No abstract

Three separate techniques were used to demonstrate B and T cells forming rosettes in unimmunized and immunized mice: a) anti-@ serum and brain-absorbed anti@ serum as control, b) anti-H-2 serum in neonatally thymectomized mice reconstituted with semiallogeneic thymus cells, c) radioiodinated anti-immunoglobulin serum to demonstrate surface immunoglobulins o n rosette-forming cells (RFC).The three methods gave very c.onsistent results. More than 80 5% of background RFC were B cells; after priming with sheep red blood cells the proportion of T RFC rose t o 40 -50 % by days 6 --10, and then declined.

The purpose of this paper was to calculate vagal tone (V) for 17 normal human fetuses in quiet sleep (QS) between 36 and 40 weeks gestation. The fetal cardiac electrical signal was captured transabdominally in 3-min blocks at a rate of 833 times per second and fetal R-waves were extracted using adaptive signal processing techniques. Fetal R-wave interbeat intervals were converted to equally spaced, time-based data, and the low-frequency component was removed using a 21-point third-order moving polynomial. The parameter V was calculated by taking the natural logarithm of the sum of the power densities between 0.3 Hz and 1.3 Hz. We found that fetal breathing was associated with an approximately 25% increase in V as compared to nonbreathing, 3.33 +/- 0.48 versus 2.57 +/- 0.47, p < 0.0001. Furthermore, there was a significant linear relationship between the mean single-fetus V during spontaneous respiration and the mean single-fetus V during normally occurring apneic periods, r = 0.772, p < 0.002. We conclude that respiratory activity is associated with a significant increase in vagal tone for normal human fetuses in QS.

A surgical technique for catheter implantation for sequential blood sampling in the pig is described. This methodology minimizes stress to the animal and chances of catheter dislodgement, both of which are detrimental to accurate long-term metabolic assessment of the animal model. The technique involves implantation of a vinyl catheter via the external jugular vein into the vena cava. To ensure catheter retention, the method uses a silicone plug fitted to the catheter and located cranial to its entry to the vein, double ligation at the venous insertion, subsequent passage of the catheter to exit 10 cm cranial to the scapula on the dorsal midline, and a denim vest fitted to the thorax. With this technique seven out of nine catheters have functioned more than 50 days, two functioned for approximately 100 days, and one for over 150 days.

Summary Antisera to mouse immunoglobulin heavy and light chains were used in vitro to inhibit the formation of rosettes in mouse spleen cell suspensions taken at intervals after sheep red blood cell immunization. Anti‐kappa produced greater than 90% inhibition of both immune and non‐immune rosettes. 65–80% inhibition of non‐immune and immune rosettes was induced by anti‐μ, up to 14 days after injection. Late in the response anti‐μ inhibited rosettes by less than 50%. Anti‐γ inhibited immune rosettes only, increasing to 42% inhibition on the 28th day of response. Anti‐α inhibited rosette formation only during the peak of the response. These results are discussed as relating to antigen‐binding receptors on rosette‐forming cells.