Bimolecular electron and energy transfer reactivity of exchange-coupled dinuclear iron(III) complexes.

Bimolecular quenching between photosensitizers and exchange-coupled transition metal complexes has been studied in an effort to experimentally establish a link between Heisenberg spin exchange and chemical reactivity. The acceptors are members of the oxo/hydroxo-biscarboxylato class of dinuclear Fe(III) compounds, where protonation of the oxo bridge provides a means for modulating the magnitude of spin exchange within the cluster. Photoexcitation of solutions containing Ru(II) polypyridyl sensitizers and the Fe(III) complexes results in quenching of emission from the (3)MLCT excited state of the Ru(II) chromophores; nanosecond time-resolved absorption measurements demonstrate that quenching occurs, in part, by electron transfer. Decoupling electron transfer driving force (DeltaG(0)(ET)) from changes in the magnitude of spin exchange was achieved by varying the bridging carboxylate to afford a series of complexes of the form [Fe(2)O(H)(O(2)CR)(2)(Tp)(2)](n)(+) (n = 0, 1, 2). Electrochemical measurements reveal a greater than 500 mV shift in cluster reduction potential across the series (i.e., R = CH(3) to CF(3)), whereas variable-temperature magnetic susceptibility measurements demonstrate a corresponding invariance in spin exchange between the metal centers (J(oxo) = -119 +/- 4 cm(-1) and J(hydroxo) = -18 +/- 2 cm(-1) for H = -2JS(1).S(2)). Structural analyses suggest that reorganization energies (lambda) associated with electron transfer should be identical for all molecules within a given series (i.e., oxo or hydroxo bridged); likewise Deltalambda between the series is expected to be small. A comparison of quenching rates for the two extended series firmly establishes that neither reorganization energy nor electron transfer driving force considerations can account for differences in reactivity between oxo-bridged (large spin exchange) and hydroxo-bridged (small spin exchange) quenchers. Upon consideration of energy transfer contributions, it is determined that reactivity differences between the oxo- and hydroxo-bridged quenchers must lie in the relative rates of Dexter energy transfer and/or electron transfer, with the origin of the latter linked to something other than DeltaG(0)(ET) or lambda. Finally, the extent to which spin exchange within the dinuclear Fe(III) quenchers can be identified as the key variable influencing these reactivity patterns is discussed.

Pulse radiolysis studies of dendritic macromolecules with biphenyl peripheral groups and a ruthenium tris-bipyridine core.

Electron-transfer reactions in Fréchet-type dendrimers with biphenyl peripheral groups and a ruthenium core were investigated by pulse radiolysis techniques. Fast electron-transfer rates found in the two ruthenium dendrimers suggest a very efficient electronic coupling between the peripheral donor groups and the core acceptor.

Thrombocytopenia in an established solitary pancreas graft recipient.

Isolated, life-threatening thrombocytopenia from a previously well tolerated pancreas allograft has not been reported in the literature. Herein we report such a case where a 31-year-old, Caucasian, Type I diabetic male developed severe thrombocytopenia 6 months following isolated pancreas transplantation and 2 wk after enteric conversion of the graft. Despite extensive diagnostic work-up, the cause remained unclear and his thrombocytopenia did not remit with standard treatment, but did resolve upon explantation. Pathologic examination of the pancreatic graft showed evidence of chronic rejection along with CMV pancreatitis. We conclude that unremitting isolated thrombocytopenia in solitary pancreas grafts may reflect a localized DIC phenomenon that requires graft explantation.

Intrasplenic hepatocyte allotransplantation in dalmation dogs with and without cyclosporine immunosuppression.

Hepatocyte allotransplantation has been performed successfully in several small animal models for the amelioration of inborn metabolic errors. Before a human clinical trial of hepatocyte allotransplantation can be attempted, preliminary experience in a large animal model is needed. We transplanted isolated mongrel hepatocytes into the spleen of dalmatians in the attempt to cure their inborn error of uric acid metabolism. Of 10 dalmatian recipients, two that received 9-10 x 10(9) mongrel hepatocytes died early after surgery of acute portal hypertension and hemorrhage. The eight long-term survivors received 5-6 x 10(9) hepatocytes and were randomized either to no treatment or to oral cyclosporine (CsA). Levels of CsA were adjusted to maintain trough levels between 400 and 800 ng/ml. In the four nonimmunosuppressed dalmatians, a reproducible average reduction in urinary uric acid excretion (UUAEx) of 23.7% was achieved; values returned to baseline within 14 days. In the CsA-immunosuppressed dalmatians, the average decline in UUAEx was 30%. The partial correction of the metabolic defect persisted for an average of 25 days in three immunosuppressed dogs, whereas in one dog, the partial correction lasted for over 90 days. No change in UUAEx was observed in two dalmatians that underwent sham laparotomy and intrasplenic injection of saline solution; CsA given alone to dalmatians did not modify UUAEx. We conclude that the dalmatian dog is a valuable large animal model for studies of the role of hepatocyte transplantation in the cure of inborn hepatic metabolic errors.

White, red and black: colour classification and illness management in Northern Ghana.

Health care facilities in Northern Ghana are not only too few, ill-equipped and under-supplied, they are also underutilized. Health care personnel have often noted the irony in the fact that the sick do not make use of the health care facilities when they most need them. Rural peoples often wait until the illness has become so serious that even with emergency measures there is little hope of survival. The author maintains that the causes of this are not simply the lack of community education, the lack of warmth and friendliness on the part of poorly paid health workers, their perceived inefficiency, the great distances to be travelled and the constant shortages of medication. More constraining than all of these are the conflicting cultures of illness management. In a time of otherwise rapid social and cultural change, peoples of Northern Ghana have not often responded to Western medical systems in ways judged appropriate to such systems and have strongly resisted education or coercion to adapt to them. The author maintains that the classificatory systems controlling illness management among the Anufo of Northern Ghana and among others of that locale are colour-coded. This coding of "white", "red" and "black" is not simply a convenient way to classify types and stages of illness, or other aspects of life, but it orders and prescribes social roles and responsibilities vis-à-vis the sick person and the illness itself. In such systems, illness is thought to progress from a "white" stage to the "red" to the "black" or return to the "white". At the onset of the illness, the white stage of individual action, innovative self-help measures are encouraged. But once the illness becomes serious it enters the red stage and innovative measures cease as the more conservative, traditional machinery for problem-solving takes over. The whole community becomes involved. Their roles and functions are strictly prescribed and stringently adhered to. Deviations are thought to exacerbate the problem. When all of the standard social obligations required in this system of illness management have been fulfilled and the person either becomes better or moribund (i.e. the situation is reclassified to either "white" or "black"), once again there is room for individual experimentation, and other forms can be tried. In Northern Ghana traditional structures of illness management block Western biomedical therapy at the exact moment when innovations would be most effective and encourage the inappropriate use of biomedical drugs and therapy at other times. The author maintains that in Northern Ghana and possibly in other rural areas of Africa an emic understanding of the roles and functions that are rigidly adhered to at the emergency "red" stage can help the Western medical systems to be more flexible in adapting to traditional systems of illness management.

The Islamic dialogue with African traditional religion: divination and health care.

In rural Africa delivering better health care is more complicated than simply offering good medical services; it must also take into account peoples' religious orientation and beliefs. Here the non-material causes of illness are at least as important as the biological or material and, in many places, one can only determine the exact nature of the problem and its corresponding remedy after the fact, through a process involving divination and sacrifice. In northern Ghana, by adapting to traditional methods of divination, Islam is gradually introducing a future perspective and expanding the possibilities of preventative action. By so doing it is bringing about a religio-epistemological transformation that is, among other things, helping people to understand and make better use of Western bio-medicine and primary health care programs. The author argues for a similar adaptation and dialogue between African traditional beliefs and Western medical institutions.

Glycocinnamoylspermidines, a new class of antibiotics. I. Description and fermentation of the organism producing the LL-BM123 antibiotics.

The producing organism for the new broad spectrum glycocinnamoylspermidine antibiotics designated LL-BM123beta, gamma1 and gamma2 was characterized as a Nocardia sp. by chemical analysis of the cell wall, growth requirements, morphology and physiological reactions. Fermentation conditions to elaborate and analytical methods to characterize these antibiotics in fermentation filtrates are described.

Analytical method for streptothricin-type antibiotics: structure of antibiotic LL-BL136.

An analytical procedure was devised which can distinguish members of the streptothricin family of antibiotics. It is based upon an analysis of the hydrolysis products of the antibiotics using a Technicon amino acid autoanalyzer under special conditions. The various fragments including the different streptolidine-amino sugar compounds were well resolved. A basic water-soluble antibiotic discovered in our laboratories and named LL-BL136 was compared to other members of this group by this technique. It was not differentiated from the antibiotic SF-701 reported by Tsuruoka. The autoanalyzer results along with other physicochemical data permitted a structure proposal for this antibiotic, which is the N-methyl-desformimino derivative of antibiotic LL-AC541.