Mitochondrial DNA sequences reveal close relationships between social parasitic ants and their host species

In the tribe Leptothoracini, the phylogenetic relationship of socially parasitic ants (Doronomyrmex kutteri, D. goesswaldi and Harpagoxenus sublaevis) and their host species Leptothorax acervorum has been controversial. Even more controversial is the relationship between the socially parasitic ant Chalepoxenus muellerianus and its host species Leptothorax unifasciatus, L. nigriceps, L. interruptus and L. recedens. On the basis of morphological, ecological and ethological criteria it has been argued that socially parasitic ants and their respective hosts always evolved from common ancestors, and hence it has been postulated that these species should be included in common taxonomical groups. This would require the division of the tribe Leptothoracini into two subgroups, one comprising the subgenus Leptothorax (s. str.) and the other the subgenus Myrafant, together with their respective parasitic genera. We have used the polymerase chain reaction (PCR) to compare a 360-bp sequence of the mitochondrial cytochrome b gene of 14 species belonging to the tribe Leptothoracini and an outgroup species Tetranorium impurum (Tetramoriini). The results generally agree with the morphological studies which suggest that a common ancestral species differentiated into host and parasite species. This relationship is very obvious within the Leptothorax (s. str.) group but less pronounced in the species belonging to the Myrafant group. Leptothorax (Temnothorax) recedens shows a greater sequence divergence than the outgroup species T. impurum.     

Differential dynamics of the peripheral and intrahepatic cytotoxic T lymphocyte response to hepatitis B surface antigen

The distribution and dynamics of the cytotoxic T lymphocyte (CTL) response to hepatitis B surface antigen (HBsAg) were studied in mice after intramuscular DNA immunization and after hepatic infection by a recombinant adenovirus that expresses the hepatitis B virus genome (Ad-HBV). CTLs specific for HBsAg accumulate preferentially in the spleen after DNA immunization but are primarily intrahepatic after Ad-HBV infection. The secondary CTL response to Ad-HBV in DNA-primed mice is characterized by rapid depletion of effector CTLs from the spleen, and their expansion in the liver where they cause hepatitis, secrete interferon gamma (IFNγ), and inhibit HBV gene expression. Suppression of HBsAg synthesis is accompanied by disappearance of intrahepatic IFNγ-producing CTLs and their reaccumulation in the spleen. The data suggest a possible explanation for the paucity and functional deficiency of HBV-specific CTLs in the periphery during chronic HBV infection, and that the severity of infection can be worsened by a preexisting CTL response if neutralizing antibody is not also present.     

Scaffold protein harmonin (USH1C) provides molecular links between Usher syndrome type 1 and type 2

Usher syndrome (USH) is the most frequent cause of combined deaf-blindness in man. USH is clinically and genetically heterogeneous with at least 11 chromosomal loci assigned to the three USH types (USH1A-G, USH2A-C, USH3A). Although the different USH types exhibit almost the same phenotype in human, the identified USH genes encode for proteins which belong to very different protein classes and families. We and others recently reported that the scaffold protein harmonin (USH1C-gene product) integrates all identified USH1 molecules in a USH1-protein network. Here, we investigated the relationship between the USH2 molecules and this USH1-protein network. We show a molecular interaction between the scaffold protein harmonin (USH1C) and the USH2A protein, VLGR1 (USH2C) and the candidate for USH2B, NBC3. We pinpoint these interactions to interactions between the PDZ1 domain of harmonin and the PDZ-binding motifs at the C-termini of the USH2 proteins and NBC3. We demonstrate that USH2A, VLGR1 and NBC3 are co-expressed with the USH1-protein harmonin in the synaptic terminals of both retinal photoreceptors and inner ear hair cells. In hair cells, these USH proteins are also localized in the signal uptaking stereocilia. Our data indicate that the USH2 proteins and NBC3 are further partners in the supramolecular USH-protein network in the retina and inner ear which shed new light on the function of USH2 proteins and the entire USH-protein network. These findings provide first evidence for a molecular linkage between the pathophysiology in USH1 and USH2. The organization of USH molecules in a mutual 'interactome' related to the disease can explain the common phenotype in USH.     

Cell-matrix interactions during development and apoptosis of the mouse mammary gland in vivo.

Epithelial cell survival is dependent on extracellular signals provided by both soluble factors and by adhesion. In the mammary gland, extensive apoptosis of epithelial cells occurs rapidly when lactation ceases, but the mechanism of apoptosis induction is not known. In tissue culture, mammary epithelial cells require laminin as a survival ligand and specific beta1 integrins are necessary to suppress apoptosis. To explore the possibility that dynamic changes in cell-matrix interactions contribute to the onset of apoptosis during mammary involution in vivo, a detailed immunohistochemical analysis of the expression of integrin subunits and their extracellular matrix ligands during mouse mammary gland development has been performed. The kinetics of apoptosis were determined by using tissue samples obtained from virgin, pregnant, lactating, and involuting gland. The maximal elevation of apoptosis occurred within 24 hr of weaning as determined by histologic analysis and caspase-3 staining. A wide variety of laminin subunits, together with nidogen-1 and -2, and perlecan were identified within the basement membrane region of epithelial ducts, lobules, and alveoli in both human and mouse mammary gland. However, no change in the distribution of any of the basement membrane proteins or their cognate integrin receptors was observed during the transition from lactation to apoptosis. Instead, we discovered that altered ligand-binding conformation of the beta1 integrin to a nonbinding state coincided with the immediate onset of mammary apoptosis. This finding may provide a novel dynamic mechanism for inhibiting the transduction of extracellular matrix survival signals, thereby contributing to the onset of apoptosis in a developmental context in vivo.     

Preventive Effects of Escherichia coli Strain Nissle 1917 on Acute and Chronic Intestinal Inflammation in Two Different Murine Models of Colitis

Escherichia coli strain Nissle 1917 (EcN) is as effective in maintaining remission in ulcerative colitis as is treatment with mesalazine. This study aims to evaluate murine models of acute and chronic intestinal inflammation to study the antiinflammatory effect of EcN in vivo. Acute colitis was induced in mice with 2% dextran-sodium sulfate (DSS) in drinking water. EcN was administered from day −2 to day +7. Chronic colitis was induced by transfer of CD4⁺ CD62L⁺ T lymphocytes from BALB/c mice in SCID mice. EcN was administered three times/week from week 1 to week 8 after cell transfer. Mesenteric lymph node (MLN) cytokine secretion (of gamma interferon [IFN-γ], interleukin 5 [IL-5], IL-6, and IL-10) was measured by enzyme-linked immunosorbent assay. Histologic sections of the colon were analyzed by using a score system ranging from 0 to 4. Intestinal contents and homogenized MLN were cultured, and the number of E. coli-like colonies was determined. EcN was identified by repetitive extragenic palindromic (REP) PCR. EcN administration to DSS-treated mice reduced the secretion of proinflammatory cytokines (IFN-γ, 32,477 ± 6,377 versus 9,734 ± 1,717 [P = 0.004]; IL-6, 231 ± 35 versus 121 ± 17 [P = 0.02]) but had no effect on the mucosal inflammation. In the chronic experimental colitis of the transfer model, EcN ameliorated the intestinal inflammation (histology score, 2.7 ± 0.2 versus 1.9 ± 0.3 [P = 0.02]) and reduced the secretion of proinflammatory cytokines. Translocation of EcN and resident E. coli into MLN was observed in the chronic colitis model but not in healthy controls. Administration of EcN ameliorated acute and chronic experimental colitis by modifying proinflammatory cytokine secretion but had no influence on the acute DSS-induced colitis. In this model, preexisting colitis was necessary for translocation of EcN and resident E. coli into MLN.     

Characterization of Coccidioides immitis isolates by restriction fragment length polymorphisms.

The marked increase in the number of cases of coccidioidomycosis in California in 1992 led to a study of isolates from various patients and environmental sources by restriction fragment length polymorphism (RFLP) analysis. Of 15 different isolates, most of the isolates (13 of 15) from California and 1 from Venezuela yielded one main RFLP pattern with evidence of two subgroups. The other two isolates (both from patients in the San Joaquin Valley of California) yielded a different RFLP pattern.     

Morphological detection and quantification of lipoprotein(a) deposition in atheromatous lesions of human aorta and coronary arteries

Summary Lipoprotein(a), as an atherogenic particle, represents an independent risk factor for coronary heart disease. In the present study the morphological distribution of apoprotein (a) and apoprotein B within the arterial wall is described. Apoprotein B, a constituent of very low-density lipoprotein, low-density lipoprotein and lipoprotein(a) has previously been demonstrated in atheromatous lesions. Lipoprotein(a) possesses an additional protein, designated apoprotein (a). Autopsy material (n=74) from the left coronary artery and from the thoracic aorta has been examined by means of immunohistochemistry and both apoprotein (a) and apoprotein B were detected, primarily associated with the extracellular matrix and accumulating in lesions in the arterial wall. The staining pattern for both antigens was almost always found to be congruent, suggesting that the detection of (a)-antigen has to be attributed at least in part to the presence of lipoprotein(a). It is concluded that both low-density lipoprotein and lipoprotein(a) have an important role in the pathogenesis of atherosclerosis.