Comparison of columnar water-vapor measurements from solar transmittance methods.

In the fall of 1997 the Atmospheric Radiation Measurement program conducted a study of water-vapor-abundance-measurement at its southern Great Plains site. The large number of instruments included four solar radiometers to measure the columnar water vapor (CWV) by measuring solar transmittance in the 0.94-mum water-vapor absorption band. At first, no attempt was made to standardize our procedures to the same radiative transfer model and its underlying water-vapor spectroscopy. In the second round of comparison we used the same line-by-line code (which includes recently corrected H(2)O spectroscopy) to retrieve CWV from all four solar radiometers, thus decreasing the mean CWV by 8-13%. The remaining spread of 8% is an indication of the other-than-model uncertainties involved in the retrieval.

Cell-free cytoplasmic polyadenylation of oogenic RNA.

The products of cell-free ATP incorporation mediated by cytoplasmic fractions prepared from unfertilized sea urchin eggs, anucleate egg halves, nucleate egg halves, emetine-treated fertilized eggs, and four-cell embryos have been characterized to determine to what extent the polymers synthesized are poly(A) and to assess the size distribution of the primers adenylated. As judged by alkaline lability, ribonuclease resistance, and retention on poly(U)-impregnated filters, greater than 92% of the label recovered after RNA extraction is present in poly(A). LiCl fractionation indicates that little, if any, free poly(A) is synthesized or cleaved from RNA primers during the reaction, and that 4S RNA is not an effective initiator. In excess of 85% of the poly(A) is associated with RNA having S-values greater than or equal to 18S. Sedimentation profiles of RNA adenylated in the unfertilized egg and anucleate egg half reactions are identical. Suppression of in vivo protein synthesis by emetine alters the profile of RNA subsequently adenylated in vitro. It is proposed that the apparent constraints on the utilization of cytoplasmic RNA or ribonucleoprotein primers of oogenic origin may be effected by RNA-associated proteins capable of regulating the selection and/or extent of their polyadenylation during early embryogenesis.

Polyadenylylation and transcription following fertilization.

Polyadenylylated RNA from sea urchin embryos concomitantly labeled with [(3)H]adenosine and [(14)C]uridine between fertilization and the four-cell stage was used to determine whether the RNA primers prerequisite to the massive polyadenylylation known to occur after fertilization are synthesized during oogenesis or subsequent to fertilization. Characterization of this RNA and unlabeled RNA via retention on nitrocellulose membranes and poly(U)-impregnated filters, molecular hybridization with [(3)H]poly(U), RNase resistance, oligo(dT)-cellulose chromatography, and size-distribution studies indicates that the poly(A) tracts synthesized after fertilization are predominantly appended to preexisting cytoplasmic primers of oogenic origin. Hence, if polyadenylylation is involved in the selective editing of presumptive genetic messages, this process is not confined to the nucleus unless a given codogenic transcript can undergo more than one cycle of adenylylation.

Cytoplasmic adenylylation and processing of maternal RNA.

Molecular hybridization between [(3)H]-poly(U) and unlabeled RNA prepared from sea urchin eggs and embryos has been used to contrast the subcellular localization as well as the size distribution of adenylylated maternal RNA preexisting in the unfertilized egg with that adenylylated as a function of fertilization. Evidence reported establishes that such preadenylylated genetic messages are predominantly located in the ovum's subribosomal fraction and that fertilization elicits a rapid reallocation of these latent transcripts into the zygote's ribosomal fraction. Examination of the size distribution of the adenylylated RNA further demonstrates that the unfertilized egg contains a substantial population of RNA transcripts of exceptionally high molecular weight that are used as primers for the 2-fold net synthesis of poly(A) that follows fertilization. The poly(A)-rich tracts are shown to be covalently bonded to RNA. Assessment of the poly(A) content of nuclear and cytoplasmic fractions suggests that the function of poly(A) is not confined to the transport of genetic messages from the nucleus.

A chemical and physical characterization of echinoid RNA during early embryogenesis.

The properties of the major RNA components prepared from Arbacia punctulata have been characterized by sedimentation in sucrose gradients and analysis of base composition. Comparison of the components found in the unfertilized egg with those observed subsequent to fertilization revealed no differences in any of the embryonic stages examined. The base composition and sedimentation profiles of RNA from unfertilized nuclear egg fragments and from 105,000 g pellet were similar to those of the intact egg. It is concluded that the early stages of embryogenesis are not accompanied by detectable alteration of the physical or chemical characteristics of the major RNA components found in the unfertilized egg.