Ksenija Cankar

Gender differences in cutaneous vascular and autonomic nervous response to local cooling

Abstract. To investigate gender differences in cutaneous vascular reactivity to local cooling we performed cold exposure of one hand and measured laser Doppler (LD) flux on fingers ipsilaterally and contralaterally in a group of 10 healthy females and a group of 10 healthy males. The females were tested twice: in the early follicular and in the mid-luteal phase of the menstrual cycle. We related the characteristics of cutaneous vascular responses to indices of autonomic nervous system activity (heart rate, blood pressure, heart rate variability) at rest and during the cold challenge. In our experimental settings females exhibited greater cutaneous vascular response to local cooling at the ipsilateral site (LD flux decreased to 48.6 ± 6.2 % of the resting value), as compared to males (LD flux decreased to 71.9 ± 6.2 % of the resting value) as well as at the contralateral site (LD flux decreased to 68.2 ± 6.1 % in females and to 85.6 ± 3.8 % in males) (p < 0.05, Dunnetts test). The more pronounced cutaneous vascular response in females seems consistent with the finding of their lower sympathetic activity at rest as well as with their heart rate variability indices of greater sympathetic system reactivity to local cold exposure. Correspondingly, males showed a higher level of sympathetic nervous system activity at rest and a predominant reactivity of the parasympathetic system during local cooling at 15 °C. The females in our study, all of whom were premenopausal, exhibited intra-menstrual cycle variability only in cutaneous vascular response at the site of local cooling (LD flux decreased during the early follicular phase to 48.6 ± 6.2 % and during the mid-luteal phase to 29.2 ± 3.2 % of the resting value, p < 0.05, paired t-test), but not contralaterally. In addition, we found no intra-menstrual cycle differences in the indices of autonomic nervous system reactivity.

The Effect of Hyperbaric Oxygenation on Postradiation Xerostomia and Saliva in Patients with Head and Neck Tumours

The study was designed to evaluate the influence of hyperbaric oxygenation (HBO) therapy on salivary gland function and the growth of salivary Streptococcus mutans,Lactobacillus and Candida albicans in patients with head and neck tumours who had undergone radiation therapy. Sixteen patients were included, with radiation doses from 58 to 70 Gy. The first examination was performed at baseline before the first HBO therapy (33.7 ± 9 months after radiation therapy), and the second after 20 daily HBO therapies in a hyperbaric chamber at 2.5 ATA (absolute atmospheres), where patients breathed 100% oxygen for 90 min each day. Measurements of salivary flow, buffer capacity, saliva pH and colony density of S. mutans,Lactobacillus and C. albicans in stimulated saliva were conducted, and xerostomia grade was assessed. Salivary flow increased from 0.20 ± 0.1 to 0.39 ± 0.2 ml/min at the end of HBO therapy (p < 0.001). Salivary pH also increased from 6.0 ± 0.2 to 6.5 ± 0.1 (p < 0.05). The colony density decreased from the time at baseline to the end of HBO therapy for S. mutans (p < 0.001), Lactobacillus (p < 0.05) and the fungus C. albicans (p < 0.05). The xerostomia grade decreased from 2.63 ± 0.2 to 1.94 ± 0.2 after HBO (p < 0.001). There was no significant change in buffer capacity. The increased salivary secretion rate and salivary pH, and decreased S. mutans and Lactobacillus colony density that were observed after HBO therapy may reduce caries progression in those patients.

The effect of glibenclamide on acetylcholine and sodium nitroprusside induced vasodilatation in human cutaneous microcirculation.

Objective:  KATP channels have an important regulatory role in resting vascular tone and during hypoxia. Their role in endothelium dependent and independent vasodilatation in human skin microcirculation is less known.

Cold perception and cutaneous microvascular response to local cooling at different cooling temperatures.

The aim of the present study was to investigate the effect of quantitatively measured cold perception (CP) thresholds on microcirculatory response to local cooling as measured by direct and indirect response of laser-Doppler (LD) flux during local cooling at different temperatures. The CP thresholds were measured in 18 healthy males using the Marstock method (thermode placed on the thenar). The direct (at the cooling site) and indirect (on contralateral hand) LD flux responses were recorded during immersion of the hand in a water bath at 20°C, 15°C, and 10°C. The cold perception threshold correlated (linear regression analysis, Pearson correlation) with the indirect LD flux response at cooling temperatures 20°C (r=0.782, p<0.01) and 15°C (r=0.605, p<0.01). In contrast, there was no correlation between the CP threshold and the indirect LD flux response during cooling in water at 10°C. The results demonstrate that during local cooling, depending on the cooling temperature used, cold perception threshold influences indirect LD flux response.

The effect of α-adrenoceptor agonists and L-NMMA on cutaneous postocclusive reactive hyperemia

Postocclusive reactive hyperemia (PRH) is considered to be a locally mediated vascular reaction independent of sympathetic activity. However, experiments on animal vascular preparations have shown that alpha(2)-adrenoceptor activity interferes with the production of endothelium-derived nitric oxide (NO) that has been found to play an important role in the PRH response. We attempted to elucidate the role of endothelium-derived NO in the cutaneous PRH response. Especially, we aimed to clarify the interference of the alpha-adrenoceptor activity with NO mechanism in cutaneous microcirculation. We studied the effect of intradermal microinjection of the NO synthase inhibitor L-NMMA alone, alpha(1)-agonist phenylephrine alone, alpha(2)-agonist clonidine alone and L-NMMA in combination with each alpha-agonist. The effect of the saline solution injection was used as a reference value. Laser-Doppler flux was monitored in 11 healthy volunteers before and after a 4-minute and an 8-minute occlusion of digital arteries. The application of L-NMMA significantly reduced resting LD-flux (p<0.05) only in combination with alpha(2)-agonist but not alpha(1)-agonist. The application of L-NMMA alone changed the time in which LD flux reached half of the preocclusive value during the PRH response (T/2) only after 4-minute (p<0.05) but not after an 8-minute occlusion. Phenylephrine (alpha(1)-agonist) alone shortened (p<0.05), while clonidine (alpha(2)-agonist) alone prolonged T/2 (p<0.05) of 8-minute PRH. The combined application of L-NMMA and clonidine abolished the effect of clonidine alone on 8-minute PRH. In contrast, the combination of L-NMMA and phenylephrine did not cause any change of the PRH response when compared to the injection of phenylephrine alone. Our finding is consistent with the hypothesis that alpha(2)-adrenoceptor activity (in the condition of maximal agonist stimulation) could interfere with NO mechanisms in cutaneous microcirculation, probably by increasing NO production.

Assessment of the dentin-pulp complex response to caries by ADC mapping

The prognostic potential of apparent diffusion coefficient (ADC) mapping was studied as complemented by high‐resolution 3D T1‐weighted MRI in the assessment of dentin‐pulp complex response to caries. Twenty‐six extracted human teeth, with or without caries lesions of different grades in accord with the International Caries Detection and Assessment System (ICDAS), were analyzed by high‐resolution MRI at 2.35 T. A signal rise in demineralized hard dental tissues in high‐resolution T1‐weighted MR images enabled assessment of the demineralization depth over the whole range of ICDAS scores. ADC maps of the teeth were calculated from corresponding diffusion‐weighted images of four different b values: 0, 132, 317, 635 s/mm2. These maps enabled reliable differentiation between intact (ADC > 1.0·10‐9 m2/s) and affected (ADC < 1.0·10‐9 m2/s) regions of dental pulp. Linear regression analyses of demineralization depth in relation to ICDAS score and then also to average ADC of dental pulp showed that a demineralization depth increase of one millimeter corresponds to an ICDAS score increase of 1.2 and an average ADC decrease of 0.07·10‐9 m2/s. Results of the study indicate that the average ADC value of dental pulp could be used as a potential marker to assess tissue response to caries comparable to that of ICDAS scoring. Copyright

Cognitive and autonomic dysfunction in presymptomatic and early Huntington's disease.

Huntington’s disease is characterized by disorders of movement, cognition and behavior. Individuals with Huntington’s disease display aberrant changes in the autonomic nervous system that are detected even before the onset of other symptoms. Subtle cognitive dysfunction may start before other clinical manifestations. The aim of the present study was to investigate the autonomic nervous system response to mental arithmetic and the relationship between the autonomic and cognitive/motor function in presymptomatic and early Huntington’s disease. We examined 15 presymptomatic Huntington’s disease gene carriers (PHD), 15 early Huntington’s disease patients (EHD) and 30 healthy controls. PHD and EHD groups were determined according to Unified Huntington’s Disease Rating Scale (UHDRS) motor score. ECG, heart rate, systolic and diastolic blood pressure, and cutaneous laser Doppler flux were measured during rest and during a simple mental arithmetic test. UHDRS cognitive test battery was applied to determine cognitive dysfunction. During mental arithmetic, the heart rate of PHD/EHD increased significantly less than that of controls. Decreased microvascular response to mental arithmetic was found in EHD. Significant correlations for the PHD/EHD group were found between laser Doppler flux response and Symbol Digit Modalities Test score, and between laser Doppler flux response and UHDRS motor score. It seems that central autonomic dysregulation of cardiovascular system in Huntington’s disease goes along with the degeneration of other central neuronal systems. This finding is relevant as it could enable simple and noninvasive testing of disease progression.

Role of alpha-adrenoceptors in the cutaneous postocclusive reactive hyperaemia.

Abstract Laser-Doppler (LD) flow measurements reveal typical flow oscillations in the descending part of the cutaneous postocclusive reactive hyperaemia (PRH). The origin of these oscillations is still poorly understood. We tested the hypothesis that the high frequency (HF) components within the frequency band 0.06-0.2 Hz are due to the local myogenic mechanism, whereas the low frequency (LF) components within frequency band 0.01-0.05 Hz reflect sympathetic vasomotor activity. LD flow was monitored on fingertips of 11 healthy volunteers before and after an 8-minute occlusion of digital arteries. We studied the effect of intradermal microinjection (1 μl) of α-antagonists (prazosine, yohimbine) and α-agonists (phenilephrine, clonidine) on PRH oscillations. We analysed the magnitude of peak flow and its duration and performed spectral power analysis to obtain fundamental HF and LF frequencies (defined as components with the highest amplitude in the part of the respective frequency band). The results (mean ± SE) for each substance were compared to the control values obtained after microinjection (1 μl) of 0.9% NaCl. The fundamental HF significantly decreased from 0.11 ± 0.008 Hz after an injection of saline solution to 0.08 ± 0.006 Hz after an application of antagonists (p<0.05). The local application of α-antagonists did not abolished HF oscillations what suggests that activity of local sympathetic nervous system is not essential in generation of these oscillations. However, the significant decrease of fundamental frequency in HF band after application of α-antagonists supports the hypothesis of their local origin and could be explained by the effect on pacemaker myogenic mechanism.

Functional impairment of precerebral arteries in Huntington disease

BACKGROUND Cardiovascular pathology of Huntington disease (HD) appears to be complex; while microvascular dysfunction seems to appear early, deaths from cardiomyopathy and stroke might occur in the late phase of HD. METHODS Our study evaluated global risk factors for coronary heart disease (CHD), structure and function of precerebral arteries in 41 HD subjects and 41 matched controls. HD subjects were divided into groups by the United Huntington disease rating scale (presymptomatic-PHD, early-EHD, midstage-MHD and late-LHD). CHD risk factors assessment and Doppler examination of precerebral arteries were performed, including measurements of the carotid artery intima-media thickness (IMT), and parameters indicating local carotid artery distensibility (stiffness index β, pulse wave velocity, pressure strain elasticity module and carotid artery compliance). RESULTS In the HD and controls we identified a comparable number of non-obstructive plaques (<50% lumen narrowing). No obstructive plaques (>50% lumen narrowing) were found. There was significantly increased IMT in MHD. In PHD and EHD the parameters of arterial stiffness were significantly higher and the carotid artery compliance was significantly lower. CONCLUSIONS Our results reveal functional vascular pathology in PHD, EHD, and MHD. Precerebral arteries dysfunction in HD therefore appears to be mostly functional and in agreement with recently described autonomic nervous system changes in HD.

Cutaneous microvascular response during local cold exposure - the effect of female sex hormones and cold perception

It is generally known that differences exist between males and females with regard to sensitivity to cold. Similar differences even among females in different hormonal balance might influence microvascular response during cold provocation testing. The aim of the present study was to measure sex hormone levels, cold and cold pain perception thresholds and compare them to cutaneous laser-Doppler flux response during local cooling in both the follicular and luteal phases of the menstrual cycle. In the luteal phase a more pronounced decrease in laser-Doppler flux was observed compared to follicular phase during local cooling at 15°C (significant difference by Dunnetts test, p<0.05). In addition, statistically significant correlations between progesterone level and laser-Doppler flux response to local cooling were observed during the follicular (R=-0.552, p=0.0174) and during the luteal phases (R=0.520, p=0.0271). In contrast, the correlation between estradiol level and laser-Doppler flux response was observed only in the follicular phase (R=-0.506, p=0.0324). Our results show that individual sensitivity to cold influences cutaneous microvascular response to local cooling; that microvascular reactivity is more pronounced during the luteal phase of the menstrual cycle; and that reactivity correlates with hormone levels. The effect of specific sex hormone levels is related to the cold-provocation temperature.