Neurosecretion and Salt and Water Balance in the Annelida and Crustacea

The possible role of the neurosecretory system in regulationof salt and water has been studied in the annelids and crustaceans.In the earthworm, Lumbricus terrestris, a brain factor influences'the salt and osmotic concentration of the blood and coelomicfluid. Removal of the brain results in the increase of waterinflux with a decrease in the salt and osmotic concentrationsof the body fluids. The decreases in salt and osmotic concentrationscan be prevented by the implantation of the brain or the injectionof brain homogenates. In the freshwater crayfish, Procambarus clarkii, a factor, presumablysecreted in the brain and released in the eyestalk, seems tomaintain the normal permeability of the body surfaces to water.Eyestalk removal, which eliminates the release site, resultsin the increased influx of water with a decrease in the saltconcentration of the blood. A brain factor also seems to beinvolved in maintaining the sodium and osmotic concentrationsof the blood. In the semi-terrestrial grapsid crab, Metopograpsus messor,the thoracic ganglion, under the control of an eyestalk element,secretes a factor involved in increasing the permeability ofthe body surfaces to water. The removal of the eyestalks, theimplantation of the thoracic ganglion, or the injection of extractsof thoracic ganglia, results in changes in the osmotic concentrationof the blood tending toward that of the medium. In all threespecies studied, the neuroendocrine factors seem to be involvedprimarily in the regulation of the permeability of the bodysurfaces to water.     

The distribution of APGWamide and RFamides in the central nervous system and ovary of the giant freshwater prawn, Macrobrachium rosenbergii

Immunohistochemistry was used to identify the distribution of both APGWamide-like and RFamide-like peptides in the central nervous system (CNS) and ovary of the mature female giant freshwater prawn, Macrobrachium rosenbergii. APGWamide-like immunoreactivity (ALP-ir) was found only within the sinus gland (SG) of the eyestalk, in small- and medium-sized neurons of cluster 4, as well as their varicosed axons. RFamide-like immunoreactivity (RF-ir) was detected in neurons of all neuronal clusters of the eyestalk and CNS, except clusters 1 and 5 of the eyestalk, and dorsal clusters of the subesophageal, thoracic, and abdominal ganglia. The RF-ir was also found in all neuropils of the CNS and SG, except the lamina ganglionaris. These immunohistochemical locations of the APGWamide-like and RF-like peptides in the eyestalk indicate that these neuropeptides could modulate the release of the neurohormones in the sinus gland. The presence of RFamide-like peptides in the thoracic and abdominal ganglia suggests that it may act as a neurotransmitter which controls muscular contractions. In the ovary, RF-ir was found predominantly in late previtellogenic and early vitellogenic oocytes, and to a lesser degree in late vitellogenic oocytes. These RFs may be involved with oocyte development, but may also act with other neurohormones and/or neurotransmitters within the oocyte in an autocrine or paracrine manner.     

Bihormonal control of oogenesis in the freshwater prawn, Macrobrachium kistnensis

The hormonal control of oogenesis has been investigated in the freshwater prawn, Macrobrachium kistnensis. Experiments using bilateral eyestalk ablation and injection of eyestalk extract supported the presence of a gonad inhibiting factor in the eyestalk of female prawns. Injections of brain and thoracic ganglion extract in normal female prawns and in those subjected to bilateral eyestalk ablation revealed the presence of a gonad stimulating factor in the central nervous tissue.     

Regulation of the Crustacean Mandibular Organ

The crustacean mandibular organ (MO) produces methyl farnesoate(MF), a juvenile hormone-related compound thought to have rolesin crustacean reproduction and development. Therefore, the controlof MF production by the MO has been of considerable interest.Current evidence indicates that the MO is negatively regulatedby peptides present in the eyestalk (MO inhibiting factor, MO-IH).Several eyestalk neuropeptides have been identified that inhibitMF synthesis by MO incubated in vitro. The amino acid sequencesof these MO-IH peptides are similar to peptides in the crustaceanhyperglycemic hormone (CHH) family of neuropeptides. In addition,there appears to be a compound in the eyestalk that lowers hemolymphlevels of MF in vivo but does not directly affect the MO invitro. The inhibition of MF synthesis by eyestalk peptides involvesthe inhibition of farnesoic acid O-methyl transferase, the lastenzyme in the MF biosynthetic pathway. The activity of thisenzyme is affected by cyclic nucleotides, suggesting that thesecompounds may be involved in the signal transduction pathwaymediating the effects of MO-IH.     

Methyl farnesoate: Its site of synthesis and regulation of secretion in a juvenile crustacean

Analogy to Insecta suggests that JH(s) may play important roles in the development and reproduction of Crustacea. It has recently been shown by Laufer et al. (1987), using LC and GC/MS that the mandibular organ of adult crabs synthesized methyl farnesoate, the unepoxidated from of JH III, and that synthesis varied according to the sex, as a function of eyestalk ablation, and stage of vitellogenesis. In experiments reported here, we found that eyestalk removal from juvenile spider crabs, Libinia emarginata, resulted in a two-fold increase in the rate of MF synthesis by MOs in vitro. Furthermore, 2 h incubations of MOs from eyestalk ablated animals with eyestalk extracts inhibited the rate of synthesis of MF by about 60%. These results suggest that MF may be a gonad stimulating hormone (GSH) reported by other workers. Secretion by the MO is inhibited by an eyestalk factor (MO-IH), and MO-IH may be similar or identical to the gonad inhibiting hormone (GIH) reported by others.     

Physiological compensation in unilateral eyestalk ablated crayfish, Cherax quadricarinatus

The eyestalks of crustaceans contain neurosecretory cells involved in the regulation of molting. In crayfish, bilateral ablation results in increased molting frequency and weight gain whereas unilateral ablation typically has no effect on molting frequency and weight gain. The effects of unilateral ablation were examined in juvenile Australian freshwater crayfish, Cherax quadricarinatus. As observed for other crayfish species, molting frequency and weight gain of unilateral ablated crayfish were not significantly different from control (intact) crayfish. Survival of unilateral ablated crayfish, however, was reduced compared to controls and was likely due to stress associated with the surgical procedure itself. Using radiolabeling techniques, protein synthesis was determined for neural tissues from the remaining eyestalk of ablated crayfish and compared to protein synthesis of neural tissues from eyestalks of control, non-ablated crayfish. Protein synthesis of ablated crayfish neural tissues was significantly higher (ca. 45%) than protein synthesis of control neural tissues. Electrophoretic analysis (SDS-PAGE and autoradiography) further demonstrated that protein synthesis increased linearly for all proteins in the remaining eyestalk of ablated crayfish. Together, these results suggest that a compensatory response occurred in unilateral ablated crayfish allowing normal physiological functions, particularly those involved in regulating growth cycles, to be maintained. J. Exp. Zool. 289:184-189, 2001.     

The distribution of a kinin-like peptide and its co-localization with a CRF-like peptide in the blood-feeding bug, Rhodnius prolixus

Rhodnius prolixus, a blood-feeding hemipteran insect, ingests large meals which are followed by rapid diuresis to eliminate excess water and salt. In Rhodnius, serotonin and an unidentified peptide(s) [33,34] have been shown to act as neurohormonal diuretic factors. In other insects, two families of diuretic peptides, the corticotropin releasing factor (CRF)-like, and kinin peptides [9], have been identified and sequenced. Recently, we demonstrated the presence of a CRF-like diuretic peptide in the CNS and digestive system of Rhodnius [47] using immunohistochemistry and bioassay.In this study, combining immunohistochemistry and radioimmunoassay (RIA) techniques, we show the presence of leucokinin-like peptide(s) in the CNS and digestive system of Rhodnius 5th instar. Additionally, double-label immunohistochemistry demonstrates that the leucokinin-like and CRF-like peptides are co-localized in the posterior lateral neurosecretory cells of the mesothoracic ganglionic mass (MTGM) and in neurohaemal areas on abdominal nerves one and two, suggesting the possibility of co-release of the peptides into the hemolymph.Partially purified extracts of the CNS and neurohaemal tissue were tested in vitro on Malpighian tubule secretion and cAMP assays. The factors eluting with increasing acetonitrile percentages from Sep-Pak cartridges were assayed in the presence or absence of ketanserin, a serotonin antagonist which blocks the effects of serotonin on Malpighian tubules. The results indicate activity of serotonin and a CRF-like diuretic peptide on Rhodnius Malpighian tubules, but fail to demonstrate activity of the leucokinin-like peptide(s).The rapid diuresis following feeding is a highly coordinated event, requiring the movement of water and salt across the epithelial cells of the crop into the hemolymph, and from the hemolymph across the cells of the Malpighian tubules. The urine then travels along the Malpighian tubules into the hindgut in order to be expelled. The presence of a leucokinin-like peptide(s) in the CNS and digestive system, which co-localizes with a CRF-like peptide(s), suggests that kinins may play a role in the rapid diuresis, although possibly not directly on the Malpighian tubules.     

Endocrine Control of Hydromineral Balance in Teleosts

Hydromineral balance in teleosts is reviewed in an effort todefine common elements, as well as inter- and intra-speciesvariation in its endocrine control. Processes at the gill, gut, kidney, and urinary bladder arecompared. The difficulty in deriving functional generalitiesis discussed; the stimulation of both sodium influx and effluxby cortisol, the ingestion of equal amounts of water by somefishes in either fresh or sea water, and the equal glomerularfiltration rates in both hypotonic and hypertonic environmentsfor other fish confound such efforts at generalization. An attemptis made to explain these inconsistencies through an examinationof variation in hormonal balances and effector organ responses.Evidence for Na+/K+-ATPase involvement at the gill, gut, kidney,and urinary bladder is summarized. Patterns in cortisol andprolactin availability as a function of synthesis, storage,and secretion are considered. A rather consistent antagonismof cortisol and prolactin in sodium movement and water permeabilityat several teleost effector organs is substantiated.     

骨骼肌的内分泌功能

长期以来,骨骼肌被认为是一种效应器官,接受神经和体液的调节。近年大量实验研究资料发现骨骼肌也具有分泌活性物质的功能,能表达、合成和分泌多种生物信号分子,包括调节肽、细胞因子和生长因子等,也是一种重要的内分泌器官。骨骼肌分泌的活性物质以旁分泌和／或自分泌方式调节骨骼肌的生长、代谢和运动功能;甚至以血液循环内分泌的方式调节机体远隔器官组织的功能。骨骼肌生成和分泌的活性物质在运动系统疾病和某些全身性疾病的发病中具有重要的作用。本文将对骨骼肌分泌的主要活性物质及其生理和病理生理学意义进行综述。     

Aquaporins of the PIP2 class are required for efficient anther dehiscence in tobacco

Several processes during sexual reproduction in higher plants involve the movement of water between cells or tissues. Before flower anthesis, anther and pollen dehydration takes place before the release of mature pollen at dehiscence. Aquaporins represent a class of proteins that mediates the movement of water over cellular membranes. Aquaporins of the plasmamembrane PIP2 family are expressed in tobacco (Nicotiana tabacum) anthers and may therefore be involved in the movement of water in this organ. To gain more insight into the role these proteins may play in this process, we have analyzed their localization using immunolocalizations and generated plants displaying RNA interference of PIP2 aquaporins. Our results indicate that PIP2 protein expression is modulated during anther development. Furthermore, in tobacco PIP2 RNA interference plants, anther dehydration was slower, and dehiscence occurred later when compared with control plants. Together, our results suggest that aquaporins of the PIP2 class are required for efficient anther dehydration prior to dehiscence.     

Movement patterns and water quality preferences of juvenile bull sharks (<Emphasis Type="Italic">Carcharhinus leucas</Emphasis>) in a Florida estuary

Acoustic telemetry was used to examine the size of daily activity space, small-scale movement patterns, and water quality preferences of juvenile bull sharks in the Caloosahatchee River, Florida. Movement pattern analysis included rate of movement, swimming depth, linearity, direction, tidal influence, diel pattern, and correlation with environmental variables. Manual tacking occurred before and after a large freshwater influx which divided the sharks into two groups based on movement patterns. The first group displayed increased rate of movement, distance traveled, and space utilization at night, and movements correlated with salinity, temperature, and dissolved oxygen. The second group had an increased rate of movement, distance traveled, and space utilization during the day, and movements correlated with temperature, dissolved oxygen, turbidity and pH. These juvenile bull sharks displayed distinct diel movement patterns that were influenced by physical factors, which may account for the distribution of this top-level predator in the Caloosahatchee River.     

Frequencies of neuroantigen-specific T cells in the central nervous system versus the immune periphery during the course of experimental allergic encephalomyelitis

Direct measurements of the frequency and the cytokine signature of the neuroantigen-specific effector cells in experimental allergic encephalomyelitis (EAE) are a continuing challenge. This is true for lymphoid tissues, and more importantly, for the CNS itself. Using enzyme-linked immunospot analysis (ELISPOT) assays, we followed proteolipid protein (PLP) 139--151-specific T cells engaged by active immunization of SJL mice. The total numbers of PLP(139--151)-specific CD4 cells were highest before disease onset. At this time, these cells resided in lymphoid and nonlymphoid tissues, but were not detected in the CNS. While the PLP(139--151)-specific cells reached high frequencies in the CNS during clinical EAE, in absolute numbers, less than 20% of them were present in the target organ, with the majority residing in the periphery throughout all stages of the disease. The numbers of PLP(139--151)-specific cells gradually declined in both compartments with time. While eventually this first wave of effector cells completely disappeared from the CNS, PLP(178--191)-specific cells became engaged, being detected first in the CNS. These data suggest that throughout all stages of EAE, the effector cells in the CNS are recruited from a vast peripheral reservoir, and that the second wave of effector cells is engaged while the first wave undergoes exhaustion.     

The response of alkaline phosphatase to osmoregulatory changes in the trout,Salmo gairdneri

Summary The relationship between alkaline phosphatase and environmental salinity was examined in the rainbow trout and the migratory rainbow (steelhead),Salmo gairdneri. The enzyme activity in tissues involved in osmoregulation was strongly correlated with the adaptation salinity and thus to the degree of salt and fluid transport in those tissues. After transfer from freshwater to seawater, the specific activity of the enzyme increased over 260% in the intestine, decreased by 50% in kidney, and was unchanged in the liver, an organ not directly involved in osmoregulation. The sea-run steelhead trout response was similar to the nonmigratory rainbow; although, the pre-migratory transformation (smoltification) had no effect on enzyme activity. Amino acid inhibitors of alkaline phosphatase significantly reduced fluid absorption in the isolated intestine of rainbow trout, reaffirming the relationship between the enzyme and fluid movement. Electrophoretic identification of trout alkaline phosphatase isozymes, clearly distinguishes the enzyme from different tissue origins. However, from the analysis of intestinal electrophoretic patterns, osmoregulatory adjustments are not associated with the induction of new alkaline phosphatase isozymes, or in the large scale preferential stimulation of one of the two existing intestinal isozymes over the other.     

地鳖多肽提取物的抗氧化衰老机制

目的探讨地鳖多肽（ESW polypeptide）提取物抗氧化衰老机制的研究。方法小鼠连续腹腔注射D-半乳糖20 d,建立衰老模型,同时小鼠灌服不同剂量地鳖多肽提取物每日（0、40、80、160 mg/kg）,观察小鼠的正常活动、运动和耐应激能力。分别采用黄嘌呤氧化酶法、分光光度法检测小鼠血液和不同组织中超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、谷胱甘肽过氧化物酶（GSH-PX）活力,以及丙二醛（MDA）和还原型谷胱甘肽（GSH）含量;免疫荧光法检测细胞核转录因子2（Nrf2）在Caco-2细胞的表达。结果与对照和多肽组比较,衰老组小鼠体重增重缓慢、组织脏器系数降低、运动时间缩短、抗应激能力降低、组织中抗氧化酶活力降低。随着地鳖多肽剂量增加,多肽组小鼠体重增加明显,肝脏、脾脏和肾脏指数增加显著,小鼠静力和动力运动时间明显延长,小鼠耐缺氧、耐高温和运动时间延长并接近对照组,血液和不同组织中的SOD、CAT、GSH-PX活力及GSH含量显著提高,但MDA含量降低。与对照组比较,地鳖多肽组Caco-2细胞核内Nrf2表达量明显增加,接近阳性对照组。结论地鳖多肽可能通过启动Nrf2-ARE抗氧化信号通路,提高D-半乳糖致衰老小鼠抗应激和抗氧化能力,从而延缓小鼠氧化衰老。     

Dynamic secretion changes in the salt glands of the mangrove tree species Avicennia officinalis in response to a changing saline environment

The specialized salt glands on the epidermis of halophytic plants secrete excess salts from tissues by a mechanism that is poorly understood. We examined the salt glands as putative salt and water bi‐regulatory units that can respond swiftly to altering environmental cues. The tropical mangrove tree species (Avicennia officinalis) is able to grow under fluctuating salinities (0.7–50.0 dS m^?1) at intertidal zones, and its salt glands offer an excellent platform to investigate their dynamic responses under rapidly changing salinities. Utilizing a novel epidermal peel system, secretion profiles of hundreds of individual salt glands examined revealed that these glands could secrete when exposed to varying salinities. Notably, rhythmic fluctuations observed in secretion rates were reversibly inhibited by water channel (aquaporin) blocker, and two aquaporin genes (PIP and TIP) preferentially expressed in the salt gland cells were rapidly induced in response to increasing salt concentration. We propose that aquaporins are involved and contribute to the re‐absorption of water during salt removal in Avicennia officinalis salt glands. This constitutes an adaptive feature that contributes to salt balance of trees growing in saline environments where freshwater availability is limited.     

Identification and Characterization of a Polypeptide from a Lobster Neurosecretory Gland that Induces Cyclic GMP Accumulation in Lobster Neuromuscular Preparations

Several observations suggest that cyclic GMP might regulate some aspect of neuromuscular physiology or metabolism in the lobster. Homarus americanus: lobster muscle is one of the richest known sources of cyclic GMP-dependent protein kinase, the preparation contains several phosphoproteins whose state of phosphorylation is affected by cyclic GMP more effectively than by cyclic AMP, and guanylate cyclase and phosphodiesterase are active in this tissue. However, no factor has yet been identified that alters lobster muscle cyclic GMP levels. We have screened extracts of neural and neurosecretory structures for the capacity to promote cyclic GMP accumulation in isolated exoskeletal muscles. Extracts of the sinus gland (a neurohemal organ found in the eyestalk) contain a factor that induces up to 100-fold increases in muscle cyclic GMP content, whereas extracts of other tissues are ineffective. This factor can also act on targets other than muscle, with hepatopancreas, testis, and neuronal tissue showing the largest responses. The sinus gland factor does not appear to affect cyclic GMP metabolism by depolarizing the preparation or by mobilizing extracellular Ca2+. The effect on cyclic GMP levels is dose-dependent and linear with time. Biological activity is destroyed by boiling and by 90% ethanol. It is also destroyed by trypsin, chymotrypsin, or pronase, which suggests that the factor is a protein or peptide. Both gel filtration chromatography and experiments using dialysis tubing with different molecular weight exclusion limits indicate that the factor has an apparent molecular weight of 5,000-12,000 daltons. A preliminary fractionation scheme, based on gel filtration, ion-exchange, and reverse-phase chromatography, gives greater than 1,300-fold purification. Our long-range goal is to purify this factor to homogeneity, compare it to other peptide hormones, and use it as a probe to evaluate the role of cyclic GMP at the neuromuscular junction.     

Immunolocalization of allatostatin-like neuropeptides and their putative receptor in eyestalks of the tiger prawn, Penaeus monodon

Allatostatin (AST)-like immunoreactivity (IR) was localized in the eyestalk of Penaeus monodon by immunohistochemistry using four anti-AST antibodies. Depending on the antisera, AST-like immunoreactivity was detected in neuronal bodies of the lamina ganglionalis, cell bodies anterior to the medulla externa and cell bodies on the anterior and posterior of the medulla terminalis. Neuronal processes in neuropiles of the medulla externa, medulla terminalis, sinus gland and nerve fibers in the optic nerve were also recognized. No IR in cell bodies or in nerve fibers was found in the medulla interna. Strong AST-like immunoreactivity was found in hundreds of cells of the X organ. The localization of AST-like peptides suggests that they function as neurotransmitters and/or neuromodulators. Antiserum to the Drosophila AST receptor (Dar-2) recognized a single protein in P. monodon eyestalk protein extracts that was identical in size to that found in Drosophila protein extracts. Using this antiserum the putative P. monodon AST receptor was localized to the sinus gland in both juvenile and adult eyestalks. To our knowledge this is the first demonstration of a neuropeptide receptor localized to the crustacean sinus gland. This suggests that ASTs may function directly on the sinus gland as a neuromodulator. In juvenile eyestalks, the putative AST receptor was also localized to neuronal X organ cells of the medulla terminalis in males but not in females. The significance of this sex-specific receptor localization is unclear but emphasizes that ASTs function within the nervous system of the eyestalk.     

Endogenous rhythms of haemolymph flow and cardiac performance in the crab Cancer magister

Heart rate and arterial haemolymph flow rates were measured in freshly trapped Dungeness crabs, Cancer magister, using a pulsed-Doppler flowmeter. In the laboratory, freshly collected subtidal crabs exhibited endogenous rhythms in both cardiac function and haemolymph flow through one or more arterial systems, of both tidal and diurnal periodicity. The strongest tidal rhythms were recorded in the sternal and paired anterolateral arteries. These endogenous rhythms of selective tissue perfusion are related to an underlying locomotor activity, but may also be involved with hormonal transport or feeding. Changes in both heart rate and stroke volume were responsible for the increases in haemolymph flow rates. These rhythms were not entrained by aerial exposure, since confinement of arhythmic crabs in intertidal cages did not re-entrain an endogenous tidal rhythm. Endogenous locomotory rhythms are known to be controlled by neurohormones released in cycles from the sinus gland on the eyestalk. These hormones may also control the endogenous cardiovascular rhythms, since these were abolished after eyestalk ablation in freshly collected Cancer magister. These results suggest that hormones synthesized and released by the X-organ/sinus gland complex may, together with pericardial hormones, play a role in modulation of crustacean cardiovascular function.     

Sex expression, sex-specific traits, and the effects of salinity on growth and reproduction of Amaranthus cannabinus (Amaranthaceae), a dioecious annual

Amaranthus cannabinus was studied to investigate some of the ecological factors thought to be involved in the evolution of dioecy and to investigate the effects of salinity on sex expression and sex-specific selection. In the field portion of this study, sex ratios, stability of sex expression, spatial distribution, allocation strategies, and phenologies of the sexes were investigated in New Jersey freshwater and salt marsh populations of water hemp. To examine the effects of salinity on vegetative and reproductive development of males and females, plants were grown in the greenhouse at three salinity levels. Adult sex ratios were found to be 1:1. Temporal deviations from a 1:1 sex ratio varied by population and were due to differences in flowering phenology and mortality between the sexes. No plants were observed to change sex expression, and there was no evidence of spatial segregation of the sexes in the field. In both the field and the greenhouse, females allocated more resources to vegetative tissues and had a longer growing period than males. The results of this study suggest that increased reproductive efficiency through sex-specific growth patterns may have been an important selective factor involved in the evolution of dioecy in A. cannabinus.