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Biomedical subjects

A Gibson

Publications and source records attributed to A Gibson.

At least 109 records · Page 6Linked to original sources
PubMed1994

Lesbian identity and the politics of representation in Betty Parsons's gallery.

Although Betty Parsons had been unusually open about her love relationships with women in the twenties and thirties, she later became reticent, retiring to the closet. Her increased discretion after World War II, during the Cold War, coincided with her rise as the art dealer most prominently associated with the international emergence of Abstract Expressionism. Parsons incurred the objections of her Abstract Expressionists, however, by showing artists who included both abstraction and naturalism in their work, such as Sonia Sekula, Forrest Bess, and Hedda Sterne. This article examines her definition of abstraction as difference through her friend Theodoros Stamos's notion of camp and helps to explain her admiration of Barnett Newman despite her refusal to devote her gallery exclusively to his narrower version of significant abstraction.

Art↗
PubMed1993

Localisation of nitric oxide synthase within non-adrenergic, non-cholinergic nerves in the mouse anococcygeus.

Immunocytochemical staining of whole mount preparations of the mouse anococcygeus muscle, using antibodies to rat brain nitric oxide synthase (NOS), revealed a dense network of NOS-immunoreactive nerve fibres running through the tissue. These fibres were resistant to the sympathetic neurotoxin 6-hydroxydopamine and are therefore likely to be the non-adrenergic nerves which mediate relaxation of this smooth muscle. Further, NOS-immunoreactive fibres were absent following denervation by cold-storage (4 degrees C; 72 h), which has been shown to abolish non-adrenergic, non-cholinergic (NANC) relaxations. The results provide strong support for the hypothesis that the L-arginine:NO pathway is responsible for the generation of the NANC transmitter in the anococcygeus.

Amino Acid Oxidoreductases↗
PubMed1993

The influence of L-NG-nitro-arginine on sympathetic nerve induced contraction and noradrenaline release in the rat isolated anococcygeus muscle.

1. The possibility of an interaction between the motor sympathetic and inhibitory non-adrenergic, non-cholinergic (NANC) nerves in the rat anococcygeus was investigated using L-NG-nitro-arginine (L-NOARG), an inhibitor of L-arginine: NO synthase. 2. L-NOARG (50 microM) increased contractions induced by field stimulation (20 s trains; 0.5-40 Hz); overall, the frequency-response curve was displaced six-fold to the left. D-NOARG (50 microM) was without effect. 3. The potentiation produced by L-NOARG was reversed by 200 microM L-, but not D-, arginine. 4. L-NOARG had no effect on contractions induced by exogenous noradrenaline (NA) or on field stimulation-induced overflow of tritium from muscles previously loaded with [3H]-NA. 5. It is concluded that the endogenous nitrate NANC transmitter does not influence release of NA from the sympathetic nerves and the potentiation of contractions induced by field stimulation in the presence of L-NOARG most probably results from removal of the opposing relaxing influence of concomitantly released NANC transmitter.

Animals↗
PubMed1993

Function ten years after Colles' fracture.

There are no data in the literature concerning the outcome of Colles' fracture beyond six years. One hundred consecutive patients with displaced Colles' fractures were reviewed ten years after the injury. Function, radiographic anatomy, osteoarthrosis, and reflex sympathetic dystrophy (algodystrophy) were all objectively assessed. By the time of this review, 35 patients had died. Eighty-five percent of those surviving had a satisfactory outcome. Forty-two percent had improved functionally in ten years and 20% had deteriorated. Initial and ten-year radial shortening and early finger stiffness significantly correlated with final outcome. Dorsal angulation influenced early but not ten-year function. Sixty-two percent of those with an unsatisfactory result had objective features of reflex sympathetic dystrophy, compared with only 6% of those with a satisfactory result. Osteoarthrosis was found in 37%, but in only 4% was it associated with an unsatisfactory outcome.

Adult↗
PubMed1993

Unicompartmental knee arthroplasty. A multicenter investigation with long-term follow-up evaluation.

Nonmental-backed, cemented, unicompartmental knee arthroplasty has a survivorship rate in this multicenter investigation at ten years of 91.4% (+/- 2.8). High levels of patient weight were associated with increased need for revision arthroplasty. Overall, men had a lower revision rate (2.4%) compared with women (3.9%). Valgus postoperative alignment was minimally associated with progression of disease as a cause for revision. No difference in revision rates between medial and lateral compartmental arthroplasty was noted. The theoretical clinical benefits of the use of metal-backed tibial components will need to be reevaluated in light of these findings.

Adult↗
PubMed1992

A new oesophageal tube: assessment of collagen/vicryl composite membrane.

Collagen/vicryl composite membrane has been previously shown to be of use in an experimental model as a patch graft in the bladder and oesophagus. Attempts to use it as a circumferential tube graft have been unsuccessful due to the development of strictures at the site of anastomosis. We inserted a polytetrafluoroethylene (PTFE) stented collagen/vicryl bioprosthetic tube into rat omentum, which served as a vascular pedicle. Subsequent histology of the graft showed serial replacement of the bioprosthesis with host collagen and the development of a blood supply. In a second stage procedure, the bioprosthesis was anastomosed to the distal ileum and brought out on the skin to form a fistula. Squamous epithelium was subsequently identified growing the full length of the graft. Therefore, we have developed a vascularised bioprosthetic tube graft which will support the growth of unspecialised epithelium. This model could be of use in bridging congenital atresias or pathological strictures.

Anastomosis, Surgical↗
PubMed1992

Complete recovery from hemorrhagic shock and encephalopathy.

We describe three infants (aged 9 weeks to 4 months) with the classic features of hemorrhagic shock and encephalopathy syndrome, including sudden onset of shock, neurologic disturbance, bleeding, disseminated intravascular coagulation, and impaired hepatic and renal function. Unlike the cases previously described, all three children recovered rapidly without evidence of long-term neurologic damage. These findings may modify the perception that this disorder has a uniformly bad outcome.

Brain Diseases↗
PubMed1992

Effects of genistein, an isoflavone isolated from Genista tridentata, on isolated guinea-pig ileum and guinea-pig ileal myenteric plexus.

The inhibitory action of the major constituent of Genista tridentata L. (Papilionaceae), 4',5,7-trihydroxyisoflavone (genistein), on contractions induced by agonists and electrical field stimulation of smooth muscle was analysed. Genistein inhibited twitches evoked by electrical-stimulation of strips of guinea-pig ileum with an IC50 value of 34 microM. Genistein (34 microM) inhibited contractions of the guinea-pig ileum by several agonists in a non-selective, antispasmodic action and had no effect on inhibition of 3H-ACh release from ileal myenteric plexus. Genistein (34 microM) produces an increase in cAMP levels of guinea-pig ileum which resulted in a smooth muscle relaxation which leads us to think that there must be a blockade of its phosphodiesterase.

Animals↗
PubMed1992

An investigation of some S-nitrosothiols, and of hydroxy-arginine, on the mouse anococcygeus.

1. The effect of five S-nitrosothiols, and of the stereoisomers of NG-hydroxy-arginine (HOARG), were investigated on the mouse anococcygeus. 2. All five S-nitrosothiols produced concentration-related (0.1-100 microM) relaxations of carbachol (50 microM)-induced tone; the order of potency was S-nitroso-L-cysteine (CYSNO) > S-nitroso-N-acetyl-D,L-penicillamine (SNAP) > S-nitrosoglutathione (GSNO) > S-nitrosocoenzyme A (CoASNO) > S-nitroso-N-acetyl-L-cysteine (NACNO). The relaxations were unaffected by the nitric oxide synthase (NOS) inhibitor, L-NG-nitro-arginine (10 microM) (L-NOARG). 3. Cold-storage of the tissue for 72 h resulted in loss of sympathetic and non-adrenergic, non-cholinergic (NANC) nerve function. NOS activity in the tissue was reduced by 97%. Despite this, relaxations induced by the S-nitrosothiols were unaffected. 4. Haemoglobin (50 microM) attenuated relaxations induced by NO and the S-nitrosothiols, although responses to 3-isobutyl-1-methyl-xanthine were unaffected. N-methyl-hydroxylamine (2 mM) which has been shown previously to produce selective inhibition of NANC and nitrovasodilator responses in this tissue, also reduced responses to all S-nitrosothiols. 5. Hydroquinone (100 microM) greatly reduced relaxations to CYSNO (by 88%) but had no effect on those to SNAP, GSNO, CoASNO or NACNO. Since hydroquinone does not reduce responses to NANC stimulation, CYSNO is unlikely to be the NANC transmitter. 6. L-HOARG by itself (up to 100 microM) had no significant effect on carbachol-induced tone or on NANC (10 Hz; 10 strain every 100 s) relaxations. However, it produced reversal of the inhibitory effects of L-NOARG (10;pM), being only slightly less potent than L-arginine. D-HOARG was without effect.L-HOARG had no effect on relaxations induced by 1.51iM NO.7. The results show that S-nitrosothiols are potent relaxants of the mouse anococcygeus; they act directly on the smooth muscle with a mechanism similar to NO and other nitrovasodilators. In addition,the results are consistent with L-HOARG being an intermediate in the biosynthesis of NO from L-arginine, although there is no evidence for it acting to stabilize NO extracellularly.

Animals↗
PubMed1991

The influence of L-NG-nitro-arginine on field stimulation induced contractions and acetylcholine release in guinea pig isolated tracheal smooth muscle.

The interaction between parasympathetic and inhibitory non-adrenergic, non-cholinergic nerves in tracheal smooth muscle was investigated by determining the effects of the NO-synthase inhibitor L-NG-nitro-arginine (L-NOARG) on contractions and the associated acetylcholine release elicited by field stimulation of the muscle. At frequencies above 2Hz contractile responses to field stimulation were potentiated by L-NOARG (50 microM). alpha-chymotrypsin pre-treatment potentiated contractile responses at all frequencies, but the effects of L-NOARG were unaltered. The effect of L-NOARG on responses to 5Hz electrical stimulation was not mimicked by D-NOARG, was reversed by L-, but not D-arginine and was unaffected by epithelium removal. L-NOARG did not affect responses to exogenous acetylcholine nor the overflow of 3H from tissues previously loaded with [3H]-choline. It is therefore concluded that field stimulation of tracheal smooth muscle induces the release of an endogenous nitrate, which, by an inhibitory action on smooth muscle, functionally antagonises the concomitantly released parasympathetic neurotransmitter.

Acetylcholine↗
PubMed1991

Purification and characterization of leucyl aminopeptidase and pyroglutamyl aminopeptidase from human skeletal muscle.

The purification and characterization of leucyl aminopeptidase and pyroglutamyl aminopeptidase from human skeletal muscle are described. The characteristics of leucyl aminopeptidase were as follows: optimum activity was at pH 9.5 in the presence of 5 mmol/l Mg2+ or 0.5 mmol Mn2+. No activation of enzyme activity was obtained following addition of other divalent cations or sulphhydryl reagents. Only the leucyl-AMC and methionyl-AMC derivatives were appreciably hydrolysed. The mol mass was estimated as 280 kDa. Approx. 50% inhibition of activity was obtained following addition of p-hydroxymercuriphenyl sulphonate (10 mumol/l), N-ethyl maleimide (2 mmol/l), o-phenanthroline (5 mmol/l), bacitracin (1 mmol/l), amastatin (1 microgram/ml) and bestatin (0.1 mumol/l); no inhibition of activity was obtained in the presence of phenylmethanesulphonyl fluoride (1 mmol/l), limabean trypsin inhibitor (100 microgram/ml) or pepstatin (100 microgram/ml). The following oligopeptides were hydrolysed by the enzyme: luliberin 7-10, proctolin and [Leu5]enkephalin; oligopeptides not appreciably hydrolysed included neurotensin, angiotensin-I, substance-P and bradykinin. Pyroglutamyl aminopeptidase had the following characteristics: optimum activity was at pH 8.5 in the presence of 1 mmol/l dithiothreitol (an absolute requirement for maintenance of enzyme activity). Maximum activity was obtained in the absence of divalent cations. Only the pyroglutamyl-AMC derivative was appreciably hydrolysed. The mol mass of this enzyme was estimated as 22 kDa. Approximately 50% inhibition of activity was obtained on addition of phenanthroline (4 mmol/l) and antipain (7 microgram/ml); no inhibition of activity was obtained following addition of phenyl methanesulphonyl fluoride (1 mmol/l), limabean trypsin inhibitor (100 microgram/ml) or pepstatin (100 microgram/ml). Only oligopeptides with a pyroglutamyl N-terminal residue (thyroliberin, neurotensin, and luliberin) were hydrolysed by the enzyme.

Cations, Divalent↗
PubMed1991

Differentiation by hydroquinone of relaxations induced by exogenous and endogenous nitrates in non-vascular smooth muscle: role of superoxide anions.

1. The influence of hydroquinone on relaxations induced by nitric oxide (NO), nitrovasodilator drugs, and non-adrenergic, non-cholinergic (NANC) field stimulation has been investigated in three tissues in which endogenous nitrates have been implicated in the NANC response; the mechanism of action of hydroquinone was also studied. 2. In mouse anococcygeus, hydroquinone (10-100 microM) produced a concentration-dependent inhibition of relaxations induced by 15 microM NO. Hydroquinone, 100 microM, which reduced responses to NO by 85%, had no effect on relaxations induced by NANC field stimulation (10 Hz; 20s trains), hydroxylamine (10 microM), sodium nitroprusside (1 microM) or sodium azide (20 microM). 3. In guinea-pig trachea, 100 microM hydroquinone reduced relaxations to 150 microM NO by 75%, but had no effect on those to NANC stimulation (10 Hz; 30 s trains) or sodium azide (5 microM). 4. In rat gastric fundus, 100 microM hydroquinone reduced relaxations to 1 microM NO by 85%, but had no effect on those to NANC stimulation (0.5 Hz; 15 s trains) or sodium azide (2 microM). 5. Superoxide dismutase (SOD; 50 u ml-1) had no effect on relaxations of the mouse anococcygeus in response to 15 microM NO or 10 Hz NANC stimulation. Further, the inhibition of responses to NO by hydroquinone was unaffected in the presence of SOD. 6. Hydroquinone (10-100 microM) failed to generate superoxide anions, as detected by a chemiluminescent assay. However, 100 microM hydroquinone, like SOD (50 u ml-1), produced almost complete inhibition of superoxide anion chemiluminescence induced by xanthine (500 microM): xanthine oxidase (0.07 u ml-1). 7. It is concluded that, in our system, hydroquinone inhibits NO by acting as a free radical scavenger rather than by generating superoxide anions. The ability of hydroquinone to block relaxations to NO, but not NANC stimulation, may suggest that the endogenous nitrate substance released by these NANC nerves may not be free NO, but may be an NO-containing, or NO-generating, molecule.

Animals↗
PubMed1991

Cyclic nucleotide content of the rat anococcygeus during relaxations induced by drugs or by non-adrenergic, non-cholinergic field stimulation.

Low concentrations of sodium nitroprusside (0.2 and 1 microM) relaxed carbachol-induced tone of the rat anococcygeus but did not affect the content of either cGMP or cAMP; higher concentrations (10,100 and 1000 microM) produced greater relaxation (greater than 60%) and a rise in cGMP but not cAMP. In the presence of the cGMP-phosphodiesterase inhibitor M&B 22948 (10 microM), 1 microM sodium nitroprusside produced greater relaxation and a selective increase in cGMP. Forskolin (0.5-250 microM) caused relaxation and a selective increase in cAMP; the concentration-response relationships of the two effects were similar. Non-adrenergic, non-cholinergic (NANC) field stimulation (10 Hz; 20 s trains) reduced tone by 52% but had no effect on cyclic nucleotide content; in the presence of 10 microM M&B 22948 or 1 microM sodium nitroprusside, NANC stimulation produced a greater degree of relaxation and increased cGMP but not cAMP content. The results show that NANC stimulation acts like sodium nitroprusside, causing a selective increase in cGMP, and this supports the proposal that NANC transmission in the rat anococcygeus involves an endogenous nitrate; the possibility that multiple pools of cGMP exist in the anococcygeus is discussed.

3',5'-Cyclic-AMP Phosphodiesterases↗