Spontaneous growth hormone secretion and plasma somatomedin-C in children of short stature

We studied 17 short prepubertal children, aged 7.5 to 17.0 years (mean +/- SD: 11.7 +/- 2.4) more than 2.0 SD below the mean height for their age and of delayed bone age (M +/- SD: 8.1 +/- 2.3), to clarify their physiological GH secretory status. The mean concentration of GH (MCGH) was calculated and was compared with the subjects' GH responses to insulin and arginine tolerance tests (IATT) and plasma somatomedin-C (SM-C). The mean 24-h MCGH value was 3.2 +/- 1.3 ng/ml (range 1.6-5.5). The mean peak GH response to the IATT was 13.0 +/- 7.5 ng/ml (range 2.4-33.9). In addition to the two patients with abnormally low GH responses to the IATT, seven with normal responses showed low 24-h MCGH values, a small number of GH pulses and low mean GH amplitude. The mean plasma SM-C in all patients was 0.60 +/- 0.20 U/ml. This was significantly lower than that of age-matched children of normal height (p less than 0.001). The 24-h MCGH was significantly correlated with plasma SM-C levels (r = 0.51, p less than 0.05) and with that of the first three hours of sleep at night (r = 0.84, p less than 0.01). These results indicate that: 1) some short children with normal GH response to pharmacological tests secrete a low amount of GH physiologically and 2) blood sampling during the first three hours of sleep as well as 24-hour sampling is suitable in evaluating the physiological secretion of GH.     

Molecular basis of enzyme abnormalities in urea cycle disorders. With special reference to citrullinemia and argininosuccinic aciduria

This paper deals with enzymological, immunochemical and molecular genetic analyses of citrullinemia and argininosuccinic aciduria. Citrullinemia has been classified by Saheki et al. [J. inher. Metab. Dis. 8: 155-156, 1985] into three types from the properties of the deficient argininosuccinate synthetase (ASS) of the patients. Analysis of hepatic mRNA coding for ASS revealed certain characteristics in type II and III citrullinemic patients whose hepatic ASS protein was low. A newly developed enzyme-linked immunosorbent assay (ELISA) of argininosuccinate lyase (ASL) protein showed that 8 out of ten cases of argininosuccinic aciduria had no detectable ASL protein in the liver, erythrocytes, cultured skin fibroblasts or cultured amniocytes.     

High lateral mobility of endogenous and transfected alkaline phosphatase: a phosphatidylinositol-anchored membrane protein

The lateral mobility of alkaline phosphatase (AP) in the plasma membrane of osteoblastic and nonosteoblastic cells was estimated by fluorescence redistribution after photobleaching in embryonic and in tumor cells, in cells that express AP naturally, and in cells transfected with an expression vector containing AP cDNA. The diffusion coefficient (D) and the mobile fraction, estimated from the percent recovery (%R), were found to be cell-type dependent ranging from (0.58 +/- 0.16) X 10(-9) cm2s-1 and 73.3 +/- 10.5 in rat osteosarcoma cells ROS 17/2.8 to (1.77 +/- 0.51) X 10(-9) cm2s-1 and 82.8 +/- 2.5 in rat osteosarcoma cells UMR106. Similar values of D greater than or equal to 10(-9) cm2s-1 with approximately 80% recovery were also found in fetal rat calvaria cells, transfected skin fibroblasts, and transfected AP-negative osteosarcoma cells ROS 25/1. These values of D are many times greater than "typical" values for membrane proteins, coming close to those of membrane lipid in fetal rat calvaria and ROS 17/2.8 cells (D = [4(-5)] X 10(-9) cm2s-1 with 75-80% recovery), estimated with the hexadecanoyl aminofluorescein probe. In all cell types, phosphatidylinositol (PI)-specific phospholipase C released 60-90% of native and transfection-expressed AP, demonstrating that, as in other tissue types, AP in these cells is anchored in the membrane via a linkage to PI. These results indicate that the transfected cells used in this study possess the machinery for AP insertion into the membrane and its binding to PI. The fast AP mobility appears to be an intrinsic property of the way the protein is anchored in the membrane, a conclusion with general implications for the understanding of the slow diffusion of other membrane proteins.     

The roles of different excision-repair mechanisms in the resistance of Micrococcus luteus to UV and chemical mutagens

M. luteus mutants showing increased sensitivity to both UV and 4-NQO were isolated after the treatment of parental ATCC4698 strain with MNNG. The mutants were also highly sensitive to mitomycin C, cis-platinum, 8-methoxypsoralen (8-MOP) plus near-UV and angelicin plus near-UV in various degrees. The endonuclease activity specific for pyrimidine dimers in UV-irradiated DNA was normally detected in extract of the mutants. With regard to host-cell reactivation ability the mutants fell into two groups. The hcr- mutants lacked the ability to reactivate UV-damaged N6 phage and were resistant to X-rays. The incision of DNA did not occur during incubation after the treatment with angelicin plus near-UV in the hcr- mutants, whereas it occurred in the parental strain. The facts indicate that the hcr- mutants are defective in the incision mechanism which has a wide substrate specificity, similar to the UVRABC nuclease of E. coli. On the other hand, the incision of DNA and the removal of UV-induced thymine dimers from DNA occurred in the hcr- mutants as well as in the parental strain, which is ascribed to the UV endonuclease activity. Compared with the hcr- mutants, hcr+ mutants were highly sensitive to X-rays, like recA- mutants of E. coli.     

Dependence of Plasmalemma Conductance and Potential on Intracellular Free Ca2+ in Tonoplast-Removed Cells of a Brackish Water Characeae Lamprothamnium

In response to hypotonic treatment internodal cells of the brackishwater Characeae Lamprothamnium regulate turgor pressure by releasingK⁺ and Cl^–, accompanying membrane depolarization and atransient increase in membrane electrical conductance (Okazakiet al. 1984b). The hypothesis that a transient increase in cytoplasmicfree Ca²⁺ concentration ([Ca²⁺]_c) caused by hypotonic treatmenttriggers release of K⁺ and Cl^– from the cell (Okazakiand Tazawa 1986a, b, c) was tested using tonoplast-removed cells.These cells did not regulate turgor pressure. The plasmalemmaconductance remained almost constant for a change in the intracellularfree Ca²⁺ concentration ([Ca²⁺],) from 10^–6 to 10^–2mol?m^–3. The results suggest that some cytoplasmic Ca²⁺-sensitizingsoluble components, which work as mediators to activate K⁺ and/orCl^– channels in the plasmalemma and/or the tonoplast,were lost after desintegration of the tonoplast. The plasmalemmapotential was depolarized under high [Ca²⁺]_i. However, no membranedepolarization was observed upon hypotonic treatment. Sincemembrane depolarization has been suggsted to occur under normal[Ca²⁺]_c in intact cells (Okazaki and Tazawa 1986a, b), its absencesuggests that some cytoplasmic factors, which induce the membranedepolarization in a Ca²⁺-independent manner, are lost in tonoplast-removedcells. ¹ Present address: Department of Biology, Osaka Medical College,Sawaragi-cho 2-41, Takatsuki, Osaka 569, Japan. (Received October 22, 1986; Accepted March 31, 1987)     

Dormancy in Dioscorea: Range, Duration and Timing of High-Temperature Treatment in Germination Inhibition of D. tokoro Seeds

The effects of temperature on induction and release of high-temperatureinhibition in seed germination of Dioscorea tokoro Makino, amonocotyledonous summer perennial of the temperate zone of EastAsia, were investigated. Germination was increasingly inhibitedwith elevation of temperature over 23°C and lengtheningof its duration. The low temperature limit for germination inhibitiondecreased with lengthening of the duration of high temperature.The most sensitive phase for high temperature was 1–2days after the start of imbibition at 20°C. The germination inhibition by high temperature was reversedby chilling at 5°C, which is the optimum temperature forbreaking the natural dormancy (primary dormancy) of this seed.This showed that the high-temperature inhibition of germinationdoes not cause mortal damage but only secondary dormancy (induceddormancy). Seeds from a cold climate (Miyagi Pref.) responded rather quicklyto both high temperature and chilling compared to seeds froma warm climate (Kagoshima Pref.). The responsiveness to hightemperature and chilling of D. tokoro seed may affect the germinationtime under natural conditions. (Received October 22, 1982; Accepted January 14, 1983)     

ATP:AMP phosphotransferase from baker''s yeast. Purification and properties

Synchronous cells of the green alga, Scenedesmus obliquus, cultured in a 14-h/10-h light/dark regime, contain a peak of ribonucleoside-diphosphate reductase activity and maximum deoxyribonucleoside 5'-triphosphate concentrations at the 12th hour of the cell cycle, coinciding with DNA synthesis and preceding the formation of eight daughter cells. The intracellular dTTP pool reaches 4.5 pmol and the other pools 2-3 pmol/10(6) cells. Algal reductase activity is sensitive to cycloheximide, but not to lincomycin. These correlations demonstrate the functioning of the NDP leads to dNDP leads to dNTP pathway of DNA precursor biosynthesis in plant cells. In the presence of 20 micrograms 5-fluorodeoxyuridine/ml, an inhibitor of thymidylate synthesis, the dTTP pool is rapidly depleted and DNA synthesis ceases. 5-Fluorouracil and methotrexate produce similar effects. At the same time the ribonucleotide reductase activity and also the dATP pool are greatly increased, especially when fluorodeoxyuridine treatment is combined with continued illumination of the algae. In contrast, arabinosylcytosine, an inhibitor of DNA replication, has no effect on ribonucleotide reduction. The control of de novo enzyme synthesis in the eucaryotic algae therefore appears to depend on the presence of dTTP (or a related nucleotide), but not directly coupled to DNA synthesis. This interdependence resembles the situation observed in HeLa cells, while it may differ in detail from control mechanisms of ribonucleotide reductase studied in bacteria.     

A new method for oligo(ADP-ribose) fractionation according to chain length

A new method was developed to separate mono- and oligo-(ADP-ribose) with chain lengths below 11 ADP-ribose units by size difference of one ADP-ribose residue. The separation was performed on a DEAE-cellulose column by elution with a NaCl gradient (0–0.3 $\text{M}$) in the presence of 7 $\text{M}$ urea at pH 7.6. Using this method, the chain length distribution of oligo(ADP-ribose) molecules attached to histones by incubation of isolated nuclei with radioactive NAD was determined. The average chain length estimated from this distribution coincided exactly with the value obtained by the phosphodiesterase digestion method, suggesting that the oligomers were synthesized directly on histones and not elongated from pre-existing ADP-ribose.     

Fatty acid composition and lipid synthesis in developing safflower seeds

Linoleic acid predominated in every lipid class during the whole period of seed development of safflower, while linolenic acid decreased with increasing maturation and it was not detected in mature seeds. Just before the initiation of triacylglycerol accumulation, the fatty acid composition of triacylglycerols changed more rapidly than those of phospholipids and glycolipids. Saturated fatty acids tended to accumulate at the 1- and 3-positions of the glycerol molecule and the more highly unsaturated acids at the 2-position. The fatty acid compositions at the 1- and 3-positions were similar in all cases investigated, but in none of the triacylglycerols was the distribution completely symmetrical. The positional distribution of linolenic acid in triacylglycerols prepared from the immature seeds 2 days after flowering and from the leaves was unusual; in spite of its highest degree of unsaturation, it was preferentially esterified at the 1- and 3-positions. When triacylglycerol was most rapidly accumulated (14–18 days after flowering), the incorporation of acetate-[U- ¹⁴C] into total lipids was also maximum and dienoic fatty acids were the principal acids labelled. Diacylglycerols and compound lipids reached the highest rate of synthesis 15 days after flowering, and then a maximum incorporation into triacylglycerol occurred 18 days after flowering. Incubation temperature affected the synthesis of individual lipid classes. Triacylglycerol was more rapidly synthesized at 32° than at 10°, while diacylglycerols and compound lipids were accumulated under the low-temperature condition. A rise of incubation temperature caused a depression in dienoic acid synthesis.