“Calcium receptors” on eukaryotic cells with special reference to the osteoclast

There is a growing list of cells that are capable of detecting and responding to changes in the concentration of extracellular calcium. The two classic examples of this behaviour are the calcitonin-secreting parafollicular cells of the thyroid and parathyroid hormone-secreting chief cells of the parathyroid gland. A more recent addition to this list is the renin-secreting juxtaglomerular cell of the kidney. Particularly intriguing has been independently the discovery by two laboratories, that the resorptive cell of bone, the osteoclast, is capable of detecting changes in ambient calcium. A common theme amongst all these so called calcium-responsive cells is that extracellular calcium increases elevate intracellular calcium levels, and this intracellular signal is either stimulatory or inhibitory to the functional response. But how these cells detect changes in the concentration of extracellular calcium, and how these recognition events are subsequently transformed into intracellular signals that regulate cell function are somewhat less clear. The commentary reveals some recent developments that seemingly provide insights into these mechanisms, with special reference to the osteoclast.     

A study of normal and regenerative growth in the pistol-crab,alpheus dentipes (Guèr.), with special reference to the phenomenon of chela reversal

Summary An analysis has been made of the normal growth of the thoracic appendages in the pistol-crab,Alpheus dentipes. The chelae are the only asymmetrical appendages and, within an extensive size range, the growth-coefficient of the large chela (crusher) is smaller than that of the small chela (nipper), even in the most rapidly growing dimensions of the segment containing the growth-centre.The partition coefficient for growth in certain dimensions of the chelae is not constant but is reduced progressively during the growthperiod, due (it is suggested) to the impracticability of maintaining the intensive heterogony developed during the early stages of growth.Regenerative growth of the chelae has been studied quantitatively after autotomy of one, the other, or both normal chelae, effected once only or repeatedly as new chelae appeared at moulting. New chelae are regenerated repeatedly with little or no waning of growth intensity but in continuously growing chelae, growth intensity is substantially reduced at the end of the instar of autotomy. The amount of growth is not correlated with thenumber of days available for regeneration. When both chelae regenerate simultaneously the larger one grows relatively slower than the smaller one to the end of the instar of autotomy but afterwards this condition is reversed. When the nipper alone is autotomised, growth of the crusher is inhibited and shrinkage may occur. Crusher autotomy, on the other hand, stimulates nipper growth and to an extent which varies with the dimension.The problem of chela reversal has been discussed and certain suggestions have been preferred.     

Chemistry and biology of reactive species with special reference to the antioxidative defence status in pancreatic β-cells

BackgroundDiabetes mellitus is a serious metabolic disease. Dysfunction and subsequent loss of the β-cells in the islets of Langerhans through apoptosis ultimately cause a life-threatening insulin deficiency. The underlying reason for the particular vulnerability of the β-cells is an extraordinary sensitivity to the toxicity of reactive oxygen and nitrogen species (ROS and RNS) due to its low antioxidative defense status.Scope reviewThis review considers the different aspects of the chemistry and biology of the biologically most important reactive species and their chemico-biological interactions in the β-cell toxicity of proinflammatory cytokines in type 1 diabetes and of lipotoxicity in type 2 diabetes development.Major conclusionThe weak antioxidative defense equipment in the different subcellular organelles makes the β-cells particularly vulnerable and prone to mitochondrial, peroxisomal and ER stress.Looking upon the enzyme deficiencies which are responsible for the low antioxidative defense status of the pancreatic β-cells it is the lack of enzymatic capacity for H₂O₂ inactivation at all major subcellular sites.General significanceDiabetes is the most prevalent metabolic disorder with a steadily increasing incidence of both type 1 and type 2 diabetes worldwide. The weak protection of the pancreatic β-cells against oxidative stress is a major reason for their particular vulnerability. Thus, careful protection of the β-cells is required for prevention of the disease.     

Maternal age and trisomy – a unifying mechanism of formation

The mechanism of trisomy formation and its relationship to increased maternal age is not understood. Molecular analysis of the pattern of inheritance of DNA markers in trisomy families shows trisomies can be grouped according to whether the affected chromosomes inherited from their mothers are heterozygous or homozygous with respect to the centromeres. Furthermore, molecular analysis reveals that those that are heterozygous have fewer chiasmata, which are located more distally, while those that are homozygous have more chiasmata proximally located. Cytogenetic analysis of human oocytes shows that the kind of imbalance predicted by the classic hypothesis of nondisjunction, i.e. extra whole chromosomes at the second metaphase, is rarely found, whereas the common expression of imbalance is seen as single chromatids. We hypothesise that one mechanism links these data: the mechanism depends on the prediction from the cytogenetic data that cohesion within the bivalent complex is severely weakened during the extended dictyate stage in older women. Consequently, when meiosis resumes, at the time of ovulation, the bivalent emerges as four chromatids held together only by its chiasmata. In accordance with the rules of orientation on the spindle, the final balanced shape of the configuration achieved at metaphase I, in this case determined by the position of the chiasmata, will dictate whether the subsequent segregation of the chromatids will result in their heterozygosity or homozygosity. It follows that the concept of "first division" and "second division" errors, i.e. of nondisjunction originating at first or second meiotic division as defined by centromeric hetero- or homozygosity, may be erroneous.     

Embryogenesis of an embryonic lethal, ‘kidney-shaped egg’ in Bombyx mori,with special reference to mesoderm differentiation

Summary

Within the kidney-shaped egg laid by the homozygous female, the embryo develops only ectodermal organs, but no mesodermal organs. The early embryogenesis of this strain was examined with light and electron microscopy. Until the early germband stage no remarkable differences are distinguishable between the normal and the kidney-shaped eggs. Afterwards, in the kidney-shaped egg large amount of cytoplasmic masses and often several cells are extruded from the presumptive head region into the yolk at the ‘pyriform’ stage, resulting in inhibiting the formation of a normal wide head lobe and an invagination occurring in its central region, the first sign of the mesoderm differentiation. This phenomenon proceeds gradually toward the posterior part and thus the differentiation of mesoderm becomes impossible throughout the entire length of germband. The results are discussed in the context of the mesoderm differentiation in Bombyx.     

Meiobenthic gradients with special reference to Plathelminthes and Polychaeta in an estuarine salt marsh creek—a small-scale model for boreal tidal coasts?

Environmental conditions in salt marsh creeks are intermediate between the open tidal coast and estuaries. A large salt marsh creek at the island of Sylt (North Sea) was studied in order to test whether its fauna is more similar to that of the open tidal coast or to that of estuaries. Because of a sandy bar at the seaward opening, the tidal range is only 10 cm in the creek, and the water level never drops below the level of the sand bar. Zoobenthos in the sandy bottom and on the sandy shores was studied at both ends and in the middle of the creek. Polychaeta and Plathelminthes were determined to species level. On an average, 2115 metazoans were found below 10 cm² of surface area. At the seaward end of the creek, abundance and taxonomic composition are similar to that of the adjoining Wadden area. Nematoda are the dominant taxon, followed by Copepoda, Plathelminthes and Oligochaeta. Taxonomic composition is different at the landward end. Plathelminthes and Nematoda are most abundant followed by Copepoda. Both Oligochaeta and Polychaeta are scarce at these newly eroded sites. Plathelminth abundance at the landward end of the creek is exceptionally high (770–935·10 cm⁻²). Contrary to what is generally found in estuaries, the species density of Plathelminthes shows a significant increase toward the land. The species composition of Polychaeta and Plathelminthes indicates that the sites below mean high tide level of the creek correspond to the adjacent eulittoral Wadden area while the fauna of the supralittoral sites of the creek is similar to the fauna of supralittoral tidal coasts. Typical sublittoral species did not occur in the salt marsh creek. Thus, salt marsh creeks may be regarded as a small-scale model for the tidal coast. In context with the results obtained, the definition of estuaries is discussed.     

Reproduction of astacid crayfish in captivity—current developments and implications for culture,with special reference to Ireland and Spain

Summary

Astacid crayfishes, native to western Eurasia and western North America, are iteroparous and long-lived (6–12 years), reaching final sizes of about 30–500 g and 90–200 mm total length, depending on species. While economically valuable, their low fecundity and slow growth makes economic aquaculture difficult. In Spain and Ireland the relatively small native white-clawed crayfish Austropotamobius pallipes (Lereboullet) carries around 70 eggs for 8–9 months and reaches first maturity at 3–4 years and 50 mm total length. The larger signal crayfish Pacifastacus leniusculus Dana, introduced to Europe from California, matures at about 70 mm and 2 years and carries some 200 eggs for 8 months. A. pallipes alone occurs in Ireland; both species in Spain. We have investigated fecundity, oviposition and subsequent egg development of diese species in field and laboratory and developed strategies to maximize egg survival in artificial incubators. Temperature manipulations may be used to maximize juvenile survival and also to modify incubation period. For successful aquaculture critical phases in captivity are mating and fertilization, pleopodal egg attachment, late embryo survival and moult from Stage 1 hatchlings to free-living Stage 2 juveniles.     

Structural specificity of aromatic compounds with special reference to mutagenic activity in Salmonella typhimurium — a series of chloro- or fluoro-nitrobenzene derivatives

The mutagenicity of 21 chloro- or fluoronitrobenzene compounds and 9 chloro- or fluorobenzene compounds in Salmonella typhimurium (strains TA98, TA1538, TA1537, TA100 and TA1535) was examined. The tests were carried out under the conditions of absence and presence of liver microsomal activation.15 nitro-group compounds had mutagenic activity; above all, compounds of fluoronitrobenzene were mutagenic for both types of strain. On the other hand, chloronitrobenzene compounds were mutagenic for base-pair substitution strains only. Mutagenic activity was exhibited by all compounds having a chloro or fluoro substituent at the para and ortho position in the nitrobenzene nucleus. All compounds without a nitro substituent showed no mutagenic activity.     

Establishment and characterization of HEPFT, a cell line derived from hepatoid carcinoma of the fallopian tube, with special reference to α-fetoprotein, lectin affinity and histogenesis

A cell line designated "HEPFT" was established from a human fallopian tubal hepatoid carcinoma. This line grew well without interruption for 13 months and was subcultivated over 35 times. The cells were spherical and polygonal in shape and showed neoplastic and pleomorphic features such as a bizarre aggregation of chromatin granules, an irregular thickening membrane and multiple large nucleoli. The cells formed epithelial colonies with a jigsaw puzzle-like arrangement and multilayering without contact inhibition. The cells contained moderate to abundant amounts of eosinophilic cytoplasm and were immunohistochemically positive for alpha-fetoprotein. The cells proliferated rapidly, and the population doubling time was about 45 h. The chromosome number showed a wide distribution of aneuploidy. The modal chromosome number was stable in the hyper triploid range and many marker chromosomes were observed. The culture cells produced bile and a large amount of lentil lectin-reactive alpha-fetoprotein. The recently developed bacterial artificial chromosome array comparative genomic hybridization facilitated detailed analysis with high resolution and sensitivity. Different profiles of genomic copy-number abnormalities were demonstrated in various chromosomal regions in HEPFT cells.     

On the origin of the supernumerary chromosome in autosomal trisomies — with special reference to Down's syndrome

Summary The differential staining methods for chromosomes have led to the demonstration of more chromosomal polymorphisms. Not rarely, these polymorphisms allow in autosomal trisomies the detection of parental origin of the supernumerary chromosome. In addition, the malsegregation may be ascribed to 1st or 2nd meiotic division in informative families.This approach of analyzing possible causes of trisomies is subject to a considerable bias. Trisomic phenotypes are twice as frequent for 2nd meiotic errors than for 1st meiotic errors. Also, rare chromosome variants seldom occur in matings where malsegregation in 1st meiotic division can be detected. In the present paper this bias is analyzed mathematically on the family as well as on the population level.From this mathematical analysis and from the data in the literature we conclude that Down's syndrome as a whole is caused about 5–10 times more often by a malsegregation in 1st meiotic than by an error in 2nd meiotic division.Mainly from experimental studies in rodents, causes for errors in 1st and 2nd meiotic division are becoming apparent. They are summarized in the context of the results of the present paper.Human population cytogenetics, a subject originated by Court Brown, has not, as yet, required mathematics at all unless we include—as I think we may correctly—the exact study of such variables as parental age and chromosomal measurements. L. S. Penrose (1970)We dedicate this paper to Professor Emeritus P. E. Becker, M.D., with our best wishes for his retirement.     

Studies on mobilization of chromium with reference to its plant availability – Role of organic acids

Metal-organic acid interactions with special reference to their plant availability have been studied. The role of organic acids in the mobilization of Cr by converting it into labile organically bound form, enhancing its availability, is highlighted. Pot experiments are conducted to investigate the effect of various organic acids on the uptake and translocation of root absorbed trivalent and hexavalent chromium by maize (z. mays) plants grown in sand and soil culture. Statistically significant increases in chromium accumulation from CrIII-treated plants in the presence of increasing concentrations of organic acid suggest the existence of CrIII – organic acid interactions in the soil plant system. In order to support the above mentioned hypothesis of formation of organically bound CrIII in the presence of various organic acids (carboxylic and amino acids), separate experiments have been performed to synthesize and estimate its respective organically bound forms. Amendments with organic acids, however, do not appear to markedly affect chromium accumulation from CrVI treatment. The results are discussed on the basis of the potential of organic acids to form complexes with CrIII.     

Histochemical localization of 3β-hydroxysteroid dehydrogenase in marmoset ovaries during pro- and diestrus,with special reference to substrate specificity

Summary We applied qualitative cytochemical procedures to investigate and compare the distribution of 3-hydroxysteroid dehydrogenases (HSDH) in pro- and diestrus ovaries of sexually mature marmosets (Callithrix jacchus) using dehydroepiandrosterone or etiocholane-3-ol-17-one as the substrate. During proestrus dehydroepiandrosterone dehydrogenase (3-5-HSDH) activity was found in the theca of tertiary follicles and in atretic granulosa cells. In granulosa cells at advanced stages of degeneration, HSDH activity was distinctly higher than in thecal cells. The activity of etiocholane-3-ol-17-one dehydrogenase (3-5-HSDH) exhibited a gradient in preovulatory follicles, ranging from high levels in granulosa cells adjacent to the basement membrane to low levels in cells bordering on the antrum and in cumulus oophorus cells. During diestrus 3-5-HSDH activity was only detected in the corpora lutea; the level of 3-5-HSDH activity was unchanged in the theca of tertiary follicles and high in the cells of the corpora lutea. HSDH activity was no longer detectable in atretic granulosa cells using either dehydroepiandrosterone or etiocholane-3-ol-17-one as the substrate. comparison of the distribution of HSDH during proestrus and diestrus revealed that steroidogenesis in marmoset ovaries occurs in follicular elements during diestrus and almost exclusively in the corpora lutea during diestrus. From this phase-dependent localization, it is possible to detemine the stage of the estrous cycle. Furthermore, our findings indicate that the localization of HSDH is dependent on the conformational structure of the substrate used.