Anion transport during maturation of erythroblastic cells

Bromide uptake was measured in single maturing erythroblastic cells of rabbits by means of X-ray microanalysis. Increase in bromide uptake as the cells matured was observed. The order of cells from low to high bromide uptake was: early erythroblast less than late erythroblast less than marrow red cells less than peripheral red blood cells. The transition from low to high bromide uptake is correlated to the accumulation of iron which begins in the late erythroblast. A decrease in rubidium uptake also occurs as iron accumulates in the cell. These results indicate that the anion and cation transport changes during maturation are parallel in time course but opposite in direction. In addition, the increase in bromide uptake can be accounted for by the increase in surface-to-volume ratios of the cells. Surface-to-volume ratios were estimated by morphometric techniques.     

Synergism of cortisol and thyrotropin-releasing hormone in lung maturation in fetal sheep

The effects of fetal infusions of cortisol and thyrotropin-releasing hormone (TRH) singly and together on pressure-volume relationships and saturated phosphatidylcholine (SPC) concentrations in the lungs were studied in 28 fetal sheep delivered at 128 days of gestation. Four groups each of 7 fetuses were infused with either saline (for 156 h), TRH (25 micrograms/h in 60-s pulses for 156 h), TRH (for 156 h) combined with cortisol (1 mg/h for 84 h), or cortisol (for 84 h). Cortisol had no effect on SPC concentrations, whereas both TRH and cortisol plus TRH increased the concentration of SPC in lavage fluid but not lung tissue. Neither cortisol nor TRH significantly affected lung distensibility [V40; 0.64 +/- 0.04 and 0.57 +/- 0.10 (SE) ml/g, respectively, vs. 0.41 +/- 0.03 ml/g in controls] or stability (V5; 0.24 +/- 0.01 and 0.35 +/- 0.07 ml/g vs. 0.24 +/- 0.03 ml/g), whereas treatment with a combination of the two hormones was associated with a fourfold increase in V40 (1.70 +/- 0.16 ml/g) and V5 (1.03 +/- 0.15 ml/g). Since raised concentrations of cortisol, triiodothyronine, and estradiol-17 beta (treatment with cortisol) had no effect on V40 and V5, whereas similar hormonal changes associated with elevated prolactin levels (treatment with cortisol plus TRH) had marked effects, we conclude that prolactin plays an essential part in the synergism of cortisol and TRH.     

Epitopes that span the tau molecule are shared with paired helical filaments

Tau protein has been shown to be an integral component of Alzheimer paired helical filaments (PHF). However, the extent to which tau is incorporated into PHF has not been clear because the antibodies used to label PHF generally do not have precisely defined epitopes. Here we define the antigenic sites for five monoclonal antibodies that react with tau and cross-react with SDS-extracted neurofibrillary tangles. The reactive sites were determined by screening a lambda gt11 sublibrary expressing small fragments of the tau sequence. The mapped epitopes were found to span almost the entire length of tau, suggesting that PHF contains tau in its entirety or nearly in its entirety. One antibody was found to cross-react with microtubule-associated protein 2, implying some degree of homology between the two proteins.     

Culture conditions for arresting and stimulating the proliferation of a rainbow trout fibroblast cell line,RTG-2

Summary Conditions for arresting and stimulating the proliferation of the rainbow trout fibroblast cell line RTG-2 have been examined and the time course of events after stimulation determined. Quiescent populations were achieved in two ways. Cultures grown to confluency without a medium change for at least 7 d had fewer than 5% of the cells in S phase and few mitotic figures. Cultures deprived of serum, which could be done for up to 3 d without a loss in cell number, also achieved quiescence. After 3 d without serum, less than 1% of cells were in S phase and mitotic figures were infrequent. Addition to these cultures of fresh serum-containing medium brought about the synchronous entry of cells into S phase and mitosis. For cultures in which either the medium had been changed after 7 d without a change or serum-containing medium had been added after 3 d of serum deprivation, DNA synthesis increased after a lag period of 20 to 24 h, was pronounced between 30 and 45 h, and then declined. This was followed by a peak in the mitotic index. These protocols for arresting and subsequently stimulating RTG-2 proliferation should allow the G₁-S transition to be studied in a representative of teleosts. This research was supported by Natural Sciences and Engineering Research Council of Canada grant to N. C. B.     

Synthesis and biological activity of novel C-terminal-extended and biotinylated growth hormone-releasing factor (GRF) analogs.

A series of novel hGRF(1-29)-NH2 analogs were synthesized and biotinylated. The immunological and biological activities of these analogs were then characterized. To distance the biotin moiety from the putative bioactive core, a C-terminal spacer arm consisting of -Gly-Gly-Cys-NH2 (-GGC) was added to hGRF(1-29)-NH2 (hGRF29) and analogs, with subsequent biotinylation performed at the cysteine residue. Neither addition of the C-terminal spacer arm nor biotinylation affected affinity of these analogs for GRF antibody. Relative to hGRF(1-44)-NH2 (hGRF44: potency = 1.0), the biotinylated analogs were equipotent in vitro to their nonbiotinylated, parent compounds: [desNH2Tyr1,D-Ala2,Ala15]hGRF29-GGC-(tpBiocyt in)-NH2 (4.7) = [Ala15]hGRF29-GGC-(tpBiocytin)-NH2 (3.9) greater than hGRF29-GGC-(tpBiocytin)-NH2 (0.8). Based upon cumulative GH release data in vivo (0-60 min postinjection), [desNH2Tyr1,D-Ala2,Ala15]hGRF29-GGC-(tpBiocyt in)-NH2, [Ala15]hGRF29-GGC-(tpBiocytin)-NH2, and hGRF29-GGC-(tpBiocytin)-NH2 displayed 8.6, 5.5, and 0.8 times, respectively, the potency of hGRF44. These in vivo potency values were not significantly different from the corresponding parent compounds (i.e., with or without the C-terminal spacer arm). In summary, biotinylated hGRF analogs have been developed that retain full immunoreactivity and potent bioactivity (in vitro and in vivo), thus permitting their use in GRF receptor isolation, ELISA, and histochemical procedures.     

Protein synthesis in the hippocampus associated with memory facilitation by corticotropin-releasing factor in rats.

The present study used pharmacological, biochemical, and behavioral methods to examine the role of protein synthesis in the hippocampus in memory processes of a passive avoidance learning in rats. Results indicated that corticotropin-releasing factor (CRF) significantly improved memory retention in rats. Both cycloheximide (CHX) and actinomycin-D (ACT-D) impaired memory at high doses. At doses of CHX and ACT-D that did not affect memory alone, they both antagonized the memory-enhancing effect of CRF. Biochemically, there were specific increases in the optical density of three protein bands in the cytosolic fraction of hippocampal cells in rats showing good memory. There were also marked increases in the optical density of two protein bands in the nucleus fraction of the same animals. Similar results were observed in animals injected with CRF. However, no significant protein alteration was observed in animals receiving stress. These results together suggest that there are new protein syntheses in the hippocampus that are specifically associated with passive avoidance learning in rats.     

Carrier detection and prenatal diagnosis of alpha-thalassemia of Southeast Asian deletion by polymerase chain reaction

Summary Alpha-thalassemia of Southeast Asian deletion (-- SEA/) is very common in Southeast Asia. Homozygosity of this genotype is the major cause of Hb Bart's hydrops fetalis in Taiwan. With polymerase chain reaction using three oligonucleotide primers bridging the common deletion breakpoint, a DNA fragment of 194 basepairs (bp) was amplified in chromosomes with the-- SEA determinant and a DNA fragment of 287 bp was amplified in chromosomes without this deletion. In our pilot study including 8 normal subjects, 20 obligate carriers, and 11 homozygotes of the deletion, all the genotypes were determined and then confirmed by Southern blotting and DNA hybridization with globin gene probe. For prenatal diagnosis, 55 at-risk pregnancies were collected. Chorionic villus sampling was done in 51 cases and early amniocentesis was done in 4 cases. Fourteen cases (25.5%) were diagnosed as normal, 25 (45.5%) as heterozygotes, and 16 (29%) as homozygotes of -- SEA. All of the diagnoses were also confirmed as aforementioned. With polymerase chain reaction, the determination of the -- SEA deletion is straightforward and is much quicker and easier than with conventional Southern blotting and DNA hybridization. In areas with a high prevalence of -- SEA deletion, this method provides a rapid tool for carrier detection and prenatal diagnosis.     

Localization of two genes for Usher syndrome type I to chromosome 11.

The Usher syndromes (USH) are autosomal recessive diseases characterized by congenital sensorineural hearing loss and progressive pigmentary retinopathy. While relatively rare in the general population, collectively they account for approximately 6% of the congenitally deaf population. Usher syndrome type II (USH2) has been mapped to chromosome 1q (W. J. Kimberling, M. D. Weston, C. M?ller, et al., 1990, Genomics 7: 245-249; R. A. Lewis, B. Otterud, D. Stauffer, et al., 1990, Genomics 7: 250-256), and one form of Usher syndrome type I (USH1) has been mapped to chromosome 14q (J. Kaplan, S. Gerber, D. Bonneau, J. Rozet, M. Briord, J. Dufier, A. Munnich, and J. Frezal, 1990. Cytogenet. Cell Genet. 58: 1988). These loci have been excluded as regions of USH genes in our data set, which is composed of 8 French-Acadian USH1 families and 11 British USH1 families. Both of these sets of families show linkage to loci on chromosome 11. Linkage analysis demonstrates locus heterogeneity between these sets of families, with the French-Acadian families showing linkage to D11S419 (Z = 4.20, theta = 0) and the British families showing linkage to D11S527 (Z = 6.03, theta = 0). Genetic heterogeneity of the data set was confirmed using HOMOG and the M test (log likelihood ratio > 10(5)). These results confirm the presence of two distinct USH1 loci on chromosome 11.     

Genetic mapping of three human homologues of murine t-complex genes localizes TCP10 to 6q27, 15 cM distal to TCP1 and PLG

Human homologues of mouse t-complex genes have been cloned and localized physically to chromosome 6p or 6q. TCP1, TCP10, and PLG are human homologues of genes located in the proximal portion of the t-complex on mouse chromosome 17. We present here results of genetic mapping of these human t-complex homologues previously localized to 6q25-q27, 6q21-q27, and 6q26-q27, respectively, by physical techniques. TCP1 and PLG do not recombine with each other and are separated from TCP10 by about 15 cM, while the corresponding mouse genes are no more than 4 cM apart. Genetic mapping with markers well localized cytogenetically places TCP1 and PLG proximal to TCP10 and localizes the latter to the cytogenetic band 6q27. It is likely that the organization of human t-complex homologues on 6q is similar to that of t haplotypes rather than that of wildtype murine chromosome 17.     

Molecular cloning and expression of the cDNA for a novel A2-adenosine receptor subtype.

A novel adenosine receptor subtype has been cloned from a rat brain cDNA library using a probe generated by the polymerase chain reaction. The cDNA, designated RFL9, encodes a protein of 332 amino acids. The structure of RFL9 is most similar to that of the recently cloned rat A2-adenosine receptor, with a sequence identity of 73% within the presumed seven transmembrane domains. Expression of RFL9 in COS-6M cells resulted in ligand binding and functional activity characteristics of an adenosine receptor that is coupled positively to adenylyl cyclase. Examination of the tissue distribution of RFL9 mRNA by Northern blot analysis showed a restricted distribution with highest levels expressed in large intestine, cecum, and urinary bladder; this pattern was distinct from that of either the A1- or A2-adenosine receptor mRNAs. In situ hybridization studies of RFL9 mRNA showed no specific hybridization pattern in brain, but a hybridization signal was readily observed in the hypophyseal pars tuberalis. Thus, RFL9 encodes a novel A2-adenosine receptor subtype.