Effect of regenerating plants cultivated in cereal crop rotations on the weediness degree

Сравнивали степень засорения хлебных злаков: ярового ячменя, овса и озимой пшеницы в зависимости от участия в севообороте промежуточных культур (клевера персидского и озимого рапса на запашку) играющих роль регенерирующих растений. В условиях исследований промежуточные культуры влияли неодинаково на заорение полей. Подсевы клевера персидского соперничая с сорняками способствовали ограничению засорения яровых хлебов. Стерневая промежуточная культура озимого рапса приводила к росту засорения последней культуры севооборота - озимой пшеницы, поскольку ее введение в севооборот принуждало к отказу от пожнивных мероприятий по обработке. В течение первой ротации севооборота наблюдалась снижающаяся тенденция в общем состоянии засорения поля и почвы, при одновременной компенсации.The weediness degree of cereals: summer barley, oats and winter wheat depending on the share of catch crops (Persian clover and winter rape cultivated for ploughing down) playing the role of regenerating plants, was compared. Under conditions of the investigations catch crops affected differently the field weediness degree. Undersowings of Persian clover as catch crop competing with weeds reduced the weediness of summer cereals. The stubble catch crop of winter rape led to a growth of weediness of winter wheat as the last crop of the crop rotation, as its introduction into the crop rotation forced to abandoning of the set o'f post-harvest tillage measures. During the first rotation a decreasing tendency in the general state of field and soil weediness at a simulta neous compensation of Chenopodium album, was observed

Effects of neurotensin and bombesin on the secretory and proliferative activity of regenerating rat adrenal cortex

Neurotensin (NT) and bombesin (BM)-like peptides are known to be involved in the regulation of the rat hypothalamo-pituitary-adrenal axis. By using selective NT- and BM-receptor antagonists (NT-A and BM-A, respectively) we investigated whether endogenous NT and BM-like peptides play a role in the control of rat adrenal secretion and growth during enucleation-induced regeneration. At day 5 of regeneration, NT-A did not affect the plasma concentrations of aldosterone (PAC) and corticosterone (PBC), but at day 8, it raised both PAC and PBC over the respective baseline value; the simultaneous administration of NT abolished this effect of NT-A. BMA did not alter PAC and PBC at day 5 of regeneration, while at day 8 it enhanced PBC, an effect reversed by BM. NT-A did not alter mitotic index, and BM-A lowered it at both day 5 and day 8 of regeneration, an effect suppressed by the simultaneous administration of BM. Collectively, these findings allow us to draw the following conclusions: 1) endogenous NT and BM-like peptides influence adrenocortical regeneration in rats; 2) NT exerts a tonic inhibitory action on both aldosterone and corticosterone secretion, without affecting cellproliferation rate; and 3) BM-like peptides exert a tonic suppressive effect on corticosterone production, coupled with a clear-cut stimulating effect on cell proliferation

Effects of neuropeptides B and W on the rat pituitary-adrenocortical axis: In vivo and in vitro studies

Neuropeptides (NP) B and W are hypothalamic peptides involved in the regulation of feeding and neuro-endocrine axes. Evidence has been provided that NPB and NPW act on both the central and the peripheral branches of the rat hypothalamic-pituitary-adrenocortical axis, and we carried out in vivo and in vitro studies to gain insight into this topic. Reverse transcription-polymerase chain reaction showed the expression of NPB, NPW and their receptors in both adrenal cortex (zonae glomerulosa and fasciculata-reticularis) and adrenal medulla, where immunocytochemistry also detected the presence of abundant NPB- and NPW-immunoreactivity. The acute subcutaneous administration of NPB (0.5 or 1.5 nmol/100 g) did not alter ACTH plasma concentration, while that of NPW (1.5 nmol/100 g) decreased it. Neither NPB nor NPW affected the blood level of aldosterone, while both peptides (0.5 nmol/100 g) raised that of corticosterone. NPB (10(-6) M) lowered ACTH-stimulated aldosterone secretion, and basal and ACTH-stimulated corticosterone production from adrenal quarters containing both cortical and medullary tissues. NPW (10(-6) M) enhanced basal aldosterone secretion from adrenal quarters, and the effect was suppressed by the beta-adrenoceptor antagonist l-alprenolol (10(-5) M). NPW did not affect corticosterone production. Collectively, our findings allow us to draw the following tentative conclusions: i) ACTH-independent extra-adrenal mechanism(s) are operative in vivo, by which NPB and NPW stimulate adrenal glucocorticoid, but not mineralocorticoid secretion; ii) in vitro the interaction of NPB with adrenal medulla activates unknown mechanism(s) hampering adrenocortical steroidogenic machinery; and iii) NPW stimulates in vitro aldosterone secretion by enhancing the release of medullary catecholamines, which in turn activate beta-adrenoceptors located on zona glomerulosa cells

Effects of endogenous galanin on the growth of regenerating rat adrenal gland as investigated by the metaphase-arrest and the PCNA-immunostaining techniques

We have investigated the effects of three subcutaneous injections of 2 nmol/100 g body weight of galanin and its receptor antagonist (galanin-A) [D-Thr 6,D-Trp 8,9,-15-ol]-galanin 1-15 on the proliferative activity of regenerating rat adrenal cortex. The metaphase-arrest and the proliferating-cell nuclear antigen (PCNA)-immunostaining techniques were used to estimate the number of M phase (metaphase index) and S phase cells (PCNA index), respectively. Galanin-A raised the metaphase index at both day 5 and day 8 of regeneration. Galanin was per se ineffective, but reversed the galanin-A effect at day 8. Neither galanin nor galanin-A changed PCNA index at day 5. Galanin evoked a moderate increase in PCNA index at day 8. Taken together, these findings indicate that endogenous galanin exerts a tonic maximal inhibitory effect on adrenal regeneration in the rat

Effects of orexins A and B on the secretory and proliferative activity of immature and regenerating rat adrenal glands

Orexins A and B are two hypothalamic peptides, involved in the central regulation of feeding, which act through two receptor subtypes, named OXIR and OX2R. OXIR is selective for orexin-A, and OX2R binds both orexins. We have investigated the effects of three subcutaneous injections of 10 nmollkg body weight of orexins on the secretion and proliferative activity of immature (20-day-old) and regenerating rat adrenal cortex. The presence of both OXIR and OX2R mRNAs has been detected by reverse transcriptionpolymerase chain reaction in adult, immature and regenerating adrenals. Orexin-A increased corticosterone plasma concentration in immature rats, but not in animals with regenerating adrenals. Both orexins raised metaphase index (%o of metaphase-arrested cells) in immature rat adrenals, orexin-B being more effective than orexin-A. In contrast, both orexins equipotently lowered adrenal metaphase index at day 5 (but not day 8) of adrenal regeneration. We conclude that orexins (1) stimulate secretion and proliferative activity of immature rat adrenals, acting through OXIR and OX2R, respectively; and (2) do not affect secretion, but inhibit proliferative activity of regenerating adrenals, mainly via the activation of OX2R

Effects of neuropeptides B and W on the secretion and growth of rat adrenocortical cells

Neuropeptide-B (NPB) and neuropeptide-W (NPW) are recently discovered endogenous ligands of the GPR7- and GPR8-receptors (R), which in humans are expressed in the hypothalamus and probably involved in the regulation of energy homeostasis and neuroendocrine axes. GPR8-Rs are absent in rodents, where the GPR8-like-R has been described. Reverse transcription-polymerase chain reaction detected the expression of NPB, NPW, GPR7-R and GPR8-like-R mRNAs in rat adrenocortical cells (both freshly-dispersed and 4-day-cultured cells). NPB did not acutely (60-min exposure) alter basal aldosterone secretion from freshly dispersed zona glomerulosa cells, while NPW raised it. Both NPB and NPW enhanced ACTH-stimulated aldosterone secretion and did not affect either basal or ACTH-stimulated corticosterone production by dispersed zona fasciculata/reticularis (ZF/R) cells. The prolonged (4-day) exposure to NPW, but not NPB, raised corticosterone secretion from cultured ZF/R cells, and both neuropeptides increased the proliferation rate of cultured cells. Taken together, our findings indicate that NPB and NPW affect rat adrenocortical function, so they may be included in that large family of peptides involved in the autocrine-paracrine stimulation of secretion and growth of adrenal cortex

Leptin prolonged administration inhibits the growth and glucocorticoid secretion of rat adrenal cortex

Leptin is an adipose-tissue secreted hormone, that acts to decrease caloric intake and to increase energy expenditure. Some of the leptin effects on the energy balance are known to be mediated by the hypothalamo-pituitary-adrenal (HPA) axis, but the role of this cytokine in the regulation of the growth and steroidogenic capacity of adrenal cortex is still controversial. Therefore, the present study was designed to explore the long-term effects of native leptin[1-147] and its biologically active fragment leptin[116-130] (6 daily subcutaneous injection of 20 nmol/kg) on the rat HPA axis. Leptin[1-147] and leptin[116-130] caused a significant adrenal atrophy, which was mainly due to the decrease in the volume of zona fasciculata (ZF) and in the number of its parenchymal cells. Both leptins provoked a marked drop in the plasma concentrations of ACTH and corticosterone, the main hormone produced by ZF cells. The effects of leptin[116-130] were more intense than those of leptin[1-147]. Leptin[1-147], but not its fragment, evoked a clear-cut rise in the plasma concentration of aldosterone. Collectively, these findings indicate that prolonged leptin administration, by inhibiting pituitary ACTH release, exerts a potent suppressive action on the growth and glucocorticoid secretory capacity of the adrenal cortex in the rat. The mechanism(s) underlying the aldosterone secretagogue action of native leptin remain(s) to be investigated

Effects of leptin on the response of rat pituitary-adrenocortical axis to ether and cold stresses

Leptin is a hormone mainly secreted by the adipose tissue, which acts through specific receptors widely distributed in the body tissues, including hypothalamopituitary-adrenal axis. We have investigated the effects of a subcutaneous bolus injection of 5 nmol/kg leptin on the pituitary-adrenocortical function in both normal and ether- or cold-stressed rats. Blood concentrations of ACTH, aldosterone and corticosterone were measured by specific RIA 2 or 4 h after the leptin injection. Leptin administration to normal rats resulted in significant rises in the blood levels of ACTH, aldosterone and corticosterone at 2 h, but not at 4 h. Ether and cold stresses markedly increased hormonal blood concentrations at both 2 and 4 h. Leptin magnified ACTH response to ether stress at 2 h, but depressed it at 4 h, and enhanced aldosterone response at 2 h, without affecting corticosterone response. Leptin increased ACTH response to cold stress at both 2 and 4 h, without altering aldosterone and corticosterone responses. In light of these findings, we conclude that: (i) leptin evokes a middle transient activation of the pituitary-adrenocortical axis of rats under basal conditions; (ii) leptin inhibits the ACTH response to ether stress, but magnifies that to cold stress; and (iii) the leptin-evoked changes in the blood level of ACTH are not paralleled by significant modifications in the secretory activity of the adrenal cortex, which probably undergoes a maximal stimulation under stressful conditions