Withdrawal from chronic phencyclidine produces a pentylenetetrazol-like discriminative stimulus.

Rats trained to discriminate the anxiogenic compound pentylenetetrazol (PTZ) from water were implanted with osmotic mini-pumps containing 7 mg/kg/day phencyclidine (PCP) or water. Rats were tested for generalization to PTZ 24 hours prior to pump removal, and 4 to 96 hours after pump removal. While the pumps were in place, rats did not generalize to PTZ. When the pumps were removed on day 10, rats in the water group did not generalize to PTZ, but 69% of the rats in the chronic PCP group responded on the PTZ lever at 4 and/or 24 hours after pump removal, suggesting that the PCP withdrawal state mimics the interoceptive cue produced by PTZ. This withdrawal phenomenon was repeatable, in that rats that generalized once to PTZ during PCP withdrawal, generalized a second time when the procedure was repeated. In addition, the phenomenon was dose-dependent, as rats that did not generalize to PTZ after 7 mg/kg/day PCP did generalize when the chronic dose of PCP was increased to 10 mg/kg/day. These findings suggest that there is an anxiogenic component of PCP withdrawal and that tolerance does not develop to this effect.     

Are humans seasonally photoperiodic?

Humans exhibit seasonal variation in a wide variety of behavioral and physiological processes, and numerous investigators have suggested that this might be because we are sensitive to seasonal variation in day length. The evidence supporting this hypothesis is inconsistent. A new hypothesis is offered here-namely, that some humans indeed are seasonally photoresponsive, but others are not, and that individual variation may be the cause of the inconsistencies that have plagued the study of responsiveness to photoperiod in the past. This hypothesis is examined in relation to seasonal changes in the reproductive activity of humans, and it is developed by reviewing and combining five bodies of knowledge: correlations of human birthrates with photoperiod; seasonal changes in the activity of the neuroendocrine pathway that could link photoperiod to gonadal steroid secretion in humans; what is known about photoperiod, latitude, and reproduction of nonhuman primates; documentation of individual variation in photoresponsiveness in rodents and humans; and what is known about the evolutionary ecology of humans.     

Mouse development and cell proliferation in the absence of D-cyclins

D-type cyclins (cyclins D1, D2, and D3) are regarded as essential links between cell environment and the core cell cycle machinery. We tested the requirement for D-cyclins in mouse development and in proliferation by generating mice lacking all D-cyclins. We found that these cyclin D1(-/-)D2(-/-)D3(-/-) mice develop until mid/late gestation and die due to heart abnormalities combined with a severe anemia. Our analyses revealed that the D-cyclins are critically required for the expansion of hematopoietic stem cells. In contrast, cyclin D-deficient fibroblasts proliferate nearly normally but show increased requirement for mitogenic stimulation in cell cycle re-entry. We found that the proliferation of cyclin D1(-/-)D2(-/-)D3(-/-) cells is resistant to the inhibition by p16(INK4a), but it critically depends on CDK2. Lastly, we found that cells lacking D-cyclins display reduced susceptibility to the oncogenic transformation. Our results reveal the presence of alternative mechanisms that allow cell cycle progression in a cyclin D-independent fashion.     

Loss of G protein gamma 7 alters behavior and reduces striatal alpha(olf) level and cAMP production

The G protein beta gamma-dimer is required for receptor interaction and effector regulation. However, previous approaches have not identified the physiologic roles of individual subtypes in these processes. We used a gene knockout approach to demonstrate a unique role for the G protein gamma(7)-subunit in mice. Notably, deletion of Gng7 caused behavioral changes that were associated with reductions in the alpha(olf)-subunit content and adenylyl cyclase activity of the striatum. These data demonstrate that an individual gamma-subunit contributes to the specificity of a given signaling pathway and controls the formation or stability of a particular G protein heterotrimer.     

Aged men display blunted biorhythmic variation of muscle performance and physiological responses.

Aging is known to disrupt the "biological clock" that governs physiological variables at rest. This study sought to determine whether aged men demonstrated biorhythmic variation in muscle performance during resistance exercise and physiological responses to that stimulus. Ten aged (75.6 +/- 1.6 yr; mean +/- SE) men completed an isokinetic testing protocol of knee extensors and flexors at 0800, 1200, 1600, and 2000 h. Although time of day variation in peak torque was detectable, significant (P < or = 0.05) oscillation was established only in the knee flexors at 3.14 rad/s. Heart rate, blood pressure, and rectal temperature displayed no significant variation, but trends (P < 0.10) in oscillation of postexercise blood pressure and rectal temperature were noted. Temporal patterns in biorhythmic variation of muscle performance, as well as thermal and cardiovascular measures, emulated those observed in a previous study involving young men where the magnitude of variation was sufficient to achieve statistical significance. Similar to our earlier findings in young men, however, pre- and postexercise testosterone and cortisol concentrations demonstrated significant variation among aged men. These data confirm the blunting of biorhythmic variation in muscle performance and physiological variables, except for circulating hormones, in aged men.     

Physical mapping of plasmid and cosmid clones in filamentous fungi by fiber-FISH

Fluorescence in situ hybridization to extended DNA fibers (fiber-FISH) serves as a powerful tool for direct physical mapping in plants and animals. Here, we show that fiber-FISH is useful for contig mapping as well as for estimating the physical distance between genetic markers in fungi. A five-cosmid contig from a chromosome of Nectria haematococca and four cloned genetic markers from a linkage map of Cochliobolus heterostrophus were chosen as models for the application of this technology. In N. haematococca, overlapping and non-overlapping clones were visually mapped on individual DNA fibers, confirming the results from conventional physical mapping perfectly. Fiber-FISH concomitantly indicated the gap size or the extent of overlap between two clones. In C. heterostrophus, the physical distance between the two pairs of genetic markers could be estimated from the microscopic measurements of the intervals. Chromosomal DNA isolated from a pulsed field gel was suitable for preparing the DNA fibers.     

Surface expression of complement receptor gC1q-R/p33 is increased on the plasma membrane of human spermatozoa after capacitation

Evidence is increasing that complement components might play a role in fertilization. C1q, the first component of the classical complement cascade, has the ability to promote sperm agglutination in a capacitation-dependent manner as well as an effect on sperm-oolemma binding and fusion. We have previously detected gC1qR, the receptor for the globular head portion of C1q, on the surface of capacitated sperm. In this study, we examined the expression of gC1qR in both fresh and capacitated human spermatozoa. We performed immunoprecipitation for gC1qR and analyzed biotinylated sperm membrane by Western blot to illustrate an increase in receptor density after overnight capacitation. These results were confirmed by flow cytometric analysis of spermatozoa using fluorescein isothiocyanate-labeled monoclonal anti-gC1qR antibody. Confocal, indirect immunofluorescence microscopy revealed an increase in receptor expression over the rostral portion of the sperm head after capacitation. In addition, the ability of live spermatozoa to bind to monoclonal anti-gC1qR antibody-coated microtiter wells was also increased after capacitation. These results suggest that gC1qR may play a role in human fertilization.     

Curly bare (cub), a new mouse mutation on chromosome 11 causing skin and hair abnormalities,and a modifier gene (mcub) on chromosome 5

In the outcrossing of a new recessive mouse mutation causing hair loss, a new wavy-coated phenotype appeared. The two distinct phenotypes were shown to be alternative manifestations of the same gene mutation and attributable to a single modifier locus. The new mutation, curly bare (cub), was mapped to distal Chr 11 and the modifier (mcub) was mapped to Chr 5. When homozygous for the recessive mcub allele, cub/cub mice appear hairless. A single copy of the dominant Mcub allele confers a full, curly coat in cub/cub mice. Reciprocal transfer of full-thickness skin grafts between mutant and control animals showed that the skin phenotype was tissue autonomous. The hairless cub/cub mcub/mcub mice show normal contact sensitivity responses to oxazolone. The similarity of the wavy coat phenotype to those of Tgfa and Egfr mutations and the map positions of cub and mcub suggest candidate genes that interact in the EGF receptor signal transduction pathway.     

Histone H2AX: a dosage-dependent suppressor of oncogenic translocations and tumors

We employed gene targeting to study H2AX, a histone variant phosphorylated in chromatin surrounding DNA double-strand breaks. Mice deficient for both H2AX and p53 (H(delta/delta)P(-/-)) rapidly developed immature T and B lymphomas and solid tumors. Moreover, H2AX haploinsufficiency caused genomic instability in normal cells and, on a p53-deficient background, early onset of various tumors including more mature B lymphomas. Most H2AX(delta/delta)p53(-/-) or H2AX(+/delta)p53(-/-) B lineage lymphomas harbored chromosome 12 (IgH)/15 (c-myc) translocations with hallmarks of either aberrant V(D)J or class switch recombination. In contrast, H2AX(delta/delta)p53(-/-) thymic lymphomas had clonal translocations that did not involve antigen receptor loci and which likely occurred during cellular expansion. Thus, H2AX helps prevent aberrant repair of both programmed and general DNA breakage and, thereby, functions as a dosage-dependent suppressor of genomic instability and tumors in mice. Notably, H2AX maps to a cytogenetic region frequently altered in human cancers, possibly implicating similar functions in man.     

WAVE2 deficiency reveals distinct roles in embryogenesis and Rac-mediated actin-based motility

The Wiskott-Aldrich syndrome related protein WAVE2 is implicated in the regulation of actin-cytoskeletal reorganization downstream of the small Rho GTPase, Rac. We inactivated the WAVE2 gene by gene-targeted mutation to examine its role in murine development and in actin assembly. WAVE2-deficient embryos survived until approximately embryonic day 12.5 and displayed growth retardation and certain morphological defects, including malformations of the ventricles in the developing brain. WAVE2-deficient embryonic stem cells displayed normal proliferation, whereas WAVE2-deficient embryonic fibroblasts exhibited severe growth defects, as well as defective cell motility in response to PDGF, lamellipodium formation and Rac-mediated actin polymerization. These results imply a non-redundant role for WAVE2 in murine embryogenesis and a critical role for WAVE2 in actin-based processes downstream of Rac that are essential for cell movement.