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Biomedical subjects

M Mather

Publications and source records attributed to M Mather.

At least 19 recordsLinked to original sources
PubMed2002

A basic study of some normoxic polymer gel dosimeters.

Polymer gel dosimeters offer a wide range of potential applications in the three-dimensional verification of complex dose distribution such as in intensity-modulated radiotherapy (IMRT). Until now, however, polymer gel dosimeters have not been widely used in the clinic. One of the reasons is that they are difficult to manufacture. As the polymerization in polymer gels is inhibited by oxygen, all free oxygen has to be removed from the gels. For several years this was achieved by bubbling nitrogen through the gel solutions and by filling the phantoms in a glove box that is perfused with nitrogen. Recently another gel formulation was proposed in which oxygen is bound in a metallo-organic complex thus removing the problem of oxygen inhibition. The proposed gel consists of methacrylic acid, gelatin, ascorbic acid, hydroquinone and copper(II)sulphate and is given the acronym MAGIC gel dosimeter. These gels are fabricated under normal atmospheric conditions and are therefore called 'normoxic' gel dosimeters. In this study, a chemical analysis on the MAGIC gel was performed. The composition of the gel was varied and its radiation response was evaluated. The role of different chemicals and the reaction kinetics are discussed. It was found that ascorbic acid alone was able to bind the oxygen and can thus be used as an anti-oxidant in a polymer gel dosimeter. It was also found that the anti-oxidants N-acetyl-cysteine and tetrakis(hydroxymethyl)phosphonium were effective in scavenging the oxygen. However, the rate of oxygen scavenging is dependent on the anti-oxidant and its concentration with tetrakis(hydroxymethyl)phosphonium being the most reactive anti-oxidants. Potentiometric oxygen measurements in solution provide an easy way to get a first impression on the rate of oxygen scavenging. It is shown that cupper(II)sulphate operates as a catalyst in the oxidation of ascorbic acid. We, therefore, propose some new normoxic gel formulations that have a less complicated chemical formulation than the MAGIC gel.

Acetylcysteine↗
PubMed2001

Adoption.

Explore the source record for details and available documents.

Adoption↗
PubMed2001

Polycations induce the release of soluble intermembrane mitochondrial proteins.

The release of proapoptotic proteins from the intermembrane space of mitochondria is an early critical step in many pathways to apoptosis. Induction of the mitochondrial permeability transition pore (PTP) was suggested to be the mechanism of the release of soluble mitochondrial intermembrane proteins (SIMP) in apoptosis. However, several studies suggested that proapoptotic proteins (e.g. Bax and Bid) can induce the release of SIMP (e.g. cytochrome c (cyt c) and adenylate kinase 2 (AK2)) in vivo and in vitro independent of PTP. We have found that a number of structurally diverse polycations, such as aliphatic polyamines (e.g. spermine and to a lesser extent spermidine), aminoglycosides (e.g. streptomycin, gentamicin and neomycin), and cytotoxic peptides (e.g. melittin), induce the release of SIMP from liver mitochondria, in vitro. All the polycations released AK2 together with cyt c, suggesting that rupture of the outer membrane is a common mechanism of cyt c release by these polycations. Several polycations (e.g. spermine, spermidine and neomycin) induced SIMP release without inducing significant swelling, and this release was not inhibited significantly by the PTP inhibitor cyclosporin. In contrast, under the same conditions, streptomycin and melittin induced swelling and SIMP release that was inhibited strongly by cyclosporin. Gentamicin-induced swelling and release of SIMP were partially inhibited by cyclosporin. The affinity of polyamines to the anionic phospholipids of the mitochondrial membranes (spermine=neomycin>gentamicin>streptomycin=spermidine) correlated roughly with their ability to induce PTP-independent release of SIMP, which suggests that the binding of polycations to the anionic phospholipids of the outer mitochondrial membrane facilitates the rupture of this membrane. However, some polycations facilitated the induction of PTP, possibly by binding to cardiolipin on the inner membrane. This dual mechanism may be relevant to the induction of SIMP release in apoptosis.

Adenylate Kinase↗
PubMed2001

How events are reviewed matters: effects of varied focus on eyewitness suggestibility.

Witnesses to a crime or an accident perceive that event only once, but they are likely to think or talk about it multiple times. The way in which they review the event may affect their later memory. In particular, some types of review may increase suggestibility if the witness has been exposed to postevent misleading information. In Experiment 1, participants viewed a videotaped crime and then received false suggestions about the event. We found that participants who were then asked to focus on specific details when reviewing the event were more suggestible on a later source memory test than participants asked to review the main points. The findings of Experiment 2 suggest that this effect was not due to a criterion shift at test. These findings indicate that the type of rehearsal engaged in after witnessing an event can have important consequences for memory and, in particular, suggestibility.

Adult↗
PubMed2001

Clinical evaluation of an automatic flossing device vs. manual flossing.

The aim of this study was to compare the effectiveness of an automatic flossing device to manual flossing. A total of seventy adult subjects (20 males and 50 females) were stratified into two groups balanced for age, sex, modified gingival index (MGI), plaque index (PI) and bleeding sites (Eastman Bleeding Index) using screening data. One group was randomly assigned the automatic power flosser and the other group was assigned manual dental floss. The subjects were instructed to brush their teeth twice a day (in the morning and before bedtime) for 30 seconds using the provided manual toothbrush and toothpaste. They were also to use their assigned dental floss or automatic power flosser once in the morning following toothbrushing. There was no significant difference between manual flossing and automatic flossing with respect to the MGI and the BI. There was, however, a significant difference at day 15 in the PI; however, this difference was only 0.73%. There was no significant difference in the PI at day 30 between the two techniques. The statistically significant difference noted in the interproximal PI at both day 15 and day 30 was less than 2%. Since the differences in plaque scores between the groups were so small, there was no apparent impact on gingival health since both flossers resulted in similar health benefits. Since there was a marked preference for the automatic flosser, patient compliance with the automatic flossing device may be better than with manual floss. Therefore, overall gingival health may benefit from this device.

Adult↗
PubMed2000

Aging enhances the activation of the permeability transition pore in mitochondria.

Aging is associated with mitochondrial dysfunction in several tissues. However, it is not known how the observed mitochondrial dysfunction is related to aging-associated tissue degeneration. We have shown previously that the activation of the permeability transition pore (PTP), which is believed to play a critical role in cell necrosis and apoptosis, is enhanced in spleen lymphocytes from old mice. Here we show that the threshold for calcium-induced, cyclosporin-sensitive, calcium release was significantly lower in isolated brain and liver mitochondria from aging mice. Thus, aging mice exhibit enhanced PTP activation in lymphocytes, brain, and liver. These results suggest that aging increases the susceptibility to calcium-dependent cell death (e.g., excitotoxicity, ischemia-reperfusion damage) in the brain, liver, and possibly other tissues. In addition, other pathways to apoptosis or necrosis that depend on PTP activation are also likely to be enhanced by aging.

Aging↗
PubMed2000

Aging and reflective processes of working memory: binding and test load deficits.

It was hypothesized that age-related deficits in episodic memory for feature combinations (e.g., B. L. Chalfonte & M. K. Johnson, 1996) signal, in part, decrements in the efficacy of reflective component processes (e.g., M. K. Johnson, 1992) that support the short-term maintenance and manipulation of information during encoding (e.g., F. 1. M. Craik. R. G. Morris. & M. L. Gick, 1990; T. A. Salthouse, 1990). Consistent with this, age-related binding deficits in a working memory task were found in 2 experiments. Evidence for an age-related test load deficit was also found: Older adults had greater difficulty than young adults when tested on 2 features rather than 1, even when binding was not required. Thus, disruption of source memory in older adults may involve deficits in both encoding processes (binding deficits) and monitoring processes (difficulty accessing multiple features, evaluating them, or both).

Adolescent↗
PubMed2000

Choice-supportive source monitoring: do our decisions seem better to us as we age?

Participants were given several 2-option choices and then asked to review how they felt about their decisions, to review the details of their decisions, or to do an unrelated task. When later asked to attribute features to the previous options, in each condition older adults (64-83 years) attributed significantly more positive and fewer negative features to their chosen options than to foregone options. Younger adults' (18-22 years) attributions were as choice-supportive as those of older adults in the affective review condition but were less so in the other conditions. The age difference was present even when older and younger adults were equated for source identification and recognition accuracy. This study suggests that as people age, their tendency to distort memory in favor of the options they chose increases. In addition, it suggests that affectively reviewing choices increases younger adults' tendency toward choice-supportive memory.

Adolescent↗
PubMed2000

Misremembrance of options past: source monitoring and choice.

This study reveals that when remembering past decisions, people engage in choice-supportive memory distortion. When asked to make memory attributions of options' features, participants made source-monitoring errors that supported their decisions. They tended to attribute, both correctly and incorrectly, more positive features to the option they had selected than to its competitor. In addition, they sometimes attributed, both correctly and incorrectly, more negative features to the nonselected option. This pattern of distortion may be beneficial to people's general well-being, reducing regret for options not taken. At the same time, it is problematic for memory accuracy, for accountability, and for learning from past experience.

Adult↗
PubMed1999

Adoption: a forgotten paediatric speciality.

OBJECTIVE: To study the medical, emotional, and developmental profile of children being considered for permanent substitute care. DESIGN: A retrospective analysis of 100 adoption/permanency medicals. SETTING: All children considered by the adoption and permanency panel in Greenwich, south east London, between 1994 and 1998. OUTCOME MEASURES: Analysis of medical reports completed using the British Agencies for Adoption and Fostering form C (under 5 years) or form D (over 5 years). These include the details of a physical examination, including vision, hearing, height, and weight; emotional and behavioural concerns expressed by the foster carer and school progress. RESULTS: These children have complex needs. Only 31 of the 100 children were considered unlikely to have significant medical, developmental, or emotional problems. CONCLUSIONS: Adoption medical work is becoming more specialised. Healthcare commissioners should establish minimum standards for the doctors involved in this work. As the NHS moves towards becoming a more primary care led organisation, this small service must not be forgotten. The NHS devotes few resources and little training to adoption. The medical input required to support adoption and fostering services should be recognised as a specialist paediatric service and adequately resourced.

Adolescent↗
PubMed1997

Unconscious influences on amnesics' word-stem completion.

Amnesic patients and control subjects were asked to complete three-letter word-stems under one of three retrieval conditions. In a direct condition, they were told to use the stems as retrieval cues for words that had just been presented in a study list. In an indirect condition, they were told to use the first word that came to mind with no reference made to the study list. Finally, in an oppositional condition, they were told to use the first word that came to mind unless it had appeared on the study list. During the study list presentation, the patients and controls had analyzed each word according to either semantic (associating to each word) or graphemic (counting letters with enclosed spaces) instructions. The results revealed that the control subjects produced a different number of study words during retrieval as a function of retrieval instructions and encoding condition. The amnesics, however, did not vary their performance as a function of retrieval instructions. Under all conditions, they completed the word-stems far more frequently with words from the study list than would be expected by chance and they consistently produced more semantic than graphemic responses. We concluded that semantic analysis might affect the fluency with which an item occurs for the amnesic, but that the item itself remains independent of the source of that fluency for these patients. Thus, the level of analysis performed on a word during study can affect the unconscious performance of amnesic patients but is unavailable for use during conscious retrieval.

Aged↗
PubMed1997

Evaluating characteristics of false memories: remember/know judgments and memory characteristics questionnaire compared.

Subjects hearing a list of associates to a nonpresented lure word later often claim to have heard the lure (Deese, 1959; Roediger & McDermott, 1995). To examine the characteristics of such false memories, subjects completed a memory characteristics questionnaire (MCQ; Johnson, Foley, Suengas, & Raye, 1988) or made remember/know (RK; Gardiner & Java, 1993) judgments for previously heard theme associates and nonpresented lures. MCQ ratings indicated that false memories for lures had less auditory detail and less remembered feelings and reactions than memories for presented words. In addition, rates of false recognition for lures were significantly lower than rates of correct recognition when items from various themes were intermixed instead of blocked at acquisition and subjects made MCQ ratings instead of RK judgments. This demonstrates that false memories can be affected both by how they are acquired and by how extensively they are examined at retrieval.

Adult↗
PubMed1995

The effect of an antiseptic mouthrinse on implant maintenance: plaque and peri-implant gingival tissues.

The purpose of this controlled double-blind, parallel, randomized clinical study was to determine the effect of antiseptic mouthrinse on parameters important to dental implant maintenance. Plaque, peri-implant gingivitis, gingival bleeding, probing depth, and attachment level were assessed over a 3-month test period. Twenty healthy adult patients each of whom had at least two dental implants, a modified gingival index > 1.5, and a modified Quigley-Hein plaque index score > 1.7 were enrolled into the study. After a thorough oral prophylaxis, patients were randomly assigned to either the antiseptic mouthrinse or a 5% hydroalcohol placebo mouthrinse group and instructed to rinse twice daily for 30 seconds with 20 ml of their assigned mouthrinse as an adjunct to their usual oral hygiene procedures. The baseline examination included plaque index, gingival index, bleeding index, probing depth measurement, and attachment level measurements. The plaque and gingival indices were rescored at 1, 2, and 3 months. Probing depths, attachment levels, and bleeding index were determined again at 3 months only. At the end of 3 months, the antiseptic mouthrinse group had statistically significant reductions in plaque index, gingival index, and bleeding index compared to the placebo group. There were no significant differences between groups in probing depth or attachment level. The results of this clinical study indicate that twice daily use of an antiseptic mouthrinse may provide benefits in the maintenance of dental implants.

Adult↗
PubMed1994

An alternative to dental floss in a personal dental hygiene program.

The concept of gingival massage on maintaining the health of the gingiva may be of value as an adjunct in the periodontal maintenance phase of treatment. This study compared dental floss to a test product, a massage device, in a randomized population of 20 male and female subjects. Clinical measurements were taken at baseline, week 3, and week 6. Patients were instructed to brush twice daily using their normal hygiene methods and to use the assigned product once daily. Plaque index (PI), bleeding index (BI) and pocket probing depths did improve in both the control and the test groups, but the differences did not favor either group over the other. The gingival index (GI) did, however, significantly decrease in the massage group, suggesting that this product may not only be an alternative to dental floss, but may provide added benefits from gingival massaging.

Adult↗
PubMed1989

A survey of drug prescribing practices of dentists.

A survey of drug prescribing habits of 357 dentists practicing in five counties in Western New York was conducted in 1986. Respondents represented both general practitioners and specialists who were graduates of 25 different dental schools. From this study it can be concluded that dentists prescribe a wide range of drugs representing over 13 drug categories. The most frequently prescribed drug categories were antibiotics, narcotic analgesics, non-steroidal inflammatory agents, non-narcotic analgesics, and fluorides. The most frequent prescribers of drugs were oral surgeons, endodontists and periodontists.

Dentists↗
PubMed1988

The nucleotide sequence of the cyd locus encoding the two subunits of the cytochrome d terminal oxidase complex of Escherichia coli.

The cytochrome d terminal oxidase complex is one of two terminal oxidases in the aerobic respiratory chain of Escherichia coli. The enzyme is located in the cytoplasmic membrane where it oxidizes ubiquinol-8 in the bilayer and reduces oxygen to water. Enzyme turnover is coupled to the generation of a proton-motive force, resulting in electrogenic translocation across the membrane of one proton per electron passing through the system. The enzyme is an alpha beta heterodimer containing four hemes. The cyd locus, encoding both subunits, has previously been genetically mapped and cloned. This work describes an insertion and deletion analysis of cyd which indicates the direction of transcription, defines the coding regions, and suggests that cyd is an operon. In addition, the complete DNA sequence of the cyd gene is reported. Two open reading frames, separated by 18 base pairs, encode the two subunits of the oxidase complex. Hydropathy profiles of the deduced protein sequence indicate that subunits I and II are each likely to have multiple transmembrane elements. There are only 10 histidines in both subunits, several of which are likely to serve as heme axial ligands.

Amino Acid Sequence↗