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PubMed2006

Radical-molecule reactions for aromatic growth: a case study for cyclopentadienyl and acenaphthylene.

Polycyclic aromatic hydrocarbon growth from acenaphthylene and cyclopentadienyl was investigated by using the B3LYP/6-31G(d,p) and BH&HLYP/6-31G(d,p) levels of theory as well as transition state theory. The reaction pathways of cyclopentadienyl bearing hydrocarbons are different from those without these moieties and cannot be adequately accounted for by the existing acetylene addition and aryl-aryl addition mechanisms. The reaction mechanisms identified in this paper lead to the formation of fluoranthene, aceanthrylene, and acephenanthrylene. Rate constants of the radical-molecule addition and subsequent intramolecular addition steps predict that the 1,2 double bond in acenaphthylene is much more reactive than the 3,4 and 4,5 double bonds. Fluoranthene is the most abundant product produced at high temperatures and the yield of acephenanthrylene is bigger than that of aceanthrylene. The computational results are discussed in light of pyrolysis experiments on CPD-indene and CPD-acenaphthylene mixtures conducted by Prof. Mulholland's research group reported in a previous work.

Acenaphthenes↗
PubMed2007

Crystal structure and photochemical behavior in solution of the 3'-N-sulfamate analogue of thymidylyl(3'-5')thymidine.

The 3'-N-sulfamate analogue of thymidylyl(3'-5')thymidine (TnsoT, 1) exhibits a preference for a C3'-endo conformation in the solution and solid states. Its photochemical behavior in solution is compared to that of its natural counterpart, thymidylyl(3'-5')thymidine (TpT, 2), to get further insight into the significance of the C3'-endo conformation on the photoproduct formation at the single-stranded dinucleotide level. Irradiation at 254 nm of 1 led to the same type of photoproducts as observed with 2. However, 1 was significantly more photoreactive than 2, and accordingly, the initial rate of photoproduct formation was enhanced in accordance with its propensity to base stack compared to 2. The corresponding quantum yields were determined and showed that the enhancement factor (1 compared to 2) is moderate for the cyclobutane pyrimidine dimer (CPD) (1.26) and much higher for the (6-4) photoproduct (1.8). These data strongly suggest that the CPD and (6-4) photoproduct arise from distinct minor stacked conformations.

Carbohydrates↗
PubMed2005

In situ quadrupole mass spectrometry study of atomic-layer deposition of ZrO2 using Cp2Zr(CH3)2 and water.

Reactions during the atomic layer deposition (ALD) process of ZrO(2) from Cp(2)Zr(CH(3))(2) and deuterated water as precursors were studied with a quadrupole mass spectrometer (QMS) at 210-440 degrees C. The detected reaction byproducts were CpD (m/z = 67) and CH(3)D (m/z = 17). Almost all (90%) of the CH(3) ligands were released during the Cp(2)Zr(CH(3))(2) precursor pulse because of exchange reactions with the OD-terminated surface, and the rest, during the D(2)O pulse. About 40% of the CpD was released during the metal precursor pulse, and 60%, during the D(2)O pulse. ALD-type self-limiting growth was confirmed from 210 to 400 degrees C. However, below 300 degrees C the growth rate was low. Precursor decomposition affected the film growth mechanism at temperatures exceeding 400 degrees C.

Journal Article↗
PubMed1999

Contrast sensitivity in patients recovered from central serous chorioretinopathy.

OBJECTIVE: To study contrast sensitivity in patients who have recovered from central serous chorioretinopathy (CSC). PATIENTS AND METHODS: Thirty-one patients who had recovered from CSC were examined with the Vistech and Pelli-Robson contrast sensitivity charts. The time from the onset of the active disease varied from 10 to 166 months (mean 60.4 +/- 42.0, SD). The visual acuity was 1.0 (logMar 0) or better. RESULTS: Contrast sensitivity of the affected eyes was significantly worse in the intermediate spatial frequencies of 3 and 6 cycles per degree (cpd) in the Vistech test compared to the fellow eyes (p = 0.032, 0.013, respectively). Contrast sensitivity of the affected eyes was significantly worse in all 5 spatial frequencies of the Vistech test and in the Pelli-Robson test compared to age-matched normal eyes (p = 0.006, 0.000, 0.000, 0.018, 0.000, 0.000, respectively). Contrast sensitivity of the fellow eyes was significantly worse in the spatial frequencies of 3 and 18 cpd in the Vistech test and in the Pelli-Robson test compared to age-matched normal eyes (p = 0.020, 0.019, 0.000, respectively). CONCLUSIONS: Contrast sensitivity does not seem to recover in all eyes after CSC even if the visual acuity has returned to normal. Therefore, contrast sensitivity testing is recommended for the patients complaining of visual impairment in spite of good visual acuity.

Adult↗
PubMed2000

Sensitivity enhanced NMR spectroscopy by quenching scalar coupling mediated relaxation: application to the direct observation of hydrogen bonds in 13C/15N-labeled proteins.

In this paper, we demonstrate that the sensitivity of triple-resonance NMR experiments can be enhanced significantly through quenching scalar coupling mediated relaxation by using composite-pulse decoupling (CPD) or.an adiabatic decoupling sequence on aliphatic, in particular alpha-carbons in 13C/15N-labeled proteins. The CPD-HNCO experiment renders 50% sensitivity enhancement over the conventional CT-HNCO experiment performed on a 12 kDa FK506 binding protein, when a total of 266 ms of amide nitrogen-carbonyl carbon defocusing and refocusing periods is employed. This is a typical time period for the direct detection of hydrogen bonds in proteins via trans-hydrogen bond 3hJ(NC') couplings. The experimental data fit theoretical analysis well. The significant enhancement in sensitivity makes the experiment more applicable to larger-sized proteins without resorting to perdeuteration.

Carbon Isotopes↗
PubMed2002

Adhesion of powders for inhalation: an evaluation of drug detachment from surfaces following deposition from aerosol streams.

PURPOSE: To evaluate micronized powder retention and detachment from inhaler surfaces following reproducible deposition by impaction, coupled with centrifugal particle detachment (CPD). METHODS: Micronized albuterol sulfate (AS) and beclomethasone dipropionate (BDP) were aerosolized as dry powders and deposited by cascade impaction onto different contact surfaces. Drug detachment from the surfaces was characterized using CPD, coupled with HPLC assay and scanning electron microscopy. RESULTS: Drugs which accumulated as aggregates on model surfaces detached with distinctive profiles for % remaining vs. applied centrifugal force; each profile showed reproducible values for the minimum force required to initiate drug detachment, Fyield. While differences occurred in the observed detachment profiles for different drugs and contact surfaces (polyacetal vs. aluminum), the deposited drug particle size had the most significant effect on these profiles, e.g., Fyield for AS (2.1-3.3 microm) was 383 +/- 12.7 microN compared with 18 +/- 13.8 microN for AS (4.7-5.8 microm). CONCLUSIONS: A technique was developed which enabled the experimental review, and subsequent data analysis, of the adhesive properties between different DPI construction materials and drug substances deposited from aerosol clouds. The technique appears to be of greater relevance to inhaler design decisions than earlier studies in the literature claiming to show differences in the adhesion of single drug particles to surfaces.

Adhesives↗
PubMed1999

Preparation, purification, and characterization of a reversibly lipidized desmopressin with potentiated anti-diuretic activity.

PURPOSE: . To prepare and characterize a reversibly lipidized dipalmitoyl desmopressin (DPP), and to compare its anti-diuretic efficacy and biodistribution with that of unmodified desmopressin (DDAVP). METHODS: Dithiothreitol (DTT) was used to reduce the intramolecular disulfide bond in DDAVP, and the reduced DDAVP was treated with a thiopyridine-containing disulfide lipidization reagent, Pal-CPD. The product, DPP, was purified by acid precipitation and, subsequently, by size-exclusion chromatography. Reversed-phase HPLC was used to analyze the purity and to evaluate the hydrophobicity of the product. Mass spectrometry was employed to characterize its molecular structure. The biological activity of DPP was demonstrated by the antidiuretic effects in vasopressin-deficient Brattleboro rats. Preliminary pharmacokinetic and biodistribution studies of intravenously injected DDAVP and DPP were carried out in CF-1 mice. RESULTS: DDAVP was readily reduced by a 2-fold molar excess of DTT at 37 degrees C for 0.5 hr. DPP was formed by the reaction of reduced DDAVP with Pal-CPD. Each DPP molecule contains two palmitic acid moieties, which link to the peptide via two disulfide bonds. After acid precipitation and size-exclusion chromatography, the purity was found to be approximately 95%, and the overall yield was 57%. When DPP was administered subcutaneously to Brattleboro rats, the potency of the anti-diuretic activity of DDAVP was enhanced to more than 250-fold. The plasma concentration of intravenously injected DDAVP in mice decreased rapidly during the first 20 min and followed by a slow elimination rate. However, in DPP administered mice, the plasma concentration actually increased in the first 20 min, followed by a slow elimination with a rate similar to that in DDAVP-injected mice. The regeneration of DDAVP was detected in the plasma of mice treated with DPP. Studies of the organ distribution in mice indicated that the liver retention of DPP was longer than that of DDAVP. On the other hand, the intestinal excretion of DPP was significantly less than that of DDAVP. CONCLUSIONS: The 250-fold increase of the anti-diuretic potency in DPP is most likely due to a slow elimination and prolonged tissue retention, together with the regeneration of active DDAVP, in the animals. Our results indicate that reversible lipidization is a simple and effective approach for improving the efficacy of many peptide drugs.

Animals↗
PubMed1997

Reproducibility of automated periodontal probing around teeth and osseointegrated oral implants.

Three different probing devices (Audio-Probe, Florida-Probe, Peri-Probe) were tested in order to determine the clinical probing depth (CPD) around clinically stable oral implants and their homologous teeth and to evaluate their reproducibility. In all 37 patients, in the age range of 24-80 years, who had undergone periodontal therapy and placement of 1 or more oral implants (ITI), were selected for the study. The CPD was determined on 75 oral implants in total and at 4 sites of both the implants and the control teeth at 3 visits, each 1 week apart. At the 1st visit, the Florida-Probe and the Audio-Probe were used. At the 2nd visit, the Florida-Probe and the Peri-Probe and, at the 3rd visit, again, the Florida-Probe and the Audio-Probe were used. At each visit bleeding on probing (BOP) was registered. A statistically significant (P < 0.05) difference between the mean scores of implant and tooth sites was found showing slightly higher values for implant sites. A tendency for the deeper pockets to bleed more frequently than the shallow pockets was observed. The comparisons of differences of the readings of the Audio-Probe on 2 different occasions were smaller than for the Florida-Probe. However, comparisons between 2 different probes showed significantly greater measurement errors than when comparing the probes alone. There was a tendency for the Peri-Probe to yield the highest and the Audio-Probe the lowest values in inflamed sites. It was concluded that all 3 probing devices appeared to have adequate reproducibility both around teeth and oral implants. For clinical use in daily practice, the Audio-Probe was found to be the most simple device with the highest reproducibility.

Adult↗
PubMed2002

Repair of cyclobutyl pyrimidine dimers in human skin: variability among normal humans in nucleotide excision and in photorepair.

BACKGROUND/AIMS: Photoreactivation (PR) of cyclobutyl pyrimidine dimers (CPD) in human skin remains controversial. Recently Whitmore et al. (1) reported negative results of experiments using two photorepair light (PRL) sources on UV-irradiated skin of volunteers. However, their PRL sources induced substantial levels of dimers in skin, suggesting that the additional dimers formed could have obscured PR. We met a similar problem of dimer induction by a PRL source. We designed and validated a PRL source of sufficient intensity to catalyse PR, but that did not induce CPD, and used it to measure photorepair in human skin. METHODS AND RESULTS: Using a solar simulator filtered with three types of UV-filters, we found significant dimer formation in skin, quantified by number average length analysis using electrophoretic gels of isolated skin DNA. To prevent scattered UV from reaching the skin, we interposed shields between the filters and skin, and showed that the UV-filtered/shielded solar simulator system did not induce damage in isolated DNA or in human skin. We exposed skin of seven healthy human volunteers to 302 nm radiation, then to the improved PRL source (control skin areas were kept in the dark for measurement of excision repair). CONCLUSIONS: Using a high intensity PRL source that did not induce dimers in skin, we found that three of seven subjects carried out rapid photorepair of dimers; two carried out moderate or slow dimer photorepair, and three did not show detectable photorepair. Excision repair was similarly variable in these volunteers. Subjects with slower excision repair showed rapid photorepair, whereas those with rapid excision generally showed little or no photoreactivation.

DNA Repair↗
PubMed2001

Bidirectional experimental effects.

Bidirectional experimental effects cannot be demonstrated by comparing measures of central tendency. Three approaches to the problem were considered: a test of homogeneity of variance, a comparison of control and experimental quartile frequencies by means of the chi-square test of association, and the cumulative-percentage-difference (CPD) curve--a graphic tool for demonstrating bidirectional effects. Two tests of significance were developed based on the CPD curve's maximum and minimum values. All 3 tests were first put to use analyzing simulated data, which incorporated 6 different patterns of experimental effect. The results of 100 repetitions of the simulations are summarized. Next, the results of a lexical-decision experiment with partial-word preview were analyzed using the procedures considered. The report ends with a presentation of guidelines for the use of the bidirectional tests.

Humans↗
PubMed1996

Influence of dialysis on plasma lipid peroxidation products and antioxidant levels.

In patients with end-stage renal failure (ESRF), the incidence of atherosclerosis and cancer is increased. The importance of lipid peroxidation (LPO) products in the pathogenesis of these complications has recently been emphasized. The LPO products malondialdehyde (MDA) and hexanal, lipophilic antioxidants and erythrocyte glutathione (GSH) were estimated in 10 pediatric hemodialysis (HD) patients before and after HD and in 11 peritoneal dialysis (CPD) patients. Before HD, MDA was elevated [median (interquartile range): 384.5 (110 to 501) nM; normal < 150 nM], whereas plasma hexanal levels were normal in all patients [130.5 (88 to 222) nM; < 320 nM]. HD decreased MDA concentrations on average by 88% but did not change hexanal levels. CPD patients exhibited high plasma MDA concentrations [371 (287 to 468) nM], whereas hexanal was in the low normal range [56 (51 to 81) nM]. Antioxidants were normal in both groups and unchanged during HD. GSH decreased slightly during HD. We hypothesize that MDA may accumulate in ESRF due to reduced plasma clearance. Our results argue against a general increase of LPO in uremia.

Adolescent↗
PubMed2005

Educational needs and employment status of Scottish dental hygienists.

AIMS AND OBJECTIVES: To investigate the educational needs and employment status of registered dental hygienists in Scotland. SUBJECTS: Three hundred and eighty one registered dental hygienists with postal addresses in Scotland. DESIGN: Structured questionnaire. RESULTS: A 76% response rate was achieved following two mailings. Of the respondents, 43% were in full-time employment albeit in more than one setting, mostly in the 'central belt' of Scotland. It was reported that 41% were employed in general dental practice with both NHS and private lists and 39% worked in a purely private setting. The introduction of extended clinical duties had been well received and 59% of subjects were interested in additional training in dental therapy, should this become available. Absence of funding for CPD was raised repeatedly, with only 41% reporting a degree of financial assistance. Greater accessibility to continuing education via distance learning, particularly in remote and rural settings, was requested by 73% of hygienists. CONCLUSIONS: This study identifies a number of issues in relation to this increasingly important group of healthcare professionals, which will inform the providers of oral healthcare. Although hygienists' involvement in CPD was commendable, results indicated that despite commitment to their profession, respondents did not always feel respected in terms of their employment status or support for continuing professional development.

Dental Hygienists↗
PubMed2006

Educational needs and employment status of Scottish dental nurses.

OBJECTIVE: To investigate the educational needs and employment status of dental nurses in Scotland. SUBJECTS: One thousand, seven hundred and thirty dental nurses with postal addresses in Scotland. DESIGN: Structured questionnaire. RESULTS: A 65% response rate was achieved following three mailings. The majority of respondents were employed in the central belt of Scotland although comparatively, substantial numbers were also recorded as being employed in Highland and Grampian regions. A total of 70% of dental nurses stated they were in full-time employment, with 74% of all participants reporting they were qualified. Of those who were unqualified, 17% (n = 191) were not in the process of formal training which may mean they are unable to work in the future, unless they conform to the GDC 'grandparenting' requirements. Induction training had only been received by 34% (n = 377) of this group, and a mere 21% (n = 234) reported regular CPD involvement. Of the 75% (n = 832) who responded to a question on funding for CPD, only 50% (412) received financial assistance. Geographical location for many nurses generated a number of difficulties in accessing education, and the possibility of distance or e-learning was requested by 65% of the sample. CONCLUSIONS: This study demonstrates clearly that there are many well-qualified dental nurses in employment in Scotland. However, unless structured career pathways are developed, access to education is simplified, and the problem of poor remuneration is addressed, then foreseeable problems may arise where there is insufficient enticement to encourage people to join what is an already underpopulated profession.

Dental Assistants↗
PubMed2006

Assessment of spatial-contrast function and short-wavelength sensitivity deficits in patients with migraine.

AIMS: To study spatial-contrast function and short-wavelength sensitivity deficits in a migraine population with a disease duration of 30 years or less. MATERIALS AND METHODS: In this prospective, cross-sectional study, we evaluated 28 subjects with migraine headache and 15 nonheadache healthy controls. Visual fields were evaluated using the Humphrey Field Analyzer 750i and the 30-2, blue and yellow threshold programme. Contrast sensitivity (CS) was measured at 1.5, 3, 6, 12, and 18 cpd spatial frequencies, using the Functional Acuity Contrast Test (F.A.C.T.). The results of the visual field parameters (mean defect (MD) and pattern standard defect (PSD)) and CS were compared with 15 age-equivalent normal subjects. RESULTS: Short-wavelength amplitude perimetry (SWAP) parameters and CS scores at all spatial frequencies were significantly altered in the migraine patients when compared with the control subjects. Visual field parameters correlated significantly with contrast sensitivity scores: positively for MD (r=0.39, P=0.01; r=0.43, P=0.005; r=0.56, P=0.0001; r=0.45, P=0.003; r=0.48, P=0.0001) and negatively for PSD (r=-0.45, P=0.003; r=-0.45, P=0.003; r=-0.51, P=0.001; r=-0.53, P=0.0001; and r=-0.67, P=0.0001) at all (1.5, 3, 6,12, and 18 cpd) spatial frequencies, respectively. Migraine duration correlated negatively with MD (r=-0.42, P=0.04) and positively with PSD (r=0.42, P=0.03). CONCLUSION: Migraineurs had significantly altered visual field and contrast function at all spatial frequencies to the normal population. These defects share some features with early stages of glaucoma and may relate a possibility for a common vascular disease pathogenesis in these two conditions.

Adult↗
PubMed2001

Mouse mismatch repair gene Msh2 is not essential for transcription-coupled repair of UV-induced cyclobutane pyrimidine dimers.

The human mutS homolog gene MSH2 is essential for DNA mismatch repair (MMR) and defects in this gene can result in increased mutagenesis, genomic instability and hereditary nonpolyposis colorectal cancer (HNPCC). Besides correcting mismatch errors arising from DNA replication, it was shown that deficiencies in bacterial and human MMR genes including MSH2 resulted in defective transcription-coupled repair (TCR) of UV-induced photolesions. Here we show that MMR-deficient fibroblasts derived from two independent isogenic mouse strains with defined Msh2 deficiencies are as proficient in TCR of UV-induced cyclobutane pyrimidine dimers (CPD) as wildtype fibroblasts. Our results indicate that in mouse cells Msh2 is not essential for TCR of UV-induced CPD in contrast to bacteria and human cells and suggest that the biological effects of UV in mouse Msh2(-/-) cells and mice are not due to defective TCR.

Animals↗
PubMed2005

Cyclobutane pyrimidine dimer formation is a molecular trigger for solar-simulated ultraviolet radiation-induced suppression of memory immunity in humans.

We tested the hypothesis that DNA is a target for solar-simulated ultraviolet radiation (ssUVR)-induced suppression of the reactivation of memory immunity in humans. T4N5 liposomes contain the DNA repair enzyme T4 endonuclease V. This cleaves DNA at the site of ultraviolet radiation (UVR)-induced cyclobutane pyrimidine dimers (CPD), initiating DNA repair. It has previously been used to show that CPDs are a key molecular trigger for UVR-induced immunosuppression in mice. To determine whether CPD formation is involved in UVR immunosuppression in humans, nickel-allergic volunteers were irradiated with a range of doses of ssUVR. T4N5 or empty liposomes were then applied after irradiation. Nickel-induced recall immunity was assessed by reflectance spectrometry. T4N5 liposomes inhibited immunosuppression and prevented ssUVR from reducing the number of epidermal dendritic cells. T4N5 liposomes also reduced macrophage infiltration into irradiated epidermis. These studies show that enhanced removal of CPDs from human skin protects from immunosuppression, hence demonstrating that these photolesions are an important molecular event in ssUVR-induced immunosuppression in humans. CPDs also triggered loss of dendritic cells and infiltration by macrophages. It is possible that these changes to antigen presenting cells contribute to ssUVR induced suppression of recall immunity to nickel in humans.

Adult↗
PubMed2006

Relapse tendency after orthodontic correction of upper front teeth retained with a bonded retainer.

OBJECTIVE: To investigate the amount and pattern of relapse of maxillary front teeth previously retained with a bonded retainer. MATERIALS AND METHODS: The study group consisted of 135 study casts from 45 patients. Recordings from study models before treatment (T1), at debonding (T2), and 1 year after removal of the retainer (T3) were present. All patients had been treated with fixed edgewise appliances. The irregularity index (sum of contact point displacement [CPD]) and rotations of front teeth toward the raphe line were calculated at T1, T2, and T3. RESULTS: The mean irregularity index at T1 was 10.1 (range 3.0-29.9, SD 5.4). At T2 it was 0.7 (range 0.0-2.1, SD 0.7), and at T3 it was 1.4 (range 0.0-5.1, SD 1.2). Fifty-five teeth in 42 patients were corrected more than 20 degrees between T1 and T2 (mean correction 31.4 degrees range 20.0-61.7), and mean relapse in this group was 7.3 degrees (range 0.0-20.5). Regarding alignment of the maxillary front teeth, the contact relationship between the laterals and centrals seems to be the most critical. A significant positive correlation was found between the amount of correction of incisor rotation and the magnitude of relapse but not between the amount of correction of CPD and the magnitude of relapse. Eighty-four percent of the overcorrected CPDs returned to a desired position. CONCLUSIONS: Minor or no relapse was noted at the 1-year follow-up.

Adolescent↗
PubMed2004

Trichothiodystrophy fibroblasts are deficient in the repair of ultraviolet-induced cyclobutane pyrimidine dimers and (6-4)photoproducts.

A photosensitive form of trichothiodystrophy (TTD) results from mutations in the same XPD gene as the DNA-repair-deficient genetic disorder xeroderma pigmentosum group D (XP-D). Nevertheless, unlike XP, no increase in skin cancers appears in patients with TTD. Although the ability to repair ultraviolet (UV)-induced DNA damage has been examined to explain their cancer-free phenotype, the information accumulated to date is contradictory. In this study, we determined the repair kinetics of cyclobutane pyrimidine dimers (CPD) and (6-4)photoproducts (6-4PP) in three TTD cell strains using an enzyme-linked immunosorbent assay. We found that all three TTD cell strains are deficient in the repair of CPD and of 6-4PP. UV sensitivity correlated well with the severity of repair defects. Moreover, accumulation of repair proteins (XPB and proliferating cell nuclear antigen) at localized DNA damage sites, detected using micropore UV irradiation combined with fluorescent antibody labeling, reflected their DNA repair activity. Importantly, mutations of the XPD gene affected both the recruitment of the TFIIH complex to DNA damage sites and the TFIIH expression. Our results suggest that there is no major difference in the repair defect between TTD and XP-D and that the cancer-free phenotype in TTD is unrelated to a DNA repair defect.

DNA Helicases↗