The formation of new microbodies induced by partial hepatectomy was studied in the liver of male rats using conventional microscopy and the peroxidase reaction for demonstrating catalase. In the early phases of the regenerative period, small smooth walled vesicles were identified adjacent to mature microbodies and these contained material similar both in appearance and in endogenous peroxidase activity to the neighboring microbody. Membrane continuity between the two organelles was identified clearly. It is suggested that the formation of new microbodies from pre-existing microbodies may be an important general method of microbody proliferation.

Histological and ultrastructural studies on the medial meniscus in the human knee joint show that nerve fibres, both myelinated and unmyelinated, extend from the periarticular plexus into the meniscus as far as the intermediate third. These neural elements are not exclusively paravascular in position and it is reasonable to postulate a function other than vasomotor or vasosensory for them.The topographical features of the innervation of the adult human knee joint, as described by Schaeffer ('42) and Hollinshead ('66) are well understood but the precise extent to which nerve fibres penetrate intra-articular structures such as the menisci remains undefined. The functional studies of Samuel ('52) and Andrew ('54) indicating that neural elements are present within periarticular structures agree with the histological findings of Rossi ('50) and Polacek ('61) but the question of meniscal innervation is not considered.Gardner ('48) in an extensive histological survey, reports that, in foetal human knee joints, some vessels and nerves enter the substance of the menisci but no exact value is given for the depth of their penetration. Freeman and Wyke ('67) state that those few nerve fibres present within menisci of adult cats are confined to the outermost layers, occupy paravascular positions and possess no specialized endformations. They report that no neural elements can be seen within the central fibrocartilaginous zone.In the histological part of this investigation, an attempt is made to determine more precisely, the extent and nature of the nerve fibres which ramify within adult human menisci. Accurately orientated portions of menisci are subjected to electron microscopy so that comparisons may be made between the histological and ultrastructural features of meniscal innervation. Medial menisci were obtained at operation from 10 male patients, aged 16 to 29 years, who had suffered traumatic knee injury. Only menisci in which the damage ANAT. REC., 165: 485-492.was clearly localized to either the anterior or posterior horn were used.( a ) Histological studies : Immediately on removal, eight menisci were fixed in 10% formalin for approximately 12 hours, after which both anterior and posterior horns were removed and discarded, thus leaving macroscopically undamaged middle portions as indicated by B ( fig. 1 ) . These portions were then placed in 10% formalin over marble chips for a further 10 days. Three portions were embedded in paraffin wax, and serial sections, representing three distinct planes were cut at a thickness of 5 v, and stained, either with haematoxylin and eosin or by Mallory's trichrome procedure. From the remaining five portions, frozen sections were cut at a thickness of 100 and impregnated with silver according to Schofield ('60).(b) Ultrastructural studies: Three specimens, each approximately 3 mm in thickness, and orientated as shown ( fig. 2) were cut at operation from the middle portion of two menisci. All peripheral connective tissue was removed and they were then immersed in phosphate b...

The liver of male rats has been studied after CPIB stimulation by using the peroxidase reaction for localizing catalase in hepatic cells . CPIB administration leads to an increase in the number of microbodies, and it is suggested that one mechanism by which microbody proliferation occurs is a process of fragmentation or budding from preexisting microbodies . Reaction product was observed not only within the microbody matrix, but outside the limiting membrane of the microbody and in association with ribosomes of adjacent rough endoplasmic reticulum . This localization of reaction product is interpreted as evidence that catalase after synthesis on rough endoplasmic reticulum may accumulate near microbodies and may be transferred directly into these organelles without traversing the cisternae of the endoplasmic reticulum or Golgi apparatus .

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