Dissociation of conditioned locomotion and Fos induction in response to stimuli formerly paired with cocaine

A discrete stimulus (flashing light) was paired with cocaine (20 mg/kg) to induce conditioned locomotion. To identify brain regions activated during this response, Fos was measured with immunohistochemistry. Although paired subjects displayed robust conditioned locomotion, Fos was not increased in any limbic brain regions analyzed. In contrast, pairing of cocaine with generalized contextual cues (whole room) produced conditioned locomotion and Fos activation in the prelimbic portion of prefrontal cortex and the nucleus accumbens core. These results suggest that the pattern of neuronal activation during cocaine-conditioned activity differs depending on whether a discrete or contextual stimulus is used as a conditioned stimulus. The possibility that expectancy and frustrative nonreward contribute to Fos expression in rats conditioned to contextual cues is discussed.     

The Lapidus Arthrodesis: Examining the Effect of the Metatarsal Base Transfixion Screw

The modified Lapidus bunionectomy is a useful and highly powerful procedure for correcting hallux abducto valgus. Traditionally reserved for “severe” deformities, this procedure has seen a recent resurgence in the podiatric community for its unique ability to achieve tri-planar correction of this challenging deformity. Although this procedure has been extensively studied in both biomechanical labs and the clinical arenas, no clear consensus has been achieved regarding optimal fixation for this thought-provoking procedure. The current study examined the differences in strength between commercially available 5-hole locking plates with interfragmentary compression vs a crossed-screw with a third “transfixation” screw construct in a controlled setting. Ten fresh-frozen cadaveric match pair limbs (20 total limbs) were used to complete this study. Ten limbs were randomly assigned to a 3-screw construct. The other 10 contralateral limbs were assigned to a commercially available 5-hole locking plate (5 stainless steel and 5 titanium alloy) with an interfragmentary lag screw construct. The first rays were then isolated and potted into a 4-point bending device. The specimens were loaded to failure in a servohydraulic load frame at a controlled rate. Failure was defined as catastrophic or 3 mm of plantar gapping at the arthrodesis site. The mean maximal load to failure was 310.9 ± 109.4 N for the 3-screw construct. The mean maximal load to failure for the locking plate constructs was 264.1 ± 100.9 N. This difference was not statistically significant (p = .328). These results suggest that a 3-screw construct for Lapidus arthrodesis is as strong as commercially available locking plate constructs.     

A technique for eliminating allele specific amplification failure during DNA amplification of heterozygous cells for preimplantation diagnosis

Advances in techniques of molecular biology have made possible the amplification of specific genes from single cells. This has a major clinical application in preimplantation diagnosis of monogenic disorders. However, the incidence of allele specific amplification failure (allele drop out) in heterozygous single cells can lead to misdiagnosis and the transfer of affected embryos. Few studies have been done to investigate the actual cause of allele drop out, although some investigators have succeeded in reducing but not eliminating it. Here we report the efficiency of amplifying both alleles in heterozygous cells lysed according to two different protocols. A total of 177 heterozygous cells from carriers of cystic fibrosis (CF) and haemoglobin C (HbC) were lysed using two different lysis buffers. Interestingly none of the cells that were lysed with sodium dodecyl sulphate/proteinase K showed any example of allele specific amplification failure whereas in those lysed by KOH/dithiothreitol it was present in 17.6 and 4.7% of the CF and HbC cells respectively. Our results suggest that the phenomenon of allele specific amplification failure is at least in part dependent on the lysis buffer used.      

Ferromagnetism and MR imaging: safety of carotid vascular clamps

Metallic extracranial carotid vascular clamps of the Selverstone, Crutchfield, Poppen-Blaylock, Salibi, Kindt, and tantalum varieties have been placed for treatment of large, giant, or inoperable intracranial aneurysms. To ascertain what adverse effect, if any, MR imaging would have on these clamps, magnetic deflection at 1.5 T was measured for various carotid clamps. Marked magnetic deflection (and torque) was displayed by stainless steel Poppen-Blaylock clamps. Relatively mild magnetic deflection was displayed by the stainless steel Selverstone, Salibi, Crutchfield, and Kindt clamps. Three patients with previously placed carotid clamps (two Selverstone, one Salibi) and one patient with a nonferromagnetic tantalum carotid clip had cranial or cervical MR studies at field strengths ranging from 0.35 to 0.60 T. No patient experienced any discomfort or neurologic sequelae as a result of MR imaging. Although the ferromagnetic clamps created severe "black-hole" artifacts and image distortion within the cervical and facial regions, no significant image degradation was apparent during spin-echo imaging of the brain. The tantalum clip created a far smaller MR artifact than did ferromagnetic clamps and allowed effective spin-echo and gradient-echo imaging in the cervical region. Our findings indicate that most patients with carotid vascular clamps (and nonferromagnetic clips) can probably be imaged safely with MR.     

Salt and Mesophase Formation in Aqueous Suspensions of Lauric Acid

The solubility and solution behavior of lauric acid (LA) and its 1:1 acid soap (potassium hydrogen dilaurate) were investigated at 32°C over a pH range of 2.5–8.5 and at varying KC1 concentrations to examine the self-association of this long-chain carboxylic acid under these conditions. LA's solubility in water exhibited the classical pH dependence of a monocarboxylic acid with no evidence of self-association. In 0.1 M KC1 between pH 6.3 and pH 7.3, filtered samples were turbid, suggesting the presence of high molecular weight aggregates (mesophase), which could be removed by ultrafiltration. The apparent LA solubility vs pH profile in ultrafiltered samples was consistent with a solid phase consisting of either the free acid (pH < 6.5) or potassium hydrogen dilaurate (pH > 6.5), again with no evidence of self-association to form low molecular weight species (dimers, etc.). Quasi-elastic light scattering (QLS) studies and mannitol trapping experiments indicated that vesicles were present in samples containing mesophase. The mesophase composition was characterized and a mass-action law for mesophase formation was developed to describe the apparent LA solubility versus pH in the mesophase region in terms of three parameters. The index of cooperativity, , indicated that the mesophase consists of approximately 25 molecules of LA with an acid:anion ratio, , of 1.7. The standard free energy of mesophase formation per mole of monomer was determined to be –6.3 kcal/mol. The aggregate size determined thermodynamically is several orders of magnitude less than that of the mesophase particle size determined by QLS measurements, suggesting that the LA monomer concentration in equilibrium with mesophase may be governed by a small unit domain of the vesicle. These observations may have a bearing on the thermodynamics of self-assembly of lipid bilayer membranes.     

Planning for hospital ethics committees: Meeting the needs of the professional staff

Hospital ethics committees (HECs) have historically been instituted top-down, often ignoring the needs of the professionals and patients who might use their services. Seventy-four physicians and 123 nurses participated in a hospital-wide needs assessment designed to [1] identify their perceptions of the functions of the HEC, [2] determine which services and educational programs were most desired, and [3] explore which forums were most preferred for discussion of ethical problems. Results indicated that utilization of the HEC focused around five areas of concern: withdrawing/withholding treatment, rationing and control of health care, children's rights, role of the patient and family in decisionmaking, and disagreements about treatment. Physicians and nurses differed widely in their attitudes. Perceptions about the appropriate functions of the HEC strongly influenced decisions regarding which HEC services to use. Needs assessment can play an important role in developing HEC goals and designing programs that meet the needs of professionals.