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PubMed1989

Dietary restriction induces microcytic change and shortened life span of erythrocytes without anemia in mice.

Dietary restriction is well known to increase mean and maximal life span in rodents and other species, although the mechanisms remain unclear. To investigate the effects of dietary restriction on erythrocyte cellular life span, mice were fed 40% restricted diet and erythrocyte properties were examined. At the end of the 8th week of a feeding period, erythrocytes in the restricted mice showed strikingly shorter life span than those in the unrestricted mice (restricted; T1/2 = 15.4 +/- 1.1 days, unrestricted; T1/2 = 18.9 +/- 1.2 days). However, the restricted mice never showed anemic conditions although they had microcytes, in addition. Significant increase in the erythrocyte count was observed in the restricted mice. These results strongly suggest that increased erythropoiesis should exist in the restricted mice, and that some unknown biophysical significance made shortened erythrocyte life span in mice fed restricted amount of diet.

Animals↗

PubMed1986

Calorie restriction, ad libitum feeding, and cancer.

The inhibition of cancer by calorie restriction was discovered over 50 years ago. By 1950 it had been well characterized and there existed sufficient data to propose a mechanism of action. For reasons that remain unclear, but are probably related to the perception of the calorie restricted rodent as "small" and the ad libitum feeding regimen as more "normal," the concept of calorie restriction has been largely ignored by investigators after this time. Hence, despite the fact that calorie restriction is one of the oldest, best-documented, and most effective ways known to reduce cancer risk in rodents, it has had little impact on modern cancer research. In this report the history of calorie restriction is briefly reviewed, and a mechanism of action is proposed that involves increased production of ACTH and decreased production of gonadotrophins. It is further proposed that these changes may come about in part from the restriction of the time during which feeding is permitted as well as from the restriction of food per se. There is renewed interest in calorie restriction due in part to the growing recognition that there are differences in the efficiency of utilization of various sources of energy, in particular that fat calories are utilized more efficiently and provide more usable energy than carbohydrate calories. New data are presented indicating that the apparent enhancement by dietary fat of mammary cancer in rats is really a manifestation of the caloric effect. Further, the effect is abolished by moderate calorie restriction of only 15-20%. The application of these findings to the prevention of cancer in humans is considered.

Adrenocorticotropic Hormone↗

PubMed1986

Effect of early feed restriction in broilers. II. Lipid metabolism.

Three experiments were conducted with broiler chicks to evaluate the effect of dietary energy restrictions on in vitro lipid metabolism. In Experiment 1, chicks were restricted from either 6 to 12 or 6 to 18 days of age and then fed ad libitum until day 27. In Experiment 2, both male and female chicks were restricted from 5 to 11 days of age and then were refed until 27 or 54 days of age. Glutamic:oxaloacetic aminotransferase (GOT), isocitrate dehydrogenase (ICD), malic enzyme (ME) and the fatty acid synthetase complex (FAS) were assayed at 27 days (Experiment 1) and at 27 and 54 days (Experiment 2). In Experiment 3, male chicks were restricted from days 6 to 12 and then were refed until day 27. In vitro lipogenesis and enzyme activities were determined during the 12 to 18-day period as the chicks were refed following the restriction. Both restriction regimes decreased (P less than .05) ME and FAS at the conclusion of the respective restriction intervals (Experiments 1 & 2). The 6 to 12-day restriction decreased (P less than .05) in vitro lipogenesis in the 12 day old chick when compared to controls. When restricted chicks were refed, in vitro lipogenesis exceeded that of the controls at both 14 and 16 days, but was less than that of the controls at 27 days.

Adipose Tissue↗

PubMed1994

An analysis of duty restrictions of aviation personnel in the Republic of Korea.

Aviation medical records were reviewed from four U.S. Army medical clinics in the Republic of Korea for flying duty restrictions over a 1-year time period. Duty restrictions were catalogued into 1 of 15 different diagnostic categories and compared by parameters of duration, time of year, crew status, age, and sex. Four hundred twenty-eight records were reviewed. Respiratory illnesses were the most common cause of flight restriction, followed by gastrointestinal and musculoskeletal problems. Flight personnel averaged 12.8 days a year on restrictions. Non-crewmembers were frequently not restricted for treatments that should have required restriction, but when restricted, averaged a significantly longer period of time than crewmembers. Females averaged significantly fewer days out for restrictions, and there were large differences in the number of days out by age for certain restrictions, but the numbers were small. There were some seasonal variation noted in patient visits with fewer visits in the spring and summer.

Absenteeism↗

PubMed1995

Energy balance of rats subjected to continuous and intermittent food restriction.

Data from our laboratory have demonstrated that food restriction leads to alterations in energy balance such as reduced energy expenditure as an energy conservation mechanism. Food restriction may be imposed on the animals in different ways. The most common is to give equal daily amounts of restricted food. Alternatively, food may be given once every two or three days so that the food intake is not constant with the animal tending to eat more on the first day and be very restricted during the subsequent days of the period. The former model may elicit habituation to the low food intake while the latter may decrease the habituation stimulus since the food intake is not constant. Energy balance was determined in 3 groups of female rats weighing 206.7 +/- 2.0 g (N = 6 each): control (C), which received food ad libitum; continuously food restricted (CR), which received 8 g of food daily, and intermittently food restricted (IR), which received 24 g of food every 3 days. On the 21st day of treatment, the animals from both food-restricted groups showed a similar reduction of body weight (-47.9 +/- 5.1 and -55.8 +/- 4.0 g for CR and IR, respectively) and body energy (-501.0 +/- 65.5 and -427.0 +/- 82.1 for CR and IR, respectively), and they had similar energy expenditure (2643 +/- 72 and 2518 +/- 97 for CR and IR, respectively) which was different from ad libitum controls (4.6 +/- 2.9 body weight gain, 277.3 +/- 42.5 body energy gain and 4574 +/- 290 energy expenditure). Body weight decreased continuously in the CR group while in the IR group it followed the pattern of food intake with up-and-down shifts. We conclude that the energy balance pattern presented by food-restricted animals is the same regardless of the form of food restriction imposed.

Animals↗

PubMed1997

Effects of recombinant human insulin-like growth factor-1 and recombinant human growth hormone on anabolism and immunity in calorie-restricted alcoholic rats.

UNLABELLED: Patients with severe alcoholic liver injury exhibit very low serum insulin-like growth factor-1 (IGF-1) concentrations, along with many of the symptoms that might occur with an IGF-1 deficiency state (including severe protein calorie malnutrition and immunosuppression). This study was performed to assess the effects of recombinant human (rh) IGF-1 and/or rh growth hormone (rhGH) on anabolism and immunity in the calorie-restricted, immunosuppressed alcoholic rat. METHODS: Undernutrition was induced by calorie restriction such that each animal consumed 40% of ad libitum-fed controls. Alcohol was administered orally in the diet such that the mean daily intake was 9.4 g/kg/day. rhIGF-1 was administered by continuous subcutaneous infusion (380 micrograms/day) using a 14-day miniosmotic pump; rhGH was given by subcutaneous injections (400 micrograms/day). Matching placebo groups were also studied. RESULTS: On this regimen, ad libitum-fed controls were well nourished and increased body weight 34%, whereas Restricted controls lost 7.7% and Restricted alcohol-fed rats lost 15.2%. Significant but incomplete reversal of undernutrition was achieved with hormone therapy. Best improvement was obtained with combined therapy: rhIGF-1 + rhGH (p < 0.005; placebo versus active treatments). Immunologic impairment was observed to be severe in both thymus and spleen. The most severe changes were seen in thymi of the calorie-restricted, alcohol-fed rats, wherein 98% of the T lymphocytes were lost. rhIGF-1 treatment, but not rhGH, produced significant improvements in thymus. This was most pronounced in control rats (p < 0.005). Splenic T lymphocytes were less impaired and were more responsive to rhIGF-1 treatment; there was a maximum loss of 71% of T cells in Restricted, alcohol-fed rats. rhIGF-1 treatment completely restored splenic cellularity, as well as each of the T lymphocytes studied: CD5, CD4, and CD8. Functional status of splenic T lymphocytes was assessed by blast transformation after concanavalin A stimulation. Calorie restriction did not impair significantly this function in controls [Lieber-DeCarli control diet (LCD)]. However, it was significantly impaired in the Restricted, alcohol-fed rats (p = 0.003). In the presence of continued calorie restriction and alcohol, this function was not restored with either hormone (rhIGF-1 and/or rhGH). Their role in facilitating functional recovery after calories is restored, and alcohol is discontinued is under investigation.

Alcoholism↗

PubMed1992

Restriction analysis of the prototype strain of enteric adenovirus type 41 using exonuclease III.

Enteric adenoviruses 40 and 41 (Ad40 and Ad41) are a prominent cause of gastroenteritis in young children. Diagnosis of these enteric types by conventional means is complicated by their fastidious growth characteristics. Enteric adenovirus growth was enhanced by cocultivation. Typing of enteric isolates currently entails analysis of the extracted viral DNA with restriction enzymes. Restriction endonuclease fragments of the Ad41 strain Tak genome were ordered by (i) double digestion, (ii) release of restriction fragments from plasmids containing 84% of the Ad41 genome in EcoRI fragments A, B and C, (iii) hybridization of Southern blotted Ad41 fragments with EcoRI fragment containing plasmids and various segments of the Ad2 genome, (iv) sequential reduction of the genome beginning with terminal restriction fragments with exonuclease III and S1 nuclease. The termini of adenovirus genomes are difficult to clone and the use of exonuclease III is a useful alternative to conventional restriction mapping. DNA restriction patterns, fragment sizes and restriction maps of the Ad4 1 strain Tak with enzymes BamHI, BglII, ClaI, EcoRI, HindIII, PstI, SalI, SmaI and XhoI are presented. Prototype strain restriction maps should enable better understanding of adenovirus type 41 and its epidemiology.

Adenoviruses, Human↗

PubMed2000

Dietary protein restriction stress in the domestic chicken (Gallus gallus domesticus) induces remodeling of adrenal steroidogenic tissue that supports hyperfunction.

The stress of dietary protein restriction in the immature domestic turkey (Meleagris gallopavo) induces adrenal steroidogenic hypofunction that is associated with an alteration in the proportion of density-dependent subpopulations of steroidogenic cells within the adrenal gland. In contrast, when imposed on immature chickens, this nutritional stressor induces long-term enhancement of adrenal steroidogenic function. However, whether this alteration in function is accompanied by a remodeling of chicken adrenal steroidogenic tissue as in the turkey is not known. To address this question, immature cockerels (2 weeks old) were fed established isocaloric synthetic diets containing either 20% (control) or 8% (restriction) soy protein for 4 weeks. Adrenal glands were processed for the isolation of defined, density-separable, adrenal steroidogenic cell subpopulations: three low-density adrenal steroidogenic cell subpopulations [LDAC-1 (rho = 1.0285-1.0430 g/ml), LDAC-2 (rho = 1. 0430-1.0485 g/ml), and LDAC-3 (rho = 1.0485-1.0500 g/ml)] and one high-density subpopulation [HDAC (rho = 1.0510-1.0840 g/ml)]. The steroidogenic function of these cell subpopulations was assessed. Protein restriction consistently, but differentially, enhanced maximal ACTH-induced corticosterone production by the subpopulations: values of LDAC-1, -2, and -3 and HDAC from protein restricted birds were, respectively, 116, 43, 33, and 20% greater than those of corresponding cell subpopulations from control birds. However, it had contrasting influences on maximal ACTH-induced aldosterone production by the cell subpopulations. Whereas the value of LDAC-1 from protein-restricted birds was 70% greater than that from control birds, the values for LDAC-2 and -3 were not different from those of the control, and the value for HDAC was 22% less than that of the control. Protein restriction also altered the cell subpopulation composition of the adrenal gland: compared to control, it increased the proportion of LDAC-1 by 46% and decreased the proportion of LDAC-3 and HDAC by 34 and 20%, respectively. Thus, dietary protein restriction increased the proportion of cells (i.e., LDAC-1) having the greatest enhancement in corticosteroid production. This pattern of remodeling of chicken adrenal steroidogenic tissue in response to dietary protein restriction contrasts sharply with the pattern that occurs in another galliform species, the domestic turkey.

Adrenal Cortex Hormones↗

PubMed1980

The ral gene of phage lambda. I. Identification of a non-essential gene that modulates restriction and modification in E. coli.

Host controlled restriction in Escherichia coli can be relieved by pre-infecting restricting cells with modified lambda helper phages. This process, in which intact unmodified phage genomes are allowed to escape restriction attack, is mediated by a newly identified lambda function called ral. The ral gene has been located by deletion mapping between cIII and N. Efficient expression of the ral gene requires the product of the regulator gene N. Polyacrylamide gel analysis of the lambda proteins specified by the cIII-N region failed to reveal the product of the ral gene, but demonstrated that protein Ea10 is encoded by a gene located immediately to the left of ral. From these results the map order cIII-Ea10-ral-TL1-N was deduced. Ral specifically alleviates restriction in E. coli K and E. coli B, but does not affect restriction systems EcoRI, EcoRII and EcoP1. In addition, ral enhances the modification activity of the EcoK and EcoB restriction enzymes: we observed that efficient modification of progeny phages obtained by propagating unmodified lambda phages in r-m+ hosts, is dependent upon the presence of ral. We thus conclude that the ral gene product acts by modulating the restriction and modification activities of the type I restriction systems in E. coli, and the possible mechanisms will be discussed.

Bacteriophage lambda↗

PubMed1988

Chromosome banding in Amphibia. XII. Restriction endonuclease banding.

Fixed metaphase chromosomes of several species of Amphibia were treated with various restriction endonucleases and subsequently stained with Giemsa. Metaphases of man and chicken were examined in parallel under the same experimental conditions for comparison. The restriction enzymes always induce subsets of the C-banding patterns present in the amphibian karyotypes. The heterochromatic regions can be either resistant or sensitive to the restriction enzyme. The modified C-banding patterns revealed by different restriction endonucleases in the karyotype of the same species can be either extremely dissimilar or almost completely congruent. Correspondingly, the action of the same restriction enzyme on the karyotypes of different species may vary greatly. There is only rarely a correlation between the type of C-banding patterns produced by different restriction endonucleases and their specific base pair recognition sequences. In contrast to mammalian and avian chromosomes, restriction enzymes induce no multiple G-banding patterns in amphibian chromosomes. This is attributed to the difference in organization of the DNA in the genomes of poikilothermic vertebrates. The possible mechanisms of restriction endonuclease banding and the various uses of this technique for amphibian chromosomes are discussed.

Amphibians↗

PubMed1991

Angiotensin II mediates hyperadrenergic activity evoked by sodium restriction in essential hypertension.

We examined the possible involvement of angiotensin II in the modulation of circulating norepinephrine produced by acute sodium restriction in essential hypertensive patients (n = 18). Sodium restriction potentiated plasma level of norepinephrine in parallel with an increased plasma renin activity (r = 0.81, F = 31.2, p less than 0.05 given by the percent changes). An intravenous infusion of sarcosine-1, isoleucine-8 angiotensin II produced a significant fall in mean arterial pressure (-6 +/- 2 mmHg, p less than 0.05) in patients on sodium restriction but not before sodium restriction, while the infusion of the antagonist produced a greater decrease (p less than 0.05) in plasma norepinephrine with sodium restriction (-158 +/- 23 pg/ml, p less than 0.05) when compared to that obtained before sodium restriction (-91 +/- 11 pg/ml, p less than 0.05). A single oral administration of an angiotensin I converting enzyme inhibitor, captopril caused a greater fall (p less than 0.01) in mean arterial pressure after sodium restriction (-32 +/- 3 mmHg, p less than 0.05) compared to that given before (-21 +/- 3 mmHg, p less than 0.05). However, sodium restriction did not affect the magnitude of reflex increase in plasma norepinephrine to hypotension evoked by captopril (from +88 +/- 16 pg/ml to +87 +/- 17 pg/ml; p greater than 0.05). It can be interpreted that acute sodium depletion results in a substantial contribution of angiotensin II to the expression of hyperadrenergic activity.

Adrenal Glands↗

PubMed1991

Different mechanisms for SOS induced alleviation of DNA restriction in Escherichia coli.

The alleviation of DNA restriction during the SOS response in Escherichia coli has been further investigated. With the EcoK DNA restriction system UV irradiated wild-type cells show a 10(4)-fold increase in ability to plate non-modified lambda phage and a 3-4 fold increase in transformation by non-modified plasmid DNA. A role for the umuDC genes of E coli in the process of SOS-induced restriction alleviation was identified by showing that a umuC122::Tn5 mutant could alleviate EcoK restriction to only 5% that of wild-type levels. Although umuDC are better characterized for their pivotal role in SOS induced mutagenesis, it is demonstrated here that umu-dependent alleviation of EcoK restriction is a transient process in which umu-dependent mutagenesis plays little part. A second form of SOS induced alleviation of DNA restriction is described in this paper involving the McrA restriction system. The mcrA gene is shown to be encoded within a defective prophage called e14 situated at the 25 min region on the Escherichia coli genetic map. e14 is known to abortively excise from the chromosome after SOS induction and it is demonstrated in this report that mcrA is lost from the genome after SOS induction as part of e14. This results in co-ordinate decrease in the level of McrA restriction within a population of cells.

Bacteriophage lambda↗

PubMed1988

New cloning vectors and techniques for easy and rapid restriction mapping.

We have modified plasmid, phage lambda and cosmid cloning vectors to be of general use for easily and unambiguously determining restriction maps of recombinant DNA molecules. Each vector is constructed so that it contains the rarely found NotI restriction site joined to a short synthetic linker sequence that is followed by a multiple cloning site. DNA cloned into these vectors may be restriction-mapped by either of two methods. In one technique, the cloned DNA is completely digested with NotI, followed by partial digestion with any other restriction enzyme. After electrophoresis and transfer to a nylon membrane, the fragments are hybridized to a labeled probe complementary to the NotI linker. In the second technique, referred to as recession hybridization detection, cloned DNA is digested with NotI and then briefly treated with exonuclease III to recess the 3' ends. After hybridizing a labeled complementary oligodeoxynucleotide to the single-stranded 5' end containing the linker sequence, the DNA is partially digested with another restriction enzyme, electrophoresed and the gel is exposed to x-ray film. With either method the size of each labeled fragment corresponds directly to the distance that a restriction site is located from the NotI linker terminus. Methods for obtaining partial restriction enzyme digests have been devised so that as many as 20 different enzymes may be conveniently mapped on a single gel in little more than a day. The vectors and techniques described may also be adapted to automated or semi-automated devices that read fragment lengths and calculate the resulting restriction map.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteriophage lambda↗

PubMed2004

Should we restrict chloride rather than sodium?

Low-salt diets have potential for prevention and treatment of hypertension, and may also reduce risk for stroke, left ventricular hypertrophy, osteoporosis, renal stones, asthma, cataract, gastric pathology, and possibly even senile dementia. Nonetheless, the fact that salt restriction evokes certain counter-regulatory metabolic responses-- increased production of renin and angiotensin II, as well as increased sympathetic activity--that are potentially inimical to vascular health, has suggested to some observers that salt restriction might not be of unalloyed benefit, and might in fact be contraindicated in some "salt-resistant" subjects. Current epidemiology indicates that lower-salt diets tend to reduce coronary risk quite markedly in obese subjects, whereas the impact of such diets on leaner subjects (who are less likely to be salt sensitive) is equivocal--seemingly consistent with the possibility that salt restriction can exert countervailing effects on vascular health. There is considerable evidence that sodium chloride, rather than sodium per se, is responsible for the known adverse effects of dietary salt. Other non-halide sodium salts, such as sodium citrate or bicarbonate, do not raise plasma volume, increase blood pressure, boost urinary calcium loss, or promote stroke in stroke-prone rats. Nonetheless, these compounds have been shown to blunt the impact of salt restriction on renin, angiotensin II, and sympathetic activity in humans. This may rationalize limited clinical evidence that organic sodium salts can decrease blood pressure in salt-restricted hypertensives. Furthermore, organic sodium salts have an alkalinizing metabolic impact favorable to bone health. These considerations suggest that restricting dietary salt to the extent feasible, while encouraging consumption of organic sodium salts in mineral waters, soft drinks, or other nutraceuticals--preferably in conjunction with organic potassium salts and taurine--may represent a superior strategy for controlling blood pressure, promoting vascular health, and preserving bone density. Further clinical studies should determine whether a moderately salt-restricted diet supplemented with organic sodium salts has a better and more uniform impact on hypertension than salt restriction alone, while rodent studies should examine the comparative impact of these regimens on rodents prone to vascular disease.

Causality↗

PubMed2005

Restriction mapping of the IGS region in Alternaria spp. reveals variable and conserved domains.

Accurate identification of Alternaria spp. is dependent upon the production of diagnostic morphological characters under defined cultural conditions and the proper assessment of character variation. This process is often compromised by variation in laboratory facilities and technical expertise. To assist taxon identification and phylogenetic studies, restriction site information from the intergenic spacer (IGS) region of nuclear rDNA was evaluated. Restriction maps were constructed from 15 species of Alternaria and Stemphylium botryosum (telemorph Pleospora herbarum) for 11 restriction enzymes using a new method for restriction mapping based on differential priming of IGS amplicons. IGS fragment size varied among species from 2.2-3.9 kb. Based upon restriction site homology among closely-related and more distantly related species, the IGS region could be divided into conserved and variable domains. The conserved domain was approximately 0.75 kb in size and was located at the 3' end of the IGS region. Restriction site homology within this region was very high, especially among closely related taxa. The remainder of the region comprised the variable domain, which encompassed considerable differences in size and restriction sites among taxa. The presence or absence of restriction sites among taxa was analyzed using methods of neighbor-joining. Phylogenetic relationships based on this method were concordant with those previously resolved based upon other methods and other genomic regions.

Alternaria↗

PubMed2002

Does rapid volume loading during transesophageal echocardiography differentiate constrictive pericarditis from restrictive cardiomyopathy?

BACKGROUND: Respiratory variation of the pulmonary venous (PV) peak flow velocities can be used to distinguish constrictive pericarditis (constriction) from restrictive cardiomyopathy (restriction). Rapid volume expansion has been used successfully to enhance diastolic pressure equalization in occult constriction. The effect of volume on the respiratory variation in constriction has not been studied previously. This study assessed the utility of volume in enhancing the PV respiratory variation of constriction to further separate it from restriction. METHODS: The study population consisted of 15 patients referred to the echocardiography laboratory for further evaluation of clinically suspected diastolic dysfunction. Pulsed-Doppler transesophageal echocardiography (TEE) of the left or right upper pulmonary vein and mitral inflow was performed with respiratory monitoring before and after infusion of 1 liter of normal saline over 5 to 10 minutes. The classification of patients as constriction (n = 8) or restriction (n = 7) was confirmed independently by cardiac catheterization or surgery. Peak velocities of the PV systolic and diastolic waves and the mitral inflow E were measured during inspiration and expiration. A mean of 3-6 respiratory cycles was obtained for each value before and after volume loading. The percent change from expiration to inspiration (%E) was calculated using the formula %E = expiration - inspiration / expiration. RESULTS: At baseline, patients with constrictive pericarditis can be separated reliably from those with restrictive cardiomyopathy based on a higher systolic/diastolic ratio and greater respiratory variation of their PV diastolic flow velocity. There were no complications in any patient due to volume expansion. Although the change from baseline to volume expansion was not statistically significant in either constriction or restriction, the %E of the PV diastolic wave became significantly higher in constriction than in restriction (P < 0.05). CONCLUSIONS: Rapid volume expansion is relatively safe during TEE and can be used for further separation of constrictive pericarditis from restrictive cardiomyopathy by significantly enhancing the respiratory variation of the PV diastolic flow velocity in constrictive pericarditis.

Adult↗

PubMed2003

The independent and combined effects of 16 weeks of vigorous exercise and energy restriction on body mass and composition in free-living overweight men--a randomized controlled trial.

This study assessed the effects of 16 weeks of energy restriction and vigorous exercise on body mass and body composition. Sixty sedentary men, mean body mass (mean +/- SD) 96.3 (13.9) kg and mean age 42.4 (5.0) years, were randomly assigned to either continue their normal energy intake or restrict energy intake by 4,186 to 6,279 kJ. d(-1). Each group was further randomized to a control light exercise program, or a vigorous exercise program for 3 half-hour sessions per week. Vigorous exercise improved maximum oxygen consumption (Vo(2max)) by approximately 24% (0.56 [95% confidence interval, 0.47 to 0.65) L. min(-1), P <.001) with no significant changes in body mass, body composition, or fat distribution. With energy restriction there was a significant reduction in body mass of 10.1 (8.0 to 12.2) kg, lean body mass (LBM) of 2.4 (1.5 to 3.3) kg, fat mass (FM) of 7.7 (5.9 to 9.6) kg, waist to hip ratio (WHR) of 0.03 (0.01 to 0.04), and the sum of 6 skinfolds of 26.9 (15.4 to 38.4) mm (P <.001). Combining vigorous exercise with energy restriction resulted in no further changes in measures of body composition. We conclude that in sedentary free-living overweight men, 16 weeks of energy restriction, but not vigorous intensity exercise, results in substantial reductions in body mass, LBM, and FM. Furthermore, vigorous intensity exercise when combined with energy restriction did not modify or enhance the changes in body fat distribution or body composition seen with energy restriction alone. The independent effects of exercise to induce changes in body mass and composition in the longer term in free-living overweight subjects on an energy-restricted diet deserve further study.

Adipose Tissue↗

PubMed2000

Novel subtype of type IIs restriction enzymes. BfiI endonuclease exhibits similarities to the EDTA-resistant nuclease Nuc of Salmonella typhimurium.

The type IIs restriction enzyme BfiI recognizes the non-palindromic nucleotide sequence 5'-ACTGGG-3' and cleaves complementary DNA strands 5/4 nucleotides downstream of the recognition sequence. The genes coding for the BfiI restriction-modification (R-M) system were cloned/sequenced and biochemical characterization of BfiI restriction enzyme was performed. The BfiI R-M system contained three proteins: two N4-methylcytosine methyltransferases and a restriction enzyme. Sequencing of bisulfite-treated methylated DNA indicated that each methyltransferase modifies cytosines on opposite strands of the recognition sequence. The N-terminal part of the BfiI restriction enzyme amino acid sequence revealed intriguing similarities to an EDTA-resistant nuclease of Salmonella typhimurium. Biochemical analyses demonstrated that BfiI, like the nuclease of S. typhimurium, cleaves DNA in the absence of Mg(2+) ions and hydrolyzes an artificial substrate bis(p-nitrophenyl) phosphate. However, unlike the nonspecific S. typhimurium nuclease, BfiI restriction enzyme cleaves DNA specifically. We propose that the DNA-binding specificity of BfiI stems from the C-terminal part of the protein. The catalytic N-terminal subdomain of BfiI radically differs from that of type II restriction enzymes and is presumably similar to the EDTA-resistant nonspecific nuclease of S. typhimurium; therefore, BfiI did not require metal ions for catalysis. We suggest that BfiI represents a novel subclass of type IIs restriction enzymes that differs from the archetypal FokI endonuclease by the fold of its cleavage domain, the domain location, and reaction mechanism.

Amino Acid Sequence↗