By horizontal sectioning of a fresh frozen piece of rat intestinal wall different parts of the villi and the crypts were isolated. Every third serial section was taken for histologic examination and the intermediate sections were combined in pairs, homogenized and used for enzyme analysis. A quantitative comparison of the distribution of alkaline phosphatase, EC 3.1.3.1, disaccharidase, EC 3.2.1 (maltase, invertase, isomaltase, trehalase, lactase and cellobiase), and dipeptidase, EC 3.4.3 (L-alanyl.L-proline dipeptidase, L. alanyl-L-glutamic acid dipeptidase and glycyl-L-leucine dipeptidase), activities was performed. All of the enzymes were present in the villi and absent from the crypts. The disaccharidase and dipeptidase activities showed a rather similar distribution. The high. est activities were found in the apical halves of the peptidases III. Characterizatiomi and deter-ANATOMICAL i)ISTRIBUTION OF SMALL INTESTINAL ENZYMES

The blanching hormone of the prawn, Pandalus borealis , is pGlu-Leu-Asn-Phe-Ser-Pro-Gly-Trp-NH 2 . Its structure was settled by a combination of mass spectrometry and Edman-dansyl analysis of a thermolysin fragment. Confirmation of the structure was obtained by chemical synthesis from amino acids. This neurosecreted hormone is active in picogram amounts when tested in shrimps.

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Both insect and mammalian genes have previously been cloned by genetic complementation in yeast. In the present report, we show that the method can be applied also to plants. Thus, we have cloned a rape cDNA for 3-isopropylmalate dehydrogenase (IMDH) by complementation of a yeast leu2 mutation. The cDNA encodes a 52 kDA protein which has a putative chloroplast transit peptide. The in vitro made protein is imported into chloroplasts, concomitantly with a proteolytic cleavage. We conclude that the rape cDNA encodes a chloroplast IMDH. However, Southern analysis revealed that the corresponding gene is nuclear. In a comparison of IMDH sequences from various species, we found that the rape IMDH is more similar to bacterial than to eukaryotic proteins. This suggests that the rape gene could be of chloroplast origin, but has moved to the nucleus during evolution.