Fine-scale spatial variability in anatoxin-a and homoanatoxin-a concentrations in benthic cyanobacterial mats: implication for monitoring and management.

AIMS: The purpose of this study was to determine the variability in anatoxin-a (ATX) and homoanatoxin-a (HTX) concentrations in benthic cyanobacterial mats within sampling sites and to assess the applicability of using a PCR-based approach to determine ATX- and HTX-production potential. METHODS AND RESULTS: ATX and HTX variability was investigated by collecting 15 samples from 10 × 10 m grids in seven rivers. ATX and HTX concentrations were determined using liquid chromatography-mass spectrometry (LC-MS). Samples from two sites contained no ATX or HTX and at one site ATX and HTX were detected in all samples. At four sites, both toxic and nontoxic samples co-occurred and these samples were sometimes spaced less than 1 m apart. PCR amplification of a region of a polyketide synthase (ks2, putatively involved in the biosynthetic pathway of ATX and HTX) successfully distinguished ATX-and-HTX- and non-ATX-and-HTX-producing cultured Phormidium strains. Results from environmental samples were more variable, and the results were in congruence with the LC-MS data in only 58% of samples. CONCLUSIONS: Fine-scale spatial variability in ATX and HTX concentrations occurs among benthic cyanobacterial mats. SIGNIFICANCE AND IMPACT OF THE STUDY: Multiple benthic cyanobacterial mat samples must be collected at a sampling site to provide an accurate assessment of ATX and HTX concentrations at that location. The PCR-based technique offers the potential to be a useful early warning technique.

The effects of UVB radiation on temperate southern hemisphere forests.

The temperate forests of the southern hemisphere are the most likely forests to be affected by increased levels of ultraviolet-B (UVB) radiation resulting from reduced ozone. The review describes these forests and then discusses the morphological changes, physiological effects, and protection mechanisms, particularly UV absorbing compounds that result from present day and increasing UVB radiation. Possible avenues for future research are explored.

Flavonoids and UV photoprotection in Arabidopsis mutants.

Wild-type Arabidopsis L. leaves exposed to low ultraviolet-B (UVB) conditions contained predominantly kaempferol glycosides, with low levels of quercetin glycosides. The flavonoid level doubled on treatment with UVB and an increase in the ratio of quercetin: kaempferol was observed. These results suggest that flavonols protect Arabidopsis plants from UVB damage, and indicate that the flavonoid 3'-hydroxylase (F3'H) enzyme, which converts dihydrokaempferol to dihydroquercetin, may play a crucial role. The tt7 mutant lacks this gene and, after treatment with sub-ambient UVB, contained kaempferol glycosides exclusively, to a level of total flavonols similar to that in wild-type Arabidopsis. Total flavonols after enhanced UVB treatment were higher in tt7 than in similarly treated wild-type plants, and only kaempferol glycosides were detected. Despite this high level, tt7 plants were less tolerant of UVB radiation than wild-type plants. These observations suggests that kaempferol is a less effective photoprotectant than quercetin. The chalcone isomerase (CHI) mutant (tt5) surprisingly did not accumulate naringenin chalcone, and this suggests that the mutation may not be restricted to the CHI gene alone. The concentration of hydroxycinnamic acid derivatives did not change with UVB treatment in most varieties indicating that their role in UV photoprotection may be subordinate to that of the flavonoids.

Cytoplasmic accumulation of flavonoids in flower petals and its relevance to yellow flower colouration.

It is widely accepted that the mix of flavonoids in the cell vacuole is the source of flavonoid based petal colour, and that analysis of the petal extract reveals the nature and relative levels of vacuolar flavonoid pigments. However, it has recently been established with lisianthus flowers that some petal flavonoids can be excluded from the vacuolar mix through deposition in the cell wall or through complexation with proteins inside the vacuole, and that these flavonoids are not readily extractable. The present work demonstrates that flavonoids can also be compartmented within the cell cytoplasm. Using adaxial epidermal peels from the petals of lisianthus (Eustoma grandiflorum), Lathyrus chrysanthus and Dianthus caryophyllus, light and laser scanning confocal microscopy studies revealed a significant concentration of petal flavonoids in the cell cytoplasm of some tissues. With lisianthus, flavonoid analyses of isolated protoplasts and vacuoles were used to establish that ca 14% of petal flavonoids are located in the cytoplasm (cf. 30% in the cell wall and 56% in the vacuole). The cytoplasmic flavonoids are predominantly acylated glycosides (cf. non-acylated in the cell wall). Flavonoid aggregation on a cytoplasmic protein substrate provides a rational mechanism to account for how colourless flavonoid glycosides can produce yellow colouration in petals, and perhaps also in other plant parts. High vacuolar concentrations of such flavonoids are shown to be insufficient.

Cell wall sited flavonoids in lisianthus flower petals.

Flavonoids are considered to be located predominantly in the vacuoles of epidermal cells and in the cuticular wax of terrestrial plants. However, recent reports have suggested that flavonoids may also reside elsewhere in the cells of green leaves. In the present study of lisianthus flower petals, it is demonstrated that ca. 30% of the whole petal flavonol glycosides are located in the cell wall. These flavonol glycosides are distinguished from the vacuolar glycosides in that they lack acylation. Evidence from light and confocal microscopy studies is corroborated by HPLC analyses of isolated protoplasts and cell wall digests, these having been produced by enzymic treatment of epidermal peels. This is the first report of the occurrence of flavonoids in petal cell walls, and it describes novel methodology for such studies.

A small-scale outdoor plant growth chamber with modulated enhancement of solar UV-B radiation.

An outdoor, solar illuminated growth chamber with modulated UV-B enhancement, is described and its performance characterized. The chamber was clad with Teflon film that transmitted both UV-A and UV-B with little absorption and whose transmission did not change significantly over 1 yr. An array of UV-B emitting fluorescent tubes with cellulose diacetate filters provided additional UV-B radiation inside the chamber with little additional UV-A, while a similar chamber with unenergized tubes provided an ambient control. Ambient and enhanced UV-B levels were measured using a pair of integrating broad band radiometers, and it was found that frequency modulation allowed control of lamp intensity over a range in excess of 100:1. Within the UV-B chamber, enhanced levels of integrated UV-B could be maintained at a constant ratio over ambient throughout the day. However, it was not sufficient simply to maintain a constant ratio of radiometer output voltages: the angular responses of the two radiometers had to be well matched. The shape of the UV-B portion of the enhanced spectrum closely followed that expected under ozone depleted skies, while the enhancement of UV-A was insignificant. The spectral profile obtained in the UV-B depended on the thickness of the cellulose diacetate filters used to block short wavelength UV radiation emitted by the fluorescent tubes. The number (thickness) of cellulose diacetate filters required to achieve this match varied with season. Although the filters did degrade with exposure to UV-B it was not necessary to replace them for several months. This was due to: (i) low rate of filter degradation because the lamps were rarely required to be run at full brilliance except at midsummer midday; and (ii) increased tube intensity compensated for reduced filter transmission.

Erythemal ultraviolet insolation in New Zealand at solar zenith angles of 30 and 45..

Solar UV radiometers with spectral responsivities that are close to the erythemal/carcinogenic action spectrum of skin have been installed at several centers of population in New Zealand, including Auckland, 37 degrees S, Wellington, 41 degrees S and Christchurch, 43.5 degrees S. The data set covers the period from the time the radiometry program commenced in 1988/1989 to the end of the southern summer, March 1995. The radiometers were recalibrated annually and the data were corrected for changes in the absolute responsivity of the radiometers. Erythemally effective UV irradiances at solar zenith angles of 30 degrees and 45 degrees were then extracted from the data set. No monotonic trend in these data is apparent, although there are statistically significant differences in mean irradiances from one year to the next. An example of this is the decrease observed in all sites following the Mt. Pinatubo eruption in June 1991. The maximum erythemally effective insolations at solar zenith angles of 30 degrees and 45 degrees were consistently lower in Christchurch than in the other two New Zealand sites. This could arise from higher levels of atmospheric turbidity and/or tropospheric ozone at this location. Also, a seasonal increase in erythemally effective UV insolation from spring to autumn was observed each year in all three New Zealand sites.

Seasonal trends in erythemal and carcinogenic ultraviolet radiation at mid-southern latitudes 1989-1991.

A network of solar carcinogenic/erythemal ultraviolet radiometers has been established in New Zealand. Daily integrated irradiances of this biologically harmful ultraviolet radiation for 1989, 1990 and 1991 are reported from radiometers located at Wellington (41 degrees S) and Christchurch (43.5 degrees S) and for 1990 and 1991 from the Auckland (37 degrees S) radiometer. Although the monitoring program has not been running sufficiently long to discern any long-term changes in levels of solar ultraviolet radiation, shorter term trends are apparent, which are attributed to a seasonal cycle in levels of ozone at midlatitudes and changes in atmospheric aerosols.

Intraureteral tumor demonstrated by computed tomography.

Two cases of papillary carcinoma of the bladder are presented in which the ureter could not be demonstrated by standard radiographic techniques. Computed tomography (CT) allowed identification of the tumor filled ureter. Intraureteral papillary tumor has a radiographic density (CT number) above that of water but less than that of the enveloping ureter.

Pseudotumor of the kidney: a sequel to regional glomerulonephritis.

An unusual case of chronic renal failure associated with an abnormal intravenous urogram simulating renal neoplasm is discussed. Extensive radiographic and histologic studies support the contention that the observed mass lesion resulted from a segmental or regional compensatory hypertrophy. It is likely that this case represents a variant of unilateral glomerulonephritis with sparing of a segment or lobe of one kidney and subsequent hypertrophy of that segment as the remaining renal mass atrophied.

Posttraumatic renal artery stenosis. Cure of hypertension by late revascularization.

Renal artery stenosis causing hypertension may be the sequel of blunt nonpenetrating abdominal trauma. Early recognition of such renal artery injury is essential. In the case reported, late recognition of unilateral traumatic renal artery stenosis led to surgical correction of the lesion and lasting cure of hypertension.

Eosinophilic infiltration of duodenum and pancreatic head: report of a case studied arteriographically.

A case of tumorlike eosinophilic infiltration of the duodenum and pancreas is reported. Arteriography and hypotonic duodenography indicated a large lesion involving both the pancreatic head and the second portion of the duodenum without encasement or obstruction of the intrinsic vasculature. This is the first reported use of angiography in this condition. The combination of findings described should suggest a benign infiltrative process.