Functional organization of input from areas 17 and 18 to an extrastriate area in the cat

In the cat, areas 17 and 18 have 2 main cortical targets: area 19 and a large region of suprasylvian cortex, referred to here as the Clare-Bishop area (Hubel and Wiesel, 1969). The functional organization of the latter area is not well understood. It seems likely that its organization reflects, in part, the organization of its inputs from areas 17 and 18, and I therefore studied the functional organization of these inputs. Responses were recorded directly from afferents terminating in the Clare-Bishop area after silencing its cells by local injections of kainic acid. Afferents were precisely ordered according to preferred orientation in a fashion resembling the columnar organization of area 17. Preferred direction was also an important organizing parameter. Within sizable regions of cortex, directional preference changed gradually or not at all, while at these regions' boundaries, preferred direction reversed by 180 degrees. Except for a loose grouping according to eye dominance, afferents were not ordered according to other response properties. It is possible that the afferent array is also compartmentalized according to the area of origin of each afferent. Inputs from areas 17 and 18, for example, might end in separate territories in the Clare-Bishop area. However, physiological recording, as well as anatomical experiments, failed to show a clear segregation. This study provides the first direct demonstration that a cortico-cortical pathway can be organized according to particular response properties. While the existence of an organization according to preferred orientation was not surprising, the high degree of order was unexpected. It is also interesting that afferents were well ordered according to 1 parameter, directional preference, that is weakly organized, at best, in area 17.     

Intraocular effects of lipoxygenase pathway products in arachidonic acid metabolism

Arachidonic acid is metabolized through the lipoxygenase pathways to hydroperoxy acids (HPETEs), hydroxy acids (HETEs), and leukotrienes, derivatives of 5-HPETE. 5-HETE, 12-HETE, 15-HETE, and 15-HPETE were injected intracamerally in rabbits and leukotriene B4 (LTB4), leukotriene C4 (LTC4 and leukotriene D4 (LTD4) were injected intracamerally in guinea pigs, rabbits and cats. The effects on the intraocular pressure, aqueous humour protein and leukocyte concentration as well as pupil diameter were assessed. 5-HETE, 12-HETE, 15-HETE and 15-HPETE did not cause any change in the parameters studied. LTB4 caused a marked accumulation of leukocytes in the aqueous humour of cats and rabbits, and to some extent in guinea pigs. LTC4 and LTD4 were ineffective in guinea pigs and rabbits, but caused an intense long-lasting non-muscarinic miosis in cats. Thus, most of the lipoxygenase products tested showed little activity in the anterior segment of the eye, except LTB4, that caused leukocyte infiltration, and LTC4 and LTD4 that caused miosis in cats.     

Complement activation in stored platelet concentrates

Activation of platelets during preparation and/or storage of platelet concentrates in plastic containers at room temperature has recently been recognized. Many different biologic causes of this activation have been postulated. Activated complement, as a multi-enzyme system, is one of the possible sources of molecules leading to platelet activation. To detect complement activation, functional complement activity and the generation of complement-derived ligands were investigated in platelet concentrate supernatant plasma during 5 days of storage at room temperature. Hemolytic tests for functional classical and alternative pathway activity were used, as was the kinetic test for complement- mediated inhibition of immune complex precipitation. The presence of C3 activation products (C3, C3c, C3dg) was investigated in plasma by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting procedures and on platelets by immunofluorescence. Activation of complement was evident during storage, and C3c and C3d fragments were clearly demonstrated in plasma. The amount of C3d fragments on platelets gradually rose during the first 3 days of storage. At the end of 5 days of storage, the platelets became C3d negative. There are two possible mechanisms of C3d disappearance–shedding and/or further degradation of C3d fragments. Those results indicated that complement activation and the generation of complement-dependent ligand-receptor interaction may be mechanisms for platelet activation in concentrates stored at room temperature.     

An experience of virtual leadership development for human resource managers

Problem  

Strong leadership and management skills are crucial to finding solutions to the human resource crisis in health. Health professionals and human resource (HR) managers worldwide who are in charge of addressing HR challenges in health systems often lack formal education in leadership and management.     

The use of visual information for planning accurate steps in a cluttered environment

When an observer walks across irregular terrain, he uses vision to plan his steps. How far in advance of each step does he acquire the critical information? We trained cats to walk accurately down a cluttered alley, and then turned out the light in mid-trial. Cats usually continued to walk without error for one to four steps, indicating that they had acquired the information to guide each step well before foot contact.