Linkage between reovirus-induced apoptosis and inhibition of cellular DNA synthesis: role of the S1 and M2 genes

The mammalian reoviruses are capable of inhibiting cellular DNA synthesis and inducing apoptosis. Reovirus strains type 3 Abney (T3A) and type 3 Dearing (T3D) inhibit cellular DNA synthesis and induce apoptosis to a substantially greater extent than strain type 1 Lang (T1L). We used T1L x T3A and T1L x T3D reassortant viruses to identify viral genes associated with differences in the capacities of reovirus strains to elicit these cellular responses to viral infection. We found that the S1 and M2 genome segments determine differences in the capacities of both T1L x T3A and T1L x T3D reassortant viruses to inhibit cellular DNA synthesis and to induce apoptosis. These genes encode viral outer-capsid proteins that play important roles in viral attachment and disassembly. To extend these findings, we used field isolate strains of reovirus to determine whether the strain-specific differences in inhibition of cellular DNA synthesis and induction of apoptosis are also associated with viral serotype, a property determined by the S1 gene. In these experiments, type 3 field isolate strains were found to inhibit cellular DNA synthesis and to induce apoptosis to a greater extent than type 1 field isolate strains. Statistical analysis of these data indicate a significant correlation between the capacity of T1L x T3A and T1L x T3D reassortant viruses and field isolate strains to inhibit cellular DNA synthesis and to induce apoptosis. These findings suggest that reovirus-induced inhibition of cellular DNA synthesis and induction of apoptosis are linked and that both phenomena are induced by early steps in the viral replication cycle.

Chimeric hepatitis B virus core particles as probes for studying peptide-integrin interactions

An RGD-containing epitope from the foot-and-mouth disease virus (FMDV) VP1 protein was inserted into the e1 loop of the hepatitis B virus core (HBc) protein. This chimeric protein was expressed at high levels in Escherichia coli and spontaneously assembled into virus-like particles which could be readily purified. These fusion particles elicited high levels of both enzyme-linked immunosorbent assay- and FMDV-neutralizing antibodies in guinea pigs. The chimeric particles bound specifically to cultured eukaryotic cells. Mutant particles carrying the tripeptide sequence RGE in place of RGD and the use of a competitive peptide, GRGDS, confirmed the critical involvement of the RGD sequence in this binding. The chimeric particles also bound to purified integrins, and inhibition by chain-specific anti-integrin monoclonal antibodies implicated alpha 5 beta 1 as a candidate cell receptor for both the chimeric particle and FMDV. Some serotypes of FMDV bound to beta 1 integrins in solid- phase assays, and the chimeric particles competed with FMDV for binding to susceptible eukaryotic cells. Thus, HBc particles may provide a simple, general system for exploring the interactions of specific peptide sequences with cellular receptors.

Withdrawal of renal replacement therapy in Newcastle upon Tyne: 1964-1993

BACKGROUND

Termination of renal replacement therapy (RRT) is common in North America and Australia but is considered to be rare in Europe.

METHODS

In order to review the phenomenon of RRT termination in all patients treated in Newcastle upon Tyne between 1964 and 1993 a retrospective study of clinical case notes was undertaken. In all RRT patients sex, age at start of RRT, renal diagnosis and history of RRT were recorded. In addition, mortality data and marital and residential status were recorded in all patients who died, and Karnofsky index, bodyweight, complications, history of bereavement, place of death, overall survival, survival after withdrawal of treatment, other medical problems, higher mental function and surgical history in all patients stopping treatment.

RESULTS

1639 patients started RRT between 1964 and September 1993 inclusive. Eighty-eight patients were identified in whom death was a result of treatment being stopped (17% of all deaths). The first was in 1985. In these patients, age was greater (62 vs 47 years, P < 0.001) and diabetes was more prevalent (15 vs 7%, P < 0.03) than in the total RRT population. The Karnofsky index was 70 at the start and 33 at withdrawal of treatment (P < 0.001). The Karnofsky index at the start of RRT was weakly related to that at withdrawal and overall survival (r = 0.36 and 0.28 respectively, P < 0.01). The Karnofsky index at treatment withdrawal correlated with the following survival (r = 0.40, P < 0.001). The median survival of patients stopping treatment was significantly lower than in all RRT patients (16 vs 74 months, P < 0.001) and the majority survived less than 2 years. After dialysis withdrawal the median survival was 8 days, 15 patients survived 3 days or less and 19 more than 10 days. The majority (80%) received terminal care in hospital. At treatment withdrawal 11 patients were demented and 34 showed signs of early dementia. Seventy-eight patients (89%) stopped treatment as a consequence of multiple medical problems. The possibility of dialysis withdrawal was raised by physicians in 50.5%, the patient in 23.8% and the patients' relatives in 21.9% of cases. Four patients (3.8%) committed suicide.

CONCLUSIONS

Death from dialysis termination is a relatively common cause of death in RRT patients in Newcastle upon Tyne. These patients are older with a higher prevalence of diabetes. In 89% of cases the decision to stop treatment was related to multiple medical problems with a recent deterioration. Physicians raised the issue of withdrawal in the majority of cases and most patients subsequently received terminal care in hospital.

Immunogenic HIV variant peptides that bind to HLA-B8 can fail to stimulate cytotoxic T lymphocyte responses

Cytotoxic T lymphocyte responses in HIV infection can be impaired through variation in the epitope regions of viral proteins such as a gag. We report here an analysis of variant epitope peptides in three gag epitopes presented by HLA B8. Fifteen variant peptides were examined for their binding to HLA-B8; all but one bound at concentrations comparable to known epitopes. All except two of those that bound could be recognized by CTL from an HLA-B8 positive HIV-1-infected patient and were therefore immunogenic. However, in a hemophiliac patient studied in detail, there was a failure to respond to two immunogenic peptide epitopes representing virus present as provirus in the patient's peripheral blood. In one case, the patient's CTL had previously responded to the peptide; in the other case, there was a good response to a peptide of closely related sequence. Thus there was a selective failure of the CTL response to some proviral epitopes. This impaired reaction to new variants could contribute to the loss of immune control of the infection.

Immunogenic HIV variant peptides that bind to HLA-B8 can fail to stimulate cytotoxic T lymphocyte responses

Cytotoxic T lymphocyte responses in HIV infection can be impaired through variation in the epitope regions of viral proteins such as a gag. We report here an analysis of variant epitope peptides in three gag epitopes presented by HLA B8. Fifteen variant peptides were examined for their binding to HLA-B8; all but one bound at concentrations comparable to known epitopes. All except two of those that bound could be recognized by CTL from an HLA-B8 positive HIV-1-infected patient and were therefore immunogenic. However, in a hemophiliac patient studied in detail, there was a failure to respond to two immunogenic peptide epitopes representing virus present as provirus in the patient's peripheral blood. In one case, the patient's CTL had previously responded to the peptide; in the other case, there was a good response to a peptide of closely related sequence. Thus there was a selective failure of the CTL response to some proviral epitopes. This impaired reaction to new variants could contribute to the loss of immune control of the infection.

Use of reverse ligation-PCR to identify transcriptional start sites in GC-rich TATA-less genes: application to the rat IGFBP-2 gene

TATA-less genes are often GC-rich in the region of transcriptional initiation and the corresponding mRNAs are prone to the formation of secondary structure. These properties have made it difficult to determine unambigously the start sites of transcription for some of these genes by conventional assays such as primer extension and nuclease protection. Using the TATA-less rat IGFBP-2 gene, we demonstrate that tobacco acid pyrophosphatase-reverse ligation polymerase chain reaction (TAP-RLPCR), a novel and sensitive assay, can be used to map the start sites of these genes. First, the validity of TAP-RLPCR was demonstrated by mapping the transcription start site of the rat insulin-like growth factor 1 (IGFBP-1) gene to the correct position (nucleotides -173 relative to ATG, +1). Using total RNA obtained from the rat liver cell line BRL-3A, the transcription start sites of the rat IGFBP-2 gene were mapped to a narrow cluster extending from nucleotides -86 to -90 (ATG, +1), 39 bp downstream of three adjacent GC boxes that are essential to the transcriptional activity of the gene. The assay was also used to map the start sites of a luciferase reporter gene driven by the fragment -1,295 to -32 of the rat IGFBP-2 promoter after transfection in the human embryonic kidney cell line 293. The hybrid gene utilized the same transcription start sites as the rat IGFBP-2 gene, indicating that the elements required for positioning of the transcription initiation complex are contained within the 3' end terminating at nucleotide -32.(ABSTRACT TRUNCATED AT 250 WORDS)

Widening of the tracheal bifurcation on chest radiographs: value as a sign of left atrial enlargement

OBJECTIVE

This study evaluated widening of the tracheal bifurcation (subcarinal and interbronchial) angle on posteroanterior chest radiographs as a sign of left atrial enlargement. The purpose was to determine the diagnostic sensitivity and specificity of the sign.

MATERIALS AND METHODS

The chest radiographs and echocardiograms of 122 clinically stable patients were retrospectively reviewed. The mean interval between examinations was 10 days (range, 0-30 days). The left atrial dimension was measured on the two-dimensional echocardiograms. Sixty-five patients had a normal left atrial dimension (mean, 34 mm), and 45 patients had an enlarged atrium (mean, 47 mm) on echocardiography. Subcarinal and interbronchial angles were jointly measured by two observers who were unaware of the echocardiographic findings. Correlation analysis was used to determine which angle measurement best predicted the left atrial size. Discriminant analysis was used to derive a threshold angle that predicted left atrial enlargement.

RESULTS

The carina was inadequately seen on 14 radiographs. Left atrial size correlated poorly with both the interbronchial (r = .33) and the subcarinal (r = .25) angel values. An interbronchial angle of 76.4 degrees and a subcarinal angle of 65.4 degrees were the best discriminators between patients with normal and those with enlarged left atrial dimensions (sensitivities, 61% and 51%, respectively; specificities, 63% and 66%).

CONCLUSION

Our findings show that widening of the tracheal bifurcation angle on chest radiographs is an insensitive and nonspecific sign of left atrial enlargement. This sign is of little value in diagnosing left atrial enlargement.

Recombinant human insulin-like growth factor (IGF)-binding protein-6 inhibits IGF-II-induced differentiation of L6A1 myoblasts

Insulin-like growth factor-binding protein-6 (IGFBP-6) is an O-linked glycoprotein that binds insulin-like growth factor-II (IGF-II) with marked preferential affinity over IGF-I. Recombinant human IGFBP-6 (rhIGFBP-6) was synthesized by COS-7 monkey kidney cells that were transiently transfected with a eukaryotic expression vector into which a complementary DNA for IGFBP-6 modified for optimal translation had been inserted. rhIGFBP-6 was similar to IGFBP-6 purified from human cerebrospinal fluid with respect to IGF binding and O-glycosylation. The effect of rhIGFBP-6 on IGF-induced L6A1 myoblast differentiation was studied using creatine kinase activity as an index of differentiation. rhIGFBP-6 inhibited differentiation initiated by IGF-II in a dose-dependent manner, inhibition was complete when rhIGFBP-6 was present in a slight molar excess. In contrast, rhIGFBP-6 had no effect on IGF-I-induced differentiation, even when coincubated in a 5-fold molar excess. These results are consistent with the preferential affinity of IGFBP-6 for IGF-II. As cell association and proteolysis have been associated with the potentiation, rather than the inhibition, of IGF action by IGFBPs, we investigated whether they occurred in the L6A1 myoblast system. After incubation of L6A1 myoblasts with rhIGFBP-6, IGFBP-6 was recovered from the medium, but not from cell lysates or extracellular matrix. In addition, [125I]IGFBP-6 did not bind to myoblast monolayers, and there was no evidence that proteolysis had occurred. Together, these results indicate that rhIGFBP-6 remains intact and soluble and, hence, inhibits IGF-II-induced differentiation. The fidelity of the IGFBP-6 expression system used for these studies will enable us to use this system to determine how structural modifications of the protein affect the modulation of IGF action by IGFBP-6.

Percutaneous aspiration thromboembolectomy: a preliminary experience

Percutaneous aspiration thromboembolectomy (PAT) is a radiological alternative to surgical embolectomy or thrombolysis in the treatment of acute arterial thromboembolic disease. We report our experience in eight patients aged 63-83 years (mean 71 years). Indications were graft thrombosis (1) or emboli from atrial fibrillation (3), abdominal aneurysm (2) or proximal angioplasty (2). PAT was performed at 10 arterial sites; common iliac (1), profunda femoris (1), superficial femoral (2), femoro-popliteal graft (1), popliteal (2) and arteries of the trifurcation (3). PAT was used as an adjunct to thrombolysis or angioplasty in five patients and as the sole procedure in three patients. It was successful in six patients (seven sites) with mean ABI rising from 0.4 pre- to 0.8 post-procedure. Two of the failures required amputations. One of these was a completely thrombosed dacron femoro-popliteal graft with poor run-off, and the second case had a failed surgical embolectomy prior to amputation. There were no major complications, and no mortality on follow-up at 1 month. PAT is a useful adjunct to thrombolysis and balloon angioplasty in the radiological treatment of acute thromboembolic disease. In patients in whom thrombolysis is contraindicated, it offers an alternative to surgical embolectomy.

The effect of inhibition of glutathione S-transferase P on the growth of the Jurkat human T cell line

To investigate the possible role of glutathione S-transferase P (GSTP) in carcinogenesis and cell proliferation, ethacrynic acid (EA) was used to inhibit GSTP in the human Jurkat T cell line. At lower doses (0-30 microM), EA led to a decreased rate of proliferation as assessed by the MTT assay. This was associated with a decreased DNA S+G2/M phase population and also a dose-dependent increase in apoptosis. At concentrations of EA > 30 microM, cells suffered non-specific cytotoxic injury and underwent necrosis. The total cell number fell over the time course of the experiment. A resistant subculture of cells which proliferated in the presence of EA at 30 microM was selected by continuous growth in the presence of EA. Although this had a higher basal rate of apoptosis than control cells, it also showed a significantly larger growth fraction as assessed by flow cytometry. GSTP is frequently overexpressed in human tumours and animal models of carcinogenesis, and is regarded as a marker of the 'drug-resistant phenotype' of initiated cells. Our findings suggest that the role of GSTP in models of chemical carcinogenesis and in tumours may be its permissive effect on cell cycle activity and downregulation of apoptosis, thus allowing expansion of a population of initiated cells.

Three clustered Sp1 sites are required for efficient transcription of the TATA-less promoter of the gene for insulin-like growth factor-binding protein-2 from the rat

Insulin-like growth factor-binding protein-2 (IGF-BP-2) transcription in rat liver varies with developmental age and fasting. To define the DNA elements required for efficient expression of the TATA-less rat IGFBP-2 gene, the native or mutated promoter was fused to a promoterless luciferase reporter gene and transfected into BRL-3A rat liver and 293 human embryonic kidney cell lines. Luciferase activity decreased approximately 25-fold with progressive 5' promoter deletions from nucleotide (nt) -581 to nt -189 (relative to ATG, +1). The smallest construct, however, still had > 21-fold greater luciferase activity than the promoterless construct. In DNase I foot-printing assays using native nt -276 to -36 promoter fragments or fragments containing block substitution mutations, BRL-3A nuclear extract and purified human transcription factor Sp1 protected a region from nt -234 to -215 containing one GC box and a broad region from nt -189 to -125 that contained three clustered but independent GC boxes. In gel retardation assays using an Sp1 oligonucleotide probe, BRL-3A extract formed two closely migrating complexes that were immunologically related to Sp1; Sp1 gave a single complex that co-migrated with the more retarded BRL-3A complex. Binding was competitively inhibited by oligonucleotides corresponding to each of the four GC boxes. The proximal three GC boxes were sufficient to allow trans-activation of the IGFBP-2 promoter by Sp1 in Drosophila SL2 cells. Independent block mutations indicated that all three of the GC boxes are required for promoter activity and are equally important. Thus, binding of Sp1 or Sp1-related proteins to three clustered GC boxes in the proximal IGFBP-2 promoter is essential for promoter activity. Multiple upstream regions also contribute to the full expression of the IGFBP-2 gene.

Resistance of a human serum-selected human immunodeficiency virus type 1 escape mutant to neutralization by CD4 binding site monoclonal antibodies is conferred by a single amino acid change in gp120

We have selected an HXB2 variant which can replicate in the presence of a neutralizing human serum. Sequencing of the gp120 region of the env gene from the variant and parental viruses identified a single amino acid substitution in the third conserved region of gp120 at residue 375 (AGT-->AAT, Ser-->Asn; designated 375 S/N). The escape mutant was found to be resistant to neutralization by soluble CD4 (sCD4) and four monoclonal antibodies (MAbs), 39.13g, 1.5e, G13, and 448, binding to epitopes overlapping that of the CD4 binding site (CD4 b.s.). Introduction of the 375 S/N mutation into HXB2 by site-directed mutagenesis confirmed that this mutation is responsible for the neutralization-resistant phenotype. Both sCD4 and three of the CD4 b.s. MAbs (39.13g, 1.5e, and G13) demonstrated reduced binding to the native 375 S/N mutant gp120. The ability to select for an escape variant resistant to multiple independent CD4 b.s. MAbs by a human serum confirms the reports that antibodies to the discontinuous CD4 b.s. are a major component of the group-specific neutralizing activity in human sera.

The effect of short-term low-dose cyclosporin on renal function and blood pressure in patients with psoriasis

The effect of short-term (mean 2.4 months), low-dose (5 mg/kg) cyclosporin A (CyA) on renal function and blood pressure was studied in eight patients with psoriasis. Studies were undertaken before, during and after treatment. Glomerular filtration rate (GFR) post-treatment was significantly higher than pretreatment or during treatment (pre, 119 +/- 7; during, 113 +/- 9; post, 133 +/- 11 ml/min per 1.73 m2; pre vs. during, NS; during vs. post, P < 0.01; pre vs. post, P < 0.05); effective renal plasma flow (ERPF) was unchanged (pre, 515 +/- 38; during, 485 +/- 49; post, 560 +/- 45 ml/min per 1.73 m2). There was no change in the urinary excretion of either albumin or the enzymes N-acetyl-glucosaminidase, lactate dehydrogenase, alanine aminopeptidase and alkaline phosphatase. There was a decrease in exchangeable sodium which persisted post-treatment (pre, 56 +/- 3; during, 49 +/- 3; post, 49 +/- 3 mmol/kg LBM; pre vs. during, P = 0.07; during vs. post, NS; pre vs. post, P = 0.06). Blood pressure assessed as either a single reading, or the mean of a 24 h ambulatory recording, increased during treatment (single reading: pre, 113/73; during, 126/83; post, 114/70 mmHg; mean 24 h: pre, 114/71; during, 123/76; post, 120/72 mmHg). Thus, short-term use of CyA at a dose of 5 mg/kg for the treatment of psoriasis is associated with a significant increase in blood pressure, but only a transient mild reduction in GFR, which did not reach significance.

Bacteraemia due to recurrent reinfection with Staphylococcus epidermidis associated with defective opsonisation and procidin function in serum

AIMS

To differentiate between reinfection and relapsing infection with Staphylococcus epidermidis in a middle-aged woman with defective opsonisation and procidin function in serum.

METHODS

Microbiological typing was done by biotyping, phage typing, and polyacrylamide gel electrophoresis of radiolabelled bacterial proteins (radioPAGE method). Polymorphonuclear cell function was assessed in vitro by phagocytosis and killing of Candida albicans; measurement of neutrophil random locomotion and chemotaxis; reduction of nitroblue tetrazolium after stimulation by opsonised Candida and a radiometric saccharomyces opsonisation assay. The effect of plasma infusions on opsonic activity was assessed by chemiluminescence using control polymorphonuclear leucocytes with a laboratory strain of S epidermidis opsonised with either patient or control serum.

RESULTS

Recurrent reinfection with different strains of Staphylococcus epidermidis rather than relapsing infection was confirmed as having occurred by typing bacterial strains. The RadioPAGE method detected all the S epidermidis strains involved in this patient's illness. The patient's serum was shown to be defective in both opsonin and procidin function. The defects were correctable in vitro by the addition of normal serum. Clinical recovery occurred after repeated infusions of normal fresh frozen plasma and prolonged antibacterial treatment; antibacterial treatment alone was insufficient.

CONCLUSIONS

The radioPAGE method is useful in distinguishing recurrent reinfection with S epidermidis from relapsing infection with this organism. Elucidation of the nature of, and underlying predisposition to, infection in the patient studied allowed a rational treatment plan of plasma infusion combined with antibacterial treatment to be devised which ultimately proved successful.

Studies on the acute lethality of diethylcarbamazine in the rat

In spite of its effectiveness against microfilariae, very little is known about diethylcarbamazine's (DEC) therapeutic mechanism of action or the toxic sequelae which can result from overdose. In preliminary studies, a precipitous decrease in heart rate was noted in rats receiving 1000 mg DEC/kg ip. This effect was less pronounced at 750 mg/kg and was non-existent at 500 mg/kg. In the present study, attempts to attenuate DEC's cardiopulmonary insult by pretreating animals with cyproheptadine failed. Atropine pretreatment failed to block the negative chronotropic effects of DEC, but did restore respiratory function and reduce the lethality associated with the drug. Biochemical studies showed that ATP:ADP ratios in the hearts from rats given high dosages of DEC were elevated over those in controls (11:1 versus 5:1). Inosine levels decreased in cardiac tissues taken from DEC-treated rats. Subsequent enzyme studies revealed that DEC has a potent inhibitory effect on calcium-dependent ATPases from a variety of tissues. Taken together, our data indicate that the mode of acute DEC-lethality involves cardiopulmonary suppression. Furthermore, the cardiac depressant effect of DEC appears related to inhibition of calcium ATPases in cardiac myocytes. To our knowledge, this is the first report of ATPase sensitivity to DEC, a finding that has interesting toxicologic and pharmacologic ramifications.

Transcription of the insulin-like growth factor-binding protein-2 gene is increased in neonatal and fasted adult rat liver

The insulin-like growth factor-binding proteins (IGFBPs) are a family of proteins that specifically bind IGF-I and IGF-II, determine their bioavailability to tissues, and modulate their actions in target tissues. Levels of IGFBPs in plasma and IGFBP mRNAs in liver are highly regulated with developmental age and metabolic status. We now demonstrate that the increase in IGFBP-2 mRNA in fasted adult rat liver and in the liver of normal neonatal rats reflects an increased rate of transcription. When adult rats were fasted for 2-3 days, IGFBP-2 mRNA was increased in liver, but not in brain or kidney. The increase in hepatic IGFBP-2 mRNA was observed after only 1 day of fasting. Levels decreased by half after 6 h of refeeding and returned to their low starting values after 2 days of refeeding. Transcription-elongation experiments indicated that transcription of the IGFBP-2 gene was increased in fasted liver. The rate of transcription increased 9.2- +/- 3.5-fold for transcripts labeled in exon 1 and 6.6- +/- 2.4-fold for transcripts labeled in exons 2, 3, and 4, suggesting that fasting causes a uniform increase in the number of RNA polymerase II molecules along the length of the IGFBP-2 gene. We infer from these results that the regulation of IGFBP-2 gene transcription in fasting occurs at the level of initiation rather than elongation. IGFBP-2 gene transcription also was increased 3.8- +/- 1.2-fold (exon 1) and 2.9- +/- 0.9-fold (exons 2, 3, and 4) in nuclei from 2-day postnatal rat liver compared with adult rat liver, consistent with the greater abundance of IGFBP-2 mRNA in neonatal rat liver.

Use of the Glu-Glu-Phe C-terminal epitope for rapid purification of the catalytic domain of normal and mutant ras GTPase-activating proteins

The C-terminal catalytic domain (residues 704-1047) of the human ras GTPase-activating protein (GAP) has been engineered so as to incorporate the tripeptide, Glu-Glu-Phe, at its C terminus. This motif is recognized by the commercially available YL1/2 monoclonal antibody to alpha-tubulin and has previously been used for the immunoaffinity purification of HIV enzymes engineered to contain this epitope (Stammers, D. K., Tisdale, M., Court, S., Parmar, V., Bradley, C., and Ross, C. K. (1991) FEBS Lett. 283, 298-302). The engineered GAP catalytic domain (GAP-344) was obtained in high yield and purity from Escherichia coli extracts by means of a single affinity column of immobilized YL1/2, eluted under mild conditions with the dipeptide, Asp-Phe. The protein had similar activity to that previously described for full-length GAP, suggesting that the addition of the epitope did not grossly affect the activity. R903K and L902I mutants of GAP-344 were constructed, and the immunoaffinity purification procedure allowed their rapid characterization. The R903K mutant had less than 3% the activity of the normal protein, whereas the L902I substitution had less than 0.5% of normal activity, suggesting an important role for Leu-902 and Arg-903, residues absolutely conserved among GAP-related proteins. This work exemplifies the general utility of the C-terminal Glu-Glu-Phe motif for the rapid purification of proteins whose function is not altered by C-terminal modification.

Foreign epitopes in immunodominant regions of hepatitis B core particles are highly immunogenic and conformationally restricted

The presentation of heterologous amino acid sequences on the surface of hepatitis B core antigen (HBcAg) particles has been studied using a defined linear neutralization site from human rhinovirus (HRV). Previous work has shown that fusion particles, in which the HRV peptide sequence is linked to the amino terminus of the HBcAg protein, induce excellent immune responses in experimental animals. Using predictive models of HBcAg particulate structure and the approximate location of the major immunogenic regions we have designed and constructed bacterial expression vectors which direct synthesis of chimeric particles in which heterologous sequences are presented within an immunodominant area on the particle. Immunological responses to the heterologous peptide sequence are improved by at least tenfold when compared with amino terminal fusions of the same peptide sequence to HBcAg. Moreover, the restriction placed on the heterologous peptide by its linkage at both ends within the HBcAg protein results in a more constrained structure. In the case of the rhinovirus peptide sequence this results in an antigenic conformation more closely resembling that on the native virus particle. Such a system lends itself well as a general approach to the induction of high titre antibodies against defined epitopes.

Recurrent CAPD peritonitis caused by coagulase-negative staphylococci: re-infection or relapse determined by clinical criteria and typing methods

Four hundred consecutive episodes of continuous ambulatory peritoneal dialysis (CAPD)-associated peritonitis in 105 patients were analysed. Of these episodes 161 (40.25%) were caused by coagulase-negative staphylococci (CNS). Thirty-seven patients developed recurrent attacks (3-10) of peritonitis and CNS accounted for 72 (60%) of these episodes. Classification of reinfection or relapse in 67 of these recurrent episodes of peritonitis was based on clinical criteria alone. This was compared with the results of three typing methods of CNS strains: biotyping plus antibiograms, immunoblotting and 35S-methionine-labelled protein patterns (radio-PAGE). Radio-PAGE was the most discriminatory method followed by biotyping with antibiograms and then immunoblotting. There was total agreement between clinical diagnosis and the three typing methods in 67.2% of episodes but there was total disagreement between the clinical diagnosis and the three typing methods in 11.9%, suggesting inaccurate clinical diagnosis, and in 20.8% typing by at least one method differed from the clinical criteria. Thus, clinical criteria alone are inadequate for the accurate distinction of reinfection from relapse in recurrent CNS peritonitis. This distinction is desirable for optimal management and accurate assessment of different therapies. We suggest that CNS strains from peritoneal dialysate are stored for future typing should the patient develop repeated episodes of peritonitis, to aid in the diagnosis and management of such patients.

Epidemiology of CAPD-associated peritonitis caused by coagulase-negative staphylococci: comparison of strains isolated from hands, abdominal Tenckhoff catheter exit site and peritoneal fluid

We identified twenty patients maintained on continuous ambulatory peritoneal dialysis who suffered repeated episodes of peritonitis caused by coagulase-negative staphylococci. We documented hand and exist-site coagulase-negative staphylococcus-associated peritonitis over a total period of 32 months, and compared hand and exit-site strains with strains isolated from dialysate fluid using three typing methods: biotyping using the API Staph kit plus antibiograms, immunoblotting using sera raised in rabbits to three standard strains of coagulase-negative staphylococci, and 35S-methionine-labelled coagulase-negative staphylococcal profiles separated on sodium dodecylsulphate polyacrylamide gel electrophoresis and visualised by autoradiography (radioPAGE). In 5 of 84 episodes, strains isolated from skin were indistinguishable by all three typing methods from the dialysate strain. In a further two episodes, hand or exit-site isolates were indistinguishable by all three typing methods from the dialysate strain isolated in the subsequent, but not the same, episode. Thus in the majority of episodes, no inference of hand or exit-site origin of dialysate infection could be drawn.

Pitfalls after total parathyroidectomy and parathyroid autotransplantation in chronic renal failure

We have described 4 patients with chronic renal failure receiving regular haemodialysis treatment who underwent total parathyroidectomy with autotransplantation of parathyroid fragments into the forearm musculature for hypercalcaemic hyperparathyroidism. In all, there was an immediate and profound fall in plasma calcium levels. Hypercalcaemia recurred 1-5 years post-operatively and was resistant to resection of the autograft. In 3 cases, thallium-technetium subtraction scanning and multiple venous sampling for estimation of parathyroid hormone levels suggested multiple sites of hypersecretion of parathyroid hormone in the neck. In 1 case, these investigations revealed a mediastinal adenoma which was successfully removed. These cases reinforce previous suggestions that total parathyroidectomy is frequently incomplete and undermine the procedure of total parathyroidectomy with autotransplantation in patients with persisting uraemia.

Thyrotropin inhibits while insulin, epidermal growth factor and tetradecanoyl phorbol acetate stimulate insulin-like growth factor binding protein secretion from sheep thyroid cells

Six insulin-like growth factor binding proteins (IGFBP) have been identified in the conditioned medium from sheep thyroid cells cultured under serum-free conditions. IGFBPs of 32, 28, 23 and 19 kDa were secreted by cells cultured for 14 days in serum-free and hormone-free medium. The constitutive secretion of IGFBP was inhibited by thyrotropin (TSH, 0.3 mU per mL). The effect was most marked on the secretion of the 28 kDa BP. High insulin concentrations stimulated the secretion of this IGFBP. The stimulatory effects of insulin were inhibited by TSH. Growth hormone treatment decreased the secretion of the 28 kDa protein. Tetradecanoylphorbol-13 acetate (TPA) and epidermal growth factor (EGF) both of which stimulate thyroid cell growth but inhibit differentiated function, markedly stimulated IGFBP secretion and induced the appearance of a 46 and a 150 kDa IGFBP. The effects of EGF and TPA were not identical. A rat IGFBP-2 cDNA reacted with sheep thyroid RNA of approximate size 1.6 kb. TPA treatment increased IGFBP-2 mRNA. Other hormones used to enhance differentiation and growth in thyroid cells in culture i.e. transferrin, somatostatin, cortisol and glycyl-histidyl-lysine acetate had no marked effects on IGFBP secretion nor on TSH-dependent, insulin-mediated iodide uptake and organification and cell growth. We show a correlation between secretion of high molecular weight IGFBP with enhanced growth but decreased function. Conversely, we find a correlation between decreased secretion of the 28 kDa BP and increased growth and function.

Cloning of the rat insulin-like growth factor-binding protein-2 gene and identification of a functional promoter lacking a TATA box

We have isolated clones encoding the rat insulin-like growth factor-binding protein-2 (IGFBP-2) gene and determined its organization and nucleotide sequence. The rat IGFBP-2 gene spans at least 8 kilobases and consists of four exons, each of which contains protein-coding sequences. The amino acid sequences of exons 1, 3, and 4 are 32-50% identical to the corresponding exons of human IGFBP-1 and IGFBP-3, and 87-91% identical to those of human IGFBP-2. The 18 cysteines in the mature binding proteins are conserved. Exon 2 shows negligible homology. Primer-extended reverse transcription indicated that the 5' end of IGFBP-2 mRNA is 151 nucleotides up-stream from the translation start site [designated nucleotide (nt) -151]. Consistent with this result, IGFBP-2 mRNA protected a genomic fragment terminating at approximately nt -148, as well as smaller fragments. A 1260 nt fragment containing 1144 nt of 5' flanking region had promoter activity when inserted in the correct orientation into a plasmid containing a promoterless luciferase reporter gene and transiently transfected into BRL-3A rat liver cells, which express IGFBP-2, but not when transfected into H4-II-E cells, which do not express IGFBP-2. The IGFBP-2 gene lacks a TATA box immediately up-stream from the transcription initiation site. It is GC rich (66% between nt -270 and +385) and contains GC boxes that might be recognized by transcription factors Sp1 or ETF. The promoter region contains multiple direct and indirect repeats. One direct repeat contains a variant Sp1 site (-158 to -150) near the consensus Sp1 site at nt -138 to -130. The 5' flanking region also contains motifs that might be recognized by transcription factors AP-1 (Jun/Fos), AP-2, and liver factor B1. The role of these sites in basal and regulated expression of the IGFBP-2 gene remains to be determined.

Higher-order structure and relational reasoning: contrasting analogical and thematic relations

A popular explanation of younger children's success in analogy tasks is that lower-level associative reasoning strategies are used. Younger children are said to have a primarily associative understanding of analogy, with the ability to coordinate sets of relations largely emerging later in development (Goldman, Pellegrino, Parseghian, & Sallis, 1982; Sternberg & Nigro, 1980). One way of testing the associative claim is to pit young children's emergent analogical abilities against thematic (associative) relations, which are known to play an important role in the knowledge structures of young children. The present experiments presented 4-, 5- and 9-year-old children with a:b::c:d analogies in a picture choice format, offering a choice between Analogy and Thematic responses. Only the Analogy responses were correct in terms of the higher-order structure of the analogies. The results showed that the Analogy responses were consistently preferred to the Thematic responses by children of all ages. It is concluded that analogy is an important building block for learning from an early age.

The expression pattern of an insulin-like growth factor (IGF)-binding protein gene is distinct from IGF-II in the midgestational rat embryo

Insulin-like growth factor-II (IGF-II), the predominant form of IGF in fetal and neonatal serum and tissues, is found in vivo complexed with IGF-binding proteins. One of these binding proteins, IGFBP-2, is present at high levels in fetal rat plasma and binds both IGF-I and IGF-II with high affinity. We here have used in situ hybridization to compare the distribution of IGFBP-2 mRNA with that of IGF-II mRNA in embryonic day 13.5-15 rat embryos. The spatial patterns of IGF-II and IGFBP-2 expression in the fetal trunk were distinct and, in general, nonoverlapping. Most mesoderm derivatives that express IGF-II at high levels contained little, if any, IGFBP-2 mRNA. Instead, IGFBP-2 mRNA was expressed at high levels in many cell types derived from ectoderm and endoderm. The expression of IGFBP-2 mRNA in the central nervous system (CNS) during this developmental period was examined in particular detail. The three most prominent sites of IGFBP-2 expression in the CNS were comprised of cells with nonneuronal phenotypes: 1) the epithelium of the choroid plexus, a tissue that produces cerebrospinal fluid; 2) the floor plate, an area that can guide axonal outgrowth from commissural neurons of the spinal cord in vitro; and 3) the infundibulum, the progenitor of the posterior pituitary that is believed to influence differentiation of the adjacent intermediate pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)

The polymerase chain reaction in the diagnosis of vertically transmitted HIV infection

The presence of HIV-1 DNA sequences in DNA from peripheral blood mononuclear cells (PBMCs) was investigated in a two-stage polymerase chain reaction ('double' PCR) using four sets of nested primers. The PBMCs tested were obtained from 46 children born to HIV-seropositive mothers, seven 'control' children born to HIV-seronegative mothers and seropositive fathers, and 45 healthy adult blood donors who were HIV seronegative. Nine of the children had symptomatic HIV infection and other laboratory features characteristic of HIV infection: all nine were PCR-positive with each set of primers in each of their 22 blood samples tested. The remaining 44 children had no clinical or laboratory evidence of HIV infection, and each of their 50 samples was PCR-negative with each set of primers, as were all blood donor samples. PCR-positive samples were tested in more detail using two of the sets of primers, which spanned hypervariable regions in the env gene. Polyacrylamide gel electrophoresis of DNA amplified from these regions yielded patterns of amplified DNA length variation which were characteristic for each child, and which changed little with time (in serial samples obtained over periods of 3-7 months). This excluded contamination as a cause of PCR positivity. This is the first report of the use of a double PCR for the diagnosis of HIV infection. The results demonstrate the specificity of this PCR method in diagnosis, with failure to reveal in this cohort any cases of vertically transmitted HIV-1 infection in addition to those already confirmed by conventional laboratory techniques.

Presentation and immunogenicity of viral epitopes on the surface of hybrid hepatitis B virus core particles produced in bacteria

We recently reported the enhanced immunogenicity of a peptide epitope when it was presented as a fusion protein with hepatitis B core antigen. In those experiments the fusion protein was expressed in vaccinia virus. We have now refined the system so that large amounts of highly immunogenic particles can be produced using a simple bacterial expression system. We describe the expression of three different viral epitopes as chimeric particles that induce good antibody responses to each epitope after one dose of low amounts of antigen. Finally we demonstrate that the immunogenicity is a reflection of both T helper cell sites within the core protein and also the particulate nature of the immunogens.

Melting chocolate and melting snowmen: analogical reasoning and causal relations

Children's performance in the classical a:b::c:d analogy task is traditionally very poor prior to the Piagetian stage of formal operations. The interpretation has been that the ability to reason about higher-order relations (the relations between the a:b and c:d parts of the analogy) is late-developing. However, an alternative possibility is that the relations used to date in the analogies are too difficult for younger children. Two experiments presented children aged 3, 4 and 6 years with a:b::c:d analogies which were based on relations of physical causality such as melting and cutting, for example chocolate bar:melted chocolate::snowman:melted snowman. Understanding of these particular causal relations is known to develop between the ages of 3 and 4 years. It was found that even 3-year-olds could solve the classical analogies if they understood the causal relations on which they were based.

Immunological properties of hepatitis B core antigen fusion proteins

The immunogenicity of a 19 amino acid peptide from foot-and-mouth disease virus has previously been shown to approach that of the inactivated virus from which it was derived after multimeric particulate presentation as an N-terminal fusion with hepatitis B core antigen. In this report we demonstrate that rhinovirus peptide-hepatitis B core antigen fusion proteins are 10-fold more immunogenic than peptide coupled to keyhole limpet hemocyanin and 100-fold more immunogenic than uncoupled peptide with an added helper T-cell epitope. The fusion proteins can be readily administered without adjuvant or with adjuvants acceptable for human and veterinary application and can elicit a response after nasal or oral dosing. The fusion proteins can also act as T-cell-independent antigens. These properties provide further support for their suitability as presentation systems for "foreign" epitopes in the development of vaccines.

Neutralizing antibodies to all seven serotypes of foot-and-mouth disease virus elicited by synthetic peptides

Uncoupled peptides from all seven serotypes of foot-and-mouth disease virus (FMDV) protein VP1 have been used to elicit neutralizing antibody responses in guinea-pigs. The responses were largely serotype specific, although some significant cross-neutralization was observed. Dimeric tandem peptides have also been used to simultaneously elicit neutralizing antibodies to two different FMDV serotypes. The possible existence of structural features common to the B-cell neutralization sites or the guinea-pig helper T-cell sites within all seven peptides are analysed and discussed.

Different tissue distribution and hormonal regulation of messenger RNAs encoding rat insulin-like growth factor-binding proteins-1 and -2

The insulin-like growth factor-binding proteins IGFBP-1 and IGFBP-2 are low mol wt IGFBPs that are similar in structure. They are not glycosylated and have a homologous amino acid sequence, including the number and position of 18 cysteine residues and a carboxyl-terminal Arg-Gly-Asp sequence that can be recognized by cell adhesion receptors. The present study demonstrates that expression of mRNAs encoding the two BPs differs in some fetal rat tissues and in the livers of adult rats after hypophysectomy, fasting, or streptozotocin-induced diabetes. As determined by Northern blot hybridization using cDNA probes for rat IGFBP-2 or human IGFBP-1, both mRNAs are expressed at high levels in liver of 21-day gestation and 1-day-old rats and at lower levels in 21- and 65-day-old rat liver. Levels of both mRNAs are higher in liver than in other fetal rat tissues. The relative abundance of the two mRNAs in most fetal tissues is similar to that in liver, except that kidney and brain have 8-fold and more than 25-fold higher relative levels of IGFBP-2 mRNA, respectively. IGFBP-2 mRNA is about 10- to 20-fold increased after hypophysectomy or fasting, whereas IGFBP-1 mRNA is relatively unchanged. IGFBP-2 mRNA levels are decreased completely by refeeding fasted rats for 3 days, but only partially decreased by treatment of hypophysectomized rats with GH, cortisone acetate, T4, and testosterone for 4 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Identification of rat cell lines that preferentially express insulin-like growth factor binding proteins rlGFBP-1, 2, or 3

The bioavailability and action of the insulin-like growth factors (IGFs) are determined by specific IGF-binding proteins (IGFBP) to which they are complexed. Complementary DNA clones have been isolated that encode three related IGFBPs: human IGFBP-1 (hIGFBP-1), human IGFBP-3 (hIGFBP-3), and rat IGFBP-2 (rIGFBP-2). IGFBP-1 and IGFBP-3 are regulated differently in human plasma, suggesting that they have different functions. In order to study the molecular basis of the regulation of the different IGFBPs, we have identified a panel of rat cell lines that express a single predominant binding protein and developed an assay strategy to distinguish the different binding proteins. Proteins in conditioned medium were examined by ligand blotting, and by immunoprecipitation and immunoblotting using antibodies to rIGFBP-2 and hIGFBP-1; RNAs were hybridized to cDNA probes for rIGFBP-2 and hIGFBP-1. 1) C6 glial cells and B104 neuroblastoma cells express an approximately 40 kilodalton (kDa) glycosylated binding protein that most likely represents rIGFBP-3, the binding subunit of the 150 kDa IGF: binding protein complex in adult rat serum. The C6 and B104 binding proteins do not react with antibodies to rIGFBP-2, and RNAs from C6 and B104 cells do not hybridize to cDNA probes for rIGFBP-2 or hIGFBP-1. 2) BRL-3A, Clone 9, and TRL 12-15 cell lines derived from normal rat liver express rIGFBP-2, a 30 kDa nonglycosylated IGF-binding protein that is recognized by antibodies to rIGFBP-2 but not by antibodies to hIGFBP-1. RNAs from these cells hybridize to a rIGFBP-2 cDNA probe, but not to a hIGFBP-1 probe. 3) H35 rat hepatoma cells express a 30 kDa nonglycosylated IGFBP that is presumptively identified as rIGFBP-1. It does not react with antibodies to rIGFBP-2, but is recognized by polyclonal and monoclonal antibodies to hIGFBP-1. RNA from H35 cells hybridizes to a hIGFBP-1 cDNA probe, but not to a rIGFBP-2 probe. Expression of rIGFBP-1 by the H35 cell line has enabled us to establish and validate specific assays for this protein that allow us to study its regulation in intact rats. Identification of a panel of rat cell lines expressing specific IGFBPs should be useful in elucidating the molecular mechanisms of IGFBP regulation.

Tissue, developmental, and metabolic regulation of messenger ribonucleic acid encoding a rat insulin-like growth factor-binding protein

Insulin-like growth factor-II (IGF-II) is the predominant insulin-like growth factor in fetal and neonatal rat serum and tissues. In serum, it occurs complexed to a 30-kDa nonglycosylated IGF-binding protein (IGFBP) that is immunologically related to the IGFBP in BRL-3A rat liver cells (rIGFBP-2). Levels of rIGFBP-2 and IGF-II decrease in rat serum after birth. Using a recently isolated cDNA clone for rIGFBP-2 as hybridization probe, we now compare the expression of rIGFBP-2 and IGF-II in fetal tissues and the effects of hypophysectomy and fasting on the abundance of these mRNAs in adult rat liver. rIGFBP-2 mRNA is expressed at high levels in term gestation liver and at lower levels in other tissues. The ratio of rIGFBP-2 to IGF-II mRNAs in stomach, kidney, and lung is similar to that seen in liver, whereas IGF-II mRNA is more abundant than rIGFBP-2 mRNA in muscle, intestine, heart, and skin. Both mRNAs are more abundant in fetal tissues than in the corresponding tissues from adult rats. Dexamethasone treatment of 4-day-old rats for 4 days caused a greater (90%) decrease in hepatic IGF-II mRNA than in rIGFBP-2 mRNA (50%), suggesting subtle differences in the developmental regulation of the two mRNAs. Even more striking differences were observed in the regulation of the two mRNAs in adult rats after hypophysectomy or fasting. Hepatic rIGFBP-2 mRNA was increased 10- to 20-fold compared to age-matched control rats, whereas IGF-II mRNA was not increased. A parallel increase in serum rIGFBP-2 was observed, suggesting that this regulation may result at least in part from the increased abundance of rIGFBP-2 mRNA. Thus, in addition to modulating the stimulation of growth and differentiation by IGF-II in fetal tissues, rIGFBP-2 may play a homeostatic role during catabolic states in the adult rat.

Head scan appearances and cognitive function in renal failure

Cognitive function was assessed, and unenhanced CT head scans were carried out in 44 patients with renal failure. Thirteen had been on regular hemodialysis for 5 years or more (long-term hemodialysis group, LTHD), 12 had received hemodialysis for less than 5 years (short-term hemodialysis, STHD), 9 were on continuous ambulatory peritoneal dialysis (CAPD group) and 10 had severe chronic renal failure and were near to-but had not reached-dialysis dependence (chronic renal failure group, CRF). Employing an index of deterioration (the "discrepancy score") based on the discrepancy between current reading skills and current performance on the Wechsler Adult Intelligence Scale, 6 LTHD patients, 2 STHD patients, 2 CAPD patients and 5 CRF patients were identified as functioning below their predicted premorbid optimum level. Cerebral sulci were abnormally wide in 22 patients (8 LTHD, 2 STHD, 6 CAPD and 6 CRF) and one of the STHD group also had cerebral ventricular dilatation. Nine patients had both an abnormal scan and evidence of cognitive deterioration, 13 had an abnormal scan in the absence of such evidence and 6 had evidence of cognitive deterioration and a normal scan. Both cognitive deterioration and the CT scan finding of widening of cerebral sulci were commoner in these patients than would be expected in an age-matched sample of the general population, but no simple relationship was found between anatomical abnormality and cognitive functioning. Statistically significant correlations were found between discrepancy score and the cumulative amount of aluminum prescribed to be taken orally in both LTHD and CAPD groups.

The fetal rat binding protein for insulin-like growth factors is expressed in the choroid plexus and cerebrospinal fluid of adult rats

The biological effects of the insulin-like growth factors, IGF-I and IGF-II, on their receptors are modulated by IGF-binding proteins. Recently, we isolated a cDNA clone for one member of the family of IGF-binding proteins, BP-3A, a 30 kilodalton (kDa) protein synthesized by the BRL-3A rat liver cell line. BP-3A is related to but distinct from two other cloned IGF-binding proteins, the human amniotic fluid binding protein and the glycosylated binding subunit of the 150 kDa IGF-binding protein complex in serum. It is expressed in multiple nonneural tissues and in serum in the fetal rat and decreases after birth, similar to the developmental pattern of IGF-II expression. IGF-I, IGF-II, and their receptors are expressed in brain. The present study examines the expression of BP-3A in the rat central nervous system. By Northern blot analysis, BP-3A mRNA is present at high levels in brain stem, cerebral cortex, and hypothalamus from 21-day gestation rats and, like IGF-II mRNA, persists in adult rat brain. The site of BP-3A mRNA synthesis was localized by in situ hybridization to coronal sections of adult rat brain using 35S-labeled oligonucleotides, 48 bases in length, complementary and anticomplementary to the coding region of BP-3A. Specific hybridization of the BP-3A probe was observed exclusively to the choroid plexus extending from the level of the medial preoptic nucleus to the arcuate nucleus of the hypothalamus, similar to the previously reported preferential localization of IGF-II mRNA to the choroid plexus. Synthesis of BP-3A mRNA by choroid plexus suggested that BP-3A might be secreted into the cerebrospinal fluid. A 30 kDa IGF-binding protein was demonstrated in rat cerebrospinal fluid that is recognized by antibodies to BP-3A and, like purified BP-3A, has equal affinity for IGF-I and IGF-II. By analogy with other transport proteins synthesized by the choroid plexus, BP-3A may facilitate the secretion of IGF-II to the cerebrospinal fluid and modulate its biological actions at distant sites within the brain.

Biological evaluation of glycoproteins mapping to two distinct mRNAs within the BamHI fragment 7 of pseudorabies virus: expression of the coding regions by vaccinia virus

Several glycoproteins from the unique short region of pseudorabies have been identified and characterized. The genes encoding at least four glycoproteins (gp50, gp63, gl, and gX) are located within the BamHI fragment 7 of pseudorabies. S1 nuclease mapping was used to determine that a 2.4-kb mRNA encompasses the coding region for gp50 and gp63 and probably represents a colinear transcript for these proteins. Using the same technique, a 2.8-kb mRNA was found to encode gl. No other mRNAs were found to be encoded on the opposite strand of DNA in this region. Various recombinant vaccinia vectors were made incorporating the coding regions for these two mRNAs. Pseudorabies recombinant vaccinia infected ST cells expressed glycoproteins that co-migrated with the authentic PRV glycoproteins upon polyacrylamide electrophoresis. Intracranial or intraperitoneal inoculation of mice with the recombinant viruses constructed to contain the mRNA coding regions resulted in various degrees of protection from a lethal challenge of pseudorabies virus.

Effect of vaccination with a bacterin containing Leptospira interrogans serovar bratislava on the breeding performance of swine herds

Swine herds suspected to be infected with Leptospira interrogans serovar bratislava were vaccinated with bacterins containing 5 or 6 leptospiral serovars in which serovar bratislava was the unique component. The principal diagnostic feature indicating an infection by this organism was demonstration of antibody against serovar bratislava in sera from stillborn pigs. For 1 breeding cycle after vaccination of herds on 3 farms, 255 of 266 (95.9%) sows and gilts given the 6-serovar bacterin farrowed. In contrast, 233 of 311 (74.9%) sows and gilts given the 5-serovar bacterin farrowed. These results, as evaluated by analysis of variance techniques, showed a significant improvement (P less than 0.01) in reproductive performance for groups vaccinated against serovar bratislava.

Molecular cloning of the cDNA for ligatin

We describe the first isolation and sequence of a partial cDNA clone encoding ligatin, a trafficking receptor for phosphoglycoproteins. The clone was isolated from a human U937 promonocyte lambda gt11 cDNA library using rabbit antiserum to rat ileal ligatin. RNA blot hybridization revealed that the intact receptor transcript in human cells is 2.4 kilobases (kb). DNA sequencing together with expression of protein fusion products in Escherichia coli demonstrated that the cloned segment begins with a 1.2 kb open reading frame potentially encoding a 7.5 × 10(3) Mr section of the 10 × 10(3) Mr receptor followed by a 3′ tail of 948 bases. The 225 bases of coding sequence correspond to the carboxyl region of ligatin and contain a potential acceptor site for asparagine-linked glycosylation. Neither a poly(A) sequence nor polyadenylation signal was found at the 3′ end of the clone. In the 3′ untranslated region there is a paired consensus sequence (TGAGnnnTTTTTCA) that is analogous to a conserved 12 base-pair sequence present in clusters in several growth-controlled mRNAs, including those for c-fos and beta-actin. The identity of this clone as ligatin was confirmed immunologically using antisera to an encoded fusion protein and three independent regions of its derived sequence. In addition, one of these antibodies produced a punctate immunofluorescence pattern within the cytosol of U937 cells in a similar fashion to anti-ligatin serum.

Nucleotide sequence and expression of a cDNA clone encoding a fetal rat binding protein for insulin-like growth factors

The insulin-like growth factors (IGFs), IGF-I and IGF-II, occur in plasma and tissue fluids complexed to specific binding proteins. Although the role of the binding proteins is not completely defined, they are capable of modulating the biological activity of the IGFs. In order to better understand the function of these proteins, we have isolated a clone from the BRL-3A rat liver cell line that encodes a protein corresponding to the IGF binding protein in fetal rat serum. The cDNA clone encodes a precursor protein of 304 amino acids (32,886 daltons), comprised of a 34-residue hydrophobic prepeptide and a 270-residue mature protein (29,564 daltons). The deduced amino acid sequence agrees with the sequence of 173 amino acid residues determined by Edman degradation. The mature protein contains 18 cysteines and no N-glycosylation sites. It contains an Arg-Gly-Asp (RGD) sequence near the carboxyl terminus. A similar sequence is present on many extracellular matrix proteins and contributes to their recognition by cellular adhesion receptors. The cloned cDNA has been transcribed in vitro and the resulting RNA expressed in Xenopus oocytes. Injected oocytes secrete a 33-kDa protein that is immunoprecipitated by polyclonal antibodies to the BRL-3A binding protein and binds IGF-I and IGF-II with the same affinity and specificity as does purified BRL-3A binding protein. The binding protein cDNA probe hybridizes to an approximately 2-kilobase mRNA in BRL-3A cells and in multiple fetal rat tissues including liver, kidney, intestine, and lung. Levels of this mRNA are greatly reduced in the corresponding adult tissues. The rat IGF binding protein is closely related to the partial amino acid sequences reported for a bovine IGF binding protein and more distantly related to a human IGF binding protein that recently has been cloned. No significant homologies were identified to other proteins. Thus, the rat IGF binding protein that we have cloned appears to be a distinct member of a family of related IGF binding proteins. We postulate that the structurally distinct IGF binding proteins may have different biological functions.

The nucleotide sequence of the structural-protein-coding region of foot-and-mouth disease virus serotype SAT3

The nucleotide sequence coding for the structural proteins and nonstructural protein P2A has been determined for a foot-and-mouth disease virus (FMDV) isolated in Africa. This virus, serotypically designated SAT3 (South African Territories type 3), shows about 60% homology at the nucleotide level to prototype viruses from the O, A and C serotypes of FMDV. The highest region of variability was shown in structural protein VP1, presumably a consequence of its position on the surface of the virus and its exposure to selection pressure by neutralising antibody. Within this region amino acids (aa) 141-160, which have been shown to represent an immunodominant region in other FMDV serotypes, showed hypervariability as well as the insertion of 5 or 9 additional aa relative to the O1 and C1 serotypes, respectively. In contrast, the sequence of nonstructural protein P2A was completely conserved indicating a probable important role in virus replication.

Host cell selection of antigenic variants of foot-and-mouth disease virus

Foot-and-mouth disease virus (FMDV) A22 Iraq 24/64 adapted to grow in BHK monolayer cells induced antibodies which neutralized many isolates belonging to the A serotype. Plaque-purified virus isolated from this stock also induced broadly reactive antibodies, showing that this property is not due to the combined response to a mixture of variants in the original stock virus. However, viruses obtained by passage in suspension BHK cells of either the monolayer cell-adapted virus or a virus cloned from this stock resulted in the selection of virus which induced antibodies with highly specific neutralizing activity. In addition to their antigenic properties the monolayer and suspension cell-adapted viruses could be distinguished by plaque morphology, tendency to aggregate and ability to attach to BHK cells. Monoclonal antibodies (MAbs) induced with the plaque-purified monolayer-adapted virus had neutralizing activity almost as broad as polyclonal serum, showing that this property can be represented by a single epitope on the virus. These neutralizing MAbs recognize a trypsin-sensitive epitope on the virus. Surprisingly, sequence analysis of the structural protein-coding regions of the genomic RNAs of monolayer and suspension cell-adapted viruses showed no amino acid differences in VP1, the protein known to contain the major neutralization epitope in FMDV and to be the only protein susceptible to cleavage by trypsin in the virus particle. Although three coding differences were found in the capsid protein these were all located in VP2.