Intensification of peroxidase-diaminobenzidine staining using gold-sulfide-silver: a rapid and highly sensitive method for visualization in immunoblotting

Zymographic assay of plant diamine oxidase on entrapped peroxidase polyacrylamide gel electrophoresis. A study of stability to proteolysis

A zymographic assay of diamine oxidase (DAO, histaminase, EC 1.4.3.6), based on a coupled peroxidase reaction, and its behavior at proteolysis in simulated gastric and intestinal conditions, are described. The DAO activity from a vegetal extract of Lathyrus sativus seedlings was directly determined on sodium dodecyl sulfate polyacrylamide electrophoretic gels containing entrapped horseradish peroxidase, with putrescine as substrate of histaminase and ortho-phenylenediamine as co-substrate of peroxidase. The accumulation of azo-aniline, as peroxidase-catalyzed oxidation product, led to well-defined yellow-brown bands on gels, with intensities corresponding to the enzymatic activity of DAO. After image analysis of gels, a linear dependency of DAO content (Coomassie-stained protein bands) and of its enzymatic activity (zymographic bands) with the concentration of the vegetal extract was obtained. In simulated gastric conditions (pH 1.2, 37 °C), the DAO from the vegetal extract lost its enzymatic activity before 15 min of incubation, either in the presence or absence of pepsin. The protein pattern (Coomassie-stained) revealed that the DAO content from the vegetal extract was kept almost constant in the simulated intestinal fluid (containing pancreatin or not), with a slight diminution in the presence of pancreatic proteases. After 10 h of incubation at 37 °C, the DAO enzymatic activity from the vegetal extract was 44.7% in media without pancreatin and 13.6% in the presence of pancreatin, whereas the purified DAO retained only 4.65% of its initial enzymatic activity in the presence of pancreatin.

Figure

Identification of novel fibronectin fragments detected specifically in juvenile urine

Ugl-Y (young age-related urinary glycoprotein) is an age-specific protein that we have previously identified in urine from healthy subjects under 18 years of age. Isoelectric focusing analysis of Ugl-Y gives a set of three bands, Y1, Y2 and Y3, in the pH region around 3. To determine the complete structure of Ugl-Y, purified Y1 and Y2 from pediatric urine were enzymatically cleaved, and the resulting peptides were analyzed by protein sequencing and/or MALDI-TOF MS. As a result, it was demonstrated that Y1 consists of 189 amino acid residues, and is identical to the region from A723 to R911 of fibronectin, whereas Y2 consists of 181 amino acid residues, and is identical to the region from A723 to R903. Electrophoretic analysis of the lysate prepared from COS-7 cells transfected with Y1- or Y2-expressing vectors gave specific bands corresponding to Y1 or Y2, respectively, showing the validity of the sequences determined. Partial purification of pediatric serum followed by western blotting revealed that Ugl-Y is derived from plasma. Furthermore, Ugl-Y was generated by in vitro digestion of fibronectin by acid protease in extracts of osteoclast cells. These findings suggest that Ugl-Y is probably produced by degradation of fibronectin comprising bone matrix during the process of vigorous bone resorption in children and adolescents. This is the first report on the identification and characterization of juvenile-specific fibronectin fragments excreted into urine.

DNase I: structure, function, and use in medicine and forensic science

In this review, available structural data of deoxyribonucleases I (DNases I) from several mammalian species, hen, snake and frog are summarized. Comparative studies on enzymatic and immunological properties and glycosylation are discussed, and several evolutionary conclusions are presented. Over the past decade, the availability of new investigative tools, including sensitive methods of electrophoresis, detection and determination, and genetically modified DNase I models has resulted in a clearer understanding of the molecular mechanisms that connect the function and usefulness of DNase I in medicine and forensic science.

Silver development in microscopy and bioanalysis: past and present

With the experience accumulated from more than a century of silver applications in biology and medicine, physical development has become a powerful bioanalytical tool for marker amplification in blotting procedures, in situ hybridization, immunocytochemistry, histochemistry, and cytochemistry. Early, empirical techniques of silver impregnation followed by development in a reducing solution (chemical developer), or a solution which contained both silver reducers and silver salts (physical developer) were often capricious and suffered from unwanted silver precipitation caused by light and self-nucleation. To accommodate the modern demand for accurate physical development, various strategies have been devised to counter these problems. One approach has been to introduce organic colloids into the developer to keep the silver ions and reducer molecules apart, whilst excluding light by using a dark-room or by covering the solution. Albumen, gelatin, and complex polysaccharides have all been tested, but gum arabic is preferred. In addition, further control can be achieved by slowing down the rate of development with low pH and by changing from silver nitrate to silver lactate, which dissociates more slowly. Effective colloid protection in a physical developer is also provided by the inclusion of tungsten salts which can delay light-catalysed silver reduction and keep the developer clear for many minutes. The same result has been achieved by complexing the silver salt in the physical developer with very large organic molecules, restricting ionization. 'Light insensitive' commercial designer products have resulted. Probably no single formulation can satisfy all conditions of use, but with increased understanding of the mechanisms of physical developers a more flexible, user-friendly approach is anticipated.

Molecular cloning of the cDNA encoding human deoxyribonuclease II

A rapid amplification of cDNA ends method, using degenerate oligonucleotides based upon the N-terminal amino acid sequence of human hepatic deoxyribonuclease II (DNase II), allowed a novel cDNA encoding DNase II to be constructed from thyroid gland RNA. The composite nucleotide sequence (1593 bases) included an open reading frame of 1080 bases, which encoded a single polypeptide of 360 amino acids (signal peptide, 16; propeptide, 91; mature protein, 253). Although the sequence of DNase II showed no significant homology to other mammalian proteins, its cDNA structural organization resembled those of the lysosomal cathepsin families. The two parts of the cDNA corresponding to the propeptide and the mature protein were expressed in Escherichia coli, and the recombinant polypeptides thus obtained were strongly stained with an anti-DNase II antibody on Western blotting. DNase II is ubiquitously expressed in human tissues, and the DNase II gene (DNASE2) was assigned to chromosome 19.

Forensic applications of genetic polymorphisms detected in human body fluids (urine, semen and blood)

The development of a new genetic marker with forensic usefulness is difficult and costly work, but it is necessary. We discovered several new markers detected in urine, semen and blood. In particular, deoxyribonuclease I-polymorphism is one of the most useful markers for practical purposes, since it has a well-balanced gene frequency, high concentration in body fluids, stability against severe conditions, and easy and accurate detectability.

A novel method for concentrating urinary type IV collagen based on precipitation with polyethylene glycol: application to its measurement by enzyme immunoassay

We investigated the efficacy of polyethylene glycol (PEG) for effective and reproducible concentration of urinary type IV collagen prior to measurement by enzyme immunoassay (EIA). Human placental type IV collagen at low concentrations (5 and 10 micrograms/L) and urinary type IV collagen were readily precipitated by PEG-4000 added at a concentration of about 150 g/L in the presence of 0.5 g/L gamma-globulin. Type IV collagen measurement by EIA from PEG-concentrated urine samples showed complete recovery and good reproducibility. Analysis of size distribution by Sephacryl S-300HR gel chromatography and Western blotting following polyacrylamide gel electrophoresis confirmed that type IV collagen in PEG-concentrated urine samples was of high molecular weight comparable to that of human placental type IV collagen. After PEG concentration, type IV collagen was detectable by EIA even in the urine of healthy subjects. Significantly higher concentrations of urinary type IV collagen were found in 30 diabetic patients with nephropathy than in 20 healthy subjects [99.5 (8.9) micrograms/L, mean (SEM) versus 21.4 (2.6) micrograms/L, P < 0.0001]. Thus, urinary type IV collagen can be measured effectively by EIA following concentration with PEG. This method has potential for the assessment of the progression of diabetic nephropathy.

Complex intermolecular interactions maintain a stable linkage between the photoreceptor connecting cilium axoneme and plasma membrane

Microtubule-membrane cross-linkers in motile and nonmotile cilia are supramolecular structures, held together by strong interactions between the constituent molecules. We have characterized these interactions in the photoreceptor connecting cilium, where cross-linkers co-fractionate and maintain their in situ location after Triton X-100 extraction of axonemes. In bovine photoreceptor cells, the transmembrane assemblage that is cross-linked to the connecting cilium axoneme contains three high molecular mass glycoconjugates of 425, 600, and 700 kDa (Horst et al., 1987). The relative amounts of the three glycoconjugates, as judged from band intensity in electrophoretograms, depend strongly on sample treatment prior to electrophoresis. The electrophoretic pattern was reproducible after several weeks of storage of the axoneme fraction in extraction buffer containing 50% sucrose. Removal of sucrose from the buffer by dialysis eliminated the 600 kDa and 700 kDa, and decreased the detected amount of the 425 kDa glycoconjugate. When samples were incubated in Laemmli sample buffer at increasing temperatures (23 degrees, 60 degrees, 95 degrees C), a gradual reduction in the intensity of the three bands was observed. The quantitative reduction of high molecular mass glycoconjugates was accompanied by the appearance of novel protein species of lower molecular mass, as detected by lectin and antibody overlays of axonemal transblots. These results suggest that the previously characterized cross-linker glycoconjugates are complex, SDS-resistant multi-molecular conglomerates. We have further used fluorescent lectins to monitor the presence of glycoconjugates on whole-mounted axonemes, in conditions aimed to selectively solubilize the cross-linkers. The cross-linker complexes could not be dissociated from the axoneme by incubation with buffers containing 1 M of either Na2SO4 or NaI. The results indicate that the connecting cilium-specific cross-linker complexes are bound via high-affinity interactions to both axoneme and overlying plasma membrane.

Salivary deoxyribonuclease I polymorphism separated by polyacrylamide gel-isoelectric focusing and detected by the dried agarose film overlay method

Isoelectric focusing of whole saliva samples on polyacrylamide gels (pH 3.5-5), followed by dried agarose film overlay detection, was employed to determine the type of salivary deoxyribonuclease I (DNase I). Since this detection method had not only a high sensitivity, but also a high band resolution, it was possible to determine DNase I types from saliva samples of 2-5 microL. Pretreatment of saliva samples with neuraminidase simplified the isozyme pattern and enhanced the sensitivity. The DNase I types in all 30 saliva samples showed a good correlation with the types found in the corresponding blood, semen, and urine samples. This preliminary trial indicates that DNase I typing from saliva samples is a new and promising method for individualization of casework samples in the field of forensic biology.

Skimmed-milk blocking improves silver post-intensification of peroxidase-diaminobenzidine staining on nitrocellulose membrane in immunoblotting

A silver-staining procedure for enhancing the sensitivity of protein detection on nitrocellulose membranes in immunoblotting is described. After completing any peroxidase-Ni-diaminobenzidine immunostaining, nitrocellulose sheets are placed in a physical developer, containing sodium tungstate and ascorbic acid, until the desired grade of silver-intensification has been reached. In this way a 16- to 64-fold amplification of intensity of the initial immunostaining can be achieved. False positive silver staining of protein bands and of background are suppressed by replacing bovine serum albumin, the blocking agent most frequently used in immunoblotting, with skimmed milk.

A new individualization marker of semen: deoxyribonuclease I (DNase I) polymorphism

We describe a method for obtaining specific and reproducible deoxyribonuclease I (DNase I) typing from liquid semen. Isoelectric focusing of the enzymes on polyacrylamide gel (IEF-PAGE, pH 3.5-5) was accomplished using a 0.5-mm thick gel. The separated isozymes were visualized by a new activity staining method, dried agarose film-overlay (DAFO). Pretreatment of semen samples with neuraminidase markedly enhanced the isozyme-band resolution and sensitivity. The method was simple and reliable, with high resolution and sensitivity. The DNase I types in semen samples were correlated with the types found in corresponding blood and urine samples. DNase I typing could therefore provide an additional discriminant characteristic in the forensic examination of semen.

Transferrin subtyping of bloodstains and semen using isoelectric focusing and immunoblotting

Transferrin (TF) subtyping was carried out on bloodstains that had been made on cotton sheeting and stored under a variety of conditions ranging from -20 degrees C to +37 degrees C. The time limit of detection was longer than 54 weeks after dry storage under each condition. Moreover the correlation between isoprotein types of the TF in blood and semen samples from the same individual was determined in 103 men. All three TF common types and two rare types in all semen samples correlated with the type found in the corresponding blood sample. A combination of isoelectric focusing separation and immuno-enzyme-linked detection may prove to be very useful for forensic TF subtyping.