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PubMed2026

In vitro fertilization-conceived offspring exhibit altered Long Interspersed Nuclear Elements-1 retrotransposition dynamics associated with long-term disease risks.

BACKGROUND: In vitro fertilization has transformed reproductive medicine, yet offspring conceived through in vitro fertilization display elevated risks for diverse long-term health conditions, with underlying mechanisms unclear. Long Interspersed Nuclear Elements-1, a mobile genetic element responsive to environmental stress, represents a potential mediator. OBJECTIVE: This study aimed to test the hypothesis that in vitro fertilization procedures may act as an embryonic stressor that alters Long Interspersed Nuclear Elements-1 dynamics, potentially contributing to genomic instability associated with long-term disease susceptibility. STUDY DESIGN: Umbilical cord blood or peripheral blood from 33 in vitro fertilization and 42 naturally conceived neonates were collected for whole-genome sequencing. Total Long Interspersed Nuclear Elements-1 proportion in individual genome was counted with Bowtie2 software. De novo Long Interspersed Nuclear Elements-1 insertion and Long Interspersed Nuclear Elements-1 deletion were detected with Mobile Element Locator Tool. Three parent-matched in vitro fertilization-naturally conceived sibling pairs were included to control for genetic background. Disease association analysis was performed for genes within 500 kb of differential Long Interspersed Nuclear Elements-1 sites in The Database for Annotation, Visualization and Integrated Discovery (DAVID). Statistical analysis was performed using the R language. RESULTS: In vitro fertilization offspring demonstrate elevated global Long Interspersed Nuclear Elements-1 content compared to naturally conceived controls (P=.04). This finding was corroborated in 3 sibling pairs from identical genetic backgrounds, where in vitro fertilization-conceived children consistently exhibited higher Long Interspersed Nuclear Elements-1 levels than their naturally conceived siblings. Eleven genomic loci with differential Long Interspersed Nuclear Elements-1 insertion frequencies and 14 loci with differential Long Interspersed Nuclear Elements-1 deletion frequencies between in vitro fertilization offspring and naturally conceived controls were identified. Notably, these differential Long Interspersed Nuclear Elements-1 sites demonstrated significant enrichment near genes implicated in metabolic, cardiovascular, neuropsychiatric, and neoplastic diseases, conditions associated with in vitro fertilization conception. CONCLUSION: These findings provide preliminary evidence that in vitro fertilization conception is associated with increased Long Interspersed Nuclear Elements-1 content and altered genomic distribution of Long Interspersed Nuclear Elements-1 elements. The proximity of these differential Long Interspersed Nuclear Elements-1 sites to disease-associated genes suggests a plausible genomic mechanism linking in vitro fertilization-associated embryonic stress to elevated disease risk. This work provides valuable molecular insights that may inform the ongoing discussion about assisted reproductive technology safety and suggests that continued attention to genomic integrity in in vitro fertilization-conceived individuals would be beneficial.

Humans↗
PubMed1979

Analysis of human spermatozoal fertilizing ability using zona-free ova.

An in vitro fertilization assay employing zona-free hamster eggs was used to analyze human spermatozoal fertilizing ability. Human spermatozoa were preincubated for 18 to 20 hours in Biggers, Whitten, and Whittingham's medium (1971) at a concentration of 1 X 10(7) sperm/ml prior to the addition of zona-free superovulated hamster eggs. Eggs were examined microscopically 2 hours later for evidence of swelling or decondensing sperm heads in the cytoplasm. A total of 6266 eggs were examined in assays for both suspected fertile and infertile donors; 50 eggs/sample were examined. The percentage fertilization was found to range from 14% to 100% in the suspected fertile group with an average of 56.3%. The sperm concentration in this fertile group ranged from 22 to 303 million/ml with an average of 114. The suspected infertile samples yielded fertilization rates of 10% or less and an average count of 50.6 million/ml. These data suggest that human spermatozoa fuse with the vitelline membrane of zona-free hamster eggs and decondense with varying efficiencies. The percentage of fertilization in this cross-species system did not show a significant correlation with sperm concentration or motility. However, suspected infertile samples always yielded 10% or less fertilization in this assay. This method may have potential value as a diagnostic tool in evaluating human spermatozoal fertilizing capacity which avoids the ethical and logistcal problems associated with fertilization of human eggs in vitro.

Animals↗
PubMed1978

Influence of seminal additives and packaging systems on fertility of frozen bovine spermatozoa.

The following recommendations and conclusions are based upon results of fertility and laboratory studies, and general trends from field investigations. Fertility results due to the addition of enzymes have been variable and contradictory. Flushing of ampules with dry, gaseous nitrogen prior to filling has become a routine practice in processing semen to be frozen. For control of Vibrio fetus and Leptospira pomona, 2,000 micrograms of streptomycin and 1,000 u polymyxin B sulfate should be added per milliliter of raw semen immediately after collection. The extender for initial dilution should contain the same concentration of antibiotics used for raw semen plus 500 u penicillin. The glycerol portion of the extender should contain 500 u penicillin per milliliter. The effect of addition of sugars on fertility has been highly variable. The primary beneficial effect is probably due to their cryoprotective properties. A myriad of concoctions have been added to bovine semen and the results have been highly variable with respect to both motility and fertility. Results of subsequent experiments have rarely proven that addition of exotic compounds or mixtures has been of value. Higher mean fertility was obtained with semen in straws in 14 of 21 comparisons with ampules. The differences in favor of straws ranged from 1.1 to 18.9; while the range in favor of ampules was .1 to 4.4 percentage points. Fertility obtained with pellets has ranged from minus 12.8 to plus 11.9 percentage points in nonreturn rate (NR), compared to the corresponding NR with semen in ampules. Fertility of semen in ampules was higher in five of eight studies. Fertility of pelleted semen has ranged from minus 9.5 to plus 6.0 percentage points compared with straws. Fertility was higher for semen in pellets in only one of five investigations. Pellets should not be used until the potential for pathogenic contamination and exchange of spermatozoa among pellets is eliminated. There is a potential for higher fertility with semen in straws as compared to other packaging systems, but the issue of liquid nitrogen (LN) entry and possible contamination of semen should be further investigated. In general, fertility obtained with semen frozen in the .25 ml straw has been equal to or higher than semen in larger packages. However, they cannot be unequivocally recommended due to other considerations. From laboratory studies, it appears that greater spermatozoan survival is obtained when semen frozen in straws is thawed in water at 35 C or above.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1979

Cytological events associated with in vitro aged and fertilized rabbit eggs.

The morphogenetic events associated with rabbit eggs aged in vitro for 12 to 50 hours prior to mixing with sperm have been examined by light and electron microscopy. After 12 hours in culture, morphological alterations of the meiotic spindle and the cortex of unfertilized eggs were evident. By 24 to 50 hours in culture, unfertilized eggs contained subnuclei, structures which formed when individual and/or groups of meiotic chromosomes dispersed and becmae invested by a double-laminated structure reminiscent of a nuclear envelope. Although most eggs obtained 11.5 to 12 hours after induced ovulation and in vitro fertilized displayed morphogenetic patterns similar to those described for in vivo fertilized ova, some (10%) contained three pronuclei. Many eggs obtained 13 to 15 hours after induced ovulation and subsequently mixed with sperm in vitro appeared to undergo processes of fertilization typical of in vivo fertilized eggs, however, approximately 30% contained subnuclei in association with the male pronucleus. Few eggs (15%) aged 12 hours prior to in vitro fertilization displayed patterns of pronuclear development and association typical of fertilized unaged ova. Subnuclei developed in many of the fertilized ova. Supernumerary sperm nuclei, which did not develop into male pronuclei, were observed in some zygotes. Cleavage of eggs aged 12 hours prior to fertilization was abnormal or retarded. After 24 hours in culture approximately 16% of the eggs fertilized. Seventy percent of the fertilized eggs failed to support the development of a male or female pronucleus.

Animals↗
PubMed1979

Metabolic similarities between fertilization and phagocytosis. Conservation of a peroxidatic mechanism.

At the time of fertilization, sea urchin eggs release a peroxidase which, together with H2O2 generated by a respiratory burst, is responsible for hardening of the fertilization membrane. We demonstrate here that the ovoperoxidase of unfertilized eggs is located in cortical granules and, after fertilization, is concentrated in the fertilization membrane. Fertilization of sea urchin eggs or their parthenogenetic activation with the ionophor A23187 also results in (a) the conversion of iodide to a trichloroacetic acid-precipitable form (iodination), (b) the deiodination of eggs exogenously labeled with myeloperoxidase and H2O2, (c) the degradation of thyroxine as measured by the recovery of the released radioiodine at the origin and in the inorganic iodide spot on paper chromatography, and (d) the conversion of estradiol to an alcohol-precipitable form (estrogen binding). The iodination reaction and the binding of estradio occurs predominantly in the fertilization membrane where the ovoperoxidase is concentrated. From the estimation of the kinetics of incorporation of iodine, we determine that the peroxidative system is active for 30 min after fertilization, long after hardening of the fertilization membrane is complete. Most of the bound iodine is lost during the hatching process. Iodination of albumin is catalyzed by the material released from the egg during fertilization, when combined with H2O2 and iodide. Iodination, thyroxine degradation, and estradiol binding are inhibited by azide, cyanide, aminotriazole, methimazole, ascorbic acid and ergothioneine, all of which can inhibit peroxidase-catalyzed reactions. These responses of the sea urchin egg to fertilization are strikingly similar to the changes induced in polymorphonuclear leukocytes by phagocytosis and, in both instances, a peroxidative mechanism may be involved.

Animals↗
PubMed1978

The transition from natural to controlled fertility in Taiwan: a cross-sectional analysis of demand and supply factors.

Three factors are usually proposed as inducing the transition from natural to regulated fertility. Fertility regulation may occur when the demand for children is reduced; when general attitudes toward fertility regulaton become positive; and, finally, when such factors as infant and child survival prospects and natural fertility conditions improve. Applying the Easterlin framework for fertility determination, this paper considers the effect of these factors in the shift from natural to regulated fertility in Taiwan in 1965. Cross-sectional data for continuously married women aged 35-44 are used. The results indicate that, at the initial stages of the fertility transition, it is primarily an increase in the potential output of surviving children and a decline in the subjective costs associated with fertility regulation, rahter than a decline in desired fertility, that distinguish the natural fertility subpopulation from the regulating subpopulation.

Adult↗
PubMed1976

Population dose from natural radionuclides in phosphate fertilizers.

The natural radionuclide content of mineral phosphate fertilizers has been determined gammaspectrometrically. The investigations comprised ca. 70% of the mineral phosphate fertilizers authorized and used in the Federal Republic of Germany (FRG). At maximum, we found specific activities of 62 nCi Unat/kg, 23 nCi 226Ra/kg, 1.6 nCi Thnat/kg and 262 nCi 40K/kg. The mean values, weighted by the percentual agricultural consumption of the main phosphate fertilizer groups in 1973/74 and related to the phosphate content, amounted to 58, 40, 2, and 584 nCi/kg P2O5 for Unat, 226Ra, Thnat, and 40K respectively. This resulted in an annual distribution due to phosphate fertilizing of about 3.9 muCi Unat, 2.7 muCi 226Ra, 0.1 muCi Thnat, and 39.9 muCi 40K per ha of arable or pasture land in 1973/74 on the average. From these values the air dose rates over agricultural areas have been estimated under extreme conservative assumptions resulting in an additional external exposure of members of the population of 0.02 mrd/a on the average and 0.4 mrd/a in the region of highest phosphate fertilizing intensity. If it is assumed that radium contained in phosphate fertilizers were completely accumulated in the soils during the last 80 years, this value would be raised to 0.3 mrd/a on the average. The occupational external radiation exposure due to natural radionuclides contained in phosphate fertilizers was estimated to be 0.1 mrd/a on the average and 2.3 mrd/a at maximum for persons working in agriculture. These estimates show that natural radionuclides in phosphate fertilizers contribute but very little to the mean terrestrial radiation exposure of the population which is 50 to 55 mrd/a in Germany. Only for the small group of persons working in fertilizer production plants or storehouses a significant increase of the external radiation exposure has to be expected which could reach a doubling of the mean natural exposure value.

Agriculture↗
PubMed1978

In vitro fertilizing ability of testicular, epididymal, and ejaculated rabbit spermatozoa.

The fertilizing ability of testicular, epididymal, and ejaculated rabbit spermatozoa was evaluated in vitro following in vitro capacitation by high ionic strength treatment. Fewer than 11% of inseminated ova were apparently fertilized (i.e., in pronuclear, two-, and four-cell stages as determined by light microscopy) when testicular sperm treated with caffeine, caput epididymal, or corpus epididymal sperm samples were tested. A greater fertilizing ability, reflected by the percentage of ova fertilized and more normal progression of embryonic development, was exhibited by cauda epididymal sperm. Of 93 ova, 68 (73.1%) were fertilized by cauda sperm, whereas ejaculated sperm from the same 10 bucks fertilized 34 (36.6%) of 93 ova (P is less than 0.005). Ultrastructural examination of selected ova apparently fertilized by sperm from levels of the male reproductive tract proximal to the cauda epididymidis revealed abnormal activation. Authentic fertilization occurred when ova were inseminated with cauda epididymal and ejaculated sperm. An unusual and infrequent form of activation involving failure of cortical granule breakdown in ova penetrated by cauda epididymal and ejaculated sperm was seen. A comparison of fertilizing ability of sperm from first, second, and third ejaculates revealed a significant decrease with the third ejaculate (P is less than 0.01).

Animals↗
PubMed1978

Fertility and family planning in rural northern Thailand.

From the mid-1960s to the mid-1970s, when fertility was declining in Thailand as a whole, especially rapid declines occurred in Northern Thailand, but they did not occur uniformly in all the region's provinces. The Northern Thailand Fertility Study, initiated in 1975 to study the reported fertility changes, gathered data in two provinces: Chiang Mai, where fertility decline has been quite rapid, and Chiang Rai, which experienced relatively little decline until 1974. This preliminary report discusses fertility levels and trends in the two provinces, fertility experience and expectations of respondents, attitudes toward and knowledge of family planning, and contraceptive practice. The results suggest that most of the difference in fertility decline is related to the different level of family planning program activity in the two provinces.

Abortion, Spontaneous↗
PubMed2026

Phenotyping of post-fertilization sperm mitophagy determinants discovered in a mammalian gamete-based cell-free system.

The targeted, substrate-specific degradation of paternal mitochondria inside the zygote, known as post-fertilization sperm mitophagy, is a crucial and evolutionarily conserved early embryonic event. It ensures the exclusive maternal inheritance of the mitochondrial genome. Post-fertilization sperm mitophagy was initially thought to only be achieved via the ubiquitin-proteasome system. Until pro-autophagic receptor proteins such as SQSTM1, GABARAP, as well as the proteasome-interacting ubiquitinated protein dislocase VCP, were identified as contributors to the degradation of the sperm mitochondria early after mammalian fertilization. This synergy of proteasomal and autophagic pathways ensures a timely degradation of sperm mitochondria shortly after fertilization. The discovery of these autophagic receptors lead researchers to believe there might be other autophagic receptors and determinants necessary for proper post-fertilization sperm mitophagy. Based on the established inventory of proteins from mass spectrometry trials of boar spermatozoa exposed to porcine oocyte extracts in an intra-specific porcine cell-free system (CFS), five candidate mitophagy determinants were further investigated in this study, namely LACTB, PRDX3, PSMA8, TOMM34, and FUNDC1. These proteins of interest were studied and validated by using in vitro fertilization (IVF) protocols, cell imaging of spermatids, spermatozoa, oocytes and zygotes, protein interactome analysis, and the porcine CFS. The proteins PSMA8 and TOMM34 behaved in accordance with our proteomic study predictions. The PSMA8 labeling increased after exposure to CFS; in agreement with the classification PSMA8 was given from the mass spectrometry findings. TOMM34 underwent a visible decrease in labeling after exposure to CFS, which also agreed with its proteomic classification; this labeling persisted in IVF zygotes. Except for LACTB, the examined proteins showed mutual interactions as well as interactions with previously identified sperm mitophagy factors in the STRING interactome analysis. Results from this study validate the novel porcine CFS as a valuable tool for the exploration of early fertilization events at a molecular level. Future phenotyping and functional studies using porcine CFS will advance the understanding of mitochondrial inheritance and zygotic development and potentially shed light on the origins of certain mitochondrial diseases arising from the failure of post-fertilization sperm mitophagy.

Animals↗
PubMed1976

In vitro fertilization, culture, and transfer of rabbit ova.

Ovulated rabbit oocytes were fertilized in vitro in chemically defined media supplemented with bovine serum albumin and either cultured up to the expanding blastocyst stage or transferred to recipients after varying periods of culture. Embryos transferred after up to 72 hours of in vitro culture were born as viable young. Oocytes from young virgin does were superior to oocytes from nonvirgin does for the purpose of in vitro fertilization (54% versus 26% fertilized, P less than 0.01). Capacitated sperm from artificially inseminated capacitators resulted in fertilization rates slightly lower than those from naturally mated does (46% versus 57% fertilized, P less than 0.025). Removal of cumulus and corona cells from oocytes with hyaluronidase and repeated aspiration through a fine pipette resulted in lowered fertilization rates (51% versus 73%, P less than 0.025). Linbro Disposo Tray wells were as good as glass tissue-culture dishes for the in vitro mixing of gametes and were more convenient to use. Modified Ham's F10 medium was used to culture the in vitro-fertilized embryos. However, when a modified Brackett's medium was used instead of modified Ham's F10 for the initial 4-hour period after mixing gametes, more oocytes were fertilized (52% versus 28%, P less than 0.01).

Animals↗
PubMed1979

Fertilization in brown algae. II. Evidence for lectin-sensitive complementary receptors involved in gamete recognition in Fucus serratus.

Fertilization in Fucus serratus is directly proportional to the number of sperm added, saturating at approximately 250 sperm per egg with an apparent Km of 120 sperm per egg. The effect of a range of lectins on fertilization has been tested. Preincubation of gametes with Con A and fucose-binding protein (FBP) inhibited fertilization. At low concentrations this was by specifically binding to eggs; at high concentrations pretreatment of either gametes inhibited fertilization probably due to cytotoxicity. Fertilization was not inhibited by simple sugar haptens, but polysaccharides containing fucosyl or mannosyl residues (yeast mannan, fucoidan, ascophyllan) inhibited fertilization by binding to sperm. Pretreatment of eggs with alpha-fucosidase or alpha-mannosidase was effective in inhibiting fertilization. All the results indirectly demonstrate that fertilization in Fucus serratus is based on an association between fucosyl- and mannosyl-containing ligands on the egg surface and specific carbohydrate-binding receptors on the sperm surface.

Carbohydrates↗
PubMed1977

Assessment of relative fertility of males (cockerels and boars) by competitive mating.

When hens were inseminated with an equal number of spermatozoa from one of 3 Leghorn (L) and one of 3 Columbian (C) cocks in the 9 possible L and C combination, a hierarchy of fertility was established based on the proportion of chicks sired by each cock. A similar hierarchy was established for 3 Duroc (D) and 3 Yorkshire (Y) boars by mating gilts in rapid succession to one D and one Y boar. A second hierarchy of fertility was established by inseminating hens with 40 x 10(6) spermatozoa from only one cock or by mating gilts to only one of the boars. The hierarchies for the cocks and boars were essentially the same for each method. Minor discrepancies were observed for males which appeared to be nearly equally fertile when used alone or in combination with another male. After homospermic insemination, the hierarchy of cocks was identical whether the ranking was based on the percentage of eggs fertilized or on hatchability of fertilized eggs. Similarly, the boars ranked highest in fertility by double mating had higher conception rates, higher embryonic survival rates and larger litter sizes when used alone. Heterospermic insemination and double mating appear to be more efficient and sensitive than methods of estimating fertility which depend on homospermic insemination of high or low numbers of spermatozoa, single matings or the examination of various characteristics of semen. The method of heterospermic insemination or double mating offers a simple and effective method of assessing the relative fertility of males.

Animals↗
PubMed2026

The Rhizosphere Microbiome: A Key Mediator of Crop Responses to Fertilization Strategies.

The rhizosphere microbiome, the plant's "second genome" is pivotal for crop nutrient acquisition, health, and stress responses. While fertilization ensures high agricultural yields, a key challenge is reshaping this microbiome to boost crop performance. This review synthesizes how mineral, organic, and bio-organic/microbial inoculant fertilizers affect rhizosphere microbial structure, diversity, and function. Long-term excessive mineral fertilizers (especially nitrogen) reduce microbial diversity, diminish beneficial groups (e.g., diazotrophs, PGPR), and disrupt microbial networks via soil acidification and altered root exudates, causing continuous cropping obstacles. In contrast, organic fertilizers improve soil microenvironments, maintaining high microbial diversity, enriching beneficial taxa (e.g., Proteobacteria, Actinobacteria), and enhancing community complexity. Bio-organic fertilizers/microbial inoculants "engineer" the microbiome by introducing exogenous beneficial microbes (e.g., Bacillus, Pseudomonas, AMF), directly promoting growth, suppressing diseases, and "reconditioning" indigenous beneficial communities. We also clarify how fertilization regulates plant-microbe dialog via root exudates and rhizosphere chemistry (e.g., pH, ion balance), discuss current challenges (causality, lab-to-field translation, genotype-microbiome-fertilization interactions), and outline future directions. Integrating rhizosphere microbiome management into fertilization is crucial for reducing chemical fertilizer reliance and advancing agricultural green transformation.

fertilization strategies microbial community assem↗
PubMed1977

Binding of concanavalin A to the surface of sea urchin eggs and its alteration upon fertilization.

The binding of concanavalin A (Con A) to Strongylocentrotus purpuratus eggs has been investigated using 125I-concanavalin A (125I-Con A). The lectin binds specifically to the egg surface and does not produce agglutination of the eggs. High 125I-Con A concentrations are necessary to saturate all of the surface binding sites. Scatchard plots of the binding data are biphasic and may be interpreted as showing two main classes of sites. Unfertilized eggs have 4 X 10(8) high affinity sites/egg (Ka=8 X 10(-7) M) and 4.5 X 10(8) istes of lower affinity (Kb=4 X 10(-6) M). The sites may be assigned to different layers of the egg surface by studying the effects of removal of egg coats on the binding reaction. Removal of the jelly coat by washing eggs at pH 4.5 has no effect on binding. However, disruption of the vitelline layer with dithiothreitol leads to a decrease in the number of high affinity sites. After fertilization, the high affinity sites are found upon the fertilization membrane produced from the vitelline layer. Low affinity sites predominate in the plasma membrane, and are not affected by treatments which alter the vitellinelayer. The number of low affinity sites double upon fertilization, with the insertion of new membrane into the egg surface, as a result of cortical granule exocytosis. The doubling of sites is not due to hyaline material released from the cortical vesicles at fertilization, and thus these sites appear to reside upon the new membrane that is inserted from the cortical vesicles. If eggs are activated with ammonia, bypassing the cortical reaction, no change in the binding of ConA occurs. Con A inhibits fertilization at concentrations higher than 0.1 mg/ml, where less than 50% of the high affinity (viteline layer) binding sites are occupied, and there is little binding to the low affinity (plasma membrane) sites. Thus, the interaction of sperm with vitelline layer components may be an obligatory step in the fertilization process. A fraction of the 125I-Con A binding sites is cleaved from the egg surface upon fertilization or after activation by the calcium ionophore A23187. This release of Con A binding sites occurs during the limited proteolysis of surface components that accompanies the cortical reaction, and does not occur with ammonia activation of the egg, where the cortical reaction does not occur. Thus, the changes in Con A binding at fertilization are caused by the massive cortical granule exocytosis that occurs within minutes of sperm penetration, and not by activation of the egg per se.

Animals↗
PubMed1977

Relative income and fertility.

The present study examines the relationship between relative income (i.e., actual income in relation to the expected income of one's socioeconomic group) and fertility, using data collected by the 1967-1968 Canadian Family Growth Study (Balakrishnan et al., 1975). We broaden the tests of relative income beyond cumulative fertility to spacing behavior and then examine some of assumptions included in the relative income model of fertility. Results of the tests, in brief, are as follows: (a) Relative income is found to be more closely related to spacing than to cumulative fertility; and (b) the relationship between relative income and fertility is strongest among those couples who plan their life ahead and have a high level of education and occupation, and when temporal alignment is brought between the measures of relative income and fertility. For the relative income model to receive confirmation, it was specified that the following hypotheses must be confirmed: (a) that fertility behavior would vary positively with relative income but the fertility norm would show no relationship with relative income: and (b) that consumption norms and behavior would show no relationship with relative income. The outcome of these tests are in the expected direction, giving support to the relative income model. In addition, there is some evidence of predictive capability of the relative income model for correlative behavior.

Birth Rate↗
PubMed1976

Reproductive performance and fertility testing in strain 13 and Hartley guinea pigs.

A study to test the effects of certain experimental manipulation on the reproductive capacity of male guinea pigs required verifying the fertility of the male guinea pigs before and after manipulation. Methods of testing fertility were evaluated, and normal reproductive data from preexperimental and control groups were tabulated and analyzed. No data from the actual experiments were included. Virgin and proven fertile males were mated with 1 (1:1) or 2 (2:1) virgin or proven fertile females. Inbred (13/N Umm) and conventional (Mfi:CFDH-ML (DH) ) guinea pigs were used. Ninety-five percent of both groups of males were fertile. Eighty-four percent of both groups of females were fertile. Male guinea pigs previously proven fertile had the same subsequent fertility rate as virgin males. Over one-third of the conceptions did not take place during the first estrus cycle (16 da) during which the males and females were mated. Strain 13 and Hartley females had litters of approximately the same size (3.1 vs 3.0), but the neonatal mortality was statistically lower (P less than 0.001) in the Hartley stock (9.3%) than in the Strain 13 guinea pigs (28.4%).

Animals↗
PubMed2026

Parenting styles and fertility intention: Mediating effects of childbearing beliefs and psychological resilience.

China's declining fertility rate is partly due to low fertility intention among childbearing population. To understand family influence on young people's fertility intention and its underlying mechanisms, this study examines how parenting styles (authoritarian vs. permissive) affect Chinese college students' fertility intention, with traditional childbearing beliefs and resilience as mediators. Data were collected from 839 participants (Age: M = 21.1, SD = 1.7 years) using structured questionnaires. Logistic regression found that a positive correlation between permissive parenting style and fertility intention, with authoritarian parenting having no impact. Mediation analysis showed the association between permissive parenting style and fertility intention was fully mediated through resilience ( = 0.0, 95%CI = [0.0,0.1]) and greater childbearing beliefs ( = 0.0, 95%CI = [0.0,0.1]). The findings indicate that permissive parenting is related to higher fertility intention in youth via resilience and childbearing beliefs. Promoting positive family environments and permissive parenting may enhance childbearing intention.

Humans↗