Postnatal development of the Mongolian gerbil uterus

The postnatal development of the gerbil uterus has been investigated. Special attention has been paid to the luminal surface epithelium. In the newborn gerbil, the uterus contains already some fluid and the uterine luminal epithelium seems to possess mechanisms for the regulation of the fluid contents. Among them are apical protrusions and microvilli, endo- and exocytotic vesicles of different nature, highly active Golgi complexes and dilated rER vesicles and also very distinct junctional complexes between the cells in the apical areas.     

Postnatal development of the testis in the Mongolian gerbil, Meriones unguiculatus

The testicular development in gerbils was studied over 16-week periods starting from birth. Testicular weight and seminiferous tubule diameter increased considerably between 1 and 11 weeks of age. At 16 weeks the testicular weight was about 540 mg. Spermatogenesis commenced at about 2 weeks when mitoses first appeared in spermatogonia. Spermatozoa appeared in a few of the seminiferous tubules by 7 weeks and consistently so in all of the tubules at 10 weeks. Epididymal spermatozoa appeared first in the cauda epididymis at 10 weeks and were consistently present at 12 weeks. Formation of mature Leydig cells with a grouped perivascular arrangement appeared by 3 weeks and continuously so thereafter. From these results, it is evident that the male Mongolian gerbil is almost sexually matured by 10 to 12 weeks of age.     

Postnatal development of GABA- and glycine-like immunoreactivity in the cochlear nucleus of the Mongolian gerbil (Meriones unguiculatus)

The maturation of the morphological substrate for inhibitory interactions was investigated in the cochlear nucleus of the gerbil with immunocytochemistry for gamma aminobutyric acid (GABA) and glycine on alternating vibratome sections. The patterns of immunostaining obtained with both antibodies in the adult closely conformed to the general mammalian scheme. Qualitative analyses revealed an age-related increase in staining intensity and in the relative numbers of immunolabelled cells after birth up to the age of 3–4 weeks. As early as birth and in all subdivisions of the cochlear nucleus, a few labelled cells and puncta in the sections were stained either with the GABA or the glycine antibody. Immunoreactive puncta and cells were, however, far less abundant than in the adult, and the staining intensity of cells was only weak. The most strikingly GABA-immunolabelled cells at birth were the Golgi cells of the granule-cell domains. The numbers of weakly GABA- and glycine-immunostained cells of the dorsal cochlear nucleus clearly increased between birth and the third postnatal week. At approximately the onset of hearing (postnatal day 12–14), some cells of the dorsal cochlear nucleus and small cells of the ventral cochlear nucleus gained adult-like GABA-staining properties. Almost adult-like labelling intensity was observed in glycine-immunoreactive cells of the deep dorsal cochlear nucleus and in some small cells of the ventral cochlear nucleus. Puncta staining to both antibodies appeared adult-like throughout the cochlear nucleus. About 2 weeks after the onset of hearing (at the latest), adult-like staining of all subsets of immunoreactive cells occurred throughout the cochlear nucleus in all specimens. Received: 25 March 1997 / Accepted: 15 March 1998     

长爪沙鼠资源开发利用进展

长爪沙鼠是源于我国的＂多功能＂实验动物资源,在某些研究领域发挥重要作用。随着研究深入,越来越多的长爪沙鼠生物学特性将被发现,这些将使长爪沙鼠资源利用更加多元化。本文对长爪沙鼠的开发研究历程及在分类学、寄生虫学、脑缺血、脂质代谢、神经性疾病和肿瘤学等研究中的应用作简要概述。     

Postnatal development of glial fibrillary acidic protein (GFAP) immunoreactivity in pituicytes and tanycytes of the Mongolian gerbil (Meriones unguiculatus)

The postnatal development (day of birth up to the end of the third month) of neurohypophyseal pituicytes and tanycytes of the median eminence (ME) and the medial basal hypothalamus (MBH) was studied immunohistochemically in the Mongolian gerbil (Meriones unguiculatus) with antibodies directed against glial fibrillary acidic protein (GFAP; the major protein subunit of glial filaments). Weak GFAP-immunoreactivity (IR) was scattered in the neural lobe (NL), the ME and the lining of the ventral 3rd ventricle at the first postnatal days. By the end of the second postnatal week, the intensity of the IR had reached a level comparable to that of adult animals. Generally, in the whole neurohypophysis a cytoarchitectonic pattern, which essentially corresponded to adult conditions, was reached around the beginning of the second month. During the first week postnatum, solely perinuclear stainings, mostly unipolar pituicytes with short processes and isolated fibers were discernible in the NL. In the course of the second and third postnatal week, a growing number of the densely arranged pituicytes appeared in form of bi- and multipolar cells. Thickness and length of pituicyte processes, as well as their degree of branching, increased progressively in the first month. The number of GFAP-positive tanycytes in the ventral 3rd ventricle and in the ME most markedly augmented in the first week postnatum. In the MBH, long tanycyte processes emerged from the ventricular lining to cross the arcuate nucleus in large bows, delimiting groups of neurons. Ependymal and subependymal tanycytes in the ME gave rise to radial processes extending to the external zone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Postnatal development of glial fibrillary acidic protein (GFAP) immunoreactivity in pituicytes and tanycytes of the Mongolian gerbil (Meriones unguiculatus)

Summary The postnatal development (day of birth up to the end of the third month) of neurohypophyseal pituicytes and tanycytes of the median eminence (ME) and the medial basal hypothalamus (MBH) was studied immunohistochemically in the Mongolian gerbil (meriones unguiculatus) with antibodies directed against glial fibrillary acidic protein (GFAP; the major protein subunit of glial filaments). Weak GFAP-immunoreactivity (IR) was scattered in the neural lobe (NL), the ME and the lining of the ventral 3rd ventricle at the first postnatal days. By the end of the second postnatal week, the intensity of the IR had reached a level comparable to that of adult animals. Generally, in the whole neurohypophysis a cytoarchitectonic pattern, which essentially corresponded to adult conditions, was reached around the beginning of the second month. During the first week postnatum, solely perinuclear stainings, mostly unipolar pituicytes with short processes and isolated fibers were discernible in the NL. In the course of the second and third postnatal week, a growing number of the densely arranged pituicytes appeared in form of bi- and multipolar cells. Thickness and length of pituicyte processes, as well as their degree of branching, increased progressively in the first month. The number of GFAP-positive tanycytes in the ventral 3rd ventricle and in the ME most markedly augmented in the first week postnatum. In the MBH, long tanycyte processes emerged from the ventricular lining to cross the arcuate nucleus in large bows, delimiting groups of neurons. Ependymal and subependymal tanycytes in the ME gave rise to radial processes extending to the external zone. Moreover, in this zone several tanycyte-like cells, whose number increased considerably in the second postnatal week, contributed to the palisadal arrangement of glial processes. In the third month, the arcuate nucleus was still penetrated by many immunopositive tanycyte processes. It was characteristic of the adult staining pattern that the highly branched processes of tanycytes and tanycyte-like cells in the ME were thicker and more variable in size than the less densely arranged tanycyte processes of the MBH. The postnatal increase of GFAP-IR intensity was paralleled by a similar development of vasopressin-IR in the ME and NL, indicating that the maturation of neurohypophyseal glia is closely linked to the functional differentiation of the neurosecretory axons.     

The development,inhibition and disinhibition of pup-cannibalism in the Mongolian gerbil

The responses of juvenile and adult gerbils towards newborn test pups were investigated. Young animals of both sexes are less likely to attack the test pup than are older animals. Mature females are more likely to attempt to cannibalize pups than are mature males. Attempted cannibalism by adult males is inhibited when their mate becomes pregnant. If the pregnant female is removed from the cage for one to three days, however, attempted cannibalism is disinhibited. On the other hand, males which have reared a previous litter will not harm test pups when the female is removed. Experience of a pregnant female and of young pups during the pre-weaning stage does not influence the incidence of attempted cannibalism in adulthood. These data suggest that gerbils take full advantage of changing social conditions.     

Social organization in the Mongolian gerbil

The Mongolian gerbil (Meriones unguiculatus) has a social system based on an adult male and female and their juvenile and infant offspring. The adult male and juveniles, as well as the adult female, interact with the infants. This species is active during the day and the night thus making it ideal for observational studies on social behaviour, particularly in relation to the rearing of the infants. Several factors are considered each of which may influence the maternal behaviour and the behavioural and physical development of the young. These factors may be varied in simple experiments which are suitable for school projects.     

Pair formation in the Mongolian gerbil

This report describes the initial phase of social organization in Mongolian gerbils, Meriones unguiculatus, in large outdoor enclosures. These conditions offer a comparatively free choice for the establishment of bonds and social structure. In five replicate 20-day studies, the only social unit that formed was the male-female pair. The order of events was related to four sequential 5-day periods: (I) males established territories by male-male competition (1st to 2nd period); (II) females visited more than one male initially (1st and 2nd period), but developed a preference for one male or territory (3rd to 4th period); (III) as the females developed a preference, they also challenged other females having a preference for the same male or territory (approximately the 3rd period); (IV) as one female became locally dominant, some territorial males started chasing all but the dominant female. Males remained more active in territorial defence throughout the study. The defence became more intense as the females became strongly attached to one male and/or territory only. However females, after having established themselves in one particular male territory, spent significantly less time in the preferred area during the day of oestrus compared with the days before and after. Copulatory behaviour patterns, where observed, did not occur exclusively in interactions between territorial mates.     

Further studies on Capillaria philippinensis: development of the parasite in the Mongolian gerbil

Capillaria philippinensis larvae from the digestive tract of a Northern Luzon freshwater fish (Hypselotris bipartita) experimentally exposed to embryonated eggs, were given by stomach tube to Mongolian gerbils (Meriones unguiculatus). The larvae developed into adults within 10 to 11 days and female worms produced larvae within 13 to 14 days. These larvae developed into second generation adults by days 22 to 24 and the second generation females produced eggs that were present in the feces of the animal on the average 26 days after infection. Most females were oviparous but a few larviparous females were always present. The gerbils died on an average of 46 days after infection, with the highest numbers of worms recovered between days 36 and 46. All stages of the parasite were generally found at necropsy. Gerbils developed patent infections after receiving 2 or 3 laeval from fish, and 852 to 5,353 worms were recovered at necropsy. These studies show that autoinfection in an integral part of the life cycle of C. philippinensis, both initially and in maintaining the infection. The natural transmission of the parasite was demonstrated when H. bipartita from a lagoon in the endemic area were fed to gerbils and 3 became infected. The parasite can also be maintained in the laboratory by transfer of worms by stomach tube from the small intestines of an infected gerbil to a clean gerbil.     

Postnatal development of uterine response to estradiol-17β in the rat

The gradual acquisition of uterine responsiveness to a single injection of estradiol-17β was studied in rats aged 5–30 days with respect to wet weight and the content of DNA, RNA, and protein. No significant response in any of these parameters was found in 5- or 10-day-old rats. In 15- and 20-day-old rats all the parameters, except DNA content, were elevated by the hormone treatment; only in 30-day-old rats was there a significant increase in DNA content.     

Postnatal development of vagina, clitoris and urethral glands of the golden hamster

We have made a histological study of the postnatal development of the clitoris, preputial glands, urethral glands and vagina of the golden hamster. The 'phallic groove' of the clitoris is closed at 10 days of life, then the urethra has a cuboidal stratified, a stratified squamous and a stratified keratinized epithelium. The preputial glands are composed of branched saccular glands. These glands develop, with few changes during their maturation period. Formation of the urethral glands begins at 5 days and the alveoli are fully developed at puberty. The hamster vagina has two origins; the upper part is Müllerian, the caudal part is sinusal. The wall of the Müllerian vagina has a cylindrical epithelium at birth, which becomes 'double epithelium' at puberty and thereafter changes cyclically in connection with the estrous cycle. The sinusal vagina is solid at birth, its lumen being formed in the first 10 days of life and its wall having a cuboidal stratified epithelium. At 15 days it becomes a stratified keratinized epithelium, which will later line the vaginal pouch. At the 5th day, an ectodermic invagination (stratified keratinized epithelium) is observed in the zone of the future introitus. At the time of vaginal opening this zone forms the distal segment.     

Paternal and maternal behaviour in the Mongolian gerbil

Twenty-seven pairs of Mongolian gerbils (Meriones unguiculatus) were observed rearing fifty-five litters in undisturbed conditions. Parental activities were performed by both parents. Males spent more time in the nest but females showed more sniffing and licking of pups and nest building. There was no difference between the parents in the amount of body contact with the pups. The frequency of occurrence of each of these activities changed with the age of the pups. These and other measures of behaviour are discussed in relation to the changing stimulation from the young and the willingness of the female to allow the male to interact with the litter.