Quantitative topography of organelles in the liver

Summary After seven days of feeding fructose the liver of Wistar rats showed enormous accumulations of glycogen, which completely altered the original pattern of distribution of organelles. A quantitative morphological method was used to analyze these changes.The cytoplasm was mapped into arbitrary distance classes corresponding to concentric rings beginning at the outer nuclear membrane. This allowed the density of organelles in a given zone to be estimated.In cells filled with glycogen as a result of the fructose feeding, the following rearrangements were found: in the intermediate zone of both cellular poles (i.e., bile canalicular pole and sinusoidal pole) the mitochondria disappeared, being replaced by glycogen.The endoplasmic reticulum was accumulated in the perinuclear zone of both cellular poles, as in control animals, but was reduced throughout the rest of cytoplasm. It showed a peripheral density maximum at the biliary canalicular pole, in contrast to the cells of control animals.These changes in the distribution of the organelles and cellular compartments correspond to histochemical findings and demonstrate an adaptive reaction in the liver parenchyma to fructose ingestion, the organelles arranging themselves in cytoplasmic regions which still show a metabolic activity.Supported by a grant from the Deutsche Forschungsgemeinschaft Az Ri 271/6-5     

A scanning electron microscopic study of the liver of the monkey Macaca speciosa

Summary The bile canalicular network of the monkey was studied by fracturing fixed liver tissue and examination by scanning electron microscopy. Bile canaliculi do not differ remarkably from those described in other species. Their course and luminal diameter vary, depending on their position in the liver lobule. In one specimen the continuity of a canaliculus with a terminal bile ductule (canal of Hering) is presented. Several constrictions occur in this part of the ductular lumen. The interlobular bile duct wall shows two kinds of niches. A single cilium arises from a primary niche. The walls of secondary niches contain numerous primary niches. Simple columnar epithelium lines the common bile duct, the main pancreatic duct and the gallbladder. A common feature is the presence of microplicae on their lateral cell surfaces.

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Zusammenfassung Das Netzwerk der Gallekanälchen beim Affen wird durch Brechen von fixiertem Lebergewebe sichtbar. Strukturen der Portalfelder und der extrahepatischen Gänge werden durch Schneiden von Gewebe dargestellt. DieGallekanälchenunterscheidensichnichtwesentlich von den bei anderen Spezies beschriebenen. Ihr unterschiedlicher Verlauf und Lumendurchmesser hängen von ihrer intralobulären Lage ab. Die Kontinuität eines Gallekanälchens mit einem Ductulus (Heringscher Kanal) wird in einem Fall dargestellt. Im ductulären Lumen kommen mehrere Konstriktionen vor. Die Wand der interlobulären Gallengänge weist zwei Arten von Nischen auf. Eine Einzelzilie kommt aus den primären Nischen. Sekundäre Nischen bestehen aus mehreren primären Nischen. Einschichtiges hochprismatisches Epithel kleidet den Ductus choledochus, den Ductus pancreaticus und die Gallenblase aus. Ein gemeinsames Merkmal ihrer lateralen Zelloberflächen sind Mikroplicae.

     

Further studies on bilitranslocase,a plasma membrane protein involved in hepatic organic anion uptake

Bilitranslocase, a plasma membrane protein involved in bilirubin and other organic anion uptake by the liver, exhibits a high molecular weight (170 000) when isolated in the presence of deoxycholate. This value is decreased to approx. 100 000 if deoxycholate is not included in the isolation medium. Both preparations can be resolved into two kinds of subunit, α and β, of 37 000 and 35 500, respectively, by reduction with 2-mercaptoethanol and addition of sodium dodecyl sulfate. Under these conditions the two subunits are still capable of high-affinity sulfobromophthalein binding and, despite the presence of the detergent, may be isolated by preparative polyacrylamide gel electrophoresis still associated with the dye. It may be suggested that the physiological subunit composition of bilitranslocase is α₂-β.     

Effect of N-ethylmaleimide on leucine transport in chang liver cells. I. Stimulatory effect on Na+-independent transport at low concentrations of leucine

Pretreatment of Chang liver cells with $\text{N-}\text{ethylmaleimide}$ (0.5 or 1 mM) stimulated Na⁺-independent uptake of leucine at low concentrations (?1 mM). The stimulatory effect of $\text{N-}\text{ethylmaleimide}$ on the uptake of leucine measured in Na⁺-replete medium was completely blocked by the addition of $\text{b-2-}\text{aminobicyclo}\text{[2,2,1]}\text{heptane}\text{-2-}\text{carboxylate}$ (5 mM), which shows that the L system participates in the stimulation. The Na⁺-dependent uptake of glycine was depressed by $\text{N-}\text{ethylmaleimide}$ pretreatment. The stimulation of the Na⁺-independent component of leucine uptake continued for at least 30 min after $\text{N-}\text{ethylmaleimide}$ treatment, while the inhibition of glycine uptake was progressive with time and the Na⁺-dependent uptake of leucine became depressed later, after the treatment. It has been demonstrated that treatment of cells with $\text{N-}\text{ethylmaleimide}$ is capable of increasing the Na⁺-independent influx of leucine and at the same time slightly decreasing the efflux of it. These results suggest that $\text{N-}\text{ethylmaleimide}$ attacks the Na⁺-independent system of amino acid transport at the reactive SH groups(s) of relevant protein(s) in favor of specific activation of that system in this cell.     

Short-term energy deficit causes net accumulation of linoleoyl-enriched triacylglycerols in rat liver

Energy depletion by reduced food intake over 4 days resulted in a 73% reduction in total rat liver triacylglycerols (TG). In liver TG of energy-depleted rats, dilinoleoyl oleoyl glycerol (OLL) and trilinoleoyl glycerol (LLL)) were quantitatively increased by 85% and 147%, respectively. The net increase in linoleoyl-enriched species could be quantitatively accounted for by the release of linoleate from monolinoleoyl species and its subsequent reacylation into dilinoleoyl species and trilinolein during energy depletion. Hence while palmitate, oleate and some linoleate are being hydrolyzed, presumably for oxidation some linoleate is retained and contributes to the remodelling of hepatic triacylglycerols during energy deficit.     

天然保肝药研究进展

本文综述了天然保肝药的筛选方法,活性成分的化学结构,以及临床应用.     

Amino Acid Neurotransmitter Receptor Changes in Cerebral Cortex in Alcoholism: Effect of Cirrhosis of the Liver

Gamma-aminobutyric acidA/benzodiazepine receptor binding sites and the N-methyl-D-aspartate subclass of glutamate receptor sites were assessed in synaptic plasma membrane homogenates of cerebral cortex tissue obtained at autopsy from cirrhotic and noncirrhotic alcoholic patients and matched control subjects. The alcoholic patients consumed an average of greater than 80 g of ethanol/day, the control subjects less than 20 g/day. Postmortem delays up to approximately 100 h caused no significant loss of any of the binding sites; the patient and subject groups were closely matched for age. The affinities (KD) of the receptor sites did not differ between the patient and subject groups, nor between cortical regions. Using three different radioligands ([3H]muscimol, [3H]flunitrazepam, and [3H]diazepam), the gamma-aminobutyric acidA/benzodiazepine receptor complex was found to have greater density (Bmax) in superior frontal gyrus in alcoholic patients (which selectively shows morphological change in alcoholic patients), but was unchanged in motor cortex. Alcoholic patients with cirrhosis had much less pronounced changes. The density of the N-methyl-D-aspartate subclass of glutamate receptors, assessed with [3H]MK-801, did not vary across patient and subject groups.     

Hepatotropin mRNA expression in human foetal liver development and in liver regeneration

A 569 bp probe against the β-chain of hepatotropin was used to examine expression of RNA for this growth factor in human adult and foetal liver, foetal kidney and pancreas, and rat liver after partial hepatectomy. Low level expression of a 6kb RNA occurred in human adult and normal rat liver. 70% hepatectomy increased expression, peaking at 10 h and returning to near normal levels 24 h after resection. The 6 kb band was strongly expressed in human foetal liver, as compared with adult, but not in foetal kidney or pancreas, suggesting a major role for hepatotropin in both foetal development and regeneration of the liver.     

A 31P-NMR study of the intact liver fluke Fasciola hepatica

³¹P-NMR techniques offer a useful method of studying changes in the metabolism of intact parasitic worms. The liver flukes, Fasciola hepatica, provide good quality ³¹P high resolution NMR spectra for at least 6 h under anaerobic conditions. The levels of ATP remain constant throughout this period. There is no signal for phosphocreatine or phosphoarginine. In contrast to the findings in mammalian tissues, there is a distinct peak for the terminal phosphate of ADP. A number of signals are observed in the phosphodiester region of the spectrum the largest of which is identified as l-α-glycerophosphoryl choline. Serotonin (5-hydroxytryptamine) causes an appreciable increase in the levels of sugar phosphates when the flukes are incubated in the absence of glucose. The addition of glucose also causes a marked increase in the signals for the hexose phosphate.