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Biomedical subjects

C Daniels

Publications and source records attributed to C Daniels.

At least 37 records · Page 2Linked to original sources
PubMed1999

Assessment of clinical case presentations for the Membership in Orthodontics, Royal College of Surgeons of England 1995, 1996.

The cases presented and treated at successive examinations by the candidates for the Membership Examination in Orthodontics in 1995 and 1996 at The Royal College of Surgeons of England, were of a very high standard and demonstrated a wide range of treatment modalities. All cases had fixed appliances, predominantly with pre-adjusted Edgewise appliances. IOTN confirmed that most cases were in great need of treatment, with PAR scores showing them to be treated to a high standard.

Dental Records↗
PubMed1999

Intravenous nitrates for pharmacological stimulation during head-up tilt testing in patients with suspected vasovagal syncope and healthy controls.

Nitrates may be used for pharmacological stimulation during tilt testing for the diagnosis of vasovagal syncope. In this study we assessed the diagnostic value of intravenous nitrates during tilt testing in patients with a typical history of vasovagal syncope. Twenty patients and 23 controls were tilted at 700 for a maximum duration of 30 minutes. After a 10-minute baseline supine phase, the test started with a continuous nitrate infusion at 1 microg/kg/min and increased every 5 minutes by 1 microg/kg/min, to a maximum of 6 microg/kg/min at the end of the test. The test was ended if the subjects developed a positive response (syncope or presyncope). Nineteen patients (95%) and 17 (74%) of the controls had a positive response. At test end sensitivity was 95%, but specificity was 26% and accuracy was 58%. Receiver operator characteristics (ROC) analysis revealed a maximum accuracy of 79% at 18 minutes, with a sensitivity of 80% and a specificity of 78%. Intravenous nitrates during tilt testing in patients with typical clinical criteria of vasovagal syncope is highly effective in provoking vasovagal syncope. Based on the ROC analysis, a maximum accuracy of 79% was attained at 18 minutes (at a dose of 4 microg/kg/min), suggesting a good diagnostic performance when tilt duration is limited to this point. A positive result requiring more than 18 minutes of stimulated tilting should be interpreted with caution, due to the accompanying considerable decrease of specificity.

Adult↗
PubMed1998

Overexpression and topology of the Shigella flexneri O-antigen polymerase (Rfc/Wzy).

Lipopolysaccharides (LPS), particularly the O-antigen component, are one of many virulence determinants necessary for Shigella flexneri pathogenesis. O-antigen biosynthesis is determined mostly by genes located in the rfb region of the chromosome. The rfc/wzy gene encodes the O-antigen polymerase, an integral membrane protein, which polymerizes the O-antigen repeat units of the LPS. The wild-type rfc/wzy gene has no detectable ribosome-binding site (RBS) and four rare codons in the translation initiation region (TIR). Site-directed mutagenesis of the rare codons at positions 4, 9 and 23 to those corresponding to more abundant tRNAs and introduction of a RBS allowed detection of the rfc/wzy gene product via a T7 promoter/polymerase expression assay. Complementation studies using the rfc/wzy constructs allowed visualization of a novel LPS with unregulated O-antigen chain length distribution, and a modal chain length could be restored by supplying the gene for the O-antigen chain length regulator (Rol/Wzz) on a low-copy-number plasmid. This suggests that the O-antigen chain length distribution is determined by both Rfc/Wzy and Rol/Wzz proteins. The effect on translation of mutating the rare codons was determined using an Rfc::PhoA fusion protein as a reporter. Alkaline phosphatase enzyme assays showed an approximately twofold increase in expression when three of the rare codons were mutated. Analysis of the Rfc/Wzy amino acid sequence using TM-PREDICT indicated that Rfc/Wzy had 10-13 transmembrane segments. The computer prediction models were tested by genetically fusing C-terminal deletions of Rfc/Wzy to alkaline phosphatase and beta-galactosidase. Rfc::PhoA fusion proteins near the amino-terminal end were detected by Coomassie blue staining and Western blotting using anti-PhoA serum. The enzyme activities of cells with the rfc/wzy fusions and the location of the fusions in rfc/wzy indicated that Rfc/Wzy has 12 transmembrane segments with two large periplasmic domains, and that the amino- and carboxy-termini are located on the cytoplasmic face of the membrane.

Alkaline Phosphatase↗
PubMed1998

A comparison of artificial saliva and pilocarpine in the management of xerostomia in patients with advanced cancer.

This was a crossover study comparing a mucin-based artificial saliva (Saliva Orthana) and pilocarpine hydrochloride (Salagen) in the management of xerostomia in patients with advanced cancer. The pilocarpine was found to be more effective than the artificial saliva in terms of mean change in visual analogue scale scores for xerostomia (P = 0.003). Furthermore, more patients reported that it had helped their xerostomia, and more patients wanted to continue with it after the study. However, the pilocarpine was found to be associated with more side-effects than the artificial saliva (P < 0.001). These side-effects were usually reported as being mild. Of the patients who used both treatments, 50% preferred the artificial saliva, and 50% preferred the pilocarpine. The commonest reason for preferring the artificial saliva was the fact that it was a spray, rather than a tablet.

Adult↗
PubMed1997

PhoP/Q regulated genes in Salmonella typhi identification of melittin sensitive mutants.

Many of the genes (pags (phoP activated genes) and prgs (phoP repressed genes)) regulated by the PhoP and PhoQ proteins (PhoP/Q) are necessary for survival of Salmonella typhimurium in murine macrophages and pathogenesis in mice. Although a great deal is known about the S. typhimurium phoP/Q regulon, little has been done with the human specific pathogen S. typhi, prompting us to investigate S. typhi phoP/Q regulated genes. Isogenic phoP12 (null) and phoP24 (constitutive) strains were constructed in S. typhi Ty2 and S. typhimurium C5 strains. Comparison of whole cell proteins from these strains by SDS-PAGE showed differences in both the number and molecular mass of PhoP/Q regulated proteins. This suggested that S. typhi and S. typhimurium may have different PhoP/Q regulated proteins and/or that their regulation may be different. A genetic procedure was developed to isolate mutations in PhoP/Q regulated genes. This involved random MudJ transposon mutagenesis of a phoP12 mutant, creating lacZ-gene fusions, and screening for Lac+ or Lac- colonies. A mobilizable plasmid carrying the phoP24 mutant gene was conjugated into these insertion mutants. Those that changed from Lac- to Lac+ were inferred to be pag::MudJ insertions and those that changed from Lac+ to Lac- were inferred to be prg::MudJ insertions. Five mutants with PhoP/Q regulated MudJ fusions were found by this scheme. The mutations were termed pqa (PhoPQ activated) and pqr (PhoPQ repressed) to distinguish them from other PhoP/Q regulated genes. The pqa/pqr::MudJ mutations were transduced into S. typhi phoP+ and phoP24 strains by Vi-l phage transduction. Characterization of the mutants (Southern blot analysis, beta-galactosidase activity on indicator plates and in liquid cultures) strongly suggested that their MudJ insertion mutations were in five different genes. Further characterization involved determining cationic peptide sensitivity and mouse virulence. Two mutants were found to be sensitive to the antimicrobial peptide melittin.

Animals↗
PubMed1996

Nova Scotia Breast Screening Program experience: use of needle core biopsy in the diagnosis of screening-detected abnormalities.

PURPOSE: To evaluate a mammography screening program that uses a multidisciplinary team approach and needle core biopsy. MATERIALS AND METHODS: A total of 10,000 asymptomatic women (aged 40-74 years) underwent screening in the Nova Scotia Breast Screening Program between June 1991 and April 1994. Women aged 50-69 years were the target group. All mammograms were read by one of four radiologists. Patients with abnormal screening findings underwent work-up, which included needle core biopsy, at one of two diagnostic centers. RESULTS: Of 10,000 women, 2,794 were aged 40-49 years; 4,097, 50-59 years; 2,941, 60-69 years; and 168, 70-74 years, with 3.9, 6.4, 12.2, and 23.8 cancers detected per 1,000 patients, respectively. The overall rate was 7.7 cancers detected per 1,000 patients. Abnormalities were detected at screening in 838 patients (8.4%), 181 of whom underwent open surgery, with malignancy diagnosed in 77 (42%). Sixty-one (79%) of 77 patients had stage 0 or I cancer. In 43 (72%) of 60 patients in whom node status was assessed, findings were negative. CONCLUSION: A screening program with needle core biopsy and a multidisciplinary team approach to diagnosis is effective.

Adult↗
PubMed1996

Sweet taste transduction in hamster: sweeteners and cyclic nucleotides depolarize taste cells by reducing a K+ current.

1. The gigaseal voltage-clamp technique was used to record responses of hamster taste receptor cells to synthetic sweeteners and cyclic nucleotides. Voltage-dependent currents and steady-state currents were monitored during bath exchanges of saccharin, two high-potency sweeteners, 8-chlorophenylthio-adenosine 3',5'-cyclic monophosphate (8cpt-cAMP), and dibutyryl-guanosine 3',5'-cyclic monophosphate (db-cGMP). 2. Of the 237 fungiform taste cells studied, only one in eight was sweet responsive. Outward currents, both voltage-dependent and resting, were reduced by all of the sweeteners tested in sweet-responsive taste cells, whereas these currents were unaffected by sweeteners in sweet-unresponsive taste cells. 3. In every sweet-responsive cell tested, 8cpt-cAMP and db-cGMP mimicked the response to the sweeteners, but neither nucleotide elicited responses in sweet-unresponsive cells. Thus there was a one-to-one correlation between sweet responsivity and cyclic nucleotide responsivity. 4. Sweet responses showed cross adaptation with cyclic nucleotide responses. This indicates that the same ion channel is modulated by sweeteners and cyclic nucleotides. 5. The sweetener- and cyclic nucleotide-blocked current had an apparent reversal potential of -50 mV, which was close to the potassium reversal potential in these experiments. In addition, there was no effect of sweeteners and cyclic nucleotides in the presence of the K+ channel blocker tetraethylammonium bromide (TEA). These data suggest that block of a resting, TEA-sensitive K+ current is the final common step leading to taste cell depolarization during sweet transduction. 6. These data, together with data from a previous study (Cummings et al. 1993), suggest that both synthetic sweeteners and sucrose utilize second-messenger pathways that block a resting K+ conductance to depolarize the taste cell membrane.

Animals↗
PubMed1994

Stereotactic fine-needle aspiration cytology of nonpalpable breast lesions: initial experience in a tertiary-care institution.

To assess the accuracy of stereotactic fine-needle aspiration cytology in the diagnosis of nonpalpable breast lesions, this procedure was performed in 226 consecutive patients, all women, immediately before needle localization and excision of the lesions. The patients were treated at a tertiary-care hospital between December 1989 and October 1991. The cytologic results (lesion benign, atypical, suspicious or malignant or insufficient material for interpretation) were compared with the histologic findings and the degree of suspicion (low, slight or high) on the basis of mammographic examination. The aspiration procedures were successful in only 159 patients (70.4%), and for 155 of these, histologic findings were available for correlation. The number of unsatisfactory specimens in this group was large: 65 of 155 (42%). When unsatisfactory specimens were included in the calculations and a cytologic finding of a suspicious or malignant lesion was treated as positive, the sensitivity of fine-needle aspiration cytology for malignancy was 23% (8/35) and the specificity 53% (63/120). The positive and negative predictive values were 89% (8/9) and 78% (63/81) respectively. A cytologic finding that the lesion was benign was unreliable in lesions for which the mammographic suspicion of malignancy was slight or high (4 of 30 malignant lesions with slight mammographic suspicion and 4 of 7 with high mammographic suspicion were classified as benign on the basis of the cytologic examination). Of the 24 cases with atypical cytologic findings, 10 involved malignancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy, Needle↗
PubMed1989

Corporate response to reproductive hazards in the workplace: results of the Family, Work, and Health Survey.

As a part of a Family, Work, and Health Survey, we analyzed corporate practices regarding reproductive hazards in the chemical and electronics manufacturing industries in Massachusetts. Over half of the 198 firms surveyed had at least one of four designated reproductive hazards in use. Among these firms, 57% provided information on reproductive risks to employees. Nearly 20% of companies excluded certain classes of workers from substances, work areas, or occupations on the basis of reproductive health concerns. Another 13% offered voluntary transfers to workers concerned about reproductive risks. With one exception, all restrictions and transfers applied to women only--even when scientific evidence supports potential reproductive risk to both sexes. Analysis of corporate practices by industry type, and size, gender stratification, and unionization of the workforce was carried out. Results of the survey raise important public health concerns about corporate practices that may restrict women's job opportunities on the basis of reproductive status while underprotecting the health of male workers.

Adolescent↗
PubMed1989

Variations in fluoroscopic and spot film techniques during extracorporeal shock wave lithotripsy.

The radiation techniques of different operators who performed extracorporeal shock wave lithotripsy of the kidney were evaluated retrospectively. The study was limited to 9 operators who each performed more than 100 procedures on the Dornier lithotriptor. The average fluoroscopic time and number of video spot films per procedure for all operators were 4.1 minutes and 6.5, respectively. However, the average fluoroscopic time per operator varied from 1.4 to 7.6 minutes and the average number of video spot films per operator varied from 3 to 13. The results illustrate the need for some operators to reduce fluoroscopic time and video spot filming.

Fluoroscopy↗
PubMed1987

Expression and rescuing of a cloned human tumour necrosis factor gene using an EBV-based shuttle cosmid vector.

A cosmid vector carrying the Epstein-Barr virus origin of replication, the EBNA-1 gene, the hygromycin phosphotransferase (hph) gene and pBR322 sequences has been constructed. This cosmid can replicate autonomously in the nucleus of human tissue culture cells, even when it carries a 35-kb long insert. The cosmid can be rescued from the transfected cells by cloning it directly into ampicillin-sensitive Escherichia coli. A gene for human tumour necrosis factor (TNF) cloned into this cosmid vector was introduced in tissue culture cells, where it was transcribed into mature mRNA.

Cell Line↗
PubMed1986

The inhibition by azatadine of the immunological release of leukotrienes and histamine from human lung fragments.

The effects of the H1 antihistamine azatadine on the antigen-induced release of slow reacting substance of anaphylaxis (leukotrienes C4 and D4) and histamine from passively sensitized human lung fragments were determined. Azatadine 0.1-10 microM significantly and dose dependently inhibited the release of leukotrienes from lung by 22-71%. Histamine release was also inhibited by azatadine 10 microM.

Cyproheptadine↗
PubMed1985

Rates of hydration of fatty acids bound to unilamellar vesicles of phosphatidylcholine or to albumin.

The rates of hydration of naturally occurring fatty acids bound to unilamellar vesicles of dimyristoylphosphatidylcholine were measured by following the rate of quenching of the inherent fluorescence of albumin. Rates of hydration of fatty acids bound to albumin could be estimated from the same data. The data show that these rates depend on the chain length and unsaturation of the fatty acid. Increasing chain length diminishes the rate of hydration whereas increasing unsaturation increases this rate. Rates of hydration of fatty acids bound to lipid vesicles appear to be rapid enough to account for intracellular movement between compartments in the absence of carrier proteins. It is uncertain whether this is true for hydration of fatty acids bound to albumin. Rates for this process are about 100-300 times slower vs. rates of hydration of fatty acids bound to lipid vesicles.

Animals↗
PubMed1985

Generator malfunctions detected by radiation waveforms.

Radiation waveforms show the variation of x-ray intensity with time. Acceptance testing was done on 15 newly installed x-ray units and the waveforms of seven showed a total of 13 generator-related faults. Of the 13 faults, six would have caused inconsistently exposed radiographs in four units. These faults were corrected before the units were used clinically. After one year of use, the waveforms from five of the 15 units showed serious malfunctions. This illustrates the need for acceptance testing, radiation waveform monitoring and an active generator quality control program.

Quality Control↗
PubMed1983

Comparison and variations of the speed of radiographic film.

A study of 50 different batches of film from 20 institutions across Ontario was conducted to measure sensitivities when exposed between intensifying screens and to white light. For films of different types but of the same nominal speed, the x-ray exposures required to produce a net optical density of 1.0 varied by a factor of up to 2.5. For films of the same type from different batches, the required exposure varied by +/- 20%. It was found that sensitivity to white light from the commonly used Wejex sensitometer was not always a good indicator of x-ray sensitivity, and therefore should not be used to compare speeds of different films or films from different batches.

Technology, Radiologic↗