Lactoferrin-mediated modulation of mononuclear cell activities: I. Suppression of the murine in vitro primary antibody response

The effect of the iron-binding glycoprotein lactoferrin (LF) on the in vitro primary antibody response of mouse splenic cells to a T-lymphocyte-dependent antigen, sheep erythrocytes (SE), and a T-lymphocyte-independent antigen, trinitrophenolated Brucella abortus, was examined. Both iron-saturated and native LF (8% saturated) at 10^?10 to 10^?6M concentrations but not transferrin (an iron-binding glycoprotein similar to LF) significantly (P < 0.05) decreased the number of direct (IgM) plaque-forming cells (PFC) to SE and trinitrophenol (TNP) as determined by the hemolytic plaque assay. LF was equally effective in decreasing the PFC response to TNP in T-lymphocyte-depleted splenic cell cultures. Concentrations of LF which decreased the PFC response were noncytotoxic. A 1-hr exposure of splenic cells to LF at the beginning of the 5-day culture period but not 1 hr prior to assaying for PFC, or exposure of isolated macrophage-rich but not lymphocyte-rich populations to LF prior to reconstitution resulted in a significant decrease in the anti-SE response. These data suggest that LF which is synthesized and released by polymorphonuclear leukocytes and present in inflammatory lesions may play a role in modulating the antibody response through an effect on the macrophage.     

Visualization and biopsy of the colon in tamarins and marmosets by endoscopy

Endoscopic visualization and biopsy have been performed under anesthesia in more than 65 tamarins and marmosets to study the pathogenesis of colitis and cancer of the colon. This procedure allows examination of the large bowel from the anus to the cecum and has been repeated at 2-6 month intervals with few complications. However, care must be exercised not to perforate the colon. Successful use of this technique will permit study of the pathogenesis of colonic diseases throughout the life of the animal and should provide cause-effect information about colitis and colon cancer in tamarins that may apply to the human diseases.     

Mechanisms and development of parent-young vocal recognition in the piñon jay (Gymnorhinus cyanocephalus)

Mutual, vocal parent-young recognition is achieved by piñon jays (Gynnorhinus cyanocephalus) by the time the young leave the nest at 21 days to form stable crèches of dependent young. Both parents and young beging producing individualistic calls, upon which recognition is based, when the young are 14 days old. Playbacks of nestlings' begging calls to adults and parents' approach calls to nestlings showed that mutaul recognition of each other's calls is learned between nestling age of 14 and 20 days. Sonographic and statistical analyses of the begging calls of nestling and fledgling jays showed the calls to be highly individualistic. Both univariate and multivariate (PCA) statistical methods were used to determined amounts of significant variation within and among the calls of different individuals and to isolate parameters which might be used by parents in offspring recognition. The analyses support two major conclusions. First, 20.4% of all variance measured in the calls is due to variation among individuals' calls. The data imply that adults may recognize their offspring's calls based on gestalt perception of simultaneous variation in a number of parameters. Second, each young bird's calls vary gradually with time, requiring parents to ‘track’ the calls of their offspring over time. These conclusions are only tentative until a correlation between statistically significant variation and biologically significant variation is demonstrated.     

Sucrose Breakdown in Relation to Fruit Growth of Acid Lime (Citrus aurantifolia)

The physiological capacity for sucrose breakdown in developingjuice sac cells of acid limes was estimated by assaying theactivity of the three enzymes of sucrose catabolism in additionto vacuolar acid hydrolysis. The maximum potential rates ofsucrose breakdown were compared with the observed rates of carbonutilization. Highest potential rates of sucrose breakdown (28.621mmol cm^–3 per hydrated active space d^–1) occurredat the initial stages of fruit development where carbon utilizationwas highest. As the fruit developed, the potential rates ofsucrose breakdown and carbon utilization declined to very lowlevels. At 80% of development, vacuolar acid hydrolysis becamethe only physiological mechanism for sucrose breakdown. Therelatively low amounts of sucrose hydrolysed by acid hydrolysisat this time were just sufficient to account for the measuredcarbon demands. The results suggest that carbon supplied bythis distinct sucrose catabolizing system is able to provideadequate levels of carbon skeletons for the observed levelsof respiration and dry weight deposition early in development,but becomes a limiting factor for growth in the later stages. Key words: Vacuolar acid hydrolysis, Citrus aurantifolia     

Studies on antigenic competition. Efforts to identify the cellular basis of competition using a cell transfer system

Antigenic competition was studied in a cell transfer system. The effect of reconstituting lethally irradiated mice with various numbers of thymus or bone marrow cells on the extent of antigenic competition was evaluated. Brucella or burro erythrocytes both caused inhibition of the immune response (Plaque-forming cell) to sheep erythrocytes when given two days prior to the test antigen. Varying the dose of thymus cells, or of bone marrow cells did not alter the degree of competition. Competition was observed even when the competing antigen was injected with bone marrow cells alone two days before the test antigen and thymus cells. The results suggest that mechanisms other than T-cell activation alone must be considered as operative in some models of antigenic competition.     

A novel small-molecule MRCK inhibitor blocks cancer cell invasion

Background

Dual oxidase maturation factor 1 (DUOXA1) has been associated with the maturation of the reactive oxygen species (ROS) producing enzyme, dual oxidase 1 (DUOX1) in the adult thyroid. However, ROS have also been implicated in the development of several tissues. We found that activated muscle satellite cells and primary myoblasts isolated from mice express robust levels of DUOXA1 and that its levels are altered as cells differentiate.

Results

To determine whether DUOXA1 levels affect muscle differentiation, we used an adenoviral construct (pCMV5-DUOXA1-GFP) to drive constitutive overexpression of this protein in primary myoblasts. High levels of DUOXA1 throughout myogenesis resulted in enhanced H₂O₂ production, fusion defects, reduced expression of early (myogenin) and late (myosin heavy chain) markers of differentiation, and elevated levels of apoptosis compared to control cells infected with an empty adenoviral vector (pCMV5-GFP). DUOXA1 knockdown (using a DUOXA1 shRNA construct) resulted in enhanced differentiation compared to cells subjected to a control shRNA, and subjecting DUOXA1 overexpressing cells to siRNAs targeting DUOX1 or apoptosis signal-regulating kinase 1 (ASK1) rescued the phenotype.

Conclusions

This study represents the first to demonstrate the importance of DUOXA1 in skeletal muscle myoblasts and that DUOXA1 overexpression in muscle stem cells induces apoptosis and inhibits differentiation through DUOX1 and ASK1.     

Bacterial tolerances to metals and antibiotics in metal-contaminated and reference streams

Anthropogenic-derived sources of selection are typically implicated as mechanisms for maintaining antibiotic resistance in the environment. Here we report an additional mechanism for maintaining antibiotic resistance in the environment through bacterial exposure to metals. Using a culture-independent approach, bacteria sampled along a gradient of metal contamination were more tolerant of antibiotics and metals compared to bacteria from a reference site. This evidence supports the hypothesis that metal contamination directly selects for metal tolerant bacteria while co-selecting for antibiotic tolerant bacteria. Additionally, to assess how antibiotic and metal tolerance may be transported through a stream network, we studied antibiotic and metal tolerance patterns over three months in bacteria collected from multiple stream microhabitats including the water column, biofilm, sediment and Corbicula fluminea (Asiatic clam) digestive tracts. Sediment bacteria were the most tolerant to antibiotics and metals, while bacteria from Corbicula were the least tolerant. Differences between microhabitats may be important for identifying reservoirs of resistance and for predicting how these genes are transferred and transported in metal-contaminated streams. Temporal dynamics were not directly correlated to a suite of physicochemical parameters, suggesting that tolerance patterns within microhabitats are linked to a complex interaction of the physicochemical characteristics of the stream.