An insight into the possible mechanism of working of two-cistronic gene expression systems and rational designing of newer systems.

The initial attempts at hyper-expressing buffalo/goat growth hormone (GH)-ORFs in Escherichia coli directly under various strong promoters were not successful despite the presence of a functional gene. High level expression of GH was achieved as a fusion protein with glutathione-S-transferase (GST). To produce native GH in an unfused state, we adapted an established strategy of two-cistronic approach in our system. In this strategy, utilizing one of the highly efficient reported sequences as the first cistron led to a nearly 1000-fold enhancement in the level of expression under an E. coli promoter (trc). In search of a newer first-cistron sequence as well as to see the generality of the two-cistronic approach, we explored the ability of different lengths of a highly expressing natural gene to act as an efficient first cistron. Surprisingly, GST, which is naturally highly expressible in E. coli, could not be fitted into a successful two-cistronic construct. In addition, placement of the entire two-cistronic expression cassette (which had earlier given high-level GH expression under trc promoter) under the T7 promoter in E. coli failed to hyper-express GH. These results suggest that the successful exploitation of the two-cistron arrangement for hyper-expression of eukaryotic ORFs in bacteria is not as straightforward as was previously thought. It appears probable that factors such as the sequence context, together with the length and codons used in the first cistron are important as well.

Influence of L-triiodothyronine on rat somatotroph cells

The L-Triiodothyronine (L-T3) has a direct influence on the population of somatotrophs in rat pituitary gland. This effect is dose-dependent and induces both proliferation of somatotrophs and striking changes in the synthesis and secretion of grwth hormone (GH). Daily injections of 5 mug L-T3 for 7 days increased significantly the synthesis and storage of GH in pituitary gland, but the GH release was partially blocked. By contrast, injections of 10 mug L-T3 promote rapid synthesis and secretion of GH with removal of the cytoplasmic stores of the hormone and a consequent rise of serum levels. A close correlation was found between levels of stimulation and proliferation or retrogression of lactotroph cell population.

Talla baja por resistencia a la hormona de crecimiento / Low height due to growth hormone resistance

El retraso de crecimiento de un niño por alteraciones en la hormona de crecimiento puede producirse por déficit en su producción o por falta de respuesta a su efecto. Ambos grupos de niños tienen características clínicas bastante similares. La hormona de crecimiento ejerce su efecto biológico a través de receptores tisulares, y si éstos están alterados se producirá un cuadro de resistencia periférica a dicha hormona. Presentamos un niño que consultó a los 14 años y 7 meses de edad por retraso severo del crecimiento, con talla de 95 cm, obesidad centrípeta, manos y pies pequeños, micropene y facies infantil, características sugerentes de un déficit de hormona de crecimiento. El estudio de laboratorio mostró concentraciones plasmáticas elevadas de hormona de crecimiento elevados y disminución de las de somatomedina-C. El paciente fue tratado con hormona de crecimiento biosintética, sin respuesta bioquímica ni clínica, lo que sugiere resistencia periférica a la acción de la somatotropina

Development, production and pharmacodynamics of human growth hormone.

With the advent of recombinant DNA technology, it is possible to produce biosynthetic human growth hormone (B-hGH). Novo Nordisk A/S has developed a method for manufacturing B-hGH which is identical to the 22K fraction of pituitary human growth hormone (P-hGH), using a nonpathogenic strain of Escherichia coli as host. B-hGH has been investigated extensively in physical, chemical and biological studies and found to be identical to P-hGH. Pharmacological studies have revealed that B-hGH possesses the same pharmacokinetic and short-term metabolic profiles as P-hGH. Long term clinical studies have shown that B-hGH induces a significant increase in height velocity in children with growth hormone deficiency (GHD) and is characterized by a low antigenicity.

Estudio inmunocitoquimico de las hormonas de la adenohipofisis humana: hormona del crecimiento / Immunocytochemical study of the human adenohypophysis hormones: growth hormone

Con el objeto de verificar el concepto de que la hormona del crecimiento esta contenida en poblaciones de celulas acidofilas, se realizo la deteccion inmunocitoquimica de la hormona en cortes histologicos de adenohipofisis humana fijados en formalina. Se utilizo la reaccion inmunocitoquimica de peroxidasa antiperoxidasa (PAP). se encontro que las celulas detectadas inmunocitoquimicamente como productoras de la hormona del crecimiento (GH), corresponden a las celulas acidofilas naranjas en la reaccion de tincion naranja G. delineadas clara y especificamente por el metodo PAP, estas celulas fueron observadas formando filas a lo largo de sinusoides. Se presenta la ultraestructura de estas celulas y se compara con las observaciones hechas por otros autores. Se describe ademas la utilidad del metodo para detectar la hormona de crecimiento en adenomas de la pituitaria y sus metastasis. Finalmente se discute el papel de la hormona en el crecimiento y se analizan las perspectivas de investigacion y la utilizacion practica de ella en el tratamiento de algunas entidades clinicas y en el incremento del crecimiento