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V A Isachenkov

Publications and source records attributed to V A Isachenkov.

54 records · Page 3Linked to original sources
PubMedDate not supplied

[Simple and rapid heterologous method of radioimmunochemical determination of luteinizing hormone in the blood serum of rats. 2. Specificity of the method].

The Heterologous hard phase radioimmunochemical method (RICM) of luteinizing hormone (LH) determination was tested in a number of experimental models for specificity. The results obtained demonstrated that a possible factor of cross reaction with the thyrotropic hormone (TTH) and the folliculo-stimulating hormone (FSH) was apparently insignificant in determination of LH in rat serum. This conclusion was based on the following. An immunosorbent used in RICM, prepared from the antisera of rabbits immunized with sheep LH, failed to interact with the FSH of rat hypophysis extracts. TTH-releasing hormone failed to alter the level of the immunoreactive LH in rat serum, whereas LH-releasing hormone increased 31-fold the LH concentration in 20 min. Besides, by means of RICM there was recorded a marked increase of the LH in the serum of rats after ovariectomy and a fall of the LH concentration in response to the administration of estradiol together with progesteron to such rats.

Animals↗
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[Luteinizing hormone content in the pineal body depending on the physiological state of rats].

The changes in the luteinizing hormone (LH) level in the pineal gland were studied in rats depending on their sex and age, and under conditions of hypophysectomy or gonadectomy. In golden hamsters these changes were studied during the sexual cycle. The LH level was determined by the radioimmunological method. The gonadotropin content in animals aged under 15 days was independent of sex. At the age of 23 days the LH content was greater in the female animals than in the male, whereas in 30- and 60-day female rats it was decreased in comparison with that in the male animals. The LH concentration (per 1 mg of protein) was maximal in the pineal gland extracts of 5-day male and female rats. Gonadectomy of rats led to an approximately double elevation of the LH content in the pineal gland on the 13th postoperative day both in male and female rats. This index was restored to control values three weeks after the operation. From the onset to the termination of diestrus in hamsters the LH content in the pineal gland decreased from 215 to 75 pg/organ, and after diestrus followed by proestrus and estrus it rose to 180 pg/organ (P less than 0.05). A reduction of the LH content to the 10th postoperative day followed hypophysectomy in male and female pubertant rats; the gonadotropin content was restored in two weeks.

Aging↗
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[Effect of androgens (testosterone, 5 alpha-dihydrotestosterone, 3 alpha, 17-beta androstanediol and 3 beta, 17 beta androstenediol) on the nocturnal activity of N-acetylserotonin methyltransferase and hydroxyindole O-methyltransferase in the pineal body of castrated rats].

To prove the effect of sex steroid hormones on the specificity of the pineal organ metabolism the activity of melatonin-synthesizing enzymes--N-acetylserotonine transferase (AST) and hydroxyindol-O-methyltransferase (HIMT) in the circadian rhythm was studied in castrated animals and in those administered androgens (testosterone 5 alpha-dihydrotestosterone, 3 alpha, 17 beta-androstandiol). Male Wistar rats, aged 30 days, kept for 12 hours under light conditions and for 12 hours in darkness were used in these experiments. Androgens (50 micrograms) were injected to rats two days after castration and 1 to 6 hours before the animals were sacrificed (at 2 a.m.). Activity of the enzymes under study was maximal at night (between 2 and 3 a.m.). Castration of rats weakened the peaks of the AST and HIMT activities by 30 and 40%, respectively. A single androgen administration stimulated the nocturnal rise of both androgens activities in 2 to 4 hours. By physiological activity the androgens were distributed in the following way: 5 alpha-dihydrotestosterone, 3 alpha, 17 beta-androstandiol, testosterone. beta-Epimer of androstandiol produced no effect on AST and HIMT activities in the epiphyses of castrated rats. Experimental data demonstrate that epiphysis serves as the target organ for sex steroid hormones, and that androgens are capable of modulating the melatonin-synthesizing enzymes' activity.

Acetylserotonin O-Methyltransferase↗
PubMedDate not supplied

[Relationship between the pineal body and the hypothalamo-hypophyseal system. V. Melatonin inhibition of the gonadotropic activity of the hypothalamo-hypophyseal system].

Effect of melatonin on the gonadotropic activity of the hypothalamo-hypophysial system was investigated. The following proved to occur under the action of melatonin in sexually immature female rats: reduction of the spontaneous activity of luteinizing hormone (LH), of the LH content in the hypophysis, and of the endogenous luliberin stores in the arcuate nucleus; response of the hypophysis to the exogenous luliberin was also diminished. Single administration of low doses (from 1 to 100 micrograms) of melatonin was accompanied by reduction of cAMP content in the hypophysis and the hypothalamus. LH, luliberin and cAMP were determined by radiochemical methods. The results obtained indicated that the inhibitory influence of the pineal gland on the reproductive system was realized by melatonin, its hormone, through the hypothalamo-hypophysial complex.

Animals↗
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[Immunochemical method of determining the biosynthesis of hypophyseal hormones. Effect of liberins and cyclic AMP on the biosynthesis of luteinizing hormone, prolactin and growth hormone in the rat pituitary].

A simple procedure is developed, which enables to estimate sequentially the biosynthesis of luteinizing hormone (LH), prolactin (LTH) and somatotropic hormone (STH) in rat hypophysis using solid-phase immunosorbents prepared on the basis of antisera to the hormones studied, copolymerized with chlorcarbonic acid isobutyl ester. The immunosorbents exhibited high specificity and pronounced immunosorption capacity. The analysis was carried out as follows: incubation of hypophyses with 14C-lysine in vitro, chromatography of the hypophysis extracts on columns with Sephadex G-25 and immunosorption of hormones. Within 4 hrs of incubation the biosynthetic processes in hypophysis were distinctly increased, reaching maximal values between 4 hrs and 6 hrs of incubation. Biosynthesis of LH and LTH in adult females exceeded 2-fold the STH biosynthesis and in 23 days old female rats the STH biosynthesis was more than 1.5- and 3-times higher than that LH and LTH synthesis. Luliberin at a dose 1.5 X 10(-6) M/hypophysis stimulated biosynthesis of LH, inhibited LTH biosynthesis but did not affect the STH synthesis in vitro. Thyroliberin (3.0 X 10(-6) M/hypophysis) stimulated LTH and STH biosynthesis and did not affect the LH synthesis. Dibutyryl-cAMP (0.5 X 10(-3) M/hypophysis) stimulated biosynthesis of all these hormones.

Animals↗
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[Absence of hydroxyindole O-methyltransferase, the terminal enzyme in melatonin synthesis, in the rat intestine].

The absence of hydroxinol-o-methyltrapherase, the terminal enzyme in the chain of melatonin biosynthesis in the gastrointestinal tract of rats was revealed by means of radioisotopic biochemical methods. A high endogenous methylation in the mucosa of the small intestine of rats with the participation of S-adenozylmethionine, differing from melatonin synthesis in the epiphysis, was revealed during this study.

Acetylserotonin O-Methyltransferase↗
PubMedDate not supplied

[Circadian rhythm of ornithine decarboxylase activity in the rat epiphysis].

A distinct 24-hour rhythm of the ornithindecarboxylase (ODC) was revealed in the epiphyses of rats kept under controlled illumination regimen (14 hours illumination and 10 hours darkness). ODC was an enzyme playing, according to modern views, a significant role in the regulation of the rate of protein biosynthesis at the level of transcription and translation. The maximum ODC activity was observed during the darkness period, and the minimum--during illumination. The 24-hour rhythm of the enzyme activity was levelled in the animals kept under constant illumination and in blinded animals. This indicated that the ODC rhythm was not oxogenous, but endogenous, circadian, whereas the external stimulus (the illumination regimen) synchronized the circadian changes in the enzyme activity with the time of the 24-hour period. The data obtained open one of the possible ways of analysing the mechanism of the pineal rhythms formation.

Animals↗
PubMedDate not supplied

[Factor from rat and bovine pineal organs immunologically and biologically related to luliberin].

Luteinizing hormone releasing hormone (LH-RH, luliberin) was revealed in the pineal organs of rats and cattle. The luliberin content per organ varied in rats from 5 to 66 ng, depending on sex and age. In some cases it could not be revealed by the direct radioimmunological method in the organ extracts, while neurohormone was detected by chromatography on carboxymethylcellulose or on Sephadex G-15. About 0.5 ng of LH-RH is contained in the bocine pineal organs, and the neurohormone competed with 125I-LH-RH for binding with a specific antiserum in the same way as synthetic luliberin. Mobility of LH-RH from the bovine and rat pineal organs during carboxymethylcellulose chromatography in the column coincided with such for synthetic LH-RH and the neurohormone from the rat hypothalamus. Besides, luliberin from the bovine pineal glands injected intraperitoneally to rats led to elevation of the LH blood level. No such effect occurred when luliberin from the epiphyses was preliminarily incubated with the LH-RH antiserum. A possible role played by luliberin in the pineal organ is discussed.

Age Factors↗
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[Role of 5-alpha-androstane-3-beta, 17-beta-diol in establishing feedback between the gonads and hypothalamo-hypophyseal system of orchidectomized adult rats].

Concentration of luteinizing hormone and content of luliberine were estimated, respectively, blood serum and in hypothalamic arccuate nucleus and median eminence of adult castrated rats after administration of testosterone, 5 alpha-androstane 3 beta, 17 beta diol and 5 alpha-androstane 3 alpha, 17 beta diol. Effect of testosterone and of its derivatives on hypothalamo-hypophysial system was distinctly dissimilar both in the intensity of the action and in the rate of its realization. 5 alpha-androstane 3 beta, 17 beta diol as well as testosterone and 5 alpha-androstane 3 alpha, 17 beta diol were shown to be active in the negative feedback mechanism between gonads and hypothalamo-hypophysial system; the effect of androgenes was dose-dependent.

Androstane-3,17-diol↗
PubMedDate not supplied

[Luteinizing hormone content in the hypothalamus in relation to the physiological status of rats].

Content and relative concentration (per 1 mg of protein) of luteinizing hormone (LH) varied in rat hypothalamus depending on the animal sex and age. In hamster hypothalamuses the hormone content correlated with the state of sexual cycle; maximal content of LH was found during estrus. Content of LH in hypothalamus depend also on the effect of light (rhythmic illumination, permanent light or darkness, duration of the light effect). After gonadectomy content of LH was increased in hypothalamus of female rats within 60 days. Simultaneous hypophys- and ovariectomies increased the LH content in hypothalamus already within 14 days after the treatment. Whole-body perfusion of rats did not alter the LH content in hypothalamus. LH was found in the middle and posterior parts of hypothalamus, particularly, in arcuate nucleus, middle eminence and mammillary bodies.

Animals↗
PubMedDate not supplied

[Bovine epiphyseal lactotropin, biologically and immunochemically related to pituitary prolactin].

A substance biologically and immunologically related to the hypophysis lactogenic hormone (HLH) was detected in a purified preparation obtained by extracting the bovine pineal glands (epiphyses) with acidified acetonic saline fractionation, precipitation in isoelectric point and gel filtration. Bioactivity of the pineal gland lactogen was evaluated according to its ability for stimulating the pigeon thyroid gland proliferation. Equal doses of the pineal gland hormone and HLH produced the same biological effect. The lactogen immunochemical properties were studied by gel precipitation in agar gel, immunoelectrophoresis and radioimmunoconcurrent technique. Absolute identity of the hormone immunochemical properties was revealed. Molecular weights of both lactogens, determined by chromatography on Sefadex C-75, were equal. The average HLH content in the organ, determined by radioimmunochemistry, was 4.7 X 10(5) micrograms for the hypophysis and 9.6 X 10(2) micrograms for the pineal gland. HLH content, calculated per 1 mg protein, was 3 X 10(3) micrograms for the hypophysis and 24 micrograms for the pineal gland. The hormone content in the epiphysis was 1000 times higher than HLH concentration in the blood serum.

Animals↗
PubMedDate not supplied

[Simple, highly specific procedures for radioimmunochemical estimation of hypophyseal protein hormones].

Immunosorbents, prepared by means of polymerization of antiserum proteins using chlorcarbonic acid isobutyl ester, were used to increased reproducibility and simplicity of the radioimmunochemical procedures for estimation of the estimation of the hypophyseal hormones. In the types of the radioimmunoassay (RIA) studied the immunosorbents were prepared by means of polymerization of the first and second antibodies. The universal immunosorbent, suitable to estimation of various antigens, was prepared from the second antibodies. The procedure enabled to use as the first antibodies the blood sera with comparatively low antibody titre. High specificity of the RIA procedures described was demonstrated in estimation of bovine hypophyseal hormones - lactogenous (LTH), somatotropic (STH) and beta-lipotropine. The calibration curves were linear in the concentration range from 2 to 20 ng/ml for LTH, and from 1 to 10 ng/ml for STH and beta-lipotropine. Estimation of LTH by means of the RIA procedure required 3 hrs, and of STH and beta-lipotropine - 16 hrs.

Animals↗
PubMedDate not supplied

[2 variants of the radioimmunochemical method of determination of LH-releasing factor (LH-RF). Distribution of LH-RF in various hypothalamic structures].

The authors elaborated two variants of the radioimmunochemical method of determination of the LH-releasing factor (LH-RF). Diluted antisera (AS) obtained by the immunization of rabbits with the LH-RF-ovalbumin were used in the first method; AS polymerized with isobutyl ester of chlorcarbonic acid were used in the second one. The minimal amount of the hormone determined in the I variant was 5 pg, and in the 11 one--20 to 30 pg. The method is highly specific, since the antisera gave no cross reaction with a wide set of protein-peptide hormones synthesized with the hypothalamus and the hypophysis. The presence in the samples of tissue components of the hypothalamus and of the cerebral cortex extractable with 2M CH3COOH failed to influence the precision of the test. In examining the LH-RF content in the brain structures there was revealed that in the sexually mature male rats the whole hypothalamus contained an average of 7.5 ng, the arcuate nuclei--1.5 ng and the medial eminence--2.5 ng of LH-RF; the supraoptic nuclei and the cerebral cortex contained no LH-RF determinable by the method described. Two weeks after the castration the mean content of the hormone in the whole hypothalamus decreased to 5.5 ng, in the medial eminence--to 0.6 ng, and showed no significant change in the arcuate nuclei.

Animals↗
PubMedDate not supplied

[Gonadotropin from the bovine pineal body. Evidence of its similarity with the luteinizing hormone of the pituitary gland].

Gonadotropin affiliated by biological and immunochemical properties to the luteinizing hormone of the hypophysis was revealed in the purified extracts from the bovine pineal glands. Biological properties of gonadotropin from the pineal glands were assessed by the reactions specific of the luteinizing hormone. Immunochemical properties of gonadotropin were studied by means of gel-precipitation in agar gel, immunoelectrophoresis and radioimmunochemical analysis. It was found that the specific content of gonadotropin in the epiphysis was 80 times lower than the specific content of the luteinizing hormone in the hypophysis, but exceeded the LH concentration in the blood serum 555 times and in the cerebrospinal fluid 6.8 times. Immunoreactive LH was absent in the extracts of the brain cortex, the liver and the ovaries. A theoretical interpretation of a possible physiological role of the LH-like gonadotropin in the endocrine regulation of the reproductive function of the organism is given in this work.

Animals↗