Biomedical subjects

R J Rodgers

Publications and source records attributed to R J Rodgers.

At least 163 records · Page 9Linked to original sources

PubMed1987

Regulation of the synthesis of 3-hydroxy-3-methylglutaryl coenzyme A reductase in the bovine ovary in vivo and in vitro.

In order to investigate the pattern of ovarian cholesterol biosynthesis during the bovine estrous cycle, tissue concentrations of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, a rate-limiting enzyme in the synthesis of cholesterol, were determined by immunoblot techniques. Medium-sized (9-11 mm) and large (14-18 mm) follicles, after removal of follicular fluid by centrifugation, and corpora lutea from the early, early-mid, late-mid, and late stages of the luteal phase were used (n = 5 per group). The specific content (per microgram of tissue homogenate protein) and total content of HMG-CoA reductase in medium-sized and large follicles were substantially lower than those of corpora lutea of the early-mid and late-mid luteal phase. The specific content was elevated in a number of the corpora lutea from the early luteal phase and was low in regressing corpora lutea. Thus during the midluteal phase, when steroid hormone production is elevated, the total and specific contents of HMG-CoA reductase are also elevated. To investigate the mechanisms whereby the levels of HMG-CoA reductase are regulated, primary monolayer cultures of bovine luteal cells (early-mid and late-mid luteal phase) were used. Cells were cultured for 24 h in Dulbecco's modified Eagle's medium containing lipoprotein-poor fetal calf serum (2% vol/vol). At this concentration there was no stimulation of the production of progesterone above that seen with no addition of serum. Under these conditions the total and specific contents, and the synthesis, of HMG-CoA reductase were stimulated by treatment with (Bu)2cAMP (1 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Levels of messenger ribonucleic acid encoding cholesterol side-chain cleavage cytochrome P-450, 17 alpha-hydroxylase cytochrome P-450, adrenodoxin, and low density lipoprotein receptor in bovine follicles and corpora lutea throughout the ovarian cycle.

To investigate the molecular basis for the pattern of ovarian steroid production during the bovine estrous cycle, the relative levels of mRNA specific for cholesterol side-chain cleavage cytochrome P-450, 17 alpha-hydroxylase cytochrome P-450, adrenodoxin, and low density lipoprotein receptor were determined in ovarian antral follicles of differing size (less than 3-18 mm) and corpora lutea from the early, early-mid, late-mid, and regressionary stages. Total and poly(A)+ RNA was size-fractionated on agarose-formaldehyde gels, transferred to nylon filters and hybridized to specific 32P-labeled probes. The levels of mRNAs for the rate-limiting enzymes in the conversion of cholesterol into progesterone, namely cholesterol side-chain cleavage cytochrome P-450 and its electron donor, adrenodoxin, were higher in corpora lutea than in follicles. Conversely the levels of mRNA specific for the key regulatory enzyme in the conversion of pregnenolone or progesterone to androgen, namely 17 alpha-hydroxylase cytochrome P-450, were high in all antral follicles examined but were low in young corpora lutea and undetectable in more mature corpora lutea. Low density lipoprotein receptor mRNA was detectable in antral follicles and corpora lutea but the levels were greater in corpora lutea. These results suggest that the pattern of changes in steroid hormone biosynthesis during the bovine estrous cycle and in the ovarian content of steroidogenic enzymes is related to and probably dependent upon the pattern of change in levels of mRNAs for steroidogenic enzymes and related proteins.

Adrenodoxin↗

PubMed1986

The insulin-like growth factor, somatomedin C, induces the synthesis of cholesterol side-chain cleavage cytochrome P-450 and adrenodoxin in ovarian cells.

The actions of insulin and somatomedin C (insulin-like growth factor I) on cholesterol side-chain cleavage activity and the synthesis of cytochrome P-450scc and adrenodoxin were investigated in primary cultures of swine ovarian (granulosa) cells. Nanomolar concentrations of pure human somatomedin C stimulated biosynthesis of progesterone and 20 alpha-hydroxypregn-4-en-3-one. Moreover, in the presence of exogenous sterol substrate for cholesterol side-chain cleavage, somatomedin C significantly enhanced pregnenolone biosynthesis in a time- and dose-dependent manner. This augmentation of functional cholesterol side-chain cleavage activity was accompanied by a dose-dependent (2-16-fold) increase in [35S]methionine incorporation into specific immunoprecipitable cytochrome P-450scc and adrenodoxin. Micromolar concentrations of insulin (but not proinsulin or desoctapeptide) also induced synthesis of cholesterol side-chain cleavage constituents by 4-7-fold. These results demonstrate that an insulin-like growth factor, somatomedin C, exerts discrete differentiating effects on ovarian cells characterized by increased synthesis of immunospecific cytochrome P-450scc and adrenodoxin. Thus, we infer that somatomedin C may serve a critical role in the differentiation of steroidogenic cells in the mammalian ovary.

Adrenodoxin↗

PubMed1986

Extended attack from a resident conspecific is critical to the development of long-lasting analgesia in male intruder mice.

Recent studies have shown that intruder mice display qualitatively different forms of analgesia in response to social encounters with resident conspecifics. An acute (non-opioid) reaction is evident when display of defeat is used as test criterion whereas a much longer-lasting (opioid) response is observed when this criterion is exceeded. Neither reaction can be readily attributed to the effects of physical stimulation per se. Two studies were conducted to determine the critical stimulus leading to a 'switchover' from non-opioid to opioid analgesia in intruder mice. The pattern of results indicates that temporal factors per se are unimportant but that extended exposure to attack is essential to the development of an enduring (opioid-typical) analgesia. It is argued that this finding is consistent with the uncontrollability hypothesis which asserts that opioid analgesia is a consequence of a failure in behavioural coping strategies.

Aggression↗

PubMed1986

Resident's scent: a critical factor in acute analgesic reaction to defeat experience in male mice.

Although it has recently been reported that defeated male mice evidence an acute non-opioid analgesia, little is currently known about the specific features of the defeat experience with which the analgesic reaction is associated. The present experiments not only confirm that defeat experience reliably induces acute antinociception in intruder mice, but show that a similar reaction also occurs as a consequence of exposure to an aggressive resident which does not attack during the brief test period, a well-characterized non-aggressive resident and the 'unoccupied' soiled home cage of an aggressive resident. Results also indicated that, with appropriate exposure duration, scent alone can give rise to a quantitatively similar analgesia to that observed in defeated mice. Furthermore, time-course comparisons and the absence of naloxone antagonism suggest that 'scent' and 'defeat' analgesias are mediated via a common non-opioid mechanism. Data are discussed in relation to the ecological significance of urinary odours in social communication in mice.

Aggression↗

PubMed1986

Acute non-opioid analgesia in defeated male mice.

Exposure to repeated attack induces a long-lasting analgesia in male mice. Although this reaction has been linked to the special biological significance of defeat, earlier research has confounded defeat and exposure to further attack. In the present studies, DBA/2 intruder mice were individually placed into the home cages of aggressive conspecifics and removed immediately upon display of the species-characteristic upright submissive posture. Under these test conditions, intruders did indeed show a profound analgesia. However, in marked contrast to the antinociceptive effects of repeated attack, this reaction was of short duration (less than 10 min), was not blocked by naloxone (1-10 mg/kg, IP) and did not show cross-tolerance either to or from morphine (5 mg/kg, IP). These findings are discussed in relation to multiple endogenous pain inhibitory systems and their possible adaptive significance in murine social behaviour.

Adaptation, Physiological↗

PubMed1986

Adverse cognitive effects of general anaesthesia in young and elderly patients.

For many years, reports have appeared indicating cognitive deficits in elderly patients following anaesthesia. However, there is no general consensus of opinion concerning the putative relationship between these deficits and the anaesthetic process. In a prospective study, 85 patients undergoing elective surgery were assessed on a battery of standardized cognitive tests, 1 day before and 2 days after surgery. Analysis of results indicated that anaesthesia does produce post-operative cognitive deficits in both young and elderly patients, and a possible causative mechanism is discussed.

Age Factors↗

PubMed1986

Cytochromes P-450scc, P-450(17)alpha, adrenodoxin, and reduced nicotinamide adenine dinucleotide phosphate-cytochrome P-450 reductase in bovine follicles and corpora lutea. Changes in specific contents during the ovarian cycle.

To investigate the basis for the pattern of ovarian steroid production during the bovine estrous cycle, the tissue concentrations of major steroidogenic enzymes, 17 alpha-hydroxylase cytochrome P-450 and cholesterol side-chain cleavage cytochrome P-450 (cytochrome P-450scc), and their respective electron donors, NADPH-cytochrome P-450 reductase and adrenodoxin, were estimated and compared with those of the nonsteroidogenic enzymes, cytochrome c oxidase and F1-ATPase. The levels of these enzymes were estimated in medium sized (9-11 mm) and large (14-18 mm) follicles after removal of follicular fluid by centrifugation, and corpora lutea from the early, early-mid late-mid, and late stages of the luteal phase (n = 5 per group). The specific contents of all enzymes and electron donors were determined by immunoblot analysis, except for cytochrome c oxidase, which was quantified by determination of specific activity. The specific (per microgram of tissue homogenate protein) and total (per follicle or corpus luteum) tissue contents of 17 alpha-hydroxylase cytochrome P-450 increased 0.5- and 5-fold respectively from medium sized to large follicles, but then decreased to undetectable levels in corpora lutea in the early luteal phase, and remained undetectable throughout the luteal phase. In contrast, the specific content of NADPH-cytochrome P-450 reductase was similar between follicles and corpora lutea. The specific contents of cytochrome P-450scc, adrenodoxin and cytochrome c oxidase in follicles were similar to those of corpora lutea of the early luteal phase. However, by the early-mid luteal phase the specific contents of luteal cytochrome P-450scc (490 +/- 46 vs. 5709 +/- 982 cpm/micrograms protein) and adrenodoxin (44 +/- 15 vs. 705 +/- 229 cpm/micrograms protein) were increased, by 12- and 15-fold, respectively (P less than 0.05). In contrast, cytochrome c oxidase activity (29.1 +/- 10.1 vs. 108.6 +/- 20.7 nmol/mg tissue protein X min) and the specific content of F1-ATPase increased only 3- to 4-fold reflective of an increase in numbers of mitochondria. The levels of these enzymes remained elevated until the late luteal phase when they declined markedly. It is concluded that the induction of synthesis of P-450scc and adrenodoxin after ovulation is specific and does not merely reflect biogenesis of mitochondria during luteinization. Moreover the changes in the types of steroids produced by the ovarian compartments throughout the estrous cycle are a reflection of changes in the tissue content of steroidogenic enzymes.

Adrenodoxin↗

PubMed1986

Synergistic actions of estradiol and the insulin-like growth factor somatomedin-C on swine ovarian (granulosa) cells.

Estradiol amplified synergistically the dose- and time-dependent stimulatory actions of human somatomedin-C on progesterone biosynthesis by cultured swine granulosa cells. This facilitative interaction was not attributable to inhibition of the catabolism of progesterone to 20 alpha-hydroxypregn-4-en-3-one, but, rather, reflected time-dependent stimulation of pregnenolone synthesis measured in the presence of exogenous soluble sterol substrate for cholesterol side-chain cleavage. Moreover, treatment with somatomedin-C was accompanied by increased synthesis of two immunoprecipitable cholesterol side-chain cleavage constituents, viz. cytochrome P-450scc and adrenodoxin. The synergism between estradiol and somatomedin-C was associated with significantly greater specific binding of somatomedin-C in estrogen-treated than control cultures, with no change in apparent receptor affinity. In vitro synergism occurred at somatomedin-C concentrations estimated by sequence-specific immunoassay to be attainable in ovarian follicular fluid in vivo and was specific in that it was not mimicked by the insulin-like peptide relaxin or by epidermal growth factor or fibroblast growth factor. However, high concentrations of insulin-like growth factor II (multiplication-stimulating activity) and insulin were able to interact with estradiol in a facilitative fashion to enhance progesterone production. In addition, the estrogenic component of the synergism was specific, since it was antagonized by the selective antiestrogen LY156758 and was mimicked sparingly by the nonaromatizable androgen 5 alpha-dihydrotestosterone. We conclude that estradiol and somatomedin-C interact synergistically in a time- and dose-dependent manner to enhance the biosynthesis of pregnenolone and progesterone by swine granulosa cells. Since estradiol and somatomedins are present in significant concentrations in the antral fluids of maturing Graafian follicles, we suggest that coordinated trophic effects of estradiol and insulin-like growth factor(s) may effectively prepare granulosa cells for the high rates of progesterone biosynthesis ultimately required after ovulation.

Animals↗

PubMed1986

Cellular composition of the sheep corpus luteum in the mid- and late luteal phases of the oestrous cycle.

Corpora lutea (CL) from naturally cycling Corriedale ewes were obtained in the mid- and late luteal phases of the oestrous cycle (Days 9 and 13; 5 ewes per group). The cellular composition of these CL was compared by ultrastructural morphometry to determine whether there were changes in numbers of large and small luteal cells consistent with differentiation of some small luteal cells to large luteal cells during the last part of the luteal phase. No differences between Days 9 and 13 were detected in luteal volume, plasma progesterone concentration, or volume density of any component of the luteal tissue. Large luteal cell numbers (mean +/- s.e.m.) were lower per unit volume of luteal tissue on Day 13 than on Day 9 (14.1 +/- 0.5 vs 18.4 +/- 1.3 X 10(3)/mm3, P less than 0.05). Mean volume of the individual large luteal cells was greater on Day 13 than on Day 9 (19.65 +/- 0.72 vs' 15.60 +/- 1.34 micrograms 3 X 10(3), P less than 0.05). However, there were no significant differences in numbers or volumes of small luteal cells between Days 9 and 13, and total numbers of large luteal cells per CL were not different between these two days. These results provide no support for the hypothesis that small luteal cells differentiate into large luteal cells during the oestrous cycle of the sheep.

Animals↗

PubMed1986

Immunolocalization of cholesterol side-chain-cleavage cytochrome P-450 and 17 alpha-hydroxylase cytochrome P-450 in bovine ovarian follicles.

Follicles were collected from cows and processed for electron microscopy and for immunofluorescent staining at the light microscope level. Key regulatory steroidogenic enzymes cholesterol side-chain-cleavage cytochrome P-450 (P-450scc) and 17 alpha-hydroxylase cytochrome P-450 (P-45017 alpha) were immunolocalized using specific IgG fractions raised against these enzymes. In larger follicles in which the theca interna had differentiated, positive staining for cytochromes P-450scc and P-450(17) alpha was observed in the cells of the theca interna. Electron microscopic examination showed that these cells were rich in endoplasmic reticulum, mainly rough, and had moderate numbers of mitochondria with tubular and lamellar cristae. Positive staining was also present in the theca of follicles undergoing atresia. Positive staining for cytochrome P-450(17) alpha was not observed in the membrana granulosa but cytochrome P-450scc was present in the membrana granulosa in some follicles, particularly in the larger antral follicles. By contrast, positive staining for both enzymes was not observed in stroma, surface epithelium or in small preantral follicles in which the theca interna had not differentiated. These results indicate good agreement between the type(s) of steroidogenic enzyme(s) present in tissues and the type(s) of steroid hormone(s) produced. It is concluded that regulation of steroid hormone production involves, at least in part, regulation of the levels of steroidogenic enzymes.

Animals↗

PubMed1986

Immunolocalization of cholesterol side-chain-cleavage cytochrome P-450 and ultrastructural studies of bovine corpora lutea.

Corpora lutea were collected from cows at four stages of the luteal phase and prepared for immunostaining at the light microscope level. Other corpora lutea, which were fully developed, were dispersed by collagenase treatment and freshly isolated and cultured cells were processed for immunostaining. Electron microscopy was carried out on mature corpora lutea and freshly isolated cells. Positive staining for cholesterol side-chain-cleavage cytochrome P-450 (P-450scc), an inner-mitochondrial membrane enzyme considered to catalyse the rate-limiting step in the conversion of cholesterol to progesterone, was observed in all corpora lutea. The intensity of staining was much greater in mature corpora lutea than in young or regressing corpora lutea. Only small and large luteal cells stained positively and cells of the vasculature and other connective tissue elements did not. When cells were cultured and had become flatter, the intensity of immunostaining was observed to be greater in large luteal cells than in small luteal cells which was interpreted to be due, in part, to the greater volume density of mitochondria in these cells. In some cultured small luteal cells the pattern of immunostaining appeared as whorls of strands encircling the nucleus. This pattern was interpreted as a three-dimensional network of mitochondria organized into 'strands', more than one mitochondrion in cross-section, perhaps formed during the process of attachment and elongation of the cells. Further observations made at the electron microscope level, included the presence of close (5-8 nm) contacts with interconnecting septa between small luteal cells in tissue.

Animals↗

PubMed1986

Control of gene expression of adrenal steroid hydroxylases and related enzymes.

Utilization of cDNA probes specific for various components of the bovine adrenocortical steroidogenic pathway have led to the conclusion that there are three levels of regulation of steroid hydroxylase gene expression. In each case it is postulated that specific classes of proteins bind to regulatory regions of these genes and modulate their transcription. Throughout adult life, cAMP-dependent regulation via SHIP protein(s) is the predominant mechanism by which optimal steroidogenic capacity is maintained. A second type of regulation is tissue-specific. One subclass of tissue-specific expression is the "all-or-none" type whereby steroid 21-hydroxylase and 11 beta-hydroxylase gene expression occur only in adrenal cortex and not in other steroidogenic tissues. A second subclass of tissue-specific expression is the "variable" type whereby 17 alpha-hydroxylase and cholesterol side chain cleavage (SCC) activity are both expressed in ovarian thecal cells but only SCC activity is expressed in corpus luteum. The third type of regulation is cAMP-independent and leads to fetal-imprinting (initial expression of steroid hydroxylase genes during fetal life).

Adrenal Cortex↗

PubMed1985

Naloxone potentiates the depressant effect of chlordiazepoxide on spontaneous activity in mice.

Recent reports suggest that at least some of the behavioural effects of benzodiazepines may involve interaction with endogenous opioid mechanisms. In the present study, chlordiazepoxide (CDP, 10-20 mg/kg, i.p.) induced dose-dependent reductions in spontaneous locomotor activity and rearing in mice. Although naloxone (1 mg/kg) was itself without effect, and did not alter behavioural changes induced by the lower dose of CDP, it enhanced the depressant effects of 20 mg/kg CDP on locomotor activity. Results are discussed in relation to previous studies in which opiate antagonists have been found to block or to have no effect upon behavioural actions of benzodiazepines.

Analysis of Variance↗

PubMed1985

Hot-plate learning in mice is unaltered by immediate post-training administration of naloxone, naltrexone or morphine.

Repeated exposure to the hot-plate assay results in shorter response latencies in both rats and mice. In view of the postulated role of endorphins in memory processes, the present study examined the effects of immediate post-trial opiate-induced manipulations on this phenomenon of hot-plate learning. In experiment 1, adult male mice were injected with naloxone (0.1-10.0 mg/kg, i.p.) immediately after initial hot-plate testing and were reassessed 24 and 48 hr later. In experiment 2, mice were similarly treated with either naltrexone (0.1-10.0 mg/kg) or morphine (0.5-5.0 mg/kg) and retested 48 and 72 hr later. Results indicated a potent training effect in all groups but failed to reveal any significant effects of drugs. These data are inconsistent with a role for endorphins in hot-plate learning and, further, may question the generality of the involvement of opioids in memory processes.

Animals↗

PubMed1985

Social conflict analgesia: studies on naloxone antagonism and morphine cross-tolerance in male DBA/2 mice.

It has recently been reported that male mice exhibit pronounced analgesia in response to attack from aggressive conspecifics. Although several studies indicate that this reaction can be blocked by opiate antagonist pretreatment, unequivocal evidence of opioid involvement is very much more limited. In the present study, the phenomenon of conflict analgesia has been studied in male DBA/2 intruder mice following exposure to a criterion level of attack from aggressive BKW residents. Our findings indicate that this analgesia is blocked and reversed by naloxone unaltered by methyl naloxone, except at high doses (75 mg/kg) and fully cross-tolerant with morphine. This profile confirms and extends earlier findings with B6AF1 mice, indicating that the opioid mediation of this biologically-relevant form of environmental analgesia is not strain specific.

Analgesia↗

PubMed1985

Benzodiazepines and their antagonists: a pharmacoethological analysis with particular reference to effects on "aggression".

A review of the literature on chlordiazepoxide indicates that the traditional view of benzodiazepines as antiaggressive drugs represents an inaccurate generalization. In fact, highly variable findings have been reported with the most significant factor in the variability being the type of aggression studied. Furthermore, considerable controversy surrounds the nature of chlordiazepoxide's influence on social conflict in rodents, with opinion divided regarding the selectivity of its inhibitory effect on offensive responding. It is argued that inappropriate behavioural methodology may have substantially contributed to this controversy. A pharmacoethological approach to the analysis of drug effects on social behaviour is described and exemplified by new data on chlordiazepoxide and midazolam. Both agents inhibit offense at doses which do not result in general response inhibition, yet their overall behavioural profiles are somewhat different. Evidence is also presented indicating low dose behavioural activity of the benzodiazepine antagonist Ro15-1788 in two test situations and suggesting possible differences in the effects of Ro15-1788 and CGS8216 on novelty-related responding. Several avenues of research are discussed which may yield insights into the manner whereby benzodiazepines influence social patterns and the significance of benzodiazepine-GABA interactions in such processes.

Aggression↗

PubMed1985

Do small and large luteal cells of the sheep interact in the production of progesterone?

Corpora lutea from cyclic ewes were dissociated by collagenase and trypsin/EGTA treatments, and enriched fractions of small and large luteal cells were prepared on gradients of Ficoll. These fractions were incubated separately or remixed before incubation. Colchicine, cytochalasin B and the calcium channel-blocker verapamil significantly reduced progesterone production by both small and large luteal cell fractions, while isoprenaline stimulated an increase in progesterone production by large luteal cell fractions only. When fractions of small and large luteal cells were remixed, no more and no less progesterone was produced than would have been predicted from equivalent fractions incubated separately. There was therefore no evidence of synergism between small and large luteal cells in the production of progesterone. Prostaglandin F-2 alpha, which can inhibit LH-stimulated progesterone production by ovine luteal tissue in vitro, had no effect on LH-stimulated progesterone production by small luteal cell fractions, but significantly inhibited that by enriched fractions of large luteal cells. Since large luteal cell fractions were contaminated with small luteal cells, which are probably responsible for the progesterone-secretory response of these fractions to LH, it was concluded that the inhibition of LH-stimulated progesterone production by small luteal cells is dependent on the presence of large luteal cells. Oxytocin added to large and small luteal cell fractions did not affect progesterone production by either fraction. It was therefore concluded that the inhibitory action of PGF-2 alpha on LH-stimulated progesterone production may require the interaction of large and small luteal cells, but that oxytocin is not likely to be an intermediary in this interaction.

Animals↗