Because many testicular toxicants cause damage to specific stages of spermatogenesis, the present study has investigated the utility of a model in which the testis is synchronized to contain only a few closely related spermatogenic stages. The susceptibility of different stages to 1,3-dinitrobenzene (1,3-DNB) toxicity was investigated in rats, the testes of which had been stage synchronized by a vitamin A depletion/repletion (VADR) procedure. 1,3-DNB (25 mg/kg, IP) or vehicle was injected 58, 61, or 78 d after vitamin A readministration, and testicular histopathology was evaluated 48 h later. At the time of sacrifice, testes in the three groups were synchronized to stages I-VI, VII-IX, or X-XIV+I. The data indicated that tubules in all stages of spermatogenesis, in both synchronized and unsynchronized animals, demonstrated histopathologic changes in response to 1,3-DNB. However, the lesion seen in synchronized animals was more severe and less stage specific than that seen in weight-matched, unsynchronized animals. This increase in degree of susceptibility could be partially explained by differences in toxicokinetics. Stage-synchronized testes could provide unique insights into stage-specific cellular and molecular events, especially for in vitro studies where the stage enrichment could be maximally exploited. However, results obtained from in vivo toxicity studies using animals subjected to VADR should be interpreted carefully in light of the confounding physiologic/metabolic perturbations potentially induced by the VADR procedure.

Animals↗

PubMedDate not supplied

Effects of left ventricular pressure unloading during LVAD support on right ventricular contractility.

The effects of left ventricular pressure (LVP) unloading with a left ventricular assist device (LVAD) on right ventricular (RV) end-systolic pressure volume relationships were studied. A Thoratec (Berkeley, CA) LVAD was implanted in open chest anesthetized pigs via apical cannulation, and an electromagnetic flow probe and computer controlled pneumatic occluder were attached to the pulmonary artery. RV and left ventricular (LV) pressures were measured with Millar catheters, and changes in RV volume during ejection were determined by integrating the flow signal. As an index of contractility, RV maximal systolic elastance (Emax) was calculated as the slope of the end systolic, pressure volume relationship between an isovolumic beat and a series of transiently occluded beats at different times in the ejection phase. After an 83 +/- 15% decrease in LV pressure time integral during LVAD pumping, there were no significant changes in cardiac output, mean systemic arterial pressure, or in RV dP/dtmax. Most important, RV Emax during LVAD unloading (0.63 +/- 0.16 mmHg/ml) was unchanged from control (0.62 +/- 0.10 mmHg/ml). Therefore, in the normal intact porcine heart, the effective contractility of the right ventricle is not altered by significant LV pressure unloading produced with a LVAD.

Animals↗

PubMedDate not supplied

Adsorption and degradation of the weak acid mesotrione in soil and environmental fate implications.

The ability of soils to adsorb and degrade pesticides strongly influences their environmental fate. This paper examines the adsorption and degradation of a weak acid, a new herbicide mesotrione 12-[4-(methylsulfonyl)-2-nitrobenzoyl]-1,3-cyclohexanedione], in 15 different soils from Europe and the USA. Experiments were conducted to understand the influence of soil properties, covering a wide range of soil textures, soil pH values (4.4 to 7.5), and organic carbon contents (0.6 to 3.35%). Mesotrione adsorption (Kd values ranged from 0.13 to 5.0 L/kg) was primarily related to soil pH, and to a lesser extent by percent organic carbon (%OC). As soil pH rose. mesotrione Kd values got smaller as mesotrione dissociated from the molecular to anionic form. Mesotrione degradation (half-lives ranged from 4.5 to 32 d) was also related to soil pH, getting shorter as soil pH rose. Simple regression of mesotrione adsorption against soil pH and %OC and against degradation provided a close fit to the data. The correlation between mesotrione adsorption and degradation means that Kd and half-life values are only relevant for use in environmental fate assessment if these values are "paired" for the same soil pH and %OC. The implications were as illustrated for leaching, raising important issues about combining pesticide adsorption and degradation behavior in environmental fate assessments.

Adsorption↗

PubMedDate not supplied

Recent increase in incidence of chlamydiosis (psittacosis) in psittacine birds in Texas.

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Animals↗

PubMedDate not supplied

A field trial of the Clinicult system for detection of asymptomatic gonorrhea in women.

Clinicult, a selective medium for culturing Neisseria gonorrhoeae, was field-tested in a gonorrhea screening program in Seattle, Wash., in 1973. The results with this medium and with the Transgrow and Thayer-Martin culture systems were compared as to sensitivity and specificity. A total of 5,141 women from three patient groups were included in the study. Group 1 consisted of 720 female patients of the venereal disease clinic of the Seattle-King County Health Department, who served as the control group. When this group was screened with the Clinicult and Thayer-Martin culture media, the Thayer-Martin medium proved superior in identifying positive carriers. Group 2 was composed of approximately 2,000 patients from five different facilities, including family planning clinics and hospital out patient services. No statistical difference in accuracy was found between the two culture systems used for this group-Clinicult and Transgrow. Group 3 was comprised of approximately 2,500 female patients who were screened with the Clinicult and Transgrow cultures by their own private physician or his staff. The Clinicult system proved significantly less effective than the Transgrow cultures in identifying infected females in group 3. The physicians varied greatly in their ability to use the Clinicult system successfully. Possible reasons for their errors may have been (a) lack of motivation and of care by their office personnel in conducting the necessary additional procedures required with Clinicult, (b) the inhibitory nature of the medium, and (c) the failure of the medium to produce colonies of adequate size. The staffs of communitywide screening programs for gonorrhea need to be highly selective in choosing the medical facilities in which to use the Clinicult culture system. When laboratory facilities are available for the full utilization of the Thayer-Martin medium, this system is preferable. When, however, standard culture procedures are not readily available, Clinicult, properly used, can reduce the central laboratory load by eliminating the need for processing negative cultures.

Bacteriological Techniques↗