The retino-recipient zone of the feline pulvinar. should it be considered as part of the lateral geniculate complex? [proceedings]

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Prophylactic transfusions of normal red blood cells during pregnancies complicated by sickle cell hemoglobinopathies

Prophylactic transfusions of normal donor red cells were administered during 37 pregnancies to women with sickle cell anemia, sickle cell-hemoglobin C disease, or sickle cell-beta thalassemia disease. Once the diagnosis was confirmed, the transfusions were administered intermittently throughout the rest of the pregnancy in such amounts and at such frequencies that no more than 60% of the circulating red cells contained hemoglobin S and the hematocrit was above 25. The maternal mortality rate was zero and maternal morbidity as the consequence of the sickle cell hemoglobinopathy was minimal. The perinatal mortality rate was appreciably reduced when compared to that previously observed without prophylactic transfusions but perinatal morbidity was still excessive. Evidence that the intrauterine environment was compromised, in spite of the transfusions consisted of an increased frequency of growth-retarded fetuses, of meconium staining of amnionic fluid, and of ominous decelerations of fetal heart rate. Morbidity from the transfusions was troublesome. Nonetheless, it is concluded tentatively that both the mother with a sickle cell hemoglobinopathy and her fetus are likely to benefit from prophylactic transfusions of normal donor red cells administered during one pregnancy according to the protocol employed in this study.

Responsiveness of cells in the cat's superior colliculus to textured visual stimuli

Responses to texture motion (visual noise) were investigated in the superior colliculus of paralysed cats, lightly anaesthetized with N2O/O2 supplemented with pentobarbitone or Althesin. Within the superficial layers two classes of texture-sensitive neurones were found: Type I units with weak responses to noise, often related to specific elements in the texture and Type II units which were driven independently of the texture structure, and tended to be recorded deep to the Type I units. Type III units recorded from the deep collicular layers were insensitive to texture. Anatomical bases for this differential sensitivity and the notion of two collicular subsystems are discussed.

Functional organization in the cat's pulvinar complex

The responses of 192 single units in the cat's pulvinar-complex, comprising the inferior, medial and lateral pulvinar nuclei, were studied in paralysed cats, lightly anaesthetized with N2O/O2 supplemented with pentobarbitone. About 60% of the cells were visually driven and their receptive fields classified as either diffuse, concentric, movement sensitive, direction sensitive or orientation sensitive. The response fields of such cells were commonly large. Response field maps for the movement and direction sensitive cells formed a heterogenous population with uniform on-off fields to more complex arrangements with on- or off-centres, often with only partial surrounds; other cells responded exclusively to moving stimuli. A dual representation of the visual field was found in the pulvinar-complex corresponding to the striate and tectal recipient zones described anatomically by others. The representation in the striate recipient zone comprised an oblique column running medio-laterally and rostro-caudally through the inferior pulvinar and lateral margin of the medial pulvinar. The peripheral visual field was represented laterally and the vertical meridian medially; the upper visual field was represented dorso-laterally in the medial pulvinar and the lower visual field caudo-ventrally within the inferior pulvinar. That this visuotopic organization corresponded to the striate recipient zone was established by tracing the retrograde transport of HRP. Medial to the striate zone evidence for a second visual field representation was found, apparently more randomly organized than the striate zone, corresponding to the presumed tectal recipient zone. These results support the assertion that cytoarchitectural boundaries do not necessarily delineate functional (visuotopically organized) regions. These observations suggest caution when comparing cytoarchitecturally defined regions between species; rather, 'functionally equivalent' regions should be compared.

Complexes containing unsaturated medium rings: The crystal and molecular structures of two rhodium(I) complexes

The crystal and molecular structures of two rhodium(I) complexes with long-chain alkyne- or alkene-α,ω-diyldiphosphines have been determined by single-crystal X-ray diffraction techniques. RhCl(CO){But2P(CH2)4C≡C(CH2)4PBut2} crystallizes in the orthorhombic space group Pna21 with a 21.991 (2), b 11.915(1), c 11.890(1) Ǻ and Z 4. The structure was refined by least-squares methods to a conventional R factor of 0.097 for 1768 independent reflections (Mo Kα diffraction data). The rhodium ion is in a square-planar coordination geometry with trans-phosphorus atoms; the unsaturated (alkynyl) group is not bonded to the rhodium. Crystals of RhCl{But2P(CH2)2CH=CH(CH2)2- PBut2} are monoclinic, space group P21/c, a 20.783(12), b 8.580(4), c 14.799(9) Ǻ, β 100.70(2)°, Z 4. The structure analysis has converged to R 0.069 for 1417 reflections (Mo Kα diffractometry); the coordination geometry of the rhodium is again planar with the ethylenic group occupying a single bonding site. The effect of ring size on the rhodium-phosphorus bond lengths is discussed.

The crystal structure of two cobalt(I) complexes containing the polyphosphine ligands PhP{(CH2)nPPh2}2 (n = 2, 3)

X-ray diffraction analysis of the two complexes [CoPhP{(CH2)3PPh2}2P(OMe)3CO] BF4,thf and [CoPhP{(CH2)2PPh2}2{P(OMe)3}2] BF4 are reported. Crystals of the first complex are triclinic, space group Pī with a 14.310(1), b 11.080(2), c 16.099(3) Ǻ, α 68.30(2), β 90.78(2), γ 75.04(1)�. The structure analysis has been based on 2964 independent reflection intensities (Cu Kα automatic diffractometry) to give R 0.11. The second complex is monoclinic, space group P21/c, with a 13.18(4), b 11.49(3), c 29.66(6) Ǻ, β 101.59(2)�. Refinement by least squares has converged to R 0.093 for the 2256 independent reflection intensities, observed by Mo Kα automatic diffractometry. The preferred stereochemistries of the five-coordinate cobalt complexes are discussed in relation to the bite angle of the chelating phosphine.

The crystal and molecular structure of the platinum(0) complex, [CH3C(CH2PPh2)3]2Pt

An X-ray analysis of single crystals of bis[1,1,1- tris(diphenylphosphinomethyl)ethane]platinum(O) is described. The crystals are triclinic, space group Aī, a 15.018(5), b 25.937(9), c 22.722(8) Ǻ; α 104.16(2)�, β 115.80(2)�, γ 88.65(2)�, Z4. ��� The diffraction data (Mo Kα; automatic diffractometry) have provided all atomic positions (with the exception of hydrogen atoms) and the scattering model has been refined by least-squares methods to R 0.084 (4774 independent reflections). The platinum has a distorted tetrahedral stereochemistry (with mean Pt-P 2.287 Ǻ), only four of the six phosphorus ligand atoms being coordinated. This stereochemistry is preserved in solution. A discussion of the metal-phosphorus bond in low-valent metal complexes is provided, it being concluded that π- bonding effects on bond lengths have been overemphasized in the past.

Structural chemistry of 1,2 dilauroyl-DL-phosphatidylethanolamine: molecular conformation and intermolecular packing of phospholipids

Crystals of 1,2 dilauroyl-DL-phosphatidyl-ethanolamine:acetic acid are monoclinic with a = 46.2, b = 7.77, c = 9.95 A, beta = 92.0 degrees ; space group P2(1)/c. The structural analysis, based on the visual estimates of 1467 reflection intensities, was achieved by direct methods, and least squares analysis convergence was to R(1) = 0.28. There are marked differences between the observed molecular conformation and those that have been predicted theoretically. The mean planes containing the lipid chains are essentially parallel to one another; the phosphodiester moiety has a double gauche conformation, while intermolecular hydrogen bonding modifies the conformation that could be anticipated for an isolated phosphatidylethanolamine molecule. The intermolecular packing produces the classical lipid bilayer structure, adjacent lipid bilayers being separated by acetic acid molecules of crystallization. The hydrocarbon chain packing can be considered either as a quasi-hexagonal type or as a complex orthorhombic subcell arrangement. One-dimensional electron density profiles across the lipid bilayer at increasing resolution clearly demonstrate the origin of features present on the low resolution profiles of both model and natural membranes.

A four-iron ferredoxin from Desulfovibrio desulfuricans

Ferredoxin from Desulfovibrio desulfuricans was isolated, purified and crystallized. It contains four iron atoms and four sulphido or ;acid-labile' sulphur atoms for a molecule of 6000 daltons. The absorption spectrum in the u.v.-visible region and the electron-paramagnetic-resonance signals of the reduced protein are similar to those observed for other four-iron ferredoxins. The amino acid composition is different from that of Desulfovibrio gigas ferredoxin. The redox potential of -0.33V at pH7.0 was determined by dye techniques.