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Factors influencing gene expression and resistance for Gram-negative organisms expressing plasmid-encoded ampC genes of Enterobacter origin.

High-level expression of AmpC beta-lactamases results in organisms resistant to multiple beta-lactam antibiotics. The mechanism of chromosomally mediated AmpC resistance has been elucidated, however the mechanism(s) driving plasmid-encoded AmpC resistance are unknown. Studies were designed to identify factors which influence expression of plasmid-encoded ampC genes and correlate these factors with resistance. As the model system, ampC genes of Enterobacter origin were used to determine how gene copy number, genetic background and genetic organization influenced resistance phenotypes. To this end, gene expression from the plasmid-encoded inducible blaACT-1 and non-inducible blaMIR-1 were compared with chromosomal ampC gene expression from both wild-type (WT) and derepressed Enterobacter cloacae isolates. RNA levels within the original clinical isolates were examined using primer extension analysis, whereas a new PCR strategy was developed to examine gene copy number. These data revealed that blaACT-1 and blaMIR-1 constitutive expression was 33- and 95-fold higher than WT expression, whereas copy numbers of the plasmid-encoded genes were 2 and 12, respectively. Differences in promoters and transcriptional starts for the respective plasmid-encoded genes were noted and contribute to increases observed in overall expression. Finally, beta-lactam MICs were increased two- to 16-fold when blaACT-1 was expressed in Escherichia coli AmpD- strains compared with E. coli AmpD+ strains. In conclusion, high-level expression of plasmid-encoded ampC genes requires interplay between multiple factors including genetic organization, promoter modifications, genetic background, and to some extent gene copy number. In addition, clinical laboratories need to be aware that genetic backgrounds of inducible plasmid-encoded genes can dramatically influence MICs for organisms not normally associated with derepressed phenotypes.

Anti-Bacterial Agents↗

Behavioral phenotype of pre-proenkephalin-deficient mice on diverse congenic backgrounds.

RATIONALE: The phenotype of genetically modified animals is thought to result from an interaction of gene manipulation with the genetic background and environmental factors. OBJECTIVES: To test the behavioral and drug responses of Penk1(-/-) mice on different genetic backgrounds. METHODS: Congenic C57BL/6J and DBA/2J mouse strains with a targeted deletion of the Penk1 gene were generated. Behavior and drug effects were tested in models of pain and anxiety. RESULTS: Penk1(-/-) mice showed exaggerated responses to painful or threatening environmental stimuli, but the expressivity of the mutant phenotype was strongly dependent on the behavioral paradigm and on the genetic background. For example, elevated levels of anxiety were readily detectable in C57BL/6J-Penk1(-/-) mice in the light-dark and startle response tests, but not in the social interaction test. In contrast, we found elevated levels of anxiety in DBA/2J-Penk1(-/-) mice only in the zero-maze and social interaction tests. In some cases, the idiosyncratic behavior masked the appearance of the knockout gene effect. The activity of the anxiogenic drug, m-chlorophenylpiperazine, but not the anxiolytic drug diazepam, was strain and genotype dependent. Mice with the Penk1 mutation on the DBA/2J, but not on other genetic backgrounds, showed an increased opioid-dependent stress-induced analgesia. CONCLUSIONS: (1) The behavioral effects of the Penk1 gene deletion persists on different genetic backgrounds, but its detection sometimes requires the use of different behavioral paradigms. (2) The behavior of the background strain should be considered in the analysis of knockout mice to avoid floor and ceiling effects, which may mask the phenotype.

Acetic Acid↗

Mutations affecting catabolite repression of the L-arabinose regulon in Escherichia coli B/r.

Expression of the L-arabinose regulon in Escherichia coli B/r requires, among other things, cyclic adenosine-3', 5'-monophosphate (cAMP) and the cAMP receptor protein (CRP). Mutants deficient in adenyl cyclase (cya-), the enzyme which synthesizes cAMP, or CRP (crp-) are unable to utilize a variety of carbohydrates, including L-arabinose. Ara+ revertants of a cya-crp- strain were isolated on 0.2% minimal L-arabinose plates, conditions which require the entire ara regulon to be activated in the absence of cAMP and CRP. Evidence from genetic and physiological studies is consistent with placing these mutations in the araC regulatory gene. Deletion mapping with one mutant localized the site within either araO or araC, and complementation tests indicated the mutants acted trans to confer the ability to utilize L-arabinose in a cya-crp- genetic background. Since genetic analysis supports the conclusion, that the mutant sites are in the araC regulatory gene, the mutants were designated araCi, indicating a mutation in the regulatory gene affecting the cAMP-CRP requirement. Physiological analysis of one mutant, araCi1, illustrates the trans-acting nature of the mutation. In a cya-crp- genetic background, araCi1 promoted synthesis of both isomerase, a product of the araBAD operon, and permease, a product of the araE operon. Isomerase and permease levels in araCi1 cya+ crp+ were hyperinducible, and the sensitivity of each to cAMP was altered. Two models are presented that show the possible mutational lesion in the araCi strains.

Adenylyl Cyclases↗

Genetic architecture of a selection response in Arabidopsis thaliana.

Quantitative trait locus (QTL) mapping has become an established and effective method for studying the genetic architecture of complex traits. In this report, we use a QTL mapping approach in combination with data from a large selection experiment in Arabidopsis thaliana to explore a response to selection of experimental populations with differentiated genetic backgrounds. Experimental populations with genetic backgrounds derived from ecotypes Landsberg and Niederzenz were exposed to multiple generations of fertility and viability selection. This selection resulted in phenotypic shifts in a number of life-history and fitness-related characters including early development time, flowering time, dry biomass, longevity, and fruit production. Quantitative trait loci were mapped for these traits and their positions were compared to previously characterized allele frequency changes in the experimental populations (Ungerer et al. 2003). Quantitative trait locus positions largely colocalized with genomic regions under strong and consistent selection in populations with differentiated genetic backgrounds, suggesting that alleles for these traits were selected similarly in differentiated genetic backgrounds. However, one QTL region exhibited a more variable response; being positively selected on one genetic background but apparently neutral in another. This study demonstrates how QTL mapping approaches can be combined with map-based population genetic data to study how selection acts on standing genetic variation in populations.

Analysis of Variance↗

Various factors (allergen nature, mouse strain, CpG/recombinant protein expressed) influence the immune response elicited by genetic immunization.

BACKGROUND: Genetic immunization is a very promising therapeutic approach for allergy treatment. In the present study we investigate the influence of the nature of the allergen, the mouse strain, and the relative amount of CpG to expressed recombinant protein on immune responses using two major peanut allergens, Ara h 1 and Ara h 4. METHODS: The cDNA of Ara h 1 and of an isoform of Ara h 4 were cloned and inserted in pcDNA3. Antigen specific IgG1, IgG2a and IgE were followed after genetic immunization with 100 microg of these clones in mouse strain SKH-Hr1 or BALB/c and with 1 microg of the clones+99 blank plasmid in SKH-Hr1. RESULTS: Genetic immunization in SKH-Hr1 with Ara h 1 elicited a classical Th1 type response, but Ara h 4 elicited a mixed Th1/Th2 response with high IgG1 and even IgE in some mice. In BALB/c both plasmids produced a high IgG1 level. Decreasing the amount of plasmid injected did not change the immune response profile. However, increasing the amount of CpG administered relative to the recombinant Ara h 4 protein expressed reversed the Th1/Th2 response pattern in SKH-Hr1 mice. CONCLUSIONS: Immune responses after genetic immunization are strongly influenced by the nature of the allergen, the mouse strain, and the ratio of CpG to recombinant protein expressed.

Allergens↗

Interindividual variations in constitutive interleukin-10 messenger RNA and protein levels and their association with genetic polymorphisms.

BACKGROUND: Genetic variations in the interleukin (IL)-10 gene promoter have been associated with levels of induced production of IL-10, disease susceptibility, and allograft rejection. Small amounts of this cytokine are constitutively produced and are important in maintaining the physiologic function of the cytokine network. In this study, we evaluated the distribution of IL-10 basal levels and its genetic regulation in a healthy Spanish population. METHODS: Polymorphisms at the -1,082, -819, and -512 positions of the IL-10 promoter were analyzed by polymerase chain reaction amplification and hybridization with fluorescent-labeled allele-specific probes in 183 Spanish people. Levels of IL-10 messenger (m)RNA were tested by real-time reverse transcription-polymerase chain reaction in 123 healthy donors. Serum concentrations of IL-10 were measured by a highly sensitive ELISA, whereas protein amounts in lipopolysaccharide culture supernatants were quantified by an in-house ELISA. RESULTS: The frequency of IL-10 promoter alleles and haplotypes in our population showed remarkable differences from other Caucasian populations. Large interindividual variations were found in mRNA and protein constitutive levels of IL-10, which allowed its classification in low and intermediate/high producers. We found statistical differences in mRNA concentration between the polymorphic variant GCC/GCC and the low producer genotypes. The G allele at position -1082 was the most important genetic factor in the regulation of constitutive IL-10 mRNA levels. Similarly, we also found an association of this polymorphic position with serum concentration greater than 2 pg/mL. CONCLUSIONS: Constitutive levels of IL-10 (mRNA and serum protein) displayed remarkable interindividual variations, which are genetically controlled by polymorphic variants at the cytokine gene promoter.

Alleles↗

The impact of population heterogeneity on risk estimation in genetic counseling.

BACKGROUND: Genetic counseling has been an important tool for evaluating and communicating disease susceptibility for decades, and it has been applied to predict risks for a wide class of hereditary disorders. Most diseases are complex in nature and are affected by multiple genes and environmental conditions; it is highly likely that DNA tests alone do not define all the genetic factors responsible for a disease, so that persons classified into the same risk group by DNA testing actually could have different disease susceptibilities. Ignorance of population heterogeneity may lead to biased risk estimates, whereas additional information on population heterogeneity may improve the precision of such estimates. METHODS: Although DNA tests are widely used, few studies have investigated the accuracy of the predicted risks. We examined the impact of population heterogeneity on predicted disease risks by simulation of three different heterogeneity scenarios and studied the precision and accuracy of the risks estimated from a logistic regression model that ignored population heterogeneity. Moreover, we also incorporated information about population heterogeneity into our original model and investigated the resulting improvement in the accuracy of risk estimation. RESULTS: We found that heterogeneity in one or more categories could lead to biased estimates not only in the "contaminated" categories but also in other homogeneous categories. Incorporating information about population heterogeneity into the original model greatly improved the accuracy of risk estimation. CONCLUSIONS: Our findings imply that without thorough knowledge about genetic basis of the disease, risks estimated from DNA tests may be misleading. Caution should be taken when evaluating the predicted risks obtained from genetic counseling. On the other hand, the improved accuracy of risk estimates after incorporating population heterogeneity information into the model did point out a promising direction for genetic counseling, since more and more new techniques are being invented and disease etiology is being better understood.

Bias↗

Reactions of GPs to a triage-controlled referral system for cancer genetics.

BACKGROUND: The demand for genetic services is increasing as public awareness about 'predictive' tests increases and commercial marketing initiatives develop. In the UK, genetic services vary widely between regions. To manage demand, an all-Wales cancer genetics service based on telephone triage and referral guidelines was designed and implemented. OBJECTIVES: The aim of this study was to examine the reactions of GPs to a cancer genetics service controlled by referral guidelines and a triage system, and the perceived impact genetics will have on general practice. METHODS: We conducted a structured qualitative study in primary care using sequential focus group discussions with 14 GPs, representing 12 practices divided into two groups (service providers and educationalists). The doctors were introduced to the 'new' genetics, briefed about the service and the referral guidelines and given an outline of the topics to be discussed. All discussions were recorded, transcribed and analysed. RESULTS: The GPs in this study had not considered how they and their teams would handle the practical implications of the 'new' genetics. They had no major objections to a triage system as a means of regulating access to a scarce specialist service, but were concerned about two issues. First, that an insistence on the completion of a postal questionnaire as a means of obtaining an initial assessment could disadvantage some individuals and, secondly, that it was not clear to either the GP or the patient that the risk assessment would be undertaken by a telephone interview. Although there was some concern about yet another set of referral guidelines, participants accepted that the potential demand for cancer genetics services had to be regulated. CONCLUSION: The acceptance by GPs of this triage system represented a reluctant acknowledgement that primary care, in its present organizational form, cannot provide high quality genetic counselling. However, the realization that this represented a relinquishment of the normal generalist role led to the emergence of ambivalence and a wish to consider how best to accommodate this new need in primary care.

Adult↗

Strain-specific modification of lethality in fucose-deficient mice.

The FX locus encodes an essential enzyme in the de novo pathway of GDP-fucose biosynthesis. Mice homozygous for a targeted mutation of the FX gene manifest a host of pleiotropic abnormalities including a lethal phenotype that is almost completely penetrant in heterozygous intercrosses on a mixed genetic background. Here we have investigated genetic suppression of FX-mediated lethality. Reduced recovery of heterozygous mice was observed while backcrossing the null FX allele to C57BL/6J (B6), but was less dramatic in an outcross to CASA/Rk and absent in an outcross to 129S1/SvImJ, indicating that genetic background modifies survival of FX+/- progeny. Substantial strain-specific differences in pre- and postnatal survival of FX-/- progeny were also detected in heterozygous crosses of C57BL/6J congenic, 129S1B6F1, and B6CASAF1 mice. Specifically, intrauterine survival of FX-/- mice was greatly increased during a heterozygous intercross on a uniform C57BL/6J genetic background compared with survival on a hybrid genetic background consisting of a mixture of C57BL/6J and 129S2/SvPas. In addition, statistically significant clustering of FX-/- progeny into litters and specific breeding cages was noted during a B6CASAF1 FX+/- intercross, suggesting a rare mechanism for modifier gene action in which parentally expressed genes define the phenotype, in this case the survival potential, of mutant offspring. Our results disclose that lethality in FX mutant mice is determined by one or more strain-specific modifier loci.

Alleles↗

The anxiety-like phenotype of 5-HT receptor null mice is associated with genetic background-specific perturbations in the prefrontal cortex GABA-glutamate system.

A deficit in the serotonin 5-HT(1A) receptor has been found in panic and post-traumatic stress disorders, and genetic inactivation of the receptor results in an anxiety-like phenotype in mice on both the C57Bl6 and Swiss-Webster genetic backgrounds. Anxiety is associated with increased neuronal activity in the prefrontal cortex and here we describe changes in glutamate and GABA uptake of C57Bl6 receptor null mice. Although these alterations were not present in Swiss-Webster null mice, we have previously reported reductions in GABA(A) receptor expression in these but not in C57Bl6 null mice. This demonstrates that inactivation of the 5-HT(1A) receptor elicits different and genetic background-dependent perturbations in the prefrontal cortex GABA/glutamate system. These perturbations can result in a change in the balance between excitation and inhibition, and indeed both C57Bl6 and Swiss-Webster null mice show signs of increased neuronal excitability. Because neuronal activity in the prefrontal cortex controls the extent of response to anxiogenic stimuli, the genetic background-specific perturbations in glutamate and GABA neurotransmission in C57Bl6 and Swiss-Webster 5-HT(1A) receptor null mice may contribute to their shared anxiety phenotype. Our study shows that multiple strains of genetically altered mice could help us to understand the common and individual features of anxiety.

Animals↗

A qualitative study of GPs' views on modern genetics.

BACKGROUND: With rapid advances in genetics and increased public awareness of genetic testing for many hereditary diseases, the demand for genetic services may increase. We wondered how developments in genetics have impacted on general practice and the position general practitioners have taken in practising the new genetics. METHOD: A qualitative study using semi-structured interviews conducted during 2003-2004 with 15 GPs practising in Sydney (New South Wales) and the Australian Capital Territory. RESULTS: General practitioners reported that genetic services had minimal impact on their practice and the number of consultations related to genetic conditions was insignificant. They felt they were often not included in the 'referral loop' of such patients. Their knowledge of advances in genetics was limited. They were wary of the possible costs of testing and the time taken to provide genetic counselling. DISCUSSION: General practitioners' attitudes toward modern genetics seems to be disengaged, and they are ambivalent toward the role they now play, or will play, in genetic services.

Attitude of Health Personnel↗

Cyclin A1 protein shows haplo-insufficiency for normal fertility in male mice.

In higher eukaryotes, the cyclins constitute a family of proteins involved in progression through the cell cycle. The cyclin A1 gene (Ccna1) is expressed during meiosis and is required for spermatogenesis. Targeted disruption of the Ccna1 gene with a LacZ reporter gene has allowed us to study the expression pattern of this gene in more detail. We have confirmed expression in mouse pre-meiotic spermatocytes and also detected expression in the accessory olfactory bulb, hippocampus and amygdala of the adult brain. We have also found that the amount of cyclin A1 protein influences the fertility of male mice and its action is modulated by genetic background. On an outbred genetic background (129S6/SvEv x MF1), Ccna1 (tm1Col) -/- animals are sterile due to spermatogenic arrest prior to the first meiotic division while Ccna1 (tm1Col) +/- mice show reduced sperm production and fertility. This is even more pronounced on an inbred genetic background (129S6/SvEv) where Ccna1 (tm1Col) +/- male mice are sterile due to a severe reduction in the total number of sperm.

Animals↗

Genetic mapping of modifier loci affecting malignant hypertension in TGRmRen2 rats.

BACKGROUND: Genetic background has a major influence on the manifestation of multifactorial diseases such as hypertension in which severe complications may be caused through an interaction with additional factors, which may be genetically determined. We have previously described a genetic model of malignant hypertension (MH) in rats carrying the mouse Ren2 gene (TGRmRen2-27), in which the phenotype is dependent on the genetic background. METHODS: Using a single homozygous TGRmRen2-27 male as transgene donor, we produced two F1 populations with (a) 100% penetrance of MH in progeny heterozygous for the Fischer F344 genetic background and (b) 58.5% penetrance in progeny heterozygous for the Lewis genetic background. To identify the modifier loci affecting the phenotype, a cohort of 252 males was produced by breeding the same single male with Fischer-Lewis F1 females. The progeny were phenotyped for clinical and pathological features of MH. RESULTS: Genome-wide screening and quantitative trait loci (QTL) analysis identified two loci, on chromosome 10 (LOD 4.4) and on chromosome 17 (LOD 3.9) close to the Ace and At1 genes, respectively, which contribute to the lethal MH phenotype. Their influence on mortality was consistent with a multiplicative effect of the two loci. In addition, we found higher plasma angiotensin-converting enzyme activity in progeny receiving the Fischer allele than in progeny receiving the Lewis allele (123.5 +/- 9.5 vs. 91.8 +/- 4.9 U/liter, P < 0.01), suggesting the association of angiotensin-converting enzyme and MH. CONCLUSIONS: Our study demonstrates the application of a transgene as a "major gene" to facilitate the identification of modifier loci, which can affect the phenotype of MH, and reveals Ace and At1 as candidate genes involved in the manifestation of the MH phenotype.

Animals↗

Hemizygous mice for the angiotensin II type 2 receptor gene have attenuated susceptibility to azoxymethane-induced colon tumorigenesis.

Evidence suggests that the use of angiotensin-converting enzyme inhibitors potentially reduces the risk of cancer, though the mechanism is unclear. To clarify a potential involvement of angiotensin II (Ang II) signaling in cancer risk, we have examined the effect of Ang II receptor deficiency on azoxymethane (AOM)-induced colon tumorigenesis. Male Ang II type 2 receptor gene-disrupted (AT(2)-null) mice with a 129/Ola and C57BL/6J genetic background, AT(2)-null mice with an SWR/J genetic background, and their corresponding control wild type mice were treated once a week with AOM (10 mg/kg, i.p., 4 consecutive weeks) or saline vehicle. All mice were killed 23-26 weeks after the initial injection of AOM, and tumor burdens were examined. AOM treatment caused the development of colon tumors in all wild type control mice regardless of genetic background (100% tumor prevalence), but only one tumor was present in AT(2)-null mice with a 129/Ola and C57BL/6J genetic background (11.1% tumor prevalence). Although the introduction of the AOMsusceptible SWR/J genetic background induced AOM susceptibility in AT(2) null mice, the tumor multiplicity (6.3) and tumor size (19.8 +/- 3.0 mm(3)) were significantly smaller than those in wild type mice (multiplicity, 12.0 and size, 36.8 +/- 3.2 mm(3)). AOM efficiently downregulated cytochrome P450 2E1 (CYP2E1) in the liver of wild type mice significantly more than in AT(2)-null mice. The levels of DNA methyl adducts formed in wild type mouse colon epithelium by AOM treatment were also significantly higher than in AT(2)-null mice. These results imply that the AT(2) receptor functions to augment AOM-induced downregulation of CYP2E1 expression in the liver, and thus increases AOM-induced tumorigenesis in the colon. The AT(2) receptor function in the liver may be a potential determinant of tumor susceptibility in chemical carcinogen-induced colon tumorigenesis.

Animals↗

Introductory guide to the language of molecular genetics.

BACKGROUND: This special section on molecular genetics was invited in order to raise awareness of the potential of molecular genetic approaches to inform child psychologists, psychiatrists and related professionals. As much of the terminology is specific to the field, this introductory guide aims to aid readers who may be unfamiliar with the approaches of this discipline. METHODS: Basic terminology and genetic processes are described, with sections covering 'The Human Genome' and 'Genetic Markers'. RESULTS: The range of genetic markers is growing all the time, but those that are thought to be functional and/or are highly variable are particularly useful. CONCLUSIONS: Genotyping approaches that offer high efficiency, thus allowing for large numbers of genotypes on large numbers of individuals, are likely to come to the fore in the next few years.

Genetic Markers↗

Genetic variation in the humoral immune responses of mice to the nematode Trichuris muris.

Genetically based differences in the antibody responses to the large intestinal nematode Trichuris muris were studied in two groups of H-2 congenic strains of mice that differed in their relative resistance to infection with this parasite. The primary antibody response to parasite excretory/secretory (E/S) antigen was predominantly an IgG response with the strains forming two distinct groups, defined by their genetic background. The more susceptible B10 genetic background mice had strikingly higher antibody levels than mice of the BALB genetic background. Superimposed upon these background effects were clearly defined influences attributable to H-2-linked genes, strains which differed genetically only at H-2 loci exhibiting differences in the kinetics of the antibody response. Only B10.G and B10.BR mice showed any great increase in IgM levels post-infection. No IgA specific to E/S antigen was detected in the peripheral circulation of any strain at any time post-infection. Antibody responses to a 40-43 kD antigen revealed clear H-2-linked gene effects, with mice sharing the H-2k haplotype (B10.BR, BALB/K) exhibiting considerably higher total antibody levels than strains expressing other haplotypes; mice of the H-2d haplotype (BALB/c, B10.D2/n) responded very weakly to this antigen. A Western blot analysis of antigen recognition by antibody revealed similarities between the mouse strains in their total antibody responses to T. muris E/S antigen. However, immunoprecipitation studies showed that in general the more susceptible B10 congenic strains had wider spectra of antigen recognition than the BALB congenics. Strains sharing the same H-2 haplotype had dissimilar antigen recognition profiles, but strains sharing the H-2b haplotype (B10, BALB/B) recognized a low mol. wt antigen (20-23 kD) not recognized by any other strain, suggesting an exclusively H-2b restriction in the recognition of this antigen. These results support the conclusion that both H-2-linked and background genes play important roles in controlling the humoral immune response to T. muris infection.

Animals↗

Photosensitivity in cutaneous lupus erythematosus: lessons from mice and men.

Mouse models are similar but not identical to human diseases. However, they are important for research into the pathogenesis underlying autoimmune diseases because they allow us to evaluate similarities and differences between human diseases and mouse models. In fact, experimental models and inbred lupus-prone mice are tools that enable a better understanding of the 'photosensitivity' or 'photocytotoxicity' phenomena in relation to autoimmunity. Genetic studies of MRL/lpr mice revealed that the appearance of macroscopic lupus erythematosus (LE)-like skin lesions needs the lpr mutation plus an additional factor in an autosomal dominant fashion. The candidate is ultraviolet (UV) B light, the susceptibility to which is regulated by the genetic background. Such a genetic background is also speculated to be important in human cutaneous LE patients. The translocation of anti-SS-A/Ro on cultured keratinocytes irradiated with UVB light is quantitatively different from photocytotoxicity, and the quantitative levels are significantly higher in systemic LE and subacute cutaneous LE than in discoid LE and normal controls. This review focuses on the lessons gleaned from mouse and human models, and discusses photosensitivity in human cutaneous LE.

Animals↗

Effect of gestation diet intake on plasma lipids and progeny birth and weaning weights of genetically lean, obese and contemporary swine.

Genetically obese (O), and lean (L) and contemporary (C) primiparous swine were assigned from day 30 to 40 of pregnancy to parturition to one of two dietary treatments: 1) 1.8 kg daily (6000 kcal DE) digestible energy, and 2) 0.6 kg daily (2000 kcal DE) of a standard corn-soybean meal-based diet. O gilts weighed less and were fatter at week 16 than L or C gilts. L and C gilts fed the low diet intake maintained constant body weight throughout pregnancy while O gilts gained approximately 10 kg. All gilts fed adequate energy gained weight. Plasma free fatty acids were higher and triglycerides were lower in pregnant gilts fed restricted energy. Plasma cholesterol and blood glucose appeared to be unaffected by genetic background, suggesting that genetic propensity to obesity is not necessarily associated with hypercholesterolemia or hyperglycemia. Pig birth weight was reduced by maternal feed restriction only in O and C pigs; survival was higher in progeny of O dams than in those of L and C dams. Maternal energy restriction had no effect on survival in L, C, or O pigs. Preweaning growth of C but not of L or O progeny was adversely affected by maternal feed restriction. The data illustrate the significance of genetic X gestation energy interactions in dam and progeny traits and suggest that a consideration of genetic background is essential in evaluating response criteria related to feed restriction during pregnancy.

Animals↗