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J C Gutiérrez

Publications and source records attributed to J C Gutiérrez.

13 recordsLinked to original sources
PubMed2001

Ciliate cryptobiosis: a microbial strategy against environmental starvation.

This review outlines the main features of ciliate resting-cyst formation or encystment. It represents a strategy against several environmental stresses (such as starvation), which involves a highly gene-regulated cell differentiation process and originates a more resistant, differentiated form or resting cyst. This process is mainly characterized by drastic cytoplasmic dehydration that induces a general metabolic rate decrease, intense autophagic activity, the formation of a permeable cyst wall protecting the cell against the adverse environmental conditions, and a gene-silencing mechanism after opening the specific encystment genes.

Adaptation, Physiological↗
PubMed2000

Resting cyst wall glycoproteins isolated from two colpodid ciliates are glycine-rich proteins.

Two glycoproteins bands isolated from the cyst wall protein pattern of two colpodid ciliates, Colpoda inflata (gp46CI) and Colpoda cucullus (gp46CC) were analysed for their amino acid composition. Both glycoproteins are very rich in glycine and have a relatively high hydrophobicity, containing additionally many leucine and alanine residues. Their high degree of similarity is both quantitative and qualitative. Compared with just two previously published reports, their amino acid compositions are similar to those found in the hydrolysed cyst wall total proteins from the ciliates C. steinii and Paraurostyla spp. The amino acid composition corroborates that they are indeed glycoproteins, because asparagine, an amino acid residue suitable for the attachment to N-acetylglucosamine by its amide group (N-glycan), is abundant in both proteins. We discuss our data in relation to other glycine-rich proteins and a comparison with amino acid composition protein databases is carried out.

Amino Acids↗
PubMed2000

DNA methylation in ciliates: implications in differentiation processes.

Much experimental evidence on the role of DNA methylation in gene expression has been reported. Here we review reports on DNA methylation in ciliated protozoa, emphasizing its implications in cell differentiation processes. Both types of methylated bases (adenine and cytosine) can be found in macronuclear DNA. The division cycle and conjugation have been studied with regard to adenine methylation, and several different functions have been assigned to the methylation changes detected in these processes. Cytosine methylation changes were analyzed during stomatogenesis of Paramecium and encystment of Colpoda inflata. A comparative analysis with other similar microbial eukaryotic differentiation processes is carried out.

5-Methylcytosine↗
PubMed1999

Drink composition, voluntary drinking, and fluid balance in exercising, trained, heat-acclimatized boys.

This study examined the effects of beverage composition on the voluntary drinking pattern, body fluid balance, and thermoregulation of heat-acclimatized trained boys exercising intermittently in outdoor conditions (wet bulb globe temperature 30.4 +/- 1.0 degreesC). Twelve boys (age 13.4 +/- 0.4 yr) performed two 3-h sessions, each consisting of four 20-min cycling bouts at 60% maximal aerobic power alternating with 25-min rest. One of two beverages was assigned: unflavored water (W) or flavored water plus 6% carbohydrate and 18 mmol/l Na (CNa). Drinking was ad libitum. Total intake was higher (P < 0.05) during CNa (1,943 +/- 190 g) compared with W (1,470 +/- 143 g). Euhydration was maintained with CNa (+0.18% body wt), but a mild dehydration resulted with W (-0.94% body wt; P < 0.05). Sweat loss, much higher than previously published for children of similar age, was similar between conditions (CNa = 1,644.7 +/- 117.5; W = 1,750.2 +/- 152.7 g). The increase in rectal temperature (CNa = 0.86 +/- 0.3; W = 0.76 +/- 0.1 degreesC), heart rate, and all perceptual variables did not differ between conditions. In conclusion, a flavored carbohydrate-electrolyte drink prevents voluntary dehydration in trained heat-acclimatized boys exercising in a tropical climate despite their large sweat losses. Because hydration changes were minor, the thermoregulatory strain observed was similar between conditions.

Acclimatization↗
PubMed1997

A rapid bioassay to detect mycotoxins using a melanin precursor overproducer mutant of the ciliate Tetrahymena thermophila.

Four different mycotoxins (patulin, T-2 toxin, diacetoxyscirpenol and roquefortine) were used to study growth inhibitory effects on a melanin precursor overproducer mutant of the ciliate Tetrahymena thermophila. This strain is especially sensitive to diacetoxyscirpenol and T-2 toxin. The secretion capacity of melanin precursors into the culture medium by this mutant and its biosensor capacity are very useful characteristics to elaborate a rapid bioassay to detect some specific mycotoxins.

Animals↗
PubMed1997

Encystment-specific mRNA is accumulated in the resting cysts of the ciliate Colpoda inflata.

From a random amplified polymorphism cDNA study using vegetative, precystic and mature resting cysts of the ciliate Colpoda inflata, a stage-specific fragment was isolated from the resting cyst cDNA population. This fragment was used as an encystment probe to study the corresponding mRNA expression during this eukaryotic cell differentiation process. This transcript is accumulated in the resting cyst of this ciliate, and it is the first time that accumulation of specific mRNA molecules associated with the ciliate cryptobiosis process is reported. The meaning of this stored mRNA in microbial cryptobiotic stages is discussed.

Animals↗
PubMed1993

Identification of an operon involved in the assimilatory nitrate-reducing system of Azotobacter vinelandii.

A number of mutants lacking nitrate reductase (Nas-) or nitrite reductase (Nis-) activities have been isolated and characterized. An operon including two new genes (nasA and nasB) has been defined and cloned from an Azotobacter vinelandii gene bank. nasA encodes for nitrite reductase apoenzyme, whereas nasB is specific for nitrate reductase activity. Nitrate reductase exerts a regulatory effect on nasAB.

Amino Acid Sequence↗
PubMed1992

Genetic characterization of Tetrahymena thermophila mutants unable to secrete capsules.

Under appropriate conditions, Alcian Blue-induced exocytosis of Tetrahymena mucocysts leads to formation of a capsule that surrounds the cell. This phenomenon is an example of regulated secretion, a mechanism of fundamental significance in eukaryotic cells. In order to dissect genetically the mechanism of mucocyst biogenesis and regulated exocytosis, mutants unable to form capsules (Caps-) were isolated. In this paper we report a genetic characterization of Caps- mutants in this collection. The mutations in mutants SB255 and SB281 behave as single recessive Mendelian mutations. The mutation in SB251 is restricted to the macronucleus, and could not be further characterized by the genetic methods we used. Complementation tests suggest the existence of at least 2 genes, named exoA and exoB; additional mutant loci are likely to be included in the mutant collection. Deletion mapping using nullisomic strains showed that exoA and exoB are located on the left arm of chromosome 4. The exo-3 mutation, which behaves as recessive and complements with exoA1 in SB255 and exoB2 in SB281, maps to chromosome 3. These Caps- mutants may be useful for the elucidation of the developmental pathway of mucocyst biogenesis and the control of regulated secretion in eukaryotic cells.

Animals↗
PubMed1990

Towards a generalized model of encystment (cryptobiosis) in ciliates: a review and a hypothesis.

In this work we propose a generalized model to explain encystment (cryptobiosis) in ciliates. The model is elaborated from both structural and physiological studies previously reported, and some hypothetical considerations. The main features of this model are the following: (a) starvation is considered as the most important inducer of ciliate encystment, and it constitutes the first trigger of this cell differentiation process; (b) the "switch on" of encystment genes involves the appearance of several new transcripts; (c) starvation involves cell autophagy and protein turnover, which provides material to synthesize the new cystic proteins; (d) cytoplasmic dehydration has an important role during the resting cyst formation; (e) a gradual loss of intracellular water can inactivate cell metabolism, leading to an ametabolic state (cryptobiosis); (f) as a late precystic event, the encysting cell forms a barrier (cyst wall), that isolates the cell from the hostile environment.

Animals↗