Retro-esophageal subclavian artery: a case report.

This case report presents the finding of an aberrant right subclavian artery during the routine dissection of 230 human adults specimens. The case which we describe appeared in an 82-year-old male donor, in whom the right retro-esophageal subclavian artery was observed as the last branch of the aortic arch. The rate of occurrence of this variation is stated to be less than 1%. This variation is described in detail; embryology and anatomy are reviewed and we discuss it in relation to other cases. The aortic arch was dissected, and its branches were described as regards their relations, length and diameter.

Stimulus frequency affects c-fos expression in the rat visual system.

We have characterised the c-fos expression patterns in various centers of the visual pathway of adult rats monocularly stimulated either by continuous or flickering light at different frequencies. Results show different immunocytochemical patterns in all centers studied, the geniculate lateral complex (LGC), superior colliculus (SC) and primary visual cortex (Oc1), depending on the physical characteristics of the stimulus (blinking frequency and light wavelength). After stimulation of the left eye, the ipsilateral pathway presents a substantial density of immunoresponsive cells, which is greater than expected with respect to the number of fibers that project ipsilaterally from the retina to the LGC and the superficial layers of the SC. A surprisingly high positive immunoresponsiveness is obtained in all cases with coherent light stimulation in the red spectrum (634 nm).

Exposure of domestic quail embryos to extremely low frequency magnetic fields.

Four hundred domestic quail eggs (Coturnix coturnix japonica) were used to study the possible teratogenic effects of extremely low frequency magnetic fields (ELF-MFs) on early embryonic development. Ten females were selected from a flock on the basis of their high fertility rate and low number of spontaneous abnormalities and they were selectivity maintained in nesting-boxes in a room where feeding and environmental conditions were carefully controlled. All the eggs used in the experiments were filiated by their progemtor, and were handled in the same way from the time they were laid until the point at which they were placed in a specially designed incubator, which dramatically reduces the stray magnetic fields produced by the heating system. Twenty eggs per experiment (10 control and 10 exposure) were placed in two different areas within the incubator. For each experiment two eggs from each of the 10 females were used. These were placed pairwise in the same position in the incubation areas (one in the control area and one in the exposure area). The first 12 experiments (240 eggs in total) were sham (ELF-MFs source turned off) in order to identify the variability of test quantities. The last eight experiments (160 eggs in total) involved magnetic fields (continuous bipolar square signal, rise and fall time 4 microseconds, in Helmholtz' coils) and they were divided into two exposure groups: the first four experiments at 50-Hz frequency and the last four at 100-Hz frequency. The magnetic flux density was different for each experiment within each frequency group, but the same sequence was always used: 0.2, 1.2, 2.2, 3.2 microtesla. The number of abnormal embryos found in the area exposed to 100 Hz was significantly higher than for their controls (Chi-square test, p = 0.048) but this difference was not significant for the 50-Hz group (p = 0.232). An ANOVA test was significant for the magnetic field variable (p < 0.05). A higher number of dead embryos was observed in the two groups of exposed eggs. Finally, a gross examination of the external morphology of the abnormal exposed embryos showed a high percentage of abnormalities of the nervous system, particularly at the cephalic level.

Growth variability in avian embryos as a source of experimental error.

To reduce variability in an embryonic population to be used in experiments with electromagnetic fields, 820 Japanese quail eggs (41 experiments, 20 eggs per experiment) were incubated to analyze different possible inputs of experimental variance. Eggs came from a randombred progenitor population obtained from a poultry farm and selectively maintained. The results show that growth variability is significantly higher in some progenies, which show bimodal distributions; this is evidence of the existence of a dichotomous population with different growth velocities within these populations. This phenomenon seems to be the result of growth factors inherited from the progenitors and not of environmental factors. A genetic selection of the progenitors used in the experimental lines dealing with growth variability in birds seems necessary to reduce any possible erroneous interpretation of the experimental results.