Motivated behavior and the estrous cycle in rats

(1) The estrous cycle in the rat may be used to study recurrent changes in motor behaviors and motivation which are strongly related to cyclic hormonal and CNS changes. (2) The peak in motivated behaviors occurs during a sharply defined period on the night between proestrus and estrus and is evident in facilitated wheel-running, lordosis, and intracranial self-stimulation. (3) Behaviors without a clearly motivated character do not show an estrous cyclicity. (4) The estrous cyclic variation in intracranial self-stimulation was observed at a specific locus — the pars campacta of the substantia nigra. (5) A neurochemical link between sexually motivated behavior, wheel running and intracranial self-stimulation is suggested. This link is in part dopaminergic but is probably also activated by many other systems.     

Neurobiology of obsessive compulsive disorder--a serotonergic basis of Freudian repression

Intrusive thoughts and images, often of a violent, horrific, or blasphemous nature are the hallmark of Obsessive Compulsive Disorder (OCD). OCD patients frequently also often have reductions in normal serotonergic (5-HT) function. This paper proposes a model of 5-HT function involving the routine filtering and suppression of violent or libidinal impulses. This model accounts for OCD as an instance of failed inhibition. The model also appears to resemble Freud's model of ego-id interactions at least in part, suggesting that it may be possible to psychobiologically substantiate a Freudian metaphor.     

Local demineralization as a model for bone strength reductions in lytic transcortical metastatic lesions.

The structural consequences of bone density changes associated with lytic metastatic lesions were investigated using an experimental model of regular, lytic metastatic lesions in bone. Circular holes were drilled in the mid-diaphyseal cortex of paired adult canine femora. The region around the defect was demineralized in one bone of each pair with 0.8 N HCl. Specimens were tested to failure in four-point bending. Defect size was determined from conventional planar radiographs as the maximum apparent defect diameter divided by the periosteal diameter. Demineralization resulted in irregular defect geometries, which increased the maximum defect dimension 33% to 57% with respect to the original drill hole diameter. Demineralization resulted in additional strength reductions beyond those expected from the original drill hole alone. Despite the irregular demineralization patterns observed, strength reductions were in close agreement with those predicted from data for regular, nondemineralized holes (r2 = 0.93). The results demonstrate that irregular diaphyseal defect borders may not require more complex fracture risk predictors than can be determined from analytic and experimental studies of regular defect geometries. Our results also demonstrate that errors of over 100% can occur when measuring diaphyseal defect size from radiographs that are not optimally aligned with respect to the defect.     

Intratemporal vascular tumors: detection with CT and MR imaging

The diagnostic contributions of computed tomography (CT) and magnetic resonance (MR) imaging were compared in 12 patients with benign intratemporal vascular tumors (hemangioma or vascular malformation). The tumors included six in the internal acoustic canal and six in the geniculate ganglion region. Clinical and histologic correlations were made. Two of the six patients with tumors in the internal acoustic canal underwent CT, and both required gas cisternography to show the tumor. Five patients in that group underwent MR imaging, and all five studies showed the tumor. All six patients with geniculate ganglion tumors underwent CT. Results in one study were questionable, and five showed the tumor. Five patients in this group underwent MR imaging, but the MR findings were positive in only two cases. MR imaging should therefore be performed before CT in the evaluation of facial nerve dysfunction, as it demonstrated all tumors in the internal acoustic canal and some in the geniculate ganglion region. If MR findings are negative, CT should then be performed to rule out a possible geniculate ganglion lesion.     

CT-guided fine needle aspiration of a periaortic collection

Patients with infected aortic grafts suffer considerable morbidity and mortality. Therefore, it is important to make the diagnosis of infection to provide a reasonable chance for survival. Clinical signs of infection are usually apparent in the postoperative period. If absent, the diagnosis becomes more difficult. CT scanning is beneficial in detecting periaortic fluid and gas collections; however, it cannot differentiate postoperative gas from infection in all cases. This is especially true during the first 2 weeks after operation. CT-guided fine needle aspiration can provide a safe and reliable means to answer this clinical question.     

Digital imaging with a photostimulable phosphor in the chest of newborns

To evaluate use of a digital photostimulable phosphor imaging system in the neonatal nursery, 150 newborns were divided into three groups of 50. In the first two groups, screen-film and computed radiographs of the chest were obtained at the same radiation exposure; in the third group, computed radiographs were obtained with a 50% dose reduction (half-exposure computed radiographs). All images were blindly evaluated by three readers who scored the quality of visualization of the mediastinum, lung, bone, soft tissues, and endotracheal and nasogastric tubes, and also image density. No statistical differences in visualization of tubes existed among the three groups. Visualization of the mediastinum, lung, bones, and soft tissues was statistically significantly better on computed radiographs than on half-exposure computed radiographs; visualization of the lungs, bones, and soft tissues was statistically significantly better on screen-film radiographs than half-exposure computed radiographs. Image density was statistically better on computed and half-exposure computed radiographs than on screen-film radiographs.