In vitro processing at the 3'-terminal region of pre-18S rRNA by a nucleolar endoribonuclease.

In an investigation of the possible involvement of a highly purified nucleolar endoribonuclease in processing of pre-rRNA at the 3' end of the 18S rRNA sequence, an in vitro synthesized pre-18S rRNA transcript containing the 3' end region of 18S rRNA and the 5' region of the first internal transcribed spacer (ITS1) was used as a substrate for the enzyme. Cleavages generated by the nucleolar RNase were localized by S1 nuclease protection analysis and by the direct release of labeled rRNA products. Precise determination of the specificity of cleavage was achieved by RNA sequence analysis with end-labeled rRNA transcripts. These data demonstrated that the purified nucleolar RNase cleaved the pre-18S rRNA transcript at three specific sites relative to the 3' region of 18S rRNA. The first two sites included the mature 3'-end 18S rRNA sequence and a site approximately 55 nucleotides downstream of the 3'-end 18S rRNA sequence, both of which corresponded directly to recent results (Raziuddin, R. D. Little, T. Labella, and D. Schlessinger, Mol. Cell. Biol. 9:1667-1671, 1989) obtained with transfected mouse rDNA in hamster cells. The other cleavage occurred approximately 35 nucleotides upstream from the mature 3' end in the 18S rRNA sequence. The results from this study mimic the results obtained from in vivo studies for processing in the 3' region of pre-18S rRNA, supporting the proposed involvement of this nucleolar endoribonuclease in rRNA maturation.

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Pituitary gland: one site of ultrashort-feedback regulation for control of thyrotropin

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1986.250.2.e121 ◽

1986 ◽

Vol 250 (2) ◽

pp. E121-E124

Author(s):

T. Kakita ◽

W. D. Odell

Keyword(s):

Feedback Regulation ◽

In Vivo Studies ◽

Pituitary Cells ◽

Site Of Action ◽

Loop Feedback ◽

Species Specific ◽

A Site ◽

Hypothalamic Level

Studies from our laboratory have previously demonstrated sensitive and specific autoregulatory control systems for thyrotropin (TSH), luteinizing hormone (LH), and follicle-stimulating hormone (FSH) in the rabbit. Because our studies of LH autoregulation showed the feedback regulation acted directly at a pituitary level, the current studies were designed to investigate whether the TSH control system also acted at the pituitary level. Two species-specific TSH assays were employed; a rabbit TSH radioimmunoassay which showed little or no reaction to human TSH, and a human TSH radioimmunoassay which showed little or no reaction to rabbit TSH. Both in vivo and in vitro studies were performed. TRH (thyrotropin-releasing hormone) in doses of 2, 10, and 50 micrograms was injected as an intravenous bolus into thyroidectomized hypothyroid rabbits during continuous perfusion with highly purified human TSH (hTSH) or with saline. In these in vivo studies, TRH-stimulated rabbit TSH (rTSH) secretion was suppressed by hTSH perfusion compared with control saline perfusion. The effect of hTSH was studied in vitro by employing short-term cultured rabbit pituitary cells. When hTSH was added to the incubation medium, TRH-stimulated rTSH secretion was inhibited. From these studies, we conclude that one site of the autoregulatory control for TSH in the rabbit is at the pituitary level. These studies do not exclude a possible additional short-loop feedback control at an hypothalamic level, but such a site of action is not required to explain the autoregulatory phenomenon.

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Regulation of vascular endothelial growth factor expression in human endometrium by steroids and hypoxia: In vitro and in vivo studies

Journal of the Society for Gynecologic Investigation ◽

10.1016/s1071-5576(97)86195-3 ◽

1998 ◽

Vol 5 (1) ◽

pp. 69A-69A

Author(s):

A SHARKEY ◽

D CHARNOCKJONES ◽

K DAY ◽

H SOWTER ◽

L SVENSSON ◽

...

Keyword(s):

Vascular Endothelial Growth Factor ◽

Growth Factor ◽

Human Endometrium ◽

In Vivo Studies ◽

Vascular Endothelial ◽

Factor Expression ◽

Growth Factor Expression ◽

Endothelial Growth Factor

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In vitro and in vivo studies of new cationic Zn(II)‐benzonaphthoporphyrazines as photosensitizers for PDT

Journal of Porphyrins and Phthalocyanines ◽

10.1002/jpp.373.abs ◽

2001 ◽

Vol 5 (8) ◽

pp. 645-651

Author(s):

M. Peeva ◽

M. Shopova ◽

U. Michelsen ◽

D. Wöhrle ◽

G. Petrov ◽

...

Keyword(s):

In Vivo Studies

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Effect of caffeine on theophyliine on cerebral blood flow response to brain activation: In vitro and in vivo studies

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/sj.jcbfm.9591524.0198 ◽

2005 ◽

Vol 25 (1_suppl) ◽

pp. S198-S198

Author(s):

Joseph R Meno ◽

Thien-son K Nguyen ◽

Elise M Jensen ◽

G Alexander West ◽

Leonid Groysman ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Brain Activation ◽

In Vivo Studies ◽

Blood Flow Response ◽

Flow Response

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Effects of Unfractionated and Low Molecular Weight Heparins on Platelet Thromboxane Biosynthesis “In Vivo”

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648988 ◽

1994 ◽

Vol 72 (06) ◽

pp. 942-946 ◽

Cited By ~ 20

Author(s):

Raffaele Landolfi ◽

Erica De Candia ◽

Bianca Rocca ◽

Giovanni Ciabattoni ◽

Armando Antinori ◽

...

Keyword(s):

Molecular Weight ◽

Unfractionated Heparin ◽

Low Molecular Weight Heparin ◽

Primary Source ◽

In Vivo Studies ◽

Low Molecular Weight ◽

Heparin Administration ◽

To Receive

SummarySeveral “in vitro” and “in vivo” studies indicate that heparin administration may affect platelet function. In this study we investigated the effects of prophylactic heparin on thromboxane (Tx)A2 biosynthesis “in vivo”, as assessed by the urinary excretion of major enzymatic metabolites 11-dehydro-TxB2 and 2,3-dinor-TxB2. Twenty-four patients who were candidates for cholecystectomy because of uncomplicated lithiasis were randomly assigned to receive placebo, unfractionated heparin, low molecular weight heparin or unfractionaed heparin plus 100 mg aspirin. Measurements of daily excretion of Tx metabolites were performed before and during the treatment. In the groups assigned to placebo and to low molecular weight heparin there was no statistically significant modification of Tx metabolite excretion while patients receiving unfractionated heparin had a significant increase of both metabolites (11-dehydro-TxB2: 3844 ± 1388 vs 2092 ±777, p <0.05; 2,3-dinor-TxB2: 2737 ± 808 vs 1535 ± 771 pg/mg creatinine, p <0.05). In patients randomized to receive low-dose aspirin plus unfractionated heparin the excretion of the two metabolites was largely suppressed thus suggesting that platelets are the primary source of enhanced thromboxane biosynthesis associated with heparin administration. These data indicate that unfractionated heparin causes platelet activation “in vivo” and suggest that the use of low molecular weight heparin may avoid this complication.

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