Anatomical and microscopic study of the volar dermal ridges of the rat (Rattus norvegicus).код для вставкиСкачать
AMERICAN JOIJRNAL OF PHYSICAL ANTHROPOLOGY 67:81-88 (1985) Anatomical and Microscopic Study of the Volar Dermal Ridges of the Rat (Rattus norvegicus) M. OKAaMA AND Y.ASAI Department ofForensrc Medzczne, Tokyo MedLcal and Dental Unluerslty, Ybhirna, Bunkyeku, Tokyo 113, Japan KEY WORDS Dermatoglyphics,Dermis, Rat ABSTRACT The epidermal ridges of the rat (Rattus norvegicus), which are distributed only on the volar pads and digital apices, were studied. Examination of the ridges was difficult on the epidermal surface, as the undulations expressed on the epidermis are weak. Therefore, the dermal surface, prepared by alkaline solution treatment, was inspected by scanning electron microscopy and staining with toluidine blue. The dermis of the pads and digital apices is composed of ridged and rippled areas. The ridged area, where sweat ducts are distributed, is constructed of grooves and ramparts. Frequently, the sweat duct is surrounded by a dermal collar, and the groove is separated by a dermal partition. The grooves and ramparts display dermatoglyphic configurations, such as whorls, loops, cusps, triradii, and some other patterns, which are peculiar to each pad and digital apex and comparable to dermatoglyphic patterns of man and other primates. The occurrence of epidermal ridges at the palmar and plantar surfaces is common in the primates, including the human species. On the other hand, this characteristic appears sporadically in other mammals and has been reported in some species of rodents, marsupials, and carnivores (Merkel, 1880; Klaatsch, 1888; Whipple, 1904; Dankmeijer, 1938; Cummins and Midlo, 1943). In the rat (Rattus noruegicus), undulations of the ridges are not sufficiently developed at the volar surface to be clearly identified with the naked eye. No systematic studies have been undertaken on the ridge arrangement in the rat, except for brief descriptions of the existence of a ridged structure by Merkel (1880) and Klaatsch (1888). Okajima (1975a) reported a technique that enables one to inspect the ridge arrangement at the dermal surface, and, at the same time, he presented dermal ridges of some animals including the rat. In this paper, we describe the anatomical structure of the epidermal ridges of the rat and its dermatoglyphic features by applying the above-mentionedtechnique. 0 1985 ALAN R. LISS, INC. MATERIALS AND METHODS About 700 adult and infant rats were collected for this study from several inbred strains reared in the National Institute of Genetics CMisima) and some conventional strains from animal dealers. Cast of the epidermal surface The volar epidermal surface of sacrificed rats was cleaned with ethanol, and a cast of volar pads and digital apices was prepared with silicone rubber. Histology Pads of the palm and sole were taken from adult rats and fixed in buffered formalin. After the specimen was embedded in celloidin, sections, 30 pm in thickness, were cut and stained with hematoxylin and eosin. Preparation of the dermal surface The original preparation technique (Oka$ma, 1975a, 1979)was modified in this study. Received August 30,1984; revision received January 21,1985; accepted January 31,1985. 82 M. OKAJIMA AND Y. ASAI The hands and feet were separated from the body proximal to the wrist and foot joints, fixed in 10% formalin, and incubated in 1 N potassium hydroxide solution at 30°C for 2 or 3 days. Then the specimens were washed in running water for 2 days. Usually, most of the epidermal tissue was separated from the dermis by this treatment alone. The remaining epidermal tissue was removed mechanically by slight touch with a cotton swab or a brushlike terminal of a thread. At this manipulation, the specimen was stained with 0.05% toluidine blue solution, so that the dermal surface and the epidermal tissue remaining on it were easily identified. Staining of the dermal surface The dermal surface thus exposed was stained with 0.05% toluidine blue solution for about 20 seconds, rinsed in water, and placed in a dish of water. The stained dermis was inspected under a stereoscopic microscope and photographed. The hand and foot were fixed in an extended position on a rubber plate with rubber strings at the proximal site and at the phalanges. When the examination was finished, the reagent was removed from the tissue by immersion in 70% ethanol and then the ethanol was replaced by water. After this, the specimen was preserved in 10% formalin, and, if necessary, the inspection was repeated using the same procedure. Scanning electron microscop,y (SEM) After the stained dermal surface was examined, pads and digital apices were taken from several rats. The specimens were washed in distilled water, postfixed for 2 hours in 1.5% osmium tetroxide, dehydrated through a graded series of ethanols into isoamyl acetate, and dried in a pressure chamber by the critical point procedure. The specimen was fixed, dermal surface up, to a n aluminum stub with silver conducting paint, coated with evaporated platinum, and viewed with an Hitachi S-700 operated a t 20 kV in the secondary electron mode. RESULTS Observation of the epidermal surface First, we examined the epidermal surface of the volar pads and digital apices of adult and infant rats with a magnifying glass and under a stereoscopic microscope. On the epi- dermal surface, the ridged structure was recognized in various grades of expression. However, the undulations and contrast were usually weak, and the ridges were, in most areas, not discernible, so that it was almost impossible to confirm the entire ridge arrangement with the naked eye. Attempts to take dermatoglyphic prints by the usual printing methods were not successful, as the furrows were too shallow. Following this, the epidermal surface was examined on the silicone rubber casts. The relief of the ridges was more clearly seen under a stereoscopic microscope than was the epidermis itself. However, the degree of expression was different from pad to pad and from site to site as well as from animal to animal. Moreover, the surface was frequently smooth, and the ridges were not visible, especially in the infant rats. Therefore, precise identification of ridge configurations was usually difficult. However, it was determined that the pores of sweat ducts are arranged on the midline of the epidermal ridge. Surface structure of the dermis The dermal surface of the volar pads and digital apices was examined by the scanning electron microscopic (SEMI procedure. The surface is characterized by two morphologically dissimilar areas, i.e., the ridged and the rippled, as defined by the different morphological features of the dermal undulations. Generally, the ridged area is localized in the higher part of the pad and digital apex, while the rippled area is located peripheral to the ridged area, usually in the lower region. As the SEM picture shows (Fig. 11, the dermal surface presents wavelike undulations that are constructed of alternate arrangements of dermal grooves and ramparts in the ridged area. The groove is a deep, linear depression of the dermis, where sweat ducts lie. The orifice of the sweat duct presents a deep, funnel-shaped cavity at the dermal surface. In the rippled area, the dermal surface is constructed of papillalike projections and lower folds. Some of them are arranged linearly, but others are distributed more or less in a n irregular image. The basic difference between the two areas is the presence of sweat ducts in the ridged area, and their absence in the rippled area. The groove corresponds anatomically to the epidermal ridge and the rampart to the epidermal furrow (Fig. 2). The sweat duct penetrates the stratum corneum of the epidermis, DERMAL RIDGES OF RAT 83 Fig. 1. Dermal surface of the first interdigital and thenar pad on the right palm of a rat (SEMI. The ridged area (Rig) is represented by an alternate arrangement of the groove (GI and the rampart (R). Sweat ducts (SD) are frequently surrounded by a collar (C) of dermal projec- tion. The groove is frequently compartmentalized by a dermal partition (PI. The rippled area (Rip) is constructed of papillalike projections and lower folds of the dermis. forming a spiral, and opens at the summit of the epidermal ridge. However, it often opens at a flat surface, because the ridged structure is not manifested. Superficial to the rippled area of the dermis, the epidermal surface is smooth, and the epidermal tissue is generally somewhat thinner than in the ridged area. In the ridged area, the groove is frequently modified by a n irregular occurrence, bifurcation, or conjunction of the ramparts. Sweat ducts are not evenly distributed in the groove. They are arranged closely in some grooves but are almost absent in others. The groove is usually narrower a t the site where there is no sweat duct. Moreover, the groove looks rudimentary and like a mere fissure where the ramparts lie closely parallel. The orifice of the sweat duct is frequently surrounded by a dermal collar, a cylindrical or a semicircular projection of the derms. In addition to the sweat ducts, the groove is frequently punctuated by low dermal partitions, which are elevated from the base and usually extend across the groove, independent from, or adjacent to, the sweat duct (Fig. 1). The summit of a rampart forms a single edge and is fairly smooth along its long axis in many rats, while in others it is fringed with small dermal projections, presenting a serrated appearance (Fig. 3). This characteristic appearance was observed on each pad and in both adults and infants. The formation of the dermal furrow a t the rampart, 84 M. OKAJIMA AND Y. ASAI Fig. 2. Histological presentation of the epidermal ridges of the rat (hematoxylin and eosin, x 60). The section was cut parallel to the long axis of the second interdigital pad of a right foot and perpendicular to the ridges. Weak undulations of the epidermal surface pres- ent epidermal ridges (ER) and furrows (EF). The dermd surface is constructed of grooves (G) and ramparts (R). Ducts (SD) of sweat glands (SG) penetrate the dermis (Der) and the epidermis (Epi) and open at the summit of the epidermal ridge. which is a common characteristic of man and other primates, was not detected in the rat. Though the appearance of the groove and the rampart is modified by many factors as stated above, their alternate arrangement displays a definitive ridged structure on the dermal surface that is comparable to the dermal ridges of the primates. Dermatoglyphic inspection by the staining method The dermal surface stained with toluidine blue presented in Figure 4 is from the same specimen as shown in Figure 1. This specimen was first stained and examined and then used for the SEM examination. The dermal projections of the ridged area stained with toluidine blue in a violet tone, while the groove remained unstained (Fig. 41, in the same manner as the dermal papillae of man and other primates. Every rampart, collar, partition, and fringe in the ridged area and the dermal papillae and folds in the rippled area, which are demonstrated in the SEM picture (Fig. 11, coinFig. 3. Fringe formation of the rampart (SEM). Hypothenar pad of a left hand. The edge of the rampart presents dermal projections arranged in a serrated pattern. 85 DERMAL RIDGES OF RAT cide exactly with the image displayed by the staining method (Fig. 4).Thus, the staining procedure permits easy identification of the arrangement of the ridges. Examples of dermatoglyphic perspectives of a palm and a sole are provided in Figures 5 and 6. As these pictures show, each pad and digital apex presents a particular ridge arrangement. The simplest and most common type is that in which the parallel ridges lie transverse to the long axis of the pad elevation. This type appears on most pads. A triradial ridge arrangement appears frequently on the first interdigitallthenar and the second to fourth interdigital pads on the palm, and on the third and fourth interdigital pads on the sole, occasionally accompanied by some particular pattern formation. The third interdigital pad of the palm is a very striking area where the ridges present abundant configurations, i.e., triradii, whorls, loops, cusps, and some other types of patterns (Fig. 7), which are similar to the dermatoglyphic patterns on the digital apex, palm, and sole of the primates. On the digital apex, although the size of the patterns is small, Fig. 5. Dermal surface of a left palm (toluidine blue ridge arrangements characteristic to each staining). Ridged structure is recognized on the first (I), digit were observed. second a), third (III), and fourth (IV)interdigital pads, and the thenar (Th)and hypothenar (Hy) pads. On the third interdigital pad, a whorl pattern is observed. Digits are represented by Arabic numerals. DISCUSSION It has long been known that all the members of the primate order and some species of rodents, carnivores, and marsupials possess friction skin. Whipple (1904) made an extensive survey of epidermal ridges in mammals. Dankmeijer (1938) undertook a systematic study of marsupials, reporting the existence of dermatoglyphic traits in some species of this order. Cummins and Midlo (1943)presented a review of dermatoglyphic traits in animals including those other than the primates. But none of these authors mentioned the presence of epidermal ridges in the rat. However, the existence of ridged structures on the volar skin of the rodents had been reported by some earlier workers. Merkel (1880) first described it in the squirrel and the rat. His statement about this characteristic in the rat was later quoted by Klaatsch (1888) as follows: “He (Merkel) found with the naked eye that the pads present a striped surface that reminds one of the finger apex Fig. 4. Dermal surface (toluidine blue staining). This of man. When the epidermis is removed by picture was prepared from the same specimen as shown in Fig. 1. Details of the dermal structure illustrated here maceration, the stripe is conditioned by papillary ridges as is found at the nail bed of coincide with those of the SEM image. 86 M. OKAJIMA AND Y. ASAI Fig. 6. Dermal surface of a lefi sole (toluidine blue staining). Ridged structure is recognized on the pads. For abbreviations, see Figure 5. man. These are carriers of numerous tactile corpuscles.” Subsequently, Whipple (1904)described the configurational arrangement of ridges on the voIar pad of the Neotoma (wood-rat) among the rodents and stated “The highest part of each pad is covered by somewhat broken ridges separated by deep furrows. The more elevated pads, such as the apical and the hypothenar of the hand, show a n approximately concentric arrangement of ridges, while upon other pads the arrangement is transverse.” In her sketch of a section perpendicular to the ridges, she presented the duct of sweat glands opening between ridges on the epidermal surface, In this illustration, remarkable undulations are demonstrated both a t the epidermal surface and the dermoepidermal junction, the epidermal furrow anatomically corresponding to the dermal groove and the epidermal ridge to one or two rows of dermal papillae. Contrary to her findings, it was observed in the present study that the orifice of the 87 DERMAL RIDGES OF RAT Fig. 7. Representative pattern types on the third interdigital pad of the palm (toluidine blue staining). a. loop. b. cusp. c. triradius. A whorl pattern is demonstrated in Figure 5. sweat ducts is not located in the furrow, but on the midline of the epidermal ridge. In addition, though the undulations at the epidermal surface are often indiscernible, histological sections showed that the epidermal ridge anatomically corresponds to the groove and the epidermal furrow to the rampart, and that the sweat duct opens at the summit of the epidermal ridge, as is the case among primates. It was confirmed in this study that the dermal surface of the volar pad and the digital apex is composed of two distinct regions, i.e., ridged and ripple areas, as defined by the presence or absence of sweat glands. The ridged area consists of an alternate arrangement of dermal grooves and ramparts, similar to that observed in the early developmental stage of human fetuses (Okajima, 1975b, 1982). Thus, the dermal furrow, as observed in fully developed primates, is absent in the rat. It is possible that the less complex morphology of the rat is associated with a weak expression of the epidermal furrow. Whipple (1904) mentioned that there are no epidermal ridges in those rodents (Mus, Microtus, etc.). However, she presented in her sketch that the epidermal ridges of the woodrat are markedly elevated. Therefore, the expression of the epidermal ridges is different between species in the rodents, and further morphological findings are needed to understand the difference. On the other hand, it is characteristic of the rat that the dermal surface is modified by formation of partitions and collars of sweat ducts and a somewhat irregular arrangement of ramparts. These dermal structures are revealed by both SEM and staining pro- cedures. In spite of these modifications, the groove maintains its linear nature and, as a whole, presents a configurational arrangement that can be defined as a dermatoglyphic trait. We have found that the ridge arrangement characterizes each volar pad. In some areas, such as the third interdigital pad of the palm, configurations quite comparable to the dermataglyphic patterns of man and other primates were observed. The staining method is practical for the dermatoglyphic analysis. We have revised the original preparation technique (Okajima, 1975a, 1979)by applying 1 N potassium hydroxide solution for 2-3 days at 30" C . By this procedure, the epidermis of the specimen can be easily and completely removed, resulting in a specimen of good quality. Primates have been considered to be the only laboratory animals available for dermatoglyphic study. However, there are limitations in the use of primates, such as their extremely high cost, the small number of animals available, long gestational periods, and the difficulty in obtaining precisely timed conceptions. The results presented here confirm that it is possible to use the rat, a conventional laboratory animal, as an experimental model for dermatoglyphic study. ACKNOWLEDGMENTS We are indebted to Mr. H. Miyamoto for technical advice in SEM preparation. This study was supported by a Grant-in-Aid for Scientific Research No. 57570238 from the Ministry of Education, Science, and Culture of Japan. 88 M. OKAJIMA AND Y. ASAI LITERATURE CITED Chacko, LW, and Vaidya, MC (1968)The dermal papillae and ridge patterns i n human volar skin. Acta Anat. 7Or99-108. Cummins, H, and Midlo, C (1943)Finger Prints, Palms and Soles. Philadelphia: Blakiston. Dankmeijer, J (1938) Zur biologischen Anatomic der Hautleisten bei den Bcuteltieren. Morph. Jahrb. 82:293-312. Klaatsch, H (1888)Zur Morphologie der Tastballen der Saugethiere. Morph. Jahrb. 14t407-435. Merkel, F (1880) h r die Endigungen der Sensiblen Nerven in der Haut der Wirbelthiere. Rostock Verlag der Stillerschen Hof. Okajima, M (1975a) Technical aspects of dermatoglyphic examination in primates. In S Kondo, M Kawai, and A Ehara (eds): Contemporary Primatology. Basel: Karger, pp. 49-53. Okajima, M (197513) Development of dermal ridges in the fetus. J. Med. Genet. 12t243-250. Okajima, M (1979) Dermal and epidermal structures of the volar skin. Birth Defects Orig. Art. Ser. 15(6):179198. Okajima, M (1982) A methodological approach to the development of epidermal ridges on the dermal surface of fetuses. Prog. Clin. Biol. Res. 84t175-188. Whipple, IL (1904) The ventral surface of the mammalian chiridium. Z.Morph. Anthropol. 7t261-368.