bluuebunny/crossref_metadata_2025_split huggingface dataset:
Why are pathogenic staphylococci so lysozyme resistant? The peptidoglycan O‐acetyltransferase OatA is the major determinant for lysozyme resistance of Staphylococcus aureus
Authors: Bera Agnieszka , Herbert Silvia , Jakob Andreas , Vollmer Waldemar , Götz Friedrich 
Published: January 2005

Summary Staphylococcus species belong to one of the few bacterial genera that are completely lysozyme resistant, which greatly contributes to their persistence and success in colonizing the skin and mucosal areas of humans and animals. In an attempt to discover the cause of lysozyme resistance, we identified a gene, oatA, in Staphylococcus aureus. The corresponding oatA deletion mutant had an increased sensitivity to lysozyme. HPLC and electrospray ionization tandem mass spectrometry analyses of the cell wall revealed that the muramic acid of peptidoglycan of the wild‐type strain was O‐acetylated at C6‐OH, whereas the muramic acid of the oatA mutant lacked this modification. The complemented oatA mutant was lysozyme resistant. We identified the first bacterial peptidoglycan‐specific O‐acetyltransferase in S. aureus and showed that OatA, an integral membrane protein, is the molecular basis for the high lysozyme resistance in staphylococci.
MicroMeeting: Who's talking to whom? Epithelial–bacterial pathogen interactions
Authors: Aldridge Phillip D. , Gray Michael A. , Hirst Barry H. , Khan C. M. Anjam 
Published: January 2005

SummaryOur perception that host–bacterial interactions lead to disease comes from rare, unsuccessful interactions resulting in the development of detectable symptoms. In contrast, the majority of host–bacterial interactions go unnoticed as the host and bacteria perceive each other to be no threat. In July 2004, a focused international symposium on epithelial–bacterial pathogen interactions was held in Newcastle upon Tyne (UK). The symposium concentrated on recent advances in our understanding of bacterial interactions at respiratory and gastrointestinal mucosal epithelial layers. For the host these epithelial tissues represent a first line of defence against invading bacterial pathogens. Through the discovery that the innate immune system plays a pivotal role during host–bacterial interactions, it has become clear that epithelia are being utilized by the host to monitor or communicate with both pathogenic and commensal bacteria. Interest in understanding the bacterial perspective of these interactions has lead researchers to realize that the bacteria utilize the same factors associated with disease to establish successful long‐term interactions. Here we discuss several common themes and concepts that emerged from recent studies that have allowed physiologists and microbiologists to interact at a common interface similar to their counterparts – epithelia and bacterial pathogens. These studies highlight the need for further multidisciplinary studies into how the host differentiates between pathogenic and commensal bacteria.
MITOTIC ACTIVITY AND CELL PROLIFERATION IN PRIMARY INDUCTION OF NEWT EMBRYO
Authors: SUZUKI AKIO , KUWABARA KAZUSHI 
Published: January 2005

Mitotic activity and cell proliferation of newt (Triturus pyrrhogaster) embryo were examined with special reference to primary induction.Mitotic activity of gastrula ectoderm gradually decreases during gastrulation. The ectoderm, which is isolated from mid‐gastrula (stage 12b) and cultured in vitro, also shows gradual decrease in mitotic activity during cultivation and the mitotic activity steeply decreases after 48 hr.The ectoderm cultured with heterologous inductor (GPL‐extract) shows a temporal suppression in mitotic activity. The ectoderm of the whole gastrula also shows a regional suppression where it is in contact with the chorda‐mesoderm.The number of the ectodermal cells increases about 2 times after 24 hr culture and to more than 3 times after 48 hr culture. Accordingly it is certain that the majority of the ectodermal cells divides at least one time in the course of 48 hr.Histological examination of the ectoderm cultured together with the inductor reveals that differentiation of undifferentiated ectoderm to neural tissues is accomplished at least within 48 hr after cultivation with the inductor.The present examination shows the possibility that the mitotic activity of the ectoderm may be temporarily suppressed by the inductor and that it then decreases along with neural cell differentiation after recovery of the activity.The results also suggest that the determination of undifferentiated ectoderm to neural tissues occurs before the second cell division after the contact with the inductor and the events occurring during the first cell cycle after activating by the inducing stimulus are critical for the primary induction.
LOCATION AND ULTRASTRUCTURE OF PRIMORDIAL GERM CELLS (PGCs) IN AMBYSTOMA MEXICANUM
Authors: IKENISHI KOHJI , NIEUWKOOP PIETER D. 
Published: January 2005

The location and ultrastructure of the primordial germ cells (PGCs) were studied in Ambystoma mexicanum larvae of stages 23 to 47.PGCs were found in the spaces between the endodermal cell mass and the lateral plate mesoderm at stages 23 to 35. Some of the PGCs at stage 35, and most of them at stages 40 and 42, were located near the Wolffian duct. At stages 46 and 47 all the PGCs were situated in the genital ridges. Cilia, which have hitherto never been reported in PGCs, were occasionally seen in PGCs of Ambystoma from stage 23 till stage 46.No “germinal plasm” was found in the PGCs prior to stage 40. Specific structures or “nuage material”, corresponding to the germinal granules or their derivatives in Xenopus, were first recognized in the vicinity of the nucleus at stage 40. Between stages 40 and 46, the amount of “nuage material” markedly increased. It was finally localized mainly in “intermitochondrial spaces”. A possible transfer of material from the nucleus to the cytoplasm or vice versa through nuclear pores was first noticed at stage 40, the material concerned being quite similar in ultrastructure to the “nuage material”.
STABILITY OF ISOLATED MITOTIC APPARATUS DURING STORAGE*
Authors: FORER ARTHUR , ZIMMERMAN A. M. 
Published: January 2005

Mitotic apparatus (MA) were isolated from sea urchin zygotes using various isolation procedures, and various properties of the isolated MA were studied and compared. MA isolated using hexylene glycol had birefringences which depended on the pH of the isolation medium, the lower the pH the higher the MA birefringence. The stability of the MA Birefringence also depended on the pH of the hexylene glycol isolation medium (the lower the pH the slower the rate of decay of birefringence), as did the final birefringence reached after prolonged storage. MA isolated using glycerol‐dimethylsulphoxide (MTME) had much more stable birefringence than MA isolated using hexylene glycol; their birefringence decay rates were about 1000 times slower than those of MA isolated using hexylene glycol.Birefringence which remained after extraction of MA with H2O, or 0.5 M KC1 was also studied; the results depended on the MA isolation medium, on the medium the MA were stored in, and on the amount of time the MA were stored after isolation, as described in detail in the text.These results are discussed, and it is suggested that several components (including, perhaps, oriented ribosomes) contribute to birefringence of isolated MA.
DEVELOPMENT OF THE SEA‐STAR, ASTERINA BATHERI GOTO
Authors: KANO YASUO T. , KOMATSU MIÉKO 
Published: January 2005

Using natural spawning and artificial fertilization, the entire process of development from eggs to juveniles was observed in the sea‐star, Asterina batheri Goto.The breeding season of this animal in Tsukumo Bay and Toyama Bay is estimated to be late summer. The spawned eggs are approximately 430 μm in diameter and float near the surface of sea water. They develop, through a wrinkled blastula stage by holoblastic. radial cleavage, into a pear‐shaped brachiolaria bearing 3 blunt brachiolar arms. Metamorphosis takes place while the brachiolariae are swimming. Ten days after fertilization, metamorphosis is complete; the resulting juveniles are about 800 μm in diameter and colored pale brown with a green tint. They bear 2 pairs of tube‐feet and a terminal tentacle in each arm.Development of this species is thus of the direct type, and very similar in every respect to that of Asterina coronata japonica, which is closely related to the present species.
MORPHOLOGICAL CHANGES OF CULTURED MYOCARDIAL CELLS DUE TO CHANGE IN EXTRACELLULAR CALCIUM ION CONCENTRATION
Authors: GOSHIMA KIYOTA , YAMANAKA HACHIRO , EGUCHI GORO , YOSHINO SHIGEO 
Published: January 2005

Increase in the extracellular Ca2+ concentration from low (≤ 10−7 M) to normal (10−3 M) caused morphological changes of cultured myocardial cells obtained from fetal mouse heart. The extracellular Na+ and K+ concentrations of the normal medium (10−3 M Ca2+) did not significantly affect the genesis of these morphological changes. Like Ca2+, Ba2+ and Sr2+, but not Mg2+, Co2+ or Ni2+, could induce morphological changes. Increase in the extracellular Ca2+ concentration from 10−8 M to 10−3M also caused excess uptake of 45Ca2+ by cultured myocardial cells. B–16CW 1 cells, which did not show these morphological changes, did not take up excess 45Ca2+ on this treatment. Treatments, such as addition of verapamil or incubation at pH 6.3, which reduced the genesis of morphological changes, reduced the rate of 45Ca2+ uptake by myocardial cells. These facts show that the morphological changes of myocardial cells induced by increasing the extracellular Ca2+ concentration from low to normal are due to excess uptake of Ca2+ by the myocardial cells.The morphological changes of cultured myocardial cells induced by increasing the extracellular Ca2+ concentration from low to normal were reversed on further incubation of the cells in medium with or without Ca2+.
An Ultrastructural Study of Cell‐to‐Cell Membrane Interaction at Early Stages of Postnatal Ontogenesis of Cortical Brain Neurons in White Rats
Authors: GLEZER I. ILYA 
Published: January 2005

In early postnatal ontogenesis of cerebral cortex (visual area) of the white rat, a wide distribution of different types of membrane contacts have been found between developing nervous cells and their processes. The following types of contacts were observed: 1. Penetration of thin filopodia into specialized invaginations having all the features of coated vesicles; 2. Contacts of filopodia with thickened surface membrane; 3. Contacts of opposit filopodia; 4. Contacts of membranes with reciprocal invaginations alternating with filopodia or surface blebs.These types of membrane interaction were regularly distributed along the surface of cells and their processes, and were situated in close approximation to typical tight junctions and other adhesional complexes. As a rule, filopodia were components of axon branches, and almost all invaginations were situated on plasma membranes of cell bodies or on dendrites, although sometimes there were invaginations on axon profiles and filopodia on dendrites.It is suggested that the distribution and structural specialization of these membrane contacts reflect their participation in the process of programmed cell‐to‐cell recognition that precedes the formation of synaptic contact. Other reports and the current data reveal the special morphogenetic role of membrane communication in the formation and stability of integrative cell systems.
Chromatin Arrangement and Axis Formation in the Spermiogenesis of a Pulmonate Snail
Authors: TERAKADO KIYOSHI 
Published: January 2005

Nuclear change in relation to axis formation and condensation during spermiogenesis was investigated in the snail, Physa acuta. In the early spermatid, characteristic thick layers (termed apical and basal plates) are formed on two sides of a nuclear envelope. Soon after the formation of these plates, a developing acrosome and a flagellum attach externally to the center of the apical and basal plates, respectively. However, most (presumably all) of the chromatin filaments become attached all over the inner surface of the apical and basal plates. This means that the plates themselves are actually the specialized forms of the nuclear envelope to which chromatin filaments become connected; by means of these plates, the chromatin filaments become arranged in parallel to the antero‐posterior axis as the nucleus elongates. This suggests that the formation of these two thick layers on opposing surfaces of the nucleus primarily determines the antero‐posterior axis of the spermatid and the direction of the arrangement of chromatin.The flattening of the nucleus prior to elongation is caused mainly by the enlargement of the basal plate. Subsequent nuclear shaping and condensation are discussed in relation to the change in the surface structures of the nucleus and the organization of the microtubules.
Differentiation of Various Cell Types during Fruiting Body Formation of Dictyostelium Discoideum*
Authors: HAYASHI MORIAKI , TAKEUCHI IKUO 
Published: January 2005

The processes of differentiation of the presumptive cells (prespore and prestalk cens) into mature spores, stalk and basal‐disc cells in Dictyotelium discoideum was investigated. The number of stalk and disc cells in pre‐labeled culminating cell masses was estimated by determining the radioactivity of the undissociable fraction separated by filtration from the dissociable fraction containing presumptive cells and spores. Changes in the proportion of amoeboid cells stainable with fluorescein‐conjugated antispore serum and encapsulated spores were also followed in the dissociable fraction.Formation of stalk and disc cells began at 17 hr of development and was completed at 26 hr, while formation of morphologically identifiable spores began at 18 hr and was completed at 20 hr, long before completion of stalk formation. At the onset of culmination, unstained cells abruptly increased with an accompanying decrease of stained cells, when unstained rear‐guard cells appeared in the hind region. Although some of the rear‐guard cells soon differentiated into basal‐disc cells, the rest remained amoeboid in the upper part of the spore mass (sorus) after complete formation of a fruiting body. Despite the presence of the amoeboid cells in mature sori, the proportion of the sorus to the stalk and disc of a fruiting body was approximately equal to that of stained (prespore) to unstained (prestalk) cells in a migrating slug.
Induction of the Synthesis of Melanin and Pteridine in Cells Isolated from the Axolotl Embryo
Authors: LØVTRUP SØREN , REHNHOLM ASTRID , PERRIS ROBERTO 
Published: January 2005

It has previously been reported that when LiCl and tyrosine is added to ectodermal cells isolated from the blastula of Ambystoma mexicanum, then the synthesis of melanin is initiated in cells not normally engaged in this activity (mesenchyme cells, nerve cells and undifferentiated animal cells). In the present paper it has been shown that to obtain this effect tyrosine (0.02 mM) has to be present in the culture medium during at least one of the first seven days of culture, thus several days before melanin is produced. It is concluded that the added tyrosine is acting as an inductor of, and not as a substrate for the synthesis of melanin.In the normal cultures it is possible to observe the spontaneous formation of yellow cells, indicating that they have produced pteridine. These cells are spherical, suggesting that they are undifferentiated embryonic cells. GTP is a precursor in the synthesis of pteridine, and in analogy with the observations made with tyrosine it was found that in the presence of LiCl a number of different cell types elaborate pteridine when GTP (0.1 mM) is added to the medium. Also in this case was it possible to show that GTP acts as an inductor, not as a substrate.
Effect of Actinomycin D and Cycloheximide on Gonadotropin‐Induced 17α, 20β‐Dihydroxy‐4‐pregnen‐3‐one Production by Intact Ovarian Follicles and Granulosa Cells of the Amago Salmon, Oncorhynchus rhodurus*
Authors: NAGAHAMA YOSHITAKA , YOUNG GRAHAM , ADACHI SHINJI 
Published: January 2005

The effect of actinomycin D and cycloheximide on gonadotropin (partially purified chum salmon gonadotropin, SGA)‐induced 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one (17α, 20β‐diOHprog, a maturation‐inducing steroid in amago salmon) production was examined in intact ovarian follicles and granulosa cells of postvitellogenic amago salmon, Oncorhynchus rhodurus. Both actinomycin D and cycloheximide blocked gonadotropin‐induced 17α, 20β‐diOHprog production by intact follicles. In contrast, gonadotropin‐induced 17α‐hydroxyprogesterone production by intact follicles was not abolished by actinomycin D, but was abolished by cycloheximide, suggesting that postvitellogenic amago salmon ovarian follicles already contain the RNAs necessary for the synthesis of 17α‐hydroxyprogesterone.In isolated granulosa cells, chum salmon gonadotropin was able to stimulate 17α, 20β‐diOHprog production only when a precursor, 17α‐hydroxyprogesterone was provided in the incubation medium, indicating that gonadotropin acts directly on granulosa cells to enhance the activity of 20β‐hydroxysteroid dehyrogenase (20β‐HSD). Total inhibition of 20β‐HSD enhancement in granulosa cells, judged by 17α, 20β‐diOHprog production, was achieved when actinomycin D was added between 1 hr before the start of incubation with 17α‐hydroxyprogesterone and gonadotropin to 6 hr after. With cycloheximide total inhibition was observed when added in the period of 1 hr before to 9 hr after the start of the incubation. These results suggest that chum salmon gonadotropin acts on granulosa cells to enhance the de novo synthesis of 20β‐HSD by a mechanism involving RNA synthesis.
U.V. Irradiation Inhibits The Electrical Block to Polyspermy in Echinoderms*
Authors: DAVID C. , MOREAU M. , VILAIN J. P. , GUERRIER P. 
Published: January 2005

Oocytes of the sea urchin Sphaerechinus granularis and the startish Marthasterias glacialis have been submitted to U.V. irradiation before fertilization. This treatment significantly increased the incidence and severity of polyspermy in the sea urchin and was also found effective on starfish oocytes. These were found more resistant to damage than sea urchin eggs and U.V. irradiation did not affect either their response to the hormone l‐methyladenine or the rate of elevation of the fertilization envelope, which assures the late and definitive block to polyspermy.Electrophysiological measurements performed on M. glacialis oocytes definitively demonstrate that U.V. irradiation completely inactivates voltage‐dependent sodium channels, without altering the other main conductances, Cl−, K+ or Ca2+. After such a treatment, the relative permeability of the membrane to Na+ as compared to K+ shifted from 0.019±0.003 to 0.003±0.002 and only the calcium component of the action potentials could be observed. However, a fertilization potential, preceded by small sperm induced steps, is still present in these conditions, although its peak and plateau level are greatly reduced.These new findings are discussed, which confirm the electrical nature of the fast block to polyspermy but question about the specificity of those sperm‐gated channels which are supposed to trigger the fertilization potential.
Behavior of Primary Mesenchyme Cells In situ Associated with Ultrastructural Alteration of the Blastocoelic Material in the Sea Urchin, Anthocidaris crassispina
Authors: KATOW HIDEKI , AMEMIYA SHONAN 
Published: January 2005

In the blastula of the sea urchin, Anthocidaris crassispina, a small number of primary mesenchyme cells (PMCs) ingressed from the blastocoel wall taking a bottle shape. The majority of the PMCs followed the first group of PMCs. These ingressed without taking the bottle shape, and became round within the blastocoel wall. After ingression, the PMCs migrated as single cells retaining their round cell contour. The average velocity of their migration was 13.3 μm/hr.The blastocoel contained Alcian blue (pH 1.0)‐positive material which changed its light microscopic configuration from being amorphous in the hatched and mesenchyme blastulae to being fibrous in the early gastrulae. Ultrastructurally, the blastocoelic material in the hatched blastulae was composed of 27 nm diameter granules. In the mesenchyme blastulae and the early gastrulae relatively long 15 nm diameter fibers were seen in addition to the 27 nm diameter granules. The 27 nm diameter granules bound the ruthenium red while the 15 nm diameter fibers did not. The 27 nm diameter granules formed aggregates in the hatched blastulae, and were bound to the 15 nm diameter fibers in the mesenchyme blastulae and early gastrulae to form a fibrous network which was observed by a light microscope.
Purification of Acetylcholinesterase from Sea Urchin (Hemicentrotus pulcherrimus) Embryos by Affinity Chromatography
Authors: AKASAKA KOJI , SASAKI HIROSHI , SHIMADA HIRAKU , SHIROYA TSUGIO 
Published: January 2005

Only one form of acetylcholinesterase (AchE) was detected in Hemicentrotus pulcherrimus embryos. In H. pulcherrimus embryos as well as in the other sea urchin embryos, AchE activity begins to increase rapidly after gastrula stage.Purification of AchE from plutei has been carried out by the procedure including affinity chromatography. Purified AchE had the activity 14,600 times higher than that of homogenate, and the final yield of AchE was 8%. The enzyme seems to be electrophoretically homogeneous, and has a molecular weight of 3 × 105 as determined by Sepharose CL–6B column chromatography.
Spermiogenesis in the Marine Shrimp, Sicyonia ingentis
Authors: SHIGEKAWA KATHERINE , CLARK WALLIS H. 
Published: January 2005

Spermiogenesis in the marine prawn Sicyonia ingentis was examined using transmission electron microscopy. The acrosomal vesicle, derived from the fusion of pro‐acrosomal vesicles blebbed from the nuclear envelope, contains the membrane pouches, anterior granule and a spike. The anterior granule is formed from the coalescence of granular aggregates within the proacrosomal vesicles. Primordia underlying the apical acrosomal vesicle membrane polymerize to form a spike approximately 6 μm long. The convoluted pouch membranes arise from the posterior acrosomal vesicle membrane. Lateral and apical portions of the acrosomal vesicle are surrounded by a pentalaminar membrane comprised of the spermatid plasma membrane and the acrosomal vesicle membrane. Subacrosomal structures include the dense saucer plate, granular core and crystalline lattice. These components condense just posterior to the acrosomal vesicle and are separated from the chromatin by a nuclear plate.The spermatid nucleus becomes surrounded by rough endoplasmic reticulum (RER) and membranous lamellar bodies. RER gives rise to smooth endoplasmic reticulum. These membrane systems degenerate, forming a band of reticular elements around the lateral and posterior portions of the nucleus. The nucleus undergoes condensation followed by decondensation with concomitant breakdown of the nuclear envelope. The resultant chromatin is fibrillar in appearance.