Subunit distribution of calcium-binding sites in Lumbricus terrestris hemoglobin

The giant, 3.6-MDa hexagonal bilayer hemoglobin (Hb) of Lumbricus terrestris consist of twelve 213-kDa globin subassemblies, each comprised of three disulfide-bonded trimers and three monomer globin chains, tethered to a central scaffolding of 36–42 linkers L1–L4 (24–32 kDa). It is known to contain 50–80 Ca and 2–4 Cu and Zn; the latter are thought to be responsible for the superoxide dismutase activity of the Hb. Total reflection X-ray fluorescence spectrometry was used to determine the Ca, Cu, and Zn contents of the Hb dissociated at pH 2.2, the globin dodecamer subassembly, and linker subunits L2 and L4. Although the dissociated Hb retained 20 Ca²⁺ and all the Cu and Zn, the globin subassembly had 0.4 to 3 Ca²⁺, depending on the method of isolation, and only traces of Cu and Zn. The linkers L2 and L4, isolated by reversed-phase high-pressure liquid chromatography at pH 2.2, had 1 Ca per mole and very little Cu and Zn. Electrospray ionization mass spectrometry of linker L3 at pH 2.2 and at neutral pH demonstrated avid binding of 1 Ca²⁺ and additional weaker binding of 7 Ca²⁺ in the presence of added Ca²⁺. Based on these and previous results which document the heterogeneous nature of the Ca²⁺-binding sites in Lumbricus Hb, we propose three classes of Ca²⁺-binding sites with affinities increasing in the following order: (i) a large number of sites (>100) with affinities lower than EDTA associated with linker L3 and dodecamer subassembly, (ii) 30 sites with affinities higher than EDTA occurring within the cysteine-rich domains of linker L3 and dodecamer subassembly, and (iii) 25 very high affinity sites associated with the linker subunits L1, L2, and L4. It is likely that the low-affinity type (i) sites are the ones involved in the effects of 1–100 mM Group IIA cations on Lumbricus Hb structure and function, namely increased stability of its quaternary structure and increased affinity and cooperativity of its oxygen binding.     

Nucleotide sequence and expression of the two genes encoding D2 protein and the single gene encoding the CP43 protein of Photosystem II in the cyanobacterium synechococcus sp. PCC 7002

The unicellular photoheterotrophic cyanobacterium Synechococcus sp. PCC 7002 was shown to encode two genes for the Photosystem II reaction center core protein D2 and one gene for the reaction center chlorophyhll-binding protein CP43. These three genes were cloned and their DNA sequences determined along with their flanking DNA sequences. Northern hybridization experiments show that both genes which encode D2, psbD1 and psbD2, are expressed at roughly equivalent levels. For each of the two psbD genes, there are 18 nucleotide differences among the 1059 nucleotides which are translated. The DNA sequences surrounding the coding sequences are nearly 70% divergent. Despite the DNA sequence differences in the genes, the proteins encoded by the two genes are predicted to be identical. The proteins encoded by psbD1 and psbD2 are 92% homologous to other sequenced cyanobacterial psbD genes and 86% homologous to sequenced chloroplast-encoded psbD genes.The single gene for CP43, psbC, overlaps the 3 end of psbD1 and is co-transcribed with it. Results from previous sequencing of psbC genes encoded by chloroplasts suggest that the 5 end of the psbC gene overlaps the 3 end of the coding sequence of psbD by 50 nucleotides. In Synechococcus sp. PCC 7002, the methionine codon previously proposed to be the start codon for psbC is replaced by an ACG (threonine) codon. We propose an alternative start for the psbC gene at a GTG codon 36 nucleotides downstream from the threonine codon. This GTG codon is preceded by a consensus E. coli-like ribosome binding sequence. Both the GTG start codon and its preceding ribosome binding sequence are conserved in all psbC genes sequenced from cyanobacteria and chloroplasts. This suggests that all psbC genes start at this alternative GTG codon. Based on this alternative start codon, the gene product is 85% identical to other cyanobacterial psbC gene products and 77% identical to eucaryotic chloroplast-encoded psbC gene products.     

Protein and gene structure of a chlorocruorin chain of Eudistylia vancouverii

The polychaete annelid, Eudistylia vancouverii, contains as oxygen carrier a hexagonal bilayer (HBL) chlorocruorin. One of the globin chains, chain a1, has 142 amino acids (Mr 16,054.99) and its sequence deviates strongly from other nonvertebrate globin sequences. Unprecedented, it displays a Phe at the distal position E7 as well as at position B10, creating a very hydrophobic heme pocket probably responsible for the low oxygen affinity of the native molecule. Phylogenetic analysis of annelid globin chains clearly proves that globin chain a1 belongs to type I of globin chains having a pattern of 3 cysteine residues essential for the aggregation into a HBL structure. The gene coding for globin chain a1 is interrupted by 2 introns at the conserved positions B12.2 and G7.0. Based on protein and gene structure it can therefore be concluded that the globin chains of chlorocruorins are not fundamentally different from other annelid globin chains.     

Semper's (zoanthid) larvae: pelagic life,parentage and other problems

Semper's larvae were obtained from <300 out of 1800 plankton tows taken in the world's oceans (1964–1993). Zoanthellae (larvae of Sphenopidae) occurred at 217 stations and zoanthinae (larvae of Zoanthidae) at 86, the two larval types showing distributions clearly delimited by a minimum sea temperature (22 °C for zoanthellae, 18 °C for zoanthinae; a statistically significant difference, P<0.001). Length of formalin-fixed zoanthellae was 2–8.6 mm and of zoanthinae 1.5–5.9 mm. Endodermal zooxanthellae were present in 9/24 zoanthinae but in no zoanthellae (of 19). Three larvae contained an endo-commensal/parasitic amphipod. Septa were externally visible in larger zoanthinae and were counted in transverse sections of other larvae, a majority of which (both kinds) had 12 septa, the normal maximum. The pattern was brachycnemic in 40/43 larvae and anomalous (but non-macrocnemic) in three. If macrocnemic genera reproduce by Semper's larvae, they should have been represented in such a large sample. The distribution of adult Epizoanthus was examined: many species are deep sea (recorded down to 5000 m) but shallow-water species are relatively plentiful in, for example, the Adriatic and North Seas. No Semper's larva has ever been recorded from either. Some Parazoanthus species also occur in shallow water, especially associated with western Atlantic reef sponges. If they produce Semper's larvae, these have never been found. It is probable that macrocnemic zoanthids settle from planulae that do not develop into recognizable zoanthellae or zoanthinae.     

rDNA targeted oligonucleotide primers for the identification of pathogenic yeasts in a polymerase chain reaction

Summary Species-specific oligonucleotide primers were designed for PCR identification of the basidiomycetous yeastsCryptococcus neoformans, Trichosporon cutaneum andRhodotorula mucilaginosa. The procedure uses standard PCR components including DNA from the test species and three primers: two universal external (upstream and downstream) limiting primers and a species-specific internal primer. Species identification requires the formation of a species-specific rDNA nucleotide segment that is significantly smaller (200 bp) than a non-target segment (600 bp). The procedure can be used to identify yeasts from single and mixed populations.This paper is dedicated to Professor Herman Jan Phaff in honor of his 50 years of active research which still continues.     

Freeze-fracture studies on the cockroach hemocyte membrane complex: Symmetric and asymmetric membrane particle distributions

Summary Freeze-fracture studies were conducted on the membranes of normal cockroach hemocytes. The plasmalemma is asymmetric with the A fracture face containing 80–100 Å membrane intercalated particles at a concentration of 2500/². The B fracture face contains 120–150 Å particles with a relatively low density (800/²). The nuclear envelope displays an asymmetry with the A fracture face containing 1500 particles/² and the B face containing 300/ ². No significant particle size differences were observed in nuclear envelope fracture faces. Two types of symmetric membranes were also found in these cells. Both A and B fracture faces of the membrane surrounding the numerous cytoplasmic inclusion bodies contain particle sizes and concentrations similar to the B face of the plasmalemma. A second type of symmetry was observed in cells apparently engaged in exocytosis. Vesicles (0.1 D) from this process were completely particle free on both fracture faces. Such particle free vesicles could be found in the cytoplasm, attached to the plasmalemma, or completely separated from the cell.Supported by a Pharmaceutical Manufacturers Association Foundation Fellowship.The author wishes to thank Ms. Annalena K. Charla for assistance in plate preparation, Dr. Julius Schultz and the Papanicolaou Cancer Research Institute for use of the freeze-etch device, and Dr. David Smith for the electron microscope facilities.     

Pepsin fragmentation of botulinum type E neurotoxin: Isolation and characterization of 112, 48, 46, and 16 kD fragments

Controlled digestion of 150 kD single chain botulinum type E neurotoxin with pepsin atpH 6.0 produced 112, 48, 46, and 16 kD fragments. These were chromatographically purified; their locations in the 1300 amino acid residue long neurotoxin were determined by identifying the amino terminal 10 residues of 112 and 48 kD fragments, 50 residues of 46 kD fragment, and 59 residues of 16 kD fragment. The 48 and 112 kD fragments contain the N-terminal segment of the neurotoxin (i.e., residue no. 1 to 425 and 1 to 990, respectively), the 46 kD fragment corresponds to 407 residues of the C-terminal region, and the 16 kD fragment contains the 140 residues from a segment nearer to the C-terminus. The 48 kD fragment is similar to the 50 kD N-terminal light chain of the 150 kD dichain neurotoxin, which is generated by tryptic cleavage of the 150 kD single chain neurotoxin, and is separated from the 100 kD C-terminal heavy chain by dithiothreitol (DTT) reduction of an intrachain disulfide bond in the presence of 2 M urea (Sathyamoorthy and DasGupta,J. Biol. Chem. 260, 10461, 1985). The pepsin-generated 48 kD fragment, unlike the light chain, was isolated without exposure to DTT and urea. The single chain 112 kD fragment following trypsin digestion yielded 48 and 60 kD fragments that were separable after DTT reduction of the intrachain disulfide which links them. The N-terminal residues of the smaller fragment were identical to that of the single chain 150 kD neurotoxin; the single chain 112 kD fragment is therefore the neurotoxin minus the 50 kD C-terminal half of the heavy chain. The biological activities of the 48 and 112 kD fragments can be demonstrated in permeabilized PC12 cells (Lomnethet al., J. Neurochem. 57, 1413, 1991); they inhibit norepinephrine release.     

Characteristics of sarcoplasmic reticulum membrane preparations isolated from skeletal muscles of active and hibernating ground squirrel Spermophilus undulatus

The total Ca-ATPase activity in the sarcoplasmic reticulum (SR) membrane fraction isolated from skeletal muscles of winter hibernating ground squirrel Spermophilus undulatus is 2.2-fold lower than in preparations obtained from summer active animals. This is connected in part with 10% decrease of the content of Ca-ATPase protein in SR membranes. However, the enzyme specific activity calculated with correction for its content in SR preparations is still 2-fold lower in hibernating animals. Analysis of the protein composition of SR membranes has shown that in addition to the decrease in Ca-ATPase content in hibernating animals, the amount of SR Ca-release channel (ryanodine receptor) is decreased 2-fold, content of Ca-binding proteins calsequestrin, sarcalumenin, and histidine-rich Ca-binding protein is decreased 3-4-fold, and the amount of proteins with molecular masses 55, 30, and 22 kD is significantly increased. Using the cross-linking agent cupric–phenanthroline, it was shown that in SR membranes of hibernating ground squirrels Ca-ATPase is present in a more aggregated state. The affinity of SR membranes to the hydrophilic fluorescent probe ANS is higher and the degree of excimerization of the hydrophobic probe pyrene is lower (especially for annular lipids) in preparations from hibernating than from summer active animals. The latter indicates an increase in the microviscosity of the lipid environment of Ca-ATPase during hibernation. We suggest that protein aggregation as well as the changes in protein composition and/or in properties of lipid bilayer SR membranes can result in the decrease of enzyme activity during hibernation.     

Mass distributions of a macromolecular assembly based on electrospray ionization mass spectrometric masses of the constituent subunits

Macromolecular assemblies containing multiple protein subunits and having masses in the megadalton (MDa) range are involved in most of the functions of a living cell. Because of variation in the number and masses of subunits, macromolecular assemblies do not have a unique mass, but rather a mass distribution. The giant extracelular erythrocruorins (Ers), ∼ 3.5 MDa, comprized of at least 180 polypeptide chains, are one of the best characterized assemblies. Three-dimensional reconstructions from cryoelectron microscopic images show them to be hexagonal bilayer complexes of 12 subassemblies, each comprised of 12 globin chains, anchored to a subassembly of 36 nonglobin linker chains. We have calculated the most probable mass distributions forLumbricus andRiftia assemblies and their globin and linker subassemblies, based on theLumbricus Er stoichiometry and using accurate subunit masses obtained by electrospray ionization mass spectrometry. The expected masses ofLumbricus andRiftia Ers are 3.517 MDa and 3.284 MDa, respectively, with a possible variation of ∼ 9% due to the breadth of the mass distributions. TheLumbricus Er mass is in astonishingly good agreement with the mean of 23 known masses, 3.524 ± 0.481 MDa.     

Characterization of the photosynthetic electron transport chain in normal and photobleachedAnabaena cylindrica by flash spectroscopy

Electron transport of normal and photobleachedAnabaena cylindrica was studied using spectral and kinetic analyses of absorbance transients induced by single turnover flashes. Between 500 and 600 nm two positive bands (540 and 566 nm) and two negative bands (515 and 554 nm) were found. Absorbance changes at 515 and 540 nm were partly characterized. None of these absorbance changes represent an electrochromic shift. Absorbance changes at 554 and 566 nm correspond to the oxidation of cytochromef and the reduction of cytochromeb ₅₆₃, respectively. We found a very slight 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) sensitivity of cytochromef in normal cells, while DCMU was completely ineffective for cytochromef reduction in photobleached cells. The absorbance change of cytochromeb ₅₆₃ increased, while the absorbance change of cytochromef was smaller than in normal cells. The increased O₂ evolution in photobleached cells and the negligible electron transport via cytochromef suggest the participation of other electron acceptor(s) in the electron-transport chain of photobleachedAnabaena cylindrica.     

Immunocytochemical,electrophoresis, and immunoblot analysis of Heliothis virescens gap junctions isolated in the presence and absence of protease inhibitors

Gap junction-enriched fractions were prepared from larvae of the tobacco budworm Heliothis virescens using the NaOH procedure in the presence or absence of protease inhibitors and were analyzed by SDS-PAGE, immunoblotting and EM immunocytochemistry. Protease inhibitor fractions contained a 48-kDa protein in addition to the 10 proteins in fractions with and without inhibitors. Three polyclonal antibodies were used as probes for gap junction plaques and proteins: R16, against an 40-kDa candidate gap junction protein from Drosophila melanogaster; R17, against the 40-kDa candidate gap junction protein from H. virescens; and R18AP, an affinity purified antibody against a consensus sequence of N-terminal amino acids 2–21 of the H. virescens 40-kDa protein. R16, R17, and R18AP stain the 40- and 48-kDa proteins, R16 and R18AP stain a 64-kDa protein, and R16 stains an 30-kDa protein in the absence of inhibitors. Inclusion of protease inhibitors had no effect on gap junction ultrastructure. R16 and R17 label gap junction plaques in crude membrane and NaOH fractions, whereas R18AP exhibits only a low level of reactivity with gap junctions in crude membrane fractions and none with gap junctions in NaOH fractions. The results show that the 30-, 40-, 48- and 64-kDa proteins are immunologically related and are associated with gap junctions in H. virescens, the N-terminus of the 40-kDa protein is relatively inaccessible or easily lost, and the 48-kDa protein is protease-sensitive.     

Mutation of the Chlamydomonas reinhardtii analogue of residue M210 of the Rhodobacter sphaeroides reaction center slows primary electron transfer in Photosystem II

Primary charge separation within Photosystem II (PS II) is much slower (time constant 21 ps) than the equivalent step in the related reaction center (RC) found in purple bacteria ( 3 ps). In the case of the bacterial RC, replacement of a specific tyrosine residue within the M subunit (at position 210 in Rhodobacter sphaeroides), by a leucine residue slows down charge separation to 20 ps. Significantly the analogous residue in PS II, within the D2 polypeptide, is a leucine not a tyrosine (at position D2-205, Chlamydomonas reinhardtii numbering). Consequently, it has been postulated [Hastings et al. (1992) Biochemistry 31: 7638–7647] that the rate of electron transfer could be increased in PS II by replacing this leucine residue with tyrosine. We have tested this hypothesis by constructing the D2-Leu205Tyr mutant in the green alga, Chlamydomonas reinhardtii, through transformation of the chloroplast genome. Primary charge separation was examined in isolated PS II RCs by time-resolved optical spectroscopy and was found to occur with a time constant of 40 ps. We conclude that mutation of D2-Leu205 to Tyr does not increase the rate of charge separation in PS II. The slower kinetics of primary charge separation in wild type PS II are probably not due to a specific difference in primary structure compared with the bacterial RC but rather a consequence of the P680 singlet excited state being a shallower trap for excitation energy within the reaction center.     

Channel gating in the absence of agonist by a homooligomeric molluscan GABA receptor expressed inXenopus oocytes from a cloned cDNA

We have previously described the isolation of a complementary DNA (cDNA) from the freshwater molluscLymnaea stagnalis encoding a polypeptide that exhibits 50% identity to the ß-subunits of vertebrate -aminobutyric acid (GABA) type A (GABA_A) receptor. When expressed inXenopus laevis oocytes fromin vitro-transcribed RNA, the snail subunit forms functional homo-oligomeric receptors possessing chloride-selective ion channels. In recordings from voltage-clamped oocytes held at –60 mV, GABA induced an inward current, whereas application of the chloride-channel blocker picrotoxin (in the absence of agonist) elicited an apparent outward current. Single channel recordings obtained from cell-attached patches have revealed a single population of 20 pS channels, with an open probability greater than 90% (at a pipette potential of –100 mV) in the absence of GABA. The relationship between single channel current and pipette potential was linear over the studied range (–100 mV to +60 mV), but the open probability was less for hyperpolarizations than for depolarizations. The spontaneous channel openings were blocked by micromolar concentrations of picrotoxin. Functional hetero-oligomeric receptors were formed when the molluscan subunit was co-expressed in oocytes with the bovine GABA_A receptor 1-subunit, but the channels gated by these receptors did not open spontaneously.     

Effects of an exotic bivalve mollusc on benthic invertebrates and food quality in the Ohio River

Effects of zebra mussels (Dreissena polymorpha) on populations of amphipods (Gammarus fasciatus) and prosobranch snails (Lithasia obovata) and on nutritional quality of benthic organic matter were examined in 20 artificial streams receiving Ohio River water and containing either mussels or small gravel. Twenty individually-marked snails were placed in each trough, and streams were allowed to colonize with other benthic species for 28 days.Dreissenids positively affected other benthic invertebrates in our stream channels. Compared to gravel channels, Gammarus biomass was significantly higher (P<0.01) in mussel channels, amphipod densities increased 300%, and snail growth rates were 50% greater. Food quality of fine benthic organic matter (FBOM) was greater in mussel channels (i.e. lower C:N), and FBOM was carbon depleted (lower ¹³C) but nitrogen enriched (higher ¹⁵N). Isotope data suggest that detrital FBOM was not the sole food source for snails and amphipods in our channels and that they were assimilating a higher quality portion of this BOM. The overall influence of dreissenids on particular benthic invertebrates may depend on the response and/or susceptibility of those species to biofouling, increased habitat heterogeneity, and changes in the quality and quantity of nutrients.     

Spectroscopic studies of bound cytochrome c and an iron-sulfur center in a purified reaction center complex from the green sulfur bacterium Chlorobium tepidum

Flash-induced optical kinetics at room temperature of cytochrome (Cyt) c ₅₅₁ and an Fe-S center (CF_A/CF_B) bound to a purified reaction center (RC) complex from the green sulfur photosynthetic bacterium Chlorobium tepidum were studied. At 551 nm, the flash-induced absorbance change decayed with a t _1/2 of several hundred ms, and the decay was accelerated by 1-methoxy-5-methylphenazinium methyl sulfate (mPMS). In the blue region, the absorbance change was composed of mPMS-dependent (Cyt) and mPMS-independent component (CF_A/CF_B) which decayed with a t _1/2 of 400–650 ms. Decay of the latter was effectively accelerated by benzyl viologen (Em –360 mV) and methyl viologen (–440 mV), and less effectively by triquat (–540 mV). The difference spectrum of Cyt c had negative peaks at 551, 520 and 420 nm, with a positive rise at 440 to 500 nm. The difference spectrum of CF_A/CF_B resembled P430 of PSI, and had a broad negative peak at 430435 nm.Abbreviations (B)Chl (bacterio)chlorophyll - Cyt cytochrome - F_A, F_B and F_X iron-sulfur center A, B and X of Photosystem I - CF_A, CF_B and CF_X F_A-,F_B- and F_X-like Fe-S center of Chlorobium - mPMS 1-methoxy-5-methylphenazinium methyl sulfate - PSI Photosystem I - RC reaction center     

Membrane differentiation in the cytoplasmic-tubule system of the intestinal absorptive cells of the lamprey,Lampetra japonica

Summary Specific membrane differentiation occurs in the cytoplasmic-tubule system of the absorptive cells lining the mucosa of the lamprey anterior intestine. The absorptive cells are characterized by the presence of abundant mitochondria and a system of well-developed cytoplasmic tubules (120 nm in diameter). The cytoplasmic tubules open on to the basolateral cell surface and contain numerous lipoprotein particles (50–100 nm diam.) in their lumina. Lipoprotein particles are also observed in the endoplasmic reticulum and the Golgi complex, and they are transfered to the lateral intercellular space and lamina propria by way of the cytoplasmic tubules. Spirally-wound parallel rows of particles are found in the luminal surface of the cytoplasmic tubules. The rows are 17 nm apart and are wound spirally at a pitch of 210 nm. Freeze-fracture images of the tubule membranes also show spiral arrays of particles (9 nm in diameter) on the P-face, and complementary shallow grooves on the E-face. From these observations, it is suggested that the cytoplasmic-tubule system of the intestinal absorptive cells serves as a channel for the transport of synthesized lipoprotein into the interstitium, and is also the site of the ion and water exchange essential for the maintenance of ionic homeostasis.     

Effect of PPX1 inactivation on the exopolyphosphatase spectra in cytosol and mitochondria of the yeast Saccharomyces cerevisiae

Inactivation of PPX1 encoding exopolyphosphatase PPX1 in Saccharomyces cerevisiae results in a change in the exopolyphosphatase spectrum in the yeast cells. In the PPX1-deficient strain, elimination of an 45 kD exopolyphosphatase is observed in the cytosol, and activity of an exopolyphosphatase with molecular mass of 830 kD increases fivefold. The latter activity differs greatly in properties from the low-molecular-mass enzyme of the parent strain. In the soluble fraction of the mutant mitochondria, exopolyphosphatase of 45 kD characteristic of the soluble mitochondrial fraction in the parent strain is eliminated, and exopolyphosphatase with a molecular mass of 440 to 830 kD is found. On PPX1 inactivation, a membrane-bound form of mitochondrial exopolyphosphatase is unaffected in its activity level and properties. Therefore, the membrane-bound exopolyphosphatase of mitochondria and the high-molecular-mass enzyme of the cytosol of S. cerevisiae are not encoded by the PPX1 gene, unlike the soluble low-molecular-mass exopolyphosphatase of mitochondria, which is probably a product of this gene with a posttranslational modification. In the PPX1 mutant, exopolyphosphatase properties in the cell as a whole undergo modifications including the ability to hydrolyze polyphosphates (polyP) with different polymer degree.     

Ion-Exchange Properties of Cell Walls Isolated from Lupine Roots

Acid–base properties of cell walls isolated from various root tissues of 7-day-old lupine seedlings and 14-day-old lupine plants grown in various media were studied. The ion-exchange capacity of root cell walls was estimated at various pH values (from 2 to 12) and constant ionic strength (10 mM). The parameters determining the qualitative and quantitative composition of cell wall ionogenic groups along the root length and in its radial direction were estimated using Gregor's model. This model fits the experimental data reasonably well. Four types of ionogenic groups were found in the cell walls: an amino group (pK _a 3), two types of carboxylic groups (pK _a 5 and 7.3, the first being the carboxylic group of galacturonic acid), and a phenolic group (pK _a 10). The number of functional groups of each type was estimated, and the corresponding ionization constant values were calculated. It is shown that the chemical composition of the ionogenic groups was constant along the root length as well as in its radial direction and did not depend on either physiological state or root nutrition, while the number of different groups varied. The content of carboxylic groups of -D-polygalacturonic acid in the root cell walls of 14-day-old plants was shown to depend on the distance from the root tip, being maximal in the zone of lateral roots. The number of these groups was 10- and 2-fold less in the central cylinder compared to that of cortex for 14-day-old plants and 7-day-old seedlings, respectively.     

A meta-analysis of the effects of exercise and/or dietary restriction on resting metabolic rate

A meta-analysis was used to examine the independent and interactive effects of dietary restriction, endurance exercise training and gender on resting metabolic rate (RMR). Sixty different group means (covering 650 subjects) were identified from the scientific literature and subjected to meta-analysis techniques. Collectively (i.e., all groups combined), body weight loss was greater (P < 0.05) for men ( 18 kg) than for women ( 12 kg). There were no statistically significant exercise training or gender effects on RMR during weight loss. Collectively (i.e., all groups combined), dietary restriction resulted in a – 0.59 kJ min^–1 ( – 12%) decrease in RMR (P < 0.05). When normalized to body weight, RMR was reduced by less than 2% (P < 0.05). These data suggest that exercise training does not differentially affect RMR during diet-induced weight loss. In addition, decreases in resting metabolism appear to be proportional to the loss of the metabolically active tissue.