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PubMed2006

Temporal changes in forest landscape patterns in Artvin Forest Planning Unit, Turkey.

Understanding the historical dynamics, composition, and environmental disturbances of forest landscapes provides a context for monitoring changes, describing trends, and establishing reference conditions. This study analyses the temporal changes in forest ecosystem structure in Artvin Forest Planning Unit (AFPU), Turkey, during 1972-2002 period based on digitized forest stand type maps using geographic information system (GIS) and interpretation of satellite data. The results showed that there was a net decrease of 450 ha in total forested areas between 1972 and 2002. Forest ecosystem structure changed over time depending on a few factors such as demographic movements, insect outbreaks, dam and road construction, unregulated management actions, and social pressure. In conclusion, temporal changes and the factors affecting these changes should be determined for sustainable management of natural resources.

Ecosystem↗

PubMed1979

Connective tissues--possible implications of the temporal changes for the aging process.

Two of the "old" mono-cause theories of aging have temporal changes in the connective tissues, especially those in collagen, as main events. The crosslinking of collagen is stable under physiological conditions shortly after the formation of fibrils and the additional physico-chemical stability attained later on probably does not influence the physiological functions of the tissues significantly. The temporal changes in collagen seen as increased thermal stability, decreased solubility and increased mechanical stiffness are discussed in relation to the underlying structural changes. It is concluded that the increased stability of the collagen (mainly type I) in the locomotive system and skin are not "true" aging phenomena. It is possible that the changes in the connective tissues of the lungs and kidneys contribute to the decrease of function with age. The "normal" increase of stiffness of type I collagen may contibute to the increased compliance and residual volume of the aging lung. Our present knowledge of the structure and function of collagens and ground substances in various basement membranes does not permit an evaluation of the role of connective tissues in the age changes in the alveolo--capillary complex, the glomeruli and the exchange between tissues and capillaries in general.

Adrenal Cortex Hormones↗

PubMed1989

Temporal changes of plasma erythropoietin level in hypobaric hypoxic mice and the influence of an altered blood oxygen affinity.

Temporal changes of plasma erythropoietin (Epo) in mice exposed to hypobaric hypoxia were studied by a fetal mouse liver cell culture method. Since a colony formation inhibitory activity was found in the mouse plasma, thirteen pretreatment procedures for bioassay were compared and the procedure of shaking with chloroform followed by dialysis was concluded to be the best. When normal mice (P50 = 40.4 +/- 2.2 Torr) were exposed to hypoxia of 350 Torr, the plasma Epo level was elevated, with peak at the 2nd to 3rd day, and afterwards declined gradually. On the contrary, cyanated mice (P50 = 30.1 +/- 1.5 Torr) showed much less of the Epo response when exposed to 350 Torr. Under 200 Torr hypoxia, both mice exhibited a similar and remarkable extent of the response. These results suggest that the renal Epo-producing tissue or its oxygen-sensing system is less hypoxic in cyanated mice than in normal mice under 350 Torr, and that the physiologically optimal oxygen affinity of blood is variable depending on hypoxic degrees. The fact that the inhibitory activity showed an inverse temporal change to that of Epo, suggested a possible important role of this activity in the regulation of erythropoiesis under hypoxia.

Administration, Oral↗

PubMed2001

Temporal changes in cardiac function and cerebral blood flow during sequential postmenopausal hormone replacement.

OBJECTIVE: The purpose was to assess the temporal changes in cardiac function and cerebral blood flow during postmenopausal administration of estrogen with and without progestogen. STUDY DESIGN: Sixteen postmenopausal volunteers were assessed during estradiol plus sequential norethindrone acetate and placebo in two 12-week periods. Temporal changes were measured by magnetic resonance flow mapping 8 times. RESULTS: Systemic vascular resistance was reduced during estradiol (-6.9%; P <.05), declined further during the addition of norethindrone acetate, and was accompanied by an increase in stroke volume (maximum increase, 5.2%; P <.05) without fluid retention. Both systolic (-5 mm Hg; P =.03) and diastolic (-3 mm Hg; P =.03) blood pressure were reduced during estradiol. Cerebral blood flow was reduced after 9 weeks of hormone replacement therapy (-37 mL/min; P =.01) but increased to baseline after the addition of norethindrone acetate. CONCLUSIONS: Sequential hormone replacement therapy is associated with changes in cardiac function, which are of therapeutic potential in cardiovascular disorders. Sequential hormone replacement therapy exhibits an overall neutral effect on cerebral blood flow.

Blood Pressure↗

PubMed1999

Temporal changes in airway protective reflexes elicited by an endotracheal tube in surgical patients anaesthetized with sevoflurane.

In order to elucidate temporal changes in airway reflex responses to prolonged tracheal intubation, 14 patients anaesthetized with sevoflurane were studied. In each spontaneously breathing patient with an endotracheal tube in place, the end-tidal concentration of sevoflurane was slowly decreased from the initial value of 1.3% until signs of airway irritation were observed. The value of end-tidal sevoflurane concentration at which the airway reflexes occurred (T(ar)) and the types of airway reflex response elicited at onset of airway reflex response were determined during the periods immediately before (presurgical period) and after surgery (post-surgical period), with an interval ranging from 2 to 7 h between the two periods. There was no significant difference in the values of T(ar) between the presurgical period (0.6 +/- 0.3%, mean +/- SD) and the post-surgical period (0.7 +/- 0.1%). There was a considerable difference in the type of airway reflexes elicited during the two different periods; the initial responses during the presurgical period were the apnoeic reflex and/or forceful expiratory efforts, whereas the initial response during the post-surgical period, in the majority of patients, was the swallowing reflex. Our results indicate that there may be adaptation mechanisms responsible for temporal changes in airway protective reflexes after prolonged endotracheal intubation in surgical patients.

Adaptation, Physiological↗

PubMed2006

Temporal changes in rates of stillbirth, neonatal and infant mortality among triplet gestations in the United States.

OBJECTIVE: The purpose of this study was to examine temporal changes in stillbirth, neonatal and infant mortality rates among triplet births in the US, and to assess the contributions of triplet delivery at < 34 weeks to these changes. STUDY DESIGN: Data on triplet live births, and fetal and infant deaths (1990-2002) delivered at > or = 22 weeks and fetuses weighing > or = 500 g (n = 66,986) were derived from the US linked birth/infant death data files. Relative risk (RR), quantifying changes in triplet stillbirth, neonatal (death within the first 28 days) and infant mortality (death within the first year) rates between 1990 and 1991 and 2001 and 2002, were derived. Temporal changes in triplet births at < 34 weeks, and changes in stillbirth, and neonatal and infant mortality rates were examined through logistic regression models before and after adjusting for confounders. RESULTS: Triplet births at < 34 weeks increased by 25% between 1990 and 1991 (48.7%) and 2001 and 2002 (60.9%). Stillbirth, neonatal and infant mortality rates declined by 52% (RR 0.48, 95% confidence interval [CI] 0.36-0.63), 32% (RR 0.68, 95% CI 0.58-0.80), and 38% (RR 0.62, 95% CI 0.53-0.71), respectively, between 1990 and 1991 and 2001 and 2002. The increase in triplet births at < 34 weeks was not associated with the stillbirth decline, but was associated with an excess 14% and 12% increase in neonatal and infant deaths, respectively. CONCLUSION: Our findings suggest that the increase in triplet births at < 34 weeks' gestation is not associated with changes in triplet stillbirths, but is associated with increases in triplet neonatal and infant mortality.

Female↗

PubMed1999

Temporal changes in disaccharide composition of dermatan sulfate in the skin after epicutaneous application of hapten.

Glycosaminoglycans change their amount, structure and distribution with age, differentiation and pathologic conditions. In order to investigate temporal changes in dermatan sulfate in the skin during inflammation and subsequent healing, 2,4-dinitrofluorobenzene (DNFB) was applied once to the dorsal skin of female BALB/cA mice, and the disaccharide composition of dermatan sulfate was examined. Application of DNFB induced a transient increase in the thickness of the dermis, which reached a maximum on day 15 and decreased to the control level on day 35. The total amount of unsaturated disaccharides from dermatan sulfate per cm2 in the DNFB-treated skin showed a temporal pattern similar to that of the thickness of the dermis. Mol% of 4,5-unsaturated 2-sulfo-hexuronic acid-4-sulfated N-acetylgalactosamine (deltaDi-diSB), the second most abundant unsaturated disaccharide from dermatan sulfate, decreased rapidly on day 3 in the DNFB-treated skin, remained less than the control on days 7 and 15, and returned to the control level on day 35. These results suggest that a single application of DNFB induces temporal changes not only in the amount but also in the structure of dermatan sulfate.

Administration, Cutaneous↗

PubMed1983

[An experimental study on temporal changes of post-operative anti-reflux effect by modified Mark IV operation for esophageal achalasia].

This study was intended to elucidate possible temporal changes of the valve and fundoplication which are formed by modified Mark IV operation as a surgical treatment of esophageal achalasia. Heller's procedure was also studied in terms of its comparison with the above operation. Adult mongrel dogs were operated on as follows and studied at the following postoperative points: Heller's procedure at the forth postoperative week, Modified Mark IV operation at the forth postoperative week, Modified Mark IV operation at the third postoperative month. Postoperative comparative studies were made on temporal changes of the anti-reflux effect by intraesophagogastric pressure and withdrawal pH examinations, measurements of intragastric pressure at reflux through simultaneous evaluation of intraesophageal pH and inner pressures at 3 points, i.e. the esophagus, the high pressure zone and the stomach, and histological and morphological examination. From the above the following conclusion was drawn: The valve formed by modified Mark IV operation showed temporally a shortening tendency, and a significant shortening of the length of valve was observed also in comparisons of values between the forth postoperative week and the third postoperative month. Also in terms of the measurement of inner pressures, a significant decrease was observed in the length and the force of high pressure zone. However, comparisons of the intragastric pressure values at reflux revealed no significant difference in values between the forth week and the third month after the modified Mark IV operation and almost similar anti-reflux effects between both in spite of a shortening of the valve. The above results suggested that more reliable and long-term sustaining of the anti-reflux effect needed more extensive formation of the fundoplication.

Animals↗

PubMed2006

Associations between exposure to polycyclic aromatic hydrocarbons and temporal change of urinary 1-hydroxypyrene levels in Taiwanese coke-oven workers.

OBJECTIVES: Our aim is to analyze the association between polycyclic aromatic hydrocarbon (PAH) exposure and the temporal change of urinary 1-hydroxypyrene (1-OHP). METHODS: Two personal air samples, eight spot urine samples, and questionnaires were used to collect PAH exposure, urinary 1-OHP, demographic data, and environmental pollutants. RESULTS: Topside-oven workers had significantly higher levels of PAH exposure and 1-OHP than side-oven workers. Urinary 1-OHP was a biomarker for PAH exposure. In topside-oven workers, the trend of 1-OHP increased sharply and reached the top in the sixth day after work and declined dramatically on days off. In side-oven workers, such a trend was not found, and those who smoked showed a slight increase in urinary 1-OHP levels on days off. CONCLUSIONS: We suggest that the pattern of temporal change of urinary 1-OHP levels is different between topside-oven and side-oven workers.

Adult↗

PubMedDate not supplied

MR navigator-echo monitoring of temporal changes in diaphragm position: implications for MR coronary angiography.

Temporal changes in respiration could influence navigator-echo (NE)-gated MR coronary angiography (MRCA), but systematic investigation of the effects of such variations and how to limit them has not been performed. We addressed these issues by studying the influence of time in the magnet on diaphragm position and respiratory patterns using NE diaphragm monitoring in volunteers and a phantom model. NE diaphragm monitoring was performed at .5 T in 10 subjects over a total period of 35 minutes. The end-expiratory position was sustained for longer (1.1 vs .4 seconds, P < .001) and with greater position stability (SD 1.9 vs 5.9 mm, P = .01) than the end-inspiratory position. Drift of the end-expiratory position occurred over time, causing a fall in scan efficiency (44-28%, P = .01). Up-drift of the end-expiratory position was most common. Loss of scan efficiency was worse with up-drift because of loss of the end-expiratory pause from the NE window (up-drift 10% mm-1, down-drift 7% mm-1, both P = .03). Scan efficiency also was reduced during sleep (to a nadir of 0%), secondary to loss of the end-expiratory pause, periodic breathing with oscillating end-expiratory position, and periods of apnea. The phantom model used actual diaphragm traces to evaluate the artifact resulting from diaphragm motion during acquisition. Artifact was considerably reduced by NE adaptive motion correction compared with NE gating alone (ghosting ratio 2.0 vs 2.8, P < .01). Artifact also was significantly reduced with up-drift if scan efficiency was maintained above 35% (P = .05). For optimal NE-gated MRCA, the following features are important: the NE window should be placed around the end-expiratory position; subjects should not sleep; scan efficiency should be monitored and the NE window should be repositioned if scan efficiency falls below 35%; and adaptive motion correction should be used.

Adult↗

PubMed1983

Temporal changes in pancreatic islet composition in C57BL/6J-db/db (diabetes) mice.

Temporal changes in non-B cell populations were determined during the period of B cell hyperplasia in diabetes-resistant C57BL/6J mice. Pancreases from normal and db/db mice between 3 and 20 weeks of age were stained immunocytochemically for glucagon, somatostatin and pancreatic polypeptide (PP), and changes in A, D and PP cell volume densities quantified by image analysis. Further, islet volumes, D cell volumes and actual D cell numbers per islet were determined by analysis of serial sections through entire islets. The volume of db/db islets was three- and ten-fold elevated above normal by 8 and 20 weeks, respectively, due mainly to B cell hyperplasia. D cell volume density exhibited a transient increase during the initial phase of B cell hyperplasia, but then showed a gradual reduction; the average number and absolute volume of D cells per islet was comparable in db/db and normal islets from older mice. In contrast, PP cell volume density remained stable throughout, suggesting that this cell type kept pace with B cell hyperplasia. A cells showed a reduced volume density throughout and were distinguished from other islet cells which all responded positively to a degree, albeit non-coordinately, to the mitogenic stimulus exerted by db gene expression. The finding that A cells shared with certain neuroectodermally-derived cell types a differentially high concentration of sn-glycerol-3-phosphate dehydrogenase further underscored the uniqueness of the A cell from other cell types.

Aging↗

PubMed2006

A mathematical theory for temporal changes in tolerance to the behavioral effects of alcohol.

Temporal changes in the tolerance to alcohol are rarely discussed. In the behavioral theory proposed here, the rate of increase in tolerance during alcohol exposure is described by linear equations with zero intercept. These equations describe the rate of tolerance growth for acute tolerance, the rate of tolerance growth after alcohol dosing (chronic tolerance), and, for cases in which tolerance has been conditioned, the equations also describe changes in the rate of growth of tolerance when the stimulus set changes. This theory does not explain tolerance acquisition, but may be useful in investigating the physiological basis for tolerance acquisition because it provides numerical values for momentary tolerance that can be compared with concurrent physiological changes. The theory is testable and most of the published behavioral data on non-conditioned tolerance are consistent with the proposed theory. New empirical data on conditioned tolerance are needed to evaluate the proposed theory, and the design for an evaluation is suggested here. Despite its limitations, the theory serves as one example of what a mathematical theory for tolerance might be and may stimulate the development of competing theories with which it could be compared empirically.

Behavior↗

PubMed1999

Temporal changes in genetic variation of north European cattle breeds.

Temporal changes in genetic variation within and between 13 North European cattle breeds were evaluated using erythrocyte antigen systems and transferrin protein as genetic markers. Current data on allele frequency distributions of markers in large commercial and smaller endangered native cattle breeds were compared to data published during 1956 to 1975. Intrabreed genetic variation was quantified by conventional parameters (e.g. heterozygosity, average number of alleles per locus) and migration by the effective migration rate. The neighbour-joining dendrogram of relationships between old and present cattle populations was constructed using Nei's standard genetic distance. Variance effective population size was estimated from changes in allele frequencies over time. Comparison of old and new data indicated some significant changes in allele frequencies. In six of the breeds, a few low-frequency alleles in the old data were absent in the present samples. Heterozygosity remained stable in most breeds. The harmonic means for variance effective population size ranged between 30 and 257. Current results indicate that despite marked declines in total population sizes, North European native cattle breeds have retained a reasonably high genetic diversity. However, their genes contribute less than previously to genetic variation of Nordic production breeds. Commercial breeds do not appear to have a larger effective population size than native breeds. The present effective population sizes imply that Nordic breeds could have lost from 1 to 11% of their heterozygosity over a 20-40-year period.

Animals↗

PubMedDate not supplied

Temporal changes in sequential quantitative thallium-201 imaging following myocardial infarction in dogs: comparison of four- and twenty-four-hour infarct images.

Thallium-201 ((201)T1) myocardial perfusion imaging allows definition of zones of myocardial infarction and ischemia. The temporal changes in sequential quantitative (201)T1 infarct imaging was studied 4 and 24 hours in dogs subjected to closed-chest anterior wall myocardial infarction. A temporal decrease in (201)T1 imaged infarct areas was noted in 10 of 13 animals. In no animal did the infarct area increase. The imaged infarct area decreased by an average of 30% from 12.9 ± 6.2 cm(2) at 4 hours to 9.1 ± 5.1 cm(2) at 24 hours (p < 0.001), and involved 34 ± 16% of the total (201)T1 left ventricular distribution at 4 hours and 22 ± 14% at 24 hours (p < 0.001). The magnitude of temporal change in imaged infarct area was not predicted by initial image defect or final histopathologic infarct size. Thus, the results of (201)T1 infarct imaging in the early period of infarction are clearly dependent upon the time at which the procedure is performed.

Animals↗

PubMed1987

Temporal changes in a complex spectral profile.

The spectral properties of a complex stimulus (rippled noise) were varied over time, and listeners were asked to discriminate between this stimulus and a flat-spectrum, stationary noise. The spacing between the spectral peaks of rippled noise was changed sinusoidally as a function of time, or the location of the spectral peaks of rippled noise was moved up and down the spectrum as a sinusoidal function of time. In most conditions, listeners were able to make the discriminations up to rates of temporal modulation of 5-10 cycles per second. Beyond 5-10 cps the rippled noise with the temporally varying peaks was indiscriminable from a flat (nonrippled) noise. The results suggest that for temporal changes in the spectral peaks of rippled noise, listeners cannot monitor the output of a single (or small number of) auditory channel(s) (critical bands), or that the mechanism used to extract the perceptual information from these stimuli is slow. Temporal variations in the spectral properties of rippled noise may relate to temporal changes in the repetition pitch of complex sounds, the temporal properties of the coloration added to sound in a reverberant environment, and the nature of spectral peak changes such as those that occur in speech-formant transitions. The results are relevant to the general issue of the auditory system's ability to extract information from a complex spectral profile.

Auditory Pathways↗

PubMed2001

Temporal changes in allele frequency, genetic variation and inbreeding depression in small populations of the guppy, Poecilia reticulata.

We established three closed lines of N = 10 for the guppy Poecilia reticulata, to evaluate the relationships among temporal changes in allele frequency, genetic variation and inbreeding depression for a fitness-related trait in small populations. Genetic variation at the allozyme loci, expressed by the proportion of polymorphic loci, number of alleles per locus and heterozygosity, decreased somewhat in two closed lines but it increased in one closed line over six generations. Effective population size (Ne) at each generation was estimated from the standardized variance in the allele frequencies. The average Ne was 24.4, 10.3 and 10.0 in the three closed lines. The inbreeding coefficient calculated from the Ne increased to 0.186, 0.321 and 0.414, respectively. As an index of the amount of inbreeding depression, changes in salinity tolerance were examined, because this trait is strongly sensitive to inbreeding depression and decreases linearly with an increase in inbreeding coefficient. The mean value of the salinity tolerance significantly decreased to 82.5%, 71.7% and 67.6% in the three closed lines during the six generations, suggesting inbreeding depression for salinity tolerance. Although a significant correlation was not observed between the amount of inbreeding depression and the genetic variation, the amount of inbreeding depression correlated with the inbreeding coefficient calculated from Ne. The regression line indicated an 8.4% decrease in the mean per 10% increase in the inbreeding coefficient and was similar to that obtained directly from full-sib matings. These results indicate that the temporal changes in the allele frequencies can provide an estimation of the amount of inbreeding depression during successive generations in small populations.

Adaptation, Physiological↗

PubMed2003

Temporal changes in incidence and prevalence of intellectual disability between two birth cohorts in Northern Finland.

We followed two separate, genetically homogeneous cohorts of children born in 1966 (n = 11,965) and 1985-1986 (n = 9,432) in Northern Finland to determine temporal changes in the incidence and prevalence of subcategories of intellectual disability within the same geographic area. The children were followed up to the age of 11.5 years. Similar study design, data ascertainment methods, and definition of intellectual disability were used. There was no change in the total incidence (12.62/1,000 in each) or in total prevalence (11.03/1,000 vs. 11.23/1,000) of intellectual disability. However, in the subcategories of intellectual disability, there was a shift from severe and moderate towards mild; whereas profound intellectual disability remained at the same level. The temporal changes followed generally similar patterns by gender.

Adolescent↗

PubMed1999

Early temporal changes in coronary flow velocity patterns in patients with acute myocardial infarction demonstrating the "no-reflow" phenomenon.

Coronary flow velocity pattern in patients with acute myocardial infarction demonstrating no-reflow phenomenon is characterized with early systolic retrograde flow and rapid deceleration of diastolic flow velocity. In this study, we investigated the early temporal changes in microvascular function in patients with the no-reflow phenomenon. Among 144 patients with a first acute myocardial infarction, 33 exhibited sizable no-reflow phenomenon after coronary reperfusion with myocardial contrast echocardiography. We assessed temporal changes in coronary flow velocity patterns with the Doppler guidewire. The early systolic retrograde flow was observed < or = 10 seconds after reperfusion in 16 patients (group A) or later in 17 patients (331 +/- 327 seconds, group B). Diastolic deceleration rate was higher in group A than in group B at 1 minute after reperfusion. It gradually increased in group B and showed comparable value to group A 10 minutes later. Group A had longer elapsed time from symptom onset to reperfusion and a greater number of infarct Q waves before reperfusion than group B (14 +/- 13 vs 5 +/- 2 hours, p <0.01; and 3 +/- 2 vs 2 +/- 1, p <0.02). In contrast, the incidence of transient ST reelevation shortly after reperfusion was higher in group B (76% vs 25%, p <0.01). Thus, the characteristic coronary flow velocity pattern is either established at the moment of coronary reperfusion or progresses thereafter in patients with no-reflow phenomenon. This suggests different mechanisms of developing ischemic microvascular injury.

Adult↗