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PubMed1996

Changes in body composition and adipocyte cellularity of male broilers subjected to varying degrees of early-life feed restriction.

Three experiments were conducted to determine growth performance, body composition changes, and adipocyte characteristics of male broilers subjected to early-life feed restriction. The purpose of Experiment 1 was to determine 42-d growth performance and body composition changes. Treatments used were full-fed control and 50% physical feed restriction during the period 6 to 12 d of age. Experiment 2 was conducted to determine the adipocyte characteristics during and after feed restriction to 42 d of age. An additional treatment involved gradual refeeding following the feed restriction period. Experiment 3 was designed to test the effect of feeding different types of dietary fat during realimentation on the abdominal fat pad (AFP) size, and lasted until 18 d of age. Three types of fats were tested, namely animal-vegetable (A-V) blend, flax oil, and animal tallow, each represented by full-fed and feed-restricted treatments. Complete compensatory growth by feed-restricted birds relative to controls was not achieved by 42 d in either Experiments 1 or 2. Early feed restriction resulted in lower body fat percentage at 12 d (P < 0.05), although by 42 d a higher rate of fat deposition mainly by hypertrophy of adipocytes resulted in no difference in fatness. Gradual reintroduction into ad libitum feeding did not alter such adipocyte hypertrophy nor improve compensatory growth response during refeeding. There was consistent improvement in feed efficiency associated with early-life feed restriction (P < 0.05). The use of different types of dietary fat did not effect the AFP when expressed as percentage body weight. Birds that were fed A-V blend during the refeeding period had bigger AFP (grams per bird), a situation that is attributable to differences in body weight. Attainment of growth compensation by the feed-restricted broilers apparently requires a more prolonged growth period or a less severe feed restriction program than that used here. Saturation of dietary fat has no effect on realimentation characteristics of the broiler.

Adipocytes↗

PubMed2001

Variable immunodominance hierarchies for H2-M3-restricted N-formyl peptides following bacterial infection.

H2-M3-restricted presentation of N-formyl methionine (f-Met) peptides to CD8(+) T cells provides a mechanism for selective recognition of bacterial infection. In this report we demonstrate that Listeria monocytogenes infection induces distinct CD8(+) T cell populations specific for each of the known Listeria-derived formyl methionine peptides presented by M3. The sum H2-M3-restricted, Listeria-specific T cell response constitutes a major fraction of the total CD8(+) T cell response to primary infection. H2-M3-restricted T cell populations expand synchronously in vivo and achieve peak frequencies approximately 2 days earlier than MHC class Ia-restricted T cell populations. Although cross-recognition of different f-Met peptides by M3-restricted T cells was previously described, costaining of CD8(+) T cells ex vivo with H2-M3 tetramers complexed with different f-Met peptides shows that the majority of Listeria-specific, M3-restricted CD8(+) T cells are peptide specific. In contrast to the highly predictable size and immunodominance hierarchies of MHC class Ia-restricted T cell responses, the magnitudes of T cell responses specific for H2-M3-restricted peptides are remarkably variable between genetically identical mice. Our findings demonstrate that H2-M3-restricted T cell responses are distinct from classically restricted T cell responses to bacterial infection.

Animals↗

PubMed2003

H2-M3-restricted memory T cells: persistence and activation without expansion.

H2-M3-restricted T cells respond more rapidly to primary Listeria monocytogenes infection than conventional MHC class Ia-restricted T cells. Reinfection with L. monocytogenes, while inducing explosive proliferation of H2-K(d)-restricted T cells, does not stimulate significant expansion of H2-M3-restricted CTL. These disparate responses to reinfection are apparent within 5 days of primary L. monocytogenes infection. However, H2-M3-restricted memory T cells are generated, and are indistinguishable from classically restricted T cells in terms of cell surface memory markers and longevity. Early responses of H2-M3- and H2-K(d)-restricted memory T cells to reinfection are similar, with increases in size and expression of activation markers. Interestingly, priming of H2-M3-restricted T cells with an L. monocytogenes-derived N-formyl peptide plus anti-CD40 generates memory T cells that expand upon re-exposure to Ag during L. monocytogenes infection. Our data indicate that disparate H2-M3- and MHC class Ia-restricted memory T cell responses reflect intrinsic differences between these T cell populations. Although distinct proliferative programs appear to be hardwired in these populations during primary L. monocytogenes infection, under different inflammatory circumstances M3-restricted T cell populations can maintain the ability to expand upon re-exposure to Ag.

Animals↗

PubMed2003

Functional characterization of class Ia- and non-class Ia-restricted Chlamydia-reactive CD8+ T cell responses in humans.

CD8(+) T cells are a key immune component for the eradication of many intracellular pathogens. This study aims to characterize the human CD8(+) T cell response to naturally processed chlamydial Ags in individuals exposed to the intracellular pathogen Chlamydia trachomatis. By using C. trachomatis-infected autologous dendritic cells (DCs) as stimulators, Chlamydia-reactive CD8(+) T cell responses were detected in all 10 individuals tested. The majority of the Chlamydia-reactive CD8(+) T cells were non-MHC class Ia restricted in all three of the individuals tested. From one donor, three non-class Ia-restricted and two class Ia-restricted Chlamydia-specific CD8(+) T cells were cloned and characterized further. All five T cell clones secreted IFN-gamma in response to autologous DCs infected with viable Chlamydia, but not with DCs pulsed with inactivated chlamydial elementary bodies. MHC class Ia-restricted and non-class Ia-restricted responses were inhibited by DC treatment with a proteasomal inhibitor and an endoplasmic reticulum-Golgi transport inhibitor, suggesting that these T cells recognize a peptide Ag translocated to the host cell cytosol during infection that is processed via the classical class Ia Ag-processing pathway. Even though both restricted and nonrestricted CD8(+) T cells produced IFN-gamma in response to Chlamydia-infected fibroblasts, only the non-class Ia-restricted cells were lytic for these targets. The class Ia-restricted CTLs, however, were capable of cytolysis as measured by redirected killing. Collectively, these data demonstrate that both class Ia-restricted and non-classically restricted CD8(+) T cells are elicited in C. trachomatis-exposed individuals. Their role in host immunity remains to be elucidated.

Antigen Presentation↗

PubMed2006

H2-M3-restricted T cells participate in the priming of antigen-specific CD4+ T cells.

H2-M3-restricted CD8+ T cells provide early protection against bacterial infections. In this study, we demonstrate that activated H2-M3-restricted T cells provide early signals for efficient CD4+ T cell priming. C57BL/6 mice immunized with dendritic cells coated with the MHC class II-restricted listeriolysin O peptide LLO(190-201) (LLO) generated CD4+ T cells capable of responding to Listeria monocytogenes (LM) infection. Inclusion of a H2-M3-restricted formylated peptide fMIGWII (fMIG), but not MHC class Ia-restricted peptides, during immunization with LLO significantly increased IFN-gamma-producing CD4+ T cell numbers, which was associated with increased protection against LM infection. Studies with a CD4+ T cell-depleting mAb indicate that the reduction in bacterial load in fMIG plus LLO immunized mice is likely due to augmented numbers of LLO-specific CD4+ T cells, generated with the help of H2-M3-restricted CD8+ T cells. We also found that augmentation of LLO-specific CD4+ T lymphocytes with H2-M3-restricted T cells requires presentation of LLO and fMIG by the same dendritic cells. Interestingly, the augmented CD4+ T cell response generated with fMIG also increased primary LM-specific responses by MHC class Ia-restricted CD8 T cells. Coimmunization with LLO and fMIG also increases the number of memory Ag-specific CD4+ T cells. We also demonstrate that CD8 T cells restricted to another MHC class Ib molecule, Qa-1, whose human equivalent is HLA-E, are also able to enhance Ag-specific CD4+ T cell responses. These results reveal a novel function for H2-M3- and Qa-1-restricted T cells; provision of help to CD4+ Th cells during the primary response.

Adoptive Transfer↗

PubMed2001

Self-restriction of medications due to cost in seniors without prescription coverage.

OBJECTIVE: Little is known about patients who skip doses or otherwise avoid using their medications because of cost. We sought to identify which elderly patients are at highest risk of restricting their medications because of cost, and how prescription coverage modifies this risk. DESIGN AND PARTICIPANTS: Cross-sectional study from the 1995-1996 wave of the Survey of Asset and Health Dynamics Among the Oldest Old, a population-based survey of Americans age 70 years and older. MEASUREMENTS: Subjects were asked the extent of their prescription coverage, and whether they had taken less medicine than prescribed for them because of cost over the prior 2 years. We used bivariate and multivariate analyses to identify risk factors for medication restriction in subjects who lacked prescription coverage. Among these high-risk groups, we then examined the effect of prescription coverage on rates of medication restriction. MAIN RESULTS: Of 4,896 seniors who regularly used prescription medications, medication restriction because of cost was reported by 8% of subjects with no prescription coverage, 3% with partial coverage, and 2% with full coverage (P <.01 for trend). Among subjects with no prescription coverage, the strongest independent predictors of medication restriction were minority ethnicity (odds ratio [OR], 2.9 compared with white ethnicity; 95% confidence interval [95% CI], 2.0 to 4.2), annual income <$10,000 (OR, 3.8 compared with income > or =$20,000; 95% CI, 2.4 to 6.1), and out-of-pocket prescription drug costs >$100 per month (OR, 3.3 compared to costs < or =$20; 95% CI, 1.5 to 7.2). The prevalence of medication restriction in members of these 3 risk groups was 21%, 16%, and 13%, respectively. Almost half (43%) of subjects with all 3 risk factors and no prescription coverage reported restricting their use of medications. After multivariable adjustment, high-risk subjects with no coverage had 3 to 15 times higher odds of medication restriction than subjects with partial or full coverage (P <.01). CONCLUSIONS: Medication restriction is common in seniors who lack prescription coverage, particularly among certain vulnerable groups. Seniors in these high-risk groups who have prescription coverage are much less likely to restrict their use of medications.

Aged↗

PubMed1992

Response of fetal and newborn piglets to maternal protein restriction during early or late pregnancy.

Dietary protein restriction during pregnancy has an adverse effect on progeny development, although the importance of the time at which the nutritional insult occurs is unclear. The objective in our study was to test the hypothesis that severe protein restriction during the first trimester of swine pregnancy has a greater detrimental effect on fetal development than restriction in late pregnancy. On the day of mating, primiparous swine were assigned to control (C, 13% protein) or protein-restricted (PR, 0.5% protein) diets and fed in 4 regimens: 1) C diet throughout pregnancy (114 +/- 2 days) (n = 5), 2) PR diet to day 44, C diet to parturition (n = 6), 3) C diet to day 80, PR diet to parturition (n = 8), and 4) PR diet throughout pregnancy (n = 6). In addition, 6 pigs fed C and 7 pigs fed PR diets were killed at day 44 to assess placental and fetal development. Maternal diet had no effect on placental or fetal weight, crown-rump length, or heart girth circumference in 44-day fetuses. Mean birth weight of newborn piglets was 1462, 1291, 1262, and 1064 g for C, PR:C, C:PR, and PR groups, respectively (C greater than PR:C = C:PR greater than PR, p less than 0.01). Plasma total protein and albumin were less (p less than 0.01) in PR than in PR:C and C:PR; all three groups were less than C (p less than 0.01). Liver weight and total liver protein, RNA, and DNA followed the same pattern (C greater than PR:C = C:PR greater than PR, p less than 0.05). Longissimus muscle total protein, RNA, and DNA were greater in group C than in all other groups (p less than 0.01). Maternal protein restriction during early pregnancy produced less developmental impairment than restriction throughout pregnancy, but the magnitude of impairment was similar to that produced by restriction during only the third trimester. The effects of early restriction were manifested at birth, even though none of the indices of stunting were observed at 44 days when the maternal protein restriction was ended. Whether the effects of early versus late restriction show the same mechanism of action has not been determined.

Animals↗

PubMed1987

Direct receptor:receptor interactions between T and B lymphocytes: idiotypic restriction in the antibody response to a cloned helper T cell receptor.

The concept of an immunological network includes the possibility of interactions between receptors on T and B lymphocytes, and such interactions, should they occur, might be expected to influence the repertoire of receptors in each set of cells. Indeed, B cell idiotype specific helper T cells, both MHC-restricted and MHC-unrestricted, have been reported and have been shown to influence the expression of the B cell repertoire. Likewise, it has been reported that B cells may influence the specificity of both regulatory and MHC-restricted T cells. However, interactions between receptors on cloned, MHC-restricted helper T cells and B cells have been difficult to document. Recently, we have taken advantage of an unusual cloned helper T cell line to demonstrate that anti-T cell receptor antibody is produced by direct receptor:receptor interactions between T and B lymphocytes, and that these interactions are not MHC restricted. However, these earlier studies did not address the question of whether such interactions led to activation of B cells expressing multiple distinct antibodies, or whether direct T cell receptor:B cell receptor interactions would lead to an idiotypically restricted B cell response. To address this question, we have now examined both monoclonal and polyclonal responses to the receptor of a conventional, MHC-restricted cloned T cell line, and have shown that these responses are of limited idiotype heterogeneity. Indeed, about 60% of antibodies produced to the receptor of this cloned line share idiotypic determinants, and appear to recognize a single epitope on the receptor. Idiotypically unrelated anti-receptor antibodies, although still specific for the cloned line, recognize what appears to be a distinct epitope on the receptor. These data suggest several conclusions. First, they demonstrate further that direct receptor:receptor interactions between helper T cells and B cells can occur, and can be mutually stimulatory for the two cell types. Second, as shown previously, such interactions are not MHC restricted. Third, such interactions can lead to an idiotypically restricted B cell response. Finally, it is interesting to compared these results with those of other investigators studying idiotype-specific helper T cells. As the cloned line used in this study is a conventional, MHC-restricted, antigen specific helper T cell bearing an alpha:beta heterodimeric receptor complex, and as its interaction with B cells is MHC unrestricted and leads to idiotypically restricted antibody responses, one might propose that such cells are candidates for a clone of an idiotype-specific helper.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMedDate not supplied

Food restriction and lysine supplementation alter growth, RNA, DNA, and protein contents of skeletal muscle.

Efficacy of supplementing total protein or a limiting amino acid to maintain muscle development during food restriction was examined in growing rats. Male rats weighing 108 +/- 8 g were assigned to one of five diet groups plus an initial group. Animals were fed either a wheat gluten-based diet or the wheat gluten-based diet supplemented with adequate levels of lysine. These diets were fed ad libitum or at a 75% restricted level. One restricted group was fed a high gluten diet designed to meet lysine requirements but at the restricted energy level. Rats were fed these diets for 6 weeks. Lysine supplementation resulted in higher levels of protein, RNA, and DNA in skeletal muscle and liver of animals fed ad libitum. Food restriction resulted in loss of protein and RNA from liver and skeletal muscle and lower ratios of protein/DNA. Initial DNA contents of plantaris and soleus muscles were not affected by food restriction; however, hepatic DNA was reduced. Supplementation of lysine to animals restricted in food intake failed to improve growth of skeletal muscle or liver, and resulted in lower protein contents in liver (11%), plantaris (6%), and soleus (38%). Increasing total protein intake for the animals with the restricted intake resulted in a higher RNA/DNA ratio without a parallel increase in protein in liver or muscle. This study demonstrates that during severe food restriction skeletal muscle DNA is preserved which maintains high potential for growth recovery. This study also indicates that during severe, prolonged food restriction supplementation of protein or limiting amino acids results in lower tissue protein contents.

Animals↗

PubMed1994

Energy restriction decreases number of circulating natural killer cells and serum levels of immunoglobulins in overweight women.

We examined the effects of energy restriction on immune response and also compared the effects of low fat (LF, 18.6 E%) and high fat (HF, 40.7 E%) diets during energy restriction on immunological parameters. Ten overweight women were fed the HF diet for 42 days (P1) to maintain their body weights. For the next 84 days (P2), the energy intake was reduced to 50% of the intake during P1 for all the women, five of them were fed the HF diet and the other five the LF diet. For the last 35 days of the study (P3), subjects remained on their respective diets, but the energy intake was increased to maintain BW to the level reached at the end of energy restriction. Serum concentrations of IgG, IgA, IgM, C3 and C4, numbers of lymphocytes and their subsets, blastogenesis of peripheral blood mononuclear cells cultured with phytohemagglutinin, concanavalin A and protein A were determined several times during the study. Delayed hypersensitivity skin (DHS) response to seven recall antigens was determined towards the end of each study period. None of the parameters studied were different between the HF and LF dietary groups. During energy restriction the subjects lost an average of 7 kg in the LF group and 9 kg in the HF group. Energy restriction caused a significant (P < 0.005) decrease in the serum concentration of IgG, IgA, C3, and the number of circulating natural killer (NK) cells. An increase in energy intake during P3 reversed some of the decreases caused by energy restriction, but the levels did not return to pre-restriction levels during these 35 days of refeeding adequate dietary energy. The numbers of circulating lymphocytes and their subsets with the exception of NK cells, serum levels of IgM and C4, and the DHS response monitored 48 h after the application of antigens were not affected by energy restriction. Health status of the women in our study did not seem to be compromised; however, it could be compromised under more drastic restrictions or with moderate restrictions in high risk subjects.

Adult↗

PubMed1995

Size-selected genomic libraries: the distribution and size-fractionation of restricted genomic DNA fragments by gel electrophoresis.

By using one-dimensional genome scanning, it is possible to directly identify the restricted genomic DNA fragment that reflects the site of genetic change. The subsequent strategies to obtain the molecular clones of the corresponding restriction fragment are usually as follows: (i) the restriction of a mass quantity of an appropriate genomic DNA, (ii) the size-fractionation of the restricted DNA on a preparative electrophoresis gel in order to enrich the corresponding restriction fragment, (iii) the construction of the size-selected libraries from the fractionated genomic DNA, and (iv) the screening of the library to obtain an objective clone which is identified on the analytical genome scanning gel. A knowledge of the size distribution pattern of restriction fragments of the genomic DNA makes it possible to calculate the heterogeneity or complexity of the restriction fragment in each size-fraction. This manuscript first describes the distribution of the restriction fragments with respect to their length. Some examples of the practical application of this theory to genome scanning is then discussed using presumptive genome scanning gels. The way to calculate such DNA complexities in the prepared size-fractionated samples is also demonstrated. Such information should greatly facilitate the design of experimental strategies for the cloning of a certain size of genomic DNA after digestion with restriction enzyme(s) as is the case with genome scanning.

Animals↗

PubMed1995

An improvement of restriction analysis of bacteriophage DNA using capillary electrophoresis in agarose solution.

Seven representatives of the serogroup B Staphylococcus aureus bacteriophages, 29, 53, 55, 83A, 85, phi 11 and 80 alpha, were examined by capillary electrophoresis (CE) for genomic homology using DNA restriction analysis. Genomic DNA of individual bacteriophages was cleaved by HindIII restriction endonuclease, and the resulting restriction fragments were separated by standard horizontal agarose slab gel electrophoresis (SGE) as well as by CE in low-melting-point agarose solutions. The number and size of restriction fragments identified by both methods were compared. The high separation power of CE makes it possible to extend the restriction fragment patterns. In most of the restriction patterns, some additional restriction fragments as small as 150 bp, not identified by SGE, were detected. With respect to speed, high separation efficiency, low sample consumption and automation, CE offers a simple procedure for processing of multiple samples cost-effectively in a reasonable time. The comparison of the complemented restriction patterns of the different phage strains and the subsequent identification of their common fragments leads to a deeper understanding of their phylogenetic relationships. The genome homologies expressed for individual phage pairs in terms of coefficient F values ranged from 15 to 69%. These values are in good accordance with the degree of DNA homology of these phages as determined by DNA hybridization studies and thermal denaturation analysis of DNA by other authors. The total size of each phage genome was estimated by adding the sizes of individual restriction fragments.

Bacteriophages↗

PubMed1999

Dietary protein restriction stress in the domestic fowl (Gallus gallus domesticus) alters adrenocorticotropin-transmembranous signaling and corticosterone negative feedback in adrenal steroidogenic cells.

Previous work with growing chickens (Gallus gallus domesticus) indicates that transient dietary protein restriction induces long-term enhancement of adrenal steroidogenic function in response to adrenocorticotropin (ACTH). The present study investigated two possible cellular functions mediating this enhanced response: (a) ACTH signal transduction and dissemination and (b) short-loop feedback inhibition of ACTH-induced corticosterone production by exogenous corticosterone. Cockerels (2 weeks old) were fed isocaloric synthetic diets containing either 20% (control) or 8% (restriction) soy protein for 4 weeks. Adrenal glands were processed for the isolation of adrenal steroidogenic cells nearly devoid of chromaffin cells ( approximately 90% adrenal steroidogenic cells). Results of experiments to assess signal transduction and dissemination indicated that protein restriction selectively enhanced ACTH-induced corticosterone production mediated by the cyclic AMP (cAMP)-dependent pathway. In addition, protein restriction substantially counteracted exogenous corticosterone-dependent inhibition of acute ACTH-induced corticosterone production (by 40.7% vs control). The proximal portion of the cAMP pathway seemed most affected by this stressor. Protein-restricted cells exhibited enhanced homologous sensitization to ACTH (136% greater than that of control cells) which appeared to be localized at a step(s) prior to or at the formation to cAMP. Also, maximal ACTH-induced cAMP production and sensitivity to ACTH in terms of cAMP production by protein-restricted cells were, respectively, 2.2 and 15.8 times those of control cells. However, variable results were obtained from other experiments designed to pinpoint the altered early steps in ACTH-transmembranous signaling. For example, with intact cells, cAMP responses to cholera toxin (CT) and forskolin (FSK) did not corroborate the results suggesting an augmentation of ACTH-signal transduction induced by protein restriction. Furthermore, basal and stimulatable (by ACTH, CT, FSK, and NaF) adenylyl cyclase activities from membranes from protein-restricted cells were, respectively, 47.2 and 40.2% less than those from control cells (normalized to 10(7) cell equivalents of crude membranes). Collectively, these findings suggest that protein restriction stress potentiates ACTH-induced corticosterone secretion by chicken adrenal steroidogenic cells in at least two ways: (1) on the proximal end, by modulating unknown factors which enhance cellular sensitivity to ACTH, ACTH receptor-adenylyl cyclase coupling, and adenylyl cyclase activity, and (2) on the distal end, by suppressing end-product corticosterone negative feedback, thus facilitating an increase in net corticosterone secretion.

Adenylyl Cyclases↗

PubMed1994

Molecular cloning and expression of a novel hydroxymethylcytosine-specific restriction enzyme (PvuRts1I) modulated by glucosylation of DNA.

The kanamycin resistance plasmid Rts1 restricts the growth of bacteriophage T2, T4 and T6. The DNA of these phage contains hydroxymethylcytosine (HMC) in place of regular cytosine and is modified by glucosylation. When HMC is not glucosylated, as in the DNA of glucosyl transferase-deficient T4 phage, this restriction becomes less apparent, a phenomenon not observed with any other known restriction systems. On the other hand, glucosylation of HMC in T6 phage leads to a less efficient restriction, while restriction of bacteriophage T2 remains unchanged. The modulating effect of glucose cannot be seen when cells contain a large amount of this enzyme, as in the case when multiple copies of its determinant are present in the cells. T-odd phage and bacteriophage lambda are not restricted by Rts1 suggesting that the restriction is specific to DNA containing HMC. The restriction phenotype is due to a single gene coding for a polypeptide of 293 amino acids. This enzyme has been named PvuRts1I. A gene with the sequence motifs similar to modification enzymes was found upstream of the gene coding for PvuRts1I. This gene, however, neither modifies the restriction phenotype of PvuRts1I, nor codes for detectable modification enzyme. T4 mutants with increased resistance to PvuRts1I appear to have deficiency in their beta-glucosyl transferase enzyme.

5-Methylcytosine↗

PubMed2004

Long-term dietary restriction causes negative effects on cognitive functions in rats.

Long-term dietary restriction is reported to increase life span and improve age-related cognitive deficits. The present study shows that the restriction increases the life span of rats but decreases their cognitive ability. Thirty-two rats were divided into restricted and ad lib feeding groups at 2.5 months of age. The restricted rats were kept at a weight of 280g. The restricted rats were poor in performing the Morris water maze task at 7-12 months. At 17-18 months, they were poor in performing the delayed matching-to-place task. At 24-27 months, the surviving 13 restricted and 5 ad lib rats performed the spatial discrimination task. The restricted rats were also poor in performing this task. Injection of glucose prior to the discrimination task improved their performance to the level of the ad lib rats. These results suggest that dietary restriction is beneficial for longevity but has negative effects on the performance of cognitive tasks, and that the cause of the negative effects may be a reduced availability of glucose in the food-restricted aged rats.

Aging↗

PubMed2006

Fasting ghrelin does not predict food intake after short-term energy restriction.

OBJECTIVE: To study the role of ghrelin as a hunger signal during energy restriction and to test the hypothesis that changes in fasting leptin concentrations during energy restriction are associated with changes in fasting ghrelin concentrations. RESEARCH METHODS AND PROCEDURES: Thirty-five healthy, lean men (23 +/- 3 years of age; BMI: 22.3 +/- 1.6 kg/m(2)) participated in a controlled intervention study. Fasting ghrelin and leptin concentrations were measured before and after 2 days of 62% energy restriction and after a 2-day period of ad libitum food intake. Energy intake during the latter period was assessed. RESULTS: On average, ghrelin concentrations did not change (0.05 mug/liter; 95% confidence interval, -0.03; 0.12) during energy restriction. Changes in ghrelin concentration during energy restriction were not associated with energy intake during the ad libitum period (r = 0.07; not significant). Ad libitum energy intake was, however, associated with the change in ghrelin concentrations during the same period (r = -0.34; p = 0.05). Ghrelin and leptin concentrations were not associated. In addition, the ratio of percentage changes in ghrelin and leptin during energy restriction was not correlated with ad libitum food intake after energy restriction (r = -0.26; p = 0.14). DISCUSSION: Fasting ghrelin concentrations did not rise after a 2-day energy restriction regimen. Moreover, changes in ghrelin concentrations during energy restriction were not associated with subsequent ad libitum food intake, suggesting that fasting ghrelin does not act as a hunger signal to the brain. The data did not support our hypothesis that leptin suppresses ghrelin levels.

Adolescent↗

PubMed2004

Is modification sufficient to protect a bacterial chromosome from a resident restriction endonuclease?

It has been generally accepted that DNA modification protects the chromosome of a bacterium encoding a restriction and modification system. But, when target sequences within the chromosome of one such bacterium (Escherichia coli K-12) are unmodified, the cell does not destroy its own DNA; instead, ClpXP inactivates the nuclease, and restriction is said to be alleviated. Thus, the resident chromosome is recognized as 'self' rather than 'foreign' even in the absence of modification. We now provide evidence that restriction alleviation may be a characteristic of Type I restriction-modification systems, and that it can be achieved by different mechanisms. Our experiments support disassembly of active endonuclease complexes as a potential mechanism. We identify amino acid substitutions in a restriction endonuclease, which impair restriction alleviation in response to treatment with a mutagen, and demonstrate that restriction alleviation serves to protect the chromosome even in the absence of mutagenic treatment. In the absence of efficient restriction alleviation, a Type I restriction enzyme cleaves host DNA and, under these conditions, homologous recombination maintains the integrity of the bacterial chromosome.

Adenosine Triphosphatases↗

PubMed1994

New polymorphism on platelet glycoprotein IIIa gene recognized by endonuclease Msp I: implications for PlA typing by allele-specific restriction analysis.

BACKGROUND: Five human platelet alloantigen systems have been shown to result from single base pair substitutions in encoding regions of platelet glycoprotein genes IIIa, Ib, IIb, and Ia. For each of the diallelic systems, at least one restriction enzyme is known to cut only one of the two haplotypes. In the PlA system, restriction endonucleases Nci I and Msp I both recognize the PlA2 allele. STUDY DESIGN AND METHODS: A causal observation of an unexpected Msp I restriction pattern of a PlA2/PlA2 individual was made. Samples from 261 blood donors were then typed for antigens of the PlA system by restriction fragment length polymorphism analysis using the Nci I and Msp I restriction enzymes. RESULTS: Applying both enzymes, concordant restriction patterns were found in 258 of 261 blood donors. Three donors had a base pair mutation on the PlA2 allele, which creates an additional restriction site for Msp I 20 base pairs downstream from the PlA polymorphic site. Nucleotide sequence analysis revealed a CT217-->CG217G base exchange resulting in a Leu40-->Arg40 polymorphism of glycoprotein IIIa. CONCLUSION: Presuming that the mutation is not a singular phenomenon and also occurs with the PlA1 haplotype, it could lead to false interpretations of restriction analysis with Msp I. To exclude that possibility, Nci I is preferred for restriction fragment length polymorphism typing in the PlA system.

Antigens, Human Platelet↗