Search PubMed⌕ Search

Biomedical subjects

G Shaw

Publications and source records attributed to G Shaw.

At least 181 records · Page 10Linked to original sources
PubMed1991

Kinetics of the DNA binding of 2-substituted anthraquinones.

The DNA-binding properties of the 2-substituted-1,4-dihydroxyanthraquinones 5-12 were examined. Compounds 5 and 6 were synthesized in this study, 7-12 were already available. Spectral studies were consistent with intercalation of 5, 6 and 8 into DNA. Affinity constants were in the range of 3 x 10(4)M-1. Compounds 7 and 10-12 showed no DNA binding, presumably being sterically excluded from binding. The kinetics of the DNA interaction of 5, 6 and 8 were studied. There is a biphasic process. This may reflect an initial reaction, with drug from this first mode of binding moving into the second binding mode (a sequential process) or independent binding of drug in two sets of sites (a parallel process). The methods used in this study do not allow us to discriminate between these models. However, if the parallel binding model is correct, the compounds show sequence selectivity of binding, and provide a lead for further development of neutral DNA-binding ligands with sequence selectivity.

Anthraquinones↗
PubMed1990

Bundling and cross-linking of intermediate filaments of the nervous system.

Ultrastructural studies have shown that neurons and glia in the mammalian nervous system contain bundles of often hundreds or more individual intermediate filaments. The means by which these bundles are formed and maintained has not been examined. We describe a series of simple experiments indicating that intermediate filament bundles derived from neuronal and glial processes are extremely stable, being resistant to a variety of extreme conditions. Furthermore, a preliminary examination of the mechanism of bundling for both types of filaments rules out several models for the production and control of cross-linking. We conclude that the long processes of both neurons and glia are stabilized by bundled intermediate filaments exhibiting strong interfilament interactions. We present a reconciliation these findings with previous data suggesting that neurofilaments are not actively cross-linked. We also describe a novel detergent-insoluble annular cytoskeletal structure, which appears to constrict bundles of axonal neurofilaments locally.

Alkaline Phosphatase↗
PubMed1990

Neurofilament immunoreactivity in myenteric neurons differs from that found in the central nervous system.

Neurofilaments are 10-nm diameter protein fibers found within neurons and are composed predominantly of a triplet of polypeptides usually referred to as low-, medium-, and high-molecular-weight subunits. We describe the results of a study of myenteric plexus neurons using a panel of neurofilament triplet protein antibodies and indirect immunofluorescence techniques. Polyclonal antibodies to each of the three neurofilament subunits reliably stained myenteric neurons and their processes, indicating the presence of all three proteins in these cells. However, several well-characterized monoclonal antibodies to epitopes on high- and medium-molecular-weight subunits showed immunoreactivity in brain tissue but not in myenteric neurons and their processes. Some of the antibodies that do not stain recognize only phosphorylated epitopes, indicating that the level of neurofilament phosphorylation is very low in enteric neurons. Other antibodies that are not thought to be sensitive to the level of neurofilament phosphorylation show reduced or no staining of enteric neurons, suggesting the presence of immunologically distinct neurofilaments in these cells. These results suggest the presence of modified neurofilament structures in enteric neurons, possibly reflecting their unique mechanical character within the moving intestinal wall.

Animals↗
PubMed1990

Psychosis in a patient with hyperkalemic periodic paralysis.

Presentation of an unusual case of a hyperkalemic periodic paralysis patient who developed a psychotic illness during the course of treatment is made in a conference format. The differential diagnosis of this psychotic episode together with some information regarding hyperkalemic periodic paralysis are discussed. The case illustrates the benefits of close cooperation between medical and psychiatric teams in the management of the psychotic patient with medical illness.

Adult↗
PubMed1990

Transient expression of neurofilament protein during hair cell development in the mouse cochlea.

A polyclonal antiserum raised against the 145 kDa neurofilament protein (NFM) has been used to study the distribution of neurofilaments both in organotypic cultures of the early postnatal mouse cochlea and during development of the mouse cochlea in vivo. In the cultures, both the inner hair cells and the outer hair cells are stained by the antibodies, as well as the innervating afferent fibres from the spiral ganglion. In cultures denervated at the time of preparation, neurofilament positive hair cells can still be detected after 7 days in vitro. NFM can also be detected by immunoblotting in such denervated cultures. Characteristic 10 nm diameter, cytoplasmic filaments can also be observed in cultured hair cells using transmission electron microscopy. Immunostaining of cryosections prepared from cochleas at embryonic days 17 and 19, and days 1, 2, 5, 10 and 21 post-partum reveals that hair cells transiently express NFM during their development in vivo. Expression of NFM in hair cells is first detected at embryonic day 19 in the basal region of the cochlea and, by 2 days post-partum, neurofilament positive hair cells are found throughout the entire length of the cochlea. By 10 days post-partum, staining of hair cells begins to diminish and, by 21 days post-partum, NFM can no longer be detected in hair cells.

Animals↗
PubMed1990

Effects of bromocriptine at parturition in the tammar wallaby, Macropus eugenii.

Female tammar wallabies were treated with the dopamine agonist bromocriptine at the end of pregnancy to suppress the peripartum pulse of plasma prolactin. The animals were subsequently observed, and a series of blood samples taken to define the hormonal profiles before and immediately after parturition. Birth was observed in 4/5 control animals and occurred in 8/9 bromocriptine-treated animals. The peripartum peak in plasma PGFM concentrations was not affected by bromocriptine although the pulse of prolactin normally seen at parturition was completely abolished. The timing of luteolysis was apparently unaffected, as plasma progesterone concentrations fell similarly in both treated and control animals immediately after parturition. However, all of the neonates of the bromocriptine-treated animals died within 24 h, possibly because of a failure to establish lactation. Subsequent onset of post-partum oestrus was delayed or absent both in control and in bromocriptine-treated animals, suggesting that the frequent blood sampling and disturbances in the peripartum period interfered with these endocrine processes. It is concluded that both prolactin and prostaglandin can induce luteolysis in the pregnant wallaby, but that the normal sequence of events results from a signal of fetal origin inducing a prostaglandin release from the uterus, which in turn releases a pulse of prolactin that induces a progesterone decline.

Animals↗
PubMed1990

Effects of prostaglandin and prolactin on luteolysis and parturient behaviour in the non-pregnant tammar, Macropus eugenii.

In Exp. 1 non-pregnant female tammars were injected, on Day 26 (the day parturition would normally occur) after removal of pouch young, with saline, 200 micrograms ovine prolactin or 5 mg PG and changes in plasma concentrations of progesterone, prolactin, PGF-2 alpha metabolite (PGFM), oestradiol-17 beta and LH were determined. Luteolysis occurred in females treated with prolactin alone, while treatment with PG first induced a rapid rise in prolactin and subsequently a significant decrease in plasma progesterone. After prolactin treatment the oestradiol peak, oestrus and the LH surge were advanced significantly compared to the saline-treated females. In Exp. 2 the effects of the same treatments as used in Exp. 1 were determined on Day 23 and again on Day 26 after removal of pouch young in non-pregnant females. On Day 23 both prolactin and PG induced significant elevations in plasma progesterone, but luteolysis did not occur. On Day 26 the treatments initially induced significant elevations in plasma progesterone but these were followed by luteolysis within 8-12 h after treatment. PG treatment induced parturient behaviour in the non-pregnant females within 3-21 min and this persisted during the period that plasma concentrations of PGFM were elevated. The results show that PG induces birth behaviour and the release of prolactin, while prolactin first induces an elevation of plasma progesterone concentrations and, in the mature CL on Day 26, subsequently induces luteolysis.

Animals↗
PubMed1990

Control of parturient behaviour by prostaglandin F-2 alpha in the tammar wallaby (Macropus eugenii).

Nulliparous female tammar wallabies during the non-breeding season and adult male wallabies were treated with PGF-2 alpha at doses of 0.008, 0.04, 0.2 and 1.0 mg/kg. All the male and female wallabies responded to the three highest doses by showing parturient behaviour. At the lowest dose 4/4 males and 1/4 females responded. The peak concentrations of PGF-2 alpha metabolite (PGFM) in the peripheral plasma after administration of 0.008, 0.04 and 0.2 mg PGF-2 alpha/kg were 0.70 +/- 0.08, 3.02 +/- 0.37 and 8.48 +/- 0.76 ng/ml (mean +/- s.e.m.). Since the peak plasma concentrations of PGFM at normal parturition are reported to be 2.5 +/- 0.9 ng/ml, parturient behaviour can be induced by physiological concentrations of exogenous PGF-2 alpha. The effectiveness of PGF-2 alpha in males indicates that parturient behaviour is probably a result of a direct action of PGF-2 alpha on the brain, rather than a response to uterine or vaginal contractions. These experiments confirm that PGF-2 alpha is an important behavioural hormone in the tammar wallaby.

Animals↗
PubMed1990

Interleukin-1 stimulation stabilizes GM-CSF mRNA in human vascular endothelial cells: preliminary studies on the role of the 3' AU rich motif.

To date, the notion that the AU rich motif in the 3' UT of GM-CSF mRNA can function as an IL-1 response element has not been adequately examined. We suspect that it must play some role because virtually all IL-1 inducible gene have AU rich 3' untranslated regions. Thus, we will continue to address these technical problems so that the hypothesis can be more clearly tested. Nonetheless, we can state with reasonable certainty that: 1) IL-1 induces expression of GM-CSF in EC by inducing accumulation of mRNA, 2) the GM-CSF gene is constitutively transcribed but the half life of the mRNA is short, 3) IL-1 induced mRNA accumulation results from stabilization of the transcript, 4) although most IL-1 responsive genes have AU-rich domains in their 3' untranslated regions, it is not yet clear that these AU-rich regions are sufficient to function as an IL-1 response element, and 5) murine L cells cannot be used for studies on the molecular biology of cytokine induction by IL-1.

Animals↗
PubMed1989

Translational blockade imposed by cytokine-derived UA-rich sequences.

The messenger RNAs specifying certain proteins involved in the inflammatory response and certain oncoproteins contain a conserved UA-rich sequence in the 3' untranslated region. This sequence, which is composed of several interspersed repeats of the octanucleotide UUAUUUAU, has been shown to destabilize mRNA in some eukaryotes. However, this effect is not seen when mRNAs are transferred to Xenopus oocytes, which made it possible to separate stability from translational regulation. For interferon, granulocyte-macrophage colony-stimulating factor, and c-fos RNAs, the UA-rich sequence was observed to preclude mRNA translation.

Animals↗
PubMed1989

Identification of previously unrecognized sequence motifs at the extreme carboxyterminus of the neurofilament subunit NF-M.

Two previously unrecognized features of neurofilament architecture are revealed by careful analysis of published neurofilament sequences. 1. The extreme C-terminus of the NF-M tail contains two highly conserved homologous sequences each of 15 amino acids, with the consensus EEK-V-TKKVEK-TS, plus another very closely related 7 amino acid sequence. 2. The C-terminus of NF-M contains sequences of consensus K-SP or K--SP which in some species are multiply repeated, are probably phosphorylated, but are distinct from the more obvious KSP repeated sequences. Sequences related to both the K-SP and K--SP sequences are found in NF-H, microtubule associated proteins tau and MAP2, suggesting a further level of immunological and potential evolutionary relationship between neurofilaments and these microtubule associated proteins. The possible significance of these findings is discussed.

Amino Acid Sequence↗
PubMed1989

Congenital cardiac anomalies in relation to water contamination, Santa Clara County, California, 1981-1983.

In November 1981, a leak of solvents from an underground storage tank was detected at an electronics manufacturing plant in Santa Clara County, California. Solvents (predominantly 1,1,1-trichloroethene, or methyl chloroform) were found in a nearby well which supplied drinking water to the surrounding community. Residents were concerned about a possible relation between adverse reproductive outcomes and consumption of contaminated water. To address this concern, the California Department of Health Services conducted two epidemiologic studies: one of these, reported here, is a county-wide study of cardiac anomalies. This study, which looked at major cardiac anomalies among births throughout Santa Clara County in 1981-1983, found an increased prevalence in the service area of the water company which operated the contaminated well. During the potentially exposed time period (January 1981 through August 1982), 12 babies with major cardiac anomalies were born to residents of this area. This represents an excess of six cases over the number expected based on the prevalence in the remainder of the county (relative risk = 2.2, 95 per cent confidence interval 1.2-4.0). No excess was observed in the unexposed time period (September 1982 through December 1983). However, the temporal distribution of major cardiac cases born during the exposed time period suggests that the solvent leak is an unlikely explanation for this excess.

California↗
PubMed1989

Zeatin Glycosylation Enzymes in Phaseolus: Isolation of O-Glucosyltransferase from P. lunatus and Comparison to O-Xylosyltransferase from P. vulgaris.

An enzyme catalyzing the formation of O-glucosylzeatin in immature embryos of Phaseolus lunatus was purified 2500-fold using ammonium sulfate precipitation followed by affinity and anion exchange chromatography. The enzyme uses trans-zeatin as substrate (K(m) 28 micromolar) but not cis-zeatin, ribosylzeatin, or dihydrozeatin. Both UDP-glucose and UDP-xylose can serve as glycosyl donors, with K(m)s of 0.2 and 2.7 millimolar, respectively, for the formation of O-glucosylzeatin and O-xylosylzeatin. In comparison, the UDPxylose-zeatin:O-xylosyltransferase (JE Turner, DWS Mok, MC Mok, G Shaw [1987] Proc Natl Acad Sci USA 84: 3714-3717) isolated by the same procedures from P. vulgaris embryos uses only UDP-xylose as donor substrate and the K(m)s for both zeatin and UDP-xylose are much lower (2 and 3 micromolar, respectively). The chromatographic behavior on affinity columns and molecular weights (approximate M(r) 44,000 daltons) of the two enzymes are similar. Results from substrate competition experiments and enzyme separation by anion exchange HPLC indicate a single, distinct, zeatin O-glycosylation enzyme occurs in embryos of each of these Phaseolus species.

Journal Article↗
PubMed1989

An enzyme mediating the conversion of zeatin to dihydrozeatin in phaseolus embryos.

A reductase catalyzing the conversion of zeatin to dihydrozeatin was detected in soluble fractions of immature Phaseolus vulgaris embryos. The enzyme was partially purified by ammonium sulfate fractionation and affinity, gel filtration, and anion exchange chromatography. NADPH was the only cofactor required for enzyme activity, and the pH optimum was 7.5 to 8.0. The enzyme did not recognize compounds closely related to zeatin, such as ribosylzeatin, cls-zeatin, O-xylosylzeatin, N(6)-(Delta(2)-isopentenyl)adenine, or N(6)-(Delta(2)-isopentenyl)adenosine. No conversion of dihydrozeatin to zeatin by the enzyme was observed. Two forms of the reductase could be separated by either gel filtration or anion exchange high performance liquid chromatography. The high molecular weight isozyme (M(r) 55,000 +/- 5,000) eluted as the second peak from the anion exchange column, while the low molecular weight isozyme (M(r) 25,000+/- 5000) was less negatively charged. The results suggest that side chain reduction occurs at the free base level. In addition, Phaseolus embryos are useful for the detection of zeatin-specific metabolic enzymes.

Journal Article↗
PubMed1989

Human vascular endothelial cells, granulopoiesis, and the inflammatory response.

We have carried out a series of in vitro studies designed to characterize the role of mononuclear phagocytes as regulators of hematopoiesis. The results of these studies have demonstrated that mononuclear phagocytes produce factors, including interleukin-1 (IL-1), that induce the expression of multilineage hematopoietic growth factors by human vascular endothelial cells. In more recent studies we and others have identified these induced factors as G-CSF, GM-CSF, IL-6, and IL-1. Interleukin 1 stimulates expression of these genes by inducing the accumulation of gene transcripts. Moreover, transcript accumulation, at least with GM-CSF, results from prolongation of mRNA half-life. Based on preliminary studies in a cell-free system, we propose that the inductive capacity of IL-1 results from its activation of ribonuclease inhibitors in the cytoplasm of IL-1-induced cells and hypothesize that this may be a general mechanism by which IL-1 induces gene expression.

Biomechanical Phenomena↗
PubMed1989

Serum placental-like alkaline phosphatase (PLAP): a novel combined enzyme linked immunoassay for monitoring ovarian cancer.

A new combined enzyme linked immunoassay (ELISA) was developed to measure both serum placental-like alkaline phosphatase (PLAP) activity (PLAPA) and concentration (PLAPC) in the same microtitre plate using an Imperial Cancer Research Fund monoclonal antibody, designated H17E2. PLAP A and PLAP C were determined together with an existing marker, CA125 in 397 serial samples from 87 patients with epithelial ovarian cancer. Retrospective assessment showed the sensitivity to increase from 73% with CA125 alone, to 88% using CA125 and PLAP A, and to 93% with all three markers in 261 samples from the patients with known active disease at the time of sampling. When the results for all 397 samples were included in the analysis, however, the specificity, sensitivity, accuracy and predictive powers of this monoclonal antibody were not sufficiently high to assist in the prospective follow up of patients with ovarian cancer. This was due to a significant number of false positive and false negative results. Our data indicate that PLAP A or PLAP C estimation with H17E2 may, therefore, only be of value in the management of those patients with known active disease who are already known to be "marker positive" for this antigen.

Adenocarcinoma↗
PubMed1988

The effect of axotomy and deafferentation on phosphorylation dependent antigenicity of neurofilaments in rat superior cervical ganglion neurons.

Previous immunocytochemical studies have shown immunological differences between neurofilaments in axons and those in dendrites and perikarya of many mature neuron types: it is now known that non-phosphorylated epitopes are normally seen in cell bodies and dendrites of mature neurons, whereas phosphorylated epitopes are observed in axons. Further studies on a variety of cell types have shown that phosphorylated epitopes are induced in the cell-body associated neurofilaments following axotomy, and we show here that comparable changes are observed in axotomized rat superior cervical ganglion neurons (SCG). We have also observed that preganglionic section induces similar changes in the levels of neurofilament phosphorylation, so that phosphorylated epitopes become visible in the cell bodies and dendrites of denervated neurons. The changes in this case appear more slowly and are accompanied by the appearance of punctate nuclear staining detectable with phosphorylation sensitive neurofilament antibodies. The acquisition of these staining patterns by both the axotomized and denervated SCG cells proved to be reversible, so that after 10-12 days no neurons in either experimental group exhibited perikaryal phosphorylated epitopes. These results indicate that changes in the level of neurofilament phosphorylation are not only associated with neuronal damage, but can also be induced by deafferentation.

Afferent Pathways↗