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Biomedical subjects

F W Smith

Publications and source records attributed to F W Smith.

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

Low-field magnetic resonance imaging for implant dentistry.

OBJECTIVE: To evaluate the use of a low-field magnetic resonance scanner for assessment of available bone for placement of osseo-integrated dental implants. METHODS: Eleven Patients were examined to assess suitability for implant placement using a 0.2 tesla 'open' scanner. Imaging/surgical templates were constructed, with gadolinium markers to allow accurate location of the implant sites. RESULTS: In all cases, localisation of potential implant sites was easily made and full information in all three planes readily available. Artefacts were few and localised, (noted on one site in one case only). Vital structures (nerves and vessels), and the variable geometry of the floor of the maxillary sinus were clearly seen, and cortical bone delineated from cancellous. The appearance of soft tissues in the scan allowed the surgeon to assess the final profile of the patient. CONCLUSION: Low-field magnetic resonance imaging has definite potential for pre-implant assessment. Full sectional information is readily available at any desired plane with no need for reformatting. The information for accurate and safe implant placement is clear. The technique uses no ionising radiation. Further work is needed to evaluate spatial distortion caused by magnetic susceptibility effects at air/tissue interfaces, but our calculations indicate that at low field, using an appropriate protocol, the effect will not be substantial.

Alveolar Process↗
PubMed1998

Staging of the axilla in breast cancer: accurate in vivo assessment using positron emission tomography with 2-(fluorine-18)-fluoro-2-deoxy-D-glucose.

OBJECTIVE: To evaluate the ability of positron emission tomography (PET) with 18F-fluoro-2-deoxy-D-glucose (18F-FDG) to determine noninvasively axillary lymph node status in patients with breast cancer. BACKGROUND: The presence of axillary lymph node metastasis is the most important prognostic factor in women with breast cancer. It signifies the presence of occult metastatic disease and indicates the need for adjuvant therapy. The only reliable way in which this important prognostic information may be obtained is by performing axillary dissection, which may be associated with significant complications and delay in discharge from the hospital. PET with 18F-FDG can visualize primary cancers in the breast and metastatic tumor deposits. METHODS: Fifty patients with untreated breast cancer had clinical examination of their axilla performed (graded as positive or negative), followed by PET of the axilla and midthorax. PET data were analyzed blindly and graded as positive or negative, depending on the presence or absence of axillary nodal metastases. Cytopathologic assessment of the axillary nodes was carried out within 1 week of PET, by fine-needle aspiration cytology in 5 patients and axillary dissection in 45; the excised specimens were examined by a single pathologist. RESULTS: The overall sensitivity of PET in 50 patients was 90% and the specificity was 97%. Clinical examination of the same patients had an overall sensitivity of 57% and a specificity of 90%. In the 24 patients with locally advanced breast cancer (T3, T4, TxN2), PET had a sensitivity of 93% and a specificity of 100%. In T1 tumors (seven patients), the sensitivity and specificity were 100%. PET had a high predictive value (>90%) and accuracy (94%) in staging the axilla. CONCLUSIONS: PET is a sensitive and specific method of staging the axilla in patients with breast cancer. It may obviate the need for axillary surgery in women with small primary tumors, define the women likely to benefit from axillary dissection, or allow radiotherapy to be substituted for surgery, particularly in post-menopausal women.

Adult↗
PubMed1998

Measurement of lumbar spine flexion-extension using a low-field open-magnet magnetic resonance scanner.

RATIONALE AND OBJECTIVES: The authors investigated the feasibility of using a low-field open-magnet magnetic resonance (MR) scanner to acquire functional flexion-extension images for range of motion (ROM) measurements on the lumbar spine. METHODS: Seventeen healthy subjects with no symptoms of back pain (age range, 22-59 years) were scanned in a low-field open-magnet MR scanner in the flexed, neutral, and extended positions. Each image was downloaded to a computer workstation for subsequent flexion-extension, lordosis, and ROM measurement. RESULTS: Data from two subjects were not analyzed because their images did not show all the lumbar vertebrae. For the remaining 15, there was a large variation in the magnitude of the ROM values (range, 9 degrees-70 degrees; mean 36.4 degrees, SD 16.5 degrees). However, there was a significant correlation between age and ROM (r = -0.63; P < 0.05). CONCLUSIONS: The low-field open-magnet MR scanner provides a method for noninvasive imaging of the lumbar spine, allowing the subject freedom of movement in the horizontal plane. This enables functional flexion-extension images of the lumbar spine to be acquired.

Adult↗
PubMed1998

Inflammatory mediators of the terminal dentition in adult and early onset periodontitis.

Based upon the prosthodontic literature, subjects who are at the transition stage between natural dentition and edentulism are called "terminal dentition" (TD) cases. The aim of the present cross-sectional investigation was to characterize the local and systemic inflammatory responses in 2 groups of patients with terminal dentition periodontitis. Eight severe adult periodontitis terminal dentition (AP-TD) subjects and 8 early onset periodontitis terminal dentition (EOP-TD) subjects were entered into the study. Our purpose was to measure an extended battery of cytokines in the gingival crevicular fluid (GCF) and in lipopolysaccharide (LPS)-stimulated monocytic culture supernatants as well as gingival mononuclear cell messenger RNA (mRNA) transcripts determined from biopsy samples. Within the GCF there were 3 tiers (levels) of mediators based upon approximate 10-fold differences in concentration. The highest tier included prostaglandin E2 (PGE2), interleukin-1 beta (IL-1 beta) and interleukin-2 (IL-2), the intermediate tier included tumor necrosis factor alpha (TNF alpha) and interferon gamma (IFN-gamma) and at the lowest concentration level were interleukin-4 (IL-4) and interleukin-6 (IL-6). Thus, the GCF analysis clearly indicated that in both AP-TD and EOP-TD groups the monocytic, i.e. IL-1 beta and PGE2 and Th1, i.e. IL-2 and IFN-gamma, inflammatory mediator levels quantitatively dominated over the Th2 mediators, i.e. IL-4 and IL-6. LPS-stimulated monocytic release of IL-1 beta, PGE2 and TNF alpha was significantly elevated in both AP-TD and EOP-TD groups compared to those of a control group of 21 subjects with moderate to advanced adult periodontitis. The cytokine mRNA expression of isolated gingival mononuclear cells showed that in both the AP-TD and the EOP-TD groups Th1 and Th2 cytokines were expressed, with low levels of IL-4 and IL-12. In conclusion, our data suggest that this cross-sectional TD periodontitis model may reflect progressive periodontal disease associated with tooth loss. Furthermore, although Th1 cytokine levels in the GCF dominate over the Th2 response, monocytic activation provides the main source of proinflammatory mediators. In addition, LPS-stimulated peripheral blood monocytes demonstrate an upregulated inflammatory mediator secretion in the terminal dentition.

Adult↗
PubMed1998

Spinal epidural abscess: the importance of early diagnosis and treatment.

OBJECTIVES: To remind clinicians of the dangers of delayed diagnosis and the importance of early treatment of spinal epidural abscess. METHODS: A review of the literature on spinal epidural abscess and a comparison of the published literature with local experience. RESULTS: Imaging with MRI or CT enables early diagnosis of spinal epidural abcess and optimal therapy is surgical evacuation combined with 6-12 weeks (median 8 weeks) of antimicrobial chemotherapy. Clinical features are fever, pain, and focal neurological signs and may be associated with preceding and pre-existing bone or joint disease. The commonest aetiological organism is S aureus. CONCLUSION: Early diagnosis and appropriate early antimicrobial chemotherapy with surgery is associated with an excellent prognosis.

Abscess↗
PubMed1997

The 'turkey wattle' sign revisited: diagnosing parotid vascular malformations in the adult.

The turkey wattle sign describes enlargement of a facial mass on dependency of the head and when the sign is present it is pathognomonic of a vascular malformation or haemangioma. We present a case of vascular malformation of the parotid gland in which this sign was demonstrated. The clinical and radiological features of this rare parotid mass are discussed with reference to the literature.

Diagnosis, Differential↗
PubMed1997

The cloning of two Arabidopsis genes belonging to a phosphate transporter family.

Two genes, APT1 and APT2, with DNA sequences that exhibit significant sequence identity to yeast and fungal H+/orthophosphate co-transporters, have been isolated from Arabidopsis thaliana. These genes are genetically linked and map to chromosome 5 between markers g4028 and m435. The genes encode almost identical 524 amino acid polypeptides and are predicted to contain 12 membrane-spanning domains. Both APT1 and APT2 are predominantly expressed in A. thaliana root tissues. The level of expression of both genes in roots is regulated by the phosphorus status of the plant, being considerably enhanced when the plants were deprived of an external phosphate supply. The APT1 and APT2 polypeptides are likely to be associated with the membrane transport of phosphate within A. thaliana roots.

Amino Acid Sequence↗
PubMed1997

Regulation of expression of a cDNA from barley roots encoding a high affinity sulphate transporter.

A cDNA encoding a high-affinity sulphate transporter has been isolated from barley by complementation of a yeast mutant. The cDNA, designated HVST1, encodes a polypeptide of 660 amino acids (M(r) = 72,550), which is predicted to have 12 membrane-spanning domains and has extensive sequence homology with other identified eukaryotic sulphate transporters. The K(m) for sulphate was 6.9 microM when the HVST1 cDNA was expressed in a yeast mutant deficient in the gene encoding for the yeast SUL1 sulphate transporter. The strong pH-dependency of sulphate uptake when HVST1 was expressed heterologously in yeast suggests that the HVST1 polypeptide is a proton/sulphate co-transporter. The gene encoding HVST1 is expressed specifically in root tissues and the abundance of the mRNA is strongly influenced by sulphur nutrition. During sulphur-starvation of barley, the abundance of mRNA corresponding to HVST1, and the capacity of the roots to take up sulphate, both increase. Upon re-supply of sulphate, the abundance of the mRNA corresponding to HVST1, and the capacity of the roots to take up sulphate, decrease rapidly, concomitant with rises in tissue sulphate, cysteine and glutathione contents. Addition of the cysteine precursor, O-acetylserine, to plants grown with adequate sulphur supply, leads to increases in sulphate transporter mRNA, sulphate uptake rates and tissue contents of glutathione and cysteine. It is suggested, that whilst sulphate, cysteine and glutathione may be candidates for negative metabolic regulators of sulphate transporter gene expression, this regulation may be overridden by O-acetylserine acting as a positive regulator.

Amino Acid Sequence↗
PubMed1997

Correlation between 99Tcm-HMPAO-SPECT brain image and a history of decompression illness or extent of diving experience in commercial divers.

OBJECTIVES: To explore the use of 99technetiumm-hexamethyl propylene amine oxime single photon computed tomography (HMPAO-SPECT) of the brain as a means of detecting nervous tissue damage in divers and to determine if there is any correlation between brain image and a diver's history of diving or decompression illness (DCI). METHODS: 28 commercial divers with a history of DCI, 26 divers with no history of DCI, and 19 non-diving controls were examined with brain HMPAO-SPECT. Results were classified by observer assessment as normal (I) or as a pattern variants (II-V). The brain images of a subgroup of these divers (n = 44) and the controls (n = 17) were further analysed with a first order texture analysis technique based on a grey level histogram. RESULTS: 15 of 54 commercial divers (28%) were visually assessed as having HMPAO-SPECT images outside normal limits compared with 15.8% in appropriately identified non-diver control subjects. 18% of divers with a history of DCI were classified as having a pattern different from the normal image compared with 38% with no history of DCI. No association was established between the presence of a pattern variant from the normal image and history of DCI, diving, or other previous possible neurological insult. On texture analysis of the brain images, divers had a significantly lower mean grey level (MGL) than non-divers. Divers with a history of DCI (n = 22) had a significantly lower MGL when compared with divers with no history of DCI (n = 22). Divers with > 14 years professional diving or > 100 decompression days a year had a significantly lower MGL value. CONCLUSIONS: Observer assessment of HMPAO-SPECT brain images can lead to disparity in results. Texture analysis of the brain images supplies both an objective and consistent method of measurement. A significant correlation was found between a low measure of MGL and a history of DCI. There was also an indication that diving itself had an effect on texture measurement, implying that it had caused subclinical nervous tissue damage.

Adult↗
PubMed1997

Inflammatory mediator response as a potential risk marker for periodontal diseases in insulin-dependent diabetes mellitus patients.

The gingival crevicular fluid (GCF) and monocytic secretion of prostaglandin E2 (PGE2) and interleukin 1 beta (IL-1 beta) were measured in a group of 39 insulin-dependent diabetes mellitus (IDDM) patients and 64 systemically healthy individuals. Diabetics were divided into Group A (gingivitis or mild periodontal disease) and Group B (moderate or severe periodontal disease). Diabetics had significantly higher GCF levels of both PGE2 and IL-1 beta as compared to non-diabetic controls who were matched with regard to periodontal disease severity (P < 0.00001 and P = 0.0005, respectively). Within the diabetic population, the GCF levels of these inflammatory mediators were almost 2-fold higher in Group B as compared to Group A (P = 0.01, P = 0.006, respectively for GCF-PGE2 and IL-1 beta). Furthermore, diabetics as a group had a significantly higher monocytic PGE2 and IL-1 beta production in response to various concentrations of both Escherichia coli and Prophyromonas gingivalis lipopolysaccharide (LPS) as compared to non-diabetic patients with adult periodontitis (P = 0.0001). LPS dose-response curves demonstrated that monocytes from Group B diabetics produced approximately 3 times more PGE2 than Group A monocytes; however, there was no significant difference in monocytic IL-1 beta secretion within the IDDM patients. The levels of GCF or monocytic mediators did not correlate with age, race, or glycosylated hemoglobin (HbA1C) levels. Our data suggest that the high GCF and monocytic secretion of PGE2 and IL-1 beta in IDDM patients may be a consequence of a systemic response trait and that the presence of Gram-negative infections such as periodontal diseases may interact synergistically to yield high local levels of these mediators and a more severe periodontal condition.

Adult↗
PubMed1997

Magnesium status and the effect of magnesium supplementation in feline hypertrophic cardiomyopathy.

Magnesium deficiency has been associated with the development of cardiovascular disease in several species. Cats may be predisposed to alterations in magnesium status because of recent changes in the composition of commercial feline diets. The purposes of this study were 1) to examine the dietary history of cats with hypertrophic cardiomyopathy (HCM), 2) to study magnesium status of cats with HCM compared to normal cats, and 3) to determine the effects of magnesium supplementation in cats with HCM. In part 1 of the study, diets of 65 cats with HCM were examined retrospectively. Forty of the 45 cats for which diets could be determined (89%) ate a diet designed to be magnesium-restricted and/or to produce an acidic urine. In part 2 of the study, 10 cats with HCM were compared to 10 healthy control cats for serum creatinine and magnesium; urine creatinine and magnesium, urine specific gravity and pH, and fractional excretion of magnesium. Urine creatinine and specific gravity were higher in control cats than in cats with HCM. No other differences were found between the 2 groups. In part 3, cats with HCM were supplemented with either 210 mg magnesium chloride (n = 15) or 210 mg lactose (n = 15) for 12 wk. No differences between the 2 groups were found for changes in either magnesium status or echocardiographic parameters. However, the 30 cats with HCM, as a group, did show significant improvements in measures of cardiac hypertrophy over the 12-week period. This was likely the result of treatment with other medications, rather than the magnesium supplementation. The results of this study suggest that cats with HCM are likely to be fed magnesium-restricted diets, but that they do not appear to have altered magnesium status compared to healthy controls.

Animals↗
PubMed1996

The selectivity for K+ versus Na+ in DNA quadruplexes is dominated by relative free energies of hydration: a thermodynamic analysis by 1H NMR.

We have studied the competition between Na+ and K+ for coordination by G quartets using the oligonucleotide d(G3T4G3) as a model system. d(G3T4G3) forms a dimeric foldback structure containing three G quartets in the presence of either NaCl or KCl. Proton chemical shifts, which are particular to the species of coordinated ion, have been used to monitor the conversion between the sodium and potassium forms under equilibrium conditions. Analysis of titration experiments indicates that at least two K+ are coordinated by the three quartets of the dimeric molecule, and perfect fits of the data are obtained for two Na+ being displaced by two K+. Our results also indicate that the conversion of [d(G3T4G3)]2 from the sodium to the potassium form is associated with a net free energy change (delta G degrees) of -1.7 +/- 0.15 kcal/mol. It has long been suggested that the greater thermal stability of DNA quadruplex structures in the presence of K+ is primarily a result of the optimal fit of this ion in the coordination sites formed by G quartets. However, a consideration of the relatively small change in free energy associated with the conversion from the sodium to the potassium form and the relatively large difference between the free energy of hydration for Na+ and K+ indicates that this cannot be correct. Rather, the preferred coordination of K+ over Na+ is actually driven by the greater energetic cost of Na+ dehydration with respect to K+ dehydration.

DNA↗
PubMed1996

Magnetic resonance imaging of thyroid swellings.

The preoperative diagnosis of some thyroid neoplasms remains difficult even with the routine use of fine-needle aspiration cytology. The potential of nuclear magnetic resonance imaging (MRI) to discriminate between different thyroid pathologies was explored prospectively and compared with the final pathology in a series of 37 patients. MRI yielded high-quality images of the thyroid swelling but did not provide additional information to differentiate benign from neoplastic lesions. MRI does not contribute to the routine management of thyroid swellings.

Carcinoma, Papillary↗
PubMed1996

The influence of stimulated echoes on contrast in fast spin-echo imaging.

Tissue contrast obtained using fast spin-echo (FSE) and conventional spin-echo (SE) sequences is not identical and a number of mechanisms are thought to contribute to these contrast differences. The effect of stimulated echoes has previously been apparently ruled out as a contributing mechanism. Signal-to-noise ratios of single-slice matched FSE and conventional SE sequences were compared in aqueous solutions of CuSO4, Cr2(SO4)3 and MnSO4 with various T1 and T2 values. Enhancement of the FSE signal was observed in short T2 solutions and the effect was greater in samples where the T1 to T2 ratio was high. Reducing the refocusing pulse flip angle to increase the contribution from stimulated echoes also resulted in slightly increased enhancement. Experimental results were verified by computer simulations. Our results show that stimulated echoes do contribute to the contrast differences between FSE and conventional SE images and may be significant in the imaging of brain hemorrhage.

Computer Simulation↗
PubMed1996

Aptamer structures from A to zeta.

Solution structures of RNA aptamers for FMN, ATP, arginine, and citrulline reveal how oligonucleotides can fold to form selective binding pockets for biological cofactors and amino acids. These structures confirm old ideas and provide new insights about three-dimensional structures of nucleic acids and their possible role in chemical reactions.

Adenosine Triphosphate↗