Blind mole rat (Spalax leucodon) masseter muscle: structure, homology, diversification and nomenclature.

BACKGROUND: It is well known that rodents are defined by a unique masticatory apparatus. The present study describes the design and structure of the masseter muscle of the blind mole rat (Spalax leucodon). The blind mole rat, which emer- ged 5.3-3.4 million years ago during the Late Pliocene period, is a subterranean, hypoxia-tolerant and cancer-resistant rodent. Yet, despite these impressive cha- racteristics, no information exists on their masticatory musculature. MATERIALS AND METHODS: Fifteen adult blind mole rats were used in this study. Dissections were performed to investigate the anatomical characteristics of the masseter muscle. RESULTS: The muscle was comprised of three different parts: the superficial mas- seter, the deep masseter and the zygomaticomandibularis muscle. The superficial masseter originated from the facial fossa at the ventral side of the infraorbital foramen. The deep masseter was separated into anterior and posterior parts. The anterior part of the zygomaticomandibularis muscle arose from the snout and passed through the infraorbital foramen to connect on the mandible. CONCLUSIONS: The construction of the deep masseter and zygomaticomandibularis muscles were of the Myomorpha type. Further studies are needed to reveal features such as muscle biomechanics, muscle types.

Comparison of type I collagens and MMP-2 proteins in temporomandibular joint of young and old mice.

BACKGROUND: The effects of ageing on the histopathological changes of tem-poromandibular joint (TMJ) and the existence and age related alterations of immunochemical expressions of type I collagen and matrix metalloproteinase-2 (MMP-2) proteins was aimed to be displayed. MATERIALS AND METHODS: In this study, 14 Balb/C type white mice (50- -80 g) were included. Groups were organised as group 1 - 2-month-old young animals (n = 7) and group 2 - 18-month-old old animals (n = 7). Of the paraffin embedded tissues 4-5 µm thick sections were taken and immunohisto-chemical stainings of haematoxylin-eosin, type-1 collagen and MMP-2 were performed. RESULTS: Collagen bundles showed sagittal and oblique localisations in the young mice, which were comprised of compact collagen bundle layers positioned alterna-tely. While collagen bundle fragmentation was observed in the disks of old mice, some disk regions showed ruptures. In the old mice a decrease in blood vessels, structural impairments and dilatation in arterioles and venules were detected. In the TMJ tissues of the young mice type I collagen and MMP-2 expressions were increased, while they were decreased in old mice. In the MMP-2 H-score evaluation young mice showed significant increase compared to the old mice. CONCLUSIONS: Occurrence of degenerations in the collagen structure of TMJ and decimation in the matrix metalloproteases were observed with age. (Folia Morphol 2018; 77, 2: 329-334).

Macroscopic anatomy of the lower respiratory system in mole rats (Spalax leucodon).

The morphologic and morphometric features of the lower respiratory system in mole rats were examined. It was seen that the low respiratory system of this species leading a special life under highly hypoxic/hypercapnic conditions underground is structurally similar to other mammals living on land in terms of the parts examined; trachea was formed by 29.5 ± 4 oval-formed cartilaginous tracheals arranged backwards and became gradually more stenotic diameter from cranial to the caudal of the neck. The trachea was separated in two principal bronchus at the fourth thoracal intercostal spatium level. The angle between the two main principal bronchi was 60.5 ± 2.35°. The lung constituted 1.29 ± 0.03% of the body weight and the right lung was heavier than the left lung. Fissura inter-lobaris was deep and separated the lung lobes wholly, and the right lung was separated in four lobes, whereas the left lung was not separated into the lobes. Also, the medial lobe of the left lung was the lightest lobe.

Macroscopic description of the coronary arteries in Swiss albino mice (Mus musculus).

A total of 25 (13 male, 12 female) adult, healthy Swiss albino mice were used to investigate the origin, course and anastomoses of coronary arteries. Coloured latex was injected into the aortic arch to enable these arteries to be clearly discerned. A. coronaria sinistra was larger than A. coronaria dextra. It was divided into a Ramus interventricularis paraconalis and a Ramus circumflexus sinister. However, in 2 specimens, the septal ramus, was observed to stem directly from the left coronary artery, and only 1 ventricular branch arose from the left circumflex. The collateral branches of the paraconal interventricular ramus had a larger diameter and more extensive distribution was observed in these specimens. The A. coronaria dextra was divided into a Ramus septalis and Ramus circumflexus dexter. The Ramus interventricularis subsinuosis was not detected in this study. The ventricular branches of the left coronary artery run intramyocardially whereas the branches of the right coronary artery course subendocardially.