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Biomedical subjects

D McRae

Publications and source records attributed to D McRae.

At least 19 recordsLinked to original sources
PubMed2001

Copy-DNA cloning and characterisation of a potato alpha-glucosidase: expression in Escherichia coli and effects of down-regulation in transgenic potato.

Polymerase chain reaction-based methodology was used to obtain a cDNA clone (MAL2) from potato (Solanum tuberosum L.) with the sequence characteristics of an alpha-glucosidase. Phylogenetic analysis of the deduced polypeptide encoded by this cDNA demonstrated that the most similar sequences were alpha-glucosidases and alpha-xylosidases of plant origin. The MAL2 cDNA was expressed in Escherichia coli and the recombinant MAL2 protein was affinity-purified. MAL2 catalysed the hydrolysis of a range of maltooligomers and p-nitrophenyl-alpha-D-glucopyranoside with a pH optimum of 5.5-5.7. The substrate with the lowest Km value was maltotetraose (3.7 mM). The MAL2 expression product did not catalyse the hydrolysis of xyloglucan oligosaccharides, p-nitrophenyl-alpha-D-xylopyranoside or gelatinised potato starch. MAL2 was down-regulated in transgenic potato plants using an antisense approach. In several independent transgenic antisense lines, MAL2 expression was severely down-regulated. Despite this, no decrease in total extractable alpha-glucosidase and alpha-xylosidase activity could be detected in tissues from the transgenic plants. In glasshouse trials, no visible phenotype, change in tuber yield or carbohydrate content was associated with MAL2 down-regulation. The implications of these results are discussed.

Cloning, Molecular↗
PubMed2000

A potato alpha-glucosidase gene encodes a glycoprotein-processing alpha-glucosidase II-like activity. Demonstration of enzyme activity and effects of down-regulation in transgenic plants.

In order to elucidate more fully the function of a potato gene (MAL1) encoding alpha-glucosidase activity, transgenic plants in which MAL1 expression was down-regulated were generated using antisense technology. In transgenic lines severely down-regulated in the expression of MAL1, total alpha-glucosidase activity was not decreased in leaves and tubers, and the contents of starch, glucose, fructose and sucrose remained unchanged in tubers. Phylogenetic analysis indicated that the MAL1 gene product was more similar to the glycoprotein-processing alpha-glucosidase II of mammalian and yeast origin than to other plant alpha-glucosidases. Using [14C-Glc]-labelled Glc2Man9GlcNAc2 as a substrate, it was demonstrated that glucosidase II activity was markedly down-regulated in microsomes isolated from tubers of four independent antisense lines studied in detail, strongly suggesting that MAL1 encodes glucosidase II activity. In field trials (but not in the glasshouse), MAL1 down-regulation produced an extremely stunted phenotype - the leaves were curled and tuber yield was decreased by 90% compared to control values. Microscopic analysis of leaves revealed significant differences between the antisense and control samples. Plants with down-regulated glucosidase II activity showed a greater degree of plasmolysis, and an increase in the size of mesophyll intracellular spaces. Analysis of cell walls also indicated changes in structure as a result of MAL1 down-regulation. In leaves from four antisense lines, the steady-state transcript level corresponding to the endoplasmic reticulum chaperone, BiP, was enhanced. This is diagnostic of stress in the endoplasmic reticulum.

Carbohydrate Metabolism↗
PubMed2000

Using handheld computers to document family practice resident procedure experience.

BACKGROUND AND OBJECTIVES: We examined the use of inexpensive handheld computers in documenting resident procedures. With a handheld computer, data is entered at the time of the procedure, eliminating the problem of double entry. METHODS: Connectivity and ease of use were important factors considered when choosing a handheld computer. All residents received a handheld computer for data entry. Residency staff downloaded the data to a desktop computer. At the same time, data useful to residents was placed on their devices. The process of generating individual and program reports required 2 hours of staff time each month. Survey data regarding use and acceptance by residents was collected. RESULTS: Eighty-eight percent of residents collected data on their handheld computer. Those residents responding to a survey felt that the handheld computer was "very useful," and 73% reported daily use. Initial costs were $310 per resident. CONCLUSIONS: Handheld computers streamlined the collection of procedure data for family practice residents. Handheld computers assisted in producing timely and useful procedural reports for both residents and the residency program. Additional uses of handheld computers were beneficial to the program and the residents.

Computers↗
PubMed1999

Manipulation of S-adenosylmethionine decarboxylase activity in potato tubers. An increase in activity leads to an increase in tuber number and a change in tuber size distribution.

S-Adenosylmethionine decarboxylase (SAMDC; EC 4.1.1.50) is a key enzyme in the biosynthesis of the polyamines spermidine and spermine from putrescine and its activity is rate limiting in this pathway. Transgenic potato (Solanum tuberosum L. cv. Desiree) plants containing both sense and antisense SAMDC constructs driven by the tuber-specific patatin promoter have been generated and analysed. In sense transformants, developing tubers expressed higher steady-state levels of the SAMDC-specific transcript, had higher levels of SAMDC activity and contained significantly higher levels of spermidine than vector-transformed controls. Additionally, there was a significant shift in tuber size distribution with larger numbers of smaller tubers but no overall change in tuber yield. In developing tubers from the antisense transformed lines, there was a decrease in SAMDC transcript level, SAMDC activity and total polyamine levels. However, no obvious phenotypic effect was detected in the tuberisation physiology of the antisense lines.

Adenosylmethionine Decarboxylase↗
PubMed1999

Antisense raf oligodeoxyribonucleotide is a radiosensitizer in vivo.

Raf-1, a cytosolic protein serine/threonine kinase, plays important roles in cell growth, proliferation, transformation, and cell survival. The aim of the present study was to evaluate the radiotherapeutic efficacy of a fully phosphorothioated and well-characterized antisense raf oligodeoxyribonucleotide (ODN) corresponding to the 3'-untranslated region of human c-raf-1 mRNA (ISIS 5132/5132). Using our recently developed liposome encapsulation of ODN approach, we first compared the pharmacokinetic parameters of a liposomal formulation of 5132 (LE-5132) and 5132. The peak plasma concentrations 5 minutes after ODN administrations (30 mg/kg i.v.) were 28.5 microg/ml and 13.5 microg/ml for LE-5132 and 5132, respectively. The decrease in plasma concentration of LE-5132 and 5132 followed a biexponential pattern, with initial distribution half-lives (t1/2alpha) of 34.8 minutes and 21.6 minutes, respectively. The terminal half-lives (t1/2beta) with LE-5132 and 5132 were 14.5 hours and 4.3 hours, respectively. The area under the plasma concentration-time curve (AUC) was 5.8 times higher with LE-5132 than with 5132. Significantly higher intact ODN levels could be measured in most organs within 48 hours of administration of LE-5132 compared with 5132 (liver 18.4-fold, spleen, 31-fold, heart 3-fold, lungs 1.5-fold). In kidneys, the level was lower with LE-5132 (0.77-fold). LE-5132 composition, unlike 5132, did not affect clotting time in vitro. Significant decline in the level of Raf-1 protein was observed in vitro in relatively radioresistant human laryngeal squamous cell carcinoma cells (SQ-20B) treated with LE-5132 compared with SQ-20B cells treated with equimolar concentration of 5132 or liposome-encapsulated mismatched 5132 (0.5 microM LE-5132, 71.3%+/-22.5%; 1.0 microM LE-5132, 79.6%+/-16.7%). In addition, LE-5132 appeared to be a more potent antitumor compound than 5132 (p < 0.001). These data established the suitability of LE-5132 for in vivo radiotherapeutic efficacy studies. Intravenous administration of LE-5132 into SQ-20B tumor-bearing athymic mice inhibited Raf-1 expression in tumor tissue compared with blank liposome-treated or untreated control groups. LE-5132 or ionizing radiation (IR) treatment alone caused significant but transient inhibition of SQ-20B tumor growth but not tumor regression. Remarkably, a combination of LE-5132 and IR treatments led to significant and sustained tumor regression for at least 27 days after the last treatment (< 0.001). Histopathologic examination of tumor samples revealed a significant proportion of cells containing fragmented chromatin in the LE-5132 + IR treatment group as compared with single agent and untreated control groups. These in vivo data support the notion that Raf-1 has proliferative and survival functions and advance the scientific and technologic bases for the use of antisense raf ODN in the management of radioresistant malignancies.

3' Untranslated Regions↗
PubMed1996

Raising airway resistance in laryngectomees increases tissue oxygen saturation.

The physiological airflow resistance from the anterior nares to the upper trachea has recently been documented. This resistance is thought to be important in preventing alveolar collapse and in maintaining the optimum lung ventilation: perfusion ratio. This resistance is lost in laryngectomees who may have a subsequent decline in lung function and arterial oxygen saturation. A stoma filter with a resistance approximating to that of the normal upper airway has been developed and laryngectomees who wear this device demonstrate a rapid increase in tissue oxygen saturation (median increase: 1.4 kPa, P = 0.0087) without significantly altering tissue carbon dioxide saturation. This finding will have a major impact on the future rehabilitation of laryngectomees and those with a temporary tracheostomy.

Airway Resistance↗
PubMed1993

Long-term sulfamethoxazole-trimethoprim in Wegener's granulomatosis.

Since 1985, a number of reports have highlighted the effectiveness of a short course of sulfamethoxazole-trimethoprim as an adjuvant to immunosuppressive drugs in the treatment of Wegener's granulomatosis. We report our experience with long-term sulfamethoxazole-trimethoprim therapy in patients with Wegener's granulomatosis. We describe recent advances in the pathogenesis of Wegener's granulomatosis, suggest a complementary mechanism of action of sulfamethoxazole-trimethoprim, and advocate long-term sulfamethoxazole-trimethoprim therapy as a treatment option in Wegener's granulomatosis.

Adult↗
PubMed1993

Computerized tomography of acute, tender peritonsillar swellings.

A randomized trial involving 40 consecutive patients with an acute painful peritonsillar swelling was set up to determine if an enhanced computerized neck tomogram was cost-effective or improved patient management. Each patient was placed into one of two groups. The first group had enhanced computerized tomography (CT) which allowed precise identification of a quinsy and this was aspirated with an 18G needle aspiration at the site directed by the scan. The second group of patients had 3-point permucosal 18G needle aspirations. A proportion of patients from each group, but primarily from the second, required immediate or delayed admission to hospital after aspiration, for persistent or recurrent symptoms. Costing each groups treatment, including the scan and hospitalization on intravenous antibiotics, we conclude that CT scanning prevents the morbidity associated with unsuccessful attempts at drainage in the patient with cellulitis and ensures complete drainage of pus, thereby optimizing patient treatment and it is cost-effective.

Biopsy, Needle↗
PubMed1992

Metastatic cervical lymph nodes: general practitioner referral patterns.

Premature excision biopsy of a cervical lymph node infiltrated by metastatic carcinoma may compromise patient survival since it is associated with an increased incidence of local wound recurrence and distant metastases. Seventy per cent of such patients have an identifiable head and neck primary, obviating the need for an excision biopsy. It is important therefore that they are examined by surgeons who are experienced in inspecting the upper aerodigestive tract and who are competent in performing definitive head and neck surgery. A questionnaire sent to all general practitioners of an Inner London and a District Health Authority revealed that only 18% and 33% respectively referred patients who they suspected of having a metastatic neck node to a department with an experienced head and neck surgeon. We conclude that greater emphasis on the correct management of these patients at both an undergraduate and postgraduate level may encourage subsequent generations of general practitioners to review their referral patterns.

Adult↗
PubMed1991

FDA fast-tracking of pet population control drugs.

Theriogenologists have been studying estrus prevention and termination of pregnancy in dogs for at least 2 decades. However, drugs approved for estrus suppression are few. No dog or cat abortifacients or male dog and cat sterilants have been approved. Marketed drugs with alternate indications that have antiestrus and antihormonal activity might be good candidates for study after obtaining an INAD from FDA. With the support of the original drug sponsor or manufacturer and appropriate safety and effectiveness studies, these products may be studied for additional label claims. New (not previously approved) drugs additionally need detailed information regarding the synthesis and manufacturing controls. Drugs offering substantial benefit over existing therapeutics may be eligible for expedited review. Prior to starting any studies in this area, clinical investigators and sponsors should communicate with FDA, an INAD must be granted, and the protocol submitted for evaluation. Approvability is evaluated after establishment of safety and effectiveness in clinical field trials.

Abortifacient Agents↗
PubMed1991

Massive haemorrhage from the vallecula: a diagnostic difficulty. Case report.

A case is presented of massive bleeding from a vessel in the vallecula. This was confused with haemoptysis and haematemesis. The bleeding may have resulted from trauma to the vessel during intubation for emergency surgery. 25 units of blood were transfused before the site of the bleeding was identified and controlled by diathermy coagulation.

Diagnosis, Differential↗
PubMed1990

Severe tissue destruction in the ear caused by alkaline button batteries.

Button batteries spontaneously leak corrosive electrolyte solution on exposure to moisture. Tissue in contact with such solution will undergo liquefaction necrosis. Three cases of skin, bone and tympanic membrane necrosis caused by a leaking button battery lodged in the external auditory meatus are described.

Aged↗
PubMed1990

Biopsy of neck lumps in adults should be preceded by examination of the upper aerodigestive tract.

Premature biopsy of a potentially malignant neck node compromises patient survival. Despite documented evidence that biopsy of a malignant neck mass prior to a search for a primary source will increase the incidence of regional recurrence and distance metastasis, patients are often referred for head and neck assessment having already had a positive neck node biopsy. We maintain that biopsy of an asymmetrically enlarged cervical lymph node in an adult should be preceded by full upper aerodigestive tract evaluation to include indirect laryngoscopy, a high resolution computed tomography scan and panendoscopy with free field biopsy.

Aged↗
PubMed1989

Button batteries in the ear, nose and cervical esophagus: a destructive foreign body.

Button batteries spontaneously leak alkaline electrolyte solution on exposure to moisture, causing liquefaction necrosis of adjacent tissue. We describe two cases in which a button battery in the external auditory meatus caused skin, bone and tympanic membrane necrosis. Review of the world literature on button batteries acting as foreign bodies reveals lower motor neurone facial nerve palsy, nasal septal perforation and fatal esophago-aortic fistula as among the ENT complications. Batteries lodged in these sites must be removed as a matter of the utmost urgency.

Alkalies↗
PubMed1989

Aspiration of middle ear effusions prior to grommet insertion an etiological factor in tympanosclerosis.

Fifty-five children with bilateral middle ear effusions were entered into a prospective randomized double blind trial to determine whether aspiration of middle ear effusions prior to ventilation tube insertion influences ventilation tube extrusion time or the development of tympanosclerosis. Following myringotomy, aspiration of the left or right ear only was performed randomly prior to ventilation tube insertion. The tympanic membranes were inspected six-monthly to determine whether ventilation tube extrusion had occurred, and at 24 months after surgery for the presence of tympanosclerosis. Results showed no significant difference in extrusion time between aspirated and non-aspirated ears. Aspiration was found to be a factor in the development of tympanosclerosis. We conclude that routine aspiration of the middle ear effusion prior to ventilation tube insertion is associated with an increased risk of tympanosclerosis.

Child↗
PubMed1987

Dose-volume and complication in interstitial implants for breast carcinoma.

A common radiotherapeutic technique for treating breast cancer is the combination of external beam radiation with an interstitial iridium-192 boost. When smaller tumors (T1 and T2) are treated using this technique, the soft tissue complication rate is small. However, with treatment of more advanced stages of disease, where large volumes of breast tissue must be treated to high radiation doses, the incidence of complication increases. This paper investigates the dose and volume relationships for breast tissue treated by interstitial technique and correlates this to the risk of soft tissue radiation injury. A method of analysis of interstitial radiation implants suitable for intra- or inter-institutional clinical evaluations is offered. The records of 111 patients treated at Georgetown University Hospital, were retrospectively analyzed and the five who had experienced radiation-related complications were compared to 51 randomly selected patients experiencing no complications. The volumes of tissue enclosed by selected isodose surfaces were calculated and used to determine a relationship between these dose-volumes and the probability of complication. The mean volume at specified dose levels between 10 Gy and 50 Gy was significantly higher (p less than .05) for the patients developing complications than those in whom no complications were seen. Using the 20 Gy isodose surface as defining our usual treated volume, a complication probability versus dose-volume curve was developed using a linear logistic model. The curve fitted the data closely (p less than .006) suggesting that, for our cases, the calculated treatment volume (within the 20 Gy isodose surface) can be used to effectively separate patients into groups that have different probabilities of developing complications. We propose this method as a basis for specification of dose and volume which can be used for clinical risk assessment, and for intra- and inter-institutional comparison.

Brachytherapy↗