Prenatal disruption of binocular interactions creates novel lamination in the cat's lateral geniculate nucleus

The elimination of retinogeniculate afferents from one eye on embryonic day 44 (E44) has pronounced effects on the formation of the cellular laminae in the cat lateral geniculate nucleus (LGN). Only two laminae form: a dorsal, "magnocellular" layer, and a ventral, "parvocellular" layer. Soma size measurements and previously reported patterns of termination of retinogeniculate axons suggest that the dorsal lamina is a coalescence of the normal A-laminae and the dorsal, magnocellular division of layer C, while the ventral layer is a composite of the parvocellular sublamina of layer C and the remaining C-laminae. This is a novel pattern of lamination in the LGN that differs from that found in the normal nucleus, not only in that there are now only two cell layers rather than the normal five, but also in that the interlaminar zone occurs in an abnormal location. This result is markedly different from that observed in other species where interlaminar zones present after early monocular enucleation are a subset of the ones which would normally be present. We suggest that, in the absence of ongoing binocular interactions, interactions between functionally distinct retinal ganglion cell classes from the remaining eye may direct the formation of cell laminae in the LGN, even when such interactions are not normally operative.     

Sedative but not anxiolytic properties of benzodiazepines are mediated by the GABA(A) receptor alpha1 subtype

Inhibitory neurotransmission in the brain is largely mediated by GABA(A) receptors. Potentiation of GABA receptor activation through an allosteric benzodiazepine (BZ) site produces the sedative, anxiolytic, muscle relaxant, anticonvulsant and cognition-impairing effects of clinically used BZs such as diazepam. We created genetically modified mice (alpha1 H101R) with a diazepam-insensitive alpha1 subtype and a selective BZ site ligand, L-838,417, to explore GABA(A) receptor subtypes mediating specific physiological effects. These two complimentary approaches revealed that the alpha1 subtype mediated the sedative, but not the anxiolytic effects of benzodiazepines. This finding suggests ways to improve anxiolytics and to develop drugs for other neurological disorders based on their specificity for GABA(A) receptor subtypes in distinct neuronal circuits.     

Interruption of pregnancy by cervical rivanol predilatation

Experience obtained in 1361 cases of first trimester pregnancy interruption with cervical Rivanol predilatation is reported. Rivanol-induced predilatation of the cervical canal prior to interruption was found to be an efficient procedure. The dilating effect of Rivanol could not be enhanced by i.m. administration of 5 IU oxytocin. After the interruption of more advanced pregnancies a higher degree of dilatation of the cervix was observed. The necessity of further dilatation prior to vacuum aspiration is, in the majority of cases, not higher than 2-2.5 H, which is insignificant on the softened cervix. The immediate complications of medical induction and interruption were infrequent and not severe. Thus, cervical predilatation with Rivanol prior to vacuum aspiration is a recommendable method of pregnancy interruption, worthy of widespread application.     

Dynamic properties of recurrent inhibition in primary visual cortex: contrast and orientation dependence of contextual effects

A fundamental feature of neural circuitry in the primary visual cortex (V1) is the existence of recurrent excitatory connections between spiny neurons, recurrent inhibitory connections between smooth neurons, and local connections between excitatory and inhibitory neurons. We modeled the dynamic behavior of intermixed excitatory and inhibitory populations of cells in V1 that receive input from the classical receptive field (the receptive field center) through feedforward thalamocortical afferents, as well as input from outside the classical receptive field (the receptive field surround) via long-range intracortical connections. A counterintuitive result is that the response of oriented cells can be facilitated beyond optimal levels when the surround stimulus is cross-oriented with respect to the center and suppressed when the surround stimulus is iso-oriented. This effect is primarily due to changes in recurrent inhibition within a local circuit. Cross-oriented surround stimulation leads to a reduction of presynaptic inhibition and a supraoptimal response, whereas iso-oriented surround stimulation has the opposite effect. This mechanism is used to explain the orientation and contrast dependence of contextual interactions in primary visual cortex: responses to a center stimulus can be both strongly suppressed and supraoptimally facilitated as a function of surround orientation, and these effects diminish as stimulus contrast decreases.     

Twenty-four hour leukocyte adherence inhibition test in thyroid cancer patients

The effect of TG cell depletion taking place during 24 hour incubation on the leukocyte adherence inhibition phenomenon was investigated in patients suffering from cancer of the thyroid and healthy volunteers. The depletion coincided with the increase of the adherence inhibition if PPD was used as antigen in both groups, but the reaction to the tumour associated antigen could not be brought into relation with the depletion of TG cells.