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ISSN : 1976-7447(Print)
ISSN : 2287-7363(Online)
Journal of Biomedical Research Vol.13 No.4 pp.326-330
DOI : https://doi.org/10.12729/jbr.2012.13.4.326

Scanning electron microscopic observation on the development of conical papillae in Korean native goats (Capra hircus)

Chungkil Won *, Gyuhyen Cho, Munki Kim, Gon-Sup Kim, Chongsup Kim
Research Institute of Life Science & Department of Veterinary Medicine, Gyeongsang National University
(Received 20 Nov. 2012, Accepted 14 Dec. 2012)

Abstract

The aim of this study was to investigate the morphological development pattern of conical papilla (CP) during prenatal and postnatal periods in native Korean goats by scanning electron microscopy. Tongues were removed from fetuses on days 90, 120, and neonates and from juveniles on days 30, 50, 60, 75, 90, 120, 150, and 180 after birth. The lengths of CP were 194~240 μm in neonates, 335~485 μm in the weaning period of 60-day-old goats, and 526~662 μm in the maturing period of 180-day-old goats. The primordia of CP in 90-day-old fetuses, shaped like mountain berry, were sprouted. The CP of 120-day-old fetuses was a cylinder shape with an apex whose center was slightly concave and the margin was sticking up like a low fence. The CP of neonates was empty inside and the secondary papillae were irregularly arranged fence-like structures on it. In 60-day-old goats, CP was an obliquely sectioned cylinder shape compacted in inner surface; the shapes of CP varied in 120-day-old goats, and had a smooth surface. A low elevation of CP was observed in 150- and 180-day-old goats. The microridges, microplicae, and micropits were well developed on the epithelial surface of lingual papillae in 60- to 120-day-old goats. These findings indicate that CP of goats has a variety of sizes and shapes during development.

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Introduction

 Many mammals have four or five different types of lingual papilla, namely filiform, fungiform, conical, vallate, and foliate papillae, on the dorsal surface of the tongue [1-5]. Scanning electron microscopic studies of the tongue papillae in various animals have been reported in cat [1], cow [2], dog [3, 6], pig [4], horse [5, 7], goat [8], camel [9], Japanese weasels [10], mouse [11], opossum [12], rat [13], and sheep [14]. Among them, a few numbers of studies were performed with ruminants. Concerning lingual papillae, goats have three different types of mechanical papilla and two different types of gustatory papilla depending on their morphological characteristics, but foliate papilla was not found. Kumar et al. [8] and Lee et al. [15] have studied filiform, fungiform, conical, vallate, and lentiform papillae. However, there have been very few studies of differences in the development and growth of lingual papillae in goats [16]. Therefore, to understand the progress of development of conical papilla (CP), we investigated the changes of its size and shape during prenatal and postnatal developments.

Materials and Methods

1. Experimental animals

 The tongues from three fetuses or juveniles of Korean native goat were used in each group. To investigate the morphological changes on prenatal development of the tongues, fetuses were removed on days 90 (E90), 120 (E120) and 150 (neonates, P0) by caesarean section performed under general anesthesia using xylazine hydrochloride (Bayer Korea Ltd., i.v., 10 mg/kg) and CP of the tongues was examined for the morphological development. To examine the morphological changes on postnatal development, the tongues were also removed from goats at 8 different postnatal stages: on days 30 (P30), 50 (P50), 60 (P60), 75 (P75), 90 (P90), 120 (P120), 150 (P150), and 180 (P180), respectively. All animal experiments were performed according to a protocol set out in the guidelines of the Animal Experiments Ethics Committee at Gyeongsang National University (Approval No. GNU-LA-10).

2. SEM measurements of length of CP

 The measurement of CP from three to five different regions was performed by measuring the height and oblique length of papillae using a scanning electron microscope (SEM) from neonates to 180-day-old goats. Briefly, the height was maximum length from lingual bottom to apex of CP and oblique length was diameter of long axis of CP. We analyzed statistical significance of differences among each group by two-tailed Student’s t-test (Prism; Graph Pad Software).

3. SEM examinations of the developing CP

 Tissues for scanning electron microscopy observations were fixed using 2.5% glutaraldehyde 4 h at room temperature and areas appropriate for inspection were dissected and osmicated in 1.0% osmium tetroxide at 4°C for 2 h. After washing with PBS three times, the tissues were dehydrated using a graded series of ethanol solutions. The specimens were dried critically to point, and then placed on spinner stubs, and coated with gold to a depth of 100 μm as SEM coating unit. The specimens were observed under a SEM (SEM-AL 300, Philips) operated at 15 KV.

Results

1. Lengths of CP after gestation

 The sizes of CP from neonate to 180-day-old goats revealed respectively (Fig. 1). The height and oblique lengths of newborn papillae were 194.0 ± 22.0 and 240.0 ± 65.0. They were 335.0 ± 32.0 and 485.0 ± 61.0 μm in the weaning period of 60-day-old goats and 526.0 ± 62.0 and 662.0 ± 68.0 μm in the maturing period of 180-day-old goats, respectively. However, there were no statistically significant differences among each age during the next 30 days.

Fig. 1. Morphological measurements of length of conical papillae. Each of height and oblique length were measured from neonates (P0) to 180-day-old Korean native goats (P180).

2. Morphological characteristics of developing CP

 In prenatal developing goats, many primordia of CP in 90-day-old fetuses, shaped like mountain berry, were sprouted (Fig. 2A). The apex of primordia of CP in 120-day-old fetus, shaped like a cylinder, had concavely digged center and low fence-like margin with sow blade-like secondary papillae sticking up (Fig. 2B). The CP of neonates was empty inside, and the secondary papillae were irregularly arranged in fence-like structures on it (Fig. 2C).

Fig. 2. Scanning electron micrographs of prenatal conical papillae of Korean native goats. (A) E90, (B) E120, and (C) E150 (neonates), CP: conical papilla, LP: lentiform papilla.

In postnatal day 30, the two types of CP were distributed at the root of the tongue directed caudally. The apex of the CP in 30-day-old goats was similar feature to sow blade-like small leaves which began to grow up densely at the base of fence inside (Fig. 3A). The base of CP on the caudal part in 30-day-old goats looked like a cylinder, which apical part retained an oval outline with depressed center (Fig. 3B). 

Fig. 3. Scanning electron micrographs of postnatal days 30 to 60 of conical papilla (CP) in Korean native goats: (A & B) P30, (C & D) P50, (E) P60, (F) Higher-magnification view of the epithelial surface in P60. Microplicae of CP are small windingly round and banding shaped. ×5,000, VP: vallate papilla. MP: microplica, MPT: micropit, MR: microridge.

 In 50-day-old goats, CP was scarcely spotted as a complete conical form resembling adult form, but some of it had shapes in a sectioned cylinder, a ticklish flower shovel, sow blade-like secondary papillae without sow blade-like structure from the top of papillae to 3/4 of it, and still an empty central part (Figs. 3C and 3D).

 The CP of 60-day-old goats was shaped like a cone, akin to a packed cylinder and sectioned obliquely. Conical tip was not observed in the center of the cylinder (Fig. 3E) which shapes were more developed in 75-day-old goats (Fig. 4A). The microplicae of CP in 60-day-old goats were small, windingly round and banding shaped (Fig. 3F). The CP of 90-day-old goats was longer, bigger, and thicker than those of 75-day-old goats (Fig. 4B).

Fig. 4. Scanning electron micrographs of postnatal day 75 to 180 of conical papillae in Korean native goats. (A) P75, (B) P90, (C) P120, (D) Higher-magnification view of the epithelial surface in P120, ×5,000, (E) P150, (F) P180, CP: conical papilla, VP: vallate papilla, MP: microplica, MR: microridge.

The CP of 120-day-old goats was various shapes such as cone. Its surfaces were smooth and its shapes were developed as complete as those of adult one (Fig. 4C). The microridges, microplicae, and micropits were very well developed on the surface (Fig. 4D). Some of CP in 150- and 180-day-old goats had a low elevation (Figs. 4E and 4F). 

Discussion

 There are many reports based on scanning electron microscopy of the three-dimensional structures of the lingual papillae in mammals. Especially, a few numbers of studies were performed with goats. Kumar et al. [8] have studied for filiform, fungiform, conical, vallate and lentiform papillae on the dorsal surface of the tongue. Lee et al. [15] also performed scanning electron microscopic studies of the tongue. However, no comparative studies on changes in three-dimensional structure of CP during development of goats have been reported. Therefore, we investigated the characteristics of CP during development in goats using SEM.

Concerning the size of lingual papillae of Korean native goats, Lee et al. [15] reported that, using Korean native goats weighting around 15 kg, the number of CP was 818.4 and the sizes of CP were 450~600 μm in height and 250~450 μm in diameter. In this study, the sizes of newborn papillae were 194~240 μm and 526~662 μm in the maturing period of 180-day-old goats in height. Although the sizes of CP in goats were similar to those of other studies, but it was gradually increased during development. 

 Concerning the development of lingual papillae, gustatory papillae grow faster than mechanical papillae in human [17]. And the primordia of filiform papillae are formed after the appearance of the rudiments of fungiform and vallate papillae in rodents [11, 13]. On the other hand, primordia of fungiform papillae are not seen in 90-day-old goat fetuses [16] while primordia of conical papillae were sprouted in 90-day-old goat fetuses in this study. Fungiform papillae in the 120-day-old fetuses are shaped like a mushroom, and their papillae in neonates appear to be shaped similar to those of adult [16]. However, some of CP had a shape of an obliquely sectioned cylinder with empty inside in 50 day-old goats and were observed to a completely compacted shape on inner surface in 60 day-old goats. Therefore, these results confirmed that the mechanism on morphogenesis and development of mechanical papillae might be different from gustatory papillae.

 Concerning the morphology of CP, Furubayashi et al. [10] reported that, in case of Japanese weasels, filiform, fungiform, vallate and foliate papillae were observed, but CP was not. Kumar et al. [8] reported that large CP with round bottom and blunt tip without process were observed in 6- to 8-month-old Jamuna pari tongues. In newborns of this study, some of CP looked like a obliquely sectioned cylinder with empty inside on whose sectioned side were 10 to 12 of secondary papillae like fencing it in the shape of sow blade, some had low fence-like outer wall on the obliquely sectioned side and depressed inside.

 The structures of lingual epithelial surface between 12-day-old rat fetuses and 15-day-old mouse fetuses were very similar [11, 13]. In this study, microridges were compactly sticking up on the surface of CP and microplicae and micropits on the epithelia surface were well-developed in 60-day-old goats with similar structures to the surface in 120-day-old goats. Therefore, the surface structures of lingual epithelia in Korean native goats are very similar to those of other species.

 Taken together, these findings indicate that goat CP has a variety of sizes and shapes during prenatal and postnatal developments.

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