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Biomedical subjects

G Walker

Publications and source records attributed to G Walker.

At least 127 records · Page 7Linked to original sources
PubMed1985

Phorbol ester-induced phosphorylation of a transmembrane glycoprotein (GP 180) in human blood platelets.

In this study we have used (phorbol-12-O-tetradecanoylphorbol 13-acetate) and its biologically inactive analogue, 4 alpha-phorbol 12,13-didecanoate), to investigate platelet protein phosphorylation with special emphasis on the properties of a membrane protein-cytoskeleton (transmembrane) complex during platelet activation. Our data indicate that phorbol-12-O-tetradecanoylphorbol 13-acetate (but not 4 alpha-phorbol 12,13-didecanoate) induces both a specific platelet shape change and the preferential phosphorylation of a 180-kDa protein (presumably due to the activation of protein kinase C on the cytoplasmic side of the membrane). Further analysis reveals that the 180-kDa protein can be iodinated by lactoperoxidase and is sensitive to trypsin treatment, indicating exposure of this protein on the outer cell surface. The 180-kDa protein has also been found to contain wheat germ agglutinin-binding sites. All evidence indicates that the 180-kDa polypeptide is a transmembrane glycoprotein and, most importantly, that this protein is found to be preferentially accumulated into a specific membrane-cytoskeleton complex during activation via phorbol-12-O-tetradecanoylphorbol 13-acetate treatment. We believe that the observed phosphorylation of this protein may be closely related to the formation of a complex between several membrane proteins and the cytoskeleton during the initial stages of platelet activation.

Blood Platelets↗
PubMed1985

Stiffness after fractures around the knee in spina bifida.

A study was made of knee stiffness after fractures around the knee in patients with spina bifida. Thirty-one patients with 45 fractures were followed up for 2 to 15 years after the fracture. Knee stiffness was found in 67% of patients; this amounted to loss of up to half the normal range of movement. The stiffness appeared at two months from the time of the fracture and was established by six months. However, in all patients it had resolved by three years, so that their mobility was not affected in the long term. It is concluded that though stiffness is common after fractures in patients with spina bifida, it should be treated expectantly as it will resolve within three years without specific treatment.

Adolescent↗
PubMed1984

The effects of multichannel compression/expansion amplification on the intelligibility of nonsense syllables in noise.

The effects of six-channel compression and expansion amplification on the intelligibility of nonsense syllables embedded in speech spectrum noise were examined for four hearing-impaired subjects. For one condition (linear) the stimulus was given six-channel amplification with frequency shaping to suit the subject's hearing loss. The other condition (nonlinear) was the same except that low level inputs, to any given channel, received expansion amplification and high level inputs received compression. For each condition, each subject received the nonsense syllables at three different input levels, representing low, average, and high intensity speech. The results of this study, like those of most other studies of multichannel compression, are mainly negative. Nonlinear processing (mainly expansion) of low intensity speech resulted in a significant degradation of speech intelligibility for two subjects and in no improvement for the others. One subject showed a significant improvement in intelligibility for the nonlinearly processed average intensity speech and another subject showed significant improvement for the high intensity input (mainly compression). Clearly, nonlinear processing is beneficial for some subjects, under some listening conditions, but further research is needed to identify the relevent characteristics of such subjects. An acoustic analysis of selected items revealed that the failure of expansion to improve intelligibility was primarily due to the very low intensity consonants /e/ and /k/, in final position, being presented at an even lower intensity in the expansion condition than in the linear condition. Expansion may be worth further investigation with different parameters. Several other problems caused by the multichannel processing were also revealed. These included alteration of spectral shapes and band interaction effects. Ways of overcoming these problems, and of capitalizing on the likely advantages of multichannel amplification, are currently being investigated.

Hearing Aids↗
PubMed1984

Problems in the early recognition of hip dysplasia.

Ten children who had clinically stable hips at birth were radiographed at one month because they had factors predisposing to hip dislocation. In all cases one or both hips gave rise to a suspicion of dysplasia, though clinical abnormalities were slow to appear. Four of these hips subsequently dislocated. We believe that infants with late presentation of acetabular dysplasia and clinical abnormality belong to a different aetiological group from those with neonatal instability due to ligamentous laxity. The significance of this differentiation is that some infants presenting late have only recently dislocated, and the diagnosis has not necessarily been "missed" at neonatal examination.

Acetabulum↗
PubMed1984

The hip in the moulded baby syndrome.

The moulded baby syndrome comprises: head moulding (plagiocephaly); pelvic obliquity with unilateral loss of hip abduction in flexion; and occasionally scoliosis, torticollis and bat ears. The hips, however, are radiologically normal and do not require the treatment used in the management of congenital dislocation or dysplasia. A review of 67 hips confirms this finding.

Female↗
PubMed1984

The dynamics of interorganizational coordination.

A theory was developed on the creation, growth, and decline of relationships among organizations and was tested, using a longitudinal study of 95 dyadic relationships among child care and health organizations in Texas. Using LISREL V, the test of the theory showed that substantial revision of the model was required to explain the data adequately. When the model was revised, important new patterns were revealed in the development of interorganizational relationships over time: (1) Perceptions of dependence on others for resources spurs the development of interorganizational relationships. Resource dependence is a powerful direct determinant of communications, resource transactions, and consensus; (2) The growth of interorganizational relationships is fostered by frequent communications to formalize the relationship and build consensus about the terms of the relationship among the parties involved; (3) Monetary transactions and client referrals entail different patterns of coordination; and (4) Consensus among parties in an interorganizational relationship is both a positive outcome of initial resource dependence and communications and has a negative influence on subsequent perceptions of resource dependence.

Analysis of Variance↗
PubMed1983

The selection of modulation rates for frequency modulated sound field stimuli.

Frequency modulated (FM) tones are used in sound field audiometry in order to avoid problems caused by standing waves. The FM stimuli to be used must be specified in terms of bandwidth (twice the frequency deviation), modulation rate and modulation waveform. This paper deals with selection of the modulation rate. Improved field uniformity obtained with FM tones relies upon the ear averaging the sound intensity as the frequency sweeps. The modulation rate must be less than about 1/3 of the frequency deviation in order to provide sufficient spectral components to ensure reasonable averaging across the frequency band. If the rate is too low threshold will be determined by the peak intensity during the sweep. For normal listeners a modulation rate of 5 Hz is just satisfactory but in the hearing impaired a higher rate is required because of their altered temporal integration characteristics. A suitable value for the modulation rate can be inferred from the literature on temporal integration and the acoustic characteristics of typical test rooms. The optimum rate increases with the stimulus centre frequency, but a constant rate of 20 Hz appears to be acceptable.

Audiometry↗
PubMed1983

Measurement of glycosylated hemoglobin on cellulose acetate membranes by mobile affinity electrophoresis.

In this method for separating glycosylated from nonglycosylated hemoglobin in blood by electrophoresis on cellulose acetate membranes, we exploit the affinity of low-molecular-mass dextran sulfate for the nonglycosylated fraction, which increases the mobility of the latter relative to that of glycosylated hemoglobin. After the membrane strips are cleared and stained, the two fractions are quantified densitometrically. As evaluated by use with blood from diabetics, results compare well with those by chromatography on short columns and by electrophoresis in commercial agar gel films.

Buffers↗
PubMed1982

Dissipation of parathion and paraoxon on citrus foliage dust and dry soil surfaces in a treated orchard.

Pesticides applied to an orchard may be transported via dust from the orchard floor to the foliage. The dust containing the pesticide facilitates oxygen analog formation. This study involves the evaluation of existing methods and new procedures for measuring pesticide fate (parathion and paraoxon) on soil surfaces in a field environment; the results were correlated with dislodgeable foliar residues. Residues in soil dust removed from the ground floor via vacuum varied considerably and did not correlate with dislodgeable foliar residues. Although residues found on masonite plates coated with a thin layer of soil were different from dislodgeable foliar residues, the ratios of paraoxon to parathion was very similar for the first 14 to 21 days. The thin-layer soil on the plates had serious deficiencies including difficulty of preparation in the field, handling of the coated plates, and physical movement of the soil from the plate due to environmental forces including rain. Soil tags prepared from fine mesh window screen saturated with soil resulted in approximately the same residue as the soil plates and at the same time avoided most of the deficiencies experienced with the plates. They were very resistant to physical forces, easy to prepare in the field, and not affected by environmental forces except appreciable quantities of rain. The results should encourage the use of soil screen tags, not in lieu of but along with other methods when conducting field studies with pesticides involving worker safety.

Citrus↗