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Biomedical subjects

B N Johnson

Publications and source records attributed to B N Johnson.

9 recordsLinked to original sources
PubMed2001

Orbital response indicates nasal pungency: analysis of biomechanical strain on the skin.

Stimulation of the human nasal passage with pungent vapor elicits motor responses in a zone around the eye. This investigation addressed whether quantification of such responses, particularly activity of the orbicularis oculi muscle, could yield a sensitive index of nasal pungency. We placed an array of small, high-contrast targets just beneath the lower eyelid and videotaped their movement to capture deformation of the skin atop the orbicularis oculi during 3 s stimulation with pungent concentrations of ethyl acetate. Eleven subjects participated. Analysis of the movements served to determine mechanical strain, which yielded a single index that we termed 'maximum strain'. This increased with concentration of the vapor and with time during and just after stimulation. Comparison with psychophysical data showed that the strain became evident at concentrations just detectable as pungent. Maximum strain measured on the skin shows promise as an objective index of pungency.

Adult↗
PubMed1998

An integrated nanoliter DNA analysis device.

A device was developed that uses microfabricated fluidic channels, heaters, temperature sensors, and fluorescence detectors to analyze nanoliter-size DNA samples. The device is capable of measuring aqueous reagent and DNA-containing solutions, mixing the solutions together, amplifying or digesting the DNA to form discrete products, and separating and detecting those products. No external lenses, heaters, or mechanical pumps are necessary for complete sample processing and analysis. Because all of the components are made using conventional photolithographic production techniques, they operate as a single closed system. The components have the potential for assembly into complex, low-power, integrated analysis systems at low unit cost. The availability of portable, reliable instruments may facilitate the use of DNA analysis in applications such as rapid medical diagnostics and point-of-use agricultural testing.

Costs and Cost Analysis↗
PubMed1998

Isotachophoretic separations on a microchip. Normal Raman spectroscopy detection.

Isotachophoretic separations of the herbicides paraquat and diquat are performed in a glass microchip etched channel and monitored on-chip by normal Raman spectroscopy. The 40-micron-wide and 75-micron-deep separation channels are chemically etched in a serpentine design to 21-cm total length. A 120-micron-thick glass cover slip is used to seal the channels. Separation field strengths up to 380 V/cm are used. The microchip is directly coupled to a Raman microprobe. No interfacing is required. Raman spectra are generated with a 2-W, 532-nm NdY-VO4 laser and collected at 8-cm-1 resolution with a holographic transmissive spectrograph and a cryogenically cooled CCD. Data acquisition is at 2-5 spectra/s. Raman isotachopherograms of the pesticides at starting concentrations as low as 2.3 x 10(-7) M (60 ppb paraquat/80 ppb diquat) are presented.

Diquat↗
PubMed1997

Applicability of VO2max criteria: discontinuous versus continuous protocols.

This study compared the classic discontinuous Taylor et al. (1955) protocol to a continuous version of the same protocol to evaluate maximal physiological responses, and the quantitative values and incidence of achievement of the various maximal oxygen uptake (VO2max) criteria in 10 males (24.1 +/- 2.5 yr). Criteria were a plateau in VO2 (change < 2.1 ml.kg-1.min-1), HR = age adjusted maximal, PER > or = 1.15, and lactate > 8 mmol.l-1. Values for VO2max (56.8 +/- 4.7 vs 55.8 +/- 4.2 ml.kg-1.min-1), ventilation (150.7 +/- 16 vs 149.5 +/- 17.5 l.min-1 BTPS), and HR (186.3 +/- 7.7 beats.min-1 vs 191.7 +/- 6.7 beats.min-1) were similar (P < 0.05) between the discontinuous protocol (DT) and the continuous protocol (CT), respectively. Values for RER (1.28 +/- 0.05 vs 1.22 +/- 0.05) and lactate (14.3 +/- 2.7 vs 11.9 +/- 2.7 mmol.l-1) were greater (P < 0.05) on the DT than the CT. Criteria achievement were the following: 40% (CT) and 10% (DT) for HR; 50% (CT) and 60% (DT) for a VO2 plateau; and, 90% (CT) and 100% (DT) for RER and lactate. It is concluded that a VO2 plateau is not a prerequisite for defining VO2max and is of limited use as the primary objective criterion for evaluating the quality of a graded exercise test. Therefore, the achievement of secondary objective criteria, specifically RER and lactate in combination, increases the likelihood that the highest VO2 value achieved is VO2max.

Adult↗
PubMed1992

Construction of Salmonella strains with both antigen O4 (of group B) and antigen O9 (of group D).

A Salmonella live vaccine causing both O4- and O9-specific immune responses would be of use, but no reported Salmonella serotype has both of these O antigens. Constructed Salmonella typhimurium strains with an rfb (O-antigen-specifying) gene cluster of type D in the chromosome and one of type B in an F'-rfb+ factor, and those with the reverse combination reacted strongly with both anti-O4 (and anti-O5) and anti-O9 sera and, if they carried recA, could be maintained in this state by growth conditions selective for retention of the F' factor. One of the two B.rfb+ gene clusters of a (P22-lysogenic) S. typhimurium strain with a tandem duplication of a chromosomal segment including hisD and B.rfb+ was replaced (by transduction) by a D.rfb+ gene cluster; the resulting strain was O1+ O4+ O5+ O9+ and stable as such after being made recA. A stable O4+ O9+ derivative of a virulent S. enteritidis (O-group D) strain was made by transducing into it first the join point of an appropriate tandem duplication strain, together with the adjacent B.rfb+ gene cluster, and then srl::Tn10 recA.

Cloning, Molecular↗
PubMed1992

Structural and immunochemical studies of the lipopolysaccharides of Salmonella strains with both antigen O4 and antigen O9.

Two Salmonella hybrid strains, SL5313 (Salmonella typhimurium with a D.rfb+ gene cluster) and SL5396 (S. enteritidis with a B.rfb+ gene cluster), each expressing both O-antigen 4 (of serogroup B) and O-antigen 9 (of serogroup D) were studied by immunofluorescence using a mixture of O4-specific mouse monoclonal and O9-specific rabbit polyclonal antibodies. Bound antibodies, detected by anti-mouse antibody labelled with fluorescein isothiocyanate and anti-rabbit antibody labelled with tetramethylrhodamine isothiocyanate showed that more than 98% of the bacteria expressed both the O4 and O9 epitopes. Phenol-water-extracted lipopolysaccharide from batch-grown cultures subjected to sugar and methylation analyses by gas-liquid chromatography and mass spectrometry were shown to contain abequose (of the O4 epitope) and tyvelose (of the O9 epitope) in ratios of 1:1.5 and 1:2.5 for SL5313 and SL5396, respectively. Isolated polysaccharide chains, obtained by weak-acid hydrolysis of the lipopolysaccharides, were found to contain both O4 and O9 specificities in the same molecule, since polysaccharide bound to O4 antibody attached to a solid-phase-adsorbed O9-specific antibody and vice versa. This demonstrates that in strains SL5313 and SL5396 O chains containing both O4 repeating units (from S. typhimurium) and O9 units (from S. enteritidis) are present.

Antibodies, Bacterial↗
PubMedDate not supplied

Histochemical and morphological identification of Kupffer cells activated by cisplatin.

Cisplatin is a potent anti-cancer agent which has been shown to activate Kupffer cells. These activated macrophages demonstrate an increase in extensions, lysosomes, and peroxisomes increasing their anti-tumor activity. Wistar rats were treated with cisplatin (9 mg/kg) and sections of liver were excised for light and electron microscopic analysis at 1, 6, 15, and thirty days post treatment. Non-specific esterase staining was used to differentiate Kupffer cells using light microscopy, morphologic criteria were used for TEM analysis. Liver sections taken 6 days post treatment showed the greatest number of activated macrophages, with the highest degree of activation. Interaction between natural killer cells and Kupffer cells was only seen 6 days post treatment. These results show that cisplatin's ability to enhance the immune system requires several days post treatment to reach maximum potency.

Animals↗