Incubation

About: Incubation is a research topic. Over the lifetime, 5748 publications have been published within this topic receiving 126541 citations.

Why Some Birds Take so Long to Hatch

Abstract: In general, incubation periods of bird eggs are positively correlated with egg weights. The eggs of some birds take much longer to hatch than expected. Highly variable and long incubation periods are explained using fork-tailed storm petrels as an example. Their eggs take two to three times as long to hatch as eggs of similar size. Egg neglect causes the extreme variability in incubation periods within a species. Low incubation temperatures prolong incubation, but long incubation periods may also be a result of selective forces that favor hatching well-developed young that can be attended infrequently. Past terminology has obscured the importance of the relationship between incubation periods and the maturity of chicks at hatching. Selection has produced a continuum between cheap eggs and expensive care for the relatively helpless (altricial) young or expensive eggs and inexpensive care for the relatively independent (precocial) young. The distant foraging habits of the Procellariiformes have favored inde...

Comparative mutagenicity of N-nitrosamines in a semi-solid and in a liquid incubation system in the presence of rat or human tissue fractions.

Abstract: The rat liver microsome-mediated mutagenicities of a series of N-nitrosodialkylamines and heterocyclic N-nitrosamines were determined in a liquid incubation system using Salmonella typhimurium TA1530. The influence on mutation frequency of the concentration of co-factors for mixed-function oxidase and composition and molarity of the buffer was investigated, using N-nitrosomorpholine as substrate. The mutagenicity of the N-nitroso compounds in the liquid incubation system under optimal reaction conditions at equimolar concentration was compared quantitatively with that obtained in a soft-agar incorporation assay. N-Nitrosodi-n-pentylamine and N-nitrosodi-n-butylamine showed no enzyme-mediated mutagenicity in the liquid incubation system, and metabolically activated N-nitroso-dimethylamine and N-nitroso-diethylamine showed negligible mutagenic activity in the soft-agar assays. In contrast with these results with the N-nitrosodialkylamines, the mutagenic effects of heterocyclic N-nitrosamines were similar in the liquid incubation system and in soft-agar incorporation assays. The heterocyclic N-nitrosamines showed rat-liver microsome-mediated mutagenicity in the following descending order: N-nitrosomorpholine greater than N-nitrosopyrrolidine greater than N-nitrosopiperidine greater than N-nitroso-N'-methylpiperazine. Seven human liver specimens converted all heterocyclic N-nitrosamines into mutagens; this activity was similar to that of rat liver, except that for N-nitroso-N'-methylpiperazine, fractions from three human liver biopsies were three to 30 times more active than those from untreated rats. The specific reversion of S. typhimurium TA1530 to histidine prototrophy provides experimental evidence that all the N-nitrosamines studied were converted by liver microsomal enzymes into monofunctional alkylating agents.

Low temperature induced non-culturability and killing of Vibrio vulnificus

Abstract: Vibrio vulnificus cells progressively lose culturability during incubation at 5°C. This process is accelerated by the addition of supernatants from non-culturable cells obtained by incubation at 5°C for 17 days. Thus the organism apparently produces a factor upon cold incubation which is triggering or causing the decline in culturability. Reversing the temperature shift can restore a culturable population comparable in numbers to the original population, but this process is largely due to regrowth. A few cells retaining the ability to grow apparently utilize the substrates released by the moribund cells, thus mimicking resuscitation of the whole population.

Studies on aggregate stability. I. Re‐formation of soil aggregates

Abstract: SUMMARY When natural soil aggregates were destroyed by crushing, techniques traditionally used for re-forming aggregates, such as wetting/drying and freezing/thawing cycles, did not produce any stable re-formed aggregates. Incubation without amendment, was similarly unsuccessful, whereas incubation with glucose amendment did produce stable aggregates, and their stability was related both to the natural soil organic matter levels and to the original stability of the natural aggregates. However, the stability induced by incubation with glucose was of a transient nature and declined over a period of 12 weeks. This behaviour was attributed to the production of microbial, extracellular polysaccharides and their subsequent decomposition. Addition of microbial polysaccharides of known structure confirmed that such polymers were capable of producing stable re-formed aggregates without the assistance of further microbial activity. Longer term incubation showed that the stability of the re-formed aggregates also declined as soil micro-organisms broke down the polysaccharide material. Neither the glucose incubation nor addition of extracellular polysaccharide was very successful in producing stable aggregates when used with soil which had been washed with salt solutions, and dialysed, to form mono-ionic soils.