Primary irritant reactions in the skin of the pika, Ochotona rufescens rufescens

The skin of the pika (Ochotona rufescens rufescens) was found to be remarkably sensitive to the primary irritation of sodium hydroxide, as compared with the skin of the rabbit. After exposure to 0.1 N sodium hydroxide for 24 hr, the pika skin showed severe erosion, ulceration and necrosis as well as crust formation and hyperkeratosis with vascular dilation, and cell infiltration. The changes appeared already within 1 hr after 1 N or 3 hr after 0.1 N sodium hydroxide application. After application of acetic acid, changes were apparent while less remarkable.     

Fine structure of the mandibular gland in pika (Ochotona rufescens rufescens)

The mandibular gland of the pika was examined by light microscopy, and transmission and scanning electron microscopies. The acinar cells were noted to be composed of serous cells and seromucous cells. The serous cells containing granules of moderate and high densities were slightly basophile and strongly positive to PAS, but were not stained with AB. The seromucous cells possessing less dense granules were light and moderately positive to PAS and AB. A sexual dimorphism was observed between these cells: Serous cells were considerably more frequent in males and seromucous cells were more numerous in females. Intercalated duct cells consisted of cuboidal light cells containing a few vesicles in the apical region. Striated ducts were comprised of two portions--a secretory portion and a typical striated portion without secretory granules. The secretory portion was composed of light and dark cells having secretory granules varying in size and density. The epithelium of typical striated portion consisted of light and dark cells containing fine vacuoles and vesicles.     

Spontaneous closure of isolated ventricular septal defect in the pika (Ochotona rufescens rufescens)

The incidence of spontaneously occurring ventricular septal defects (VSD) in PIKA neonates and its fate during development are investigated. A total of 160 PIKAs were used in the present study. They consisted of three groups; first, 56 live neonates, second, 37 3-week-old live animals and third, 68 animals which had died during the first two weeks after birth from unknown causes. As high as 8.9% (5 cases out of 56) of the live neonates revealed isolated ventricular septal defects of membranous type. Decreased incidence (2.7%) was seen in 3-week-old PIKAs. Its implication and significance are evaluated in the discussion.     

Biological features of the skin of the pika, Ochotona rufescens rufescens: histological structure and enzymatic histochemical reactivity

To examine the usefulness of the pika, Ochotona rufescens rufescens, as an experimental animal for skin irritability tests, the histological structure and enzymatic histochemical reactivity of pika skin were investigated. The pika had a hair cycle similar to that of the rabbit. The skin and epidermis of the pika trunk were 1.16mm and 29.5 microns thick, on the average, respectively. Both of them were the thickest in the dorsal region followed by the interscapular area, while they were the thinnest in the abdominal region. In the epidermis of the pika, the strata corneum, granulosum, spinosum and basale were rather clearly distinguished. The cell arrangement in the stratum basale was more compact than that in the rabbit. Dermal mast cells, which are distributed in the stratum reticulare in rabbits and guinea pigs, were distributed in the stratum papillare right beneath the epidermis. The mast cell of the pika in the TEM images had granules of low electron density and with relatively long microvilli and rather large mitochondria. The activities of the enzymes, SDH, MDH, LDH, beta HBDH, alpha GPDH, ALD, G6PDH and GPR, in the hair follicles and sebaceous glands of the pika were similar to those of the rabbit.     

A quantitative immunohistochemical study on the pituitary LH gonadotrophs in the female Afghan pika after copulation

The female Afghan pika is known as a species of copulatory ovulators exhibiting persistent estrus unless copulatory stimuli are employed. The plasma LH concentration rose quickly after copulation, peaked at 6 h and descended thereafter until 12 h. Before copulation (estrus), immunoreactive LH-containing cells of the pituitary in this species were filled with numerous large electron dense secretory granules, but the Golgi apparatus and the granulated endoplasmic reticulum were not well developed. One hour later the stainability of the cells was faint, their secretory granules were malls in size and in number, and were of low electron density. These alterations were the most predominant at 12 h after copulation. No exocytotic extrusion of secretory granules was observed throughout the experiment.     

Opioid receptor types in the brain of the Afghan pika (Ochotona rufescens), a species which is naturally tolerant to morphine

The rabbit is normally sensitive to morphine while another lagomorph, the Afghan pika Ochotona rufescens is naturally tolerant to the analgesic effects elicited by the opium alkaloid. In spite of the different responsiveness of the two species to morphine we find that the pika brain and the rabbit brain both contain a mixture of mu-, delta- and kappa-opioid sites in nearly the same proportions: 46-47% mu, 23% delta and 28-30% kappa. Moreover, apparent binding of morphine in pika and rabbit brain membranes is inhibited in the presence of Na+ ions and/or of 5-guanylylimidodiphosphate indicating that morphine should behave as an opiate agonist (analgesic) not only in rabbits, which it does but also in pikas, which it does not. Taken together these results suggest that the natural tolerance of the Afghan pika to morphine may not reside in modified opioid receptor types and that its origin should be sought elsewhere.     

Biological features of the skin of the pika, Ochotona rufescens rufescens--concentration of histamine in the skin

The quantity of histamine and the number of mast cells in the skin of the pika were measured and compared with rabbits, guinea pigs and rats. The ranking of regional histamine levels in the skin of the pika was: perianal region greater than abdomen greater than interscapular region = back greater than lumbus greater than head greater than auricle, and the average value of the 7 regions was 22.6 micrograms/g. The level of histamine in the 6 regions, except the auricle, was 2-5 times that of rabbits and guinea pigs. In the auricle of each of the 4 kinds of animal (pika, rabbit, guinea pig and rat), the levels were almost identical. With respect to histamine levels, those in the pika resembled those in rats. The number of mast cells in the skin of the pika was less than in rats, and was greater than that in rabbits and guinea pigs. The average value was 9.9/mm2.     

Characteristics of paravertebral muscles – fibre type distribution pattern in the pika, Ochotona rufescens (Mammalia: Lagomorpha)

The evolution of the locomotor apparatus in vertebrates is marked by major reorganizations in trunk's musculature. The hypothesized functions of mammalian back muscles in the literature are discussed under consideration of the distribution and proportion of oxidative, type‐I‐fibres, oxidative‐glycolytic, type‐IIa‐fibres and glycolytic, type‐IIb‐fibres in paravertebral muscles of a small mammal. The fibre type distribution was examined from a complete series of histological sections maintaining topographical relationships between the muscles as well as within the muscle, in order to establish the overall distribution pattern. The deep and short muscles showed the highest percentage of oxidative fibres. The larger, superficial paravertebral muscles contained the highest percentage of glycolytic fibres. Two muscles were intermediate in their proportion of fibre types. All epaxial muscles together can be interpreted as an antigravity muscle–complex counteracting enduringly against the rebound tendency caused by gravitation, comparable with antigravity muscles in limbs. A gradient from deep to superficial, or a clear regionalization of oxidative muscle fibres in central deep regions around a large intramuscular tendon was found in the m. spinalis and the m. quadratus lumborum, respectively. Concepts of the function of human back muscles as those of A. Bergmark (1989: Acta Orthop. Scand. 230 , 1) or S.G.T. Gibbons & M.J. Comerford (2001: Orthop. Division Rev. March/April, 21) were exposed to be more general within mammals. Functional specializations of different muscles and muscle parts are discussed under the consideration of evolutionary reorganization of the paravertebral musculature in tetrapods. Along the cranio‐caudal axis, the percentage of oxidative fibres was decreased in caudal direction within the same muscles, whereas the proportion of glycolytic fibres was increased. Therefore, classifications of muscles as ‘glycolytic’ or ‘oxidative’ based on biopsies or analyses of single cross‐sections may result in wrong interpretations. Changes in the proportions of the fibre type distribution pattern were mostly due to oxidative and glycolytic fibre types, whereas the percentage of oxidative‐glycolytic fibres had only minor influence. A significant positive correlation between the cross‐sectional area of the single fibre and its percentage in the area investigated were observed for oxidative fibres, whereby the size was positive correlated to the proportion of the oxidative fibres.     

Joint study on the teratogenic sensitivity of the Pika (Ochotona rufescens rufescens) to selected drugs

A collaborative study was conducted to investigate the teratological susceptibility of the Pika (Ochotona rufescens rufescens) to selected teratogenic chemicals: cyclophosphamide, 6-mercaptopurine, 5-fluorouracil, 6-aminonicotinamide, actinomycin D, ethylurethan, ampicillin, tetracycline, thalidomide, diphenylhydantoin, hypervitaminosis A, aspirin, dexamethasone, betamethasone and bredinin. Some of the chemicals were shown to be teratogenic in the Pika, but this animal was generally more resistant to their teratogenicity than the rabbit and rodents. In the Pika, thalidomide did not induce any typical limb defects, which have been produced in the rabbit. Pikas reproduce well and appear to have no substantial disadvantages as an animal species for teratological studies. Thus, the Pika may be useful as a new non-rodent species for teratological testings.     

Immunohistochemical localization of anterior pituitary hormones in S-100 protein-positive cells in the rat pituitary gland

In the anterior and intermediate lobes of the rat pituitary gland, non-hormone-producing cells that express S-100 protein coexist with various types of hormone-producing cells and are believed to function as phagocytes, supporting and paracrine-controlling cells of hormone-producing cells and stem cells, among other functions; however, their cytological characteristics are not yet fully understood. Using a transgenic rat that expresses green fluorescent protein under the promoter of the S100β protein gene, we immunohistochemically detected expression of the luteinizing hormone, thyroid-stimulating hormone, prolactin, growth hormone and proopiomelanocortin by S-100 protein-positive cells located between clusters of hormone-producing cells in the intermediate lobe. These findings lend support to the hypothesis that S-100 protein-positive cells are capable of differentiating into hormone-producing cells in the adult rat pituitary gland.     

Genetic structure and differentiation of four populations of Afghan Pika (Ochotona rufescens) in Iran based on mitochondrial cytochrome b gene

The population genetics of the Afghan Pika (Ochotona rufescens) was studied in Northern Khorasan Province, Iran. For prediction of the genetic differentiation of four populations, the DNA of mitochondrial cytochrome b of 32 individuals from four areas was sequenced and a Bayesian analysis based on the HKY model was constructed. In total, 15 polymorphic sites, 1125 conserved sites (98.7%) and 14 different haplotypes were found. The phylogenetic tree resulting from the Bayesian analysis and network analysis showed that all samples were clustered in two major groups and the haplotypes of the four populations did not separate geographically. An analysis of molecular variance (AMOVA) indicated that a large majority of the genetic variance was due to the variance within populations. The results of fixation indices showed significant genetic structure among populations in both methods. The pairwise F_st revealed that two northern populations have a significant genetic differentiation from two southern populations, but no significance pairwise F_st value was demonstrated between the closed populations. Nei's genetic distances between closed populations were not significant, while significant values occurred between distant populations. It seems that there is not a major discontinuity between populations of Afghan Pika based on cyt-b mitochondrial gene. However, phylogenetic analysis did not separate populations and a large majority of the genetic variance was found within populations. However, AMOVA analysis showed a significant level of genetic structure among populations (p?<?0.001) and between groups (p?<?0.5). It seems that these results suggest shallow genetic differentiation between populations of different geographic groups.     

The steppe pika Ochotona pusilla in Britain, and a new northerly record

The known localities for steppe pika Ochotona pusilla, which occurred in Britain during Late Pleistocene times, are reviewed. A previously misidentified lower jaw, from Helsfell Cave in the Lake District, Cumbria extends the known range of this species in Britain 100 km further north.