Hair cell regeneration in the chick inner ear following acoustic trauma: ultrastructural and immunohistochemical studies

The regeneration of hair cells in the chick inner ear following acoustic trauma was examined using transmission electron microscopy. In addition, the localization of proliferation cell nuclear antigen (PCNA) and basic fibroblast growth factor (b-FGF) was demonstrated immunohistochemically. The auditory sensory epithelium of the normal chick consists of short and tall hair cells and supporting cells. Immediately after noise exposure to a 1500-Hz pure tone at a sound pressure level of 120 decibels for 48 h, all the short hair cells disappeared in the middle region of the auditory epithelium. Twelve hours to 1 day after exposure, mitotic cells, binucleate cells and PCNA-positive supporting cells were observed, and b-FGF immunoreactivity was shown in the supporting cells and glial cells near the habenula perforata. Spindle-shaped hair cells with immature stereocilia and a kinocilium appeared 3 days after exposure; these cells had synaptic connections with the newly developed nerve endings. The spindle-shaped hair cell is considered to be a transitional cell in the lineage of the supporting cell to the mature short hair cell. These results indicate that, after acoustic trauma, the supporting cells divide and differentiate into new short hair cells via spindle-shaped hair cells. Furthermore, it is suggested that b-FGF is related to the proliferation of the supporting cells and the extension of the nerve fibers.     

Experimental analyses of the rearrangement of ectodermal cells during gastrulation and neurulation in avian embryos

The rearrangement of ectodermal cells was studied in chimeras in which grafts were transplanted during late gastrula and early neurula stages to heterotopic locations in avian embryos. Three types of experiments were done. In all experiments, Hensen's node was extirpated completely and replaced with an epithelial plug derived from 1 of 3 regions of the prospective ectoderm. In type-1 experiments, Hensen's node was replaced with a plug consisting of precursor cells of the floor plate of the neural tube. In type-2 experiments, Hensen's node was replaced with a plug consisting of precursor cells of the lateral wall of the neural tube. In type-3 experiments, Hensen's node was replaced with a plug consisting of precursor cells of the epidermal ectoderm. In all experiments, the amount and direction of cell rearrangement that occurred in the transplanted ectodermal plug was essentially typical for prospective ectodermal cells normally residing within Hensen's node. That is, transplanted ectodermal cells underwent lateralto-medial cell-cell intercalation and contributed to the ventral midline of the neural tube along its entire rostrocaudal extent. In most embryos, a notochord was reconstituted from host cells, despite the fact that Hensen's node — the prime source of prospective notochordal cells in intact embryos — was extirpated completely; however, a few embryos had long notochordal gaps. In such essentially notochordless embryos, the ventral midline of the neural tube still derived from grafted cells, but it failed to form a floor plate, providing further confirmation of the results of several previous studies that the notochord is required to induce the floor plate. Collectively, our results provide evidence that the rearrangement of ectodermal cells does not require the presence of a trail of prospective floor plate cells (laid down by the regressing Hensen's node), or of a notochordal substrate, and that the continued presence of an organizer per se, ostensibly Hensen's node, is not required. In addition, our results demonstrate that the rearrangement of cells still occurs in the absence of boundaries between ectodermal cells of different phenotypes (e.g., between cells of the floor plate and lateral walls of the neural tube). Finally, our results reveal further that the amount and direction of cellular rearrangement is not regulated in a cell-autonomous fashion, but rather it is determined by the overall magnitude and vector of the displacement of the community of rearranging cells within a developmental field.     

我国家居蜚蠊细菌的研究

从我国不同地区的147头家居蜚蠊中分离获得562株细菌分属于13个属,其优势菌群属于埃希氏菌属、芽抱杆菌属、短杆菌属共422株菌,占总菌数的75．09％;其次为沙雷氏菌属、假单胞菌属共85株,占总数的15．12％;其他8个属仅43株菌,占总数的9．25％。比较了德国小蠊、美洲大蠊和黑胸大蠊及它们的体表、体腔、中肠和粪便所携带的细菌类群和数量,其结果有很大差异。该文讨论了蜚蠊细菌与人类疾病之间的关系。     

Immunohistochemical localization of iodopsin in the retina of the chicken and Japanese quail

Summary Localization of iodopsin in the retina of the chicken and Japanese quail was investigated immunohistochemically with the use of monoclonal antibodies (R1-R4) highly specific for R-photopsin (protein moiety of iodopsin). In paraffin sections of the retina, the outer segments of double cones (principal and accessory cones) and of one particular type of single cones were labeled with the antibodies. In addition, reticular cytoplasmic structures, probably representing the Golgi apparatus in a position close to the vitreous pole of the paraboloid and to the outer limiting membrane were intensely stained in the cone cells bearing an immunoreactive outer segment. In whole-mount preparations, 5 types of cone cells were identified according to the color of oil droplets, i.e., red, yellow, pale-green (principal member of double cones), pale-blue and clear, in addition to a sixth type devoid of an oil droplet (accessory member of double cones). The immunohistochemical analysis of the preparations revealed that R-photopsin (suggesting the presence of iodopsin) is localized in the outer segments of both the principal and accessory members of double cones, and the population of single cones displaying a red oil droplet. Other cones endowed with a yellow, blue or clear oil droplet were not labeled with the antibodies used. Similar results were obtained in the retina of the Japanese quail.     

The ultrastructure of the intestinal nerve of Remak in the domestic fowl

Summary An ultrastructural study was made of the neurons, satellite cells and vesiculated axons of the intestinal nerve of the domestic fowl. Broad membrane-to-membrane contacts between adjacent nerve cell bodies were sometimes observed. The cell bodies and processes were not always separated from the extracellular space by a capsule of satellite cells. Following fixation using potassium permanganate, catecholamine (CA)-containing neurons in the intestinal nerve, unlike those in the lumbar parasympathetic ganglia, did not possess any small granular vesicles (SGV). Following exposure to noradrenaline, SGV could be demonstrated in the cell bodies of the juxta-ileal ganglia but not the juxta-rectal ganglia of the intestinal nerve. Non-CA axons were examined in tissue from birds that had been pretreated with 6-hydroxydopamine. Approximately one half of the non-CA axons formed axo-somatic contacts. Most of the non-CA axons contained varying proportions of small clear vesicles, large clear vesicles and large granular vescles. Statistical analysis showed that the non-CA axons could not be subdivided according to their vesicle content. CA-axons contained many SGV and were found in close apposition to neuronal somata and processes, and in the neuropil.     

An attempt at genetic transformation in chickens through cock sperm irradiation

Summary Two experiments were conducted to verify the real possibility for use of the genetic transformation technique as described by Pandey and Patchel in chickens in commercial poultry breeding. Multiple recessive and multiple dominant marker stocks were employed, as well as a tester and a donor line. Recipient tester females were first inseminated with dominant donor semen which was irradiated with doses of ⁶⁰Co gamma irradiation ranging from 100 to 800 Gy (control group) and 24 h later were reinseminated with unirradiated, normal semen of the recipient strain (experimental group). One genetic transformed chicken was found in the first experiment; no genetic transformed event occurred in the second experiment but one embryo was present in the 600 Gy irradiated group with parthenogenetic development capable of giving a live chick. One hundred Gy was observed not to be enough to destroy completely sperm fertilizing ability. An increased frequency of parthenogenetic development was found in all groups after insemination with irradiated semen. There were 11 individuals with developmental abnormalities from the total of 1264 analysed embryos which died after the 18th day of incubation. We concluded that egg transformation is a rare event in domestic fowl and further research for use of this technique in commercial poultry breeding is needed.     

Immunogold identification of the somatotrophs of domestic fowl of different ages

Summary The somatotrophs of the pituitary gland of the male domestic fowl were identified by means of an immuno-electron-microscopic method based on gold as the electron-opaque label and an antibody to growth hormone. Gold particles indicating sites of growth hormone were restricted to cells in which virtually all of the granules were labelled. Little, if any, gold label was found outside the granules in these cells designated as somatotrophs, or at sites outside these cells. The size of these gold-labelled secretory granules presumed to contain growth hormone decreased with age, from a mean sectional diameter of 256±6.2 nm (SEM) at 4–6 weeks to 221±5.7 nm at 11–18 weeks and 205±8.6 nm at 24–30 weeks of age. On the basis of these values for mean sectional diameters the change between the first two periods represents a decrease in granule volume of about 36%. However, during the same period the growth hormone concentration of the granules increased. Accordingly, growth hormone content per granule changed little if at all. In contrast, from 11–18 weeks to 24–30 weeks of age there was a decrease of 31% in growth hormone content per granule. These data indicate that growth hormone packaging in the chicken somatotroph changes with age. The first change results in the production of smaller granules of higher growth hormone concentration. During this period growth hormone content per granule remains relatively constant. The later change results in the production of granules of lower growth hormone content than that of younger animals.This is a paper of the Journal Sciences, New Jersey Agriculture Experimental Station supported in part by the State and Hatch Act Funds and a grant from the National Science Foundation (PMC-8022727)     

Investigation of wild boar (Sus scrofa) for porcine reproductive and respiratory syndrome in some territories of Russia

Samples of blood sera and internal organs were collected from 90 shot wild boars (Sus scrofa) in five regions of Russian Federation. Blood sera were tested for antibodies against porcine reproductive and respiratory syndrome virus (PRRSV) using enzyme-linked immunosorbent assay (ELISA). In addition, samples of internal organs (lungs, lymph nodes, spleen) were tested by polymerase chain reaction (nested PCR) for PRRSV antigen. The result of our investigation showed that all samples were negative. However, PRRSV is widespread in domestic swine throughout Russia including the examined regions. Since the results show the absence of PRRSV infection in wild boars in the five examined regions of Russia, wild boars seem not to play any role in the epidemiology of PRRSV in Russia.     

Assessing the impact of fostering on children’s outcomes in Niger

This article measures the impact of fostering on children’s outcomes in Niger. We estimate a simultaneous equations model with three outcomes for children (school attendance, hours of market work and hours of domestic work) and a treatment variable (fostering). Nonlinearity provides identification by functional form of the causal effect of fostering. We further use information on the historical level of community integration of the child’s ethnicity and the relative importance of the ethnicity in the neighborhood to build a plausibly exogenous exclusion restriction in order to correct for the potential endogeneity of fostering. Our results sustain the overall conclusion that fostering has a positive impact on children’s school attendance and hours of domestic work. However, while foster boys and girls are both engaged in longer hours of domestic labor, only foster boys are advantaged in terms of schooling.