Effects of long-term treatment with an inhaled corticosteroid on growth and pulmonary function in asthmatic children

In a controlled prospective study we have measured growth and pulmonary function in children with asthma during long-term treatment with inhaled budesonide and compared these findings with those obtained from children not treated with corticosteroids. Two hundred and sixteen children were followed at 6 monthly intervals for 1-2 years without inhaled budesonide and then for 3-6 years on inhaled budesonide. Sixty-two children treated with theophylline, beta 2-agonists and sodium-cromoglycate but not with inhaled steroids were also followed for 3-7 years (controls). During the period of budesonide therapy the mean daily dose decreased from 710 to 430 micrograms (P < 0.01) and no signs of tachyphylaxis to the treatment were seen. Budesonide treatment was associated with a significant reduction in the number of annual hospital admissions due to acute severe asthma (from 0.03 to 0.004 per child, P < 0.001). In patients not treated with budesonide an annual decrease in % predicted FEV1 of 1-3% was seen. In contrast FEV1 improved significantly with time during budesonide treatment, both compared with the run-in period and with the control group (P < 0.01). Furthermore, there was a significant (P = 0.01) relationship between the duration of asthma at the start of budesonide and the annual increase in FEV1 during budesonide therapy. After 3 years of treatment with budesonide, children who started this therapy later than 5 years after the onset of asthma had significantly lower FEV1 (96%) than the children who received budesonide within the first 2 years after the onset of asthma (101%) (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of long-term treatment with inhaled budesonide on adult height in children with asthma

BACKGROUND

Short-term studies have shown that inhaled corticosteroids may reduce the growth of children with asthma. However, the effect of long-term treatment on adult height is uncertain.

METHODS

We conducted a prospective study in children with asthma to examine the effect of long-term treatment with inhaled budesonide on adult height. We report on 211 children who have attained adult height: 142 budesonide-treated children with asthma, 18 control patients with asthma who have never received inhaled corticosteroids, and 51 healthy siblings of patients in the budesonide group, who also served as controls.

RESULTS

The children in the budesonide group attained adult height after a mean of 9.2 years of budesonide treatment (range, 3 to 13) at a mean daily dose of 412 microg (range, 110 to 877). The mean cumulative dose of budesonide was 1.35 g (range, 0.41 to 3.99). The mean differences between the measured and target adult heights were +0.3 cm (95 percent confidence interval, -0.6 to + 1.2) for the budesonide-treated children, -0.2 cm (95 percent confidence interval, -2.4 to +2.1) for the control children with asthma, and +0.9 cm (95 percent confidence interval, -0.4 to +2.2) for the healthy siblings. The adult height depended significantly (P<0.001) on the child's height before budesonide treatment. Although growth rates were significantly reduced during the first years of budesonide treatment, these changes in growth rate were not significantly associated with adult height.

CONCLUSIONS

Children with asthma who have received long-term treatment with budesonide attain normal adult height.

Codon usage determines translation rate in Escherichia coli

We wish to determine whether differences in translation rate are correlated with differences in codon usage or with differences in mRNA secondary structure. We therefore inserted a small DNA fragment in the lacZ gene either directly or flanked by a few frame-shifting bases, leaving the reading frame of the lacZ gene unchanged. The fragment was chosen to have "infrequent" codons in one reading frame and "common" codons in the other. The insert in these constructs does not seem to give mRNAs that are able to form extensive secondary structures. The translation time for these modified lacZ mRNAs was measured with a reproducibility better than plus or minus one second. We found that the mRNA with infrequent codons inserted has an approximately three-seconds longer translation time than the one with common codons. In another set of experiments we constructed two almost identical lacZ genes in which the lacZ mRNAs have the potential to generate stem structures with stabilities of about -75 kcal/mol. In this way we could investigate the influence of mRNA structure on translation rate. This type of modified gene was generated in two reading frames with either common or infrequent codons similar to our first experiments. We find that the yield of protein from these mRNAs is reduced, probably due to the action in vivo of an RNase. Nevertheless, the data do not indicate that there is any effect of mRNA secondary structure on translation rate. In contrast, our data persuade us that there is a difference in translation rate between infrequent codons and common codons that is of the order of sixfold.

Efficacy and safety of inhaled corticosteroids in asthma. Report of a workshop held in Eze, France, October 1992

Inhaled glucocorticosteroids have now become first-line therapy for the treatment of chronic asthma in many countries. They are the most effective asthma therapy currently available, and numerous studies have documented their long-term efficacy in asthma control in adults and in children. Inhaled steroids suppress inflammation in asthmatic airways, although their precise molecular mechanism of action is not yet certain. It is likely that steroids affect the transcription of several steroid-responsive genes, and, of particular importance, they may inhibit cytokine gene transcription and cytokine effects, thereby reducing the chronic inflammation in asthmatic airways. Inhaled steroids are now used at a much earlier stage in asthma therapy, and there is a strong argument for their early introduction in both adults and children to prevent asthma morbidity and mortality and possibly the structural changes resulting from uncontrolled chronic inflammation, which may lead to irreversible airflow obstruction in some patients. Of paramount importance is the question of safety as inhaled steroids are likely to be required for a long time. Local side effects caused by oropharyngeal deposition of the inhaled steroid may be reduced by the use of spacer devices and mouthwashing. Systemic side effects caused by gastrointestinal absorption of the fraction deposited in the oropharynx may also be reduced by these devices. There are differences in the systemic bioavailability of the different inhaled steroids currently in use, and inhaled steroids with the lowest bioavailability should be chosen when high doses of inhaled steroids are required for asthma control. Systemic side effects are usually observed only when daily doses of > 800 micrograms are inhaled, and whether effects on very sensitive biochemical indices are relevant to long-term deleterious effects is not yet certain. There is now overwhelming evidence that the doses of inhaled steroids required to control asthma in the majority of adults and children are safe and without systemic side effects. It is important to control asthma with the minimum dose of inhaled steroids possible, however. In the future it may be possible to develop inhaled steroids with even fewer systemic effects if the fraction absorbed from the respiratory tract can be rapidly metabolized in the bloodstream.

Patterns of protein synthesis in E. coli: a catalog of the amount of 140 individual proteins at different growth rates

The amount of 140 individual proteins of E. coli B/r was measured during balanced growth in five different media. The abundance of each protein was determined from its absolute amount in 14C-glucose-minimal medium and a measurement of its relative amount at each growth rate using a double labeling technique. Separation of the proteins was carried out by two-dimensional gel electrophoresis. This catalog of proteins, combined with 50 additional ribosomal proteins already studied, comprises about 5% of the coding capacity of the genome, but accounts for two thirds of the cell's protein mass. The behavior of most of these proteins could be described by a relatively small number of patterns. 102 of the 140 proteins exhibited nearly linear variations with growth rate. The remaining 38 proteins exhibited levels which seemed to depend more on the chemical nature of the medium than on growth rate. Proteins, including the ribosomal proteins, that increase in amount with increasing growth rate account for 20% of total cell protein by weight during growth on acetate, 32% on glucose-minimal medium and 55% on glucose-rich medium. Proteins with invariant levels in the various media comprise about 4% of the cell's total protein.

ClpB is the Escherichia coli heat shock protein F84.1

ClpB is thought to be involved in proteolysis because of its sequence similarity to the ClpA subunit of the ClpA-ClpP protease. It has recently been shown that ClpP is a heat shock protein. Here we show that ClpB is the Escherichia coli heat shock protein F84.1. The F84.1 protein was overproduced in strains containing the clpB gene on a plasmid and was absent from two-dimensional gels from a clpB null mutation. Besides possessing a slower growth rate at 44 degrees C, the null mutant strain had a higher rate of death at 50 degrees C. We used reverse transcription of in vivo mRNA to show that the clpB gene was expressed from a sigma 32-specific promoter consensus sequence at both 37 and 42 degrees C. We noted that the clpB+ gene also caused the appearance of a second protein spot, F68.5, on two-dimensional gels. This spot was approximately 147 amino acids smaller than F84.1 and most probably is the result of a second translational start on the clpB mRNA. F68.5 can be observed on many published two-dimensional gels of heat-induced E. coli proteins, but the original catalog of 17 heat shock proteins did not include this spot.

Management of asthma: a consensus statement

In developing these international guidelines there were several unifying themes in the diagnosis and simple management of childhood asthma. For the purposes of the meeting, asthma was operationally defined as 'episodic wheeze and/or cough in a clinical setting where asthma is likely and other rarer conditions have been excluded'. In making a diagnosis of asthma, a full history is a prerequisite. Additional tests are only used to support clinical impression and to provide objective evidence for therapeutic recommendations. General features of a multidisciplinary approach include an appreciation of the importance of psychosocial factors, counselling, and education. Drugs should be prescribed in a rational sequence: beta 2-stimulants for mild episodic wheeze; sodium cromoglycate for mild to moderate asthma; inhaled steroids for moderate to severe asthma; with xanthines, ipratropium bromide, and oral steroids having their place in more persistent and severe cases. Children and their parents should be reassured that if asthma is properly controlled there is no reason why the child should not lead a normal and physically active life. The management of asthma is rewarding and return to 'normal' lifestyle is nearly always possible with active participation in sporting activities.

Chemical measurement of steady-state levels of ten aminoacyl-transfer ribonucleic acid synthetases in Escherichia coli

Polypeptide chains of 10 aminoacyl-transfer ribonucleic acid synthetases (those for arginine, glutamine, glutamic acid, glycine, isoleucine, leucine, lysine, phenylalanine, threonine, and valine) have been identified in lysates of Escherichia coli resolved by the O'Farrell two-dimensional gel system. By labeling cells uniformly with [14C]glucose and by measuring the total amounts of these polypeptides by their radioactivity, estimations of the steady-state, molecular amounts of these enzymes were made and compared to the number of ribosomes and elongation factors in these cells. Portions of a reference culture grown on glucose and labeled with [14C]leucine or [35S]sulfate were mixed with four cultures grown in widely different media containing [3H]leucine or [3H]leucine plus [3H]isoleucine. From the isotope ratios of the total protein and of the spots containing the synthetase chains, the chemical amount of each synthetase relative to that of the reference culture was determined. The results, where comparable, show reasonable agreement with enzyme activity measurements. In general, these synthetases each exhibit a positive correlation with growth rate in unrestricted media, indicating a strong tendency for the levels of transfer ribonucleic acid, synthetases, elongation factors, and ribosomes to remain approximately, though not exactly, in balance at different growth rates.

Absolute in vivo translation rates of individual codons in Escherichia coli. The two glutamic acid codons GAA and GAG are translated with a threefold difference in rate

We have determined the absolute translation rates for four individual codons in Escherichia coli. We used our previously described system for direct measurements of in vivo translation rates using small, in-frame inserts in the lacZ gene. The inserts consisted of multiple synthetic 30 base-pair DNA oligomers with high densities of the four individual codons, GAA (Glu), GAG (Glu), CCG (Pro) and CGA (Arg). Our method is independent of expression level, of mRNA half-life and of transcription rate. Codon GAA was found to be translated with a rate of 21.6 codons/second whereas codon GAG was translated 3.4-fold slower (6.4 codons/s). These two codons are read by the same tRNA species. Codon CCG and CGA are both read by abundant tRNA species but nevertheless we found them to be translated slowly with rates of 5.8 and 4.2 codons/second, respectively. The context of these codons were varied, but we found no significant influence of context on their translation rates and we suggest a mechanism for why context may not affect translation rates. One insert with a low translation rate gave results that most readily can be explained by assuming queue formation of ribosomes on the insert. Such a queue was found to reduce the expression level by approximately 35%. Our experiments allowed us to estimate the average distance between ribosomes and thereby the translation initiation frequency on the wild-type lacZ mRNA. This was found to be one per three seconds.

Interstitial hyperthermia of colorectal liver metastases with a US-guided Nd-YAG laser with a diffuser tip: a pilot clinical study

Ultrasound (US)-guided interstitial hyperthermia performed with the neodymium yttrium aluminum garnet laser with a diffuser tip involves placement of a laser fiber in solid tissue followed by irradiation from within the center of the tumor to be treated. The authors previously described the development of a US-guided technique that permits simultaneous interstitial laser irradiation and temperature measurements, with real-time US monitoring. With the use of a dedicated diffuser tip modification of the bare laser fiber, it has proved possible to produce spherical coagulations with a diameter comparable to that of liver metastases of clinical relevance. This technique was used in 11 patients with 16 colorectal liver metastases, 12 of which were radically ablated. Real-time US and interstitial temperature monitoring during treatment had a positive predictive value of 86% and negative predictive value of 100% in judging the final result. The technique is feasible, effective, and safe, but the effect on patient survival must be tested in future randomized clinical studies.

Importance of inhaler devices in the management of airway disease

The delivery of drugs by inhalation is an integral component of asthma and chronic obstructive pulmonary disease (COPD) management. However, even with effective inhaled pharmacological therapies, asthma, particularly, remains poorly controlled around the world. The reasons for this are manifold, but limitations of treatment guidelines in terms of content, implementation and relevance to everyday clinical life, including insufficient patient education, access to health care and cost of medication as well as poor inhaler technique are likely to contribute. Considering that inhalation therapy is a cornerstone in asthma and COPD management, little advice is provided in the guidelines regarding inhaler selection. The pressurised metered dose inhaler (pMDI) is still the most frequently prescribed device worldwide, but even after repeated tuition many patients fail to use it correctly. In addition, the correct technique can be lost over time. Although several improvements in pMDIs such as a change in the propellant and actuation have resulted in improvements in lung deposition, many dry powder inhalers (DPIs) are easier to use. However, these devices also have limitations such as dependency of drug particle size on flow rate and loss of the metered dose if the patient exhales through the device before inhaling. Improvements in using inhalation devices more efficiently, in inhaler design for supporting patient compliance, and advances in inhaler technology to assure drug delivery to the lungs, have the potential to improve asthma and COPD management and control. New and advanced devices are considered being helpful to minimise the most important problems patients have with current DPIs.

Reduction and alkylation of proteins in preparation of two-dimensional map analysis: why, when, and how?

The standard procedure adopted up to the present in proteome analysis calls for just reduction prior to the isoelectric focusing/immobilized pH gradient (IEF/IPG) step, followed by a second reduction/alkylation step in between the first and second dimension, in preparation for the sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) step. This protocol is far from being optimal. It is here demonstrated, by matrix assisted laser desorption/ionization-time of flight (MALDI-TOF)-mass spectrometry, that failure to reduce and alkylate proteins prior to any electrophoretic step (including the first dimension) results in a large number of spurious spots in the alkaline pH region, due to "scrambled" disulfide bridges among like and unlike chains. This series of artefactual spots comprises not only dimers, but an impressive series of oligomers (up to nonamers) in the case of simple polypeptides such as the human alpha- and beta-globin chains, which possess only one (alpha-) or two (beta-) -SH groups. As a result, misplaced spots are to be found in the resulting two-dimensional (2-D) map, if performed with the wrong protocol. The number of such artefactual spots can be impressively large. In the case of analysis of complex samples, such as human plasma, it is additionally shown that failure to alkylate proteins results in a substantial loss of spots in the alkaline gel region, possibly due to the fact that these proteins, at their pI, regenerate their disulfide bridges with concomitant formation of macroaggregates which become entangled with and trapped within the polyacrylamide gel fibers. This strongly quenches their transfer in the subsequent SDS-PAGE step.

Growth of asthmatic children during treatment with budesonide: a double blind trial

OBJECTIVE

To determine whether the inhaled glucocorticosteroid budesonide has any adverse effect on short term linear growth in children with mild asthma.

SETTING

Outpatient clinic in secondary referral centre.

PATIENTS

15 children aged 6-13 years with normal statural growth velocity during the previous year, no signs of puberty, and no use of systemic or topical steroids in the two months before the study. DESIGN OF INTERVENTIONS: Double blind, randomised crossover trial with two active periods in which budesonide was given in divided daily doses of 200 micrograms and 800 micrograms. During run in and two washout periods placebo was given. After the second washout period the children received open treatment with 400 micrograms budesonide daily. All periods were of 18 days' duration.

MAIN OUTCOME MEASURE

Growth of the lower leg as measured twice a week by knemometry.

RESULTS

Mean growth velocity of the lower leg was 0.63 mm/week during run in and during washout 0.64 mm/week. Budesonide treatment was associated with a significant dose related reduction of growth velocity: the mean reduction in growth velocity during treatment was 0.11 (95% confidence interval -0.15 0.36 (0.13 to 0.59) mm/week with 800 micrograms budesonide (p less than 0.05; Page's test). During treatment with 400 micrograms budesonide a reduction of 0.17 (-0.10 to 0.45) mm/week was found.

CONCLUSIONS

Treatment with inhaled budesonide is associated with a dose related suppression of short term linear growth in children with mild asthma.

The Validity of the "Diradical" Hypothesis: Direct Femtoscond Studies of the Transition-State Structures

Direct studies of diradicals, the molecular species hypothesized to be archetypal of chemical bond transformations in many classes of reactions, have been made using femtosecond laser techniques with mass spectrometry in a molecular beam. These studies are aimed at "freezing" the diradicals in time and in the course of the reaction. The passage of these species through the transition-state region was observed and the effect of total energy and alkyl substitution on the rates of bond closure and cleavage was examined. The results establish the nature of these intermediates and define their existence during reactions.

Escherichia coli ribosomes translate in vivo with variable rate

The question of whether or not 'rare' codons are translated with the same rate as 'common' codons was investigated by measuring the translation time for two genes, lacI and bla, rich in rare codons, and comparing the results with the translation times measured on fus, tsf, tuf and rpsA which have very few rare codons. The rate of synthesis of the lac repressor was first measured with the up-promoter mutation lacIq1 present on the high copy number plasmid pBR322. In such a strain the average translation times for lacI and bla were 50% slower than the rate calculated from the translation time for the four ribosomal proteins. In a strain having lacIq1 on an F'lac episome this difference was much smaller, thus slow translation of genes rich in rare codons is exaggerated in strains with increased drain on the rare codon tRNAs. The data do not exclude that only a subset of the rare codons is translated more slowly. Translation times were also measured in cells growing in different media, and the translation chain growth rate was found to increase by approximately 40% going from acetate medium to a fully supplemented medium.

Influence of inspiratory flow rate upon the effect of a Turbuhaler

The effect of a new breath actuated dry powder inhaler, the Turbuhaler, was found to be reduced at inhalations slower than 28 1/minute. This flow rate could be generated by virtually all children aged greater than or equal to 6 years, by 42 of 57 children less than 6 years (74%), and by six of 15 preschool children with acute wheeze (40%).

Ribosomal protein S1 is required for translation of most, if not all, natural mRNAs in Escherichia coli in vivo

We have deleted the chromosomal rpsA gene, encoding ribosomal protein S1, from an Escherichia coli strain carrying a plasmid where rpsA was controlled by the lac promoter and operator. This exogenous source of protein S1 was essential for growth. Thus we have verified the absolute requirement for protein S1. To see if translation of individual mRNAs differed in the requirements for protein S1, we removed the inducer and followed the time-course of the synthesis of several individual proteins and of total RNA, DNA and protein. Growth immediately shifted from being exponential to being linear, with a rate of protein synthesis defined by the pre-existing amount of protein S1. The expression pattern of the individual proteins indicated that the translation of all mRNAs was dependent on protein S1. Unexpectedly, we found that depletion for protein S1 for extended periods introduced a starvation for amino acids. Such starvation was indicated by an increased synthesis of ppGpp and could be reversed by addition of a mixture of all 20 amino acids. Measurements of the peptide chain elongation rate in vivo showed that ribosomes without protein S1 were unable to interfere with the peptide chain elongation rate of the active ribosomes and that, therefore, protein S1 was unable to diffuse from one ribosome to another during translation. We conclude that protein S1-deficient ribosomes are totally inactive in peptide chain elongation on most, if not all, naturally occurring E. coli mRNAs.

Budesonide treatment of moderate and severe asthma in children: a dose-response study

OBJECTIVE

The purpose of the study was to evaluate the dose-response relationships of the inhaled corticosteroid budesonide in a double blind crossover study in 19 children with moderate and severe asthma.

METHODS

A 2-week placebo treatment period (run-in) was followed by three 4-week treatment periods during which 100, 200, and 400 micrograms of budesonide were given per day in randomized order. Urinary cortisol excretion, lung functions, and protection against exercise-induced asthma were assessed at the end of run-in and each treatment period. Furthermore, morning and evening peak expiratory flow rates, day and night symptoms, and use of rescue beta 2-agonists were recorded throughout the study.

RESULTS

One hundred micrograms of budesonide per day markedly improved symptoms, morning and evening peak expiratory flow rates, and use of rescue beta 2-agonists (p < 0.01). No further improvement was seen in these parameters with increasing doses of budesonide. In contrast, a significant dose-response effect was found on lung functions measured at the hospital and fall in lung functions after exercise (p < 0.001); 200 micrograms was significantly better than 100 micrograms, and 400 micrograms was significantly better than 200 micrograms. About 53% of the maximum effect against exercise-induced asthma was achieved by the lowest budesonide dose (p < 0.001), and about 83% by the highest dose. No significant differences were seen in urinary cortisol excretion between run-in and the various budesonide doses.

CONCLUSIONS

Low doses of budesonide, which are not associated with any systemic side effects, have a marked antiasthma effect in children. Protection against exercise-induced asthma requires higher doses than achievement of symptom control.

Errors in inhalation technique and efficiency in inhaler use in asthmatic children

256 asthmatic children receiving regular inhalation therapy demonstrated how they used their inhalers. Pulmonary function measurements (PFM) were made before and after the demonstrations, and errors in technique were recorded. 242 children had reversible airway obstruction on the day of study. In only 109 (45%) did the inhalation result in an increase in FEV1 greater than or equal to 15% (efficient technique). An efficient inhalation technique was found in 46% of children who demonstrated a pressurized aerosol, 59% who demonstrated a tube spacer aerosol and 46% who demonstrated a rotahaler, and the frequency of efficient technique varied from 17% to 84% between six different groups of instructors. 87% of children controlled and 25% not controlled with PFM at the time of prescription had an efficient technique. Children under 6 years had a more inefficient and a more faulty technique than older children, but otherwise age did not influence the result. Neither was time since instruction of any importance for efficiency or number of errors. The errors recorded that seem to influence efficiency most were: coordination problems, rapid inspirations, ceasing to inspire when the aerosol was fired, and inhalation through the nose. The results emphasize the paramount importance of clear instructions and control of inhalation technique at the time the treatment is prescribed.

Synthesis of proteins in Escherichia coli is limited by the concentration of free ribosomes. Expression from reporter genes does not always reflect functional mRNA levels

Induction of beta-galactosidase from high copy-number plasmids was found to reduce the synthesis of other cellular proteins in Escherichia coli. The reduction depends on the protein in question and on the induction level of the beta-galactosidase. It could be observed transiently within one minute after induction and in some cases also during steady-state induction. Our interpretation is that the concentration of the free ribosomal subunits decreases after induction, leading to an increased competition among the individual ribosome binding sites for ribosomes. The immediate reduction in the synthesis individual proteins after induction of beta-galactosidase was used as an assay to measure in vivo the efficiency of a ribosome binding site. These efficiencies were compared to the calculated affinities between the ribosome binding site of specific mRNA species and the 3' end of 16 S RNA. For several mRNAs with similar Shine-Dalgarno sequences, the sensitivity to competition differed twofold. Our results show, that both transiently during induction of lacZ and also at very high steady-state expression levels, the expression from reporter genes, including the lacZ gene itself, does not reflect the levels of the mRNAs in a simple way.

Assignment of an autosomal sex reversal locus (SRA1) and campomelic dysplasia (CMPD1) to 17q24.3-q25.1

We have mapped the autosomal sex reversal locus, SRA1, associated with campomelic dysplasia (CMPD1) to 17q24.3-q25.1 by three independent apparently balanced de novo reciprocal translocations. Chromosome painting indicates that the translocated segment of 17q involves about 15% of chromosome 17 in all three translocations, corresponding to a breakpoint at the interphase between 17q24-q25. All three 17q breakpoints were localized distal to the growth hormone locus (GH), and proximal to thymidine kinase (TK1). Due to the distal location of the breakpoints, previously mentioned candidate genes, HOX2 and COL1A1, can be excluded as being involved in CMPD1/SRA1. The mouse mutant tail-short (Ts) which maps to the homologous syntenic region on mouse chromosome 11, displays some of the features of CMPD1.

Regulation of urokinase receptors in monocytelike U937 cells by phorbol ester phorbol myristate acetate

A specific surface receptor for urokinase plasminogen activator (uPA) recognizes the amino-terminal growth factor-like sequence of uPA, a region independent from and not required for the catalytic activity of this enzyme. The properties of the uPA receptor (uPAR) and the localization and distribution of uPA in tumor cells and tissues suggest that the uPA/uPAR interaction may be important in regulating extracellular proteolysis-dependent processes (e.g., invasion, tissue destruction). Phorbol myristate acetate (PMA), an inducer of U937 cell differentiation to macrophage-like cells, elicits a time- and concentration-dependent increase in the number of uPAR molecules as shown by binding, cross-linking, and immunoprecipitation studies. The effect of PMA is blocked by cycloheximide. Overall, the data indicate that PMA increases the synthesis of uPA. PMA treatment also causes a decrease in the affinity of the uPAR for uPA, thus uncovering another way of regulating the interaction between uPA and uPAR. In addition, the PMA treatment causes a modification of migration of the cross-linked receptor in mono- and bidimensional gel electrophoresis.

Functional mRNA half lives in E. coli

Analysis of the synthetic rate of individual protein species at various times after complete inhibition of transcription with either streptolygidin or rifampicin was carried out by two-dimensional polyacrylamide electrophoresis of total Escherichia coli cell extracts. The decay rate of the potential to synthesize different proteins was assumed to be equal to the functional decay rate of the corresponding mRNA. We conclude the following: (a) The tufA and tufB messengers have different half lives (3.0 and 2.4 min, respectively). (b) Different genes within the same transcriptional unit can have different half lies (S7, EGF and EFTuA--2.5, 3.8 and 3.0 min, respectively). (c) There is at least a twenty-fold variation in individual mRNA half lives in E. coli; ribosomal protein S1 mRNA was observed to have the shortest half life in the cell (40 sec), while the longest observed half life was approximately 20 min (all values at 30 degrees C). (d) Addition of rifampicin increases the absolute rate of RNA polymerase subunit alpha and beta synthesis two-fold. (e) The induction of the synthesis of alpha subunit of RNA polymerase takes place without a concomitant induction of ribosomal protein S4 and L17, which are reported to be on either side of alpha in the same transcriptional unit.