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Biomedical subjects

F Stewart

Publications and source records attributed to F Stewart.

At least 19 recordsLinked to original sources
PubMed2001

Uterocalin, a lipocalin provisioning the preattachment equine conceptus: fatty acid and retinol binding properties, and structural characterization.

The equine conceptus is surrounded by a fibrous capsule that persists until about day 20 of pregnancy, whereupon the capsule is lost, the conceptus attaches to the endometrium and placentation proceeds. Before attachment, the endometrium secretes in abundance a protein of the lipocalin family, uterocalin. The cessation of secretion coincides with the end of the period during which the conceptus is enclosed in its capsule, suggesting that uterocalin is essential for the support of the embryo before direct contact between maternal and foetal tissues is established. Using recombinant protein and fluorescence-based assays, we show that equine uterocalin binds the fluorescent fatty acids 11-(dansylamino)undecanoic acid, dansyl-D,L-alpha-amino-octanoic acid and cis-parinaric acid, and, by competition, oleic, palmitic, arachidonic, docosahexaenoic, gamma-linolenic, cis-eicosapentaenoic and linoleic acids. Uterocalin also binds all-trans-retinol, the binding site for which is coincident or interactive with that for fatty acids. Molecular modelling and intrinsic fluorescence analysis of the wild-type protein and a Trp-->Glu mutant protein indicated that uterocalin has an unusually solvent-exposed Trp side chain projecting from its large helix directly into solvent. This feature is unusual among lipocalins and might relate to binding to, and uptake by, the trophoblast. Uterocalin therefore has the localization and binding activities for the provisioning of the equine conceptus with lipids including those essential for morphogenesis and pattern formation. The possession of a fibrous capsule surrounding the conceptus might be an ancestral condition in mammals; homologues of uterocalin might be essential for early development in marsupials and in eutherians in which there is a prolonged preimplantation period.

Animals↗
PubMed2001

Evaluation of a media campaign to increase knowledge about emergency contraception.

Our objective was to evaluate a media campaign designed to increase knowledge about emergency contraception. Random telephone surveys were conducted before and after the campaign to measure changes in knowledge about emergency contraception. Change in the volume of calls to the Emergency Contraception Hotline (1-888-NOT-2-LATE) was a secondary measure of impact. Significant increases occurred in the proportions of women who knew that something could be done after intercourse to prevent pregnancy, who knew the term emergency contraception, who knew of the 72-h time limit, and who had heard of the Hotline. In addition, the number of calls to the Hotline increased substantially. A public education media campaign resulted in significant increases in knowledge about emergency contraception. The first contraception advertisement ever shown on television did not provoke controversy.

Advertising↗
PubMed2000

A novel uterine lipocalin supporting pregnancy in equids.

Horses, donkeys, and therefore, probably all equids, secrete a nonglycosylated, progesterone-dependent, 19-kDa protein (P19) into the uterine lumen during early pregnancy, and significant quantities of it are taken up by the developing conceptus. Sequence analysis and structural modelling have identified P19 as a lipocalin with greatest similarity to the murine major urinary protein lipocalins. However, lack of strong identity with any particular group of lipocalins and several unusual structural features, including a unique amino acid triplet within one of the invariant domains and an unusual external tryptophan residue, classify it as a new member of the lipocalin family. P19 is therefore likely to be a transport protein involved in supporting early embryonic development. Preliminary evidence using recombinant-derived P19 and fluorescently tagged ligands suggests that it may transport a fatty acid or retinol-like molecule. Although an initial search failed to identify homologues of P19 in other mammals, they may nevertheless exist but are synthesised and secreted in much smaller quantities, making them difficult to detect. Equids appear to need particularly large quantities of the protein during early pregnancy because of the unusually late implantation in this species and the presence of a capsule surrounding the conceptus until about day 23 of gestation.

Animals↗
PubMed2000

Horse conceptuses secrete insulin-like growth factor-binding protein 3.

Insulin-like growth factor-I (IGF-I) promotes early embryonic development in several species. In the rabbit, IGF-I binds to the embryonic coats from Day 3 of development onward by a 38-kDa protein that is probably insulin-like growth factor-binding protein 3 (IGFBP3). In the present study, ligand, Western, and Northern blot analyses were used to demonstrate the presence of IGF-I-binding activity, several immunoreactive IGFBP3 proteins, and IGFBP3 mRNA in horse conceptuses with particularly large amounts of immunoreactive IGFBP3 in the conceptus capsule. In addition, immunoprecipitation of radiolabeled proteins showed that cultured horse conceptuses secreted IGFBP3 into the culture medium. Endometrial samples from mares also contained IGFBP3 mRNA and protein; but there was no evidence of secretion of IGFBP3 into the uterine lumen by ligand blot analysis, and there was evidence of only very small amounts by Western blot analysis. These results indicate that the horse conceptus secretes significant quantities of IGFBP3 toward the conceptus capsule from as early as Day 10 after ovulation. Thus, most of the IGFBP3 contained within the capsule, which binds IGF-I to this special extracellular matrix of the preimplantation horse conceptus, is likely to be embryonic in origin. IGFBP3 in the horse conceptus capsule may enhance or modulate the action of IGFs on the developing conceptus.

Animals↗
PubMed2000

In vitro and in vivo expression of endothelial von Willebrand factor and leukocyte accumulation after fractionated irradiation.

Previous investigations have demonstrated an increased release of von Willebrand factor (VWF; also known as vWF) in endothelial cells after high single-dose irradiation in vitro. We have also found increased levels of Vwf protein in mouse glomeruli after a high single dose of renal irradiation in vivo. In addition, increased numbers of leukocytes were observed in the renal cortex after irradiation in vivo. The aim of the present study was to investigate and quantify these biological processes after clinically relevant fractionated irradiation and to relate them to changes in renal function. A significantly greater increase in release of VWF was observed in cultured human umbilical vein endothelial cells (HUVECs) after fractionated irradiation (20 x 1.0 Gy) than after a single dose of 20 Gy (147% compared to 115% of control, respectively, P < 0.0005). In contrast with the in vitro observations, glomerular Vwf staining was lower after fractionated irradiation in vivo (20 x 2.0 Gy or 10 x 1.6 Gy +/- re-irradiation) than after a single dose of 16 Gy. The number of leukocytes accumulating in the renal cortex was also lower after fractionated in vivo irradiation than after a single radiation dose. The onset of these events preceded renal functional and histopathological changes by approximately 10 weeks. These data indicate that radiation-induced changes in endothelial VWF expression after in vivo irradiation may be distinct from the in vitro observations. Increased VWF expression may reflect pivotal processes in the pathogenesis of late radiation nephropathy and provide a clue to appropriate timing of pharmacological intervention.

Animals↗
PubMed2000

Rapid onset of stupor.

Catatonia is a syndrome with many causes that can be difficult to diagnose. In this report, we describe a case of rapid onset of stupor and loss of consciousness, subsequent evaluation, and treatment of catatonia in an HIV-positive man.

Adult↗
PubMed1999

Factors controlling epidermal growth factor (EGF) gene expression in the endometrium of the mare.

Previous studies showed a dramatic increase in EGF gene expression in the endometrial glands of pregnant mares around day 40 after ovulation. To investigate how the steroid hormones of pregnancy might regulate this expression, in situ hybridization was used to monitor the levels of EGF mRNA in endometrial biopsies obtained from seasonally anoestrous or ovariectomised mares given exogenous progesterone and oestrogen, alone or in combination, for up to 46 days. Biopsies were also taken from mares during the non-pregnant cycle, during normal pregnancies and pregnancies compromised by endometrial pathology (endometriosis) or because of incompatible extraspecific embryo transfers (donkey-in-horse pregnancies). Only a few samples showed weak EGF expression during the late luteal phase of the oestrous cycle. During normal pregnancy, the previously observed dramatic increase of expression after day 40 of gestation was confirmed. Although aged mares suffering from endometriosis and mares carrying an extraspecific donkey conceptus showed the same increase of EGF mRNA in normal glands, this was virtually absent from gland cross-sections compromised due to inflammatory or fibrotic changes. Administration of various doses and combinations of progesterone and oestrogen for < 35 days yielded negative or only weakly positive hybridization results, whereas progesterone alone for > or = 40 days upregulated EGF expression strongly irrespective of additional treatment with oestrogen. This is the first experimental evidence that EGF expression in the endometrium can be induced by progesterone alone. The requirement for prolonged progesterone priming is of considerable interest in the context of the unusually late stage of gestation at which placental attachment commences in equids.

Animals↗
PubMed1999

Clearance kinetics of CD34+ cells from peripheral blood: an independent predictor of hematologic recovery after high-dose chemotherapy and hematopoietic stem cell transplantation.

We measured the concentration of CD34+ cells in peripheral blood (PB) (1/2) h prior to and (1/2), 1, 3, 6, and 12 h following hematopoietic stem cell (HSC) infusion in 34 breast cancer patients treated with high-dose chemotherapy (HDC). The decrease in these concentrations over time enabled us to determine the clearance kinetics of CD34+ cells from PB. The absolute number of CD34+ cells in PB generally peaked at (1/2) h after infusion, then rapidly declined from 1 to 3 h post infusion and continued to fall until 12 h post transplant, but more slowly. In univariate analysis, CD34+cells/kg infused, CFU-GM/kg infused, the CD34+ count at (1/2) h, and the 12-h clearance of CD34+ cells from PB were predictors of hematologic recovery, as were each of the two phases of clearance when the slope was divided into rapid and slow phases (from (1/2) to 3 and from 3 to 12 h post transplant, respectively). We then stratified our population by the number of CD34+ cells/kg infused. In group 1, patients received </=7.5 x 10(6) CD34+ cells/kg; in group 2, >7.5 x 10(6) CD34+ cells/kg. After adjusting for CD34+ cells injected, age, and purged or unpurged graft in multivariate analysis, the 12 h clearance remained a predictor of hematologic recovery in group 1. In addition, the second phase of clearance (from 3 to 12 h after infusion) was an even better predictor than the 12 h clearance. In group 2, however, no statistically significant correlation was observed, even with the number of HSC injected. Results suggest that rapidity of clearance of CD34+cells from PB is an independent indicator of hematologic recovery in patients receiving lower doses of CD34+ cells. When the cell dose injected is over a threshold, PB clearance correlations with hematologic recovery are masked.

Adult↗
PubMed1999

Lessons to be learned: a case study approach: severe hyponatraemia induced by primary hypothyroidism and associated with possible increased hepatic sensitivity to thyroxine replacement.

The case is presented of a 74 year-old woman who was admitted with severe hypo-osmolar hyponatraemia associated with inappropriately raised urinary osmolality, and who was subsequently discovered to have primary hypothyroidism. A normal serum sodium concentration was restored by means of judicious fluid restriction and thyroid hormone replacement. Low dose thyroxine therapy led to rapid but modest increases in the serum activities of alanine aminotransferase (ALT) and alkaline phosphatase (ALP); both returned to normal over a period of three weeks. These sub-clinical enzyme changes may indicate tissue 'hyperthyroidism'; and in this case, the fact that they occurred acutely at only low doses of thyroxine possibly suggests an increased hepatic sensitivity to the hormone.

Aged↗
PubMed1999

Cloning, sequencing and functional expression of zebra (Equus burchelli) LH.

Although donkey luteinizing hormone exhibits a very high degree of amino acid sequence identity with horse LH, its FSH activity in non-equine species is tenfold lower. The coding regions of the common zebra (Equus burchelli) glycoprotein hormone alpha-subunit and LH beta-subunit transcripts were cloned by reverse transcription-PCR from pituitary gland RNA to investigate more precisely the structure-function relationships of this gonadotrophin family. Zebra LH was then expressed in COS-7 cells and its LH and FSH activities were assessed in a rat Leydig cell bioassay (for LH) and in a cell line stably expressing the human FSH receptor bioassay (for FSH). The recombinant zebra LH, although displaying LH activity similar to that of recombinant donkey and horse LH, had no detectable FSH activity. The LH amino acid sequences of these three species are very similar, leaving only very few amino acids as potential candidates to explain the difference in their FSH activities. Moreover, according to the difference in FSH bioactivity and to the percentage identity between the sequences, the common zebra is phylogenetically closer to the donkey than it is to the horse.

Amino Acid Sequence↗
PubMed1999

Cell proliferation patterns in the equine endometrium throughout the non-pregnant reproductive cycle.

Immunohistochemical detection of the proliferation marker Ki-67 antigen was used to monitor mitotic activity in the endometrium of mares. The monoclonal antibody MIB1 was validated for use on equine tissues by demonstrating its reaction with activated peripheral blood lymphocytes, and endometrial biopsies were recovered from 26 non-pregnant mares at selected stages during the reproductive cycle. The proportion of positively stained nuclei was counted in five random areas on each histological section to determine the percentage and type of proliferating cells. Multiplication rates in the types of cell found in the superficial strata, comprising the luminal epithelium, the epithelium of the gland necks and the stromal cells of the stratum compactum, were greatest during oestrus, presumably under the influence of oestrogens secreted by the growing ovarian follicles. In contrast, the mitotic activity in the cells of the deeper secretory portions of the endometrial glands was restricted to a brief phase between day 3 and day 7 of dioestrus, most likely as a delayed response to the decreasing oestrogen concentrations after ovulation. Some of the degenerate glands in subfertile mares did not follow this pattern of increased epithelial proliferation at that stage. After day 7 of dioestrus, the proliferation rates of cells in the endometrium decreased to basal values and remained low for as long as progesterone concentrations remained evaluated, even during prolonged dioestrus. The technique enabled characterization of normal cell proliferation patterns in the endometrium of mares and it will be a useful tool in the future for monitoring the endometrial responses of reproductively healthy and subfertile mares.

Analysis of Variance↗
PubMed1999

Cell proliferation patterns during development of the equine placenta.

Placentation involves considerable growth and reorganization of both maternal and fetal tissues. In this investigation, immunohistochemical localization of the proliferation marker Ki-67 antigen was used to monitor cell division during placentation in mares. Endometrial biopsies were obtained from eight mares between day 14 and day 26 of pregnancy and from eight anoestrous mares that had been treated with various combinations of progesterone and oestrogen. Samples of endometrium and fetal membranes were obtained from 19 mares carrying normal horse conceptuses between day 30 and day 250 of gestation and from three failing extraspecific donkey-in-horse pregnancies. Proliferation in the superficial strata of the endometrium was increased by day 18 of gestation and this effect could be mimicked by supplementing with oestradiol benzoate during the last 6 days of a prolonged period (18-36 days) of progesterone administration. Fetal chorionic girdle cells were proliferating vigorously at days 30-32 of gestation, but stopped dividing after they invaded the endometrium, while the trophoblast cells of the allantochorion showed an increase in mitotic activity after day 38. The luminal epithelium of the endometrium started to proliferate only after the primary villi of the true epitheliochorial placenta had been formed, and during days 58-70 this effect was seen only in the pregnant horn in which placentation was further advanced. During the second half of gestation, most of the mitotic activity was confined to the periphery of the microcotyledons which were still growing. In the donkey-in-horse pregnancies, proliferation rates of the maternal and fetal epithelial at day 70 of gestation were markedly reduced in areas of heavy endometrial lymphocyte infiltration and poor placentation. These results provide a basis for further studies on factors that influence invasive and non-invasive placentation.

Animals↗
PubMed1998

Promoting emergency contraception.

The use of available oral contraceptive agents for emergency contraception has been judged safe and effective by the U. S. Food and Drug Administration and other agencies. Yet implementation by physicians has been limited, and only a small percentage of women take advantage of this option each year. Lack of a specially packaged--and marketed--product for this indication has been a major barrier.

Contraceptives, Postcoital↗
PubMed1998

The genetics of epigenetics.

Cis-acting binding sites for transcription activators cannot explain the patterned expression of genes during development, nor a large range of phenomena that result from gene transplacement. Heritable states of transcriptional regression or activation sequences are influenced not only by the chromosomal context of the promoter but also by modifications of histones and DNA, and long-range interactions between distant chromosomal elements. The molecular dissection of these epigenetic phenomena has become an exciting topic of research, revealing highly conserved mechanisms at work in chromatin-mediated gene control.

Animals↗
PubMed1998

What does photodynamic therapy have to offer radiation oncologists (or their cancer patients)?

Major advances have recently been made in photodynamic therapy (PDT) for clinical application, including the development of more powerful photosensitizers and light sources and suitable light applicators. PDT is emerging as an attractive new form of cancer therapy, suitable for treating superficial lesions (less than 1 cm in depth) and carcinoma in situ, or as an adjuvant to surgery for more bulky disease. PDT is therefore complementary to radiotherapy which is better suited to treating larger tumours. There are some qualitative similarities between light distribution in tissue during superficial illumination and ionizing radiation dose distributions during external beam irradiation, or between interstitial PDT and brachytherapy, although the geometric scale is very different (visible light penetrates a maximum of 5-10 mm in tissue). The contribution of scattered light to tissue irradiance is much greater than for ionizing radiation and in situ light dosimetry is very important (although rather complicated) to ensure adequate illumination without over-treating. Dosimetry and treatment planning are highly advanced for ionizing radiation and are routine in all radiotherapy departments. Proper in situ light dosimetry and dose distribution calculation for PDT is in its infancy. Physicists have an important role to play in the further optimization of clinical PDT and much of the infrastructure and expertise present in the radiotherapy department is ideally suited to accommodate PDT. In this review, parallels and contrasts are made between PDT and ionizing radiation for both mechanistic and dosimetric aspects of the therapies. A summary of the most interesting clinical applications is also given.

Humans↗
PubMed1998

Transfer of a uterine lipocalin from the endometrium of the mare to the developing equine conceptus.

One of the major, progesterone-dependent proteins secreted into the uterine lumen of the mare is a 19-kDa lipocalin (P19). It associates strongly with the embryonic capsule that envelops the young horse conceptus in early gestation, suggesting that it may be involved in sustaining early development. However, it was not known whether the protein was transported through the capsule and/or trophoblast layer and into the yolk sac cavity. To address this question, polyclonal antisera were raised against a C-terminal peptide (based on the deduced amino acid sequence of P19) and a recombinant-derived P19 fusion protein. The antiserum raised against the C-terminal peptide recognized P19 on Western blots of denatured uterine secretions (subjected to SDS-PAGE), but it did not bind to the protein in tissue sections. However, the antiserum raised against the recombinant-derived fusion protein recognized P19 both on Western blots and in histological sections. Western blot analysis of tissues and fluids collected from early-pregnant mares demonstrated significant quantities of P19 in the endometrium and uterine secretions and in the embryonic capsule, the chorion, and the yolk sac fluid, showing that the protein is transferred through to the developing embryo. Concentrations of immunoreactive P19 declined during gestation so that, by Day 30, it had virtually disappeared from both maternal and fetal tissues and fluids. Immunohistochemical staining of endometrial biopsies collected during early pregnancy localized P19 to the glandular and luminal epithelia and to the lumina of the endometrial glands. The capsule and the trophoblast layer of the chorion from early (Days 16-17) horse conceptuses also stained positively with localization of P19 to the apical surface of the trophoblast cells. There was no detectable staining either in or on the embryonic disc. The presence of P19 in both the trophoblast layer and the yolk sac fluid suggests that P19 passes into the yolk sac fluid via trophoblast cells.

Animals↗