Cloning and DNA sequence of plasmid determinant iss, coding for increased serum survival and surface exclusion, which has homology with lambda DNA

Summary Escherichia coli K12 cells carrying a cloned 1.4 kb HindIII fragment from plasmid ColV2-K94, showed increased survival in guinea pig serum. The recombinant plasmid also conferred group II surface exclusion, i.e. the cells were reduced in recipient ability towards the incoming plasmid R538drd in conjugation experiments. Southern blotting suggested homology with bacteriophage lambda DNA and to the insertion element IS2. Determination of the DNA sequence of the fragment demonstrated the presence of a truncated IS2 (165 bp), separated by 250 bp from a 900 bp stretch of homology with lambda DNA, beginning within the Rz gene and continuing in the rightward direction on the lambda map. A 97 amino acid open reading frame (ORF) adjacent to Rz and on the opposite strand, remained intact in iss, with several amino acid changes. The ORF in iss is preceded by sequences resembling prokaryotic ribosome binding sites and promoters.     

Chemically induced alterations in maternal homeostasis and histology of conceptus: their etiologic significance in rat fetal anomalies

Possible relationships between maternal acid-base-electrolyte imbalance, histological changes in the maternal/extraembryonic tissues (decidua, placenta, membranes enclosing cavities), and fetal anomalies induced by maternotoxic doses of ethylene glycol, sodium salicylate, and cadmium chloride in rats were investigated. Acid-base-electrolyte, histologic and, teratologic studies were conducted concurrently with, as far as feasible, a similar protocol. Ethylene glycol caused 1) maternal homeostatic changes including metabolic acidosis and hyperosmolality, 2) extraembryonic lesions with degeneration of allantois and reduced villigenesis being more prevalent, and 3) materno-fetal effects such as decreases in fetal and maternal body weights, decreased maternal food intake, and fetal abnormalities (vertebral, rib, and sternebral defects). Few of these changes occurred when NaHCO3, an endogenous agent known to correct metabolic acidosis, was coadministered with ethylene glycol. Ethylene glycol-induced maternal metabolic acidosis, concurrent with hyperosmolality, was suspected to contribute toward reduction in villigenesis and fetal anomalies, including body weight reductions. Sodium salicylate induced the following: 1) mild maternal acidosis, hypokalemia, and hypophosphatemia with no significant change in pH; 2) maternal hemorrhage in extraembryonic cavities, papillary proliferation of the visceral yolk sac endoderm, and failure to form the chorioallantoic labyrinth; and 3) resorptions, hydrocephaly, rib defects, and fetal body weight reduction. Upon simultaneous treatment with sodium salicylate, NaHCO3 significantly reduced, and NH4Cl enhanced the incidence of the above histologic and teratologic effects, without significantly altering acid-base values. An etiologic association between the above salicylate-induced maternal and extraembryonic lesions and teratogenicity was likely. Cadmium chloride, whether administered by the intraperitoneal (ip) or intravenous (iv) route, caused 1) hydrocephaly, anophthalmia, vertebral and rib defects, reduction in fetal body weight, resorptions and maternal toxicity (acute peritonitis by the ip route only), and 2) extensive necrosis and hemorrhage in the decidua basalis, hemorrhage in the ectoplacental cone and around Reichert's membrane, and absence of chorioallantoic labyrinth. An etiologic relationship between these teratologic and histologic effects seemed probable, since both were dose-related. From the above studies, it was hypothesized that maternal factors--metabolic acidosis, hyperosmolality, hemorrhages in the ectoplacental cone, extraembryonic cavities, and around Reichert's membrane, and necrosis of decidua basalis--may have, directly or indirectly, reduced fetal nutrition and materno-embryonic gaseous exchange, which ultimately altered fetal development.     

Maternal toxicity: a possible etiological factor in embryo-fetal deaths and fetal malformations of rodent-rabbit species

Data from animal teratology studies were surveyed to determine whether embryo-fetal mortality and fetal malformations result from a primary action of the agent on the conceptus or if they are secondary to maternal toxicity--a consequence of administration with high dose levels of test chemicals. A fairly strong association between embryo-fetal mortality and maternal toxicity was revealed by analysis of data from hamsters, mice, rats, and rabbits in 234 studies of chemical and physical agents, of which 83 were conducted at both maternotoxic and nonmaternotoxic doses, 94 only at maternotoxic doses, and 49 at nonmaternotoxic doses. In the above studies, only nine chemicals (four each in hamsters and rabbits and one in rats) were reported to induce embryo-fetal deaths at apparently nonmaternotoxic doses. These findings tend to suggest a contributory role for maternal toxicity in the induction of embryo-fetal deaths. The previously reported hypothesis that certain fetal defects in mice may perhaps be caused by maternal toxicity was also found to be true in a review of data on hamsters, rats, and rabbits. Salient maternal toxicity-associated fetal malformations were exencephaly, encephalocele, micro- or anophalmia, and fused ribs in hamsters and defective (fused, missing, or extra) ribs, vertebrae, and sternebrae, ex-, an-, or microphthalmia, and cleft palate in rats and rabbits. These malformations occurred at low frequencies, generally with no readily apparent dose-response relationship. Presumptive evidence indicates that embryo-fetal deaths, and the above-mentioned fetal malformations in experimental animals, which in published literature are presently attributed to chemical induction for a large number of chemicals, may be a consequence of maternal toxicity per se.     

Ultrasonic radiation induced lipid peroxidation in liposomal membrane

Summary Ultrasonic radiation produced a dose dependent linear increase in lipid peroxidation (MDA formation) in the liposomal membrane. The yield of MDA was significantly inhibited by butylated hydroxytoluene (BHT), the antioxidant, sodium formate, the OH radical scavenger, and EDTA, the metal ion chelator. Ascorbic acid at low concentration increased the ultrasonic induced MDA formation while high concentrations inhibited lipid peroxidation. A mechanism of ultrasound induced lipid peroxidation is suggested.     

Production by K 562 cells of an inhibitor of adherence-related functions of human neutrophils

Certain tumor cells generate factors that inhibit neutrophil chemotaxis. Our study was designed to explore whether such factors are produced by K 562 malignant cells and whether these have a broader effect in altering neutrophil functions. After 48 h of in vitro culture of K 562 cells, the culture medium and the cells were separated, lyophilized, and extracted with ethanol. These K 562 products, i.e., either the cell or supernatant extract, inhibited both nonstimulated locomotion and locomotion induced either by FMLP or activated serum. Furthermore, K 562 products inhibited neutrophil adherence and oxidative burst induced by opsonized zymosan, whereas oxidative burst induced by PMA or FMLP was not altered. K 562 products had an inhibitory effect on the PMN binding to iC3b-coated particles. They did not modify Mo1 expression of resting cells, did not alter the up-regulation of the receptor induced by FMLP but inhibited the FMLP-induced capping of Mo1 Ag. Con A capping was also inhibited. Actin polymerization in FMLP-stimulated PMN, as measured by flow cytometry and phalloidin binding to F-actin, was inhibited by K 562 products. The inhibitory factor present in K 562 products (cell and culture supernatant) was purified in three steps including gel filtration, ion-exchange chromatography, and IEF. The eluted active fraction corresponded to single band of about 8 kDa on SDS-PAGE. From these experiments, it is concluded that K 562 malignant cells in culture contain and release a low molecular mass factor (congruent to 8 kDa) that inhibits all adherence-related functions of neutrophils, whereas it does not alter FMLP- or PMA-induced oxidative burst. Further studies are needed to assess whether products of other tumor cells also act on the neutrophil by inhibiting adherence-related functions, Mo1 function and capping, and actin polymerization.     

Effects of anatomic variability on blood flow and pressure gradients in the pulmonary capillaries

Dhadwal, Amit, Barry Wiggs, Claire M. Doerschuk, and RogerD. Kamm. Effects of anatomic variability on blood flow and pressure gradients in the pulmonary capillaries. J. Appl. Physiol. 83(5): 1711-1720, 1997.Atheoretical model is developed to simulate the flow of blood throughthe capillary network in a single alveolar septum. The objective is tostudy the influence of random variability in capillary dimension andcompliance on flow patterns and pressures within the network. Thecapillary bed is represented as an interconnected rectangular grid ofcapillary segments and junctions; blood flow is produced by applying apressure gradient across the network. Preferred flow channels are shownto be a natural consequence of random anatomic variability, the effectof which is accentuated at low transcapillary pressures. Thedistribution of pressure drops across single capillary segments widenswith increasing network variability and decreasing capillary transmuralpressure. Blockage of one capillary segment causes the pressure dropacross that segment to increase by 60%, but the increase falls to<10% at a distance of three segments. The factors that causenonuniform capillary blood flow through the capillary network arediscussed.

     

Maternal toxicity--a possible factor in fetal malformations in mice

The assumption that major fetal malformations are indicative of a chemical's teratogenic potential was not supported by a literature review of teratology studies conducted in mice. In these studies, dose levels of test agents that manifested maternal toxicity as suggested by reduction in dam's body weight, clinical signs of toxicity, or deaths, also invariably caused reduction in fetal body weight, increased resorptions, and rarely fetal deaths. In several such studies, conducted with maternotoxic doses of structurally unrelated test agents, a consistent pattern of fetal defects was discovered. These defects included exencephaly, open eyes, hemivertebrae, fused arches or centra of lumbar or thoracic vertebrae, fused, missing or supernumerary ribs, and fused or scrambled sternebrae. These defects were absent at drug dosages that were distinctly nontoxic for the mother. In a few studies conducted at two or more maternally toxic doses, the degree and severity of maternal toxicity showed a positive correlation with the incidence and severity of above fetal defects. It is hypothesized that maternal toxicity, on its own, may have an etiologic role in these fetal defects.     

The growth hormone binding protein as a paradigm of the erythropoietin superfamily of receptors.

The growth hormone (GH) receptor belongs to a novel receptor family which shares significant amino-acid sequence homology and includes prolactin receptors, erythropoietin receptors and several cytokines' receptors. GH and three other members of this family of receptors have been shown to have circulating soluble forms. The present review summarizes our knowledge on receptor related binding proteins, discusses their possible biological effects and suggests their use in novel assays for their ligands. The GH-binding protein (GH-BP) was the first to have been described and is used as a model for the concept. A series of indirect pieces of evidence suggest that the measurement of circulating GH-BP may enable an evaluation of the GH-receptor. When covalently bound to GH, GH-BP has been shown to slow the clearance of GH. On the other hand GH-BP competes with the GH-receptor for GH binding and, thus, diminishes the biological effect of GH. We suggest a biological role for GH-BP as follows: an increase in the availability of GH results not only in the upregulation of the GH-receptor but also in increased turnover of this receptor, its internalization and recycling. This is followed by a concomitant increase in GH-BP which, in turn, mitigates the effect of GH by competing with the receptor on GH binding. The extracellular domain of the GH-receptor is homologous, to a large extent, with the sequence of several receptors for hormones and cytokines, which have recently been cloned.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fine structural observations of the cotyledons in germinating seeds ofPelargonium XHortorum Bailey: With normal and mutant plastids

Summary The fine structural changes in cotyledon cells of germinatingPelargonium seeds are studied on the first to fifth day of seedling emergence. Initially there is a rapid change in the cell fine structure, marked most conspicuously by the progressive liberation of the lipid and protein food reserves and the formation of an extensive thylakoid system within the plastids, but gradually the cells start to senesce. The subcellular changes in mutant cells are similar except that the plastids lack the usual thylakoid system and develop only deranged prolamellar bodies. They may store starch and they possess plastoglobuli, but seem not to contain plastid ribosomes. In rare mixed cells normal and mutant plastids remain quite distinct.