Parent reports on willingness to accept childhood immunizations during urgent care visits.

OBJECTIVES: To 1) describe whether parents would be willing to accept childhood immunizations at urgent care visits; and 2) identify predictors of parents' willingness to accept childhood immunizations at urgent care visits. DESIGN AND PARTICIPANTS: Cross-sectional telephone survey of parents of children aged 18 to 24 months who were underimmunized according to a computerized immunization tracking system and who had recently made an urgent care visit in a regional group-model health maintenance organization in Northern California. Chart review was conducted to confirm immunization status and to identify contraindications to vaccination. RESULTS: Of the 424 eligible participants, 351 (83%) completed interviews. Children with contraindications to vaccination and children who were actually up-to-date at the time of the urgent care visit were excluded, leaving 263 families in the final analysis. Among these parents, 75% said they would have been willing to have their child immunized at the urgent care visit in question if the physician had suggested it. An additional 11% said they would have accepted vaccination if the physician told them that the shot would be safe and strongly encouraged them to accept it. Overall, 86% reported they theoretically would have accepted an immunization during the urgent care visit. In the multivariate analysis, the strongest predictors of stated willingness to accept shots at the urgent care visit were the parent: 1) not being aware that their child was underimmunized (odds ratio [OR] 3.5, 95% confidence interval [CI], 1.6-7.7); 2) perceiving that the child was not very sick at the visit (OR 1.8, 95% CI, 1.1-3.0); 3) being less concerned about the risk of shots (OR 1.8, 95% CI, 1.2-2.5); and 4) being of nonwhite race (OR 3.6, 95% CI, 1.6-7.7). Income and education were not significantly associated with reported willingness to accept immunization. CONCLUSIONS: We conclude that most parents of underimmunized toddlers report being willing to accept immunizations during urgent care visits if the clinician recommends it. More effective ways of alerting providers in urgent care settings when immunizations are due, such as indications on a chart or registration form, hold promise for improving immunization coverage rates.

A reversibly glycosylated polypeptide (RGP1) possibly involved in plant cell wall synthesis: purification, gene cloning, and trans-Golgi localization.

We purified from pea (Pisum sativum) tissue an approximately 40 kDa reversibly glycosylated polypeptide (RGP1) that can be glycosylated by UDP-Glc, UDP-Xyl, or UDP-Gal, and isolated a cDNA encoding it, apparently derived from a single-copy gene (Rgp1). Its predicted translation product has 364 aminoacyl residues and molecular mass of 41.5 kDa. RGP1 appears to be a membrane-peripheral protein. Immunogold labeling localizes it specifically to trans-Golgi dictyosomal cisternae. Along with other evidence, this suggests that RGP1 is involved in synthesis of xyloglucan and possibly other hemicelluloses. Corn (Zea mays) contains a biochemically similar and structurally homologous RGP1, which has been thought (it now seems mistakenly) to function in starch synthesis. The expressed sequence database also reveals close homologs of pea Rgp1 in Arabidopsis and rice (Oryza sativa). Rice possesses, in addition, a distinct but homologous sequence (Rgp2). RGP1 provides a polypeptide marker for Golgi membranes that should be useful in plant membrane studies.

Purification of 1,3-beta-D-glucan synthase activity from pea tissue. Two polypeptides of 55 kDa and 70 kDa copurify with enzyme activity.

From pea plasma membranes isolated by aqueous polymer two-phase partitioning we have purified 1,3-beta-D-glucan synthase [glucan synthase-II (GS-II) or callose synthase], an enzyme that several reports have suggested consists of between six and nine different subunits. The procedure involves (a) preliminary removal of peripheral proteins by 0.1% digitonin; (b) solubilization of GS-II with 0.5% digitonin; (c) precipitation of activity-irrelevant proteins from the digitonin extract by Ca2+, spermine and cellobiose, which are GS-II effectors needed in step (d); (d) product entrapment by formation of 1,3-beta-D-glucan from UDP-Glc by GS-II in the presence of the mentioned effectors, followed by centrifugal sedimentation of product micelles and elution of proteins therefrom with buffer; (e) preparative isoelectric focusing (IEF) of product-entrapped proteins; and (f) glycerol gradient centrifugation of the fractions of peak GS-II activity from IEF. The procedure yields 300-fold enrichment of GS-II specific activity over that in isolated plasma membranes, and 5500-fold over that in the original homogenate. Out of approximately six principal polypeptides that occur after the product entrapment step, the glycerol gradient GS-II activity peak contains only two major polypeptides, one of 55 kDa and another of 70 kDa, plus minor amounts of one or two others whose distribution and occurrence indicate are not responsible for GS-II activity. Antisera against either the 55-kDa or the 70-kDa polypeptide adsorb more than 60% of the GS-II activity from a product-entrapped preparation. After native gel electrophoresis, GS-II activity is associated with a single protein band of very large molecular mass, whose principal components are the 55-kDa and 70-kDa polypeptides, accompanied by minor amounts of a few other polypeptides most of which do not occur in enzyme preparations purified by the previously described procedure. The 55-kDa but not the 70-kDa component can be labeled by ultraviolet irradiation of the plasma membranes in the presence of [alpha-32P]UDP-Glc under GS-II assay conditions. It seems likely, therefore, that the 55-kDa and 70-kDa polypeptides form a large catalytic complex of which the 55-kDa component is the UDP-Glc-binding subunit.

Salmonella enteritidis immune leukocyte-stimulated soluble factors: effects on increased resistance to Salmonella organ invasion in day-old Leghorn chicks.

Cytokines, derived from either concanavalin A-stimulated Salmonella enteritidis-immune chicken T lymphocytes [SE-immune Lymphocyte Stimulated Soluble Factor (LSSF)] or lipopolysaccharide-stimulated SE-immune chicken macrophages [SE-immune Macrophage Stimulated Soluble Factor (MSSF)], were evaluated for their ability to increase resistance to SE organ invasion in day-old Leghorn chicks. In Trial 1, day of hatch chicks were injected i.p. with either SE-immune LSSF or SE-nonimmune LSSF (control). In Trial 2, chicks were similarly injected with either SE-immune MSSF, SE-nonimmune MSSF, or SE-immune LSSF (positive control). Thirty minutes postinjection, all chicks were gavaged with an invasive dose of SE. Twenty-four hours later, livers and spleens from all chicks were cultured for SE. In Trial 1, SE-immune LSSF caused a rapid and marked protection (P < .01) against SE infection as determined by the number of chicks that were culture positive regardless of challenge dose. In Trial 2, SE-immune MSSF was not associated with protection against SE organ infection. These experiments demonstrate that SE-immune LSSF, but not MSSF, are able to confer protection against SE organ invasion in day-old Leghorn chicks. Thus, it appears that the stimulated immune T cell, and not the macrophage, is responsible for producing the soluble products that protected the chicks.

Genus-specific detection of salmonellae using the polymerase chain reaction (PCR).

Oligonucleotide primers for the polymerase chain reaction (PCR) that enable genus-specific detection of members of the genus Salmonella were developed. The primers amplify a 496-bp genetic sequence of members of the genus Salmonella. Amplification of DNA extracted from all other genera of the family Enterobacteriaceae and various other gram-positive aerobic and anaerobic bacteria yielded negative results. Applications of the PCR using these genus-specific primers are discussed.

Molecular size and separability features of pea cell wall polysaccharides : implications for models of primary wall structure.

Relative molecular size distributions of pectic and hemicellulosic polysaccharides of pea (Pisum sativum cv Alaska) third internode primary walls were determined by gel filtration chromatography. Pectic polyuronides have a peak molecular mass of about 1100 kilodaltons, relative to dextran standards. This peak may be partly an aggregate of smaller molecular units, because demonstrable aggregation occurred when samples were concentrated by evaporation. About 86% of the neutral sugars (mostly arabinose and galactose) in the pectin cofractionate with polyuronide in gel filtration chromatography and diethylaminoethyl-cellulose chromatography and appear to be attached covalently to polyuronide chains, probably as constituents of rhamnogalacturonans. However, at least 60% of the wall's arabinan/galactan is not linked covalently to the bulk of its rhamnogalacturonan, either glycosidically or by ester links, but occurs in the hemicellulose fraction, accompanied by negligible uronic acid, and has a peak molecular mass of about 1000 kilodaltons. Xyloglucan, the other principal hemicellulosic polymer, has a peak molecular mass of about 30 kilodaltons (with a secondary, usually minor, peak of approximately 300 kilodaltons) and is mostly not linked glycosidically either to pectic polyuronides or to arabinogalactan. The relatively narrow molecular mass distributions of these polymers suggest mechanisms of co- or postsynthetic control of hemicellulose chain length by the cell. Although the macromolecular features of the mentioned polymers individually agree generally with those shown in the widely disseminated sycamore cell primary wall model, the matrix polymers seem to be associated mostly noncovalently rather than in the covalently interlinked meshwork postulated by that model. Xyloglucan and arabinan/galactan may form tightly and more loosely bound layers, respectively, around the cellulose microfibrils, the outer layer interacting with pectic rhamnogalacturonans that occupy interstices between the hemicellulose-coated microfibrils.

Changes in molecular size of previously deposited and newly synthesized pea cell wall matrix polysaccharides : effects of auxin and turgor.

Effects of indoleacetic acid (IAA) and of turgor changes on the apparent molecular mass (M(r)) distributions of cell wall matrix polysaccharides from etiolated pea (Pisum sativum L.) epicotyl segments were determined by gel filtration chromatography. IAA causes a two- to threefold decline in the peak M(r) of xyloglucan, relative to minus-auxin controls, to occur within 0.5 hour. IAA causes an even larger decrease in the peak M(r) concurrently biosynthesized xyloglucan, as determined by [(3)H]fucose labeling, but this effect begins only after 1 hour. In contrast, IAA does not appreciably affect the M(r) distributions of pectic polyuronides or hemicellulosic arabinose/galactose polysaccharides within 1.5 hours. However, after epicotyl segments are cut, their peak polyuronide M(r) increases and later decreases, possibly as part of a wound response. Xyloglucan also undergoes IAA-independent changes in its M(r) distribution after cutting segments. In addition, the peak M(r) of newly deposited xyloglucan increases from about 9 kilodaltons shortly after deposition to about 30 kilodaltons within 0.5 hour. This may represent a process of integration into the cell wall. A step increase in turgor causes the peak M(r) of previously deposited xyloglucan (but not of the other major polymers) to increase about 10-fold within 0.5 hour, returning to its initial value by 1.5 hours. This upshift may comprise a feedback mechanism that decreases wall extensibility when the rate of wall extension suddenly increases. IAA-induced reduction of xyloglucan M(r) might cause wall loosening that leads to cell enlargement, as has been suggested previously, but the lack of a simple relation between xyloglucan M(r) and elongation rate indicates that loosening must also involve other wall factors, one of which might be the deposition of new xyloglucan of much smaller size. Although the M(r) shifts in polyuronides may represent changes in noncovalent association, and for xyloglucan this cannot be completely excluded, xyloglucan seems to participate in a dynamic process that can both decrease and increase its chain length, possible mechanisms for which are suggested.

Plant polypeptides reversibly glycosylated by UDP-glucose. Possible components of Golgi beta-glucan synthase in pea cells.

In pea membranes, UDP[14C]Glc glycosylates a approximately 40-kDa polypeptide doublet. This label rapidly disappears if excess unlabeled UDP-Glc, or UDP, is added, indicating that the glycosylation is reversible, and suggesting that the glycosylated polypeptides might be intermediates in a glycosyl transfer reaction. Glycosylation of the doublet requires a divalent cation, the effective ions being the same (except for Zn2+) as those that activate Golgi-localized beta-glucan synthase (GS-I) activity. Treatments that inhibit GS-I also inhibit doublet glycosylation. The doublet is associated with Golgi (and to a minor extent with plasma) membranes and occurs also in the soluble fraction. The Golgi-bound doublet may be a component of the GS-I system. Immunological, inactivation, and fractionation evidence indicates that at least one other polypeptide is required in GS-I activity.

Isoelectric Focusing of Plant Plasma Membrane Proteins : Further Evidence that a 55 Kilodalton Polypeptide Is Associated with beta-1,3-Glucan Synthase Activity from Pea.

Detergent-solubilized plasma membrane proteins from pea (Pisum sativum L.) stem tissue were separated by isoelectric focusing (IEF) using a Bio-Rad Rotofor cell, with the goal of identifying protein(s) involved in beta-1,3-glucan synthase (GS-II) activity. Ordinary IEF procedures result in membrane protein precipitation. Inclusion of 10% glycerol mitigates this problem in digitonin-solubilized preparations, but not in those solubilized in 3-[(-cholamidopropyl)dimethylammonio]-1-propanesulfonate. Loss of GS-II activity during IEF is minimized by improved cooling of the Rotofor cell. GS-II focuses at pH 5.1. Antiserum against a 55 kilodalton (kD) polypeptide that was recognized from other evidence as involved in GS-II activity, detects this polypeptide in exact correspondence with the GS-II activity peak. A presumptive P-type ATPase, detected using an antibody against corn root plasma membrane 97 kD ATPase, focuses at pH 5.3. In this digitonin/glycerol medium, most of the membrane proteins focus within the relatively narrow pH range of 4.5 to 6, compared to pH 5.5 to 8.5 for IEF in the presence of 9 molar urea, 2% Nonidet P-40 (NP-40), and 5% mercaptoethanol, a medium that inactivates GS-II. This latter medium increases the apparent isoelectric point (pl) values of the abovementioned 55 and 97 kD polypeptides to 5.8 and 7.3, respectively. In the digitonin/glycerol medium, membrane polypeptides apparently focus at pH values lower than their true pls, because of adhering negatively charged phospholipids, which can be at least partially removed by the detergent NP-40 in the presence of urea. These results provide independent evidence that the 55 kD polypeptide is associated with the GS-II activity and indicate that inclusion of urea and a strong nonionic detergent such as NP-40 is necessary if membrane proteins are to be focused at pH values near their true pls.

A 55 kDa plasma membrane-associated polypeptide is involved in beta-1,3-glucan synthase activity in pea tissue.

By glycerol gradient centrifugation of a detergent-solubilized plasma membrane fraction from pea tissue, we find a polypeptide of 55 kDa that copurifies with beta-1,3-glucan synthase activity. An antiserum against this polypeptide adsorbs glucan synthase activity and the 55 kDa polypeptide from digitonin-solubilized plasma membrane. These results indicate that the 55 kDa polypeptide is involved in pea beta-1,3-glucan synthase activity.

Auxin Enhancement of mRNAs in Epidermis and Internal Tissues of the Pea Stem and Its Significance for Control of Elongation.

The epidermis has been considered the site of auxin action on elongation of stems and coleoptiles. To try to identify mRNAs that might mediate auxin stimulation of cell enlargement, we compared, using in vitro translation assays, mRNA enhancement by indoleacetic acid (IAA) in the epidermis, with that in the internal tissues, of pea (Pisum sativum L., cv Alaska) third internode segments. We used seedlings that had been grown under red light, which enables the epidermis to be peeled efficiently from the internode. Most of the ;early' IAA enhancements previously reported using etiolated peas, plus several hitherto undescribed enhancements, occur in both the epidermis and the internal tissue of the light-grown plants after 4 hours of IAA treatment. These enhancements, therefore, do not fulfill the expectation of elongation-specific mRNAs localized to the epidermis. One epidermis-specific IAA enhancement does occur, but begins only subsequent to 1 hour (but before 4 hours) of auxin treatment. Similarly, the previously mentioned IAA enhancements common to epidermis and internal tissue do not begin, in the light-grown plants, within 1 hour of IAA treatment. Since IAA stimulates elongation in light-grown internodes within 15 minutes, it appears that none of these mRNAs can be responsible for auxin induction of elongation. We confirmed, with our methods, the previous reports that some of these mRNAs are enhanced by IAA within 0.5 hour in etiolated internodes. This indicates that we could have detected an early enhancement in light-grown tissue had it occurred.

Mapping of four translocation breakpoints within the Duchenne muscular dystrophy gene.

There are over 20 females with Duchenne or Becker muscular dystrophy (DMD or BMD) who have X-autosome translocations that break the X chromosome within band Xp21. Several of these translocations have been mapped with genomic probes to regions throughout the large (approximately 2000 kb) DMD gene. In this report, a cDNA clone from the 5' end of the gene was used to further map the breakpoints in four X-autosome translocations. A t(X;21) translocation in a patient with BMD and a t(X;1) translocation in a patient with DMD were found to break within a large 110-kb intron between exons 7 and 8. Two other DMD translocations, t(X;5) and t(X;11), were found to break between the first and the second exon of the gene within a presumably large intron (greater than 100 kb). These results demonstrate that all four translocations have disrupted the DMD gene and make it possible to clone and sequence the breakpoints. This will in turn determine whether these translocations occur by chance in these large introns or whether there are sequences that predispose to translocations.

Light-mediated changes in two proteins found associated with plasma membrane fractions from pea stem sections.

Irradiation of etiolated pea (Pisum sativum L.) seedlings with white light affects two proteins, both of monomer molecular mass near 120 kDa. Both proteins have been detected in association with plasma membrane fractions. The first is identifiable in that it becomes heavily phosphorylated when the membranes are incubated with exogenous ATP. The second of these proteins is phytochrome, as determined by electrophoretic transfer (Western) blot analysis. Measurable phosphorylation and phytochrome (the latter detected by antigenicity) decline when the tissue is irradiated with white light prior to membrane isolation and in vitro phosphorylation. The phosphorylated protein is probably not phytochrome for three reasons. (i) It shows a slightly different distribution in sucrose gradients. (ii) Red light causes a gradual decline in the phytochrome that is associated with membrane fractions but has a negligible effect on the phosphorylatable protein; blue light, on the other hand, causes significantly slower loss of phytochrome than does red light but brings about a rapid decline in the phosphorylation signal. (iii) The molecular masses are not identical. The association of both proteins with membrane fractions is probably neither ionic nor, at least for the phosphorylatable protein, the consequence of entrapment of soluble proteins in vesicles formed during tissue extraction. Phytochrome is lost from the membrane fractions during irradiation, as judged by loss of antigenicity. Whether the phosphorylatable protein is lost, a specific kinase is lost, phosphatase activity increases, or phosphorylatable sites are blocked as a consequence of blue light treatment is not known.

Effect of Indoleacetic Acid- and Fusicoccin-Stimulated Proton Extrusion on Internal pH of Pea Internode Cells.

Using (31)P nuclear magnetic resonance spectroscopy, we followed cytoplasmic and vacuolar pH in pea (Pisum sativum cv Alaska) internode segments during treatment with indoleacetic acid (IAA) or fusicoccin (FC) in continuously perfused, oxygenated buffer. Although IAA and FC induced normal H(+) extrusion, elongation, and glucan synthase activity responses during the measurements, neither the cytoplasmic nor the vacuolar pH showed significant change at any time between 5 minutes and 1 to 3 hours of treatment. Changes in cytoplasmic pH as small as about 0.04 pH unit were detected after treatment with 1-naphthyl acetate. Therefore, cytoplasmic pH changes do not appear to mediate IAA or FC stimulation of H(+) extrusion or other metabolic responses to these effectors.

Involvement of Macromolecule Biosynthesis in Auxin and Fusicoccin Enhancement of beta-Glucan Synthase Activity in Pea.

In pea stem segments whose cuticle has been made permeable by abrading it, actinomycin D (ActD) and 80S ribosomal protein synthesis inhibitors such as cycloheximide (CHI) inhibit enhancement by indole 3-acetic acid (IAA) of the activity of the cell wall biosynthetic enzyme, glucan synthase I (GS). This supersedes earlier, negative results with inhibitors, obtained with segments having an intact cuticle, which prevents adequate inhibitor uptake. Since these inhibitors also block IAA-stimulated H(+) extrusion, which according to earlier results is involved in the GS response, the significance of these inhibitions would be ambiguous without additional evidence. ActD does not inhibit fusicoccin (FC) enhancement of GS activity, which indicates existence of a post-transcriptional control mechanism for GS, but does not preclude involvement of transcription in the GS response to IAA. Although protein synthesis inhibitors such as CHI do not block FC-stimulated H(+) extrusion, they do inhibit FC enhancement of GS activity, indicating an involvement of protein synthesis in the GS response to FC, and presumably also to IAA. However, protein synthesis inhibitors (but not ActD) by themselves paradoxically elevate GS activity, less strongly than IAA does but resembling the IAA enhancement in several characteristics. These results suggest that IAA may enhance GS activity at least in part by inhibiting the synthesis or action of a labile repressor of the transcription of, or a labile destabilizer of, mRNA for GS or some polypeptide that enhances GS activity. However, resemblances between the IAA and FC effects on GS suggest that IAA also has a posttranscriptional GS-enhancing action like that of FC. Lipid biosynthesis may be involved in this aspect of the response since both IAA and FC enhancements of GS activity are inhibited by cerulenin.

Auxin and Fusicoccin Enhancement of beta-Glucan Synthase in Peas : An Intracellular Enzyme Activity Apparently Modulated by Proton Extrusion.

Fusicoccin (FC), like indoleacetic acid (IAA), causes Golgi-localized beta-1,4-glucan synthase (GS) activity to increase when applied to pea third internode segments whose GS activity has declined after isolation from the plant. This suggests that GS activity is modulated by H(+) extrusion; in agreement, vanadate and nigericin inhibit the GS response. The GS response is not due to acidification of the cell wall. Treatment of tissue with heavy water, which in effect raises intracellular pH, mimics the IAA/FC GS response. However, various treatments that tend to raise cytoplasmic pH directly, other than IAA- or FC-induced H(+) extrusion, failed to increase GS activity, suggesting that cytoplasmic pH is not the link between H(+) extrusion and increased GS activity. Although FC stimulates H(+) extrusion more strongly than IAA does, FC enhances GS activity at most only as much as, and often somewhat less than, IAA does. This and other observations indicate that GS enhancement is probably not due to membrane hyperpolarization, stimulated sugar uptake, or changes in ATP level, but leave open the possibility that GS is controlled by H(+) transport-driven changes in intracellular concentrations of ions other than H(+).

Regulation of Cytoplasmic and Vacuolar pH in Maize Root Tips under Different Experimental Conditions.

(31)P-Nuclear magnetic resonance spectra of perfused maize (Zea mays L., hybrid WW x Br 38) root tips, obtained at 10-minute intervals over 12 hours or longer, indicate that no cytoplasmic or vacuolar pH changes occur in these cells in the presence of 25 millimolar K(2)SO(4), which induces extrusion of 4 to 5 microequivalents H(+) per gram per hour. In contrast, hypoxia causes cytoplasmic acidification (0.3-0.6 pH unit) without a detectable change in vacuolar pH. The cytoplasm quickly returns to its original pH on reoxygenation. Dilute NH(4)OH increases the vacuolar pH more than it does the cytoplasmic pH; after NH(4)OH is removed, the vacuole recovers its original pH more slowly than does the cytoplasm. The results indicate that regulation of cytoplasmic pH and that of vacuolar pH in plant cells are separate processes.

Early auxin-regulated polyadenylylated mRNA sequences in pea stem tissue.

Polyadenylylated mRNA from etiolated pea stem segments treated with or without 20 muM indoleacetic acid (IAA) for various periods of time was assayed by translating it in a wheat germ extract containing [(35)S]methionine and separating the translation products by two-dimensional gel electrophoresis. Within 2 hr IAA causes at least five mRNA sequences to increase in translational activity, relative to initial levels and to simultaneous controls; three of these rise significantly within 20 min after exposure of tissue to IAA but are apparently not elevated at 10 min, whereas the others begin to increase at successive times later than 30 min, and still others begin to change only later than 2 hr. These observations indicate an early, highly selective IAA regulation of mRNA amounts or activities, becoming progressively more extensive with time. The earliest detected enhancement seems close to the primary action of IAA but appears not to be rapid enough to be responsible for auxin induction of cell enlargement.

Inhibition by light of growth and Golgi-localized glucan synthetase in the maize mesocotyl.

When dark-grown maize (Zea mays L.) seedlings were exposed to red light (R), Golgi-localized glucan synthetase activity in the mesocotyl began to decrease within 1 h, and fell by approx. 70% in 12 h. The response required at least 10(-2) µmol m(-2) R and saturated at 100 µmol m(-2). Far-red light (FR) alone inhibited glucan synthetase, and FR reversed the inhibition by R back to the level caused by FR alone. Density gradient fractionation indicated that of the major membrane markers only the Golgi-localized glucan-synthetase activity was affected by R. Golgi-localized latent inosine-diphosphatase activity was unaffected. The kinetics of the response, the photon fluence dependence, and the reversibility by FR all correlated with the inhibition by light of elongation of the mesocotyl, indicating that light inhibits growth and glucan synthetase activity by a similar mechanism.

Auxin controls Golgi-localized glucan synthetase activity in the maize mesocotyl.

Decapitation or red light irradiation (R) inhibited growth and Golgi-localized glucan synthetase (GS I) activity in the mesocotyl of intact maize (Zea mays L.) seedlings. Applied auxin (indole-3-acetic acid) prevented the effects of R and of decapitation on both growth and GS I. Auxin applied several hours after irradiation prevented any further decline in GS I but did not restore it. Mesocotyl segments incubated in solution elongated in response to auxin but lost GS I with time regardless of the presence of exogenous auxin. An attached seed was necessary for maintenance of GS I in the dark-grown mesocotyl.