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At least 271 records · Page 15Linked to original sources
PubMed1991

Gas exchange in isolated perfused frog skin as a function of perfusion rate.

Patches of skin were removed from bullfrogs and perfused with a red cell suspension through the cutaneous artery to define the gas exchange characteristics of frog skin without complications caused by in vivo regulatory mechanisms. Oxygen uptake was primarily perfusion limited at low perfusion rates but primarily diffusion limited at perfusion rates that were similar to cutaneous blood flows previously reported in vivo. Diffusing capacity (DO2) increased only slightly as perfusion rate increased. Because the DO2 in isolated skin, in which DO2 should be maximal, was not significantly higher than estimates of DO2 in vivo, there seems to be little opportunity for increasing cutaneous DO2 or oxygen uptake in vivo.

Animals↗
PubMed1983

An improved method for perfusion of the isolated brain of the rat-influence of perfusion conditions and application of analeptic and anticonvulsant drugs.

A method for the perfusion of the isolated brain of the rat with synthetic fluorocarbon emulsion is described. The functional states of the brains were investigated using biochemical, biophysical, and histological methods. After 4.5 h of perfusion, all brains were in excellent condition and comparable to the in vivo state. The influence of perfusion conditions on the viability of the brains was studied. Deep hypothermia was well tolerated; at 13 degrees the EEG exhibited a mean frequency of about 8 Hz, while the mean amplitude was about 40% lower than at 28 degrees or 36 degrees. Constant-pressure perfusion did not affect brain function, provided that the pressure amplitude was very slowly decreased. During application of pentylenetetrazole (PTZ) it was found that the threshold concentration of PTZ in the perfusion medium to induce epileptic seizure discharges was 0.13 mg/ml. However, after repeated application of PTZ, the threshold concentration decreased exponentially, indicating a kindling phenomenon. It could be shown that not PTZ as such, but the spike potentials provoked by PTZ, induced the kindling effect. This was inhibited by application of primidone or phenobarbital.

Adenosine Triphosphate↗
PubMed2000

Perfusion-assisted direct coronary artery bypass: selective graft perfusion in off-pump cases.

BACKGROUND: Hemodynamic instability during multivessel off-pump coronary artery bypass grafting can lead to hypotension, progressive myocardial ischemia, further hypotension, and the need for urgent cardiopulmonary bypass. METHODS: In 10 patients undergoing off-pump coronary artery bypass grafting, a novel technique of pressure-controlled blood delivery has been used that allows the immediate restoration of arterial blood to distal coronary beds after distal coronary anastomosis. This technique utilizes a servo-controlled pump to allow delivery of blood at systemic or suprasystemic pressures, and provides the option for infusion of supplemental additives for myocardial resuscitation, myocardial vasodilation, and enhancement of myocardial performance. RESULTS: Myocardial perfusion was successfully enhanced via one or two grafts in all 10 patients with an average graft flow of 98+/-8 mL/min. In 3 patients, a 27% increase in perfusion pressure led to a 59% increase in perfusate flow. All patients were hemodynamically stable after initiation of selective graft perfusion. CONCLUSIONS: Based on this preliminary patient series, the selective perfusion of grafted vessels seems to facilitate multivessel off-pump coronary artery bypass grafting by promoting rapid recovery of grafted segments, by enhanced hemodynamic stability during subsequent anastomoses, and by providing increased flexibility in the sequence of grafting.

Aged↗
PubMed1997

Reoxygenated effluent of Tyrode-perfused heart affects papillary muscle contraction independent of cardiac perfusion.

OBJECTIVE: We determined, via a bioassay, if inotropic factors are released in the coronary circulation of the rat heart and if changes in cardiac perfusion change papillary muscle inotropy. METHODS: An isolated isometrically contracting rat papillary muscle (n = 5, acceptor) was superfused with Tyrode or with reoxygenated coronary venous effluent from an isolated isovolumically beating rat heart (donor) at 27 degrees C, which was perfused with Tyrode according to Langendorff. The superfusion solution in the muscle bath was exchanged completely in 90 s. During coronary venous effluent superfusion, the flow of the heart (donor) was changed in steps. RESULTS: The peak force of the papillary muscle (acceptor) was unaffected by a change from Tyrode to coronary venous effluent superfusion, but time to half relaxation (RT 1/2) significantly increased by 23.0 +/- 9.0% (mean +/- s.d.) and positive dF/dtmax significantly decreased by 14.6 +/- 4.7%. These twitch characteristics were unaffected by changes in coronary perfusion while in the heart isovolumic developed left ventricular pressure did increase with perfusion (the Gregg phenomenon). CONCLUSIONS: Factors that affected papillary muscle contractility are released into the coronary circulation, but their effect is independent of the magnitude of coronary perfusion.

Animals↗
PubMed1997

Rhabdomyolysis and renal function impairment after isolated limb perfusion--comparison between the effects of perfusion with rhTNF alpha and a 'triple-drug' regimen.

The aim of this study was to monitor serum and perfusate levels of myoglobin (MB) and creatine kinase (CK) during isolated limb perfusion (ILP) in order to identify those at risk of renal failure. We investigated the release of MB and CK in 40 patients who underwent ILP for melanoma (n = 15) or sarcoma (n = 25) using rhTNF alpha/melphalan (n = 28) or a triple-drug regimen (n = 12). Serial determinations of CK and MB were performed in both perfusate and systemic circulation during and after ILP and renal function was assessed. A significant increase of MB could be detected in the perfusate during ILP. After ILP, an up to 100-fold increase with a double peak of MB at 4 h and 24 h postoperatively was observed. The maximum elevation of serum activity of CK was at 30 h. The increase for both proteins was highly significant (P < 0.001). ILP with rhTNF alpha/melphalan yielded significantly (P < 0.001) higher serum values of MB and CK and also the impairment of the renal function was more pronounced. The peak values of MB after ILP occur early and allow the patients most at risk of developing renal failure to be identified. Rhabdomyolysis can be detected early by determination of MB from the perfusate. Further measurements twice daily for 2-3 days post ILP from serum samples as well as daily assessment of MB in the urine is helpful for detecting myoglobinuria and imminent renal failure.

Adult↗
PubMedDate not supplied

Effect of perfusate albumin on organ viability and vascular responses in the in vitro dual-perfused rat liver.

Inclusion of albumin in the perfusate has been previously shown to be detrimental to liver function, but its effect on hepatic vascular reactivity remains unknown. The aim of this study was to determine the effects of albumin on hepatic arterial vascular reactivity and liver viability in the isolated dual-perfused rat liver. A total of 12 rat livers were perfused with Krebs-Bülbring buffer without (Group 1) and with (Group 2) addition of 1% bovine serum albumin (BSA) through the hepatic artery and portal vein for up to 5 h. Hepatic arterial responses to acetylcholine and sodium nitroprusside were studied at 30-min intervals. Liver viability was assessed by bile volume production, release of aspartate serine aminotransferase (AST) and lactic acid dehydrogenase (LDH), and histological examination. Hepatic arterial responses to acetylcholine were significantly attenuated in Group 2. No significant differences in sodium nitroprusside responses were noted. However, bile volume production in Group 2 was significantly decreased compared to Group 1. Effluent AST and LDH release increased significantly in Group 1 but not in Group 2. Histological results showed that sinusoidal endothelial cells and hepatocytes were well preserved without significant deterioration in either group, although there was a marked decrease in vasodilatation to acetylcholine in Group 2. This data suggested that the presence of albumin in the perfusate did not improve retention of smooth muscle reactivity and reduced endothelium-dependent vasodilatation and bile volume production during perfusion. However, improved liver parenchymal cell function was observed.

Acetylcholine↗
PubMed1999

The erythrocyte-perfused "working heart" model: hemodynamic and metabolic performance in comparison to crystalloid perfused hearts.

A brief period of ischemia was used to evaluate an erythrocyte-enriched Krebs-Henseleit (KH) buffer (n=8) compared to KH only (n=8) in an isolated working rabbit heart. Experimental protocol was as follows: preischemic baseline, 5 min of global ischemia followed by 45 min of reperfusion. Preischemic heart rate was identical, coronary flow was significantly lower (2.7 versus 5.6 mL/min/g wet wt, p<0.01), the other hemodynamic and biochemical values were significantly higher in erythrocyte-perfused hearts: aortic flow 23.5 versus 12.0, p<0.01; cardiac output 26.2 versus 17.6, p<0.01; all in mL/min/g wet wt; dp/dt max 1286 versus 997 mmHg/s, p<0.01; myocardial oxygen consumption 3.5 versus 2.3 micromol/min/g wet wt, p<0.05. During early reperfusion, in the erythrocyte-perfused hearts, coronary flow further increased (p<0.003), the other hemodynamic parameters returned to baseline values in both groups. High-energy phosphates showed significantly higher values (ATP 2.0+/-0.1 versus 1.3+/-0.1, p<0.05; CrP 2.0+/-0.2 versus 1.6+/-0.1, p<0.05 all in micromol/g wct wt), water content was significantly lower (81% versus 74%, p<0.05) in erythrocyte-perfused hearts. It can be concluded that the erythrocyte-perfused working heart model provides excellent oxygenation, leading to superior hemodynamic and metabolic performance. Additionally, in the erythrocyte-perfused hearts preservation of coronary flow reserve underlines the physiological competency of this preparation.

Adenine Nucleotides↗
PubMed2004

Adding sodium and calcium ions to the contrast medium iodixanol reduced the risk of ventricular fibrillation during perfusion of the left coronary artery in pigs: effects of electrolytes, viscosity, and chemotoxicity of an isotonic perfusate.

RATIONAL AND OBJECTIVES: The effects of electrolytes, viscosity, and chemotoxicity of a plasma-isotonic iodine contrast medium iodixanol were compared with regard to its propensity to cause ventricular fibrillation (VF). MATERIALS AND METHODS: The left coronary artery of pigs was perfused with five isotonic solutions: iodixanol 320 mg I/mL with 19 mmol/L NaCl + 0.3 mmol/L CaCl2, Iod 320+Mann (iodixanol 320 mg I/mL + 50 mmol/L mannitol), Mann+Na/Ca (240 mmol/L mannitol with 19 mmol/L NaCl + 0.3 mmol/L CaCl2), Mann (275 mmol/L mannitol) and Ringer. The first two solutions have at 37 degrees C a viscosity of approximately 13 mPa x s while the others have a viscosity < 1 mPa x s. In eight pigs, each test solution was injected twice into the left coronary artery in random order for 10 seconds (injection volume, 20 mL). In 15 pigs, each of the solutions was injected in random order for 11-40 seconds through the end-hole of a wedged 5F balloon catheter in left coronary artery. Injection rate was 0.5 mL/sec until VF occurred. If VF occurred, injection was stopped and the heart was defibrillated. If VF did not occur, the perfusion period was 40 seconds. RESULTS: The 10-second perfusions caused no VF. The 40-second perfusions with iodixanol 320 mg I/mL with 19 mmol/L NaCl + 0.3 mmol/L CaCl2 or Ringer caused no VF (0%). Iod 320+Mann caused nine VF (60%) after 35 +/- 4 seconds (SEM). Mann+Na/Ca caused 14 VF (93%) after 30 +/- 2 seconds. Mann caused 15 VF (100%) after 24 +/- 2 seconds. Iodixanol 320 mg I/mL with 19 mmol/L NaCl + 0.3 mmol/L CaCl2 and Ringer caused fewer VF than all other solutions (P < .05-.001). Iod 320+Mann caused fewer VF than Mann (P < .05). Iod 320+Mann caused VF later than Mann+Na/Ca or Mann (P < .02 and P < .01). Mann+Na/Ca caused VF later than Mann (P < .05). CONCLUSION: The results fit with a concept that VF starts when the electrolyte composition of the interstitial fluid in the myocardium is sufficiently nonphysiologic. The more physiologic the electrolyte composition of the perfusion fluid, and the higher its viscosity, the slower the composition of the interstitial fluid will be changed, and VF will occur later (or not at all).

Animals↗
PubMed1985

Sinus node responses to perfusion pressure changes, ischaemia and hypothermia in the isolated blood-perfused dog atrium.

Sinus node responses to perfusion pressure changes, ischaemia and hypothermia were evaluated in 22 isolated blood-perfused dog atria. Sinus cycle length (SCL) was measured and sinoatrial conduction time (SACT) was estimated using the premature atrial stimulation technique (PAS) and the constant atrial pacing method (CAP). There was a good correlation between the results obtained with both techniques (r = 0.8297) but CAP had less depressing action on sinus node automaticity. Increasing the perfusion pressure from 100 to 200 mmHg did not influence estimated SACT nor SCL. However, a reduction in perfusion pressure (from 100 to 50 mmHg) markedly shortened SCL without significantly decreasing estimated SACT. Lowering temperature from 37 to 25 degrees C caused a linear increase in estimated SACT and SCL. Occlusion of the sinus node artery induced a sinus tachycardia which was not blocked by sotalol. Estimated SACT was significantly shorter 1 min after occlusion and longer 3 min after occlusion; this increase was significantly inhibited by atropine infusion. Thus, the increase in estimated SACT seen after occlusion might be related to cholinergic activity. However, the sinus tachycardia following a decrease in perfusion pressure might be due to activation of the stretch-receptors while the one seen after reduction in blood flow and occlusion of the sinus node artery seems more likely to be a consequence of ischaemia.

Animals↗
PubMed1994

Optimal perfusion pressure for experimental retrograde cerebral perfusion.

We evaluated cerebral metabolism during retrograde cerebral perfusion (RCP) and circulatory arrest during profound hypothermia, and also investigated the effects of perfusion pressure on RCP. Twenty-four adult mongrel dogs were placed on cardiopulmonary bypass and cooled to a nasopharyngeal temperature of 20 degrees C. At this temperature, hypothermic circulatory arrest (HCA; n = 6), and RCP with a perfusion pressure of 10 mmHg (RCP10; n = 6), 20 mmHg (RCP20; n = 6), and 30 mmHg (RCP30; n = 6) were carried out for 60 minutes. RCP was performed with oxygenated blood via the bilateral maxillary veins, and the retrograde flow rate was regulated to maintain a mean perfusion pressure of 10, 20, or 30 mmHg in the external jugular vein. At 60 minutes of RCP, we measured nasopharyngeal temperature; regional cerebral blood flow (rCBF); cerebral oxygen consumption, carbon dioxide excretion, and excess lactate; cerebral tissue adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and energy charge; and cerebral tissue water content. In the RCP10 group, there was excess cerebral lactate, and ATP and energy charge were low. In the RCP30 group, the water content of cerebral tissue was significantly higher than in other groups. In the RCP20 group, temperature was maintained in a narrow range, oxygen consumption and carbon dioxide excretion could be observed, there was no excess lactate, and ATP and energy charge were significantly higher than in the HCA group. In conclusion, RCP can provide adequate metabolic support for the brain during circulatory arrest, and a perfusion pressure of 20 mmHg is most appropriate for RCP.

Animals↗
PubMed1990

Effects of some autacoids on breathing and perfusion flow in the isolated perfused rat lung.

The effects of three autacoids [5-hydroxytryptamine (5-HT), bradykinin and acetylcholine (Ach)) on breathing and pulmonary circulation were studied in the isolated perfused and ventilated rat lung after intravascular injection or intrabronchial instillation. 5-HT, bradykinin and Ach all caused a dose related reduction in breathing, after injection into the pulmonary artery, with Ach being the most potent. With regard to effects on the pulmonary circulation, a dose-related reduction in perfusate flow was noted with bradykinin and 5-HT with bradykinin being about 10 times more potent than 5-HT. Ach did not reduce or increase perfusate flow. After intrabronchial instillation only 5-HT caused reduced perfusate flow. Effects on breathing were difficult to evaluate with this route of administration. The isolated perfused and ventilated lung seems to be a usable model to simultaneously study effects on respiration and pulmonary circulation.

Acetylcholine↗
PubMed1985

Effects of plasma- and cell-free perfusates on filtration coefficient of perfused canine lungs.

The filtration coefficient (Kf,c) of the microvessels in isolated dog lungs were studied for whole and diluted blood, whole and diluted plasma, Tyrode's solution, and Tyrode's plus dextran (4%, 63,000 mol wt) perfusates. When whole blood and plasma were diluted, Kf,c increased abruptly at a plasma protein concentration between 4 and 5 g/l, an effect which was not dependent on the erythrocyte mass. Both Tyrode's and Tyrode's plus dextran produced increases in Kf,c (60 and 30%, respectively). The difference in Kf,c measured between these latter perfusates was completely abolished when Kf,c were corrected for viscosity differences. Thus the pulmonary microvasculature responds similarly to the systemic circulation in that complete removal of plasma proteins from the perfusate increases Kf,c by 50%. This effect is independent of erythrocyte mass or colloid osmotic pressure of the perfusate, since perfusion with dextran solutions alone also increased Kf,c.

Animals↗
PubMed1998

Lectin intravital perfusion studies in tumor-bearing mice: micrometer-resolution, wide-area mapping of microvascular labeling, distinguishing efficiently and inefficiently perfused microregions in the tumor.

Intravital lectin perfusion was combined with computer-guided scanning digital microscopy to map the perfused elements of the vasculature in tumor-bearing mice. High-precision composite images (spatial precision 1.3 micron and optical resolution 1.5 micron) were generated to permit exact positioning, reconstruction, analysis, and mapping of entire tumor cross-sections (c. 1 cm in diameter). Collation of these mosaics with nuclear magnetic resonance maps in the same tumor plane identified sites of rapid contrast medium uptake as tumor blood vessels. Digitized imaging after intravital double labeling allowed polychromatic visualization of two different types of mismatched staining. First, simultaneous application of two lectins, each bearing a different fluorochrome, revealed organ-specific differential processing in the microvascular wall. Second, sequential application of two boluses of one lectin, bearing different fluorochromes successively, distinguished between double-labeled microvessels, representing efficiently perfused vascular segments, and single-labeled microvessels, with inefficient or intermittent perfusion. Intravital lectin perfusion images of blood vessels in the vital functional state thus highlighted biologically significant differences in vessel function and served as high-resolution adjuncts to MR imaging.

Adenocarcinoma↗
PubMed2002

Development and evaluation of a new apparatus for continuous perfusion of isolated perfused pig heart.

To develop a better model of isolated perfused heart, a new apparatus of coronary artery cannula- fixed-in-aortic tube was developed for continuous normothermic perfusion and compared to the Casalis apparatus with cold ischemia. Eight mongrel pigs with the body weight of 18 to 24 kg were divided half into two groups. All the continuous perfusion experimental hearts resumed a spontaneous heart beat and stabilized earlier than the control hearts without the need of defibrillator or pacemaker, indicating no reperfusion injury on the heart. All the experimental hearts did not show fibrillation nor stopped beating during the entire experiment, whereas the control hearts fibrillated. Two control hearts stopped beating, and only one of the two survived with the help of pacemaker.The coronary systolic, diastolic, and mean pressures were more stable with low variation in the experimental hearts than the cold ischemic control hearts. The experimental hearts consumed more oxygen than the control hearts, indicating more cardiac output. According to these results, the continuous normothermic perfusion method by the new cannula, even though with a short-period of hypothermic perfusion, provided better myocardial protection than the cold ischemia.

Animals↗
PubMedDate not supplied

Effect of perfusion rate on the local disposition of cefixime in liver perfusion system based on two-compartment dispersion model.

The effect of perfusion flow rate upon the estimated parameters in the two-compartment (non-equilibrium) dispersion model, such as dispersion coefficient, volume of the blood space, partition ratio, and irreversible transfer (or elimination) rate constant, was evaluated in the rat liver perfusion system, using cefixime as a test drug. The rats were divided into five groups and the perfusion experiments were performed at various perfusion rates (Q = 6.4, 11.3, 14.1, 16.3, and 19.6 ml/min/liver). The two-compartment dispersion model was fitted to the outflow cefixime concentration profiles after bolus input into the portal vein using the nonlinear least squares program MULTI(FILT). Results of curve fitting suggested that the corrected dispersion coefficient (DC) and the volume of blood space (VB) increased with increase in flow rate. In contrast, the partition ratio (k'), which is a measure of the extent of drug partition between the blood and the hepatic tissues, decreased when flow rate increased. The single-pass extraction ratio of cefixime is small, and the irreversible transfer rate constant (ke) was independent of flow rate. These parameters were correlated to the moment characteristics such as the recovery ratio (FH), the mean hepatic transit time (tH), and the relative variance of the transit time (sigma 2/tH2). FH and sigma 2/tH2 were independent of the flow rate, whereas tH decreased and the apparent distribution volume (VH) increased with increase in perfusion rate.

Animals↗
PubMed2006

Benefits of terminal noncardioplegic warm blood retrograde perfusion after terminal warm blood cardioplegia perfusion prior to aortic unclamping in open heart surgery.

AIM: The benefits of terminal noncardioplegic warm blood retrograde perfusion (TNWB) and terminal warm blood cardioplegia perfusion (TWBC) after intermittent cold blood cardioplegia perfusion during aortic clamping were studied. METHODS: The clinical results of consecutive 128 patients who underwent on pump coronary artery bypass grafting (CABG) or valvular surgery were studied retrospectively. The aortic cross-clamp was removed (1) after five-minute TWBC and sequential three-minute TNWB in 59 patients (TNWB group), (2) immediately after five-minute TWBC in 29 patients (TWBC group), or (3) with neither TWBC or TNWB in 36 patients (control group). RESULTS: The incidence of spontaneous heart beat recovery was best in TNWB group, second in TNBC, and worst in control group (TNWB: 86, TWBC: 42, CONTROL: 14%). The duration from aortic unclamping to heart beat recovery was shorter in TNWB group than TWBC group (TNWB: 2.1, TWB: 4.3 min). Cardiopulmonary bypass duration after aortic unclamping was shortest in TNWB group, second in TWBC group, and longest in control group (TNWB: 21.3, TWB: 27.5, CONTROL: 46.9 min). The postoperative CPK-MB was lowest in TNWB group (TNWB: 65.3, TWB: 87.7, CONTROL: 91.9U/L). Duration of intubation in TNWB group or TWBC group was shorter than control. CONCLUSIONS: Combination of the terminal noncardioplegic warm blood perfusion and terminal warm blood cardioplegic perfusion contributes to increase the incidence of spontaneous heart beat recovery, shortens cardiopulmonary bypass duration following aortic unclamping, and lowers postoperative CPK-MB.

Aorta↗
PubMed1990

Pulmonary ventilation and perfusion abnormalities and ventilation perfusion imbalance in children with pulmonary atresia or extreme tetralogy of Fallot.

Xenon-133 lung ventilation and perfusion scans were done preoperatively after cardiac catheterization and cineangiocardiography in 19 children; 6 had pulmonary atresia with an intact ventricular septum and hypoplastic right ventricle, 4 pulmonary atresia with associated complex univentricular heart, and 9 extreme Tetralogy of Fallot. The four patients with discrepancies in the sizes of the left and right pulmonary arteries on angiography had marked asymmetry of pulmonary perfusion and ventilation-perfusion imbalance on scintigraphy. Similar degrees of asymmetry and imbalance were present in 6 of the 15 children with equal-size pulmonary vessels. Asymmetry of pulmonary perfusion and ventilation-perfusion imbalance were associated with a poor prognosis.

Child↗
PubMed1983

Ultrastructure of isolated perfused proximal tubules from rabbit kidney. A comparison with proximal tubules fixed by perfusion in vivo.

This study was carried out to determine whether the ultrastructure of proximal tubules isolated and perfused in vitro was comparable to the ultrastructure of tubules fixed by perfusion in vivo. The kidneys of female white rabbits were either fixed by perfusion in vivo with glutaraldehyde (controls) or removed for dissection (experimentals) of proximal convoluted tubules and late proximal straight tubules. The isolated tubules were perfused in vitro with Krebs-Ringers bicarbonate solution for 1 hour after which the tubules were fixed with glutaraldehyde. The experimental tubules and the control tubules were processed for electron microscopy, compared qualitatively, and analyzed morphometrically to evaluate the volume densities and surface densities of different cell organelles and the cell membrane. Qualitatively, there were no differences in the appearance of cell organelles in experimental tubules and control tubules, except that cells in some experimental tubules accumulated small lipid droplets which were located close to mitochondria. Only a few quantitative changes were found, the most noteworthy being a 40% decreased surface density of the brush border in experimental proximal convoluted tubules and late proximal straight tubules. Damaged experimental tubules showed an increased number of vacuoles in the inverted microscope. In the electron microscope the vacuoles corresponded to swollen and disintegrated mitochondria and enlarged endocytic vacuoles. However, small degrees of tubular damage were not observable in the inverted microscope, as very small vacuoles could only be seen in the electron microscope. The results show that proximal tubules can be dissected and perfused in vitro for 1 hour without major ultrastructural changes. It should be emphasized that tubules showing an increased vacuolization in the inverted microscope may be damaged and, thus, not function optimally, and even if the tubules appear undamaged in the light microscope they may show signs of cellular degeneration in the electron microscope.

Animals↗