Disruption of keratin filaments in embryonic epithelial cell types.

The murine keratins Endo B and Endo A, which are homologs of the human keratins K18 and K8, constitute the intermediate filaments (IFs) that are found in all simple epithelia of the adult and in the first epithelial derivatives of the early embryo. The cellular role of simple epithelial keratins in development and differentiation was investigated by inducing filament collapse in HR9 endoderm and F9 embryonal carcinoma cells in which mutant Endo B protein was constitutively expressed. By immunolocalization techniques a perturbation of the keratin network was revealed as well as concomitant disruption of vimentin IFs and displacement of surface desmosomal proteins, demonstrating an intimate structural association of Endo B/A filaments with these cellular components. In aggregates of differentiating F9 cells displaying altered Endo A/B IFs, the formation of a compact, polarized visceral endoderm layer was significantly compromised. These results indicate that an intact keratin network influences the three-dimensional formation of cell-cell or cell-substratum contacts in embryonic visceral endoderm.     

The use of the Cole/Hurlbert C8 association coefficient in inverse ecological classification

Abstract. Inverse classification is routinely used in vegetation surveys to produce groups of sociologically similar species. However, no classification methods have been proposed specifically for this purpose, nor has any evaluation been made of the suitability of existing methodsforthe purpose. Anewvariant of Cluster Analysis is introduced, i. e. using the Cole/Hurlbert association measure C₈ as coefficient, and named for convenience Cole Cluster Analysis. This method, and four standard ones, were used on saltmarsh vegetational data from New Zealand. Ecophysiological data were obtained from salt-tolerance experiments. These data, and distributional information, were used as independent criteria against which to compare the inverse vegetation classifications. Information Analysis did not prove suitable for inverse analysis in this test. Nor did Cluster Analysis with the Simple Matching Coefficient or with Jaccard's coefficient. Indicator Species Analysis was more suitable, but the new Cole Cluster Analysis seemed the most effective on these data.     

Pyrimidine deoxyribonucleotide metabolism during maturation and germination of white spruce (Picea glauca) somatic embryos: metabolic fate of C-labelled cytidine, deoxycytidine and thymidine

Pyrimidine deoxyribonucleotide metabolism was investigated during maturation and germination of white spruce somatic embryos by following the metabolic fate of [2‐¹⁴C]cytidine, [2‐¹⁴C]deoxycytidine and [2‐¹⁴C]thymidine. The de-novo pathway of deoxyribonucleotides was estimated indirectly, by the ability of the tissue to incorporate cytidine into DNA after conversion to dCTP. The salvage pathway was estimated by the utilization of labelled cytidine, deoxycytidine and thymidine for synthesis of deoxyribonucleotides and nucleic acids. Utilization of cytidine for DNA synthesis, via the de novo pathway, was always lower than that observed for RNA throughout the course of the experiment. Incorporation of cytidine into RNA was found to occur either directly, after conversion to CTP, mediated by the enzymes cytidine kinase, nucleoside monophosphate kinase and nucleoside diphosphate kinase, or indirectly, after conversion to UTP via uridine and UMP. Active incorporation of uridine into RNA of white spruce-cultured cells was demonstrated previously. Salvage of deoxycytidine and thymidine was operative in maturing and germinating white spruce somatic embryos, as label from both compounds was recovered in nucleotides and DNA. However, the utilization of these precursors by the cells was different. Salvage of deoxycytidine was always higher than that observed for thymidine, which was extensively catabolized to CO₂ at all stages of embryo development.     

Evaluating Restoration Success on Lyell Island, British Columbia Using Oblique Videogrammetry

In degraded ecosystems where the impact on wildlife and the destruction of natural systems is high, restoration becomes a critical component of recovery. Monitoring restoration activities plays a key role in determining end points for restoration and assessing effectiveness. Appropriate monitoring of major systems, particularly in assessing vegetation reestablishment and slope stabilization, requires a long‐term commitment to annual assessment of change and improvement over time. However, intrinsic factors built into government or public management systems, such as budgeting and staffing limitations, limit the ability for long‐term monitoring of critical restoration projects. In the research reported in this article, we devised and assessed a new remote method for assessing restoration success and tested it on restoration and monitoring requirements in Lyell Island, British Columbia. We developed a system (the oblique data fusion system [ODFS]) to extract spatial information from oblique aerial video imagery. The ODFS enables low‐cost change detection and database updates at a range of operational scales. System tests show an absolute spatial accuracy on the order of ±2.1 m. The evaluation, based on digitized historical data, ground surveys, and the ODFS‐derived data, indicates that the landslide rate (new area/year) tapered off following treatment; after 5 years it had been reduced by a factor of 3 relative to the background rate. The recovery is deemed sufficient to initiate secondary restoration tasks. The evaluation demonstrates the accuracy and utility of the ODFS for long‐term monitoring of landscape restoration efforts, particularly in remote areas. In conclusion, this new innovative method shows considerable promise for park managers.     

An Origin of Transfer (oriT) on the Conjugative Element pRS01 from Lactococcus lactis subsp. lactis ML3

Previous analysis of the Tra1 region of the conjugative element pRS01 from Lactococcus lactis subsp. lactis ML3 suggested that an origin of transfer (oriT) was present. Deletion derivatives of this cloned Tra1 region were assayed for mobilization in the presence of the wild-type pRS01 element in trans. The pRS01 oriT was localized to a 446-nucleotide segment in the intergenic region between open reading frames ltrD and ltrE. Sequence analysis of this region revealed a cluster of direct and inverted repeat structures characteristic of oriT regions associated with other conjugative systems.     

Optimization of bud induction in cotyledonary explants of Pinus canariensis

A method is described for using liquid pulsing as an alternative to the conventional induction protocol for Pinus canariensis. Using Day 0 and Day 3 explants, the best exposure time was 8 h and 4 h respectively, in a non-buffered 100 M N⁶-benzyladenine solution, followed by culture on half-strength Bornman's medium containing 3% sucrose and 0.8% Difco Bacto^R agar. With this procedure, 97% of the cotyledonary explants produced about 14 buds/explant. These results were comparable to a 14-day induction period on full-strength Bornman's medium containing 10 M N⁶-benzyladenine.     

Isolation of a variant family of mouse minor satellite DNA that hybridizes preferentially to chromosome 4

Two cosmids (HRS-1 and HRS-2) containing mouse minor satellite DNA sequences have been isolated from a mouse genomic library. In situ hybridization under moderate stringency conditions to metaphase chromosomes from RCS-5, a tumor cell line derived from the SJL strain, mapped both HRS-1 and HRS-2 to the centromeric region of chromosome 4. Sequence data indicate that these cloned minor satellite DNA sequences have a basic higher order repeat of 180 bp, composed of three diverged 60-bp monomers. Digestion of mouse genomic DNA with several restriction enzymes produces a ladder of minor satellite fragments based on a 120-bp repeat. The restriction enzyme NlaIII (CATG) digests all the minor satellite DNA into three prominent bands of 120, 240, and 360 bp and a weak band of 180 bp. Thus, the majority of minor satellite sequences in the genome are arranged in repeats based on a 120-bp dimer, while the family of minor satellite sequences described here represents a rare variant of these sequences. Our results raise the possibility that there may be other variant families of minor satellites analogous to those of alphoid DNA present in humans.     

Ultrastructural studies of the commensal suctorian,Choanophyra infundibulifera hartog

Summary Tentacle structure, movement and feeding of the commensal suctorian Choanophrya infundibulifera have been examined by light, scanning and transmission electron microscopy. The tentacles possess a flattened tip and rounded shaft externally, with a neck and root region internally. There is a microtubule canal consisting of 150 ring microtubules within which are 20–35 curved lamellae each containing about 20 microtubules. Novel structural features include pairs of short oblique arranged microtubules at the tip, and a collar of epiplasm in the neck region. No haptocysts are found in Choanophrya but the tentacle cytoplasm contains two types of inclusions named solenocysts and spherical vesicles. These features are discussed in relation to the processes of tentacle movement and feeding. The rapid longitudinal movements of the tentacles are described and compared to those of other suctorians and possible mechanisms are suggested. Ingestion in Choanophrya is described and several theories involving tentacle microtubules in the feeding process are examined.This investigation was supported by the J.S. Dunkerley Fellowship in Protozoology, awarded by the University of Manchester.     

The development of ribonuclease and acid phosphatase during germination of Pisum arvense

1. Development of ribonuclease activity in the cotyledons of germinating peas is biphasic, the time of appearance of the two phases depending on the conditions of growth. 2. Acid phosphatase exhibits a single phase of development. 3. Cycloheximide inhibits development of ribonuclease activity in phase II but not in phase I. 4. (14)C-labelled amino acids are not incorporated into ribonuclease isolated during phase I. 5. The buoyant density of ribonuclease isolated during phase I is not affected by imbibition of the seed in 80% deuterium oxide. 6. Acid phosphatase was isolated from the supernatant fraction of the cotyledons of germinating peas and partially purified. 7. Development of acid phosphatase activity during germination is inhibited by treatment of the seed with cycloheximide or actinomycin D. 8. Partial purification of acid phosphatase from peas germinated in the presence of (14)C-labelled amino acids suggests that the enzyme is radioactively labelled. 9. Germination of peas in the presence of 80% deuterium oxide results in an increase in the buoyant density of acid phosphatase. 10. The results suggest that increase in ribonuclease activity during the first 4 days of germination does not result from synthesis of protein de novo, but that the corresponding increase in acid phosphatase activity does result from synthesis de novo.