Gerald Duhamel - Academia.edu (original) (raw)

Papers by Gerald Duhamel

$Research paper thumbnail of The cytolethal distending toxin B sub-unit of \u3ci\u3eHelicobacter hepaticus\u3c/i\u3e is a Ca\u3csup\u3e2+\u3c/sup\u3e- and Mg\u3csup\u3e2+\u3c/sup\u3e-dependent neutral nuclease$

The cytolethal distending toxin B (CdtB) of the mouse pathogen Helicobacter hepaticus has cation ... more The cytolethal distending toxin B (CdtB) of the mouse pathogen Helicobacter hepaticus has cation binding and DNA catalysis residues in common with members of the mammalian deoxyribonuclease I (DNase I) family. The purpose of the present study was to characterize CdtB nuclease. To establish optimal digestion conditions and to evaluate co-factor requirements, a novel and sensitive fl uorometric assay that quantitatively determines double stranded DNA digestion was developed. Although the Ca2+- and Mg2+-dependence and neutral properties of CdtB were similar to DNase I, hydrolysis of DNA by CdtB was approximately 100-fold less active than DNase I and was considerably more resistant to inhibition by ZnCl2 and G-actin

$Research paper thumbnail of Ileocolitis Associated with \u3ci\u3eAnaerobiospirillum\u3c/i\u3e in Cats$

Ileocolitis associated with spiral bacteria identified as an Anaerobiospirillum sp. was found in ... more Ileocolitis associated with spiral bacteria identified as an Anaerobiospirillum sp. was found in six cats. Two cats had acute onset of gastrointestinal signs characterized by vomiting and diarrhea in one cat and vomiting in another cat, one cat had chronic diarrhea that was refractory to medical therapy; one cat had acute onset of anorexia and lethargy, and two cats had clinical signs that were not related to the gastrointestinal tract. The presence of an Anaerobiospirillum sp. was demonstrated on the basis of ultrastructural morphology of spiral bacteria associated with intestinal lesions and PCR amplification of a genus-specific 16S rRNA gene from affected tissues from each cat. The colons of three clinically healthy cats without lesions and one cat with mild colitis not associated with spiral bacteria were negative for Anaerobiospirillum spp. in the same assay. Comparative nucleotide sequence analysis of cloned PCR products from three affected cats further suggested that the spir...

$Research paper thumbnail of Enhanced pathogenicity of \u3ci\u3eCandida albicans \u3c/i\u3epre-treated with subinhibitory concentrations of fluconazole in a mouse model of disseminated candidiasis$

Objectives: To investigate the relative pathogenicity of Candida albicans treated with subinhibit... more Objectives: To investigate the relative pathogenicity of Candida albicans treated with subinhibitory concentrations of fluconazole in a mouse model of disseminated candidiasis. Previous studies indicate that these cells secrete 10 times more farnesol than do untreated cells. In our usage, subinhibitory means a concentration which causes a prominent decrease in turbidity but still allows some cell growth. Methods: C. albicans A72 cells were grown overnight in 0–5.0 mM fluconazole, washed, and inoculated in mice by tail vein injection. Groups of 15 or 16 mice were injected with 1.3 • 106cells and mortality was recorded for 7 days post-inoculation. The levels of farnesol in control and treated C. albicans were determined by GC/MS. Results: The MIC50 for strain A72 was 0.125 mg/L (0.4 mM). Mice administered C. albicans pre-treated with 0.5 to 1.0mMfluconazole died 2.5 to 4 days earlier and had 2 to 4 times higher mortality rates than mice given untreated C. albicans. Fluconazole (0.5 to...

2nd International Conference on Colonic Spirochaetal Infections in Animals and Humans, 2003

Canine enteric coronavirus (CCoV) is an alphacoronavirus infecting dogs that is closely related t... more Canine enteric coronavirus (CCoV) is an alphacoronavirus infecting dogs that is closely related to enteric coronaviruses of cats and pigs. While CCoV has traditionally caused mild gastro-intestinal clinical signs, there are increasing reports of lethal CCoV infections in dogs, with evidence of both gastrointestinal and systemic viral dissemination. Consequently, CCoV is now considered to be an emerging infectious disease of dogs. In addition to the two known serotypes of CCoV, novel recombinant variants of CCoV have been found containing spike protein N-terminal domains (NTDs) that are closely related to those of feline and porcine strains. The increase in disease severity in dogs and the emergence of novel CCoVs can be attributed to the high level of recombination within the spike gene that can occur during infection by more than one CCoV type in the same host.

Four canine weakly β-hemolytic intestinal spirochetes associated with intestinal spirochetosis (I... more Four canine weakly β-hemolytic intestinal spirochetes associated with intestinal spirochetosis (IS-associated WBHIS) were compared with IS-associated human and porcine WBHIS and the type species for Serpulina hyodysenteriae and S. innocens by using phenotypic and genotypic parameters. The IS-associated canine, human, and porcine WBHIS belonged to a phyletic group distinct from but related to previously described Serpulina type species

Lincoln cooperating with the Co unties and the United States Department of Agriculture. Un ivers ... more Lincoln cooperating with the Co unties and the United States Department of Agriculture. Un ivers ity of Nebras ka-Lincoln Extension educa tional programs abide with the nondiscrimination policies of the Un iversity of Neb raska-Lincoln and the United States Department of Agriculture.

$Research paper thumbnail of \\u3ci\\u3eLegionella pneumophila \\u3c/i\\u3eEntry Gene \\u3ci\\u3ertxA\\u3c/i\\u3e Is Involved in Virulence$

Successful parasitism of host cells by intracellular pathogens involves adherence, entry, surviva... more Successful parasitism of host cells by intracellular pathogens involves adherence, entry, survival, intracellular replication, and cell-to-cell spread. Our laboratory has been examining the role of early events, adherence and entry, in the pathogenesis of the facultative intracellular pathogen Legionella pneumophila. Currently, the mechanisms used by L. pneumophila to gain access to the intracellular environment are not well understood. We have recently isolated three loci, designated enh1, enh2, and enh3, that are involved in the ability of L. pneumophila to enter host cells. One of the genes present in the enh1 locus, rtxA, is homologous to repeats in structural toxin genes (RTX) found in many bacterial pathogens. RTX proteins from other bacterial species are commonly cytotoxic, and some of them have been shown to bind to β2 integrin receptors. In the current study, we demonstrate that the L. pneumophila rtxA gene is involved in adherence, cytotoxicity, and pore formation in addit...

Large Animal Internal Medicine, 2020

Journal of the American Veterinary Medical Association, 2022

CASE DESCRIPTION Outbreaks of sudden death in apparently healthy weaned dairy calves due to Stron... more CASE DESCRIPTION Outbreaks of sudden death in apparently healthy weaned dairy calves due to Strongyloides papillosus parasitism were diagnosed on 2 separate and independent New York (NY) dairies. CLINICAL FINDINGS Most calves were found dead; however, 1 calf observed while dying showed signs of tachycardia, tachypnea, vocalization, and convulsions shortly before death. In 6 affected heifers that underwent post-mortem examination, precocious bilaterally symmetric mammary gland enlargement was seen. A portion of their parasitized living cohorts also demonstrated similar mammary gland enlargement. A diagnosis of S papillosus hyperinfection was made based upon the presence of high numbers of S papillosus ova in feces, and confirmation by S papillosus–specific PCR assays. Consistent histopathological findings in affected calves included generalized mammary gland vascular congestion, interstitial edema and hemorrhage with ductal hyperplasia. Mild multifocal cardiomyocyte degeneration was ...

This article cites 46 articles, 30 of which can be accessed free

Sel1L is an adaptor protein for the E3 ligase Hrd1 involved in endoplasmic reticulum-associated d... more Sel1L is an adaptor protein for the E3 ligase Hrd1 involved in endoplasmic reticulum-associated degradation (ERAD). Its physiological importance in mammalian ERAD, however, remains to be established. Here, using the inducible Sel1L knockout mouse and cell models, we provide the first in vivo evidence that Sel1L is indispensable for Hrd1 stability, ER homeostasis and survival. Acute loss of Sel1L leads to premature death in adult mice within 3 weeks with profound pancreatic atrophy. Contrary to current belief, our data show that mammalian Sel1L is required for Hrd1 stability and ERAD function both in vitro and in vivo. Sel1L deficiency disturbs ER homeostasis, activates ER stress, attenuates translation and promotes cell death. Serendipitously, using biochemical approach coupled with mass spectrometry, we found that Sel1L deficiency causes the aggregation of both small and large ribosomal subunits. Thus, Sel1L is an indispensable component of mammalian ERAD and ER homeostasis, which ...

bioRxiv, 2021

Intestinal lacteals are the essential lymphatic channels for absorption and transport of dietary ... more Intestinal lacteals are the essential lymphatic channels for absorption and transport of dietary lipids and drive pathogenesis of debilitating metabolic diseases. Yet, organ-specific mechanisms linking lymphatic dysfunction to disease etiology remain largely unknown. In this study, we uncover a novel intestinal lymphatic program that is linked to the left-right (LR) asymmetric transcription factor Pitx2. We show that deletion of the asymmetric Pitx2 enhancer, ASE, alters normal lacteal development through the lacteal-associated contractile smooth muscle lineage. ASE deletion leads to abnormal muscle morphogenesis induced by oxidative stress, resulting in impaired lacteal extension and defective lymphatic-dependent lipid transport. Surprisingly, activation of lymphatic-independent trafficking directs dietary lipids from the gut directly to the liver, causing diet-induced fatty liver disease. In summary, our studies reveal the molecular mechanism linking gut lymphatic development to t...

Journal of Comparative Pathology, 2018

Journal of clinical microbiology, 1995

Four canine weakly beta-hemolytic intestinal spirochetes associated with intestinal spirochetosis... more Four canine weakly beta-hemolytic intestinal spirochetes associated with intestinal spirochetosis (IS-associated WBHIS) were compared with IS-associated human and porcine WBHIS and the type species for Serpulina hyodysenteriae and S. innocens by using phenotypic and genotypic parameters. The IS-associated canine, human, and porcine WBHIS belonged to a phyletic group distinct from but related to previously described Serpulina type species.

Journal of the American Veterinary Medical Association, 2019