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The DAPI (4',6-diamidino-2-phenylindole)-fluorochrome was used to demonstrate phagocytized Cryptococcus neoformans using the mouse peritoneal cavity technique. These yeast cells were chosen because they are large and their capsules exhibit a deep yellow fluorescence which contrasts very well with the blue fluorescent nuclei of the phagocytes (preferentially macrophages). In other words, DAPI stains both, acid mucopolysaccharides and nuclear DNA. The capacity of the phagocyte nuclei to surround or even enclose the yeast cells was the most remarkable result. Generally, the application of DAPI in these phagocytosis experiments provides valuable information rapidly, easily and specifically.

One of the etiological agents of urethritis and prostatitis is Chlamydia trachomatis which reveals obligatory intracellular parasitism. Patient specimens (smears of the urethra, urine, first portion, expressed prostatic fluid, ejaculate) are centrifuged onto special cell cultures, so-called McCoy cells, and induce characteristic cytoplasmatic inclusions. Giemsa staining or DNA-binding fluorochromes (DAPI or Hoechst 33258) are suitable procedures to identify chlamydia inclusions. Serologic tests to establish infections due to Chlamydia trachomatis are only of limited diagnostic value.

An agar diffusion test to directly stain mycoplasma colonies using a new fluorochrome 4,6-diamidino-2-phenyl-indol (DAPI) is described. Next to a colony in question a well is punched into the agar and filled with DAPI. 30 min later the colonies in the diffusion zone show a light yellow - light green fluorescence. Due to the high affinity of DAPI to DNA it is easily possible to distinguish between granular mycoplasma colonies and unspecific substances e.g. proteins and lipids from clinical material.

In suspension tests it could be found, that tyrothricin, isolated from bacteria, possesses an anti-infectious activity against Sendai virus. Concentrations of 10(2) to 10(3) ID50-units of Sendai virus were incubated with 0.5 and/or 1.0 mg tyrothricin per 5 ml for 30 minutes at 37 degrees C (pH 7.5). These mixtures were tested in embryonated eggs and showed a marked decrease of viral infectivity. Tween 80 added after the incubation period leads to an incomplete reactivation of the virus infectivity. According to these results and further preliminary studies on herpes simplex virus we suppose a virustatic effect of tyrothricin also in the case of other lipophilic viruses.

Microbiological analysis of semen in andrology is mainly performed in cases of infertility and artificial insemination. In order to localize the suggested infection and to detect urethral (asymptomatic) colonization, we recommend to analyse additional specimens of the patient, i.e. urethral swabs and first portion of urine. As a rule, quantitative microbiological analysis is necessary in cases of bacteria belonging to the group of potentially pathogenic flora. In isolating pathogenic ("specific") bacteria, the detection of a few microorganisms indicates an infectious process. We recommend the careful microscopical examination of the ejaculate to detect phagocytes, abnormal spermatozoa, trichomonads, yeasts and other cells. As a rapid microscopical examination we employ the DAPI-fluorochrome-technique. Microbiological cultures should take into consideration the isolation and identification of ureaplasmas and chlamydia trachomatis. In order to achieve a comparison of microbiological results with those of other laboratories, it is essential to define the terms "significant bacteriospermia" and "significant leukocytospermia". In other words, it is necessary to introduce a borderline between contamination and infection concerning the "nonspecific" potentially pathogenic flora.

300 human ejaculates from a andrological group of patients were stained for visualisation of the spermatozoal morphology with the new fluorochrome DAPI (4',6-diamidino-2-phenylindol) and examined by fluorescence microscopy. DAPI has proven to be stable, since the preparations do not fade even after long storage periods. It can be utilized in small amounts and has a special affinity for the spermatozoon nucleus, which it stains light yellow, in contrast to the acrosomal parts which are fluorescent green. The method is surprisingly simple and can be carried out in a few minutes. A further advantage of the DAPI procedure lies in the additional staining of leucocytes and microorganisms, so that inflammatory processes of the male accessory organs can be diagnosed as well.

The practicability of 4',6-diamidino-2-phenylindole (DAPI) in the fluorescent microscopical demonstration of bacterial and other cellular structures for medical diagnostic purposes was investigated. Polar bodies in diphtheria bacilli and spores of spore-forming bacteria showed up well. The demonstration of phagocytosed bacteria in urinary sediment and the morphology of human spermatozoa are particularly impressive. Noteworthy advantages of DAPI are its stability (no bleaching of stained preparations), its use in minute quantities, rapid staining (within minutes), and simplicity of use.

A new fluorescent dye for the identification of trichomonas vaginalis is described. Specimens under investigation were mixed with 4',6-diamidino-2-phenylindol (Dapi) and examined using white light and UV-light. The combined use of the two techniques allows to recognize the mobile non fluorescing and the dead intensive yellow fluorescing trichomonads. Devitalized epithelial cells, bacteria and leucocytes in contrast to living trichomonas are stained yellow in a few minutes. This is of diagnostic help.