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Biomedical subjects

David Fisher

Publications and source records attributed to David Fisher.

7 recordsLinked to original sources
PubMed2004

Direct determination of lead isotopes (206Pb, 207Pb, 208Pb) in arctic ice samples at picogram per gram levels using inductively coupled plasma-sector field MS coupled with a high-efficiency sample introduction system.

Adopting strict cleanroom procedures, ice samples from the Canadian High Arctic have been analyzed for Pb concentrations and Pb isotopes (206Pb, 207Pb, 208Pb) using ICP-SMS. The detection limit for Pb (0.06 pg g(-1)) was approximately 2 orders of magnitude lower than the lowest concentration of Pb in the ice samples (range, 4.3-1660 pg g(-1); median, 45 pg g(-1)). Acidification of ice samples with high-purity HNO3 for stabilization purposes contributed only 0.004 pg of Pb g(-1), which is an insignificant source of Pb. Using a new sample introduction system consisting of a heated (140 degrees C) minicyclonic spray chamber and a Peltier cooled condenser (2 degrees C) and by replacing the conventional sample cone with a high-performance cone, signal intensities for Pb were increased by approximately 1 order of magnitude. Thus, it was possible not only to measure Pb isotope ratios directly using ICP-SMS but also to achieve reasonable precision (approximately 0.2%) at low picogram per gram concentrations of total Pb. This precision is comparable to that achievable by thermal ionization mass spectrometry at such low Pb concentrations, but the ICP-SMS requires much less sample volume (approximately 2 mL), needs no sample pretreatment, and therefore is considerably faster and less expensive than the conventional approach. Even though absolute Pb concentrations in two ice samples dating from 1974 and 1852 were very similar (9 and 6 pg g(-1)) their fundamentally different isotopic signature (206Pb/207Pb: 1.169 +/- 0.002 vs 1.147 +/- 0.003) clearly indicates different sources of Pb. The analytical procedures described here, therefore, offer great promise for fingerprinting the predominant sources of atmospheric Pb in polar snow and ice.

Journal Article↗
PubMed2003

Cytologic diagnosis of peritoneal cestodiasis in dogs caused by Mesocestoides sp.

BACKGROUND: Canine peritoneal larval cestodiasis caused by tapeworm larvae of the genus Mesocestoides is an uncommon and possibly fatal disease that can result in ascites and peritonitis. Although abdominal fluid analysis is recommended for dogs with ascites, the cytologic features of Mesocestoides infection have not been described fully. OBJECTIVE: Our goal was to describe the cytologic features of Mesocestoides larvae and of associated ascitic fluid that was collected from the peritoneal cavity of 4 infected dogs. METHODS: Abdominal fluid was obtained from 4 dogs with Mesocestoides sp infection. Gross, chemical, and microscopic evaluations of the fluid were performed using standard techniques. RESULTS: Cytologic findings in 1 dog included intact acephalic metacestodes (larvae without 4 suckers, not tetrathyridia) in various stages of asexual development, whereas fluid from the other 3 dogs contained primarily calcareous corpuscles, remnant tissue specific to cestodes. Abdominal fluid typically was an exudate, with suppuration, hemorrhage, and evidence of necrosis. Total protein concentrations ranged from 2.4 to 5.3 g/dL. CONCLUSIONS: Abdominal fluid cytology was useful in the diagnosis of Mesocestoides larval infections in the peritoneal cavity of dogs with ascites. Observation of characteristic calcareous corpuscles or intact metacestodes can provide a definitive diagnosis of canine peritoneal larval cestodiasis in dogs.

Animals↗
PubMed2003

Dose range checking in a computer order entry system.

We recently implemented a computer order entry (COE) system which uses decision support for dose range checking. In addition to providing decision support at the point of order entry via "alerts", the system tracks data regarding the occurrence of alerts related to dosing errors. We reviewed the dosing alerts for a "high risk" medications in a COE system. Telephone alerts were more likely to trigger alerts. There were more low dose than high dose alerts. Some alerts could be avoided by adjusting the threshold.

Drug Therapy, Computer-Assisted↗
PubMed2002

Establishment of a bone-anchored auricular prosthesis (BAAP) program.

OBJECTIVE: Bone-anchored auricular prostheses (BAAPs) are indicated for treatment of congenital or acquired microtia in children. This paper reports on our experience in establishing a BAAP program, including treatment algorithms, protocols and a discussion of the methodology, complications and patient satisfaction. METHODS: Eleven consecutive children using BAAPs were reviewed. Outcome measures include patient selection criteria, long-term stability of the BAAP, skin reactions around the site, and patient satisfaction. RESULTS: A patient selection program was developed and implemented, followed by a management protocol for surgery and follow-up. All children (100%) achieved osseointegration, with only one site revision necessary. A variable degree of skin irritation was noted in just over one third (39%) of cases. All children were satisfied with their prosthesis. CONCLUSIONS: The use of BAAPs in a pediatric population is a safe and viable method to correct disfiguring microtia. The final result is generally very acceptable to the child.

Adolescent↗
PubMed2002

New light shed on fluid formation in the seminiferous tubules of the rat.

In this study the effects of perfusing isolated seminiferous tubules of the testes are reported for the first time. Initial perfusion studies (fast rate perfusion) resulted in gross morphological damage to the seminiferous tubules. The recorded transepithelial potential (V(t)) was close to 0 mV. Slow perfusion rates eliminated morphological damage to the perfused tubules. These tubules exhibited a V(t) of -5.4 +/- 1.8 mV which was significantly different (P < 0.0001) from tubules that were perfused at a fast rate. Additional non-perfusion electrophysiological experiments (oil-gap and agar probe techniques) provided the confirmation that tubules not morphologically compromised produced a higher V(t) which was not statistically different (P < 0.0001) from slowly perfused tubules. A revised hypothesis on fluid secretion is postulated. In brief, that the seminiferous tubule is solely responsible for the production of its luminal fluid. This hypothesis is contrary to the long standing 'Tuck' hypothesis which suggested that the source of luminal fluid in the seminiferous tubule originated from secretions of Sertoli cells as well as from distal testicular structures, e.g. the rete testis.

Aerobiosis↗
PubMed2002

The melanocyte-specific isoform of the microphthalmia transcription factor affects the phenotype of human melanoma.

The microphthalmia transcription factor MITF plays a pivotal role in the development and differentiation of melanocytes. The purpose of this work was to investigate the expression and function of the melanocyte-specific isoform MITF-M in human melanoma. We found that MITF-M is repressed in 8 of 14 established melanoma cell lines tested. Transfection of MITF-M into a melanoma cell line (518A2) lacking the M-isoform and into a permanent cell line established from normal melanocytes (NMel-II) resulted in slower tumor growth in a severe combined immunodeficient-mouse xenotransplantation model. The growth difference between vector control-transfected tumors derived from the NMel-II cell line (mean tumor weight +/- SD, 3.2 g +/- 1.13) and MITF-M (+) transfectants (mean tumor weight +/- SD, 1.1 g +/- 0.49) was significant (P = 0.018). The mean tumor weight of control-transfected 518A2 tumors was 0.99 g +/- 0.22 and of MITF-M (+) transfectants, 0.69 g +/- 0.32. The difference in growth between 518A2 controls and the MITF-M (+) transfectants was clear, however it did not reach statistical significance (P = 0.08). In addition to the growth-inhibitory effects, MITF-M expression led to a change in the histopathological appearance of tumors from epitheloid toward a spindle-cell type in vivo. These results indicate a role for the MITF-M isoform in the in vivo growth control and the phenotype of human melanoma. In conclusion, MITF-M may qualify as a marker capable of identifying subgroups of melanoma patients with different tumor biology and prognosis.

Animals↗