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 role of alpha1- and alpha2-adrenoceptors in gender differences in cutaneous LD flux response to local cooling.

The present study was designed to assess the hypothesis that alpha2-adrenergic response plays a predominant role in sex differences in cutaneous microvascular response to cold. For this purpose, we studied the effect of the selective alpha1-antagonist prazosin (1 microl of 1.2 mM solution) and the alpha2-antagonist yohimbine (1 microl of 12 mM solution) microinjected into the skin area where the laser-Doppler (LD) flux response to local cooling was measured in healthy male and female subjects. Multiple regression analysis showed correlation between LD flux response at the site of local cooling (direct response) and gender (P = 0.039). The LD flux decrease was smaller in males. The application of the yohimbine significantly diminished the LD flux response at the site of local cooling in females but not in males (P < 0.05). In contrast, the injection of prazosin did not significantly affect the response. These findings strongly support the suggestion of a decisive role of alpha2-adrenoceptors in cold-induced gender difference at the level of cutaneous microvasculature at the site of local cooling. Multiple regression analysis of LD flux response to cold exposure at the site distant to cooling (indirect response) also confirmed correlation between LD flux response and gender (P = 0.022). The LD flux decrease was smaller in males. The alpha1-antagonist abolished the LD flux response to cold exposure (P = 0.000). These results corroborate the importance of alpha1-adrenoceptors in skin microcirculatory response to indirect local cooling mediated by the sympathetic vascular reflex.

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

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 microl) of alpha-antagonists (prazosine, yohimbine) and alpha-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 microl) 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 alpha-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 alpha-antagonists supports the hypothesis of their local origin and could be explained by the effect on pacemaker myogenic mechanism.

Gender differences in cutaneous laser doppler flow response to local direct and contralateral cooling.

To investigate the role of sympathetic neurovascular reactivity in the gender differences of cutaneous, cold-induced vasomotor response, we compared direct (at the site of cooling) and indirect (at a site remote from the cooling site) response measured by laser Doppler (LD) flowmetry in 12 healthy males and 12 healthy females. The females underwent testing twice, once in the follicular and once in the luteal phase of the menstrual cycle. We measured LD flow before and during local cooling of one hand at 15 degrees C. We found that local cooling evokes a significantly greater decrease in cutaneous LD flow in females than in males in direct as well as in indirect response conditions (p < 0.05). Comparing the response in females in the different phases of menstrual cycle, we obtained a significantly greater direct response to local cooling in the luteal phase than in the follicular phase (p < 0.05). In contrast, there was no menstrual-cycle-dependent difference in the indirect response to cold. The results of our study strongly indicate that sympathetic neural reactivity, as assessed by way of an indirect response to a cold stimulus, significantly contributes to gender differences in the response to local cooling. In contrast, the variation in microvascular responsiveness to cold exposure due to the menstrual cycle is most probably caused by local vascular mechanisms rather than by variation in sympathetic neural reactivity to local cooling.

Microvascular skin response to local cooling and body tilt early after digital replantation.

To elucidate the alteration in cutaneous microvascular reactivity early after replantation (14-21 days), laser Doppler (LD) flow changes evoked by direct and indirect local cooling and head-up body tilt were studied in the replanted digits (n = 10) and compared with those evoked in the healthy contralateral digits of the same patients (n = 10). During the first 3 minutes of direct cooling of the injured hand, LD flow increased significantly compared with the LD flow before cooling, which confirms that moderate vasodilation is the dominant component of the response to local cooling in skin microcirculation in the early period after replantation. During body tilt, LD flow in the healthy contralateral digit decreased significantly in only the first minute, while LD flow in the replanted digit started to decrease in the second minute after tilting; the decrease was significant from the third to the sixth minute. These results are consistent with the hypothesis that increased human skin alpha-adrenergic receptor sensitivity may be present as early as 2 to 3 weeks after replantation.

Pressure sensitivity of flow oscillations in postocclusive reactive skin hyperemia.

Skin blood flow was monitored using a laser-Doppler (LD) flowmeter in 21 healthy volunteers after an occlusion of the digital arteries. The peripheral vascular bed was exposed to occlusion ischemia of varying duration (1, 4, or 8 min) and to a change in digital arterial pressure produced by different positions of the arm above heart level to characterize the pattern of LD flow oscillations in postocclusive reactive hyperemia (PRH) and to elucidate the relevance of metabolic and myogenic mechanisms in governing its fundamental frequency. The descending part of the hyperemic flow was characterized by the appearance of conspicuous periodic oscillations with a mean fundamental frequency of 7.2 +/- 1.5 cycles/min (SD, n = 9), as assessed by a Fourier transform frequency analysis of 50-s sections of flow. The mean respiratory frequency during the periods of flow frequency analysis was 17.0 +/- 2.2 (SD, n = 9), and the PRH oscillations remained during apnea in all tested subjects. The area under the maximum flow curve increased significantly with prolongation of the occlusion (paired t test, P < 0.001; n = 9), but showed no dependence on the estimated blood pressure in the digital arteries, which suggests the predominant role of a metabolic component in this part of the PRH response. In contrast, the fundamental frequency of PRH oscillations exhibited a significant decrease with a reduction in the estimated digital arterial pressure (linear regression, b = 0.08, P < 0.001; n = 12), but did not change with the prolongation of arterial occlusion despite a significant increase in mean LD flow (paired t test, P < 0.001; n = 9).(ABSTRACT TRUNCATED AT 250 WORDS)

Pattern electroretinogram recorded by skin electrodes in early ocular hypertension and glaucoma.

Diagnostic value of transient pattern electroretinogram (PERG), recorded by skin electrodes, was compared with Goldmann perimetry in cases of ocular hypertension and glaucoma. According to the assumption that the PERG mostly reflects activity of the retinal ganglion cells, and histological evidence that 30-50% atrophy of the retinal ganglion cells is necessary to cause defects in visual field, we wanted to assess if i) this method could be more sensitive in detecting early glaucomatous damage than routine Goldmann perimetry in eyes with normal or only borderline elevated intraocular pressure in the time of PERG recording (first group of patients), and ii) how the PERG amplitude corresponds to ganglion cell loss, expected in the eyes with already detectable initial glaucomatous visual field defects, according to Goldmann II/2 isopter, with normal or borderline elevated intraocular pressure in the time of PERG recording (second group). In the group with no visual field defects subnormal amplitude of the major positive component of the PERG, N1-P1, was detected in three of 30 eyes (10%), while in the group with initial visual field defects N1-P1 amplitude was subnormal in 6 of 11 eyes (54%). The amplitude of the major negative PERG component, P1-N2, was found normal in all eyes of the first group and subnormal in 5 eyes (45%) of the second group.