Biomedical subjects

D D Varonos

Publications and source records attributed to D D Varonos.

At least 19 recordsLinked to original sources

PubMed2003

Propylthiouracil-induced hypothyroidism is associated with increased tolerance of the isolated rat heart to ischaemia-reperfusion.

The present study investigated the response of the hypothyroid heart to ischaemia-reperfusion. Hypothyroidism was induced in Wistar rats by oral administration of propylthiouracil (0.05%) for 3 weeks (HYPO rats), while normal animals (NORM) served as controls. Isolated hearts from NORM and HYPO animals were perfused in Langendorff mode and subjected to zero-flow global ischaemia followed by reperfusion (I/R). Post-ischaemic recovery of left ventricular developed pressure was expressed as % of the initial value (LVDP%). Basal expression of protein kinase C epsilon (PKCepsilon) and PKCdelta and phosphorylation of p46 and p54 c-jun NH(2)-terminal kinases (JNKs) in response to I/R were assessed by Western blotting. LVDP% was found to be significantly higher in HYPO hearts than in NORM. At baseline, PKCepsilon expression was 1.4-fold more in HYPO than in NORM hearts, P<0.05, while PKCdelta was not changed. Furthermore, basal phospho-p54 and -p46 JNK levels were 2.2- and 2.6-fold more in HYPO than in NORM hearts, P<0.05. In response to I/R, in NORM hearts, phospho-p54 and -p46 JNK levels were 5.5- and 6.0-fold more as compared with the baseline values, P<0.05, while they were not significantly altered in HYPO hearts. HYPO hearts seem to display a phenotype of cardioprotection against ischaemia-reperfusion and this is associated with basal PKCepsilon overexpression and attenuated JNK activation after I/R.

Animals↗

PubMed2001

Long-term thyroxine administration increases heat stress protein-70 mRNA expression and attenuates p38 MAP kinase activity in response to ischaemia.

The present study was undertaken to investigate heat stress protein (HSP)-70 mRNA induction and p38 MAP kinase (MAPK) activity in response to ischaemic stress in the hyperthyroid rat heart. L-Thyroxine (T(4)) (25 microg/100 g body weight) was administered to Wistar rats for 2 days (THYRacute) or 14 days (THYR), while animals treated similarly with normal saline served as controls (NORMacute and NORM). In addition, abdominal aortic banding was performed in another group of rats to produce constriction-induced hypertrophy (HYP), while sham-operated (SOP) animals served as controls. Isolated rat hearts were perfused in a Langendorff mode. Hearts from NORMacute (n=6), THYRacute animals (n=8), NORM (n=6), THYR (n=6), SOP (n=5) and HYP (n=7) animals were subjected to 20 min of zero-flow global ischaemia followed by 45 min of reperfusion. HSP70 mRNA expression and phosphorylated p38 MAPK protein expression were detected in response to ischaemia and protein kinase C-epsilon (PKCepsilon) protein expression was detected at baseline. Thyroid hormones were measured in plasma. Long-term T(4) administration and aortic constriction resulted in the development of cardiac hypertrophy. Thyroid hormones were increased in both THYR and THYRacute as compared with normal groups (P<0.05). HSP70 mRNA induction was increased 2.3-fold in THYR as compared with NORM hearts (P<0.05), whereas there was not any difference between THYRacute and NORMacute hearts (P>0.05). Phosphorylated p38 MAPK protein expression was 2.2-fold more in NORM than in THYR hearts (P<0.05), but it was not different between NORMacute and THYRacute hearts (P>0.05). HSP70 mRNA induction was 1.8-fold greater in HYP than in SOP hearts (P<0.05), whereas phosphorylated p38 MAPK protein expression was similar between the two groups (P>0.05). PKCepsilon protein expression at baseline was 1.7-fold more in NORM than in THYR hearts (P<0.05), and not different between NORMacute and THYRacute hearts (P>0.05) as well as HYP and SOP hearts (P>0.05). This study shows that HSP70 mRNA expression is increased, whereas p38 MAPK activation is attenuated in response to ischaemia in long-term T(4)-treated rat hearts as compared with normal and acute hyperthyroid hearts.

Animals↗

PubMed2001

Phenylephrine induced aortic vasoconstriction is attenuated in hyperthyroid rats.

BACKGROUND: Abnormal vascular responsiveness to vasoconstrictors may play an important role in peripheral vascular resistance in hyperthyroidism. The aim of the present study was to evaluate whether the vascular response to potassium chloride and phenylephrine is abnormal in a rat model of thyroxine-induced cardiac hypertrophy. METHODS: Left ventricular hypertrophy was induced in Wistar rats by subcutaneous administration of L-thyroxine for two weeks ("THYR"), n=17. Animals treated with normal saline served as controls, ("NORM"), n=20. The thoracic aorta was dissected and cut into rings that were suspended in an isolated organ bath with Krebs-Henseleit buffer. Maximal tension, Tmax, in g was measured in response to KCl and PE at the highest concentration in rings with endothelium (+E) and without endothelium (-E) in both groups. Relaxation response (Relax percent) to acetylcholine administration was expressed as percent of the maximal tension induced by phenylephrine. RESULTS: Left ventricular weight was 0.9 (SEM, 0.04) g for THYR group vs 0.7 (0.02) g for the NORM group, p<0.05. With KCl, Tmax was not different between the THYR and NORM groups with and without endothelium. With PE, there was a difference in Tmax between THYR+E and NORM+E, 1.2 (0.05) g vs 1.5 (0.09) g, p<0.05. Tmax was also different between THYR-E and NORM-E, 1.5 (0.08) g vs 1.7 (0.07) g, p<0.05. Relax percent was not significantly different between THYR+E and NORM+E (45.9 percent vs 42.8 percent, p>0.05). CONCLUSIONS: We conclude that: a) Vascular tension of the thoracic aorta in response to PE is lower in thyroxine-treated rats as compared to controls, probably due to enhanced PE-induced vasorelaxation at high concentration. b) Relaxation response of the thoracic aorta to acetylcholine is not different between THYR and NORM groups.

Acetylcholine↗

PubMed2000

Effect of nifedipine in cyclosporine-induced nephrotoxicity in rats: roles of the thromboxane and endothelin systems.

Cyclosporine (CsA) (45 mg/kg/day for 7 days) administration in female Wistar rats induced significant decrease in creatinine clearance (Ccr) and body weight loss (BWL). Urine volume (V) was not altered and proteinuria (PU) not provoked. These changes were associated with increased urinary endothelin 1 (ET-1) and thromboxane B(2)(TXB(2)) concentrations, and decreased urinary ratios of prostaglandin (6ketoPGF(1 alpha)and PGE(2)) to TXB(2)excretions. Nifedipine (NFD) (0.1 mg/kg/day for 7 days), a calcium channel blocker, administrated in addition to CsA, to another group of animals, significantly augmented Ccr and urine V but did not prevent BWL in comparison to CsA-only treated rats. The urinary ET-1 and TXB(2)concentrations displayed significant and non-significant decrease respectively, while the urinary excretion ratios of 6ketoPGF(1 alpha)/TXB(2)and PGE(2)/TXB(2)were significantly enhanced.These observations indicate that the partial protection of NFD in CsA-induced nephrotoxicity could be attributed to augmented urinary prostanoid ratios of renal vasodilators (6ketoPGF(1 alpha)and PGE(2)) to vasoconstrictor (TXB(2)) excretions, and also to reduced release of rather renal origin ET-1, the most potent mamalian vasoconstrictor peptide known to date. In a previous study, we found that NFD only slightly prevented structural renal damage, induced by CsA. So, the NFD protection refers only to functional toxicity and not to structural damage, mediated at least in part by the preservation of relatively high renal TXB(2)levels. However, other nephrotoxic factors and additional mechanisms could also be implicated in this CsA-induced syndrome.

6-Ketoprostaglandin F1 alpha↗

PubMed2000

Propranolol diminishes cardiac hypertrophy but does not abolish acceleration of the ischemic contracture in hyperthyroid hearts.

This study was undertaken to define the contributions of left ventricular hypertrophy (LVH) and increased adrenergic activity to the acceleration of ischemic contracture (IC) that occurs in chronic hyperthyroid rat heart. Acute and chronic hyperthyroidism (THYR) were induced by thyroxine administration for 2 and 14 days, respectively, and normal animals (NORM) served as controls. Isolated hearts were perfused in a Langendorff mode. NORM alpha acute, n = 6; THYR alpha acute, n = 8; and THYR alpha, n = 13; and NORM alpha, n = 13 were subjected to 20-min zero-flow global ischemia (I) and 45-min reperfusion (R). Additional THYR and NORM hearts treated with propranolol (prop) were subjected to 30-min I; THYR beta prop, n = 6 and NORM beta prop, n = 8, and THYR beta, n = 6, NORM beta, n = 8 served as controls. Acceleration of IC was measured by the time to peak contracture (Tmax). Left ventricular hypertrophy (LVH) was assessed by the ratio of left ventricular weight in milligrams (LVW) to animal body weight (BW) in grams. Cardiac hypertrophy developed in chronic but not acute hyperthyroidism. Propranolol reduced the extent of LVH. Contracture occurred earlier in chronic than in acute hyperthyroid and normal hearts. Propranolol did not alter contracture. In conclusion, IC is accelerated by thyroxine administration, and this is probably not due to LVH or increased beta-adrenergic activity. Propranolol diminishes LVH in hyperthyroidism.

Adrenergic beta-Antagonists↗

PubMed1997

Relationship between the thymus and neurochemical changes in the hypothalamus-preoptic area and prefrontal cortex in female rats with delayed puberty.

In female rats, aged 55-58 days with delayed puberty due to deficient growth and environmental stress, 5-hydroxyindoleacetic acid levels and serotonin turnover rate in the hypothalamus-preoptic area as well as body weight, body weight gain and relative weight of ovaries, uterus, adrenals and preputial glands were lower while serotonin and 5-hydroxyindoleacetic acid levels in the prefrontal cortex were higher when compared to normal rats with the latest onset of puberty aged 42-52 days. In rats with delayed puberty, multiple regression analysis revealed a significant negative dependence on dopamine turnover in the hypothalamus-preoptic area for body weight gain and, of all organs, for the relative weight of the thymus. A similar negative significant dependence on serotonin turnover rate in the prefrontal cortex was also found for the relative weight of thymus and spleen. The same analysis in the opposite direction revealed a significant negative dependence of 3,4-dihydroxyphenylacetic acid levels and dopamine turnover rate in the hypothalamus-preoptic area as well as serotonin turnover rate in the prefrontal cortex only on thymus weight. After separation of delayed pubertal rats into two groups, based on absolute ovarian weight, the rats in the low ovarian weight range and no signs of puberty exhibited: lower body weight gain, lower body weight, and lower relative weight only of thymus, ovaries and preputial glands in parallel with an increased dopamine turnover rate in the hypothalamus-preoptic area and serotonin turnover rate in the prefrontal cortex compared to the delayed pubertal rats in the high ovarian weight range and early signs of puberty. The results suggest that in rats with delayed puberty: (1) serotonergic activation in the hypothalamus-preoptic area is lower compared to normal puberty rats; (2) dopaminergic activation in the hypothalamus-preoptic area negatively affects body weight gain, thymus weight and initiation of puberty and (3) thymus weight is negatively implicated in dopaminergic activation in the hypothalamus-preoptic area and serotonergic activation in the prefrontal cortex and positively related to ovarian weight and early signs of puberty.

Animals↗

PubMed1990

Canine capillary formation in vitro.

Microvascular endothelial cells derived from canine subcutaneous adipose tissue formed knob-like and tube-like structures in vitro without tumor-conditioned medium or special substrate. The knob-like structures consisted of acidic and basic glycosaminoglycans arranged in order. Knob-like structures were built from cell extrudates and were responsible for capillary lumen formation in vitro. Transmission electron microscopy confirmed the endothelial nature of the cells which expressed extensive phagolysosomal activity.

Animals↗

PubMed1988

Behavioural and biochemical effects of haloperidol during the oestrous cycle of the rat.

The effects of two doses (1 and 2 mg/kg, i.p.) of haloperidol (HAL) on catalepsy, on concentrations of DA and DOPAC in frontal cortex, nucleus accumbens and striatum and on serum levels of oestradiol were investigated in intact female rats during the 4-day oestrous cycle. Catalepsy induced by haloperidol did not vary much during phases of the cycle. The turnover of DA in the cortex induced by haloperidol was significantly greater on proestrus and smaller on oestrus. The effect of haloperidol on the turnover of DA in the nucleus accumbens and in striatum was marginally affected by the oestrous cycle being greatest on oestrus. The levels of serum oestradiol were higher on proestrus and lower on oestrus. No significant differences were detected between diestrus and metestrus. After haloperidol there was a dramatic increase in serum oestradiol on oestrus, a slight increase on metestrus and diestrus and a decrease on proestrus. However, serum levels of oestradiol were not significantly different between phases of the cycle in rats treated with haloperidol. The results indicate that the oestrous cycle has a detectable influence on DAergic mechanisms in the frontal cortex and possibly in the tuberoinfudibular system, brought about by treatment with haloperidol.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1987

Apomorphine-induced behaviour during the oestrous cycle of the rat.

The effect of various doses of apomorphine (APO) (25, 250, 400 and 750 micrograms/kg, s.c.) on open field behaviour, stereotyped behaviour, body temperature and concentrations of serum oestradiol was studied in cycling females and in ovariectomized rats. With the exception of grooming, the hormonal variations during the cycle, or the ovariectomy, did not have an effect on behaviour related to stimulation of presynaptic dopamine (DA) receptors. The endocrine status on proestrus (PE), characterized by an increase in serum oestradiol, did influence hyperlocomotion and hypothermia induced by apomorphine; the former being attenuated and the latter increased, as compared to the other phases of the cycle. Ovariectomy resulted in an increase in the stimulatory effect of apomorphine on locomotion. Stereotypy induced by apomorphine was unaltered by hormonal variations during the cycle and it was slightly attenuated by removal of the ovaries. During phases of low levels of oestrogen (oestrus, metestrus) apomorphine significantly increased the levels of serum oestradiol, determined 30 min after the administration of drug. It is concluded that the various DAergic mechanisms in brain are differentially affected by hormonal variations during the cycle and by ovariectomy.

Animals↗

PubMed1987

Intravenous cocaine-induced place preference: attenuation by haloperidol.

Cocaine reward was demonstrated by establishing a conditioned place preference (CPP) to a distinctive location paired with cocaine administered either intravenously (i.v., 0.5 mg/kg) or intraperitoneally (i.p., 10 mg/kg). Significant i.p. or i.v. cocaine CPP was observed following the second conditioning trial. Haloperidol (0.2 mg/kg) pretreatment disrupted CPP induced by i.v., but not i.p., cocaine. The haloperidol effect built up over successive trials. The involvement of dopaminergic transmission in i.v. cocaine-induced CPP is discussed.

Animals↗

PubMed1985

Piracetam attenuates the changes in the surface potential of the phosphatidylcholine monolayer produced by alcohols.

The surface potential changes produced by three alcohols on the phosphatidylcholine (PC) monolayer, either alone or in combination with piracetam were studied. The PC monolayer was formedon 145 mM KCL in a teflon trough and the surface change was measured by means of a Kiethley electrometer, with the high impedence output connected to an Americium 241 air electrode and the low impedence output to a calomel reference electrode. The alcohols produced a negative going change in the surface charge of the monolayer, proportional to the chain length of carbon atoms and amount of alcohol added. 10 microliter (2 mg) of piracetam applied to the PC monolayer before adding the alcohols partially inhibited the changes produced by them. It seems that in vitro piracetam opposes the action of alcohols on this membrane model.

Alcohols↗

PubMed1984

Do general anaesthetics perturb lipid membranes? The role of cholesterol.

The effect of enflurane and methoxyflurane on the permeability of liposomes to H+ was rested. Liposomes were prepared with phospholipids alone or as mixtures of cholesterol and phospholipids having the ratios of 1:2 or 1:1. Both anaesthetic drugs facilitated the release of H+ from pure phospholipid liposomes and from those with a 1:2 ratio. The facilitated release of H+ was prevented by the presence of high concentrations of cholesterol. As the cholesterol:phospholipid ratio in synaptic vesicles is of the order 1:2, it is expected that their permeability might be affected by volatile anaesthetics, leading to a modification of synaptic transmission.

Animals↗

PubMed1982

Environmental lead pollution in Greece.

The blood lead concentration, an index of the environmental lead pollution, was measured in groups of individuals from many parts of greece. The mean blood lead value for urban area individuals was 27.03 micrograms/100 mL for adults, 32.30 for children and 31.03 for neonates; while for rural area individuals it was 18.81 micrograms/100 mL for adults, 22.98 for children and 21.66 for neonates. Twenty one percent of the urban individuals had laboratory evidence of "undue lead absorption" (blood lead level greater than 40 micrograms/100 mL) compared to 1.7% of the rural individuals. Children with elevated blood lead levels were found to have anemia.

Adolescent↗

PubMed1981

Concentration of antibacterial agents in rat bone. A comparative study of gentamicin, ampicillin and cephaloridine.

The concentrations of Gentamicin, Ampicillin and Cephaloridine in thigh rat bone were studied. Measurements were done after a 24 h administration for 3 different times. Measurable quantities in the bone for the three antibiotics were detected. The best levels in relation with the M.I.C. of 4 microorganisms occurred in Cephaloridine (and in measurements of serum and bone (microgram/g). The concentration in the serum does not represent concentration in the bone. The most convenient parity was for Cephaloridine. The elimination of the drug in the bone was impressive after 2h. The slower fall occurred in Cephaloridine. Ampicillin had the same level in 4 and 6h. Gentamicin and Cephaloridine had failed to present measurable quantities in some of the animals of the last measurement.

Ampicillin↗

PubMed1980

The influence of acetylsalicylic acid, phenylbutazone, indomethacin, and flufenamic acid on the kinetics of leucocytes during acute inflammation.

Five groups of ten male Wistar rats each were used for the purpose of this experiment. All subjects suffered from sterile acute inflammation in the peritoneal cavity. A sterile beef heart infusion broth reinforced with proteose-peptone was injected to cause the inflammation. The following substances mixed with tragacanth gum were given orally at in 12 h intervals: --Acetalsalicylic acid 150 mg/kg body weight to the first group; --Phenylbutazone 100 mg/kg body weight to the second group; --Indomethacin 15 mg/kg body weight to the third group; --Flufenamic acid 100 mg/kg body weight to the fourth group. Finally the fifth group received only tragacanth gum. The rats were sacrificed after 48 hours and leucocytes were collected from the peritoneal cavity by washing with 5 ml 0.9% NaCl solution. The total leucocyte number and the percent of each type were estimated for each group individually. A statistically significant decrease in the number of leucocytes migrated to the peritoneal cavity due to the inflammation was observed in rats that received one of the drugs (group I to IV) when compared to rats that received only the excipient (group V). Likewise, significant differences were noted in the composition of each type.

Analgesics↗

PubMed1980

[Immunological state of reaction and healing of osteotomy (author's transl)].

The influence of immune reaction on rats - achieved through C. F. A. - on the healing of incomplete osteotomy of the femur was experimentally examined. It was found that the production of immune reaction, manifested by the appearance of polyarthritis, leads in a great percentage (60% of the animals) in extensive bone destruction in the vicinity of the osteotomy. The results were examined clinically, radiologically and histologically. The type of reacton in the area of bone destruction was of immunological origin (histological examination).

Animals↗

PubMed1980

[Bone reaction to metal and bone cement implants at immunologic reaction level in rats (author's transl)].

After the fact that femoral osteotomy in rats results in destruction of the entire bone (in the majority of experimental animals) due to an immunological reaction by means of Complete Freund's Adjuvant, we have investigated whether or not the implantation of bone cement or Kirschner wires affects additionally the condition of the bone. We have found that bone cement or metallic material within the bone cavity aggravates osteolysis if there is an immunologic reaction present. The conditions of the immunologic mechanism and the applied orthopedic procedures are discussed and an attempt has been made to explain the phenomenon.

Animals↗

PubMed1979

The incidence of dipyrone-induced agranulocytosis in Greece during 1975.

A retrospective epidemiological study was conducted in Greece during 1975 to assess the incidence of agranulocytosis following treatment with dipyrone. Twenty-four cases of agranulocytosis were reported, of which fifteen were possibly associated with medication. If all fifteen cases are attributed to dipyrone, the incidence of agranulocytosis following treatment with this drug lies between one case in every 133,000 and one case in every 466,000 treatments.

Adult↗