerful tool for the semiclassical quantization and analysis of quantum spectra of both classically integrable and chaotic dynamical systems. Various computational procedures have been proposed for this purpose. Our aim is to find out which method is numerically most efficient. To this end, we summarize and discuss the different techniques and compare their accuracies by way of two example systems.

Journal Article↗
PubMed2001

Cervico-thoracic disc protrusions in controlled compressed-air diving: clinical and MRI findings.

Prevalence of cervical and thoracic disc protrusions was investigated by MRI in 24 military long-term compressed-air divers and 24 controls. A total of 26 disc protrusions (17 cervical disc protrusions) were detected in 58% of the divers whereas 18 protrusions were detected in 38 % of the controls (13 disc cervical protrusions). There was no significant difference between groups and no correlation with the diving experience. Neurological examination revealed no clinical abnormalities. In contrast to a recent study, our results suggest that long-term divers are at no increased risk for accumulating spinal disc protrusions or intramedullary abnormalities.

Adult↗
PubMed2000

Neurologic outcome of controlled compressed-air diving.

The authors compared the neurologic, neuropsychological, and neuroradiologic status of military compressed-air divers without a history of neurologic decompression illness and controls. No gross differences in the neuropsychometric test results or abnormal neurologic findings were found. There was no correlation between test results, diving experience, and number and size of cerebral MRI lesions. Prevalence of cerebral lesions was not increased in divers. These results suggest that there are no long-term CNS sequelae in military divers if diving is performed under controlled conditions.

Adult↗
PubMed2000

Respiratory rhythmicity in the activity of postganglionic neurones supplying the rat tail during hyperthermia.

It has been suggested that thermoregulatory stimulation changes respiration-related rhythmicity in the activity of postganglionic sympathetic neurones supplying the rat tail to a distinct modulation independent of respiration. To study this possibility, single and few fibre recordings were made from ten filaments split from the ventral collector nerves of the rat during whole body warming. Sympathetic activity was analysed by autocorrelation and phrenic-triggered summation. All neurones except one were gradually inhibited and lost their on-going activity above a core temperature of 39-39.5 degrees C while the frequency of the phrenic bursts increased significantly. During hyperthermia, all neurones tested exhibited a prominent respiratory modulation in their activity which, compared to normothermia, was significantly increased in strength, or even newly acquired. No other rhythm emerged. These results speak against the hypothesis that in the rat sympathetic pathways controlling the tail vasculature and thus involved in thermoregulation, during hyperthermia become controlled by central oscillators distinct from the respiratory rhythm generator. Rather, respiratory modulation appears to remain the dominant rhythm as is common for sympathetic neurones supplying other cardiovascular targets.

Action Potentials↗
PubMed2000

Reflex patterns in preganglionic sympathetic neurons projecting to the superior cervical ganglion in the rat.

Reflex patterns in preganglionic neurons projecting in the cervical sympathetic trunk (CST) were analyzed in response to stimulation of various afferent systems. We focused on the question whether these preganglionic neurons can be classified into functionally distinct subpopulations. Reflex responses were elicited by stimulation of trigeminal and spinal nociceptive, thermoreceptive as well as baroreceptor and chemoreceptor afferents. Multi- and single fiber preparations were studied in baroreceptor intact and sino-aortically denervated animals. Spontaneous activity of 36 preganglionic single neurons ranged from 0.2 to 3.5 imp/s (median= 1.11 imp/s). The degree of cardiac rhythmicity (CR) in the activity of sympathetic neurons was 69.5+/-13% (mean+/-S.D.; N=52; range=39-95%). Noxious stimulation of acral skin activated the majority (67%) of sympathetic preparations by 37+/-25% (N=35) above pre-stimulus activity; 15% were inhibited. In these neurons the response to noxious stimulation of acral skin was significantly correlated with the degree of CR (P<0.001, N=52) in that neurons showing the strongest excitation to noxious stimulation displayed the strongest CR. Noxious mechanical stimulation of body trunk skin (N=60) inhibited the majority (80%) of fiber preparations tested (by 34+/-18% of pre-stimulus activity, N=48); an activation was not observed. Cold stimulation of acral (N=9) and body trunk skin (N=42) activated most fiber preparations. Trigeminal stimulation evoked a uniform reflex activation of preganglionic neurons (+79+/-73% of pre-stimulus activity, N=32). Chemoreceptor stimulation by systemic hypercapnia elicited inhibitory (-31+/-19%, N=8) as well as excitatory (+59+/-5%, N=4) responses. These results show that preganglionic sympathetic neurons projecting to target organs in the head exhibit distinct reflex patterns to stimulation of various afferent systems; however, a clear classification into different functional subgroups did not emerge. Furthermore, reflex patterns showed a segmental organization to noxious cutaneous stimulation of acral parts and body trunk reflecting a differential central integration of spinal afferent input. Compared with the cat the reflex organization of sympathetic neurons projecting to the head seems to be less differentiated in the anesthetized rat.

Action Potentials↗
PubMed2000

Influence of magnetic fields on electron-Ion recombination at very low energies

Radiative recombination (inverse photoionization) is believed to be well understood since the beginning of quantum mechanics. Still, modern experiments consistently reveal excess recombination rates at very low electron-ion center-of-mass energies. In a detailed study on recombination of F6+ and C6+ ions with magnetically guided electrons we explored the yet unexplained rate enhancement, its dependence on the magnetic field B, the electron density n(e), and the beam temperatures T( perpendicular) and T( ||). The excess scales as T(-1/2)( perpendicular) and, surprisingly, as T(-1/2)( ||), increases strongly with B, and is insensitive to n(e). This puts strong constraints on explanations of the enhancement.

Journal Article↗
PubMed1999

Hypoventilation recruits preganglionic sympathetic fibers with inspiration-related activity in the superior cervical trunk of the rat.

Activity in preganglionic sympathetic neurons projecting in the cervical sympathetic trunk (CST) of rats was analysed with respect to changes in the pattern of the respiratory modulation during a long lasting hypoventilation. Under normal acid-base status (pH: 7.36+/-0.04, pCO2: 42.1+/-6.1 mm Hg, pO2: 135.8+/-43 mm Hg) a maximum of activity during expiration (expiration-related activity) was observed in all nerve recordings (n = 27). No other pattern of respiratory modulation was observed under this condition. Under a hypoventilation a dissociation between the duration of phrenic nerve activity and that of the inspiratory inhibition in neurons with expiration-related activity was observed as the inhibition was significantly prolonged by 49+/-24.9% and outlasted inspiration in 5/7 multifibers. When acid-base status was systematically changed (pH: 7.15+/-0.05, pCO2: 80.4+/-11.8 mm Hg, pO2: 62.8+/-17.5 mm Hg [n = 7]) by a hypoventilation lasting for several hours activity with a maximum peak during central inspiration (inspiration-related activity) emerged and disappeared when control conditions were reestablished. Neurons with expiration-related activity showed a cardiac rhythmicity (CR) of 62.5+/-14.6% (n = 27) and were inhibited to baroreceptor stimulation whereas neurons with inspiration-related activity showed no discernible CR (23.1+/-5.1%; n = 7) and were not inhibited to baroreceptor stimulation. Furthermore, expiration-related neurons were inhibited by 32.5+/-18.3% (n = 27) during noxious cutaneous stimulation while neurons with inspiration-related activity were activated by 21.5+/-12.1% (n = 7). These findings suggest that the respiratory modulation of preganglionic sympathetic activity in the CST consists of expiration-related activity in normal acid-base status. During hypoventilation neurons with inspiration-related activity are recruited. These neurons show reflex patterns distinct from expiration-related neurons and probably constitute a subgroup of sympathetic neurons which is activated under increased respiratory drive.

Adrenergic Fibers↗
PubMed1999

Rhythmicity in single fiber postganglionic activity supplying the rat tail.

Rhythmicity in single fiber postganglionic activity supplying the rat tail. The temporal pattern of ongoing sympathetic vasoconstrictor activity may play an important role for neurovascular transmission. Here we analyzed the activity of postganglionic fibers projecting into the ventral collector nerve of anesthetized and artificially ventilated vagotomized Wistar rats with respect to the presence of rhythmic firing under normocapnic conditions. Most of the fibers studied were likely vasoconstrictor and involved in thermoregulation. Accumulated histograms of sympathetic activity were produced synchronized with the electrocardiogram to detect cardiac rhythmicity, with phrenic nerve activity to detect modulation with the central respiratory cycle, and with tracheal pressure to uncover a reflex modulation associated with artificial ventilation. Sympathetic activity, phrenic activity, and tracheal pressure also were examined by spectral analysis and autocorrelation to detect rhythmicities distinct from respiration. Twenty-seven filaments containing two to seven fibers with spontaneous activity and 51 single fibers were analyzed. Ongoing activity was 1.12 +/- 0.65 imp/s (mean +/- SD, n = 51); conduction velocity was 0.62 +/- 0.06 m/s (n = 30). Cardiac rhythmicity in sympathetic activity was weak (46.2 +/- 16.4%). The dominant rhythm in the activity of 19/27 few-fiber preparations and 37/51 single fibers corresponded to the central respiratory cycle. The pattern consisted of an inhibition during inspiration and an activation in expiration. In 10/19 few-fiber preparations and 21/37 single fibers of this group, there was also a concomitant, less prominent rhythm related to artificial ventilation. By contrast, 8/27 few-fiber preparations and 11/51 single fibers exhibited a dominant pump-related modulation, whereas phrenic-related rhythmicity was subordinate. The dominant rhythm in the activity of two single fibers was related to neither central respiration nor artificial ventilation. We conclude that the ongoing activity of most postganglionic neurons supplying the rat tail is modulated by the central respiratory rhythm generator, suggesting that changes in respiratory drive may alter perfusion of the tail and therefore heat dissipation. Reflex modulation in parallel with artificial ventilation, independent of vagal afferents and possibly due to ventilatory changes of baroreceptor activity, is also an important source of rhythmicity in these neurons.

Animals↗
PubMed1997

Responses of rat postganglionic sympathetic vasoconstrictor neurons following blockade of nitric oxide synthesis in vivo.

The hypothesis was tested that the activation of postganglionic sympathetic neurons contributes to the peripheral vasoconstriction and the blood pressure increase which are observed in rats after systemic blockade of nitric oxide synthase by substituted L-arginine analogues. Single and multifiber postganglionic sympathetic activity supplying hindlimb hairy skin and the activity in the caudal lumbar sympathetic trunk supplying mainly hindlimb skeletal muscle were recorded in anaesthetized, paralysed and artificially ventilated Wistar rats before, during and up to 1 h after intravenous injection of a supramaximal dose (10 or 35 mg/kg) of N(G)-nitro-L-arginine methyl ester. This elicited a sustained rise of arterial blood pressure, a long-lasting decrease in heart rate and vasoconstriction in hindlimb skin and skeletal muscle as measured by laser Doppler flowmetry. With intact buffer nerves all sympathetic neurons analysed responded with a decrease in their ongoing activity in parallel with the vasoconstriction and the increased blood pressure, except for one neuron which was unresponsive. These responses were probably mediated by the arterial baroreceptors. since it was shown that N(G)-nitro-L-arginine methyl ester did not impair the function of both the afferent and the efferent limb of the reflex. Furthermore, baroreceptor denervation almost abolished the inhibitory responses in sympathetic neurons. In baroreceptor denervated animals, with a latency of about 15 min after N(G)-nitro-L-arginine methyl ester there was an increase in sympathetic activity without a further increase in blood pressure. It was concluded that sympathetic vasoconstrictor neurons which supply the rat hindlimb do not contribute by neurogenic means to the vasoconstriction and the blood pressure increase occurring after blockade of the nitric oxide synthase. Instead, the results suggest that sympathetic vasoconstrictor neurons, via the baroreceptor loop, counteract the vasoconstriction caused by the blockade of endothelium-derived nitric oxide. Therefore nitric oxide does not seem to play a role in the central regulation of activity in the sympathetic vasoconstrictor pathways studied here. The long latency increase in sympathetic activity observed after N(G)-nitro-L-arginine methyl ester in baroreceptor-denervated animals may be due to an impairment of blood flow in the brainstem.

Animals↗
PubMed1996

Two distinct mechanisms generate the respiratory modulation in fibre activity of the rat cervical sympathetic trunk.

Preganglionic multifibre activity was recorded in the cervical sympathetic trunk of vagotomized Wistar rats and analysed for its respiratory modulation. The aim of the study was to investigate whether both a central and a reflex component of respiratory modulation are observed in sympathetic activity of rats as was previously demonstrated in cats. For this purpose, sympathetic activity was summed over several hundred cycles (i) with respect to phrenic nerve discharge as an indicator for central respiration and (ii) with respect to tracheal pressure as an indicator for artificial ventilation. As a consequence of vagotomy both cycles were desynchronized. Sympathetic activity which was analysed exhibited a central respiratory modulation with a minimum during inspiration and a broad peak during expiration. Additionally, in the activity of 44/49 filaments a ventilation-related modulation was seen in parallel with the falling phase of the blood pressure waves accompanying artificial ventilation. The analysis of the latter rhythm during central apnoea and after complete sino-aortic denervation proved its reflex origin and its independence of the central respiratory modulation. We conclude that in rats respiratory modulation of sympathetic activity is caused by two distinct mechanisms, one being of central and one being of reflex, probably baroreceptor, origin.

Adrenergic Fibers↗
PubMed1996

p53-dependent cell cycle arrest induced by N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal in platelet-derived growth factor-stimulated human fibroblasts.

Proteases are known to play important roles in cell growth control, although the underlying mechanisms are still poorly understood. Here we show that the protease inhibitor N-acetyl-L-leucinyl-L-leucinyl-L-norleucinal induced cell cycle arrest in platelet-derived growth factor-stimulated human fibroblasts at the G1/S boundary of the cell cycle by inhibiting the proteasome. Inhibition of the proteasome resulted in accumulation of the tumor suppressor p53, which was followed by an increase in the amount of the cyclin-dependent kinase-inhibitor p21. As a consequence, both phosphorylation and activity of the cyclin-dependent kinase 2/cyclin E complex were inhibited. We further observed that the retinoblastoma gene product, pRb, remained in the hypophosphorylated state, thus preventing cells from progression into the S-phase. These studies strongly support the hypothesis that the proteasome is a key regulator in the G1-phase of cell cycle progression.

Calpain↗
PubMed1996

Functional properties of postganglionic sympathetic neurones supplying the submandibular gland in the anaesthetized rat.

Sympathetic neurones supplying the submandibular salivary gland innervate blood vessels, secretory and myoepithelial cells. Here we examined whether these functionally different sympathetic neurones show distinct reflex response patterns. In anaesthetized rats, single unit activity was recorded from postganglionic axons projecting to the gland. Neurones were tested for their responses to stimulation of baroreceptors, cutaneous nociceptors and cold receptors and to gustatory stimuli applied to the tongue. Respiratory modulation was also analysed. Only a few postganglionic neurones identified electrically (5-10%) were spontaneously active. They were excited by noxious and cold stimuli, inhibited by baroreceptor stimulation and exhibited respiratory modulation. None of the units responded to gustatory stimuli. Thus, in anaesthetized rats spontaneously active sympathetic neurones supplying the submandibular gland behave like vasoconstrictor neurones. Sympathetic neurones with other functions are probably silent.

Anesthesia, General↗