Histological and ultrastructure of the peripheral nerve in cadaveric embalmed specimens and in fresh cadavers: the efficacy of several fixatives.

Objective: The study is to observe the histological structure and the ultrastructure of the peripheral nerve from cadaveric embalmed specimens and from fresh specimens by light microscope and by transmission electron microscope. Also to study the efficacy of the embalmed fixative to the tissue. Methods: The peripheral nerves were dissected from the arms of five cadavers of the Department of Anatomy, Faculty of Medicine Siriraj Hospital, Mahidol University, and from fresh cadavers. Each specimen was bissected, one put into 10% formaldehyde which was prepared for routine H&E staining and study by light microscope. The other was put into 2.5% glutaraldehyde, the best preserved specimen was then chosen to prepare for the TEM study. Results: There is no significant difference between the peripheral nerves of the cadaveric embalmed and the fresh specimens when viewed with the light microscope. On the otherhand when viewed by transmission electron microscope, the lipid part of the myelin sheath of the peripheral nerves from the cadaveric embalmed specimens are totally degenerated while the protein part is still intact. While in the fresh specimens which are fixed by 2.5% glutaraldyhyde, there is a complete preservation of the lipid and protein part of the myelin sheath. Conclusion: The cadavers were fixed by excess formalin injection into the femoral artery and embalmed in formalin for at least 1 year, this could not preserve the lipid part of the myelin sheath. However, in the fresh peripheral nerves fixed in 2.5% glutaraldehyde it could preserve the lipid and proetin parts of the myelin sheath perfectly.

The ultrastructure of the parathyroid gland in cadaveric embalmed specimens.

Objective: This study is to observe ultrastructurally of the parathyroid gland from cadaveric embalmed specimens by light microscopy and by transmission electron microscopy. Methods: The parathyroid glands were carefully dissected from the posterior surface of thyroid glands of the cadavers of the Department of Anatomy, Faculty of Medicine Siriraj Hospital, Mahidol University. Each parathyroid was bisected into two, one put into 10% formaldehyde and the other to the 2.5% glutaraldehyde. The first group was prepared for routinely HE staining for light microscopy. The one which the specimen with the best preserved was chosen to prepare for the TEM. Results: The parathyroids of the cadavers were all well preserved as viewed by light microscopy. They are all reviewed the chief and oxyphil cells which easily distinguishable. The chief cells are more numerous and acquired the characters of actively synthesis of materials. These are the basophilic cytoplasm and large clear nucleus. The oxyphil cells are less numerous and acquired its characters of larger cells, red cytoplasm and dense dark nuclei. When viewed by TEM, it is cleared that the cells are well preserved. The chief cells are characterized by large heterochromatic nucleus and the cytoplasm is filled with the secretory vesicles, some of which the RER and the Golgi apparatus can be observed. Conclusion: The human tissue from the cadavers of the Department of Anatomy, Faculty of Medicine Siriraj Hospital was well preserved even viewed by TEM. This may be due to the fact that the fixative was pushed through the great vessels until it circulated throughout the blood vessels of the whole body. Especially the endocrine glands such as the parathyroids which were richen in blood supplies, the fixative might be forced through the capillary sinusoid and then this tissue is highly preservation.

The ultrastructure of the secretory cells of the human carotid body.

Objective: The purpose of this study was to study the ultrastructure of the human carotid body by using transmission electron microscopy. This is to distinguish the secretory cells of the human carotid body and classify the cells by the characteristic size, shape and electron density of the secretory granules, since nowadays there is still no data about TEM of the human carotid body. There is also no report about the exact secretions of the organ. Methods: 4 carotid bodies at the carotid bifurcations were identified and dissected from 2 fresh cadavers. The specimens were prepared for routinely TEM. Results: There are at least 3 secretory cell types in the human carotid body accordings to TEM. The cells were classified by the characteristic size, shape and the electron density of the secretory granules. The type I has large clear membrane bound granules, type II has small electron dense membrane bound granules and type III has large moderately electron dense membrane bound granules while type IV is thought to be the degranulated form of the type I. Conclusion: There are at least 3 types of secretory cell in the human carotid body and there may be 3 types of secretion as well. The immunocytochemical technique will be performed in future to identify the secretions.

The presence of the peroneus tertius muscle in Thai people.

The peroneus tertius is a small partially separated portion of the extensor digitorum longus, as its fifth tendon, but has an important role in locomotion and in the evolution of human beings. It supports and stabilizes the longitudinal arches of the foot while standing and locomotion during bipedalism. In particular, it assists in everting the foot, which is a characteristically human movement. This study was performed by dissecting 247 legs from 144 cadavers. In these cadavers, we found a high percentage of the presence of this muscle, the peroneus tertius, (95.55%). The absence of the muscle was rare, only in 4.45%. Regarding the muscle size, which was calibrated at the ankle joint and compared with the common tendon of the extensor digitorum longus at the same area, the proportion was very large a t34.77% in the right leg and 39.55% in the left leg. The results of this study emphasized and clarified the important role of this muscle.

Histology of the carotid body.

The histological study of the carotid bodies of human cadavers was performed using light microscopy and hematoxylin and eosin staining technique. We found good criteria to distinguish the cell types of this structure. The carotid body is a small neurovascular structure situated at the bifurcation of the common carotid artery. It is divided into 6-8 lobules, each of which consists of groups of cells and several sinusoids with large diameters surrounded by a thin capsule with small nerve bundles lying close to it. There are 4 cell types in each group, the glomus type I cell, the glomus type II cell, the ganglion cell and the fibroblast. The glomus type I cell are the principal cells which have oval or round nuclei function. The glomus type II cells have round nuclei with deeply staining and acidophilic cytoplasm indicating that they are in a resting atage. The ganglion cells, either separated or a group of few cells, are situated at the periphery of each group and near the blood sinusoids. The hypothesis that the glomus type I cell and the glomus type endocrine gland and the cells gradually differentiate from a resting into the active stage. Further studies are needed to confirm whether the type I cells are in APUD series and this will be done by only transmission electron microscopy.