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Biomedical subjects

A H Brook

Publications and source records attributed to A H Brook.

At least 19 recordsLinked to original sources
PubMed1993

Small primary tooth-crown size in low birthweight children.

As part of a longitudinal study of dental development in a group of low birthweight children (LBW), study models of 72 children at age 7 years were measured to determine the tooth-crown size of primary molars and canines and to compare the findings with equivalent measurements in 60 normal birthweight (NBW) controls. Mesiodistal (length) and buccolingual (width) dimensions were measured manually, using dial calipers. Primary canines and molars were smaller in the LBW than the controls, with significance values ranging from P < 0.001 for the mesiodistal dimension of maxillary and mandibular canine (> 4% difference) to a non-significant difference P < 0.2 for the buccolingual dimension mandibular first primary molar (1.8% difference). Within the LBW group there was a positive correlation between birthweight and mesiodistal tooth size. Small primary tooth size in LBW children may be influenced by both genetic and environmental factors. The shorter prenatal growth period and poor perinatal and early postnatal development may influence the developing deciduous dentition. Small primary tooth-crown size, associated with LBW, should be considered in all population studies of tooth size.

Child↗
PubMed1990

Enamel defects in the primary dentition of children born weighing less than 2000 g.

The findings for enamel defects in the primary dentition of a group of low birthweight (LBW) children were related to their perinatal medical histories. Examination of 110 LBW children and 93 control children aged 5 years showed that significantly more of the LBW children (71%) had hypoplasia than controls (15%), but there was no difference in opacities alone (LBW 25%, control 26%). In the LBW group, defects were seen more often in children classified as ill during the perinatal period, who received ventilator support or intravenous alimentation and in those children born at less than 32 weeks gestation, compared to the LBW children without these perinatal problems. It is speculated that the high incidence and the cause of enamel defects in sick preterm infants may be due to oxygen deprivation and mineral substitute depletion.

Analysis of Variance↗
PubMed1987

Vasopressin release in sheep following various degrees of rehydration.

Restriction of the water intake of sheep to 0.5 1/day for 7-9 days increases plasma arginine vasopressin (pAVP), and voluntary rehydration causes a rapid fall in pAVP with no change in plasma osmolality. The extent of that inhibition of AVP release was assessed by comparing the decline of pAVP after drinking with pAVP disappearance curves obtained in the same sheep after stopping a constant infusion of AVP at 0.5 micrograms/h, which increased pAVP to the dehydration level. The fall in pAVP after drinking was almost identical with the disappearance curve showing that AVP release was almost completely inhibited during the 2-3 min taken for the sheep to drink 3-5 liters to satiate themselves. The response seemed, therefore, to be cued before the intake reached the satiating volume. When dehydrated sheep drank only 0.5 or 1.0 liter, in 30 s or less, pAVP again fell rapidly but only to a minimum approximately 15 min after drinking. The pAVP was unaltered in dehydrated sheep presented with water but denied access to it. Thus satiation was not necessary for rapid inhibition of AVP release after drinking, but satiation was necessary for this inhibition to be maintained. The initial inhibition was associated with falls in hematocrit and plasma total protein but not plasma osmolality. This isosmolar dilution occurred even in sheep that saw but were denied access to the water and suggests a shift of fluid from the extravascular space.

Animals↗
PubMed1986

An image analysis system for the determination of tooth dimensions from study casts: comparison with manual measurements of mesio-distal diameter.

A first comparison of an image analysis method with classical hand measurement was made using the mesio-distal diameter data derived by the simplest image analysis method, the jawview mode. Fifty casts of male Hong Kong Chinese dental students, mean age 20.4 years, were examined by both methods. The two techniques gave comparable overall results, the correlation coefficients generally being greater than 0.9. A combination of the buccal and occlusal image analysis views gave the best correlation with hand measurement with a comparable variability for different tooth types. For certain teeth, particularly posteriors, reproducibility was better using hand measurement. Optimal weighting of the data from these two different image analysis views can give an "estimated hand measurement" value. Further development of the method to deal with differing orientations of teeth is possible.

Adult↗
PubMed1985

Haemophilic pseudotumours of the mandible: report of a case in a one-year-old child.

Pseudotumours of bone are an uncommon complication of severe haemophilia and only seven cases occurring in the mandible have been reported previously in the English literature. If treated early the condition appears to have a better prognosis and so it should be included in the differential diagnosis of any slowly progressive swelling of hard and soft tissues occurring in a patient with severe haemophilia. However aspiration and biopsy should be avoided if possible. Previous authors have advocated a variety of invasive procedures for this condition. A further case is described which is unique in the age at which the bilateral lesions developed, in the successful outcome of conservative management and in the dental observations.

Diagnosis, Differential↗
PubMed1985

Acute reduction of plasma vasopressin levels by rehydration in sheep.

Sheep were depleted of water by restricting water intake to 500 ml/day for 7-9 days and were then rehydrated by three treatments: voluntary intake of water, administration of water by tube into the stomach, or voluntary intake of 0.9% NaCl solution (saline). The volumes of fluids drunk within 2-3 min, or administered by tube, were approximately equal to the animal's weight loss. Plasma vasopressin rose from 4.4 +/- 0.6 to 16.8 +/- 1.0 pg/ml during water restriction. After drinking water plasma vasopressin fell from 19.0 +/- 1.9 to 7.5 +/- 0.4 pg/ml (P less than 0.001) in 15 min and gradually fell to 3.2 +/- 0.4 pg/ml over 6 h. Plasma osmolality fell from 302.4 +/- 0.9 to 301.0 +/- 1.1 mosmol/kg (NS) 15 min after water drinking and then gradually fell to subnormal levels. Sheep given water by stomach tube showed a similar decline in plasma osmolality, but the fall in plasma vasopressin was attenuated. The fall in plasma vasopressin in the first 30 min after drinking saline was almost identical with the fall after drinking water, but plasma osmolality was unaltered. Plasma vasopressin fell so rapidly after drinking water or saline as to suggest that the act of drinking caused almost complete inhibition of vasopressin release without a change in plasma osmolality. The results are consistent with earlier evidence that oropharyngeal receptors initiate the inhibition of vasopressin release after drinking.

Animals↗
PubMed1984

A unifying aetiological explanation for anomalies of human tooth number and size.

Genetic and environmental factors are implicated in the aetiology of supernumerary teeth, hypodontia, megadontia and microdontia ; these anomalies tend to be associated. 1115 school children aged 11-14 years examined clinically and radiographically provided prevalence data. A further 703 children with dental anomalies were studied. 153 of these became probands for a family study and 327 of their first-degree relatives were examined. There were much higher frequencies (p less than 0.001) of all anomalies among the relatives of probands than in the general population. Males more often had supernumerary teeth and megadontia and females more frequently had hypodontia (p less than 0.05) and microdontia . For hypodontia, the proportion of relatives affected varied with the severity of the condition in the proband (p less than 0.05). In the prevalence study, there was an association between hypodontia and microdontia (p less than 0.001). These findings may be explained by a multifactorial model having a continuous scale, related to tooth number and size, with thresholds. Position on the scale usually depends upon the combination of numerous genetic and environmental factors, each with a small effect, but occasionally a chromosomal anomaly, a major single gene or a major environmental insult may have a large effect. The finding that the estimated difference between the means of the sexes was the same for each anomaly, within the limits of experimental error, supports the validity of the model.

Adolescent↗