Effect of IFN-γ receptor gene deletion on vaccinia virus virulence

Summary.  Two vaccinia virus (VV) strains, WR and Praha, were selected for a study undertaken to determine whether the virus-encoded interferon-γ receptor (IFN-γR) plays any role in virus virulence. Both of the viruses expressed the B8R gene coding for IFN-γR in infected cell cultures. The nucleotide sequence of the Praha virus B8R gene was determined, and, when compared with the published sequence of the WR virus, it only displayed one silent nucleotide substitution. Mutants of the WR and Praha viruses with deleted B8R gene were constructed. In rabbits, skin lesions produced by the WR B8R-deleted mutants were smaller and tended to disappear earlier than those caused by wild-type WR virus. Similar results were obtained with both independently prepared WR B8R-deleted mutants. These data strongly suggested that the product of B8R gene did play a role in virus virulence. A similar comparison of the wild-type Praha virus and its mutant could not be done because of the very low virulence of the parental virus for rabbits. Received March 13, 2000 Accepted August 16, 2000     

Effects of adrenalectomy and gonadectomy on sex and stress-induced differences in bicuculline-induced convulsions

The effects of adrenalectomy, gonadectomy and combined adrenalectomy plus gonadectomy on the previously described sex-dependent anticonvulsive effect of swim stress were studied in rats. The convulsive signs (myoclonic twitch, generalized convulsions, tonic hindlimb extension) were produced by constant i.v. infusion of γ-aminobutyric acid_A (GABA_A) antagonist bicuculline, which started 15 min after termination of swim stress (10-min swim at 18–19°C). Adrenalectomy decreased the threshold doses of bicuculline producing the first myoclonic twitch and the onset of generalized convulsions only in females. In adrenalectomized females, but not in males, swim stress enhanced the threshold dose of bicuculline producing generalized convulsions, but, unlike in adrenal-intact animals, it failed to enhance the dose of bicuculline producing tonic hindlimb extension. In gonadectomized stressed and unstressed animals all sex differences disappeared, and swim stress enhanced in both sexes only the threshold doses of bicuculline producing tonic hindlimb extension. Adrenalectomized plus gonadectomized animals displayed clear sex differences in doses of bicuculline necessary to produce all the convulsive signs. In the same animals swim stress postponed, especially in females, the onset of the first myoclonic twitch and generalized convulsions, but not the onset of tonic hindlimb extension. In summary, our results suggest that hormones of the adrenal and gonadal glands are only partly responsible for decreased susceptibility, especially of female rats, to the GABA_A antagonist bicuculline. Moreover, they have demonstrated that stress produces a gender-specific anticonvulsive effect even in the animals completely deprived of steroid hormones of peripheral origin. Received: 4 June 1998 / Accepted: 11 June 1999     

Rapid diagnosis of parasitic diseases: current scenario and future needs

Background

Parasitic diseases are one of the world's most devastating and prevalent infections, causing millions of morbidities and mortalities annually. In the past, many of these infections have been linked predominantly to tropical or subtropical areas. Nowadays, however, climatic and vector ecology changes, a significant increase in international travel, armed conflicts, and migration of humans and animals have influenced the transmission of some parasitic diseases from ‘book pages’ to reality in developed countries. It has also been noted that many patients who have never travelled to endemic areas suffer from blood-borne infections caused by protozoa. In the light of existing knowledge, this new trend can be explained by the fact that in the process of migration a large number of asymptomatic carriers become a part of the blood bank donor and transplant donor populations. Accurate and rapid diagnosis represents the crucial weapon in the fight against parasitic infections.

Can a part of an inducer become incorporated into interferon?

Highly purified and concentrated interferons obtained from L cells or from mouse peritoneal leukocytes (MPL) after induction with³H-uridin labeled double-stranded RNA of f₂ phageE. coli (phage ds-RNA) were analysed by poly-acrylamide gel electrophoresis. A coincidence of the discrete radioactivity peak with one of the interferon activity peaks was demonstrated.     

Distribution of putative adhesins in different seropathotypes of Shiga toxin-producing Escherichia coli

The distribution of eight putative adhesins that are not encoded in the locus for enterocyte effacement (LEE) in 139 Shiga toxin-producing Escherichia coli (STEC) of different serotypes was investigated by PCR. Five of the adhesins (Iha, Efa1, LPF(O157/OI-141), LPF(O157/OI-154), and LPF(O113)) are encoded in regions corresponding to genomic O islands of E. coli EDL933, while the other three adhesins have been reported to be encoded in the STEC megaplasmid of various serotypes (ToxB [O157:H7], Saa [O113:H21], and Sfp [O157:NM]). STEC strains were isolated from humans (n = 54), animals (n = 52), and food (n = 33). They were classified into five seropathotypes (A through E) based on the reported occurrence of STEC serotypes in human disease, in outbreaks, and in the hemolytic-uremic syndrome (M. A. Karmali, M. Mascarenhas, S. Shen, K. Ziebell, S. Johnson, R. Reid-Smith, J. Isaac-Renton, C. Clark, K. Rahn, and J. B. Kaper, J. Clin. Microbiol. 41:4930-4940, 2003). The most prevalent adhesin was that encoded by the iha gene (91%; 127 of 139 strains), which was distributed in all seropathotypes. toxB and efa1 were present mainly in strains of seropathotypes A and B, which were LEE positive. saa was present only in strains of seropathotypes C, D, and E, which were LEE negative. Two fimbrial genes, lpfA(O157/OI-141) and lpfA(O157/OI-154), were strongly associated with seropathotype A. The fimbrial gene lpfA(O113) was present in all seropathotypes except for seropathotype A, while sfpA was not present in any of the strains studied. The distribution of STEC adhesins depends mainly on serotypes and not on the source of isolation. Seropathotype A, which is associated with severe disease and frequently is involved in outbreaks, possesses a unique adhesin profile which is not present in the other seropathotypes. The wide distribution of iha in STEC strains suggested that it could be a candidate for vaccine development.     

Comparative studies on intestine ultrastructure of third-stage larvae and adults of Cystidicoloides ephemeridarum (Nematoda, Cystidicolidae)

The intestinal epithelium of third-stage larvae and adults of Cystidicoloides ephemeridarum from haemocoel of mayflies and stomach of brown trout was studied by electron microscopy and cytochemistry. In section, the intestine of both stages is composed of a single layer of about ten undifferentiated intestinal cells in a ring. A labyrinth of deep invaginations is present in the basal region of each cell. The apical surface is modified into well developed, regularly arranged microvilli. These, together with numerous organelles engaged in metabolism and a well defined gut lumen filled with unidentifiable material suggest that the intestine may function in digestion and absorption during both stages. The adults seem to feed upon the semifluid content of the stomach of brown trout. Fortuitous oral infection with undetermined bacteria in vitro led to degenerative changes in the intestinal tissue and probably caused death of the infected specimens. Up to 75% of the cell volume in the L₃ is occupied by glycogen deposits. In the adults, a minor portion of glycogen, together with lipid droplets, has been observed. The adults are considered to rely more on aerobic metabolism, whereas anaerobic metabolism (glycolysis) may prevail in L₃.     

Adenovirus type 12 tumor antigen. II. Immunoprecipitation of protein kinase from infected and transformed cells by antisera to T antigen and some normal rat sera.

Protein kinase was found to be precipitated from adenovirus type 12 (Ad12)-infected KB cells and Ad12-transformed hamster cells by sera of tumor-bearing hamsters and rats: Immunoprecipitates obtained with T antigen reactive sera catalyzed transfer of ³²P from [γ-³²P]ATP to the γ-chain of IgG. Analogous products of control cells were without significant activity. Control hamster sera precipitated no protein kinase from infected and transformed cells. Some control rat sera (syngeneic with immune sera), however, were found to precipitate protein kinase from infected and transformed cells; particularly active in this respect were sera of female breeder rats. When partially purified, highly immunoreactive T antigen preparations from transformed cells were used as a source of enzymatic activity, protein kinase was detected only in precipitates obtained with immune sera.     

Telomeric and interstitial telomeric sequences in holokinetic chromosomes of Lepidoptera: Telomeric DNA mediates association between postpachytene bivalents in achiasmatic meiosis of females

Telomeres, besides their main role in the protection and maintenance of chromosome ends, have several other vital functions in the cell cycle. We studied their role in the achiasmatic meiosis of female Lepidoptera, insects with holokinetic chromosomes. By fluorescence in-situ hybridization (FISH) with the insect telomeric probe, (TTAGG) _n , we mapped the distribution of telomeric and interstitial telomeric sequences (ITS) in female meiotic chromosomes of two species, Orgyia antiqua with a reduced chromosome number (2n=28) and Ephestia kuehniella mutants, possessing a radiation-induced chromosome fusion in the genome (2n=59). In addition to the strong typical telomeric signals, O. antiqua displayed weaker hybridization signals in interstitial sites of pachytene bivalents. The observed ITS most probably reflect remnants of chromosomal rearrangements and support the hypothesis that the Orgyia karyotype had arisen by multiple fusions of ancestral chromosomes. On the other hand, the absence of ITS in the chromosome fusion of Ephestia indicated the loss of telomeres before the two original chromosomes fused. When the telomeric probe was amplified by enzymatic reaction with tyramid, the number of ITS observed increased in Orgyia, and a few ITS were also observed in several chromosomes of Ephestia but not in the fused chromosome. This suggests that the genomes of both species also contain ITS other than those originating from chromosome fusions. The analysis of female meiotic prophase I revealed non-homologous associations of postpachytene bivalents mediated by telomeric DNA, which were not observed in the pachytene stage. Surprisingly, in early postpachytene nuclei the telomeric associations also involved ITS, whereas later postpachytene nuclei displayed chains of bivalents interconnected only by true telomeres. This finding favours a hypothesis that telomeric associations between bivalents play a role in chromosome segregation in the achiasmatic meiosis of female Lepidoptera. This revised version was published online in July 2006 with corrections to the Cover Date.