Multimodal interneurones in the polyclad flatworm,Alloeoplana californica

Summary Two morphological types of interneurones were found in the brainof Alloeoplana californica (Figs. 1, 2). Both respond to water vibration and to light offset (Fig. 3). These responses are blocked by Mg⁺⁺ or Cd⁺⁺ (Fig. 4), and habituate to repetitive stimuli (Figs. 6, 10). Even when the light response is habituated, light offset will dishabituate the vibration response (Figs. 7, 10); no other regime tested produced dishabituation of either response. These neurones receive higher-order sensory input, and make subthreshold excitatory synapses on motor pathways; intracellular tetraethylammonium lengthens the time course of the spikes (Fig. 5), and each such spike elicits a contraction in the anterior margin of the animal. We believe that they form part of the neuronal circuitry underlying arousal.Abbreviation TEA tetraethylammonium     

Regulatory function of sorbose-resistance gene C in sugar transport of Neurospora

Summary A sorbose-resistant double mutant sor ^r A-10/sor ^r C-17 produces larger colonies in sorbose containing test-medium than the respective single mutants; wildtype colonies remain very small. Resistance of the single mutants was shown to be connected with a decreased rate of sorbose-uptake into their conidia; however, sorbose uptake of the double mutant had not been measured. To check, whether the improved performance of the double mutant on test medium is correlated with a further decrease of sorbose uptake in this strain, studies on the uptake of fructose, sorbose and deoxyglucose by ungerminated conidia of the two single mutants, the double mutant and the wildtype were conducted, using C¹⁴-marked sugars, the millipore filter technique, and conidia either untreated or pretreated with 1% sorbose for 4 hours.If sorbose uptake is referred to that of fructose as basis of calculations, as in the earlier studies, the sorbose uptake by cells of the double mutant is smaller than that of both single mutants for conidia not pretreated with sorbose (Fig. 7a). However, for conidia pretreated with sorbose, this correlation does not hold. Rather, cells of the double mutant take up less sorbose than those of the C-mutant, but as much or slightly more than those of the A-mutant (Fig. 7b). If sorbose uptake is referred to that of deoxyglucose for an independent point of reference, cells of the double mutant take up less sorbose than those of the C-mutant, but much more than those of the A-mutant. This holds for untreated and sorbose pretreated cells (Fig. 5 a and b). These data rule out a correlation between colony size and transport defect for at least one of the strains used here, i.e. the C-mutant.The following data suggest a new interpretation: In contrast to the earlier findings with germinated conidia, ungerminated untreated cells of the C-mutant take up much more fructose and sorbose than those of the wildtype (Fig. 3 a and 1a). The uptake of fructose by cells of the C-mutant can not be improved by sorbose pretreatement (Fig. 3 b), but in both wildtype and A-mutant it is increased (Figs. 1b and 2b). Uptake of deoxyglucose was nearly equal for all three strains either untreated or pretreated. Untreated cells of the A-mutant take up as much sorbose as those of the wildtype (Figs. 2 a and 1 a). On pretreatment their sorbose uptake remains nearly constant (Figs. 2b), in contrast to wildtype cells, where it increases drastically and without an increase of fructose uptake by an equivalent amount (Fig. 1b).The new interpretation suggests that gene C is of the regulator type. Mutation of it in the C-strain used here has lead to the simultaneous de-repression of a system for fructose and sorbose uptake. Deoxyglucose uptake is not served by this system. Gene A is a structural gene, harbouring the information for the inducible synthesis of a carrier or permease specifically engaged in sorbose uptake. It is not under the controll of gene C.This interpretation is supported by results on untreated cells of the double mutant. However, fructose uptake of such cells is roughly equal to that of C-mutant cells (Fig. 6a) and sorbose uptake is less (Fig. 5a). Hence, a secondary effect of the A-gene, i.e. on the amount of de-repression of sorbose uptake by mutation in gene C, is indicated.     

Behavioral plasticity in aDrosophila mutant,dunce DE276

Summary Drosophila X-linked mutantdunce ^DB276 fails to display learning in an olfactory learning paradigm, in spite of being able to sense odorants and shock (Byers, 1977; Fig. 1). However, conditions exist under which the flies display associative behavior (Table 1, Figs. 3, 5). Memory appears to be short-lived (Table 1, Figs. 3, 5) and labile (Figs. 3, 4). It is suggested that thedunce ^DB276 mutation affects an early memory phase.I thank G. Bicker, D. Byers and W.G. Quinn for valuable comments. This work was supported by a grant from the United States-Israel Binational Science Foundation, Jerusalem. The author is incumbent of the Barecha Foundation Career Development Chair.     

The innervation and chemical sensitivity of single aesthetasc hairs

Summary Each aesthetasc hair of the lateral antennule of the California spiny lobsterPanulirus interruptus (Randall) is shown by light and scanning electron microscopy to be innervated by a basally situated cluster of sensory neurons encased in a glial sheath which isolates each cluster from those of other hairs (Figs. 1, 3, 4). The dendrites of these neurons penetrate the aesthetasc hairs and their axons extend to the central nervous system. Extracellular recordings with suction electrodes from the axons of single neuronal clusters were used to determine the responsiveness of individual hairs to a spectrum of amino acids, amines, amides, carbohydrates, carboxylic acids, nucleotides, and a tripeptide (Tables 1, 2, Figs. 6, 8). Randomly selected hairs from the antennules of juvenile, and male and female adult lobsters were shown to be broadly sensitive to a variety of stimuli and are homogeneous in their breadth of responsiveness (Figs. 5, 7). Cluster analysis does not reveal distinct chemoreceptive hair types based on their response spectra, suggesting that the receptor populations of single hairs are uniformly competent to respond to diverse chemical stimuli (Figs. 6, 8). Further, the sensitivity profile of aesthetascs to these stimuli correlates well with behavioral responses ofPanulirus interruptus to these same stimuli (Tables 1, 2).Abbreviation ² Chi-squared     

Permeation through Phospholipid Bilayers,Skin‐Cell Penetration,Plasma Stability,and CD Spectra of α‐ and β‐Oligoproline Derivatives

After a survey of the special role, which the amino acid proline plays in the chemistry of life, the cell‐penetrating properties of polycationic proline‐containing peptides are discussed, and the widely unknown discovery by the Giralt group (J. Am. Chem. Soc. 2002 , 124, 8876) is acknowledged, according to which fluorescein‐labeled tetradecaproline is slowly taken up by rat kidney cells (NRK‐49F). Here, we describe details of our previously mentioned (Chem. Biodiversity 2004 , 1, 1111) observation that a hexa‐β³‐Pro derivative penetrates fibroblast cells, and we present the results of an extensive investigation of oligo‐L ‐ and oligo‐D ‐α‐prolines, as well as of oligo‐β²h‐ and oligo‐β³h‐prolines without and with fluorescence labels ( 1 – 8 ; Fig. 1). Permeation through protein‐free phospholipid bilayers is detected with the nanoFAST biochip technology (Figs. 2–4). This methodology is applied for the first time for quantitative determination of translocation rates of cell‐penetrating peptides (CPPs) across lipid bilayers. Cell penetration is observed with mouse (3T3) and human foreskin fibroblasts (HFF; Figs. 5 and 6–8, resp.). The stabilities of oligoprolines in heparin‐stabilized human plasma increase with decreasing chain lengths (Figs. 9–11). Time‐ and solvent‐dependent CD spectra of most of the oligoprolines (Figs. 13 and 14) show changes that may be interpreted as arising from aggregation, and broadening of the NMR signals with time confirms this assumption.     

Changes in mitotic indices in roots of Vicia faba

Roots of Vicia faba were treated with solutions of colchicine or IAA or both. Mitotic indices and the frequencies of the different stages of mitosis were determined immediately after a three hour treatment or following a 24 hour period of recovery. Roots scored after treatment with colchicine for three hours showed several effects, none of which were reversed by simultaneous treatment with IAA. Treatment with IAA for three hours had little detectable effect on mitotic index (MI) on the frequencies of the various stages of mitosis. After a recovery period, following a three hour treatment, of 24 hours, colchicine treated roots showed a significant increase in their MI; this was due largely to an increase in the number of metaphases but it was also due in part to the presence of tetraploid cells in division. IAA treated roots revealed an inhibition of mitotic activity, which was most marked at 3.13–6.26×10^–4 M IAA. The results from roots treated with mixtures of colchicine and IAA for three hours and fixed 24 hours later showed: 1) the increase in MI induced by colchicine is reversed by IAA, the intensity of the reversal increasing with increasing concentrations of IAA; 2) reductions in the total numbers of cells in prophase or in metaphase occur after treatment with different concentrations of IAA; 3) IAA leads to a reduction in the number of tetraploid cells seen in division.It appears that colchicine induces a change in the pattern of mitotic activity 24 hours after the end of treatment and its effects are reversed by IAA. At 4.2×10^–4 M IAA a balance occurs between the opposing effects of colchicine and IAA and the MI is not significantly different from that of the controls. It is suggested that one result of a treatment with colchicine is a change in the level of growth factors in root meristems. This change, which appears to result in a temporary increase in MI is reversed by the addition of IAA. Thus one of the growth factors, the level of which has been affected, is replaceable by exogenous IAA.     

Increases in nuclear volume and cell size in meristematic cells arrested by 5-aminouracil

Summary Lateral roots ofVicia faba were treated with a solution of 5-aminouracil (3.93 × 10^–3 M). They were either treated for 6 hours and allowed to recover for up to 10 hours, or were treated continuously for up to 24 hours. Mitotic index decreased as the duration of treatment increased,e.g., it was < 0.5 after 6 hours treatment and 4 hours recovery and 0.23 after 12 hours continuous treatment. During this period of low mitotic activity nuclei and cells increased in size: mean nuclear volume, for example, was 1505±651 m³ 8 hours after the end of a 6 hours treatment. In roots treated continuously, nuclear volume increased from 559±204 m³ at 0 hour to 1272±636 m³ at 12 hours. In the first 3 hours it was the larger nuclei that grew,i.e., nuclei that would have proceeded into mitosis if they had not been blocked by 5-AU. But between 3 and 12 hours of continuous exposure to 5-AU all nuclei increased in volume. Cells, on the other hand, showed no response during the first 6 hours of treatment; their areas did not increase till 6–12 hours had elapsed. It appears that in cells blocked by 5-AU growth continues for about 12 hours. Initially, nuclei grow disproportionately large, suggesting that synthesis of nuclear components is favoured at the expense of cytoplasmic constituents, at least during the first 6 hours of treatment; there is an internal imbalance between nuclear and cell growth and a temporary change in the nuclear cytoplasmic ratio. When cells recover from the 5-AU block and enter mitosis their prophase nuclei are also much larger than those of untreated cells. The response to 5-AU is discussed in terms of internal restrictions on cell growth, due to the presence of cell walls, and the heterogeneity in nuclear volumes.     

The in vitro synthesis and characteristics of ribosomal RNA in imaginal discs of Drosophila melanogaster

Summary Late third instar imaginal discs of Drosophila melanogaster cultured in vitro in Robb's tissue culture medium synthesize 38S, 28S and 18S ribosomal RNAs which are qualitatively indistinguishable from their in vivo synthesized counterparts (Fig. 1). As found in other insect systems, the 38S molecule appears to be the precursor for both the 28S and 18S rRNAs (Figs. 2, 3 and 4). The 28S rRNA and a portion of the 38S pre-rRNA shift in sedimentation value upon exposure to heat or dimethylsulfoxide (Figs. 5 and 8). Studies of the thermal denaturations of these molecules (Figs. 6, 7 and 9) indicate the existence of a single class of 28S rRNA, but three classes of 38S pre-rRNAs. The addition of -ecdysone to the in vitro culture medium stimulates the net amount of rRNA synthesized, increases the rate of processing of the 38S precursor and increases the relative amount of 18S material produced (Figs. 10 and 12).This work was supported in part by grants from the National Science Foundation (GB-8176) and from the Atomic Energy Commission (AT-04-3-34).Predoctoral Trainees, PHS Training Grant No. 2-Tl-GM367 from Research Training Grants Branch, National Institute of General Medical Sciences.1 For purposes of simplification we shall refer to the rRNA molecules of D. melanogaster as being 38S, 30S, 28S and 18S; however, it should be noted that these values are approximate (see Hastings and Kirby, 1966; Greenberg, 1969; Tartof and Perry, 1970).     

Systemic immune effects of adjuvant chemotherapy with 5-fluorouracil,epirubicin and cyclophosphamide and/or radiotherapy in breast cancer: a longitudinal study

Immunotherapy is being increasingly utilized for adjuvant treatment for breast cancer (BC). We have previously described immune functions during primary therapy for BC. The present study describes immune recovery patterns during long-term, unmaintained follow-up after completion of adjuvant therapy.A group of patients with primary BC had been treated with adjuvant radio-chemotherapy (RT + CT) 5-fluorouracil, epirubicin and cyclophosphamide (FEC) (n = 21) and another group with radiotherapy (RT) (n = 20) alone. Immunological testing of NK and T-cell functions was performed initially at the end of adjuvant treatment and repeated after 2, 6 and 12 months. NK cell cytotoxicity was significantly higher (P < 0.05) at all time-points in patients than in age-matched controls and did not differ between the two treatments groups during one year observation. In contrast, lower numbers of CD4 T-cells and lower expression of CD28 on T-cells was observed particularly in RT + CT patients and did not normalize during the observation period. The numbers of T_reg cells (CD4⁺CD25^high) were low in the RT + CT group during follow-up, as well as expression of TCRξ, Zap70, p56^lck, P59^fyn and PI3 k in CD4⁺ cells. In contrast, expression of intracellular cytokines (IFN-γ, IL-2, IL-4) in CD4 and CD8 T cells were significantly higher in RT + CT patients than in the RT group and the difference increased during follow-up. In conclusion, NK-cell cytotoxicity increased during unmaintained long-term follow-up whereas CD4 and regulatory T cells as well as signal transduction molecules remained low following adjuvant radio-chemotherapy.     

Root Permeability as Affected by Picloram and Other Chemicals

The effects of picloram (4-amino 3,5,6-trichloropicolinic acid) and several other chemicals on root permeability were studied. Initially, effects on cell permeability were investigated by measuring the betacyanin efflux from red beet (Beta vulgaris L.) root sections. Picloram solutions ranging from 10^-3M to 10^-6M had no significant effect on betacyanin efflux when compared to controls. Similar results were found for 10^-4M and 10^-5M 2-methoxy-3,6-dichlorobenzoic acid (dicamba), 10^-4M 2,4-dichlorophenoxyacetic acid (2,4-D) and 10 μl/l of ethylene. Compounds that caused significant pigment leakage were 10^-4M and 10^-5M phenylmercuric acetate (PMA), 10^-3M and 10^-4M 2,4-dinitrophenol (DNP), 10^-3M and 10^-4M 2,4,5–trichlorophenoxyacetic acid (2,4,5-T) and 10^-3M 2,4-D. The effects of picloram on root permeability were also studied with bean plants (Phaseolus vulgaris L. cv. Black Valentine) grown in nutrient solution under controlled environmental conditions. Roots treated for 3 hours with 10^-5M picloram showed no significant electrolyte leakage as determined by conductivity measurements of the root-bathing solution over a period of 52 hours. When bean plants were root-trated for 3 hours with 10^-5M, and 10^-7M picloram and then decapitated, increased stem exudation by the treated plants as compared to controls was observed. Xylem exudate of the teated plants also showed increased electrolytic conductivity. The increased exudation rate accompanied by increased conductivity indicates that picloram has little effect on root cell membrane integrity, appears not to act as a metabolic inhibitor in the root system, and in some way stimulates salt secretion into the xylem.     

Effect of Abscisic Acid on the Transpiration of Zea mays

Intact plants of Zea mays L. were treated with foliar sprays of cis-trans-abscisic acid (ABA) at concentrations from 10⁻⁹ to 10⁻⁴M. Even the lowest concentration caused a reduction of the transpiration rate as measured between 1 and 33 h after spraying. With increasing ABA concentrations, there was a nearly linear relationship between the logarithm of the ABA concentration and the (decreasing) transpiration rate within that period. Subsequently a partial recovery of the transpiration rate set in, beginning progressively later as the ABA concentration was increased. After 5 1/2 days the transpiration rate of plants treated with 10⁻⁹ and 10⁻⁸M was nearly back to normal, whereas plants treated with 10⁻⁴M transpiration at only about 2/3 their normal rate. In experiments with detached maize leaves supplied with water or ABA solutions (10⁻⁸ to 10⁻⁵M) through their cut bases, the transpiration of control leaves decreased gradually to a low level in 24 h. ABA caused a marked and rapid reduction of the transpiration rate compared to that of the controls. After a few hours, the transpiration of the treated leaves decreased at a slower rate than that of the controls, thus approaching the control values. After 35 h, the transpiration of leaves treated with 10⁻⁵M ABA was nearly the same as in untreated leaves. Exchanging the ABA solution for distilled water after 24 h had little effect on the subsequent course of the transpiration rate.     

Cytotoxic effects of thiopyrimidines

The cytotoxic action of 2-thiouracil, 2-thiocytosine, 2-thiouridine and 4-thiouridine was studied in cultures of a clone of Chinese hamster cells with a generation time of 16 hours (S — 8 hours, G₂ — 2 hours, and G₁ plus M — 6 hours). The cells were synchronized at metaphase by the method of reversal of colcemid inhibition and cell survival was measured by their colony-forming ability. The four analogs induced cytotoxic effects which increased with the concentration of the chemical and the length of the exposure time. Exposure to 4 × 10^?4 M 2-thiocytosine, 2-thiouridine or 4-thiouridine for a period of 20 hours reduced cell survival to less than 10% of the controls. The other analog (2-thiouracil) was less effective when tested at similar concentrations and time of exposure and decreased the survival to only 35% of the controls. Short periods of treatment (one hour) produced little effect at concentrations of 4 × 10^?5M, and affected the survival of cells differently when 4 × 10^?4 M were administered at different stages of the cell cycle. Two peaks of maximum sensitivity, one at late G₁ and the other at G₂ were observed. These peaks correspond to the peaks of maximum RNA synthesis described for synchronized mammalian cells. Therefore, it is likely that the cytotoxic effects of thiopyrimidine analogs are related to interference with RNA synthesis.     

Enantiomeric and Diastereoisomeric (Mixed) L/ D‐Octaarginine Derivatives – A Simple Way of Modulating the Properties of Cell‐Penetrating Peptides

Cell‐penetrating peptides (CPPs) are promising vehicles for delivery of drugs, antibiotics, proteins, nucleic acid derivatives, etc. into eukaryotic and prokaryotic target cells. To prevent premature degradation, CPPs consisting of D ‐ or β‐amino acid residues have been used. We present simple models for the various modes of delivery of physiologically active cargoes by CPPs, depending on the nature of their conjugation (Fig. 1), and we describe the plasma stability of oligoarginines (OAs) 1 – 4 , the most common unnatural CPPs. Fluorescein‐labeled L ‐octaarginine 1 was found to have a half‐life (t_1/2) of <0.5 min, the D ‐enantiomer ( 2 ) of >7 d (Fig. 2). For possible medicinal applications, the former type of derivative would be too unstable, and the latter one undesirably persistent. Thus, seven of the 256 possible ‘mixed’ Flua‐L /D ‐octaarginine amides, 4a – 4g , were synthesized and shown to have half‐lives in heparine‐stabilized human plasma between 8 min and 5.5 h (Figs. 3 and 4). The cell penetration of the new OAs was investigated with ‘healthy’ and with apoptotic HEK cells (Figs. 5–8), and their interactions with phospholipid bilayers were studied, using anionic lipid vesicles (Figs. 9 and 10). There are surprisingly large differences in the rates of cell penetration and binding to vesicle walls between the various stereoisomeric octaarginine derivatives 1, 2 , and 4a – 4g (Figs. 5 and 7). – The role of D ‐amino acids and D ‐peptides in nature and in drug design is briefly discussed and referenced.     

18F-FDG Is a Surrogate Marker of Therapy Response and Tumor Recovery after Drug Withdrawal during Treatment with a Dual PI3K/mTOR Inhibitor in a Preclinical Model of Cisplatin-Resistant Ovarian Cancer

AIM: Targeting the phosphoinositide 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) pathway is a potential means of overcoming chemoresistance in ovarian cancer. We investigated the capability of ¹⁸F-fluororodeoxyglucose (¹⁸F-FDG) small-animal positron emission tomography (SA-PET) to predict the effects of a dual PI3K/mTOR inhibitor (BEZ-235) in a cisplatin-resistant ovarian cancer model. METHODS: In a first experiment, nude rats bearing subcutaneous SKOV3 tumors received BEZ-235 for 3 days given alone or after paclitaxel and were compared to controls (either untreated or that were given the excipients of paclitaxel and BEZ-235). SA-PET was performed at baseline, on day 3, and day 7. In a second experiment aiming at further exploring the kinetics of ¹⁸F-FDG tumor uptake during the first 48 hours following drug cessation, untreated controls were compared to rats receiving BEZ-235, which were imaged at baseline, on day 3, on day 4, and on day 5. SA-PET results were compared to cell proliferation assessment (Ki-67), PI3K/mTOR downstream target expression studies (pAKT and phospho-eukaryotic translation initiation factor 4E-binding protein 1), and apoptosis evaluation (cleaved caspase-3). RESULTS: In the first experiment, BEZ-235, compared to untreated controls, induced a marked decrease in ¹⁸F-FDG uptake on day 3, which was correlated to a significant decrease in cell proliferation and to a significant PI3K/mTOR pathway inhibition. No tumor necrosis or apoptosis occurred. Four days following treatment cessation, tumor recovery (in terms of PI3K/mTOR inhibition and cell proliferation) occurred and was identified by ¹⁸F-FDG SA-PET. Paclitaxel plus BEZ-235 showed results similar to BEZ-235 alone. In the second experiment, PI3K/mTOR pathways exhibited partial recovery as early as 24 hours following treatment cessation, but both ¹⁸F-FDG SA-PET and cell proliferation remained unchanged. CONCLUSIONS:¹⁸F-FDG SA-PET is a surrogate marker of target inhibition during treatment with BEZ-235 and predicts tumor recovery 4 days after drug withdrawal, but not during the first 48 hours following drug cessation, when a lag between PI3K/mTOR pathway recovery and metabolic recovery is observed. ¹⁸F-FDG SA-PET could be used for therapy monitoring of PI3K/mTOR inhibitors, but our results also raise questions regarding the potential impact of the delay between PET imaging and the last drug intake on the accuracy of FDG imaging.     

Some Mechanisms of Disturbances and Recovery of T-Lymphocyte Migratory Properties In Irradiated Mice

Abstract Migration of ⁵¹Cr-labelled T cells from irradiated mice into lymph nodes of syngeneic unirradiated recipients decreased in a dose-dependent fashion. Influx of labelled T cells between 4 and 24 hr after injection (secondary migration) is more radiosensitive than lymph-node migration of T cells in the first 4 hr (primary migration). Treatment of T cells from irradiated mice in vitro with Con A or with trypsin does not enhance radiation-induced alteration of their migratory properties, but irradiation enhances the effects of Con A and trypsin on T-cell migration. Recovery of primary migration of irradiated T cells is completed 3 months after irradiation; it is probably caused by T-cell renewal. the defect of T-cell secondary migration is more stable: it remains 6 months after irradiation in a dose of 4 Gy. Post-irradiation defects of the T-cell differentiation process as a cause of long-lasting alteration of T-cell secondary migration are discussed.     

Ultraviolet reactivation of the single stranded DNA phage phiX 174.

Summary When UV-irradiated X174 was grown in pre-irradiated host cells of various strains, ultraviolet reactivation (UVR) was observed only in recombination proficient strains such as E. coli C (uvrA ⁺ recA ⁺) and HF4704 (uvrA ^- recA ⁺), but not in the recombination deficient strain HF4712 (uvrA ⁺ recA ^-). By increasing the multiplicity of infection, no rise in the amount of such reactivation was observed. From the study of the neutral and alkaline sucrose gradient sedimentation patterns of DNA samples extracted from unirradiated cells infected with unirradiated phage, it appears that after the conversion of the viral single stranded (SS) DNA to the double stranded form (DS), nicks or scissions were produced on it within all three strains, which were ultimately sealed up in the recA ⁺ but persisted within the recA ^- host cells. When UV-irradiated phage infected unirradiated host cells, such nicking of the DS DNA appeared to be much more extensive in uvrA ⁺ recA ⁺, but slightly reduced in uvrA ⁺ recA ^- and severely suppressed in uvrA ^- recA ⁺ strains. When the host cells were also UV-irradiated, the conversion of the infecting viral SS DNA to DS DNA as well as its subsequent nicking were reduced in all the three strains to a much greater extent. Although nicking of the DS DNA molecule is an essential step even in the normal intracellular replication of X DNA, the production and the sealing up of such nicks appear not to have any positive correlation with UVR of these phages. A drastic reduction in nicking due te pre-irradiation of the host cells might, however, mean slowing down of the replication of the damaged parental RF molecules which would facilitate their repair perhaps through recombination with the homologous parts of the host genome.     

Time-lapse cinematography study of the germinal vesicle behaviour in mouse primary oocytes treated with activators of protein kinases A and C

Previous studies have shown that early embryos contain information that can alter the developmental fate of adjacent cells and transferred nuclei. In this report we show that a specific combination of cells from early murine embryos, a single blastomere from an eight-cell embryo placed under the zona pellucida with a two-cell embryo, results in a difference in incorporation of ³H-uridine and expression of two protein bands between the chimeric treatment group and the nonchimeric controls, a single blastomere from an eight-cell embryo in a separate zona pellucida and a two-cell embryo. The incorporation of ³H-uridine in the chimeric group and nonchimeric control group was significantly different at 45 hours after chimerization (P < .02). A stage-specific protein band (52k) on a polyacrylamide gel detected with fluorography was found to be qualitatively different (present more often; P < .01) and another stage-specific protein band (48k) was found to be quantitatively different (more protein; P equals; .07) in the chimeric treatment vs. the nonchimeric controls at 45 hours after chimerization. These results suggest communication between the cells resulting in a change in their incorporation of uridine and protein synthetic profiles.     

Le contrôle automatique du flux lumineux dans l'oeil composé des Diptères

In the compound eye of the fly Musca, tiny pigment granules move within the cytoplasm of receptor cells Nos. 1–6 and cluster along the wall of the rhabdomeres under light adaptation, thus attenuating the light flux to which the visual pigment is exposed (Kirschfeld and Franceschini, 1969). Two recently developed optical methods (the neutralization of the cornea and the deep pseudopupil) combined with antidromic and orthodromic illumination of the eye (Fig. 1) make it possible to analyse the properties of the mechanism at the level of the single cell, in live and intact insects (Drosophila and Musca). The mechanism is shown to be an efficient attenuator in the spectral range (blue-green) where cells Nos. 1–6 have been reported to be maximally sensitive (Figs. 4c and d, 5b and 11b). In spite of the fact that the granules do not penetrate into the rhabdomere, the attenuation spectrum they bring about closely matches the absorption spectrum of the substance of which they are composed (ommochrome pigment, dotted curve in Fig. 11b). The dramatic increase in reflectance of the receptors after light adaptation (Figs. 3, 4b, 5a and 11a) can be explained as a mere by-product of the high absorption index of the ommochrome pigment, especially if one takes into account the phenomenon of anomalous dispersion (Chapter 8). The vivid green or yellow colour of the rhabdomeres would thus have a physical origin comparable to a metallic glint. Contrasting with the lens eye in which the pupillary mechanism is a common attenuator for both receptor types (rods and cones), the compound eye of higher Diptera is equiped with two types of pupils adapted respectively to both visual subsystems. A scotopic pupil is present in each of the six cells (Nos. 1–6) whose signals are gathered in a common cartridge of the first optic ganglion. This pupil comes into play at a moderate luminance (0,3 cd/m² in Drosophila; 3 to 10 cd/m² in Musca. Figs 13, 14, 15, 16). A photopic pupil is present in the central cell No. 7 whose signal reaches one column of the second optic ganglion. Attenuating the light flux for both central cells 7 and 8, the photopic pupil has its threshold about two decades higher than the scotopic pupil, just at the point where the latter reaches saturation (Fig. 3b, e-State II of Figs. 6b and 15). The photopic pupil itself saturates at a luminance one to two decades higher still (Fig. 3c, f=State III of Figs. 6c and 15). The two-decades-shift in threshold of these pupil-mechanisms supports the view that receptors 1–6 are a scotopic subsystem, receptors 7 and 8 a photopic subsystem of the dipteran eye. The luminance-threshold of the scotopic pupil (as determined with the apparatus described in Fig. 2) appears to be located at least 3.5 decades (Drosophila) or even 5 decades (Musca) higher than the absolute threshold of movement perception (Fig. 16). After a long period (1 hr) of darkness a light step of high intensity can close the scotopic pupil within about 10 sec (time constant 2 sec as in Fig. 9) and the photopic pupil within no less than 30–60 sec. Some mutants of Drosophila possess only a scotopic pupil (w , Figs. 4 and 5) whereas ommochrome deficient mutants lack both types of pupil (v, cn, see Fig. 7c, d). Comparable reflectance changes, accomplished within about 60 sec of light adaptation, are described for two insects having fused rhabdomes: the bee and the locust (Fig. 17).     

Induction of diapausing amictic eggs in Synchaeta pectinata

Amictic females of a clone of S. pectinata from Star Lake (Norwich, Vermont) may produce diapausing as well as non-diapausing (subitaneous) eggs. The proportion of diapausing eggs produced in cultures was unaffected by temperature (12 vs 19 °C) or rotifer population density (minima of 0.33 vs 3 ind. ml^–1) at 19 °C. However, at 19 °C this proportion was higher in cultures maintained at a low food level suppressing reproduction (5 × 10³ cells ml^–1 Cryptomonas erosa) than in those maintained at a high food level (2 × 10⁴ cells ml^–1); the treatment effect was marginally significant (p=0.067). Consistent with the effect of low food availability, a period of starvation was very effective in inducing the development of diapausing eggs. None of 19 females cultured individually from hatching at 19 °C on C. erosa (2 × 10⁴ cells ml^–1) in 1-ml volumes produced any diapausing eggs in 4 days (0 out of 349 eggs), while 13 out of 16 females subjected to a 15-hour starvation period 6 hours after birth produced one or more diapausing eggs during that time (34% of the 158 eggs produced by the 16 females were diapausing). Diapausing eggs produced and left at 19 °C hatched after 4 to 13 days. Those produced in cultures with a low food level took significantly longer to hatch (9.7 days) than those produced in cultures with a high food level (8.1 days) (p=0.022). In natural communities, S. pectinata should be able to respond directly and rapidly to poor food conditions by producing eggs that undergo an obligatory dormant period before resuming development.