Cannabinoid receptor type 1 activation by arachidonylcyclopropylamide in rat aortic rings causes vasorelaxation involving calcium-activated potassium channel subunit alpha-1 and calcium channel, voltage-dependent, L type, alpha 1C subunit

Cannabinoids are key regulators of vascular tone, some of the mechanisms involved include the activation of cannabinoid receptor types 1 and 2 (CB); the transient receptor potential cation channel, subfamily V, member 1 (TRPV1); and non-(CB(1))/non-CB2 receptors. Here, we used the potent, selective CB(1) agonist arachidonylcyclopropylamide (ACPA) to elucidate the mechanism underlying vascular tone regulation. Immunohistochemistry and confocal microscopy revealed that CB(1) was expressed in smooth muscle and endothelial cells in rat aorta. We performed isometric tension recordings in aortic rings that had been pre-contracted with phenylephrine. In these conditions, ACPA caused vasorelaxation in an endothelium-independent manner. To confirm that the effect of ACPA was mediated by CB(1) receptor, we repeated the experiment after blocking these receptors with a selective antagonist, AM281. In these conditions, ACPA did not cause vasorelaxation. We explored the role of K(+) channels in the effect of ACPA by applying high-K(+) solution to induce contraction in aortic rings. In these conditions, the ACPA-induced vasorelaxation was about half that observed with phenylephrine-induced contraction. Thus, K(+) channels were involved in the ACPA effect. Furthermore, the vasorelaxation effect was similarly reduced when we specifically blocked calcium-activated potassium channel subunit alpha-1 (KCa1.1) (MaxiK; BKCa) prior to adding ACPA. Finally, ACPA-induced vasorelaxation was also diminished when we specifically blocked the calcium channel, voltage-dependent, L type, alpha 1C subunit (Ca(v)1.2). These results showed that ACPA activation of CB(1) in smooth muscle caused vasorelaxation of aortic rings through a mechanism involving the activation of K(Ca)1.1 and the inhibition of Ca(v)1.2.

Effect of chronic administration of forskolin on glycemia and oxidative stress in rats with and without experimental diabetes

Forskolin is a diterpene derived from the plant Coleus forskohlii. Forskolin activates adenylate cyclase, which increases intracellular cAMP levels. The antioxidant and antiinflammatory action of forskolin is due to inhibition of macrophage activation with a subsequent reduction in thromboxane B2 and superoxide levels. These characteristics have made forskolin an effective medication for heart disease, hypertension, diabetes, and asthma. Here, we evaluated the effects of chronic forskolin administration on blood glucose and oxidative stress in 19 male Wistar rats with streptozotocin-induced diabetes compared to 8 healthy male Wistar rats. Rats were treated with forskolin, delivered daily for 8 weeks. Glucose was assessed by measuring fasting blood glucose in diabetic rats and with an oral glucose tolerance test (OGTT) in healthy rats. Oxidative stress was assessed by measuring 8-hydroxydeoxyguanosine (8‑OHdG) in 24-h urine samples. In diabetic rats, without forskolin, fasting blood glucose was significantly higher at the end than at the beginning of the experiment (8 weeks). In both healthy and diabetic rats, forskolin treatment lowered the fasting glucose at the end of the experiment but no effect was found on oral glucose tolerance. The 8-OHdG levels tended to be less elevated in forskolin-treated than in untreated group. Our results showed that chronic administration of forskolin decreased fasting blood glucose levels; however, the reductions of 8-OHdG were not statistically significant.

Effects of chronic caffeine administration on blood glucose levels and on glucose tolerance in healthy and diabetic rats

OBJECTIVE

To analyse the effect of chronic caffeine use on risk reduction and prognosis of diabetes mellitus.

METHODS

In this 60-day study, five groups of 11 healthy male Wistar rats were selected to receive one of four doses (37.5, 56.2, 75.0 or 93.0 mg/kg per day) of caffeine orally or no caffeine (control). The effect of caffeine on glycaemia and glucose tolerance was evaluated. After 15 days, each group was treated with 60 mg/kg of streptozotocine to induce diabetes mellitus, and glycaemia and glucose tolerance were assessed for a further 45 days.

RESULTS

In nondiabetic rats, caffeine had no effect on blood glucose. Compared with controls, the fasting blood glucose levels declined significantly in two caffeine-treated groups (93.0 mg/kg per day and 56.2 mg/kg per day) during the first 15 days following diabetes induction. Glucose tolerance was significantly improved 120 min after glucose loading in all caffeine-treated groups. The mean ± SE half-maximal effective concentration of caffeine was 35.79 ± 2.44 mg/dl.

CONCLUSIONS

Blood glucose levels decreased, and glucose tolerance improved, in diabetic rats administered increasing doses of caffeine.

[Evaluation of alignment on knees through a software]

INTRODUCTION

Diseases of the musculoskeletal system are often accompanied by postural deformity or malalignment. Genu varo or genu valgo can be found in the knees. It is necessary to have a diagnostic support test for diagnosis as well as for follow-up of cases since these diseases are frequently progressive and over time have serious repercussions on patient quality of life. Objective. To evaluate a software program that processes digitalized photographs as a diagnostic test for measuring the mechanical axis in patients with genu varo and genu valgo.

MATERIALS AND METHODS

The mechanical axis in both knees was measured by means of radiography (golden standard) and by means of a software program (proposed diagnostic test) in one hundred patients. Mechanical axis was considered to be abnormal when the angle was equal to or greater than four degrees. Sensitivity, specificity, positive predictive value, and negative predictive value were determined. Interobserver variation was evaluated with kappa statistics.

RESULTS

In relation to right knee genu varo, sensitivity, specificity, positive predictive value, and negative predictivie value were 0.84, 0.87, 0.84, and 0.87, respectively, and for the left knee values were 0.86, 0.87, 0.84, and 0.89, respectively. For genu valgo in the right knee, sensitivity, specificity, positive predictive value, and negative predictive value were 0.78, 0.98, 0.95, and 0.92, respectively, and in the left knee were 0.88, 0.95, 0.88, and 0.95, respectively. Kappa value was 0.9 in the right knee and 0.8 in the left knee.

CONCLUSION

The software program (diagnostic test) was useful for diagnosing genu varo or genu valgo, representing a safe and low-cost study.

Cervical human papillomavirus infection in Mexican women with systemic lupus erythematosus or rheumatoid arthritis

Cervical human papillomavirus (HPV+) infection is associated with an increased risk of cervical dysplasia. Although the frequency of HPV+ in systemic lupus erythematosus (SLE) has been investigated in some races its prevalence in Hispanic women is still unknown. This cross-sectional study evaluated the prevalence of cervical HPV+ in Mexican women with SLE ( n = 34) or rheumatoid arthritis (RA) ( n = 43) and in healthy controls ( n = 146). These women were interviewed about risk factors for sexually transmitted infections and cervical cytology analysis was performed. HPV+ viral types were identified using PCR: HPV+ was observed in 14.7% of SLE, 27.9% of RA and 30.8% of controls. High-risk HPV types were observed in 11.7% of women with SLE, 27.9% of women with RA, and in 26% of the controls. High-risk viral types 58, 35 and 18 were the most frequently identified in SLE. Two women with SLE had a high-grade squamous intraepithelial lesion and one had cervical cancer. An association was observed between methotrexate utilization, longer duration of therapy with prednisone, and HPV+ in RA or SLE. Thus, there is a high prevalence of cervical HPV infection in Mexican women with SLE or RA, and physicians must be vigilant in preventing the development of cervical dysplasia.

Glibenclamide increases post-fatigue tension in slow skeletal muscle fibers of the chicken

In contrast to fast-twitch skeletal muscle fibers of the chicken, slow-twitch fibers are fatigue-resistant. In fast fibers, the fatigue process has been related to K(ATP) channels. In the present study, we investigated the action of glibenclamide (an anti-diabetic sulphonylurea that acts on K(ATP) channels) on fatigued slow skeletal muscle, studying twitch and tetanus tension after inducing the muscle to fatigue by continuous electrical stimulation. Our results showed that glibenclamide (150 μM) increased post-fatigue twitch tension by about 25% with respect to the fatigued condition (P < 0.05). In addition, glibenclamide (150 μM) increased post-fatigue tetanic tension (83.61 ± 15.7% in peak tension, and 85.0 ± 19.0% in tension-time integral, P = 0.02, and 0.04, respectively; n = 3). Moreover, after exposing the muscle to a condition that inhibits mitochondrial ATP formation in order to activate K(ATP) channels with cyanide (10 mM), tension also diminished, but in the presence of glibenclamide the effect produced by cyanide was abolished. To determine a possible increase in intracellular calcium concentration, the effects of glibenclamide on caffeine-evoked contractures were explored. After muscle pre-incubation with glibenclamide (150 μM), tension of caffeine-evoked contractures increased (6.5 ± 1.5% in maximal tension, and 5.9 ± 3.8% in tension-time integral, P < 0.05). These results suggest a possible role of K(ATP) channels in the fatigue process, since glibenclamide increases twitch and tetanus tension in fatigued slow muscle of the chicken and during metabolic inhibition, possibly by increasing intracellular calcium.

[Comparison of three therapeutic exercises protocols to lumbar hyperlordosis improvement in asyntomatic youths]

INTRODUCTION

One of the causes of low back pain is lumbar hyperlordosis. There are different protocols of therapeutic exercises for its correction, which do not involve all of corporal segments. A modified protocol is proposed, which involves all such segments.

OBJECTIVE

To evaluate the efficacy of proposed protocol with two established protocols for correction of lumbar hyperlordosis.

MATERIALS AND METHODS

Simple-blind clinical trial on 42 students of the Faculty of Medicine at University of Colima. The three protocols: A) Pérez-Olmedo (proposed, n = 14), B) Williams (n = 15) and C) Jeffrey Saal (n = 13) were randomly assigned. Clinical and radiological evaluations were performed. Lumbar hyperlordosis was considered when Ferguson's angle was > or = 30 degrees, measured on lateral spine x-ray pictures. During two months they underwent supervised and directed exercise sessions. The improvement in lumbar hyperlordosis correction of each protocol was compared through paired Student t-test and ANOVA.

RESULTS

Average age was 18 +/- 0.9 years. Lumbar hyperlordosis frequency was 31% (n = 15). There was not significative difference on Ferguson's angle average comparation between three treatment groups. There was lumbar hyperlordosis improvement with following percentages: group A = 60%, Group B = 16% and group C = 0%.

CONCLUSION

Protocol of therapeutic exercises proposed (Pérez-Olmedo) could be an alternative to lumbar hyperlordosis improvement in asyntomatic youhts.

Forskolin compared with beclomethasone for prevention of asthma attacks: a single-blind clinical trial

This single-blind study compared the efficacy of oral forskolin versus inhaled beclomethasone for mild or moderately persistent adult asthma. Patients were randomly assigned to receive forskolin (one 10-mg capsule orally per day; n = 30) or beclomethasone (two 50 microg inhalations every 12 h; n = 30) for 2 months. No statistically significant improvement occurred in any lung function parameter in the forskolin-treated patients. Subjects in the beclomethasone-treated group presented a slight but statistically significant improvement in percentage forced expiratory volume in 1 s (FEV(1)), percentage forced expiratory flow in the middle (25 - 75%) expiratory phase (FEF(25 - 75%)) and percentage forced vital capacity (FVC) after 2 months of treatment, though the improvement in absolute values for FEV(1), FEF(25 - 75%), FVC and FEV(1):FVC did not reach statistical significance. There was no statistically significant difference between the forskolin and beclomethasone treatment groups for any lung function parameter at baseline or after treatment. None of the beclomethasone-treated patients had an asthma attack and one forskolin-treated patient had a mild asthma attack during the 2-month study period. More studies are needed in adult asthma patients to confirm whether forskolin may be a useful preventive treatment for mild or moderately persistent adult asthma.

Progesterone regulates corticosterone elevation and alterations in spatial memory and exploratory behavior induced by stress in Wistar rats

The hippocampus is sensitive to high levels of glucocorticoids. During stress response, it suffers biochemical and cellular changes that affect functions such as spatial memory and exploratory behavior. In this study, we analyzed the influence of the neurosteroid progesterone (PROG), on stress-induced changes in urinary corticosterone (CORT) levels, spatial memory and exploratory behavior. Castrated adult male rats were implanted with PROG or vehicle (VEHI), and then exposed to chronic stress by overcrowding or ultrasonic noise for ten days. PROG and CORT levels were assessed in urine using high-performance liquid chromatography (HPLC). Implanted PROG inhibited stress-induced CORT raise, prevented spatial memory impairment in the Morris water maze, and eliminated increased exploratory behavior in the hole-board test. These results suggest protective effects of PROG against the corticosteroids raise and behavioral deficit generated by both stressful situations, possibly mediated by its anxiolytic mechanisms.

[Alternative method for measuring the mechanical axis of the knee]

OBJECTIVE

To identify the existence of significant differences in the degrees of mal-alignment of the mechanical axis of the knee between a traditional measuring method and an alternative method. MATERIALS AND METHODS. One hundred mechanical axes of the knee were determined in patients of both sexes. The degree of axis mal-alignment was obtained first using the traditional measuring method and subsequently using the alternative method. The results obtained from the two methods were then compared. The measurement variable control was standardised by positioning the patients in the same place during radiography when beginning mechanical axis determination. A wooden ruler on which each centimetre was indicated by a metal strip and numbered at every 10-centimeter interval was used to evaluate the degree of pelvic mal-alignment. The ruler was then used as a mechanical axis correction reference in accordance with the characteristics of each patient.

RESULTS

The following results were obtained from 100 mechanical axes evaluated by the traditional method and by the alternative method, respectively: varus deformity of the right pelvic segment was 21 degrees +/- 16 degreesuv. 7 ++/-6. degrees varus deformity of the left pelvic segment was 22 _+/-170 degreesvs. 8 ++/-50 degrees valgus deformity of the right pelvic segment was 21 - /-150 degreess. 8 + +/-; and valgus deformity of the left pelvic segment was 16 +/- 11 vs. 6 +/- 5 degrees.

CONCLUSIONS

Our results suggest that the proposed method provides more accurate mechanical axis measurement and that the correction is exponential: the greater the angle measured traditionally, the greater the correction with our proposed method.

Effects of verapamil and gadolinium on caffeine-induced contractures and calcium fluxes in frog slow skeletal muscle fibers

In this work, we tested whether L-type Ca(2+ )channels are involved in the increase of caffeine-evoked tension in frog slow muscle fibers. Simultaneous net Ca(2+) fluxes and changes in muscle tension were measured in the presence of caffeine. Isometric tension was recorded by a mechanoelectrical transducer, and net fluxes of Ca(2+) were measured noninvasively using ion-selective vibrating microelectrodes. We show that the timing of changes in net fluxes and muscle tension coincided, suggesting interdependence of the two processes. The effects of Ca(2+)channel blockers (verapamil and gadolinium) were explored using 6 mM: caffeine; both significantly reduced the action of caffeine on tension and on calcium fluxes. Both caffeine-evoked Ca(2+) leak and muscle tension were reduced by 75% in the presence of 100 microM: GdCl(3), which also caused a 92% inhibition of net Ca(2+) fluxes in the steady-state condition. Application of 10 microM: verapamil to the bath led to 30% and 52% reductions in the Ca(2+)leak caused by the presence of caffeine for the peak and steady-state values of net Ca(2+) fluxes, respectively. Verapamil (10 microM): caused a 30% reduction in the maximum values of caffeine-evoked muscle tension. Gd(3+)was a more potent inhibitor than verapamil. In conclusion, L-type Ca(2+) channels appear to play the initial role of trigger in the rather complex mechanism of slow fiber contraction, the latter process being mediated by both positive Ca(2+)-induced Ca(2+ )release and negative (Ca(2+) removal from cytosol) feedback loops.

Effects of Cannabinoids on Synaptic Transmission in the Frog Neuromuscular Junction

This study aimed to investigate the function of the cannabinoid receptor in the neuromuscular junction of the frog (Rana pipiens). Miniature end-plate potentials were recorded using the intracellular electrode recording technique in the cutaneous pectoris muscle in the presence of the cannabinoid agonists WIN55212-2 (WIN; R-(+)-[2,3-dihydro-5-methyl-3-[(morpholinyl)]-pyrolol[1,2,3de]-1,4-benzoxazinyl]-(1-naphthalenyl)methanone) and arachidonylcyclopropylamide [ACPA; N-(2-cyclopropyl)-5Z,8Z,11Z,147-eicosatetraenamide] and the cannabinoid antagonists 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide (AM281) and 6-iodo-2-methyl-1-[2-(4-morpholinyl)ethyl]-1H-indol-3-yl](4-methoxyphenyl)methanone (AM630). Adding WIN to the external medium decreased the frequency and amplitude of the miniature end-plate potentials (MEPPs); the WIN EC50 value was 5.8+/-1.0 microM. Application of ACPA, a selective agonist of cannabinoid receptor CB1, also decreased the frequency of the MEPPs; the ACPA EC50 value was 115.5+/-6.5 nM. The CB2 antagonist AM630 did not inhibit the effects of WIN, indicating that its action is not mediated through the CB2 receptor. However, the CB1 antagonist AM281 inhibited the effects of WIN and ACPA, suggesting that their actions are mediated through the CB1 receptor. Pretreatment with the pertussis toxin inhibited the effects of WIN and ACPA, suggesting that their effects are mediated through Gi/o protein activation. The N-type Ca2+ channel blocker omega-conotoxin GVIA (omega-CgTX) diminished the frequency of the MEPPs, with an omega-CgTX EC50 value of 2.5+/-0.40 microM. Blocking the N-type Ca2+ channels with 5 microM omega-CgTX before addition of ACPA to the bath had no additional inhibitory effect on the MEPPs, whereas in the presence of 1 microM omega-CgTX, ACPA had an additional inhibition effect. These results suggest that cannabinoids modulate transmitter release in the end-plate of the frog neuromuscular junction by activating CB1 cannabinoid receptors in the nerve ending.

Forskolin versus sodium cromoglycate for prevention of asthma attacks: a single-blinded clinical trial

To determine the efficacy of forskolin in preventing asthma attacks, we performed a single-blinded clinical study in children and adult out-patients at a public hospital in Mexico. Forty patients of either sex with mild persistent or moderate persistent asthma were assigned randomly to 6 months of treatment with forskolin at 10 mg/day orally (capsules) or with two inhalations of sodium cromoglycate every 8 h, i.e. three times a day. The number of patients who had asthma attacks during the treatment period was significantly lower among those receiving forskolin (8/20, 40%) than among those receiving sodium cromoglycate (17/20, 85%). Values of forced expiratory volume in 1 s and forced expiratory flow, mid-phase, A similar in the two groups during the treatment period. We conclude that forskolin is more effective than sod cromoglycate in preventing asthma attacks in patients with mild persistent or moderate persistent asthma.

Blink reflex, H-reflex and nerve-conduction alterations in leprosy patients

Peripheral nerve lesions are the most important cause of disability in leprosy patients. Electrophysiological studies are used in the diagnosis and prognosis of neuropathy. Nerve conduction is the most frequently used electrophysiological test method to detect neuropathy, although it evaluates only a part of the peripheral nervous system. Blink reflex and H-reflex are electrophysiological tests which evaluate facial and trigeminal nerve function. This study determined the frequencies of blink reflex, H-reflex and motor and sensory nerve conduction alterations in twenty five heterogeneous, clinic patients with lepromatous leprosy and a control group of 20 healthy subjects. Study results showed a decrease in motor and sensory nerve conduction in 40% and 30%, respectively. In blink reflex (BR), right R1 was altered in latency in 20% of patients, left R1 in 20%, right ipsilateral R2 in 16%, left ipsilateral R2 in 20%, and right and left contralateral R2 were altered in 32% of patients. There was an absence of H-reflex in 16% (n = 4) and prolonged latency in 4% (n = 1).

Electrophysiological abnormalities in type 2 diabetic patients with reduced levels of insulin-like growth factor I

This cross-sectional study investigated electrophysiological abnormalities in type 2 diabetics with normal and reduced insulin-like growth factor I (IGF-I) levels. Sixty patients and 20 non-diabetic controls were included in the study. The fasting serum glucose was measured and IGF-I levels were determined by radioimmunoassay in all patients. Nerve conduction tests were performed in all the study participants on the ulnar nerve and lower extremities. Compared with the controls, all the patients showed a reduction in the peak amplitude of the motor response, 58% showed a reduction in the motor conduction velocity and 55% showed a reduction in the sensory conduction velocity. There was no statistically significant correlation between the electrophysiological changes and the glucose or IGF-I levels. In conclusion, there does not appear to be a correlation between serum glucose or IGF-I levels and electrophysiological abnormalities in patients with type 2 diabetes mellitus.

Cannabinoids and dopamine receptors' action on calcium current in rat neurons

OBJECTIVE

To study the effects of cannabinoid, glutamate, and dopamine agonists and antagonists on the calcium current rat sympathetic neurons.

METHODS

Calcium current was recorded using the whole-cell variant of the patch-clamp technique. After expression in neuronal membranes of the cannabinoid CB1, glutamate mGluR2, or dopamine D1 receptor (by microinjection of the levant receptor's cDNA into the neuron's nucleus) agonists' and antagonists' effects were observed.

RESULTS

Applications of agonists of the expressed receptor (0.1-10 microM) decreased the calcium current. The calcium current was increased after application of cannabinoid antagonists (AM251 and AM630); these compounds thus act as inverse agonists in this preparation. Glutamate and dopamine antagonists had no effects on the calcium current by themselves. Combined application of cannabinoids and dopamine, but not glutamate, agonists produced a decrement in the calcium current that was bigger than either of the effects seen when one agonist was applied alone.

CONCLUSIONS

These results suggest that cannabinoid with dopamine receptors have an interactive inhibitory effect on the calcium current in this preparation, indicating that within the nervous system, receptor interactions may be important in the regulation of ion-channel functions.

F-wave and H-reflex alterations in recently diagnosed diabetic patients

OBJECTIVE

To explore the frequency of F-wave and H-reflex alterations in recently diagnosed type 2 diabetes mellitus patients and to determine if the alterations are dependent on the levels of glycemia.

METHODS

A cross-sectional study was carried out on 50 asymptomatic patients, with a mean age of 45.4 +/- 9.8 years and a disease evolution of less than 10 years. Patients were classified as either normoglycemic (7 mmol/L; n = 20) or hyperglycemic (7 mmol/L; n = 30). H-reflex (HR), F-wave (FW), and nerve-conduction measurements (NCM) between the diabetic and non-diabetic (control) groups were compared.

RESULTS

The H-reflex was absent in 22% of the patients, while the M-component of this reflex was altered in 58% of patients. The F-wave was altered in 12% of the patients. The motor nerve compound action potential showed a diminution in amplitude (26% of patients, n = 13), area (32%, n = 16), and conduction velocity (20%, n = 10). No positive correlation between glycemia levels and the above alterations was found.

CONCLUSIONS

This study demonstrated that asymptomatic diabetic patients showed a high incidence of subclinical neurophysiological abnormalities.

Folding-unfolding of FN-III domains in tenascin: an elastically coupled two-state system

In a single-molecule atomic force microscopy (AFM) experiment, the tenascin molecule is stretched by an external force causing an elongation which is due to the unfolding of the FN-III modules. The features of the force-extension curves depend on the pulling speed and show a saw-tooth pattern (lower speeds) or a smooth pattern (higher speeds). In any case, the unfolded domains are elastically coupled to the unfolded modules, acting as transmitters of the external force. In this communication, the folding-unfolding process of the FN-III domains in tenascin is studied using reaction rate theory and a simple two-state model. The main hypothesis of the study is that, at microscopic level, the force needed to unfold a domain and the unfolding rate (unfolding velocity) can mimic the macroscopic process of measurement by AFM. As the external force is applied, the probability of unfolding increases as dictated by the reaction rate theory. Within this context, a relationship between the unfolding force and the unfolding velocity is obtained. The latter relation will describe microscopically the process in a phenomenological fashion. Moreover, while relating the results of this study with other experimental (AFM measurements) and theoretical (Monte Carlo simulations) data, we found that the graph of unfolding force-unfolding velocity is similar to that of external force-pulling velocity. The refolding process can also be studied within this model and the results show similar trends. The latter suggests a generic and universal behavior of such kind of molecular domains at least in the light of the proposed model.