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.     

Changes of sodium and urea concentrations in the renal papillary interstitial fluid on dehydration of rats

1. The isolated renal papillae of a rat were centrifuged in a two tube assembly which allowed fluid from the tissue to separate into the lower tube.2. The papillae were centrifuged for 15 min at 300 g and 1500 g consecutively.3. After intraperitoneal injection of Na (131)I-diatrizoate, the activities of urine, and fluid samples obtained from the papilla, were compared. It was found at 1500 g that the median value for papillary fluid activity was 1.52% of the activity of urine. This is evidence that the papillary fluid was virtually free from any contamination from the terminal collecting ducts.4. It is considered that the fluid sample obtained from the papillae by centrifugation at 1500 g is a representative and reproducible sample of interstitial fluid.5. The method was used to demonstrate changes in solute concentrations in the renal papillary fluid, following dehydration of rats.     

CM1 ligation initiates apoptosis in a caspase 8-dependent manner in Ramos cells and in a mitochondria-controlled manner in Raji cells

Burkitt lymphoma (BL) is a tumor with the characteristics of germinal center B cells. We previously reported that the CM1 (centrocyte/-blast marker 1) molecule is expressed only in germinal center B cells, specifically, in a subpopulation of centroblasts and centrocytes. In the present study, we investigated the apoptosis induced by anti-CM1 in the Ramos and Raji human BL cell lines. The Ramos is protected from apoptosis by the crosslinking of sIgM and the calcium ionophore by the ligation of CD40 with anti-CD40 monoclonal antibodies (mAb) or soluble CD40 ligand (sCD40L). In this investigation on the effect of CM1 on apoptosis in BL cell lines, we found that cellular signaling by CM1 induces apoptosis and decreases cell viability, in BL cell lines cultured for 24 hours with protein-G agarose beads conjugated anti-CM1 mAb. Stimulation by CD40 ligated with sCD40L protected Raji cells from CM1-induced apoptosis, but did not protect Ramos cells. Furthermore, after anti-CM1 mAb stimulation, CD95 expression was upregulated and CD40 expression was unaltered or slightly decreased in Ramos cells, whereas CD95 was downregulated and CD40 was slightly upregulated in Raji cells. The engagement of CD40 by sCD40L enhanced CD95 expression, but the level of CM1 expression was unchanged in Ramos. However, sCD40L downregulated both CD95 and CM1 expression in Raji. In addition, the caspase-8 specific inhibitor blocked CM1-induced apoptosis in Ramos cells, but not in Raji cells. Increased mitochondrial membrane permeabilization was observed only in Raji cells. Moreover, the effector caspase inhibitor, z-DEVD, blocked CM1-mediated apoptosis in both cell lines. We found that CM1-induced apoptosis is achieved via different initiation pathways, which are cell-type dependent.     

CD4+ T-cell memory: generation and multi-faceted roles for CD4+ T cells in protective immunity to influenza

Summary: We have outlined the carefully orchestrated process of CD4⁺ T‐cell differentiation from naïve to effector and from effector to memory cells with a focus on how these processes can be studied in vivo in responses to pathogen infection. We emphasize that the regulatory factors that determine the quality and quantity of the effector and memory cells generated include (i) the antigen dose during the initial T‐cell interaction with antigen‐presenting cells; (ii) the dose and duration of repeated interactions; and (iii) the milieu of inflammatory and growth cytokines that responding CD4⁺ T cells encounter. We suggest that heterogeneity in these regulatory factors leads to the generation of a spectrum of effectors with different functional attributes. Furthermore, we suggest that it is the presence of effectors at different stages along a pathway of progressive linear differentiation that leads to a related spectrum of memory cells. Our studies particularly highlight the multifaceted roles of CD4⁺ effector and memory T cells in protective responses to influenza infection and support the concept that efficient priming of CD4⁺ T cells that react to shared influenza proteins could contribute greatly to vaccine strategies for influenza.     

Variation in coat protein genes among five geographicallydifferent isolates of rice tungro spherical virus

Summary.  The variation in the sequence of the coat protein genes of four isolates of rice tungro spherical virus from different countries, Malaysia, Thailand, India and Bangladesh, was compared with an isolate from the Philippines. The evidence from RT-PCR, Southern blot hybridization and sequences of the coat protein genes indicated that the isolates appeared to fall into two groups. One comprised the Philippine and Malaysian isolates (about 95% sequence similarity) and the other the Bangladeshi and Indian isolates, the sequences of which differed by about 15% from that of the Philippine isolate. The Thai isolate seemed to be a mixture of these two subgroups. Received March 4, 1997 Accepted April 23, 1997     

Anorectal dysfunction in systemic sclerosis.

This study was aimed to evaluate the anorectal dysfunction in systemic sclerosis (SSc) and propose the clinical significance of anorectal manometry in patients with SSc. Seven patients with SSc were evaluated with manometry for anorectal function and an additional 11 normal subjects were collected as a control group. The study group underwent esophageal manometry as well and the correlation between the degree of anorectal and esophageal dysfunction was evaluated. Patients showed a lower tolerance for balloon distention of the rectum than controls (minimal sensory volume and urgency volume, P < 0.05). The resting and squeezing pressure of the anal sphincter and the functional length of the anal canal showed no significant difference in these two groups. Rectoanal inhibitory reflex was absent in one (14%) and diminished in two (29%) of seven patients with SSc. SSc patients also showed abnormal esophageal manometry findings, notably decreased LES pressure and body amplitude of distal 2/3 esophagus. The comparison between manometric profiles of anorectum and esophagus showed no significant correlation by statistical analysis. In conclusion, our data could suggest that anorectal function may be impaired in patients with SSc which could reflect the involvement of the anorectum by the disease, and that anorectal manometric studies can be useful to detect such dysfunction in patients with SSc, even before clinical symptoms.     

Altered p53 expression in Epstein Barr virus positive T cell lymphomas.

Recent studies have suggested a probable association between Epstein-Barr virus (EBV) and nasal/nasopharyngeal T cell lymphomas but the role of oncogenes or tumor suppressor genes is poorly understood. We have studied the frequency of p53 expression and its relation to the EBV infection in 33 Korean patients with head and neck (H&N) lymphomas. All cases (23 B cell & 10 T cell) were immunostained for p53 protein using the mAb D07 (Novocastra) and the avidin biotin peroxidase method. EBER in situ hybridization was performed using a fluorescein conjugated EBV oligonucleotide probe (Dako). Among 33 lymphomas, 16 cases stained positively for p53 protein. P53 expression was frequent both in higher grade lymphomas and in advanced stage. Nine cases were EBER positive, EBER was more commonly found in T cell lymphomas than in B cell lymphomas (70% vs 8.7%). EBER positive lymphomas showed a higher frequency of p53 positivity than EBER negative lymphomas (78% vs 38%), although the difference was not statistically significant (p = 0.095). These findings indicate altered expression of p53 protein occurs in H&N lymphomas, especially in late event lymphoma progression and appears to play a role in the development of EBER positive T cell lymphomas.