Indications that the Cgamma2 homology region is not a regular domain

The Cgamma2 homology region of rabbit IgG does not behave like a domain. Thus, there is no trans-interaction between the two Cgamma2 regions; instead there is an unusual cis-interaction between Cgamma2 and Cgamma3 regions. The observations were made on the plasmin digestion products Facb (IgG minus the Cgamma3 region) and pFc' (Cgamma3 region), which did not dissociate under neutral conditions but dissociated in 3M guanidine solution (that is, cis-interaction between Cgamma2 and Cgamma3). The Facb fragment split into subunits with equal molecular weights under neutral conditions on partial reduction and alkylation (that is, lack of trans-interaction between the two Cgamma2 in the molecule).     

Design of a CMOS Potentiostat Circuit for Electrochemical Detector Arrays

High-throughput electrode arrays are required for advancing devices for testing the effect of drugs on cellular function. In this paper, we present design criteria for a potentiostat circuit that is capable of measuring transient amperometric oxidation currents at the surface of an electrode with submillisecond time resolution and picoampere current resolution. The potentiostat is a regulated cascode stage in which a high-gain amplifier maintains the electrode voltage through a negative feedback loop. The potentiostat uses a new shared amplifier structure in which all of the amplifiers in a given row of detectors share a common half circuit permitting us to use fewer transistors per detector. We also present measurements from a test chip that was fabricated in a 0.5-mum, 5-V CMOS process through MOSIS. Each detector occupied a layout area of 35 mumtimes15 mum and contained eight transistors and a 50-fF integrating capacitor. The rms current noise at 2-kHz bandwidth is ap110 fA. The maximum charge storage capacity at 2 kHz is 1.26times10⁶ electrons     

Effect of mechanical design of the suspension on dynamic loading process

In designing a load/unload system utilized in hard disk drives, necessary care needs to be taken to ensure that the slider does not damage the disk surface during loading and unloading processes. However, a small deviation in the design point of the preload between the load-dome and flexure can lead to undesirable loading processes resulting in an adverse number of slider/disk contacts. In this study, we show that if the preload between the load-dome and flexure is too low, the slider can oscillate causing the corners of the slider to contact the disk multiple times even though the slider is a few microns away from the disk. In addition, the slider can be sucked down towards the disk resulting in a complete separation of the load-dome from the flexure assembly leading to uncontrolled loading conditions. This separation occurs while the suspension is still on the ramp, and thus no preload is exerted on the slider immediately following the separation. Consequently, the slider flies at a flying height higher than the design point until the gap between the load-dome and flexure closes. Hence, the suspension must be carefully designed to suppress slider oscillation and to ensure that the load-dome does not separate during the loading process.     

Structure in thin superfluid helium films

Precision measurements of third sound in atomically thin⁴He films on Ne, Ar, and CO₂ substrates reveal a periodic structure not corresponding to whole layers. Treating the He film as an incompressible, continuous fluid, the data indicate that the chemical potential has a contribution proportional to l^–6, where l is the He coverage in layers, which is modulated at intervals of 0.62±0.04 layers and which weakens the van der Waals potential. Alternatively the data indicates the existence in the film of a damped smectic density wave with a 0.54±0.40 layer periodicity.     

Effects of preload, afterload and inotropy on dynamics of ischemic segmental wall motion

OBJECTIVES: This study sought to explore the separate and combined effects of changes in preload, afterload and contractility on the dynamics of systolic bulging. BACKGROUND: The extent of ischemic systolic bulging has been shown to be mechanically disadvantageous to left ventricular pump performance. The factors that determine ischemic segmental wall motion have not been systematically studied. METHODS: Fourteen beagles were instrumented with sonomicrometers, micromanometer pressure gauges and a balloon in the inferior vena cava. Regional function was evaluated before and after 90 s of proximal left circumflex coronary artery occlusion. Occlusions were repeated after increasing systolic pressure by 5 to 10 (afterload I) and 15 to 20 mm Hg (afterload II) with graded aortic occlusion during inotropic stimulation with dobutamine (2.5 and 5 micrograms/kg body weight per min intravenously), with simultaneous 5 micrograms/kg per min dobutamine infusion and afterload II and during 2.5% halothane (negative inotrope) concentration. A 20-min recovery period was allowed between each stage of the experiment so that regional function returned to its preocclusion level. Ischemic wall motion was characterized by percent systolic bulging and its peak positive systolic lengthening rate (+dL/dt). RESULTS: Because bulging is markedly influenced by regional preload, systolic bulging was characterized over a wide range of end-diastolic lengths of the ischemic segment during caval balloon occlusion. During each intervention, a decrease in regional preload increased the extent of percent systolic bulging. This preload dependency was more pronounced with dobutamine infusions. An increase in afterload was not associated with increased percent systolic bulging at any given preload. At a predetermined preload, bulging was not appreciably altered when an increase in left ventricular systolic pressure was not associated with a change in peak positive first derivative of left ventricular pressure (+dP/dt) but was significantly worse when peak +dP/dt increased. Dobutamine caused a dose-dependent increase in percent systolic bulging and peak +dL/dt that was positively correlated with peak +dP/dt. CONCLUSIONS: By using different loading and inotropic interventions and analyzing the regional wall motion behavior over a range of regional preloads, we can conclude that preload and rate of pressure (tension) development are the principal determinants of systolic bulging. Increases in left ventricular pressure alone had a minimal effect on systolic bulging.     

Effects of cigarette smoking and age on the maturation of human oocytes

We investigated whether cigarette smoking, measured by follicular fluid concentrations of cotinine (a major metabolite of nicotine), affects the maturity of oocytes from women undergoing in-vitro fertilization (IVF) and embryo transfer. In 234 women, follicular fluid samples were assessed for cotinine and their 2020 oocytes were assessed for maturity stage. Data on individual proportions of oocytes which were mature (OM) and were fertilized (OF) were analysed by regression in relation to age and follicular fluid cotinine. OF gave an independent assessment of oocyte maturity. Both age and follicular fluid cotinine entered the OM and OF regressions and were significant. The age-adjusted regression coefficients for log cotinine were positive; greater cotinine concentrations usually accompanied greater OM and OF. The cotinine effect on OM was positive in younger women, but it became negative (decreased OM with increasing cotinine concentrations) in older women (> or = 40 years). We further found in older women an average reduction of approximately 50% in the number of mature oocytes; this reduced number was lower than the number of embryos usually transferred. Smoking can reduce the number of mature oocytes even further, therefore risking a negative IVF-embryo transfer outcome. This may be the reason why the negative effects of smoking become clinically detectable in older women.     

Autologous lymphokine-activated killer cell therapy of Epstein-Barr virus-positive and -negative lymphoproliferative disorders arising in organ transplant recipients

Lymphoreticular malignancies, collectively called posttransplant lymphoproliferative disorders (PTLD), eventually develop in 2-5% of organ transplant recipients. They frequently undergo regression when immunosuppression is reduced or stopped. This feature has been associated with a previous or de novo Epstein-Barr virus (EBV) infection. We herein describe immunotherapy with autologous lymphokine-activated killer (LAK) cells in seven patients with PTLD (four EBV-positive patients and three EBV-negative patients). Autologous peripheral blood mononuclear cells were obtained by leukapheresis, depleted of monocytes, and cultured in the presence of interleukin 2 for 10 to 11 days. A single dose of 5.2 x 10(9) to 5.6 x 10(10) LAK cells was given intravenously. Systemic interleukin 2 was not administered. The four patients with EBV+ PTLD had complete tumor regression; two of them developed controllable rejection. Three patients are well 13-16 months after treatment; the fourth patient died of pneumonia 41 days after infusion. Three patients with EBV- lymphomas had no response despite prior evidence that their tumors also were subject to immune surveillance. Two of these three patients died after being given other treatment, and the third patient has persistent tumor. In conclusion, autologous LAK cell infusion was effective for treatment of four EBV+ organ transplant recipients. LAK cell efficacy for three patients with EBV- PTLD was not evaluable under the management circumstances in which this treatment was utilized.