The phage T4 nrdB intron: a deletion mutant of a version found in the wild

Bacteriophage T4 possesses three self-splicing group I introns. Two of the three introns are mobile elements; the third, in the gene encoding a subunit of the phage nucleotide reductase (nrdB), is not mobile. Because intron mobility offers a reasonable explanation for the paradoxical occurrence of large intervening sequences in a space-efficient eubacterial phage, it is puzzling that the nrdB intron is not mobile like its compatriots. We have discovered a larger nrdB intron in a closely related phage, and we infer from comparative sequence data that the T4 intron is a deletion mutant derived from this larger intron. This larger nrdB intron encodes an open reading frame of 269 codons, which we have cloned and overexpressed. The overexpressed protein shows a dsDNA endonuclease activity specific for the intronless nrdB gene, typical of mobile introns. Thus, we believe that all three introns of T4 are or were mobile "infectious introns" and that they have entered into and been maintained in the phage population by virtue of this efficient mobility.     

Amphiphysin IIm, a novel amphiphysin II isoform, is required for macrophage phagocytosis

Phagocytosis of pathogens by macrophages initiates the innate immune response, which in turn orchestrates the adaptive immune response. Amphiphysin II participates in receptor-mediated endocytosis, in part, by recruiting the GTPase dynamin to the nascent endosome. We demonstrate here that a novel isoform of amphiphysin II associates with early phagosomes in macrophages. We have ablated the dynamin-binding site of this protein and shown that this mutant form of amphiphysin II inhibits phagocytosis at the stage of membrane extension around the bound particles. We define a signaling cascade in which PI3K is required to recruit amphiphysin II to the phagosome, and amphiphysin II in turn recruits dynamin. Thus, amphiphysin II facilitates a critical initial step in host response to infection.     

Human mini-chromosomes in mouse embryonal stem cells

We have introduced human mini-chromosomes of 4 Mb and approximately 15 Mb in size into mouse embryonal stem cells. Although these human mini- chromosomes are stable in hamster and chicken cells, they re-arrange or segregate aberrantly in the embryonal stem cells and are rapidly lost in the absence of selection. However, one of the mini-chromosomes re- arranged, acquired mouse centromeric sequences and was then stably maintained for at least 60 population doublings in culture. This mini- chromosome, which is 4 Mb in size, is a candidate for a mouse germ line chromosome vector.      

Determination of the parent of origin in nine cases of prenatally detected chromosome aberrations found after intracytoplasmic sperm injection

Prenatal cytogenetic analysis of 71 fetuses conceived by intracytoplasmic sperm injection (ICSI) resulted in the detection of nine (12.7%) chromosome aberrations including two cases of 47,XXY, four cases involving a 45,X cell line and three autosomal trisomies. Molecular analysis of the parental origin of the deleted or supernumerary chromosome was performed by using polymorphic microsatellite markers. Six cases involving a sex chromosome abnormality were found to be of paternal origin while the two trisomic cases that could be analysed were of maternal origin. Two cases involved the same infertile couple who had two consecutive ICSI pregnancies terminated because of a chromosome abnormality. The replaced embryos in both cases originated from a single batch of ICSI fertilized oocytes of which part was used to initiate the first pregnancy and part was cryopreserved and used to initiate the second pregnancy.      

Mitogenicity of Entamoeba histolytica extracts for murine lymphocytes.

Aqueous extracts or aqueous extracts of delipidated Entamoeba histolytica (E.h.e.) contain a mitogenic principle for murine lymphocytes. As detected by [3H]-thymidine incorporation and blast transformation, E.h.e. acted predominantly on T cells of splenic origin, but not on thymocytes or bone marrow cells. Furthermore, E.h.e. induced proliferation of a subset of non-T-cells which is present in the spleen of athymic nude mice, adhered to nylon wool, but could not be activated to produce antibody. It seems possible that polyclonal activation of lymphocytes by E. histolytica might play a role in the disturbance of the immune system as manifested in the impaired cell mediated immune response of E. histolytica infected hosts.     

Hypothalamic obesity following knife cuts that minimize arterial damage

Parasagittal knife cuts that separate the medial hypothalamus from the lateral hypothalamus produce obesity. It has been assumed that the obesity results from the cutting of axons. However, these cuts also appear to sever arteries. The present study demonstrates that the severing of arteries is not necessary for the production of obesity. Knife cuts were placed at an angle so as to separate the medial hypothalamus from the lateral hypothalamus with minimal damage to arteries. These rats overate and became obese just as rapidly as rats with parasagittal cuts.     

Antigenic and immunologic characterization of an allogeneic colon carcinoma vaccine

In the present prospective, census-based study we have investigated the prevalence of organ-specific and non-organ-specific autoantibodies (AAb) in 152 unselected Cameroonians aged 60 years and older living in the community. AAb were detected in 49% of the participants. Non-organ-specific AAb (47%) predominated over organ-specific AAb (7%). Anti-TPO, anti-Tm, anti-Tg and anti-PC AAb were completely absent. RF was the most frequent AAb, being found in 57 (38%) cases. The prevalences of anti-SMA and RF were significantly higher in women than in men (respectively, P=0.023 and P=0.016). Higher serum concentrations of gammaglobulins were accompanied by a higher prevalence of RF (P < 0.0001) and a lower prevalence of ANA (P=0.036). The overall prevalence of AAb was higher in the filaria-infected (60%) compared to the non-infected (42%) participants (P=0.046). There was no significant influence of the vitamin D status, number of pregnancies, physical activity or medication use on the prevalence of AAb. In this study a heterogeneous pattern for the presence of the various AAb was found. Some AAb, which are commonly encountered in other studies on elderly subjects, were completely absent in this population. This diversified pattern of AAb prevalence therefore argues in favour of exogenous influences in the occurrence of AAb in elderly populations.     

Glucose regulation of memory for reward reduction in young and aged rats

Although baseline blood glucose levels in aged Fischer-344 rats are comparable to those of young rats, the rise in blood glucose in response to training-related stress is substantially attenuated. The diminished response may contribute to increased depletion of extracellular brain glucose levels during training in aged rats; the depletion is blocked and memory is enhanced by systemic injections of glucose. The present experiment examined the role of glucose in regulating memory for reward reduction training. Blood glucose levels exhibited a significant rise after reward reduction trials in young adult but not 2-year-old rats. Although young and aged rats exhibited comparable learning during the day of reward reduction training, aged rats exhibited more rapid forgetting of the learning response. Post-training glucose injections (200 mg/kg, i.p.) facilitated memory formation and slowed the rate of forgetting in young and old rats, consistent with the view that deficiencies in circulating glucose responses to training may contribute to the rapid forgetting evident in aged Fischer-344 rats.     

Does ICSI affect early serum beta-HCG in pregnancies achieved after IVF?

This study was conducted to compare early serum human chorionic gonadotrophin (HCG) concentrations in singleton pregnancies achieved after intracytoplasmic sperm injection (ICSI), with those achieved after conventional in-vitro fertilization (IVF). Early serum HCG, 14-16 days after embryo transfer, was analysed in 99 IVF pregnancies achieved after ICSI (group A), and compared to 105 conventional IVF pregnancies (group B). All women were treated at the IVF Unit, Lis Maternity Hospital. Records were studied retrospectively. The mean +/- SE serum HCG concentration on day 14 after embryo transfer in group A was 190.5 +/- 17.4 mIU/ml, compared to 195.7 +/- 14.03 mIU/ml in group B. HCG concentration 14 days after embryo transfer in both groups A and B was higher in women with mechanical factor than in couples with male factor infertility or unexplained infertility (246 +/- 31.4, 183.3 +/- 16.4, 177.98 +/- 14.3 mIU/ml respectively). On the 16th day after embryo transfer, the HCG concentration increased, and the difference between the groups was maintained. Only in the subgroup of unexplained infertility did we find a difference in concentrations of HCG between ICSI and conventional IVF: on the 16th day following embryo transfer in this group there was a significant difference in HCG concentrations (395. 8 +/- 21 and 545.6 +/- 45.7 respectively; P = 0.04). HCG concentrations did not differ overall in the conventional IVF pregnancies compared with those achieved by ICSI. However, a statistical difference in early serum HCG concentrations was found in relation to the aetiology of infertility.