Restoration of dysgenic murine (mdg) myotube contraction after addition of Schwann cells from normal mice in vitro

Muscular dysgenesis in mutant mice is characterised by failure of excitation-contraction (E-C) coupling and consequent loss of skeletal muscle contraction. Contractile activity is restored in vitro by the addition of normal mice cells (11) (18) (7). In the present study we show a new model: contraction and ultrastructural organization of dysgenic myotubes are restored by coculture with Schwann cells from normal mice.     

Cardiomyocyte remodeling and sarcomere addition after uniaxial static strain in vitro.

Individual cardiomyocytes are lengthened in dilated cardiomyopathy. However, it is not known how the new sarcomeres are added to preexisting myofibrils. Using a three-dimensional microtextured culturing system, a 10% mechanical static strain was applied to aligned, well-attached cardiomyocytes from neonatal rat. The morphology of the myofibrils and the ends of the myocytes were examined. Disruptions of the sarcomeric pattern for actin showed a progression from weak to intense staining over 4 hr. The lightly stained sarcomeres were common at 1 hr after being strained, peaked at 2 hr, and then subsided. In contrast, the numbers of intensely stained sarcomeres were initially low, peaked at 3 hr, and then began to decline when compared with control values. The myocyte ends showed elongations and convolutions after 3 hr and 4 hr of mechanical strain when observed with alpha-actinin and N-cadherin staining. We suggest that myocytes from neonatal rat hearts remodel by insertion of new sarcomeres throughout the cell length and also by enhancement at the intercalated discs.     

Increase in the level of cold lymphocytotoxins in the blood serum after autohemostimulation

Activity of natural cold isolymphocytotoxins (NCILCT) was studied in the serum of 16 volunteers who received whole auto blood injections. Autohemostimulation was shown to result in the increased activity of NCILCT. The evidence obtained allowed the conclusion that autohemostimulation can be used for preparation of active NCILCT test sera.     

The biotransformation in vitro of cysteinyl leukotrienes in blood of normal and asthmatic subjects

The metabolism of exogenous leukotriene C4 (LTC4), LTD4 and LTE4 (10(-8) M) was studied in vitro in blood of normal and asthmatic subjects for up to 2 hr by reverse-phase high performance liquid chromatography. In whole blood, incubation of LTC4 (T1/2 = 11.5 min) resulted in the formation of LTD4 and LTE4 whose biosynthesis was inhibited by serine borate (30 mM). Similar experiments performed with LTD4 (T1/2 = 5 min) produced a single metabolite (LTE4) which was inhibited by L-cysteine (10 mM). On the other hand, LTE4 represented a highly stable product in our in vitro system. The bioconversion of LTC4 or LTD4 was slower in plasma but this effect appeared more pronounced for the cysteinylglycinyl derivative. The bioconversion of LTD4 in whole blood or plasma was almost twice as rapid as LTC4. Experiments performed with asthmatic blood showed no significant difference in the survival of LTC4. These results suggest that blood may play a role in regulating the bioavailability of cysteinyl-containing LTs which could be of relevance to their excretion in man.     

The dielectrophoresis of blood platelets as affected by hemophilic traits

We find that there are moderate differences in the electrical polarizabilities of normal and various hemophilic canine blood platelets. The technique of dielectrophoresis, using the effect of nonuniform fields on neutral bodies, was used to perform rapid assays of the platelets. At present the dielectrophoretic test can only distinguish reliably between relatively large groups of animals on a statistical basis. The present technique shows a unique ability however, to distinguish even between normal canine platelets and the transmitter female canine platelets. In studies of the effects of various chemical agents upon the dielectrophoresis of platelets, inhibitors such as NaF, sodium iodacetate, NaCN, and NaN₃ had marked effects at low concentration. Ions such as Na⁺ K⁺, Mg⁺⁺, and La⁺⁺⁺, as well as NO₃ ⁻, SO₄ ⁼, and mellitic ion had lesser effects. In some cases the presence of trace quantities of the chemical agent “stabilizes” the cellular dielectrophoretic response, enabling the platelet to continue to be attracted by the nonuniform field for longer than usual. The CN⁻ and F⁻ ions appear to do this. This may have useful application. From the shape of the frequency spectrum of the dielectrophoretic response we suggest that the peaks at about 0.1 to 10 MHz imply a Maxwell-Wagner type of response, typical of an interface between bulk regions of differing conductivity, as at the cell boundary. From a lack of low frequency response, we suggest that the platelet interface with the surrounding aqueous medium must be singularly free of ionic double layers — or at least that the ionic double layers present must be of unusually low charge density. The technique of dielectrophoresis has been used in comparative study of canine blood platelets, from (1) normal dogs, (2) female dogs that transmit Factor VIII deficiency to their offspring, (3) male dogs with Factor VIII deficiency, and (4) female dogs with Factor VIII deficiency. The study showed that differences exist between the 4 groups of dogs in the average dielectrophoretic responses at 1 MHz. The effect of several chemical agents, i.e., NaCN and NaF on normal canine platelets was to effectively stabilize the platelets against deteriorationin vitro.