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At least 19 recordsLinked to original sources
PubMedDate not supplied

The effect on fecundity of pill acceptance during postpartum amenorrhea in rural Bangladesh.

The length of the interval from last live birth to the subsequent pregnancy was studied for 121 contraceptive pill acceptors who were in postpartum amenorrhea at the time of acceptance and 121 matched nonacceptors in a prospective study in Matlab, Bangladesh. Half of the pill acceptors discontinued use within seven months, and as a group the pill acceptors had a significantly shorter interval to the next pregnancy than the matched nonacceptors. These findings suggest that unless continuation rates can be improved, it is better not to encourage women in rural Bangladesh to start the contraceptive pill during postpartum amenorrhea.

Adult↗
PubMed1991

Factors affecting treatment decisions for a life-threatening illness: the case of medical treatment of breast cancer.

Despite notions that patients are now playing a more proactive role in directing their own health care, our study of breast cancer patients considering adjuvant therapy indicates that, at least for a life-threatening illness, patients still rely heavily on their physicians to make treatment decisions. Out of 100 patients, 80.0% accepted their physician's primary treatment recommendation. Using behavioral decision-making theory we examined why some patients chose to disregard the physician's treatment recommendation despite its importance within the decision-making process. The discriminant function analysis performed to examine the factors influencing acceptance or rejection of a physician's treatment recommendation identified two sets of factors. Factors related to the amount and specificity of information about treatments conveyed to the patients, and the strength of the treatment recommendation itself. Patients who did not accept their physician's treatment recommendation were told in more specific terms what the benefits of treatment would be; they also rated side effects of treatment to be more probable and more severe than patients who did concur with the physician's treatment recommendation. These patients also rated their physicians' treatment recommendations as less strong than other physicians'. Nonacceptor patients were also better educated and were more likely to be risk takers. This study supports the findings of other studies that patients want more specific disease and treatment information, but suggests that the provision of this information might lead to therapy decisions which diverge from physicians' recommendations.

Breast Neoplasms↗
PubMed1976

An investigation of the effects of the intrauterine contraceptive device based on a longitudinal study of a self-selected sample of Barbadian women.

The results of longitudinal study of a self-selected sample of 1,790 Barbadian women who accepted the intrauterine contraceptive device (IUD) as their method of contraception are reported. The accumulated experience of 44,000 woman months of IUD use is presented. The demographic, medical, and obstetric data on admission for 2,797 IUD acceptors and 4,296 nonacceptors are contrasted. The reproductive experience of the two groups prior to the insertion of an IUD with respect to live births, stillbirths, and miscarriages is similar while the incidence of ectopic pregnancy is shown to be different. The association between the IUD and the incidence of tubal pregnancy is evaluated, and the literature dealing with this topic is reviewed. Estimates of the relative risk of an ectopic pregnancy in a woman with an IUD in utero are given.

Abortion, Spontaneous↗
PubMed1991

Differences between Asn-Xaa-Thr-containing peptides: a comparison of solution conformation and substrate behavior with oligosaccharyltransferase.

A series of tripeptides that satisfy the -Asn-Xaa-Thr/Ser- primary sequence requirement [Marshall, R. D. (1972) Annu. Rev. Biochem. 41, 673-702] for N-glycosylation have been synthesized and examined as potential acceptors in an oligosaccharyltransferase assay. Of these, six (Ac-Asn-Ala-Thr-NH2, Ac-Asn-Leu-Thr-NH2, Ac-Asn-Asp-Thr-NH2, Ac-Asn-D-Ala-Thr-NH2, Ac-Asn-Pro-Thr-NH2, and Ac-Asn-AIB-Thr-NH2) were examined for solution conformational properties in dimethyl sulfoxide with use of amide proton temperature coefficients, 3JHN alpha analysis [Pardi, A., et al. (1984) J. Mol. Biol. 180, 741-751], and 2-D ROESY experiments [Bothner-By, A. A., et al. (1984) J. Am. Chem. Soc. 106, 811-813]. The analysis reveals that the peptides that serve as acceptors in the transferase assay demonstrate similar conformational properties in solution. These are highlighted by a secondary structural motif that involves the interaction between the asparagine side-chain carboxamide and the backbone amide of the threonine. The peptides that show very poor acceptor, or even nonacceptor, properties in the oligosaccharyltransferase assay demonstrate different conformational features in solution. These observations may explain the distinct biological activity observed for these peptides.

Amino Acid Sequence↗
PubMed2000

Highly sensitive detection of hybridization of oligonucleotides to specific sequences of nucleic acids by application of fluorescence resonance energy transfer.

We show a new application of fluorescence resonance energy transfer (FRET) in two stages to detect specific sequences of nucleic acids. In the first stage, two fluorescently tagged oligonucleotides hybridize with a complementary target molecule to produce FRET. The sequences of the oligonucleotides and spectral properties of fluorophores are chosen to provide a basis for an efficient energy transfer. In the next step, the specificity of hybridization is tested by competition of labeled probes with an excess of unlabeled oligonucleotides of the same sequence. The resulting emission spectra, one obtained in the excess of unlabeled donor probe and the other produced in the excess of unlabeled acceptor probe, are compared with the spectrum from the first stage to look for differences in the emission pattern of the fluorescent labels. We show that it is possible to detect the existence of specific hybrids composed of the two probes and complementary target molecule even in very unfavorable conditions, such as the presence of unhybridized probes in the final reaction mixture, secondary nonacceptor quenching of donor probe fluorescence, and strong background emission of acceptor produced by its direct excitation with a donor excitation light.

Binding, Competitive↗
PubMed1989

Structural requirements for protein N-glycosylation. Influence of acceptor peptides on cotranslational glycosylation of yeast invertase and site-directed mutagenesis around a sequon sequence.

To understand better the structural requirements of the protein moiety important for N-glycosylation, we have examined the influence of proline residues with respect to their position around the consensus sequence (or sequon) Asn-Xaa-Ser/Thr. In the first part of the paper, experiments are described using a cell-free translation/glycosylation system from reticulocytes supplemented with dog pancreas microsomes to test the ability of potential acceptor peptides to interfere with glycosylation of nascent yeast invertase chains. It was found that peptides, being acceptors for oligosaccharide transferase in vitro, inhibit cotranslational glycosylation, whereas nonacceptors have no effect. Acceptor peptides do not abolish translocation of nascent chains into the endoplasmic reticulum. Results obtained with proline-containing peptides are compatible with the notion that a proline residue in an N-terminal position of a potential glycosylation site does not interfere with glycosylation, whereas in the position Xaa or at the C-terminal of the sequon, proline prevents and does not favour oligosaccharide transfer, respectively. This statement was further substantiated by in vivo studies using site-directed mutagenesis to introduce a proline residue at the C-terminal of a selected glycosylation site of invertase. Expression of this mutation in three different systems, in yeast cells, frog oocytes and by cell-free translation/glycosylation in reticulocytes supplemented with dog pancreas microsomes, leads to an inhibition of glycosylation with both qualitative and quantitative differences. This may indicate that host specific factors also contribute to glycosylation.

Amino Acid Sequence↗
PubMed1991

Peptide binding by protein disulfide isomerase, a resident protein of the endoplasmic reticulum lumen.

Previously we had demonstrated by photoaffinity labeling that a 57-kDa protein of the endoplasmic reticulum can bind and become covalently linked to glycosylatable photoreactive peptides containing the sequence-Asn-Xaa-Ser/Thr-. Subsequently, it was found that this protein, called glycosylation site-binding protein, was a multifunctional protein, i.e. it was identical to protein disulfide isomerase (PDI), the beta-subunit of prolyl hydroxylase and thyroid hormone-binding protein. In this study, the peptide specificity for binding to this 57-kDa protein, hereafter called PDI, has been investigated in more detail using photoaffinity probes. The results reveal that although N-glycosylation by oligosaccharyl transferase in the endoplasmic reticulum has an absolute requirement for an hydroxyamino acid in the third amino acid residue of the glycosylation site sequence, no such specificity is observed in the binding of such peptides to PDI. In addition to the lack of specificity for an hydroxyamino acid in the third residue position, no specificity was observed for the asparagine residue in the first position. Thus, binding is not restricted to peptides containing N-glycosylation sites. We have investigated the discrepancy between this apparent lack of sequence specificity and earlier results indicating that binding of peptides to PDI was specific for N-glycosylation site sequences. We now demonstrate that PDI in the lumen of microsomes is more efficiently labeled by peptides containing photoreactive-Asn-Xaa-Ser/Thr- sequences than by nonacceptor site sequences because the former become glycosylated. This increased labeling does not occur because the glycosylated form of the probes are preferentially recognized by PDI. Rather, it appears that increased polarity of the affinity probe after attachment of the oligosaccharide chain prevents its exit from the sealed microsomes, in effect concentrating it within the lumen of the microsome. These results, coupled with other studies on the multifunctional nature of PDI, suggest that the observed peptide binding may be a manifestation of the ability of PDI to recognize the backbone of polypeptides in the lumen of the endoplasmic reticulum.

Affinity Labels↗
PubMed1985

Active site-directed photoaffinity labeling and partial characterization of oligosaccharyltransferase.

Oligosaccharyltransferase, the enzyme that catalyzes the transfer of the oligosaccharide chain of dolichol-P-P-GlcNAc2Man9Glc3 to asparagine residues in -Asn-X-Thr/Ser- sites within polypeptides, has been radiolabeled using a photoactivatable azido tripeptide acceptor, N alpha-[3H]Ac-Asn-Lys(N epsilon-p-azidobenzoyl)-Thr-NH2. As determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the molecular mass of the oligosaccharyltransferase polypeptide from hen oviduct microsomes is 60 kDa. Radiolabeling of the 60-kDa polypeptide was completely dependent upon photolysis of hen oviduct endoplasmic reticulum preparations in the presence of the azido peptide and Mn2+, which is required for enzymatic activity. Labeling of the enzyme was not inhibited in the presence of a 10-fold excess of the nonacceptor peptides, unacetylated Asn-Lys(N epsilon-p-azidobenzoyl)-Thr-NH2 or unacetylated Asn-Leu-Thr-NH2, whereas it was completely abolished by the presence of a 10-fold excess of the competing acceptor peptide, N alpha-Bz-Asn-Leu-Thr-NH2. Thermal inactivation of oligosaccharyltransferase was achieved by heating endoplasmic reticulum preparations to 60 degrees C. This loss of enzyme activity at 60 degrees C paralleled a comparable decrease in radiolabeling of the 60-kDa polypeptide, whereas temperatures of 50 degrees C and lower had no effect on either process. Oligosaccharyltransferase itself may be an N-linked glycoprotein, because the 60-kDa radiolabeled polypeptide binds to concanavalin A-agarose and is susceptible to digestion by beta-endohexosaminidase H.

Affinity Labels↗
PubMed1983

Substrate recognition by oligosaccharyl transferase. Inhibition of co-translational glycosylation by acceptor peptides.

In a microsome system rendered competent in protein translation by the addition of rabbit reticulocyte lysate, co-translational insertion and glycosylation of N-linked glycoproteins is observed when the appropriate mRNA is supplied. We have utilized this system to examine the ability of acceptor tripeptides of the type Asn-X-Thr/Ser to inhibit co-translational glycosylation. Using endogenous oligosaccharide-lipid as the carbohydrate donor, dog pancreas microsomes efficiently glycosylated N alpha-[3H]Ac-Asn-Leu-Thr-NHCH3 (apparent Km = 100 microM). Glycopeptide formation was essentially complete within 20 min. In the presence of mRNA from vesicular stomatitis virus or chicken ovalbumin, a similar tripeptide, N alpha-Ac-Asn-Leu-Thr-NH2, inhibited co-translational glycosylation. Translocation of the nascent chains was not affected. Thus, in the absence of peptide, all translated G protein was glycosylated and found within the microsomes, whereas in the presence of the peptide a mixture of glycosylated and nonglycosylated G protein was sequestered. Inhibition of nascent chain glycosylation was competitive and not merely the result of oligosaccharide lipid depletion, because preincubation of the microsomes with the peptide followed by its removal did not affect subsequent glycosylation of ovalbumin or G protein. Six derivatives of Asn-Leu-Thr-NH2, three of which were acceptors and three of which were not, were tested for their ability to inhibit co-translational glycosylation. The three acceptor peptides, N alpha-Ac-Asn-Leu-Thr-NH2, N alpha-Oc-Asn-Leu-Thr-NH2, and N alpha-Bz-Asn-Leu-Thr-NH2, effectively inhibited nascent chain glycosylation. In contrast, the three nonacceptors, N alpha-Ac-Gln-Leu-Thr-NH2, N alpha-Ac-Asn(N beta-Me)-Leu-Thr-NH2, and Asn-Leu-Thr-NH2, had no effect. Taken together, these data indicate that the inhibition of co-translational glycosylation by a peptide is dependent on its ability to compete for the active site of the oligosaccharyl transferase.

Animals↗
PubMed1984

Laser-induced lanthanide luminescence as a probe of metal ion-binding sites of human Factor Xa.

7F0 ---- 5D0 excitation spectroscopy of Eu(III) has shown that human Factor Xa has two high affinity lanthanide ion-binding sites. The deuterium isotope effect on the reciprocal lifetime (tau-1) of excited Eu(III) in human Factor Xa has indicated that 2 to 3 water molecules remain on Eu(III) after being complexed by Factor Xa, suggesting that 3-6 ligand atoms are provided by the protein, probably through two or three gamma-carboxyglutamic acids (GLA). F orster -type interlanthanide energy transfer has been utilized to measure the distance between the high affinity metal ion-binding sites of human Factor Xa using Tb(III) as an energy donor and Nd(III), Ho(III), or Er(III) as energy acceptors. Tau-1 values of Tb(III) in the presence of the acceptor ions Nd(III), Ho(III), and Er(III) were 1.90, 1.66, and 1.76 ms-1, respectively, which compared to 1.31 ms-1 in the presence of the nonacceptor ion Gd(III), yield energy transfer efficiencies of 0.29, 0.20, and 0.24, respectively. From these efficiencies and published critical distances (R0) ( Horrocks , W. DeW ., Jr., Rhee , M-J., Snyder, A. P., and Sudnick , D. R. (1980) J. Am. Chem. Soc. 102, 3650-3652), the distance between two high affinity sites is estimated to be 10.7 A. Based on these data, we propose that the two high affinity sites of human Factor Xa consist of two paired GLA residues; GLA-19, GLA-20 and GLA-25, GLA-26 together with one of the remaining single GLA residues for each site.

1-Carboxyglutamic Acid↗
PubMed1986

Acceptance of contraceptive practice by grandmultiparae in Benin City, Nigeria.

Five hundred sixty grandmultiparous women were interviewed as to their contraceptive awareness, desirability and use in the three major hospitals in Benin City, Nigeria, between October 1, 1980 and September, 1981. Their parity ranged from 5 to 14 with a mean of 6.7. There was high level of awareness of contraceptive availability and usefulness (65%), but low level of practice (27.1%). The main causes of the low practice level included opposition from husband and other relatives, complications of previous methods used and the desire to have a large family. Oral contraceptives were the preferred method, followed by intrauterine devices. Educational attainment had a positive relationship to acceptance of contraceptive practice. We believe that with more concerted effort at family planning counseling, the community will be rid of the hazards and menace of grandmultiparity.

Adolescent↗
PubMed1988

Problems and help seeking in high-risk adolescent patients of health clinics.

In this study, 2787 adolescents between the ages of 13 and 18 years living in inner-city communities were interviewed about their mental and physical health and their clinic use. The patients used consolidated mental and physical health clinics located in neighborhoods, hospitals, or schools; or traditional neighborhood or hospital health clinics. Analyses of selected patient problems reveal that less than one third of adolescent patients with suicide ideation, conduct disorder, and substance abuse or dependency sought or received care for those problems. Only half of the adolescents with major depression sought or received care for depression, and only two thirds of the sexually active females sought or received help with birth control. A special effort needs to be made to attract troubled youth to clinics and to identify and treat their problems, particularly when those problems involve mental health concerns.

Adolescent↗
PubMed1986

A study of women requesting interval contraceptive sterilization who do and do not return for surgery.

With the use of initial records of 1128 women who presented for interval tubal ligation, characteristics of those who were sterilized were juxtaposed with characteristics of those who did not return for surgery. Follow-up telephone interviews were conducted to explore regret after sterilization among 268 sterilized women. The subsequent histories of 144 women who did not return for surgery were examined, to determine whether failure to return might have screened, selectively, the women at greatest risk of regret. High levels of subsequent unwanted conception and pregnancy wastage were found in the nonreturn group. Institutional factors were often implicated in failure to return. Variables available at initial presentation are proposed to identify women who risk adverse consequences of postponed sterilization, to facilitate return without increasing regret.

Adult↗