Search PubMed⌕ Search

Biomedical subjects

R Nuccitelli

Publications and source records attributed to R Nuccitelli.

79 records · Page 5Linked to original sources
PubMed1975

The pulse current pattern generated by developing fucoid eggs.

Using a newly developed extracellular vibrating electrode, we have made the first study of the spatial distribution of the growth currents around a single developing egg. This pattern was studied during the current pulses wihic traverse two-celled Pelvetia embryos. These pulses can be stimulated to occur with a periodicity of 70 min by mild acidification of the dea water medium. Current enters only at the growing rhizoid's tip while leaving both the base of the rhizoid cell and the whole outer membrane of the thallus cell. The field in front of the rhizoid cell falls off as the inverse cube of the distance from the rhizoid cell's center in the manner of a dipole field. The total inward and outward currents are equal, agreeing with theory. The current density at the rhizoid cell's base is twice that at the top of the thallus cell and this probably represents a change in the outer membrane's properties. There are no significant differences in the durrent density over the thallus cell. These results suggest a model in which the pulse current leaks in through newly opened channels in the growing tip and leaks out elsewhere due to the resultant fall in the membrane potential.

Electrodes↗
PubMed1975

Large electrical currents traverse growing pollen tubes.

Using a newly developed vibrating electrode, we have explored the electric fields around lily pollen germinating in vitro. From these field measurements, we infer that each weeted pollen drives a steady current of a few hundred picoamperes through itself. Considered as a flow of positive ions, this current enters an ungerminated grain's prospective growth site and leaves it opposite end. After a grain germinates and forms a tube, this current enters most of the growing tube and leaves the whole grain. The current densities over both of these extended surface regions are relatively uniform, and the boundary zone, near the tube's base, is relatively narrow. This current continues as long as the tube grows, and even continues when elongation, as well as cytoplasmic streaming, are blocked by 1 mug/ml of cytochalasin B. After a otherwise indistinguishable minority of tubes have grown to lengths of a millimeter or more, their current comes to include an endless train of discrete and characteristic current pulses as well as a steady component. These pulses are about 30s long, never overlap, recur every 60-100s, and seem to enter a region more restricted to be growing tip than the steady current's sink. In most ways, the current through growing lily pollen resembles that known to flow through focoid eggs.

Cytochalasin B↗
PubMed1974

Spontaneous current pulses through developing fucoid eggs.

Using a newly developed, extracellular vibrating electrode, we can now measure the electrical currents that traverse a single developing cell. We have studied the eggs of the common seaweed, Pelvetia, during their first 2 days of development and find that the endogenous electrical current through them includes a pulse component as well as a relatively steady component. Both of these enter the egg's growing tip and leave the rest of the embryo. The current pulses first appear a few hours after growth begins and have a characteristic shape that is independent of amplitude. They have a duration of about 100 sec, an average frequency of 1-5 per hr, and enter with peak surface intensities of 3-10 (and rarely up to 30) muA/cm(2). By the two-cell stage they account for about a fourth of the total transembryonic current. Since they may overlap to any degree and (as is documented elsewhere) are generally accompanied by peak membrane depolarizations of only 2-6 mV, their course does not seem to be voltage-controlled. Thus, they seem essentially different from action potentials. We also find that the rate at which the egg grows in length is roughly proportional to the size of the steady current traversing it.

Cell Division↗
PubMed1974

An ultrasensitive vibrating probe for measuring steady extracellular currents.

We describe a vibrating probe system for measuring relatively steady electrical current densities near individual living cells. It has a signal-to-noise ratio at least 100 times greater than previously available techniques. Thus it can be used to detect current densities as small as 10 nA/cm(2) in serum when a 30-microm diameter probe is vibrated at 200 Hz between two points 30 microm apart, and the amplifier's time constant is set at 10 s. Moreover, it should be generally insensitive to interference by concentration gradients. It has been first used to reveal and study 100-s long current pulses which developing fucoid embryos drive through themselves.

Cell Physiological Phenomena↗