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PubMed2005

[Evaluation of species distribution of yeasts isolated from intensive care units during the four years period].

The aim of this study was to evaluate the distributions of yeast species according to the years and to detect the emerging pathogens in intensive care units (ICU). For this purpose, yeast isolation rates were detected retrospectively, in the following time periods: Period I: April-December 2001; period II: January-December 2002; period III: January-December 2003; period IV: January-December 2004. A total of 490 yeast isolates recovered from 462 clinical specimens obtained from 360 different ICU patients were investigated during these periods. Urine (62.1%), blood (13.6%) and tracheal aspirate (8.7%) samples were detected as the most common specimens. Of these isolates, 53.3% were identified as Candida albicans, 14.5% as C. tropicalis, 12.2% as C. glabrata, 6.5% as C. parapsilosis, 4.5% as Trichosporon spp., 3.9% as C. kefyr, 1.6% as C. krusei, 1.4% as Geotrichum candidum and 2.1% as other Candida species. The isolation rates of C. albicans in the periods of I to IV were found as 47.7%, 55.5%, 41.7% and 62.4%, respectively. The decrease between the second and third periods, and increase between third and fourth periods were statistically significant (chi2 = 4.15, p = 0.04 and chi2 = 8.32, p = 0.004). C. glabrata was the second most common species in the first and second periods (14.8% and 15.5%, respectively), followed by C. tropicalis (12.5% and 10.0%, respectively), however this array has changed in the third and fourth periods (C. tropicalis was the second with the rates of 16.7% and 16.8%, while C. glabrata placed in the third line with the rates of 14.8% and 7.6%, respectively). It was concluded that C. albicans has still been the most frequent species among yeast isolates of ICU's in our hospital; however, the incidence of non-albicans species like C. glabrata and C. tropicalis has increased.

Candida↗
PubMed2005

Influence of the war in Croatia on the frequency of gynecological cancer in the University Hospital Osijek in the period from 1985 to 2002.

The aim of this study is to estimate the influence of war in Croatia on the frequency of gynecological cancer (cancer of corpus and cervix uteri and ovary) in the Clinical Hospital Osijek, particularly the relation between the pre-war and post-war period. We analyzed 1455 patients with corpus uteri and cervix uteri cancer and ovarian cancer treated in the Clinical Hospital Osijek in the period 1985-2002 (group I). Patients from Osjecko-Baranjska County were analyzed separately--1273 women, (group II) and in the group III there were 182 patients from other counties. The analyzed period was divided into: pre-war 1985-1990, war 1991-1993 and post-war period 1997-2002. In all three groups the number of patients treated for gynecological cancer was significantly larger in the post-war period (group I, N = 611, group II, N = 498, group III, N = 113) than in the pre-war period (group I, N = 457, group II, N = 433, group III, N = 24). The analysis of cancer frequency in relation to the site shows that a total number of patients treated for cervical cancer was larger in the post-war (N = 229) than in the pre-war period (N = 214), but the difference wasn't significant. However, the number of patients from Osjecko-baranjska County treated for cervical cancer was larger in the pre-war (N = 207) than in the post-war period (N = 178) but still, the difference wasn't significant. The number of patients treated for corpus uteri cancer and ovarian cancer was significantly larger for the I group in the post-war (N = 225 and N = 157 respectively) than in the pre-war period (N = 136, and N = 107 respectively). In the group II the number of patients treated for corpus uteri cancer and ovarian cancer was larger in the post-war (N = 196 and N = 124 respectively) than in the pre-war period (N = 130 and N = 96 respectively) but the difference was significant only for corpus uteri cancer. Significantly more women were treated for gynecological cancer in the post-war than in the pre-war period. However, the war had probably an indirect influence on the increased number of patients treated for gynecological cancer mainly because many more women arrived from other counties.

Adult↗
PubMed1998

Fractal dimension and approximate entropy of heart period and heart rate: awake versus sleep differences and methodological issues.

1. Investigations that assess cardiac autonomic function include non-linear techniques such as fractal dimension and approximate entropy in addition to the common time and frequency domain measures of both heart period and heart rate. This article evaluates the differences in using heart rate versus heart period to estimate fractal dimensions and approximate entropies of these time series.2. Twenty-four-hour ECG was recorded in 23 normal subjects using Holter records. Time series of heart rate and heart period were analysed using fractal dimensions, approximate entropies and spectral analysis for the quantification of absolute and relative heart period variability in bands of ultra low (<0.0033 Hz), very low (0. 0033-0.04 Hz), low (0.04-0.15 Hz) and high (0.15-0.5 Hz) frequency.3. Linear detrending of the time series did not significantly change the fractal dimension or approximate entropy values. We found significant differences in the analyses using heart rate versus heart period between waking up and sleep conditions for fractal dimensions, approximate entropies and absolute spectral powers, especially for the power in the band of 0.0033-0.5 Hz. Log transformation of the data revealed identical fractal dimension values for both heart rate and heart period. Mean heart period correlated significantly better with fractal dimensions and approximate entropies of heart period than did corresponding heart rate measures.4. Studies using heart period measures should take the effect of mean heart period into account even for the analyses of fractal dimension and approximate entropy. As the sleep-awake differences in fractal dimensions and approximate entropies are different between heart rate and heart period, the results should be interpreted accordingly.

Adult↗
PubMed1991

Reversible oxidative activation and inactivation of protein kinase C by the mitogen/tumor promoter periodate.

The oxidant mitogen/tumor promoter, periodate, was used to selectively modify either the regulatory domain or the catalytic domain of protein kinase C (PKC) to induce oxidative activation or inactivation of PKC, respectively. Periodate, at micromolar concentrations, modified the regulatory domain of PKC as determined by the loss of ability to stimulate kinase activity by Ca2+/phospholipid, and also by the loss of phorbol ester binding. This modification resulted in an increase in Ca2+/phospholipid-independent kinase activity (oxidative activation). However, at higher concentrations (greater than 100 microM) periodate also modified the catalytic domain, resulting in complete inactivation of PKC. The oxidative modification induced by low periodate concentrations (less than 0.5 mM) was completely reversed by a brief treatment with 2 mM dithiothreitol. In this aspect, the modification induced by periodate was different from that of the previously reported irreversible modification of PKC induced by H2O2. However, the inactivation of PKC induced by periodate at concentrations greater than 1 mM was not reversed by dithiothreitol. Among the phospholipids and ligands of the regulatory domain tested, only phosphatidylserine protected the regulatory domain from oxidative modification. In the presence of phosphatidylserine, the catalytic site was selectively modified by periodate, resulting in formation of a form of PKC that exhibited phorbol ester binding but not kinase activity. Both reversible and irreversible oxidative activation and inactivation of PKC also were observed in intact cells treated with periodate. Taken together these results suggest that periodate, by virtue of having a tetrahedral structure, binds to the phosphate-binding regions present within the phosphatidylserine-binding site of the regulatory domain and the ATP-binding site of the catalytic domain, and modifies the vicinal thiols present within these sites. This results in the formation of intramolecular disulfide bridge(s) within the regulatory domain or catalytic domain leading to either reversible activation or inactivation of PKC, respectively. Thus, oxidant mitogen/tumor promoters such as periodate may be able to bypass normal transmembrane signalling systems to directly activate pathways involved in cellular regulation.

Binding Sites↗
PubMed1990

Periodicity analysis of sleep EEG in the second and minute ranges--example of application in different alpha activities in sleep.

To investigate the temporal organization of EEG sleep activity in the second and minute ranges we developed a method which, based on Fourier transformation, allows the presentation of periodic oscillations of spectral power and coherence. The application of this method is demonstrated in 3 subjects with different types of alpha activity during sleep: (a) alpha-sleep pattern (a physiological variant of NREM sleep activity); (b) abnormally increased arousal alpha activity. The results show that differences in the temporal organization of these alpha activities can be determined with the following parameters: period length, duration of sequences with periodic activity, number and rate of these sequences, and proportion of periodicities generated simultaneously in the left and right hemispheres. The physiologically modulated periodicities of the alpha-sleep pattern are contrary to a stereotyped 40-60 sec periodicity of abnormal arousal alpha activity. Such abnormal periodicity corresponds to periodicities occurring in association with other sleep disturbances, such as sleep apnea or periodic movements in sleep. Periodicity analysis gives additional criteria for a more refined evaluation of normal as well as abnormal sleep structure.

Adult↗
PubMed1987

The association of the supernormal period and the depolarizing afterpotential in myelinated frog and rat sciatic nerve.

Excitability properties of isolated frog and rat sciatic nerve fibers were examined using intra-axonal and sucrose-gap recording techniques. Paired stimulation experiments on rat myelinated fibers indicate that a small proportion (11%; n = 84) of these axons demonstrate decreased threshold indicative of a supernormal period. In contrast, 81% (n = 23) of frog axons displayed a supernormal period. A depolarizing afterpotential was observed in most of the rat and frog fibers having a supernormal period and the depolarizing afterpotential increased in magnitude and duration during hyperpolarization. In addition to whole nerve stimulation, a supernormal period could be induced by stimulation of a single axon via current passage through the recording microelectrode. Brief (2-5 ms) subthreshold depolarizing pulses were followed by a slowly decaying depolarization and a period of increased excitability that mimicked the supernormal period. A supernormal period was also observed in the whole nerve preparation using a sucrose-gap technique. The magnitude and duration of the supernormal period, as measured in the sucrose-gap, were greater for frog nerve than for rat nerve. Additionally, a larger postspike negativity, the extracellular equivalent of the intra-axonally observed depolarizing afterpotential, was present in sucrose-gap recordings for frog nerve than for rat nerve. The results indicate that the depolarizing afterpotential is an important determinant of the supernormal period, and that both the depolarizing afterpotential and supernormal period are more prominent in frog than in rat sciatic nerve.

Action Potentials↗
PubMed1997

The atomic basis of biological symmetry and periodicity.

Geometric derivations and mathematical formulas have shown how the symmetrical patterns of plants, animals and crystals, follow similar mathematical solutions. These transformations have had the great value of indicating relationships between different types of patterns. However, they could neither shed light on the material processes that led to the emergence of symmetries in nature, nor explain their transfer to higher levels of organization, as evolution proceeded from simple molecular systems to complex living organisms. Several phenomena contribute to elucidate the material processes that have led to the emergence and transfer of symmetries. Their characteristics can be summarized: (1) symmetries are inherent to the structure of matter, since they already occur in the elementary particles, such as the neutrino; (2) simple atoms, such as oxygen and hydrogen produce a six-ray symmetry in water crystals a pattern from which these crystals cannot depart; (3) the mechanism of twinning, common in minerals, obliges several components to associate in a regular fashion guided by the properties of their atoms; (4) the symmetries of crystals are decided by the electronic properties of their constituent atoms. Since living organisms consist of the same atoms that are found in the minerals, it is not surprising that the symmetries of the minerals were transferred intact to the cell and organism levels; (5) another atomic property that has been preserved is periodicity. The existence of the Periodic Table of the elements shows how this phenomenon is so well established at the atomic level. This periodicity was also transferred to the living organism level. Both biological structures and functions display periodicity; (6) the recurrence of the same type of symmetry in minerals, plant organs and animal structures is an expression of the preservation of this periodicity; (7) another manifestation of the periodicity is found in the recurrence of the same symmetry in flowers of a large number of plant families which are not closely related in evolutionary terms; (8) the re-emergence of the same symmetry at different levels of organization is also elucidated by the fact that different atom combinations can display the same form and even the same function. This is what has been called molecular mimicry. Examples are the minerals with quite different chemical compositions which display the same symmetry and the proteins, that although they consist of different amino acid sequences, result in the same structural pattern and the same function. Due to the occurrence of molecular mimicry, in the cell's main macromolecules, an organism does not even need to have the same genes to exhibit a symmetry that appeared long ago in evolution; and (9) support for the concept that the biological periodicity is anchored on the chemical periodicity is found, among other features, on the fact that the six atoms that build the main macromolecules of the cell: the nucleic acids and proteins are all simple atoms that are located in a 'niche' on the right side of the Periodic Table of the chemical elements. The basis of biological symmetry and periodicity is now starting to be elucidated in atomic terms.

Anatomy, Comparative↗
PubMed1997

Differences in refractory-period response of canine subendocardium and subepicardium to bunazosin, an alpha1-adrenoceptor antagonist, and propranolol during myocardial ischemia.

Our objective was to investigate the effects of alpha1- or beta-adrenoceptor blockers on endocardial and epicardial refractory-period changes during myocardial ischemia in alpha-chloralose-anesthetized dogs. The first and second diagonal branches of the left anterior descending coronary artery were ligated. The refractory period was determined by an S1-S2 extrastimulus method. Dogs were treated with the alpha1-blocker bunazosin (0.1-0.2 mg/kg, i.v.; n = 16), the beta-blocker propranolol (0.2 mg/kg, i.v.; n = 15), or saline (n = 11). Dogs that developed ventricular tachycardia/fibrillation (VT/VF) during the experiment were excluded from the statistical assessment in refractory periods. In all groups, coronary ligation produced a significant shortening of the refractory period of ischemic epicardial tissue (p < 0.05) but only minimal shortening of ischemic endocardial refractory periods, resulting in an increased difference in repolarization time between the endo- and epicardial sites. Treatment with bunazosin ameliorated this ischemia-related shortening of refractory periods at both the endo- and epicardial sites, with a greater effect seen epicardially (p < 0.05), resulting in values similar to those in the nonischemic tissue. Treatment with propranolol prolonged refractory periods more in the epicardial (p < 0.01) than in endocardial sites, exacerbating the disparity in the refractory period between the endo- and epicardial sites (p < 0.05). Propranolol also prolonged the refractory period of nonischemic tissue (p < 0.05 and p < 0.01 in endo- and epicardial sites, respectively), resulting in a significant difference between the ischemic and normal myocardium at the endocardial site (p < 0.05). Results suggest that the alpha1-blocker bunazosin reduces the refractory-period disparity between the ischemic and normal myocardium without increasing the disparity between the endo- and epicardial surfaces, whereas propranolol produces a greater disparity.

Adrenergic alpha-1 Receptor Antagonists↗
PubMed2002

Period differences between segmental oscillators produce intersegmental phase differences in the leech heartbeat timing network.

Considerable experimental and theoretical effort has been exerted to understand how constant intersegmental phase relationships are produced between oscillators in segmentally organized pattern generating networks. The phase relationship between the segmental oscillators in the isolated timing network of the leech heartbeat central pattern generator is quite regular within individual preparations. However, it varies considerably among different preparations. Our goal is to determine how the phase relationships in this network are established. Here we assess whether inherent period differences, as suggested by the excitability-gradient hypothesis, play a role in establishing the phase relationships between the two coupled segmental oscillators of the leech heartbeat timing network. To do this we developed methods for reversibly uncoupling the segmental oscillators (sucrose knife) and pharmacological manipulation of the individual oscillators (split bath). Differences in inherent cycle periods between the third and fourth segmental oscillators (G3 and G4) were present in most (20 of 26) preparations. These period differences correlated with the phase differences observed between the segmental oscillators in the recoupled timing network, such that the oscillator with the faster cycle period, regardless of the segment in which it was located, led in phase in proportion to its period difference with the other oscillator. The phase differences between the original (coupled) and recoupled states of individual preparations were similar. Thus application and removal of the sucrose knife did not alter the period difference between the segmental oscillators in the timing network. Pharmacological manipulation of the uncoupled oscillators to alter the period difference between the oscillators led to similar correlated phase differences in the recoupled timing network. Across all experiments the uncoupled segmental oscillator with the faster cycle period established the cycle period of the timing network when recoupled. In conclusion, our findings indicate that an excitability-gradient plays a role in establishing the phase relationship between the segmental oscillators of the leech heartbeat central pattern generator since inherent period differences present between the oscillators are correlated to the phase relationships of the coupled/recoupled timing network.

Animals↗
PubMed1989

Embryology, ethology and ecology of ontogenetic critical periods in fish.

Overviews of critical period concepts, as they appear at several biological levels, are presented. In embryology, critical periods generally refer to restricted periods in development during which undifferentiated groups of cells can be induced to differentiate. In neurobiology, critical periods are those during which neural circuits are particularly plastic and subject to molding by cellular processes and by experience. The ethological critical period concept advances the idea that an individual's behavioral characteristics can be more strongly influenced by a given event (some stimulus) at one stage of development than at others. For example, this is the period during which young birds imprint upon their parent(s) and learn their species' songs, or during which young salmon imprint to the odor of their home streams. The fisheries science critical period, an ecological concept, refers to a restricted time in the early life history of fish during which there is massive mortality. For many fish, this event is generally considered the primary factor controlling the size of the adult population. The cause of variable mortality between years is thought to be a result of differential food availability and predation during a critical stage in early fish larval development. At each biological level of the critical period, spatial and temporal overlap between the developing organism and specific environmental input is essential. It is likely that critical periods in embryology, neurobiology and ethology are causally interrelated in a hierarchical manner and that they can be manifested as ecological critical periods.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Bayesian detection of periodic mRNA time profiles without use of training examples.

BACKGROUND: Detection of periodically expressed genes from microarray data without use of known periodic and non-periodic training examples is an important problem, e.g. for identifying genes regulated by the cell-cycle in poorly characterised organisms. Commonly the investigator is only interested in genes expressed at a particular frequency that characterizes the process under study but this frequency is seldom exactly known. Previously proposed detector designs require access to labelled training examples and do not allow systematic incorporation of diffuse prior knowledge available about the period time. RESULTS: A learning-free Bayesian detector that does not rely on labelled training examples and allows incorporation of prior knowledge about the period time is introduced. It is shown to outperform two recently proposed alternative learning-free detectors on simulated data generated with models that are different from the one used for detector design. Results from applying the detector to mRNA expression time profiles from S. cerevisiae showsthat the genes detected as periodically expressed only contain a small fraction of the cell-cycle genes inferred from mutant phenotype. For example, when the probability of false alarm was equal to 7%, only 12% of the cell-cycle genes were detected. The genes detected as periodically expressed were found to have a statistically significant overrepresentation of known cell-cycle regulated sequence motifs. One known sequence motif and 18 putative motifs, previously not associated with periodic expression, were also over represented. CONCLUSION: In comparison with recently proposed alternative learning-free detectors for periodic gene expression, Bayesian inference allows systematic incorporation of diffuse a priori knowledge about, e.g. the period time. This results in relative performance improvements due to increased robustness against errors in the underlying assumptions. Results from applying the detector to mRNA expression time profiles from S. cerevisiae include several new findings that deserve further experimental studies.

Algorithms↗
PubMed2003

Pollen tubes exhibit regular periodic membrane trafficking events in the absence of apical extension.

The growing pollen tube provides an excellent single cell model system in which to study the mechanisms determining growth regulation, polarity and periodic behaviour. Previously, using FM4-64, we identified periodic movements within the apical vesicle accumulation that were related to the period of oscillatory growth. This suggested a more complex interdependence between membrane traffic, apical extension and periodicity than previously thought. To investigate this a comparison was made between normally growing and Brefeldin-A-treated, non-growing, tubes. Brefeldin-A treatment established an intriguing, stable yet dynamic system of membrane aggregations in the pollen tube tip that exhibited regular movements of material with a 5-7 second period compared with the normal approximately 30 second periodicity observed in growing tubes. Heat treatment was found to reduce period length in both cases. After BFA treatment membrane was demonstrated to flow from the extreme pollen tube apex back through a distinct subapical Brefeldin-A-induced membrane accumulation. The effects of Brefeldin-A on the distribution of ER- and Golgi-targeted fluorescent proteins revealed that ER did not contribute directly to the system of membrane aggregations while only certain compartments of the Golgi might be involved. The involvement of membrane derived from the apical vesicle accumulation was strongly implicated. Calcium measurements revealed that Brefeldin-A abolished the typical tip-focused calcium gradient associated with growth and there were no obvious periodic fluctuations in apical calcium associated with the continued periodic Brefeldin-A membrane aggregation associated movements. Our experiments reveal an underlying periodicity in the pollen tube that is independent of secretion, apical extension and the oscillating tip-focused calcium gradient normally associated with growth, but requires an active actin cytoskeleton.

Actin Cytoskeleton↗
PubMed2003

Milk production and feed intake of Holstein cows given short (30-d) or normal (60-d) dry periods.

Eighty-four Holstein cows were utilized to evaluate effects of dry period (60 d vs. 30 d), with or without estradiol cypionate (ECP) injections to accelerate mammary involution, on prepartum and postpartum dry matter intake (DMI), body weight (BW), body condition score (BCS), and subsequent milk yield (MY). Treatments were arranged in a 3 x 2 x 2 factorial design that included dry period (30 d dry, 30 d dry + ECP, and 60 d dry), prepartum and postpartum bovine somatotropin (bST; 10.2 mg/d), and prepartum anionic or cationic diets. To accelerate mammary involution, ECP (15 mg) was injected intramuscularly at dry-off. No interaction of bST or prepartum diet with dry period length was detected on BW, BCS, or MY. No significant effects of dry period length on prepartum DMI, BW, or BCS were detected. Cows with shorter dry periods maintained postpartum BCS better and tended to have greater DMI immediately postpartum. Mean daily yields of milk for dry period groups did not differ during overall lactation period (1 to 21 wk). Injection of ECP at the onset of the 30-d dry period did not affect MY. No significant differences due to dry period length were detected for milk, 3.5% FCM, or SCM yields during first 10 wk of lactation. Data indicated that a short dry period protocol can be used as a management tool with no loss in the subsequent milk production of dairy cows.

Animal Nutritional Physiological Phenomena↗
PubMed1987

A classification of European skulls from three time periods.

We analyze the taxonomic structure of European populations at three time periods, the Early Middle Ages, the Late Middle Ages and the Recent Period. The data consist of sample means for 10 cranial variables based on 137, 108, and 183 samples for the three periods. Clustering by standard numerical taxonomic procedures reveals that the data are represented only poorly as hierarchic classifications. The clusters form significant and moderately strong associations with an arrangement of the samples by regions (geography) and by language family. Whereas during the early period, language family showed a stronger association with clusters based on cranial morphology, in the recent populations these clusters correspond better with geography than with language. Ordinations of these populations by means of nonmetric multidimensional scaling shows the continuity of the taxonomic structure at all three periods. Only a few populations are outliers. The relations between phenetic distances (cranial morphology), geography, and language are examined by means of multiple Mantel tests. At all three periods geography is correlated somewhat more strongly with phenetics than is language affiliation, but the correlation with the latter increases with time. When the data are pooled over the three periods, the populations tend to group by language affiliation more than they do by period. Ordination of the pooled data reveals language patterns rather than patterns due to period, showing strong shifts in cranial measurements through time. These analyses show that while there is no clear-cut taxonomic structure in European populations that would justify the traditional classifications based on the crania, there are significant and important associations with both language affiliation, geography, and time period, in this order. These patterns are likely to have become established through the migration and subsequent expansion of populations into their areas of occupation during the time interval studied rather than by geographic differentiation in situ.

Cephalometry↗
PubMed2000

The excitability of human cortical inhibitory circuits responsible for the muscle silent period after transcranial brain stimulation.

The silent period after transcranial magnetic brain stimulation mainly reflects the activity of inhibitory circuits in the human motor cortex. To assess the excitability of the cortical inhibitory mechanisms responsible for the silent period after transcranial stimulation, we studied, in 15 healthy human subjects, the recovery cycle of the silent period evoked by transcranial and mixed nerve stimulation delivered with a paired stimulation technique. The recovery cycle is defined as the time course of the changes in the size or duration of a conditioned test response when pairs of stimuli (conditioning and test) are used at different conditioning-test intervals. The recovery cycle of the duration of the silent period in the first dorsal interosseous (FDI) muscle during maximum voluntary contraction after transcranial magnetic stimulation was studied by delivering paired magnetic shocks (a conditioning shock and a test shock) at 120% motor-threshold intensity. Conditioning-test intervals ranged from 20-550 ms. The recovery cycle of the silent period in the FDI muscle during maximum voluntary contraction after nerve stimulation was evaluated by paired, supramaximum bipolar electrical stimulation of the ulnar nerve at the wrist (conditioning-test intervals ranging from 20 to 550 ms). Electromyographic activity was recorded by a pair of surface-disk electrodes over the FDI muscle. The recovery cycle of the silent period after transcranial magnetic stimulation delivered through the large round coil showed two phases of facilitation (lengthening of the silent period), one at 20-40 ms and the other at 180-350 ms conditioning-test intervals, with an interposed phase of inhibition (shortening of the silent period) at 80-160 ms. The conditioning magnetic shock left the size of the test motor-evoked potentials statistically unchanged during maximum voluntary contraction. Paired transcranial stimulation with a figure-of-eight coil increased the duration of the test silent period only at short conditioning-test intervals. Conditioning nerve stimulation left the silent period produced by test nerve stimulation unchanged. In conclusion, after a single transcranial magnetic shock, inhibitory circuits in the human motor cortex undergo distinctive short-term changes in their excitability, probably involving different mechanisms.

Adult↗
PubMed2006

Endothelial functions are more severely impaired during active disease period in patients with Behcet's disease.

Oral apthous ulcers and skin lesions are the primary symptoms of Behcet's disease (BD). To date, there is no study to investigate possible associations between these lesions and endothelial functions. We have hypothesized that active BD period with oral and skin lesions might have more deteriorating effect on endothelial functions. Thirty-five patients with BD were registered for the study. Each subject was evaluated two times in both active and inactive disease periods. The subject with at least 30 days of lesion-free period was regarded in the inactive disease period, and the subject with any oral and/or skin lesions was regarded in the active disease period. For the control group, 35 healthy age- and sex-matched subjects were registered. In each subject, flow-mediated dilation (FMD) of the brachial artery after transient ischemia was evaluated in both active and inactive disease periods. High-sensitivity C-reactive protein (hsCRP) values (3.30 +/- 5.76 vs 14.19 +/- 13.55 vs 1.82 +/- 1.31, P < 0.001) and FMD values (13.89 +/- 5.57 vs 8.53 +/- 4.78 vs 15.83 +/- 5.29, P < 0.001) were significantly different among the BD patients in inactive and active disease periods and among control subjects. FMD values in inactive and active disease periods modestly correlated to hsCRP and low-density lipoprotein cholesterol values. Brachial FMD is more prominently impaired in BD patients within the active disease period. BD patients are possibly more vulnerable to cardiovascular manifestations when they are in the active disease period.

Adolescent↗
PubMed1982

Masseter inhibitory periods and sensations evoked by electrical tooth pulp stimulation in patients with oral-facial pain and mandibular dysfunction.

The masseter inhibitory period (silent period) and sensations evoked by tooth-pulp stimulation were examined in 12 healthy subjects and 12 patients with oral-facial pain and mandibular dysfunction (MPD). Trains of 30 pulses were applied to an upper incisor and the threshold intensities for detecting sensation, for detecting pain sensation and for the masseter inhibitory period were determined. Masseter activity was monitored during tooth stimulation by electromyographic recordings from surface electrodes. Electrical tooth stimulation elicited three different configurations of masseter inhibitory periods in both groups: single, double and merged. MPD patients exhibited a greater proportion of single inhibitory periods. The combined average total durations of the three types of configurations were less in MPD. The findings are consistent with the hypothesis that there is an increase in excitability of the central masseter motorneuron pool in MPD, resulting in a reduction in the effective duration of the masseter inhibitory period. The higher incidence of single inhibitory periods in MPD patients also could result from this increased central excitatory state. There was no difference between masseter inhibitory periods evoked in either painful or non-painful muscles, and no particular configuration associated with pain sensation. The findings do not support the hypothesis that nociceptive input contributes to the increase in duration of the silent period in MPD. Although there were no significant differences between masseter inhibitory period threshold, detection thresholds or pain threshold for both groups, MPD patients had detection thresholds higher than their masseter inhibitory thresholds. These effects may be related to differential central neural influences on sensory-discriminative and reflex pathways in the trigeminal system.

Adolescent↗
PubMed1985

Mechanisms mediating the sympathetic silent period: studies in the isolated spinal cord of the neonatal rat.

The properties of the sympathetic silent period were examined using the isolated spinal cord of the neonatal rat. In all spontaneously active sympathetic preganglionic neurons (PGN) examined, repetitive stimulation of the ventral root gave rise to a prolonged inhibition (up to 30 s) of spontaneous activity. The silent period could also be demonstrated in most 'silent' PGN using a condition-test paradigm. The characteristics of the silent period in this preparation resembled those previously reported in the adult cat. Using several paradigms, we were able to show a dissociation between the duration of the silent period and the recent firing history of the PGN. This indicates that the silent period is not due solely to recovery processes intrinsic to the PGN. By stimulating adjacent ventral roots or rostral and caudal bundles of the same ventral root, we found that the system producing the silent period was confined to a restricted anatomical locus. Activation of the silent period was capable of inhibiting glutamate-evoked activity, implying that the inhibition impinges directly on the PGN. We found no evidence of a cholinergic mediation of the silent period. However, experiments with naloxone indicated that opiate mechanisms play an unsuspected role in modulating the silent period. We conclude that at least some component of the silent period is mediated by a synaptic mechanism extrinsic to the PGN.

Animals↗