Biomedical subjects
M W Reed
Publications and source records attributed to M W Reed.
Spontaneous simultaneous internal and external biliary fistulae.
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Radiation exposure during dynamic hip screw operation.
Exposure to radiation by surgeon and patient was measured in ten cases during insertion of a dynamic hip screw, using image intensified screening. There were low levels of irradiation of the thyroid and eyes of the surgeon. However, the dominant hand of the surgeon was often exposed to higher levels. The use of a memory during screening significantly reduced the level of radiation measured (P less than 0.05). Recommendations are made for reducing radiation exposure by the surgeon, and a method is described to measure the irradiation of surgeons' hands.
Curriculum for: preparing the dental student to meet tomorrow's dental practice.
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A clinical evaluation of a sodium fluoride dentifrice.
A double-blind study to determine the anticaries efficacy of a neutral pH dentifrice containing sodium fluoride and a high Beta-phase calcium pyrophosphate was conducted among elementary school children in Kansas City, Missouri. A sample of 567 children ages 8-13 were recruited and randomly assigned to test and control groups: the test group received a sodium fluoride high Beta-phase calcium pyrophosphate dentifrice, and the control group received a calcium pyrophosphate dentifrice without the active ingredient. The sodium fluoride dentifrice contained fluoride at the level of 1000 ppm. Caried examinations were conducted at initiation, after 12 months, and again after 24 months at the study's termination. All examinations (clinical and radiographic) were performed by the same investigator. At 12 months the sodium fluoride dentifrice demonstrated a caries reduction of 24.1% (DMFS). At 24 months the reduction demonstrated was 30.1% (DMFS); this reduction is significant at alpha = 0.05.
Clinical evaluation of three concentrations of sodium fluoride in dentifrices.
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Trauma to an unerupted deciduous tooth.
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Measurement of space loss resulting from tooth ankylosis.
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A comparative analysis of radiological and surgical placement of central venous catheters.
PURPOSE: To compare the differences in practice and outcome of all radiologically and surgically placed central venous catheters retrospectively over a 2-year period simultaneously, at a single institution. METHODS: A total of 253 Hickman catheters were inserted in 209 patients; 120 were placed radiologically in 102 patients and 133 were placed surgically in 107 patients. The indication was chemotherapy in 76% of radiological and in 47% of surgical cases; the remainder were for total parenteral nutrition and venous access. RESULTS: There were 6 (4.5%) primary surgical failures and a further 17 (13%) surgical cases requiring multiple placement attempts. Pneumothorax occurred once (0.8%) surgically and four times (3.3%) radiologically. There were no radiological primary misplacements but there were five (3.7%) surgical ones. Catheter or central vein thrombosis occurred in four (3.3%) radiological and five (3.7%) surgical cases. The rate of infection per 1000 catheter-days was 1.9 in radiologically placed catheters and 4.0 in surgically placed ones (p < 0.001). Average catheter life-span was similar for the two placement methods (100 +/- 23 days). CONCLUSION: Radiological placement is consistently more reliable than surgical placement. There are fewer placement complications and fewer catheter infections overall.
Acridine- and cholesterol-derivatized solid supports for improved synthesis of 3'-modified oligonucleotides.
New solid supports are described which allow the direct synthesis of oligonucleotides bearing either cholesterol or acridine at the 3'-terminus. A stereochemically defined amino diol was prepared by reduction of N-Cbz-hydroxy-L-proline. This linker molecule was first acylated with the desired conjugate molecule, then protected as the dimethoxytrityl ether. The remaining secondary hydroxyl group was succinylated and immobilized on a controlled-pore glass support. 3'-Modified oligodeoxynucleotides (ODNs) were prepared from these supports by using standard phosphoramidite coupling and deprotection conditions. A cholesterol-modified support was prepared from cholesterol chloroformate and the amino diol linker. Two types of acridine-modified solid supports were prepared from acridine tetrafluorophenyl esters with linker arms of different length. In an alternative synthesis of 3'-derivatized ODNs, these active esters were also utilized for acylation of a 3'-amine-modified ODN. A thermal denaturation study was done to determine the effect of the different linker arms on hybridization to a complementary ODN target. Facile synthesis and purification of the 3'-modified ODNs makes these functionalized solid supports especially useful for preparation of oligonucleotides bearing these and other modifications.
Preparation and in vivo evaluation of an N-(p-[125I]iodophenethyl)maleimide-antibody conjugate.
Protein sulfhydryl reactive N-(4-[125I]iodophenethyl)maleimide (IPEM, 5) was obtained from N-[4-(tri-n-butylstannyl)phenethyl]maleimide in 59-100% radiochemical yield. Conjugation of 5 to NR-ML-05 Fab, a murine anti-melanoma antibody Fab fragment that had been previously reduced with dithiothreitol (DTT), was effected in an average of 85% yield. Results from in vitro chemical challenges and serum stability studies on the IPEM conjugate of NR-ML-05 Fab (6) indicated a stable covalent attachment of the radioiodine. A biodistribution study of the IPEM conjugate in tumor-bearing athymic nude mice showed lack of significant accumulation of radioiodine in the thyroid and stomach which was an indication of in vivo stability. The observed uptake in tumor was consistent with that obtained for Chloramine-T- or p-iodobenzoate-labeled NR-ML-05 Fab conjugates.
An improved CPG support for the synthesis of 3'-amine-tailed oligonucleotides.
A new controlled-pore glass (CPG) support is described that allows for the direct synthesis of oligonucleotides bearing a 3'-aminohexyl tail. This solid support (AH-CPG) exhibits superior performance as compared to a commercially available 3'-amine CPG. The AH-CPG is prepared from 6-aminohexan-1-ol with a unique protecting group for the amine that also functions as the site of attachment to the CPG. A 3'-amine-tailed oligodeoxynucleotide (ODN) was prepared from this support using standard phosphoramidite coupling and deprotection conditions. The 3'-amine-tailed ODN was subsequently modified with an acridinylpropionic acid tetrafluorophenyl ester. Facile synthesis of the AH-CPG and the stability of the deprotected product makes this functionalized solid support especially useful for preparation of oligonucleotides bearing 3'-amine tails and other modifications.
Synthesis and evaluation of nuclear targeting peptide-antisense oligodeoxynucleotide conjugates.
An endogenous nuclear enzyme, RNase H, is an important component in determining the efficacy of antisense oligodeoxynucleotides (ODNs). In an effort to improve the potency of antisense ODNs, conjugates with three different nuclear targeting signal peptides were prepared. These short peptide sequences have been shown to facilitate transport of macromolecules into the nucleus of cells. Efficient chemistry for the synthesis of ODN-peptide conjugates is described. Reaction of 5'-aminohexyl-modified ODNs with iodoacetic anhydride gave pure iodoacetamide ODNs (IA-ODNs) in good yield. These electrophilic intermediates were reacted with thiol-containing peptides to give ODN-peptides in excellent yield and purity. The ODN-peptides were further characterized by proteolysis with trypsin. Thermal denaturation studies with ssDNA targets showed little effect of the 5'-peptide modifications on the hybridization properties of the ODN. The effect of the nuclear signal peptides on antisense potency was evaluated in the freshwater ciliate Paramecium. A 3'-hexanol-modified 24-mer antisense ODN, complementary to the mRNA for calmodulin, alters regulation of membrane ion channels and swimming behavior of these cells. A 2'-O-methyl analog of this ODN was inactive, thus providing evidence that this activity in Paramecium is mediated by RNase H. Antisense ODN-nuclear signal peptide conjugates were transfected into the cells by electroporation. Surprisingly, these conjugates showed no antisense effects in comparison to a 5'-unmodified control ODN. Random peptides or amino acids conjugated to the 5'-terminus did not decrease antisense activity.
Synthesis of 125I-labeled oligonucleotides from tributylstannylbenzamide conjugates.
A rapid and efficient method for the synthesis of 125I-labeled oligodeoxynucleotides ([125I]ODNs) is described. The key intermediates are tributylstannylbenzamide-modified ODNs (Sn-ODNs). Reaction conditions are described for the preparation of 5'-modified Sn-ODNs. Treatment with NaI and chloramine T gave conversion to the desired I-ODN, which was easily isolated by reversed phase chromatography. Thermal denaturation (Tm) studies showed that hybridization properties were not disturbed by the 4-iodobenzamide modification. An [125I]ODN was prepared and characterized by hybridization to 32P-labeled DNA targets. Sequence specific cleavage of the target DNA strand by 125I was measured.
Synthesis and reactivity of aryl nitrogen mustard-oligodeoxyribonucleotide conjugates.
A versatile method is described for preparing aryl nitrogen mustard-oligodeoxyribonucleotide (mustard-ODN) conjugates under anhydrous conditions. The chemistry uses DMSO soluble triethylammonium or tributylammonium salts of the ODNs. A G/A motif triplex forming ODN was chosen for study since it had been shown earlier to bind with high affinity and specificity to a duplex DNA target. A 5'-hexylamine derivative of this ODN was reacted with three different 2,3,5,6-tetrafluorophenyl ester derivatives of aryl nitrogen mustards which were designed to have different alkylation rates. An HPLC assay was used to determine reaction rates of these mustard-ODNs under various conditions. The reactivity of the mustard groups depended on chloride concentration and the presence of nucleophiles. Conjugation of mustards to G/A-containing ODNs decreased their aqueous stability. Hydrolysis and alkylation rates of these agents were consistent with reaction via an aziridinium intermediate. Rates of sequence specific alkylation within a triplex were determined by denaturing gel electrophoresis and shown to depend on inherent reactivity of the mustard group. The improved synthesis and chemical characterization of mustard-ODNs should facilitate their use as sequence specific alkylating agents and as probes for nucleic acid structure.
Introducing antisense oligodeoxynucleotides into Paramecium via electroporation.
A method utilizing electroporation to deliver antisense oligodeoxynucleotides into Paramecium tetraurelia has been developed. For these studies antisense oligonucleotides directed to different regions of the calmodulin mRNA were used. It was found that a pulse delivered at 150-250 V (375-625 V/cm field strength) for 3.9-4.2 ms using a 275 microF capacitor with resistance set at 13 Ohms was sufficient to achieve measurable incorporation of fluorescently-labeled oligodeoxynucleotides in up to 95% of the cells treated. Optimal parameters included using oligodeoxynucleotides of at least 12 bases in length with a 3' blocking group at a dose of around 10 microM. In addition, multiple oligodeoxynucleotides directed to the same target mRNA resulted in at least a 10-fold reduction in the dose of oligodeoxynucleotide required to achieve the desired effects. Taken together, these results indicate that the use of antisense oligodeoxynucleotides can be an easy and useful method for linking genes to specific functions in Paramecium tetraurelia. Finally, this report discusses how different 3' blocking groups and the use of combinations of oligodeoxynucleotides directed to different regions of the same target mRNA can help address concerns about specificity.
Characterisation of an experimental model of chronic lower limb ischaemia in the anaesthetised rat.
Reperfusion injury is responsible for the failure of up to 15% of otherwise successful lower limb bypass procedures for critical limb ischaemia. It is also responsible for complications in myocardial revascularisation, organ transplantation and free flap transfers. The majority of experimental work investigating reperfusion injury has studied acute ischaemia in normal tissues which may reflect the situation in organ transplantation and free flap transfers, but in vascular reconstructive surgery the distal limb circulation is severely compromised prior to surgery. In the present study a model of chronic ischaemia in the rat hind limb has been produced by ligation of the left common iliac artery. Femoral artery blood pressure and flow measurements showed a mean reduction to 53% and 41% respectively when compared to the contralateral limb. These changes were maintained for up to nine weeks following ligation of the common iliac artery. Contrast arteriography was used to establish the anatomy of the collaterals and demonstrated that the femoral artery is an end artery. This technique provides a model of experimental chronic ischaemia which is stable for up to nine weeks and may be used to investigate the mechanisms involved in the reperfusion injury.
The change in clinical DMFT scores of Kansas City school children over a ten year period.
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