RESUMEN
Biosurfactant-mediated oil recovery may be an economic approach for recovery of significant amounts of oil entrapped in reservoirs, but evidence that biosurfactants can be produced in situ at concentrations needed to mobilize oil is lacking. We tested whether two Bacillus strains that produce lipopeptide biosurfactants can metabolize and produce their biosurfactants in an oil reservoir. Five wells that produce from the same Viola limestone formation were used. Two wells received an inoculum (a mixture of Bacillus strain RS-1 and Bacillus subtilis subsp. spizizenii NRRL B-23049) and nutrients (glucose, sodium nitrate, and trace metals), two wells received just nutrients, and one well received only formation water. Results showed in situ metabolism and biosurfactant production. The average concentration of lipopeptide biosurfactant in the produced fluids of the inoculated wells was about 90 mg/liter. This concentration is approximately nine times the minimum concentration required to mobilize entrapped oil from sandstone cores. Carbon dioxide, acetate, lactate, ethanol, and 2,3-butanediol were detected in the produced fluids of the inoculated wells. Only CO(2) and ethanol were detected in the produced fluids of the nutrient-only-treated wells. Microbiological and molecular data showed that the microorganisms injected into the formation were retrieved in the produced fluids of the inoculated wells. We provide essential data for modeling microbial oil recovery processes in situ, including growth rates (0.06 +/- 0.01 h(-1)), carbon balances (107% +/- 34%), biosurfactant production rates (0.02 +/- 0.001 h(-1)), and biosurfactant yields (0.015 +/- 0.001 mol biosurfactant/mol glucose). The data demonstrate the technical feasibility of microbial processes for oil recovery.
Asunto(s)
Bacillus/química , Aceites/química , Petróleo , Tensoactivos/química , Carbonato de Calcio/química , Restauración y Remediación Ambiental/métodos , Redes y Vías Metabólicas , Tensión SuperficialRESUMEN
Chlamydia trachomatis is a significant etiologic agent responsible for pelvic inflammatory disease leading to tubal infertility. A screening test aimed at identifying women at risk for Chlamydia trachomatis would be of great utility. The Papanicolaou smear is the most widely used screening test in the world. The association of inflammatory cells in the Papanicolaou smear to Chlamydia infection is controversial. We retrospectively examined the Papanicolaou smears of 80 Chlamydia-negative patients with 80 age-matched Chlamydia-positive patients in a high-risk population to see if a significant difference in inflammation was noted between the two groups. We found a statistically significant difference in inflammation scores between the Chlamydia-positive and Chlamydia-negative groups, evidenced by a sensitivity of 83% and a positive predictive value of 65% when using inflammation on Papanicolaou smears as a marker for Chlamydia infection. Grading of inflammation in the Papanicolaou smear can be of potential use in defining patients at highest risk for Chlamydia in a group considered to be at high risk based on sexual history.
Asunto(s)
Infecciones por Chlamydia/diagnóstico , Chlamydia trachomatis , Prueba de Papanicolaou , Enfermedad Inflamatoria Pélvica/microbiología , Frotis Vaginal , Adulto , Infecciones por Chlamydia/patología , Chlamydia trachomatis/aislamiento & purificación , Femenino , Humanos , Linfocitos/patología , Neutrófilos/patología , Enfermedad Inflamatoria Pélvica/patología , Dolor Pélvico , Estudios Retrospectivos , Factores de Riesgo , Sensibilidad y EspecificidadRESUMEN
While allogeneic stem cell transplantation (SCT) is curative for a significant number of patients with AML, relapse of disease within the bone marrow and/or extramedullary (EM) sites following high-dose therapy continues to limit the success of this treatment. Between October 1985 and December 1996, 81 adults underwent allogeneic SCT for de novo AML at our centre. Forty-two patients remain alive and free of leukaemia with a median follow-up of 50 months. The 5-year actuarial event-free survivals (EFS) for all patients and for those undergoing SCT in CR1 or with advanced disease were 46% (95% confidence interval (CI) 34-58%), 63% (CI 46-76%), and 19% (CI 7-36%), respectively. Twenty-two patients relapsed at a median of 8 (range 1.6-54.5) months with the actuarial risk of relapse for all, CR1 and advanced disease patients being 38%, (CI 27-52%), 23% (CI 13-40%) and 68% (CI 46-88%), respectively. Ten patients relapsed at EM sites; six of these (27% of relapses) had an isolated EM relapse at a median of 31 (range 8.5-54) months. Three of the patients with isolated EM relapse survived > or =24 months following relapse and two patients remain disease-free at 29+ and 33+ months. BuCy conditioning followed by allogeneic SCT in AML results in satisfactory EFS although there is a significant risk of late isolated EM relapse.
Asunto(s)
Busulfano/administración & dosificación , Ciclofosfamida/administración & dosificación , Trasplante de Células Madre Hematopoyéticas , Inmunosupresores/administración & dosificación , Leucemia Mieloide Aguda/tratamiento farmacológico , Leucemia Mieloide Aguda/terapia , Acondicionamiento Pretrasplante , Adolescente , Adulto , Supervivencia sin Enfermedad , Femenino , Enfermedad Injerto contra Huésped/etiología , Trasplante de Células Madre Hematopoyéticas/efectos adversos , Humanos , Masculino , Persona de Mediana Edad , Recurrencia , Acondicionamiento Pretrasplante/efectos adversos , Trasplante HomólogoRESUMEN
There have been encouraging reports of the use of recombinant tissue plasminogen activator (tPA) in established veno-occlusive disease (VOD). Haemodialysis has been considered a contraindication to this therapy in view of the potential haemostatic complications. We report a case of a woman who developed moderately severe VOD complicated by anuria following an allogeneic bone marrow transplant for relapsed acute myeloid leukaemia. Following initiation of peritoneal dialysis she received tPA at a dose of 10 mg/day for 5 days. There was rapid improvement in her urine output and liver function with no bleeding complications. This case suggests that the requirement of dialysis may not preclude the use of tPA in established VOD and therefore warrants further study.
Asunto(s)
Trasplante de Médula Ósea/efectos adversos , Enfermedad Veno-Oclusiva Hepática/terapia , Leucemia Mieloide Aguda/terapia , Activador de Tejido Plasminógeno/uso terapéutico , Adulto , Femenino , Enfermedad Veno-Oclusiva Hepática/etiología , Humanos , Diálisis Peritoneal , Proteínas Recombinantes/uso terapéuticoRESUMEN
Because the architectural and biochemical properties of skeletal muscle dictate its force, velocity, and displacement properties, the major extensors (triceps brachii) and flexors (biceps brachii, brachialis, and brachioradialis) of the elbow in a primate (cynomolgus, monkey) were studied. Functional cross-sectional areas (CSA) were calculated from muscle mass, mean fiber length (normalized to a 2.20 microns sarcomere length), and angle of fiber pinnation measurements from each muscle. Fiber-type distributions were determined and used as a gross index of the biochemical capacities of the muscle. The extensor group had a shorter mean fiber length (31 vs. 47 mm), a larger CSA (13 vs. 8 cm2), and a higher overall percentage of slow-twitch fibers (47 vs. 26%). Consequently, the elbow extensors had a relatively greater potential for force production and force maintenance than the flexors. In contrast, the flexors were designed to optimize their length-velocity potentials; i.e., they had relatively long fibers and a higher fast-twitch fiber composition than the extensors. These morphologic differences between antagonistic muscle groups should be considered when evaluating the motor control mechanisms regulating reciprocal movements about the elbow.
Asunto(s)
Codo/anatomía & histología , Macaca fascicularis/anatomía & histología , Macaca/anatomía & histología , Músculos/anatomía & histología , Animales , Glucólisis , Histocitoquímica , Masculino , Contracción Muscular , Músculos/metabolismo , Oxidación-Reducción , Factores de TiempoRESUMEN
The architectural and histochemical properties of the anatomically distinct compartments of the semitendinosus muscle (ST) of mice, rats, guinea pigs, and rabbits show that the ST is composed of two separate compartments aligned in series--a distal compartment (STd) and a proximal one (STp). The STp is further subdivided into a ventral head (STpv) and a dorsal head (STpd). The muscle fibers were arranged in parallel to the line of muscle pull within each compartment. The STd has the longest and the STpv the shortest fibers in all species. The physiological cross-sectional area and the estimated tetanic tension was greatest in the STd. Based on the staining pattern for myosin ATPase (alkaline preincubation) and an oxidative indicator (NADH or SDH), the STpv has the highest percentage of slow-oxidative (SO) or SO plus fast-oxidative-glycolytic (FOG) fibers of any portion of the muscle. The differences in fiber-type distributions and architectural designs of the separate compartments suggest a specialization of function of the individual compartments.
Asunto(s)
Músculos/anatomía & histología , Animales , Cobayas , Miembro Posterior , Histocitoquímica , Ratones , Ratones Endogámicos , Músculos/enzimología , Músculos/fisiología , Tamaño de los Órganos , Conejos , Ratas , Ratas EndogámicasRESUMEN
The effects of iron deficiency anemia and iron treatment on blood gas and acid-base balance at rest and during exercise were studied. Eight Sri Lankan males and 13 females were randomly divided into an iron treatment or placebo group. Their initial hemoglobin (Hb) levels were 6.2 +/- 0.5 and 5.5 +/- 0.7 g/100 ml (mean +/- SEM) with serum iron levels of 41 +/- 8 and 30 +/- 6 micrograms/100 ml, respectively. Hemoglobin concentration was increased significantly within 7 days after iron treatment to 7.2 +/- 0.4 g/100 ml. Resting lactate was higher than normal, while base excess, buffer base, and actual bicarbonate were lower, maintaining a normal pH. Heart rates during exercise at a given work load and lactate production following exercise decreased after the elevation of Hb. Venous blood PCO2 rose as Hb concentration increased, preceding a significant increase in resting O2 content, 16 days after iron treatment. With anemia, O2 delivery is potentially maintained by a shift of the O2-dissociation curve to the right due, in part, to 2,3-diphosphoglycerate. There was no significant change in PO2 or Hb-O2% saturation following exercise or iron treatment. These data suggest that severe iron deficiency anemia results in lactate accumulation in blood even at rest but pH is maintained within normal limits. It was also suggested that severe anemia may impair CO2 transport capacity of blood which could limit continuation of muscle metabolism.
Asunto(s)
Anemia Hipocrómica/sangre , Dióxido de Carbono/sangre , Hierro/uso terapéutico , Oxígeno/sangre , Esfuerzo Físico , Equilibrio Ácido-Base , Adulto , Anemia Hipocrómica/tratamiento farmacológico , Anemia Hipocrómica/fisiopatología , Prueba de Esfuerzo , Femenino , Hemoglobinas/metabolismo , Humanos , Masculino , Persona de Mediana EdadRESUMEN
A new method for monitoring tablet disintegration in vivo was developed. In this method, the tablets were labeled with a short-lived radionuclide, technetium 99m, and monitored by a gamma camera. Several innovations were introduced with this method. First, computer reconstruction algorithms were used to enhance the scintigraphic images of the disintegrating tablet in vivo. Second, the use of a four-pinhole collimator to acquire multiple views of the tablet resulted in high count rates and reduced acquisition times of the scintigraphic images. Third, the magnification of the scintigraphic images achieved by pinhole collimation led to significant improvement in resolution. Fourth, the radioinuclide was incorporated into the granulation so that the whole mass of the tablet was uniformly labeled with high levels of activity. This technique allowed the continuous monitoring of the disintegration process of tablets in vivo in experimental animals. Multiple pinhole collimation and the labeling process permitted the acquisition of quality scintigraphic images of the labeled tablet every 30 sec. The resolution of the method was tested in vitro and in vivo.
Asunto(s)
Cintigrafía/métodos , Comprimidos , Tecnología Farmacéutica , Computadores , Cintigrafía/instrumentación , Solubilidad , TecnecioRESUMEN
Six weeks of glucocorticoid treatment (triamcinolone-acetonide-21-phosphate, 1 mg/kg of body weight daily) resulted in a similar pattern of fibre type atrophy in jaw and hind-limb muscles. Fast-twitch glycolytic fibres were significantly atrophied in all muscles investigated. Fast-twitch oxidative glycolytic fibres were affected only in the fast (white) regions of the mixed muscles, while slow-twitch oxidative fibres were unaffected. The results from pair-fed controls (food intake matched to the glucocorticoid-treated animals) showed that the glucocorticoid produced an atrophic response in addition to that produced by the decreased food intake in the experimental animals. These results suggest that the jaw musculature shares the wasting effects induced by elevated circulating glucocorticoid levels often found in stress situations.
Asunto(s)
Atrofia Muscular/inducido químicamente , Triamcinolona Acetonida/análogos & derivados , Animales , Privación de Alimentos , Miembro Posterior , Masculino , Músculos Masticadores/patología , Músculos/patología , Atrofia Muscular/patología , Ratas , Ratas Endogámicas , Triamcinolona Acetonida/efectos adversosRESUMEN
The time course of metabolic and physiological adjustment to moderate iron deficiency anemia (MIDA, 8 g Hb/dl) and to severe iron deficiency anemia (SIDA, 4 g Hb/dl) was studied in adult, male Sprague-Dawley rats at 3, 7, 14, 30, 60, 90, 150, and 360 days, respectively. Our previous studies using the same rats used in the present study indicated that bone marrow iron was absent and plasma iron was significantly lower (p less than 0.001) in MIDA and SIDA relative to control. The following results with MIDA and SIDA rats are all expressed relative to control values. Red cell 2,3-diphosphoglycerate ranged from 45 to 146% greater in MIDA over the 360-day period and was 130% greater in SIDA at 30 days. Exhaustive run time consistently averaged 64 +/- 3% (SEM) less in MIDA over the time course and was further lowered to 18% in SIDA at 30 days. Heart rates of MIDA were elevated (p less than 0.05) at 180 days but lower (p less than 0.001) at 360 days in response to exercise. Resting heart rates of MIDA were the same at 180 and 360 days. Heart rates of SIDA were elevated (p less than 0.05) at rest and during exercise at 30 days. Organ weight/body weight changes indicated cardiomegaly in MIDA from 90 to 150 days which reverted to normal at 360 days; splenomegaly in MIDA from 90 to 360 days; and kidney atrophy in MIDA at 60 and 90 days which reverted to normal thereafter; in SIDA cardiomegaly and splenomegaly were present at 30 days. These results indicate that the onset and magnitude of physiological and metabolic adjustments occur in proportion to the severity of the anemia, and despite compensatory adjustments in parameters related to work performance, a new stable, lowered level of work tolerance is reached.
Asunto(s)
Anemia Hipocrómica/fisiopatología , Esfuerzo Físico , Adaptación Fisiológica , Envejecimiento , Anemia Hipocrómica/metabolismo , Animales , Venodisección , Complejo IV de Transporte de Electrones/metabolismo , Frecuencia Cardíaca , Hemoglobinas/metabolismo , Lactatos/sangre , Ácido Láctico , Masculino , Tamaño de los Órganos , Resistencia Física , Ratas , Ratas Endogámicas , DescansoRESUMEN
Thyroidal trophic effects on slow-twitch skeletal muscle properties were compared in normally innervated and denervated soleus of rats maintained at different thyroid states. Hypothyroidism caused fast to slow changes in fiber type composition (99% decrease in proportion of type II fibers), ATPase activities (down 20-30%), myosin light chain pattern (54% less fast light chains), calcium uptake by SR (down 60%), LDH activity (down 11%), and isozyme pattern (9% decrease in M-subunits). Changes of similar magnitude but opposite in direction were induced by thyrotoxicosis. Denervations reversed, to varying degrees, the fast to slow transformations observed in hypothyroidism. However the slow to fast changes found in hyperthyroidism were facilitated rather than inhibited by denervation. These latter results clearly show that the hormone effect can be elicited in the absence of motor innervation. Furthermore, denervation alone caused slow to fast changes in euthyroid muscles. From these results, it is proposed that denervation and dysthyreosis alter muscle properties by independent mechanisms. Our data favor a direct action of thyroid hormone over a neurally mediated mechanism.
Asunto(s)
Hipertiroidismo/metabolismo , Hipotiroidismo/metabolismo , Músculos/metabolismo , Adenosina Trifosfatasas/metabolismo , Animales , Calcio/metabolismo , Desnervación , L-Lactato Deshidrogenasa/metabolismo , Masculino , Neuronas Motoras/fisiología , Músculos/enzimología , Miosinas/metabolismo , RatasRESUMEN
3-Hydroxyacyl-CoA dehydrogenase (HAD) has been widely used to assess the capacity for fatty acid oxidation by different muscle fiber types, with various Krebs cycle enzymes as a base for comparison. We have measured this enzyme in individual lyophilized fibers of the guinea pig soleus and the white and red portions of the vastus lateralis, and compared its activity in each fiber with that of lipoamide dehydrogenase (LAD), which as a part of the pyruvate dehydrogenase complex fulfills a function similar to HAD in forming acetyl-CoA, but from pyruvate and, thus, mainly from a carbohydrate source. The mean HAD/LAD ratio was 17.2 +/- 3 in the red vastus, 24.9 +/- 3 in the white vastus, and 43.7 +/- 10 in the soleus, all differences being highly significant. The two types of fast fibers were not distinguished from one another by the enzyme ratio within either the white or the red portion of the vastus lateralis. Data from all of the fast fibers taken together indicate a close correlation (0.93) between the two enzymes, whereas values from the soleus indicate a specialization of the mitochondria of the slow muscle fibers for the oxidation of fatty acids.
Asunto(s)
3-Hidroxiacil-CoA Deshidrogenasas/metabolismo , Dihidrolipoamida Deshidrogenasa/metabolismo , Animales , Metabolismo Energético , Cobayas , Cinética , Masculino , Mitocondrias Musculares/enzimologíaRESUMEN
Effects of thermal dehydration without exercise on leukocyte differentials, serum protein fractions, and other hematologic characteristics were studied in six healthy subjects. Both leukocyte and serum total protein levels increased beyond that predicted by hemoconcentration alone. Eosinophil counts decreased significantly, although other leukocyte counts tended to increase. Serum globulin concentrations tended to increase, but the albumin level did not change. Serum K+ concentration was elevated, but Na+ and Cl- were unaffected. It is suggested that thermal dehydration affects blood leukocyte composition and protein metabolism in many of the same ways as physical exercise.
Asunto(s)
Deshidratación/sangre , Leucocitos/fisiología , Adulto , Proteínas Sanguíneas/análisis , Peso Corporal , Femenino , Calor , Humanos , Recuento de Leucocitos , Masculino , Baño de VaporAsunto(s)
Comprimidos , Animales , Química Farmacéutica/métodos , Perros , Cintigrafía , Solubilidad , Factores de TiempoRESUMEN
The effect of a mild weight-lifting program on the progress of glucocorticoid-induced atrophy was investigated. Groups of rats were either injected daily for 6 weeks with triamcinolone acetonide, 1 mg/kg (group S), subjected to a weight-lifting program 4 times per week (group T), or subjected to the injection and weight-lifting programs concurrently (group ST). The training program, besides decreasing the normal body weight gain of control (group C) rats, had no effects on gastrocnemius and soleus muscles. In group ST, the extent of gastrocnemius atrophy was less severe than in group S, and the mean areas of all fiber types were greater in similar proportion. Gastrocnemius muscles were also tetanically stronger (g, g/g body weight) in group ST than group S. The soleus muscles of groups ST and S were similar in all indices of size and strength, except for a significantly decreased fast-twitsch-oxidative-glycolytic (FOG) mean fiber area in the ST seleus muscles. The extent of fast-twitsch muscle atrophy resulting from chronic glucocorticoid treatment can be lessened by mild weight-lifting exercise. Differences in fiber area responses between soleus and gastrocnemius may reflect recruitment and/or metabolic differences of similar fiber types in the two muscles.
Asunto(s)
Músculos/fisiopatología , Atrofia Muscular/fisiopatología , Condicionamiento Físico Animal , Animales , Peso Corporal/efectos de los fármacos , Masculino , Contracción Muscular , Tono Muscular , Músculos/anatomía & histología , Atrofia Muscular/inducido químicamente , Tamaño de los Órganos/efectos de los fármacos , Ratas , Factores de Tiempo , Triamcinolona Acetonida/efectos adversosRESUMEN
Various metabolic, histochemical, and contractile measurements were made on soleus and gastrocnemius muscles of adult rats treated with triamcinolone acetonide (1 mg . kg-1 . day-1 for 6 wk), and compared to similar measurements in pair-fed and control animals. Contractile measurements were performed in situ under pentobarbital anesthesia. Gastrocnemius muscles from steroid-treated rats showed higher twitch and tetanic tensions when expressed in grams/gram of muscle, compared to control rats. Similar, although less marked, trends occurred in the less atrophied gastrocnemius muscles from pair-fed rats. Soleus muscles from steroid-treated rats exhibited significantly higher (139% of control) twitch tension (grams/gram of muscle), and elevated twitch/tetanus ratios, compared to control and pair-fed groups. No alterations occurred in muscle contractile speed in either muscle. The greater atrophy of fast compared to slow fiber types in gastrocnemius muscles under both experimental conditions did not occur in the soleus, a predominantly slow-twitch muscle. The atrophic and contractile responses of fast and slow muscles to these two conditions were quantitatively as well as qualitatively different.
Asunto(s)
Privación de Alimentos/fisiología , Contracción Muscular/efectos de los fármacos , Músculos/fisiología , Triamcinolona Acetonida/farmacología , Adenosina Trifosfatasas/metabolismo , Animales , Atrofia , Peso Corporal/efectos de los fármacos , Dihidrolipoamida Deshidrogenasa/metabolismo , Glicerolfosfato Deshidrogenasa/metabolismo , Histocitoquímica , Masculino , Músculos/enzimología , Músculos/patología , RatasRESUMEN
Changes in haemoglobin (Hb), work performance, heart rate and postexercise blood lactate were studied in iron deficient, anaemic subjects for 16 d following total dosage infusion of iron dextran, i.v. (30-50 ml). Six adult men and 14 women were subjects with initial Hb levels of 6.6 +/- 0.6 g/dl (mean +/- SEM) for the iron treatment group (n=10) and 8.0 +/- 0.7 for the placebo group (saline infusion, n=10). Serum levels were 0.51 +/- 0.15 and 0.67 +/- 0.12 mg/l for the two groups, respectively. Haemoglobin and maximal work time increased significantly within 4 d after iron treatment and continued to increase up to 16 d. No changes were found in the placebo subjects. Heart rates at a given exercise intensity were lower in the iron treatment group than in control subjects who had the same Hb levels but had not been treated with iron. Post-exercise venous blood lactate was similar on succeeding days after iron treatment even though the subjects reached higher work loads. These results demonstrate the treatment of iron deficient, anaemic subjects with iron dextran results in improved work capacity within 4 d and a lower heart rate at a given work load after treatment which cannot be accounted for totally by the elevation of Hb concentration.
Asunto(s)
Anemia Hipocrómica/tratamiento farmacológico , Frecuencia Cardíaca , Lactatos/sangre , Esfuerzo Físico , Adulto , Anciano , Femenino , Hemoglobinometría , Humanos , Hierro/uso terapéutico , Masculino , Persona de Mediana Edad , Factores de TiempoAsunto(s)
Atrofia Muscular/fisiopatología , Animales , Gatos , Isocitrato Deshidrogenasa/metabolismo , Masculino , Contracción Muscular/efectos de los fármacos , Proteínas Musculares/metabolismo , Atrofia Muscular/inducido químicamente , Atrofia Muscular/metabolismo , Tamaño de los Órganos , Fosfofructoquinasa-1/metabolismo , Succinato Deshidrogenasa/metabolismo , TriamcinolonaAsunto(s)
Anemia Hipocrómica/metabolismo , Hierro/metabolismo , Músculos/metabolismo , Envejecimiento , Animales , Recuento de Células Sanguíneas , Venodisección , Complejo IV de Transporte de Electrones/metabolismo , Hematócrito , Hemoglobinas/metabolismo , Hierro/administración & dosificación , Masculino , Mioglobina/metabolismo , Fosfofructoquinasa-1/metabolismo , RatasRESUMEN
The expression of asparagine synthetase activity [L-aspartate:ammonia ligase (AMP-forming), EC 6.3.1.1] in cultured Chinese hamster ovary (CHO) cells is regulated by asparagine. After transfer of CHO cells from an asparagine-supplemented medium to a medium lacking asparagine, activity increases 1.5- to 2-fold. If asparagine is added back to the medium, activity returns to control levels. To test the possible involvement of Asn-tRNAAsn in regulating the levels of asparagine synthetase, we have examined the levels of asparagine synthetase in a mutant of CHO cells containing a temperature-sensitive asparaginyl-tRNA synthetase [L-asparagine:tRNA ligase (AMP-forming), EC 6.1.1.22]. Under conditions of limited asparaginyl-tRNA synthetase activity in the mutant, there is a 2- to 3-fold increase in the level of asparagine synthetase activity. Under identical conditions, there is no change in asparagine synthetase activity in the wild type. This correlation between asparaginyl-tRNA synthetase activity and asparagine synthetase levels may be a consequence of a direct role of tRNAAsn in the regulation of the in vivo expression of the asparagine synthetase structural gene.