Phosphorus release from sediments in a river-valley reservoir in the northern Great Plains of North America

Aside from a companion investigation to this study, there are currently no peer-reviewed phosphorus (P) release rate data for northern North American (i.e., Canadian) reservoirs. Using Lake Diefenbaker, Saskatchewan, Canada as a case study, we tested the effect of variation in overlying water DO conditions on the P release rates from sediment cores. Sediment cores from four down-reservoir locations in Lake Diefenbaker were incubated under high (>8 mg l⁻¹), low (2–3 mg l⁻¹), or anoxic (<1 mg l⁻¹) DO concentrations. Sediment cores were then analyzed for total P (TP) and three geochemical P fractions to assess how the DO regime influenced sediment P inventory. Maximum P release rates were highest under anoxic conditions and similar among sites (15.0–20.3 mg m⁻² day⁻¹), with the low-DO rates intermediate to the high-DO and anoxic P fluxes. Predictive internal P loading models considering only hypolimnetic anoxia may therefore oversimplify and thus underestimate P mobilization in situ. Non-apatite inorganic P (54 ± 10% across sites) from the top 1 cm of the sediment profile was the main source of P released during incubations, indicating that sampling on a coarser scale of resolution could obscure the relationship between sediment geochemistry and short-term P flux.

     

Bordetella adenylate cyclase toxin interacts with filamentous haemagglutinin to inhibit biofilm formation in vitro

Bordetella pertussis, the causative agent of whooping cough, secretes and releases adenylate cyclase toxin (ACT), which is a protein bacterial toxin that targets host cells and disarms immune defenses. ACT binds filamentous haemagglutinin (FHA), a surface‐displayed adhesin, and until now, the consequences of this interaction were unknown. A B. bronchiseptica mutant lacking ACT produced more biofilm than the parental strain; leading Irie et al. to propose the ACT‐FHA interaction could be responsible for biofilm inhibition. Here we characterize the physical interaction of ACT with FHA and provide evidence linking that interaction to inhibition of biofilm in vitro. Exogenous ACT inhibits biofilm formation in a concentration‐dependent manner and the N‐terminal catalytic domain of ACT (AC domain) is necessary and sufficient for this inhibitory effect. AC Domain interacts with the C‐terminal segment of FHA with ～650 nM affinity. ACT does not inhibit biofilm formation by Bordetella lacking the mature C‐terminal domain (MCD), suggesting the direct interaction between AC domain and the MCD is required for the inhibitory effect. Additionally, AC domain disrupts preformed biofilm on abiotic surfaces. The demonstrated inhibition of biofilm formation by a host‐directed protein bacterial toxin represents a novel regulatory mechanism and identifies an unprecedented role for ACT.     

Ultrastructure and Development of Pasteuria sp. (S-1 strain), an Obligate Endoparasite of Belonolaimus longicaudatus (Nemata: Tylenchida)

Pasteuria sp., strain S-1, is a gram-positive, obligate endoparasitic bacterium that uses the phytoparasitic sting nematode, Belonolaimus longicaudatus, as its host in Florida. The host attachment of S-1 appears to be specific to the genus Belonolaimus with development occurring only in juveniles and adults of B. longicaudatus. This bacterium is characterized from other described species of Pasteuria using ultrastructure of the mature endospore. Penetration, development, and sporogenesis were elucidated with TEM, LTSEM, and SEM and are similar to other nematode-specific Pasteuria. Recent analysis of 16S rDNA sequence homology confirms its congeneric ranking with other Pasteuria species and strains from nematodes and cladocerans, and corroborates ultrastructural, morphological, morphometric, and host-range evidence suggesting separate species status.     

Dental Health Diet and Social Status among Central African Foragers and Farmers

An oral health survey of African pygmies and Bantu revealed significant contrasts that can be explained by differences in diet, social status, and oral hygiene. Pygmy men have fewer carious lesions and less tooth loss than pygmy women. Ethnographic data suggest that this results from sex differences in eating habits and access to cariogenic foods. Pygmy "leaders" have much better dental health than "nonleaders." This status difference appears to be explained by social and dietary variables.     

Identification of a potential HIV-induced source of bystander-mediated apoptosis in T cells: Upregulation of TRAIL in primary human macrophages by HIV-1 tat

The induction of apoptosis in T cells by bystander cells has been repeatedly implicated as a mechanism contributing to the T cell depletion seen in HIV infection. It has been shown that apoptosis could be induced in T cells from asymptomatic HIV-infected individuals in a Fas-independent, TNF-related apoptosis-inducing ligand (TRAIL)-dependent manner if the cells were pretreated with anti-CD3. It has also been shown that T cells from HIV-infected patients were even more sensitive to TRAIL induction of apoptosis than they were to Fas induction. Recently, it has been reported that in an HIV-1 SCID-Hu model, the vast majority of the T cell apoptosis is not associated with p24 and is therefore produced by bystander effects. Furthermore, few apoptotic cells were associated with neighboring cells which were positive for either Fas ligand or TNF. However, most of the apoptotic cells were associated with TRAIL-positive cells. The nature of these TRAIL-positive cells was undetermined. Here, we report that HIV infection of primary human macrophages switches on abundant TRAIL production both at the RNA and protein levels. Furthermore, more macrophages produce TRAIL than are infected by HIV, indicating that a bystander mechanism may, at least in part, upregulate TRAIL. Exogenously supplied HIV-1 Tat protein upregulates TRAIL production by primary human macrophages to an extent indistinguishable from infection. The results suggest a model in which HIV-1-infected cells produce extracellular Tat protein, which in turn upregulates TRAIL in macrophages which then can induce apoptosis in bystander T cells.     

Bcl-2 upregulation by HIV-1 tat during infection of primary human macrophages in culture

The ability of cells of the human monocyte/macrophage lineage to host HIV-1 replication while resisting cell death is believed to significantly contribute to their ability to serve as a reservoir for viral replication in the host. Although macrophages are generally resistant to apoptosis, interruption of anti-apoptotic pathways can render them susceptible to apoptosis. Here we report that HIV-1(BAL )infection of primary human monocyte-derived macrophages (MDM) upregulates the mRNA and protein levels of the anti-apoptic gene, Bcl-2. Furthermore, this upregulation can be quantitatively mimicked by treating MDM with soluble HIV-1 Tat-86 protein. These results suggest that in infecting cells of the monocyte/macrophage lineage, HIV-1 may be benefiting from additional protection against apoptosis caused by specific upregulation of cellular anti-apoptotic genes.     

The effects of MAPK p38α on AZT resistance against reactivating HIV-1 replication in ACH2 cells

Molecular and Cellular Biochemistry - Changes in wall shear stress of blood vessels are assumed to be an important component of many physiological and pathophysiological processes. However, due to...     

Antibodies against a multiple-peptide conjugate comprising chemically modified human immunodeficiency virus type-1 functional Tat peptides inhibit infection

We demonstrated recently that selective side-chain modification of functional cysteine-rich (Tat(21-40)) and arginine-rich (Tat(53-68)) domains of the HIV-1 Tat protein blocks pathogenic activities of these peptides while retaining their immunological characteristics. In the present study, we have synthesized a multiple-peptide conjugate system comprising modified Tat(21-40) and Tat(53-68) peptides (HIV-1-Tat-MPC). Immunization of mice with this highly homogeneous 10.7 kDa HIV-1-Tat-MPC synthetic construct induced an effective immune response in mice. The antibodies generated against HIV-1-Tat-MPC efficiently suppressed Tat-induced viral replication and significantly reduced HIV-associated cytopathic effects in human monocytes. These results indicate that epitope-specific antibodies directed against functional sites of Tat protein using non-pathogenic peptides inhibit HIV pathogenesis. The HIV-1-Tat-MPC, therefore, has potential for the development of a safe, effective, and economical therapeutic vaccine to reduce the progression of HIV infection.