Observation of cavitation in a mechanical heart valve in a total artificial heart

Recently, cavitation on the surface of mechanical heart valves has been studied as a cause of fractures occurring in implanted mechanical heart valves. The cause of cavitation in mechanical heart valves was investigated using the 25 mm Medtronic Hall valve and the 23 mm Omnicarbon valve. Closing of these valves in the mitral position was simulated in an electrohydraulic totally artificial heart. Tests were conducted under physiologic pressures at heart rates from 60 to 100 beats per minute with cardiac outputs from 4.8 to 7.7 L/min. The disk closing motion was measured by a laser displacement sensor. A high-speed video camera was used to observe the cavitation bubbles in the mechanical heart valves. The maximum closing velocity of the Omnicarbon valve was faster than that of the Medtronic Hall valve. In both valves, the closing velocity of the leaflet, used as the cavitation threshold, was approximately 1.3-1.5 m/s. In the case of the Medtronic Hall valve, cavitation bubbles were generated by the squeeze flow and by the effects of the venturi and the water hammer. With the Omnicarbon valve, the cavitation bubbles were generated by the squeeze flow and the water hammer. The mechanism leading to the development of cavitation bubbles depended on the valve closing velocity and the valve stop geometry. Most of the cavitation bubbles were observed around the valve stop and were generated by the squeeze flow.     

Implantation study of a novel hydroxyapatite/collagen (HAp/col) composite into weight-bearing sites of dogs

A hydroxyapatite/type I collagen (HAp/Col) composite, aligning hydroxyapatite nanocrystals along collagen molecules, has been prepared. The biocompatibility, osteoconductive activity, and efficacy as a carrier of rhBMP-2 of this novel biomaterial implanted in the weight-bearing site have been examined. The HAp/Col implants (15 mm in diameter and 20 mm in length) with a surface cross-linked layer containing rhBMP-2 (0 or 400 microg/ml) were implanted into bone defects of tibiae in three beagle dogs and fixed according to the Ilizarov method. As a control, bone defects of 20 mm in two beagle dogs did not receive implants, and the dogs were allowed to walk using an Ilizarov extraskeletal fixator. The specimens were removed from one dog in each group after 12 weeks. Also, the Ilizarov fixators in the rhBMP-treated dogs were removed after 12 weeks, after which full weight bearing started. The specimens were further taken out after 18 and 24 weeks in the rhBMP-treated and non-rhBMP-treated dogs, and after 24 weeks in the control group. The change of bone mineral density, as well as radiological and histological findings, suggest that the implants are able to induce bone remodeling units and are a superior carrier of rhBMP-2 due to the stimulation of early callus and new bone formation.     

The effects of lifestyle and type a behavior on the life-stress process

To evaluate the effects of personal factors such as lifestyle and Thpe A behavior on the life-stress process, we analyzed data randomly collected from 428 metropolitan Tokyo residents. Path analysis techniques were implemented to examine the direct and indirect effects of lifestyle and the Type A behavior pattern between life events, subjective stress and depressive symptoms. The following results were obtained: 1. Persons with a healthy lifestyle perceived a lower subjective stress level. 2. Although females with a healthy lifestyle had fewer direct depressive symptoms, males with a healthy lifestyle had fewer indirect depressive symptoms due to alleviation of subjective stress. 3. Type A males perceived a lower subjective stress level and Type A females experienced more life events. It is suggested that mental health is modified not only by lifestyle but also by Type A behavior in the life-stress process. In particular, the preservation and promotion of a healthy lifestyle appear to reduce subjective stress and may be an important factor for the improvement of mental ill health.     

Flow cytometric analysis of the DNA content of thymomas

In this study, the prognostic value of determining the nuclear DNA content of thymomas by flow cytometry was evaluated. Of a total 31 resected thymomas, 10 (32%) showed DNA aneuploidy, the presence of which was significantly correlated with an advanced clinical stage of disease. The patients with an aneuploid tumor had a poorer prognosis than those with a diploid tumor, demonstrating a survival rate of 50% at 7 postoperative years, which was considerably less favorable than that of the patients with a diploid tumor, being 100% in the same period (p<0.05). Moreover, patients with a high DNA index (DI), i.e., a DI1.5, tended to have a poorer prognosis than those with a low DI. These findings indicated that the DNA content can be an important prognostic index in patients with thymomas.     

Parkinsonism induced by atypical neuroleptics in a patient with severe iron deficiency.

Although still controversial, iron deficiency has been indicated as one of the risk factors for developing neuroleptic-induced extrapyramidal symptoms (EPSs), including akathisia, dystonia, and neuroleptic malignant syndrome. Here we report our experience of iron supplementation and alternating neuroleptics for treating Parkinsonism in a schizophrenic female patient having severe iron deficient anemia.     

Microsurgical anatomy of the abducens nerve

The aim of this study is to demonstrate and review the detailed microsurgical anatomy of the abducens nerve and surrounding structures along its entire course and to provide its topographic measurements. Ten cadaveric heads were examined using ×3 to ×40 magnification after the arteries and veins were injected with colored silicone. Both sides of each cadaveric head were dissected using different skull base approaches to demonstrate the entire course of the abducens nerve from the pontomedullary sulcus to the lateral rectus muscle. The anatomy of the petroclival area and the cavernous sinus through which the abducens nerve passes are complex due to the high density of critically important neural and vascular structures. The abducens nerve has angulations and fixation points along its course that put the nerve at risk in many clinical situations. From a surgical viewpoint, the petrous tubercle of the petrous apex is an intraoperative landmark to avoid damage to the abducens nerve. The abducens nerve is quite different from the other nerves. No other cranial nerve has a long intradural path with angulations and fixations such as the abducens nerve in petroclival venous confluence. A precise knowledge of the relationship between the abducens nerve and surrounding structures has allowed neurosurgeon to approach the clivus, petroclival area, cavernous sinus, and superior orbital fissure without surgical complications. Clin. Anat. 25:1030–1042, 2012. © 2012 Wiley Periodicals, Inc.