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Biomedical subjects

S L Turner

Publications and source records attributed to S L Turner.

At least 55 records · Page 3Linked to original sources
PubMed1995

Hybridization of DNA targets to glass-tethered oligonucleotide probes.

Hybridization of nucleic acids to surface-tethered oligonucleotide probes has numerous potential applications in genome mapping and DNA sequence analysis. In this article, we describe a simple standard protocol for routine preparation of terminal amine-derivatized 9-mer oligonucleotide arrays on ordinary microscope slides and hybridization conditions with DNA target strands of up to several hundred bases in length with good discrimination against mismatches. Additional linker arms separating the glass surface from the probe sequence are not necessary. The technique described here offers a powerful tool for the detection of specific genetic mutations.

Base Sequence↗
PubMed1995

Continuous hyperfractionated accelerated radiotherapy in the treatment of carcinoma of the columella and vestibule of the nose.

Twenty-one patients with squamous cell carcinoma of the nasal columella and vestibule were treated at the Mount Vernon Centre for Cancer Treatment between March 1986 and January 1994. Tumours ranged from 15 to 55 mm in maximum dimension (median 25 mm). All patients were treated with radical intent with continuous hyperfractionated accelerated radiotherapy (CHART). This group was analysed with respect to tumour control, tumour cell kinetics and radiation-induced morbidity at a median time to last follow-up of 40 months. Particular attention was paid to the detailed evaluation of late radiation changes. Patients who were still alive were assessed as to the satisfaction with the cosmesis of their treated nose. Four patients had relapse of disease either at the primary site alone (2), in neck nodes (1) or in both regions (1). One patient was successfully salvaged with surgery. Cell kinetic studies showed that cancers at this site may have potential for rapid cellular repopulation similar to cancers developing at other head and neck sites. CHART was well tolerated by patients. Late skin changes were remarkedly slight (despite full skin dose) and overall cosmesis excellent with this radiotherapy schedule.

Adult↗
PubMed1995

External beam radiation therapy as an agent in the aetiology of carcinoma of the bile duct: a report on two patients.

Two cases of biliary duct carcinoma occurring in patients who had received prophylactic abdominal irradiation 17 years previously are described. Although external beam radiation has been implicated in the aetiology of many malignancies, there is only one previous report of it being associated with carcinoma of the bile duct. All patients receiving external beam irradiation for curable malignancies require long term follow-up so that treatment induced malignancies may be detected.

Adult↗
PubMed1995

Advances in genosensor research.

Microfabricated devices containing arrays of nucleic acid hybridization sites, known as genosensors, are being developed for a variety of uses in genomic analysis. A great deal of the overall genosensor development effort involves optimization of experimental conditions in the actual use of genosensors. Here we describe a "low-tech" form of genosensor technology, involving arrays of oligonucleotides on glass microscope slides, which can be used to define optimal operating conditions and to develop applications of hybridization arrays in genome mapping and sequencing. In addition, we describe a porous silicon genosensor, which can be operated in a flowthrough mode, and discuss its advantages over current flat-surface designs. Porous silicon genosensors containing arrays of DNA fragments offer several unique capabilities in genome analysis.

Base Sequence↗
PubMed1994

Developmental regulation of the TCR zeta-chain. Differential expression and tyrosine phosphorylation of the TCR zeta-chain in resting immature and mature T lymphocytes.

The zeta subunit of the TCR complex targets receptor surface expression, is phosphorylated on tyrosine residues upon T cell activation, and is implicated in signal transduction after TCR ligation. Here we show that, although intrathymic expression of the murine TCR-associated zeta-chain relative to the other chains of the Ag receptor complex remains unchanged during early thymocyte development, there is a doubling of TCR-associated zeta-chain surface expression upon thymocyte maturation. The ratio of tyrosine-phosphorylated relative to nonphosphorylated TCR-associated zeta-chain also changes with thymocyte development. This ratio was quantified after the purification and detergent extraction of receptor complexes from freshly isolated immature or mature thymocytes. Immunoprecipitation of the zeta-chain released from the complex allowed for the isolation of the tyrosine-phosphorylated and nonphosphorylated forms of TCR-associated zeta-chain. Intracellular free zeta-chain was characterized by immunoprecipitation after clearing the cell lysate of intact TCR complexes. Densitometric analysis of immunoblots indicated that surface phosphorylated zeta-chain is more abundant in immature relative to mature T cell populations, whereas the inverse is true of intracellular phosphorylated zeta-chain. Surface phosphorylated zeta-chain also migrated at a higher m.w. than its cytoplasmic counterpart, suggesting that it is more highly modified on some or all of its available tyrosines. These findings demonstrate that the stoichiometry and post-translational modification of the TCR complex are regulated, in vivo, and may determine the functional maturation of T cell signaling, selection, and activation.

Animals↗
PubMed1993

Synchronous radiotherapy and chemotherapy in the treatment of nasopharyngeal carcinoma.

PURPOSE: Because of the high rates of local tumor control obtained by combining moderate doses of external beam radiotherapy and synchronous 5-fluorouracil/mitomycin C chemotherapy in the treatment of squamous and basiloid cancers of the anal canal, we chose to investigate this regimen for nasopharyngeal cancer which shows significant local and distant failure rates after treatment with radiotherapy alone. METHODS AND MATERIALS: Between 1983 and 1990, 43 patients with previously untreated squamous cell and undifferentiated nasopharyngeal cancer, without evidence of distant metastases at diagnosis were treated with radical radiotherapy and concurrent chemotherapy using mitomycin C (10 mg/m2 i.v. day 1 of radiotherapy) and 5-fluorouracil (1000 mg/m2 continuous i.v. infusion days 1-4 of radiotherapy and repeated at least 28 days later). Ninety-one percent of cases had Stage IV tumors and 93% had clinically involved regional lymph nodes. RESULTS: Actuarial rates of survival, local control, regional nodal control and distant metastases at 5 years were 37%, 71%, 94%, and 53%. Grade 3 or 4 skin and mucosal reactions occurred in 30% and 34% of patients, respectively. Only one patient developed greater than Grade 2 myelosuppression and he died of overwhelming sepsis. A second patient died of malnutrition 4 months after treatment giving a 5% incidence of treatment-related mortality. Nine percent of patients developed significant late complications of treatment. CONCLUSION: Despite the morbidity observed, the treatment outcome is not obviously superior to that reported for radiotherapy as a single modality of treatment.

Adult↗
PubMed1993

Restructuring an interdomain linker in the dihydrolipoamide acetyltransferase component of the pyruvate dehydrogenase complex of Escherichia coli.

The lipoyl, subunit-binding and catalytic domains of the dihydrolipoamide acetyltransferase subunits (E2p) of the Escherichia coli pyruvate dehydrogenase complex are connected by linker sequences which are characteristically rich in alanine and proline residues. By facilitating domain movement these linkers are thought to promote interactions between the three types of active site that participate in the catalytic cycle of the complex. To investigate functional constraints associated with linker composition and sequence, the natural linker of an E2p subunit containing one lipoyl domain was replaced by shorter sequences containing: mixtures of alanine plus proline residues; mainly alanine; mainly proline; and mainly charged residues. Each artificial linker possessed a central histidine residue for assessing linker flexibility by 1H-NMR spectroscopy. The resultant complexes exhibited 181% (proline), 74-79% (alanine plus proline), 63% (alanine) and 7% (charged residues) of parental activity compared with a value of 75% expected for a complex with a comparably shortened linker. The 1H-NMR spectra showed that the alanine plus proline linkers are flexible but the alanine linker and the proline linker are relatively inflexible. Substantial variations in linker sequence and composition were tolerated without loss of function, and the enhanced activity conferred by the proline linker was attributed to the combined effects of length and relative inflexibility.

Acetyltransferases↗
PubMed1992

Genetic control of the immune response to collagen by the major histocompatibility complex in the rat: I. Humoral responses to bovine and chick type II collagen.

A number of congenic and recombinant rat strains with different RT1 haplotypes on a PVG/c background were immunised with native bovine or chick type II collagen. Only strains with the "u" haplotype were good responders to bovine type II collagen whilst all strains responded to chick type II collagen. However, the "u" haplotype was again associated with the production of the highest amounts of antibody. All the strains responded to a non-collagenous antigen, keyhole limpet haemocyanin, showing that this effect was not a general one relating to all antigens. When antibodies were produced to the immunising collagen, binding of antibodies to native rat type II collagen was also seen. This association, of high amounts of antibody with the "u" haplotype, was inherited in a dominant fashion when F1 and F2 hybrids between low responder (RT1a) and high responder (RT1u) were examined. The recombinant r1 (class I av1, class II c) and r8 (class I av1 and class II u) strains showed that "u" haplotype at class II rather than at class I was associated with the strong response to type II collagen. The absence of arthritis in the "u" haplotype rats, suggests that the "u" haplotype alone is insufficient for arthritis induction after immunisation with type II collagen. It suggests that background genes outside the RT1 complex influence arthritis production as Wistar rats with the RT1u haplotype (but different minor genes outside RT1 complex) give an arthritis incidence of 50% under identical immunisation protocols.

Animals↗
PubMed1992

Selection of a thermostable variant of chloramphenicol acetyltransferase (Cat-86).

The moderate thermophile Bacillus stearothermophilus was used as a host in which to detect more thermostable variants of the B.pumilus chloramphenicol acetyltransferase (Cat-86) protein. Seventeen mutants were isolated and detected by their ability to grow in the presence of chloramphenicol at a previously restrictive temperature (58 degrees C). The genes encoding these proteins were sequenced; all 17 mutants carried the same C to T transition that conferred an amino acid substitution of alanine by valine at position 203 of the protein sequence. The wild-type and one mutant Cat-86 protein were purified to homogeneity using affinity chromatography, and kinetic and thermal stability studies were undertaken. Both enzymes had similar sp. act. in the region of 215 U/mg, with Km values for chloramphenicol in the range 13.8-15.4 microM and for acetyl CoA in the range 13.6-15.5 microM. The A203V mutant shows greater stability than the wild-type Cat-86 protein at temperatures above 50 degrees C and appears to pass through a transition state between 48 and 50 degrees C.

Bacillus↗
PubMed1992

Identification of an immunodominant B-cell epitope in bovine type II collagen and the production of antibodies to type II collagen by immunization with a synthetic peptide representing this epitope.

Using epitope scanning of 272 short, synthetic peptides representing the amino acid sequence of the CB-11 peptide of type II collagen, we have shown that five strains of rat, immunized with type II collagen, produce antibodies to a region 37-45 amino acids from the amino end of CB-11 peptide. Antibodies to this region always gave the highest binding values suggesting that it is an immunodominant region. Wistar rats immunized with a synthetic peptide representing this region, coupled to keyhole limpet haemocyanin, produced antibodies to this peptide which could still be detected at 1:4000 to 1:8000 dilution but none developed clinical arthritis. All sera also showed binding of antibodies to denatured bovine type II collagen but not to native type II collagen, keyhole limpet haemocyanin or to bovine serum albumin by ELISA. Sera from peptide-immunized rats were examined for antibody binding to the 272 short peptides of the CB-11 peptide and to the synthetic peptides representing shortened forms of the immunodominant region and forms of it with substituted amino acids. These results showed that the antibodies in the peptide-immunized rats were not identical to those produced to that peptide by rats immunized with type II collagen but may represent subpopulations of them. These findings suggest caution in interpreting the role of antibodies to individual peptides in arthritis induction without knowledge of their fine specificity.

Animals↗
PubMed1991

Splenocyte response to T cell-derived cytokines in thymectomized Xenopus.

A miniaturized, "hanging-drop" bioassay reveals that splenocytes from early-thymectomized (Tx) Xenopus can respond (by enhanced thymidine incorporation) to thymic-dependent "cytokines" generated in PHA- or alloantigen-stimulated cultures. Preliminary evidence, using fluorescence activated cell sorting, indicates that surface IgM- splenocytes, rather than sIgM+ cells, from Tx toads are sensitive to the crude, splenocyte-derived, active supernatants. Although these responsive cells display residual, but low, reactivity to PHA, their thymus independence is suggested by flow cytometric observations using the anti-T cell monoclonal antibody XT-1. The development of "T-like" cells in Tx Xenopus is discussed.

Animals↗
PubMed1991

Radical radiotherapy for carcinoma of the larynx--Westmead Hospital experience.

Between January 1980 and December 1988, 141 patients were treated with radical radiotherapy for carcinoma of the larynx. One hundred and ten (78%) tumours arose on the vocal cords, twenty nine (21%) from the supraglottis and two (1%) from the subglottis. All 63 stage T1 cases, and all except three of 62 T2 cases seen in the time period, were treated by radiotherapy. In addition 14 selected T3 and 5 T4 cases were irradiated. Only 7% had clinical evidence of regional lymph node metastases at presentation. Median follow up is 47.5 months and 2+ year actuarial local control rates are T1-87%, T2-63%, T3-79% and T4-53%. The rates for vocal cord primaries are T1-86%, T2-58%, and T3-75%. Median time to local failure was 8 months with none occurring beyond 21 months. Two of 130 N0 cases (1.5%) relapsed in cervical lymph nodes with a policy of selective prophylactic irradiation of the regional lymphatic areas. Thirty three/thirty seven patients with locoregional failure underwent salvage surgery with 27/32 (84%) evaluable patients achieving ultimate locoregional control with median follow up of 18.5 months from salvage. Four patients (3%) developed distant metastases and 21 (15%) developed a second primary malignancy (including 13 lung cancers) with an actuarial rate of second primary tumours of 23% at five years. Three year actuarial survival for the whole group is 77% but 66% of deaths were due to causes other than larynx cancer. Tumour specific mortality by stage is T1-1.6%, T2-12%, T3,4-21%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Regulation of brain nicotinic receptors by chronic agonist infusion.

Several studies have demonstrated that chronic treatment with nicotine elicits an increase in the number of brain nicotinic receptors. To determine whether this effect is elicited by other nicotinic agonists found in tobacco, the effects of chronic infusion with nicotine on brain nicotinic receptors were compared with those after anabasine and lobeline. C57BL/6 mice were infused with saline or equimolar doses (18.5 mumol/kg/h) of nicotine, anabasine, or lobeline for 8 days. Nicotinic receptors, quantified by the binding of [3H]nicotine and [125I]iodo-alpha-bungarotoxin (alpha-[125I]BTX), and muscarinic receptors, quantified by the binding of [3H]quinuclidinyl benzilate ([3H]QNB), were then assayed in eight brain regions. An increase in [3H]nicotine binding was observed in all regions except cerebellum following chronic infusion with nicotine and anabasine, whereas lobeline did not alter the number or affinity of these binding sites. This increase was due to changes in Bmax and not in the affinity of the receptor for the ligand (KD). A slight increase in alpha-[125I]BTX binding was observed in cortex following chronic anabasine infusion. [3H]QNB binding sites were largely unaltered following chronic infusion with any of the nicotinic analogs. The levels of the agonists in the brain were also determined after chronic treatment, and the amounts of lobeline and anabasine were found to be higher than that of nicotine. Thus, the failure of lobeline to elicit changes in nicotine binding is not due to reduced brain concentrations.

Anabasine↗
PubMed1991

Locally advanced (stage III and IV) head and neck cancer: Westmead Hospital experience.

Two hundred and fifty-one patients with Stage III and IV (UICC staging system) squamous cell cancers of the oral cavity, oropharynx, hypopharynx and larynx were assessed between January 1980 and December 1988 at Westmead Hospital. Of these, 50 patients received palliative treatment or were not treated and the remaining 201 patients received treatment with curative intent by various combinations of radiotherapy, surgery and chemotherapy. Thirty-nine operable cases were entered into a multimodality protocol initiated in April 1985, which consisted of induction chemotherapy (cisplatin 100 mg/m2 i.v. day 1, 5-fluorouracil 1000 mg/m2 per 24 h i.v. days 1-5, q3w x 2) followed by surgery and postoperative radiotherapy. The median follow-up for all 251 patients was 57 months. Actuarial 3-year survival rate for all 201 patients receiving radical treatment was 48% (Stage III 66%, Stage IV 36%; P less than 0.001). Overall actuarial local and nodal control rates at 3 years were 67% and 69%. Thirty-two of 201 patients (16%) developed distant metastases at a median time of 11 months. Twenty-one patients (10%) had a previous or subsequent second primary cancer. In the group of 39 protocol patients, overall actuarial survival, local and nodal control rates are 68%, 77% and 73% at 3 years. A group of 22 'protocol' patients was compared with a group of 22 patients treated prior to commencement of the protocol, matched as closely as possible on the basis of site, stage, age, sex and ECOG status.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Selective changes in sensitivity to cholinergic agonists and receptor changes elicited by continuous physostigmine infusion.

A reduction in nicotinic receptors has been observed in brains of patients with Alzheimer's disease, and physostigmine, an indirect acting cholinergic agonist, has been suggested as a treatment of this disease. However, the effects of physostigmine treatment have not been thoroughly characterized. The central and peripheral effects of physostigmine were evaluated in C57BL/6 mice using a battery of behavioral and physiological tests that included respiratory rate, Y maze crossing and rearing activities, heart rate and body temperature. With the exception of the heart rate test, which was blocked by a peripheral muscarinic antagonist, all responses to physostigmine measured in the test battery seem to be mediated centrally. Sensitivity to physostigmine and to nicotine and oxotremorine were examined as were nicotinic and muscarinic receptors after continuous infusion of physostigmine. Mice (C57BL/6) continuously infused with physostigmine (0.1 mg/kg/h) for 10 days developed marked tolerance to physostigmine and exhibited a slight decrease in sensitivity to nicotine; sensitivity to oxotremorine was largely unaltered. Chronic physostigmine treatment resulted in a 62% inhibition of AChE activity and elicited a significant increase in the amount of L-[3H] nicotine binding in midbrain, hippocampus, striatum and colliculi; alpha-[125I]bungarotoxin and [3H]quinuclidinyl benzilatl binding were not changed. Although physostigmine treatment might partially reverse the reduction of brain nicotinic receptors seen with Alzheimer's disease, it is questionable whether it would be effective for a prolonged period since the up-regulated nicotinic receptors may not have normal function.

Acetylcholinesterase↗
PubMed1990

Reasons for exceeding average length of stay in the terminal patient: one center's experience.

1. LOS was not significantly influenced by the type of insurance carrier. 2. Age was not a factor in LOS of the terminal patient. However, Medicare patients averaged the greatest number of days lost/patient. 3. Terminal Medicare cancer patients whose physician was an oncologist had a shorter LOS. 4. The growing commitment to home hospice will result in a decreasing number of patients coming into the hospital to die. 5. The decreasing number of terminal cancer patients who expire within 72 hours of admission will result in an increase in the average LOS of those remaining hospitalized cancer patients.

Female↗