bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Fishery‐Independent Indices of Larval and Juvenile Gag Abundance in the Southeastern United States
Authors: Adamski Kyle M. , Buckel Jeffrey A. , Shertzer Kyle W. , Martin Gretchen Bath , Taylor J. Christopher
Published: August 2011

We developed an index describing the abundance of gags Mycteroperca microlepis at the planktonic postlarval stage, and we assessed the index's potential for use in stock assessment. Data on postlarval gags were collected weekly at the Pivers Island bridge near Beaufort Inlet, North Carolina, during the National Oceanic and Atmospheric Administration's bridgenet program (ichthyoplankton sampling, November–May 1986–2008); additionally, ichthyoplankton were sampled nightly during spring in 2007 and 2008. Catch of juvenile gags was examined in relation to several factors to assist in developing and refining fishery‐independent surveys; juveniles were sampled with a small trawl in seagrass beds at 15–20 randomly selected stations near Beaufort Inlet every 2 weeks during June–September 2007 and 2008. Catches of postlarval and juvenile gags were low in both gear types. From 1986 to 2008, weekly concentrations of postlarval gags were highest from mid‐April to mid‐May, and peak ingress coincided with new moon periods. Juvenile gags were caught throughout the June–September sampling period, and the highest catch per unit effort was observed in July and August. Time of year, percent seagrass coverage, seagrass species, and location inside the estuary influenced juvenile gag catch per unit effort. Growth rates of juvenile gags were rapid (∼1.5 mm/d) during summer months and did not differ between years. An annual index of postlarval abundance (adjusted for lunar effects) was developed. The spawning stock biomass from the most recent gag stock assessment was positively correlated with the postlarval abundance index; therefore, this index could be used as a fishery‐independent index of spawning stock biomass.
The myosin-related motor protein Myo2 is an essential mediator of bud-directed mitochondrial movement in yeast
Authors: Förtsch Johannes , Hummel Eric , Krist Melanie , Westermann Benedikt
Published: August 2011

The inheritance of mitochondria in yeast depends on bud-directed transport along actin filaments. It is a matter of debate whether anterograde mitochondrial movement is mediated by the myosin-related motor protein Myo2 or by motor-independent mechanisms. We show that mutations in the Myo2 cargo binding domain impair entry of mitochondria into the bud and are synthetically lethal with deletion of the YPT11 gene encoding a rab-type guanosine triphosphatase. Mitochondrial distribution defects and synthetic lethality were rescued by a mitochondria-specific Myo2 variant that carries a mitochondrial outer membrane anchor. Furthermore, immunoelectron microscopy revealed Myo2 on isolated mitochondria. Thus, Myo2 is an essential and direct mediator of bud-directed mitochondrial movement in yeast. Accumulating genetic evidence suggests that maintenance of mitochondrial morphology, Ypt11, and retention of mitochondria in the bud contribute to Myo2-dependent inheritance of mitochondria.
The COG complex interacts directly with Syntaxin 6 and positively regulates endosome-to-TGN retrograde transport
Authors: Laufman Orly , Hong WanJin , Lev Sima
Published: August 2011

The conserved oligomeric Golgi (COG) complex has been implicated in the regulation of endosome to trans-Golgi network (TGN) retrograde trafficking in both yeast and mammals. However, the exact mechanisms by which it regulates this transport route remain largely unknown. In this paper, we show that COG interacts directly with the target membrane SNARE (t-SNARE) Syntaxin 6 via the Cog6 subunit. In Cog6-depleted cells, the steady-state level of Syntaxin 6 was markedly reduced, and concomitantly, endosome-to-TGN retrograde traffic was significantly attenuated. Cog6 knockdown also affected the steady-state levels and/or subcellular distributions of Syntaxin 16, Vti1a, and VAMP4 and impaired the assembly of the Syntaxin 6–Syntaxin16–Vti1a–VAMP4 SNARE complex. Remarkably, overexpression of VAMP4, but not of Syntaxin 6, bypassed the requirement for COG and restored endosome-to-TGN trafficking in Cog6-depleted cells. These results suggest that COG directly interacts with specific t-SNAREs and positively regulates SNARE complex assembly, thereby affecting their associated trafficking steps.
Cobordism categories of manifolds with corners
Authors: Genauer Josh
Published: August 2011

In this paper we study the topology of cobordism categories of manifolds with corners. Specifically, if

Cob

d
,
⟨
k
⟩

\text {Cob}_{d,\langle k\rangle }

is the category whose objects are a fixed dimension

d
d

, with corners of codimension

≤

k

\leq \;k

, then we identify the homotopy type of the classifying space

B

Cob

d
,
⟨
k
⟩

B\text {Cob}_{d,\langle k\rangle }

as the zero space of a homotopy colimit of a certain diagram of the Thom spectra. We also identify the homotopy type of the corresponding cobordism category when an extra tangential structure is assumed on the manifolds. These results generalize the results of Galatius, Madsen, Tillmann and Weiss (2009), and their proofs are an adaptation of the methods of their paper. As an application we describe the homotopy type of the category of open and closed strings with a background space

X
X

, as well as its higher dimensional analogues. This generalizes work of Baas-Cohen-Ramirez (2006) and Hanbury.
Constructing 𝑘-radius sequences
Authors: Blackburn Simon , McKee James
Published: August 2011

An

n
n

-ary

k
k

-radius sequence is a finite sequence of elements taken from an alphabet of size

n
n

such that any two distinct elements of the alphabet occur within distance

k
k

of each other somewhere in the sequence. These sequences were introduced by Jaromczyk and Lonc to model a caching strategy for computing certain functions on large data sets such as medical images. Let

f
k

(
n
)

f_k(n)

be the shortest length of any

k
k

-radius sequence. We improve on earlier estimates for

f
k

(
n
)

f_k(n)

by using tilings and logarithms. The main result is that

f
k

(
n
)
∼

1
k

(

n
2

)

f_k(n)\sim \frac {1}{k}\binom {n}{2}

as

n
→
∞

n\rightarrow \infty

whenever there exists a tiling of

Z

π
(
k
)

\mathbb {Z}^{\pi (k)}

by a certain cluster of

k
k

hypercubes. In particular this result holds for infinitely many

k
k

, including all

k
≤
194

k\le 194

and all

k
k

such that

k
+
1

k+1

or

2
k
+
1

2k+1

is prime. For certain

k
k

, in particular when

2
k
+
1

2k+1

is prime, we get a sharper error term using the theory of logarithms.
Pseudonodule Formation by Wild-Type and Symbiotic Mutant Medicago truncatula in Response to Auxin Transport Inhibitors
Authors: Rightmyer Adriana P. , Long Sharon R.
Published: August 2011

Rhizobium and allied bacteria form symbiotic nitrogen-fixing nodules on legume roots. Plant hormones play key roles in nodule formation. We treated Medicago truncatula roots with auxin transport inhibitors (ATI) N-(1-naphthyl)phthalamic acid (NPA) and 2,3,5-triiodobenzoic acid (TIBA) to induce the formation of pseudonodules. M. truncatula mutants defective for rhizobial Nod factor signal transduction still formed pseudonodules in response to ATI. However, a M. truncatula ethylene-insensitive supernodulator, sickle 1-1, did not form pseudonodules in response to TIBA, suggesting that the ethylene response pathway is involved in ATI-induced pseudonodule formation. We compared the transcriptional responses of M. truncatula roots treated with ATI to roots inoculated with Sinorhizobium meliloti. Some genes showed consistently parallel expression in ATI-induced and Rhizobium-induced nodules. For other genes, the transcriptional response of M. truncatula roots 1 and 7 days after ATI treatment was in the opposite direction to roots treated with S. meliloti; then, by 21 days, the transcriptional patterns for the two conditions became similar. We silenced 17 genes that were upregulated in both ATI and S. meliloti treatments to determine their effect on nodule formation. Some gene-silenced roots showed a decrease in nodulation efficiency, suggesting a role in nodule formation but not in later nodule functions.
Live non‐invasive Shigella dysenteriae 1 strain induces homologous protective immunity in a guinea pig colitis model
Authors: Barman Soumik , Kumar Ranajit , Chowdhury Goutam , Rani Saha Dhira , Wajima Takeaki , Hamabata Takashi , Ramamurthy Thandavarayan , Balakrish Nair Gopinath , Takeda Yoshifumi , Koley Hemanta
Published: August 2011

A non‐invasive live transconjugant Shigella hybrid (LTSHΔstx) strain was constructed from a Shiga toxin gene deleted mutant of Shigella dysenteriae 1 by introducing a plasmid vector pPR1347 that carried a lipopolysaccharide biosynthesis gene (rfb and rfc) of Salmonella typhimurium. In guinea pigs, four successive oral administrations of LTSH Δstx showed complete protection against rectal challenge with wild type S. dysenteriae 1 strain. Exponential increase of the serum IgG and IgA titer against lipopolysaccharide of LTSH Δstx was observed during immunization, peaked on day 28 and remained at that level until day 35 after the initiation of the immunization. In intestinal lavage of the immunized animals, significant increase of IgA titer against lipopolysaccharide of LTSH Δstx was also observed. These data suggested that LTSH Δstx could be a useful candidate to induce protective immunity against S. dysenteriae 1 infection.
Alteration of inhibitory and activating natural killer cell receptor expression on T cells in human immunodeficiency virus‐infected Chinese
Authors: Jiang Yongjun , Wu Shanshan , Zhou Fangyuan , Bice Tristan , Zhang Zining , Liu Jing , Ding Haibo , Han Xiaoxu , Shang Hong
Published: August 2011

T cell expression of NKRs can trigger or inhibit cell‐mediated cytotoxicity. However, few studies on T lymphocyte NKR expression in HIV infection exist. Here, we examined the expression patterns of NKG2D, NKG2A, and KIR3DL1 on CD8+ and CD3+CD8− cells by multicolor flow cytometry in groups of patients with HIV, AIDS or HAART‐treated AIDS, as well as HIV‐negative normal controls. Individual analysis of KIR3DL1 on CD3+CD8+ or CD3+CD8− cells revealed no significant differences among any of the groups (P > 0.05). In contrast, the percentage of NKG2A+NKG2D−CD8+ T cells was higher in the AIDS group than in the HIV‐negative normal control group (P < 0.01). Meanwhile, the prevalence of NKG2D+NKG2A−CD8+T cells was lower in the AIDS group than in HIV‐negative normal controls (P < 0.001). Similar results were also observed for the percentage of NKG2A+NKG2D− on CD3+CD8−cells. However, in contrast to CD8+ T cells, the frequencies of NKG2D+NKG2A− on CD3+CD8− cells were higher in AIDS and HIV patients than in HIV‐negative normal controls (P < 0.01, P < 0.05, respectively). The percentage of NKG2A+NKG2D−CD8+ T cells was negatively correlated with CD4+ T cell counts (r=−0.499, P < 0.01), while the percentage of NKG2D+NKG2A−CD8+ T cells was positively correlated with CD4+ T cell counts (r= 0.494, P < 0.01). The percentage of NKG2D+NKG2A−CD3+CD8− T cells was also positively correlated with viral load (r= 0.527, P < 0.01) and negatively correlated with CD4+ T cell counts (r=−0.397, P < 0.05). Finally, HAART treatment reversed the changes in NKR expression caused by HIV infection. These results indicate that the expression of NKRs on T cells may be correlated with HIV disease progression.
Clinical applications of aptamers and nucleic acid therapeutics in haematological malignancies
Authors: Shigdar Sarah , Ward Alister C. , De Abhijit , Yang Chaoyong J. , Wei Mingqian , Duan Wei
Published: August 2011

Haematological malignancies result from a heterogeneous mix of genetic mutations and chromosome aberrations and translocations. Targeted therapies, such as the anti‐CD20 antibody rituximab, or the BCR‐ABL1 inhibitor imatinib, have proven to be effective treatments in the management of some of these malignancies, though relapsing or refractory disease is still common. Nucleic acid‐based therapies have also entered the clinical arena, providing an alternative, complementary approach. The forerunner of these therapies were the antisense oligonucleotides, but their scope has expanded to include short‐interfering RNA (siRNA), microRNA, decoy oligonucleotides and aptamers. These can be used either as mono‐therapeutics, in conjunction with current chemotherapy regimens, or in combination with each other to improve therapeutic efficacy. Not only can these nucleic acid‐based therapies silence target genes, they also have the potential of restoring gene function. While challenges remain in delivering effective doses of nucleic acid in vivo, these are steadily being met, suggesting an optimistic future in the treatment of haematological malignancies. This review summarizes the application of nucleic acid‐based therapeutics, particularly aptamers, in the diagnosis and treatment of haematological malignancies.
Deregulation of FGFR1 and CDK6 oncogenic pathways in acute lymphoblastic leukaemia harbouring epigenetic modifications of the MIR9 family
Authors: Rodriguez‐Otero Paula , Román‐Gómez José , Vilas‐Zornoza Amaia , José‐Eneriz Edurne San , Martín‐Palanco Vanesa , Rifón José , Torres Antonio , Calasanz María José , Agirre Xabier , Prosper Felipe
Published: August 2011

The role of epigenetic mechanisms in the regulation of microRNAs (miRNAs) with a tumour‐suppressor function in human neoplasms has recently been established. Several miRNAs have been found to be inappropriately regulated by DNA methylation in patients with acute lymphoblastic leukaemia (ALL). We analysed the methylation status of the three members of the MIR9 family (MIR9‐1, MIR9‐2 and MIR9‐3) in a uniformly treated cohort of 200 newly diagnosed ALLs. MIR9 was methylated in 54% of the patients and was associated with downregulation of MIR9 (P < 0·01). Hypermethylation of MIR9 was an independent prognostic factor for disease‐free survival, overall survival and event‐free survival in a multivariate analysis (P < 0·01). Epigenetic downregulation of MIR9 induced upregulation of its targets, FGFR1 and CDK6, while treatment of ALL cells with FGFR1 (PD‐173074) and CDK6 (PD‐0332991) inhibitors induced a decrease in cell proliferation and an increase in apoptosis of ALL cells. Our results indicate that the MIR9 family is involved in the pathogenesis and clinical behaviour of ALL and provide the basis for new therapeutic strategies in the treatment of ALL, targeting the epigenetic regulation of miRNAs and/or the FGFR1 or CDK6‐RB pathway directly.
One Mouse per Child: interpersonal computer for individual arithmetic practice
Authors: Alcoholado C. , Nussbaum M. , Tagle A. , Gomez F. , Denardin F. , Susaeta H. , Villalta M. , Toyama K.
Published: August 2011

Single Display Groupware (SDG) allows multiple people in the same physical space to interact simultaneously over a single communal display through individual input devices that work on the same machine. The aim of this paper is to show how SDG can be used to improve the way resources are used in schools, allowing students to work simultaneously on individual problems at a shared display, and achieve personalized learning with individual feedback within different cultural contexts. We used computational fluency to apply our concept of ‘One Mouse per Child’. It consists of a participatory approach that makes use of personal feedback on an interpersonal computer for the whole classroom. This allows for N simultaneous intelligent tutoring systems, where each child advances at his or her own pace, both within a lecture and throughout the curricular units. Each student must solve a series of mathematical exercises, generated according to his or her performance through a set of pedagogical rules incorporated into the system. In this process, the teacher has an active mediating role, intervening when students require attention. Two exploratory studies were performed. The first study was a multicultural experience between two such distanced socio‐economic realities as Chile and India. It showed us that even in different environmental conditions, it is possible to implement this technology with minimal equipment (i.e. a computer, a projector, and one mouse per child). The second study was carried out in a third grade class in a low‐income school in Santiago de Chile. The students were asked to solve mainly addition exercises. We established statistically relevant results and observed that the software proved most beneficial for the students with the lowest initial results. This happens because the system adapts to the students' needs, reinforcing the content they most need to work on, thus generating a personalized learning process.
Detection of dichroism with the microscope
Authors: Goldstein D. J.
Published: August 2011

Two simple, sensitive, visual methods are described for the detection of dichroism in microscopic objects.

1. The object is oriented at ±45° between crossed polars, and either the polarizer or the analyser is rotated through an equal angle alternately clockwise and anti‐clockwise. A dichroic object will brighten as the polar is rotated in one direction and darken as the polar is rotated in the other. If the optic axis of the object lies north‐east to south‐west and the transmission axes of polarizer and analyser respectively east‐west and north‐south, a positively dichroic object will darken as the polarizer is rotated anti‐clockwise, or the analyser is rotated clockwise.

2. A formally similar method, which avoids the need to rotate either polar, is to orient the object at ± 45° between crossed polars, and insert a Nakamura plate between the polars in an optical plane conjugate with the specimen. Dichroism is indicated by inequality of the apparent brightness of the specimen on either side of the dividing line of the plate.

Both methods are more sensitive than visual techniques traditionally used in microscopy.

The sign of the dichroism of polished smears of dye particles is discussed. It is suggested that polishing in the dry state orients individual dye molecules, while polishing of a damp smear orients dye molecule aggregates.

The relation of dichroism to the colour of stained histological structures, as seen either between crossed polars or with bright‐field illumination, is discussed, and the elementary optical theory of dichroism is summarized.
Demonstration of β‐glucuronidase with naphthol AS‐BI‐β‐D‐glucosiduronic acid by simultaneous coupling
Authors: Jeffree Grace M.
Published: August 2011

Using unfixed cryostat sections, well‐localized staining for β‐glucuronidase with Naphthol AS‐BI‐βD‐glucosiduronic acid as substrate was obtained by simultaneous coupling at pH 5·0 with Fast Bordeaux OL and Fast Red Violet LB salts and with diazotized pararosanilin. With some other diazonium salts, enzyme inhibition or background staining led to unsatisfactory results.
A simplified time‐lapse cinemicrographic unit
Authors: Burton Alexis L.
Published: August 2011

Time‐lapse mechanisms, specially intended for use in conjunction with the microscope, are described. They are extremely simplified and of very low cost. An unmodified camera is driven continuously at low speed and the exposure is made by means of an electronic flashlight. Synchronization of the flash is secured by a microswitch which activates the flashlight when the shutter of the camera is open. Two equipments (for 35 mm and 16 mm film) of this type were built and found very satisfactory.
Stereology, or the quantitative evaluation of microstructures
Authors: Underwood E. E.
Published: August 2011

A general survey is presented of the basic equations of stereology, that is, the quantitative relationships that exist between quantities measured on the two‐dimensional plane of polish or section and the magnitudes of microstructural features that occur in three‐dimensional space. A new and important branch of stereology concerns the quantitative relationships between structures in a thin foil and their projected images. Basic equations are given in the absence of overlap and truncation; then overlap and truncation corrections are indicated for simple cases. The methods of determining the size distribution of particles or grains are outlined. Finally, other important parameters are described, such as the mean free distance and the mean intercept length.

The subject of stereology is not completely new to some, but there are still many experiments to be run and methods to be perfected. It is hoped that microscopists dealing with microstructures will be encouraged to apply quantitative methods in their work in order to advance our knowledge in this fascinating field.
Measurements from electron micrographs of organelle size in relation to their shape: A refinement applied to the epidermal melanosome and basal lamella
Authors: Waterhouse J. P. , Squier C. A.
Published: August 2011

The mean value of measurements of organelles made from electron‐microscope sections cut in random planes is not an accurate expression of any important dimension of a nonspherical organelle; realistic measurements of organelles in electron micrographs must take into account the three‐dimensional shape of the organelle. Stereological methods offer ways of calculating surface areas and volumes of organelles in electron‐microscope sections but do not provide an easy means of deriving three‐dimensional structures. If, however, the three‐dimensional shape of an organelle is known, it is possible to select profiles which contain what is approximately a major or a minor axis. The frequency distribution of the values from profiles so chosen are skewed, and the median provides the best estimate of the dimension of the organelle. The median and the interquartile range (P25–P75) are presented for measurements made in this way of melanosomes and the basal lamella and lamina lucida of mammalian oral epithelium.
A method of processing third‐stage larvae of the nematode Trichostrongylus colubriformis for electron microscopy
Authors: Smith K.
Published: August 2011

A method for processing third‐stage larvæ for electron microscopy is described. Using simple apparatus larvæ are separated from fæcal material by migration to a warmed area; they are then immobilized and chopped up in agar prior to fixation. No cellular distortion is observed in ultra‐thin sections.
The use of liquid photographic emulsion for demonstrating blood vessels in histological sections
Authors: Olson Ian A. , Skuse Dorothy E.
Published: August 2011

Autoradiographic liquid coating emulsion was exposed to strong light and then injected at body temperature into the right or left ventricle of 400–1000 g guineapigs. Bouin‐ or Zenker‐fixed tissues were processed routinely, embedded in ester wax and sections mounted on standard glass slides. These were developed in photographic developer before staining by a variety of methods. The sections were examined under incident‐light illumination which demonstrated the general microcirculation of the tissue at low magnifications as a shining silver pattern displaying many vessels not visible in transmitted light. It was thereafter possible to examine and identify the vessels so demonstrated, as the fine grains of silver did not obscure the histological detail under high magnification in standard transmitted light.
Visibility and resolution of periodic structure in oblique dark‐ground illumination: Images of diatoms with rectangulate and triangulate arrays of fine structure
Authors: Hewlett P. S.
Published: August 2011

Dark‐ground images of selected diatoms have been investigated and the resolution attained has been found compatible throughout with the Abbe theory of image formation when correctly applied. At the same time, resolution beyond that indicated by the formula conventionally quoted for dark ground is frequently possible. This is because the conventional formula is based on the imaging of a line grating, but additional diffraction maxima permitting increased resolution occur when certain other forms of periodic structure are examined under dark‐ground illumination. Some suspect claims made in the past for resolution of diatoms in dark ground are examined. Several are undoubtedly justified, though the general statement that dark‐ground resolution is equal to that in bright field is not.
Increasing the camera constant of the EM6 microscope
Authors: Duggan B. J. , Greene G. W.
Published: August 2011

When identifying compounds by electron diffraction it is necessary to consider the error introduced in the calculated lattice spacings (‘d‐values’) during measurement of the patterns. This becomes particularly important for very complex patterns with large d‐values such as 4PbO. PbSO4, where only spots very close to the centre spot are characteristic. There are several methods for increasing the camera constant to reduce this error, but the one described has the advantage of retaining the required facility of selected‐area diffraction. The method was developed on an AEI EM6 microscope.
An electron‐optical lens effect as a possible source of contrast in biological preparations
Authors: Haydon Glen B.
Published: August 2011

Heavy‐metal stain aggregates on the surface of thin sections of biological material have higher contrast than those embedded within the sections and both have greater contrast than can be accounted for by the amplitude image. Disturbances of the incident illumination by a specimen in both light‐ and electron‐optical systems and their possible contribution to image contrast are considered. The hypothesis is proposed that a lens effect produced by the stain aggregates may account for their contrast in the electron microscope in a similar manner to the contrast of glass beads in the light microscope with a low numerical aperture.
Quantitative studies on the preservation of choline and ethanolamine phosphatides during tissue preparation for electron microscopy
Authors: Cope G. H. , Williams M. A.
Published: August 2011

The loss of 14C ethanolamine‐ and 3H choline‐labelled phospholipids from rat liver during tissue preparation for electron microscopy has been examined. Column and thin‐layer chromatography combined with double‐label scintillation spectrometry were used to analyse the radioactive phospholipid content of the livers of rats injected simultaneously with 14C aminoethanol and 3H choline chloride. After 4 h (in vivo) the 14C and 3H labels were mainly incorporated into phosphatidyl ethanolamine and phosphatidyl choline respectively but some 14C label had been incorporated into phosphatidyl choline. Chopped rat liver was fixed in glutaraldehyde or osmium tetroxide or both sequentially and tissues were dehydrated in ethanol and embedded in Araldite. In each procedure examined the choline label proved more labile than the ethanolamine. After glutaraldehyde fixation alone complete loss of phosphatidyl choline occurred and half of the phosphatidyl ethanolamine was also lost. Following osmium tetroxide fixation negligible loss of either phosphatide occurred. In terms of phospholipid retention, no advantage was gained by glutaraldehyde fixation prior to osmium tetroxide fixation. The results show that both ethanols and embedding monomers are potent phospholipid solvents. The data also suggests that EM autoradiography of these two phosphatides may be carried out with reasonable confidence although it must be pointed out that a high degree of retention does not necessarily imply retention in situ.
An apparatus for fixation and continuous dehydration of specimens for paraffin sections
Authors: Turler Sonia , Frei Ulrich
Published: August 2011

Stimulated by the paper describing an apparatus for continuous dehydration by Evans (1966) we have developed an apparatus of our own. The chief differences between this and that mentioned above are:

(1) The use of a hypodermic needle which assures an absolutely constant flow of dehydrating fluid. Any given speed is reproducible by a simple change of needle and is not influenced by normal changes of temperature or by the quantity of liquid in the reservoir.

(2) The elimination of a stirrer shaft, whereby space is gained and the use of one large basket is made possible.

(3) The apparatus can be connected to a vacuum pump for fixation, or to a water tap for rinsing.

(4) The apparatus can be placed in an oven.

One of our aims was to eliminate handling of the specimens as far as possible. The apparatus, which has now been successfully in use for over a year, allows us to leave the specimens untouched from the fresh state right up to the transfer to paraffin.
High‐voltage electron microscopy of inorganic particles in intact blood cells
Authors: Clarke J. A. , Cosslett V. E. , Salsbury A. J.
Published: August 2011

Preliminary results obtained by examining intact fixed human red and white blood cells containing inorganic particles under the high‐voltage transmission electron microscope are described. Iron filings and ferritin ingested in vitro by granulocytes were observed as were inorganic particles in red cells from a case of lead poisoning. The nature of the particles in red cells is discussed. A faint intracellular network was seen in normal red cells and in cells from a case of lead poisoning. It was found possible to focus the electron microscope at different planes within the cell. The optimum accelerating voltage for red cells appeared to be around 750 kV, whereas a clear image of granulocytes was obtained at voltages between 750 and 1000 kV. The first results indicate that it is possible to examine intact blood cells under the high‐voltage electron microscope. Further work is in progress to determine if more information can be acquired by this technique.
The effect of the electron beam on various mounting and coating media in scanning electron microscopy
Authors: Muir M. D. , Rampley D. N.
Published: August 2011

Eight commonly used specimen adhesives were examined under the ‘Stereo‐scan’ scanning electron microscope to determine the effects of the electron beam on their surface topography. The adhesives were initially examined uncoated, and then coated variously with carbon, and seven different metals and alloys. The effect of the beam on the coated and uncoated adhesives was recorded. The results are presented in tabular form. The purpose of the experiments was to determine the extent of the damage, if any, produced by the beam, on the adhesive, and to try to discover the most damage‐resistant combinations. While combinations are damage‐free, some of the more easily damaged adhesives are regarded as being suitable for certain specialized purposes, where their special properties over‐ride their susceptibility to beam damage.
A roll film camera for the AEI‐EM6 electron microscope
Authors: Pedler C. M. H. , Mould G.
Published: August 2011

The currently available plate camera for the AEI EM6 and 6B microscopes is inconvenient for the photography of large numbers of serial sections: firstly because it has to be reloaded relatively frequently and secondly because the restricted format of 70 mm film does not allow a large enough field to be examined at low power. The camera described was designed and built in these laboratories to obviate these problems.
The dimensions and numbers of small vesicles in cells, endothelial and mesothelial and the significance of these for endothelial permeability*
Authors: Casley‐Smith J. R.
Published: August 2011

Measurements were made of the diameters, numbers and other parameters of small, smooth‐surfaced vesicles in the endothelium of blood capillaries and lymphatics, and in the mesothelial cells of the diaphragms of mice. Some measurements were also made on the aortic endothelium. With a few exceptions, there were no morphological differences between the various sites.

It was found that between 25% and 35% of the non‐nuclear cell volume was composed of vesicles, whose membranes accounted for about 55% of their volumes. Their internal volumes were ∼ 70,000 nm3, totalling ∼ 0·04 μm3/μm2 of luminal surface area. For each 1 μm2 there were ∼ 135 vesicles attached to each surface membrane of the cell, and between ∼ 200 and ∼ 350 vesicles lying free in the cytoplasm. There was probably a slight amount of shrinkage during the preparation of the material, and the true linear dimensions were probably ∼ 105% of those actually observed. Thus the values for the internal volumes were probably ∼ 85,000 nm3 and ∼005 μm3 respectively; the vesicular numbers were probably ∼ 125 attached to each surface and between ∼ 175 and ∼ 300 free.

The vesicles attached to the plasma membranes often had quite long stalks; these were estimated to be ∼ 30 nm at the moment of rupture. Thus the vesicles must be released an appreciable distance away from the membrane. This modifies the conclusions of Shea & Karnovsky (1966), since it can now be shown that Brownian movement alone is capable of accounting for the release of the vesicles, their movements within the cells and their transportation of material.

By combining these results with others estimating the endothelial permeability coefficients, it can be calculated that the average free lifetime of a vesicle is ∼1½ sec, from union with one plasma membrane to the next. It can also be shown that the average time of such an attachment is ∼ 2½ sec. There are many possible sources of error relating to these measurements; they must only be regarded as tentative. It appears likely, however, that they are of about the correct order of magnitude as they accord well with other data.
Computer‐generated distribution functions as an aid to the quantitative interpretation of electron micrographs of shadowed macromolecules
Authors: Rowe A. J. , Rowe H. J.
Published: August 2011

Using the mica‐replication technique of Hall, it is possible to visualize small, metal‐shadowed biological macromolecules. Consideration is given to the interpretation of micrographs obtained in this way, in order that molecular dimensions may be inferred.

It is shown that the width of the shadow cast by a macromolecule can be measured precisely. A method is developed whereby the histogram of the experimentally determined shadow widths is interpreted by reference to computer‐generated histograms, based upon models of assumed dimensions. Results are presented illustrating the use of this new method.
A capillary fluorescence standard for microfluorometry*
Authors: Sernetz M. , Thaer A.
Published: August 2011

Quartz glass capillaries of about 6 μm inside diameter were filled with fluorochrome solutions of accurately known concentrations and embedded as microscopical objects. The fluorescence intensity of a constant capillary volume has been found to be directly proportional to the amount of the excited fluorochrome in this volume within the fluorochrome concentration range 1:103. The capillary volume can be determined accurately by microinterferometric measurement of the inside diameter.

The capillary section irradiated by the exciting light may be considered as very small in comparison with the total length of the capillary tube. During and after irradiation the excited part of fluorochrome solution is continuously renewed by convectional flow and diffusion. Therefore photodecomposition does not affect the measured fluorescence intensity, and the standard value remains unchanged even after numerous measurements. Thus, these fluorescence standards may be used to make successive calibrations of a microfluorometer and to check the constancy and reproducibility of measuring conditions. In certain circumstances it also permits measured fluorescence intensity to be interpreted in terms of the amount of fluorochrome or fluorescent substance.

The results achieved with the capillary fluorescence standard are compared with those obtained by means of conventional methods. In addition, some essential optical properties of the microfluorometer equipment required for the proper use of this standard are discussed.
Electron cytochemical localization of cystine in plant cell walls
Authors: Thompson E. , Colvin J. Ross
Published: August 2011

A method for specific, cytochemical staining of cystine residues was applied to thin sections of human hair keratin, two yeasts, one fungus and one green alga, for observations in the electron microscope. The method, which deposits granules of metallic silver at or close to the site of cystine residues, may be a useful means of investigating the detailed distribution of disulphide bonds in cells provided that the following criteria are rigorously applied. First, grains of metallic silver must remain after exhaustive sodium thiosulphate extraction; second, the deposition of grains of metallic silver must be inhibited by prior alkylation of the disulphide linkage. Finally, the method should be used in conjunction with other available means of analysis.
Electron staining of synaptic vesicles using the Champy‐Maillet technique
Authors: de Iraldi Amanda Pellegrino , Suburo Angela Maria
Published: August 2011

Synaptic vesicles from rat pineal nerves can be stained by Champy‐Maillet mixtures containing osmium tetroxide and a soluble iodide. Two components of the vesicle (the matrix and the dense core) are revealed in a different way depending on at least two factors: the iodide employed and the final pH of the mixture. We have tried the following mixtures: zinc iodide at pH 5·5 (ZIO), cadmium iodide at pH 6·0 (CIO) and potassium iodide at pH 7·2 (KIO‐7) or pH 5·5 (KIO‐5). The matrix is more reactive with ZIO, while the dense core is more reactive with CIO and especially with KIO‐7. With the only difference of a lower pH, KIO‐5 stains the whole matrix of some vesicles and also reveals some tubular structures which are more frequently found in preterminal axons.
Silver staining of collagen and reticulin fibres and cerebral capillaries by means of physical development
Authors: Gallyas F.
Published: August 2011

A method for demonstrating collagen and reticulin fibres and the network of brain capillaries has been worked out on the basis of a new silver staining principle. It may be applied to sections as thick as 200 μm from both frozen and embedded material. The principle is as follows: the 1,2‐glycol groups of tissue elements, including connective tissues, are converted to aldehyde groups by periodic acid. The aldehyde groups form colloidal silver particles in an ammoniated silver nitrate solution of pH 13. At this pH value, however, it is only the connective tissue that can bind the colloidal silver which is being formed. After the silver ions have been washed out of the sections, the silver grains deposited in the connective tissue are finally enlarged to microscopic dimensions by physical development.
A simple microscope warm stage
Authors: Guntrip A. V.
Published: August 2011

Microscopical examination of cells, particularly spermatozoa, often necessitates the preservation of a temperature of 37°C on the stage itself. A microscope warm stage should provide a surface at this temperature and allow microscopical examination of a series of pre‐warmed sample slides. A further desirable quality would be the total absence of ancillary apparatus. An apparatus has been designed and built which effectively provides these features. It measures 10·5 × 6·5 × 1·3 cm, weighs 320 g with wiring and plug and provides a thermostatically controlled temperature of 37 ± 0·5°C 5 min after connection with the electrical supply (240 V A.C.).
Enhanced contrast in electron microscopy of unstained biological material: II. Defocused contrast of large objects
Authors: Johnson H. M. , Parsons D. F.
Published: August 2011

A contrast minimum is observed when 88 nm diameter polystyrene latex spheres are underfocused, which is related to the wide‐angle scattering peaks. Images due to scattered and non‐scattered wave components are displaced due to objective‐lens spherical aberration and defocus. Maximum overlap of these components produces a contrast minimum at underfocus, related to the spherical aberration of the particular lens used.

Similarly, a high‐contrast band at carbon‐film edges arises from spherical aberration and defocus separation of non‐scattered and wide‐angle scattered waves. This band increases in contrast with film thickness and in width with lens defocus.

These geometrical effects account for the well‐known ‘blinking’ of contrast of large biological objects upon swinging through focus without an objective aperture, and for the general contrast increase of defocused large objects. Fresnel fringes account for only a narrow band of enhanced contrast at distinct edges and cannot account for contrast enhancement of large objects lacking distinct edges.
Examination of rock surfaces with the scanning electron microscope
Authors: Gillott J. E.
Published: August 2011

A fracture surface of rock (greywacke) was examined with the scanning electron microscope prior to, and after, surface etching for successively increasing time intervals in 2 m NaOH at 38°C (100°F). The same area of rock was successfully relocated in the microscope so that the effect of the alkali upon minerals and micro‐structure could be observed by direct comparison of micrographs. Layer‐structure silicates showed exfoliation.
Polyester resin as a mounting medium for light microscopy
Authors: Senior W.
Published: August 2011

The use of a commercially available polyester resin is described for the production of whole‐mount preparations and as a mounting medium for histological sections. Any standard technique can be used which involves xylene as the clearing agent. It is considered that the slides produced are much stronger than those made with traditional mounting media and do not require long drying times before use. The method is particularly suitable for mounting thick specimens for teaching purposes.
Reduction of compression artifacts in ultra‐thin sections by the application of heat
Authors: Roberts I. M.
Published: August 2011

Cutting compression in ultra‐thin sections prepared for electron microscopy was decreased when sections floating in the knife trough were exposed to radiation from a V‐shaped, heated wire filament. The apparatus is called a ‘heat pen’ and consists of a filament mounted in a ball‐point pen body and heated by a step‐down transformer. The method gave less residual compression than conventional solvent vapour methods without any apparent ill effects on staining properties, specimen stability or resolution. For specimens which were prone to wrinkling caused by shrinkage following vapour stretching, this technique gave much improved results. Heat stretching also eliminates the need to use solvent vapours which may be harmful to the microtomist.
Permanent fluorescent test slides
Authors: Walker P. J. , Watts Janet M. A.
Published: August 2011

Permanent test slides for fluorescence microscopy can easily be prepared by suspending Helecon fluorescent pigments, numbers 2225 and 2266, in DPX and mounting under a cover glass in the usual way. These two pigments simulate the excitation and emission of fluorescein conjugates and acridine orange. Eight other pigments have been tested and their properties are described.
A modified aldehyde perfusion technique for preventing certain artifacts in electron microscopy of the central nervous system
Authors: Schultz Robert L. , Case Norman M.
Published: August 2011

The production of vacuolated mitochondria and myelin figures can be markedly reduced with aldehyde perfusion fixation by perfusing a concentrated aldehyde solution before the conventional perfusate. A method is presented for accomplishing this with no practical time delay. Factors causing myelin figures and damaged mitochondria are discussed.

Gum acacia helps prevent ‘washed‐out’ cells and processes, and seems to aid myelin preservation. A clear solution is necessary for a good perfusion. Techniques for accomplishing this are presented.

A concentrated formaldehyde solution perfused as a small volume immediately prior to the conventional perfusate causes alterations of the endoplasmic reticulum, including the subsurface cisterns, and an increase in numbers of spine apparatuses. Evidence is presented by using tubes of gelatin containing Schiff's reagent that formaldehyde is the fastest penetrating aldehyde but that it only fixes about half the distance it penetrates. Acrolein penetrates more rapidly than glutaraldehyde but fixes only as far as formaldehyde. Glutaraldehyde fixes as far as it penetrates.
The effects of various pre‐treatments on the freeze‐etching of root tips
Authors: Fineran B. A.
Published: August 2011

Results of experiments on the pre‐treatment of root tips for freeze‐etching are outlined. Successful freeze‐fixation of viable roots was obtained using seedlings of Avena, Triticum and Zea. The seeds were germinated in contact with water, then placed on top of tubes of filter paper impregnated with glycerol; this allowed aeration of the roots. Most roots grew slightly on exposure to glycerol and remained turgid. Avena and Triticum gave good freeze‐fixation after 7 days in contact with 20% glycerol and after contact with 20% glycerol for 3 days followed by 25% glycerol for 3 days. Good preservation was also obtained with Zea but results were more variable than in Avena and Triticum.

Root tips fixed in glutaraldehyde, either in glycerol or followed by glycerol, gave consistent freeze‐fixation in all species. Results were comparable to those obtained from viable material. However, in some instances there was shrinkage of the organelles and the plane of fracture within certain membranes was altered.
Polarized light and phase‐contrast studies of stained and unstained plant cell nucleoli
Authors: Kordan H. A.
Published: August 2011

Nucleolar morphology in interphase nuclei of non‐growing and growing plant cells has been studied by polarized light and phase‐contrast microscopy. Variation in the optical properties of the nucleoli in unstained preparations are indicative of different morphological stages of this cell organelle with respect to the physiological status of the cells in which these variations occur. A filamentous nucleolar component, the nucleolonema, was evident in unstained nucleoli of explants cultured in vitro and in hypocotyls of germinating seeds. Unstained and stained preparations indicate that the polarized‐light effects observed in nucleoli of previous investigations are primarily associated with this filamentous nucleolar structure.
Leaf wax fine structure and ontogeny in Eucalyptus demonstrated by means of a specialized fixation technique
Authors: Hallam N. D.
Published: August 2011

The epidermal cells of Eucalyptus leaves are not well preserved by the conventional sectioning methods used for electron microscopy. More satisfactory preservation results from the use of an in vivo perfusion technique using glutaraldehyde or glutaraldehyde‐formaldehyde mixtures. This technique preserves wax on the cuticle surface, rendering it insoluble in the organic solvents used for dehydration and embedding in epoxy resins. Using this method, no direct connection is apparent between leaf wax, cuticle, cell wall and cytoplasm. The Golgi bodies appear to produce vesicles which migrate only in the direction of the outer cell wall, and which might liberate wax precursors into the wall, from where they could diffuse through cuticular lamell to polymerize or oxidize at the leaf surface as waxes of characteristic morphology.