Systolic cessation of the flow in the mid stent segment of the previously stented ostial vein graft with normal flow during diastole. A case report and brief review.

We present a case of intermittent cessation of blood flow through stent struts during systole, with normal flow during diastole in the previously stented ostial vein graft. After reviewing the initial procedure, we discovered that the operator had difficulty in positioning the stent. After stent deployment, the ostial stent was malpositioned and was protruding more than 50% into the aorta. During systole, the contrast in the stent struts, which are situated in the aorta, was being washed off by systolic blood flow, while in the diastole, the flow of contrast was normal. This is the first case report of this observation with a brief review.     

Resolution of homonymous visual field loss documented with functional magnetic resonance and diffusion tensor imaging.

A 68-year-old man developed right homonymous hemianopic paracentral scotomas from acute infarction of the left extrastriate area. He was studied over the ensuing 12 months with visual fields, conventional MRI, functional MRI (fMRI), and diffusion tensor imaging (DTI). As the visual field defect became smaller, fMRI demonstrated progressively larger areas of cortical activation. DTI initially showed that the lesioned posterior optic radiations were completely interrupted. This interruption lessened in time and had disappeared by one year after onset. fMRI and DTI are innovative measures to follow functional and structural recovery in the central nervous system. This is the first reported application of these imaging techniques to acute cerebral visual field disorders.     

Comparison of dynamic and step-and-shoot intensity-modulated radiation therapy planning and delivery.

Intensity-modulated radiation therapy (IMRT) is commonly delivered using the dynamic or segmental mode of multileaf collimators (DMLC or SMLC). Both methods are designed to deliver intensity-modulated beams as determined by inverse planning software. In this study, we have used the Helios IMRT planning system to generate ideal treatment plans for 10 cases of 2 common treatment sites (prostate and head and neck) and have investigated the actual treatment fluence distributions generated for each of the MLC leaf motion choices. The 2 dose delivery techniques were dosimetrically compared to each other and to the treatment plans. For each technique, point doses were measured in a water phantom using ionization chambers. Also for each technique, 2-dimensional dose distributions at a selected depth in a plastic phantom were obtained, using extended range film. The total delivery time and the number of monitor units (MU) delivered by each method were also compared. Our results indicate that the 2 delivery methods produce comparable results dosimetrically. For the cases reviewed, the delivery time was an average of 15% longer for SMLC deliveries, while the number of MUs (beam-on time) required by SMLC was an average of 15% fewer, than that for the DMLC. In the interest of simplicity, lower beam-on time, and potentially fewer mechanically-related problems, we think that the SMLC delivery technique may be the better choice when Helios is used for planning and Varian linear accelerators are used for delivery.     

Emergence and scattering of multiple neurofibromatosis (NF1)-related sequences during hominoid evolution suggest a process of pericentromeric interchromosomal transposition

Type 1 neurofibromatosis (NF1) gene encodes for a member of the GTPase activating protein family and is considered to be a tumor suppressor gene. Its very high rate of de novo mutation in humans led us to study a specific feature of this gene: the presence of numerous NF1-related sequences. According to our results, the human genome contains at least 11 NF1-related sequences, nine of which are scattered near centromeric sequences of seven different chromosomes. These NF1-related sequences, whose extent is quite varied according to loci, are unprocessed copies of the NF1 gene, and bear numerous mutations. A phylogenetic analysis of the six largest sequences indicates that they are all derived from a common ancestor, which would have appeared 22-33 million years ago, and was subsequently duplicated several times during hominoid evolution. The most recent duplication and interchromosomal transposition occurred in the last million years suggesting that the process could still be ongoing. Intriguing similarities between the evolution of alpha- satellite DNA and NF1-related sequences suggest the involvement of a common genetic mechanism for the generation and pericentric spreading of these NF1 partial copies.      

Slipped capital femoral epiphysis: rationale for the technique of percutaneous in situ fixation

In pinning a slipped capital femoral epiphysis (SCFE), the position of the pin within the center of the femoral head is important for two reasons. The pin may disrupt the lateral epiphyseal artery and cause avascular necrosis (AVN), or pin penetration in certain locations may go unrecognized on radiographs. To place the pin accurately, the surgeon must be aware of where the femoral head lies in relation to the femoral neck and the shaft. Radiographs of models and of patients in various positions support the view that the femoral head in most cases of chronic SCFE rotates around the axis of the femoral neck and does not slip inferiorly. Therefore, the starting point for an in situ fixation device is the anterior femoral neck, the exact location depending on the amount of slipping.     

Magnetic resonance angiography (MRA) of the circle of Willis: a prospective comparison with conventional angiography in 54 subjects

We prospectively correlated the findings of magnetic resonance angiography (MRA) with those of transfemoral four-vessel angiography in 54 patients to investigate the direction of flow within the circle of Willis. Our primary goal was to assess the direction of flow using the size of the vessel and signal intensity, without saturation techniques. Analysis of the circle of Willis, especially the communicating arteries, was performed double-blind by two groups of two radiologists. Three types of arteries were identified: high flow or cross-cerebral circulation, patent and nonvisualised arteries. Cerebral angiography was the standard for comparison between the two methods. MRA did not reveal any arteries invisible on angiography, thus providing a specificity of 100%. The sensitivity of MRA was 89.2% for the anterior and 81.3% for the posterior communicating arteries, and 100% for the anterior, middle and posterior cerebral arteries. MRA was shown to be a useful technique for the assessment of patency of the circle of Willis.     

Morphine place conditioning is differentially affected by CCKA and CCKB receptor antagonists.

In the present study we have examined the interaction between the selective cholecystokinin (CCK)A and CCKB receptor antagonists, devazepide and L365-260 on morphine conditioned place preference (CPP). Using an unbiased procedure, morphine (1.5 mg/kg) produced a reliable CPP which was observed irrespective of the conditioning compartment type. Pretreatment with devazepide (0.001-0.01 mg/kg s.c.) produced a dose related attenuation of this response. At higher doses (0.1-1 mg/kg) this antagonism became variable and dependent on the training compartment with blockade only observed when conditioning was to the white/rough textured environment. This profile has also been reported for the serotonin (5-HT)3 receptor antagonist ondansetron. The CCKB antagonist L365-260 (0.000001-0.01 mg/kg) failed to antagonize the morphine CPP, if anything a mild potentiation was observed. To study this further we examined the interaction between L365-260 (0.01 mg/kg) and a subthreshold dose of morphine (0.3 mg/kg). At these doses neither drug elicited CPP, however when co-administered a significant CPP was recorded. Finally, L365-260 at 1 mg/kg induced a mild but significant CPP when administered alone. These results suggest a differential role of CCK receptor subtypes on reward-related behaviour and complement previous studies suggesting bimodal effects of CCK systems on mesolimbic dopamine function.     

Ventilatory effects of dexmedetomidine, atipamezole, and isoflurane in dogs.

Dexmedetomidine (DMED) is a novel alpha 2 adrenergic agonist that has been shown to have potent analgesic and anesthetic sparing effects. This study was designed to investigate the effects of DMED, both alone and combined with isoflurane, on resting ventilation, the hypercapnic response, and the hypoxic response in dogs. When given alone, 1 microgram/kg decreased resting ventilation by 22% but at larger doses (10, 20, and 100 micrograms/kg) resting ventilation increased, doubling at 100 micrograms/kg. Doses of 10 micrograms/kg and greater caused a maximum depression of 60% in the slope of the hypercapnic response, but no dose had a significant effect on the hypoxic ventilatory response. A dose of 3 micrograms/kg of DMED reduced isoflurane MAC from 1.3% to 0.37%, and the ventilatory effects of this 1 MAC combination were intermediate between the awake values and those of isoflurane-anesthetized (1.3%) dogs. Atipamezole is a specific centrally acting alpha 2 receptor antagonist and when given with DMED in isoflurane-anesthetized dogs prevented the ventilatory depression. However, atipamezole alone also ventilatory stimulating effects, which may indicate tonic alpha 2 adrenergic activity. The ventilatory depression caused by DMED, either alone or combined with isoflurane, at doses that significantly reduce anesthetic requirements are relatively mild.