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Biomedical subjects

T Schaefer

Publications and source records attributed to T Schaefer.

30 records · Page 2Linked to original sources
PubMed1994

Study of drug distribution in hair by infrared microscopy visualization.

Infrared microscopy has been shown to be a unique method of analysis for drugs-of-abuse determinations in hair, with the ability to analyze only the central core, or medulla region, of sectioned hair. By spectrally mapping infrared functional groups related to the various drugs, a three-dimensional image of the drug location can be obtained from cross-sectional and laterally microtomed hairs. This technique eliminates the question of externally contaminated hair by analyzing only that portion of the hair that is formed from within the root where ingested material would be transported. Results from these tests have shown a direct correlation between drug and medulla presence in the hair. There are occasional occurrences of drug in nonmedullated hair, but the drug distribution across the hair is entirely different in these cases. Spiked or doped hair has been shown to be the exact opposite of drug-ingested hair; the drugs spike into the hair better in nonmedullated portions. From these mapped images, two routes of drug incorporation into the hair can be postulated. The more prominent would be through the root, where the hair shaft is formed, with the drug binding to the medulla material. A second less prevalent route would be from the exterior through the cuticle via perspiration, as in spiking. The spectral data have also shown that different drugs bind differently to the various hair materials.

Hair↗
PubMed1993

Hair analysis by infrared microscopy for drugs of abuse.

Hair analysis overcomes many of the drug testing problems associated with urinalysis. However, hair analysis has its own unique problem in that passive contamination of the exterior surface of the hair can taint the analysis with false positive. Infrared microscopy can examine the interior of the hair and differentiate passive contamination from drugs absorbed into the hair from ingestion. By microtoming the hair either cross-sectionally or laterally, infrared spectra can be obtained of the cortex and medulla of a single hair with a nominal spatial resolution of 10 microns. Three dimensional infrared imaging is possible with Fourier transform infrared (FT-IR) microscopy and yields a plot that can be understood by the layman.

Drug Overdose↗
PubMed1993

Detection of amphetamine and methamphetamine in urine by gas chromatography/Fourier transform infrared (GC/FTIR) spectroscopy.

New methods for identification of amphetamines have been employed using gas chromatography/Fourier transform infrared spectroscopy (GC/FTIR). These methods have provided identification of the drug and its metabolites, with detection at the low picogram levels or less than 10 ng/mL. Developments in cryogenic sample deposition for GC/FTIR spectroscopy have increased the sensitivity of GC/FTIR to levels that match or surpass that of gas chromatography/mass spectrometry (GC/MS). This advancement in technology has allowed the highly selective ability of infrared spectroscopy to be used for identification and quantitation in studies where the analytes are in low concentrations. The limits of detection (LOD), quantitation (LOQ), and linearity (LOL), and precision have been determined in this study, and these instrumental parameters have been compared with those of established techniques.

Amphetamine↗
PubMed1992

Migration of a human keratinocyte cell line (HACAT) to interstitial collagen type I is mediated by the alpha 2 beta 1-integrin receptor.

The migratory response of the human keratinocyte cell line HaCaT to collagen type I and the molecular mechanism underlying collagen-mediated migration have been analyzed. The migratory response of HaCaT cells to collagen type I consisted of a dose-dependent migration to insoluble step gradients of substratum-bound collagen (haptotaxis) and to gradients of soluble collagen (chemotaxis). Checkerboard analysis demonstrated a minor chemokinetic component. Denatured collagen type I was less chemoattractive than the native triple-helical form. Pre-treatment of cells with 25-250 micrograms/ml of synthetic peptides containing the fibronectin cell-recognition sequence RGD (Arg-Gly-Asp) resulted in a concentration-dependent inhibition of fibronectin-mediated chemotaxis, whereas chemotaxis to collagen was not affected. We then investigated the role of VLA/collagen-receptors for collagen type I-induced chemotaxis. Monoclonal antibody (MoAb) 5E8, which selectively blocks function of the alpha 2 subunit of the VLA-2/collagen receptor, dose-dependently inhibited the chemotactic response of HaCaT cells to collagen. This effect was specific for collagen-mediated chemotaxis because the chemotactic response to fibronectin remained unaffected. In contrast, a function blocking MoAb directed to the alpha 3 subunit of the coexpressed VLA-3 receptor, which is also capable of binding collagen, had no effect. However, function blocking MoAb directed to the beta 1-chain of integrins completely inhibited chemotaxis to collagen type I. Based on our results, we propose that the chemotactic migration of the human keratinocyte cell line (HaCaT) to collagen type I is specifically mediated by the RGD independent VLA-2/collagen receptor (alpha 2 beta 1) of the integrin family.

Amino Acid Sequence↗
PubMed1989

An assessment of emergency medicine residency graduates' perceptions of the adequacy of their residency training.

A study of emergency medicine residency training graduates was conducted to determine their perceptions of the quality of their graduate training. A sample of 300 individuals was randomly selected from a population of 1,000 persons graduating from 1982 through 1984. Respondents were asked to use a scale of 1 to 5 (with 1 being highest) to rate the adequacy of their residency training relative to 20 major core content areas. A 50% response rate (N = 151) was achieved. Mean ratings of residents' perceptions of the adequacy of their training relative to the core content ranged from 1.7 to 3.24. Training in resuscitation and stabilization, principles of emergency care, and general assessment were among the most highly rated, while training in physician interpersonal skills, disorders related to the immune system, and cutaneous disorders were rated the lowest. Overall, residents were quite positive in their perceptions regarding the quality of their training. They indicated plans to attend continuing medical education programs to reinforce some of their training and to address some of the deficiencies they perceived in residency training. Programs are encouraged to conduct similar surveys with their own graduates to assess particular strengths and weaknesses.

Adult↗
PubMed1987

Transcutaneous monitoring as trigger for therapy of hypoxemia during sleep.

Based on results on central chemosensitivity in cats, paired stimuli were applied for therapy to infants with central respiratory insufficiency of various degrees. An unspecific respiratory stimulus, e.g. light for 1 s, was followed by a jet of either O2 or 2% CO2 in O2 for 1.5 s. The unspecific and the chemical stimuli were interspaced by 0.5 s. The combined stimulation was repeated every 10 s. The program was triggered by using threshold values of transcutaneous pO2. In infants with intratrachial tubes or tracheostoma we used the end tidal pCO2 for triggering the stimulation. The method could prevent hypoxemia during sleep in non-ventilated subjects with sleep apnea syndromes or in infants with severe hypoxemia during sleep after being rescued from Sudden Infant Death Syndrome (SIDS). In patients with Ondine's Curse Syndrome (OCS) with its CO2 insensitivity, paired stimuli were used in order to condition the chemical function of the respiratory system. Polysomnograms from 310 clinically healthy infants including healthy siblings of SIDS victims revealed instability of arterial pO2 and low CO2 sensitivity during sleep within the second month and the fourth to ninth month of life, respectively. These data challenge the described method as a potential preventive or therapeutic measure to defeat SIDS and sleep apnea syndromes in conjunction with disturbed chemical regulation of respiration.

Arousal↗
PubMed1986

Setting nursing hours standards. Part 1.

Data were collected and prepared for entry to a computer. Analysis then was done to provide standard hours of care per patient classification level. Further options for use of this data and details on data analysis will be presented in Part 2 (February 1986 issue).

Data Collection↗
PubMed1985

Galactose and galactitol in the urine of children with compound heterozygosity for Duarte variant and classical galactosemia (GtD/gt) after an oral galactose load.

An oral dose of galactose, 1 g/kg of body weight, was administered to 24 children with the Duarte variant/classical galactosemia genetic compound (GtD/gt) and to 16 controls ranging in age from 0.3 to 10.7 years. Urine was then collected for 3h. Excreted amounts of galactose and galactitol increased with age in all subjects, but were consistently greater in the compound heterozygotes. If related to urinary creatinine, galactosuria and galactitoluria were no longer age-dependent, although as compared with the controls, urinary galactose was about three times and urine galactitol twice as high in the patients (p less than 0.01 for both). We found a statistically significant correlation between urinary galactitol and galactose in these patients. Moreover, urinary galactitol and galactose each correlated positively with the area under the plasma galactose curve, as well as with the peak value for plasma galactose after galactose ingestion.

Aging↗
PubMed1980

Tick paralysis in a western harvest mouse.

An engorging female Ixodes pacificus was observed on a western harvest mouse (Reithrodontomys megalotis) in Humboldt County, California. The mouse demonstrated a flaccid paraplegia, but it appeared to recover fully after the tick was removed.

Animals↗