Histochemical Studies of the Masseter, the Temporal and Small Zygomaticomandibular, and the Temporomandibular Masticatory Muscles from Aged Male and Female Humans. Fiber Types and Myosin Isoforms

ABSTRACT

The purpose of this study was to investigate the histology of two small masticatory muscles from females and males of more than 70 years of age. By using immuno- and enzyme histochemistry the muscles were characterized by their fiber types and myosin heavy chain pattern. The observations were compared with similar studies of the masseter and temporalis muscles. Previously the two small muscles have been described based solely upon their gross anatomy. One muscle originates from the anterior, deep surface of the temporal fascia and inserts in the temporal tendon: the temporomandibular muscle (TM). The other muscle originates from the upper part of the temporal surface of the frontal process of the zygomatic bone and the adjacent part of the frontal bone and inserts in the temporal tendon: the zygomaticomandibular muscle (ZM). In the masseter, TM, and ZM, most of the autopsy samples contained an abundant number of fibers containing neonatal myosin heavy chains while in the temporal muscle specimens, such fibers were sparse and scattered. Electrophoresis followed by immuno-staining of Western blots supported the histochemical findings. There was no obvious correspondence between fiber typing based upon ATPase activity and the neonatal myosin heavy chain content in the muscle fibers. Neither did the fibers show accordance in their content of adult slow and fast myosin heavy chains and in their content of neonatal myosin heavy chain.

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Notes on contributors

Svend Kirkeby

Dr. Svend Kirkeby has an M.D. and a Ph.D. in anatomy. His research is mainly focused on the study of the masticatory muscles and the glycosylation of muscles. Currently, Dr. Kirkeby is involved in a research project on aging of the orofacial muscles. He works at the Panum Institute in Copenhagen, Denmark.

Charly Garbarsch

Dr. Charly Garbarsch is an associate professor at the Institute of Medical Anatomy at the University of Copenhagen. He graduated from that same university as an M.D. in 1962 and completed a doctoral thesis in 1976 dealing with Experimental Arteriosclerosis. He is an anatomist and a histochemist and the bulk of his research for several years concentrated on connective tissue and in the past twelve years on the musculoskeletal system as well. His research is coordinated with the Department of Rheumatology at the Hvidovre Hospital, Copenhagen, and the studies on muscles with the Department of Oral Physiology, Institute of Odontology, the Faculty of Health Sciences at the University of Copenhagen.