Investigation of the geometry of the dendritic tree of retinal ganglion cells

Two parameters are proposed for classifying the structure of the dendritic trees of retinal ganglion cells: the mean distance between the ends of the terminal segments of the dendrites from the soma ( ) and the ratio between the number of horizontal and vertical dendritic segments (a). By using these parameters the dendritic trees of ganglion cells were divided into four types. To describe the two-dimensional structure of dendritic trees the following parameters are used: the distribution of intermediate and terminal dendritic segments in each series of branches depending on the angle of their orientation relative to the boundaries of the inner plexiform layer — p_Z (), q_Z (), and depending on their length — P_Z (1), q_Z (1). Histograms of these functions are given. By means of these histograms the two-dimensional structure of the dendritic tree can be drawn in such a way as to reproduce the structural features of actual dendritic trees with the accuracy of the parameters defining their appearance. The structural and functional significance of the parameters used is discussed.Kaunas Medical Institute. Translated from Neirofiziologiya, Vol. 5, No. 3, pp. 307–314, May–June, 1973.     

Action potential duration and force-frequency relationship in isolated rabbit,guinea pig and rat cardiac muscle

The effect of action potential duration and elevated cytosolic sodium concentration on the forcefrequency relationship in isolated rabbit, guinea pig and rat papillary muscle preparations was studied. Shortening of action potential duration in guinea pig and rabbit from 150–200 ms to values characteristic of rat (20–40 ms), using the K_(ATP) channel activator levkromakalim (15 mol·l^–1), markedly reduced the force of contraction and converted the positive force-frequency relationship into negative one at longer pacing cycle lengths. This conversion was greatly enhanced in the presence of acetylstrophanthidin (0.2–1 mol·l^–1), an inhibitor of the Na-K pump. Acetylstrophanthidin (1 mol·l^–1) alone, however, had no effect on the forcefrequency relationship. Prolongation of action potential duration in rat with inhibitors of cardiac K channels (4-aminopyridine [10 mmol·l^–1] plus tetraethylammonium [2 mmol·l^–1) increased the force of contraction and abolished the negative force-frequency relationship observed in rat at longer pacing-cycle lengths. It is concluded that both action potential duration and cytosolic sodium concentration are major determinants of the force-frequency relationship in mammalian myocardium.Abbreviations AC acetylstrophanthidin - APD action potential duration - APD ₅₀ and APD ₉₀ action potential duration measured at 50% and 90% level of repolarization, respectively - SR sarcoplasmic reticulum     

Light,temperature and flow regimes of the Vaal River at Balkfontein,South Africa

A detailed investigation into light, temperature and flow regimes of the Vaal River was done for the first time. The Vaal River is ecologically and economically one of the most important rivers in South Africa. In a South African context, the Vaal River, with an average Secchi disk depth (Z _sd) of 0.41 m and an average euphotic zone depth (Z _eu) of 1.3 m, is a moderately turbid system. Red light (approx. 670 nm) penetrated Vaal River water to a greater degree than other components of the light spectrum. Water temperature in the Vaal River (min. = 10, max. = 27 °C at midday), closely followed seasonal changes in average atmospheric temperatures. The water-column shows little temperature stratification. The Vaal River is a highly regulated system with relatively high discharge rates at Balkfontein (average 112 m³ s^–1), but relatively low current velocity (approx. 0.35 m s^–1). Discharge was the most important variable to influence transparency of Vaal River water. Higher discharge resulted in higher total suspended solids (TSS) concentration and higher extinction coefficient (k) values as well as in higher turbidity and thus in lower Z _eu and Z _sd. From the mean TSS (141 mg l^–1) it was calculated that the Vaal River (mean annual run-off of 3532 million m³) transported 498016 tonnes of suspended solids per annum.     

Total synthesis of ichthyotoxic macrolides from the skin of the marine mollusk <Emphasis Type="Italic">Aplysia depilans</Emphasis>

A convergent pathway is described for the synthesis of natural aplyolides A–E (1–5), ichthyotoxic macrolides isolated from the skin of the marine mollusk Aplysia depilans. Aplyolide A (1) was prepared using ethyl (S)-lactate as chiral source. Key diols for the preparation of aplyolides B–E (2–5) were obtained stereoselectively by Sharpless asymmetric dihydroxylation of eneyne precursors. An improved procedure, based on cesium carbonate as base for alkynide preparation, was used in key steps of the synthesis involving coupling reactions between copper (I) alkynides and propargylic halides for the formation of skipped diyne systems. Finally, the crucial step of macrocyclization was accomplished using the Yamaguchi methodology.     

Autonomic nervous system responses correlate with mental rehearsal in volleyball training

The aim of this study was to assess objectivèly the processes of mental rehearsing (imagery) by measuring variations of the autonomic nervous system (or ANS responses) during an open-ended complex motor skill in two actual experiments (volleyball) and during mental rehearsing taking place between them. Comparison between pre- and post-test (volleyball) scores related to imagining and non-imagining performances revealed significant improvement in the former (²=20.9, P<0.00001) while in the latter ²=27, P<0.9, NS. The ANS parameters (skin potential and resistance, skin temperature and heat clearance, instantaneous heart rate and respiratory frequency) were quantified by original techniques and indices. Results from a principal component analysis showed a strong correlation between the responses in actual tasks (pre- and post-test volleyball) and during mental imagery, since the same preferential variables appeared on the main axis in 87% of cases. Thus the same autonomic channels seemed to be used during the actual activity and during the mental imagery of this activity. So far as phasic results were concerned, the main finding was a differing development of skill between imagining and non-imagining volleyball players. No clear difference was seen between pre- and post-tests in non-imaginers, except an increase in the median of the duration of the response observed in heat clearance, m₁ and m₂ respectively [m₁= 5.8 (SD 4.1) s, m₂= 7.6 (SD 3.9) s, P<0.001]. Conversely, for other ANS parameters, a significant decrease was seen in the post-test responses compared to pre-test responses in the imagining group [for instance, the median of the duration of the resistance responses decreased from m₁= 12.6 (SD 4.3) s, and m₂= 7.8 (SD 4.5) s, P<0.0001 in imaginers, while no change was observed in non-imaginers: 9.6 (SD 6.0) s vs 9.5 (SD 6.1) s, NS] except in the duration of the heat clearance response where an␣increase was seen [m₁= 7.3 (SD 5.0) s vs m₂= 7.6 (SD␣3.1) s, NS]. Compared to the non-imagining group, the latter result may also have been associated with a response decrease in the imagining group. Thus mental rehearsing induced a specific pattern of autonomic response: decreased amplitude, shorter duration and negative skin potentials compared to the control group. As this pattern was associated with better performance in the tests it can be suggested that in the case of open-ended motor activity, mental rehearsing may help in the construction of schema which can be reproduced, without thinking, in actual practice. Thus a neural information process might develop in the central nervous system changing from a parallel into a serial treatment. Accepted : 23 October 1997     

Ulva rigida (Ulvales,Chlorophyta) tank culture as biofilters for dissolved inorganic nitrogen from fishpond effluents

Ulva rigida was cultivated in 7501 tanks at different densities with direct and continuous inflow (at 2, 4, 8 and 12 volumes d^–1) of the effluents from a commercial marine fishpond (40 metric tonnes, Tm, of Sparus aurata, water exchange rate of 16 m³ Tm^–1) in order to assess the maximum and optimum dissolved inorganic nitrogen (DIN) uptake rate and the annual stability of the Ulva tank biofiltering system. Maximum yields (40 g DW m^–2 d^–1) were obtained at a density of 2.5 g FW 1^–1 and at a DIN inflow rate of 1.7 g DIN m^–2 d^–1. Maximum DIN uptake rates were obtained during summer (2.2 g DIN M^–2 d^–1), and minimum in winter (1.1 g DIN m^–2 d^–1) with a yearly average DIN uptake rate of 1.77 g DIN m^–2 d^–1 At yearly average DIN removal efficiency (2.0 g DIN m^–2 d^–1, if winter period is excluded), 153 m² of Ulva tank surface would be needed to recover 100% of the DIN produced by 1 Tm of fish.Abbreviations DIN= dissolved inorganic nitrogen (NH _inf4 ^sup+ + NO _inf3 ^sup– + NO _inf2 ^sup– ); - FW= fresh weight; - DW= dry weight; - PFD= photon flux density; - V= DIN uptake rate     

Phthalide mono- and dimers from the radix of Angelica sinensis

Phytochemical investigation of the radix of Angelica sinensis has led to the isolation and identification of a new phthalide dimer, (3Z)-(3aR,6S,3′R,8′S)-3a.8′,6.3′-diligustilide (1), along with three known phthalide dimers, including riligustilide (2), levistolide A (3), senkyunolide O (4), and three known phthalide monomers, including 3,9-dihydroxyl-ligustilide (5), (Z)-butylidene phthalide (6), (Z)-ligustilide (7). Their structures were determined by spectroscopic methods including IR, NMR (¹H NMR, ¹³C NMR, COSY, HSQC, HMBC and NOESY) and MS. Meanwhile, the possible biosynthesis pathways of compounds 1 and 5 were hypothesized.     

Permeability parameters of the toad isolatedstratum corneum

Summary A technique for isolating thestratum corneum from the subjacent layers of the epithelium was developed which permits studying thestratum corneum as an isolated membrane mounted between half-chambers. The method basically consists of an osmotic shock induced by immersing a piece of skin in distilled water at 50°C for 2 min. When the membrane is bathed on each surface by NaCl-Ringer's solution, its electrical resistance is 14.1±1.3 cm² (n=10). This value is about 1/100 of the whole skin resistance in the presence of the same solution. The hydraulic filtration coefficient (L _p ) measured by a hydrostatic pressure method, with identical solutions on each side of the membrane, is 8.8×10^–5±1.5×10^–5 cm sec^–1 atm^–1 (n=10) in distilled water and 9.2×10^–5±1.4×10^–5 cm sec^–1 atm^–1 (n=10) in NaCl-Ringer's solution. These values are not statistically different and are within the range of 1/80 to 1/120 of the whole skinL _p . Thestratum corneum shows an amphoteric character when studied by KCl diffusion potentials at different pH's. The membrane presents an isoelectric pH of 4.6±0.3 (n=10). Above the isoelectric pH the potassium transport number is higher than the chloride transport number; below it, the reverse situation is valid. Divalent cations (Ca⁺⁺ or Cu⁺⁺) reduce membrane ionic discrimination when the membrane is negatively charged and are ineffective when the membrane fixed charges are protonated at low pH.     

Stomatal conductance in a tropical xerophilous shrubland at a lava substratum

Diurnal variation in leaf stomatal conductance (g _s) of three xerophilous species (Buddleia cordata, Senecio praecox and Dodonaea viscosa) was measured over a 10-month period during the dry and wet seasons in a shrubland that is developing in a lava substratum in Mexico. Averaged stomatal conductances were 147 and 60.2 (B. cordata), 145 and 24.8 (D. viscosa) and 142.8 and 14.1 mmol m^–2 s^–1 (S. praecox) during the wet and dry season respectively. Leaf water potential () varied in a range of –0.6 to –1.2 (S. praecox), –0.6 to –1.8 (B. cordata) and –0.9 to –3.4 MPa (D. viscosa) during the same measurement periods. Stomata were more sensitive to changes in irradiance, air temperature and leaf–air vapour pressure difference in the rainy season than the dry season. Although stomatal responses to were difficult to distinguish in any season (dry or rainy), data for the entire period of measurement showed a positive correlation, stomata tending to open as increased, but there is strong evidence of isohydric behaviour in S. praecox and B. cordata. A multiplicative model relating g _s to environmental variables and to accounted for 79%–83% of the variation of g _s in three sites (pooled data); however, the performance of the model was poorer (60%–76%) for individual species from other sites not included in the pooled data.     

Assessment of cardiac output from noninvasive determination of arterial pressure profile in subjects at rest

The stroke volume of the left ventricle (SV) was calculated from noninvasive recordings of the arterial pressure using a finger photoplethysmograph and compared to the values obtained by pulsed Doppler echocardiography (PDE). A group of 19 healthy men and 12 women [mean ages: 20.8 (SD 1.6) and 22.2 (SD 1.6) years respectively] were studied at rest in the supine position. The ratio of the area below the ejection phase of the arterial pressure wave (A _s) to SV, as obtained by PDE, yielded a calibration factor dimensionally equal to the hydraulic impedance of the system (Z _ao =A _s ·SV ^–1). TheZ _ao amounted on average to 0.062 (SD 0.018) mmHg · s · cm^–3 for the men and to 0.104 (SD 0.024) mmHg · s · cm^–3 for the women. TheZ _ao was also estimated from the equation:Z _ao = a · (d + b ·HR + c ·PP + e ·MAP)^–1, whereHR was the heart rate,PP the pulse pressure,MAP the mean arterial pressure and the coefficients of the equation were obtained by an iterating statistical package. The value ofZ _ao thus obtained allowed the calculation of SV from measurements derived from the photoplethysmograph only. The mean percentage error between the SV thus obtained and those experimentally determined by PDE amounted to 14.8 and 15.6 for the men and the women, respectively. The error of the estimate was reduced to 12.3 and to 11.1, respectively, if the factorZ _ao, experimentally obtained from a given heart beat, was subsequently applied to other beats to obtain SV from theA _s measurement in the same subject.     

Comparative carbon-specific ingestion rates of phytoplankton by Acartia tonsa,Centropages velificatus and Eucalanus pileatus grazing on natural phytoplankton assemblages in the plume of the Mississippi River (northern Gulf of Mexico continental shelf)

During four cruises in continental shelf waters of the northern Gulf of Mexico in the winters of 1981–83, we performed quantitative studies on the grazing of the copepods Acartia tonsa, Centropages velificatus, and Eucalanus pileatus, on phytoplankton using natural particulate assemblages as food. Stations were in, or adjacent to the plume of the Mississippi River, thereby providing wide spectra of phytoplankton and suspended riverine particulate concentrations. Phytoplankton cell volume was converted to carbon, and this, coupled with carbon content measurements of these three copepod species, allowed comparisons of daily ingestion effort even though the copepods were of different sizes. Data were expressed in the same units (% of copepod body carbon ingested copepod ^–1 d^–1) for each species. Over similar ranges of phytoplankton carbon concentrations (0.21–92.06 gCl^–1), Acartia tonsa had higher carbon-specific ingestion rates (x = 22.31%, range = 0.08–152.37%) than C. velificatus (x = 2.8%, range = 0.00–31.09 %) or E. pileatus (x = 1.27%, range = 0.10–2.80%). Carbon-specific ingestion rates increased with increasing phytoplankton carbon concentration for A. tonsa (R² = 0.81) and there was no evidence of saturated feeding on the carbon concentrations offered. A similar, but weaker trend was evident for E. pileatus (R² = 0.71), but not C. velificatus (R² = 0.49). Over a wide range of suspended particulate concentrations (10.6–95.2 mg l^–1), there was no systematic effect of particulates on carbon-specific ingestion rate for any of the three copepod species. However, A. tonsa appeared more adept at grazing in highly turbid water than C. velificatus or E. pileatus.     

Arsenic concentrations in water and fish from Chautauqua Lake,New York

Synopsis Arsenic persists in Chautauqua Lake, New York waters 13 years after cessation of herbicide (sodium arsenite) application and continues to cycle within the lake. Arsenic concentrations in lake water ranged from 22.4–114.81 g l^–1, = 49.0 ag l^–1. Well water samples generally contained less than 10 g l^–1 arsenic. Arsenic concentrations in lake water exceeded U.S. Public Health Service recommended maximum concentrations (10 g l^–1) and many samples exceeded the maximum permissible limit (50 g l^–1). Fish accumulated arsenic from water but did not magnify it. Fish to water arsenic ratios ranged from 0.4–41.6. Black crappie (Pomoxis nigromaculatus) contained the highest arsenic concentrations (0.14–2.04 g g^–1 ), X = 0.7 g g^–1) while perch (Perca flavescens), muskellunge (Esox masquinongy) and largemouth bass (Micropterus salmoides) contained the lowest concentrations (0.02–0.13 g g^–1). Arsenic concentrations in fish do not appear to pose a health hazard for human consumers.     

Cl− channels in basolateral renal medullary memnbranes: III. Determinants of single-channel activity

Summary We evaluated the effects of vawrying aqueous Cl^– concentrations, and of the arginyl- and lysyl-specific reagent phenylglyoxal (PGO), on the properties of Cl^– channels fused from basolaterally enriched renal medullary vesicles into planar lipid bilayers. The major channel properties studied were the anion selectivity sequence, anionic requirements for, channel activity. and the efects of varying Cl^– concentrations and/or PGO on the relation between holding voltageV _H -mV) and open-time probability (P _o).Reducingcis Cl^– concentrations, in the range 50–320mm, produced a linear reduction in fractional open time (P _v) with a half-maximal reduction inP _o atcis Cl^–170mM. Channel activity was sustained by equimolar replacement ofcis Cl^– with F^–, but not with impermeant isethionate. Fortrans solutions, the relation between Cl^– concentration andP ₀ at 10mm Cl^–. Reducingcis Cl^– had no effect on the gating charge (Z) for channel opening, but altered significantly the voltage-independent, energy (G) for channel opening.Phenylglyoxal (PGO) reducedZ and altered G for Cl^– channel activity when added tocis, but nottrans solutions, Furthermore, in the presence ofcis PGO, reducing thecis Cl^– concentration had no effect onZ but altered G. Thus we propose thatcis PGO and,cis Cl^– concentrations affect separate sites determining channel activity at the extracellular faces of, these Cl^– channels.     

Limnological effects of anthropogenic desiccation of a large, saline lake, Walker Lake, Nevada

Walker Lake is a monomictic, nitrogen-limited, terminal lake located in western Nevada. It is one of only eight large (Area>100 km², Z _{{ mean}}>15 m) saline lakes of moderate salinity (3–20 g l^–1) worldwide, and one of the few to support an endemic trout fishery (Oncorhynchus clarki henshawi). As a result of anthropogenic desiccation, between 1882 and 1996 the lake's volume has dropped from 11.1 to 2.7 km³ and salinity has increased from 2.6 to 12–13 g l^–1. This study, conducted between 1992 and 1998, examined the effects of desiccation on the limnology of the lake. Increases in salinity over the past two decades caused the extinction of two zooplankton species, Ceriodaphnia quadrangula and Acanthocyclops vernalis. Recent increases in salinity have not negatively affected the lake's dominant phytoplankton species, the filamentous blue-green algae Nodularia spumigena. In 1994 high salinity levels (14–15 g l^–1) caused a decrease in tui chub minnow populations, the main source of food for Lahontan cutthroat trout, and a subsequent decrease in the health of stocked trout. Lake shrinkage has resulted in hypolimnetic anoxia and hypolimnetic accumulation of ammonia (800–2000 g-N l^–1) and sulfide (15 mg l^–1) to levels toxic to trout. Internal loading of ammonia via hypolimnetic entrainment during summer wind mixing (170 Mg-N during a single event), vertical diffusion (225–500 Mg-N year^–1), and fall destratification (540–740 Mg-N year^–1) exceeds external nitrogen loading (<25 Mg-N year^–1). Increasing salinity in combination with factors related to hypolimnetic anoxia have stressed trout populations and caused a decline in trout size and longevity. If desiccation continues unabated, the lake will be too saline (>15–16 g l^–1) to support trout and chub fisheries in 20 years, and in 50–60 years the lake will reach hydrologic equilibrium at a volume of 1.0 km³ and a salinity of 34 g l^–1.     

Three-year field response of young olive trees (Olea europaea L., cv. Arbequina) to soil salinity: Trunk growth and leaf ion accumulation

Irrigated olive is rapidly increasing in arid and semiarid areas, many of which may be negatively affected by soil salinity. We evaluated changes in trunk growth and leaf Cl^–, Na⁺ and K⁺ concentrations in young Arbequina olives (Olea europaea L.) grown in a saline-sodic field over a three-year period. The trunk diameter was measured at the beginning and the end of the 1999 (70 trees), 2000 (59 trees) and 2001 (42 trees) growing periods. Leaves, sampled in August of each year, were analyzed for Cl^–, Na⁺ and K⁺ concentrations. Soil salinity (apparent electrical conductivity, ECa) of each monitored tree was measured 14 times during the 1999–2001 experimental period with an electromagnetic sensor and converted to root zone electrical conductivity of the soil saturation extract (ECe) based on ECa–ECe calibration curves. Salinity tolerance was determined using the Maas and Hoffman threshold–slope response model. Based on salinity thresholds (ECe_thr), the tolerance of olive in terms of trunk growth was high in 1999 (ECe_thr = 6.7 dS m^–1), but declined with age and time of exposure to salts by 30% in 2000 (ECe_thr = 4.7 dS m^–1) and by 55% in 2001 (ECe_thr = 3.0 dS m^–1). Based on the high absolute slopes obtained in all years (values between 16% and 23% dS^–1 m), olive was classified as very sensitive to ECe values above the threshold. Trunk growth thresholds based on leaf ion concentrations varied, depending on years, between 2.6 and 4.0 mg g^–1 (Cl_thr) and between 1.0 and 1.2 mg g^–1 (Na_thr), indicating that Arbequina olive was less sensitive to leaf Cl^– and much more sensitive to leaf Na⁺ than values reported as toxic in greenhouse studies. Leaf K⁺ slightly decreased with increasing salinity, whereas the K⁺/Na⁺ ratio sharply decreased with increasing salinity. We concluded that the initial salinity tolerance of olive was high, but declined sharply with time of exposure to salts and became quite sensitive due primarily to increasing toxic concentrations of Na⁺ in the leaves.     

Decay Kinetics of Tyrosine Radical (YZ •) in Chloride Anion-Depleted Photosystem 2 Studied by Time-Resolved EPR

The decay of tyrosine cation radical was found to be biphasic at 253 K. The fast phase corresponds to the Y_Z component while the slow phase corresponds to the tyrosine D radical (Y_D ) component. At 253 K, the t_1/2 value was 28.6 s for the fast phase and 190.7 s for the slow phase. The fast phase is attributed to the recombination of charges between Y_Z and Q_A ^–. The activation energy for the reaction of Y_Z with Q_A ^– between 253 and 293 K was 48 kJ mol^–1 in Cl^–-depleted photosystem 2 (PS2) membranes. Both the decay rate and the amplitude of the PAR -induced signal of Y_Z were affected by addition of chloride anion. Change in the decay rate and the amplitude of the PAR-induced signal of Y_Z was observed when other anions like Br^–, I^–, F, HCO₃ ^–, NO₃ ^–, PO₄ ^3– were substituted in the Cl^–-depleted PS2.     

Animal coat color and radiative heat gain: A re-evaluation

Summary Thermal resistance and heat gain from simulated solar radiation were measured over a range of wind velocities in black and white pigeon plumages. Plumage thermal resistance averaged 39% (feathers depressed) or 16% (feathers erected) of that of an equivalent depth of still air. Feather erection increased plumage depth four-fold and increased plumage thermal resistance about 56%. At low wind speeds, black plumages acquired much greater radiative heat loads than did white plumages. However, associated with the greater penetration of radiation into light than dark plumages, the radiative heating of white plumages is affected less by convective cooling than is that of black plumages. Thus, the heat loads of black and white plumages converge as wind speed is increased. This effect is most prominent in erected plumages, where at wind speeds greater than 3 ms^–1 black plumages acquire lower radiative heat loads than do white plumages. These results suggest that animals with dark-colored coats may acquire lower heat loads under ecologically realistic conditions than those forms with light-colored coats. Thus, the dark coat colors of a number of desert species and the white coat color of polar forms may be thermally advantageous.These results are used to test a new general model that accounts for effects of radiation penetration into a fur or feather coat upon an animal's heat budget. Even using simplifying assumptions, this model's predictions closely match measured values for plumages with feathers depressed (the typical state). Predictions using simplifying assumptions are less accurate for erected plumages. However, the model closely predicts empirical data for erected white plumages if one assumption is obviated by additional measurements. Data are not sufficient to judge whether this is also the case for erected black plumages.List of Symbols A body surface area (m²) - a _L long-wave absorptivity of coat - a _s short-wave absorptivity of coat - d characteristic dimension (m) - E evaporative water loss (kg m^–2 s^–1) - h coat thermal conductance (W m^–2 °C^–1) - k convection constant (s^1/2 m^–1) - l coat thickness (m) - L _i long-wave irradiance at coat surface (W m^–2) - M metabolic heat production (W m^–2) - m body mass (kg) - P plumage mass (kg) - p probability per unit coat depth that a penetrating ray will strike a coat element (m^–1) - q(Z) radiation absorbed at level z (W m^–2) - R _abs radiation absorbed by animal (W m^–2) - r _e external resistance to convective and radiative heat transfer (s m^–1) - r _Ha boundary layer resistance to convective heat transfer (s m^–1) - r _Hb whole-body thermal resistance (s m^–1) - r _Hc coat (plumage) thermal resistance (s m^–1) - r _Ht tissue thermal resistance (s m^–1) - r _s apparent resistance to radiative heat transfer (s m^–1) - r(Z) thermal resistance from level z to coat surface (s m^–1) - S _i short-wave irradiance at coat surface (W m^–2) - S ^– radiant flux going toward skin surface (W m^–2) - S ⁺ radiant flux going away from skin surface (W m^–2) - T _a air temperature (°C) - T _b core body temperature (°C) - T _e equivalent black-body temperature (°C) - T _e air temperature plus temperature increment due to longwave radiation (°C) - u wind velocity (m s^–1) - V heat load on animal from short-wave radiation (W m^–2) - z depth within coat (m) - short-wave absorptivity of individual hairs or feather elements - emissivity - {ie211-1} - latent heat of vaporization of water (J kg^–1) - short-wave reflectivity of individual hairs or feather elements - {ie211-2} short-wave reflectivity of coat - {ie212-1} short-wave reflectivity of skin - c _p volumetric specific heat of air (J m^–3 °C^–1) - Stefan-Boltzmann constant (W m^–2 °K^–4) - short-wave transmissivity of individual hairs or feather elements - {ie212-2} short-wave transmissivity of coat     

A comparison of responses from olfactory receptor neurons of<Emphasis Type="Italic"> Heliothis subflexa</Emphasis> and<Emphasis Type="Italic"> Heliothis virescens</Emphasis> to components of their sex pheromone

Single-cell electrophysiological recordings were obtained from olfactory receptor neurons in sensilla trichodea on male antennae of the heliothine species Heliothis subflexa and the closely related congener H. virescens. A large percentage of sensilla (72% and 81%, respectively, of all sensilla sampled) contained a single odor-responsive receptor neuron tuned to the major pheromone component of both species, Z-11-hexadecenal. A second population of sensilla on H. subflexa antennae (18%) housed receptor neurons that were tuned to Z-9-hexadecenal but also responded with less sensitivity to Z-9-tetradecenal. A similar population of sensilla (4%) on H. virescens male antennae housed receptor neurons that were shown to be tuned specifically only to Z-9-tetradecenal, with no response to even high dosages of Z-9-hexadecenal. A third population of sensilla (comprising 8% and 16% of the sensilla sampled in H. subflexa and H. virescens, respectively) housed two olfactory receptor neurons, one of which was tuned to Z-11-hexadecenyl acetate and the other tuned to Z-11-hexadecenol. In H. subflexa the Z-11-hexadecenyl acetate-tuned neuron also responded to Z-9-tetradecenal with nearly equivalent sensitivity. The behavioral requirements of males of these two species for distinct pheromonal blends was, therefore, reflected by the subtle differences in the tuning properties of antennal olfactory receptor neurons.Abbreviations MGC macroglomerular complex - ORN olfactory receptor neuron - Z9–14:Ald (Z)-9-tetradecenal - Z9–16:Ald (Z)-9-hexadecenal - Z11–16:Ac (Z)-11-hexadecenyl acetate - Z11–16:Ald (Z)-11-hexadecenal - Z11–16:OH (Z)-11-hexadecenol     

Photosynthesis and Water Use Efficiency in Twenty Tropical Tree Species of Differing Succession Status in a Brazilian Reforestation

Leaf gas exchange characteristics were measured in twenty woody species that differ in succession status ranging from pioneer species (PS) to late succession species (LS) in a Brazilian rain-reforestation ecosystem. Photon-saturated photosynthetic rate, calculated per either a leaf area (P _NA) or a dry mass (P _NM) basis, differed among species. P _NA and P _NM were highest in PS and lowest in LS. Variation among species was 3-fold (from 7 to 23 mol m^–2 s^–1) for P _NA, and 5-fold (from 50 to 275 mol kg^–2 s^–1) for P _NM. The highest P _NA (23 mol m^–2 s^–1) and P _NM (275 mol kg^–2 s^–1) values were recorded in PS Croton urucurana, while the lowest P _NA (7 mol m^–2 s^–1) and P _NM (50 mol kg^–2 s^–1) values were recorded in LS Aspidosperma cylindrocarpon. A considerable overlap was recorded between PS and LS in values of stomatal conductance (g _s), transpiration rate (E), and leaf mass to area ratio (ALM). However, C. urucurana also showed highest g _s and E. P _NM was highly correlated with ALM in both PS and LS (r=–0.75 and –0.90, respectively). The high values of instantaneous transpiration efficiency (ITE) and intrinsic water use efficiency (WUE_i) were also observed in the PS when compared with the LS.