Exogenous Regulators Research Articles

Lack of effect of hormones and inducers of intracellular messengers on plasminogen activator production by bovine embryos in vitro.

Several hormones and inducers of intracellular messengers, known to affect plasminogen-activator (PA) production in other systems, were investigated for putative effects on bovine embryos. Day 8 embryos were cultured for 5 days in a humidified atmosphere of 5% CO2 in air at 37 degrees C in media containing different concentrations of progesterone, oestradiol, dexamethasone, retinoic acid, dibutyryl cyclic AMP (dbcAMP) and phorbol myristate acetate (PMA). At intervals of 24 h, the medium was recovered for PA analysis and overall embryonic diameter was measured. While none of the hormones and agents tested affected PA production (P > 0.05), dimethyl sulfoxide, which was used to dissolve PMA, inhibited PA production during the first 72 h of culture (P < 0.05). PA production was affected by duration of culture (P < 0.05). Concentrations of plasminogen activator in the media were low during the first 48 h, had increased after 72 and 96 h in culture, and either remained high or decreased slightly toward the end of the culture period. With the exceptions of dbcAMP and PMA, the hormones tested in this study did not affect embryonic size. Dibutyryl cAMP caused a progressive decrease in embryonic diameter. PMA resulted in embryo death at high concentrations but at lower concentrations it enhanced overall embryonic diameter throughout the time of culture (P < 0.05). These results suggest that cultured bovine embryos produce PA in a fixed, time-dependent manner, independent of exogenous hormonal regulation.

Suppression of human alveolar macrophage-derived cytokines by amiloride.

Various human alveolar macrophage (AM)-derived cytokines in the lungs have been shown to be present under conditions of normal homeostasis as well as during the pathogenesis of inflammation. Although extensive investigation has demonstrated the induction of cytokines from AM, relatively little is known regarding endogenous and exogenous regulation of their production. Several pharmacologic agents, including corticosteroids, cyclooxygenase inhibitors, prostaglandins, and methyl-xanthines have been examined for their role in the modulation of mononuclear phagocyte-derived cytokines. In this study, we examine the role of amiloride for the regulation of AM-derived interleukin (IL)-8, tumor necrosis factor (TNF), IL-6, and IL-1 beta. Amiloride in concentrations of 10(-4) to 10(-6) M, concentrations capable of being achieved in the distal airways via nebulization, were shown to inhibit lipopolysaccharide-stimulated, AM-derived IL-8 and TNF in both a time- and dose-dependent fashion. In addition, 5-(N,N-hexamethylene) amiloride hydrochloride, an amiloride analogue with specific sodium channel antiport inhibition, resulted in a similar dose-dependent suppression of lipopolysaccharide-stimulated, AM-derived IL-8 production. Furthermore, the suppressive effect of amiloride appeared to be at the level of mRNA for IL-8, TNF, IL-1 beta, and IL-6, whereas steady-state levels of beta-actin mRNA remained unaltered. These findings would suggest that amiloride has a potentially important modulating influence for the regulation of AM-derived cytokines.

Endogenously-mediated, pretranslational suppression of cytochrome P4501A in PCB-contaminated flounder

Gonadally mature fish display strong sex-related differences in the content and activity of P4501A, the major polynuclear aromatic hydrocarbon-inducible P450 form in teleosts. Such differences appear related to plasma levels of the female sex steroid, estradiol (E 2); however, neither the mechanism of estradiol suppression of P4501A nor the capacity for hormonal regulation to overcome P4501A induction by high concentrations of potent inducers are known. Gonadally mature flounder ( Pseudopleuronectes americanus) were collected from Fox Island (FI), Rhode Island, a reference site, and New Bedford Harbor (NB), Massachusetts, a site highly contaminated with polychlorinated biphenyls (PCBs). Differences in flounder P4501A expression were determined at the level P4501A catalytic activity (measured as ethoxyresorufin-O-deethylase, EROD), P4501A protein content (immunoquantitated), and P4501A mRNA content (by Northern blot) as they relate to sex, reproductive status, and hepatic PCB content. Our results confirm that suppression of P4501A in gonadally mature female fish is probably due, at least in part, to elevated E 2 titers, and demonstrate that such suppression occurs at a pretranslational level and, further, that endogenous regulation of P4501A expression can ‘override’ exogenous regulation by even high concentrations of P4501A inducers.

Exogenous opioid regulation of the hypothalamic-pituitary-adrenal axis in fetal sheep.

To test the hypothesis that endogenous opioids participate in the regulation of the ontogenic development of the hypothalamic-pituitary-adrenal axis in fetal sheep, we measured changes in immunoreactive (ir) ACTH and cortisol concentrations in response to bolus injections of either the [Met]-enkephalin analogue, [D-Ala2,N-Phe4,Met(0)ol5]-enkephalin (FK 33-824; 25 micrograms), the opioid antagonist naloxone (1 mg), a combination of both, or saline vehicle, administered to chronically catheterized fetal sheep through late gestation. There were no effects of either FK 33-824, naloxone or saline on the release of ir-ACTH and cortisol at the earliest stage of gestation studied (days 110-115). By days 125-130, FK 33-824 caused a rapid but short-lived (30 min) increase in plasma ir-ACTH (P less than 0.05) which was accompanied by a smaller but nonsignificant increase in cortisol. Naloxone given concurrently with FK 33-824 abolished this response, thus providing evidence for a specific effect through opioid receptors. Naloxone given alone was without effect. At days 135-140, FK 33-824 caused a significant increase in ir-ACTH which was of similar duration and magnitude to that which occurred at days 125-130. There was a larger basal variation in plasma concentrations of cortisol than at days, 125-130, and a greater increase in cortisol after FK 33-824, although this did not reach statistical significance. Naloxone again reversed the effects of FK 33-824 but was without effect when given alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Exogenous and endogenous regulations of human megakaryocytopoiesis.

Megakaryocytopoiesis may be viewed as a developmental continuum which begins when an undifferentiated hematopoietic stem cell commits to maturation within this lineage (for recent review see ref.#l) The process of commitment results in the generation of megakaryocyte progenitor cells (CFU-Meg). When appropriately stimulated, CFU-Meg are capable of intense proliferative activity which determines the numbers of megakaryocytes which will ultimately populate the bone marrow. As proliferative activity declines, CFU-Meg progeny mature into precursor cells which terminally differentiate into polyploid megakaryocytes capable of releasing several thousand platelets each into the circulation.

Exogenous regulation of the time of oviposition in the domestic fowl

This review is concerned with the regulation of the time of oviposition in the domestic fowl as influenced by such environmental signals as light, temperature, sound and feeding schedules. The patt...

Control of cell differentiation during proliferation: I. Monocytic differentiation of HL-60 promyelocytes

The cell proliferation relating an uncommitted precursor cell to a differentiated terminal cell has been quantitated. HL-60 promyelocytes, a bipotent precursor cell capable of differentiating along either the myeloid or monocytic pathway, were induced by a human lymphocyte-conditioned medium (CM) to differentiate into macrophage-like cells. The promyelocytes had a generation time of approx. 42 h. Most promyelocytes which differentiated became macrophage-like cells after only one cell division. Some, a minority, underwent more than one division. The time between induction of differentiation and expression of differentiated characteristics could thus be very short. Labelled S-phase promyelocytes could differentiate after traversing S, G2 and undergoing mitosis. Some, approx. 21%, required a subsequent complete cell cycle before differentiating. The data suggest a model in which cells must undergo a S-phase-specific differentiation control event in the presence of CM in order to differentiate in the subsequent G1 phase. This model proposes that a discrete time in S phase exists when cells are susceptible to exogenous regulation directing them to yield differentiated daughter cells.

Endogenous and exogenous regulation of human alpha- and beta-adrenergic receptors.

Regulation of human beta 2-adrenergic receptors in lymphocytes (determined by (+/-)-125iodocyanopindolol (ICYP) binding) and alpha 2-adrenergic receptors in platelets (determined by 3H-yohimbine binding) was studied. While beta 2-adrenergic receptor number did not change with age, a significant negative correlation between the number of alpha 2-adrenergic receptors and age was found; plasma catecholamines, on the contrary, were elevated in the elderly. In healthy women during normal menstrual cycle the number of alpha 2-adrenergic receptors decreased with increasing plasma estradiol levels. Incubation of lymphocyte membranes with isoprenaline (100 microM) and of platelet membranes with clonidine (1-100 microM) led to a reduction of the number of beta 2- and alpha 2-receptors, respectively, without changes in the KD-values. Treatment of hypertensive patients with clonidine (3x150 micrograms/die) for 7 days reduced the number of alpha 2-adrenergic receptors in platelets. In platelet membranes from such treated patients inhibition of 3H-yohimbine binding by clonidine and adrenaline was not affected by 10(-4)M GTP. It is concluded, that human alpha- and beta-adrenergic receptors undergo regulatory mechanisms similar to those recently described for adrenergic receptors in a variety of animal models.

Effect of Plant Growth Regulators on Nitrate Utilization by Roots of Nitrogen-Depleted Dwarf Bean

We examined the effect of pretreatments (18 h at 5 //mol dm-3) with abscisic acid, the ethylene-releasing substance 'Ethephon', gibberellic acid, indoleacetic acid, kinetin and zeatin on nitrate uptake and in vivo nitrate reductase activity (NRA) in roots of nitrogen-depleted Phaseolus vulgaris L. Nitrate uptake showed an apparent induction pattern with a steady state after about 6 h, in all treatments. The nitrate uptake rate after 6 h was unaffected or at most 30% lower after treatments with the plant growth regulators. Gibberellic acid, kinetin and zeatin induced substantial NRA in roots in the absence of nitrate, whereas Ethephon enhanced NRA only during nitrate nutrition. Kinetin-induced NRA (Ki-NRA) was maximal after a pretreatment at 1 //mol dm~3, and showed a lag phase of 6-8 h. Ki-NRA was additive to nitrate-induced NRA (NOj-NRA) for at least 24 h, independent of the induction sequence. After full induction, Ki-NRA approximated 20% of NO7-NRA. Abscisic acid counteracted the development of Ki-NRA, but not of NOj-NRA. Cycloheximide and tungstate were equally effective to suppress the development of nitrate reductase activity after supply of kinetin or NO3. Our data are consistent with the operation of two independent enzyme fractions (Ki-NRA and NO7-NRA) with apparently identical properties but with separate control mechanisms. The absence of major effects of plant growth regulators on the time-course and rate of nitrate uptake suggests that exogenous regulators, and possibly endogenous phytohormones are of minor importance for initial nitrate uptake. The differential effect of some regulators on nitrate uptake and root NRA furthermore indicates that the processes of uptake and reduction of NOj are not obligatory or exclusively coupled to each other.

Transport of exogenous substrate and cell volume regulation in bivalve molluscs

AbstractBased on published values for transport kinetics, it has been suggested that uptake of free amino acids from the environment could not play a significant role in altering the intracellular pool of free amino acids during hypersaline acclimation in euryhaline bivalves. A review of more recent findings indicates that this suggestion requires reexamination. It has also been suggested that extracellular sources of amino acids within the animals could be utilized in altering the intracellular pool. Available data having bearing on that hypothesis are reviewed.

Leaf Formation and Peroxidases from Arabidopsis Callus

Summary A progressive decline of leaf formation capacity was observed in long-term cultures of Arabidopsis callus on 2,4-D. It corresponded to a gradual loss of activity of total peroxidase and of specific isoperoxidases. A passage on media without auxin was required to restore the morphogenetic capacity. It was accompanied by a general increase of activity for most of the isoperoxidases. Leaf formation by passing on a third medium with low IAA level and high kinetin content paralleled a continuous increased enzyme activity as mentioned before by different authors on other materials. The results suggested that morphogenetic potential is dependent upon an endogenous hormonal balance controlled by the exogenous regulators.

The regulative role of food consumption in the induction of rat liver cell proliferation by drugs and environmental pollutants.

alpha-hexachlorocyclohexane (alpha-HCH) was used to stimulate cell proliferation in rat liver. Food consumption at two different stages of the replicative cycle was found to be required for the enhancement of DNA synthesis by this agent: (1) Before or at the time of alpha-HCH administration (G0), (2) 12--15 hours later, i.e. 5--8 hours before initiation of DNA synthesis ("R"-point). Other alpha-HCH mediated changes in the liver i.e. organ enlargement and the induction of drug-metabolising enzymes, remained unaffected by the absence of food. This suggests that the nutritional control is specific for induction of DNA synthesis. It is concluded that food consumption, in addition to specific stimuli of liver growth, is an exogenous regulator of liver cell proliferation.

Exogenous regulators in the mycelium of Pleurotus ostreatus after exogenous application.

The mycelium of the fungus Pleurotus ostreatus was cultured on a synthetic medium with growth regulators. Best growth was observed on media with 100 ppm IAA, 200 ppm GA3 and 200 ppm of kinetin. Growth of terminal hyphae and the appearance of colonies differed characteristically. Auxin bio-assays showed that the content of substances in younger mycelium slowly increased during cultivation without conspicuous changes in the medium. After exogenous application of IAA the content of auxins in younger mycelium increased and the content of IAA decreased gradually in the culture medium. Gibberellin bio-assays showed their content in the mycelium fell during cultivation and while it increased in the medium. Application of GA3 to the medium leads to a significant increase in these substances in the young mycelium and in the medium their level remains the same. Cytokinin bio-assays showed their content to vary during cultivation. An addition to kinetin to the nutrient medium results in an increase of cytokinins in the mycelium while in the medium the level of cytokinins is maintained. Addition of one substance thus influences the levels of other endogenous regulators.

Replication of mouse mammary tumor cells in monolayer cultures stimulated with embryo extract.

A particulate fraction derived from homogenized chicken embryos was added to primary monolayer cultures of mouse mammary tumor cells. All culture media contained fetal calf serum (10%). After 4 days, the extract had stimulated a twofold increase (relative to controls lacking the extract) in (1) total DNA per culture; (2) the rate of incorporation of labeled DNA precursors; (3) epithelial cell number, and (4) total protein. This integrated growth activity is discussed in terms of the nature and exogenous regulation of neoplastic growth.

The role of exogenous plant regulators in the dormancy of onion bulbs

SUMMARYExperiments were conducted to study the effect of plant injection with growth regulators on the dormancy of onion bulbs cv. Elba Globe. Application of abscisic acid induced early senescence of the leaves and prolonged the rest period of the bulbs. This effect was partially overcome by subsequent applications of gibberellin, auxin or cytokinin and totally overcome with the application of a mixture of the three hormones. Maleic hydrazide application prolonged the rest period by inhibiting both sprouting and rooting of the bulbs throughout the storage period. This inhibitory effect was not overcome by the subsequent application of auxin, gibberellin, kinetin, or their combinations. Ethephon application increased rooting of bulbs and partially overcame the effect of abscisic acid on dormancy.

Metabolic control of synthesis of the different forms of dihydrofolate reductase of the amethopterin-resistant Streptococcus faecium var. durans A k

The metabolic regulation of the synthesis of the folate reductase and the specific dihydrofolate reductase of the amethopterin-resistant bacterium Streptococcus faecium var. durans A k was investigated. Under growth conditions for maximum synthesis, the differential rate increased two fold during exponential growth. Synthesis of both reductases was coordinate and air-sensitive. The interrelated growth requirements of the bacterium contribute to the complexity of regulation. Folate acts as a “positive” inducer of both types of reductase. Purines and thymine or their metabolic derivatives are interdependent in exerting an action which may antagonize the folate effect. These regulator agents apparently have little selective effect on any of the electrophoretically distinct forms of dihydrofolate reductase. Proportionate synthesis of the folate reductase (the major form), of the specific dihydrofolate reductase (the minor form) and of a minor component of folate reductase occurred in the presence and absence of the exogenous regulators. Amethopterin appears to act as a protective agent of reductase-active protein synthesized during exponential growth.

FEATURES OF THE WINTER WHITE CABBAGE VARIETIES GENERATIVE DEVELOPMENT

One of the modern selection tasks in vegetable growing is quality products improving, obtaining high yields of environmentally safe wide assortment vegetables. To the new varieties of vegetable crops including winter white cabbage are specified new requirements such as market competitiveness, resistance to unfavorable environmental conditions, heat resistance of the varieties and F1 hybrids. The article is shown investigation results about studies of exogenous treatment by solutions on the base of physiologically active compounds of hormonal nature on the started process of stem extension stage activation and flowering of winter white cabbage plants. For the first time in the Dagestan conditions has been studied the possibility of hormonal regulation of the premature stem extension stage and flowering prevention of winter white cabbage after the initiation of natural induction. In our studies with an early planting there are not more than 20% of blooming plants, most varieties showed a high propensity to premature stem extension stage and flowering. The possibility of the hormonal exogenous regulation of the unfavorable winter white cabbage flowering has been revealed. The most pronounced effect on the transition to stem extension stage and flowering were provided by auxin nature preparations. In particular, treatment with NAS at a dose of 5 mg / l significantly reduced the number of blossom plants, krezatsin (50 mg / l) had a similar effect, but it was less pronounced. The use of cabbage in winter crops makes it possible to obtain two or three yields per year from the same area. Creation and introduction into production of promising and high-yielding varieties and hybrids will allow increasing production and reducing its cost.

Exogenous Regulation of Oviposition in Chicken

THE circadian rhythm of oviposition in chickens is well established, but the exogenous stimuli which influence the release of humoral factors involved in egg production are not. This study considers the influence of sound, feeding time, and light on time of egg-laying by chickens.In his review on diurnal rhythms, Aschoff (1963) has defined the “Zeitgebers” as the periodic factors of the environment by which free-running circadian oscillations can be synchronized. Shifting laying hens from 14 hours of light per day to 24 hours continuous light results in eggs being laid at a uniform rate throughout the 24 hours (Warren and Scott, 1936). Shifting the time of lighting alters the time of oviposition, according to Bastian and Zarrow (1955), Lanson and Sturkie (1958), and Biellier and Ostmann (1960). The use of 1-minute periods of intermittent light resulted in eggs being laid near the light period (Wilson and Abplanalp, 1956). A…