The metabolic clearance of progesterone in the pregnant rat: absence of a physiological role for the lung

The metabolic clearance rate (MCR) of progesterone is among the highest for all steroid hormones studied, yet it is difficult to apportion this high MCR to specific organ contributions. The isolated lung has been shown to metabolize progesterone, and since this tissue receives the entire cardiac output, potentially it could make a major contribution to the overall MCR. This possibility was examined in the present study by measuring lung extraction of [3H]progesterone under steady-state conditions in the intact pregnant rat. Anesthetized rats (n = 6) were infused with [3H]progesterone via a femoral vein for 100 min on Day 16 of pregnancy. After the onset of steady state (40 min), four blood samples were obtained at 20-min intervals from the right ventricle and from the aorta, and the concentrations of [3H]progesterone and its metabolites were determined. Throughout the sampling period, mean arterial pressure and heart rate remained stable (two-way analysis of variance), as did the production rate (3.76 +/- 0.35 mg/day; mean +/- SEM) and the MCR (34.8 +/- 3.5 ml/min) of progesterone. Despite this high rate of clearance, there was no difference between the concentration of [3H]progesterone in arterial and right ventricular blood, indicating no net extraction of progesterone during passage through the lung. Furthermore, there was no change in the concentration of either lipid-soluble or aqueous-soluble [3H]progesterone metabolites during trans-lung passage. These observations demonstrate that the lung does not contribute to the MCR of progesterone when measured under physiological and steady-state conditions. Therefore, the relationship, MCR (ml/min) = whole-body extraction (%) x cardiac output (ml/min), is upheld for progesterone in the rat.     

Localization of the circadian pacemakers of Hemideina thoracica (Orthoptera; Stenopelmatidae)

The location of the circadian pacemakers of the orthopteran Hemideina thoracica (White) has been investigated through observation of the effects of surgical removal of brain tissues (principally optic lobes and tracts) on free-running and entrained locomotor rhythms. Bilobectomy and severance of optic tracts invariably resulted in arrhythmicity, whereas rhythmicity was sustained following unilateral lobectomy, generally with increases in the free-running period (FRP) and decreases in both the active-phase lengths and activity-to-rest ratios of the rhythm. Bilobectomized subjects could be entrained by temperature cycles, but exhibited no transients or residual rhythmicity, indicating that temperature brought about a direct response or masking effect. These results support the hypothesis that the circadian locomotor pacemakers of Hemideina are located within each optic lobe, and that there are no extraoptic centers for the control of the timing of locomotor activity. Although confirmation of the pacemaker role of the optic lobes requires transplantation of the tissues, the conclusion may be drawn by inference from other studies (e.g., Leucophaea maderae--Page, 1983; Gryllus bimaculatus--Tomioka and Chiba, 1986). Light entrainment continued after surgical binding and blackening of the compound eyes and ocelli, supporting the view that direct illumination of neural tissue through the cuticle may be one possible pathway for light entrainment.     

Frostbite and the significance of a temperature-sensation scale in field and laboratory conditions

The literature indicates that rapid thawing in water between 42 and 45C provides the best prognosis for frostbitten limbs.A temperature:sensation scale for the normal hand was derived and tested in laboratory and field conditions. The scale permitted the preparation of water suitable for frostbite treatment by the majority of subjects without access to a thermometer. The maximum observed inaccuracy was 1.2C outside the preferred range but was well withing the safe range for treatment.

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Zusammenfassung Die beste Prognose zur Behandlung von Erfrierungen bietet nach den Erfahrungen in der Literatur das schnelle Auftauen von erfrorenen Gliedern bei Wassertemperaturen von 42–45C. Für die gesunde Hand wurde eine Temperatur-Wahrnehmungsskala aufgestellt und unter verschiedenen Bedingungen im Laboratorium und im Freien geprüft. Ohne Zugang zu einem Thermometer gestattete die Skala in der Mehrzahl der FÄlle die ErwÄrmung von Wasser auf Temperaturen, die für die Behandlung von Erfrierungen geeignet sind. Die grösste Ungenauigkeit zwischen SchÄtzwert und Thermometerwert war 1.2C ausserhalb des gewünschten aber noch innerhalb des für die Behandlung zulÄssigen Bereiches.

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Résumé D'après les indications de plusieurs auteurs, le meilleur traitement de membres gelés consiste à les dégeler dans de l'eau à une temperature entre 42 et 45C. Une échelle température-sensation pour la main normale a été mise au point et vérifiée au laboratoire ainsi qu'en plain air.Cette méthode a permis la préparation d'eau en vue d'un traitement de gelures sans faire usage d'un thermomètre dans la plupart des cas. L'erreur maximum observée était de 1,2 C sans que les limites de l'intervalle propice à un traitement ne soient jamais dépassées.

     

Evidence of biotic resistance to exotic plant invasion in degraded Bornean forests

Intact tropical forests are generally considered to be resistant to invasions by exotic species, although the shrub Clidemia hirta (Melastomataceae) is highly invasive in tropical forests outside its native range. Release from natural enemies (e.g., herbivores and pathogens) contributes to C. hirta invasion success where native melastomes are absent, and here we examine the role of enemies when C. hirta co-occurs with native Melastomataceae species and associated herbivores and pathogens. We study 21 forest sites within agricultural landscapes in Sabah, Malaysian Borneo, recording herbivory rates in C. hirta and related native Melastoma spp. plants along two 100-m transects per site that varied in canopy cover. Overall, we found evidence of enemy release; C. hirta had significantly lower herbivory (median occurrence of herbivory per plant = 79% of leaves per plant; median intensity of herbivory per leaf = 6% of leaf area) than native melastomes (93% and 20%, respectively). Herbivory on C. hirta increased when closer to native Melastoma plants with high herbivory damage, and in more shaded locations, and was associated with fewer reproductive organs on C. hirta. This suggests host-sharing by specialist Melastomataceae herbivores is occurring and may explain why invasion success of C. hirta is lower on Borneo than at locations without related native species present. Thus, natural enemy populations may provide a “biological control service” to suppress invasions of exotic species (i.e., biotic resistance). However, lower herbivory pressures in more open canopy locations may make highly degraded forests within these landscapes more susceptible to invasion.     

In vivo micro-CT scanning of a rabbit distal femur: repeatability and reproducibility

Before in vivo micro-CT scanning can be used to investigate femoral trabecular microarchitecture over time in rabbits, its repeatability and reproducibility must be demonstrated. To accomplish this, both distal femurs of two 6-month-old New Zealand white rabbits were scanned five times each in 1 day under different conditions (repeatability). Scanning was done at 28 microm isotropic voxel size to produce five image stacks of each femur. Three operators then followed a standard image processing protocol (reproducibility) to isolate two separate cubes from each anterior femoral condyle [total n = (8 cube sites)(5 scans)(3 operators) = 120]. Bone volume fraction (BV/TV) of the eight different cube sites (sample) ranged from 0.408 to 0.501 (mean: 0.453); trabecular thickness (Tb.Th) ranged from 158.1 to 185.5 microm (mean: 168.6 microm); and trabecular separation (Tb.Sp) ranged from 179.4 to 233.1 microm (mean: 204.7 microm). Using ANOVA and the variance component method, the total process variation was +/- 14.1% of the mean BV/TV of 0.453. The sample variation was +/- 13.9% (p < 0.001), the repeatability was +/- 2.1% (p < 0.001), and the reproducibility was +/- 0.1% (p > 0.05). Results were similar for Tb.Th and Tb.Sp. Though the contribution due to repeatability was statistically significant for each of the three indices, the natural sample differences were far greater than differences caused by repeated scanning under different conditions or by different operators processing the images. These findings suggest that in vivo micro-CT scanning of rabbit distal femurs was repeatable and reproducible and can be used with confidence to measure differences in trabecular bone microarchitecture at a single location in a longitudinal study design.     

Assessment of river condition at a large spatial scale using predictive models

1. RIVPACS-type predictive models were developed at a relatively large spatial scale for the Australian state called New South Wales (NSW, 801 428 km²). Aquatic macroinvertebrate samples and physical and chemical data were collected from 250 reference sites (little affected by human activities) and 23 test sites (with known human impacts) throughout NSW in autumn and spring 1995 and identified mostly to family level. Reference sites were grouped based on their macroinvertebrate data using classification (UPGMA) and ordination techniques. Relationships between macroinvertebrate and environmental data were established using principal axis correlations and stepwise multiple discriminant function analysis. models for predicting invertebrate assemblages were developed separately for edge and riffle habitats for autumn and spring data sets and for combined autumn and spring data sets. 2. Sites in the lowland sections of the western flowing rivers were characterized by low taxonomic richness and were distinct from the sites in the eastern part of the state. Sites on the western slopes of the Great Dividing Range in southern and northern NSW mostly fell into separate groups. In eastern NSW, site groups did not represent a north, central and south division. Sites on highland streams, coastal fringe streams and large rivers mostly formed distinct groups, but most of the sites on east-flowing rivers fell into large site groups that did not have clear geographic boundaries. 3. Environmental variables that were strongly correlated with ordinations of macroinvertebrate presence/absence at sites were water temperature, altitude, longitude and maximum distance from source. The predictor variables determined by DFA for the six models created included alkalinity, altitude, location (longitude and/or latitude), stream size and substratum composition. These are generally in common with the variables determined for other large geographic areas in Australia and the United Kingdom. 4. Model outputs from reference sites suggest that, among the six models, the riffle model combining autumn and spring is likely to give the most reliable predictions. The combined edge model also performed well but refinements are needed for single season models to provide reliable outputs. 5. Combined season models both for riffles and for edges detected biological impairment at all but one of the test sites. Single season riffle models also detected impairment while single season edge models characterized sites as unimpaired despite other models’ indications of impaired fauna. Riffle models may be more sensitive than edge models but the sampling of riffles is often limited by flow. Edge habitats are available at most sites but there may be few riffles in floodplain rivers. Available resources, desired model sensitivity, and river type should be considered jointly to determine the most useful habitat to sample.     

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

Intense photon emission induced by fracture of γ–irradiated Dy‐, Tm‐, Sm‐ and Mn‐doped CaSO4 single crystals

When an γ‐irradiated Dy‐, Tm‐, Sm‐ or Mn‐doped CaSO₄ crystal is impulsively deformed, two peaks appear in the ML intensity versus time curve, whereby the first ML peak is found in the deformation region and the second in the post‐deformation region of the crystals. In this study, intensities I_m1 and I_m2 corresponding to first and second ML peaks, respectively, increased linearly with an impact velocity v₀ of the piston used to deform the crystals, and times t_m1 and t_m2 corresponding to the first and second ML peaks, respectively, decreased with impact velocity. Total ML intensity initially increased with impact velocity and then reached a saturation value for higher values of impact velocity. ML intensity increased with increasing γ‐doses and size of crystals. Results showed that the electric field produced as a result of charging of newly‐created surfaces caused tunneling of electrons to the valence band of the hole‐trapping centres. The free holes generated moved in the valence band and their subsequent recombination with electron trapping centres released energy, thereby resulting in excitation of luminescent centres. Copyright © 2012 John Wiley & Sons, Ltd.