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Biomedical subjects

H T Groeneveld

Publications and source records attributed to H T Groeneveld.

At least 19 recordsLinked to original sources
PubMed2001

The effect of frog pressure and downward vertical load on hoof wall weight-bearing and third phalanx displacement in the horse--an in vitro study.

A shoe was designed to combine the advantages of a reverse shoe and an adjustable heart bar shoe in the treatment of chronic laminitis. This reverse even frog pressure (REFP) shoe applies pressure uniformly over a large area of the frog solar surface. Pressure is applied vertically upward parallel to the solar surface of the frog and can be increased or decreased as required. Five clinically healthy horses were humanely euthanased and their dismembered forelimbs used in an in vitro study. Frog pressure was measured by strain gauges applied to the ground surface of the carrying tab portion of the shoe. A linear variable distance transducer (LVDT) was inserted into a hole drilled in the dorsal hoof wall. The LVDT measured movement of the third phalanx (P3) in a dorsopalmar plane relative to the dorsal hoof wall. The vertical component of hoof wall compression was measured by means of unidirectional strain gauges attached to the toe, quarter and heel of the medial hoof wall of each specimen. The entire limb was mounted vertically in a tensile testing machine and submitted to vertical downward compressive forces of 0 to 2,500 N at a rate of 5 cm/minute. The effects of increasing frog pressure on hoof wall weight-bearing and third phalanx movement within the hoof were determined. Each specimen was tested with the shoe under the following conditions: zero frog pressure; frog pressure used to treat clinical cases of chronic laminitis (7 N-cm); frog pressure clinically painful to the horse as determined prior to euthanasia; frog pressure just alleviating this pain. The specimens were also tested after shoe removal. Total weight-bearing on the hoof wall at zero frog pressure was used as the basis for comparison. Pain-causing and pain-alleviating frog pressures decreased total weight-bearing on the hoof wall (P < 0.05). Frog pressure of 7 N-cm had no statistically significant effect on hoof wall weight-bearing although there was a trend for it to decrease as load increased. Before loading, the pain-causing and pain-alleviating frog pressures resulted in a palmar movement of P3 relative to the dorsal hoof wall compared to the position of P3 at zero frog pressure (P < 0.05). This difference remained statistically significant up to 1300 N load. At higher loads, the position of P3 did not differ significantly for the different frog pressures applied. It is concluded that increased frogpressure using the REFP shoe decreases total hoof wall weight-bearing and causes palmar movement of P3 at low weight-bearing loads. Without a shoe the toe and quarter hoof wall compression remained more constant and less in magnitude, than with a shoe.

Animals↗
PubMed1998

Relationship between juvenile bruxing and craniomandibular dysfunction.

A longitudinal study was conducted over 5 years to investigate the relationship between juvenile bruxing and craniomandibular disorders. A total of 150 bruxers between the ages of 6 and 9 years were examined for oral parafunctions and TMJ symptoms. Of these, 126 were re-examined for the same signs and symptoms after 5 years. The results showed that only 17 individuals had retained their bruxing habit. In common with other studies, we found that symptoms reduced with age. It was concluded that juvenile bruxing was a self-limiting condition which does not progress to adult bruxism and which appeared to be unrelated to TMJ symptoms.

Aging↗
PubMed1997

Dental asymmetry, maternal obesity, and smoking.

This study examines the levels of fluctuating dental asymmetry in four samples of school children: those whose mothers were obese and had smoked during the pregnancy concerned (n = 111); those whose mothers were obese non-smokers (n = 114); those whose mothers were non-obese smokers (n = 104); and those whose mothers were lean non-smokers (n = 111). The degree of fluctuating asymmetry was assessed by means of a rescaled asymmetry measure. Obesity was defined as Quetelet's index in excess of 30, and smoking status as at least 20 cigarettes per day during the pregnancy concerned. When the magnitudes of fluctuating asymmetry in children of lean smokers were compared to the control group of lean non-smokers, no significant univariate differences were found. Children of obese mothers, whether these smoked or not, were found to have significantly raised levels of asymmetry. An analysis of variance confirmed that the combination of obesity and maternal smoking was a significant predictor of fluctuating dental asymmetry. The teeth involved tended to be the maxillary first incisor and molars. It is concluded that maternal obesity has a destabilizing effect on the developing fetus and that this effect appears to be enhanced in obese mothers who smoked. This effect was absent in lean mothers, irrespective of their smoking status.

Adolescent↗
PubMed1996

Nucleolar organizer regions (AgNORs) in odontogenic cysts and ameloblastomas.

The aim of this study was to determine whether nucleolar organizer regions (AgNORs) may be of value in distinguishing various odontogenic cysts from the unicystic ameloblastoma. Histological sections were prepared from fifteen cases each of odontogenic keratocyst, residual cyst, dentigerous cyst, unicystic ameloblastoma and conventional ameloblastoma. In each case intra-nuclear AgNOR dots were counted in 100 consecutive basal nuclei. Statistical comparison of the least squares means showed that those areas of unicystic ameloblastomas lined by characteristic epithelium had a significantly lower AgNOR count than the other groups (P < 0.05). The dentigerous cysts had significantly higher AgNOR counts than the residual cysts and unicystic ameloblastomas (P < 0.05). These differences may or may not be indicative of variations in metabolic, proliferative or transcriptional activity. We conclude that AgNOR counts are not of diagnostic significance and cannot be used to distinguish the various odontogenic cysts from one another nor from the unicystic ameloblastoma.

Ameloblastoma↗
PubMed1996

Delayed tooth formation in children exposed to tobacco smoke.

Panoramic radiographs of 203 Caucasoid children between the ages of seven and ten years were examined for an evaluation of dental development. Four groups were studied: a control group in which neither parent had smoked during the pregnancy concerned, a group exposed to tobacco smoke from the mother only, a group exposed to smoke from the father only, and finally a group exposed to tobacco smoke from both parents. In each case, the dental age (determined according to the method of Moorrees) was contrasted to the chronological age of the subject. Overall results showed that there were no differences in dental ages related to gender. Maximum differences between chronological and dental ages were found in children subjected to cigarette smoke from both parents. Here, a 35% reduction in dental maturation was noted. Most affected teeth were the maxillary second premolars, while the central incisors were the least affected.

Child↗
PubMed1995

Microclimatic effect on vertical migration of Haemonchus contortus and Haemonchus placei third-stage larvae on irrigated Kikuyu pasture.

The influence of microclimate on numbers of third-state larvae of haemonchus contortus and Haemonchus placei in four strata of irrigated Kikuyu pasture was assessed. On 36 different, interspersed days three replicates of pasture samples were collected on three occasions per day from 1990-1992 for larval recovery and the log10 mean counts of the larvae recovered were analysed by use of ANOVA models. Because the ground-surface area from which herbage was collected was standardized, estimated larval counts for the different strata could be compared; this was not possible in our previous studies. For H. contortus, the estimated larval counts in the four strata were predicted by microclimatic air temperature, relative humidity and soil moisture, with the coefficient-of-determination (R2) values ranging from 0.15-0.35. Of these, air temperature had the greatest effect. The same three predictors, together with illumination and wind speed, featured for H. placei, with R2 values of 0.19-0.52. With the exception of wind speed and illumination, which (for H. placei) had the opposite effect, all the microclimatic parameters listed, predicted an increase in numbers of larvae from a lower to an upper strata.

Africa↗
PubMed1995

Determinants of blood pressure in Sowetan infants.

A study of the effect of different variables on the blood pressure of Sowetan infants was undertaken with the Birth-to-Ten (BTT) cohort as the study population. Variables studied at 1 year included anthropometric indices, aspects of feeding practices and relationship to maternal blood pressure. Systolic blood pressure was recorded in 792 infants at 1 year; 29,3% of the variance was determined by weight, upper arm circumference, age at which formula feeds were started, length and volume of formula feeds (in order of significance). Amount of salt added to diet approached statistical significance. Data available for 353 of the 752 infants showed a correlation between the infants' and the mothers' blood pressure. The maternal blood pressure only accounted for an additional 2% of the variance; approximately 70% of blood pressure variance is therefore still unexplained. Firm recommendations with regard to use of formula feeds and the addition of salt to infants' diet are difficult to make on the basis of this limited follow-up.

Anthropometry↗
PubMed1995

Inequalities in the pattern of dental delivery in South Africa.

The pattern of dental delivery of three groups of private general practitioners were evaluated. The first group consisted of dentists who charged fees based on the National Schedule of the Dental Association of South Africa, the second charged fees at the recommended Scale of Benefit and served an urban population, while the last group served township dwellers at the Scale of Benefits. In each case, sequential claims of 500 medical scheme members were evaluated for ten randomly selected dentists within each group. Uni- and multivariate analyses revealed significant differences between these groups which centred on the use of cast restorations, bleaching of vital teeth and treatment of diseases of the oral mucosa. Because these differences do not conform to documented differences in dental needs between the two groups, it is concluded that other non-clinical factors influence the delivery of private dentistry.

Analysis of Variance↗
PubMed1993

An environmental and respiratory health survey of workers in a grain mill in the Johannesburg area, South Africa.

A respiratory health survey was conducted in a grain mill and the relationship of health indicators to quantitative measures of airborne dust, fungal, and bacterial contamination was examined. Respiratory symptoms were more prevalent in the high dust exposure categories; lung function levels were also higher in the high dust exposure categories, consistent with a "healthy" worker effect. Workers in the three higher dust exposure categories showed either no change or a decrease in lung function over the working week, while workers in the low exposure category demonstrated an improvement in lung function over the working week. Total dust and microbiological (fungal and bacterial) load were found to be significantly related to each other, and the relationship of microbiological load to lung function level and changes over the working week were similar to those found for total dust.

Adult↗
PubMed1993

Relationship of respiratory health status to grain dust in a Witwatersrand grain mill: comparison of workers' exposure assessments with industrial hygiene survey findings.

Objective measures of exposure furnished by dust monitoring are both costly and time consuming and require a sufficient level of technology. However, they are important in demonstrating exposure-response relationships, in furnishing information necessary to establish environmental control levels, and to assess if interventions, for instance, improving dust control, have been effective. In this paper respiratory symptoms and cross-shift changes in spirometric lung function were related to dust exposure level in a grain mill assessed in two ways, subjectively (by workers themselves on a four point scale) and objectively (by personal dust monitoring). Health indicators that depend on the individual's perception (e.g., symptoms) correlated more closely with the subjectively assessed dust category, while health indicators that were measured objectively (e.g., cross-week FVC and FEV1 change) correlated more closely with the objectively assessed dust category. However, the patterns of relationship of respiratory health indicators to either dust category were similar, and exposure assessed by one method was, to a large extent, a proxy for the other. The most significant predictor of workers' choice of dust exposure category was the measured dust level. These findings indicate that exposure categories based on workers' assessment of dustiness can be a useful tool in etiologic research, in particular in establishing exposure-response relationships.

Dust↗
PubMed1993

Investigations into lymphocyte transformation and histamine release by basophils in sheep repeatedly infested with Rhipicephalus evertsi evertsi ticks.

The immune response of a natural host of Rhipicephalus evertsi evertsi to feeding by this tick species was investigated with respect to the effects of tick salivary gland extracts on the transformation of peripheral blood lymphocytes and the release of histamine by basophils obtained from repeatedly infested sheep. The results indicated that there was no stimulation of lymphocyte transformation but that histamine release was elevated 10 fold after four infestations. Although this suggests a hypersensitivity reaction, believed to be a major factor in resistance to tick feeding, it was observed that ticks fed normally even after four infestations with 28 day intervals in between. These results emphasize the adaptation of ticks to feeding on their natural hosts.

Animals↗
PubMed1993

Effects of time, from collection to processing, on the recovery of Haemonchus contortus third-stage larvae from herbage.

Being able to obtain accurate estimates for the number of Haemonchus contortus third-stage larvae (L3) on pasture is essential to any type of strategy intended for control. The objective of this experiment was to study the effect of the time, from collection to processing, on the recovery rate of H. contortus L3 from herbage. Separate herbage samples were inoculated with two treatments of a known amount of larvae on Day 1 and then samples were processed from Day 1 to Day 30. This simulated infective herbage was collected, refrigerated, and processed over a period of 1 month. A drop in the recovery rate over time was found. Treatment 2 (5000 L3) exhibited a sharper decline in recovery rate than Treatment 1 (1800 L3). These findings suggest that the effect of time, from collection to processing, as well as larval concentration on the herbage, must be considered when performing any type of larval recovery technique.

Animals↗
PubMed1992

Alcohol consumption as a risk factor for hepatocellular carcinoma in urban southern African blacks.

Our purpose was to ascertain whether alcohol abuse is a risk factor for the development of hepatocellular carcinoma in urban southern Africa blacks and, if so, to relate alcohol consumption to other possible risk factors such as persistent hepatitis-B-virus infection, smoking, male sex, in this subpopulation. A prospective, hospital-based, case-control format involving 101 patients with hepatocellular carcinoma and 101 controls was used. The mean age of the patients was 53.7 +/- 1.85 years and the male:female ratio 3.2:1. An increased risk was found, but only in urban men over the age of 40 years who habitually drank more than 80 g of ethanol daily. The risk remained after adjusting for chronic hepatitis-B infection, smoking, and sex (odds ratio 4.4, 95% confidence interval 1.3 to 16.6; p = 0.003). Smoking proved not to be a risk factor, either alone or in concert with alcohol consumption. Hepatitis-B infection was confirmed as a major risk in younger men and in women, but in urban men over the age of 40 years alcohol abuse was a greater risk. Current hepatitis-B infection and alcohol abuse were additive risks.

Adult↗
PubMed1992

Family history as a risk factor for coronary heart disease in South African families.

This article presents data on, and applies a procedure for the statistical quantification of, family history as a risk factor for coronary heart disease (CHD) in three sub-samples (groups) of families: I--a healthy control group; II--families with familial hypercholesterolaemia (FH); and III--families identified by an index case with CHD. With regard to the average family history of CHD (calculated as an index for each family, and as a mean index for each group), group II differs significantly from group I and marginally significantly from group III; family groups I and III do not differ from each other statistically. By means of significance tests developed for this purpose, the groups of families are shown to be significantly heterogeneous, by being composed of families highly resistant against and susceptible to CHD. This is illustrated for example in group II, where some FH families can be shown to be highly resistant to CHD, compared with other FH families with a very strong history of CHD. The exact number and proportion of such families at different levels of significance is calculated and the actual families with the highest and lowest calculated family indices, respectively, are then identified (illustrated by examples). The practical significance of the statistical procedure of quantifying and applying family history as a risk factor for CHD, is discussed in terms of epidemiological and preventive health considerations.

Adolescent↗
PubMed1992

A preliminary study of the effect of microclimate on third-stage larvae of Haemonchus contortus and Haemonchus placei on irrigated pasture.

Assessments were made on the influence of several microclimatic variables on the availability of third-stage larvae of Haemonchus contortus and Haemonchus placei on four strata of irrigated Kikuyu pasture. Three replicates of these pasture samples were collected on 18 sample days over 12 months and the log10 mean counts of the larvae recovered were analysed by a step-wise regression model. Predictors for the log counts of the four strata for the two nematode species included relative humidity, illumination, air temperature and windspeed. The effect of air temperature on larvae of both Haemonchus species was similar; as air temperature increased, the number of larvae on pasture increased. The inverse was true for windspeed; as windspeed increased larval counts decreased. For H. contortus, relative humidity increased as the number of larvae increased on all strata except upper herbage. The R2 values ranged from 0.11 to 0.21 for H. contortus and from 0.04 to 0.12 for H. placei. Under the conditions of this study, only 21% of the effect on H. contortus and 12% on H. placei third-stage larvae on pasture can be explained by microclimatic conditions.

Animals↗
PubMed1992

Sex allocation of skeletal material by analysis of the proximal tibia.

In this study we contrasted the confidence with which individuals may be grouped and then reallocated on the basis of a set of measurements from the proximal tibia. The data were derived from 100 Caucasoid (50 male) and 102 Negro (50 male) tibia housed in the R.A. Dart Collection. Multivariate discrimination was effected by means of canonical and stepwise discriminant analyses, whilst probabalistic models were used to allocate individuals. High levels of correct classification (84.62-92%) were matched by high levels of reallocation, suggesting that, in contrast to dental or craniobasal measurements, those of the proximal tibia may be usefully employed to allocate an individual on the basis of sex.

Black People↗
PubMed1992

Mandibulodental allometry in the African wild dog, Lycaon pictus.

Mandibulodental relations were evaluated in a sample of 34 adult Lycaon pictus crania (18 males, 16 females). Standard mesiodistal and buccolingual measurements, together with 8 mandibular measurements (intercondylar distance, intercarnassial breadth, mandibular length, arch length, condylar height, canine-condylar length, mandibular width, mandibular height) were allometrically scaled to total skull length. These results were then compared with those of domestic dogs and of 3 smaller southern African canids, Vulpes chama, Canis adustus and C. mesomelas. The results highlighted the differences in mandibulodental relations between males and females and provided support for the theory that females have relatively larger postcanine tooth sizes to match the higher masticatory demands of lactation and pregnancy. The African wild dog is shown to be more closely related dentally to the domestic dog than has previously been supposed.

Animals↗