Characterization of cytoplasmic male sterility in Petunia hybrida and Zea mays. Localization and activity of cytochrome c oxidase

Summary Anthers of male fertile, cytoplasmic male sterile (cms), and restored male fertile Petunia hybrida, are analyzed for cytochrome c oxidase (cox) activity in subsequent stages of microsporogenesis, and compared with anthers of male fertile, cms-S and cms-C Zea mays. The cox activity is determined in anther extracts and cytochemically. In petunia anthers, the first differences in cox activity occur from meiosis onward. However, at these stages, the initial symptoms of degeneration are already apparent. It is suggested that the decline in enzyme activity of the cms petunia anthers is the result rather than the cause of the non-formation of functional pollen.In maize anthers, the cox activity of sterile-type anthers is reduced in comparison with fertile-type anthers from premeiosis onward. There are also consistent cytochemical differences in the mitochondrial organization of cox activity between pollen of cms-S and male ferile maize anthers. In fertile-type mitochondria, the DAB reaction product indicating cox activity is localized in the cristae and within the space between the outer and inner limiting membranes of the organelles. In mitochondria of pollen of cms-S maize, cox activity is only observed between the outer and inner membranes of the mitochondria. The biochemical and cytochemical differences are observed at stages of development at which no structural signs of degeneration are apparent. The results suggest that cms in maize correlates with deviations in cytochrome c oxidase activity.Abbreviations cox cytochrome c oxidase - DAB 3,3-diaminobenzidine     

Characterization of cytoplasmic male sterility in Petunia hybrida. I. Localization,composition and activity of esterases

Summary Anthers of male fertile, cytosterile and restored male fertile clones of Petunia hybrida were compared for esterase activity and composition in subsequent stages of microsporogenesis. Three methods were applied (i) ultra-thin layer isoelectric focussing on polyacryl amide gels, (ii) quantitative spectrophotometrical assay, (iii) histochemical determination of total esterase activity associated to the azo-coupling method (Pearse, 1972).In male fertile and restorer idiotypes the isozyme patterns were quite similar. Both the number and intensity of bands increased gradually till the tetrad stage. In contrast, esterase activity in cytosterile anthers remained at a low level and hardy any new bands showed up in later stages. This unvariable, low activity level in cytosterile anthers was also found in the spectrophotometric assay. Histochemical determinations revealed that in male fertile anthers esterase activity is concentrated in the outer tapetal layer at late prophase and that it accumulates there till the early microspore stage. In male sterile anthers esterase accumulation in the tapetal cells stops at the moment that tapetal breakdown becomes visible. This suggests that differences in esterase activity and composition are an effect rather than a cause of the failing pollen formation.     

Damming insights: Variable impacts and implications of river regulation on platypus populations

1. River regulation has extensively changed the ecology and hydrology of rivers worldwide, particularly downstream of dams, affecting the viability of freshwater species. The platypus (Ornithorhynchus anatinus) is a semiaquatic monotreme, endemic to eastern Australia, with a distribution overlapping Australia’s most regulated rivers.
2. Dams and changes to flow regimes have affected critical platypus habitat, yet our understanding of the impacts of these threatening processes on platypus ecology remains poor. Over a period of 3 years (2016–2018), platypuses were surveyed across three regions (Upper Murray, Snowy, and Border river regions), above and below large dams, and in adjacent unregulated rivers, comparing captures, demographics, abundances, and densities. We hypothesized that platypus captures and abundances would be lower downstream of dams, owing to altered flow regimes that have secondary impacts on the demographics of these populations.
3. In the Upper Murray Rivers region, captures were significantly lower in the Mitta Mitta River below Dartmouth Dam, compared with captures upstream of the dam and the unregulated Ovens River, probably reflecting significant alteration to the seasonality and temperature of flows caused by the dam. Conversely, there were no significant differences in captures or abundance and density estimates above and below the dams in the Snowy or Border river regions, where the extent of regulation was less severe, probably as a result of restoration efforts in recent years on some rivers.
4. Low proportions of juveniles on the Snowy River and Mitta Mitta River downstream of the dams, compared with upstream, raises concerns of other impacts of altered flow regimes to platypus breeding success and juvenile survival, given the sensitivity of juveniles to unseasonably high flows.
5. The results highlighted the potential impact of river regulation, with direct implications for the management of regulated rivers, providing opportunities to mitigate impacts through improved management of the seasonality and temperature of flows, to the benefit of platypuses and other freshwater species.

     

Alpha-chloralose poisoning in dogs and cats: a retrospective study of 33 canine and 13 feline confirmed cases

Alpha-chloralose (AC) is an anaesthetic compound also used as a rodenticide, and has dose-dependent central nervous system mixed effects of excitation and depression. The objectives of this study were to detail the clinical and clinicopathological characteristics, as well as the treatment and prognosis, of AC toxicosis in dogs and cats. Medical records were retrospectively reviewed for AC poisoning between the years 1989 and 2004, and 33 dogs and 13 cats were included in the study. The most common clinical signs were seizures, muscle tremor, hyperaesthesia, hypothermia, salivation, myosis, stupor, coma and ataxia. Coma was more common, while salivation and ataxia were less common in cats compared to dogs. Although hypothermia was very common, especially in cats (90.9%), hyperthermia was frequently observed in dogs (21%). Treatment in all patients was supportive and symptomatic, and the most commonly used anticonvulsants were diazepam and barbiturates; however, severe unresponsive seizures in three dogs had to be controlled with inhalant gas anaesthesia. The hospitalisation period was 1-3 days, and the overall mortality rate was 6.5%. Alpha-chloralose poisoning seems to have a favourable prognosis in dogs and cats.