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Biomedical subjects

S Mason

Publications and source records attributed to S Mason.

At least 73 records · Page 4Linked to original sources
PubMed1998

Improved healing with a collagen-alginate dressing in the chemical matricectomy.

A prospective clinical trial was conducted to evaluate the efficacy of a collagen-alginate wound dressing in the postoperative management of chemical matricectomies. The study involved 20 patients and 23 separate procedures. The collagen-alginate-dressing treatment group had an average healing time of 24.4 days, compared with 35.8 days for the control group, which received treatment consisting of soaks and daily dressing changes (P < .05). The authors suggest that using a collagen-alginate wound dressing in the postoperative management of chemical matricectomies will shorten healing time, thus reducing infection rates and increasing patient compliance and satisfaction.

Adolescent↗
PubMed1997

The interaction of synaptic vesicle-associated membrane protein/synaptobrevin with botulinum neurotoxins D and F.

Botulinum neurotoxins type D and F are zinc-endopeptidases with a unique specificity for VAMP/synaptobrevin, an essential component of the exocytosis apparatus. VAMP contains two copies of a nine residue motif, termed V1 and V2, which are determinants of the interaction with tetanus and botulinum B and G neurotoxins. Here, we show that V1 plays a major role in VAMP recognition by botulinum neurotoxins D and F and that V2 is also involved in F binding. Site-directed mutagenesis of V1 and V2 indicates that different residues are the determinants of the VAMP interaction with the two endopeptidases. The study of the VAMP-neurotoxins interaction suggest a pairing of the V1 and V2 segments.

Animals↗
PubMed1997

Role of the casein kinase I isoform, Hrr25, and the cell cycle-regulatory transcription factor, SBF, in the transcriptional response to DNA damage in Saccharomyces cerevisiae.

In the budding yeast, Saccharomyces cerevisiae, DNA damage or ribonucleotide depletion causes the transcriptional induction of an array of genes with known or putative roles in DNA repair. The ATM-like kinase, Mec1, and the serine/threonine protein kinases, Rad53 and Dun1, are required for this transcriptional response. In this paper, we provide evidence suggesting that another kinase, Hrr25, is also involved in the transcriptional response to DNA damage through its interaction with the transcription factor, Swi6. The Swi6 protein interacts with Swi4 to form the SBF complex and with Mbp1 to form the MBF complex. SBF and MBF are required for the G1-specific expression of G1 cyclins and genes required for S-phase. We show that Swi6 associates with and is phosphorylated by Hrr25 in vitro. We find that swi4, swi6, and hrr25 mutants, but not mbp1 mutants, are sensitive to hydroxyurea and the DNA-damaging agent methyl methane-sulfonate and are defective in the transcriptional induction of a subset of DNA damage-inducible genes. Both the sensitivity of swi6 mutants to methyl methanesulfonate and hydroxyurea and the transcriptional defect of hrr25 mutants are rescued by overexpression of SWI4, implicating the SBF complex in the Hrr25/Swi6-dependent response to DNA damage.

Casein Kinase I↗
PubMed1997

Do patients need to fast for a 13C-urea breath test?

OBJECTIVE: The 13C-urea breath test (13C-UBT) is a useful non-invasive method of diagnosing Helicobacter pylori infection. One of its limitations, however, is that patients have to fast for 4 h before testing. We have compared the accuracy of a non-fasting 13C-UBT (NF13C-UBT) with a fasting 13C-UBT (F13C-UBT) test and against a gold standard. DESIGN: An unblinded prospective crossover study. METHODS: H. pylori status was assessed by histology, culture and rapid urease test. Patients were defined as H. pylori positive if two or more tests gave a positive result and negative if all tests were negative. H. pylori status was indeterminate if only one test gave a positive result. Following endoscopy patients had a F13C-UBT and then a further NF13C-UBT up to 14 days later after eating two slices of toast with jam or honey and tea or coffee. RESULTS: Of the 222 patients recruited to the study, 123 were gold standard H. pylori positive and 94 were negative with five patients having indeterminate status. Compared to this gold standard the NF13C-UBT had a 98% sensitivity and 96% specificity and the F13C-UBT had a 96% sensitivity and 97% specificity. The NF13C-UBT and F13C-UBT agreed in 217/222 (98%) cases. CONCLUSION: Relaxation of the fasting state does not reduce the accuracy of the 13C-UBT, making this test more convenient for patients.

Biopsy↗
PubMed1997

Spinal and cutaneous schwannomatosis is a variant form of type 2 neurofibromatosis: a clinical and molecular study.

OBJECTIVE: To delineate the clinical phenotype, molecular basis, and implications for screening in patients and families with multiple schwannomas not generally involving the cranium. METHODS: As part of a United Kingdom clinical and genetic study of type 2 neurofibromatosis (NF2) patients and families with multiple schwannomas who do not fulfil diagnostic criteria for NF2 have been identified. The clinical phenotype was studied in the extended families and molecular analysis was carried out at the NF2 gene locus on chromosome 22. RESULTS: Patterns of inheritance in five families with schwannomatosis are consistent with inheritance of an autosomal dominant gene. The consistency of phenotype, with relative sparing of the cranium, is constant in these families. However, families which initially seem to be indicative of schwannomatosis may develop into classic NF2 as shown by a sixth family. Many of the tumours found in these families were referred to as "neurofibroma" when they were clearly schwannomas. This difference in classification has major implications for the relative risk of each particular type of neurofibromatosis and neuropathological review may be important in some cases. Genetic linkage analysis in the two largest families is entirely consistent with primary involvement of the NF2 gene. CONCLUSIONS: Variant forms of neurofibromatosis have presented a dilemma in classification and determination of recurrence risks in families. Previous reports have suggested that schwannomatosis is a sporadic non-hereditary condition. Patients with multiple schwannomas are likely to have a variant form of NF2 and up to a 50% risk of passing on a gene predisposing to multiple schwannoma.

Adolescent↗
PubMed1997

Keynote lecture: objective measures.

The number of young children receiving cochlear implants for management of profound hearing loss is increasing world-wide. In these children, objective measures play a vital role both before and after implantation. They have the capability to assess the degree of hearing loss, guide the selection of the ear and patient for implantation, and provide valuable assistance with the tuning of the device in the difficult-to-test and very young children. There is considerable opportunity for further development of these techniques in the future and, in particular, for accessing central perception and cognition.

Audiometry↗
PubMed1996

Intracellular expression of a single-chain antibody directed to the EGFR leads to growth inhibition of tumor cells.

A gene encoding a single-chain antibody (scFv) which specifically binds the epidermal growth factor receptor (EGFR) has been constructed from hybridoma cells producing the R1 monoclonal antibody. The gene, designated scFv-R1R, was introduced into EGFR transformed NIH3T3 cells via retroviral infection. scFv-R1R was directed to the lumen of the endoplasmic reticulum (ER) where it bound the extracellular domain of the receptor inhibiting its appearance on the plasma membrane. In these cells, EGF induced tyrosine phosphorylation of the EGFR and several substrates was greatly reduced. Furthermore, intracellular retention of EGFR caused a partial inhibition in the transformed growth of the cells. Intracellular expression of receptor tyrosine kinase directed scFvs is a novel approach for affecting tumor cell growth. We have recently shown that scFv-5R directed to ErbB2, another member of the ErbB family, blocks the anchorage independent growth of ErbB2 transformed cells. In order to examine the effects of scFv-R1R and scFv-5R on the long-term growth of tumor cells overexpressing either EGFR or ErbB2, retroviruses encoding the two scFvs were used to infect various human tumor cell lines. Intracellular expression of the scFvs resulted in a marked inhibition of stable colony formation in some of the cell lines. In general, inhibition was observed when overexpressed receptor was targeted. However, in some cases expression of both scFvs was incompatible with long term cell growth suggesting that heterodimers of ErbB2 and EGFR are essential for the growth of some human tumor cell lines.

3T3 Cells↗
PubMed1996

Electric response audiometry in young children before cochlear implantation: a short latency component.

OBJECTIVE: Evaluation of a short latency component (SLC) observed in profoundly deaf young children during recordings of the auditory brain stem response (ABR) before cochlear implantation. DESIGN: Seventy young children (ages 2 to 11 yr) were investigated as part of their routine audiologic and diagnostic assessment, before cochlear implantation. The ABR was evoked using click stimuli and tone pips (500 Hz and 1 kHz) at intensity levels up to 105 dB nHL. The incidence of the SLC arising at a latency of 3 msec with high level click stimuli, in addition to residual ABR waves, was assessed. RESULTS: An SLC was observed in a total of 18 of the 70 children investigated. It was present in 15 out of 31 congenitally deaf children (48%) compared with only 2 out of 33 children deafened after meningitis (6%). A chi-squared test employing a 2 x 2 contingency table shows that this dependency on etiology of deafness is highly statistically significant (p < 0.001). The presence of the SLC in the congenitally deaf children is related to age at the time of the Electric Response Audiometry test and is more likely to be observed in the younger child (p < 0.01). CONCLUSIONS: Interpretation of the ABR in profoundly deaf children should take into consideration the possible presence of the SLC. An evoked potential arising from stimulation of the vestibular system, particularly the vestibular nuclei, is proposed as a likely origin for this component. Damage to sensory cells in the vestibular portion of the labyrinth might explain why an SLC is seen rarely in cases of deafness after meningitis.

Artifacts↗
PubMed1996

[Electrophysiologic and other objective tests in pediatric cochlear implantation].

Various electrophysiological procedures have been developed and utilized in pediatric cochlear implant patients. During surgery and just before implantation, recording of Electrically-Evoked Auditory Brainstem Responses (EABR) by electrical stimulation via a promontory needle electrode is a useful tool to select the suitable ear for implantation in the absence of other criteria. After implantation, peroperative assessment of the Electrically-Evoked Stapedius Reflex thresholds allows an estimation of the comfort levels not to be exceeded during the first tuning sessions. Recording of Averaged Electrode Voltages (AEV) provides assurance against general device failure, and can localize defectives electrodes which will be disactivated. Finally EABR obtained by electrical stimulation via the implant is the last control showing objective auditory responses. Furthermore there is a strong correlation between EABR thresholds and behavioral thresholds which will be obtained during the first tuning session. When a device malfunction is suspected after implantation, recording of AEV and EABR are performed, and the results are compared with the preoperative data.

Age Factors↗
PubMed1995

Eleven novel mutations in the NF2 tumour suppressor gene.

Eleven novel mutations were identified in the NF2 tumour suppressor gene in a panel of British NF2 patients. Screening was performed using a combination of heteroduplex and single-strand conformation polymorphism analysis on polymerase chain reaction amplified material.

Base Sequence↗
PubMed1995

Krox20 may play a key role in the stabilization of long-term potentiation.

Long-term potentiation-inducing stimulation of the perforant path was followed in dentate gyrus granule cells by a dramatic increase of mRNA and protein for Krox20, a zinc-finger-containing transcription factor. Induction of Krox20 required stimulation sufficient to induce LTP and was prevented by NMDA antagonists CPP and MK-801, which block LTP induction. Krox20 protein increased within 20 min of tetanization, was maximal between 1 and 8 h, and was still significantly elevated at 24 h after LTP induction. This prolonged appearance is in striking contrast with the more transient induction of the related molecule, Krox24. The elevation in the mRNA for Krox20 and Krox24 was of similar duration, suggesting that the Krox20 protein has a greater stability and may play a key role in the stabilization of long-term potentiation.

Animals↗
PubMed1994

Detection of respiratory syncytial virus infection in nasal aspirate samples by flow cytometry.

HYPOTHESES: (i) Flow cytometry has the potential for rapid detection of respiratory viral antigens. (ii) This technique can be applied to viral diagnosis in clinical samples. OBJECTIVES AND STUDY DESIGN: (i) To study the identification of six common respiratory viral pathogens by flow cytometry, in virus infected and uninfected cultured cells, as models of positive and negative clinical samples. (ii) To compare flow cytometry with the established techniques of viral isolation and immunofluorescent microscopy in the diagnosis of respiratory syncytial virus infection in 68 naso-pharyngeal aspirates taken from children and sent to the virology laboratory for routine virological diagnosis. RESULTS: (i) For each virus analysed, populations of infected and non-infected cells were clearly discernable, confirming potential for this method in rapid viral diagnosis in clinical samples. (ii) Two definitions were employed for a sample to be positive by flow cytometry, these were compared with the combined established techniques. The sensitivity, specificity, positive and negative predictive values of flow cytometry were 41%, 98%, 92% and 71% for the first definition and 74%, 88%, 80% and 84% for the second definition respectively. CONCLUSIONS: As tested in this study, flow cytometry is less sensitive than established techniques as well as recently developed rapid diagnostic techniques for the diagnosis of respiratory syncytial virus infection. Further evaluation of the potential of flow cytometry in rapid viral diagnosis is warranted.

Journal Article↗
PubMed1994

Germline mutations in the neurofibromatosis type 2 tumour suppressor gene.

The recent identification of the NF2 tumour suppressor gene has enabled large scale screening for pathological mutations in the gene. We have sought germline mutations in the NF2 gene by SSCP and heteroduplex analysis of cDNA and genomic DNA samples followed by cloning and sequencing of mutant alleles. In the present report we describe 11 putative pathological mutations, including five nonsense mutations, three short insertions or deletions causing frameshifts and three missense mutations. Most stop mutations and frameshift mutations were found in individuals expressing a severe phenotype while one of the three missense mutations was associated with a mild phenotype. Four unrelated NF2 patients of the 93 tested were found to have identical nonsense mutations caused by a C to T transition (C169) in a CpG dinucleotide, which is a potential mutational hotspot in the NF2 tumour suppressor gene.

Base Sequence↗
PubMed1994

Women's health care centers: multiple definitions.

Feminist health and holistic health movements predate and contribute to the current changes in women's health care. Recently, there has been a rivitalization of women's health centers reflecting three approaches to women's health: (1) centers with an exclusive focus on one health problem, e.g., breast cancer, chemical dependency (2) centers with a predominantly reproductive focus, and (3) centers with a holistic/feminist health care focus. Based on an exploratory survey of women's centers in a large city, this paper identifies differences among them and discusses the potential for misguidance that may occur with the current increase in women's health centers. It also discusses the implications of this growth for social work education and clinical practice.

Adolescent↗