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Biomedical subjects

G W Thompson

Publications and source records attributed to G W Thompson.

At least 55 records · Page 3Linked to original sources
PubMed1985

Changes in neurofilament transport coincide temporally with alterations in the caliber of axons in regenerating motor fibers.

The delivery of neurofilaments via axonal transport has been proposed as an important mechanism for regulating axonal caliber. If this hypothesis is correct, alterations in axonal caliber should appear coincident with changes in the delivery of neurofilaments to the axon. The purpose of this study was to determine whether alterations in the caliber of axons in the proximal stumps of transected motor fibers precede, coincide with, or occur substantially later than changes in the delivery of neurofilaments via axonal transport. Between 3 d and 12 wk after crushing the sciatic nerves of 7-wk-old rats, lumbar motor neurons were labeled by the intraspinal injection of [35S]methionine. In neurons labeled between 3 d and 6 wk after axotomy, the relative amount of neurofilament protein in the slow component, as reflected by the ratio of the radioactivities of the 145-kD neurofilament protein to tubulin, was reduced to 30-40% of the control value. Moreover, as determined by immunoreactivity on blots, the amounts of neurofilament protein and tubulin in these nerve fibers were reduced fourfold and twofold, respectively. Thus, changes in the ratio of labeled neurofilament protein to tubulin correlated with comparable changes in the quantities of these proteins in nerve fibers. This decrease in the quantity of neurofilament proteins delivered to axons coincided temporally with reductions in axonal caliber. After regeneration occurred, the delivery of neurofilament proteins returned to pre-axotomy levels (i.e., 8 wk after axotomy), and caliber was restored with resumption of normal age-related radial growth of these axons. Thus, changes in axonal caliber coincided temporally with alterations in the delivery of neurofilament proteins. These results suggest that the majority of neurofilaments in these motor fibers continuously move in the anterograde direction as part of the slow component of axonal transport and that the transport of neurofilaments plays an important role in regulating the caliber of these axons.

Animals↗
PubMed1984

Effects of aluminum and manganese on the growth of ectomycorrhizal fungi.

Cenococcum graniforme, Suillus luteus, Thelephora terrestris, and three isolates of Pisolithus tinctorius were cultured on modified Melin-Norkrans medium at pH 3.4 and adjusted to 0 to 500 ppm (0 to 500 mug/ml) of aluminum or manganese sulfate. Except for T. terrestris, which was intolerant of aluminum at 150 and 250 to 500 ppm, and P. tinctorius isolate 250, which was intolerant of aluminum at 450 ppm, all fungi showed some growth at all concentrations of aluminum. S. luteus was the most tolerant to aluminum. Manganese was less fungitoxic than aluminum, with all fungi showing at least 65% growth at 500 ppm as compared with the control. C. graniforme was not inhibited at any concentration of manganese, and S. luteus was only affected at 500 ppm. P. tinctorius isolate 230 showed no significant variation in growth when subjected to various concentrations of three forms of manganese salts. Significant differences in growth were detected in response to three aluminum salts, but no detectable pattern was apparent. Genotypic responses to aluminum and manganese were evident for P. tinctorius. Isolates 210 and 230 were more tolerant to manganese than was isolate 250. Aluminum tolerance was in the order of isolate 230 > 210 > 250. Results of in vitro studies concerning tolerance responses of ectomycorrhizal fungi to aluminum and manganese were not consistent with field observations of the successional sequence of these fungi on acid coal spoils.

Journal Article↗
PubMed1980

A family study of craniofacial dimensions in the Burlington Growth Centre sample.

Lateral cephalometric radiographs were used to study the similarities in craniofacial dimensions between members of 147 families. Standard product-moment and intraclass correlation coefficients were calculated for a selected series of measurements to compare parents to offspring and sibs to sibs. To assess further the use of the parents' records in predicting a child's craniofacial features, r2 values were calculated and multiple regression analyses were performed for the various pairings of related individuals. Results show a high level of significant correlations between first-degree relatives which are compatible with a polygenic theory of inheritance. These data give no evidence of added effects of autosomal dominance and sex-linkage. As might be expected, the use of multiple measurements from both parents gives the best results when one is attempting to predict a child's craniofacial dimensions. This suggests that information from the parents and siblings of a patient can be quite useful in clinical orthodontic treatment.

Adolescent↗
PubMed1980

Interpretation and use of the dental admission and aptitude tests.

Despite the fact that all dental school applicants in Canada are required to take the Dental Aptitude Test (DAT) and their counterparts in the United States take the Dental Admission Test (DAT), there is an apparent lack of understanding in the translation and application of the information provided by the test. A review of the literature might assist admissions committee members in interpreting DAT results and in making more sound decisions in selecting students, To put the information into perspective, a brief overview of the history of the DAT, its composition, underlying concepts, and the problems of validation and guidelines for its use are presented.

Aptitude Tests↗
PubMed1979

Maxillary diastema: indications for treatment.

1. In comparing characteristics associated with the presence or absence of diastema at the age of 16 years, generalized spacing was the only significant factor. 2. In the 230 children who had a diastema of 0.5 mm. or greater at age 9, there was a significant association between the diastema and the amounts of crowding or spacing at age 16. 3. A clinician must analyze the individual case in order to determine whether the diastema is to close through normal development or if there exists a likelihood of its persistence.

Adolescent↗
PubMed1979

Clinical evaluation of spiramycin and erythromycin in control of periodontal disease.

Two studies are reported. Each was double-blind in which Spiramycin was compared to Erythromycin and a placebo, to determine the value of Spiramycin as a therapeutic agent in the control of periodontal disease. In Study 1, 48 adults with varying degrees of periodontal disease were randomly assigned to treatment and control groups. Assessments of gingival index, plaque height, pocket depth, crevicular fluid volume and wet plaque weight were made. During this 4-week clinical trial, the patients maintained their usual oral hygiene. The medication was administered systemically for 5 days, starting at the conclusion of week 2. Spiramycin significantly reduced the scores for the five parameters recorded. When comparison were made, the greatest recorded effect with Spiramycin treatment was found in patients with advanced periodontal disease. The indication of this trend favouring Spiramycin led to an extension of this clinical trial involving only patients with advanced periodontal lesions. This second study comprised 54 adults. The same parameters were measured over the same time period as in Study 1. Spiramycin again was responsible for the greatest reduction in the recorded scores. For example, average pocket depth was decreased by approximately 30%, whereas Erythromycin produced a reduction of 15%. It would appear that Spiramycin is of definite benefit in the management of periodontal disease, especially in the more advanced cases.

Administration, Oral↗
PubMed1978

Molar polymorphisms and body growth.

Body growth at adolescence was later in children of the serial experimental sample of the Burlington Growth Centre who had agenesis of third molars of 4-cusped mandibular permanent first molars. These groups of children tended to have later maximum increment of growth, later completion of the growth spurt, less adolescent prepeak gain and greater postpeak gain in height and weight than the children with four third molars and 5-cusped first molars. Growth of the boys differed significantly (P less than 0.05) according to absence or presence of third molars, whereas in girls it differed significantly (P less than 0.05) by the number of cusps of the mandibular first molars. In skeletal age, the children with the molar reductions were slightly advanced before adolescence, fell behind during prepeak adolescent growth, and caught up to the other children by the end of their growth spurt. Later maturation in association with dental reduction may be an evolutionary trend in man.

Adolescent↗
PubMed1977

Tooth, chin, bone and body size correlations.

Correlations of size of teeth, chin, bone and body were investigated in 118 males and 102 females of the Burlington Growth Centre. In the males, the mesiodistal widths of the mandibular lateral incisors and canines were independently related to the thickness of the cortex of the second metacarpal and to body weight. Bone cortex thickness was significantly related to metacarpal width in males and to body weight in females. Chin depth of the males was significantly related to bone width and to body height, negatively related to tooth width when bone width or body weight was held constant in partial correlations. Bone width and length were significantly related to body height in both sexes.

Adolescent↗
PubMed1977

Craniofacial templates for orthodontic case analysis.

1. Age-, sex-, and growth-type-specific craniofacial templates represent a practical approach to orthodontic case analyses and craniofacial growth. 2. The Burlington Growth Centre Cephalometric Analysis is a practical adjunct to treatment planning. 3. This cephalometric analysis, which combines many analyses, is an assessment of the relative proportions of the face in length, width, and height (static analysis) and an estimation of the future changes (dynamic analysis). 4. As an aid in diagnosis, the template and/or analysis in conjunction with a cephalogram, with provide information pertaining to (q) cranial base length angle, (b) upper and lower face height and maxillary and mandibular height, (c) size and proportions of the facial bones, both anteroposteriorly and in width, (d) denture relationship, both anteroposteriorly and in width, and (e) expected general growth changes.

Adolescent↗
PubMed1977

The maxillary interincisal diastema and its relationship to the superior labial frenum and intermaxillary suture.

From the analysis of histories, dental casts, and cephalograms of 471 children of the Burlington Growth Centre sample, interrelationships between the degree of spacing, crowding, diastema and frenum and suture type were derived and the following conclusions were drawn: 1. Suture type remains more constant through development than frenum type. 2. Frenum type is reasonably constant but may change from low to medium or high attachments, but only to a higher level of attachment. 3. Frenum and suture type are related; frenum types 5 and 6 (low attachment) are associated with spacing and with suture types 3 and 4. 4. The primary factors contributing to maxillary diastema appear to be degree of spacing or crowding in most cases, the specific types of sutures and frenum making a minor contribution.

Adolescent↗