Unveiling the genetic blueprint of a desert scorpion: A chromosome-level genome of Hadrurus arizonensis provides the first reference for Parvorder Iurida

Over 400 million years old, scorpions represent an ancient group of arachnids and one of the first animals to adapt to life on land. Presently, the lack of available genomes within scorpions hinders research on their evolution. This study leverages ultra-long nanopore sequencing and Pore-C to generate the first chromosome level assembly and annotation for the desert hairy scorpion, Hadrurus arizonensis. The assembled genome is 2.23 Gb in size with an N50 of 280 Mb. Pore-C scaffolding re-oriented 99.6% of bases into nine chromosomes and BUSCO identified 998 (98.6%) complete arthropod single copy orthologs. Repetitive elements represent 54.69% of the assembled bases, including 872,874 (29.39%) LINE elements. A total of 18,996 protein-coding genes and 75,256 transcripts were predicted, and extracted protein sequences yielded a BUSCO score of 97.2%. This is the first genome assembled and annotated within the family Hadruridae, representing a crucial resource for closing gaps in genomic knowledge of scorpions, resolving arachnid phylogeny, and advancing studies in comparative and functional genomics.

Congruence between ultraconserved element-based matrices and phylotranscriptomic datasets in the scorpion Tree of Life

Scorpions are ancient and historically renowned for their potent venom. Traditionally, the systematics of this group of arthropods was supported by morphological characters, until recent phylogenomic analyses (using RNAseq data) revealed most of the higher-level taxa to be non-monophyletic. While these phylogenomic hypotheses are stable for almost all lineages, some nodes have been hard to resolve due to minimal taxonomic sampling (e.g. family Chactidae). In the same line, it has been shown that some nodes in the Arachnid Tree of Life show disagreement between hypotheses generated using transcritptomes and other genomic sources such as the ultraconserved elements (UCEs). Here, we compared the phylogenetic signal of transcriptomes vs. UCEs by retrieving UCEs from new and previously published scorpion transcriptomes and genomes, and reconstructed phylogenies using both datasets independently. We reexamined the monophyly and phylogenetic placement of Chactidae, sampling an additional chactid species using both datasets. Our results showed that both sets of genome-scale datasets recovered highly similar topologies, with Chactidae rendered paraphyletic owing to the placement of Nullibrotheas allenii. As a first step toward redressing the systematics of Chactidae, we establish the family Anuroctonidae (new family) to accommodate the genus Anuroctonus.

Neglected no longer: Phylogenomic resolution of higher-level relationships in Solifugae

Advanced sequencing technologies have expedited resolution of higher-level arthropod relationships. Yet, dark branches persist, principally among groups occurring in cryptic habitats. Among chelicerates, Solifugae ("camel spiders") is the last order lacking a higher-level phylogeny and have thus been historically characterized as "neglected [arachnid] cousins". Though renowned for aggression, remarkable running speed, and xeric adaptation, inferring solifuge relationships has been hindered by inaccessibility of diagnostic morphological characters, whereas molecular investigations have been limited to one of 12 recognized families. Our phylogenomic dataset via capture of ultraconserved elements sampling all extant families recovered a well-resolved phylogeny, with two distinct groups of New World taxa nested within a broader Paleotropical radiation. Divergence times using fossil calibrations inferred that Solifugae radiated by the Permian, and most families diverged prior to the Paleogene-Cretaceous extinction, likely driven by continental breakup. We establish Boreosolifugae new suborder uniting five Laurasian families, and Australosolifugae new suborder uniting seven Gondwanan families using morphological and biogeographic signal.

A first molecular characterization of the scorpion telson microbiota of Hadrurus arizonensis and Smeringurus mesaensis

Scorpions represent an ancient lineage of arachnids that have radiated across the globe and are incredibly resilient-since some thrive in harsh environments and can exist on minimal and intermittent feedings. Given the emerging importance of microbiomes to an organism's health, it is intriguing to suggest that the long-term success of the scorpion bauplan may be linked to the microbiome. Little is known about scorpion microbiomes, and what is known, concentrates on the gut. The microbiome is not limited to the gut, rather it can be found within tissues, fluids and on external surfaces. We tested whether the scorpion telson, the venom-producing organ, of two species, Smeringurus mesaensis and Hadrurus arizonensis, contain bacteria. We isolated telson DNA from each species, amplified bacterial 16S rRNA genes, and identified the collection of bacteria present within each scorpion species. Our results show for the first time that telsons of non-buthid scorpion species do indeed contain bacteria. Interestingly, each scorpion species has a phylogenetically unique telson microbiome including Mollicutes symbionts. This study may change how we view scorpion biology and their venoms.

Amazonian scorpions and scorpionism: integrating toxinological, clinical, and phylogenetic data to combat a human health crisis in the world's most diverse rainfores

Venom from Amazonian scorpions of the genus Tityus contains components capable of eliciting a distinct clinical, mostly neurological, syndrome. This contrasts with the mainly autonomic manifestations produced after envenomation by congeneric southern and northern South American species. Herein, we summarize Pan-Amazonian scorpionism by synthesizing available toxinological, clinical, and molecular data gathered from all affected areas in Amazonia, including Brazil, Ecuador, Colombia, Peru, Venezuela, and French Guiana. We searched multiple databases, as well as our own records, for reports of scorpion envenomations in Amazonia by confirmed Tityus spp., and compared the clinical manifestations. To help uncover clinical and venom relationships among problematic species, we explored phylogenetic relationships with a rate-calibrated analysis of mitochondrial COI data from available species. The possible existence of diversity gradients for venom toxic and immunogenic components despite the predicted strong phylogenetic association among species is underscored by discussed clinical and toxinological findings. A multicentric effort, involving all nations affected by this neglected disease, is urgently needed to offer alternatives for treating and understanding this pathology, including the preparation of neutralizing antibodies with a broad range of efficacy.

Three new species of Olivierus (Scorpiones: Buthidae) from Kazakhstan and Uzbekistan

Following Graham et al. (2019), the recently described desert species Olivierus gorelovi (Fet et al., 2018) from Central Asia is herein restricted to Turkmenistan and southern Uzbekistan. In this contribution, we described other populations formerly included in O. gorelovi as three new species: O. mikhailovi sp. n. (southern Kazakhstan, Uzbekistan), O. tarabaevi sp. n. (Kazakhstan) and O. voldemari sp. n. (Uzbekistan: Ferghana Valley).

Genetic and toxinological divergence among populations of Tityus trivittatus Kraepelin, 1898 (Scorpiones: Buthidae) inhabiting Paraguay and Argentina

Envenoming by scorpions in genus Tityus is a public health problem in Tropical America. One of the most medically significant species is Tityus trivittatus, which is known to occur from southwest Brazil to central-northern and eastern Argentina. In this work, we studied the lethality, composition, antigenicity, and enzymatic activity of venom from a T. trivittatus population found further north in urban areas of eastern Paraguay, where it has caused serious envenomation of children. Our results indicate that the population is of medical importance as it produces a potently toxic venom with an LD50 around 1.19 mg/kg. Venom neutralization in preliminary mouse bioassays was complete when using Brazilian anti-T. serrulatus antivenom but only partial when using Argentinean anti-T. trivittatus antivenom. Venom competitive solid-phase enzyme immunoassays and immunoblotting from Argentinean and Paraguayan T. trivittatus populations indicated that antigenic differences exist across the species range. SDS-PAGE showed variations in type and relative amounts of venom proteins between T. trivitattus samples from Argentina and Paraguay. MALDI-TOF mass spectrometry indicated that while some sodium channel toxins are shared, including β-toxin Tt1g, others are population-specific. Proteolytic activity by zymography and peptide identification through nESI-MS/MS also point out that population-specific proteases may exist in T. trivitattus, which are postulated to be involved in the envenoming process. A time-calibrated molecular phylogeny of mitochondrial COI sequences revealed a significant (8.14%) genetic differentiation between the Argentinean and Paraguayan populations, which appeared to have diverged between the mid Miocene and early Pliocene. Altogether, toxinological and genetic evidence indicate that T. trivitattus populations from Paraguay and Argentina correspond to distinct, unique cryptic species, and suggest that further venom and taxonomic diversity exists in synanthropic southern South American Tityus than previously thought.

Venom diversity in the Neotropical scorpion genus Tityus: Implications for antivenom design emerging from molecular and immunochemical analyses across endemic areas of scorpionism

Scorpions of the Neotropical genus Tityus are responsible for most severe envenomations in the Caribbean, South America, and Lower Central America (LCA). Although Tityus is taxonomically complex, contains high toxin polymorphism, and produces variable clinical manifestations, treatment is limited to antivenoms produced against species with restricted distributions. In this study, we explored the compositional and antigenic diversity of Tityus venoms to provide improved guidelines for the use of available antivenoms at a broader geographic scale. We used immunoblotting, competitive ELISA, and in vivo studies to compare reactivity against commercial antivenoms from Brazil, Venezuela, and Mexico, as well as MALDI-TOF mass spectrometry, cDNA sequencing, and phylogenetic analyses to assess venom sodium channel-active toxin (NaTx) content from medically important Tityus populations inhabiting Brazil, Colombia, Costa Rica, Ecuador, Panama, Trinidad and Tobago, and Venezuela. Additionally, we raised rabbit antibodies against Tityus venoms from LCA to test for cross-reactivity with congeneric species. The results suggest that Tityus spp. possess high venom antigenic diversity, underlying the existence of four toxinological regions in Tropical America, based on venom composition and immunochemical criteria: LCA/Colombia/Amazonia (Region I), Venezuela (Region II), southeast South America (Region III), and a fourth region encompassing species related to toxinologically divergent Tityus cerroazul. Importantly, our molecular and cross-reactivity results highlight the need for new antivenoms against species inhabiting Region I, where scorpions may produce venoms that are not significantly reactive against available antivenoms.

Genome-wide SNP data and morphology support the distinction of two new species of Kovarikia Soleglad, Fet & Graham, 2014 endemic to California (Scorpiones, Vaejovidae)

Morphologically conserved taxa such as scorpions represent a challenge to delimit. We recently discovered populations of scorpions in the genus Kovarikia Soleglad, Fet & Graham, 2014 on two isolated mountain ranges in southern California. We generated genome-wide single nucleotide polymorphism data and used Bayes factors species delimitation to compare alternative species delimitation scenarios which variously placed scorpions from the two localities with geographically adjacent species or into separate lineages. We also estimated a time-calibrated phylogeny of Kovarikia and examined and compared the morphology of preserved specimens from across its distribution. Genetic results strongly support the distinction of two new lineages, which we describe and name here. Morphology among the species of Kovarikia was relatively conserved, despite deep genetic divergences, consistent with recent studies of stenotopic scorpions with limited vagility. Phylogeographic structure discovered in several previously described species also suggests additional cryptic species are probably present in the genus.

Scorpion envenoming in Morona Santiago, Amazonian Ecuador: Molecular phylogenetics confirms involvement of the Tityus obscurus group

Scorpion envenoming by species in the genus Tityus is hereby reported from rural locations in the Amazonian province of Morona Santiago, southeastern Ecuador. Twenty envenoming cases (18 patients under 15 years of age) including one death (a 4-year-old male) were recorded at the Macas General Hospital, Morona Santiago, between January 2015 and December 2016 from the counties of Taisha (n=17), Huamboyo (n=1), Palora (n=1), and Logroño (n=1). An additional fatality from 2014 (a 3-year-old female from Nayantza, Taisha county) is also reported. Leukocytosis and low serum potassium levels were detected in most patients. We observed a significant negative correlation between leukocytosis and hypokalemia. Scorpions involved in three accidents from Macuma, Taisha County, were identified as genetically related to Tityus obscurus from the Brazilian Amazonian region based on comparison of mitochondrial DNA sequences encoding cytochrome oxidase subunit I. These cases, along with previously reported envenoming from northern Manabí, reinforce the notion that scorpionism is a health hazard for children in Ecuador and emphasizes the need to supply effective antivenoms against local species, which are not currently available. The genetic affinity of the Ecuadorian specimens with T. obscurus may underlay toxinological, clinical, and venom antigenic relationships among Amazonian scorpions that deserves further exploration for designing therapeutic strategies to treat scorpionism in the region.

Should an increase in cerebral neurochemicals following head kicks in full contact karate influence return to play?

Background:

Cerebral neurochemicals are markers of traumatic brain injury (TBI).

Objectives:

The aim of the study was to determine whether kicks to the head (KTH) in full contact karate significantly increased serum concentrations of protein S-100B, and neurone specific enolase (NSE). Kicks to the body (KTB) were also quantified to asses muscle tissue injury. Muscle damage was assessed by analysis of serum total creatine kinase (CK).

Methods:

Twenty-four full contact karate practitioners were observed and filmed during actual competition and divided into two main groups post event: (1) Kicks to the head and body group (KTH): n = 12; mean ± SD; age, 30.4 ± 6.7 years; height, 1.74 ± 0.1 m; weight, 79.1 ± 2.1 kg; and (2): Kicks to the body group (KTB): n = 12; mean ± SD; age, 28.2 ± 6.5 years; height, 1.75 ± 0.1 m; weight, 79.2 ± 1.7 kg. The KTH group received direct kicks to the head, while group KTB received kicks and punches to the body. Blood samples were taken before and immediately post-combat for analysis of serum S-100B, NSE, CK and cardiac troponin.

Results:

Significant increases in serum concentrations of S-100B (0.12 ± 0.17 vs. 0.37 ± 0.26, µg.L−1) and NSE (11.8 ± 4.1 vs. 20.2 ± 9.1 ng.mL−1) were encountered after combat in the KTH group and CK (123 ± 53 vs. 184 ± 103 U.L−1) in the KTB group (all P <0.05).

Conclusions:

Head kicks in full contact karate cause elevation of neurochemical markers associated with damaged brain tissue. The severity of injury is related to the early post-traumatic release of protein S-100B and NSE. The early kinetics and appearance post injury can reflect intracranial pathology, and suggest S-100B and NSE are extremely sensitive prognostic markers of TBI.

Pseudouroctonus peccatum, a new scorpion from the Spring Mountains near "Sin City," Nevada (Scorpiones, Vaejovidae)

A new scorpion species is described from the Spring Mountain Range near Las Vegas, Nevada. The new species appears to be geographically isolated from other closely related species of Uroctonites Williams & Savaryand Pseudouroctonus Stahnke. We tentatively place the new species in Pseudouroctonus and provide detailed descriptions and illustrations of type material. We compare the new species to 17 congeneric taxa, briefly discuss the taxonomic history of Pseudouroctonus, and provide DNA barcodes for two paratypes to assist ongoing research on the systematics of family Vaejovidae.

As Old as the hills: montane scorpions in Southwestern North America reveal ancient associations between biotic diversification and landscape history

Background

The age of lineages has become a fundamental datum in studies exploring the interaction between geological transformation and biotic diversification. However, phylogeographical studies are often biased towards lineages that are younger than the geological features of the landscapes they inhabit. A temporally deeper historical biogeography framework may be required to address episodes of biotic diversification associated with geologically older landscape changes. Signatures of such associations may be retained in the genomes of ecologically specialized (stenotopic) taxa with limited vagility. In the study presented here, genetic data from montane scorpions in the Vaejovis vorhiesi group, restricted to humid rocky habitats in mountains across southwestern North America, were used to explore the relationship between scorpion diversification and regional geological history.

Results

Strong phylogeographical signal was evident within the vorhiesi group, with 27 geographically cohesive lineages inferred from a mitochondrial phylogeny. A time-calibrated multilocus species tree revealed a pattern of Miocene and Pliocene (the Neogene period) lineage diversification. An estimated 21 out of 26 cladogenetic events probably occurred prior to the onset of the Pleistocene, 2.6 million years ago. The best-fit density-dependent model suggested diversification rate in the vorhiesi group gradually decreased through time.

Conclusions

Scorpions of the vorhiesi group have had a long history in the highlands of southwestern North America. Diversification among these stenotopic scorpions appears to have occurred almost entirely within the Neogene period, and is temporally consistent with the dynamic geological history of the Basin and Range, and Colorado Plateau physiographical provinces. The persistence of separate lineages at small spatial scales suggests that a combination of ecological stenotopy and limited vagility may make these scorpions particularly valuable indicators of geomorphological evolution.

Wernerius inyoensis, an elusive new scorpion from the Inyo Mountains of California (Scorpiones, Vaejovidae)

A new scorpion species is described from the Inyo Mountains of California (USA). The presence of a strong subaculear spine, along with other characters, places the new species within Wernerius, an incredibly rare genus that until now consisted of only two species. Wernerius inyoensissp. n. can be most easily distinguished from the other members of the genus by smaller adult size, femur and pedipalp dimensions, and differences in hemispermatophore morphology. Previous studies have suggested that the elusive nature of this genus may be attributed to low densities and sporadic surface activity. Herein, we provide another hypothesis, that Wernerius are primarily subterranean. Mitochondrial sequence data are provided for the holotype.

Concentrations of salivary testosterone, cortisol, and immunoglobulin A after supra-maximal exercise in female adolescents

The aim of this study was to examine the effect of supra-maximal exercise on circulating concentrations of salivary testosterone, salivary cortisol, and salivary immunoglobulin A in female adolescents. Nineteen apparently healthy females aged 15-16 years participated in this study. All participants completed 668 s sprints, interspersed with 30 s recovery intervals on a cycle ergometer. Salivary testosterone, cortisol, and immunoglobulin A samples were taken before and 5 min after exercise. Experimental procedures continued over two mornings, at least 3 h after a light breakfast. Participants refrained from performing any strenuous physical activity for at least 24 h prior to the exercise test. None of the participants were engaged in a structured training programme. The group mean (± s) for peak power output was 562 ± 113.0 W. Female adolescents recruited for this study showed no changes in salivary testosterone, cortisol or immunoglobulin A following repeated bouts of supra-maximal cycling (P > 0.05). To date, there has been a paucity of information concerning adolescents' hormonal and mucosal immune function responses to supra-maximal exercise. Our data provide further guidance with regard to physical activities and sports prescription for female adolescents. Further research, on a larger sample of females, is required to elucidate the physiological significance of these findings.

Steroid and prescription medicine abuse in the health and fitness community: A regional study

BACKGROUND

The purpose of this study was to identify the prevalence of abuse of certain prescription medicines (POM) amongst health club attendees. The non-therapeutic use of such medicines has previously been considered to be restricted to the professional athlete.

METHODS

In the summer of 2005, health club users in the South Wales area were given questionnaires and asked to return them in a stamped, addressed envelope. Anonymity of the respondents was assured.

RESULTS

From the distribution of 210 questionnaires, the response rate was 69.5% (146 questionnaires). The mean age of the sample was 33.6+/-6.7 years (range 15-72 years). Anabolic-androgenic steroid (AAS) use is prominent amongst recreational gym users in this regional sample, with 70% (102 individuals) reporting AAS use, 65.8% (96 individuals) of whom were currently still using. Some 7% of respondents (10 individuals) were female and they also reported taking medication. This research demonstrated an enormous increase in the use of growth hormone (24%), insulin (14%), and tamoxifen (22%), with smaller increases in other drugs.

CONCLUSION

Drug users were from all levels of society and reported various physiological and psychological side effects from their use. The present study indicated that the most used medicine/drug from less than reputable sources was still AAS but that, as a consequence of the internet revolution, they were being caught up by the more expensive designer drugs, particularly growth hormone. Physicians and medical personnel must become aware that the use of AAS and other prescription medicines is on the increase and appears to be predominantly used for cosmetic reasons.

Homocysteine induced cardiovascular events: a consequence of long term anabolic-androgenic steroid (AAS) abuse

OBJECTIVES

The long term effects (>20 years) of anabolic-androgenic steroid (AAS) use on plasma concentrations of homocysteine (HCY), folate, testosterone, sex hormone binding globulin (SHBG), free androgen index, urea, creatinine, haematocrit (HCT), vitamin B12, and urinary testosterone/epitestosterone (T/E) ratio, were examined in a cohort of self-prescribing bodybuilders.

METHODS

Subjects (n = 40) were divided into four distinct groups: (1) AAS users still using AAS (SU; n = 10); (2) AAS users abstinent from AAS administration for 3 months (SA; n = 10); (3) non-drug using bodybuilding controls (BC; n = 10); and (4) sedentary male controls (SC; n = 10).

RESULTS

HCY levels were significantly higher in SU compared with BC and SC (p<0.01), and with SA (p<0.05). Fat free mass was significantly higher in both groups of AAS users (p<0.01). Daily energy intake (kJ) and daily protein intake (g/day) were significantly higher in SU and SA (p<0.05) compared with BC and SC, but were unlikely to be responsible for the observed HCY increases. HCT concentrations were significantly higher in the SU group (p<0.01). A significant linear inverse relationship was observed in the SU group between SHBG and HCY (r = -0.828, p<0.01), indicating a possible influence of the sex hormones in determining HCY levels.

CONCLUSIONS

With mounting evidence linking AAS to adverse effects on some clotting factors, the significantly higher levels of HCY and HCT observed in the SU group suggest long term AAS users have increased risk of future thromboembolic events.

Fractal or biologically variable delivery of cardioplegic solution prevents diastolic dysfunction after cardiopulmonary bypass

OBJECTIVE

To determine whether myocardial protection is improved by restoring physiologic variability to the cardioplegia pressure signal during cardiopulmonary bypass, we compared cardiac function in pigs in the first hour after either conventional cold-blood cardioplegia (group CC) or computer-controlled biologically variable pulsatile cardioplegia (group BVC).

METHODS

Invasive monitors and sonomicrometry crystals were placed, and cardiopulmonary bypass was initiated. The aorta was crossclamped, and cold blood cardioplegic solution was infused intermittently through the aortic root with either conventional cardioplegia (n = 8) or biologically variable pulsatile cardioplegia (n = 8; mean pressure, 75 mm Hg for 85 minutes). The crossclamp was released, cardiac function was restored, and separation from cardiopulmonary bypass was completed. With stable temperature and arterial blood gases, hemodynamics and systolic and diastolic indices were compared at 15, 30, and 60 minutes after cardiopulmonary bypass.

RESULTS

Diastolic stiffness doubled from 0.027 +/- 0.016 mm Hg/mm (mean +/- SD) at baseline to 0.055 +/- 0.036 mm Hg/mm (P =.003) at 1 hour after bypass in group CC, associated with increased left ventricular end-diastolic pressure from 9 +/- 2 to 11 +/- 2 mm Hg (P =.001), mean pulmonary artery pressure from 14 +/- 2 to 20 +/- 3 mm Hg (P =.003), and serum lactate levels from 2.0 +/- 0.5 to 5.6 +/- 2.3 mmol/L (P =.008). Systolic function was not affected. In group BVC diastolic stiffness, left ventricular end-diastolic pressure, and pulmonary artery pressure values were not different from control values at any time after bypass, and serum lactate levels were significantly less than with conventional cold blood cardioplegia. Peak pressure variability with biologically variable pulsatile cardioplegia fit a power-law equation (exponent = -3.0; R(2) = 0.97), indicating fractal behavior.

CONCLUSION

Diastolic cardiac function is better preserved after cardiopulmonary bypass with biologically variable pulsatile cardioplegia and fractal perfusion. This may be attributed to enhanced microcirculatory perfusion with improved myocardial protection. A model supporting these results is presented.

Evasion of human innate and acquired immunity by a bacterial homolog of CD11b that inhibits opsonophagocytosis

Microbial pathogens must evade the human immune system to survive, disseminate and cause disease. By proteome analysis of the bacterium Group A Streptococcus (GAS), we identified a secreted protein with homology to the alpha-subunit of Mac-1, a leukocyte beta2 integrin required for innate immunity to invading microbes. The GAS Mac-1-like protein (Mac) was secreted by most pathogenic strains, produced in log-phase and controlled by the covR-covS two-component gene regulatory system, which also regulates transcription of other GAS virulence factors. Patients with GAS infection had titers of antibody specific to Mac that correlated with the course of disease, demonstrating that Mac was produced in vivo. Mac bound to CD16 (FcgammaRIIIB) on the surface of human polymorphonuclear leukocytes and inhibited opsonophagocytosis and production of reactive oxygen species, which resulted in significantly decreased pathogen killing. Thus, by mimicking a host-cell receptor required for an innate immune response, the GAS Mac protein inhibits professional phagocyte function by a novel strategy that enhances pathogen survival, establishment of infection and dissemination.

Global differential gene expression in response to growth temperature alteration in group A Streptococcus

Pathogens are exposed to different temperatures during an infection cycle and must regulate gene expression accordingly. However, the extent to which virulent bacteria alter gene expression in response to temperatures encountered in the host is unknown. Group A Streptococcus (GAS) is a human-specific pathogen that is responsible for illnesses ranging from superficial skin infections and pharyngitis to severe invasive infections such as necrotizing fasciitis and streptococcal toxic shock syndrome. GAS survives and multiplies at different temperatures during human infection. DNA microarray analysis was used to investigate the influence of temperature on global gene expression in a serotype M1 strain grown to exponential phase at 29 degrees C and 37 degrees C. Approximately 9% of genes were differentially expressed by at least 1.5-fold at 29 degrees C relative to 37 degrees C, including genes encoding transporter proteins, proteins involved in iron homeostasis, transcriptional regulators, phage-associated proteins, and proteins with no known homologue. Relatively few known virulence genes were differentially expressed at this threshold. However, transcription of 28 genes encoding proteins with predicted secretion signal sequences was altered, indicating that growth temperature substantially influences the extracellular proteome. TaqMan real-time reverse transcription-PCR assays confirmed the microarray data. We also discovered that transcription of genes encoding hemolysins, and proteins with inferred roles in iron regulation, transport, and homeostasis, was influenced by growth at 40 degrees C. Thus, GAS profoundly alters gene expression in response to temperature. The data delineate the spectrum of temperature-regulated gene expression in an important human pathogen and provide many unforeseen lines of pathogenesis investigation.

Toward a genome-scale understanding of group A Streptococcus pathogenesis

Recent significant contributions have been made to the understanding of Group A Streptococcus (GAS) pathogenesis. New regulatory pathways have been discovered, insight into the molecular basis of epidemics of serotype M1 disease has been obtained, the crystal structures of four toxins have been reported and a genome sequence of one GAS strain has been determined. Genome-scale approaches to the study of GAS pathogenesis are now rapidly emerging and will advance our fundamental understanding of the molecular basis of host-pathogen interactions.

Biologically variable ventilation increases arterial oxygenation over that seen with positive end-expiratory pressure alone in a porcine model of acute respiratory distress syndrome

OBJECTIVES

We compared biologically variable ventilation (BVV) (as previously described) (1) with conventional control mode ventilation (CV) in a model of acute respiratory distress syndrome (ARDS) both at 10 cm H2O positive end-expiratory pressure.

DESIGN

Randomized, controlled, prospective study.

SETTING

University research laboratory.

SUBJECTS

Farm-raised 3- to 4-month-old swine.

INTERVENTIONS

Oleic acid (OA) was infused at 0.2 mL/kg/hr with FIO2 = 0.5 and 5 cm H2O positive end-expiratory pressure until PaO2 was < or =60 mm Hg; then all animals were placed on an additional 5 cm H2O positive end-expiratory pressure for the next 4 hrs. Animals were assigned randomly to continue CV (n = 9) or to have CV computer controlled to deliver BVV (variable respiratory rate and tidal volume; n = 8). Hemodynamic, expired gas, airway pressure, and volume data were obtained at baseline (before OA), immediately after OA, and then at 60-min intervals for 4 hrs.

MEASUREMENTS AND MAIN RESULTS

At 4 hrs after OA injury, significantly higher PaO2 (213+/-17 vs. 123+/-47 mm Hg; mean+/-SD), lower shunt fraction (6%+/-1% vs. 18%+/-14%), and lower PaCO2 (50+/-8 vs. 65+/-11 mm Hg) were seen with BVV than with CV. Respiratory system compliance was greater by experiment completion with BVV (0.37+/-0.05 vs. 0.31+/-0.08 mL/cm H2O/kg). The improvements in oxygenation, CO2 elimination, and respiratory mechanics occurred without a significant increase in either mean airway pressure (14.3+/-0.9 vs. 14.9+/-1.1 cm H2O) or mean peak airway pressure (39.3+/-3.5 vs. 44.5+/-7.2 cm H2O) with BVV. The oxygen index increased five-fold with OA injury and decreased to significantly lower levels over time with BVV.

CONCLUSIONS

In this model of ARDS, BVV with 10 cm H2O positive end-expiratory pressure improved arterial oxygenation over and above that seen with CV with positive end-expiratory pressure alone. Proposed mechanisms for BVV efficacy are discussed.

Biologically variable ventilation prevents deterioration of gas exchange during prolonged anaesthesia

We have studied the time course of changes in gas exchange and respiratory mechanics using two different modes of ventilation during 7 h of isoflurane anaesthesia in pigs. One group received conventional control mode ventilation (CV). The other group received biologically variable ventilation (BVV) which simulates the breath-to-breath variation in ventilatory frequency (f) that characterizes normal spontaneous ventilation. After baseline measurements with CV, animals were allocated randomly to either CV or BVV (FIO2 1.0 with 1.5% end-tidal isoflurane). With BVV, there were 376 changes in f and tidal volume (VT) over 25.1 min. Ventilation was continued over the next 7 h and blood gases and respiratory mechanics were measured every 60 min. The modulation file used to control the ventilator for BVV used an inverse power law frequency distribution (I/fa with a = 2.3 +/- 0.3). After 7 h, at a similar delivered minute ventilation, significantly greater PaO2 (mean 72.3 (SD 4.0) vs 63.5 (6.5) kPa) and respiratory system compliance (1.08 (0.08) vs 0.92 (0.16) ml cm H2O-1 kg-1) and lower PaCO2 (6.5 (0.7) vs 8.7 (1.5) kPa) and shunt fraction (7.2 (2.7)% vs 12.3 (6.2)%) were seen with BVV, with no significant difference in peak airway pressure (16.3 (1.2) vs 15.3 (3.7) cm H2O). A deterioration in gas exchange and respiratory mechanics was seen with conventional control mode ventilation but not with BVV in this experimental model of prolonged anaesthesia.

Left ventricular systolic and diastolic function is unaltered during propofol infusion in newborn swine

Propofol is a cardiac depressant with minimal diastolic effects in the adult myocardium. Cardiac effects of propofol in the newborn are unknown. We examined hemodynamic variables and systolic and diastolic left ventricular function in 12 newborn pigs exposed to propofol at three different infusion rates (7.5, 15, and 30 mg x kg(-1) x h(-1)) in random order with a background of fentanyl (100 microg x kg(-1) x h(-1)). Left ventricular (LV) pressure (Plv) and LV anterior-posterior dimension, determined by sonomicrometry, were continuously monitored. Mean arterial pressure (MAP), heart rate (HR), and LV end-diastolic pressure (LVEDP) were determined at every infusion. Systolic function was assessed by the maximal pressure-time derivative (dP/dt(max)), the slope of the end-systolic pressure-dimension relationship (ESP-D), and by the preload recruitable stroke work index (PRSWI). Diastolic function was assessed by relaxation indices, the minimal pressure-time derivative (dP/dt(min)) and the relaxation time constant (tau), and by a stiffness index, the slope of the EDP-D relationship. MAP decreased approximately 25%, from 75.9 +/- 15.6 to 56.3 +/- 14.8 mm Hg (P < 0.05) with propofol, with no dose effect. HR and LVEDP were unchanged from control. Both dP/dt(max) and dP/dt(min) decreased with propofol infusion, but load-independent indices of systolic function (ESP-D slope and PRSWI) and tau were unchanged. Diastolic stiffness was not affected with either 7.5- or 30-mg x kg(-1) x h(-1) infusions but decreased significantly from 0.27 +/- 0.18 mm Hg/mm at control to 0.18 +/- 0.18 mm Hg/mm (P < 0.05) with propofol 15 mg x kg(-1) x h(-1). With this profile, propofol may be useful for the newborn requiring anesthesia.

IMPLICATIONS

Most anesthetics depress heart function in the newborn. We examined both heart contraction and relaxation during anesthesia with propofol in newborn pigs. Propofol had minimal influence on heart function in this model at the doses studied. This may therefore be a useful anesthetic to test in the newborn human.

Cloning and characterization of the exbB-exbD-tonB locus of Pasteurella haemolytica A1

A recombinant plasmid (pMG1) carrying Pasteurella haemolytica A1 DNA which complements a tonB mutation of Escherichia coli has been isolated. E. coli tonB metE which carries pMG1 exhibits growth kinetics in the presence of vitamin B12 similar to that of the wild-type host. In addition, the complemented E. coli is susceptible to killing by bacteriophage phi 80 and colicin B. Analysis of the nucleotide sequence in the complementing DNA showed that it codes for three genes in the order of exbB-exbD-tonB. This genetic organization has been reported in Haemophilus influenzae, H. ducreyi, Pseudomonas putida and Vibrio cholerae, and may represent a separate lineage of evolution from that of the Enterobacteriaceae in which tonB is unlinked with the accessory genes exbB and exbD. A comparison of the DNA flanking the exbB-exbD-tonB locus in P. haemolytica A1 and H. influenzae showed that the flanking regions are completely different between the two organisms.

Isoflurane and halothane impair both systolic and diastolic function in the newborn pig

PURPOSE

Volatile anaesthetics have considerable effects on diastolic relaxation in the adult myocardium. We hypothesized that isoflurane (1) and halothane (H) may have even greater effects on diastolic function in the newborn, as the newborn heart has increased passive stiffness and altered calcium handling relative to the adult. Using a newborn pig model, we compared I and H at three clinically relevant concentrations with respect to both systolic and diastolic function.

METHODS

Sixteen newborn pigs were randomized for study at control (background fentanyl 100 micrograms.kg-1.hr-1 and 0.5, 1.0 and 1.5 MAC of I (n = 8) or H (n = 8). Temperature, arterial blood gases, and LVEDP were controlled. Left ventricular pressure (LVP) was monitored continuously and LV anterior-posterior dimension was determined by using sonomicrometry crystals. Systolic function was assessed by peak positive dP/dT (dP/dTmax) and the slope of the end-systolic pressure-dimension (ESP-D) relationship. Diastolic relaxation was given by peak negative dP/dT (-dP/dTmax) and the time constant for ventricular relaxation (tau). Left ventricular stiffness was calculated from the slope of the end-diastolic pressure-dimension (EDP-D) relationship.

RESULTS

At equal MAC concentrations, I and H were identical in effect for every variable studied. Systolic function was depressed at all anaesthetic concentrations. Control dP/dTmax (I:1815 +/- 561 (SD) mmHg.sec-1, H:1841 +/- 509) decreased to 832 +/- 341 with 1.5 MAC I and 691 +/- 127 with 1.5 MAC H (P < 0.05 vs control). ESP-D slope decreased from 62 +/- 31 mmHg.mm-1 at control to 15 +/- 11 with 1.5 MAC I and from 79 +/- 16 to 37 +/- 15 with 1.5 MAC H (P < 0.05 vs control). Diastolic function was affected only at higher MAC anaesthesia. Control tau increased from 18.0 +/- 6 msec to 29.1 +/- 7.5 with 1.5 MAC I and from 20.8 +/- 5.9 to 30.0 +/- 11.3 with 1.5 MAC H (P < 0.05). EDP-D slope was increased at both 1 and 1.5 MAC anaesthesia. EDP-D slope increased from 0.16 +/- 0.24 mmHg.mm-1 at control to 0.58 +/- 0.46 with I MAC I and from 0.16 +/- 11 to 0.50 +/- 0.35 with 1 MAC H. The -dP/dTmax decreased at every MAC level of anaesthesia.

CONCLUSION

These combined systolic and diastolic effects help to explain the increased sensitivity of the newborn myocardium to volatile anaesthetics.

Neuroanesthesia adjunct therapy (mannitol and hyperventilation) is as effective as cerebrospinal fluid drainage for prevention of paraplegia after descending thoracic aortic cross-clamping in the dog

We compared cerebrospinal fluid (CSF) drainage (Group D; n = 8) to neuroanesthesia adjunct therapy (hyperventilation and mannitol administration; Group N; n = 8) for the prevention of paraplegia using a canine model of descending thoracic aortic cross-clamping (AXC; 2.5 mm distal to the left subclavian artery for 30 min). We expected no difference in neurologic outcome between groups. After surgical preparation and a 30-min stabilization period, dogs in Group D had CSF drained prior to application of the AXC. During the period of AXC, CSF was allowed to drain freely in an attempt to have cerebrospinal fluid pressure (CSFP) no greater than central venous pressure (CVP). Dogs in Group N were hyperventilated (PaCO2 28-32 mm Hg) and received 2 g/kg of mannitol prior to AXC and then 1 g.kg-1.hr-1 during clamping. Systemic hemodynamics, CSFP, and arterial blood gases were measured at 1) baseline, 2) 2 min after AXC, 3) 20 min after AXC, 4) 5 min after AXC release, and 5) 30 min after resuscitation. With release of the AXC, PaCO2 was not controlled in Group D; in Group N the minute ventilation was further increased to maintain PaCO2 constant. At precisely 24 h after AXC, the animals were assessed for incidence and severity of paraplegia, using the Tarlov score, by an observer unaware of the experimental protocol. The animals were then killed, and the entire spinal cord was removed for histologic assessment. Multiple sections of the lumbar spinal cord were processed and stained with hematoxylin and eosin, then examined by light microscopy for nonviable neurons in the anterior spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Paraplegia following thoracic aortic cross-clamping in dogs. No difference in neurological outcome with a barbiturate versus isoflurane

BACKGROUND AND PURPOSE

We compared the incidence and severity of paraplegia following thoracic aortic cross-clamping in dogs for two anesthetic regimens. Animals were randomly assigned to receive methohexital (group M; n = 9) or isoflurane (group I; n = 9). We expected a better neurological outcome in animals administered methohexital because of superior neuronal protection and greater spinal cord perfusion pressure (mean arterial pressure below the cross-clamp site minus mean cerebrospinal fluid pressure).

METHODS

After surgical preparation and a 30-minute stabilization period, dogs in group M received 14 +/- 6 mg.kg-1 i.v. methohexital to induce an isoelectric electroencephalogram followed by a continuous infusion of methohexital at 20 mg.kg-1 x h-1. Dogs in group I received 1.4 +/- 0.2% end-tidal isoflurane (1 minimum alveolar concentration). The thoracic aorta was then occluded 2.5 cm distal to the left subclavian artery for 30 minutes and then released. Hemodynamics and cerebrospinal fluid pressure were measured at (1) baseline, (2) 2 minutes after aortic cross-clamping, (3) 20 minutes after aortic cross-clamping, (4) 5 minutes after aortic unclamping, and (5) 30 minutes after resuscitation. At 24 hours a neurological assessment was performed. After the clinical assessment the dogs were killed and the spinal cord removed immediately for histopathologic study.

RESULTS

There were no differences in nasopharyngeal temperature, PaCO2, pH, or hemoglobin at any time between groups. With cross-clamping, the spinal cord perfusion pressure decreased precipitously. However, there was no difference in spinal cord perfusion pressure between groups at any time (P = .5555). The neurological outcome, assessed at 24 hours after thoracic aortic cross-clamping by a veterinarian unaware of the anesthetic protocol, was not different between groups (P > .5, two-tailed Mann-Whitney rank-sums test). When anesthetized with methohexital 5 of 9 dogs were paraplegic; with isoflurane 7 of 9 dogs were paraplegic. By Spearman's rank test, a strong inverse correlation between the Tarlov score and the ratio of dead to total lumbar anterior spinal cord neurons was seen (Spearman's correlation coefficient = -.8358; P = .0001).

CONCLUSIONS

We conclude that no advantage was offered by the choice of anesthesia to neurological outcome after 30 minutes of thoracic aortic cross-clamping in this canine model.

Use of neuroanesthesia adjuncts (hyperventilation and mannitol administration) improves neurological outcome after thoracic aortic cross-clamping in dogs

BACKGROUND AND PURPOSE

Using a canine model of thoracic aortic cross-clamping, we compared the incidence and severity of paraplegia with and without standard neuroanesthesia adjuncts (mannitol administration and deliberate hyperventilation). Better outcome was predicted for animals treated with mannitol and hyperventilation.

METHODS

Nineteen dogs (mean +/- SD weight, 21 +/- 3 kg) were anesthetized with methohexital to an isoelectric electroencephalogram. Animals were randomized to group C (control; n = 9) or group M (mannitol administration and deliberate hyperventilation; n = 10). In group C, animals were maintained normocapnic (PaCO2, 38 to 42 mm Hg). In group M, animals were hyperventilated to a PaCO2 of 28 to 32 mm Hg and received mannitol 2 g.kg-1 during surgical preparation, then 1 g.kg-1.h-1 by continuous infusion. The thoracic aorta was cross-clamped for 30 minutes. Systemic hemodynamics, cerebrospinal fluid pressure, and arterial blood gases were measured at (1) baseline, (2) 2 minutes after cross-clamp, (3) 20 minutes after cross-clamp, (4) 5 minutes after cross-clamp release, and (5) 30 minutes after resuscitation. No attempt was made to control the hemodynamic consequences of cross-clamping in either group. With release of the cross-clamp, PaCO2 was not controlled in group C; in group M the minute ventilation was further increased to maintain PaCO2 constant. At precisely 24 hours after cross-clamp the animals were assessed for incidence and severity of paraplegia, using the Tarlov score, by an observer unaware of the experimental protocol. The animals were killed, and the entire spinal cord was removed for histological assessment. Multiple sections of the lumbar spinal cord were processed and stained with hematoxylin and eosin.

RESULTS

With application of the cross-clamp, cerebrospinal fluid pressure and central venous pressure increased significantly in both groups. However, in group M the maximal mean cerebrospinal fluid pressure never exceeded baseline values in group C. With cross-clamp release, spinal cord perfusion pressure (distal mean aortic pressure minus mean cerebrospinal fluid pressure) was significantly greater in group M (86 +/- 23 vs 65 +/- 17 mm Hg; P = .0017 between groups). Acid-base balance was better maintained in group M. The incidence and severity of paraplegia were significantly lower in group M (P = .043; Mann-Whitney rank-sums test, two-tailed). In this group 10 of 10 animals could walk and 4 of 10 had complete recovery. In group C 4 of 9 animals were paraplegic. There was a strong negative correlation between the Tarlov score and the ratio of dead to total anterior spinal cord neurons in the lumbar region as assessed by light microscopy (P = .0004; Spearman's rank test).

CONCLUSIONS

We conclude that a protocol using standard neuroanesthesia adjuncts (mannitol administration and deliberate hyperventilation) is associated with improved neurological outcome after thoracic aortic cross-clamping of 30 minutes' duration in dogs anesthetized with methohexital.

A nuclear magnetic resonance study of the metal binding sites in bacitracin

Carbon-13 nuclear magnetic resonance spectroscopy has been used to identify sites in bacitracin which bind Cu2+ and Mn2+. Results are presented which implicate the free carboxyl groups of the aspartic and glutamic acid residues and the imidazole ring of the histidine residue as metal complexation sites between pH 6 and 8. Evidence is presented which also indicates that the thiazoline ring of bacitracin binds Mn2+. Bacitracin does not bind Cu2+ or Mn2+ at pH values of 2.5 or less.