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Biomedical subjects

R Oren

Publications and source records attributed to R Oren.

At least 109 records · Page 6Linked to original sources
PubMed1988

Selective stabilization by the bacteriophage 434 repressor of the plasmid expressing bovine growth hormone in Escherichia coli.

The maintenance of a plasmid vector-host system that selects for bacteria carrying the plasmid without the need for antibiotics is described. In this system, the bacteriophage 434 repressor gene cloned on the plasmid protects the host from lysis by a lambda imm434 cI- prophage. Cells that occasionally lose the plasmid are killed by prophage induction and therefore do not accumulate in the growing culture. The presence of the phage 434 repressor in the cells does not interfere with the process of lambda repressor inactivation and the high-level production of bovine growth hormone.

Animals↗
PubMed1987

Water transport in maize roots : measurement of hydraulic conductivity, solute permeability, and of reflection coefficients of excised roots using the root pressure probe.

A root pressure probe has been used to measure the root pressure (P(r)) exerted by excised main roots of young maize plants (Zea Mays L.). Defined gradients of hydrostatic and osmotic pressure could be set up between root xylem and medium to induce radial water flows across the root cylinder in both directions. The hydraulic conductivity of the root (Lp(r)) was evaluated from root pressure relaxations. When permeating solutes were added to the medium, biphasic root pressure relaxations were observed with water and solute phases and root pressure minima (maxima) which allowed the estimation of permeability (P(Sr)) and reflection coefficients (sigma(sr)) of roots. Reflection coefficients were: ethanol, 0.27; mannitol, 0.74; sucrose, 0.54; PEG 1000, 0.82; NaCl, 0.64; KNO(3), 0.67, and permeability coefficients (in 10(-8) meters per second): ethanol, 4.7; sucrose, 1.6; and NaCl, 5.7. Lp(r) was very different for osmotic and hydrostatic gradients. For hydrostatic gradients Lp(r) was 1.10(-7) meters per second per megapascal, whereas in osmotic experiments the hydraulic conductivity was found to be an order of magnitude lower. For hydrostatic gradients, the exosmotic Lp(r) was about 15% larger than the endosmotic, whereas in osmotic experiments the polarity in the water movement was reversed. These results either suggest effects of unstirred layers at the osmotic barrier in the root, an asymmetrical barrier, and/or mechanical effects. Measurements of the hydraulic conductivity of individual root cortex cells revealed an Lp similar to Lp(r) (hydrostatic). It is concluded that, in the presence of external hydrostatic gradients, water moves primarily in the apoplast, whereas in the presence of osmotic gradients this component is much smaller in relation to the cell-to-cell component (symplasmic plus transcellular transport).

Journal Article↗
PubMed1987

IgM nephropathy: morphological study related to clinical findings.

This study describes 10 cases of IgM nephropathy in whom the main morphological findings consisted of diffuse mesangial deposition of IgM and varying degrees of mesangial cell proliferation. In addition, focal segmental sclerosis was present in 1 patient and global sclerosis in another. An ill-defined electron-dense deposit was seen within the mesangial area in 1 case. Except for 1 patient, who had hematuria only, all suffered from nephrotic syndrome without deterioration of renal function. In view of the constant and characteristic finding of a diffuse mesangial IgM deposition, it is suggested that this form of nephropathy constitutes an entity separate from focal glomerulosclerosis or minimal change disease.

Adolescent↗
PubMed1985

The streaming liver.

Twenty male adult rats weighing 200 g were injected with tritiated thymidine (3HTdR). The animals were then killed in groups of five, at the following times: 1 h, 1, 3 and 5 weeks. Autoradiograms of sections through the liver were prepared. The distances between labelled cells and the portal space rim were measured. One hour after labelling most labelled cells were confined to a region extending from the portal space rim up to a distance of 700 micron, which roughly corresponds to Rappaport's hepatic acinus zones-1 and -2. Throughout the experiment lasting 5 weeks labelled cells entered zone-3 and advanced toward the terminal hepatic vein. Hepatocytes travelled at a daily velocity of 1.44 micron, covering daily 0.324% of the acinus diameter. During the experiment acinus size did not change appreciably. The estimated mean hepatocyte cell cycle time was 37 days and its life expectation, 201 days. These experiments show that the liver is essentially a slowly renewing cell population. Hepatocytes nascent at the portal space gradually stream toward the terminal hepatic vein where they are probably eliminated by apoptosis. Their journey lasts 201 days. Since hepatocytes are glued together with tight junctions, all have to advance toward their terminal hepatic veins en masse. During their voyage, they traverse the three acinus zones, and since in each they produce different enzymes, each zone represents a differentiation state of the advancing cell. It is suggested further that the streaming hepatocyte carries with it its nerve supply and is accompanied by sinusoidal endothelium and Kupffer cells.

Animals↗
PubMed1985

Paracetamol overdosage in Jerusalem.

Forty-nine subjects were identified in the years 1978-83 in four major hospitals in Jerusalem as suspected of paracetamol overdosage. The apparent yearly incidence of paracetamol overdosage in the Jewish population in Jerusalem increased from 0.6/100,000 in 1978 to 4.5/100,000 in 1983. Two subgroups were identified: 13 children, the majority aged 2 to 4 years; and 36 young adults less than 39 years old, mostly in the 18- to 21-year age-group. In children, overdosage was caused by accident, in adults by attempted suicide. Morbidity was minimal, and transient liver function disturbances were found in only two subjects. Toxic levels were found in 2 of the 20 cases tested for paracetamol plasma concentration. Nevertheless, 31 subjects (63%) were hospitalized, and 29 of these were treated with N-acetylcysteine. The availability of the plasma paracetamol assay for diagnosis and of N-acetylcysteine as a specific antidote makes it possible to deal more effectively with the problem of paracetamol overdosage as a community health hazard.

Acetaminophen↗
PubMed1979

Coupling factor ATPase complex of Rhodospirillum rubrum. Purification and characterization of an oligomycin and N,N'-dicyclohexylcarbodiimide-sensitive (Ca+ + Mg2+)-ATPase.

An ATPase complex sensitive to the energy transfer inhibitors oligomycin, dicyclohexylcarbodiimide and venturicidin has been solubilized from Rhodospirillum rubrum chromatophores with Triton X-100 and further purified by centrifugation on a glycerol gradient. The partially purified RrFo . F1 contains 13 distinct polypeptide subunits, as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, including the subunits of the oligomycin-sensitive, water-soluble RrF1 ATPase. The ATPase activity of RrF0 . F1 as that of the membrane-bound enzyme complex depends on Ca2+ or Mg2+ and from detailed kinetic studies it is concluded that the divalent cation-ATP complex is the substrate for both ATPase complexes. Free ATP and free Mg2+ act as competitive inhibitors, with Ki values of 1 mM and 7 muM, respectively. The subunit composition of the purified RrFo . F1 and its similarity to the membrane-bound ATPase with respect to cation dependence and sensitivity to energy transfer inhibitors suggests that it contains all the subunits of the R. rubrum coupling factor-ATPase complex.

Aurovertins↗
PubMed1978

Fine structure of the cell surface and Golgi apparatus of Ochromonas.

Ochromonas danica has an unusually flexible cell surface capable of producing projections of varying sizes and shapes: large projections, 340-360 nm long, and small projections, 50-110 nm long. These projections have been demonstrated by transmission and scanning electron microscopy; some of them may break off into the medium and be the source of extracellular membranes and vesicles reported in the cell-free O. danica growth medium. Ruthernium red stained the acid mucopolysaccharide layer just outside the cell surface as well as small blebs at the cell surface. The Golgi complex of O. danica, Ochromonas malhamensis, Ochromonas sociabilis and Ochromonas sp. produced small coated vesicles which may move toward and fuse with the plasma membrane. The role of the several vesicles is unknown but possible functions are discussed.

Animals↗