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PubMed2003

Tail profile: a more accurate system for analyzing DNA damage using the Comet assay.

The Comet assay (single cell gel electrophoresis assay) measures DNA strand breaks in individual cells. In the assay cells are embedded in agarose, lysed, and electrophoresed under low voltage, allowing migration of damaged DNA. The DNA is stained and subsequently viewed with an epifluorescent microscope. If DNA damage has occurred the electrophoresed DNA fragments appear as a diffuse tail behind the nucleus known as a "comet". Many computer-aided analysis systems are currently in use to quantify the amount of DNA damage that is represented by a comet image. Here, we present a novel method of analysis known as "tail profile". This method of analysis provides several advantages over currently employed methods, which rely primarily on the "tail moment" method of analysis. We compared the amount of DNA damage reported from both the tail profile and tail moment methods of analysis and observed a 26% (P<0.0001) increase in damage detected by tail profile across the 10-25 microm range of tail length, where the majority of the relevant comet data is concentrated. We further report that this increase in sensitivity is not only limited to assessing DNA damage, but also to gathering data from DNA repair assays. Furthermore, we demonstrate increased functionality and extended data analysis capabilities with the use of a compressed collection of images called a "comet chip" and through a visual representation of data called a "profile plot". Use of the custom macros enabled us to detect an unexpected characteristic of the electrophoretic profile, giving us novel insight into the nature of comet analysis. In addition to the increased analytical sensitivity proffered by this system, the tail profile macros are upgradeable and platform independent.

Comet Assay↗
PubMed1999

EEG spectral profile to stage Alzheimer's disease.

OBJECTIVE: The present study was undertaken to investigate whether a synoptic parameter of quantitative EEG (qEEG), such as the power spectral profile, may be used as a simple marker to stage Alzheimer's disease (AD) in the clinical setting. METHODS: To this purpose, the qEEG spectral profile was examined in 48 patients (mean age: 73 years) with probable (NINCDS-ADRDA criteria) AD, who were divided into 4 groups, according to the Global Deterioration Scale (GDS; score: 3-6). The spectral profile of each patient was expressed by the relative power of seven frequency bands (2-3.5, 4-5.5, 6-7.5, 8-9.5, 10-11.5, 12-13.5, 14-22.5 Hz). Mean values in each of the four GDS groups as well as in a control group of 18 healthy elderly subjects underwent multivariate analysis of variance. RESULTS: A normally shaped but shifted-to-the left spectral profile was found in GDS 3 group, whereas a reduced background rhythm with various increase in slow activity power characterized both GDS 4 and 5 groups. Finally, an 'exponential asymptotic' profile with the highest power in the lowest frequencies was the hallmark of GDS 6 group. Overall, the 4-5.5 Hz and the 10-11.5 Hz band powers showed the highest statistical significance in differentiating the patient groups between one another and from controls (P < 0.0001). CONCLUSIONS: These data show that spectral profile is a very simple parameter which can be used to stage the disease on a pathophysiological basis.

Aged↗
PubMed1994

Use of plasmid profile typing for surveillance of Salmonella enteritidis phage type 4 from humans, poultry and eggs.

Plasmids were found in 1022 of 1089 (94%) of drug-sensitive strains of Salmonella enteritidis phage type 4 from humans (sporadic and outbreak cases), poultry (chickens) and eggs in England and Wales in the 5-year period 1988-92 and 25 plasmid profile patterns were identified. Strains characterized by a single plasmid of 38 MDa predominated (= plasmid profile type SE 38), comprising over 90% of isolates from humans, 70% from poultry and 92% from eggs. Eleven profile types were identified in strains from humans, 21 in strains from poultry and 3 in strains from eggs. Eight of the 11 patterns identified in human isolates were found in strains from poultry and 2 in strains from eggs. In contrast 15 patterns seen in poultry were not found in strains from humans. Four percent of strains from humans and 13% from poultry did not carry the 38 MDa plasmid but all strains from eggs were found to carry this plasmid. The second most common profile type in strains isolated between 1981 and 1988 was not identified in strains isolated from 1988-92. It is concluded that plasmid profile typing is a useful method for rapid differentiation within phage type 4 of S. enteritidis but that methods which can discriminate within the predominant profile type, SE 38, are now required.

Animals↗
PubMedDate not supplied

Visual resolution with epi-retinal electrical stimulation estimated from activation profiles in cat visual cortex.

Blinds with receptor degeneration can perceive localized phosphenes in response to focal electrical epi-retinal stimuli. To avoid extensive basic stimulation tests in human patients, we developed techniques for estimating visual spatial resolution in anesthetized cats. Electrical epi-retinal and visual stimulation was combined with multiple-site retinal and cortical microelectrode recordings of local field potentials (LFPs) from visual areas 17 and 18. Classical visual receptive fields were characterized for retinal and cortical recording sites using multifocal visual stimulation combined with stimulus-response cross-correlation. We estimated visual spatial resolution from the size of the cortical activation profiles in response to single focal stimuli. For comparison, we determined activation profiles in response to visual stimuli at the same retinal location. Activation profiles were single peaked or multipeaked. In multipeaked profiles, the peak locations coincided with discontinuities in cortical retinotopy. Location and width of cortical activation profiles were distinct for retinal stimulation sites. On average, the activation profiles had a size of 1.28 +/- 0.03 mm cortex. Projected to visual space this corresponds to a spatial resolution of 1.49 deg +/- 0.04 deg visual angle. Best resolutions were 0.5 deg at low and medium stimulation currents corresponding to a visus of 1/30. Higher stimulation currents caused lower spatial, but higher temporal resolution (up to 70 stimuli/s). In analogy to the receptive-field concept in visual space, we defined and characterized electrical receptive fields. As our estimates of visual resolutions are conservative, we assume that a visual prosthesis will induce phosphenes at least at this resolution. This would enable visuomotor coordinations and object recognition in many indoor and outdoor situations of daily life.

Animals↗
PubMed2000

High-concentration band profiles and system peaks for a ternary solute system

High-concentration HPLC band profiles of single solutes and the individual band profiles of the components of binary and ternary mixtures are reported for benzyl alcohol, 2-phenylethanol, and 2-methylbenzyl alcohol. These solutes were eluted from a C18 column by a binary mobile phase (MeOH:H2O = 1:1, v/v). High-concentration system peaks were obtained using mixtures of benzyl alcohol and 2-phenylethanol at different relative concentrations as the feed and 2-methylbenzyl alcohol as the strong mobile phase additive. Band profiles and system peak profiles were calculated using the equilibrium-dispersive model of chromatography. The adsorption equilibrium in the multicomponent system was characterized by the competitive Langmuir model. Excellent quantitative agreement was found between the experimental and the calculated profiles. This work confirms that extremely unusual system peak profiles can be obtained even when the adsorption behavior is quite simple. Under certain circumstances, the use of a properly chosen additive could markedly increase the separation between bands and hence the production rate, the recovery yield, and/or the purity of the fractions.

Journal Article↗
PubMed1989

2-Acetylthiamin pyrophosphate (acetyl-TPP) pH-rate profile for hydrolysis of acetyl-TPP and isolation of acetyl-TPP as a transient species in pyruvate dehydrogenase catalyzed reactions.

Rate constants for the hydrolysis of acetyl-TPP were measured between pH values of 2.5 and 7.5 and plotted as log kobs versus pH. The pH-rate profile defined two legs, each with a slope of +1 but separated by a region of decreased slope between pH 4 and pH 6. The rates were insensitive to buffer concentrations. Each leg of the profile reflected specific-base-catalyzed hydrolysis of acetyl-TPP, analogous to the hydrolysis of 2-acetyl-3,4-dimethylthiazolium ion [Lienhard, G.E. (1966) J. Am. Chem. Soc. 88, 5642-5649]. The separation of the two legs of this profile has been shown to be caused by the ionization of a group exhibiting a pKa of 4.73 within acetyl-TPP that is remote from the acetyl group, the amino-pyrimidine ring, which is protonated below pH 4.73. The protonation level of this ring has been shown to control the equilibrium partitioning of acetyl-TPP among its carbinolamine, keto, and hydrate forms. The differential partitioning of these species is a major factor causing the separation between the two legs of the pH-rate profile. The characteristic pH-rate profile and the availability of synthetic acetyl-TPP [Gruys, K.J., Halkides, C.J., & Frey, P.A. (1987) Biochemistry 26, 7575-7585] have facilitated the isolation and identification of [1-14C]acetyl-TPP from acid-quenched enzymatic reaction mixtures at steady states. [1-14C]Acetyl-TPP was identified as a transient species in reactions catalyzed by the PDH complex or the pyruvate dehydrogenase component of the complex (E1). The pH-rate profile for hydrolysis of [1-14C]-acetyl-TPP isolated from enzymatic reactions was found to be indistinguishable from that for authentic acetyl-TPP, which constituted positive identification of the 14C-labeled enzymic species.

Hydrogen-Ion Concentration↗
PubMed2003

Current combustion-related sources contribute to polychlorinated naphthalene and dioxin-like polychlorinated biphenyl levels and profiles in air in Toronto, Canada.

Polychlorinated naphthalenes (PCNs) and mono- and non-ortho substituted PCBs were analyzed in air from two sites in Toronto, Ontario, Canada to determine whether current combustion-related sources contribute to the levels and profiles of PCNs found in urban air. High-volume air samples were collected periodically at the University of Toronto (UT, a downtown site) and in north Toronto at the Meteorological Service of Canada (MSC). SigmaPCN concentrations ranged from 31 to 78 pg m(-3) at UT and from 7 to 84 pg m(-3) at MSC with concentrations lower at MSC than UT for paired samples. Ambient air congener profiles contrasted between the two sites with MSC profiles indicating inputs from combustion-related sources when compared to combustion fly ash and technical PCN and PCB mixture profiles. Combustion markers, including CN-44, -29, and -54, the more toxic CN-66 and -67 congeners, and non-ortho PCBs, were enriched in air at MSC on a mass percent basis in several samples. As a result, CN-66/67 contributed proportionally more to dioxin toxic equivalents at MSC than at UT. Downtown air PCN profiles resembled those of technical PCN and PCB mixtures, reflecting evaporative emissions from past uses, while PCN levels and profiles at MSC, a more industrialized location, are also influenced by current combustion sources, contributing as much as an estimated 54% of sigmaPCN in samples collected.

Air Pollutants↗
PubMed2005

Trifluoroacetate profiles in the Arctic, Atlantic, and Pacific Oceans.

A series of depth profiles was collected at 22 sites in the Arctic, North and South Atlantic, and Pacific Oceans to determine spatial patterns for trifluoroacetate (TFA) concentrations in the marine environment and to investigate possible natural sources of TFA. Profiles were also taken over underwater vents in the North and South Pacific and the Mediterranean Sea. At the profile sites, TFA values ranged from <10 ng/L in the Pacific Ocean to greater than 150 ng/L in the Atlantic Ocean. Samples from the Canada Basin of the Arctic Ocean exhibited variable TFA concentrations (60-160 ng/L) down to 700 m. Below this depth, in water having 14C ages exceeding 1000 years, the TFA concentrations were constant (150 ng/L). Water returning to the Atlantic through the Canadian Arctic Archipelago had constant high TFA values. Profiles from the Northern Atlantic exhibited high values at all depths but were more consistent in the Western Atlantic. The northwestern Pacific Ocean surface profile sites exhibited low TFA concentrations in the top 100 m increasing to a maximum of 60 ng/L with depth. Samples from the South Pacific Ocean site had generally low values with a few depths (>800 m) having concentrations of 50 ng/L or more. To determine if underwater vents could contribute to the TFA concentrations in the oceans, profiles were taken over three vents in the Pacific and Mediterranean Oceans. The results suggest that some deep-sea vents may be natural sources of TFA.

Arctic Regions↗
PubMed1997

Evaluation of direct curve comparison metrics applied to pharmacokinetic profiles and relative bioavailability and bioequivalence.

PURPOSE: The intent was to investigate three direct curve comparison metrics, the Rescigno Index, f1, and the Chinchilli Metric as tools to assess relative bioavailability (BA) and bioequivalence (BE). The specific objectives were to 1) estimate relative bioavailability and bioequivalence and 2) compare detection of profile shape differences with typical (i.e. AUC and Cmax) criteria. METHODS: Product bioequivalence was estimated and the degree of concordance with typical criteria in detecting profile differences was determined from the eighteen bioequivalence studies (390 subjects). Descriptive statistical analysis was carried out on the concordant and discordant profile subsets. RESULTS: 1) Three of the eighteen studies failed typical criteria (AUC and Cmax). Of the curve metrics, 12 studies failed the Chinchilli metric criteria and 13 failed f1 criteria. Using three different exponents in the Rescigno Index calculation, 17 (exponent = 3), 13 (exponent = 1), and 11 (exponent = 1/3) failed the criteria for bioequivalence. The frequency of profiles found to be different was comparable across the metrics, but the specific profiles found to be different or not different varied across the metrics. The Chinchilli Metric and f1 agreed 71% and 72% with typical criteria in judging profiles to be different or not different. Descriptive evaluation suggested that the direct curve metrics more effectively detect differences in absorption time lags but less effectively detect differences in Cmax. The Rescigno Index showed dependence on the direction of the difference between test and reference concentrations. CONCLUSIONS: With the limits used here, the direct curve metrics represent a more conservative approach to evaluate product bioequivalence. With further investigation and development, the direct curve approach may be used effectively to evaluate relative BA and BE.

Area Under Curve↗
PubMed2002

Comparative analysis of the outer membrane protein profiles of isolates of the Pasteurella multocida (B:2) associated with haemorrhagic septicaemia.

Outer membrane proteins (OMP) of P. multocida (serotype B:2) field isolates (n = 6) and a vaccine strain (P-52) were extracted by a sarkosyl method and characterized using SDS-PAGE and immunoblotting. About 20 polypeptide bands were observed in the profile of the vaccine strain with MW ranging from 16 to 90 kDa and, based on band thickness and intensity of staining, three polypeptides of MW 31, 33 and 37 kDa were considered to be the major OMPs. The profiles of the field isolates showed minor differences when compared with that of the vaccine strain. The OMP of 33 kDa was only expressed by the vaccine strain. Four field isolates expressed an OMP of 39 kDa, which did not appear in the profiles of the remaining two field isolates and the P-52 strain. Similarly, an OMP of 25 kDa was exclusively seen in the profile of a single isolate. By immunoblotting studies, using anti-P. multocida (P-52) whole-cell hyperimmune serum raised in rabbits as well as buffalo immune sera, it became evident that the polypeptide of 37 kDa was the most antigenic OMP in the profiles of all the isolates, including the P-52 strain. Other polypeptides were either weakly antigenic or visible in the profile of only a few of the isolates. The study thus identified the major OMP of P. multocida (B:2) and suggested that this highly antigenic 37 kDa OMP has potential for further protective and immunodiagnostic studies.

Animals↗
PubMed2003

Unexpected clobetasol propionate profile in human stratum corneum after topical application in vitro.

PURPOSE: The validity of using drug amount-depth profiles in stratum corneum to predict uptake of clobetasol propionate into stratum corneum and its transport into deeper skin layers was investigated. METHODS: In vitro diffusion experiments through human epidermis were carried out using Franz-type glass diffusion cells. A saturated solution of clobetasol propionate in 20% (V/V) aqueous propylene glycol was topically applied for 48 h. Steady state flux was calculated from the cumulative amount of drug permeated vs. time profile. Epidermal partitioning was conducted by applying a saturated drug solution to both sides of the epidermis and allowing time to equilibrate. The tape stripping technique was used to define drug concentration-depth profiles in stratum corneum for both the diffusion and equilibrium experiments. RESULTS: The concentration-depth profile of clobetasol propionate in stratum corneum for the diffusion experiment is biphasic. A logarithmic decline of the drug concentration over the first four to five tape strips flattens to a relatively constant low concentration level in deeper layers. The drug concentration-depth profile for the equilibrium studies displays a similar shape. CONCLUSIONS: The shape of the concentration-depth profile of clobetasol propionate is mainly because of the variable partitioning coefficient in different stratum corneum layers.

Administration, Topical↗
PubMed2002

The relationship between mean birth weight and poverty using the Townsend deprivation score and the Super Profile classification system.

Super Profiles have been used as alternative methods of characterising the deprivation of an area. Some reports suggest that Super Profiles are as accurate as established indices such as the Townsend score (TS). This was a test of this assertion.A total of 138 696 live born singleton births to Birmingham residents born between 1986 and 1996 (inclusive) were allocated to enumeration districts (EDs) by linkage from the postcode. We allocated the TS of the individual's ED. We allocated a Lifestyle and Target Market (TM) from Super Profiles by linkage to the ED. We examined the gradient between mean birth weight and the 10 Super Profile Lifestyles and compared this to the gradient between 10 Townsend groups and mean birth weight. We repeated this approach using the 40 TMs and 40 Townsend groups. We used both the median income and a census-derived deprivation measure to rank Lifestyles and TMs. The gradient between mean birth weight and area deprivation was linear for Townsend groups but not linear using either Lifestyles or TMs whichever method of ranking Lifestyles or TMs was used. Where Lifestyles or TMs were out of line with their neighbours, the TS of that group mostly explained this. As Super Profiles are generated using nationally representative data, applying the affluence ranking to small areas can lead to inaccuracies, as shown in this data. We conclude that Super Profiles are probably unsuitable as measures of deprivation of small areas.

Birth Certificates↗
PubMed2006

Reference profiling of the genomic response induced by an antimicrotubule agent, TZT-1027 (Soblidotin), in vitro.

TZT-1027 is an antimicrotubule agent targeting beta-tubulin that is undergoing clinical development. The genomic response of cancer cells to TZT-1027 was profiled to evaluate its biochemical activity. A lung cancer cell line, PC-14, was exposed to antimicrotubule agents including dolastatins, Vinca alkaloids and taxanes at an equivalent toxicity level. Alterations in the TZT-1027-induced gene expression of approximately 600 genes were then examined using microarray technology and the resulting gene profiles were compared with those for cells exposed to the other antimicrotubule agents. A principle component analysis using the whole gene set demonstrated that TZT-1027 produced similar gene profiles to those produced by dolastatin 10, but that these gene profiles differed from those produced by other agents. The agents were classified according to their induced genomic response in a molecular structure-dependent manner. Genes whose expression profiles differed according to drug class included intermediate filaments, extracellular matrix protein and Rho regulatory genes that may be involved in cytoskeletal and angiogenesis processes that are regulated by microtubule dynamics. TZT-1027 produces a unique genomic response profile distinct from that of Vinca alkaloids and taxanes, suggesting that this agent has a different mechanism of action. The selected genes may act as pharmacodynamic biomarkers allowing the unique mode of action of TZT-1027 to be discriminated from those of other antimicrotubule agents.

Antineoplastic Agents↗
PubMed2002

Elderly people with hypothalamic-pituitary disease and untreated GH deficiency: clinical outcome, body composition, lipid profiles and quality of life after 2 years compared to controls.

OBJECTIVE: Elderly patients with GH deficiency (GHD) have significant impairments in multiple aspects of quality of life (QOL) but similar lipid profiles compared to age-matched control subjects. There are, however, no data on changes in these parameters with time. This study assessed the impact of untreated GHD over a period of 2 years in a group of elderly patients with hypothalamic-pituitary disease in relation to new illnesses and differences in body composition, circulating lipid profile levels and QOL. Control subjects were also followed for 2 years. SUBJECTS: Twenty-seven elderly patients (> 65 years) with hypothalamic-pituitary disorders and GHD (mean peak stimulated GH response 1.6 mIU/l, range 0.6--5.0) were studied initially. Two years later 21 (13 males) agreed to attend for reassessment. Mean age was then 72.7 +/- 5.04 years (range 67--85). Eighteen patients had pituitary tumours, three had craniopharyngiomas. Twenty-seven control subjects were studied at baseline and 17 (7 males) agreed to attend for reassessment. Mean age was then 75.9 +/- 6.97 years (range 67--88). METHODS: Weight, body mass index (BMI), total fat mass (FM) (bioelectrical impedance), serum IGF-1 and fasting lipid profile (total cholesterol, triglyceride, HDL cholesterol, LDL cholesterol) were measured. QOL was assessed in both groups using five interviewer-administered self-rating questionnaires: the Nottingham Health Profile, Short Form-36, Hospital Anxiety and Depression Scale, Mental Fatigue Questionnaire and Life Fulfillment Scale. The GHD group also completed the Disease Impact Scale. RESULTS: Two of the 27 patients with GHD died during the 2-year follow-up (myocardial infarction and probable cerebrovascular accident). Four controls could not be traced but there were no deaths in the other 23. In the 21 GHD patients after 2 years, mean serum IGF-1 and BMI were unchanged (12.6 +/- 5.8 vs. 13.3 +/- 5.1 nmol/l, P = 0.5 and 28.3 +/- 4.3 vs. 29.1 +/- 4.2, P = 0.5, respectively) at the 2-year follow-up and there were no significant changes in the lipid profiles. However, there was a significant reduction in fat mass (31.7 +/- 11.2 vs. 28.5 +/- 10.9%, P = 0.04). In the 17 control subjects after 2 years, serum IGF-1 levels (17.2 +/- 4.0 vs. 15.7 +/- 5.6 nmol/l, P = 0.4), BMI and fat mass were unchanged. However, there was a significant fall in total cholesterol levels over the 2-year follow-up (6.3 +/- 0.9 vs. 5.7 +/- 0.9 mmol/l, P < 0.0001), although LDL cholesterol, triglycerides and HDL cholesterol were unchanged. Analysing the QOL data, the GHD patients had less energy (P < 0.05), more depression (P < 0.05), more pain (P < 0.05) and lower life fulfillment scores (P < 0.01) after 2 years. However, the control subjects also had less energy (P < 0.05), less vitality (P < 0.05) and lower self-esteem (P < 0.05), more depression (P < 0.05), worse mental health (P < 0.05), life fulfillment personal (P < 0.01), life fulfillment material (P < 0.02), physical functioning and role physical functioning (P < 0.05) after 2 years. Comparing the patients and controls at baseline, there were significant differences in IGF-1, BMI, FM, LDL cholesterol, personal life fulfillment, mental fatigue, general health and mental health. However, after 2 years, only BMI and depression scores were significantly different. CONCLUSION: These patients with untreated GHD did not have deterioration of body composition or lipid profiles when reassessed after a period of 2 years. In fact, fat mass fell. The control subjects did have a significant decrease in total cholesterol but no change in other lipids or body composition. Some quality of life domains did deteriorate in the patients with GHD. However, the control subjects also had worse quality of life scores after 2 years which were then little different from the GHD patients. These results raise doubts about the benefits of GH replacement in elderly people with GHD.

Adenoma↗
PubMed1998

In vivo pressure profiles of thigh-length graduated compression stockings.

BACKGROUND: The aim of the study was to assess whether the appropriate pressure profile is generated by thigh-length graduated compression stockings in human subjects. The effect of leg posture on the pressure profile was assessed in three commonly used brands of graduated compression stockings. METHODS: The study involved 17 human volunteers from the Department of Orthopaedic Surgery. Three different brands of stockings commonly recommended for the prevention of deep vein thrombosis were applied to each individual and the interface pressure profile under the stocking was measured. The effect of posture was assessed by comparing the interface pressure profile with the subject supine and in standing and sitting positions. RESULTS: Appropriate median pressure profiles were achieved only with the subject standing or supine. In the sitting position with the knee flexed, a high median interface pressure in excess of 28 mmHg was generated at the popliteal fossa. Overall, inconsistent performance was found in all three brands of stockings; fewer than 30 per cent of the pressure readings fell within 20 per cent of the 'ideal'. Reversed pressure profile was observed in over 70 per cent of subjects. CONCLUSION: Thigh-length graduated compression stockings may be most effective in bedridden patients. Knee-length stockings may be more suitable for the prevention of deep vein thrombosis in ambulant patients.

Bandages↗
PubMed2003

Child health profiles: the viewpoints of adults.

UNLABELLED: THE CHILD HEALTH PROFILE: The teenage years have been identified as an important time to influence attitudes and behaviour likely to affect current and future health. The child health profile was developed partly to provide appropriate health information to young people aged 10 and older, but was also intended to recognize their right to assume greater responsibility for their health records. It was seen as an extension of the popular parent held record for younger children. METHODS: A Scottish child health profile was introduced through schools in three health board areas. Data about usage and views were obtained from children and relevant adults by means of questionnaires. In this paper, the perspectives of parents, health professionals and teachers are reported. FINDINGS: The majority of the adults were keen on the idea of the profile in principle. However, most parents knew little about it, even though all their children had been issued with one. Teachers had little involvement with the profile and the majority of health professionals had some doubts about its application. The adults indicated that a small number of children made effective use of the profile, but information from both adults and children indicated that it was seldom discussed during consultations with health professionals, few of whom routinely asked to see it. CONCLUSIONS: The paper outlines implications for the provision of health information and records for this age group.

Adolescent↗
PubMed1999

Characterization of Saccharomyces cerevisiae strains from spontaneously fermented maize dough by profiles of assimilation, chromosome polymorphism, PCR and MAL genotyping.

Several isolates of Saccharomyces cerevisiae from indigenous spontaneously fermented maize dough have been characterized with the purpose of selecting appropriate starter cultures and methods for their subspecies typing. The techniques applied included assimilation of carbon compounds by the API ID 32 C kit, determination of chromosome profiles by PFGE, PCR and MAL genotyping. For the 48 isolates investigated, use of the API ID 32 C kit resulted in eight different assimilation profiles. The most common assimilation profile was the ability of 50% of the isolates to assimilate galactose, saccharose, DL-lactate, raffinose, maltose and glucose. Both chromosome and PCR profiles could be used for subspecies typing of the isolates and on this basis, the isolates were grouped into clusters. The discriminative power of the two techniques was equal; a few isolates not separated by their chromosome profiles could be separated by their PCR profiles and vice versa. Four different MAL genotypes were observed with MAL11 and MAL31 predominating. MAL11 was seen for all isolates whereas no evidence of MAL21 and MAL41 was observed. Based on the results obtained, a high number of Saccharomyces cerevisiae isolates were found to be involved throughout the spontaneous fermentation of maize dough. All methods included appeared to be suitable for subspecies typing. However, the discriminative power was highest for the PFGE and PCR techniques.

Carbohydrate Metabolism↗
PubMed1999

Profiles of effective tutors in problem-based learning: scaffolding student learning.

OBJECTIVES: Research on tutoring in problem-based learning has not focused so far on the variation in tutoring and how this variation can be interpreted by conceptions about effective tutoring. DESIGN: This study focuses on the profiles of tutors generated by means of an instrument, the so-called Tutor Intervention Profile (TIP), and tries to determine which profiles are more or less effective. The TIP contains four dimensions of tutor behaviour: (1) elaboration; (2) directing the learning process; (3) integration of knowledge; and (4) stimulating interaction and individual accountability. SETTING: The medical school of the University of Maastricht, The Netherlands. SUBJECTS: Sixty-seven tutors who run 67 tutorial groups across three units (courses) in the academic year 1996-97. RESULTS: It appeared that high, average and low performing tutors differ in their performance on each of the four dimensions of the TIP. Several different profiles of tutor performance could be distinguished, which were more or less effective. One group of tutors demonstrated a tutor intervention profile that was characterized as relying more on the use of expert knowledge, whereas another group of tutors was characterized as relying more on their abilities to stimulate the learning process in the tutorial group. The tutor intervention profile that was perceived by students as most effective showed high scores on each of the four dimensions, as expected. Notably, a tutor stressing the learning process in the tutorial group was perceived as more effective than a tutor stressing content (expert tutor). This is especially true for a relatively poor scoring tutor. CONCLUSIONS: The results of this study are consistent with research on human tutoring and research on tutoring in problem-based learning.

Educational Measurement↗