Factors affecting hematology and plasma biochemistry in the southwest carpet python (Morelia spilota imbricata)

Despite increased worldwide popularity of keeping reptiles as pets, we know little about hematologic and biochemical parameters of most reptile species, or how these measures may be influenced by intrinsic and extrinsic factors. Blood samples from 43 wild-caught pythons (Morelia spilota imbricata) were collected at various stages of a 3-yr ecological study in Western Australia. Reference intervals are reported for 35 individuals sampled at the commencement of the study. As pythons were radiotracked for varying lengths of time (radiotransmitters were surgically implanted), repeated sampling was undertaken from some individuals. However, because of our ad hoc sampling design we cannot be definitive about temporal factors that were most important or that exclusively influenced blood parameters. There was no significant effect of sex or the presence of a hemogregarine parasite on blood parameters. Erythrocyte measures were highest for pythons captured in the jarrah forest and at the stage of radiotransmitter implantation, which was also linked with shorter time in captivity. Basophil count, the only leukocyte influenced by the factors tested, was highest when the python was anesthetized, as was globulin concentration. Albumin and the albumin:globulin ratio were more concentrated in summer (as was phosphorous) and at the initial stage of radiotransmitter placement (as was calcium). No intrinsic or extrinsic factors influenced creatinine kinase, aspartate aminotransferase, uric acid, or total protein. This study demonstrates that factors including season, location, surgical radiotransmitter placement, and anesthetic state can influence blood parameters of M. s. imbricata. For accurate diagnosis, veterinarians should be aware that the current reference intervals used to identify the health status of individuals for this species are outdated and the interpretation and an understanding of the influence of intrinsic and extrinsic factors are limited.     

Stratification of a population of intracranial aneurysms using blood flow metrics

Indices of the intra-aneurysm hemodynamic environment have been proposed as potentially indicative of their longitudinal outcome. To be useful, the indices need to be used to stratify large study populations and tested against known outcomes. The first objective was to compile the diverse hemodynamic indices reported in the literature. Furthermore, as morphology is often the only patient-specific information available in large population studies, the second objective was to assess how the ranking of aneurysms in a population is affected by the use of steady flow simulation as an approximation to pulsatile flow simulation, even though the former is clearly non-physiological. Sixteen indices of aneurysmal hemodynamics reported in the literature were compiled and refined where needed. It was noted that, in the literature, these global indices of flow were always time-averaged over the cardiac cycle. Steady and pulsatile flow simulations were performed on a population of 198 patient-specific and 30 idealised aneurysm models. All proposed hemodynamic indices were estimated and compared between the two simulations. It was found that steady and pulsatile flow simulations had a strong linear dependence (r ≥ 0.99 for 14 indices; r ≥ 0.97 for 2 others) and rank the aneurysms in an almost identical fashion (ρ ≥ 0.99 for 14 indices; ρ ≥ 0.96 for other 2). When geometry is the only measured piece of information available, stratification of aneurysms based on hemodynamic indices reduces to being a physically grounded substitute for stratification of aneurysms based on morphology. Under such circumstances, steady flow simulations may be just as effective as pulsatile flow simulation for estimating most key indices currently reported in the literature.     

Measurement of pulmonary blood flow by fractal analysis of flow heterogeneity in isolated canine lungs

Barman, Scott A., Laryssa L. McCloud, John D. Catravas, andIna C. Ehrhart. Measurement of pulmonary blood flow by fractalanalysis of flow heterogeneity in isolated canine lungs. J. Appl. Physiol. 81(5):2039-2045, 1996.Regional heterogeneity of lung blood flow can bemeasured by analyzing the relative dispersion (RD) of mass(weight)-flow data. Numerous studies have shown that pulmonary bloodflow is fractal in nature, a phenomenon that can be characterized bythe fractal dimension and the RD for the smallest realizable volumeelement (piece size). Although information exists for theapplicability of fractal analysis to pulmonary blood flow in wholeanimal models, little is known in isolated organs. Therefore, thepresent study was done to determine the effect of blood flow rate onthe distribution of pulmonary blood flow in the isolated blood-perfusedcanine lung lobe by using fractal analysis. Four different radiolabeledmicrospheres (¹⁴¹Ce,⁹⁵Nb,⁸⁵Sr, and⁵¹Cr), each 15 µm in diameter,were injected into the pulmonary lobar artery of isolated canine lunglobes (n = 5) perfused at fourdifferent flow rates ( flow1 = 0.42 ± 0.02 l/min;flow2 = 1.12 ± 0.07 l/min;flow 3 = 2.25 ± 0.17 l/min; flow 4 = 2.59 ± 0.17 l/min), and the pulmonary blood flow distribution was measured. Theresults of the present study indicate that under isogravimetric bloodflow conditions, all regions of horizontally perfused isolated lunglobes received blood flow that was preferentially distributed to themost distal caudal regions of the lobe. Regional pulmonary blood flowin the isolated perfused canine lobe was heterogeneous and fractal innature, as measured by the RD. As flow rates increased, fractal dimension values (averaging 1.22 ± 0.08) remained constant, whereas RD decreased, reflecting more homogeneous blood flowdistribution. At any given blood flow rate, high-flow areas of the lobereceived a proportionally larger amount of regional flow, suggestingthat the degree of pulmonary vascular recruitment may also be spatially related.

     

Effect of alveolar liquid on distribution of blood flow in dog lungs.

Previous studies have shown that a shift in blood flow away from edematous regions does not occur until the alveoli contain liquid. The present experiments were designed to examine the separate effect of air space liquid, air space plus interstitial liquid, and reduced lung volume on blood flow. We found that reduced lung volume was not associated with significant changes in blood flow and that no systematic change in blood flow occurred when alveoli were filled with isosmotic liquid (autologous plasma). However, when hyposmotic liquid (dilute plasma) was instilled so that both the air space and the alveolar wall interstitial space were filled, blood flow was systematically reduced. This suggested that interstitial liquid was responsible raising vascular resistance in these experiments and that it might also be important in raising local vascular resistance in pulmonary edema. This latter hypothesis was tested in isolated perfused lobes where rapid freezing and quantitative histology showed that the number of open capillaries was significantly reduced in the liquid-filled alveoli (P less than 0.001). These observations suggest that interstitial pressure rises in pulmonary edema with the result that the transmural pressure of the alveolar vessels falls and vascular resistance is increased.     

Hemodynamic effects of python neuropeptide gamma in the anesthetized python, Python regius

The effects of python neuropeptide gamma (NPgamma) on hemodynamic parameters have been investigated in the anesthetized ball python (Python regius). Bolus intra-arterial injections of synthetic python NPgamma (1-300 pmol kg-1) produced a dose-dependent decrease in systemic arterial blood pressure (Psys) concomitant with increases in systemic vascular conductance (Gsys), total cardiac output and stroke volume, but only minor effects on heart rate. The peptide had no significant effect on pulmonary arterial blood pressure (Ppul) and caused only a small increase in pulmonary conductance (Gpul) at the highest dose. In the systemic circulation, the potency of the NK1 receptor-selective agonist [Sar9,Met(0(2))11] substance P was >100-fold greater than the NK2 receptor-selective agonist [betaAla8] neurokinin A-(4-10)-peptide suggesting that the python cardiovascular system is associated with a receptor that resembles the mammalian NK1 receptor more closely than the NK2 receptor. Administration of the inhibitor of nitric oxide synthesis, L-nitro-arginine-methylester (L-NAME; 150 mg kg-1), resulted in a significant (P<0.05) increase in Psys as well as a decrease in Gsys, but no effect on Ppul and Gpul. Conversely, the nitric oxide donor, sodium nitroprusside (SNP; 60 microg kg-1) produced a significant (P<0.05) decrease in Psys along with an increase in Gsys and pulmonary blood flow. However, neither L-NAME nor indomethacin (10 mg kg-1) reduced the cardiovascular responses to NPgamma. Thus, nitric oxide is involved in regulation of basal vascular tone in the python, but neither nitric oxide nor prostaglandins mediate the vasodilatory action of NPgamma.     

Validation of fluorescent-labeled microspheres for measurement of relative blood flow in severely injured lungs.

The aim of the study was to validate a nonradioactive method for relative blood flow measurements in severely injured lungs that avoids labor-intensive tissue processing. The use of fluorescent-labeled microspheres was compared with the standard radiolabeled-microsphere method. In seven sheep, lung injury was established by using oleic acid. Five pairs of radio- and fluorescent-labeled microspheres were injected before and after established lung injury. Across all animals, 175 pieces were selected randomly. The radioactivity of each piece was determined by using a scintillation counter. The fluorescent dye was extracted from each piece with a solvent without digestion or filtering. The fluorescence was determined with an automated fluorescent spectrophotometer. Perfusion was calculated for each piece from both the radioactivity and fluorescence and volume normalized. Correlations between flow determined by the two methods were in the range from 0.987 +/- 0.007 (SD) to 0.991 +/- 0.002 (SD) after 9 days of soaking. Thus the fluorescent microsphere technique is a valuable tool for investigating regional perfusion in severely injured lungs and can replace radioactivity.     

Cardiovascular actions of python bradykinin and substance P in the anesthetized python, Python regius

The cardiovascular actions of python bradykinin (BK) and substance P (SP) have been investigated in the anesthetized ball python, Python regius. Bolus intra-arterial injections of python BK (0.03-3 nmol/kg) produced concentration-dependent increases in arterial blood pressure, heart rate (HR), and cardiac output concomitant with small decreases in systemic resistance and stroke volume. Intra-arterial injection of 3 nmol/kg python BK produced a tenfold increase in circulating concentration of norepinephrine, but epinephrine levels did not change. BK-induced tachycardia was attenuated (>90%) by the beta-adrenergic receptor antagonist sotalol, and the hypertensive response was attenuated (>70%) by the alpha-adrenergic receptor antagonist prazosin, indicating that effects of python BK are mediated at least in part by activation of the extensive network of adrenergic neurons present in vascular tissues. Bolus intra-arterial injections of python SP in the range 0. 01-30 pmol/kg produced concentration-dependent decreases in arterial blood pressure and systemic peripheral resistance concomitant with increases in cardiac output and stroke volume but with only minor effects on HR. The data suggest that kinins play a physiologically important role in cardiovascular regulation in the python.