A study of external skeletal fixation systems for unstable pelvic fractures

This study was undertaken to determine the feasibility of constructing an anterior pelvic external fixator capable of resisting displacement of vertical shear fractures. Newly designed tapered thread pins for cancellous bone had better bone pin fixation and their greater 6-mm diameter provided more than twice the stiffness of Hoffmann 4-mm pins when tested in clusters. Using these pins and a more rigid anterior frame as one model, various pelvic fixators were tested to determine their resistance to vertical shear forces. These tests determined that this new fixator was 16 times stiffer than a Bonnel single anterior frame and five times stiffer than a double anterior frame (both constructed of Hoffmann components). Extrapolation from the data shows that 13 mm of posterior fracture displacement would occur with loads of one half body weight using the new fixator. Additionally it was noted that Hoffmann frames constructed with two 5-mm pins performed as well as those using three 4-mm pins.     

Distribution pattern of cell bodies and fibers with neurotensin-like immunoreactivity in the cat hypothalamus

Neurotensin is widely distributed in the central and peripheral nervous systems. Extensive radioimmunoassay and immunohistochemical studies in rats show that the neurotensin immunoreactive perikarya and fibers are most prominent in the hypothalamus. Radioimmunoassay studies have suggested that the levels of neurotensin in the hypothalamus of cats may be six times higher than that of rats. We studied the distribution pattern of neurotensin immunoreactivity within the hypothalamus of the cat by avidin-biotin modification immunohistochemical methods: (1) to define its distribution pattern within the hypothalamus, and (2) to compare our findings with the patterns that have been described in rats. Results show that neurotensin immunoreactive cell bodies and fibers are most prominent in the rostral and intermediate regions of the cat hypothalamus. Cell bodies with neurotensin-like immunoreactivity are seen maximally in the medial preoptic region, the infundibular nucleus, and the lateral hypothalamus. The neurotensin positive fibers are dense in the periventricular regions of the entire rostro-caudal extent of the hypothalamus. This pattern of distribution of neurotensin immunoreactivity is similar to that described in rats. The suprachiasmatic nuclei of the cat hypothalamus, however, contained a significant number of neurotensin immunoreactive cell bodies, an observation not noted in the rat hypothalamus. The neurotensin immunoreactive neurons were more numerous in the lateral hypothalamus than has been reported in rats, but the paraventricular nucleus of the hypothalamus in cats contained fewer neurotensin immunoreactive perikarya. The presence of neurotensin immunoreactive perikarya in the suprachiasmatic nucleus and the apparent increase in the number of neurotensin immunoreactive neurons in the lateral hypothalamus may account for the increased levels of neurotensin reported in cats. Neurotensin has been speculated to play a role in nociception, thermoregulation, and control of arterial pressure by acting as a hormone or a neurotransmitter. Details of the pattern of colocalization of neurotensin with that of other neuropeptides and neurotransmitters will aid in our understanding of its role in these functions.     

Optimization of BMD measurements to identify high risk groups for treatment--a test analysis.

INTRODUCTION: The aim of this study was to develop a methodology to optimize the role of BMD measurements in a case finding strategy. We studied 2113 women > or = 75 years of age randomly selected from Sheffield, UK, and adjacent regions. Baseline assessment included hip BMD and clinical risk factors. Outcomes included death and fracture in women followed for 6723 person-years. MATERIALS AND METHODS: Poisson models were used to identify significant risk factors for all fractures and for death with and without BMD and the hazard functions were used to compute fracture probabilities. Women were categorized by fracture probability with and without a BMD assessment. A 10-year fracture probability threshold of 35% was taken as an intervention threshold. Discordance in categorization of risk (i.e., above or below the threshold probability) between assessment with and without BMD was examined by logistic regression as probabilities of re-classification. Age, prior fracture, use of corticosteroids, and low body mass index were identified as significant clinical risk factors. RESULTS: A total of 16.8% of women were classified as high risk based on these clinical risk factors. The average BMD in these patients was approximately 1 SD lower than in low-risk women; 21.5% of women were designated to be at high risk with the addition of BMD. Fifteen percent of all women were reclassified after adding BMD to clinical risk factors, most of whom lay near the intervention threshold. When a high probability of reclassification was accepted (without a BMD test) for high risk to low risk (p1< or = 0.8) and a low probability accepted for low to high risk (P2 < or = 0.2), BMD tests would be required in only 21% of the population. CONCLUSION: We conclude that the use of clinical risk factors can identify elderly women at high fracture risk and that such patients have a low average BMD. BMD testing is required, however, in a minority of women--a fraction that depends on the probabilities accepted for classification and the thresholds of risk chosen. These findings need to be validated in other cohorts at different ages and from different regions of the world.     

Relationship between acrosome reaction and in vitro fertilization of zona-free hamster eggs by bonnet monkey (Macaca radiata) spermatozoa

The relationship between acrosome reaction, as studied by FITC-RCA staining technique, and the penetration of bonnet monkey spermatozoa into zona-free hamster eggs was investigated. The acrosomes of unreacted spermatozoa fluoresced, whereas those of acrosome-reacted sperm did not fluoresce owing to decreased binding of the lectin. The percentage of acrosome-reacted sperm increased following 3 h of incubation in BWW medium. The assessment of acrosome reaction by the FITC-RCA staining technique correlates well with the in vitro fertilization of zona-free hamster eggs.     

Anatomical evidence for cortical projections from the striatum in the cat

Several anatomical and physiological studies have thus far failed to confirm the existence of striatocortical projections proposed in 1895 by Cajal. Evidence for such striatocortical projections was obtained in the present study using the horseradish peroxidase (HRP) tracing method. When 0.1–0.8 μ1 of 30–50% HRP in saline was injected into different cortical regions in cats, HRP was transported to cells in different thalamic nuclei, striatum and the globus pallidus. Only large striatal cells, 30–60 μm in their long axes, contained HRP reaction product. After injection in area AI, the striatocortical cells were located in the dorsal parts of the middle third of putamen, where auditory cortical afferents are known to project, thereby suggesting reciprocal connections between the cerebral cortex and the striatum.