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1. 3-Mercaptopicolinic acid (SK&F 34288) inhibited gluconeogenesis in vitro, with lactate as substrate, in rat kidney-cortex and liver slices. 2. In perfused rat livers, gluconeogenesis was inhibited when lactate, pyruvate or alanine served as substrate, but not with fructose, suggesting pyruvate carboxylase or phosphoenolpyruvate carboxylase as the site of inhibition. No significant effects were evident in O(2) consumption, hepatic glycogen, urea production, or [lactate]/[pyruvate] ratios. 3. A hypoglycaemic effect was evident in vivo in starved and alloxan-diabetic rats, starved guinea pigs and starved mice, but not in 4h-post-absorptive rats. 4. In the starved rat the hypoglycaemia was accompanied by an increase in blood lactate. 5. A trace dose of [(14)C]lactate in vivo was initially oxidized to a lesser extent in inhibitor-treated rats, but during 90min the total CO(2) evolved was slightly greater. The total amount of the tracer oxidized was not significantly different from that in the controls.

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A series of substituted 1,3-diaryltriazenes has been synthesized and tested for anorectic activity. Several members of the series were effective; one compound, 1,3-bis[2-cyano-5-(trifluoromethyl)phenyl]triazene, was particularly active, causing weight loss in rats, dogs, and squirrel monkeys. It was devoid of overt central nervous system activity, and compared to previously reported biologically active triazenes, it was relatively nontoxic up to 30 days of drug administration.

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2 Brain Hormone (BH) -4. Function.-Moulting in insects is initiated by neurosecretory cells of the brain which secrete a prothoracotropic hormone. The latter, commonly known as Brain (or Activation) Hormone, stimulates the prothoracic glands to release Moulting Hormone. It has been suggested3 that in addition to its tropic action on the prothoracic gland, BH has a direct action on tissues, acting synergistically with ecdysone. The observation4 that in the cockroach, Periplaneta americana, an elevation of the disaccharide trehalose (the principal circulatory carbohydrate in many insects) is produced by brain extracts (of Periplaneta) takes on new interest following Sacktor's very recent and exciting discovery6 of the presence of the enzyme trehalase in mammalian tissues.Although many other effects have been attributed to BH,2b a complete understanding of its action is still to be developed. B.Chemistry.-In 1962, Kobayashi et aL6 isolated 4 mg. of a crystalline substance by painstakingly dissecting 220,000 'brains' of the silkworm, Bornbyx mori, and apparently demonstrated the hormonal activity of the extract. Subsequent studies7 established unequivocally that the isolated material was cholesterol. That BH is purportedly cholesterol was in direct conflict with other published views. For example, Ischikawa and Ishizaki had previously8 demonstrated that BH (similarly isolated from Bombyx mori) was water (and not ether) soluble. Based on its non-dialysable character, its response to typical protein precipitants, and its deactivation by proteolytic enzymes, it was subsequently concludedD that BH is a protein in nature.Casting doubt on the probability of BH being cholesterol (cholesterol is a normal constituent of the insect diet and would, perhaps, not be expected to exert hormonal effects), Carlisle and Ellislo convincingly demonstrated that pure cholesterol had no effect on moulting in the locust, Locusta migratoria migratorioides; BH does induce moulting in this species.A third view of the chemical nature of BH has been presented by Gersch.1l From both the central nervous system and the cerebrum of the cockroach, Periplaneta americana, Gersch has been able to isolate the neurohormones C1, D1, C2, and D,. Only neurohormone D1, a crystalline peptide, had dernonstrable metamorphosis activity in the Calliphora assay. In his recent review Novak2b agrees that BH is a polypeptide, his support for Gersch's conclusion resting on the observation that known vertebrate-active peptides can affect the insect organism in a way similar to that of the insect neurohormones. In the

N.m.r. of Steroidal a-HaloketonesSir:The discovery' that axial hydrogens are more highly shielded than corresponding equatorial ones increased the use of n.m.r. chemical shift data in structural studies of cyclohexane systems. Interpretations of this differential shielding have been p r o p o~e d~,~~,~~d and scattered examples of exceptions to the rule have been reported.lbs4 We have found that a carbonyl group adjacent to a monohalogenated carbon in ster-(1) (a)