Control of prothoracic gland activity in larvae of Galleria mellonella

Prothoracic glands of last instar wax moth larvae maintain spontaneous secretory activity both in decapitated larvae and in isolated abdomens into which they have been transplanted, as judged by their ability to induce secretion of a new cuticle. Their activity is hormonally stimulated by the brain and inhibited by the prothoracic and mesothoracic ganglia. The subesophageal ganglion seems to suppress the inhibitory influence of the thoracic ganglia. The prothoracic glands of larvae decapitated at different times during the last instar all respond to brain implantation, and this response does not change when brains are implanted at increasing intervals after decapitation. The prothoracotropic activity of the isolated brain is highest in brains of pupae and adults but is relatively and consistently low in brains of last instar larvae. The results demonstrate that the control of prothoracic glands is a complex process governed by the nervous integration of various stimuli.     

Metabolic Changes in Cerebral Cortex, Hippocampus, and Cerebellum During Sustained Bicuculline-Induced Seizures

Abstract— The objective of the present experiments was to study metabolic correlates to the localization of neuronal lesions during sustained seizures. To that end, status epilepticus was induced by i.v. administration of bicuculline in immobilized and artificially ventilated rats, since this model is known to cause neuronal cell damage in cerebral cortex and hippocampus but not in the cerebellum. After 20 or 120 min of continuous seizure activity, brain tissue was frozen in situ through the skull bone, and samples of cerebral cortex, hippocampus, and cerebellum were collected for analysis of glycolytic metabolites, phosphocreatine (PCr), ATP, ADP, AMP, and cyclic nucleotides. After 20 min of seizure activity, the two “vulnerable” structures (cerebral cortex and hippocampus) and the “resistant” one (cerebellum) showed similar changes in cerebral metabolic state, characterized by decreased tissue concentrations of PCr, ATP, and glycogen, and increased lactate concentrations and lactate/ pyruvate ratios. In all structures, though, the adenylate energy charge remained close to control. At the end of a 2-h period of status epilepticus, a clear deterioration of the energy state was observed in the cerebral cortex and the hippocampus, but not in the cerebellum. The reduction in adenylate energy charge in the cortex and hippocampus was associated with a seemingly paradoxical decrease in tissue lactate levels and with failure of glycogen resynthesis (cerebral cortex). Experiments with infusion of glucose during the second hour of a 2-h period of status epilepticus verified that the deterioration of tissue energy state was partly due to reduced substrate supply; however, even in animals with adequate tissue glucose concentrations, the energy charge of the two structures was significantly lowered. The cyclic nucleotides (cAMP and cGMP) behaved differently. Thus, whereas cAMP concentrations were either close to control (hippocampus and cerebellum) or moderately increased (cerebral cortex), the cGMP concentrations remained markedly elevated throughout the seizure period, the largest change being observed in the cerebellum. It is concluded that although the localization of neuronal damage and perturbation of cerebral energy state seem to correlate, the results cannot be taken as. evidence that cellular energy failure is the cause of the damage. Thus, it appears equally probable that the pathologically enhanced neuronal activity (and metabolic rate) underlies both the cell damage and the perturbed metabolic state. The observed changes in cyclic nucleotides do not appear to bear a causal relationship to the mechanisms of damage.     

Juvenile hormone-binding protein and juvenile hormone esterase activity in hemolymph from last-instar nymphs of Leucophaea maderae

The concentration of the juvenile hormone-binding protein (JHB) in hemolymph was determined throughout the last nymphal instar. It was found to be 3.9 μM at the molt to the instar, rising to 13 μM by mid-instar, and dropping to 6.7μM the day before emergence. Endocrine control of its production during the last nymphal instar could not be established. The apparent juvenile hormone esterase (JHF) activity was low at the molt to the last instar, but rose about fivefold by mid-instar, and then modestly declined. On the day of emergence, JHF activity rose to the highest level observed. A four- to fivefold increase in absolute JHF activity was determined during the first half of the last nymphal instar. This increase is not regulated by JH. Removal of the JHB from hemolymph samples by precipitation with a polyclonal specific antibody increased the JHF activity up to 1,000-fold. Thus, changes in the concentrations of JHB can affect the apparent activity of JHE, which is unrelated to the production or degradation of the JHF.     

Characterization of β-amylase alleles in 79 barley varieties with pyrosequencing

β-Amylase is involved in the starch degradation process and therefore influences grain quality. Starch degradation efficiency is dependent on the enzyme thermostability during malting and mashing. Four alleles resulting in different enzyme thermostability are known. These alleles are distinguished by coding single nucleotide polymorphism (cSNP). Pyrosequencing was used for cSNP genotyping of β-amylase alleles in 79 spring barley varieties by using analyser PSQ MA96 System (Pyrosequencing, Biotage). A new cSNP was revealed by means of Pyrosequencing analysis of sequence flanking cSNP⁶⁹⁸, thus recognizing a fifth β-amylase allele. Pyrosequencing is a high-throughput, fast, and precise system for barley SNP genotyping.     

Cyanobacteria — a neglected component of biodiversity: patterns of species diversity in inland marshes of northern Belize (Central America)

Cyanobacterial mats, widely distributed in the inland alkaline marshes of northern Belize and other regions in the Caribbean, are not only important and functionally complex components of these habitats, but they are also significant reservoirs of biological diversity. Highly diverse and (relatively) isolated marshes have provided conditions suitable for cyanoprokaryotic organisms and conditioned the adaptation and stabilization of numerous specialized eco‐ and morphotypes. Species richness of cyanobacteria assemblages follows the conductivity gradient and is highest in the marshes of medium conductivity (c. 1000–2000 µS cm^?1) and decreases at low (< 500 µS cm^?1) and high (> 3000 µS cm^?1) conductivities. This ecologically unique cyanobacterial microflora is very sensitive to nutrient enrichment, both directly and indirectly through shading by expanding macrophytes. Species richness of cyanobacterial assemblages decreases dramatically as a result of eutrophication. Similar cyanobacterial communities are widely distributed in limestone‐based areas of Florida, Central America and Caribbean but none of them is currently under any legal protection status. The purpose of this paper is to bring attention to an ecologically important group of organisms that have traditionally not been considered in species diversity evaluations or conservation efforts.