Marked differences between two isoforms of human pyruvate dehydrogenase kinase

Pyruvate dehydrogenase kinase (PDK) isoforms 2 and 3 were produced via co-expression with the chaperonins GroEL and GroES and purified with high specific activities in affinity tag-free forms. By using human components, we have evaluated how binding to the lipoyl domains of the dihydrolipoyl acetyltransferase (E2) produces the predominant changes in the rates of phosphorylation of the pyruvate dehydrogenase (E1) component by PDK2 and PDK3. E2 assembles as a 60-mer via its C-terminal domain and has mobile connections to an E1-binding domain and then two lipoyl domains, L2 and L1 at the N terminus. PDK3 was activated 17-fold by E2; the majority of this activation was facilitated by the free L2 domain (half-maximal activation at 3.3 microm L2). The direct activation of PDK3 by the L2 domain resulted in a 12.8-fold increase in k(cat) along with about a 2-fold decrease in the K(m) of PDK3 for E1. PDK3 was poorly inhibited by pyruvate or dichloroacetate (DCA). PDK3 activity was stimulated upon reductive acetylation of L1 and L2 when full activation of PDK3 by E2 was avoided (e.g. using free lipoyl domains or ADP-inhibited E2-activated PDK3). In marked contrast, PDK2 was not responsive to free lipoyl domains, but the E2-60-mer enhanced PDK2 activity by 10-fold. E2 activation of PDK2 resulted in a greatly enhanced sensitivity to inhibition by pyruvate or DCA; pyruvate was effective at significantly lower levels than DCA. E2-activated PDK2 activity was stimulated >/=3-fold by reductive acetylation of E2; stimulated PDK2 retained high sensitivity to inhibition by ADP and DCA. Thus, PDK3 is directly activated by the L2 domain, and fully activated PDK3 is relatively insensitive to feed-forward (pyruvate) and feed-back (acetylating) effectors. PDK2 was activated only by assembled E2, and this activated state beget high responsiveness to those effectors.

Regression of poloxamer 407-induced atherosclerotic lesions in C57BL/6 mice using atorvastatin

HMG-CoA reductase inhibitor drugs or 'statins' have been shown to effectively reduce plasma total cholesterol (CHOL), CHOL associated with low-density-lipoprotein (LDL), and triglycerides (TG). In addition, slight elevations in HDL-CHOL are also typically observed. Poloxamer 407 (P-407), a nonionic surfactant, effectively elevates both plasma CHOL and especially TG in a dose-controlled fashion and results in formation of atherosclerotic lesions in the aortas of C57BL/6 mice without the requirement of dietary cholic acid [1,2]. The purpose of the present study was to assess whether a typical statin, namely atorvastatin (Lipitor(R)) would significantly reduce P-407-induced hypercholesterolemia and hypertriglyceridemia as well as cause regression of atherosclerotic lesions resulting from administration of P-407 to C57BL/6 mice. C57BL/6 mice in the present study were treated with either normal saline (C, controls), 0.5 g/kg of P-407 (P), or a high-fat, high-cholesterol, cholate-containing diet (HF) for 120 days. Mice in all groups were then equally and randomly divided and treated with either atorvastatin or saline for an additional 120 days. Beginning at Day 121 and using mice in groups P and HF as an example, one-fourth of the mice in each group received 20 mg/kg per day of atorvastatin with either concomitant HF feeding or P-407 administration ('progression' treatment groups), one-fourth received 20 mg/kg per day of atorvastatin following cessation of HF feeding or P-407 administration, one-fourth received saline (placebo) with either simultaneous HF feeding or P-407 administration ('progression' placebo groups), and one-fourth received saline (placebo) following cessation of HF feeding or P-407 administration. Total plasma CHOL was significantly (P<0.01) lower for mice in groups P and HF when administered atorvastatin relative to saline, but remained significantly (P<0.05) elevated compared to total plasma CHOL of C mice. With discontinuation of either P-407 administration or HF feeding, total plasma CHOL declined rapidly in both P and HF mice with atorvastatin-treated mice generally demonstrating lower plasma CHOL concentrations relative to saline-treated mice. Total plasma TG was significantly (P<0.01) lower for mice in group P administered atorvastatin relative to saline, but remained significantly (P<0.05) elevated compared to plasma TG of C mice. With discontinuation of P-407 administration, total plasma TG declined rapidly in P mice with atorvastatin-treated mice typically demonstrating lower plasma TG concentrations relative to saline-treated P mice. Aortas of mice treated with 20 mg/kg per day of atorvastatin in both groups P and HF, whether maintained on the HF-diet or treated with P-407 from Day 120 to 240 or whether each treatment was terminated at Day 120, revealed no presence of atherosclerotic lesions relative to saline-treated mice and were indistinguishable from aortas retrieved from C mice. Atorvastatin at a dose of 20 mg/kg per day not only significantly reduced the plasma CHOL and TG concentrations, but also resulted in regression of atherosclerotic lesions induced in C57BL/6 mice by administration of P-407 or ingestion of a HF-diet containing cholic acid.

Potential downregulation of HMG-CoA reductase after prolonged administration of P-407 in C57BL/6 mice

This study investigated the potential alteration in the amount of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase messenger RNA (mRNA) and lipoprotein lipase (LPL) mRNA in the livers of C57BL/6 mice after long-term (200 days) treatment with the nonionic surfactant called poloxamer 407 (P-407). Previously, P-407 has been used to produce a dose-controlled hyperlipidemic state in C57BL/6 mice with subsequent formation of atherosclerotic lesions. Five groups of mice were studied; controls (C); mice fed a standard chow diet enriched with only cholic acid (CH); mice fed the high-cholesterol, high-fat Paigen diet (HF); mice treated with 0.5 g/kg P-407 every third day (P); and mice administered 0.5 g/kg P-407 every third day while consuming a diet identical to that of mice in group CH (PC). Neither a significant (p < 0.05) weight loss nor alteration in liver enzymes (AST and ALT) were observed for any group throughout the study when compared with the control mice. Total plasma cholesterol (CHOL) was significantly elevated compared with controls for mice in groups HF, P, and PC, whereas total plasma triglycerides (TG) were significantly increased for mice in only groups P and PC. Long-term ingestion of a high-fat diet or a diet enriched in cholic acid resulted in a significant (p < 0.05) reduction in HDL-CHOL when compared with controls. Plasma samples assayed at 200 days for mice in groups HF and P showed a shift in the lipoprotein fraction distribution primarily to VLDL-CHOL as compared with mice in group C in which, as expected, most of the CHOL was contained in the HDL fraction. The biologic activity of HMG-CoA reductase assayed in hepatic microsomal homogenates was significantly reduced for mice in groups CH (p < 0.01), HF (p < 0.01), and PC (p < 0.05), but not for mice in group P, when compared with control. A statistical analysis of the data demonstrated significant (p < 0.05) reductions in the HMG-CoA reductase mRNA levels in hepatic tissue for all treatment groups relative to mRNA levels determined for mice in group C. In contrast, no treatment group demonstrated a significant difference in hepatic LPL mRNA levels when compared with mRNA levels determined for control animals. These data demonstrate that P-407 administration to C57BL/6 mice significantly decreased the amount of HMG-CoA reductase mRNA detected in liver.

Wnt signaling in Xenopus embryos inhibits bmp4 expression and activates neural development

We report a new role for Wnt signaling in the vertebrate embryo: the induction of neural tissue from ectoderm. Early expression of mouse wnt8, Xwnt8, beta-catenin, or dominant-negative GSK3 induces the expression of neural-specific markers and inhibits the expression of Bmp4 in Xenopus ectoderm. We show that Wnt8, but not the BMP antagonist Noggin, can inhibit Bmp4 expression at early gastrula stages. Furthermore, inhibition of beta-catenin activity in the neural ectoderm of whole embryos by a truncated TCF results in a decrease in neural development. Therefore, we suggest that a cleavage-stage Wnt signal normally contributes to an early repression of Bmp4 on the dorsal side of the embryo and sensitizes the ectoderm to respond to neural inducing signals from the organizer. The Wnt targets Xnr3 and siamois have been shown previously to have neuralizing activity when overexpressed. However, antagonists of Wnt signaling, dnXwnt8 and Nxfrz8, inhibit Wnt-mediated Xnr3 and siamois induction, but not neural induction, suggesting an alternative mechanism for Bmp repression and neuralization. Conversely, dnTCF blocks both Wnt-mediated Xnr3 and neural induction, suggesting that both pathways require this transcription factor.

Experimental model of type II bovine viral diarrhea virus-induced thrombocytopenia in neonatal calves

Thrombocytopenia has been associated with type II bovine viral diarrhea virus (BVDV) infection in immunocompetent cattle, but the mechanism is unknown. The purpose of the present study was to develop and characterize a model of type II BVDV-induced thrombocytopenia. Colostrum-deprived Holstein calves were obtained immediately after birth, given a BVDV-negative and BVDV antibody-negative plasma transfusion, housed in an isolation facility, and randomly assigned to either control (n = 4) or infected (n = 5) groups. Infected calves were inoculated by intranasal instillation on day 3 of age with 10(7) TCID50 of the prototype type II isolate, BVDV 890, whereas control calves were sham inoculated. Blood counts and virus isolations from serum, white blood cells, and platelets were performed daily until day 12 after infection, at which time all experimental calves were euthanatized, and pathologic, virologic, and immunohistochemical examinations were performed. On physical examination, the control calves remained normal, but the infected calves developed pyrexia and diarrhea characteristic of type II BVDV infection. The platelet count decreased in all infected calves, and a statistically significant difference in the platelet count between control and infected calves was observed on days 7-12 after infection. In addition, the mean platelet volume and white blood cell counts also decreased. Examination of the bone marrow from the infected calves revealed immunohistochemical staining for BVDV antigen in megakaryocytes and evidence of concurrent megakaryocyte necrosis and hyperplasia.

Effect of experimentally induced type II bovine viral diarrhea virus infection on platelet function in calves

OBJECTIVE

To evaluate platelet aggregation responses in calves experimentally infected with a thrombocytopenia-inducing type II bovine viral diarrhea virus (BVDV) isolate (BVDV 890).

ANIMALS

9 neonatal male Holstein calves.

PROCEDURE

5 calves were inoculated with BVDV 890, and 4 were used as controls. Platelet aggregation studies and attempts to isolate BVDV from platelets were performed 2 days before, the day of, and every 2 days for 12 days after inoculation. Platelet function was assessed by means of optical aggregometry, using adenosine diphosphate and platelet-activating factor as agonists. Bovine viral diarrhea virus was isolated from purified platelet preparations by use of an immunoperoxidase monolayer assay.

RESULTS

Maximum percentage aggregation and slope of the aggregation curve decreased over time in calves infected with BVDV. Bovine viral diarrhea virus was not isolated from platelets from control calves, but it was isolated from infected calves from 4 through 12 days after inoculation.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that platelet function may be depressed in calves infected with type II BVDV. Although the mechanism for altered platelet function was not determined, it likely involved an increase in the percentage of aged platelets in the circulation, a direct virus-platelet interaction, or an indirect virus-platelet interaction. Platelet dysfunction, in addition to thrombocytopenia, may contribute to the hemorrhagic syndrome associated with acute type II BVDV infection in calves.

Analysis of ruminant respiratory syncytial virus isolates by RNAse protection of the G glycoprotein transcripts

Two different respiratory syncytial virus (RSV) radiolabeled probes were used to characterize the genetic heterogeneity of 25 ruminant RSV isolates by the ribonuclease protection assay. A 32P-radiolabeled antisense RNA probe was transcribed from cloned ovine and bovine RSV G glycoprotein genes and then hybridized with total RNA isolated from infected cells with various ruminant RSV isolates. The results of this study, along with previously published nucleotide sequence data of the ovine RSV G glycoprotein gene, suggest the presence of at least 2 ruminant RSV subgroups. One subgroup is represented by RSV isolated from respiratory disease outbreaks from calves and goats, and the other is represented by RSV isolated from sheep.

Comparison of type I and type II bovine viral diarrhea virus infection in swine

Some isolates of type II bovine viral diarrhea virus (BVDV) are capable of causing severe clinical disease in cattle. Bovine viral diarrhea virus infection has been reported in pigs, but the ability of these more virulent isolates of type II BVDV to induce severe clinical disease in pigs is unknown. It was our objective to compare clinical, virologic, and pathologic findings between type I and type II BVDV infection in pigs. Noninfected control and BVDV-infected 2-month-old pigs were used. A noncytopathic type I and a noncytopathic type II BVDV isolate were chosen for evaluation in feeder age swine based upon preliminary in vitro and in vivo experiments. A dose titration study was performed using 4 groups of 4 pigs for each viral isolate. The groups were inoculated intranasally with either sham (control), 10(3), 10(5), or 10(7) TCID50 of virus. The pigs were examined daily and clinical findings were recorded. Antemortem and postmortem samples were collected for virus isolation. Neither the type I nor type II BVDV isolates resulted in clinical signs of disease in pigs. Bovine viral diarrhea virus was isolated from antemortem and postmortem samples from groups of pigs receiving the 10(5) and the 10(7) TCID50 dose of the type I BVDV isolate. In contrast, BVDV was only isolated from postmortem samples in the group of pigs receiving the 10(7) TCID50 dose of the type II BVDV isolate. Type I BVDV was able to establish infection in pigs at lower doses by intranasal instillation than type II BVDV. Infection of pigs with a type II isolate of BVDV known to cause severe disease in calves did not result in clinically apparent disease in pigs.

Dietary antioxidants and magnesium in type 1 brittle asthma: a case control study

BACKGROUND

Type 1 brittle asthma is a rare form of asthma. Atopy, psychosocial factors and diet may contribute to this condition. As increased dietary magnesium has a beneficial effect on lung function and selenium, vitamins A, C and E have antioxidant properties, a study was undertaken to test the hypothesis that patients with brittle asthma have diets deficient in these nutrients compared with subjects with non-brittle asthma and healthy adults.

METHODS

A case control study of the dietary intakes of 20 subjects with brittle asthma, 20 with non-brittle asthma, and 20 healthy adults was performed using five day weighed dietary records. Intake of magnesium was the primary outcome measure with selenium and vitamins A, C and E as secondary outcomes. Serum levels were measured at the same time as the dietary assessment.

RESULTS

Sixty subjects (27 men) of mean age 49.5 years were recruited and completed the study. Subjects with brittle asthma had statistically lower median dietary intakes of vitamins A and E than the other groups (vitamin A: brittle asthma 522.5 micrograms/day, non-brittle asthma 869.5 micrograms/day, healthy adults 806.5 micrograms/day; vitamin E: brittle asthma 4.3 mg/day, non-brittle asthma 4.6 mg/day, healthy adults 4.5 mg/day). Median dietary intakes for the other nutrients were not significantly different between groups. Serum levels were within normal ranges for each nutrient in all subjects. Intakes less than the reference nutrient intake (RNI) for magnesium and vitamins A and C, and less than the safe intake (SI) for vitamin E were more likely in patients with brittle asthma than in those with non-brittle asthma.

CONCLUSION

Nutrient deficiency and reduced antioxidant activity may contribute to disease activity in type 1 brittle asthma, although a prospective study of replacement therapy will be needed to confirm this hypothesis.

Drosophila dSmad2 and Atr-I transmit activin/TGFbeta signals

BACKGROUND

Much is known about the three subfamilies of the TGFbeta superfamily in vertebrates-the TGFbetas, dpp/BMPs, and activins. Signalling in each subfamily is dependent on both shared and unique cell surface receptors and Smads. In invertebrates, mutants for BMP pathway components have been extensively characterized, but thus far, evidence for an activin- or TGFbeta-like pathway has been lacking, preventing the use of the extensive genetic tools available for studying several key issues of TGFbeta signalling.

RESULTS

Here we report the identification of dSmad2, a new Drosophila Smad which is most related to the activin/TGFbeta-pathway Smads, Smad2 and Smad3. We show that dSmad2 induces activin responsive genes in Xenopus animal cap assays. dSMAD2 is phosphorylated by ATR-I and PUNT, but not by activated THICK VEINS, and translocates to the nucleus upon activation. Furthermore, we show that dSMAD2 complexes with MEDEA only in the presence of ATR-I and PUNT. dSmad2 is expressed in the imaginal disks and in the outer proliferation centre of the larval brain, suggesting that it may have important proliferative and patterning roles during Drosophila development.

CONCLUSION

Our data provide evidence for the existence of an activin/TGFbeta pathway in Drosophila. We show that dSmad2 participates in this pathway, and that it functions with Atr-I and punt. We show that Medea also participates in this pathway, indicating the conservation of roles for Co-Smads in diverse phyla. Expression patterns of dSmad2 suggest that it functions in imaginal disks and in the brain, in tissues that undergo extensive patterning and proliferation.

Two 22q telomere deletions serendipitously detected by FISH

Cryptic telomere deletions have been proposed to be a significant cause of idiopathic mental retardation. We present two unrelated subjects, with normal G banding analysis, in whom 22q telomere deletions were serendipitously detected at two different institutions using fluorescence in situ hybridisation (FISH). Both probands presented with several of the previously described features associated with 22q deletions, including hypotonia, developmental delay, and absence of speech. Our two cases increase the total number of reported 22q telomere deletions to 19, the majority of which were identified by cytogenetic banding analysis. With the limited sensitivity of routine cytogenetic studies (approximately 2-5 Mb), these two new cases suggest that the actual prevalence of 22q telomere deletions may be higher than currently documented. Of additional interest is the phenotypic overlap with Angelman syndrome (AS) as it raises the possibility of a 22q deletion in patients in whom AS has been ruled out. The use of telomeric probes as diagnostic reagents would be useful in determining an accurate prevalence of chromosome 22q deletions and could result in a significantly higher detection rate of subtelomeric rearrangements.

Solar particle events and the International Space Station

The high inclination orbit for the International Space Station poses a risk to astronauts on EVA during occasional periods of enhanced high energy particle flux from the sun known as Solar Particle Events. We are currently unable to predict these events within the few-hour lead time required for evasive action. Compounding the threat is the fact that station construction occurs during increasing solar activity and through the peak of the solar cycle. In this paper we present an overview of the risk, the current methods to provide forecasts of SPEs, and potential risk mitigation options.

Bovine respiratory syncytial virus

Since the first report of BRSV in the 1970s, the understanding of this agent and its respective disease has increased dramatically. Current evidence supports a major role for this virus in bovine respiratory disease. Advances in diagnostics have increased the ability to demonstrate this virus in field outbreaks of respiratory disease. The clinical signs and pathologic features have been well described, and vaccines are available to aid in prevention and control. Still, many questions remain to be answered with respect to BRSV. It appears there may be antigenic subgroups of BRSV, but the epidemiologic significance and relevance to immunization of this remains unknown. The question of differences in virulence among isolates of this virus has yet to be addressed. From an epidemiologic standpoint, the means by which BRSV perpetuates in the cattle population has yet to be elucidated. Although progress has been made in understanding the pathogenesis and immune response to BRSV, the mechanism of disease production and immune protection is incomplete. Lastly, efficacy testing of existing vaccines need to continue, as well as the development of new vaccines and new approaches to vaccination.

From receptor to nucleus: the Smad pathway

The transforming growth factor-beta (TGF-beta) superfamily plays a central role in the specification and patterning of cells in the early embryo. Several years ago, the TGF-beta s were shown to signal through serine/threonine receptor kinases. Now, with the identification of Smad proteins, we can trace the TGF-beta signal transduction pathway from the receptors into the nucleus.

Is there an abnormal phenotype associated with maternal isodisomy for chromosome 2 in the presence of two isochromosomes?

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Otitis media in preweaned Holstein dairy calves in Michigan due to Mycoplasma bovis

Mycoplasma bovis was isolated from the tympanic bullae of dairy calves with an exudative otitis media. The history, clinical signs, gross and histologic lesions, and bacteriologic findings are described for 5 preweaned Holstein calves with otitis media from a 600-cow dairy in Michigan. Clinical findings consisted of unilateral or bilateral ear droop, epiphora, head tilt, and recumbency in severely affected calves. Postmortem examination revealed unilateral or bilateral fibrinosuppurative to caseous exudate in the tympanic bullae. Histologically, a marked fibrinosuppurative to caseous exudate filled the tympanic air spaces. The partially ulcerated tympanic mucosa was markedly thickened with mononuclear cell infiltration and proliferation of fibrous connective tissue. Bone remodeling and periosteal hyperostosis were present in some osseous septa. Mycoplasma bovis was isolated from the tympanic bullae of all 5 calves and from the lungs of 2 calves and the frontal sinus of 1 calf. Mycoplasma bovis was isolated at > 100,000 colony forming units/ml from the bulk milk tank of the farm of origin. The isolation of M. bovis from the bulk milk tank, indicating subclinical mycoplasmal mastitis coupled with the feeding of waste milk from mastitic cows to calves is suggestive of a possible source of the infection resulting in otitis media in preweaned dairy calves.

Neutralizing antibodies to type 1 and 2 bovine viral diarrhea viruses: detection by inhibition of viral cytopathology and infectivity by immunoperoxidase assay

Neutralizing antibodies to type 1 and 2 bovine viral diarrhea virus (BVDV) strains were measured by a microtiter virus neutralization test (MVNT) in cell culture. Antibodies (neutralizing) were detected by inhibition of viral infectivity, by the absence of viral cytopathology for cytopathic strains, or by immunoperoxidase staining for noncytopathic strains. The immunoperoxidase-stained monolayers could be detected without the aid of light microscopy. Twenty BVDV strains were used as challenge viruses in the in vitro MVNT, including 14 type 1 and 6 type 2 strains. Representative noncytopathic and cytopathic strains of both types were used. Positive control serum samples available for diagnostic testing contained both type 1 and type 2 BVDV antibodies. There did not appear to be major differences in antibody titers among the respective type strains, regardless of biotype (cytopathic or noncytopathic). In a study with sera from calves receiving a modified live virus or inactivated BVDV vaccine, the calves receiving type 1 strains responded with higher antibody titers to type 1 strains than to type 2 strains.

Phosphoprotein profile analysis of ruminant respiratory syncytial virus isolates

OBJECTIVE

To determine the apparent molecular weight for 24 ruminant respiratory syncytial viruses (RSV) on the basis of differences in the electrophoretic mobility of the phosphoprotein (P protein).

PROCEDURE

29 bovine RSV (BRSV), 20 of which were not previously tested, 3 ovine RSV, and 1 caprine RSV isolates were selected for determination of electrophoretic mobility of the P protein. Virus radiolabeled with [35S]methionine was immunoprecipitated with polyclonal antiserum to BRSV and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

RESULTS

On the basis of apparent molecular size of the P protein, all isolates could be categorized into 2 electropherotypes, low molecular size of 36 kd and high molecular size of 38 kd. Twenty-three BRSV, the 3 ovine RSV, and 1 caprine RSV isolates had a high molecular size P protein; 6 BRSV isolates had a low molecular size P protein.

CONCLUSIONS

The apparent molecular size of the P protein of the ruminant RSV strains is greater than that of the human RSV subgroups, providing further evidence of their distinctiveness. Whether categorization of electrophoretic mobility of the P protein of BRSV underlies distinct antigenic subgroups, as it does in human RSV, requires further antigenic and genetic analysis.

CLINICAL RELEVANCE

Antigenic subgroups of ruminant RSV may have relevance in the development of new vaccines for control of the disease.

A novel mesoderm inducer, Madr2, functions in the activin signal transduction pathway

A functional assay to clone mouse mesoderm inducers has identified the mouse gene Mad related 2 (Madr2). Madr2 induces dorsal mesoderm from Xenopus ectoderm and can mimic the organizer in recruiting neighboring cells into a second axis. By analyzing the expression of a lacZ/Madr2 fusion protein, we find Madr2 confined to the nucleus in the deep, anterior cells of the second axis, whereas in epidermal and more posterior cells the protein is cytoplasmically localized. This context-dependent nuclear localization suggests that in certain regions of the embryo, Madr2 responds to a localized signal and amplifies this signal to form the second axis. Furthermore, although Madr2 remains unlocalized in ectodermal explants, addition of activin enhances the concentration of Madr2 in the nucleus. Significantly, a functional lacZ fusion to a carboxy-terminal portion of Madr2 is nuclear localized even in the absence of activin. This indicates that Madr2 contains a domain that can activate downstream components and a repressive domain that anchors the protein in the cytoplasm. Nuclear localization of Madr2 in response to activin, and the activin-like phenotypes induced by overexpression of Madr2, indicate that Madr2 is a signal transduction component that mediates the activity of activin.

A human Mad protein acting as a BMP-regulated transcriptional activator

The TGF-beta/activin/BMP cytokine family signals through serine/threonine kinase receptors, but how the receptors transduce the signal is unknown. The Mad (Mothers against decapentaplegic) gene from Drosophila and the related Sma genes from Caenorhabditis elegans have been genetically implicated in signalling by members of the bone-morphogenetic-protein (BMP) subfamily. We have cloned Smad1, a human homologue of Mad and Sma. Microinjection of Smad1 messenger RNA into Xenopus embryo animal caps mimics the mesoderm-ventralizing effects of BMP4. Smad1 moves into the nucleus in response to BMP4. Smad1 has transcriptional activity when fused to a heterologous DNA-binding domain, and this activity is increased by BMP4 acting through BMP-receptor types I and II. The transactivating activity resides in the conserved carboxy-terminal domain of Smad1 and is disrupted by a nonsense mutation that corresponds to null mutations found in Mad and in the related gene DPC4, a candidate tumour-suppressor gene in human pancreatic cancer. Additionally, we show that DPC4 contains a transcriptional activation domain. The results suggests that the Smad proteins are a new class of transcription factors that mediate responses to the TGF-beta family.

The clinical manifestations of bovine viral diarrhea infection

BVDV infections may result in a wide range of clinical manifestations ranging from subclinical infections to a severe, highly fatal form referred to as MD. In recent years, a better understanding of pathogenesis has been achieved that has allowed for a better understanding of the different clinical forms of BVDV infection. Knowledge in this area continues to evolve. The clinical forms of BVDV infections are best understood by breaking them into categories that include infections in immunocompetent cattle, fetal infections, and infections in cattle that are immunotolerant to BVDV.

Prevalence of cattle persistently infected with bovine viral diarrhea virus in 20 dairy herds in two counties in central Michigan and comparison of prevalence of antibody-positive cattle among herds with different infection and vaccination status

All cattle in 20 dairy herds randomly selected from herds participating in the Dairy Herd Improvement Association program in 2 counties in central Michigan were tested for the presence of bovine viral diarrhea virus (BVDV). Virus-positive animals were retested to ascertain persistent infection with the virus. A total of 5,481 animals were tested for presence of BVDV. In 9 of the herds, all animals were also tested for virus neutralizing antibody titer. Based on infection and vaccination status, these 9 herds were divided into 3 different herd categories: A, 5 herds with currently no cattle persistently infected (PI) with BVDV and without any vaccination program against BVDV in recent years; B, 2 herds with no current PI cattle but using killed BVDV vaccines; and C, 2 herds with PI cattle. PI cattle were detected in 3 out of 20 herds (15%). A total of 7 of 5,481 animals (0.13%) were PI. The mean prevalences of antibody carriers in herd categories A, B, and C were 28.8%, 76.4% and 90.6%, respectively. For one herd in category A, antibody analyses indicated that mostly young stock was seropositive, suggested recent BVDV infection in a previously closed and naive herd. Cattle in category B herds were vaccinated with killed vaccine from the age of 15 months. These herds had several antibody negative animals among the younger cows, suggesting incomplete protection against BVDV infection. In the 3 herds in which PI animals were detected, all cattle had been vaccinated with killed vaccine. The antibody-positive animals had antibody titers that were significantly different both among herds and among herd categories.(ABSTRACT TRUNCATED AT 250 WORDS)

Application of antibody titers against bovine viral diarrhea virus (BVDV) as a measure to detect herds with cattle persistently infected with BVDV

Based on the distribution of antibody titers against bovine viral diarrhea virus (BVDV) in 10 Michigan dairy herds, it was calculated that screening of 5 young stock for BVDV antibody titer could be used to distinguish herds with persistently infected (PI) animals from herds without such animals. The herds were selected to represent 3 different herd categories: A, herds without use of vaccination and without PI animals (5 herds); B, herds with use of killed vaccine but no PI animals (2 herds); C, herds with use of killed vaccine and presence of PI animals (3 herds). The animals were described as having high antibody titers (> or = 128) or low antibody titers (< or = 64). For animals from 9 to 18 months of age, the probability of obtaining at least 3 animals with high titers among a screening sample of 5 animals was calculated as < 0.001 for all herds in category A, < 0.01 for the 2 herds in category B, and > 0.99 for all herds in category C. Thus, among herds in this study, by categorizing 9-18-month-old animals as having high titers (> or = 128) or low titers (< or = 64), herds with PI cattle could be distinguished from other herds by testing only 5 animals.

Role of C-terminal B-chain residues in insulin assembly: the structure of hexameric LysB28ProB29-human insulin

BACKGROUND

LysB28ProB29-human insulin (Humalog), a fully potent insulin analog in which the prolyl, lysyl sequence at the C-terminal end of the B-chain is inverted, exhibits a decreased association of monomers to dimers leading to rapid in vivo absorption. This provides important benefits for the insulin-requiring diabetic. In spite of its monomeric nature, LysB28ProB29-human insulin can exist as a discrete hexameric structure in the presence of both zinc and phenol. Studies of the crystal structure of LysB28ProB29-human insulin in a hexameric complex were initiated to gain a molecular understanding of the effect of the sequence inversion on the analog's self-association properties and, consequently, its in vivo efficacy.

RESULTS

Under the conditions reported, LysB28ProB29-human insulin crystallized as a T3Rf3 hexamer that is isomorphous with the uncomplexed T3Rf3 native human insulin hexamer previously known as '4Zn insulin'. The three-dimensional structure of the T3Rf3 hexamer was determined by X-ray crystallographic methods to a resolution of 2.3 A. The prolyl, lysyl sequence inversion leads to local conformational changes at the C termini of the B-chains which eliminate two critical hydrophobic interactions and weaken two terminal beta-sheet hydrogen bonds that stabilize the dimer.

CONCLUSIONS

The loss of these native dimer interactions weakens the hexameric LysB28ProB29-human insulin complex formed in the presence of phenolic ligands. Thus, it is hypothesized that the diffusion of the phenolic ligands from the site of injection results in the dissociation of hexamers directly to monomers, thereby maintaining the rapid time-action of the monomeric analog in spite of the hexameric conformation in therapeutic formulations.

Production and characterization of monoclonal antibodies to bovine respiratory syncytial virus

Monoclonal antibodies to the SmithKline Beecham Animal Health BRSVR vaccine strain (375 isolate of Bovine Respiratory Syncytial Virus) were produced and then characterized by radioimmunoprecipitation followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, virus neutralization, inhibition of viral-induced fusion and isotype. Nineteen hybridomas produced antibodies that were reactive with the F0, F1, N or P viral proteins of bovine respiratory syncytial virus. One hybridoma (1E72C4) produced antibodies that immunoprecipitated the F0 glycoprotein, neutralized virus (1:8) in the presence of complement, but did not inhibit fusion. Another hybridoma (8B21E7) produced antibodies that immunoprecipitated the F0, F1 and F2 glycoproteins, neutralized virus (1:4) with and without complement and inhibited fusion. Antibodies from 11 hybridomas immunoprecipitated N and F1 proteins, one hybridoma immunoprecipitated the N and P protein, and 5 hybridomas immunoprecipitated the N protein. All monoclonal antibodies were of the IgG2b subtype with either kappa or lambda light chains.

Recombinant expression and evaluation of the lipoyl domains of the dihydrolipoyl acetyltransferase component of the human pyruvate dehydrogenase complex

The subunits of the dihydrolipoyl acetyltransferase (E2) component of mammalian pyruvate dehydrogenase complex (PDC) associate to form a large inner core with a protruding structure composed of three globular domains connected by mobile linker regions. This exterior region of E2 includes two lipoyl domains which engage not only in the intermediate reactions of the complex but also have integral roles in the kinase-phosphatase regulatory interconversion of the pyruvate dehydrogenase (E1) component. To facilitate understanding of these roles, lipoyl domain constructs of the E2 component of human PDC were expressed as glutathione S-transferase (GST)-linked fusion proteins from plasmid inserts prepared by polymerase chain reaction procedures. The NH2-terminal lipoyl domain, E2L1, and the interior lipoyl domain, E2L2, are connected by a 30-amino-acid hinge region, H1. Constructs designed and expressed were E2L1(1-98), E2L1.H1(1-128), E2L2(120-233), E2H1.L2(98-233), and E2L1.H1.L2(1-233), where numbers in parentheses give the amino acid sequence for the portions of the E2 component incorporated into a construct. The domains were expressed in Escherichia coli with and without lipoate supplementation. GST constructs were purified to homogeneity by affinity chromatography and selectively released by thrombin treatment. Sequencing of insert DNAs and NH2-terminal sequencing confirmed that domains were produced as designed. Measurement of masses by electrospray mass spectrometry indicated that constructs with lipoylated, nonlipoylated, and octanoylated forms were produced when expression was with E. coli grown without lipoate supplementation and that fully lipoylated forms were produced upon lipoate supplementation. The lipoylation status was confirmed, following delipoylation with Enterococcus faecalis lipoamidase, by the expected decrease in mass and by the observation in native gel electrophoresis of a shift to a slower mobility (possibly less compact) form. Constructs were used in E1-catalyzed reductive-acetylation reaction in proportion to their degree of lipoylation and were effective substrates in a NADH-dependent dihydrolipoyl dehydrogenase reduction reaction. Thus, we have produced lipoyl domain constructs that can be employed in sorting the specific roles of E2L1 and E2L2 in facilitating catalytic and regulatory processes.

Binding of the pyruvate dehydrogenase kinase to recombinant constructs containing the inner lipoyl domain of the dihydrolipoyl acetyltransferase component

The dihydrolipoyl acetyltransferase (E2) component of the mammalian pyruvate dehydrogenase complex forms a 60-subunit core in which E2's inner domain forms a dodecahedron shaped structure surrounded by its globular outer domains that are connected to each other and the inner domain by 2-3-kDa mobile hinge regions. Two of the outer domains are approximately 10 kDa lipoyl domains, an NH2-terminal one, E2L1, and, after the first hinge region a second one, E2L2. The pyruvate dehydrogenase kinase binds tightly to the lipoyl domain region of the oligomeric E2 core and phosphorylates and inactivates the pyruvate dehydrogenase (E1) component. We wished to determine whether lipoyl domain constructs prepared by recombinant techniques from a cDNA for human E2 could bind the bovine E1 kinase and, that being the case, to pursue which lipoyl domain the kinase binds. We also wished to gain insights into how a molecule of kinase tightly bound to the E2 core can rapidly phosphorylate 20-30 molecules of the pyruvate dehydrogenase (E1) component which are also bound to an outer domain of the E2 core. We prepared recombinant constructs consisting of the entire lipoyl domain region or the individual lipoyl domains with or without the intervening hinge region. Constructs were made and used both as free lipoyl domains and fused to glutathione S-transferase (GST). Using GSH-Sepharose to selectively bind GST constructs, tightly bound kinase was shown to rapidly transfer in a highly preferential way from intact E2 core to GST constructs containing the E2L2 domain rather than to ones containing only the E2L1 domain. GST-E2L2-kinase complexes could be eluted from GSH-Sepharose with glutathione. Delipoylation of E2L2 by treatment with lipoamidase eliminated kinase binding supporting a direct role of the lipoyl prosthetic group in this association. Transfer to and selective binding of the kinase by E2L2 but not E2L1 was also demonstrated with free constructs using a sucrose gradient procedure to separate the large E2 core from the various lipoyl domain constructs. E2L2 but not E2L1 increased the activity of resolved kinase by up to 43%. We conclude that the kinase selectively binds to the inner lipoyl domain of E2 subunits and that this association involves its lipoyl prosthetic group. We further suggest that transfer of tightly bound kinase between E2L2 domains occurs by a direct interchange mechanism without formation of free kinase (model presented).(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of the prevalence and incidence of infection with bovine virus diarrhoea virus (BVDV) in Denmark and Michigan and association with possible risk factors

Based on 2 previous surveys on the occurrence of infection with bovine virus diarrhoea virus (BVDV) in Danish and Michigan dairy herds, the prevalence and incidence of the infection were compared. The presence of certain possible risk factors for the occurrence of infection in the 2 areas were summarized and it was investigated if any of these risk factors had significant effect on the presence of animals persistently infected (PI) with BVDV in the dairy herds. Information on the cattle population density in the 2 areas was obtained from statistical yearbooks. Further information for the individual farms on age distribution, housing of animals, herd size, pasturing and purchasing policy was gathered. The prevalence of PI animals was more than 10 times higher in Denmark as compared to Michigan. In herds without PI animals, the annual incidence of seroconversion as calculated from the age specific prevalence of antibody carriers varied in most age groups between 20-25% in Denmark and between 5-10% in Michigan. All investigated risk factors except for herd size were in favour of a lower prevalence of infection in Michigan. The use of having animals on pasture and at the same time having purchased more than 40 animals within recent 3 1/2-4 years were significantly associated with presence of PI animals in the dairy herds (p = 0.01) when tested by the Mantel-Haenszel chi 2. Using multivariable logistic regression, the occurrence of PI animals was found to be significantly related to the study area (Michigan and Denmark) as well as to herd size and purchase intensity.

Imaging fluid/solid interactions in hydrocarbon reservoir rocks

The environmental scanning electron microscope (ESEM) has been used to image liquid hydrocarbons in sandstones and oil shales. Additionally, the fluid sensitivity of selected clay minerals in hydrocarbon reservoirs was assessed via three case studies: HCl acid sensitivity of authigenic chlorite in sandstone reservoirs, freshwater sensitivity of authigenic illite/smectite in sandstone reservoirs, and bleach sensitivity of a volcanic reservoir containing abundant secondary chlorite/corrensite. The results showed the suitability of using ESEM for imaging liquid hydrocarbon films in hydrocarbon reservoirs and the importance of simulating in situ fluid-rock interactions for hydrocarbon production programmes. In each case, results of the ESEM studies greatly enhanced prediction of reservoir/borehole reactions and, in some cases, contradicted conventional wisdom regarding the outcome of potential engineering solutions.

Hemorrhagic diathesis associated with a hereditary platelet disorder in Simmental cattle

A severe bleeding disorder in Simmental cattle has been described in widespread locations in the USA and Canada. The clinical findings are consistent with a hemophilia-like disease or, more precisely, a hereditary hemorrhagic diathesis and include spontaneous epistaxis, hematuria, and excessive bleeding associated with trauma or standard management procedures such as tattooing, ear tagging, and castration. A preliminary investigation of this defect showed that blood-platelet numbers and coagulation profiles of affected cattle were normal. Affected animals have a marked dysfunction of platelets (thrombopathy), termed Simmental hereditary thrombopathy. The defect is very similar or identical to that described in the same breed by 2 other laboratories.

Pharmacokinetic evaluation of ceftiofur in serum, tissue chamber fluid and bronchial secretions from healthy beef-bred calves

Ceftiofur is a new broad spectrum cephalosporin marketed for the treatment of acute bovine respiratory disease. In this investigation ceftiofur was administered by intramuscular injection, at 24 h intervals, to healthy beef-bred calves for four days at dosages of 2.2 and 4.4 mg/kg of body weight, with 4 wk intervals between dosing regimens. Serum, tissue chamber fluid (TCF), and bronchial secretion (BS) concentrations of ceftiofur were measured by microbiological assay after the first and fourth dose of each dosing regimen. Peak serum concentrations (Cmax) of 8.8 micrograms/mL and 17.3 micrograms/mL were obtained approximately 2 h (Tmax), the time of mean peak concentration) after single injections of 2.2 mg/kg and 4.4 mg/kg, respectively. The Cmax was increased approximately twofold following multiple doses of 2.2 mg/kg (Cmax = 13.1 micrograms/mL) and 4.4 mg/kg (Cmax = 24.1 micrograms/mL). Ceftiofur accumulated slowly into TCF and peak concentrations were found to be approximately 14% of those observed in serum after the first dose and approximately 24% after multiple dosing. Concentrations of ceftiofur in BS were obtained rapidly with peak concentrations reaching 45% of the serum Cmax after the first dose. After multiple dosing the Cmax for BS was approximately 25% of the serum Cmax. This study found that both the 2.2 mg/kg and 4.4 mg/kg dosing regimens resulted in continuous serum, TCF and BS concentrations of ceftiofur that exceeded the minimal concentration required to inhibit the bacteria most frequently isolated from calves with acute bovine respiratory disease.

Identification of subgroups of bovine respiratory syncytial virus

The occurrence of antigenic variation among nine isolates of bovine respiratory syncytial virus (BRSV) was determined by examining their reaction patterns to human respiratory syncytial virus (HRSV) subgroup A and B monoclonal antibodies (MAbs) by enzyme immunoassay and radioimmunoprecipitation with fractionation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis by using MAbs and polyclonal antisera to HRSV and BRSV. Shared epitopes were demonstrated on four of five structural proteins between BRSV and both subgroups A and B of HRSV. The nine isolates of BRSV showed different patterns of reactivity in enzyme immunoassays with panels of MAbs to HRSV subgroups A and B. Major variations in the molecular weights of the P (phosphoprotein) and F (fusion protein) proteins were demonstrated among the BRSV isolates tested. These results suggest that BRSV belongs to a different antigenic grouping than HRSV and that BRSV is composed of two distinct subgroups.

An outbreak of fetal and neonatal losses associated with the diagnosis of bovine viral diarrhea virus

A severe outbreak of dairy herd pregnancy wastage was investigated. At the beginning of the outbreak, a total of 121 lactating cattle were pregnant and considered to be at risk. Overall, 33.1% of the population at risk aborted, while 25.6% gave birth to calves that either died during the early neonatal period or demonstrated signs compatible with congenital defects (abnormal births). A laboratory diagnosis of bovine viral diarrhea virus (BVDV) infection was made in two surviving neonatal calves with symptoms of cerebellar hypoplasia and blindness. An on-farm investigation was conducted to determine if the abortions and abnormal births were associated with BVDV infection. The rate of abortions versus abnormal births was biphasic when graphed by the date of occurrence. The cases of abortion occurred early in the outbreak and were followed by the neonatal losses. Within the population at risk, the mean values for gestational age at the beginning of the outbreak were different between the subpopulations described by gestational outcome. The outcome of each pregnancy that existed at the beginning of the outbreak was determined. Classifications included normal birth (birth of a normal calf), abnormal birth (a neonatal loss of the type described above), abortion, and continued gestation (normal, uncompleted pregnancy). The average gestational age at the time of the index case (the first cases of pregnancy wastage) for these four pregnancy outcome classfications was 142.0, 106.2, 86.7 and 31.3 days, respectively. Reasons for assuming that this outbreak was related to BVDV are discussed.

Characterization of the alpha-2C adrenergic receptor subtype in the opossum kidney and in the OK cell line

The alpha-2 adrenergic receptors have been subdivided into two pharmacological subtypes known as alpha-2A and alpha-2B. The OK cell, a cell line derived from an opossum kidney, expresses an alpha-2 adrenergic receptor which has pharmacological characteristics different from both the alpha-2A and alpha-2B subtypes, and thus may be a third subtype. To test this hypothesis, we compared the affinities (Ki values from radioligand binding) of 49 drugs in the OK cell with their affinity for the alpha-2A (HT-29 cells) and alpha-2B (neonatal rat lung) adrenergic receptor subtypes. Eight drugs (spiroxarine, prazosin, WY 27127, L-657,743, ARC 239, akuammigine, rauwolscine and oxymetazoline) were identified whose Ki differed by 10-fold or more between the OK cells and HT29 cells. Five drugs (BAM 1303, raubasine, WB 4101, akuammigine and rauwolscine) differentiated, by at least 10-fold, between OK cells and neonatal rat lung. Correlations of pKi values between the OK cell and tissues or cell lines expressing either the alpha-2A or alpha-2B subtypes were poor, confirming that the OK cell receptor could not be classified as either alpha-2A or alpha-2B. In contradistinction, there was a good correlation between pKi values for the OK cell line and opossum kidney showing that they express the same subtype. In addition, ratios of subtype-selective drug Ki values were similar for the OK cell and opossum kidney, but different from other tissues or cell lines expressing either the alpha-2A or alpha-2B subtypes. We conclude that the OK cell line and opossum kidney express a novel subtype of alpha-2 adrenergic receptor which we term the alpha-2C subtype.

Effects of bovine respiratory syncytial virus on airway function in neonatal calves

Respiratory syncytial virus (RSV) infection causes severe lower respiratory tract disease in infants and calves. Neonatal respiratory tract infection in children often produces persistent changes in lung function. The specific objective of this study was to determine whether neonatal calves have transient or persistent alterations in pulmonary function and airway reactivity following RSV infection. Six 2- to 3-day-old Holstein bull calves were inoculated with 10 ml of bovine respiratory syncytial virus (BRSV) inoculum (10(2.7) to 10(3.8) cell culture infective doses/ml) intranasally and 10 ml of BRSV inoculum (10(4.8) to 10(5.9) cell culture infective doses/ml) intratracheally for 4 consecutive days, and 5 other calves were sham-inoculated. Prior to inoculation (day 0) and on days 4, 14, and 30 after the last inoculation, body weight (kg), dynamic compliance (Cdyn), pulmonary resistance (RL), and 2 indices of airway reactivity (effective dose [ED] 65Cdyn and ED200RL) were measured. Control calves gained weight progressively throughout the study, whereas RSV-inoculated calves failed to gain weight for 14 days, but equaled control calf weight by 30 days after inoculation. The Cdyn of control calves increased significantly by 30 days, but did not in the RSV-infected calves. Pulmonary resistance was increased significantly at 4, 14, and 30 days, but was unaffected by sham inoculation. The ED65Cdyn and ED200RL indicated an age-dependent increase in reactivity to histamine and an increase in responsiveness in the infected group beginning at 14 days and persisting until the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental reproduction of respiratory tract disease with bovine respiratory syncytial virus

An experiment was conducted to reproduce respiratory tract disease with bovine respiratory syncytial virus (BRSV) in one-month-old, colostrum-fed calves. The hypothesized role of viral hypersensitivity and persistent infection in the pathogenesis of BRSV pneumonia was also investigated. For BRSV inoculation a field isolate of BRSV, at the fifth passage level in cell culture, was administered by a combined respiratory tract route (intranasal and intratracheal) for four consecutive days. Four groups of calves were utilized as follows: Group I, 6 calves sham inoculated with uninfected tissue culture fluid and necropsied 21 days after the last inoculation; Group II, 6 calves inoculated with BRSV and necropsied at the time of maximal clinical response (4-6 days after the last inoculation); Group III, 6 calves inoculated with BRSV and necropsied at 21 days after the last inoculation; Group IV, 6 calves inoculated with BRSV, rechallenged with BRSV 10 days after initial exposure, and necropsied at 21 days after the initial inoculation. Clinical response was evaluated by daily monitoring of body temperature, heart rate, respiratory rate, arterial blood gas tensions, hematocrit, total protein, white blood cell count, and fibrinogen. Calves were necropsied and pulmonary surface lesions were quantitated by computer digitization. Viral pneumonia was reporduced in each principal group. Lesions were most extensive in Group II. Disease was not apparent in Group I (controls). Significant differences (p less than 0.05) in body temperature, heart rate, respiratory rate, arterial oxygen tension, and pneumonic surface area were demonstrated between control and infected calves. Results indicate that severe disease and lesions can be induced by BRSV in one-month-old calves that were colostrum-fed and seropositive to BRSV. BRSV rechallenge had minimal effect on disease progression. Based on clinical and pathological response, results did not support viral hypersensitivity or persistent infection as pathogenetic mechanisms of BRSV pneumonia.

The role of passive immunity in bovine respiratory syncytial virus-infected calves

The role of passive immunity in bovine respiratory syncytial virus (BRSV) infections in neonatal calves was evaluated. Calves were divided into groups as follows: colostrum-deprived, sham-inoculated; colostrum-deprived, BRSV-inoculated; and colostrum-fed, BRSV-inoculated. Calves were inoculated with a low-passage field isolate of BRSV for 4 consecutive days by a combined respiratory tract route and were euthanized 6 days after receiving the last inoculation. Arterial oxygen tension (Pao2) decreased significantly over time in colostrum-deprived, BRSV-inoculated calves (P less than .01) and was significantly different among treatment groups (P less than .05). A significant decrease in arterial oxygen saturation was observed in this same group over time (P less than .01). Mean percentage of pneumonic lung volume (determined by computer data digitalization) was significantly greater in infected, colostrum-deprived calves compared with the other groups (P less than .01), and BRSV antigen was detected in these calves by avidin-biotin immunoperoxidase staining. Thus, passive immunity derived from colostrum feeding decreased the severity of BRSV infections in calves.

The severity of diabetes is a major determinant of myocardial damage in the rat

The severity of insulin-dependent diabetes mellitus had a marked effect upon the development of myocardial sequelae in the rat. Even with the same degree of hyperglycemia, glycosuria, polydipsia, and polyuria, moderately diabetic animals did not develop the degenerative ultrastructural changes seen in myocardium from more severely diabetic rats. These included decreased cardiocyte size, loss and disorganization of myofibrils, and loss of sarcoplasmic reticulum and transverse tubules. Since hyperglycemia and glycosuria are frequently used as the primary, and often sole, criteria for identifying diabetes in experimental animals, this study demonstrates the need to more specifically define the severity of the disease in studies of the heart.

Human and bovine respiratory syncytial virus: immunopathologic mechanisms

Human respiratory syncytial virus (HRSV) is the major respiratory tract pathogen of infants and young children. Bovine respiratory syncytial virus (BRSV) is recognised as an important cause of respiratory tract disease in calves. Both of these viruses and their respective diseases share many similarities. Immunopathologic mechanisms have been proposed to be involved in the pathogenesis of respiratory syncytial virus (RSV) infections. This review examines the current understanding of the role of immunopathologic mechanisms in RSV infections. The role of vaccines in inducing hypersensitivity is also examined. Additionally, non-immunopathogenic mechanisms involved in RSV infections are discussed.

Clinical aspects of bovine virus diarrhoea virus infection

Bovine virus diarrhoea virus (BVDV) infection of cattle results in a wide range of clinical manifestations. This article reviews the clinical responses associated with BVDV and discusses these diseases in terms of acute infection in immunocompetent cattle, fetal infection, infection in cattle immunotolerant to and persistently infected with BVDV and finally mucosal disease.

Granulocyte plasma membrane damage by leukotoxic supernatant from Pasteurella haemolytica A1 and protection by immune serum

Bovine respiratory disease caused by Pasteurella haemolytica may be partially mediated by a leukotoxin secreted by the microorganism. We examined the effect of leukotoxic Pasteurella supernatants on leakage of the cytosol enzyme lactate dehydrogenase and the lysosomal enzyme arylsulfatase from bovine granulocytes. Lactate dehydrogenase release (94%) was much higher than arylsulfatase release (38%) over 30 minutes of incubation. The Pasteurella supernatants inhibited superoxide production by stimulated granulocytes at concentrations which also caused substantial cell death as measured by failure to exclude trypan blue. Both toxic effects were prevented by serum from aerosol-immunized calves, and protection appeared to be antibody-specific by comparison with fetal bovine serum or with serum absorbed against intact P. haemolytica. These findings suggest that the leukotoxin may selectively disrupt the granulocyte plasma membrane, and that antibody directed against a surface component of the microorganism is also capable of protecting against the leukotoxin effect.

Transmission of a vaccinal strain of infectious bovine rhinotracheitis virus from intranasally vaccinated steers commingled with nonvaccinated steers

Ninety-seven feeder steers, averaging 7 months of age, were allotted to 3 groups. Group I (n = 33) was vaccinated intranasally with an infectious bovine rhinotracheitis virus (IBRV) vaccine on postinoculation day (PID) 0; group II (n = 31) was not vaccinated on PID 0 but was commingled with group I; and group III (n = 33) served as controls housed in the same facility, but was physically separated from groups I and II. On PID 20, all steers were given a modified-live IBRV vaccine IM. Virus isolation attempts from nasal swab specimens collected on PID 10 resulted in IBRV isolation from 19 (57.6%) of group I, 4 (12.9%) of group II, and 0 of group III. By PID 20, geometric mean titer for serum antibody to IBRV had increased in group I but had decreased in groups II and III. By PID 40, geometric mean titer for serum antibody to IBRV had increased in the 3 groups in response to IM vaccination given on PID 20. Seemingly, transmission of a vaccinal strain of IBRV to nonvaccinated steers did not take place at a frequency that elicited a humoral immune response similar to that of vaccinated steers.

Calcium ion involvement in the action of Pasteurella haemolytica leukotoxin

The influence of Ca2+ ions on the cytotoxic activity of Pasteurella haemolytica leukotoxin was investigated. The divalent cation influenced the cytotoxic effect of the leukotoxin for sensitive BL-3 target cells, but its absence did not eliminate cytotoxicity. In short-term 1-h assays using neutral red uptake as a measure of cell viability, depletion of Ca2+ either by exhaustive dialysis or by addition of the Ca2+ chelators EDTA and EGTA eliminated the cytolytic effect of low doses of the toxin. Addition of Ca2+ to target cell cultures depleted of the divalent cation restored the cytolytic effect of the leukotoxin. Prolonged exposure of the BL-3 cells to the toxin abrogated the protective effect of EDTA and EGTA. Cell death measured by uptake of neutral red, exclusion of trypan blue and 51Cr release indicated that protection observed in the absence of free Ca2+ was temporary. Toxin-induced cytolysis equivalent to that observed in the presence of Ca2+ occurred following the initial 2-h exposure. In addition, verapamil, a Ca2+ channel blocker, prevented cell death during 1-h cytotoxicity assays. The protection afforded by verapamil was dose-dependent and was influenced by the concentration of Ca2+ in the buffer medium. The results suggest that Ca2+ positively influences the rapid initial phase of cell death resulting from exposure to the toxin, but is not required for the entirety of the cytolytic process.

Proteolytic cleavage of encephalomyocarditis virus capsid region substrates by precursors to the 3C enzyme

Picornavirus protease 3C is normally released from its P3 precursor by two successive self-cleavage reactions. The free enzyme can then catalyze most of the remaining processing events within the viral polyprotein. To investigate the role of the 3C precursors in the processing cascade, we constructed cDNA clones which expressed genetically altered forms of the encephalomyocarditis P3 region in vitro. Site-specific substitutions were introduced into the Gln-Gly residues at the 3B-3C and 3C-3D junctions, and the resulting proteins were tested for their ability to self-process and to catalyze cleavage of viral capsid precursors in cell-free protease assays. We determined that three P3 region precursor proteins (3ABC, 3CD, and P3), harboring inactive cleavage sites, were as active as the free enzyme (3C) in processing assays with capsid substrates. Further, we found that in addition to the naturally occurring Gln-Gly and Gln-Ser amino acid pairs, the encephalomyocarditis 3C enzyme was able to process Gln-Cys but not Gln-Thr, Gln-Ile, Gln-Tyr, Arg-Gly, or Leu-Gly combinations when these residues were substituted into normal cleavage site contexts.

Failure to detect antibody to bovine respiratory syncytial virus in bovine fetal serum

Sera obtained from 147 bovine fetuses estimated to be between 120 and 270 days of gestation at an abattoir were tested for antibody to bovine respiratory syncytial virus. Antibody to bovine respiratory syncytial virus was not detected in any of the sera examined. Based on the results of this study and a review of the literature, it appears that transplacental infection by bovine respiratory syncytial virus does not occur, or is uncommon.

Alterations in levels of 5'-adenyl dinucleotides following DNA damage in normal human fibroblasts and fibroblasts derived from patients with xeroderma pigmentosum

Levels of 5'-adenyl dinucleotides, measured as diadenosine-5',5'''-P1,P4-tetraphosphate (Ap4A), were found to accumulate in cultured human fibroblasts following treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), the radiomimetic drug bleomycin, and nitroquinoline-1-oxide (NQO) or UV-irradiation in the presence of cytosine arabinofuranoside (araC). In contrast, cells derived from patients with xeroderma pigmentosum complementation group A (XP-A) did not demonstrate an increase in DNA-strand breaks following UV irradiation or NQO in the presence of araC nor an increase in Ap4A levels. Ap4A accumulation did occur in XP-A cells following treatment with MNNG. Cells derived from patients characterized as XP variants, which are incision repair-proficient, accumulated 5'-dinucleotides following bleomycin, MNNG and UV or NQO in the presence of araC. Taken together, these data suggest that Ap4A accumulates as a response to DNA-strand breaks.

Near-UV stress in Salmonella typhimurium: 4-thiouridine in tRNA, ppGpp, and ApppGpp as components of an adaptive response

We have examined the role of 4-thiouridine in the responses of Salmonella typhimurium to near-UV irradiation. Mutants lacking 4-thiouridine (nuv) and mutants defective in the synthesis of ppGpp (guanosine 5'-diphosphate-3'-diphosphate) (relA) were found to be sensitive to killing by near-UV. Near-UV induced the synthesis of a set of proteins that were not induced in the nuv mutant. Some of these proteins were identified as oxidative defense proteins, and others were identified as ppGpp-inducible proteins. Over 100-fold increases in ApppGpp (adenosine 5', 5"'-triphosphoguanosine-3"'-diphosphate, the adenylylated form of ppGpp) were observed in wild-type cells after near-UV irradiation but not in the 4-thiouridine-deficient mutant. These data support a model in which ppGpp and ApppGpp, a dinucleotide proposed to be synthesized by tRNA-aminoacyl synthetases as a response to the cross-linking of 4-thiouridine in tRNA by near-UV, induce the synthesis of proteins necessary for resistance to near-UV irradiation.