Responses to questions by medical students about family practice

Medical students frequently have questions about the specialty of family practice. Responses to 30 questions commonly asked about family practice are presented with a review of recent literature. These responses may assist medical students and their advisors in considering the choice of family practice as a career.     

IMMUNOHISTOCHEMICAL DISTRIBUTION OF CANNABINOID CB 1 RECEPTOR IN THE RAT CENTRAL NERVOUS SYSTEM

IMMUNOHISTOCHEMICAL DISTRIBUTION OF CANNABINOID CB 1 RECEPTOR IN THE RAT CENTRAL NERVOUS SYSTEM@邹冈     

Suppression of noxious stimulus-evoked expression of Fos protein-like immunoreactivity in rat spinal cord by a selective cannabinoid agonist

In rats, cannabinoids inhibit behavioral responses to noxious stimulation with a potency and efficacy similar to that of morphine. However, because cannabinoids depress motor function, it has not been possible to state beyond any doubt that these effects were related to a dampening of noxious sensory input. Therefore, c-fos immunocytochemistry was used to explore the possibility that cannabinoids reduce behavioral responses to noxious stimuli by decreasing spinal processing of nociceptive inputs. Rats received systemic injections of the potent and selective cannabinoid agonist WIN 55,212-2, the receptor-inactive enantiomer WIN 55,212-3 or vehicle prior to observations in a model of tonic pain, the formalin test. As demonstrated previously, plantar injections of formalin led to lifting and licking of the injected paw, with two peaks of activity occurring at 5 and 30 min after injection. The cannabinoid agonist suppressed these pain responses and produced a reduction in mobility. Immunocytochemical processing of sections with an antibody to the Fos protein revealed that the cannabinoid markedly suppressed pain-evoked c-fos expression in the superficial and neck regions of the spinal dorsal horn, but not in the nucleus proprius. Decreased expression of c-fos also occurred in the ventral horn. The specificity of this effect and its probable mediation by cannabinoid receptors are suggested by three findings: (i) the suppression by the drug of both behavioral and immunocytochemical responses to pain was dose-dependent; (ii) neither the behavioral nor the immunocytochemical response to the noxious stimulus was significantly affected by the receptor-inactive enantiomer of the agonist; (iii) animals rendered tolerant to cannabinoids by repeated injections of the agonist showed reduced responses to the drug. These findings suggest that cannabinoids inhibit the spinal processing of nociceptive stimuli and support the notion that endogenous cannabinoids may act naturally to modify pain trnasmission within the central nervous system.     

Role of the superior colliculus in the motor effects of cannabinoids and dopamine

We studied the cellular distribution of CB1 cannabinoid receptors in the superior colliculus of the rat using an antibody raised against the N-terminal of the receptor. The effect of unilateral cannabinoid receptor stimulation in the intermediate layers of the superior colliculus on rotational behavior in rats was also explored. The antibody against CB1 receptors outlined the crossed descending system of the superior colliculus (predorsal bundle output system) as well as the collicular commisure. The potent cannabinoid agonist CP55,940 (5 microgram/0.25 microliter) induced strong contralateral turning when microinjected unilaterally into the lateral intermediate layers of the superior colliculus. The levels of turning obtained with the intracollicular administration of the cannabinoid were comparable to the highest levels obtained with dopamine agonists in the basal ganglia. The D(2) dopamine agonist quinpirole or the D(1) dopamine agonist SKF82958 reversed this contralateral rotation but failed to affect motor behavior on their own. A new motor pathway for cannabinoids is discussed.     

Failures of Cu-Cu Joints under Temperature Cycling Tests

In this study, the failure mechanisms of Cu-Cu joints under thermal cycling were investigated. Two structures of dielectrics (PBO/underfill/PBO and SiO₂) were employed to seal the joints. Stress gradients induced in the joints with the different dielectrics were simulated using a finite element method (FEM) and correlated with experimental observations. We found that interfacial voids were forced to move in the direction from high stress regions to low stress ones. The locations of migrated voids varied with the dielectric structures. Under thermal cycling, such voids were likely to move forward to the regions with a small stress change. They relocated and merged with their neighboring voids to lower the interfacial energy.     

Direct observation therapy with appropriate treatment regimens was associated with a decline in second-line drug-resistant tuberculosis in Taiwan

The resistance of Mycobacterium tuberculosis (MTB) to second-line drugs (SLDs) is growing worldwide; however, associations between the appropriateness of treatment for tuberculosis (TB) and whether the directly observed treatment, short course (DOTS)/DOTS-plus programs had an impact on the prevalence of SLD-resistant MTB are still uncertain. We performed a retrospective analysis of resistance profiles among MTB isolates obtained from 6,035 consecutive patients from 2004 to 2011 at two TB referral hospitals in Taiwan. There was a significant decrease (all p-values <0.01) in the prevalence of MTB isolates that were resistant to fluoroquinolones, injectable SLDs, and orally administered SLDs, and multidrug-resistant (MDR) and extensively drug-resistant (XDR) MTB isolates over time. There was a significant increase in the coverage rate of DOTS/DOTS-plus programs and that of administering appropriate first-line and second-line regimens (all p?<?0.01). Compared with isoniazid-susceptible isolates, high-level (1.0 mg/L) isoniazid-resistant and MDR isolates showed extensive cross resistance to ofloxacin (5.9 %, p?<?0.01 and 33.6 %, p?<?0.01), levofloxacin (9.6 %, p?<?0.01 and 38.1 %, p?<?0.01), moxifloxacin (11.1 %, p?<?0.01 and 26.5 %, p?<?0.01), kanamycin (6.8 %, p?<?0.01 and 16.7 %, p?<?0.01), ethionamide (6.4 %, p?<?0.01 and 16.2 %, p?<?0.01), and para-aminosalicylic acid (13.1 %, p?<?0.01 and 20.4 %, p?<?0.01), but not to capreomycin (2.0 %, p?=?0.06 and 1.6 %, p?=?0.08). The decline in prevalence of resistance to SLDs was negatively correlated with the rise in rates of administering appropriate regimens as well as the DOTS/DOTS-plus programs, but not with the increase in usage of second-line regimens. The implementation of DOTS/DOTS-plus programs with appropriate regimens was associated with a decrease in the prevalence of SLD-resistant and XDR TB.     

Allele-specific differential expression of a common adiponectin gene polymorphism related to obesity

Adiponectin gene polymorphisms have recently been reported to be associated with obesity, insulin sensitivity, and the risk of type 2 diabetes. We examined a T94G polymorphism of the adiponectin gene in 245 ostensibly normal nondiabetic subjects. The G allele frequency was lower among subjects with higher BMI (> or =27) than in those with lower BMI. BMI was inversely correlated with the dose of G allele. Multivariate linear regression analyses showed that the adiponectin genotypes were significantly related to BMI after adjusting for age and gender. The dose of the G allele was associated with a reduction of approximately 1.12 kg/m(2) in BMI. We further found that the relative mRNA levels of G allele were consistently higher than those of T allele in the omental adipose tissue from 21 heterozygous subjects. Finally, we observed that the expression levels of adiponectin affected insulin-stimulated glucose uptake in differentiated 3T3-L1 adipocytes. In conclusion, the allele-specific differential expression of this common polymorphism could be responsible for its biological effects observed in this and the other studies.     

Oxidative stress and metal ions regulate a ferritin-like gene, dpr, in Streptococcus pyogenes

Bacteria encounter oxidative stress by exposure to reactive oxygen species (ROS) present in the aerobic environment and during immune responses. In Streptococcus pyogenes, Dpr has been identified as a stress protein conferring resistance to hydrogen peroxide and multiple other stresses. The expression of Dpr is under perR (peroxide stress response regulator) control. However, the exact molecular mechanism of PerR regulation of Dpr is not clear. In this study, a perR deletion mutant was constructed by double cross-over mutagenesis. The profile of Dpr expression, performed by Western blot assay, revealed growth-phase dependency under normal culture conditions. Dpr expression decreased under iron-restricted conditions, whereas iron, zinc, nickel, and hydrogen peroxide induced its expression. The perR mutant does not induce Dpr as well when exposed to environmental signals. PerR binds the promoter region of dpr. Increased iron and hydrogen peroxide concentrations decreased PerR binding to the promoter region of dpr, suggesting that regulation of Dpr by environmental signals is mediated by PerR directly.     

Plasma homocysteine status in patients with ankylosing spondylitis

Homocysteine (Hcy), a sulfur-containing amino acid, is eliminated through B vitamins-dependent pathways. Hyperhomocysteinemia has been found to be an independent risk factor for atherosclerotic cardiovascular, cerebrovascular, and peripheral vascular diseases. Recently, psoriasis, lupus, and rheumatoid arthritis were reported to be associated with hyperhomocysteinemia. This study was aimed to evaluate the changes of plasma Hcy level before and after sulfasalazine and MTX therapy in patients with ankylosing spondylitis (AS). One hundred and two patients with AS and ten normal controls were enrolled in the cross-sectional case-control study. Fasting plasma Hcy levels were determined by ELISA kits (IMX, Abbott). Hcy levels were compared to their Bath AS disease activity index (BASDAI) and the usage of sulfasalazine and/or MTX. Active disease was defined by BASDAI as more than 3 in a 10-cm scale with ESR >20 mm/h. For those patients with plasma Hcy ≥15 μmol/l, a perspective trial of daily supplement of vitamin B-12 0.5 mg, B-6 50 mg, and folic acid 5 mg for 2 weeks were also tested for the efficacy. Plasma Hcy level increased significantly in AS patients under sulfasalazine (10.4±3.8 μmol/l, p<0.05), MTX (11.9±4.7, p<0.05) and sulfasalazine/MTX combination treatment (11.2±2.6, p<0.05) compared with normal controls (8.6±1.2 μmol/l) and AS patients without DMARD(9.4± 2.6μmol/l). No correlation between disease activity and plasma Hcy level was found. Daily supplement of vitamin B-12 0.5 mg, B-6 50 mg, and folic acid 5 mg can lower Hcy level in 2 weeks (32.3±24.0 vs 15.6±11.1 μmol/l, p=0.007). Plasma homocysteine level did significantly increase in AS patients under sulfasalazine or MTX treatment. B-vitamins should be considered as a routine supplementation for patients who underwent sulfasalazine and/or MTX treatment. Further longitudinal studies are required to confirm the conclusions.