No effects of DC and 60-Hz AC magnetic fields on the first mitosis of two species of sea urchin embryos

The early divisions of sea urchin eggs was used as a model to study the effects of static and of 60 Hz sinusoidal magnetic fields. Two species were used (Sphaerechinus granularis and Paracentrotus lividus). Eggs were fertilized and exposed in two separate coils to the fields (up to 8 mT). Great care was taken to control the temperature of each sample. No difference was found in the time of the first division that could not be attributed to a temperature difference between samples. Comparison is made with other published data on various species.     

Calculation of electric fields induced near metal implants by magnetic resonance imaging switched-gradient magnetic fields

Electric (E) fields induced near metal implants by MRI switched-gradient magnetic fields are calculated by a new equivalent-circuit numerical technique. Induced E-field results are found for a metallic spinal-fusion implant consisting of two thin wires connected to the metallic case of a current generator as well as for its subsections: a bare U-shaped wire, an insulated U-shaped wire, a cut insulated wire, and a generator. The presence of the metallic implants perturbs the E field significantly. Near the ends of the bare U-shaped wire, the E field is 89.7 times larger than in the absence of the wire. The greatest E field concentration occurs near the ends of the cut insulated wire, where the E field is 196.7 times greater than in the absence of the wire. In all cases, the perturbation of the induced E field by the implanted wire is highly localized within a few diameters of the wire.     

Vertical circularly polarized ELF magnetic fields and induced electric fields in culture media

Some properties of induced electric fields in cell culture media produced by vertical circularly polarized magnetic fields are examined. The described geometry is not advantageous for determining effects that may be attributable to induced electric fields or currents.     

A Mathematical model for prediction of currents,magnetic fields,melt velocities,melt topography and current efficiency in Hall-Héroult cells

The magnetic fields, current densitites, metal and electrolyte velocities, current efficiencies and topography of the electrolyte-metal interface within the Hall-Héroult cell used to produce aluminum have been predicted from first principles. The computation of current densities was carried out by solving Ohms law enabling the calculation of magnetic field vectors from the Biot-Savart law. The cross product of the current densities and magnetic fields then yielded the electromagnetic stirring forces acting on the molten metal and electrolyte. By employing a turbulence model and the time averaged Navier-Stokes equations, velocities within these two liquids could be calculated. The solution of the fluid flow equations yielded the pressure distribution within both elecrolyte and metal, permitting the calculation of the shape of the interface between these two liquids.     

Apoptosis induced by fast neutrons versus 60Co gamma-rays in human peripheral blood lymphocytes

Gunshot and air weapon wounds in children have become a significant source of morbidity and mortality in our community in the last four years. Ninety five children, 15 years of age and younger, were admitted to the Pediatric Surgical Service for gunshot and air mechanism wounds during this period. Review of the circumstances of injury revealed that more than 50% were accidental 71% were male patients, and 65% were caused by gunshots and outside of the home. Thoracic region was affected in 42%; abdomen, 20%; skull, face and neck, 13.4%; lower extremities, 13.4%; upper extremities 9%; genitalia, 2.0%; and perineal region, 0.8%. Rapid resuscitation and triage of major injury allowed us a survival of 97%. Social service intervention and educational task can offer significant benefit to these children but, ultimately gun control laws with strict enforcement are needed to stop this type of violence toward children.     

Nerve terminal currents induced by autoreception of acetylcholine release

The activation of autoreceptors is known to be important in the modulation of presynaptic transmitter secretion in peripheral and central neurons. Using whole-cell recordings made from the free growth cone of myocyte-contact motoneurons of Xenopus cell cultures, we have observed spontaneous nerve terminal currents (NTCs). These spontaneous NTCs are blocked by d-tubocurarine (d-TC) and alpha-bungarotoxin (alpha-BuTx), indicating that endogenously released acetylcholine (ACh) can produce substantial membrane depolarization in the nerve terminals. Local application of NMDA to the growth cone increased the frequency of spontaneous NTCs. When the electrical stimulations were applied at the soma to initiate evoked-release of ACh, evoked ACh-induced potentials were recorded in the nerve terminals, which were inhibited by d-TC and hexamethonium but not by atropine. Replacement of normal Ringer's solution with high-Mg2+, low-Ca2+ solution also reversibly inhibited evoked ACh-induced potentials. The possible regulatory role of presynaptic nicotinic autoreceptors on the synaptic transmission was also examined. When the innervated myocyte was whole-cell voltage-clamped to record synaptic currents, application of hexamethonium inhibited the amplitude of evoked synaptic currents at a higher degree than that of iontophoretic ACh-induced currents. Furthermore, hexamethonium markedly reduced the frequency of spontaneous synaptic currents at high-activity synapses. Pretreatment of neurons with alpha-BuTx also inhibited the evoked synaptic currents in manipulated synapses. These results suggest that ACh released spontaneously or by electrical stimulation may act on the presynaptic nicotinic autoreceptors of the same nerve terminals to produce membrane potential change and to regulate synaptic transmission.     

Induction of apoptotic cell death in human leukemic cell line, HL-60, by extremely low frequency electric magnetic fields: analysis of the possible mechanisms in vitro

An anthropomorphic Rando phantom was used to compare radiation doses sustained during helical and conventional axial CT of the pelvis. The values obtained with the Rando phantom were validated against cadaveric phantoms, and show good agreement. For the authors' particular CT unit, helical scanning was found to deliver a lower radiation dose than conventional axial scanning. This was most prominent at 1.0-s tube rotation times (average dose ratio 1.24). For realistic scanning parameters and exposure factors, the ratio of radiation dose to pelvic organs can be expected to lie in the range of 40-100 mGy. The whole-body effective dose (ED) depends on selection of scanning parameters and patients anatomy. In a favourable case scenario, the ED for CT scanning of the pelvis in a male can be expected to be between 10 and 20 mSv if the scrotum is not included in the radiation field, while the ED in a female will be approximately 20 mSv. An examination of scatter radiation fall-off curves from a single slice shows that the spread of scatter radiation is only marginally affected by slice thickness. A total of 10-12 cm of human soft tissue acts as a good barrier against internal scattered radiation. The use of such scatter fall-off curves, together with manufacturers' dosimetry specifications, allows a fast estimate of absorbed dose.