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Biomedical subjects

W Bacon

Publications and source records attributed to W Bacon.

At least 19 recordsLinked to original sources
PubMed1998

Changes in distribution of glycosaminoglycans during the progression of cholesterol induced atherosclerosis in Japanese quail.

The temporal and spatial distribution and relative concentration of the proteoglycan glycosaminoglycan component were studied during the progression of atherosclerosis in the systemic arteries of Japanese quail selected for cholesterol induced atherosclerosis (CIA). The CIA quail were placed on either control or 0.5% added cholesterol diets at 3 months of age. The major systemic arteries (dorsal aorta, right and left brachiocephalic) were collected at 1- or 2-week intervals over the 10-week period of cholesterol feeding. In the cholesterol fed quail, alcian blue staining of the dorsal aorta showed elevations of glycosaminoglycans in regions of the artery with atherosclerotic plaque, beginning at the 6-week time point. By biochemical analysis, increases in glycosaminoglycan relative concentration was detected at the 10-week time point. In addition to the change in glycosaminoglycan relative concentration and distribution, the cholesterol fed animals also formed foam cells characteristic of atherosclerotic plaques. Therefore, the conclusion reached was that the CIA line of Japanese quail is a valid animal model for the study of alterations in proteoglycan metabolism in atherosclerotic plaques induced by hypercholesterolemia.

Animals↗
PubMed1997

Malocclusion in the deciduous dentition of Caucasian children.

In this study the occlusal characteristics of the deciduous dentition in a sample of young children were investigated to determine whether consensual trends exists, and if the occlusal characteristics in the primary dentition may be considered as acceptable predictors for occlusal relationships in the permanent dentition. Four hundred and seven boys and three hundred and eighty-two girls aged 4-6 years participated in the epidemiological study. Recording of the occlusal traits was made according to the method described by the Fédération Dentaire Internationale in 1973, adapted to the primary dentition. Lack of space was frequent (24 per cent in the upper anterior segments), as well as lateral crossbites (16 per cent), excessive overjet of 6 mm or more (6 per cent), Class II relationships (26 per cent) and anterior open bites (37.4 per cent). Obvious similarities could be seen with other investigations on occlusal traits of the primary dentition of Caucasian children. Cross-comparison with available data suggest that the development of the occlusion is a continuum for many aspects, with most of the major occlusal trends characterizing the permanent dentition in Europoid populations detectable at early stages. The striking difference in the primary dentition was the much higher prevalence of anterior open bites: this is the only figure expected to decrease dramatically in the permanent dentition. With due reservation inherent to the nature of epidemiological data on malocclusion and their interpretation, it is concluded that, provided the patient's cooperation is satisfactory, early attention may be given to malocclusion, but should mainly be focused on lateral crossbites and sagittal malrelationships.

Chi-Square Distribution↗
PubMed1995

Determinants of effective continuous positive airway pressure in obstructive sleep apnea. Role of respiratory effort.

We investigated whether cephalometric measurements, nocturnal indices of negative intrathoracic pressure, or the frequency of sleep-related breathing disorders were related to the level of effective continuous positive airway pressure (CPAP) in patients with obstructive sleep apnea (OSA). We examined 22 OSA patients who underwent two consecutive polysomnographic recordings, the first for diagnosis and the second for CPAP titration. Cephalometric measurements, spirometric data, and blood-gas analysis results were available for all subjects. In the diagnostic polysomnography, at least 30 apneas were analyzed during non-rapid-eye-movement (NREM) sleep and 10 apneas during rapid eye movement (REM) sleep for each patient. Swings in esophageal pressure (Pes) during the preapneic period and during the beginning and the end of obstructive apneas were calculated as the average of three consecutive breaths (or ineffective efforts). The difference in Pes from the minimal initial to the maximal final apneic respiratory effort (DPes) and the rate of increase in Pes (RPes = DPes/apnea duration) during apnea were computed. Within an apnea, the lowest Pes always occurred during the first three occluded breaths and the highest during the last three, with a more marked difference in NREM sleep. The level of effective CPAP was correlated with the length of the soft palate (r = 0.69, p = 0.000), RPes (r = 0.55, p = 0.008), and DPes (r = 0.49, p = 0.02). The correlations of effective CPAP level with body mass index and apnea + hypopnea index were not significant. A model including length of the uvula, DPes, and RPes accounted for 56 to 59% of the variability in effective CPAP.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1995

[A cephalometric study of the pterygoid process during growth].

This study consists in a three dimensional cephalometric approach of the pterygoid process and its relationships with the neighbouring cranio-facial structures, using biostatistical analysis. The authors present the results of this method comparing the variations of the pterygoid process in relation to the variations of the basi-cranium and the face.

Adult↗
PubMed1993

Specialist postgraduate orthodontic training: a comparison of two European universities.

The background to current specialist training programmes in orthodontics in the United Kingdom and France is discussed, and the examination structure in the two countries compared with reference to those pertaining in Glasgow and Strasbourg. A sample of 40 of the most recently treated cases submitted by students in each of these two Universities for their final examinations is compared revealing marked differences in case type and treatment philosophy. The differences are explained, to some extent, by the circumstances pertaining to the delivery of orthodontic care in the two countries.

Adolescent↗
PubMed1992

The cranial base in subjects with dental and skeletal Class II.

The aim of this study was to test to what extent the cranial base variations may be involved in Class II facial organization. Using Bonferonni probabilities, cranial base size and shape, and facial divergence were compared in two groups: an experimental group of 45 subjects with dental and skeletal Class II and an homologous control group of 41 subjects with a natural Class I ideal occlusion. In all individuals of the experimental group the Class II molar relationship was at least equal to the width of one premolar and the ANB angle was greater than the value of the mean +2 standard deviations of the ANB in the control group. Spacing and crowding was less than 2 mm at each arch in both groups; all subjects were between 10 and 12 years old. The anterior part of the cranial base (SN length and SNBa angle) was identical in the two groups, but in Class II, cranial base flexure (BaSN angle) was more obtuse (P less than 0.05) and posterior cranial base angle (SBaN) was more acute (P less than 0.01). These variations co-existed in the same group with a more retruded position of the condylar neck in the face (P less than 0.01) favouring per se a post-normal relationship of the mandible to the maxilla. The increased extension of the saddle angle in Class II could not be considered here as related to an hyperdivergent facial pattern since facial divergence was unchanged in Class II. Saddle angle and divergence correlated in Class I (r = 0.40; P less than 0.01), but not in Class II.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalometry↗
PubMed1992

[Pharyngeal obstruction and the functional adaptation of the natural posture of the head and the hyoid bone in sleep apnea syndrome].

Variations in natural head posture (NHP) and hyoid bone (HB) positioning impart changes in the size and shape of the pharyngeal airways. In SAS, which was shown to be correlated with detrimental craniofacial anatomical conditions, control of pharyngeal permeability is lost during sleep. The aim of this study was determine if functional adaptation of NHP and HB position to these detrimental conditions could be observed, using Bonferonni probabilities, in a cephalometric comparison of 38 SAS adults in the wakeful state and a control group of 38 healthy adults. Since HB relationships with craniofacial anatomical structures vary with the positioning of the head, the cephalograms were taken according to the preliminarily tested NHP, thus making the method reproducible. In SAS craniovertical angulation was unchanged, but the head was maintained in a forward position (increased cervico-vertical angulation, P < 0.001). Maintenance of an acceptable pharyngeal permeability was associated with a more distant positioning of HB from the cervical column (P < 0.01) and from craniofacial references (P < 0.001). In spite of these facts lower pharynx opening was still reduced (P < 0.05). Soft palate and facial divergence were expectedly increased in the apneic group. All the individuals but one control could be correctly reclassified with the help of soft palate length, facial divergence, and two HB related variables. Prevention of pharyngeal collapsibility in SAS seems to be commonly associated with functional adaptation of NHP and HP position. The precise control mechanisms of this adaptation remains to be elucidated. Skeletal predispositions to SAS do probably develop already during infancy.

Adaptation, Physiological↗
PubMed1990

Fat embolism syndrome complicating intraarterial chemotherapy with cis-platinum.

A 19-year-old man with telangiectatic osteosarcoma of the left proximal femur was started on a course of neoadjuvant chemotherapy consisting of intraarterial administration of cis-platinum. Within 72 hours of receiving the first intraarterial dose, the patient developed signs and symptoms of fat embolism syndrome (FES). A physical examination revealed cyanosis, tachycardia, and seizure activity. Laboratory studies demonstrated a pO2 of less than 65 mmHg, lipuria, and a drop in hematocrit of three percentage points. There was no clinical or roentgenographic evidence of pathologic fracture. Tumor necrosis secondary to intraarterial cis-platinum therapy in this patient with osteosarcoma may have caused a sudden release of free fatty acids and embolization of fat macroglobules that precipitated this episode of FES. FES in association with the intraarterial administration of cis-platinum seems not to have been previously reported.

Adult↗
PubMed1989

[Vertical typology and natural posture of the head].

The relationship between head posture and vertical typology were evaluated in a sample of 98 young adults. Sub groups of opposite typology were also compared. A strong correlation existed between head posture and facial divergence when evaluated with the variable SN/PM and face post./face ant. Head posture is in extension when facial divergence is important. No correlation existed between posture and % face inf. Face post./face ant. was the best variable in evaluating the relationship between vertical typology and head posture.

Adult↗
PubMed1989

[The question of root resorption. Is the risk of root resorption related to the typology of the face?].

The mechanisms involved in root resorption are of the same nature than those leading to bone resorption. The state of calcification and the local conditions in the microenvironment are responsible for the different responses of alveolar bone and root with regard to calcified matrix resorption. Root resorption is commonly observed in association with impacted cuspids, acute chronical trauma, inflammatory or idiopathic conditions. Root resorption is more frequent in females and is independent on facial typology or orthodontic technique. Critical conditions to root integrity are often associated with heavy forces and periodontal ligament disruption. Root anatomy may also be a predisposing factor to resorption. Systematic radiological examination is the only way to control the onset of a root resorption process in orthodontic therapy.

Cephalometry↗
PubMed1989

[Bone resorption in orthodontic tooth movement: an attempted schematization].

The osteoclast is the major cellular agent of bone resorption. Hormonal stimulation of bone resorption is indirect and depends on the osteoblastic function. Protease production is the final common pathway through which osteoblastic cells initiate osteoclastic resorption. Exposition of the mineralised matrix and contact with the osteoclasts always comes before resorption, regardless of the stimulating agent involved in the resorption process. In orthodontic conditions, production and activation of osteoclasts may be attained through different ways. Inflammation subsequent to tissue damage and bioelectric perturbations associated to alveolar bending can be considered as two major events which may lead to increase bone resorption and orthodontic tooth displacement. The precise transduction mechanism of an orthodontic force into cellular resorbing activity is still obscure.

Alveolar Process↗
PubMed1987

The treatment of bulimia nervosa.

We review treatment approaches to bulimia nervosa, with particular emphasis on methodology and research design. The following treatments are considered: behaviour therapy, cognitive behaviour therapy, pharmacological treatment, group therapy, psychoanalytic psychotherapy, self-help and support groups, hypnosis and miscellaneous (family therapy and nutritional approaches). Several directions for future research and methodological recommendations are suggested.

Anticonvulsants↗
PubMed1985

Developmental expression of a synaptic vesicle-specific protein in the rat retina.

In order to examine the appearance of synaptic vesicles and to correlate it with the formation of the synaptic layers, we have determined the staining pattern of a murine monoclonal antibody (SV 48) to a synaptic vesicle-associated protein in developing rat retina. The antigen was detected by the indirect immunofluorescence technique using cryostat sections of paraformaldehyde-fixed retinas. In the adult retina, the antibody stained both the outer plexiform (OPL) and the inner plexiform layers (IPL). The nuclear layers and the nerve fiber layer (NFL) were devoid of any staining. In prenatal and early postnatal (P) retinas, the antibody stained two bands which corresponded to the respective locations of the NFL and IPL. Staining in the NFL increased until P-4 and began to decline subsequently, and by P-8 little staining was left in this layer. In contrast, in the IPL, the intensity of staining increased gradually and leveled off by P-10. In the outer retina, a band of fluorescence corresponding to the OPL was first observed at P-5 and increased in intensity up to P-10. Immunoblotting studies showed that the major immunoreactive material from adult and embryonic retinas had a Mr approximately 65,000-67,000. As expected from its developmental pattern, all bands appeared initially in the central retina and subsequently in the peripheral retina. Our results show that the synaptic vesicle-protein is present in the nerve fiber layer before synaptogenesis in the central nervous system. Subsequently, the protein is lost from the NFL, possibly as a consequence of synapse formation.

Animals↗