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Biomedical subjects

P McAllister

Publications and source records attributed to P McAllister.

13 recordsLinked to original sources

Medical device regulation for manufacturers.

Manufacturers of medical devices are held to a higher standard than manufacturers of many other products due to the potential severity of the consequences of introducing inferior or unsafe products to the market-place. In Canada, the medical device industry is regulated by Health Canada under the Medical Device Regulations of the Food and Drug Act. The Medical Device Regulations define requirements of medical device design, development and manufacture to ensure that products reaching the public are safe and effective. Health Canada also requires that medical device manufacturers maintain distribution records to ensure that devices can be traced to the source and consumers can be contacted successfully in the event that a device is recalled. Medical devices exported from Canada must be compliant with the regulations of the country of import. The Canadian Medical Device Regulations were based on the Medical Device Directives of the European Union thus facilitating approval of Canadian devices for the European market. The United States Food and Drug Administration has separate and distinct requirements for safety and quality of medical devices. While effort has been made to facilitate approval and trade of Canadian medical devices in the United States and the European Union, obtaining approval from multiple regulatory bodies can result in increased device development time and cost. The Global Harmonization Task Force is an organization composed of members from Japanese, Australian, European, Canadian and American medical device regulatory bodies. This organization was formed with the objective of harmonizing medical device regulations in an effort to facilitate international trade and standardize the quality of medical devices available to all countries. This paper discusses the requirements that must be met by manufacturers when designing and manufacturing medical devices.

Canada↗

Setting system suitability criteria for detectability in high-performance liquid chromatography methods using signal-to-noise ratio statistical tolerance intervals.

For pharmaceutical products, one approach developed to assure that different chromatographic systems are capable of generating valid results is the system suitability test. Typically, a system suitability test involves numerical limits for predefined chromatographic parameters such as theoretical plates, tailing factor, injector reproducibility, etc. An estimation of the ratio of signal compared to baseline is one way to measure system performance, according to a valid method, independent of the instrument. However, since this comparison relates the height of the signal to the height of the noise, it is difficult to relate to the peak area measurements that are typically used for quantification of samples. Additionally, although peak area and peak height may be highly correlated over a wide region, peak area at very low concentrations can be more sensitive to all components of noise due to peak shape. To establish a system suitability criterion, one can use the ratio of the area signal to the baseline noise for replicate injections for samples prepared at concentration equal to the limit of quantitation during the validation studies. A lower limit for this ratio can be derived using statistical tolerance intervals. This lower limit can be applied as a system suitability criterion to measure that any system is performing adequately for measuring low level components in the sample for all future use of the method.

Chromatography, High Pressure Liquid↗

The effect of regional gene therapy with bone morphogenetic protein-2-producing bone-marrow cells on the repair of segmental femoral defects in rats.

BACKGROUND: Recombinant human bone morphogenetic proteins (rhBMPs) can induce bone formation, but the inability to identify an ideal delivery system limits their clinical application. We used ex vivo adenoviral gene transfer to create BMP-2-producing bone-marrow cells, which allow delivery of the BMP-2 to a specific anatomical site. The autologous BMP-2-producing bone-marrow cells then were used to heal a critical-sized femoral segmental defect in syngeneic rats. METHODS: Femoral defects in five groups of rats were filled with 5 x 10(6) BMP-2-producing bone-marrow cells, created through adenoviral gene transfer (twenty-four femora, Group I); twenty micrograms of rhBMP-2 (sixteen femora, Group II); 5 x 10(6) beta-galactosidase-producing rat-bone-marrow cells, created through adenoviral gene transfer of the lacZ gene (twelve femora, Group III); 5 x 10(6) uninfected rat-bone-marrow cells (ten femora, Group IV); or guanidine hydrochloride-extracted demineralized bone matrix only (ten femora, Group V). Guanidine hydrochloride-extracted demineralized bone matrix served as a substrate in all experimental groups. Specimens that were removed two months postoperatively underwent histological and histomorphometric analysis as well as biomechanical testing. RESULTS: Twenty-two of the twenty-four defects in Group I (BMP-2-producing bone-marrow cells) and all sixteen defects in Group II (rhBMP-2) had healed radiographically at two months postoperatively compared with only one of the thirty-two defects in the three control groups (beta-galactosidase-producing rat-bone-marrow cells, uninfected rat-bone-marrow cells, and guanidine hydrochloride-extracted demineralized bone matrix alone). Histological analysis of the specimens revealed that defects that had received BMP-2-producing bone-marrow cells (Group I) were filled with coarse trabecular bone at two months postoperatively, whereas in those that had received rhBMP-2 (Group II) the bone was thin and lace-like. Defects that had been treated with bone-marrow cells producing beta-galactosidase (Group III), uninfected bone-marrow cells (Group IV), or guanidine hydrochloride-extracted demineralized bone matrix only (Group V) demonstrated little or no bone formation. Histomorphometric analysis revealed a significantly greater total area of bone formation in the defects treated with the BMP-2-producing bone-marrow cells than in those treated with the rhBMP-2 (p = 0.036). Biomechanical testing demonstrated no significant differences, with the numbers available, between the healed femora that had received BMP-2-producing bone-marrow cells and the untreated (control) femora with respect to ultimate torque to failure or energy to failure. CONCLUSIONS: This study demonstrated that BMP-2-producing bone-marrow cells created by means of adenoviral gene transfer produce sufficient protein to heal a segmental femoral defect. We also established the feasibility of ex vivo gene transfer with the use of biologically acute autologous short-term cultures of bone-marrow cells.

Animals↗

Postoperative magnetic resonance imaging with titanium implants of the thoracic and lumbar spine.

Within recent years, the technologies of radiological imaging and spinal instrumentation have exponentially increased. New methods of preoperative imaging, that is, magnetic resonance imaging (MRI) and computed tomography, have allowed for a better understanding of surgical pathology. Such an understanding is likely to lead to a more successful surgical experience, which certainly is the case with spine surgery with instrumentation. However, after implantation of most instrumentation, imaging is greatly impaired. Metallurgic advancements in titanium were sought to reduce postoperative imaging problems. The purpose of this study is to assess the presence and extent of artifacts seen on postoperative MRI scans in patients with titanium spinal implants. Six patients, four with degenerative spine disease and two with neoplasms, had thoracic and/or lumbar spinal fixation performed with titanium instrumentation. All patients underwent postoperative conventional MRI with the use of T1-weighted, T2-weighted, and gradient-echo sequences. The scans and individual sequences were then analyzed for image quality. A progressive and significant increase in imaging artifact related to the titanium spinal instrumentation was observed on the T1-weighted, T2-weighted, and gradient-echo sequences. Titanium spinal instruments do not allow optimal postoperative imaging on conventional MRI scanners.

Adult↗

Intracerebral hematoma related to thrombolysis for myocardial infarction.

The incidence of intracerebral hematomas after myocardial infarction increases after thrombolysis. As noted in the case described, clots formed after the administration of thrombolytic agents may remain liquid, and this blood can be drained by a catheter. However, in this case, the patient continued to bleed locally. This problem requires the development of methods to stop such ongoing local bleeding. It may be prevented in the future by improved thrombolytic drugs.

Aged↗

A comparison study of human papillomavirus prevalence by the polymerase chain reaction in low risk women and in a gynaecology referral group at elevated risk for cervical cancer.

The reported prevalence of human papillomavirus (HPV) type 16 in the genital tracts of women with various gynaecological conditions is highly variable. In particular, some results with the polymerase chain reaction (PCR) technique have suggested that HPV-16 is a ubiquitous or very common virus. We undertook this study to help clarify the current confusion. PCR with HPV consensus L1 primers and specific E6 primers was used to study 89 women attending two gynaecology referral clinics, as well as 99 women attending a health maintenance organization (HMO) clinic; 70 of these latter women had no current or prior history of genital HPV disease. HPV-16 was detected in less than 5% of cytologically normal women from either group and in 17% (6/36) and 31% (9/29) of women with cervical intraepithelial neoplasia (CIN) from the referral clinic and the HMO, respectively. The other high-risk or intermediate-risk HPVs (types 18, 31, 33 or 35) were less prevalent than HPV 16 in all groups of women. A majority of the HPV types detected by the L1 primers in normal women were uncharacterized HPVs. Overall these uncharacterized HPVs were detected in 37% (46/123) of the normal women and in 48% (31/65) of the women with CIN. Using the most sensitive PCR product detection method employed in the study, HPV DNA was detected in 36% (4/11) of swab specimens obtained from the external abdomen.

Base Sequence↗

Chronic extradural haematomas: indications for surgery.

Non-invasive neuro-imaging has led to the detection of minimally symptomatic or asymptomatic chronic extradural haematomas. Our experience and review of the literature suggests that, as in the case of chronic subdural haematomas, there is development of membranes and liquifaction of the clot which may permit drainage of such collections through twist drill or burrholes. The time from development and the neuro-imaging chanes on CT and MRI can suggest the age and nature of the clot and thus permit timing of surgery so that drainage may be accomplished with a minor procedure.

Adult↗

Human papillomavirus type 56: a new virus detected in cervical cancers.

A new human papillomavirus type (HPV-56) was identified by low stringency Southern blot analysis with an HPV-31 DNA probe, in a cervical intraepithelial neoplasm (CIN). The DNA of this virus was molecularly cloned and shown to be a new HPV type based on the absence of cross-reactivity to HPV types 1 to 55 under high-stringency hybridization conditions. At low stringency, HPV-56 was most related to HPV types 30 and 45. The deduced organization of the open reading frames of HPV-56, from hybridization and partial nucleotide sequence analyses, reveals a typical HPV genome. HPV-56 was detected in two of 464 normal cervical tissues, in five of 227 cervical condylomas and CIN, and in two of 84 invasive cancers of the cervix.

Amino Acid Sequence↗