Retinal remodeling in human retinitis pigmentosa.

Retinitis Pigmentosa (RP) in the human is a progressive, currently irreversible neural degenerative disease usually caused by gene defects that disrupt the function or architecture of the photoreceptors. While RP can initially be a disease of photoreceptors, there is increasing evidence that the inner retina becomes progressively disorganized as the outer retina degenerates. These alterations have been extensively described in animal models, but remodeling in humans has not been as well characterized. This study, using computational molecular phenotyping (CMP) seeks to advance our understanding of the retinal remodeling process in humans. We describe cone mediated preservation of overall topology, retinal reprogramming in the earliest stages of the disease in retinal bipolar cells, and alterations in both small molecule and protein signatures of neurons and glia. Furthermore, while Müller glia appear to be some of the last cells left in the degenerate retina, they are also one of the first cell classes in the neural retina to respond to stress which may reveal mechanisms related to remodeling and cell death in other retinal cell classes. Also fundamentally important is the finding that retinal network topologies are altered. Our results suggest interventions that presume substantial preservation of the neural retina will likely fail in late stages of the disease. Even early intervention offers no guarantee that the interventions will be immune to progressive remodeling. Fundamental work in the biology and mechanisms of disease progression are needed to support vision rescue strategies.

Dysmorphic photoreceptors in a P23H mutant rhodopsin model of retinitis pigmentosa are metabolically active and capable of regenerating to reverse retinal degeneration.

This study evaluated the capacity of Xenopus laevis retina to regenerate photoreceptor cells after cyclic light-mediated acute rod photoreceptor degeneration in a transgenic P23H mutant rhodopsin model of retinits pigmentosa. After discontinuation of cyclic light exposure, we monitored histologic progression of retinal regeneration over a 3 week recovery period. To assess their metabolomic states, contralateral eyes were processed for computational molecular phenotyping. We found that retinal degeneration in the P23H rhodopsin mutation could be partially reversed, with regeneration of rod photoreceptors recovering normal morphology (including full-length rod outer segments) by the end of the 3 week recovery period. In contrast, retinal degeneration mediated by directly induced apoptosis did not recover in the 3 week recovery period. Dystrophic rod photoreceptors with truncated rod outer segments were identified as the likely source of rod photoreceptor regeneration in the P23H retinas. These dystrophic photoreceptors remain metabolically active despite having lost most of their outer segments.

PAR(2) expression in peripheral blood monocytes of patients with rheumatoid arthritis.

OBJECTIVES: Proteinase-activated receptor 2 (PAR(2)) is a G protein-coupled receptor activated by serine proteinases with proinflammatory activity. A study was undertaken to investigate the presence and functional significance of PAR(2) expression on rheumatoid arthritis (RA)-derived leucocyte subsets. METHODS: Venous blood was obtained from patients with RA and osteoarthritis (OA) as well as healthy control subjects. Surface expression of PAR(2) on peripheral blood mononuclear cells (PBMCs) was analysed by flow cytometry and interleukin 6 (IL-6) generation by ELISA. RESULTS: Patients with RA had elevated but variable surface expression of PAR(2) on CD14+ monocytes compared with control subjects (median (1st to 3rd quartiles) 1.76% (0.86-4.10%) vs 0.06% (0.03-0.81%), p<0.0001). CD3+ T cells showed a similar pattern with significantly higher PAR(2) expression in patients with RA compared with controls (3.05% (0.36-11.82%) vs 0.08% (0.02-0.28%), p<0.0001). For both subsets, PAR(2) expression was significantly higher (p<0.00001) in patients with high levels of disease activity: PAR(2) expression for both CD14+ and CD3+ cells correlated to C reactive protein and erythrocyte sedimentation rate. Furthermore, in a cohort of patients with newly diagnosed RA, elevated PAR(2) expression in both CD14+ and CD3+ cells was significantly reduced 3 months after methotrexate or sulfasalazine treatment and this reduction correlated significantly with the reduction in the 28-joint Disease Activity Scale score (p<0.05). PAR(2) expression on cells from patients with OA was low, similar to levels seen in control subjects. Generation of IL-6 by monocytes in response to a selective PAR(2) agonist was significantly greater in patients with RA than in patients with OA and control subjects (p<0.05). CONCLUSIONS: These findings are consistent with a pathogenic role for PAR(2) in RA.

Hot flushes, vascular reactivity and the role of the α-adrenergic system.

ABSTRACT Background Seventy percent of postmenopausal women suffer from hot flushes but the pathophysiology is poorly understood. Proposed mechanisms include altered peripheral vascular reactivity and a narrowed thermoneutral zone. A trigger has not yet been identified; however, the α-adrenergic system, and specifically noradrenaline, has been implicated. Aim To assess the role of the α-adrenergic system by studying the effect of clonidine (α-adrenergic agonist) on flushes and cutaneous microvascular perfusion. Methods Thirty-two postmenopausal women with severe flushing and 14 non-flushing postmenopausal women were recruited. Cutaneous microvascular perfusion was measured using laser Doppler imaging and endothelial function was assessed by iontophoresis (administration of vasoactive agents through the skin by an electric current) of acetylcholine (ACh - endothelium-dependent) and sodium nitroprusside (SNP - endothelium-independent). In a double-blind, longitudinal, cross-over study, clonidine (an α-adrenergic agonist) was compared to placebo in its ability to modulate this response in the flushing group of women. Results The response of the subcutaneous vessels was greater in women who flushed than those who did not (ACh, p < 0.001 and SNP, p = 0.001). However, even though the intensity and number of flushes were decreased by clonidine, there was no difference compared to placebo (p = 0.21) and this 'placebo effect' was also noted in perfusion responses (ACh, p = 0.98; SNP, p = 0.50). Conclusion There was a significant 'placebo effect' for both clinical response and the reactivity of the subcutaneous vessels, making conclusions regarding the role of the α-adrenergic nervous system in hot flushing difficult to determine at a peripheral level. The mechanism for the change in vascular reactivity remains unclear.

Moderate exercise protects against joint disease in a murine model of osteoarthritis.

Exercise is recommended as a non-pharmacological therapy for osteoarthritis (OA). Various exercise regimes, with differing intensities and duration, have been used in a range of OA rodent models. These studies show gentle or moderate exercise reduces the severity of OA parameters while high intensity load bearing exercise is detrimental. However, these studies were largely conducted in rats or in mouse models induced by severe injury, age or obesity, whilst destabilization of the medial meniscus (DMM) in mice has become a widely accepted model due to its lower variability, moderate progression and timescale. The present study was undertaken to provide insight into the effect of moderate exercise on early joint pathology in the DMM mouse model. Exercise was induced a week after induction by forced wheel walking for three or 7 weeks. Joints were analyzed by microcomputed tomography and histology. Assessment of skeletal parameters revealed that exercise offered protection against cartilage damage after 7 weeks of exercise, and a temporary protection against osteosclerosis was displayed after 3 weeks of exercise. Furthermore, exercise modified the metaphyseal trabecular microarchitecture of the osteoarthritic leg in both time points examined. Collectively, our findings corroborate previous studies showing that exercise has an important effect on bone in OA, which subsequently, at 8 weeks post-induction, translates into less cartilage damage. Thus, providing an exercise protocol in a surgical mouse model of OA, which can be used in the future to further dissect the mechanisms by which moderate exercise ameliorates OA.

Proliferative reactive gliosis is compatible with glial metabolic support and neuronal function.

BACKGROUND: The response of mammalian glial cells to chronic degeneration and trauma is hypothesized to be incompatible with support of neuronal function in the central nervous system (CNS) and retina. To test this hypothesis, we developed an inducible model of proliferative reactive gliosis in the absence of degenerative stimuli by genetically inactivating the cyclin-dependent kinase inhibitor p27Kip1 (p27 or Cdkn1b) in the adult mouse and determined the outcome on retinal structure and function. RESULTS: p27-deficient Müller glia reentered the cell cycle, underwent aberrant migration, and enhanced their expression of intermediate filament proteins, all of which are characteristics of Müller glia in a reactive state. Surprisingly, neuroglial interactions, retinal electrophysiology, and visual acuity were normal. CONCLUSION: The benign outcome of proliferative reactive Müller gliosis suggests that reactive glia display context-dependent, graded and dynamic phenotypes and that reactivity in itself is not necessarily detrimental to neuronal function.

Vascular function and cardiovascular risk factors in women with severe flushing.

BACKGROUND: Seventy per cent of postmenopausal women suffer from hot flushes causing significant morbidity in 25%. Oestrogen replacement provides symptom relief, but its use has declined following safety issues and there is, as yet, no good alternative. Pathophysiology is poorly understood, but one proposed mechanism is altered peripheral vascular reactivity. It has recently been suggested that the presence of flushing may be a marker of underlying cardiovascular risk. AIM: To measure (i) peripheral vascular reactivity in subcutaneous vessels (ii) routine and novel cardiovascular risk factors in postmenopausal women who flush, and compare results to a matched group of women who do not flush. METHODS: Thirty-two postmenopausal women with at least 20 flushes/week and 14 nonflushing postmenopausal women were recruited. Cutaneous microvascular perfusion was measured using laser Doppler imaging, and endothelial function was assessed by iontophoresis (administration of vasoactive agents through the skin by an electric current) of acetylcholine [Ach] (endothelial-dependent) and sodium nitroprusside [SNP] (endothelial independent). Blood samples for risk factors were taken following vascular assessment. RESULTS: Both study groups were well matched demographically. The response of the subcutaneous vessels was greater in women who flushed than those who did not, following administration of both the endothelium-dependent and independent vasodilators, (ACh, P ≤ 0·001, SNP, P = 0·001, 2-way anova). By contrast, levels of High Density Lipoprotein (HDL)-cholesterol and ApoA1 were significantly lower in the flushing women compared with the control women (P = 0·02 and 0·002, respectively), and levels of inter-cellular adhesion molecule-1 (ICAM-1) were higher (P = 0·03), findings robust to adjustment for confounders, suggesting an adverse cardiovascular risk profile. CONCLUSION: These results confirm a better vascular response in women but paradoxically, such women appear to have worse (not better) cardiovascular disease risk factors in particular lower HDL-cholesterol but also higher non-HDL-c to HDL-c ratio and increased ICAM-1. Further studies are needed to assess vascular risk factors in women who flush.

Effects on carbon storage of conversion of old-growth forests to young forests.

Simulations of carbon storage suggest that conversion of old-growth forests to young fast-growing forests will not decrease atmospheric carbon dioxide (CO(2)) in general, as has been suggested recently. During simulated timber harvest, on-site carbon storage is reduced considerably and does not approach old-growth storage capacity for at least 200 years. Even when sequestration of carbon in wooden buildings is included in the models, timber harvest results in a net flux of CO(2) to the atmosphere. To offset this effect, the production of lumber and other long-term wood products, as well as the life-span of buildings, would have to increase markedly. Mass balance calculations indicate that the conversion of 5 x 10(9) to 1.8 x 10(9) megagrams of carbon to the atmosphere.

Laser Doppler perfusion imaging of skin blood flow using red and near-infrared sources.

At present, scanning laser Doppler imaging uses a 633-nm helium-neon laser (RED) as the only light source, but this restricts its ability to measure blood flow (i) at darkly pigmented skin and (ii) from deeper or subdermal structures. Because near-infrared (NIR) light is known to penetrate deeper into tissue and to be less absorbed than RED, two imagers were adapted to include a NIR laser diode source (one of 830 nm for UK studies; one of 780 nm for leprosy field trials) in parallel with the existing RED source. In human hands representing a range of skin pigmentations, RED scans were unobtainable at the darkest areas of skin, but intact NIR scans could be collected in all cases. In experiments at the rat knee and the dorsal human hand, NIR and RED values were similar on normal skin. Over underlying vessels, however, NIR values greatly exceeded RED values, an effect abolished by occlusion. Similarly, in patients with leprosy and in healthy controls in Spain, fingerpulp NIR values exceeded RED values to the greatest degree when thermoregulatory flow was highest, i.e., when the deeper-lying arteriovenous anastomoses were open. Over areas of experimental inflammation, NIR gave higher values and also exhibited a greater degree of spatial heterogeneity than RED. We conclude that some current limitations of laser Doppler imaging technology can be overcome by the use of NIR laser diode sources.

Acute inflammation in the rat knee joint attenuates sympathetic vasoconstriction but enhances neuropeptide-mediated vasodilatation assessed by laser Doppler perfusion imaging.

The effect of sympathetic nerve stimulation and topical application of substance P and calcitonin gene-related peptide on the blood flow of the exposed rat knee joint capsule was investigated. The responses of normal animals were compared to those of animals with acutely inflamed joints induced by intra-articular injection of 2% carrageenan. Laser Doppler perfusion imaging was used to examine the spatial distribution of blood flow in the knee joint capsule. Animals with acute joint inflammation showed markedly reduced vasoconstrictor responses to sympathetic nerve stimulation, but enhanced vasodilator responses to both substance P and calcitonin gene-related peptide when compared to normal. Prior application of either substance P or calcitonin gene-related peptide to the normal joint attenuated sympathetic vasoconstrictor responses. In the acutely inflamed knee, sympathetic vasoconstriction was replaced by a vasodilator response in the presence of neuropeptides. The reduced effectiveness of sympathetically mediated vasoconstriction and enhanced responsiveness to substance P and calcitonin gene-related peptide could contribute to the hyperaemia characteristic of inflamed joints.

Specific neurokinin receptors mediate plasma extravasation in the rat knee joint.

1 Plasma extravasation in the rat knee joint was induced by intra-articular injection of neurokinins and specific neurokinin receptor agonists. 2 Pronounced plasma extravasation was produced by substance P (SP, 4-185 microM) and to a lesser extent by neurokinin-B (NKB, 83-413 microM), whereas neurokinin-A (NKA, 88-440 microM) and calcitonin gene-related peptide (CGRP, 26-130 microM) had no significant effect. 3 The specific neurokinin1 receptor agonist [Sar9, Met(O2)11]-substance P (NK1 agonist) in doses of 0.4-70 microM appeared to be more potent than SP in eliciting plasma extravasation. The neurokinin2 receptor agonist [Nle10]-neurokinin A4-10 (NK2 agonist) was not effective at 70 microM but produced a small and significant effect at 330 microM, whereas the neurokinin3 receptor agonist [MePhe7]-neurokinin B (NK3 agonist) was without effect at 40 microM or 400 microM. 4 Injections of SP or NKA into the synovial cavity of the rat knee were equally effective in producing marked plasma extravasation in remote sites such as the forelimb and hindlimb paws. 5 Co-administration experiments showed that the effects of SP were synergistic with NKA or the NK1 receptor agonist, but not with CGRP or the NK2 receptor agonist. 6 The rank order of potency was NK1 agonist greater than or equal to SP greater than NKB greater than NK2 agonist suggesting that NK1 receptors mediate plasma extravasation in the rat knee joint.

The role of the endothelium in mediating the actions of ATP, adenosine and acetylcholine on flow through blood vessels in the rabbit knee joint.

1. An in vitro preparation of the rabbit knee joint, perfused with oxygenated Locke solution, was used to investigate the presence of purinoceptors and the role of endothelium within articular blood vessels. 2. The basal tone of the blood vessels was not affected by adenosine or acetylcholine. Adenosine 5'-triphosphate (ATP) injection produced vasoconstriction which was unaffected by removal of the endothelial layer, but diminished by alpha, beta methylene ATP, a compound which desensitizes P2-purinoceptors. 3. When knee joint blood vessel tone was raised by perfusion with vasopressin (10(-8) M) or 5-hydroxytryptamine (10(-5) M), acetylcholine, ATP and adenosine were all found to induce concentration-dependent relaxation of these vessels. ATP was found to have a dual effect of transient constriction followed by longer-lasting dilatation. 4. 3-Methylxanthine, a P1-purinoceptor antagonist significantly reduced the relaxation response to adenosine but had no effect on the vasodilator effect of ATP. 5. Removal of the endothelial layer virtually abolished the vasodilator effects of acetylcholine and ATP but not adenosine. 6. These results demonstrate that articular blood vessels supplying the rabbit knee contain P1-purinoceptors located on the vascular smooth muscle which mediate vasodilatation. P2-purinoceptors mediating a constrictor effect are also present on this smooth muscle. It is likely that the vasodilator effect of ATP is mediated via P2-purinoceptors located on the endothelial layer.

Sympathetic innervation and alpha-adrenoceptor profile of blood vessels in the posterior region of the rabbit knee joint.

1. Experiments were performed to determine the nature of adrenoceptors mediating neurally-induced vasoconstriction of blood vessels in the posterior region of the rabbit knee joint capsule. 2. Electrical stimulation of the posterior articular nerve resulted in frequency-dependent vasoconstriction which was maximal at 10 Hz. This response was mediated predominantly by alpha 2-adrenoceptors as it was only slightly reduced by prazosin administration and was not only abolished but converted into a dilator response by the alpha 2-adrenoceptor antagonist rauwolscine. Further experiments with another specific alpha 1-adrenoceptor antagonist YM-12617 showed that the frequency-response curve in the presence of this antagonist did not differ significantly from control. 3. Neurally-induced vasoconstriction did not appear to have a purinergic component as it was unaffected by the P2x-purinoceptor desensitiser alpha, beta methylene ATP. 4. The rank-order of potency of alpha-adrenoceptor agonists given as a bolus by close intra-arterial injection was: adrenaline = UK-14304 > clonidine > phenylephrine, suggesting that the vasoconstrictor effects were mediated predominantly by postjunctional alpha 2-adrenoceptors. 5. The alpha 2-adrenoceptor antagonist rauwolscine converted the constrictor response to close intra-arterial injection of adrenaline into a dilator response. The vasoconstrictor responses to UK-14304, clonidine and phenylephrine were substantially inhibited by rauwolscine. The alpha 1-adrenoceptor antagonist prazosin failed to inhibit the vasoconstrictor responses to adrenaline, clonidine and UK-14304 and resulted in enhancement of their constrictor effects. 6. The enhancement of the responses to the a, and a2 agonists by prazosin appeared to be specifically related to this agent as administration of YM-12617 did not show such enhancement. The dose-response curves to both clonidine and UK-14304 in the presence of YM-12617 did not differ significantly from control responses. Responses to phenylephrine were significantly reduced by YM-12617, indicating the presence of post-junctional a,-adrenoceptors.7. These results show almost complete reversal of the adrenoceptor profile compared to results obtained in an earlier in vitro study, where responses were mediated predominantly by ax,-adrenoceptors with a small population of postjunctional a2-adrenoceptors (Ferrell & Khoshbaten, 1989). This suggests that the differing environment in vitro may not completely reflect the conditions prevailing in vivo.

Effects of interactions of naturally-occurring neuropeptides on blood flow in the rat knee joint.

1. Changes of blood flow in the rat knee joint, measured by laser Doppler flowmetry, were produced by topical application of naturally-occurring neuropeptides to the joint capsule. 2. Substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) all produced dose-dependent transient vasodilatation of the rat knee joint microvasculature. NKB showed significantly smaller vasodilator responses compared to SP and NKA which were similar in their potencies. 3. Calcitonin gene-related peptide (CGRP) produced dose-dependent vasodilatation which was more pronounced than that produced by the neurokinins. The rank order of potency was: CGRP > SP = NKA > NKB. The vasodilator effect of CGRP was also more prolonged and this extended phase was abolished by co-administration of SP. 4. Cross-tachyphylaxis was not observed with the different neurokinins, but SP and NKA showed novel antagonistic effects on NKB-induced vasodilatation. 5. Co-administration of 1 nmol of the specific NK1 receptor antagonist, CP-96345, with 1 nmol of each of the neurokinins produced significant inhibition of the vasodilator response to SP but did not affect vasodilator responses to NKA and NKB. Co-administration of CP-96345 with the neurokinins plus superfusion of the rat knee joint with a solution containing 0.1 mM CP-96345 further reduced the vasodilator responses to SP but again the vasodilator responses to NKA and NKB were not significantly altered. 6. The results suggest that multiple neurokinin receptor types may be present in the rat knee joint which could mediate the vasodilator responses of the different neurokinins. Co-release of neuropeptides from sensory nerve endings in the rat knee joint may have inter-regulatory actions on their individual responses on the microvasculature.

Modulation of synovial blood flow by the calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP(8-37).

1. The effect of the calcitonin gene-related peptide (CGRP) receptor antagonist, CGRP(8-37) on blood flow in the knee joint of the anaesthetized rat was investigated. 2. Synovial blood flow in both exposed and intact, skin-covered knees was measured by laser Doppler perfusion imaging. 3. Topical application of CGRP(8-37) caused a dose-dependent fall in synovial blood flow in the exposed knee joint of the rat. At low (1.5 nmol) doses of CGRP(8-37) there was no significant effect on synovial blood flow. In rats treated with 7.5 nmol CGRP(8-37) there was a fall in synovial blood flow (maximum effect at 10 min: -28.8 +/- 4.6%; n=7), which returned to resting levels within 30 min. The highest dose (15 nmol) of antagonist used in this study caused a marked (maximum at 10 min: -35.6 +/- 9.3%; n=8), and prolonged (up to 30 min) fall in blood flow. 4. Ten days after surgical denervation, CGRP(9-37) (15 nmol, topical) had no significant effect on blood flow in the rat exposed knee joint (change in flux at 10 min: -5.1+/-3.6%; n=4). This suggests that CGRP(8-37) acts selectively to antagonize the actions of a neurally derived product, probably CGRP, on the rat synovial vasculature. 5. In skin-covered knee joints, intra-articular injection of CGRP(8-37) (15 nmol; bolus) elicited a significant fall in synovial blood flow (maximum effect at 10 min: -15.5 +/- 5.8%; n=6). 6. CGRP (0.01, 0.1 or 1.0 nmol; topical) caused a dose-dependent increase in exposed knee joint blood flow, which was attenuated by co-administration of 1.5 nmol CGRP(8-37). For example, 1 nmol CGRP elicited a peak increase in flux at 10 min of 94.7 +/- 31.8% (n=8) and 28.8 +/- 8.9% (n=7) in the absence and presence of CGRP(8-37), respectively. The vasodilator responses induced by acetylcholine (ACh) (10 nmol, topical; n=4-5) or sodium nitroprusside (SNP) (10 nmol, topical; n=4-5) were unaltered in the presence of CGRP(8-37) (1.5 nmol, topical). 7. Thus, the CGRP receptor antagonist CGRP(8-37) elicits vasoconstriction in the rat synovium. This suggests that the endogenous, basal release of CGRP may play a physiological role in the regulation of blood flow in the rat knee joint.

Spatial heterogeneity of the effects of calcitonin gene-related peptide (CGRP) on the microvasculature of ligaments in the rabbit knee joint.

1. Experiments were performed in anaesthetized rabbits to examine the effects of calcitonin gene-related peptide (CGRP) and the CGRP antagonist CGRP8-37 on blood flow to the medial collateral ligament of the knee joint. 2. Topical application of CGRP (10(-13) to 10(-9) mol) to the exposed external surface of eight knee joints resulted in dose-dependent dilatation of vessels in both the ligament and the joint capsule. The magnitude of this response varied significantly in different regions of the medial collateral ligament, with the 10(-9) mol dose of CGRP giving the maximum response (101.5 +/- 25.3% increase) at the femoral insertion site of the medial collateral ligament and lowest (23.1 +/- 8.8%) at the tibial insertion site. 3. Topical application of CGRP8-37 (0.1, 1 and 10 nmol) produced dose-dependent constriction of vessels in the ligament and the joint capsule in five knees, with a trend towards the greatest effect occurring at the femoral insertion site (45.8 +/- 8.1% reduction in blood flow). With the 10 nmol dose, the vasoconstrictor response at the femoral insertion site differed significantly (P<0.05) from the responses obtained at the tibial insertion and joint capsule sites. 4. Topical application of CGRP8-37 (0.1, 1 and 10 nmol) to four chronically denervated knees produced substantially smaller vasoconstrictor responses at all sites. At the femoral insertion site, where 10 nmol CGRP8-37 normally produces a 45.8 +/- 8.1% reduction in blood flow (n=8), ten days following denervation this response was reduced to 6.5 +/- 6.1%, this difference being significant (P=0.01). 5. Adrenaline was applied topically to augment blood vessel tone, in order to establish how effectively co-administration of CGRP would offset this increase in tone. Adrenaline (10(-10) mol) produced vasoconstriction at all sites (n=6). In the capsule this vasoconstriction was virtually abolished when CGRP (10(-9) mol) was co-administered with adrenaline but in the ligament vasodilatation occurred at all sites. This vasodilatation was significantly greater at the femoral insertion site compared to the tibial insertion and mid ligament sites (P<0.05 for both) and the capsule (P<0.01). 6. Topical application of substance P (10(-10) or 10(-9) mol) failed to elicit dilatation of ligament blood vessels. 7. These results suggest that endogenous CGRP may play an important role in regulating blood flow to different structures in and around the knee joint.

Tachykinin regulation of basal synovial blood flow.

1. Experiments were performed to investigate the role of endogenously released tachykinins in the regulation of blood flow to the rat knee joint. Synovial perfusion was assessed by laser Doppler perfusion imaging, which permitted spatial measurement of relative changes in perfusion from control (pre drug administration), expressed as the percentage change. Most experiments were performed on the exposed medial aspect of the knee joint capsule. 2. Neither the selective tachykinin NK1 receptor antagonist, FK888, nor the selective tachykinin NK2 receptor antagonist, SR48968, significantly influenced synovial blood flow at doses of 10(-12), 10(-10) and 10(-8) mol. However, topical co-administration of these agents produced significant dose-dependent reductions in basal synovial perfusion of 6.3 +/- 4.6 and 12.0 +/- 3.4 and 19.9 +/- 2.6%, respectively; n = 29. The non-selective tachykinin NK1/NK2 receptor antagonist, FK224, also produced significant (at 10(-10) and 10(-8) mol), but less potent, reductions in perfusion of 5.3 +/- 4.0, 8.4 +/- 2.2 and 5.9 +/- 2.8%, respectively; n = 25. 3. Topical administration of the alpha 1-, alpha 2-adrenoceptor antagonist phenoxybenzamine elicited a 31.3 +/- 6.2% increase in blood flow which was substantially reduced to 10.4 +/- 3.8% by co-administration of the FK888 and SR48968 (both at 10(-8) mol; n = 8-13), suggesting that normally there is sympathetic vasoconstrictor "tone' which is opposed by the vasodilator action of endogenous tachykinins. 4. One week after surgical interruption of the nerve supply to the knee joint, co-administration of FK888 and SR48968 (both at 10(-8) mol) now produced slight vasodilatation (6.7 +/- 4.6%; n = 9) which did not differ significantly from vehicle treatment. Depletion of tachykinins from sensory nerve fibres by systemic capsaicin administration also resulted in abolition of the vasoconstrictor effect of FK888 and SR48968 (both at 10(-8) mol), with these agents only producing a slight vasodilatation (2.5 +/- 5.3%; n = 6). 5. By use of a near infra-red laser source it was possible to image knee joint perfusion transcutaneously, the overlying skin being left intact. In this more physiological situation, close intra-arterial injection of the combination of FK888 and SR48968 (both at 10(-8) mol) again elicited vasoconstriction (48.8 +/- 16.2% reduction in blood flow; n = 4). 6. These results indicate that endogenous tachykinins may be continuously released from sensory fibers innervating the joint. Basal release of tachykinins could therefore be an important physiological influence opposing sympathetic vasoconstrictor tone.

Improved imaging diagnosis by sequentially combined confidence judgments.

Consultation among radiologists improves diagnostic efficacy. However, it is unclear in practice when consultation is indicated, and consultation may be logistically difficult. We present a computerized method of noninteractive consultation that supersedes these problems, using radiograph readers' confidence judgments in their decisions. Individual categorical confidence judgments of excretory urogram diagnoses were transformed into diagnostic probabilities, then combined sequentially by computer simulation with other radiologists' probabilities until sufficient group confidence was achieved. Appropriate stopping rules were defined empirically. Analysis of cost effectiveness of this model--considering the cost of sequential interpretations and a range of costs for false-positive and false-negative errors--indicates that mathematically combined sequential decisions are more efficacious and less costly than individuals interpreting urograms alone.

Interactive, mathematical, and sequential consultative methods in diagnosing renal masses on excretory urograms.

Using the clinical setting of diagnosing renal masses on excretory urograms, we compared the diagnostic efficacy and costs resulting from different consultative methods. These included face-to-face interactive consultation, mathematical combination of a fixed number of radiologists' confidence judgments, and computerized sequential decision making. This last method mathematically combines a variable number of individual judgments into an aggregate diagnosis based on diagnostic certainty. Six radiologists interpreted 42 proven urograms individually, with face-to-face consultation for selected cases, and interactively in groups of three. Individual diagnostic probability estimations were mathematically combined for the mathematical and sequential models. All models of consultation resulted in both higher diagnostic accuracy and lower costs than individual radiologists interpreting urograms alone. While the sequential model provided the highest diagnostic efficacy, it was only slightly more accurate than the other models tested. Radiologists interactively consulting on cases they considered difficult was the least costly method, approximating the projected costs of sequential decision making. Interactive consultation among radiologists is a cost-effective practice; sequential decision-making is a promising technique for improving diagnostic efficacy and reducing costs, and further evaluation is warranted.

Age-dependent changes in position sense in human proximal interphalangeal joints.

Using a position matching paradigm, the ability of subjects to detect displacements at the proximal interphalangeal joint of the index finger was tested. These displacements were imposed at an angular velocity of 2 degrees per minute which is below the threshold for movement detection. An older group of subjects whose mean age (+/- s.e.m.) was 56.6 +/- 3.2 years showed significantly poorer performance in detecting the position of the index finger than a group of younger subjects (23.7 +/- 0.5 years). Analysis of the correlation between age and magnitude of matching error gave a positive correlation coefficient of 0.466 which was statistically significant. However, there was no systematic bias in judgements of finger position by the older group. These results indicate that the sense of position of the fingers decrements with age.