Quantitative immunochemical determination of lysoqyme (muramidase) in serum and urine

An ultrasensitive paper-based SERS sensor for detection of nucleolin using silver-nanostars, plastic antibodies and natural antibodies

A state-of-the-art, ultrasensitive, paper-based SERS sensor has been developed using silver nanostars (AgNSs) in combination with synthetic and natural antibodies. A key component of this innovative sensor is the plastic antibody, which was synthesized using molecularly imprinted polymer (MIP) technology. This ground-breaking combination of paper substrates/MIPs with AgNSs, which is similar to a sandwich immunoassay, is used for the first time with the aim of SERS detection and specifically targets nucleolin (NCL), a cancer biomarker. The sensor device was carefully fabricated by synthesizing a polyacrylamide-based MIP on cellulose paper (Whatman Grade 1 filter) by photopolymerization. The binding of NCL to the MIP was then confirmed by natural antibody binding using a sandwich assay for quantitative SERS analysis. To facilitate the detection of NCL, antibodies were pre-bound to AgNSs with a Raman tag so that the SERS signal could indicate the presence of NCL. The composition of the sensory layers/materials was meticulously optimized. The intensity of the Raman signal at ∼1078 cm-1 showed a linear trend that correlated with increasing concentrations of NCL, ranging from 0.1 to 1000 nmol L-1, with a limit of detection down to 0.068 nmol L-1 in human serum. The selectivity of the sensor was confirmed by testing its analytical response in the presence of cystatin C and lysozyme. The paper-based SERS detection system for NCL is characterized by its simplicity, sustainability, high sensitivity and stability and thus embodies essential properties for point-of-care applications. This approach is promising for expansion to other biomarkers in various fields, depending on the availability of synthetic and natural antibodies.

Antimicrobial peptides and proteins in human biological fluids

Antimicrobial peptides and proteins (AMPs) are endogenous compounds that have a direct antimicrobial effect on bacteria (e. g., by disrupting bacterial membranes), as well as on fungi and viruses. AMPs are the main component of the innate immunity of living organisms and are produced by both epithelial cells (skin cells, cells of respiratory tract, intestine, urinary and genital tracts) and cells of the immune system and are secreted into secretory fluids. AMPs can also act as chemoattractants for immunocompetent cells (neutrophils, monocytes, T lymphocytes, dendritic cells) in the inflammation site and affect the antigen presenting cells by modulating adaptive T cell immune responses. The representatives of the main 15 AMP classes, that we describe in this review, are the most studied group of the large pool of these compounds. We discuss their localization, expression, and concentration in various biofluids of humans under normal and pathological conditions.

Molecularly Imprinted Polyscopoletin for the Electrochemical Detection of the Chronic Disease Marker Lysozyme

Herein we report the electropolymerization of a scopoletin based molecularly imprinted polymer (MIP) for the detection of lysozyme (Lyz), an enzymatic marker of several diseases in mammalian species. Two different approaches have been used for the imprinting of lysozyme based, respectively, on the use of a monomer-template mixture and on the covalent immobilization of the enzyme prior to polymer synthesis. In the latter case, a multi-step protocol has been exploited with preliminary functionalization of gold electrode with amino groups, via 4-aminothiophenol, followed by reaction with glutaraldehyde, to provide a suitable linker for lysozyme. Each step of surface electrode modification has been followed by cyclic voltammetry and electrochemical impedance spectroscopy, which has been also employed to test the electrochemical responses of the developed MIP. The sensors show good selectivity to Lyz and detect the enzyme at concentrations up to 292 mg/L (20 μM), but with different performances, depending on the used imprinting approach. An imprinting factor equal to 7.1 and 2.5 and a limit of detection of 0.9 mg/L (62 nM) and 2.1 mg/L (141 nM) have been estimated for MIPs prepared with and without enzyme immobilization, respectively. Competitive rebinding experiment results show that this sensing material is selective for Lyz determination. Tests were performed using synthetic saliva to evaluate the potential application of the sensors in real matrices for clinical purposes.

FRET-Based Aptasensor for the Selective and Sensitive Detection of Lysozyme

Lysozyme is a conserved antimicrobial enzyme and has been cited for its role in immune modulation. Increase in lysozyme concentration in body fluids is also regarded as an early warning of some diseases such as Alzheimer’s, sarcoidosis, Crohn’s disease, and breast cancer. Therefore, a method for a sensitive and selective detection of lysozyme can benefit many different areas of research. In this regard, several aptamers that are specific to lysozyme have been developed, but there is still a lack of a detection method that is sensitive, specific, and quantitative. In this work, we demonstrated a single-molecule fluorescence resonance energy transfer (smFRET)-based detection of lysozyme using an aptamer sensor (also called aptasensor) in which the binding of lysozyme triggers its conformational switch from a low-FRET to high-FRET state. Using this strategy, we demonstrated that the aptasensor is sensitive down to 2.3 picomoles (30 nM) of lysozyme with a dynamic range extending to ~2 µM and has little to no interference from similar biomolecules. The smFRET approach used here requires a dramatically small amount of aptasensor (~3000-fold less as compared to typical bulk fluorescence methods), and it is cost effective compared to enzymatic and antibody-based approaches. Additionally, the aptasensor can be readily regenerated in situ via a process called toehold mediated strand displacement (TMSD). The FRET-based aptasensing of lysozyme that we developed here could be implemented to detect other protein biomarkers by incorporating protein-specific aptamers without the need for changing fluorophore-labeled DNA strands.

Competition-mediated pyrene-switching aptasensor: probing lysozyme in human serum with a monomer-excimer fluorescence switch

Lysozyme (Lys) plays crucial roles in the innate immune system, and the detection of Lys in urine and serum has considerable clinical importance. Traditionally, the presence of Lys has been detected by immunoassays; however, these assays are limited by the availability of commercial antibodies and tedious protein modification and prior sample purification. To address these limitations, we report here the design, synthesis, and application of a competition-mediated pyrene-switching aptasensor for selective detection of Lys in buffer and human serum. The detection strategy is based on the attachment of pyrene molecules to both ends of a hairpin DNA strand, which becomes the partially complementary competitor to an anti-Lys aptamer. In the presence of target Lys, the aptamer hybridizes with part of the competitor, which opens the hairpin such that both pyrene molecules are spatially separated. In the presence of target Lys, however, the competitor is displaced from the aptamer by the target, subsequently forming an initial hairpin structure. This brings the two pyrene moieties into close proximity to generate an excimer, which, in turn, results in a shift of fluorescence emission from ca. 400 nm (pyrene monomer) to 495 nm (pyrene excimer). The proposed method for Lys detection showed sensitivity as low as 200 pM and high selectivity in buffer. When measured by a steady-state fluorescence spectrum, the detection of Lys in human serum showed a strong fluorescent background, which obscured detection of the excimer signal. However, time-resolved emission measurement (TREM) supported the potential of the method in complex environments with background fluorescence by demonstrating the temporal separation of probe fluorescence emission decay from the intense background signal. We have also demonstrated that the same strategy can be applied to the detection of small biomolecules such as adenosine triphosphate (ATP), showing the generality of our approach. Therefore, the competition-mediated pyrene-switching aptasensor is promising to have potential for clinical and forensic applications.

Cerebrospinal fluid lysozyme in bacterial and viral meningitis

The concentration of lysozyme (LZM) in cerebrospinal fluid was determined in 25 patients with bacterial meningitis, in 18 patients with viral meningitis and in 25 control patients who had other fibrile illnesses. The concentration of LZM was less than 1.5 microgram/ml in all control patients, and slightly to markedly raised in 10 patients with viral meningitis and in 11 out of 13 patients with untreated bacterial meningitis. The concentration of LZM was significantly different in the viral and bacterial meningitis patients (p less than 0.001). Most raised concentrations of cerebrospinal fluid LZM persisted for at least one week after the start of antibiotic treatment. The concentrations of LZM correlated well with concentrations of lactic dehydrogenase. These results show that the determination of cerebrospinal fluid LZM is a useful tool in the differential diagnosis of meningitis, particularly when the prehospital treatment with antibiotics may be responsible for a diagnostically misleading negative bacterial culture of the cerebrospinal fluid and altered cerebrospinal fluid cytology.

Lactoferrin and lysozyme in arthritic exudates

Lactoferrin (LF) has been assayed by radioimmunoassay in plasma and arthritic exudates and compared with lysozyme (LZ) levels and leukocyte counts. The mean LF concentration in 38 rheumatoid arthritis (RA) exudates was 9.1 mg/l (range 0.02-39.2). In 30 non-RA exudates LF was 3.3 mg/l (range 0.01-14.6). The corresponding LZ levels were 7.4 mg/l (range 2.5-18.5) in RA and 4.7 (range 1.0-12.5) in non-RA fluids. Exudate/plasma ratios were much higher for LF than for LZ and higher in RA than in non-RA exudates, whereas leukocyte counts did not differ. The LF/leukocyte count ratio was significantly higher in RA than in the non-RA group. The data suggest a more prominent release of neutrophilic granulocyte components in RA than in non-RA arthritis.

Colorimetric detection of lysozyme based on electrostatic interaction with human serum albumin-modified gold nanoparticles

In this study, an aqueous solution of 13-nm gold nanoparticles (AuNPs) covalently bonded with human serum albumin (HSA) was used for sensing lysozyme (Lys). HSA molecules were good stabilizing agents for AuNPs in high-salt solution and exhibited the ability to bond with Lys electrostatically. The aggregation of HSA-AuNPs was achieved upon the addition of high-pI proteins, such as Lys, alpha-chymotrypsinogen A, and conalbumin. Not the same was achieved, however, when low-pI proteins such as ovalbumin, bovine serum albumin, and alpha-lactalbumin were added. Matrix-assisted desorption/ionization mass spectrometry was used to demonstrate the interaction between HSA-AuNPs and Lys. It was found that the sensitivity of HSA-AuNPs for Lys was highly dependent on the HSA concentration. The Lys-induced aggregation of HSA-AuNPs was suggested based on the London-van der Waals attractive force. We further improved the selectivity of the probe by adjusting the pH solution to 8.0. Under the optimum conditions, the selectivity of this system for Lys over other proteins in high-salt solutions was remarkably high, even when their pI was very close to the Lys. The lowest detectable concentration of Lys in this approach was 50 nM. The applicability of the method was validated through the analyses of Lys in chicken egg white.

Possible correlation between urinary muramidase (E.C.3.2.1.27) and oesophageal cancer

The diagnostic value of determination of low-mass enzymes in urine is very important, especially for early detection of some diseases. There are several investigations about lysozyme (muramidase, E.C.3.2. 1.27) and its correlation with some malignancies, but until now nothing has been reported about the lysozyme, and oesophageal cancer. This study was undertaken for determination of lysozyme concentration in urine of 32 oesophageal cancer patients to evaluate if this enzyme activity changes in oesophageal cancer used for detection of this cancer especially in its early stage. We used high performance liquid chromatography (HPLC) for determination of urinary muramidase after Sep-pac pre-purification of the samples. The mean results of lysozymuria in patients in comparison with the mean of enzyme activity in normal controls were statistically high (12.14+/-0.403 vs. 2.04+/-0.134, P</=0.001) Our finding also indicated that the severity of lysozymuria in these patients is stage dependent.

Methods for quantitation of human neutrophil proteins, a survey

Neutrophils contain a variety of proteins that endow the cell with its capacity to migrate towards and eliminate microbial pathogens. Many of these proteins are largely or exclusively localized to neutrophils. It is therefore of interest to quantitate these proteins in a variety of clinical settings as well as in basic research. The aim of this survey is to give an introduction to some of the more commonly used methods for quantitation of neutrophil proteins and to discuss advantages and problems of the different methods and the relevance of quantitating neutrophil proteins in different biological settings.

Microparticle-enhanced nephelometric immunoassay of lysozyme in milk and other human body fluids

Quantitation of lysozyme in human milk was performed by a microparticle-enhanced nephelometric immunoassay based on the measurement of the light scattered during the competitive immunoagglutination of a microparticle–lysozyme conjugate with an anti-lysozyme antiserum. This immunoassay has a detection limit of 8 μg/L of reaction mixture and can be performed using diluted milk (1:6000, in reaction mixture), excluding sample pretreatment. Human milk lysozyme can be quantified over the concentration range 0.09–1.50 g/L, with within- and between-run coefficients of variation &lt;5%. Changes in the lysozyme concentration of human milk during lactation were determined in 636 samples. Lysozyme concentrations (mean ± SE) decreased from colostrum (0.36 ± 0.02 g/L) to transitional milk (0.30 ± 0.01 g/L) and mature milk during days 15–42 (0.30 ± 0.01 g/L), then increased in the mature milk during days 43–56 (0.35 ± 0.01 g/L) and especially during days 57–84 (0.83 ± 0.05 g/L). The proportion of lysozyme contributing to total protein was found to rise during lactation and was as follows: colostrum (1.7%), transitional milk (2.3%), and mature milk from days 15–28 (2.7%), days 29–42 (3.1%), days 43–56 (3.8%), and days 57–84 (7.3%). The assay developed for milk was also suitable for the determination of lysozyme in other human body fluids.

The importance of tubulointerstitial injury in the early phase of primary glomerular disease

OBJECTIVES

As tubulointerstitial damage is regarded secondary to glomerular injury in primary glomerulopathies, we assessed lesions to renal tubulointerstitium in recently diagnosed primary glomerular diseases and evaluated their impact on progression of the disease during the first 2 years after diagnosis.

DESIGN

A nonrandomized prospective study assessing tubulointerstitial morphometry at diagnosis, markers of tubular function within the next 6 months and progression of the disease (creatinine clearance) during 24 months' follow-up.

SETTING

Single tertiary referral centre.

SUBJECTS

Forty-six patients with primary glomerular disease, the diagnostic oligobiopsy performed within 2 months of the onset of clinical symptoms.

INTERVENTIONS

All patients were subjected to antiinflammatory/immunosuppressive treatment.

MAIN OUTCOME MEASURES

Alterations in results of tubulointerstitial morphometry and tubular function tests, correlations between these variables and parameters of nephrosis/renal function, selection of the most accurate predictor of disease progression within 24 months after diagnostic biopsy.

RESULTS

Function of proximal tubules, markedly deteriorated at the time of diagnosis, significantly improved 6 months later (urinary beta2-microglobulin: P < 0.0025), along with reduction in proteinuria (P < 0.00125). No appreciable alterations in function of distal tubules were noted. Morphometric indices revealing interstitial expansion and tubular atrophy significantly correlated with creatinine clearance at 6 months (P = 0.032) and were the best predictors of deteriorating renal function at 24 months. Excretion of beta2-microglobulin at the time of diagnosis was the best marker for impairment of glomerular filtration 6 months later.

CONCLUSIONS

Significant damage to cortical tubulointerstitium occurs concurrently with glomerular injury in primary glomerulopathies and may predict the clinical course of the disease already in its initial phase.

Early detection of anastomotic leaks after low anterior resection of the rectum

PURPOSE

Lysozyme destroys the mucopolysaccharide chains of the cell wall of gram-negative bacteria. It is a component of local defense and is formed in macrophages. Determination of lysozyme content in the wound seems to be the most reliable method for early recognition of wound infection.

METHODS

In a prospective randomized study on the efficacy of single vs. double staple technique in anterior rectum resection, the effluent from the pelvic drain was examined with regard to its lysozyme activity.

RESULTS

Lysozyme activity in drained secretion remained stable for more than 24 hours at room temperature. When the single staple technique was used, enzyme activity was sharply increased (mean, 9.6 mg/dl on the first postoperative day) compared with the double staple technique (mean, 5.5 mg/dl on the first postoperative day). The difference was statistically significant (P < 0.0001). Mean lysozyme activity was increased in those patients with clinically (18 mg/dl on the first postoperative day) and radiologically (15.3 mg/dl on the first postoperative day) detected dehiscence (P < 0.0001).

CONCLUSION

Lysozyme determination may be reproduced by detection of enzyme stability in drained secretion. Determination of lysozyme content seems to be a new possibility for early recognition of anastomotic dehiscence.

Measurement of lysozyme by an enzyme-linked immunosorbent assay

In this study an enzyme-linked immunosorbent assay has been developed for the determination of lysozyme in saliva, serum and urine. The assay relies on the detection of specific protein rather than lytic activity, a property which has been shown to be most suitable for the quantitation of lysozyme in mucin containing substances. Our results indicate that no pretreatment is necessary for the immunochemical method. The assay is sensitive to concentrations as low as 1 microgram lysozyme/l. The intra-assay and inter-assay coefficients of variation were 5.9% and 15.8% respectively. The lysozyme level in whole saliva was 55.53 +/- 30.35 mg/l, in serum the level was 0.64 +/- 0.15 mg/l and in urine it was 0.17 +/- 0.22 mg/l. Comparisons between immunochemical determination and lytic assays showed a good correlation (serum, r = 0.79, P less than 0.01; saliva, r = 0.85, P less than 0.005; treated saliva, r = 0.96, P less than 0.001).

Measurement of lysozyme in human body fluids: comparison of various enzyme immunoassay techniques and their diagnostic application

Three variants of the immunoenzymometric assay of human lysozyme with HRP-labeled antibodies were compared. The highest sensitivity (with a detection limit of 0.2 micrograms lysozyme/L) was achieved by a one-step assay lasting 2 h. Between-batch precision for the techniques was 6-11%. Lysozyme reference values were determined in serum, cerebrospinal fluid and urine. In serum they are age-dependent and in urine sex-dependent when related to creatinine excretion. Serum lysozyme is increased in only 57% of the patients with active rheumatoid arthritis and is also unreliable for indicating remission. In Crohn's disease the serum lysozyme reflects activity better, but it does not exceed the diagnostic value of alpha-1-acidic glycoprotein (orosomucoid). The lysozyme quantification in cerebrospinal fluid is useful in distinguishing between viral or bacterial meningitis.

Diagnostic significance of urinary enzymes: development of a high performance liquid chromatographic method for the measurement of urinary lysozyme

We describe a new high pressure liquid chromatography (HPLC) method for quantitative determination of urinary lysozyme. The method is simple, reproducible and with detection limit of 0.2 microgram. Before HPLC analysis the urine was purified using a Sep-Pak C18 cartridge. Lysozyme concentration was significantly higher in patients with chronic renal failure than in a control group (p less than 0.001). The concentration of lysozyme in urine is shown to be a sensitive indicator of renal damage.

A rapid and sensitive non-competitive avidin-biotin immuno-enzymatic assay for lysozyme

A non-competitive avidin-biotin immuno-enzymatic assay (NABA) for lysozyme is described. The assay was found to be more sensitive than a competitive assay with biotinylated lysozyme. The lower detection limit of NABA was 0.1 ng lysozyme/ml compared to 1 ng/ml for the competitive assay. The intra-assay and inter-assay coefficients of variation for NABA were 5.9 and 9.1%, respectively. The total time for NABA can be decreased (to less than 1 h) without influencing the detection limit or the analytical range. Serum lysozyme levels measured by NABA and the enzymatic assay in 32 samples showed a correlation coefficient of r = 0.97.

The distribution of lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin in normal hematopoietic cells and in myeloid leukemias: an immunoperoxidase study on cytocentrifuge preparations, smears, and paraffin sections

Blood and bone marrow samples from 20 individuals with reactive conditions and 26 cases of acute and chronic myeloid leukemias were tested for the presence of lysozyme, alpha-1-antitrypsin (alpha-1-AT), and alpha-1-antichymotrypsin (alpha-1-ACT). We compared the reactivity of samples in smears, cytocentrifuge preparations, and paraffin sections. Lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin were found only in polymorphonuclear leukocytes and monocytes and their precursors. Lymphocytes, E-rosetting cells, Con A-activated lymphocytes, natural killer (NK) cells, red blood cells, erythroblasts, and megakaryocytes were consistently negative. Leukemic myeloblasts showed definite reactivity for both alpha-1-antitrypsin and alpha-1-ACT, but not for lysozyme. By contrast, lysozyme was present in poorly differentiated leukemic monoblasts, while alpha-1-antitrypsin and alpha-1-antichymotrypsin showed only weak reactivity. More mature myeloid and moncytic cells showed positive staining for all three antigens tested with differences in staining distribution and intensity. In four cases of chronic myeloid leukemia (CML), circulating mature polymorphonuclear leukocytes were deficient in both lysozymne and alpha-1-antitrypsin. The use of lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin identifies normal and leukemic cells of the myeloid-monocytic series at all stages of maturation and is applicable to a variety of sample preparations.

In vitro evidence that human airway lysozyme is cleaved and inactivated by Pseudomonas aeruginosa elastase and not by human leukocyte elastase

The in vitro effects of Pseudomonas aeruginosa elastase (P. aeruginosa E) and of human leukocyte elastase on human airway lysozyme (HAL) were investigated. P. aeruginosa E inactivated and cleaved HAL, whereas human leukocyte elastase had no effect. Total inactivation of HAL by P. aeruginosa E was observed after 120 min of incubation at 37 degrees C, for an elastase-to-lysozyme molar ratio of 1:5. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of reaction mixtures containing HAL and P. aeruginosa E in an elastase-to-lysozyme molar ratio of 1:10 showed a progressive disappearance of the HAL band upon increasing the incubation time with P. aeruginosa E. Gel filtration chromatography indicated that HAL was cleaved into at least three peptide fragments. The cleavage of HAL by P. aeruginosa E was accompanied by parallel losses of its bacteriolytic activity and its immunoreactive property.

Determination of lysozyme in serum, urine, cerebrospinal fluid and feces by enzyme immunoassay

Conjugates of human lysozyme and horseradish peroxidase (HRP) were prepared by means of the heterobifunctional reagent N-succinimidyl 3-(2-pyridyldithio) propionate. A conjugate containing 2 mol HRP/mol lysozyme was isolated by gel filtration and used as a labeled antigen in competitive enzyme immunoassays, in which anti-lysozyme rabbit IgG had been bound to wells of microtiter plates. The assay can detect as little as 1 microgram lysozyme/l. The following reference intervals have been established: 950-2450 micrograms/l for serum, 1.7-123 micrograms/l for urine, 17.6-118 micrograms/l for cerebrospinal fluid and 0.04-1.5 microgram/g for feces.

Development of an enzyme-linked immunosorbent assay for determination of lysozyme in human parotid and submandibular-sublingual salivas

The specificity of lysozyme determinations in human parotid and submandibular-sublingual salivas of two subjects was assessed by comparison of lysozyme concentrations in native acidified salivas with purified enzyme obtained by immunoadsorbent fractionation of the salivas. Lysozyme concentrations were measured by the turbidimetric catalytic method and by a newly developed enzyme-linked immunosorbent assay (ELISA). The validity of the assays was established by comparing assay results with enzyme concentration values determined from optical density-extinction coefficient calculations of the purified lysozyme peak. Values for purified enzyme were found to be similar, irrespective of the assay used to determine lysozyme concentrations, and were in agreement with extinction coefficient calculations. Based on the ELISA technique, recoveries of lysozyme from both parotid and submandibular-sublingual salivas were greater than 75 and 90%, respectively. Similar recoveries were noted for parotid saliva when determinations were based on the turbidimetric assay. However, the ELISA and turbidimetric assays differed with respect to lysozyme levels in submandibular-sublingual saliva because of the apparent presence of an enhancement factor which gave rise to higher lysozyme values in the catalytic assay and therefore resulted in low recoveries of purified enzyme. This catalytic enhancement factor was present in the nonadsorbed fraction of both subjects, as higher lysozyme activities were noted when nonadsorbed fractions were added to affinity-purified lysozymes. Lysozyme levels were also determined in the parotid and submandibular-sublingual salivas of caries-resistant and -susceptible adults. In general, levels of lysozyme in parotid saliva were lower in comparison to submandibular -sublingual saliva; however, significant differences in enzyme concentration were not evident between the caries-resistant and caries-susceptible subjects.

Kidney function in stainless steel welders

Seventeen male manual metal-arc stainless steel welders (mean exposure time 20 years) had far higher levels of chromium in urine than individually matched controls (medians 23 vs 1.5 mumol/mol creatinine; 10.5 vs 0.7 microgram/g creatinine). However, there were no signs of kidney damage in tests of function of tubuli (beta-hexosaminidase, lysozyme, and beta 2-microglobuline) or glomeruli (albumine clearance).

Carcinoembryogenic antigen and lysosomal enzymes in gastric juice as an aid in the diagnosis of gastric cancer

Malignant transformation in cells is accompanied by enzymatic changes that may be useful markers of malignancy. Studies of oncofetal antigens in gastric juice show an increased concentration in patients with gastric carcinoma. The object of the present study was to test if the concentration of lysosomal enzymes and carcinoembryonic antigen (CEA) were altered in patients with gastric carcinoma compared to patients earlier operated with gastric resection--a supposedly premalignant condition. The results show that no differences could be found in CEA and beta-hexosaminidase levels between the patients with gastric carcinoma and those with gastric resection. However, lysozyme content was significantly higher in gastric carcinoma and might prove useful for screening of patients after gastric resection. Both CEA, beta-hexosaminidase, and lysozyme levels were significantly higher in patients with gastric carcinoma than in a control population, and can therefore have a role in screening of asymptomatic patients.

Lysis of Streptococcus mutans BHT by salivary lysozyme

The aim of this work was to study the bacteriolytic ability of human salivary lysozyme (HSL) on Streptococcus mutans BHT. The cells were grown in a synthetic medium containing 3H-thymidine to monitor DNA release after incubation with either HSL, purified by ion exchange chromatography, or hen egg white lysozyme (HEWL). The experiments demonstrated that HSL as well as HEWL could liberate DNA from cells. The lysis was dependent on enzyme concentration as well as incubation-time. Approximately 80% of the 3H-thymidine was released at final concentrations of 4.5 micrograms/ml and incubation-times exceeding 16 hr. Additional treatment of the suspensions with DNase increased the levels of released radioisotopes. The lytic ability of HSL and HEWL was similar at low concentrations. HSL inactivated with goat antiserum to human lysozyme decreased the liberation of DNA by about 70%. This study suggests that HSL can lyse S. mutans BHT without presence of inorganic ions.

Turbidimetric determination of lysozyme with Micrococcus lysodeikticus cells: reexamination of reaction conditions

Factors affecting the activity of human lysozyme (EC 3.2.1.17) toward cell suspensions of Micrococcus lysodeikticus were reexamined. Effects of substrate concentration, pH, and ionic strength and matrix effects of protein were assessed with special emphasis on the interdependence of various parameters. On the basis of these evaluations, an optimized kinetic turbidimetric method for lysozyme assay was set up. The method was applied for automation with a System Olli 3000 analyzer. The new automated lysozyme assay proved good for routine clinical use in regard to analysis speed, sensitivity, linearity, and reproducibility. Reference values for serum, urinary, and cerebrospinal fluid lysozyme were assessed with the automated method.

Immunoassay of tear lysozyme in conjunctival diseases

The tear lysozyme content in 111 normal subjects and in 159 patients with various conjunctival diseases was determined by a single radial immunodiffusion technique. Tear lysozyme level in normal people was 1.33/mg/ml. (SI conversion: mg/ml = g/l.) The mean tear lysozyme levels in patients with chronic irritative conjunctivitis (0.97 mg/ml) and nutritional deficiency with epithelial xerosis (0.76 mg/ml) were significantly lower than in the normal controls. The mean tear lysozyme levels in tears from patients with vernal conjuctivitis (1.20 mg/ml), phlyctenular conjunctivitis (1.10 mg/ml), and acute bacterial conjunctivitis (1.48 mg/ml) were not significantly different from those in the normal controls. Superimposition of acute bacterial conjunctivitis on trachoma did not alter the low tear lysozyme level that existed before in these patients.

Immunochemical characterization and quantification of larval brine shrimp malate dehydrogenase

The cytosolic malate dehydrogenase (s-MDH) from larval brine shrimp has been immunochemically characterized by quantitative rocket immunoelectrophoresis (IEP) and antibody catalytic inhibition studies. Monospecific rabbit antiserum produced against purified naupliar s-MDH was used for rocket IEP as a quantitative assay for the cytoplasmic isozyme, Since cross-reactivity was not observed against the mitochondrial MDH (m-MDH), the assay allows specific measurement of the s-MDH in crude naupliar supernatants in the presence of contaminating m-MDH. The assay has a sensitivity of approximately 100 nanograms s-MDH protein using either purified enzyme solutions or crude supernatant preparations. Catalytic inhibition studies using the monospecific antiserum gave 85% inhibition of s-MDH but did not give significant inhibition of the m-MDH. Lack of complete s-MDH inhibition by the antiserum suggests a difference between the enzyme active site and immunological binding site. Although the antiserum was produced against s-MDH from nauplii of the San Francisco Bay population, the antiserum inhibits equally well the s-MDH of Great Salt Lake (Utah) nauplii, indicating little if any structural difference in the immunological sites of the s-MDHs from these two geographical sources. Porcine (s- and m-MDH), bovine (m-MDH), and pigeon (m-MDH) were also tried as antigens against the brine shrimp s-MDH antiserum, but antigen-antibody reactivity was not observed during rocket IEP or catalytic inhibition experiments.

Immunochemical quantitation of human submandibular-sublingual lysozyme

A method for quantitating lysozyme by using carbamylated antiserum (commercially available) to human lysozyme in a electroimmunodiffusion technique has been developed. The method measures specific protein not lytic activity as the lyso-plate method does. We have applied this method to tears, parotid saliva, submandibular-sublingual saliva, nasal secretions, serum, and minor salivary gland secretions. We specifically selected submandibular-sublingual saliva for a comparison test with the lyso-plate method because of the known mucin content of the submandibular-sublingual saliva. Our findings indicate that no pretreatment is necessary for the electroimmunodiffusion technique. The lyso-plate method, on the other hand, requires pretreatment with Tris-acetate pH 4.5 to dissociate the mucin-lysozyme complex and give accurate values.

Serum lysozyme: evaluation of a nephelometric assay

A nephelometric lysozyme (LZM) assay method was compared to two commonly used enzymatic LZM assay methods. LZM concentrations obtained with the nephelometric method correlated well with those obtained with the spectrophotometric (r = + 0.98) and the lysoplate (r =+ 0.93) methods. The precision of the nephelometric method was 5.1% (CV). The nephelometric LZM assay offers a simple, reproducible and rapid assay method for serum LZM determinations.

A simple lysoplate method of lysozyme determination with samples dried on filter paper

A simple method for quantifying lysozyme in serum and urine has been established by modifying the procedures of sample application in the lysoplate method reported by Osserman and Lawlor [1]. A strip of filter paper is partially immersed in a liquid sample, dried at room temperature and cut into discs which are later placed on the surface of an agarose gel containing Micrococcus lysodeikticus. The follow-ng procedures for determination are carried out as described in the lysoplate method. There was no statistically significant loss of enzyme activity during the sample preparation. Lysozyme dried on filter paper is so stable that it can be stored at room temperature for at least 13 weeks and can be mailed. The sensitivity of the method is increased by pretreatment of the filter paper with Triton X-100 and consequently corresponds to that of the lysoplate method. The reproducibility of our method is practically good since the variation coefficient of the diameters of lytic zones within assays is around 1%. There is a very close correlation between lysozyme levels determined by this method and by the lysoplate method with serum samples obtained from patients with various hematological diseases (r = +0.994). The method can be utilized for routine clinical determinations of lysozyme.

[Determination of lysozyme in biological fluids by a semi-automatic kinetic technique. Discussion of the method (author's transl)]

A rapid and semi-automatic determination of lysozyme in biological fluids using kinetic analysis and turbidimetry is described and compared to other commonly used techniques. The specificity of the method is satisfactory while that of clarification of a gel medium is apparently not. Normal values and standard errors for plasma, urine, and leucocytes are given. A standardised expression of lysozyme activity is proposed and discussed. The importance of the means by which the blood sample is collected and prepared is underlined: plasma, decanted soon after collection, is preferable to serum.

Elevated plasma lysozyme in Hodgkin's disease. An indicator of increased macrophage activity?

Plasma lysozyme levels were studied in 42 patients with Hodgkin's disease and were found significantly increased. Plasma lysozyme varied with the stage of the disease and with symptoms, but did not correlate with the histological subtype or with blood neutrophil and monocyte counts. Serial measurements in four patients on MOPP treatment showed a rapid decrease following treatment. The increased plasma lysozyme in Hodgkin's disease stems most likely from the macrophage system, either because the macrophages are hyperactive and/or because the malignant cell in Hodgkin's disease is of macrophage origin.

Urinary lysozyme phenotypes in monocytic leukemia

A method of two-dimensional electrophoresis has been devised to allow the study of the electrophoretic mobility of urinary lysozyme. Three different phenotypes have been defined in a study of thirteen purified lysozymes obtained from different patients with monocytic leukemia.

Electrophoresis of lysozyme into Microscoccus-containing agarose gel: quantitative and analytical applications

Electrophoresis of lysozyme into agarose gel containing Micrococcus lysodeikticus causes lysis of the microorganism, allowing the development of two methods, one for quantitation ("lyso-rocket electrophoresis") and the other for electrophoretic characterization ("crossed lyso-electrophoresis") of lysozyme. The lyso-rocket technique provides an alternative to the method currently used for quantitative assay. By the use of crossed lyso-electrophoresis we have provided evidence, for the first time, of the electrophoretic heterogeneity of urinary lysozyme from patients with monocytic leukemia. We halve also documented the influence of concentration on the electrophoretic mobility of lysozyme.

Effect of agarose variability on the measurement of lysozyme activity

Lysozyme assays are often performed by a diffusion technique utilizing agarose gels impregnated with substrate organisms (lysoplates), but the results differ greatly from those obtained with spectrophotometric or immunologic techniques. We have investigated the effect of agarose composition on the lysoplate assay utilizing 10 different gels varying in ionic parameters. Standard curves generated with purified human lysozyme solutions were parallel, but the diameters of the zones of lysis varied inversely with gel sulfate content. The different agaroses had variable effects on determinations of normal serum lysozyme, and the results obtained on any given gel agreed with neither those found on other gels nor with independent assay in another system. The lysoplate assay should be utilized only in those laboratories that can obtain uniform agarose preparations and extensively calibrate normal ranges for their gels.

Lysozyme activity and flow rate of mixed saliva in children, adolescents and adults

Reports of lysozyme activity in mixed saliva differ greatly from lysozyme determination in pure form. In this study lysozyme activity of mixed saliva was determined by turbidimetric method in healthy children, adolescents, and adults, 111 subjects altogether. The salivary flow rate was estimated. The lysozyme activity of mixed saliva in 24 children was 129.4 +/- 42.4, in 21 adolescents 160.9 +/- 58.2, and in 66 adults 165.7 +/- 36.7 (mug/ml hen's egg white lysozyme). The flow rate of mixed saliva was similar in different groups. No statistically significant linear dependence between saliva lysozyme and flow rate was found. The lysozyme activities obtained correspond with the results of saliva lysozyme in pure form.

Connective tissue lysozyme in health and disease

As the lysozyme story continues to unfold, rheumatic disease is one area where the study of this fascinating protein will be most important. The special biochemical features of lysozyme--its hexosaminidase function, its ability to bring about transglycosylation, its homology to alpha-lactalbumin, and its cationic nature--suggest that the connective tissues may prove to be the key to the understanding of the function of lysozyme. As methods for its accurate measurement become standardized, better data on the activity of the enzyme in various tissues and body fluids, in both health and disease, will be forthcoming. As additional studies are done to ascertain which of the hypothetical functions attributed to lysozyme are of significance in vivo, it will be the student of the connective tissues and the diseases thereof who can be expected to profit most from an udnerstanding of the role of lysozyme in mammalian biology.

Low molecular weight proteinuria and slight hyperlipoproteinemia in three mentally retarded brothers

Mental retardation in combination with proteinuria and a slight hyperlipoproteinemia was found in three brothers. The increased urinary protein excretion was dominated by albumin and the low molecular weight proteins retinol-binding protein (RBP) and beta2-microglobulin, indicating the presence of proximal tubular dysfunction. However, there was no glucosuria, phosphaturia or amino aciduria and the renal concentrating and acidification capacities were normal. A kidney biopsy in one of the patients revealed morphologic evidence of glomerular damage but a normal tubular structure. A mild hyper-beta-lipoproteinemia was found in the patients but not in their healthy siblings. The cause of this syndrome, hitherto not described, is unknown.