Biomedical subjects

D Hansen

Publications and source records attributed to D Hansen.

166 records · Page 10Linked to original sources

PubMedDate not supplied

Nicotine increases ciliary beat frequency by a direct effect on respiratory cilia.

We studied the direct effects of nicotine on the ciliary beat frequency (CBF) undisturbed by interference from mucus secretion by using epithelial strips from ferret tracheae which contain no goblet cells and, because the glands were left behind in the submucosa, no gland tissue either. Strips were studied in a chamber perfused with medium M-199 at 37 degrees C at a perfusion rate of 1.6 ml min-1 using a perfusion pump (Braun, Melsungen). CBF was determined photometrically, the signal being subjected to a fast Fourier transformation. We measured CBF continuously for 10 min (5 min with and 5 min without perfusion). Under baseline conditions without nicotine, it decreased from 23.4 +/- 0.8 to 22.2 +/- 0.5 Hz during perfusion and increased from 22.0 +/- 0.8 to 23.3 +/- 0.8 Hz during the subsequent period without perfusion. Nicotine increased CBF transiently, i.e., the effect was demonstrable only during perfusion, being strongest during the first 3 min of perfusion. At 10(-5) M, the increase in CBF was significant only during the 3rd minute, but at 10(-4) and 10(-3) M, CBF was elevated significantly throughout most of the perfusion period compared with control tissues perfused with medium M-199 only. Thus, at 2 min, CBF was 22.8 +/- 0.6 (mean +/- SE) in tissues perfused with medium M-199 only but was 24.3 +/- 0.8 Hz (NS, Student's unpaired t-test), 26.6 +/- 0.5 Hz (P = 0.001), and 26.8 +/- 1.2 Hz (P = 0.01) in tissues perfused with 10(-5), 10(-4), and 10(-3) M nicotine (dissolved in medium M-199), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMedDate not supplied

The acute and chronic toxicity of ammonia to marine fish and a mysid.

The acute toxicity (96-hr LC50) of un-ionized ammonia to mysids (Mysidopsis bahia) and larval inland silversides (Menidia beryllina) was influenced by pH and salinity in a species specific manner. With mysids, NH3 was most toxic at pH 7.0 and less toxic at pH 8.0 and 9.0. In contrast, NH3 toxicity to inland silversides was greatest at pH 7.0 and 9.0 and lowest at pH 8.0. A drop in salinity from 31 g/kg to 11 g/kg uniformly increased toxicity to mysids over this pH range. In contrast, in silversides at 11 g/kg, NH3 toxicity was less at pH 7.0, greater at pH 8, and slightly less at pH 9, relative to the toxicity at 31 g/kg. Temperature had no significant effect on the acute toxicity of un-ionized ammonia with acclimated mysids tested at 18, 25 and 32.5 degrees C, but did have a small effect with acclimated larval sheepshead minnows (Cyprinodon variegatus) tested at 13, 25 and 32.5 degrees C. The chronic toxicity value (the geometric mean of the highest no-effect concentration and lowest effect concentration) at pH 8.0, 25 degrees C and 31 g/kg salinity is 0.061 mg NH3/L for inland silversides and 0.232 mg NH3/L for mysids; the acute:chronic ratio is 21.3 and 7.2, respectively.

Ammonia↗

PubMedDate not supplied

Cyanoguanidine CHS 828 induces programmed cell death with apoptotic features in human breast cancer cells in vitro.

The cyanoguanidine CHS 828 was recently shown to possess potent anti-tumour effects both in vitro and in vivo. The exact mechanism of action of CHS 828 is not known, but recent results have indicated that induction of programmed cell death may be one mechanism by which CHS 828 exerts its anti-tumour effects. To investigate this aspect in more detail, we studied the effect of CHS 828 and the reference compound Taxol beta on programmed cell death in human breast cancer cells in vitro. Both compounds were found to induce DNA fragmentation in the cells. However, microscopic examination of the cells demonstrated that CHS 828 and Taxol triggered different types of cell death. In the CHS 828-treated cultures most cells were found to be Annexin-V positive, indicating that these cells were early apoptotic cells, while no morphological characteristics of classical apoptosis were seen. In contrast, the cells in the Taxol-treated cultures displayed morphological features characteristic of classical apoptotic cells, but no Annexin-V positive cells could be observed. These findings together with the previously reported potent effects of CHS 828 on tumour cells, makes CHS 828 a promising new agent for the treatment of cancer patients.

Annexin A5↗

PubMedDate not supplied

The National Workshop to Develop the Chiropractic Research Agenda.

OBJECTIVE: To convene a national meeting to develop a research agenda for the chiropractic profession that targets the need to increase chiropractic's research capacity. DESIGN: The project was funded by a contract between the U.S. Health Resources and Services Administration Bureau of Health Professions (HRSA BHPr) and Palmer College of Chiropractic. Groundwork was established through a literature review and creation of position papers by teams of recognized authorities on the current status and recommendations for the future on the topics of clinical, educational, outcomes, basic science, and health services research and research infrastructure in chiropractic. The workshop took place July 12-14, 1996, in Washington, DC, with participants representing relevant segments of the research community of the health care professions, health professions education, health care policy, and all portions of the chiropractic community, including researchers, practitioners, faculty, administrators, and members of professional organizations. Work groups in each of the five target areas developed recommendations based on the seed material presented in the position papers. The results were incorporated into the final position papers. RESULTS: The primary outcome of the workshop was the completion of five position papers, one for each of the topics addressed. Also, a consensus process was initiated at the workshop on infrastructure needs of the profession but, because of the diversity of experience and opinions and the broad scope of the topic, was not completed by the end of the project year. CONCLUSIONS: Consensus was not reached on the development of a research agenda for the chiropractic profession, and a continuation of the contract has been agreed upon by HRSA BHPr to continue the process for another project year.

Chiropractic↗