CLOTTING PROCESSES IN CRUSTACEA DECAPODA

1. In Limulidae, all the factors involved in the coagulation processes are located inside the amoebocytes. The cellular coagulogen is a single 20,000-polypeptide-chain protein. It is converted into a non-covalently crosslinked gel by a serine protease enzyme which cleaves a single peptide bond, releasing peptice C.
2. Pro-clotting enzyme can be activated by two independent pathways: coagulation is induced by either LPS or 1,3-β-D-glucan, both of which result in gel formation. The two pathways comprise a complex enzyme cascade with several limited protein proteolyses.
3. In Decapoda, clotting factors are found in both the cell-free plasma and haemocyte compartments. Analogous factors are present in Insecta.
4. Plasma coagulogen is a 400,000 molecular weight protein with both lipid and carbohydrate moieties. Its soluble polymers are converted into covalently crosslinked polymers of coagulin by Ca²⁺-dependent transglutaminase. In crayfish, it is also found in other tissues such as soft integument and calcified cuticle. Its concentration varies greatly with the species investigated. It seems to possess many diversified functions such as plasma coagulation, protein transport of tanning agents, lipid and sugar transport and protein storage, and resembles fibronectin.
5. A type of cellular coagulogen seems to be present in the haemocytes of Decapoda. It can be converted to a gel by a serine protease pro-clotting enzyme. This pro-enzyme can be activated by either LPS or 1,3-β-D-glucans. The mechanism of LPS action is not entirely clear. 1,3-β-D-glucans also activate the prophenoloxidase system and cause phenoloxidase attachment to foreign surfaces of haemocyte lysates. The latter system is restricted to semi-granular and granular haemocytes, and plays an important part in host-defence reactions.
6. The evolutin of clotting processes throughout the phylogenetic tree is discussed.     

INSECT HORMONES IN DEVELOPMENT

Advances in studies of prothoracicotropic hormone (ecdysiotropin), ecdysteroids and juvenile hormones in the past decade are considered:
1. Until recently there has been little progress with prothoracicotropic hormone. The development of a sensitive bioassay for the hormone promises to produce rapid advances.
2. Current methods of hormone analysis are described, with detection limits. The application of these methods in studies of hormones at different stages and in different tissues of insects have revealed a far greater complexity in hormone titres than was predicted from classical studies.
3. Very few studies employ chemical characterization of hormones and some assays do not distinguish biologically inactive metabolites of the hormones from the active hormones. Many studies have thus failed to reveal the numerous rapid fluctuations in hormone titre necessary for insect development.
4. While ecdysteroids act, via a receptor, on specific chromosome sites, the cellular mode of action of juvenile hormone in larval development is still unknown. Recent evidence suggests that juvenile hormone acts prior to the time at which its effects are realized by ecdysteroids.
5. Insect hormones produce dramatic changes in gene activity and their co-ordinate control of specific protein synthesis has been the basis for a number of 'model systems' of gene control in higher eukaryotes.     

NITROGEN EXCRETION IN MARINE AND FRESH-WATER CRUSTACEA

1. The major characteristic of aquatic Crustacea is ammonotelism as shown by the relative importance of various nitrogenous end-products of their nitrogen metabolism.
2. In contrast to urico- and ureo-genesis pathways, ammoniogenesis pathways have received recent attention; some specific enzymes such as glutamate dehydrogenase, AMP-deaminase and glutaminase are now admitted to play a possible key role in ammoniogenesis of various crustacean species.
3. Processes involved in ammonia output through the gill epithelium (diffusion and/or ionic exchanges) are discussed though few data related to Crustacea are as yet available compared to those obtained in ammonotelic fishes.
4. The effects of some environmental factors as well as the physiological state of animals on nitrogen excretion of Crustacea are envisaged. The effects of temperature, salinity and NH₄ concentration in the external medium are discussed first, followed by the changes in nitrogen excretion associated with the moult cycle, the nutritional state of animals and possible neuroendocrine control. It is demonstrated that the response of the excretion rate to these factors presents various patterns according to the species, its osmoregulatory abilities and its body reserves. Changes can also occur in the requisite metabolic pathways, thus increasing the difficulty of generalization.
5. In spite of the great diversity encountered within Crustacea an attempt to bring out general trends of their nitrogen excretion is proposed.
6. The present review is focused on metabolic and physiological aspects of crustacean nitrogen excretion but the significance of nitrogen release in nutrient regeneration in marine and fresh-water ecosystems is foreseen.     

CALCIUM BALANCE AND MOULTING IN THE CRUSTACEA

1. Crustaceans have a high content of calcium, which is chiefly located in the skeleton as calcium carbonate. Calcium is generally the most abundant cation in the body. 2. During intermoult, the exoskeleton is usually fully calcified and the animal is in calcium equilibrium with its environment. 3. In the premoult stages calcium is resorbed from the skeleton and may be lost to the environment or stored within the body. Typically, losses are high and storage is small in aquatic species, whilst most terrestrial forms store much larger amounts of calcium and losses are reduced. Loss of calcium in soluble form by aquatic species must be by outward transport across the gills. 4. Calcium is stored in a variety of different ways, usually with a common taxonomic theme. The main forms are as calcium phosphate granules in cells of the midgut gland (Brachyura), gastroliths (Astacidea and some Brachyura), the haemocoel (some Brachyura) the posterior midgut caeca (Amphipoda) and the ventral portion of the body generally in the Isopoda. 5. At ecdysis, the skeleton is shed and the calcium remaining in it is lost from the body. 6. Recalcification begins immediately, or shortly after, ecdysis using calcium mobilized from the stores. Simultaneously, or when the stores are exhausted, other sources of calcium are utilized. These are calcium in the water (aquatic species), the food (aquatic and terrestrial species) and the exuviae (chiefly terrestrial species). 7. Marine species store little calcium and must obtain the bulk of their requirement (ca. 95%) from the water. Fresh-water species also store little calcium but have, seemingly, adapted to the lower availability of calcium by increasing the affinity of the calcium-absorbing mechanism. The rates of uptake of calcium are consequently similar in marine and fresh-water species. 8. A high degree of storage is essential for terrestrial crustaceans as they do not have access to a large aquatic reservoir of calcium. These large reserves enable the animals to reach an advanced stage of calcification, allowing the resumption of foraging and feeding necessary for completion of calcification. 9. The control of calcium metabolism during the intermoult cycle is poorly under stood. β Ecdysone appears to control the resorption of calcium and the formation of calcium stores during premoult, but the mechanism of control of calcium metabolism during postmoult and intermoult is unknown. 10. The concentration of calcium in the haemolymph of most species is high, but a large proportion of this is in non-ionized form. In premoult, total calcium levels rise as a result of calcium resorption but little change occurs in the concentration of ionized calcium. Postmoult generally sees a fall in blood calcium, sometimes below the intermoult value.     

THE PRODUCTION OF HORMONES IN HIGHER PLANTS

• 1 Although much is known about the effects of plant hormones and their role in the control of growth and differentiation, little is known about the way in which hormone production is itself controlled or about the cellular sites of hormone synthesis. The literature on hormone production is discussed in this review in an attempt to shed some light on these problems.
• 2 The natural auxin of plants, indol-3yl-acetic acid (IAA) is produced by a wide variety of living organisms. In animals, fungi and bacteria it is formed as a minor by-product of tryptophan degradation. The pathways of its production involve either the transamination or the decarboxylation of tryptophan. The transaminase route is the more important.
• 3 In higher plants auxin is also produced as a minor breakdown product of trypto phan, largely via transamination. In some species decarboxylation may occur but is of minor importance. Tryptophan can also be degraded by spontaneous reaction with oxidation products of certain phenols.
• 4 The unspecific nature of the enzymes involved in IAA production and the probable importance of spontaneous, nonenzymic reactions in the degradation of tryp to phan make it unlikely that auxin production from tryptophan can be regulated with any precision at the enzymic level. The limiting factor for auxin production is the availability of tryptophan, which in most cells is present in insufficient quantities for its degradation to occur to a significant extent. Tryptophan levels are, however, considerably elevated in cells in which net protein breakdown is taking place as a result of autolysis.
• 5 An indole compound, glucobrassicin, occurs in Brassica and a number of other genera. It breaks down readily to form a variety of products including indole aceto-nitrile, which can give rise to IAA. There is, however, no evidence to indicate that glucobrassicin is a precursor of auxin in vivo.
• 6 Conjugates of IAA, e.g. IAA-aspartic acid and IAA-glucose, are formed when IAA is supplied in unphysiologically high amounts to plant tissues. These and other IAA conjugates occur naturally in developing seeds and fruits. There is no persuasive evidence for the natural occurrence of IAA-protein complexes.
• 7 Tissues autolysing during prolonged extraction with ether produce IAA from tryptophan released by proteolysis. IAA is produced in considerable quantities by autolysing tissues in vitro.
• 8 During the senescence of leaves proteolysis results in elevated levels of trypto phan. Large amounts of auxin are produced by senescent leaves.
• 9 Coleoptile tips have a vicarious auxin economy which depends on a supply of IAA, IAA esters and other compounds closely related to IAA from the seed. These move acropetally in the xylem and accumulate at the coleoptile tip. The production of auxin in coleoptile tips involves the hydrolysis of IAA esters and the conversion of labile, as yet unidentified compounds, to IAA. There is no evidence for the de novo synthesis of IAA in coleoptiles.
• 10 Practically all the other sites of auxin production are sites of both meristematic activity and cell death. The production of auxin in developing anthers and fertilized ovaries takes place in the regressing nutritive tissues (tapetum, nucellus, endosperm) as the cells break down. In shoot tips, developing leaves, secondarily thickening stems, roots and developing fruits auxin is produced as a consequence of vascular differ entiation; the differentiation of xylem cells and most fibres involves a complete auto-lysis of the cell contents; the differentiation of sieve tubes involves a partial autolysis. There is no evidence that meristematic cells produce auxin.
• 11 The lysis and digestion of cells infected with fungi and bacteria results in elevated tryptophan levels and the production of auxin. Viral infections reduce the levels of tryptophan and are asSociated with reduced levels of auxin.
• 12 Crown-gall tissues produce auxin. It is suggested that the crown-gall disease may involve at any given time the death of a minority of the cells which produce auxin and other hormones as they autolyse; the other cells grow and divide in response to these hormones.
• 13 Auxin is produced in soils, particularly those rich in decaying organic matter, by micro-organisms. This environmental auxin may be important for the growth of roots.
• 14 There is no convincing evidence that auxin is a hormone in non-vascular plants. The induction of rhizoids in liverworts by low concentrations of auxin can be ex plained as a response to environmental auxin.
• 15 Abscisic acid is synthesized from mevalonic acid in living cells. It is possible that under certain circumstances, abscisic acid or closely related compounds are formed by the oxidation of carotenoids.
• 16 The sites of gibberellin production are sites of cell death. It is possible that precursors of gibberellins, such as kaurene, are oxidized to gibberellins when cells die.
• 17 Cytokinins are present in transfer-RNA (tRNA) of animals, fungi, bacteria and higher plants. They are probably formed in plants by the hydrolysis of tRNA in autolysing cells. There is evidence that they are also formed in living cells in root tips.
• 18 Ethylene is produced in senescent, dying or damaged cells by the breakdown of methionine.
• 19 It was shown many years ago that wounded and damaged cells produced sub stances which stimulate cell division. It now seems likely that the production of wound hormones and the normal production of hormones as a consequence of cell death are two aspects of the same phenomenon. Wounded cells can produce auxin, gibberellins, cytokinins and ethylene.
• 20 The control of hormone production in living cells is a biochemical problem which remains unsolved. The control of production of hormones formed as a con sequence of cell death depends on the control of cell death itself. Cell death is con trolled by hormones which are themselves produced as a consequence of cell death.
• 21 In spite of the fact that dying cells are present in all vascular plants, in all wounded and infected tissues, in certain differentiating tissues in animals, in cancerous tumours and in developing animal embryos, the biochemistry of cell death is a subject which has been almost completely ignored. Dying cells are an important source of hormones in plants; some of the many substances released by dying cells may also be of physiological significance in animals.

     

刺楸种子层积过程中内源植物激素的动态变化及激素在种子休眠中的作用

本文主要以高效液相色谱为主要手段,结合生物测定方法,测定了4种不同层积条件下激素动态变化。结果表明刺楸干种子中存在有两种抑制物质-脱落酸(ABA)和香豆素(C),在种子层积的不同阶段又相继有GA₃,IAA和Z出现,并在层积后熟过程中呈现非常有规律的变化。根据激素的变化,可把种子整个后熟过程分三个阶段;即阶段Ⅰ,以抑制物质(ABA,C)和IAA水平迅速减少为主要特征,阶段Ⅱ主要表现为GA₃和Z合量的上升,阶段Ⅲ各种激素处于相对稳定的状态。种子的休眠与否可能主要取决于阶段Ⅱ的状况。在刺楸种子胚形态后熟期间,胚的生长与分化同ABA和C水平有很高的相关性,但同时也受GA₃和IAA的调节。生理后熟主要与Z有关,同ABA和C无明显相关性。同时本文还对激素相对水平做了初步研究,发现GA₃/ABA+IAA,Z/GA₃+IAA和GA₃/C+IAA^*,在种子后熟期间的变化同胚生长发育存在高度的一致性。认为激素的相对水平对种子休眠起重要的控制作用,还推测激素的作用可能类似于"板机"机制。     

水稻体内两种甾类性激素的研究

以三系杂交水稻的不育系（珍汕９７Ａ,丛广４１Ａ和马协Ａ）为实验材料,以其相应的保持系（珍汕９７Ｂ,丛广４１Ｂ和马协Ｂ）为对照,用放射免疫分析法测定不同发育时期的叶片和幼穗睾酮和雌二醇含量,结果表明,在供试水稻各时期叶片中睾酮和雌二醇含量均比穗中高,同时不论是叶片不是穗中,睾酮含量均高于雌二醇,但是睾酮和雌二醇在供试的３个组合的不育系和保持系内没有明显差异。     

植物激素在柑桔育苗中的应用

本文概述了在柑桔种苗生产中,植物激素对砧木种子萌发、嫁接成活、砧木苗和嫁接苗生长以及扦插生根的影响。