Galactose-1-phosphate uridyltransferase of lemurs: A comparison of four species

Erythrocyte galactose-1-phosphate uridyltransferase (Gal-1-PUT) was studied in four species of lemurs. Electrophoretic phenotypes of Lemur fulvusand Lemur macacowere indistinguishable and different from the phenotypes of Lemur cattaand Lemur variegatus,which were different from each other. Enzymatic activity of hemolysates was species specific, with that of Lemur variegatusabout twice that of either Lemur fulvusor Lemur macacoand almost three times that of Lemur catta.Only minor interspecific differences were demonstrated in pH optima and k_m for galactose-1-phosphate; however, thermal stability varied considerably with phenotype. Antibody inhibition studies indicated that differences in enzyme activity of hemolysates from these species are probably due to differences in enzyme concentration.     

Food Intake and Dietary Overlap in Native Lemur catta and Propithecus verreauxi and Introduced Eulemur fulvus at Berenty,Southern Madagascar

The introduction of Eulemur fulvus in 1975 into the Berenty Reserve and their recent attainment of population densities comparable to those of Lemur catta led us to analyze food partitioning among the 3 large prosimian species in the gallery forest. We assessed the diets of ring-tailed lemurs (Lemur catta), brown lemurs (Eulemur fulvus) and sifakas (Propithecus verreauxi) from food intake measurements during 3 successive short-term studies. All species exhibited marked seasonal changes in their major food categories. Dietary overlap was very high between ring-tailed lemurs and brown lemurs during 2 of 3 seasons, including the middle of the dry season. During the latter period, Eulemur appeared to compensate for a low quality diet by increasing the amount of food eaten. In contrast, Lemur fed on lower amounts of food and seemed more efficient at coping with fibrous plant materials. There is low dietary overlap of Lemur catta and Eulemur fulvus versus Propithecus, which exhibit by far the highest dietary diversity of the 3 species. We discuss sustainable coexistence among them, based on respective dietary adaptations and potential for dietary flexibility.     

Responses of Lemur fulvus to Scents of Different Subspecies of L. fulvus and to Scents of Different Species of Lemuriformes

Captive Lemur fulvus were presented with scents of their own subspecies, scents of other subspecies of L. fulvus, and scents of other species of sympatric Lemuriformes. The results suggest that L. fulvus do not distinguish between scents of different subspecies of L. fulvus, and that they do distinguish between scents of their own species and other sympatric species of Lemuriformes.     

Differences in male-female interaction betweenLemur fulvus andL. macaco

Interspecific differences were found betweenLemur fulvus andLemur macaco in heterosexual pair-tests.L. fulvus showed more mutual grooming and were more active in exploration thanL. macaco. The absence of a naked anal region inL. macaco females causes a virtual absence of foreheadmarking on this region by males.L. macaco males have a stronger tendency to mark the body of the female with their anogenital region after a nose-anogenital contact thanL. fulvus, indicating that the behaviour is more ritualized inL. macaco males.     

Soil Consumption of Two Groups of Semi-free-ranging Lemurs {Lemur catta and Lemur fulvus)

Soil consumption of two Malagasy lemurs, Lemur catta and Lemur fulvus was observed in an enclosure simulating a natural habitat at Duke University Primate Center (Durham, USA). Soil eaten by L. catta contained more Na than random soil samples. Concentrations of the four major minerals in soil eaten by L. fulvus did not differ from random samples. L. fulvus stopped soil ingestion in summer when they ate large amounts of foliage rich in K and Mg, also in winters after being fed with MgCl₂. It is suggested that, in this study, soil was consumed in relation to its mineral content and not for physical properties related to its structure. Some non physiological factors that might influence food selection are discussed.     

The enigma of antipredator behavior in lemurs: Evidence of a large extinct eagle on Madagascar

Numerous zoologists who study diurnal lemurs on Madagascar have noted that they react strongly to the presence of birds of prey. For two of the most intensively studied lemurs, Propithecus verreauxiand Lemur catta,there are few documented cases of raptor predation. Thus, the maintenance of this stereotypic response is enigmatic. Bird bones recovered from cave surface deposits in southwestern Madagascar include the remains of an eagle (Aquila),a genus that has disappeared from Madagascar and that would have been capable of hunting animals the size of adult P. verreauxi and L. catta.The stereotypic response of these two lemurs toward raptors may have been retained from the period when this extinct eagle inhabited the island and is reinforced by rare acts of predation by extant birds of prey.     

The banded chromosomes of coquerel’s sifaka,Propithecus verreauxi coquereli (Primates,Indriidae)

The karyotype of Propithecus verreauxi coquereli isdescribed in this report using G-, Q-, and C-banding and silver staining for nucleolus organizer regions. The banded chromosomes of P. v. coquereli(family Indriidae) are compared with those of Lemur fulvus fulvus(family Lemuridae), revealing few karyotypic similarities between the two groups and suggesting a wellestablished phylogenetic divergence between these families.     

Feeding behavior ofLemur catta andLemur fulvus

The feeding behavior of two sympatric species of lemurs, Lemur cattaand Lemur fulvus,was studied in an enclosure simulating a natural habitat at the Duke University Primate Center. L. fulvusspent less time feeding during the day than L. catta.But the former species ate more fruit and had longer feeding bouts on preferred food items than L. catta.They also had a shorter food passage time than L. cattaand their choice of resting places was more influenced by food distribution. Furthermore, the two lemur species ate parts of different plant species and showed different reactions to chemical plant components. According to these results, L. fulvusis a more conservative feeder than L. catta.These interspecific differences in feeding behavior may be one of a number of differences that allow the two species to coexist. In allopatry, however, L. fulvusmay also adopt feeding patterns similar to those of L. catta.But L. cattawas never found to change its feeding strategies in different areas. It may be this option of L. fulvusto adopt different feeding strategies in different situations that allows this species to have the widest range of all Malagasy lemurs. Duke University Primate Center Publication No. 259.     

A possible role of plantations for primate conservation in Madagascar

The utilization of eucalyptus plantations by seven sympatric species of prosimians was studied in the eastern rainforest of Madagascar. The species were Avahi laniger, Cheirogaleus major, Hapalemur griseus, Indri indri, Lemur fulvus, Lepilemur mustelinus, and Microcebus rufus. None of the lemurs was ever found in young eucalyptus plantations with little undergrowth. This was mainly due to the lack of travel opportunities within the shrub layer and between the shrubs and the canopy. Food (mainly berries) is seasonally available in the shrub layer but cannot be exploited because frugivorous lemurs cannot reach it. Old eucalyptus plantations with dense undergrowth are used by all prosimian species. They provide food as well as travel and resting facilities. Mixed tree plantations in the western part of Madagascar were used by groups of Lemur fulvus, Lepilemur mustelinus, and Propithecus verreauxi. According to these results, old eucalyptus plantations and mixed tree species plantations could be used to provide firewood and construction wood for the human population. They also might extend the habitat for lemurs and serve as buffers against human disturbance.     

Immobilization of lactase for the continuous hydrolysis of whey permaete

The production of lactose-based sweeteners is considered very promising. Fungal lactase has been immobilized on crosslinked chitin to develop a process for the continuous hydrolysis of demineralized whey permaete. The optimization of lactase immobilization on chitin and chitosan was performed, activities of 4 · 10⁵ and 2.2 · 10⁵ u/kg at yields of 33 and 23% were obtained for both supports, respectively. The chitin based catalyst was selected for further studies and a procedure was developed for in-situ enzyme immobilization. The kinetic behaviour of the catalyst was determined to propose a kinetic model for the initial rate of lactose hydrolysis. Pseudo steady-state and long term operation of packed bed reactors with chitin-immobilized lactase ranging from small laboratory to pre-pilot unit was carried out. The results are discussed and compared with commercial immobilized lactases. Preliminary economic evaluation for the production of ultrafiltered whey protein and hydrolyzed lactose syrup, within a dairy industry in Chile, was satisfactory in terms of profitability, both for the chitin immobilized lactase developed and for a commercial immobilized lactase.List of Symbols a moles/m³ glucose concentration in Eq. (1) - C _i US$ total annual cost (without considering plant depreciation) - D US$ annual depreciation - F m³/h flowrate - h m³/h volumetric mass transfer coefficient - i moles/m³ galactose concentration in Eqs. (1) and (2) - K _A moles/m³ dissociation constant for glucose in Eq. (1) - K _A moles/m³ dissociation constant for glucose in Eq. (1) - K _I moles/m³ inhibition constant for galactose in Eqs. (1) and (2) - K _m moles/m³ Michaelis constant for substrate in Eqs. (1) and (2) - k _D h^–1 first-order thermal deactivation constant - P kg dry weight of catalyst - PV US$ net present value - R % discounted cash-flow rate of return - s moles/m³ substrate concentration - s₀ moles/m³ feed substrate concentration - S _n US$ annual sales income - TC US$ total capital income - t _1/2 h catalyst half-life - v moles/h · kg initial rate of reaction - V _MAX moles/h · kg maximum reaction rate in Eqs. (1) and (2) - V _MAX moles/h · kg maximum reaction rate in Eq. (1) - ¯V _max moles/h initial rate of reaction - V _R m³ reaction volume free of catalyst particles - X substrate degree of conversion = s₀–s/s₀ - Damkoehler number = ¯V _MAX /h k _m - moles/(m³ · h) reactor productivity in Eq. (3)     

Trehalose absorption related with trehalase in developing ovaries of the silkworm,Bombyx mori

Summary The mechanism of trehalose absorption was examined in developing ovaries of the silkworm,Bombyx mori. Trehalose and glucose absorption followed saturation kinetics giving an apparentK _m value of 8.4 mM and a V_max of 12.5 moles/30 min per g ovaries for trehalose absorption, and an apparentK _m value of 26.4 mM and a V_max of 36.6 moles/30 min per g ovaries for glucose uptake. Trehalose absorption was clearly inhibited by addition of NaCN or NaN₃ to the incubation medium.Cellobiose, maltose, sucrose and turanose were taken up by ovaries at much lower rates than trehalose. Among the disaccharidases which hydrolyse these sugars, trehalase activity was highest. The correlation between trehalase activity and trehalose absorption rate was also demonstrated by a reduction of trehalase activity accompanied by reduced absorption rates after extirpation of the suboesophageal ganglion (SG). During trehalose absorption, glucose was released into the incubation medium, but after SG removal, no liberation of glucose was observed. Furthermore, no accumulation of¹⁴C-trehalose, added to the medium, was observed in the cells and almost all radioactivity was recovered as glucose and glycogen in the ovaries.These results suggest that in developing silkworm ovaries, trehalose is absorbed by a specific carriermediated and energy-dependent system, in which the hydrolysis by trehalase is an obligatory step.     

Pyruvate carboxylase from rainbow trout liver

Summary A method is described for the partial purification of pyruvate carboxylase from rainbow trout liver. The enzyme has a pH optimum of about 8.0, possesses an absolute requirement for activation by acetylCoA, and prefers MgATP over other nucleoside triphosphates. K⁺ causes a decrease in the apparentK _m for HCO ₃ ^– . AcetylCoA activation shows positive cooperativity withK _a=0.072 mM andn _H=1.78 at pH 7.7, 2.5 mM free Mg²⁺, 100 mM K⁺, and saturating concentrations of substrates. A high acetylCoA concentration causes a decrease in the apparentK _m values for MgATP and HCO ₃ ^– and a biphasic double reciprocal plot with pyruvate as the varied substrate. MgADP and AMP are competitive inhibitors with respect to MgATP. The enzyme shows a U-type response to the adenylate energy charge and retains considerable activity throughout a wide range of energy charge values. It is proposed that intramitochondrial acetylCoA concentration and the adenylate energy charge control the rate of pyruvate carboxylation in vivo.Abbreviations DTT dithiothreitol - PMSF phenylmethylsulfonylfluoride     

Acetate oxidation to CO2 via a citric acid cycle involving an ATP-citrate lyase: a mechanism for the synthesis of ATP via substrate level phosphorylation in Desulfobacter postgatei growing on acetate and sulfate

Desulfobacter postgatei is an acetate-oxidizing, sulfate-reducing bacterium that metabolizes acetate via the citric acid cycle. The organism has been reported to contain a si-citrate synthase (EC 4.1.3.7) which is activated by AMP and inorganic phosphate. It is show now, that the enzyme mediating citrate formation is an ATP-citrate lyase (EC 4.1.3.8) rather than a citrate synthase. Cell extracts (160,000xg supernatant) catalyzed the conversion of oxaloacetate (apparent K _m=0.2 mM), acetyl-CoA (app. K _m=0.1 mM), ADP (app. K _m=0.06 mM) and phosphate (app. K _m=0.7 mM) to citrate, CoA and ATP with a specific activity of 0.3 mol·min^-1·mg^-1 protein. Per mol citrate formed 1 mol of ATP was generated. Cleavage of citrate (app. K _m=0.05 mM; V _max=1.2 mol · min^-1 · mg^-1 protein) was dependent on ATP (app. K _m=0.4 mM) and CoA (app. K _m=0.05 mM) and yielded oxaloacetate, acetyl-CoA, ADP, and phosphate as products in a stoichiometry of citrate:CoA:oxaloacetate:ADP=1:1:1:1. The use of an ATP-citrate lyase in the citric acid cycle enables D. postgatei to couple the oxidation of acetate to 2 CO₂ with the net synthesis of ATP via substrate level phosphorylation.     

Phosphoenolpyruvate carboxylase from Acetobacter aceti

In Acetobacter aceti growing on pyruvate as the only source of carbon and energy, oxaloacetate (OAA) is produced by a phosphoenolpyruvate (PEP) carboxylase (EC 4.1.1.31). The enzyme was purified 122-fold and a molecular weight of about 380,000 was estimated by gel filtration.The optimum pH was 7.5 and the K _m values for PEP and NaHCO₃ were 0.49 mM and about 3 mM, respectively. The enzyme needed a divalent cation; the K _m for Mn²⁺, Co²⁺ and Mg²⁺ were 0.12, 0.26 and 0.77 mM, respectively. Maximal activity was only obtained with Mg²⁺. Mn²⁺ and Co²⁺ became inhibitory at high concentrations.The activity was inhibited by succinate and, to a lesser extent, by fumarate, citrate, -ketoglutarate, aspartate and glutamate.As compared with the corresponding enzyme from A. xylinum, the PEP carboxylase of A. aceti showed the following differences: a) It had an absolute requirement for acetyl CoA (K _a 0.18 mM) or propionyl CoA (K _a 0.2 mM). b) It was not affected by ADP. c) It was sensitive to thiol blocking agents.Abbreviations PEP phosphoenolpyruvate - OAA oxaloacetate - MW molecular weight - TEMG buffer 50 mM Tris-HCl, pH 7.5, 1 mM EDTA, 5 mM MgCl₂, 1 mM glutathione - HEPES N-2-hydroxyethylpiperazine-N-ethanesulfonic acid     

Primate red cell enzymes: glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase

Glucose-6-phosphate dehydrogenase (E. C.: 1.1.1.49) phenotypes and 6-phosphogluconate dehydrogenase (E. C.: 1.1.1.44) phenotypes were determined by starch-gel electrophoresis of red cell hemolysates of Galago crassicaudatus subspp., Propithecus verreauxi, Lemur spp., Hapalemur griseus, and Macaca mulatta. A single glucose-6-phosphate dehydrogenase (G6PD) phenotype was found in each species. A single 6-phosphogluconate dehydrogenase (6PGD) phenotype was found in Lemur spp., Hapalemur griseus, and Galago crassicaudatus argentatus. In a group of six Propithecus verreauxi, three 6PGD phenotypes, PGD A, PGD AB, and PGD B, were found. Three phenotypes, PGD A, PGD AB, and PGD B, were found in 38 G. c. crassicaudatus. The three phenotypes in each species are apparently the products of two codominant autosomal alleles, PGD^A and PGD^B. The frequency of PGD^A in G. c. crassicaudatus is 0.263. A population of 260 free-ranging macaques displays a polymorphism at the 6PGD locus. Three phenotypes, PGD A, PGD AB, and PGD B, were found. These also appear to be controlled by two codominant autosomal alleles, PGD^A and PGD^B the frequency of PGD^A = 0.913. Additional analysis of three well-defined troops within the macaque population indicated that there are no significant differences between the troops or within the population at the 6PGD locus.     

Kinetic analysis of lactate dehydrogenase in situ in mouse liver determined with a quantitative histochemical technique

Summary The kinetics of lactate dehydrogenase in situ were studied in sections of unfixed liver of the male mouse using a quantitative histochemical technique. The sections were incubated on substrate-containing gel films. The absorbance of the final reaction products deposited in a single hepatocyte was measured continuously during the incubation as a function of incubation time using a scanning microdensitometer. The absorbance increased non-linearly during the first minute of incubation, but linearly for at least the next 3 min afterwards. The initial velocity (v _i ) of the dehydrogenase was calculated from two equations proposed previously by us, v _i=2.82 °A and v _i =v+2°A, where v and °A are, respectively, the gradient and intercept o linear regression line of absorbance on time for incubation times between 1 and 3 min.The dependence of v _i on lactate concentration gave the following mean kinetic constants. For periportal hepatocytes, the apparent K _m =14 mM and V _max =80 moles hydrogen equivalents formed cm^–3 hepatocyte cytoplasm min^–1. For pericentral hepatocytes, K _m =12 mM and V _max =87 moles hydrogen equivalents cm^–3 min^–1. The K _m values are very similar to those determined previously from biochemical assays. The concentrations of the enzyme in single hepatocytes calculated from the V _max values are in good agreement with those obtained by another method. These data substantiate the validity of our equations.     

Characterization flavanone 3β-hydroxylase expressed from <Emphasis Type="Italic">Populus euphratica</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis> and its application in dihydroflavonol production

Flavanone 3β-hydroxylase plays very important role in the biosynthesis of flavonoids. A putative flavanone 3β-hydroxylase gene (Pef3h) from Populus euphratica was cloned and over-expressed in Escherichia coli. Induction performed with 0.1 mM IPTG at 20°C led to localization of PeF3H in the soluble fraction. Recombinant enzyme was purified by Ni-NTA affinity. The optimal activity of PeF3H was revealed at pH 7.6 and 35°C. The purified enzyme was stable over pH range of 7.6–8.8 and had a half-life of 1 h at 50°C. The activity of PeF3H was significantly enhanced in the presence of Fe²⁺ and Fe³⁺. The K _M and V _max for the enzyme using naringenin as substrate were 0.23 mM and 0.069 μmoles mg–1min-1, respectively. The K _m and V _max for eriodictyol were 0.18 mM and 0.013 μmoles mg^–1min^–1, respectively. The optimal conditions for naringenin bioconversion in dihydrokaempferol were obtained: OD₆₀₀ of 3.5 for cell concentration, 0.1 mM IPTG, 5 mM α-ketoglutaric acid and 20°C. Under the optimal conditions, naringenin (0.2 g/L) was transformed into 0.18 g/L dihydrokaempferol within 24 h by the recombinant E. coli with a corresponding molar conversion of 88%. Thus, this study provides a promising flavanone 3β-hydroxylase that may be used in biosynthetic applications.     

Energization of potassium uptake in Arabidopsis thaliana

Plant roots accumulate K⁺ from micromolar external concentrations. However, the absence of a firm determination of the trans-plasma-membrane electrochemical gradient for K⁺ in these conditions has precluded an assessment of whether K⁺-accumulation requires energization in addition to the driving force provided by the inside-negative membrane electrical potential (E_m). To address this question unequivocally, we measured E_m, and the cytosolic and external K⁺-activities in root cells of Arabidopsis thaliana (L.) Heynh. cv. Columbia in conditions in which net K⁺-accumulation occurs at low external K⁺ (10 M). In these conditions, net K⁺-uptake was about 0.1 mol · (g FW)^-1 · h^-1, E_m varied between-153 and -129 mV and the cytosolic K⁺-activity, determined with K⁺-selective electrodes, was 83 ± 4 mM. These values yield an outwardly-directed driving force on K⁺ of at least 6.5 kJ · mol^-1. Only if external potassium is raised to the region of 1 mM does E_m become sufficient to drive net K⁺-accumulation. It is therefore concluded that at micromolar external K⁺-activities which prevail in most soils, K⁺-uptake cannot be solely energized by E_m — as exemplified by a channel-mediated mechanism. The nature of the energization mechanism is discussed in relation to processes operating in fungal and algal cells.Abbreviations and Symbols AAS atomic absorption spectrometry - E_m membrane potential - electrochemical potassium gradient - F Faraday constant (96500 C · mol^-1) We thank Peter Barraclough, Roger Leigh, David Walker and Tony Miller (Rothamsted Experimental Station, Harpenden, UK) for helpful discussions. Financial support was provided by the Agricultural and Food Research Council (Grant PG87/529).     

Chromosomal evolution in Malagasy lemurs: X. chromosomal banding studies of Propithecus diadema edwardsi and Indri indri and phylogenic relationships between all the species of the Indriidae

The R-banded karyotypes of two Indriidae, Propithecus diadema and Indri indri, are described and compared with each other and with those of the other species of this family, previously reported, Avahi laniger and Propithecus verreauxi. These comparisons show that 30 chromosomal rearrangements, including 21 Robertsonian translocations and eight pericentric inversions, differentiate these karyotypes. A phylogenic diagram is proposed, showing the early separation of Avahi and the relatively late divergence of the three other species. A populational evolution has occurred between the three other species, but Indri is clearly separated from the two other species by at least five complex rearrangements, although it shares four Robertsonian translocations with P. verreauxi but not P. diadema.