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Homeobox genes encode DNA-binding transcription regulators that participate in the formation of embryonic pattern or contribute to cell-type specificity during metazoan development. Homeobox genes that regulate aial patterning and segmental identity (Hox/HOM genes) share a conserved clustered genomic organization. Mammals have four clusters that have likely arisen from the duplication of a single ancestral cluster. The number of Hox-type genes in other deuterostomes was estimated by using a polymerase chain reaction sampling method. Increased Hox gene complements are associated with the appearance of chordate and vertebrate characters. Our data suggest the presence of one Hox duster in the acorn worm, a hemichordate; two Hox clusters in amphioxus, a cephalochordate; and three in the lamprey, a primitive vertebrate.

The influences of low root temperature on soybeans (Glycine max IL.1Merr. cv. Wells) were studied by germinating and maintaining plants at root temperatures of 13 and 20 C through maturity. At 42 days from the beginning of imbibition, 13 and 20 C plants were switched to 20 and 13 C, respectively. Plants were harvested after 63 days. Control plants (13 C) did not nodulate, whereas those switched to 20 C did and at harvest had C2H2 reduction rates of 0.2 micromoles per minute per plant. Rates of C2H2 reduction decreased rapidly in plants switched from 20 to 13 C; however, after 2 days, rates recovered to original levels (0.8 micromoles per minute per plant) and then began a slow decline until harvest. Arrhenius plots of C2H2 reduction by whole plants indicated a large increase in the energy of activation below the inflection at 15 C. Highest C2H2 reduction rates (1.6 micromoles per minute per plant) were at 58 days for the 20 C control. Root respiration rates followed much the same pattern as C2H2 reduction in the 20 C control and transferred plants. At harvest, roots from 13 C-treated plants had the highest activities for malate dehydrogenase, glutamate oxaloacetate transaminase, and phosphoenolpyruvate carboxylase. Roots from transferred plants had intermediate activities and those from the 20 C treatment the lowest activities. Newly formed nodules from plants switched from 13 to 20 C had much higher glutamate dehydrogenase than glutamine synthetase activity.Photosynthetic rates on a leaf area basis were about three times as high in the 20 C control as compared to 13 C control plants. Photosynthetic rates of plants switched from 20 to 13 C decreased to less than half the original rate within 2 days. Photosynthetic rates of plants switched from 13 to 20 C recovered to rates near those of the 20 C control plants within 2 weeks. All leaf enzymes assayed at harvest, with the exception of nitrate reductase, were highest in activity in the 20 C control plants.There have been few investigations on low temperature effects on roots. However, in legumes, low soil or root temperature decreases both nodulation and rates of N2 fixation (7,17,19,26,32). Many adverse effects of low soil temperature on chillingsensitive plants can be attributed to low-temperature-induced membrane phase transitions which slow protoplasmic streaming, increase permeability, and decrease the activities of membranebound enzymes by increasing Eas3 (13,14,25).

A markedly elevated BB isoenzyme fraction of serum creatine kinase was noted in four male siblings and correlated with typical radiographic findings of autosomal dominant osteopetrosis Type II (ADO Type II). Patients with other sclerosing bone diseases had no elevation of CK‐BB. The precision of the electrophoretic mobility patterns and correlation by I‐125 tagged radioimmunoassay method confirms that this is CK‐BB. We postulate that the dysfunctional and/or immature osteoclasts in ADO are more dependent on CK‐BB than on the usual tricarboxylic acid cycle for the production of energy. The correlation of marked elevation of serum CK‐BB with radiographic evidence of ADO Type II may prove to be of value as a biologic marker in the early diagnosis of the illness and lead to better understanding of the metabolism of bone.