A method to detect particle-specific antibodies against Ku and the DNA-dependent protein kinase catalytic subunit in autoimmune sera

Sera from patients with systemic lupus erythematosus, polymyositis, scleroderma, and mixed connective tissue disease are frequently characterized by the presence of high levels of autoantibodies directed against linked sets of nuclear proteins. One of these autoantigen systems is made up of Ku and the DNA-dependent protein kinase catalytic subunit (DNA-PKcs), proteins that are essential for double-strand DNA break repair and for the related process of V(D)J recombination. Ku and DNA-PKcs bind avidly to DNA ends in vivo and in vitro and form an active protein kinase complex. One hypothesis is that this assembled nucleoprotein particle, rather than its component proteins, is a primary trigger for the autoimmune response and thus a major target for the resulting autoantibodies. To screen for particle-specific antibodies, we developed an assay in which the fully native nucleoprotein particle is reconstituted in vitro and is tethered to the surface of an ELISA plate via a streptavidin-biotin linkage. These particles are recognized efficiently by monoclonal antibodies and by autoantibodies present in patient sera. The assay may detect a broader spectrum of epitopes than a conventional ELISA in which Ku and DNA-PKcs are adsorbed directly to a plastic surface. The method will be advantageous for high-throughput screening for antibodies and other ligands that bind the assembled DNA-dependent protein kinase complex.

Cytoprotective influence of ZVAD-fmk and glycine on gel-entrapped rat hepatocytes in a bioartificial liver

BACKGROUND

This study was designed to determine if an anti-necrotic compound, glycine, and/or an anti-apoptotic agent, ZVAD-fmk, improved the viability and function of hepatocytes in a bioartificial liver.

METHODS

Isolated rat hepatocytes were entrapped in collagen gel (1.0-10.0 x 10(6) cells/mL) and cultured in serum-free medium (1:10 ratio of gel:media) supplemented with glycine alone, ZVAD-fmk alone, or glycine and ZVAD-fmk. The cytoprotective effects of glycine and ZVAD-fmk on gel-entrapped rat hepatocytes (GERH) were determined after anoxic exposure (0-20 hours). Cell functionality (measured by urea production), cell viability (quantitated by vital staining with fluorescein diacetate:ethidium bromide [FDA:EB]), and the mechanism of cell death (verified by electron microscopy and DNA fragmentation studies) were determined for each condition.

RESULTS

The viability of GERH declined gradually and then stabilized 12 hours after hepatocyte isolation. The rate of urea production by GERH was directly proportional to the number of viable hepatocytes. Apoptotic death predominated at low cell density, and necrotic cell death became significant at high cell density. Hepatocyte necrosis became more significant after exposure to longer periods of anoxia (4, 8, 12, and 20 hours). ZVAD-fmk provided dose-dependent cytoprotection to GERH with an optimum benefit at a concentration of 60 mumol/L. After anoxic exposure or under high cell density culture, glycine demonstrated a maximum benefit of inhibiting necrosis at a concentration of 3 mmol/L. The beneficial effects of glycine and ZVAD-fmk were additive.

CONCLUSIONS

The metabolic activity of a hepatocyte bioartificial liver may benefit from the use of cytoprotective agents such as ZVAD-fmk and glycine.

Bacterial colonization and healing of gastric ulcers: the effects of epidermal growth factor

Experimental gastric ulcers are rapidly colonized by various bacteria, resulting in significantly impaired healing. Epidermal growth factor (EGF) is capable of preventing bacterial colonization of the healthy intestinal mucosa. In this study, we examined the possibility that EGF accelerates gastric ulcer healing by reducing bacterial colonization of the ulcer. Gastric ulcers were induced by serosal application of acetic acid. The effect of daily administration of EGF on ulcer healing and bacterial colonization was assessed and compared with the effect of daily treatment with broad-spectrum antibiotics. EGF administration reduced colonization levels and accelerated ulcer healing as effectively as the antibiotic treatment. EGF was without effect on acid secretion or neutrophil infiltration into the ulcer. Bacterial growth was not inhibited in the presence of EGF in vitro. These results demonstrate that EGF reduces bacterial colonization during an established infection of a compromised mucosal surface. This effect may contribute to the ability of EGF to accelerate gastric ulcer healing. This effect is acid independent and not due to an anti-inflammatory effect or to direct bactericidal actions.

Influence of human fulminant hepatic failure sera on endogenous retroviral expression in pig hepatocytes

A porcine endogenous retrovirus (PERV) has been shown to infect human embryonic kidney 293 (HEK293) cells in vitro. The PERV proviral sequence exists in the genome of all porcine cells, including hepatocytes used in a bioartificial liver (BAL). We examined the possibility of PERV infection in HEK293 cells during exposure to supernatant from cultured pig hepatocytes. Pig hepatocytes were cultured in media supplemented with serum from patients in fulminant hepatic failure (FHF) to simulate conditions of an extracorporeal BAL. Pig hepatocytes were cultured in serum-free media for 24 hours and then exposed to fresh medium containing serum from a patient with FHF (22 patients tested). Twenty-four hours later, supernatant was collected and analyzed by polymerase chain reaction (PCR), with and without reverse transcriptase. Primers targeting the pol gene of PERV were used for PCR. Products of amplification were detected by an enzyme-linked immunosorbent assay-based technique using an internal capture probe also targeting the pol gene. Levels of PERV sequences were estimated by serial dilution. All positive samples were tested for infectivity in HEK293 cells. Porcine kidney 15 cell supernatant and fresh culture media were studied as positive and negative controls, respectively. Pig hepatocytes were also studied in the absence of FHF sera and in the presence of mitogenic stimulation with phytohemagglutinin (PHA) and phorbol 12-myristate-13-acetate (PMA). PERV DNA and PERV RNA were detected in all supernatants of cultured pig hepatocytes. The level of PERV RNA in the supernatant of pig hepatocytes was not altered by exposure to human FHF serum or stimulation with PHA and PMA. In addition, PERV RNA was undetectable in the supernatant of HEK293 cells for up to 50 days after exposure to pig hepatocyte supernatant (with or without FHF sera). These findings show that production of PERV by cultured pig hepatocytes was unaffected by exposure to growth factors and cytokines present in human FHF sera.

Human RNA Helicase A Is a Lupus Autoantigen That Is Cleaved During Apoptosis

Proteolytic cleavage by caspases is the central event in cells undergoing apoptosis. Cleaved proteins are often targeted by autoantibodies, suggesting that the cleavage of self Ags enhances immunogenicity and is prone to induce an autoimmune response. We found autoantibodies that immunoprecipitated a 140-kDa RNA-associated protein, provisionally designated Pa, in 11 of 350 patient sera that were positive for antinuclear Abs in an immunofluorescence test. The Pa protein gave rise to three fragments with m.w. ranging from 120–130 kDa during anti-Fas-activated apoptosis. Pure caspase-3 cleaved the Pa protein into a 130-kDa fragment corresponding to the largest of these three products. Peptide sequence analysis of a tryptic digest from immunoaffinity-purified Pa showed 100% identity to human RNA helicase A (RHA). The identity of Pa with RHA was further confirmed by immunoblotting with rabbit anti-RHA Ab using anti-Pa immunoprecipitates as substrates. All 10 anti-RHA-positive patients who were clinically analyzed were diagnosed as having systemic lupus erythematosus, and 7 of them had lupus nephritis. RHA is a multifunctional protein with roles in cellular RNA synthesis and processing. Inactivation of RHA by cleavage may be an important part of the process leading to programmed cell death. The cleaved RHA fragments that are produced during apoptosis may trigger an autoimmune response in systemic lupus erythematosus.

Human RNA helicase A is a lupus autoantigen that is cleaved during apoptosis

Proteolytic cleavage by caspases is the central event in cells undergoing apoptosis. Cleaved proteins are often targeted by autoantibodies, suggesting that the cleavage of self Ags enhances immunogenicity and is prone to induce an autoimmune response. We found autoantibodies that immunoprecipitated a 140-kDa RNA-associated protein, provisionally designated Pa, in 11 of 350 patient sera that were positive for antinuclear Abs in an immunofluorescence test. The Pa protein gave rise to three fragments with m.w. ranging from 120-130 kDa during anti-Fas-activated apoptosis. Pure caspase-3 cleaved the Pa protein into a 130-kDa fragment corresponding to the largest of these three products. Peptide sequence analysis of a tryptic digest from immunoaffinity-purified Pa showed 100% identity to human RNA helicase A (RHA). The identity of Pa with RHA was further confirmed by immunoblotting with rabbit anti-RHA Ab using anti-Pa immunoprecipitates as substrates. All 10 anti-RHA-positive patients who were clinically analyzed were diagnosed as having systemic lupus erythematosus, and 7 of them had lupus nephritis. RHA is a multifunctional protein with roles in cellular RNA synthesis and processing. Inactivation of RHA by cleavage may be an important part of the process leading to programmed cell death. The cleaved RHA fragments that are produced during apoptosis may trigger an autoimmune response in systemic lupus erythematosus.

The role of the epidermal growth factor receptor in microbial infections of the gastrointestinal tract

The epidermal growth factor receptor (EGFr) is a transmembrane glycoprotein with an intrinsic tyrosine kinase. Ligand-binding to the EGFr activates cell signaling, phosphorylates protein kinases, and rearranges cytoskeletal proteins - responses that resemble those induced by microbial attachment to cell surfaces, a process known to be mediated by host cell receptors in a number of cases. This article critically reviews the possible role played by the EGFr in microbial colonization, and discusses how modulation of the EGF-EGFr axis may affect infection of the gastrointestinal tract.

Effect of a dietary nonionic surfactant on small intestinal nutrient transport

Nonionic surfactants are commonly present in many prepared foods and drug formulations as stabilizing agents. The aim of the current study was to examine the effect of the common nonionic surfactant Tween-80 on jejunal glucose transport. New Zealand White rabbits (800-1200 g) were fasted for 24 hr. Jejunal tissue was stripped and mounted in short-circuited Ussing chambers. Unidirectional 3-O-methyl glucose fluxes were determined during a 15-min basal transport period and a subsequent 15-min experimental period after the mucosal addition of Tween-80 at final concentrations of 0.001%, 0.01%, 0.05%, and 0.1%. Tween-80 at final concentrations of 0.1% and 0.05% significantly increased net 3-O-methyl glucose transport over basal levels. The increase in Jnet was due to a significant increase in the absorptive Jm-s flux. Tween-80 at 0.01% and 0.001% did not significantly alter net glucose transport although Jm-s was significantly increased in the presence of 0.01% Tween-80. Tween-80, in concentrations commonly found in prepared foods, enhances the intestinal absorption of glucose.

Transfer of porcine endogenous retrovirus across hollow fiber membranes: significance to a bioartificial liver

BACKGROUND

A porcine endogenous retrovirus (PERV) capable of infecting human cells has been identified. This study was designed to determine whether hollow fiber membranes, such as those used in a bioartificial liver, block the transfer of PERV.

METHODS

Three hollow fiber cartridges (HFCs) were studied in duplicate: cellulose fibers with 70 kD nominal molecular weight cut-off (MWCO), polysulfone fibers with 400 kD MWCO, and mixed cellulose fibers with 200 nm porosity. PK15 cells (porcine kidney cell line), known to produce PERV, were grown in the intraluminal compartment of HFCs fiber cartridges. Samples of medium were collected from both intraluminal and extraluminal compartments of the HFCs fiber cartridge during 14 days of culture. Samples were screened for PERV using reverse transcription polymerase chain reaction. All positive samples were tested for PERV infectivity in human 293 cells.

RESULTS

PERV was detected in all samples from the intraluminal space and all intraluminal samples seemed to infect 293 cells. All extraluminal samples from the fibers of 200 nm porosity tested positive for PERV. Detection of PERV in the extraluminal space was delayed by fibers of 400 kD MWCO and 70 kD MWCO until at least day 3 and day 7, respectively, after inoculation of PK15 cells. Positive extraluminal samples from fibers of 400 kD MWCO and 70 kD MWCO did not infect 293 cells.

CONCLUSION

Pore size, membrane composition, and duration of exposure influenced the transfer of PERV across HFCs. Some HFCs decrease the risk of viral exposure to patients during bioartificial liver therapy.

A critical evaluation of enzyme immunoassays for detection of antinuclear autoantibodies of defined specificities. I. Precision, sensitivity, and specificity

OBJECTIVE

To determine the performance characteristics of enzyme-based immunoassay (EIA) kits for the detection of antinuclear and other autoantibodies of defined specificities.

METHODS

Nine manufacturers of EIA kits to detect antibodies of defined specificities participated in a study in which they received coded sera from the Centers for Disease Control and Prevention. These coded sera contained different dilutions of antibody of one specificity mixed with sera containing antibodies of other specificities. The manufacturers were asked to use their standard technology to determine antibody content and send the data to a committee of the International Union of Immunological Societies for analysis. The data were analyzed for sensitivity and specificity in the detection of anti-double-stranded DNA (anti-dsDNA), anti-single-stranded DNA, antihistone, anti-Sm, anti-U1 RNP, anti-SSA/Ro, anti-SSB/La, anti-Scl-70 (DNA topoisomerase I), anticentromere, and anti-Jo-1 antibodies. In addition, replicate samples were included in the coded sera to evaluate the precision of each EIA method.

RESULTS

Lack of sensitivity and specificity was most evident in the anti-dsDNA and anti-Sm kits, although 2 kits for anti-dsDNA achieved acceptable sensitivity and specificity. Generally, anti-SSA/Ro, anti-SSB/La, anti-Scl-70, anticentromere, and anti-Jo-1 kits performed well. Many false-positive results were obtained with a multiple myeloma serum containing cryoprecipitates, but multiple myeloma sera without cryoprecipitates presented no problem in the EIA system. Precision, based on evaluation of replicate samples, varied from very good to poor.

CONCLUSION

No single manufacturer was clearly superior to others in terms of their products' overall sensitivity, specificity, and precision. Areas that needed improvement were in kits for the detection of antibodies to dsDNA and to Sm antigen. Some EIA kits achieved good sensitivity and specificity. Individual manufacturers were informed of the performance of their respective kits so they could take measures to correct perceived deficiencies and thus improve the reliability of a group of important diagnostic assays used in the evaluation of systemic rheumatic diseases.

Macromolecular transport across the rabbit proximal and distal colon

BACKGROUND

Although many studies have investigated macromolecular uptake in the stomach and small intestine, little is known about macromolecular uptake in the colon.

AIMS

To investigate the mechanisms involved in the transport of large antigenically intact macromolecules across the proximal and distal colonic epithelium in the rabbit.

METHODS

The mucosal to serosal movement of bovine serum albumin (BSA) was examined in modified Ussing chambers under short circuited conditions. The mucosal surface was exposed to varying concentrations of BSA, and after a 50 minute equilibration period, the mucosal to serosal flux of immunologically intact BSA was determined by ELISA. Total BSA flux was determined by the transport of radiolabelled 125I-BSA.

RESULTS

Intact BSA transport in proximal and distal colonic tissue showed saturable kinetics. Intact BSA transport in the proximal and distal segment was 7% and 2% of the total 125I-BSA flux respectively. Immunologically intact BSA transport in the distal segment was significantly less than that in the proximal segment. Intact BSA transport in the proximal colon was significantly reduced following treatment with sodium fluoride, colchicine, and tetrodotoxin. Cholinergic blockade had no effect on the uptake of intact BSA.

CONCLUSION

The findings indicate that the transport of intact macromolecules across the proximal and distal large intestine is a saturable process. Further, intact BSA transport in the proximal colon is an energy dependent process that utilises microtubules and is regulated by the enteric nervous system.

Role of actin in EGF-induced alterations in enterocyte SGLT1 expression

Na+-glucose cotransporter (SGLT1) expression and the role of actin in epidermal growth factor (EGF)-induced alterations in glucose transport and brush-border surface area were examined in New Zealand White rabbit jejunal loops. In separate experiments, EGF or EGF concurrent with cytochalasin D, an inhibitor of actin polymerization, was administered to the experimental loop and compared with its vehicle control. SGLT1 expression was measured by Western blot in brush-border membrane vesicles (BBMV) after 5-min and 1-h exposure. Glucose kinetics were determined by a rapid filtration technique, and brush-border surface area was examined by electron microscopy after 1-h exposure. The effect of cytochalasin D alone on BBMV glucose kinetics and brush-border surface area was also assessed. EGF resulted in a significant increase in BBMV SGLT1 expression (P < 0.05), glucose maximal uptake (Vmax; P < 0.001), and absorptive brush-border surface area (P < 0.001). These effects were abolished with concurrent cytochalasin D treatment. Cytochalasin D alone had no effect on glucose transport or brush-border surface area. The findings suggest that EGF acutely upregulates jejunal brush-border surface area and the Vmax for jejunal glucose uptake via the recruitment and insertion of SGLT1 from an internal pool into the brush border by a mechanism that is dependent on actin polymerization.

The effect of epidermal growth factor on brush border surface area and function in the distal remnant following resection in the rabbit

BACKGROUND

Epidermal growth factor (EGF) has been shown to increase intestinal absorptive surface area and transport function in normal animals.

AIMS

To examine the effect of EGF on absorptive surface area and brush border membrane function in a model of massive small bowel resection.

METHODS

New Zealand white rabbits were randomised into two groups: a resected group (60% proximal small bowel resection); and an unmanipulated control group. Distal remnant tissue was examined 10 and 21 days postsurgery. In separate experiments oral EGF (40 g/kg/day) was administered to resected animals from days 3 to 8 and animals were studied on day 10.

RESULTS

Ten days postsurgery brush border surface area and total absorptive surface area were significantly increased in remnant tissue while brush border membrane vesicle (BBMV) glucose uptake was significantly decreased compared with controls. By 21 days brush border surface area returned to control levels though BBMV glucose uptake remained depressed. EGF treatment induced a further increase in brush border surface area in remnant intestine but did not alter BBMV glucose uptake.

CONCLUSIONS

Surgical resection results in significant elevations in absorptive surface area coupled with a decrease in brush border membrane transport function distal to the site of anastomosis. EGF enhances glucose uptake in remnant intestine via recruitment of additional microvillus membrane into the brush border.

Human autoantibodies recognizing a native macromolecular structure composed of Sm core proteins in U small nuclear RNP particles

OBJECTIVE

Monoclonal antibody (mAb) F78 recognizes a heat-labile particle composed of Sm core proteins designated F78P. The objective of this study was to identify human autoantibodies recognizing the conformational structure of F78P.

METHODS

Immunoblots using HeLa cell extracts without heating prior to sodium dodecyl sulfate-polyacrylamide gel electrophoresis were used to identify autoantibodies recognizing F78P. To confirm reactivities with F78P, immunoprecipitates of mAb F78 were used as a substrate for immunoblots. To identify reactivities against the F78P structure in classic anti-Sm-positive sera, autoantibodies to individual Sm core proteins were absorbed with purified U1 small nuclear RNP before immunoblotting.

RESULTS

We identified 2 sera that, like F78, recognized only F78P and not its component polypeptides. When classic anti-Sm antibodies were preabsorbed, the presence of F78-like, particle-specific antibodies was revealed in all of the anti-Sm-positive sera tested.

CONCLUSION

Autoantibodies against the F78P structure were commonly present in sera from patients with systemic rheumatic diseases, often in combination with4=1998 M autoantibodies.

Effects of orally administered epidermal growth factor on enteropathogenic Escherichia coli infection in rabbits

The increased intestinal absorption induced by epidermal growth factor (EGF) is associated with diffuse lengthening of brush border microvilli. The aim of this study was to examine the in vivo effects of oral administration of EGF during infection with enteropathogenic Escherichia coli. New Zealand White rabbits (4 weeks old) received orogastric EGF daily starting 3 days prior to infection with enteropathogenic E. coli RDEC-1 and were compared with sham-treated infected animals and uninfected controls. Weight gain, food intake, fecal E. coli, and stool consistency were assessed daily. On day 10, segments of jejunum, ileum, proximal, and distal colon were assessed for gram-negative bacterial colonization, disaccharidase activities, and epithelial ultrastructure. Effects of EGF on E. coli RDEC-1 proliferation were studied in vitro. E. coli RDEC-1 caused diarrhea and reduced weight gain. Seven days postinfection, the small and large intestines were colonized with numerous bacteria, brush border microvilli were disrupted, and maltase and sucrase activities were significantly reduced in the jejunum. Daily treatment with EGF prevented the occurrence of diarrhea and reduction of weight gain. These effects were associated with significant inhibition of E. coli colonization in the small and large intestine, improved jejunal maltase and sucrase activities and reduced microvillous injury. EGF did not affect the proliferation of E. coli in vitro. The findings suggest that EGF protects the gastrointestinal tract against colonization by enteropathogenic E. coli.

Atrial natriuretic peptide-induced secretory responses in rabbit vs rat ileum

The aim of this study was to characterize and compare the effect of atrial natriuretic peptide (ANP) on ileal transport function in two common laboratory animals, the Hooded-Lister rat and the New Zealand White rabbit. ANP 1 microM produced a maximal increase in short circuit current (Isc) that was Cl- dependent in both rat and rabbit. The maximal response in rat tissue was twice the magnitude of that seen in the rabbit. Furthermore, the rabbit Isc response was rapid and transient compared with that of the rat. In both rats and rabbits, the ANP response was dependent on extracellular Ca++. Neural blockade had no effect on the rat ANP response but significantly inhibited the ANP response in rabbits. In the rat, the effect of ANP is mediated by seratonin (5-HT) acting through 5-HT2 receptors. In contrast, no role for 5-HT could be seen in the rabbit ileal ANP response. In intact tissue in both rat and rabbit, ANP stimulated a significant rise in cGMP levels. ANP had no effect on cAMP levels in either species. The findings suggest a separate and distinct mechanism for ANP-mediated intestinal Cl- secretion in the rat ileum compared with the rabbit.

Range of antinuclear antibodies in "healthy" individuals

OBJECTIVE

To determine the range of antinuclear antibodies (ANA) in "healthy" individuals compared with that in patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc; scleroderma), Sjögren's syndrome (SS), rheumatoid arthritis (RA), or soft tissue rheumatism (STR).

METHODS

Fifteen international laboratories experienced in performing tests for ANA by indirect immunofluorescence participated in analyzing coded sera from healthy individuals and from patients in the 5 different disease groups described above. Except for the stipulation that HEp-2 cells should be used as substrate, each laboratory used its own in-house methodology so that the data might be expected to reflect the output of a cross-section of worldwide ANA reference laboratories. The sera were analyzed at 4 dilutions: 1:40, 1:80, 1:160, and 1:320.

RESULTS

In healthy individuals, the frequency of ANA did not differ significantly across the 4 age subgroups spanning 20-60 years of age. This putatively normal population was ANA positive in 31.7% of individuals at 1:40 serum dilution, 13.3% at 1:80, 5.0% at 1:160, and 3.3% at 1:320. In comparison with the findings among the disease groups, a low cutoff point at 1:40 serum dilution (high sensitivity, low specificity) could have diagnostic value, since it would classify virtually all patients with SLE, SSc, or SS as ANA positive. Conversely, a high positive cutoff at 1:160 serum dilution (high specificity, low sensitivity) would be useful to confirm the presence of disease in only a portion of cases, but would be likely to exclude 95% of normal individuals.

CONCLUSION

It is recommended that laboratories performing immunofluorescent ANA tests should report results at both the 1:40 and 1:160 dilutions, and should supply information on the percentage of normal individuals who are positive at these dilutions. A low-titer ANA is not necessarily insignificant and might depend on at least 4 specific factors. ANA assays can be a useful discriminant in recognizing certain disease conditions, but can create misunderstanding when the limitations are not fully appreciated.

Mast cell hyperplasia and increased macromolecular uptake in an animal model of giardiasis

Giardiasis has been associated with an increase in allergic disease following infection suggesting an alteration in mucosal immune function. Jejunal in vivo and in vitro macromolecular transport, epithelial permeability, and mucosal and connective tissue mast cell counts were examined in Mongolian gerbils (35-45 g) orogastrically inoculated (I) with a pathogenic strain of Giardia lamblia and compared to age- and weight-matched, sham-treated controls (C) 6 and 21 days postinoculation. Macromolecular uptake was significantly increased in infected tissue at 6 days both in vivo (I 134 +/- 19 vs. C 74 +/- 17 ng/hr; n = 8; P < 0.05) and in vitro (I 125 +/- 17 vs. C 67 +/- 8 ng/hr/cm; n = 12; P < 0.05). Macromolecular uptake did not differ between groups at 21 days. Infection had no effect on mucosal permeability of [51Cr]EDTA. Mucosal mast cell counts did not differ at 6 days but were significantly elevated in infected tissue at 21 days (I 33.3 +/- 6.8 vs. C 2.7 +/- 0.4 per high magnification field; n = 5; P < 0.01) as were connective tissue mast cell counts (I 1.7 +/- 0.2 vs. C 1.0 +/- 0.1 per high magnification field; n = 13; P < 0.005). The findings indicate that during the peak phase of giardiasis, jejunal active antigen uptake is increased leading to a delayed recruitment of mucosal and connective tissue mast cells. These changes may play a role in the increased incidence of hypersensitivity reactions associated with Giardia infection.

DNA-dependent protein phosphorylation activity in Xenopus is coupled to a Ku-like protein

DNA-dependent protein kinase (DNA-PK) is a nuclear enzyme and functions as a serine/threonine kinase that has been well characterized in both the human and the mouse. The regulatory subunit of DNA-PK is the Ku autoantigen. To demonstrate that a Ku-like protein is present in Xenopus oocytes, we used immunoprecipitation analysis with a monoclonal antibody raised against human Ku antigen and autoimmune serum containing anti-Ku antibodies. Metabolic labeling studies indicate that the Ku-like protein is synthesized mainly in late vitellogenic oocytes. By using a specific peptide substrate for DNA-PK, we demonstrate the activity of a DNA-dependent protein kinase in oocyte extracts. The kinase activity requires the Ku-like protein, since extracts depleted of Ku protein by immunoadsorption with human anti-Ku antibodies fail to demonstrate the DNA-dependent phosphorylation activity. The increased enzyme activity in vitellogenic oocytes may be correlated to the increased levels of Ku protein observed in these oocytes compared to the pre- and early vitellogenic oocytes.

Range of antinuclear antibodies in "healthy" individuals

OBJECTIVE

To determine the range of antinuclear antibodies (ANA) in "healthy" individuals compared with that in patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc; scleroderma), Sjögren's syndrome (SS), rheumatoid arthritis (RA), or soft tissue rheumatism (STR).

METHODS

Fifteen international laboratories experienced in performing tests for ANA by indirect immunofluorescence participated in analyzing coded sera from healthy individuals and from patients in the 5 different disease groups described above. Except for the stipulation that HEp-2 cells should be used as substrate, each laboratory used its own in-house methodology so that the data might be expected to reflect the output of a cross-section of worldwide ANA reference laboratories. The sera were analyzed at 4 dilutions: 1:40, 1:80, 1:160, and 1:320.

RESULTS

In healthy individuals, the frequency of ANA did not differ significantly across the 4 age subgroups spanning 20-60 years of age. This putatively normal population was ANA positive in 31.7% of individuals at 1:40 serum dilution, 13.3% at 1:80, 5.0% at 1:160, and 3.3% at 1:320. In comparison with the findings among the disease groups, a low cutoff point at 1:40 serum dilution (high sensitivity, low specificity) could have diagnostic value, since it would classify virtually all patients with SLE, SSc, or SS as ANA positive. Conversely, a high positive cutoff at 1:160 serum dilution (high specificity, low sensitivity) would be useful to confirm the presence of disease in only a portion of cases, but would be likely to exclude 95% of normal individuals.

CONCLUSION

It is recommended that laboratories performing immunofluorescent ANA tests should report results at both the 1:40 and 1:160 dilutions, and should supply information on the percentage of normal individuals who are positive at these dilutions. A low-titer ANA is not necessarily insignificant and might depend on at least 4 specific factors. ANA assays can be a useful discriminant in recognizing certain disease conditions, but can create misunderstanding when the limitations are not fully appreciated.

The effects of "decelerated" rehabilitation following anterior cruciate ligament reconstruction on a hyperelastic female adolescent: a case study

Current concepts in postoperative anterior cruciate ligament (ACL) reconstruction management include participation in an "accelerated" rehabilitation program. There are no published reports examining the effects of accelerated or conservative rehabilitation on subjects with generalized ligamentous hyperelasticity. The purpose of this case study was to examine the effects of a conservative or "decelerated" rehabilitation program on the functional outcome of a hyperelastic female adolescent athlete following ACL reconstruction. The subject was a 15-year-old female basketball player who sustained a unilateral ACL tear and underwent subsequent ACL reconstruction using a patellar tendon autograft. The subject immediately began participation in a "decelerated" rehabilitation program in which the intensity and rate of progression was decelerated, emphasizing a prolonged period of maximum graft protection. Progress was objectively quantified with a battery of diagnosis-specific tests at scheduled intervals. Results at 52 weeks postoperative revealed normal range of motion, proprioception, balance, knee stability, quadriceps strength, hamstring strength, and subjective assessment values, and only a 4.0% deficit in functional scores. Our results suggest a "decelerated" rehabilitation program may be appropriate for the population with generalized ligamentous hyperelasticity by yielding excellent functional results without compromising the integrity of the graft and, ultimately, knee stability.

Transport of albumin into the intestinal lumen of the rat

The intestine is considered a major site for the breakdown and clearance of serum proteins. The mechanism of transport of macromolecules from the serosa into the lumen is unclear. The present study was designed to characterize the serosal to mucosal movement of albumin. Transport of bovine serum albumin (BSA) was assessed in short-circuited Ussing chambers, using stripped rat jejunum devoid of Peyer's patches. To define the kinetics of serosal to mucosal albumin transport the serosal surface was exposed to BSA at varying concentrations (0.5-5 mg.mL-1). Fluids from the mucosal compartment were sampled over time and assayed for immunologically intact BSA by ELISA. All subsequent experiments utilized a concentration of cold BSA (2 mg.mL-1) that produced maximal levels of intact BSA transport. To assess total BSA transport (intact BSA plus degraded BSA), 10 microCi (1 Ci = 37 GBq) 125I-labelled BSA was added to the serosal surface in addition to 2 mg.mL-1 cold BSA. To further characterize BSA transport tissues were treated with sodium fluoride (NaF) (metabolic inhibitor) or colchicine (an inhibitor of microtubule polymerization) or with the nerve blocker tetrodotoxin (TTX). All experiments using inhibitors were performed in paired tissues obtained from the same animal. Transport of intact BSA into the intestinal lumen was a saturable process, with a Vmax of 251 +/- 13 ng.cm-2.h-1 and a Km of 0.72 +/- 0.1 mg.mL-1, and represented 7% of the total BSA flux into the intestinal lumen. In the presence of NaF (2 x 10(-3) M), transport of both intact and total BSA was significantly inhibited (intact: control 374 +/- 80 vs. NaF 46 +/- 11, 88% inhibition; total: control 3288 +/- 296 vs. NaF 2550 +/- 235 ng.cm-2.h-1, 22% inhibition; p < 0.05). In addition, colchicine significantly inhibited intact BSA transport (control 339 +/- 15 vs. colchicine 206 +/- 13 ng.cm-2.h-1, 39% inhibition; p < 0.05). TTX had no effect on intact BSA flux. The findings suggest that transport of intact BSA from the serosa into the intestinal lumen is a saturable, energy-dependent process, which involves microtubules but is not under neural regulation.