Cytolytic Enzymes Research Articles

Comparison of Soybean Oil- and Olive Oil-based Lipid Emulsions on Hepatobiliary Function and Serum Triacylglycerols Level during Realimentation

This study compared the effects of soybean oil- versus olive oil-based lipid emulsions on hepatobiliary function and serum triacylglycerols in patients who required transient parenteral nutrition support for significant weight loss. Patients who received a parenteral ready-to-use industry admixture including either soybean oil- (n = 10) or olive oil-based lipid emulsion (n = 11) for 2 weeks were retrospectively analysed. Cholestatic and cytolytic enzymes, conjugated bilirubin and serum triacylglycerols were sampled before and 1 day after completing parenteral nutrition support. Significant deterioration of cholestatic enzymes occurred in five patients in the soybean oil group and in one in the olive oil group. Serum triacylglycerols significantly deteriorated in seven patients in the soybean oil group and in one patient in the olive oil group. No differences were recorded for cytolytic enzyme abnormalities. In conclusion, the olive oil-based emulsion induced abnormalities of cholestatic enzymes and serum triacylglycerols significantly less frequently than the soybean oil-based emulsion.

Diseases affect cold-water corals too: Eunicella verrucosa (Cnidaria: Gorgonacea) necrosis in SW England

The first recorded incidence of cold-water coral disease was noted in Eunicella verrucosa, a coral on the international 'red list' of threatened species, at a marine protected area in SW England in 2002. Video surveys of 634 separate colonies at 13 sites revealed that disease outbreaks were widespread in SW England from 2003 to 2006. Coenchyme became necrotic in diseased specimens, leading to tissue sloughing and exposing skeletal gorgonin to settlement by fouling organisms. Sites where necrosis was found had significantly higher incidences of fouling. No fungi were isolated from diseased or healthy tissue, but significantly higher concentrations of bacteria occurred in diseased specimens. Of 21 distinct bacteria isolated from diseased tissues, 19 were Vibrionaceae, 15 were strains of Vibrio splendidus and 2 others closely matched Vibrio tasmaniensis. Vibrios isolated from E. verrucosa did not induce disease at 15 degrees C, but, at 20 degrees C, controls remained healthy and test gorgonians became diseased, regardless of whether vibrios were isolated from diseased or healthy colonies. Bacteria associated with diseased tissue produced proteolytic and cytolytic enzymes that damaged E. verrucosa tissue and may be responsible for the necrosis observed. Monitoring at the site where the disease was first noted showed new gorgonian recruitment from 2003 to 2006; some individuals had died and become completely overgrown, whereas others had continued to grow around a dead central area.

Ligation of CD8α on human natural killer cells prevents activation‐induced apoptosis and enhances cytolytic activity

It has been previously shown that the subset of human natural killer (NK) cells which express CD8 in a homodimeric alpha/alpha form are more cytotoxic than their CD8- counterparts but the mechanisms behind this differential cytolytic activity remained unknown. Target cell lysis by CD8- NK cells is associated with high levels of effector cell apoptosis, which is in contrast to the significantly lower levels found in the CD8alpha+ cells after lysis of the same targets. We report that cross-linking of the CD8alpha chains on NK cells induces rapid rises in intracellular Ca2+ and increased expression of CD69 at the cell surface by initiating the influx of extracellular Ca2+ ions. We demonstrate that secretion of cytolytic enzymes initiates NK-cell apoptosis from which CD8alpha+ NK cells are protected by an influx of exogenous calcium following ligation of CD8 on the NK-cell surface. This ligation is through interaction with fellow NK cells in the cell conjugate and can occur when the target cells lack major histocompatibility complex (MHC) Class I expression. Protection from apoptosis is blocked by preincubation of the NK cells with anti-MHC Class I antibody. Thus, in contrast to the CD8- subset, CD8alpha+ NK cells are capable of sequential lysis of multiple target cells.

Efficacy of a Fusobacterium necrophorum-Arcanobacterium pyogenes Bacterin-Toxoid as an Aid in the Prevention of Liver Abscesses in Cattle

Condemnation of bovine livers because of liver abscesses causes a substantial economic loss to meat packers. Fusobacterium necrophorum and Arcano-bacterium pyogenes are believed to act synergistically to cause liver abscesses in cattle on high energy diets. A leukotoxin and a hemolysin have been shown to be important virulence factors of F. necrophorum and A pyogenes, respectively. The lysis of neutrophils and macrophages by the leukotoxin is thought to lead to the release of reactive oxygen radicals and cytolytic enzymes that damage the hepatic cells. The studies reported herein were done to test the efficacy of single-dose, bivalent F. necrophorum-A. pyogenes bacterin-toxoid to aid in the reduction of liver abscess incidence and severity under field conditions and natural challenge.

Cellular participation in delayed xenograft rejection of hCD55 transgenic pig hearts by baboons.

Delayed xenograft rejection (DXR) of pig organs by baboons currently represents the major obstacle to successful xenotransplantation. Although antibodies (Abs) are believed to play a fundamental role in this form of rejection, so far little is known concerning the potential cellular component. Biopsies taken during DXR of human CD55 transgenic pig hearts by non-treated (n = 2), alpha-Gal immunoadsorbed (n = 2), or immunosuppressed (n = 9) baboons were studied. The cellular element was explored by determining not only its phenotype by classical immunohistochemical techniques but also its activity in terms of cytokines, cytolytic enzymes and other mediators using quantitative reverse transcription polymerase chain reaction. All porcine xenografts underwent DXR; within 5 days in non-treated and immunoadsorbed animals but significantly delayed (6 to 29 days) in immunosuppressed animals. Cellular infiltration in non-immunosuppressed grafts consisted predominantly of monocytes/macrophages, CD8 cells and a few CD4 T-cells. The predominant baboon transcripts detectable were the proinflammatory cytokines interleukin1-alpha and tumor necrosis factor-alpha, the lymphokine interferon-gamma and the cytotoxic enzyme granzyme B. However, these cellular components were lacking in the immunosuppressed animals. Despite these differences, strong immunoglobulin M (IgM) and C5b-9 complement deposition was observed in all animals at rejection. Together our findings suggest that although the humoral response plays a predominant role in DXR through IgM Abs and complement activation, there is a clear cellular infiltrate in DXR in this model that is likely to contribute to rejection through a strong pro-inflammatory and cytotoxic environment, necessitating substantial immunosuppression for a prolonged graft survival.

Protective role of tauroursodeoxycholate during harvesting and cold storage of human liver: a pilot study in transplant recipients.

Ischemia-reperfusion injury is a major cause of early graft dysfunction after liver transplantation. Tauroursodeoxycholic acid (TUDCA), a natural amidated hydrophilic bile salt, protects from cholestasis and hepatocellular damage in a variety of experimental models, as well as from ischemia-reperfusion injury. We investigated in the human liver transplantation setting the effect of the addition of TUDCA at time of liver harvesting and cold storage on the intra- and postoperative enzyme release and liver histopathology at the end of cold storage, at reperfusion, and 7 days after transplantation. Eighteen patients undergoing elective liver transplantation were studied, including 6 serving as controls. In six patients, TUDCA was added to the University of Wisconsin solution used during harvesting and cold storage, to reach final concentrations of 2 mM. In three of these patients, TUDCA (3 g) was infused in the portal vein of the donor before organ explantation; in the other three cases, TUDCA was given through both routes. The use of TUDCA did not cause adverse events. The release of aspartate aminotransferase in the inferior vena cava blood during liver flushing was significantly lower (P=0.05) in TUDCA-treated than in control grafts, as were cytolytic enzyme levels in peripheral blood during the first postoperative week (P<0.02). At electron microscopy, an overt endothelial damage (cytoplasmic vacuolization, cell leakage, and destruction with exposure of hepatocytes to the sinusoidal lumen) was invariably found in control grafts, both at reperfusion and at day 7 after transplant. These features were significantly ameliorated by TUDCA (P<0.001). Several ultrastructural cytoplasmic abnormalities of hepatocytes were seen. Among these, damage to mitochondria matrix and crystae was significantly reduced in TUDCA-treated versus control grafts (P<0.01). Mild to severe damage of bile canaliculi was a constant feature in control biopsies, with dilatation of canalicular lumen and loss of microvilli. Both these abnormalities were markedly ameliorated (P<0.001 by TUDCA). The best preservation was observed when TUDCA was given through both routes. The use of TUDCA during harvesting and cold storage of human liver is associated with significant protection from ischemia-reperfusion injury. The clinical significance of this findings must be studied.

Rôle de la monoxyde d'azote synthase-III et du guanosine 3':5'-monophosphate cyclique dans la protection exercée par le monoxyde d'azote lors d'une ischémie-reperfusion hépatique

Nitric oxide (NO) exerts cytoprotective effects against hepatic ischemia-reperfusion damage. This study was designed to evaluate which isoform of NO synthase (NOS) is implicated in the generation of cytoprotective NO and to investigate whether NO effects are mediated by cyclic GMP (cGMP). After partial ischemia for 45 min, liver damage was estimated by the release into plasma of cytolytic enzymes. Ischemia-reperfusion induced marked increases in plasma creatine kinase and lactate dehydrogenase after 1 h of reperfusion and of aminotransferases after 6 h of reperfusion. The pretreatment of ischemied rats with 8-bromo-cGMP (16 mg/kg iv 30 min before ischemia) or with L-arginine (the endogenous precursor of NO, 100 mg/kg iv) significantly diminished the ischemia-reperfusion-induced release of all these enzymes. This demonstrates that cGMP possesses hepatoprotective properties. By immunohistochemistry, we observed, after 6 h of reperfusion, an increase in endothelial NOS-III immunoreactivity, particularly in the small arteries and sinusoids. This NOS-III accumulation in endothelial cells could protect the liver against ischemia-reperfusion by the local generation of NO probably via cGMP.

Sjögren's Syndrome: Pathogenesis

Sjögren's syndrome is a chronic inflammatory disease of the lacrimal and salivary gland with subsequent keratoconjunctivitis sicca and xerostomia. Histopathologic findings include damaged acini of the lacrimal and salivary glands with mononuclear cell infiltrates of lymphocytic and plasma cell type. The cause of the damage is cell-mediated cytotoxicity. The pathogenesis of Sjögren's syndrome is still unknown. The role of viral infections failed to show a causative effect. On the other hand, tissue destruction was shown to be mediated by activated T cells of CD4+ type that home into the lacrimal gland. This process is signal-mediated through the T-cell receptor that interacts with class II antigen on the epithelial cells of exocrine glands. This, in turn, induces the expression of Fas/APO-1 and Fas-mediated apoptosis of acinar cells. Granzyme A and perforin are cytolytic enzymes secreted by activated T lymphocytes that seem to participate in acinar cell destruction.

PH dependent cytotoxicity of N-dodecylimidazole: a compound that acquires detergent properties under acidic conditions.

N-dodecylimidazole is a compound which acquires detergent properties under acidic conditions and might be useful in killing selectively cells in those regions of solid tumours which have a reduced extracellular pH (pHe). We have therefore studied the effects of N-dodecylimidazole against malignant cells in tissue culture. N-dodecylimidazole displayed pHe-dependent cytotoxicity against EMT-6 and MGH U1 cells; cell killing was dose dependent and was 100-fold greater at pHe 6.0 than pHe 7.0. Reduced toxicity of N-dodecylimidazole was observed at higher cell concentrations (> 10(6) cells ml-1), and only minor effects were observed against multicellular tumour spheroids. Potential mechanisms of action of N-dodecylimidazole include detergent-mediated lysis of the cell membrane at low pHe, and selective uptake into lysosomes where detergent activity leads to rupture of the lysosomal membrane and release of cytolytic enzymes. Inhibition of activity of cysteine proteases by the inhibitor E-64 did not protect cells against the toxicity of N-dodecylimidazole, suggesting that these lysosomal enzymes do not play a major role in the mechanism of action of this compound. Lysis of erythrocytes (which contain no lysosomes) was observed with low concentrations of N-dodecylimidazole. Dependence of cell lysis on cell concentration was similar to that observed for two other detergents that act on the plasma membrane, Triton X-100 and sodium dodecyl sulfate. We conclude that N-dodecylimidazole causes pHe dependent cell killing in two cultured tumour cell lines, and that its mechanism of action is probably due to acid mediated production of detergent activity which acts primarily on the cell plasma membrane.

Mechanisms of rhabdomyolysis.

Rhabdomyolysis is a common disorder that occurs as a primary disease or as a complication of a broad spectrum of other diseases. Although some cases are caused by hereditary metabolic or structural abnormalities of the skeletal muscle cell, the majority of cases occur in healthy persons as a result of exhaustive exercise, infections, intoxications, deficiency states, or trauma. Although the causes of rhabdomyolysis are diverse, current evidence suggests that there may be a common final pathway that mediates cellular injury. Thus some noxious factor, perhaps a drug that injures the plasma membrane of the cell, a toxin that activates a cytolytic enzyme, a factor that interferes with metabolism and disrupts the integrity of the skeletal muscle cell, a cytokine such as tumor necrosis factor, or simple hypoxia that reduces energy production by the cell, serves to increase cellular permeability to sodium ions. When sodium ions accumulate in the cytoplasm of the cell, an increase of cytosolic or mitochondrial calcium follows. Calcium activates a variety of proteolytic enzymes that injure the cell membrane, allowing efflux of cellular components into the circulation. The ability to identify some of these components, such as myoglobin or creatine kinase, facilitates clinical recognition of rhabdomyolysis. The cytosolic components released into the circulation, under appropriate conditions, may be life threatening, eg, release of potassium causes hyperkalemic cardiotoxicity. In this review, I attempt to describe a variety of factors that are known to be injurious to skeletal muscle cells and, when possible, describe the apparent mechanism whereby these factors result in injury and disruption of the muscle cell.

Medium chain acyl-CoA dehydrogenase deficiency.

From 65 reported cases of medium chain acyl-CoA dehydrogenase deficiency, we found an average presenting age of 13.5 months and a mean age at death of 18.5 months. One quarter of patients died of a Reye-like syndrome and/or sudden infant death. In half the cases there had been at least one sibling death. Asymptomatic cases were not uncommon (12% of cases). The crises were generally induced by a prolonged fast and after a viral prodromal phase in three quarters of cases. The crises consisted of somnolence progressing to lethargy which could lead to coma. Vomiting was frequent (60% of cases). Seizures, which were found in 29% of cases, represented a bad prognosis. The physical examinations revealed frequently a variable and regressive anicteric hepatomegaly. Blood and urine analysis revealed in most instances hypoglycaemia (96% of cases) with hypoketonuria and sometimes metabolic acidosis. Hepatic and muscular cytolytic enzymes were frequently raised, as were plasma ammonia, urea, and uric acid. Plasma total or free carnitine concentrations, especially non-fasting, were diminished in most cases. Plasma saturated medium chain fatty acids and particularly unsaturated cis-4-decenoate were on the other hand raised during the crises or during fasting. Urinary organic acid analysis revealed a characteristic profile of medium chain aciduria: C6-C10 dicarboxylic acids, hydroxy acids, glycine conjugates, and carnitine conjugates. Oral loading tests with carnitine or phenylpropionate allow a precise diagnosis. The diagnosis is confirmed by specific assays in various tissues. Avoidance of prolonged fasting seems to be the mainstay of treatment.

Natural killer cell cytolytic granule-associated enzymes. I. Purification, characterization, and analysis of function of an enzyme with sulfatase activity.

An enzyme with sulfatase activity has been isolated from the granules of a rat NK leukemia cell line, CRNK-16. The enzyme has been purified from crude preparation, with a specific activity of 52 nmol/min/mg of protein, by DEAE ion exchange and Con A-Sepharose affinity chromatography, resulting in a specific activity of 230 nmol/min/mg of protein. The molecular mass of the purified enzyme was estimated to be 40 kDa by gel filtration chromatography at pH 7.4, but the enzyme had the ability to complex to molecular masses of greater than 300 kDa at low pH when crude granule extract was used as the starting sample, suggesting that it associates with other granule components. The enzyme was determined to be an arylsulfatase by its ability to (a) hydrolyze p-nitrophenyl sulfate (Km = 26.0 mM) and p-nitrocatechol sulfate (pNC sulfate) (Km = 1.1 mM) and (b) be inhibited by sulfite (Ki = 6.0 x 10(-7) M), sulfate (Ki = 1 x 10(-3) M), and phosphate (Ki = 4 x 10(-5) M) in a competitive manner. The pH optimum for enzymatic activity was determined to be 5.6. The role of this enzyme in cytolytic function was investigated by examining the effect of its substrates and inhibitors on granule- and cell-mediated lysis. pNC sulfate was shown to cause a dose-dependent inhibition of target cell lysis by isolated cytolytic granules (complete inhibition at 12.5 mM). Sulfite induced an incomplete inhibition (50% at 1 mM), whereas phosphate was essentially without inhibitory effect. Sulfate, on the other hand, altered lytic activity in a biphasic manner, inasmuch as it induced an inhibition of lysis at high concentrations and an increase of lysis at low concentrations. Cell-mediated lysis was inhibited by pNC sulfate in a dose-dependent fashion at concentrations greater than 2.5 mM, with nearly complete inhibition at 50 mM. Sulfate also altered the lytic activity by intact cells in a biphasic manner, although the effect was much less pronounced. Sulfite and phosphate caused only a 30% inhibition of lytic activity. These results suggest that the sulfatase enzyme is involved in NK cytolytic function, presumably at the lethal hit stage.

In Vitro Penetration of Human Corneal Epithelium by Acanthamoeba castellanii: A Scanning and Transmission Electron Microscopy Study

Human corneal buttons were exposed to Acanthamoeba castellanii trophozoites and cysts for 12 hours at 35 degrees C. The buttons examined by light microscopy and scanning and transmission electron microscopy had severe epithelial ulceration and penetration by trophozoites. Observations on trophozoites below the surface suggest that penetration is accomplished by both secreted cytolytic enzymes and phagocytosis. It is likely that the secretion of one or more enzymes constitutes the initial step in preparing the host tissue for endocytosis or that the secretory mechanism is used by the amebas to move through the outer squamous layer to the basement epithelium where phagocytosis occurs. Based on this study and a previous study, it appears that entry into the cornea is a two-step process involving adherence and penetration by trophozoites.

Histopathology of an aphid,Schoutedenia lutea, parasitized by a gall midge,Pseudendaphis sp

Pseudendaphis sp. (Barnes) [Diptera: Cecidomyiidae] is a larval endoparasitoid of the aphidSchoutedenia lutea (van der Goot) [Aphididae: Greenideinae]. A brief investigation of the biology ofPseudendaphis sp. revealed that parasitization by this species occurs only in viviparous instar III to adult life stages of the host aphid. Comparative histology of parasitized, unparasitized and starved aphids was used to evaluate proposed mechanisms of pathogenesis. Parasitization byPseudendaphis sp. was found to cause the destruction of host embryos and pathological changes in the host fat body, yet resulted in an increase in the number of host mycetocytes. There was no evidence of injury to host tissues through direct physical attack, a cytolytic enzyme or starvation-like factors. Remaining hypotheses for altered host histologies in parasitized aphids are selective nutrient depletion and production of a non-cytolytic bioactive substance by thePseudendaphis larvae.

Serum type-2 macro-creatine kinase isoenzyme is not a useful marker of severe liver diseases or neoplasia

We studied the creatine kinase (CK) isoenzyme pattern in sera from 332 patients affected by hepatic cirrhosis and several neoplastic diseases (102 cirrhosis, 36 hepatocarcinoma, 16 metastatic liver tumor, 40 breast cancer, 18 other neoplastic diseases and 120 cases of leukemia or lymphoma) to evaluate both its diagnostic utility for cancer diagnosis and its power as a prognostic index. Type-2 macro CK (mitochondrial creatine kinase) was detected, with no statistical difference in cirrhosis (14%), hepatocarcinoma (16%), metastatic liver tumor (31%), breast cancer (5%) and other tumors (6%). It was not detected in any patient with leukemia or lymphoma. The presence of type-2 macro CK was unrelated to the stage of either cirrhosis or hepatocarcinoma, according to Child and Okuda, respectively, nor was it correlated to serum cytolytic enzyme levels or to gamma-globulin levels. In cirrhotics, type-2 macro CK was not linked to serum levels of the following tumor markers: alpha-fetoprotein, pseudouridine and gamma-glutamyltransferase isoenzymes complexed to low-density lipoprotein. In addition, the atypical band persisted in several patients with cirrhosis monitored for six months who did not show any evidence of evolution toward hepatocarcinoma. Thus, type-2 macro CK has poor diagnostic sensitivity for neoplastic diseases, and lacks prognostic value both in cirrhosis and neoplastic diseases.

Immunoultrastructural studies of human NK cells: II. Effector-target cell binding and phagocytosis.

The binding of NK cells to a target cell appears to be a necessary step for NK cell-mediated cytolysis. In this report, we demonstrated effector-target binding by immunoelectron microscopy by using monoclonal antibodies against NK cells (Leu-7, Leu-11a) and T-cell subsets (Leu-2a/T8, Leu-3a/T4). The surfaces of NK and K562 cells were characterized by antitransferrin receptor antibody and various lectins. In addition, the controversial phagocytic activity of NK cells was studied by incubation of peripheral blood mononuclear cells with opsonized Staphylococcus aureus and labeling with anti-Leu-7 or anti-Leu-11a antibody. Results showed that only Leu-11a+ cells displayed a broad cell-to-cell contact with the target by a shallow intercellular interdigitation of cytoplasmic projections, while Leu-7+, Leu-2a+, or Leu3a+ cells showed only a partial contact with target without interdigitation. The Leu-11a+ cells were frequently observed in small clusters and in close association with monocytes. Cluster formation and association with monocytes were not observed in other NK and T-cell immunophenotypes. In Leu-11a+ cells conjugated with target cells, membrane-bound granules, small vesicles, parallel tubular arrays, Golgi apparatus, endoplasmic reticulum, and small vacuoles were evident and concentrated toward the target. The surface of NK cells was intensely stained for glycoprotein by chromic acid-phosphotungstic acid, whereas target cells were not stained. Transferrin receptors were stained only on the surface of target cells. Only the lectins RCA and UEA labeled the surfaces of both NK and target cells. Phagocytic vacuoles containing cell debris or fragments and ingested bacteria were found in the cytoplasm of Leu-11a+ cells but not in Leu-7+ cells. NK cells were also found within the cytoplasm of K562 target cells. All these findings suggest that Leu-11a+ cells are the true functional NK cells involved in NK cell-mediated cytolysis, phagocytosis, and emperipolesis. Therefore, the NK cell is probably "a phagocyte in lymphocyte's clothing." The presence of peroxidase in the small vesicles of NK cells and endocytotic vesicles of target cells at the effector-target contact area indicates that cytolytic enzymes or factors derived from NK cells may be transported into the target by endocytosis.

Bacillus thuringiensis var. israelensis δ-endotoxin: Evidence of neurotoxic action

The neurotoxic, cytolytic, and lethal properties of a 25-kDa protein isolated from the δ-endotoxin of Bacillus thuringiensis subsp. israelensis (Bti) were compared with those of the alkaline-dissolved whole extract of the δ-endotoxin and the cytolytic enzyme phospholipase A 2. In situ electrophysiological measurements of the ventral nerve cord of larval Trichoplusia ni treated at 15 and 25°C with various dosages of the three protein preparations showed that only the whole extract of the δ-endotoxin induced hyperexcitation. When the appearance of lactate dehydrogenase activity in the haemolymph of toxin-injected larvae was used to quantitate cell lysis, the cytolytic 25-kDa protein was found to be a potent cytotoxic factor like phospholipase A 2, whereas cytotoxicity of the whole δ-endotoxin extract was relatively low. Bioassays at 28, 17, and 9°C demonstrated a positive temperature correlation with mortality for the whole toxin extract, but showed inverse correlations for the two cytolytic materials. This and previous studies indicate that insect mortality is not solely due to the cytolytic activity of the Bti δ-endotoxin upon injection into T. ni. An unidentified neurotoxic factor(s) exists within the Bti δ-endotoxin which induces hyperexcited activity in the insect nervous system. This and/or other factors impart the δ-endotoxin with biological and physiological activities different from the isolated cytolytic component.

Control of activity and regression of the silk glands in the last-larval instar of Galleria mellonella

The weight increase of silk glands in isolated larval abdomens is enhanced by brain implants which stimulate RNA and protein synthesis. It is proposed that, in intact last-instar larvae, a blood-borne factor from the brain promotes silk gland activity during the facultative feeding period. In the post-feeding larvae, some starving larvae and in isolated larval abdomens the silk glands regress. The regression is accelerated and the glands degenerate under the action of 20-hydroxyecdysone. This effect is not associated with an increase in protease and RN-ase activities. In the normal larvae, the protease activity increases gradually during the last instar to a maximum at the time of regression and drops in the degenerating glands. RN-ase activity is maintained at a high level in the fully active, regressing and degenerating glands The results indicate that regression and degeneration of the silk glands are caused by structural cell reorganization rather than by an appearance of cytolytic enzymes.

Cytolytic enzymes in relation to the breakdown of the chelae muscle of the land crab, Gecarcinus lateralis

1. 1. In the land crab, Gecarcinus lateralis, the claw muscle undergoes degeneration and regeneration during specific stages of the molt cycle. 2. 2. Correlative in time with the degeneration, there is a three-fold increase in latent cathepsin D activity and a two-fold increase in latent acid phosphatase activity, where latency is defined as activity released by Triton X-100. 3. 3. The activity may be in either muscle cells themselves or connective tissue elements, including macrophages.

DEVELOPMENT OF CYTOLYTIC ENZYME ACTIVITIES DURING GERMINATION OF DIFFERENT BARLEYS

The development of three cytolytic enzyme activities was assessed at sequential stages of germination for water-steeped and also gibberellic acid-treated samples of six barley (Hordeum vulgare L.) cultivars. The cytolytic enzymes were barley-β-glucan endo-hydrolase, endo-β 1,4-glucanase and endo-β 1,3-glucanase. Significant differences in the activity development profiles of the three enzymes were noted. Differences between cultivars were quite apparent for the barley-β-glucan endo-hydrolase activities but not for the other two activities. Gibberellic acid enhanced the barley-β-glucan endo-hydrolase activity within cultivars to varying degrees, slightly increased endo-β 1,3-glucanase activity and had no effect on endo-β 1,4-glucanase activities.