The capitulum and feeding mechanism of Ixodes hexagonus Leach. II

Parasitology ◽  
1953 ◽  
Vol 42 (3-4) ◽  
pp. 187-191 ◽  
Author(s):  
D. R. Arthur
Keyword(s):  
Lower Surface ◽  
Homogeneous Material ◽  
Artificial Membranes ◽  
Feeding Mechanism ◽  
Ixodes Hexagonus ◽  
Dermal Cells

1. The action of the mouthparts of Ixodes hexagonus during the penetration of artificial membranes is described.2. Above the hypostomal groove, the chelicerae are closely apposed in the mid-line, but on the inner lower surface each inner cheliceral sheath is drawn into a ventral, toothed lobe, which overlies the hypostomal groove. This lobe disappears in front of the labro-hypostomal groove.3. A lamellate mass of homogeneous material surrounds the rostrum in the skin and at the tip of the hypostome there is marked cytolysis of the dermal cells. There are some pyknotic nuclei visible in this region, and the endothelial walls of the capillaries are swollen, and some contain many polymorphs.

The capitulum and feeding mechanism of Ixodes hexagonus Leach

Parasitology ◽  
1951 ◽  
Vol 41 (1-2) ◽  
pp. 66-81 ◽  
Author(s):  
D. R. Arthur
Keyword(s):  
Lower Surface ◽  
Tissue Reaction ◽  
Lower Wall ◽  
Feeding Mechanism ◽  
External Structure ◽  
Basal Lobe ◽  
Ixodes Hexagonus ◽  
Pharyngeal Muscles ◽  
Pharyngeal Teeth

1. The external structure of the capitulum of Ixodes hexagonus is described in detail, and the differences between it and the closely allied I. cookei are noted.2. The capitulum is divisible into two portions, an extra-basis and basis regions. The former is divided into the hypostomal groove, the labrohypostomal groove and the labro-hypostomal gutter. Internally the basis is divided into dorsal and ventral chambers by the subcheliceral plate. The dorsal chamber houses the chelicerae while the pharynx and the salivary ducts occupy the ventral portion.3. The so-called ‘stylet-like process’ is the anterior prolongation from the basal lobe of the labrum, and forms the mid-rib of a lamella which divides the hypostome into a dorsal salivary channel and a ventral food conduit.4. There are rows of teeth on the internal faces of the anterior fifth of the pharynx. Two series of pharyngeal muscles are present: (i) those having a dorsal attachment to the floor of the salivary chamber, and (ii) those having similar attachments to the subcheliceral plates.5. During feeding the first incision is made by the denticulate apices of the digits and into it the hypostome is then forced. Further cutting by the digits enables the hypostome to penetrate to its base. At the same time the palps splay out. The blood is then drawn up the food conduit by the action of the sucking pharynx. The lower surface of the labrum is produced into a tooth-like projection that fits into a groove of the lower wall of the pharynx. Presumably it functions as a valve to prevent regurgitation of blood. The pharyngeal teeth may function as a supplementary valvular apparatus or else serve for the breakdown of erythrocytes.6. The tissue reaction of a stoat's skin to penetration by the capitulum of I. hexagonus is described.

Video real-time imaging of artificial membranes during freeze-drying by cryo-electron microscopy

1988 ◽  
Vol 46 ◽  
pp. 16-17
Author(s):  
Alan S. Rudolph ◽  
Ronald R. Price
Keyword(s):  
Real Time ◽  
Self Assembly ◽  
Freeze Drying ◽  
Video Capture ◽  
Drying Process ◽  
Artificial Membranes ◽  
The Past ◽  
Cryo Electron Microscopy ◽  
Spherical Structures ◽  
Capture Techniques

We have employed cryoelectron microscopy to visualize events that occur during the freeze-drying of artificial membranes by employing real time video capture techniques. Artificial membranes or liposomes which are spherical structures within internal aqueous space are stabilized by water which provides the driving force for spontaneous self-assembly of these structures. Previous assays of damage to these structures which are induced by freeze drying reveal that the two principal deleterious events that occur are 1) fusion of liposomes and 2) leakage of contents trapped within the liposome [1]. In the past the only way to access these events was to examine the liposomes following the dehydration event. This technique allows the event to be monitored in real time as the liposomes destabilize and as water is sublimed at cryo temperatures in the vacuum of the microscope. The method by which liposomes are compromised by freeze-drying are largely unknown. This technique has shown that cryo-protectants such as glycerol and carbohydrates are able to maintain liposomal structure throughout the drying process.

Ion thinning of integrated circuit transverse specimens for transmission electron microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1426-1427
Author(s):  
F. Shaapur
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Integrated Circuit ◽  
Substrate Surface ◽  
Homogeneous Material ◽  
Material System ◽  
Ion Milling ◽  
Cross Sectional ◽  
Transmission Electron ◽  
Motion Profile

Non-uniform ion-thinning of heterogenous material structures has constituted a fundamental difficulty in preparation of specimens for transmission electron microscopy (TEM). A variety of corrective procedures have been developed and reported for reducing or eliminating the effect. Some of these techniques are applicable to any non-homogeneous material system and others only to unidirectionalfy heterogeneous samples. Recently, a procedure of the latter type has been developed which is mainly based on a new motion profile for the specimen rotation during ion-milling. This motion profile consists of reversing partial revolutions (RPR) within a fixed sector which is centered around a direction perpendicular to the specimen heterogeneity axis. The ion-milling results obtained through this technique, as studied on a number of thin film cross-sectional TEM (XTEM) specimens, have proved to be superior to those produced via other procedures.XTEM specimens from integrated circuit (IC) devices essentially form a complex unidirectional nonhomogeneous structure. The presence of a variety of mostly lateral features at different levels along the substrate surface (consisting of conductors, semiconductors, and insulators) generally cause non-uniform results if ion-thinned conventionally.

Larval Feeding: Mechanisms, Rates, and Performance in Nature

2018 ◽  
Keyword(s):  
Marine Invertebrates ◽  
Spatial Scales ◽  
Size Spectrum ◽  
Larval Feeding ◽  
Natural Habitats ◽  
Feeding Mechanism ◽  
Temporal And Spatial ◽  
And Performance ◽  
Bioenergetics Models ◽  
Many Particles

Larvae of many marine invertebrates must capture and ingest particulate food in order to develop to metamorphosis. These larvae use only a few physical processes to capture particles, but implement these processes using diverse morphologies and behaviors. Detailed understanding of larval feeding mechanism permits investigators to make predictions about feeding performance, including the size spectrum of particles larvae can capture and the rates at which they can capture them. In nature, larvae are immersed in complex mixtures of edible particles of varying size, density, flavor, and nutritional quality, as well as many particles that are too large to ingest. Concentrations of all of these components vary on fine temporal and spatial scales. Mechanistic models linking larval feeding mechanism to performance can be combined with data on food availability in nature and integrated into broader bioenergetics models to yield increased understanding of the biology of larvae in complex natural habitats.

AN EXPERIMENTAL AND NUMERICAL STUDY OF HEAT TRANSFER IN A SIMULATED COLLECTOR FOR A SOLAR DRYER

1993 ◽  
Vol 17 (2) ◽  
pp. 145-160
Author(s):  
P.H. Oosthuizen ◽  
A. Sheriff
Keyword(s):  
Heat Transfer ◽  
Numerical Study ◽  
Local Heat Transfer ◽  
Lower Surface ◽  
Local Heat ◽  
Electrical Heating ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Transfer Rates ◽  
Thermocouple Probe

Indirect passive solar crop dryers have the potential to considerably reduce the losses that presently occur during drying of some crops in many parts of the “developing” world. The performance so far achieved with such dryers has, however, not proved to be very satisfactory. If this performance is to be improved it is necessary to have an accurate computer model of such dryers to assist in their design. An important element is any dryer model is an accurate equation for the convective heat transfer in the collector. To assist in the development of such an equation, an experimental and numerical study of the collector heat transfer has been undertaken. In the experimental study, the collector was simulated by a 1m long by 1m wide channel with a gap of 4 cm between the upper and lower surfaces. The lower surface of the channel consisted of an aluminium plate with an electrical heating element, simulating the solar heating, bonded to its lower surface. Air was blown through this channel at a measured rate and the temperature profiles at various points along the channel were measured using a shielded thermocouple probe. Local heat transfer rates were then determined from these measured temperature profiles. In the numerical study, the parabolic forms of the governing equations were solved by a forward-marching finite difference procedure.

scholarly journals Omp35, a New Enterobacter aerogenes Porin Involved in Selective Susceptibility to Cephalosporins

2004 ◽  
Vol 48 (6) ◽  
pp. 2153-2158 ◽  
Author(s):  
Charléric Bornet ◽  
Nathalie Saint ◽  
Lilia Fetnaci ◽  
Myrielle Dupont ◽  
Anne Davin-Régli ◽  
...  
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Antibiotic Susceptibility ◽  
Enterobacter Aerogenes ◽  
Artificial Membranes ◽  
Specific Location ◽  
Outer Membrane Permeability ◽  
Constriction Region ◽  
High Conductance

ABSTRACT In Enterobacter aerogenes, β-lactam resistance often involves a decrease in outer membrane permeability induced by modifications of porin synthesis. In ATCC 15038 strain, we observed a different pattern of porin production associated with a variable antibiotic susceptibility. We purified Omp35, which is expressed under conditions of low osmolality and analyzed its pore-forming properties in artificial membranes. This porin was found to be an OmpF-like protein with high conductance values. It showed a noticeably higher conductance compared to Omp36 and a specific location of WNYT residues in the L3 loop. The importance of the constriction region in the porin function suggests that this organization is involved in the level of susceptibility to negative large cephalosporins such as ceftriaxone by bacteria producing the Omp35 porin subfamily.

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