bluuebunny/crossref_metadata_2025 huggingface dataset:
Keratin expression in human mammary epithelial cells cultured from normal and malignant tissue: relation to in vivo phenotypes and influence of medium
Authors: Taylor-Papadimitriou J. , Stampfer M. , Barter J. , Lewis A. , Boshell M. , Lane E. B. , Leigh I. M.
Published: April 2021

The luminal and basal epithelial cells in the human mammary gland can be distinguished in tissue sections on the basis of the pattern of keratins they express. Moreover, the invasive cells in primary carcinomas show a keratin profile that corresponds to that of the dominant luminal cell (7, 8, 18, 19). When homogeneous populations of luminal epithelial cells from milk or from breast cancer metastases are cultured the profile of keratin expression seen in vivo is maintained. We have therefore used monospecific antibodies reactive with individual keratins to examine the phenotype of cells cultured in three different media from reduction mammoplasty tissue that contains both luminal and basal cells. The phenotype of cells cultured from primary breast cancers in one of these media (MCDB 170) has also been examined. In characterizing cell phenotypes, antibodies to a polymorphic epithelial mucin (PEM) expressed in vivo by luminal cells, and to smooth muscle (a) actin, expressed in vivo by basal cells, have also been used. Our results show that proliferation of different cell phenotypes is selected for in different media. In milk mix (MX) developed for growth of luminal cells from milk, only the luminal cell phenotype proliferates (for only 1 or 2 passages). In medium MCDB 170, which was developed for long-term growth of human mammary epithelial cells from reduction mammoplasty organoids, cells from the basal layer proliferate, while in MM medium the basal phenotype dominates, but a few cells with the luminal phenotype are found. Around passage 3, in medium MCDB 170, most cells senesce and a subpopulation of cells proliferates on further passage. These cells retain expression of the basal epithelial keratins but also express some features characteristic of luminal epithelial cells, suggesting that the basal layer may contain a stem cell that can develop along the luminal lineage. In culture, however, they do not express keratin 19, which in vivo is a feature of the fully differentiated luminal cell. The cells cultured from primary breast cancer in medium MCDB 170 have a similar keratin profile to that of the normal cells cultured in this medium. They do not express keratin 19, even though the invasive cells in primary cancers homogeneously express this keratin in vivo. The invasive phenotype, which in its keratin profile corresponds to the differentiated luminal cell and that of the metastatic cancer lines, cannot be cultured from primary breast cancers using MX, which supports proliferation of the corresponding normal cell.
Proliferative behaviour of fibroblasts in plasma-rich culture medium
Authors: Umeno Yoshikazu , Okuda Atsuyuki , Kimura Genki
Published: April 2021

We examined the proliferative behaviour in tertiary culture cells of human skin fibroblasts (HSF) as well as cells of the rat 3Y1 diploid fibroblast line placed on a plastic substratum in a nutrient-rich medium containing high concentrations of platelet-poor plasma (PPP). Autochthonous human PPP was used for the HSF cells and heat-treated (at 56 °C for 30 min) bovine PPP was used for the 3Y1 cells. In both types of cells, the saturation cell density rose with increasing PPP concentration and reached a plateau at 30–90% PPP. When the cells were cultivated in serum, the saturation densities were the same as those with the same concentrations of corresponding PPP in both the HSF and 3Y1 cells. When the cells were arrested at a saturation cell density in a medium containing 10% PPP and then were refed with a fresh medium containing 90% PPP, DNA synthesis and cell division occurred in both types of fibroblasts. This effect was either reduced in the HSF cells or enhanced in the 3Y1 cells by the addition of platelet lysate. TGF-β1 added to the fresh medium containing 90% PPP also inhibited the induction of DNA synthesis in the HSF cells but not in the 3Y1 cells. The inhibitory effect of the platelet lysate was neutralized by anti-TGF-β1 IgG. On the other hand, PDGF added to the fresh medium had no effect on either type of cells. These results suggest that cultured fibroblasts are capable of proliferating on a plastic substratum under fluid conditions that essentially reflect the fluid environment of the body, as long as sufficient nutrients are supplied. Platelet lysate represses the proliferation of HSF cells, possibly through the inhibitory effect of TGF-β1, and promotes the proliferation of 3Y1 cells by growth factor(s) other than PDGF and TGF-β1.
The first transition point of the mutant cdc2.33 in the fission yeast Schizosaccharomyces pombe
Authors: Novak B. , Mitchison J. M.
Published: April 2021

We show that the first of the two transition points of cdc2.33, a mutant of Schizosaccharomyces pombe, exists in exponential phase cells. Using flow cytometry and a double-block experiment, we have measured the position of this transition point both in the single mutant and in the double mutant cdc2.33 wee 1.6. In the single mutant, this point is in early G1 In the double mutant, however, this point is only delayed slightly, if at all, despite much larger delays in the S period and in the transition point of cdc10, another‘start’ mutant. There istherefore a significant dissociation in the timing of what are thought to be two start events, and the first one appears not to be subject to a size controf and to be associated with the completion of mitosis rather than the G1/S boundary.
Cytoskeletal interactions with post-mitotic migrating nuclei in the oyster mushroom fungus, Pleurotus ostreatus: evidence against a force-generating role for astral microtubules
Authors: Kaminskyj S. G. W. , Yoon K. S. , Heath I. B.
Published: April 2021

Nuclei of Pleurotus ostreatus migrate in a highly predictable manner foflowing conjugate mitosis at clamp connections. Parameters were determined by observations in living hyphae and these data were used to predict the living behaviour of freeze-substituted nuclei. Three of four classes of nucleus migrate immediately after telophase and move at similar speeds. Freeze-substitution electron microscopy shows that these nuclei have prominent nucleus-associated organelles (NAOs) with large astral microtubule (MT) arrays. Although the NAOs do not have a consistent position with respect to the nuclear motion, they are preferentially located near the hyphal axis. The fourth class of nucleus remains in the developing clamp until it fuses with the main hypha, whereupon it migrates to its interphase position at a rate much faster than the other classes. This class of nucleus has a small NAO and no astral MTs. Treatment of hyphae with a MT-disrupting drug, MBC, reduced the astral arrays in the first three classes but did not slow their rate of movement. Moreover, serial section analysis of drug-treated nuclei whose migration rate at the time of fixation was known showed no relationship, positive or negative, between astral MT number and rate of movement. These data suggest that astral MTs neither generate nor transduce force for post-mitotic nuclear migration in P. ostreatus. The rofe of astral MTs and possible mechanisms of postmitotic nuclear migration are discussed.
Translocation of precursor proteins into the mitochondrial matrix occurs through an environment accessible to aqueous perturbants
Authors: Sztul Elizabeth S. , Chu Tom W. , Strauss Arnold W. , Rosenberg Leon E.
Published: April 2021

We have identified translocational intermediates generated during import of precursor proteins into the mitochondrial matrix and have characterized their association with mitochondrial membranes. Partially translocated forms of mitochondrial malate dehydrogenase (MDH) and ornithine transcarbamylase (OTC) were generated during import of the corresponding precursors (pMDH and pOTC) into mitochondria at 2°C. Import at this temperature results in the formation of intermediate-sized MDH (iMDH) and OTC (iOTC) produced by the removal of a portion of the leader peptide, and in the production of mature-sized MDH. All of these forms contain NHz termini located within the mitochondrial matrix, although the majority of theirpofypeptide chains remain extramitochondrial. All three are strongly associated with mitochondrial membranes, but can be extracted by protein denaturants such as urea. These translocational intermediates appear to be hydrophilic proteins, on the basis of their partitioning properties during extraction with the nonionic detergent Triton X-114. The data indicate that the translocation of pofypeptide chains into mitochondria occurs in a microenvironment that is aqueous in nature and is mediated by integral membrane proteins.
The early expression of myofibrillar proteins in round postmitotic myoblasts of embryonic skeletal muscle
Authors: Colley Nansi Jo , Tokuyasu K. T. , Singer S. J.
Published: April 2021

Previous reports on skeletal muscle myogenesis have shown that postmitotic spindle-shaped myoblasts express muscle-specific proteins, some of which are organized into nascent myofibrils. However, we show that, in skeletal muscle cultures derived from 12-day chick embryos, by 6h after plating the predominant mononucleated cell type that expresses muscle-specific proteins is a round cell. These round myoblasts appear to precede spindle-shaped myoblasts in development, since the latter are more abundant in later cultures and contain larger amounts of muscle proteins and more highly organized myofibrils. By double immunofluorescence microscopy using antibodies specific for the muscle proteins titin, myosin heavy chain (MHC) and zeugmatin we find that 18 h after plating approximately 20% of the round myoblasts that are titin-positive are negative for myofibrillar MHC and zeugmatin. On the other hand, all spindle-shaped myocytes that are positive for titin are also positive for myofibrillar MHC and zeugmatin. These results suggest that titin expression precedes that of myofibrillar MHC and zeugmatin in the non-synchronized round myoblasts, and is consistent with earlier suggestions that titin may function as an initial organizer of myofibrillar proteins during myogenesis. Immunofluorescence data indicate that the earliest localization of the myofibrillar proteins titin, MHC, zeugmatin and a-actinin in the round myoblasts is surrounding the nucleus with no. immunofluorescent labeling of the cytoplasm or near the plasma membrane. Furthermore, pairwise double immunofluorescence experiments show that these four myofibrillar proteins are all co-localized, at the light-microscopic level of resolution, in irregular patterns that may appear in either a punctate or a basket-like distribution. These labeling patterns around the nucleus are resistant to extraction with Triton X-100, suggesting that the proteins are associated in a stable array. These Triton X-100-resistant assemblies in round myoblasts appear to be composed solely of structural myofibrillar proteins, since the non-structural myofibrillar protein creatine kinase (CK) does not colocalize with the other myofibrillar proteins. These results indicate that in early myoblasts myofibrillar proteins form stable pre-myofibrillar assemblies surrounding the nucleus, and raise the possibility that these initial assemblies may play an organizing role during subsequent early stages of myofibrillogenesis.
Monoclonal antibodies to the adhesive cell coat secreted by Pythium aphanidermatum zoospores recognise 200×103Mr glycoproteins stored within large peripheral vesicles
Authors: Estrada-Garcia M. Teresa , Callow James A. , Green Jonathan R.
Published: April 2021

During encystment the motile zoospores of the plant pathogen Pythium aphanidermatum secrete an adhesive cell coat that is involved in their attachment to roots. Previous ultrastructural studies have indicated that the adhesive material is pre-packaged within large peripheral vesicles underlying the zoospore plasma membrane. In the present study, four monoclonal antibodies (MAbs) designated PAЗ-6, which were raised against zoospores and cysts of P. aphanidermatum, were used to re-examine the formation of the adhesive cell coat and to study its molecular nature. Immunogold labelling of zoospores and cysts shows that all the antibodies recognise material contained within the large peripheral vesicles of zoospores. These structures are morphologically distinct from the microbodies, which also underly the plasma membrane, and the latter are not labelled by the antibodies. During encystment the material recognised by the MAbs is secreted to form a cell coat around the zoospores and cysts and this can be seen to be separated from the cyst plasma membrane by a distinct layer (cyst wall). The MAbs also label material within vesicles that are located towards the centre of the cyst cytoplasm. Western blotting and antigen-modification techniques have shown that all the MAbs bind to carbohydrate epitopes of a set of high molecular weight glycoproteins (>200×103Mr). One of the antibodies, PA6, also binds to several lower molecular weight components. Overall, the results show that the adhesive material secreted by P. aphanidermatum zoospores is stored within large peripheral vesicles and is composed of several glycoproteins. The results are discussed in the context of studies on the secretion of adhesive material by zoospores of related oomycete fungi.
Modulation of type X collagen gene expression by calcium β-glycerophosphate and levamisole: implications for a possible role for type X collagen in endochondral bone formation
Authors: Thomas J. Terrig , Boot-Handford Raymond P. , Grant Michael E.
Published: April 2021

Chondrocytes from the cephalic region of 18-day chick embryo sterna were cultured within type I collagen gels in the presence of increasing concentrations of calcium β-glycerophosphate (Ca PGP) (2.5 mM, 5mM and 10 mM) or 2mM levamisole. Addition of Ca β-GP produced an increase in type X collagen synthesis and when 10 mM Ca β-GP was used, mineral deposits were observed in the matrix elaborated by the chondrocytes. Measurement of mRNA levels of type II and type X collagen μg−1 total RNA revealed that the level of αl (II) mRNA decreased whereas the level of αl(X) mRNA remained relatively constant in the presence of Ca β-GP. Thus, Ca β-GP appears to increase type X collagen synthesis by enhancing the rate of collagen type X mRNA translation. In levamisole-treated cultures the synthesis of type X collagen and its deposition within the matrix were inhibited. Measurement of mRNA levels μg−1 total RNA revealed that the level of al (II) mRNA increased whereas the level of al(X) mRNA was markedly decreased in the presence of levamisole. Consequently, it must be concluded that levamisole inhibits type X collagen synthesis by inhibiting type X collagen gene transcription.

These results add support for type X collagen having an important role in the mineralization process and have demonstrated that type X collagen synthesis is probably regulated at the mRNA translational stage during chondrocyte hypertrophy.
The α6β1 (VLA-6) and α6β4 protein complexes: tissue distribution and biochemical properties
Authors: Sonnenberg A. , Linders C. J. T. , Daams J. H. , Kennel S. J.
Published: April 2021

A member of the integrin family, the α6β4 complex was previously identified on human and mouse carcinoma cell lines by using a rat monoclonal antibody to α6. Here we describe two monoclonal antibodies that recognize epitopes on the β1subunit of the human and mouse α6β4 complexes. The monoclonal antibodies against β1 were able to preclear α6β4, but not α 6β4from cell line extracts. A substantial fraction of the total β4 subunits present on the cell surface was not associated with α6, as it could not be removed by anti-α6 antibodies, but remained precipitable with anti-β4 antibodies. There was no evidence for novel a subunits associated with pi.

The α6 subunit consists of disulfide-linked heavy and light chains. The variability in size of these two chains from different cell types is largely due to differences in modifications of N-linked glycans. Additional heterogeneity may be caused by differential proteolytic cleavage of the α6 precursor.

Immunoperoxidase staining of tissue sections of neonatal and adult mice revealed that pi expression is limited to epithelial tissues and peripheral nerves. The α6 subunit has a wider distribution that includes all tissues and cells stained by antibodies against β4 Cells and tissue that are positive for α6, but negative for β4, may express the α6β4 complex.
Total internal reflection fluorescence (TIRF) microscopy I. Modelling cell contact region fluorescence
Authors: Reichert W. M. , Truskey G. A.
Published: April 2021

Total Internal Reflection Fluorescence (TIRF) is a powerful technique for visualizing focal and close contacts between the cell and the surface. Practical application of TIRF has been hampered by the lack of straightforward methods to calculate separation distances. The characteristic matrix theory of thin dielectric films was used to develop simple exponential approximations for the fluorescence excited in the cell-substratum contact region during a TIRF experiment. Two types of fluorescence were examined: fluorescently labeled cell membranes, and a fluorescent water-soluble dye. By neglecting the refractive index of the cell membrane, the fluorescence excited in the cell membrane was modelled by a single exponential function while the fluorescence in the membrane/substratum water gap followed a weighted sum of two exponentials. The error associated with neglecting the cell membrane for an incident angle of 70 degrees never exceeded 2.5%, regardless of the cell-substratum separation distance. Comparisons of approximated fluorescence intensities to more exact solutions of the fluorescence integrals for the three-phase model indicated that the approximations are accurate to about 1 % for membrane/substratum gap thicknesses of less than 50 nm if the cytoplasmic and water gap refractive indices are known. The intrinsic error of this model in the determination of membrane/substratum separations was 10 % as long as the uncertainties in the water gap and cytoplasmic refractive indices were less than 1 %.
Phosphorylation of algal centrin is rapidly responsive to changes in the external milieu
Authors: Martindale Valerie E. , Salisbury Jeffrey L.
Published: April 2021

Centrin, a calcium-sensitive contractile phosphoprotein, is the major component of the striated flagellar roots of the flagellate green alga, Tetraselmis striata. Flagellar roots contract in response to elevated calcium levels. Data presented here indicate that the level of centrin phosphorylation is rapidly responsive to changes in the cell’s external environment. Centrin is dephosphorylated in response to elevated calcium or to heat shock. An increase in centrin phosphorylation accompanies pH shock or ethanol treatment. These changes are compared with flagellar excision, flagellar root contraction, and protein synthesis under the same treatments. We conclude that under certain conditions phosphorylation/dephosphorylation of centrin and extension/contraction of the flagellar root are uncoupled. Possible role(s) of centrin phosphorylation independent of force generation in the flagellar root are discussed.
Cytoplasmic pool of histone H1 in mammalian cells
Authors: Zlatanova J. S. , Srebreva L. N. , Banchev T. B. , Tasheva B. T. , Tsanev R. G.
Published: April 2021

Two types of cell populations, nondividing mouse liver cells and exponentially growing Friend erythroleukemia cells, were studied for the presence of a histone H1 pool in the cytoplasm. Purified cytoplasmic fractions were extracted with 5% perchloric acid and the resulting protein preparation was characterized by two types of electrophoresis, gel filtration, peptide mapping, ELISA and immunoblotting. The occurrence of significant quantities of H1 in isolated cytoplasmic fractions was confirmed by indirect immunofluorescence on whole cells. The existence of a cytoplasmic pool of H1 contrasts with the lack of detectable amounts of core histones in the cytoplasm. This indicates that the observed H1 pool is not just a reflection of its cytoplasmic synthesis but probably has some functional significance.
Ultrastructural localization of the regulatory (RII) subunit of cyclic AMP-dependent protein kinase to subcellular compartments active in endocytosis and recycling of membrane receptors
Authors: Griffiths Gareth , Hollinshead Ruth , Hemmings Brian A. , Nigg Erich A.
Published: April 2021

The subcellular distribution of the regulatory (RII) subunit of cyclic AMP-dependent protein kinase (PK-A) was analyzed at the electron-microscopical level using thawed cryo-sections of Madin Darby Bovine Kidney (MDBK) cells. The highest density of labelling for RII was found on membranes of the prelysosomal compartment (PLC; marked with the cation-independent mannose 6-phosphate receptor, MPR) and the trans-Golgi network, TGN (at 20°C, marked with the G protein of vesicular stomatitis virus, VSV), as well as in coated buds on the latter. Significant labelling was also localized to the cytoplasmic surface of the plasma membrane, including clathrin-coated pits and microvilli, and to early endosomes (identified using internalized HRP). In contrast, no significant label was seen over the Golgi compartments proximal to the TGN, the endoplasmic reticulum (ER) or over lysosomes. From these results we conclude that PK-A type II is associated with the membranes of precisely those subcellular compartments that are active in endocytosis and recycling of cell surface receptors. We believe these findings to be related to the well-established role of cyclic AMP in signal transduction. In particular, we propose that activation of PK-A in endocytic compartments may contribute to regulation (via phosphorylation) of the subcellular distribution of internalized surface receptors or their functional coupling to effector systems involved in signal propagation.
Use of conjugates made between a cytolytic T cell clone and target cells to study the redistribution of membrane molecules in cell contact areas
Authors: André Pascale , Benoliel Anne-Marie , Capo Christian , Foa Colette , Buferne Michel , Boyer Claude , Schmitt-Verhulst Anne-Marie , Bongrand Pierre
Published: April 2021

In many models of cell-cell adhesion, it was reported that some cell membrane molecules might be redistributed into contact areas. However, this phenomenon was not subjected to precise quantification. In the present work, fluorescence microscopy, immunolabelling and digital image processing were combined to analyse quantitatively the spatial organization of specific or nonspecific conjugates made with a cytolytic T (CTL) lymphocyte clone (BM3.3) and target cells (EL4 or RDM4). Binding was achieved under calcium-free conditions to study the earliest steps of cell interaction, preceding CTL activation. Fluorescent antibodies were used to label class I histocompatibility molecules on both killer and target cells, and T cell receptor, CD3, CDS and LFA-1 (CD18/CDlla) on the killer cells. Membrane bilayers were stained with a fluorescent phospholipid, glycoconjugates were labelled with periodic oxidation and Lucifer Yellow uptake, and polymerized actin was revealed with a fluorescent phallacidin derivative. Also, the fine geometry of killer–target interaction area was studied with electron microscopy and computer-assisted contour analysis.

It is concluded that: (1) qualitative examination of fluorescence photomicrographs cannot permit accurate comparison between different fluorescence densities. (2) The cell–cell contact area was about fourfold higher in specific conjugates than in nonspecific ones. (3) The surface density of adhesion molecules exhibited similar increases (between 30 and 80%) in the contact areas of both specific and nonspecific conjugates. (4) However, the amount of redistributed surface molecules was higher when cell-cell interaction was enhanced either by specific immunological recognition (in specific conjugates) or periodate oxidation. (5) Since redistribution did not require extracellular calcium and it was detected on nonspecific conjugates, this did not require full lymphocyte activation.

Spatial reorganization of cell surface molecules may thus be a general consequence of adhesion, cell surface mobility and intermolecular forces.
Selective internalization of the apical plasma membrane and rapid redistribution of lysosomal enzymes and mannose 6-phosphate receptors during osteoclast inactivation by calcitonin
Authors: Baron Roland , Neff Lynn , Brown William , Louvard Daniel , Courtoy Pierre J.
Published: April 2021

The effects of inhibition of bone resorption by the peptide hormone calcitonin have been studied at the level of the osteoclast. Although not epithelial, the osteoclast is polarized with the secretion of newly synthesized lysosomal enzymes and of acid occurring specifically at the apical pole, facing the bone compartment. The membranes composing the apical (ruffled-border) and basolateral domains contain topologically restricted antigens, a 100×103Mr lysosomal membrane protein and the Na+,K+-ATPase, respectively. It was found that calcitonin induces a rapid (15–60 min) redistribution of the apical marker as well as of markers of the secretory compartment of the osteoclast (arylsulfatase and cation-independent mannose 6-phosphate (Man6P) receptors). The apical plasma membrane, in contrast to the basolateral membrane, is selectively internalized. This internalization leads to the disappearance of the ruffled border. The vesicular translocation of apical membranes is reminiscent of the events occurring ingastric oxyntic cells and in kidney tubule intercalated cells during the regulation of acid secretion. In parallel, the synthesis of both the lysosomal enzyme arylsulfatase and Man6P receptors is arrested. The products that were already present in the secretory pathway seem to be rerouted to intracellular vacuoles instead of being targeted to the plasma membrane, leading to marked accumulation of enzymes in the inhibited cells. These results suggest that the rapid inhibition of bone resorption by calcitonin involves the vesicular translocation of the apical membranes and the rapid arrest in the synthesis and secretion of lysosomal enzymes in osteoclasts.
Centriole and centrosome cycle in the early Drosophila embryo
Authors: Callaini Giuliano , Riparbelli Maria Giovanna
Published: April 2021

Centriole and centrosome cycles were examined by indirect immunofluorescence and electron microscopy techniques in the early Drosophila embryo. The centrosomes, which are already divided at interphase, appear as compact spheres during prophase and metaphase, expand and flatten from anaphase to telophase and split into two units in late telophase. Centriole separation starts in late metaphase, becomes evident in anaphase and increases during telophase. Procentrioles appear during the following interphase.
Localization of two fibronectin-binding glycoproteins in rat liver and primary hepatocytes: Co-distribution in vitro of integrin (α5β1) and non-integrin (AGp110) receptors in cell-substratum adhesion sites
Authors: Stamatoglou Stamatis C. , Sullivan Kate H. , Johansson Staff An , Bayley Peter M. , Burdett Ian D. J. , Hughes R. Colin
Published: April 2021

We have compared the localization of integrin α5β 1 and AGp100 (apical glycoprotein of Mr 110×103) in rat liver parenchyma and in primary hepatocyte cultures. Integrin α5β 1 is a heterodimeric fibronectin receptor. AGp110 is a newly described monomeric glycoprotein of the apical (bile canalicular) membrane domain of liver parenchyma that binds in an RGD-independent manner to fibronectin and mediates spreading of hepatocytes onto fibronectin-coated substrata. Using Western blotting of fractionated liver membranes and immunocytochemistry of liver sections at light- and electron-microscope levels, we have confirmed that AGp110 is a canalicular glycoprotein and have established that integrin is located in approximately equal proportions in the sinusoidal, lateral and canalicular membrane domains. In the canalicular surface domain both glycoproteins are associated with microvilli. Examination of immunolabelled primary hepatocytes spread on fibronectin-coated substrata by light and laser scanning confocal microscopy revealed colocalization of AGp110, integrin, actin and vinculin in substratum-attached microextensions at the periphery of the basal cell surface. Actin filaments that terminated at these cell processes originated from circular sub-cortical actin fibres. Interference reflection microscopy revealed focal adhesive contacts at the edge of the basal cell periphery at the same location where AGp110 and integrin were observed by immunofluorescence. In vitro, a proportion of the primary hepatocytes seeded onto fibronectin-coated substrata aggregated into colonies of several cells with intercellular contacts between neighbouring cells. Cell-substratum contacts containing integrin, AGp110, actin and vinculin followed the contours of these colonies in the same manner as they delineated the basal periphery of single, substratum-attached cells. We conclude that both integrin and AGp110 contribute to hepatocyte-fibronectin adhesive interactions and that intercellular adhesion and cooperation among hepatocytes in their response to fibronectin matrices leads to colony formation and morphological differentiation of parenchymal cell monolayers in vitro.
Timing of events in overlapping cell reproductive sequences and their mutual interactions in the alga Scenedesmus quadricauda
Authors: Zachleder V. , ŠetlÍk I.
Published: April 2021

Synchronous populations of the chlorococcal alga Scenedesmus quadricauda were subjected to various irradiances, photoperiods, heterotrophic growth and chloramphenicol treatment in order to induce different cell cycle patterns. The courses of cellular and nuclear division, and of commitments to them, were followed to measure duration of growth and reproductive steps and to analyze their mutual interactions in overlapped cell reproductive sequences. Duration of the growth steps (precommitment periods) was inversely proportional to the irradiance applied. It was prolonged if the growth was retarded by chloramphenicol. It is argued that light has an exclusively trophic function in regulating growth steps and can be replaced by glucose. The number of growth steps, and consequently the number of reproductive sequences, at a given irradiance can be experimentally changed by the photoperiod. The reproductive steps (postcommitment periods) are triggered by the termination of corresponding growth steps. They do not require any supply of external energy, and can therefore be terminated in darkness or in the presence of chloramphenicol. By varying the number of growth steps and their duration, a different extent of overlapping consecutive reproductive steps can be obtained. This overlapping is the major factor affecting the duration of reproductive steps which are proportional to the extent of overlapping. Complex interactions between growth conditions and overlapped reproductive steps resulted in substantial variations in the duration of the whole cell cycle. The present findings do not support the operation of a timing mechanism such as a pacemaker (Zeitgeber) or circadian rhythms, either in regulating the duration of the cell cycle or in the duration of reproductive steps.
Dermal cell populations show variable competence in epidermal cell support: stimulatory effects of hair papilla cells
Authors: Reynolds Amanda J. , Oliver Roy F. , Jahoda Colin A. B.
Published: April 2021

A study was made of the comparative abilities of adult rat vibrissa dermal papilla cells, skin fibroblasts and 3T3 cells to support the initial attachment and subsequent growth and division of directly associated newborn rat skin basal epidermal cells. These associations were made under sub-optimal conditions; that is, in the absence of specific epidermal growth-promoting supplements, in order to assess more accurately the epidermal sustaining capacities of each dermal support Analysis of epidermal cell counts and close photographic scrutiny revealed that low-passage dermal papilla cells, closely followed by transformed dermal papilla cells, were conducive to the successful attachment and subsequent proliferation of epidermal cell populations under three different experimental protocols. In contrast skin fibroblasts did not support epidermal cell growth under any circumstances.

These findings are particularly interesting in that they constitute a rare in vitro example of epidermal cells that are not only supported, but also encouraged to proliferate, by an actively dividing adult skin-derived dermal cell population.
Membrane hyperpolarization activates trout sperm without an increase in intracellular pH
Authors: Boitano Scott , Omoto Charlotte K.
Published: April 2021

Sperm from trout, like other sperm, are immotile in the seminal tract and initiate motility upon dilution into an appropriate fertilizing environment. Trout sperm motility is inhibited by high extracellular [K+] and can be activated by dilution of extracellular [K+]. Activation of trout sperm by the dilution of extracellular [K+] suggests regulation by membrane potential. Using the membrane potential-sensitive fluorescent dye 3,3’-dipropylthiocarbocyanine iodide (diS-C3-(5)) we directly measured the K+ contribution to the membrane potential. Manipulating the membrane potential with Cs+ and the ionophore valino-mycin can override K+ regulation. We show that trout sperm can also be activated in the presence of inhibitory [K+] by the addition of divalent cations. Activation by divalent cations is explained by the cations’ ability to mask membrane surface potential and thus alter the potential sensed by membrane voltage sensors. Using the surface potential-sensitive dye, l-anilino-8-naphthosulfonate (ANS), we directly measure the divalent cations’ ability to mask surface potential. We propose a model where membrane hyperpolarization is the trigger that initiates the cascade of events leading to trout sperm activation.

An increase in intracellular pH has been suggested to be a conserved step in the activation of sperm motility. We show that increasing intracellular pH by procedures that activate sea urchin and mammalian sperm does not activate trout sperm. In contrast, there is a decrease in intracellular pH upon activation of trout sperm motility. Artificially decreasing intracellular pH is not sufficient for activation of motility in trout sperm in an inhibitory [K+]. Thus, unlike some other sperm, changes in intracellular pH do not regulate trout sperm motility.
The fission yeast γ-tubulin is essential for mitosis and is localized at microtubule organizing centers
Authors: Horio Tetsuya , Uzawa Satoru , Jung M. Katherine , Oakley Berl R. , Tanaka Kenji , Yanagida Mitsuhiro
Published: April 2021

γ-Tubulin exists in fission yeast as the product of an essential gene, encoding a 446 amino acid protein that is 77.3% identical to Aspergillus nidulans γ-tubulin. The gene disruption caused cell lethality, displaying condensed, undivided chromosomes with aberrant spindle structures. Anti-γ-tubulin staining showed that γ-tubulin is located, throughout the wild-type cell cycle, at the spindle pole bodies (SPBs), indicating that γ-tubulin associates with interphase SPB in the absence of microtubules. In addition, anti-γ-tubulin immunofluorescence staining revealed cytoplasmic, cell-equatorial putative MTOCs (microtubule organizing centers), which appear only during mitotic telophase and cytokinesis, and are located at the centers for the new cytoplasmic microtubule arrays of the two daughter cells. In the multiple-SPB mutant cutl-cdcll, anti-γ-tubulin antibodies revealed many dots on the periphery of the nucleus. These results confirm that γ-tubulin is an important member of the tubulin superfamily, suggest that it may be a universal component of MTOCs, and are consistent with a role for γ-tubulin in controlling microtubule formation in vivo.
On the Teeth on the Tongues of Mollusca
Authors: Ray J. E. G
Published: April 2021

Lister, Leeuwenhoeck, Swammerdam, Poli, Cuvier, Fleming, Delle Chiaje, Verany, Eydoux, Souleyet, Van Beneden, Oersted, and some other naturalists, have, at various and distant periods, described and figured the teeth on the tongues of isolated species of Mollusca.
A few Remarks on a Paper, read before the Royal Society by Dr. J. W. Griffith, on the Angular Aperture of Object-Glasses
Authors: D’Alquen Dr. F.
Published: April 2021

In the last number of the ‘Microscopical Journal’ an abstract of the above paper was given, and, if you think the subject of sufficient interest to your readers, I should feel obliged if the following observations could appear in your next number, in refutation of the only novel point in Dr. Griffith’s paper.
Geological society: On the Microscopical Structure of Freshwater Marls and Lime- stones
Authors: Sorby H. Clifton
Published: April 2021

The author first described the general conclusions he had arrived at with respect to the condition of the mineral portion of calcareous organisms, which he considered is first deposited in the form of crystalline granules of variable size, that afterwards undergo more or less of crystalline coalescence. In some cases this scarcely occurs at all; but in others it does to a very considerable extent during the life of the organism, and this produces a great difference in the character of the particles into which it is resolved by decay. The falling to powder that then takes place is the result of the oxidization and removal of the organic portion, and, if no crystalline coalescence had occurred, the shell or other body might be resolved into the very minute, ultimate, crystalline granules ; whereas, if much coalescence had taken place, it would break up into much larger ones, showing in many instances its minute organic structure.
Hartig on the Phytozoa of Antheridia
Authors: Currey F.
Published: April 2021

Was wird aus der Schwamfaden der Antheridien ? Dr. Hartig has devoted a section of his essay on the development of the vegetable cell, now in course of publication in the ‘Botanische Zeitung,’ to a consideration of the above question, and the results he has arrived at are highly curious and interesting. Should further investigation lead to a confirmation of Dr. Hartig’s views, the consequence will be that several genera of the Infusoria must be transferred to the vegetable kingdom. Dr. Cohn’s lately-published observations, will have already prepared the minds of the friends of the Infusoria for such a result, and will cause the blow aimed by Dr. Hartig at the animal nature of some of Professor Ehrenberg’s favourites to be less keenly felt. In the following pages we purpose giving the substance of Dr. Hartig’s paper, which is of great interest to microscopical observers ; the experiments are such as may be repeated without difficulty.
Further Observations on the Structure of Appendicularia Flabellum (Chamisso)
Authors: Huxley T. H.
Published: April 2021

In a paper read before the Royal Society in 1851, I gave an account of a very singular animal which had been frequently observed and described under various names, as Appendicularia (Chamisso), Oikopleura (Mertens), Fritillaria (Quoy and Gaimard), Vexillaria (J. Müller), and Eurycercus (Busch), but whose precise place in the animal kingdom was still a matter of doubt. The essential points in that account will be found in the following extracts :—*
Further Observations on the Similarity of Forms observed between Snow Crystals and those of Camphor
Authors: Glaisher James
Published: April 2021

The field of inquiry thus opened by Mr. Spencer has since engaged a portion of my attention. The following are some of the results of observation carried on at intervals, the solution being provided by Mr. Spencer, and a part, I believe, of that employed by him in his own experiments. The following are my notes on the subject.
Rudiments of Pathological Histology
Authors: Wedl Carl , Busk George
Published: April 2021

The Sydenham Society has done unspeakable service for the medical profession by presenting its members with numerous works on Anatomy, Physiology, Medicine and Surgery, in an English form, which, but for it, would ever have remained in this country sealed books, unread and perhaps unknown to the vast majority.
On Dysteria; a new genus of Infusoria
Authors: Huxley Thomas H.
Published: April 2021

The credit of the discovery of the animal which will be described in the following pages is due to my friend Mr. Dyster, of Tenby; and many of the most important statements regarding its structure and habits are based upon his observations. I think, therefore, I cannot do better than name the genus of which it wil form the type after him.*
On the presence of Silica in the Rubiaceæ and in Achillea Ptarmica
Authors: Leipner Adolph
Published: April 2021

Amongst the various inorganic elements which we find present in plants, there is hardly one more interesting than silica, either to the amateur microscopist or to the truly scientific botanist. Some microscopic preparations of siliceous parts, obtained from the Equisetaceæ, Gramineæ, from the Deutzia scabra, and some other plants in which it has been discovered, are rarely wanting in the limited collection of the tyro, whom they please,—and never, I may say, in the cabinet of the experienced physiologist, whom they still, to some extent, puzzle.
Archives of medicine
Authors: Beale Lionel
Published: April 2021

This is the first number of a new medical periodical, but how often it is to appear the editor does not inform us. The object of the editor is to publish papers of a more thoroughly scientific character than are usually found in medical periodical literature, and to have these papers freely illustrated. The subjects on which he wishes to receive papers are as follows: Practical clinical observations.Original researches in Physiology and Pathology.Chemical and Microscopical examination of the solids and fluids of the body.Descriptions of scientific processes.Condensed reports of researches published elsewhere.
Notice of the Occurrence of a Nematoid Parasite in the Ovum of Limax griseus
Authors: Barthélemy M. A.
Published: April 2021

In studying the development of Limax griseus, I was not a little surprised to discover in the first ovum submitted to microscopic examination a minute Nematoid worm, in which might still be observed some vitelline granules. In other ova, more advanced in development, I have noticed similar vermicules, often to the number of three or four, and which had apparently undergone a development corresponding to that of the creature whose domicile they had invaded. At this stage they were large enough to be readily seen with a simple lens, performing tolerably active movements. In most cases they remain at some distance from the embryo, though occasionally I have noticed one of them attached to the vesicle which surmounts the head of the future mollusc. Lastly, in some ova still further advanced, the parasite had destroyed its host, the walls of the ovum were collapsed, and the Nematoid worms might be observed in the interior arrived at their full development—that is to say, furnished with the reproductive organs.
Tobacco and its adulterations with illustrations, drawn and etched
Authors: Prescott Henry P.
Published: April 2021

Many substances used for the adulteration of articles of commerce, which formerly defied all kinds of investigation, are now easily discovered by the aid of the microscope. The medical man was the first to apply this instrument in the detection of fraudulent adulterations of food and medicine. The Government has been slow to appreciate its use in the cases where it might have been employed to detect fraud on taxed articles of consumption. We are, however, glad to be able to congratulate the Inland Revenue department on the possession of an officer who is so capable of appreciating the value of microscopic aid in the detection of adulterations as Mr. Prescott appears to be. It has been long known that chemistry is of little service in detecting the adulteration of tobacco. In fact, for many years, it seems, that instead of chemistry detecting frauds in the adulteration of tobacco, it was the unintentional source of fraud by the Government, who fined tobacconists for having tobacco in their possession which contained sugar, when it afterwards turned out that all tobacco naturally contains a certain quantity of sugar.
On the Structure and Mode of Formation of Starch Granules, according to the Principle of “Molecular Coalescence.”
Authors: Rainey George
Published: April 2021

Starch, from its physiological importance, remarkable structural peculiarities, and general diffusion through the vegetable kingdom, has been a favourite subject of investigation with physiologists and microscopists. However, not-, withstanding the attention which has been devoted to its structure and development, it is acknowledged by the greatest physiologists to be known but little of. (See Mr. Busk’s paper on “Starch Granules,” in the number of the ‘Quarterly Journal of Microscopical Science’ for April, 1853.) There are, doubtless, intrinsic difficulties attending the investigation of this substance, but these have been very much augmented by the principle on which the examination has been conducted, namely, the cellular hypothesis. If this hypothesis had been in itself correct, and admissible as a basis of explanation of the facts connected with the structure and mode of formation of the starch granule, it ought, considering the amount of talent and ingenuity which have been employed in its application to these inquiries, to have thrown more light upon these much disputed, and as yet entirely unsettled questions.
Descriptions of Diatomaceæ, chiefly of those found in “Elide” (Lower California) Guano
Authors: Johnston Christopher
Published: April 2021

I am fully aware of the fallacies which beset the diatomist who establishes new species from the inspection of rare, isolated, and prepared valves; but I am of opinion that science is made the gainer by his efforts, provided he is careful not to substitute names for things, and fancy for the sense. If the observer states the circumstances under which he obtained his facts, it is certainly pardonable in him to group these together in such a manner as to guide ethers in extending the limits of knowledge, whether ‘by verifying his specification, or by modifying it, when accumulated observations justify the emendation.
On the Distinguishing of Elevations and Depressions under the Microscope
Authors: Welcker H.
Published: April 2021

It cannot be contested that the most important point in every microscopical investigation is the correct interpretation of the visible image presented to us. But, as in the latest classical work by Dr. Harting (‘Das Microskop,’ &c.) the subject of Microscopic Diagnosis does not appear to me to have been treated so fully or so correctly as it might have been, I venture to recur to the subject, which has already been noticed by me in papers on Microscopic Technology formerly published in this Journal. *
Atmospheric Micrography. Observations on the Corpuscles suspended in the Atmosphere
Authors: Pouchet M.
Published: April 2021

(‘Comptes rendus/March 21st, 1859.)

The atmosphere contains, in suspension, numerous corpuscles, consisting of the detritus of the mineral crust of the earth, animal and vegetable particles, and the minutely divided débris of the various articles employed in our wants. These various kinds of corpuscles are more numerous and more voluminous in proportion to the degree in which the atmosphere is agitated by the wind; and they constitute what we term “dust.”