Homocysteine increases cyclin-dependent kinase in aortic rat tissue.

BACKGROUND: Hyperhomocyst(e)inemia is strongly associated with occlusive arterial disease. A direct effect of homocysteine on the proliferation of smooth muscle cells was proposed recently. This observation led us to examine the effect of homocysteine on cyclin-dependent kinase, the starter of mitosis and reflecting proliferation. METHODS AND RESULTS: Seventy Him:OFA rats were divided into seven groups. For 12 weeks, 10 rats were fed homocysteine 25 mg/kg body weight per day, 10 were fed 50 mg/kg body wt per day, and 10 were fed 100 mg/kg body weight per day; 10 were given homocysteic acid 100 mg/kg body weight per day, 10 were administered cysteine 100 mg/kg body weight per day, and 10 were given ascorbic acid 270 mg/kg body weight per day. Ten remained untreated and served as controls. Aortic cyclin-dependent kinase was determined at the transcriptional (mRNA) and protein levels. Phosphokinase C and aortic homocyst(e)ine also were evaluated in aortic tissue. Aortic cyclin-dependent kinase protein was significantly (P = .0001) elevated in the three homocysteine-treated groups, and mRNA cyclin-dependent kinase levels were significantly elevated in the rats given the 50 and 100 mg/kg body weight per day protocol. Endothelial damage was shown at higher homocysteine doses as reflected by circulating ACE and von Willebrand factor changes. Proliferation of cells of the aortic wall by bromodeoxyuridine incorporation could be shown in the high-dose homocysteine group only. CONCLUSIONS: Our findings indicate that homocysteine specifically stimulates aortic cyclin-dependent kinase at the transcriptional level, with the possible consequence of proliferation of aortic cells as revealed by incorporation of bromodeoxyuridine in the aortic wall.

Decreased tumor incidence and increased survival by one year oral low dose arginine supplementation in the mouse.

The effects of arginine on tumor growth, antitumor mechanisms and a potential therapeutic role have been reviewed recently. In these studies, however controversial they were, high dose protocols for arginine treatment have been applied. Based upon own recent findings that low dose arginine stimulates the immune system and blocks lipid peroxidation, we performed preventive treatment with low dose (50 mg/kg body weight per day, orally administered) L-arginine in 150 mice for a period of one year. We compared survival and total number of tumors at the end of the feeding period to that found in 150 mice given taurine in the same dosage and in 150 mice without treatment. Survival of the arginine treated group was statistically significant as compared to that of the control group without treatment (p < 0.05): 116 mice were alive in the control group, 122 in the group administered taurine and 132 in the arginine treated group. The total number of tumors was significantly lower in the arginine treated group vs. the control group (p < 0.01). The total number of malign and benign tumors was significantly lower in the arginine treated group, whereas taurine significantly reduced the number of benign tumors only (p < 0.05). Arginine and taurine stimulate the immune system at the lymphocyte level. Arginine also acts at the macrophage level, inducing nitric oxide mediated cytotoxicity against tumor cells. Both compounds are known to block the formation of lipid peroxidation products. We therefore suggest that these two mechanisms are responsible for the decreased total number of tumors and the concomitant increase in survival.

Reduced tumour incidence in mice with inherited seborrhoeic dermatitis.

121 mice homozygous for the gene seb (inherited seborrhoeic dermatitis) and their 142 unaffected heterozygous littermates were kept for their natural lifespan. Heterozygotes showed 84.1% total tumour incidence in males and 95.9% in females. The most common neoplasms were lymphomas, osteomas, lung tumours and neoplasms of the female genital tract. Homozygotes showed a tumour incidence of 36.1% in males and 45.0% in females. The reduction in incidence included all types of neoplasms except epithelial tumours of the skin: skin tumours were detected in 11 homozygous but only in one heterozygous animal. Life expectancy was not affected significantly by genotype. Homozygous mice showed rough and greasy fur and became alopecic with age. Energy intake was increased but growth and depository fat was reduced compared with heterozygous mice. Higher heat loss may incompletely be compensated by higher metabolic rate and thus 'dietary restriction' results in decreased tumour rates. As females show small gonads and a higher increase in food consumption hormonal factors may also be involved.

Multiple osteomas in mice.

Osteomas (dense compact neoplasms of mature bone tissue) are rare in nearly all strains and stocks of mice. Of 224 Him:OF1 mice maintained until natural death or until terminally ill, 116 (51.8%) had one or more osteomas. Osteomas had a predilection for the skull and the larger bones of the limbs. Plasma alkaline phosphatase concentrations were elevated significantly in osteoma-bearing mice (446 +/- 153 U/liter versus 206 +/- 65 U/liter in age-matched controls without osteomas). Only very large osteomas resulted in clinical signs, and longevity was not shortened. Histologic examination showed clearly separated dense bony tissue irregularly arranged and forming a mosaic pattern, with distinct cement lines and medullary spaces filled with fibroreticular connective tissue. Electron microscopic examination revealed virus-like structures in osteoblasts, osteocytes, and fibroblasts and in the place of remnants of necrotic cells.

The effect of homocysteine thiolactone and its alpha methylated derivative on bone matrix in the mouse.

Homocysteine (HC) is a radiation protector but toxic to bone. Its derivative homocysteine thiolactone (HCTL) and the alpha-alkylated analogue (A-methyl-HCTL) was fed to mice for a period of six weeks in a daily dose of 50 mg/kg body weight. Parameters for bone matrix as collagen content, acid solubility of bone collagen, urinary bone collagen cross links (pyridinolines) and urinary acid glycosaminoglycans were determined. Urinary acid glycosaminoglycans were significantly reduced in the HCTL treated group but not in the alpha-methyl-homocysteine thiolactone (A-methyl-HCTL) group (controls: 45 ± 7 mg/mmol creatinine, homocysteine thiolactone 38 ± 5 mg/mmol creatinine, A-methyl HCTL 45 ± 6 mg/mmol creatinine).No differences were found for the parameters of bone collagen between the groups. The potent radiation protecting methylated derivative therefore did not change bone matrix and should be a candidate for further toxicological studies.

[The tumor spectrum of Him:OFA rats]. / Das Tumorspektrum von Him: OFA-Ratten.

The longevity and incidence of spontaneous tumors was investigated in 92 male and 182 female rats of the Sprague-Dawley (SD) derived stock Him: OFA. The overall tumour incidence was 85.9% in males and 97.8% in females with 32 different types of tumors in males and 30 in females. The most frequent neoplasms were mammary tumours in females with 84.6% incidence, followed in this sex by adrenal (36.8%), pituitary (32.9%) and thyroid neoplasms (10.9%). The incidence of all neoplasms in female genital tract was 12.6%. In male rats tumours of the adrenals have the highest incidence (53.2%, most of them cortical) followed by pituitary tumours (31.5%) and neoplasm of the mesenteric lymph nodes (14.1%, which is uncommonly high compared with other Sprague-Dawley stocks). All other tumours are below 10% incidence. The mean lifespan of females is with 719 +/- 142 d shorter than that of males with 752 +/- 108 d because of the high incidence of mammary tumours between 16 to 18 months of age.

Biological activity of alpha-alkyl-amino acids.

A series of alpha-alkyl-amino acids were tested for some biological functions in the mouse (OF-1 Himberg) by adding them to the animal chow (30 mg/kg/day) for a period of six weeks. No differences in fluid or food uptake could be observed during the feeding period, as compared to a control group. Histology of liver and kidney did not show any changes. Testing routine clinical chemical parameters (serum substrates and enzymes) revealed the following changes: Hex-Ala and But-Abu increased the serum glucose levels. But-Abu dramatically lowered the triglycerides. Serum albumin was increased by Pent-Ala, Me-Val, and But-Abu. LDH was inhibited by But-Abu.

Inherited seborrheic dermatitis--a new mutant in mice.

A new mutation, affecting skin and hair, occurred in an expansion colony of Him:OF1 mice. Test crosses showed that a single autosomal recessive gene was responsible for this trait. Homozygotes have sparse greasy fur and lower viability and fertility than normal littermates. Histological observations showed hypertrophy of sebaceous glands, hyperkeratosis, parakeratosis, acanthosis and signs of inflammation. The disease was named 'inherited seborrheic dermatitis' and the gene name seb is proposed.

[Effect of superoxide dismutase on an arthritis model in the rabbit. A scanning electron microscopy study]. / Einfluss von Superoxid-Dismutase (SOD) auf ein Arthrosemodell beim Kaninchen. Eine rasterelektronenmikroskopische Studie.

The effect of superoxide dismutase (SOD) was studied in an experimental arthrosis model (fixation arthrosis in rabbits). Out of a total of 40 animals, 20 of which were to be treated with SOD and 20 with placebos, 5 animals each were given padded stiffened bandages to immobilize their right knee joints for 1 week, 2 weeks, 3 weeks and 4 weeks respectively. After removing the bandage and a two-week recovery period the SOD or placebo treatment respectively was begun. During this period the animals were allowed to move freely. In 20 animals 0.5 mg SOD in 0.2 ml of a 0.5% xylocaine solution were applied intraarticularly in both popliteal spaces once a week for a total of 4 weeks. 20 control animals likewise received 0.2 ml of a 0.5% xylocaine solution (placebo) in both popliteal spaces in the same time intervals. After treatment the animals were killed and examined. A further 5 animals were not given a stiffened bandage, but for 4 weeks they received intraarticular injections once a week of 0.2 ml of a 0.9% saline to act as controls. The evaluation of the changes in the joints was by histological examination and examination by scanning electron microscope. In comparison to the placebo treatment the SOD treatment in this animal experiment did not lead to a significant change in the arthrotic process.

Induction of arthritic processes by synovial fluids of rheumatoid arthritis patients in long-term experiments with mice.

Diluted synovial fluids derived from three patients with rheumatoid arthritis (RA) and applied subcutaneously once as a single dose in Swiss mice caused arthritic processes after a long period of latency (10 months). The arthritis-inducing effect was enhanced by storing the original synovial fluids at 4 degrees C for three months. The effects were followed histologically for at least 18 months. In contrast to the theory that RA is based on immunological processes, these preliminary observations support the finding of other authors that a transmissible agent which is rather slow-acting exists in the synovial fluid of RA patients.

[Histologic studies of the effect of superoxide dismutase on an arthrosis model in rabbits]. / Histologische Untersuchungen über die Wirkung der Superoxid-Dismutase (SOD) an einem Arthrosemodell beim Kaninchen.

The effect of the enzyme superoxide dismutase (SOD) on experimentally induced osteoarthritis was investigated. Immobilization of the right knee of rabbits over variable periods (1-4 weeks) was used as the model for the study. SOD was applied intraarticularly. Distinct histological changes were detected in the immobilized joints in contrast to the freely mobile joints. In the group of rabbits treated with SOD, erosions, necroses, and inflammatory symptoms were more frequent than in the placebo group. The changes found in animals after SOD application indicate the enzyme has an intensifying effect on osteoarthritis.