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Biomedical subjects

M Maki

Publications and source records attributed to M Maki.

At least 199 records · Page 11Linked to original sources
PubMed1987

Structure and physiological actions of rat atrial natriuretic factor.

Natriuretic substances were purified from rat atrium (atrial natriuretic factor, ANF) and were shown to be identical with the inhibitor of norepinephrine-induced contraction of smooth muscle. Four native forms were isolated and their amino acid sequences were determined. The presence of a high-molecular-weight prohormone was shown. Complementary DNA (cDNA) encoding for the precursor was cloned and used to deduce the amino acid sequence of the prohormone. Genomic DNA for ANF was cloned and two introns were found. Several ANF peptides were synthesized. Structure-function studies showed that the ring structure was essential for the activity. Antibodies produced against the synthetic 25-amino acid residue ANF were used to develop a radioimmunoassay. The presence of ANF in rat plasma demonstrated that ANF is a circulating hormone. ANF was also found in the hypothalamus of rats. The ANF in plasma was found to be a low-molecular form, whereas that in atria and hypothalamus consisted of both the high-molecular-weight precursor and low-molecular-weight active ANF. The presence of messenger RNA for ANF was determined using ANF cDNA as a probe and was considered as evidence for ANF synthesis in the brain, atrium, and ventricles. ANF was shown to be released from the brain. ANF administered intracerebroventricularly was shown to inhibit angiotensin II and thirst-induced dipsogenesis. In vitro and in vivo experiments showed ANF inhibits release of vasopressin from posterior pituitary and renin from the kidneys. The hypotensive effect of ANF was examined at various doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1987

Formation of polycystic ovary in mature rats by the long-term administration of human chorionic gonadotropin.

The critical role of high level of serum LH in polycystic ovary syndrome was evaluated in rats by the long-term administration of hCG. Wistar-Imamichi strain mature female rats (age; 12 weeks) which showed at least two consecutive estrous cycles in vaginal smears were daily injected 10 IU hCG subcutaneously from diestrus for 80 days. Control rats were received saline solutions. On the next day after the last administration the rats were killed, and serum hormone levels and histological changes in the ovaries were examined. In 8 of 11 control rats the vaginal smears showed the regular estrous cycles (group 1) during the experimental period. None of the controls exhibited polycystic ovaries. In 19 of 25 experimented rats there were old corpora lutea and degenerated follicles (group 2). The remained animals (n = 6; group 3) showed polycystic ovaries and no corpora lutea except one. HCG treatment elevated the serum prolactin and estradiol levels in group 3, but reduced the progesterone level. Thus, it was suggested that the hCG-induced formation of PCO in rats might be able to refer to the pathogenesis in polycystic ovary syndrome.

Animals↗
PubMed1987

[Correlation between disaturated phosphatidylcholine in amniotic fluid and fetal lung maturation].

The concentrations of disaturated phosphatidylcholine (DSPC), the major component of pulmonary surfactant, were quantified on 528 amniotic fluid samples, which did not show the contamination of blood or meconium and were uncomplicated by polyhydramnios or severe congenital anomalies incompatible with life. 396 samples of amniotic fluid (29 RDS cases) obtained 72 hours before delivery were used to evaluate the reliability of DSPC as a specific indicator in pedicting fetal lung maturation. DSPCs were determined according to the method described by Mason et al. and lecithin/sphingomyelin (L/S) ratios were measured by using two dimensional thin-layer chromatography. The critical points of DSPC and L/S ratio were defined as 1.0mg/dl, 2.0 respectively. The results are as follows. There was a gradual increase in DSPC levels of amniotic fluid with increasing maturity until 35 weeks of gestational age and a rapid rise from 36 weeks to term. About 70% of the amniotic fluids having a significantly higher DSPC level greater than or equal to 5.0mg/dl within 35 weeks of gestation were found to be obtained from pregnant women whose pregnancy was complicated by PROM, threatened premature labor or cervical incompetency and who eventually underwent preterm labor. Out of 58 samples, in which DSPC and the L/S ratio were measured simultaneously, two markers agreed in 47 cases in an immature or a mature value for predicting fetal lung maturation. RDS was correctly predicted in 27 of 60 cases (false negative, 55.0%) with DSPC levels less than 1.0mg/dl. When DSPC levels were 1.0mg/dl or more, there were only two of 336 (0.6%), false positives.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed1987

The mechanism of hormonal receptor regulation in the rat ovary following administration of gonadotropin and prolactin.

In order to understand the role of hormonal receptors in patients with hyperprolactinemia, changes in the ovarian receptors for prolactin and LH and in the serum hormone levels were studied in mature female rats. Wistar-Imamichi strain rats were pretreated with ovine prolactin (oPRL; 1IU), hCG (10IU) or hMG (20IU) for 4 days and oPRL, hCG, oPRL plus hCG for 8 days. The ovarian LH receptor levels fell significantly in rats stimulated with hCG, oPRL or hCG plus oPRL for 4 or 8 days. The serum estradiol level rose with hCG, and fell with oPRL. Combined treatment with oPRL and hCG synergistically reduced LH receptor to below the control level, and the estradiol level near the control compared with that by hCG alone. A decrease in LH receptor (60%) after the 4-day treatment with oPRL was further lowered to 53% of the control level after the 8 day treatment. Prolactin receptor levels rose with hCG after the 4-day administration, and then returned to normal after the 8-day treatment. The hMG treatment for 4 days raised the serum estradiol and progesterone levels to 9 times and twice those of the controls, respectively, without changing ovarian receptor levels. Prolactin seems to lower the ovarian LH receptor levels under certain conditions, and this may be one of the causes of the refractory reaction to gonadotropin therapy in patients with hyperprolactinemia.

Animals↗
PubMed1987

[Gap junction formation in the myometrial muscle cells of ovariectomized mid-pregnant rats during premature labor induced by estradiol].

In order to obtain a better understanding of gap junction (GJ) formation in the myometrial muscle cells of rats during the time of premature delivery, the myometrial GJs and nuclear estradiol receptor (nE2R) levels, as well as serum estradiol (E2) and progesterone (P) levels were simultaneously determined in mid-pregnant ovariectomized (OVX) rats both with and without E2 administration. Artificial premature deliveries were not induced in either the rats which were OVX on day 15 of gestation with the E2 treatment, or which were OVX on day 16 with the vehicle treatment. However, there were significant decreases in serum P and significant increases in the number of myometrial GIs in these rats compared to the levels of the non-OVX pregnant rats treated with the vehicle. These results suggest that serum P withdrawal and GJ formation are not sufficient to induce premature delivery, and that other factors are involved. Artificial premature delivery was induced in the rats which were OVX on day 16 with the E2 treatment. They were given 2.5 micrograms E2 twice daily, for two days. A significant decrease in serum P, a marked increase in the number of GJ and a significant correlation between the myometrial GJs and serum E2 levels were found in both the "premature" delivery rats and the "prior to" delivery rats. A significant difference between the nE2R levels of the two groups was found, however. These profiles closely resembled those of the full-term rats during spontaneous delivery as we reported earlier.

Animals↗
PubMed1987

Gap junction formation in the human uterine muscle cell of the corpus and cervix during the menstrual cycle and pregnancy.

The difference between sex steroid hormone dependency on gap junction (GJ) formation in human uterine muscle cells of the cervix and corpus was investigated using electron microscopic morphometry and steroid hormone radio-immunoassay. The results obtained are summarized as follows: The number of GJ in human uterine cervical muscles changed during the menstrual cycle and became greater in the periovulatory phase, whereas the GJ of myometrial muscle changed little in number during the menstrual cycle. During pregnancy, the number of GJ in myometrial muscle increased at delivery (before labor v.s. during labor 8.1 +/- 0.6 v.s. 12.8 +/- 1.0, n = 7-2, p less than 0.01), while the number of GJ in the cervix showed no significant change. When the number of myometrial as well as cervical muscle GJ around the third trimester was compared to that of the nonpregnant (luteal phase) status, there was a significant increase in the number of GJ (luteal phase v.s. during labor 6.6 +/- 1.2 v.s. 12.8 +/- 1.0, p less than 0.05 in the myometrium and 4.6 +/- 1.0 v.s. 9.6 +/- 0.7, p less than 0.05 in the cervix). This increase in the number of myometrial GJ correlated well with the increase in the circulating E2 to P ratio (r = 0.75, p less than 0.001), whereas a slight correlation was found between cervical GJ and these levels (r = 0.42, p less than 0.05). The results of the present study support the hypothesis of an estrogen-dependent formation of myometrial muscle GJ, although the current observations of the human cervix continue to raise the question whether or not identical mechanisms may operate in the cervix.

Cell Communication↗
PubMed1986

Evidence for the repetitive domain structure of pig calpastatin as demonstrated by cloning of complementary DNA.

A clone of complementary DNA (cDNA) coding for pig heart calpastatin was isolated using synthetic oligonucleotide probes. The amino acid sequence deduced from the nucleotide sequence revealed the occurrence of a repetitive sequence at the interval of 140 amino acids, substantiating the multidomain structure of calpastatin. A portion of the sequence of 251 amino acid residues predicted for pig heart calpastatin (107 kDa) was found to be identical with that of a peptide fragment derived from pig erythrocyte calpastatin (68 kDa) and sequenced by Edman degradation.

Amino Acid Sequence↗
PubMed1986

Modulation of testicular receptors for LH, FSH and prolactin by the administration of ovine prolactin in mature rat.

To elucidate the role of prolactin on testicular function, we treated mature rats with ovine prolactin (oPRL) and investigated the dose and time-dependent changes in testicular LH, FSH and prolactin receptors as well as in serum gonadotropin and steroid levels. Twelve week-old rats were injected sc with a single dose of various amounts of oPRL (0.2, 1 and 5 IU) and killed on the first, second and third days after the treatment. Testicular LH receptor decreased to 59% of the control level as a function of time while prolactin receptor increased to 244% maximally of the control level on the second day. In contrast, FSH receptor changed in a different fashion. Smaller amounts of oPRL (0.2 and 1 IU) raised the receptor level to 193% of the control level on the first day whereas a larger amount (5 IU) did not change the receptor, which tended to remain in a low level throughout the experimental period. The serum FSH level significantly increased in every group on the second day, then returned to the control range by the third day. On the other hand, the serum testosterone level changed in a characteristic manner, decreased significantly in every group on the first day though not in a dose-dependent fashion, returned to normal on the second day and significantly increased in the 0.2 IU group on the third day (p less than 0.01). Similarly, the serum estradiol level decreased in the oPRL-treated groups on the first day and was restored on the second day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Enhanced ovarian gonadotropin receptors in the testosterone-induced polycystic ovary in rats.

To establish the role of hormone receptors in patients with polycystic ovary (PCO), PCO rats were prepared by treating with testosterone propionate (TP). Five-day old immature female rats were subcutaneously injected with 1.25 mg TP in sesame oil. They were then killed at the age of 12 weeks. The ovarian receptors for LH and FSH as well as serum hormone levels were investigated in PCO rats and also in control rats at the various stages of the estrous cycle. The LH receptor binding in the TP-treated ovaries was elevated almost as high as that of proestrus control, and was observed to be higher than the other control. The FSH receptor binding of PCO rats was elevated to 173% of that of diestrus control, which showed the highest value throughout the cycle. Thus, the gonadotropin receptors in PCO rats appeared to be in an activated state. High levels of the receptor binding were due to an increase in receptor binding sites. Serum LH level was significantly higher than that of diestrus control but still remained lower than that of proestrus control. In contrast, FSH level was as low as that of diestrus control. Prolactin level was markedly elevated and 17- and 2-fold higher than that of diestrus and proestrus control, respectively. Estradiol level was higher than that of diestrus control, increasing to almost the same level during proestrus control. While progesterone level was largely depressed to 23 and 13% of that of diestrus and proestrus control, respectively, testosterone level was almost the same as that of diestrus control. From these results, it was suggested that tonic secretion of LH, low level of FSH, and markedly high levels of prolactin would increase the gonadotropin receptors and result in extremely low production of progesterone in rat ovaries. Clinically, elevated levels of the LH and FSH receptors may be a relevant occurrence in PCO patients.

Animals↗
PubMed1986

Ovarian membrane receptors for LH, FSH and prolactin during the menstrual cycle and in polycystic ovary syndrome.

To investigate the role of ovarian membrane receptors for LH, FSH and prolactin of patients with developing polycystic ovary (PCO) syndrome, seven patients were selected and the receptor function was studied in relation to changes of several serum hormone levels. The results were compared with those from individuals with regular menstrual cycles in the late follicular (LF; n = 6) and midluteal (ML; n = 6) phases. LH receptor binding in the normal cycle remained low (1.73 +/- 0.14 fmole/mg homogenate protein) in the LF phase and elevated 3 fold in the ML phase. LH receptors in the PCO patients maintained a higher binding level than that in the LF phase, being close to the ML level. FSH receptors were at a high level in the LF phase (4.09 +/- 0.40 fmole/mg homogenate protein), but decreased by 23% in the ML phase. In the PCO group the ovarian FSH receptor showed a high level, near to that in the LF phase. Prolactin receptors showed no significant changes among the two controls and PCO group. PCO patients showed increased levels of serum LH and testosterone and a raised ratio of estrone to estradiol, although there was no change in the serum FSH level. These data suggested that the LH receptor binding in PCO was not so low as to the LF level. A lack of the down-regulation mechanism of LH receptors, in spite of the high level of serum LH in PCO, might be one of the clues to elucidate the pathophysiological mechanism in developing PCO syndrome. Elevated levels of the gonadotropin receptors, especially FSH receptors, seem to be involved in the high incidence of ovarian hyperstimulation during hormone treatment.

Adult↗