Comparison of proteoglycans synthesized by porcine normal and polycystic renal tubular epithelial cells in vitro

Newly synthesized porcine tubular epithelial cell proteoglycans were labeled in vitro with Na2[35S]SO4. At the beginning of the labeling period (24 h) [35S] sulfate incorporated into macromolecules was measured following PD-10 chromatography. There was a significant reduction in the amount of 35S-labeled macromolecules isolated from polycystic cells compared to that from normal cells. The distribution of recovered radiolabeled material among the medium, cell surface, and intracellular fractions was similar for both normal and polycystic cells. Analysis of the proteoglycans in polycystic cells demonstrated that 86 and 73% of 35S-labeled macromolecules were of the heparan sulfate type in polycystic and normal cells, respectively. The remainder was chondroitin sulfate. Proteoglycans were characterized using DEAE-Sephacel ion-exchange chromatography, chondroitinase ABC, heparitinase, and nitrous acid digestion followed by Sepharose CL-4B gel permeation chromatography. The majority of radiolabeled material in the medium, cell surface, and intracellular fractions eluted between 0.35 and 0.39 M NaCl. However, a second peak (peak II) that eluted at 0.25 M NaCl was found in the medium from polycystic cells. This peak accounted for 27% of the total macromolecules secreted into the medium. Proteoglycans in the major peak were susceptible to nitrous acid and chondroitinase ABC digestion. A similar proportion of peak II was degraded by chondroitinase ABC. However, the remainder was only slightly susceptible to treatment with nitrous acid or heparitase. In normal cells a small amount of material eluted at a similar low charge; the proteoglycans were the same as those found in the major peak and appeared as a shoulder on this peak.     

1,25-Dihydroxyvitamin D3 increases serum levels of the vitamin K-dependent bone protein

1,25-dihydroxyvitamin D₃ increases serum levels of bone Gla protein (BGP). The maximal increase occurs 12 h after injection and is given by 350 ng 1,25(OH)₂D₃ per 180 g body weight. In both 2 and 11 month-old male rats, the maximal increase is about 3 times the normal level, while in 2 month old female rats, the maximal increase is 2 times the normal level. These effects of 1,25(OH)₂D₃ in rats parallel the previously described effects of the vitamin on BGP secretion by rat osteosarcoma cells in culture.BGP is the first bone-specific protein whose synthesis in animals is dramatically increased by 1,25(OH)₂D₃. The possible functions of BGP in the biological actions of 1,25(OH)₂D₃ on bone are discussed.     

Heat capacity microcalorimetry of the in vitro reconstitution of calf brain microtubules.

The self-assembly of calf brain tubulin, purified by the modified Weisenberg procedure, was examined in an adiabatic differential heat capacity microcalorimeter. Tubulin solutions at concentrations between 6 and 17 mg/mL were heated from 8 to 40 degrees C at heating rates between 0.1 and 1.0 deg/min in a pH 7.0 phosphate buffer containing 1 X 10(-3) M GTP, 1.6 X 10(-2) M MgCl2, and 3.4 M glycerol. The heat capacity change, deltaCp of the microtubule growth reaction was found to be -1600 +/- 500 cal/(deg mol) per 110 000 molecular weight tubulin dimer incorporated into microtubules, in agreement with the reported van't Hoff deltaCp value of -1500 cal/(deg mol) [Lee, J.C., & Timasheff, S.N. (1977) Biochemistry 16, 1754-1765]. The assembly reaction is characterized by a complex heat uptake pattern comprising both endothermic and exothermic processes.     

Hormonal control of urine-marking in wild and domestic Norway rats

Wild and domestic Norway rats will actively urine-mark a small rod suspended across their home cage. Administration of testosterone to castrated male rats indicated that the urine-marking response is hormone dependent.     

Methodichlorophen as anti-tumor drug.

Methodichlorophen was given to 26 patients with terminal malignant disease. Eight patients received adequate doses, and five of them showed objective evidence of tumour regression while three failed to respond. Those who responded included four out of five patients with lung cancer (three with squamous-cell carcinoma and one with oat-cell carcinoma) and a patient with hypernephroma. Two patients with testicular teratomas and one with acute myeloid leukemia failed to respond. The drug may be given safely by mouth to outpatients if certain precautions are taken.     

Biogeography of dinoflagellate cysts in northwest Atlantic estuaries

Few biogeographic studies of dinoflagellate cysts include the near‐shore estuarine environment. We determine the effect of estuary type, biogeography, and water quality on the spatial distribution of organic‐walled dinoflagellate cysts from the Northeast USA (Maine to Delaware) and Canada (Prince Edward Island). A total of 69 surface sediment samples were collected from 27 estuaries, from sites with surface salinities >20. Dinoflagellate cysts were examined microscopically and compared to environmental parameters using multivariate ordination techniques. The spatial distribution of cyst taxa reflects biogeographic provinces established by other marine organisms, with Cape Cod separating the northern Acadian Province from the southern Virginian Province. Species such as Lingulodinium machaerophorum and Polysphaeridinium zoharyi were found almost exclusively in the Virginian Province, while others such as Dubridinium spp. and Islandinium? cezare were more abundant in the Acadian Province. Tidal range, sea surface temperature (SST), and sea surface salinity (SSS) are statistically significant parameters influencing cyst assemblages. Samples from the same type of estuary cluster together in canonical correspondence analysis when the estuaries are within the same biogeographic province. The large geographic extent of this study, encompassing four main estuary types (riverine, lagoon, coastal embayment, and fjord), allowed us to determine that the type of estuary has an important influence on cyst assemblages. Due to greater seasonal variations in SSTs and SSSs in estuaries compared to the open ocean, cyst assemblages show distinct latitudinal trends. The estuarine context is important for understanding present‐day species distribution, the factors controlling them, and to better predict how they may change in the future.     

Obestatin acts in brain to inhibit thirst

Derived from the same prohormone, obestatin has been reported to exert effects on food intake that oppose those of ghrelin. The obestatin receptor GPR39 is present in brain and pituitary gland. Since the gene encoding those two peptides is expressed also in those tissues, we examined further the possible actions of obestatin in vivo and in vitro. Intracerebroventricular administration of obestatin inhibited water drinking in ad libitum-fed and -watered rats, and in food-and water-deprived animals. The effects on water drinking preceded and were more pronounced than any effect on food intake, and did not appear to be the result of altered locomotor/behavioral activity. In addition, obestatin inhibited ANG II-induced water drinking in animals provided free access to water and food. Current-clamp recordings from cultured, subfornical organ neurons revealed significant effects of the peptide on membrane potential, suggesting this as a potential site of action. In pituitary cell cultures, log molar concentrations of obestatin ranging from 1.0 pM to 100 nM failed to alter basal growth hormone (GH) secretion. In addition, 100 nM obestatin failed to interfere with the stimulation of GH secretion by GH-releasing hormone or ghrelin and did not alter the inhibition by somatostatin in vitro. We conclude that obestatin does not act in pituitary gland to regulate GH secretion but may act in brain to alter thirst mechanisms. Importantly, in rats the effects of obestatin on food intake may be secondary to an action of the peptide to inhibit water drinking.     

Origin of the phosphate at the ligation junction produced by self-splicing of Tetrahymena thermophila pre-ribosomal RNA

The exons of the self-splicing pre-ribosomal RNA of Tetrahymena thermophila are joined accurately in vitro, even when only 33 nucleotides of the natural 5' exon and 38 nucleotides of the natural 3' exon remain. RNA fingerprint analysis was used to identify the unique ribonuclease T1 oligonucleotide generated by exon ligation. Secondary digests of the ligation junction oligonucleotide with ribonuclease A confirmed the identity of the fragment and demonstrated that the phosphate group that forms the phosphodiester bond at the ligation junction is derived from the 5' position of a uridine nucleotide in the RNA. This observation supports the prediction that the splice junction phosphate is derived from the 3' splice site. These results emphasize the mechanistic similarities of RNA splicing reactions of the group I introns, group II introns and nuclear pre-mRNA introns.