The effect of the iontophoretic administration of glutamate on the organization of interneuronal interactions in the rabbit motor cortex]

The multiunit activity of neurons in the motor cortex was recorded in 6 rabbits during glutamate (or physiological saline) iontophoretic application. Interaction between the neighboring neurons was evaluated by means of statistical cross-correlation analysis of spike trains. It was found that glutamate did not produce significant changes in cross-correlations.     

The latitudinal,but not the longitudinal,geographic range positions of haematophagous ectoparasites demonstrate historical signatures

We tested whether geographic range position of fleas parasitic on small mammals in the Palearctic is affected by environmental niche conservatism or geographic range conservatism by measuring phylogenetic signal in range centroids and boundaries. We predicted that stronger phylogenetic signal in latitudinal than longitudinal range positions would indicate the important role of niche conservatism as a driver of the evolution of fleas’ geographic ranges. Phylogenetic signals in geographic range positions were measured across 120 species, as well as within five flea lineages (subfamily/family rank) of different evolutionary ages. To investigate the temporal pattern of the geographic range position’s evolution, we fitted the phylogenetic patterns in the geographic coordinates of range centroids and border extremes to four models of trait evolution. We consistently detected significant phylogenetic signals in the latitudes of the range centroids and the northern range borders. The latitudes of the southern range borders and the longitudes of the eastern/western borders demonstrated phylogenetic signals less often, whereas no signal was found for the longitudes of the range centroids. The phylogenetic signal in range position was more pronounced in younger lineages. The phylogenetic signal indices mainly suggested the evolution of range positions according to the Brownian motion model, whereas the best fit was often provided by the Orstein-Uhlenbeck model. This contradiction forced us to invoke a parsimonious explanation that the phylogenetic signal in range positions results from the interplay between the footprint of the speciation pattern and limited dispersal from the ancestral ranges.     

Investigation of Bartonella acquisition and transmission in Xenopsylla ramesis fleas (Siphonaptera: Pulicidae)

Bartonella are emerging and re-emerging pathogens affecting humans and a wide variety of animals including rodents. Horizontal transmission of Bartonella species by different hematophagous vectors is well acknowledged but vertical transmission (from mother to offspring) is questionable and was never explored in fleas. The aim of this study was to investigate whether the rodent flea, Xenopsylla ramesis, can acquire native Bartonella from wild rodents and transmit it transovarially. For this aim, Bartonella-free laboratory-reared X. ramesis fleas were placed on six naturally Bartonella-infected rodents and six species-matched Bartonella-negative rodents (three Meriones crassus jirds, two Gerbillus nanus gerbils and one Gerbillus dasyurus gerbil) for 7 days, 12-14h per day. The fleas that were placed on the Bartonella-positive rodents acquired four different Bartonella genotypes. Eggs and larvae laid and developed, respectively, by fleas from both rodent groups were collected daily for 7 days and molecularly screened for Bartonella. All eggs and larvae from both groups were found to be negative for Bartonella DNA. Interestingly, two of five gut voids regurgitated by Bartonella-positive fleas contained Bartonella DNA. The naturally infected rodents remained persistently infected with Bartonella for at least 89 days suggesting their capability to serve as competent reservoirs for Bartonella species. The findings in this study indicate that X. ramesis fleas can acquire several Bartonella strains from wild rodents but cannot transmit Bartonella transovarially.     

Effects of ectoparasite infestation during pregnancy on physiological stress and reproductive output in a rodent-flea system

Biotic and abiotic stressors impose various fitness costs on individuals across a variety of taxa. In vertebrates, these stressors typically trigger complex neuroendocrine responses that stimulate glucocorticoid (GC) secretion from the adrenal cortex. Short-term elevation of GCs can be adaptive as it shifts energy toward physiological processes that cope with acute stressors; however, chronic increases in GC levels could have detrimental effects on fitness. Parasitism can be considered an important biotic stressor in nature and a possible cause of reproductive failure that could substantially affect an individual’s fitness. Thus, we aimed to test the effects of parasitism and maternal stress, as measured by GCs, during pregnancy and the relationship between these variables and measures of reproductive output using a rodent-flea system. Female Egyptian spiny mice (Acomys cahirinus) were randomly assigned to flea (Parapulex chephrenis) infested or uninfested treatments before and during pregnancy. The offspring of these females were flea-free. Feces were collected at five time points during the experiment to determine maternal fecal glucocorticoid metabolite (FGCM) concentrations. Overall, infested females had lower FGCM levels during gestation but higher FGCM levels post-parturition and larger mass changes than uninfested females. Additionally, models related to pup quality and quantity often included some measure of maternal investment or body condition moderating relationships between infestation and stress. This suggests that flea parasitism or high GC levels alone might not significantly impact host reproduction but rather females can experience different effects depending on their level of investment, which could be limited by body condition and/or the number of pups present in a litter.     

Ecological correlates of body size in gamasid mites parasitic on small mammals: abundance and niche breadth

We studied ecological correlates of body size (abundance and niche breadth) in gamasid mites parasitic on small mammals in 28 regions of the Palearctic. We predicted that smaller species would be characterized by higher abundance than larger species, all else (e.g. host species) being equal. We also predicted that host specificity of mites would decrease (that is, number of host species they use would increase) with an increase in their body size. We focused on mites collected from host bodies that include a) species that feed solely on host’s blood (obligate exclusive haematophages), b) species that feed on both host’s blood and small arthropods (obligate non‐exclusive haematophages), and c) facultative haematophages. We expected that the relationship between body size and abundance and/or host specificity would be more pronounced in obligate exclusively haematophagous mites than for obligate non‐exclusively and facultative haematophagous mites. Across all mite species across regions, mean abundance correlated negatively with body size. The same was true for obligate haematophagous species, but not for facultative haematophages. When mite communities on the same host in a location were considered, the negative body mass–abundance relationship was found in only 3 of 44 communities. Nevertheless, a meta‐analytic (across host species) estimate of the slope of this relationship appeared to be significantly negative. No significant relationship between mite body size and host specificity was found in the analyses across all mite species as well as in obligate exclusive or obligate non‐exclusive haematophages. However, the number of hosts used by facultative haematophagous mites decreased significantly with an increase in their body size. We explain the relationships between morphological (body size) and ecological (abundance and niche breadth) properties of ectoparasites by their interactions with hosts or physical environment.     

The adhesive properties of salmonellae in the dynamics of the infectious process

In patients with toxic infections salmonellae were identified in 31% of cases. The patients were divided into two groups: the control group receiving treatment with infusion solutions and the test group treated, in addition to the usual scheme of therapy, with indomethacin in a daily dose of 150 mg. The study revealed that salmonellae isolated at the initial stages of the disease possessed highly pronounced adhesive properties. The adhesive properties of salmonellae isolated at the stage of convalescence from the patients of the test group were considerably less pronounced than those of salmonellae isolated from the same patients at the peak of the disease. In the control group no differences in the adhesive properties of salmonellae isolated from the same patients were established.     

Effect of weaning time on the growth rate and food intake of the spiny mouse pup

The spiny mouse Acomys cahirinus produces well-developed pups although it is a relatively small mammal (45 g). We envisioned two opposing hypotheses on the effect of early weaning on the growth rate of pups. The first predicts little effect since the increase in energy intake of dams above non-reproducing females is relatively low, suggesting that pups consume a large portion of their energy as solid food, and the pups are very well developed at birth. The second predicts a substantial effect since the 'index of precociality', that is the energy intake for maintenance of a pup as a proportion of that predicted for a rodent of its body mass, falls within values for altricial rodents, suggesting an extended maternal dependence of the young. To test these hypotheses, we measured the growth rate and food intake of pups weaned after either 7, 14, 21 or 28 days. Only three of 12 pups weaned after 7 days survived and, consequently, the latter hypothesis was supported. All pups weaned at 14–28 days survived. There was a significant decrease in growth rate during the first day after weaning in pups weaned at 7, 14 and 21 days but not after 28 days, suggesting that pups did not require parental care by day 28. Peak growth rate in pups weaned at 14 days occurred in the second week but occurred in the third week in pups weaned at 21 and 28 days. In spite of these differences, pups in all treatments had similar body mass at 64 days, indicating compensatory growth. We concluded that pups of A. cahirinus are precocial from a morphological aspect in that they are well developed at birth but altricial from a nutritional aspect in that they require extended maternal support.     

Bartonella Genotypes in Fleas (Insecta: Siphonaptera) Collected from Rodents in the Negev Desert,Israel

Fleas collected from rodents in the Negev Desert in southern Israel were molecularly screened for Bartonella species. A total of 1,148 fleas, collected from 122 rodents belonging to six species, were pooled in 245 pools based on flea species, sex, and rodent host species. Two Bartonella gene fragments, corresponding to RNA polymerase B (rpoB) and citrate synthase (gltA), were targeted, and 94 and 74 flea pools were found positive by PCR, respectively. The Bartonella 16S-23S internal transcribed spacer (ITS) region was also targeted, and 66 flea pools were found to be positive by PCR. Sixteen different Bartonella gltA genotypes were detected in 94 positive flea pools collected from 5 different rodent species, indicating that fleas collected from each rodent species can harbor several Bartonella genotypes. Based on gltA analysis, identified Bartonella genotypes were highly similar or identical to strains previously detected in rodent species from different parts of the world. A gltA fragment 100% similar to Bartonella henselae was detected in one flea pool. Another 2 flea pools contained gltA fragments that were closely related to B. henselae (98% similarity). The high sequence similarities to the zoonotic pathogen B. henselae warrant further investigation.Bartonellae are small Gram-negative bacilli belonging to the alpha-2 subdivision of the Proteobacteria. Different Bartonella species were detected in a wide range of vertebrate animals. There are currently 30 known species or subspecies, among which 14 have been associated with human diseases (7). Bartonella organisms are parasites of mammalian erythrocytes and endothelial cells and are transmitted by fleas and lice and potentially by other blood-feeding arthropods such as ticks and flies (2). Infection in the natural host commonly causes a chronic bacteremia, which is asymptomatic in most cases.Rodents are being extensively studied and were found to have a high prevalence of Bartonella infection, with a high diversity of Bartonella spp. and strains (3). The close contacts between human and rodent populations around the world create excellent conditions for transmission of Bartonella spp. from animals to humans (28). The transmission routes of Bartonella bacteria by arthropod vectors among rodents and between rodents and other mammalian hosts have public health implications. In order to understand the extent to which rodents serve as source of human infections, investigations of rodent-borne Bartonella are essential (28). A few cases of human infections with Bartonella bacteria of rodent origin have been reported: B. elizabethae was associated with endocarditis, B. washoensis was associated with cases of myocarditis and meningitis, B. vinsonii subsp. arupensis was reported to cause fever and neurologic symptoms, and B. grahamii was isolated from the intraocular fluids of a patient with neuroretinitis (5, 11, 12, 25, 29).An earlier survey carried out in the Tel Aviv region, Israel, demonstrated the occurrence of Bartonella strains closely related to B. elizabethae and B. tribocorum in commensal rats (Rattus rattus) (8). Another study has surveyed wild rodents and their fleas for Bartonella spp. in 19 geographical locations in Israel from the Upper Galilee in the north to Beer Sheba in the south. Bartonella DNA was detected in spleen samples of 19 out of 79 (24%) black rats (R. rattus), in 1 of 4 (25%) Cairo spiny mice (Acomys cahirinus), and in 15 of 34 (44%) flea pools collected from black rats (R. rattus) (21). The objectives of the current study were to screen fleas collected from rodents inhabiting the Negev Desert south to Beer Sheba for Bartonella infection and to compare Bartonella prevalences between male and female fleas.     

Heterologous expression of secreted biologically active human interleukin-10 in Bifidobacterium breve

Construction of Bifidobacterium breve capable of production of secreted biologically active human interleukin-10 (hIL-10) is described. ORF coding for full-length mature human interleukin-10 was cloned into a series of expression vectors. This resulted in generation of translational fusions between hIL-10 and signal peptides sequences derived from Bifidobacterium breve genes sec2, apuB and B. adolescentis gene amyB under the control of constitutively active bifidobacterial promoter. We have shown that fusion to amyB signal peptide resulted in highest expression level of hIL-10 at the mRNA and protein level. Secreted hIL-10 was highly unstable in bifidobacterial culture supernatants in standard growth conditions. However, incubation of stationary cultures in buffered tissue culture medium resulted in production of stable biologically active hIL-10, albeit in low amounts (1.9 ng/ml).