The conversion of nitrobenzene (NB) to p-aminophenol (PAP) takes place by way of an initial partial hydrogenation to produce phenylhydroxyl amine (PHA) which then undergoes an in situ acid-catalyzed rearrangement to PAP. This reaction is most commonly run using Pt/C catalysts in the presence of aqueous sulfuric acid and a surfactant to assist in dispersing the NB throughout the reaction medium. The yield of PAP is closely related to those reaction parameters which facilitate first the partial hydrogenation step and second the acid-promoted rearrangement before further hydrogenation to aniline can take place. The effect which a number of reaction parameters such as hydrogen pressure, reaction temperature, stirring rate, and the amounts of NB, the catalyst, and the surfactant present in the reaction mixture had on the rate and selectivity of the hydrogenation was examined. Optimization of these parameters led to the formation of PAP at a selectivity (PAP/AN) of 5.4 with a productivity of over 80,000 g PAP/g Pt/h.

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A state of tolerance to MHC mismatched allografts can be generated in rodents by treatment with CD4 and CD8 monoclonal antibodies (mAb). In order to transpose this type of therapy to large animals and ultimately to the clinic, a suitable model is required. To this end we have generated a series of mAb to the canine CD4, CD8, and Thy-1 antigens and have tested their ability to prevent rejection of renal allografts. Donor-recipient pairs were selected from a colony of mongrel dogs in which untreated rejection of two haplotype-mismatched kidneys occurred by day 7 (defined as a serum creatinine > 300 mumol/l). Therapy with either the CD4 or the CD8 mAb, using no other immunosuppression, did not prolong graft survival. Depletion of T cells by a Thy-1 mAb prior to surgery only extended graft survival to day 9. However, treating with combinations of mAb up to day 10 (CD4 plus Thy-1; CD4 plus CD8; or CD4 plus CD8 plus Thy-1) prolonged renal allograft function up to 25 days. Combination of the triple mAb therapy with a sub-therapeutic immunosuppressive drug regimen (cyclosporin A plus azathioprine that alone gave a median survival of 15 days) favored survival to a median of 38 days. This protocol also inhibited the antiglobulin response that had curtailed the effects of mAb treatment, opening the way to more extended, and potentially tolerizing, mAb plus drug regimens.

absorption isotherm may be constructed as in Figure 4. From such data, Hill plots15 may be constructed, Figure 5, which in turn give the apparent oxygen binding constants listed in Table I. The Hill plots show slopes of 0.56 ± 0.02, indicating a negative cooperativity between the Co binding sites.10 This translates as meaning that as oxygen is bound by the first cobalt sites, subsequent binding by further sites is inhibited. This is the reverse