Land-use and climatic causes of environmental novelty in Wisconsin since 1890.

Multiple global change drivers are increasing the present and future novelty of environments and ecological communities. However, most assessments of environmental novelty have focused only on future climate and were conducted at scales too broad to be useful for land management or conservation. Here, using historical county-level data sets of agricultural land use, forest composition, and climate, we conduct a regional-scale assessment of environmental novelty for Wisconsin landscapes from ca. 1890 to 2012. Agricultural land-use data include six cropland types, livestock densities for four livestock species, and human populations. Forestry data comprise biomass-weighted relative abundances for 15 tree genera. Climate data comprise seasonal means for temperature and precipitation. We found that forestry and land use are the strongest cause of environmental novelty (NoveltyForest  = 3.66, NoveltyAg  = 2.83, NoveltyClimate  = 1.60, with Wisconsin's forests transformed by early 20th-century logging and its legacies and multiple waves of agricultural innovation and obsolescence. Climate change is the smallest contributor to contemporary novelty, with precipitation signals stronger than temperature. Magnitudes and causes of environmental novelty are strongly spatially patterned, with novelty in southern Wisconsin roughly twice that in northern Wisconsin. Forestry is the most important cause of novelty in the north, land use and climate change are jointly important in the southwestern Wisconsin, and land use and forest composition are most important in central and eastern Wisconsin. Areas of high regional novelty tend also to be areas of high local change, but local change has not pushed all counties beyond regional baselines. Seven counties serve as the best historical analogues for over one-half of contemporary Wisconsin counties (40/72), and so can offer useful historical counterparts for contemporary systems and help managers coordinate to tackle similar environmental challenges. Multi-dimensional environmental novelty analyses, like those presented here, can help identify the best historical analogues for contemporary ecosystems, places where new management rules and practices may be needed because novelty is already high, and the main causes of novelty. Separating regional novelty clearly from local change and measuring both across many dimensions and at multiple scales thus helps advance ecology and sustainability science alike.

The effects of repeated exposure to hypercapnia on arousal and cardiorespiratory responses during sleep in lambs.

Arousal and cardio-respiratory responses to respiratory stimuli during sleep are important protective mechanisms that rapidly become depressed in the active sleep state when episodes of hypoxia or asphyxia are repeated: whether responses to repeated hypercapnia are similarly depressed is not known. This study aimed to determine if arousal and cardio-respiratory responses also become depressed with repeated episodes of hypercapnia during sleep and whether responses differ in active sleep and quiet sleep. Eight newborn lambs were instrumented to record sleep state and cardio-respiratory variables. Lambs were subjected to two successive 12 h sleep recordings, assigned as either sequential control and test days, or test and control days performed between 12.00 and 00.00 h. The control day was a baseline study in which the lambs breathed air to determine spontaneous arousal probability. During the test day, lambs were exposed to a 60 s episode of normoxic hypercapnia (Fractional inspired CO2 (F(ICO2)) = 0.08 and Fractional inspired O2(F(IO2)) = 0.21 in N2) during every quiet sleep and active sleep epoch. The probability of lambs arousing during the hypercapnic exposure exceeded the probability of spontaneous arousal during quiet sleep (58% versus 21%, chi2 = 54.0, P < 0.001) and active sleep (39% versus 20%, chi2 = 10.0, P < 0.01), though the response was less in active sleep. Exposure to hypercapnia also resulted in a significant increase in ventilation in quiet sleep (150 +/- 22%) and active sleep (97 +/- 23%, P < 0.05), though the increase was smaller in active sleep (P < 0.05). Small (< 5%) blood pressure increases and heart rate decreases were evident during hypercapnia in quiet sleep, but not in active sleep. Arousal and cardio-respiratory responses persisted with repetition of the hypercapnic exposure. In summary, although arousal and cardio-respiratory responses to hypercapnia are less in active sleep compared with quiet sleep, these protective responses are not diminished with repeated exposure to hypercapnia.

Sympathetic nervous control of the cerebral circulation in sleep.

Cerebral vessels are extensively innervated by sympathetic nerves arising from superior cervical ganglia, and these nerves might play a protective role during the large arterial pressure surges of active sleep (AS). We studied lambs (n=10) undergoing spontaneous sleep-wake cycles before and after bilateral removal of the superior cervical ganglia (SCGx, n=5) or sham ganglionectomy (n=5). Lambs were instrumented to record cerebral blood flow (CBF, flow probe on the superior sagittal sinus), carotid arterial pressure (P(ca)), intra-cranial pressure (P(ic)), cerebral perfusion pressure (Pcp=Pca-Pic) and cerebral vascular resistance (CVR). Prior to SCGx, CBF (mL min-1) was significantly higher in AS than in Quiet Sleep (QS) and Quiet Wakefulness (QW) (17+/-2, 13+/-3, and 14+/-3 respectively, mean+/-SD, P<0.05). Following SCGx, baseline CBF increased by 34, 31, and 29% respectively (P<0.05). CVR also decreased in all states by approximately 25% (P<0.05). During phasic AS, surges of Pca were associated with transient increases in Pcp, Pic and CBF. Following SCGx, peak CBF and Pic during surges became higher and more prolonged (P<0.05). Our study is the first to reveal that tonic sympathetic nerve activity (SNA) constricts the cerebral circulation and restrains baseline CBF in sleep. SNA is further incremented during arterial pressure surges of AS, limiting rises in CBF and Pic, possibly by opposing vascular distension as well as by constricting resistance vessels. Thus, SNA may protect cerebral microvessels from excessive distension during AS, when large arterial blood pressure surges are common.

Autoregulation of the cerebral circulation during sleep in newborn lambs.

Autoregulation is a vital protective mechanism that maintains stable cerebral blood flow as cerebral perfusion pressure changes. We contrasted cerebral autoregulation across sleep-wake states, as little is known about its effectiveness during sleep. Newborn lambs (n= 9) were instrumented to measure cerebral blood flow (flow probe on the superior sagittal sinus) and cerebral perfusion pressure, then studied during active sleep (AS), quiet sleep (QS) and quiet wakefulness (QW). We generated cerebral autoregulation curves by inflating an occluder cuff around the brachiocephalic artery thereby lowering cerebral perfusion pressure. Baseline cerebral blood flow was higher (P < 0.05) and cerebral vascular resistance lower (P < 0.05) in AS than in QW (76 +/- 8% and 133 +/- 15%, respectively, of the AS value, mean +/-s.d.) and in QS (66 +/- 11% and 158 +/- 30%). The autoregulation curve in AS differed from that in QS and QW in three key respects: firstly, the plateau was elevated relative to QS and QW (P < 0.05); secondly, the lower limit of the curve (breakpoint) was higher (P < 0.05) in AS (50 mmHg) than QS (45 mmHg); and thirdly, the slope of the descending limb below the breakpoint was greater (P < 0.05) in AS than QS (56% of AS) or QW (56% of AS). Although autoregulation functions in AS, the higher breakpoint and greater slope of the descending limb may place the brain at risk for vascular compromise should hypotension occur.

Sleep-dependent changes in the coupling between heart period and arterial pressure in newborn lambs.

This study assessed whether sleep-dependent changes in the relationship between heart period (HP) and mean arterial pressure (MAP) occur in newborn life. Electrodes for electrocorticographic, electromyographic, and electrooculographic monitoring and an arterial catheter for blood pressure recordings were implanted in 11 newborn lambs. HP and MAP beat-to-beat values were computed from 120-s blood pressure recordings during quiet wakefulness, active sleep, and quiet sleep. For each recording, the time shift at which the maximum of the HP versus MAP cross-correlation function was attained was identified. For each lamb and wake-sleep state, an average correlation coefficient was then computed corresponding to the median value of such time shifts. The maximum of the cross-correlation function was attained with HP lagging behind MAP. The corresponding mean correlation coefficient was significantly higher in quiet sleep (0.51 +/- 0.05) than either in quiet wakefulness (0.31 +/- 0.05) or in active sleep (0.29 +/- 0.03). Sleep-related differences in the correlation between HP and MAP were maintained after HP and MAP data were low-pass filtered at 0.3 Hz to remove their fast ventilatory oscillations. In conclusion, data indicate that the relationship between spontaneous fluctuations in HP and those in MAP is sleep-state dependent in newborn lambs. A positive HP versus MAP correlation with HP lagging behind MAP is consistent with baroreflex control of HP. Heart rhythm thus may be more tightly controlled by the baroreceptor reflex and less dependent on central autonomic commands in quiet sleep than either in quiet wakefulness or in active sleep.

Influence of fetal breathing movements on pulmonary hemodynamics in fetal sheep.

During fetal development, pulmonary vascular resistance (PVR) is high, and, as a result, blood flow through the fetal lungs is low. Although PVR markedly decreases at the time of birth, the factors that regulate pulmonary blood flow (PBF) and PVR before and immediately after birth are not clear. Our aim was to examine the relationship between episodes of fetal breathing movements (FBM) and pulmonary hemodynamics during late gestation to further understand the relationship among lung luminal volume, phasic changes in intrapulmonary pressure, and PVR before birth. In chronically catheterized fetal sheep (120-128 d gestation; n = 5; term approximately 147 d), PBF and PVR were measured during periods of FBM and apnea. Episodes of FBM were divided into periods of accentuated (amplitude of >3.5 mm Hg change in tracheal pressure) and nonaccentuated periods of FBM. During accentuated episodes of FBM, mean PBF was increased to 159.5 +/- 23.4% (p < 0.0025) of the preceding apneic period and was associated with a 19.1 +/- 5.2% reduction in PVR. In addition, during accentuated episodes of FBM, the retrograde flow of blood through the left pulmonary artery was reduced to 90.1 +/- 1.0% of the preceding apneic period, which most likely contributed to the increase in mean PBF at this time. Although a change in PBF and PVR could not be detected during nonaccentuated FBM, compared with the preceding apneic period, PBF was linearly and positively correlated with the amplitude (change in pressure) of FBM. We conclude that PVR is decreased and PBF is increased during accentuated episodes of FBM, possibly as a result of phasic reductions in intrapulmonary pressures.

Sleep-related changes in the regulation of cerebral blood flow in newborn lambs.

STUDY OBJECTIVES: The interplay between cerebral perfusion pressure (CPP) and vascular resistance leads to fluctuations in cerebral blood flow (CBF). The relationship between fluctuations in CBF and those in CPP provides insight into the impact of the regulation of vascular resistance on CBF. The aim of this work was to study sleep-related changes in CBF regulation in newborn lambs, by quantifying the extent to which variability in CBF is related to that of CPP in the different wake-sleep states. DESIGN: Repeated-measurement within-subject. PARTICIPANTS: 8 newborn lambs. INTERVENTIONS: Chronic instrumentation with electrodes (electrocorticogram, electrooculogram, nuchal electromyogram), an arterial catheter (arterial pressure), a subdural catheter (intracranial pressure), and an ultrasonic flow probe around the superior sagittal sinus (CBF). MEASUREMENTS AND RESULTS: The CPP (difference between arterial and intracranial pressure) and CBF data sequences during quiet wakefulness, rapid-eye-movement (REM) sleep and non-REM sleep were subject to spectral analysis. The fraction of CBF variability explained by CPP variability (CPP vs CBF squared coherence in the range 0.05-0.3 Hz) was highest in REM sleep (0.653) and lowest in non-REM sleep (0.413). The CBF variability (coefficient of variation due to fluctuations in the range 0.05-0.3 Hz) was higher than CPP variability in all states, albeit not significantly in REM sleep. CONCLUSIONS: Results suggest that synchronized vasomotor fluctuations accounting for a quota of CBF variability not explained by CPP variability occur in all states in newborn lambs. Their relative contribution to CBF variability differs among wake-sleep states, being highest during non-REM sleep and lowest during REM sleep.

Right atrial pressure as a measure of ventricular constraint arising from positive end-expiratory pressure during mechanical ventilation of the neonatal lamb.

OBJECTIVE: By constraining the heart, the chest wall, lungs, and pericardium limit diastolic filling and thus have a major role in determining cardiac output. Although intermittent positive pressure ventilation and the application of positive end-expiratory pressure amplifies this constraint, no clinical method exists to assess the impact that positive end-expiratory pressure has on ventricular constraint in the newborn. In this study, we tested the hypothesis that a change in right atrial pressure (Pra) reflects the change in ventricular constraint associated with a change in airway pressure. DESIGN: Experimental, comparative animal study. SETTING: Ritchie Centre for Baby Health Research cardiovascular laboratory. SUBJECTS Neonatal (4-wk-old, n = 6) and newborn (3-day-old, n = 6) Merino/Border-Leicester cross lambs. INTERVENTIONS: Lambs were anesthetized (alpha-chloralose and ketamine), ventilated, and instrumented to record Pra, thoracic inferior vena caval pressure (Pivc, saline-filled catheters), and pericardial pressure (Pper, liquid-containing balloon). MEASUREMENTS AND MAIN RESULTS: Changes (Delta) in Pra, Pivc, and Pper were assessed while airway pressure was rapidly reduced from four set levels of continuous positive airway pressure (2.5, 5, 7.5, and 15 cm H2O) to atmospheric pressure. A strong linear relationship was observed between DeltaPra and DeltaPper (DeltaPra = 0.90 DeltaPper - 0.02, r =.98), and between DeltaPivc and DeltaPper (DeltaPivc = 0.86 DeltaPper - 0.02, r =.98) in both the 4-wk-old lambs and the 3-day-old lambs. CONCLUSIONS: Our experiments demonstrate that, in the newborn and neonatal lamb, DeltaPra provides an accurate measure of the change in ventricular constraint that accompanies a change in airway pressure, and thus may provide a means of quantifying the magnitude of ventricular constraint imposed by positive end-expiratory pressure and mechanical ventilation during neonatal intensive care.

Periodoncia: en la tradicion de Orban y Gottlieb

Traduccion del titulo original; Periodontics: in the tradition of Orban Gottlieb, 5th edition

Periodoncia: en la tradicion de Orban y Gottlieb

Traduccion del titulo original; Periodontics: in the tradition of Orban Gottlieb, 5th edition