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Biomedical subjects

G Juez

Publications and source records attributed to G Juez.

At least 19 recordsLinked to original sources
PubMed1997

Osmotically induced response in representatives of halophilic prokaryotes: the bacterium Halomonas elongata and the archaeon Haloferax volcanii.

Haloferax volcanii and Halomonas elongata have been selected as representatives of halophilic Archaea and Bacteria, respectively, to analyze the responses to various osmolarities at the protein synthesis level. We have identified a set of high-salt-related proteins (39, 24, 20, and 15.5 kDa in H. elongata; 70, 68, 48, and 16 kDa in H. volcanii) whose synthesis rates increased with increasing salinities. A different set of proteins (60, 42, 15, and 6 kDa for H. elongata; 63, 44, 34, 18, 17, and 6 kDa for H. volcanii), some unique for low salinities, was induced under low-salt conditions. For both organisms, and especially for the haloarchaeon, adaptation to low-salt conditions involved a stronger and more specific response than adaptation to high-salt conditions, indicating that unique mechanisms may have evolved for low-salinity adaptation. In the case of H. volcanii, proteins with a typical transient response to osmotic shock, induced by both hypo- and hyperosmotic conditions, probably corresponding to described heat shock proteins and showing the characteristics of general stress proteins, have also been identified. Cell recovery after a shift to low salinities was immediate in both organisms. In contrast, adaptation to higher salinities in both cases involved a lag period during which growth and general protein synthesis were halted, although the high-salt-related proteins were induced rapidly. In H. volcanii, this lag period corresponded exactly to the time needed for cells to accumulate adequate intracellular potassium concentrations, while extrusion of potassium after the down-shift was immediate. Thus, reaching osmotic balance must be the main limiting factor for recovery of cell functions after the variation in salinity.

Adaptation, Physiological↗
PubMed1996

Differentially transcribed regions of Haloferax volcanii genome depending on the medium salinity.

To identify genomic regions involved in osmoregulation in the extremely halophilic archaeon Haloferax volcanii, we used a technique which involves hybridization of cDNAs obtained at different salinities against a cosmid library of the organism. Both low and high salt concentrations trigger differential expression; however, adaptation to low salinities seems to elicit a wider response. The presence of a large domain within the largest of the megaplasmids with a strong response to low salt concentrations is noteworthy.

Blotting, Northern↗
PubMed1995

Long stretches of short tandem repeats are present in the largest replicons of the Archaea Haloferax mediterranei and Haloferax volcanii and could be involved in replicon partitioning.

We report the presence of long stretches of tandem repeats in the genome of the halophilic Archaea Haloferax mediterranei and Haloferax volcanii. A 30 bp sequence with dyad symmetry (including 5 bp inverted repeats) was repeated in tandem, interspersed with 33-39 bp unique sequences. This structure extends for long stretches--1.4 kb at one location in H. mediterranei chromosome and about 3 kb in the H. volcanii chromosome. The tandem repeats (designated TREPs) show a similar distribution in both organisms, appearing once or twice in the H. volcanii and H. mediterranei chromosomes, and once in the largest, probably essential megaplasmid of each organism but not in the smaller replicons. Sequencing of the structures in both H. volcanii replicons revealed an extremely high sequence conservation in both replicons within the species, as well as in the different organisms. Homologous sequences have also been found in other more distantly related halophilic members of the Archaea. Transformation of H. volcanii with a recombinant plasmid containing a 1.1 kb fragment of the TREPs produced significant alterations in the host cells, particularly in terms of cell viability. The introduction of extra copies of TREPs within the vector significantly alters the distribution of the genome among the daughter cells, as observed by DAPI staining. Although the precise biological role cannot be completely ascertained, all the data conform with the tandem repeats being involved in replicon partitioning in halobacteria.

Base Sequence↗
PubMed1994

Effects of salt and temperature on plasmid topology in the halophilic archaeon Haloferax volcanii.

We report here the effect of environmental parameters, salinity, temperature, and an intercalating drug on plasmid topology in the halophilic archaeon Haloferax volcanii. We first studied the topological state of the plasmid pHV11 in media of different salt compositions and concentrations. The superhelical density of plasmid PHV11 varies in a way that depends on the kind of salt and on the concentrations of individual salts. With respect to growth temperature, the plasmid linking number increased at higher temperature in a linear way, contrary to what has been reported for Escherichia coli, in which the plasmid linking number decreased at higher temperature. These results suggest that some of the mechanisms that control DNA supercoiling in halophilic Archaea may be different from those described for E. coli. However, homeostatic control of DNA supercoiling seems to occur in haloarchaea, as in Bacteria, since we found that relaxation of DNA by chloroquine triggers an increase in negative supercoiling.

Archaea↗
PubMed1994

[Intrauterine growth in full-term twins without risk factors].

Twins are analysed according to the intrauterine growth curve constructed for single fetus. The relationship of twins with length, weight, head circumference and the weight length-index is studied. Twins over 36 weeks gestation age, without maternal or fetal pathologies were selected. It is concluded the twins pregnancy "per se" constitutes on its own, a risk factor regarding the intrauterine growth curve, particularly in relation with the weight curve.

Birth Weight↗
PubMed1993

Transcription at different salinities of Haloferax mediterranei sequences adjacent to partially modified PstI sites.

Two genomic sequences from the halophilic archaeon Haloferax mediterranei, where we had found PstI restriction-pattern modifications depending on the salinity of the growth medium, have been studied. A markedly salt-dependent differential expression has been detected in the nearby regions. Two of the open reading frames characterized correspond to two of the differentially expressed transcripts. In both cases the PstI sites were included in purine-pyrimidine alternancies suggestive of Z-DNA structures and located in non-coding regions with frequent repetitive motifs. A long alternating adenine-thymine tract also appears in the upstream regions of one of these open reading frames. A possible role of local DNA configuration in osmoregulation in this organism is discussed.

Amino Acid Sequence↗
PubMed1990

Evidence for salt-associated restriction pattern modifications in the archaeobacterium Haloferax mediterranei.

DNA restriction pattern modifications were detected when Haloferax mediterranei was grown in low (10%) salt concentrations. After cells were grown again in optimal (25%) salt concentrations, the original pattern was recovered. These salt-associated DNA modifications were revealed with 5% of the 160 DNA fragments cloned and used as probes in hybridization experiments. Patterns obtained when genomic DNA was digested with different restriction enzymes showed that these modifications are related not to insertions or deletions in genome but to modifications of some specific sequences.

Archaea↗
PubMed1985

Fertility regulation in nursing women: VII. Influence of NORPLANT levonorgestrel implants upon lactation and infant growth.

The objective of this study was to test the influence of NORPLANT implants upon lactation and infant growth. The results obtained during the first postpartum year are reported. One-hundred women were enrolled in the implant group. The control group was formed by 100 women who received a Copper T IUD. Treatments were administered at day 55 +/- 3. At admission all subjects were in exclusive breastfeeding with an adequate weight increase of the infant. No significant differences were found between the treated and control groups in the percentage of women in full nursing at different postpartum intervals, except for the 12th month postpartum where a lower percentage of cases from the NORPLANT group was in the full nursing category. No difference was found in the time of weaning. The infants showed a normal weight gain rate in both groups although the girls from the NORPLANT group showed a significantly lower daily weight increase during the 4th month than the girls from the IUD group. No pregnancies were diagnosed. No women asked for implant removal during the first year. No serious side effects related to treatment were detected. Bleeding irregularities were rare during breastfeeding which is in contrast with what occurs in non-nursing women treated with NORPLANT implants. Levonorgestrel concentrations found in milk were variable and individual values ranged from 23 to 311 pg/ml. The dose received by the infant can be estimated around 15 to 18 ng/Kg/day during the first month of treatment when the higher plasma values of levonorgestrel are observed. These levels is conjunction with the clinical observations reported here minimize the potential problems associated with levonorgestrel transference through maternal milk. Nevertheless, long-term studies are required to settle this matter and until more information is available, NORPLANT implant use in lactating women should be limited to cases who require a highly effective contraceptive method and where non-hormonal methods of similar effectiveness are contraindicated or unacceptable.

Adolescent↗
PubMed1985

Fertility regulation in nursing women: VIII. Progesterone plasma levels and contraceptive efficacy of a progesterone-releasing vaginal ring.

The objectives of this trial were to test the contraceptive efficacy and measure progesterone plasma levels of women using progesterone-releasing rings during lactation. Two types of rings delivering an average of about 5 mg or 10 mg of progesterone per day were tested in 128 healthy nursing women. A control group was formed by 127 Copper T users. Rings were inserted at day 60 postpartum and replaced every 3 months with a new one. Initially progesterone plasma levels were around 10 nmol/l and 15 nmol/l for rings releasing 5 and 10 mg per day, respectively, and decreased slightly after 30 days. Levels observed in subsequent segments of use approximated those of the first segment. These levels are within the range shown to inhibit fertility in lactating women. One pregnancy was diagnosed in 739 woman-months of progesterone ring use, and none occurred in 794 woman-months of Copper T use, which contrasts with the high incidence of pregnancy in a group of untreated nursing women where 19 pregnancies resulted during 677 woman-months. No deleterious effects were detected lactation and infant growth or maternal and infant health. It is concluded that the vaginal rings releasing progesterone are a suitable contraceptive method for lactating women.

Clinical Trials as Topic↗
PubMed1984

Fertility regulation in nursing women. VI. Contraceptive effectiveness of a subdermal progesterone implant.

Six progesterone pellets implanted subdermally were tested as contraceptive method for lactating women. One pregnancy was diagnosed in 1614 woman-months of observation, a failure rate which was similar to that observed in a contemporary group of Copper T users. Nineteen pregnancies were diagnosed in the 677 woman-months observed in untreated lactating women. The progesterone implants were effective when administered either at 30, 60 or 240 days after delivery. The duration of the effective life was 5 months and fertility was quickly restored afterwards. There were no deleterious effects upon maternal or infant health or upon lactation and the rate of child growth. The main problem encountered was the occurrence of pellet expulsion at a variable rate which appeared related to the manufacturing procedure.

Adolescent↗