Diminished growth of atrioventricular cushion tissue in stage 24 retinoic acid-treated chicken embryos.

Stage 34 chicken hearts have shown a spectrum of looping disturbances, changed hemodynamics, and changed growth of both right ventricular myocardium and atrioventricular cushion tissue after retinoic acid treatment. To obtain more information about the onset of the malformations we studied stage 24, the stage between the previously studied stage 34 and the moment of treatment. Sixteen stage 24 chicken embryos were examined after treatment with 1 microg all-trans retinoic acid at stage 15 and compared with 6 sham operated embryos. Morphological examination was supported by graphic reconstructions. Absolute volumes of atrial, atrioventricular, and ventricular myocardia were measured by a point counting method. The absolute volumes of the endocardial cushions were measured as well. Fifteen (15/16) retinoic acid-treated hearts did not show marked malformations as far as could be detected with our current macroscopic and microscopic techniques. One (1/16) retinoic acid-treated heart showed an abnormal tubular C-shape with a less bended inner curvature and with an abnormal horizontally oriented atrioventricular canal. The dorsal cushion tissue of this atrioventricular canal was discontinuous with the dorsal mesocardium and covered the malpositioned myocardial border between the atrium and the atrioventricular canal. The volume measurements did show a difference between retinoic acid treatment and sham operations. The retinoic acid-treated hearts showed a significant volume decrease of the atrioventricular cushions. No significant differences were found in the volumes of the ventricular myocardium compared to the sham operated embryos. We hypothesize that, between stages 15 and 24, retinoic acid directly affects the myocardial wall and the cushion tissue formation. In the present material this has resulted in decreased atrioventricular cushion growth, in changed hemodynamics, and in a severe looping disturbance of one embryo. We further hypothesize that, between stages 24 and 34, the malformations with minor looping disturbances will become apparent. Thus, development beyond stage 24 would result in the spectrum of looping disturbances as has been found at stage 34. These latter morphological malformations would lead to increasing hemodynamic changes, resulting in changes in growth as a secondary effect

Mechanical harvesting and cleaning of Calendula officinalis and Dimorphotheca pluvialis

From 1990 to 1994 the research institutes of the Agricultural Research Department in the Netherlands (DLO-NL) investigated potential new arable oilseed crops for industrial application as part of the National Oilseeds Programme (NOP). The Institute of Agricultural and Environmental Engineering (IMAG-DLO) studied the mechanical harvesting and cleaning of Crambe abyssinica, Dimorphotheca pluvialis, Calendula officinalis and Euphorbia lagascae. This paper describes the research conducted on the crops Calendula officinalis and Dimorphotheca pluvialis, using three harvesting methods: combining (New Holland 8070), combining after chemical desiccation and combining after windrowing. Gross yield, moisture content of harvested seeds and foliage, seed losses and impurities of the seeds were measured. It was found that both crops could best be harvested with a combine harvester after chemical desiccation. Timely harvest seemed to be important to avoid weather damage and excessive seed shedding. Calendula seeds were cleaned using an air-screen cleaner, Dimorphotheca seeds using an air-screen cleaner, a brushing machine and an indented cylinder separator