An unusual cause of haemobilia: biliary ascariasis

A case of haemobilia following biliary ascariasis is presented. Angiography confirmed an aneurysm of the left hepatic artery, which was successfully embolised. The patient made an uneventful recovery.

Prejunctional histamine H3-receptors inhibit electrically evoked endogenous noradrenaline overflow in the portal vein of freely moving rats

The effects of intra-arterial injection of different doses of the selective histamine H3-receptor agonist R-alpha-methylhistamine and the selective histamine H3-receptor antagonist thioperamide on basal and electrically evoked noradrenaline overflow in the portal vein as well as on mean arterial pressure (MAP) and heart rate (HR) were investigated in permanently instrumented freely moving rats. R-alpha-Methylhistamine (0.01, 0.1 and 1 mumol/kg) inhibited the evoked noradrenaline overflow up to 43%, the ED50 value being 0.013 mumol/kg. Thioperamide (0.1, 0.5 and 1.0 mumol/kg) antagonized the effect of 1.0 mumol/kg R-alpha-methylhistamine dose-dependently, evoked overflow returning to control values at 1.0 mumol/kg of the antagonist; thioperamide alone had no effect on electrically evoked noradrenaline overflow. Basal noradrenaline levels, blood pressure and heart rate were not at all influenced by R-alpha-methylhistamine and thioperamide, alone or in combination. The results clearly show the presence of prejunctional histamine H3-receptors inhibiting the electrically evoked noradrenaline overflow from vascular sympathetic nerve terminals in the portal vein of freely moving rats.

Pilin-based anti-Pseudomonas vaccines: latest developments and perspectives

Among the several adhesins produced by Pseudomonas aeruginosa (Pa), the type-4 pilus promotes the majority of the adherence capability of the bacterium to epithelial cells and it is a major virulence factor in an AB.Y/SnJ mouse infection model. Vaccines targeting the disulfide loop (DSL) adherence binding domain of the pilin protein should therefore provide an effective protection against initial colonization and infection with Pa. To selectively elicit adherence blocking antibodies, the pilin DSL domain was chosen as peptide antigen for the construction of recombinant protein and live vaccines. While synthetic peptide-carrier protein conjugates provided some strain-specific protection, chimeric proteins with N- or C-terminally fused pilin DSL peptides did not engender protective IgG titers mice. Integral fusions of the pilin DSL peptide with the minor coat protein of filamentous phage or surface exposed regions of an outer membrane protein resulted in a display of the peptide on the surface of the phage particles and bacterial cells respectively. However, in immunization studies neither of these live vaccines were effective immunogens. The paracrystalline S-layer of Caulobacter crescentus combines several advantages of an effective antigen surface display system. Recombinant S-layer proteins with singlecopy insertions of a pilin peptide did not engender significant IgG titers, whereas multiple tandem insertions of the same peptide increased the serum IgG response in mice a thousand times. Multiple insertions of DSL peptides from different frequent pilin prototypes may be an interesting alternative for a recombinant cross-protective anti-Pseudomonas vaccine.

Linker mutagenesis of the Caulobacter crescentus S-layer protein: toward a definition of an N-terminal anchoring region and a C-terminal secretion signal and the potential for heterologous protein secretion

Linker insertion mutagenesis was used to modify the paracrystalline surface layer (S-layer) protein (RsaA) of the gram-negative bacterium Caulobacter crescentus. Eleven unique BamHI linker insertions in the cloned rsaA gene were identified; at the protein level, these linker insertions introduced 4 to 6 amino acids at positions ranging from the extreme N terminus to the extreme C terminus of the 1,026-amino-acid RsaA protein. All linker-peptide insertions in the RsaA N terminus caused the secreted protein to be shed into the growth medium, suggesting that the RsaA N terminus is involved in cell surface anchoring. One linker-peptide insertion in the RsaA C terminus (amino acid 784) had no effect on S-layer biogenesis, while another (amino acid 907) disrupted secretion of the protein, suggesting that RsaA possesses a secretion signal lying C terminal to amino acid 784, near or including amino acid 907. Unlike extreme N- or C-terminal linker-peptide insertions, those more centrally located in the RsaA primary sequence had no apparent effect on S-layer biogenesis. By using a newly introduced linker-encoded restriction site, a 3' fragment of the rsaA gene encoding the last 242 C-terminal amino acids of the S-layer protein was expressed in C. crescentus from heterologous Escherichia coli lacZ transcription and translation initiation information. This C-terminal portion of RsaA was secreted into the growth medium, confirming the presence of a C-terminal secretion signal. The use of the RsaA C terminus for the secretion of heterologous proteins in C. crescentus was explored by fusing 109 amino acids of an envelope glycoprotein from infectious hematopoietic necrosis virus, a pathogen of salmonid fish, to the last 242 amino acids of the RsaA C terminus. The resulting hybrid protein was successfully secreted into the growth medium and accounted for 10% of total protein in a stationary-phase culture. Based on these results and features of the RsaA primary sequence, we propose that the C. crescentus S-layer protein is secreted by a type I secretion system, relying on a stable C-terminal secretion signal in a manner analogous to E. coli alpha-hemolysin, the first example of an S-layer protein secreted by such a pathway.

Influence of adrenodemedullation on beta 2- and beta 3-adrenoceptors mediating relaxation of oesophageal smooth muscle of spontaneously hypertensive rats

1. In oesophageal smooth muscle strips from spontaneously hypertensive rats (SHR) of 8-10 and 22-24 weeks of age, respectively, beta-adrenoceptor-mediated relaxation was investigated, by use of the beta-agonists, (-)-isoprenaline and fenoterol (both in the absence and presence of the beta 2-selective antagonist ICI 118,551) and the selective beta 3-agonist, BRL 37,344. 2. In preparations from 8-10 week SHR, (-)-isoprenaline- and fenoterol-induced concentration-response curves (CRCs) were hardly antagonized by ICI 118,551 at concentrations up to 1 microM, indicating only a minor contribution of beta 2-adrenoceptors. pA2-values for ICI 118,551 of 5.30 ((-)-isoprenaline as agonist) and 5.46 (fenoterol as agonist), estimated from the shifts at the highest (10-100 microM) antagonist concentrations, are consistent with affinity at a beta 3-adrenoceptor, similar to that in Wistar rat oesophageal smooth muscle. 3. In 8-10 week SHR, adrenodemedullated at 4 weeks of age (SHR-ADM4) the potency of fenoterol was markedly increased and CRCs were shallow. In addition, ICI 118,551 (0.1 microM) now produced a clear rightward shift accompanied by a steepening of the CRC. A marked further shift was observed only at 100 microM of the antagonist. The data are compatible with the involvement of both beta 2- and beta 3-adrenoceptors. 4. In 22-24 week animals, the same differences between SHR and SHR-ADM4 were observed with fenoterol as in 8-10 week animals, though beta-adrenoceptor responsiveness was slightly decreased. The potency of ICI 118,551 at beta 3-adrenoceptors (pA2 = 5.11) was significantly different from the pA2 value of 5.46 obtained with the younger animals. 5. Responses to the beta 3-adrenoceptor agonist, BRL 37,344, were similar in Wistar rat and SHR preparations. In 8-10 week SHR, a small decrease in the maximal response was observed, which in animals of 22-24 weeks of age was accompanied by a small decrease in the pEC50 value as well. 6. The results clearly indicate that beta 2-adrenoceptors in SHR oesophageal muscularis mucosae are desensitized, whereas beta 3-adrenoceptor-mediated responses are unaffected and similar to the responses observed in the Wistar rat oesophagus. The functional presence of beta 2-adrenoceptor-responses in SHR-ADM4 suggests a major role for adrenal-derived adrenaline in the desensitization of the beta 2-adrenoceptor-population.

Threshold effect of liver iron content on hepatic inflammation and fibrosis in hepatitis B and C

BACKGROUND/AIMS

In hepatitis C, iron depletion may improve serum aminotransferases and the response to interferon, but it is not known whether inflammation and fibrosis correlate with hepatic iron content. Our aim was to establish whether hepatic iron content correlates with histological and serum indices of hepatic inflammation and fibrosis in hepatitis B and C.

METHODS

Total hepatic iron was measured using computerized histomorphometry, and hepatic inflammation and fibrosis using a modified Knodell score, on histological slides from 31 patients with chronic hepatitis B and 38 with hepatitis C.

RESULTS

Total hepatic iron was similar in the hepatitis B and C groups (0.82 +/- 1.72% and 0.56 +/- 1.12%; mean +/- SD). No iron was detectable in 11 patients with hepatitis B and 13 with hepatitis C. Alanine aminotransferase (85.96 +/- 67.1 vs 44.2 +/- 39.7 p < 0.05), aspartate aminotransferase (93.8 +/- 75.6 vs 47 +/- 33.5 IU/ml p < 0.05) and histological inflammatory score (9.33 +/- 3.51 vs 7.79 +/- 3.3 p = 0.07) were increased in those with stainable hepatic iron compared to those without. However, where iron was present, no association was found between the amount of hepatic iron and inflammatory or fibrosis scores. In hepatitis C, fibrosis was minimal in 77% of patients if iron was absent vs 24% with iron present, while marked fibrosis was present in 56% with iron vs 15% without iron (p < 0.01, Fisher's exact test).

CONCLUSION

Hepatic iron is associated with increased hepatic inflammation in chronic hepatitis B and hepatitis C and with high fibrosis scores in hepatitis C. There is a threshold effect, and once present, increasing iron does not correlate with increasing inflammation or fibrosis.

The extreme N-terminus of the Caulobacter crescentus surface-layer protein directs export of passenger proteins from the cytoplasm but is not required for secretion of the native protein

The paracrystalline surface layer (S-layer) of Caulobacter crescentus is composed of a single protein (RsaA, 1026 amino acids) that associates noncovalently with the lipopolysaccharide of the outer membrane. Like many other extracellular proteins of Gram-negative bacteria, the S-layer protein is not processed during transport to the cell surface. To study the secretion of RsaA, several N-terminal deletions of the protein were made by modifying the 5'-region of the rsaA gene. This analysis showed that portions of the N-terminus totalling the first 775 N-terminal amino acids (75% of the protein) could be removed from RsaA without abolishing secretion of the remainder of the protein. Although the RsaA N-terminus was not required for secretion, an N-terminal domain consisting of either 34 or 52 RsaA-derived amino acids promoted export of the alkaline phosphatase reporter (PhoA) and a cellulase reporter (delta CenA) from the cytoplasm; using the cellulase reporter, the efficiency of hybrid protein export was estimated at 9%. No enzyme activity was detected in the cell-free culture fluids as the result of expressing any gene fusion, indicating that no hybrid protein was completely secreted from the cell. RsaA:PhoA hybrid proteins were also exported from the E. coli cytoplasm, a bacterium not expected to contain the necessary machinery for the secretion of RsaA. Taken together, these data indicate that the secretion pathway of RsaA relies on a C-terminal secretion signal and that once separated from the context of the native protein, the extreme N-terminus of RsaA can act as an inefficient cryptic export signal that is not used during native RsaA secretion.

Co-released adrenaline markedly facilitates noradrenaline overflow through prejunctional beta 2-adrenoceptors during swimming exercise

The effect of intravenously applied (-)-adrenaline, taken up by and released from sympathetic nerves, on swimming exercise-induced noradrenaline overflow in permanently cannulated adrenal demedullated rats was studied. Adrenaline (100 ng/min) was infused for 2 h, during which a plasma concentration of 500 pg/ml (approximately 2.5 nM) was reached. One hour later plasma adrenaline had returned to undetectable levels. During swimming, adrenaline was released into the plasma in concentrations up to 133 pg/ml and the noradrenaline concentration was markedly enhanced as well. The total catecholamine increase amounted to 178% of control (saline infusion) in the first 3 min of swimming and 165% for the whole 20 min. Cocaine (2.5 mg/kg plus 0.05 mg/kg/min), infused together with adrenaline and continued throughout the experiment, prevented the exercise-induced release of adrenaline and no increase in plasma noradrenaline concentration was observed. Yohimbine (0.25 mg/kg) strongly further enhanced the exercise-induced overflow of both noradrenaline and adrenaline. This further increase was completely blocked by the selective beta 2-adrenoceptor antagonist ICI 118,551 ((+/-)-1-[(2,3-dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methyleth yl) amino]-2-butanol) (1.0 mg/kg). These results demonstrate that adrenaline can be taken up by sympathetic nerve endings through cocaine-sensitive uptake carriers and is released from these nerves during swimming exercise. Neuronally released adrenaline markedly enhances exercise-induced catecholamine overflow through activation of prejunctional beta 2-adrenoceptors.

Light scattering and absorption caused by bacterial activity in water

There is a growing class of elementary particle detectors, large-water Čerenkov detectors, that have a body of water (thousands of tons) as a sensitive medium. Particles are detected when they interact with the water and produce Čerenkov light, so detection efficiency relies on the transparency of the water. These detectors are active typically for many years, so biological activity (primarily bacterial growth) is one of the means by which the transparency of the water may be reduced. We present the results of a measurement of light scattering and absorption from a population of Escherichia coli in water, which is used as a model for bacteria in general. One can separate the scattering and absorption by varying the refractive index of the medium by using a solute of high molecular weight. We show that the results can be understood simply in terms of light scattering from small spheres (radius ≈ wavelength) with an effective refractive index, n(b), plus a small amount of absorption in the ultraviolet. We compare his scattering with Rayleigh scattering in pure water.

Characterization of mutants of Caulobacter crescentus defective in surface attachment of the paracrystalline surface layer

Strains of Caulobacter crescentus express a paracrystalline surface layer (S-layer) consisting of the protein RsaA. Mutants of C. crescentus NA1000 and CB2, isolated for their ability to grow in the absence of calcium ions, uniformly no longer had the S-layer attached to the cell surface. However, RsaA was still produced, and when colonies grown on calcium-sufficient medium were examined, large two-dimensional arrays of S-layer were found intermixed with the cells. Such arrays were not found in calcium-deficient medium even when high levels of magnesium ions were provided. The arrays could be disrupted with divalent ion chelators and more readily with the calcium-selective ethylene glycol-bis (beta-aminoethyl ether)N,N,N',N'-tetraacetic acid (EGTA). Thus, the outer membrane surface was not needed as a template for self-assembly, but calcium likely was. The cell surface and S-layer gene of assembly-defective mutants of NA1000 were examined to determine the basis of the S-layer surface attachment defect. Mutants had no detectable alteration in the rough lipopolysaccharide (LPS) or a characterized capsular polysaccharide, but another polysaccharide molecule was greatly reduced or absent in all calcium-independent mutants. The molecule was shown to be a smooth LPS with a core sugar and fatty acid complement identical to those of the rough LPS and an O polysaccharide of homogeneous length, tentatively considered to be composed of 4,6-dideoxy-4-amino hexose, 3,6-dideoxy-3-amino hexose, and glycerol in equal proportions. This molecule (termed SLPS) was detectable by surface labeling with a specific antiserum only when the S-layer was not present. The rsaA genes from three calcium-independent mutants were cloned and expressed in an S-layer-negative, SLPS-positive strain. A normal S-layer was produced, ruling out defects in rsaA in these cases. It is proposed that SLPS is required for S-layer surface attachment, possibly via calcium bridging. The data support the possibility that calcium binding is required to prevent an otherwise lethal effect of SLPS. If true, mutations that eliminate the O polysaccharide of SLPS eliminate the lethal effects of calcium-deprived SLPS, at the expense of S-layer attachment.

Sustained prejunctional facilitation of noradrenergic neurotransmission by adrenaline as a co-transmitter in the portal vein of freely moving rats

1. The duration of the facilitatory effect of adrenaline on the electrically evoked overflow of noradrenaline was studied in the portal vein of permanently adreno-demedullated freely moving rats. 2. Rats were infused with adrenaline (20 or 100 ng min-1) for 2 h. After an interval of 1 h, when plasma adrenaline had returned to undetectable levels, electrical stimulation resulted in an enhanced catecholamine overflow amounting to 219% (noradrenaline) and 241% (noradrenaline plus adrenaline) of control (saline infusion), respectively. 3. When stimulation was applied again, in the same animal, at 24, 48 and 72 h after the first stimulation episode, the evoked noradrenaline overflow was 150, 111 and 102% (after 20 ng ml-1 adrenaline) and 158, 134 and 105% (after 100 ng min-1 adrenaline) of control. 4. The beta 2-adrenoceptor antagonist, ICI 118,551 (0.3 mg kg-1), blocked the facilitatory effect obtained after the 100 ng min-1 adrenaline infusion on all days. 5. The results show that adrenaline, after being taken up by and released from sympathetic nerve terminals, is able to facilitate the evoked noradrenaline overflow through activation of prejunctional beta 2-adrenoceptors for at least 48 h after administration.

Alkaline phosphatase and a cellulase reporter protein are not exported from the cytoplasm when fused to large N-terminal portions of the Caulobacter crescentus surface (S)-layer protein

Using a gene fusion approach, hybrid proteins were created by linking alkaline phosphatase (PhoA) or a cellulase reporter (delta CenA) to four large N-terminal portions of the Caulobacter crescentus surface (S)-layer protein (RsaA; 1026 amino acids). Three of the sites (amino acids 189, 220, 315) were selected on the basis of TnphoA experiments that suggested the first 250-350 amino acids of RsaA could mediate export of PhoA from the cytoplasm while the fourth lay only 21 amino acids from the C-terminus. Expression of all fusions except rsaA(315):delta cenA and rsaA(315):phoA was toxic to C. crescentus. None of the gene fusions were toxic when expressed by Escherichia coli DH5 alpha, where all the hybrid proteins accumulated as inclusion bodies. The toxicity of hybrid proteins encoding 189, 220, and 1005 RsaA-derived amino acids was related to the nature of the hybrid protein itself because truncated RsaA peptides lacking their reporter domains were nontoxic. Further study of RsaA(delta C21) showed that this and presumably other truncated RsaA derivatives were neither secreted nor prone to intracellular accumulation. Although C. crescentus tolerated the expression of rsaA(315):delta cenA and rsaA(315):phoA, the encoded hybrid proteins were not exported in significant quantities from the cytoplasm. These results extend and confirm earlier work that large portions of the S-layer protein N-terminus cannot mediate export of passenger proteins from the cytoplasm and that the entire native S-layer protein may be required to properly interact with the RsaA secretion machinery.

Heterogeneity of prejunctional neuropeptide Y receptors inhibiting noradrenaline overflow in the portal vein of freely moving rats

The effects of intraportal infusions of different doses of neuropeptide Y, its selective neuropeptide Y Y1 receptor analogue, [Leu31,Pro34]neuropeptide Y, and the Y2-selective C-terminal fragment, neuropeptide Y-(18-36), on basal and electrically evoked noradrenaline overflow in the portal vein as well as on mean arterial pressure and heart rate were investigated in permanently instrumented freely moving rats. Neuropeptide Y dose dependently (2-2000 ng/kg/min) attenuated the electrically evoked noradrenaline overflow and almost complete blockade was reached at the highest dose used. [Leu31,Pro34]Neuropeptide Y also dose dependently (20-20,000 ng/kg/min) attenuated the evoked overflow, reaching a maximum of 55% inhibition at the highest dose (20,000 ng/kg/min). Neuropeptide Y-(18-36) attenuated the evoked release only at 20,000 ng/kg/min (by 46%). Only at the highest dose did neuropeptide Y (2000 ng/kg/min) and [Leu31,Pro34]neuropeptide Y (20,000 ng/kg/min) significantly enhance mean arterial pressure and decrease heart rate and basal plasma noradrenaline levels, the latter two effects being due to the baroreceptor reflex. Neuropeptide Y-(18-36) did not influence these parameters at all doses used. The results indicate the presence of prejunctional neuropeptide Y Y1 receptors, and possibly the coexistence of Y1 and Y2 receptors, in the portal vein of freely moving rats, which in conjunction are able to inhibit markedly electrically evoked noradrenaline overflow. Postjunctional neuropeptide Y receptors mediating an increase in blood pressure in the freely moving rat are solely of the Y1 subtype.

The Caulobacter crescentus holdfast: identification of holdfast attachment complex genes

Caulobacters are biofilm bacteria that attach to surfaces via a holdfast, an adhesive expressed at discrete cell surface sites. We have described a cluster of at least three genes involved in the adhesive attachment of the holdfast of Caulobacter crescentus CB2A to the cell, analyzing the sequence of two genes, hfaAB. Here we report hfaC and a fourth open reading frame, hfaD. hfaC predicts a protein of 41 kDa homologous to ATP-binding transport-related proteins, with ChvD of Agrobacterium tumefaciens as best match. HfaD is predicted to be 28 kDa with three membrane spanning regions. hfaA, hfaC, and hfaD were expressed in Escherichia coli; Western analysis with antisera against a holdfast-enriched preparation indicated HfaA was likely holdfast-associated. Cumulative findings predict HfaA and HfaB are developmentally regulated and one or both enhance hfaC transcription, HfaA is a mediator of adhesion, possibly between holdfast and a membrane-bound HfaD, and HfaC mediates export of an unidentified component required for holdfast attachment.

Identification of genes affecting production of the adhesive holdfast of a marine caulobacter

Caulobacters are stalked bacteria that produce a structure termed a holdfast which enables firm attachment to surfaces. Tn5 insertion mutagenesis was used to identify genes affecting holdfast production or function in the marine strain MCS6. Twelve thousand Tn5 insertion mutants were screened for adhesion defects by an assay involving the attachment of cells to polystyrene microtiter dish wells. Among adhesion-defective mutants, those with multiple polar (pleiotropic) defects were excluded and the remainder were examined for the presence of holdfast. Forty-one mutants that produced no detectable holdfast or a significantly reduced amount were found. Southern blot and pulsed-field gel electrophoresis analyses indicated that 11 unique Tn5 insertions were clustered in three regions of the genome. In addition, 71 mutants that adhered poorly or not at all to polystyrene, yet still produced a holdfast, were found. Southern blot and pulsed-field gel electrophoresis analyses of 15 of these mutants showed eight unique Tn5 insertion sites clustered in two additional regions of the genome. An assay involving attachment to glass treated with siloxane chemicals (producing surfaces with varying degrees of hydrophobicity or hydrophilicity) was used to attempt characterization of this phenotype. Unexpectedly, no simple pattern of differences in binding between the mutants and wild-type caulobacters was found. In particular, no reduction in the ability of the mutants to bind to hydrophobic surfaces was noted. Complementation with cosmid clones was successful in nearly all cases and confirmed the designation of five genomic regions of holdfast-related genes. No detectable cross-hybridization was observed with several holdfast-related gene regions from a freshwater caulobacter, providing further evidence that the marine and freshwater caulobacters are genetically distinct.

Strong activation of vascular prejunctional beta 2-adrenoceptors in freely moving rats by adrenaline released as a co-transmitter

The effect of adrenaline on the electrically evoked noradrenaline overflow in the portal vein of adrenal demedullated freely moving rats was studied. Adrenaline (100 ng/min) was infused for 2 h into the portal vein. After a 1-h interval when plasma adrenaline had returned to pre-infusion undetectable levels, the portal vein nervus plexus was electrically stimulated. During stimulation (2 Hz, 3 ms, 5 mA) adrenaline and noradrenaline were released. The stimulus-evoked noradrenaline overflow was facilitated to 194% of the control-evoked overflow (infusion of saline). Total catecholamine overflow (noradrenaline plus adrenaline) was enhanced to 258%. The facilitation of the evoked overflow of both noradrenaline and adrenaline was blocked by the selective beta 2-adrenoceptor antagonist, ICI 118,551 (0.3 mg/kg). Cocaine (2.5 mg/kg plus 0.05 mg/kg per min) infused together with adrenaline prevented the evoked release of adrenaline and no facilitation of the stimulus-induced noradrenaline overflow occurred. Inhibition of prejunctional inhibitory alpha 2-adrenoceptors with yohimbine (0.5 mg/kg) further enhanced, to 577%, the electrically evoked catecholamine overflow after adrenaline infusion. The results demonstrate that adrenaline can be taken up by sympathetic nerve endings through cocaine-sensitive uptake carriers, and is released from these nerves during electrical stimulation of the portal vein nervus plexus. Neuronally released adrenaline can strongly facilitate electrically evoked neurotransmitter overflow through activation of prejunctional beta 2-adrenoceptors.

Successful foscarnet therapy for acyclovir-resistant mucocutaneous infection with herpes simplex virus in a recipient of allogeneic BMT

A 41-year-old recipient of matched unrelated BMT acquired a severe mucocutaneous herpes simplex virus (HSV) type I infection during acyclovir prophylaxis. He was subsequently treated with high-dose acyclovir, but the HSV infection continued. In vitro analysis of the HSV isolate, obtained before and after the administration of high-dose acyclovir, demonstrated marked resistance to acyclovir but sensitivity to the antiviral agent foscarnet. The mucocutaneous HSV infection healed completely to a 16 day course of foscarnet. However, relapse of the acyclovir-resistant HSV infection occurred 202 days after the first foscarnet treatment but he responded again to a second foscarnet course. These data indicate that, with the rising frequency of acyclovir-resistant HSV infections observed in immunocompromised hosts, viral isolates should be tested for susceptibility to different antiviral drugs in recipients of BMT with recurrent or persistent HSV infections.

An "all-purpose" cellulase reporter for gene fusion studies and application to the paracrystalline surface (S)-layer protein of Caulobacter crescentus

The secreted endoglucanase (CenA) from the Gram-positive bacterium Cellulomonas fimi and a deletion derivative (delta CenA) lacking the N-terminal leader peptide of native CenA were used to explore the potential of delta CenA as a reporter molecule in Caulobacter crescentus. Expression of cenA in C. crescentus yielded extracellular endoglucanase activity, suggesting that the N-terminal leader peptide of CenA could direct the enzyme to the periplasm where it subsequently leaked into the medium. In contrast, expression of delta cenA yielded only cell-associated endoglucanase activity; this suggested that the enzyme retained activity in the C. crescentus cytoplasm. Using the putative cytoplasmic and periplasmic forms of delta CenA as markers, a simple assay for periplasmic delta CenA hybrids was developed. This assay indicated that delta CenA activity was largely independent of cellular location. To facilitate the use of delta CenA as a reporter, a broad host range translational fusion vector (pEC215) incorporating delta cenA was constructed. This vector was used to investigate factors important to the expression of the gene (rsaA) encoding the paracrystalline surface protein (S-layer) of the bacterium. It was found that altering the 5' untranslated region of the rsaA mRNA reduced gene expression by 70%. One rsaA:delta cenA gene fusion resulting from these experiments that incorporated only rsaA translation initiation information was further modified to serve as a general reporter for creating transcriptional gene fusions with other promoters. Gene fusions between alkaline phosphatase (phoA) and either cenA or lacZ were used to supplement information about RsaA secretion derived from rsaA:phoA gene fusions. It was found that linkage of the N-terminal leader peptide of CenA to PhoA yielded 50-100 times more cell-associated PhoA activity in C. crescentus than linkage of the RsaA N terminus. Taken together, these experiments indicated that delta CenA was useful for tagging proteins localized to the cytoplasm, exported to the periplasm, or secreted from the cell, as well as for monitoring events in the cytoplasm such as examining factors important to the level of gene expression. Further, because delta CenA was active in all cell compartments, it could be used to estimate the efficiency of hybrid protein export-secretion from enzyme activity measurements alone. In short, delta CenA possessed many of the attributes of an "all-purpose" reporter.

Root growth and water use efficiency of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine (Pinus contorta Dougl.) seedlings

One-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and lodgepole pine (Pinus contorta Dougl.) seedlings were grown for 17 weeks in 100-cm deep, 7.8-liter containers. Two Douglas-fir provenances, one from a wet and one from a dry site in coastal British Columbia, and two lodgepole pine provenances, one from a wet and one from a dry site in interior British Columbia, were grown in wet (522% water content) or dry (318% water content) peat/vermiculite soil in a factorial design. Each container was sealed so that water loss occurred only through the seedling. Five harvests were made at three to five week intervals and water use, dry matter increment, root length and root weight were determined at each harvest. Stomatal conductance and shoot water potentials were measured during the last 12 weeks of the experiment. Lodgepole pine seedlings had greater dry matter production, water use, stomatal conductance and new root length than Douglas-fir seedlings. New root weight of lodgepole pine seedlings exceeded that of Douglas-fir seedlings during the last five weeks of the experiment, and specific root length (root length per unit root weight) of new roots was higher for lodgepole pine seedlings throughout the experiment. Douglas-fir seedlings showed higher water use efficiency (WUE) than lodgepole pine seedlings, and both species showed higher WUE in the dry soil treatment. Douglas-fir seedlings had lower water potentials and higher water uptake rates per unit of new root length than lodgepole pine seedlings, although water uptake rates per unit of root dry weight showed little difference between species. Soil water treatment influenced specific root length of new roots, water uptake per unit of new root length, and WUE in Douglas-fir seedlings more than in lodgepole pine seedlings.

Identification, isolation, and structural studies of the outer membrane lipopolysaccharide of Caulobacter crescentus

The lipopolysaccharide (LPS) of the outer membrane of Caulobacter crescentus was purified and analyzed. Two distinct strains of the species, NA 1000 and CB2A, were examined; despite differences in other membrane-related polysaccharides, the two gave similar LPS composition profiles. The LPS was the equivalent of the rough LPS described for other bacteria in that it lacked the ladder of polysaccharide-containing species that results from addition of variable amounts of a repeated sequence of sugars, as detected by gel electrophoresis in smooth LPS strains. The purified LPS contained two definable regions: (i) an oligosaccharide region, consisting of an inner core of three residues of 2-keto-3-deoxyoctonate, two residues of alpha-L-glycero-D-mannoheptose, and one alpha-D-glycero-D-mannoheptose unit and an outer core region containing one residue each of alpha-D-mannose, alpha-D-galactose, and alpha-D-glucose, with the glucose likely phosphorylated and (ii) a region equivalent to the lipid A region of the archetype, consisting primarily of an esterified fatty acid, 3-OH-dodecanoate. The lipid A-like region was resistant to conclusive analysis; in particular, although a variety of analytical methods were used, no amino sugars were detected, as is found in the lipid A of the LPS of most bacteria.

The S-layer of Caulobacter crescentus: three-dimensional image reconstruction and structure analysis by electron microscopy

The regular surface protein structure (S-layer) of Caulobacter crescentus was analyzed by electron microscopy and three-dimensional image reconstruction to a resolution of 2 nm. Projections showed that the S-layer is an array of ring structures, each composed of six subunits that are arranged on a lattice with p6 symmetry. Three-dimensional reconstructions showed that the ring subunits were approximately rod-shaped structures and were perpendicular to the plane of the array, with a linker arm emanating from approximately the middle of the rod, accounting for the connections between the rings. The calculated subunit mass was ca. 100 kDa, very close to the size of RsaA (the protein known to be at least the predominant species in the S-layer) predicted from the DNA sequence of the rsaA gene. The core region of the rings creates an open pore 2.5 to 3.5 nm in diameter. The size of the gaps between the neighboring unit cells is in the same range, suggesting a uniform porosity predicted to exclude molecules larger than ca. 17 kDa. Attempts to remove membrane material from S-layer preparations with detergents revealed that the structure spontaneously rearranged into a mirror-image double layer. Negative-stain and thin-section electron microscopy examination of colonies of C. crescentus strains with a mutation in a surface molecule involved in the attachment of the S-layer showed that shed RsaA protein organized into large sheets. The sheets in turn organized into stacks that tended to accumulate near the upper surface of the colony. Image reconstruction indicated that these sheets were also precise mirror-image double layers, and thickness measurements obtained from thin sections were consistent with this finding. The sheets were absent when these mutant strains were grown without calcium, supporting other data that calcium is involved in attachment of the S-layer to a surface molecule and perhaps in subunit-subunit interactions. We propose that when the membrane is removed from S-layer fragments by detergents or the attachment-related surface molecule is absent, the attachment sites of the S-layer align precisely to form a double layer via a calcium interaction.

Coeval 40Ar/39Ar Ages of 65.0 Million Years Ago from Chicxulub Crater Melt Rock and Cretaceous-Tertiary Boundary Tektites

(40)Ar/(39)Ar dating of drill core samples of a glassy melt rock recovered from beneath a massive impact breccia contained within the 180-kilometer subsurface Chicxulub crater in Yucatán, Mexico, has yielded well-behaved incremental heating spectra with a mean plateau age of 64.98 +/- 0.05 million years ago (Ma). The glassy melt rock of andesitic composition was obtained from core 9 (1390 to 1393 meters) in the Chicxulub 1 well. The age of the melt rock is virtually indistinguishable from (40)Ar/(39)Ar ages obtained on tektite glass from Beloc, Haiti, and Arroyo el Mimbral, northeastern Mexico, of 65.01 +/- 0.08 Ma (mean plateau age for Beloc) and 65.07 +/- 0.10 Ma (mean total fusion age for both sites). The (40)Ar/(39)Ar ages, in conjunction with geochemical and petrological similarities, strengthen the recent suggestion that the Chicxulub structure is the source for the Haitian and Mexican tektites and is a viable candidate for the Cretaceous-Tertiary boundary impact site.

Proximal impact deposits at the Cretaceous-Tertiary boundary in the Gulf of Mexico: a restudy of DSDP Leg 77 Sites 536 and 540

Restudy of Deep Sea Drilling Project Sites 536 and 540 in the southeast Gulf of Mexico gives evidence for a giant wave at Cretaceous-Tertiary boundary time. Five units are recognized: (1) Cenomanian limestone underlies a hiatus in which the five highest Cretaceous stages are missing, possibly because of catastrophic K-T erosion. (2) Pebbly mudstone, 45 m thick, represents a submarine landslide possibly of K-T age. (3) Current-bedded sandstone, more than 2.5 m thick, contains anomalous iridium, tektite glass, and shocked quartz; it is interpreted as ejecta from a nearby impact crater, reworked on the deep-sea floor by the resulting tsunami. (4) A 50-cm interval of calcareous mudstone containing small Cretaceous planktic foraminifera and the Ir peak is interpreted as the silt-size fraction of the Cretaceous material suspended by the impact-generated wave. (5) Calcareous mudstone with basal Tertiary forams and the uppermost tail of the Ir anomaly overlies the disturbed interval, dating the impact and wave event as K-T boundary age. Like Beloc in Haiti and Mimbral in Mexico, Sites 536 and 540 are consistent with a large K-T age impact at the nearby Chicxulub crater.

The phylogeny of marine and freshwater caulobacters reflects their habitat

Caulobacter is a distinctive genus of prosthecate bacteria. Because caulobacters adhere to surfaces and are found in diverse locales, their role in oligotrophic environments and bacterial biofilm communities is of interest. The phylogenetic relationships of a group of marine and freshwater caulobacters were examined in part to address whether the taxonomic grouping of these bacteria (based primarily on morphological characters) was consistent with 16S rRNA sequence divergence. The caulobacters examined (9 marine and 11 freshwater species or strains) were affiliated with the alpha proteobacteria. They made up a diverse yet, with the possible exception of a strain of Caulobacter subvibrioides, coherent assemblage. The diversity was most apparent in a comparison of freshwater and marine isolates; an early divergence within the main caulobacter lineage generally corresponded to strains isolated from freshwater and marine habitats. The marine caulobacter assemblage was not exclusive; it also embraced strains of marine hyphomonads and Rhodobacter capsulatus. We hypothesize that these genera are derived from more ancestral caulobacters. Overall, the data are consistent with the interpretation that all of the caulobacters examined, with the possible exception of C. subvibrioides, are ancestrally related, albeit anciently, and that most often division by terrestrial and marine habitats corresponds to an early evolutionary divergence within the genus.