Rapid backward movement of anaphase chromosome whose kinetochore fibers were cut by ultraviolet microbeam irradiation

Summary— kinetochore spindle fibers in meiosis I and II grasshopper spermatocytes were cut with a heterochromatic ultraviolet (UV) microbeam converging on the specimen to form a slit-shaped microspot 1.5 × 8 μm or 3 × 8 μm. A total exposure of 3 × 10^?8 joules per μm² was administered within 0.8–2.4 s, which was sufficient for severing. The cells were observed with a high extinction polarizing microscope or phase contrast optics and a record made by time-lapse video microscopy, continuously before, during and after the irradiation. When kinetochore fibers were irradiated i anaphase with UV, an area of reduced birefringence (ARB) was produced at the exposed site. The newly created + ends of the microtubules rapidly disassembled poleward, at a constant speed of 17 μm/min. The — ends at the edge of ARB also depolymerized at a slower rate. When a kinetochore fiber was cut with UV in early anaphase at which time its associated chromosome had not disjoined from the partner chromosome, the chromosome of the irradiated kinetochore fiber moved rapidly back to its partner. The speed during this movement was faster than the normal poleward chromosome movement in anaphase by an order to magnitude or more. When a kinetochore and its associated kinetochore fiber were included in the irradiation are, the effects were more pronounced than the effects of irradiation on a kinetochore fiber alone; the direction of the line connecting the irradiated half-bivalent with the partner half-bivalent deviated so much from the longitudinal axis of the original spindle with time that the division assumed a tripolar figure.     

Female sand gobies prefer good fathers over dominant males

Female preference for males successful in male-male competition is generally assumed to result in mating with high quality males. Here I report results from an experiment disentangling the effects of intra- and intersexual selection in the sand goby, Pomatoschistus minutus, a marine fish that exhibits paternal care. I show that large males are successful in male–male competition, but contrary to what one would expect, dominants are not preferred by females and are not better at taking care of the eggs. Female preference, however, correlated with the subsequent hatching success of the eggs. Thus, female choice selects for good parenting. Hence, direct benefits in the form of superior paternal care can explain female choice in this species, supporting a good parent process of sexual selection. However, choosing on the outcome of male–male competition does not enable females to mate with the ''best'' males.     

A versatile gel casting cum electrophoresis apparatus

A simple apparatus for vertical.,in situ, polyacrylamide or agarose gel casting as well as for the subsequent electrophoresis is described. The apparatus is completely leakproof and does not require any special device like clamps, O-rings, gaskets, grease etc. for sealing. Slab gels of various thickness (0.04 to 1.0 cm) can be made and the apparatus can be used for analytical or preparative purposes. Gel rods can also be cast and run in the device. Forward as well as reverse polarity electrophoresis of a sample can be run simultaneously in the apparatus. NCL Communication No.: 3077.     

Synthesis and bioassay of isoprenoid 3-alkylthio-1,1,1-trifluoro-2-propanones: Potent,selective inhibitors of juvenile hormone esterase

Four 3-alkylthio-1,1,1-trifluoro-2-propanones with juvenile hormone-like side chains were prepared from citronellol and homogeraniol. These substrates were designed as possible transition-state analogs for the juvenile hormone (JH)-specific esterases present in insects. These four isoprenoid trifluoromethyl ketones were assayed in vitro with JH esterase and general esterases from larvae of the cabbage looper, Trichoplusia ni (Lepidoptera, Noctuidae), and with eel acetylcholinesterase and bovine chymotrypsin. JH esterase inhibition I₅₀ values were in the nanomolar range for all four compounds, while the other esterases had I₅₀'S which were 10³ to 10⁵ higher. The high selectivity of these inhibitors is believed to be due to their similarity in size and functionality to natural JH III. Treatment of T. ni larvae in vivo with solutions of the most active analog, 3-[(E)-4,8-dimethyl-3,7-nonadienylthio]-1,1,1-trifluoro-2-propanone (DNTFP) causes a dose-dependent delay in pupation and a concurrent selective inhibition of JH esterase. These data support the hypothesis that the reduction in in vivo JH titer in larval T. ni is due, in part, to hydrolysis of the hormone by selective esterases. DNTFP appears to be competing with JH for the active site of JH esterase.     

1 alpha, 25-Dihydroxyvitamin D3 directly induces fusion of alveolar macrophages by a mechanism involving RNA and protein synthesis, but not DNA synthesis

The results of our present study indicate that 1 alpha, 25-dihydroxyvitamin D3[1 alpha, 25(OH)2D3] directly induces fusion of mouse alveolar macrophages without any participation of T-lymphocytes by a mechanism involving RNA and protein synthesis but not DNA synthesis. We have reported that 1 alpha, 25(OH)2D3 induces fusion of alveolar macrophages by a direct mechanism and by a spleen cell-mediated indirect mechanism [(1983) Proc. Natl. Acad. Sci. USA 80, 5583-5587]. Alveolar macrophages pretreated with or without anti-Thy 1.2 antibody and complement fused similarly when they were incubated with 1 alpha, 25(OH)2D3. The vitamin suppressed DNA synthesis, but it significantly enhanced RNA and protein synthesis. The 1 alpha, 25(OH)2D3-induced fusion was blocked by adding actinomycin D or cycloheximide, but not by hydroxyurea.     

Holling's “hungry mantid” model for the invertebrate functional response considered as a Markov process. III. Stable satiation distribution

In this paper, we study an analytical model describing predatory behaviour. It is assumed that the parameter describing the predator's behaviour is its satiation. Using semigroup methods and compactness arguments we prove that a stable satiation distribution is reached if t. Furthermore, using a Trotter-Kato theorem we justify the transition to the much simpler problem that is obtained if the prey biomass tends to zero.     

beta-Endorphin: structure-activity relationships in the guinea pig ileum and opiate receptor binding assays.

The opiate activities of some derivatives and enzymatic digests of camel and human β-endorphin were determined in the guinea pig ileum and rat brain opiate receptor binding assays. Derivatives of β-endorphins altered within the amino-terminal five residues showed pronounced losses in activity. Anisylation of the C-terminal glutamic acid residue of β_h-endorphin produced only small reductions in activity. Chymotryptic digestion greatly weakened the opiate activities of β_h-endorphin, whereas carboxypeptidase A, tryptic and leucine aminopeptidase digests showed only small losses in potency. The C-terminus of β-endorphin appears to contribute little directly to opiate activity. Amino acid analysis and assay of the leucine aminopeptidase digests suggest that the larger potency of β-endorphin relative to Met-enkephalin may be a consequence of its greater resistance to exopeptidase attack.     

Effects of microtubule-disruptive and membrane-stabilizing agents on low density lipoprotein metabolism by cultured human fibroblasts

The cellular mechanisms involved in the uptake and metabolism of low density lipoprotein (LDL) by cultured normal human fibroblasts have been investigated with the aid of drugs known to disrupt cytoplasmic microtubules or to inhibit membrane fusion.Two drugs which disrupt microtubules by differing mechanisms, colchicine and vinblastine, each reduced the high affinity surface binding of ¹²⁵I-labelled LDL by fibroblasts. Associated reductions of the endocytosis and degradation of the lipoprotein could be attributed almost entirely to this effect. In contrast, lumicolchicine, an analogue of colchicine without microtubule-disruptive activity, had little or no effect on ¹²⁵I-labelled LDL metabolism.Each of two groups of membrane-stabilizing agents, the phenothiazines and the tertiary amine local anaesthetics, directly inhibited both the internalization of ¹²⁵I-labelled LDL following high affinity binding to cell surface receptors and the catabolism of the lipoprotein subsequent to endocytosis, supporting previous morphological evidence for the importance of membrane fusion in these processes.     

Circadian effect of ACTH 1-17 on mitotic index of the corneal epithelium of BALB/C mice

The objective was to determine the effect of ACTH 1-17, an adrenocorticotropin analogue, on the mitotic index in the corneal epithelium of mice standardized in 12 hr of light alternating with 12 hr darkness. A question asked was whether the time of administration along the 24-hr time scale influenced any response found. The findings showed that ACTH 1-17 could, depending upon when it was administered, bring about a statistically significant decrease, an increase or even no such change in the mitotic index. The greatest responses found were increases, especially when ACTH 1-17 was administered during the dark span. Also the time after injection when the responses occurred varied. The greatest response recorded was at 12 hr after injection when ACTH 1-17 was given at 2 hr into the dark with a 641% and a 718% increase with a low (0.02 IU/kg) and a higher (20 IU/kg) dose, respectively. A 3-way analysis of variance supported the conclusion that the kind-of-treatment, time-of-treatment and treatment-to-kill interval (sampling time) are important factors when determining any response to ACTH 1-17 on the mitotic index.