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Biomedical subjects

A A Smith

Publications and source records attributed to A A Smith.

At least 19 recordsLinked to original sources
PubMed2004

Intracranial germ cell tumors: a single institution experience and review of the literature.

There is little literature to guide therapy in children and young adults with intracranial germ cell tumors. We present 17 consecutively diagnosed intracranial germ cell tumors at The Children's Hospital, Denver, from 1995 to 2001. Of 17 patients, 3 had considerable delay in diagnosis. Two with suprasellar tumors presented with dementia, blindness and pan-hypopituitarism and another with recurrent subarachnoid hemorrhage. Seven had germinoma, three were metastatic at diagnosis. Ten had non-germinomatous germ cell tumors (NGGCT), 5/10 were alpha feto-protein (AFP) positive only, one beta-human chorionic growth (betaHCG) factor positive only, 3 positive for AFP and betaHCG, and 1 malignant teratoma. Therapy for metastatic patients consisted of chemotherapy followed by craniospinal radiation (CSI). Patients with localized disease received chemotherapy followed by focal radiation. Two patients received chemotherapy only, one because she died of sepsis while receiving chemotherapy and one because of neurologic injury incurred during surgery parents elected for no therapy. Three patients have died, one of tumor recurrence, one from a remote complication of surgery and one of sepsis. Twelve patients are alive without evidence of disease from 10 to 68 months (median 31.5 months). All five children with only AFP positivity, treated with chemotherapy and focal radiation are alive without evidence of disease at 10, 16, 22, 41 and 41 months. Thus, there is little evidence that CSI is necessary in non-metastatic germinomas and AFP positive NGGCTs when combined chemotherapy and radiation therapy is used. However, complications of delayed diagnosis, surgery and chemotherapy are important causes of mortality, with only one patient dying of tumor.

Adult↗
PubMed2004

Rising burden of immature sheep ticks (Ixodes ricinus) on red grouse (Lagopus lagopus scoticus) chicks in the Scottish uplands.

The sheep tick Ixodes ricinus (L.) (Acari: Ixodidae) is an ectoparasite of major economic and pathogenic importance in Scotland. Its distribution in the Scottish uplands is assumed to be governed by the abundance and distribution of its definitive hosts (deer and sheep) and climatic variables such as temperature and rainfall. As the numbers of its major host in Scotland, red deer, have increased dramatically and climatic conditions have become more favourable, the level of parasitism could have been expected to rise. We use data gathered from tick counts on over 4000 red grouse chicks Lagopus lagopus scoticus Latham (Galliformes: Tetraonidae) in various experiments over the past 19 years to ascertain whether the intensity and prevalence of parasitism has been increasing. From 1985 to 2003 the average tick burden of a parasitized red grouse chick has grown from 2.60 +/- 1.12 ticks per chick to 12.71 +/- 1.44. Over this period the percentage of chicks of a given brood parasitized has also increased from 4 +/- 2% to 92 +/- 3%. The possible implications of this increase in parasitism for red grouse production are discussed.

Animals↗
PubMed2003

Oxygen supplementation before or after submaximal exercise in patients with chronic obstructive pulmonary disease.

BACKGROUND: Evidence for improved exercise tolerance or relief of breathlessness by short term use of oxygen before or after exercise in patients with chronic obstructive pulmonary disease (COPD) is scant, and guidelines for this treatment are lacking despite widespread provision in the UK. METHODS: The effect of oxygenation either before or after exercise on perception of breathlessness and walk distance was studied in a group of patients with moderate to severe COPD (mean forced expiratory volume in 1 second (FEV(1)) 34% of predicted, mean 6 minute walk distance on air 283 m), all of whom desaturated by at least 4% on submaximal exercise. Oxygen (28%) or air was delivered double blind and in random order, either for 5 minutes before a standard 6 minute walk test (n=34) or for 5 minutes following the end of the test (n=18). Exercise tolerance was measured as the distance achieved and breathlessness was assessed using visual analogue scales (VAS) which were scored before and after exercise and during recovery. RESULTS: No increase in mean walk distance after oxygen (288 v 283 m) and no improvement in mean breathlessness scores (58 v 54 mm) or recovery times occurred with oxygen taken either before (177 v 184 seconds) or after exercise (182 v 151 seconds). CONCLUSIONS: This group of patients with COPD derived no physiological or symptomatic benefit from oxygen breathed for short periods before or after submaximal exercise. Domiciliary oxygen should only be prescribed for such patients if they have shown objective evidence of benefit on exercise testing.

Aged↗
PubMed2002

Specific staining of tissue components with metal-hematoxylin complexes.

The older metal-hematoxylin stains stain a broad spectrum of tissue components. Several recently introduced metal-hematoxylin stains are highly selective. This selectivity is usually bought at the price of severe limitations on the choice of fixative. A very dilute (2 x 10(-4)M) aluminum hematoxylin is selective for nucleic acids in tissues fixed in organic solvents alone. Vanadate hematoxylin is selective for basic proteins in tissues fixed in formaldehyde or mercuric salts. Bismuth hematoxylin is selective for arginine residues and thus for histones and myelin basic protein in tissues fixed in strong acids (Bouin's fluid or SUSA fluid). Zirconyl hematoxylin is selective for acidic mucins. Zirconyl hematoxylin does not restrict the choice of fixative.

Animals↗
PubMed2001

Structural determinants for potent, selective dual site inhibition of human pp60c-src by 4-anilinoquinazolines.

The kinetic mechanisms for the inhibition of pp60(c-src) tyrosine kinase (Src TK) by 4-anilinoquinazolines, an important class of chemicals as protein kinase inhibitors, were investigated. 4-Anilinoquinazolines with a bulky group at the 4'-position of the anilino group were shown to be competitive with both ATP and peptide, whereas molecules lacking such a bulky group only displayed an inhibition pattern typical of those competitive with ATP and noncompetitive with peptide. Modifications of the substituents on the carbocyclic ring did not perturb the inhibition pattern although the affinities of these modified inhibitors for Src TK were affected. Structural modeling of Src TK with inhibitor and peptide substrate bound indicated a direct atomic conflict between the bulky 4-position group and the hydroxy of the peptide tyrosyl to which the gamma-phosphate of ATP is transferred during the kinase reaction. This atomic conflict would likely prevent simultaneous binding of both inhibitor and peptide, consistent with the observed kinetic competitiveness of the inhibitor with peptide. The dual site inhibitors appeared to have both enhanced potency and selectivity for Src TK. One such inhibitor, 4-(4'-phenoxyanilino)-6,7-dimethoxyquinazoline, had a 15 nM potency against Src TK and was selective over receptor tyrosine kinases VEGFR2 by 88-fold and C-fms by 190-fold.

Adenosine Triphosphate↗
PubMed2000

Zirconyl hematoxylin: a new stain for acidic mucins.

Most stains for acidic mucins are time-consuming to prepare and have poor stability. Zirconyl hematoxylin is easily prepared and works for a year or more. It is made by adding 5 ml freshly-made 0.1% aqueous sodium iodate, 400 mg zirconyl chloride octahydrate, and 40 ml 25% aqueous glycerol, in that order, to 100 mg of hematoxylin in 5 ml of absolute ethanol and stirring for 5 min. Stain 10 min and do not "blue" the stain. Chlorazole black or kernechtrot and fast green are good counterstains. Zirconyl hematoxylin stains acidic mucins violet or red violet, regardless of how they are fixed. It stains the same mucins as alcian blue in mouse and sheep salivary glands. It shows goblet cells in mouse rectum as well as alcian blue. It stains the same stomach regions in a lizard as alcian blue. Like alcian blue and colloidal iron, zirconyl hematoxylin stains the mucin of cancerous prostate, but not normal prostate.

Animals↗
PubMed1999

Impaired pulmonary diffusion during exercise in patients with chronic heart failure.

BACKGROUND: Pulmonary diffusion is impaired at rest in patients with chronic heart failure (CHF) and has been implicated in the generation of symptoms and exercise intolerance. The aim of this study was to determine whether pulmonary diffusion is impaired during exercise in CHF, to examine its relationship to pulmonary blood flow, and to consider its functional significance in relation to metabolic gas exchange. METHODS AND RESULTS: Carbon monoxide transfer factor (TLCO) and pulmonary blood flow (Q(C)) were measured by a rebreathe technique at rest and during steady-state cycling at 30 W in 24 CHF patients and 10 control subjects. Both patients and control subjects were able to raise TLCO and Q(C) during exercise. However, the patient group had a lower diffusion for a given blood flow (TLCO/Q(C)) both at rest (3.6+/-0.16 and 4.8+/-0.23 mL x L(-1) x mm Hg(-1); P<0.001) and during exercise (2.8+/-0.16 and 3.4+/-0.13 mL x L(-1) x mm Hg(-1) for CHF patients and control subjects, respectively; P<0.05). TLCO/Q(C) was related to the ventilatory equivalent for carbon dioxide (VEVCO(2)) production at 30 W (TLCO/Q(c) versus VEVCO(2), r = -0.58, P<0.01) and to peak exercise oxygen consumption measured during a progressive test (TLCO/Qc versus VO(2peak), r = 0.57, P<0.01) in these patients. CONCLUSIONS: Patients with CHF are able to recruit reserves of TLCO and Q(C) during exercise. However, the TLCO/Q(C) ratio is consistently impaired in these patients and relates to both exercise hyperpnea and peak exercise oxygen consumption. Whether this impairment in alveolar gas exchange is reversible in CHF and therefore is a potential target for therapy has yet to be determined.

Cardiac Output, Low↗
PubMed1999

Perceived family dynamics of persons with chronic pain.

This qualitative study was conducted to gain an understanding of the experiences of persons with chronic pain and their relationships with family members and the family as a whole. The framework of systemic organization was used to define the areas of investigation guiding the formulation of broad questions relative to family functioning. Thirty persons with chronic pain (age 31-82 years, 73% women, 83% married, 83% European-American, 17% African-American) participated in the study. A semi-structured interview was conducted to elicit narrative descriptions of the participants' perspective of the pain experience and family functioning. The data were analysed using a constant comparison method of analysis described by Strauss. The dominant themes that emerged included: (i) emotional distress, (ii) distancing from family members, (iii) inability to share difficult feelings, (iv) intense mutual involvement with family members and identification with others' problems, (v) family isolation from community, and (vi) attempt at healing. A mid-range theory developed out of the data and explicated with the framework of systemic organization, was one of balancing and counterbalancing connectedness (spirituality) with personal autonomy or separateness (control) in order to find congruence for the family and individuals within. The pain sometimes acted as a mechanism regulating the distance and closeness among family members. Based on this information, nurses can facilitate better understanding among family members, encourage autonomy, assist individuals to express feelings and needs more directly, and facilitate members to respond to each other.

Adult↗
PubMed1999

Upper extremity salvage using the tensor fascia lata flap: report of two cases.

The tensor fascia lata pedicled flap was successfully used to salvage 3 severely injured upper extremities in 2 patients. Both patients had undergone 3 prior free tissue transfers without complete closure of their wounds. All 3 tensor fascia lata flaps (2 myocutaneous, 1 myofascial) survived entirely. We believe this flap offers a distinct advantage compared with the groin flap when pedicled flap coverage of the upper extremity is required.

Adult↗
PubMed1998

Characterization of two distinct families of transcription factors that bind to the CCAAT box region of the human COL1A2 gene.

Both the mouse and human alpha2(I) procollagen promoters contain an inverted CCAAT box at -80, but only the human promoter contains an additional regulatory element, the collagen modulating element (CME), immediately downstream of the CCAAT box [Collins et al. (1997): Biochem J 322:199-206]. In this study, the transcription factors that bind to the G/CBE and CME within the human promoter were characterized in SVWI-38 and CT-1 nuclear extracts. Two distinct proteins bind to the CME, and both were identified as heat-labile factors that were sensitive to high ionic strengths and required Zn2+ for DNA-binding activity. These proteins had Stokes radii of 4.12 and 3.15 nm, sedimentation coefficients of 3.9 and 3.2 S and native molecular weights of 66 and 41 kDa, respectively. On the basis of biochemical and DNA-binding properties, the CME binding proteins are probably novel factors involved in the regulation of the human alpha2(I) procollagen gene. By contrast, the G/CBE binding proteins were more resistant to heat, ionic strength, and divalent metal ion chelators, demonstrating that the G/CBE and CME binding proteins had distinct DNA-binding properties. The above properties suggest that this factor is a member of the previously characterized family of CCAAT box-binding factors, CBF, NF-Y, CP-1 and alpha-CP1. Taken together, these physicochemical properties of the COL1A2 CCAAT box and CME-binding proteins demonstrated that they were distinct unrelated transcription factors. These results also suggest that there is a distinct difference in the DNA-binding activity between the equivalent region of the mouse and human alpha2(I) procollagen promoters.

Animals↗
PubMed1998

Innervation of the supranasal sac of the puff adder.

BACKGROUND: The supranasal sac is an invagination of the skin between the supranasal and nasal shields of many true vipers. Viperinae behavior suggests that many true vipers hunt by thermal cues. METHODS: The supranasal sacs of two puff adder (Serpentes: Viperinae) were examined with modern histological and neurohistological techniques, including Kiernan's silver stain. RESULTS: There are nerve endings in the supranasal sac of the puff adder that resemble the nerve endings in the labial pits of boas. CONCLUSION: This suggests that the supranasal sac of true vipers is, like the labial pits of boas, a heat detector.

Animals↗
PubMed1998

Lag-screw technique in free osseous mandibular reconstruction.

The surgical registry was reviewed for mandibular reconstruction from 1988 to 1992. During this time, 51 patients underwent mandibular reconstruction. Of this group, 17 patients had their microvascular bone grafts secured with lag-screw fixation. An AO technique, utilizing 2.7-mm cortical screws, was used to provide rigid fixation. Mandibular defects ranged from 6 to 20 cm. AO vascularized bone grafts were studied with bone scans and remained viable. Follow-up revealed no flap losses or oral cutaneous fistulae. Lag-screw fixation, in conjunction with mandibular reconstruction, results in rigid fixation, obviates the need for mandibulamaxillary fixation, has the advantage of ease of application, and is safe to use.

Adult↗
PubMed1997

Family involvement in the nursing home: family-oriented practices and staff-family relationships.

Staff-family cooperation in caring for elders in nursing homes is recommended but poorly understood. Family involvement and staff-family interactions in nursing homes with differing family orientations were investigated. Friedemann's (1995) system-based family theory guided the study. Of all 208 licensed nursing homes in southern Michigan, 143 completed a survey about their family-oriented practices. Family orientation was ranked accordingly. Twenty-four nursing homes were randomly selected to conduct semistructured telephone interviews with 177 family members. Data were analyzed by thematic interpretation. Findings showed a wide range of involvement patterns that promoted family connectedness, maintenance of control, growth, and learning. Families desired various types of staff cooperation and were given such opportunities in homes with high family orientation.

Adult↗
PubMed1997

A triangulation approach to testing a family instrument.

Sequential triangulation was used to test the validity of the Assessment of Strategies in Families (ASF), a screening tool for family effectiveness, and its application to families experiencing chronic pain. First, 30 subjects with chronic pain completed the questionnaire. Next, for the purpose of item validation, the subjects explained their thought process for each choice on the questionnaire. Results showed that they interpreted the items as intended. Subjects then responded to a semistructured interview about their perception about family stability and growth patterns. Thematic analysis suggested a tendency toward isolation from the community, intense involvement in each other's lives, and rigid control of family operations. ASF results reflected the trends by a low family-growth subscore, and a high or low stability score, depending on the success in achieving cooperation of family members. The findings suggest the instrument is valid and appropriate to screen families with chronic pain.

Adaptation, Psychological↗
PubMed1997

Bismuth hematoxylin stain for arginine residues.

Bismuth ions complex with hematoxylin oxidized by sodium iodate to form a dark blue dye that stains structures with high arginine content. In citrate buffer at pH 5.2, staining is confined to cell nuclei and myelin sheaths. Extraction of nucleic acids has little effect on the stain. Blockade of the guanidino groups of arginine completely abolishes staining.

Animals↗
PubMed1997

Tissue expansion in the upper extremities.

In this article, the authors demonstrate current concepts of soft-tissue reconstruction using tissue expansion principles. History, pathophysiology, and biomechanics of tissue expansion are reviewed. Anatomic areas of expander use in the upper extremity have been delineated, as well as new concepts of nerve and arterial elongation using intraoperative expansion techniques. The authors outline their current technique of upper extremity tissue expansion in the preoperative, intraoperative, and postoperative settings, allowing the reader to appreciate the technique of tissue expansion and its role in soft-tissue reconstruction of the upper extremity.

Adult↗
PubMed1996

Field edge smoothing for multileaf collimators.

PURPOSE: To smooth the scalloped dose pattern that occurs for stepped leaves at a treatment field edge defined by a multileaf collimator. METHODS AND MATERIALS: Fields with centers shifted slightly in space were superimposed to blur the staggered dose distribution at the field edge. Film dosimetry was used to monitor changes. The dose distribution for a single field position was compared to the distribution for one and three shifts. Three depths were examined and divergent alloy blocks were included in the comparison. RESULTS: The structure that appears at an edge for a single field when leaves are staggered was nearly eliminated when the field was shifted three times to give a total of four different positions. However, shifting the field one time so that two fields were superimposed gave an intermediate result with only slight improvement in the undulating dose distribution. For the four superimposed fields, the 50% isodose pattern converged to a smoothed line running along the center of the original undulating pattern. The 80 and 20% isodoses did not converge to the center of their scalloped patterns. Instead, these isodose lines were spread leaving a larger penumbra width than a divergent alloy block. CONCLUSIONS: Shifting and adding fields is an effective method for smoothing the staggered dose distribution that results when the leaves of a multileaf collimator are stepped to form an irregular field pattern. However, the width of the penumbra for the combined fields is wider than the penumbra for a cerrobend block.

Radiotherapy↗