Analysis of COVID-19 vaccine uptake among people with underlying chronic conditions in 2022: A cross-sectional study

Background

COVID-19 has been a global burden and vaccinations have proven to be the most effective measure to fight this pandemic. Since the approval and distribution of the vaccines, approximately 75% of District of Columbia residents have been fully vaccinated leaving a quarter of the population at risk. With the availability and approval of the booster doses to people with high-risk chronic conditions, it is important to understand the attitude of people towards vaccinations.

Objective

The objective of this research study is to analyze the COVID-19 vaccination uptake among people with underlying chronic conditions residing in District of Columbia residents and to determine the reason for the hesitancy to perform targeted outreach to unvaccinated populations.

Study design/methods

In 2022, we conducted a cross sectional study via a short online survey that was distributed to the target populations via email and social media. Multivariable Regression Analyses were conducted to determine the factors associated with the acceptance of the vaccination across various demographics.

Results

The findings of the study demonstrate that the acceptance of COVID-19 vaccination was low among people with chronic conditions compared to those with no underlying chronic conditions, and vaccination rates strongly differ based on social determinants like education, employment, and area of residence across District of Columbia.

Conclusion

The public health significance of this study is to understand the reason behind the vaccine hesitancy so that we can work towards building trust, extending outreach, creating targeted health education, and increasing access to vaccination to all communities across District of Columbia.

Adaptive selection and coevolution at the proteins of the Polycomb repressive complexes in Drosophila

Polycomb group (PcG) proteins are important epigenetic regulatory proteins that modulate the chromatin state through posttranslational histone modifications. These interacting proteins form multimeric complexes that repress gene expression. Thus, PcG proteins are expected to evolve coordinately, which might be reflected in their phylogenetic trees by concordant episodes of positive selection and by a correlation in evolutionary rates. In order to detect these signals of coevolution, the molecular evolution of 17 genes encoding the subunits of five Polycomb repressive complexes has been analyzed in the Drosophila genus. The observed distribution of divergence differs substantially among and along proteins. Indeed, CAF1 is uniformly conserved, whereas only the established protein domains are conserved in other proteins, such as PHO, PHOL, PSC, PH-P and ASX. Moreover, regions with a low divergence not yet described as protein domains are present, for instance, in SFMBT and SU(Z)12. Maximum likelihood methods indicate an acceleration in the nonsynonymous substitution rate at the lineage ancestral to the obscura group species in most genes encoding subunits of the Pcl-PRC2 complex and in genes Sfmbt, Psc and Kdm2. These methods also allow inferring the action of positive selection in this lineage at genes E(z) and Sfmbt. Finally, the protein interaction network predicted from the complete proteomes of 12 Drosophila species using a coevolutionary approach shows two tight PcG clusters. These clusters include well-established binary interactions among PcG proteins as well as new putative interactions.

Hole spin relaxation in InAs/GaAs quantum dot molecules

We calculate the spin-orbit induced hole spin relaxation between Zeeman sublevels of vertically stacked InAs quantum dots. The widely used Luttinger-Kohn Hamiltonian, which considers coupling of heavy- and light-holes, reveals that hole spin lifetimes (T1) of molecular states significantly exceed those of single quantum dot states. However, this effect can be overcome when cubic Dresselhaus spin-orbit interaction is strong. Misalignment of the dots along the stacking direction is also found to be an important source of spin relaxation.

Valence band mixing of cubic GaN/AlN quantum dots

We study the spin purity of the hole ground state in nearly axially symmetric GaN/AlN quantum dots (QDs). To this end, we develop a six-band Burt-Foreman Hamiltonian describing the valence band structure of zinc blende nanostructures with cylindrical symmetry and calculate the effects of eccentricity variationally. We show that the aspect ratio is a key factor for spin purity. In typical QDs with small aspect ratio the ground state is essentially a heavy hole (HH) whose spin purity is even higher than that of InGaAs QDs of similar sizes. When the aspect ratio increases, mixing with light-hole (LH) and split-off (SO) subbands becomes important and, additionally, the ground state becomes sensitive to QD anisotropy, which further enhances the mixing. We finally show that, despite the large GaN hole effective mass, an efficient magnetic modulation is feasible in QDs with aspect ratio ~1, which can be used to modify the ground state symmetry and hence the optical spectrum properties.

[Residual leukocyte counting in plasma by a real-time genomic amplification assay]

BACKGROUND

Systematic plasma leukoreduction, which was introduced in France in April 1st 2001, has given rise to more sensitive methods for residual leukocytes counting. The technologies in application at this moment (Nageotte hemocytometers and flow cytometry methods) have been modified by a thirty fold sample concentration prior to analysis, inducing frequent downgrading of the plasma unit. So, in order to improve the detection threshold, we developed a more sensitive assay using "Real-Time Polymerase Chain Reaction" technology.

MATERIALS AND METHODS

Real-time polymerase chain reaction was performed on a highly conserved HLADQalpha1 gene sequence. In order to determine the analytical performances of the method (accuracy, sensitivity, linearity and specificity) serial dilutions series ranging from 10(4) to 1 cells/ml were performed. A total of 18 series were prepared from three leukocyte stock solutions, by 1 in 10 serial dilutions in three plasmas completely devoided of white cells (called negative plasmas). To examine the specificity of the assay two negative controls were analyzed in each run.

RESULTS

a sensitivity of 10 cells/ml (10(4) leukocytes/l) was achieved and the assay was linear between 10 and 10(4) cells/ml. The slope (-3.72) of the average standard curve calculated from all series, showed an amplification yield of 92.85%.

CONCLUSION

we developed a quantitative assay for residual leukocytes in leukodepleted plasma, that agreed with the quality control requirement specifications.

Changes in the recombinational environment affect divergence in the yellow gene of Drosophila

The complete coding region of the yellow (y) gene was sequenced in different Drosophila species. In the species of the melanogaster subgroup (D. melanogaster, D. simulans, D. mauritiana, D. yakuba, and D. erecta), this gene is located at the tip of the X chromosome in a region with a strong reduction in recombination rate. In contrast, in D. ananassae (included in the ananassae subgroup of the melanogaster group) and in the obscura group species (D. subobscura, D. madeirensis, D. guanche, and D. pseudoobscura), the y gene is located in regions with normal recombination rates. As predicted by the hitchhiking and background selection models, this change in the recombinational environment affected synonymous divergence in the y-gene-coding region. Estimates of the number of synonymous substitutions per site were much lower between the obscura group species and D. ananassae than between the species of the obscura group and the melanogaster subgroup. In fact, a highly significant increase in the rate of synonymous substitution was detected in all lineages leading to the species of the melanogaster subgroup relative to the D. ananassae lineage. This increase can be explained by a higher fixation rate of mutations from preferred to unpreferred codons (slightly deleterious mutations). The lower codon bias detected in all species of the melanogaster subgroup relative to D. ananassae (or to the obscura group species) would be consistent with this proposal. Therefore, at least in Drosophila, changes in the recombination rate in different lineages might cause deviations of the molecular-clock hypothesis and contribute to the overdispersion of the rate of synonymous substitution. In contrast, the change in the recombinational environment of the y gene has no detectable effect on the rate of amino acid replacement in the Yellow protein.

Nucleotide variation at the yellow gene region is not reduced in Drosophila subobscura: a study in relation to chromosomal polymorphism

In contrast to Drosophila melanogaster and Drosophila simulans, the yellow (y) gene region of Drosophila subobscura is not located in a region with a strong reduction in recombination. In addition, this gene maps very close to the breakpoints of different inversions that segregate as polymorphic in natural populations of D. subobscura. Therefore, levels of variation at the y gene region in this species relative to those found in D. melanogaster and D. simulans may be affected not only by the change in the recombinational environment, but also by the presence of inversion polymorphism. To further investigate these aspects, an approximately 5.4-kb region of the A (=X) chromosome including the y gene was sequenced in 25 lines of D. subobscura and in the closely related species Drosophila madeirensis and Drosophila guanche. The D. subobscura lines studied differed in their A-chromosomal arrangements, A(st), A(2), and A(1). Unlike in D. melanogaster and D. simulans, levels of variation at the y gene region of D. subobscura are not reduced relative to those found at other genomic regions in the same species (rp49, Acp70A, and Acph-1). This result supports the effect of the change in the recombinational environment of a particular gene on the level of neutral variation. In addition, nucleotide variation is affected by chromosomal polymorphism. A strong genetic differentiation is detected between the A(1) arrangement and either A(st) or A(2), but not between A(st) and A(2). This result is consistent with the location of the y gene relative to the breakpoints of inversions A(1) and A(2). In addition, the pattern of nucleotide polymorphism in A(st)+A(2) and A(1) seems to point out that variation at the y gene region within these chromosomal classes is in the phase transient to equilibrium. The estimated ages of these arrangements assuming a star genealogy indicate that their origin cannot predate the D. madeirensis split. Therefore, the present results are consistent with a chromosomal phylogeny where Am(1), which is an arrangement present in D. madeirensis but absent in current populations of D. subobscura, would be the ancestral arrangement.

The Drosophila fl(2)d gene, required for female-specific splicing of Sxl and tra pre-mRNAs, encodes a novel nuclear protein with a HQ-rich domain

The Drosophila gene female-lethal(2)d [fl(2)d] interacts genetically with the master regulatory gene for sex determination, Sex-lethal. Both genes are required for the activation of female-specific patterns of alternative splicing on transformer and Sex-lethal pre-mRNAs. We have used P-element-mediated mutagenesis to identify the fl(2)d gene. The fl(2)d transcription unit generates two alternatively spliced mRNAs that can encode two protein isoforms differing at their amino terminus. The larger isoform contains a domain rich in histidine and glutamine but has no significant homology to proteins in databases. Several lines of evidence indicate that this protein is responsible for fl(2)d function. First, the P-element insertion that inactivates fl(2)d interrupts this ORF. Second, amino acid changes within this ORF have been identified in fl(2)d mutants, and the nature of the changes correlates with the severity of the mutations. Third, all of the phenotypes associated with fl(2)d mutations can be rescued by expression of this cDNA in transgenic flies. Fl(2)d protein can be detected in extracts from Drosophila cell lines, embryos, larvae, and adult animals, without apparent differences between sexes, as well as in adult ovaries. Consistent with a possible function in posttranscriptional regulation, Fl(2)d protein has nuclear localization and is enriched in nuclear extracts.

The relationship between allozyme and chromosomal polymorphism inferred from nucleotide variation at the Acph-1 gene region of Drosophila subobscura

The Acph-1 gene region was sequenced in 51 lines of Drosophila subobscura. Lines differ in their chromosomal arrangement for segment I of the O chromosome (O(st) and O(3+4)) and in the Acph-1 electrophoretic allele (Acph-1(100), Acph-1(054), and Acph-1(>100)). The ACPH-1 protein exhibits much more variation than previously detected by electrophoresis. The amino acid replacements responsible for the Acph-1(054) and Acph-1(>100) electrophoretic variants are different within O(st) and within O(3+4), which invalidates all previous studies on linkage disequilibrium between chromosomal and allozyme polymorphisms at this locus. The Acph-1(>100) allele within O(3+4) has a recent origin, while both Acph-1(054) alleles are rather old. Levels of nucleotide variation are higher within the O(3+4) than within the O(st) arrangement except for nonsynonymous sites. The McDonald and Kreitman test shows a significant excess of nonsynonymous polymorphisms within O(st) when D. guanche is used as the outgroup. According to the nearly neutral model of molecular evolution, this excess is consistent with a smaller effective size of O(st) relative to O(3+4) arrangements. A smaller population size, a lower recombination, and a more recent bottleneck might be contributing to the smaller effective size of O(st).

The acid phosphatase-1 gene region in the Drosophila species of the subobscura cluster

The acid phosphatase-1 (Acph-1) gene region was sequenced in three species of Drosophila: D. subobscura, D. madeirensis and D. guanche. These three closely related species, which are included in the obscura group, form the subobscura cluster. The different functional regions of the gene were identified by similarity with the sequence of D. melanogaster. The structure of Acph-1 is conserved in the four species. Average divergence at synonymous and nonsynonymous sites between D. melanogaster and the species of the subobscura cluster is Ks = 1.1354 and Ka = 0.1743, respectively. The rather high Ka value confirms that ACPH-1 is a rapidly evolving enzyme in Drosophila, as previously suggested by immunological studies. Amino acid replacements are not randomly distributed along the gene. In fact, an excess of replacements is detected in exon I, indicating that the signal peptide encoded by this exon evolves even faster than the rest of the protein. Divergence at the Acph-1 gene region is further evidence that D. madeirensis and D. subobscura are more closely related than D. guanche is to any of them. In addition, both silent divergence in noncoding regions and synonymous divergence in the coding region indicate that the split of the D. guanche lineage is about twice as old as the split of the lineages leading to D. madeirensis and D. subobscura. These phylogenetic relationships are, however, not supported by divergence at nonsynonymous sites since the lowest Ka estimate is between D. guanche and D. subobscura.

Efficiencies of four versions of the AMPLICOR HIV-1 MONITOR test for quantification of different subtypes of human immunodeficiency virus type 1

Three versions of a commercial human immunodeficiency virus (HIV) type 1 (HIV-1) load test (the AMPLICOR HIV-1 MONITOR Test versions 1. 0, 1.0+, and 1.5; Roche Diagnostics, Branchburg, N.J.) were evaluated for their ability to detect and quantify HIV-1 RNA of different genetic subtypes. Plasma samples from 96 patients infected with various subtypes of HIV-1 (55 patients infected with subtype A, 9 with subtype B, 21 with subtype C, 2 with subtype D, 7 with subtype E, and 2 with subtype G) and cultured virus from 29 HIV-1 reference strains (3 of subtype A, 6 of subtype B, 5 of subtype C, 3 of subtype D, 8 of subtype E, 3 of subtype F, and 1 of subtype G) were tested. Detection of subtypes A and E was significantly improved with versions 1.0+ and 1.5 compared to that with version 1. 0, whereas detection of subtypes B, C, D, and G was equivalent with the three versions. Versions 1.0, 1.0+, and 1.5 detected 65, 98, and 100% of the subtype A-infected samples from patients, respectively, and 71, 100, and 100% of the subtype E-infected samples from patients, respectively. Version 1.5 yielded a significant increase in viral load for samples infected with subtypes A and E (greater than 1 log10 HIV RNA copies/ml). For samples infected with subtype B, C, and D and tested with version 1.5, only a slight increase in viral load was observed (<0.5 log10). We also evaluated a prototype automated version of the test that uses the same PCR primers as version 1.5. The results with the prototype automated test were highly correlated with those of the version 1.5 test for all subtypes, but were lower overall. The AMPLICOR HIV-1 MONITOR Test, version 1.5, yielded accurate measurement of the HIV load for all HIV-1 subtypes tested, which should allow the test to be used to assess disease prognosis and response to antiretroviral treatment in patients infected with a group M HIV-1 subtype.

Molecular population genetics of the rp49 gene region in different chromosomal inversions of Drosophila subobscura

Nucleotide variation at the ribosomal protein 49 (rp49) gene region has been studied in 75 lines of Drosophila subobscura belonging to four chromosomal arrangements (Ost, O3+4, O3+4+8, and O3+4+23). The location of the rp49 gene region within the inversion loop differs among heterokaryotypes: it is very close to one of the breakpoints in heterozygotes involving Ost chromosomes, while it is in a more central position in all other heterokaryotypes. The distribution of nucleotide polymorphism in the different arrangements is consistent with a monophyletic origin of the inversions. The data also provide evidence that gene conversion and possibly double crossover are involved in shuffling nucleotide variation among gene arrangements. The analyses reveal that the level of genetic exchange is higher when the region is located in a more central position of the inverted fragment than when it is close to the breakpoints. The pairwise difference distributions as well as the negative values of Tajima's and Fu and Li's statistics further support the hypothesis that nucleotide variation within chromosomal arrangements still reflects expansion after the origin of the inversions. Under the expansion model, we have estimated the time of origin of the studied inversions.

Molecular and chromosomal phylogeny in the obscura group of Drosophila inferred from sequences of the rp49 gene region

A region of approximately 1.6 kb encompassing the ribosomal protein 49 gene (rp49) has been sequenced and compared in nine species of the obscura group of Drosophila: four species belonging to the obscura subgroup, three to the pseudoobscura subgroup, and two to the affinis subgroup. Our data provide strong support that the nearctic species (pseudoobscura and affinis subgroups) are monophyletic and place D. bifasciata with the other species of the obscura subgroup. Nucleotide sequence information at the rp49 gene region (located very close to one of the breakpoints of inversion O3) has also been used to infer the phylogeny of the O chromosome in the subobscura species cluster. Analysis based both on parsimony-informative sites and on genetic distances confirms that the O3 gene arrangement, present in D. guanche (together with inversion g) and in D. madeirensis, is ancestral to gene arrangements O3 + 4 and Ost present in extant populations of D. subobscura.

Divergence of the yellow gene between Drosophila melanogaster and D. subobscura: recombination rate, codon bias and synonymous substitutions

The yellow (y) gene maps near the telomere of the X chromosome in Drosophila melanogaster but not in D. subobscura. Thus the strong reduction in the recombination rate associated with telomeric regions is not expected in D. subobscura. To study the divergence of a gene whose recombination rate differs between two species, the y gene of D. subobscura was sequenced. Sequence comparison between D. melanogaster and D. subobscura revealed several elements conserved in noncoding regions that may correspond to putative cis-acting regulatory sequences. Divergence in the y gene coding region between D. subobscura and D. melanogaster was compared with that found in other genes sequenced in both species. Both, yellow and scute exhibit an unusually high number of synonymous substitutions per site (ps). Also for these genes, the extent of codon bias differs between both species, being much higher in D. subobscura than in D. melanogaster. This pattern of divergence is consistent with the hitchhiking and background selection models that predict an increase in the fixation rate of slightly deleterious mutations and a decrease in the rate of fixation of slightly advantageous mutations in regions with low recombination rates such as in the y-sc gene region of D. melanogaster.

Chromosomal homology and molecular organization of Muller's elements D and E in the Drosophila repleta species group

Thirty-three DNA clones containing protein-coding genes have been used for in situ hybridization to the polytene chromosomes of two Drosophila repleta group species, D. repleta and D. buzzatii. Twenty-six clones gave positive results allowing the precise localization of 26 genes and the tentative identification of another nine. The results were fully consistent with the currently accepted chromosomal homologies and in no case was evidence for reciprocal translocations or pericentric inversions found. Most of the genes mapped to chromosomes 2 and 4 that are homologous, respectively, to chromosome arms 3R and 3L of D. melanogaster (Muller's elements E and D). The comparison of the molecular organization of-these two elements between D. melanogaster and D. repleta (two species that belong to different subgenera and diverged some 62 million years ago) showed an extensive reorganization via paracentric inversions. Using a maximum likelihood procedure, we estimated that 130 paracentric inversions have become fixed in element E after the divergence of the two lineages. Therefore, the evolution rate for element E is approximately one inversion per million years. This value is comparable to previous estimates of the rate of evolution of chromosome X and yields an estimate of 4.5 inversions per million years for the whole Drosophila genome.

Regulation of the gene Sex-lethal: a comparative analysis of Drosophila melanogaster and Drosophila subobscura

The Drosophila gene Sex-lethal (Sxl) controls the processes of sex determination and dosage compensation. A Drosophila subobscura genomic fragment containing all the exons and the late and early promotors in the Sxl gene of D. melanogaster was isolated. Early Sxl expression in D. subobscura seems to be controlled at the transcriptional level, possibly by the X:A signal. In the region upstream of the early Sxl transcription initiation site are two conserved regions suggested to be involved in the early activation of Sxl. Late Sxl expression in D. subobscura produces four transcripts in adult females and males. In males, the transcripts have an additional exon which contains three translational stop codons so that a truncated, presumably nonfunctional Sxl protein is produced. The Sxl pre-mRNA of D. subobscura lacks the poly-U sequence presented at the polypirimidine tract of the 3' splice site of the male-specific exon present in D. melanogaster. Introns 2 and 3 contain the Sxl-binding poly-U stretches, whose localization in intron 2 varies but in intron 3 is conserved. The Sxl protein is fully conserved at the amino acid level in both species.

Comparative evaluation of three assays for the quantitation of human immunodeficiency virus type 1 RNA in plasma

Reverse transcriptase-coupled polymerase chain reaction (Amplicor HIV-1 Monitor), the branched DNA (bDNA) method (Quantiplex HIV-1 RNA) and the nucleic acid sequence-based assay (NASBA HIV-1 RNA QT) were comparatively evaluated for the quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in plasma. Among 60 plasma specimens from HIV-1 infected patients, HIV-1 RNA was detected in 56 by Amplicor (sensitivity, 93.3%), in 41 by bDNA (sensitivity, 68.3%), and in 60 by NASBA (sensitivity, 100%). HIV-1 RNA was not detected by any of these methods in 34/34 plasma specimens from HIV-1-seronegative blood donors (specificity, 100%). The HIV-1 RNA levels as determined by the different methods were correlated significantly. The frequency of concordant results (log difference < 0.50) was 80.4% between Amplicor and NASBA, 77.5% between Amplicor and bDNA, and 58.6% between bDNA and NASBA. After initiation of antiviral therapy, HIV-1 RNA level variations observed with the three methods were similar. HIV-1 RNA levels were inversely correlated with the CD4+ T cell counts, whereas no correlation was found with HIV-1 p24-antigen levels. When the methods were evaluated for reproducibility, coefficients of variation ranged from 11% to 40% for Amplicor, from 6% to 35% for bDNA, and from 13% to 62% for NASBA. Quantitation of HIV-1 RNA in culture supernatants from HIV-1 subtype A to H strains showed that bDNA can be used to quantitate RNA from all HIV-1 subtypes, whereas Amplicor failed to detect RNA from subtype A strains and NASBA subtype G strains.

Cloning and characterization of the scute (sc) gene of Drosophila subobscura

The scute (sc) gene, a member of the achaete-scute complex of Drosophila melanogaster, has dual functions: sisterless (sis-b) function required for sex determination and dosage compensation and scute function, which is involved in neurogenesis. The sc homologue of D. subobscura was cloned. It lacks introns and encodes a single 1.7-kb transcript slightly larger than that of D. melanogaster (1.6 kb). The sc protein of D. subobscura is slightly larger than that of D. melanogaster (382 vs. 345 amino acids). Sequence comparisons between both species show the Sc protein to have a highly conserved bHLH domain. Outside this domain, amino acid replacements are not randomly distributed. Two additional conserved domains, of 20 and 36 amino acids, are present near the C-terminal end. They may represent domains confering specificity upon the Sc protein with respect to other proteins of the achaete-scute complex. In its 3' untranslated region, Sc RNA contains uridine stretches, putative Sxl protein DNA-binding sites. The D. subobscura Sc protein can cooperate with other D. melanogaster bHLH proteins because D. subobscura sc supplies sis-b function when introduced into D. melanogaster transgenic flies mutant for sc.

Differentiation of Muller's chromosomal elements D and E in the obscura group of Drosophila

Twenty-two markers located on Muller's elements D or E have been mapped by in situ hybridization in six species of the obscura group of Drosophila and in D. melanogaster. The obscura species can be grouped into a Palearctic cluster (D. subobscura, D. madeirensis and D. guanche) and a Nearctic one (D. pseudoobscura, D. persimilis and D. miranda). Eleven of the probes contain known genes: E74, Acp70A, Est5, hsp28/23, hsp83, emc, hsp70, Xdh, Acph-1, Cec and rp49. The remaining probes are recombinant phages isolated from a D. subobscura genomic library. All these markers hybridize to the putative homologous chromosome or chromosomal arm of elements D and E. Thus, these elements have conserved their genic content during species divergence. Chromosomal homologies proposed previously for each element among the species of the same cluster have been compared with the present results. The distribution of markers within each element has changed considerably as inferred from pairwise comparisons of obscura species included in the two different clusters. Only chromosomal segments defined by closely linked markers have been conserved: one such segment has been detected in element D and three in element E between D subobscura and D. pseudoobscura.

Sicca syndrome associated with hepatitis C virus infection

OBJECTIVE

To determine the prevalence of hepatitis C virus (HCV) infection in patients with sicca syndrome, and to determine the clinical, immunologic, and genetic characteristics of sicca syndrome associated with HCV.

METHODS

We conducted a prospective study in a university hospital immunology-rheumatology department. Sixty-two consecutive patients with sicca syndrome according to the European criteria for Sjögren's syndrome were included. HCV infection was diagnosed in patients with positive recombinant immunoblot assay findings and the presence of viral RNA in serum and saliva. Rheumatoid factor (RF), cryoglobulins, antinuclear antibodies, and anti-SS-A/SS-B antibodies were sought. HLA typing was performed on all patients.

RESULTS

The prevalence of HCV infection in patients with sicca syndrome was 19%. The incidence of neurologic involvement was significantly increased in patients with sicca syndrome associated with HCV infection (24% versus 4%; P < 0.03), as was elevations in transaminase levels (87.5% versus 16%; P < 0.0001). RF and cryoglobulins were more frequent in HCV-positive sicca syndrome patients (62% versus 30%; P < 0.03, and 56% versus 10%; P < 0.001, respectively). In contrast, anti-SS-A/SS-B antibodies were present in 38% of HCV-negative sicca syndrome patients, but in only 1 HCV-positive sicca syndrome patient (P < 0.01). No significant difference in HLA type was observed. Viral RNA was present in the saliva of 83% of HCV-positive sicca syndrome patients, but in none of the HCV-negative sicca syndrome patients.

CONCLUSION

We observed a high prevalence of HCV infection in our patients with sicca syndrome. HCV-positive sicca syndrome patients had specific clinical characteristics and were seronegative for SS-A/SS-B antibodies. Moreover, HCV RNA was present in the saliva of patients with HCV-associated sicca syndrome.

P1 clones from Drosophila melanogaster as markers to study the chromosomal evolution of Muller's A element in two species of the obscura group of Drosophila

Thirty P1 clones from the X chromosome (Muller's A element) of Drosophila melanogaster were cross-hybridized in situ to Drosophila subobscura and Drosophila pseudoobscura polytene chromosomes. An additional recombinant phage lambda Dsuby was also used as a marker. Twenty-three (77%) of the P1 clones gave positive hybridization on D. pseudoobscura chromosomes but only 16 (53%) did so with those of D. subobscura. Eight P1 clones gave more than one hybridization signal on D. pseudoobscura and/or D. subobscura chromosomes. All P1 clones and lambda Dsuby hybridized on Muller's A element (X chromosome) of D. subobscura. In contrast, only 18 P1 clones and lambda Dsuby hybridized on Muller's A element (XL chromosomal arm) of D. pseudoobscura; 4 additional P1 clones hybridized on Muller's D element (XR chromosomal arm) of this species and the remaining P1 clone gave one hybridization signal on each arm of the X chromosome. This latter clone may contain one breakpoint of a pericentric inversion that may account for the interchange of genetic material between Muller's A and D elements in D. pseudoobscura. In contrast to the rare interchange of genetic material between chromosomal elements, profound differences in the order and spacing of markers were detected between D. melanogaster, D. pseudoobscura and D. subobscura. In fact, the number of chromosomal segments delimited by identical markers and conserved between pairwise comparisons is small. Therefore, extensive reorganization within Muller's A element has been produced during the divergence of the three species. Rough estimates of the number of cytologically detectable inversions contributing to differentiation of Muller's A element were obtained. The most reliable of these estimates is that obtained from the D. pseudoobscura and D. melanogaster comparison since a greater number of markers have been mapped in both species. Tentatively, one inversion breakpoint about every 200 kb has been produced and fixed during the divergence of D. pseudoobscura and D. melanogaster.

Molecular characterization of the breakpoints of an inversion fixed between Drosophila melanogaster and D. subobscura

The two breakpoints of a chromosomal inversion fixed since the split of Drosophila melanogaster and D. subobscura lineages have been isolated and sequenced in both species. The regions spanning the breakpoints initially were identified by the presence of two signals after interspecific in situ hybridization on polytene chromosomes. Interspecific comparison of the sequenced regions allowed us to delineate the location of the breakpoints. Close to one of these breakpoints a new transcription unit (bcn92) has been identified in both species. The inversion fixed between D. melanogaster and D. subobscura does not seem to have broken any transcription unit. Neither complete nor defective transposable elements were found in the regions encompassing the breakpoints. Short thymine-rich sequences (30-50 bp long) have been found bordering the breakpoint regions. Although alternating Pur-Pyr sequences were detected, these putative target sites for topoisomerase II were not differentially clustered in the breakpoints.

Colonization of America by Drosophila subobscura: the founder event and a rapid expansion

The recent colonization of the American continent by Drosophila subobscura offers a unique opportunity to analyze the response of different genomic entities to a new environment. Here, results from a study of 15 allozyme loci in six North American and seven South American populations are compared with existing data from Palearctic populations. In general, only alleles with a frequency higher than 0.1 in European populations are present in America. The observed alteration in allele frequencies can be explained by a founder event. Although some significant latitudinal clines for allozyme frequencies have been detected, the results obtained are not as clear-cut as are those for chromosomal inversions. Overall heterozygosity is similar between North and South American populations and does not differ from that of Palearctic populations. This observation experimentally corroborates the results provided by theoretical models in which the average heterozygosity per locus depends not only on the size of bottleneck but also on the rate of population growth. The resemblance between North and South American populations is clearly manifested by a geometrical representation using Bhattacharyya's distance and a multidimensional scaling technique. Furthermore, these American populations are clearly differentiated from the Palearctic populations.

[A prognostic multifactorial study of sepsis in an internal medicine service]

All cases of sepsis attended at the Service of Internal Medicine from 1985 to 1989, both inclusive, were retrospectively analyzed by the statistical study of several clinical, epidemiological, bacteriological and laboratory factors. The parameters acting as prognosis factors were analyzed using Cox's method of logistic regression, in order to obtain more reliable information on the multifactorial spectrum determining "death due to sepsis". The unifactorial analysis (UFA) suggested that the following factors were associated to an statistically significant increase in the mortality due to sepsis: age above 70; male sex; presence of shock upon hospitalization; nosocomial etiology; high levels of urea, creatinine and LDH; proteinuria; family of the causal germ (gram-positive coccus) and underlying pathology. The relative risks (RR) or "odd ratios" of creatinine and LDH were, respectively, 2.8 and 2.9 in the UFA; 3 and 3.3 in the multivariant analysis (MVA). In the older patients developing sepsis within their communities, RR were respectively 2.7 and 1.98 in the UFA and 1.1 and 2.7 in the MFA. The results of the univariant and multivariant analysis showing the relative risk (odd ratio) associated to each of these variables with statistical significance, demonstrate that the mortality rate due to sepsis increases with age, nosocomial etiology and elevation of creatinine and lactodehydrogenase (LDH) levels. We stress the great importance of the LDH as a prognostic factor of sepsis.

Nucleotide divergence of the rp49 gene region between Drosophila melanogaster and two species of the Obscura group of Drosophila

A 2.1-kb SstI fragment including the rp49 gene and the 3' end of the delta-serendipity gene has been cloned and sequenced in Drosophila pseudoobscura. rp49 maps at region 62 on the tip of chromosome II of this species. Both the coding and flanking regions have been aligned and compared with those of D. subobscura. There is no evidence for heterogeneity in the rate of silent substitution between the rp49 coding region and the rate of substitutions in flanking regions, the overall silent divergence per site being 0.19. Noncoding regions also differ between both species by different insertions/deletions, some of which are related to repeated sequences. The rp49 region of D. pseudoobscura shows a strong codon bias similar to those of D. subobscura and D. melanogaster. Comparison of the rates of silent (Ks) and nonsilent (Ka) substitutions of the rp49 gene and other genes completely sequenced in D. pseudoobscura and D. melanogaster confirms previous results indicating that rp49 is evolving slowly both at silent and nonsilent sites. According to the data for the rp49 region, D. pseudoobscura and D. subobscura lineages would have diverged some 9 Myr ago, if one assumes a divergence time of 30 Myr for the melanogaster and obscura groups.

Molecular organization of the X chromosome in different species of the obscura group of Drosophila

Nine single copy regions located on the X chromosome have been mapped by in situ hybridization in six species of the obscura group of Drosophila. Three Palearctic species, D. subobscura, D. madeirensis and D. guanche, and three Nearctic species, D. pseudoobscura, D. persimilis and D. miranda, have been studied. Eight of the regions include known genes from D. melanogaster (Pgd, zeste, white, cut, vermilion, RNA polymerase II 215, forked and suppressor of forked) and the ninth region (lambda DsubF6) has not yet been characterized. In all six species, as in D. melanogaster, all probes hybridize to a single site. Established chromosomal arm homologies of Muller's element A are only partly supported by present results since two of the probes (Pgd and zeste) hybridize at the proximal end of the XR chromosomal arm in the three Nearctic species. In addition to the centric fusion of Muller's A (= XL) and D (= XR) elements, the metacentric X chromosome of the Nearctic species requires a pericentric inversion to account for this result. Previously proposed homologies of particular chromosomal regions of the A (= X) chromosome in the three species of the D. subobscura cluster and of the XL chromosomal arm in the three species of the D. pseudoobscura cluster are discussed in light of the present results. Location of the studied markers has changed drastically not only since the divergence between the melanogaster and obscura groups but also since the Palearctic and Nearctic species of the obscura group diverged.

[Effect of the absence of vitamins in the diet on the excretion of giardia cysts: experimental study]

We have studied the effect of vitamin absence in the diet on the evolution of an experimental giardiasis in mice inoculated with Giardia muris cysts. Our study shows that although there is no decrease in the intestinal parasitation, the peak is delayed, and there is a significant decrease in the cysts elimination in stools. These features may have their clinical significance.