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Biomedical subjects

S Best

Publications and source records attributed to S Best.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effect of heat treatment on pulsed laser deposited amorphous calcium phosphate coatings.

Amorphous calcium phosphate coatings were produced by pulsed laser deposition from targets of nonstoichiometric hydroxyapatite (Ca/P = 1.70) at a low substrate temperature of 300 degrees C. They were heated in air at different temperatures: 300, 450, 525 and 650 degrees C. Chemical and structural analyses of these coatings were performed using X-ray diffraction (XRD), FTIR, and SEM, XRD analysis of the as-deposited and heated coatings revealed that their crystallinity improved as heat treatment temperature increased. The main phase was apatitic, with some beta-tricalcium phosphate in the coatings heated at 525 and 600 degrees C. In the apatitic phase there was some carbonate substitution for phosphate and hydroxyl ions at 450 degrees C and almost solely for phosphate at 525 and 600 degrees C as identified by FTIR. This was accompanied by a higher hydroxyl content at 525 and 600 degrees C. At 450 degrees C a texture on the coating surface was observable by SEM that was attributable to a calcium hydroxide and calcite formation by XRD. These phases almost disappeared at 600 degrees C, probably due to a transformation into calcium oxide.

Calcium Phosphates↗
PubMed1997

Endogenous retroviruses and the evolution of resistance to retroviral infection.

The current AIDS epidemic has rekindled interest in the evolution of retroviruses and the development of resistance to infection. Retroviruses and their vertebrate hosts have coexisted for millions of years, during which time a variety of host defence mechanisms has evolved. One repeated strategy is to use endogenous retroviruses to combat infection by their exogenous relatives.

Animals↗
PubMed1997

The dependence of osteoblastic response on variations in the chemical composition and physical properties of hydroxyapatite.

Two synthetic hydroxyapatite powders (A and B), supplied by different manufacturers, were physically and chemically characterized before being die pressed and sintered at 1250 degrees C. The powders were characterized using X-ray diffraction (XRD), infrared spectroscopy (IRS), X-ray fluorescence, surface area analysis (BET), particle size analysis and scanning electron microscopy (SEM). The materials were then pressed and sintered to produce hydroxyapatite discs of similar densities and grain sizes for in vitro evaluation. The ceramics were seeded with osteoblastic cells and after 15 days in culture the cell morphology was assessed using scanning electron microscopy (SEM), the ultrastructure of the cells was studied using transmission electron microscopy (TEM) with EDAX, and the rate of cell growth was assessed using biochemical techniques. The results clearly showed that the rate of cell proliferation but not the rate of alkaline phosphatase production, was highly dependent on the composition of the hydroxyapatite powders that were used to make the ceramic discs. The ultrastructural studies confirmed the relative viabilities of the cells and the nature of the ceramic interface indicating visually the marked differences in the performance of the two materials.

Journal Article↗
PubMed1996

Positional cloning of the mouse retrovirus restriction gene Fv1.

Vertebrate evolution has taken place against a background of constant retrovirus infection, and much of the mammalian genome consists of endogenous retrovirus-like elements. Several host genes have evolved to control retrovirus replication, including Friend-virus-susceptibility-1, Fv1, on mouse chromosome 4 (refs 3, 4). The Fv1 gene acts on murine leukaemia virus at a stage after entry into the target cell but before integration and formation of the provirus. Although restriction is not absolute, Fv1 prevents or delays spontaneous or experimentally induced viral tumours. In vitro, Fv1 restriction leads to an apparent 50-1,000 fold reduction in viral titre. Genetic evidence implicates a direct interaction between the Fv1 gene product and a component of the viral preintegration complex, the capsid protein CA (refs 7-9). We have now cloned Fv1: the gene appears to be derived from the gag region of an endogenous retrovirus unrelated to murine leukaemia virus, implying that the Fv1 protein and its target may share functional similarities despite the absence of nucleotide-sequence homology.

Amino Acid Sequence↗
PubMed1996

Mullerian inhibiting substance in humans: normal levels from infancy to adulthood.

Mullerian-inhibiting substance (MIS) is a gonadal hormone synthesized by Sertoli cells of the testis and granulosa cells of the ovary. To facilitate the use of MIS for the evaluation of intersex disorders and as a tumor marker in women with MIS-expressing ovarian tumors, we measured MIS in 600 serum samples from males and females. These data show that mean MIS values for males rise rapidly during the first year of life and are highest during late infancy, then gradually decline until puberty. In contrast, MIS values in females are lowest at birth and exhibit a minimal increase throughout the prepubertal years. Whereas MIS is uniformly measurable in all prepubertal boys studied, it is undetectable in most prepubertal female subjects. These data reveal an easily discernible sexually dimorphic pattern of expression and confirm that MIS can be used as a testis-specific marker during infancy and early childhood. MIS values that are above the upper limits for females are discriminatory for the presence of testicular tissue or ovarian tumor, and those below the lower limits for males are consistent with dysgenetic or absent testes or the presence of ovarian tissue. These data will enable normal and abnormal levels of MIS to be differentiated with higher precision and will facilitate the use of MIS in the management of gonadal disorders.

Adolescent↗
PubMed1995

Genetic map of the region surrounding the retrovirus restriction locus, Fv1, on mouse chromosome 4.

The Friend virus susceptibility-1 (Fv1) gene maps to mouse Chromosome (Chr) 4 close to a cluster of four endogenous murine leukemia viruses (MLVs). To investigate the feasibility of cloning Fv1 by a positional approach, we have performed an extensive genetic analysis of this region of Chr 4. We have typed 368 backcross mice for the four proviruses, Nppa, Lck, and D4Smh6b. Recombinant animals were screened in a hierarchical fashion with a variety of other markers, including Fv1 and the isozyme marker Gpd1. A detailed genetic map of the region surrounding Fv1 was derived. Three markers, Xmv9, Nppa, and Iap3rc11, were identified that showed no recombination with Fv1. By combining backcross and recombinant inbred strain data, we estimated that Xmv9 and Nppa must lie within 0.6 cM of one another and Fv1.

Animals↗
PubMed1994

Structure and expression of the hairless gene of mice.

The hairless mutation of mice was caused by insertion of a murine leukemia virus. Starting with sequences flanking the provirus, a series of overlapping clones surrounding the viral integration site were obtained. By using a combination of sequencing, PCR, and exon-trapping techniques, the hairless gene was identified. It encodes a predicted protein of 1182 amino acids, including a potential zinc-finger domain. The expression patterns of the gene closely reflect the phenotype of animals carrying the hairless mutation.

Amino Acid Sequence↗
PubMed1992

Mothers' and fathers' perceptions of stress and coping with children who have severe disabilities.

Stress in families with children who have special needs, which has been the focus of much research interest, is usually assessed solely from a maternal perspective. In this study, the short form of the Questionnaire on Resources and Stress (QRS-F, Friedrich, Greenberg, & Crnic, 1983) was completed separately by mothers and fathers of children with severe developmental disabilities. To compare responses of mothers and fathers, we employed factor analysis of parcels using the parallel analysis criterion rather than the more traditional item level analysis with minimum eigenvalue criterion. Results indicated that the QRS-F differed only slightly in both factor structure and correlates as a function of parental gender. Overall, validity of the QRS-F for use with both mothers and fathers of children with severe disabilities was supported.

Activities of Daily Living↗
PubMed1991

Characterization of the breakpoint of a 3.5-kb deletion of the beta-globin gene.

The precise extent and breakpoints of a deletion of the beta-globin gene in a Thai patient have been determined using direct sequencing of a PCR product. This lesion is not detectable by current screening methods using PCR to analyze the beta-globin genes and is, therefore, a potential source of error in the diagnosis and prenatal detection of beta-thalassemia.

Base Sequence↗
PubMed1991

Planning for community care. Long-stay populations of hospitals scheduled for rundown or closure.

Using the Community Placement Questionnaire, the long-stay populations of five hospitals were surveyed. The results suggest that there is little need for large hospitals if adequate community provision is made. However, a small number of patients continue to accumulate for whom community placement is hard to envisage. Investigating the characteristics of the 'new long-stay' patients suggests that the usual definition should be extended to include those over 65 years old with no diagnosis of dementia and those in hospital for 1-10 years. About 20% of 'new long-stay' patients have organic diagnoses and the needs of this group require assessment.

Adult↗
PubMed1990

The molecular basis of beta-thalassemia in Thailand: application to prenatal diagnosis.

To enable the prenatal diagnosis of beta-thalassemia by direct detection of the mutant beta-globin genes, we have determined the spectrum of mutations causing this disease in Thailand. The techniques employed included a combination of synthetic oligonucleotide probe hybridization, direct sequencing of genomic DNA enzymatically amplified by the polymerase chain reaction, and cloning and sequencing of the beta-globin genes. A total of 116 beta-thalassemia genes from 78 Hb E/beta-thalassemia patients and from 19 homozygous beta-thalassemia patients were analyzed, and the mutation was characterized in 112/116 (97%) of them. Eleven mutations were found, of which four (-CTTT in codon 41/42, AAG----TAG in codon 17, C----T in position 654 of the IVS-2 region, and A----G in position -28 upstream of the beta-globin gene) accounted for 83%; two previously undescribed mutations have been identified. The spectrum of beta-thalassemia mutations is similar to that reported among the Chinese. However, within the Thai population itself, patients with homozygous beta-thalassemia show a wider spread of mutations in comparison with the Hb E/beta-thalassemia group, in whom the frameshift 41/42 mutation predominates at a frequency of 62%. This difference in distribution may reflect the difference in ethnic origin of the two groups. Characterization of these mutations should aid the planning of a prenatal diagnosis program for beta-thalassemia in Thailand.

Base Sequence↗
PubMed1987

Can psychiatric nurses 'catch' schizophrenia?

The incidence of schizophrenia among psychiatric and general trained nurses was investigated for the period 1955-1979 in Northern Ireland. No difference was found. These results do not support the hypothesis of schizophrenia as a horizontally transmitted infectious disease.

Adult↗
PubMed1986

Fatty acyl chain specificity of phosphatidylcholine hydrolysis catalyzed by lipoprotein lipase. Effect of apolipoprotein C-II and its (56-79) synthetic fragment.

Mixed acyl chain phosphatidylcholine molecules in Triton N-101 micelles were employed as substrates for lipoprotein lipase to test which substrate acyl chain has the greatest effect on activation of the enzyme by apolipoprotein C-II. The phospholipase A1 activity of lipoprotein lipase was measured by pH-stat. The activation factor (lipoprotein lipase activity plus apolipoprotein C-II/activity minus apolipoprotein C-II) increased monotonically with apolipoprotein C-II concentration up to 1 microM apolipoprotein C-II at an enzyme concentration of 0.01 microM. The maximal activation factor for phosphatidylcholine substrate molecules with sn-2 acyl chain lengths of 14 averages 14.8. By contrast, for sn-2 acyl chain lengths of 16 the activation factor was 29.2. Varying the sn-1 acyl chain length had no significant effect on the activation factor. The chain-length dependence of the activation factor is similar with the apolipoprotein C-II peptide fragment comprising residues 56-79, which does not include the lipid-binding region of apolipoprotein C-II. These data are consistent with a model for activation of lipoprotein lipase in which residues 56-79 bind to lipoprotein lipase and alter the interaction of the sn-2 acyl chain of the phosphatidylcholine (PC) substrate or the lysoPC product within the activated state complex.

Apolipoprotein C-II↗
PubMed1986

Characteristics of children with phonologic disorders of unknown origin.

Descriptive data are presented from three studies of children referred for assessment of a developmental speech disorder of unknown origin. Group findings indicate that these children have involvements in mechanism, cognitive, and psychosocial areas that warrant attention in theoretical explication of and early intervention for their communication deficits. The reliability, learnability, and efficiency of a diagnostic classification system that attempts to provide characteristic speech profiles for diagnostic subtypes is also considered.

Child↗