1,720,979 research outputs found
Synthesis and characterization of tetramethylrhodaminethiocarbamoyl-(Glu(1))-epidermal mitosis-inhibiting pentapeptide
No full textA fluorescent analog of epidermal mitosis-inhibiting pentapeptide ŽpGlu–Glu–Asp–Ser–Gly. was synthesized by reacting tetramethylrhodamine isothiocyanate with ring-opened epidermal mitosis-inhibiting pentapeptide. The ring-opening reaction of the pyrrolidone moiety was performed with mild acidic hydrolysis and the product purified by reversed-phase high-performance liquid chromatography.
Tetramethylrhodaminethiocarbamoyl-ŽGlu1.–epidermal mitosis-inhibiting pentapeptide was purified by chromatography on Sephadex G-25 and reversed-phase high-performance liquid chromatography. After characterization by amino acid analysis, the analog was incubated in presence of A431 cell line to visualize the cellular localization of the epidermal mitosis-inhibiting pentapeptide. The data gave negative results
Seasonal changes in angiotensin converting enzyme activity in male and female frogs (Rana esculenta)
No full textGonad, lung, kidney and serum angiotensin converting enzyme (ACE) activities were determined by specific substrate hydrolysis in male and female Rana esculenta over 1 year. Ovary ACE activity showed the highest values among the different tissues, with a significant peak (223+-52 nmol min-1 mg protein-1) in late winter-early spring. Testis ACE activity followed a significant seasonal cycle, increasing from September to peak in April (2.5+-0.8 nmol min-1 mg protein-1) and then decreased in the post-reproductive period. Lung and kidney ACE activities were not correlated with the annual reproductive cycle phases. In serum a peak of activity was present in the post-reproductive period both in male and female frogs. The present data show a correlation between ACE and the annual reproductive cycle of R. esculenta
Synthetic seminal plasma peptide inhibits testosterone production in rat Leydig cells.
No full textNative peptides, extracted from human and bovine seminal plasma, were characterized at the endocrine and paracrine level as modulators of follicle stimulating hormone activity. Similarly to other peptides extracted from chromatin of various tissues, seminal plasma peptides show regulatory activity on RNA synthesis by exerting inhibitory effects on transcription in vitro and in neoplastic and fast-growing cells. Biochemical and mass spectrometry analysis of highly purified fraction from seminal plasma allowed to design and synthesize a peptide with the following amino acid sequence: pGlu-Val-Ala-Asp-Ser-Asp-Gln-Asn (Mancinelli et al. Biol. Chem. 380: 31-40, 1999). Preliminary data on the activity of synthetic peptide have shown an inhibition of testosterone production by frog testes incubated in presence of peptide. The aim of our research was to study the role of synthetic peptide in mammalian testicular steroidogenesis. Continuous, isoosmotic Percoll gradient was utilized to isolate highly purified Leydig cells from rat testicular interstitial cell suspensions. 5 x 104 cells were incubated with increasing doses of synthetic peptide in presence of 50 mU LH for 180 min at 37°C. Testosterone levels in the incubation medium were measured by radioimmunoassay. The results showed the inhibition of testosterone production by Leydig cells with a bell-shape curve. 10-8 M synthetic peptide exerted the highest testosterone inhibition (58%). The basal production of testosterone, without LH stimulation, remained unchanged after treatment of rat Leydig cells with synthetic seminal plasma peptide. Toxicological analysis of synthetic peptide was carried out on carcinoma cell line A431 with negative results. These data suggest a probable role of synthetic seminal plasma peptides in modulating testicular steroidogenesis
Bioavailability of thymic humoral factor gamma2.
No full textDespite the considerable progress made in peptide drug research, many serious obstacles, the most important being that of obtaining sufficient bioavailability for maintaining pharmacological efficiency, still hinder the use of peptides as useful therapeutic agents. Thymic Humoral Factor gamma2 (THF-gamma2) is an immunoregulatory peptide present in thymic extract, identified as an octapeptide of the structure Leu-Glu-Asp-Gly-Pro-Lys-Phe-Leu. THF-gamma2 increases T-cell functions as the response to T-cell lectins and interleukin-2 production. THF-gamma2 has been used as an immunomodulator in clinical conditions associated with immune impairment and dysregulation. The degradation of THF-gamma2 by enzymes present in human plasma, has been investigated. The cleavage of THF-gamma2 was insensitive to classical proteinase inhibitors, but sensitive to metalloproteinase and aminopeptidase inhibitors. The degradation was completely blocked by specific inhibitors of angiotensin converting enzyme (ACE) and aminopeptidase. The sites of cleavage were identified by HPLC analysis and amino acid analysis. Leu1-Glu2 and Lys6-Phe7 bounds were cleaved by aminopeptidase and ACE, respectively. After human ACE purification, some kinetic parameters were determined. Km and Kcat values for THF-gamma2 were 0.273 mM and 107 s-1, respectively. The optimum of pH was 7.6 . I50 for captopril and lisinopril, two specific ACE inhibitors, were 1.052±0.140 nM and 25.770±1.079 nM. The data obtained are useful to modifying the peptide structure so as to reduce recognition by proteinases and to prolong the biological activity
Modulazione della sintesi ovarica di prostaglandine e steroidi nel tritone crestato (Triturus carniflex).
No full textNel presente lavoro è stato valutato il possibile effetto del pituitary adenylate cyclase-activating peptide 38 (PACAP 38) sulla sintesi di prostaglandine e steroidi da parte dell'ovario del tritone crestato , triturus carnifex. Il PACAP 38 è stato estratto dal cervello e dall'ovario di tritone con una metodica HPLC. L'ovario di tritone è stato incubato per 30 e 60 min in presenza di PACAP 38 sintetico, PACAP 38 di ovario e di cervello in presenza di inibitori della cicloossigenasi (COX)), dell'adenlato ciclasi (AC) e della fosfolipasi C (PLC). I tre tipici PACAP 38 hanno aumentato la sintesi ovarica di prostaglandine E2 (PGE2) (30 e 60 min) e quella di progesterone e corticosterone (60 min), inoltre hanno diminuito la sintesi di estradiolo-17beta (60 min). Gli inibitori della COX e della PLC hanno annullato gli effetti del PACAP 38 sulla sintesi ovarica di PGE2, progesterone, corticosterone ed estradiolo-17 beta,mentre l'inibitore della AC ha annullato gli effetti sulla sintesi di progesterone, corticosterone ed estradiolo-17beta. Questi dati ci hanno fatto ipotizzare che nell'ovario di Triturus carnifex il PACAP 38 agisce sulla PLC provocando un aumento della PGE2, questa prostaglandina, a sua volta, agisce sulla AC inducendo l'aumento del progesterone e del corticosterone e la diminuzione dell'estradiolo-17beta
Purification of swine serum angiotensin converting enzyme with high recovery of activity using lisinopril coupled to epoxy-activated sepharose 6B.
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Inhibition of steroidogenesis in frog testis "in vitro" by synthetic seminal plasma peptide
No full textSeminal plasma peptide (pGlu-Val-Ala-Asp-Ser-Asp-Gln-Asn), synthesized following data obtained from biochemical and mass spectrometry analysis of a highly purified fraction from bovine seminal plasma, was characterized at paracrine level as an “in vitro” modulator of testosterone production in rat Leydig cells. 10-8 M synthetic peptide exerted the highest testosterone inhibition in rat Leydig cells stimulated with 50 mU of LH. The basal testosterone production (without LH stimulation) was not influenced by synthetic seminal plasma peptide.
In Rana esculenta, spermatogenesis is well characterized at morphological, endocrine and paracrine levels. Spermatogonial multiplication occurs in late winter-early spring, while spermatocytes (I and II) and spermatids are rare or totally absent. Progression of spermatogenesis lasts until autumn with spermatids and appearance of spermatozoa. After the winter stasis, in the germinal compartment of the testis, only spermatogonia and spermatozoa are observed, due to the degeneration of the other stages.
The aim of our research was to study the influence of synthetic seminal plasma peptide in amphibian testicular steroidogenesis during the annual reproductive cycle of the male frog, Rana esculenta. Male frogs were captured at different times throughout the year and testes were removed, placed in DMEM in presence of 10 mM Hepes, 0.1 U/ml penicillin G and 0.1 mg/ml streptomycin and incubated for 6 h at 25 °C with increasing doses of synthetic peptide. Testosterone levels in the incubation medium were measured by radioimmunoassay. Preliminary results showed inhibition of testosterone production by frog testis with the highest value (42%) in summer at a peptide concentration of 10-6 M, suggesting the influence of synthetic seminal plasma peptide in spermatocyte differentiation
Small acidic peptides from wheat germ chromatin. I. Isolation and biochemical characterization.
No full textRNA synthesis in cell and cell-free systems is inhibited by a family of acidic, low molecular weight chromatin peptides (CPs). These peptides were extracted from deproteinized DNA of prokaryotic and eukaryotic cells, but the low yield of purified material by this procedure hinders efforts aimed at understanding their action mechanism in gene regulation. In this report we describe two purification methods of CPs from an easily available source, wheat germ. A comparison is made between the method starting from deproteinized DNA and the method from purified chromatin. The biological effects (inhibition of L1210 cell growth and DNA in vitro transcription) of CPs from wheat germ together with their chemical characteristics (molecular weight, amino acid composition and presence of phosphoserine) show strong homology with those of CPs from other sources. These results suggest a possible role of these chromatin peptides in controlling gene expression
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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