Measurement of energy and directional distribution of neutron ambient dose equivalent for the 7Li(p,n)7Be reaction

Double differential neutron fluence distributions were measured in the 7Li(p,n)7Be reaction for proton beam energies 7, 9 and 12 MeV. Seven liquid scintillator based detectors were employed to measure neutron fluence distributions using the Time of Flight technique. Neutron ambient dose equivalents were determined from the measured fluence distribution using ICRP (International Commission on Radiological Protection) recommended fluence to dose equivalent conversion coefficients. Neutron dose equivalents were also measured using a conventional BF3 detector based REM counter. Ambient dose equivalent measured by the REM counter is found to be in agreement with that determined from the neutron fluence spectra within their uncertainties. Angular distributions of the ambient dose equivalents were also determined from the measured fluence distributions at different angles.

Viral activation and ecological restructuring characterize a microbiome axis of spaceflight-associated immune activation

Maintenance of astronaut health during spaceflight will require monitoring and potentially modulating their microbiomes, which play a role in some space-derived health disorders. However, documenting the response of microbiota to spaceflight has been difficult thus far due to mission constraints that lead to limited sampling. Here, we executed a six-month longitudinal study centered on a three-day flight to quantify the high-resolution microbiome response to spaceflight. Via paired metagenomics and metatranscriptomics alongside single immune profiling, we resolved a microbiome "architecture" of spaceflight characterized by time-dependent and taxonomically divergent microbiome alterations across 750 samples and ten body sites. We observed pan-phyletic viral activation and signs of persistent changes that, in the oral microbiome, yielded plaque-associated pathobionts with strong associations to immune cell gene expression. Further, we found enrichments of microbial genes associated with antibiotic production, toxin-antitoxin systems, and stress response enriched universally across the body sites. We also used strain-level tracking to measure the potential propagation of microbial species from the crew members to each other and the environment, identifying microbes that were prone to seed the capsule surface and move between the crew. Finally, we identified associations between microbiome and host immune cell shifts, proposing both a microbiome axis of immune changes during flight as well as the sources of some of those changes. In summary, these datasets and methods reveal connections between crew immunology, the microbiome, and their likely drivers and lay the groundwork for future microbiome studies of spaceflight.

Microbiome and metagenomic analysis of Lake Hillier Australia reveals pigment-rich polyextremophiles and wide-ranging metabolic adaptations

Lake Hillier is a hypersaline lake known for its distinctive bright pink color. The cause of this phenomenon in other hypersaline sites has been attributed to halophiles, Dunaliella, and Salinibacter, however, a systematic analysis of the microbial communities, their functional features, and the prevalence of pigment-producing-metabolisms has not been previously studied. Through metagenomic sequencing and culture-based approaches, our results evidence that Lake Hillier is composed of a diverse set of microorganisms including archaea, bacteria, algae, and viruses. Our data indicate that the microbiome in Lake Hillier is composed of multiple pigment-producer microbes, including Dunaliella, Salinibacter, Halobacillus, Psychroflexus, Halorubrum, many of which are cataloged as polyextremophiles. Additionally, we estimated the diversity of metabolic pathways in the lake and determined that many of these are related to pigment production. We reconstructed complete or partial genomes for 21 discrete bacteria (N = 14) and archaea (N = 7), only 2 of which could be taxonomically annotated to previously observed species. Our findings provide the first metagenomic study to decipher the source of the pink color of Australia's Lake Hillier. The study of this pink hypersaline environment is evidence of a microbial consortium of pigment producers, a repertoire of polyextremophiles, a core microbiome and potentially novel species.

Supervised Machine Learning Enables Geospatial Microbial Provenance

The recent increase in publicly available metagenomic datasets with geospatial metadata has made it possible to determine location-specific, microbial fingerprints from around the world. Such fingerprints can be useful for comparing microbial niches for environmental research, as well as for applications within forensic science and public health. To determine the regional specificity for environmental metagenomes, we examined 4305 shotgun-sequenced samples from the MetaSUB Consortium dataset-the most extensive public collection of urban microbiomes, spanning 60 different cities, 30 countries, and 6 continents. We were able to identify city-specific microbial fingerprints using supervised machine learning (SML) on the taxonomic classifications, and we also compared the performance of ten SML classifiers. We then further evaluated the five algorithms with the highest accuracy, with the city and continental accuracy ranging from 85-89% to 90-94%, respectively. Thereafter, we used these results to develop Cassandra, a random-forest-based classifier that identifies bioindicator species to aid in fingerprinting and can infer higher-order microbial interactions at each site. We further tested the Cassandra algorithm on the Tara Oceans dataset, the largest collection of marine-based microbial genomes, where it classified the oceanic sample locations with 83% accuracy. These results and code show the utility of SML methods and Cassandra to identify bioindicator species across both oceanic and urban environments, which can help guide ongoing efforts in biotracing, environmental monitoring, and microbial forensics (MF).

A global metagenomic map of urban microbiomes and antimicrobial resistance

We present a global atlas of 4,728 metagenomic samples from mass-transit systems in 60 cities over 3 years, representing the first systematic, worldwide catalog of the urban microbial ecosystem. This atlas provides an annotated, geospatial profile of microbial strains, functional characteristics, antimicrobial resistance (AMR) markers, and genetic elements, including 10,928 viruses, 1,302 bacteria, 2 archaea, and 838,532 CRISPR arrays not found in reference databases. We identified 4,246 known species of urban microorganisms and a consistent set of 31 species found in 97% of samples that were distinct from human commensal organisms. Profiles of AMR genes varied widely in type and density across cities. Cities showed distinct microbial taxonomic signatures that were driven by climate and geographic differences. These results constitute a high-resolution global metagenomic atlas that enables discovery of organisms and genes, highlights potential public health and forensic applications, and provides a culture-independent view of AMR burden in cities.

A comprehensive metagenomics framework to characterize organisms relevant for planetary protection

BACKGROUND

Clean rooms of the Space Assembly Facility (SAF) at the Jet Propulsion Laboratory (JPL) at NASA are the final step of spacecraft cleaning and assembly before launching into space. Clean rooms have stringent methods of air-filtration and cleaning to minimize microbial contamination for exoplanetary research and minimize the risk of human pathogens, but they are not sterile. Clean rooms make a selective environment for microorganisms that tolerate such cleaning methods. Previous studies have attempted to characterize the microbial cargo through sequencing and culture-dependent protocols. However, there is not a standardized metagenomic workflow nor analysis pipeline for spaceflight hardware cleanroom samples to identify microbial contamination. Additionally, current identification methods fail to characterize and profile the risk of low-abundance microorganisms.

RESULTS

A comprehensive metagenomic framework to characterize microorganisms relevant for planetary protection in multiple cleanroom classifications (from ISO-5 to ISO-8.5) and sample types (surface, filters, and debris collected via vacuum devices) was developed. Fifty-one metagenomic samples from SAF clean rooms were sequenced and analyzed to identify microbes that could potentially survive spaceflight based on their microbial features and whether the microbes expressed any metabolic activity or growth. Additionally, an auxiliary testing was performed to determine the repeatability of our techniques and validate our analyses. We find evidence that JPL clean rooms carry microbes with attributes that may be problematic in space missions for their documented ability to withstand extreme conditions, such as psychrophilia and ability to form biofilms, spore-forming capacity, radiation resistance, and desiccation resistance. Samples from ISO-5 standard had lower microbial diversity than those conforming to ISO-6 or higher filters but still carried a measurable microbial load.

CONCLUSIONS

Although the extensive cleaning processes limit the number of microbes capable of withstanding clean room condition, it is important to quantify thresholds and detect organisms that can inform ongoing Planetary Protection goals, provide a biological baseline for assembly facilities, and guide future mission planning. Video Abstract.

Shotgun transcriptome, spatial omics, and isothermal profiling of SARS-CoV-2 infection reveals unique host responses, viral diversification, and drug interactions

In less than nine months, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) killed over a million people, including >25,000 in New York City (NYC) alone. The COVID-19 pandemic caused by SARS-CoV-2 highlights clinical needs to detect infection, track strain evolution, and identify biomarkers of disease course. To address these challenges, we designed a fast (30-minute) colorimetric test (LAMP) for SARS-CoV-2 infection from naso/oropharyngeal swabs and a large-scale shotgun metatranscriptomics platform (total-RNA-seq) for host, viral, and microbial profiling. We applied these methods to clinical specimens gathered from 669 patients in New York City during the first two months of the outbreak, yielding a broad molecular portrait of the emerging COVID-19 disease. We find significant enrichment of a NYC-distinctive clade of the virus (20C), as well as host responses in interferon, ACE, hematological, and olfaction pathways. In addition, we use 50,821 patient records to find that renin-angiotensin-aldosterone system inhibitors have a protective effect for severe COVID-19 outcomes, unlike similar drugs. Finally, spatial transcriptomic data from COVID-19 patient autopsy tissues reveal distinct ACE2 expression loci, with macrophage and neutrophil infiltration in the lungs. These findings can inform public health and may help develop and drive SARS-CoV-2 diagnostic, prevention, and treatment strategies.

First Observation of Multiple Transverse Wobbling Bands of Different Kinds in ^{183}Au

We report the first observation of two wobbling bands in ^{183}Au, both of which were interpreted as the transverse wobbling (TW) band but with different behavior of their wobbling energies as a function of spin. It increases (decreases) with spin for the positive (negative) parity configuration. The crucial evidence for the wobbling nature of the bands, dominance of the E2 component in the ΔI=1 transitions between the partner bands, is provided by the simultaneous measurements of directional correlation from the oriented states ratio and the linear polarization of the γ rays. Particle rotor model calculations with triaxial deformation reproduce the experimental data well. A value of spin, I_{m}, has been determined for the observed TW bands below which the wobbling energy increases and above which it decreases with spin. The nucleus ^{183}Au is, so far, the only nucleus in which both the increasing and the decreasing parts are observed and thus gives the experimental evidence of the complete transverse wobbling phenomenon.

Shotgun Transcriptome and Isothermal Profiling of SARS-CoV-2 Infection Reveals Unique Host Responses, Viral Diversification, and Drug Interactions

The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has caused thousands of deaths worldwide, including >18,000 in New York City (NYC) alone. The sudden emergence of this pandemic has highlighted a pressing clinical need for rapid, scalable diagnostics that can detect infection, interrogate strain evolution, and identify novel patient biomarkers. To address these challenges, we designed a fast (30-minute) colorimetric test (LAMP) for SARS-CoV-2 infection from naso/oropharyngeal swabs, plus a large-scale shotgun metatranscriptomics platform (total-RNA-seq) for host, bacterial, and viral profiling. We applied both technologies across 857 SARS-CoV-2 clinical specimens and 86 NYC subway samples, providing a broad molecular portrait of the COVID-19 NYC outbreak. Our results define new features of SARS-CoV-2 evolution, nominate a novel, NYC-enriched viral subclade, reveal specific host responses in interferon, ACE, hematological, and olfaction pathways, and examine risks associated with use of ACE inhibitors and angiotensin receptor blockers. Together, these findings have immediate applications to SARS-CoV-2 diagnostics, public health, and new therapeutic targets.

International Nosocomial Infection Control Consortium (INICC) report, data summary of 45 countries for 2012-2017: Device-associated module

BACKGROUND

We report the results of International Nosocomial Infection Control Consortium (INICC) surveillance study from January 2012 to December 2017 in 523 intensive care units (ICUs) in 45 countries from Latin America, Europe, Eastern Mediterranean, Southeast Asia, and Western Pacific.

METHODS

During the 6-year study period, prospective data from 532,483 ICU patients hospitalized in 242 hospitals, for an aggregate of 2,197,304 patient days, were collected through the INICC Surveillance Online System (ISOS). The Centers for Disease Control and Prevention-National Healthcare Safety Network (CDC-NHSN) definitions for device-associated health care-associated infection (DA-HAI) were applied.

RESULTS

Although device use in INICC ICUs was similar to that reported from CDC-NHSN ICUs, DA-HAI rates were higher in the INICC ICUs: in the medical-surgical ICUs, the pooled central line-associated bloodstream infection rate was higher (5.05 vs 0.8 per 1,000 central line-days); the ventilator-associated pneumonia rate was also higher (14.1 vs 0.9 per 1,000 ventilator-days,), as well as the rate of catheter-associated urinary tract infection (5.1 vs 1.7 per 1,000 catheter-days). From blood cultures samples, frequencies of resistance, such as of Pseudomonas aeruginosa to piperacillin-tazobactam (33.0% vs 18.3%), were also higher.

CONCLUSIONS

Despite a significant trend toward the reduction in INICC ICUs, DA-HAI rates are still much higher compared with CDC-NHSN's ICUs representing the developed world. It is INICC's main goal to provide basic and cost-effective resources, through the INICC Surveillance Online System to tackle the burden of DA-HAIs effectively.

Brucellosis in India: results of a collaborative workshop to define One Health priorities

Brucellosis is an important zoonosis worldwide. In livestock, it frequently causes chronic disease with reproductive failures that contribute to production losses, and in humans, it causes an often-chronic febrile illness that is frequently underdiagnosed in many low- and middle-income countries, including India. India has one of the largest ruminant populations in the world, and brucellosis is endemic in the country in both humans and animals. In November 2017, the International Livestock Research Institute invited experts from government, national research institutes, universities, and different international organizations to a one-day meeting to set priorities towards a "One Health" control strategy for brucellosis in India. Using a risk prioritization exercise followed by discussions, the meeting agreed on the following priorities: collaboration (transboundary and transdisciplinary); collection of more epidemiological evidence in humans, cattle, and in small ruminants (which have been neglected in past research); Economic impact studies, including cost effectiveness of control programmes; livestock vaccination, including national facilities for securing vaccines for the cattle population; management of infected animals (with the ban on bovine slaughter, alternatives such as sanctuaries must be explored); laboratory capacities and diagnostics (quality must be assured and better rapid tests developed); and increased awareness, making farmers, health workers, and the general public more aware of risks of brucellosis and zoonoses in general. Overall, the meeting participants agreed that brucellosis control will be challenging in India, but with collaboration to address the priority areas listed here, it could be possible.

Optimization of beam dump shielding for K-130 cyclotron at VECC

A compact and efficient beam dump shield has been designed using Monte Carlo simulation code FLUKA to facilitate low background measurement of neutron and gamma rays using K130 cyclotron at Variable Energy Cyclotron Centre, Kolkata (VECC). Iron, lead and high density Polyethylene (HDPE) were considered in the design of the beam dump shield. Representative FLUKA simulation results have been validated using in-beam experiment performed on the same beam dump constituents. Experimental neutron and gamma-rays energy spectra have been found to be in fair agreement with the simulation results. Activation of various beam dump shield components were also carried out.

Book Review: Ipshita Chanda and Jayeeta Bagchi (Eds), Shaping the Discourse: Women’s Writings in Bengali Periodicals 1865–1947

Ipshita Chanda and Jayeeta Bagchi (Eds), Shaping the Discourse: Women’s Writings in Bengali Periodicals 1865–1947. Kolkata: Bhatkal & Son, 2015, 466 pages, ₹550, ISBN 978-8190676052.

Detection of Replication Origin Sites in Herpesvirus Genomes by Clustering and Scoring of Palindromes with Quadratic Entropy Measures

Replication in herpesvirus genomes is a major concern of public health as they multiply rapidly during the lytic phase of infection that cause maximum damage to the host cells. Earlier research has established that sites of replication origin are dominated by high concentration of rare palindrome sequences of DNA. Computational methods are devised based on scoring to determine the concentration of palindromes. In this paper, we propose both extraction and localization of rare palindromes in an automated manner. Discrete Cosine Transform (DCT-II), a widely recognized image compression algorithm is utilized here to extract palindromic sequences based on their reverse complimentary symmetry property of existence. We formulate a novel approach to localize the rare palindrome clusters by devising a Minimum Quadratic Entropy (MQE) measure based on the Renyi's Quadratic Entropy (RQE) function. Experimental results over a large number of herpesvirus genomes show that the RQE based scoring of rare palindromes have higher order of sensitivity, and lesser false alarm in detecting concentration of rare palindromes and thereby sites of replication origin.

Schematic for efficient computation of GC, GC3, and AT3 bias spectra of genome

Selection of synonymous codons for an amino acid is biased in protein translation process. This biased selection causes repetition of synonymous codons in structural parts of genome that stands for high N/3 peaks in DNA spectrum. Period-3 spectral property is utilized here to produce a 3-phase network model based on polyphase filterbank concepts for derivation of codon bias spectra (CBS). Modification of parameters in this model can produce GC, GC3, and AT3 bias spectra. Complete schematic in LabVIEW platform is presented here for efficient and parallel computation of GC, GC3, and AT3 bias spectra of genomes alongwith results of CBS patterns. We have performed the correlation coefficient analysis of GC, GC3, and AT3 bias spectra with codon bias patterns of CBS for biological and statistical significance of this model.

Numeracy and Medicare Part D: the importance of choice and literacy for numbers in optimizing decision making for Medicare's prescription drug program

Studies on decision making have come to challenge the idea that having more choice is necessarily better. The Medicare prescription drug program (Part D) has been designed to maximize choice for the consumer but has simultaneously created a highly complex decision task with dozens of options. In this study, in a sample of 121 adults, we examined the impact that increasing choice options has on decision-making abilities in older versus younger adults. Consistent with our hypotheses, we found that participants performed better with less choice versus more choice, and that older adults performed worse than younger adults across conditions. We further examined the role that numeracy may play in making these decisions and the role of more traditional cognitive variables such as working memory, executive functioning, intelligence, and education. Finally, we examined how personality style may interact with cognitive variables and age in decision making. Regression analysis revealed that numeracy is related to performance across the lifespan. When controlling for additional measures of cognitive ability, we found that although age was no longer associated with performance, numeracy remained significant. In terms of decision style, personality characteristics were not related to performance. Our results add to the mounting evidence for the critical role of numeracy in decision making across decision domains and across the lifespan.

Diethylcarbamazine: effect on lysosomal enzymes and acetylcholine in Wuchereria bancrofti infection

We measured the levels of lysosomal enzymes and acetylcholine in Wuchereria bancrofti-infected asymptomatic microfilaraemic human serum, and found a significant decrease in the activity of beta-glucuronidase and acid phosphatase compared to normal serum. Acetylcholine levels were also decreased during infection. However, after giving diethylcarbamazine (6 mg/kg body wt/day) the level of lysosomal enzymes and acetylcholine increased and reached a normal value after two weeks of therapy. It is proposed that parasites secrete acetylcholinesterase in the circulation which degrades acetylcholine. Since acetylcholine stimulates the release of lysosomal enzymes and phagocytosis, the immune response of the host is suppressed during infection. During diethylcarbamazine (DEC) therapy the parasitic enzyme is inhibited by the drug and the normal level of acetylcholine is resumed, which again stimulates the release of lysosomal enzyme and the process of phagocytosis.

A Ca2+-dependent autoregulation of lipopolysaccharide-induced IL-8 receptor expression in human polymorphonuclear neutrophils

IL-8, a potent neutrophil chemotactic agent, is known to be a key mediator in several inflammatory diseases. We found that 10 ng/ml of serum-activated LPS (Escherichia coli) efficiently up-regulated IL-8R on the surface of neutrophils within 30 min of LPS stimulation by 115 to 120% through de novo protein synthesis. After 30 min of LPS stimulation, reduction of IL-8R level was initiated and the normal level was restored within 2 h of LPS interaction. EDTA or EGTA and bestatin separately inhibited the receptor down-regulation by 98%, indicating the involvement of metalloprotease(s), more specifically an aminopeptidase in the process. Induction and subsequent reduction of IL-8 binding in serum-activated LPS-stimulated cells have been demonstrated in autoradiography. Intracellular Ca2+ level in these stimulated neutrophils was increased and decreased with alteration of IL-8R level. Although IL-8 binding was drastically reduced, the total IL-8R level, as detected by anti-IL-8R Ab measured by 125I-labeled anti-rabbit IgG, remained almost unaltered, indicating that minimal proteolysis occurred in IL-8R. Anti-IL-8R Ab and IL-8 itself could prevent this down-regulation significantly, suggesting that the susceptible epitope(s) might be in the IL-8 binding domain of the receptor. Under Ca2+-depleted conditions, the proteolysis was inhibited, which was accelerated upon addition of 1 mM of CaCl2. The study demonstrates that LPS-induced up-regulation of IL-8R leads to amplified IL-8-mediated biologic responses of neutrophils that are restored to normal level by activation of a Ca2+-dependent aminopeptidase. This may be useful for understanding the regulation of LPS-mediated inflammatory responses of neutrophils during bacterial infection.

An aminopeptidase regulates LPS stimulated interleukin-8 receptor on the surface of human neutrophils

A large number of inflammatory diseases are mediated by interleukin-8, an inflammatory neutrophil chemotactic agent. Since the cytokine acts through a cell surface receptor, detailed knowledge about the regulation of receptor expression is very important. We found that LPS in serum became activated and triggered the expression of IL-8 receptor by more than two folds within 30 min. After that period, the receptor attained normal level within 2 hr of SA-LPS stimulation. EDTA and bestatin could block this downregulation of IL-8 receptor. Intracellular Ca2+ level was increased till 45 min of SA-LPS stimulation and then the level was reduced. Addition of CaCl2 accelerated and depletion of Ca2+ inhibited the downregulation of the IL-8 receptor. The ligand could fully protect the loss of receptor from downregulation. It suggests that during SA-LPS stimulation, increase in intracellular Ca2+ level activates an aminopeptidase which presumably cleaves the N-terminal region of the receptor, critically essential for the function of IL-8. Thus the activated aminopeptidase regulates the functions of IL-8. The study is important for understanding the regulation of IL-8 receptor expression by LPS during bacterial infection.

A Ca2+-dependent autoregulation of lipopolysaccharide-induced IL-8 receptor expression in human polymorphonuclear neutrophils

IL-8, a potent neutrophil chemotactic agent, is known to be a key mediator in several inflammatory diseases. We found that 10 ng/ml of serum-activated LPS (Escherichia coli) efficiently up-regulated IL-8R on the surface of neutrophils within 30 min of LPS stimulation by 115 to 120% through de novo protein synthesis. After 30 min of LPS stimulation, reduction of IL-8R level was initiated and the normal level was restored within 2 h of LPS interaction. EDTA or EGTA and bestatin separately inhibited the receptor down-regulation by 98%, indicating the involvement of metalloprotease(s), more specifically an aminopeptidase in the process. Induction and subsequent reduction of IL-8 binding in serum-activated LPS-stimulated cells have been demonstrated in autoradiography. Intracellular Ca2+ level in these stimulated neutrophils was increased and decreased with alteration of IL-8R level. Although IL-8 binding was drastically reduced, the total IL-8R level, as detected by anti-IL-8R Ab measured by 125I-labeled anti-rabbit IgG, remained almost unaltered, indicating that minimal proteolysis occurred in IL-8R. Anti-IL-8R Ab and IL-8 itself could prevent this down-regulation significantly, suggesting that the susceptible epitope(s) might be in the IL-8 binding domain of the receptor. Under Ca2+-depleted conditions, the proteolysis was inhibited, which was accelerated upon addition of 1 mM of CaCl2. The study demonstrates that LPS-induced up-regulation of IL-8R leads to amplified IL-8-mediated biologic responses of neutrophils that are restored to normal level by activation of a Ca2+-dependent aminopeptidase. This may be useful for understanding the regulation of LPS-mediated inflammatory responses of neutrophils during bacterial infection.

Regulation of interleukin-8 receptor expression in human polymorphonuclear neutrophils

Interleukin-8, a neutrophil chemotactic agent, is known to have an active role in the induction of inflammatory response in a number of diseases. Although the activity of IL-8 is known to be through a receptor (IL-8R) on the surface of neutrophils, no information is available regarding the regulation of the IL-8R expression. The present study demonstrates that serum activated LPS at a concentration of 10 ng/ml induces expression of functionally active IL-8R by 120% within 30 min through de novo protein synthesis. The upregulated receptors could be detected by anti-IL-8R antibody and could also be demonstrated by autoradiography with crosslinking 125I IL-8. The serum-activated LPS-stimulated neutrophils migrated faster and showed higher Ca2+ flux over the unstimulated cells. The LPS-induced receptors were downregulated rapidly, about 85% of the receptor activity being lost within 90 min of incubation at 37 degrees C. The downregulation could be partially prevented by treatment with a cocktail of protease inhibitors, suggesting the possible involvement of protease(s) in this process. Both EDTA (100 microM) and bestatin (40 microM) afforded almost complete protection of the receptor from proteolytic cleavage indicating that the enzyme involved is a metalloprotease, possibly an aminopeptidase. The study shows that stimulation of PMNs with LPS leads to induction of IL-8R expression enhancing the IL-8-mediated biological responses and also provides evidence for post-stimulatory restoration of receptor level on the neutrophil surface by proteolytic cleavage of the amino-terminal end of the receptor.