HISTOCHEMICAL DEMONSTRATION OF A TRYPSIN-LIKE ESTERASE ACTIVITY IN MAST CELLS

Ruomuhmumuu (J. Histochem . 9: 87, 1961) imo the summimmuanv of huis article omm the iomvestigatioou into the histocheouuistny of chitin states that this substance camu he itleoutified by its l)Ositive periodic acid Scimiff (PAS), Hale amid alcian bluoc reactions Thuese concluisioous si-crc arrived at after study of time omcuvly secreted raduslae of Patella rmolgata, mind corufirommed ut-itim freshly secreted Calliphora pmtpariunm . Pearse (Histochemistry; Little, Brow-n amud Coomupany, 1960, p. 236) on the contrary, gives these samuue reactions as negative for chitin. It is possible, as Ruimuhanm concludes, that only freshly secreteti chitimu reacts l)Ositivel3’ to these tests, mumud omegative results are dume to tanning and hardeouing of olden chitinm, as occurs iou time insect cuticle. Host-even, fuorther light muiay h)e throw-n on the vmulidity of these tests in identifying the presence of chitiom by investigations pursued by the si-riter. These studies employed the imutegunuent and the foneguot us-ith the peritnophic mmmenubraoue taken fmomum time cockroaches, Blattus germa nicus antI Blaberus giganteus, and the integunueomt of fourth amud fifth instan Rhodnius prolixus. Sections have been ouuoutic of the imutegunuent at all stages of developnuent, fronu nmymphs to adults, aomd from freshly ouuolted to time tanmmed cuticles of these iousects. Specimuueoms si-crc also inclusded of the devebopioug epidcnmuuis of iousects before muuoltiomg. Iom omo case si-mis a positive result obtained to tue PAS, Hale on mulcian blume neactionus for time cimitimu of time cuticle. The omuly stnumctusnc givimmg a 1)ositivc stmoimmiomg withu these reactiomms were time denouual gimmouds, whichm huave beemu simousou to produce mm oumui(iom-like muuatenial (Balduviom amid Saithoumse, J. Ins. Physiol 3: 345, 1959). Whucom sectiooms of hue uomutommumued custicles of omcuvl ’ ouuolted immsects us-crc hydrolyzed in S N HC1 for 30 muuimmuites at 45#{176}C,time chitin stained deeply with alciamu bluoe, thouogh not by the PAS muuethod. Older tammned cuuticles after this treatonent were unstained. On the other haomd, in sect.iomms of the foregut the perit.rophic membramme uva.s strongly positive to the PAS, Hale mmmd alcian biuoe reactions. Furthermore, this positive staiouioug ut’as not removed by digestion of the sections for prolonged periods in diastase or fl-glucuronidase solutions. The peritrophic menuh)ramme of insects has generally been considered to be a single on muuumltilayened chitin-containing sheath (Waterhouse, Ann. Rev. Entomol., 2: 1, 1957). Thus, it omuight appear that in this case chitiom had reacted positively to these reactions. However, prelimiomary X-ray diffraction studies (Baldwin and Salthousse, tonpublished data) strongly indicate that though the cuticles of the insects investigated cooutaiom chitin, the penitrophic omueouubrane does not. From a comuiparisomu of the nesuslt.s obtaiomed by the si-miter si’ith those reported by Ruonham, it si-ould appear that the identification of chitin by the PAS, Hale or alciaom blue reactionus is sonicus-hat ounomabouss. Thouss, it is felt that these reactions cnunnot be used as evidence for on against the presence of chitimu, h)ut denuonstrate thme present lack of reliable amid specific histocheouuical muuethods for the detection of this substance.