Publications by authors named "Juan A Segura"

Article Synopsis
  • This study investigated ticks as parasites on cattle, collecting over 6,700 samples from farms in Magdalena Medio Antioquia, focusing on their role as vectors for various pathogens that affect health and agriculture.!* -
  • It used molecular techniques to detect pathogens like Anaplasma marginale, Babesia bigemina, and others, finding a significant presence of these microorganisms in Rhipicephalus microplus ticks.!* -
  • The findings highlight the diversity of microorganisms in ticks and stress the importance of integrating tick surveillance with medical and agricultural control measures at both regional and national levels.!*
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Introduction: Psittacosis is a zoonotic disease caused by Chlamydia psittaci, a bacterium classified as an agent with bioterrorist potential. It has caused multiple outbreaks in exposed poultry workers around the world. Colombia has no epidemiological follow-up of the infection and a big knowledge gap.

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Tick infestation affects about 80% of livestock globally while transmitting various pathogens causing high economic losses. This study aimed to determine the degree of tick infestation in two regions, North and Middle Magdalena in Antioquia, Colombia, to identify the ixodid tick species found and the associated risk factors. A cross-sectional study was carried out in 48 farms distributed in six municipalities of Antioquia.

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Background: Glutaminase isoenzymes GLS and GLS2 play apparently opposing roles in cancer: GLS acts as an oncoprotein, while GLS2 (GAB isoform) has context specific tumour suppressive activity. Some microRNAs (miRNAs) have been implicated in progression of tumours, including gliomas. The aim was to investigate the effect of GLS and GAB expression on both miRNAs and oxidative status in glioblastoma cells.

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Rhipicephalus microplus is recognized as a tick species highly prevalent in cattle, with a wide pantropical distribution that seems to continue spreading geographically. However, its role as a biological vector has been scarcely studied in the livestock context. In this study, a 16S rRNA next-generation sequencing analysis was used to determine bacterial diversity in salivary glands and gut of R.

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Ticks (Ixodida) are hematophagous ectoparasites that harbor and transmit diverse species of viruses, some of which cause serious diseases with worldwide veterinary and human health consequences. Rhipicephalus microplus is an important cattle tick in Colombia, where it causes significant economic losses. Despite the importance of this tick, its viral profile is unknown.

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Glutaminase (GA) catalyzes the first step in mitochondrial glutaminolysis playing a key role in cancer metabolic reprogramming. Humans express two types of GA isoforms: GLS and GLS2. GLS isozymes have been consistently related to cell proliferation, but the role of GLS2 in cancer remains poorly understood.

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The characteristics and quality of home-made dry cured sausages can be recognized and associated with the region of origin. The characteristics of this type of sausages result from the superficial mycobiota that spontaneously colonizes the products. The aim of this study was to identify the house mycobiota associated with home-made dry cured sausages from different localities of Argentina and characterize the populations of Penicillium nalgiovense present by morphological and biochemical markers.

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Background: Metabolic reprogramming of tumours is a hallmark of cancer. Among the changes in the metabolic network of cancer cells, glutaminolysis is a key reaction altered in neoplasms. Glutaminase proteins control the first step in glutamine metabolism and their expression correlates with malignancy and growth rate of a great variety of cancers.

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Cancer cells develop and succeed by shifting to different metabolic programs compared with their normal cell counterparts. One of the classical hallmarks of cancer cells is their higher glycolysis rate and lactate production even in the presence of abundant O (Warburg effect). Another common metabolic feature of cancer cells is a high rate of glutamine (Gln) consumption normally exceeding their biosynthetic and energetic needs.

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Glutamate is the principal excitatory neurotransmitter in the central nervous system and its actions are related to the behavioral effects of psychostimulant drugs. In the last two decades, basic neuroscience research and preclinical studies with animal models are suggesting a critical role for glutamate transmission in drug reward, reinforcement, and relapse. Although most of the interest has been centered in post-synaptic glutamate receptors, the presynaptic synthesis of glutamate through brain glutaminases may also contribute to imbalances in glutamate homeostasis, a key feature of the glutamatergic hypothesis of addiction.

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The expression of glutaminase in glial cells has been a controversial issue and matter of debate for many years. Actually, glutaminase is essentially considered as a neuronal marker in brain. Astrocytes are endowed with efficient and high capacity transport systems to recapture synaptic glutamate which seems to be consistent with the absence of glutaminase in these glial cells.

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Article Synopsis
  • Mitochondrial glutaminase (GA) is crucial for cancer cell metabolism, but the specific roles of its isozymes (KGA and GAB) in cancer are not fully understood.
  • Silencing KGA in glioma cells led to reduced cell survival, increased apoptosis markers, and mitochondrial dysfunction, while GAB overexpression showed different but significant effects.
  • Combining GA expression modulation with oxidizing agents like arsenic trioxide or hydrogen peroxide enhances the therapeutic effects against glioma cells, suggesting a new approach for cancer treatment.
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Tumor cells suffer a metabolic reprogramming which allows them to use metabolic fuels (glucose, glutamine, lipids) through anabolic fates to support their enhanced proliferation and other carcinogenesis-related features. The present review tries to address and summarize the broad and growing information available about this reprogramming, whose pieces, put together, make up a complex scheme that encompasses different complexity scales, from cells to systemic networks.

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The oxygen paradox tells us that oxygen is both necessary for aerobic life and toxic to all life forms. Reactive oxygen species (ROS) touch every biological and medical discipline, especially those involving proliferative status, supporting the idea that active oxygen may be increased in tumor cells. In fact, metabolism of oxygen and the resulting toxic byproducts can cause cancer and death.

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The prevention of oxidation is an essential process in all cells, as decreased antioxidant protection may lead to cytotoxicity, mutagenicity and carcinogenicity. The mechanisms by which oxidative stress contributes to carcinogenesis include modulation of gene expression and induction of genetic modifications. Cellular methylation and antioxidant metabolism are linked by the transsulfuration pathway, which converts the methionine cycle intermediate, homocysteine, to cysteine, the limiting reagent in glutathione synthesis.

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Oxidants have critical functions inside healthy and unhealthy cells. Deregulated cell cycle and apoptosis, both regulated by oxidative stress, have been described as hallmarks of mitotic (cancer) and postmitotic (neuronal) cells. This review provides an updated revision of the oxidant effects of some environmental contaminants such as dioxins and the heavy metals cadmium, cobalt, and copper.

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Glutaminase is considered as the main glutamate producer enzyme in brain. Consequently, the enzyme is essential for both glutamatergic and gabaergic transmissions. Glutamine-derived glutamate and ammonia, the products of glutaminase reaction, fulfill crucial roles in energy metabolism and in the biosynthesis of basic metabolites, such as GABA, proteins and glutathione.

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Glutamine is a multifaceted amino acid that plays key roles in many metabolic pathways and also fulfils essential signaling functions. Although classified as non-essential, recent evidence suggests that glutamine is a conditionally essential amino acid in several physiological situations. Glutamine homeostasis must therefore be exquisitely regulated and mitochondria represent a major site of glutamine metabolism in numerous cell types.

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The synthesis of neurotransmitter glutamate in brain is mainly carried out by glutaminase enzymes. This synthesis must be exquisitely regulated because of its harmful potential giving rise to excitotoxic damage. It is noteworthy that two glutaminase isozymes coded by different genes are expressed in the brain of mammals.

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The synthesis of glutamate in brain must be exquisitely regulated because of its harmful potential giving rise to excitotoxic damage. In this sense, a stringent control based on multiple regulatory mechanisms should be expected to be exhibited by the biosynthetic enzymes responsible of glutamate generation, to assure that glutamate is only synthesized at the right place and at the right time. Glutaminase is considered as the main glutamate-producer enzyme in brain.

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Oxidative stress can be defined as the imbalance between cellular oxidant species production and antioxidant capability. Reactive oxygen species (ROS) are involved in a variety of different cellular processes ranging from apoptosis and necrosis to cell proliferation and carcinogenesis. In fact, molecular events, such as induction of cell proliferation, decreased apoptosis, and oxidative DNA damage have been proposed to be critically involved in carcinogenesis.

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A human brain cDNA clone coding for a novel PDZ-domain protein of 124 amino acids was previously isolated in our laboratory. The protein was termed glutaminase-interacting protein (GIP), because it interacts with the C-terminal region of the human L-type glutaminase (LGA). The pattern of expression and functions of GIP in brain are completely unknown, so its significance remains undefined.

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Glutamine behaves as a key nutrient for tumors and rapidly dividing cells. Glutaminase is the main glutamine-utilizing enzyme in these cells, and its activity correlates with glutamine consumption and growth rate. We have carried out the antisense L-type glutaminase inhibition in human MCF7 breast cancer cells, in order to study its effect on the hexosamine pathway and the pattern of protein O-glycosylation.

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