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Biomedical subjects

W Lohmann

Publications and source records attributed to W Lohmann.

At least 19 recordsLinked to original sources
PubMed1992

[In vivo autofluorescence. Measurements of human crystalline lenses with cataract and normal findings after excitation with monochromatic light].

In 25 eyes with nuclear cataract, 18 eyes with posterior subcapsular cataract, 25 eyes with cortical cataract, and 23 eyes without any pathological lens changes, the maximal fluorescence intensity was determined after excitation with monochromatic light at 365 nm, 405 nm, 436 nm, and 485 nm. The coefficient of variation was smaller than 5%. All eyes with cataract underwent cataract surgery a few days after the fluorescence measurements. The fluorescence spectrometer, especially constructed for in vivo measurements, consists of a modified slit lamp (Zeiss 75 SL) and an optical multichannel analyser (OMA) for gauging the data. The clinical trial was undertaken to determine whether, considering the influence of age, there is a difference between the fluorescence intensities in eyes with the above named cataracts and noncataractous eyes. The data were analyzed to determine the effect of age upon fluorescence intensity for all excitation wavelengths in both cataractous and noncataractous eyes. Age had an influence on the fluorescence intensities for all four excitation wavelengths. Assuming that the influence of age was not dependent on the state of the lens, it was quantified for all measurements and an "age-corrected" fluorescence intensity was calculated. The statistical analyses of these "age-corrected" fluorescence intensities revealed a significant difference (P < 0.001) for all of the types of cataracts examined and for normal eyes. The cataract types examined and the normal eyes showed differences in their fluorescence feature. To assess the fluorescence intensities obtained after excitation with the wavelengths mentioned above, one must take into consideration the influence of age on the measurements.

Adult↗
PubMed1989

Native fluorescence of the cervix uteri as a marker for dysplasia and invasive carcinoma.

A non-invasive and non-destructive fluorescence technique developed recently for an in situ detection of melanomas has been applied for determining in vitro dysplasia and invasive carcinomas in the cervix uteri. The cervices uteri exhibit a fluorescence band with a peak at about 475 nm if excited with 365 nm. The fluorescence intensity increases concomitantly with the degree of dysplasia, ranging from 30 counts/100 ms (healthy) to approximately 200 counts per 100 ms (CIN 3). At the rim of a malignancy, the intensity is 250 counts/100 ms and higher and decreases towards the healthy region. In the tumor region, the intensity is about zero or very small, at the most. The naturally occurring chromophore being responsible for the fluorescence observed seems to be NADH.

Cervix Uteri↗
PubMed1989

[Absorption and fluorescence spectrometry measurement of intraocular lenses].

Light absorption and fluorescence measurements can be used to detect accumulations of small molecules in intraocular lenses (IOLs). It was shown that HEMA IOLs can store and to some extent release a variety of drugs and fluorescein. PMMA and silicone IOLs, however, do not have this characteristic. UV-blocking IOLs absorb UV light completely. The absorption limit varies between 390 and 410 nm, depending on the make. Neither absorption nor fluorescence response were affected by exposure to UV light or heat.

Acebutolol↗
PubMed1989

[Natural fluorescence of nuclear cataract lenses and melanomas of the eye].

For various reasons, it is desirable to have an objective cataract classification system that does not depend on either the opinion of the physician or the patient. Since both highly molecular protein aggregates and chromophores are formed in cataractous lenses, which fluoresce under suitable stimulation, we have developed a fluorescence apparatus that illuminates the lens with five monochromatic wavelengths between 350 and 500 nm in situ. The fluorescence spectrum is recorded up to 100 ms with an optical multi-channel analyzer. This fluorescence method is non-invasive and does not harm the eye; it also uses the native fluorophore. The set of fluorescence spectra obtained by this method describes the condition of the cataractous lens both quantitatively and qualitatively. Because of the sensitivity of the method, it can also be used to assess the disease objectively in the early stages and to test and determine the effectiveness of anti-cataract drugs. Another use was discovered by using the fluorescence measurements for the diagnosis of malignant melanomas. With this equipment, melanomas in the eye and the surrounding area can be diagnosed both rapidly and precisely.

Cataract↗
PubMed1988

Native fluorescence of platelets from patients with occlusive arterial disease.

Healthy platelets exhibit a fluorescence band with a peak at 475 nm if excited at 360 nm. This peak increases first with the progression of occlusive arterial disease (OAD) followed by a decrease at an advanced stage. Concomitantly, a new fluorescence band at 445 nm will appear, which increases steadily with the progression of OAD. These findings can be explained by the oxidation of NADH (fluorescence at 475 nm) to NAD (445 nm) and support, thus, the assumption that oxidative processes are involved in the formation of OAD.

Arterial Occlusive Diseases↗