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J J Carson

Publications and source records attributed to J J Carson.

8 recordsLinked to original sources
PubMed1996

Behavioural evidence that magnetic field effects in the land snail, Cepaea nemoralis, might not depend on magnetite or induced electric currents.

Although extremely low frequency (ELF) magnetic fields (<300 Hz) appear to exert a variety of biological effects, the magnetic field sensing/transduction mechanism(s) remains to be established. Here, using the inhibitory effects of magnetic fields on endogenous opioid peptide-mediated "analgaesic" response of the land snail, Cepaea nemoralis, we addressed the mechanism(s) of action of ELF magnetic fields. Indirect mechanisms involving both induced electric fields and direct magnetic field detection mechanisms (e.g., magnetite, parametric resonance) were evaluated. Snails were exposed to a static magnetic field (B(DC) = 78 +/- 1 mu T) and to a 60 Hz magnetic field (B(AC) = 299 +/- 1 mu T peak) with the angle between the static and 60 Hz magnetic fields varied in eight steps between 0 degrees and 90 degrees. At 0 degrees and 90 degrees, the magnetic field reduced opioid-induced analgaesia by approximately 20 percent, and this inhibition was increased to a maximum of 50 percent when the angle was between 50 degrees and 70 degrees. Because B(AC) was fixed in amplitude, direction, and frequency, any induced electric currents would be constant independent of the B(AC)/B(DC) angle. Also, an energy transduction mechanism involving magnetite should show greatest sensitivity at 90 degrees. Therefore, the energy transduction mechanism probably does not involve induced electric currents or magnetite. Rather, our results suggest a direct magnetic field detection mechanism consistent with the parametric resonance model proposed by Lednev.

Animals↗
PubMed1995

Possible mechanisms by which extremely low frequency magnetic fields affect opioid function.

Although extremely low frequency (ELF, < 300 Hz) magnetic fields exert a variety of biological effects, the magnetic field sensing/transduction mechanism (or mechanisms) remain to be identified. Using the well-defined inhibitory effects that magnetic fields have on opioid peptide mediated antinociception or "analgesia" in the land snail Cepaea nemoralis, we show that these actions only occur for certain frequency and amplitude combinations of time-varying sinusoidal magnetic fields in a manner consistent with a direct influence of these fields. We exposed snails with augmented opioid activity to ELF magnetic fields, which were varied in both amplitude and frequency, along with a parallel static magnetic field. When the peak amplitude (0-547 microT) of a magnetic field of 60 Hz was varied systematically, we observed a nonlinear response, i.e., a nonlinear reduction in analgesia as measured by the latency of a defined response by the snails to a thermal stimulus. When frequency (10-240 Hz) was varied, keeping the amplitude constant (141 microT), we saw significant inhibitory effects between 30 and 35 Hz, 60 and 90 Hz and at 120 and 240 Hz. Finally, when the static field was varied but the amplitude and frequency of the time-varying field were held constant, we observed significant inhibition at almost all amplitudes. This amplitude/frequency "resonance-like" dependence of the magnetic field effects suggests that the mechanism (or mechanisms) of response to weak ELF fields likely involves a direct magnetic field detection mechanism rather than an induced current phenomenon. We examined the implications of our findings for several models proposed for the direct sensing of ELF magnetic fields.

Analgesia↗
PubMed1990

Time-varying magnetic fields increase cytosolic free Ca2+ in HL-60 cells.

Electromagnetic fields have been reported to cause a variety of biological effects. It has been hypothesized that many of these phenomena are mediated by a primary effect on the concentration of cytosolic free calcium ([Ca2+]i). We investigated the effects of exposure to electromagnetic fields on [Ca2+]i in HL-60 cells using the Ca2(+)-sensitive fluorescent indicator indo-1. Indo-1-loaded cell samples were exposed to a radiofrequency electromagnetic field, a static magnetic field, and a time-varying magnetic field, which were generated by a magnetic resonance imaging (MRI) unit. We found that a 23-min exposure to all three fields, in combination, induced a significant increase in [Ca2+]i of 31 +/- 8 (SE) nM (P less than 0.01, n = 13) from a basal level of 121 +/- 8 nM. Also, cells exposed to only the time-varying magnetic field had a mean [Ca2+]i that was 34 +/- 10 nM (P less than 0.01, n = 11) higher than parallel control samples. Separate exposure to the radio-frequency (6.25 MHz) or static field (0.15 T) had no detectable effects. These results demonstrate that time-varying magnetic fields alter [Ca2+]i and suggest that at least some of the reported biological effects of time-varying magnetic fields may arise from elevation of [Ca2+]i.

Calcium↗
PubMed1979

Gallium-67 citrate scanning--a new adjunct in the detection and follow-up of extrapulmonary tuberculosis: concise communication.

Gallium-67 citrate scans were obtained in 11 patients considered at risk for extrapulmonary tuberculosis. Radiographic and bacteriologic studies were performed routinely and tissue biopsy selectively. Of five patients with proven extrapulmonary tuberculosis, there were three with renal tuberculosis, one with Pott's disease, and one with peritoneal tuberculosis. The Ga-67 scan correctly predicted presence or absence of active extrapulmonary foci in all 11 patients. Follow-up scans correlated well with clinical response to therapy. The diagnosis of extrapulmonary tuberculosis is often overlooked because of nonspecific symptoms and frequent lack of concurrent lung involvement. Scanning with Ga-67 citrate offers a reliable and simple means of screening patients at risk and of monitoring response to treatment.

Gallium Radioisotopes↗