Improved cytosine base editors generated from TadA variants

Cytosine base editors (CBEs) enable programmable genomic C·G-to-T·A transition mutations and typically comprise a modified CRISPR-Cas enzyme, a naturally occurring cytidine deaminase, and an inhibitor of uracil repair. Previous studies have shown that CBEs utilizing naturally occurring cytidine deaminases may cause unguided, genome-wide cytosine deamination. While improved CBEs that decrease stochastic genome-wide off-targets have subsequently been reported, these editors can suffer from suboptimal on-target performance. Here, we report the generation and characterization of CBEs that use engineered variants of TadA (CBE-T) that enable high on-target C·G to T·A across a sequence-diverse set of genomic loci, demonstrate robust activity in primary cells and cause no detectable elevation in genome-wide mutation. Additionally, we report cytosine and adenine base editors (CABEs) catalyzing both A-to-I and C-to-U editing (CABE-Ts). Together with ABEs, CBE-Ts and CABE-Ts enable the programmable installation of all transition mutations using laboratory-evolved TadA variants with improved properties relative to previously reported CBEs.

Assessment of beliefs and attitudes about electroconvulsive therapy posted on Twitter: An observational study

BACKGROUND

Electroconvulsive therapy (ECT) is an effective and safe medical procedure that mainly indicated for depression, but is also indicated for patients with other conditions. However, ECT is among the most stigmatized and controversial treatments in medicine. Our objective was to examine social media contents on Twitter related to ECT to identify and evaluate public views on the matter.

METHODS

We collected Twitter posts in English and Spanish mentioning ECT between January 1, 2019 and October 31, 2020. Identified tweets were subject to a mixed method quantitative-qualitative content and sentiment analysis combining manual and semi-supervised natural language processing machine-learning analyses. Such analyses identified the distribution of tweets, their public interest (retweets and likes per tweet), and sentiment for the observed different categories of Twitter users and contents.

RESULTS

"Healthcare providers" users produced more tweets (25%) than "people with lived experience" and their "relatives" (including family members and close friends or acquaintances) (10% combined), and were the main publishers of "medical" content (mostly related to ECT's main indications). However, more than half of the total tweets had "joke or trivializing" contents, and such had a higher like and retweet ratio. Among those tweets manifesting personal opinions on ECT, around 75% of them had a negative sentiment.

CONCLUSIONS

Mixed method analysis of social media contents on Twitter offers a novel perspective to examine public opinion on ECT, and our results show attitudes more negative than those reflected in studies using surveys and other traditional methods.

Use of the Minimum Basic Data Set as a tool for the epidemiological surveillance of mesothelioma

BACKGROUND

Mesothelioma is a very aggressive tumor that appears after several decades of asbestos exposure. The Minimum Basic Data Set (MBDS) has been validated for the incidence of mesothelioma in Italy, but not in Spain. The objectives of this investigation are: to estimate the prevalence, incidence and mortality of mesothelioma in the Community of Madrid (CM); to evaluate the distribution of this risk within the territory; and to explore validity of the MBDS in the epidemiological surveillance of mesothelioma.

METHODS

Prevalence, incidence and mortality mesothelioma rates were calculated for the CM from data of the MBDS (2016 and 2017), and mortality data of the Spanish National Statistics Institute (INE) for the same period. The geographical distribution of cases and deaths, and its correlation at municipal level was studied. Statistical analysis with R and Excel tools was carried out.

RESULTS

The incidence of mesothelioma in the CM was higher than in previous years. Mortality estimated by the MBDS and calculated using INE data for 2016 were similar in the CM. The correlation between the geographical patterns of risk of mesothelioma obtained from the two sources was high (r = 0.86). The aggregation of cases continues in municipalities in the south, detecting the maximum risk in Aranjuez.

CONCLUSION

The MBDS and INE are good resources for monitoring the risk of mesothelioma. New studies that investigate the aggregation of cases in Aranjuez are required.

[Epidemiology and public health in the COVID-19 epidemic]

In the last year, all have suffered the devastating consequences of the SARS-CoV-2 epidemic. Over the course of a few months, the news media has bombarded us with messages about incidences, lethality, or even more technical measurements such as R0 or the attack rate. With this update, we hope to clarify basic concepts on the dynamic of the epidemic as well as present what is known about it as of the time of writing. To do so, the information available from international bodies such as the World Health Organization as well as the Ministry of Health has been extracted and used. In no case is it to be understood as a fixed or known situation; it is a situation that, in contrast, is invariably changeable.

Molecular Basis of Bacillus subtilis ATCC 6633 Self-Resistance to the Phosphono-oligopeptide Antibiotic Rhizocticin

Rhizocticins are phosphono-oligopeptide antibiotics that contain a toxic C-terminal ( Z) -l -2-amino-5-phosphono-3-pentenoic acid (APPA) moiety. APPA is an irreversible inhibitor of threonine synthase (ThrC), a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the conversion of O-phospho-l-homoserine to l-threonine. ThrCs are essential for the viability of bacteria, plants, and fungi and are a target for antibiotic development, as de novo threonine biosynthetic pathway is not found in humans. Given the ability of APPA to interfere in threonine metabolism, it is unclear how the producing strain B. subtilis ATCC 6633 circumvents APPA toxicity. Notably, in addition to the housekeeping APPA-sensitive ThrC ( BsThrC), B. subtilis encodes a second threonine synthase (RhiB) encoded within the rhizocticin biosynthetic gene cluster. Kinetic and spectroscopic analyses show that PLP-dependent RhiB is an authentic threonine synthase, converting O-phospho-l-homoserine to threonine with a catalytic efficiency comparable to BsThrC. To understand the structural basis of inhibition, we determined the crystal structure of APPA bound to the housekeeping BsThrC, revealing a covalent complex between the inhibitor and PLP. Structure-based sequence analyses reveal structural determinants within the RhiB active site that contribute to rendering this ThrC homologue resistant to APPA. Together, this work establishes the self-resistance mechanism utilized by B. subtilis ATCC 6633 against APPA exemplifying one of many ways by which bacteria can overcome phosphonate toxicity.

Experimental study of the application of a new bone cement loaded with broad spectrum antibiotics for the treatment of bone infection

OBJECTIVES

To evaluate the in vivo behaviour of a new bone cement loaded with antibiotics, in a rabbit bone infection model.

MATERIAL AND METHODS

Sixteen New Zealand rabbits divided into 4 groups were used, depending on the cement (commercial or experimental) and the antibiotic (vancomycin or linezolid) used to control a bone infection caused by Staphylococcus aureus. The commercial cement is Palacos^® R and the experimental cement has been achieved by adding PLGA to the solid phase of Palacos^® R cement. A novel histological staging method based on bone histoarchitecture has been used. This staging allows us a global vision of bone repair capacity, in the presence of modified cement, and also allows us to correlate the damage generated with the functionality of the tissue.

RESULTS

The degree of bone destructuration found depended on the type of cement and antibiotic, and was higher in the groups with commercial cement than in the experimental group (P<.01) and in the groups with linezolid with respect to vancomycin (P=.04) The percentage of macrophages varied exclusively depending on the antibiotic used, and was higher in the vancomycin groups (P=.04).

DISCUSSION

The development of new formulations of bone cement that release more, and more prolonged, new generation antibiotics such as linezolid, present an in vivo behaviour superior to commercial cement, respecting the bone structure. This behaviour would have a clinical implication in fighting infections by increasingly resistant germs in the treatment of prosthetic infection.

Two Flavoenzymes Catalyze the Post-Translational Generation of 5-Chlorotryptophan and 2-Aminovinyl-Cysteine during NAI-107 Biosynthesis

Lantibiotics are ribosomally synthesized and post-translationally modified antimicrobial peptides containing thioether rings. In addition to these cross-links, the clinical candidate lantibiotic NAI-107 also possesses a C-terminal S-[(Z)-2-aminovinyl]-d-cysteine (AviCys) and a unique 5-chloro-l-tryptophan (ClTrp) moiety linked to its potent bioactivity. Bioinformatic and genetic analyses on the NAI-107 biosynthetic gene cluster identified mibH and mibD as genes encoding flavoenzymes responsible for the formation of ClTrp and AviCys, respectively. The biochemical basis for the installation of these modifications on NAI-107 and the substrate specificity of either enzyme is currently unknown. Using a combination of mass spectrometry, liquid chromatography, and bioinformatic analyses, we demonstrate that MibD is an FAD-dependent Cys decarboxylase and that MibH is an FADH₂-dependent Trp halogenase. Most FADH₂-dependent Trp halogenases halogenate free Trp, but MibH was only active when Trp was embedded within its cognate peptide substrate deschloro NAI-107. Structural comparison of the 1.88-Å resolution crystal structure of MibH with other flavin-dependent Trp halogenases revealed that subtle amino acid differences within the MibH substrate binding site generates a solvent exposed crevice presumably involved in determining the substrate specificity of this unusual peptide halogenase.

New Insights into the Biosynthetic Logic of Ribosomally Synthesized and Post-translationally Modified Peptide Natural Products

Ribosomally synthesized and post-translationally modified peptides (RiPPs) are a large group of structurally diverse natural products. Their biological activities and unique biosynthetic pathways have sparked a growing interest in RiPPs. Furthermore, the relatively low genetic complexity associated with RiPP biosynthesis makes them excellent candidates for synthetic biology applications. This Review highlights recent developments in the understanding of the biosynthesis of several bacterial RiPP family members, the use of the RiPP biosynthetic machinery for generating novel macrocyclic peptides, and the implementation of tools designed to guide the discovery and characterization of novel RiPPs.

Substrate specificity of the lanthipeptide peptidase ElxP and the oxidoreductase ElxO

The final step in lanthipeptide biosynthesis involves the proteolytic removal of an N-terminal leader peptide. In the class I lanthipeptide epilancin 15X, this step is performed by the subtilisin-like serine peptidase ElxP. Bioinformatic, kinetic, and mass spectrometric analysis revealed that ElxP recognizes the stretch of amino acids DLNPQS located near the proteolytic cleavage site of its substrate, ElxA. When the ElxP recognition motif was inserted into the noncognate lanthipeptide precursor NisA, ElxP was able to proteolytically remove the leader peptide from NisA. Proteolytic removal of the leader peptide by ElxP during the biosynthesis of epilancin 15X exposes an N-terminal dehydroalanine on the core peptide of ElxA that hydrolyzes to a pyruvyl group. The short-chain dehydrogenase ElxO reduces the pyruvyl group to a lactyl moiety in the final step of epilancin 15X maturation. Using synthetic peptides, we also investigated the substrate specificity of ElxO and determined the 1.85 Å resolution X-ray crystal structure of the enzyme.

Association of toll-like receptor four single nucleotide polymorphisms with incidence of infectious bovine keratoconjunctivitis (IBK) in cattle

Toll-like receptor 4 (TLR4) is a receptor protein that binds pathogen ligands, which are mainly associated with Gram-negative bacteria. The objective of this study was to investigate the association of nucleotide polymorphisms in TLR4 with infectious bovine keratoconjunctivitis (IBK), or pinkeye, incidence in American Angus cattle. Animals with previously calculated breeding values for IBK susceptibility were used to identify two SNPs in TLR4; Int1 (A/G) in intron1 (-26 Ex2 position) and Ex3 (C/T) in exon3 (1,678 position). To investigate the possible role of these SNPs in IBK susceptibility, the disease incidence information was collected on 370 calves raised in Iowa at two time points-June or August (disease season) and October (at weaning) and genotyped using PCR-RFLP protocols. In statistical models including year, pasture management group, and SNP, the Int1 SNP had a significant effect on IBK infection rates both in-season (P < 0.05) and at weaning (P < 0.01), whereas the Ex3 SNP was not significant (P > 0.79) at either time point. Furthermore, the Int1 SNP alone could account for 2.1% of phenotypic variation in IBK infection during the disease season and 3.0% of phenotypic variation in IBK infection at the time of weaning. These data indicate that there is a relationship between Int1 genotype and the rate of IBK infection in American Angus cattle.

Thrombospondin-1 suppresses spontaneous tumor growth and inhibits activation of matrix metalloproteinase-9 and mobilization of vascular endothelial growth factor

Growth of tumors and metastasis are processes known to require neovascularization. To ascertain the participation of the endogenous angiogenic inhibitor thrombospondin-1 (TSP1) in tumor progression, we generated mammary tumor-prone mice that either lack, or specifically overexpress, TSP1 in the mammary gland. Tumor burden and vasculature were significantly increased in TSP1-deficient animals, and capillaries within the tumor appeared distended and sinusoidal. In contrast, TSP1 overexpressors showed delayed tumor growth or lacked frank tumor development (20% of animals); tumor capillaries showed reduced diameter and were less frequent. Interestingly, absence of TSP1 resulted in increased association of vascular endothelial growth factor (VEGF) with its receptor VEGFR2 and higher levels of active matrix metalloproteinase-9 (MMP9), a molecule previously shown to facilitate both angiogenesis and tumor invasion. In vitro, enzymatic activation of proMMP9 was suppressed by TSP1. Together these results argue for a protective role of endogenous inhibitors of angiogenesis in tumor growth and implicate TSP1 in the in vivo regulation of metalloproteinase-9 activation and VEGF signaling.

Vascular repair after menstruation involves regulation of vascular endothelial growth factor-receptor phosphorylation by sFLT-1

Regeneration of the endometrium after menstruation requires a rapid and highly organized vascular response. Potential regulators of this process include members of the vascular endothelial growth factor (VEGF) family of proteins and their receptors. Although VEGF expression has been detected in the endometrium, the relationship between VEGF production, receptor activation, and endothelial cell proliferation during the endometrial cycle is poorly understood. To better ascertain the relevance of VEGF family members during postmenstrual repair, we have evaluated ligands, receptors, and activity by receptor phosphorylation in human endometrium throughout the menstrual cycle. We found that VEGF is significantly increased at the onset of menstruation, a result of the additive effects of hypoxia, transforming growth factor-alpha, and interleukin-1beta. Both VEGF receptors, FLT-1 and KDR, followed a similar pattern. However, functional activity of KDR, as determined by phosphorylation studies, revealed activation in the late menstrual and early proliferative phases. The degree of KDR phosphorylation was inversely correlated with the presence of sFLT-1. Endothelial cell proliferation analysis in endometrium showed a peak during the late menstrual and early proliferative phases in concert with the presence of VEGF, VEGF receptor phosphorylation, and decrease of sFLT-1. Together, these results suggest that VEGF receptor activation and the subsequent modulation of sFLT-1 in the late menstrual phase likely contributes to the onset of angiogenesis and endothelial repair in the human endometrium.

Antimycobacterial activity of new quinoxaline-2-carbonitrile and quinoxaline-2-carbonitrile 1,4-di-N-oxide derivatives

The compounds being reported in this paper have all been evaluated within the TAACF Antituberculosis Screen Program, and some of them have been shown to possess high growth inhibition activity against Mycobacterium tuberculosis and Mycobacterium avium in the run of the first and second level in vitro screenings. The three compounds which have shown a good SI (Selectivity Index) are 2b, 4b and 4d; in addition, 6,7-dimethyl-3-[4-(4'-nitrophenyl)piperazinl-yl]quinoxaline-2-carbonitrilo 1,4-di-N-oxide (4b) is currently being tested within the in vivo antituberculosis screening in view of its very good in vitro activity.

Nutritional regulation of nucleoside transporter expression in rat small intestine

BACKGROUND & AIMS

Concentrative nucleoside transporters CNT1 (pyrimidine preferring) and CNT2 (purine preferring) may be involved in the uptake of nucleoside-derived drugs used in antiviral and chemical therapies. The possibility that nucleoside carrier isoform expression is modulated by nutrient availability has been studied.

METHODS

CNT1 and CNT2 tissue distribution was determined by Western blot analysis. The effect of 48-hour starvation on CNT expression was then studied. Nucleoside transporter expression and uptake activity were measured in jejunal brush border plasma membrane vesicles from fed and starved rats. The expression of nucleoside transporters was later determined in a second model of nutrient deficiency: rats fed a purified diet with or without nucleotides for 10 days.

RESULTS

CNT1 and CNT2 nucleoside transporters were expressed in a wider variety of tissues than expected from messenger RNA distribution analysis. CNT1 was sensitive to nutrient availability in small intestine and, accordingly, jejunal brush border membrane vesicles from 48-hour-fasted rats showed increased expression of CNT1 and enhanced Na(+)-dependent thymidine and gemcitabine uptake. This effect was mimicked by feeding semipurified diets lacking nucleotides.

CONCLUSIONS

Substrate availability modulates nucleoside transporter expression (CNT1) in rat jejunum in vivo.

Antiangiogenic domains shared by thrombospondins and metallospondins, a new family of angiogenic inhibitors

The growth of solid tumors has been shown to depend on neovascularization. By understanding the mechanisms that control the neovascular response, it may be possible to design therapeutic strategies to selectively prevent or halt pathologic vascular growth and restrain cancer progression. Thrombospondin-1 is an extracellular matrix protein that among several functions suppresses capillary growth in angiogenesis assays. We have demonstrated that within the context of the mammary gland TSP1 can modulate normal development of blood vessels. Expression of TSP1 in transgenic animals under the control of the MMTV promoter was associated with a 50-72% reduction in capillary growth. In addition, TSP1 reduced tumor size in transgenic overexpressors. The data suggest an important role for TSP1 in modulating vascular growth in both normal and pathologic tissues. The antiangiogenic region of TSP1 has been mapped to the type I (properdin) repeats. To identify novel proteins with such a domain, we have cloned two cDNAs (METH-1 and METH-2) which also have antiangiogenic properties. In addition to carboxyterminal thrombospondin-like domains they also contain metalloproteinase and disintegrin sequences. Expression of both proteins is broad but nonoverlapping. Recombinant fragments from these sequences have strong antiangiogenic potential in the CAM and cornea pocket assays. At the same molar ratio, METH-1 and METH-2 are about 20-fold more potent than TSP1. We predict that these proteins are likely endogenous modulators of vascular growth with relevant therapeutic potential in cancer and other disease states.

New quinoxalinecarbonitrile 1,4-di-N-oxide derivatives as hypoxic-cytotoxic agents

We report the synthesis and biological in vitro activities of 16 new 2-quinoxalinecarbonitrile 1,4-di-N-oxides. These compounds present new basic lateral chains (piperazines and anilines) in the 3 position as well as different substituents in the 6 and/or 7 positions of the quinoxaline ring. Among piperazine derivatives, 4b (a 7-chloro-3-(4-methylpiperazin-1-yl) derivative) was the most potent (P = 0.5 x10(-6) M). In general, aniline derivatives were more potent and selective than the former, compound 12b (with a 4-(methylphenyl)amino moiety in the 3 position and a chlorine atom in the 7 position) being the best one (P = 3 x 10(-6) 16).

METH-1, a human ortholog of ADAMTS-1, and METH-2 are members of a new family of proteins with angio-inhibitory activity

We have studied two related proteins that contain a repeated amino acid motif homologous to the anti-angiogenic type 1 repeats of thrombospondin-1 (TSP1). Complete sequence analysis revealed no other similarities with TSP1, but identified unique signal sequences, as well as metalloprotease and disintegrin-like domains in the NH(2) termini. We named these proteins METH-1 and METH-2 due to the novel combination of metalloprotease and thrombospondin domains. Overall amino acid sequence identity between METH-1 and METH-2 is 51. 7%, yet transcript distribution revealed non-overlapping patterns of expression in tissues and cultured cell lines. To characterize these proteins functionally, we isolated full-length cDNAs, produced recombinant protein, and generated antisera to the recombinant proteins. Both METH-1 and METH-2 represent single copy genes, which encode secreted and proteolytically processed proteins. METH proteins suppressed fibroblast growth factor-2-induced vascularization in the cornea pocket assay and inhibited vascular endothelial growth factor-induced angiogenesis in the chorioallantoic membrane assay. Suppression of vessel growth in both assays was considerably greater than that mediated by either thrombospondin-1 or endostatin on a molar basis. Consistent with an endothelial specific response, METH-1 and METH-2 were shown to inhibit endothelial cell proliferation, but not fibroblast or smooth muscle growth. We propose that METH-1 and METH-2 represent a new family of proteins with metalloprotease, disintegrin, and thrombospondin domains. The distinct distribution of each gene product suggests that each has evolved distinct regulatory mechanisms that potentially allow for fine control of activity during distinct physiological and pathological states.

Synthesis and antituberculosis activity of new 2-quinoxalinecarbonitrile 1,4-di-N-oxides

With the advent of multidrug-resistant Mycobacterium tuberculosis strains, new and effective therapies are rapidly needed to combat infections caused by these strains. Some new 2-quinoxalinecarbonitrile 1,4-di-N-oxides have been synthesized and tested as antituberculosis agents and interesting results have been obtained from the first screening.

New quinoxaline 1,4-di-N-oxides for treatment of tuberculosis

Some quinoxaline 1,4-di-N-oxides derivatives with very different substituents in 2, 3, 6 and 7 positions have been synthesized in order to obtain new hypoxia selective agents. Some of these products have been tested as antituberculosis agents and very interesting results have been obtained from the first screening.

[Sexual dysfunction with antidepressive agents. Effect of the change to amineptine in patients with sexual dysfunction secondary to SSRI]

Sexual dysfunction secondary to the use of antidepressants, especially clomipramine or SSRI's is an adverse effect that is often underestimated and according to earlier studies, this can affect approximately 60% of the patients. This presents as a decrease in libido, alterations in the ability to reach orgasm/ejaculation, and an erectile dysfunction or a decreased vaginal lubrication. This dysfunction appears to be related with the resulting increase in serotonin and with the stimulation of serotonin 5HT2 receptors.

OBJECTIVES

1) Evaluate the effect of amineptine, a drug with an increased dopamine transmission and scant serotonin transmission, on the sexual function of depressed patients who begin treatment, and 2) evaluate whether the change to amineptine improves the sexual function in patients who presented sexual dysfunction after beginning treatment with a SSRI.

MATERIAL AND METHODS

Prospective, observational, open and multicentric design. 111 patients with an average age of 41.3 years (36 men, 75 women) were distributed into three groups: Group 1 (n= 26): patients with depression (DSM IV) who begin de novo treatment with amineptine 200 mg/day. Group 2 (n= 47): depressed patients undergoing treatment with a SSRI who show a favorable response and who present sexual dysfunction secondary to a poorly tolerated treatment, so the treatment is changed to 200 mg/day of amineptine. Group 3 (n= 38): patients with the same characteristics as those of group 2, but whose treatment was changed to 20 mg/day of paroxetine. The <<Questionnaire for the Measure of Sexual Dysfunction Secondary to the use of Psychotropic Drugs>> (Montejo et al, 1996) was used together with the Hamilton Depression Scale, the IGC Scale, and an adverse events scale, over a 6 months follow up period during which visits took place at: baseline, month 1, month 2, month 3, and month 6.

RESULTS

In group 1, treated with amineptine from the beginning, of the 5 patients who showed a decrease in the libido at the beginning of the treatment, only one still presented this in the 6th month. The Hamilton Scale decreased from 23.12 (baseline) to 5.25 after 6 months. After substituting amineptine for SSRI's in patients with sexual dysfunction, the incidence of any type of sexual dysfunction decreased significantly from 100% (baseline) to 55.3% after 6 months. (P< 0.001). The incidence of delayed orgasm dropped to 15.8%, anorgasmia to 17.4%, and impotence dropped to 15.8% in this group, with the antidepressant effect that had already been achieved with the SSRI being maintained. However, in group 3 there was barely any improvement on the sexual function after changing to paroxetine (20 mg/day), with the baseline incidence being 100% and the incidence after 6 months being 89.7%. In this last group the antidepressant effect present at the baseline level, was maintained.

CONCLUSIONS

Amineptine was shown to be an effective antidepressant in the patients studied, and did not cause secondary sexual dysfunction, and even improved the dysfunction that was present in some patients. In those patients previously treated with SSRI's, amineptine is able to significantly improve the sexual dysfunction and yet maintain the efficacy of the antidepressive treatment used before these 6 months. On the other hand, Paroxetine did not improve the sexual dysfunction of the people in whom this drug substituted another SSRI, as this is an adverse effect common to the entire group of selective serotonin re-uptake inhibiting drugs. Amineptine showed a good safety and tolerance profile. Its most common side effect (anxiety/restlessness) disappeared 2 months after the beginning of the treatment.

Isolation of efficient antivirals: genetic suppressor elements against HIV-1

The development of general approaches for the isolation of efficient antivirals and the identification and validation of targets for drug screening are becoming increasingly important, due to the emergence of previously unrecognized viral diseases. The genetic suppressor element (GSE) technology is an approach based on the functional expression selection of efficient genetic inhibitors from random fragment libraries derived from a gene or genome of interest. We have applied this technology to isolate potent genetic inhibitors against HIV-1. Two strategies were used to select for GSEs that interfere with latent virus induction and productive HIV-1 infection based on the expression of intracellular and surface antigens. The selected GSEs clustered in seven narrowly defined regions of the HIV-1 genome and were found to be functionally active. These elements are potential candidates for the gene therapy of AIDS. The developed approaches can be applied to other viral pathogens, as well as for the identification of cellular genes supporting the HIV-1 life cycle.

Synthesis and antituberculosis activity of some new 2-quinoxalinecarbonitriles

Tuberculosis, an ancient disease undergoing recent control by public hygiene and drug therapy, has experienced a recrudescence throughout the world. New and effective therapies are rapidly needed to combat infections caused by these strains. Some new 2-quinoxalinecarbonitriles have been synthesized and tested as antituberculosis agents and interesting results have been obtained from the first screening.

Hepatotoxic agent thioacetamide induces biochemical and histological alterations in rat small intestine

We have assessed the effect of the oral ingestion of thioacetamide on small intestine structure and function. Thioacetamide-treated rats showed diminished mucosa weight; protein, DNA, and RNA content; and leucine aminopeptidase activity as compared to controls in both jejunum and ileum. In the jejunum, there was a reduction in the activities of alkaline phosphatase, ATPase, glucose-6-phosphatase, and myeloperoxidase, whereas in the ileum, maltase, lactase, and gamma-glutamyltranspeptidase were reduced. In both jejunum and ileum we found enlarged intercellular spaces, dark epithelial enterocytes, and lymphocyte infiltration. Enterocytes showed lobulated nuclei, deranged mitochondria with loss of their cristae, dilated rough endoplasmic reticulum containing dense material, and vesiculation of the smooth endoplasmic reticulum and the Golgi apparatus. Smooth muscle cells of the intestine exhibited ultrastructural alterations. These findings indicate that chronic oral intake of thioacetamide mimics not only hepatic alterations but also small intestine alterations normally associated with human cirrhosis.

Actin gene structure in two Artemia species, A. franciscana and A. parthenogenetica

Genomic clones coding for actin have been isolated from two species of the crustacean Artemia, A. parthenogenetica and A. franciscana. The Act211 isoform gene was isolated from A. parthenogenetica, and the two other isoform genes, Act302 and Act403, were isolated from A. franciscana. The comparison of the nucleotide sequence of genomic and cDNA clones showed an interspecific divergence of 4% in translated and 6.1% in untranslated regions. However, the establishment of the partial structure of the Act211 gene in A. franciscana and of the Act302 gene in A. parthenogenetica suggests their similarity in the two species. The Act211 gene is divided into four exons, the Act302 gene into six exons, and the Act403 gene into seven exons. The three genes have introns in the 5' untranslated region and between codons 41 and 42. The Act211 and 403 genes have one common intron in codon 168. The Act302 and 403 genes have common introns between codons 121-122, 246-247, and within codon 301. While introns in the 5' untranslated region and between codons 41-42 and 121-122 are present in many organisms, the introns in positions 168 and 246-247 had only been found previously in actin genes from the nematode Onchocerca volvulus and the green alga Volvox carterii, respectively. The intron in position 301 had not been reported before. The transcription initiation sites of these three genes as well as the nucleotide sequences of the promoter regions have been also determined.

Deprivation of dietary nucleotides decreases protein synthesis in the liver and small intestine in rats

BACKGROUND & AIMS

Dietary nucleotides are reported to influence the growth and functioning of the liver and small intestine. The aim of this study was to examine the mechanism by which nucleotides exert their effects in these tissues by assessing protein synthesis activity and related parameters in the presence or absence of dietary nucleotides.

METHODS

Rats were fed a purified diet with or without nucleotides for 10 days. Fractional protein synthesis rate, RNA and DNA concentrations, polysome size distribution, and number of ribosomes were assessed.

RESULTS

Fractional protein synthesis rates of the liver and small intestine were lower in the nucleotide-deprived group than in the control group. In the liver, RNA concentration was also lower in the nucleotide-deprived group, but values in the small intestine were similar in the two groups. In the liver, deprivation of nucleotides resulted in a reduction in the number of ribosomes and in polysome breakdown. Protein and DNA concentrations did not vary in the liver; however, the concentration of DNA was lower in the small intestine of the nucleotide-deprived group than in the control group.

CONCLUSIONS

Dietary nucleotides can modulate protein synthesis in the liver and small intestine as a result of tissue-specific nucleic acid changes.

Age-related response of the small intestine to severe starvation and refeeding in rats

The impact of severe starvation and refeeding on the intestinal mucosa of rats of different ages has been studied in a diet-controlled model. Structural and functional alterations of the small intestinal mucosa were assessed by standard parameters including mucosal protein, DNA content as well as maltase, sucrase and leucine aminopeptidase enzymatic activities. Decreases in mucosal mass, DNA, protein and leucine aminopeptidase activity in both the jejunum and ileum caused by starvation, diminished with age. The depression of disaccharidase activities increased with age in the jejunum but not in the ileum. Except for jejunal protein and leucine aminopeptidase activity, the recovery from starvation, after refeeding, was complete for the other parameters studied, regardless of age.

Detection of donor-derived cells by polymerase chain reaction in neonatally tolerant mice. Microchimerism fails to predict tolerance

Although it has long been appreciated that establishment of chimerism is important in the acquisition and maintenance of allograft tolerance, the importance of this relationship has been reemphasized recently. Using the exquisite sensitivity of the polymerase chain reaction we have studied qualitatively and quantitatively the presence of donor-derived chimeric cells in relation to the ability of neonatally injected mice to display skin graft tolerance or rejection. We have found that virtually all mice that receive neonatal injections of F1 hematopoietic cells acquire donor-derived chimerism that is detectable in blood, spleen, lymph nodes, and thymus. Surprisingly, neither the presence nor the quantity of chimeric cells predicts whether a particular neonatally injected mouse will accept or reject donor-specific skin allografts. Moreover, whether the test skin allograft is accepted (tolerance) or rejected by neonatally injected mice, chimerism typically remains detectable within recipient lymphoid tissues. In functionally tolerant mice, challenge with a test skin allograft actually leads to a remarkable expansion in donor-derived genetic sequences, implying that donor-derived cells have been induced by the graft to undergo proliferation. Since persistence of chimerism without proliferation after test grafting is characteristic of mice that fail to display tolerance, we believe that achievement of a threshold level of donor-derived alloantigen may be necessary to retain the tolerant state. We conclude that chimerism is essential for the induction of neonatally induced tolerance, and its expansion may play an important role in the maintenance of that tolerance, when challenged by an allograft.

Dietary nucleotides accelerate intestinal recovery after food deprivation in old rats

Previous studies in very young rats have shown that dietary nucleotides improve small intestine repair after injury or malnutrition. To investigate the potential effect of nucleotides in old rats, which have a diminished capability for intestinal repair, 17-mo-old rats were deprived of food for 5 d and then fed a nucleotide-free diet or a nucleotide-supplemented diet for 3 or 6 d. Intestinal jejunal and ileal mucosal weight, protein and DNA were evaluated as intestinal growth markers, and brush-border maltase, sucrase, lactase and aminopeptidase activities were evaluated as intestinal differentiation markers. The adenine nucleotide pool and the adenylate energy charge were also evaluated as indices of nucleotide availability. Food deprivation significantly decreased mucosal growth markers as well as differentiation markers in both jejunum and ileum. The ATP pool was also significantly depressed, but the adenylate energy charge was not significantly altered. To a certain extent, refeeding restored the losses, but in the rats that were fed the nucleotide-free diet, the restoration of the jejunum was significantly slower and the restoration of the ileum differentiation markers was incomplete compared with the rats fed the nucleotide-supplemented diet. The results suggest that dietary nucleotide intake in the elderly may accelerate the normal physiological intestinal response to refeeding after food deprivation.

Maturation status of small intestine epithelium in rats deprived of dietary nucleotides

We describe the changes of several brush-border enzymatic activities in different subpopulations of epithelial cells, separated sequentially from the villus tip-to-crypt axis of the small intestine, induced by deprivation of dietary nucleotides for different periods of time in adult rats. Deprivation of dietary nucleotides lead to a decrease in the content and specific activity of alkaline phosphatase, leucine-aminopeptidase, maltase, sucrase and lactase in the villus tip, but had little effect on the crypt zone. The effect of the nucleotide deprivation on the enzymatic activity progressively increased towards the tip of the villus. Since these enzymes are maturation markers of the intestinal cells, these results support the idea that dietary nucleotides affect the maturation status of small-intestine epithelium.

Gene expression after resumption of development of Artemia franciscana cryptobiotic embryos

The steady-state levels of six different mRNAs have been studied during Artemia franciscana development. Some of these mRNAs are present in the cryptobiotic cyst, like those coding for cytoplasmic actins, sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase, and the Na+, K(+)-ATPase alpha-subunit isoform coded by the clone pArATNa136. The expression of these mRNAs is markedly induced during cyst development. A small increase in mRNA levels can be observed for some genes at very early stages of development (2 h). The main increase is observed between 4 and 16 h of development for all these genes, although the time course of mRNA accumulation is different for each one of the genes studied. Some other genes, like those coding for muscle actin (actin 3) or the Na+, K(+)-ATPase alpha-subunit isoform coded by the cDNA clone alpha 2850, are not expressed in the cyst before resumption of development and their expression is induced after 10 or 6 h of development, respectively. These data on the kinetic of mRNA accumulation provide the information required to determine transcriptionally active developmental stages, necessary to study in more detail the mechanisms of transcriptional regulation during activation of cryptobiotic cysts and resumption of embryonic development.

Percutaneous balloon valvotomy for patients with severe mitral stenosis

Thirty-five patients with severe mitral stenosis underwent percutaneous mitral valvotomy (PMV). There were 29 female and six male patients (mean age 49 +/- 3 years, range 13 to 87). After transseptal left heart catheterization, PMV was performed with either a single- (20 patients) or double- (14 patients) balloon dilating catheter. Hemodynamic and left ventriculographic findings were evaluated before and after PMV. There was one death. Mitral regurgitation developed or increased in severity in 15 patients (43%). One patient developed complete heart block requiring a permanent pacemaker. PMV resulted in a significant decrease in mitral gradient from 18 +/- 1 to 7 +/- 1 mm Hg (p less than .0001) and a significant increase in both cardiac output from 3.9 +/- 0.2 to 4.6 +/- 0.2 liters/min (p less than .001) and in mitral valve area from 0.8 +/- 0.1 to 1.7 +/- 0.2 cm2 (p less than .0001) Effective balloon dilating diameter per square meter of body surface area correlated significantly with the decrease in mitral gradient but did not correlate with the degree of mitral regurgitation. There was no correlation of age, prior mitral commissurotomy or mitral calcification with hemodynamic results. PMV is an effective nonsurgical procedure for patients with mitral stenosis, including those with pliable valves, those with previous commissurotomy, and even those with mitral calcification.

Ascending aorta-right pulmonary artery anastomosis in children with complex cardiac malformations. Long-term results in 30 cases

In this report, we shall analyze the results obtained with palliative treatment in 30 patients with congenital heart disease who were operated upon at the University Hospital of Caracas during the period 1968 to 1972. In all cases, an ascending aorta-right pulmonary artery anastomosis was performed. Although we believe that the Blalock-Taussig and Potts shunt are satisfactory operations in some cases, at the present time we prefer the aorta-right pulmonary branch anastomosis in Fallots tetralogy and other congenital heart diseases such as single ventricle. In Fallot's tetralogy, particularly, this procedure provides better results, because the anastomosis can be closed through the aorta when these patients are later subjected to total correction with extracorporeal circulation.