Survival of frozen-thawed human red cells as a function of cooling and warming velocities

Human red cells were equilibrated for 30 min at 20degreesC in buffered saline containing 2 M glycerol and then frozen to --196degreesC at 0.27, 1.7, 59, 180, 480, 600, and 1300degreesC/min and warmed at 0.47, 1, 26, 160, and 550degreesC/min. Cells frozen at 600 and 1300degreesC/min responded in the classical fashion for cells containing intracellular ice; i.e., survivals were low when warming was slow (less than 10%), but increased progressively with increasing warming rate. The sensitivity to slow warming presumably reflects the recrystallization of intracellular ice. Cells frozen at 59 and 180degreesC/min yielded high survivals at all warming rates. This response is also consistent with the findings for other cells cooled just slowly enough to preclude intracellular ice. Cells frozen very slowly at 0.27 and 1.7degreesC/min, however, responded differently; survivals were considerably higher when warming was slow (0.47 or 1degreesC/min) than when it was 26, 160, or 550degreesC/min. This response is analogous to that observed recently by others in mouse embryos and in higher plant tissue-culture cells and to that observed for many years in higher plants. It also confirms previous observations of Meryman in human red cells. It may reflect osmotic shock from rapid dilution but, if so, the basis of the osmotic shock is uncertain.     

Hypernephroma in the solitary kidney: experience with 20 cases and review of the literature

Twenty patients with renal cell carcinoma in anatomically or functionally solitary kidneys were treated and followed for up to 18 years. Factors pertinent to management and survival of these patients and 66 other well documented similar patients reported in the literature are analyzed. Most of the patients were unusually young and a significant number had had nephrectomy for contralateral renal cell carcinoma. Survival was closely related to the earlier presence of malignant disease in the other kidney, the duration of the interval between detection of the 2 neoplasms and the stage of the lesion in the solitary kidney. Partial nephrectomy has been the most successful treatment. The mean survival in the Mayo Clinic series has been 6 years for patients still alive and 2.4 years for those dead at the time of this analysis. Results in this and other series emphasize the importance of thorough long-term followup after nephrectomy for hypernephroma and of aggressive therapy when the remaining kidney becomes involved. It is foolhardy to abandon hope merely because there is a malignant tumor in a solitary kidney.     

Number of glomeruli in normal and hypertrophied kidneys of mice and guinea-pigs

1. In mice and guinea-pigs, the number of glomeruli was counted in kidneys during normal growth and in hypertrophy induced by unilateral nephrectomy. 2. In mice, the number of glomeruli increased sharply during the first 2 weeks in life, and more slowly afterwards. Unilateral nephrectomy, when performed during this period of natural increase, induced the formation of supplementary nephrons in the contralateral kidney. 3. In guinea-pigs, the number of glomeruli was almost complete at birth. No evidence of a supplementary increase in the number of nephrons was found in hypertrophied kidneys following unilateral nephrectomy. 4. These results, together wit previous data obtained in the rat, suggest that the ability to induce new nephrons after unilateral nephrectomy in different species would depend more on the state of kidney maturity at birth than on differences in the renal mechanisms which lead to hypertrophy.     

Moderate exercise increases postexercise thresholds for vasoconstriction and shivering

The purpose of this study was to evaluate the effect of exercise on the subsequent postexercise thresholds for vasoconstriction and shivering. On two separate days, with six subjects (3 women), a whole body water-perfused suit slowly decreased mean skin temperature (approximately 7.0 degreesC/h) until thresholds for vasoconstriction and shivering were clearly established. Subjects were then rewarmed by increasing water temperature until both esophageal and mean skin temperatures returned to near-baseline values. Subjects either performed 15 min of cycle ergometry (65% maximal O2 consumption) followed by 30 min of recovery (Exercise) or remained seated with no exercise for 45 min (Control). Subjects were then cooled again. We mathematically compensated for changes in skin temperatures by using the established linear cutaneous contribution of skin to the control of vasoconstriction and shivering (20%). The calculated core temperature threshold (at a designated skin temperature of 30.0 degreesC) for vasoconstriction increased significantly from 36.64 +/- 0.20 to 36.89 +/- 0.22 degreesC postexercise (P < 0.01). Similarly, the shivering threshold increased from 35.73 +/- 0.13 to 36.13 +/- 0.12 degreesC postexercise (P < 0.01). In contrast, sequential measurements, without exercise, demonstrate a time-dependent decrease in both the vasoconstriction (0.10 degreesC) and shivering (0.12 degreesC) thresholds. These data indicate that exercise has a prolonged effect by increasing the postexercise thresholds for both cold thermoregulatory responses.     

Neural factors contributing to renin release during reduction in renal perfusion pressure and blood flow in cats

1. The participation of neural mechanisms in mediating the renin release induced by reduction of renal perfusion pressure was explored in anaesthetized cats by comparing renin release from the two kidneys, one acutely denervated and the other intact. 2. Suprarenal aortic stenosis of 10 min duration reduced renal perfusion pressure to 50 mmHg and halved blood flow to both kidneys, but cause a greater release of renin from the innervated kidney than from the contralateral denervated one (increments of 72 +/- 17 and 29 +/-20 pmol/min respectively). 3. A study of the time-course of the response during aortic stenosis of 30 min duration showed early release of renin from the innervated kidney at a time (5 min) when little release occurred from the denervated one. In later samplings (15 and 30 min) the response of the innervated kidney levelled out at somewhat lower values, and that of the denervated organ progressively increased, but remained smaller than on the side with intact nerves. 4. There was no parallelism between renin release and renal vasomotor changes induced by aortic stenosis, as vasomotor changes were equal in the two kidneys and remained constant from beginning to end of stenosis. It is concluded that a significant part of the renin release induced by aortic stenosis is dependent on neural mechanisms: the neural differs from the non-neural component in being of more rapid onset and probably of shorter duration.     

Cryopreservation of unfertilized mouse oocytes: the effect of replacing sodium with choline in the freezing medium

Although embryo cryopreservation has become commonplace in many species, effective methods are not available for routine freezing of unfertilized eggs. Cryopreservation-induced damage may be caused by the high concentration of sodium ions in conventional freezing media. This study investigates the effect of a newly developed low-sodium choline-based medium (CJ2) on the ability of unfertilized, metaphase II mouse eggs to survive cryopreservation and develop to the blastocyst stage in vitro. Specifically, the effects of cooling to subzero temperatures, thawing rate, LN2 plunge temperature, and equilibration with a low-sodium medium prior to freezing are examined. In contrast to cooling to 23, 0, or -7.0 degreesC in a sodium-based freezing medium (ETFM), cooling in CJ2 had no significant negative effect on oocyte survival or development. Oocytes frozen in CJ2 survived plunging into LN2 from -10, -20, or -33 degreesC at significantly higher rates than oocytes frozen in ETFM. With the protocol used (1.5 M PrOH, 0.1 M sucrose, -0.3 C/min, plunging at -33 degreesC) rapid thawing by direct submersion in 30 degreesC water was more detrimental to oocyte survival than holding in air for 30 or 120 s prior to transfer to water. Equilibration of unfertilized oocytes with a low-sodium medium prior to cryopreservation in CJ2 significantly increased survival and blastocyst development. These results demonstrate that the high concentration of sodium in conventional freezing media is detrimental to oocyte cryopreservation and show that choline is a promising replacement. Reducing the sodium content of the freezing medium to a very low level or eliminating sodium altogether may allow oocytes and other cells to be frozen more effectively.     

Vicryl mesh for repair of severely injured kidneys: an experimental study

We evaluated the efficacy of wrapping the kidney with semi-elastic Vicryl mesh for control of hemorrhage and preservation of renal function following grade III kidney lacerations (shattered kidney) in dogs in which nephrectomy was indicated clinically. Wrapping of fragmented kidneys resulted in prompt, sustained hemostasis and reapposition of the renal parenchyma. At an average of 80 days after injury the renal lacerations were well healed. The Vicryl mesh had been fully reabsorbed and there was considerably less scar tissue at the site of parenchymal rupture and neither perirenal or intrarenal abscess nor hematoma was found, grossly or microscopically. Among 12 dogs with grade III kidney lacerations, the mean ratio of the effective renal plasma flow (ERPF) in the affected kidney to the ERPF in the uninjured contralateral kidney was 0.53 +/- 0.22. The mean ratio of creatinine clearance of the injured kidney to that of the uninjured contralateral kidney was 0.41 +/- 0.23. Changes in the serum renin levels were not statistically significant following injury. Our results seem to confirm that simple and rapid surgical treatment of severely shattered kidneys using semi-elastic Vicryl mesh is possible. The method may also be suitable for uncontrollable bleeding during nonextirpative kidney surgery.     

Protective effect of exogenous nitric oxide on the renal function and inflammatory response in a model of ischemia-reperfusion

BACKGROUND: Tissue subjected to a period of ischemia undergoes morphological and functional damage that increases during the reperfusion phase. The aim of the present work was to assess the possible improvement induced by exogenous administration of nitric oxide (NO) on renal injury and inflammatory reaction in an experimental animal model of renal ischemia-reperfusion (I-R). METHODS: Ischemia was achieved by ligation of the left arteria and vein for 60 min, followed first by contralateral nephrectomy and then reestablishment of blood flow. Molsidomine, used as an NO donor, was administered by systemic injection 30 min before reperfusion. The effect of molsidomine was compared with the effect of hydralazine, a non-NO donor hypotensive agent. RESULTS: Treatment with molsidomine improved the renal dysfunction (increase in plasma creatinine and urea levels) caused by I-R. Moreover, molsidomine blunted the enhanced production of proinflammatory cytokines (tumor necrosis factor [TNF]-alpha and interleukin [IL] 1alpha), the increase in tissular levels of superoxide anions and oxygen free radical scavengers, and the neutrophilic infiltration observed in the ischemic kidney. One hundred percent survival was achieved in the group of animals treated with the NO donor, whereas the groups of animals undergoing I-R that did not receive molsidomine showed a 40% mortality from the second day after reperfusion. CONCLUSIONS: The present work demonstrated that systemic treatment with an NO donor before reperfusion improved renal function and diminished inflammatory responses in a kidney subjected to an I-R process.     

Effect of sugars on headgroup mobility in freeze-dried dipalmitoylphosphatidylcholine bilayers: solid-state 31P NMR and FTIR studies

The effect of the carbohydrates trehalose, glucose, and hydroxyethyl starch (HES) on the motional properties of the phosphate headgroup of freeze-dried dipalmitoylphosphatidylcholine (DPPC) liposomes was studied by means of 31P NMR, Fourier transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). The results show that trehalose, which is a strong glass former (Tg = 115 degreesC), elevates the onset of the lipid headgroup rotations and preserves some rotational mobility of the phosphate headgroups after cooling from the liquid-crystalline state. Glucose (Tg = 30 degreesC), a very effective depressant of the phase transition temperature of freeze-dried DPPC, markedly elevates the initiation of the temperature of headgroup rotations. On the other hand, the monosaccharide does not preserve the headgroup disordering when cooled from the liquid-crystalline state. These effects are consistent with formation of hydrogen bonds between the OH groups of the sugar and the polar headgroups of DPPC. They show, however, that hydrogen bonding is not sufficient for preservation of the dynamic properties of freeze-dried DPPC. HES, although a very good glass former (Tg > 110 degreesC), does not depress the phase transition temperature and affects only slightly the rotational properties of freeze-dried DPPC. This lack of effect of HES is associated with the absence of direct interactions with the lipid phosphates, as evidenced by the FTIR results. These data show that vitrification of the additive is not sufficient to affect the dynamic properties of dried DPPC.     

Acute hepatic coma. Experimental study on the predictive value of clinical-chemical findings for the prognosis of acute hepatic coma

In order to determine the validity of clinical-chemical parameters for the prognosis of hepatic failure, 28 pigs were subjected to liver ischemia for 40--160 minutes duration. The following parameters were studied: GOT, GPT, gamma-GT, LAP, LDH, GlDH, AP and isoenzymes, total bilirubin, potassium, sodium and chloride. In a statistical comparison in the surviving animals, an unexplainable increase in GlDH activity was observed. In the other clinical-chemical parameters none was seen to be of use for the prognosis for either life or death in acute hepatic failure.     

Pharmacokinetics of troglitazone, a PPAR-gamma agonist, in patients with hepatic insufficiency

The natural history of multicystic dysplastic kidney (MCDK) is not well established. We analyzed kidney growth and renal function in 33 children with prenatally diagnosed unilateral MCDK in a long-term study. The mean observation period was 4.9 years with a range of 1-11.6 years. Abnormalities of the contralateral kidney were found in 10 of 33 patients (30%): ureteropelvic junction obstruction (5), ureterovesical junction obstruction (2), and vesicoureteral reflux (3). In 6 children the dysplastic kidney had been removed. Complete involution was observed in 48% and a decrease of size in 33% of 27 dysplastic kidneys. At the time of last examination, 27 of 29 children showed a volume of the contralateral kidney above the normal range (>145%). Hypertrophy of the contralateral kidney, defined as kidney length above 2 standard deviation scores (SDS), was seen in 24% of 33 children at birth, thus showing that hypertrophy of the contralateral kidney starts in utero and continues throughout childhood. The extent of contralateral hypertrophy was independent of associated abnormalities in this study. Mean creatinine was increased in the whole group (mean +1.13 SDS). Calculated creatinine clearance in 21 patients over 2 years was within normal limits, with a median of 102 ml/min per 1.73 m2 (range 84-143). Based on the results of this and previous studies, nephrectomy cannot be recommended in typical cases, but a regular follow-up of these patients seems necessary.     

Multiple kinetic intermediates accumulate during the unfolding of horse cytochrome c in the oxidized state

The unfolding kinetics of horse cytochrome c in the oxidized state has been studied at 10, 22, and 34 degreesC as a function of guanidine hydrochloride (GdnHCl) concentration. Rapid (millisecond) measurements of far-UV circular dichroism (CD) as well as fluorescence quenching due to tryptophan to heme excitation energy transfer have been used to monitor the unfolding process. At 10 degreesC, the decrease in far-UV CD signal that accompanies unfolding occurs in two phases. The unobservable burst phase is complete within 4 ms, while the slower phase occurs over tens to hundreds of milliseconds. The burst phase unfolding amplitude increases cooperatively with an increase in GdnHCl concentration, exhibiting a transition midpoint of 3.2 M at 10 degreesC. In contrast, no burst phase change in fluorescence occurs during unfolding at 10 degreesC. At 22 and 34 degreesC, both the fluorescence-monitored unfolding kinetics and the far-UV CD-monitored unfolding kinetics are biphasic. At both temperatures, the two probes yield burst phase unfolding transitions that are noncoincident with respect to the transition midpoints as well as the dependency of the burst phase amplitudes on GdnHCl concentration. The results suggest that at least two kinetic unfolding intermediates accumulate during unfolding. One burst phase intermediate, IU1, has lost virtually all the native-state secondary structure, while the other burst phase intermediate, IU2, has lost both secondary structure and native-like compactness. The presence of kinetic unfolding intermediates is also indicated by the nonlinear dependence of the logarithm of the apparent unfolding rate constant on GdnHCl concentration, which is particularly pronounced at 10 and 22 degreesC. Analysis of the burst phase unfolding transitions obtained using the two probes shows that the stabilities of IU1 and IU2 decrease steadily with an increase in temperature from 10 to 34 degreesC, suggesting that the structures present in them are stabilized principally by hydrogen bonding interactions.     

Inhibition of intercellular adhesion molecule-1 with antisense deoxynucleotides prolongs renal isograft survival in the rat

BACKGROUND: Delayed graft function from ischemia-reperfusion injury has a negative impact on long-term renal graft survival. We tested the utility of antisense oligodeoxynucleotide (ODN) against intercellular adhesion molecule-1 (ICAM-1) in the pretransplant treatment of renal isografts in improving long-term graft survival. METHODS: Three groups of 16 inbred Lewis rats each underwent unilateral nephrectomy and were then transplanted with a kidney from a Lewis donor rat, which had received antisense ODN, reverse sense ODN, or saline vehicle six hours prior to nephrectomy. The kidneys were subjected to one hour of warm ischemia and 30 minutes of cold ischemia, which when untreated results in delayed graft function. The remaining native kidney was removed 10 days later. Serum creatinine and urinary protein excretion were measured in surviving rats at weeks 2, 4, 6, 8, 12, 16, and 20 after native nephrectomy. RESULTS: A Kaplan-Meier analysis revealed that by week 6 one half of the animals receiving reverse sense ODN and saline vehicle treatment had died, while all but 2 rats in the antisense ODN-treatment group survived to 20 weeks. Serum creatinine concentrations and urine protein excretion of surviving reverse sense and saline vehicle-treated rats were significantly higher than antisense treated rats at every time point. Histology at week 20 revealed marked interstitial fibrosis, focal glomerular sclerosis, vascular intimal and medial thickening and tubular atrophy in reverse sense and saline vehicle-treated kidneys, while antisense ODN-treated kidneys showed only modest changes. Immunohistochemistry showed macrophage and lymphocyte infiltration, as well as substantial up-regulation of MHC class II, in reverse sense and saline vehicle-treated kidneys compared to antisense ODN-treated kidneys. CONCLUSIONS: These results suggest that by ameliorating acute nonimmunological renal isograft injury, the long-term chronic nonimmunologic processes are improved as well. Furthermore, the data suggest that an antisense ODN strategy directed against ICAM-1 may have utility in human kidney transplantation.     

Analysis of phosphorylated sphingolipid long-chain bases reveals potential roles in heat stress and growth control in Saccharomyces

Sphingolipid long-chain bases and their phosphorylated derivatives, for example, sphingosine-1-phosphate in mammals, have been implicated as signaling molecules. The possibility that Saccharomyces cerevisiae cells also use long-chain-base phosphates to regulate cellular processes has only recently begun to be examined. Here we present a simple and sensitive procedure for analyzing and quantifying long-chain-base phosphates in S. cerevisiae cells. Our data show for the first time that phytosphingosine-1-phosphate (PHS-1-P) is present at a low but detectable level in cells grown on a fermentable carbon source at 25 degreesC, while dihydrosphingosine-1-phosphate (DHS-1-P) is only barely detectable. Shifting cells to 37 degreesC causes transient eight- and fivefold increases in levels of PHS-1-P and DHS-1-P, respectively, which peak after about 10 min. The amounts of both compounds return to the unstressed levels by 20 min after the temperature shift. These data are consistent with PHS-1-P and DHS-1-P being signaling molecules. Cells unable to break down long-chain-base phosphates, due to deletion of DPL1 and LCB3, show a 500-fold increase in PHS-1-P and DHS-1-P levels, grow slowly, and survive a 44 degreesC heat stress 10-fold better than parental cells. These and other data for dpl1 or lcb3 single-mutant strains suggest that DHS-1-P and/or PHS-1-P act as signals for resistance to heat stress. Our procedure should expedite experiments to determine how the synthesis and breakdown of these compounds is regulated and how the compounds mediate resistance to elevated temperature.     

Segmental calculus disease: potential of parital nephrectomy

Partial nephrectomy was performed on 71 renal units between 1962 and 1978 for segmental calculus disease. Parenchymal scarring associated with an infundibulocalyceal stone, which was usually branched, was the indication for resection. Stone analysis demonstrated an equal incidence of idiopathic and struvite stones. Perioperative morbidity was minimal, but pyelocutaneous urinary drainage prolonged the hospitalization of 5 patients. In 2 cases, the cause was an obstructing retained calculus. Retained calculi occurred in 3 other patients, one requiring early nephrectomy for sepsis. Fifty-seven patients were followed for longer than twelve months. Ipsilateral calculi recurred in 12 per cent of kidneys, and contralateral new calculi developed in the same number. Ninety-four per cent of patients with preoperative urinary tract infections had sterile urine at follow-up. From the results of this and other series, partial nephrectomy compares favorably with extended pyelolithotomy and anatrophic nephrotomy for segmental calculus disease associated with parenchymal scarring and/or a deformed collecting system.     

Multicystic kidney dysplasia: a prospective study on the natural history of the affected and the contralateral kidney

In a 6-year period, 41 young infants with multicystic kidney dysplasia were seen in our department. In 30 cases, the diagnosis had already been suspected by prenatal ultrasonography. A prospective protocol was proposed to the parents which comprised ultrasound evaluation every 3 months until the age of 24 months and renal function assessment at the age of 18 months. In 33 patients, the study was completed as scheduled. At the start of the study, the maximal diameter of the multicystic kidney was above the mean length of normal kidneys in all cases where precise measurement was possible. Within 24 months, 7 of the dysplastic kidneys disappeared, 20 regressed in size, 1 remained unchanged and only 5 increased in size. Between the age of 0 to 3 months, renal length of the contralateral kidney was within the normal range in 19 infants and above +2SD in 14 cases. At the age of 18 to 24 months, renal length was, with few exceptions, between 0 and +4SD. Inulin clearance was normal in all 33 individuals with a median value of 112 ml/min per 1.73 m2. CONCLUSION: As a rule, multicystic kidneys shrink in the first 2 years of life. In most cases the contralateral kidney maintains a normal renal function as a consequence of progressive compensatory hypertrophy.     

Erythropoietin production in rats with post-ischemic acute renal failure

To study the role of erythropoietin (Epo) in the pathogenesis of anemia in acute renal failure (ARF), organ Epo mRNA was measured by RNase protection assay in rats with ARF induced by a one hour-occlusion of the left renal artery. Hematocrit was significantly decreased two hours, 24 hours and one week after renal artery occlusion. A significant reduction in serum haptoglobin at two hours and an increase in serum LDH at 24 hours indicated that hemolysis was the likely cause of the initial fall in hematocrit. However, despite the reduced hematocrit, serum Epo concentrations were not significantly different from controls, suggesting that the anemia is maintained because of lack of an appropriate Epo response. Right renal Epo mRNA levels were not significantly different in all groups, but Epo mRNA levels in post-ischemic kidneys were 50 to 67% lower than in contralateral kidneys. However, Epo mRNA in the post-ischemic kidney was increased sixfold by acute hemorrhage, a rise comparable to the ninefold increase observed in contralateral kidneys. In ARF rats exposed to 7.5% O2 for four hours, right kidney Epo mRNA increased 200-fold over normoxic levels, to a value similar to sham-operated hypoxic controls. Epo mRNA in the post-ischemic kidney also increased 200-fold, to 50% of the level in the contralateral kidney. Hepatic Epo mRNA levels were elevated to comparable levels in both groups. In this ARF model, mild anemia is associated with relative Epo deficiency. In the post-ischemic kidney, a substantial capacity for Epo production is retained but the sensitivity of the Epo response to blood oxygen availability is significantly reduced.     

A study of the indication for conservative surgery in adult hydronephrosis based on presurgery post-contrast computed tomography (CT) finding

BACKGROUND AND OBJECT: The cases with adult hydronephrosis are usually performed either conservative surgery or nephrectomy according to the grade of residual renal function. The residual renal function of adult hydronephrosis are usually suspected with analysis of concentration and/or clearance of the renal urine content after percutaneous nephrostomy. However, percutaneous nephrostomy is invasive and risky. On the other hand, post-contrast computed tomography (CT) is non-invasive. We studied whether post-contrast CT is available for the assessment of residual renal function of adult hydronephrosis and also studied the indication for conservative surgery of adult hydronephrosis on post-contrast CT. MATERIALS AND METHODS: Conservative surgery or nephrectomy was performed in 14 patients with adult hydronephrosis in the duration from April, 1986 to March, 1995. All of 14 patients (14 kidneys) hydronephrosis were retrospectively studied of the character in the indication for conservative surgery by post-contrast CT before surgery. RESULTS: The indication for conservative surgery of adult hydronephrosis on post-contrast CT are (1) well enhanced renal parenchyma exist round the kidney, even if it is very thin, and (2) excretion of contrast medium to renal calyx are showed. CONCLUSION: It was concluded that post-contrast CT might be useful for the assessment of residual renal function of adult hydronephrosis.     

Lipid peroxidation after acute renal ischemia and reperfusion in rats: the effect of trimetazidine

Lipid peroxidation is a critical pathway of reactive oxygen species inducing tissue injury in postischemic acute renal failure. In order to evaluate the effect of renal ischemia reperfusion on kidneys, renal tissue malondialdehyde (MDA, nmol/g wet weight) concentration was measured in 29 male Wistar rats subjected to a midline abdominal incision and 60 min occlusion of the left renal artery. A right nephrectomy was performed at the beginning of the ischemic period. The animals were separated in four groups. Groups 1 (n = 7) and 3 (n = 7) underwent 60 min of ischemia and 15 min of reperfusion, respectively. Groups 2 (n = 8) and 4 (n = 7) were subjected to the same procedure but, in addition, they received 2.5 mg/kg TMZ into the tail vein 2 h prior to the left renal artery occlusion. A significant elevation of MDA after 60 min of ischemia (1.43 vs. 2.1, p < 0.001), which was augmented after 15 min of reperfusion (1.4 vs. 3.72, p < 0.001) was observed. Furthermore, there was a significant reduction of renal tissue MDA in ischemic rats treated with TMZ (group 3) (2.1 vs. 1.52, p < 0.001). The maximum reduction of renal tissue MDA was observed in ischemic-reperfused rats (group 4) that had received TMZ (3.72 vs. 1.36, p < 0.001). It is suggested that lipid peroxidation is a critical event in postischemic acute renal failure, and TMZ is a useful protective agent of renal damage from oxygen free radicals.     

Glucose-induced thermal stabilization of the native conformation of GLUT 1

The glucose transporter, GLUT 1, was purified from erythrocyte membranes and incorporated into vesicles of erythrocyte lipids. These protein-containing vesicles were studied with differential scanning calorimetry. It was found that the protein underwent an irreversible denaturation at 68.5 +/- 0.2 degreesC (at a scan rate of 0.25 degreesC/min) which was shifted to 72.6 +/- 0.2 degreesC in the presence of 500 mM D-glucose, while 500 mM L-glucose or 10 microM cytochalasin B did not produce a significant shift. The calorimetric enthalpy was found to be 150 kcal/mol, independent of the presence of D-glucose. On a weight basis this value is lower than that for soluble proteins, but it is comparable to values obtained with other integral membrane proteins. The van't Hoff enthalpy is similar to the calorimetric enthalpy, within the experimental error, indicating that the transition is not likely to be cooperative. The activation energy is estimated from both the scan rate dependence of the transition temperature and from the shape of the DSC curve. The presence of 500 mM D-glucose slightly decreases the activation energy. It is concluded that the shift to a higher denaturation transition temperature in the presence of D-glucose is not a result of increased kinetic stability of GLUT 1.