Relationship between Protein Synthesis in Tuber Discs and the Protein Synthetic Activity of a Cell-Free Preparation

A cell-free system which synthesizes protein was isolated from `aged' discs of Jerusalem artichoke tubers. The synthetic activity was largely associated with the fraction containing mitochondria. Preparations from freshly cut tissue were virtually inactive but increasingly active preparations were obtained from discs `aged' for progressively longer periods; those from 24 hour discs showing maximum activity. The characteristics of this change are reminiscent of the rate of development of invertase, a marker for protein synthesis in the intact disc. Extensive investigations showed that bacterial contamination was not a significant factor in the synthetic activity.     

MORPHOLOGICAL AND CHEMICAL STUDIES OF COLLAGEN FORMATION : I. The Fine Structure of Guinea Pig Granulomata

This paper describes electron microscopic studies of developing connective tissue in granulomata induced by the subcutaneous injection of carrageenin into guinea pigs. Seven days after injection the granulomata contained many fibroblasts and exhibited rapid production of collagen. The fibroblasts were characterised by an extensively developed endoplasmic reticulum and showed numbers of fine, unstriated filaments in the outer regions of the cytoplasm. The filaments, about 50 A in diameter, tended to lie parallel to and closely adjacent to the cell boundary. The cytoplasmic membrane was frequently ill defined or disrupted, particularly bordering regions in which filaments occurred. In longitudinal sections of extended cell processes, filaments were abundant and, in some instances, the cytoplasmic membrane was barely detectable. In the extracellular space striated collagen fibrils were usually accompanied by filaments, 50 to 100 A in diameter, and these often exhibited the characteristic periodicity of collagen, particularly after intense electron bombardment. Much cellular debris was present in the extracellular space. These observations have led to the suggestion that connective tissue precursors are released from fibroblasts by the disintegration or dissolution of the cytoplasmic membrane and the shedding of cytoplasmic material, as in the apocrine gland cells. In some instances this release may take the form of the elongation from the cell of extended processes; disintegration of the cytoplasmic membrane surrounding these processes then leaves the contents in the extracellular phase.     

Echovirus 22 is an atypical enterovirus

Although echovirus 22 (EV22) is classified as an enterovirus in the family Picornaviridae, it is atypical of the enterovirus paradigm, typified by the polioviruses and the coxsackie B viruses. cDNA reverse transcribed from coxsackievirus B3 (CVB3) RNA does not hybridize to genomic RNA of EV22, and conversely, cDNA made to EV22 does not hybridize to CVB3 genomic RNA or to molecular clones of CVB3 or poliovirus type 1. EV22 cDNA does not hybridize to viral RNA of encephalomyocarditis virus or to a molecular clone of Theiler's murine encephalomyelitis virus, members of the cardiovirus genus. The genomic RNA of EV22 cannot be detected by the polymerase chain reaction using generic enteroviral primers. EV22 does not shut off host cell protein synthesis, and the RNA of EV22 is efficiently translated in vitro in rabbit reticulocyte lysates. Murine enterovirus-immune T cells recognize and proliferate against EV22 as an antigen in vitro, demonstrating that EV22 shares an epitope(s) common to enteroviruses but not found among other picornaviruses.     

Plasma lipoproteins and apolipoproteins in the preruminant calf, Bos spp: density distribution, physicochemical properties, and the in vivo evaluation of the contribution of the liver to lipoprotein homeostasis

The in vivo role of the liver in lipoprotein homeostasis in the preruminant calf, a functional monogastric, has been evaluated. To this end, the hydrodynamic and physicochemical properties, density distribution, apolipoprotein content, and flow rates of the various lipoprotein particle species were determined in the hepatic afferent (portal vein and hepatic artery) and efferent (hepatic vein) vessels in fasting, 3-week-old male preruminant calves. Plasma lipoprotein profiles were established by physicochemical analyses of a series of subfractions isolated by isopycnic density gradient ultracentrifugation. Triglyceride-rich very low density lipoproteins (VLDL) (d less than 1.018 g/ml) were minor plasma constituents (approximately 1% or less of total d less than 1.180 g/ml lipoproteins). The major apolipoproteins of VLDL were apoB-like species, while the complement of minor components included bovine apoA-I and apoC-like peptides. Particles with diameters (193-207 A) typical of low density lipoproteins (LDL) were present over the density interval 1.026-1.076 g/ml; however, only LDL of d 1.026-1.046 g/ml were present as a unique and homogeneous size subspecies, containing the two apoB-like species as major protein components in addition to elevated cholesteryl ester contents. LDL represented approximately 10% of total d less than 1.180 g/ml lipoproteins in fasting plasma from all three hepatic vessels. Overlap in the density distribution of particles with the diameters of LDL and of high density lipoproteins (HDL) occurred in the density range from 1.046 to 1.076 g/ml; these HDL particles were 130-150 A in diameter. HDL were the major plasma particles (approximately 90% of total d less than 1.180 g/ml substances) and presented as two distinct populations which we have termed light (HDLL) and heavy (HDLH) HDL. Light HDL (d 1.060-1.091 g/ml) ranged in size from 120 to 140 A, and were distinguished by their high cholesteryl ester (29-33%) and low triglyceride (1-3%) contents; apoA-I was the principal apolipoprotein. Small amounts of apolipoproteins with Mr less than 60,000, including apoC-like peptides, were also present. Heavy HDL (d 1.091-1.180 g/ml) accounted for almost half (47%) of total calf HDL, and like HDLL, were also enriched in cholesteryl ester and apoA-I; they ranged in size from 93 to 120 A. The protein moiety of HDLH was distinct in its possession of an apoA-IV-like protein (Mr 42,000). Blood flow rates were determined by electromagnetic flowmetry, thereby permitting determination of net lipoprotein balance across the liver. VLDL were efficiently removed during passage through the liver (net uptake 1.06 mg/min per kg body weight).(ABSTRACT TRUNCATED AT 400 WORDS)