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Biomedical subjects

L J Harris

Publications and source records attributed to L J Harris.

At least 19 recordsLinked to original sources
PubMed2006

A novel gene cluster in Fusarium graminearum contains a gene that contributes to butenolide synthesis.

The development of expressed sequence tag (EST) databases, directed transformation and a sequenced genome has facilitated the functional analysis of Fusarium graminearum genes. Extensive analysis of 10,397 ESTs, derived from thirteen cDNA libraries of F. graminearum grown under diverse conditions, identified a novel cluster of eight genes (gene loci fg08077-fg08084) located within a 17kb region of genomic sequence contig 1.324. The expression of these genes is concomitantly up-regulated under growth conditions that promote mycotoxin production. Gene disruption and add-back experiments followed by metabolite analysis of the transformants indicated that one of the genes, fg08079, is involved in butenolide synthesis. The mycotoxin butenolide is produced by several Fusarium species and has been suggested, but not proven, to be associated with tall fescue toxicoses in grazing cattle. This is the first report of the identification of a gene involved in the biosynthetic pathway of butenolide.

4-Butyrolactone↗
PubMed2005

The maize An2 gene is induced by Fusarium attack and encodes an ent-copalyl diphosphate synthase.

Using the technique of differential display, a maize transcript was identified whose silk tissue expression is induced in the presence of the ear rot pathogen Fusarium graminearum. The 3445 nt transcript includes a 727 nt 5' untranslated leader with the potential for extensive secondary structure and represents the maize gene An2. An2 encodes a copalyl diphosphate synthase (CPS)-like protein with 60% amino acid sequence identity with the maize An1 gene product involved in gibberellin (GA) biosynthesis. Recombinant expression and functional analysis demonstrated that both AN1 and AN2 are ent-copalyl diphosphate (ent-CPP) synthases (ent-CPS). Notably, the presence of an additional ent-CPS gene is consistent with previous reports that maize GA biosynthesis can proceed in the absence of An1. In addition, northern blot analysis showed that An2 transcript levels were strongly up-regulated by Fusarium attack, with an increase in silk, husk and ear tip tissues as early as 6 h after inoculation of silk channels with spore suspensions of various Fusarium sp. Gene expression of a third maize CPS-like gene, Cpsl1, is not affected by Fusarium infection. The Fusarium-inducible nature of An2 is also consistent with a previous report that cell-free extracts from maize seedlings produce ent-CPP derived diterpenes in response to Fusarium infection. However, it is not known whether An2 is involved in defense-related secondary metabolism in addition to GA synthesis.

5' Untranslated Regions↗
PubMed2005

An international outbreak of salmonellosis associated with raw almonds contaminated with a rare phage type of Salmonella enteritidis.

During the winter of 2000 to 2001, an outbreak due to Salmonella Enteritidis (SE) phage type 30 (PT30), a rare strain, was detected in Canada. The ensuing investigation involved Canadian and American public health and food regulatory agencies and an academic research laboratory. Enhanced laboratory surveillance, including phage typing and pulsed-field gel electrophoresis, was used to identify cases. Case questionnaires were administered to collect information about food and environmental exposures. A case-control study with 16 matched case-control pairs was conducted to test the hypothesis of an association between raw whole almond consumption and infection. Almond samples were collected from case homes, retail outlets, and the implicated processor, and environmental samples were collected from processing equipment and associated farms for microbiological testing. One hundred sixty-eight laboratory-confirmed cases of SE PT30 infection (157 in Canada, 11 in the United States) were identified between October 2000 and July 2001. The case-control study identified raw whole almonds as the source of infection (odds ration, 21.1; 95% confidence interval, 3.6 to infinity). SE PT30 was detected in raw whole natural almonds collected from home, retail, distribution, and warehouse sources and from environmental swabs of processing equipment and associated farmers' orchards. The frequent and prolonged recovery of this specific organism from a large agricultural area was an unexpected finding and may indicate significant diffuse contamination on these farms. Identification of almonds as the source of a foodborne outbreak is a previously undocumented finding, leading to a North American recall of this product and a review of current industry practices.

Adolescent↗
PubMed2004

Tri1 in Fusarium graminearum encodes a P450 oxygenase.

Gibberella zeae (asexual state Fusarium graminearum) is a major causal agent of wheat head blight and maize ear rot in North America and is responsible for contamination of grain with deoxynivalenol and related trichothecene mycotoxins. To identify additional trichothecene biosynthetic genes, cDNA libraries were prepared from fungal cultures under trichothecene-inducing conditions in culture and in planta. A gene designated LH1 that was highly expressed under these conditions exhibited only moderate (59%) similarity to known trichothecene biosynthetic cytochrome P450s. To determine the function of LH1, gene disruptants were produced and assessed for trichothecene production. Gene disruptants no longer produced 15-acetyldeoxynivalenol, which is oxygenated at carbon 7 (C-7) and C-8, but rather accumulated calonectrin and 3-deacetylcalonectrin, which are not oxygenated at either C-7 or C-8. These results indicate that gene LH1 encodes a cytochrome P450 responsible for oxygenation at one or both of these positions. Despite the relatively low level of DNA and amino acid sequence similarity between the two genes, LH1 from G. zeae is the probable homologue of Tri1, which encodes a cytochrome P450 required for C-8 oxygenation in F. sporotrichioides.

Base Sequence↗
PubMed2002

Invasion of vascular cells in vitro by Porphyromonas endodontalis.

AIM: The objective of this study was to determine whether laboratory strains and clinical isolates of microorganisms associated with root canal infections can invade primary cultures of cardiovascular cells. METHODOLOGY: Quantitative levels of bacterial invasion of human coronary artery endothelial cells (HCAEC) and coronary artery smooth muscle cells (CASMC) were measured using a standard antibiotic protection assay. Transmission electron microscopy was used to confirm and visualize internalization within the vascular cells. RESULTS: Of the laboratory and clinical strains tested, only P. endodontalis ATCC 35406 was invasive in an antibiotic protection assay using HCAEC and CASMC. Invasion of P. endodontalis ATCC 35406 was confirmed by transmission electron microscopy. DISCUSSION: Certain microorganisms associated with endodontic infections are invasive. If bacterial invasion of the vasculature contributes to the pathogenesis of cardiovascular disease, then microorganisms in the pulp chamber represent potential pathogens.

Bacteroidaceae Infections↗
PubMed2001

The effects of freezing and thawing on the survival of Escherichia coli O157:H7 in apple juice.

Unpasteurized apple juice, adjusted to pH 3.6 to 7.0 was inoculated (10(7) CFU/ml) with single strains of E. coli O157:H7 to evaluate the effect of frozen storage on the viability of this organism. Samples were stored under frozen conditions (-20+/-2 degrees C) for up to 16 days. Cell populations were determined at regular intervals by plating onto tryptic soy agar with added pyruvate (TSAP) or onto sorbitol MacConkey agar (SMA). Populations in the neutralized juice remained unchanged during frozen storage. Populations in non-neutralized juice decreased by 1-3 log10 CFU/ml depending on the strain tested and the pH of the juice. The greatest population decrease was observed with the first freeze/thaw cycle of frozen storage (24 h) and a slow decline in survival occurred thereafter. Injury was observed after 2 weeks of storage when juice pH was at or below pH 4.2. When samples were subjected to multiple freeze/thaw cycles, loss of viability and injury increased with each freeze/thaw cycle.

Beverages↗
PubMed2001

Do unilateral right and left face contractions induce positive and negative emotions? A further test of Schiff and Lamon's (1989) hypothesis.

Schiff and Lamon (1989) proposed that unilateral face contractions induce positive or negative changes in emotion depending on the side of contraction; support for this proposal, however, has been mixed. In a new test, 40 right-handed and 38 left-handed men performed four alternating face contractions (LRLR or RLRL) and, after each one, completed a different version of the Depression Adjective Checklist (Lubin, 1994). A repeated-measures ANCOVA failed to reveal any significant effect of side of face contraction or handedness on direction of emotion change. Instead, regardless of side of contraction, the subjects' negative emotional state increased significantly across the four contractions with the degree of change being significantly related to the subjects' reported level of difficulty in holding the contraction irrespective of whether the more difficult side was the left or the right.

Adult↗
PubMed2001

Efficacy and reproducibility of a produce wash in killing Salmonella on the surface of tomatoes assessed with a proposed standard method for produce sanitizers.

The reproducibility of a method developed to evaluate point-of-use sanitizers for fresh produce was tested at three different laboratories. Mixtures of five Salmonella serotypes were inoculated on the surface of ripe tomatoes. After the inoculum was dry, tomatoes were placed inside a plastic bag and sprayed with sterile USP water, Dey and Engley (D/E) neutralizer broth, or a prototype Fit produce wash (PW), an alkaline solution comprised of generally recognized as safe ingredients (water, oleic acid, glycerol, ethanol, potassium hydroxide, sodium bicarbonate, citric acid, and distilled grapefruit oil), and rubbed for 30 s. The tomatoes were rinsed 10 s with 195 ml of D/E neutralizer broth (rinse solution), then combined with 20 ml of D/E neutralizer (residual wash solution) and rubbed by hand to remove residual Salmonella. Populations of Salmonella were determined for each tomato in the rinse solution and residual wash solution. Treatment with PW resulted in reductions in the number of Salmonella 2 to 4 logs greater than those achieved with the sterile water or D/E neutralizer broth controls. Consistent results were obtained across the three study sites, indicating reproducible results were obtained using the test method. The method used to determine the efficacy of killing or removing Salmonella from tomatoes in this study is suggested as a standard method for measuring the efficacy of sanitizers on tomatoes and other similar fruits and vegetables with rigid, smooth surfaces.

Colony Count, Microbial↗
PubMed2001

Survival of Salmonella spp. and Escherichia coli O157:H7 on fresh and frozen strawberries.

For maximum shelf life, fresh strawberries are harvested directly without washing into retail containers. Frozen berries are usually hulled in the field and washed prior to freezing, sometimes with the addition of sucrose. To determine survival of potential bacterial contaminants, cut or intact surfaces of fresh strawberries were spot inoculated with five- or six-strain cocktails of Salmonella or Escherichia coli O157:H7 (log 7.0 CFU/sample). Inoculated strawberries were dried for 1 h at 24 degrees C and were stored in closed containers at 5 or 24 degrees C. Sliced strawberries with or without added 20% sucrose were inoculated with one of two strains of E. coli O157:H7 and frozen at -20 degrees C. An initial population reduction of approximately 0.5-log cycles was observed on intact but not cut berries after the 1-h drying period. During storage at 24 degrees C for up to 48 h, populations of Salmonella and E. coli O157:H7 did not decline further. When strawberries were stored at 5 degrees C for up to 7 days, populations of both pathogens remained constant on cut surfaces but decreased by 1 - to 2-log cycles on intact surfaces. After 30 days of frozen storage, the population of E. coli O157:H7 had declined by 0.7- to 2.2-log cycles (with and without sucrose, respectively). Results of this study indicate that E. coli O157:H7 and Salmonella are capable of survival but not growth on the surface of fresh strawberries throughout the expected shelf life of the fruit and can survive in frozen strawberries for periods of greater than 1 month.

Colony Count, Microbial↗
PubMed2001

Standardization of a method to determine the efficacy of sanitizers in inactivating human pathogenic microorganisms on raw fruits and vegetables.

The efficacy of sanitizers in killing human pathogenic microorganisms on a wide range of whole and fresh-cut fruits and vegetables has been studied extensively. Numerous challenge studies to determine the effects of storage conditions on survival and growth of pathogens on raw produce have also been reported. Results of these studies are often difficult to assess because of the lack of sufficient reporting of methods or, comparatively, because of variations in procedures for preparing and applying inocula to produce, conditions for treatment and storage, and procedures for enumerating pathogens. There is a need for a standard method to accurately determine the presence and populations of pathogenic microorganisms on produce. The adoption of standard, well-characterized reference strains would benefit a comparative assessment of a basic method among laboratories. A single protocol will not be suitable for all fruits and vegetables. Modifications of a basic method will be necessary to achieve maximum recovery of pathogens on various types of produce subjected to different sanitizer or storage treatments. This article discusses parameters that must be considered in the course of developing a basic standard method against which these modifications could be made.

Anti-Bacterial Agents↗
PubMed2001

Development of a proposed standard method for assessing the efficacy of fresh produce sanitizers.

A series of studies was done for the purpose of developing a proposed standard method to evaluate point-of-use home sanitizers for fresh produce. Preliminary experiments were done to determine the survival of Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes after inoculation onto the surface of ripe tomatoes and drying for up to 24 h at 22 +/- 2 degrees C. Within 2 h, the initial population (6.88 log10 CFU/tomato) of E. coli O157:H7 was reduced by approximately 3 log10, while reductions in similar initial populations of Salmonella and L. monocytogenes were approximately 1 and 0.6 log10 CFU/tomato, respectively, after 40 min and 3 h. A pilot study evaluated treatment with 200 ppm free chlorine and a prototype Fit produce wash (Fit) for their efficacy in killing a five-serotype mixture of Salmonella or L. monocytogenes spot inoculated on tomatoes using the proposed inoculation and recovery procedures. Inoculated tomatoes were sprayed with chlorinated water, Fit, or sterile distilled water (control) and hand rubbed for 30 s. Each tomato was then placed in a plastic bag and rinsed with 200 ml of sterile water by vigorously agitating for 30 s to simulate a procedure consumers might use for sanitizing and rinsing produce in a home setting. Each tomato was transferred to a second bag, and 20 ml of sterile 0.1% peptone was added; tomatoes were rubbed by hand for 40 s. Populations of Salmonella or L. monocytogenes in the rinse water and the 0.1% peptone wash solution were determined. Treatment with 200 ppm chlorine and Fit resulted in > or = 3.07 and > 6.83 log10 reductions, respectively, in Salmonella. Treatment with 200 ppm chlorine and Fit reduced the number of L. monocytogenes by > or = 3.33 and > or = 4.96 log10 CFU/tomato, respectively. The proposed standard method for testing the efficacy of point-of-use produce sanitizers needs to be evaluated for reproducibility of results through a larger scale series of experiments.

Chlorine↗
PubMed2001

Phosphate buffer increases recovery of Escherichia coli O157:H7 from frozen apple juice.

It is common practice to dilute food products in 0.1% peptone before microbiological analysis. However, this diluent may not be appropriate for detection of injured organisms present in acidic foods. Shelf-stable unclarified apple juice (pH 3.6) was inoculated with approximately 1 x 10(7) CFU/ml of Escherichia coli O157:H7 and held at 23 +/- 2 degrees C (control) or frozen to -20 +/- 2 degrees C for 24 h to induce injury before sampling. Unfrozen or frozen and thawed juice was diluted 1:1 or 1:10 in 0.1% (wt/vol) peptone (pH 6.1) or 0.1 M phosphate buffer (pH 7.2). Juice samples were plated onto tryptic soy agar with 0.1% (wt/vol) sodium pyruvate (TSAP) to measure survival or onto sorbitol MacConkey agar (SMA) to indicate injury. Counts on TSAP or SMA were the same for control samples held in peptone or phosphate buffer for up to 45 min. However, populations of E. coli in frozen and thawed samples declined rapidly upon dilution in 0.1% peptone. Within 20 min, E. coli underwent a >1-log10 CFU/ml reduction in viability as measured on TSAP and a >2-log10 CFU/ml reduction to below the limit of detection (1.6 or 2.3 log10 CFU/ml) on SMA. In contrast, populations of E. coli in frozen and thawed samples diluted in phosphate buffer did not decrease significantly on TSAP and decreased by <0.6 log CFU/ml on SMA during a 45-min holding period. The acidity of apple juice appears to interfere with the recovery of freeze-thaw-injured E. coli O157:H7 during sampling. Using 0.1 M phosphate buffer (pH 7.2) as a diluent results in superior recovery of these organisms on both selective and nonselective plating media.

Beverages↗
PubMed2000

Isolation and characterization of Carnobacterium, Lactococcus, and Enterococcus spp. from cooked, modified atmosphere packaged, refrigerated, poultry meat.

The microbiota of commercially produced, cooked and modified atmosphere packaged poultry meat was followed during storage at 3.5 degrees C for up to 7 weeks. The dominant microbiota consisted of Lactococcus raffinolactis (117 isolates), Carnobacterium divergens (61 isolates), Carnobacterium piscicola (11 isolates), Lactococcus garvieae (four isolates), Lactococcus lactis (one isolate) and Enterococcus faecalis (three isolates). All isolates were screened for production of bacteriocins. Only C. piscicola isolates produced an inhibitory substance active against other lactic acid bacteria and against several Listeria spp. Species-specific polymerase chain reaction (PCR) primers were used for the differentiation of Carnobacterium, L. raffinolactis, L. lactis, and L. garvieae strains associated with the modified atmosphere packaged poultry products. No false PCR products were observed with other closely related bacterial species.

Animals↗
PubMed2000

On the evolution of handedness: a speculative analysis of Darwin's views and a review of early studies of handedness in "the nearest allies of man".

Scientists today who seek clues into the evolutionary origins of human handedness make extensive use of evidence from comparative studies, that is, studies that ask whether handedness occurs in other species, especially apes and monkeys, as the Darwinian principle of continuity would seem to imply, or whether it is uniquely human. Early investigations had the same goal and drew on much the same kind of evidence. In this article, I review studies of animal handedness in the period before 1859, when Darwin published On the Origin of Species, and afterward, through the 1st decade of the 20th century. Inasmuch as Darwin's published writings contain hardly any statements about handedness and none at all about its evolution and continuity across species, I also speculate about what Darwin himself might have said on the subject. To do this, I draw on his statements on related matters, such as the form and structure of the hand and the transition from a quadrupedal to bipedal stance, on other writers' reports and opinions about handedness with which he was familiar or likely to have been familiar, and finally, on clues from his own and only statement about animal handedness in an unpublished letter. I conclude by asking whether and how early investigators, lacking any statement by Darwin on the evolution of handedness, invoked his theory of evolution and his views on related matters in the interpretation of their findings.

Animals↗
PubMed1999

Microorganisms and microbial toxins.

The primary concern in food safety issues focuses on microorganisms and microbial toxins. Effective food preservation requires that the growth and proliferation of hazardous microorganisms be well controlled, and that the presence of significant quantities of microbial toxins in foods be prevented. The traditional effective preservation methodologies, such as canning, are being supplemented by new technologies which are less destructive of the food qualities. New strategies are therefore needed to prevent the transmission of microbial contamination or to prevent the formation of microbial toxins which remain in food. This paper discusses the role of modern processing methodologies in helping protect consumers from hazards of microbial origin.

Bacterial Toxins↗
PubMed1999

Early theory and research on hemispheric specialization.

This article provides an account of early theory and research on hemispheric specialization. It begins by tracing theory and research on localization of function that set the stage for the discovery of hemispheric specialization. After that, it describes the studies of Paul Broca, John Hughlings-Jackson, and others on hemisphere specialization and reviews some of the proposed explanations for the phenomenon. It then turns to the study of hemispheric specialization and mental illness, and it ends by identifying some of the linkages between theory and research from the past and the present.

Cerebral Cortex↗
PubMed1999

Growth of Listeria monocytogenes and Yersinia enterocolitica on cooked modified-atmosphere-packaged poultry in the presence and absence of a naturally occurring microbiota.

Cooked poultry cuts were inoculated with five-strain composite mixtures of either Listeria monocytogenes or Yersinia enterocolitica (1,000 CFU/150-g piece), packaged in 44:56 CO2-N2, and stored at 3.5, 6.5, or 10 degrees C for up to 5 weeks. Both L. monocytogenes and Y. enterocolitica grew under all test conditions. The presence of a naturally occurring microbiota did not influence the growth of either pathogen. Addition of lactate with the shelf life extender ALTA 2341 lengthened the lag phases of L. monocytogenes and Y. enterocolitica but did not prevent their growth.

Animals↗