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Biomedical subjects

K S Harris

Publications and source records attributed to K S Harris.

At least 37 records · Page 2Linked to original sources
PubMed1988

Poliovirus proteinase 3C: large-scale expression, purification, and specific cleavage activity on natural and synthetic substrates in vitro.

Proteinase 3C of poliovirus type 2 (Sabin) was expressed at 4% total protein in Escherichia coli. The protein was soluble and could be purified by a simple scheme. It was weakly active on the capsid precursor P1 (expressed in vitro), which contains two cleavage sites. The products of processing P1 were 1ABC and 1D (VP1). The activity was insensitive to Triton X-100. Crude extracts of cells infected with poliovirus type 1 (Mahoney) gave strong processing and yielded 1AB (VP0), 1C (VP3), and 1D in the same assay system but were sensitive to detergent. 3C from cell extracts that was separated from its precursors resembled the recombinant proteinase in its activity. Recombinant 3C cleaved the peptide dansyl-Glu-Glu-Glu-Ala-Met-Glu-Gln-Gly-Ile-Thr-Asn-Lys-NH2 at the Gln-Gly bond. We conclude that 3C is merely the core of the Gln-Gly-cleaving activity which processes P1 in vivo and that there is probably a hydrophobic contact between a larger 3C precursor and its P1 substrate which allows the second processing reaction: 1ABC, 1D----1AB, 1C, 1D.

3C Viral Proteases↗
PubMed1987

Palatoglossus activity during nasal/nonnasal vowels of Hindi.

Prior electromyographic (EMG) research reveals a lack of agreement as to the role of the palatoglossus muscle in speech. Some reports have concluded that it bears primary responsibility for lowering the velum and that it actively controls velar lowering on nasal sounds in speech, whereas others have concluded that it acts to assist in the tongue-body movements associated with the production of back vowels and linguavelar articulations. To clarify these conflicting claims, EMG recordings were obtained from the palatoglossus (as well as the levator palatini) muscle of a native speaker of Hindi who produced CVC nonsense and meaningful syllables containing a nasal or nonnasal vowel in a symmetric consonantal environment. The results showed the following: Palatoglossus activity for the central and back nasal and nonnasal vowels was moderately to considerably higher than for the front nasal and nonnasal vowels. The levels of palatoglossus activity for the back rounded nasal vowels and for the front nasal vowel /e/ were comparable to those for the corresponding nonnasal vowels, while in all other vowels, the nasal vowels exhibited relatively higher levels of palatoglossus activity than their nonnasal counterparts. In all nonnasal vowels, the increase in palatoglossus activity occurred simultaneously with strong levator palatini activity. On the other hand, in nasal vowels, the increase in palatoglossus activity and the decrease in levator palatini activity were virtually synchronous for the front nasal vowels, while the increase in palatoglossus activity began much earlier than the decline in levator palatini activity for the central and back nasal vowels. This difference in temporal relationship between palatoglossus activation and levator suppression for different vowel types is important since it unambiguously supports the 'gate-pull' model (that is, active velar lowering) for the production of front nasal vowels whereas in the case of central and back vowels, nasal and nonnasal, the palatoglossus appears to be primarily involved in moving the tongue-body.

Electromyography↗
PubMed1983

Converging evidence for the role of relative timing in speech.

In an earlier article (Tuller, Kelso, & Harris, 1982a) we suggested that the timing of consonant-related muscle activity was constrained relative to the period between onsets of muscle activity for successive vowels. Here, we reexamine those data based on reservations posed by Barry (1983). Next, we present a kinematic study of articulation that extends and strongly supports our original observations. Finally, we very briefly survey some converging lines of evidence for a functionally significant vowel-to-vowel period in speech and how this may relate to the role of temporal invariance in motor skills in general.

Electromyography↗
PubMed1982

Temporal patterns of coarticulation: lip rounding.

According to some theories, anticipatory coarticulation occurs when phones for which a feature is unspecified precede one for which the feature is specified, with consequent migration of the feature value to the antecedent phones. Carryover coarticulation, on the other hand, is often attributed to "articulatory sluggishness." In this paper, EMG evidence is provided that this formulation is inadequate, since the beginning of EMG activity associated with vowel lip rounding is independent of measures of the acoustic duration of adjacent lingual consonants. We suggest that the vowel-rounding gesture simply co-occurs during predictable intervals with portions of preceding and following lingual consonant articulations.

Acoustics↗
PubMed1982

Stress and rate: differential transformations of articulation.

Early theorizing in speech production considered variations in syllable stress and speaking rate to be identical transformations of motor activity [e.g., Lindblom, J. Acoust. Soc. Am. 35, 1773-1781 (1963)]. More recent work, however, suggests that modulation of stress and rate have different acoustic and perceptual effects, and thus may have independent "signatures" in production. The experiments reported here examined these hypotheses. In the first experiment, electromyographic activity from two muscles, one primarily related to vowel production and the other to consonant production, was examined during utterances whose stress and rate characteristics were systematically varied. The results support the hypothesis that stress and rate modulations have differential effects on muscle activity. The second experiment addressed the same basic question but examined a broader set of muscles. In all cases, the changes in duration and peak amplitude of muscle activity for altered stress were not equivalent to the changes for altered rate. Decreases in stress produced decreases in peak amplitude and duration of vowel-related muscle activity that were consistent across speakers. In contrast, activity patterns associated with rate contrasts varied considerably across muscles and speakers.

Adult↗
PubMed1981

A temporal model of speech production.

Existing models of speech production and coarticulation have failed to account for observations of real speech because they have considered timing to be a by-product of articulatory events instead of an integral organizing parameter of the speech motor plan. The model offered here considers time and timing relationships to be intrinsic to speech motor organization and the units of speech to be inherently dynamic gestures rather than static vocal tract configurations or invariant commands to the articulators.

Electromyography↗
PubMed1980

Glycolate in the diet and its conversion to urinary oxalate in the rat.

Less than 3 per cent of the [1-14C]glycolate administered, orally to fasted and nonfasted male Wistar rats was excreted in the feces in 48 hr. This finding indicates that the glycolate was readily absorbed from the digestive tract. An average of 3 per cent of the administered [1-14C]glycolate was also recovered in 48 hr as urinary [14C]oxalate from fasted and nonfasted rats. Significant amounts of glycolate were found in the vegetables, fruits, and beverages analyzed, but much lower amounts were found in meats and milk. Inasmuch as glycolate is naturally present in the diet and contributes to the formation and excretion of urinary oxalate, restricting the intake of glycolate may be beneficial in treating oxalate stone-forming patients.

Animals↗
PubMed1979

Anticipatory coarticulation: some implications from a study of lip rounding.

The anticipation of articulatory features, in particular lip rounding in anticipation of a rounded vowel, has been reported to occur as many as four segments before the segment for which the feature is specified. In the data presented here, we find that the moter commands for the rounding gesture for /u/ begin a fixed time before the onset of the vowel. This timing is unaffected by the number of consonant segments in the preceding string. Thus, the initiation of lip rounding appears to be linked to other features of the vowel articulation.

Electromyography↗
PubMed1977

Continuous negative chest-wall pressure therapy for assisting ventilation in older children with progressive respiratory insufficiency.

Continuous negative chest-wall pressure (CNP) was used to assist ventilation in 14 children, 6 months to 14 years of age, who had progressive respiratory insufficiency caused by diffuse bilateral alveolar disease. Before the start of CNP therapy, each child had a respiratory rate greater than 50/min, arterial oxygen tension (PaO2) less than 70 mmHg (FIO2 greater than or equal to 50%), and arterial carbon dioxide tension (PaCO2) less than 45 mmHg. The mean intrapulmonary right-to-left shunt was 28.7 +/- 3.8%. Within 6 hours after therapy was started, PaO2 increased from 55.4 +/- 15.9 to 81.6 +/-17.7 mmHg (p less than 0.005). This improvement was sustained and within 24 hours permitted a decrease in fractional concentration inspired oxygen (FIO2) from 51.8 +/- 6.2 to 41.0 +/- 8.4% (p less than 0.001) and in respiratory rate from 78.1 +/-23.0 to 56.4 +/- 21.3 (p less than 0.01). There was a concomitant decrease in intrapulmonary right-to-left shunt. Four of the 14 patients developed pneumothorax that was successfully decompressed. Ten patients survived. These observations establish CNP therapy as an effective means of improving arterial oxygenation in spontaneously breathing older children. Of added significance, this mode of therapy eliminates the need for endotracheal intubation and prolonged use of muscle relaxants and sedatives. It also minimizes exposure to high FIO2, thereby minimizing the hazards of pulmonary oxygen toxicity.

Adolescent↗
PubMed1977

Management of severe respiratory insufficiency due to Pneumocystis carinii pneumonitis in immunosuppressed hosts: the role of continuous negative-pressure ventilation.

Continuous negative-pressure therapy was used to assist ventilation in 19 spontaneously breathing patients, 6 months to 17 years of age, who developed progressive respiratory insufficiency (arterial PO2 less than 70 mm Hg despite a fraction of inspired O2 larger than or equal to 50 per cent) due to Pneumocystis carinii pneumonitis. Within 1 hour of therapy, arterial PO2 increased from a mean +/- SE of 61.9 +/- 3.7 to 75.4 +/- 7.0 mm Hg (P less than 0.05) and, by 6 hours, to 79.9 +/- 4.7 mm Hg (P less than 0.005). In the 14 survivors, these improvements were sustained and, within 24 hours, permitted a decrease in inspired O2 concentration from a mean +/- SE of 50.4 +/- 1.2 per cent to 40.1 +/- 1.6 per cent (P less than 0.005). By contrast, in nonsurvivors, O2 requirements could not be decreased significantly despite increases in negative pressure. Improvements in arterial oxygenation were associated with decreases in alveolar-arterial PO2 differences in all patients; however, significant decreases occurred only with pressures of -8 to -12 cm H2O. Higher negative pressures were ineffective and usually produced pulmonary air leak. Since the introduction of continuous negative-pressure therapy as a means of assisting ventilation in management of progressive respiratory insufficiency, the over-all survival rate among patients with Pneumocystis carinii pneumonitis at this institution has increased from 69 to 89 per cent.

Adolescent↗