Biomedical subjects

S Prat

Publications and source records attributed to S Prat.

At least 19 recordsLinked to original sources

PubMed2001

[Spinal tuberculosis: early surgical treatment combined with medical treatment].

BACKGROUND: Spinal tuberculosis can produce kyphosis with neurologicaldeficit, despite antibiotic treatment. When there is no response to medical treatment, the recommended procedure is debridementand interbody fusion with bone autograft. The biological characteristicsof Mycobacterium tuberculosis do not prevent osteosynthesisof the infected bone from being performed. PATIENTS AND METHOD: Five patients with spinal tuberculosis and neurological deficitunderwent debridement, interbody fusion and anterior osteosynthesisin addition to medical treatment. In order to ensure stability, posterior fusion was also performed in three patients. All 5 patientsdisplayed weakness and paralysis of their lower extremities, two patients suffered an L4 radiculopathy, one developed paraparesiaand one was excluded due to a short follow-up. Mean value of vertebralkyphosis was 22,8 degrees and mean follow-up was 3,1 years. RESULTS: No patient had septic loosening or progression of the disease. Correction of kyphosis was 104,5% postoperatively and 80,5% atthe end of follow-up. All patients, apart from one with an L4radiculopathy, exhibited neurological recovery. CONCLUSIONS: Anterior instrumentation allows spinal decompression, septic focusdebridement, deformity correction and autologous bone grafting. In severe kyphotic flattening, it is advisable to associate alimited posterior arthrodesis. When pathological fractures appearor there is no response to antibiotic treatment, the combinationof medical and surgical treatment improves patients' outcome.

Adult↗

PubMed2001

Gibberellins signal nuclear import of PHOR1, a photoperiod-responsive protein with homology to Drosophila armadillo.

S. tuberosum ssp. andigena potato plants require short days (SD) for tuberization. We have isolated PHOR1 (photoperiod-responsive 1), which shows upregulated expression in induced leaves (SD). PHOR1 encodes an arm repeat protein with homology to the Drosophila segment polarity protein armadillo. Antisense inhibition of PHOR1 produces a semidwarf phenotype similar to that of GA-deficient plants, and the antisense lines show reduced GA responsiveness combined with a higher endogenous GA content than wild-type plants. Feedback regulation of GA biosynthetic genes is also altered in these lines. Conversely, transgenic lines overexpressing PHOR1 show an enhanced response to GA. GA application induces rapid migration of PHOR1-GFP protein to the nucleus. Thus, PHOR1 appears to be a general component of GA signaling pathways that relocalizes to the nucleus in the presence of GA.

Active Transport, Cell Nucleus↗

PubMed2001

A rapeseed-specific gene, acetyl-CoA carboxylase, can be used as a reference for qualitative and real-time quantitative PCR detection of transgenes from mixed food samples.

Polymerase chain reaction (PCR) methods are very useful techniques for the detection and quantification of genetically modified organisms (GMOs) in food samples. These methods rely on the amplification of transgenic sequences and quantification of the transgenic DNA by comparison to an amplified reference gene. Reported here is the development of specific primers for the rapeseed (Brassica napus) BnACCg8 gene and PCR cycling conditions suitable for the use of this sequence as an endogenous reference gene in both qualitative and quantitative PCR assays. Both methods were assayed with 20 different rapeseed varieties, and identical amplification products were obtained with all of them. No amplification products were observed when DNA samples from other Brassica species, Arabidopsis thaliana, maize, and soybean were used as templates, which demonstrates that this system is specific for rapeseed. In real-time quantitative PCR analysis, the detection limit was as low as 1.25 pg of DNA, which indicates that this method is suitable for use in processed food samples which contain very low copies of target DNA.

Acetyl-CoA Carboxylase↗

PubMed2001

[Phage typing of Salmonella enteritidis isolated from clinical, food, and poultry samples in Chile].

Since 1994 an extensive epidemic of infections with Salmonella enteritidis (S. enteritidis) has affected Chile. In order to understand the diversity of infective sources, the possible origin of the epidemic, and the epidemiological relationships between clinical, food, and poultry isolates, we carried out phage typing of three groups of samples: 1) 310 S. enteritidis clinical samples collected between 1975 and 1996, 2) 47 food isolates obtained during S. enteritidis outbreaks, and 3) 27 strains isolated in surveillance studies of poultry-raising establishments. With the clinical samples, a total of 13 phage types were identified, 2 isolates could not be typed, and 1 was considered atypical. The phage types that were identified most frequently were 1 (56.8%) and 4 (31.3%), trailed by type 8 (4.8%) and type 28 (1.9%). Over time and in different regions of the country there were major changes in the distribution of the phage types. In the first years of collection the only phage types registered were 8 and 28, which disappeared around 1980 and then began reappearing sporadically in 1996. With the gradual S. enteritidis expansion that started in 1988, in the central and southern areas of the country phage type 4 began to appear; that type had not been found before in Chile. In 1991 in the northern area of the country phage type 1 began to predominate; it was another type that had not been reported before in Chile. In the food isolates the only phage types identified were 1 and 4, which were also the most common in the poultry isolates. Phage typing of S. enteritidis has proved to be useful in guiding the epidemiological analysis of the infections caused by this pathogen.

Animals↗

PubMed2000

Changes in GA 20-oxidase gene expression strongly affect stem length, tuber induction and tuber yield of potato plants.

Gene StGA20ox1 encoding potato GA 20-oxidase is expressed to relatively high levels in leaves and regulated by daylength. To investigate whether this gene is involved in photoperiodic regulation of tuber formation, we have obtained transgenic potato plants expressing sense and antisense copies of the StGA20ox1 cDNA. Over-expression of this cDNA resulted in taller plants that required a longer duration of a short day photoperiod (SD) to tuberize. Tubers from these plants had a decreased time of dormancy and developed sprouts with elongated internodes. Plants expressing antisense copies of the StGA20ox1 cDNA had shorter stems, a decreased length of the internodes and tuberized earlier than control plants, showing increased tuber yields. Antisense inhibition of this gene had no visible effect on the time of dormancy of the tubers, although at the end of dormancy these formed sprouts with shortened internodes. Decreased levels of endogenous GA20 and GA1 were detected in the apex and first leaves of the antisense lines. These results demonstrate the involvement of the GA 20-oxidase activity encoded by StGA20ox1 in the control of stem elongation and in tuber induction but not in tuber dormancy, indicating that the latter may be regulated by another member of the gene family.

DNA, Complementary↗

PubMed2000

Regulation of transcript levels of a potato gibberellin 20-oxidase gene by light and phytochrome B.

Up to three gibberellin (GA) 20-oxidase genes have now been cloned from several species including Arabidopsis, bean (Phaseolus vulgaris), and potato (Solanum tuberosum). In each case the GA 20-oxidase genes exhibit different patterns of tissue expression. We have performed extensive northern analysis on one of the potato GA 20-oxidase genes (StGA20ox1), which is the only one that shows significant transcript levels in leaves. We show that levels of StGA20ox1 transcript are elevated in transgenic antisense plants that have reduced levels of phytochrome B (PHYB) compared with wild-type plants, implicating PHYB in the control of GA biosynthesis. We show that StGA20ox1 transcript levels vary in leaves of different age throughout the plant and cycle throughout the day, furthermore they are up-regulated by light and down-regulated in the dark. The degree of the response to the light-on signal is similar in potato plants deficient in phytochrome A or PHYB and wild-type plants. The induction of StGA20ox1 by blue light raises the possibility that a blue light receptor may be involved in the control of this gene by light.

Antisense Elements (Genetics)↗

PubMed2000

[Detection of Salmonella enteritidis in samples of poultry products for human consumption in the Chilean metropolitan area].

BACKGROUND: Salmonella enteritidis (SE) is a frequent cause of diarrhea, and is transmitted mainly by SE contaminated eggs or poultry meat. The frequency of SE contaminated eggs or chicken meat and the risk for acquiring this pathogen is unknown in Chile. AIM: To measure SE contamination in eggs poultry meat and entrails offered in retail markets in the Metropolitan Area during two consecutive years (1998-1999). MATERIAL AND METHODS: Samples were placed in sterile bags and transported to the laboratory before 4 hours at 4 degrees C. Microbiologic detection was done using a standard procedure and an immunodetection assay. RESULTS: SE was found in one of 1081 egg samples (0.09%). The contaminated sample was offered in a supermarket under their own commercial name. Six percent of 1154 poultry meat samples were contaminated by SE and 2.3% by other Salmonella serotypes. Entrails had even higher rates with 10.2% of 370 samples harboring SE and 2.7% other serotypes. Total Salmonella sp. isolates and SE isolates declined during 1999. Nine SE phagotypes were identified, predominating types 4 and 7. CONCLUSIONS: Eggs and other avian products are contaminated by different SE phagotypes and other Salmonella serotypes, implicating a risk for the consumers (Rev Méd Chile 2000; 128: 1075-83).

Animals↗

PubMed1999

Leaf C40.4: a carotenoid-associated protein involved in the modulation of photosynthetic efficiency?

Comparative analysis by differential RNA display (DDRT-PCR) of the expression patterns of potato plants induced and non-induced to tuberize, led to the isolation of a cDNA clone, C40.4, that is strongly upregulated in the leaves of tuberizing plants. Leaf expression of this transcript was shown to be light-dependent, with increased levels of mRNA and protein being detected during the light hours. Sequence analysis revealed near complete identity to potato CDSP34, a thylakoid protein induced by drought stress, and strong homology to the carotenoid-associated proteins fibrillin, ChrB and PAP from pepper fruit, and CHRC from cucumber flowers. By using an antibody against pepper fibrillin, we were able to demonstrate a chloroplastic location of the C40.4 protein in association with the thylakoid membranes. Two-dimensional analysis of thylakoid pigment-protein complexes showed a specific association of the protein with the photosystem II (PSII) multi-subunit complex. Antisense plants with reduced levels of accumulation of C40.4 showed a stunted growth and decreased tuber yield and exhibited reduced values of non-photochemical quenching of chlorophyll a fluorescence. Altogether, these results indicate a preferential association of the C40.4 protein with the light harvesting complex of photosystem II (LHCII) antenna pigment complexes, and suggest a functional role of this protein in photosynthesis, by modulating photosynthetic efficiency and dissipation of excess absorbed light energy within the antenna complex.

Amino Acid Sequence↗

PubMed1999

Feedback control and diurnal regulation of gibberellin 20-oxidase transcript levels in potato.

Tuber formation in potato (Solanum tuberosum) is promoted by short photoperiods and is inhibited by gibberellins (GAs). Endogenous levels of GA1 were shown to decrease in stolons and leaves of potato plants induced to tuberize, which suggests that photoperiodic regulation of GA biosynthesis may play a role in tuber induction. We report the isolation of three potato cDNA clones (StGA20ox1-3) encoding GA 20-oxidase, a key regulatory enzyme in the GA-biosynthetic pathway. Using northern analysis, we detected a differential pattern of tissue-specific expression of the mRNAs corresponding to these clones. StGA20ox mRNAs were also very abundant in leaves of the potato ga1 mutant, which is blocked in the 13-hydroxylation step, and were strongly down-regulated by gibberellic acid, suggesting a feedback regulation of these genes. In plants grown in short-day (inductive) conditions, levels of the StGA20ox transcripts in leaves fluctuated during a 24-h period, with a peak of accumulation observed about 4 h after the lights were turned off. Interruption of the night with a 30-min "night break" of light (noninductive conditions) did not have a marked effect on the levels of accumulation of the three GA 20-oxidase mRNAs during the day, but it induced a second peak of expression of StGA20ox1 and StGA20ox3 transcripts late in the night. This observation, together with the finding that StGA20ox1 mRNA is expressed at high levels in leaves, suggests that night-break induction of this gene might play a role in the control of tuberization by regulating endogenous levels of GAs in response to daylength conditions.

Amino Acid Sequence↗

PubMed1998

Characterization of the wound-induced metallocarboxypeptidase inhibitor from potato. cDNA sequence, induction of gene expression, subcellular immunolocalization and potential roles of the C-terminal propeptide.

A partial cDNA clone for the potato wound-inducible metallocarboxypeptidase inhibitor (PCI) was isolated from a cDNA library constructed from mRNA of abscisic acid (ABA)-treated potato leaves. The full 5' region of the cDNA was obtained through a RACE-PCR protocol. PCI mRNA encodes a precursor polypeptide which comprises a 29 residue N-terminal signal peptide, a 27 residue N-terminal pro-region, the 39 residue mature PCI protein, and a 7 residue C-terminal extension. Northern blot analysis demonstrates that the PCI gene is transcriptionally activated by wounding, and wound signaling can be induced by ABA and jasmonic acid. Subcellular localization of the protein was investigated by immunocytochemistry and electron microscopy, showing that PCI accumulates within the vacuole. A partial PCI precursor form, comprising the mature protein and the C-terminal extension, has been expressed in Escherichia coli and characterized. Its inability to inhibit carboxypeptidases, and stability to carboxypeptidase digestion, suggest that the C-terminal pro-domain may have, besides a probable vacuolar sorting function, a role in modulation of the inhibitory activity of PCI.

Abscisic Acid↗

PubMed1998

Highly heterogeneous families of Ty1/copia retrotransposons in the Lycopersicon chilense genome.

We have used the degenerated oligonucleotide primers-PCR (DOP-PCR) technique to determine the presence of Ty1/copia-related retrotransposons in the wild species of tomato, Lycopersicon chilense. Using degenerated oligonucleotides corresponding to highly conserved domains in the Ty1/copia retrotransposons, fragments of roughly 300 bp were obtained by PCR amplification. These were cloned in a plasmid vector and the nucleotide sequence determined for 20 clones, 19 of which showed sequence homology to retrotransposon-related sequences. Comparison of the deduced amino-acid sequence of these clones with those reported for other retrotransposons has allowed their classification into four distinct families: TLC1-TLC4. The level of amino-acid sequence similarity between these elements extends from 66.7% (between TLC1 and TLC2) to 42.6% (between TLC2 and TLC3). Altogether, the four families comprise about 0.17% of the L. chilense genome. RT-PCR analysis shows that the four TLC families are transcriptionally active, suggesting a mechanism for the generation of the observed diversity between the L. chilense retrotransposons.

Amino Acid Sequence↗

PubMed1998

A -308 deletion of the tomato LAP promoters is able to direct flower-specific and MeJA-induced expression in transgenic plants.

Tomato and potato leucine aminopeptidase (LAP) mRNAs are induced in response to mechanical wounding and the wound signal molecules, ABA and jasmonic acid. Here, we report the isolation of two LAP genes, LAP17.1A and LAP17.2, from tomato. Functional analysis in transgenic tomato and potato plants show that fusions of the corresponding 5' non-coding regions to the gusA gene are constitutively expressed in flowers and induced in leaves upon wounding or by treatment with methyl jasmonate (MeJA). Comparison of the 5' non-coding regions of the two genes revealed a region from -317 to -3 relative to the ATG, which is strongly conserved in both promoters. This 0.3 kb proximal promoter fragment is sufficient to direct flower-specific and MeJA-inducible GUS activity in transgenic potato plants, and thus contains a MeJA-responsive element that mediates induction by MeJA. Dimeric TGACG motifs or G-box elements similar to those found in other MeJA-inducible genes are not observed in this region, which suggests that a different DNA sequence is involved in MeJA induction of the LAP genes.

Acetates↗

PubMed1998

Expression of the Arabidopsis abi1-1 mutant allele inhibits proteinase inhibitor wound-induction in tomato.

Abscisic acid (ABA) is an essential component in the wound signalling cascade. Increased levels of endogenous ABA were observed after wounding and shown to be a requisite for wound-induced expression of the proteinase inhibitor II genes. We have taken advantage of the dominant character of the Arabidopsis abi1-1 mutation, to investigate whether ABl1 has a function in ABA signalling in response to wounding. Transgenic tomato plants carrying copies of either the wild-type ABI1 or the mutant abi1-1 alleles were obtained and assayed for wound-induction of the pin2 or LAP genes. While normal levels of gene induction were observed in the transgenic ABI1 plants, the abi1-1 transformants displayed a severe wilty phenotype and reduced seed dormancy. Expression of the abi1-1 dominant mutation blocked accumulation of the drought-induced TAS14 and LE25 mRNAs in response to ABA, as well as ABA- and wound-induced expression of the defense-associated pin2 and LAP transcripts. MeJA-induction of the pin2 and LAP mRNAs, on the contrary, was not affected in the abi1-1 transformants. These results indicate that abi1-1 inhibits wound-induced expression of the pin2 and LAP transcripts by blocking ABA-induction of these genes. This implicates ABI1 in wound-signalling and suggests that a common early ABA signalling pathway may function in the responses to wounding and water stress.

Alleles↗

PubMed1998

Phytochrome B affects the levels of a graft-transmissible signal involved in tuberization

Grafting experiments between phytochrome B antisense and wild-type potato (Solanum tuberosum L. subsp. andigena [line 7540]) plants provide evidence that phytochrome B is involved in the production of a graft-transmissible inhibitor of tuberization, the level of which is reduced in the antisense plants, allowing them to tuberize in noninducing photoperiods.

Journal Article↗

PubMed1997

Cloning and expression analysis of a gene that shows developmental regulation upon tuberization in potato.

Differential screening of a potato leaf cDNA library with cDNA probes made from tuberizing and non-tuberizing Solanum demissum plants led to the identification of a clone that is upregulated in leaves and other tissues upon tuberization. This clone was also shown to have a high level of expression in green tomato fruit, its expression falling off as the fruit turns red. No sucrose or hormonal regulation of the expression of this clone was observed and it did not respond to wounding or heat stress. Clone 32B is 532 bp long and contains an open reading frame encoding a small protein of 98 amino acids. The deduced protein sequence has a putative signal peptide for ER transport and a 10 amino acid domain in the C-terminal region of the protein, both of which are also found in the cotton LEA5, Arabidopsis Di21 and the mungbean Arg2 proteins.

Amino Acid Sequence↗

PubMed1997

A cDNA clone highly expressed in ripe banana fruit shows homology to pectate lyases.

A cDNA clone (Ban17), encoding a protein homologous to pectate lyase, has been isolated from a cDNA library from climacteric banana fruit by means of differential screening. Northern analysis showed that Ban17 mRNA is first detected in early climacteric fruit, reaches a steady-state maximum at the climacteric peak, and declines thereafter in overripe fruit. Accumulation of the Ban17 transcript can be induced in green banana fruit by exogenous application of ethylene. The demonstrates that expression of this gene is under hormonal control, its induction being regulated by the rapid increase in ethylene production at the onset of ripening. The deduced amino acid sequence derived from the Ban17 cDNA shares significant identity with pectate lyases from pollen and plant pathogenic bacteria of the genus Erwinia. Similarity to bacterial pectate lyases that were proven to break down the pectic substances of the plant cell wall suggest that Ban17 might play a role in the loss of mesocarp firmness during fruit ripening.

Amino Acid Sequence↗

PubMed1997

[Salmonella enteritidis, an emergent pathogen in Chile].

BACKGROUND: Salmonella enteritidis infections have increased worldwide in the last years. Isolation of this pathogen was remarkably rare in Chile until 1994, when the still ongoing outbreak emerged. AIM: To assess the main epidemiological characteristics of the Salmonella enteritidis epidemic in Chile. MATERIALS AND METHODS: Cases of clinical infections by Salmonella enteritidis were recorded from bacteriological and demographic notifications obtained at The National Reference Laboratory for Enterobacteria. Infection rates were calculated using the total Chilean population and the population of the different Health Services along the country. RESULTS: Until 1993, 13.67 Salmonella enteritidis strains per year were received at the Reference Laboratory. The figures increased to 478 and 432 in 1994 and 1995, respectively. National rates were 3.41 and 3.04 notifications/100,000 inhabitants in 1994 and 1995 respectively. Northern regions were the most affected and 90% of observed cases during 1994 came from Arica and Antofagasta. At the present time, 20% of cases are observed in Santiago, located in the mid-portion of the country. The outbreak has mainly affected children and young adults (70% of cases). Strains have been isolated from stool cultures, suggesting gastrointestinal infections as the main clinical presentation. More than 98% of strains are susceptible to chloramphenicol, ampicillin, tetracycline, sulfa-trimetroprim, cefotaxime or ciprofloxacin. CONCLUSIONS: The obtained data clearly indicate the existence of an epidemic outbreak of Salmonella enteritidis infections, with a geographic progression from North to South.

Chile↗

PubMed1994

A novel DNA binding protein with homology to Myb oncoproteins containing only one repeat can function as a transcriptional activator.

A cDNA clone encoding a novel Myb-related protein, designated MybSt1, was isolated from a potato cDNA expression library by South Western screening using the CaMV 35S promoter domain A as a probe. Sequence comparison shows a small region with some homology to the highly conserved DNA binding domain of the c-myb proto-oncogene consisting of three imperfect repeats. The Myb motif of the MybSt1 protein is distinct from the plant Myb DNA binding domain described so far. In contrast to the known plant Myb proteins, with two repeats required for the DNA binding activity, the clone mybSt1 contains only one such repeat. Nevertheless, the Myb-related protein MybSt1 is able to bind to DNA in a sequence-specific manner. In addition to the Myb-like region, the protein MybSt1 contains an acidic segment in its central region as well as a proline-rich region near the C-terminus. Applying the random binding site selection technique, high-affinity DNA binding sites for MybSt1 were identified, sharing the core motif GGATA. In transient expression assays using plant protoplasts, clear evidence was obtained for this myb clone functioning as a transcriptional activator.

Amino Acid Sequence↗