Pericyte loss and microaneurysm formation in PDGF-B-deficient mice

Platelet-derived growth factor (PDGF)-B-deficient mouse embryos were found to lack microvascular pericytes, which normally form part of the capillary wall, and they developed numerous capillary microaneurysms that ruptured at late gestation. Endothelial cells of the sprouting capillaries in the mutant mice appeared to be unable to attract PDGF-Rbeta-positive pericyte progenitor cells. Pericytes may contribute to the mechanical stability of the capillary wall. Comparisons made between PDGF null mouse phenotypes suggest a general role for PDGFs in the development of myofibroblasts.     

Leydig cell steroidogenesis in aging rats

Recent studies from our and other laboratories have shown that Leydig cells, the testicular cells responsible for testosterone production; become steroidogenically hypofunctional with age. Herein we review some of what we now know about the mechanisms by which this occurs, and some among the many remaining uncertainties in our understanding of Leydig cell aging. To help shed light on how Leydig cells age, we also briefly discuss the regulation of Leydig cell differentiation during puberty and of Leydig cell function in adult animals.     

Patient selection in outpatient parenteral antimicrobial therapy

Outcome data as well as reported anecdotal experience over the past 20 years indicate that any infection can be safely treated with parenteral antimicrobials outside the hospital setting. However, outpatient parenteral antimicrobial therapy (OPAT) is a reasonable option only when the final decision for patient selection is based on the judgment of a knowledgeable, experienced physician, and when an experienced qualified provider is available. Criteria to be considered include clinical status, patient acceptance, ability to comply with the plan of treatment, home environment, support systems, and reimbursement. Physician direction and participation in appropriate patient selection will become increasingly important as the growth of managed care increases the importance of cost-savings.     

Leukocyte Adhesion Deficiency Type II is a generalized defect of de novo GDP-fucose biosynthesis. Endothelial cell fucosylation is not required for neutrophil rolling on human nonlymphoid endothelium

Leukocyte Adhesion Deficiency Type II (LAD II) is a recently described syndrome and the two patients with this defect lack fucosylated glycoconjugates. These glycoconjugates include the selectin ligand, sialyl LewisX, and various fucosylated blood group antigens. To date, the molecular anomaly in these patients has not been identified. We localized the defect in LAD II to the de novo pathway of GDP-fucose biosynthesis, by inducing cell-surface expression of fucosylated glycoconjugates after exposure of lymphoblastoid cell lines from the LAD II patients to exogenous fucose. This defect is not restricted to hematopoietic cells, since similar findings were elicited in both human umbilical vein endothelial cells (HUVEC) and fibroblasts derived from an affected abortus. We have used these LAD II endothelial cells to examine the consequence of fucosylation of endothelial cells on the rolling of normal neutrophils in an in vitro assay. Neutrophil rolling on LPS-treated normal and LAD II HUVEC was inhibited by an E-selectin monoclonal antibody at both high and low shear rates. LAD II HUVEC lacking fucosylated glycoproteins supported leukocyte rolling to a similar degree as normal HUVEC or LAD II cells that were fucose-fed. At low shear rates, an L-selectin antibody inhibited neutrophil rolling to a similar degree whether the LAD II cells had been fucose-fed or not. These findings suggest that fucosylation of nonlymphoid endothelial cells does not play a major role in neutrophil rolling and that fucose is not a critical moiety on the L-selectin ligand(s) on endothelial cells of the systemic vasculature.     

Platelet-derived growth factor and fibronectin-stimulated migration are differentially regulated by the Rac and extracellular signal-regulated kinase pathways

Directed cell migration is essential for a variety of important biological processes ranging from development and angiogenesis to metastasis. Ras plays a pivotal role in the signaling cascade that governs chemotaxis of fibroblasts toward platelet-derived growth factor-BB (PDGF-BB). Ras activates multiple downstream pathways, which include the extracellular signal-regulated kinase (ERK), Rac, and Ral signaling cascades. We therefore investigated the role of the Rac and ERK pathways in cell migration. We showed that migration of fibroblasts toward PDGF-BB is inhibited by expression of dominant negative Asn-17 Rac1. Blocking of the ERK pathway by either expression of dominant negative Ala-218/Ala-222-mitogen-activated protein kinase kinase (A218/A222-MEK1) or by a MEK-specific inhibitor did not inhibit migration toward PDGF-BB. In contrast, migration toward soluble fibronectin was suppressed by inhibition of the ERK pathway but not by Asn-17 Rac1 expression. These results indicate that directed cell migration mediated by different receptor classes in response to different ligands differentially utilizes the Rac and ERK pathways and suggest that Rac might play a critical role in pathological processes such as angiogenesis and metastasis.     

Specific identification of Mycobacterium tuberculosis with the luciferase reporter mycobacteriophage: use of p-nitro-alpha-acetylamino-beta-hydroxy propiophenone

We have previously described a luciferase reporter mycobacteriophage (LRP) assay that can detect Mycobacterium tuberculosis and characterize mycobacterial drug susceptibility patterns within 24 to 48 h in positive cultures. One drawback of this LRP protocol is the ability of the recombinant mycobacteriophage phAE40 to infect a variety of Mycobacterium species, thus limiting its specificity for the detection of M. tuberculosis. In this study, we have (i) explored the host range of phAE40, (ii) developed a modified LRP assay that exploits the selective inhibitory effect of the compound p-nitro-alpha-acetylamino-beta-hydroxy propiophenone (NAP) against members of the M. tuberculosis complex to differentiate between the tubercle bacillus and other mycobacterial species, and (iii) tested over 300 samples, including primary clinical isolates and drug-resistant strains of M. tuberculosis, demonstrating the ability of the NAP-modified LRP assay to identify M. tuberculosis complex organisms with high degrees of sensitivity and specificity.     

Adenocarcinoma colon

Research areas of immunodiagnosis and vaccination in Cystic Echinococcosis (CE) are reviewed. Particular attention is given to recent progress into improved specificity in immunodiagnosis in human CE, and sensitivity and specificity in ovine CE, by purification of subunit peptides of Ag B. With regard to diagnosis in definitive hosts, the advantages of coproantigen test ELISA are discussed in comparison with the classic arecoline purgation test. Recent data from studies on vaccination in sheep populations are reported, and the enormous potential of an effective vaccine in a Hydatid control programme is underlined.     

Novel mutations and DNA-based screening in non-Jewish carriers of Tay-Sachs disease

We have evaluated the feasibility of using PCR-based mutation screening for non-Jewish enzyme-defined carriers identified through Tay-Sachs disease-prevention programs. Although Tay-Sachs mutations are rare in the general population, non-Jewish individuals may be screened as spouses of Jewish carriers or as relatives of probands. In order to define a panel of alleles that might account for the majority of mutations in non-Jewish carriers, we investigated 26 independent alleles from 20 obligate carriers and 3 affected individuals. Eighteen alleles were represented by 12 previously identified mutations, 7 that were newly identified, and 1 that remains unidentified. We then investigated 46 enzyme-defined carrier alleles: 19 were pseudodeficiency alleles, and five mutations accounted for 15 other alleles. An eighth new mutation was detected among enzyme-defined carriers. Eleven alleles remain unidentified, despite the testing for 23 alleles. Some may represent false positives for the enzyme test. Our results indicate that predominant mutations, other than the two pseudodeficiency alleles (739C-->T and 745C-->T) and one disease allele (IVS9+1G-->A), do not occur in the general population. This suggests that it is not possible to define a collection of mutations that could identify an overwhelming majority of the alleles in non-Jews who may require Tay-Sachs carrier screening. We conclude that determination of carrier status by DNA analysis alone is inefficient because of the large proportion of rare alleles. Notwithstanding the possibility of false positives inherent to enzyme screening, this method remains an essential component of carrier screening in non-Jews. DNA screening can be best used as an adjunct to enzyme testing to exclude known HEXA pseudodeficiency alleles, the IVS9+1G-->A disease allele, and other mutations relevant to the subject's genetic heritage.