Leu-enkephalin-stimulated growth hormone and prolactin release in the rat: comparison with the effect of morphine

The effect of Leu⁵-enkephalin on growth hormone (GH) and prolactin (PRL) release was studied $\text{in vivo}$ in the infant rat and compared to that of morphine. In 10 day-old pups, intracerebroventricular injection of Leu⁵-enkephalin (50, 75 and 100 μg) resulted in a dose-related increase in plasma GH; morphine was active as GH releaser at the dose of 5 and 10 μg, but not at 2.5 μg. Pretreatment with naloxone (2 mg/kg ip) suppressed the GH-releasing effect of either Leu⁵-enkephalin (100 μg) or morphine (10 μg). Leu⁵-enkephalin (75 and 100 μg) induced a rise in plasma PRL which was neither dose-related nor antagonized by naloxone; morphine (5 and 10 μg) was active as PRL releaser and its effect was antagonized by naloxone. These results indicate that: 1) Leu⁵-enkephalin stimulates both GH and PRL release; 2) the release of GH by Leu⁵-enkephalin but likely not that of PRL involves specific opiate receptors; 3) morphine releases GH and PRL through specific opiate receptors.     

Deoxyribonucleic acid synthesis and deoxyribonucleic acid-polymerase activity during early germination of wheat embryos at high and low viability

³H-thymidine incorporation and DNA-polymerase activity during early hours of wheat embryo germination at two viability levels have been studied. The patterns of two biosynthetic activities, as well as the dependence of DNA synthesis on protein synthesis, indicated the presence of a delay in the early phase of imbibition of the aged embryos with respect to viable germs.     

Interstitial deletion (2)(p13p15)

Summary A dysmorphic 5-year-old girl with severe growth and mental deficiency was studied. She presented a de novo interstitial 2p deletion. Karyotype: 46,XX,del(2)(p13p15).     

Fast Atom Bombardment-High Field Magnet Mass Spectrometry of 6000 Dalton polypeptides

Using a combination of Fast Atom Bombardment lonisation and High Field Magnet — Mass Spectrometry we demonstrate here the ability to observe, for the first time, the accurate molecular weights of polypeptides or other important bioorganic substances up to 6000 Dalton in size. This claim is substantiated with data on intact unreduced Insulin and on the intact sweet protein Monellin, which consists of three polypeptide chains.     

The role of Mg2+ in the regulation of the structural and functional steady-states in rat liver mitochondria

A possible relationship between mitochondrial Mg²⁺ levels, structural configurations, and functional steady states has been studied in rat liver mitochondria. The results show that the concentration of mitochondrial Mg²⁺ in respiratory state 4 is definitely higher than in respiratory state 3. The metabolic transition from state 3 to state 4 and vice-versa is associated with reversible influx-efflux of about 10 nmol of Mg²⁺ per mg protein. The net uptake of this aliquot of Mg²⁺ is a necessary condition in order for the metabolic transition to state 4, both structurally and functionally, to occur. This process requires a threshold concentration of external Mg²⁺ greater than 5 mM. The phosphorylative mechanism does not appear to depend on the presence or absence of external Mg²⁺. The role of Mg²⁺ on the attainment and maintenance of the structural and functional steady state 4 seems to be correlated with its regulatory effect on the concentration of the mitochondrial P_i.     

Endocytosis of lysosomal alpha-galactosidase A by cultured fibroblasts from patients with Fabry disease.

The endocytosis of alpha-galactosidase A was studied in cultured fibroblasts from patients with Fabry disease. Alpha-galactosidase A was purified from human placenta by chromatography on concanavalin A-Sepharose, DEAE-cellulose, and N-epsilon-aminocaproyl-alpha-D-galactosylamine-Sepharose. Separation of the high-uptake form of the enzyme from the low-uptake form was accomplished by chromatography on ECTEOLA-cellulose. With the high-uptake form of the enzyme, the uptake was linear at low concentrations of enzyme and had a Kuptake of 0.01 U/ml of medium that corresponds to a Km of 5.0 x 10(-9) M. At high concentrations of enzyme, it became saturated. The high-uptake form could be converted to the low-uptake form by treatment with acid phosphatase. Mannose-6-P strongly inhibited the active uptake of the enzyme. Once taken up into the lysosomes of Fabry disease fibroblasts, alpha-galactosidase A activity was rapidly lost in the first 2 days of incubation at 37 degrees C, but was fairly stable for the next 6 days. The half-life of internalized alpha-galactosidase A activity was calculated to be 4 days. Crosslinking of the enzyme with hexamethylene diisocyanate did not increase the intracellular stability of alpha-galactosidase A activity.     

Meiotic transmission of T-DNA genes inArabidopsis thaliana plants and their expression after 5-azacytidine treatment

Arabidopsis thaliana tumors were induced by octopine strain ofAgrobacterium tumefaciens B6S3 and its derivatives with modified T-DNA. Flowering shoots appeared sponta-neously onin vitro cultivated tumors and set seeds. R₁ and R₂ progeny of octopine synthesizing plants segregated in opine synthesis activities 3:1 and 15:1. Octopine synthase activity showed absolute linkage with agropine synthesis in most lines. In R₃ and R₄ progenies, the fraction of octopine synthase and agropine synthesis positive plants was lower than expected, but Mendelian segregation was restored if plants were cultivated on medium with 5-azacytidine. The most probable mechanism of disapearance of opine synthesis is cytosine methylation. The effect of 5-azacytidine lasted for at least next two generations.     

Fluorescence characterization of the interaction of various transfer RNA species with elongation factor Tu.GTP: evidence for a new functional role for elongation factor Tu in protein biosynthesis

The ubiquity of elongation factor Tu (EF-Tu)-dependent conformational changes in amino-acyl-tRNA (aa-tRNA) and the origin of the binding energy associated with aa-tRNA.EF-Tu.GTP ternary complex formation have been examined spectroscopically. Fluorescein was attached covalently to the 4-thiouridine base at position 8 (s4U-8) in each of four elongator tRNAs (Ala, Met-m, Phe, and Val). Although the probes were chemically identical, their emission intensities in the free aa-tRNAs differed by nearly 3-fold, indicating that the dyes were in different environments and hence that the aa-tRNAs had different tertiary structures near s4U-8. Upon association with EF-Tu.GTP, the emission intensities increased by 244%, 57%, or 15% for three aa-tRNAs due to a change in tRNA conformation; the fourth aa-tRNA exhibited no fluorescence change upon binding to EF-Tu.GTP. Despite the great differences in the emission intensities of the free aa-tRNAs and in the magnitudes of their EF-Tu-dependent intensity increases, the emission intensity per aa-tRNA molecule was nearly the same (within 9% of the average) for the four aa-tRNAs when bound to EF-Tu-GTP. Thus, the binding of EF-Tu.GTP induced or selected a tRNA conformation near s4U-8 that was very similar, and possibly the same, for each aa-tRNA species. It therefore appears that EF-Tu functions, at least in part, by minimizing the conformational diversity in aa-tRNAs prior to their beginning the recognition and binding process at the single decoding site on the ribosome. Since an EF-Tu-dependent fluorescence change was also observed with fluorescein-labeled tRNA(Phe), the protein-dependent structural change is effected by direct interactions between EF-Tu and the tRNA and does not require the aminoacyl group. The Kd of the tRNA(Phe).EF-Tu.GTP ternary complex was determined, at equilibrium, to be 2.6 microM by the ability of the unacylated tRNA to compete with fluorescent Phe-tRNA for binding to the protein. Comparison of this Kd with that of the Phe-tRNA ternary complex showed that in this case the aminoacyl moiety contributed 4.3 kcal/mol toward ternary complex formation at 6 degrees C but that the bulk of the binding energy in the ternary complex was derived from direct protein-tRNA interactions.(ABSTRACT TRUNCATED AT 400 WORDS)