The effect of meal composition on specific dynamic action in burmese pythons (Python molurus)

We quantified the specific dynamic action (SDA) resulting from the ingestion of various meal types in Burmese pythons (Python molurus) at 30 degrees C. Each snake was fed a series of experimental meals consisting of amino acid mixtures, simple proteins, simple or complex carbohydrates, or lipids as well as meals of whole animal tissue (chicken breast, beef suet, and mouse). Rates of oxygen consumption were measured for approximately 4 d after feeding, and the increment above standard metabolic rate was determined and compared to energy content of the meals. While food type (protein, carbohydrate, and lipid) had a general influence, SDA was highly dependent on meal composition (i.e., amino acid composition and carbohydrate structure). For chicken breast and simple carbohydrates, the SDA coefficient was approximately one-third the energetic content of the meal. Lard, suet, cellulose, and starch were not digested and did not produce measurable SDA. We conclude that the cost of de novo protein synthesis is an important component of SDA after ingestion of protein meals because (1) simple proteins, such as gelatin and collagen, did not stimulate levels of SDA attained after consumption of complete protein, (2) incomplete mixtures of amino acids failed to elicit the SDA of a complete mixture, and (3) the inhibition of de novo protein synthesis with the drug cycloheximide caused a more than 70% decrease in SDA. Stomach distension and mechanical digestion of intact prey did not cause measurable SDA.     

Prior exposure to indole-3-carbinol decreases the incidence of specific cyclophosphamide-induced developmental defects in mice

BACKGROUND: Indole-3-carbinol (I3C) is a product of the hydrolysis of glucobrassicin that is found in cruciferous vegetables. I3C can intervene in toxic processes that are mediated by oxidative mechanisms because it possesses the chemical and pharmacokinetic properties necessary to provide a free radical trap. Cyclophosphamide (CP) is a bifunctional alkylating agent known to produce DNA damage and to cause developmental toxicity, including malformations, in laboratory animals. METHODS: Pregnant CD-1 mice were given a 100 mg/kg dose of I3C 24 or 48 hr before administration of 20 mg/kg CP on gestation day 10 (GD 10). Controls were given the vehicle (DMSO), I3C, or CP. This regimen was carried out to determine if I3C could protect against the developmental toxicity of alkylating agents, such as CP. Dams were sacrificed on GD 17 and their litters were examined for adverse effects. RESULTS: Treatment with I3C 48 hr before CP administration was associated with decreased fetal limb and tail malformations. Limb malformation incidences were reduced from 42% litters affected in the CP control to 16% in the I3C/CP 48-hr treatment group, and tail malformations were reduced from 45% in the CP control to 16% in the I3C/CP 48-hr treatment group, indicating a protective effect of prior exposure to I3C. I3C given 24 hr before CP had no significant protective effect, while having an apparently adverse consequence with regard to the incidence of talipes. CONCLUSIONS: Exposure of a developing mammal to indole-3-carbinol before exposure to cyclophosphamide during organogenesis can influence the teratogenicity of cyclophosphamide.     

The activity profile of the NhaD-type Na+(Li+)/H+ antiporter from the soda Lake Haloalkaliphile Alkalimonas amylolytica is adaptive for the extreme environment

In extreme alkaliphiles, Na(+)/H(+) antiporters play a central role in the Na(+) cycle that supports pH homeostasis, Na(+) resistance, solute uptake, and motility. Properties of individual antiporters have only been examined in extremely alkaliphilic soil Bacillus spp., whereas the most alkaline natural habitats usually couple high pH with high salinity. Here, studies were conducted on a Na(+)(Li(+))/H(+) antiporter, NhaD, from the soda lake haloalkaliphile Alkalimonas amylolytica. The activity profile of A. amylolytica NhaD at different pH values and Na(+) concentrations reflects its unique natural habitat. In membrane vesicles from antiporter-deficient Escherichia coli EP432 (DeltanhaA DeltanhaB), the pH optimum for NhaD-dependent Na(+)(Li(+))/H(+) antiport was at least 9.5, the highest pH that could be tested; no activity was observed at pH < or =8.5. NhaD supported low Na(+)/H(+) antiport activity at pH 9.5 that was detectable over a range of Na(+) concentrations from 10 mM to at least 800 mM, with a 600 mM optimum. Although A. amylolytica nhaD was isolated by complementing the Li(+) sensitivity of the triple mutant E. coli strain KNabc (DeltanhaA DeltanhaB DeltachaA), sustained propagation of nhaD-bearing plasmids in this strain resulted in a glycine (Gly(327))-->serine mutation in a putative cytoplasmic loop of the mutant transporter. The altered activity profile of NhaD-G327S appears to be adaptive to the E. coli setting: a much higher activity than wild-type NhaD at Na(+) concentrations up to 200 mM but lower activity at 400 to 600 mM Na(+), with a pH optimum and minimal pH for activity lower than those of wild-type NhaD.     

The Mrp Na+/H+ antiporter increases the activity of the malate:quinone oxidoreductase of an Escherichia coli respiratory mutant

Mrp catalyzes secondary Na+/H+ antiport and was hypothesized to have an additional primary energization mode. Mrp-dependent complementation of nonfermentative growth of an Escherichia coli respiratory mutant supported this hypothesis but is shown here to be related to increased expression of host malate:quinone oxidoreductase, not to catalytic activity of Mrp.     

Increased protein stability causes DNA methyltransferase 1 dysregulation in breast cancer

We report that DNA methyltransferase 1 (DNMT1) expression is dysregulated in breast cancer. The elevated protein levels are not a result of increased mRNA levels, but rather an increase in protein half-life. We found that DNMT1 protein levels were elevated in breast cancer tissues and in MCF-7 breast cancer cells relative to normal human mammary epithelial cells (HMECs) without a concomitant increase in DNMT1 mRNA or proliferative fraction. Although DNMT1 mRNA levels were properly S-phase-regulated in both cell types, DNMT1 protein levels did not follow S-phase fraction in MCF-7 cells. Rather, an increase in DNMT1 protein stability was found for MCF-7 cells relative to HMECs, and a destruction domain was mapped to the N-terminal 120 amino acids of DNMT1, which was required for its proper ubiquitination and degradation in HMECs. Furthermore, overexpression of DNMT1 with this deleted destruction domain in HMECs resulted in significantly increased genomic 5-methylcytosine levels relative to overexpression of the full-length protein. The regulation of DNMT1 destruction via this domain may be dysfunctional in cancer cells leading to subsequent cytosine hypermethylation in the genome.     

Trichinella spiralis: enteric mucin-related response to experimental infection in conventional and SPF pigs

Duodenal and jejunal responses to infection with Trichinella spiralis were compared in weaned piglets with a "normal dirty" vs. a "clean SPF" gut flora. Histochemical staining of neutral, acidic, sialylated, and sulphated residues was used to assess biosynthetic responses in mucin-secreting goblet cells. Peanut and Ulex lectins were also used to assess responses within the intestinal glycocalyx. Histomorphometric analysis was undertaken to evaluate the distribution and staining patterns of goblet cells in villi and crypts. Our analysis showed that stored mucin within goblet cells increased more in the infected conventional animals than in the infected SPF group. This was accompanied by changes in the pattern of sulphation and sialylation in the duodenum and jejunum. The thickness of the glycocalyx was increased in both duodenum and jejunum in both infected groups. However, this effect was greater for the infected SPF animals than the infected conventional animals. No significant differences were observed between uninfected conventional and uninfected SPF pigs.     

Multiple V1/V2 env variants are frequently present during primary infection with human immunodeficiency virus type 1

Human immunodeficiency virus type 1 (HIV-1) exists as a complex population of multiple genotypic variants in persons with chronic infection. However, acute HIV-1 infection via sexual transmission is a low-probability event in which there is thought to be low genetic complexity in the initial inoculum. In order to assess the viral complexity present during primary HIV-1 infection, the V1/V2 and V3 variable regions of the env gene were examined by using a heteroduplex tracking assay (HTA) capable of resolving these genotypic variants. Blood plasma samples from 26 primary HIV-1-infected subjects were analyzed for their level of diversity. Half of the subjects had more than one V1/V2 viral variant during primary infection, indicating the frequent transmission of multiple variants. This observation is inconsistent with the idea of infrequent transmission based on a small transmitting inoculum of cell-free virus. In chronically infected subjects, the complexity of the viral populations was even greater in both the V1/V2 and the V3 regions than in acutely infected subjects, indicating that in spite of the presence of multiple variants in acute infection, the virus does pass through a genetic bottleneck during transmission. We also examined how well the infecting virus penetrated different anatomical compartments by using the HTA. Viral variants detected in blood plasma were compared to those detected in seminal plasma and/or cerebral spinal fluid of six individuals. The virus in each of these compartments was to a large extent identical to virus in blood plasma, a finding consistent with rapid penetration of the infecting variant(s). The low-probability transmission of multiple variants could be the result of transient periods of hyperinfectiousness or hypersusceptibility. Alternatively, the inefficient transfer of a multiply infected cell could account for both the low probability of transmission and the transfer of multiple variants.     

The Australian White Ibis (Threskiornis molucca) as a Reservoir of Zoonotic and Livestock Pathogens

Over the last 20 years, Australian white ibis populations (Threskiornis molucca) have expanded into urban areas, leading to increased contact between ibis, domestic animals, and humans. This has led to concern that ibis may transmit pathogens that threaten public health or food production. Here we report results from a study of ibis viral serology and bacterial culture that indicate that ibis are hosts of zoonotic and livestock pathogens such as Salmonella spp., Newcastle disease virus, avian influenza virus, and flaviviruses in Australia. We also performed a behavioral study to measure contact rates among ibis, people, and livestock that determine the potential for disease transmission.