Changes in the surface morphology of the rabbit endometrium related to the estrous and progestational stages of the reproductive cycle

Summary Changes occurring on the surface of the uterine luminal epithelium of the rabbit during the estrous and progestational stages of the reproductive cycle were examined by scanning and transmission electron microscopy. The findings demonstrate that the uterine epithelium, or endometrium, contains two cell types: ciliated cells and nonciliated, microvillous cells. In estrous animals, ciliated cells, although not very numerous, were usually observed in small groups. However, at increasing intervals of time following mating, ciliated cells progressively disappeared from the endometrium until approximately eight to ten days post coitum, when they became scare. From several hours to four to five days following mating, extensive changes occurred on the surfaces of microvillous cells. When observed by TEM, these elements contained organelles typical of cells involved in the synthesis and secretion of glycoproteins. Furthermore, microvillous cells during this period displayed numerous apical protrusions of different sizes and shapes and containing material of varying electron density. Parallel SEM examinations of the same material confirmed the presence of these protrusions. Some of the protrusions appeared as spheroidal masses attached to the cytoplasm by means of a cytoplasmic strand. Other surface masses were clearly unattached to the cell surface and were distributed (1) on the surface of microvillous cells, (2) on the cilia of adjacent ciliated cells, and (3) on the surface of spermatozoa.Changes occurring on the luminal surface during the early postcoital period are interpreted as an expression of morphodynamic processes likely involving coupled secretion (exocytosis) and resorption (endocytosis) of luminal material. The observations presented here also demonstrate that between six and ten days post coitum, the rabbit endometrium contained increasing numbers of enlarged, nonciliated cells that probably arose by the fusion of smaller, microvillous elements.The work reported here was supported by C.N.R. contracts No. CT 760128809 and CT 77014239 (to P.M.) and NIH. Grant HD-04274 (to J.V.B.)     

Use of immunocytochemical staining of somatostatin for correlative light and electron microscopic investigation of D cells in the pancreatic islet of Xiphophorus helleri H. (Teleostei)

Summary Somatostatin-containing cells have been demonstrated by immunocytochemistry in semithin sections of the pancreatic islet of the teleost fish, Xiphophorus helleri. These cells were shown by correlative light and electron microscopy to be identical with D cells previously defined in this species by the silver impregnation method of Hellman and Hellerström.Supported in part by grants from the British Council and from the Medical Research Council of Great Britain     

Thermal denaturation of nucleosomal core particles.

Thermal denaturation of very homogeneous preparations of core particles from chicken erythrocyte chromatin is studied by several techniques. The change in absorbance, which is very closely paralleled by changes in heat capacity, which is very closely paralleled by changes in heat capacity, is a biphasic process with inflexions at 60 degrees C and 74 degrees C. In contrast, isolated DNA of the same length denatures in a single transition around 44 degrees C. Monitoring the circular dichroism of the cores during thermal denaturation reveals biphasic changes in the secondary structure of the DNA, preceding the base unstacking by 10 degrees C in the first and 3 degrees C in the second phase. However, measurable alterations in the secondary structure of the histones are confined to the second phase with a melting temperature at 71 degrees C. Increase in the ionic strength of the buffer from 1 mM to 10 mM leads to almost monophasic melting curves as measured by absorbance and CD, while not causing any measurable conformational changes at room temperature. The melting of core particles is interpreted as a denaturation of about 40 base pairs in the first phase, followed by a massive breakdown of the native structure of a tight histone-DNA complex, which frees the remaining 100 base pairs for unstacking.     

Sub-antarctic House mice: colonization, survival and selection

House mice have colonized and survived successfully on a number of Sub-Antarctic islands, where the mean annual temperature is only about 5°C, but where there is little seasonal fluctuation in climate. Surprisingly this allows almost continuous breeding. On at least two islands (Macquarie and Marion), there are significant changes in gene frequency in electro-phoretically detected enzymes between young (less than three months of age) and old animals from the same population. This indicates natural selection acting in opposite directions at different stages of the life cycle. However the genetical compositions of the Macquarie and Marion populations are more distinct from each other than either is from most British samples. This means that detailed studies of the Sub-Antarctic mouse populations are likely to reveal much about local adaptation, while comparison between the responses of different populations may lead to important generalisations about the possible reaction to evolutionary challenges of a species living close to its physiological limit.     

Cyclic nucleotide hydrolysis in the thyroid gland. General properties and key role in the interrelations between concentrations of adenosine 3':5'-monophosphate and guanosine 3':5'-monophosphate.

Phosphodiesterase activities of horse (and dog) thyroid soluble fraction were compared with either cyclic AMP (adenosine 3':3'-monophosphate) or cyclic GMP (guanosine 3':5'-monophosphate) as substrate. Optimal activity for cyclic AMP hydrolysis was observed at pH 8, and at pH 7.6 for cyclic GMP. Increasing concentrations of ethyleneglycol bis(2-aminoethyl)-N,N'-tetraacetic acid inhibited both phosphodiesterase activities; in the presence of exogenous Ca2+, this effect was shifted to higher concentrations of the chelator. In a dialysed supernatant preparation, Ca2+ had no significant stimulatory effect, but both Mg2+ and Mn2+ increased cyclic nucleotides breakdown. Mn2+ promoted the hydrolysis of cyclic AMP more effectively than that of cyclic GMP. For both substrates, substrate velocity curves exhibited a two-slope pattern in a Hofstee plot. Cyclic GMP stimulated cyclic AMP hydrolysis, both nucleotides being at micromolar concentrations. Conversely, at no concentration had cyclic AMP any stimulatory effect on cyclic GMP hydrolysis. 1-Methyl-3-isobutylxanthine and theophylline blocked the activation by cyclic GMP of cyclic GMP of cyclic AMP hydrolysis, whereas Ro 20-1724 (4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone), a non-methylxanthine inhibitor of phosphodiesterases, did not alter this effect. In dog thyroid slices, carbamoylcholine, which promotes an accumulation of cyclic GMP, inhibits the thyrotropin-induced increase in cyclic AMP. This inhibitory effect of carbamoylcholine was blocked by theophylline and 1-methyl-3-isobutylxanthine, but not by Ro 20-1724. It is suggested that the cholinergic inhibitory effect on cyclic AMP accumulation is mediated by cyclic GMP, through a direct activation of phosphodiesterase activity.     

The binding of carbon monoxide to cytochrome c oxidase.

The effect of CO on the optical absorbance spectrum of partially reduced cytochrome c oxidase has been studied. The changes at 432 and 590 nm suggest that the cytochrome alpha2/3+ - CO compound is formed preferentially and that concomitantly a second electron is taken up by the enzyme. From the CO-induced changes at 830 nm it is concluded that in the partially reduced enzyme addition of CO causes reoxidation of the copper component of cytochrome c oxidase. Addition of CO to partially reduced enzyme (2 electrons per 4 metal ions) also brings about a decrease in the intensities of electron paramagnetic resonance signals of high-spin heme iron near g = 6 and of the low-spin heme at g = 2.6. Concomitantly both the low-spin heme a signal at g = 3 and the copper signal at g = 2 increase in intensity. These results demonstrate that formation of the reduced diamagnetic cytochrome a3 - CO compound is accompanied by reoxidation of both the copper component detectable by electron paramagnetic resonance and possibly also by cytochrome a.     

Different types of mitochondria in parenchymal and non-parenchymal rat-liver cells.

1. Intact and pure parenchymal and non-parenchymal cells were isolated from rat liver. The specific activities of several mitochondrial enzymes were determined in both parenchymal and non-parenchymal cell homogenates to characterize the mitochondria in these liver cell types. 2.In general the activities of mitochondrial enzymes were lower in non-parenchymal liver cells than in parenchymal cells. The specific activity of pyruvate carboxylase in non-parenchymal cells expressed as the percentage of that in parenchymal cells was onlu 2% for glutamate dehydrogenase 4.3% and for cytochrome c oxidase 79.4%. Monoamine oxidase, as an exception, has an equal specific activity in both cell types. 3. The activity ratio of pyruvate carboxylase at 10 mM pyruvate over 0.1 mM pyruvate is 3.35 for parenchymal cells and 1.50 for non-parenchymal cells. This indicates that non-parenchymal liver cells only contain the high affinity form of pyruvate carboxylase in contrast to parenchymal cells. 4. The ratio of glycerol-3-phosphate cytochrome c reductase over succinate cytochrome c reductase activity differs from parenchymal (0.01) and non-parenchymal cells (0.10). This might indicate that the glycerol-3-phosphate shuttle, which is important for the transport of reduction equivalents for cytosol to mitochondria is relatively more active in non-parenchymal cells than in parenchymal cells. 5. The activity pattern of mitochondrial enzymes in parenchymal and non-parenchymal cell homogenates indicates that these cell types contain different types of mitochondria. The presence of these different cell types in liver will therefore contribute to the heterogeneity of isolated rat liver mitochondria in which the mitochondria from non-parenchymal cells might be considered as "non-gluconeogenic".     

Strain improvement inStreptomyces galilaeus,a producer of anthracycline antibiotics galirubins

The production of ε-pyrromycinone glycosides inStreptomyces galilaeus increased 12-fold, with respect to the wild strain, as a result of a sequential procedure including both natural selection and treatment with mutagens (nitrous acid, UV light and γ-irradiation). Nitrous acid exhibited the highest mutagenic effect, both in increasing the productivity and in inducing blocked mutants. A mutant strain blocked in the biosynthesis of glycosides and accumulating free ε-pyrromycinone as the principal metabolite was obtained.