The isolation of a hexaheme cytochrome from Desulfovibrio desulfuricans and its identification as a new type of nitrite reductase

Desulfovibrio desulfuricans (ATCC 27774), a strictly anaerobic sulfate-reducing bacteria, is able to perform anaerobic nitrate respiration in which nitrate is first reduced to nitrite by the action of nitrate reductase, and nitrite reductase then catalyzes the six-electron reduction of nitrite to ammonia. The nitrite reductase was found to be a membrane-bound enzyme and has been purified to electrophoretic homogeneity. The purified enzyme has a minimal Mr = 66,000 as judged by sodium dodecyl sulfate gel electrophoresis and contains 6 c-type heme groups/molecule. Pure nitrite reductase exhibits a typical c-type cytochrome absorption spectrum with reduced alpha-band at 552.5 nm. NADH and NADPH do not function as direct electron donors for the nitrite reductase. Desulfovibrio vulgaris hydrogenase, however, is able to transfer electrons from H2 to the nitrite reductase using FAD as the electron transfer mediator. The dithionite-reduced nitrite reductase was demonstrated to be auto-oxidizable even in the presence of potassium cyanide. On addition of nitrite, the dithionite-reduced enzyme is re-oxidized immediately. Hydroxylamine, however, can only partially re-oxidize the reduced enzyme. Ascorbate reduces the enzyme to a limited extent and the partially reduced enzyme is neither auto-oxidizable nor re-oxidizable by nitrite or hydroxylamine. Purified nitrite reductase has a pH optimum in the range of 8.0-9.5 and optimal activity at 57 degrees C. Purified nitrite reductase also has hydroxylamine reductase activity, and the Km for nitrite was determined to be 1.14 mM and that for hydroxylamine is 113.5 mM. The difference in Km values seems to exclude the possibility of hydroxylamine being a free intermediate in the reduction of nitrite.

A predischarge unit in a long-stay hospital for subnormality

A newly built residential ward in the grounds of a long-stay mental subnormality hospital was converted into a predischarge unit to cater for those patients who could probably be discharged after some special training. So far 31 residents have been trained over the past two years; 18 (58%) have been discharged to community residences, and five were waiting for discharge. The high success rate shows the value and usefulness of a predischage unit in a long-stay hospital, and also shows that a purpose-built building is not necessary so long as the staff have the initiative and will to succeed.

Clinical experience with sulthiame (Ospolot)

The anticonvulsants now in general use have made epilepsy among the mentally subnormal no longer the problem it was. However, the treatment of long standing epilepsy associated with behaviour problems or personality disorders in the so-called temporal lobe syndrome still remains a challenge. Surgical intervention seldom has a place in cases with severe and diffuse brain damage complicated by subnormal intellectual functioning, frequent seizures and personality changes.