Molecular weight distributions of milk fat triglycerides from seven species

The triglyceride compositions of the milk fats of man, dog, guinea pig, cow, sheep, goat, and horse were compared by gas-liquid chromatography of the intact triglycerides and of the butyl esters of the component fatty acids. The milk fats of man, dog, and guinea pig, which were largely made up of long-chain fatty acids, showed a common pattern with major contributions made by the glycerides with 48-54 acyl carbon atoms. The milk fats of cow, sheep, and goat, which were rich in short-chain acids, showed significant proportions of triglycerides with 28-54 acyl carbon atoms. Horse milk, which contains large amounts of medium-chain fatty acids, gave a characteristic triglyceride pattern in the 26-54 carbon atoms range. The experimentally determined distributions of the molecular weights of the triglycerides of all milk fats deviated significantly from the distributions predicted by random association of the fatty acids from a single pool. The data suggest that in all species the milk fat may be formed by a partial resynthesis of preformed glycerides.     

Egg yolk triglycerides during development of the domestic chicken

The triglycerides isolated from egg yolk lipids of eggs at various stages of incubation were fractionated according to the degree of unsaturation by argentation chromatography, and individual fractions were analyzed for their fatty acids by gas liquid chromatography. The proportions of the various fractions were constant during development. Fatty acid composition of the fractions were constant also. Fractions with one saturated fatty acid and two monoenoic fatty acids (SM₂) constituted over 40% of the total triglyceride. Palmitic acid constituted over 30%, and oleic acid over 45% of the fatty acid of total triglycerides. It is suggested that during development of thick embryo there is no selective utilization of the egg yolk triglycerides.     

Molecular interactions of syndecans during development

The syndecans, cell surface heparan sulfate proteoglycans (HSPGs), bind numerous ligands via their HS glycosaminoglycan chains. The response to this binding is flavored by the identity of the core protein that bears the HS chains. Each of the syndecan core proteins has a short cytoplasmic domain that binds cytosolic regulatory factors. The syndecans also contain highly conserved transmembrane domain and extracellular domains for which important activities are slowly emerging. These protein domains, which will be the focus of this review, localize the syndecan to sites at the cell surface during development where they collaborate with other receptors to regulate signaling and cytoskeletal organization.     

Interactions of Fusarium species during prepenetration development

Interspecies interactions between Fusarium avenaceum, Fusarium culmorum, Fusarium graminearum, Fusarium poae, and Fusarium tricinctum were studied during early growth stages of isolates on model surfaces. Additionally, germination and germ tube growth of the pathogens were studied on attached and detached wheat leaves at 10 °C and 22 °C. Two-species interactions between Fusarium isolates during germination and germ tube growth were assessed after 8 hours of incubation. All species except F. tricinctum germinated and grew faster at higher than lower temperature. All species were able to germinate with more than one germ tube per conidium cell; and germination and germ tube growth were faster on leaves than on glass surface. Interactions among Fusarium species during germination and germ tube growth were predominantly competitive with macroconidia-producing species being more competitive. It is concluded that the type of conidia as well as environmental factors influence the competitiveness of Fusarium species during early stages of growth.     

Molecular species of mitochondrial phosphatidylcholine in rat liver and lung

The acyl species of mitochondrial phosphatidylcholine from rat liver and lung were analysed by HPLC separation of the 1,2-diacyl-3-naphthylurethane derivatives. Comparison of phosphatidylcholine species patterns in microsomal, mitochondrial and submitochondrial fractions revealed only minor differences, whereas mitochondria from liver and lung differed markedly in the molecular composition of their respective phosphatidylcholine species.     

Molecular study of the rat liver NADH: Cytochrome c oxidoreductase complex during development and aging

The mechanisms involved in ageing are yet to be fully understood but it is thought that changes produced in energy transfer pathways occurring in the mitochondria may be responsible for the lack of energy typical of the later stages of life. The aim of the present investigation was to determine the enzymatic activity of the liver NADH cytochrome c oxidorectuctase complex (Complex I-III) in mitochondria isolated from the liver of rats of 3 different age groups: lactating, animals (15-17 days), adult females (3-5 months) and old animals (26-30 months). The activities of the unbound Complexes I and III were also determined.An increase in Complex I-III activity was detected during development (142 ± 10 vs. 447 ± 23 mol cyt. c/mg/min, p < 0.001) ang ageing (447 ± 23 vs. 713 ± 45 mol cyt. c/mg//min, p < 0.001). However, unbound Complex I showed a reduction in activity during the ageing period whilst Complex III activity moderately increased. Immunological studies indicated only a moderate increase in the amount of Complex I-III and studies on the purified complex suggested that the increase in activity was due to effects other than an increase in enzyme quantity. The analysis of protein bands and the quantification of prosthetic groups showed particular reductions in the relative concentrations of Complex I subunits including the 51 kDa unit, which binds FMN, confirmed by a similar reduction in levels of the nucleotide. In contrast, 4 of the 5 subunits which increased during the lifetime of the animals corresponded to those of Complex III. These subunits are responsible for the binding of catalytic groups. The results suggest that, in addition to the increase in the amount of enzyme, binding factors between Complexes I and III may also play an important role in the observed increase in Complex I-III activity.     

Rat liver hexokinases during development.

The four glucose-phosphorylating isozymes from rat liver were separated by DEAE-cellulose column chromatography at several ages during development. The isozymes exhibited a sequential mode of appearance. The isozymes A, B, and C reached maximal values of activity at days +1, +3, and +7, respectively, decaying afterwards to the low characteristic adult value. Isozyme D activity was detected in very low levels as early as day +3, rising from day +18 to reach constant adult values at day +30. A fraction of the glucose phosphorylating activity was found associated with particulate material in prenatal and newborn rats. From day +15 onwards, no particulate activity could be detected. The particulate activity was found to be composed of three low-Km isozymes as of the corresponding soluble fraction.     

Tubulin microheterogeneity during mouse liver development

Liver tubulin was analyzed and characterized during the development of the mouse, from embryonic stages to adult. Separation and identification of isotubulins were achieved by isoelectric focusing, two-dimensional gel electrophoresis and peptide mapping. Liver tubulin is a heterogeneous population composed of 7 isoforms, 4 α and 3 β. By comparison with the events occurring at the tubulin level during brain development, we observed that 1) tubulin heterogeneity is less important in liver than in brain 2) no appearance of new isotubulins takes place during development 3) the only developmental change detectable in our gels is an accumulation of an α tubulin subunit which is absent from brain isotubulin population. The relationship between this α isotubulin accumulation and liver secretion during development is discussed.     

肝脏发育过程中转录因子的调控

肝脏的发育经历了一系列内胚层和中胚层之间复杂的相互作用,其中转录因子扮演着重要角色。肝脏发育主要可分为两个阶段,首先是前肠内胚层感受心脏中胚层的信号而建立响应态(competence),肝向特化基因逐渐表达并形成新生肝芽。此阶段受到转录调控网络的控制,其中FoxA家族,锌指结构转录因子GATA4/6,同源结构域因子Hhex、Onecut1、Onecut2和Prox1发挥了重要的作用。其次是肝脏内细胞群体如肝细胞和胆管细胞的分化成熟阶段。这个过程的完成主要受肝富集转录因子HNF1α、HNF4、HNF6和C/EBPα的调控。本文概述了肝脏发育中复杂的转录调控网络及其发挥的作用。     

Retinoid metabolism during development of liver cirrhosis

The changes in retinoid metabolism have been documented in liver cirrhosis. However, the dynamic alterations in levels of this vitamin between circulation and liver during development of the liver cirrhosis are not well understood. The aim of this study was to measure retinoids in the liver and circulation in parallel, during and after development of cirrhosis induced by carbon tetrachloride and thioacetamide. Retinoid levels were measured by HPLC. A decrease in retinaldehyde and total retinol, together with an increase in retinoic acid was evident in liver from both carbon tetrachloride or thioacetamide treated rats within a month after initiation of treatment. Activity of enzymes involved in retinoid metabolism such as retinaldehyde oxidase, retinaldehyde dehydrogenase, and retinaldehyde reductase were decreased in the liver. In parallel, levels of retinol and retinaldehyde in the serum were increased while retinoic acid was decreased. This study indicates that during development of cirrhosis, there is reciprocal transfer of retinoid metabolites between the circulation and the liver.     

Chromatin phospholipid changes during rat liver development

The chromatin extracted from rat hepatocytes of different ages has been shown to contain a phospholipid fraction representing 0.47-0.59 per cent of total chromatin in newborn animals and 0.22 per cent in 45-day-old animals. No such age-related differences are observed in the nuclei. The phospholipid composition of the nuclei at different ages shows a higher level of sphingomyelin and a lower level of phosphatidylserine in newborn than in adult animals. Chromatin phospholipids have a completely different composition from that of nuclei with respect to age, particularly in newborn rats, where there is a decrease in phosphatidylcholine and an increase in phosphatidylserine.     

Thymidine kinase in rat liver during development

1. The activity of thymidine kinase in rat liver supernatant decreased with development to a value in the adult that was 1% of that in the 17-day foetus. 2. The foetal enzyme was more stable than the adult to gel filtration on Sephadex G-25 at 0 degrees . 3. The greater stability of the foetal enzyme to incubation at 45 degrees was attributable to the presence of higher concentrations of nucleotides in foetal liver supernatant. 4. The K(m) values for foetal and adult enzymes were approx. 2.5mum- and 2.1mum-thymidine respectively. 5. The foetal enzyme was more sensitive to inhibition by thymidine triphosphate. 6. The decline in enzyme activity during the neonatal period was correlated with a shift in the enzyme properties from the foetal to the adult type, and may reflect the decrease in the proportion of haemopoietic tissue in the liver.     

Serum triglycerides, the liver and the pancreas

Massive hypertriglyceridaemia associated with fatty liver and abdominal pain or frank pancreatitis (the chylomicronaemia syndrome) is uncommon, but clinically important and under-recognized. It may arise as a result of severe genetic defects in lipolysis or, more commonly, from a moderate primary hypertriglyceridaemia that is exacerbated by a secondary cause. The latter include several drugs, among which the protease inhibitors, used for the treatment of human immunodeficiency virus infection, are increasingly apparent. In the acute situation plasma exchange, fat-free parenteral nutrition and acute insulin treatment, even in nondiabetic persons, may be valuable. A potentially major advance in prophylaxis is the use of high-dose antioxidant therapy, which has been shown to reduce attacks of pancreatitis even in the absence of a reduction in serum triglycerides. Asymptomatic patients with abnormal liver function tests are common in the lipid clinic, and can be a difficult group in which to make management decisions. Among those who are not taking excessive amounts of alcohol, many will have nonalcoholic steatohepatitis. The care of these patients is discussed, but there remains considerable uncertainty regarding their optimum management and prognosis.     

Rapid increase of profilin-like proteins during liver development

Extraction of the cytoplasm of rat liver with 5% PCA and subsequent TCA (20%) treatment resulted in the recovery of only a few proteins, the predominant one having an apparent molecular weight of 12K. This 12K protein increased sharply (9-fold) between 2 weeks and 10-20 weeks and then decreased until at least 2 years after birth. 12K protein was separated into two components, 12K-1 (larger) and 12K-2 (smaller), by gel chromatography which had similar amino acid compositions to those of profilin (from Acanthamoeba and hog thyroid). Like profilin, 12K-1 protein inhibited the rate of actin polymerization, while 12K-2 protein did not. These findings suggest that liver profilin-like proteins increase sharply during development.