Decrease of Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenase Activities in the Xylem of Populus gelrica on Budding

The activities of glucose 6-phosphate and 6-phosphogluconate dehydrogenases, transketolase, phosphoglucose isomerase, and fructose 6-phosphate kinase were studied in extracts of wintering poplar (Populus gelrica) xylem. The xylem of wintering poplar showed high levels of transketolase, glucose 6-phosphate, and 6-phosphogluconate dehydrogenases. On recommencement of growth, the two dehydrogenase activities decreased. The three remaining enzymes appeared to be unchanged. In spring and early summer, glucose 6-phosphate dehydrogenase of the xylem was extremely low. On the other hand, 6-phosphogluconate dehydrogenase, which also became lower during the metabolic shift from winter to spring, was readily detected, and was several times higher than glucose 6-phosphate dehydrogenase throughout the year. The low dehydrogenase activities lasted into late October and then appeared to resume their original activity. A shift of metabolism at the beginning of growth was also observed by measuring the amount of sugar phosphates, soluble amino acids and amides, and proteins in the xylem. In contrast to the decrease of the two dehydrogenases and soluble proteins at the time of budding, incorporation of lysine-U-¹⁴C into the xylem protein ramained constant. A method to transfuse radioactive compounds into a section of stem was described.     

Coordinate and Noncoordinate Changes in Enzyme Activities in Pentose Phosphate Cycle in Poplar: A Control of Enzyme Activities in Differentiated Xylem

Activities of glucose 6-phosphate and 6-phosphogluconate dehydrogenases,transketolase and transaldolase in twigs of Populus gelricawere measured throughout a year. In the living bark, activitiesof the four enzymes of the pentose phosphate cycle changed atabout the same time in the life cycle of the plant. In the differentiatingxylem cells there also occurred a simultaneous change in thefour enzyme activities. After differentiation of cambium toxylem, the high levels of the four enzyme activities fell graduallyand reached minimum levels by early September. In early September,the former two dehydrogenase activities began to rise again,while the latter two transferase activities continued to decrease.The elevated levels of the two dehydrogenases in the differentiatedxylem remained unchanged in the non-growing period of the lifecycle of the plant. Such a changing pattern of enzyme activitiesin the life cycle suggested that the pentose phosphate cyclein the differentiated xylem is interrupted in part at the stepof transketolase reaction, which results in an increased supplyof pentoses and NADPH. Moreover, these characteristic changesin the enzyme activities in the xylem are correlated with thechanges in the fine structures of the cells. ¹ Contribution No. 2272 from the Institute of Low TemperatureScience, Hokkaido University, Sapporo, Japan (Received June 26, 1981; Accepted September 28, 1981)     

Endogenous levels of oxygen,carbon dioxide and ethylene in stems of Norway spruce trees during one growing season

Summary The trees sampled in this study came from two stands of Norway spruce, Picea abies (L.) Karst., near Stockholm, Sweden, differing in mean age and height. Holes were bored perpendicular to the stem surface, and gas samples were taken from the outer part of the sapwood throughout one growing season. Endogenous levels of molecular oxygen (O₂), carbon dioxide (CO₂) and ethylene in the outer sapwood were determined by combined gas chromatography — mass spectrometry (GC-MS) and GC. O₂ concentrations began to decrease as growth started in spring. The lowest levels (<5%) were recorded around mid-summer. In the younger stand concentrations remained below 5% until September. In October, O₂ concentrations in the sapwood were similar to those of air. Concentrations of CO₂ were below 1% in spring, but began to rise in May, peaking a month later at approximately 10%. Thereafter a slow decrease occurred until October, by which time levels had returned to those recorded in spring. Ethylene concentrations in the older stand reached 75 ppm early in May, while levels in the younger stand peaked at around 30 ppm later in May. Thereafter ethylene levels in both stands started to decrease down to ppb levels. The correlation between determined gas levels and physiological events associated with the seasonal growth cycle in temperate zones is discussed.     

Glyoxylate metabolism and fatty acid oxidation in mango fruit during development and ripening

Throughout the development (maturation) of mango fruit the contents of citric and glyoxylic acids increased steadily. As the fruit matured the levels of isocitrate lyase, malate lyase and alanine: glyoxylate aminotransferase increased and reached maximum values prior to the time of harvesting. At and after harvest the levels of malate lyase and alanine : glyoxylate aminotransferase began to decrease but that of isocitrate lyase remained high until after the harvest when it decreased. The level of glyoxylate reductase was highest in the early developmental stage but declined as the fruit matured and ripened. As the fruit ripened, after harvest, the amounts of citric and glyoxylic acids decreased concomitant with a considerable increase in the levels of isocitrate dehydrogenase, malic dehydrogenase, malic enzyme and glyoxylate dehydrogenase.Fatty acid oxidizing capacity of mitochondria isolated from immature (developing) and postclimacteric fruit pulps was much less than that observed with mitochondria from preclimacteric and climacteric fruit. Glyoxylate stimulated the oxidation of caprylic, lauric, myristic and palmitic acids and inhibited the activity of isocitrate dehydrogenase in vitro.     

Injuries of Cold Acclimatized Poplar Twigs Resulting from Enzyme Inactivation and Substrate Depression during Frozen Storage at Ambient Temperatures for a Long Period

Wintering twigs of poplar could be stored in frozen state forabout one year, but longer storage resulted in metabolic dysfunctionand death of the twigs. Analyses of enzyme activities revealedthat most of the activity of glucose-6-phosphate and 6-phosphogluconatedehydrogenases and glutathione reductase present normally inthe twigs disappeared. Another four enzyme activities assayedalso decreased to some extent. In the twigs, glucose 6-phosphatedecreased to a level of 10^–5 M and glutathione was presenttotally in the disulfide form. The extent of the decrease ofascorbate and ATP was considerably less than that of the abovetwo. Peroxide levels rose slightly, but lipid hydroperoxidelevels rose several fold. It is suggested that the reactions catalyzed by glucose-6-phosphatedehydrogenase and related ones are obligatory to the cells evenin the frozen state and that the activity to supply glucose6-phosphate, hence NADPH, is limited to a certain period oftime. Beyond this capacity, a decrease in the ability to removeperoxide may also occur, due to a shortage of NADPH supply,resulting in inactivation of some enzymes and the formationof lipid hydroperoxide in cellular membranes. (Received April 26, 1985; Accepted June 20, 1985)     

Limited Survival Period of Cold Acclimatized Trees in Frozen Ambient Temperatures

Cold-acclimatized twigs of poplar exhibited metabolic dysfunctionwithin a year at –10°C. The symptoms were depressionof glucose-6-phosphate and reduced glutathione levels, followedby a decrease in a number of enzyme activities, particularlyin the xylem, suggesting that the injury to the cambial zoneof the twigs came from the xylem side. (Received April 14, 1986; Accepted June 25, 1986)     

Insulin-like effect of vanadate on malic enzyme and glucose-6-phosphate dehydrogenase activities in streptozotocin-induced diabetic rat liver

The effect of oral administration of sodium orthovanadate on hepatic malic enzyme (EC 1.1.1.40) and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) activities was investigated in nondiabetic and diabetic rats. Streptozotocin-induced diabetic rats were characterized by 4.7-fold increase in plasma glucose and 82% decrease in plasma insulin levels. The activities of hepatic malic enzyme and glucose-6-phosphate dehydrogenase were also diminished (P less than 0.001). Vanadate treatment in diabetic rats led to a significant decrease (P less than 0.001) in plasma glucose levels and to the normalization of enzyme activities, but it did not alter plasma insulin levels. In nondiabetic rats vanadate decreased the plasma insulin level by 64% without altering the enzyme activities. Significant correlation was observed between plasma insulin and hepatic lipogenic enzyme activities in untreated and vanadate-treated rats. Vanadate administration caused a shift to left in this correlation suggesting improvement in insulin sensitivity.     

Settling-site selection and survival of two scale insects,Ceroplastes rubens andC. ceriferus,on citrus trees

We studied settling-site selection and the resulting survival of two sessile scale insects, Ceroplastes rubens and C. ceriferus, in the citrus tree, Citrus unshiu, in central Japan. C. rubens preferred 0-year-old twigs most as a settling-site; the density of nymphs settling on 0-year-old twigs was significantly higher than those on ≥1-year-old twigs, and few nymphs settled on ≥3-year-old twigs. The mean survival rates from settling until reproduction in the next year were significantly higher on more preferred twigs than on less preferred ones. In C. ceriferus, nymphs significantly preferred 1- and 2-year-old twigs to 0- and ≥3-year-old ones, and the mean survival rates on the more preferred 1- and 2-year-old twigs were significantly higher than those on less preferred ≥3-year-old twigs. However, the survival rate on less preferred 0-year-old twigs was slightly higher than those on 1- and 2-year-old ones. Thus, in both species of scale, it was the preferred twigs which were more profitable sites for survival after settling, except for less preferred 0-year-old twigs for C. ceriferus. In both scale species, most mortality was due to growth cessation, which is believed to be related to the twig quality as a food source. Predators and parasitoids were minor mortality factors. Both species showed constant survival rates until the density of settled nymphs exceeded double the “upper-limit” density, whereupon they decreased drastically. Nymphs of C. rubens settling on twigs of high scale density showed a spacing-out distribution, those of C. ceriferus did not. In C. rubens, an increase in preference for originally less profitable twigs at the later stage of the settling season was observed, but not in C. ceriferus. Accordingly, individuals of C. rubens showed a stronger tendency to avoid conspecifics than did C. ceriferus. Although nymphs of the two scales clearly preferred more profitable sites, their settling-site selection did not agree with the predictions from the ideal free distribution theory (Fretwell and Lucas, 1970). The discrepancies were (1) frequent settling on less profitable sites at the early stage of the settling season, (2) insufficient utilization of the most profitable twigs, and (3) virtually 100% mortality on overcrowded twigs under conditions where unoccupied profitable twigs still remained. These discrepancies are thought due to the limited dispersal time of nymphs.     

Changes in activity of enzymes metabolizing glucose 6-phosphate during development of the basidiomycete Schizophyllum

During the formation of fruit bodies in the basidiomycete Schizophyllum commune, there are changes in the specific activities of the enzymes utilizing glucose 6-phosphate. These include a 50% increase in the relative amount of glucose-6-phosphate dehydrogenase followed by a decrease in this enzyme and a 90% decrease in phosphoglucomutase activity. This results in a 10-fold change in the relationship between these two enzymes during development. The activities in several mutants were examined and abnormal enzyme levels were found in some cases. The activity of 6-phosphogluconate dehydrogenase was also examined, and its contribution to the assay of the other enzymes was determined.     

Changes in the levels of catecholamines, hexokinase and glucose 6-phosphate dehydrogenase in red cell aging

The activity of the enzymes hexokinase and glucose 6-phosphate dehydrogenase and the level of catecholamines were measured in isolated rat Red Blood Cells (RBC) during cellular aging. The results clearly showed a linear decline in the two enzyme profiles with corresponding increase in age of RBC. A decrease of 75-85% in the activities were found in the oldest cell fractions as compared to the youngest. The levels of glycosylated haemoglobin and catecholamines were found to increase with aging. A correlation can probably be established between the enzyme activities, the levels of glycosylated haemoglobulin and catecholamines during aging.     

Biochemical and Enzymatic Changes in Apple Leaf Tissue during Autumnal Senescence

The biochemical changes occurring during the natural senescence of apple leaf tissue (Pyrus malus L., Golden Delicious) coincided with specific changes in the environment. Protein, sugars, and total nitrogen began declining in leaf tissue when the daylength first became less than 14 hours in the second week of August. The activity of triose phosphate dehydrogenase declined shortly afterwards, while the activities of malate dehydrogenase, glutamic dehydrogenase, and aspartate aminotransaminase increased. Chlorophyll, DNA, RNA, and fresh weight began declining when the daylength first became less than 12 hours at the end of September. At the same time sugars and the activities of RNase, polyphenol oxidase, and proteolytic enzymes began increasing. Protein synthesis, total nitrogen, and the activities of malate dehydrogenase, glutamic dehydrogenase, and aspartate aminotransaminase began declining rapidly and amino acids began to accumulate after the first frost of the year. RNase, polyphenol oxidase, and proteolytic activity reached their highest specific activities after the first frost.     

Dosage compensation of sex-linked genes in Drosophila melanogaster. The activities of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in flies with normal and disturbed genetic balance

Summary The phenomenon of dosage compensation in Drosophila melanogaster which consists in doubling of the activity of the X-chromosome genes in males as compared to those in females was studied.The specific activities of 6-phosphogluconate dehydrogenase (6PGD) and glucose-6-phosphate dehydrogenase (G6PD) determined by the sex-linked structural genes Pgd and Zw respectively were studied in flies carrying duplications for different regions of the X-chromosome. The increase in dose of Pgd and Zw in females resulting from the addition of an extra X-chromosome or X-fragments leads to a proportional rise in the specific activities of 6PGD and G6PD. On the other had the addition to females of the X-chromosome carrying no Pgd gene or X-fragments lacking Pgd and Zw has no effect on the enzyme activities. Thus we failed to reveal in the X-chromosome any compensatory genes envisaged by Muller, which would repress sex-linked structural genes proportional to their dose.The 6PGD and G6PD levels in phenotypically male-like intersexes carrying two X-chromosomes and three autosome sets (2X3A) is 30% higher than in diploid (2X2A) or triploid (3X3A) females. However the specific activities of the enzymes in female-like intersexes are the same as in regular females. The levels of 6PGD and G6PD per one X-chromosome are 1.5–2.0 times higher in the intersexes than in the normal females and metafemales (3X2A). The results indicate that the level of expression of the X-chromosome is determined by the X:A ratio. It is suggested that the decreased X:A ratio in males is responsible for the hyperactivation of their X-chromosomes.     

Bud burst in Norway spruce (Picea abies): preliminary evidence for age-specific rest patterns

This study examines the effect of chilling and photoperiod on rest completion and bud burst in Norway spruce [Picea abies (L.) Karst.] using twigs from both 15-year-old (young trees) and 56-year-old (old trees) trees. The material was transferred between September and May from outdoors to experimental forcing conditions with four different photoperiods. The bud burst percentage of the twigs from young trees generally increased in all photoperiods until the end of the year. After that it decreased until vernal equinox (March 20) and then increased steeply towards spring. This new observation of transient rest completion during autumn suggests that young trees have (I) a transient time window during late autumn when ontogenetic development is possible, and (ii) a secondary rest culminating approximately at the time of vernal equinox. In twigs from old trees the transient rest completion was much weaker as the bud burst percentages generally remained under 20 during autumn and winter. At vernal equinox there were no burst buds in twigs from the old trees in any photoperiod and after that the bud burst percentage increased basically in the same manner as in the young trees. The bud burst percentage of the twigs from young trees was generally higher as the photoperiod increased. However, no evidence for absolute long photoperiod requirement of rest completion was observed.     

DEVELOPMENTAL CHANGES OF ENZYMES ASSOCIATED WITH ENERGY METABOLISM AND THE SYNTHESIS OF SOME NEUROTRANSMITTERS IN DISCRETE AREAS OF HUMAN NEOCORTEX

Developmental changes in pyruvate kinase (PK), lactate dehydrogenase (LDH), α-glycerophosphate dehydrogenase (α-GPD), glucose-6-phosphate dehydrogenase (G6P), succinate dehydrogenase (SDH), glutamate dehydrogenase (GDH), choline acetyltransferase (CAT), glutamate decarboxylase (GAD), activities were measured in early autopsy material in the following areas of human neocortex: area 4 (motor cortex), area 17 (visual cortex), area 40 (gyrus supramarginalis, associative cortex). Changes with age were analysed from 8 fetal weeks to adult age. The important points emerging from this study are: 1. Enzymes associated with glycolytic pathways show a high activity in early fetal period, decline through to the end of the active phase of neurogenesis and then, rise continuously to the end of the first year of life. 2. G6P, an enzyme associated with the oxidative segment of the pentose phosphate pathway, shows a high activity at 8 fetal weeks and, gradually declines through to the end of the active phase of neurogenesis; it then either does not change significantly (motor cortex) or increases slightly. 3. Enzymes related to the tricarboxylic pathway have a low level of activity throughout the first half of gestation, and then rise markedly during the last fetal months and the first year after birth. SDH increase is of much higher magnitude (× 10) than that observed for glycolytic enzymes (×4). For the enzymes of oxidative metabolism, motor cortex is the most advanced area, while associative cortex matures more slowly. 4. CAT activity at 8 fetal weeks is high in visual cortex and declines to the fifth month. After that time, there is a continuous rise until the age of 11 years. Although the time pattern in reaching the adult value is different in motor and associative cortex, there exists a continuous increase from fetal onset to adult level in both areas. Developmental changes in GAD activity are very unusual. The development of activity lags behind that of CAT and commences after birth. After a steady rise in the first year of life, the activity decreases after this age.     

BIOMASS,PRODUCTION, AND LITTERFALL IN THE COASTAL SAGE SCRUB OF SOUTHERN CALIFORNIA

A 22-year-old stand of coastal sage scrub in the coastal mountains of southern California had a peak standing aboveground biomass of 1,417 g/m², determined by dimension analysis. Annual aboveground net primary production was 255 g/m²/yr, determined by monthly twig harvests of dominant species and the clipping production of subordinate species. The stand was codominated by two drought-deciduous species, Salvia leucophylla and Artemisia californica, which together comprised 81% of the biomass. Annual litterfall was measured at 194 g/m²/yr. These biomass, production, and litterfall values are less than those measured in most evergreen chaparral communities in California. Seasonally, the two dominant shrubs began aboveground production in the winter soon after the first rains and continued growth for six months until early summer. A massive leaf fall occurred in May–June as the summer drought began, but twig and inflorescence production for both species continued at a high rate into the summer months. Salvia leucophylla had two shoot types: 1) an early spring canopy shoot that elongated rapidly, produced the inflorescence, and died in mid-summer; and 2) a short side shoot produced in late spring with small dense leaves that were retained during the summer drought and early winter. Artemisia californica produced a single cohort of twigs in the early spring, most of which carried inflorescences by late summer.     

Observations on parasitic gastroenteritis and bronchitis in grazing calves: Untreated calves

Pott J. M., Jpones R. M. and Cornwell R. L. 1978. Observations on parasitic gastroenteritis and bronchitis in grazing calves: untreated calves. International Journal for Parasitology8: 331–339. The epidemiology of parasitic gastroenteritis (p.g.e.) and incidental observations on lungworm infection were studied on two equal-sized paddocks of permanent pasture on a Kent farm in 1970. Groups of 10 Friesian calves were exposed for the first time to each paddock in May and grazed until the end of October. Faeces were monitored, body weights recorded and clinical signs observed. Herbage samples were examined for larvae throughout the year. Five ‘cumulative’ tracer calves exposed at the commencement were removed at monthly intervals and 5 ‘short term’ tracer calves exposed at successive monthly intervals for 1 month were killed for worm counts. A similar pattern of events occurred on both paddocks. Moderate herbage larval levels of Ostertagia and Cooperia fell to almost zero during April/May but rose quickly in July to high levels in August/September. Lower levels continued until the end of the year. Faecal egg excretion began in the test calves at the end of May, showed peaks in July and September and fell to low levels in October. D. viviparus larval excretion occurred in most calves with greater counts on Paddock 2. Clinical signs of p.g.e. complicated by lungworm infection occurred in August/September. Body weight gain which was initially rapid levelled off in June due partly to drought in addition to the parasitic infection. Weight loss occurred in August and there were 2 deaths on Paddock 1 and one on Paddock 2. Survivors gained weight again in September/October.Worm burdens in tracer calves showed quite heavy infections with Ostertagia and Cooperia as early as June/July. Massive infections complicated by lungworm disease accompanied clinical signs and death. There was evidence that aquisition of resistance to Cooperia and Dictyocaulus was acquired more readily than to Ostertagia. Inhibition of development of Ostertagia and Cooperia also became evident at the end of the trial period.     

Autosomal Factors with Correlated Effects on the Activities of the Glucose 6-Phosphate and 6-Phosphogluconate Dehydrogenases in DROSOPHILA MELANOGASTER

Isogenic lines, in which chromosomes sampled from natural populations of D. melanogaster are substituted into a common genetic background, were used to detect and partially characterize autosomal factors that affect the activities of the two pentose phosphate pathway enzymes, glucose 6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). The chromosome 3 effects on G6PD and 6PGD are clearly correlated; the chromosome 2 effects, which are not so great, also appear to be correlated, but the evidence in this case is not so strong. Examination of activity variation of ten other enzymes revealed that G6PD and 6PGD are not the only pair of enzymes showing a high positive correlation, but it is among the highest in both sets of lines. In addition, there was some evidence that the factor(s) affecting G6PD and 6PGD may also affect two other metabolically related enzymes, transaldolase and phosphoglucose isomerase.—Rocket immunoelectrophoresis was used to estimate specific CRM levels for three of the enzymes studied: G6PD, 6PGD and ME. This experiment shows that a large part of the activity variation is accounted for by variation in CRM level (especially for chromosome 3 lines), but there remains a significant fraction of the genetic component of activity variation that is not explained by CRM level.—These results suggest that the autosomal factors are modifiers involved in regulation of the expression of the X-linked structural genes for G6PD and 6PGD, but a role in determining part of the enzymes' primary structure cannot be excluded with the present evidence.     

Distribution of non-structural nitrogen and carbohydrate compounds in mature oak trees in a temperate forest at four key phenological stages

The distribution of nitrogen (N) and carbon (C) pools in 100-year-old sessile oaks was investigated in situ at four key periods of tree phenology. Leaves, twigs, trunk and roots were sampled, and total non-structural nitrogen compounds (TNNC) and total non-structural carbohydrates (TNC) were quantified. TNC concentrations decreased more than 50 % between February and May, especially in the above-ground parts. During the same period, TNNC concentrations drastically decreased especially in twigs (more than 55 % below the winter baseline). This indicates high sink strength of new organs at bud break. TNC concentrations increased in summer in all tree compartments highlighting the TNC storage. TNNC deposition for storage constitution began in autumn during leaf senescence. The first organs acting as a N store were coarse roots followed by twigs; whereas all oak tree compartments were potential C store organs except phloem tissue. Arginine and asparagine were the two prevailing amino acids involved in both storage and transport. Besides identifying the compounds involved in the storage and transportation of N, our results highlight that oak seasonal cycles of C and N are not in phase: after intensive use of C and N stores in spring, the replenishment of N stores lags behind that of C stores.     

Population Dynamics of Frankliniella occidentalis on Different Rose Cultivars and Flowering Stages

Seasonal occurrence and damaged aspects of Frankliniella occidentalis (Pergande) on various rose cultivars were investigated from three greenhouses (one experimental greenhouse and two commercial greenhouses) during 1999 to 2000. In the experimental greenhouse, first detection of F. occidentalis on yellow sticky trap was observed in early April, gradually increased till early May and greatest densities occurred during June each year. In commercial rose greenhouses where insecticides were applied >2.2 times per month for the control of F. occidentalis, relatively low levels of F. occidentalis populations were captured on the traps. The population levels were 40% of the level of F. occidentalis populations collected from the experimental greenhouse. In preference of rose cultivar and color, yellow-colored cultivars were the most preferred by F. occidentalis and second was white flower. However, there was no preference difference within same colored cultivars. First inhabitation of F. occidentalis adults was observed at stage F2 (sepal uncovered the bud partly and corolla protruding from the calyx) of rose flowers. The number of adults was increased as the stage was developed from the stage F2 to F4 (flower began to senesce), but the proportions of adults were decreased as the stages were developed.     

Inhibition of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in sea urchin eggs by palmitoyl-coenzyme a and reversal by polyamines

Palmitoyl-CoA inhibited crude glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase in the eggs of the sea urchin, Hemicentrotus pulcherrimus. Fifty percent inhibition of the glucose 6-phosphate dehydrogenase in the supernatant of unfertilized eggs was obtained with 0.43 ± 0.05 μm palmitoyl-CoA, and of 6-phosphogluconate dehydrogenase with 4.41 ± 0.20 μm palmitoyl-CoA. Also, these enzymes in fertilized eggs 30 min after fertilization were inhibited by palmitoyl-CoA almost as much as in unfertilized eggs. Na-Palmitate, coenzyme A, acetyl-CoA, palmitoylcarnitine, and carnitine failed to exert any inhibitory effect on the activities of these dehydrogenases. The intracellular concentration of long-chain fatty acyl-CoA in unfertilized eggs (3.08 ± 0.33 nmol/10⁶ eggs) was high enough for the inhibition of these enzymes, and decreased following fertilization to a low level (1.49 ± 0.08 nmol/10⁶ eggs 30 min after fertilization). Spermine and spermidine canceled the inhibition of these enzymes by palmitoyl-CoA. In view of the inhibition of glucose 6-phosphate dehydrogenase and of 6-phosphogluconate dehydrogenase by palmitoyl-CoA, these dehydrogenases in the pentose monophosphate cycle are probably inhibited in unfertilized eggs by long-chain fatty acyl-CoA and released from the inhibited state by both the decrease in the level of long-chain acyl-CoA and the increase in the level of polyamines following fertilization.