B cell dependent T cell function blocked by perinatal exposure of mice to anti-IgM antibodies

Mice born to mothers deprived of B lymphocytes by their chronic treatment with anti-IgM antibodies (Su/N) do not possess naturally occurring anti-ids (present in sera of normal mice at 2 weeks of age) up to 10 weeks, despite the presence of normal levels of B cells and serum Ig (in these animals). Su/N mice of the same age also lack a T cell subset which together with anti-ids are thought to participate in an antisuppressor regulatory pathway. It is suggested that early development of these T cells may be linked and be dependent on the presence of these anti-ids synthesized early in ontogeny, providing one explanation for a selective T cell deficiency of B cell-deprived mice.     

The visual sensitivity of the retina of the conger eel

We measured the visual sensitivity of the conger eel retina by means of its electroretinogram (e.r.g.) and whole nerve responses. The spectral sensitivity of the retina closely corresponded to a prediction based on the density spectrum of the conger visual pigment, measured in situ. The pigment density in the conger eel retina is high, perhaps as high as 1.0. Thus, the predicted spectral sensitivity would be much broader than is observed if the absorption spectrum of the pigment governed the visual sensitivity. The reason why the visual spectral sensitivity corresponds to the density spectrum and not to the absorption spectrum is that the photoreceptors in the conger eye are arranged in tiers and only the inner tier contributes to vision.     

New World Monkeys and Color

The visual worlds of most primates are rich with potential color signals, and many representatives of the order have evolved the biological mechanisms that allow them to exploit these sources of information. Unlike the catarrhines, platyrrhines typically have sex-linked polymorphic color vision that provides individuals with any of several distinct types of color vision, including both trichromatic and dichromatic variants. In recent years, this polymorphism has been the target of an expanding range of research efforts. As a result, researchers now reasonably understand the proximate biology underlying the polymorphisms, and a number of ideas have emerged as to their evolution. Progress has also been made in illuminating how color vision capacities may be related to the particular visual tasks that New World monkeys face.