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P T Quinn

Publications and source records attributed to P T Quinn.

13 recordsLinked to original sources
PubMed2006

SAOZ measurements of NO2 at Aberystwyth.

We present in this paper fifteen years' measurements, from March 1991 to September 2005, of stratospheric NO2 vertical columns measured by a SAOZ zenith-sky visible spectrometer. The instrument spent most of its time at Aberystwyth, Wales, with occasional excursions to other locations. The data have been analysed with the WinDOAS analysis program with low-temperature high-resolution NO2 cross-sections and fitting a slit function to each spectrum. Because of a change in detector in May 1998 there is some uncertainty about the relative changes before and after this date, which are partially constrained by the results of an intercomparison exercise. However, the effect of the Mt Pinatubo aerosol cloud is very evident in the data from 1991-94, with a decrease of 10% in NO2 in the summer of 1992 (the SAOZ was located in Lerwick, Scotland during the winter of 1991-92 and observed very low NO2 values but these cannot be directly compared to the Aberystwyth data). To focus more on interannual and long-term variations in NO2, a seasonal variation comprising an annual and semi-annual component was fitted to the morning and evening twilight separately from 1995 to the present. This fit yielded average NO2 columns of 4.08 x 10(15) cm(-2) and 2.68 x 10(15) cm(-2) for the evening and morning twilight, respectively, with a corresponding annual amplitude of +/-2.08 x 10(15) cm(-2) and +/-1.50 x 10(15) cm(-2). Departures from the fitted curve show a trend of 6% per decade, consistent with that reported elsewhere, for the period 1998-2003, but in the past two years a distinct interannual variation of amplitude of approximately 8% has emerged.

Air Pollutants↗
PubMed2000

Synthesis and characterization of a peptide identified as a functional element in alphaA-crystallin.

Eye lens alpha-crystallin is a member of the small heat shock protein (sHSP) family and forms large multimeric structures. Earlier studies have shown that it can act like a molecular chaperone and form a stable complex with partially unfolded proteins. We have observed that prior binding of the hydrophobic protein melittin to alpha-crystallin diminishes its chaperone-like activity toward denaturing alcohol dehydrogenase, suggesting the presence of mutually exclusive sites for these proteins in alpha-crystallin. To investigate the mechanism of the interaction between alpha-crystallin and substrate proteins, we determined the melittin-binding sites in alpha-crystallin by cross-linking studies. Localization of melittin-binding sites in alpha-crystallin resulted in the identification of RTLGPFYPSR and FVIFLDVKHFSPEDLTVK of alphaA-crystallin and FSVNLDVK of alphaB-crystallin as the chaperone sites. Of these sites, FVIFLDVKHFSPEDLTVK and FSVNLDVK were identified earlier as 1,1'-bi(4-anilino) naphthalene-5,5'-disulfonic acid (bis-ANS)-binding hydrophobic sites. Here we also report the synthesis and characterization of the peptide, KFVIFLDVKHFSPEDLTVK, having the melittin as well as bis-ANS-binding sequence of alphaA-crystallin. We show that this peptide has characteristics similar to that of alphaA-crystallin by in vitro thermal aggregation assay, gel filtration study, CD spectroscopy, and bis-ANS interaction studies. The peptide sequence corresponds to the beta3 and beta4 region present in the alpha-crystallin domain of sHSP 16.5. We hypothesize that the alpha-crystallin domain in other sHSPs may have a similar function and would likely possess the anti-aggregation property even when separated from the native protein.

Alcohol Dehydrogenase↗
PubMed1983

Control of upper airway structures during nonspeech tasks in normal and cerebral-palsied subjects: EMG findings.

Electromyographic (EMG) recordings taken from 13 orofacial and mandibular muscles during a sequence of nonspeech movements were compared in six normal and six cerebral-palsied adult subjects. Abnormalities in the amplitude of muscle activity and timing of muscle control in the cerebral-palsied subjects were borne out in statistically significant differences between the two subject groups on five measures of muscle activity. The findings do not support hypotheses that weakness affects individual upper airway muscles in cerebral-palsied persons or that a pathological imbalance between positive and negative oral reactions is present in these subjects. A possible mechanism for hypertonicity in facial muscles in cerebral palsy is suggested, based on inappropriate activation patterns across muscles. The results are consistent with a previous proposal that a defect in the specification of motor commands and/or their communication to muscles is a fundamental abnormality in cerebral-palsied individuals which affects both speech and nonspeech motor control.

Adult↗
PubMed1981

Procedures for verification of electrode placement in EMG studies of orofacial and mandibular muscles.

Many muscles used in speech are small and intimately interconnected. There is a need for anatomical and physiological data which would allow identification of the particular muscle fibers being recorded in electromyographic (EMG) investigations. EMG recordings were taken from eighteen orofacial and mandibular muscles while gestures believed to be specific to each muscle were performed. The anatomic criteria for the placement of the electrodes, the quality of the EMG spikes and interference patterns obtained, and the degree of differentiation of the temporal sequence of activity from that in neighboring muscles were used to decide on the degree of certainty that a particular muscle was being recorded. The appropriateness of each gesture as a stimulus to any muscle was determined on the basis of the level of activation occurring with the gesture relative to other muscles and its degree of variability between subjects.

Electrodes↗
PubMed1980

Dysarthria of adult cerebral palsy: I. Intelligibility and articulatory impairment.

The speech intelligibility and articulatory impairment of 32 spastic and 18 athetoid males, aged 17-55, were examined. Selection was based on a definite diagnosis of cerebral palsy, and adequate intelligence, hearing, and ability to perform the required tasks. Two estimates of speech intelligibility were obtained from naive listeners: single words correctly recognized and prose intelligibility rating. Diadochokinetic (DDK) syllable rates and percent correct articulation of selected phonemes were employed as indices of articulatory impairment. The 50 subjects were, on average, judged to be 50% intelligible on both intelligibility estimates. Group mean DDK rate was 2.9 syllables per second and 78% of phonemes were transcribed as correctly articulated. :The mean scores of the spastic subjects were superior to the athetoids on all speech measures, significantly so for single-word intelligibility and DDK rate even when group inequalities for physical disability and I.Q. were adjusted. In this sample, spastics were less physically disabled and had lower I.Q.'s than athetoids. Specific phonemic features characteristic of the dysarthria in cerebral-palsied subjects were: (1) anterior lingual place inaccuracy; (2) reduced precision of fricative and affricate manners; and (3) inability to achieve the extreme positions in the vowel articulatory space. A comparison of these results with those reported for children with cerebral palsy suggests that the consonantal place and manner problems are fairly stable features of cerebral palsy dysarthria.

Adolescent↗
PubMed1979

Tonic stretch reflexes in lip, tongue and jaw muscles.

Despite considerable speculation it remains unclear as to whether stretch reflexes perform a functional role in speech articulator muscles. Recent research, however, has shown that long loop stretch reflex mechanisms are brought into play during voluntary contraction of limb muscles and a functional role in oscillatory damping has been suggested. It was decided, therefore, to use a method and a technique of analysis similar to that used in limb muscles to search for tonic stretch reflex (TSR) responses in lip, tongue and jaw muscles during sustained voluntary contraction. The term 'action TSR' is used to differentiate stretch reflex responses measured from voluntary activity from those measured at rest. Simultaneous electromyogram (EMG) recordings were taken from the lip, tongue and jaw musculature in normal, stutterer and cerebral spastic subjects. Subjects were instructed to hold the appropriate articulator in a fixed position while the experiment applied an irregular, continuously changing, stretching force. The stretch and EMG signals were analyzed using a cross correlation and spectral analysis technique. This provided a sensitive means of detecting any EMG fluctuations which covaried with applied stretch and might therefore be classified as reflex. No suggestion of such action TSR responses could be found in lip or tongue muscles of any of the subjects tested, including the cerebral spastic subjects with dysarthric speech. It is therefore concluded that action TSR mechanisms are not operative in control of lip and tongue muscles in man. Furthermore, dysarthric speech in cerebral spasticity cannot be attributed to exaggerated tone of lip and tongue muscles resulting from hypersensitivity of TSR mechanisms. In contrast, clear action TSR responses were demonstrable in jaw closing muscles while in jaw opening muscles, small amplitude responses were detected but were not substantial in comparison with background activity. Since the action TSR is present in jaw and limb muscles, but absent in lip and tongue muscles, the suggestion of a functional role of this reflex in damping mechanical oscillations associated with inertial loads is further supported.

Adult↗
PubMed1977

Cerebral dominance for language in cerebral palsy.

A test of cerebral dominance for language was administered to 51 cerebral palsied adults. The test consisted of dichotically presented words and in normal speaking adults had previously demonstrated very marked right ear superiority, interpreted as left cerebral dominance. The group of cerebral palsied subjects did not show the predicted right ear superiority. This finding may represent a chance maldistribution of side of cerebral injury within the 51 subjects. If substantiated, however, it would suggest either that the cortical damage in cerebral palsy is commonly widespread or else that the inherent left cerebral dominance of neonates is less tenacious than is generally assumed.

Adolescent↗
PubMed1977

Neurological stuttering-a clinical entity?

Stuttering associated with neurological pathology in normal adult speakers is uncommon, has no consistent clinicopathological picture, and its significance is too easily dismissed. A case is reported showing that stuttering may be a presenting symptom of progressive neurological disease, and another case demonstrates that a speech disorder which is indistinguishable from common stuttering may follow cerebral follow injury in adulthood.

Adult↗
PubMed1972

Stuttering: an investigation into cerebral dominance for speech.

Over the past decade research has suggested that stutterers have bilateral cerebral motor or auditory speech areas. Three typical adult stutterers showed normal unilateral left cerebral dominance for speech on the intracarotid sodium amylobarbitone (amytal) test, but one 'dysphatic' stutterer had bilateral cortical speech representation. The latter is a very rare finding in right handed individuals and presumably is a consequence of the head injury induced aphasia that preceded the onset of stuttering.

Adult↗