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Biomedical subjects

P Hartman

Publications and source records attributed to P Hartman.

At least 19 recordsLinked to original sources
PubMed2004

Modeling of Escherichia coli inactivation by UV irradiation at different pH values in apple cider.

This study examined the effects and interactions of UV light dose (1,800 to 20,331 microJ/cm2) and apple cider pH (2.99 to 4.41) on the inactivation of Escherichia coli ATCC 25922, a surrogate for E. coli O157:H7. A predictive model was developed to relate the log reduction factor of E. coli ATCC 25922 to the UV dose. Bacterial populations for treated and untreated samples were enumerated with the use of nonselective media. The results revealed that UV dose was highly significant in the inactivation of E. coli, whereas pH showed no significant effect at higher UV doses. Doses of 6,500 microJ/cm2 or more were sufficient to achieve a greater than 5-log reduction of E. coli. Experimental inactivation data were fitted adequately by a logistic regression model. UV irradiation is an attractive alternative to conventional methods for reducing bacteria in unpasteurized apple cider.

Beverages↗
PubMed2000

Effects of caffeine on sensorimotor gating of the startle reflex in normal control subjects: impact of caffeine intake and withdrawal.

RATIONALE: Prepulse inhibition (PPI), a cross-species measure of sensorimotor gating, is impaired in certain neuropsychiatric disorders. This study was designed to assess caffeine effects on PPI in normal humans, as part of an effort to understand cross-species differences and similarities in the neurochemical regulation of PPI. METHODS: Startle was measured during a screening session; 7 days later, subjects were retested after placebo or caffeine (200 mg; double-blind design). Subjects were characterized as low versus high caffeine drinkers based on established scales (range 11-628 mg/day), and either maintained ad libitum caffeine intake (Ad lib study; n=18) or refrained from caffeine consumption for > or =15 h prior to testing (Withdrawal study; n=12). Autonomic and self-rating measures, acoustic and tactile startle, and unimodal and cross-modal PPI, were measured in divided sessions for 3 h post-treatment. RESULTS: There were significant effects of caffeine and/or caffeine withdrawal on several self-rating and autonomic measures, and on startle reflex habituation, but not on acoustic or tactile startle magnitude or PPI. Difference scores of startle data from screening versus test days revealed no group effects on startle magnitude, but PPI difference scores revealed that caffeine had opposite effects on low versus high caffeine drinkers (means=57 versus 258 mg/day) in the two withdrawal states. In the absence of withdrawal, caffeine reduced PPI in heavy caffeine drinkers; during withdrawal, caffeine increased PPI in heavy caffeine drinkers. The opposite pattern was evident in low caffeine drinkers. CONCLUSIONS: While a physiologically active dose of caffeine has no simple effects on PPI in normal humans, both withdrawal states and normal levels of caffeine consumption may be important factors in understanding this drug's effects on sensorimotor gating.

Adolescent↗
PubMed1997

The characterization and description of representatives of 'G' bacteria from activated sludge plants.

The name Tetracoccus cechii is proposed for two strains of the tetrad arranged cocci, previously known as 'G' bacteria, which were isolated from laboratory scale activated sludge plants in the Czech Republic and in Italy. They were morphologically, phenotypically and phylogenetically characterized and found to comprise a novel lineage in the alpha-3 group of the proteobacterial phylum in the domain Bacteria. The strains are Gram-negative and produce intracellular inclusions of poly-beta-hydroxybutyrate. Although commonly seen in activated sludge mixed liquor as cocci 1-2 microns in diameter, arranged in tetrads, in pure culture they can also grow in amorphous aggregations and the cells are generally more variable in their size and shape with coccobacilli as well as cocci being present. They are not able to grow phototrophically, nor can they reduce nitrate beyond nitrite nor grow anaerobically. The closest phylogenetic neighbours of T. cechii are Rhodobacter sphaeroides and R. capsulatus which are 93% similar by 16S rDNA comparison. Tetracoccus cechii is oxidase- and catalase-positive, non-motile and has an optimal growth temperature between 25 degrees and 35 degrees C. The 16S rRNA of T. cechii has a 21 nucleotide deletion in the V9 region (Escherichia coli positions 1258-1278) and this feature is a unique molecular synapomorphy in the alpha-3 group.

Base Sequence↗
PubMed1997

Morphological and compositional shifts in an experimental bacterial community influenced by protists with contrasting feeding modes.

In a two-stage continuous-flow system, we studied the impacts of different protozoan feeding modes on the morphology and taxonomic structure of mixed bacterial consortia, which were utilizing organic carbon released by a pure culture of a Rhodomonas sp. grown on inorganic medium in the first stage of the system. Two of three second stages operated in parallel were inoculated by a bacterivorous flagellate, Bodo saltans, and an algivorous ciliate, Urotricha furcata, respectively. The third vessel served as a control. In two experiments, where algal and bacterial populations grew at rates and densities typical for eutrophic waters, we compared community changes of bacteria, algae, and protozoa under quasi-steady-state conditions and during the transient stage after the protozoan inoculation. In situ hybridization with fluorescent oligonucleotide probes and cultivation-based approaches were used to tentatively analyze the bacterial community composition. Initially the cell size distribution and community structure of all cultivation vessels showed similar patterns, with a dominance of 1- to 2.5-(mu)m-long rods from the beta subdivision of the phylum Proteobacteria ((beta)-Proteobacteria). Inoculation with the ciliate increased bacterial growth in this substrate-controlled variant, seemingly via a recycling of nutrients and substrate released by grazing on algae, but without any detectable effect on the composition of bacterial assemblage. In contrast, an inoculation with the bacterivore, B. saltans, resulted in a decreased proportion of the (beta)-Proteobacteria. One part of the assemblage (<4% of total bacterial numbers), moreover, produced large grazing-resistant threadlike cells. As B. saltans ingested only cells of <3 (mu)m, this strategy yielded a refuge for (symbl)70% of total bacterial biomass from being grazed. Another consequence of the heavy predation in this variant was a shift to the numerical dominance of the (alpha)-Proteobacteria. The enhanced physiological status of the heavily grazed-upon segment of bacterial community resulted in a much higher proportion of CFU (mean, 88% of total bacterial counts) than with other variants, where CFU accounted for (symbl)30%. However, significant cultivation-dependent shifts of the bacterial community were observed toward (gamma)-Proteobacteria and members of the Cytophaga/Flavobacterium group, which demonstrated the rather poor agreement between cultivation-based approaches and oligonucleotide probing.

Journal Article↗
PubMed1996

The nematode Caenorhabditis elegans is up to 39 times more sensitive to gamma radiation generated from 137Cs than from 60Co.

Survival after gamma irradiation (generated from either a 137Cs or 60Co source) was determined for two strains of the nematode Caenorhabditis elegans. Animals were between 1.3 and 39 times more sensitive to cesium than to cobalt. The magnitude of this differential sensitivity was dependent upon the strain, developmental stage and sex tested. Several control experiments eliminated trivial explanations for this difference. Since cobalt- and cesium-generated gamma particles have nearly identical energy depositions, the differential sensitivity likely reflects different mechanisms of processing the slightly different spectra of DNA damage induced by these two radiations. Sex-specific differences in radiation sensitivity were also noted and were likely due to the fact that males possess a single X chromosome rather than two, as do hermaphrodites.

Animals↗
PubMed1995

Nematode development is inhibited by methyl viologen and high oxygen concentrations at a rate inversely proportional to life span.

Eight strains of C. elegans, including seven recombinant inbred (RI) strains with mean life spans ranging from 10.9 to 28.8 days, were reared under two conditions (95% oxygen or methyl viologen) known to elevate the concentration of free radicals. Both agents inhibited development, as ascertained by measuring the lengths of animals at regular intervals. The degree of inhibition correlated inversely with mean life span with both agents; that is, development of short-lived strains was inhibited more profoundly than was development of long-lived strains. Thus, at least some of the polygenes which prominently influence aging are the same as those which control resistance to free radicals. These genes likely influence aging and response to oxidative stress in many ways, both direct and indirect.

Animals↗
PubMed1993

Application of the periodic bond chain (PBC) theory and attachment energy consideration to derive the crystal morphology of hexamethylmelamine.

The habit (external morphology) of a crystal is controlled by both the external (environmental) conditions of crystallization and the internal (structural) factors of the crystal. In order to separate the effects of the crystal structure and of the solvent and other external factors on the experimentally observed growth habit, the theoretical habit can be derived from the crystal structure using the periodic bond chain (PBC) theory and attachment energy considerations. According to the PBC theory the crystal habit is governed by a set of uninterrupted chains of strong bonds formed in the crystal lattice. In addition, the attachment energy (E(att)) is defined as the energy released per mole when a new layer is deposited on a crystal face. Since the habit of a crystal is determined by the relative growth rate (R) of the various faces, by taking R proportional to E(att), the theoretical habit can thus be derived from E(att). Using this approach, we obtained the theoretical crystal habit of an antitumor drug, hexamethylmelamine (HMM). The possible effect of solvents on the habit modification of HMM is discussed. This technique, based purely on the knowledge of the crystal structure, is directly applicable to other pharmaceuticals in deriving their theoretical crystal habit.

Altretamine↗
PubMed1993

4-Methylumbelliferyl-beta-N-Acetylglucosaminide Hydrolysis by a High-Affinity Enzyme, a Putative Marker of Protozoan Bacterivory.

Hydrolysis of an artificial fluorogenic substrate, 4-methylumbelliferyl-beta-N-acetylglucosaminide, has been studied in a monoculture predator-prey system with either a flagellate (Bodo saltans) or a ciliate (Cyclidium sp.) fed upon pure bacterial culture (Aeromonas hydrophila or Alcaligenes xylosoxidans). Aeromonas hydrophila produced a low-affinity beta-N-acetylglucosaminidase-like enzyme (K(m), >>100 mumol liter) but Alcaligenes xylosoxidans did not. Inoculation of both bacterial strains with bacterivorous protozoa induced the occurrence of another, high-affinity, beta-N-acetylglucosaminidase-like enzyme (K(m), <0.5 mumol liter). The latter enzyme showed significant, close correlations with total grazing rates of both B. saltans (r = 0.96) and Cyclidium sp. (r = 0.89) estimated by using uptake of fluorescently labelled bacteria. Further significant correlations between several protozoan parameters and kinetic parameters of this enzyme suggest its likely protozoan origin. If both types of enzyme occurred together, they could be satisfactorily distinguished by using kinetic data analysis. Hence, measurements of beta-N-acetylglucosaminidase-like activities might be promising to use to improve estimations of protozoan bacterivory.

Journal Article↗
PubMed1991

Does trans-lesion synthesis explain the UV-radiation resistance of DNA synthesis in C. elegans embryos?

Over 10-fold larger fluences were required to inhibit both DNA synthesis and cell division in wild-type C. elegans embryos as compared with other model systems or C. elegans rad mutants. In addition, unlike in other organisms, the molecular weight of daughter DNA strands was reduced only after large, superlethal fluences. The molecular weight of nascent DNA fragments exceeded the interdimer distance by up to 19-fold, indicating that C. elegans embryos can replicate through non-instructional lesions. This putative trans-lesion synthetic capability may explain the refractory nature of UV radiation on embryonic DNA synthesis and nuclear division in C. elegans.

Animals↗
PubMed1988

Elevated levels of PA IgG in thrombocytopenic patients are not related to the presence of microthrombocytes or megathrombocytes.

Platelet-associated (PA) IgG levels were measured on peripheral blood samples from 63 thrombocytopenic patients with the use of fluorescein isothiocyanate (FITC)-conjugated anti-IgG antibody. Test specificity was investigated by examining the influence of variables such as the platelet count in platelet-rich plasma (PRP), platelet loss after the assay procedure, and platelet size distribution (including the percentage of microthrombocytes and megathrombocytes) on the PA IgG levels. Additionally, PA IgG levels were compared with PA albumin levels and with levels of nonspecific adherence of FITC anti-IgG by the platelets to ascertain if elevated levels were specific. Elevated PA IgG levels showed only significant correlations (P less than 0.05) with a mean platelet size below normal range and to increased PA albumin levels but not to PRP count, platelet loss after assay procedure, the percentage of microthrombocytes and megathrombocytes, and nonspecific adherence of FITC anti-IgG.

Albumins↗
PubMed1988

Increased levels of platelet associated IgG in patients with thrombocytopenia are not confined to any particular size class of platelets.

Patients with immune thrombocytopenia have an increased percentage of microthrombocytes/platelet fragments and megathrombocytes. It has been suggested that increased levels of platelet associated IgG (PA-IgG) found in these patients might be related to the presence of this abnormal platelet size distribution. In this study we used flow cytometry to investigate the distribution of PA-IgG within a population of platelets and, in particular, we examined the relationship between platelet size and PA-IgG determined simultaneously on individual platelets. Platelet samples from 10 normals and 31 thrombocytopenic patients were studied. PA-IgG was estimated using immunofluorescent FITC anti-IgG antibody. Binding of FITC anti-IgG to the platelets was quantitated in the flow cytometer as relative mean fluorescence (RMF) which was calibrated against values (in fg/plt of FITC anti-IgG) obtained by spectrofluorometry after solubilization of the platelets. A high correlation (r = 0.89) was found between flow cytometric RMF value and spectrofluorometric FITC anti-IgG values. The flow cytometric studies showed that platelet samples with abnormally elevated levels of FITC anti-IgG (greater than 1.7 fg/plt) not only have a higher percentage of platelets with elevated FITC anti-IgG, but that these platelets also have increased levels of FITC anti-IgG as compared to platelets from normal samples. Platelet size was measured by the amount of forward light scatter in the flow cytometer. A low but significant correlation (r = 0.33 +/- 0.12) was found between size (FALS) and fluorescent signals in samples with elevated FITC anti-IgG. The contribution of 10% of the smallest platelets by FALS and 10% of the largest platelets by FALS to the total levels of flow cytometer platelet fluorescence in these samples was only 4.4% and 19.4% respectively which was not higher than obtained with samples with normal levels of FITC anti-IgG. In conclusion, this study showed that increased levels of PA-IgG found among thrombocytopenic patients were not confined to any particular size class of platelets.

Blood Platelets↗
PubMed1988

Isolation and identification of a morpholine-degrading bacterium.

A gram-positive, slowly growing rod effectively utilizing morpholine as the sole source of organic carbon, nitrogen, and energy was isolated from a mixed culture in a laboratory reactor. The strain was tentatively identified as Mycobacterium aurum. Its growth characteristics at 20 degrees C and pH 6.5 were as follows: maximum specific growth rate, 0.052 h-1; half-velocity constant, 1.3 mg/liter; and yield, 0.37 g/g. The optimum temperature and pH were 31 degrees C and 6.0, respectively.

Biodegradation, Environmental↗
PubMed1988

Light scatter and total protein signal distribution of platelets by flow cytometry as parameters of size.

The use of flow cytometry for determination of platelet size was investigated by measurement of forward-angle light-scatter (FALS) signals and the fluorescent right-angle signals from platelets incubated with the fluorescent protein dye fluorescein isothiocyanate (FITC). Both FALS and fluorescence signals displayed a unimodal log normal pattern of distributions that were almost identical to distributions obtained by resistive particle sizing. As measured on 12 platelet samples from normal individuals, FALS, FITC, and resistive particle size data exhibited a high degree of fit to log normal distributions as shown by the coefficients of determination (R2), which were 0.9962 +/- 0.0035, 0.9966 +/- 0.0056, and 0.9987 +/- 0.0012, respectively. The geometric standard deviation (GSD), reflecting the heterogeneity of the FALS, FITC, and resistive particle size signals, was almost identical: 1.69 +/- 0.03, 1.67 +/- 0.04, and 1.69 +/- 0.02, respectively, for spherical platelets from normal individuals. Platelet FALS signal distributions were compared with Coulter resistive particle size distributions by using platelet samples from 12 normal patients and 27 patients with thrombocytopenia. Significant correlation was found between mean FALS and mean resistive particle size (r = 0.83) and between GSD of FALS and GSD of resistive particle size (r = 0.74) with the platelet samples from the 39 subjects studied. These studies, which document the high degree of correspondence among these three independent measurements of platelet size, based on three entirely different principles, strongly suggest that platelet size is log normal distributed and that the GSD value shown above reflects actual heterogeneity in size. The FALS signal distribution was, however, found to be markedly influenced by changes in platelet shape and internal structure.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1984

Use of Adsol preservation solution for prolonged storage of low viscosity AS-1 red blood cells.

A new red cell preservation solution is described in which the red cells may be stored for 49 d with greater than 75% mean post-transfusion recovery. Blood is drawn into Anticoagulant Citrate Phosphate Dextrose Solution, centrifuged, the plasma removed and the cells resuspended in 100 ml of a solution containing saline, adenine, dextrose and mannitol (Adsol Preservation Solution, Fenwal Laboratories, Deerfield, Illinois). The final product, AS-1 Red Blood Cells, has a haematocrit of approximately 0.60 and flow properties that are similar to those of whole blood. After storage, red cell haemolysis is minimal and erythrocyte adenosine triphosphate is well preserved. This study documents that red cells may be stored in a protein-poor electrolyte medium for periods of 49 d with good post-transfusion survival.

Adenine↗
PubMed1982

Radiology information system--let's phase it.

This article describes the phases of the Systems Development Life Cycle for Information Systems: evaluation and recommendation, scope, user specifications, engineering, programming and implementation, and post-implementation review. This methodology provides a means to approach the development process in an organized, logical fashion, providing checkpoints and cost/benefit data throughout.

Computers↗
PubMed1982

Endogenous synthesis of volatile nitrosamines: model calculations and risk assessment.

A kinetic model for estimating the gastric synthesis of N-nitroso compounds and a method for estimating the risk from exposure to volatile nitrosamines are described. A tentative calculation of the possible risks for human gastric cancer, based on extrapolating from literature data on the induction of tumours in rats, suggests that the endogenous formation of non-volatile N-nitroso compounds is more important than that of volatile nitrosamines.

Food Analysis↗