摘要:

ABSTRACT.The metabolism of leucine byLeishmania donovaniwas investigated. Washed promastigotes were incubated with (1‐14C]‐or [U‐14C]leucine or [1 ‐14C]α‐ketoisocaproate (KIC) and14C02release was measured. The amount of KIC‐derived acetyl‐CoA oxidized in the citric acid cycle was computed. Promastigotes from mid‐stationary phase cultures oxidized each of these labeled substrates less rapidly than cells from late log phase cultures, and significantly less acetyl‐CoA derived from KIC oxidation was oxidized in the citric acid cycle. Glucose was a stronger inhibitor than was acetate of CO2formation in the citric acid cycle in log phase promastigotes, but the reverse was observed in cells from mid‐stationary phase. Alanine also inhibited leucine catabolism, but glutamate had little effect. Acute hypo‐osmotic stress did not affect leucine catabolism, but hyper‐osmotic stress caused appreciable inhibition of leucine oxidation. Cells grown under hypo‐or hyper‐osmotic conditions showed no changes in the effects of hypo‐or hyper‐osmotic stress on leucine catabolism, i.e.L. donovaniis not an osmoconformer with respect to leucine metabolism. Leucine utilization in L. donovani was insensitive to a number of drugs that affect leucine metabolism in mammalian cells, indicating that the leucine pathway inL. donovaniis not regulated in the s

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06075.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.Major fatty acid components ofAcanthamoeba castellaniilipids extracted after growth at 30°C include myristate, palmitate, stearate and the polyunsaturates linoleate, eicosadienoate, eicosatrienoate and arachidonate, with oleate as the sole major monounsaturated fatty acid. By comparison, growth at 15°C gave increased linoleate, eicosatrienoate and arachidonate, but decreased oleate and palmitate. When the growth temperature was shifted downwards from 30°C to 15°C, increased lipid unsaturation occurred over a period of 24 h; thus decreases of oleate and eicosadienoate were accompanied by increases in linoleate, eicosatrienoate, arachidonate and eicosapentaenoate. An upwards shift from 15°C to 30°C gave negligible alterations in fatty acid composition over a similar period. At 15°C organisms rapidly use [1‐14C] acetate for de novo fatty acid synthesis; stearate is converted via oleate to further desaturation and chain elongation products. Similar short term experiments at 30°C indicate only de novo synthesis and Δ9‐desaturation; synthesis of polyunsaturates was a much slower process. Rapid incorporation of [1‐14C] oleate at 30°C was not accompanied by metabolic conversion over two hours, whereas at 15°C n‐6 desaturation to linoleate was observed. Temperature shift of organisms from 15°C to 30°C in the presence of [1‐14C] acetate revealed that over half of the fatty acids in newly‐synthesised lipids were saturated, but the proportions of unsaturated fatty acids increased with time until the total polyenoate components reached 17% after 22 h. A shift of temperature in the reverse direction gave a corresponding figure of 60% for polyunsaturated fatty acids. These results emphasize the importance of n‐6 desaturation in the low temperature adaptation

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06076.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.Three acidic proteins (42 kD, 43 kD and 50 kD) were present in unusually high concentrations in cortical preparations of theTetrahymenapattern mutantbroadened cortical domains (bcd).Antisera to the 42‐kD and 50‐kD proteins bound to discharging mucocysts and food vacuole contents in both wild‐type and mutant cells. Subsequent analysis revealed thatbcdmutant cell pellicles possess five times more “docked” mucocysts than their wild‐type c

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06077.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.The light microscopic and ultrastructural characteristics of a microsporidium provisionally identified asToxoglugea chironomi(Debaiseux, 1931) Jírovec, 1936, is described. It was isolated from oenocytes and adipose tissue of a midge larva of the genusDicrotendipes. Merozoites are diplokaryotic. The sporogony produces, by fragmentation, eight monokaryotic spores in a sporophorous vesicle. Mature spores are horse‐shoe shaped. The total length is about 5.8 μm, the width 0.8‐0.9 μm, the external height of the curve 2.3‐3.5 μm, and the external width of the curve 3.5‐5.2 μm. The polaroplast has lamellar compartments of two types: narrow and closely packed anteriorly, and wider and more loosely arranged posteriorly. The isofilar polar filament is arranged in 8–10 coils in the posterior fourth of the spore. The external nuclear membrane is sometimes continuous with the endoplasmic reticulum. Lamellar and tubular material of exospore construction are present in the episporontal space from the beginning of sporogony. Teratological and normal spores sometimes occur together in the sporophorous vesicle. The identification of the species is discussed and the ultrastructure is compared toToxoglugea variabilis, the only further species of the genus with known ultrastruc

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06078.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.The enzyme NADH‐fumarate reductase associated with the membrane fraction ofTrypanosoma bruceiprocyclic trypomastigotes, can be solubilized by more than 50% when increasing the ionic strength to the equivalent of 150 mM KCI. The apparent KMs for NADH (125 μM) and fumarate (50 μM) remain close to those previously reported for the membrane‐bound form of this enzyme. Other electron acceptors (i.e. oxygen or cytochrome c) appear to accept electrons in the absence of fumarate (KMfor cytochromec= 50 μM). The drug L‐092,201 (Merck, Sharp and Dohme Research Laboratories, Rahway, NJ), an inhibitor of the membrane‐bound fumarate reductase, also blocked the solubilized enzyme. Given the relatively high ionic strength of the intracellular environment we propose that, in vivo, the enzyme fumarate reductase is in the mitochondrial matrix or in the soluble fraction of another intracellular c

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06079.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.Total or kinetoplast DNA (kDNA) from 72 isolates and clones ofTrypanosoma cruzias well as from nine related trypanosomatids were analyzed by dot hybridization using nonradioactive kDNA or cloned minicircle fragments as probes. Biotinylated‐kDNA probes generated by nick‐translation proved reliable for distinguishing Zymodeme 1 and Zymodeme 2bol ofT. cruziparasites. In contrast, digoxigenin‐labeled kDNA obtained by random‐priming did not distinguish amongT. cruziisolates but did distinguish among New World leishmanias. Cloned minicircle fragments labeled with digoxigenin gave the same results as digoxigenin‐labeled kDNA, except for a 10‐fold decrease in sensitivity. Digoxigenin‐labeled DNA probes proved useful in unambiguously detectingT. cruzifrom different geographic regions of America. However,T. rangeliandT. cruzi marinkelleiwere not distinguished by

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06080.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.Paramecium calkinsifrom tidal marshes survive a wide salinity range. Fluid output of contractile vacuoles of these cells decreased as salinity of the medium to which they were acclimated increased, and both pulse rate and vacuole volume were used to regulate output. When cells were first exposed to more dilute medium, contractile vacuoles greatly increased volume so that fluid output increased even though pulse rate decreased. In cells shifted to a more concentrated medium, contractile vacuole output decreased by decreasing pulse rate. The contractile vacuole is surrounded by a set of collecting structures which change form as the salinity changes. Distensible ampullae are found in media of low salinity and collecting canals are found in media of high salinity. When cells are shifted from high salinity to low, the number of ampullae increases and the number of canals decreases. When cells are shifted from low salinity to high, the number of ampullae decreases and the number of canals decreases. Other non‐contracting vacuoles also appear in response to a hypoosmotic shock. These include vacuoles within the cell as well as “blisters” on the surface. The number and frequency of blisters increases with the size of the hypoosmotic shock. They detach from cells without resulting in any visible loss of cytoplasm. Non‐contractile vacuoles may play a role in sequestering and removing excess water that the contractile vacuoles cannot

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06081.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

ABSTRACT.A survey forBabesia microtiin rodents was conducted at six sites within Grand Teton National Park, Wyoming. Blood and spleen smears, hematocrits, and reticulocyte counts were made on all of the animals to evaluate parameters for the diagnosis of babesiosis. Ticks were removed for identification. Of 257Microtus montanus, 103 were infected withB. microti.In addition, five of 12Microtus pennsylvanicusand one of threeArvicola richardsoniwere parasitized byB. microti. Peromyscus maniculatus(n = 40) were not infected. Concurrent infections byHepatozoonsp.,Trypanosomasp., and the bacterium,Grahamellasp., were noted in blood smears from a number ofM. montanus.Splenomegaly and reticulocytosis were significant parameters associated with babesiosis while decreased hematocrit was not. Ticks removed from the voles were identified asIxodes eastoniand were the probable vectors of theB. microti.

ISSN:0022-3921    

DOI:10.1111/j.1550-7408.1991.tb06082.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY