The hearing abilities of the prawn Palaemon serratus

The mechanism of sound reception and the hearing abilities of the prawn (Palaemon serratus) have been studied using a combination of anatomical, electron microscopic and electrophysiological approaches, revealing that P. serratus is responsive to sounds ranging in frequency from 100 to 3000 Hz. It is the first time that the Auditory Brainstem Response (ABR) recording technique has been used on invertebrates, and the acquisition of hearing ability data from the present study adds valuable information to the inclusion of an entire sub-phylum of animals when assessing the potential impact of anthropogenic underwater sounds on marine organisms. Auditory evoked potentials were acquired from P. serratus, using two subcutaneous electrodes positioned in the carapace close to the supraesophageal ganglion and the statocyst (a small gravistatic organ located below the eyestalk on the peduncle of the bilateral antennules). The morphology of the statocyst receptors and the otic nerve pathways to the brain have also been studied, and reveal that P. serratus possesses an array of sensory hairs projecting from the floor of the statocyst into a mass of sand granules embedded in a gelatinous substance. It is the purpose of this work to show that the statocyst is responsive to sounds propagated through water from an air mounted transducer. The fundamental measure of the hearing ability of any organism possessing the appropriate receptor mechanism is its audiogram, which presents the lowest level of sound that the species can hear as a function of frequency. The statocyst of P. serratus is shown here to be sensitive to the motion of water particles displaced by low-frequency sounds ranging from 100 Hz up to 3000 Hz, with a hearing acuity similar to that of a generalist fish. Also, recorded neural waveforms were found to be similar in both amplitude and shape to those acquired from fish and higher vertebrates, when stimulated with low-frequency sound, and complete ablation of the electrophysiological response was achieved by removal of the statocyst.     

Effect of thermal acclimation on subunit cooperativity in Palaemon serratus glutamate dehydrogenase

Glutamate dehydrogenase (GDH) from the abdominal muscle of the shrimp Palaemon serratus displays a complex cooperatively pattern with respect to the cofactor (NAD) and substrate (glutamate) concentrations: at low concentrations negative cooperativitiy is predominant whereas positive cooperativity prevails at high concentrations. GDH is sensitive to thermal variations of the environment and to conditions of thermal acclimation. The maximum cooperativity indexes (positive and negative) are obtained at 13° for NAD irrespective of the acclimation temperature (13 or 18°). In contrast, for glutamate, positive cooperativity is only observed at temperatures near the acclimation temperature. At 13° for animals adapted at 18° and at 27° for animals adapted at 13° a complete loss of subunit cooperativity and a Michaelian kinetic pattern are observed.     

Short term cadmium intoxication of the shrimp Palaemon serratus: Effect on adenylate metabolism

• 1.1. Shrimps were exposed for 96 hr to various concentrations of cadmium under laboratory conditions. The LC₅₀ was around 4 ppm Cd in water, which corresponded to 0.180 μg/g wet weight of cadmium in tail muscles.
• 2.2. The effect of various concentrations of cadmium on adenylates was analyzed in tail muscles: At subletal cadmium concentrations, no variation of ATP, ADP and of the adenylate sum occurred, while the AMP concentration began to decrease from 0.06 ppm.

At the LC₅₀, the ATP, ADP and AMP concentrations dropped acutely, the ATP/ADP ratio increased acutely.The apparent equilibrium constant of the adenylate kinase reaction increased significantly from 2 ppm Cd, indicating an impairment in energetic metabolism.Cadmium intoxication did not influence the value of the adenylate energy charge.     

Studies on lactate dehydrogenase activity in the shrimp Palaemon serratus

The influence of seasonal variations in the temperature of the environment on the kinetic parameters of LDH have been followed in the shrimp Palaemon serratus. The results obtained show that this system compensates partially the effects of the temperature on its activity. The complex pattern of the monthly variations of Km values along the year can be resolved into a 2 plateaux system corresponding to the extreme temperature of the environment.     

Circadian variations of haemolymph lipoprotein of Palaemon serratus

The electrophoretic behaviour of haemolymph lipoprotein was determined throughout a 24 h light-dark cycle. All of the 14 lipoprotein bands did not always appear at the same time, and their level did not remain constant, showing mainly tri- and tetracircadian variations. Values are not the same in males and females. Despite the fact that the lipoprotein variation was not closely synchronized with circadian periodicity, some lipoproteins were responsible for light-dark transition.     

Effect of acclimatization temperatures on incorporation of amino acids into proteins of abdominal muscle from the shrimp Palaemon serratus

The effect of thermal acclimatization on the incorporation of [³H]-l-leucine into muscular acid-soluble amino acids, soluble proteins and into the lactate dehydrogenase was studied in the shrimp Palaemon serratus As far as protein synthesis is concerned, a period of time of 10 to 15 days is required for the achievement of the process. During acclimatization to 10° or 20° three periods can be distinguished. During the first 3–4 days the temperature increment exert a direct decreasing or increasing effect on the protein synthesis. The system then tends to reach a new equilibrium respectively below or above the initial level: the synthesis mechanisms were able to partially compensate the effect of thermal variations. The synthesis of LDH follows the general pattern of incorporation of the labelled precursor into the macromolecules     

Ontogeny and optics of the eyes of the common prawn Palaemon (Palaemon) serratus (Pennant, 1777)

A brief review of the work on crustacean compound eyes is given. Two main types of eye have been recognized: apposition and superposition. The ontogeny of the eyes of the common prawn Palaemon serratus is examined using a variety of methods: photography of live specimens, histological sections, SEM and TEM. In common with other decapod larvae, the common prawn hatches with apposition eyes having circular lenses packed hexagonally. After metamorphosis the gradual squaring of the eye facets, begun during the larval phase, is completed. This is an essential prerequisite for the functioning of the facultative superposition reflecting optics found in long-bodied decapods (e.g. shrimps, prawns and lobsters) and some Anomura. The possible phylogenetical significance of superposition, reflecting optics is also discussed.     

Ghrelin: Impact on Muscle Energy Metabolism in Sepsis

We investigated the effects of exogenous ghrelin on energy levels and tissue histology in skeletal muscle in experimentally lipopolysaccharide (LPS) induced septic rats. Male Wistar albino rats 200–250 g were separated into four groups; Control, LPS (5 mg/kg), Ghrelin (10 nmol/kg i.v.), and ghrelin+LPS. Gastrocnemius muscle tissue was taken and stained using modified Gomori trichrome (MGT), succinic dehydrogenase (SDH), and cytochrome oxidase (COX) and hematoxylin and eosin. In stained sections, histological score value was calculated according to the intensity and the distribution for MGT, SDH and COX stainings. Creatine, creatine phosphate, adenosine triphosphate (ATP), adenosine monophosphate (AMP) levels, and the ratios of AMP/ATP and CreaP/ATP were investigated using high performance liquid chromatography (HPLC) in muscle tissue. Significances between experimental groups were calculated with an analysis of variance (ANOVA) followed by Tukey’s tests. Myopathic changes were seen in the 50% of rats in the LPS group as rounding of muscle fibers and fiber size variation. In the ghrelin+LPS group, ghrelin treatment was reduced damage in skeletal muscle structure. There was no change in creatine or AMP levels between the groups. Ghrelin treatment significantly increased ATP values (P?<?0.01) and improved tissue histology in septic rats. Ratios of both AMP/ATP and CreaP/ATP were found increased in the septic group, but there were decreaments in both the ghrelin and ghrelin-treated septic groups. Ghrelin could play an important role in energy balance and muscle morphology in skeletal muscle during sepsis.     

Ultrastructural Studies on Gametogenesis of the Prawn Palaemon serratus (Pennant). I. Oogenesis

The oogenesis of the common prawn P. serratus is described. The reproductive cycle is annual and there is little evidence for a second spawning period. Oogenesis under the electron microscope follows a typical crustacean pattern and has been divided into seven stages according to the structure of the oocytes. The production of yolk is mainly intra-oocytic, with a small extra-oocytic contribution. Yolk, in the form of small granules, arises within the lamellar elements of the rough endoplasmic reticulum. These were then transformed into finely granular yolk bodies. Lipid droplets, as in other crustacean species, arise de novo in the cytoplasm and there is no association between lipids and cell organelles.     

Variations in the lactate dehydrogenase activity during the development of the shrimp Palaemon serratus

• 1.1. The lactate dehydrogenase (LDH) from Palaemon serratus muscle has been studied throughout the development of the animal.
• 2.2. Enzymatic activities have been traced by polyacrylamide gel electrophoresis and kinetic studies.
• 3.3. The existence of two enzymes (L₁ and L₂) has been demonstrated.
• 4.4. During the larval development, both L₁ and L₂ remain at a low level.
• 5.5. After the larvae hatch L₁ and L₂ gradually rise although L₁ is predominant.
• 6.6. Measurement of kinetic parameters shows that the general behaviour of the enzymes of the embryo resembles that of the adult enzymes.
• 7.7. However, one can observe during the development a constant increase in the affinity of the enzyme towards its substrate, lactate.

     

Ultrastructural Studies on Gametogenesis of the Prawn Palaemon serratus (Pennant). II. Spermiogenesis

Spermiogenesis in Palaemon serratus is described. The mature sperm has an atypical form and is highly modified. In early stages of spermiogenesis mitochondria, golgi complexes, stacks of annulate lamellae and endoplasmic reticulum are present but disappear later in development. Two modified mitochondria are present in the mature sperm. This latter consists of a cup-shaped nucleus, a cross-striated “spike”, has a centriole and lacks an acrosome. The nucleus contains membrane-bounded vesicles which arise by pinocytosis. The “spike” may be a flexible posterior organ which suggests a mode of fertilization requiring limited mobility.     

Purification and partial characterization of an AMP deaminase from the marine invertebrate Palaemon serratus

• 1.1. AMP deaminase from Palaemon serratus tail muscle was partially purified by chromatography on cellulose phosphate.
• 2.2. Muscle homogenates expressed very low enzyme activities and the presence of ATP was necessary to detect AMP deaminase. The specific activity and substrate affinity of the purified enzyme were also very low.
• 3.3. The purified prawn muscle AMP deaminase was contaminated by contractile proteins, one of the major contaminants being actin.
• 4.4. The enzyme displayed a very high affinity for actomyosin which was only partially abolished by pyrophosphate.

     

Characterization of histones and chromatin of the hepatopancreas in Palaemon serratus (Crustacea Natantia)]

The chromatin of shrimp hepatopancreas has been extracted from isolated nuclei and characterized. Nuclei were prepared in the presence of Cu++ and phenyl methyl sulfonyl fluoride in order to inhibit the nuclease and protease activities throughout the different purification steps. The purified nuclei are heterogenous in size and show a density of 1,367 g/ml determined on saccharose - glucose gradients. After washing in 0,14 M NaCl and then in 10(-2) M Tris-HCL, pH = 7,6, the nuclei were disrupted in water. The solubilized chromatin was precipitated in 0,15 M.NaCl. This chromatin is characterized by a high level of RNA (RNA/DNA = 0,38) and of non histone proteins (NHP/DNA = 0,6). The denaturation curve showed only one Tm at 69 degrees in 2.10(-4) M.EDTA. When the chromatin was extracted in the presence of staphylococcal nuclease, the Tm reached 80 degrees C. The kinetics of the digestion by the staphylococcal nuclease have been studied and show that 10 per cent of hydrolysis occurs within the first minute. The repeat length of DNA as determined with the polymers of higher order is 189 +/- 5 base pairs. The existence of nucleosomes was confirmed by electron microscopy. The superstructure of chromatin was not completely destroyed after solubilisation with a Potter. The histones were studied by gel electrophoresis after differential staining. The most important feature consists in the presence of two H1, two H2A and two H4. The acetylation levels of the histones were followed after injection of 14C-acetate in vivo. The subfraction H1, 0 was acetylated. Only one H3 was present and the two H2A fractions showed the same level of acetylation. H2B migrated faster than the H2A fractions like in Echinoderms. The two H4 fractions corresponded to two differently acetylated forms. Shrimp hepatopancreas histones were fractionated by molecular sieving on Biogel P 100 and characterized according to their electrophoretic properties as well as their amino-acid content. The amino-acid compositions of the different histone fractions were nearer to Echinoderm and Sipunculid histones, than Calf thymus homologue histones. All the fractions show a weaker basicity. The H3 fraction was the only one showing a lesser variability when compared to Calf thymus H3. The non histone proteins were extracted in 10(-2) M Tris-HCL, pH = 8 and 0.1 per cent SDS. A series of 50 proteins was detected. 80 per cent of the total amount of protein was localized in a molecular weight range comprised between 40 000 and 80 000 daltons. These proteins were compared to the histones and total proteins of sonicated chromatin solubilized by SDS in order to detect proteasic effects.     

External Mg2+ is required for hyperpolarization to occur in ovulated oocytes of the prawn Palaemon serratus

Immediately after dissection, the ovulated oocyte of the prawn Palaemon serratus had a resting potential E_m of −42 ± 2 mV and a membrane resistance R_m of 15 ± 5 MΩ; the membrane was more permeable to Cl⁻ than to K⁺. The oocyte spontaneously hyperpolarized and E_m gradually reached −70 mV 20–30 min after removal of the oocyte from the female, due to increased membrane permeability to K⁺. However, the hyperpolarization occured only if Mg²⁺ was present in the seawater; external Ca²⁺ was not required. Long-term incubation without external Mg²⁺ depolarized the membrane and increased membrane resistance. After preincubation in Mg²⁺-free ASW, oocytes transferred to standard artificial seawater (ASW) transiently hyperpolarized and then repolarized, before gradually hyperpolarizing to a sustained value of −62 ± mV. The respective roles of external Mg²⁺ and fertilization in eliciting the electrical response of the prawn egg at natural spawning are discussed.     

Localization of serotonin-like immunoreactivity in the eyestalk of the prawn Palaemon serratus (Crustacea, Decapoda, Natantia)

A serotonin-like substance in the organ of Bellonci in the eyestalks of embryos, larvae, and adults of the prawn Palaemon serratus was visualized by the use of two specific antisera against serotonin (5-hydroxytryptamine; 5-HT) in combination with peroxidase-antiperoxidase (PAP). The organ of Bellonci, characterized by compact onion bodies distally and degenerating onion bodies proximally, was the only site of the serotonin-like substance in adults, as well as during development in embryos and larvae. Variations in the content of the 5-HT analogue in the adult were detected during the molting cycle. There was more immunoreactivity in specimens fixed at night than in those fixed in daytime. Likewise, colchicine and nialamide injections enhanced the immunoreactivity of the serotonin-like substance. Extirpations of the medulla externa X organ (MEX), a neurosecretory cell group of the optic ganglion medulla externa, produced the same effect.     

The Effect of the Creatine Analogue Beta-guanidinopropionic Acid on Energy Metabolism: A Systematic Review

Background

Creatine kinase plays a key role in cellular energy transport. The enzyme transfers high-energy phosphoryl groups from mitochondria to subcellular sites of ATP hydrolysis, where it buffers ADP concentration by catalyzing the reversible transfer of the high-energy phosphate moiety (P) between creatine and ADP. Cellular creatine uptake is competitively inhibited by beta-guanidinopropionic acid. This substance is marked as safe for human use, but the effects are unclear. Therefore, we systematically reviewed the effect of beta-guanidinopropionic acid on energy metabolism and function of tissues with high energy demands.

Methods

We performed a systematic review and searched the electronic databases Pubmed, EMBASE, the Cochrane Library, and LILACS from their inception through March 2011. Furthermore, we searched the internet and explored references from textbooks and reviews.

Results

After applying the inclusion criteria, we retrieved 131 publications, mainly considering the effect of chronic oral administration of beta-guanidinopropionic acid (0.5 to 3.5%) on skeletal muscle, the cardiovascular system, and brain tissue in animals. Beta-guanidinopropionic acid decreased intracellular creatine and phosphocreatine in all tissues studied. In skeletal muscle, this effect induced a shift from glycolytic to oxidative metabolism, increased cellular glucose uptake and increased fatigue tolerance. In heart tissue this shift to mitochondrial metabolism was less pronounced. Myocardial contractility was modestly reduced, including a decreased ventricular developed pressure, albeit with unchanged cardiac output. In brain tissue adaptations in energy metabolism resulted in enhanced ATP stability and survival during hypoxia.

Conclusion

Chronic beta-guanidinopropionic acid increases fatigue tolerance of skeletal muscle and survival during ischaemia in animal studies, with modestly reduced myocardial contractility. Because it is marked as safe for human use, there is a need for human data.     

季节性模拟对大绒鼠能量代谢的影响

本实验主要阐明大绒鼠Eothenomys miletus在季节性模拟过程中体质量调节和能量代谢的变化。实验组大绒鼠在模拟夏季环境中(25℃,16L∶8D)驯化14 d后转入模拟冬季环境中(5℃,8L∶16D)驯化8 d,实验中每隔1 d测定大绒鼠的体质量、摄食量,每隔7 d测定其静止代谢率,实验结束后测定体脂含量和血清瘦素浓度。结果表明:季节性模拟条件下大绒鼠的体质量变化差异具有统计学意义(F=1.911,P0.05),22 d后实验组体质量比对照组下降12.54%;摄食量变化差异具有高度统计学意义(F=8.850,P0.01),22 d后实验组摄食量比对照组显著增加58.23%;静止代谢率变化差异具有高度统计学意义(F=9.969,P0.01),22 d后实验组比对照组显著增加82.22%;体脂含量和血清瘦素浓度呈显著正相关。以上实验结果表明:大绒鼠在模拟夏季转冬季的过程中主要通过降低体质量、增加摄食量和产热等来适应冷环境的胁迫。此外,瘦素有可能参与了大绒鼠在该环境下的体质量调节。