Selected contribution: redistribution of pulmonary perfusion during weightlessness and increased gravity.

To compare the relative contributions of gravity and vascular structure to the distribution of pulmonary blood flow, we flew with pigs on the National Aeronautics and Space Administration KC-135 aircraft. A series of parabolas created alternating weightlessness and 1.8-G conditions. Fluorescent microspheres of varying colors were injected into the pulmonary circulation to mark regional blood flow during different postural and gravitational conditions. The lungs were subsequently removed, air dried, and sectioned into approximately 2 cm(3) pieces. Flow to each piece was determined for the different conditions. Perfusion heterogeneity did not change significantly during weightlessness compared with normal and increased gravitational forces. Regional blood flow to each lung piece changed little despite alterations in posture and gravitational forces. With the use of multiple stepwise linear regression, the contributions of gravity and vascular structure to regional perfusion were separated. We conclude that both gravity and the geometry of the pulmonary vascular tree influence regional pulmonary blood flow. However, the structure of the vascular tree is the primary determinant of regional perfusion in these animals.     

Role of positive airway pressure on pulmonary acinar perfusion heterogeneity.

Perfusion of the pulmonary acinus has been shown to be generally homogeneous, but there is a significant component that is heterogeneous. To investigate the contribution of the alveolar septal capillary network to acinar perfusion heterogeneity, the passage of fluorescent dye boluses through the subpleural microcirculation of isolated dog lung lobes was videotaped using fluorescence microscopy. As the videotapes were replayed, dye-dilution curves were recorded from each of the tributary branches of Y-shaped venules that drained single acini. For each Y-shaped venule, the mean appearance time difference between the pair of tributary branches was calculated from the dye curves. When the complex septal capillary networks were derecruited by high positive airway pressure, venular perfusion became proportionally more homogeneous. This result shows that septal capillary resistance and pathlength differences are important contributors to intra-acinar perfusion heterogeneity.     

Effects of age on pulmonary perfusion heterogeneity measured by magnetic resonance imaging.

Normal aging is associated with a decline in pulmonary function and efficiency of gas exchange, although the effects on the spatial distribution of pulmonary perfusion are poorly understood. We hypothesized that spatial pulmonary perfusion heterogeneity would increase with increasing age. Fifty-six healthy, nonsmoking subjects (ages 21-76 yr) underwent magnetic resonance imaging with arterial spin labeling (ASL) using a Vision 1.5-T whole body scanner (Siemens Medical Systems, Erlangen, Germany). ASL uses a magnetically tagged bolus to generate perfusion maps where signal intensity is proportional to regional pulmonary perfusion. The spatial heterogeneity of pulmonary blood flow was quantified by the relative dispersion (RD = SD/mean, a global index of heterogeneity) of signal intensity for voxels within the right lung and by the fractal dimension (D(s)). There were no significant sex differences for RD (P = 0.81) or D(s) (P = 0.43) when age was considered as a covariate. RD increased significantly with increasing age by approximately 0.1/decade until age 50-59 yr, and there was a significant positive relationship between RD and age (R = 0.48, P < 0.0005) and height (R = 0.39, P < 0.01), but not body mass index (R = 0.07, P = 0.67). Age and height combined in a multiple regression were significantly related to RD (R = 0.66, P < 0.0001). There was no significant relationship between RD and spirometry or arterial oxygen saturation. D(s) was not related to age, height, spirometry, or arterial oxygen saturation. The lack of relationship between age and D(s) argues against an intrinsic alteration in the pulmonary vascular branching with age as being responsible for the observed increase in global spatial perfusion heterogeneity measured by the RD.     

Contributions of pulmonary perfusion and ventilation to heterogeneity in VA/Q measured by PET

Treppo, Steven, Srboljub M. Mijailovich, and José G. Venegas. Contributions of pulmonary perfusion and ventilation toheterogeneity in A/measured by PET. J. Appl. Physiol. 82(4): 1163-1176, 1997. To estimate the contributions of the heterogeneity in regionalperfusion () and alveolar ventilation(A) to that of ventilation-perfusionratio (A/), we haverefined positron emission tomography (PET) techniques to image localdistributions of andA per unit of gas volume content(s and sA,respectively) and VA/ indogs. sA was assessed in two ways:1) the washout of ¹³NN tracer after equilibrationby rebreathing (sA_i), and2) the ratio of an apneic image after a bolus intravenousinfusion of ¹³NN-saline solution to an image collectedduring a steady-state intravenous infusion of the same solution(sA_p).sA_p was systematically higher than sA_i in allanimals, and there was a high spatial correlation betweens andsA_p in both body positions(mean correlation was 0.69 prone and 0.81 supine) suggesting thatventilation to well-perfused units was higher than to those poorlyperfused. In the prone position, the spatial distributions ofs, sA_p, and A/ were fairlyuniform with no significant gravitational gradients; however, in thesupine position, these variables were significantly more heterogeneous,mostly because of significant gravitational gradients (15, 5.5, and10%/cm, respectively) accounting for 73, 33, and 66% of thecorresponding coefficient of variation (CV)² values. Weconclude that, in the prone position, gravitational forces in blood andlung tissues are largely balanced out by dorsoventral differences inlung structure. In the supine position, effects of gravity andstructure become additive, resulting in substantial gravitationalgradients in s andsA_p, with the higherheterogeneity inA/ caused by agravitational gradient in s, only partially compensated by that in sA.

     

Relative contribution of neurotransmission failure to diaphragm fatigue

Two procedures were used to estimate the relative contribution of neurotransmission failure (NF) to fatigue of the rat diaphragm at different rates of phrenic nerve stimulation. In one, direct muscle stimulation was intermittently superimposed on neural stimulation of the diaphragm, and the relative contribution of NF was estimated by the difference in generated tension. In a second procedure, diaphragm fatigue was induced by using either direct muscle stimulation (with complete blockade of the neuromuscular junction by d-tubocurare) or phrenic nerve stimulation. The relative contribution of NF to diaphragm fatigue was then estimated by comparing the force loss during these two modes of stimulation. With both procedures, it was observed that 1) the relative contribution of NF to diaphragm fatigue was less than 45% at each frequency of phrenic nerve stimulation; 2) the relative contribution of NF to diaphragm fatigue increased at higher rates of phrenic stimulation, reaching a maximum at 75 pulses/s; and 3) the relative contribution of NF to diaphragm fatigue reached a plateau after 2 min of repetitive stimulation.     

Relative contribution of bronchial flow to subpleural region in dog lung.

The bronchial flow is approximately 1% of the total pulmonary flow. Anastomosis between the bronchial and pulmonary vessels occurs primarily at the microcirculatory level. It is assumed that bronchopulmonary anastomoses are present in a homogeneous manner throughout lung parenchyma. To investigate this issue, an in situ blood-perfused left lower lung lobe (500 ml/min) was prepared in a live dog. The bronchial flow rate in the entire lobe was monitored using the rate of volume gain in the reservoir while the pulmonary and bronchial flow in the subpleural region was monitored using laser-Doppler flowmetry. The results were expressed as ratio of bronchial to pulmonary flow rate for the entire lobe and for the subpleural region. We found that, for the entire lobe, bronchial flow was 1.0% of pulmonary flow, while for the subpleural region this ratio was much higher, with an average of 12%. In two different experimental conditions that were imposed to affect the global bronchial flow, these ratios changed in the same direction as the global bronchial flow. After transfusion of blood into the animal, bronchial flow increased to 1.7%, while the subpleural bronchial flow increased to 18% of the subpleural pulmonary flow. During elevation of venous pressure, bronchial flow decreased to 0.6%, while the subpleural bronchial flow decreased to 10% of the subpleural pulmonary flow. The differences in the ratios between the global and subpleural region may be explained by having low pulmonary blood flow in the periphery compared with the interior regions of the lung.(ABSTRACT TRUNCATED AT 250 WORDS)     

A contribution to the autecology ofphragmites communis Trin. 1. Physiological heterogeneity of leaves

The plantPhragmites communis was subject to an analysis of physiological gradients along the leaf blade and level of insertion of separate leaves. The gradients were established in the following aspects: fresh weight, dry matter, specific leaf area, water content, water saturation deficit and its resaturation, rate of desiccation and photosynthetic capacity. Indistinct gradients under normal conditions become more marked in extreme circumstances. The significance of leaf heterogeneity for all sorts of eco-physiological analysis of the plant under study was discussed.     

Spatial correlation of regional pulmonary perfusion.

Despite the heterogeneous distribution of pulmonary blood flow, perfusion appears to be spatially ordered, with neighboring regions of lung having similar magnitudes of flow. This premise was tested by determining the spatial correlation of regional flow [rho(d)] as a function of distance (d) between regions. Regional pulmonary perfusion was measured in both supine and prone positions in seven anesthetized mechanically ventilated dogs with radiolabeled microspheres. After excision and drying, the lungs were cubed into pieces 1.2 cm on a side, with a three-dimensional coordinate assigned to each piece. The microsphere-determined flow to each piece was measured by radioactive counts, and rho(d) was calculated for all paired pieces within the same lobe. rho(d) was greatest for adjacent pieces (d = 1.2 cm) and decreased with increasing d, becoming negative at large distances in all dogs and positions. The spatial correlation of flow between adjacent pieces, rho(1.2 cm), was greater in the supine than in the prone position (0.66 vs. 0.72, P less than 0.05). The observations for each dog and position were fit to the equation rho(d) = d(a)+b.d+c, and the coefficients were used to compare rho(d) in the supine and prone positions. rho(d) differed in the two positions (P less than 0.05), with rho(d) falling off more rapidly with distance in the supine position. When trends in flow due to gravity were mathematically removed, differences between supine and prone positions were no longer observed. The spatial correlation of regional pulmonary perfusion was anisotropic in both supine and prone positions. The observation that regional pulmonary perfusion is highly correlated over large spatial distances has important implications for models of flow distribution.     

Relative contribution of lipid sources to eggs of lesser scaup

Studies of how birds mobilize nutrients to eggs have traditionally considered a continuum of possible allocation strategies ranging from income breeding (rely on food sources found on the breeding grounds) to capital breeding (rely on body reserves stored prior to the breeding season). For capital breeding, stored body reserves can be acquired either on or away from the breeding grounds, but it has been difficult to quantify the relative contribution of each, precluding identification of key habitats for acquiring nutrients for clutch formation. During 2006–2009, we explored the importance of spring‐staging habitats versus breeding‐area habitats for egg‐lipid formation in female lesser scaup Aythya affinis using stable carbon (δ¹³C) isotope analyses. Although δ¹³C values for abdominal lipid reserves brought to the breeding grounds overlapped those of local amphipods, we were able to quantify the importance of local plant carbohydrates (seeds of emergent wetland plants) to the production of eggs. We compared the importance of local wetland seeds (overall δ¹³C: ?29.1 ± 0.9‰ SD) to combined lipid stores and lipids from local amphipods (overall δ¹³C: ?23.8 ± 2.2‰). Local seeds and stored body lipids contributed equally to egg lipid formation across years but we found evidence of annual variation in their relative importance. Wetland seeds contributed 39% (SE = 10%) to egg lipid production, and the importance of this source varied by year (90% CI = 47–75% in 2006, 13–42% in 2007, 29–65% in 2008, and 7–30% in 2009). In contrast to earlier studies that suggest lesser scaup predominantly employ a capital breeding strategy, our results suggest that in some years females may attain half of their energy for clutch formation from foods on the breeding grounds.     

Relative contribution of LFA-1 and Mac-1 to neutrophil adhesion and migration.

To differentiate the unique and overlapping functions of LFA-1 and Mac-1, LFA-1-deficient mice were developed by targeted homologous recombination in embryonic stem cells, and neutrophil function was compared in vitro and in vivo with Mac-1-deficient, CD18-deficient, and wild-type mice. LFA-1-deficient mice exhibit leukocytosis but do not develop spontaneous infections, in contrast to CD18-deficient mice. After zymosan-activated serum stimulation, LFA-1-deficient neutrophils demonstrated activation, evidenced by up-regulation of surface Mac-1, but did not show increased adhesion to purified ICAM-1 or endothelial cells, similar to CD18-deficient neutrophils. Adhesion of Mac-1-deficient neutrophils significantly increased with stimulation, although adhesion was lower than for wild-type neutrophils. Evaluation of the strength of adhesion through LFA-1, Mac-1, and CD18 indicated a marked reduction in firm attachment, with increasing shear stress in LFA-1-deficient neutrophils, similar to CD18-deficient neutrophils, and only a modest reduction in Mac-1-deficient neutrophils. Leukocyte influx in a subcutaneous air pouch in response to TNF-alpha was reduced by 67% and 59% in LFA-1- and CD18-deficient mice but increased by 198% in Mac-1-deficient mice. Genetic deficiencies demonstrate that both LFA-1 and Mac-1 contribute to adhesion of neutrophils to endothelial cells and ICAM-1, but adhesion through LFA-1 overshadows the contribution from Mac-1. Neutrophil extravasation in response to TNF-alpha in LFA-1-deficient mice dramatically decreased, whereas neutrophil extravasation in Mac-1-deficient mice markedly increased.     

Relative contribution of abundant and rare species to species-energy relationships

A major goal of ecology is to understand spatial variation in species richness. The latter is markedly influenced by energy availability and appears to be influenced more by common species than rare ones; species-energy relationships should thus be stronger for common species. Species-energy relationships may arise because high-energy areas support more individuals, and these larger populations may buffer species from extinction. As extinction risk is a negative decelerating function of population size, this more-individuals hypothesis (MIH) predicts that rare species should respond more strongly to energy. We investigate these opposing predictions using British breeding bird data and find that, contrary to the MIH, common species contribute more to species-energy relationships than rare ones.     

Relative contribution of delaying senescence to growth compensation after defoliation

Delaying senescence as a response to tissue losses has been reported in some studies, but there is no information about its influence in growth compensation. We performed a first test of the relative contribution of delaying senescence after defoliation to growth compensation in Dactylis glomerata L. by means of an iterative growth analysis modified to estimate tissue losses to senescent leaves. We show that Dactylis glomerata overcompensated for relative growth rate after defoliation, mainly by slowing down senescence, and to a lesser extent by increasing the newly assimilated mass allocated to leaves.     

Taiwanese aborigines: genetic heterogeneity and paternal contribution to Oceania

In the present study, for the first time, 293 Taiwanese aboriginal males from all nine major tribes (Ami, Atayal, Bunun, Rukai, Paiwan, Saisat, Puyuma, Tsou, Yami) were genotyped with 17 YSTR loci in a attend to reveal migrational patterns connected with the Austronesian expansion. We investigate the paternal genetic relationships of these Taiwanese aborigines to 42 Asia-Pacific reference populations, geographically selected to reflect various locations within the Austronesian domain. The Tsou and Puyuma tribes exhibit the lowest (0.1851) and the highest (0.5453) average total genetic diversity, respectively. Further, the fraction of unique haplotypes is also relatively high in the Puyuma (86.7%) and low in Tsou (33.3%) suggesting different demographic histories. Multidimensional scaling (MDS) and analysis of molecular variance (AMOVA) revealed several notable findings: 1) the Taiwan indigenous populations are highly diverse. In fact, the level of inter-population heterogeneity displayed by the Taiwanese aboriginal populations is close to that exhibited among all 51 Asia-Pacific populations examined; 2) the asymmetrical contribution of the Taiwanese aborigines to the Oceanic groups. Ami, Bunun and Saisiyat tribes exhibit the strongest paternal links to the Solomon and Polynesian island communities, whereas most of the remaining Taiwanese aboriginal groups are more genetically distant to these Oceanic inhabitants; 3) the present YSTR analyses does not reveal a strong paternal affinity of the nine Taiwanese tribes to their continental Asian neighbors. Overall, our current findings suggest that, perhaps, only a few of the tribes were involved in the migration out of Taiwan.     

Relative contribution of humoral and metastatic factors to the pathogenesis of hypercalcaemia in malignancy.

Some relations between metastatic bone disease and calcium homoeostasis were determined in a consecutive series of 81 patients with solid malignant tumours attending for radionuclide bone scans. Biochemical evaluation showed that bone resorption from metastatic disease was generally not enough to account for hypercalcaemia. While skeletal metastases were present in about half of the patients who developed hypercalcaemia, biochemical indices of bone resorption in these subjects were greatly increased and disproportionate to the extent of metastatic disease detected by the bone scans. Furthermore, a reduced renal phosphate threshold and increased tubular calcium reabsorption were generally observed in hypercalcaemic patients when compared with their normocalcaemic counterparts. These findings suggest that in most cases malignancy associated hypercalcaemia may be caused by the release of a humoral factor by tumour tissue which exhibits "parathyroid-hormone-like" activity with regard to bone resorption, renal phosphate threshold, and renal calcium handling. It may be postulated that this putative humoral mediator predisposes to hypercalcaemia both by stimulating generalised osteolysis and in most cases also by impairing the renal excretion of the resultant increase in filtered calcium load. While hypercalcaemia may arise as a result of metastatic bone disease alone, these data indicate that this may be the exception rather than the rule. Hence the term "metastatic hypercalcaemia" should probably be reserved for patients with extensive skeletal tumour disease in whom biochemical evaluation fails to yield evidence of an underlying humorally mediated cause.     

Relative contribution of hemopoietic and pulmonary parenchymal cells to lung inducible nitric oxide synthase (inos) activity in murine endotoxemia

Acute lung injury is an important feature of sepsis and increased iNOS expression and NO production contribute to the pathogenesis of this syndrome. We generated bone marrow-transplanted chimeric mice with iNOS expression limited to either inflammatory or pulmonary parenchymal cells, and assessed pulmonary iNOS activity and systemic levels of NO metabolites in an endotoxemic model of sepsis. We found that while both pulmonary parenchymal cells and inflammatory cells contribute to the increased lung iNOS activity in endotoxemia, pulmonary parenchymal cells contribute to a significantly greater degree. Using measurement of plasma NO(-)(x), whole body NO production was assessed in this model. We found that the main source of NO(-)(x) was again, parenchymal cells and not inflammatory cells. This is the first study to demonstrate that most of the increased NO production in this model of endotoxemic sepsis derives from parenchymal cells rather than inflammatory cells.