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Biomedical subjects

G Bellomo

Publications and source records attributed to G Bellomo.

At least 91 records · Page 5Linked to original sources
PubMed1995

Presence of autoantibodies against oxidatively modified low-density lipoprotein in essential hypertension: a biochemical signature of an enhanced in vivo low-density lipoprotein oxidation.

OBJECTIVE: We have previously reported that low-density lipoproteins (LDL) isolated from patients with essential hypertension are more susceptible to in vitro oxidation than lipoproteins isolated from normotensive control subjects. In the present study we investigated the occurrence of in vivo LDL oxidation in hypertensive patients. DESIGN: The presence of antioxidatively modified LDL autoantibodies was taken as a suitable index of in vivo LDL oxidation because, after oxidative modifications, LDL express antigenic epitopes that elicit an immune response. The antibody titres were measured in plasma from untreated patients with newly diagnosed essential hypertension. METHODS: An enzyme-linked immunosorbent assay method was employed, using native LDL, Cu(2+)-oxidized LDL and malondialdehyde-derivatized LDL (MDA-LDL) as antigens. Human serum albumin and MDA human serum albumin were also used to monitor cross-reactivity with other oxidized molecules. The antibody titre was expressed as the ratio between anti-modified and anti-native antigen absolute values. RESULTS: The patients with essential hypertension had an antibody ratio significantly higher than control subjects with respect to anti-Cu(2+)-oxidized LDL immunoglobulins G and M, and with respect to anti-MDA-LDL immunoglobulins G and M. A significant positive correlation was found between anti-MDA-LDL and anti-Cu(2+)-oxidized LDL antibody titres. The anti-MDA human serum albumin antibody titre was not different in the two groups of patients. An inverse correlation was detected between the anti-MDA-LDL immunoglobulin M titre and the age of the patients. CONCLUSIONS: The results obtained are consistent with the view that, during the early phases of hypertension development, LDL undergo in vivo oxidation that is mirrored by the generation of autoantibodies against epitopes of oxidized LDL. The oxidation process appears specific for LDL and might be relevant both for the progression of hypertension and for the development of the atherosclerosis that often complicates hypertension itself.

Antibody Specificity↗
PubMed1995

Twenty four-hour ambulatory blood pressure monitoring in women with pre-eclampsia.

The aim of our study was to evaluate by means of ambulatory 24 h monitoring the diurnal systolic (SBP) and diastolic (DBP) blood pressure profiles in a group (n = 18) of gravid patients with pre-eclampsia compared with a group (n = 17) of healthy control subjects matched for age and week of gestation to assess whether: (i) ambulatory BP is also raised in pre-eclampsia; (ii) the increase of BP, if present, occurs to the same extent during both daytime and night; and (iii) a blunted BP pattern is consistently present in pre-eclampsia. BP was recorded at intervals of 15 min for 25 h using a TM2420 non-invasive pressurometer. The presence of a circadian rhythm of BP was assessed by cosinor analysis. SBP was higher in women with pre-eclampsia (24 h average 115 +/- 11 vs. 136 +/- 12, P = 6 x 10(-6); daytime 117 +/- 12 vs. 139 +/- 13, P = 6 x 10(-6); night 110 +/- 11 vs. 129 +/- 14, P = 5 x 10(-5) as well as DBP (24 h average 67 +/- 5 vs. 86 +/- 6, P = 8 x 10(-12); daytime 69 +/- 6 vs. 89 +/- 5, P = 2 x 10(-11); night 62 +/- 4 vs. 80 +/- 8, P = 5 x 10(-10).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Evidence for a sodium-dependent calcium influx in isolated rat hepatocytes undergoing ATP depletion.

ATP depletion caused by menadione and triethyllead in isolated hepatocytes is associated with intracellular acidosis and a sustained increase in intracellular Na+ and Ca2+ concentrations. Removal of Na+ from the incubation medium as well as the inclusion of EGTA largely prevented the increase in cytosolic Ca2+, thus indicating that Ca2+ was mobilized from the extracellular medium in response to Na+ load. To further validate these findings, hepatocytes were incubated with a combination of sodium propionate and ouabain in order to induce intracellular acidosis and inhibit Na+ extrusion. This treatment promoted a marked increase in intracellular Na+ and Ca2+ concentrations that was prevented by omission of Na+ from the incubation medium as well as by agents that inhibited cellular Na+ influx. These data indicate that following Na+ load, Ca2+ can be accumulated in hepatocytes via a Na+/Ca2+ antiporter operating on a reverse mode.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

Thyroxine pretreatment and halothane administration alter Ca2+ transport and transmembrane potential in rat liver mitochondria. An additional mechanism for halothane-induced liver damage in the hyperthyroid rat model.

Male rats pretreated with thyroid hormones and exposed to halothane in non-hypoxic conditions develop acute liver damage. In order to investigate the mechanisms leading to liver damage in this animal model, the effects of thyroxine (T4) pretreatment and halothane administration on Ca2+ transport and transmembrane potential were studied in isolated rat liver mitochondria. Five-day T4-pretreatment reduced the mitochondrial Ca2+ loading capacity and increased the rate of Ca2+ cycling across the mitochondrial membrane. Halothane administration further increased Ca2+ cycling and produced a time- and dose-dependent loss of transmembrane potential which was more pronounced in mitochondria from T4-pretreated rats than in euthyroid animals. When mitochondria from T4-pretreated rats were incubated in the presence of the Ca2+ chelator EGTA, membrane potential was well preserved. In contrast, when Ca2+ concentration in the extramitochondrial medium was increased, mitochondria deenergization occurred earlier. These findings confirm that alterations in Ca2+ transport and mitochondrial function can be interrelated events and suggest that a Ca(2+)-dependent, halothane-induced loss of transmembrane potential could participate in generating acute liver damage in hyperthyroid rats exposed to halothane in non-hypoxic conditions.

Animals↗
PubMed1994

Alterations of hepatocyte Ca2+ homeostasis by triethylated lead (Et3Pb+): are they correlated with cytotoxicity?

Isolated rat hepatocytes were used to investigate the biochemical mechanisms of toxicity of triethyllead (Et3Pb+), a highly neurotoxic degradation product of the antiknocking petrol additive tetraethyllead. As early as 5 min from the addition of 50 microM Et3Pb+ to hepatocyte suspensions a decrease of mitochondrial membrane potential and of the capacity of mitochondria and microsomes to retain Ca2+ occurred. A dose-dependent release of mitochondrial Ca2+ as well as an inhibition of microsomal Ca(2+)-ATPase activity were also evident when Et3Pb+ (from 2.5 microM up to 50 microM) was added to, respectively, isolated liver mitochondria and microsomes. Further experiments using hepatocytes loaded with the Ca2+ indicator Fura-2AM demonstrate that 1 min from addition of Et3Pb+ the cytosolic free Ca2+ levels increased by about 3-fold. High affinity plasma membrane Ca(2+)-ATPase activity was also significantly inhibited in hepatocytes treated with Et3Pb+, suggesting that an impairement of the mechanisms controlling the efflux of extracellular Ca2+ was concomitantly involved in the rise in cytosolic Ca2+ concentration. The increase in the cytosolic Ca2+ levels caused by Et3Pb+ was followed by a rapid decline of cell viability. However, the addition of EGTA or of the intracellular Ca2+ chelator BAPTA/AM did not affect either the time-course or the extent of cytotoxicity. Conversely, fructose, a glycolytic substrate that was able to support ATP production, prevented hepatocyte death. Thus, the depletion of cellular energy stores rather than the increase in cytosolic Ca2+ appears to be the mechanism by which Et3Pb+ causes irreversible injury in isolated hepatocytes.

Animals↗
PubMed1994

Enhanced LDL oxidation in uremic patients: an additional mechanism for accelerated atherosclerosis?

Since oxidized low-density lipoprotein (LDL) is more atherogenic than native LDL, LDL oxidation was investigated in uremic patients who often develop accelerated atherogenesis. Three groups of uremic patients were studied (10 on predialysis conservative therapy, 11 on repetitive hemodialysis, 13 on peritoneal dialysis) and compared with seventy matched controls. LDL oxidation was evaluated in all patients as: (i) the susceptibility to in vitro oxidation (by measuring the resistance to Cu(++)-induced formation of conjugated dienes), (ii) vitamin E concentration in LDL, and (iii) presence of plasma anti-oxidized LDL antibodies, expressed as the ratio anti-oxLDL/anti-nativeLDL antibodies. The lipid profile was studied in all patients. Vitamin E concentration did not differ between the various groups, although LDL from uremic patients appeared more susceptible to in vitro and in vivo oxidation (as demonstrated by an earlier generation of conjugated dienes and by the presence of an higher antibody ratio) compared to control subjects. Subclass analysis of the different patients revealed that peritoneal dialysis treatment ameliorated the oxidation markers. However, a prolonged dialytic treatment caused a decrease in vitamin E concentration in LDL and increased their susceptibility to oxidation.

Arteriosclerosis↗
PubMed1994

Autoantibodies against oxidatively-modified LDL in uremic patients undergoing dialysis.

Target-specific oxidation processes in LDL generate molecular epitopes that are more atherogenic than the native forms and are able to elicit an immunological reaction leading to the formation of anti-oxLDL autoantibodies (oxLDL-Ab) that may participate in the overall process of atherogenesis. Thus, the detection of oxLDLAb, in addition to mirroring the occurrence of in vivo LDL oxidation, will give valuable information on the occurrence of this immune response. Plasma oxLDLAb (IgG and IgM) were measured in 72 control subjects (CS) and in 80 patients with chronic renal failure (CRF), undergoing repetitive hemodialysis (N = 56) or peritoneal dialysis (N = 24), with an ELISA method using native LDL, CuSO4-oxidized LDL (oxLDL) or malondialdehyde-derivatized LDL (MDA-LDL) as antigens. To monitor cross reactivity of the antibodies detected with other oxidatively-modified proteins, human serum albumin (HSA) and MDA-derivatized HSA (MDA-HSA) were also employed as antigens. The antibody titer was calculated as the ratio of antibodies against modified versus native proteins. CRF patients had an antibody ratio significantly higher than CS as concerning anti-oxLDL IgG (1.39 +/- 0.36 vs. 1.05 +/- 0.3, P < 0.05) and IgM (2.15 +/- 0.75 vs. 1.43 +/- 0.43, P < 0.01), and anti-MDA-LDL IgG (3.05 +/- 0.74 vs. 2.04 +/- 0.42, P < 0.01) and IgM (5.55 +/- 1.79 vs. 2.9 +/- 0.85, P < 0.01). The anti-MDA-HSA antibody titer was also higher in CRF patients than in CS (2.49 +/- 0.5 vs. 1.46 +/- 0.39, P < 0.01 for IgG and 2.80 +/- 1.03 vs. 1.26 +/- 0.43, P < 0.01 for IgM).(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗
PubMed1994

LDL oxidation in patients with severe carotid atherosclerosis. A study of in vitro and in vivo oxidation markers.

Among the various risk factors involved in the development and progression of carotid atherosclerosis, the oxidation of LDL has been proposed to play a relevant role. LDL oxidation has been investigated in 94 patients with severe carotid atherosclerosis undergoing elective carotid artery endarterectomy and in 42 matched control subjects. LDL oxidation was evaluated in all patients as (1) the susceptibility to in vitro oxidation, (2) vitamin E concentration and its efficiency in LDL, and (3) the presence of autoantibodies against oxidatively modified lipoprotein to monitor the occurrence of the oxidative processes taking place in vivo. No difference was detected between control subjects and patients concerning vitamin E concentration and the kinetics of conjugated diene formation in isolated LDL exposed to CuSO4. However, vitamin E efficiency was lower (9.6 +/- 4.2 versus 30.2 +/- 7.6 min/nmol vitamin E) and the duration of the vitamin E-independent lag phase was longer (105.5 +/- 16.5 versus 58 +/- 11.8 minutes) in the patient group. Autoantibodies against oxidatively modified lipoproteins were measured with an ELISA method using native LDL, Cu(2+)-oxidized LDL (oxLDL), or malondialdehyde-derivatized LDL (MDA-LDL) as antigens. To monitor cross-reactivity of the antibodies detected with other oxidatively modified proteins, human serum albumin (HSA) and MDA-derivatized HSA (MDA-HSA) were also employed. The antibody titer was calculated as the ratio of antibodies against modified versus native proteins.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1993

CoA and fatty acyl-CoA derivatives mobilize calcium from a liver reticular pool.

The effect of CoA and fatty acyl-CoA esters on Ca2+ fluxes has been studied in isolated liver microsomes and in digitonin-permeabilized hepatocytes. When microsomes were loaded with increasing concentrations of Ca2+ (6-29 nmol/mg of protein), the extent to which CoA and palmitoyl-CoA released Ca2+ increased. At 23 nmol of Ca2+/mg of protein, half-maximal [CoA] and [palmitoyl-CoA] were 35 and 50 microM respectively. Under conditions of minimal Ca2+ loading, net release of Ca2+ was absent, but Ca2+ translocation from a CoA-sensitive to a CoA-insensitive pool took place. The effect of CoA required the presence of fatty acids, probably to form fatty acyl esters. In permeabilized hepatocytes, the pool(s) mobilized by CoA (or by palmitoyl-CoA) appeared to be different from that mobilized by Ins(1,4,5)P3.

Acyl Coenzyme A↗
PubMed1993

Intraluminal calcium of the liver endoplasmic reticulum stimulates the glucuronidation of p-nitrophenol.

The relationship between the intraluminal Ca2+ content of endoplasmic reticulum and the rate of the glucuronidation of p-nitrophenol was investigated in isolated rat hepatocytes. Different agents which decrease the Ca2+ level in the endoplasmic reticulum [calcium ionophores (A23187, ionomycin) or Ca(2+)-ATPase inhibitors(thapsigargin,2,5-di-(t-butyl)-1,4-benzohydroquinone+ ++)] inhibited the conjugation of p-nitrophenol. Depletion of intracellular Ca2+ stores by preincubation of hepatocytes in the absence of free Ca2+ (in the presence of excess EGTA) also decreased the rate of glucuronidation; Ca2+ re-admission to EGTA-treated hepatocytes restored glucuronidation. In intact liver microsomes the p-nitrophenol UDP-glucuronosyl-transferase activity was not modified by varying the external free Ca2+ concentrations within a cytosol-like range. Emptying of the Ca2+ from the lumen of microsomal vesicles by A23187, after MgATP-stimulated Ca2+ sequestration, decreased the glucuronidation of p-nitrophenol. A similar effect was observed in filipin-permeabilized hepatocytes. In native and in detergent-treated microsomes, Ca2+ (1-10 mM) increased the p-nitrophenol UDP-glucuronosyltransferase activity. It is suggested that the physiological concentration of Ca2+ in the lumen of the endoplasmic reticulum is necessary for the optimal activity of p-nitrophenol UDP-glucuronosyltransferase; the depletion of Ca2+ decreases the activity of the enzyme.

Animals↗
PubMed1993

Physiological concentrations of inorganic phosphate affect MgATP-dependent Ca2+ storage and inositol trisphosphate-induced Ca2+ efflux in microsomal vesicles from non-hepatic cells.

1. MgATP-dependent 45Ca2+ uptake by microsomes obtained from various non-hepatic tissues, namely rat brain, rat solid Morris hepatoma 3924A and human platelets, was measured in the presence of P(i) at low, cytosol-like, concentrations. 2. Increasing P(i) concentrations (0.5-3 mM) caused a progressive enlargement of the 45Ca(2+)-storage capacity of all the microsomal fractions. 3. As a result of P(i) stimulation of Ca2+ uptake, 45Ca2+ and [32P]P(i) were co-accumulated by the three microsomal fractions. 4. The time course for 45Ca2+ and [32P]P(i) accumulation in brain microsomes revealed a biphasic 45Ca2+ uptake: a rapid phase was followed by a second, slower, phase, which depended on the presence of P(i). During the P(i)-dependent phase, the uptake of 45Ca2+ was paralleled by the uptake of [32P]Pi. 5. The passive efflux of Ca2+ was paralleled by the efflux of P(i) and vice versa. In fact, the inhibition of active Ca2+ uptake by excess EGTA, or lowering the P(i) concentration of the incubation system by dilution, caused the release of 45Ca2+ and [32P]P(i) from 45Ca2+ or [32P]P(i) pre-loaded brain microsomes. The Ca2+ ionophore A23187 also released 45Ca2+ and [32P]P(i). 6. Ca2+ efflux by A23187 was rapid (t 1/2 approx. 2 s) and independent of the extent of intravesicular Ca2+ loading, which indicates that Ca2+ and P(i) do not form intravesicular insoluble complexes. 7. The progressive increase in Ca2+ accumulation, depending on P(i) stimulation, resulted in a proportional increase in the amount of Ca2+ releasable by InsP3 in the three non-hepatic microsomal fractions and in digitonin-permeabilized platelets. 8. Concomitantly to Ca2+, microsomal P(i) was also released by InsP3.

Adenosine Triphosphate↗
PubMed1993

Ca2+ and endonuclease activation in radiation-induced lymphoid cell death.

Exposure of lymphoid cells to X-irradiation caused an increase in cytosolic Ca2+ ([Ca2+]i) in rat thymocytes but not in rat splenocytes. The Ca2+ elevation in rat thymocytes was transitory and by 2 h postirradiation, when the chromatin degradation began to be appreciable, the [Ca2+]i had returned to control level. Inhibitors of RNA and protein syntheses prevented the radiation-induced [Ca2+]i rise in thymocytes. Pretreatment of both cell types with Ca2+ chelators also prevented DNA fragmentation, chromatin condensation, and cell death caused by X-irradiation. These data suggest that Ca2+ plays an important role in the perpetuation of apoptosis in both thymocytes and splenocytes although a Ca2+ elevation, which may serve as a signal in thymocytes, does not appear to be required to initiate radiation-induced DNA fragmentation in splenocytes.

Animals↗
PubMed1993

Low-density lipoprotein oxidation in essential hypertension.

OBJECTIVES: To investigate the occurrence of enhanced low-density lipoprotein (LDL) oxidation as an additional factor promoting atherosclerosis progression in hypertensive patients. DESIGN: The oxidation of plasma LDL was investigated in a group of untreated patients with mild-to-moderate essential hypertension without clinically evident target organ damage and in a group of control subjects. METHODS: LDL oxidation was evaluated as both the susceptibility to oxidation in vitro and the presence of plasma anti-oxidized LDL antibodies (as an index for oxidation in vivo). RESULTS: LDL from hypertensive subjects exhibited enhanced susceptibility to oxidation in vitro as revealed by early and accelerated generation of conjugated dienes after exposure to CuSO4. Vitamin E concentration in LDL from hypertensive subjects was slightly but significantly decreased and its efficiency in protecting LDL from oxidation was impaired. Furthermore, a higher plasma anti-oxidized LDL titre was found in hypertensive patients. Subclass analysis revealed that the contemporary presence of hypercholesterolaemia did not significantly modify either the increased susceptibility of LDL to oxidation or the presence of plasma anti-oxidized LDL antibodies detected in hypertensive patients. Moreover, no correlation was found between LDL oxidation parameters and blood pressure values. CONCLUSIONS: LDL from hypertensive patients is more susceptible to oxidation in vitro and is more promptly oxidized in vivo. These findings suggest a possible participation of LDL oxidation in promoting and accelerating the atherosclerosis that often develops in hypertensive patients.

Adult↗
PubMed1993

Low-density lipoprotein oxidation and antioxidized LDL antibodies in peritoneal dialysis patients.

Due to the potential atherogenic effects of oxidized low-density lipoproteins (LDLs), LDL oxidation was studied in a group of uremic patients on chronic peritoneal dialysis. The results were compared with those obtained in a group of 70 controls, 10 uremic patients on predialytic conservative therapy, and 11 patients on repetitive hemodialysis. LDL oxidation was evaluated in all subjects as the susceptibility to in vitro oxidation (monitoring the resistance to Cu(2+)-induced formation of conjugated dienes, lag-phase minutes) and the presence of plasma antioxidized LDL antibodies, expressed as the ratio anti-ox-LDL/antinative LDL antibodies. Vitamin E (main antioxidant agent) content in LDLs was also measured and the lipid profile studied. No significant changes in vitamin E concentration were found, although LDLs from uremic patients appeared more susceptible to in vitro and in vivo oxidation (as demonstrated by an earlier production of conjugated dienes and by the presence of a higher antibody ratio), as compared to control subjects. Analysis of the different groups of uremic patients revealed that peritoneal dialysis, not hemodialysis, significantly ameliorated the oxidation markers. However, prolonged treatment with peritoneal dialysis caused a decrease in vitamin E concentration in LDLs and increased their susceptibility to oxidation.

Antibodies↗
PubMed1992

Permeability of rat liver microsomal membrane to glucose 6-phosphate.

Light-scattering measurements of osmotically induced changes in the size of rat liver microsomal vesicles pre-equilibrated in a low-osmolality buffer revealed the following. (1) The increase in extravesicular osmolality by addition of glucose 6-phosphate or mannose 6-phosphate (25 mM each) caused a rapid shrinking of microsomal vesicles. After shrinkage, a rapid swelling phase (t1/2 approx. 22 s) was present with glucose 6-phosphate but absent with mannose 6-phosphate, indicating that the former had entered microsomal vesicles, but the latter had not. (2) Almost identical results were obtained in the absence of any glucose 6-phosphate hydrolysis, i.e. with microsomes pre-treated with 100 microM-vanadate. (3) The anion-channel blocker 4,4'-di-isothiocyanostilbene-2,2'-disulphonic acid (DIDS) suppressed the glucose 6-phosphate-induced swelling phase. (4) The swelling phase was more prolonged as the glucose 6-phosphate concentration increased (t1/2 = 16 +/- 3, 22 +/- 3 and 35 +/- 4 s with 25 mM, 37.5 mM- and 50 mM-glucose 6-phosphate respectively). The behaviour of glucose-6-phosphatase activity of intact and disrupted microsomes measured in the presence of high concentrations (less than 30 mM) of substrate also indicated the saturation of the glucose 6-phosphate permeation system by extravesicular concentrations of glucose 6-phosphate higher than 20-30 mM. Additional experiments showed that vanadate-treated microsomes pre-equilibrated with 0.1 mM- and 1.0 mM-glucose 6-phosphate (and [1-14C]glucose 6-phosphate as a tracer) rapidly (t1/2 less than 20 s) released [1-14C]glucose 6-phosphate when diluted in a glucose 6-phosphate-free medium. The efflux of [1-14C]glucose 6-phosphate was largely prevented by DIDS, allowing an evaluation of the intravesicular space of glucose 6-phosphate of approx. 1.0 microliter/mg of microsomal protein.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗