PubMed Health⌕ Search

Biomedical subjects

T Davis

Publications and source records attributed to T Davis.

At least 19 recordsLinked to original sources
PubMed1992

Synthesis of [D-Ala2,4'-125I-Phe3,Glu4]deltorphin and characterization of its delta opioid receptor binding properties.

Both [D-Ala2,Glu4]Deltorphin and [D-Ala2,4'-I-Phe3,Glu4]Deltorphin are highly selective ligands for delta, relative to mu, opioid receptors. Radiolabeled [D-Ala2, 4'-125I-Phe3,Glu4]Deltorphin ([125I]Deltorphin) was prepared with a specific activity of 2200 Ci/mmol from [D-Ala2, 4'-NH2-Phe3, Glu4]Deltorphin through a diazonium salt intermediate. The inhibition of [125I]Deltorphin binding to rat brain membranes by ligands selective for mu, delta, and kappa opioid receptors is consistent with binding by the radioligand to a single site having the properties of a delta opioid receptor. The results of these studies are in good agreement with those obtained by structurally different delta opioid receptor ligands. The similarity between the delta receptor site labeled by [125I]Deltorphin and those labeled by other delta receptor agonists, in contrast to differences seen by in vivo studies of their analgesic effects, is discussed.

Animals↗
PubMed1992

Trisomy 15 mosaicism in an IVF fetus.

Prenatal diagnosis of an IVF pregnancy in a woman aged 41 years showed a fetus mosaic for trisomy 15. The fetus had dysmorphic features, hypoplastic adrenal glands, and an accessory spleen. Both IVF and advanced maternal age would seem to increase the risk of trisomy 15.

Abortion, Eugenic↗
PubMed1992

Recognizing panic in cardiac patients.

Patients presenting with apparent myocardial infarctions may in fact be suffering from panic attacks; many symptoms of the latter mimic those of the former. Cardiovascular nurses who know what to listen for in patients' descriptions can recognize indications that panic may be occurring. This article describes panic attacks, panic disorder, and the long-term consequences that often accrue when this highly treatable problem is not recognized. Particularly when no evidence of myocardial damage is found, a cardiovascular nurse's recognition of panic can lead to a referral for appropriate psychological treatment, preventing years of needless suffering and unnecessary health care costs.

Female↗
PubMed1991

T2 open reading frame from the Shope fibroma virus encodes a soluble form of the TNF receptor.

A transcriptionally active open reading frame (T2) from Shope Fibroma Virus was recently shown to have striking sequence homology with members of a new superfamily of cell surface proteins, including a receptor for human tumor necrosis factor. Here we report that recombinant T2 protein expressed in COS cells is a soluble, secreted glycoprotein which specifically binds human TNF alpha and beta, and inhibits binding of these cytokines to native TNF receptors on cells. T2 binding of TNF is not inhibited by nerve growth factor, although the nerve growth factor receptor is also a member of the same family, nor by nine other recombinant cytokines. Further, the repeating domain structure of T2 most closely resembles that of the type I TNF receptor (p75) and is significantly different from other family members, including the type II TNF receptor (p55). Since T2 possesses a leader sequence but lacks a transmembrane domain, these results confirm the original suggestion (1) that T2 represents a soluble form of the type I TNF receptor which is secreted from virally infected cells, and whose function is to immunosuppress the host by abrogating the potentially destructive effects of TNF. This is the first such virally-encoded soluble cytokine receptor to be identified, and may represent a more general mechanism by which viruses subvert the host immune system.

Amino Acid Sequence↗
PubMed1991

Venous valvular insufficiency: influence of a single venous valve (native and experimental).

This report evaluates the ability of a single competent (native or experimental) superficial femoral vein valve to correct canine hindlimb venous insufficiency. The time to maximal ankle venous pressure after standing (VFT) and to 90% of that time after exercise (VRT90), and the minimal pressure after exercise (AVP) were measured in 17 greyhounds before intervention, after only the superficial femoral vein valve remained (n = 5), and after complete lower limb venous valvulotomy (n = 17). Three weeks later, 12 dogs underwent a native (n = 4) or experimental (n = 8) autogenous venous valve transplantation. Immediately and at 3 weeks after transplantation, venous pressure measurements were obtained. The manual strip test confirmed valve competence at the time of sacrifice. Only one valve transplant became incompetent. Immediately after single superficial femoral vein valve construction, VFT, AVP, and VRT90 measurements were not significantly different from normal. Three weeks after transplantation the AVP measurements were consistent with an insufficient venous system, whereas the VRT90 measurements were between and statistically different from both the control and totally incompetent system (p less than 0.05). After the native valve but not the experimental valve transplantations VFT normalized. These data suggest that insertion of a single competent superficial femoral vein valve into an incompetent lower limb venous system corrects venous pressure measurements initially but soon provides only a partially competent system. The experimental valve, although competent, is less responsive than a native valve.

Animals↗
PubMed1991

Molecular cloning and expression of the type 1 and type 2 murine receptors for tumor necrosis factor.

Clones encoding the type 1 (p80) and type 2 (p60) forms of the murine receptors for tumor necrosis factor (TNF) were isolated by cross-hybridization using probes derived from the cloned human TNF receptors. Each of the murine receptors shows strong sequence homology to the corresponding human receptor (approximately 65% amino acid identity) throughout the molecule but only modest homology, limited to ligand-binding domains, between themselves. The ligand-binding characteristics of the recombinant murine receptors mirror those of the human homologs: both receptor types bind TNF-alpha and -beta with multiple affinity classes, and the ligands cross-compete. Analysis of the murine transcripts encoding these receptors revealed the presence of RNAs for one or both forms of the receptors in all cells examined. It was also demonstrated that for both types of human TNF receptor, variably sized transcripts are observed in different cells. The murine cDNAs were further used to determine the chromosomal locations of the TNF receptor genes. They are not linked, in contrast to the ligands, and map to chromosomes 4 (type 1) and 6 (type 2).

Amino Acid Sequence↗
PubMed1991

Tone-dependent responses to endothelin in the isolated perfused fetal sheep pulmonary circulation in situ.

Pulmonary vascular responses to endothelin (ET-1), a peptide derived from endothelial cells in culture, were investigated in the ovine fetus delivered by cesarean section from chloralose-anesthetized ewes with intact umbilical circulation. Circulation to the lower left lobe of the fetal lung was isolated in situ and perfused at constant flow with blood withdrawn from the inferior vena cava. Injection of graded doses of ET-1 into the left pulmonary artery decreased pulmonary arterial perfusion pressure in a dose-related manner. At doses of 100, 300, and 1,000 ng, pulmonary vascular resistance per kilogram body weight (PVR/kg) was decreased 30, 40, and 42%, respectively. However, when fetuses were ventilated with 100% oxygen, 100- and 300-ng doses of ET-1 decreased PVR/kg by 5 and 9%, respectively. In contrast, injection of 1,000 ng of ET-1 resulted in a reversal of the response, and PVR/kg was increased by 70%. Ventilation of the right lung alone resulted in a similar reversal of the vasodilator response to 1,000 ng of ET-1, and a 138% increase in PVR/kg was recorded. These studies demonstrate for the first time that ET-1 has vasodilator activity in the normally high-tone ovine fetal pulmonary circulation. In addition, these results show that ET-1 has vasoconstrictor activity in the newly ventilated low-tone pulmonary vasculature. The present data indicate the pulmonary vascular responses to ET-1 are tone dependent in the ovine fetal pulmonary circulation.

Animals↗
PubMed1991

Viscoelastic properties of transformed cells: role in tumor cell progression and metastasis formation.

The micropipette aspiration technique was used to investigate the deformation properties of a panel of nontransformed and transformed rat fibroblasts derived from the same normal cell line. In this method, a step negative pressure is applied to the cell via a micropipette and the aspiration distance into the pipette as a function of time is determined using video techniques. A standard solid viscoelastic model was then used to analyze the viscoelastic properties of the cell. From these results, it is concluded that a direct correlation exists between an increase in deformability and progression of the transformed phenotype from a nontumorigenic cell line into a tumorigenic, metastatic cell line.

Animals↗
PubMed1991

Alternative forms of the human G-CSF receptor function in growth signal transduction.

Two forms of the human granulocyte colony-stimulating factor (G-CSF) receptor (HuG-CSFR), differing only at the carboxyl terminus, were recently identified by cDNA cloning. In this report we show that transfection and subsequent expression of either cDNA clone in the interleukin-3 (IL-3)-dependent murine cell line BAF/BO3 converts the cells to G-CSF-responsiveness. The transfected cells bound HuG-CSF in a manner indistinguishable from the native receptors. Expression of a mutant form of the HuG-CSFR, with a deletion in the cytoplasmic domain, in BAF/BO3 cells failed to convert the cells to HuG-CSF-responsiveness. In a similar manner, expression of these two HuG-CSFRs in the interleukin-6 (IL-6)-dependent murine hybridoma B9 resulted in the ability of these cells to grow in HuG-CSF [corrected]. These results strongly suggest that sequences in the first 96 amino acids of the cytoplasmic domain of the HuG-CSFR are required for signal transduction in response to ligand binding.

Animals↗
PubMed1991

The cervical cap.

The cervical cap is a barrier contraceptive method with an efficacy similar to that of the diaphragm. It has several advantages over other barrier contraceptives. In particular, it can be left in place for up to 48 hours, and repeated applications of spermicide are not necessary, even if sexual intercourse occurs more than once. In addition, the side effects seen with other barrier methods do not occur with the cervical cap. In some women, Papanicolaou tests may become abnormal, especially during the first three months of cap use. Therefore, careful monitoring of cervical cap users is essential.

Contraceptive Devices, Female↗
PubMed1990

Expression cloning of a human granulocyte colony-stimulating factor receptor: a structural mosaic of hematopoietin receptor, immunoglobulin, and fibronectin domains.

We report the isolation from a placental library, of two cDNAs that can encode high affinity receptors for granulocyte colony-stimulating factor (G-CSF) when expressed in COS-7 cells. The cDNAs are predicted to encode integral membrane proteins of 759 and 812 amino acids in length. The predicted extracellular and membrane spanning sequences of the two clones are identical, as are the first 96 amino acids of their respective cytoplasmic regions. Different COOH termini of 34 or 87 residues are predicted for the two cDNAs, due apparently to alternate splicing. The receptor with the longer cytoplasmic domain is the closest human homologue of the murine G-CSF receptor recently described by Fukunaga et al. (Fukunaga, R., E. Ishizaka-Ikeda, Y. Seto, and S. Nagata. 1990. Cell. 61:341). A hybridization probe derived from the placental G-CSF receptor cDNA detects a approximately 3-kb transcript in RNAs isolated from placenta and a number of lymphoid and myeloid cells. The extracellular region of the G-CSF receptors is composed of four distinct types of structural domains, previously recognized in other cell surface proteins. In addition to the two domains of the HP receptor family-defining region (Patthy, L. 1990. Cell. 61:13) it incorporates one NH2-terminal Ig-like domain, and three additional repeats of fibronectin type III-like domains. The presence of both an NH2-terminal Ig-like domain and multiple membrane-proximal FN3-like domains suggests that the G-CSF receptor may be derived from an ancestral NCAM-like molecule and that the G-CSF receptor may function in some adhesion or recognition events at the cell surface in addition to the binding of G-CSF.

Amino Acid Sequence↗
PubMed1990

A receptor for tumor necrosis factor defines an unusual family of cellular and viral proteins.

Tumor necrosis factor alpha and beta (TNF-alpha and TNF-beta) bind surface receptors on a variety of cell types to mediate a wide range of immunological responses, inflammatory reactions, and anti-tumor effects. A cDNA clone encoding an integral membrane protein of 461 amino acids was isolated from a human lung fibroblast library by direct expression screening with radiolabeled TNF-alpha. The encoded receptor was also able to bind TNF-beta. The predicted cysteine-rich extracellular domain has extensive sequence similarity with five proteins, including nerve growth factor receptor and a transcriptionally active open reading frame from Shope fibroma virus, and thus defines a family of receptors.

Amino Acid Sequence↗
PubMed1990

The molecular analysis of the el-noc complex of Drosophila melanogaster.

The el-noc complex spans a distance of about 200 kb on chromosome 2L. It consists of three discrete genetic regions el, l(2)35Ba and noc, each of which has a distinct phenotype when mutant. The noc locus itself is complex, including three separate regions. The el locus has been characterized by mapping 30 aberration breakpoints to the DNA. It extends over a distance of about 80 kb. It can be divided into two parts by the aberrations In(2LR)DTD128 and T(Y;2)A80. These break between two sets of el alleles yet are both phenotypically wild type for elbow. The simplest explanation is that el consists of two transcription units elA and elB. The locus pu, which appears to be unrelated to the el-noc complex, is found to map between the two el loci very close to elB (the distal el locus). The loci l(2)35Ba and nocA have been separated by only two l(2)35Ba+nocA- deletions and a nocA- inversion. No l(2)35Ba-nocA+ aberrations have been found. At the molecular level these loci are found to occupy almost the same region, and are probably identical.

Animals↗
PubMed1990

A novel transvection phenomenon affecting the white gene of Drosophila melanogaster.

The zeste mutation of Drosophila melanogaster suppresses the expression of white genes in the eye. This suppression is normally dependent on there being two copies of w+ located close to each other in the genome--they may either be in cis (as in a tandem duplication of w+) or in trans, i.e. on homologous chromosomes. Duplicated w+ genes carried by a giant transposing element, TE146(Z), are suppressed by z whether they are in direct (tandem) or inverted order. The tandem form of the TE is very sensitive to a rearrangement on the homologous chromosome--many rearrangements with breakpoints "opposite" the TE's insertion site prevent the interaction between the white genes on a z background. These aberrations act as dominant suppressors of zeste that are specific to the tandemly duplicated form of TE146(Z). The inverted form of the TE146(Z) presumably pairs as a hairpin loop; this is more stable than the tandem form by the criterion that its zeste phenotype is unaffected by any of the aberrations. This effect of rearrangements has been used as the basis for a screen, gamma-ray induced aberrations with at least one breakpoint opposite the TE site were recovered by their suppression of the zeste phenotype.

Animals↗
PubMed1990

Temperature sensitivity of equine herpesvirus isolates: a brief review.

This article reviews the findings on temperature sensitivity of equine herpesvirus isolates with an emphasis on equine herpesvirus 3, etiological agent of equine coital exanthema. The hypothesis is presented that the relative apathogenic nature of this herpesvirus may be an indirect result of its inability to synthesize and/or process glycoproteins needed by the virus to produce infectious virions at the normal body temperature of its natural host. It is suggested that equine herpesvirus 3 is the more evolved and naturally attenuated member of the equine herpesviruses.

Animals↗
PubMed1990

Primary adrenal insufficiency: a new cause of reversible gastric stasis.

Primary adrenal insufficiency is known to cause a wide spectrum of sometimes severe upper gastrointestinal symptoms; however, it has not previously been shown to be the cause of reversible gastric stasis. We have documented such a case in which the symptoms and physiologic abnormalities associated with gastric stasis were reversed by steroid replacement. A follow-up radionuclide gastric-emptying study after physiologic steroid replacement showed complete normalization of gastric emptying. Although gastric stasis has long been suspected of being present with primary adrenal insufficiency, this represents the first case in which it has been documented, and so should be included in the differential diagnosis of patients presenting with chronic nausea and vomiting.

Adrenal Cortex Diseases↗