Platyamoeba nucleolilateralis n. sp. from the Chesapeake Bay Region

Members of the genus Platyamoeba are among the most common of the free-living brackish and marine amoebae; yet, to date only twelve species have been documented in the literature and only a limited number of habitats have been sampled globally. During the course of a systematic survey of salt-marsh amoebae along the east coast of the United States, a new species of Platyamoeba was discovered in sediment samples obtained from a salt marsh at Assateague Island, VA. The species can be distinguished from all other described species within the genus by the presence of a nucleus with a single parietal nucleolus and a floating form with long tapering pseudopods. Its shape varies from flabellate to spatulate as described for species of Platyamoeba and Vannella. The fine structure of the glycocalyx, however, is characteristic of Platyamoeba.     

Twenty years of therapy for HIV-1 infection

Antiretroviral therapy, where available, has transformed HIV-1 disease into a treatable and somewhat chronic infection. This article summarizes the accomplishments thus far and what lies ahead in our struggle to improve the treatment of, and possibly eliminate, HIV-1 infection.     

Trapping and marking terrestrial mammals for research: integrating ethics, performance criteria, techniques, and common sense

We propose that researchers integrate ethics, performance criteria, techniques, and common sense when developing research trapping programs and in which members of institutional animal care and use committees address these topics when evaluating research protocols. To ask questions about ethics is in the best tradition of science, and researchers must be familiar with codes of ethics and guidelines for research published by professional societies. Researchers should always work to improve research methods and to decrease the effects on research animals, if for no other reason than to minimize the chances that the methods influence the animals' behavior in ways that affect research results. Traps used in research should meet performance criteria that address state-of-the-art trapping technology and that optimize animal welfare conditions within the context of the research. The proposal includes the following criteria for traps used in research: As Criterion I, killing-traps should render >/= 70% of animals caught irreversibly unconscious in /= 70% of animals with 相似文献   

Spectral analysis of stereo-electroencephalograms: preictal slowing in partial epilepsies

A substantial challenge in epileptology consists of reliable seizure anticipation ahead in time (minutes). We propose a procedure which derives from our demonstrating here that seizure outbreak shares the pretransitional behaviour characterizing nonequilibrium phase transitions with instabilities found in a number of domains. We investigated stereo-electroencephalograms, using chronically implanted cerebral electrodes, and found preictal (that is, preseizure) slowing. The method employed rests on reconstructing a high-dimensional phase orbit, projecting the orbit back to a scalar time series, namely Lerner's density function which is shown here to play the role of an order parameter, and Fourier-transforming the latter. This reduces the problem to comparing spectral characteristics of interictal and preictal states. The preictal states behaved alike for temporal-lobe and frontal-lobe partial seizures, as well as for the one subclinical temporal-lobe seizure studied. These signs of universality are in accordance with nonequilibrium phase-transitions being in essence the amplification up to a macroscopic size of fluctuations, which may be conjectured here to consist of synchronized neuronal assemblies. Received: 10 January 2000 / Accepted in revised form: 8 May 2000     

Organic matter processing by chironomid larvae (Diptera: Chironomidae)

In laboratory experiments, we used fluorescent dye markers to investigate processing of organic matter by larvae of Psectrocladius limbatellus (Holm.) (Diptera: Chironomidae). 59% of the organic matter used was incorporated into tubes, 39% was present in faecal pellets (both after 24 h), and 2% was found in the larval gut at the end of experiments. Ingested matter passed through the gut rapidly, resulting in the gut being emptied more than 20 times each day. Further 24-h experiments using dye-marked faecal pellets showed that 6% of pellets produced were re-ingested and 12% were incorporated into tubes. There was no preference for conditioned faecal pellets as food over those that had recently been egested and tubes also provided a food reserve on which larvae feed. Chironomid larvae recycle organic matter resulting in its mineralization and their ‘engineering’ has a dramatic effect on the substratum. This revised version was published online in July 2006 with corrections to the Cover Date.     

A description of Mallomonas marsupialis nov. sp. (Synurophyceae), a new chrysophyte from Australia, with comments on the endemicity of Australian freshwater algae

Mallomonas marsupialis is described and illustrated by TEM and SEM micrographs, being found in Australia on sub-tropical Fraser Island and in cool-temperate Tasmania. Its taxonomic location within the genus Mallomonas (sect. Mallomonopsis, ser. Marsupiales) is discussed, together with its inclusion in a suite of unusual endemic algae which have been described from Australian sites largely protected from human interference.     

Inhibition of Membrane Lipid Peroxidation by a Radical Scavenging Mechanism: a Novel Function for Hydroxyl-Containing Ionophores

In the present study we show that K⁺/H⁺ hydroxyl-containing ionophores lasalocid-A (LAS) and nigericin (NIG) in the nanomolar concentration range, inhibit Fe²⁺-citrate and 2,2'-azobis(2-amidinopropane) di-hydrochloride (ABAP)-induced lipid peroxidation in intact rat liver mitochondria and in egg phosphatidyl-choline (PC) liposomes containing negatively charged lipids—dicetyl phosphate (DCP) or cardiolipin (CL)—and KCl as the osmotic support. In addition, monensin (MON), a hydroxyl-containing ionophore with higher affinity for Na⁺ than for K⁺, promotes a similar effect when NaCl is the osmotic support. The protective effect of the ionophores is not observed when the osmolyte is sucrose. Lipid peroxidation was evidenced by mitochondrial swelling, antimycin A-insensitive O₂ consumption, formation of thiobarbituric acid-reactive substances (TBARS), conjugated dienes, and electron paramagnetic resonance (EPR) spectra of an incorporated lipid spin probe. A time-dependent decay of spin label EPR signal is observed as a consequence of lipid peroxidation induced by both inductor systems in liposomes. Nitroxide destruction is inhibited by buty-lated hydroxytoluene, a known antioxidant, and by the hydroxyl-containing ionophores. In contrast, vali-nomycin (VAL), which does not possess alcoholic groups, does not display this protective effect. Effective order parameters (S_eff), determined from the spectra of an incorporated spin label are larger in the presence of salt and display a small increase upon addition of the ionophores, as a result of the increase of counter ion concentration at the negatively charged bilayer surface. This condition leads to increased formation of the ion-ionophore complex, the membrane binding (uncharged) species. The membrane-incorporated complex is the active species in the lipid peroxidation inhibiting process. Studies in aqueous solution (in the absence of membranes) showed that NIG and LAS, but not VAL, decrease the Fe²⁺-citrate-induced production of radicals derived from piperazine-based buffers, demonstrating their property as radical scavengers. Both Fe²⁺-citrate and ABAP promote a much more pronounced decrease of LAS fluorescence in PC/CL liposomes than in dimyristoyl phosphatidyl-choline (DMPC, saturated phospholipid)-DCP liposomes, indicating that the ionophore also scavenges lipid peroxyl radicals. A slow decrease of fluorescence is observed in the latter system, for all lipid compositions in sucrose medium, and in the absence of membranes, indicating that the primary radicals stemming from both inductors also attack the ionophore. Altogether, the data lead to the conclusion that the membrane-incorporated cation complexes of NIG, LAS and MON inhibit lipid peroxidation by blocking initiation and propagation reactions in the lipid phase via a free radical scavenging mechanism, very likely due to the presence of alcoholic hydroxyl groups in all three molecules and to the attack of the aromatic moiety of LAS.     

Discrete consumers,small scale resource heterogeneity,and population stability

We present a consumer-resource model in which individual consumers subsist on a continuum of resource distributed over a very large number of small “bite-sized” patches, each patch being sufficiently small that all its resource is eaten whenever a consumer visits. This form of consumer–resource interaction forces a heterogeneous distribution of resource among the patches, and may dampen out the large amplitude, consumer-resource cycles that are predicted by traditional models of well-mixed, spatially homogeneous systems. The resource equilibrium does not increase with enrichment, a prediction that distinguishes this model from models that invoke direct or indirect consumer density dependence as a stabilizing mechanism.     

Albumin synthesis after intense intermittent exercise in human subjects

Yang, Roger C., Gary W. Mack, Robert R. Wolfe, and Ethan R. Nadel. Albumin synthesis after intense intermittent exercise inhuman subjects. J. Appl. Physiol.84(2): 584-592, 1998.We measured hepatic albumin synthesis infive volunteers (4 men and 1 woman) at 3 and 6 h after recovery fromintense exercise. A primed-constant infusion of a stable isotopictracer of phenylalanine was used to determine hepatic fractionalsynthetic rate (FSR) and absolute synthetic rate (ASR) of albumin fromthe enrichment of phenylalanine in albumin. The infusion of the stableisotope tracer began 2 h after upright exercise or upright rest.Albumin FSR and ASR were 6.39 ± 0.48%/day and 120 ± 9 mg · kg bodywt¹ · day¹,respectively, 3-6 h after recovery from exercise; the FSR and ASRon the time control study day were 5.94 ± 0.47%/day and 104 ± 9 mg · kg bodywt¹ · day¹,respectively. The 6 and 16% increases(P < 0.05) in FSR and ASR afterexercise were associated with an elevated plasma albumin content at 5 and 6 h of recovery (P < 0.05), anincreased total protein content throughout recovery(P < 0.05), and a negative freewater clearance (P < 0.05) at 2, 3, and 6.5 h of recovery compared with baseline values; these variableswere unchanged from their baselines on the time control study day.Increased albumin content and reduced free water clearance contributeto a retention of fluid within the circulation after intense exercise. The measured increase in albumin synthesis could not account for theentire increase in albumin content at 6 h of recovery from exercise.However, we estimate that if the increased activity was maintained forthe next 18 h, it could account for the expected increase in albumincontent at 24 h of recovery.