PubMed Health⌕ Search

Biomedical subjects

A Segre

Publications and source records attributed to A Segre.

At least 19 recordsLinked to original sources
PubMed1998

Corpeptins, new bioactive lipodepsipeptides from cultures of Pseudomonas corrugata.

The structure of the corpeptins, bioactive lipodepsipeptides produced in culture by Pseudomonas corrugata, the causal agent of tomato pith necrosis, has been determined. The combined use of FAB-mass spectrometry, NMR spectroscopy and chemical procedures has allowed us to assign the following primary structure to the peptide moiety: Dhb-Pro-Ala-Ala-Ala-Val-Val-Dhb-Hse-Val-alle-Dhp-Ala-Ala-Ala-Val-D hb-aThr-Ala-Dab-Ser-Ile with the terminal carboxy group closing a macrocyclic ring on the hydroxy group of the allo-threonine residue. The N-terminus is in turn acylated by 3-hydroxydecanoate in corpeptin A and by cis-3-hydroxy-5-dodecenoate in corpeptin B. Some preliminary data on the biological activity of corpeptins are included.

Acylation↗
PubMed1995

Structure-activity relationships in open ansa-chain rifamycin S derivatives as inhibitors of HIV-1 reverse transcriptase.

Three types of open ansa-chain rifamycin S derivatives have been prepared: derivatives with the ansa-chain open at C(29) and the original dihydrofuranone ring; derivatives with the ansa-chain open at C(29) and a furane ring; derivatives with the ansa-chain at open NH-C(15). Only derivatives of the first type are weak inhibitors of HIV-1 reverse transcriptase (IC50 ca.300 microM) while derivatives of the two other types are inactive. It has been hypothesized that the active derivatives inhibit the viral enzyme interacting through the groups C(14)H3, C(13)H3, and C(1)O at the same site as the well-known inhibitors TIBO and Nevirapine. In particular C(13)H3 must be unhindered and in an appropriate position out of the plane containing the chromophore-rings. The open ansa-chain seems to play the role of a lipophylic substituent.

Antiviral Agents↗
PubMed1994

Novel bioactive lipodepsipeptides from Pseudomonas syringae: the pseudomycins.

The covalent structure and most of the stereochemistry of the pseudomycins, bioactive metabolites of a transposon-generated mutant of a Pseudomonas syringae wild-type strain proposed for the biological control of Dutch elm disease, have been determined. While two pseudomycins are identical to the known syringopeptins 25-A and 25-B, pseudomycins A, B, C, C' are new lipodepsinonapeptides. For all of these the peptide moiety corresponds to L-Ser-D-Dab-L-Asp-L-Lys-L-Dab-L-aThr-Z-Dhb-L-Asp(3-OH) -L-Thr (4-Cl) with the terminal carboxyl group closing a macrocyclic ring on the OH group of the N-terminal Ser. This is in turn N-acylated by 3,4-dihydroxytetradecanoate in pseudomycin A, by 3-hydroxytetradecanoate in pseudomycin B, by 3,4-dihydroxyhexadecanoate in pseudomycin C, and by 3-hydroxyhexadecanoate in pseudomycin C'. Some preliminary data on the biological activity of pseudomycin A are reported.

Amino Acid Sequence↗
PubMed1994

Episodic changes of serum procollagen type I carboxy-terminal propeptide levels in fertile and postmenopausal women.

The aim of the present study was to optimize the use of serum procollagen type I carboxy-terminal propeptide (PICP) as a possible marker of postmenopausal-376lted changes of bone metabolism. Postmenopausal (n = 20) and healthy fertile young (n = 4) women were studied after informed consent. The postmenopausal women were subdivided in 4 groups: (1) nontreated; (2) treated with estrogen-progestogen replacement therapy; (3) treated with calcitonin, or (4) with kidney or liver diseases. Blood samples were collected at 15-min time intervals for 4, 6 or 8 h. Serum concentration of PICP was measured by radioimmunoassay, in duplicate at two different dilutions. In postmenopausal women mean +/- SEM serum PICP levels were slightly but nonsignificantly higher than in fertile women. Serum PICP levels in estrogen-progestogen or calcitonin-treated women were significantly lower than in non-treated postmenopausal women. Episodic changes of circulating PICP level were observed in fertile and postmenopausal women. The pulses of serum PICP levels did not show significant differences among the groups of women studied. The present study showed that the measurement of serum PICP levels is a useful marker for investigating the changes of bone metabolism. In particular, low PICP levels in postmenopausal women under steroid hormone or calcitonin treatment in part reflect the changes of bone turnover. The pulses of serum PICP levels during a time interval suggest that collagen metabolism in women undergoes a rapid turnover.

Adult↗
PubMed1992

The brain as a target organ of gonadal steroids.

Gonadal steroids have many effects in the central nervous system. Through a feedback mechanism, they influence the synthesis and release of hypothalamic gonadotropin-releasing hormone (GnRH) and/or pituitary gonadotropic hormones (luteinizing hormone, LH, and follicle stimulating hormone, FSH). Endogenous opioid peptides (EOPs) represent one of the key factors modulating the activity of sex steroids on the hypothalamus-pituitary-gonadal (HPG) axis. In particular, these peptides control the secretion of LH by inhibiting the activity of the hypothalamic neurons which produce GnRH. The EOP effect is dependent on the steroid hormone milieu, as shown by different responses to naloxone administration, both in animals and in humans. For the naloxone-induced increase in LH secretion to occur, relatively high levels of sex steroids are required. In humans, LH release is absent before sexual maturation. In fertile women, naloxone administration increases LH levels in the luteal phase but not in the follicular phase. In the postmenopausal period, naloxone has no effect on LH release; estrogen/progestin therapy does restore the LH response.

Aging↗
PubMed1992

Maternal hyperoxygenation in the treatment of intrauterine growth retardation.

OBJECTIVE: In the current study the efficacy of maternal hyperoxygenation on growth-retarded fetuses was evaluated. STUDY DESIGN: Thirty-six pregnant women with intrauterine growth retardation were studied. The patients were divided in oxygen-treated (n = 17) and untreated (n = 19) groups. Doppler analysis of the fetal circulation was performed on the arrival to the hospital, after 12 hours, and thereafter on alternate days until delivery. Fetal blood was sampled by cordocentesis for immediate blood gas analysis at entrance to the study and the day of delivery. RESULTS: Significant improvement in Doppler flow patterns in treated patients were found when compared with untreated women. The Doppler variations were associated with complementary modifications in fetal blood gas. These differences resulted in a significant modification in perinatal mortality with an incidence of 29% and 68% (p less than 0.01) in treated and untreated groups, respectively. CONCLUSION: Our data suggest a benefit of maternal hyperoxygenation in the treatment of fetal growth retardation.

Arteries↗
PubMed1992

Rifamycins as inhibitors of retroviral reverse transcriptase from M-MuLV, RAV-2, and HIV-1.

29 Rifamycins were tested for inhibition of Reverse Transcriptase (RT) as potential anti HIV drugs. Two purified commercial enzymes from M-MuLV and RAV-2 were used. Anti-RT activity was also measured on a crude lysate of HIV-1. The results show that some derivatives have interesting levels of activity on isolated M-MuLV and RAV-2 RTs, while they are less active on the RT in the crude HIV-1 lysate. The active derivatives include oximes and hydrazones, alkylaminoderivatives, open ansa-chain derivatives and derivatives carrying a modified nucleoside.

HIV Reverse Transcriptase↗
PubMed1991

Syringopeptins, new phytotoxic lipodepsipeptides of Pseudomonas syringae pv. syringae.

The primary structure of some new lipodepsipeptides named syringopeptins, produced by plant pathogenic strains of Pseudomonas syringae pv. syringae has been determined by a combination of chemical methods, 1H and 13C NMR spectroscopy and FAB mass spectrometry. Two syringomycin-producing strains afforded 3-hydroxydecanoyl-Dhb-Pro-Val-Val-Ala-Ala-Val-Val-Dhb-Ala-Val-Ala- Ala-Dhb-aThr-Ser-Ala-Dhb-Ala-Dab-Dab-Tyr, with Tyr acylating a Thr to form a macrolactone ring, and smaller amounts of the 3-hydroxydodecanoyl homologue. Evidence was obtained that a third syringomycin-producing strain and a syringotoxin-producing strain synthesize 3-hydroxydecanoyl-Dhb-Pro-Val-Ala-Ala-Val-Leu-Ala-Ala-Dhb-Val-Dhb- Ala-Val-Ala-Ala-Dhb-aThr-Ser-Ala-Val-Ala-Dab-Dab-Tyr, with Tyr and aThr forming again the macrolactone ring, and smaller amounts of the 3-hydroxydodecanoyl homologue.

Amino Acid Sequence↗
PubMed1991

Reduced spinal bone density in young women with amenorrhoea.

To assess the influence of diminished oestrogen production on bone density, we studied 23 amenorrhoeic women and 20 controls (age range 16-29 years) divided into four groups: group 1: 6 patients with idopathic hypogonadotrophic hypogonadism with primary amenorrhoea (IHH); group 2: 5 patients with delayed puberty owing to thalassaemia major (TM); group 3: 12 patients with secondary hypothalamic amenorrhoea (HA); group 4: 20 women with normal menses (controls). Secondary sexual characteristics had developed in all except the women with TM. Groups 1 and 2 had never menstruated and group 3 had been amenorrhoeic for 6 months to 3 years. The control group was studied during the follicular phase of the cycle. None of the patients were taking oestrogens at the time of observation. Plasma concentrations were determined for 17 beta-oestradiol (E2), deidroepiandrosterone sulphate (DHEA-S), cortisol (F), prolactin (PRL), thyroid hormones (T3 and T4), and gonadotrophins (LH and FSH). Spinal bone mineral density (BMD g/cm2) was assessed by dual photon absorbiometry. BMD (mean +/- 1SD) was reduced in the patients (group 2: 0.920 +/- 0.95; group 1: 0.980 +/- 0.94; and group 3: 1.037 +/- 0.75) as compared with the controls (1.290 +/- 0.95) (P less than 0.01). In the three groups of patients, plasma E2 levels were lower than 50 pg/ml and were positively correlated with the BMD. As expected, plasma gonadotrophin levels were highly and significantly reduced (P less than 0.01) in the patients, compared with that of the controls. These results suggest that reduced spinal BMD in hypogonadic women may be related to the lack of oestrogenic influence on bone metabolism.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Structure of syringotoxin, a bioactive metabolite of Pseudomonas syringae pv. syringae.

The covalent structure of syringotoxin, a bioactive metabolite of Pseudomonas syringae pv. syringae isolates, pathogenic on various species of citrus trees, has been deduced from 1D and 2D 1H- and 13C-NMR spectra combined with extensive FAB-MS data and results of some chemical reactions. Similarly to syringomicins and syringostatins, produced by other plant pathogenic strains of P. syringae pv. syringae, syringotoxin is a lipodepsinonapeptide. Its peptide moiety corresponds to Ser-Dab-Gly-Hse-Orn-aThr-Dhb-(3-OH)Asp-(4-Cl)Thr with the terminal carboxy group closing a macrocyclic ring on the OH group of the N-terminal Ser, which in turn is N-acetylated by 3-hydroxytetradecanoic acid.

Amino Acid Sequence↗
PubMed1990

Epidermal growth factor and transferrin receptor expression in human embryonic and fetal epidermal cells.

Epidermal growth factor receptors (EGFR) and transferrin receptors (TFR) are known to be involved in cell proliferation and to be expressed in normal human epidermis. To date little is known about EGFR and TRF expression in human skin during embryonic and fetal development. In the present work, we studied skin specimens from 30 aborted embryos and fetuses ranging from 7 to 31 weeks estimated gestational age. Monoclonal antibodies to EGFR and TFR were applied on frozen skin sections using an amplification biotin-streptavidin-fluorescein technique. TFR was faintly expressed on epidermal basal cells throughout embryonic and fetal development, as it is in adult epidermis. Up to week 12, EGFR was uniformly expressed on cells of the basal, intermediate and periderm cell layers. From the midfetal period onwards, the suprabasal cell layers showed a decreased staining compared with the basal layer. During the third trimester the cornified cell layer was completely negative. The hair germ and heir peg cells were positive. Later, the outer root sheath and hair bulb remained labelled, with less staining of the hair cone. The sebaceous and eccrine sweat glands were also labelled. These results suggest that in embryonic and fetal epidermis, TFR expression is not correlated with cellular proliferation, whereas EGFR appear to be associated with proliferating and undifferentiated cells.

Adult↗
PubMed1989

The structure of syringomycins A1, E and G.

By a combination of 1D and 2D 1H- and 13C-NMR, FAB-MS, and chemical and enzymatic reactions carried out at the milligram level, it has been demonstrated that syringomycin E, the major phytotoxic antibiotic produced by Pseudomonas syringae pv. syringae, is a new lipodepsipeptide. Its amino acid sequence is Ser-Ser-Dab-Dab-Arg-Phe-Dhb-4(Cl)Thr-3(OH)Asp with the beta-carboxy group of the C-terminal residue closing a macrocyclic ring on the OH group of the N-terminal Ser, which in turn is N-acylated by 3-hydroxydodecanoic acid. Syringomycins A1 and G, two other metabolites of the same bacterium, differ from syringomycin E only in their fatty acid moieties corresponding, respectively, to 3-hydroxydecanoic and 3-hydroxytetradecanoic acid.

Amino Acid Sequence↗
PubMed1989

Intra-uterine growth retardation is associated with increased levels of magnesium in amniotic fluid.

Magnesium (Mg) and zinc (Zn) levels were measured in amniotic fluid of 30 normal pregnancies between the 16th and the 42nd week of amenorrhea and in 15 cases of intra-uterine growth retardation (IUGR) at 30-38th week of pregnancy. While Zn levels were stable throughout physiological pregnancy, the Mg concentration decreased progressively from 1.09 +/- 0.31 mg/100 ml (mean +/- SD) at the end of the second trimester to 0.75 +/- 0.20 (p less than 0.02) at term. In the case of IUGR, Mg levels (1.22 +/- 0.28) were higher than in controls (0.89 +/- 0.27, p less than 0.01) matched for gestational age. No differences in Zn levels were found between the two groups. Although the mechanisms leading to Mg accumulation in the amniotic fluid of growth-retarded fetuses remain unknown, these data support the role played by Mg in fetal growth.

Amniotic Fluid↗
PubMed1989

Plasma and amniotic fluid immunoreactive neuropeptide-Y level changes during pregnancy, labor, and at parturition.

This study was designed to determine the presence of and possible changes in plasma and amniotic fluid immunoreactive neuropeptide-Y (irNPY) levels in pregnant women during gestation and at parturition. We studied 127 healthy pregnant and 12 nonpregnant women. The peptide was extracted from plasma or amniotic fluid with a propanolformic acid mixture and measured by RIA. The mean plasma irNPY concentration in 15 pregnant women during the first trimester of gestation was 129 +/- 12 (+/- SE) pmol/L, compared to 40 +/- 8 pmol/L in nonpregnant women (p less than 0.01). The mean values were 144 +/- 13 and 156 +/- 24 pmol/L, respectively, in 15 pregnant women during the second trimester and 33 women during the third trimester. These values did not differ from that during the first trimester. Amniotic fluid irNPY levels were similar to those in plasma and did not vary among the 3 groups of women studied during the various trimesters of gestation. During labor, plasma irNPY levels progressively increased, reaching the highest levels at the most advanced stages of cervical dilatation (greater than 8 cm, 351 +/- 38 pmol/L) and at the time of vaginal delivery (416 +/- 73 pmol/L). Plasma irNPY levels then decreased significantly 2 h after vaginal delivery. The amniotic fluid irNPY levels in women during the early or late stages of labor were similar. Moreover, plasma and amniotic fluid irNPY levels at the time of elective cesarean section also were similar. These results indicate that pregnant women have high plasma and amniotic fluid irNPY levels and that the stress of labor results in a further increase in plasma levels, suggesting a possible role of NPY in human pregnancy and parturition.

Adult↗
PubMed1989

[Transvesical cesarean section].

On the basis of a clinical case the authors report the technique of laparotomic transvesical incision for cesarean section, which, nevertheless, has limited and special indications.

Adult↗