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H F Thomas

Publications and source records attributed to H F Thomas.

At least 19 recordsLinked to original sources
PubMed1995

Identification of regulatory elements necessary for the expression of the COL1A1 promoter in murine odontoblasts.

Recent studies have indicated that odontoblasts and osteoblasts have unique regulatory mechanisms that control COL1A1 gene expression. We are currently examining the regulation of COL1A1 gene expression in odontoblasts and have produced transgenic mice containing various collagen promoter constructs fused to the indicator gene, chloramphenicol acetyl transferase (CAT). Mandibular first molars were removed from jaws of transgenic mice. Some teeth were assayed for CAT activity (CAT diffusion assays), others were fixed and prepared for immunohistochemistry (CAT antibodies). Our results indicate the CAT activity was present in tooth germs containing promoter constructs longer than 1.719 kb. Immunoreactivity to CAT was confined to the odontoblast cell layer. No CAT activity was present in tooth germs containing a 1.670 kb construct. These data suggest that there are important regulatory elements located between -1.719 kb and -1.670 kb on the collagen promoter in odontoblasts. Examination of sequences in this region of the promoter demonstrates consensus with those known to be involved with binding of translation products of homeobox genes.

Animals↗
PubMed1995

Root formation.

This paper provides an overview of recent studies that have enhanced our understanding of the biological mechanisms that operate during root development. For the most part, these studies have been performed on rodents. As significant species differences have been shown to exist, this data cannot necessarily be extrapolated to the human model. The events associated with root odontoblast differentiation are reviewed in comparison to similar events in coronal odontoblast differentiation. Morphological as well as phenotypic differences are outlined and the inductive role of the epithelial root sheath is discussed. Both acellular and cellular cementum formation are reviewed highlighting morphological and phenotypic differences. The potential influence of the epithelial root sheath in the formation of both tissues is compared and contrasted. Finally, a discussion of the fate of the epithelial root sheath is presented with emphasis placed upon the possible roles of apoptosis and epithelium-mesenchymal transition.

Animals↗
PubMed1994

Upstream regulatory elements necessary for expression of the rat COL1A1 promoter in transgenic mice.

The activity of fusion genes containing fragments of the COL1A1 promoter was measured in tissues from 6- to 8-day-old transgenic mice. ColCAT3.6 contains approximately 3.6 kb (-3521 to 115 bp) of the rat COL1A1 gene, the chloramphenicol acetyltransferase (CAT) reporter gene, and the SV40 splice and polyadenylation sequences. ColCAT2.3 and ColCAT1.7 are deletion constructs that contain 2296 and 1667 bp of COL1A1 upstream from the RNA start site, respectively. For each transgene, up to six lines of mice were characterized. Both ColCAT3.6 and ColCAT2.3 had similar activity in bone and tooth; ColCAT1.7 was inactive. In transgenic calvariae, levels of transgene mRNA paralleled levels of CAT activity. In tendon, the activity of ColCAT2.3 was 3- to 4-fold lower than that of ColCAT3.6, and the activity ColCAT1.7 was 16-fold lower than that of ColCAT2.3. There was little activity of the ColCAT constructs in liver and brain. These data show that DNA sequences between -2.3 and -1.7 kb are required for COL1A1 promoter expression in bone and tooth; sequences that control expression in tendon are distributed between -3.5 and -1.7 kb of the promoter, with sequences downstream of -1.7 kb still capable of directing expression to this tissue. The cis elements that govern basal expression of COL1A1 in transgenic calvariae appear to be different from those required for optimal expression of the COL1A1 promoter in stably transfected osteoblastic cells.

Animals↗
PubMed1992

Dogs that bite.

Explore the source record for details and available documents.

Animals↗
PubMed1992

Acute pesticide poisoning in the UK and information and training needs of general practitioners: recording a conundrum.

A postal questionnaire of all general practitioners (n = 68) in a District Health Authority was undertaken to identify the information and training they had received on acute pesticide poisoning. Fifty-six (82%) replies were received. The responses showed that 33 (59%) had not seen the standard Department of Health Guide to acute pesticide poisoning and only 20 (36%) of the respondents thought that their practice had a copy of this publication. None of those surveyed had ever used Health and Safety Executive Guidance Notes on pesticides. Ten practitioners (18%) reported that they had at some time diagnosed a case of acute pesticide poisoning and three (5%) had done so in the last two years. Only three respondents (5%) considered they had sufficient information to diagnose all the main pesticides listed in the Department of Health Guide but 24 (43%) considered they had sufficient information to diagnose rodenticide poisoning. Twenty-three (41%) considered they had insufficient information to diagnose any acute pesticide poisoning category. The sources of information used in cases of suspected acute pesticide poisoning were the National Poisons Information Services (e.g., Guy's Hospital) for 30 (54%); Accident and Emergency Departments for 19 (34%); and industry for nine (16%). Four (7%) considered they had sufficient training as a medical student to diagnose cases of acute pesticide poisoning and four (7%) considered they had sufficient training since graduating to diagnose such cases. Some of the problems related to the identification and diagnosis of acute pesticide poisoning are discussed and a number of specific recommendations are made to improve the information and training available to general practitioners.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1992

Differential utilization of regulatory domains within the alpha 1(I) collagen promoter in osseous and fibroblastic cells.

Type I collagen is expressed in a variety of connective tissue cells and its transcriptional regulation is highly complex because of the influence of numerous developmental, environmental, and hormonal factors. To investigate the molecular basis for one aspect of this complex regulation, the expression of alpha 1(I) collagen (COL1A1) gene in osseous tissues, we fused a 3.6-kb DNA fragment between bases -3,521 and +115 of the rat COL1A1 promoter, and three deletion mutants, to the chloramphenicol acetyltransferase (CAT) marker gene. The expression of these ColCAT transgenes was measured in stably transfected osteoblastic cell lines ROS 17/2.8, Py-la, and MC3T3-E1 and three fibroblastic lines NIH-3T3, Rat-1, and EL2. Deletion of the distal 1.2-kb fragment of the full-length ColCAT 3.6 construct reduced the promoter activity 7- to 30-fold in the osteoblastic cell lines, twofold in EL2 and had no effect in NIH-3T3 and Rat-1 cells. To begin to assess the function of COL1A1 upstream regulatory elements in intact animals, we established transgenic mouse lines and examined the activity of the ColCAT3.6 construct in various tissues of newborn animals. The expression of this construct followed the expected distribution between the high and low collagen-producing tissues: high levels of CAT activity in calvarial bone, tooth, and tendon, a low level in skin, and no detectable activity in liver and brain. Furthermore, CAT activity in calvarial bone was three- to fourfold higher than that in the adjacent periosteal layer. Immunostaining for CAT protein in calvaria and developing tooth germ of ColCAT3.6 mice also confirmed the preferred expression of the transgene in differentiated osteoblasts and odontoblasts compared to fibroblast-like cells of periosteum and dental papilla. This study suggests that the 3.6-kb DNA fragment confers the strong expression of COL1A1 gene in high collagen producing tissues of intact animals and that the 5' flanking promoter sequence between -3,521 and -2,295 bp contains one or more stimulatory elements which are preferentially active in osteoblastic cells.

3T3 Cells↗
PubMed1992

Investigation of the role of Von Korff fibers during murine dentinogenesis.

The existence and significance of Von Korff fibers during early dentinogenesis are still very controversial. The purpose of the present study was to re-examine the questions of the existence, nature and significance of Von Korff's fibers using light microscopy and immunohistochemistry. Specimens were obtained from 3 days-old CD-I mice and mandibles were carefully dissected under constant irrigation and immediately fixed in 10% neutral buffered formalin for light microscopy. Sections were treated or not with collagenase prior to silver staining. For immunohistochemistry, specimens were fixed in 95% ethanol and embedded in paraffin. Sections were reacted with goat anti-human-bovine type I or type III collagen and a rhodamine (RITC) labelled rabbit anti-goat IgG was then reacted as a secondary antibody. Slides were then examined under a Zeiss II photomicroscope equipped with epifluorescence. Our results have confirmed the presence of argyrophilic material concentrated at the periphery of the dental papilla and stretching from the subodontoblastic layer to the future dentino enamel junction. The distribution of type III collagen was very similar to the distribution of the silver staining at the cervical loop area. Type I collagen distribution was different and concentrated in areas where odontoblasts were fully differentiated. Our study showed that Von Korff fibers are not artefactual. We have established the presence of an apical compartment containing type I collagen fibers and a basal compartment containing type III collagen to explain the image of continuous silver staining crossing the entire thickness of the odontoblast layer.

Animals↗
PubMed1991

Audit of an ophthalmology waiting list.

The hospital case notes of 209 (98%) of the 213 patients placed on an adult ophthalmic surgical waiting list between mid 1984 and mid 1985 were reviewed. Information on referral sources, previous eye surgery, outpatient visits, and treatment up to the end of 1987 was recorded. The vital status of patients up to the end of 1988 was also ascertained. Waiting list patients (123 women, 86 men) were elderly (73% over 65 years) and most (70%) were listed for cataract surgery. By the end of 1987 (30-42 months after waiting list entry) 64% of all patients (and 56% of cataract patients) had received surgery under the care of the health authority. The remainder had either died (12%), received surgery elsewhere (7%), were still on the waiting list (7%), no longer wanted or were unfit for surgery (6%), or had left the district (4%). By the end of 1988 (42-54 months after waiting list entry) 28% of the original waiting list population had died.

Adolescent↗
PubMed1991

A survey of dog bites in Salisbury.

A recent survey of patients attending an Accident and Emergency (A&E) department serving several economically depressed Thanet coastal towns found that around 3 per 1000 of the resident population attended each year for the treatment of dog bite injuries (Thomas and Banks, 1990). We report a study of dog bite injuries treated in the A&E department serving Salisbury, a small prosperous Cathedral city, and surrounding villages. In comparison with Thanet, age specific incidence rates for dog bites show a similar pattern but only about half the overall incidence. Some reasons for these findings are suggested and extrapolations for national treatment figures are made.

Adolescent↗
PubMed1991

How well do family practitioner committee and general practice records agree? Experience in a semi-rural practice.

General practice notes may be inaccurate for various reasons. A study was carried out in one semi-rural practice to investigate the agreement between records held by the family practitioner committee and those kept in the practice. Details on the practice notes and the family practitioner committee list were compared for 800 patients. The details examined included name, sex, date of birth, address and National Health Service number. While 58% of records agreed, discrepancies occurred in 339 records (42%). The most common discrepancies concerned the patient's address (30.6%), date of birth (9.4%) and NHS number (8.0%). Nearly 5% of the practice notes appeared to be for patients who were no longer on the practice list or dependent on its care. These findings have implications under the new general practitioner contract where screening programmes, target related payments, and increased capitation fees require accurate practice records.

Documentation↗
PubMed1989

Differentiation of odontoblasts in grafted recombinants of murine epithelial root sheath and dental mesenchyme.

The epithelial root sheath (ERS) was isolated from first molars of 5-day-old post-natal CD-1 mice using trypsin. After isolation, ERS cells remained viable in vitro and immunohistochemical examination of cultures confirmed the epithelial phenotype and the absence of mesenchymal contamination. Recombinants of isolated ERS and dental papilla resulted in odontoblast differentiation within cells of the dental papilla, and the formation of root-like fragments of dentine after 2 weeks of intra-ocular grafting. These findings indicate the inductive influence of the ERS on dental papilla cells.

Animals↗