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Biomedical subjects

M Lehrer

Publications and source records attributed to M Lehrer.

34 records · Page 2Linked to original sources
PubMed1989

[Medium-term tonometric results of trabeculectomies performed after trabeculoretraction using an argon laser in chronic primary open-angle glaucoma].

Following unsuccessful Argon Laser Trabeculoplasty (ALT), 93 eyes were tracked for periods of 6 to 42 (mean: 24 months). The total failure rate of 20% is similar to the generally known failure rate of the trabeculectomies. However, failures are more frequent (37%) when trabeculectomy is performed between the second and third month after ALT. This may suggest not to operate on too soon after ALT or to perform filtering surgery with 5 Fluoro-uracil.

Adult↗
PubMed1987

Bees perceive illusory colours induced by movement.

Certain black-and-white patterns, when rotated at appropriate speeds, can create the artificial perception of hues. We report that this illusion is not confined to human vision, but is also perceived by an insect, the honeybee. The findings suggest that certain features underlying the processing of colour information are shared by man and bee.

Animals↗
PubMed1987

Drug screening in the workplace.

Drug use is pervasive in our society. Because Americans who use and abuse drugs are part of the working population, employers will continue to be affected by employees with substance abuse problems. The social, economic, and legal costs to business have created a new awareness, and companies are recognizing the need to take special measures to control drug and alcohol use. Urine drug screening has been identified as a valuable tool in discovering, documenting, and ultimately controlling drug use in the workplace. This article deals with the complex issues involved in designing and implementing an industrial drug screening program. The various laboratory techniques are identified and discussed, with special emphasis on their advantages and limitations.

Employee Discipline↗
PubMed1986

Laboratory diagnosis of cocaine: intoxication and withdrawal.

The clinical diagnosis of cocaine abuse is more difficult than previously recognized. The laboratory can play an important role in helping identify cocaine abusers and also in monitoring the progress of their recovery. An overview of the role of the laboratory is presented with the goal of optimizing the clinician's ability to apply available technology in an efficient manner. Various chromatographic and competitive binding techniques for the detection of cocaine and its metabolites in biological fluids are discussed and limits of each technique is identified. The cases of false negative and false positive results are explored and an approach to maximize benefits and economics of testing is described.

Arousal↗
PubMed1986

Effects of anti-convulsants on fatty acid metabolism in human serum.

The effects of diphenylhydantoin and phenobarbital on lipids metabolism were studied by quantification of lipids in human serum with GC-MS. The ratios of palmitic acid to stearic, oleic and linoleic acids decreased in patients on diphenylhydantoin therapy. Increases of free palmitic, stearic and oleic acids concentrations as well as higher cholesterol ester levels were observed in patients receiving either diphenylhydantoin or phenobarbital. With respect to fatty acids composition of cholesterol esters and phosphatidyl-choline, higher concentrations of palmitic, oleic and linoleic acids were observed in patients on diphenylhydantoin and phenobarbital therapy. Although the concentration of palmitic acid in serum phosphatidylcholine remained the same for all groups, a marked decrease in stearic, oleic and linoleic acids concentrations in serum phosphatidylcholine was observed in diphenylhydantoin treated group, and oleic acid in phenobarbital treated group. These results suggested the relationship to lecithin-cholesterol acyltransferase activity by these drugs.

Anticonvulsants↗
PubMed1985

Visual scanning behaviour in honeybees.

Freely flying bees were rewarded with sugar solution on a variety of black-and-white shapes as well as on coloured gratings in various training situations. In subsequent dual-choice tests, the bees' discrimination between the various shapes was measured. In addition, the bees were video-filmed while flying in front of the shapes. The scanning patterns thus obtained were then quantified in order to characterize scanning behaviour and its relationship to the geometrical parameters of the scanned shapes, investigate whether scanning plays a role in pattern discrimination and examine the influence of training on the characteristics of scanning. The scanning patterns clearly mirror the contours of the scanned shape in all cases, i.e. the bees fly along the contours contained in the shape. This behaviour does not depend on whether the scanned shape is one that was previously rewarded, or one that is completely novel to the bees. Comparison of the results of quantifying the scanning patterns with the results of dual-choice tests reveals that scanning behaviour is independent of discrimination performance. On the average, horizontal scanning directions occur more often than vertical directions. Variations of the training situation produce measurable differences in scanning behavior. However, except in the case of vertical scanning on a vertical grating, these differences are quite small, indicating that following contours is a largely stereotyped behaviour. Horizontal gratings are very well discriminated from vertical ones even if they offer contrast to only one receptor type, i.e. blue or green, demonstrating that the direction of contours is visible to the pattern recognition system even under these conditions. However, vertical and horizontal coloured gratings offering only blue-contrast do not elicit contour-following, whereas gratings offering only green-contrast do. Thus, the bees' scanning behaviour is colour-blind and most probably governed by the green receptors. We suggest that contour-following is the by-product of a behavioural mode which serves to prevent retinal image movement during flight in front of a contoured visual pattern.

Animals↗
PubMed1985

Temporal resolution of colour vision in the honeybee.

The temporal resolution of colour vision was measured in freely-flying honeybees by testing the performance of trained bees in discriminating between two stimuli, one of which presented a steady, homogeneous mixture of two colours, while the other offered a heterochromatic flicker between the two colours at various temporal frequencies. Pairwise combinations of the colours uv, blue and green were used, corresponding to the three receptor classes in the bee retina. For each colour combination, we determined a cutoff frequency beyond which discrimination no longer exists. For a given colour combination, the cutoff frequency depends upon the ratio of the intensities of the component colours, and is maximum at a particular ratio. The cutoff frequency at the optimum intensity ratio is approximately 100 Hz for each of the 3 colour combinations blue-green, green-uv and uv-blue, implying that colour computation requires ca. 10 ms. From the optimum intensity-ratios for the three colour combinations, we infer that the relative sensitivities of the green, blue and uv channels are approximately 1:1.3:24.

Animals↗
PubMed1976

Chemical ionization mass spectrometry for rapid assay of drugs in serum.

A rapid procedure has been devised for analyzing anti-epileptic drugs in serum by chemical ionization mass spectrometry. An internal standard, 5-(p-methylphenyl)-5-phenylhydantoin (MPPH), is added to serum diluted in buffer at pH 12. The mixture is washed with diethyl ether to remove neutral lipids, acidified, extracted with chloroform and the chloroform extract evaporated to dryness. The residue is then dissolved in methanol and an aliquot, corresponding to approximately 2% of the original mixture, is deposited in the glass capillary sample cup of the solid probe inlet of the mass spectrometer. The sample is then volatilized by heat into the ion source of the mass spectrometer, where it reacts with ionized methane reagent gas. As the temperature of the probe is increased, quasimolecular ion peaks of the protonated anticonvulsants appear, rise and fall on the oscilloscope tracing, indicating similar but not identical rates of volatilization. We recorded these peaks photographically by opening the shutter of the oscilloscope camera for the entire heating cycle. The concentrations of the anticonvulsants were estimated from the ratio of the height of the peaks of the drug to that of the internal standard on the photograph. The peak-height ratios were proportional to concentration within, above and below the therapeutic range. Other drugs, including barbiturates, carbamazepine, nicotine and caffeine, were readily identified when present. With one solid probe inlet, an assay could be performed every 2 min.

Anticonvulsants↗
PubMedDate not supplied

Urinary tricyclic antidepressant screening: comparison of results obtained with Abbott FPIA reagents and Syva EIA reagents.

Human urine was tested for tricyclic antidepressants with fluorescence polarization immunoassay (FPIA) reagents on Abbott's ADx system and with EIA reagents on Syva's ETS system. A 75-ng/mL imipramine calibrator cutoff was used with the ADx system and a 300-ng/mL nortriptyline calibrator cutoff with the ETS system. The ETS system was adapted to analyze tricyclic antidepressant (TCA) samples using the Syva Emittox serum TCA assay. Negative urine was spiked with various tricyclic and tetracyclic antidepressants, phenothiazines, and other medications with potential to interfere with the assays. Verification of samples was performed by thin-layer chromatography and gas chromatography/mass spectrometry. The different compounds were added to urine at concentrations of 200, 400 and 1,000 ng/mL. At 1,000 ng/mL all TCA compounds tested gave positive results with the ADx and ETS systems. However, some non-TCA medications spiked at 1,000 ng/mL gave false positive results with both systems. The tetracyclic antidepressants did not cross-react and gave negative results. Clomipramine-spiked urine at 400 ng/mL yielded a false negative result on the ETS system.

Antibody Specificity↗
PubMedDate not supplied

Nonpenetrating deep sclerectomy: a 6-year retrospective study.

PURPOSE: Nonpenetrating trabeculectomy, also called nonpenetrating deep sclerectomy (NPDS), is a filtering surgery where the internal wall of Schlemm's canal is excised, allowing subconjunctival filtration without actually entering the anterior chamber. This, technique was developed to minimize the complications of trabeculectomy. The authors investigated its safety and efficacy in a retrospective noncomparative study. METHODS: A total of 258 eyes (179 patients, mean age 61.4 +/- 11.56 years) with uncontrolled open angle glaucoma with prior medical therapy were treated. NPDS with a biocompatible collagen device (157 eyes) sutured to deep scleral bed or with the use of a 5-fluorouracil sponge (90 eyes) were analyzed. The main outcome measure was postoperative intraocular pressure (IOP) with an average follow-up of 54.4 +/- 17.07 months (range 1-85). Efficacy was determined 1 month, 3 months, and every 6 months after the procedure for 6 years. RESULTS: Mean preoperative IOP was 24.47 +/- 5.92 mmHg. Mean postoperative IOP was 14.44 +/- 5.31 mmHg (average lowering of the IOP was 38.94 +/- 23.81%) at 1 month, 15.16 +/- 4.57 mmHg (35.73 +/- 21.35%) at 3 months, 15.87 +/- 4.24 mmHg (32.45 +/- 20.52%) at 6 months, 16.32 +/- 4.53 mmHg (29.96 +/- 23.69%) at 12 months, 17.12 +/- 4.45 mmHg (26.51 +/- 23.93%) at 18 months, 16.77 +/- 4.44 mmHg (28.18 +/- 21.73%) at 24 months, 16.43 +/- 4.15 mmHg (28.89 +/- 23.69%) at 30 months, 16.34 +/- 4.12 mmHg (30.05 +/- 21.61%) at 36 months, 16.16 +/- 4.01 mmHg (30.06 +/- 22.55%) at 42 months, 15.71 +/- 3.74 mmHg (32.49 +/- 19.08%) at 48 months, 15.61 +/- 3.48 mmHg (31.26 +/- 21.01%) after 5 years, and 15.81 +/- 3.79 mmHg (33.73 +/- 20.9%) after 6 years. YAG goniopuncture was performed in 47.3% of cases with a mean follow-up of 12 +/- 13 months. These goniopunctures were effective in lowering IOP after a long-term follow-up (24 months). Additional 5-fluorouracil injections were used in 7% of cases. Visual field (Octopus or Humphrey mean defect and corrected loss variance or loss variance) was not modified (p < 0.01). Number of preoperative glaucoma medications was 2.01 +/- 0.58 and number of postoperative glaucoma medications was 0.85 +/- 0.92. Complications were peroperative microperforations in 27 eyes (10.5%), shallow anterior chamber in 2 eyes, hyphema in 2 eyes (0.8%), cataract in 5 eyes (2%), and dellen in 1 eye (0.4%). No cases of endophthalmitis or choroidal detachment were found. After surgery, 23 eyes (8.9%) required a new filtering surgical procedure, and diode laser cyclophotocoagulation was necessary in 2 eyes (0.8%). The probability success rate, defined as an IOP lower than 21 mmHg, was 66.46% (Kaplan Meier) at 60 months off all glaucoma medications and 80.32% with medical or new surgical treatment. CONCLUSIONS: NPDS appears to be an effective and safe filtering procedure for lowering IOP and could be an alternative to trabeculectomy in open angle glaucoma with the advantage of having fewer complications.

Adult↗
PubMedDate not supplied

Perinatal toxicology screening: comparison of various maternal and neonatal samples.

OBJECTIVES: Because cocaine metabolites are concentrated in amniotic fluid, we designed this study to assess the usefulness of amniotic fluid and that of neonatal gastric aspirate for perinatal drug screening and to compare the concentration of cocaine metabolites in various maternal and neonatal specimens. STUDY DESIGN: We compared the reliability of various maternal and neonatal specimens for detecting drug exposure and the concentration of cocaine metabolites in these specimens. RESULTS: Our data showed that screening for perinatal drug abuse with any single specimen leads to false-negative results. Drug screening with neonatal amniotic fluid, gastric aspirate, or cord blood did not improve the reliability of perinatal drug screening. CONCLUSION: Testing more than one type of body fluid may increase the reliability of perinatal drug screening.

Amniotic Fluid↗