逐日羽化的赤眼蜂品质的比较

本文报道了逐日羽化的赤眼蜂(Trichogramma maidis Pint.et Voeg)品质的比较结果.第1天羽化的雌蜂是群体中生活力最强的个体;第2和第3天羽化的雌蜂生殖力、寿命、个体大小和性比等4项指标逐渐下降;而第4天羽化的雌蜂质量最差.当逐日(第1—第4天)羽化的赤限蜂先分别用地中海粉斑螟卵繁殖1代,然后分别收集第1天内羽化的赤眼蜂试验时,子代(F₁)雌蜂的质量有了明显的提高.母代为第3和第4天羽化的赤限蜂,其子代雌蜂的质量分别超过母代.试验表明,通过实验室选择培养可以改进和提高大量培养赤眼蜂的质量.     

Data entry on a computer terminal: repetitive work strains on the oculomotor and central nervous systems

Continuous telemetric recordings including E.K.G., E.O.G., and E.E.G. were carried out on two subjects during 4 working days: 1 day of "reference work" or classical clerical activities, 3 days of "data entry work". Although the time allowed for the task was not limited, the performance assessed from oculomotor patterns remained stable throughout the day, from one day to the next and from one subject to another. This stability was reflected on the stereotyped E.E.G. patterns recorded during the work period, the differences occurring between reading and typing were more acute in the left cortical hemisphere than in the right. As a result of these stable patterns, the ultradian oscillations of the behavioural and physiological parameters were less during data entry than during work reference. The only possible time adjustments were the interruptions or breaks between two document pages and their variations could be considered as indicators of work load.     

The effect of experience on the hunting success of newly emerged spiderlings

Initial interactions with prey may affect a predator's subsequent foraging success. With experience, second-instar Misumena vatia spiderlings (Thomisidae) that had recently emerged from their egg sacs oriented faster to fruit flies (Drosophila melanogaster) than n?ive individuals. Orientation time of these spiderlings decreased rapidly for the first two to three runs (every third day) in a simple laboratory setting, and then remained low and relatively constant. Time to capture a fly also declined initially, but subsequently became extremely variable, increasing prior to moult. Increase in capture time and the failure to capture prey appeared associated with impending moult, rather than satiation. Spiderlings oriented to prey more rapidly at the beginning of the third instar than at the start of the second instar, suggesting that experience still enhanced performance after a moult cycle. Overall capture times at the beginning of the third instar decreased from those at the end of the second instar, but did not differ significantly from the beginning of the second instar, although spiderlings gaining the most biomass had the shortest mean capture times. In a second experiment, time to orient and time to capture prey did not differ in n?ive, second-instar siblings run 1 and 3 days after emergence from their egg sacs. However, 3-day individuals that had captured prey each day (confiscated before they could feed) oriented faster than n?ive 3-day-old siblings, but did not differ in the time taken to capture prey. Experience, rather than age or energetic condition, best explains these changes in performance. Copyright 2000 The Association for the Study of Animal Behaviour.     

Plasma catecholamines and pituitary adrenal hormones in response to noise exposure

To evaluate the immediate effect of exposure to a high level of noise on the sympatho-adrenal and pituitary-adrenal systems, measurements were made of circulating catecholamines, growth hormone, ACTH, and cortisol in seven normal male subjects. They were studied on two random experimental days: a control day and a noise-exposure day with an intermittent noise alternating between 99 dB (A) and 45 dB (A) for 2 h. Analysis did not reveal any variation in the plasma levels of norepinephrine (NE), epinephrine (E) or dopamine (D), measured every 20 min, which might have been related to noise exposure. Similarly, analysis of the 2-h urine samples collected from 8 a.m. to 2 p.m. revealed no significant changes in urinary catecholamine excretion. Plasma levels of GH and ACTH did not differ significantly from those for control days, but cortisol showed a brief, significant levelling-off in its pattern during the exposure period. The data demonstrate that exposure to a high level of noise, although considered as "unpleasant", does not induce any important endocrinological changes in man. These conclusions differ from those for studies on animals where reactions to noise may be related to a more general stressing situation.     

Further assessments of the relationship between jet lag and some of its symptoms

The disruption of circadian rhythms following time-zone transitions gives rise to the syndrome of jet lag. The power of some of the symptoms of jet lag to predict the amount of jet lag measured at the same and at different times of the day has been investigated. Eleven healthy subjects were studied in an Isolation Unit for two days after a simulated flight from the UK to Beijing (8 time zones to the east). At six time-points (08:30, 11:00, 14:00, 17:00, 20:00, and 23:00 h), the subjects recorded their jet lag, and the differences from "normal" (that is, from days in which there is no jet lag) of alertness, hunger, indigestion, concentration, motivation, and irritability. They recorded at 08:30 h the type of food they had eaten since rising at 08:00h and, at the other times, the type of food eaten in the last three hours. Assessments were made by visual analogue scales or, in the case of type of food, by a nominal scale. Following the time-zone transition, the adjustment of meals appeared to be complete almost immediately. Jet lag and its symptoms were present during both experimental days. Jet lag tended to rise during the course of the daytime, accompanied by falls in alertness, motivation, and concentration. Correlation matrices between jet lag and each of the other variables were produced, using lags between the variable (from up to 5 time-points before the assessment of jet lag to 5 time-points afterwards) and pooling the results from both days. These matrices indicated that significant correlations existed only between jet lag and alertness, concentration, and motivation, and then only when these other variables were assessed at the same time as jet lag or 1 or 2 time-points earlier. Jet lag was then treated as the dependent variable and the symptoms as covariates in analysis of covariances (ANCOVAs), with the days treated as a random effect. This analysis enabled the significance of potential predictors of jet lag, together with their beta-coefficients (the relationship between a unit change of each significant predictor and the change in jet lag), to be calculated. Falls in alertness and motivation were significant predictors of increased jet lag, provided that they were measured at the same time, when they accounted for about 50% of the jet lag; when measured at other time-points, they did not act as significant predictors. It is concluded that the amount of jet lag varies during the course of the day and that it can be predicted from contemporaneous assessments of alertness and motivation-but not from assessments made at other times of the day, nor from other variables that are symptoms of jet lag, even though these other variables are significantly increased. In considering the results of this and our previous study, we reiterate the view that the exact meaning of "jet lag" is complex and that the particular combination of factors that contribute to it might vary with the time of day that the assessment is made. Inferences about any decrements due to time-zone transitions cannot be made reliably at times of the day that differ from the time when jet lag is assessed.     

Stand characteristics of ozone-stressed populations of Pinus jeffreyi (Pinaceae): extent,development, and physiological consequences of visible injury

The development and physiological consequences of ozone-induced visible injury was investigated in native populations of Jeffrey pine (Pinus jeffreyi) that were exposed to chronic levels of anthropogenic ozone. Stand structure analyses demonstrated that the expression of visible ozone injury symptoms within self-regenerating populations of Jeffrey pine was highly variable. Of the 975 trees surveyed, 90% exhibited some degree of visible injury and 10% were classified as resistant to ozone. Needles of the most sensitive trees developed a chlorotic mottle characteristic of ozone injury 1 year after their initiation and prematurely abscised in their third year (normal needle retention is 5–6 years). Average needle retention was not different between diameter size categories but was the most variable within the smallest size category and the least variable in the largest size category. Gas exchange measurements indicated a negative correlation between photosynthetic rate and needle surface area covered by chlorotic mottle. Chlorophyll fluorescence kinetics of the current-year needles did not differ between symptomatic and asymptomatic trees but did differ between the oldest needles, suggesting an uncontrolled physiological decline in needles about to abscise in sensitive trees. The high degree of variability of ozone-induced visible injury coupled with the reduction of physiological capacity associated with visible injury suggest that mixed conifer forests growing in polluted regions could potentially undergo shifts in community structure if sensitive Jeffrey pine individuals were to experience differential mortality as a result of ozone exposure. Intraspecific variation in ozone sensitivity may potentially lead to increased population tolerance to oxidative air pollutants, but long-term population analyses will be required to address genetic changes in response to ozone stress.     

Advanced monitoring of high-rate anaerobic reactors through quantitative image analysis of granular sludge and multivariate statistical analysis

Four organic loading disturbances were performed in lab-scale EGSB reactors fed with ethanol. In load disturbance 1 (LD1) and 2 (LD2), the organic loading rate (OLR) was increased between 5 and 18.5 kg COD m(-3) day(-1), through the influent ethanol concentration increase, and the hydraulic retention time decrease from 7.8 to 2.5 h, respectively. Load disturbances 3 (LD3) and 4 (LD4) were applied by increasing the OLR to 50 kg COD m(-3) day(-1) during 3 days and 16 days, respectively. The granular sludge morphology was quantified by image analysis and was related to the reactor performance, including effluent volatile suspended solids, indicator of washout events. In general, it was observed the selective washout of filamentous forms associated to granules erosion/fragmentation and to a decrease in the specific acetoclastic activity. These phenomena induced the transitory deterioration of reactor performance in LD2, LD3, and LD4, but not in LD1. Extending the exposure time in LD4 promoted acetogenesis inhibition after 144 h. The application of Principal Components Analysis determined a latent variable that encompasses a weighted sum of performance, physiological and morphological information. This new variable was highly sensitive to reactor efficiency deterioration, enclosing variations between 27% and 268% in the first hours of disturbances. The high loadings raised by image analysis parameters, especially filaments length per aggregates area (LfA), revealed that morphological changes of granular sludge, should be considered to monitor and control load disturbances in high rate anaerobic (granular) sludge bed digesters.     

Comparison of the egg flotation and egg candling techniques for estimating incubation day of Canada Goose nests

ABSTRACT Both egg flotation and egg candling have been used to estimate incubation day (often termed nest age) in nesting birds, but little is known about the relative accuracy of these two techniques. We used both egg flotation and egg candling to estimate incubation day for Canada Geese (Branta canadensis interior) nesting near Cape Churchill, Manitoba, from 2000 to 2007. We modeled variation in the difference between estimates of incubation day using each technique as a function of true incubation day, as well as, variation in error rates with each technique as a function of the true incubation day. We also evaluated the effect of error in the estimated incubation day on estimates of daily survival rate (DSR) and nest success using simulations. The mean difference between concurrent estimates of incubation day based on egg flotation minus egg candling at the same nest was 0.85 ± 0.06 (SE) days. The positive difference in favor of egg flotation and the magnitude of the difference in estimates of incubation day did not vary as a function of true incubation day. Overall, both egg flotation and egg candling overestimated incubation day early in incubation and underestimated incubation day later in incubation. The average difference between true hatch date and estimated hatch date did not differ from zero ( days) for egg flotation, but egg candling overestimated true hatch date by about 1 d (true – estimated; days). Our simulations suggested that error associated with estimating the incubation day of nests and subsequently exposure days using either egg candling or egg flotation would have minimal effects on estimates of DSR and nest success. Although egg flotation was slightly less biased, both methods provided comparable and accurate estimates of incubation day and subsequent estimates of hatch date and nest success throughout the entire incubation period.     

Club Cell-16 and RelB as Novel Determinants of Arterial Stiffness in Exacerbating COPD Patients

Background

Exacerbations of chronic obstructive pulmonary disease (COPD) are acute events of worsened respiratory symptoms that may increase the risk of cardiovascular disease (CVD), a leading cause of mortality amongst COPD patients. The utility of lung-specific inflammatory mediators such as club cell protein-16 (CC-16) and surfactant protein D (SPD) and that of a novel marker of CV outcomes in COPD- RelB- in predicting adverse cardiovascular events during exacerbation is not known.

Methods

Thirty-eight subjects with COPD admitted to the hospital for severe exacerbation were included in this analysis. Clinical, physiological and arterial stiffness measurements were performed within 72 hours of admission; this was followed by measurements taken every 3 days until hospital discharge, then once a week until 30 days after discharge, and then again at 90 and 180 days. Plasma concentrations of inflammatory mediators were measured from peripheral venous blood taken at admission, and at days 15, 30, 90 and 180.

Results

CC-16 and RelB concentrations were increased at day 15 of exacerbations whereas SPD concentrations were decreased. The course of change in CC-16 and RelB levels over time was inversely associated with that of carotid-femoral pulse wave velocity, the gold-standard measure of arterial stiffness. Increases in CC-16 could predict a decreased number of subsequent exacerbations during follow-up.

Conclusions

Lung-specific (CC-16) and novel (RelB) biomarkers are associated with systemic cardiovascular changes over time. CC-16 can predict subsequent exacerbations in subjects with severe COPD and may be an important biomarker of pulmonary and systemic stress in COPD.     

The advantage of the aggregate culture of isolated ovarian cell types over the monolayer culture

Ovarian cells such as theca interna, granulosa and corpus luteum cells were isolated from pig ovaries and cultured in Erlenmayer flasks (25 ml) containing 3.5 ml of culture medium. The media were replaced every second day and frozen to -20°C for later steroid analysis. The reaggregation of cells was completed within 2–3 days and this was then followed by a period of cell migration. During the subsequent 5–6 day period the reaggregates became larger. The best results were obtained in cultures of isolated theca alone and in combination with granulosa cells, as well as of early corpus luteum cells. Granulosa cells did not aggregate as easily or as completely as the corpus luteum cells. All types of cells investigated were able to secrete progesterone into the culture medium. They secreted more progesterone and for a longer time than cells cultured as monolayers. The aggregate culture seems to be a good model to study the secretion of ovarian cells, by creating the tri-dimensional, and thus more physiological, culture system.     

Genetic and environmental influences on short-day responsiveness in Siberian hamsters (Phodopus sungorus)

Siberian hamsters are photoperiodic rodents that typically exhibit several physiological changes when exposed to a short-day photoperiod. However, development of the winter phenotype in short days is largely conditional on prior photoperiod history: Hamsters that have been reared in an exceptionally long day length (18 L) do not usually exhibit the winter phenotype after transfer to short days, whereas animals reared under "moderately" long days (16 L) are more variable in responsiveness to subsequent short-day exposure, with 20% to 30% generally failing to exhibit winter-type responses. Hamsters reared exclusively in an "intermediate" day length (14 L) are almost uniformly responsive to short photoperiod. In the present study, the authors examine the influence of photoperiod history on short-day responsiveness in a breeding line of hamsters that has been subjected to artificial selection for resistance to the effects of short days. The results demonstrate that photoperiod history is an important determinant of short-day responsiveness in both random-bred (UNS) hamsters and animals artificially selected and bred for nonresponsiveness to short photoperiod (PNR). The PNR hamsters have a reduced requirement for long-day exposure to evoke a state of unresponsiveness to short days. The results are discussed in relation to possible significance for the origin of population and species differences in photoperiod responsiveness.     

Robustness of neuroprosthetic decoding algorithms

We assessed the ability of two algorithms to predict hand kinematics from neural activity as a function of the amount of data used to determine the algorithm parameters. Using chronically implanted intracortical arrays, single- and multineuron discharge was recorded during trained step tracking and slow continuous tracking tasks in macaque monkeys. The effect of increasing the amount of data used to build a neural decoding model on the ability of that model to predict hand kinematics accurately was examined. We evaluated how well a maximum-likelihood model classified discrete reaching directions and how well a linear filter model reconstructed continuous hand positions over time within and across days. For each of these two models we asked two questions: (1) How does classification performance change as the amount of data the model is built upon increases? (2) How does varying the time interval between the data used to build the model and the data used to test the model affect reconstruction? Less than 1 min of data for the discrete task (8 to 13 neurons) and less than 3 min (8 to 18 neurons) for the continuous task were required to build optimal models. Optimal performance was defined by a cost function we derived that reflects both the ability of the model to predict kinematics accurately and the cost of taking more time to build such models. For both the maximum-likelihood classifier and the linear filter model, increasing the duration between the time of building and testing the model within a day did not cause any significant trend of degradation or improvement in performance. Linear filters built on one day and tested on neural data on a subsequent day generated error-measure distributions that were not significantly different from those generated when the linear filters were tested on neural data from the initial day (p<0.05, Kolmogorov-Smirnov test). These data show that only a small amount of data from a limited number of cortical neurons appears to be necessary to construct robust models to predict kinematic parameters for the subsequent hours. Motor-control signals derived from neurons in motor cortex can be reliably acquired for use in neural prosthetic devices. Adequate decoding models can be built rapidly from small numbers of cells and maintained with daily calibration sessions.     

Hyperammonemia induces polymerization of brain tubulin

Rats were made hyperammonemic by feeding them a diet containing ammonium acetate. The tubulin content in their brain increased 30% after 20 days on the diet. All the increase was found in polymerized tubulin; no increase in free tubulin was noted. When rats on the ammonium diet were then fed the standard diet, the tubulin increased slightly on the first day but decreased markedly on the second day, reaching control values on the third day. It should be noted that brain tubulin synthesis, was not reduced on the first day of feeding the standard diet but was markedly inhibited (to 40% of control) on the second day, returning to control values on the third day. On the first day of refeeding there is a remarkable disassembly of microtubules with a large, proportional increase (50%) of free tubulin. Both free and polymerized tubulin levels returned to control values on the third day. These results indicate that in hyperammonemia changes in the degree of polymerization of tubulin preceded those in tubulin synthesis.     

Day-to-day variation in nitrogenase activity of Alnus incana explained by weather variables: a multivariate time series analysis

A modelling system is described that indicates the extent to which day-to-day variations in nitrogenase activity in young Alnus incana (L.) Moench, grown in defined conditions in the field, may be affected by weather conditions both during and prior to the day of measurement. Nitrogenase activity (acetylene reduction activity, ARA) was measured weekly on intact field-grown grey alder (A. incana) plants, 0.15–0.42 m tall at planting, nodulated with Frankia. The measurements were done at noon on two groups of plants in 1987 and on two other groups in 1988. Each group was made up of five or six plants. Seven weather variables: daily sunshine hours, daily mean, maximum and minimum air temperature, daily mean and 1300 h relative humidity, and daily rainfall were used. The relation between log(ARA/leaf area) and the weather variables were analysed using a PLS model (partial least squares projection to latent structures). The advantage of PLS is that it can handle x-variables that are correlated. Data from 1987 were chosen as a training set. Multivariate PLS time series analysis was made by adding, in a stepwise manner, the weather data up to 5 d before the day of measurement. This procedure gave six models with n * 7 x-variables (n= 1–6). With the models from the time series analysis of 1987 data, true predictions of ARA per leaf area were made from weather data 1988 (test set 1) and from ‘early-season’ weather data from 1987 and 1988 (test set 2). The variation in ARA/leaf area could be predicted from the weather conditions. The predictions of the two test sets improved when the weather conditions one and two days before the day of measurements were added to the model. The further addition of weather data from 3 to 5 d before the day of measurement did not improve the model. The good predictions of ARA/leaf area show that the alders responded to the variable weather conditions in the same way in 1988 as in 1987, despite the ten-fold difference in size (leaf area) at the end of the growing season. Among the weather variables, air temperature and the daily sunshine hours were positively correlated to ARA, while relative air humidity and rainfall were negatively correlated to ARA. The daily minimum temperature and rainfall appeared to have least impact on ARA. By use of PLS, we could extract information out of a data set containing highly correlated x-variables, information that is non-accessible with conventional statistical tools such as multiple regression. When making measurements of nitrogenase activities under field conditions, we propose that attention should be paid to the weather conditions on the days preceding the day of measurement. The day-to-day variation in nitrogenase activity is discussed with reference to known effects of stress factors under controlled conditions.     

苦瓜采后某些生理生化变化与其衰败的关系

对采后常温贮藏的蓝山大白苦瓜的呼吸速率、乙烯释放速率及SOD、POD、CAT活性和AsA、GSH的含量进行了测定。结果表明,适期采收的食用苦瓜呼吸速率呈下降趋势,第8天叶绿素消失、瓜皮转黄前后转为上升,一直延续至苦瓜衰败,其呼吸类型属晚峰型;苦瓜采后乙烯释放呈上升趋势,初期乙烯释放微弱,增加缓慢,从第6天开始急剧增加。乙烯释放速率上升早于呼吸上升,二者在采收6d后迅速同步上升。苦瓜采后1～4d,保护酶系统的SOD、POD、CAT活性出现适应性上升,非保护酶系统的AsA、GSH含量也上升;在4～8d,除POD活性迅速下降后又急剧上升及AsA含量在6d后下降外,SOD、CAT活性和GSH含量均稳中有降,保持相对稳定;在叶绿素消失、瓜皮转黄的第8天后,AsA、GSH含量急剧减少,而SOD、POD、CAT活性急剧增强,视为衰老迅速恶化的结果。     

Factors affecting walking activity at estrus during postpartum period and subsequent fertility in dairy cows

The postpartum period is critical for efficient reproduction, and certain features of the normal estrus cycle during this period have been associated with subsequent reproductive performance. The objectives of the present investigation were to evaluate the effects of environmental, production, and reproductive factors on walking activity at estrus as determined using pedometers during the first 50 days in milk (DIM) (study 1). In a second study, we tried to establish whether pedometer measurements recorded during this period could be used to predict subsequent fertility by considering the number of cows becoming pregnant before 90 DIM. We analyzed data derived from 995 parturitions in a single herd. Detection of estrus was performed using a pedometer system. Variables were screened for associations with walking activity by analysis of variance (ANOVA) through generalized linear model procedures (PROC GLM). Increased milk production and parity, and a mean relative humidity (RH) higher than 95% were associated with lower pedometer measurements. A higher number of animals simultaneously in estrus rendered higher pedometer readings. No significant effects of the year, season, DIM, number of previous estruses, and climatic data other than high mean RH were observed. Relationships between pedometer measurements and other variables recorded during the first 50 days postpartum, and subsequent fertility were assessed by applying logistic regression models. We detected no significant effects of year, milk production, season, and mean activity increase at estrus on high fertility. The likelihood of pregnancy before 90 DIM decreased for each additional lactation and for cows in anestrus between days 0 and 50 postpartum. However, pedometer readings during the first 50 days postpartum were unable to accurately predict subsequent fertility.     

"Stationary phase aging" of cell culture: an attempt of evaluation of growth medium "age" effect

Cell proliferation rate and 3H-thymidine labeling index of "young" (i. e. harvested in 3 days after subcultivation) cultured Chinese hamster cells (B11 dii-FAF28 line) have been determined in growth medium conditioned by the same cells for various periods of time during their growth and subsequent "stationary phase aging" (medium of different "age"). Cells were serially cultured in Eagle's medium with 10 % bovine serum. The experiment was conducted as follows. The "young" cells were seeded in Carrel's flasks (4500 cells/cm2) with fresh growth medium and placed at 37 degreesC. At definite time intervals, media from 3 randomly selected flasks were filtrated and stored in small glass flasks at 4 degreesC. The cells from all 3 flasks were collected by trypsin treatment and counted with hemocytometer. During the period of 26 day cultivation we collected a set of media of different "age" corresponding to certain points of the growth and "stationary phase aging" curve of the culture. Then, the "young" cells in fresh medium were seeded into tissue culture plates with cover slips placed into wells of the plates (26,600 cells/cm2) and grown at 37degreesC, 5 % CO2 for 2 h. At this point, the medium was replaced with media of different "age". 22 h later (i. e. on the first day after seeding) cell density was evaluated microscopically in all the wells. On the next day (i. e. in 2 days after seeding) 3H-thymidine was added to every well to final concentration 1.85 x 10(4) Bq/ml. After next 24 h (i. e. in 3 days after seeding) cell density was counted again, and the medium was removed. The cover slips were rinsed with Hank's solution and air-dried. Autoradiography was performed in standard manner by photoemulsion exposing for 5 days and subsequent developing in amidol developer. The relative number of nuclei with 10 and more "grains" was revealed microscopically. Based on the obtained results, two basic parameters were evaluated for every "age" medium: 1) cell proliferation activity index calculated as log2 (N3/N1), where N1 - cell density on the first day after seeding, and N3 - the same parameter on the third day after seeding; 2) cell labeling index calculated as percentage of cells with nuclei labeled by 3H-thymidine during incubation from 2nd to 3rd day of cultivation. These two indexes for cell growth in different "age" media appeared to be highly correlating (R = 0.85). Besides, it was found that the observed "age-related" diminishing of ability of the growth media of different "age" to stimulate proliferation of "young" cells cannot completely explain the "stationary phase aging" phenomenon (in particular, even for the "oldest" medium cell labeling index was 65 %). We conclude that the phenomenon is based on exactly intrinsic changes of cells, most likely on molecular level, though environmental effects cannot be entirely excluded. The authors are grateful to the Russian Basic Research Foundation for support (grants 03-04-49030 and 00-04-48049).     

Absence of direct effects of prostaglandins on rabbit blastocysts in vitro

A total of 27 monkeys (M. Fascicularis) whose control cycle lengths ranged from 28 to 32 days were used in this study. All the treatments described below started either on day 17 or 18 of the cycle. Six monkeys received daily injections of 20 μg estradiol-17β (E₂) for 5 consecutive days. Although a drop in blood progesterone (P) did occur due to this treatment, no shortening of the luteal phase of the cycle was recorded. Seven monkeys received daily injections of 15 mg PGF_2α (prostaglandin-F_2α) for 4 or 5 days. These monkeys also showed a drop in blood P levels; moreover 5 of these monkeys had vaginal bleeding for 2–3 days starting either on day 19 or 20 of the cycle. This bleeding did not appear to be a normal physiological menstrual flow, since all of the monkeys commenced menstrual flow at the expected time. Four monkeys received daily injections of 10 mg P for 3 days. These monkeys also had normal cycle lengths in spite of the treatment. Finally 9 monkeys received daily injections of 20 μg E₂ for 3 days, and starting on the third day of E₂ treatment these monkeys also received injections of 15 mg PGF_2α for 4 or 5 days. Shortened cycle lengths were recorded in 8/9 monkeys in this group. Six monkeys had 22-day cycles, 2 monkeys had 24-day cycles and the remaining monkey had a cycle length of 26 days. Thus 8/9 monkeys had shortened luteal phases due to sequential treatment of E₂ and PGF_2α. The cycle lengths in all the treatment groups were normal subsequent to treatments. These results provide potentially useful information for further studies in the human as a method of contraception.     

Synthesis and oligonucleotide incorporation of fluorescent cytosine analogue tC: a promising nucleic acid probe

The tricyclic cytosine, tC, is a fluorescent base analogue with excellent properties for investigating intrinsic characteristics of nucleic acid as well as interactions between nucleic acids and other molecules. Its unique fluorescence properties and insignificant influence on overall structure and dynamics of nucleic acid after incorporation makes tC particularly interesting in fluorescence resonance energy transfer and anisotropy measurements. We here describe a straightforward synthesis of the standard monomer form of tC for DNA solid-phase synthesis, the tC phosphoramidite, and its subsequent incorporation into oligonucleotides. The total synthesis of the tC phosphoramidite takes approximately 8 days and its incorporation and the subsequent oligonucleotide purification an additional day.     

The influence of electric field exposure on bone growth and fracture repair in rats

Rats were exposed to a 60-Hz electric field at an unperturbed field strength of 100 kV/m to determine its affect on bone growth and fracture repair. Exposure of immature male and female rats for 20 h/day for 30 days did not alter growth rate, cortical bone area, or medullary cavity area of the tibia. In another experiment, midfibular osteotomies were performed and the juvenile rats were exposed at 100 kV/m for 14 days. Evaluation by resistance to deformation and breaking strength indicated that fracture repair was not as advanced in the exposed animals as in the sham-exposed animals. In another experiment measurements of resistance to deformation were made in adult rats at 16, 20, and 26 days after osteotomy. Fracture repair was slower in exposed compared to control animals at day 20 and, to a lesser extent, at day 16, but not at day 26.