Intrauterine embryo reduction in the mare

The site of a hypothesized embryo reduction mechanism was studied. The number of normal-sized embryos and undersized embryos (>2 standard deviations below the mean embryo diameter in control mares) was determined at day 7 and 11 post-ovulation in single-ovulating control mares and in multiple-ovulating pituitary extract-treated mares in which all ovulations occurred on a single day. In two additional groups (control and treated), the embryonal enlargement was monitored by rectal palpation until day 49. An average of 0.7 normal-sized embryos per control mare at day 7 and at day 11 and 0.6 vesicles per control mare at day 49 was found. More normal-sized embryos (P<0.05) were recovered per extract-treated mare at day 7 (2.9 embryos/mare) than at day 11 (0.7), and fewer undersized embryos per extract-treated mare (P<0.05) were recovered at day 7 (0.1) than at day 11 (1.1). The total number of embryos (normal-sized plus undersized) per treated mare was greater (P<0.05) at day 7 and at day 11 than the number of palpated vesicles per treated mare at day 49. The number of mares with more than one normal-sized embryo in the day 7 treated group (10/14) was greater (P<0.05) than in the day 11 treated group (1/14) and was greater than the number of mares with more than one palpated vesicle in the day 49 treated group (2/14). Intrauterine reduction was therefore manifested between days 7 and 11 in multiple-ovulating mares, as demonstrated by the number of multiple normal-sized blastocysts recovered at day 7 and by the reduced number of normal-sized and the increased number of undersized blastocysts recovered at day 11.     

Sex differences in bone resorption in the mouse femur

Summary In male and female dd-mice at 4, 7, and 14 weeks of age and in 7 and 14-week-old mice gonadectomized at 4 weeks of age, the number of osteoclasts and the number and size of bone resorption areas along the surface of bone trabeculae in the distal metaphysis of the femur were determined. Osteoclasts were counted at the light-microscopic level in paraffin sections of decalcified femora. The number and size of the bone resorption areas were examined by scanning electron microscopy of femora after removing organic material by means of KOH and NaOCl treatment. In untreated mice, the number of osteoclasts and the number and size of bone resorption areas showed no sex differences at 4 weeks of age but were larger in females than males at 7 and 14 weeks of age. In gonadectomized mice, the number of osteoclasts and the bone resorption areas increased in males and decreased in females. The results of the gonadectomy experiments suggest that bone resorption in young adult mice is stimulated by female sex hormone and inhibited by male sex hormone.     

Hormone-sensitive stages in the sexual differentiation of laryngeal muscle fiber number in Xenopus laevis

The number of muscle fibers in the vocal organ of the adult male African clawed frog, Xenopus laevis, exceeds that of adult females. This sex difference is the result of rapid fiber addition in males between the end of metamorphosis, post-metamorphic stage 0 (PM0) and PM2. At PM0, male and female frogs have similar numbers of laryngeal muscle fibers. Males then add more muscle fibers than females and achieve an adult value that is 1.7 times the female number. Males castrated at PM0 have the same fiber number as females. Ovariectomy at PM0 does not alter muscle fiber addition in females. Gonadectomy at PM2 has no effect on fiber addition in either sex. Females attain masculine muscle fiber number if their ovaries are replaced with a testis at metamorphosis. Exogenous testosterone treatment at PM0 significantly increases fiber number in females but not in males. Exogenous testosterone given at PM2 has no effect on fiber number in females but decreases fiber number in males. We conclude that the testes are necessary for the marked addition of laryngeal muscle fibers seen in male X. laevis between PM0 and PM2. The masculine pattern of muscle fiber addition can be induced in females provided with a testis. Androgen secretion from the testes most probably accounts for masculinization of laryngeal muscle fiber number. After PM2, androgens are no longer necessary for muscle fiber addition and cannot increase fiber number in females.     

Poleward force at the kinetochore in metaphase depends on the number of kinetochore microtubules

To examine the dependence of poleward force at a kinetochore on the number of kinetochore microtubules (kMTs), we altered the normal balance in the number of microtubules at opposing homologous kinetochores in meiosis I grasshopper spermatocytes at metaphase with a focused laser microbeam. Observations were made with light and electron microscopy. Irradiations that partially damaged one homologous kinetochore caused the bivalent chromosome to shift to a new equilibrium position closer to the pole to which the unirradiated kinetochore was tethered; the greater the dose of irradiation, the farther the chromosome moved. The number of kMTs on the irradiated kinetochore decreased with severity of irradiation, while the number of kMTs on the unirradiated kinetochore remained constant and independent of chromosome-to-pole distance. Assuming a balance of forces on the chromosome at congression equilibrium, our results demonstrate that the net poleward force on a chromosome depends on the number of kMTs and the distance from the pole. In contrast, the velocity of chromosome movement showed little dependence on the number of kMTs. Possible mechanisms which explain the relationship between the poleward force at a kinetochore, the number of kinetochore microtubules, and the lengths of the kinetochore fibers at congression equilibrium include a "traction fiber model" in which poleward force producers are distributed along the length of the kinetochore fibers, or a "kinetochore motor-polar ejection model" in which force producers located at or near the kinetochore pull the chromosomes poleward along the kMTs and against an ejection force that is produced by the polar microtubule array and increases in strength toward the pole.     

Effects of thyroid state alterations in ovo on the plasma levels of thyroid hormones and on the populations of fibers in the plantaris muscle of male and female chickens.

Propylthiouracil (PTU), thyroxine (T4) or thyreoliberin (TRH) were injected in ovo to modify the thyroid state of chicken embryos. Significant sexual differences were observed in the effects of these treatments on the plasma concentrations of thyroid hormones and on plantaris muscle characteristics (DNA, RNA, populations of muscle fibers) in 3- and 35-day old male and female chickens. The T4 plasma concentration is lower in control males; it is decreased in PTU treated females and in the T4 treated females at 35 days. The T3 plasma concentration is lowered at 3 days in all treated chickens and also at 35 days in the TRH treated animals. The slow (STnO) and the fast (FTOG) fibers of the plantaris are always more numerous in males. In controls, the number of FTOG fibers remains steady between 3 and 35 days; at the same time, the number of STnO fibers rises in males only. Both PTU and T4 treatments increase the number of the FTOG and the STnO fibers respectively before and after the 3rd day. TRH treatment increases the number of STnO fibers at 3 and 35 days in males, but reduces it at 3 days in females. Thus changes in the number of FTOG fibers can be induced during in ovo myogenesis, whereas the number of STnO fibers may increase after hatching.     

Changes in the protein spectrum of the chick embryo mesonephros and metanephros in the course of development

The protein spectra of two fractions (the soluble and the membrane fraction) of chick embryo kidney homogenates were isolated by electrophoresis on polyacrylamide gels with the aim of detecting the kidney differentiation process at the molecular level and, at the same time, of evaluating similarities in the construction of the mesonephros and metanephros at this level. Corresponding stages of the above two types of kidney were chosen for studying changes in protein structure during differentiation--i.e. the outset of differentiation (the 6-day mesonephros, the 11-day metanephros) and the stage of full maturity (the 14-day mesonephros, the 20-day metanephros). A total of 36 proteins was distinguished. The analysis of the protein spectra showed that the number of proteins changes but slightly during differentiation; the protein composition of the two types of kidney during differentiation altered by 20-35% of the total number of proteins; the similarity of the protein composition of the corresponding stages of mesonephros and metanephros, expressed as the proportion of the number of identical proteins, was greater than the mutual similarity of different developmental stages of the same type of kidney. The percentage of different proteins at corresponding stages of the kidneys varied from 5% to 23% of the total number of proteins detected.     

Nycthemeral variations of mitotic activity in the adrenal cortex of the rat]

Working on histologic sections 7 microns thick in the equatorial part of male rat adrenal cortex, we found two high mitotic activity periods. The first one stays at midnight and shows an average number of 42 mitoses per section; the second one occurs at 5 a.m. with an average number of mitoses of 70,1 per section. If we except these particular points, the mitotic activity is low, the average number of mitoses being 13,2 per section.     

Number of dictyosomes in a single cell of the green algaMicrasterias

The numbers of dictyosomes in cells ofM. crux-melitensis andM. pinnatifida were counted at various stages in the cell cycle. Dictyosomes synchronously doubled in number by dividing at the premitotic stage and then were separated into two groups by the septum, thus reducing the dictyosomal number to the ordinal number in each new cell. The number remained the same throughout the cell cycle until the next premitotic stage.     

An anchorage-dependent locus in the cell cycle for the growth of 3T3 cells

Mouse fibroblasts, 3T3 cells, require a solid surface for continuous growth, but when 3T3 cells, during their exponential phase in Petri dishes, were transferred to a suspension culture, the number of cells roughly doubled by 30 h. During the suspension culture the number of pairing cells (c₂) increased, but that of the single cells decreased. When cells synchronized at mitosis or at the G1-S boundary were transferred to the suspension culture, the number of pairing cells peaked at 30 min and at 10 h, respectively. DNA synthesis began immediately after the cells, which were cultured for 16 h in the suspension, had settled onto the surface of the Petri dishes. When cells in a confluent culture were arrested at an early G1 period and were suspended, the number of pairing cells did not increase. These results indicate that the most important locus for anchorage growth seems to be at a late G1 period of the cell cycle.     

Bloodsucking midges from the nests of birds in the foothills of Western Sikhote-Alin

The specific composition and number of midges in nest biotopes of birds of forest formations of Western Sikhote-Alin are given. 17 species of the genus Culicoides were found to attack 17 species of birds during the nesting period. The number of midges in nests depends both on the biotopical distribution of nests and mode of living of birds and on the total number of midges in nature. The most high percentage of females engorged with blood at nests was recorded in the obsoletus group, which is most abundant on man and at nests of birds of anthropogenic complex.     

The effect of corticosteroids on dendritic development in the rat brain

Sprague-Dawley rats were given 0.02 ml of methylprednisolone (0.06 g/g body wt) 6, 9, or 12 days postnatally. When compared with saline-treated controls, the following effects on dendritic development in layers 3 and 5 of the parietal cortex were observed: (1) no significant alteration in number of basal dendrites; (2) initial increase (at 3 wk of age) in branchings near the perikaryon in the group treated at 12 days; (3) decrease in number of branches at distances ≥270 μm from the perikaryon in layers 3 and 5 in all steroid-treated groups when sacrificed at 6 wk; (4) decrease in number of intersections in layer 5 in all steroid-treated groups when sacrificed at 6 wk; and (5) decrease in number of terminations in layers 3 and 5 in all steroid-treated groups when sacrificed at 6 wk.     

Ultracentrifugation in the Concentration and Detection of Enteroviruses

Ultracentrifugation has been evaluated as a method of concentrating enteroviruses from suspensions whose initial titers ranged from 1.7 × 10⁸ to 1.6 × 10^-2 plaque-forming units (PFU) per ml. A technique employing a “trap” of 0.1 ml of 2% gelatin solution at the point at which the pellet forms in tubes for the number 30 and number 50 rotors of the Spinco model L preparative ultracentrifuge has been tested and found to have a number of advantages. Qualitative studies have been performed to determine the sensitivity of the ultracentrifuge technique in detecting the presence of enteroviruses in very dilute suspensions. There was found to be at least a 50% probability of detecting virus present initially at levels as low as 0.12 PFU per ml by means of the number 50 rotor. The input level for similar results with the number 30 rotor was found to be 0.025 PFU per ml.     

Diurnal variations in the photoreceptor synaptic terminals of the newt retina

Newt photoreceptor synaptic terminals undergo a variety of morphological changes over a 24-hr (LD 12:12) cycle. During the day, dense-cored synaptic vesicles were found to increase in number and accumulate near the synaptic lamellae; during the dark phase, the dense-cored vesicles decreased in number, while large clear vesicles and profiles of smooth endoplasmic reticulum increased in frequency. The most marked change in photoreceptor synaptic terminal morphology occurred after 10 hr of darkness, at 0730 hr. At this time, photoreceptor synaptic terminal cross-sectional area was found to increase dramatically. Morphometric analysis showed that the number of synaptic vesicles in these terminals remained constant throughout the day, as did the perimeter of photoreceptor terminal profiles. The observed increase in area of synaptic terminals at 0730 hr was found to be due to a decrease in the folding of the terminal plasma membrane. Qualitative observations showed endocytosis to be occurring at a rapid rate at this time as well; and since the number of synaptic vesicles and terminal perimeter did not change, exocytosis of synaptic vesicles was assumed to be occurring at an equally rapid rate. These findings support an extension to the hypothesis of Monaghan and Osborne (1975), suggesting that photoreceptor synaptic vesicles become "supercharged" with transmitter substance in the light.     

Plasticity of reproductive traits responding to variation in light availability at the rosette stage of the first year in a strict biennial,Pedicularis torta,from a field on the Qinghai–Tibet Plateau,China

Light is a fundamental heterogeneous environmental factor for plants and often varies at both spatial and temporal scales. In the present study, we carried out a shading experiment to investigate the effect of variable light availability at the rosette stage of the first year in the strict biennial species Pedicularis torta (an endemic species of the Qinghai‐Tibet Plateau) on reproductive traits (i.e. total number of flowers per plant, total number of fruits per plant/total number of flowers per plant, the number of seeds per fruit, mean individual seed mass and estimation of the total number of seeds per plant, plant size at maturity in the second year and on the relationships between reproductive traits and plant size at this stage). We found that light availability affected most of the reproductive traits (except for mean individual seed mass), plant size at maturity in the second year, and the relationship between the total number of flowers per plant and plant size at this stage. Our results indicate that reproductive traits respond to changes in light availability during the rosette plant stage.     

Heliogeophysical correlates of early biodemographic variables in the south of western Siberia

In order to verify associations between solar and geomagnetic activities and perinatal variables the monthly distributions of population characters in Novosibirsk region over the period 1980-2001 were compared by stepwise correlation analysis with monthly averaged physical parameters at lags from 0 to 10 months. Three indices used were as follows: the number of sunspots, solar flux at 10.7 cm wavelength and Ak index measured at local ionospheric station near Novosibirsk city. Official data on the number of single and multiple live births, stillbirths and infant deaths at the age under one year by the type of population and sex were provided by State Statistical Committee. All three physical parameters positively correlated with the number of single births and infant mortality rate and negatively with twin births in both populations, urban and rural, irrespective of lags. The direct association between Ak index and relative number of stillbirths in urban setting was mostly pronounced at a lag of 5 months. The number of live births increased along with Ak index due to the enhanced proportion of female births whereas the number of stillbirths after the increase in solar and geomagnetic activities elevated because of male deaths.     

Distribution of Spermatozoa in the Genital Tract of Artificially Inseminated Heifers

Eight heifers were artificially inseminated in the uterine body with 160×106 spermatozoa frozen in French mini-straws. The heifers were slaughtered 2 (n = 4) or 12 (n = 4) h after insemination and spermatozoa were recovered by flushing defined segments of the reproductive tract. The efficiency of the method was checked in different ways. There was a slight underestimation of the number of recovered spermatozoa. This underestimation was randomly distributed among heifers and genital tract segments. The total number of spermatozoa recovered was higher at 2 than at 12 h (14.6 vs 0.6 % of the total number inseminated). Most spermatozoa were found in the vagina both at 2 and 12 h after insemination and in greater number at 2 h. In uterus there was a slight decline in the number of spermatozoa recovered at 2 versus 12 h after insemination. The number of spermatozoa recovered from the oviducts were similar at 2 (89.6 × 103) and 12 h (71.5 × 103) after insemination. At 2 h spermatozoa were found in all parts of the oviduct with the majority located in the utero tubal junction, whereas at 12 h the most were recovered from isthmus. More spermatozoa were recovered from the left than from the right side of the tract in 6 of the 8 heifers. Only in 1 heifer were the majority of spermatozoa found in the oviduct ipsilateral to the follicle bearing ovary.     

双季稻区两类生境稻田节肢动物群落结构比较

用吸虫器采样法,对双季稻区中处于多样化生境及单一生境中的两类稻田中的节肢动物群落结构特征进行了比较研究。结果表明：在早稻生长发育初期和晚稻生长全期,多样化生境稻田中捕食性节肢动物的物种数和个体数量都显著高于单一化生境稻田。同时,多样化生境中稻田植食性昆虫的物种丰富度高于单一化生境稻田,但其个体数量较低。非稻田生境主要作为稻田捕食性节肢动物群落的种库,能促进稻田捕食性节肢动物群落的重建。     

24-hour recording in personnel employed in the intensive cardiac care unit]

The authors, expecting confirmation of arrhythmogenic effects of work at the Intensive Cardiological Care Unit (ICCU), recorded a 24-hour ECG in the employed staff. Together 20 healthy individuals (mean age 31.6 years) were tested. ECG was recorded twice at the unit, and repeated at home. Ventricular arrhythmia was noted in 60% of tested individuals at home (mean number of excitations 6 per 24 hours). It was 2.5 times more frequent at ICCU (mean number of excitations 15 per 24 hours) involving 75% of tested individuals. Atrial arrhythmia was noted also in 60% of the tested individuals at home (mean number 16 per 24 hours) whereas it was noted in 85% of the tested individuals at ICCU, i.e. 2.5 times more frequently than at home (mean value 40/24 hours). Both atrial and ventricular arrhythmias are significantly more frequent during night rest at ICCU than that at home. Results suggest that the employment at ICCU is arrhythmogenic.     

Age-related alteration of taste bud distribution in the common marmoset

Alteration in the number of taste buds on the soft palate (SP), fungiform (FF), foliate (FL) and circumvallate (CV) papillae in the common marmoset at different postnatal ages was examined histologically. After paraffin embedding, complete serial sections at 10 microm thickness were made and stained by HE. Digitized images for each section were examined carefully. The number of FF taste buds at day 1 was 334. While only 20% of all the taste buds at birth possessed a taste pore, 39% of 174 SP taste buds at day 1 possessed a taste pore. The number of taste buds with pores at day 1 was small for the center CV (19 of 59), one side CV (7 of 25), and one side FL (2 of 16). These results suggest that the functional maturation of SP taste buds may precede maturation in other areas of the tongue. The total number of taste buds increased with increasing age, reached a maximum at 2 months of age: FF, 1069; SP, 609; CV-center, 530; CV-side, 390; FL, 201, and decreased thereafter. Almost all taste buds possessed a taste pore after 2 months of age. The decrease in the number of taste buds in the oral cavity with increase in age may change taste sensitivity.     

Competition and fruit set in the Washington navel orange

In the Washington navel orange [ Citrus sinensis (L.) Osbeck] an increase in the number of flowers results in a reduction of flower weight at anthesis and the initial fruit growth rate, and the number of developing fruitlets increases. Most of these fruitlets are shed during post-anthesis, and the final set of fruit is unrelated to the number of flowers and to the total amount of metabolites and mineral elements used up in fructification but appears to be controlled by the capacity of the tree to supply metabolites to the developing fruitlets during post-anthesis. When the number of flowers is too large, there is a reduction both in the number of initially developing fruitlets and in their growth rate. The final set of fruit is reduced through a different mechanism acting at anthesis and involving differences in mineral composition, which impairs the capacity of the fruit to act as a sink.