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Digitale Medien

Effects of lactation on the regulation of hepatic metabolism in the rat and sheep: adrenergic receptors and cyclic AMP responses (1992)

Dunphy, A. M. ; Snell, K. ; Clegg, R. A.

Springer

Molecular and cellular biochemistry 117 (1992), S. 35-42

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ISSN: 1573-4919

Schlagwort(e): hepatic β-adrenoceptor ; hepatic metabolism ; isoprenaline ; lactation

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie , Chemie und Pharmazie , Medizin

Notizen: Abstract The number and coupling efficiency of β-adrenoceptors in liver membranes and intact hepatocytes of lactating and non-lactating female rats were compared to assess whether or not alterations in this signalling system could contribute towards the changed pattern of hepatic metabolism during lactation. In view of the different adaptations of hepatic metabolism to lactation in ruminants, the adrenergic receptor profile of sheep liver membranes was also determined. Post-receptor responses at two stages ‘down-stream’ of cyclic AMP generation were also evaluated in rat hepatocytes in response to the β-adrenergic agonist isoprenaline. No changes in the number or affinity of hepatic β-adrenoceptors were found in sheep or rats when lactating and non-lactating individuals were compared. Sheep liver was found to have a much greater concentration of β-adrenoceptors than rat liver, and a much higher ratio of β:α1. The sensitivity and responsiveness of cyclic AMP generation in response to isoprenaline were similar in hepatocytes prepared from lactating and non-lactating rats, although the response to saturating concentrations of glucagon was diminished in hepatocytes from lactating rats. The activity ratio of cyclic AMP-dependent protein kinase (PK-A) also reacted similarly (in respect of both responsiveness and sensitivity) to isoprenaline in these two groups of hepatocytes. Contrastingly, the sensitivity of rat hepatocyte phosphorylase activity to β-adrenergic stimulation was greatly diminished during lactation.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00230408

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Digitale Medien

A three-phase pattern in growth, monoclonal antibody production, and metabolite exchange in a hybridoma bioreactor culture (1993)

Bushell, M. E. ; Bell, S. L. ; Scott, M. F. ; [weitere]

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 42 (1993), S. 133-139

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ISSN: 0006-3592

Schlagwort(e): hybridoma ; kinetics ; curve fitting ; fermentation ; Chemistry ; Biochemistry and Biotechnology

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung

Notizen: The use of partial cubic spline data interpolation for the calculation of volumetric metabolite exchange rates suggested the existence of three distinct metabolic phases during bioreactor culture of a hybridoma cell line. During phase 1, a rapid amino acid uptake rate and ammonia release rate were observed. The growth rate was low and glutamine synthetase activity fell. In phase 2, maximum growth rate and minimum glutamine assimilation and ammonium production rates were observed. Attempts to corroborate the apparent ammonia assimilation in this phase using 15NH4Cl resulted in low incorporation rates into alanine and glutamine. Maximum glutamine synthetase activity took place during this period. Maximum antibody production rate was observed during phase 3 during which peaks in glutamine assimilation, ammonia release, and glutamine synthetase activity were observed. The apparent existence of the three phases prompted us to carry out Northern blot analysis of glutamine synthetase RNA at appropriate times during the process. This revealed a pattern of appearance and dis-appearance of mRNA consistent with the three phases indicated by the fermentation parameters. © 1993 John Wiley & Sons, Inc.

Zusätzliches Material: 7 Ill.