Biology subjects

Brown, J. K.

Publications and source records attributed to Brown, J. K..

3 recordsLinked to original sources

bioRxiv2020

Genetic diversity of Bemisia tabaci Genn. characterized by analysis of ISSR and cytochrome c oxidase subunit I at Qassim, Saudia Arabia.

Problems of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) that increased and escalated in the last 40 years seem to be related to one or more aggressive biotypes that appeared to spread steadily worldwide. As well, some biological characteristics of B. tabaci have led some entomologists to change and multiply their methodology to update with the change in the pest genetic structures. This study is the 1st of its kind in Qassim region in KSA in respect of B. tabaci biotypes. Four identification methods (Squash Silverleaf Symptoms (SSL), cross mating, Cytochrome oxidase subunit I (COI) sequences, and ISSR-PCR analysis) were carried out to determine the biotypes of B. tabaci at Qassim regions. Slight SSL symptoms were observed with varying degrees on squash leaves caused by B. tabaci population at Qassim, KSA. Cross-mating among the populations that have the same or similar genetic structures produced fertilized offspring, females and males with higher sex ratios in favor of females, and produced a higher number of eggs. Whereas, B. tabaci populations that varied greatly in their genetic structures produced unfertilized eggs, which produce males only. In the same trend, ISSR-PCR analysis revealed that B. tabaci populations at Qassim regions varied genetically and gathered into four genetic groups. In conclusion, COI analysis is a perfect tool for classification between biotypes in B. tabaci. Therefore, this study declares that B. tabaci that colonized and infest Qassim horticulture has not the same genetic structures but belonging to B biotypes. It could be named as Bemisia species complex.

zoology↗

bioRxiv2018

The antiparasitic drug atovaquone inhibits arbovirus replication through the depletion of intracellular nucleotides.

Arthropod-borne viruses represent a significant public health threat worldwide yet there are few antiviral therapies or prophylaxis targeting these pathogens. In particular, the development of novel antivirals for high-risk populations such as pregnant women is essential to prevent devastating disease such as that which was experienced with the recent outbreak of Zika virus (ZIKV) in the Americas. One potential avenue to identify new and pregnancy friendly antiviral compounds is to repurpose well-known and widely used FDA approved drugs. In this study, we addressed the antiviral role of atovaquone, a FDA Pregnancy Category C drug and pyrimidine biosynthesis inhibitor used for the prevention and treatment of parasitic infections. We found that atovaquone was able to inhibit ZIKV and chikungunya virus virion production in human cells and that this antiviral effect occurred early during infection at the initial steps of viral RNA replication. Moreover, we were able to complement viral replication and virion production with the addition of exogenous pyrimidine nucleosides indicating that atovaquone is functioning through the inhibition of the pyrimidine biosynthesis pathway to inhibit viral replication. Finally, using an ex vivo human placental tissue model, we found that atovaquone could limit ZIKV infection in a dose-dependent manner providing evidence that atovaquone may function as an antiviral in humans. Taken together, these studies suggest that atovaquone could be a broad-spectrum antiviral drug and a potential attractive candidate for the prophylaxis or treatment of arbovirus infection in vulnerable populations, such as pregnant women.\n\nAuthor SummaryThe ability to protect vulnerable populations such as pregnant women and children from Zika virus and other arbovirus infections is essential to preventing the devastating complications induced by these viruses. One class of antiviral therapies may lie in known pregnancy-friendly drugs that have the potential to mitigate arbovirus infections and disease yet this has not been explored in detail. In this study, we show that the common antiparasitic drug, atovaquone, inhibits arbovirus replication through intracellular nucleotide depletion and can impair ZIKV infection in an ex vivo human placental explant model. Our study provides a novel function for atovaquone and highlights that the rediscovery of pregnancy-acceptable drugs with potential antiviral effects can be the key to better addressing the immediate need for treating viral infections and preventing potential birth complications and future disease.

microbiology↗

bioRxiv2018

Impaired expected value computations in schizophrenia are associated with a reduced ability to integrate reward probability and magnitude of recent outcomes.

ABSTRACTO_ST_ABSBackgroundC_ST_ABSMotivational deficits in people with schizophrenia (PSZ) are associated with an inability to integrate the magnitude and probability of previous outcomes. The mechanisms that underlie probability-magnitude integration deficits, however, are poorly understood. We hypothesized that increased reliance on \"value-less\" stimulus-response associations, in lieu of expected value (EV)-based learning, could drive probability-magnitude integration deficits in PSZ with motivational deficits.\n\nMethodsHealthy volunteers (n= 38) and PSZ (n=49) completed a reinforcement learning paradigm consisting of four stimulus pairs. Reward magnitude (3/2/1/0 points) and probability (90%/80%/20%/10%) together determined each stimulus EV. Following a learning phase, new and familiar stimulus pairings were presented. Participants were asked to select stimuli with the highest reward value.\n\nResultsPSZ with high motivational deficits made increasingly less optimal choices as the difference in reward value (probability*magnitude) between two competing stimuli increased. Using a previously-validated computational hybrid model, PSZ relied less on EV (\"Q-learning\") and more on stimulus-response learning (\"actor-critic\"), which correlated with SANS motivational deficit severity. PSZ specifically failed to represent reward magnitude, consistent with model demonstrations showing that response tendencies in the actor-critic were preferentially driven by reward probability.\n\nConclusionsProbability-magnitude deficits in PSZ with motivational deficits arise from underutilization of EV in favor of reliance on value-less stimulus-response associations. Consistent with previous work and confirmed by our computational hybrid framework, probability-magnitude integration deficits were driven specifically by a failure to represent reward magnitude. This work reconfirms the importance of decreased Q-learning/increased actor-critic-type learning as an explanatory framework for a range of EV deficits in PSZ.

neuroscience↗