Competition in utero between twin lambs

1956 ◽  
Vol 48 (2) ◽  
pp. 245-249 ◽  
Author(s):  
H. P. Donald ◽  
A. F. Purser
Keyword(s):  
Sex Differences ◽  
Birth Weight ◽  
Sex Difference ◽  
In Utero ◽  
Sex Distribution ◽  
Sources Of Variation ◽  
Males And Females ◽  
Limited Supply ◽  
Image Position

1. The weights at birth of 822 pairs of twin lambs have been studied with respect to the differences between males and females. Data were obtained during five lambing seasons from various breeds and crosses in five flocks.2. The sex distribution of twin pairs came close to the ratio .3. Analyses made within season and within the major breed categories showed that sex differences were small relative to other sources of variation, but that there was a significant effect of sex of co-twin on birth weight. The following average differences were found (the sex of co-twin being indicated in brackets):These differences had an average S.E. of 0·078 lb. (Table 3). The sex difference in litters of mixed sex was twice as large as that obtained from like-sexed litters.4. The data for particular flocks and seasons suggest that in addition to these average effects, there may be some interaction between sex and breed or season which can cause deviations from the averages.5. These results are interpreted to mean that there is competition between twins for some element of growth in limited supply; and that in twins of mixed sex, the result tends to favour the male.

Abstract 302: Sex Differences In Nonlinear Dynamics And Their Circadian Variation In Control Dogs And In A New Arrhythmogenic Canine Model Of Heart Failure

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Yujie Zhu ◽  
Steven M Pogwizd
Keyword(s):  
Nonlinear Dynamics ◽  
Heart Failure ◽  
Sex Differences ◽  
Sex Difference ◽  
Circadian Variation ◽  
Holter Monitoring ◽  
Canine Model ◽  
Nonlinear Parameters ◽  
Arrhythmogenic Substrate ◽  
Males And Females

Introduction: Females can be more arrhythmogenic than males, and this sex difference can persist with development of chronic heart failure (CHF). The aim of this study was to investigate sex differences in the arrhythmogenic substrate in control dogs and in a new arrhythmogenic canine model of CHF. Methods: CHF was induced in 30 dogs by aortic insufficiency and aortic constriction. Holter monitoring assessed VT and PVCs from 30 dogs, as well as traditional HRV measures and nonlinear dynamics (including correlation dimension (CD), detrended fluctuations analysis α1 (DFAα1), and Shannon entropy (SE)) at baseline, 240 days (240d) and 720 days (720d) after CHF induction. Results: At baseline, females had lower LF/HF (0.27±0.03 vs 0.33±0.02, p=0.04), CD (1.60±0.17 vs 2.21±0.15, p=0.01), DFAα1 (0.62±0.03 vs 0.72±0.03, p=0.03), and SE (2.99±0.02 vs 3.10±0.03, p=0.03 vs males). Females lacked circadian variation in LF/HF, DFAα1, and SE while males had circadian variation in all of these. Of 11 dogs with frequent runs of VT and PVCs, 95% and 91% of total VT runs and total PVCs, respectively, were in females. With CHF, all these linear and nonlinear parameters progressively declined in males and females. CHF females had less decline in LF/HF than males so that by 720 days there was no more sex difference (0.24±0.06, 0.17±0.03 in females vs 0.22±0.05, 0.18±0.01 in males at 240d, 720d). However, for nonlinear parameters of CD, DFAα1, and SE, CHF females had lower values than males (CD: 1.56±0.21, 0.99±0.32 vs 1.87±0.24, 1.50±0.34; DFAα1: 0.51±0.05, 0.43±0.04 vs 0.54±0.07, 0.48±0.04; and SE 2.93±0.08, 2.76±0.08 vs 3.01±0.11, 2.91±0.04 in females vs males at 240d, 720d). With CHF, circadian variation in CD, DFAα1, and SE were lost in both males and females. Conclusions: There are sex differences in the arrhythmogenic substrate in control dogs and in this new arrhythmogenic canine model of moderate CHF. At baseline, females have lower sympathetic stimulation, reduced cardiac chaos, and loss of circadian variation in nonlinear dynamics. With CHF, sex differences in nonlinear dynamics persist; this reflects a loss of complexity and fractal properties that could contribute to increased arrhythmias in female CHF dogs.

Sex Differences in Recognizing the Correct Answer to a Problem

1965 ◽  
Vol 17 (2) ◽  
pp. 532-534 ◽  
Author(s):  
Ronald J. Burke
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
Correct Answer ◽  
Males And Females

Previous research has shown the superiority of performance of males over that of females in solving Maier's horse trading problem. This investigation represented an attempt to reduce this sex difference by requiring Ss only to recognize the correct answer and its underlying reason. Consistent with earlier findings, 67.4% of the males and 34.2% of the females correctly solved the problem ( p < .01). Comparison with results of Hoffman and Maier (1961) suggests that the modified version of the problem had little effect on the percentage of males and females correctly solving the problem.

Sex differences in the circadian control of hamster wheel-running activity

1983 ◽  
Vol 244 (1) ◽  
pp. R93-R105 ◽  
Author(s):  
F. C. Davis ◽  
J. M. Darrow ◽  
M. Menaker
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
Wheel Running ◽  
Phase Shifts ◽  
Light Cycle ◽  
Dark Cycle ◽  
Running Activity ◽  
Wheel Running Activity ◽  
Activity Onset ◽  
Males And Females

The circadian pacemaker that underlies the wheel-running activity of hamsters was studied in males and females. Sex differences were found in the mechanism by which the pacemaker entrains to light-dark cycles and in the timing of activity onset. When exposed to a light-dark cycle with a period of 24.75 h (with 1 h of light/cycle), males show a greater ability to maintain entrainment than do females. This difference in the upper limit of entrainment appears due to a sex difference in the magnitude of light-induced phase shifts. A small difference in free-running period may also contribute to the sex difference in entrainment. Two weeks after castration of adults, the sex difference in entrainment is not affected, indicating that the difference does not depend on circulating gonadal steroids or on estrous cyclicity of the female. However, castration of females at an early age increases their ability to entrain, whereas long-term castration of males seems to reduce entrainment ability. During entrainment to a 24-h light-dark cycle (LD 14:10), females were found to begin their daily activity before males and before castrated females. This difference is consistent with a sex difference in the magnitude of light-induced phase shifts and in entrainment of the pacemaker. However, evidence is given that the sex difference in activity onset might also be caused by a sex difference in the relationship of locomotor activity to the pacemaker in intact males and females.

Some reflections on sex differences in aggression and violence

1999 ◽  
Vol 22 (2) ◽  
pp. 232-233
Author(s):  
Stephen C. Maxson
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
Evolutionary Explanation ◽  
Men And Women ◽  
Human Aggression ◽  
Intrasexual Aggression ◽  
Males And Females ◽  
Evolutionary Explanations

Four issues relevant to sex differences in human aggression and violence are considered. (1) The motivation for play and serious aggression in children and juvenile animals is different. Consequently, the evolutionary explanations for each may be different. (2) Sex differences in intrasexual aggression may be due to effects of the attacker or the target. There is evidence that both males and females are more physically aggressive against males and less physically aggressive against females. The evolutionary explanation for each component of the sex difference in intrasexual aggression may be different. (3) Aggression and violence are defined. The former is the attack, and the latter is the consequent injury or death. The evolutionary explanation for each may not be the same. (4) Most men and women are neither physically aggressive nor criminally violent. The evolutionary explanations of sex differences in aggression and violence should take this polymorphism into account.

scholarly journals Strategies and Methods for Research on Sex Differences in Brain and Behavior

Endocrinology ◽  
2005 ◽  
Vol 146 (4) ◽  
pp. 1650-1673 ◽  
Author(s):  
Jill B. Becker ◽  
Arthur P. Arnold ◽  
Karen J. Berkley ◽  
Jeffrey D. Blaustein ◽  
Lisa A. Eckel ◽  
...  
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
Disease Susceptibility ◽  
Gonadal Steroids ◽  
Laboratory Animals ◽  
Health And Disease ◽  
Males And Females ◽  
Brain And Behavior ◽  
And Behavior ◽  
Hormonal Condition

Abstract Female and male brains differ. Differences begin early during development due to a combination of genetic and hormonal events and continue throughout the lifespan of an individual. Although researchers from a myriad of disciplines are beginning to appreciate the importance of considering sex differences in the design and interpretation of their studies, this is an area that is full of potential pitfalls. A female’s reproductive status and ovarian cycle have to be taken into account when studying sex differences in health and disease susceptibility, in the pharmacological effects of drugs, and in the study of brain and behavior. To investigate sex differences in brain and behavior there is a logical series of questions that should be answered in a comprehensive investigation of any trait. First, it is important to determine that there is a sex difference in the trait in intact males and females, taking into consideration the reproductive cycle of the female. Then, one must consider whether the sex difference is attributable to the actions of gonadal steroids at the time of testing and/or is sexually differentiated permanently by the action of gonadal steroids during development. To answer these questions requires knowledge of how to assess and/or manipulate the hormonal condition of the subjects in the experiment appropriately. This article describes methods and procedures to assist scientists new to the field in designing and conducting experiments to investigate sex differences in research involving both laboratory animals and humans.

scholarly journals Assessment of Epigenetic Contributions to Sexually-Dimorphic Kiss1 Expression in the Anteroventral Periventricular Nucleus of Mice

Endocrinology ◽  
2012 ◽  
Vol 153 (4) ◽  
pp. 1875-1886 ◽  
Author(s):  
Sheila J. Semaan ◽  
Sangeeta Dhamija ◽  
Joshua Kim ◽  
Eric C. Ku ◽  
Alexander S. Kauffman
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
Cell Number ◽  
Cpg Methylation ◽  
Histone Deacetylation ◽  
Sexually Dimorphic ◽  
Transcriptional Repressors ◽  
Pharmacological Blockade ◽  
In Silico Identification ◽  
Males And Females

The Kiss1 gene, which encodes kisspeptin and is critical for reproduction, is sexually differentiated in the hypothalamic anteroventral periventricular (AVPV)/rostral periventricular (PeN) nuclei. Specifically, female rodents have higher AVPV/PeN Kiss1 expression than males, but how this Kiss1 sex difference is induced in early development is poorly understood. Here, we explored the contribution of epigenetic mechanisms to the establishment of the AVPV/PeN Kiss1 sex difference, focusing on histone deacetylation and DNA methylation. First, we utilized postnatal pharmacological blockade of histone deacetylation and analyzed Kiss1 expression in the AVPV/PeN. Postnatal disruption of histone deacetylase modestly increased AVPV Kiss1 cell number in both sexes but did not alter the Kiss1 sex difference. Next, we assessed whether the level of CpG methylation, which can influence transcription factor binding and gene expression, in the murine Kiss1 gene differs between males and females. We found significant sex differences in methylation at several CpG sites in the putative promoter and first intron of the Kiss1 gene in the AVPV/PeN, but not in the arcuate (which lacks adult Kiss1 sex differences), suggesting that differential methylation of the Kiss1 gene may influence sexually-dimorphic Kiss1 expression in the AVPV/PeN. Transgenic impairment of methyl CpG-binding protein-2 function did not eliminate the Kiss1 sex difference, indicating that other methylation factors are involved. Interestingly, CpG methylation in the AVPV/PeN was lower in males than females, suggesting that transcriptional repressors may contribute to the AVPV/PeN Kiss1 sex difference, a possibility supported by in silico identification of putative repressor binding sites near some of the sexually-dimorphic CpG.

SEX DIFFERENCES IN LENGTH OF GESTATION IN MAMMALS

1956 ◽  
Vol 13 (3) ◽  
pp. 309-318 ◽  
Author(s):  
THOMAS McKEOWN ◽  
BRIAN MacMAHON
Keyword(s):  
Sex Differences ◽  
Guinea Pig ◽  
Sex Difference ◽  
Litter Size ◽  
Alternative Explanation ◽  
Prenatal Growth ◽  
Males And Females ◽  
The Difference ◽  
Duration Of Gestation ◽  
Length Of Gestation

Observations on length of gestation of males and females are presented for man, the guinea-pig, sheep, pig and rabbit; from the literature, data are also available for the cow, horse, camel and goat. Pregnancy is longer for males than for females in the cow, horse and possibly the sheep and camel; it is longer for females than for males in man and possibly the guinea-pig. No definite conclusion is reached about the pig and rabbit, in which litter-size is normally large, or about the goat, in which the number of observations on record is small. The sex differences in length of gestation are reflected in the sex ratios of offspring born after different periods of gestation, and in the percentage distribution of the sexes by duration of gestation. The difference in length of gestation can be attributed to a sex difference in foetal weight in man, but not in the guinea-pig or in species such as the cow, in which gestation is longer for males than for females. It is suggested that in the cow the longer male gestation may be due to the fact that the proportion of males conceived is higher if mating takes place early, rather than late, in heat. (The only alternative explanation is a sex difference, attributable to something other than weight of foetus, in the period between fertilization and birth.) In man the earlier birth of males is apparently due to their greater weight, attributable wholly or in part to a sex difference in rate of prenatal growth. This observation does not exclude the possibility that in man, as in the cow, the proportion of males conceived is higher if mating occurs early in the cycle, since the method of recording length of gestation (from onset of menstruation) gives no information about time of mating.

scholarly journals The effect of body composition on strength and power in male and female students

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Ghassen Ben Mansour ◽  
Asma Kacem ◽  
Mohamed Ishak ◽  
Laurent Grélot ◽  
Foued Ftaiti
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
Body Fat ◽  
Fat Mass ◽  
Maximal Exercise ◽  
Relative Difference ◽  
Female Students ◽  
Male Students ◽  
Jump Test ◽  
Males And Females

Abstract Purpose The aim of this study is to determine and to compare the effect of sex differences in percentage of body fat on the strength and power performances of the legs and arms during short maximal exercise. Methods 72 male and 64 female students aged 20 to 23 years were enrolled in this study. After assessing their morphological characteristics (body mass, height and percentage of fat mass), a squat jump test (SJ), a 5 successive jump test (5JT), a hand gripping (HG) and back strength (BS) tests have been conducted for each subject. Male students were re-tested after being weighed down with a weight equivalent to the mean differences in body fat recorded between the two sexes in the form of a loaded worn vest. Results Male are 15.7% heavier and 7.4% taller and presented a percentage of fat mass (17.2 ± 1.8%) significantly (p < 0.001) lower than that of women subject (25.0 ± 2.5%) (difference male vs female for fat mass: -45.5%). HG, BS, 5JT and SJ performances were significantly higher in males (44 ± 5 kg, 141 ± 2 kg, 11 ± 1 m and 32.4 ± 2,7 cm, respectively) than in females (31.0 ± 4 kg, 81.6 ± 13 kg, 8.7 ± 0.7 m and 21.1 ± 1.9 cm, respectively). In the control (unloaded) condition, the relative difference between males and females represented 23.5% and 34.7% of the male performances for 5JT and SJ, respectively. In the weighted condition, the relative difference between weighted males and females still represented 11.7% and 23.8% of the weighted male performances for 5JT and SJ, respectively. Cancelling the sex difference in fat mass by adding weight in males reduced by 50.1% the sex difference during 5JT and 31.4% and 71.7% for hight and power results, respectively during SJ test. Conclusion During short and maximal exercise, male performed better with their hands, back and legs than female students. Excess fat for female students has a disadvantageous effect on vertical and horizontal jumps performances. The persistence of sex differences after weighting of male students indicates that body fat is responsible for 30 to 70% of the observed differences between sexes performances and power outcomes during jump tests.

scholarly journals Male and female guppies differ in problem-solving abilities

2019 ◽  
Vol 66 (1) ◽  
pp. 83-90 ◽  
Author(s):  
Tyrone Lucon-Xiccato ◽  
Elia Gatto ◽  
Angelo Bisazza
Keyword(s):  
Sex Differences ◽  
Problem Solving ◽  
Sex Difference ◽  
Fish Species ◽  
Teleost Fish ◽  
Food Reward ◽  
Poecilia Reticulata ◽  
Mammalian Species ◽  
Male And Female ◽  
Males And Females

Abstract In a number of species, males and females have different ecological roles and therefore might be required to solve different problems. Studies on humans have suggested that the 2 sexes often show different efficiencies in problem-solving tasks; similarly, evidence of sex differences has been found in 2 other mammalian species. Here, we assessed whether a teleost fish species, the guppy, Poecilia reticulata, displays sex differences in the ability to solve problems. In Experiment 1, guppies had to learn to dislodge a disc that occluded a feeder from which they had been previously accustomed to feed. In Experiment 2, guppies had to solve a version of the detour task that required them to learn to enter a transparent cylinder from the open sides to reach a food reward previously freely available. We found evidence of sex differences in both problem-solving tasks. In Experiment 1, females clearly outperformed males, and in Experiment 2, guppies showed a reversed but smaller sex difference. This study indicates that sex differences may play an important role in fish’s problem-solving similar to what has previously been observed in some mammalian species.

scholarly journals The Human Female Paradox: Biological Disadvantage Preimplantation, Biological Advantage, Thereafter

2021 ◽  
Vol 4 (1) ◽  
pp. 397-404
Author(s):  
Migeon BR
Keyword(s):  
Sex Differences ◽  
Sex Difference ◽  
In Utero ◽  
Vital Statistics ◽  
Significant Loss ◽  
Human Female ◽  
X Chromosomes ◽  
Fetal Survival ◽  
Biological Advantage ◽  
Eighth Decade

The vital statistics show that human females outlive males at every biological stage. Once the embryo arrives in the uterus, more males die at every stage, at least until the eighth decade when the majority of survivors are female. Unexpectedly, the same statistics also show that more boys are born than girls, which is difficult to explain, because the sperm that determine the sex of the fetus, are not skewed toward males. Recently, new data reveal the reason for the increased number of male births; they imply the significant loss of females before the fetus arrives in the womb. Thereafter, there is an excessive loss of males – not only in utero but throughout their lives. One likely reason for the sex differences in fetal survival is the way that humans compensate for the sex difference in number of X chromosomes.

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