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Biomedical subjects

A Richards

Publications and source records attributed to A Richards.

At least 91 records · Page 5Linked to original sources
PubMed1994

Primary biliary cirrhosis. Sole presentation with rampant dental caries.

A 55-year-old woman was referred by her general dental practitioner for management of rampant dental caries of recent onset. Examination revealed a very dry mouth, angular stomatitis, and multiple carious lesions. Labial salivary gland biopsy showed features consistent with Sjögren's syndrome. Hematologic investigations showed antimitochondrial antibodies at a titer of 1 in 320, highly suggestive of primary biliary cirrhosis that was confirmed by liver biopsy.

Autoantibodies↗
PubMed1994

The upper airway and sleep apnoea in the Prader-Willi syndrome.

Obesity, short stature, hypotonia and excessive daytime sleepiness are characteristic features of the Prader-Willi syndrome. Excessive daytime sleepiness has been attributed to obstructive sleep apnoea (OSA). To investigate the role of anatomical factors in OSA in the Prader-Willi syndrome, clinical and ENT assessment, radiology of the upper airway and polysomnography including sleep oximetry were done in 14 subjects. Excessive daytime sleepiness was present in eight of 14 subjects as determined by a mean sleep latency to non-rapid eye movement stage I-II of < 5 min and/or self-rating sleepiness score > 9 (Epworth Sleepiness scale). Seven subjects were snorers or mouth breathers and dental abnormalities were present in 11. Sleep apnoea, as determined by a combined apnoea-hypopnoea index of more than 10 respiratory events per hour was present in 12 of 14 subjects. On clinical assessment, the nasopharynx, oropharynx and hypopharynx were small in one subject. No subject had redundant pharyngeal mucosa or an enlarged tongue. However, radiological studies performed in the awake supine posture showed a slight reduction in the cross-sectional area in nine subjects at the oropharyngeal level and in four subjects at the nasopharyngeal level as compared with normal control subjects. Sleep apnoea and minor radiological evidence of narrowing of the upper airway are common in the Prader-Willi syndrome, although clinical otolaryngological examination is often unremarkable. Excessive daytime sleepiness occurs in approximately 50% of all patients with Prader-Willi syndrome. Although obstructive sleep apnoea is one important factor related to sleepiness, an additional central disturbance of sleep mechanisms is present.

Adult↗
PubMed1994

Proton probe and acid etching for determining fluoride profiles in porous porcine enamel.

An acid-etch technique and a proton probe were used to obtain profiles of changes in fluoride concentrations across enamel of 24 normal and 24 fluorotic porcine teeth. Polished and unpolished sections were used for probe measurements, and blocks of enamel cut from tissue adjacent to the sections were used for acid etching. Additional blocks were etched with acid containing dye to study penetration of acid beyond the sampling sites. Probe-derived values were characterized by wide fluctuations. They were also higher than acid-etch values, and this difference was reduced but not eliminated by polishing the sections prior to scanning. Profiles obtained with the two methods followed a parallel course in fluorotic and normal enamel. Thus, errors due to chemical estimations of enamel depth with the etch technique were not demonstrated, although penetration of acid deep to the surface of the porous fluorotic enamel was observed. Further development of the precision of the probe method is required to optimize the unique advantage provided by the potential accuracy, speed of data collection, and spatial resolution of this method.

Acid Etching, Dental↗
PubMed1994

Dental tissue effects of fluoride.

It is now well-established that a linear relationship exists between fluoride dose and enamel fluorosis in human populations. With increasing severity, the subsurface enamel all along the tooth becomes increasingly porous (hypomineralized), and the lesion extends toward the inner enamel. In dentin, hypomineralization results in an enhancement of the incremental lines. After eruption, the more severe forms are subject to extensive mechanical breakdown of the surface. The continuum of fluoride-induced changes can best be classified by the TF index, which reflects, on an ordinal scale, the histopathological features and increases in enamel fluoride concentrations. Human and animal studies have shown that it is possible to develop dental fluorosis by exposure during enamel maturation alone. It is less apparent whether an effect of fluoride on the stage of enamel matrix secretion, alone, is able to produce changes in enamel similar to those described as dental fluorosis in man. The clinical concept of post-eruptive maturation of erupting sound human enamel, resulting in fluoride uptake, most likely reflects subclinical caries. Incorporation of fluoride into enamel is principally possible only as a result of concomitant enamel dissolution (caries lesion development). At higher fluoride concentrations, calcium-fluoride-like material may form, although the formation, identification, and dissolution of this compound are far from resolved. It is concluded that dental fluorosis is a sensitive way of recording past fluoride exposure because, so far, no other agent or condition in man is known to create changes within the dentition similar to those induced by fluoride. Since the predominant cariostatic effect of fluoride is not due to its uptake by the enamel during tooth development, it is possible to obtain extensive caries reductions without a concomitant risk of dental fluorosis.

Amelogenesis↗
PubMed1993

Detection of measles, mumps, and rubella antibodies in saliva using antibody capture radioimmunoassay.

Antibody capture radioimmunoassays were developed for detecting virus specific IgM (MACRIA) and IgG (GACRIA) to measles, mumps, and rubella and used to investigate saliva as an alternative specimen to serum for diagnosis. Saliva was collected from 63 patients with measles, 19 with mumps, and 150 with rubella, which were all clinically diagnosed and serologically confirmed. Virus specific IgM was detected in 92% of measles, 75% of mumps, and 100% of rubella saliva samples collected during the first week of illness. Between 1 and 5 weeks after onset virus specific IgM was detected in 100% of saliva specimens. After the 5th week the proportion of reactive specimens declined. The specificity of the MACRIA tests was established by testing saliva samples collected from blood donors for measles (88), mumps (88), and rubella IgM (91). All of the saliva specimens tested for measles and rubella specific IgM were unreactive, 1/88 specimens tested for mumps specific IgM contained significant reactivity. Saliva specimens collected from acute cases of MMR were tested in all 3 MACRIAs. A small proportion of saliva samples contained detectable IgM of more than one virus infection. Rubella and measles specific IgG was detected in the saliva of all cases from the 4th or 5th day of illness, respectively. Detection of mumps specific IgG was less successful. We have demonstrated that virus specific IgM can be reliably detected in saliva samples collected from acute cases of measles, mumps, and rubella and identified 1-5 weeks after onset of illness as the optimum time for collection of samples.

Adolescent↗
PubMed1993

Wide variation in patient response to midazolam sedation for outpatient oral surgery.

Intravenous midazolam in doses of between 0.07 mg/kg and 0.1 mg/kg has been recommended for sedation in dentistry and some medical procedures and investigations. This study examined the variable sensitivity of patients to midazolam. One hundred and thirty-four fit but anxious patients between the ages of 16 and 63 years received midazolam intravenously for sedation for minor oral surgery. Doses required ranged from 0.04 to 0.40 mg/kg. Nineteen patients required doses less than 0.07 mg/kg; 59 patients required doses greater than 0.1 mg/kg. The mean dose per kilogram required for males was significantly less than for females. The wide variation in sensitivity to midazolam is confirmed.

Adolescent↗
PubMed1993

Gingival and periodontal health in systemic lupus erythematosus.

This study compared the periodontal health of patients with SLE with that of healthy controls. Patients with systemic lupus erythematosus had significantly lower periodontal probing depths compared with healthy controls. It is possible that systemic drugs such as corticosteroids and NSAIDS may be responsible for these reduced probing depths but this study did not reveal a statistically significant effect of drugs. There is thus no evidence for a predisposition to increased periodontal disease in SLE.

Adjuvants, Immunologic↗
PubMed1993

A T+6 to C+6 mutation in the donor splice site of COL3A1 IVS7 causes exon skipping and results in Ehlers-Danlos syndrome type IV.

Ehlers-Danlos syndrome type IV is usually caused by mutations in COL3A1, the gene coding for type III collagen. In a woman with a milder form of this disease, analysis of type III collagen synthesised by her cultured skin fibroblasts showed an apparently shorter form of the protein. Amplification of overlapping cDNAs, encoding the triple helical region of the molecule, showed a deletion near the 5' end of the gene. Sequencing showed that exon 7 was missing from the cDNA sequence. Analysis of genomic DNA showed that this was the result of a T+6 to C+6 mutation in the donor splice site of intron 7. The proband's parents and 35 normal controls were homozygous for T+6 at this position, indicating that the C+6 mutation was causative.

Adult↗
PubMed1993

The substitution of glycine 661 by arginine in type III collagen produces mutant molecules with different thermal stabilities and causes Ehlers-Danlos syndrome type IV.

Previous studies have shown that Ehlers-Danlos syndrome type IV (EDS IV) is caused by mutations of type III collagen (COL3A1). Here we have characterised the most amino-terminal glycine substitution so far described in a patient with EDS IV. A combination of peptide mapping and chemical cleavage analysis of cDNA localised the mutation in cyanogen bromide peptide CB5. Sequence analysis showed a G to A mutation, converting glycine 661 to arginine, which was a new dominant mutation. Analysis of type III collagen secreted by cultured fibroblasts showed an overmodified mutant protein with normal thermal stability. However, the intracellularly retained form melted 2 degrees C lower than normal. This indicated that molecules resulting from the same mutation can differ in their thermal stabilities.

Arginine↗
PubMed1993

Differential metabolic and electrical activity in the somatic sensory cortex of juvenile and adult rats.

We have examined relative levels of metabolic and electrical activity across layer IV in the primary somatic sensory cortex (S1) of the rat in relation to regions of differential postnatal cortical growth. Each of several indices used--mitochondrial enzyme histochemistry, microvessel density, Na+/K+ pump activity, action potential frequency, and deoxyglucose uptake--indicate regional variations of metabolic and electrical activity in this part of the brain in both juvenile (1-week-old) and adult (10-12-week-old) animals. At both ages, areas of the somatic sensory map related to special sensors such as whiskers and digital pads showed evidence of the most intense activity. Thus, mitochondrial enzyme staining, blood vessel density, and Na+/K+ ATPase activity were all greatest in the barrels and barrel-like structures within S1, and least in the adjacent interbarrel cortex and the cortex surrounding S1. Multiunit recordings in and around the posteromedial barrel subfield of anesthetized animals also showed that the average ratio of evoked to spontaneous activity was greater in barrels than in the surrounding, metabolically less active cortex. Furthermore, autoradiograms of labeled deoxyglucose accumulation in awake behaving animals indicated systematic differences in neural activity across S1 barrels and barrel-like structures showed more deoxyglucose accumulation than interbarrel, nonbarrel, or peri-S1 cortex. These regional differences in neural activity correspond to regional differences in neocortical growth (Riddle et al., 1992). The correlation of greater electrical activity, increased metabolism, and enhanced cortical growth during postnatal maturation suggests that neural activity foments the elaboration of circuitry in the developing brain.

Action Potentials↗