Neurobiology: The Eye within the Brain

SummaryAll vertebrates except mammals have photoreceptors within their brains; however, the light-sensitive cells have never been unambiguously identified. A new paper provides direct evidence of photosensitivity in cerebrospinal fluid (CSF)-contacting neurons in quail brain that mediate the seasonal reproductive response

Burdening the Plaintiff: Proving Employment Discrimination after \u3ci\u3eKastanis v. Educational Employees Credit Union\u3c/i\u3e

In Kastanis v. Educational Employees Credit Union, the Washington Supreme Court held that a plaintiff who presents direct, undisputed evidence of discrimination bears the burden of persuading the jury that the employer\u27s actions were not justified by business necessity. By substantially increasing the plaintiff\u27s burden, this decision will make it more difficult for plaintiffs to successfully litigate employment discrimination claims in Washington State. Not only is the court\u27s reasoning contrary to existing state and federal law, but there are also strong policy reasons arguing against the continued application of the court\u27s rule

The Philosopher\u27s Diagnosis: Sickness in Plato, Nietzsche, Kierkegaard, and Heidegger

Senior Project submitted to The Division of Social Studies of Bard College

Effect of Transplanting Suprachiasmatic Nuclei from Donors of Different Ages into Completely SCN Lesioned Hamsters

The suprachiasmatic nucleus (SCN) is the primary circadian pacemaker in mammals. Ralph and colleagues/14/provided recent new evidence for this by transplanting SCNs between golden hamsters with different genetically determined periods and producing circadian rhythmsof running wheel activity with periods characteristic of the donor. We have extended these studies in order to evaluate the age range of donor tissue that can be used for transplantation. SCN of hamsters from embryonic day 11 through postnatal day 12 can serve as functional grafts to restore rhythmicity to arrhythmic SCN lesioned animals. The time between SCN transplantation and onset of rhythmicity does not depend on the age of the donor. The presence of patches containing vasoactive intestinal peptide (VIP) immunoreactive cells is a good indicator of graft success, while its absence is correlated with a lack of transplant effect. The 18 day span during which SCN tissue can be harvested for transplantation should expand the uses to which this technique can be put. Our results also suggest that it would be advantageous to examine the age range of neural tissue that ca’n be used in other transplantation models

Factors Determining the Restoration of Circadian Behavior by Hypothalamic Transplants

The expression of locomotor activity by golden hamsters is temporally controlled by circadian oscillators contained within the suprachiasmatic nucleus (SCN). A genetic mutation has been found that alters the freerunning period of the locomotor activity rhythm from the wild-type value of ~24 hours to ~20 hours in homozygous mutants. It has been shown previously that a transplant of fetal hypothalamic tissue containing the SCN to a host rendered arrhythmic by a complete lesion of the SCN restores rhythmicity with the freerunning period which is normally expressed by the donor genotype. To investigate the mechanisms by which the SCN controls the temporal organization of behavior, we made partial lesions to the SCN of hosts of one genotype, and then placed hypothalamic implants from fetal donors of a different genotype into the lesion site. By varying the size of the host's partial SCN lesion and the duration of time between lesioning and transplantation, we have attempted to alter the relative amount of host and donor control over the expression of locomotor activity. We found that the expression of donor rhythmicity requires the presence of a lesion to the host SCN, and that the incidence of donor expression increased as a function of host SCN lesion size. Neither the duration of time between lesioning and transplantation, nor the location of the transplant within the third ventricle had independent effects on the incidence of donor rhythm expression; however, there was a strong suggestion of an effect of their interaction