Compensatory hypertrophy in radiothyroidectomized dwarf rats.

The aim of the study was to clarify whether growth hormone and thyroid hormones play a role in compensatory organ hypertrophy. Radiothyroidectomized dwarf rats with serious disorder of growth hormone production due to the loss of thyroid function were used in the experiments. As regards growth hormone production these animals may be considered as having been "hypophysectomized". The loss of thyroid function and growth hormone deficiency did not affect the degree of compensatory hypertrophy of the kidney, the adrenal and the gonad. The observation indicates that the hormones under study are not of decisive importance in the mechanism of compensatory organ enlargement. Further investigations are needed to clarify whether organ enlargement in the hypometabolic rat occurring at the level observed in the controls is associated with enhanced function.     

Control of methyl farnesoate synthesis in the mandibular organ of the crayfish Procambarus clarkii: Evidence for peptide neurohormones with dual functions

Summary

Red pigment-concentrating hormone stimulates the mandibular organ of Procambarus clarkii to synthesize methyl famesoate. The mandibular organs of male crayfish were more active than those of females. Hormonal stimulation can be mimicked by calcium ionophore A23187 and the activity of the gland can be reduced by replacing calcium in the media with lanthanum. Mandibular organ synthetic activity is inhibited by pigment-dispersing hormone.     

Metabolic effects of the major component of bovine growth hormone

Bovine growth hormone, subjected to DEAE-cellulose chromatography, yielded one major and several minor components. The various chromatographic fractions of bovine growth hormone were compared with the parent material for their ability to promote hormone effects in vivo and in vitro. The major component of bovine growth hormone was homogeneous by acrylamide-gel electrophoresis, rechromatography and sedimentation equilibrium. Its amino acid composition was similar to that of the parent hormone. The major component possessed all the qualitative activities present in the original heterogeneous material, including promotion of acute hypoglycaemia and hypolipaemia. In studies in vitro in adipose-tissue segments the major component of the hormone increased entry of glucose and its oxidation to CO₂, conversion of glucose into glyceride glycerol, release of glycerol and incorporation of histidine into adiposetissue protein. Other chromatographic fractions of bovine growth hormone were not homogeneous and possessed some but not all of the metabolic activities attributed to the hormone preparations or its major component. Thus, the metabolic effects obtained with bovine growth-hormone preparations in vivo and in vitro can be obtained with the major homogeneous component of the hormone. This observation precludes the possibility that the metabolic effects obtained with bovine growth-hormone preparations are due to the combined actions of a number of components found therein.     

The tomato ethylene receptor gene family: Form and function

Phytohormones are essential for integrating many aspects of plant development and responses to the environment. Regulation of hormonally controlled events occurs at multiple levels: synthesis, catabolism and perception (Trewavas 1983, Bradford and Trewavas 1994). At the level of perception, sensitivity to hormones can be regulated both spatially and temporally during the life cycle. An example of spatial regulation is the differential response to a hormone that occurs during organ abscission. Temporally, sensitivity of an organ to a hormone may change during maturation, as occurs during fruit ripening. In this review, we will focus on the initial event in recognition of one hormone, ethylene. The ethylene receptor was the first plant hormone receptor to be unambiguously identified. Over the last few years, great progress has been made in elucidating the genes involved in ethylene action. Nonetheless, the mechanisms of signal transduction remain to be established. Here, we will address the status of the tomato receptor gene family and the evidence that regulation of receptor gene expression can influence the response of the plant to the hormone.     

甲状腺激素在两栖动物变态过程中的作用

两栖动物的幼体变态是研究甲状腺激素调节组织和器官重构的理想模式。本文主要综述了近年来两栖动物甲状腺激素合成过程中3种脱碘酶D1、D2和D3的特点及其生物学功能;甲状腺激素受体的蛋白结构、类型和机能;以及甲状腺激素对两栖动物幼体变态过程中各个类型组织和器官重构的调节;甲状腺激素、甲状腺激素受体和脱碘酶的互作,并展望了今后的研究方向。     

Towards mechanistic models of plant organ growth

Modelling and simulation are increasingly used as tools in the study of plant growth and developmental processes. By formulating experimentally obtained knowledge as a system of interacting mathematical equations, it becomes feasible for biologists to gain a mechanistic understanding of the complex behaviour of biological systems. In this review, the modelling tools that are currently available and the progress that has been made to model plant development, based on experimental knowledge, are described. In terms of implementation, it is argued that, for the modelling of plant organ growth, the cellular level should form the cornerstone. It integrates the output of molecular regulatory networks to two processes, cell division and cell expansion, that drive growth and development of the organ. In turn, these cellular processes are controlled at the molecular level by hormone signalling. Therefore, combining a cellular modelling framework with regulatory modules for the regulation of cell division, expansion, and hormone signalling could form the basis of a functional organ growth simulation model. The current state of progress towards this aim is that the regulation of the cell cycle and hormone transport have been modelled extensively and these modules could be integrated. However, much less progress has been made on the modelling of cell expansion, which urgently needs to be addressed. A limitation of the current generation models is that they are largely qualitative. The possibilities to characterize existing and future models more quantitatively will be discussed. Together with experimental methods to measure crucial model parameters, these modelling techniques provide a basis to develop a Systems Biology approach to gain a fundamental insight into the relationship between gene function and whole organ behaviour.     

The Hormonal Regulation of Flower Development

Homeotic genes comprising the ABCE classes partly detail the genetic networks that control aspects of floral organ initiation, development, and architecture, but less is known about how these gene functions are translated into changes at the cellular level in growth and cellular differentiation that are involved in the formation of diverse floral organs with specific shapes and sizes. Hormones are the principal transducers of genetic information, and due to recent advances in understanding hormone function in floral development, it is timely to review some of these findings. Flower development is the result of a regulated balance between meristem size and coordination and organ initiation. Floral meristem size is regulated by cytokinin, gibberellin, and auxin, and auxin plays a major role in organ initiation and organogenesis. How hormones contribute to the development of each organ is partly known, with stamen development reliant on almost all hormones, petal development is affected by gibberellins, auxin, and jasmonic acid, and gynoecium development is predominantly regulated by auxin. Furthermore, the interconnections between genetic hierarchies and hormones are being elucidated, and as almost all hormone groups are implicated in floral development, points of hormone crosstalk are being revealed.     

Studies on immunoassays of peptide factors. III. Gastrin/iso-1-cytochrome C as immunogen for raising anti-gastrin antisera

Iso-1-cytochrome c contains in penultimate position of its sequence a cysteine residue which in analogy to the known tertiary structures of cytochromes c should be exposed on the surface of the protein. Its selective reaction with N alpha-maleoyl-beta-alanyl-human-little-gastrin-I-[2-17] led to a well characterized and homogeneous gastrin conjugate to be used as immunogen in rabbits. The antisera raised by this procedure exhibited a degree of specificity for the hormone gastrin parallel to that of the gastrin receptor. This is clearly documented by comparison of the immune crossreactivities of gastrin-peptides of increasing chain length and of fragments corresponding to various regions of the hormone molecule with their biological activity. The immune response provoked in the animals by the use of an homogeneous immunogen was found to be highly reproducible in terms of specificity of the antigastrin antibodies.     

Chemical synthesis of insulin-like growth factor II

Human insulin-like growth factor II (IGF-II) with 67 amino acids and three disulfide bridges has been synthesized by the solid-phase method. The synthetic hormone is shown to be homogeneous in high performance liquid chromatography (HPLC), high performance partition chromatography (HPPC), and chromatofocusing. It is indistinguishable from natural hormone in HPLC, peptide map of thermolysin digests, amino acid composition and radioreceptor binding assay. Thus, synthetic and natural IGF-II are identical.     

Antigonadal effects of blinding in the presence of antibody against circulating melatonin

The effect of melatonin on reproductive function in the rat was studied. Reproductive organ weights and sex hormone levels were compared between sighted controls and animals which were either blinded, blinded and pinealectomized or blinded and immunized against circulating melatonin. Circulating androgens as measured by accessory sexual organ weights were significantly reduced by blinding. This effect was reversed by pinealectomy but not by immunization. Blinding also increased pineal melatonin levels but there were no differences in the plasma levels of luteinizing hormone. Circulating testosterone levels and pineal melatonin levels of immunized animals did not differ from those of blinded controls. These findings confirm reports that pineal stimulation by blinding enhances pineal melatonin content and inhibits accessory sex organ development. Circulating melatonin does not appear to be the mediator of the stimulated pineal's antigonadal effects in the rat since, in contrast to pinealectomy, neutralization of circulating melatonin failed to reverse accessory organ regression.     

An attempt at transmission of hormonal imprinting between foreign cell lines

Hormonal imprinting is transmitted from imprinted to virgin cells of the same cell line. No transmission of imprinting occurred between Chinese hamster ovary (CHO) and human Chang liver cells, and the presence of the latter reduced rather than enhanced the thyrotropic hormone (TSH) binding capacity of the CHO cells. While hormone binding capacity was relatively homogeneous in the control and the mixed cell cultures, it was not homogeneous in the homologous imprinted plus virgin cell population, indicating a continuous transmission of imprinting from the former to the latter.     

Preparation of highly purified human somatotropin (growth hormone)

A method for preparation of highly purified human somatotropin on large-scale basis is described. Starting from deep-frozen pituitary gland, less time is needed to obtain highly purified hormone than with other published methods for preparation of human somatotropin. The hormone obtained in this fasion is chromatographically and electrophoretically homogeneous; it shows high biological and radioimmunological growth hormone activity and is free of other pituitary hormone activities. The effects of various experimental conditions upon aggregation of somatotropin are critically evaluated.     

Developmentally regulated primary glucocorticoid hormone induction of chick retinal glutamine synthetase mRNA

We have characterized the glucocorticoid hormone induction of glutamine synthetase mRNA in embryonic chick retinal organ cultures by quantitative dot hybridization using a cDNA clone derived from chick retinal RNA. Hydrocortisone (Kapp = 3-4 nM) and dexamethasone (Kapp = 1-2 nM) produce an approximate 30-fold increase in glutamine synthetase mRNA after incubation of organ cultures derived from embryonic day 12 retinae with either hormone for 3 hr. Progesterone is a poor inducer. The glucocorticoid-mediated rise is rapid (t1/2 = 2-3 hr) and occurs in the presence of either of the protein synthesis inhibitors cycloheximide or puromycin, indicating that the induction is a primary or direct response to the hormone. However, the magnitude of the hormonal response observed in culture increases markedly during retinal development. These observations, coupled with the previously reported absence of a hormonal induction in embryonic liver, raise the possibility of a synergistic mechanism, involving tissue-specific regulatory molecules in addition to the glucocorticoid hormone receptor, to explain the retinal-specific primary glucocorticoid hormone induction of glutamine synthetase mRNA.     

The biochemical profile of rat testicular tissue as measured by magic angle spinning 1H NMR spectroscopy

The testis is the principal organ of male fertility, responsible for the production of spermatozoa and their maturation into sperm. However, the underlying biochemistry of the testis is relatively understudied. The fluidic and homogeneous nature of the testis makes it an ideal organ for high resolution magic angle spinning (MAS) 1H NMR spectroscopy. In this study we have catalogued the low molecular weight metabolites. The testis contains large amounts of creatine, of which a substantial proportion was shown to be extracellular using bipolar gradients to measure apparent diffusion coefficients. The tissue also contained relatively high amounts of uridine.     

Prothoracic gland involution related to moulting hormone levels during the metamorphosis of Tenebrio molitor L.

Prothoracic gland (PG) of Tenebrio shows ultrastructural changes which can be correlated with ecdysteroid levels (measured by radioimmunoassay) during larval-pupal development. However, the gland cells begin to degenerate before pupal-adult ecdysis: the PG involution is completed before the moulting hormone peak which triggers pupal-adult development. These facts strongly suggest that another endocrine organ produces moulting hormone needed for adult development.     

Thyroid hormone regulation of hepatic genes in vivo detected by complementary DNA microarray

The liver is an important target organ of thyroid hormone. However, only a limited number of hepatic target genes have been identified, and little is known about the pattern of their regulation by thyroid hormone. We used a quantitative fluorescent cDNA microarray to identify novel hepatic genes regulated by thyroid hormone. Fluorescent-labeled cDNA prepared from hepatic RNA of T3-treated and hypothyroid mice was hybridized to a cDNA microarray, representing 2225 different mouse genes, followed by computer analysis to compare relative changes in gene expression. Fifty five genes, 45 not previously known to be thyroid hormone-responsive genes, were found to be regulated by thyroid hormone. Among them, 14 were positively regulated by thyroid hormone, and unexpectedly, 41 were negatively regulated. The expression of 8 of these genes was confirmed by Northern blot analyses. Thyroid hormone affected gene expression for a diverse range of cellular pathways and functions, including gluconeogenesis, lipogenesis, insulin signaling, adenylate cyclase signaling, cell proliferation, and apoptosis. This is the first application of the microarray technique to study hormonal regulation of gene expression in vivo and should prove to be a powerful tool for future studies of hormone and drug action.     

Organ culture of the terminal abdominal segment of an adult female lepidopteron

Summary Organ cultures containing the sex pheromone gland ofDiatraea saccharalis (F.) (sugarcane borer) were maintained for over 2 months. Juvenile hormone but not ecdysterone appeared to be essential for the maintenance of integrity of the sex pheromone gland in the organ culture system. Muscles associated with these cultures pulsated during hte entire culture period with or without juvenile hormone, suggesting that the hormone requirement was specific for the sex pheromone gland and not a general requirement of the cells of the organ-cultured segment.     

Effect of chromatin associated factors on the activity of thyroid hormone receptors in rat liver and brain

Receptors for thyroid hormones were extracted by 0.4 M KCl from the nuclei of rat liver and brain, and their binding properties compared to the properties of these receptors in unextracted nuclear suspensions. The inhibititory effect of a non-iodinated thyroid hormone analogue, 3,5,dimethyl-3′-isopropyl-l-thyronine (DIMIT) on [¹²⁵I]-T₃ binding was observed in the nuclear suspension of brain, but absent when the solubilized receptors of the same organ were tested. The initial properties of the receptor could be restored in a system containing the receptor and the extracted chromatin. Moreover, when the liver solubilized receptor was supplemented with the brain chromatin extract, the hepatic receptor acquired the binding ability of the brain receptors. The data suggest that chromatin associated components may confer organ specificity in thyroid hormone effects, and play a role in the selectivity of the recognition of thyroid hormone analogues by the receptor.     

INVOLUTION OF MOUSE MAMMARY GLANDS DURING WHOLE ORGAN CULTURE OCCURS VIA APOPTOSIS OF EPITHELIAL TISSUE

Apoptosis was measured in mammary glands during whole organ culture, to determine whether regression resulting from hormone withdrawal results in epithelial cell death as in vivo involution. Glands were evaluated for morphology and DNA degradation prior to whole organ culture, after lobulo-alveolar development and 2, 4, or 6 days after hormone withdrawal. The data indicated that mammary regression during whole organ culture mimics in vivo involution and results in part from apoptosis of epithelial tissue.     

Evidence for one essential tryptophan residue at the active site of relaxin.

The hormone relaxin, which is responsible for the rapid widening of the birth channel in mammals prior to parturition, was purified from hog ovarian extracts and shown to be homogeneous by exclusion chromatography in 6 M guanidine hydrochloride and SDS gel electrophoresis. Of the two disulfide-linked chains that comprise relaxin, the larger chain was shown to contain two tryptophan residues, one of which could be completely oxidized in native relaxin without measurable effect on its biological activity. Oxidation of the second residue completely inactivated the hormone. Modifications of lysine side chains or carboxymethylation of a single methionine residue at low pH did not impair the effectiveness of relaxin.