[Combined XEN and Baerveldt implant-principles and management of complications]

The treatment of congenital glaucoma requires special expertise and often novel surgical approaches. The combined use of a XEN and a Baerveldt implant is an alternative to conventional tube implants and may be less harmful for long-term corneal endothelial damage. If this technique does not provide sufficient long-term control of intraorbital pressure (IOP), a direct implantation of the Baerveldt tube can be easily performed in a second intervention.

[Trabeculectomy with mitomycin C : Video article]

Trabeculectomy is the most proven method for the treatment of open angle glaucoma. The long-term results of this method show an 80% success rate in lowering intraocular pressure over 20 years. The surgical technique is demonstrated in detail with the help of a video of the operation and which is available online. For more than 15 years trabeculectomy has been performed with the use of antifibrotic substances, such as mitomycin C. Long-term treatment with antiglaucoma eyedrops leads to a proven inflammation of the conjunctiva and the ocular surface with an increase in lymphocytes, mast cells, and fibroblasts. Discontinuation of antiglaucoma therapy in turn allows regeneration of the ocular surface. From the knowledge gained from these histopathological studies it has been recommended to stop glaucoma treatment prior to glaucoma surgery and to pretreat the conjunctiva with eyedrops containing cortisone. Administration of nonsteroidal antiphlogistic substances or local steroids to the conjunctiva 4 weeks prior to surgery increases long-term success of the filtering bleb function.

[Differentiation of ocular hypertension]

The term ocular hypertension has been used for more than 30 years. It is defined as an elevated intraocular pressure above the statistical norm without detectable optic nerve head or visual field damage. The number of patients with ocular hypertension in Germany is estimated to be approximately 3-5 million. Increased intraocular pressure is a risk factor for conversion to primary open-angle glaucoma. Most patients with ocular hypertension (and no risk factors) can be followed on a regular basis without any treatment. Each visit should include measurement of intraocular pressure, optic nerve head examination with a slit lamp, imaging and perimetric examinations. Currently known risk factors are high intraocular pressure, higher age, myopia, a thin cornea and darkly pigmented skin. If risk factors are present, antiglaucomatous therapy is indicated.

Peripapillary Choroidal Thickness and Choroidal Area in Glaucoma, Ocular Hypertension and Healthy Subjects by SD-OCT

BACKGROUND

The exact pathogenesis of open angle glaucoma and ocular hypertension remains unclear. Hemodynamic influences are discussed as potential risk factors and the choroid may play an important role in the pathogenesis of open angle glaucoma or ocular hypertension. The current study investigates peripapillary choroidal thickness and choroidal area in patients with open angle glaucoma, subjects with ocular hypertension and healthy subjects using spectral-domain OCT. It furthermore assesses the association between peripapillary choroidal thickness and age, central corneal thickness, refractive error and intraocular pressure.

PATIENTS AND METHODS

Prospectively recorded data of 213 eyes of 177 open angle glaucoma patients, 73 eyes of 50 subjects with ocular hypertension and 152 eyes of 116 healthy control subjects were analyzed by fitting a linear mixed model including age and disease.

RESULTS

Peripapillary choroidal thickness was thinnest in glaucoma patients (125 µm), followed by healthy subjects (127 µm) and ocular hypertensive subjects (135 µm). A marginally significant difference was present between ocular hypertension and glaucoma (p=0.059). Thickest choroids were found superiorly and thinnest choroids inferiorly. Choroidal area was highest in the supero-nasal and lowest in the infero-temporal sectors. Choroidal thickness decreased with age, no significant correlation was evident between peripapillary choroidal thickness and refractive error or intraocular pressure. Peripapillary choroidal thickness and central corneal thickness are significantly negative correlated in healthy subjects.

CONCLUSIONS

There is a trend towards thicker choroids in ocular hypertensive subjects compared to healthy subjects or glaucoma patients. Thickest choroids are found superiorly, thinnest inferiorly. Interestingly, choroidal area is thinnest in the temporal-inferior sector, one of the regions where glaucomatous damage tends to start.

Establishment of tumor-specific copy number alterations from plasma DNA of patients with cancer

With the increasing number of available predictive biomarkers, clinical management of cancer is becoming increasingly reliant on the accurate serial monitoring of tumor genotypes. We tested whether tumor-specific copy number changes can be inferred from the peripheral blood of patients with cancer. To this end, we determined the plasma DNA size distribution and the fraction of mutated plasma DNA fragments with deep sequencing and an ultrasensitive mutation-detection method, i.e., the Beads, Emulsion, Amplification, and Magnetics (BEAMing) assay. When analyzing the plasma DNA of 32 patients with Stage IV colorectal carcinoma, we found that a subset of the patients (34.4%) had a biphasic size distribution of plasma DNA fragments that was associated with increased circulating tumor cell numbers and elevated concentration of mutated plasma DNA fragments. In these cases, we were able to establish genome-wide tumor-specific copy number alterations directly from plasma DNA. Thus, we could analyze the current copy number status of the tumor genome, which was in some cases many years after diagnosis of the primary tumor. An unexpected finding was that not all patients with progressive metastatic disease appear to release tumor DNA into the circulation in measurable quantities. When we analyzed plasma DNA from 35 patients with metastatic breast cancer, we made similar observations suggesting that our approach may be applicable to a variety of tumor entities. This is the first description of such a biphasic distribution in a surprisingly high proportion of cancer patients which may have important implications for tumor diagnosis and monitoring.

Complex tumor genomes inferred from single circulating tumor cells by array-CGH and next-generation sequencing

Circulating tumor cells (CTC) released into blood from primary cancers and metastases reflect the current status of tumor genotypes, which are prone to changes. Here, we conducted the first comprehensive genomic profiling of CTCs using array-comparative genomic hybridization (CGH) and next-generation sequencing. We used the U.S. Food and Drug Administration-cleared CellSearch system, which detected CTCs in 21 of 37 patients (range, 1-202/7.5 mL sample) with stage IV colorectal carcinoma. In total, we were able to isolate 37 intact CTCs from six patients and identified in those multiple colorectal cancer-associated copy number changes, many of which were also present in the respective primary tumor. We then used massive parallel sequencing of a panel of 68 colorectal cancer-associated genes to compare the mutation spectrum in the primary tumors, metastases, and the corresponding CTCs from two of these patients. Mutations in known driver genes [e.g., adenomatous polyposis coli (APC), KRAS, or PIK3CA] found in the primary tumor and metastasis were also detected in corresponding CTCs. However, we also observed mutations exclusively in CTCs. To address whether these mutations were derived from a small subclone in the primary tumor or represented new variants of metastatic cells, we conducted additional deep sequencing of the primary tumor and metastasis and applied a customized statistical algorithm for analysis. We found that most mutations initially found only in CTCs were also present at subclonal level in the primary tumors and metastases from the same patient. This study paves the way to use CTCs as a liquid biopsy in patients with cancer, providing more effective options to monitor tumor genomes that are prone to change during progression, treatment, and relapse.

[Optical coherence tomography (OCT) in glaucoma diagnostics]

Optical coherence tomography (OCT) provides high resolution objective and quantitative measurements of the optic disc parameters and RNFL thickness and has been widely used for detection of glaucomatous damage and disease progression. The recent introduction of spectral domain (SD)-OCT technology, also known as Fourier domain (FD)-OCT offers significant advantages over the previous time domain (TD)-OCT, allowing 3 D imaging of the retina and optic disc with ultra-high acquisition speed and ultra-high resolution. The higher resolution of (SD)-OCT offers enhanced visualisation and improved segmentation of the retinal layers, providing a higher accuracy in identification of subtle changes of the optic disc and RNFL thinning associated with glaucoma.

[Glaucoma diagnosis using scanning laser polarimetry]

Scanning laser polarimetry (SLP) is another technology for early glaucoma diagnosis. This technique (represented in the GDx from Carl Zeiss Meditec, Jena, Germany) is based on polarimetry and measures the retinal nerve fiber layer (RNFL) thickness. Compared with previous instruments without customized corneal compensation, the variable corneal compensation technology enables improved differentiation between glaucoma and healthy eyes. Limitations are the atypical birefringence patterns that exist in some eyes, showing false high RNFL values. The newest software uses enhanced corneal compensation (ECC) technology to avoid these atypical patterns and to improve glaucoma diagnosis. Advantages of SLP include independence from drawing a contour line and a reference plane. Follow-up using SLP is limited, but with the use of the new ECC technology, trend and event analyses are possible. Long-term studies will determine the effectiveness of this method.

Comparison of the iCare rebound tonometer and the Goldmann applanation tonometer over a wide IOP range

BACKGROUND

The aim of this study was to compare the intraocular pressure (IOP) results measured by the iCare rebound tonometer with those obtained by the Goldmann applanation tonometer (GAT) over a wide range of IOP values. Furthermore, the comfort level of the iCare measurement was evaluated.

METHOD

The study included 75 eyes of 75 patients. The patients were divided into three groups (7-15 mmHg n = 25, 16-22 mmHg n = 25, 23-60 mmHg n = 25). The measurements were taken by two independent observers in a masked fashion. All patients were asked about discomfort during the iCare measurement. To establish the agreement between the two devices, a Bland-Altman analysis was performed.

RESULTS

Overall, the 95% confidence interval of the differences between the two devices was -8.67 to 10.25 mmHg and in 62.7%, the iCare measurement was within +/-3 mmHg of the GAT measurements. The distribution of the differences in IOP was similar, from 7-22 mmHg. In the higher IOP range (23-60 mmHg), however, the deviation was almost twice as large. The measurement with the iCare tonometer was well tolerated; 100% of the patients denied any discomfort.

CONCLUSIONS

The iCare tonometer is a mobile alternative to GAT in a low to moderate IOP range, but our findings show a greater deviation than previously reported. In high IOP values, measurements with the iCare tonometer do not correlate well with GAT.

Results of a screening programme to identify plants or plant extracts that inhibit ruminal protein degradation

One aim of the EC Framework V project, ’Rumen-up’ (QLK5-CT-2001-00 992), was to find plants or plant extracts that would inhibit the nutritionally wasteful degradation of protein in the rumen. A total of 500 samples were screenedin vitrousing14C-labelled casein in a 30-min incubation with ruminal digesta. Eight were selected for further investigation using a batch fermentation system and soya protein and bovine serum albumin as proteolysis substrates; proteolysis was monitored over 12 h by the disappearance of soluble protein and the production of branched SCFA and NH3. Freeze-dried, ground foliage ofPeltiphyllum peltatum,Helianthemum canum,Arbutus unedo,Arctostaphylos uva-ursiandKnautia arvensisinhibited proteolysis (P < 0·05), whileDaucus carota,Clematis vitalbaandErica arboreahad little effect. Inhibition by the first four samples appeared to be caused by the formation of insoluble tannin–protein complexes. The samples were rich in phenolics and inhibition was reversed by polyethyleneglycol. In contrast,K.arvensiscontained low concentrations of phenolics and no tannins, had no effect in the 30-min assay, yet inhibited the degradation rate of soluble protein (by 14 %,P < 0·0001) and the production of branched SCFA (by 17 %,P < 0·05) without precipitating protein in the 12-h batch fermentation. The effects showed some resemblance to those obtained in parallel incubations containing 3 μm-monensin, suggesting thatK.arvensismay be a plant-derived feed additive that can suppress growth and activity of key proteolytic ruminal micro-organisms in a manner similar to that already well known for monensin.

Glaucoma detection using the GDx nerve fiber analyzer and the retinal thickness analyzer (RTA)

PURPOSE

To compare the ability of the nerve fiber analyzer (GDx) and the retinal thickness analyzer (RTA) to discriminate between glaucomatous and healthy eyes.

METHODS

Thirty-seven glaucoma patients (early to moderate severity) and 34 healthy controls were included. Glaucoma patients were defined as those with two repeatable abnormal visual fields by automated perimetry within 1 year. All subjects were examined with a GDx scanning laser polarimeter and RTA. Twelve GDx retinal nerve fiber layer parameters and 12 RTA optic disk topography parameters were obtained. GDx and RTA measurements were compared between both experimental groups using t-tests. Areas under the receiver operating characteristic curves (AUROC) for discriminating between healthy and glaucomatous eyes using GDx and RTA parameters were calculated and compared, and sensitivities at >or=80% and >or=95% specificity were reported.

RESULTS

Statistically significant differences between glaucomatous and healthy eyes were found for most GDx and RTA parameters. For GDx, the parameter with the largest AUROC for discriminating between healthy and glaucomatous eyes was the number (AUROC = 0.91, sensitivity = 85% at specificity = 84%, sensitivity = 73% at specificity = 95%). For RTA, the parameter with the largest AUROC was mean cup depth (AUROC = 0.79, sensitivity = 61% at specificity = 82%, sensitivity = 33% at specificity = 95%). The AUROC for the GDx number was significantly larger than the AUROC for RTA mean cup depth (p<0.05).

CONCLUSIONS

GDx showed better discrimination and better sensitivities at fixed specificities than RTA. The currently available RTA optic disk analysis software likely cannot replace GDx RNFL analysis software for successful glaucoma diagnosis.

Goldmann-Applanationstonometrie und dynamische Konturtonometrie

BACKGROUND

The aim of the study was to compare intraocular pressure (IOP) measurements between Goldmann applanation tonometry (GAT) and dynamic contour tonometry (DCT) during product certification according to the international requirements for ophthalmic instruments (tonometers, ISO 8612:2001).

METHODS

The study included 160 eyes of 80 subjects. IOP measurements were performed four times consecutively on each instrument in randomized order. The difference of mean IOP measurements between GAT and DCT was analyzed. Furthermore, Bland and Altman analysis was performed to assess agreement between the instruments.

RESULTS

The mean difference between DCT and GAT IOP measurements was 0.30+/-2.18 mmHg. At low to normal IOP values of 7-16 mmHg and higher IOP values of > or =23 mmHg, the difference between DCT IOP measurements and GAT IOP measurements increased in the opposite direction (1.44+/-1.59 mmHg and -1.47+/-2.57 mmHg). The Bland and Altman analysis revealed a fixed bias of -0.4+/-2.0 mmHg.

CONCLUSIONS

The test tonometer DCT exceeds the requirements for the international standard for tonometers ISO 8612:2001. The results are valid for a central corneal thickness of 540+/-40 microm.

Scanning laser polarimetry and retinal thickness analysis before and after laser in situ keratomileusis

PURPOSE

To evaluate changes in retinal nerve fiber layer (RNFL) thickness after laser in situ keratomileusis (LASIK) using a scanning laser polarimeter with fixed corneal compensation (GDx) and the retinal thickness analyzer (RTA).

METHODS

Thirty-eight eyes of 19 healthy subjects (10 female and 9 male; mean age 37.0-/+8.8 years) underwent GDx and RTA measurements before and after LASIK. All subjects revealed mild to high myopia (mean spherical refraction: -4.0-/+2.75 D). Measurements using GDx were followed by RTA measurements after pupil dilation. All measurements were performed the day before LASIK and 1 week postoperatively.

RESULTS

GDx revealed a decrease in nerve fiber layer thickness measurements after LASIK, but did not reach statistical significance (p>0.05). Using RTA, mean RNFL thickness (MRNFL) and RNFL cross sectional area decreased significantly after LASIK (p=0.03 and p=0.02, respectively).

CONCLUSIONS

Scanning laser polarimetry revealed a slight decrease in RNFL thickness measurements after LASIK. MRNFL and RNFL cross section were significantly lower after LASIK using RTA. The changes might be artifacts in a small group of myopic subjects.

[Reproducibility of measurements of the peripapillary retinal nerve fibre layer thickness. Optical coherence tomography versus retinal thickness analyzer]

PURPOSE

The aim of this study was to compare the intra- and inter-examiner reproducibility of measurements obtained by optical coherence tomography (OCT) and retinal thickness analyzer (RTA).

PATIENTS AND METHODS

During a period of 2 months, 22 eyes of 16 patients and 6 healthy subjects were included. Two examiners (EMH, RK) successively performed three measurements of the peripapillary retinal nerve fibre layer (RNFL) thickness with RTA and OCT. The reproducibility of three individual measurements of one examiner (intra-examiner) as well as the reproducibility of the measurements between both examiners (inter-examiner) was evaluated using the Friedman test and sign test.

RESULTS

The average thickness of the peripapillary RNFL was 154.4 microm for the first investigator (EMH) and 155.1 microm for the other investigator (RK) measured with RTA. The results obtained by OCT were 137.3 microm (EMH) and 138.9 microm (RK), respectively, generally indicating a threefold smaller range. Comparing the three measurements of one single examiner, no appreciable intra-observer dependency neither for RTA (EMH: p=0.19, RK: p=0.95) nor for OCT (EMH: p=0.51, RK: p=0.62) was observed. Inter-examiner analysis for RTA and OCT also revealed an acceptable reproducibility.

CONCLUSIONS

Measurements of peripapillary RNFL thickness using RTA and OCT exhibited intra- and inter-observer agreement.

[Laser in situ keratomileusis (LASIK) and scanning laser ophthalmoscopy]

BACKGROUND

To determine the influence of Laser in situ keratomileusis (LASIK) on the measurements of retinal thickness and optic nerve head topography using the Retinal Thickness Analyzer (RTA).

METHODS

RTA measurements were performed before and after LASIK. Forty-eight eyes of 25 healthy subjects were included. Mean age was 40.0+/-10.6 years. Mean preoperative refractive error (spherical equivalent) was -3.3+/-3.6 dpt, and 0.2+/-0.9dpt postoperatively. Correlation between ablation depth and duration and change of retinal thickness postoperatively was performed. All patients received a pachymetry preoperatively.

RESULTS

Postoperatively, mean retinal nerve fiber layer thickness (MRNFL) and cross sectional area (RNFL cross section area) significantly decreased after LASIK (MRNFL preop: 0.18 mm, postop: 0.11 mm, P =0.026, RNFL cross section preop: 1.17 mm(2), postop: 0.71 mm(2), P =0.015). Ablation depth revealed a significant correlation with changes in retinal thickness measurements postoperatively (Delta MRNFL: Ablation depth, P =0.001, r=-0.5). Duration of the ablation was not significantly correlated to the MRNFL measurements postoperatively (P =0.27, r=-0.08). No correlation was found between the central corneal thickness and the change in retinal thickness after LASIK (P =0.51).

CONCLUSION

Due to changes in corneal architecture after LASIK, measurements using RTA reveal a decrease in MRNFL and RNFL cross section area. These changes are likely artifacts. Further studies with a longer follow-up are desirable.

Supplementation of barley straw with Sesbania pachycarpa leaves in vitro: effects on fermentation variables and rumen microbial population structure quantified by ribosomal RNA-targeted probes

Tropical livestock is often maintained on roughage-based diets deficient in N, and therefore requires supplementation with protein-rich substrates to achieve reasonable production levels. The optimum inclusion rate of a potential supplement is usually determined by in vivo feeding trials or by in vitro incubation of the diet components to estimate the feed value of the complete diet. The present work simulates a supplementation experiment in vitro, by incubating a pure roughage (barley straw), a pure supplement (Sesbania pachycarpa leaves) and mixtures of the two, with increasing inclusion levels of the supplement, in a short-term batch incubation system. Fermentation kinetics were followed by the release of fermentation endproducts (gas and short-chain fatty acids). Microbial biomass was estimated using ribosomal (r) RNA as internal marker for bacteria and eukaryotes separately. Cell-wall-degrading subpopulations were quantified by hybridisation with taxon-specific oligonucleotide probes targeting Chytridiomycetes, Fibrobacter spp., Ruminococcus albus and R. flavefaciens. Carboxymethylcellulase (CMCase) was assayed as an indicator for cell-wall-degrading activity. The addition of S. pachycarpa leaves stimulated fermentation in all cases. Gas production, and especially rRNA concentration, showed clear maxima at 40 % S. pachycarpa inclusion, rates that significantly exceeded the values interpolated from the incubations of the pure substrates. Short-chain fatty acid yield changed only slightly, but in the same way. The analysis of the microbial population structure showed that the positive effects were mainly mediated through enhanced growth of Ruminococcus spp. Increasing proportions of S. pachycarpa leaves in the diet led to a drastic decline in the total eukaryotic population. This points to a defaunation, which may also have added to the positive effects. The eukaryotic subpopulation of the rumen fungi were affected to a lesser degree. Although the cell-wall-degrading organisms showed positive responses to the supplementation, the CMCase activity was not affected significantly by the supplementation. The present work shows that it is possible to predict optimum inclusion levels for a new feed supplement in vitro and thus reduce in vivo experiments. It was also demonstrated that true supplementation effects occur particularly for the microbial biomass production, which is the primary source of amino acids for the ruminant animal. The analysis of microbial population structure in context with conventional metabolic measurements adds valuable information to interpret the observed effects on production-related variables.

Effects of Moringa oleifera seed extract on rumen fermentation in vitro

Moringa oleifera is a pantropical tree of the family Moringaceae. A previously undescribed property of an aqueous extract from the seeds of this plant is the modulation of ruminal fermentation patterns, especially protein degradation, as demonstrated in a short-term batch incubation system. Gas, short chain fatty acids (SCFA) and cellulolytic enzyme activities were determined as general fermentation parameters. A dot blot assay able to directly detect true protein in rumen fluid samples was used to quantify protein degradation. For complex substrates the interpretation of protein degradation profiles was amended by polyacrylamide gel electrophoresis (PAGE) of the samples. When incubated with pure carbohydrates at a concentration of 1 mg ml(-1), the extract reduced microbial degradation of the model protein, bovine serum albumin (BSA), such that its concentration was at least 40% above the control after 12 h of incubation. Total protein degradation was thus delayed by approximately 9 h. When fermented along with wheat straw, leaf protein (Rubisco) was almost entirely protected during 12 h of fermentation. The degradation of soy proteins was retarded by at least 4-6 h, depending on the protein band. There were strong side effects on the fermentation of pure cellulose (SCFA yield-60% after 12 h), whereas cellobiose and starch fermentation were less affected (-18 and -8%, respectively). When the complex substrates were fermented, SCFA yield was reduced by approximately 30% after 12 h. In our work we clearly demonstrate the efficacy of the new substance, which is neither a tannin nor a saponin, in an in vitro system, using pure as well as complex substrates. The properties shown in vitro for the crude extract suggest that it could have a positive effect on the protein metabolism of ruminants under intensive management and that negative side effects can be overcome by an optimized dosage. If the chemical nature of the active substance and its mechanism of action can be clarified, it may provide an alternative to replace critical synthetic feed additives (such as antibiotics) for high yielding dairy cows.

A modified dot-blot method of protein determination applied in the tannin-protein precipitation assay to facilitate the evaluation of tannin activity in animal feeds

Tannins have received considerable attention from animal nutritionists as potential agents for modifying ruminal fermentation patterns, or for exploring new feed resources. This group of secondary plant compounds is defined by their ability to form complexes with proteins. A widely accepted method for assaying the biological activity of extracted tannins is the precipitation of bovine serum albumin. The protein carries a radioactive label (125I) to allow direct quantification from the precipitate. Tannin-protein complexes dissolve in sodium dodecylsulfate solution. A dot-blot assay for protein determination, which is based on the reversible binding of a fluorochrome, benzoxanthene yellow, to the protein spots and is not disturbed by the presence of detergents, can replace the radioactive method by a fluorimetric measurement. A novel alternative to the last part of the dot-blot assay is to scan the stained protein spots in situ using a video camera and computer image analysis. Several filter sets were tested and, within a concentration range of 0.1-2.0 mg protein/ml, each of them yielded results identical to the original method while the time required was only 30 % of the working time consumed by the original procedure. The modified dot-blot assay should be applicable to the evaluation of tannin activity in all shrub and tree foliages considered as animal feed.

Mechanism of serum resistance among Brucella abortus isolates

It was shown in this study that complement-resistant Brucella abortus used were unable to activate complement in the absence of specific antibody. Complement-resistant isolates possessed O-antigen, but complement-sensitive organisms used are O-antigen deficient. Since B. abortus LPS does not activate the alternative pathway of complement, we concluded that activation of bovine complement must be due to some other mechanism. In this study, it was shown that bovine C1 binds to the outer membrane proteins of B. abortus. Isolated outer membrane proteins of both smooth (O-antigen positive) and rough (O-antigen negative) B. abortus used bind to C1q. However, only rough isolates were killed by complement. All of the O-antigen positive B. abortus isolates were complement-resistant. We propose that O-antigen shields outer membrane proteins and blocks C1q binding.

A dye binding assay for the quantification of soluble and cell-bound acidic polysaccharides produced by red algae

Polysaccharides produced in technical scale from red algae serve in a variety of industrial applications. Ruthenium red (RR) is a cytochemical stain which has been used to visualize these mostly acidic polysaccharides in light microscopy. The binding of RR to algal polysaccharides is highly dependent on the ionic strength of the surrounding medium. The dye is firmly bound at low ionic strength, but is released at increasing salt concentrations. These properties were exploited to develop a new method to quantify the amount of cell wall material synthesized by algal cells under different physiological conditions. Soluble or extracted polysaccharides are quantified by a dot-blot procedure with subsequent image analysis, while cell-bound polysaccharides are determined in situ by a dye-binding assay followed by photometry. In comparison to the current methods of quantification, the new assay is quick, reliable, and avoids extensive use of hazardous chemicals.

Serum sensitivity of field isolates and laboratory strains of Brucella abortus

OBJECTIVE

To evaluate the ability of bovine complement to kill a variety of field isolates and laboratory strains of Brucella abortus.

DESIGN

The experimental approach was to determine the sensitivity of B abortus isolates to killing by bovine serum, and to document the role of complement in brucellacidal activity.

SAMPLE POPULATION

Six laboratory isolates and 12 field isolates of B abortus were tested.

PROCEDURE

The ability of B abortus to survive exposure to undiluted bovine serum for 2 hours at 37 C was assessed. The role of complement in killing was determined by examining the ability of heat (56 C for 60 minutes) and cobra venom factor to obliterate the activity in serum, and by detecting binding of the ninth component of bovine complement to serum-sensitive target cells.

RESULTS

Isolates of B abortus that were resistant to the bactericidal activity of normal bovine serum were revealed. These included field isolates and laboratory strains. Furthermore, the study confirmed earlier reports that bovine serum-mediated killing of B abortus is caused by the complement cascade.

CONCLUSIONS

Some isolates of B abortus, like other gram-negative bacteria, were resistant to complement-mediating killing. Resistance was associated with smooth colony morphology. Isolates lacking detectable O antigen were serum sensitive.

Contradictory roles for antibody and complement in the interaction of Brucella abortus with its host

The ability of serum complement to kill bacteria has been linked to host resistance to Gram-negative bacteria. A mechanism for killing extracellular organisms during early invasion, following release from infected phagocytic cells, or during bacteremia would contribute to a host's ability to resist disease. In fact, the ability of serum complement to kill bacteria has been linked to disease resistance. Brucella abortus are Gram-negative intracellular pathogens. Resistance to these bacteria involves the coordinated activities of the cellular and humoral immune systems. The existence of serum-resistant forms of B. abortus has been established, and it has been shown that these bacteria can resist the killing action of complement even in the presence of specific antibody. Antibody is usually necessary for complement-mediated killing of smooth (virulent) forms of Gram-negative bacteria. An anomolous situation exists with some isolates of smooth B. abortus. Sera containing high titers of specific antibody do not support killing unless they are diluted. In the bovine, this phenomenon is associated with IgG1 and IgG2 antibodies. This finding may account for the lack of positive correlation between antibody levels and resistance to disease, which has led, perhaps wrongly, to the idea that antibody and complement are not important in resistance to brucellosis. Available evidence suggests that antibody may have contradictory roles in the interactions between a host and bacteria. Avirulent (rough) forms of the organism would be rapidly killed by complement shortly after invasion, but serum-resistant smooth forms of the organism would survive and invade resident phagocytic cells. During the process of invasion and phagocytosis, the bacteria would initiate an immune response. With time, some B. abortus organisms would be released from infected phagocytic cells. In the early stages of this process, the bacteria would encounter IgM antibody and low concentrations of IgG antibody. These would cause complement-mediated killing, and infection would be restricted to resident phagocytic cells. However, the immune response to B. abortus antigens would be intensified, and IgG antibody levels would increase. High concentrations of antibody do no support complement-mediated killing of extracellular B. abortus, but the bacteria would be opsonized by antibody and complement component fragments. This would lead to increased phagocytosis of extracellular B. abortus as they appear, and concomitant extension of disease. Because of high levels of antibody would block complement-mediated killing of B. abortus, resistance to disease at this point would be dependent on cell-mediated immunity.

Inhibition of complement-mediated killing of Brucella abortus by fluid-phase immunoglobulins

Bovine immunoglobulin preparations from normal serum and from sera containing antibodies against Brucella abortus interfered with the brucellacidal action of bovine serum, whereas unfractionated normal serum and antisera were not inhibitory. The inhibitory property of immunoglobulin appeared to be attributable to some anticomplementary property because it also interfered with serum-mediated hemolysis of antibody-coated erythrocytes. The supernatant phase obtained after ultracentrifugation of bovine anti-B abortus immunoglobulin did not inhibit brucellacidal activity of normal bovine serum. Results of this study indicate that bovine anti-B abortus immunoglobulin preparations contain microaggregates of protein that can inhibit the ability of bovine serum to kill B abortus. The most likely mechanism is nonspecific activation of complement by microaggregated immunoglobulin, which consumes complement and makes it unavailable for bactericidal activity.

Blocking antibodies specific for human albumin interfere with the hemolytic activity of the membrane attack complex of complement

Earlier, we showed that antibodies specific for human serum albumin are able to bind to erythrocyte-associated albumin and inhibit complement mediated hemolysis. In the present study we determine if inhibition is occurring at the membrane attack phase of complement activation or at an earlier step. We show that although cell-bound anti-albumin antibodies do not inhibit binding and activation of C3 or uptake of C9, they do appear to cause cells to become refractory to lysis by the membrane attack complex as they inhibit both the kinetics and the extent of hemolysis in a reactive lysis system which employs preformed C5b6 plus C7, C8, and C9. We believe that this is the first report of inhibition of the hemolytic activity of the membrane attack complex by antibodies bound to an erythrocyte surface antigen.

Antibodies specific for human albumin function as blocking antibodies when attached to erythrocyte-bound albumin

Albumin is shown to be firmly bound to human red blood cells using the techniques of flow cytometry, immunoblotting, and complement fixation. The interactions between antibodies attached to the cell bound albumin and the complement system are examined. Antibodies specific for human serum albumin bind to albumin on erythrocytes and activate both homologous and heterologous complement in the absence of hemolysis. Moreover, treatment of erythrocytes with anti-albumin antibodies renders the cells resistant to classical pathway mediated lysis initiated by a passive lysis system. Thus, erythrocyte-bound anti-albumin antibodies appear to function in a manner similar to "blocking" antibodies described in some bactericidal systems.

Purification of the ninth component of the bovine complement cascade

Conditions for purification of the ninth component of bovine complement (C9) were established. The conditions for binding and elution from diethylaminoethyl cellulose and hydroxylapatite were different than for human C9. Serum albumin, a frequent contaminant of bovine C9 preparations, was removed by chromatography on reactive-red agarose. The calculated molecular weight of bovine C9 was 66,000, and reduction with 2-mercaptoethanol affected its migration on polyacrylamide gel electrophoresis. Some preparations of bovine C9 migrated as 2 bands when partially reduced, but extensively reduced preparations had a single band.

Evaluation of serologic and cellular immune responses of cattle to a nonlipopolysaccharide antigen from Brucella abortus

Cows naturally infected with Brucella abortus developed antibody (Ab) responses to a nonlipopolysaccharide antigen (NLA) purified from B abortus strain 1119-3. Sera from strain 19-vaccinated cows did not have detectable amounts of Ab. Weak lymphoproliferative responses to NLA were observed in blood mononuclear cell suspensions obtained from infected cows. There was no evidence of NLA-specific lymphoproliferation in cell suspensions from healthy cows. Nonlipopolysaccharide antigen binding to bovine blood mononuclear cells was observed by antigen-consumption assays and direct binding of radiolabeled antigen. Cells from infected cows bound less NLA than did cells from healthy cows when assays were conducted with intact blood mononuclear cell preparations (monocytes plus lymphocytes). Monocytes obtained from any group did not bind NLA. Purified B lymphocytes from infected and healthy vaccinated cows bound about 3 times more NLA than did T lymphocytes, but there were no apparent differences between the 2 groups in extent of binding. Results of the study indicate that bovine lymphocytes have binding sites for a NLA purified from B abortus strain 1119-3.

Restriction of cell lysis by homologous complement: II. Protection of erythrocytes against lysis by newly activated complement

Our previous work revealed that homologous complement (C) was ineffective in lysing antibody-sensitized erythrocytes (EA) even at high concentrations. It was also shown that activation of complement on homologous EA resulted in the binding of C9 and the formation of EA bearing complement proteins C1 through C9 (EAC1-9), yet few hemolytic sites were formed. Instead, as shown here, the formation of homologous EAC1-9 caused the cells to become resistant to lysis even by heterologous complement during a second incubation. In contrast, when homologous EAC1-8 were produced by incubating EA with C9-depleted serum, such intermediates were not protected against lysis by heterologous complement during a second incubation. Furthermore, homologous C9 on EAC1-9 was able to reduce the hemolytic efficiency of heterologous complement without blocking C activation and the formation of new C5b-9 complexes. Protection was not modified when homologous EAC1-9 were produced in one step, by incubation of EA with serum, or sequentially by adding C9 to EAC1-8. The minimum number of 9-sites required to confer a protective effect on EAC1-9 was less than 200 per cell. Thus, in addition to its known effect in heterologous cell killing, homologous C9 is capable of protecting homologous cells against inadvertent complement lysis.

Restriction of cell lysis by homologous complement: I. An analysis of membrane attack complex formation on target membranes

The hemolytic efficiency and binding of C9 to homologous and heterologous erythrocytes was evaluated by using a standardized passive sensitization procedure to prepare antigen- and antibody-coated erythrocytes (EA) and human serum for lysis. Heterologous bovine EA were readily lysed by human serum, whereas human EA were quite resistant to lysis. Human EA bound as many C8 and C9 molecules per cell as bovine EA when incubated under identical conditions, but four times as much bound C9 was required to lyse an equal number of human EA compared with bovine EA. The susceptibility of human erythrocytes did not increase when increased volumes of undiluted human serum were used although C9 binding increased to as much as 100,000 molecules per cell. Sodium dodecyl sulfate-resistant polymerized C9 (poly(C9)) was detected on both lysed ghosts and unlysed EA bearing complement proteins C1 through C9 (EAC1-9) after incubation with undiluted human serum; however, the ratio of poly(C9) to monomeric C9 was higher on unlysed cells than on ghosts. Although bovine and human EA bound equal amounts of human C9 at the end point, the rate of lysis and C9 uptake was slower on homologous cells. The rate-limiting step occurred before C9 binding and lysis because the rates of lysis and C9 binding were equal on homologous and heterologous EAC1-8 targets, but the extent of lysis of homologous cells was still lower than lysis of heterologous cells. Human erythrocytes lose restriction against homologous hemolysis during storage in autologous plasma or in isotonic buffers.

The use of a passive hemolysis system to evaluate the complement activities of six mammalian species

A passive hemolysis assay system was developed which permitted comparisons of the hemolytic activities of complement (C) from six species. This system employs a single antigen and an antiserum raised in one species. Thus, variations resulting from different target antigens and those inherent in using antibodies (of different affinities and isotypes) raised in a variety of species were minimized. Of the erythrocytes (E) examined, those from horses and guinea pigs were most susceptible to lysis, and either would be suitable, as a tentative choice, for measuring C activity of a previously unstudied species. Horse serum had the lowest C activity of any of the sera tested. It lysed certain cells only at high concentrations, and the hemolytic activity dropped off sharply with minimal dilution. The data presented in this paper could also be used for selecting target E for C studies using direct lysis with antibodies raised against the cells.

Promoter and nucleotide sequences of the Zymomonas mobilis pyruvate decarboxylase

DNA sequence analysis showed that pyruvate decarboxylase (one of the most abundant proteins in Zymomonas mobilis) contains 559 amino acids. The promoter for the gene encoding pyruvate decarboxylase was not recognized by Escherichia coli, although the cloned gene was expressed at relatively high levels under the control of alternative promoters. The promoter region did not contain sequences which could be identified as being homologous to the generalized promoter structure for E. coli. Hydropathy plots for the amino acid sequence indicated that pyruvate decarboxylase contains a large number of hydrophobic domains which may contribute to the thermal stability of this enzyme.

[Problems of exposure to organic mercury compounds in pregnancy]

On account of oral intake of mercury by contaminated foodstuff (eggs eaten by pregnant women) due to non-observance of legal decisions increased mercury concentrations in the maternal and infantile blood, in the urine and hair of the mother, in the placenta, the amnion, the cord blood and the breast milk could be proved in comparison to non-exposed pregnant women. Clinical and laboratory-chemical parameters did not show any symptoms of an intoxication in mothers and children. Demands for observance of the legal decisions and avoidance of professional dealing are particularly important for pregnant women.

Purification of nonlipopolysaccharide antigen from Brucella abortus during preparation of antigen used for indirect hemolysis test

The indirect hemolysis test (IHLT) for the diagnosis of brucellosis uses a lipopolysaccharide (LPS) antigen obtained by dimethyl sulfoxide extraction of Brucella abortus. We showed that a non-LPS antigen can be obtained as a by-product of the IHLT antigen preparation. The antigen was purified to homogeneity by a combination of gel-filtration chromatography and ion-exchange chromatography. The substance contained 8% protein and about 65% carbohydrate. The molecular weight of the primary unit was 19,750, when analyzed by polyacrylamide gel electrophoresis under denaturing conditions. The non-LPS antigen, which is serologically identical to B. abortus smooth LPS O antigen, did not bind to cell membranes. However, it could be used to detect specific antibodies by complement fixation, precipitation in agarose gels, and inhibition of the IHLT.

Production of Brucella abortus-specific protein A-reactive antibodies (IgG2) in infected and vaccinated cattle

The IgG2 anti-Brucella antibody response of cattle to Brucella vaccination and infection was measured. Three groups of animals were studied; Group 1 contained 11 non-vaccinated cows, Group 2, 17 cows vaccinated with a low dose of Strain 19 vaccine and Group 3, 17 cows vaccinated with a high dose of Strain 19 vaccine. All animals were challenged at Week 33 with an infectious isolate of B. abortus (Strain 2308). Studies of the IgG2 antibodies response indicated an absolute correlation between anti-Brucella IgG2 levels and infection of the animal. All animals showing reciprocal titers of greater than or equal to 3000 (16 of 45 tested) were found to be positive for the challenge organism at slaughter. Animals with reciprocal IgG2 titers less than or equal to 1000 (29 of 45 tested) were found to be negative for the challenge organism at the time of slaughter. The predictive value of IgG2 antibody levels for infection held for animals in all three groups and consequently this suggests that monitoring of specific IgG2 anti-Brucella antibody levels may be of value in detection of Brucella-infected cattle.

Evidence for restriction of the ability of complement to lyse homologous erythrocytes

This research explored the possibility that a mechanism for the inhibition of C exists that is capable of restricting lysis of antibody-sensitized homologous E. The ability of C to lyse E from six species was compared by using a passive lysis system that employed E coated with B. abortus LPS and bovine antibodies specific for B. abortus. A system was developed that permitted comparisons of the hemolytic efficiencies of heterologous and homologous C target cell combinations. C from all of the species tested lysed heterologous E effectively, but homologous E were poorly lysed. Furthermore, a serum factor appeared to be involved with restriction of lysis of homologous E:LPS:Ab by heterologous C, and the restriction was specific for homologous E. Human E:LPS:Ab that were washed after incubation with CH were resistant to subsequent lysis by heterologous C. This restriction did not occur at 0 degrees C or in the absence of antibodies. Incubation of homologous C with EH:LPS:Ab resulted in consumption of C1, C2, C3, and C4, but not C5. The treated CH would lyse sheep EAC1423, but it would not lyse sheep EA, EACI, or EAC142. Late reacting C components (C5 through C9) were not detectable on EH:LPS:Ab after incubation with CH, but C4 and C3 were bound to the cells. Rat late-reacting C components (rat C-EDTA) were capable of detecting C3 convertase sites on EH:LPS:Ab that had been reacted with CH. However, homologous late-reacting components and guinea pig late-reacting components were unable to detect the C3 convertase sites.

Evidence for restriction of the ability of complement to lyse homologous erythrocytes

This research explored the possibility that a mechanism for the inhibition of C exists that is capable of restricting lysis of antibody-sensitized homologous E. The ability of C to lyse E from six species was compared by using a passive lysis system that employed E coated with B. abortus LPS and bovine antibodies specific for B. abortus. A system was developed that permitted comparisons of the hemolytic efficiencies of heterologous and homologous C target cell combinations. C from all of the species tested lysed heterologous E effectively, but homologous E were poorly lysed. Furthermore, a serum factor appeared to be involved with restriction of lysis of homologous E:LPS:Ab by heterologous C, and the restriction was specific for homologous E. Human E:LPS:Ab that were washed after incubation with CH were resistant to subsequent lysis by heterologous C. This restriction did not occur at 0 degrees C or in the absence of antibodies. Incubation of homologous C with EH:LPS:Ab resulted in consumption of C1, C2, C3, and C4, but not C5. The treated CH would lyse sheep EAC1423, but it would not lyse sheep EA, EACI, or EAC142. Late reacting C components (C5 through C9) were not detectable on EH:LPS:Ab after incubation with CH, but C4 and C3 were bound to the cells. Rat late-reacting C components (rat C-EDTA) were capable of detecting C3 convertase sites on EH:LPS:Ab that had been reacted with CH. However, homologous late-reacting components and guinea pig late-reacting components were unable to detect the C3 convertase sites.

Enhanced uptake of liposomes by bovine macrophages after opsonization with antibodies to Brucella abortus

Phosphatidylcholine:cholesterol liposomes containing 4(5) carboxyfluorescein were modified by incorporation of Brucella abortus lipopolysaccharide. These vesicles were opsonized with bovine anti-B abortus or anti-B abortus plus complement. The fluorescent marker entrapped in antibody-opsonized liposomes was taken up by cultured bovine macrophages more effectively than was the same compound which had been loaded into nonopsonized liposomes. The addition of bovine complement to antibody-opsonized liposomes did not increase the extent of 4(5) carboxyfluorescein uptake over that caused by antibodies alone. The system, described in this report, could be used as a model for evaluation of the efficacy of selectively directing liposomes containing antibiotics to macrophages infected with intracellular B abortus, since macrophages possess Fc receptors capable of binding antibody-opsonized liposomes.

Failure of Brucella abortus lipopolysaccharide (LPS) to activate the alternative pathway of complement

Bovine erythrocytes (E) coated with either crude or purified preparations of Brucella abortus LPS were not lysed by human complement (C) in the presence of the chelating agent ethyleneglycol-bis-N, N'-tetraacetic acid (EGTA). On the other hand, bovine red cells coated with Salmonella typhimurium LPS were lysed by human C in EGTA. B. abortus LPS preparations did not cause fluid phase human C consumption in the presence of calcium and magnesium ions. However, as expected, S. typhimurium LPS consumed C from human serum in a dose-dependent fashion. The results of these experiments indicate that B. abortus LPS differs from the Enterobacterial LPSs in that it cannot activate the alternative pathway of C in human serum. Furthermore, the failure of B. abortus LPS to consume C in the fluid phase in the presence of calcium and magnesium ions suggests that the LPS cannot cause antibody-independent activation of the classical pathway.

Immunoradiometric assay for examination and quantitation of Brucella abortus-specific antibodies reactive with the antigen(s) used in the indirect hemolysis test

An immunoradiometric assay was designed to quantitate antibodies which bind to Brucella abortus antigens adsorbed to bovine erythrocytes. This allowed examination of antibodies specific for B. abortus antigens detectable in the indirect hemolysis test for bovine brucellosis. Assay parameters were optimized for measuring antigen-specific immunoglobulin G1 (IgG1), IgG2, and IgM antibodies. The immunoradiometric assay allowed examination of binding interactions which occur during the indirect hemolysis test. Affinity-purified antibovine IgG1, IgG2, and IgM were used to detect specific bovine antibodies of these classes (and subclasses). The binding of the anti-immunoglobulins was linear as a function of immunoglobulin concentration. However, the binding of bovine antibodies of the different classes and subclasses to B. abortus antigen was nonlinear. Since B. abortus-specific antibodies of all classes and subclasses were present in the "standard serum" during the immunoradiometric assays, it is possible that the non-linearity was due to competition between antibodies for antigenic sites. IgG2 and IgM antibodies specific for B. abortus antigen(s) appeared to be capable of binding independently to antigen(s). However, the binding efficiencies of IgG1 antibodies changed as the ratio of antigenic sites to antibodies was increased.

Survival of enteroviruses and coliform bacteria in a sludge lagoon

Enteroviruses associate with aerobically and anaerobically digested sludge were determined before the addition of the sludge to a sludge lagoon. The fate of sludge-associated viruses was followed during detention of sludge in the lagoon and after application of sludge to land for disposal. While digested sludge was being added to the lagoon, enteroviruses were readily detected in grab samples of sludge from the lagoon. Sludge-associated viruses dropped to low or undetectable levels after disposal of sludge on land and during periods when addition of digested sludge to the lagoon was suspended. Changes in the levels of fecal coliforms in the lagooned sludge paralleled changes in the numbers of enteroviruses. Enteroviruses were not detected in water from deep wells located on the sludge disposal site or near the lagoon. During the initial part of the study, poliovirus serotypes accounted for greater than 90% of the viruses identified. Later, poliovirus serotypes comprised less than 40% of the virus isolates, and echoviruses and Coxsackieviruses were the most common enteroviruses identified.

Inhibitors of complement derived from the erythrocyte membrane in paroxysmal nocturnal hemoglobinuria

Extracts of the membranes of normal red cells and red cells from all subpopulations of paroxysmal nocturnal (PNH) red cells inhibited antibody-mediated complement activation. These extracts were shown to accelerate decay of the complement complex. C42, and the relative amount of inhibitory activity was similar in normal and PNH membranes. Inhibitors derived from normal red cells markedly decreased lysis of both PNH and normal cells when antibody was present in excess and complement was limiting. These same inhibitors decreased PNH cell lysis to a much lesser degree when complement was activated with cobra venom or acidified serum. The susceptibility of the PNH cell to complement lysis because of an increased fixation of C3 to its membrane is not due to a difference in membrane-associated accelerator of the decay of the C42 complex.

Conditions for conducting the indirect hemolysis test for detection of antibodies to Brucella abortus

Some conditions were examined for performing the indirect hemolysis test for bovine brucellosis. An antigen extracted by using dimethyl sulfoxide was used for all of the assays. Optimal results were obtained by using bovine erythrocytes coated with alkali-treated antigen at a concentration of 800 micrograms/ml. Exceeding this level did not give greater sensitivity. The sensitivity of the test could be decreased by increasing the number of coated erythrocytes used in the test. Evidence was also provided for the presence of heat-labile antibodies in the sera of vaccinated cattle. Heat treatment (58 degrees C for 50 min) caused a reduction in titer of all sera tested. It was also shown that lysis of erythrocytes was complete in less than 60 min. Therefore, it would be possible to reduce the time needed for analysis. Non-alkali-treated ("native") antigen would bind to bovine erythrocytes, but it was less effective in the test than alkali-treated material. Erythrocytes coated with relatively large amounts of the native antigen were less suspectible to lysis than were cells which had been treated with lower concentrations.

Inhibition of complement-mediated lysis of sheep erythrocytes by cell-free preparations from Streptococcus mutans BHT

A cell-free extract from the spent medium of Streptococcus mutans BHT was tested for anti-complementary activity with sheep erythrocytes (E) as target cells. It was determined that this extract was enriched for extracellular lipoteichoic acid (LTA) and that the LTA bound to the surfaces of sheep E. Furthermore, sheep E, sheep E plus antibodies (EA), and sheep cells in the intermediate stage of complement (C) component fixation EAC14 became refractory to C-mediated lysis after treatment with the LTA-rich extract. Sheep E in the intermediate states EAC142 and EAC1423567 were unaffected despite the fact that LTA could be detected on the surfaces of these cells with the passive hemagglutination procedure. Preliminary results showed that the C inhibitory activity co-purified with LTA, and LTA (both crude and purified) from other bacteria were anticomplementary. Both crude extracellular material from S. mutans BHT and partially purified extracellular LTA from the same bacteria caused consumption of whole human C activity.

Purification of lipoteichoic acids by using phosphatidyl choline vesicles

Lipoteichoic acid (LTA) is a component of nearly all gram-positive membranes and recently has been found to be excreted into growth media by certain lactic acid bacteria. Cell-free extracts of LTA are usually contaminated with proteins, polysaccharides, and nucleic acids, thus causing problems to investigators studying the true biological function(s) of LTA. This report describes the preparation of purified extracellular LTA of Streptococcus mutans BHT and intracellular LTA of S. mutans AHT by three techniques: gel filtration, hydrophobic interaction chromatography, and adsorption to phospholipid vesicles. Gel filtration, the most commonly employed method for LTA purification, was found to remove nucleic acids, teichoic acids, and much polysaccharide while greatly concentrating LTA. But gross amounts of antigenic carbohydrate and protein remained associated with the LTA preparation. Hydrophobic interaction chromatography employing octyl Sepharose-4B allowed the separation of protein but not polysaccharide from partially purified BHT LTA preparations. By means of a new technique described in this paper, synthetic membranes (vesicles) were found to effectively separate all contaminants from the intracellular (AHT) and extracellular (BHT) LTA of S. mutans. This rapid method, on a comparative basis, proved to be the most effective approach for the purification of LTA from two widely differing sources.

Identification of RNA as a complement inhibitory component in an extract of Ehrlich ascites tumor cells

A factor capable of inhibiting complement was obtained from intact Ehrlich ascites tumor cells by mild extraction with phosphate-buffered saline (PBS). The inhibitor caused a decrease in extent of lysis of EAC14 with a concomitant extension of Tmax. EA, EAC1, EAC4 and EAC142 were all less susceptible to complement-mediated lysis after treatment with the tumor cell extract. Partial purification of a complement inhibitor was accomplished. The inhibitor was rich in RNA and its activity was totally destroyed by RNAase but not DNAase. RNA from mouse tissues, yeast, and Escherichia coli also inhibited complement hemolytic activity. The partially purified material only inhibited lysis of EAC1 and EAC14. Slow inhibition of fluid phase C1 was also demonstrated. In addition, RNA-rich partially purified tumor cell extract was capable of precipitating with purified human C1q.

The use of sucrose as a cryoprotective agent for the labile sheep erythrocyte-complement component--intermediate complex, EAC142

Sucrose (15% w/v) was found to be a useful agent for cryopreservation of sheep erythrocytes in the intermediate state EAC142. The ordinarilly very labile SAC142, associated with the cells, did not decay to any appreciable degree during periods of storage of 1, 72 or 132 days at -65 to -70 degrees C. Recovery of erythrocytes after freezing and thawing varied. Our best recovery was 76.6% and the poorest was 43.0%. The poorest recoveries were obtained during the latter part of the 132 day experiment after the freezer malfunctioned on day 35 causing a temperature rise to -50 degrees C which lasted for 3 days. The average spontaneous lysis of cells before freezing and thawing was 5.6%. The average spontaneous lysis for cells which had been stored in the frozen state was 6.9%.