Minor Labeling Research Articles

Uptake of 13C‐glucose by cell suspensions of carrot (Daucus carota) measured by in vivo NMR: Cycling of triose‐, pentose‐ and hexose‐phosphates

After a lag phase of 2 days, batch‐grown cells of carrot (Daucus carota L.) cv. Flakkese entered the exponential growth phase and started to accumulate sucrose and hexoses. Short‐term feeding 13C‐glucose in this period resulted in only minor labelling of sucrose or fructose. CO2 production from [1‐13C]‐ and [6‐13C]‐glucose revealed, that at least 40% of the added glucose passed through the oxidative pentose phosphate pathway (OPPP), up to 40% through glycolysis leaving only minor 13C‐glucose for incorporation in various cell components in the exponential growth phase. After about 11 days of culture, the medium sugars were exhausted, cells entered the stationary growth phase and consumed stored sugar. Both neutral and acid invertase (EC 3.2.1.26) and sucrose synthase (EC 2.4.1.13) increased 50% from day 0 to days 11–13; thereafter their levels decreased again. Labelling with 13C‐glucose resulted in the accumulation of labelled sucrose and fructose during the stationary growth phase. Sucrose labelling was transient, i.e. after 6 h its level started to decrease again. Labelled fructose, however, evolved slower and increased even after 8 h. In sucrose and fructose up to 20% of the 13C‐label was exchanged from C‐1 to C‐6 carbons, indicating intensive cycling of at least 40% of the carbon between hexoses and triose phosphates. In the stationary phase only 10% of the labelled glucose passed through the OPPP and about 30% passed through the respiratory pathway; the remaining 60% was incorporated in cell constituents and sugars. Comparing the various cycles revealed that the regulation of the OPPP operated relatively independently from the cytosolic cycling of hexose phosphates through sucrose and from the cycling between hexose phosphates and triose phosphates.

Being Asian American

The interplay between individualist and collectivist orientations, ethnic identity, and beliefs about stereotypes was explored among Asian Americans. The authors proposed four components of Asian American Identity: feelings of interdependence with family, a sense of connectedness to heritage and tradition, a belief that achievement would reflect well on one's family and group generally, and an awareness of structural barriers and racism. A sample of 162 Asian American university students perceived stereotypes about Asian Americans as focusing primarily on school achievement and secondarily on social attributes. Although rarely engaging in strategies to avoid being academically labeled, students engaged in strategies to avoid labeling in other domains. Students varied in their valuation of the model minority label, with those high in Asian American Identity, collectivism, and work ethic more likely to view the label positively.

Diversity and equity for Asian American students in science education

Asian American students have been described as a “model minority” for their academic achievements, particularly in the natural sciences and related fields. The model minority label, however, has serious flaws and masks the learning needs of many students. This article addresses issues of diversity and equity with Asian American students in science education. The article first describes barriers as well as promising practices in science learning with Asian American students. Then, current science education reform and its implications for Asian American students are discussed. Finally, equity agenda with Asian American students in science education are proposed. In contrast to a sizable body of research on achievement tests and attitude surveys, the literature provides little specific information about effective instructional practices or programs with the Asian American student population. Science educators need to look beyond stereotypes for a better understanding of the strengths and limitations of Asian American students for science achievement, as well as ways to enhance their social and emotional adjustment. © 1997 John Wiley & Sons, Inc. Sci Ed 81:107–122, 1997.

DNTP Binding to HIV-1 Reverse Transcriptase and Mammalian DNA Polymerase β as Revealed by Affinity Labeling with a Photoreactive dNTP Analog

The dNTP binding pocket of human immunodeficiency virus type 1 reverse transcriptase (RT) and DNA polymerase beta (beta-pol) were labeled using a photoreactive analog of dCTP, exo-N-[beta-(p-azidotetrafluorobenzamido)-ethyl]-deoxycytidine-5'- triphosphate (FABdCTP). Two approaches of photolabeling were utilized. In one approach, photoreactive FABdCTP and radiolabeled primer-template were UV-irradiated in the presence of each enzyme and resulted in polymerase radiolabeling. In an alternate approach, FABdCTP was first UV-cross-linked to enzyme; subsequently, radiolabeled primer-template was added, and the enzyme-linked dCTP analog was incorporated onto the 3'-end of the radiolabeled primer. The results showed strong labeling of the p66 subunit of RT, with only minor labeling of p51. No difference in the intensity of cross-linking was observed with either approach. FABdCTP cross-linking was increased in the presence of a dideoxyterminated primer-template with RT, but not with beta-pol, suggesting a significant influence of prior primer-template binding on dNTP binding for RT. Mutagenesis of beta-pol residues observed to interact with the incoming dNTP in the crystal structure of the ternary complex resulted in labeling consistent with kinetic characterization of these mutants and indicated specific labeling of the dNTP binding pocket.

Immunoblot and ultrastructural analysis of antigens extracted from Dichelobacter nodosus with potassium thiocyanate.

The antigens extracted from Dichelobacter nodosus with potassium thiocyanate were analyzed by western blotting with sera from footrot-free sheep and from sheep infected with D. nodosus to identify components specific for infection. Several components with molecular mass < 33 kD were associated with infection, particularly bands of 32.5 kD, 30.5 kD, and 28 kD. Components with molecular mass > 56 kD may be responsible for false-positive reactions observed when sera of footrot-free sheep react with the potassium thiocyanate extract in solid phase enzyme-linked immunosorbent assays (ELISAs). Bands of 62.5 kD, 56 kD, 40 kD, and 19 kD were recognized for most sheep regardless of their disease status or ELISA reactivity and therefore do not appear to be detected by the ELISA. No components of the potassium thiocyanate extract were completely specific for infection. Antigens in the extract were identified primarily on the cell envelope by immunogold electron microscopy. Labeling was concentrated in the periplasm, with minor labeling of the cell surface. The extract consisted of tangled strands of particles with electron-dense cores, and few vesicular structures were observed.

African American female faculty at large research universities: Their need for information

African American female faculty at large research universities are given the same responsibilities as other faculty. They must teach, conduct research, engage in worthwhile service to the university community, and regularly disseminate the results of their work in scholarly publications. Rewards from the university are directly tied to the level of success that the faculty member experiences. The minority label is often a barrier to the African American female faculty member's search for full standing in the university's community of scholars. To overcome this barrier, African American women must find and use the best information available to help them. This includes finding a good mentor, mastering a variety of information sources, and building a strong personal and professional network.

Immunocytochemical localization of pathogenesis‐related proteins in roots of Norway spruce infected with Heterobasidion annosum

SummaryThe occurrence and accumulation of β‐1, 3‐glucanase and chitinase in seedling roots of spruce (Picea abies) following challenge by the root‐rot pathogen Heterobasidion annosum were studied. Chitinase activity increased 2–3 fold following inoculation, whereas no significant increase in the activity levels of glucanase was recorded during infection. With TEM immunogold labelling, the enzymes were localized in protein aggregates in host tissues and in the cell walls of intercellular hyphae. Gold particles were sparse and irregularly distributed within host‐cell walls. Only minor labelling was observed on hyphal walls coated with electron‐dense materials. The labelling intensity increased with infection time and was always higher than in non‐infected seedling roots. When this experiment was repeated using root samples inoculated with the saprophyte Phlebiopsis gigantea, a similar labelling pattern was observed. The cross reactivity of antisera raised against sugar‐beet chitinase and glucanase with spruceroot enzyme extracts was demonstrated using dot‐blot assays and ELISA.

Photoaffinity labeling of mitochondrial proteins with 2-azido [ 32P]palmitoyl CoA

A long-chain fatty acyl CoA photolabel, 2-azido [ 32P]palmitoyl CoA, was synthesized and its covalent interaction with mitochondrial membrane proteins examined. On binding of 2-azido [ 32P]palmitoyl CoA to beef heart mitochondria, two polypeptides were primarily labeled, the 30 kDa ADP/ATP carrier and a 41 kDa protein of unknown identity. Car☐yatractyloside and palmitoyl CoA completely protected against labeling of the 30 kDa protein indicating that it was the ADP/ATP carrier. With inverted submitochondrial particles, only the 30 kDa polypeptide was labeled by 2-azido [ 32P]palmitoyl CoA. The labeling was inhibited by bongkrekic acid and palmitoyl CoA but not car☐yatractyloside, providing evidence that the ADP/ATP carrier was covalently bound from the matrix side of the membrane. In brown adipose tissue mitochondria, 2-azido [ 32P]palmitoyl CoA photolabeled the ADP/ATP carrier and the 32 kDa uncoupling protein with some minor labeling of 36 and 68 kDa polypeptides. The results indicated that this physiological photolabeling reagent with the azido group on the CoA portion of the molecule interacts like 2-azido ADP with nucleotide binding sites of a number of important enzymes in cell metabolism. Moreover, the evidence strongly supports the hypothesis that long chain fatty acyl CoA esters are natural ligands for key nucleotide binding proteins.

Immunochemical Characterization of the β2 Subunit of the GABAA Receptor

To date three beta subunits of the GABAA receptor have been identified in rat brain as a result of cDNA library screening. The beta 2 subunit has been reported to have a wide distribution in rat brain based on in situ hybridization studies quantifying beta 2 mRNA. To study the beta 2 subunit more directly, we have raised a polyclonal antibody to a synthetic peptide representing residues 315-334 of the intracellular loop of the beta 2 subunit. The antibody, which had been affinity-purified, recognized the beta 2 peptide but did not immunolabel homologous beta 1 and beta 3 subunit peptides, indicating that this antibody is specific for the beta 2 subunit of the receptor. In western blots of the purified receptor, the antibody recognized a major diffuse band of 54-58 kDa and exhibited minor labeling of lower-molecular-mass polypeptides. In western blots of cortex homogenate, the antibody exhibited nervous system-specific labeling of a 55-kDa band that comigrated with the 55-kDa band of the purified receptor. Quantitative immunolabeling of this 55-kDa polypeptide permitted direct determination of the relative amounts of the beta 2 subunit in different brain regions. The brainstem contained the highest relative specific activity of the beta 2 subunit, followed by the inferior colliculus, olfactory lobe, and cerebellum. Lower levels of immunolabeling were seen in hypothalamus, hippocampus, thalamus, and cortex.

Membrane topology and omeprazole labeling of the gastric H+,K(+)-adenosinetriphosphatase.

The gastric H+,K(+)-ATPase is an alpha beta heterodimer with close homology to the Na+,K(+)-ATPase. Digestion of intact cytoplasmic-side-out vesicles at a trypsin to protein ratio of 1/4 removed most of the cytoplasmic protein, leaving membrane-spanning pairs in high yield. These were visualized on gels and poly(vinylidene difluoride) (PVDF) membranes by sodium dodecyl sulfate solubilization of the membrane-embedded segments and labeling of the cysteine residues with fluorescein maleimide prior to electrophoresis. The membrane-spanning residues of the alpha subunit were found between positions 104 and 162 (M1/M2), 291 and 358(M3/M4), 776 and 835 (M5/M6), and 853 and 946 (M7/M8). Although this method did not detect membrane retention of the hydrophobic sequences subsequent to position 946, it provided biochemical evidence for at least eight membrane segments in the catalytic subunit. Intact vesicles containing this enzyme transport acid in the presence of KCl, valinomycin, and MgATP. Omeprazole accumulates in these acidified vesicles and converts to a cationic sulfenamide. This forms disulfides with accessible cysteines. The reaction with this extracytoplasmic thiol reagent inhibits ATPase activity. Full inhibition was obtained with a stoichiometry of 2.2 mol of omeprazole bound/mg of protein. Only the alpha subunit was labeled. The cysteines reacting with omeprazole were defined by proteolytic cleavage of 3H- or 14C-omeprazole-labeled enzyme followed by peptide sequencing of fragments separated on tricine gradient gels and transferred to PVDF membranes. Tryptic digestion at a 1/40 trypsin to protein ratio in the presence of ligands that stabilize the E2P form of the enzyme produced two large fragments, one of 68 kDa stretching from Glu47 to probably Arg666 that contained minor labeling and the other of 333 kDa beginning at Ala671 and extending to probably Arg946 that contained greater than 85% of the label. Digestion of labeled vesicles at 1/75 or 1/4 trypsin to protein ratios gave radioactive patterns consistent with labeling at Cys813 and/or Cys822 and at Cys892 and/or Cys927 and/or Cys938. V8 protease digestion of the solubilized alpha subunit produced a fragment extending from Ser838 to possible Asp900 that was omeprazole-labeled, showing that Cys892 was labeled and Cys927 and Cys938 were not. Hence, omeprazole labels the H+,K(+)-ATPase at cysteines within the M5/M6 and M7/M8 regions of the alpha subunit, accounting for its inhibitory action in vivo and in vitro.

Organization of rodent auditory cortex: anterograde transport of PHA-L from MGv to temporal neocortex.

In the present study we analyzed the organization of the thalamocortical projections of the specific auditory relay nucleus of the thalamus, the ventral division of the medial geniculate body (MGv), using the anterograde axonal tracer Phaseolus vulgaris leucoagglutinin. All injections of MGv produced dense labeling of axonal fibers in temporal cortex. In all cases, labeled axons were predominantly concentrated in cortical layers III and IV and, to a lesser extent, at the junction of layers V and VI. Injections confined to the medial regions of MGv, and specifically to the ovoid nucleus of MGv (OV, pars ovoidea), resulted in anterograde labeling of TE1, with minor labeling of the ventral quarter of TE1, designated subarea TE1v. Injections placed in lateral regions of MGv and occupying the lateral ventral subnucleus (LV), or injections in the mediolateral center of MGv and occupying parts of LV and OV, also resulted in labeling of area TE1 and minor labeling of TE1v. However, these injections also produced labeling in areas TE2 and TE3. Thus, area TE1 (excluding subarea TE1v) receives heavy projections from all aspects of MGv and appears to be the core target of MGv. While regions of MGv also project to surrounding cortical belt areas, these projections tend to be lighter and to vary depending on the region of MGv examined. These results, together with other connectional findings, and cytoarchitectonic and physiological studies, suggest that TE1 (possibly excluding subarea TE1v) is the primary auditory cortex in the rat.

Subcellular Localization of Glycolipids as Revealed by Immuno-Electronmicroscopy.

New insights in the distribution of lipids over the various intracellular organelles have been gained by a newly developed method for the immuno-localization of lipids. The method involves the labeling of an antigenic lipid with an antibody followed by a protein A-gold probe. Labeling is performed on ultrathin sections after freeze-substitution and low temperature embedding of aldehyde-fixed and cryo-protected cells. In a first study, Forssman glycolipid was localized in epithelial MDCK cells. Abundant labeling of the plasma membrane, the Golgi complex, and the membranes of the endocytic pathway was in contrast with the complete absence of labeling from mitochondrial and peroxisomal membranes. This demonstrated the specificity of the method. Recently, the method has also been applied to the(glycophospho)lipid phosphatidylinositol 4, 5-bisphosphate(PIP2), the central component of the phosphoinositide signal transduction pathway. In MDCK cells, two monoclonal antibodies labeled the plasma membrane, whereas membranes of the Golgi complex were virtually negative. One monoclonal in addition yielded abundant labeling over the heterochromatin in the nuclear matrix, whereas the other monoclonal antibody yielded only minor labeling dispersed over the nuclear matrix. This labeling in the nuclear matrix suggests the occurrence of a non membrane-associated form of PIP2, most likely complexed to a nuclear protein. The general applicability of the method is discussed.

Detection of G Proteins in Bovine Brain Clathrin Coated Vesicles with Common Alpha and Beta Subunits Antibodies.

Clathrin coated vesicles (CV) from bovine brain were analyzed via Western blots for the presence of the alpha and beta subunits of guanine nucleotide regulatory proteins. The results with the common alpha antibody GA/1 revealed the presence of apparently undissociated G-protein subunits migrating at approximately 80 kDa. The predominant band was of about 39-41 kDa, with minor labeling observed in the 41-52 kDa range. Western blot analysis for G beta subunit(s) revealed the presence of a single band of about 35-36 kDa.

Detection of G Proteins in Bovine Brain Clathrin Coated Vesicles with Common Alpha and Beta Subunits Antibodies

Clathrin coated vesicles (CV) from bovine brain were analyzed via Western blots for the presence of the alpha and beta subunits of guanine nucleotide regulatory proteins. The results with the common alpha antibody GA/1 revealed the presence of apparently undissociated G-protein subunits migrating at approximately 80 kDa. The predominant band was of about 39-41 kDa, with minor labeling observed in the 41-52 kDa range. Western blot analysis for G beta subunit(s) revealed the presence of a single band of about 35-36 kDa.

Affinity labeling of rat liver and kidney type I 5'-deiodinase. Identification of the 27-kDa substrate binding subunit.

Extrathyroidal production of 3,3',5-triiodothyronine from the thyroid secretory product, thyroxine, is catalyzed by tissue-specific iodothyronine 5'-deiodinases. Type I 5'-deiodinase (5'D-I) produces greater than 75% of the T3 found in the circulation and in thyroid hormone-responsive tissues and is most abundant in rat liver and kidney. In this study, we used the bromoacetyl derivatives of T4 (N-bromoacetyl-[125I]L-thyroxine, BrAcT4) and T3 (N-bromoacetyl-[125I]3,3',5-triiodothyronine, BrAcT3) as alkylating affinity labels to identify 5'D-I-related protein(s). BrAcT4 and BrAcT3 rapidly and irreversibly inactivated 5'D-I activity in liver and kidney microsomes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of affinity labeled 5'D-I preparations showed that approximately 80% of the affinity label was incorporated into a protein with a Mr of 27,000 (p27). 5'D-I substrates and inhibitors specifically blocked affinity labeling of p27 with a rank order of potency (BrAcT4 greater than BrAcT3 greater than 3,5,3'-triiodothyronine (rT3) approximately flavone EMD 21388 greater than iodoacetate greater than N-acetyl-T4 (NAcT4) greater than N-acetyl-T3 (NAcT3] identical to that determined for inhibition of 5'-deiodination. Hyper- and hypothyroidism-induced increases and decreases in 5'D-I activity, respectively, were matched by comparable changes in the quantity of affinity labeled p27. BrAcT3 was a less effective affinity label for p27 and minor labeling of a new band with 53 kDa was observed. Molecular sieve chromatography of detergent-solubilized 5'D-I showed coincident peaks of p27 and 5'-deiodinating activity with an apparent Mr approximately 51,000. Two-dimensional gel electrophoresis showed that p27 was a single polypeptide with a pI of 6.1. Approximately 2-5 pmol of p27 were present per mg of liver microsomal protein, equal to previous estimates for 5'D-I content. Our results suggest that p27 represents the substrate binding subunit of type I 5'-deiodinase, the enzyme catalyzing the key reaction in the activation of T4 to the thyromimetically active T3.

Brainstem projections to cats' upper lumbar spinal cord: implications for abdominal muscle control

Unilateral L 1 L 2 gray matter HRP injections labeled neurons bilaterally in nucleus retroambiguus (expiratory neuron region of caudal ventral respiratory group) and ventromedial reticular formation. Minor labeling occurred in raphe, vestibular, and medial parabrachial nuclei, lateral reticular formation, and C 1 C 2. Midsagittal lesions between C 1 and obex prevented nucleus retroambiguus labeling (except 1 contralateral cell adjacent an incomplete lesion), indicating that these neurons decussate between C 1 and obex and have collaterals that recross the spinal cord.

Functional characterization of skeletal F‐actin labeled on the NH2‐terminal segment of residues 1–28

Rabbit skeletal alpha-actin was covalently labeled in the filamentous state by the fluorescent nucleophile, N-(5-sulfo-1-naphthyl)ethylenediamine (EDANS) in the presence of the carboxyl group activator 1-(3-dimethyl-aminopropyl)-3-ethylcarbodiimide (EDC). The coupling reaction was continued until the incorporation of nearly 1 mol EDANS/mol actin. After limited proteolytic digestion of the labeled protein and chromatographic identification of the EDANS-peptides, about 80% of the attached fluorophore was found on the actin segment of residues 1-28, most probably within the N-terminal acidic region of residues 1-7. A minor labeling site was located on the segment that consists of residues 40-113. No label was incorporated into the COOH-terminal moiety consisting of residues 113-375. The isolated EDANS-G-actin undergoes polymerization in the presence of salts but at a rate significantly greater than unlabeled actin. The EDANS-F-actin could be complexed to skeletal chymotryptic myosin subfragment 1 (S-1) and to tropomyosin. The complex formed between EDANS-F-actin and S-1 could not be further crosslinked by EDC but the two proteins were readily joined by glutaraldehyde as observed for native actin-S-1, suggesting that the EDANS-substituted carboxyl site is also involved in the EDC crosslinking of native actin to S-1. Moreover, the EDANS labeling of F-actin resulted in a 20-fold increase in the Km of the actin-activated Mg2+.ATPase of S-1. Thus, this labeling, while it did not much affect the rigor actin-S-1 interaction, changes the actin binding to the S-1-nucleotide complexes significantly. The selective introduction of a variety of spectral probes, like EDANS, or other classes of fluorophores, on the N-terminal region of actin, through the reported carbodiimide coupling reaction, would provide several different derivatives valuable for assessing the functional role of the negatively charged N-terminus of actin during its interaction with myosin and other actin-binding proteins.

Catalytic and noncatalytic nucleotide binding sites of the Escherichia coli F 1 ATPase Amino acid sequences of β-subunit tryptic peptides labeled with 2-azido-ATP

Under appropriate conditions tight, noncovalent binding of 2-azido-adenine nucleotides to either catalytic or noncatalytic binding sites on the E. coli F 1-ATPase occurs. After removal of unbound ligands, UV-irradiation results primarily in the covalent incorporation of nucleotide moieties into the β-subunit in both catalytic and noncatalytic site labeling experiments. Minor labeling of the α-subunit was also observed. After trypsin digestion and purification of the labeled peptides, microsequencing studies identified two adjacent β-subunit tryptic peptides labeled by 2-azido-ADP or -ATP. These β-subunit peptides were labeled on tyrosine-331 (catalytic sites) and tyrosine-354 (noncatalytic sites) in homology with the labeling patterns of the mitochondrial and chloroplast enzymes.

3H]Muscimol photolabels the γ-aminobutyric acid receptor binding site on a peptide subunit distinct from that labeled with benzodiazepines

Affinity column-purified GABA-benzodiazepine receptor protein from bovine brain was photoaffinity labeled with both [3H]flunitrazepam and [3H]muscimol. Gel electrophoresis in sodium dodecyl sulfate revealed that the benzodiazepine binding site labeled with [3H]flunitrazepam was primarily associated with a major peptide subunit revealed by protein staining with Mr = 52 kiloDaltons, with minor labeling of a second peptide of Mr = 57 kiloDaltons, corresponding to a second major stained band. Covalent incorporation of [3H]muscimol was limited to the 57 kiloDalton band, with no labeling of the 52 kiloDalton peptide, showing that the GABA binding site is carried by a subunit distinct from that carrying the benzodiazepine binding site.

Location of C-protein, H-protein and X-protein in rabbit skeletal muscle fibre types.

The locations of C-protein, H-protein and X-protein in rabbit psoas, plantaris and soleus muscles have been investigated with fluorescently tagged specific antibodies. Two systems have been examined: isolated myofibrils allowed the locations of these proteins within the sarcomere to be determined, while cryosections allowed a comparison of the amounts of these proteins between different types of fibre in the three muscles. Using antibody-labelled cryosections, we find that the amounts of each of these proteins depends closely on the fibre type. In all the muscles studied, C-protein is present in the largest amounts in fast white and fast intermediate fibres and is absent from slow red fibres, while X-protein is absent from fast white fibres and is present in the largest amounts in fast and slow red fibres. In psoas muscle, H-protein is present in the largest amounts in fast white fibres and is absent in fast and slow red fibres. In plantaris muscle, however, H-protein is absent from fast white fibres but occurs in some slow red fibres. All psoas myofibrils label with anti-C and anti-H and a minority label with anti-X. In each case the pattern of labelling is a zone in each half of the A-band. Measured across the middle of the A-band, the zones for H-protein are much closer together than for C-protein; the centre-to-centre spacings are 0.35 micron for anti-H and 0.64 micron for anti-C. The fluorescent zones for X-protein are slightly but significantly closer (0.52 micron) than those for C-protein. All soleus myofibrils label with anti-X but the centre-to-centre spacing was greater (0.67 micron). With plantaris myofibrils, where labelling occurs with anti-C or anti-H, the spacings resemble those in psoas myofibrils, but with anti-X the spacing resembles that in soleus myofibrils. The spacing of the fluorescent zones in an A-band, whether produced by anti-C, anti-X or anti-H does not vary with sarcomere length. We conclude that X-protein and H-protein, like C-protein, are thick filament components. With both fibres and myofibrils, there is no simple relationship between the amount of X-protein and the amount of C-protein. Many fast intermediate fibres in psoas and plantaris muscle label as strongly with anti-C as do fast white fibres but also label as strongly with anti-X as do fast and slow red fibres.(ABSTRACT TRUNCATED AT 400 WORDS)