Biomedical subjects

N Hofmann

Publications and source records attributed to N Hofmann.

81 records · Page 5Linked to original sources

PubMedDate not supplied

Guidance of shrinkage vectors vs irradiation at reduced intensity for improving marginal seal of class V resin-based composite restorations in vitro.

This study evaluated the influence of radiation intensity on polymerization of a resin-based composite (RBC) and compared the influence of guidance of shrinkage vectors vs irradiation at reduced light intensity on the marginal seal of Class V RBC restorations in vitro. The degree of cure was studied indirectly by measuring the Vickers hardness (1.96 N, 30 seconds) at the bottom of disc-shaped specimens 2 mm in height at different periods of time after light irradiation. After one hour, irradiation using a high-intensity curing light (Heliolux GTE, Vivadent, 600 mW/cm2) [HICL] from close distance for 20 seconds, 40 seconds or 60 seconds or a low-intensity curing light (Vivalux, 250 mW/cm2) [LICL] from close distance for 60 seconds produced higher hardness values compared to 20 seconds or 40 seconds using the LICL or using the HICL from a distance of 10 mm. After three and 24 hours, higher hardness was observed for all irradiation protocols. After 24 hours, only specimens irradiated by the HICL for 20 seconds or 40 seconds from 10 mm distance featured significantly lower hardness compared to the remaining curing modes. The influence of different irradiation strategies on marginal seal of Class V RBC restorations was evaluated in vitro using dye penetration after water storage (60 days, 37 degrees C) and thermocycling (2500 cycles 5 degrees-55 degrees C). The HICL produced more dye penetration than the LICL. Placing the light tip directly over or 10 mm above the center of the cavity ("standard irradiation, ["distance irradiation"]") resulted in similar penetration values. In contrast, positioning the light tip apical to the cervical margin and moving it slowly to the center of the cavity ("cervical start irradiation") compromised the marginal seal.

Analysis of Variance↗

PubMedDate not supplied

Transformed spermatocytes constituting the ejaculate of an infertile man.

In the ejaculate of an infertile man exclusively free immature germ cells were found. Electron microscopic examination of their cytology revealed some characteristics of primary spermatocytes. After having been released from the germinal epithelium, these cells, however, have developed into totally new cell forms, which finally degenerate and disintegrate.

Adult↗

PubMedDate not supplied

[Spermatologic studies in 300 patients with varicocele of different degrees of severity and in various age classes].

Spermatologic investigations were made in 227 patients with varicocele at the age of 19-23 years (average age 20.4 years) and in 73 patients with varicocele at the age of 24-40 years (average age 28.0 years). The spermatologic findings of the patients with varicocele were compared with the results of 55 andrologic healthy young men without varicocele. The diverse degrees have a different effect to the sperm quality. Only patients with the clinical signs of the varicocele-orchidiopathy present a decreased sperm quality. The degree varicocele combined with other testicular disorders shows the worst sperm quality. The results in the higher age group explain, that the damage of the testicle increases with longer duration of the varicocele. Differentiating the spermatozoal morphology according to the "Düsseldorf morphological classification" you can find characteristic forms with hyperelongation of the head in patients with varicocele and spermatozoa with acrosomal defects in the degree varicocele combined with other testicular disorders.

Adult↗

PubMedDate not supplied

[Morphologic studies of spermatozoa in disorders of motility].

On the basis of microscopical examination and further differentiation by special stain techniques, a new classification of defects of midpieces and tails of spermatozoa will be presented: First degree disorders i.e. abnormalities of the staining behaviour and minor structural defects, second degree disorders revealing breakes and coiling of spermatozoa tail, and finally severe third degree disorders only exhibiting a rudimentary anlage of the terminal segment of spermatozoa. The staining abnormalities of the first degree disorders are characterized by nonreactivity to the Polychrome stain of the Papanicolaou technique as well as to scarlet red stain of the Shorr technique. Although the majority of these spermatozoa do not exhibit morphological aberrations, they have to be regarded completely immotile. Considering this classification, we have observed a highly significant correlation between morphological findings of midpieces and tails and the total motility as well as the progressive motility of spermatozoa.

Autoimmune Diseases↗

PubMedDate not supplied

[Analysis of spermatozoa with flow cytophotometric determination of DNA].

Semen samples of fertility patients and fertile men were analysed by an improved technique of flow cytophotometry. The DNA-contents of mature spermatozoa were measured with a high level of accuracy. Besides spermatozoa, peaks of spermiogenetic cells and other seminal cells could be demonstrated. Complementary to the results of semen analyses the complex histograms of pulse cytophotometry investigations may give further informations on the nature of the underlying disturbances of spermatogenesis.

Adult↗

PubMedDate not supplied

[Disintegration of human spermatozoa in flow cytometry of semen].

In some cases, the pretreatment of human spermatozoa produced desintegration of various degrees, while in others a reduced staining was observed. For the evaluation of these phenomena the following techniques were applied: papain/DTE solution at pH 5.5 and 6.4, pepsin solution and a staining procedure without any preceeding decondensation of the spermatozoa nuclei. Pathological spermatozoa from patients with severe disorders of spermatogenesis showed an extended resistance to the pretreatment procedures, the spermatozoa being stained after papain/DTE pretreatment at pH 5.5 only. Contrary to this finding, normal spermatozoa and spermatozoa with slight morphological aberrations desintegrated when papain/DTE solutions were used. In this group the abortion rate was high.

Cytological Techniques↗

PubMedDate not supplied

[Pepsin pretreatment of human semen as a standard procedure for flow cytometry].

The 30 minutes pepsin incubation of human semen has proved to be a standard pretreatment procedure for impuls cytophotometry (ICP). This method, in comparison to papain treatment, shows a better preservation of the material and avoids the phenomenon of "disintegration" and reduced staining property. The CV of 1C peak is small enough. Additionally, the immature spermatozoa, earlier dissociated late elongated spermatids, diploid spermatozoa, dual forms and diploid semen cells (spermatogenetic cells, leukocytes, epithelial cells are demonstrated in small peaks, a fact which can help explain the disturbances in pathological cases.

Diploidy↗

PubMedDate not supplied

Human sperm motility--enhancement and inhibition measured by laser Doppler spectroscopy.

Laser Doppler spectroscopy is an excellent instrument to measure motility parameters of human spermatozoa. Experiments have been performed by the aid of a now commercially available instrumental setup called LAZYMOT to study enhancement and inhibition as well as influences of different physical treatments on the motility of human spermatozoa. The motility enhancing influence of Kallikrein (up to 40% with 4 KU/ml) and prostaglandin E2 could be proven, thereby verifying some sort of mechanism of action within the Kallikrein-Kinin system. Furthermore tested substances in this context were bradykinin (no effect), caffeine (enhancement), salicylic acid (slight decrease), and other prostaglandins (no effect). The influence of washing, centrifugation, resuspension liquid, and temperature has been examined. It turned out that the lowest motility degradation is to be achieved by washing twice at a pH value of 7.4 at forces of 200 g for 10 min each time. The optimal temperature during this process and the measurements thereafter was found to be 36 degrees C. Unsaturated fatty acids like arachidonic acid have been found to be very strong motility inhibiting substances, which can totally block any movement of spermatozoa.

Bucladesine↗

PubMedDate not supplied

[Use of the ultrasonic Doppler stethoscope in the diagnosis of varicocele].

In cases of varicocele the reverse venous blood flow can be detected by the use of the Doppler-stethoscope in a simple way. Applied to the basic examination of fertility patients this method has proved to be a valuable non-invasive screening in the evaluation of varicoceles including cases with minor clinical symptoms. According to our results, "subclinical varicocele" as a entity of venous diseases shows special clinical features. Varicocele-orchiopathy is caused by the reverse venous blood flow, when peritesticular venous anastomoses and crosses are less developed or insufficient in their compensatory function.

Humans↗