Effects In Female Mice Research Articles

REVIEW ARTICLE: Status of Contraceptive Vaccines

Problem This is a review of anti‐sperm contraceptive vaccines (CV), and synthesis of human scFv antibodies that can be used as immunocontraceptives.Method of study Various methods of proteomics and genomics, peptide synthesis, phage display technology, and antibody engineering were used to obtain multi‐epitope vaccines and human scFv antibodies from immunoinfertile and vasectomized men. The present review primarily focuses on the effect of multi‐epitope vaccines and Izumo on fertility, and synthesis and characterization of sperm specific human scFv antibodies.Results The immunization with Izumo peptides causes a contraceptive effect in female mice. The efficacy is enhanced by combination vaccination, including peptides based on other sperm antigens. Using phage display technology, we were able to synthesize at least four novel scFv antibodies with unique complementarity determining regions (CDRs) that reacted with specific fertility‐related sperm antigens. These antibodies inhibited human sperm function in vitro, and their immunocontraceptive effect in vivo by these antibodies is currently being investigated.Conclusion The multi‐epitope vaccines may provide an efficacious and viable approach to contraception. The human scFv antibodies, if they block fertility in vivo, may provide unique and novel immunocontraceptives, the first of its kind for human use. The multi‐epitope CV and preformed engineered antibodies of defined specificity may obliterate the concern related to inter‐individual variability of the immune response.

Effect of ER-β gene disruption on estrogenic regulation of anxiety in female mice

It has been shown that long-term estrogen treatment in gonadectomized female mice increases anxiety levels. On the other hand, a recent study has reported that estrogen may down-regulate the levels of anxiety by acting through estrogen receptor (ER) β. In the present study, we investigated the role of ER-β in the regulation of anxiety levels in female mice after long-term estrogen treatment. Gonadectomized ER-β knockout (βERKO) female mice and their wild type (βWT) littermates were implanted several different doses (experiment 1: 2.0 μg/day, experiment 2: 1.0, 0.4, 0.2 or 0.1 μg/day) of an estradiol benzoate (EB) or placebo pellet. Ten days after pellet implant, behavioral tests commenced to measure the anxiety levels (experiment 1: light–dark transition test (LDT), experiment 2: LDT, elevated plus maze test (EPM) and social investigation test (SIT)). We found that, at higher-doses, long-term treatment of EB had anxiogenic effects in both βWT and βERKO mice as indicated by a decrease of the time spent in the light side and the number of transitions between two sides during LDT. In contrast, several behavioral measurements indicated that the lower-doses treatment of EB might reduce the anxiety levels possibly through ER-β. Particularly, the anxiolytic effects of EB in the SIT were more pronounced in βWT mice than βERKO mice. Together, the findings in the present study suggest that estrogen may have both anxiolytic and anxiogenic effects in female mice, and that ER-β gene disruption did not affect anxiogenic regulation by estrogen in female mice, but partially affected anxiolytic regulation.

Female mice respond differently to costly foraging versus food restriction

Experimental manipulation of foraging costs per food reward can be used to study the plasticity of physiological systems involved in energy metabolism. This approach is useful for understanding adaptations to natural variation in food availability. Earlier studies have shown that animals foraging on a fixed reward schedule decrease energy intake and expenditure. However, the extent to which these changes depend on decreased food intake or increased foraging costs per se has never been tested. We manipulated foraging costs per food reward in female Hsd:ICR(CD-1) laboratory mice, comparing animals faced with low (L) and high (H) foraging costs to non-foraging animals receiving a food restriction (R) matched to the intake of H animals. Mice in the H group ran as much as L mice did but ate significantly less. They concurrently reduced daily energy expenditure and resting metabolic rate, decreased the size of major metabolic organs and utilized body fat stores; mass-specific resting metabolic rate did not differ between groups. We found evidence that these alterations in energy balance may carry fitness costs. As a secondary response to our experimental treatment, H females and, eventually, some R females ceased to show signs of estrous cyclicity. Surprisingly, results of an immune challenge with keyhole limpet hemocyanin showed that primary immune response did not differ between L and H groups, and was actually higher in R mice. Our results demonstrate that high foraging costs per se--the combination of high activity and low food intake--have pronounced physiological effects in female mice.

Immunocontraceptive effect of Izumo and enhancement by combination vaccination

Sperm proteins are being investigated for their applications in the development of contraceptive vaccines (CV) in several laboratories. In the present study, various synthetic peptides based upon four sperm proteins, namely Izumo, fertilization antigen-1 (FA-1), YLP(12), and SP56 that are involved in various steps of the fertilization cascade were examined for their immunocontraceptive effect. The synthetic peptides were conjugated to four carrier proteins namely keyhole limpet hemocyanin (KLH), bovine serum albumin (BSA), chicken gamma-globulin, and chicken ovalbumin. Female mice were immunized with various peptide vaccines and each booster injection was given with the peptide conjugated to a different carrier protein. Two different fertility trials with different doses of the peptide vaccines were conducted to examine the contraceptive effect. Injection of 150 microg of the peptides (Trial II) caused a significantly higher immune response in serum as well as in the vaginal tract causing enhanced contraceptive effect than those observed after injection with 75 microg of the peptides (Trial I). Immunization with the peptide vaccines based upon Izumo, which is involved in sperm-egg plasma membrane fusion, caused a significant reduction in fertility. The contraceptive effect was enhanced by immunizing with the peptides based upon other antigens (FA-1, YLP(12), and SP56), resulting in an overall 73.33% reduction in fertility. When the antibodies against the peptides disappeared after >9-10 months from circulation and genital tract, all the animals regained fertility. These findings indicate for the first time that the immunization with Izumo and other sperm peptides namely FA-1, YLP(12), and SP56 induces antibodies in serum and genital tract that cause a reversible long-term contraceptive effect in female mice. The data further indicate that the proteins involved in sperm-egg fusion can also be used for contraceptive vaccine development. The contraceptive effects are enhanced by immunizing with the multipeptide vaccines.

Regulation of Sulfotransferase Enzymes by Prototypical Microsomal Enzyme Inducers in Mice

In the present study, the regulation of the mRNA of 11 sulfotransferases (Sults) and two 3'-phosphoadenosine 5'-phosphosulfate synthase (PAPSs) isozymes by 15 microsomal enzyme inducers (MEI) in livers of male mice and five MEIs in livers of female mice was examined. These MEIs represent the transcriptionally mediated pathways: aryl hydrocarbon receptor (AhR), pregnane X receptor (PXR), constitutive androstane receptor (CAR), peroxisomal proliferator-activated receptor alpha (PPARalpha), and NF-E2-related factor 2 (Nrf2). AhR ligands suppress the expression of Sults, especially the Sult1 isoenzymes in female mice. CAR activators up-regulate several Sults and PAPSs2 in female but not in male mice. PXR ligands cause marked induction of Sult1e1 in male, Sult2a1/2a2 in female, and PAPSs2 in both male and female mice. PPARalpha ligands do not have a marked effect on Sult expression in males, but they tend to suppress the expression of several Sult isoforms in female mice. Nrf2 activators appear to induce the mRNA expression of Sults in male and have mixed effects in female mice. In silico analysis indicated the presence of putative binding sites for all five transcription factors in the promoter region of many Sult and PAPSs isoforms. In conclusion, induction of Sults by typical MEIs is not as marked as the induction of P450 enzymes in mice. In addition to gender differences in basal expression of Sults, there is also a marked gender difference in the inducibility of various Sult isoenzymes in mice by MEIs.

Effect of fertilization antigen (FA‐1) DNA vaccine on fertility of female mice

Vaccination of female mice with recombinant fertilization antigen (FA-1) causes a long-term reversible contraceptive effect. Also, a DNA vaccine based upon a dodecamer sequence YLP(12) present in sperm causes a reduction in fertility. In the present study, the effects of FA-1 DNA vaccine alone, and FA-1 and YLP(12) DNA vaccines together were examined. FA-1 495-bp DNA was cloned into pVAX1 vector to prepare the DNA vaccine. Four groups of female mice were immunized intradermally by using a gene gun with FA-1 DNA, FA-1 DNA + YLP(12) DNA, FA-1 DNA + YLP(12) DNA mixed with exogenous synthetic CpG oliogodeoxynucleotide (ODN), or vector DNA alone, respectively. Vaccination with all three formulations caused a significant reduction in fertility, with FA-1 DNA + YLP(12) DNA mixed with exogenous synthetic CpG ODN showing the highest reduction. Vaccination with all three formulations raised antibody response in both the sera as well as locally in the vaginal tract, with ODN mixed group demonstrating the highest titers. There was no antibody response in the mice injected with the vector alone. In sera, the highest titers were obtained for the IgG class for all vaccine formulations followed by the IgA class. In vaginal washing, the highest titers were obtained by the IgA class followed by the IgG class. Within the IgG class, the titers for the IgG2a subclass were significantly greater than the IgG1 subclass. The immunocontraceptive effects were long-lasting over 1 year of the observation period and increased with time. These novel findings indicate that the intradermal immunization with a sperm-specific FA-1 DNA vaccine causes a long-term circulating and local immune response resulting in immunocontraceptive effects in female mice. The anti-fertility effects were enhanced when FA-1 DNA vaccine was combined with YLP(12) DNA vaccine and injected with ODN.

Effect of sperm DNA vaccine on fertility of female mice

Our laboratory has identified a sperm-specific dodecamer peptide sequence, designated as YLP(12), vaccination with which causes a long-term reversible immunocontraceptive effect in female mice. In the present study, the effects of YLP(12) DNA vaccine were examined. YLP(12) 36 bp cDNA was cloned into pVAX1 vector to prepare the DNA vaccine. Two additional vaccine constructs were made by in frame cloning of one and two CpG repeats in the YLP(12)-cDNA vaccine. Five groups of female mice were immunized intradermally by using gene gun with YLP(12)-cDNA, YLP(12)-cDNA-CpG, YLP(12)-cDNA-CpG-CpG, YLP(12)-cDNA mixed with exogenous synthetic CpG oligodeoxynucleotide (ODN), or vector DNA alone, respectively. Vaccination with all three constructs and the YLP(12) vaccine mixed with exogenous ODN raised antibody response both in the sera as well as locally in the vaginal tract. There was no antibody response in the mice injected with the vector alone. In sera, the highest titers were obtained for the IgG class for all constructs and formulation followed by IgA class. In vaginal washings the highest titers were obtained for the IgA class followed by IgG class. Within the IgG class, the titers for the IgG2a subclass were significantly greater than the IgG1 subclass. Immunization with all constructs and formulation caused a significant (P < 0.05 to <0.001) reduction (20-43%) in fertility of female mice. The highest reductions were seen in mice immunized with YLP(12)-cDNA-CpG-CpG (two repeats) (43% reduction) and with the YLP(12) vaccine administered with exogenous CpG ODN (42% reduction). T lymphocytes obtained from DNA-vaccinated mice showed clearly distinguished comparative RT-PCR analysis of cytokine mRNA expression for Th1 and Th2 immune responses compared to T lymphocytes obtained from control animals injected with vector DNA. Expression of both Th1 cytokines (IL-2 and IFN-gamma) and Th2 cytokines (IL-4 and IL-10) was enhanced after DNA vaccination as compared to controls, with a bias towards Th1 response. The immunocontraceptive effects were long-lasting observed up to 1.3 years of the observation period and increased with time. These novel findings indicate that the intradermal immunization with a sperm-specific DNA vaccine causes a long-term circulating and local immune response resulting in immunocontraceptive effects in female mice.

The effects of BIS-GMA and TEG-DMA on female mouse fertility

The current study evaluated the effect of bisphenol A glycerolate dimethacrylate (BIS-GMA) and triethyleneglycol dimethacrylate (TEG-DMA) on female mouse fertility. Adult female mice were exposed to BIS-GMA or TEG-DMA (0, 25 and 100 microg/kg) intragastrically daily for 28 d and then mated with sexually mature untreated male mice and after mating their fertility was assessed. In females exposed to BIS-GMA at both doses significant increases in the total number of resorptions out of the total number of implantations were observed, with a significant increase in the number of animals with resorptions at the higher dose. Significant reductions in body weights and significant increases in ovary weights were also observed. Exposure to TEG-DMA at a dose of 100 microg/kg resulted in significant reductions in pregnancy rates and a significant increase in the total number of embryonal resorptions. Significant reductions in body and uterine weights were also observed in females exposed to TEG-DMA. The results suggest that both BIS-GMA and TEG-DMA have reproductive toxic effects in female mice.

Helplessness in the Tail Suspension Test Is Associated with an Increase in Ethanol Intake and Its Rewarding Effect in Female Mice

Depression is frequently observed in drug abusers. However, depression may be a primary factor of predisposition to drug abuse or a consequence of drug abuse. The aim of this study was to analyze the influence of a preexisting depressive-like state/helplessness on subsequent alcohol responsiveness in mice. Male and female CD1 mice were selected according to their immobility time in the tail suspension test, and only mice with "high immobility" and "low immobility" time were retained. Using a two-bottle free-choice paradigm, these mice were given continuous access to tap water or solutions of ethanol (3-20% v/v), quinine (12.5-50 mg/liter), or sucrose (1-4% w/v). In female mice, rewarding and aversive effects of ethanol (1.5 and 3 g/kg, intraperitoneally) were also investigated using the conditioned place preference and the conditioned taste aversion paradigms. Female mice were more immobile and drank more ethanol than male mice. No striking sex difference was observed in quinine consumption. Sucrose intake was higher in female than in male mice, whatever the solution concentration. At the 4% concentrated solution, a sucrose-induced increase in daily fluid intake was observed only in female mice. Female mice with high immobility time (HI) consumed more ethanol at the highest concentration than female mice with low immobility time (LI), whereas no difference was observed between HI and LI male mice. Moreover, whereas LI female mice failed to express place conditioning induced by the 3-g/kg dose of ethanol, HI female mice were strongly responsive to the rewarding effect of this high ethanol dose. Ethanol dose-dependently induced a conditioned taste aversion with a similar magnitude in both LI and HI female mice. The findings indicate that female CD1 mice tend to drink greater amounts of ethanol or sucrose solutions than male CD1 mice, suggesting that female mice may be a better model of excessive alcohol intake. Furthermore, no relationship was found between immobility scores and ethanol consumption in male mice. On the contrary, within female mice, HI mice consumed higher amounts of ethanol than LI mice probably because they experienced greater rewarding effects of ethanol. The present results support the hypothesis that depressive-like responses may predispose to ethanol abuse in female mice.

The Citrus-Derived Flavonoid Naringenin Exerts Uterotrophic Effects in Female Mice at Human Relevant Doses

The Citrus-Derived Flavonoid Naringenin Exerts Uterotrophic Effects in Female Mice at Human Relevant Doses

The Citrus‐Derived Flavonoid Naringenin Exerts Uterotrophic Effects in Female Mice at Human Relevant Doses

Gavage administration of the citrus flavonoid naringenin, 3',4,5,7-tetrahydroxyflavanon for 4 consecutive days, to immature female mice (postnatal day 17-20) at 4 or 100 mg/kg b.wt. significantly increased uterine weights 3 and 4 times, respectively. Analysis of uterine oestrogen receptor alpha revealed that naringenin significantly increased the cytosolic concentration of oestrogen receptor alpha, whereas in nuclei the oestrogen receptor alpha concentration was significantly decreased as compared to the solvent control. This was in contrast to the positive control 17 beta-oestradiolacetate which acted as a true oestrogen by increasing the concentration of both total and nuclear oestrogen receptor alpha. Both naringenin and 17 beta-oestradiolacetate, however, significantly, induced nuclear oestrogen receptor alpha in the liver, suggesting a tissue specific effect of naringenin on oestrogen receptor alpha distribution. In order to investigate the tissue levels at which the uterotrophic effect was observed, the distribution of an oral dose of tritiated naringenin (4 mg/kg) was investigated in 3-week-old female mice. The radioactivity content (ng naringenin equivalents/g tissue) was found to be highest in the gastrointestinal-tract, followed by the kidneys and liver. Uterus and ovaries were also found to contain relatively high and approximately equal amounts of naringenin. The concentration of naringenin in uterus and ovaries was found to be ten times higher as compared to the mammary tissue. The urinary excretion of more than 25% of the administered dose, within 8 hr after dosing indicated that naringenin is absorbed extensively in mice. The plasma concentration of 0.5 microM found in the present study is similar to the peak plasma concentration of naringenin (0.6 microM) observed in man following ingestion of 400-760 ml of orange juice (Erlund et al. 2001). This could be taken to suggests that ingestion of orange juice and other citrus fruits and juices may give rise to sufficiently high tissue levels of naringenin in man to exert a biological effect.

Suppression of Atherogenesis in Female Low-Density Lipoprotein Receptor Knockout Mice following Magnesium Fortification of Drinking Water: The Importance of Diet

Objective: Magnesium (Mg) has previously been found to modulate blood lipid levels, atherogenesis and atherosclerosis in rabbits when used as a dietary supplement. In addition, we have reported that Mg fortification of drinking water can attenuate atherogenesis in male low-density lipoprotein (LDL)-receptor-deficient mice, but had a mild and nonsignificant effect on female mice fed a high-cholesterol diet supplemented with cholic acid. The aim of this study was to examine whether Mg has an antiatherogenic effect in female mice fed a high-cholesterol diet without cholic acid. Methods: Two groups of female LDL-receptor-deficient mice were included. The mice received either distilled water or water with 50 g of Mg sulfate per liter. In the first (12 weeks) and second (6 weeks) stages of the experiment, the mice received low- and high-cholesterol diets, respectively, both without cholic acid. At the end of each stage of the experiment, blood was drawn for the determination of plasma Mg, calcium and lipid levels. In addition, the extent of atherosclerosis was determined at the aortic sinus level. Results: Mg fortification was associated with higher levels of plasma Mg while the mice were on a high-cholesterol diet, and the extent of atherosclerosis at the aortic sinus was significantly decreased in the female mice that received high levels of Mg compared with the female mice that received distilled water. The female mice that received water fortified with Mg had lower levels of triglycerides after stage 2, whereas no differences regarding cholesterol levels were found. Conclusion: These results confirm that Mg fortification of drinking water is capable of inhibiting atherogenesis also in female LDL-receptor-deficient mice fed a high-cholesterol diet, and demonstrate the importance of the nutritional composition of diet in this experimental model.

Dominant lethal and heritable translocation tests with chlorambucil and melphalan in male mice

Chemicals used in the treatment of cancer include several that are potent mutagens in a range of in vitro and in vivo assays. For some, genetic effects have also been demonstrated in humans, detected as chromosomal aberrations in peripheral lymphocytes. Because (1) many of these agents are confirmed mutagens, (2) humans are exposed to them in relatively high doses, and (3) an increasing number of early cancer victims are surviving to reproductive age, it is important that information be available on the genetic and reproductive hazards associated with exposure to these agents. Chlorambucil and melphalan are structurally related chemicals that are included in our efforts to identify and assess such hazards among cancer chemotherapy agents. To date, both have been reported to induced specific locus mutations in germ cells of male mice (Russell et al., 1989; Russell et al., 1992b) and melphalan is one of very few chemicals shown to induced such mutations in spermatogonial stem cells. More recently, both chemicals were found to have strong reproductive effects in female mice (Bishop and Generoso, 1995, in preparation). In the present studies, these chemicals were tested for the induction of dominant lethal mutations and heritable translocations in male mice. Both chemicals were found to have reproductive effects attributable to cytotoxicity in specific male germ cell stages and to induce dominant lethal mutations and heritable translocations in postmeiotic germ cells, particularly in mid to early stage spermatids. Thus, relatively extensive data are now available for assessing the genetic and reproductive hazards that may result from therapeutic exposures to these chemicals.

Opioid modulation of sucrose intake in CD-1 mice: Effects of gender and housing conditions

The effects of naltrexone (1 mg/kg, sc.) on consumption of a 5% sucrose solution were observed in nondeprived adult female CD-1 mice and in male mice. Males were either individually housed or were housed in pairs. Naltrexone significantly reduced the consumption of the sucrose in both female and male mice; in the case of the males the administration of naltrexone produced an intake pattern identical to that obtained for a less palatable (1.5%) sucrose solution in control conditions. There was no difference between subordinate and dominant males, neither in sucrose intake nor in the response to the naltroxone treatment. In a second experiment, it was shown that switching from a 5% to a 10% solution was sufficient to overcome naltrexone's suppressant effect in female mice, conversely this was not seen in the males. In general, the data are consistent with the view that opioid antagonists reduce effective palatability of sweet sucrose solutions in mice. There was no evidence that social isolation and stress related to subordination affected male mice's sucrose intake and response to the naltrexone challenge.

Failure to detect a second-generation effect in female mice after neonatal treatment with an estrogen (diethylstilbestrol).

Inbred female mice of the NMRI strain were treated subcutaneously with 5 micrograms diethylstilbestrol (DES) in olive oil or vehicle only for the first 5 days after birth. One group of DES-treated females was killed at the age of 8-12 weeks, and the uterine cervix and adjacent parts of the vagina and uterine horns prepared for histological studies. In all preparations, the cervical epithelial lining contained regions with heterotopic columnar epithelium (HCE) along 69-100% of the length of the common cervical canal. Ovaries from neonatally DES-treated females were grafted to 8-week-old ovariectomized control hosts and these hosts were mated to control males 2 weeks later. The hosts gave birth to normal-sized litters. The female offspring from these litters had a normal cervical epithelial lining and, in turn, gave birth to normal-sized litters. These results indicate that treatment of neonatal female mice with DES does not affect the female germ cells as far as concerns factors associated with the development of HCE or reduced fertility in the next generation.

Promotion of the Whitten effect in female mice by synthetic analogs of male urinary constituents.

Two volatile constituents of male mouse urine, 2-(sec-butyl)-4,5-dihydrothiazole and dehydro-exo-brevicomin, were synthesized and tested for their ability to induce estrous cycle in female mice (the Whitten effect). The suppression of ovarian cycling activity that resulted from grouping the females was abolished by exposure to normal male urine. The synthetic compounds, when added together in appropriate concentrations to the (previously inactive) urine of castrated males, or even to water, were found to be as effective as normal male urine. The action of the synthetic compounds appears attenuated for singly caged females.

Carcinogenic potential of phthalic acid esters and related compounds: structure-activity relationships.

Chronic toxicity and carcinogenicity studies of several phthalic acid esters (PAEs) and compounds containing a 2-ethylhexyl moiety were conducted in Fischer 344 rats and B6C3F1 (hybrid) mice. The compounds studied were phthalic anhydride, di(2-ethylhexyl) phthalate, butyl benzyl phthalate, diallyl phthalate, di(2-ethylhexyl) adipate, tris(2-ethylhexyl) phosphate, and 2-ethylhexyl sulfate (sodium salt). Estimated maximum tolerable doses and fractionally lower doses of each compound were administered to groups of 50 male and 50 female rats and mice for 2 years, followed by sacrifice, necropsy, and histopathological examination of major organs and tissues. The low toxic potencies of most of the compounds allowed for relatively high doses to be given during the chronic studies. In general, the toxic manifestations of the PAEs were closely correlated with their ester substituents. Although many of the PAEs possessed some carcinogenic activity, target sites for such effects were dissimilar, suggesting the absence of a common mode of action. In contrast, all of the 2-ethylhexyl-containing compounds studied possessed some hepatocarcinogenic activity, indicating that this moiety may have a propensity for causing hepatocarcinogenesis in mice, particularly those of the female sex. The 2-ethylhexyl compound that caused the greatest hepatocarcinogenic response in mice, di(2-ethylhexyl) phthalate, was also hepatocarcinogenic in rats. Similarly, those with a relatively greater effect in female mice were also active in male mice. Thus, sex and species differences in 2-ethylhexyl-induced hepatocarcinogenesis in rodents are probably quantitative rather than qualitative in nature.

Relationships between scent marking by male mice and the pheromone-induced secretion of the gonadotropic and ovarian hormones that accompany puberty in female mice.

Many mammals use specific olfactory cues (pheromones) as an integral part of their intrapopulation communication. These compounds can be conveniently categorized according to function as:(a) signalling pheromones, which elicit a more or less immediate change in behavior (if indeed a response does occur), and (b) priming pheromones, which trigger neuroendocrine and endocrine activity. Sex attractants are an example of the former:the regulatory effect of urinary odors on the mouse estrous cycle is an example of the latter. Much of the recent interest in mammalian pheromones stems from the discovery in the 1950’s of a series of dramatic primer effects in female mice (e.g., Whitten, 1956:Bruce, 1959). Many contributions have since been made by ethologists, psychologists, and reproductive physiologists:but work by chemists and neuro-physiologists is conspicuously absent. Recent reviews include Bronson (1968, 1971, 1974), Bruce (1966, 1967, 1970), Cheal and Sprott (1971), Eisenberg and Kleiman (1974), Gleason and Reynierse (1969), Mykytowycz (1970), Ralls (1971), Schultz and Tapp (1974), Whitten (1966), and Whitten and Bronson (1970).KeywordsScent MarkingUterine WeightImmature FemaleSubordinate MaleEstradiol BenzoateThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Further Studies on Parasitic Obesity in Mice, Deer Mice, and Hamsters

Accelerated weight gain caused by infection with spargana of Spirometra mansonoides occurs in male mice as well as females, and in older mice approximating 40 g starting weight, as well as in younger animals. Below a starting weight of 10 g the effect is greatly reduced and delayed if seven spargana per mouse are used. Deer mice, Peromyscus, show the same response. The oriental worm, S. ranarum, has an even greater stimulating effect than mansonoides, but is more antigenic, becoming encapsulated in the first 2 months, after which the effect is lost. The weight gain effect is additive, increasing with the number of spargana, but reaches a plateau at about 12 worms per 20-g mouse, after which either no further gain occurs, or gains are offset by increased mortality of the mice. Hamsters show an even more pronounced effect. Both males and females respond. In this case the infected animals grow at a very similar accelerated rate, while the controls show wide variation. True growth as well as obesity is involved, since infected hamsters are not only heavier but larger as shown by inspection and by X-ray. Small numbers of spargana appear to have no effect on longevity; a group of the original experiments allowed to die off naturally showed similar mortality rates for both experimental and control mice. Nor is there any effect on reproduction. Infected mice and hamsters breed as well as controls if given the opportunity. Mueller (1963a) described accelerated weight gain in mice infected with small numbers of plerocercoids of Spirometra mansonoides. In the original experiments only female mice were used at an average starting weight that varied from 11.7 to 21.4 g. The numbers of spargana per mouse varied from seven to eight. For smaller numbers of worms the effect was shown to be additive. The obesity effect was not dependent upon the strain of mouse since white mice from various suppliers reacted similarly. Gains of experimental mice over controls at 20 weeks averaged 17.60%, the larger gains tending to occur in mice of greater starting weight. Mice infected at a starting weight of 11.68 g showed an initial lag, but in the 2nd week overtook and passed the controls, thereafter increasing their advantage. ADDITIONAL EXPERIMENTS ON MICE This phenomenon has now been examined in greater detail, with preliminary results published in abstract (Mueller, 1963b, 1965). In five experiments on male mice (21 experimental, 20 control), at starting weights ranging from 9.5 to 38.75 g, and continuing for periods of 2 months or more, four experiments showed marked acceleration of the infected animals over the controls (Fig. 1), the maximum occurring in one experiment (E-93) where starting weight was 22.5 g. In male Received for publication 23 February 1965. mice with starting weight of 9.5 g (E-90) the experimentals lagged behind the controls for the first 4 weeks and then surpassed them, achieving an advantage in weight increase of 11% at the end of 12 weeks, but with the differential diminishing from 14 to 29 weeks (Fig. 2). Twenty-two further experiments have been done on the effect in female mice (185 experimental, 114 control animals1) ranging in weight from 10 to 39 g. With females of 10 and 11 g starting weight (E-95 AB, CD) there occurred only minimal gains over controls (5 and 12% respectively at 11 weeks) and then only after an initial period of several weeks in which the experimental animals lagged behind the controls (Fig. 3), as in the case of young male mice. It is thus clear that any advantage in weight gain bestowed on mice by this type of parasitism is minimal if the animals are infected at or below 10 g in weight, and it seems probable that below this weight the effect disappears altogether, or could be demonstrated only with a smaller number of worms. Contrary to expectation, a weight gain was also produced in older female mice (E-117, E-105) of 33.5 and 39 g starting weight, respectively (Fig. 4). The gains over controls The numerical asymmetry results from the fact that some of the experiments had multiple groups of mice, infected with different numbers of worms, with only a single set of controls.