RESUMO
The aim of this work is to study the features of a simple replicator chemical model of the relation between kinetic stability and entropy production under the action of external perturbations. We quantitatively explore the different paths leading to evolution in a toy model where two independent replicators compete for the same substrate. To do that, the same scenario described originally by Pross (J Phys Org Chem 17:312-316, 2004) is revised and new criteria to define the kinetic stability are proposed. Our results suggest that fast replicator populations are continually favored by the effects of strong stochastic environmental fluctuations capable to determine the global population, the former assumed to be the only acting evolution force. We demonstrate that the process is continually driven by strong perturbations only, and that population crashes may be useful proxies for these catastrophic environmental fluctuations. As expected, such behavior is particularly enhanced under very large scale perturbations, suggesting a likely dynamical footprint in the recovery patterns of new species after mass extinction events in the Earth's geological past. Furthermore, the hypothesis that natural selection always favors the faster processes may give theoretical support to different studies that claim the applicability of maximum principles like the Maximum Metabolic Flux (MMF) or Maximum Entropy Productions Principle (MEPP), seen as the main goal of biological evolution.
Assuntos
Evolução Biológica , Evolução Molecular , Modelos Químicos , Modelos Teóricos , Planeta Terra , Entropia , Meio Ambiente , Seleção Genética , Processos EstocásticosRESUMO
Oscillating biochemical reactions are common in cell dynamics and could be closely related to the emergence of the life phenomenon itself. In this work, we study the dynamical features of some classical chemical or biochemical oscillators where the effect of cell volume changes is explicitly considered. Such analysis enables us to find some general conditions about the cell membrane to preserve such oscillatory patterns, of possible relevance to hypothetical primitive cells in which these structures first appeared.
Assuntos
Relógios Biológicos , Termodinâmica , Membrana Celular/metabolismo , Tamanho Celular , Modelos BiológicosRESUMO
For over 40 years, NASA's global network of satellite laser ranging (SLR) stations has provided a significant percentage of the global orbital data used to define the International Terrestrial Reference Frame (ITRF). The current NASA legacy network is reaching its end-of-life and a new generation of systems must be ready to take its place. Scientific demands of sub-millimeter precision ranging and the ever-increasing number of tracking targets give aggressive performance requirements to this new generation of systems. Using lessons learned from the legacy systems and the successful development of a prototype station, a new network of SLR stations, called the Space Geodesy Satellite Laser Ranging (SGSLR) systems, is being developed. These will be the state-of-the-art SLR component of NASA's Space Geodesy Project (SGP). Each of SGSLR's nine subsystems has been designed to produce a robust, kilohertz laser ranging system with 24/7 operational capability and with minimal human intervention. SGSLR's data must support the aggressive goals of the Global Geodetic Observing System (GGOS), which are 1 millimeter (mm) position accuracy and 0.1 mm per year stability of the ITRF. This paper will describe the major requirements and accompanying design of the new SGSLR systems, how the systems will be tested, and the expected system performance.
RESUMO
An ethological approach to attention predicts that organisms orient preferentially to valuable sources of information in the environment. For many gregarious species, orienting to other individuals provides valuable social information but competes with food acquisition, water consumption and predator avoidance. Individual variation in vigilance behaviour in humans spans a continuum from inattentive to pathological levels of interest in others. To assess the comparative biology of this behavioural variation, we probed vigilance rates in free-ranging macaques during water drinking, a behaviour incompatible with the gaze and postural demands of vigilance. Males were significantly more vigilant than females. Moreover, vigilance showed a clear genetic component, with an estimated heritability of 12%. Monkeys carrying a relatively infrequent 'long' allele of TPH2, a regulatory gene that influences serotonin production in the brain, were significantly less vigilant compared to monkeys that did not carry the allele. These findings resonate with the hypothesis that the serotonin pathway regulates vigilance in primates and by extension provoke the idea that individual variation in vigilance and its underlying biology may be adaptive rather than pathological.
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In a recent study, investigating the time course of both GH and cAMP secretion induced by GH-releasing hormone (GHRH) in the superfusion system, we found that the amount of cAMP liberated from the cells was not proportional to GH release and that cAMP discharged after a GHRH pulse alone cannot maintain the release of GH. In the present study, two potent antagonists of GHRH, MZ-4-71 ([Ibu0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]human GHRH-(1-28)Agm) and MZ-4-243 ([Nac0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]human GHRH-(1-28)Agm) were evaluated for their long term effect in the superfusion system and for their ability to influence the release of GH and cAMP. Our present findings showed that after a 9-min preincubation, antagonist MZ-4-71 and MZ-4-243 at 3 and 1 nM, respectively, caused an inhibition of GH release, stimulated by 1 nM GHRH, similar to that caused by the 100-nM dose of the standard antagonist ([Ac-Tyr1,D-Arg2]human GHRH-(1-29)NH2). The standard antagonist at 100 nM did not influence the GHRH-induced GH response 30 min later, and the inhibition caused by MZ-4-71 at 30 nM decreased gradually to 30% 120 min after the treatment, but the 30-nM dose of MZ-4-243 reduced the GH response by more than 90% even 270 min after its administration. During a 2-h incubation with 1 nM GHRH in combination with a 30-min infusion of the standard antagonist, MZ-4-71, MZ-4-243, or somatostatin, from the 30th to the 60th min, the decrease in GH discharge preceded the inhibition of cAMP release. After infusion of the antagonists or somatostatin was stopped, GH release resumed sooner than that of cAMP. Simultaneous determinations of cAMP and GH in the samples showed that changes in GH levels were never preceded by a rise or decrease in cAMP release, in contrast to existing information. The participation of more than one signal transduction mechanism in the mediation of the effect of GHRH is very likely, and the balance of these mechanisms may vary with the dose and duration of stimulation.
Assuntos
AMP Cíclico/metabolismo , Hormônio Liberador de Hormônio do Crescimento/antagonistas & inibidores , Hormônio do Crescimento/metabolismo , Hipófise/metabolismo , Sermorelina/análogos & derivados , Animais , Células Cultivadas , Relação Dose-Resposta a Droga , Hormônio Liberador de Hormônio do Crescimento/fisiologia , Masculino , Hipófise/citologia , Hipófise/efeitos dos fármacos , Radioimunoensaio , Ratos , Ratos Sprague-Dawley , Sermorelina/farmacologia , Transdução de Sinais , Fatores de TempoRESUMO
Following the observation that the activity of gonadotropin-releasing hormone III (GnRH-III) in the suppression of growth of MDA-MB-231 and MCF-7 breast cancer cells surpasses that of GnRH and other analogs thereof, analogs of GnRH-III were synthesized to investigate the structural basis for the improved antitumor activity. Compounds synthesized include analogs with changes in the central sequence in which GnRH-III differs from GnRH and in the C- and N-terminal regions. The results indicate that a salt bridge between Asp6 and Lys8 stabilizes the active conformation of GnRH-III and show the importance of the Trp7. Replacement of the C-terminal Gly-NH2 with D-Ala-NH2 was not well tolerated, but replacement with ethylamide was. Replacement of pGlu1 with Ac-D-Trp appears to have a significantly deleterious effect on a unique conformation of GnRH-III which is responsible for its binding to the receptors on cancer cell lines and the resultant antitumor activity.
Assuntos
Antineoplásicos/síntese química , Hormônio Liberador de Gonadotropina/análogos & derivados , Oligopeptídeos/síntese química , Oligopeptídeos/farmacologia , Antineoplásicos/química , Antineoplásicos/farmacologia , Divisão Celular/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão , Cromatografia em Camada Fina , Hormônio Liberador de Gonadotropina/síntese química , Hormônio Liberador de Gonadotropina/química , Hormônio Liberador de Gonadotropina/farmacologia , Humanos , Oligopeptídeos/química , Conformação Proteica , Relação Estrutura-Atividade , Células Tumorais CultivadasRESUMO
The effect of a 6-h infusion of gonadotrophin-releasing hormone (GnRH) or its analogues on dispersed anterior pituitary cells from male or female rats was investigated. The cells were stimulated with 3-min pulses of K(+) and GnRH. Thereafter GnRH (1 nM) or GnRH analogues ([D-Trp(6) ]GnRH-ethylamide ([D-Trp(6) ]GnRH, 50 pM), [D-Phe(6) , Gln(8) ]GnRH-ethylamide (Folligen, 100 pM) and [Asu(6) ]GnRH-ethylamide ([Asu(6) ]GnRH, 33 pM)) were applied for 6 h. In cells from female rats this treatment resulted in a 20-fold increase in luteinizing hormone (LH) secretion during the first 90-min period of the 6-h incubation. Following this a gradual decrease in LH release occurred, and during the fourth 90-min period the amount of LH secreted was only one-third or less of the initial value. The pituitary cells of male rats responded to the same treatment with only a 7-fold rise of LH secretion during the first period. In the second 90-min of the 6-h incubation a 20% to 30% increase was observed. Even in the fourth 90-min period the amount of LH secreted was two-thirds or more greater than that of the first 90-min period. When using 10-fold greater concentrations of the same peptides in males, the increase in hormone secretion in the second 90-min was not seen and the hormone release decreased to around 50%. We found definite differences in the responses of male and female rat pituitary cells to the 6-h infusion of GnRH or its analogues: the initial amplitude of the response in females was higher but desensitization was stronger. In males, the initial response was weaker; however, even using doses one magnitude greater, the level of desensitization did not reach the values obtained in females. The results were similar both with GnRH and the analogues. The responses to 3-min K(+) and GnRH stimuli given after the 6-h incubation were strongly reduced in cells from female rats compared to the initial responses; however, in cells from male rats the reaction was higher or unchanged. The ratio of LH released by the final K(+) stimulus relative to the actual LH content of the cells decreased in females but increased in males. Our data show that the differences between the pattern of desensitization in cells from male and female rats may be caused by the differences in the amount and ratio of immediately releasable hormone and the hormone replenishment into these pools.
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Lamprey gonadotropin releasing-hormone (LGnRH)-III, a hypothalamic neurohormone recently isolated from sea lamprey, was reported to have a selective stimulatory effect on follicle-stimulating hormone (FSH) release in rats and suggested to be the mammalian FSH-releasing factor. In this study, we determined the relative luteinizing hormone (LH)- and FSH-releasing potency of LGnRH-III compared to mammalian gonadotropin-releasing hormone (LHRH) in normal female rats, ovariectomized (OVX) and oestrogen/progesterone substituted rats and the superfused rat-pituitary cell system. The specificity of LGnRH-III for the mammalian LHRH receptor was investigated by blocking the receptor with an LHRH antagonist, MI-1544. In vitro, LGnRH-III dose-dependently stimulated both LH and FSH secretion from rat pituitary cells at 10(-7) to 10(-5) M concentrations, while LHRH stimulated gonadotropin secretion at a 1000-fold lower doses (10(-10) to 10(-8) M). The difference between its LH- and FSH-releasing potency was similar to that of LHRH. LGnRH-III bound to high affinity binding sites on rat pituitary cells with a Kd of 6.7 nM, B(max)=113 +/- 27 fmol/mg protein. In vivo, LGnRH-III also stimulated both LH and FSH secretion in a dose-dependent manner and, similar to LHRH, induced a greater rise in the serum LH than the FSH level. In normal cycling rats, it showed 180-650-fold weaker potency than LHRH in stimulating LH secretion and 70-80-fold weaker effect in stimulating FSH secretion. In OVX rats, LGnRH-III demonstrated a similarly weak effect on both gonadotropins. It was found to be 40-210-fold less potent than LHRH regarding LH release and 50-160-fold weaker regarding FSH release. LHRH-receptor antagonist MI-1544 prevented both the LH- and the FSH-releasing effect of LGnRH-III both in vitro and in vivo. These results do not support the hypothesis that LGnRH-III might be the mammalian FSH-releasing factor but demonstrate that it is a weak agonist for the pituitary LHRH receptor and stimulates both gonadotropins in a dose-dependent fashion.
Assuntos
Hormônio Foliculoestimulante/metabolismo , Hormônio Liberador de Gonadotropina/análogos & derivados , Hormônios/farmacologia , Oligopeptídeos/farmacologia , Animais , Relação Dose-Resposta a Droga , Feminino , Hormônio Foliculoestimulante/sangue , Hormônio Liberador de Gonadotropina/farmacologia , Lampreias , Hormônio Luteinizante/sangue , Hormônio Luteinizante/efeitos dos fármacos , Hormônio Luteinizante/metabolismo , Ovariectomia/métodos , Hipófise/citologia , Hipófise/efeitos dos fármacos , Hipófise/metabolismo , Ácido Pirrolidonocarboxílico/análogos & derivados , Ratos , Ratos Wistar , Receptores LHRH/antagonistas & inibidores , Receptores LHRH/fisiologia , Taxa Secretória/efeitos dos fármacos , Fatores de TempoRESUMO
In the search for more potent antagonists of hGH-RH, 20 new analogs were synthesized, purified and tested in vitro. All the analogs were based on the N-terminal sequence of 28 or 29 amino acid residues of hGH-RH, but contained D-Arg2 and Nle27 modifications. Most analogs had Phe (pCl)6 and Agm29 substituents. The effect of other substitutions such as Abu8 and/or Abu15 and Ala15 and various hydrophobic and hydrophilic D or L amino acids at position 8 were also investigated. All the peptides were acylated at the N-terminus in an attempt to increase the antagonistic activity. In the superfused rat pituitary cell system, most analogs inhibited more powerfully the GH release induced by GH-RH than the standard antagonist [Ac-Tyr1, D-Arg2]hGH-RH (1-29)-NH2. Some antagonists were long acting. Among the peptides synthesized, antagonist PhAc[D-Arg2, Phe(pCl)6, Abu15, Nle27]hGH-RH (1-28) Agm (MZ-5-156) appeared to be the most potent and inhibited GH release in vitro 63-200 times more powerfully than the standard antagonist. MZ-5-156 and other antagonists showed high binding affinities to membrane receptors for GH-RH. Some of these hGH-RH antagonists could be further developed for possible onocological applications.
Assuntos
Hormônio Liberador de Hormônio do Crescimento/antagonistas & inibidores , Hormônio Liberador de Hormônio do Crescimento/síntese química , Animais , Linhagem Celular , Cromatografia Líquida de Alta Pressão , Hormônio do Crescimento/sangue , Hormônio do Crescimento/química , Hormônio Liberador de Hormônio do Crescimento/análogos & derivados , Hormônio Liberador de Hormônio do Crescimento/metabolismo , Humanos , Ligação Proteica , Inibidores da Síntese de Proteínas/metabolismo , Inibidores da Síntese de Proteínas/farmacologia , RatosRESUMO
Female rats were treated in vivo with estrogen for three weeks. The pituitaries were then removed and their responses to somatostatin, dopamine, TRH, hGHRH(1-44)NH2, or their combination were examined in a superfused pituitary cell system. Somatostatin did not decrease basal prolactin secretion in the control cells, but it caused a dose-dependent decrease in prolactin release from the estrogen pretreated cells. Estrogen pretreatment did not alter the sensitivity of pituitary cells to dopamine; dopamine was equally effective in the control and estrogen pretreated pituitaries in decreasing the basal prolactin secretion and TRH induced prolactin release. Prolactin release from the estrogen pretreated cells, stimulated by 25 nM TRH was inhibited by 1 nM somatostatin and nearly totally abolished by 25 nM somatostatin, whereas in the control cells only the higher dose of somatostatin caused some decrease in the prolactin release. Estrogen pretreated cells showed a reduced response to GHRH. Somatostatin did not decrease the basal secretion of GH in either group, but at 1 nM dose it completely abolished the GH release induced by equimolar concentration of GHRH. However, after somatostatin was eliminated from the system, a delayed GH release could be observed that was greater in the control pituitaries than in the estrogen pretreated pituitaries. It is concluded that in vivo treatment with estrogen reduces GH secretion in response to GHRH and increases prolactin secretion after TRH stimulation. After estrogen treatment, the basal and TRH stimulated prolactin release can be effectively reduced by somatostatin. These effects could be observed in vitro using estrogen free tissue culture medium for up to 36 hours after the removal of the pituitaries. The reciprocal changes in GH and prolactin secretion support the concept of the transdifferentiation of GH and prolactin secreting cells.
Assuntos
Estrogênios/farmacologia , Hormônio do Crescimento/metabolismo , Prolactina/metabolismo , Animais , Células Cultivadas , Relação Dose-Resposta a Droga , Estradiol/farmacologia , Feminino , Hormônio do Crescimento/efeitos dos fármacos , Adeno-Hipófise/citologia , Adeno-Hipófise/efeitos dos fármacos , Prolactina/efeitos dos fármacos , Ratos , Ratos Sprague-DawleyRESUMO
The effect of a 6-h infusion of 1 nM gonadotropin-releasing hormone (GnRH) on LH release from dispersed anterior pituitary cells from rats in metoestrus ("metoestrus cells"), intact male rats ("male cells"), ovariectomized rats ("ovx cells"), and from orchidectomized rats ("orchidex cells") was investigated. Using metoestrus cells the initial amplitude of the response was high but desensitization was strong: the amount of LH secreted in the last 90-min period of the 6-h incubation was less than 20% of the initial value. In male cells, the immediate response was weaker; however, in the second 90-min of the 6-h incubation a 20% to 30% increase was observed and even in the fourth 90-min period the amount of LH secreted was more than 70% of the initial levels. Gonadectomy diminished the gender specific differences. Desensitization became less pronounced when ovx cells were used and its level was found to increase in orchidex cells, as compared to metoestrus cells and male cells, respectively. The responses to 3-min pulses of GnRH and KCl given after the 6-h incubation were strongly reduced in metoestrus cells but increased in male cells, compared to the initial peaks. Gonadectomy nullified these differences, too. Our data show that gonadectomy causes alterations in the intracellular pools of LH available for immediate and prolonged release in male and female rats. Decrease of estrogen in the sex steroid balance of female rats reduces the amount of LH available for immediate release and relatively increases the rate of replenishment into the immediate release pool. This allows a more stable secretion of LH during the 6-h stimulation. Decrease in androgens causes opposite changes. These phenomena could be observed in vitro, after keeping the pituitaries in a hormone free milieu for 16-28 h.
Assuntos
Hormônio Liberador de Gonadotropina/farmacologia , Ovário/fisiologia , Adeno-Hipófise/efeitos dos fármacos , Adeno-Hipófise/metabolismo , Testículo/fisiologia , Animais , Resistência a Medicamentos , Feminino , Técnicas In Vitro , Hormônio Luteinizante/metabolismo , Masculino , Orquiectomia , Ovariectomia , Ratos , Ratos Wistar , Caracteres SexuaisRESUMO
The pericentromeric regions of human chromosomes pose particular problems for both mapping and sequencing. These difficulties are due, in large part, to the presence of duplicated genomic segments that are distributed among multiple human chromosomes. To ensure contiguity of genomic sequence in these regions, we designed a sequence-based strategy to characterize different pericentromeric regions using a single (162 kb) 2p11 seed sequence as a point of reference. Molecular and cytogenetic techniques were first used to construct a paralogy map that delineated the interchromosomal distribution of duplicated segments throughout the human genome. Monochromosomal hybrid DNAs were PCR amplified by primer pairs designed to the 2p11 reference sequence. The PCR products were directly sequenced and used to develop a catalog of sequence tags for each duplicon for each chromosome. A total of 685 paralogous sequence variants were generated by sequencing 34.7 kb of paralogous pericentromeric sequence. Using PCR products as hybridization probes, we were able to identify 702 human BAC clones, of which a subset, 107 clones, were analyzed at the sequence level. We used diagnostic paralogous sequence variants to assign 65 of these BACs to at least 9 chromosomal pericentromeric regions: 1q12, 2p11, 9p11/q12, 10p11, 14q11, 15q11, 16p11, 17p11, and 22q11. Comparisons with existing sequence and physical maps for the human genome suggest that many of these BACs map to regions of the genome with sequence gaps. Our analysis indicates that large portions of pericentromeric DNA are virtually devoid of unique sequences. Instead, they consist of a mosaic of different genomic segments that have had different propensities for duplication. These biologic properties may be exploited for the rapid characterization of, not only pericentromeric DNA, but also other complex paralogous regions of the human genome.
Assuntos
Centrômero/química , Centrômero/genética , Genoma Humano , Mosaicismo/genética , Conformação de Ácido Nucleico , Mapeamento Cromossômico , DNA Satélite/química , Humanos , Hibridização In Situ , Dados de Sequência MolecularRESUMO
The release of growth hormone (GH) and cAMP was studied in superfused rat pituitary cells by infusing growth hormone-releasing hormone (GHRH) at different doses or a combination of GHRH and somatostatin 14 (SS-14). Three-minute pulses of GHRH caused a dose-dependent GH and cAMP release (effective concentration of 50% of the maximal biological effect is 0.21 nM and 52.5 nM, respectively). The lowest effective doses of GHRH in the superfusion system were 0.03 nM for GH release and 0.3 nM for cAMP discharge when 3-min pulses were applied. The amount of cAMP liberated from the cells was not proportional to GH release: cAMP responses to low doses of GHRH were disproportionally small, and the gradual increase in the release of cAMP after high doses of GHRH was not followed by a parallel rise in GH release. The desensitization induced by repeated pulses or prolonged infusion of GHRH resulted in a greater reduction in GH release than in cAMP liberation. A simultaneous infusion of SS-14 completely blocked GH release stimulated by GHRH but did not inhibit the immediate release of cAMP caused by GHRH. An abrupt decrease in GHRH-stimulated GH release induced by SS-14 was followed by only a minimal reduction in cAMP liberation 9 min later. Our findings indicate that a discharge of cAMP is stimulated after a GHRH pulse, but this effect alone cannot maintain the release of GH. Other steps of the signal transduction mechanisms that are independent of the cAMP route may participate in the process of GH release. The nature of the mechanisms involved in the mediation of GH release may vary with the doses of GHRH used.
Assuntos
AMP Cíclico/metabolismo , Hormônio do Crescimento/metabolismo , Hipófise/efeitos dos fármacos , Sermorelina/farmacologia , Animais , Relação Dose-Resposta a Droga , Humanos , Técnicas In Vitro , Cinética , Masculino , Hipófise/metabolismo , Ratos , Ratos Sprague-Dawley , Sermorelina/síntese química , Fatores de TempoRESUMO
The publication of the human genome draft sequence provides, for the first time, a global view of the structural properties of the human genome. Initial sequence analysis, in combination with previous published reports, reveals that more than half of the transition regions between euchromatin and centromeric heterochromatin contain duplicated segments. The individual duplications originate from diverse euchromatic regions of the human genome, often containing intron-exon structure of known genes. Multiple duplicons are concatenated together to form larger blocks of wall-to-wall duplications. For a single chromosome, these paralogous segments can span >1 Mb of sequence and define a buffer zone between unique sequence and tandemly repeated satellite sequences. Unusual pericentromeric interspersed repeat elements have been identified at the junctions of many of these duplications. Phylogenetic and comparative studies of pericentromeric sequences suggest that this peculiar genome organization has emerged within the last 30 million years of human evolution and is a source of considerable genomic variation between closely related primate species. Interestingly, not all human pericentromeric regions show this proclivity to duplicate and transpose genomic sequence, suggesting at least two different models for the organization of these regions.
Assuntos
Eucromatina/genética , Genoma Humano , Heterocromatina/genética , Evolução Molecular , Duplicação Gênica , HumanosRESUMO
Epidermal growth factor (EGF) and its receptors (EGFR) play important roles in tumorigenesis. In various experimental cancers, treatment with antagonists of bombesin/gastrin-releasing peptide (BN/GRP) produces a reduction in EGFRs, concomitant to inhibition of tumor growth. To investigate the mechanisms involved, we monitored concentrations of BN/GRP antagonist RC-3095 in serum of mice, rats, and hamsters given a single subcutaneous or intravenous injection of this analog. In parallel studies, we measured levels and mRNA expression of EGFRs in estrogen-dependent and independent MXT mouse mammary cancers, following a single subcutaneous administration of RC-3095 to tumor-bearing mice. Peak values of RC-3095 in serum were detected 2 min after intravenous or 15 min after subcutaneous injection. The levels of RC-3095 declined rapidly and became undetectable after 3-5 hr. In the estrogen-dependent MXT tumors, the concentration of EGF receptors was reduced by about 60% 6 hr following injection and returned to original level after 24 hr. Levels of mRNA for EGFR fell parallel with the receptor number and were nearly normal after 24 hr. In the hormone-independent MXT cancers, the number of EGFRs decreased progressively, becoming undetectable 6 hr after injection of RC-3095, and returned to normal values at 24 hr, but EGFR mRNA levels remained lower for 48 hr. Thus, in spite of rapid elimination from serum, BN/GRP antagonist RC-3095 can induce a prolonged decrease in levels and mRNA expression of EGFRs. These findings may explain how single daily injections of BN/GRP antagonists can maintain tumor growth inhibition.
Assuntos
Bombesina/análogos & derivados , Bombesina/antagonistas & inibidores , Receptores ErbB/metabolismo , Neoplasias Mamárias Experimentais/metabolismo , Fragmentos de Peptídeos/farmacologia , RNA Mensageiro/genética , Animais , Anticarcinógenos/sangue , Anticarcinógenos/farmacologia , Bombesina/sangue , Bombesina/farmacologia , Cricetinae , Receptores ErbB/genética , Feminino , Masculino , Mesocricetus , Camundongos , Camundongos Nus , Fragmentos de Peptídeos/sangue , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
Bombesin-like and GRP-like peptides may act as autocrine growth factors in the proliferation of some cancers. A pseudononapeptide bombesin antagonist, [D-Tpi6,Leu13 psi(CH2NH)-Leu14]bombesin(6-14), and related analogs synthesized in our laboratory significantly inhibit tumor growth in various cancer models. A radio-immunoassay (RIA), suitable for determination of RC-3095 and its congeners in unextracted serum, was developed in order to facilitate further experimental and clinical evaluation of this bombesin/GRP receptor antagonist for the treatment of various tumors. Antibodies were generated against RC-3095 and Des-Tpi1-RC-3095, conjugated to bovine serum albumin with glutaraldehyde. Antiserum JH-631b was selected for further experiments based on the antibody characterization. At an antiserum dilution of 1:189,000, this antibody bound approximately 50% of 7 fmol of added radiolabeled Tyr1-RC-3095. The antibody crossreacted with C-terminal fragments of RC-3095. Fragments without the C-terminus and naturally existing peptides of the bombesin family or structurally unrelated peptides did not cross-react. The minimum detectable dose of RC-3095 was 0.4 pg/tube. Intra- and interassay coefficients of variation ranged from 3.2 to 4.4% and from 5.6 to 12.8%, respectively. The RIA is suitable for direct determination of RC-3095 in serum. The RIA should be of value for monitoring levels of this analog in serum during long-term therapy.
Assuntos
Antineoplásicos/análise , Bombesina/análogos & derivados , Bombesina/antagonistas & inibidores , Oligopeptídeos/análise , Fragmentos de Peptídeos/análise , Peptídeos/antagonistas & inibidores , Radioimunoensaio , Animais , Antineoplásicos/farmacocinética , Antineoplásicos/farmacologia , Bombesina/análise , Bombesina/farmacocinética , Bombesina/farmacologia , Peptídeo Liberador de Gastrina , Masculino , Oligopeptídeos/farmacologia , Fragmentos de Peptídeos/farmacocinética , Fragmentos de Peptídeos/farmacologia , Ratos , Ratos Sprague-Dawley , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
Analogs of the 29 amino acid sequence of human growth hormone-releasing hormone (hGH-RH) with agmatine (Agm) in position 29, desaminotyrosine (Dat) in position 1, norleucine (Nle) in position 27, and L-alpha-aminobutyric acid (Abu) in position 15 have been synthesized, and their biological activity was evaluated. Some peptides contained one or two residues of ornithine (Orn) instead of Lys in positions 12 and 21 and additional replacements in positions 8 and 28. All analogs were found to be more potent than hGH-RH-(1-29)-NH2 in the superfused rat pituitary cell system. In tests in vivo in rats after subcutaneous administration, the analogs JI-22, [Dat1, Orn12,21, Abu15, Nle27, Agm29]hGH-RH-(1-29); JI-34, [Dat1, Orn12,21,Abu15,Nle27, Asp28, Agm29]hGH-RH-(1-29); JI-36, [Dat1, Thr8, Orn12,21, Abu15,Nle27,Asp28,Agm29]hGH-RH-(1-29); and JI-38, [Dat1,Gln8, Orn12,21,Abu15,Nle27,Asp28,Agm29]hGH-RH-(1 -29) displayed a potency 44.6,80.9,95.8, and 71.4 times greater, respectively, than that of hGH-RH-(1-29)-NH2 at 15 min and 217.1, 89.7, 87.9, and 116.8 times greater at 30 min. After intravenous administration, JI-22, JI-36, and JI-38 were 3.2-3.8 times more potent than hGH-RH-(1-29)-NH2 at 5 min and 6.1-8.5 times more active at 15 min. All analogs were found to have higher binding affinities for GH-RH receptors on rat pituitary cells than hGH-RH-(1-29)-NH2. Because of high activity and greater stability, these analogs could be considered for therapy of patients with growth hormone deficiency.
Assuntos
Hormônio Liberador de Hormônio do Crescimento/análogos & derivados , Hormônio Liberador de Hormônio do Crescimento/síntese química , Hormônio do Crescimento/metabolismo , Oligopeptídeos/farmacologia , Hipófise/metabolismo , Sequência de Aminoácidos , Animais , Hormônio do Crescimento/sangue , Hormônio Liberador de Hormônio do Crescimento/agonistas , Hormônio Liberador de Hormônio do Crescimento/farmacologia , Humanos , Técnicas In Vitro , Masculino , Dados de Sequência Molecular , Oligopeptídeos/síntese química , Hipófise/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Receptores de Neuropeptídeos/metabolismo , Receptores de Hormônios Reguladores de Hormônio Hipofisário/metabolismo , Relação Estrutura-AtividadeRESUMO
CFY male rats anaesthetized with pentobarbital were used in different groups for inducing acute pancreatitis by the retrograde injection either of 1 mg elastase, 5 mg trypsin, 4 mg lysolecithin, 10 mg Na-taurocholate in 0.2 ml volume or of 0.3 m. sunflower oil. In each group laparatomized animals served for control. The animals with pancreatitis were treated either with 15 mug/b.w.kg/hour glucagon or with physiological saline for 72 hours. Twenty-four and 72 hours after inducing pancreatitis glucagon did not influence the significant fall in blood pressure elicited by the intraductal injection of trypsin or elastase or in the plasma calcium level in pancreatitis induced by trypsin or sunflower oil. Neither did glucagon affect the significant increase of plasma lipase activity in pancreatitis induced by trypsin or taurocholate. It also failed to reduce the 24-hour mortality rate and the extension of fat tissue necrosis in the abdominal cavity of pancreatitic animals. In contrast, glucagon treatment significantly reduced the amount of abdominal exudate associated with bile salt induced pancreatitis and, probably due to its pancreatic blood flow increasing effect, seemed to moderate the degree of tissue damage elicited in the pancreas by detergents such as taurocholate or lysolecithin.