LY3041658/ interleukin-8 complex structure as targets for IL-8 small molecule inhibitors discovery using a combination of in silico methods

Since interleukin-8 (IL-8/CXCL8) and its receptor, CXCR1 and CXCR2, were known in the early 1990s, biological pathways related to these proteins were proven to have high clinical value in cancer and inflammatory/autoimmune conditions treatment. Recently, IL-8 has been identified as biomarker for severe COVID-19 patients and COVID-19 prognosis. Boyles et al. (mAbs 12 (2020), pp. 1831880) have published a high-resolution X-ray crystal structure of the LY3041658 Fab in a complex human CXCL8. They described the ability to bind to IL-8 and the blocking of IL-8/its receptors interaction by the LY3041658 monoclonal antibody. Therefore, the study has been designed to identify potential small molecules inhibiting interleukin-8 by targeting LY3041658/IL-8 complex structure using an in silico approach. A structure‑based pharmacophore and molecular docking models of the protein active site cavity were generated to identify possible candidates, followed by virtual screening with the ZINC database. ADME analysis of hit compounds was also conducted. Molecular dynamics simulations were then performed to survey the behaviour and stability of the ligand-protein complexes. Furthermore, the MM/PBSA technique has been utilized to evaluate the free binding energy. The final data confirmed that one newly obtained compound, ZINC21882765, may serve as the best potential inhibitor for IL-8.

Ectopic expression of GmHP08 enhances resistance of transgenic Arabidopsis toward drought stress

Ectopic expression of Glycine max two-component system member GmHP08 in Arabidopsis enhanced drought tolerance of transgenic plants, possibly via ABA-dependent pathways. Phosphorelay by two-component system (TCS) is a signal transduction mechanism which has been evolutionarily conserved in both prokaryotic and eukaryotic organisms. Previous studies have provided lines of evidence on the involvement of TCS genes in plant perception and responses to environmental stimuli. In this research, drought-associated functions of GmHP08, a TCS member from soybean (Glycine max L.), were investigated via its ectopic expression in Arabidopsis system. Results from the drought survival assay showed that GmHP08-transgenic plants exhibited higher survival rates compared with their wild-type (WT) counterparts, indicating better drought resistance of the former group. Analyses revealed that the transgenic plants outperformed the WT in various regards, i.e. capability of water retention, prevention of hydrogen peroxide accumulation and enhancement of antioxidant enzymatic activities under water-deficit conditions. Additionally, the expression of stress-marker genes, especially antioxidant enzyme-encoding genes, in the transgenic plants were found greater than that of the WT plants. In contrary, the expression of SAG13 gene, one of the senescence-associated genes, and of several abscisic acid (ABA)-related genes was repressed. Data from this study also revealed that the ectopic expression lines at germination and early seedling development stages were hypersensitive to exogenous ABA treatment. Taken together, our results demonstrated that GmHP08 could play an important role in mediating plant response to drought, possibly via an ABA-dependent manner.

Ectopic Expression of Glycine maxGmNAC109 Enhances Drought Tolerance and ABA Sensitivity in Arabidopsis

The NAC (NAM, ATAF1/2, CUC2) transcription factors are widely known for their various functions in plant development and stress tolerance. Previous studies have demonstrated that genetic engineering can be applied to enhance drought tolerance via overexpression/ectopic expression of NAC genes. In the present study, the dehydration- and drought-inducible GmNAC109 from Glycine max was ectopically expressed in Arabidopsis (GmNAC109-EX) plants to study its biological functions in mediating plant adaptation to water deficit conditions. Results revealed an improved drought tolerance in the transgenic plants, which displayed greater recovery rates by 20% to 54% than did the wild-type plants. In support of this finding, GmNAC109-EX plants exhibited lower water loss rates and decreased endogenous hydrogen peroxide production in leaf tissues under drought, as well as higher sensitivity to exogenous abscisic acid (ABA) treatment at germination and early seedling development stages. In addition, analyses of antioxidant enzymes indicated that GmNAC109-EX plants possessed stronger activities of superoxide dismutase and catalase under drought stress. These results together demonstrated that GmNAC109 acts as a positive transcriptional regulator in the ABA-signaling pathway, enabling plants to cope with adverse water deficit conditions.

Lumbar Spinal Stenosis Severity by CT or MRI Does Not Predict Response to Epidural Corticosteroid versus Lidocaine Injections

BACKGROUND AND PURPOSE

Epidural steroid injections may offer little-to-no short-term benefit in the overall population of patients with symptomatic spinal stenosis compared with lidocaine alone. We investigated whether imaging could identify subgroups of patients who might benefit most.

MATERIALS AND METHODS

A secondary analysis of the Lumbar Epidural Steroid Injections for Spinal Stenosis prospective, double-blind trial was performed, and patients were randomized to receive an epidural injection of lidocaine with or without corticosteroids. Patients (n = 350) were evaluated for qualitative and quantitative MR imaging or CT measures of lumbar spinal stenosis. The primary clinical end points were the Roland-Morris Disability Questionnaire and the leg pain numeric rating scale at 3 weeks following injection. ANCOVA was used to assess the significance of interaction terms between imaging measures of spinal stenosis and injectate type on clinical improvement.

RESULTS

There was no difference in the improvement of disability or leg pain scores at 3 weeks between patients injected with epidural lidocaine alone compared with corticosteroid and lidocaine when accounting for the primary imaging measures of qualitative spinal stenosis assessment (interaction coefficients for disability score, -0.1; 95% CI, -1.3 to 1.2; P = .90; and for the leg pain score, 0.1; 95% CI, -0.6 to 0.8; P = .81) or the quantitative minimum thecal sac cross-sectional area (interaction coefficients for disability score, 0.01; 95% CI, -0.01 to 0.03; P = .40; and for the leg pain score, 0.01; 95% CI, -0.01 to 0.03; P = .33).

CONCLUSIONS

Imaging measures of spinal stenosis are not associated with differential clinical responses following epidural corticosteroid injection.

Effects of Inflammation on Multiscale Biomechanical Properties of Cartilaginous Cells and Tissues

Cells within cartilaginous tissues are mechanosensitive and thus require mechanical loading for regulation of tissue homeostasis and metabolism. Mechanical loading plays critical roles in cell differentiation, proliferation, biosynthesis, and homeostasis. Inflammation is an important event occurring during multiple processes, such as aging, injury, and disease. Inflammation has significant effects on biological processes as well as mechanical function of cells and tissues. These effects are highly dependent on cell/tissue type, timing, and magnitude. In this review, we summarize key findings pertaining to effects of inflammation on multiscale mechanical properties at subcellular, cellular, and tissue level in cartilaginous tissues, including alterations in mechanotransduction and mechanosensitivity. The emphasis is on articular cartilage and the intervertebral disc, which are impacted by inflammatory insults during degenerative conditions such as osteoarthritis, joint pain, and back pain. To recapitulate the pro-inflammatory cascades that occur in vivo, different inflammatory stimuli have been used for in vitro and in situ studies, including tumor necrosis factor (TNF), various interleukins (IL), and lipopolysaccharide (LPS). Therefore, this review will focus on the effects of these stimuli because they are the best studied pro-inflammatory cytokines in cartilaginous tissues. Understanding the current state of the field of inflammation and cell/tissue biomechanics may potentially identify future directions for novel and translational therapeutics with multiscale biomechanical considerations.

Biology, propagation and utilization of elite coconut varieties (makapuno and aromatics)

Coconut farming is not only a vital agricultural industry for all tropical countries possessing humid coasts and lowlands, but is also a robust income provider for millions of smallholder farmers worldwide. However, due to its longevity, the security of production of this crop suffers significantly from episodes of natural disasters, including cyclone and tsunami, devastating pest and disease outbreaks, while also affected by price competition for the principal products, especially the oil. In order to reduce these pressures, high-value coconut varieties (makapuno and aromatics) have been introduced in some regions, on a limited scale, but with positive outcomes. Even though these two varieties produce fruit with delicious solid or flavoursome liquid endosperm, their distinct biochemical and cellular features unfortunately prevent their in situ germination. In fact, embryo rescue and culture have been developed historically to nurture the embryo under in vitro conditions, enabling effective propagation. In an attempt to provide a comprehensive review featuring these elite coconut varieties, this paper firstly introduces their food values and nutritional qualities, and then discusses the present knowledge of their biology and genetics. Further possibilities for coconut in general are also highlighted, through the use of advanced tissue culture techniques and efficient seedling management for sustainable production of these highly distinct and commercially attractive varieties of coconut.

Tissue culture and associated biotechnological interventions for the improvement of coconut (Cocos nucifera L.): a review

The present review discusses not only advances in coconut tissue culture and associated biotechnological interventions but also future research directions toward the resilience of this important palm crop. Coconut (Cocos nucifera L.) is commonly known as the 'tree of life'. Every component of the palm can be used to produce items of value and many can be converted into industrial products. Coconut cultivation faces a number of acute problems that reduce its productivity and competitiveness. These problems include various biotic and abiotic challenges as well as an unstable market for its traditional oil-based products. Around 10 million small-holder farmers cultivate coconut palms worldwide on c. 12 million hectares of land, and many more people own a few coconut palms that contribute to their livelihoods. Inefficiency in the production of seedlings for replanting remains an issue; however, tissue culture and other biotechnological interventions are expected to provide pragmatic solutions. Over the past 60 years, much research has been directed towards developing and improving protocols for (i) embryo culture; (ii) clonal propagation via somatic embryogenesis; (iii) homozygote production via anther culture; (iv) germplasm conservation via cryopreservation; and (v) genetic transformation. Recently other advances have revealed possible new ways to improve these protocols. Although effective embryo culture and cryopreservation are now possible, the limited frequency of conversion of somatic embryos to ex vitro seedlings still prevents the large-scale clonal propagation of coconut. This review illustrates how our knowledge of tissue culture and associated biotechnological interventions in coconut has so far developed. Further improvement of protocols and their application to a wider range of germplasm will continue to open up new horizons for the collection, conservation, breeding and productivity of coconut.

Evaluation of drought tolerance of the Vietnamese soybean cultivars provides potential resources for soybean production and genetic engineering

Drought is one of the greatest constraints to soybean production in many countries, including Vietnam. Although a wide variety of the newly produced cultivars have been produced recently in Vietnam through classical breeding to cope with water shortage, little knowledge of their molecular and physiological responses to drought has been discovered. This study was conducted to quickly evaluate drought tolerance of thirteen local soybean cultivars for selection of the best drought-tolerant cultivars for further field test. Differences in drought tolerance of cultivars were assessed by root and shoot lengths, relative water content, and drought-tolerant index under both normal and drought conditions. Our data demonstrated that DT51 is the strongest drought-tolerant genotype among all the tested cultivars, while the highest drought-sensitive phenotype was observed with MTD720. Thus, DT51 could be subjected to further yield tests in the field prior to suggesting it for use in production. Due to their contrasting drought-tolerant phenotypes, DT51 and MTD720 provide excellent genetic resources for further studies underlying mechanisms regulating drought responses and gene discovery. Our results provide vital information to support the effort of molecular breeding and genetic engineering to improve drought tolerance of soybean.

Discovery of new antagonists aimed at discriminating UII and URP-mediated biological activities: insight into UII and URP receptor activation

BACKGROUND AND PURPOSE

Recent evidence suggested that urotensin II (UII) and its paralog peptide UII-related peptide (URP) might exert common but also divergent physiological actions. Unfortunately, none of the existing antagonists were designed to discriminate specific UII- or URP-associated actions, and our understanding, on how these two endogenous peptides can trigger different, but also common responses, is limited.

EXPERIMENTAL APPROACH

Ex vivo rat and monkey aortic ring contraction as well as dissociation kinetics studies using transfected CHO cells expressing the human urotensin (UT) receptors were used in this study.

KEY RESULTS

Ex vivo rat and monkey aortic ring contraction studies revealed the propensity of [Pep(4)]URP to decrease the maximal response of human UII (hUII) without any significant change in potency, whereas no effect was noticeable on the URP-induced vasoconstriction. Dissociation experiments demonstrated the ability of [Pep(4)]URP to increase the dissociation rate of hUII, but not URP. Surprisingly, URP, an equipotent UII paralog, was also able to accelerate the dissociation rate of membrane-bound (125)I-hUII, whereas hUII had no noticeable effect on URP dissociation kinetics. Further experiments suggested that an interaction between the glutamic residue at position 1 of hUII and the UT receptor seems to be critical to induce conformational changes associated with agonistic activation. Finally, we demonstrated that the N-terminal domain of the rat UII isoform was able to act as a specific antagonist of the URP-associated actions.

CONCLUSION

Such compounds, that is [Pep(4)]URP and rUII(1-7), should prove to be useful as new pharmacological tools to decipher the specific role of UII and URP in vitro but also in vivo.

Spiers Memorial Lecture. Breeding and building molecular spies

To circumvent the limited spatial resolution of fluorescent protein imaging, we are developing genetically encoded tags for electron microscopy (EM).

An analysis of the healthcare informatics and systems in Southeast Asia: a current perspective from seven countries

This paper presents an overview of the healthcare systems in Southeast Asia, with a focus on the healthcare informatics development and deployment in seven countries, namely, Singapore, Cambodia, Malaysia, Thailand, Laos, the Philippines and Vietnam. Brief geographic and demographic information is provided for each country, followed by a historical review of the national strategies for healthcare informatics development. An analysis of the state-of-the-art healthcare infrastructure is also given, along with a critical appraisal of national healthcare provisions.

Response of the adult prostate to prepubertal and postpubertal obstruction of the vas deferens in the rat

OBJECTIVES

To determine whether obstruction of the vas deferens alters several general measures of prostate development during puberty and during prostate maintenance in the adult rat. Previous reports have suggested the possibility that vasectomy results in alterations of prostate function in experimental animals and humans.

METHODS

Adult rats and 10-day-old rats were subjected to bilateral sham operations or bilateral vasectomy, and the prostates were extirpated either 14 or 60 days later. The total prostate weight and dorsolateral and ventral lobe total protein per milligram tissue, DNA per milligram tissue, and DNA per milligram protein were determined. Dorsolateral and ventral prostate lobe sections from each group were also stained with hematoxylin-eosin and subjected to histologic examination.

RESULTS

The histologic features of the adult rat prostate were not qualitatively altered by vasectomy whether it occurred before puberty or in adult animals with mature prostates. Furthermore, vasectomy did not significantly alter the prostate weight or the protein or DNA content of either the dorsolateral or ventral lobes of the prostate compared with the sham-operated animals of either age.

CONCLUSIONS

Vas deferens obstruction does not significantly alter the parameters associated with the development or maintenance of the adult rat prostate measured in this study.

Construction of a two-photon microscope for video-rate Ca(2+) imaging

We describe the construction of a video-rate two-photon laser scanning microscope, compare its performance to a similar confocal microscope, and illustrate its use for imaging local Ca(2+) transients from cortical neurons in brain slices. Key features include the use of a Ti-sapphire femtosecond laser allowing continuous tuning over a wide (700-1000 nm) wavelength range, a resonant scanning mirror to permit frame acquisition at 30 Hz, and efficient wide-field fluorescence detection. Two-photon imaging provides compelling advantages over confocal microscopy in terms of improved imaging depth and reduced phototoxicity and photobleaching, but the high cost of commercial instruments has limited their widespread adoption. By constructing one's own system the expense is greatly reduced without sacrifice of performance, and the microscope can be more readily tailored to specific applications.

Myocardial contractile responsiveness to endothelin-1 in the post-infarction rat model of heart failure: effects of chronic quinapril

Cardiac endothelin-1 (ET-1) levels and ET receptor expression are increased in congestive heart failure (CHF). In order to determine whether this results in increased responsiveness of ET-A or ET-B receptors to ET-1, we evaluated the contractile effects of ET-1 in isolated papillary muscles isolated from hearts of control rats and from rats 4 weeks post myocardial infarction (MI) having received no therapy or chronic quinapril therapy. The ET-1 dose-response was biphasic in normal muscles. The use of the selective ET-A receptor antagonist BQ123 and the selective ET-B receptor antagonist BQ788 revealed that the initial decrease in tension was the result of ET-B receptor stimulation. Blockade of nitric oxide (NO) production with L-NAME abolished the initial decrease in tension. MI resulted in CHF that was partially reversed by quinapril. In MI, the positive inotropic effects of ET-1 were enhanced due to the loss of the initial ET-B receptor mediated decrease in tension, as well as an increase in the positive inotropic effects of ET-A receptors. This was associated with an increase in ET-A and ET-B receptor mRNA and a decrease in cardiac ecNOS protein. Four weeks of therapy with quinapril attenuated the positive inotropic effects of ET-1 and prevented the increase in ET-A receptor mRNA. Although quinapril did not restore the effects of ET-B receptor stimulation or prevent the increase in ET-B mRNA, it did restore cardiac ecNOS protein expression. Thus, the inotropic response to ET-1 is biphasic due to an overall positive inotropic effect of ET-A receptor stimulation and an ET-B receptor mediated decrease in contractility at low ET-1 concentrations which appears to be mediated by cardiac ecNOS (NO). In post-MI CHF, responsiveness to ET-A receptors increases and the ET-B mediated negative inotropic response is lost despite an increase in both receptor subtypes. Quinapril therapy attenuates these effects and normalises cardiac ecNOS protein.

Long-term effects of nonselective endothelin A and B receptor antagonism in postinfarction rat: importance of timing

BACKGROUND

Some controversy exists as to the effects of endothelin (ET) receptor antagonism on long-term post-myocardial infarction (MI) evolution, particularly as it relates to the timing of the intervention after MI (<24 hours versus 10 days).

METHODS AND RESULTS

Sham rats and rats surviving an acute MI for >20 hours (n=301) were assigned to treatment with saline or the nonselective ET(A) and ET(B) receptor antagonist LU 420627 (LU) started <24 hours (early) or 10 days (late) after MI and continued for 100 days. Long-term LU treatment led to increased mortality of rats with large MI, regardless of the timing of initiation of therapy. Early initiation of LU reduced survival from 61% to 16% (P<0.001 versus untreated), and later initiation reduced survival to 36% (P=0.012 versus untreated and P<0.001 versus early initiation). Early initiation of LU led to scar thinning, further left ventricular (LV) dilatation, LV dysfunction, and an excessive rise in right ventricular systolic pressure. Later initiation of LU did not modify scar formation but resulted in LV dilatation and dysfunction compared with the untreated group. Cardiac fibrosis tended to increase in the LU-treated MI groups. LU in the sham group reduced cardiac endothelial constitutive nitric oxide synthase but did not modify the changes that occurred with a large MI.

CONCLUSIONS

The use of the nonselective ET(A) and ET(B) receptor antagonist LU results in reduced survival, ventricular dilatation, and dysfunction whether started early or late after MI. Early initiation of LU resulted in scar expansion and a particularly unfavorable outcome.

Imaging neuronal subsets in transgenic mice expressing multiple spectral variants of GFP

We generated transgenic mice in which red, green, yellow, or cyan fluorescent proteins (together termed XFPs) were selectively expressed in neurons. All four XFPs labeled neurons in their entirety, including axons, nerve terminals, dendrites, and dendritic spines. Remarkably, each of 25 independently generated transgenic lines expressed XFP in a unique pattern, even though all incorporated identical regulatory elements (from the thyl gene). For example, all retinal ganglion cells or many cortical neurons were XFP positive in some lines, whereas only a few ganglion cells or only layer 5 cortical pyramids were labeled in others. In some lines, intense labeling of small neuronal subsets provided a Golgi-like vital stain. In double transgenic mice expressing two different XFPs, it was possible to differentially label 3 neuronal subsets in a single animal.

Nerve terminals form but fail to mature when postsynaptic differentiation is blocked: in vivo analysis using mammalian nerve-muscle chimeras

To better understand the role of the postsynaptic cell in the differentiation of presynaptic terminals, we transplanted muscles that lacked postsynaptic differentiation from mutant mice into normal adult immunocompatible hosts and attached the host nerve to the grafts. Host motor axons innervated wild-type grafted muscle fibers and established normal appearing chimeric neuromuscular junctions. By repeated in vivo imaging, we found that these synapses were stably maintained. Results were different when nerves entered transplanted muscles derived from mice lacking muscle-specific receptor tyrosine kinase (MuSK) or rapsyn, muscle-specific components required for postsynaptic differentiation. Initial steps in presynaptic differentiation (e.g., formation of rudimentary arbors and vesicle clustering at terminals) occurred when wild-type neurites contacted MuSK- or rapsyn deficient muscle fibers, either in vivo or in vitro. However, wild-type terminals contacting MuSK or rapsyn mutant muscle fibers were unable to mature, even when the chimeras were maintained for up to 7 months. Moreover, in contrast to the stability of wild-type synapses, wild-type nerve terminals in mutant muscles underwent continuous remodeling. These results suggest that postsynaptic cells supply two types of signals to motor axons: ones that initiate presynaptic differentiation and others that stabilize the immature contacts so that they can mature. Normal postsynaptic differentiation appears to be dispensable for initial stages of presynaptic differentiation but required for presynaptic maturation.

Immunnohistological assessment of intestinal eosinophil activation in patients with eosinophilic gastroenteritis and inflammatory bowel disease

OBJECTIVE

To assess the activation grade of intestinal eosinophils in patients with eosinophilic gastroenteritis (EOG), ulcerative colitis (UC), Crohn's disease (CD), and controls by immunohistochemistry.

METHODS

Cecal biopsies were collected from healthy controls and from patients with EOG, CD, UC, and other noninflammatory GI diseases. Immunohistochemistry was performed in sequential sections stained with monoclonal antibodies directed against eosinophil cationic protein (ECP) or eosinophil protein X (EPX) stored in eosinophil granules (EG1) and that secreted by activated eosinophils (EG2). The ratio of EG1 to EG2-positive eosinophils expressed as percentage of lamina propria cells was calculated. ECP and EPX were measured in serum and feces.

RESULTS

The percentage of EG1 and EG2-positive lamina propria cells was elevated in EOG and slightly, but not significantly, in UC. The ratio of EG1 to EG2-positive cells was decreased in CD, UC, and other patients as compared to healthy controls. Particularly low EG1 to EG2 ratios were found in EOG. Correspondingly, fecal and serum levels of ECP and EPX, respectively, were highest in patients with EOG. The EG1 to EG2 ratio was negatively correlated with fecal ECP and EPX levels. At sites of actively inflamed mucosa, the EG1 to EG2 ratio was lower than in noninflamed tissue.

CONCLUSIONS

Our data strongly suggest that the EG1 to EG2 ratio may be a marker of tissue eosinophil activation. Low ratios (<1) indicate eosinophil activation, whereas ratios > or =1 are found in healthy controls. Furthermore, we show that EOG is characterized by a pronounced intestinal eosinophil accumulation and activation, whereas in CD and UC, eosinophils seem to be activated but their number is not or only slightly elevated compared to controls.

The carboxyl methyltransferase modifying G proteins is a metalloenzyme

The prenylated protein carboxyl methyltransferase (PPMT) catalyzes the posttranslational methylation of isoprenylated C-terminal cysteine residues found in many signaling proteins such as the small monomeric G proteins and the gamma subunits of heterotrimeric G proteins. Here we report that both membrane-bound PPMT from rat kidney and the recombinant bacterially expressed form of the enzyme required divalent cations for catalytic activity. Unlike EDTA and EGTA, the metal chelator 1,10-phenanthroline strongly inhibited the PPMT activity of kidney intracellular membranes in a dose- and time-dependent manner. 1,10-Phenanthroline was found to inhibit the methylation of the prenylcysteine analog N-acetyl-S-all-trans-geranylgeranyl-l-cysteine, a synthetic substrate for PPMT, with an IC(50) of 2.2 mM. Gel electrophoretic analysis demonstrated that 1,10-phenanthroline almost totally abolished the labeling of methylated proteins in kidney intracellular membranes. Immunoblotting analysis showed that one of the two major peaks of (3)H-methylated proteins in intracellular membranes comigrated with the small G proteins Ras, Cdc42, RhoA, and Rab1. In addition, the methylation of immunoprecipitated Ras and RhoA from kidney intracellular membranes was strongly inhibited when 1,10-phenanthroline was present. Treatment of kidney intracellular membranes with 1,10-phenanthroline increased the proteolytic degradation of PPMT by exogenous trypsin, compared to untreated membranes. We conclude from these data that metal ions are essential for the activity and the stabilization of PPMT. The finding that PPMT is a metalloenzyme may provide new insights into the functions played by this methyltransferase in signal transduction processes.

Novel human erythrovirus associated with transient aplastic anemia

Erythrovirus (formerly parvovirus) B19 causes a wide range of diseases in humans, including anemia due to aplastic crisis. Diagnosis of B19 infection relies on serology and the detection of viral DNA by PCR. These techniques are usually thought to detect all erythrovirus field isolates, since the B19 genome is known to undergo few genetic variations. We have detected an erythrovirus (V9) markedly different from B19 in the serum and bone marrow of a child with transient aplastic anemia. The B19 PCR assay yielded a product that hybridized only very weakly to the B19-specific probe and whose sequence diverged more from those of 24 B19 viruses (11 to 14%) than the divergence found within the B19 group (</=6.65%). Restriction enzyme analysis of the V9 genome revealed that this genetic divergence extended beyond the amplified region. Interestingly, serological tests failed to demonstrate a response characteristic of acute B19 infection. V9 could be a new erythrovirus, and new diagnostic tests are needed for its detection.

Alternatively spliced isoforms of nerve- and muscle-derived agrin: their roles at the neuromuscular junction

Agrin induces synaptic differentiation at the skeletal neuromuscular junction (NMJ); both pre- and postsynaptic differentiation are drastically impaired in its absence. Multiple alternatively spliced forms of agrin that differ in binding characteristics and bioactivity are synthesized by nerve and muscle cells. We used surgical chimeras, isoform-specific mutant mice, and nerve-muscle cocultures to determine the origins and nature of the agrin required for synaptogenesis. We show that agrin containing Z exons (Z+) is a critical nerve-derived inducer of postsynaptic differentiation, whereas neural isoforms containing a heparin binding site (Y+) and all muscle-derived isoforms are dispensable for major steps in synaptogenesis. Our results also suggest that the requirement of agrin for presynaptic differentiation is mediated indirectly by its ability to promote postsynaptic production or localization of appropriate retrograde signals.

Endothelin A receptor blockade causes adverse left ventricular remodeling but improves pulmonary artery pressure after infarction in the rat

BACKGROUND

Endothelin A (ETA) receptor antagonists have been shown to improve ventricular remodeling and survival in rats when started 10 days after infarction. Whether starting them earlier would have a more or less beneficial effect is uncertain.

METHODS AND RESULTS

Rats surviving an acute myocardial infarction (MI) for 24 hours (n=403) were assigned to saline or the ETA receptor antagonist LU 127043 or its active enantiomer LU 135252 for 4 weeks. Chronic LU treatment had no effect on survival, with 46% of LU rats and 47% of saline-treated rats with large MI surviving to the end of the study. LU treatment led to scar thinning, further left ventricular (LV) dilatation, an increase in LV end-diastolic pressure, and an increase in wet lung weight (P<0.05). Despite this detrimental effect on LV function, LU led to a significant decrease in RV systolic (50+/-2 to 44+/-2 mm Hg, P<0.05 vs saline) and right atrial pressures. LU treatment also prevented the increase in pulmonary ET-1 found in saline-treated rats with large MI but did not modify the increase in cardiac ET-1 in hearts with large MI.

CONCLUSIONS

The early use of the ETA receptor antagonists LU 127043 or its active enantiomer LU 135252 after infarction in the rat leads to impaired scar healing and LV dilatation and dysfunction. This is accompanied by a decrease in RV systolic and right atrial pressures and a decrease in pulmonary but not cardiac ET-1 levels. It would thus appear that the early use of ETA receptor antagonists after infarction may be detrimental.

Coordinated upregulation of the cardiac endothelin system in a rat model of heart failure

The potent vascular, cardiac, and renal actions of endothelin-1 (ET-1) suggest a role for this vasoconstrictor peptide in the pathophysiology of heart failure (HF). Recent studies have shown increased levels of ET-1 peptide accompanied by increased ETB receptor binding in the left ventricle during experimental HF. However, much less is known about the regulation of mRNA expression of these genes in HF. We compared the levels of mRNA expression for ET-1 and ET receptors (ETA and ETB) in the left ventricle of rats with HF induced by coronary artery ligation (n = 6) vs. sham-operated animals (n = 6). Levels of mRNA for ET-1 were determined by ribonuclease protection assay (RPA) using beta-actin as the internal control, whereas ET receptors were quantified by quantitative-competitive RT-PCR. Compared with sham animals, ET-1, ETA, and ETB receptor mRNA levels were markedly upregulated in the left ventricle by 6.6 +/- 1.8-fold (p < 0.01), 3.2 +/- 0.6-fold (p < 0.05), and 3.5 +/- 1.0-fold (p < 0.05), respectively. ET-1 mRNA levels were measured in two additional groups of rats (HF and sham; n = 6 each) treated for 4 weeks with the selective ETA receptor antagonist LU135252. This treatment had no significant effect on ET-1 mRNA expression in sham animals but reduced the upregulation of ET-1 expression in the HF group by 41 +/- 19% (p < 0.05). This study confirms the potential importance of ET-1 in HF and suggests that increased expression of ET-1 and ET receptors in the failing ventricle may contribute to alteration in basal cardiac contractility and myocardial remodeling.

Large-scale analysis of hepatitis C virus serological typing assay: effectiveness and limits

The HCV (hepatitis C virus) Serotyping 1-6 Assay (Murex Laboratories) was evaluated on 303 French HCV-infected patients. Serological typing results were compared to the genotypes obtained from sequence analyses of the 5' noncoding regions of the virus genome from 46 HCV-infected patients, and assay specificity was found to be high (97.6%). The serological typing assay, run in 257 consecutive HCV-infected patients, yielded an assay sensitivity lower (70.6%) than that previously reported. This finding was attributed mainly to nonreactive sera from human immunodeficiency virus (HIV)-positive patients (P < 0.001) and perhaps reflected cryoglobulin positivity in others. No anti-type 6 reactivity was detected, and the overall serological type distribution values for types 1 to 5 were 67.3, 7.9, 16.4, 6.6, and 0.9%, respectively. A higher prevalence of type 4 was noted among HIV-infected patients (P < 0.001). In addition, serotype 2 was significantly more frequent in cryoglobulinemia positive than in cryoglobulinemia-negative patients (P < 0.05). Although an initial high level (7%) of mixed serological typing reactivities was found, after predilution of serum only two mixed infections could be confirmed (0.9%). It is suggested, therefore, that mixed reactivities have to be interpreted carefully and retested with prediluted serum, particularly when the optical density of the reactivity is > 2.5 or remains > 0.4 after competition with all type-specific peptides. The high specificity and relatively good sensitivity even in immunocompromised patients obtained with this assay indicate that it can be used routinely. Because response to treatment is linked to HCV type, this assay could be used to identify HCV serotype to guide therapeutic decisions.

mRNAs coding for neurotransmitter receptors and voltage-gated sodium channels in the adult rabbit visual cortex after monocular deafferentiation

It has been postulated that, in the adult visual cortex, visual inputs modulate levels of mRNAs coding for neurotransmitter receptors in an activity-dependent manner. To investigate this possibility, we performed a monocular enucleation in adult rabbits and, 15 days later, collected their left and right visual cortices. Levels of mRNAs coding for voltage-activated sodium channels, and for receptors for kainate/alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), N-methyl-D-aspartate (NMDA), gamma-aminobutyric acid (GABA), and glycine were semiquantitatively estimated in the visual cortices ipsilateral and contralateral to the lesion by the Xenopus oocyte/voltage-clamp expression system. This technique also allowed us to study some of the pharmacological and physiological properties of the channels and receptors expressed in the oocytes. In cells injected with mRNA from left or right cortices of monocularly enucleated and control animals, the amplitudes of currents elicited by kainate or AMPA, which reflect the abundance of mRNAs coding for kainate and AMPA receptors, were similar. There was no difference in the sensitivity to kainate and in the voltage dependence of the kainate response. Responses mediated by NMDA, GABA, and glycine were unaffected by monocular enucleation. Sodium channel peak currents, activation, steady-state inactivation, and sensitivity to tetrodotoxin also remained unchanged after the enucleation. Our data show that mRNAs for major neurotransmitter receptors and ion channels in the adult rabbit visual cortex are not obviously modified by monocular deafferentiation. Thus, our results do not support the idea of a widespread dynamic modulation of mRNAs coding for receptors and ion channels by visual activity in the rabbit visual system.

Hyperinnervation of neuromuscular junctions caused by GDNF overexpression in muscle

Overexpression of glial cell line-derived neurotrophic factor (GDNF) by muscle greatly increased the number of motor axons innervating neuromuscular junctions in neonatal mice. The extent of hyperinnervation correlated with the amount of GDNF expressed in four transgenic lines. Overexpression of GDNF by glia and overexpression of neurotrophin-3 and neurotrophin-4 in muscle did not cause hyperinnervation. Thus, increased amounts of GDNF in postsynaptic target cells can regulate the number of innervating axons.

Hepatitis C virus genotypes implicated in mixed cryoglobulinemia

Recent reports suggest that hepatitis C virus (HCV) might be a causative agent of mixed cryoglobulinemia. To determine whether the HCV genotype is a factor implicated in the onset of cryoglobulinemia, genotyping by direct sequencing of polymerase chain reaction products of the 5' non coding region was carried out among 45 HCV-infected patients. Genotypes 1 and 2 were found more prevalent in symptomatic cryoglobulinemia patients. Due to the presence of genotypes 4 and 5 found in this panel of French patients (9.3%), HCV genotyping based on sequence determination is recommended.

Hepatitis C virus genotypes implicated in mixed cryoglobulinemia

Recent reports suggest that hepatitis C virus (HCV) might be a causative agent of mixed cryoglobulinemia. To determine whether the HCV genotype is a factor implicated in the onset of cryoglobulinemia, genotyping by direct sequencing of polymerase chain reaction products of the 5' non coding region was carried out among 45 HCV-infected patients. Genotypes 1 and 2 were found more prevalent in symptomatic cryoglobulinemia patients. Due to the presence of genotypes 4 and 5 found in this panel of French patients (9.3%), HCV genotyping based on sequence determination is recommended.

Prevalence of cryoglobulins and hepatitis C virus infection in HIV-infected patients

PURPOSE AND METHODS

In order to evaluate the prevalence of positive hepatitis C virus (HCV) serology and cryoglobulinemia in human immunodeficiency virus (HIV)-infected patients, the prevalence and the clinical significance of cryoglobulinemia were prospectively studied in a cohort of 86 HIV-infected subjects seen as outpatients. They were compared to a control group consisting of 101 HIV-HCV+ patients being followed at the same hospital.

RESULTS

HCV serology was positive in 53/86 (61.6%) patients, 25 (47.2%) of whom had detectable cryoglobulins in their sera although only 1 had clinical symptoms consistent with cryoglobulinemia. Cryoglobulinemia was also detected in 9/33 (27.3%) HCV- patients, with only one of them presenting clinical symptoms. Although the mean cryoglobulin concentration was lower for HIV+ patients than in controls (268 versus 585 mg/l, p < 0.01), their prevalence (39.5% and 27.2%, respectively) was higher (p < 0.03).

CONCLUSION

Cryoglobulinemia is frequently detected in HIV-infected patients, regardless of their HCV serology, but is poorly correlated with clinical symptoms.

Thrombin-induced membrane currents in native Xenopus follicles

The presence and properties of thrombin receptors have been investigated in Xenopus Laevis follicles. In follicles, voltage-clamped at -60 mV or -80 mV, sub-micromolar concentrations of thrombin (Thr) induce smooth inward currents carried by chloride ions, which desensitize over tens of minutes. This desensitization is prevented by PKC inhibitors (staurosporine and H7). Responses are inhibited by hirudin. Inconsistent responses can be observed in defolliculated oocytes. Thr responses, readily recorded in hypo-osmotic solution are abolished by perfusion of normal frog "Ringer" or by the addition of 50 mM sucrose. Thus Thr acts on receptors present in the follicular cells triggering the opening of chloride channels by acting on receptors, likely to be located on follicular cells, via a PKC-regulated pathway.

The presence of direct repeats does not influence coding joint formation during V(D)J recombination

During the recombination process that assembles immunoglobulin and T-cell receptor gene segments, the coding ends to be joined are extensively processed. Contradictory reports have been made in the past about the existence of homology directed mechanisms in V(D)J recombination. In this study we analyse coding end processing and the influence of the presence of homology stretches on coding joint formation using artificial substrates in which short sequence changes creating direct repeats have been introduced. These changes were monitored 3 bp away from the termini in order to avoid any differences due to the initiation steps of V(D)J recombination. Our results show that the sequence of the coding ends influences joint formation, but no evidence was found for a mechanistic bias due to the presence of direct repeats.

Pharmacological characterization of SR 142801: a new non-peptide antagonist of the neurokinin NK-3 receptor

Pharmacological and biochemical assays were performed to characterize SR 142801, a new NK-3 receptor antagonist, and its [R]-enantiomer, SR 142806. The compounds were tested (1) in the guinea pig isolated ileum stimulated with [MePhe7]NKB (NK-3 system) in order to evaluate onset and duration of action and to estimate the apparent affinity of the antagonist in terms of pA2 at 140 min after application; (2) in 6 selected monoreceptor systems, the rabbit (rb) vena cava for the NK-1rb receptor, the rabbit pulmonary artery and the hamster (hs) urinary bladder for the NK-2rb and NK-2hs receptors, the rat (r) portal vein for the NK-3r receptor, and in two multireceptor systems adequately treated with NK-1 or NK-2 receptor antagonists to obtain monoreceptor-mediated biological responses (the rat urinary bladder treated with SR 48968 for evaluating the NK-1r and the guinea pig-gp-ileum treated with CP-99994 for measuring the antagonist affinity on the NK-3gp receptor), in order to evaluate the antagonist selectivity, and (3) in various plasma membrane preparations containing NK-3-binding sites from rats, guinea pigs, and man. The data presented indicate that SR 142801 is a potent, fairly selective non-peptide antagonist of the functional (pA2 9.4) and binding (Ki 0.11 nmol/l) site of the guinea pig and human (Ki 0.21 nmol/l) NK-3 receptors, while being much less active on the Nk-3 receptors of other species, particularly the rat (pA2 7.0; Ki 15 nmol/l). SR 142801 shows a slow onset of action and acts as a long-lasting irreversible antagonist, specific for neurokinin receptors, especially the NK-3 sites of guinea pigs and man.

Mechanism of synapse disassembly at the developing neuromuscular junction

Throughout the developing nervous system of higher vertebrates, synaptic connections are concurrently being established and eliminated. The consequence of this synaptic remodeling is that axons strengthen their connections with some targets while completely disconnecting from other postsynaptic cells. The transition from multiple to single axonal innervation of skeletal muscle fibers is the most accessible example of this developmental reorganization. In muscle, the elimination of axonal input appears to be driven by a protracted competition between different axons co-innervating the same junction, with the muscle fiber as intermediary. Asynchronous synaptic activity may be the factor that differentiates the competing inputs. In some circumstances, synapses can also be lost in ways that are independent of activity. Similarities between activity-dependent and activity-independent synapse elimination provide insights into mechanisms underlying developmental synaptic reorganization.

Neurokinin receptors in the guinea pig ileum

Experiments were performed in the longitudinal muscle strip of the guinea pig ileum to characterize the receptors involved in the contractile response of this preparation to neurokinins. Antagonists for the NK-1 (CP 96345, CP 99994) and NK-2 (SR 48968) receptors, atropine for NK-3 receptors, as well as diphenhydramine (histamine H1 receptor antagonist) and indometacin (cyclooxygenase inhibitor) were used to determine the relative contribution of neurokinin receptors and some endogenous agents to the myotropic effects of substance P (SP) and neurokinin receptor selective agonists. The present findings indicate that the three neurokinin receptor types take part in the contractile activities of SP-related peptides. NK-1 receptors, probably localized in the smooth muscle, are inhibited only by the two CP compounds and not by atropine or the other agents. NK-2 receptors contribute to the contraction by 5-10% and are blocked by SR 48968. NK-3 receptors act indirectly through the release of acetylcholine from the myenteric plexus, since activities of [MePhe7]NKB and senktide are blocked by atropine. Septide behaves as a selective NK-1 receptor agonist and does not show any difference with SP, except for higher sensitivity to CP antagonists. The same is observed with Ac[Arg6,Sar9,Met(O2)11]SP(6-11), another NK-1-selective fragment. Discrepancies between antagonist pA2 values obtained against undeca- and hexapeptide agonists are interpreted as due to a stronger binding affinity of undecapeptide agonists as compared with the hexapeptides. Results of binding assays confirm data from the literature by showing that undecapeptide agonists have higher affinities than hexapeptides, particularly septide,, and such discrepancies (with the biological assays) can also be explained by the reduction or absence of the cationic charge at the N terminal of septide.

The two isoforms of mouse terminal deoxynucleotidyl transferase differ in both the ability to add N regions and subcellular localization

Two alternatively spliced terminal deoxynucleotidyl transferase transcripts, TdTS and TdTL which code respectively for proteins of 509 and 529 amino acids have been previously identified in the mouse thymus. Here we show that the same two transcripts are also present in B lineage cells from bone marrow. In addition we demonstrate that the corresponding 20 amino acid insertion found near the carboxy-terminal end of TdTL significantly alters the function of the enzyme. In contrast to TdTS, TdTL does not catalyse N region insertions at the recombination junction of a V(D)J site-specific recombination substrate. In an attempt to explain the lack of N region insertions we have characterized the different parameters which distinguish the two isoforms of TdT. Examination of transfected cell extracts revealed a reduced capacity of TdTL to add nucleotides to the 3' end of DNA, consistent with a lower terminal transferase activity. Furthermore, the half-life of the TdTL protein in these cells is 2-fold shorter than that of TdTS. Finally, despite the fact that TdTL has the same nuclear localization signal as TdTS, the cellular localization of the two isoforms was strikingly different. In contrast to nuclear TdTS, TdTL was found exclusively in the cytoplasm. All these characteristics could contribute to the functional difference between the two isoforms of TdT. However, the subcellular localization of TdTL on its own can account for its inability to add N regions.

A Windows software package to record from voltage-clamped Xenopus oocytes

We have written a software package to record, display and analyze membrane currents elicited by neurotransmitter receptors or voltage-activated channels in voltage-clamped Xenopus oocytes. This suite, which consists of 4 applications, runs on IBM-PC compatible microcomputers under Windows 3.1. The recording programs use Direct Memory Access (DMA) to access the analog-digital board. The first program, NicPulse, is aimed at studying voltage-activated channels. It delivers voltage steps to the voltage-clamp and records the resulting membrane current. The second program, NicScope, emulates a dual-trace digital oscilloscope. It operates either in continuous or triggered mode, and is used chiefly to display neurotransmitter-induced responses in oocytes. The third recording program, VRamp, automatically determines the voltage-current relationship of drug-activated responses (I/V curve), by applying a voltage ramp and recording the subsequent clamping current. The last program, NicView, is designed to analyze records taken with NicScope and NicPulse. The present paper will discuss several issues regarding the design of these programs, and will give a brief description of each application.

A two-filter model for frequency discrimination

In this paper, we explore a two-filter model, the simplest version of multi-channel models for frequency discrimination of simple tones. According to this model, frequency discrimination is based on a change in the relative output levels of two auditory filters, one centered below and the other above the frequency of the tone. This idea can explain the experimental results that frequency discrimination is relatively unaffected by randomization of stimulus level. Moreover, it suggests a close relationship between the ability of listeners to perform frequency discrimination of simple tones and spectral-shape discrimination of two-tone complexes. The ability of three listeners to perform these two tasks was measured at six frequencies (from 0.25 to 8 kHz). The results from the spectral-shape-discrimination task were used to predict frequency-difference limens. There was a high correlation between obtained and predicted values.

Two NK-3 receptor subtypes: demonstration by biological and binding assays

The existence of two neurokinin NK-3 receptor subtypes has been suggested on the basis of results obtained in binding assays. In the present study, we have confirmed the two NK-3 receptor subtypes by using data obtained in both biological and binding assays. Experiments have been performed in the rat portal vein and in the guinea-pig ileum treated with NK-1 and NK-2 selective antagonists, namely CP 96345 and SR 48968. Orders of potency of agonists on the rat portal vein are as follows: for neurokinins, NKB > NKA > SP; for tachykinins, KAS > ELE > PHY; and for selective agonist: [MePhe7]NKB >> senktide. On the guinea-pig ileum, the agonist rank orders of potency are: NKB > SP > NKA, ELE > KAS > PHY; and for selective agonist: [MePhe7]NKB = senktide. The apparent affinity of antagonists shows differences in both biological and binding assays. In fact, on the rat portal vein, SR 48968 is almost inactive (pA2 or IC50 approximately 4.8), while R-486 [Trp7, beta Ala8]NKA(4-10) shows a pA2 value of 7.45 and an IC50 of 5.6. An opposite pattern of activity is observed in the guinea-pig ileum, where SR 48968 shows a pA2 of 6.05 and an IC50 of 6.7, while R-486 has a pA2 of 6.1 and an IC50 of < 5.0. These results confirm the existence of two NK-3 sites differing pharmacologically. It is proposed to name NK-3A the receptor of the guinea-pig ileum and NK-3B the receptor of the rat portal vein.

Electrophysiological properties of newborn and adult rat spinal cord glycine receptors expressed in Xenopus oocytes

The properties of glycine receptors (GlyRs) from newborn and adult rat spinal cord were studied in Xenopus oocytes injected with whole mRNA or the heavy (H) or light (L) mRNA fractions encoding their respective GlyRs. Mean open times and conductances of channels gated by H- or L-GlyRs were determined by noise analysis or voltage jumps. We found that adult H- and L-GlyRs opened channels that differed in their mean open time but had the same channel conductance. Both H- and L-GlyRs gated Cl- currents that displayed a similarly strong outward rectification. Nevertheless, single channels of adult H- and L-GlyRs did not rectify and their mean open times were only slightly altered by voltage. It follows that the outward rectification of adult GlyRs is due mainly to a reduction in the number of open channels. In contrast to H-GlyRs, whose characteristics seem to remain essentially unchanged with age, L-GlyRs from newborn and adult rats have different properties. Channels of newborn L-GlyRs have a higher conductance, longer open time, and greater voltage dependency than those from the adult. Interestingly, properties of newborn GlyRs expressed by whole mRNA were markedly different from those encoded by newborn or adult L or H mRNA. These results demonstrate that the functional heterogeneity of GlyRs is developmentally regulated.

Bradykinin receptor types and B2 subtypes

Bradykinin, desArg9BK, some agonist analogues and several antagonists have been tested in isolated organs in order to identify bradykinin B2 receptor subtypes. The initial pharmacological characterization was made in the rabbit jugular vein and the guinea pig ileum, two widely used B2 preparations which have shown marked differences in their sensitivities to both agonists and antagonists. The study has then been extended to peripheral tissues (stomach, colon, urinary bladder) of four species (the rat, guinea pig, rabbit and man) and to isolated vessels (rabbit jugular vein, rabbit vena cava, guinea pig pulmonary artery, rat portal vein) in order to determine if pharmacologic receptor subtypes may be related to species. It has been shown that B2 receptors in rat and guinea pig tissues belong to a similar pharmacological entity, a receptor which is different from that mediating the responses of rabbit and human tissues. Agonists order of potency ([Hyp3]BK > BK > [Aib7]BK) obtained in the rabbit jugular vein is different from that found in the guinea pig ileum (BK < or = [Aib7]BK > [Hyp3]BK). Affinities of competitive antagonists (for instance DArg[Hyp3,DPhe7,Leu8]BK) in rabbit tissues are higher than in guinea pig and rat tissues by at least 2 log units, while the non peptidic compound WIN 64338 is more active (also by two log units) in guinea pig than in human and rabbit tissues. The non competitive long-acting antagonist HOE 140 is very potent and equally active in the four species. Some antagonists (peptides without unnatural residues, peptides with unnatural residues, non peptides) have been shown to be specific for kinin receptors and selective for the B2. Altogether, the present results a) confirm the existence of two B2 receptor subtypes, b) suggest that receptor subtypes may be species dependent and c) indicate that the B2 receptor subtype found in the rabbit is similar to that found in man.

Neurokinin receptor subtypes characterized by biological assays

Neurokinin receptors have been characterized by biological assays using naturally occurring and selective agonists as well as peptide and non peptide antagonists. Six preparations have been used: the rabbit vena cava and the rat urinary bladder, treated with a NK-2 receptor antagonist for the NK-1 receptor, the rabbit pulmonary artery and the hamster urinary bladder for the NK-2, the rat portal vein and the guinea pig ileum, treated with a NK-1 receptor antagonist, for the NK-3. Treatment with antagonists was required because of the presence (in some preparations) of two functional sites contributing to the biological effect. Differences in the order of potency of agonists between each couple of receptors have been demonstrated, especially with tachykinins and the selective agonists. Such differences are even more evident with antagonists, some of which show apparent affinity (pA2) values 1.5 to 3 log units higher in one than in the other member of each couple. Based on data obtained in pharmacological experiments, it is concluded that NK-1, NK-2 and NK-3 receptors show differences strong enough to justify the assumption that their coding and/or expression diverge among species.

mRNAs coding for neurotransmitter receptors in rabbit and rat visual areas

Levels of mRNAs encoding neurotransmitter receptors in the visual cortex, lateral geniculate nucleus, and superior colliculus of the rabbit and rat, and properties of the receptors expressed, were studied using Xenopus laevis oocytes. mRNA extracted from these areas was injected into the oocytes, which then acquired functional receptors. Electrical recordings of neurotransmitter-induced membrane currents reflect the relative amounts of mRNAs encoding the corresponding receptors. Receptors to gamma aminobutyric acid (GABA), kainate, glutamate, and serotonin exhibited uniformly high levels of expression, whereas expression of receptors to glycine and N-methyl-D-aspartate was uniformly low. In contrast, the expression of receptors to acetylcholine and substance P was highly non-uniform. Expression of acetylcholine receptors was high in oocytes injected with mRNA from the visual cortex, low for the lateral geniculate nucleus, and very low or absent for the superior colliculus. Conversely, the currents elicited by substance P were large in oocytes injected with superior colliculus mRNA, but were small or absent in oocytes injected with mRNAs from the other regions. Immunohistochemical analysis, at the light and electron microscopic levels, was used to localize choline acetyltransferase, the acetylcholine-synthesizing enzyme, and substance P-containing synaptic boutons in the three visual areas. Their presence closely paralleled the potency of mRNAs coding for acetylcholine and substance P receptors. The ability of rat mRNA, from each visual area, to induce neurotransmitter receptors was similar to that observed in the corresponding rabbit mRNAs. In addition to the marked differential distribution of mRNA encoding neurotransmitter receptors in the visual system, our findings reveal the probable existence of as yet uncharacterized receptors, whose new molecular forms may be revealed by further study. Our results also provide the basic information required for subsequent studies on the effect of monocular deprivation on the expression of neurotransmitter receptors in the visual system.

Auditory profile analysis of harmonic signals

Spectral shape discrimination for harmonic complexes with 100-, 200-, or 400-Hz fundamental was investigated in two sets of experiments. In the first set, the signal was an increment in a single component of an otherwise equal-amplitude complex. The results of these experiments showed nearly a 30-dB increase in thresholds as the signal frequencies increased from 1000 to 5000 Hz. A transformation of data based on the assumption that the critical detection quantity is the change in the level in a critical band centered at the signal frequency was applied to remove the effects of the nonsignal components. The corrected thresholds have a bowl-like shape similar to that seen in studies of spectral shape discrimination of stimuli with components equally spaced on a logarithmic frequency scale. Additional experiments examined the effects of the number of components in the complex and the relative phase of the components of the harmonic complex. In the second set of experiments, the effects of local masking were examined either by increasing the level of several adjacent components, or by removing nonsignal components near a single signal component. Again, the results with harmonic signals are similar to those obtained with components spaced at equal intervals on a logarithmic frequency scale, if one calculates the increment in the level produced in a critical band centered at the signal frequency.

Differential splicing in mouse thymus generates two forms of terminal deoxynucleotidyl transferase

A new form of TdT mRNA has been identified by screening a mouse thymus cDNA library. It contains an open reading frame of 1527 base pairs corresponding to a protein containing 509 aminoacids, whereas the previously identified mouse TdT mRNA is composed of 1587 base pairs and encodes a protein of 529 aminoacids. Analysis of a mouse genomic clone containing the 3' portion of the TdT gene shows that these twenty additional aminoacids are encoded by an additional exon located between exons X and XI. Both forms of TdT mRNA are present in the thymus and could be generated by alternative splicing. The cDNA reported here corresponds to the major form of TdT mRNA in Balb/c mice and closely resembles human and bovine TdT cDNA. Expression of this cDNA in mammalian cells shows that it encodes a functional protein capable of catalysing N region insertions at the recombination junction of an episomic recombination substrate.