Life history and interspecies relationships of Chirocephalus diaphanus Prévost and Tanymastix stagnalis (L.), (Crustacea,Anostraca) inhabiting a group of mountain ponds in Latium,Italy

Life histories of two coexisting Anostracan species, inhabiting a group of mountain ponds in Latium (Pantani di Forca Canapine) are described and discussed, with particular regard to hatching requirements, growth rate, fecundity and life span.Unlike previously assumed (Mura, 1985), the cysts of the two species Tanymastix stagnalis and Chirocephalus diaphanus seem to respond to the same hatching stimuli, since their nauplii coexist and can be separated by morphological differences.Significant differences recorded as to size, time in attaining sexual maturity, fecundity and life span, are in favour of a niche separation by size and by time. In particular, size differences are supposed to reflect significant differences also at filtering apparatus level, thus allowing prey selection by size.     

Nuclear changes and morphology of the epidermis in the hibernating frog

Cytochemical changes of chromatin and DNA in frog epidermal cells were correlated with some morphological features to investigate the skin physiology during hibernation in comparison with the active period. The epidermal cells of hibernating frogs showed less condensed chromatin in all the layers; a greater loss of DNA was found during the transition from the middle to the superficial layer. In the germinative layer, a lesser frequency of hyperdiploid cells and a remarkably low amount of mitoses were detected; this is accompanied by the increase of epidermal thickness and the presence of two layers of cornified cells. The slowing of tissue differentiation and cell renewal kinetics during hibernation can be related to lowered activity of the frog skin. Further, the smaller intercellular spaces as well as the scarcity of puffed ER and vacuoles may be indicative of a lower ion transport in epidermal cells during hibernation.     

Gentamicin-induced chronotoxicity: use of body temperature as a circadian marker rhythm

Aminoglycoside antibiotics produce varying degrees of ototoxicity, dependent on dosage time, in animals synchronized for rhythm study. Herein, we illustrate the use of an economical and reliable system to telemeter body temperature of laboratory animals as an endogenous marker rhythm for gentamicin-induced ototoxicity. Two groups of 3 male Sprague-Dawley rats (250-400 gm) were housed in separate cages in a temperature-controlled room programmed with a 12:12 LD schedule and monitored for hearing thresholds at the frequencies of 8kHz, 16 kHz, 24 kHz and 32 kHz at 2-week intervals. Each rat was dosed with 100 mg/kg/day gentamicin subcutaneously for a duration of 28 days. The animals from one group were dosed at their daily temperature maximum, while the animals of the other group were dosed at their daily temperature minimum. Both after 14 and 28 days of gentamicin treatment there was no important changes in auditory thresholds from baseline values when treatment was timed daily to the circadian peak of body temperature. Animals dosed daily at the trough of the circadian temperature rhythm evidenced an auditory threshold shift of between 5 and 25 dB after 14 days of treatment and a total hearing loss (80-90 dB) after 28 days of such treatment. These results document a dramatically greater level of hearing loss induced in those animals dosed with gentamicin at the body temperature trough (diurnal rest span) as compared to those dosed at the acrophase (nocturnal activity span). The findings indicate that the peak and trough of the circadian pattern of body temperature serve as meaningful markers of the resistance and susceptibility, respectively, of gentamicin-induced ototoxicity in rodent models.     

Gentamicin-Induced Chronotoxicity: Use of Body Temperature as a Orcadian Marker Rhythm

Aminoglycoside antibiotics produce varying degrees of ototoxicity, dependent on dosage time, in animals synchronized for rhythm study. Herein, we illustrate the use of an economical and reliable system to telemeter body temperature of laboratory animals as an endogenous marker rhythm for gentamicin-induxed ototoxicity. Two groups of 3 male Sprague-Dawley rats (250-400 gm) were housed in separate cages in a temperature-controlled room programmed with a 12:12 LD schedule and monitored for hearing thresholds at the frequencies of 8kHz, 16kHz, 24kHz and 32kHz at 2-week intervals. Each rat was dosed with 100 mg/kg/day gentamicin subcutaneously for a duration of 28 days. The animals from one group were dosed at their daily temperature maximum, while the animals of the other group were dosed at their daily temperature minimum. Both after 14 and 28 days of gentamicin treatment there was no important changes in auditory thresholds from baseline values when treatment was timed daily to the circadian peak of body temperature. Animals dosed daily at the trough of the circadian temperature rhythm evidenced an auditory threshold shift of between 5 and 25 dB after 14 days of treatment and a total hearing loss (80-90 dB) after 28 days of such treatment. These results document a dramatically greater level of hearing loss induced in those animals dosed with gentamicin at the body temperature trough (diurnal rest span) as compared to those dosed at the acrophase (nocturnal activity span). The findings indicate that the peak and trough of the circadian pattern of body temperature serve as meaningful markers of the resistance and susceptibility, respectively, of gentamicin-induced ototoxicity in rodent models.     

Factors Influencing the Seasonal Phenology and Composition of Zooplankton Communities in Mountain Temporary Pools

In 2001 nine temporary pools of the northern Apennines (Italy) were visited on 13 occasions during the ice‐free season (May to October). The aims of this research were to define the relationships between hydroperiod and other environmental variables and the zooplankton. In total, 49 zooplankton taxa were identified: 36 rotifers, 5 cladocerans, 6 copepods and 2 anostracans. Our results indicate that hydroperiod is a major determinant affecting zooplankton species richness. The highest number of taxa was found in the pond having the longest duration. Distinctive species assemblages were observed in different habitat types: pools with the shortest hydroperiod were characterised by organisms with brief life cycles (e.g. rotifers) and/or typical of temporary habitat (e.g. anostracans). Of the physical and chemical characteristics, pH and chlorophyll‐a appeared to have the largest influence on zooplankton distribution in the studied pools. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Modifications in DARPP‐32 phosphorylation pattern after repeated palatable food consumption undergo rapid habituation in the nucleus accumbens shell of non‐food‐deprived rats

In non‐food‐deprived rats a palatable meal induces a transient increase in dopamine output in the prefrontal cortex and nucleus accumbens shell and core; habituation to this response develops with a second palatable meal, selectively in the shell, unless animals are food‐deprived. A palatable meal also induces time‐dependent modifications in the dopamine and cAMP‐regulated phosphoprotein of Mr 32 000 (DARPP‐32) phosphorylation pattern that are prevented when SCH 23390, a selective dopamine D₁ receptor antagonist, is administered shortly after the meal. This study investigated whether dopaminergic habituation in the shell had a counterpart in DARPP‐32 phosphorylation changes. In non‐food‐deprived rats, two consecutive palatable meals were followed by similar sequences of modifications in DARPP‐32 phosphorylation levels in the prefrontal cortex and nucleus accumbens core, while changes after the second meal were blunted in the shell. In food‐deprived rats two consecutive meals also induced similar phosphorylation changes in the shell. Finally, SCH 23390 administered shortly after the first palatable meal in non‐food‐deprived rats inhibited DARPP‐32 phosphorylation changes in response to the first meal, and prevented the habituation to a second meal in terms of dopaminergic response and DARPP‐32 phosphorylation changes. Thus, dopamine D₁ receptor stimulation plays a role in the development of habituation.     

Forced unbinding of GPR17 ligands from wild type and R255I mutant receptor models through a computational approach

Background  

GPR17 is a hybrid G-protein-coupled receptor (GPCR) activated by two unrelated ligand families, extracellular nucleotides and cysteinyl-leukotrienes (cysteinyl-LTs), and involved in brain damage and repair. Its exploitment as a target for novel neuro-reparative strategies depends on the elucidation of the molecular determinants driving binding of purinergic and leukotrienic ligands. Here, we applied docking and molecular dynamics simulations (MD) to analyse the binding and the forced unbinding of two GPR17 ligands (the endogenous purinergic agonist UDP and the leukotriene receptor antagonist pranlukast from both the wild-type (WT) receptor and a mutant model, where a basic residue hypothesized to be crucial for nucleotide binding had been mutated (R255I) to Ile.     

Platinum drugs and neurotoxicity: effects on intracellular calcium homeostasis

[Pt(O,O′-acac)(γ-acac)(DMS)] (PtAcacDMS) is a new platinum compound showing low reactivity with nucleobases and specific reactivity with sulfur ligands intracellularly. It induces apoptosis in breast cancer cells, but appears to be less neurotoxic to the developing cerebellum than cisplatin (cisPt). The aim of this study was to assess the neurotoxicity of platinum compounds on calcium homeostasis in the dentate gyrus and Cornu Ammonis regions of the hippocampal formation during rat postnatal development. Two intracellular calcium homeostasis systems were taken for measurement, calbindin, a calcium buffer protein, and a plasma membrane calcium ATPase (PMCA1). The platinum compounds showed different effects on these markers in the two areas. One day after injection (PD11), cisPt decreased calbindin immunoreactivity and PMCA1 labeling in both regions; at PD17, the downregulation of PMCA1 persisted. Instead, PtAcacDMS produced varying effects on calbindin immunoreactivity in the two regions at PD11 and PD17; but in all cases, the changes incurred in calbindin immunoreactivity were counterbalanced by changes produced in PMCA1 expression. In conclusion, PtAcacDMS seems to affect calcium homeostasis in the central nervous system differently than cisPt. Both the platinum compounds act early to alter the calbindin buffering system. However, the most important difference between cisPt and PtAcacDMS is that, in vivo, the latter acts early to stimulate calcium efflux from nerve cells as reflected by its effect on PMCA1. The rapid onset of an activated calcium pump appears to be essential to cope with the excessive intracellular calcium concentration stemming from the downregulation of calbindin which could damage neuron function and morphology.     

On the occurrence of Streptocephalus torvicornis Waga 1842 (Crustacea,Anostraca) on a coastal island off Italy

The presence of Streptocephalus torvicornis on one coastal island off Italy (Cottarelli & Mura, 1995) is confirmed. Two years of sampling revealed an erratic pattern of occurrence, however, likely related to the unstable nature of the environmental characteristics. Such an unpredictability might be alternatively explained by a colonization-extinction process, or by adaptation to variations in annual weather (Donald, 1983). This revised version was published online in July 2006 with corrections to the Cover Date.