The virulence plasmid of Salmonella dublin: detailed restriction map and analysis by transposon mutagenesis

A detailed restriction map of the virulence plasmid of Salmonella dublin has been determined and used for comparison with the virulence plasmid from S. typhimurium. Two regions were identified which appeared to be similar based on blotting and restriction data. One, of about 22 kb, encompassed the virulence region; the other, of about 8 kb, was outside it. The locations of 259 transposon insertions on the S. dublin plasmid were determined and related to their effect on virulence. One gene involved in virulence but outside the essential virulence region was shown to affect citrate metabolism.     

Testicular development and maturation of the hypothalamic-pituitary-testicular axis in the male tammar, Macropus eugenii

Testicular growth and maturation of the hypothalamic-pituitary-testicular axis were assessed in male tammars from 12 to 25 months of age to establish the time of sexual maturity. The testicular dimensions and body weights of 20 male tammars, approximately 12 months of age at the beginning of the study, were measured monthly for 1 year. Groups of 3 animals were castrated at 13, 19 and 25 months of age and their testes sectioned for histological examination. Testicular volume increased between 12 and 24 months of age and was highly correlated with body weight (r = 0.91). In the 13-month group the seminiferous tubules were closed with few mitotic figures. Spermatogenesis had begun in 2 of the 19-month animals. All stages of spermatogenesis were present in the other 19-month male, and in all of the 25-month males. Basal FSH concentrations increased with the age of the animal (21.0 +/- 32.48, 94.40 +/- 55.18 and 193.05 +/- 40.21 ng/ml (mean +/- s.d.) at 19, 20 and 25 months respectively) while basal LH concentrations were similar at 20 months and 25 months (0.43 +/- 0.18 and 0.58 +/- 0.25 ng/ml respectively). Basal testosterone concentrations were also similar 0.11 +/- 0.04, 0.35 +/- 0.16 and 0.22 +/- 0.10 ng/ml in 13-, 19- and 25-month-old animals. LHRH injection in tammars at 13, 19 and 25 months of age induced release of both LH and testosterone 10-30 min after injection. The hormone concentrations increased in both magnitude and duration with increasing age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Detection of a rare allele with the pMP6d-9/MspI RFLP near the cystic fibrosis locus

Summary We report a rare allele detected using pMP6d-9, a probe very closely linked to cystic fibrosis (CF), on digestion with MspI. This allele has been found in normal and CF chromosomes, and therefore cannot be related to the mutation causing the disease.     

Nucleotide sequence of the Rickettsia prowazekii ATP/ADP translocase-encoding gene

The Rickettsia prowazekii ATP/ADP translocase (Tlc) gene (tlc), previously cloned in Escherichia coli was localized to a 1.6-kb chromosomal fragment. Nucleotide sequence analysis of this fragment revealed an open reading frame of 1494 bp that could encode a hydrophobic protein of 497 amino acids (aa) with an M_r of 56 668. Analysis of the deduced aa sequence revealed that it contained twelve potential membrane-spanning regions. Comparisons between the deduced aa sequence of the R. prowazekii ATP/ADP Tlc and the sequences of mitochondrial (mt) Tic revealed no detectable homologies between the rickettsial and mt sequences. The major protein synthesized in E. coli minicells containing the rickettsial gene exhibited an M_r of approx. 34000.     

Increased regional vascular albumin permeation in the rat during anaphylaxis

The changes in vascular albumin permeation induced by systemic anaphylaxis were studied simultaneously in 21 different tissues of the same animal. Before Ag challenge sensitized rats were injected i.v. with 125I-albumin (test tracer), 51Cr-RBC (vascular space marker) and 57Co-EDTA (extravascular space marker). The index of vascular permeation used was the tissue to blood isotope ratio (tbir), which was obtained by dividing the ratio of 125I/51Cr counts in each tissue by the ratio of the same isotopes in the arterial blood sample. After Ag challenge, the increase in the tbir varied considerably among the different tissues. The most pronounced increase was noted in the lymph node (ninefold) followed by the aorta and mesentery (six- to sevenfold) and the various parts of the gastrointestinal tract (four- to sixfold). In the skin less than skeletal muscle less than lung less than liver and eye two- to fourfold increases occurred. Relatively minor increases in albumin permeation (less than twofold) were observed in the brain less than kidney less than heart and less than spleen. The testis was the only organ in which no significant change occurred. For some of the tissues there was also an increase in the tbir for 57Co/51Cr (an index of the extracellular fluid space) suggesting edema formation. The highest increase was noted in the aorta (fourfold). Minor increases occurred in the atrium of the heart, stomach, duodenum, and lymph nodes. There was also a 36% increase in hematocrit. Therefore, systemic anaphylaxis caused extensive extravasation of albumin and hemoconcentration.     

Molecular genetic study of the frequency of monosomy 22q11 in DiGeorge syndrome

It is well established that DiGeorge syndrome (DGS) may be associated with monosomy of 22q11-pter. More recently, DNA probes have been used to detect hemizygosity for this region in patients with no visible karyotypic abnormality. However, DGS has also been described in cases where the cytogenetic abnormality does not involve 22q11; for instance, four cases of 10p- have been reported. In this study we have prospectively analyzed patients, by using DNA markers from 22q11, to assess the frequency of 22q11 rearrangements in DGS. Twenty-one of 22 cases had demonstrable hemizygosity for 22q11. Cytogenetic analysis had identified interstitial deletion in 6 of 16 cases tested; in 6 other cases no karyotype was available. When these results are combined with those from our previous studies, 33 of 35 DGS patients had chromosome 22q11 deletions detectable by DNA probes.     

Metabolism of halogenated bisphosphonates by the cellular slime mould Dictyostelium discoideum.

Methylenebisphosphonate and its monofluoro-, difluoro- and dichloro- derivatives inhibited growth of amoebae of Dictyostelium discoideum. Dichloromethylenebisphosphonate was the most potent inhibitor of amoebal growth whereas difluoromethylenebisphosphonate was the least potent inhibitor. Each of the bisphosphonates was taken up by the amoebae and incorporated into the corresponding beta, gamma-methylene analogue of adenosine triphosphate. Two of the bisphosphonates were also incorporated into the corresponding analogues of diadenosyl tetraphosphate. No correlation was found between the ability of the bisphosphonates to inhibit amoebal growth and the extent to which they were metabolised.     

Releasing genetically engineered plants: Present proposals and possible hazards

Worldwide the majority of current proposals to release genetically modified organisms concern plants; most are for small changes in common crop plants and present little apparent hazard. However, there is much confusion about how plants become pests, and implausible risk factors are appearing in the literature and before committees. It is dangerous to estimate the risks from first principles because of the immaturity of plant population biology and the lack of empirical data. Regulatory agencies should concentrate on obtaining realistic assessment of hazards, and not attempt to balance notional benefits and disbenefits.     

Recombination associated with replication of malarial mitochondrial DNA.

Mitochondrial DNA of the malarial parasite Plasmodium falciparum comprises approximately 20 copies per cell of a 6 kb genome, arranged mainly as polydisperse linear concatemers. In synchronous blood cultures, initiation of mtDNA replication coincides with the start of the 4-5 doublings in nuclear DNA that mark the reproductive phase of the erythrocytic cycle. We show that mtDNA replication coincides with a recombination process reminiscent of the replication mechanism used by certain bacteriophages and plasmids. The few circular forms of mtDNA which are also present do not replicate by a theta mechanism, but are themselves the product of recombination, and we propose they undergo rolling circle activity to generate the linear concatemers.     

Improved Cultivation Systems for Isolation of the Colorado Potato Beetle Spiroplasma

In North America, the Colorado potato beetle, Leptinotarsa decemlineata, is often infected with the host-specific, gut-inhabiting Colorado potato beetle spiroplasma (CPBS). CPBS is apparently a commensal, but it may be useful in biocontrol if it can be transformed to express an insect-lethal gene. Difficulty in cultivating the organism, however, has hindered the development of a suitable transformation system. In this study, we eliminated the need for coculturing CPBS with insect cells. CPBS was reliably isolated with the BBL Anaerobic GasPak Jar system (low redox, enhanced CO(inf2)), which was easier to use and less expensive than insect cell coculture methods. A further advantage is a reduction in contaminating insect cell components. Use of anaerobiosis should facilitate early-passage screening of isolates for extrachromosomal elements, for use in gene vector constructs. The unique spiral (decreasing amplitude of coils) morphology of CPBS was preserved by anaerobiosis. The use of low-pH (6.0 to 6.5) media allowed aerobic adaptation of CPBS to M1D and SP-4 broth media. These formulations permitted the first cultivation of CPBS on solid media, an accomplishment that will simplify the selection of molecular transformants. Potato beetles collected at four sites in Poland yielded CPBS strains similar to those previously obtained from populations in North America.