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Biomedical subjects

Per Hansson

Publications and source records attributed to Per Hansson.

At least 19 recordsLinked to original sources
PubMed2006

On the repeatability of brush-evoked allodynia using a novel semi-quantitative method in patients with peripheral neuropathic pain.

Using a semi-quantitative method the repeatability of brush-evoked allodynia was examined within and between days in nine patients with spontaneous ongoing pain and dynamic mechanical allodynia due to peripheral neuropathy. In addition, the relationship between the intensity of spontaneous ongoing pain and the total brush-evoked pain intensity was addressed. The brush stimulus was applied in the innervation territory of the lesioned nervous structure by lightly stroking 60 mm of the skin four times with an 8 mm wide brush. Using a computerized visual analogue scale the patients continuously rated the intensity and duration of brush-evoked allodynia and the total brush-evoked pain intensity was calculated as the area under the curve. The patients were examined 4 days during one month, i.e. at day 1, 3, 28 and 30 and each study day the stimulus was repeated four times with an inter-stimulus interval of 10 min. The variation between repeated assessments was analyzed using the intraclass correlation coefficient and the total brush-evoked pain intensity within days ranged from 0.89 to 0.95 ("very good repeatability") and between days from 0.77 to 0.97 ("very good repeatability"). A significant positive correlation was demonstrated between the mean intensity of spontaneous ongoing pain and the mean total brush-evoked pain intensity (r(s)=0.68, P<0.042, "a moderate to good correlation").

Adult↗
PubMed2006

Heterotopic noxious conditioning stimulation (HNCS) reduced the intensity of spontaneous pain, but not of allodynia in painful peripheral neuropathy.

In 15 patients with painful peripheral neuropathy and dynamic mechanical allodynia, the influence of spontaneous ongoing neuropathic pain on pain sensitivity in a remote pain-free area was examined, as was the influence of ischemia-induced heterotopic noxious conditioning stimulation (HNCS) on the intensity of ongoing pain and brush-evoked allodynia. In addition, the modulating effect of HNCS on pain sensitivity in a pain-free area was investigated. Pain thresholds to pressure and heat as well as the sensitivity to suprathreshold pressure- and heat pain were assessed in the pain-free area. Dynamic mechanical allodynia was induced by a recently developed semi-quantitative brushing technique and the patients continuously rated the intensity of the allodynia using a computerized visual analogue scale (VAS). The total brush-evoked pain intensity was calculated as the area under the VAS curve. At baseline, no significant difference in pain sensitivity was found between patients and their healthy controls in the pain-free area, indicating a lack of activation of pain modulatory systems from the spontaneous pain. Compared to baseline, the patients rated the ongoing neuropathic pain intensity significantly lower during the HNCS-procedure (p<0.05). In contrast, there was no influence from HNCS on the total brush-evoked pain intensity. In the pain-free area higher pressure pain thresholds were demonstrated during conditioning stimulation in patients and controls alike (p<0.01). In controls only, a significantly higher heat pain threshold was found during the HNCS-procedure (p<0.01). The main finding of the present study was that HNCS altered differentially spontaneous and brush-provoked pain in patients with painful peripheral neuropathy.

Adult↗
PubMed2006

PHosphatidylethanol (PEth) concentrations in blood are correlated to reported alcohol intake in alcohol-dependent patients.

AIMS: Phosphatidylethanol (PEth) is an abnormal phospholipid formed only in the presence of ethanol by the enzyme phospholipase D. PEth in blood is a promising new marker for ethanol abuse. None of the biological markers used at the present time is sensitive and specific enough for the diagnosis of alcoholism. METHODS: The most frequently used alcohol markers [carbohydrate deficient transferrin (CDT), gamma-glutamyltransferase (GGT), and mean corpuscular volume (MCV)] were studied together with PEth in actively drinking alcohol-dependent patients (inpatients and outpatients), with regard to correlation to ethanol intake and diagnostic sensitivity of the markers. The relation between the markers was also studied. RESULTS: PEth, CDT, and GGT correlated to ethanol intake, with the strongest correlation found for PEth. The diagnostic sensitivity for PEth was 99%, and for other markers it varied between 40 and 77%. Only when CDT was combined with GGT was a sensitivity of 94% reached. PEth correlated to CDT and GGT but not to MCV. CDT did not correlate to GGT or MCV. CONCLUSIONS: Blood concentrations of PEth are highly correlated to ethanol intake, and the present results indicate that its diagnostic sensitivity is higher than that for previously established alcohol markers.

Adult↗
PubMed2006

Time dependent differences in pain sensitivity during unilateral ischemic pain provocation in healthy volunteers.

Plurisegmental endogenous pain inhibitory mechanisms related to diffuse noxious inhibitory controls (DNIC) were demonstrated in animal experiments to act on multireceptive neurons of the entire cord outside the conditioned segment without any side differences. Human experiments have demonstrated altered pain sensitivity to pressure, heat and electrical stimulation during heterotopic noxious conditioning stimulation (HNCS). The purpose of the study was to examine if side and/or time differences in pain thresholds and suprathreshold pain sensitivity for pressure and heat, respectively, could be detected during HNCS. Perception thresholds to pressure and heat pain as well as the sensitivity to suprathreshold pressure (SPP) and heat pain (SHP) were assessed in 18 healthy volunteers bilaterally at the thighs before, during and following ischemia-induced pain of the left forearm (HNCS). The assessments started with either the right (10 subjects) or the left thigh (8 subjects). During HNCS the pressure pain threshold increased significantly (p<0.001) on both sides alike. No significant difference in the magnitude of the altered pressure pain threshold was seen between sides for the first or the lastly assessed side. On the lastly assessed side only SPP and SHP increased significantly on both sides alike (p<0.02 and p<0.03, respectively), without magnitude differences between sides. During unilateral HNCS of the left arm, a time factor was demonstrated only for alterations in suprathreshold pain sensitivity, without any differences in magnitude between sides. Therefore, the results have implications for future design of HNCS-related experimental and clinical studies.

Adult↗
PubMed2006

Interaction between covalent DNA gels and a cationic surfactant.

The interaction of covalently cross-linked double-stranded (ds) DNA gels and cetyltrimethylammonium bromide (CTAB) is investigated. The volume transition of the gels that follows the absorption of the oppositely charged surfactant from aqueous solution is studied. As do other polyelectrolyte networks, DNA networks form complexes with oppositely charged surfactant micelles at surfactant concentrations far below the critical micelle concentration (cmc) of the polymer-free solution. The size of the absorbed surfactant aggregates is determined from time-resolved fluorescence quenching (TRFQ). At low surfactant concentrations, small discrete micelles (160 < N < 210) are found, whereas large micelles (N > 500) form at surfactant concentrations of 1 mM. When the DNA is in excess of the surfactant, the surfactant binding is essentially quantitative. The gel volume decreases by 90% when the surfactant to DNA charge ratio, beta, increases from 0 to 1.

Animals↗
PubMed2005

Ion-exchange controls the kinetics of deswelling of polyelectrolyte microgels in solutions of oppositely charged surfactant.

The kinetics of deswelling of sodium polyacrylate microgels (radius 30-140 microm) in aqueous solutions of dodecyltrimethylammonium bromide is investigated by means of micropipet-assisted light microscopy. The purpose of the study is to test a recent model (J. Phys. Chem. B 2003, 107, 9203) proposing that the rate of the volume change is controlled by the transport of surfactant from the solution to the gel core (ion exchange) via the surfactant-rich surface phase appearing in the gel during the volume transition. Equilibrium swelling characteristics of the gel network in surfactant-free solutions and with various amounts of surfactant present are presented and discussed with reference to related systems. A relationship between gel volume and degree of surfactant binding is determined and used in theoretical predictions of the deswelling kinetics. Experimental data for single gel beads observed during deswelling under conditions of forced convection are presented and compared with model calculations. It is demonstrated that the dependences of the kinetics on initial gel size, the surfactant concentration in the solution, and the liquid flow rate are well accounted for by the model. It is concluded that the deswelling rates of the studied gels are strongly influenced by the mass transport of surfactant between gel and solution (stagnant layer diffusion), but only to a minor extent by the transport through the surface phase. The results indicate that, during the volume transition, swelling equilibrium (network relaxation/transport of water) is established on a relatively short time scale and, therefore, can be treated as independent of the ion-exchange kinetics. Theoretical aspects of the kinetics and mechanisms of surfactant transport through the surface phase are discussed.

Acrylic Resins↗
PubMed2005

Specific and sensitive detection of the conifer pathogen Gremmeniella abietina by nested PCR.

BACKGROUND: Gremmeniella abietina (Lagerb.) Morelet is an ascomycete fungus that causes stem canker and shoot dieback in many conifer species. The fungus is widespread and causes severe damage to forest plantations in Europe, North America and Asia. To facilitate early diagnosis and improve measures to control the spread of the disease, rapid, specific and sensitive detection methods for G. abietina in conifer hosts are needed. RESULTS: We designed two pairs of specific primers for G. abietina based on the 18S rDNA sequence variation pattern. These primers were validated against a wide range of fungi and 14 potential conifer hosts. Based on these specific primers, two nested PCR systems were developed. The first system employed universal fungal primers to enrich the fungal DNA targets in the first round, followed by a second round selective amplification of the pathogen. The other system employed G. abietina-specific primers in both PCR steps. Both approaches can detect the presence of G. abietina in composite samples with high sensitivity, as little as 7.5 fg G. abietina DNA in the host genomic background. CONCLUSION: The methods described here are rapid and can be applied directly to a wide range of conifer species, without the need for fungal isolation and cultivation. Therefore, it represents a promising alternative to disease inspection in forest nurseries, plantations and quarantine control facilities.

Ascomycota↗
PubMed2005

Segregation of lipid and polymer in emulsion droplets captured by confocal laser scanning microscopy.

The phase behaviors of the subsystems of the ethyl acetate (EtAc)/monoolein/polyethylene glycol-poly(D,L-lactide-co-glycolide) (PLG)/water system have been determined. EtAc simultaneously solves MO and PLG in a liquid phase, denoted L. Lipid/polymer composite particles have here been formed by emulsification of such an L phase into aqueous solutions. Characterization, by means of confocal laser scanning microscopy, revealed that distinctive lipid domains appear inside the particles. In aqueous solutions, these lipid domains swell and finally leave the concentrated polymer matrix. The system exhibits a suitable phase behavior in order to form lipid/polymer composite particles. These composite particles may be interesting for drug delivery applications.

Chemistry, Physical↗
PubMed2005

Single microgel particle studies demonstrate the influence of hydrophobic interactions between charged micelles and oppositely charged polyions.

The binding of two cationic surfactants, dodecyltrimethylammonium bromide (DoTAB) and N-(1,1,2,2-tetrahydroperfluorodecanyl)pyridinium bromide (HFDePB), to covalently cross-linked sodium poly(styrenesulfonate) (PSS) microgels has been investigated by means of micromanipulator-assisted time-resolved light microscopy on single gels. It is demonstrated that repeated measurements on the same microgel under conditions of controlled liquid flow give highly reproducible results. The two surfactants are found to behave very differently with respect to degree of swelling, surfactant distribution in the gels, both during shrinking and at equilibrium, and kinetics of volume changes induced by them. The main difference is attributed to the presence of a hydrophobic interaction between PSS and the DoTAB micelles, absent in the case of HFDePB. Kinetic shrinking curves are recorded and analyzed using a model for steady-state transport of surfactant between the solution and the gels. Aggregation numbers for DoTAB in PSS solutions obtained from fluorescence quenching measurements are presented. A strong dependence on the surfactant-to-polyion concentration ratio is observed. Relations between surfactant binding isotherms, phase diagrams for linear polyelectrolyte/surfactant/water systems, and the binding to gels are discussed.

Binding Sites↗
PubMed2005

Dynamic mechanical allodynia: on the relationship between temporo-spatial stimulus parameters and evoked pain in patients with peripheral neuropathy.

The relationship between temporo-spatial stimulus parameters and evoked pain intensity as well as duration was examined in patients with peripheral neuropathy and brush-evoked allodynia, i.e. dynamic mechanical allodynia. Brush-evoked allodynia was induced in the innervation territory of the lesioned nervous structure in 18 patients by lightly stroking different distances of the skin (20, 40, 60 mm) two or four times with brushes of different widths (4, 8, 16 mm). Pain intensity and duration of brush-evoked allodynia was recorded using a computerized visual analogue scale. The total brush-evoked pain intensity, including painful aftersensation was calculated as the area under the curve. Following each stimulus, the patients selected pain descriptors from a validated instrument. Significantly increased total brush-evoked pain intensity was demonstrated with increased brushing length and number of strokes (P<0.001), but not while altering brush width. Lack of influence of brush width was further underlined by the finding that activation of equivalent areas (e.g. 160 mm2) resulted in higher total brush-evoked pain intensity if brushing the skin with a thin brush (4 mm) over a longer distance (40 mm) than a thick brush (8 mm) over a shorter distance (20 mm). Significantly increased duration of aftersensation was demonstrated only following increased brushing length (P<0.008). The most commonly used sensory-discriminative pain descriptors were pricking, burning and sore and for the affective descriptors, annoying and troublesome. This is the first study demonstrating a relationship between evoked pain and some temporo-spatial stimulus parameters during brush-evoked allodynia.

Adult↗
PubMed2004

Appearance of pure fluorocarbon micelles surveyed by fluorescence quenching of amphiphilic quinoline derivatives in fluorocarbon and hydrocarbon surfactant mixtures.

A halide-sensitive fluorescence probe was utilized to evaluate the miscibility of fluorocarbon and hydrocarbon surfactants in aqueous micellar systems. The fluorescence of 6-methoxy-N-1,1,2,2-tetrahydroheptadecafluorodecylquinolinium chloride, FC10MQ, was quenched by halide ions dissociated from the surfactant. The fluorescence in micellar solutions showed an initially rapid decay. This suggests that halide ions effectively quench FC10MQ fluorescence at the micellar surface. The subsequent slow decay corresponds to the quenching of FC10MQ fluorescence in the aqueous bulk phase by the free counterions. The Stern-Volmer plots for fluorescence quenching gave a distinct break at the critical micelle concentration of the cationic surfactants. The abrupt increase in fluorescence quenching is attributed to the solubilization of the probe in the micelles. The fluorescence quenching behavior provides direct information about the immiscibility of fluorocarbon and hydrocarbon species in micelles, and the results indicate that almost pure fluorocarbon micelles appear in surfactants mixtures.

Journal Article↗
PubMed2004

Brainstem involvement in the initial response to pain.

The autonomic responses to acute pain exposure usually habituate rapidly while the subjective ratings of pain remain high for more extended periods of time. Thus, systems involved in the autonomic response to painful stimulation, for example the hypothalamus and the brainstem, would be expected to attenuate the response to pain during prolonged stimulation. This suggestion is in line with the hypothesis that the brainstem is specifically involved in the initial response to pain. To probe this hypothesis, we performed a positron emission tomography (PET) study where we scanned subjects during the first and second minute of a prolonged tonic painful cold stimulation (cold pressor test) and nonpainful cold stimulation. Galvanic skin response (GSR) was recorded during the PET scanning as an index of autonomic sympathetic response. In the main effect of pain, we observed increased activity in the thalamus bilaterally, in the contralateral insula and in the contralateral anterior cingulate cortex but no significant increases in activity in the primary or secondary somatosensory cortex. The autonomic response (GSR) decreased with stimulus duration. Concomitant with the autonomic response, increased activity was observed in brainstem and hypothalamus areas during the initial vs. the late stimulation. This effect was significantly stronger for the painful than for the cold stimulation. Activity in the brainstem showed pain-specific covariation with areas involved in pain processing, indicating an interaction between the brainstem and cortical pain networks. The findings indicate that areas in the brainstem are involved in the initial response to noxious stimulation, which is also characterized by an increased sympathetic response.

Adult↗
PubMed2004

Context-dependent deactivation of the amygdala during pain.

The amygdala has been implicated in fundamental functions for the survival of the organism, such as fear and pain. In accord with this, several studies have shown increased amygdala activity during fear conditioning and the processing of fear-relevant material in human subjects. In contrast, functional neuroimaging studies of pain have shown a decreased amygdala activity. It has previously been proposed that the observed deactivations of the amygdala in these studies indicate a cognitive strategy to adapt to a distressful but in the experimental setting unavoidable painful event. In this positron emission tomography study, we show that a simple contextual manipulation, immediately preceding a painful stimulation, that increases the anticipated duration of the painful event leads to a decrease in amygdala activity and modulates the autonomic response during the noxious stimulation. On a behavioral level, 7 of the 10 subjects reported that they used coping strategies more intensely in this context. We suggest that the altered activity in the amygdala may be part of a mechanism to attenuate pain-related stress responses in a context that is perceived as being more aversive. The study also showed an increased activity in the rostral part of anterior cingulate cortex in the same context in which the amygdala activity decreased, further supporting the idea that this part of the cingulate cortex is involved in the modulation of emotional and pain networks.

Adaptation, Psychological↗
PubMed2003

An investigation of dynamic surface tension, critical micelle concentration, and aggregation number of three nonionic surfactants using NMR, time-resolved fluorescence quenching, and maximum bubble pressure tensiometry.

Several physicochemical properties have been determined for N-dodecyllactobionamide (LABA), maltose 6'-O-dodecanoate (C12-maltose ester), and tetra(ethylene oxide) dodecyl amide (TEDAd). The increase in the flexibility of the sugar headgroup, enabling more possible molecular conformations, reduces the minimum area/molecule at the liquid-vapor interface obtained at the critical micelle concentration (cmc). The obtained cmc's were 0.35 mM (LABA), 0.3 mM (C12-maltose ester), and 0.5 mM (TEDAd). The monomer diffusion coefficient decreased with the molecular weight and increasing headgroup flexibility of the sugar headgroup, and values were in the range from 3.1 x 10(-10) to 3.6 x 10(-10) m2/s. The micelle diffusion coefficients (0.46 x 10(-10) to 0.68 x 10(-10) m2/s) indicated that the TEDAd micelles deviated most from spherical shape. The micelle aggregation numbers determined by time-resolved fluorescence quenching (TRFQ) were estimated to be 120+/-10 (LABA), 90+/-10 (C12-maltose ester), and 130+/-10 (TEDAd). The dynamic surface tension measurements show that the adsorption of TEDAd onto the liquid-vapor interface at short surface lifetimes is diffusion-limited, whereas an adsorption barrier is present for the sugar surfactants. The analysis of the dynamic surface tension data above the cmc shows that the rate of demicellization is faster for TEDAd than for the two sugar-based surfactants.

Journal Article↗
PubMed2003

Perceptual integration of intramuscular electrical stimulation in the focal and the referred pain area in healthy humans.

The aim of the study was to investigate the perceptual integration of simultaneous stimulation in a focal and a referred pain area to investigate whether referred pain is mainly caused by facilitation of on-going input from the referred pain area by stimulation in the focal pain area or if referred pain is a consequence of misinterpretation of the origin of inputs from the focal pain area. Pain was induced in twelve healthy individuals by intramuscular electrical stimulation in the left infraspinatus muscle (MI) or the left dorsolateral upper arm (UA), i.e. the area of referral commonly reported from stimulation in MI. Conditioning stimulation consisted of, in a counterbalanced order, no stimulation (baseline) and pain intensity rated as 2/10 and 4/10, respectively, on a category scale. During conditioning stimulation in MI, sensitivity to test stimuli was assessed in UA and vice versa. The test stimuli consisted of i.m. electrical stimulation corresponding to the perception threshold to innocuous electrical stimulation, the electrical pain threshold (EPT), and pain intensity rated as 2/10, 4/10 and 6/10, respectively. Conditioning stimulation corresponding to 2/10 did not result in a statistically significant change in sensitivity to any test stimuli in either location. During conditioning stimulation corresponding to 4/10 in m. infraspinatus, all twelve subjects reported referred pain in the dorsolateral upper arm. Compared to baseline, EPTs decreased in the referred pain area (P<0.001), while no other statistically significant changes in sensitivity to test stimuli were seen. Conditioning stimulation corresponding to 4/10 in the dorsolateral upper arm gave rise to referred pain in one individual (area of m. biceps brachii), and no statistically significant changes were seen in the sensitivity to electrical stimuli in m. infraspinatus. In conclusion, an effect at pain threshold level only was documented during simultaneous stimulation in the focal and referred pain area, which does not support facilitation of inputs from the referred pain area as the main mechanism generating referred pain. Instead, referred pain is most likely a consequence of misinterpretation of the origin of input from the stimulated focal pain area, due to excitation of neurones somewhere along the neuroaxis with projected fields in the referred pain area. The fact that conditioning stimulation in m. infraspinatus generated referred pain in the dorsolateral upper arm, but not vice versa suggests that the divergence of the input is not reciprocally arranged.

Adult↗
PubMed2003

Painful and non-painful neuropathy in HIV-infected patients: an analysis of somatosensory nerve function.

Fifteen to 50% of AIDS-patients suffer from distal predominantly sensory neuropathy (DSP), which is commonly associated with painful symptoms. In the present study, we have focused on the function of fine calibre nerve channels, in 36 consecutive HIV-1-infected patients with painful (PPN) (n=20; 54%) and non-painful (PN) (n=16) sensory neuropathy, assessed by clinical, quantitative thermal testing (QTT) (31/36), and peripheral nerve conduction examination (32/36). Control QTT data were obtained from 49 healthy subjects with a corresponding age- and sex distribution. Demographics, antiviral treatment, immunological status, and nerve conduction examination did not differ between patients with and without painful symptoms. Hypoaesthesia to warmth, cold, and heat pain was observed in both neuropathy groups when compared to healthy controls. However, the perception threshold to warmth was more often impaired (p<0.01) and the level of impairment was more pronounced (p<0.001) in patients with painful neuropathy. Furthermore, increased pain sensitivity to cold was found only in patients with painful symptoms (p<0.05). An abnormal outcome of any QTT parameter was found in all patients with pain, but only among 62% of patients without pain, p<0.01, and the cumulative frequency of abnormalities in any of the four thermal percepts (warmth, cold, heat pain, and cold pain) was higher in patients with painful symptoms, p<0.0001. This study demonstrates a more pronounced impairment of C-fibre-mediated innocuous warm perception in patients with painful neuropathy, which in the setting of impaired or absent heat pain perception suggests a more generalised loss of function in somatosensory C-fibre channels.

Acquired Immunodeficiency Syndrome↗
PubMed2003

Somatosensory perception in patients suffering from long-term trapezius myalgia at the site overlying the most painful part of the muscle and in an area of pain referral.

In subgroups of patients with localised musculoskeletal pain spread of pain and signs of altered somatosensory processing at painful sites, both focal and referred areas have been reported. The purpose of the study was to examine somatosensory processing in patients with mainly unilateral long-term (> or =1 year) trapezius myalgia with ongoing pain for the last 3 months in the trapezius muscle in conjunction with ongoing or recurrent referral of pain to the ipsilateral arm. Ten patients with trapezius myalgia and 10 age- and sex-matched healthy controls participated. Pressure pain sensitivity, low threshold mechanoreceptive function and thermal sensitivity, including thermal pain, were assessed at the site overlying the most painful part of the trapezius muscle and in an area of pain referral in the ipsilateral upper arm/forearm as well as in the corresponding contralateral areas. No significant difference in sensibility was found in the most affected trapezius muscle and contralaterally compared to the corresponding areas in controls. In the area of pain referral there was a significantly increased sensitivity to pressure pain compared to the homologous contralateral area (p<0.01) as well as to the corresponding area in controls (p<0.009). Compared to controls a bilaterally decreased sensitivity to light touch was found in patients in the area of referred pain (p<0.01). No differences were found in the outcome of thermal testing. These findings suggest altered central processing of somatosensory input from the area of referred pain in patients with trapezius myalgia.

Adult↗