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Biomedical subjects

M A Lewis

Publications and source records attributed to M A Lewis.

At least 37 records · Page 2Linked to original sources
PubMed2001

Dredging impact on an urbanized Florida bayou: effects on benthos and algal-periphyton.

Environmental effects of dredging events have been uncommonly reported for shallow, residential estuaries characteristic of the Gulf of Mexico region. The objective of this study was to determine the impact of hydraulic dredging on an urbanized estuary. Physicochemical quality, benthic community composition, whole sediment toxicity, periphytic algal community composition and trace metal tissue quality were determined prior to and after dredging. The effects on surface water pH, dissolved oxygen, and temperature were negligible but photosynthetically active radiation was decreased at several stations. Dredging significantly reduced benthic diversity and density (P < 0.05). However, the sediments were not acutely toxic to the epibenthic, Americamysis bahia (formerly Mysidopsis bahia); survival averaged 93% (post-dredging) and to 98% (pre-dredging). There were several post-dredging taxonomic structural changes in the diatom-dominated, periphyton community but differences in mean density and three diversity indices were not significant. Trace metal concentration in periphyton after dredging were reduced from an average of 4-65% and significantly for mercury, zinc and chromium in several areas. It was concluded that the environmental impact of small-scale dredging events in urbanized near-coastal areas, based on the selected parameters, are likely to be localized and of short-term environmental consequence. The choice of the target biota, response parameters and chemical analysis are important considerations in the environmental impact assessment of these periodic episodic events.

Animals↗
PubMed2001

Electron capture dissociation of gaseous multiply charged ions by Fourier-transform ion cyclotron resonance.

Fourier-transform ion cyclotron resonance instrumentation is uniquely applicable to an unusual new ion chemistry, electron capture dissociation (ECD). This causes nonergodic dissociation of far larger molecules (42 kDa) than previously observed (<1 kDa), with the resulting unimolecular ion chemistry also unique because it involves radical site reactions for similarly larger ions. ECD is highly complementary to the well known energetic methods for multiply charged ion dissociation, providing much more extensive protein sequence information, including the direct identification of N- versus C-terminal fragment ions. Because ECD only excites the molecule near the cleavage site, accompanying rearrangements are minimized. Counterintuitively, cleavage of backbone covalent bonds of protein ions is favored over that of noncovalent bonds; larger (>10 kDa) ions give far more extensive ECD if they are first thermally activated. This high specificity for covalent bond cleavage also makes ECD promising for studying the secondary and tertiary structure of gaseous protein ions caused by noncovalent bonding.

Cyclotrons↗
PubMed2001

A molecular epidemiological study of sequential oral isolates of Candida albicans from terminally ill patients.

The pattern of candidal colonisation was studied in a group of terminally ill patients receiving antifungal treatment for oral candidosis. A total of 43 isolates of C. albicans was collected pre- and post-antifungal treatment from patients up to a maximum period of 4 weeks. Isolates were analysed by electrophoretic karyotyping (EK) and by inter-repeat polymerase chain reaction (IR-PCR). Fifteen electrophoretic karyotypes and 17 IR-PCR profiles were identified. Sequential isolates from 10 patients yielded identical profiles in both EKs and IR-PCR analyses. In the case of four patients, minor differences in the profiles were obtained by either EK or IR-PCR. The findings suggest that antifungal treatment in this patient group fails to eradicate the original C. albicans strain, thereby allowing recolonisation of the oral cavity. The present study has also shown that either EK or IR-PCR is a useful typing approach in such epidemiological investigations.

Antifungal Agents↗
PubMed2001

Correlates of actual and perceived knowledge of prostate cancer among African Americans.

While digital rectal examination, prostate-specific antigen, and transrectal ultrasound have been identified as effective means of early detection of prostate cancer, African American men tend to underuse these services as compared to white men. Using a nonrandom sample of 108 African American men, the authors conducted an exploratory investigation of the effects of education, income, age, and health insurance coverage on actual and perceived knowledge of prostate cancer. The extent to which the use of prostate cancer screening services may be attributed to actual and perceived knowledge of prostate cancer was also explored. Respondents demonstrated a poor knowledge of prostate cancer and less than 40% reported having had prostate cancer screening as part of their annual physical examination. The results of the study also revealed that (a) there was a moderately strong correlation between actual and perceived knowledge of prostate cancer, (b) use of prostate cancer screening service was positively associated with actual and perceived knowledge of the disease, (c) actual knowledge of prostate cancer was negatively correlated with education, age, and income, and (d) actual and perceived knowledge of prostate cancer were both correlated with having health insurance coverage.

Adult↗
PubMed2001

Strain persistence of invasive Candida albicans in chronic hyperplastic candidosis that underwent malignant change.

OBJECTIVES: The aim of this study was to assess persistence and tissue invasion of Candida albicans strains isolated from a 65 year-old patient with chronic hyperplastic candidosis (CHC), that subsequently developed into squamous cell carcinoma (SCC). MATERIALS AND METHODS: C. albicans (n=7) were recovered from the oral cavity of the patient over seven years. Confirmation of CHC and SCC in this patient was achieved by histopathological examination of incisional biopsy tissue. DNA fingerprinting was performed on the seven isolates from the CHC patient together with a further eight isolates from patients with normal oral mucosa (n=2), chronic atrophic candidosis (n=1), SCC (n=1) and CHC (n=4). Genotyping involved the use of inter-repeat PCR using the eukaryotic repeat primer 1251. Characterisation of the tissue invasive abilities of the isolates was achieved by infecting a commercially available reconstituted human oral epithelium (RHE; SkinEthic, Nice, France). After 24 h, C. albicans tissue invasion was assessed by histopathological examination. RESULTS: DNA fingerprinting demonstrated strain persistence of C. albicans in the CHC patient over a seven year period despite provision of systemic antifungal therapy. The strain of C. albicans isolated from this patient was categorised as a high invader within the RHE compared to other isolates. CONCLUSIONS: Candidal strain persistence was evident in a patient with CHC over seven years. This persistence may be due to incomplete eradication from the oral cavity following antifungal therapy or subsequent recolonisation from other body sites or separate exogenous sources. The demonstration of enhanced in vitro tissue invasion by this particular strain may, in part, explain the progression to carcinoma.

Aged↗
PubMed2001

Oral health status of adults from a California regional center for developmental disabilities.

The oral health status and treatment needs of developmentally disabled adults (18 years and older) from a Los Angeles Regional Center who live in a variety of settings were measured as part of a comprehensive study to determine their overall health status. A dental assessment was performed on a sample of 325 persons which was similar in demographic composition to the entire population at the center. Approximately 80% of clients reported a personal dentist of record, and 73% brushed their own teeth. Edentulism was 9%. The mean number of retained teeth per person was 22. Subjectively, 15.7% of the sample was rated as having "good" overall dental health, 77.7% "fair," and 6.6% "poor." The major reasons rendering fair or poor assessments were oral hygiene, clinical periodontal disease, and dental caries. More females than males were assessed as having "good" overall dental health. The overall appearance of the teeth for a majority of the sample (76.5%) was rated as "same as most." Persons who brushed their own teeth had fewer missing teeth than those who did not. Persons with a dentist of record had fewer decayed and more filled teeth. Persons living at home with family or friends had a significantly lower DMFT index than those living independently or in facilities. In general, these findings are encouraging; however, caution must be exercised, since efforts to improve the oral health status of this population require continued attention.

Adult↗
PubMed2001

PCR fingerprinting of Candida albicans associated with chronic hyperplastic candidosis and other oral conditions.

The purpose of this study was to genotype strains of Candida albicans to determine whether specific types were associated with chronic hyperplastic candidosis (CHC). A total of 67 candidal isolates from CHC patients (n = 17) and from patients with other oral conditions (n = 21) were genotyped by PCR fingerprinting employing two interrepeat primer combinations (1245 and 1246 primers or 1251 primer) and a single minisatellite-specific M13 primer. The most suitable primer for fingerprint analysis was found to be primer 1251, yielding well-resolved banding patterns. For the 67 isolates tested, PCR fingerprinting delineated 25 (1245 and 1246 primers), 27 (1251 primer), and 25 (M13 primer) profiles. The majority of C. albicans isolates from multiple sites within the mouth produced identical profiles (six out of nine subjects examined). For patients for whom a series of longitudinal isolates was available, strain persistence for up to 7 years was evident for five out of eight individuals, despite episodes of antifungal therapy. Computer-assisted comparison of the interrepeat PCR fingerprints identified seven distinct profiles that were shared among isolates from different individuals. However, no association was evident among isolates of C. albicans from specific clinical conditions. Eight isolates that were initially identified as C. albicans but having atypical PCR profiles were later confirmed as Candida dubliniensis. In conclusion, the genotypic data do not indicate clonal restriction of C. albicans with respect to CHC. Furthermore, these results have demonstrated that in the majority of individuals, colonizing populations of C. albicans are clonal in nature and exhibit strain persistence.

Candida albicans↗
PubMed2001

Sediment chemical contamination and toxicity associated with a coastal golf course complex.

The increasing density of golf courses represents a potential source of sediment contamination to nearby coastal areas, the chemical and biological magnitude of which is almost unknown. The objective of this study was to determine the concentrations of contaminants and toxicities of sediments impacted by a coastal golf course complex. Sediment contaminant concentrations were determined at least twice during the two-year study period at 14 sampling stations. In addition, a combination of acute and chronic bioassays were conducted exposing four invertebrate test species to whole sediments and associated pore waters. Overall, the Florida, USA, golf course complex had a measurable impact on sediment chemical quality, particularly in near-field areas. Higher concentrations of several trace metals and organochlorine pesticides were detected in many golf course-associated sediments compared with reference areas; however, concentrations decreased seaward and only a few, primarily chlorinated pesticides, exceeded proposed sediment quality guidelines. Chromium, zinc, and mercury were detected more frequently than other trace metals. The DDT and associated metabolites, dieldrin and chlordane, were the more commonly detected organic contaminants. Acute toxicity was uncommon and occurred consistently for sediment collected from one coastal location. In contrast, chronic toxicity occurred at several study sites based on the response of Mysidopsis bahia. It was concluded that the impact of golf course runoff on sediment quality may be subtle and sensitive biological assessment methods, such as chronic toxicity tests, will be needed to detect adverse effects.

Animals↗
PubMed2001

Identification of Candida dubliniensis, based on ribosomal DNA sequence analysis.

Differentiation of Candida albicans and the recently described C. dubliniensis has proven difficult due to the high degree of phenotypic similarity of these species. The present study examines sequence variations in the ribosomal DNA (rDNA) intergenic transcribed spacer (ITS) regions of C. albicans (n = 5) and C. dubliniensis (n = 7) strains, with a view to identifying sequence differences that would enable consistent differentiation of these two species by restriction fragment length polymorphism (RFLP) analysis. The ITS1 and ITS2 regions, together with the entire 5.8S rRNA gene of the strains, were amplified by the polymerase chain reaction (PCR), using primers ITS1 and ITS4, PCR products from both C. albicans and C. dubliniensis were of similar size (around 540 bp); however, sequence analysis revealed over 20 consistent base differences between the products of the two species. On the basis of sequence variation, the restriction enzyme MspA1 I was selected and used to differentiate the PCR products of C. albicans and C. dubliniensis by RFLP analysis. MspA1 I yielded two discernible fragments from C. albicans PCR products, whilst those from C. dubliniensis appeared undigested, thereby providing an approach to differentiate the two species.

Candida↗
PubMed2001

Drug use and adverse event monitoring in German children.

OBJECTIVE: To assess drug use and the incidence of mild to moderate adverse drug effects (AE) in children aged 0 - 16 years, with 2 different approaches. METHODS: All 185 pediatric practices in the State of Brandenburg, Germany, were surveyed (95% positive response). A random sample of 50 practices servicing 36,000 children participated in the study as sentinel physicians reporting any AE among their patients. Twenty practices servicing 14,000 children were included in a drug utilization component (DUC) which documented diagnoses, prescribing and AE in all children seen in a 3-month period. RESULTS: The results on the DUC are based on 12,628 children with 26,168 physician contacts, 34,465 diagnoses and 33,140 drug prescriptions given to 85% of the children seen (average age: 6.7 years). Practice size ranged from 94 to 1,473 children seen in a 3-month period. The average number of physician contacts per child was 2. 1, with 10% seeing a physician 5 times and more. The diagnoses were respiratory ailments (30%), skin- (12%), injection- (11%) and trauma- (10%) related diagnoses. Major drug uses were respiratory (34% of prescriptions), anti-infective (22%), dermatological (13%), gastrointestinal (9%) and psychotropic agents (8%). One hundred and fifty-two AE affecting 150 children were documented in the DUC, 60% of these occurring within 3 days after treatment initiation. 83% of AE were mild (up to 4 on a scale from I -6), and 85% were considered by physicians to be attributable. Only 4 reports of very severe events were received. 47% of reports were related to antibiotic uses, 31% to immunizations, 11% to respiratory, and 4% to gastrointestinal agents. While there are no differences in the occurrence of AE by gender, AE decreases significantly by age, maintaining the same patterns of AE type and causative medication. Over a 3-month period, the incidence of mild to moderate ADR in children given medications is estimated as 1,200 per 100,000, or about 1%. CONCLUSIONS: Underreporting of AE remains an issue even when a monitoring scheme suggests compliance. The results of this study show that while AE in children are generally non-serious, 1% of treatments might elicit mild AE leading to a consultation. Direct practice recording produces more reports than a sentinel system.

Adolescent↗
PubMed2000

Invasion speeds in fluctuating environments.

Biological invasions are increasingly frequent and have dramatic ecological and economic consequences. A key to coping with invasive species is our ability to predict their rates of spread. Traditional models of biological invasions assume that the environment is temporally constant. We examine the consequences for invasion speed of periodic and stochastic fluctuations in population growth rates and in dispersal distributions.

Animals↗
PubMed2000

Electron capture dissociation for structural characterization of multiply charged protein cations.

For proteins of < 20 kDa, this new radical site dissociation method cleaves different and many more backbone bonds than the conventional MS/MS methods (e.g., collisionally activated dissociation, CAD) that add energy directly to the even-electron ions. A minimum kinetic energy difference between the electron and ion maximizes capture; a 1 eV difference reduces capture by 10(3). Thus, in an FTMS ion cell with added electron trapping electrodes, capture appears to be achieved best at the boundary between the potential wells that trap the electrons and ions, now providing 80 +/- 15% precursor ion conversion efficiency. Capture cross section is dependent on the ionic charge squared (z2), minimizing the secondary dissociation of lower charge fragment ions. Electron capture is postulated to occur initially at a protonated site to release an energetic (approximately 6 eV) H. atom that is captured at a high-affinity site such as -S-S- or backbone amide to cause nonergodic (before energy randomization) dissociation. Cleavages between every pair of amino acids in mellitin (2.8 kDa) and ubiquitin (8.6 kDa) are represented in their ECD and CAD spectra, providing complete data for their de novo sequencing. Because posttranslational modifications such as carboxylation, glycosylation, and sulfation are less easily lost in ECD than in CAD, ECD assignments of their sequence positions are far more specific.

Amino Acid Sequence↗
PubMed2000

Spread rate for a nonlinear stochastic invasion.

Despite the recognized importance of stochastic factors, models for ecological invasions are almost exclusively formulated using deterministic equations [29]. Stochastic factors relevant to invasions can be either extrinsic (quantities such as temperature or habitat quality which vary randomly in time and space and are external to the population itself) or intrinsic (arising from a finite population of individuals each reproducing, dying, and interacting with other individuals in a probabilistic manner). It has been long conjectured [27] that intrinsic stochastic factors associated with interacting individuals can slow the spread of a population or disease, even in a uniform environment. While this conjecture has been borne out by numerical simulations, we are not aware of a thorough analytical investigation. In this paper we analyze the effect of intrinsic stochastic factors when individuals interact locally over small neighborhoods. We formulate a set of equations describing the dynamics of spatial moments of the population. Although the full equations cannot be expressed in closed form, a mixture of a moment closure and comparison methods can be used to derive upper and lower bounds for the expected density of individuals. Analysis of the upper solution gives a bound on the rate of spread of the stochastic invasion process which lies strictly below the rate of spread for the deterministic model. The slow spread is most evident when invaders occur in widely spaced high density foci. In this case spatial correlations between individuals mean that density dependent effects are significant even when expected population densities are low. Finally, we propose a heuristic formula for estimating the true rate of spread for the full nonlinear stochastic process based on a scaling argument for moments.

Animals↗