Influence of cooling rate on activity of ionotropic glutamate receptors in brain slices at hypothermia

Hypothermia is a known approach in the treatment of neurological pathologies. Mild hypothermia enhances the therapeutic window for application of medicines, while deep hypothermia is often accompanied by complications, including problems in the recovery of brain functions. The purpose of present study was to investigate the functioning of glutamate ionotropic receptors in brain slices cooled with different rates during mild, moderate and deep hypothermia. Using a system of gradual cooling combined with electrophysiological recordings in slices, we have shown that synaptic activity mediated by the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and N-methyl-D-aspartate receptors in rat olfactory cortex was strongly dependent on the rate of lowering the temperature. High cooling rate caused a progressive decrease in glutamate receptor activity in brain slices during gradual cooling from mild to deep hypothermia. On the contrary, low cooling rate slightly changed the synaptic responses in deep hypothermia. The short-term potentiation may be induced in slices by electric tetanization at 16  °C in this case. Hence, low cooling rate promoted preservation of neuronal activity and plasticity in the brain tissue.     

Why Did a Female Penis Evolve in a Small Group of Cave Insects?

The evolution of a female penis is an extremely rare event and is only known to have occurred in a tribe of small cave insects, Sensitibillini (Psocodea: Trogiomorpha: Prionoglarididae). The female penis, which is protrudable and inserted into the male vagina‐like cavity during copulation to receive semen, is thought to have evolved independently twice in this tribe, in the Brazilian Neotrogla and the African Afrotrogla. These findings strongly suggest that there are some factors unique to Sensitibillini that have facilitated female penis evolution. Here, several hypothetical factors are presented that may have enabled the evolution of the female penis in Sensitibillini. The female–female competition for nutritious semen, the oligotrophic environment, and the twin insemination slots with switching valve are considered to be the driving factors for female penis evolution. Additionally, the following factors are considered responsible for relaxing the constraint against female penis evolution: preexistence of the female‐above mating position, the elongated duct connecting the female pre‐penis with the sperm storage organ, and the small male genital cavity accepting the female genital tubercle bearing the opening of this duct. Understanding the factors enabling female penis evolution may also shed light on the evolution of the male penis.     

Sex chromosomal abnormalities associated with equine infertility: validation of a simple molecular screening tool in the Purebred Spanish Horse

Chromosomal abnormalities in the sex chromosome pair (ECAX and ECAY) are widely associated with reproductive problems in horses. However, a large proportion of these abnormalities remains undiagnosed due to the lack of an affordable diagnostic tool that allows for avoiding karyotyping tests. Hereby, we developed an STR (single‐tandem‐repeat)‐based molecular method to determine the presence of the main sex chromosomal abnormalities in horses in a fast, cheap and reliable way. The frequency of five ECAX‐linked (LEX026, LEX003, TKY38, TKY270 and UCDEQ502) and two ECAY‐linked (EcaYH12 and SRY) markers was characterized in 261 Purebred Spanish Horses to determine the efficiency of the methodology developed to be used as a chromosomal diagnostic tool. All the microsatellites analyzed were highly polymorphic, with a sizeable number of alleles (polymorphic information content > 0.5). Based on this variability, the methodology showed 100% sensitivity and 99.82% specificity to detect the most important sex chromosomal abnormalities reported in horses (chimerism, Turner's syndrome and sex reversal syndromes). The method was also validated with 100% efficiency in 10 individuals previously diagnosed as chromosomally aberrant. This STR screening panel is an efficient and reliable molecular–cytogenetic tool for the early detection of sex chromosomal abnormalities in equines that could be included in breeding programs to save money, effort and time of veterinary practitioners and breeders.     

Isolation of CA1 Nuclear Enriched Fractions from Hippocampal Slices to Study Activity-dependent Nuclear Import of Synapto-nuclear Messenger Proteins

Studying activity dependent protein expression, subcellular translocation, or phosphorylation is essential to understand the underlying cellular mechanisms of synaptic plasticity. Long-term potentiation (LTP) and long-term depression (LTD) induced in acute hippocampal slices are widely accepted as cellular models of learning and memory. There are numerous studies that use live cell imaging or immunohistochemistry approaches to visualize activity dependent protein dynamics. However these methods rely on the suitability of antibodies for immunocytochemistry or overexpression of fluorescence-tagged proteins in single neurons. Immunoblotting of proteins is an alternative method providing independent confirmation of the findings. The first limiting factor in preparation of subcellular fractions from individual tetanized hippocampal slices is the low amount of material. Second, the handling procedure is crucial because even very short and minor manipulations of living slices might induce activation of certain signaling cascades. Here we describe an optimized workflow in order to obtain sufficient quantity of nuclear enriched fraction of sufficient purity from the CA1 region of acute hippocampal slices from rat brain. As a representative example we show that the ERK1/2 phosphorylated form of the synapto-nuclear protein messenger Jacob actively translocates to the nucleus upon induction of LTP and can be detected in a nuclear enriched fraction from CA1 neurons.     

Astrocytic Piezo1-mediated mechanotransduction determines adult neurogenesis and cognitive functions

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Excitatory neural control of posterograde heartbeat by the frontal ganglion in the last instar larva of a lepidopteran, Bombyx mori

The frontal ganglion of the silkworm (Bombyx mori) gives rise to a visceral nerve, branches of which include a pair of anterior cardiac nerves and a pair of the posterior cardiac nerves. Forward-fill of the visceral nerve with dextran labeled with tetramethyl rhodamine shows the anterior cardiac nerves innervate the anterior region of the dorsal vessel. Back-fill of the anterior cardiac nerves with Co²⁺ and Ni²⁺ ions and the fluorescent dye reveals that the cell bodies of two motor neurons are located in the frontal ganglion. Injection of 5, 6-carboxyfluorescein into the cell body of an identified motor neuron shows that the neuron gives rise to an axon running to the visceral nerve. Unitary excitatory junctional potentials (EJPs) were recorded from a myocardial cell at the anterior end of the heart. They responded in a one-to-one manner to electrical stimuli applied to the visceral nerve, or to impulses generated by a depolarizing current injected into the cell body. EJPs induced by stimuli at higher than 0.5 Hz showed facilitation while those induced at higher than 2 Hz showed summation. Individual EJPs without summation, or a train of EJPs with summation, caused acceleration in the phase of posterograde heartbeat and heart reversal from anterograde heartbeat to posterograde heartbeat. It is likely that the innervation of the anterior region of the dorsal vessel by the motor neurons, through the anterior cardiac nerves is responsible for the control of heartbeat in Lepidoptera, at least in part.     

Examination of protein sequence homologies: IV. Twenty-seven bacterial ferredoxins

Summary Sequence homologies of 27 bacterial ferredoxins were examined using a computer program that quantitatively evaluates extent of similarity as a correlation coefficient. The results of a similarity search among the sequences demonstrated that the basal sequence consists of a pair of extremely similar segments of 26 amino acids connected by a three-amino acid group. The segment pairs, which would have arisen from gene duplication, are termed the first and second units. Because of the gene duplication, the connector sequence appears to have been introduced as a structurally important chain reversal. Each of the two units contains four cysteine residues, which are inserted one by one among seven, two, two, three, and eight amino acid alignments, respectively. The bacterial ferredoxins were categorized with regard to basal constitution as follows: group 1, in which both units closely conform to the basal structure; group 2, in which the second unit is modified in a characteristic manner among members; group 3, in which the first unit is modified in a characteristic manner, while the conforming second unit is accompanied by a long accessory sequence; group 4, in which there are modifications before and/or after the units, of which the respective central domains remain nearly intact; and group 5, where only the former of two Fe:S cluster ligation sets of four cysteines is estimated to remain intact, whereas the latter set is extremely modified. It is noteworthy that throughout all bacterial ferredosins, one of two cysteine sets never fails to be completely intact and, moreover, the connector of three amino acids also exists intact. Based on this grouping and on the correspondences among the groups, average correlation coefficients among all members were computed, and the respective evolutionary relationships were examined. The results supported the proposition that transposition had occurred in theAzotobacter-type ferredoxins of group 3.