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Biomedical subjects

M R Jones

Publications and source records attributed to M R Jones.

At least 19 recordsLinked to original sources
PubMed1992

Construction and characterization of a mutant of Rhodobacter sphaeroides with the reaction center as the sole pigment-protein complex.

A strain of Rhodobacter sphaeroides has been constructed in which the photosynthetic reaction center is the sole pigment-protein complex. The strain, named RCO1, is capable of photoheterotrophic growth and possesses assembled and functional reaction centers which can undergo photochemical charge separation and are reduced by electrons derived from the cytochrome b/c1 complex. The circular dichroism and linear dichroism of reaction centers in membranes from strain RCO1 are similar to those described previously for reaction centers isolated in detergent solution. A second strain, named RCLH11, which is devoid of the peripheral LH2 antenna complex has also been constructed. A description of the properties of these strains is presented.

Bacteriochlorophylls↗
PubMed1992

Extradural abscess complicating extradural anaesthesia for caesarean section.

Extradural abscess has been described infrequently as a complication of extradural anaesthesia and analgesia. We describe an abscess that developed 5 days after operation in a patient who had extradural anaesthesia for Caesarean section and postoperative analgesia, and review the literature on extradural abscess complicating extradural catheterization, including a discussion on pathogenesis, clinical presentation, diagnosis and management. There have now been 16 reported cases of extradural catheter-related extradural abscess. Only one previous case has been in obstetric practice, despite the widespread use of these techniques in this specialty. A disproportionate number of cases have involved thoracic catheters. Duration of catheterization ranged from 40 h to 6 weeks, the majority of catheters being in place for 5 days or less. The time from catheter placement to development of symptoms ranged from 72 h to 5 months. The causative organism was isolated in 11 cases: Staphylococcus aureus was identified in nine (82%) and Staphylococcus epidermidis in two (18%). Outcome was reported in 15 cases, of which seven (47%) had a full or near full recovery and eight (53%) had a persistent neurological deficit. One case was managed successfully without surgery. Fifty percent of all cases have been reported in the past 5 years. With the increasing use of extradural techniques for anaesthesia and analgesia, this serious complication may be seen more frequently in the future.

Abscess↗
PubMed1992

Mutants of Rhodobacter sphaeroides lacking one or more pigment-protein complexes and complementation with reaction-centre, LH1, and LH2 genes.

The photosynthetic apparatus of Rhodobacter sphaeroides is comprised of three types of pigment-protein complex: the photochemical reaction centre and its attendant LH1 and LH2 light-harvesting complexes. To augment existing deletion/insertion mutants in the genes coding for these complexes we have constructed two further mutants, one of which is a novel double mutant which is devoid of all three types of complex. We have also constructed vectors for the expression of either LH1, LH2 or reaction-centre genes. The resulting system allows each pigment-protein complex to be studied either as part of an intact photosystem or as the sole complex in the cell. In this way we have demonstrated that reaction centres can assemble independently of either light-harvesting complex in R. sphaeroides. In addition, the isolation of derivatives of the deletion/insertion mutants exhibiting spontaneous mutations in carotenoid biosynthesis provides an avenue for examining the role of carotenoids in the assembly of the photosynthetic apparatus. We show that the LH1 complex is assembled regardless of the carotenoid background, and that the type of carotenoid present modifies the absorbance of the LH1 bacteriochlorophylls.

Carotenoids↗
PubMed1992

Stimulation of early gene expression by angiotensin II in bovine adrenal glomerulosa cells: roles of calcium and protein kinase C.

The adrenal glomerulosa cell is a major site of action of angiotensin II (AII), which binds to AT1 receptors to stimulate phosphoinositide hydrolysis and Ca2+ mobilization, and the subsequent production of aldosterone. All also influences adrenal growth and proliferation and promotes thymidine incorporation in adrenocortical cells. In primary cultures of bovine glomerulosa cells, AII was found to induce the expression of several early growth response genes (c-fos, c-jun, JunB, and Krox 24). This effect of AII was dose-dependent and was blocked by [Sar1,IIe8] AII and the nonpeptide antagonist DuP 753, indicating that it is mediated by the AT1 subtype of the AII receptor. ACTH, which elevates cAMP in glomerulosa cells, was a relatively weak inducer of c-fos expression but was as potent as AII in stimulating the expression of JunB. ACTH did not further enhance the maximal effect of AII on c-fos expression. The role of the AII-induced cytoplasmic Ca2+ increase in generating the c-fos response was suggested by the ability of the Ca2+ ionophore ionomycin to induce c-fos expression. However, mobilization of intracellular Ca2+ by the Ca2+ ATPase inhibitor thapsigargin, as well as the stimulation of Ca2+ influx by depolarization with potassium, were less potent stimuli of c-fos expression. Omission of Ca2+ from the extracellular medium, which abolishes the plateau phase of the AII-induced Ca2+ signal without affecting the early increase due to Ca2+ mobilization, enhanced the early phase of the AII-induced c-fos response, indicating that Ca2+ also has an inhibitory effect on the early gene response. Activation of protein kinase C by phorbol 12-myristate, 13-acetate (PMA) also stimulated c-fos expression, but the combination of PMA and ionomycin did not further increase the c-fos response. Inhibition of protein kinase C by staurosporine, or its depletion by prolonged exposure to PMA, prevented the c-fos response to PMA but only partially inhibited the response to AII, suggesting the involvement of other factors in stimulus-transcription coupling from the AT1 receptor.

1-Sarcosine-8-Isoleucine Angiotensin II↗
PubMed1992

Passive immunization with antiserum to adrenocorticotropin increases weight gain in normal female rats.

Passive immunization against ACTH was used to test the hypothesis that growth in female rats is constrained by physiological concentrations of glucocorticoids. When animals were stressed by 15-min exposure to ether before blood sampling by cardiac puncture, serum concentrations of corticosterone were lower (P less than .05) in immunized rats than in stressed controls. The maximum effect was apparent 2 h after injection of ACTH antiserum, and no effect was apparent 6 h after injection. To examine the effects of ACTH immunization on growth, rats received daily injections of either saline, sheep immunoglobulin G, or ACTH antiserum, 2 h before the afternoon peak in plasma concentrations of corticosterone. After 7 d of treatment, rats treated with ACTH antiserum had gained 37% more body weight than saline-injected controls, and this effect was accompanied by a 59% reduction in peak plasma concentrations of corticosterone. Immunoglobulin G purified from normal sheep serum had no effect on weight gain. It is concluded that growth rate in normal female rats can be stimulated through the suppression of adrenal activity.

Adrenocorticotropic Hormone↗
PubMed1992

The development of corticosteroid binding globulin-like activity in fetal sheep blood.

Parturition in sheep is initiated by the fetus and is preceded by a rise in fetal cortisol and corticosteroid-binding globulin (CBG) late in gestation. In this study plasma cortisol and CBG concentrations were measured in fetal and maternal circulation from 40 days gestation to early post-partum. The fetal cortisol profile was shown to be triphasic in nature; being high in both the first and last trimester but low in the middle period of gestation. In the last trimester, total cortisol increased steadily, reaching it's highest level just prior to parturition (145 days gestation), before falling to maternal levels over the first 10 days post-partum. The changes seen in CBG concentrations throughout gestation and post-partum mirrored the triphasic nature seen in cortisol levels. CBG was significantly higher at 40, 56 and 140 days gestation than at mid-gestation (77 and 90 days). However, at 145 days gestation there was a significant fall in CBG levels. CBG levels were higher at 1 day post-partum when compared to 145 days gestation, the former rapidly falling to maternal levels over the subsequent 9 days. The maximum binding capacity at 40, 56, 70 and 90 days gestation exceeds the total serum cortisol concentration. However at 140 and 145 days gestation and 1 day post-partum the total serum cortisol exceeds the Bmax. The highest cortisol:Bmax ratio is seen at 145 days gestation due to the fall of CBG binding capacity at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1992

Amino acid solutions for CAPD: rationale and clinical experience.

Protein-calorie malnutrition is present in a sizable proportion of dialysis patients. In CAPD patients, constant glucose absorption from dialysate may displace other calorie sources, such as protein, and may suppress the appetite, thus contributing to malnutrition. Use of amino acids in place of glucose as the osmotic agent has been studied extensively. Ultrafiltration and small-molecule clearance similar to that with glucose can be achieved with amino acid solutions, but nitrogenous waste produced by amino acids limits the extent to which they can replace hypertonic glucose. Side effects of CAPD with amino acids appear to be minor and easily manageable. Most studies have found at least some nutritional benefit of amino acid solutions in addition to that of lowering the glucose load. Short-term studies of amino acid solutions for dialysis indicate that they may improve protein nutrition in malnourished CAPD patients.

Amino Acids↗
PubMed1979

AHR-6646: a new, long-acting neuroleptic.

1. AHR-6646 blocked d-amphetamine lethality in mice under aggregated conditions when the pretreatment interval was between one hour and seven days. 2. Conditioned avoidance responding in mice and cats was suppressed by AHR-6646 in doses that did not impair escape behavior. The duration of this effect was markedly prolonged. 3. AHR-6646 produced catalepsy in rats. The onset of this effect was delayed and the duration was prolonged when compared with that of chlorpromazine. 4. Apomorphine-induced pivoting in mice with unilateral lesions of the caudate nucleus was suppressed by AHR-6646. 5. AHR-6646 was a potent antiemetic agent in dogs, with a delayed onset and prolonged duration of action.

Animals↗
PubMed1979

Memory for symmetry: real or artifact.

Subjects recalled nonrandom digit sequences according to either (a) free recall or (b) a serial recall mode in a series of three studies. Sequential structure was varied with specific rules determining higher-order structure of either (a) arithmetic, (b) symmetrical, or (c) haphazard types. In Experiment I, 18 temporal patterns of 12 digits each were presented visually. Although symmetric patterns were easier than the other two pattern types, this superiority was not determined by recall mode. In Experiment II, 6 temporal patterns of 18 digits each were presented visually, with results similar to those of Experiment I. Auditory patterns equivalent to those of Experiment II were presented in Experiment III. In this study, although the free recall mode produced slightly superior recall with symmetrical sequences, this difference was not statistically significant. It was concluded that superior memory for symmetries cannot be wholly accounted for by organizational strategies made possible by a free recall mode.

Female↗
PubMed1979

Late isolated left ventricular tamponade. Clinical, hemodynamic, and echocardiographic manifestations of a previously unreported postoperative complication.

A unique case of late postoperative left ventricular tamponade, hemodynamically indistinguishable from severe left ventricular failure, is reported in a patient 1 month after an apparently uncomplicated aortic valve replacement. An echo-free space behind the left ventricle led to surgical exploration and successful resolution of the disease process. To our knowledge, this is the first documented case of isolated left ventricular tamponade in the literature. The findings highlight the importance of postoperative echocardiography in the evaluation of the patient having cardiac surgery.

Aneurysm, Infected↗
PubMed1978

Phenylalanine metabolism in uremic and normal man.

The metabolism of phenylalanine and tyrosine was evaluated in six normal men, five chronically uremic men, and three men undergoing maintenance hemodialysis. Phenylalanine, tyrosine, and 13 acidic metabolites of those amino acids were measured in plasma postabsorptively and in plasma and urine after a phenylalanine load of 100 mg/kg. In addition, five normal subjects and five dialysis patients ingested L-[14C]-phenylalanine (uniformly labeled) with the load. In uremic and dialysis patients, plasma phenylalanine rose higher and fell more gradually after the load, and tyrosine rose more slowly. The 24-hr urinary concentrations of phenylalanine and tyrosine were similar in the three groups. At 24 hr, cumulative expiration of 14CO2 was 20.2% in the dialysis patients and 28.4% in the normal subjects. Plasma phenylalanine levels and 14CO2 expiration varied with protein intake in normal subjects. In uremic and dialysis patients, plasma phenyllactic acid, p-hydroxyphenylacetic acid, and p-hydroxybenzoic acid were elevated, the last one markedly so. Moreover, plasma phenylpyruvic acid (PPA) and mandelic acid were detected only in dialysis patients. After the phenylalanine load, plasma conjugated phenylacetic acid rose in uremic patients, and PPA increased transiently in some dialysis patients. In urine of dialysis patients, concentrations of benzoic acid and conjugated o-hydroxyphenylacetic acid were decreased, and PPA was sometimes increased. The data suggest a mild impairment in the hydroxylation of phenylalanine which does not result in marked changes in plasma or in urinary metabolites after a phenylalanine load.

Acetates↗
PubMed1978

Valine metabolism in normal and chronically uremic man.

Valine metabolism was investigated in five normal and three nondialyzed chronically uremic subjects eating 40 +/- SEM 1 and 53 (range 40 to 80) protein diets respectively, in a metabolic research unit. Subjects were injected iv with a tracer dose of L-valine-1-14C while they fasted, and specific activity of plasma valine-14C and expiration of 14CO2 were monitored for two hours. Plasma valine was significantly lower in the uremic patients than in the normal subjects (P less than 0.05). In the uremic patients, specific activity of plasma valine fell less rapidly and remained higher, and expiration of 14CO2 was not different from normal subjects. A two-pool model for valine metabolism was derived which indicated that in uremic patients there was a significant decrease in both valine pools and in the rate of irreversible loss, i.e., valine incorporated into larger molecules, degraded, or excreted. Valine degradation was estimated to be decreased in the uremic patients.

Adult↗
PubMed1978

Thinking.

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Concept Formation↗