scholarly journals Studies on the Comparative Physiology of Digestion

1923 ◽  
Vol 1 (1) ◽  
pp. 15-64
Author(s):  
C. M. YONGE
Keyword(s):  
Muscle Fibres ◽  
Visceral Mass ◽  
Amylolytic Enzyme ◽  
Excretory Function ◽  
Organic Debris ◽  
Ciliary Action ◽  
Homologous Structure ◽  
Food Groove ◽  
Micro Organisms ◽  
Food Value

The observations recorded in this paper on the feeding, the alimentary organs, and the digestive processes in Mya arenaria, may be epitomised as follows:-- 1. The food consists of organic debris, sand particles, and micro-organisms suspended in food currents, which are created by the ciliary action of the gills, and conveyed to the mouth by ciliary currents on the surface of the gills and labial palps. 2. Particles are carried towards the ventral margin of the demibranchs, where they are caught in the currents created by the large cilia present in the region of the marginal food groove, and carried towards the mouth. A third anterior current, also created by large cilia, runs along the gill axis. 3. The direction of the ciliary currents on the labial palps has been described in detail, and the view expressed that the ciliary mechanism present on the inner face of the palps is devoted entirely to the separation of the food into large and small particles, the former being despatched to the tip of the palp, and the latter carried forward to the mouth. 4. Coarser particles which do not reach the gills, and other particles rejected by the gills and palps, are carried away by ciliary currents present on the visceral mass and mantle, and are finally expelled from the mantle chamber. 5. The anatomy and histology of the alimentary canal and the hepatopancreas have been described. 6. The presence of muscle fibres in the wall of the gut is practically restricted to the œsophagus and rectum, but the entire alimentary tract, with the exception of the area of the gastric shield, is ciliated and abundantly provided with mucussecreting glands. 7. The presence of ciliary currents in all parts of the gut has been demonstrated. 8. The ciliary currents present in the stomach have been described, and the definite separation of the food into larger and smaller particles, particularly by the mechanism of the grooved area, has been shown. The larger particles are carried straight into the intestine and the smaller particles to the base of the gastric shield, where they are caught in the substance of the tip of the style. 9. The universal presence of phagocytes or wandering cells throughout the gut has been noted, and their special activity in the grooved area of the stomach described. The balance of evidence has been shown to be in favour of the view that they are nutritive in function, although they may also have an excretory function, as they have been shown to be capable of ingesting matter of absolutely no food value. 10. The histology of the style-sac, the origin of the style, and the ciliary currents present in the sac have been described. 11. The mature style has been described and evidence brought forward to prove that it is an albuminoid mass saturated with an amylolytic enzyme, which is revolved, and, at the same time, pushed forward into the stomach by the action of the various cilia present on the epithelium of the style-sac. The tip bears against the gastric shield and is gradually worn down against this surface and through the action of the hepatopancreatic secretion. 12. The permanence of the style in Mya has been shown to be due to its protection from the corroding effects of the protease present in the hepatopancreatic secretion owing to the possession of a separate style-cæcum. 13. The importance of the style as a factor in the evolution of the higher Lamellibranchs, the presence of an homologous structure in certain of the Gastropods, and the question of its taxonomic importance have been touched upon. 14. The periodicity of digestion, as contrasted with the mechanical regularity of feeding, has been discussed. 15. The absence of digestive enzymes in the intestine, together with the evidence of previous workers, has been advanced in favour of the assertion that digestion takes place in the stomach only, and absorption in the stomach, mid-gut, and rectum. 16. The hepatopancreatic secretion has been shown to possess amylolytic, proteolytic, and lipolytic enzymes, and the action of these has been examined. 17. The style enzyme has been examined and found to reduce starch and glycogen but not sucrose. The optimum medium has been shown to be neutral, the optimum temperature to lie near 32°C, and the temperature of destruction at 51°C. Experiments in which the concentration of the enzyme and substrate were varied gave results which prove that the style enzyme has the typical properties of such a substance. 18. The presence of reserve supplies of glycogen and fat has been shown.

Memoirs: On the Structure of the Nephridia and ‘funnels’ of the Indian Leech Hirudinaria with remarks on these organs in Hirudo

1938 ◽  
Vol s2-81 (321) ◽  
pp. 27-80
Author(s):  
M. L. BHATIA
Keyword(s):  
Early Stage ◽  
Fibrous Tissue ◽  
Outer Wall ◽  
Central Canal ◽  
The Body ◽  
Main Lobe ◽  
Excretory Function ◽  
Ciliary Action ◽  
Apical Lobe ◽  
Discrete Structures

1. The nephridial system of Hirudinaria consists of a series of seventeen pairs of nephridia metamerically arranged in somites VI to XXII. The first sis pairs occur in the pretesticular segments (VI-XI), while the remaining eleven pairs lie in the testicular segments (XII-XXII). 2. A typical nephridium consists of the following parts: (i) the initial lobe, (ii) the apical lobe, (iii) the inner lobe, (iv) the main lobe, (v) the vesicle-duct and the vesicle. All the nephridia in the testicular region possess ‘funnels’ (ciliated organs) which are enclosed within the ampullae of the perinephrostoniial sinus. There is no continuity or connexion of these ‘funnels’ with the nephridia in the adult leech. 3. The inner end of the initial lobe is directed towards the testis-sac and either ends freely within the connective tissue without coming in contact with the testis-sac, o r- is embedded in fibrous tissue in external contact with the wall of the sac, or becomes incorporated within the outer wall of the perinephrostomial sinus. 4. The initial lobe (testis-lobe) forms a very long coiled string of cells round the apical lobe and part of the inner lobe. The inner lobe (the ‘recurrent lobe’ of Bourne) forms a distinct strip of nephridial tissue enclosed between the two limbs of the main lobe besides a small piece which runs alongside the apical lobe. The inner lobe canals serve to connect the intra-cellular canals of all the lobes with one another. 5. The cells of the different lobes of the nephridium are tunnelled through by intra-cellular canals and canaliculi which form a continuous branching network throughout the body of the nephridium. Besides, there is an intra-cellular central canal which makes 1 3/4 ‘rounds’ through the various lobes of the nephridium and opens into the vesicle. The intra-cellular canals and canaliculi open directly or indirectly into the central canal. 6. The vesicle has no muscular layer, and its wall is not contractile. The evacuation of the contents of the vesicle is brought about by the contraction of ventro-lateral mameles of the bodywall that extend across all the resides. The vesicle and the terminal excretory duet do not develop from the rudiments of the true nepfaritliam, but are formed from an ingrowth of the epidermis. 7. A fully developed adult ‘funnel’ (ciliated organ) is a compound structure consisting of (1) a central reservoir and (2) a large number of small independent funnels set on the reservoir and opening into it. The funnels are profusely dilated. Each funnel is composed of five to six cells, and has the appearance of an ear-lobe with a broad distal and a narrow proximal end. 8. The reservoir is the seat of manufacture of corpuscles which are thrown out of the reservoir through the funnels into the surrounding sinus by the active movements of the cilia of the numerous funnels. 9. The ‘funnel’ is not a degenerate structure. It has, infact, multiplied into numerous small ciliated funnels, which, are much more effective in their ciliary action than a single funnel, even of a large size, could be. Cilia of the funnels show very vigorous movements which keep the fluid in the sinus in constant active circulation. The ciliated organ, instead of serving a renal excretory function, has here become subservient to the sinus-system. 10. The botryoidal vessels are in direct communication with the perinephrostomial sinus. Possibly the corpuscles take up pigment and become the chloragogen cells in the botryoidal vessels. 11. In the embryonic condition the ‘funnel’ is a solid mass of cells which is distinctly continuous with the nephridinm by means of a delicate strand of cells. This connexion of the ‘funnel’ with the nephridium snaps later, and the two become discontinuous and discrete structures. In the embryonic solid ciliated organ the funnel-forming cells can be clearly distinguished from the cells of the reservoir. The ‘funnel’ becomes enclosed at an early stage in the perinephrostomial sinus, which is a part of the reduced coelom. 12. The nephridial system of Hirudo is essentially similar to that of Hirudinaria. In Hirudo the initial lobe does not coil round the apical lobe, but forms one mass round the ampullae of the perinephrostomial sinus and another between the apical and main lobes. The inner end of the nephridium is closed as in Hiradinaria. The ‘funnels’ have the same structure and perform the same function as in Hirudinaria.

On the Ciliary Mechanisms and Interrelationships of Lamellibranches

1943 ◽  
Vol s2-84 (334) ◽  
pp. 187-256
Author(s):  
DAPHNE ATKINS
Keyword(s):  
The Other ◽  
Muscle Fibres ◽  
Frontal Surface ◽  
Posterior Portion ◽  
Food Groove ◽  
Longitudinal Muscles ◽  
Free Edges

In the gill axes of the Microciliobranchia the most important muscles are longitudinal and transverse. The longitudinal muscles are: (a) those extending from one extremity of the gill axis to the other, inserted on the shell anteriorly, and (b) those in the free posterior portion of the axis, inserted on the shell where the axis becomes attached. Together these muscles act as branchial retractors. Withdrawal of the gills prevents (a) their being caught and crushed by the edges of the shell when the valves are suddenly closed, and (b) excessive fouling with sudden intake of muddy or noxious water. The transverse muscles below the chitinous structure arching the axial food groove serve to draw the demibranchs of a gill together, while those above the arch serve to separate them. Such swaying movements of the demibranchs serve to rid them of unwanted material. In the demibranchs are:--(1) muscles of the free edges. These include (a) muscles responsible for movements of the walls of the food grooves, and (b) longitudinal muscles, which effect antero-posterior contraction and assist the longitudinal muscles of the axis in retraction of the gills; (2) vertical muscles of the demibranchs, found chiefly in the Pteriacea, and responsible for dorso-ventral contraction of the demibranchs; (3) muscles of the interlamellar junctions serving to draw the two lamellae of a demibranch together, expelling the contained water; (4) horizontal muscles of the lamellae, present in forms with plicate and heterorhabdic gills and effecting by their action changes in shape of the frontal surface of the principal filaments and movements of the plicae important in connexion with the ciliary sorting mechanism; their contraction increases the folding of the lamellae and decreases the length of the gill: and (5) fine muscle-fibres forming the intrafilamentar ‘septum’.

scholarly journals Studies on the Comparative Physiology of Digestion

1925 ◽  
Vol 2 (3) ◽  
pp. 373-388
Author(s):  
C. M. YONGE
Keyword(s):  
Secretory Cells ◽  
Muscle Fibres ◽  
Lipolytic Enzyme ◽  
Mucous Cells ◽  
Comparative Physiology ◽  
Ciliary Action ◽  
Neutral Media ◽  
Large Round ◽  
Hind Gut ◽  
Stomach Epithelium

1. The oesophagus is characterised by a great development of mucous glands and cilia, and its function is essentially that of transport. 2. The stomach epithelium contains many secretory cells and is in all probability the site of the elaboration of the digestive enzymes. There are no mucous cells. 3. The hind-gut possesses no secretory cells other than mucous cells. Large round or elliptical cells with prominent nuclei and cytoplasm colouring darkly with all glycogen stains are numerous and are also present occasionally in the stomach. 4. The hind-gut is the only part of the gut which possesses muscle-fibres in its walls, food being transported through the gut by ciliary action. Mucous cells are very plentiful and there are also secretory cells--quite unlike those of the stomach--whose function is problematic. 5. Starch, glycogen and sucrose are digested, the amylolytic ferment having an optimum temperature of between 42° and 43°C. and being destroyed at 64°C. 6. A lipolytic enzyme is present. 7. There is a very weak proteolytic enzyme which acts only in alkaline and neutral media with the formation of albuminoses, but there is no sign of amino-acids after 14 days' digestion. 8. The glucosides salicin and amygdalin are split up. 9. Absorption takes place primarily in the mid-gut, to a smaller extent in the stomach, and very slightly in the hind-gut. 10. The gut allows dissolved substances to diffuse through it in either direction, but the action of the epithelium causes fluid to flow out of the gut even against strong osmotic pressure. 11. Glycogen is found in the branchial sac, throughout the gut (except the œsophagus) and in the ovary. It is most plentiful in the glycogen cells of the mid-gut and stomach. Fat is present in the œsophagus, stomach, and ovary. Quantitative estimations show that the gut possesses the highest content of fat (including lecithin) and the ovary the highest content of glycogen.

Disinfection of the root canal system: what should the protocol be?

Dental Update ◽  
2021 ◽  
Vol 48 (10) ◽  
pp. 836-844
Author(s):  
Stephen J Bonsor
Keyword(s):  
Root Canal ◽  
Aetiological Factor ◽  
Root Canal Preparation ◽  
Clinical Protocol ◽  
Canal System ◽  
Root Canal Therapy ◽  
Disinfection Methods ◽  
Organic Debris ◽  
Root Canal System ◽  
Micro Organisms

The presence of micro-organisms within the root canal system is the critical aetiological factor in peri-radicular periodontitis. During root canal treatment (RCT) it is imperative that this infection and other organic debris are removed from the root canal system. This is challenging because complex tooth anatomy, the presence of a biofilm and the smear layer complicate the process. There are a number of irrigant chemicals and adjunctive systems available in contemporary endodontic practice that are used to disinfect the root canal system during root canal preparation. This article reviews the available evidence concerning these disinfection methods and concludes by presenting a clinical protocol supported by the literature. CPD/Clinical Relevance: A clinical protocol, supported by the literature, is presented for effective decontamination of the root canal system during root canal therapy.

scholarly journals Study of copper-charged membranes for control of fouling due to bacteria and algae organic matter

2015 ◽  
Vol 5 (4) ◽  
pp. 516-527 ◽  
Author(s):  
Sunitha Asapu ◽  
Santosh Pant ◽  
Peyman Majid ◽  
Isabel C. Escobar ◽  
Cyndee L. Gruden
Keyword(s):  
Organic Matter ◽  
Biofilm Formation ◽  
Fluorescent Microscopy ◽  
Operating Costs ◽  
Permeate Flux ◽  
Membrane Cleaning ◽  
Organic Debris ◽  
Dead End ◽  
Micro Organisms ◽  
Charged Membranes

The accumulation of micro-organisms, along with the presence of nutrients, forms biofilms. Biofoulants that are typically encountered in desalination systems include cellular organisms (e.g. bacteria or algae) and organic debris, including algae organic matter. The accumulation of these micro-organisms is problematic to membranes by causing irreversible fouling. The most adverse effects due to biofouling include declines in permeate flux and salt rejection. In addition, biofilm formation necessitates frequent membrane cleaning, increasing operating costs and decreasing membrane life. The goal of this research was to investigate the performance of low-fouling copper-charged membranes for microbial resistance. The extent of fouling on the microbial resistant membranes was characterized by assessing surface area coverage by image analysis. Fluorescent microscopy was used to determine activity of biofilm cells on the surface. The presence of extracellular polymeric substance was verified using Fourier transform infrared spectroscopy. The permeate flux values were compared for both unmodified and copper-charged membranes by conducting dead-end filtration experiments using synthetic brackish water.

scholarly journals Memoirs: Some Observations on the Pedal Gland of Milax

1926 ◽  
Vol s2-70 (280) ◽  
pp. 647-667
Author(s):  
R. AILEEN BARR
Keyword(s):  
Posterior Part ◽  
Muscular Contraction ◽  
Body Cavity ◽  
The Body ◽  
Muscle Fibres ◽  
Forward Movement ◽  
Excretory Function ◽  
Compact Mass ◽  
Glandular Cells ◽  
Excretory Canal

1. The pedal gland of Milax is a compact mass of secreting cells traversed by a tube, the excretory canal, "which is free from the gland for about one-third of its length. The gland lies free in the body cavity, held down to the foot by small muscles. The pedal artery runs along the top of the gland. The canal has a projection from the roof into the lumen in the posterior part, and the floor shows a groove and two humps covered with cilia, forming three ciliated tracts running the whole length of the gland. The cilia in the groove are longer, and have a slower movement, than those on the humps. 2. The gland in Milax differs in position and structure from that in Limax : (a) It is not embedded in the foot. (b) It has no muscle fibres among the glandular cells. (c) A part of the canal is free from the gland at the posterior end. 3. The excretory canal is not emptied by muscular contraction (as in Limax) but (a) by the movement of the cilia ; (b) by the fact that the slime is very tenacious and, therefore, when the slug touches the ground and then moves forward, the slime is drawn out in a long string from the orifice of the canal. 4. The main uses of the mucus secretion are : (a) To provide a smooth track on which the pedal waves of the foot can function in forward movement. (b) To enable the animal to adhere firmly to the substratum. (c) To form a slime-string by means of which the animal can descend from trees to the ground : this is also used to suspend the two slugs during the act of copulation. (d) To assist the mucus glands of the skin in keeping the body moist. 5. The animal cannot progress in the usual way without the slime-track, i.e. if the gland is cauterized the animal moves, not rhythmically, but after the manner of a looper caterpillar. 6. The chief function of the pedal gland is to supply mucus to form the slime-track on which the animal moves. It is also probable, as Cuénot suggested, that the posterior part of the roof of the canal in this gland has an excretory function.

scholarly journals The Structure and Function of the Cutaneous Glands in Helix aspersa

1961 ◽  
Vol s3-102 (58) ◽  
pp. 195-216
Author(s):  
MARY CAMPION
Keyword(s):  
Calcium Carbonate ◽  
Connective Tissue ◽  
Waste Product ◽  
Helix Aspersa ◽  
Structure And Function ◽  
Muscle Fibres ◽  
Green Food ◽  
And Function ◽  
Micro Organisms ◽  
Sole Of The Foot

The glands discharging ‘slime’ on to the surface of the mantle collar and foot of Helix aspersa have been investigated histologically and histochemically on chemically fixed and frozen-dried material. All the glands are unicellular; they lie in the connective tissue and discharge by pores passing between the epidermal cells; some are club-shaped, others are polygonal with a distinct and usually long duct. At least 8 different kinds of gland are found: 4 extruding various kinds of mucus, one protein, one calcium carbonate granules, one a pigmented secretion containing a flavone, and one releasing fatglobules. The histology of the mantle collar is very similar to that of the dorsal and lateral surfaces of the foot except that the glands in the mantle are usually larger. All kinds of secretion are extruded from these parts. The glands of the sole of the foot are mostly of a distinct kind and produce mucus combined with protein. The mechanism of discharge is discussed: some of the gland cells are enclosed in a network of muscle-fibres which are thought to be concerned in the removal of the secretion, in other cases no fibres have been found and it seems likely that changes in pressure in the haemocoel are involved. The composition of the slime changes from colourless and viscous to yellow and watery when the animal is irritated. It is usually slightly alkaline, is not distasteful to man, and does not inhibit the growth of micro-organisms. The mucous component acts as a lubricant, and on the sole for adhesion. The calcium carbonate granules and the protein may be concerned in defence, while the flavone is a waste-product varying with the amount of green food eaten. The epiphragm is formed by the secretion of part of the mantle collar and is probably dissolved away by a protein-splitting enzyme which has been demonstrated in the slime.

Application of a Simple Cold Stub to the Direct Observation of Frozen Hydrated Sand

1973 ◽  
Vol 31 ◽  
pp. 212-213
Author(s):  
John M. Wehrung ◽  
Richard J. Harniman
Keyword(s):  
United States ◽  
Surface Water ◽  
Direct Observation ◽  
Controlled Study ◽  
Clay Particles ◽  
Organic Debris ◽  
Rock Formations ◽  
Water Tables ◽  
Permeable Rock ◽  
Natural Means

Water tables in aquifer regions of the southwest United States are dropping off at a rate which is greater than can be replaced by natural means. It is estimated that by 1985 wells will run dry in this region unless adequate artificial recharging can be accomplished. Recharging with surface water is limited by the plugging of permeable rock formations underground by clay particles and organic debris.A controlled study was initiated in which sand grains were used as the rock formation and water with known clay concentrations as the recharge media. The plugging mechanism was investigated by direct observation in the SEM of frozen hydrated sand samples from selected depths.

Review of the Radiation Damage Problem of Organic Specimens in Electron Microscopy

1973 ◽  
Vol 31 ◽  
pp. 476-477
Author(s):  
L. Reimer
Keyword(s):  
Electron Microscopy ◽  
Radiation Damage ◽  
Irradiation Time ◽  
Dose Effect ◽  
Primary Process ◽  
Thin Specimen ◽  
Secondary Damage ◽  
Small Doses ◽  
Micro Organisms ◽  
Damage Processes

Most information about a specimen is obtained by elastic scattering of electrons, but one cannot avoid inelastic scattering and therefore radiation damage by ionisation as a primary process of damage. This damage is a dose effect, being proportional to the product of lectron current density j and the irradiation time t in Coul.cm−2 as long as there is a negligible heating of the specimen.Therefore one has to determine the dose needed to produce secondary damage processes, which can be measured quantitatively by a chemical or physical effect in the thin specimen. The survival of micro-organisms or the decrease of photoconductivity and cathodoluminescence are such effects needing very small doses (see table).

Functional amyloid: widespread in Nature, diverse in purpose

2014 ◽  
Vol 56 ◽  
pp. 207-219 ◽  
Author(s):  
Chi L.L. Pham ◽  
Ann H. Kwan ◽  
Margaret Sunde
Keyword(s):  
Spider Silk ◽  
Epigenetic Inheritance ◽  
Fibrillar Structure ◽  
Cytoplasmic Polyadenylation ◽  
Functional Amyloid ◽  
Interacting Protein ◽  
Diverse Range ◽  
Element Binding Protein ◽  
Functional Amyloids ◽  
Micro Organisms

Amyloids are insoluble fibrillar protein deposits with an underlying cross-β structure initially discovered in the context of human diseases. However, it is now clear that the same fibrillar structure is used by many organisms, from bacteria to humans, in order to achieve a diverse range of biological functions. These functions include structure and protection (e.g. curli and chorion proteins, and insect and spider silk proteins), aiding interface transitions and cell–cell recognition (e.g. chaplins, rodlins and hydrophobins), protein control and storage (e.g. Microcin E492, modulins and PMEL), and epigenetic inheritance and memory [e.g. Sup35, Ure2p, HET-s and CPEB (cytoplasmic polyadenylation element-binding protein)]. As more examples of functional amyloid come to light, the list of roles associated with functional amyloids has continued to expand. More recently, amyloids have also been implicated in signal transduction [e.g. RIP1/RIP3 (receptor-interacting protein)] and perhaps in host defence [e.g. aDrs (anionic dermaseptin) peptide]. The present chapter discusses in detail functional amyloids that are used in Nature by micro-organisms, non-mammalian animals and mammals, including the biological roles that they play, their molecular composition and how they assemble, as well as the coping strategies that organisms have evolved to avoid the potential toxicity of functional amyloid.

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