Seasonal timing of sperm production in roe deer: interrelationship among changes in ejaculate parameters, morphology and function of testis and accessory glands.

Roe deer are seasonal breeders with a short rutting season from mid-July to mid-August. The seasonality of reproductive activity in males is associated with cyclic changes between growth and involution of both testes and the accessory sex glands. This study characterizes morphological and functional parameters of these organs prior to, during and after breeding season in live adult roe deer bucks. Size and morphology of the reproductive tract was monitored monthly by transcutaneous (testes, epididymis) and transrectal (accessory glands) ultrasonography. Semen was collected by electroejaculation. Concentration, motility and morphological integrity of spermatozoa as well as the content of proteins and testosterone in semen plasma were evaluated. Proportions of haploid, diploid and tetraploid cells were estimated by flow cytometry in testicular tissue biopsies. Serum testosterone was measured by enzyme immunoassay. Most parts of the male reproductive tract showed distinct circannual changes in size and texture. These changes were most pronounced in the testes, seminal vesicles, and prostate. All reproductive organs were highly developed during the rut only. The volume of ejaculates, total sperm number and percentages of motile and intact spermatozoa also showed a maximum during this period and corresponded with high proportions of haploid cells in the testis. The highest percentages of tetraploid cells were found in the prerutting period. The production of motile and intact spermatozoa correlated with both the protein content of semen plasma and the concentration of testosterone in semen plasma and blood serum. These results suggest the importance of combined actions of the testes and accessory sex glands and the crucial role of testosterone in facilitating the optimal timing of intensified semen production to ensure sufficient numbers of normal spermatozoa in seasonal breeders.

Quantitative regional blood volume studies in rat myocardium in vivo.

Many pathophysiological processes in the myocardium are in close relation to changes of the regional blood volume and regional myocardial blood flow or perfusion. Only few methods exist to obtain quantitative values for these parameters. Quantitative regional blood volume (RBV) studies in rat myocardium are presented using snapshot fast low angle shot (FLASH) inversion recovery T1 measurements with two different blood pool contrast agents, gadolinium diethylenetriaminopentaacetic acid (Gd-DTPA) albumin and Gd-DTPA polylysine. In contrast to previous attempts, each snapshot FLASH image acquisition was ECG-triggered under breathhold conditions. To measure relaxation times shorter than a heart cycle, each T1 sequence was repeated two times with different delays between inversion pulse and first image acquisition. The experiments were performed on a Bruker Biospec 70/21 using a homogeneous transmitter coil and a circularly polarized surface receiver coil, a special ECG trigger unit, and a respirator that is controlled by the pulse program. Based on a fast exchange model RBVm maps were calculated from the relaxation time maps for different concentrations of the two blood pool contrast agents. A significant dependence of the RBVm values on blood T1 was found. This is in accordance with a model that has been developed recently relating the dependence of RBVm on T1 of blood to perfusion. For Gd-DTPA albumin, the application of the model to the experimental data yields realistic values for RBV and perfusion. The values, which are in accordance with literature data, were obtained at highest contrast agent concentrations i.e., lowest relaxation times of blood (ca. 200 ms).

[The verification of optimized 3D-dosage distributions with an MR Fricke gel]. / Verifikation optimierter 3D-Dosisverteilungen mittels MR-Fricke-Gel.

PURPOSE: Complex 3D treatment planning techniques require a dose verification throughout the irradiated volume. Conventional dosimetry techniques only unsatisfyingly serve these needs. MATERIAL AND METHOD: The chemical dosimeter FeSO4 solution can be used for measuring spatial dose distributions with the help of magnetic resonance imaging by fixing the iron ions in a gelatin matrix. A 3D dosimetry method was developed for 3D verification in an homogeneous, anthropomorphic phantom. The verification is achieved by juxtaposition or superposition of measured and calculated isodoses. RESULTS: Different gel compositions were studied in view of their applicability as clinical 3D dosimeter concerning dose response, linearity and diffusion behaviour. A gel with 5% gelatin and 1 mM of ferrous ions proved to be the most suitable. The inverse spin-spin relaxation time T2(-1) is an indicator of the ferric ion concentration that showed to be linear with the dose in the range between 0 and 40 Gy (R2 = 0.996). The dose response was 0.057 per second and Gy. The observed diffusion of the iron ions was only influenced little by different gel compositions. To isolate the restrictions in the clinical application, measurements on the disturbing effects like, e.g. the inhomogeneous spatial response and the gel surface effects, were made and eliminated with the subtraction method. The clinical use of the method is demonstrated for the examples of the verification of calculated 3D dose distributions of a shielded 192Ir afterloading vaginal applicator and a head and neck 3-field plan with the use of asymmetric jaws and compensators. CONCLUSION: The study demonstrates the clinical applicability of the method and shows its limitations.