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Biomedical subjects

T H Lippert

Publications and source records attributed to T H Lippert.

At least 73 records · Page 4Linked to original sources
PubMed1992

Eicosanoid production in human umbilical cord vessels: effect of 17 beta-estradiol.

This study was designed to investigate the effects of 17 beta-estradiol on prostanoid formation from exogenous arachidonic acid in homogenates of human umbilical cord vessels. The veins produced more prostanoids than the arteries and predominantly 6-keto-PGF1 alpha. 17 beta-estradiol had no effect on the rate of production of prostanoids in either vessels. Thus, at least in our in vitro system, the regulation of the vascular tone by prostanoids seems not to be altered by the addition of 17 beta-estradiol.

Arachidonic Acid↗
PubMed1992

[Production of prostacyclin in human umbilical cord blood vessels. Effect of natural and synthetic estrogen].

This investigation was conducted to evaluate the effects of 17 beta-estradiol and 17 alpha-ethinylestradiol on prostacyclin PGI2-production in homogenates of human umbilical cord arteries and veins in the presence of exogenous arachidonic acid. The incubation of 17 beta-estradiol at 2 different concentrations (10(-8) and 10(-6) M) in the presence of arachidonic acid for various times (5 min up to 24 h) effected an increase in the production of PGI2 (measured as 6-keto-prostaglandin F1 alpha) of 36-47% in the artery and 16-21% in the vein over basal values (100%). Under the same experimental conditions with 17 alpha-ethinylestradiol we observed an increases of 30-40% in the artery and 1-18% in the vein compared with basal values. For both estrogens this was not significantly different compared with untreated samples. In our in vitro system, natural and synthetic estrogens had no clear effect on PGI2 production in homogenates of human umbilical vessels.

6-Ketoprostaglandin F1 alpha↗
PubMed1991

Depression of serum melatonin in patients with primary breast cancer is not due to an increased peripheral metabolism.

Serum melatonin and its main metabolic product 6-sulfatoxymelatonin were determined in 17 patients with breast cancer (BC) with either a fresh primary tumor (nine) or a secondary tumor (eight) as well as in four patients with untreated benign breast disease (controls). Circadian rhythms were detected in all groups with acrophases around 2 AM for melatonin and around 3 AM for 6-sulfatoxymelatonin. The nocturnal melatonin and 6-sulfatoxymelatonin concentrations were significantly depressed in the group of patients with primary breast cancer compared with controls (P less than 0.01, P less than 0.025). The circadian amplitudes of melatonin and 6-sulfatoxymelatonin were also depressed by 81% (P less than 0.01) and 63% (P less than 0.01). In contrast, patients with secondary BC had nocturnal melatonin and 6-sulfatoxymelatonin concentrations and amplitudes similar to controls. These results demonstrate that the depression of circulating melatonin in patients with primary BC is not due to an enhanced degradation to 6-sulfatoxymelatonin in the liver but must be due to a reduced activity of the pineal gland.

Adult↗
PubMed1991

[Role of the pineal body in reproduction and in gynecologic tumors].

According to the current view, the main function of the pineal gland and its hormone melatonin is to convey information on environmental photoperiods to the endocrine, central nervous and immune systems, allowing their optimal adjustment to the time of the day and season. Within the endocrine system, the gonads are a major target; maturation of the female reproductive organs during pubertal development is inhibited by the pineal hormone. During the reproductive phase, melatonin seems to act as a coordinating signal for the menstrual cycle by timing the LH-peak and supporting progesterone production. A gradual decline of circulating melatonin with age suggests a role in age-associated endocrine changes, e.g. during menopause. Due to its important role in the female reproductive system, the pineal gland has been implicated in the aetiology of human breast cancer. Serum melatonin is depressed in patients with primary mammary cancer and experimental tumours are inhibited, a finding suggesting a therapeutic potential of melatonin. In addition, other potent antineoplastic substances exist in the pineal gland, which may become useful tools for future anti-cancer therapies.

Animals↗
PubMed1991

Distribution of immunoreactive relaxin in the genital tract and in the mammary gland of non-pregnant women.

Relaxin was determined in healthy and pathological tissue samples from mammary gland, ovary, myometrium and cervix uteri of non-pregnant women. Relaxin could be detected in all groups of tissues examined. The highest values were found in healthy ovary, the lowest concentrations in the cervix, which is known as a target organ for relaxin activity during pregnancy. Mammary parenchyma showed the highest specific activity of all healthy tissues examined. The relaxin concentration in myoma tissue is significantly higher than in healthy myometrium.

Breast↗
PubMed1990

Effect of the mammary carcinogen 7,12-dimethylbenz[a]anthracene on pineal melatonin biosynthesis, secretion and peripheral metabolism.

The aim of this study was to establish whether the nocturnal peak concentrations of circulating melatonin are affected by a single dose of 7,12-dimethylbenz[a]anthracene (DMBA) in female Sprague-Dawley rats as used for mammary tumor induction. Prior to this, the circadian rhythms of melatonin (N-acetyl-5-methoxytryptamine) and 6-sulfatoxymelatonin, the main metabolic product of melatonin, were determined in female Sprague-Dawley rats. The cosinor analysis revealed significant circadian rhythms with very similar acrophases around 1.00 a.m. for both substances. To enable explanations for possible changes in plasma melatonin after DMBA treatment, the biosynthesis in the pineal and the major metabolic product in the liver, 6-sulfatoxymelatonin, were measured 2 and 7 days after DMBA. Plasma melatonin was depressed by 31-37% (p less than 0.05) 2 and 7 days after DMBA but the pineal melatonin content remained unchanged. 2 days after DMBA, pineal serotonin and N-acetylserotonin showed a transient elevation of 35% (p less than 0.025) and 25% (p less than 0.05), respectively. The plasma concentrations of 6-sulfatoxymelatonin were the same in DMBA- and vehicle-treated animals. An elevation of the 6-sulfatoxymelatonin/melatonin ratio indicated a relative increase in the metabolism of melatonin due to DMBA. The absence of an absolute increase in 6-sulfatoxymelatonin after DMBA could be caused by an additional shift within the spectrum of different metabolic products of melatonin due to the carcinogen. Possible mechanisms are discussed.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Stage-dependent depression of melatonin in patients with primary breast cancer. Correlation with prolactin, thyroid stimulating hormone, and steroid receptors.

Serum melatonin was determined over 24 hours in 35 patients with breast cancer with either a fresh primary tumor (n = 23) or a secondary tumor (n = 12) and in 28 patients with untreated benign breast disease (controls) having a fibroadenoma (n = 10), fibrocystic mastopathy (n = 14), or other breast diseases (n = 4). Circadian rhythms existed in all groups with acrophases at 2 a.m. A 50% depression of peak and amplitude occurred in the group of patients with primary breast cancer compared with age-matched controls (P less than 0.001, P less than 0.01). The peak declined with increasing tumor size: 27% at Stage T1, 53% at T2 (P less than 0.001), and 73% at T3 (P less than 0.05). In contrast, patients with secondary breast cancer, particularly those receiving antiestrogen therapy, had a melatonin peak similar to controls. These results demonstrated a transient depression of pineal melatonin secretion in primary breast cancer and indicated a dynamic role of the pineal gland in malignancy. To investigate some endocrine effects of a depressed melatonin peak, the 24-hour rhythms of prolactin (PRL) and thyroid stimulating hormone (TSH) were determined in patients with primary breast cancer and compared with patients with secondary breast cancer. The PRL had significant circadian rhythms in both groups; but acrophases occurred at midnight in patients with secondary breast cancer, and there were unusually high concentrations at noon in patients with primary breast cancer. Circadian rhythms were not seen for TSH, but the 24-hour average secretion was depressed by 45% (P less than 0.01) in patients with primary breast cancer. The abnormal concentrations of PRL and TSH in these patients could be due to a depressed melatonin peak normally serving as a central circadian synchronizer and modulator of the secretion of adenohypophysial hormones. Additionally, a positive correlation existed between the nocturnal melatonin peak and progesterone and androgen receptor concentrations in primary tumors indicating a direct involvement of melatonin in the growth control of breast cancer.

Adult↗
PubMed1989

[The hormone profile in serum and cervix secretions in the course of a menstrual cycle].

Serum and cervico-vaginal secretion were examined for LH, E2, progesterone and relaxin content throughout a cycle. Estimations were carried out using radioimmunoassays. LH, E2 and progesterone were found in markedly lower concentrations in cervical-vaginal secretion than in serum. Relaxin was detected only in cervical-vaginal secretion with the exception of one serum sample.

Adult↗
PubMed1989

The action of oxytocin on sperm motility. In vitro experiments with bull spermatozoa.

The effect of oxytocin on sperm motility of bull spermatozoa was investigated over a period of 2.5 hours. Measurements were carried out with a Lazymot apparatus, depending on the Laser-Doppler principle. In a concentration of 10 IU/ml, oxytocin was found to significantly increase the percentage of motile spermatozoa and sperm velocity compared with saline controls.

Animals↗
PubMed1988

Immunoreactive relaxin in human cervico-vaginal secretion.

Relaxin was measured in cervico-vaginal secretion of non-pregnant women of reproductive age using the heterologous radioimmuno-assay for porcine relaxin. It was detected in about three-quarters of the samples collected. The mean value of the 529 samplers tested was 599 pg/ml. There was a slight trend to higher relaxin values during the second week of the menstrual cycle.

Adult↗
PubMed1988

Relaxin and human chorionic gonadotropin concentrations in blood serum during the first trimester of normal and pathological pregnancy.

Relaxin and human chorionic gonadotropin (HCG) were determined in the blood serum of women during normal and pathological pregnancy in the 1st trimester. In normal pregnancy, the hormones showed similar behavior in their secretion pattern up to the 7th week with continuously increasing concentrations. Thereafter different patterns in their secretion developed. In pathological pregnancy, both relaxin and HCG concentrations were significantly lower than in undisturbed pregnancy, following an almost parallel course without peaks.

Chorionic Gonadotropin↗