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In mice, three alleles, Hbbs, Hbbd and Hbbp, have been found at the beta-chain locus of haemoglobin. Analytical polyacrylamide gel electrophoresis revealed the presence of almost the same four haemoglobin bands (E-I, E-II, E-III and X) in all of the lysates of peripheral blood cells from 12-day-old foetuses of C57BL/6J (Hbbs), A/He (Hbbd) and PON (Hbbp). All were embryonic-type haemoglobins; the most anodal band (X) seemed to be a product of polymerization of E-I. Electrophoretic patterns of the haemolysates from 12-day-old foetuses were not affected by alkylation with iodoacetamide or maleic anhydride. Almost the same electrophoretic patterns in subunit analysis, using acid starch and acid-urea polyacrylamide gels, were obtained in 12-day-old foetuses of C57BL/6J, A/He and PON. E-I comprised alphia and x-chains, E-II, alpha- and y-chains, and E-III, alpha- and z-chains. In adults, two haemoglobin bands, s and Y, were present in the haemolysate of C57BL/6J, while three, dmaj, dmin and Y, existed in A/He, and three, pmaj, pmin and Y, in PON. All were adult-type haemoglobins. Haemoglobin Y, which was not demonstrable after alkylation of the haemolysates, seemed to be a product of polymerization of major haemoglobins (s, dmaj and pmaj). Each haemoglobin possessed common alpha-chains, while the beta-chains of major haemoglobins were different from those of minor haemoglobins. Developmental changes of the haemolysates from foetuses of C57BL/6J, A/He and PON were similar to each other. Haemolysates of the liver cells of developing foetuses contained only adult-type haemoglobins. Our techniques used here were not able to demonstrate the presence of foetal-type haemoglobins.

The development of the notochord, perichordal sheath and vertebrae was studied in C57BL/6 and Danforth's short-tail (Sd) mutant mice on days 9-14 of gestation, using histochemical stains to detect possible extracellular matrix (ECM) components or precursors. Stains used were periodic-acid Schiff (PAS) after diastase treatment (glycoproteins, neutral polysaccharides) and alcian blue (glycosaminoglycans). Embryos from C57BL/6Sfd mice were analyzed to establish a normal baseline. In 9-day normal (C57BL/6Sfd; +/+) embryos the notochord is an uninterrupted structure and contains PAS-positive, diastase-resistant granules, whereas in abnormals (Sd/+; Sd/Sd) the notochord is discontinuous and exhibits few, if any, granules. A notochordal sheath is present in normal and abnormal embryos on day 10 and stains with PAS, alcian blue and aniline blue; subsequently, it increases in thickness in normal, but not defective, embryos. In normal embryos, the notochord shows dilatations, and notochordal cells become vacuolated from 13 to 14 days. In contrast, the notochordal fragments of abnormals never develop dilatations, nor do the cells vacuolate. Organization of mesenchymal cells into specific patterns is observed initially in 11-day normal embryos; further mesenchymal organization into vertebral and intervertebral disc analgen occurs during days 13-14. In abnormal embryos, disturbance of mesenchymal cell organization is evident as early as day 11, and by day 12 aberrant patterns of organization have emerged. Mesenchymal cells of abnormal embryos also lack the typical distribution of PAS-positive, diastase-resistant granules that occurs in normal speciments. The possible relationship of these granules in notochordal and mesenchymal cells to ECM materials is discussed.

Embryos recovered at 62 and 80 h post coitum from reproductive tracts of yellow (Ay/a) and black (a/a) female mice mated to Ay/a males were examined ultrastructurally to define the developmental defect of lethal Ay homozygotes. No abnormalities were observed in five embryos from control matings (female a/a x male Ay/a). Of 24 morulae and blastocysts from Ay/a x Ay/a matings, six were observed to possess some morphological aberration. Two of the six abnormal embryos were morulae and contained isolated blastomeres which had developmental features typical of younger embryos; remaining cells of these embryos were normal. The third, an early blastocyst, contained a degenerating trophoblast cell' other cells of this embryo were also abnormal but not in an advanced stage of degeneration. The fourth abnormal embryo (late cleavage stage) was in an advanced stage of degeneration affecting all blastomeres. Finally, the remaining two abnormal morulae had a unique nucleolar morphology and an unusual abundance of intra-cisternal A particles. Presumably, one or more of the six abnormal embryos from Ay/a x Ay/a matings were Ay homozygotes. However, no single ultrastructural alteration characteristic of Ay/Ay embryos was found.