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Biomedical subjects

D D Varonos

Publications and source records attributed to D D Varonos.

33 records · Page 2Linked to original sources
PubMed1975

Serum alkaline phosphatase and urinary hydroxyproline values in children receiving phenobarbital with and without vitamin D.

Concentrations of serum alkaline phosphatase and total urinary hydroxyproline were measured in 36 children to study the effect of phenobarbital administration with respect to the development of rickets in patients receiving anticonvulsive medications over prolonged periods of time. Administration of phenobarbital led to the appearance of increased AP and HOP values very early in the course of treatment and without any obvious bone changes suggestive of rickets; a single large oral dose of vitamin D had no appreciable effects in restoring the biochemical derangement. On the other hand, the administration of vitamin D in a daily dose of 4,000 IU for a period of two months hampered the appearance, or restored already existing changes of latent rickets, in children receiving anticonvulsive medication. The results in the present study favor the concept that phenobarbital administration is implicated in the development of rickets. The need for simultaneous daily administration of supplements of vitamin D in subjects receiving anticonvulsive drugs is stressed.

Adolescent↗
PubMedDate not supplied

How harmless is FFA enhancement?

Standard heparin as well as low molecular weight heparin (LMWH) increase lipid levels in serum. It has been reported that a diet rich in long chain saturated fatty acids can enhance the susceptibility to experimental thrombosis. The mechanism by which serum fatty acids may provoke thrombosis is not clear. It is possible that the fatty acids change the properties of the cell membrane and thereby modify the response of platelets to aggregating agents. Heparin and its LMW fractions, by mobilising lipoprotein lipase that hydrolyses serum triglycerides (TG), cause the serum TG to increase, a well known "clearing effect' of heparin in turbid lipemic plasma. This effect may have no significance when it lasts for a short time; however, a long-lasting heparin effect on TG serum levels may have important consequences. The purpose of this study was to examine the time span of the action of heparin and its fractions and to investigate variations in the concentration of digoxin, which is a compound with narrow therapeutic width. The investigated substances after 2 days administration, provoked serum concentration increases of free fatty acids (FFA), TG and HDL-C. Seven days after stopping drug administration, FFA and HDL-C levels remained high, while triglycerides declined. Serum total cholesterol remained unchanged throughout. Digoxin levels increased non-significantly after heparin administration and during swimming stress, while a lipid diet caused a serum digoxin concentration increase.

Animals↗
PubMedDate not supplied

Does stress influence ampicillin concentration in serum and tissues?

Exercise produces changes of drug levels in plasma and increases the concentration of free fatty acids (FFAs), which may interfere with drug-protein binding. FFAs seem to play an antagonistic role to drugs since they have a strong binding capacity to serum albumin. The aim of this study was to evaluate the influence of the consecutive exercise-induced stress in ampicillin levels. Two groups of Wistar rats were used. Group A consisted of six subgroups that were subjected to cold swimming (4 degrees C) for 5, 10, 15, 20,25, 30 days respectively. Group B was the control group. The animals were injected im. with ampicillin (1 g/Kg/8h in 5 doses). Results showed that exercise enhanced stress parameters (FFAs, adrenal weight, Ht%) and led to an ampicillin increase in all experimental groups comparatively to controls.

Adrenal Glands↗
PubMedDate not supplied

Role of prostanoids and endothelins in the prevention of cyclosporine-induced nephrotoxicity.

Cyclosporine A nephrotoxicity includes both functional toxicity and histological changes, whose seriousness is dependent upon the dose and the duration of the drug administration. Several vasoactive agents have been found to be implicated in cyclosporine induced nephrotoxicity, among which prostanoids and endothelins are the most important. In previous studies we were able to prevent the early stage (7 days) of cyclosporine (37.4 micromol [45 mg]/kg/day) induced nephrotoxicity in rats either by the administration, i) of OKY-046, a thromboxane A(2)synthase inhibitor, ii) of ketanserine, an antagonist of S(2)serotonergic, a(1)adrenergic, and H(1)histaminergic receptors and iii) of nifedipine, a calcium channel blocker, or by diet supplementation either with evening primrose oil or fish oil. All these protective agents elevated ratios of excreted renal prostanoid vasodilators (prostaglandins E(2), 6ketoF(1 alpha)) to vasoconstrictor (thromboxane B(2)), a ratio which was decreased by the administration of cyclosporine alone. Nifedipine averted the cyclosporine induced increase of urinary endothelin-1 release. All protections were associated with the reinstatement of glomerular filtration rate forwards normal levels whereas renal damage defence, consisting of a decrease of the cyclosporine induced vacuolizations, was variable. Ketanserine and evening primrose oil were the only agents which prevented the animal body weight loss. These data suggest that prostanoids and endothelin-1 may mediate functional toxicity while thromboxane A(2)is involved the morphological changes too, provoked in the early stage of cyclosporine treatment. However, other nephrotoxic factors and additional mechanisms could also be implicated in the cyclosporine induced nephrotoxicity.

Animals↗
PubMedDate not supplied

[How does bone behave when an immunologic reaction (caused by administration of antigen) is induced a long time after metal implantation].

It has been ascertained that metal implantation in the femoral bone of rats with simultaneously induction of immunological reaction leads in all probability to intense bone damage. It is possible that the sum of all qualitative and quantitative haemodynamic and biochemical consequences from the bone injury (implantation) and the immunological reaction are responsible for this result. To investigate the above possibility, we carried out this study with a monthly delay of antigen administration after metal implantation. We found that: a) Bone alterations occur in approximately 50% of experimental animals which received antigen. b) These bone changes are shown radiologically as osteolysis of immunological reaction, respectically. c) These changes are of less intensity than those produced in simultaneous implantation and antigen administration, but of practical importance. d) None of the control animals (without antigen administration) showed any radiologically visible bone alteration. We discuss the clinical usefulness of these results.

Animals↗