Molecular nature of Spemann's organizer: the role of the Xenopus homeobox gene goosecoid.

This study analyzes the function of the homeobox gene goosecoid in Xenopus development. First, we find that goosecoid mRNA distribution closely mimics the expected localization of organizer tissue in normal embryos as well as in those treated with LiCl and UV light. Second, goosecoid mRNA accumulation is induced by activin, even in the absence of protein synthesis. It is not affected by bFGF and is repressed by retinoic acid. Lastly, microinjection of goosecoid mRNA into the ventral side of Xenopus embryos, where goosecoid is normally absent, leads to the formation of an additional complete body axis, including head structures and abundant notochordal tissue. The results suggest that the goosecoid homeodomain protein plays a central role in executing Spemann's organizer phenomenon.     

Overexpression of a homeodomain protein confers axis-forming activity to uncommitted Xenopus embryonic cells.

The anteroposterior character of mesoderm induced by a peptide growth factor (XTC-MIF) was tested by transplantation into host Xenopus gastrulae. Both retinoic acid and a homeodomain protein were able to override the anteriorizing effect of the growth factor. Microinjection of a posteriorly expressed homeobox mRNA can respecify anteroposterior identity, transforming head mesoderm into tail-inducing mesoderm. Unexpectedly, overexpression of XIHbox 6 protein in the transplanted cells, without addition of growth factors, caused the formation of tail-like structures. The cells overexpressing XIHbox 6 were able to recruit cells from the host into the secondary axis. The results suggest that vertebrate homeodomain proteins are part of the biochemical pathway leading to the generation of the body axis.     

Macrophage oxidation of L-arginine to nitrite and nitrate: nitric oxide is an intermediate

Previous studies have shown that murine macrophages immunostimulated with interferon gamma and Escherichia coli lipopolysaccharide synthesize NO2-, NO3-, and citrulline from L-arginine by oxidation of one of the two chemically equivalent guanido nitrogens. The enzymatic activity for this very unusual reaction was found in the 100,000g supernatant isolated from activated RAW 264.7 cells and was totally absent in unstimulated cells. This activity requires NADPH and L-arginine and is enhanced by Mg2+. When the subcellular fraction containing the enzyme activity was incubated with L-arginine, NADPH, and Mg2+, the formation of nitric oxide was observed. Nitric oxide formation was dependent on the presence of L-arginine and NADPH and was inhibited by the NO2-/NO3- synthesis inhibitor NG-monomethyl-L-arginine. Furthermore, when incubated with L-[guanido-15N2]arginine, the nitric oxide was 15N-labeled. The results show that nitric oxide is an intermediate in the L-arginine to NO2-, NO3-, and citrulline pathway. L-Arginine is required for the activation of macrophages to the bactericidal/tumoricidal state and suggests that nitric oxide is serving as an intracellular signal for this activation process in a manner similar to that very recently observed in endothelial cells, where nitric oxide leads to vascular smooth muscle relaxation [Palmer, R. M. J., Ashton, D. S., & Moncada, S. (1988) Nature (London) 333, 664-666].     

A map of barley chromosome 2 using isozymic and morphological markers

The F₂ progeny of a cross between a chromosome 2 multiple marker stock and an adapted cultivar of barley were analyzed for four morphological markers and electrophoretic patterns of eight leaf isozymes. TheIdh-2 locus was linked to thePer-5 locus (27.96±5.07 cM) and to thee locus (10.26±3.13 cM). Also, thePer-5 ande loci were located on the short arm of chromosome 2. In additionIdh-2 was also located on barley chromosome 2 and was linked to thev locus (13.18±3.56 cM), which is located on the long arm of chromosome 2. Two other marker genes,li andwst,,B, were linked (26.50±5.24 cM) on chromosome 2 but segregate independently of the other loci evaluated. This project was supported by funds from the U.S.-Spain Joint Committee for Scientific and Technological Cooperation.     

Pregnancy diagnosis by the ultrasonographical device and observation of fetal growth in the squirrel monkey (Saimiri sciureus)

This paper describes usefulness of the ultrasonographical device (USD) for the diagnosis of pregnancy and the observation of fetal growth in the squirrel monkeys (Saimiri sciureus) conceived under group breeding conditions. Pregnancy was diagnosed on the basis of the detection of gestational sac (GS) in the uterus. The GS was first detected 127 +/- 10 days before delivery. The heart beat of embryo was detected around 114 days before delivery. It was able to judge conditions of fetal growth by measuring the size of GS and the biparietal diameter. No difference in uterine size between nonpregnant and pregnant animals was observed 135 days before delivery.     

Heterogeneity of adrenocortical ferredoxin

Bovine adrenocortical ferredoxin (adreno-ferredoxin) was purified from adrenocortical mitochondria by an improved method that included hydrophobic chromatography on Toyopearl gels. The purified ferredoxin was electrophoretically homogeneous. It was further separated into five fractions by hydrophobic chromatography on a TSK-gel phenyl-5PW column with a high-pressure liquid chromatography system. The properties of the three main fractions were examined. The fractions had identical absorption spectra and almost the same activity in an NADPH-cytochrome c reducing system. Their amino-terminal sequences all corresponded to the reported sequence, but the carboxyl-terminal residues were glycine or serine, not alanine as reported. These results indicate that these adreno-ferredoxins had additional amino acid residues at the carboxyl end. It seems that adreno-ferredoxin extracted from mitochondria undergoes proteolytic attack during purification to become heterogeneous.     

Internal structure of the postcapillary high-endothelial venules of rodent lymph nodes and Peyer's patches and the transendothelial lymphocyte passage

Scanning electron microscopy (SEM) shows that the postcapillary high-endothelial venules of lymph nodes and Peyer's patches consist of two segments each with a different surface relief: a proximal segment with a cobblestone surface pattern and a distal segment of interlacing cytoplasmic plates. Both segments have deep adluminal crevices in which lymphocytes are lodged. The internal structural configuration of this endothelium has been examined by transmission electron microscopy (TEM) of serial sections of lymph nodes and Peyer's patches of mice, rats, and guinea pigs. The serial sections revealed that the endothelial cell bodies and their cytoplasmic extensions were disposed in a direction generally lateral to the luminal surface and intruded into the intercellular spaces of similarly disposed neighboring endothelial cells, resulting in a complex interlacing cellular pattern. Lymphocytes penetrated the endothelial cell body and secondarily followed an intracellular pathway through which they entered the extravascular compartment. At the exposed surfaces of the adluminal venule wall, recirculating lymphocytes were seen in SEM images to enter the endothelium by penetrating the endothelial cell body. The mode of migration of lymphocytes lodged in the endothelial crevices could be determined by SEM and has been examined by TEM of serial sections. At these locations as at the exposed surfaces, lymphocytes also entered the venule by penetrating the endothelial cell body. At both sites this transcellular pathway was followed by lymphocyte entry into the intercellular spaces from which they migrated into the extravascular compartment.