Microspore cultures as donor tissue for the initiation of embryogenic cell suspensions in barley

We have initiated embryogenic cell suspension cultures of barley (Hordeum vulgare L.) Igri from isolated microspore cultures. Data were obtained on the time required for establishment, frequency of establishment, i.e. number of calluses out of the total number of initiations giving rise to suspensions, and embryogenic capacity of the suspension cultures. For comparison, establishment of embryogenic cell suspensions from callus derived from immature zygotic embryos of Igri, Dissa and Golden Promise was also carried out. The results revealed that embryogenic suspension cultures were established in half the time and with a seven-fold higher frequency from microspore cultures than from zygotic embryo-derived calluses. The suspension cultures were still capable of embryo formation after two years. However, only albino plantlets were regenerated. For comparison, long term callus cultures derived from microspores, anthers and zygotic embryos were established. From the anther and zygotic embryo-derived callus cultures green plants were continuously regenerated, whereas the microspore-derived callus cultures lost this ability after the second subculture.     

Inhibition of HIV-1 IIIb replication in AA-2 and MT-2 cells in culture by two ligands of poly (ADP-ribose) polymerase: 6-amino-1,2-benzopyrone and 5-iodo-6-amino-1,2-benzopyrone

The effects of two adenosine diphosphoribose transferase (ADPRT) enzyme inhibitory ligands, 6-amino-1,2-benzopyrone and its 5-iodo-derivative, were determined in AA-2 and MT-2 cell cultures on the replication of HIV-1 IIIb, assayed by an immunochemical test for the HIV protein p24, and syncytium formation, characteristic of HIV-infected cells. Intracellular concentrations of both drugs were sufficient to inhibit poly(ADP-ribose) polymerase activity within the intact cell. Both drugs inhibited HIV replication parallel to their inhibitory potency on ADPRT, but distinct differences were ascertained between the two cell lines. In AA-2 cells both p24 and syncytium formation were depressed simultaneously, whereas in MT-2 cells only syncytium formation was inhibited by the drugs, and the p24 production, which remained unchanged during viral growth, was unaffected. Both drugs only moderately depressed the growth rate of the AA-2 and MT-2 cells and there was no detectable cellular toxicity. Results suggest the feasibility of the development of a new line of ADPRT ligand anti-HIV drugs that fundamentally differ in their mode of action from currently used chemotherapeutics.     

Phagocytosis of erythrocytes by the proximal tubule of the rat kidney

Summary Morphological examination of kidney biopsies from patients with glomerulonephritis and hematuria has revealed the presence of erythrocytes within epithelial cells of the proximal tubule. This observation suggested that the proximal tubule might be capable of phagocytizing morphologically intact erythrocytes. To examine this possibility small quantities of heparinized autologous blood were injected into surface convolutions of proximal tubules of the rat kidney using standard micropuncture techniques. At time intervals ranging from 10 min to 120 h after injection, the kidneys were preserved for light and transmission electron microscopy by drip-fixation with a half-strength Karnovsky's glutaraldehyde-formaldehyde fixative.During the initial 6 h there was a flattening of the brush border and accumulation of electron-dense material representing hemoglobin in apical vacuoles and in lysosome-like structures. From 6 to 15 h after micropuncture, there was progressive loss of the brush border and the simultaneous formation of pseudopodia-like evaginations that extended from the apical plasma membrane and surrounded the individual erythrocytes. By 18 and 24 h, erythrocytes were observed in the proximal tubule cells. At later time intervals, edema, lymphocytic infiltration, and fibrosis were observed in the interstitium. In addition, crystalline structures were present in the lumen and the cells of both proximal and distal tubules. These findings suggest that in addition to their well-established ability to pinocytize hemoglobin and other proteins, the cells of the proximal tubule are capable of phagocytizing morphologically intact autologous erythrocytes. It is possible that phagocytosis by the proximal tubule cells may play a role in the disposal of erythrocytes from the tubular fluid in hematuric conditions.     

Rates of growth, ribosome synthesis and elongation factor synthesis in a tufA defective strain of E. coli

Summary A tufA defective strain of E. coli was isolated which by a single deletion event acquired a tufA-lacZ fusion gene and lost the normal functional tufA gene (see accompanying paper). A correlation between the growth rate and the rate of ribosome synthesis showed that the average rate of protein synthesis was decreased to about 50% in the tufA defective strain whereas the number of EF-Tu molecules per ribosome was about 80% compared to a normal strain. The results indicate that tufB gene expression was preferentially stimulated in the tufA defective strain but the increased EF-TuB synthesis was not sufficient to make up for the loss of normal EF-TuA synthesis. Introduction of a plasmid that carries a complete tufA gene and the preceeding fusA gene but not the str-promotor into the tufA defective strain did not alleviate the slow growth or low rate of EF-Tu synthesis showing that the high rate of EF-TuA synthesis compared to the other proteins in the str operon is not augmented by a strong second promotor for the tufA gene. The tufA-lacZ fusion which takes the place of the normal tufA gene was expressed at a high rate and the -galactosidase activity increased with the growth rate as expected.     

A family with a high risk of segregation for an autosomal unbalanced reciprocal translocation

Summary A family with autosomal reciprocal translocation t(4;13) (q25;q31) with a sibship comprising 2 children with unbalanced karyotypes, der(13) partial trisomy 4q, 1 child with the balanced translocation, and 2 abortions were studied. The segregation risk of unbalanced derivation in reciprocal translocations is discussed. The clinical picture of the 2 children with partial trisomy 4q is compared with similar cases.     

Induction of type C virions from normal rat kidney cells by 2-deoxy-D-glucose.

The sugar 2-deoxy-D-glucose (2-DG) induced the release of type C virions from an established line of normal rat kidney (NRK) cells. Within 20 h after the addition of 5 mg of 2-DG per ml to exponentially growing NRK clutures, more than 80% of the cells expressed the mammalian type C virus interspecies-specific antigen (p30) as determined by indirect cytoplasmic immunofluorescence. Maximal virion release occurred 1 to 2 days after 2-DG was added for 24 h to the growth medium although a low level of virion production was detected as early as 2.5 h after 2-DG treatment. Studies with inhibitors of RNA synthesis indicated a requirement for de novo RNA synthesis after the addition of 2-DG. Sensitivity of NRK cells to type C virion induction was limited to a relatively short period of in vitro growth and preceded spontaneous virion release by 8 to 10 subculture generations. A model is presented for the sequential derepression of latent type C virus information in serially propagated NRK cells.