Insulin-specific T cell hybridomas derived from (H-2b x H-2k)F1 mice preferably employ F1-unique restriction elements for antigen recognition

T cell hybridomas of (B10 X B10.BR)F1 genotype with reactivity to bovine insulin (BI) were established to analyze the restriction and antigen fine specificity of (H-2b X H-2k)F1 T cells towards BI. Our data indicate a focusing of the response on two epitopes on the insulin molecule, the A chain loop determinant comprising amino acids A8 and A10, as well as the glutamic acid residue in position 4 of the A chain. Both were recognized either separately or in conjunction. Unexpectedly, the T cell hybridomas exhibited a marked preference for recognizing insulin in the context of F1-unique restriction elements of Ab alpha Ak beta type rather than parental high-responder I-Ab molecules. Analysis of the response of primed lymph node T cells of (B10 X B10.BR)F1 mice towards BI corroborated the finding of a preponderant corecognition of F1-unique I-A molecules.     

Production of fimbrial adhesins K99 and F41 by enterotoxigenic Escherichia coli as a function of growth-rate domain.

The production of fimbrial adhesins K99 and F41 by enterotoxigenic Escherichia coli has been measured in steady-state chemostat experiments at various specific growth rates (microseconds) and in a recycling fermentor across a range of mu values falling to less than 0.004 h-1. It has been demonstrated that the production of K99 and F41 fimbriae is correlated with mu both in aerobic and anaerobic chemostat experiments. A significant production of fimbriae was only detected at mu values higher than 0.2 h-1. This behavior was further examined by culturing the bacteria in a recycling fermentor with complete biomass retention. It could be shown that the production of K99 and F41 fimbriae only occurred during balanced growth, with a high biomass yield at mu values higher than 0.04 h-1 corresponding to mass doubling times (td) of less than 17 h. The production of both fimbriae halted during balanced growth with a lower biomass yield (at mu values between 0.012 and 0.04 h-1 corresponding to td values between 17 and 58 h) and unbalanced stringent growth (at mu values lower than 0.012 h-1 or td values higher than 58 h). The external pH of the medium greatly influenced the production of both K99 and F41 fimbriae. At pH values lower than 7, the production of fimbriae was strongly inhibited. Also, at pH values higher than 7, a decrease in production was observed. The consequences of the observed phenomena for the pathogenic behavior of this E. coli strain are discussed.     

Changes in excitability of the theta activity generating substrate by ACTH 4–10 in the rat

Summary The present experiments tested the sensitivity of theta activity to ACTH 4–10 a peptide known to facilitate the maintenance of conditioned behaviors. Hippocampal theta activity was induced by electrical stimulation of the reticular formation in freely moving rats. The administration of ACTH 4–10 produced a typical 0.5 c/s shift in dominant frequency and an increase in 7.5–9.0 c/s components of induced theta activity. The effects were maximal between 60–120 min after subcutaneous injection and lasted several hours. The fact, that a similar effect could be obtained by an increase in stimulus intensity suggests an elevated excitability in the theta generating system in the presence of the peptide. The possible significance of this finding for the maintenance of learned behavior is discussed.     

Comparison of various techniques for determining viability of Paracoccidioides brasiliensis yeast-form cells.

The viability of Paracoccidioides brasiliensis yeast-form cells was determined by colony-forming units, direct fluorescent staining, and production of germ tubes in slide culture. The first procedure was unreliable and time consuming; the latter two showed better correlation with hemacytometer total cell counts and required significantly less time.     

Influence of human leukocyte interferon on IgG on the replication of herpes simplex virus in nervous tissue in vitro.

Herpes simplex virus type 1 (HSV-1) replicated productively in rabbit and guinea pig ganglia and nerve organ cultures when inoculated in high titres. Treatment with IgG 20 hr before and 48 hr after infection produced a delay of 4 to 7 days in the recovery of HSV-1 by the method of co-cultivation. The same result was obtained when IgG was combined with human leukocyte interferon. There was no difference in the period up to HSV recovery between the groups treated with interferon alone and the HSV control. Morphological evidence by light and electron microscopy of viral productive infection was obtained in all the cell types of nervous tissues infected in vitro.     

TT virus infection in human immunodeficiency virus type 1 infected mothers and their infants

Serum TT virus (TTV) DNA was determined in 83 human immunodeficiency virus type 1 (HIV 1) infected mothers [46 intravenous drug user and 37 non-intravenous drug user women] and their infants. Twenty-nine (34.9%) mothers were TTV infected. Infection was more frequent among intravenous drug user than non-intravenous drug user mothers [21/46 (45.6%) vs. 8/37 (21.6%); relative risk (RR): 2.1; 95% confidence limits (95% CL): 1.1-4.2; P = 0.023] and among intravenous drug users who carried on injecting than in those who had given it up [10/14 (71.4%) vs. 11/32 (34.3%); RR: 2.1 (95%CL: 1.2-3.7); P = 0. 021]. Infection was not related to age, CD4-positive T-lymphocyte counts, HIV 1 load, hepatitis B (HBV), G/GB-C (GBV-C/HGV), C (HCV) virus exposure. Eight (27.5%) infants born to TTV infected (but none of those born to TTV uninfected) mothers were TTV infected at a median age of 1.5 (range: 0.6-2.8) months. Infants born by vaginal/emergency caesarean delivery were more frequently infected than those born by elective caesarean delivery [7/16 (43.7%) vs. 1/13 (7.6%); RR: 2.1; 95%CL: 1.2-3.5; P = 0.033]. Infection in infants was not related to maternal CD4-positive T-lymphocyte counts, HIV 1 load, and HIV 1, HBV, GBV-C/HGV, or HCV transmission. No infant became TTV infected thereafter. No TTV infected child [follow-up: 31 (median; range: 6-60) months] showed signs of liver disease; five infants cleared TTV DNA after 22 (median; range: 6-60) months. TTV infection in HIV 1 infected women is prevalently related to intravenous drug user. The findings suggest that infants may acquire TTV at birth. Infection may persist without evident liver disease.     

Predominance of a 6 bp deletion in exon 2 of the LDL receptor gene in Africans with familial hypercholesterolaemia

In South Africa, the high prevalence of familial hypercholesterolaemia (FH) among Afrikaners, Jews, and Indians as a result of founder genes is in striking contrast to its reported virtual absence in the black population in general. In this study, the molecular basis of primary hypercholesterolaemia was studied in 16 Africans diagnosed with FH. DNA analysis using three screening methods resulted in the identification of seven different mutations in the coding region of the low density lipoprotein (LDLR) gene in 10 of the patients analysed. These included a 6 bp deletion (GCGATG) accounting for 28% of defective alleles, and six point mutations (D151H, R232W, R385Q, E387K, P678L, and R793Q) detected in single families. The Sotho patient with missense mutation R232W was also heterozygous for a de novo splicing defect 313+1G→A. Several silent mutations/polymorphisms were detected in the LDLR and apolipoprotein B genes, including a base change (g→t) at nucleotide position −175 in the FP2 LDLR regulatory element. This promoter variant was detected at a significantly higher (p<0.05) frequency in FH patients compared to controls and occurred in cis with mutation E387K in one family. Analysis of four intragenic LDLR gene polymorphisms showed that the same chromosomal background was identified at this locus in the four FH patients with the 6 bp deletion. Detection of the 6 bp deletion in Xhosa, Pedi, and Tswana FH patients suggests that it is an ancient mutation predating tribal separation approximately 3000 years ago.


Keywords: apolipoprotein B; hypercholesterolaemia; low density lipoprotein receptor; mutation     

Long-term regeneration of fast and slow murine skeletal muscles after induced injury by ACL myotoxin isolated from Agkistrodon contortrix laticinctus (broad-banded copperhead) venom

The aim of the present work was to analyze the regenerated muscle types I and II fibers of the soleus and gastrocnemius muscles of mice, 8 months after damage induced by ACL myotoxin (ACLMT). Animals received 5 mg/kg of ACLMT into the subcutaneous lateral region of the right hind limb, near the Achilles tendon; contralateral muscles received saline. Longitudinal and cross sections (10 microm) of frozen muscle tissue were evaluated. Eight months after ACLMT injection, both muscle types I and II fibers of soleus and gastrocnemius muscles still showed centralized nuclei and small regenerated fibers. Compared with the left muscle, the incidence of type I fibers increased in the right muscle (21% +/- 03% versus 12% +/- 06%, P = 0.009), whereas type II fibers decreased (78% +/- 02% versus 88% +/- 06%, P = 0.01). The incidence of type IIC fibers was normal. These results confirm that ACLMT induced muscle type fiber transformation from type II to type I, through type IIC. The area analysis of types I and II fibers of the gastrocnemius revealed that injured right muscles have a higher percentage of small fibers in both types I and II fibers (0-1,500 microm2) than left muscles, which have larger normal type I and II fibers (1,500-3,500 microm2). These results indicate that ACLMT can be used as an excellent model to study the rearrangement of motor units and the transformation of muscle fiber types during regeneration.     

HLA-Cw*1602: a new susceptibility marker of Behçet's disease in southern Spain

Abstract: Genotyping of the HLA-C locus by PCR-SSP in Behçet's disease patients from southern Spain reveals a statistically significant association with Cw*1602 (OR 20.15, corrected ρ<0.05). This is an uncommon allele absent from the healthy control group, which seems to confer higher relative risk than B51 in this study (OR 1.85). Stratified frequencies do not show statistically significant differences but suggest that the Cw*1602-B51 haplo-type could be the main HLA marker of Behçet's disease in the analyzed population.