Mechanisms of pain arising from articular tissues

This paper reviews the peripheral and central neural mechanisms underlying pain from articular tissues innervated by spinal and trigeminal afferents. The paper especially addresses trigeminal mechanisms related to pain from the temporomandibular joint and its associated craniofacial musculature. Recent studies have shown the existence of articular nociceptive primary afferents that project to the spinal cord dorsal horn and trigeminal brainstem complex. A particular feature of most neurones receiving these deep nociceptive afferent inputs is their responsivity also to cutaneous nociceptive afferent inputs. This suggests the involvement of these neurones not only in the detection of acute articular pain, but also in the hyperalgesia and poor localization, spread, and referral of pain that characterize many painful conditions of joints and other deep structures. While only limited information is available on related higher brain centre mechanisms, convergence and interaction between cutaneous and deep afferent inputs also seem to be a characteristic of somatosensory neurones in the thalamus and somatosensory cerebral cortex. Muscle and autonomic reflexes may be induced by such deep noxious stimuli, but the functional significance of some of these effects (e.g., in relation to clinical concepts of myofascial dysfunction) requires further study in more appropriate functional settings.     

Disturbance mediates the effects of nutrients on developing assemblages of epibiota

Local dynamics such as resource enhancement (e.g. nutrient supply) and stochastic events of destruction (disturbances that provide new space) are hypothesized to counteractively affect species diversity and composition. We tested the independent and interactive effects of nutrients and disturbance on the development of assemblages of epibiota attached to vertical surfaces in an oligotrophic system. Nutrient concentrations were manipulated at three levels (ambient, medium and high) while disturbance was manipulated by removing biomass at seven frequencies (0×, 2×, 3×, 4×, 5×, 7×, 12×). Nutrient and disturbance regimes had opposing effects on diversity such that species richness increased with resource enhancement (nutrients) and declined with disturbance. These results support the model that increased heterogeneity of distribution of limiting resources allows the coexistence of species with low and high resource requirements.     

ST-segment elevation associated with allergic reaction to echocardiographic contrast agent administration

We report a case of an allergic reaction after the administration of an echocardiographic contrast agent which resulted in ST-segment elevation. Hypersensitivity and allergic reactions are known causes of acute cardiovascular events. However, only limited reports are available which suggest the exact mechanism of the occurrence of angina or myocardial infarction during severe allergic reactions. In our case, through invasive imaging (coronary angiography and IVUS) we have shown for the first time a transient coronary spasm in the absence of intra-coronary thrombus and only minimal neointimal hyperplasia.     

Influence of single-level lumbar degenerative disc disease on the behavior of the adjacent segments—A finite element model study

The current study investigated mechanical predictors for the development of adjacent disc degeneration. A 3-D finite element model of a lumbar spine was modified to simulate two grades of degeneration at the L4–L5 disc. Degeneration was modeled by changes in geometry and material properties. All models were subjected to follower preloads of 800 N and moment loads in the three principal directions of motion using a hybrid protocol. Degeneration caused changes in the loading and motion patterns of the segments above and below the degenerated disc. At the level (L3–L4) above the degenerated disc, the motion increased due to moderate degeneration by 21% under lateral bending, 26% under axial rotation and 28% under flexion/extension. At the level (L5-S1) below the degenerated disc, motion increased only during lateral bending by 20% due to moderate degeneration. Both the L3–L4 and L5-S1 segment showed a monotonic increase in both the maximum von Mises stress and shear stress in the annulus as degeneration progressed for all loading directions, expect extension at L3–L4. The most significant increase in stress was observed at the L5-S1 level during axial rotation with nearly a ten-fold increase in the maximum shear stress and 103% increase in the maximum von Mises stress. The L5-S1 segment also showed a progressive increase in facet contact force for all loading directions with degeneration. Nucleus pressure did not increase significantly for any loading direction at either the caudal or cephalic adjacent segment. Results suggest that single-level degeneration can increase the risk for injury at the adjacent levels.     

Transplantation of organic surface horizons of boreal soils into warmer regions alters microbiology but not the temperature sensitivity of decomposition

Changes in soil carbon, the largest terrestrial carbon pool, are critical for the global carbon cycle, atmospheric CO₂ levels and climate. Climate warming is predicted to be most pronounced in the northern regions and therefore the large soil carbon pool residing in boreal forests will be subject to larger global warming impact than soil carbon pools in the temperate or the tropical forest. A major uncertainty in current estimates of the terrestrial carbon balance is related to decomposition of soil organic matter (SOM). We hypothesized that when soils are exposed to warmer climate the structure of the ground vegetation will change much more rapidly than the dominant tree species. This change will alter the quality and amount of litter input to the soil and induce changes in microbial communities, thus possibly altering the temperature sensitivity of SOM decomposition. We transferred organic surface soil sections from the northern borders of the boreal forest zone to corresponding forest sites in the southern borders of the boreal forest zone and studied the effects of warmer climate after an adaptation period of 2 years. The results showed that initially ground vegetation and soil microbial community structure and community functions were different in northern and southern forest sites and that 2 years of exposure to warmer climate was long enough to cause changes in these ecological indicators. The rate of SOM decomposition was approximately equally sensitive to temperature irrespective of changes in vegetation or microbial communities in the studied forest sites. However, as temperature sensitivity of the decomposition increases with decreasing temperature regime, the proportional increase in the decomposition rate in northern latitudes could lead to significant carbon losses from the soils.     

The addition of CO2 to traditional taste solutions alters taste quality

Previous studies of the effect of carbonation on taste perception have suggested that it may be negligible, manifesting primarily in increases in the perceived intensity of weak salt and sour stimuli. Assuming CO2 solutions in the mouth stimulate only trigeminal nerve endings, this result is not altogether surprising; however, there are neurophysiological data indicating that CO2 stimulates gustatory as well as trigeminal fibers. In that case, carbonation might alter the quality profile of a stimulus without producing substantial changes in overall taste intensity--much as occurs when qualitatively different taste stimuli are mixed. To address this possibility, subjects were asked to rate the total taste intensity of moderate concentrations of stimuli representing each of the basic tastes and their binary combinations, with an without added carbonation. They then subdivided total taste intensity into the proportions of sweetness, saltiness, sourness, bitterness and 'other taste qualities' they perceived. The addition of carbonation produced only small increases in ratings of total taste intensity. However, rather dramatic alterations in the quality profiles of stimuli were observed, particularly for sweet and salty tastes. The nature of the interaction is consistent with a direct effect of carbonation/CO2 on the gustatory system, although the possibility that at least some of the observed effects reflect trigeminal-gustatory interactions cannot be ruled out.      

Psychophysical evidence of taste dysfunction in burning mouth syndrome

Because subjects with burning mouth syndrome (BMS) frequentlyreport impaired taste, the present study was carried out on47 BMS subjects and 27 age–and sex-matched control subjectsto determine if there was any psychophysical evidence of tastedysfunction in BMS. Taste detection thresholds and taste intensityscaling for the modalities of sweet, salt, bitter and sour wereobtained. Compared with control subjects, BMS subjects as awhole displayed statistically significant alterations in sensorydysfunction both at threshold (for sweet) and at suprathresholdlevels (for sweet and sour). The BMS subjects were subsequentlydivided into those subjects who reported a dysgeusic tase (–75and 60% of the BMS subjects tested at threshold and suprathresholdlevels, respectively) and those without a dysgeusic taste ({smalltilde}24 and 40% of the subjects tested at threshold and suprathresholdlevels, respectively). When the data of these two groups werecompared with those of the control subjects, it became evidentthat at suprathreshold levels, differences in taste functionoriginated mainly from those BMS subjects with complaints ofa dysgeusic taste. These findings therefore indicate that psychophysicalevidence of taste dysfunction can be demonstrated in BMS andthat the changes in taste perception are particularly evidentin those BMS subjects with a self-reported symptom of dysgeusia.