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PubMed1988

Distribution of sarcoplasmic reticulum Ca-ATPase and of calsequestrin at the polar regions of rat, rabbit and cat intrafusal fibers.

Sarcoplasmic reticulum (SR) Ca2+-pumping ATPase (Ca-ATPase) and calsequestrin (CaS) were visualized by indirect immunofluorescence at the polar regions of adult rat, rabbit and cat intrafusal fibers. The immunohistochemical reaction products were regarded as histochemical markers of the SR and as valid indicators of the distribution of the two Ca2+-sequestering proteins. Static nuclear bag2 fibers displayed lower levels of both Ca-ATPase and CaS than the other two intrafusal fiber types. Nuclear chain fibers presented the highest Ca-ATPase levels and, together with dynamic nuclear bag1 fibers, they also exhibited relatively high amounts of CaS. The level of Ca-ATPase was lower in bag 1 fibers than in nuclear chain fibers, but not as low as in bag2 fibers. The comparatively high levels of Ca-ATPase and CaS seen in nuclear chain fibers coincided with their reported faster contractile speeds compared to nuclear bag fibers.

Animals↗
PubMedDate not supplied

[Spectral properties of the green alga Trebouxia--a phycobiont of cryptoendolithic lichens in the high-latitude polar regions of Antarctica].

An algologically pure culture of the green alga Trebouxia, a phycobiont of cryptoendolithic lichens, was isolated from the sandstone samples collected in the high-altitude polar regions of Antarctica. The absorption and the second-derivative absorption spectra of the acetone extract of the Antarctic phycobiont cells were studied in comparison with those of the Trebouxia phycobiont isolated recently from the Parmeliaceae lichen in the Mid-European climatic zone. The cells of the Antarctic phycobiont were characterized by a lower content of chlorophyll a and a higher ratio of chlorophyll b and carotenoids to chlorophyll a as compared to the Mid-European phycobiont. Furthermore, the carotenoids of the Antarctic phycobiont were more diverse. The low-temperature fluorescence spectra of the Antarctic phycobiont were characterized by an increased intensity of the short-wavelength fluorescence peak of chlorophyll a and a diminished intensity of fluorescence in the long-wavelength spectral region.

Antarctic Regions↗
PubMed1981

Pattern formation along the anteroposterior axis of the chick wing: the increase in width following a polarizing region graft and the effect of X-irradiation.

A study is made of the widening of the chick limb bud that occurs after a graft of an additional polarizing region. Such buds are about 50% wider than controls, after 36 h. By contrast, growth along the proximodistal axis in unaffected. This widening is reduced by treating the host embryo with 10 Gy X-irradiation and the altered pattern of digits is consistent with a diffusible morphogen model for the specification of positional information along the anteroposterior axis.

Animals↗
PubMed1994

[An information model of the adaptation process in sailors under the conditions of the polar regions on the Kola Peninsula].

On the basis of information concept an attempt to create a model of adaptation process was made with the purpose of revealing the general features of man's adaptation for the conditions of the Kola [correction of Kolsk] Peninsula polar region. In the authors' opinion it is necessary to study this problem from the point of view of thermodynamic approaches. The model obtained in the result of studies reflects the process of adaptation and gives the possibility to prognosticate the health status of sailors depending on their "polar continuous service".

Adaptation, Physiological↗
PubMed1998

[A case of ill-defined vitiliginous lesions in the posterior polar regions of both eyes].

In a 34-year-old man, who was examined for binocular visual disturbance as chief complaint at the department of ophthalmology, we found ill-defined vitiliginous lesions of a size about 1/5 approximately 1/7 the diameter of the papilla in the fundal posterior polar regions of both eyes. Fluorescein angiography (FA) revealed hyperfluorescence of the vitiligo. Blood tests showed increased herpes simplex and herpes zoster varicellosus antibody titers and positive antinuclear antibodies (spekled type). Following steroid treatment, the vitiligo remitted, but reappeared later. Indocyanine green infrared fluorescein angiography (IA) revealed hyperfluorescence of the vitiligo. Fundus findings suggested multiple evanescent white dot syndrome (MEWDS), but were judged to be negative because 1. the vitiliginous lesions were morphologically different; 2. the onset site of the vitiligo was more posterior and polar-sided, 3. onset of the vitiligo was binocular, 4. the vitiligo recurred and 5. late hypofluorescence was not observed in IA.

Adult↗
PubMedDate not supplied

[The absorption and fluorescence spectra of the cyanobacterial phycobilins of cryptoendolithic lichens in the high-polar region of Antarctica].

The algologically pure cultures of the green-brown cyanobacterium Chroococcidiopsis sp. and three cyanobacteria of the genus Gloeocapsa, the blue-green Gloeocapsa sp.1, the brown Gloeocapsa sp.2, and the red-orange Gloeocapsa sp.3, were isolated from sandstones and rock fissures in the high-polar regions of Antarctica. These cyanobacteria are the most widespread phycobionts of cryptoendolithic lichens in these regions. The comparative analysis of the absorption and the second-derivative absorption spectra of the cyanobacteria revealed considerable differences in the content of chlorophyll a and in the content and composition of carotenoids and phycobiliproteins. In addition to phycocyanin, allophycocyanin, and allophycocyanin B, which were present in all of the cyanobacteria studied, Gloeocapsa sp.2 also contained phycoerythrocyanin and Gloeocapsa sp.3 phycoerythrocyanin and C-phycoerythrin (the latter pigment is typical of nitrogen-fixing cyanobacteria). The fluorescence spectra of Gloeocapsa sp.2 and Gloeocapsa sp.3 considerably differed from the fluorescence spectra of the other cyanobacteria as well. The data obtained suggest that various zones of the lichens may be dominated either by photoheterotrophic or photoautotrophic cyanobacterial phycobionts, which differ in the content and composition of photosynthetic pigments.

Antarctic Regions↗
PubMed2002

Psychrophiles and polar regions.

Most reviews of microbial life in cold environments begin with a lament of how little is known about the psychrophilic (cold-loving) inhabitants or their specific adaptations to the cold. This situation is changing, as research becomes better focused by new molecular genetic (and other) approaches, by awareness of accelerated environmental change in polar regions, and by strong interest in the habitability of frozen environments elsewhere in the solar system. This review highlights recent discoveries in molecular adaptation, biodiversity and microbial dynamics in the cold, along with the concept of eutectophiles, organisms living at the critical interface inherent to the phase change of water to ice.

Adaptation, Physiological↗
PubMedDate not supplied

A conserved polar region in the cell division site determinant MinD is required for responding to MinE-induced oscillation but not for localization within coiled arrays.

A region in the cell division site determinant MinD required for stimulation by MinE and which determines MinD topological specificity along coil-like structures has been identified. Structural modeling of dimeric MinD and sequence alignment of 24 MinD proteins revealed a conserved polar region in Gram-negative bacterial MinD proteins, corresponding to residues 92-94 of Neisseria gonorrhoeae MinD (MinD(Ng)). Using MinD(Ng) as a paradigm for MinD functionality in Gram-negative organisms, mutation of these conserved residues did not abrogate MinD(Ng) self-association, nor its interaction with MinE(Ng) and the cell division inhibitor MinC. Although the MinD(Ng) mutant dimerized in the presence of ATP, its ATPase activity was not stimulated by MinE(Ng), unlike wild-type MinD(Ng). GFP fusions to either MinD(Ng) or to Escherichia coli MinD bearing simultaneous or individual mutations to residues 92-94 localized within coiled arrays along the E. coli inner cell periphery, similar to wild-type GFP-MinD. However, unlike wild-type GFP-fusions, the mutant proteins were distributed uniformly throughout the array, despite the presence of MinE, which normally imparts topological specificity to MinD by inducing the latter to oscillate from pole-to-pole and away from midcell. Hence, despite localizing along the inner cell periphery as a polymeric structure, the mutant MinD proteins in this study have lost the ability to be efficiently stimulated by MinE(Ng), resulting in a loss of distinct pole-to-pole oscillation.

Adenosine Triphosphatases↗
PubMed1980

Human-specific nuclear protein that associates with the polar region of the mitotic apparatus: distribution in a human/hamster hybrid cell.

We describe the first example of a predominantly nuclear protein which during mitosis becomes part of the mitotic apparatus. This protein has been termed the nuclear-mitotic apparatus (NuMA) protein. In interphase cells NuMA protein is restricted to the nucleus and is a constituent of isolated nuclear matrices, but in mitotic cells it is observed by indirect immunofluorescence microscopy to be concentrated at the polar regions of the mitotic apparatus. This mitotic localization is dependent on the integrity of the spindle, since treatments which disrupt the spindle result in dispersion of NuMA protein throughout the cell. Comparison to the subcellar distribution of tubulin at different stages of the cell cycle indicates that NuMA protein is distinct from the previously identified components of the mitotic spindle. Its association with the nuclear matrix and its localization during mitosis to the site of nuclear reassembly suggest the interesting possibility that NuMA protein could be representative of a class of proteins involved in the early events of nuclear reassembly. NuMA is present in the nuclei and mitotic spindle of all types of human cells that have been examined, but proteins of similar molecular weight (300,000 daltons in dissociating solvents) or immunological specificity are not detected in cells of other species (including monkey). However, the NuMA protein is synthesized in a human/Chinese hamster hybrid cell containing a reduced number of human chromosomes. Immunofluorescence studies of this hybrid cell showed that the distribution of NuMA protein is equivalent to that in human cells. These results suggest that the human gene coding for NuMA protein, unlike other genes coding for human specific nuclear proteins, can be expressed in human/hamster hybrid cells and that the cell hybrids will be useful in further characterization of NuMA protein.

Animals↗
PubMed1997

The Drosophila gene abnormal spindle encodes a novel microtubule-associated protein that associates with the polar regions of the mitotic spindle.

abnormal spindle, a gene required for normal spindle structure and function in Drosophila melanogaster, lies immediately adjacent the gene tolloid at 96A/B. It encodes a 220-kD polypeptide with a predicted pI of 10.8. The recessive mutant allele asp1 directs the synthesis of a COOH terminally truncated or internally deleted peptide of approximately 124 kD. Wild-type Asp protein copurifies with microtubules and is not released by salt concentrations known to dissociate most other microtubule-associated proteins. The bacterially expressed NH2-terminal 512-amino acid peptide, which has a number of potential phosphorylation sites for p34(cdc2) and MAP kinases, strongly binds to microtubules. The central 579-amino acid segment of the molecule contains one short motif homologous to sequences in a number of actin bundling proteins and a second motif present at the calmodulin binding sites of several proteins. Immunofluorescence studies show that the wild-type Asp protein is localized to the polar regions of the spindle immediately surrounding the centrosome. These findings are discussed in relation to the known spindle abnormalities in asp mutants.

Amino Acid Sequence↗
PubMed2000

Cholesterol effects on the phosphatidylcholine bilayer polar region: a molecular simulation study.

A molecular dynamics (MD) simulation of a fully hydrated, liquid-crystalline dimyristoylphosphatidylcholine (DMPC)-Chol bilayer membrane containing approximately 22 mol% Chol was carried out for 4.3 ns. The bilayer reached thermal equilibrium after 2.3 ns of MD simulation. A 2.0-ns trajectory generated during 2.3-4.3 ns of MD simulation was used for analyses to determine the effects of Chol on the membrane/water interfacial region. In this region, 70% of Chol molecules are linked to DMPC molecules via short-distance interactions, where the Chol hydroxyl group (OH-Chol) is 1) charge paired to methyl groups of the DMPC choline moiety ( approximately 34%), via the hydroxyl oxygen atom (Och); 2) water bridged to carbonyl ( approximately 19%) and nonester phosphate ( approximately 14%) oxygen atoms, via both Och and the hydroxyl hydrogen atom (Hch); and 3) directly hydrogen (H) bonded to carbonyl ( approximately 11%) and nonester phosphate ( approximately 5%) oxygen atoms, via Hch ( approximately 17% of DMPC-Chol links are multiple). DMPC's gamma-chain carbonyl oxygen atom is involved in 44% of water bridges and 51% of direct H bonds formed between DMPC and Chol. On average, a Chol molecule forms 0.9 links with DMPC molecules, while a DMPC molecule forms 2.2 and 0.3 links with DMPC and Chol molecules, respectively. OH-Chol makes hydrogen bonds with 1.1 water molecules, preferentially via Hch. The average number of water molecules H bonded to the DMPC headgroup is increased by 7% in the presence of Chol. These results indicate that inclusion of Chol decreases interlipid links and increases hydration in the polar region of the membrane.

Cholesterol↗
PubMed1993

Cooperative activation of Chox-4 homeobox genes by factors from the polarizing region and the apical ridge in chick limb morphogenesis.

When a mouse zone of polarizing activity (ZPA) at the posterior margin of the limb bud was grafted at the anterior margin of the chick limb bud, we found that expression of the chick homeobox genes, Chox-4.7 and -4.8, was induced prior to the formation of chick extra digits. The induction was observed in the restricted domain close to both grafted mouse ZPA and the chick apical ectodermal ridge (AER). When the posterior half of the AER was removed, the normal expression was diminished in the posterodistal region. Thus, it is likely that at least two distinct factors, one from the ZPA and the other from the AER, provide positional information to induce cooperatively the sequential expression of the Chox-4 genes.

Animals↗
PubMed1989

Cellular contribution to symmetrical forelimbs from triploid-marked "polarizing region" in the embryo of axolotl, Ambystoma mexicanum.

Grafts of posterior tissue placed anterior to the limb bud in the salamander embryo exert a polarizing influence. To explain this result, the idea that the anteroposterior axis of the developing forelimb is polarized by a diffusible morphogen has been proposed. An alternative hypothesis, and the working hypothesis of the present study, is that the polarization of the developing salamander forelimb is accomplished by short-range cellular interactions resulting in intercalation rather than by the more global influence of a diffusible morphogen. One prediction of this intercalation hypothesis is that cells will be contributed to the limb from the "polarizing tissue." To test this idea, grafts of triploid marked polarizing tissue were implanted anterior to the limb bud in 82 diploid axolotl embryos at stages 32-34 of development. A total of 27 (33%) of the limbs that resulted were symmetrical and ranged in complexity from one to seven digits. Histological analysis of a subgroup of the original symmetrical limbs revealed that mesodermally derived tissues in the anterior side of these limbs (the side which formed as a duplication in response to the influence of the graft) contained high percentages of trinucleolate cells (muscle, 12.1%; connective tissue tissue, 12.5%; and cartilage, 13.4%) when compared to similar tissues in the posterior side of the same symmetrical limbs (muscle, 1.8%; connective tissue , 0.7%; and cartilage, 0.6%). When symmetrical limbs were amputated, 73% regenerated symmetrical limbs. When these regenerated limbs were again amputated, 63% formed symmetrical secondary regenerates. Histological analysis of the first generation of regenerated limbs revealed that the pattern of distribution of trinucleolate cells in each regenerate was similar to the pattern seen in the original symmetrical limb. These results indicate that there is considerable cellular contribution to the anterior side of the symmetrical forelimb from the mesoderm of grafted "polarizing tissue." This result supports the idea that short-range cellular interaction are sufficient for formation of symmetrical forelimbs in salamander embryos.

Ambystoma↗