12 research outputs found
Metabolic and cardiac adaptation to chronic pharmacologic blockade of facilitative glucose transport in murine dilated cardiomyopathy and myocardial ischemia
Abstract GLUT transgenic and knockout mice have provided valuable insight into the role of facilitative glucose transporters (GLUTs) in cardiovascular and metabolic disease, but compensatory physiological changes can hinder interpretation of these models. To determine whether adaptations occur in response to GLUT inhibition in the failing adult heart, we chronically treated TG9 mice, a transgenic model of dilated cardiomyopathy and heart failure, with the GLUT inhibitor ritonavir. Glucose tolerance was significantly improved with chronic treatment and correlated with decreased adipose tissue retinol binding protein 4 (RBP4) and resistin. A modest improvement in lifespan was associated with decreased cardiomyocyte brain natriuretic peptide (BNP) expression, a marker of heart failure severity. GLUT1 and −12 protein expression was significantly increased in left ventricular (LV) myocardium in ritonavir-treated animals. Supporting a switch from fatty acid to glucose utilization in these tissues, fatty acid transporter CD36 and fatty acid transcriptional regulator peroxisome proliferator-activated receptor α (PPARα) mRNA were also decreased in LV and soleus muscle. Chronic ritonavir also increased cardiac output and dV/dt-d in C57Bl/6 mice following ischemia-reperfusion injury. Taken together, these data demonstrate compensatory metabolic adaptation in response to chronic GLUT blockade as a means to evade deleterious changes in the failing heart
Language with Vision: a Study on Grounded Word and Sentence Embeddings
Grounding language in vision is an active field of research seeking to
construct cognitively plausible word and sentence representations by
incorporating perceptual knowledge from vision into text-based representations.
Despite many attempts at language grounding, achieving an optimal equilibrium
between textual representations of the language and our embodied experiences
remains an open field. Some common concerns are the following. Is visual
grounding advantageous for abstract words, or is its effectiveness restricted
to concrete words? What is the optimal way of bridging the gap between text and
vision? To what extent is perceptual knowledge from images advantageous for
acquiring high-quality embeddings? Leveraging the current advances in machine
learning and natural language processing, the present study addresses these
questions by proposing a simple yet very effective computational grounding
model for pre-trained word embeddings. Our model effectively balances the
interplay between language and vision by aligning textual embeddings with
visual information while simultaneously preserving the distributional
statistics that characterize word usage in text corpora. By applying a learned
alignment, we are able to indirectly ground unseen words including abstract
words. A series of evaluations on a range of behavioural datasets shows that
visual grounding is beneficial not only for concrete words but also for
abstract words, lending support to the indirect theory of abstract concepts.
Moreover, our approach offers advantages for contextualized embeddings, such as
those generated by BERT, but only when trained on corpora of modest,
cognitively plausible sizes. Code and grounded embeddings for English are
available at https://github.com/Hazel1994/Visually_Grounded_Word_Embeddings_2
How direct is the link between words and images?
Current word embedding models despite their success, still suffer from their
lack of grounding in the real world. In this line of research, Gunther et al.
2022 proposed a behavioral experiment to investigate the relationship between
words and images. In their setup, participants were presented with a target
noun and a pair of images, one chosen by their model and another chosen
randomly. Participants were asked to select the image that best matched the
target noun. In most cases, participants preferred the image selected by the
model. Gunther et al., therefore, concluded the possibility of a direct link
between words and embodied experience. We took their experiment as a point of
departure and addressed the following questions. 1. Apart from utilizing
visually embodied simulation of given images, what other strategies might
subjects have used to solve this task? To what extent does this setup rely on
visual information from images? Can it be solved using purely textual
representations? 2. Do current visually grounded embeddings explain subjects'
selection behavior better than textual embeddings? 3. Does visual grounding
improve the semantic representations of both concrete and abstract words? To
address these questions, we designed novel experiments by using pre-trained
textual and visually grounded word embeddings. Our experiments reveal that
subjects' selection behavior is explained to a large extent based on purely
text-based embeddings and word-based similarities, suggesting a minor
involvement of active embodied experiences. Visually grounded embeddings
offered modest advantages over textual embeddings only in certain cases. These
findings indicate that the experiment by Gunther et al. may not be well suited
for tapping into the perceptual experience of participants, and therefore the
extent to which it measures visually grounded knowledge is unclear.Comment: Accepted in the Mental Lexicon Journal:
https://benjamins.com/catalog/m
A novel FRET-based screen in high-throughput format to identify inhibitors of malarial and human glucose transporters
The glucose transporter PfHT is essential to the survival of the malaria parasite Plasmodium falciparum and has been shown to be a druggable target with high potential for pharmacological intervention. Identification of compounds against novel drug targets is crucial to combating resistance against current therapeutics. Here, we describe the development of a cell-based assay system readily adaptable to high-throughput screening that directly measures compound effects on PfHT-mediated glucose transport. Intracellular glucose concentrations are detected using a genetically encoded fluorescence resonance energy transfer (FRET)-based glucose sensor. This allows assessment of the ability of small molecules to inhibit glucose uptake with high accuracy (Z′ factor of >0.8), thereby eliminating the need for radiolabeled substrates. Furthermore, we have adapted this assay to counterscreen PfHT hits against the human orthologues GLUT1, -2, -3, and -4. We report the identification of several hits after screening the Medicines for Malaria Venture (MMV) Malaria Box, a library of 400 compounds known to inhibit erythrocytic development of P. falciparum. Hit compounds were characterized by determining the half-maximal inhibitory concentration (IC(50)) for the uptake of radiolabeled glucose into isolated P. falciparum parasites. One of our hits, compound MMV009085, shows high potency and orthologue selectivity, thereby successfully validating our assay for antimalarial screening
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Exploring the influence of semantics on the German plural system: a wug study
The role of semantics in inflectional morphology has long been debated (Huang & Pinker, 2010; Pinker & Prince, 1988; Ramscar, 2002) with most of the focus on the English past tense. This paper explores whether an effect of semantics can be found for German noun plural generalisation, a system as yet only poorly understood. German speakers were asked to first freely produce and then rate plural forms of 24 new wug words, presented in a semantically manipulated context. We expected that the German plural class ending in -n should be used more frequently with nouns presented as persons than as objects (Gaeta, 2008). While this hypothesis was not confirmed, the post-hoc discovery of other semantic influences prevents us from completely rejecting the original hypothesis. In light of these results we discuss possible sources of the observed pattern of plural classes and stress the importance of replicating wug studies with novel sets of wug words. We conclude that generalisation of the German plural system cannot easily be explained by phonological nor semantic influences
How trial-to-trial learning shapes mappings in the mental lexicon: Modelling Lexical Decision with Linear Discriminative Learning
Priming and antipriming can be modelled with error-driven learning (Marsolek,
2008), by assuming that the learning of the prime influences processing of the
target stimulus. This implies that participants are continuously learning in
priming studies, and predicts that they are also learning in each trial of
other psycholinguistic experiments. This study investigates whether
trial-to-trial learning can be detected in lexical decision experiments. We
used the Discriminative Lexicon Model (DLM; Baayen et al., 2019), a model of
the mental lexicon with meaning representations from distributional semantics,
which models incremental learning with the Widrow-Hoff rule. We used data from
the British Lexicon Project (BLP; Keuleers et al., 2012) and simulated the
lexical decision experiment with the DLM on a trial-by-trial basis for each
subject individually. Then, reaction times for words and nonwords were
predicted with Generalised Additive Models, using measures derived from the DLM
simulations as predictors. Models were developed with the data of two subjects
and tested on all other subjects. We extracted measures from two simulations
for each subject (one with learning updates between trials and one without),
and used them as input to two GAMs. Learning-based models showed better model
fit than the non-learning ones for the majority of subjects. Our measures also
provided insights into lexical processing and enabled us to explore individual
differences with Linear Mixed Models. This demonstrates the potential of the
DLM to model behavioural data and leads to the conclusion that trial-to-trial
learning can indeed be detected in psycholinguistic experiments.Comment: 38 pages, 13 figure
Modeling Morphology With Linear Discriminative Learning: Considerations and Design Choices
This study addresses a series of methodological questions that arise when
modeling inflectional morphology with Linear Discriminative Learning. Taking
the semi-productive German noun system as example, we illustrate how decisions
made about the representation of form and meaning influence model performance.
We clarify that for modeling frequency effects in learning, it is essential to
make use of incremental learning rather than the endstate of learning. We also
discuss how the model can be set up to approximate the learning of inflected
words in context. In addition, we illustrate how in this approach the wug task
can be modeled in considerable detail. In general, the model provides an
excellent memory for known words, but appropriately shows more limited
performance for unseen data, in line with the semi-productivity of German noun
inflection and generalization performance of native German speakers.Comment: 38 pages, 5 figures, 10 tables; acknowledgements adde