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Biomedical subjects

V R O'Sullivan

Publications and source records attributed to V R O'Sullivan.

15 recordsLinked to original sources
PubMed2006

Pierre Fauchard: the 'father of modern dentistry'.

The development of the modern practice of dentistry can be traced to the work and life of Pierre Fauchard, a French dentist who worked in the first half of the eighteenth century. Fauchard was an exceptionally gifted and talented practitioner, who introduced many innovations to dentistry. In a significant break with the tradition of the time, he shared his knowledge and techniques with colleagues, and published these in the first comprehensive dental textbook. This paper reviews his life and contribution to modern dentistry.

Dental Care↗
PubMed2005

Pierre Fauchard and his rôle in the development of obturators.

The design and fabrication of oral appliances to replace parts of the palate missing due to congenital defects or lost through tumours, infection or trauma has been a considerable challenge for clinicians throughout the history of dentistry. Significant advances were made during the eighteenth century towards resolving the problem of constructing satisfactory obturators by the first 'surgeon-dentist', Pierre Fauchard. This paper reviews his innovative designs.

Equipment Design↗
PubMed1998

A four-rooted primary upper second molar.

Both primary upper second molars were extracted from a young male patient. The left had a normal root pattern but the right had four well-defined roots. The accessory root appeared to be the mesiopalatal which had a distinctly rounded cross-sectional profile. The other roots had the typical form characteristic of primary molar roots. Some degree of bifurcation can occur in the mesiobuccal roots of upper molars and the accessory root described in this report may represent an extreme example of such bifurcation.

Child↗
PubMed1997

External resorption presenting as an intracoronal radiolucent lesion in a pre-eruptive tooth.

A large intracoronal radiolucent lesion in an unerupted permanent molar was found during the routine assessment of a young male Caucasian prior to orthodontic treatment. The tooth was extracted. Histological examination indicated the lesion was caused by external resorption. The defect extended widely into the enamel and dentine, and was repaired in part by bone. The pulp chamber was not involved. The aetiology of these lesions is often obscure but in this case it appeared to have originated in the floor of two developmental pits on the occlusal surface of the tooth.

Child↗
PubMed1994

A survey to assess the ultrastructural preservation of fixed biological samples after air-drying from tetramethylsilane.

A scanning electron microscope (SEM) survey assessed the quality of ultrastructural preservation of a wide range of tissues from the laboratory rat and from a limited number of botanical and fly-larval samples, air-dried from tetramethylsilane (TMS) after chemical fixation and dehydration. Comparisons were made with critical point drying (CPD) and air-drying from acetone. CPD produced good results in all cases. TMS gave acceptable results with 75%, and acetone with 31%, of rat tissues. Air-drying was unacceptable for the botanical and fly-larval samples. It is concluded that air-drying from TMS is generally useful for mammalian tissues in preparation for the SEM.

Animals↗
PubMed1991

Central-peripheral transitional zone of the spinal accessory nerve in the rat.

The spinal accessory nerve rootlets emerge from the lateral aspect of the upper five segments of the cervical spinal cord underlying the nerve trunk. They cross the lateral funiculus of the cord with a slight rostral inclination. Here some pursue a relatively straight course while others have a dorsal convexity. The transitional zones may be classified into three distinct types, related to their orientation as they traverse the glia limitans to emerge as free rootlets. The fibres in Type 1 rootlets bend sharply rostrally on reaching the glia limitans. Type 2 rootlets turn ventrally to run in the glia limitans in the transverse plane of the cord before emerging. Type 3 rootlets are found only at C1. Their fibres initially turn caudally in the glia limitans and then loop rostrally. The morphology of the central-peripheral transitional zones of the spinal accessory rootlets closely resembles that of cervical ventral rootlets, and is therefore correlated with the motor function of these rootlets rather than with their intermediate location between the ventral and dorsal cervical rootlets.

Accessory Nerve↗
PubMed1990

The influence of dietary folate supplementation on the incidence of teratogenesis in zinc-deficient rats.

Two studies were conducted to investigate the possibility that pteroylmonoglutamic acid supplementation would alleviate teratogenesis in zinc-deficient rats. Pregnant rats of the Wistar strain were fed on Zn-deficient (less than 0.5 mg Zn/kg) or Zn-supplemented (75 or 95 mg Zn/kg) diets from mating until day 18.5 of gestation. The basal level of pteroylmonoglutamic acid added to all diets (0.56 mg/kg) was supplemented with 30-200 mg/kg in selected diets. Dietary Zn deprivation resulted in fetal resorption, fetal growth retardation and reduced concentrations of Zn in fetuses and maternal plasma and tibia. Low maternal body-weight at conception emerged as an important determinant of risk of resorption in Zn-deficient rats. Dietary Zn deficiency resulted in reduced maternal plasma folate concentrations and these values were inversely correlated with litter size or weight in Zn-deficient rats. Pteroylmonoglutamic acid supplementation increased maternal plasma folate concentrations, but did not reduce the high incidence of teratogenesis which occurred in Zn-deficient rats. Supplementation of Zn-deficient rats with pteroylmonoglutamic acid significantly increased the incidence of clubbed foot and tended to increase the incidence of brain or meningeal abnormalities, or both, and cleft palate, but did not reduce maternal or fetal Zn status. Pteroylmonoglutamic acid supplementation also increased the weights of Zn-supplemented control fetuses.

Animals↗
PubMed1989

Age changes in axon number along the cervical ventral spinal nerve roots in rats.

Axon counts were made at two standardised levels of C7 ventral spinal nerve roots from 46 female rats representing nine ages between birth and 500 days. The objective was to provide a definitive account of proximodistal changes in axon numbers and of age changes in axon numbers both during postnatal development and at several stages during maturity. At each age there is a proximodistal increase in the numbers of axons in all categories examined (myelinated, promyelin, transitional, and fetal) between levels midway along the subarachnoid course of the root and where it is apposed to but separate from the dorsal root ganglion. During maturation and throughout maturity axon totals change similarly at both levels: After a slight increase immediately postnatum, they decline sharply between 4 and 20 days due to a marked loss of unmyelinated axons. A gradual decline in myelinated axon numbers continues to 500 days. While these changes are occurring, axon numbers in all categories show a proximodistal increase throughout. The magnitude of this increase lessens with age for all but the transitional category due to a preferential decrease in numbers distally. Though these observations do not differentiate between axon branching and looping of sensory axons into the ventral root as a cause of the proximodistal increase in numbers, they tend to support the former. At each age during maturation axon proportions at proximal and distal levels correspond well for each animal, indicating that axon segregation proceeds at related rates within each root. Age changes in axon proportions within the transitional and fetal categories indicate that the postnatal stage of axon segregation results from axon loss, rather than Schwann cell proliferation.

Aging↗
PubMed1988

The central-peripheral transitional regions of cranial nerves. Oculomotor nerve.

Oculomotor nerve rootlets varied more markedly in size and in transitional zone length and form than those of any other nerve studied to date. However, they could be classified into four main types, each of which was associated with a characteristic type of central-peripheral transitional zone. Type 1 rootlets emerged from the brainstem through a tongue-shaped elevation of the glia limitans. This type of central-peripheral transition is found elsewhere only in a minority of abducent rootlets (Fraher et al. 1988). Type 2 rootlets contained long segments made up entirely of central nervous tissue and were the only motor rootlets so far described to contain a segment of this kind. Type 3 rootlets were the commonest and the largest. Before leaving the brainstem they ran laterally on its surface as the emergent rootlet segments, forming plexuses with one another. These rootlets contained a unique wedge-shaped type of central tissue projection. Over its entire length one surface of this coincided with the rootlet surface and a thin tapering strip of peripheral nervous tissue extended proximally for a considerable distance into the emergent rootlet segment. Type 4 rootlets emerged from the brainstem surface obliquely and contained a glial fringe.

Animals↗
PubMed1988

The central-peripheral transitional regions of cranial nerves. Trochlear and abducent nerves.

Unlike all other nerves containing somatic efferent fibres, the trochlear nerve emerges from the dorsal aspect of the brainstem. It generally emerges as a single trunk which resembles a dorsal rather than a ventral spinal nerve rootlet in terms of its size and of the morphology and position of the central tissue projection which it contains. The morphology of the central-peripheral transition of the trochlear nerve is therefore correlated with its dorsal location rather than with the nature of its constituent fibres. By contrast, abducent nerve rootlets emerge from the ventral aspect of the neuraxis, in line with other cranial and with spinal ventral nerve rootlets which also contain somatic efferent fibres. Its rootlets resemble the latter in terms of their size, being much smaller than those of dorsal rootlets or the trochlear nerve. They possess two distinct types of central-peripheral transitional zone: those of the rostral rootlets resemble zones of cervical ventral spinal rootlets. Many of these emerge through a circumscribed thickening of the astrocytic glia limitans. Caudal abducent rootlets emerge through a tongue-shaped glial elevation projecting above the level of the surrounding brainstem surface, resembling Type 1 oculomotor rootlets.

Abducens Nerve↗