Demonstration of facilitatory I wave interaction in the human motor cortex by paired transcranial magnetic stimulation

1. Transcranial magnetic stimulation (TMS) of the human motor cortex results in multiple discharges (D and I waves) in the corticospinal tract. We tested whether these volleys can be explored non-invasively with paired TMS. The intensity of the first stimulus (S1) was set to produce a motor-evoked potential (MEP) of 1 mV in the resting contralateral abductor digiti minimi (ADM) muscle; the second stimulus (S2) was set to 90 % of the resting motor threshold. At interstimulus intervals of 1.1-1.5, 2.3-2.9 and 4.1-4.4 ms the MEP elicited by S1 plus S2 was larger than that produced by S1 alone. 2. Varying the S1 intensity between 70 and 130 % resting motor threshold with S2 held constant at 90 % resting motor threshold showed that the threshold for the first MEP peak was <= 70 % resting motor threshold. The second and third MEP peaks appeared only at higher S1 intensities. The latency of all peaks decreased with increasing S1 intensity. 3. Varying the S2 intensity with S1 held constant to produce a MEP of 1 mV on its own showed that the amplitude of all MEP peaks increased with S2 intensity, but that their timing remained unchanged. 4. Paired TMS in the active ADM (S1 clearly suprathreshold, S2 just above threshold; interstimulus interval, 1 ms) produced strong MEP facilitation. The onset of this facilitation occurred later by about 1.5 ms than the onset of the MEP evoked by S2 alone. No MEP facilitation was seen if the magnetic S2 was replaced by anodal or cathodal transcranial electrical stimulation. 5. It is concluded that the MEP facilitation after paired TMS, at least for the first MEP peak, is due to facilitatory interaction between I waves, and takes place in the motor cortex at or upstream from the corticospinal neurone.

Stimulation and inhibition of adenylyl cyclases mediated by distinct regulatory proteins

Adenylyl cyclases are under positive and negative control by guanine nucleotides and hormones. Stimulatory responses are mediated by a guanine nucleotide- and Mg-binding regulatory component (Ns), a protein that has been purified to homogeneity. Inhibitory responses have been hypothesized to be mediated by an analogous regulatory component (Ni) distinct from Ns, but definitive proof for this is lacking and these effects may result from modulation of Ns activity. Recently, Bordetella pertussis toxin has been shown to ADP-ribosylate a peptide that is not part of Ns, and this coincides with attenuation of hormonal inhibition of adenylyl cyclase. We show here that cyc- S49 cells contain a substrate for ADP-ribosylation by pertussis toxin and that the toxin alters GTP dependent inhibition of cyc- adenyl cyclase activity. As cyc- S49 cells do not contain Ns by several criteria, we conclude that Ni is a distinct and separate regulatory component of adenylyl cyclase.

Pertussis toxin substrate, the putative Ni component of adenylyl cyclases, is an alpha beta heterodimer regulated by guanine nucleotide and magnesium

The final step in a scheme for the purification of the guanine nucleotide- and Mg2+-binding stimulatory regulatory component (Ns) of adenylyl cyclase [adenylate cyclase; ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] from human erythrocyte membranes involves chromatography over hydroxylapatite (HAP) which yields two fractions. The first fraction (HAP I) contains predominantly two peptides that, upon sodium dodecyl sulfate/polyacrylamide gel electrophoresis, migrate with Mr values of 39,000 and 35,000. The second fraction (HAP II) contains predominantly Ns formed of two peptides of Mr 42,000 and 35,000. The HAP I, Mr 39,000 peptide is shown to be a substrate for the ADP-ribosylating toxin of Bordetella pertussis (pertussis toxin). Upon sucrose density gradient centrifugation, both the Mr 39,000 and the Mr 35,000 peptides of HAP I migrate at about 4 S. Treatment of HAP I with guanine nucleotide and Mg2+ prior to centrifugation results in a coordinated change in the migration of both peptides to 2 S. It is postulated that HAP I contains an alpha beta heterodimeric protein composed of an alpha subunit of Mr 39,000 and a beta subunit of Mr 35,000. Further, this protein dissociates under the influence of guanine nucleotides and Mg2+ into its individual alpha and beta subunits. Because previous studies have shown that treatment of cells and cell membranes with pertussis toxin results in attenuation of the effects of hormones that inhibit adenylyl cyclase activity, and because this effect correlates with the ADP-ribosylation of a Mr approximately equal to 40,000 peptide, we believe that we have purified a guanine nucleotide- and Mg2+-binding inhibitory regulatory component of adenylyl cyclases--i.e., the Ni.

Prediction of success from a multidisciplinary treatment program for chronic low back pain

STUDY DESIGN

The study included 90 disabled patients with chronic low back pain recruited from a pain clinic who were admitted to an 8-week program of functional restoration and behavioral support. Initial evaluations included a medical examination, rating of the physical impairment, a personal interview, a visual analogue scale to record pain intensity, an assessment of limitations for daily activities, a pain disability index, a depression and psychovegetative scale, and a scale to evaluate general living standards. The physical assessment included different flexibility measurements, measurement of power and endurance through standardized exercises, and measurements of isokinetic trunk and lifting strength and general endurance. The measurements were repeated at the end of the 8-week program and thereafter an intervals of 6 and 12 months. Final analyses were carried out on 82 patients.

OBJECTIVES

To determine whether objective or subjective signs most influence the outcome of rehabilitation.

SUMMARY OF BACKGROUND DATA

In recent years, several studies have shown that active and intensive multimodal treatment of chronic low back pain is successful. Until now there has been lack of information about which patients will respond to the therapy and what is the most effective part of treatment.

METHODS

Prognostic factors (return to work, pain intensity, self-assessment of treatment success by patients) were tested by studying variance and regression analyses for their ability to predict treatment outcome.

RESULTS

Certain factors were identified that had a significant impact on determining the probability of a patient's return to work and the reduction of pain intensity. These factors included self-evaluation for predicting a return to work, the length of absence from work, application for pension, and a decrease is disability after treatment. Overall satisfaction with treatment was best determined by the number of medical consultations before treatment, the extent of disability, previous measures taken for coping with the disease, and reduction of disability during treatment. Medical background, medical diagnosis, and physical impairment had no predictive value. Physical variables (i.e., mobility, strength, endurance, and physical performance) also demonstrated only limited predictive value.

CONCLUSION

This study has demonstrated that the most important variable in determining a successful treatment of chronic low back pain is the reduction of subjective feelings of disability in patients.

Pharmacological control of facilitatory I-wave interaction in the human motor cortex. A paired transcranial magnetic stimulation study

A novel paired transcranial magnetic stimulation (TMS) paradigm with a suprathreshold first and a subthreshold second stimulus was used in healthy volunteers to investigate the acute effects of a single oral dose of various CNS-active drugs on short-interval motor evoked potential (MEP) facilitation. MEPs were recorded from the relaxed abductor digiti muscle. Three peaks of MEP facilitation were consistently observed at interstimulus intervals of 1.1-1.5 ms, 2.3-2.7 ms, and 3.9-4.5 ms. The size of these MEP peaks was transiently suppressed by drugs which enhance gamma-aminobutyric acid (GABA) function in the neocortex (lorazepam, vigabatrin, phenobarbital, ethanol), while the GABA-B receptor agonist baclofen, anti-glutamate drugs (gabapentin, memantine), and sodium channel blockers (carbamazepine, lamotrigine) had no effect. The interstimulus intervals effective for the production of the MEP peaks remained unaffected by all drugs. The MEP peaks are thought to be due to a facilitatory interaction of I-(indirect) waves in the motor cortex. Therefore, the present results indicate that the production of I-waves is primarily controlled by GABA related neuronal circuits. The potential relevance of this non-invasive paired TMS protocol for the investigation of I-waves in patients with neurological disease will be discussed.

Validation of the German version of the Fear-Avoidance Beliefs Questionnaire (FABQ)

Fearful avoidance of physical activities is a major factor in low back pain (LBP) and disability. In 1993 Waddell et al. developed the Fear-Avoidance Beliefs Questionnaire (FABQ) focusing on patients' beliefs about how physical activity and work affect LBP. The focus of our study was to analyse and validate the German version of the FABQ. Three-hundred and two consecutive LBP outpatients participating on a functional restoration programme filled in the FABQ. Factor analysis yielded three factors which accounted for nearly 65% of the total variance of the questionnaire. Whereas the factor 'physical activity' (8.9% of the variance) remained the same as in the English version, the second factor of the original version split into two: one related to, 'work as cause of pain' (43.4% of the variance) and the other to patients' assumptions of their probable return to work (11.8% of the variance). Both work-related subscales showed a good internal consistency (alpha = 0.89, resp. alpha = 0.94), whereas the consistency of the subscale 3 'physical activity' was only modest (alpha = 0.64). Test-re-test reliability score was fair to good for the whole scale (r = 0.87;n = 30). Regression analysis demonstrated that fear-avoidance beliefs account for the highest proportion of variance (35%) regarding disability in activities of daily living and work loss. Patients out of work demonstrated more fear-avoidance beliefs in comparison to those who were still working. It can be concluded that the German version of the FAQB is a reliable and valid instrument, but it shows a different factor structure from the original English version. The FABQ has been proven to identify patients with maladaptive beliefs which have to be focused on in proper treatment.

Abdominal distension alters regional pleural pressures and chest wall mechanics in pigs in vivo

Abdominal distension (AD) occurs in pregnancy and is also commonly seen in patients with ascites from various causes. Because the abdomen forms part of the "chest wall," the purpose of this study was to clarify the effects of AD on ventilatory mechanics. Airway pressure, four (vertical) regional pleural pressures, and abdominal pressure were measured in five anesthetized, paralyzed, and ventilated upright pigs. The effects of AD on the lung and chest wall were studied by inflating a liquid-filled balloon placed in the abdominal cavity. Respiratory system, chest wall, and lung pressure-volume (PV) relationships were measured on deflation from total lung capacity to residual volume, as well as in the tidal breathing range, before and 15 min after abdominal pressure was raised. Increasing abdominal pressure from 3 to 15 cmH2O decreased total lung capacity and functional residual capacity by approximately 40% and shifted the respiratory system and chest wall PV curves downward and to the right. Much smaller downward shifts in lung deflation curves were seen, with no change in the transdiaphragmatic PV relationship. All regional pleural pressures increased (became less negative) and, in the dependent region, approached 0 cmH2O at functional residual capacity. Tidal compliances of the respiratory system, chest wall, and lung were decreased 43, 42, and 48%, respectively. AD markedly alters respiratory system mechanics primarily by "stiffening" the diaphragm/abdomen part of the chest wall and secondarily by restricting lung expansion, thus shifting the lung PV curve as seen after chest strapping. The less negative pleural pressures in the dependent lung regions suggest that nonuniformities of ventilation could also be accentuated and gas exchange impaired by AD.

Lumbar range of motion: reliability and validity of the inclinometer technique in the clinical measurement of trunk flexibility

STUDY DESIGN

This study examines the reliability and validity of measuring lumbar range of motion with an inclinometer.

OBJECTIVES

To find out whether a manual determination of the reference points for measuring lumbar range of motion is as reliable as radiologic determination for positioning the inclinometers, lumbar range of motion was determined in degrees by evaluating radiographs and by using the inclinometer technique of Loebl.

SUMMARY OF BACKGROUND DATA

Reliability and validity of the inclinometer technique as a clinical measurement of trunk flexibility were investigated. Fifty-four patients participated in the study.

METHODS

Lumbar range of motion measurements were taken with and without radiologic control of the T12 and S1 vertebrae as reference points for positioning of the inclinometers. An interrater correlation was done of the inclinometer techniques of a physician and a physiotherapist. Functional radiographs were investigated in a standing position. Lumbar range of motion measurements based on radiographs and those taken using the inclinometer alone were correlated to validate the inclinometer technique.

RESULTS

Lumbar range of motion measurements taken with and without radiologic determination showed a very close correlation (r = 0.93; P < 0.001). Flexion alone also demonstrated a close correlation (r = 0.95; P < 0.001), whereas extension showed a somewhat smaller correlation (r = 0.82; P < 0.001). Total lumbar range of motion (r = 0.94; P < 0.001) and flexion (r = 0.88; P < 0.001) were closely related, as indicated by the interrater correlation, whereas extension (r = 0.42; P < 0.05) showed a lesser correlation. Correlation of the measurements taken radiographically and by inclinometer demonstrated an almost linear correlation for measurements of the total lumbar range of motion (r = 0.97; P < 0.001) and flexion (r = 0.98; P < 0.001), whereas extension (r = 0.75; P < 0.001) did not correlate as well.

CONCLUSIONS

The noninvasive inclinometer technique proved to be highly reliable and valid, but the measurement technique for extension needs further refinement.

Increased surface tension favors pulmonary edema formation in anesthetized dogs' lungs

The possibility that surface tension may affect the hydrostatic transmural pressure of pulmonary vessels and the development of pulmonary edema was studied in anesthetized, open-chested dogs. Isogravimetric pressure (the static intravascular pressure at which transmural osmotic and hydrostatic pressures are balanced such that net fluid flux is zero and lung weight is constant) was measured in nine animals under three conditions: (a) control, normal surface tension, at an alveolar pressure of 30 cm H2O with the apenic lung at room temperature; (b) after increasing surface tension by cooling and ventilating at a low functional residual capacity, at an alveolar pressure sufficient to produce the same lung volume present during control measurements; and (c) after restoring surface tension by rewarming while holding the lung at a high inflation volume, again at the control lung volume. Lung volumes were established from external dimensions and confirmed +/- 10% by deflation spirometry. The isogravimetric pressure (relative to alveolar pressure) was significantly less with increased surface tension than during either the initial control condition (P less than 0.01), or when the surface tension has been restored (P less than 0.01). Similar changes occurred in each of three additional studies performed with control alveolar pressures of 10 cm H2O. Thus, increased surface tension favors fluid leakage presumably because it increases the microvascular transmural pressure.

Role of subunit diversity in signaling by heterotrimeric G proteins

The heterotrimeric G proteins are extensively involved in the regulation of cells by extracellular signals. The receptors that control them are often the targets of drugs. There are many isoforms of each of the three subunits that make up these proteins. Thus far, genes for at least sixteen alpha subunits, five beta subunits, and eleven gamma subunits have been identified. In addition, some of these proteins have splice variants or are differentially modified. Based upon what is already known, there are well over a thousand possible G protein heterotrimer combinations. The role of subunit diversity in heterotrimer formation and its effect on signaling by G proteins are still not well understood. However, many current lines of research are leading toward an understanding of these roles. The functional significance of subunit heterogeneity is related to the mechanisms used by G proteins to transmit and integrate the many signals coming into cells through this system. Described here are the basic mechanisms by which G proteins integrate cellular responses, the possible role of subunit heterogeneity in these mechanisms, and the evidence for and against their physiological significance. Recent studies suggest the likely possibility that subunit heterogeneity plays an important role in signaling by G proteins. This role has the potential to extend substantially the flexibility of G proteins in mediating cellular responses to extracellular signals. However, the details of this are yet to be worked out, and they are the subject of many different avenues of research.

Effectiveness of a multimodal treatment program for chronic low-back pain

In recent years, multidisciplinary pain programs were seen to successfully treat patients by basing treatment on a combination of physical exercise and psychological interventions. However, in spite of their effectiveness, it still remains to be clarified exactly which features of these programs were responsible for patient improvement. Cognitive-behavioral models posit that improvement is due, in part, to changes in patient coping strategies. Nonetheless, as reflected by the conflicting opinions present in the literature, it is questionable whether a so-called 'cognitive shift' is an accurate indicator for return to work of disabled patients. Ninety patients with chronic low back pain took part in a multidisciplinary treatment program. Therapeutic environment reinforces wellness behavior and enhances the patients' sense of control over their pain and resulting disability. The main therapeutic target point was to facilitate return to work. Ways of coping were measured by a well studied coping inventory in the German language (FEKB). Factor analysis revealed three factors: 'catastrophizing', 'search for information' and 'cognitive control'. In addition, assessment included measurements of pain intensity, depression, disability, flexibility of the lumbar spine, and different performance parameters. All of them were measured prior to and at the end of treatment, and following intervals of 6 and 12 months after discharge from program. Measurements showed significant changes over time, but more importantly, nearly all results were seen to stabilize at the 6- and 12-month evaluation following treatment. The coping strategies demonstrated little or poor change. In addition, coping measures and change in coping behavior showed poor prognostic relevance. But other psycho-social parameters like self-evaluation of potential return-to-work, application for pension, the length of pre-absence from work, and a decrease in subjective disability following treatment were effective indicators for 'back-to-work'. Other objective parameters, such as medical history, physical impairment and general physical variables were seen to have little predictive value in determining a return to work. The results suggest that the primary target point for further investigation is the analysis of the patients' beliefs about their pain. Our results indicate that future research must be attentive to the complex interactions between environmental factors and the coping demands posed by the specific nature of pain problems.

Preparation and antibacterial activities of new 1,2,3-diazaborine derivatives and analogues

1,2-Dihydro-1-hydroxy-2-(organosulfonyl)areno[d] [1,2,3]diazaborines 2 (arene = benzene, naphthalene, thiophene, furan, pyrrole) were synthesized by reaction of (organosulfonyl)hydrazones of arene aldehydes or ketones with tribromoborane in the presence of ferric chloride. The activities of 2 against bacteria in vitro and in vivo (Escherichia coli) were determined and structure-activity relationships are discussed. Included in this study are 2,3-dihydro-1-hydroxy-2-(p-tolylsulfonyl)-1H-2,1-benzazaborole+ ++ (3) and 1-hydroxy-1,2,3,4-tetrahydro-2-(p-tolylsulfonyl)-2,1-benzazabor ine (4) as well as the carbacyclic benzodiazaborine analogue 4-hydroxy-3-(p-tolylsulfonyl)isoquinoline (7). The nature of the active species is briefly discussed.

Menstrual cycle-associated changes in blood levels of interleukin-6, alpha1 acid glycoprotein, and C-reactive protein

Based on previous studies we hypothesized that interleukin-6 (IL-6) plasma levels would increase during the menstrual cycle, in analogy to the increase in IL-1 levels seen during the luteal phase. Thus we have investigated menstrual cycle-associated changes in IL-6, alpha1 acid glycoprotein (AGP), and C-reactive protein (CRP). The study design was cross-sectional and was conducted in 18 healthy premenopausal women with regular menstrual cycles and in 15 age-matched men. The women had blood drawings in the follicular phase, at midcycle, and in the luteal phase of the menstrual cycle. A single blood sample was obtained from men to compare IL-6 levels between sexes. The median IL-6 level was 0.68 pg/ml (95% confidence interval (CI): 0.60 to 1.05) in the follicular phase and did not change significantly during the menstrual cycle. IL-6 levels did not differ between women and men (0.79 pg/ml; CI: 0.66 to 1.05; p > 0.05). Median AGP levels decreased by 6% (CI: -14% to 1%) during the luteal phase (p = 0.005), and a significant correlation between mean AGP and IL-6 levels was found (r = 0.60; p = 0.01). Median CRP levels increased by 44% (CI: 27% to 59%; p < 0.001) at midcycle and by 31% (CI: 17% to 68%; p = 0.002) in the luteal phase, and there was a significant correlation between the relative increase in CRP at midcycle and the relative increase in progesterone levels during midcycle (r = 0.60; p = 0.01) and the luteal phase (r = 0.71; p = 0.001). In conclusion, we found no sustained menstrual cycle-dependent changes in systemic IL-6 plasma levels. AGP and CRP levels may be differentially regulated during the menstrual cycle of healthy women: AGP levels correlated with IL-6 levels, and AGP levels decreased during the menstrual cycle, whereas CRP levels increased during the menstrual cycle and correlated with the increase in progesterone levels. The reason for the observed changes in CRP levels remains to be elucidated.

Sex differences in concentrations of exhaled nitric oxide and plasma nitrate

Nitric oxide (NO) is generally considered as an endogenous vasoprotective agent. Various studies indicate that the female sex hormone estradiol, that contributes to the well known gender differences in cardiovascular disease, may enhance NO-production. Thus we studied sex differences in NO-generation by measuring single breath NO-exhalation and plasma levels of nitrate (NO3), the stable endmetabolite of NO. In this observational trial 22 male and 21 female volunteers, 19 to 38 years of age, were studied on 3 days at weekly intervals. Median concentrations of NO were 20 parts per billion (95% CI: 16 to 32 ppb) in women and 34 ppb (95% CI: 31 to 58 ppb) in men. The median plasma concentrations of NO3 were 14 microM/L (95% CI: 11 to 23 microM/L) in women and 27 microM/L (95% CI: 24 to 47 microM/L) in men. Thus, men exhaled 59% more NO (p < 0.001) and had 99% higher NO3 levels than women (p < 0.0001). Even when exhaled NO concentrations were corrected for body weight, men exhaled 50% more NO than women (p = 0.024). No significant changes in measured endpoints were seen during the menstrual cycle (p > 0.05) in women. In view of the diversity of NO-actions, the finding of marked sex differences in NO-production is basic to the elucidation of gender differences in a number of (patho)-physiologic conditions.

Identification of Gbetagamma binding sites in the third intracellular loop of the M(3)-muscarinic receptor and their role in receptor regulation

Gbetagamma binds directly to the third intracellular (i3) loop subdomain of the M(3)-muscarinic receptor (MR). In this report, we identified the Gbetagamma binding motif and G-protein-coupled receptor kinase (GRK2) phosphorylation sites in the M(3)-MR i3 loop via a strategy of deletional and site-directed mutagenesis. The Gbetagamma binding domain was localized to Cys(289)-His(330) within the M(3)-MR-Arg(252)-Gln(490) i3 loop, and the binding properties (affinity, influence of ionic strength) of the M(3)-MR-Cys(289)-His(330) i3 loop subdomain were similar to those observed for the entire i3 loop. Site-directed mutagenesis of the M(3)-MR-Cys(289)-His(330) i3 loop subdomain indicated that Phe(312), Phe(314), and a negatively charged region (Glu(324)-Asp(329)) were required for interaction with Gbetagamma. Generation of the full-length M(3)-MR-Arg(252)-Gln(490) i3 peptides containing the F312A mutation were also deficient in Gbetagamma binding and exhibited a reduced capacity for phosphorylation by GRK2. A similar, parallel strategy resulted in identification of major residues ((331)SSS(333) and (348)SASS(351)) phosphorylated by GRK2, which were just downstream of the Gbetagamma binding motif. Full-length M(3)-MR constructs lacking the 42-amino acid Gbetagamma binding domain (Cys(289)-His(330)) or containing the F312A mutation exhibited ligand recognition properties similar to wild type receptor and also effectively mediated agonist-induced increases in intracellular calcium following receptor expression in Chinese hamster ovary and/or COS 7 cells. However, the M(3)-MRDeltaCys(289)-His(330) and M(3)-MR(F312A) constructs were deficient in agonist-induced sequestration, indicating a key role for the Gbetagamma-M(3)-MR i3 loop interaction in receptor regulation and signal processing.

Receptor docking sites for G-protein betagamma subunits. Implications for signal regulation

We report the direct interaction of Gbetagamma with the third intracellular (i3) loop of the M2- and M3-muscarinic receptors (MR) and the importance of this interaction relative to effective phosphorylation of the receptor subdomain. The i3 loop of the M2- and the M3-MR were expressed in bacteria and purified as glutathione S-transferase fusion proteins for utilization as an affinity matrix and to generate substrate for receptor subdomain phosphorylation. In its inactive heterotrimeric state stabilized by GDP, brain G-protein did not associate with the i3 peptide affinity matrix. However, stimulation of subunit dissociation by GTPgammaS/Mg2+ resulted in the retention of Gbetagamma, but not the Galpha subunit, by the M2- and M3-MR i3 peptide resin. Purified Gbetagamma bound to the M3-MR i3 peptide with an apparent affinity similar to that observed for the Gbetagamma binding domain of the receptor kinase GRK2 and Bruton tyrosine kinase, whereas transducin betagamma was not recognized by the M3-MR i3 peptide. Effective phosphorylation of the M3-MR peptide by GRK2 required both Gbetagamma and lipid as is the case for the intact receptor. Incubation of purified GRK2 with the i3 peptide in the presence of Gbetagamma resulted in the formation of a functional ternary complex in which Gbetagamma served as an adapter protein. Such a complex provides a mechanism for specific spatial translocation of GRK2 within the cell positioning the enzyme on its substrate, the activated receptor. The apparent ability of Gbetagamma to act as a docking protein may also serve to provide an interface for this class of membrane-bound receptors to an expanded array of signaling pathways.

Fear-Avoidance Behavior and Anticipation of Pain in Patients With Chronic Low Back Pain: A Randomized Controlled Study

OBJECTIVE AND DESIGN

In a randomized controlled study, we investigated whether pain anticipation and fear-avoidance beliefs will lead to behavioral avoidance.

PATIENTS

Fifty patients with chronic low back pain (CLBP) performed a simple leg-flexion task. Before the test, members of a control group were informed that the movement would not result in any increase of pain, whereas experimental group participants were told that a slight increase of pain could occur.

OUTCOME MEASURES

All patients completed the Fear-Avoidance-Beliefs Questionnaire (FABQ) and the Pain Disability Index (PDI). As dependent variables, different behavioral performance parameters were registered by a computerized protocol: number of flexion movements, mean range of motion, and mean work ratio. Furthermore, patients were asked about their pain intensity as well as their fear (at the moment) and finally were asked to judge the unpleasantness of the experiment (using visual analogue scales for each of the three variables).

RESULTS

Inducing pain anticipation (by instruction) led to significantly lower levels of behavioral performance as well as increased pain intensity and fear during the test. Behavioral performance was significantly correlated with fear-avoidance beliefs.

CONCLUSIONS

Results confirm that pain anticipation and fear-avoidance beliefs significantly influence the behavior of patients with low back pain in that they motivate avoidance behavior. Therapists must be aware of the powerful effects of cognitive processes, which can give rise to fear of pain and, consequently, avoidance behavior.

The membrane-bound spermatozoal adenylyl cyclase system does not share coupling characteristics with somatic cell adenylyl cyclases

Membrane-bound adenylyl cyclases from ram, dog, and human sperm are unresponsive to fluoride and guanylylimidodiphosphate [GMP-P(NH)P], two agents that stimulate the adenylyl cyclases of somatic cells by an action on the stimulatory guanine nucleotide-binding regulatory (Ns) component of adenylyl cyclase. We have investigated whether this is because the sperm cell catalytic unit is functionally uncoupled from Ns but, nevertheless, capable of interacting with it, or because the sperm cell adenylyl cyclase system is unique and regulated differently from that of somatic cells. Sperm cells were found to be deficient in Ns, as evidenced by the inability of detergent extracts from sperm cell membranes and fractions to reconstitute Ns-mediated regulation of the adenylyl cyclase of cyc- S49 cells. In addition, attempts to label Ns in sperm cell membranes by [32P]ADP ribosylation with cholera toxin revealed that, if present, Ns is less than 1% of that found in human erythrocyte membranes. This, however, was not the only reason for the unresponsiveness of sperm cell adenylyl cyclase, since fluoride stimulation of the sperm cell enzyme could not be induced by reconstituting it with Ns purified from human erythrocytes (hRBC). When intact hRBC membranes were added to sperm cell fractions in the presence of fluoride, the activities that resulted were greater than the sum of the individual activities. This apparent reconstitution of fluoride regulation of sperm cell adenylyl cyclase could be blocked by lima bean trypsin inhibitor and appears to have resulted from proteolytic activation of the hRBC adenylyl cyclase by sperm proteases. Sperm cell membranes also appear to lack a functional inhibitory regulatory protein of the adenylyl cyclase system (Ni), since they did not contain an ADP-ribosylatable substrate for pertussis toxin action. These results suggest that the sperm cell adenylyl cyclase system is unique and different from that of somatic cells. Sperm cells appear to neither contain Ns or Ni nor possess the ability of their adenylyl cyclase system to interact with Ns from an exogenous source.