Parietal (contact) digestion

1960 ◽  
Vol 49 (1) ◽  
pp. 10-13 ◽  
Author(s):  
A. M. Ugolev
Keyword(s):  
Contact Digestion

Thermophilic Anaerobic Contact Digestion of Palm Oil Mill Effluent

1985 ◽  
Vol 17 (2-3) ◽  
pp. 155-166 ◽  
Author(s):  
A. Ibrahim ◽  
B. G. Yeoh ◽  
S. C. Cheah ◽  
A. N. Ma ◽  
S. Ahmad ◽  
...  
Keyword(s):  
Palm Oil ◽  
Liquid Waste ◽  
Palm Oil Mill Effluent ◽  
Organic Load ◽  
Anaerobic Digesters ◽  
Effective System ◽  
Contact Digestion ◽  
Palm Oil Mill ◽  
High Level ◽  
Anaerobic Pretreatment

The palm oil industry is one of the major agro-based industries in Malaysia whose production accounts for more than 90% of the world export. The industry, however, also generates enormous quantities of liquid waste with high organic load causing serious pollution problems. In view of the high level of organics, anaerobic pretreatment is usually practised prior to aerobic breakdown. Most of the anaerobic digesters installed at the mills are currently operated under mesophilic conditions. However, the inherently high temperature of the effluent suggests that thermophilic digestion would bring about a much more effective system. This paper reports on results obtained from a pilot plant study on thermophilic anaerobic contact digestion of palm oil mill effluent which has been conducted and includes a microbiological study associated with the investigation.

In vivo metabolism of tritiated LHRH by the whole kidney and individual tubules of rats

1983 ◽  
Vol 244 (6) ◽  
pp. F628-F632
Author(s):  
M. A. Stetler-Stevenson ◽  
G. Flouret ◽  
S. Nakamura ◽  
B. Gulczynski ◽  
F. A. Carone
Keyword(s):  
High Performance ◽  
Rat Kidney ◽  
Venous Blood ◽  
Urinary Metabolites ◽  
Proximal Tubules ◽  
Radioactive Label ◽  
Intracellular Degradation ◽  
Contact Digestion ◽  
Distal Tubules

[pyroglutamyl-3,4-3H]Luteinizing hormone-releasing hormone ([3H]LHRH) and [14C]inulin were infused into individual nephrons in Inactin-anesthetized rats and the amount of radioactive label and the identity of the radioactively labeled material in urine were determined. The site of infusion was identified by latex injection and microdissection. [3H]LHRH was microinfused at 1.5 X 10(-5 M (concentration 10(6)-10(7) higher than in plasma) and analysis of urinary metabolites was performed by high-performance liquid chromatography. The urinary recovery of tritium label was 81% when proximal tubules were infused and 94% when distal tubules were infused. For proximal tubules 90% of the label recovered in urine appeared as pGlu-His (metabolite 2), pGlu-His-Trp (metabolite 3), and pGlu-His-Trp-Ser (metabolite 4), and 10% as LHRH. With distal tubules only LHRH was detected in the urine. [3H]LHRH was presented to the renal artery of the filtering rat kidney in vivo, and urine and renal venous blood were analyzed for breakdown products. The urine contained metabolites 2, 3, and 4 and no LHRH, whereas venous blood contained mainly pGlu, metabolite 4, and LHRH. When [3H]LHRH was perfused in vivo through the nonfiltering rat kidney or rat lower limb, renal or femoral venous blood was found to contain only LHRH. These studies suggest that [3H]LHRH undergoes glomerular filtration and contact digestion by brush border enzymes of the proximal tubule to produce metabolites 2, 3, and 4. These metabolites and possibly LHRH are partially reabsorbed and undergo further intracellular degradation to produce pGlu. Endothelial and interstitial cells in the kidney and leg do not appreciably metabolize [3H]LHRH.

Studies on gut ultrastructure and digestive physiology in Cyathostoma lari (Nematoda: Strongylida)

Parasitology ◽  
1971 ◽  
Vol 62 (2) ◽  
pp. 273-283 ◽  
Author(s):  
J. Barry Colam
Keyword(s):  
Acid Phosphatase ◽  
United States Public Health ◽  
Buccal Capsule ◽  
The United States ◽  
Digestive Physiology ◽  
Lysosomal Hydrolases ◽  
Prosthetic Group ◽  
Distal Surface ◽  
Group A ◽  
Contact Digestion

Histological, histochemical and ultrastructural methods have been used to study the gut structure and digestive physiology in the parasitic nematode Cyathostomalari E. Banchard, 1849. The nematode is parasitic in the orbito-nasal sinuses of its host and feeds exclusively upon blood.Three gland cells are present in the oesophagus, one in each sector. The two subventral gland ducts open into the lumen of the oesophagus at the level of the nerve ring, and the dorsal gland duct into the base of the buccal capsule. It is suggested that the latter gland may produce an anticoagulin, histolytic and/or haemolytic secretions, histochemically-inactive in situ. The intestine is syncytial, with no differentiation into secretory components, and its distal surface is provided with a prominent brush border of long microvilli.A non-specific esterase, thought to originate in the oesophageal gland secretions, causes haemolysis of ingested erythrocytes. The major part of haemoglobin digestion is extracellular, partly by a process of contact digestion on the microvilli, initiated by the esterase, and the protein is then further broken down by an exopeptidase of the ‘leucine aminopeptidase’ type, and the products absorbed into the gastrodermis possibly with the aid of an acid phosphatase present on or in the microvilli. An insoluble iron-containing compound, which is not haematin, results from breakdown of the prosthetic group. A smaller proportion of haemoglobin is taken up by the gastrodermis and digested intracellularly by the action of lysosomal hydrolases. An endopeptidase and an acid phosphatase are present in the gastrodermis, possibly in sacs of GER which are suggested to be primary lysosomes and which fuse with the endocytosed heterophagosomes. The insoluble pigment haematin results from digestion within the heterolysosomes, and this gives rise to the iron-containing gastrodermal pigment granules. The products of extracellular digestion are absorbed by the gastrodermis where they are synthetized into lipid by a lipase, which probably resides in whorls of GER.This investigation was supported in part by Research Grant AI 06295 of the United States Public Health Service. The final manuscript was prepared during the tenure of a Postdoctoral Fellowship from the British Egg Marketing Board. I wish to extend my gratitude to Dr J. B. Jennings for advice and encouragement throughout this work.

Some interface phenomena in parasitic protozoa and platyhelminths

1973 ◽  
Vol 51 (3) ◽  
pp. 367-377 ◽  
Author(s):  
J. D. Smyth
Keyword(s):  
Molecular Mimicry ◽  
Intimate Contact ◽  
Interface Phenomena ◽  
Contact Digestion ◽  
Membrane Contact ◽  
Membrane Type ◽  
Host Parasite ◽  
Type 3

The host–parasite interface is defined broadly as a region of intimate contact between host and parasite surfaces. The limitations of this definition are considered. The difficulties of studying the morphology, ultrastructure, and physiology of this region are discussed. Possible host–parasite interfaces appear to fall (theoretically) into one of the following categories: type 1: membrane-to-membrane; type 2A: cytoplasm-to-membrane; type 2B: membrane-to-cytoplasm; type 3: cytoplasm-to-cytoplasm. Phenomena associated with the interface region are various forms of membrane transport, pinocytosis, excretion, secretion, and membrane (= contact) digestion. The apparent role of the interface in differentiation in the protozoan Gregarina polymorpha and the cestode Echinococcus granulosus are discussed. The immunological significance of intimate contact between host and parasite and the various hypotheses to account for the (apparent) 'molecular mimicry' by the parasite, of host surface antigens, are briefly summarized.

Studies on gut ultrastructure and digestive physiology in Rhabdias bufonis and R. sphaerocephala (Nematoda: Rhabditida)

Parasitology ◽  
1971 ◽  
Vol 62 (2) ◽  
pp. 247-258 ◽  
Author(s):  
J. Barry Colam
Keyword(s):  
Acid Phosphatase ◽  
United States Public Health ◽  
Buccal Capsule ◽  
The United States ◽  
Parasitic Nematodes ◽  
Digestive Physiology ◽  
Light Microscope Level ◽  
Inactive Form ◽  
Contact Digestion ◽  
Lung Capillaries

Histological, histochemical and ultrastructural methods have been used to study gut structure and digestive physiology in the parasitic nematodes Rhabdias bufonis (Schrank, 1788) and R. sphaerocephala (Goodey, 1924). Both species are parasitic in the lungs of their amphibian hosts and feed entirely upon blood drawn from the lung capillaries.Three gland cells are present in the oesophagus, one in each sector. The two subventral ducts open, by way of ampullae, into the lumen of the oesophagus about a quarter of its length from the anterior end. The dorsal gland opens similarly into the base of the buccal capsule. It is suggested that the glands produce a B-esterase, in an histochemically inactive form in situ, which is responsible for haemolysis and the bulk of extracellular digestion. Only one cell type is present in the intestine and this is entirely absorptive in function.The major part of haemoglobin digestion is extracellular, partly by a process of contact digestion involving the B-esterase and acid phosphatase which are present in association with the microvilli. Haematin results from this process and is precipitated in the gut lumen. A smaller proportion of haemoglobin is taken up by the gut cells and is broken down intracellularly by lysosomes, originating in Golgi in the basal gastrodermis. These show endopeptidase activity and later acid phosphatase in some of the bodies of the lysosomal sequence and only at the light microscope level. The iron-containing pigment haemosiderin resulting from digestion is retained in the lysosome residues and forms the pigment granules in the gastrodermis. The products of extracellular digestion absorbed by the gastrodermis are synthetized into lipid by a lipase, probably produced by GER.This investigation was supported in part by Research Grant AI 06295 of the United States Public Health Service. The final manuscript was prepared during the tenure of a Postdoctoral Fellowship from the British Egg Marketing Board. I wish to extend my gratitude to Dr J. B. Jennings for advice and encouragement throughout this work.

Some aspects of nutrition in Philophthalmus burrili (Trematoda: Digenea)

Parasitology ◽  
1971 ◽  
Vol 62 (1) ◽  
pp. 133-144 ◽  
Author(s):  
M. J. Howell
Keyword(s):  
Acid Phosphatase ◽  
Ventral Sucker ◽  
Close Association ◽  
Food Material ◽  
Research Scholarship ◽  
National University ◽  
Contact Digestion ◽  
A Site

The effects of P. burrili adults on the chicken host are outlined. There was no evidence that infections of up to 20 flukes caused marked pathological changes in the nictitating membrane to which flukes attach in an intimate 'placental' manner by the ventral sucker.The food material of adult flukes is largely lacrimal secretion; it appears that blood can be excluded from the diet since the caecal contents are colourless and haemoglobin was not detected histochemically. Little material was detected in the caeca by the histochemical techniques used. The presence of a mucus coat around flukes was noted and it is suspected that materials of nutritional significance may be conserved in this coat for long periods. Glucose was demonstrated in the parenchyma surrounding the uterus. It is suggested that this might indicate either (a) polysaccharide degradation in this region; (b) polysaccharide synthesis; or (c) a site of accumulation of glucose which enters through the tegument and caeca. The presence of greatest activity in the uterine region may be indicative of nutritional dependence of the developing miracidium on the parent fluke.The gastrodermis of the caeca is regular, consisting of flattened cells with a very prominent PAS positive, striated border of microvilli. The cytoplasm of the cells contains appreciable amounts of RNA. Protease, acid phosphatase and possibly esterase have been demonstrated in the gastrodermis.Possible esterase activity occurs in the ventral sucker, alkaline phosphatase is present in the lining of the excretory ducts, and acid phosphatase has also been demonstrated in the pharynx, both suckers, and subcuticular region.Ferritin was ingested by flukes in vivo and this enabled the digestion cycle to be followed. Flukes ingested little or no ferritin in vitro. Digestion was completed within 13 h and appeared to take place in close association with the striated border rather than in the lumen. The possibilities are that (a) material is digested intracellularly within the microvilli; (b) membrane (contact) digestion takes place; (c) extracellular digestion, in close association with the striated border, takes place. These processes are not necessarily mutually exclusive.I should like to thank Professor J. D. Smyth for his helpful advice. This study was carried out during the tenure of an Australian National University Research Scholarship.

Membrane (contact) digestion in the three species of tapeworm Hymenolepis diminuta, Hymenolepis microstoma and Moniezia expansa

Parasitology ◽  
1968 ◽  
Vol 58 (3) ◽  
pp. 535-546 ◽  
Author(s):  
E. W. Taylor ◽  
J. N. Thomas
Keyword(s):  
Electron Microscope ◽  
Hymenolepis Diminuta ◽  
Contact Digestion ◽  
Rate Of Hydrolysis ◽  
Membrane Contact ◽  
Rats And Mice ◽  
Meat Market ◽  
Hydrolysis Of ◽  
Hymenolepis Microstoma

The presence of living tapeworm increases the rate of hydrolysis of starch by α-amylase in vitro. This effect indicates that ‘membrane digestion’ may be one function of the tegument of tapeworms. The effect varies with the surface area and region of the tapeworm. Fixed tapeworm pieces do not enhance starch hydrolysis. The results may provide evidence both for and against the current explanations of membrane digestion. Some possible mechanisms involved in membrane digestion in tapeworms are considered. The importance of membrane digestion in the physiology of gut parasites and the possibility of its wide occurrence are discussed.We wish to thank Dr J. Llewellyn for his criticism and advice during the preparation of this manuscript and for providing rats and mice infected with Hymenolepis. We also thank Dr R. A. Thornhill for examining some tapeworm tissue under the electron microscope; also Mr A. Wilson of the Meat Inspection Department of the Birmingham Meat Market for his unfailing co-operation.

Membrane (Contact) Digestion

1965 ◽  
Vol 45 (3) ◽  
pp. 555-595 ◽  
Author(s):  
A. M. Ugolev
Keyword(s):  
Contact Digestion ◽  
Membrane Contact
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