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Biomedical subjects

R Crittenden

Publications and source records attributed to R Crittenden.

At least 19 recordsLinked to original sources
PubMed2005

Probiotic research in Australia, New Zealand and the Asia-Pacific region.

Although the epicentres of probiotic research in the past decade have been Japan and Europe, researchers in the Asia-Pacific region have actively contributed to the growing understanding of the intestinal microbial ecosystem, and interactions between gut bacteria, diet and health of the human host. A number of new probiotic strains have been developed in the region that have been demonstrated to have beneficial impacts on health in animal and human trials, including improved protection against intestinal pathogens and modulation of the immune system. Probiotics targeted to animals, including aquaculture, feature heavily in many Asian countries. Developments in probiotic technologies have included microencapsulation techniques, antimicrobial production in fermented meats, and synbiotic combinations. In particular, the impact of resistant starch on the intestinal environment and fermentation by intestinal bacteria has been intensively studied and new probiotic strains selected specifically for synbiotic combinations with resistant starch. This paper provides an overview of probiotic research within Australia, New Zealand and a number of Asian countries, and lists scientists in the Asia-Pacific region involved in various aspects of probiotic research and development.

Academies and Institutes↗
PubMed2002

Gut bacteria and health foods--the European perspective.

Probiotics, prebiotics, and synbiotics aimed at improving intestinal health currently represent the largest segment of the functional foods market in Europe, Japan and Australia. Evidence continues to emerge demonstrating that these ingredients have the potential to improve human health in specific intestinal disorders. The European Commission, through its 5th Framework Programme, is presently focusing on a substantial effort in the science of the intestinal microbiota, its interaction with its host and methods to manipulate its composition and activity for the improvement of human health and well being. Eight multicentre and multidisciplinary research projects now cover a range of topics required for the development of efficacious probiotic foods, from understanding probiotic mechanisms at a molecular level; developing technologies to ensure delivery of stable products; and demonstrating safety and efficacy of specific probiotics in defined treatment targets. This concerted research effort promises to provide us with an enhanced understanding of the human intestinal microbiota's role in health and disease, and new approaches and products to tackle a variety of intestinal problems.

Digestive System↗
PubMed2001

Quality assurance criteria for probiotic bacteria.

Acid and bile stability and intestinal mucosal adhesion properties are among the criteria used to select probiotic microbes. The quality control of probiotic cultures in foods traditionally has relied solely on tests to ensure that an adequate number of viable bacteria are present in the products throughout their shelf lives. Viability is an important factor, but not the only criterion for quality assurance. To be effective, probiotic strains must retain the functional health characteristics for which they were originally selected. Such characteristics include the ability to survive transit through the stomach and small intestine and to colonize the human gastrointestinal tract. In vitro test protocols can be readily adopted to examine the maintenance of a strain's ability to tolerate acidic conditions, survive and grow in the presence of bile, and metabolize selective substrates. Molecular techniques are also available to examine strain stability. Adhesion characterization may be an important quality-control method for assessing gut barrier effects. Adhesion has been related to shortening the duration of diarrhea, immunogenic effects, competitive exclusion, and other health effects. Adhesion properties should be carefully monitored, including adhesion to intestinal cells (eg, Caco-2) and human intestinal mucus. This article outlines the types of in vitro testing that can be used to ensure quality control of functional probiotic strains.

Bacteria↗
PubMed2001

Surveying graduates of one school to determine regional workforce demand.

PURPOSE: To study the demand for physician graduates from one school in one region of the country. The use of demand as a measure of potential regional variation should be of interest to medical educators and policymakers. METHOD: All residency graduates of the University of Washington School of Medicine between 1975 and 1995 (n = 3,824) were surveyed about their ability to gain employment in a timely manner and whether they were recruiting physicians for their practices. RESULTS: The response rate was 50.29%. A non-responder survey was done using a subsample (n = 200), with a 28% return. Over 95% of the graduates had found employment in their desired specialties and locations within two years of finishing their residencies. This was the same for graduates over all years. Approximately 30% of all practices of respondents within the Northwest region were recruiting for new physicians (26% of specialty practices and 34% of generalist practices were recruiting). There was no difference between recruitment in the urban and rural practices or between respondents to the initial survey and those responding to the follow up. CONCLUSIONS: Despite a significant oversupply of specialist physicians and at least a sufficient supply of generalist physicians nationally, there appears to be a strong demand for both specialists and generalists in the Northwest region of the country. This raises questions concerning the use of national averages to inform the education policies in specific regions of the country. More validated measures of demand are needed for future studies.

Data Collection↗
PubMed2001

Adhesion of bifidobacteria to granular starch and its implications in probiotic technologies.

Adhesion of 19 Bifidobacterium strains to native maize, potato, oat, and barley starch granules was examined to investigate links between adhesion and substrate utilization and to determine if adhesion to starch could be exploited in probiotic food technologies. Starch adhesion was not characteristic of all the bifidobacteria tested. Adherent bacteria bound similarly to the different types of starch, and the binding capacity of the starch (number of bacteria per gram) correlated to the surface area of the granules. Highly adherent strains were able to hydrolyze the granular starches, but not all amylolytic strains were adherent, indicating that starch adhesion is not a prerequisite for efficient substrate utilization for all bifidobacteria. Adhesion was mediated by a cell surface protein(s). For the model organisms tested (Bifidobacterium adolescentis VTT E-001561 and Bifidobacterium pseudolongum ATCC 25526), adhesion appeared to be specific for alpha-1,4-linked glucose sugars, since adhesion was inhibited by maltose, maltodextrin, amylose, and soluble starch but not by trehalose, cellobiose, or lactose. In an in vitro gastric model, adhesion was inhibited both by the action of protease and at pH values of < or =3. Adhesion was not affected by bile, but the binding capacity of the starch was reduced by exposure to pancreatin. It may be possible to exploit adhesion of probiotic bifidobacteria to starch granules in microencapsulation technology and for synbiotic food applications.

Bacterial Adhesion↗
PubMed1999

The changing landscape of health care financing and delivery: how are rural communities and providers responding?

Rural communities have not kept pace with the recent dramatic changes in health care financing and organization. However, the Medicare provisions in the Balanced Budget Act of 1997 will require rural providers to participate in the new systems. Case studies revealed the degree of readiness for change in six rural communities and charted their progress along a continuum, as reflected in three sets of activities: the development of networking; the creation of new strategies for managing patient care; and the adoption of new methods for contracting with health insurers. Some communities had constructed highly integrated systems, whereas others were just beginning to change their billing practices; a few were signing contracts for capitated care, in contrast to those that were resisting discounts in current fee structures. These six rural areas still have considerable ground to cover before their health care organization and financing reach the levels achieved by urban communities.

Aged↗
PubMed1997

Proto-oncogene Sno expression, alternative isoforms and immediate early serum response.

The mouse Sno gene, a Ski proto-oncogene homolog, expresses two isoforms, SnoN and SnoN2 (also called sno -dE3), which differ from each other in a location downstream from the site of alternative splicing previously described in the human SNO gene. SnoN2 is missing a 138 nt coding segment present in mouse SnoN and human SNON . We have cloned and sequenced the human ortholog of mouse SnoN2 , the existence of which was predicted from conservation of the alternative splice donor site that produces the SnoN2 isoform. Mouse SnoN2 and SnoN are expressed throughout embryonic development, in neonatal muscle and in many adult tissues. SnoN2 is the major species in most tissues, but SnoN and SnoN2 are expressed at approximately equal levels in brain. In human tissues, SNON2 is the less abundantly expressed isoform. Expression of mouse SnoN and SnoN2 mRNAs is induced with immediate early kinetics upon serum stimulation of quiescent fibroblasts, even in the presence of the protein synthesis inhibitor cycloheximide, while Ski is not. Interestingly, although both isoforms of Sno are induced, SnoN2 induction is much higher than SnoN . These data are consistent with a role for Sno in the response to proliferation stimuli.

Alternative Splicing↗
PubMed1995

The ski/sno protooncogene family in hematopoietic development.

The ski/sno protooncogenes encode nuclear proteins that may act as transcription factors. We examined ski and sno mRNA expression in hemolymphopoietic lineages. The ski protooncogene is expressed in B- and T-lineage cells, mature macrophages, and mast cells. In normal murine marrow-derived progenitors analyzed by single-cell reverse transcription-polymerase chain reaction (RT-PCR), ski expression is limited to dual-lineage megakaryocyte/erythrocyte colony-starts. Expression of sno is more limited than ski in mature cells; it is expressed in T lymphopoietic cells, but not in B-lineage cells. The sno protooncogene is expressed more widely than ski in myeloid progenitors, as it is found consistently in tri-, dual-, and single-lineage progenitors. Both ski and sno are cell cycle-regulated in synchronized factor-dependent mouse myeloid cells. Expression of ski mRNA peaks in mid G1 in cells synchronized by isoleucine deprivation in the presence of growth factor, but falls off rapidly when growth factor is withdrawn. Expression of sno mRNA is maximal in early to mid G1 and then oscillates as the cells continue through cycle. These results suggest that the ski/sno protooncogenes play a role in hematopoiesis, growth factor responses, and cell cycle-regulation, with the two members of the family showing differing properties.

Animals↗
PubMed1993

Zymomonas mobilis--science and industrial application.

Zymomonas mobilis is undoubtedly one of the most unique bacterium within the microbial world. Known since 1912 under the names Termobacterium mobilis, Pseudomonas linderi, and Zymomonas mobilis, reviews on its uniqueness have been published in 1977 and 1988. The bacterium Zymomonas mobilis not only exhibits an extraordinarily uniqueness in its biochemistry, but also in its growth behavior, energy production, and response to culture conditions, as well as cultivation techniques used. This uniqueness caused great interest in the scientific, biotechnological, and industrial worlds. Its ability to couple and uncouple energy production in favor of product formation, to respond to physical and chemical environment manipulation, as well as its restricted product formation, makes it an ideal microorganism for microbial process development. This review explores the advances made since 1987, together with new developments in the pure scientific and applied commercial areas.

Carbohydrate Metabolism↗
PubMed1991

Long-term marrow cultures: human and murine systems.

The intramedullary control of marrow cell production has been a difficult area to approach experimentally. The introduction by Dr. Dexter and colleagues of long-term stromal dependent culture systems for murine marrow and the adaptation of these systems to human marrow growth have allowed for in-vitro studies of stromal dependent hemopoiesis. Despite some controversy in this area, most studies appear to show that adherent murine or human stromal cells are capable of producing a relatively large number of hemopoietic growth factors including G-CSF, GM-CSF, CSF-1, IL-6 and, at least by PCR analysis, IL-3. Other work indicates that the most primitive hemopoietic cells which appear to be multifactor responsive adhere directly to these stromal cells presumably through mediation of various adherence proteins. An early acting, multilineage factor termed hemolymphopoietic growth factor-1 (HLGF-1) has been isolated from a murine stromal cell line and may be identical to the recently described ligand for the c-kit receptor. This may represent an important early survival/maintenance factor for stem cells in this system. Studies on primitive stem cells, especially the high proliferative potential colony forming cell (HPP-CFC), indicate that they are responsive to varying combinations of growth factors and that with increasing numbers of growth factors, as studied in serum-free systems, decreasing concentrations of the factors may be biologically active. These observations altogether suggest that intramedullary hemopoiesis may be regulated by the positioning of early multifactor responsive stem cells via adherent proteins in juxtaposition to synergistically acting combinations of growth factors attached to stromal cell surfaces or the extracellular matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗