Pigmented Cell Layer Research Articles

Intracellular Potential Measurements from the Ciliary Processes of the Rabbit Eye in vivo and in vitro

AbstractThe ciliary processes in the rabbit's eye were explored by micro‐electrodes. On penetrating the epithelial layers with the electrode two well defined levels of potential difference were measured between the penetrating electrode and the external reference electrode. In experiments conducted in vitro the first potential step was about – 30 mV and is suggested to appear when the electrode penetrated the unpigmented cell layer. The second step is suggested to appear when the electrode penetrated the pigmented cell layer. The measured potential difference between the electrodes was – 60 mV during this step. At further penetration it was found that the stroma was nearly equi‐potential with the external fluid. These potential differences disappeared when the preparation was kept in a potassium free solution and when it was poisoned by cyanide.A small number of successful experiments in vivo confirmed the findings made in vitro.

THE DEVELOPMENT OF THE SEED OF ABUTILON THEOPHRASTI. II. SEED COAT

Winter, Dorothy M. (Iowa State U., Ames.) The development of the seed of Abutilon theophrasti. II. Seat coat. Amer. Jour. Bot. 47(3) : 157—162. Illus. 1960.–The integuments of Abutilon theophrasti Medic. undergo a rapid increase in size, predominantly by anticlinal cell divisions during the first 3 days after fertilization. Within 7 days, the outer epidermis of the inner integument becomes thick walled. At maturity this compact, lignified, and cutinized palisade layer accounts for more than half the thickness of the seed coat. During early growth, the palisade cells form a continuous layer in the micropylar region. In the chalazal region the palisade layer is discontinuous in a slit‐shaped region, 60 × 740 microns. The shape of this discontinuity constitutes a major difference between dormant‐seeded Abutilon and non‐dormant Gossypium seeds. Exterior to the palisade layer is the outer integument which consists of a small‐celled layer and a large‐celled layer sparsely covered with unicellular, lignified hairs. Interior to the palisade is the thick mesophyll of the inner integument which is largely digested during seed growth and leaves only 2 pigmented cell layers in most regions at maturity. The inner epidermis is small‐celled, pigmented and cutinized and adheres tightly to the endosperm. Seed coat impermeability increases with seed maturity. Even immature seeds will germinate, if scarified, indicating a lack of embryo dormancy.

Vitreous Membranes Upon the Iris with Adherent Leucoma of the Cornea

This is a report of the findings of histologic studies of iris removed in three cases, and of similar appearances observed clinically in eight others. These irides presented small pits, the floor of which was covered with a homogeneous membrane behaving like a vitreous formation upon the iris. Such membranes were sometimes covered with a single layer of flat pigment cells, but were generally bare. It is ascribed to the endothelium of the posterior surface of the cornea. Contributed from the University Eye Clinic of Kyoto in the service of Professor Ichikawa.