Synthesis of acid phosphatase during dehydration of the yeast Saccharomyces cerevisiae

Summary During the dehydration of exponentially growing yeast cells for 24 h at 37° C, a 2–3 fold increase in the activity of acid phosphatase was observed. This increase is inhibited by cycloheximide and 2-deoxy-D-glucose and therefore is indicative of de novo synthesis. The presence of exogenous orthophosphate during drying does not affect the specific activity of this enzyme, thus indicating the constitutive character of the newly formed acid phosphatase.Freeze-etching showed some rearrangement of the plasmalemma structure of yeast cells during dehydration.     

Diminished transmission of drug resistant HIV-1 variants with reduced replication capacity in a human transmission model

Background

Different patterns of drug resistance are observed in treated and therapy naïve HIV-1 infected populations. Especially the NRTI-related M184I/V variants, which are among the most frequently encountered mutations in treated patients, are underrepresented in the antiretroviral naïve population. M184I/V mutations are known to have a profound effect on viral replication and tend to revert over time in the new host. However it is debated whether a diminished transmission efficacy of HIV variants with a reduced replication capacity can also contribute to the observed discrepancy in genotypic patterns.As dendritic cells (DCs) play a pivotal role in HIV-1 transmission, we used a model containing primary human Langerhans cells (LCs) and DCs to compare the transmission efficacy M184 variants (HIV-M184V/I/T) to HIV wild type (HIV-WT). As control, we used HIV harboring the NNRTI mutation K103N (HIV-K103N) which has a minor effect on replication and is found at a similar prevalence in treated and untreated individuals.

Results

In comparison to HIV-WT, the HIV-M184 variants were less efficiently transmitted to CCR5⁺ Jurkat T cells by both LCs and DCs. The transmission rate of HIV-K103N was slightly reduced to HIV-WT in LCs and even higher than HIV-WT in DCs. Replication experiments in CCR5⁺ Jurkat T cells revealed no apparent differences in replication capacity between the mutant viruses and HIV-WT. However, viral replication in LCs and DCs was in concordance with the transmission results; replication by the HIV-M184 variants was lower than replication by HIV-WT, and the level of replication of HIV-K103N was intermediate for LCs and higher than HIV-WT for DCs.

Conclusions

Our data demonstrate that drug resistant M184-variants display a reduced replication capacity in LCs and DCs which directly impairs their transmission efficacy. As such, diminished transmission efficacy may contribute to the lower prevalence of drug resistant variants in therapy naive individuals.

     

Subclinical inflammation on MRI of hand and foot of anticitrullinated peptide antibody–negative arthralgia patients at risk for rheumatoid arthritis

Introduction

It is known that anticitrullinated peptide antibody (ACPA)–positive rheumatoid arthritis (RA) has a preclinical phase. Whether this phase is also present in ACPA-negative RA is unknown. To determine this, we studied ACPA-negative arthralgia patients who were considered prone to progress to RA for local subclinical inflammation observed on hand and foot magnetic resonance imaging (MRI) scans.

Methods

We studied a total of 64 ACPA-negative patients without clinically detectable arthritis and with arthralgia of the small joints within the previous 1 year. Because of the character of the patients’ symptoms, the rheumatologists considered these patients to be prone to progress to RA. For comparisons, we evaluated 19 healthy, symptom-free controls and 20 ACPA-negative RA patients, who were identified according to the 1987 American Rheumatism Association criteria. All participants underwent MRI of unilateral wrist, metacarpophalangeal and metatarsophalangeal joints. Synovitis and bone marrow oedema (BME) were scored according to the OMERACT rheumatoid arthritis magnetic resonance imaging scoring system, and the scores were summed to yield the ‘MRI inflammation score’. Scores were compared between groups. Among the ACPA-negative arthralgia patients, MRI inflammation scores were related to C-reactive protein (CRP) levels and the tenderness of scanned joints.

Results

MRI inflammation scores increased progressively among the groups of controls and ACPA-negative arthralgia and RA patients (median scores = 0, 1 and 10, respectively; P < 0.001). The MRI inflammation scores of ACPA-negative arthralgia patients were significantly higher than those of controls (P = 0.018). In particular, the synovitis scores were higher in ACPA-negative arthralgia patients (P = 0.046). Among the ACPA-negative arthralgia patients, inflammation was observed predominantly in the wrist (53%). The synovitis scores were associated with CRP levels (P = 0.007) and joint tenderness (P = 0.026). Despite the limited follow-up duration, five patients developed clinically detectable arthritis. These five patients had higher scores for MRI inflammation (P = 0.001), synovitis (P = 0.002) and BME (P = 0.003) compared to the other patients.

Conclusion

Subclinical synovitis was observed in the small joints of ACPA-negative arthralgia patients, and especially in patients whose conditions progressed to clinically detectable arthritis. This finding suggests the presence of a preclinical phase in ACPA-negative RA. Further longitudinal studies of these lesions and patients are required to confirm this hypothesis.     

Phenotypic variability and therapeutic implications of Candida species in patients with oral lichen planus

We investigated the prevalence and phenotypic variation of Candida species in oral lichen planus (OLP) and the therapeutic implications of our findings. Eighty patients with clinically and histopathologically confirmed cases of OLP (64 non-erosive, 16 erosive) and a control group of 80 healthy individuals with no predisposing factors for oral candidiasis were examined for evidence of Candida infection. Oral swabs and smears were obtained for cytology and culture. Identification, speciation and antifungal susceptibility tests of Candida isolates were performed using an automated microbial identification system. Fifty percent of erosive OLP cases, 28% of non-erosive cases and none of the controls showed evidence of Candida. Candida albicans was found predominantly in non-erosive OLP, while other Candida species were predominate in erosive OLP. Non-Candida albicans isolates (C. glabrata, C. krusei) were resistant to the commonly used antifungals, clotrimazole and fluconazole. Candida infection is common in cases of OLP. We recommend antifungal sensitivity testing prior to antifungal therapy for the erosive form of OLP.     

Estrogen-Induced Synthesis of Yolk Proteins in Roosters

Vitellogenin is the serum precursor of the yolk proteins -lipovitellin,rß-lipovitellin, and phosvitin. The precursor canbe dissociated to produce the yolk proteins only by proteolyticenzymatic action, to which it is very susceptible. Denaturationin sodium dodecyl sulfate, combined with reduction of disulfidebridges and blocking of thiols, yields a complex with a molecularweight of 200,000 to 250,000. -Lipovitellin contains three polypeptides,with molecular weights of about 135,000, 105,000, and 40,000,and rß-lipovitellin is composed of two polypeptidechains with molecular weights of 135,000 and 30,000. The 40,000subunit of -lipovitellin and both rß-lipovitellinsubunits are phosphopeptides We tested RNA isolated from the liver of estrogen-treated roostersfor mRNA activity in a cell-free reticulocyte system. The vitellogeninmRNA has a sedimentation coefficient greater than 28S and thuscontains enough information to code for a long polypeptide chain.Estrogen administration to roosters induces the appearance ofvitellogenin and a lowdensity lipoprotein, the syntheses ofwhich are not coordinated. The course of vitellogenin synthesiswas calculated from accumulation and turnover data, and it wasfound that from about 25 hr after estradiol-17rß administrationthe rate of vitellogenin synthesis increases linearly for severaldays, paralleling an increase in vitellogenin-synthesizing polysomes.Thus, we estimate a constant translation rate of about 8 aminoacids per ribosome per sec. A "memory" effect is observed when a second hormone dose isgiven some time after the vitellogenin induced by the firstdose has disappeared from the blood. After the second dose vitellogeninsynthesis is detected sooner, and its initial increase is morerapid, than after the first dose. Although the synthesis ofvitellogenin starts 3 to 4 hr after the second as well as afterthe first injection, the rate of synthesis after the first injectionincreases much more slowly during the first 15 hr than duringthe subsequent period of linear accumulation, whereas afterthe second injection the linear increase in the rate of synthesisbegins immediately after the lag period of 3 to 4 hr. The "memory"effect is undiminished even 50 days after the first hormonedose; thus, the causative factor either is very stable or issynthesized in great excess during the first stimulation. Whenthe second injection is given during the descending part ofthe turnover curve, an increase in vitellogenin synthesis isobserved within 3.5 hr. There are thus at least three different effects of estradiol;(i) the "memory" effect, which probably is due to commitmentor differentiation of vitellogenin-synthesizing cells; (ii)the effect that causes the committed cells to give full responseafter the 3- to 4-hr lag period; and (iii) the effect that causesthe immediate response. To explain these results we suggestthat committed cells can synthesize vitellogenin mRNA only duringa certain period of the cell cycle.     

Nucleotide sequence of a chicken vitellogenin gene and derived amino acid sequence of the encoded yolk precursor protein

The gene encoding the major vitellogenin from chicken has been completely sequenced and its exon-intron organization has been established. The gene is 20,342 base-pairs long and contains 35 exons with a combined length of 5787 base-pairs. They encode the 1850-amino acid pre-peptide of vitellogenin, which is the precursor of the mature yolk proteins, the serine-rich and heavily phosphorylated phosvitin and the lipovitellin. The 217-amino acid phosvitin polypeptide occupies an internal position (residue 1112 through 1328) within the vitellogenin molecule. The 125,000 and 30,000 Mr lipovitellin polypeptides are encoded by the sequences at the N-terminal and the C-terminal sides of the phosvitin section, respectively. The main features of the gene and protein sequences, and the evolutionary implications, are discussed.     

Specific stimulation of ribosomal RNA synthesis in E. coli by a protein factor

Summary Ribosomal RNA synthesis in a purified system is stimulated by a crude protein fraction prepared from E. coli. The positive effector which is not associated with RNA polymerase, nor is the sigma factor, increases the initiation frequency on a rRNA operon. The additional rRNA synthesis is inhibited by ppGpp to the same extent as the basal one.The evidence presented points to the existence of a positive control element for rRNA synthesis, which activity depends upon the physiological state of the cell.