Foraging as an evidence accumulation process

A canonical foraging task is the patch-leaving problem, in which a forager must decide to leave a current resource in search for another. Theoretical work has derived optimal strategies for when to leave a patch, and experiments have tested for conditions where animals do or do not follow an optimal strategy. Nevertheless, models of patch-leaving decisions do not consider the imperfect and noisy sampling process through which an animal gathers information, and how this process is constrained by neurobiological mechanisms. In this theoretical study, we formulate an evidence accumulation model of patch-leaving decisions where the animal averages over noisy measurements to estimate the state of the current patch and the overall environment. Evidence accumulation models belong to the class of drift diffusion processes and have been used to model decision making in different contexts. We solve the model for conditions where foraging decisions are optimal and equivalent to the marginal value theorem, and perform simulations to analyze deviations from optimal when these conditions are not met. By adjusting the drift rate and decision threshold, the model can represent different strategies, for example an increment-decrement or counting strategy. These strategies yield identical decisions in the limiting case but differ in how patch residence times adapt when the foraging environment is uncertain. To account for sub-optimal decisions, we introduce an energy-dependent utility function that predicts longer than optimal patch residence times when food is plentiful. Our model provides a quantitative connection between ecological models of foraging behavior and evidence accumulation models of decision making. Moreover, it provides a theoretical framework for potential experiments which seek to identify neural circuits underlying patch leaving decisions

Mechanical Surface Waves Accompany Action Potential Propagation

Many studies have shown that a mechanical displacement of the axonal membrane accompanies the electrical pulse defining the Action Potential (AP). Despite a large and diverse body of experimental evidence, there is no theoretical consensus either for the physical basis of this mechanical wave nor its interdependence with the electrical signal. In this manuscript we present a model for these mechanical displacements as arising from the driving of surface wave modes in which potential energy is stored in elastic properties of the neuronal membrane and cytoskeleton while kinetic energy is carried by the axoplasmic fluid. In our model these surface waves are driven by the traveling wave of electrical depolarization that characterizes the AP, altering the compressive electrostatic forces across the membrane as it passes. This driving leads to co-propagating mechanical displacements, which we term Action Waves (AWs). Our model for these AWs allows us to predict, in terms of elastic constants, axon radius and axoplasmic density and viscosity, the shape of the AW that should accompany any traveling wave of voltage, including the AP predicted by the Hodgkin and Huxley (HH) equations. We show that our model makes predictions that are in agreement with results in experimental systems including the garfish olfactory nerve and the squid giant axon. We expect our model to serve as a framework for understanding the physical origins and possible functional roles of these AWs in neurobiology.Comment: 6 pages 3 figures + 2 page supplemen

Detection of bla SHV and bla CTX-M genes in ESBL producing Klebsiella pneumoniae isolated from Egyptian patients with suspected nosocomial infections

The correct identification of the genes involved in ESBL mediated  resistance is necessary for the surveillance and epidemiological studies of their transmission in hospitals. The aim of the present study was to find the prevalence of ESBL producing Klebsiella pneumoniae among K. pneumoniae isolates separated from Egyptian patients with suspected nosocomial infections, to detect their drug resistance pattern and to look for bla SHV and bla CTX-M genes in such organisms.Subjects and methods: 138 K. pneumoniae isolates from Egyptian patients with suspected nosocomial infections were screened for ESBL production by the pattern of antimicrobial susceptibilities. Phenotypic identification for ESBL production was confirmed by double disc synergy test, phenotypic confirmatory double disc test and by MicroScan panel system. bla SHV and bla CTX-M genes in ESBL producing K. pneumoniae were detected using multiplex PCR. Results: The prevalence of ESBL producing K. pneumoniae was 21% (30/138). Their pattern of antimicrobial susceptibility showed that 90% was resistant to (Sulphamethoxazole/Trimethoprim), 70% was resistant to(Amoxicillin/Clavulanate), 63.3% was resistant to Cefotaxime and Ceftazidime, 60% was resistant to Amikacin, 46.7% was resistant to Doxycycline, Cefoxitin, Ceftriaxone and Levofloxacin, 40% was resistant to Cefepime, 20% was resistant to Ertapenem and  (Sulbactam/Cefoperazone), 13.3% was resistant to (Piperacillin/Tazobactam), 10% was resistant to (Imipenem/Cilastatin) and Gentamycin and 6.7% was resistant to Meropenem and Ciprofloxacin. Among the ESBL producing K. pneumoniae, three out of 30 (10%) and 16 out of 30 (53.3%) were positive for bla SHV and bla CTX-M genes respectively. It could be concluded that ESBL producing isolates of K. pneumoniae have been increasingly recognized in the hospital settings in Egypt and are associated with multiple drug resistance. Thus, molecular identification of the genes encoding beta lactamases would be essential for a reliable epidemiological investigation of their transmission in hospitals and antimicrobial resistance

Detection of occult HBV infection by nested PCR assay among chronic hepatitis C patients with and without hepatocellular carcinoma

Occult hepatitis B virus infection (OBI) has been reported among patients with chronic hepatitis C virus (HCV) infection and hepatocellular carcinoma (HCC). This study aimed to evaluate the prevalence of OBI in chronic hepatitis C patients with and without hepatocellular carcinoma. A total of 40 chronic hepatitis C patients who were negative for HBsAg, were enrolled into the study. They were classified into two groups: Group I which included 20 patients with chronic hepatitis C only whereas Group II included 20 patients with chronic hepatitis C and HCC. Detection of HBV DNA was done by nested-PCR using two sets of primers specific for surface and X viral genomes in serum and liver tissue of patients. Genotyping system based on PCR using type-specific primers was done for HBV-DNA positive intrahepatic samples. OBI was detected in the liver tissue in 23/40 (57.5%) of chronic HCV infected patients, 18 (78.3%) of whom belonged to group II, conferring a 90% prevalence of this group. In serum, HBV-DNA was detected in 9/40 patients (22.5%), 7 (77.8%) of whom belonged to group II. Among the 23 positive intrahepatic HBV-DNA samples studied, HBV-genotype D (34.8%) and B (26.1%) were more predominant, whereas HBV-genotype C (13.1%) and A (8.7%) infections were the least observed, respectively; mixed genotypes were detected in 17.4% (n= 4), 3 of them were with HBV-genotype D and B, and 1 was with HBV-genotype C and A. In conclusion OBI is a fact in our community; it was detected in liver tissue of chronic HCVinfected patients, especially in cases of chronic HCC. In addition, OBI might be related to severity of necroinflammatory activity and fibrosis. Large studies are needed to confirm that co-infection could determine a worse progress of chronic liver disease in this population. Also, detection of intrahepatic HBV-DNA is more useful in diagnosis of OBI.Keywords: Occult hepatitis B virus infection (OBI); Chronic hepatitis C virus infection (CHC); Hepatocellular carcinoma (HCC); HBV-DNA; Nested PC

Can copper amino acid chelates reduce the physiological strain of growing rabbits under summer conditions?

[EN] This study was conducted at the Poultry Research Centre, Faculty of Agriculture, Alexandria University, Egypt, during the summer season (July and August months) 2018. For five weeks, until 63 d of age, a total number of 140 weaned V line rabbits were randomly distributed into seven groups of 20 rabbits each. Rabbits of groups 2 and 3 were fed basal diet plus copper sulphate (100 and 200 mg Cu-Sul/kg, respectively). Groups 4 and 5 were fed basal diet plus copper methionine (100 and 200 mg Cu-Meth/kg, respectively) and groups 6 and 7 were fed basal diet plus copper glycine (100 and 200 mg Cu-Gly/kg, respectively), while the first group was fed basal diet only as control. Rabbits fed diet supplemented with higher level (200 mg/kg) of Cu-Meth or Cu-Gly chelates had significantly higher body weight and daily body weight gain (P<0.05) compared to those fed diets supplemented with both levels of Cu-Sul. Rabbits fed diets supplemented with Cu-Meth or Cu-Gly chelates had significantly increased (P<0.05) red blood cells, lymphocyte, high-density lipoprotein and Cu values in blood. Within the studied Cu sources, serum total lipids values of rabbits were significantly lower than in the control group. However, serum total antioxidant capacity, glutathione peroxidase and superoxide dismutase were higher by both organic chelates studied than other groups. In general, copper supplementation improves productive performance and physiological status under summer conditions.Goodb, F.; Soliman, F.; Elghalid, O.; Abd El-Hady, AM. (2022). Can copper amino acid chelates reduce the physiological strain of growing rabbits under summer conditions?. World Rabbit Science. 30(4):277-286. https://doi.org/10.4995/wrs.2022.1384827728630

Detection of antimicrobial resistance genes of Helicobacter pylori strains to clarithromycin, metronidazole, amoxicillin and tetracycline among Egyptian patients

Background: Antibiotic resistance of Helicobacter pylori (H. pylori) treatment is on the rise, and is affecting the efficacy of current used therapeutic regimens.Aim: We aimed to enhance the understanding of antimicrobial resistance rates of H. pylori strains recovered from patients at Theodor Bilharz Research Institute Hospital in Egypt, as a mandatory step before starting treatment.Subjects and methods: Mutant genes conferring metronidazole, amoxicillin, clarithromycin, and tetracycline resistance were detected in 60 H. pylori strains recovered from patients who underwent upper endoscopic examination. Patients were considered to be infected with H. pylori when rapid urease test and detection of 16S rRNA in gastric biopsies recorded positive. Molecular detection of resistant genes to metronidazole (rdx gene) and amoxicillin (pbp1A gene) was carried out by conventional PCR followed by sequencing of PCR products. While detection of 23S rRNA gene conferring clarithromycin resistance and detection of 16S rRNA mutation gene conferring tetracycline resistance were carried out by realtime PCR.Results:  H. pylori resistance rates to metronidazole, and amoxicillin were 25% and 18.3% respectively. While for clarithromycin and tetracycline, point mutations in 23S rRNA types A2142G and A2143G and in 16S rRNA of H. pylori were assessed by real time PCR assay respectively. Resistance mutant genes were found to be 6.7% of clarithromycin and 1.7% of tetracycline. Combined resistance rates to metronidazole and amoxicillin was (11.6%) followed by metronidazole and clarithromycin (5%), while patterns of clarithromycin and amoxicillin (1.6%), metronidazole, clarithromycin and amoxicillin (1.6%) were revealed.Conclusion: Data concerning antimicrobial resistance genes play an important role in empiric treatment of H. pylori infection. According to our results, H. pylori resistance to metronidazole and amoxicillin was relatively high. Clarithromycin is still a good option for first line anti-H. pylori treatment. Combined resistant strains are emerging and may have an effect on the combination therapy.Keywords: H. pylori, Antimicrobial resistance, Gene mutations, Rdx gene, Clarithromycin resistance, Tetracycline resistanc

Detection of Helicobacter pylori vacA, cagA and iceA1 virulence genes associated with gastric diseases in Egyptian patients

Background: Helicobactor pylori (H. pylori) virulence markers would be useful to predict peptic ulcer disease (PUD) or gastric cancer.Aim: In Egypt, since inadequate data are present regarding H. pylori virulence–related genes in different age group patients with gastro-duodenal diseases, it becomes crucial to study the clinical status of cagA, vacA and iceA1 genotypes of H. pylori strains recovered from patients with dyspepsia.Subjects and methods: The study included 113 dyspeptic patients who were exposed to upper gastrointestinal endoscopic examination. Four antral biopsies were obtained from each patient for the analysis of H. pylori infection by rapid urease test and detection of 16S rRNA.Results: Sixty (53.1%) patients were confirmed to be infected with H. pylori. Upon endoscopy, gastritis was revealed in 27 patients (45%) and10 patients (16.7%) had PUD. Of the 60 H. pylori strains, 39 (65%) had at least one virulence gene. Six different genotypic forms were recognized; vacA (9/60), iceA1 (1/60), vacA/cagA (7/60), vacA/iceA1 (13/60), vacA/cagA/iceA1 (8/60) only one of cagA/iceA type and we could not detect cagA. The overall vacA, iceA1and cagA genes identified were 61.6%, 38.8%, 26.6% respectively, by PCR-based molecular testing. The vacA gene status was highly significant related to gastritis patient (P 0.036). The vacA s1m1 and s2m2 alleles were significantly found in 50% of H. pylori infected patients with PUD and with gastritis 57.1% respectively (P 0.01).Conclusion: In conclusion, the main genotype combinations in the studied Egyptian patients were; vacAs2m2/iceA1, vacAs1m1/cagA, mostly associated with gastritis, and vacAs1/cagA/icA, mainly in PUD. The less virulent (s2, s2m2) H. pylori genotypes were found in patients aged over 43 years