The role of pH* and buffer capacity in the recovery of function of smooth muscle cooled to −13 °C in unfrozen media

It has often been suggested that pH changes may be implicated in the injury sustained by biological systems during cooling. This particular mechanism of cryoinjury, however, has received little attention undoubtedly because of the difficulties encountered in making accurate pH measurements at low temperatures.New pH* scales established for some mixtures of dimethyl sulfoxide and water at low temperatures are used in this study to assess the effect of pH* and buffering ability upon the integrity of mammalian smooth muscle stored at −13 °C in a variety of unfrozen solutions containing 30% (w/v) Me₂SO. Smooth muscle, as a component of every organ, is a good model tissue intermediate between cells and organs. Furthermore, its overall function is conveniently tested by measuring isometric contractile responses to the drug histamine. In this way the function of strips of guinea pig taenia coli were examined at 37 °C before and after storage at −13 °C in potassiumrich media containing a variety of zwitterionic buffers. Functional recovery depends markedly on the pH* with a welldefined optimum at the surprisingly high pH*₋₁₃ of 9.2. In medium containing TES buffer, which has a maximum buffer capacity at pH*₋₁₃= 8.6, the cooled muscles recover 50% of their control contractility but in medium containing the buffer Tricine, which has a maximum capacity at the optimum pH* for recovery, the contractile response upon rewarming improves to 70%.These data are the first to quantify the effect of pH in cryopreservation on a sound theoretical basis and some of the possible underlying mechanisms are discussed.     

Modulation of antigen-induced T cell proliferation by alpha 2M-trypsin complexes

Proteinase-complexed alpha 2-macroglobulin (alpha 2M) could be shown to interfere with T cell proliferation in response to antigen presented by autologous antigen-pulsed monocytes (M phi) (antigen-induced M phi-T cell interaction, MTI). Addition of alpha 2M-trypsin (alpha 2M X T) complexes to cultures of T cells and antigen-pulsed M phi led to a dose-dependent decrease of T cell proliferation (up to 91% inhibition of the T cell response), whereas the same concentrations of free (native) alpha 2M had no effect on antigen-induced MTI. The observed interference with MTI could be attributed to residual enzymic activity of the alpha 2M X T complex. Addition of aprotinin, a low Mr protein proteinase inhibitor able to penetrate to the enzyme entrapped within the alpha 2M molecule and thus bind to and inactivate the enzyme's active site, resulted in a reversal of the alpha 2M X T-induced biological effect. Inactivation of the enzyme's active site within alpha 2M X T was monitored by a decrease in the hydrolytic activity of the complex. Kinetic studies (addition of alpha 2M X T 24 to 48 hr after culture onset was shown to be still inhibitory) indicated an effect at the level of the T cell or its mediators, but an overnight incubation of T cells with alpha 2M X T did not alter these cells' capacity to proliferate in response to an antigenic stimulus. An additional effect of alpha 2M X T on the antigen-presenting cell cannot be ruled out at present. However, alpha 2M X T did not alter the percentage of monocytes expressing HLA-DR, -DP, and -DQ or interfere with interleukin 1 release if added to M phi at concentrations that significantly inhibited MTI. Furthermore, incubation of M phi with alpha 2M X T for 1 hr before antigen pulsing had no effect on the M phi antigen presenting capacity.     

An “orientation sphere” visualization for examining animal head movements

1. Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.
2. Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head‐mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head “movement” is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing (“environmental framing”).
3. We propose a new approach to visualize the data of such head‐mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by “longitude” position and head pitch by “latitude” on this “orientation sphere” (O‐sphere).
4. We construct the O‐sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading‐independent head rotation, and propose the derivation of O‐sphere‐metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors.
5. Visualizations of the O‐sphere provide an intuitive representation of animal behavior manifest via head orientation and rotation. This has ramifications for quantifying and understanding behaviors ranging from navigation through vigilance to feeding and, when used in tandem with body movement, should provide an important link between perception of the environment and response to it in free‐ranging animals.

     

The spread of somatosensory-evoked potentials within the nervous system

Four thalamic and cortical recordings were carried out in 5 patients. The thalamic-evoked potentials were typical and revealed a triphasic complex, but their latencies showed a relatively high standard deviation. They could be divided into two groups according to their latencies, both of which had low SD. These data suggested that there could be two types of latency of thalamic SEP, because the 4 patients' body sizes were very similar. More detailed surface, cortical and depth recordings are needed to resolve these questions.     

Characterization of messenger RNA from epimastigotes and metacyclic trypomastigotes of Trypanosoma cruzi

The cell-free translation products of polyribosomal and post-polyribosomal mRNAs from the non-infective epimastigotes and the infective metacyclic trypomastigotes of the parasitic protozoan Trypanosoma cruzi were compared by two-dimensional polyacrylamide gel electrophoresis. The result show that although many polypeptides are conserved, quantitative and qualitative differences are observed between both differentiation stages. The results also indicate the existence of post-polyribosomal mRNAs in equilibrium with polyribosomal counterparts. The immunoprecipitation of the in vitro synthesized polypeptides with chagasic human serum and the serum raised against an 85-kDa glycoprotein (P2-WGA), potentially involved in the process of T. cruzi penetration into mammalian cells, shows that while the chagasic serum recognizes the same 72-kDa, 68-kDa and 46-kDa polypeptides in both differentiation stages, the anti-P2-WGA serum immunoprecipitates a single 48-kDa polypeptide from in vitro translation products of metacyclic trypomastigotes.     

Changes in glycosylated haemoglobin after poor control in insulin-dependent diabetics.

Glycosylated haemoglobin (HbA1) was measured in seven insulin-dependent diabetic patients before, during, and after a seven-day period of monitored poor control. There was considerable individual variation in the pattern and degree of change in HbA1 concentration induced by poor control and the time when it occurred. Greater increases in HbA1 were seen during the period of metabolic derangement than in the subsequent two months. More information is required before HbA1 estimations are widely used clinically to monitor control in individual diabetics.     

Comparison of optimization methods for fed-batch cultures of hybridoma cells

Two methods for the calculation of optimal trajectories for the input variables of a fed-batch culture of hybridoma cells are compared. It pointed out that a gradient method based on Pontryagins' minimum principle based yields a significant better performance with respect to computational effort and the calculated minimum than a dynamic programming approach which has been presented in a previous paper [1] as the most suitable method.