In Vitro Susceptibility of Acanthamoeba Culbertsoni to Inhibitors of Folate Biosynthesis1

ABSTRACT. The effects of different sulphonamides, dihydrofolate reductase inhibitors and other inhibitors of folate metabolism on growth of Acanthamoeba culbertsoni in a chemically defined medium are reported. Among the sulphonamides, sulphamethoxazole and sulphadiazine were most effective followed by sulphanilamide and sulphaguanidine. Inhibition by each sulphonamide was reversed by p-aminobenzoic acid as well as folic acid. 7-Methylguanosine, a pteridine synthesis-inhibitor, did not inhibit multiplication of A. culbertsoni. Among the dihydrofolate reductase inhibitors, pyrimethamine blocked the amoebic growth at 100 μg/ml, while trimethoprim and cycloguanil palmoate failed to cause significant inhibition of growth even at 250 μg/ml. Metoprine inhibited amoebic growth completely at 50 μg/ml. Methotrexate and a thymidylate synthetase inhibitor 5-fluorouracil inhibited growth strongly, with IC₅₀ values (the concentration of the drug which causes 50% inhibition of the growth at 72 h) of 1.97 and 2.45 μg/ml, respectively. Inhibition by methotrexate, metoprine or 5-fluorouracil could not be reversed by folic acid, folinic acid, thymidine, or folinic acid plus thymidine. the results indicate unusual features in A. culbertsoni folate metabolism.     

Formation of Valine in the Presence of Sodium Acrylate Monomer by Glutamic Acid Producing Bacteria

Glutamic acid producing bacteria accumulated a large amount of valine in the presence of the excess biotin, when sodium acrylate monomer (Na-AM) was added at the earlier phase of culture. Brevibacterium roseum ATCC 13825, particularly, accumulated the large amount of valine among bacteria tested and the conditions of valine accumulation by this strain were investigated.

The most effective addition time of Na-AM was at the earlier phase of logarithmic phase. The optimal concentration of Na-AM for the accumulation of valine was 1.0 per cent (v/v). Most effective nitrogen sources were the combination of 1.0 per cent urea and 0.2 per cent ammonium sulphate. The additions of Mn²⁺ and Fe²⁺ increased valine accumulation. By the excess concentration of biotin for growth, 20 μg/liter or more, did not affected valine accumulation, while the presence of the suboptimal condition of biotin for growth was not good for the formation of valine even in the presence of Na-AM. The accumulation of valine reached 9.0 mg/ml from 75.0 mg/ml of glucose in the presence of 50 μg/liter of biotin and 1.0 per cent (v/v) of Na-AM.

This strain possessed considerable activity of valine formation regardless of the addition of Na-AM and promoted the accumulation of valine by the addition of Na-AM.     

Induced Resistance to Sulfonamides in Chilomonas paramecium

SUMMARY. Strains of Chilomonas paramecium differing in degree of resistance to sulfanilamide have been established through acclimatization to this sulfonamide at 50, 100 and 200 mg. %. Resistant strains differ from the normal stock in their enhanced sensitivity to p -aminobenzoic acid. In the normal stock, sulfanilamide inhibition is reversed at an SA/PABA ratio of 10,000 but not at 20,000; in the least resistant strain, at a ratio of 400,000 but not at 800,000. In resistant strains inhibition is reversed by folk acid, methionine, adenine, cytosine and thymine; in the normal stock, none of these metabolites produces reversal. In high concentrations of PABA (10–20 mg. %) growth of the normal stock is only retarded, whereas the strain least resistant to sulfanilamide fails to recover from exposure to 20 mg. % PABA. The strain most resistant to sulfanilamide is most susceptible to PABA in high concentrations. The data suggest that resistance to sulfanilamide in C. paramecium may depend mainly upon an accelerated synthesis of PABA.     

Acaricidal activity of Cassia alata against Rhipicephalus (Boophilus) annulatus

Using adult immersion test, the acaricidal activity of ethanolic extracts of leaves of Cassia alata L. was studied against Rhipicephalus (Boophilus) annulatus. The efficacy was assessed by measuring per cent adult mortality, inhibition of fecundity and hatching rate. The ethanolic extract of C. alata produced a concentration dependant increase in the adult tick mortality. The highest mortality (45.8%) and inhibition of fecundity (10.9%) were observed at the highest concentration tested (100 mg/ml). The plant extract did not affect egg hatchability.     

Growth, Sex Expression and Yield of Squash Melon (Citrullus vulgarisvar. fistulosus) as Influenced by 2(chloroethyl)phosphonic acid, 2,3,5-tri-iodobenzoic acid and (2-chloroethyl) trimethyl-ammonium chloride

Single aqueous sprays of 2(chloroethyl)phosphonic acid (CEPA) 250, 500 and 1000 mg/1; 2,3,5-triiodobenzoic acid (TIBA) 25, 50 and 100 mg/1; and (2-chloroethyl) trimethyl-ammonium chloride (CCC) 250, 500 and 1000 mg/1 were applied to squash melon (Citrullus vulgaris Schrad. var. fistu-losus Stocks.) at the 2–3 leaf stage. Though the final length of the main axis and number of lateral branches were not affected by any treatment, CEPA retarded growth of young plants by reducing the internodal length. It did not change the flowering pattern but delayed flowering and reduced the production of both pistillate and staminate flowers. However, it increased the per cent femaleness as a result of comparatively more suppression of staminate flowers. The TIBA 25 and 50 mg/1 and CCC 500 mg/1 did not affect the staminate flower production but increased the pistillate flowers, which increased the per cent femaleness. The CEPA decreased while both TIBA 25 and 50 mg/1, and CCC 500 mg/1 increased the number of fruits per plant and the yield. The mode of action of the chemicals has been discussed.     

A microbiological test system for determining dioxidine levels in biological fluids

A microbiological procedure for determining dioxidine concentrations in biological fluids with using E. coli AB 2472 rec A 16, a reparation deficient strain as a test organism is described. Cell suspension of the strain 24-hour culture is added to 1.2 per cent agar with Hottinger digest (140 mg per cent of amine nitrogen), 3 g/l of disubstituted sodium phosphate and 0.4 per cent of glucose cooled to 50 degrees C. 10 ml of the medium are added to every Petri dish with metallic cylinders put on the agar. After the medium solidification the cylinders are removed and 0.1 ml of the solution being tested is added to every well. The dishes are incubated for 24 hours under anaerobic conditions. The test system sensitivity is 0.2 microgram/ml of dioxidine. The relationship between the growth inhibition zone and the drug concentration is linear within dioxidine concentrations of 0.2 to 3.2 micrograms/ml.     

Preservation of red blood cells with purines and nucleosides. III. Synthesis of adenine, guanine, and hypoxanthine nucleotides

Purine nucleotides of fresh human red cells and of red cells during storage at 4 degrees and 25 degrees C with additions of adenine, guanine, guanosine and inosine were estimated by HPLC. Six nucleotides were found in red cells: ATP, ADP, AMP, GTP, GDP, and IMP. The adenine nucleotides represented 92 per cent of the total purine nucleotides, guanine nucleotides 7 per cent and IMP less than 1 per cent. In red cells stored with adenine the total concentration of purine nucleotides increased to 125 per cent of the normal value. An adenine-free but guanine and guanine + inosine containing medium caused a decrease of the concentration of purine nucleotides by 10 to 20 per cent. When red cells were stored without adding guanine or guanosine the content of the guanine nucleotides decreased from 0.32 to 0.17 mumol/g Hb due to the decrease in the GTP content, but the GDP concentration increased slightly. In CPD-AG blood, however, the concentration of guanine nucleotides increased considerably up to 0.6 mumol/g Hb. IMP was estimated in all investigated stored red cells. In CPD-A and in CPD-AG blood 0.4 mumol/g Hb were produced during 3 weeks of storage, but twice of that in CPD-AI blood. The principles of the synthesis and the degradation of purine nucleotides in stored red cells are discussed in detail.     

Amitrole Absorption by Bean (Phaseolus vulgaris L. cv ;Red Kidney') Roots : Mechanism of Absorption

The mechanism of transport of the herbicide 3-amino-1,2,4-triazole (amitrole) into Phaseolus vulgaris roots appears to be passive, as judged by the effect of temperature (Q₁₀ = 1.3 between 15 and 25°C) and the lack of sensitivity to metabolic inhibition afforded by 2,4-dinitrophenol and NaN₃. Amitrole absorption is a linear function of external concentration over several orders of magnitude and, thus, is not facilitated by a carrier mechanism. The absorption of amitrole is sensitive to external pH, being stimulated under acid conditions. This stimulation of amitrole absorption is seen at low (≤1 millimolar) amitrole concentrations, but not at high (50 millimolar) amitrole levels. While the apparent octanol-water partition coefficient varies with the pH of the aqueous phase, there is no clear correspondence between absorption and the apparent partition coefficient. Roots do not accumulate amitrole above concentration equilibrium; however, at a time when the net amitrole content of the root tissue begins to saturate, amitrole can be detected in the xylem stream. On a fresh-weight basis, amitrole absorption by roots is equal to that accomplished by trifoliate-leaf tissue. An estimate of the permeability coefficient (according to the analysis of Tyree et al. 1979 Plant Physiol 63: 367-374) suggests that amitrole possesses near-optimal permeability for an ambimobile solute, on the order of 2.12 (± 0.47) × 10⁻⁹ meters per second.     

Vegetative Growth Responses of Pea Plants to CCC and Phosfon in Relation to Phosphorus Nutrition

The effects of 2-chloroethyltrimethylammonium chloride (CCC)and 2,4-dichlorobenzyl-tributylphosphonium chloride (Phosfon)on the growth of pea plants in sand culture at two rates ofapplied phosphorus (P), were studied in controlled-environmentgrowth chambers. CCC at 1 and 10 mg/1, and to a lesser degreePhosfon at 0.1 mg/1, stimulated growth. CCC at 1000 mg/1 andPhosfon at 100 mg/1 retarded growth, due mainly to shortenedstems. The magnitude of such effects depended on the level ofapplied P. Reductions in plant height by the 1000 mg/1 CCC treatmentwere 13 and 50 per cent respectively at the high (160 mg/1)and low (8 mg/1) rates of applied P. Similar decreases due to100 mg/1 Phosfon were 30 and 57 per cent respectively. At thehigh P rate, both CCC and Phosfon had no significant effecton total uptake of P, or on relative distribution in the leaf,stem, and root. At the low P rate, the root, relative to leafand stem, retained more P, at a CCC concentration of 1000 mg/1.With Phosfon at 100 mg/1 relative leaf P content increased whilethat of the stem and root decreased. Phosfon was more activethan CCC in terms of the concentration required to cause a givenmagnitude of growth effect.     

Insecticidal and antifungal potentials of a proteinaceous extract of Cassia occidentalis (Linn.) seeds

Proteinaceous extract obtained from Cassia occidentalis seeds with purification fold of 3.91 and 82.7% of bovine trypsin inhibitory activity was assessed at different concentrations (25, 50, 100, 200, 400 and 800 μg/ml) against Spodoptera litura. Assay of larval feeding suggested proteinaceous extract to be toxic as prepupal (80.16%) and pupal mortalities (100%) along with growth deterrent effect with only 16.71% pupation was observed at 800 μg/ml. Fifty per cent mortality (LC₅₀) was observed at 132.91 μg/ml. Also the inhibitor affected fecundity, longevity and percentage of egg hatching. Nutritional indices were adversely affected as both efficiency of conversion of ingested and digested food decreased while approximate digestibility and metabolic cost increased. In vitro studies on proteolytic enzymes of S. litura revealed inhibition of trypsin and chymotrypsin in lumen and faecal matter at all tested concentrations. Also proteinaceous extract inhibited mycelial growth in Fusarium oxysporum, Alternaria brassicicola and Alternaria alternata at 100 μg/ml.     

The Accumulation of Zinc by the Mosquito

The zinc content of mosquitoes in various developmental stages was determined by spectrographic and microchemical analysis and use of zinc⁶⁵ and found to be five to ten times higher than other trace elements. Also the concentration of zinc in the mosquito was much greater than in other insects of different biological orders. Over 90 per cent of this element was localized in the Malpighian tubules at a concentration of 32 µg zinc per mg dry weight. The non-dialyzable form of zinc is loosely bound, for it was dissociated upon dialysis against ethylenediamine tetraacetate. The uptake of this trace element was correlated during larval growth with weight increase and required the presence of food particles. Furthermore, this uptake was different from that of cobalt which was not accumulated when offered as an inorganic salt or as vitamin B₁₂. Zinc was not detectable in pooled egg masses, and once embodied by the larvae, was retained under fasting conditions and at a constant level throughout the pupal stage and as long as 14 days' adult life. Supplementation of the media with EDTA caused a marked inhibition of growth that could be completely reversed by the addition of zinc or zinc plus lead. The resultant pupae, however, contained less than 5 per cent of the normal amount of zinc and were essentially zinc-free; yet their rate of growth and gross appearance were normal.     

The effects of coumarin on the growth and viability of sporelings of red algae

Summary The growth of sporelings of the red algae Plumaria elegans, Antithamnion plumula and Polysiphonia brodiaei was markedly influenced by coumarin. Growth of Plumaria and Antithamnion was totally inhibited by immersion for 7 days in media containing 200 mg coumarin/l, and showed 46% and 41% growth inhibition respectively in 100 mg coumarin/l; a significant reduction in growth was obtained in 50 mg/l of the phytostatic agent (e.g. 15% growth inhibition with Plumaria; and 10% with Antithamnion). A noticeable stimulation of growth was observed in 10 mg coumarin/l. The viabilities of the sporelings remained high after immersion in the toxic agent. The inhibitory effects were of a similar order both with the young plants treated immediately after commencement of growth, and with sporelings grown normally for 14 days before contact with coumarin. With Plumaria sporelings the maximum inhibitory effects were observed after 3 days immersion in 200 mg coumarin/l, and after 5 days in 100 mg coumarin/l. Immersion for 7 days in 200 mg/l of the reagent induced irreversible changes in the sporelings; such effects were less marked at 100 mg/l; and at 50 mg/l there was a complete recovery from the effects of the compound when speorelings were transferred to normal culture medium. The significance of the results is discussed in terms of the possible factors involved which may influence sporeling growth.     

The Carbohydrate Nutrition of Tomato Roots: VI. The Inhibition of Excised Root Growth by Galactose and Mannose and its Reversal by Dextrose and Xylose

The addition of 0.01–0.015 per cent. galactose or 0.005–0.01per cent, mannose reduces by 50 per cent, the linear growthof excised tomato roots cultured in a I per cent, sucrose medium.An addition of 0.03–0.04 per cent, of either sugar causesnot less than a 90 per cent, inhibition of growth. The survivalof meriste-matic activity is higher in presence of fully inhibitoryconcentrations of mannose than of galactose. Roots inhibitedby galactose are distinguishable from those inhibited by mannose. The inhibitory effect of concentrations of galactose up to 0.15per cent, and of mannose up to 0.4 per cent, can be fully antagonizedby the simultaneous addition to the culture medium of dextrose.The minimum ratio of dextrose: inhibitory sugar for maximumantagonism of the growth inhibition is with galactose 5: 1 andwith mannose 3.5: 1. Growth of roots in a dextrose-containingmedium does not protect them from subsequent inhibition by eithergalactose or mannose. d-xylose has significant activity as an antagonist of mannoseinhibition and even more so of galactose inhibition. However,the restoration of growth achievable from the addition of xyloseis not comparable with that resulting from the addition of dextrose.The inhibition of growth by xylose is not alleviated by thesimultaneous addition of dextrose. Maltose has low activityas an antagonist of galactose and mannose inhibition. All othersugars tested and the sugar alcohols corresponding to galactoseand mannose were quite inactive as antagonists of the growthinhibition by these two sugars. Mixtures of partially inhibitory concentrations of galactoseand mannose were less inhibitory than their more inhibitorycomponent. The concentration of dextrose required to reversethe inhibitory activity of such mixtures was not greater thanthe minimum concentration required to antagonize the actionof the more inhibitory component. The antagonism of galactose inhibition by dextrose is not dueto dextrose impeding galactose uptake.     

Growth inhibition of Candida albicans by folate pathway inhibitors. Their potential in the selection of auxotrophs

Growth studies were conducted on C. albicans in a glucose — salts — biotin (GSB) medium in the presence of folate inhibitors. Sulfanilamide inhibited growth which was restored by PABA or tetrahydrofolate (THF). Aminopterin inhibited growth to about the same level as did sulfanilamide, but this inhibition was not reversed with PABA nor THF, singly or in combination. Inhibition by combined sulfanilamide and aminopterin was synergistic, reducing growth by more than 90% for 48 h. The sulfanilamide component of the combined inhibition was reversed by PABA or THF to the level of that of aminopterin alone. Cytochrome synthesis was not affected by the inhibitors, but marked increases occurred in -ketoglutarate, malate, isocitrate, and pyruvate dehydrogenases, especially in the presence of both inhibitors. The pyrimidines in combination with sulfanilamide were as inhibitory as was the combination of aminopterin and sulfanilamide, but they had no effect when added alone or in combination with aminopterin. Unlike the pyrimidines, the purines stimulated about a 50% recovery from inhibition by either of the inhibitors. Growth inhibition by combined sulfanilamide and aminopterin was overcome by about 50% by the addition of the THF-mediated end-produits: deoxythymidylate, adenine, histidine and methionine. The use of GSB medium containing adenine, histidine, methionine and the folate inhibitors but without deoxythymidylate resulted in thymineless death of prototrophic cells providing a method for the selection of auxotrophic mutants.     

一种高尿酸血症大鼠模型诱导方法的改良和效果评价研究

目的: 探索短期内诱导高尿酸血症大鼠模型的有效方法,并对模型效果进行评价。方法: 雄性SD大鼠随机分为对照组(CT组,6只)和5个模型组(M1-M5组),每组8只;M1组(每天酵母膏10 g/kg+腺嘌呤100 mg/kg 2次灌胃,于模型诱导的第7日1次性腹腔注射氧嗪酸钾300 mg/kg)、M2组(每天酵母膏10 g/kg+腺嘌呤100 mg/kg灌胃2次,于模型诱导第1、3、7日每天腹腔注射1次氧嗪酸钾300 mg/kg)、M3组(每天酵母膏10 g/kg+腺嘌呤100 mg/kg灌胃 2次,每天腹腔注射1次氧嗪酸钾300 mg/kg)、M4组(每天酵母膏20 g/kg+腺嘌呤100 mg/kg灌胃 2次,每天腹腔注射1次氧嗪酸钾300 mg/kg)、M5组(每天酵母膏30 g/kg+腺嘌呤100 mg/kg灌胃2次,每天腹腔注射1次氧嗪酸钾300 mg/kg)、CT组(5个模型组按相同的时间、体重计算等体积灌胃和腹腔注射生理盐水),造模7 d;分别在造模结束时和2周后采集24 h尿样和血样检测尿酸、肌酐水平,取肾脏和胃称重,观察肾脏病理变化。结果: 与CT组相比,造模结束后,所有模型组大鼠体重均显著降低(P＜0.01);除M2组外,其他造模组大鼠均有亡,M4组和M5组因死亡率高未做后续分析,M1和M3组分别死亡4例和2例;造模结束后,模型大鼠血尿酸、尿尿酸水平明显升高(P＜0.01),并且M2组的血尿酸水平显著高于其他各组(P＜0.05);继续喂养2周后,各模型组的血尿酸和尿尿酸水平仍显著升高(P＜0.05);各模型组大鼠肾脏重量也明显增加(P＜0.01);病理检查显示,模型组大鼠肾脏出现明显炎症反应和结构破坏。结论: 采用酵母膏(10 g/kg)、腺嘌呤(100 mg/kg)联合氧嗪酸钾(300 mg/kg)间隔(第1、3、7日)注射的方案可在短期内安全地诱导高尿酸血症大鼠模型,模型效果持续时间较长,适合在相关研究中应用。     

ANALYSIS OF THE MAJOR AMINO ACIDS OF RAT BRAIN AFTER IN VIVO INHIBITION OF GABA TRANSAMINASE BY ETHANOLAMINE O-SULPHATE

The effect of in vivo inhibition of GABA transaminase by ethanolamine O-sulphate on the content of the free amino acids in rat brain has been studied. Intracisternal injection of 2.0 mg/kg resulted in a progressive increase in GABA levels with time, to reach after 8 h a 100 per cent increase over saline-injected control animals. The effect of injection of 0.5, 1.0 and 2.0 mg/kg was studied 24 h after injection and the results showed that the increased GABA levels were dependent on the dose of inhibitor employed. Apart from the substantial increase in the GABA concentration of the brain there were no significant changes in the content of the other amino acids except for a small but significant decrease in aspartic acid in one experiment. When the extent of inhibition of the transaminase was correlated with the rise in GABA concentration it was shown that no elevation occurred until more than half of the enzymic activity had been inhibited.     

Galactose as an Inhibitor of the Expansion of Root Cells

The inhibition of the growth of cultured tomato roots by galactoseis due to an inhibition of cell expansion. Galactose is rapidlyabsorbed during the first 8 h following application and thefull inhibitory effect on extension growth of the roots is exertedwithin the first 24 h. At a concentration of 0·05 percent or less (50 per cent inhibition occurs at 0·035per cent) the galactose is not toxic and growth continues for7 days at the partially inhibited rate. The simultaneous presenceof glucose reduces galactose uptake but significant galactoseuptake continues at sites insensitive to a high concentrationof external glucose. In presence of an appropriate level ofglucose, although galactose uptake proceeds, the growth inhibitoryeffect of the galactose is fully reversed. Galactose reduces the content in the cell walls of the -cellulosefraction and during feeding with (I-¹⁴C) galactose all the cellwall fractions become labelled. The -cellulose fraction thenyields galactose of high specific activity. Glucose inhibitsthe incorporation of carbon from galactose into the -cellulosefraction and galactose inhibits the incorporation into thisfraction of the carbon of sucrose. The hypothesis is developedthat galactose inhibits cell expansion by a disruption of cellulosesynthesis which involves a direct incorporation of the externallyapplied galactose into the a-cellulose fraction of the cellwalls.     

Preservation of red blood cells with purines and nucleosides. II. Uptake and utilization of purines and nucleosides by stored red blood cells

The uptake of adenine, guanine, guanosine and inosine by stored red cells was investigated in whole blood and red cell resuspensions at initial concentrations of 0.25, 0.5 and 0.75 mM for adenine and 0.5 mM for the other additives using a rapid ion-exchange chromatographic microanalysis of purines and nucleosides in plasma and whole blood. Increasing adenine concentrations from 0.25 to 0.75 mM in blood elevated the adenine uptake from 0.3 up to 0.8 mmol/l red cells during 2 hours after collecting blood. The intra-/extracellular distribution ratio changed from 1 : 1.3 to 1: 1.7. Some 2 hours after withdrawing blood into CPD--solution with purines and nucleosides the uptake of adenine and guanine resulted in 40 per cent and 70 per cent respectively and of guanosine and inosine in 80 and 90 per cent respectively. The replacement of plasma by a resuspending solution gave the same uptake rates for purines and nucleosides. The nucleosides were rapidly split to purines and R-1-P and disappeared from blood during one week. Adenine and guanine were utilized to 80 to 90 per cent only after 3 weeks. During the same period the utilization of guanine was smaller by 40 per cent than that of adenine due to the different activity of the purine nucleoside phosphorylase for these substrates. The plasma of all analyzed blood samples contained hypoxanthine and inosine, but guanine and guanosine were detected only in those samples to which one of them was added. After 3 weeks of storage the highest concentration of hypoxanthine was found in CPD-AI blood with 600 microM in plasma and the highest concentration of synthesized inosine in CPD-AG blood with a concentration of 100 microM in plasma. Three ways of utilization of purines by stored red cells were discussed : the synthesis of nucleotide monophosphates, the formation of nucleosides, and the deamination. The portions of these ways change during storage. The most effective concentrations of adenine and guanosine in stored blood seems to be 0.25 and 0.5 mM respectively. The full utilization of the nucleoside requires the addition of inorganic phosphate.     

Production of L-Isoleucine by AHV Resistant Mutants of Brevibacterium flavum

The growth of Brevibacterium flavum No. 2247A was inhibited by α-amino-β-hydroxy-valeric acid (AHV), and the inhibition was partially reversed by L-isoleucine.

AHV resistant strain ARI-129, which was isolated on a medium supplemented with 2 mg/ml of AHV, produced 11 g/liter of L-isoleucine.

No difference was observed in threonine dehydratase between No. 2247A and ARI–129. Homoserine dehydrogenase from ARI–129 was insensitive to the feedback inhibition by L-isoleucine and L-threonine.

O-Methyl-L-threonine resistant mutant, strain AORI–126, which was derived from ARI–129, produced 14.5 g/liter of L-isoleucine. Specific activity of threonine dehydratase from AORI–126 increased about two-fold higher than those from No. 2247A and ARI–129, whereas degree of inhibition of the enzyme by L-isoleucine was the same among three strains.

Among auxotrophic mutants derived from ARI–129, adenine and lysine auxotrophs produced more L-isoleucine than the parent did.

In the adenine auxotroph, L-isoleucine production was markedly reduced by the addition of excess adenine.     

Some effects of chloramphenicol on the metabolism of chlorella

Summary A chloramphenicol concentration of 3 mg per ml inhibits uptake of ¹⁴C-labelled phenylalanine, lysine, and adenine by Chlorella cells. Incorporation into both the free pool and the TCA insoluble fraction is inhibited. The inhibition is not related to inhibition of protein synthesis since cycloheximide (a specific inhibitor of protein synthesis in Chlorella) does not inhibit uptake of the ¹⁴C-labelled amino acids. Uptake of ¹⁴C-uracil is not inhibited by chloramphenicol.Both chloramphenicol and 2.4-dinitrophenol stimulate endogenous respiration of Chlorella, but whereas the latter reduces the internal concentration of ATP, the former (in concentrations of 1–3 mg/ml) stimulates it about two-fold. Similar concentrations of chloramphenicol decreases slightly the concentration of ADP, and it is therefore suggested that in Chlorella, chloramphenicol concentrations of 1–3 mg per ml inhibit some energy-linked reactions by preventing ATP utilization.