Search PubMed⌕ Search

Biomedical subjects

G E Rice

Publications and source records attributed to G E Rice.

At least 127 records · Page 7Linked to original sources
PubMed1986

Prose recall: effects of aging, verbal ability, and reading behavior.

This paper describes an exploratory multivariate analysis designed to determine the relative contributions of age, verbal ability, education, reading habits, and recall strategies to the explanation of variation in performance on prose recall tasks among adults. Four hundred twenty-two adults in three age groups--young (18 to 32), middle (40 to 54) and old (62 to 80)--read and recalled in writing two 388-word prose passages and answered questions about their background, reading habits, and recall strategies. Results indicate that a decrease in quantity of recall appears with increasing age, though verbal ability is a better predictor of recall than is age. In addition, a recall strategy factor representing a paragraph-by-paragraph retrieval strategy produces the highest simple correlations with total recall and contributes significantly to the other recall measures.

Adolescent↗
PubMed1986

Secretion of oxytocin and progesterone by ovine corpora lutea in vitro.

The mechanisms involved in the control of oxytocin and progesterone secretion by the ovine corpus luteum have been investigated in vitro using luteal slice incubations. Oxytocin and progesterone were secreted at constant rates from luteal slices for 2 h of incubation (366 +/- 60 pg X mg X h and 18.9 +/- 0.18 ng X mg X h, respectively). Secretion of progesterone, but not of oxytocin, was significantly (p less than 0.02) stimulated in the presence of ovine luteinizing hormone. Incubation of luteal slices in medium containing 100 mM potassium, however, resulted in increased secretion of oxytocin and, to a lesser extent, of progesterone (294 +/- 59% and 142 +/- 15%, respectively, p less than 0.05). Basal oxytocin secretion was reduced during incubation in calcium-free medium, compared to secretion in the presence of calcium (70 +/- 15 and 175 +/- 25 pg X mg X 20 min, respectively, p less than 0.01), whereas progesterone secretion was not altered in the absence of calcium. Secretion of both hormones by luteal slices was stimulated by the addition of the calcium ionophore A23187 (p less than 0.05). Addition of prostaglandin F2 alpha (2.8 microM) had no effect on secretion of either oxytocin or progesterone. We have demonstrated that oxytocin and progesterone can be stimulated, independently, from corpus luteum slices incubated in vitro. The pattern of release is consistent with the proposal that oxytocin, but not progesterone, is associated with and actively released from luteal secretory granules. Our results also indicated that prostaglandin F2 alpha does not directly stimulate release of oxytocin or progesterone from luteal cells in vitro.

Animals↗
PubMed1986

Comparison of particle-associated progesterone and oxytocin in the ovine corpus luteum.

The subcellular distribution of progesterone and oxytocin within the ovine corpus luteum was investigated using differential and density gradient centrifugation. Progesterone and oxytocin were associated with particles which sedimented to a density of 1.049-1.054 g/ml and 1.054-1.061 g/ml respectively. Particle-associated progesterone did not, however, display physical or biochemical characteristics consistent with its storage within secretory granules. When particle-associated progesterone was incubated in HEPES buffer at 37 degrees C, 70% of the total progesterone was recovered in the incubation medium. The remaining stable particle-associated progesterone was not affected by treatments which stimulated oxytocin release and which have been shown to cause the release of peptides and biogenic amines from secretory granules. These results suggest that particle-associated progesterone represents the intercalation of progesterone into cell membranes and they do not support the hypothesis that progesterone is stored, in a protein-bound form, in luteal secretory granules.

Animals↗
PubMed1986

Characterization of particle-associated choriomammotrophin and progesterone in ovine placentomes.

The subcellular distribution and compartmentalization of choriomammotrophin (CM) and progesterone within ovine placentomes was investigated using differential and density gradient centrifugation techniques. Approximately 67% of placental CM and 45% of progesterone was associated with subcellular particles. The 10,000 g particulate fraction contained the highest specific activity of both CM and progesterone (19.1 +/- 3.8 (S.E.M.) micrograms/mg and 71.5 +/- 9.2 pmol/mg protein respectively). This fraction was also shown to contain electron-dense granules with morphology similar to that of hormone-containing secretory granules isolated from other endocrine tissues. Particle-associated CM sedimented to a density of 1.051-1.054 g/ml in colloidal silica gradients and displayed physicochemical characteristics consistent with its storage in secretory granules. During in-vitro incubations, particle-associated CM was stable for up to 90 min, but dissociated when incubated in hypoosmotic medium. Particulate progesterone, which was also present in the CM-rich fraction and was stable for up to 90 min of incubation, was not affected by decreasing the osmolality of the incubation medium. These data suggest that ovine CM (but not progesterone) is stored within a population of secretory granules located within placentomes.

Animals↗
PubMed1985

Plasma concentrations of arginine vasotocin, prolactin, aldosterone and corticosterone in relation to oviposition and dietary NaCl in the domestic fowl.

The osmolality and concentrations of Na, K, Cl and the hormones arginine vasotocin (AVT), prolactin, aldosterone and corticosterone were measured in plasma as functions of time in relation to oviposition, changing NaCl content of the diet, and feeding-inanition. AVT was significantly increased immediately after oviposition (but not during the hour before) with a calculated average value of 38.0 +/- 4.1 pg/ml at oviposition. A moderate increase in concentrations of prolactin and corticosterone were observed immediately after oviposition. Oviposition was not associated with detectable changes in plasma osmolality (and electrolyte concentrations) nor with the concentration of aldosterone. After a sudden change from a high NaCl diet to a low NaCl diet the plasma osmolality and concentrations of NaCl, AVT and prolactin reached new stable levels in 24 hr, whereas the plasma aldosterone concentration required more than 4 days to reach a steady level. After resalination plasma aldosterone was suppressed in less than 8 hr. Both osmolality and concentrations of AVT and prolactin showed transient overshoots during the first 24 hr. NaCl depletion resulted in a transient increase of corticosterone.

Aldosterone↗
PubMed1985

Subcellular localization of oxytocin in the ovine corpus luteum.

The subcellular localization of oxytocin within the corpus luteum of sheep was investigated using differential and density gradient centrifugation. Oxytocin was associated with a particulate fraction which sedimented to a density of 1.054-1.061 g/mL. The exclusion of [3H]oxytocin from this particulate fraction is indicative that particulate oxytocin represents endogenous compartmentalization. Particulate oxytocin, incubated in buffered medium at 37 degrees C, was stable for up to 1 h and the release of oxytocin was not affected by the pH of the incubation medium, over the range 5.5-8.5. Oxytocin release, however, was stimulated by incubating particle-bound oxytocin in buffered medium of low osmolality (less than 200 mosmol). These data are similar to the physicochemical properties reported for peptide-containing neurohypophysial secretory granules. Ultrastructural analysis of oxytocin-containing fractions revealed the presence of electron-dense granules (diameter, 200-250 nm). These data are suggestive that oxytocin, in the corpus luteum of sheep, is contained within a population of secretory granules which occur in high numbers during the midluteal phase of the oestrous cycle.

Animals↗
PubMed1983

Aging-related reduced release of LH-releasing hormone from hypothalamic granules.

The effects of aging on the secretory function of hypothalamic granules containing luteinizing hormone releasing hormone (LHRH) were examined, using chelated copper as a test substance. Granules prepared from old and young female rats were each incubated with various concentrations of CuATP and the kinetic constants of LHRH release estimated. The LHRH content of the hypothalamus of old female rats (3.4 +/- 0.1 ng; mean +/- S.E.; n = 3 determinations) was lower than that of young female rats (4.7 +/- 0.1 ng; n = 3). CuATP-stimulated LHRH release (pg/hypothalamus) from granules isolated from old animals was significantly (p less than 0.001) lower than that from granules isolated from young animals; Vmax being 58.5 +/- 1.6 pg (n = 36) and 76.7 +/- 2.7 pg (n = 34) of LHRH released/min, respectively. In contrast, the fractional amount of CuATP-stimulated release of LHRH from granules isolated from old and young rats was similar; Vmax being 60 +/- 0.5% and 62 +/- 1% of granule LHRH released, respectively. In addition, the apparent Km for CuATP-stimulated release of LHRH from granules of old and young rats was also similar, 5.1 and 5.5 microM copper, respectively. These results are suggestive that aging does not alter the responsiveness of LHRH-containing granules to a secretion-stimulus such as copper but it does alter the capacity (amount) of peptide released.

Adenosine Triphosphate↗
PubMed1983

Copper-induced release of immunoreactive alpha-melanotropin from isolated hypothalamic granules.

Previously, we demonstrated that copper chelates stimulate the release of luteinizing hormone releasing hormone (LHRH) from isolated hypothalamic granules. To assess the generality of the copper-stimulated release process, we determined the effects of copper on the release of immunoreactive alpha-melanotropin (alpha-MSHi) from isolated granules. When granules were incubated with various copper complexes, CuATP stimulated alpha-MSHi release by 54 +/- 6% (mean +/- S.E.), Cu tartarate by 56 +/- 4%, CuBSA by 32 +/- 5% and Cu histidine by 29 +/- 2%. CuATP-stimulated alpha-MSHi release from granules incubated under N2 was 57% of that incubated under air. Furthermore, the reducing agent dithiothreitol (DTT) inhibited CuATP-stimulated alpha-MSHi release (p less than 0.01), whereas oxidized DTT did not do so. Pretreatment of granules with the thiol-blocking reagents iodoacetic acid or 5, 5'-dithiobis-(2-nitrobenzoic acid) inhibited CuATP-stimulated alpha-MSHi release by 52 +/- 3 and 38 +/- 4%, respectively. Thus, chelated copper, rather than ionic copper, is the active form of the metal and the action of copper involves the oxidation of thiols. These data are similar to those previously observed for the copper-stimulated release of LHRH. Hence, the effects of copper on the permeability of granule membranes may be a generalized phenomenon which underlies susceptibility of storage granules to the reduction-oxidation status of the cellular milieu.

Animals↗
PubMed1983

A possible role for copper-mediated oxidation of thiols in the regulation of the release of luteinizing hormone releasing hormone from isolated hypothalamic granules.

A role for copper in the release of luteinizing hormone releasing hormone (LHRH) from hypothalamic neurons has been previously proposed. To elucidate further the mechanism of action of copper, we addressed two questions: (a) what is the active form of copper that interacts with the LHRH granule (ionic or chelated)? and (b) is copper-stimulated LHRH release a result of an interaction of copper with thiol groups and, if so, does it require oxygen? Granules were isolated from hypothalami of adult male rats and were then incubated at 37 degrees C for 3-5 min in a buffered medium. When granules were incubated with various copper complexes, CuATP stimulated LHRH release by 45 +/- 4% (mean +/- SE), copper tartrate by 44 +/- 4%, CuBSA by 27 +/- 7%, and copper histidine by 16 +/- 6%. Neither CuEDTA nor CuCl2 stimulated LHRH release. CuATP-stimulated LHRH release from granules incubated under N2 was 50% of that incubated under air. Furthermore, the CuATP-stimulated release of LHRH was completely inhibited by dithiothreitol or glutathione (10(-3) M each), partially (40-50%) by iodoacetate or 5,5-dithiobis-(2-nitrobenzoic acid), and not at all by oxidized dithiothreitol. Thus, chelated copper, rather than ionic copper, is the active form of the metal, and the action of copper involves an oxidation reaction and granule thiol groups. The precise mechanism of action of copper, however, has yet to be elucidated. We propose that copper may affect LHRH release as follows: copper, bound to an intracellular chelator (protein, peptide, or amino acid), oxidizes thiols of the LHRH granule, leading to a change in granule-membrane permeability and hence to LHRH release.

Adenosine Triphosphate↗
PubMed1981

Information recalled from prose by young, middle, and old adult readers.

The effects of organizational variables in prose on recall are examined for college-educated adults in three age groups. If older adults suffer a deficit in organizational processes [3], this may be manifest in lower in lower quantities of prose recall, difficulty in identifying and following the text's structure and main ideas, and diminished "levels effects" (information high in the hierarchical text structure recalled better than information low). The study reported tests these implications using Meyer's [15] prose analysis system to identify text structure. No age differences were found in total recall and recall of main ideas. However, young adults exhibited the typical " levels effects," while middle and old adults did not. This difference was attributed to the effects of current schooling practices on the youngest group, rater than organizational or reading comprehension deficits in the aged.

Adult↗
PubMed1980

Slow fluorescence fluctuations following high light to low light or dark transitions in Chlamydomonas reinhardi.

Slow fluorescence transients in Chlamydomonas reinhardi arise after transitions from high light intensities to low light or dark conditions. Characteristics of the newly described transient phenomena include: (a) A slow biphasic decrease in fluorescence yield occurs in the dark, followed by an even slower, hour long, increase in fluorescence. (b) A similar, but faster, fluorescence yield decrease and subsequent increase also occurs during low intensity illumination periods separating high light intervals, or after transitions from high intensity to low intensity light. (c) Short (several seconds) flashes of light given during a dark period have no effect on the dark fluorescence decay, regardless of the flash frequency. Such flash regimes accurately monitor the dark decline of the M2 level by tracing the parallel decay of flash-generated P2 (Kautsky) peaks. However, flashes during a low light illumination period do influence the decay kinetics. Frequent flashes allow decay similar to that occurring in dark, but less frequent flashes inhibit the decrease in fluorescence yield.

Chlamydomonas↗
PubMedDate not supplied

Immunoreactive prostaglandin G/H synthase content increases in ovine cotyledons during late gestation.

In this study, using gel electrophoresis and Western blotting, we have demonstrated that the content of irPGHS in ovine placenta increases during late gestation prior to the onset of labour. This increase in PGHS tissue content may contribute to the corresponding increased production of prostaglandins by the ovine placenta during this period of pregnancy. Although the mechanism by which PGHS tissue content is elevated at this time remains to be established, one possibility which is currently being investigated in our laboratory is that increased PGHS content reflects an increased level of PGHS gene expression.

Animals↗
PubMedDate not supplied

Effect of nuclear factor-kappa B inhibitors and peroxisome proliferator-activated receptor-gamma ligands on PTHrP release from human fetal membranes.

Parathyroid hormone-related protein (PTHrP) has been implicated in many processes during normal and pathological pregnancies. In the human fetal membranes, PTHrP exhibits cytokine-like actions. We have recently shown that inhibitors of the nuclear factor-kappa B (NF-kappaB) and activators of the peroxisome proliferator-activated receptor (PPAR)-gamma signalling pathways down-regulate cytokine release from human gestational tissues. Therefore, the aim of this study was to determine whether NF-kappaB and PPAR-gamma also regulate PTHrP release from human fetal membranes. Human amnion and choriodecidua explants were incubated in the absence (control) or presence of two known NF-kappaB inhibitors (1, 5 and 10 mM sulphasalazine (SASP) or 5, 10 and 15 mM N-acetyl-cysteine (NAC)), and two PPAR-gamma ligands (15 and 30 microM 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) or 15 and 30 microM troglitazone), under basal conditions. After 18 h incubation, the tissues were collected and NF-kappaB p65 DNA binding activity in nuclear extracts was assessed by ELISA, and the incubation medium was collected and the release of PTHrP was quantified by RIA. Treatment of amnion and choriodecidual tissues with SASP concentrations greater than 5 mM, 15 mM NAC, 30 microM 15d-PGJ(2) and 30 microM troglitazone significantly reduced the release of PTHrP (p < 0.05). This study demonstrates that PTHrP release from human fetal membranes is regulated by inhibitors of NF-kappaB, and ligands of PPAR-gamma.

Acetylcysteine↗
PubMedDate not supplied

Stimulation of ovine choriomammotrophin release, in vitro, by phospholipase C.

Phospholipid metabolites have previously been implicated in receptor-mediated stimulation of protein hormone secretion. As the factors which regulate the release of choriomammotrophin remain to be elucidated, we investigated the potential involvement of phospholipase C-induced phospholipid metabolism in the release of this placental hormone. Phospholipase C (PLC) caused a dose-dependent release of choriomammotrophin from ovine placenta, incubated in vitro. At a concentration of 0.2 units/ml (0.25 microgram protein/ml), PLC caused the release of choriomammotrophin from placental tissue to approximately double that observed in control incubations (7.08 +/- 0.4 micrograms/50 mg/h and 3.26 +/- 0.3 micrograms/50 mg/h, respectively). PLC treatment did not significantly alter plasma membrane permeability, as indicated by the release of lactate dehydrogenase and protein. PLC-stimulated release of oCM was completely abolished by incubation in calcium-free medium or by preincubation with the inorganic calcium-channel blocking agents cobalt chloride (4 mM) and lanthanum chloride (1 mM). The effects of PLC treatment on ovine choriomammotrophin (oCM) release were also inhibited by preincubation of placental tissue with inhibitors of arachidonic acid metabolism: ibuprofen (10(-5) M), naproxen (10(-4) M) or nordihydroguaiaretic acid (NDGA) 5 X 10(-6) M). These results suggest that the effects of PLC on the release of choriomammotrophin are mediated via metabolites of arachidonic acid.

Animals↗