Role of Lys-110 of human NADH-cytochrome b5 reductase in NADH binding as probed by site-directed mutagenesis

Lys-110 of human NADH-cytochrome b5 reductase was replaced by Ala, Met, or Arg by site-directed mutagenesis to evaluate the role of the residue. Km values of purified Lys-110-->Ala and Lys-110-->Met mutants for NADH were approximately 200-fold and 1,100-fold higher than that of the wild-type, respectively, while the value of the Arg mutant was almost the same as that of the wild-type. These results indicate that the positive charge at position 110 is important for NADH binding. The kcat value of Lys-110-->Ala was not affected, indicating that the residue only participates in the binding process in the reaction by forming an ionic interaction with phosphoryl group of NADH.

Fixed drug eruption due to allylisopropylacetylurea

We report a case of fixed drug eruption due to allylisopropylacetylurea. A 21-year-old female developed purplish-red round eruptions on her neck and left thigh after taking an analgesic containing isopropylantipyrine, allylisopropylacetylurea, phenacetin and anhydrous caffeine. Patch testing with the analgesic and its ingredients on the eruptive area showed positive reactions to the analgesic and allylisopropylacetylurea, while patch testing on the non-eruptive area showed negative reactions. We diagnosed her condition as a fixed drug eruption due to allylisopropylacetylurea in an analgesic.

Endogenous erythropoietin and salt sensitivity of blood pressure in patients with essential hypertension

To investigate a possible involvement of endogenous erythropoietin (EPO) in the salt sensitivity of blood pressure in essential hypertensive (EHT) patients, plasma EPO concentrations were measured during different salt intakes in 14 patients with EHT. All patients were given low salt (34 mmol NaCl/day) and high salt (342 mmol NaCl/day) diet of 7 days each. The plasma EPO concentrations were significantly higher on the high salt diet than those of low salt diet (23.5 +/- 1.9 v 18.7 +/- 1.8 mIU/ml, mean +/- SD, P < .05). The percentage change of plasma EPO concentration with salt loading correlated positively with hematocrit (Ht) at high salt diet (r = -0.62, P < .02) and tended to be correlated with plasma hemoglobin at high salt diet (r = 0.52, P < .10). These results suggest that the secretion of EPO is increased in response to hemodilution caused by the salt loading and the increased EPO concentration in plasma which may contribute to the increase in blood pressure through an expansion of total blood volume due to an enhanced red cell generation in combination with salt and water retentions.

Renal hypouricemia due to enhanced tubular secretion of urate associated with urolithiasis: successful treatment of urolithiasis by alkalization of urine K+, Na(+)-citrate

We encountered a case of hypouricemia with increases both in urate clearance (Cur) and in the ratio of Cur to creatinine clearance (Cur/Ccr), the normal daily urinary excretion of urate, and urolithiasis. Pyrazinamide markedly decreased Cur and Cur/Ccr, and both probenecid and benzbromarone markedly increased Cur and Cur/Ccr, however, benzbromarone did not increase either Cur or Cur/Ccr under pretreatment with pyrazinamide in the patient. Thus, the diagnosis was made of renal hypouricemia due to enhanced tubular secretion of urate. The urinary pH of the patient tended to be acidic. Three months after the start of alkalization of the patient's urine by K+, Na(+)-citrate, both urolithiasis and the symptoms related to urolithiasis disappeared. These results suggest that renal hypouricemia due to enhanced tubular secretion of urate can result in urolithiasis and the alkalization of urine may be an effective treatment for uric acid stones.

Pathogenesis of autoimmune hypothyroidism induced by lymphokine-activated killer (LAK) cell therapy: in vitro inhibition of human thyroid function by interleukin-2 in the presence of autologous intrathyroidal lymphocytes

Lymphokine-activated killer (LAK) cell therapy frequently results in primary hypothyroidism. To elucidate the responsible mechanism, we investigated the effects of interleukin-2 (IL-2) on thyroid function of cultured human thyroid follicles in the presence or absence of autologous thyroid-derived lymphoid cells (TDLC). Human thyroid follicles, obtained by subtotal thyroidectomy from patients with Graves' disease, were cultured in serum-free medium containing bTSH and various concentrations of human IL-2, with or without TDLC. After 5 days of culture, 125I was added, and after an additional 3 days of culture, 125I incorporated into thyroid follicles and organic 125I (125I-T4 + 125I-T3) released into the culture medium were estimated. In the absence of TDLC, IL-2 did not affect bTSH-induced thyroid function. In the presence of TDLC, however, IL-2 inhibited the bTSH-stimulated thyroid function in a concentration-dependent manner. The minimum IL-2 concentration required to inhibit thyroid function was 1 U/ml. At 100 U/ml, IL-2 inhibited thyroid function completely. IL-2 increased the concentration of IFN-gamma in the culture medium conditioned by TDLC but not by thyroid follicles. When both were cocultured, IL-2 more significantly increased the concentration of IFN-gamma to an extent sufficient for inhibiting thyroid function per se. Furthermore, the addition of anti-IFN-gamma antibody to the medium partially restored the IL-2-inhibited thyroid function. In summary, by coculturing human thyroid follicles and autologous intrathyroidal lymphocytes with IL-2, it was possible to reproduce the thyroid dysfunction associated with LAK cell therapy. Our data indicate that IL-2 inhibits thyroid function, at least partly, by stimulating production of IFN-gamma, a potent inhibitory cytokine for thyroid cells.

Spontaneous rupture of splenic angiosarcoma: a case report of chemotherapeutic approach and review of the literature

Angiosarcoma of the spleen is a rare disease, and the prognosis of this disease is extremely unfavorable. We herein review the case of a 45-year-old Japanese woman, who received a combined chemotherapy with cyclophosphamide, Adriamycin, vincristine, and prednisone after splenectomy and experienced a good response. The various types of chemotherapy for this disease are also discussed with references to the above case because no effective chemotherapeutic protocol for angiosarcomas has yet to be established.

Peculiar nuclear clearing composed of microfilaments in papillary carcinoma of the thyroid

BACKGROUND

Papillary carcinoma of the thyroid frequently occurs in young women. Four cases of papillary carcinoma were found in women in their 20s, and the disease was characterized by unusual morphologic and clinical features.

METHODS

Four cases were analyzed clinically, grossly, microscopically, ultrastructurally, and immunohistochemically and compared with control cases of papillary carcinoma.

RESULTS

The tumors histologically showed various appearances with trabecular, solid cribriform, follicular, and papillary patterns. A striking finding was that stratified cancer cell nests with prominent nuclear clearings were scattered in the tumors. Ultrastructurally, the nuclear clearings were composed of fine thread-like fibrils, and they were bound unselectively to various antibodies against hormones and intermediate filaments. The four patients also had common clinicopathologic features as follows: they were all women in their 20s and their preoperative serum thyroglobulin levels were all normal despite the large size of their thyroid tumors. The tumors were grossly well encapsulated, and there was no lymph node metastasis, except in one patient who had only one positive node.

CONCLUSIONS

The peculiar nuclear features were distinct from intranuclear cytoplasmic inclusions or ground-glass nuclei, and these have not been reported previously to the authors' knowledge in conventional thyroid neoplasms. These tumors might represent another subtype of papillary thyroid carcinoma.

Effects of fatty acyl-coenzyme A esters on prostaglandin synthesis in rabbit kidney medulla microsomes

The effects of fatty acyl-coenzyme A (CoA) esters (palmitoyl-, stearoyl-, oleoyl-, linoleoyl- and arachidonoyl-CoA) on the synthesis of prostaglandins (PGs) in rabbit kidney medulla microsomes were examined. Medulla microsomes were incubated with arachidonic acid in 0.1 M-Tris/HCl buffer (pH 8.0) containing reduced glutathione and hydroquinone and the formed PGE2, PGF2 alpha and PGD2 were measured by high-pressure liquid chromatography using 9-anthryldiazomethane for derivatization. Under our incubation conditions rabbit kidney medulla was found to produce PGE2 mainly. The addition of fatty acyl-CoA esters inhibited total PG formation (the sum of PGE2, PGF2 alpha and PGD2) in a dose-dependent manner. Palmitoyl-, stearoyl- and oleoyl-CoA were about 10 times more potent than linoleoyl- and arachidonoyl-CoA as inhibitors of total PG formation. Linoleic acid was slightly more effective than linoleoyl-CoA, while palmitic acid had no influence on PG formation. All the fatty acyl-CoA esters inhibited the formation of PGE2. Simultaneously, the production of PGF2 alpha and PGD2 was increased. These results suggest that the CoA derivatives of palmitic, stearic and oleic acids have the potential to modulate PGE2, PGF2 alpha and PGD2 synthesis by affecting the activities of both-cyclooxygenase and endoperoxide E2 isomerase.

Effect of tert-butyl hydroperoxide on cyclooxygenase and lipoxygenase metabolism of arachidonic acid in rabbit platelets

The effect of tert-butyl hydroperoxide (t-BOOH) on the formation of thromboxane (TX) B2, 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT) and 12-hydroxy-5,8,10,14-eicosatetraenoic acid (12-HETE) from exogenous arachidonic acid (AA) in washed rabbit platelets was examined. t-BOOH enhanced TXB2 and HHT formation at concentrations of 8 microM and below, and at 50 microM it inhibited the formation, suggesting that platelet cyclooxygenase activity can be enhanced or inhibited by t-BOOH depending on the concentration. t-BOOH inhibited 12-HETE production in a dose-dependent manner. When the platelets were incubated with 12-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12-HPETE) instead of AA, t-BOOH failed to inhibit the conversion of 12-HPETE to 12-HETE, indicating that the inhibition of 12-HETE formation by t-BOOH occurs at the lipoxygenase step. Studies utilizing indomethacin (a selective cyclooxygenase inhibitor) and desferrioxamine (an iron-chelating agent) revealed that the inhibitory effect of t-BOOH on the lipoxygenase is not mediated through the activation of the cyclooxygenase and that this effect of t-BOOH is due to the hydroperoxy moiety. These results suggest that hydroperoxides play an important role in the control of platelet cyclooxygenase and lipoxygenase activities.

Risk factors associated with postoperative persistent hypertension in patients with primary aldosteronism

BACKGROUND

Unilateral adrenalectomy was performed in 63 patients with primary aldosteronism. During a mean follow-up time of 4.1 years, none of the patients showed recurrence of hyperaldosteronism. However, 24 patients (38%) had persistent hypertension. The purpose of this study was to determine factors responsible for postoperative persistent hypertension.

METHODS

A stepwise multivariate logistic regression analysis was performed to assess the combined predictive effects of the clinicopathologic variables.

RESULTS

Age, sex, and pathologic findings were the best predictive factors of postoperative persistent hypertension. For a patient aged 50 years or more, the odds of persisting hypertension are 10.6:1, compared with those of a patient under 40 years of age. A male patient appears to have a greater chance of hypertension than a female patient; the odds ratio is 5.9:1. Persistent hypertension develops in patients with multiple adenomas or with an adenoma associated with macronodules more frequently than in those patients with a solitary adenoma; the odds ratio is 8.1.

CONCLUSIONS

This study suggests that early surgical intervention at a younger age results in a more favorable outcome for patients with primary aldosteronism. The presence of macronodules in association with an adenoma is a cautious predictor of persistent hypertension after adrenalectomy.

[Recent progress in endocrine surgery: more refined and rational interventions for varied endocrine diseases]

Better understanding of pathogenesis and natural history of various endocrine diseases along with development of new and sensitive assays for accurate measurement of hormones and of modern image diagnostic procedures for clear demonstration of pathological tissues has enabled us to detect many kinds of endocrine diseases much more frequently than before and to perform a more refined and rational surgical intervention. Endocrine surgery is now a challenging and fascinating field of general surgery. This fact is best exemplified as follows: (1) different therapeutic approaches for intrathyroidal and extrathyroidal papillary carcinomas of the thyroid, (2) early detection and 131I treatment of clinically occult hematogenous metastasis of follicular carcinoma of the thyroid, (3) clinical usefulness of the serum calcitonin and CEA concentrations as sensitive tumor markers in the treatment of medullary thyroid carcinoma, (4) rational use of preoperative localization test and unilateral neck exploration for parathyroid adenoma, and specific surgical intervention for metastatic parathyroid carcinoma, (5) how to treat adrenal incidentalomas and a trial of subclassification of pheochromocytomas into epinephrine- and norepinephrine-secreting tumors, and (6) intraoperative localization of insulinoma by ultrasound and newly developed surgical approaches for gestrinoma.

[Mechanism to induce scoliosis in Duchenne muscular dystrophy--a study of paraspinal muscle by X-ray computed tomography]

We studied mechanism to induce scoliosis in Duchenne muscular dystrophy (DMD) by use of X-ray computed tomography (CT) of paraspinal muscles. CT examination of paraspinal muscles was performed on 15 DMD patients at the following six levels; 1. Th3 vertebrae (upper thoracic spine level) 2. Th6 vertebrate (middle thoracic spine level) 3. Th10 vertebrae (lower thoracic spine level) 4. L1 vertebrae (upper lumbar spine level) 5. L3 vertebrae (middle lumbar spine level) 6. L5 vertebrae (lower lumbar spine level). We evaluated the degeneration of paraspinal muscle by a decrease in radio-density of the muscle which indicates infiltration of fatty tissue. The degeneration of the lateral portion of paraspinal muscle was more marked than that of the medial portion. The muscle was most severely affected at the middle lumbar spine level, showing a tendency to increase degeneration at the lower level of the spine. In cases showing laterality of the degeneration of paraspinal muscle, the less affected muscle on CT was located at the convex site of scoliosis. We speculate that the scoliosis occurs when DMD patients have asymmetrical paraspinal muscle degeneration, leading them to take compensatory posture.

[A caruncular oxyphilic adenoma with an appearance of apocrine type secretion]

The histopathological and cytological findings of a caruncular oxyphilic adenoma (oncocytoma) in a 85 year-old male is described. The columnar or polygonal tumor cells contained numerous eosinophilic fine granules (mitochondria). They showed papillary proliferation and cyst formation. Electron microscopically, some tumor cells contained amorphous cytoplasm and small numbers of mitochondria in their apical snout, and secreted the contents in the extracellular spaces. It seemed that the tumor cells originated from the ductal epithelia in the caruncle and microscopically some cells simulated apocrine type secretion.

[A new method of gait analysis in Duchenne muscular dystrophy]

We assessed gait in Duchenne muscular dystrophy (DMD) mainly by determining alteration of foot pressure using a new gait analyzing procedure. DMD patients showed a characteristic foot pressure pattern according to their degree of dysfunction. In stage I disease, the observed pattern was the same as that of normal controls. In stage II, the period during which the center of foot pressure was seen in the front part of the foot was prolonged. This change became more marked in stage III. In stage IV, the center of foot pressure began at the head of the ossis metatarsalis primi and moved back and toward the lateral side. Thereafter, the center of foot pressure again moved forward along the outside of the foot. These changes were considered to be the result of talipes equinus and waddling gait, which are commonly demonstrated in patients with DMD.

Analysis of thyroid carcinoma based on material registered in Japan during 1977-1986 with special reference to predominance of papillary type

BACKGROUND

As geographic differences have been observed in the characteristics of thyroid carcinoma, an analysis was made on thyroid carcinoma in the iodine rich country of Japan.

METHODS

A total of 10,973 patients with histologically confirmed thyroid carcinoma registered in Japan from 1977-1986 were analyzed. Cases detected incidentally at autopsy and cases of nonepithelial tumor were excluded. This series included approximately 27% of all thyroid carcinoma cases in Japan.

RESULTS AND CONCLUSIONS

Histologic distribution showed that papillary carcinoma accounted for 78.4% of cases, follicular carcinoma accounted for 17.2%, medullary carcinoma for 1.4%, squamous cell carcinoma for 0.3%, and anaplastic carcinoma for 2.7%. There is a tendency in Japan to diagnose papillary carcinoma as follicular carcinoma and to diagnose malignant lymphoma as anaplastic carcinoma. It was considered that the percentage of papillary carcinoma was higher and the percentage of follicular carcinoma and anaplastic carcinoma was lower than foregoing values. The characteristics of thyroid carcinoma in Japan were described, and the low incidence of nonpapillary carcinoma compared with papillary carcinoma was discussed in relation to iodine excess as an etiologic factor.

Acidic tripeptidyl aminopeptidase in rat liver tritosomes: partial purification and determination of its primary substrate specificity

We have found the enrichment in rat liver tritosomes of an enzyme which hydrolyzed the synthetic substrate, Ala-Ala-Phe-pNA, under acidic conditions. The enzyme cleaved the substrate in an exopeptidolytic manner, releasing Ala-Ala-Phe. The enzyme was solubilized from tritosomes and partially purified. Beside Ala-Ala-Phe-pNA, the obtained enzyme was shown to cleave angiotensin III (Arg-Val-Tyr-Ile-His-Pro-Phe) and des-1Tyr-dynorphin A 1-8 (Gly-Gly-Phe-Leu-Arg-Arg-Ile) with tripeptide units. The results obtained suggested that the enzyme preferred an aromatic amino acid at the third position of a substrate peptide.

Effect of 22R-hydroxycholesterol on the action of sphingomyelinase from Bacillus cereus toward bovine erythrocytes

The incorporation of 22R-hydroxycholesterol [(22R)-5-cholestene-3 beta,22-diol] into the bovine erythrocyte membranes remarkably enhanced the degradation of sphingomyelin in erythrocyte membranes by the action of sphingomyelinase from Bacillus cereus, causing much faster hemolysis of erythrocytes. The stimulative effect of 22R-hydroxycholesterol on the breakdown of sphingomyelin was maximal in the presence of Mg2+. On the other hand, in spite of the presence of 22R-hydroxycholesterol, the breakdown of sphingomyelin was inhibited by increasing concentrations of Ca2+. Also, the incorporation of 22R-hydroxycholesterol into the erythrocyte membranes facilitated the specific adsorption of the enzyme onto the surface of the erythrocyte membranes. The specific adsorption of sphingomyelinase amounted to 20-40% of the total activity in the presence of Mg2+ and the absence of divalent metal ions. In the presence of Ca2+, the incorporation of 22R-hydroxycholesterol enhanced the enzyme adsorption, exceeding more than 90% of the total activity. Therefore, the incorporation of 22R-hydroxycholesterol into bovine erythrocyte membranes remarkably accelerates the breakdown of sphingomyelin in the presence of Mg2+, and the specific adsorption of sphingomyelinase onto erythrocytes in the presence of Ca2+.

The effects of xanthoangelol E on arachidonic acid metabolism in the gastric antral mucosa and platelet of the rabbit

The effects of a new chalcone derivative, xanthoangelol E, isolated from Angelica keiskei Koidzumi, on arachidonic acid metabolism in the gastric antral mucosa and platelet of the rabbit were examined. When gastric antral mucosal slices were incubated with xanthoangelol E (0.05-1.0 mM), there was no significant effect on the production of prostaglandin (PG) E2, PGF2 alpha and their metabolites. On the other hand, this compound inhibited effectively the production of thromboxane B2 and 12-hydroxy-5,8,10-heptadecatrienoic acid from exogenous arachidonic acid in platelets, and the concentration required for 50% inhibition (IC50) was approximately 5 microM. The formation of 12-hydroxy-5,8,10,14-eicosatetraenoic acid was also reduced by this drug (IC50, 50 microM). These results suggest that xanthoangelol E has the potential to modulate arachidonic acid metabolism in platelets and that this action may participate in some pharmacological effect of the plant.

The effects of arachidonic acid and its CoA ester on the catabolism of prostaglandin E2 in rabbit kidney cortex

The effects of arachidonic acid and arachidonoyl CoA on the catabolism of prostaglandin E2 in a 105000 x g supernatant fraction from rabbit kidney cortex were examined. Arachidonic acid reduced the 15-hydroxy prostaglandin dehydrogenase activity by 50% at 20 microM, while arachidonoyl CoA showed weak inhibition for the enzyme activity (15% at 20 microM). However, arachidonoyl CoA strongly inhibited the prostaglandin delta 13 reductase activity, the concentration required for 50% inhibition being about 3 microM. The dehydrogenase inhibition by arachidonic acid was non-competitive with regard to NAD+ and prostaglandin E2, respectively. Arachidonoyl CoA was also a non-competitive inhibitor for the reductase with regard to NADH and 15-keto prostaglandin E2, respectively. These results suggest that arachidonic acid and arachidonoyl CoA can be important modulating factors in prostaglandin catabolism by the kidney cortex.

Retrospective analysis of prognostic factors affecting the thyroid functional status after subtotal thyroidectomy for Graves' disease

To determine the factors causing thyroid dysfunction after surgery for Graves' disease, we studied 321 patients who underwent subtotal thyroidectomy during the 7-year period from 1981 to 1987. Thyroid functional status was evaluated biochemically and the patients were divided into four categories: recurrent hyperthyroidism, euthyroidism, latent hypothyroidism, and hypothyroidism. The following factors were analyzed: sex, age at onset of the disease, indication for surgery, serum titer of antimicrosomal hemagglutination antibody (MCHA), weight of resected thyroid tissue, size of remnant thyroid relative to body surface area, pathological findings of lymphoid follicles, and lymphocytic infiltration in the thyroid tissue. Probabilities of failure (recurrent hyperthyroidism and hypothyroidism) were estimated by the Kaplan-Meier method. Prognostic factors for failure were identified by using Cox's proportional hazards model. The incidence of hyperthyroidism and hypothyroidism 5 years after subtotal thyroidectomy was 16.2% and 9.6%, respectively. Significant factors for hyperthyroidism were relatively large thyroid remnant, high serum titer of MCHA (greater than or equal to 1:3200), and age at onset of the disease less than 20 years. The significant factor for hypothyroidism was severe lymphocytic infiltration. The level of postoperative thyroid stimulating hormone (TSH)-binding inhibition immunoglobulins (TBII) in patients with recurrence was significantly higher than in patients in remission. It is reasonable to determine the amount of remnant thyroid tissue in relation to patient body surface area. Although subtotal thyroidectomy can induce immunological remission by reduction of antigen, if the remission disappears, that is if TBII increases, recurrence of hyperthyroidism may develop even in patients without the unfavorable factors.

The role of epinephrine, norepinephrine, and dopamine in blood pressure disturbances in patients with pheochromocytoma

Fifty-six patients with pheochromocytoma underwent surgery during the 9-year period from 1981 to 1990. These patients were divided into two groups according to whether the dominant plasma concentration was of epinephrine or norepinephrine. Plasma levels of the catecholamines were stratified into three grades at 5 and 10 times the normal upper limit. Pre-operative disturbances of blood pressure, sustained or paroxysmal, and normal blood pressure were highly correlated with the dominantly secreted catecholamine and its plasma concentration. Thirteen patients with high plasma norepinephrine levels (greater than or equal to 10 times normal) had sustained hypertension while 18 patients with moderate to high plasma epinephrine levels (greater than or equal to 5 times normal) had paroxysmal hypertension. In the majority of normotensive patients (12 of 14), plasma catecholamine levels were less than 10 times the upper normal limit. Urinary excretion of dopamine and size of the tumor were analyzed according to these patient groups. In the norepinephrine dominant group, urinary dopamine excretion tended to be proportional to the plasma epinephrine levels and when the patients were normotensive, urinary dopamine excretion decreased. In norepinephrine-secreting patients, urinary dopamine tended to be inversely correlated with the plasma norepinephrine level; however dopamine did not prevent the hypertensive action of norepinephrine. Tumor size showed no correlation with the plasma levels of catecholamine in the moderate to high plasma catecholamine groups. We conclude that the plasma catecholamine type and its level are the most important factors in determining the patterns of blood pressure disturbances of patients with pheochromocytoma.

Neurotransmitter release from synaptotagmin-deficient clonal variants of PC12 cells

Synaptotagmin (p65) is an abundant synaptic vesicle protein of neurons and contains regions similar to the regulatory domain of protein kinase C. These domains are thought to be involved in calcium-dependent interaction with membrane phospholipids during exocytosis. To assess the functional role of synaptotagmin, synaptotagmin-deficient clonal variants of PC12 cells were isolated. All of the variant cells released catecholamine and adenosine triphosphate in response to elevated intracellular concentrations of calcium, which suggests that synaptotagmin is not essential for secretion of catecholamine and adenosine triphosphate from PC12 cells.

Antenatal diagnosis of fetal abnormality by ultrasonic real time scanner

Recent progress in antenatal diagnosis has made it possible to detect most fetal malformations which can be treated and cured by neonatal surgery. In this study an analysis of antenatal diagnosis by ultrasonography in the author's clinic is reported.

[Formation and removal of active oxygen species and lipid peroxides in biological systems]

The mechanisms of formation and removal of active oxygen species and lipid peroxides in biological systems have been briefly reviewed. Cytotoxic active oxygen species can be classified into two types: (a) radical species such as O2-. (superoxide) and HO. (hydroxyl radical) and (b) non-radical species such as H2O2 (hydrogen peroxide) and 1O2 (singlet oxygen). The direct or indirect attack of active oxygen species on polyunsaturated fatty acids, essential constituents of biological membranes, has been shown to result in the formation of a number of peroxidative lipid breakdown-products: LOOH (lipid hydroperoxide), LOO. (lipid peroxyl radical) and LO. (lipid alkoxyl radical). The lipid peroxide decomposition is probably dependent on the presence of ferric-ferrous ions. These processes are called lipid peroxidation reactions. In recent years, there has been a renewed interest in the role played by lipid peroxidation in many disease states. The multiple lines of defense against toxic oxygen intermediates consist of enzymatic systems, glutathione peroxidase, catalase and superoxide dismutase, and furthermore involves antioxidant capacities such as those of vitamin E and vitamin C. In biological systems, there are naturally occurring lipid-soluble (vitamin E and ubiquinone) and water-soluble (vitamin C, reduced glutathione and uric acid) antioxidants. Therefore, so long as homeostasis is maintained between the rate of radical generation and the rate of radical dissipation, the cellular generation of radicals may not be harmful. In contrast, this balance can be disturbed if cellular defenses are decreased or if there is a significant increase in the flux of radical generation. Once lipid peroxidation is initiated, the reactive intermediate formed induces cell damage.(ABSTRACT TRUNCATED AT 250 WORDS)