SCENT-MARKING, DOMINANCE AND FLEHMEN BEHAVIOR IN DOMESTIC RABBITS IN AN ARTIFICIAL LABORATORY TERRITORY

The olfactory exploratory and scent-marking behavior of domesticrabbits were observed in an artificial laboratory enclosure.The rabbits tended to mark certain objects more frequently thanothers with their chin gland secretion (chinning), apparentlyguided by visual characteristics; however, they preferred tosniff and chin objects which had been chinned previously overthose that had never been chinned. They chinned more frequentlywhen faecal pellets were present. Dominant male rabbits chinnedobjects more frequently, and subordinate male rabbits less frequently,in a freshly marked environment than in a clean one; similarlydominant males chinned more frequently and subordinates lessfrequently when urine from another rabbit was present. Rabbitspreferentially chinned urine and faecal pellets from other rabbitsover their own. The dominance relations of the rabbits were determined by analyzingthe behavior patterns correlated with chasing and fleeing. Oneof the most characteristic features of encounters between tworabbits was a complete sexual display. Long periods of sniffing of certain substances, usually urine,by the rabbits were analyzed and found to be basically similarto sniffing and flehmen patterns shown by cats. The data supportthe hypothesis that the whole flehmen pattern including lickingand headshaking is involved with transporting substances insolution to the vomeronasal organ. ^* Present Address: Laboratory of Neurophysiology, UCLA MentalRetardation Center, Los Angeles, California 90024. ^** Present address: Laboratory of Animal Physiology, Kruislaan320, Amsterdam, The Netherlands.     

Ctenophore kairomones and modified aminosugar disaccharides alter the shadow response in a larval crab

Zoea larvae of the estuarine crab Rhithropanopeus harrisii (Gould)descend in the water column upon sudden decreases in irradiance,which serves as a shadow response for the avoidance of zooplanktonpredators such as ctenophores. This study tested the hypothesesthat (i) kairomones from either the ctenophore Mnemiopsis leidyior the fish Fundulus heteroclitus increase the shadow-responsesensitivity by reducing the minimum decrease in irradiance necessaryto evoke the response (i.e. threshold); and (ii) a similar increasein shadow-response sensitivity as occurs with ctenophore kairomonesis also induced by the external mucus of ctenophores and modifiedaminosugar disaccharide hydrolysis products of acidic mucopolysaccharides.Light-adapted R. harrisii Stage I zoea were conditioned to chemicaltreatments for 3 h, and their photoresponses were tested inan apparatus that mimicked the underwater angular light distribution.In clean sea water, the shadow response was induced by a 50%reduction in irradiance (threshold). The threshold decreasedto 30% in sea water with fish kairomones and 9% in sea waterwith ctenophore kairomones. A minimum concentration of 1.0 gwet weight ctenophore mucus l^-1 was required to reduce the shadow-responsethreshold. Chondroitin sulfate A disaccharides had an effectsimilar to kairomones and mucus in reducing the threshold, withthe greatest effect at a concentration of 10^-6 M. Tests withother disaccharides indicated that only acetylamine-containingaminosugars were effective. The test hypotheses were supported;predator kairomones, ctenophore external mucus, and purifiedaminosugar disaccharides having acetylamine functionality reducedthe threshold decrease in irradiance needed to evoke shadowresponses in crab larvae.     

BMI and levels of zinc,copper in hair,serum and urine of Turkish male patients with androgenetic alopecia

ObjectiveMale pattern androgenetic alopecia is characterized by progressive hair loss from the scalp. It is known that imbalances of some trace elements play a role in the pathomechanism of many forms of alopecia. The aim of this study was to evaluate the levels of zinc and copper in hair, serum and urine samples of Turkish males with male pattern androgenetic alopecia and to compare with healthy controls.Material and methods116 males with male pattern androgenetic alopecia and 100 controls were involved in this study.ResultsLevels of zinc and copper in hair were decreased significantly in the patients (p < 0.05), although zinc and copper levels of serum and urine were not different between patients and controls (p > 0.05). Body mass index of patients were higher than control group. In addition, in the group with body mass index of 25 and lower zinc level in hair and urine, copper level in serum were significantly higher (p < 0.05). Body mass index was negatively correlated with hair zinc levels.ConclusionWe thought that decreased zinc and copper levels in hair may play a role in the etiology of male pattern androgenetic alopecia. In addition, obesity by making changes in the balance of the trace elements in hair, serum and urine may play a role in male pattern androgenetic alopecia. Hence, assessing the levels of trace elements in hair of male pattern androgenetic alopecia patients may be more valuable compared to serum and urine for treatment planning.     

Zinc deficiency enhanced NAD(P)H-dependent superoxider radical production in plasma membrane vesicles isolated from roots of bean plants

The production of superoxide radical (O₂^–) was studiedin plasma membrane vesicles isolated by aqueous polymer two-phasepartitioning from roots of zinc-sufficient and zinc-deficientbean (Phaseolus vulgaris L. cv. Prélude) plants. Thetwo populations of vesicles were highly enriched in plasma membraneand had similar composition as evidenced by the specific membranemarker enzymes. Vesicles from zinc-deficient roots showed higherrates of NAD(P)H oxidation compared to vesicles from zinc-sufficientplants. The NAD(P)H-dependent formation of O₂^– in plasmamembrane vesicles was also highly increased by zinc deficiency.For both activities, a higher response to zinc deficiency wasobserved when NADPH was used as electron source. Re-supply ofzinc to deficient plants for 24 h substantially decreased therates of NAD(P)H oxidation and 0₂^– production in isolatedvesicles. The NADPH-dependent O₂^– generation was stronglystimulated by FAD and showed a high pH optimum; it was scarcelyaffected by Triton X-100 or even inhibited in the presence ofFAD and was almost insensitive to Antimycin A. The results suggest the presence at the plasma membrane of beanroots of an O₂^– generating activity, preferentially utilizingNADPH, which is affected by the zinc nutritional status of theplant. This finding, together with previous observations oncytosolic and microsomal fractions prepared from zinc-deficientroots of different plants, is consistent with a role of zincin membrane stabilization by controlling the level of oxidizingO₂ species. Key words: NAD(P)H oxidase, superoxide radical, plasma membrane, zinc deficiency     

Absolute configuration of 2-sec-butyl-4,5-dihydrothiazole in male mouse urine

The absolute configuration of 2-sec-butyl-4,5-dihydrothiazole (DHT) in urine of adult male mice was determined through chiral trifluoroacetyl derivative capillary chromatography by comparing the retention time with synthetic standards. (S)-DHT was extracted from fresh urine, while neither (R)-DHT nor the racemization of (S)-DHT were detected. We can conclude that DHT in urine possesses the S configuration, although we cannot exclude a minor component in the R configuration. (S)-DHT was then characterized for binding to the complex of major urinary proteins of male mouse urine (MUP) and for a behavioral response, the competitive scent marking behavior (countermarking). The binding constant of (S)-DHT to MUP (determined by competitive displacement) was 8.2 +/- 0.6 microM (mean +/- SD) and was 10.5 +/- 0.6 microM for R-DHT, thus excluding a relevant difference in binding. (S)-DHT modified countermarking in a peculiar way. Male mice were slow in countermarking urinary spots streaked 2 days earlier and on top of which (S)-DHT was added shortly before the test. This response was not seen when adding (S)-DHT to freshly streaked urinary spots or to clean paper. Unlike (S)-DHT, (R)-DHT prompted countermarking rather than delaying it. We can further conclude that (S)-DHT in male mouse urine is an aversive chemosignal for countermarking.     

Abscission: Response to Red and Far-Red Light

Craker, L. E., Zhao, S. Y. and Decoteau, D. R. 1987. Abscission:response to red and far-red light.—J. exp. Bot. 38: 883–888. The dose-response and time relationship of red and far-red lightin the inhibition and promotion, respectively, of dark-inducedleaf abscission was quantified using cuttings of coleus (ColeusBlumei Benth.). A continuous photon flux of approximately 15nM m^–2 s^–1 of red light was sufficient to preventleaf abscission. Abscission was promoted by exposure to a photonflux of approximately 10 nM m^–2 s^–1 of far-red lightThe inhibition of abscission by red light could be reversedby treatment with far-red and the promotion of abscission byfar-red light could be reversed by treatment with red lightThe data were consistent with a phytochrome receptor systemlocated in the leaves that controlled the presence of an abscission-inhibitingsubstance in the abscission zones. Key words: Abscission, Coleus Blumei, far-red light red light     

Light Quality and Vernalization Interact in Controlling Late Flowering in Arabidopsis Ecotypes and Mutants

The late flowering ecotypes of Arabidopsis thaliana L. (Heyn.)Eifel, Pitztal and Innsbruck responded to 10 d vernalization(cold treatment) by flowering earlier with less with less thanhalf the number of leaves of non-induced plants. The vernalizationresponse was cumulative: increased numbers of days of vernalizationinduced earlier flowering up to an apparent saturation in responseafter 30 to 40 d. The ratio of red:far-red (R:FR) light alsoaffected non-vernalized time-to-flower. When grown under fluorescentplus incandescent lamps (R:FR = 1·0), time-to-flowerwas approximately half that required by plants grown under fluorescentlamps (R:FR = 5·8) at the same photon flux density andphotoperiod. Leaf production rate was unaffected by either vernalizationor light quality changes and time-to-flower and leaf numberwere highly correlated (r² = 0·973). The late flowering mutants of Landsberg erecta were grown underlighting which displayed a gradient of R:FR. Some mutants likeco, flowered at the same time in all R:FR treatment, while otherlike fca took nearly twice as long to flower, with double thenumber of leaves at R:FR ratio of 5·8 compared with theR:FR = 1 treatment. The ranking of the response from least tomost responsive was co, fe, gi, WT, fd, fwa, ft, fha, fpa, fy,fve and fca. Vernalization of these Landsberg mutants always resulted inearlier flowering, although only fca, fve, fy and fpa were significantlymore sensitive to thermoinduction than the wild type parent.There was a high correlation (r² = 0·89 between the responseto thermoinduction and to R:FR ratio. Vernalization of fca for24 d largely eliminated the R:FR time-to-flower response. Vernalizationand photoinduction similarly affect late flowering and can substitutefor each another.Copyright 1993, 1999 Academic Press Light quality, vernalization, flowering, Arabidopsis thaliana, phytochrome, thermoinduction, photoperiod, photoinduction, growth conditions, photon flux density, daylength, spectral quality, far-red light     

Chronic intermittent hypoxia alters Ca2+ handling in rat cardiomyocytes by augmented Na+/Ca2+ exchange and ryanodine receptor activities in ischemia-reperfusion

This study examined Ca²⁺ handling mechanisms involved in cardioprotection induced by chronic intermittent hypoxia (CIH) against ischemia-reperfusion (I/R) injury. Adult male Sprague-Dawley rats were exposed to 10% inspired O₂ continuously for 6 h daily from 3, 7, and 14 days. In isolated perfused hearts subjected to I/R, CIH-induced cardioprotection was most significant in the 7-day group with less infarct size and lactate dehydrogenase release, compared with the normoxic group. The I/R-induced alterations in diastolic Ca²⁺ level, amplitude, time-to-peak, and the decay time of both electrically and caffeine-induced Ca²⁺ transients measured by spectrofluorometry in isolated ventricular myocytes of the 7-day CIH group were less than that of the normoxic group, suggesting an involvement of altered Ca²⁺ handling of the sarcoplasmic reticulum (SR) and sarcolemma. We further determined the protein expression and activity of ⁴⁵Ca²⁺ flux of SR-Ca²⁺-ATPase, ryanodine receptor (RyR) and sarcolemmal Na⁺/Ca²⁺ exchange (NCX) in ventricular myocytes from the CIH and normoxic groups before and during I/R. There were no changes in expression levels of the Ca²⁺-handling proteins but significant increases in the RyR and NCX activities were remarkable during I/R in the CIH but not the normoxic group. The augmented RyR and NCX activities were abolished, respectively, by PKA inhibitor (0.5 µM KT5720 or 0.5 µM PKI_14-22) and PKC inhibitor (5 µM chelerythrine chloride or 0.2 µM calphostin C) but not by Ca²⁺/calmodulin-dependent protein kinase II inhibitor KN-93 (1 µM). Thus, CIH confers cardioprotection against I/R injury in rat cardiomyocytes by altered Ca²⁺ handling with augmented RyR and NCX activities via protein kinase activation. cardioprotection; intracellular calcium     

Intracellular signal transduction during gastrin-induced histamine secretion in rat gastric ECL cells

Activation of G_qprotein-coupled receptors usually causes a biphasic increase inintracellular calcium concentration ([Ca²⁺]_i)that is crucial for secretion in nonexcitable cells. In gastric enterochromaffin-like (ECL) cells, stimulation with gastrin leads to aprompt biphasic calcium response followed by histamine secretion. Thisstudy investigates the underlying signaling events in this neuroendocrine cell type. In ECL cells, RT-PCR suggested the presence of inositol 1,4,5-trisphosphate receptor (IP₃R) subtypes1-3. The IP₃R antagonist 2-aminoethoxydiphenyl borateabolished both gastrin-induced elevation of[Ca²⁺]_i and histamine release. Thapsigarginincreased [Ca²⁺]_i, however, without inducinghistamine secretion. In thapsigargin-pretreated cells, gastrinincreased [Ca²⁺]_i through calcium influxacross the plasma membrane. Both nimodipine and SKF-96365 inhibitedgastrin-induced histamine release. The protein kinase C (PKC) activatorphorbol 12-myristate 13-acetate induced histamine secretion, an effectthat was prevented by nimodipine. In summary, gastrin-stimulatedhistamine release depends on IP₃R activation andplasmalemmal calcium entry. Gastrin-induced calcium influx wasmediated by dihydropyridine-sensitive calcium channels that appear tobe L-type channels activated through a pathway involving activation of PKC.

     

Zinc Deficiency and Anther Development in Maize

With the onset of male reproductive phase at 28 days, zinc waswithdrawn from fifty percent of maize (Zea mays L. cv. Ganga2) plants grown in refined sand at 0.13 mg Zn liter^–1.Plants from which zinc was withdrawn developed zinc deficiencysymptoms in young leaves after 38 days and were low in tissuezinc. Their tassel formation and pollen development was retarded.Anthers failed to develop beyond freshly liberated young pollengrain stage and vessels were formed in place of sporogenoustissue in sixty percent anthers of the younger of the two florets.Anthers from these plants showed low zinc concentration andstimulated specific activities of catalase, peroxidase, ribonucleaseand acid phosphatase. On resuming normal zinc (0.13 mg Zn liter^–1) through rootsto the plants from which it was withdrawn for 17 days, vegetativegrowth was partially renewed and short axillary buds were formedbut the development of anthers remained retarded. (Received April 11, 1986; Accepted October 15, 1986)     

Tunicamycin increases intracellular calcium levels in bovine aortic endothelial cells

Tunicamycin is anucleoside antibiotic that inhibits protein glycosylation andpalmitoylation. The therapeutic use of tunicamycin is limited inanimals because of its toxic effects, particularly in cerebralvasculature. Tunicamycin decreases palmitoylation of the endothelialisoform of nitric oxide synthase, stimulates nitric oxide synthesis,and increases the concentration of intracellular calcium([Ca²⁺]_i)in bovine aortic endothelial cells (B. J. Buckley and A. R. Whorton.FASEB J. 11: A110, 1997). In the present study,we investigated the mechanism by which tunicamycin alters[Ca²⁺]_iusing the Ca²⁺-sensitive dye fura2. We found that tunicamycin increased[Ca²⁺]_iwithout increasing levels of inositol phosphates. When cells wereincubated in the absence of extracellularCa²⁺,[Ca²⁺]_irapidly rose in response to tunicamycin, although a full response wasnot achieved. The pool of intracellularCa²⁺ mobilized by tunicamycinoverlapped with that mobilized by thapsigargin. Extracellular nickelblocked a full response to tunicamycin when cells were incubated in thepresence of extracellular Ca²⁺.The effects of tunicamycin on[Ca²⁺]_iwere partially reversed by washing out the drug, and the remainder ofthe response was inhibited by removing extracellularCa²⁺. These results indicate thattunicamycin mobilizes Ca²⁺ fromintracellular stores in a manner independent of phospholipase Cactivation and increases the influx ofCa²⁺ across the plasma membrane.

     

Endothelial response to stress from exogenous Zn2+ resembles that of NO-mediated nitrosative stress, and is protected by MT-1 overexpression

While nitric oxide (NO)-mediated biological interactions have been intensively studied, the underlying mechanisms of nitrosative stress with resulting pathology remain unclear. Previous studies have demonstrated that NO exposure increases free zinc ions (Zn²⁺) within cells. However, the resulting effects on endothelial cell survival have not been adequately resolved. Thus the purpose of this study was to investigate the role of altered zinc homeostasis on endothelial cell survival. Initially, we confirmed the previously observed significant increase in free Zn²⁺ with a subsequent induction of apoptosis in our pulmonary artery endothelial cells (PAECs) exposed to the NO donor N-[2-aminoethyl]-N-[2-hydroxy-2-nitrosohydrazino]-1,2-ethylenediamine. However, NO has many effects upon cell function and we wanted to specifically evaluate the effects mediated by zinc. To accomplish this we utilized the direct addition of zinc chloride (ZnCl₂) to PAEC. We observed that Zn²⁺-exposed PAECs exhibited a dose-dependent increase in superoxide (O₂^–·) generation that was localized to the mitochondria. Furthermore, we found Zn²⁺-exposed PAECs exhibited a significant reduction in mitochondrial membrane potential, loss of cardiolipin from the inner leaflet, caspase activation, and significant increases in TdT-mediated dUTP nick end labeling-positive cells. Furthermore, using an adenoviral construct for the overexpression of the Zn²⁺-binding protein, metallothionein-1 (MT-1), we found either MT-1 overexpression or coincubation with a Zn²⁺-selective chelator, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylene-diamide, in PAECs significantly protected the mitochondria from both NO and Zn²⁺-mediated disruption and induction of apoptosis and cell death. In summary, our results indicate that a loss of Zn²⁺ homeostasis produces mitochondrial dysfunction, increased oxidative stress, and apoptotic cell death. We propose that regulation of Zn²⁺ levels may represent a potential therapeutic target for disease associated with both nitrosative and oxidative stress. reactive nitrogen species; apoptosis mitochondrial dysfunction     

Involvement of a Calcium-Dependent Protein Kinase in Hypoosmotic Turgor Regulation in a Brackish Water Characeae Lamprothamnium succinctum

Calcium ion is a key messenger in turgor regulation of internodalcells of Lamprothamnium succinctum in response to hypoosmotictreatment. An increase in the concentration of cytosolic freecalcium ion ([Ca²⁺]_c) is prerequisite for the turgor regulation[Okazaki and Tazawa (1990) J. Membr. Biol. 114: 189], We examinedwhether or not a calcium-dependent protein kinase (CDPK) isinvolved in the Ca²⁺-mediated turgor regulation of Lamprothamniumcells. A 53-kDa CDPK which phosphorylated preferentially histoneH1 but poorly myelin basic protein or casein, was detected inthe cell extract of Lamprothamnium by an in-gel protein kinaseassay. This protein kinase was detected by Western blottingand was immunoprecipitated using an anti-Dunaliella tertiolectaCDPK antibody which can neutralize the Dunaliella CDPK activity[Yuasa et al. (1995) Plant Cell Physiol. 36: 699]. The 53-kDaCDPK was partially purified from Lamprothamnium and its activitywas shown to be inhibited by the antibody and K-252a, a proteinkinase inhibitor. Microinjection of the antibody into the cytosblof Lamprothamnium cells inhibited the decrease in turgor pressurein response to hypoosmotic treatment. However, a transient increasein [Ca²⁺]_c, which was suggested by a transient reduction ofthe velocity of cytoplasmic streaming, was induced in antibody-injectedcells after hypoosmotic treatment. Turgor regulation upon hypoosmotictreatment was inhibited when the cells were treated with K-252a.These results imply that CDPK of Lamprothamnium functions ata down-stream position of Ca²⁺-mobilization in processing turgorregulation in response to hypoosmotic treatment. ² These authors contributed equally to the work.     

Susceptibility to ultraviolet radiation in Calanus finmarchicus and Lepeophtheirus salmonis and the adaptive value of external filtering (Crustacea: Copepoda)

Copepods were exposed to UVB with a spectral irradiance maximumat 313 nm and additional visible light. In the holopelagic Calanusfinmarchicus, with a carotenoid concentration of 0.85 µgmg^-1, the LD₅₀ dose was 29 kJ m^-2 whereas in the parasitic copepodLepeophtheirus salmonis the LD₅₀ was 84 kJ m^-2. The abilityto photorepair was demonstrated for both species. The survivaldata were Weibull distributed, and this result is discussedrelative to a mechanistic ‘Weibull model’. Attenuationof UVB (306 nm) was measured in the inner Oslo fjord (K_d = 3.9m^-1). The adaptive significance of behavioural avoidance isassessed in model simulations; the results of the survival experimentsare used in connection with the Morowitz formula. Two caseswere compared; when Calanus was assumed incapable of activeexternal filtering the specimens would be safe if the depthof the mixed layer was deeper than 7 m in the inner Oslo fjord,however, with the ability of behavioural avoidance, Calanuswould be protected if they avoided the upper 1 m. The adaptivevalue associated with behavioural avoidance of toxic radiation,and the implications relative to vertical migration are discussed.     

Status of Ca2+/calmodulin protein kinase phosphorylation of cardiac SR proteins in ischemia-reperfusion

Although the sarcoplasmic reticulum (SR) is known to regulatethe intracellular concentration ofCa²⁺ and the SR function has beenshown to become abnormal during ischemia-reperfusion in theheart, the mechanisms for this defect are not fully understood. Becausephosphorylation of SR proteins plays a crucial role in the regulationof SR function, we investigated the status of endogenousCa²⁺/calmodulin-dependent proteinkinase (CaMK) and exogenous cAMP-dependent protein kinase (PKA)phosphorylation of the SR proteins in control, ischemic (I), andischemia-reperfused (I/R) hearts treated or not treated withsuperoxide dismutase (SOD) plus catalase (CAT). SR and cytosolicfractions were isolated from control, I, and I/R hearts treated or nottreated with SOD plus CAT, and the SR protein phosphorylation by CaMKand PKA, the CaMK- and PKA-stimulated Ca²⁺ uptake, and the CaMK, PKA,and phosphatase activities were studied. The SR CaMK andCaMK-stimulated Ca²⁺ uptakeactivities, as well as CaMK phosphorylation ofCa²⁺ pump ATPase (SERCA2a) andphospholamban (PLB), were significantly decreased in both I and I/Rhearts. The PKA phosphorylation of PLB and PKA-stimulatedCa²⁺ uptake were reducedsignificantly in the I/R hearts only. Cytosolic CaMK and PKA activitieswere unaltered, whereas SR phosphatase activity in the I and I/R heartswas depressed. SOD plus CAT treatment prevented the observedalterations in SR CaMK and phosphatase activities, CaMK and PKAphosphorylations, and CaMK- and PKA-stimulated Ca²⁺ uptake. These resultsindicate that depressed CaMK phosphorylation and CaMK-stimulatedCa²⁺ uptake in I/R hearts may bedue to a depression in the SR CaMK activity. Furthermore, prevention ofthe I/R-induced alterations in SR protein phosphorylation by SOD plusCAT treatment is consistent with the role of oxidative stress duringischemia-reperfusion injury in the heart.

     

Intrachloroplast Localization of 65Zn and 63Ni in a Zn-tolerant Plant, Ocimum basilicum Benth

Intrachloroplast localization studies of ⁶⁵Zn and ⁶³Ni weremade in a Zn-tolerant plant Ocimum basilicum var. purpurascensBenth. in order to investigate the mechanism and specificityof metal tolerance. The isotopes were supplied in solution tothe roots 14 d before fractionation. It was observed that ⁶⁵Znactivity was comparatively greater in the chloroplast envelopemembranes and stroma than the ⁶³Ni; and ⁶³Ni was largely foundin the lamellar and stroma fractions. Further analysis of lamellaerevealed that photosystem II (PS II) particles were richer inradioactivity than photosystem I (PS I) particles. The photochemicalevents of photosynthesis were less affected in Zn-treated plantsthan in the Ni-treated plants. The changed levels of the electrontransport chain intermediates including cytochromes, plastocyaninand ferredoxin provide supporting evidence for the localizationstudies. The activity of carbonic anhydrase, a zinc metalloprotein,was increased in Zn-treated plants with increase in nutrientZn concentration, indicating the binding of zinc to a proteinmoiety in the chloroplasts.     

Sexual experience does not compensate for the disruptive effects of zinc sulfate--lesioning of the main olfactory epithelium on sexual behavior in male mice

Recent studies point to an important role for the main olfactory epithelium (MOE) in regulating sexual behavior in male mice. We asked whether sexual experience could compensate for the disruptive effects of lesioning the MOE on sexual behavior in male mice. Male mice, which were either sexually naive or experienced, received an intranasal irrigation of either a zinc sulfate solution to destroy the MOE or saline. Sexual behavior in mating tests with an estrous female was completely abolished in zinc sulfate-treated male mice regardless of whether subjects were sexually experienced or not before the treatment. Furthermore, zinc sulfate treatment clearly disrupted olfactory investigation of both volatile and nonvolatile odors. Destruction of the MOE by zinc sulfate treatment was confirmed by a significant reduction in the expression of Fos protein in the main olfactory bulb following exposure to estrous female urine. By contrast, vomeronasal function did not seem to be affected by zinc sulfate treatment: nasal application of estrous female urine induced similar levels of Fos protein in the mitral and granule cells of the accessory olfactory bulb (AOB) of zinc sulfate- and saline-treated males. Likewise, the expression of soybean agglutinin, which stains the axons of vomeronasal organ neurons projecting to the glomerular layer of the AOB, was similar in zinc sulfate- and saline-treated male mice. These results show that the main olfactory system is essential for the expression of sexual behavior in male mice and that sexual experience does not overcome the disruptive effects of MOE lesioning on this behavior.     

Role of the Quality of Light in the Photoperiodic Flowering Response in Four Latitudinal Ecotypes of Chenopodium rubrum L.

The effect of the quality of light on the photoperiodic floweringresponse in four latitudinal ecotypes of Chenopodium rubrumwas examined. Two southern ecotypes, Sel-184 (50°10' N)and Sel-194 (34°20' N), displayed an obligate short-dayplant under white (W), red (R) and blue (B) light. Sel-372 (62°46'N),the most northern ecotype, was day-neutral in B and W lightand had an ambiphotoperiodic response in R light. Sel-374 (60°47'N) was an ambiphotoperiodic in B light and had a short-day responsein W and R light. In the B light regimens, the flowering ofSel-374 was modified from a typical ambiphotoperiodic to day-neutralresponse by changing the temperature from 20°C to 12°C. The photopriodic flowering response in the 8–16 hr photoperiodwas suppressed severely by the reducing light intensity from3,000 to 1,500 ergs.cm^–2.sec^–1, but that in continuousillumination was lowered only slightly by decreasing the lightintensity. The ambiphotoperiodic flowering response differedin its reaction to light; flowering in the 8-18 hr photoperiodrequired a high intensity light independent of the quality oflight, and flowering in the 24 hr photoperiod was promoted byB light. We considered the ambiphotoperiodic flowering responseto be a combination of the obligate short-day flowering responseand the flowering response for an extreme long-day condition,which is favored by B light. Therefore, this photoperiodic responseprobably is an intermediate step in the short-day and day-neutralresponses in day-neutralization. (Received December 8, 1980; Accepted February 20, 1981)     

Contrasting shade avoidance responses in two perennial grasses: a field investigation in simulated sparse and dense canopies

We designed an experiment with potted plants grown outdoors to investigate the expression of shade avoidance in simulated sparse and dense canopies by two perennial grasses known to express contrasting responses to low red:far-red ratios (R:FR). Plants were grown in canopy microenvironments designed to lower the R:FR by reflection of horizontally propagated FR from neighbors and by direct attenuation of R by filters located above plants. Two specific hypotheses were tested: (1) Paspalum dilatatum will express greater shade avoidance than Schizachyrium scoparium to low R:FR in both sparse and dense canopies, and (2) low R:FR will produce greater expressions of shade avoidance in sparse than in dense canopies in both species. P. dilatatum was more responsive to low R:FR than S. scoparium in both the sparse and dense canopies and lower ramet number plant^–1 was the only common shade avoidance response between species in sparse canopies. P. dilatatum also showed significant reductions in juvenile ramet initiation, juvenile ramet mass, total shoot mass, and shoot:root ratios in sparse canopies, but only juvenile ramet initiation was reduced in dense canopies. The suppression of juvenile ramet initiation in the dense canopy was at least partially modulated by the vertically propagated R:FR because a similar reduction in PFD and horizontally propagated R:FR showed 42% greater juvenile ramet initiation in the respective control. S. scoparium only showed a significant reduction in ramet number plant^–1 and a significant increase in blade length in sparse canopies, but no significant responses occurred in dense canopies. Consequently, neither hypothesis was rejected. Variable shade avoidance responses between species and canopy densities indicate that both interspecific variation and various proportions of vertically and horizontally propagated low R:FR can influence the expression of shade avoidance responses of perennial grasses in field settings.     

Upregulation of collecting duct aquaporin-2 by metabolic acidosis: role of vasopressin

Metabolic acidosis is associated with alteration in fluid and electrolyte reabsorption in a number of nephron segments. However, the effects of metabolic acidosis on urine osmolality and aquaporin-2 (AQP-2) remain poorly understood. In these studies, we examined the effects of chronic metabolic acidosis on water handling by the kidney. Rats were placed in metabolic cages and subjected to water (control) or 280 mM NH₄Cl loading for 120 h to induce metabolic acidosis. The results indicated a significant increase in urine osmolality with no change in urine volume or urinary Na⁺ excretion in acid-loaded animals. This effect was independent of alteration in fluid intake or salt/Cl^- loading. Immunoblotting and Northern hybridization studies indicated that AQP-2 protein abundance and mRNA expression levels increased significantly along the collecting duct system of NH₄Cl-but not NaCl-loaded animals. RIA results indicated that metabolic acidosis was associated with a fourfold increase in circulating levels of vasopressin (AVP) and a significant increase in brain AVP mRNA expression levels. In conclusion, metabolic acidosis upregulates the expression levels of AQP-2 and increases urine osmolality, suggesting an adaptive increase in water reabsorption in the collecting duct. A concomitant increase in AVP synthesis and secretion likely plays an essential role in the adaptation of AQP-2 in metabolic acidosis. kidney; acid-base; urine osmolality; sodium excretion rate