RECONNECTING CELL AND ANIMAL LINEAGES: WHAT DO CELL LINEAGES TELL US ABOUT THE EVOLUTION AND DEVELOPMENT OF SPIRALIA?

Cell lineage studies in the clade Eutrochozoa, and especially the Spiralia, remains a rich and relatively untapped source for understanding broad evolutionary developmental problems; including (1) the utility of cell timing formation for phylogenetic hypotheses; (2) the evolution of cell timing changes and its relation to heterochronic patterns; (3) stereotypy or lack thereof in rates of change of cell growth during evolution and its relation to both evolutionary history and current usage; and (4) how mosaic cleavage timing variation may be expected to differ from other groups. A compilation of available cell timing information was made from previous studies where each division was explicitly followed and the total number of cells followed was greater than 24. From that compilation, we performed a series of heuristic and quantitative analyses, including a phylogenetic analysis using cell timing data as characters and analyses of timing variation across all taxa. Our results show that: (1) cell lineage data reconstructs a phylogenetic hypothesis that has similarities, especially among the Mollusca. to the patterns found in morphological and molecular analyses; (2) the mesentoblast (4d) is a unique cell compared to other cell in that it speeds up and slows down relative to other cells in taxa with both unequal and equal cell sizes; (3) some cells that form in the same quartet at the same point in the cell lineage hierarchy have much lower variations than analogous other cells, arguing for architectural constraint or stabilizing selection acting on those cells; and (4) although variation in cell timing generally increases during development, timing of formation of progeny cells in the first quartet has lower variation than the parent cells, arguing that some regulation-like behavior might be present.     

THE LIVING CELL: A COMPLEX AUTODYNAMIC MULTI‐OSCILLATOR SYSTEM?

Life cannot be simply defined in biochemical terms but it is associated with autodynamic behaviour. This fact implies that all aspects of cell biology should be viewed in terms of the resultant temporal features. Theoretical arguments indicate that the dynamic state can be explained only by the existence of periodicity. In accordance with this view, experimental evidence indicates the existence of multiple oscillators and at least some are highly complex, implying that failure to understand aspects of cell biology can stem from inadequate concepts.     

ESTABLISHMENT OF AVIAN FEATHER PULP CULTURE METHOD AND STUDY ON THE CELL DIVISION

It is difficult to obtain enough metaphase chrolmosomes for avian cytogene-tic analysis by conventional peripheral blood culture technique.Up to now,the bone marrow technique is applied in a few of avian studies.But this te-chnique can not be used for conservation.     

ARE CELL KINETIC DATA RELEVANT FOR THE DESIGN OF TUMOUR CHEMOTHERAPY SCHEDULES?*

The data on the importance of the application of information on cell kinetics for the success of tumour chemotherapy are critically reviewed. It is concluded that the data on cell sensitivity to drugs as affected by cell kinetic variables are as yet insufficient to permit the prediction of optimal dosage schedules for tumour therapy. More information is needed on differential responses and differential kinetic features of normal and malignant tissues. Optimistic views of cell kinetics as an easy answer to the problems of drug dosage schedule design are unjustified, but so is the disenchantment with cell kinetics as a fruitful approach. Much further work, especially on the drug sensitivity of cellular compartments in slow growing tumours, is needed before a complete evaluation of this tool is possible.     

CELL AND MOLECULAR BIOLOGY

One of the highest-ranking journals In biology with an Impact factor of 6.787! BioEssays Editor: Adam S. Wilkins, Cambridge, UK BioEssays offers readers in-depth review articles and serves as a resource for education and new ideas by exploring a wide range of biological topics. Researchers and teachers are presented with a unique tool for learning how findings in molecular, cellular,     

MICRURGICAL STUDIES IN CELL PHYSIOLOGY : V. THE ANTAGONISM OF CATIONS IN THEIR ACTIONS ON THE PROTOPLASM OF AM?BA DUBIA.

I. The Plasmalemma. 1. On the plasmalemma of amebæ CaCl₂ antagonizes the toxic action of LiCl better than it does NaCl, and still better than it does KCl. MgCl₂ antagonizes the toxic action of NaCl better than it does LiCl and still better than it does KCl. 2. CaCl₂ antagonizes the toxic action of LiCl and of KCl better than does MgCl₂: MgCl₂ antagonizes NaCl better than does CaCl₂. II. The Internal Protoplasm. 3. The antagonizing efficiency of CaCl₂ and of MgCl₂ are highest against the toxic action of KCl on the internal protoplasm, less against that of NaCl, and least against that of LiCl. 4. CaCl₂ antagonizes the toxic action of LiCl better than does MgCl₂: MgCl₂ antagonizes the toxic action of NaCl and of KCl better than does CaCl₂. 5. LiCl antagonizes the toxic action of MgCl₂ on the internal protoplasm more effectively than do NaCl or KCl, which have an equal antagonizing effect on the MgCl₂ action. III. The Nature of Antagonism. 6. When the concentration of an antagonizing salt is increased to a toxic value, it acts synergistically with a toxic salt. 7. No case was found in which a potentially antagonistic salt abolishes the toxic action of a salt unless it is present at the site (surface or interior) of toxic action. 8. Antagonistic actions of the salts used in these experiments are of differing effectiveness on the internal protoplasm and on the surface membrane.     

MICRURGICAL STUDIES IN CELL PHYSIOLOGY : III. THE ACTION OF CO2AND SOME SALTS OF NA,CA, AND K ON THE PROTOPLASM OF AM?BA DUBIA.

I. Plasmalemma. 1. Of the salts used in these experiments the anions have only a modifying effect on the cations. The dispersive action of Na and, to a lesser extent, of K, predominates. Borate increases the toxicity of Na and acetate decreases it. 2. CO₂ and carbonates dissolve the plasmalemma readily. 3. Na lactate tends to dissolve the surface especially when brought into contact with it from the interior by injection. Lactate antagonizes the stimulating effect of Ca on the plasmalemma. II. The Internal Protoplasm. 4. Acid phosphate of Na and K, when injected, causes a membrane to form around the granular endoplasm within the ameba. 5. Na borate increases the toxicity of Na inside the cell. 6. Bubbles of CO₂, injected into the cell, cause an increase of fluidity of the internal protoplasm. These bubbles shrink and disappear from the cell more readily than air bubbles. 7. The anions modify the typical cation effect. Carbonates accentuate the liquefying and solvent action of Na. Phosphates prevent a complete rounding of the ameba caused by Na. Lactate inhibits the solidification and pinching off effect caused by Ca. III. Physiological Significance of Salts. 8. The buffer salts can be injected in high concentrations without toxic effects but amebæ can be immersed in them only in very dilute solutions without injury. 9. The inhibiting action of lactate and the dispersive effect of CO₂, carbonates, and lactate on the plasma membrane, must be of importance in a consideration of the functions of the organism and perhaps in the production of pathological changes.     

THE BREEDING STATUS OF THE CAPE VULTURE IN THE TRANSVAAL DURING 1980—1985

Benson, P. C., Tarboton, W. R., Allan, D. G. & Dobbs, J. C. 1990. The breeding status of the Cape Vulture in the Transvaal during 1980–1985. Ostrich 61: 134–142.

Ten of the 11 extant Cape Vulture Gyps coprotheres colonies in the Transvaal were censused using aerial and/or ground census techniques in the 1980–1985 breeding seasons. Minimum counts were obtained and best estimates of total numbers of “active nests” were determined using correction factors to compensate for incomplete photocoverage in the aerial technique and nest failures prior to the census dates. In 1985, the year when the most complete data were available, a minimum of 2741 and a best estimate of 2987 active nests were determined to be present in the Transvaal. At the large colonies, which were intensively monitored, breeding numbers did not fluctuate greatly from year to year, and it is thus estimated that about 3000 pairs of birds bred yearly in the Transvaal during the study period. Although the data indicate that the total numbers are greater than previously thought this is due to improved census techniques, rather than an increase in the population. Ninety-eight percent of breeding occurred at six colonies and 82% at three (Kransberg, Blouberg and Manutsa). The large colonies are associated with communal grazing (homelands) Private cattle and game farming and nature conservation areas, where the use of poison for predator control is minimal. The vulnerable status afforded the Cape Vulture in the South African Red Data Book—Birds (Brooke 1984) is justified because of the bird's disappearance from some breeding colonies, reduction in numbers at others and its vulnerability to poisoning.     

ON THE LARVAE OF THE CHINESE SPECIES OF THE SUBFAMILY CHRYSOMYINAE(DIPT.CALLIPHORIDAE)

In this paper, the author described the larvae of Chinese Chrysomyine flies. All larval specimens of the seven species studied in this paper were reared in the laboratory. The 7 species of Chrysomyinae are as follows: Chrysomya megacephala (Fab., 1794). Fig.1. Ch. pinguis (Wlk., 1858). Ch. bezziana Vill., 1914, Fig.2. Ch. defixa (Wlk., 1857), Fig.3. Achaetandrus rufifacies (Macq., 1842). Fig. 4a.b. Ach. villeneuvii (Patton. 1922). Fig. 4b. (right 5, 8.) Ceylonomyia nigripes (Aubt., 1932). Fig. 5. The larvae of following species are described for the first time.     

ON THE LARVAE OF THE CHINESE SPECIES OF THE TRIBE LUCILIINI (DIPT.CALLIPHORIDAE)

The present paper deals with the larvae of 10 species of Luciliini from China. The 10 species of Luciliini are as follows: Hypopygiopais infumata (Bigot, 1877), Fig. 1. Hemipyrellia ligurriens (Wied., 1830), Fig. 2. Lucilia sericata (Meig., 1826), Fig. 3. L. cuprina (Wied., 1830), Fig. 4. L. illustris (Meig., 1826), Fig. 5. L. caesar (L., 1758), Fig. 6. L. porphyrina (Walk., 1857), Fig. 7. L. ampullacea laoshanensis Quo, 1952, Fig. 8.     

METAMORPHOSIS OF THE LARVA OF THE POLYCHAETE ARENICOLA CRISTATA. MORPHOLOGY OF THE ‘HOUR-GLASS’ STAGE

The constricted ‘waist’ of the metamorphosing larva of the polychaete Arenicola cristata is described, using light and electron microscopy. The constriction is shown to be the consequence of the discharge and collapse of a post-trochal ring of epithelial cells which remain as functional components of the post-metamorphic juvenile. Morphological differentiation of neuro-effector and interneuronal contacts is initiated at this time. Muscular and neural changes are discussed in terms of their role in effecting metamorphosis.     

THE POTENTIAL FOR PALAEOBOTANY IN THE EXPLANATION OF CHINA''''S PLANT GEOGRAPHY

The distributions of many plant taxa in China at the present day indicate centres of floristic importance which may be ancient,and have evolutionary significance,or which may be only their latest locations in a Cenozoic history of migrations.This paper summarizes the present and Cenozoic distributions in China of the following taxa:Nitraria,Ephedra,Carya,Liquidamber,Pterocarya,Betulaceae.It is concluded that the centres of importance of the named genera are different now from what they were at some time in the Cenozoic past;each has accomplished major migrations and suffered significant extinctions during that period.The history of the Betulaceae is less clear but in principle soluble.     

MANAGING THE ST. LUCIA ESTUARY—MESSAGES FROM THE MUD

Summary

The infaunal macrobenthic community of the St Lucia estuary has been exposed to natural disturbance in the form of salinity fluctuations arising from floods and hypersaline conditions, and human-induced interference arising from dredging and beam trawling. The responses of the benthos to these disturbances have been recorded between 1983 and 1994 and are discussed in the light of management options for the estuary. A simple benthic sampling strategy is suggested to monitor the important benthic species.