The alpha- and the beta-tubulin genes of the hypotrichous ciliate Euplotes octocarinatus were isolated from a size-selected macronuclear DNA library. The alpha-tubulin gene is located on a 1,587 bp macronuclear DNA molecule and the beta-tubulin gene on a 1,524 bp macronuclear DNA molecule. Sequencing revealed that all the cysteine residues of the two genes are encoded by the common cysteine codons UGU and UGC and none by an UGA codon. This is in contrast to the genes of E. octocarinatus sequenced so far, where some of the cysteines are encoded by the opal codon UGA. The tubulin genes end like other Euplotes genes with a TAA. They do not contain introns. The last codon for an amino acid in the alpha-tubulin gene is a GAA which codes for glutamic acid. This is in contrast to what has been reported for most alpha-tubulin genes, but it supports for other hypotrichous ciliates. No evidence for the existence of more than one type of alpha- and one type of beta-tubulin genes could be obtained.

Amino Acid Sequence↗

PubMedDate not supplied

Molecular characterization of the D surface protein gene subfamily in Paramecium tetraurelia.

When Paramecium tetraurelia expresses the D serotype, detectable by serum tests, high molecular mRNA could be isolated, which corresponds to the molecular mass of the D surface protein. Using this D specific mRNA as a probe for screenings in different genomic libraries a subfamily of five very similar genes was found, named alpha-51D, gamma 1-51D, gamma 2-51D, delta-51D, and epsilon-51D. Each of them is about 8-kb long, they show regions of identity to each other, and there is no evidence that any are defective genes or pseudogenes. Up to now serotype D is the only known serotype showing this phenomenon. Another novel feature is that two of the D isogenes are closely linked. The sequence for the entire coding region of the alpha-51D gene has been determined, as well as the upstream and downstream noncoding regions. Its deduced amino acid sequence shows the same characteristic cysteine periodicity displayed by all other immobilization antigen (i-ag) genes from Paramecium. However, in contrast to most other such genes, tandem repeats are missing from the 7599-bp long coding region of the alpha-51D gene. When the sequences of the type 51D genes are compared to each other, the similarity is very high and extends to coding as well as to noncoding regions. Similarity within noncoding regions is usually only observed for allelic i-ag genes. We conclude that the type D genes constitute a family of isogenes that are nonallelic. They contain slightly different consensus sequences with possible functions as regulatory regions.

Amino Acid Sequence↗

PubMedDate not supplied

Is oxygen consumption of surviving tissues determined by the oxygen tension of the suspension medium?

Oxygen tension in the suspension medium and oxygen uptake of the isolated diaphragm of the mouse have been determined simultaneously with systematic variation of shaking frequency and oxygen concentration of the gas phase. Oxygen tension in the suspension medium reaches its final value during the usual equilibration period of 10 minutes and remains constant for the whole measuring period. Each combination of shaking frequency and oxygen concentration of the gas phase results in a reproducible value of oxygen tension in the medium. Equal oxygen tension in the fluid phase can be attained by different combinations of shaking frequency and oxygen concentration of the gas phase. Oxygen uptake at the same oxygen tension of the suspension medium can be very different; it is the higher the higher the shaking rate in the combination. On the other hand the same oxygen consumption of the tissue samples can be observed with highly different oxygen tensions in the medium. It must be concluded from the data in this paper, that the influence of shaking rate per se on the oxygen uptake of isolated tissue can be of the same order as the influence of oxygen tension.

Animals↗

PubMedDate not supplied

Effect of mechanical traumatization on rate and constancy of oxygen uptake of isolated diaphragms.

Diaphragms of mice were traumatized by division parallel or transversally to the muscle fibres. The extent of traumatization was varied by the degree of subdivision. Oxygen uptake was measured by the Warburg technique. Undivided diaphragms as control displayed constant oxygen uptake for the four hours of observation. With divided diaphragms oxygen uptake was unstable. Division parallel to the muscle fibres resulted in continuous decrease of oxygen uptake after a normal initial phase; the decline was significantly steeper was increasing extent of traumatization. Division transversally to the muscle fibres resulted in an initial increase of oxygen uptake followed in a second phase by a continuous decrease. The initial increase as well as the final decrease of oxygen uptake was more pronounced with higher extent of subdivision.

Animals↗

PubMedDate not supplied

[The influence of mode and intensity of homogenization on the absolute value and stability of oxygen consumption of guinea pig liver homogenates (author's transl)].

The influence of five different methods of homogenisation (1. The method according to Potter and Elvehjem, 2. A modification of this method called Potter S, 3. The method of Dounce, 4. Homogenisation by hypersonic waves and 5. Coarce-grained homogenisation with the "Mikrofleischwolf") on the absolute value and stability of oxygen uptake of guinea pig liver homogenates has been investigated in simultaneous measurements. All homogenates showed a characteristic fall of oxygen uptake during measuring time (3 hours). The modified method according to Potter and Elvehjem called Potter S showed reproducible results without any influence by homogenisation intensity.

Animals↗

PubMedDate not supplied

[Circadian rhythm of metabolic rate in isolated tissue (author's transl)].

The circadian variation of oxygen uptake of isolated mouse diaphragm has been measured by means of the direct Warburg-technique in two series with sets of each 8 successive experiments. Under our experimental conditions oxygen uptake in the isolated diaphragm remains constant for 5 hours at least. The 24-hour period could therefore be completed with 8 single measurements of each 10--20 isolated diaphragms started at 3 h intervals with a overlap in experimental time of 2 h hours between each single experiment. Similar to the results concerning the spontaneous locomotive activity of the mouse (ASCHOFF 1955) we found maximum values of metabolic rate during the night, minimum values during day time and a interpolated relative maximum of oxygen uptake between 6(00)--8(00) h. Oxygen uptake after the stabilisation period of approximately 1 h seems to be determined by the time of the death of the animal.

Animals↗