Structure and magnetism of [M3](6/7+) metal chain complexes from density functional theory: analysis for copper and predictions for silver.

The ground-state electronic structure of the trinuclear complex Cu3(dpa)4Cl2 (1), where dpa is the anion of di(2-pyridyl)amine, has been investigated within the framework of density functional theory (DFT) and compared with that obtained for other known M3(dpa)4Cl2 complexes (M = Cr, Co, Ni) and for the still hypothetical Ag3(dpa)4Cl2 compound. Both coinage metal compounds display three singly occupied x2-y2-like (delta) orbitals oriented toward the nitrogen environment of each metal atom, generating antibonding M-(N4) interactions. All other metal orbital combinations are doubly occupied, resulting in no delocalized metal-metal bonding. This is at variance with the other known symmetric M3(dpa)4Cl2 complexes of the first transition series, which all display some delocalized bonding through the metal backbone, with formal bond multiplicity decreasing in the order Cr > Co > Ni. An antiferromagnetic coupling develops between the singly occupied MOs via a superexchange mechanism involving the bridging dpa ligands. This magnetic interaction can be considered as an extension to the three aligned Cu(II) atoms of the well-documented exchange coupling observed in carboxylato-bridged dinuclear copper compounds. Broken-symmetry calculations with approximate spin projection adequately reproduce the coupling constant observed for 1. Oxidation of 1 removes an electron from the magnetic orbital located on the central Cu atom and its ligand environment; 1+ displays a much weaker antiferromagnetic interaction coupling the terminal Cu-N4 moieties via four ligand pathways converging through the x2-y2 orbital of the central metal. The silver homologues of 1 and 1+ display similar electronic ground states, but the calculated magnetic couplings are stronger by factors of about 3 and 4, respectively, resulting from a better overlap between the metal centers and their equatorial ligand environment within the magnetic orbitals.

Factitious triplegia: case report.

A 37-year-old woman was admitted for rehabilitation of triplegia with diagnoses of conversion disorder and possible multiple sclerosis. Attempts to manage the patient with techniques often effective with conversion disorders were unsuccessful, and the patient was discharged to a nursing home. After the development of further symptoms and a second extensive medical work-up, the factitious nature of her symptoms became evident. Awareness of the characteristics of factitious disorders, early background investigation, and psychiatric consultation can facilitate the appropriate management and referral of these patients, and spare rehabilitation providers the frustrations and possible medicolegal complications of patients with this disorder.

Medical rehabilitation for the indigent in Louisiana: a primer for physicians.

The impact of a stroke, head injury, spinal cord injury, or other disabling condition can be especially devastating for individuals without health insurance. Fortunately, a comprehensive system has evolved to address the needs of the indigent for medical rehabilitation services in Louisiana. The purpose of this paper is to familiarize readers with this complex system, and thereby to assist practicing physicians and other health care providers in better serving this large and medically needy population. First, state and federal medical assistance programs which cover rehabilitation services are reviewed; next, services available through Louisiana Rehabilitation Services are discussed; and finally, services available through the Handicapped Children's Services Program and various voluntary organizations are described.

Climatic correlates of live-bearing in squamate reptiles.

We use a stepwise multiple regression procedure to correlate geographic patterns in the distribution of live-bearing reptilian species with patterns in climatic variables, in both Australia and North America. Previous authors have interpreted reptilian live-bearing as an evolutionary adaptation to cold climates. Our results indicate that environmental temperature and irradiance measures are no more highly correlated with the percent live-bearing species than are measures of precipitation, evaporation and humidity. We conclude that, except in very cold environments in North America, environmental temperatures seem to play little role in the relative success of live-bearing versus egg-laying reptilian reproductive strategies. It appears from previous work that reptilian live-bearing evolves mainly, or exclusively, because of the advantage it confers in enabling successful reproduction in cold climates. The present study suggests that the subsequent radiation of live-bearing reptilian species may be due to entirely different selective forces.

A case of congenital hypomyelination neuropathy. Clinical, morphological, and chemical studies.

Developmental failure of the peripheral nervous system to form myelin is advanced as the probable mechanism of a severe neuropathy in young child. The hypothesis evolved from evaluation of clinical, electromyographic, and muscle biopsy studies at 9 months and 51/2 years of age and electron microscopic and biochemical studies of the sural nerve at the latter age. The clinical state was characterized by loss of sensation to modalities, usually ascribed as transmitted by large myelinated axons; those carried by smaller axons being relatively preserved. Thus, at the age of 51/2 years, ataxia due to absent peripheral orientation was the chief deficit. Muscle strength was decreased but still remarkable considering the histologically confirmed absence of myelin in intramuscular nerves and extremely low conduction velocities (2 to 3 m/sec) at both ages. Histological and ultrastructural features of the intramuscular and sural nerves included almost total lack of myelin sheaths, good preservation of axons, and marked proliferation of Schwann cells and their basement membranes with onion-bulb formation. The morphological findings correlated well with the absence of cholesterol esters and the presence of the normal myelin lipids in extremely small amounts in the lipid study of the sural nerve.

Effect of vitamin E deficiency on the lipid class and fatty acid composition of rat brain gray and white matter.

Three-week old male Sprague-Dawley rats were placed on a control or vitamin E-deficient diet for 9 months. The total lipid and cholesterol contents of brain gray and white matter areas in the vitamin E-deficient group did not differ from controls. The concentration of cerebrosides was lower in white matter but higher in gray matter of deficient animals. However, sulfatide was significantly (P less than 0.001) higher in white and gray matter of deficient animals compared with controls. Lysolecithin was not found in vitamin E-deficient gray matter but was present in control gray matter lipids. No marked differences were found in the concentrations or relative amounts of sphingomyelin, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, or phosphatidyl inositol in the phospholipids of gray or white matter of vitamin E-deficient rats as compared to controls. In addition, no remarkable differences were found in the fatty acid composition of total lipid extracts of gray or white matter from vitamin E-deficient rats when compared with controls.

Conversion of glutamate into aspartate in guinea-pig cerebral-cortex slices.

1. When guinea-pig cerebral-cortex slices were incubated with [U-(14)C]glutamate as substrate, the specific radioactivities of the citric acid-cycle intermediates were lower than that of the aspartate isolated from the same vessels. 2. Aspartate was significantly labelled when [5-(14)C]glutamate was used as substrate and the aspartate contained almost no label when [1-(14)C]glutamate was present as substrate. 3. When specifically labelled glutamate was used as substrate, the label was found in the isolated aspartate in the position that would be predicted by citric acid-cycle mechanisms. 4. The results are consistent with the theory of ;compartmentation' of amino acid metabolism.