161 research outputs found
Hepatic lipase mRNA is expressed in rat and human steroidogenic organs
Rat and human steroidogenic organs contain an enzyme activity that is indistinguishable from hepatic lipase present in liver. Using primers that recognize exons 5 and 8 of the rat and human HL gene, a 596-bp product was found by RT-PCR in rat liver, adrenal, ovaries and testes, but not in heart and kidney. A similar product was also observed with human hyperplastic adrenocortical tissue. Identity of this product with part of the HL cDNA was confirmed by restriction mapping and internal re-amplification. Our results indicate that the HL gene is transcribed in steroidogenic tissues that also contain HL protein
Hepatic lipase gene is transcribed in rat adrenals into a truncated mRNA
Rat adrenals contain a lipase activity that is indistinguishable from
hepatic lipase (HL) present in liver. Expression of HL mRNA in adrenals
was studied using the method of reverse transcription-polymerase chain
reaction (RT-PCR). A 596-bp fragment of HL cDNA spanning exons 5 to 8 was
amplified when using total RNA from rat adrenals and liver, but not from
heart or kidney. The abundance of HL mRNA was quantified by competitive
RT-PCR using a standard RNA that was generated in vitro by transcription
from a deleted HL cDNA construct. Adrenals contained 0.4 attomoles of HL
mRNA per microgram of total RNA, compared to 16 attomoles in liver. In
hypertrophic adrenals isolated from corticotrophin-treated rats, the
abundance also amounted to 0.4 attomoles of mRNA per microgram of total
RNA. However, amplification of full-length cDNA from either control or
hypertrophic adrenals was never observed. Detailed analysis by PCR using
different combinations of primers indicated that exons 3 to 9 including
the 3'-unt
Intracellular activation of rat hepatic lipase requires transport to the Golgi compartment and is associated with a decrease in sedimentation velocity
Hepatic lipase (HL) is an N-glycoprotein that acquires triglyceridase
activity somewhere during maturation and secretion. To determine where and
how HL becomes activated, the effect of drugs that interfere with
maturation and intracellular transport of HL protein was studied using
freshly isolated rat hepatocytes. Carbonyl cyanide m-chlorophenyl
hydrazone (CCCP), castanospermine, monensin, and colchicin all inhibited
secretion of HL without affecting its specific enzyme activity. The
specific enzyme activity of intracellular HL was decreased by 25-50% upon
incubation with CCCP or castanospermine, and increased 2-fold with
monensin and colchicin. Glucose trimming of HL protein was not affected by
CCCP, as indicated by diges
Hepatic lipase: a pro- or anti-atherogenic protein?
Hepatic lipase (HL) plays a role in the metabolism of pro- and
anti-atherogenic lipoproteins affecting their plasma level and
composition. However, there is controversy regarding whether HL
accelerates or retards atherosclerosis. Its effects on different
lipoprotein classes show that, potentially, HL may promote as well as
decrease atherogenesis. Studies in animals with genetically modulated HL
expression show that it depends on the model used whether HL acts pro- or
anti-atherogenic. In humans, HL activity seems to correlate inversely with
atherosclerosis in (familial) hypercholesterolemia, and positively in
hypertriglyceridemia. In normolipidemia, HL activity is weakly associated
with coronary artery disease (CAD). Genetically low or absent HL activity
is usually associated with increased CAD risk, especially if plasma lipid
transport is impaired due to other factors. Since HL promotes the uptake
of lipoproteins and lipoprotein-associated lipids, HL may affect
intracellular lipid content. We hypothesize that the prime role of HL is
to maintain, in concert with other factors (e.g., lipoprotein receptors),
intracellular lipid homeostasis. This, and the uncertainties about its
impact on human atherosclerosis, makes it difficult to predict whether HL
is a suitable target for intervention to lower CAD risk. First, the
physiological meaning of changes in HL activity under different conditions
should be clarified
Rat liver contains a limited number of binding sites for hepatic lipase
The binding of hepatic lipase to rat liver was studied in an ex vivo
perfusion model. The livers were perfused with media containing partially
purified rat hepatic lipase or bovine milk lipoprotein lipase. The
activity of the enzymes was determined in the perfusion media before and
after passage through the liver. During perfusion with a
hepatic-lipase-containing medium the lipase activity in the medium did not
change, indicating that there was no net binding of lipase by the liver.
In contrast, more than 80% of the lipoprotein lipase was removed from the
med
Hoogveen en klimaatverandering in Nederland
Voor de instandhouding en ontwikkeling van hoogveen zijn het neerslagoverschot, de temperatuur en de positie in het landschap belangrijk. Gunstige ontwikkelingen doen zich voor in gebieden waar het (actieve) hoogveen water uit zijn omgeving ontvangt. De landelijke instandhoudingsdoelen voor Natura 2000-habitattype Actieve hoogvenen kunnen waarschijnlijk ook onder het klimaatscenario W+ worden gerealiseerd: behoud van kwaliteit en oppervlakte zijn kansrijk en verbetering van kwaliteit en uitbreiding van oppervlakte zijn mogelijk. Voorwaarden hierbij zijn een optimale waterhuishouding. Dat wil zeggen voldoende hoge grondwaterstanden in de zandondergrond en de veenbasis in combinatie met een waterondoorlatende (veen)laag en/of de toevoer van lokaal grondwater. Om hoogvenen op de lange termijn in Nederland te behouden onder het W+- scenario zijn waterhuishoudkundige maatregelen nodig, zoals de aanleg en inrichting van bufferzones en compartimenten en/of door het bevorderen van kwel
Natuurherstel: van standplaats naar landschap
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