Cell attached patch recordings have been made from
zona-free mouse eggs. Potassium channels which show
anomalous and delayed rectification have been observed.
The conductance of these channels was as high as 160pS.
They have been shown to open and shut independently of
one another. Another channel with a conductance of
about 50pS has been noted and is believed to be a
chloride channel. Calcium channels with mean current
amplitudes of 1.10 + 0.33pA (mean + SD, n=35) and a
conductance in the range 7.5 to 20pS, have also been
recorded.
Before insemination the membrane potential of
zona-free hamster eggs, measured with intracellular
electrodes lay in the range -8 to -47mV (whilst bathed
in a modified Krebs Ringer solution - called "normal").
In five eggs impaled during this study, the membrane
potential was more negative than -61mV. In these eggs
calcium action potentials could be evoked by
depolarizing pulses. It is suggested that eggs which
do not show such action potentials suffer from
impalement leaks or have possibly undergone "in vitro
deterioration".
Inward channel currents have been observed in
synchrony with the rising phase of the action
potential.
Preliminary data are presented on whole cell
recording experiments.
In zona-free hamster eggs current clamped at
potentials more negative than about -80mV, sperm egg
fusion was associated with a depolarization, which in
some cases elicited an action potential. Such
depolarizations or sperm evoked action potentials were
also observed in eggs bathed in a solution resembling
oviducal fluid, with a potassium concentration of 25mM
or in a solution with a sodium concentration of ImM.
Such depolarizations were followed by transient
recurring depolarizations.
During fertilization of eggs with low membrane
potentials, no response was observed at the time of
sperm fusion, but transient recurring
hyperpolarizations were later recorded (as seen by
other workers).
Similar results were obtained during
fertilizations in calcium free solutions containing
substituted magnesium and strontium.
"Action currents" have been measured, during
fertilization with cell attached patch pipettes.
Results of these experiments reveal the presence of (i)
spikes superimposed on the repolarizing phase of
transient recurring hyperpolarizations, (ii) the latter
are sometimes followed by after depolarizations and
(iii) these responses were superimposed on a
depolarizing shift.
Trinitrotoluene is a nitro explosive belonging
to the Benzene Group and is hence a coal tar product,
and therefore similar in origin to Aniline, the basis
of Aniline Dyes.
Toluene is Methyl Benzene C₆H₅(CH)3₆₂₃₄₅₆ and T.N.T. is
obtained by nitrating this substance by a mixture of
nitric and sulphuric acids.
Toluene (sometimes incorrectly called Toluol) is a colourless liquid and is obtained by the fractional
distillation of coal tar - a by- product in the manufacture of coal gas.
It is lighter than water, having a sp.gr. of .8824
and it boils at 1100 C.
