An immunocytochemical study of keratin reactivity during rat odontogenesis

Summary The cytokeratin distribution in the developing rat enamel organ from day 15 of gestation through to 11 days post partum was examined immunohistochemically using a panel of monoclonal antibodies. A temporo-spatial programme of keratin expression was observed during odontogenesis and positive reactivity of the enamel organ was seen with the pan keratin antibodies CK1 (clone LP34 — reacts with a number of keratins including 6 and 18) and AE1-3 (reacts with most acidic and basic keratins). No reactivity was observed in the enamel organ with the other antibodies examined (Ks 8.12 [reacts with keratins 13 and 16], Ks 8.60 [reacts with keratins 10 and 11) and MCA157 [reacts with rat liver antigen]), although these antibodies did stain other epithelial tissues. This study supports the view that the epithelial cells of the enamel organ synthesize a tissuspecific subset of keratins which are related to the differentiation of the cells.     

Comparison of zona cutting and zona drilling as techniques for assisted fertilization in the mouse

Zona cutting and zona drilling of the mouse oocyte significantly increased the fertilization rate (3.8-90%) at low sperm concentrations (less than 200,000/ml) compared with zona-intact controls (0-45%). More oocytes were fertilized after zona drilling. Zona cutting was associated with a low loss of oocytes (less than 1%), no increase in polyspermy and normal development in vitro and in vivo after fertilization. There was a 4% oocyte loss rate after zona drilling, mostly due to extrusion of the oocyte from the zona during the procedure. Hatching of blastocysts occurred about 12 h earlier for zona-drilled than for zona-cut and zona-intact control oocytes. Zona drilling was associated with a higher, but not statistically significant, rate of polyspermy at all sperm concentrations tested. The proportion of zygotes developing to the blastocyst stage was not different between the techniques (zona cut, 77%; zona drilled, 66%; control, 71%). Similarly, no difference was found in the percentage of embryos implanting after blastocyst transfer to the uterine horns of pseudopregnant female mice (zona cut, 67%; zona drilled, 68%; control, 77%). Transmission electron microscopy demonstrated the induced defects in the zona with no damage to the oocyte or oolemma. Parthenogenetic activation was not seen after either of the micromanipulative techniques. Both techniques have promise for application to the human.     

Differential effects of largemouth and smallmouth bass on habitat use by stoneroller minnows in stream pools

Previous investigations of within-reach distribution patterns of the stoneroller minnow, Campostoma anomalum Rafinesque, suggest that this species behavioural response to piscivorous bass differs among streams with different bass species. This study compares the responses of Camposloma to two common piscivorous fishes, largemouth bass, Micropterus salmoides Lacepede, and smallmouth bass, M. dolomieui Lacepede. Field experiments in Brier Creek, Oklahoma, U.S.A. showed that Campostoma responded to the presence of adult largemouth bass by shifting to shallow water habitats (commonly < 20 cm), but responded weakly or not at all to adult smallmouth bass. The magnitude of the response of Campostoma was positively related to activity level of the predators. Differences in behaviour between these two predator species may contribute to the differences in spatial distribution patterns of Micropterus and Campostoma observed in earlier investigations, but differences in stream channel morphology and temperature regimes among streams may also be important.     

A protoplast to plant system in roses

High yields of protoplasts were isolated from embryogenic suspension cultures of Rosa persica x xanthina and Rosa wichuraiana using an enzyme mixture comprising 20 g l^-1 cellulase Onozuka R10, 1 g l^-1 Pectolyase Y-23 and 10 g l^-1 hemicellulase. Agarose-immobilized protoplasts gave the most consistent growth at a plating density of 5×10⁴ protoplasts ml^-1 on the basic medium of Kao & Michayluk (KM8p) containing 2 mg l^-1 naphthaleneacetic acid and 1 mg l^-1 benzylaminopurine. At 25°C in the dark, 0.004% of R. persica x xanthina protoplasts developed into colonies. Using similar culture conditions, but with a plating density of 9×10⁴ protoplasts ml^-1, 0.017% of R. wichuraiana protoplasts developed into colonies. On transfer of R. persica x xanthina colonies to Schenk & Hildebrandt's medium containing 3 mg l^-1 2,4-dichlorophenoxyacetic acid, globular and later stage embryos were formed. Approximately 30% of these embryos developed into plantlets on transfer to basal Schenk & Hildebrandt's medium. Further development of the plantlets took place on cellulose plugs (Sorbarods) soaked in Murashige & Skoog's medium containing 0.05 mg l^-1 naphthaleneacetic acid, 0.05 mg l^-1 indole-3-butyric acid and 0.1 mg l^-1 benzylaminopurine. Rose breeding is now open to the full range of in vitro genetic manipulation techniques involving protoplast technology.     

Dark matter in the solar system: Hydrogen cyanide polymers

In the presence of a base such as ammonia liquid HCN (bp 25 °C) polymerizes readily to a black solid from which a yellow-brown powder can be extracted by water and further hydrolyzed to yield-amino acids. These macromolecules could be major components of the dark matter observed on many bodies in the outer solar system. The non-volatile black crust of comet Halley, for example, may consist largely of such polymers, since the original presence on cometary nuclei of frozen volatiles such as methane, ammonia, and water makes them possible sites for the formation and condensed-phase polymerization of hydrogen cyanide. It seems likely, too, that HCN polymers are among the dark —CN bearing solids identified spectroscopically by Cruikshanket al. in the dust of some other comets, on the surfaces of several asteroids of spectral class D, within the rings of Uranus, and covering the dark hemisphere of Saturn's satellite Iapetus. HCN polymerization could account also for the yellow-orange-brown coloration of Jupiter and Saturn, as well as for the orange haze high in Titan's atmosphere. Implications for prebiotic chemistry are profound. Primitive Earth may have been covered by HCN polymers through cometary bombardment or terrestrial synthesis, producing a proteinaceous matrix that promoted the molecular interactions leading to the emergence of life.