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PubMed1993

The muscle silent period following transcranial magnetic cortical stimulation.

Transcranial magnetic stimulation (TMS) of the motor cortex during tonic muscle contraction produces a motor evoked potential followed by a silent period in the electromyogram. We sought to characterize the TMS induced silent period and to compare it to the silent period induced by supramaximal peripheral nerve stimulation. TMS was delivered to the motor cortex using a 9 cm diameter circular coil and the surface electromyogram was recorded from the contralateral abductor pollicis brevis muscle in six normal subjects. Increasing TMS stimulus intensity from 10 to 50% above threshold resulted in an increase in the duration of the silent period from a mean of 50 ms to 185 ms. Increasing the level of tonic muscle contraction from 5% of maximum to maximum resulted in a decrease in silent period duration from a mean of 155 ms to 133 ms. In contrast, the duration of the silent period following supramaximal median nerve stimulation showed greater shortening under similar conditions, from a mean of 160 ms at 5% of maximum contraction to 99 ms at 75% of maximum contraction. The TMS induced silent period was present during a TMS induced increase in the reaction time for a ballistic movement, the onset of movement being delayed until the end of the silent period. Peripheral nerve stimulation did not produce a delay in movement onset. The present findings favour a cortical origin for the TMS induced silent period, probably on the basis of intracortical inhibition, rather than peripheral inhibition of spinal motoneurones which is considered to be the basis for the silent period following peripheral nerve stimulation.

Adult↗
PubMed1989

Factors terminating nonventilatory periods in the turtle, Chelydra serpentina.

PaO2, PaCO2 and pHa were measured via an extracorporeal loop in conscious snapping turtles (Chelydra serpentina) breathing air or hypoxic (10, 15% O2), hyperoxic (30% O2), or hypercapnic (2% CO2) gases. Turtles breathed into an inverted funnel ventilated with the test gas. Breathing was recorded with a differential pressure transducer. In all turtles, nonventilatory periods were interrupted by breathing episodes containing multiple breaths. In normoxia, PaO2 at the end of nonventilatory periods ranged from 22-128 mm Hg, although PaCO2 showed a less than 5 mm Hg variation about the mean. There was a positive correlation between PaCO2 at the end of the nonventilatory period and the number of breaths in the succeeding period of ventilation. PaCO2 at the end of nonventilatory periods did not change significantly in hyperoxia, although mean PaO2 was significantly increased. In hypoxia, on the other hand, mean PaO2 was significantly reduced and PaCO2 at the end of the nonventilatory period was slightly, but significantly lower. Nonventilatory periods were shorter when turtles breathed 15% O2 (9.3 +/- 1.2 min) or 10% O2 (5.5 +/- 0.3 min) than when they breathed air (17.6 +/- 3.4 min). The results indicate that, in undisturbed turtles, the most important stimulus triggering a breathing episode is the rise in PaCO2 to a critical value during the preceding nonventilatory period. An increase in hypoxic drive shortens the nonventilatory period. However, in normoxia, PaO2 at the end of many nonventilatory periods probably does not fall sufficiently to stimulate O2-sensitive chemoreceptors.

Animals↗
PubMed1976

A strain of Plasmodium vivax characterized by prolonged incubation: the effect of numbers of sporozoites on the length of the prepatent period.

The North Korean strain of Plasmodium vivax was characterized by its extraordinarily prolonged incubation period in certain circumstances. It was clearly demonstrated by quantitative observations that the phenomenon may be elicited by the inoculation of small numbers of sporozoites. After the intradermal inoculation of 10 or 100 sporozoites, the incubation period was delayed for periods varying between 262 and 628 days; after u,000 sporozoites, with one exception, the same delay occurred; after 100,000 sporozoites, the incubation period was always of normal duration (13--16 days). Two laboratory-acquired infections in workers who had taken a prophylactic drug showed incubation periods of 315 and 329 days, respectively. Various theories for the phenomenon of prolonged prepatent periods are examined, and the most satisfactory one is based on the presumed existence of two populations of sporozoites in P. vivax. In temperate strains, sporozoites requiring long prepatent periods (LPP) for development are present in great excess over a much smaller proportion of sporozoites characterized by short prepatent periods (SPP); thus small doses will elicit the phenomenon, though doses of over 1,000 sporozoites will mask the effect as the few SPP sporozoites will produce an infection with a normal (i.e. short) prepatent period. In tropical strains, the relative proportions are different, perhaps in equal numbers, and even in small doses some SPP sporozoites will be present and normal prepatent periods should ensure whatever the dosage."

Humans↗
PubMed1992

Evidence for separate control of estrous and circadian periodicity in the golden hamster.

To study the relationship between estrous and circadian periodicity, we investigated the period of the estrous cycle in two types of female golden hamsters: normals (circadian period approximately 24 h) and tau mutants (circadian period approximately 20 h). Records of running wheel activity, general locomotor activity, body temperature, vaginal secretion, and sexual receptivity of hamsters kept under constant lighting conditions indicated an estrous period of approximately 96 h for both groups of animals. The fact that animals with different circadian periods have the same estrous period suggests the existence of separate mechanisms in the control of circadian and estrous periodicity. Circadian periodicity is determined by a pacemaker located in the suprachiasmatic nuclei, whereas estrous periodicity is determined by positive and negative feedback loops involving the hypothalamus, pituitary, and gonads. Coupling of the two mechanisms takes place under at least some conditions, but additional research is necessary to elucidate the mechanisms by which this is accomplished.

Animals↗
PubMed2005

Gating of SEPs by contraction of the contralateral homologous muscle during the preparatory period of self-initiated plantar flexion.

To investigate the centrifugal change in somatosensory information processing caused by contraction of the contralateral homologous muscle, we recorded the somatosensory-evoked potentials (SEPs) during the preparatory period of a self-initiated plantar flexion. The SEPs following stimulation of the right tibial nerve at the popliteal fossa were recorded in nine healthy subjects. Self-initiated plantar flexion of the left ankle was performed once every 5 to 7 s. The electrical stimulation was delivered continuously, and the subjects were instructed to concentrate on the movement and not to pay attention to the electrical stimulation. Based on the components of movement-related cortical potential, Bereitschaftspotential (BP) and Negative slope (NS), the preparatory period was divided into four sub-periods (NS, BP-1, BP-2, and Pre-BP). To obtain pre-movement SEPs, the signals following stimulation in each sub-period were averaged. SEPs were attenuated in the preparatory period, especially in the NS sub-period. The amplitude of N40 component was significantly attenuated compared with that in the stationary state and other sub-periods. The amplitude of P53 and N70 was smaller in the NS sub-period than other pre-movement sub-periods. Since there was no centripetal effect on SEPs in the preparatory period, these findings suggested that the activity of motor-related areas modulated the somatosensory information from the contralateral non-movement limb (centrifugal gating). It was assumed that an inhibition on the somatosensory inputs from contralateral limb was caused by the projection via either the corpus callosum or ipsilateral cortico-cortical projections.

Adult↗
PubMed2006

Bleeding after use of the levonorgestrel regimen of emergency contraception: concordance between women's reports of their menstrual periods and an objective algorithm.

OBJECTIVE: To compare concordance between periods as recorded by women on daily diaries with those determined objectively by an algorithm used in an earlier study to assess bleeding patterns after taking the emergency contraceptive pill (ECP) regimen consisting of 1.5 mg levonorgestrel. METHODS: We asked 120 women who had been treated with the regimen to keep daily bleeding diaries for 9 weeks. We compared menstrual periods recorded on the diary cards and reported in follow-up interviews with those determined by an algorithm adapted from the World Health Organization (WHO). RESULTS: Altogether, 111 subjects contributed diary cards on which the algorithm could identify at least one period; a total of 261 periods were identified by the algorithm. In 87% of these periods, women recorded on the diary a start date that was the same as or only 1 day later, but in 8% their recorded start day was more than 7 days later. For the first period following use of the regimen, concordance was lower: 81% and 14%, respectively. CONCLUSION: We found generally good concordance between the starts of menstrual periods as determined by an algorithm adapted from the WHO and the date of the start of a period as reported by participants on diary cards. In our earlier study, we found that the earlier in the cycle a woman took 1.5 mg levonorgestrel, the earlier was the next period. Had we relied on women's recording of the first period on the diary card, we would not have reached that conclusion.

Adolescent↗
PubMed2006

Effects of preparatory period on anticipatory postural control and contingent negative variation associated with rapid arm movement in standing posture.

We investigated CNS motor preparation state and anticipatory postural muscle activation while subjects performed bilateral rapid arm movement at various intervals between warning and response stimulus (preparatory period) during standing. Motor preparation state was evaluated by integrated values of the late components of the contingent negative variation (late CNV), obtained by averaging electroencephalograms during the last 100ms of the preparatory period. For quantifying anticipatory postural muscle activation, we measured the onset of burst activity in postural muscles (lumbar paraspinal, biceps femoris, and gastrocnemius) with respect to anterior deltoid activity and integrated values of preceding activation. Subjects performed the arm movement with minimal delay in the warning stimulus-response stimulus-motor response paradigm under preparatory periods of 2.0, 3.0 and 3.5s. Late CNV did not differ between the 2.0-s and 3.0-s period, but was significantly smaller in the 3.5-s period than in the 2.0-s period, suggesting difficulty in predicting response timing in the 3.5-s period. No change was found on integrated values of preceding activations of postural muscles. Burst onset of all postural muscles significantly preceded anterior deltoid activation in all periods. Burst activity for gastrocnemius only occurred earlier in the 3.5-s period than in the 2.0-s and 3.0-s periods. Weak correlations were observed between late CNV and onset time of gastrocnemius activity. It is suggested that earlier activation of gastrocnemius is a strategy adopted when response stimulus timing is relatively difficult to predict.

Adult↗
PubMed2002

Periodicity in prokaryotic and eukaryotic genomes identified by power spectrum analysis.

We used a power spectrum method to identify periodic patterns in nucleotide sequence, and characterized nucleotide sequences that confer periodicities to prokaryotic and eukaryotic genomes and genomes. A 10-bp periodicity was prevalent in hyperthermophilic bacteria and archaebacteria, and an 11-bp periodicity was prevalent in eubacteria. The 10-bp periodicity was also prevalent in the eukaryotes such as the worm Caenorhabditis elegans. Additionally, in the worm genome, a 68-bp periodicity in chromosome I, a 59-bp periodicity in chromosome II, and a 94-bp periodicity in chromosome III were found. In human chromosomes 21 and 22, approximately 167- or 84-bp periodicity was detected along the entire length of these chromosomes. Because the 167-bp is identical to the length of DNA that forms two complete helical turns in nucleosome organization, we speculated that the respective sequences may correspond to arrays of a special compact form of nucleosomes clustered in specific regions of the human chromosomes. This periodic element contained a high frequency of TGG. TGG-rich sequences are known to form a specific subset of folded DNA structures, and therefore, the sequences might have potential to form specific higher order structures related to the clustered occurrence of a specific form of the speculated nucleosomes.

Animals↗
PubMed2004

Treatment of diabetic foot lesions in hospital: results of 2 successive five-year periods, 1989-1993 and 1994-1998.

OBJECTIVES: To assess the impact of an educational training program we initiated in 1994 for GPs about diabetic foot ulcer (DFU) management, we compared the rate and level of lower limb amputation (LLA) in diabetic patients performed in our unit between two consecutive five-year periods, 1989-1993 and 1994-1998. PATIENTS AND METHODS: During the first period, 132 patients with 163 lesions (9.2% of the total admissions for diabetes) were compared with 176 with 183 lesions (10.5%) during the second period. Patients' mean age was the same in both periods: 59.6 +/- 11.7 in 1989-1993 and 58.3 +/- 13.1 in 1994-1998 [Not statistically significant, NS]. RESULTS: Patients age, sex ratio, type of diabetes and severity of the lesion (as assessed according to Wagner classification) were essentially the same during the two periods. Most of the foot lesions ( approximately 90%) were purely neuropathic or neuro-ischaemic, with no change in repartition between the two periods. Primary healing was 59.1% in the 1st period and 56.8% in the second. No change in minor and major amputation rate was observed between the 1st period (14.4 and 15.9%, respectively) and the second (11.4 and 16.5%, respectively). The in-hospital mortality rate was unchanged (9.1 vs 8.5%, NS), while the percentage of patients who left hospital against medical advice and dropped out of follow up increased from 1.5 to 6.8% (p<0.04). Mean length of hospitalisation was identical, about 43 days. CONCLUSIONS: In spite of implementing educational program for GPs, no improvement in the DFU management was noted as emphasised by absence of any significant change in amputation rate before (1st period) and after initiating the program (2nd period). These disappointing results can be explained by several factors: weakness of our educational program, lack of motivation from GPs, absence of a structured multidisciplinary prevention approach. The main problem, common to developing countries, remains the insufficiency of financial resources. Moreover, civil disturbances can make the problem more difficult to manage, as in Algeria since 1991.

Algeria↗
PubMed2006

Reactions of methyl fluoride with atomic transition-metal and main-group cations: gas-phase room-temperature kinetics and periodicities in reactivity.

Reactions of CH(3)F have been surveyed systematically at room temperature with 46 different atomic cations using an inductively coupled plasma/selected-ion flow tube tandem mass spectrometer. Rate coefficients and product distributions were measured for the reactions of fourth-period atomic ions from K(+) to Se(+), of fifth-period atomic ions from Rb(+) to Te(+) (excluding Tc(+)), and of sixth-period atomic ions from Cs(+) to Bi(+). Primary reaction channels were observed corresponding to F atom transfer, CH(3)F addition, HF elimination, and H(2) elimination. The early-transition-metal cations exhibit a much more active chemistry than the late-transition-metal cations, and there are periodic features in the chemical activity and reaction efficiency that maximize with Ti(+), As(+), Y(+), Hf(+), and Pt(+). F atom transfer appears to be thermodynamically controlled, although a periodic variation in efficiency is observed within the early-transition-metal cations which maximizes with Ti(+), Y(+), and Hf(+). Addition of CH(3)F was observed exclusively (>99%) with the late-fourth-period cations from Mn(+) to Ga(+), the fifth-period cations from Ru(+) to Te(+), and the sixth-period cations from Hg(+) to Bi(+) as well as Re(+). Periodic trends are observed in the effective bimolecular rate coefficient for CH(3)F addition, and these are consistent with expected trends in the electrostatic binding energies of the adduct ions and measured trends in the standard free energy of addition. HF elimination is the major reaction channel with As(+), while dehydrogenation dominates the reactions of W(+), Os(+), Ir(+), and Pt(+). Sequential F atom transfer is observed with the early-transition-metal cations, with the number of F atoms transferred increasing across the periodic table from two to four, maximizing at four for the group 5 cations Nb(+)(d(4)) and Ta(+)(d(3)s(1)), and stopping at two with V(+)(d(4)). Sequential CH(3)F addition was observed with many atomic cations and all of the metal mono- and multifluoride cations that were formed.

Cations↗
PubMed2001

[The importance of access-to-patient-period in the emergency service].

INTRODUCTION: The "period-to-help" (Hilfsfrist) is defined by the federal states as a measure for further planning and structure the emergency services. This period is composed of distinct time intervals and ends with the arrival of the rescue team at the emergency. From a physician's point of view it is merely the time to the first contact with the patient that is of vital interest. Data on the discrepancy between arrival at the emergency scene and the first contact with the patient are lacking. METHODS: We analysed prospectively 680 emergencies outside the hospital and calculated the so-called "access-to-patient" period (Zugangszeit). 552 emergencies supplied with an ambulance and 128 emergencies supplied with a helicopter ambulance service were analysed. RESULTS: The mean total time period for the ambulance arriving at the patient was 8.17 minutes +/- 30.3 seconds while being 10.52 minutes +/- 73.3 seconds for the helicopter ambulance service. The "access-to-patient" period was 50.9 minutes +/- 8.2 seconds for the ambulance and 75.7 minutes +/- 21.7 seconds for the helicopter ambulance service. For road accidents the "access-to-patient" period was significantly shorter for both the ambulance (12.4 +/- 4.1 seconds) and the helicopter (19,6 +/- 10,8 seconds), while in emergencies taking place inside closed buildings these time intervals were 5 and 6.5 times longer (ambulance 64.2 +/- 10,9 seconds). As outer circumstances counted most to prolonged access-to-patient periods the latter did not correlate with the severity of the injury or the emergency. Appropriate guidance and briefing of the crew of an emergency service at the scene is able to minimize the access-to-patient period (74.5 versus 60.4 seconds for the ambulance and the helicopter, respectively). Delays were caused in 22.6 % of all emergencies, mostly due to imprecise orders, impassable terrain and the inability to identify the building. CONCLUSION: If we consider that road accidents count for merely 10 % of all emergencies it seems appropriate to re-define the so-called "period-to-help" (Hilfsfrist) that takes into account the "access-to-patient" period (Zugangszeit) that is on average 50 seconds. The primary goal of any further planning must be to keep the interval without sufficient therapy as short as possible.

Accidents, Traffic↗
PubMed1997

Temporal trends in diabetes mortality among American Indians and Hispanics in New Mexico: birth cohort and period effects.

Rates of diabetes mortality are disproportionately high among ethnic minorities in the United States. To describe ethnic trends and cohort effects in diabetes mortality in New Mexico, the authors examined the trends in mortality rates for non-Hispanic whites. Hispanics, and American Indians in the state during the period 1958-1994. Age-specific rates were examined graphically to qualitatively describe the contribution of calendar period and birth cohort effects to changes in the rates. The authors also fit age-period-cohort models to these data. Age-adjusted diabetes mortality rates for American Indians and Hispanics surpassed rates for non-Hispanic whites for all but the earliest two time periods. In the 1993-1994 period, the age-adjusted mortality rate for American Indians was 3.8 times higher for men and 5.6 times higher for women than for their non-Hispanic white counterparts. Rates for American Indian men and women increased sharply over the 37-year period, by 565% and 1,105%, respectively. Mortality rates increased among Hispanics over the period of study but less rapidly than did rates among American Indians. Graphical analyses of age-specific rates were consistent with birth cohort effects among both American Indians and Hispanics and also with a period effect among American Indians. Results from age-period-cohort models indicate a birth cohort effect starting with the 1912 cohort in American Indians and the 1902 cohort in Hispanics. A period effect was present during the 1960s in American Indians. American Indians have experienced an epidemic rise in diabetes mortality in New Mexico; if current trends continue, diabetes may become the leading cause of mortality among American Indians in the state.

Adult↗
PubMed2005

Egg storage period and weight effects on hatchability of ostrich (Struthio camelus) eggs.

We studied the affects of storage period and egg weight on the hatchability of 314 ostrich (Struthio camelus) eggs. Eggs were stored at 20 degrees C and 65% RH before incubation at the Poultry Research, Teaching and Extension Center at Texas A&M University (College Station, TX). Eggs were classed by storage period (< or = 5, > 5 < or = 10, > 10 < or = 15, or > 15 < 24 d) and egg weight (< or = 1,450, > 1,450 < or = 1,650, or > 1,650 g) to determine the influence of storage period and egg weight on hatchability, egg weight loss, incubation period, and absolute and relative chick weights. Eggs were incubated at 36.5 to 37.0 degrees C and 25% RH through 38 d of incubation and 36 degrees C and 30% RH thereafter. Mean egg weight loss was greater from eggs of the longest storage period group (> 15 < 24 d) at 21 or 38 d when compared with eggs of the shorter storage periods, but there were no differences at 7, 14, or 28 d among all storage period groups. Mean hatchability was higher in eggs stored < or = 10 d than eggs stored > 15 < 24 d, but hatchability of eggs stored >10 < or = 15 d was not different from eggs stored < or = 10 d or > 15 < 24 d. Incubation period was longer, and absolute and relative weights were higher in eggs stored >15 d than was observed in eggs stored < or = 15 d. Negative correlations were detected between egg weight and moisture loss at 38 d (-0.55) and between hatch time and moisture loss (-0.25). Hatchability was higher in small eggs than medium eggs (< or = 1,650 g). A positive correlation was observed between chick and egg weights (0.84). The results indicated that storage period and egg weight affected egg weight loss. Our results suggested that the most effective storage period was less than 15 d to maintain hatchability for ostrich eggs when incubated at 36.5 to 37.0 degrees C with 25% RH.

Animals↗
PubMed1987

Fifty cases of late prosthetic valve endocarditis: improvement in prognosis over a 15 year period.

The clinical course, prognostic factors, and management of 50 cases of late prosthetic valve endocarditis, occurring more than two months after valve replacement, were reviewed. Twenty nine cases that presented from 1971 to 1980 were compared with 21 cases that presented from 1981 to 1985. Apart from an appreciable decrease in the frequency of neurological complications between the first period (38%) and the second period (10%) no differences in clinical or bacteriological features were seen. Seventeen (59%) of the 29 cases in the earlier period and four (19%) of the 21 cases in the later period died. The rationale for antimicrobial treatment was similar during both periods. Cardiac surgery was performed in eight of 29 cases between 1971 and 1980 and in 11 of 21 between 1981 and 1985; the mean (SD) time between diagnosis of endocarditis and operation was 28 (19) days and 43 (44) days respectively. Six of the eight cases operated on in the first period died as did two of the 11 operated on in the second period. Twenty seven of the 29 cases presenting between 1971 and 1980 were treated with anticoagulants--either warfarin (15 of 27) or heparin sodium (12 of 27). Sixteen of the 21 cases presenting later were given anticoagulants and 15 of these cases were given heparin sodium. Control of anticoagulation was inadequate in nine of the 27 cases treated with anticoagulants during the first period and in only two of 16 treated during the second period. During the first treatment period neurological complications were more frequent when control of anticoagulation was inadequate.

Adult↗
PubMed2000

Epidemiology of ectopic pregnancy during a 28 year period and the role of pelvic inflammatory disease.

OBJECTIVES: We analysed the epidemiology of ectopic pregnancy (EP) during a 28 year period, 1970-97, using methods applicable to ecological studies in order to test the hypothesis that a reduction of pelvic inflammatory disease (PID) will be associated with a decrease of EP. METHODS: Hospital records of patients aged 15-54 admitted to our department of gynaecology were reviewed for EP and PID for the period 1 January 1970 to 31 December 1997. EP for the period 1970-4 was based on available statistics. The total number for EP was 1270 and for PID 2559. The total population for the catchment area was 100,000-120,000 during the study period. Incidences were age standardised and calculated using official population statistics to represent the average female population in the five 5 year periods 1970-4, 1975-9, 1980-4, 1985-9, 1990-4, and in each of the consecutive years 1995, 1996, and 1997. Incidences for EP were calculated per 1000 women and per 1000 pregnancies while those for PID per 1000 women. National statistical data of EP were available for 1975-94 and were used for comparison with the local study. RESULTS: The EP incidences increased from 7.7 per 1000 pregnancies in the first 5 year period to 13.4 in the second, and continued to rise for another decade reaching the peak figures of 16.6 in 1985-9--that is, more than a twofold increase. Since then and to 1997 the EP incidence has decreased by 30%. PID admissions increased during the study period from 2.7 per 1000 women in the first 5 year period to 3.2 in the second. From then on they continuously decreased and reached a low of 0.5 in 1997. The greatest changes occurred in women < or = 24 years of age. The peak incidence for this age group was 7.7 in 1975-9, and the lowest was 0.4 per 1000 women in 1996. The greatest reduction of EPs was noted for women < or = 24 years old, from a high of 10.0 in 1975-9, coinciding with the peak incidence of PID, to a low of 4.0 in 1997, a reduction of 58.4%. The incidence of EP was two to three times higher in women > or = 25 years old, most obvious in those > or = 30 years, with peak figures of 20.9 per 1000 pregnancies in 1985-9, and 13.9 in 1997, a reduction of 33.4% and the lowest figures for the past 23 years. For women aged 25-29 years the incidence peaked in the previous 5 year period 1980-4--that is, one 5 year period later than for those < or = 24 years, which we interpret as cohort effects in relation to PID. CONCLUSIONS: Reduction of PID was strongly associated with a decline of EP. The decline was greater and immediate for women < or = 24 years old, than for those > or = 25 years. The two to three times higher EP incidence in women > or = 25 years of age was most probably due to a cohort effect as the peak of PID occurred a decade earlier in women < or = 24 years old. Prevention of PID may not only reduce EP but also reduce adverse effects on tubal patency.

Adolescent↗
PubMed1997

Effect of age, birth cohort, and period of death on cerebrovascular mortality in Spain, 1952 through 1991.

BACKGROUND AND PURPOSE: The continued decrease in cerebrovascular disease in Spain remains unexplained. Age-period-cohort analysis enables description of birth cohort and period-of-death components. This study sought to describe these effects on the decline of stroke mortality in Spain. METHODS: Deaths due to cerebrovascular diseases in the period from 1952 through 1991 and the corresponding population figures were grouped into 11 age groups and 8 5-year periods, from which age-specific mortality rates for 18 birth cohorts were then computed. These were plotted for graphical presentation purposes and fitted to Poisson regression models to assess age, period, and cohort effects. RESULTS: An exponential age effect was present for both sexes regardless of cohort or period. A definite downward period effect was observable from 1962 to 1991, except for a sharp fall and peak in the periods 1967 to 1971 and 1972 to 1976, respectively, which was possibly ascribable to changes in diagnostic and coding practices. Age- and period-adjusted stroke mortality increased for earlier cohorts and decreased for generations born between 1892 and 1940. For post-1940 generations, there was an increasing risk of stroke mortality. CONCLUSIONS: The results suggest that a decrease in incidence coupled with an increase in survival may account for the observed decline in stroke mortality, but further studies on the Spanish population are needed to assess these findings. Although not yet definitive, there are signs of an increase in incidence among the more recent generations. If the decreasing period effect fails to offset this increase, future years may see a deceleration in the current decline in stroke mortality.

Adult↗
PubMed1999

Entrainment of blood pressure and heart rate oscillations by periodic breathing.

Cheyne-Stokes respiration (CSR) is a form of periodic breathing associated with periodic oscillations in blood pressure (BP) and heart rate (HR), which have been attributed to hypoxia and arousals from sleep. We hypothesized that periodic alterations in ventilation alone would promote oscillations in BP and HR. Seven healthy, wakeful subjects breathed in three patterns, as follows: (1) regular breathing (RB); (2) periodic breathing with three (PB3: cycle frequency = 0.035 Hz) augmented breaths alternating with 20-s apneas; and (3) periodic breathing with five (PB5: cycle frequency = 0.030 Hz) augmented breaths alternating with 20-s apneas. SaO2 remained above 95% throughout. During periodic breathing, peaks in BP and HR occurred during the ventilatory period and troughs occurred during apnea. The magnitudes of systolic BP oscillations increased significantly from RB (14 +/- 5 mm Hg) to PB3 (20 +/- 4 mm Hg) and PB5 (25 +/- 7 mm Hg; p < 0.005). HR oscillations also increased from regular breathing (13 +/- 6.0 beats/min) to PB3 (20.2 +/- 2.3 beats/min) and PB5 (20.2 +/- 4.7 beats/ min; p < 0.01). Spectral analysis showed that during periodic breathing there were discrete peaks in the spectral power of ventilation, BP, and R-wave-to-R-wave interval at the periodic breathing cycle frequencies. We conclude that oscillations in ventilation occurring during periodic breathing can amplify and entrain oscillations in BP and HR in the absence of hypoxia or arousals from sleep.

Adult↗
PubMed2002

Dry deposition (downward, upward) concentration study of particulates and water-soluble ionic species during daytime, night-time period at the traffic sampling site of Sha-Lu, Taiwan.

Ambient suspended particulate (dry deposition, TSP) was collected in the traffic sites Sha-Lu, central Taiwan. In addition, the related water-soluble ionic species (Cl-, NO3(-), SO4(2-), Na+, NH4(+), K+, Mg2+ and Ca2+) were analysed and wind speed, wind direction and temperature were also measured in this study. The downward dry deposition fluxes (averaged 54.07 microg/m2-sec) were about twice that of upward dry deposition fluxes (averaged 26.48 microg/m2-sec) in the daytime period. Furthermore, the average downward dry deposition fluxes (averaged 26.22 microg/m2-sec) were also about twice that of upward dry deposition fluxes (averaged 12.11 microg/m2-sec) in the night-time period. The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 microg/m3) were higher than in the night-time period (averaged 560.7 microg/ m3). The results showed that the total suspended particulate concentrations of particulate mass in the daytime period (averaged 996.2 microg/m3) were higher than in night-time period (averaged 560.7 microg/ m3). As for water-soluble ionic species, the average dry deposition order and velocity for downward ionic species were Cl- > Ca2+ > NO3(-) > K+ (2.09 cm/sec > 1.46 cm/sec > 1.46 cm/sec > 1.07 cm/sec) anions during the daytime period. And the average dry deposition order and velocity for downward ionic species were NO3(-) > Cl- > K+ > Ca2+ (2.92 cm/sec > 2.74 cm/sec > 0.96 cm/sec > 0.93 cm/sec) anions during the night-time period. The average dry deposition order and velocity for upward ionic species were Cl- > Ca2+ > K+ > Mg2+ (4.69 cm/sec > 0.62 cm/sec > 0.59 cm/sec > 0.55 cm/sec) anions during the daytime period. And the average dry deposition order and velocity for upward ionic species were Cl- > Ca2+ > Mg2+ > K+ (1.65 cm/sec > 0.43 cm/sec > 0.37 cm/sec > 0.33 cm/sec) anions during the night-time period. The results also indicated that the sodium and chloride concentrations in total suspended particulate were highly positively related, indicating that the sea-salt aerosols were the major contributors for these species at this sampling site of central Taiwan.

Chromatography, Ion Exchange↗