Biomedical subjects

D M Davis

Publications and source records attributed to D M Davis.

At least 55 records · Page 3Linked to original sources

PubMed1997

Implant supported overdentures--the King's experience.

OBJECTIVES: Astra Tech implants have been used to provide implant supported overdentures for 25 people, 13 with paired stud retention, 10 with paired magnetic retention and two with magnetic retention on three fixtures. RESULTS: The first case was completed in June 1990 and the last in May 1992. Of the 52 fixtures which were used initially, one became loose after 6 months and one fractured after 12 months. Healing following Stage I surgery was classified as good for 14 people, moderate for eight and poor for three. Healing following Stage II surgery was problem-free in 14 people, with problems encountered in 11 people in six of whom the problem was caused by selecting healing abutments which were too short. There were 58 events of post-insertion care for the magnet group, which resulted in 104 visits and 60 events of post-insertion care for the stud group, which resulted in 89 visits. The need for post-insertion care was greatest during the first year with the magnet group having 33 events and the stud group 36 events. Twenty four of the participants rated treatment success as good and one as moderate. CONCLUSIONS: Implant supported overdentures in the mandible using two isolated abutments are a successful treatment option by they can be demanding in continuing care.

Adult↗

PubMed1997

The binding site of NK receptors on HLA-C molecules.

The protection of cells expressing class I HLA molecules from NK lysis is mediated by natural killer cell inhibitory receptors (NKIR). Using site-directed mutagenesis, residues on HLA-C that determine the locus specificity (alphaVal-76), allotype group specificity (a dimorphism alphaAsn-80/Lys-80), and affinity of NKIR binding (a second pair of dimorphisms, alphaAla-73, Asp-90 or alphaThr-73, Ala-90) have been identified. Thus the "footprint" of the NKIR on the alpha1 helix of the class I MHC molecule HLA-C and its associated beta strands are similar in position to the site occupied by superantigens on and behind the alpha1 helix of the class II MHC molecule HLA-DR1, but further toward its C-terminus. The intermediate affinity binding of NKIR to HLA-C, determined by alpha73 and alpha90, has an essential role in preventing cross-reactivity and ensuring the availability of NK cells for immunosurveillance; low affinity and high affinity mutants are both physiologically impaired.

Adult↗

PubMed1997

Human NK cells: their ligands, receptors and functions.

The expression, or lack thereof, of class I MHC glycoproteins has a marked influence on natural killer cell function. Cells which do not express class I MHC molecules are susceptible to lysis by NK cells, and transfection of these targets with class I MHC genes can render these cells resistant to NK attack. This inhibition of NK-killing is mediated by a novel family of receptors expressed mainly on NK cells, but also found on some T-cells. The function of these class I MHC binding receptors when expressed on T-cells is discussed also and a novel co-stimulatory activity of NKAR described. Lastly, a novel mechanism by which human cytomegalovirus evades immune surveillance by NK cells is documented.

Humans↗

PubMed1997

Implant-stabilized overdentures.

Implant-stabilized overdentures can be used successfully to restore the edentulous mouth, and there are many good reasons why this treatment should be selected in preference to using fixed dentures. However, as with any treatment, there must be a strong commitment to after care if the overdenture is to remain successful. This article discusses the advantages and disadvantages of using implants to stabilize overdentures, examines their success rates and discusses the extent of after care.

Dental Implantation, Endosseous↗

PubMed1996

Enhancement of class II-restricted T cell responses by costimulatory NK receptors for class I MHC proteins.

An important feature of the human immune system is the ability of T cells to respond to small quantities of antigen. Class II major histocompatibility complex (MHC)-restricted T cells that expressed a costimulatory natural killer (NK) cell receptor for class I MHC proteins were cloned. In the presence of low doses of superantigen, the proliferative response of these T cell clones was three- to ninefold greater when the T cells were costimulated by way of the NK receptor. Thus, the action of costimulatory NK receptors on T cells may play a significant role in initiating and sustaining immune responses.

B-Lymphocytes↗

PubMed1996

Follow up and maintenance of implant supported prostheses: a comparison of 20 complete mandibular overdentures and 20 complete mandibular fixed cantilever prostheses.

Two independently selected groups of 20 patients who were edentulous in te mandible, were followed up on a regular basis over a 5-year period following restoration with a lower implant stabilised prosthesis and conventional upper denture. Significantly more treatment was required by those who received complete mandibular overdentures than those provided with complete fixed mandibular prostheses. In addition to adjustment for the relief of denture trauma to the mucosa, more mechanical problems arose with overdenture implant prostheses.

Dental Abutments↗

PubMed1996

Protection from natural killer cell-mediated lysis by HLA-G expression on target cells.

The outermost layer of the human placenta is devoid of classical class I human leukocyte antigens (HLA-A, HLA-B, and HLA-C) and class II proteins (HLA-DR, HLA-DQ, and HLA-DP). Although this prevents recognition by maternal T lymphocytes, the lack of class I molecules leaves these cells susceptible to attack by natural killer (NK) cells. However, trophoblast cells directly in contact with the maternal tissues express the class I molecule HLA-G, which may be involved in protecting the trophoblast from recognition by NK cells. Here evidence is provided that expression of HLA-G is sufficient to protect otherwise susceptible target cells from lysis by activated NK1 and NK2 cell lines and clones that are specific for distinct groups of HLA-C alleles. The receptors on NK cells that recognize HLA-G are also identified.

CD56 Antigen↗

PubMed1996

The fluorescence and circular dichroism of proteins in reverse micelles: application to the photophysics of human serum albumin and N-acetyl-L-tryptophanamide.

Evidence is presented that a compartmentalised protein exists in its native state only within a particular size of aqueous cavity. This behaviour is shown to exist in AOT reverse micelles using fluorescence quenching and circular dichroism (CD) studies of human serum albumin (HSA). In particular, far ultraviolet CD measurements show that a reduction in quencher accessibility to the fluorophore is consistent with the protein being nearest to its native conformation at a waterpool size of around 80 A diameter. We also show that the biexponential fluorescence decay of N-acetyl-L-tryptophanamide (NATA) in AOT reverse micelles arises from the probe being located in two distinct sites within the interfacial region. The more viscous of these two sites is located on the waterpool side of the interface and the other is located on the oil side of the interface.

Chemical Phenomena↗

PubMed1996

Recombinant hepatitis B vaccination of neonates and infants: emerging safety data from the Vaccine Adverse Event Reporting System.

OBJECTIVES: To evaluate the postmarketing safety of recombinant hepatitis B (HB) vaccine given to neonates and infants in the US. METHODS: US reports associated with HB vaccination and received between January 1, 1991, and May 31, 1995, by the national Vaccine Adverse Events Reporting System (VAERS) were reviewed as a case series. RESULTS: During 1991 through 1994, 12,520 (32%) VAERS reports were received for events temporally associated with administration of HB vaccine, of which 14% were received for neonates and infants. More reports described serious outcomes for neonates (< 0.1 year old) than for other age groups (40% vs. 6 to 15%). HB alone was administered to 58 (97%) neonates; review of these reports did not reveal unexpected serious events. Among infants (0.1 to 0.9 years old) 192 (9%) received HB vaccine alone and 1469 (66%) received HB in combination with diphtheria-tetanus-pertussis (DTP) vaccine. Similar serious adverse events reported in neonates and infants included fever, agitation and apnea. Events reported for infants receiving HB/DTP and DTP alone were similar and differed from reports filed for infants receiving HB vaccine alone, suggesting that these events may be associated with use of DTP vaccine. CONCLUSIONS: This review shows no unexpected adverse events in neonates and infants given HB vaccine despite use of at least 12 million doses of vaccine given in these age groups. Although VAERS lacks the ability to distinguish coincidental events from true vaccine reactions, this database represents the largest case series of events temporally associated with HB vaccination of neonates and infants.

Adolescent↗

PubMed1995

Agonist properties of a stable hexapeptide analog of neurotensin, N alpha MeArg-Lys-Pro-Trp-tLeu-Leu (NT1).

The major signal transduction pathway for neurotensin (NT) receptors is the G-protein-dependent stimulation of phospholipase C, leading to the mobilization of intracellular free Ca2+ ([Ca2+]i) and the stimulation of cyclic GMP. We investigated the functional actions of an analog of NT(8-13), N alpha MeArg-Lys-Pro-Trp-tLeu-Leu (NT1), and other NT related analogs by quantitative measurement of the cytosolic free Ca2+ concentration in HT-29 (human colonic adenocarcinoma) cells using the Ca(2+)-sensitive dye fura-2/AM and by effects on cyclic GMP levels in rat cerebellar slices. The NT receptor binding affinities for these analogs to HT-29 cell membranes and newborn (10-day-old) mouse brain membranes were also investigated. Data obtained from HT-29 cell and mouse brain membrane preparations showed saturable single high-affinity sites and binding densities (Bmax) of 130.2 and 87.5 fmol/mg protein, respectively. The respective KD values were 0.47 and 0.39 nM, and the Hill coefficients were 0.99 and 0.92. The low-affinity levocabastine-sensitive site was not present (K1 > 10,000) in either membrane preparation. Although the correlation of binding between HT-29 cell membranes and mouse brain membranes was quite significant (r = 0.92), some of the reference agents had lower binding affinities in the HT-29 cell membranes. The metabolically stable compound NT1 plus other NT analogs and related peptides [NT, NT(8-13), xenopsin, neuromedin N, NT(9-13), kinetensin and (D-Trp11)-NT] increased intracellular Ca2+ levels in HT-29 cells, indicating NT receptor agonist properties. The effect of NT1 in mobilizing [Ca2+]i blocked by SR 48692, a non-peptide NT antagonist. Receptor binding affinities of NT analogs to HT-29 cell membranes were positively correlated with potencies for mobilizing intracellular calcium in the same cells. In addition, NT1 increased cyclic GMP levels in rat cerebellar slices, confirming the latter findings of its NT agonist action. These results substantiate the in vitro NT agonist properties of the hexapeptide NT analog NT1.

Amino Acid Sequence↗

PubMed1995

A self-help group for complete denture wearers.

Denture provision is a frequent source of frustration and misunderstanding for both patients and dentists. This study investigates the role of a self-help group in helping denture wearers with long standing problems to come to terms with their difficulties and to reduce their demands on the dentist. Eleven people with clinically satisfactory dentures and long standing perceived problems were invited to join the programme. Evaluation at 2 and 12 months afterwards indicated everyone had benefited in some way. Benefits included eating foods previously avoided, the opportunity for social intercourse and reducing the visits to the dentist.

Adaptation, Psychological↗

PubMed1994

Implant supported fixed distal extension prostheses.

The distal extension fixed implant supported prosthesis is now available as an alternative to a partial denture. However, not all patients will be suitable for such treatment. Limitations imposed on fixture length, the effect of gape upon instrumentation, the size of abutment components and the design of the superstructure are discussed in this article, to assist the general practitioner in case referral.

Contraindications↗

PubMed1993

A retrospective study comparing duplication and conventionally made complete dentures for a group of elderly people.

The duplication technique is a well recognised method of replacing complete dentures. Advantages claimed for this technique are that patients adapt more easily to their new complete dentures and the numbers of treatment visits are reduced. The case notes of 100 patients were examined retrospectively, 50 of whom had had dentures constructed by undergraduates using a duplication technique and 50 with a conventional technique. In addition, a questionnaire was sent to the patients to obtain their views on the replacement dentures. The 'duplication group' required fewer visits for the delivery of the dentures, but there was no statistical difference between the numbers of post-insertion visits, for the two groups, needed to make the dentures comfortable. The only identifiable reason for selecting a duplication technique was the failure of construction of new dentures by a conventional method in 15 patients. Apart from this the two groups appeared remarkably similar when comparing age of dentures being replaced, period of edentulousness, number of previous complete dentures and medical histories. As judged by the questionnaire more patients in the duplication group continued to wear their new dentures compared to the conventional group.

Aged↗

PubMed1993

Childhood precursors of schizophrenia: facial expressions of emotion.

OBJECTIVE: This study sought to determine whether affective abnormalities could be detected in home movies of children who later developed schizophrenia. METHOD: Trained observers coded facial expressions of emotion of 32 schizophrenic patients and 31 of their healthy siblings from home movies made when they were children. All of the patients met the DSM-III criteria for schizophrenia with onset in late adolescence or early adulthood. The sibling comparison subjects had no history of psychiatric illness. Nine emotions and a neutral category were rated. RESULTS: Analyses revealed significantly lower proportions of joy expressions among the total expressions of the preschizophrenic female subjects than among the same-sex healthy siblings. This difference extended from infancy through adolescence. Among the male subjects, there were inconsistent differences between diagnostic groups in expressions of joy across age levels. However, both the preschizophrenic male subjects and the preschizophrenic female subjects showed greater negative affect than their same-sex comparison groups. CONCLUSIONS: These findings lend support to the assumption that vulnerability to schizophrenia may be subtly manifested in emotional behavior long before the onset of clinical symptoms.

Adolescent↗

PubMed1993

The use of two implant systems for providing implant supported overdentures in the mandible--a clinical appraisal.

The objective of this paper is to compare the Nobelpharma implant system with that designed by Astra-Tech. The main difference between the two is in the design of the fixture-abutment linkage. With the Astra system, the abutment and screw form one unit, whilst with the Nobelpharma system there is a separate abutment screw. Both systems have been used to support overdentures. Linked bar retention between two implants has been used with the Nobelpharma implants, and individual magnetic or stud retention has been used with the Astra system. Each attachment mechanism has produced patient satisfaction.

Dental Abutments↗

PubMed1992

Arthrotomy versus arthroscopy and partial synovectomy for treatment of experimentally induced infectious arthritis in horses.

To evaluate the clinical, laboratory, and histologic effects of 2 methods of treatment for infectious arthritis in horses, Staphylococcus aureus (3.4 to 3.9 x 10(3) colony-forming units) was inoculated into the tarsocrural joints of 8 horses on day 0. Each horse was treated with phenylbutazone (2 g, PO, q 24 h) and gentamicin sulfate (2.2 mg/kg of body weight, IV, q 8 h) for 14 days. On day 2, general anesthesia was induced, and each horse had 1 tarsocrural joint treated by arthrotomy, with removal of accessible fibrin and lavage with 3 L of sterile balanced electrolyte solution. An indwelling plastic drain was placed in the standing horse to provide a means for lavage with 3 L of balanced electrolyte solution twice daily for 72 hours. The contralateral tarsocrural joint was treated via arthroscopic debridement, synovectomy, and lavage with 3 L of balanced electrolyte solution. Arthrotomy and arthroscopic portals were allowed to heal by second intention. Lameness and thermographic examinations, analysis and bacteriologic culture of synovia, CBC, and WBC differential count were performed prior to inoculation and on days 1, 3, 6, 8, and 13. On day 14, each horse was euthanatized, and the joints were measured, opened, and photographed. Synovium and articular cartilage were obtained for semiquantitative histologic (H&E stain) and histochemical (safranin O fast green stain) evaluation. Lameness and joint circumference were significantly (P less than 0.05) greater in limbs treated by arthroscopy, synovectomy, and lavage. Arthrotomy with lavage eliminated the S aureus infection significantly (P less than 0.05) earlier than arthroscopy, synovectomy, and lavage, however, both treatments eliminated the infection in all but a single joint.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Hypoglycemia and hepatic ischemic necrosis after small intestinal incarceration through the epiploic foramen in a horse.

A 16-year-old stallion was presented to the Louisiana State University Veterinary Teaching Hospital for evaluation of acute abdominal pain. Physical examination and diagnostic procedures indicated a strangulating obstruction of the small intestine. At exploratory celiotomy, a strangulating incarceration of the jejunum through the epiploic foramen was found. The incarcerated small intestine was reduced, then resection of the nonviable bowel and anastomosis performed. After surgery, the horse exhibited clinical signs and laboratory findings associated with hypoglycemia and died in spite of emergency treatment. On post-mortem examination, a large thrombus was present in the portal vein at the level of the epiploic foramen and the liver had multiple large infarcted areas. The post-operative signs of hypoglycemia and necropsy findings of widespread hepatic ischemic necrosis are complications of epiploic foramen incarceration of the small intestine not previously reported and may in part explain the high mortality rate described for this lesion.

Abdominal Pain↗

PubMed1991

Resection of a cervical tracheal bronchus in a foal.

A 3-day-old Thoroughbred foal developed a large, air-distended, midcervical swelling that was diagnosed as a congenital tracheal bronchus with associated ectopic lung tissue. Clinical signs consisted of a compressible air-filled sac that enveloped the trachea. The nature and extent of the defect were evaluated endoscopically and radiographically. Surgical resection of the bronchus and associated air-filled sac resulted in a functionally and cosmetically acceptable outcome.

Animals↗