Characterization and genomic analysis of the Lyme disease spirochete bacteriophage ϕBB-1

Lyme disease is a tick-borne infection caused by the spirochete Borrelia (Borreliella) burgdorferi. Borrelia species have highly fragmented genomes composed of a linear chromosome and a constellation of linear and circular plasmids some of which are required throughout the enzootic cycle. Included in this plasmid repertoire by almost all Lyme disease spirochetes are the 32-kb circular plasmid cp32 prophages that are capable of lytic replication to produce infectious virions called ϕBB-1. While the B. burgdorferi genome contains evidence of horizontal transfer, the mechanisms of gene transfer between strains remain unclear. While we know that ϕBB-1 transduces cp32 and shuttle vector DNA during in vitro cultivation, the extent of ϕBB-1 DNA transfer is not clear. Herein, we use proteomics and long-read sequencing to further characterize ϕBB-1 virions. Our studies identified the cp32 pac region and revealed that ϕBB-1 packages linear cp32s via a headful mechanism with preferential packaging of plasmids containing the cp32 pac region. Additionally, we find ϕBB-1 packages fragments of the linear chromosome and full-length plasmids including lp54, cp26, and others. Furthermore, sequencing of ϕBB-1 packaged DNA allowed us to resolve the covalently closed hairpin telomeres for the linear B. burgdorferi chromosome and most linear plasmids in strain CA-11.2A. Collectively, our results shed light on the biology of the ubiquitous ϕBB-1 phage and further implicates ϕBB-1 in the generalized transduction of diverse genes and the maintenance of genetic diversity in Lyme disease spirochetes.

Characterization and genomic analysis of the Lyme disease spirochete bacteriophage ϕBB-1

Lyme disease is a tick-borne infection caused by the spirochete Borrelia (Borreliella) burgdorferi. Borrelia species have highly fragmented genomes composed of a linear chromosome and a constellation of linear and circular plasmids some of which are required throughout the enzootic cycle. Included in this plasmid repertoire by almost all Lyme disease spirochetes are the 32-kb circular plasmid cp32 prophages that are capable of lytic replication to produce infectious virions called ϕBB-1. While the B. burgdorferi genome contains evidence of horizontal transfer, the mechanisms of gene transfer between strains remain unclear. While we know that ϕBB-1 transduces cp32 and shuttle vector DNA during in vitro cultivation, the extent of ϕBB-1 DNA transfer is not clear. Herein, we use proteomics and long-read sequencing to further characterize ϕBB-1 virions. Our studies identified the cp32 pac region and revealed that ϕBB-1 packages linear cp32s via a headful mechanism with preferentially packaging of plasmids containing the cp32 pac region. Additionally, we find ϕBB-1 packages fragments of the linear chromosome and full-length plasmids including lp54, cp26, and others. Furthermore, sequencing of ϕBB-1 packaged DNA allowed us to resolve the covalently closed hairpin telomeres for the linear B. burgdorferi chromosome and most linear plasmids in strain CA-11.2A. Collectively, our results shed light on the biology of the ubiquitous ϕBB-1 phage and further implicates ϕBB-1 in the generalized transduction of diverse genes and the maintenance of genetic diversity in Lyme disease spirochetes.

Effect of altering milking interval when milking 3 times in 2 days on milk and component yields in pasture-based dairy systems

Dairy farmers face challenges attracting and retaining staff, partly due to the difficulty meeting the desires of the modern workforce. These include flexible work hours and regular time off. The task of milking fundamentally affects the ability of dairy farmers to meet these desires. Milking contributes to a large proportion of the hours spent working on dairy farms. The number of milkings (milking frequency) and their timing (milking interval) within a day influence the number of hours spent milking and what time in the day they occur. Milking 3 times in 2 d (3-in-2) reduces the amount of time spent milking compared with milking twice a day (TAD), without reducing milk yield as much as milking once a day (OAD). However, long intervals between 3-in-2 milkings can still lead to a long workday if farmers are expected to work between milkings. The objective of this study was to determine the effect of milking interval within a 3-in-2 milking frequency on milk yield and composition at 2 stages of lactation and compare these with OAD and TAD milking. Cows (n = 200) were milked in 5 groups of 40 at 3 intervals of 3-in-2: 8-20-20 h, 10-19-19 h, and 12-18-18 h, along with 24 h (OAD), and 10 and 14 h (TAD), for 6 wk at early lactation (mean 24 d in milk ± 7 d, SD) and again at mid lactation (mean 136 d in milk ± 18 d). Milk yields were recorded at each milking and milk samples collected weekly to determine composition. At both early and mid lactation there were no significant differences in milk, fat, protein, or lactose yields between the three 3-in-2 intervals. Cows milked 3-in-2 produced 8% less milk than cows milked TAD and 14% more than cows milked OAD, with smaller differences observed at mid lactation between TAD and 3-in-2. For a 3-in-2 milking frequency, a shorter milking interval can be implemented on the days when cows are milked twice. This may allow farmers to shorten the working day when using 3-in-2, without compromising milk or component yields.

Antigen-Specific CD4 T Cell and B Cell Responses to Borrelia burgdorferi

Long-lived T-dependent B cell responses fail to develop during persistent infection of mice with Borrelia burgdorferi, the causative agent of Lyme disease, raising questions about the induction and/or functionality of anti-B. burgdorferi adaptive immune responses. Yet, a lack of reagents has limited investigations into B. burgdorferi-specific T and B cells. We attempted two approaches to track B. burgdorferi-induced CD4 T cells. First, a B. burgdorferi mutant was generated with an influenza hemagglutinin (HA) peptide, HA111-119, inserted into the B. burgdorferi arthritis-related protein (Arp) locus. Although this B. burgdorferi arp::HA strain remained infectious, peptide-specific TCR transgenic CD4 T cells in vitro, or adoptively transferred into B. burgdorferi arp::HA-infected BALB/c mice, did not clonally expand above those of recipients infected with the parental B. burgdorferi strain or a B. burgdorferi mutant containing an irrelevant peptide. Some expansion, however, occurred in B. burgdorferi arp::HA-infected BALB/c SCID mice. Second, a (to our knowledge) newly identified I-Ab-restricted CD4 T cell epitope, Arp152-166, was used to generate Arp MHC class II tetramers. Flow cytometry showed small numbers of Arp-specific CD4 T cells emerging in mice infected with B. burgdorferi but not with Arp-deficient Borrelia afzelii. Although up to 30% of Arp-specific CD4 T cells were ICOS+PD-1+CXCR5+BCL6+ T follicular helper cells, their numbers declined after day 12, before germinal centers (GCs) are prominent. Although some Arp-specific B cells, identified using fluorochrome-labeled rArp proteins, had the phenotype of GC B cells, their frequencies did not correlate with anti-Arp serum IgG. The data suggest a failure not in the induction, but in the maintenance of GC T follicular helper and/or B cells to B. burgdorferi.

c-di-GMP regulates activity of the PlzA RNA chaperone from the Lyme disease spirochete

PlzA is a c-di-GMP-binding protein crucial for adaptation of the Lyme disease spirochete Borrelia (Borreliella) burgdorferi during its enzootic life cycle. Unliganded apo-PlzA is important for vertebrate infection, while liganded holo-PlzA is important for survival in the tick; however, the biological function of PlzA has remained enigmatic. Here, we report that PlzA has RNA chaperone activity that is inhibited by c-di-GMP binding. Holo- and apo-PlzA bind RNA and accelerate RNA annealing, while only apo-PlzA can strand displace and unwind double-stranded RNA. Guided by the crystal structure of PlzA, we identified several key aromatic amino acids protruding from the N- and C-terminal domains that are required for RNA-binding and unwinding activity. Our findings illuminate c-di-GMP as a switch controlling the RNA chaperone activity of PlzA, and we propose that complex RNA-mediated modulatory mechanisms allow PlzA to regulate gene expression during both the vector and host phases of the B. burgdorferi life cycle.

The glycerol-3-phosphate dehydrogenases GpsA and GlpD constitute the oxidoreductive metabolic linchpin for Lyme disease spirochete host infectivity and persistence in the tick

We have identified GpsA, a predicted glycerol-3-phosphate dehydrogenase, as a virulence factor in the Lyme disease spirochete Borrelia (Borreliella) burgdorferi: GpsA is essential for murine infection and crucial for persistence of the spirochete in the tick. B. burgdorferi has a limited biosynthetic and metabolic capacity; the linchpin connecting central carbohydrate and lipid metabolism is at the interconversion of glycerol-3-phosphate and dihydroxyacetone phosphate, catalyzed by GpsA and another glycerol-3-phosphate dehydrogenase, GlpD. Using a broad metabolomics approach, we found that GpsA serves as a dominant regulator of NADH and glycerol-3-phosphate levels in vitro, metabolic intermediates that reflect the cellular redox potential and serve as a precursor for lipid and lipoprotein biosynthesis, respectively. Additionally, GpsA was required for survival under nutrient stress, regulated overall reductase activity and controlled B. burgdorferi morphology in vitro. Furthermore, during in vitro nutrient stress, both glycerol and N-acetylglucosamine were bactericidal to B. burgdorferi in a GlpD-dependent manner. This study is also the first to identify a suppressor mutation in B. burgdorferi: a glpD deletion restored the wild-type phenotype to the pleiotropic gpsA mutant, including murine infectivity by needle inoculation at high doses, survival under nutrient stress, morphological changes and the metabolic imbalance of NADH and glycerol-3-phosphate. These results illustrate how basic metabolic functions that are dispensable for in vitro growth can be essential for in vivo infectivity of B. burgdorferi and may serve as attractive therapeutic targets.

Lyme disease (borreliosis) is the most common tick-borne disease in the Northern hemisphere and its prevalence is increasing. Borrelia burgdorferi, the etiological agent of Lyme disease, is an enzootic pathogen that alternates between a tick vector and vertebrate host. Humans are considered an incidental host after transmission of B. burgdorferi following the bite of an infected tick. The mechanisms by which B. burgdorferi persists in the Ixodid tick, transmits to a vertebrate host and establishes infection are not well understood. Therefore, identifying virulence factors and uncovering the pathogenic strategies in the spirochete remain important to address the public health concerns of Lyme disease. In this study, we identify an enzyme involved in three-carbon metabolism, GpsA, as a new virulence factor with an effect on persistence in ticks. GpsA and GlpD, another enzyme, constitute a bidirectional metabolic node connecting lipid biosynthesis and glycolysis, which serves as the linchpin for regulating carbon utilization for B. burgdorferi throughout its enzootic cycle. Disruption of this node causes a lethal metabolic imbalance revealing a potential therapeutic target for the treatment of Lyme disease.

Characterization of 6S RNA in the Lyme disease spirochete

6S RNA binds to RNA polymerase and regulates gene expression, contributing to bacterial adaptation to environmental stresses. In this study, we examined the role of 6S RNA in murine infectivity and tick persistence of the Lyme disease spirochete Borrelia (Borreliella) burgdorferi. B. burgdorferi 6S RNA (Bb6S RNA) binds to RNA polymerase, is expressed independent of growth phase or nutrient stress in culture, and is processed by RNase Y. We found that rny (bb0504), the gene encoding RNase Y, is essential for B. burgdorferi growth, while ssrS, the gene encoding 6S RNA, is not essential, indicating a broader role for RNase Y activity in the spirochete. Bb6S RNA regulates expression of the ospC and dbpA genes encoding outer surface protein C and decorin binding protein A, respectively, which are lipoproteins important for host infection. The highest levels of Bb6S RNA are found when the spirochete resides in unfed nymphs. ssrS mutants lacking Bb6S RNA were compromised for infectivity by needle inoculation, but injected mice seroconverted, indicating an ability to activate the adaptive immune response. ssrS mutants were successfully acquired by larval ticks and persisted through fed nymphs. Bb6S RNA is one of the first regulatory RNAs identified in B. burgdorferi that controls the expression of lipoproteins involved in host infectivity.

The Stringent Response-Regulated sRNA Transcriptome of Borrelia burgdorferi

The Lyme disease spirochete Borrelia (Borreliella) burgdorferi must tolerate nutrient stress to persist in the tick phase of its enzootic life cycle. We previously found that the stringent response mediated by Rel_Bbu globally regulates gene expression to facilitate persistence in the tick vector. Here, we show that Rel_Bbu regulates the expression of a swath of small RNAs (sRNA), affecting 36% of previously identified sRNAs in B. burgdorferi. This is the first sRNA regulatory mechanism identified in any spirochete. Threefold more sRNAs were Rel_Bbu-upregulated than downregulated during nutrient stress and included antisense, intergenic and 5′ untranslated region sRNAs. Rel_Bbu-regulated sRNAs associated with genes known to be important for host infection (bosR and dhhp) as well as persistence in the tick (glpF and hk1) were identified, suggesting potential mechanisms for post-transcriptional regulation of gene expression.

Genetic Transformation and Complementation

The disciplines of Borrelia (Borreliella) burgdorferi microbiology and Lyme disease pathogenesis have come to depend on the genetic manipulation of the spirochete. Generating mutants in these recalcitrant bacteria, while not straightforward, is routinely accomplished in numerous laboratories, although there are several crucial caveats to consider. This chapter describes the design of basic molecular genetic experiments as well as the detailed methodologies to prepare and transform competent cells, select for and isolate transformants, and complement or genetically restore mutants.

Do regional brain volumes and major depressive disorder share genetic architecture? A study of Generation Scotland (n=19 762), UK Biobank (n=24 048) and the English Longitudinal Study of Ageing (n=5766)

Major depressive disorder (MDD) is a heritable and highly debilitating condition. It is commonly associated with subcortical volumetric abnormalities, the most replicated of these being reduced hippocampal volume. Using the most recent published data from Enhancing Neuroimaging Genetics through Meta-analysis (ENIGMA) consortium's genome-wide association study of regional brain volume, we sought to test whether there is shared genetic architecture between seven subcortical brain volumes and intracranial volume (ICV) and MDD. We explored this using linkage disequilibrium score regression, polygenic risk scoring (PRS) techniques, Mendelian randomisation (MR) analysis and BUHMBOX. Utilising summary statistics from ENIGMA and Psychiatric Genomics Consortium, we demonstrated that hippocampal volume was positively genetically correlated with MDD (r_G=0.46, P=0.02), although this did not survive multiple comparison testing. None of the other six brain regions studied were genetically correlated and amygdala volume heritability was too low for analysis. Using PRS analysis, no regional volumetric PRS demonstrated a significant association with MDD or recurrent MDD. MR analysis in hippocampal volume and MDD identified no causal association, however, BUHMBOX analysis identified genetic subgrouping in GS:SFHS MDD cases only (P=0.00281). In this study, we provide some evidence that hippocampal volume and MDD may share genetic architecture in a subgroup of individuals, albeit the genetic correlation did not survive multiple testing correction and genetic subgroup heterogeneity was not replicated. In contrast, we found no evidence to support a shared genetic architecture between MDD and other regional subcortical volumes or ICV.

Genome-wide association study of borderline personality disorder reveals genetic overlap with bipolar disorder, major depression and schizophrenia

Borderline personality disorder (BOR) is determined by environmental and genetic factors, and characterized by affective instability and impulsivity, diagnostic symptoms also observed in manic phases of bipolar disorder (BIP). Up to 20% of BIP patients show comorbidity with BOR. This report describes the first case-control genome-wide association study (GWAS) of BOR, performed in one of the largest BOR patient samples worldwide. The focus of our analysis was (i) to detect genes and gene sets involved in BOR and (ii) to investigate the genetic overlap with BIP. As there is considerable genetic overlap between BIP, major depression (MDD) and schizophrenia (SCZ) and a high comorbidity of BOR and MDD, we also analyzed the genetic overlap of BOR with SCZ and MDD. GWAS, gene-based tests and gene-set analyses were performed in 998 BOR patients and 1545 controls. Linkage disequilibrium score regression was used to detect the genetic overlap between BOR and these disorders. Single marker analysis revealed no significant association after correction for multiple testing. Gene-based analysis yielded two significant genes: DPYD (P=4.42 × 10-7) and PKP4 (P=8.67 × 10-7); and gene-set analysis yielded a significant finding for exocytosis (GO:0006887, PFDR=0.019; FDR, false discovery rate). Prior studies have implicated DPYD, PKP4 and exocytosis in BIP and SCZ. The most notable finding of the present study was the genetic overlap of BOR with BIP (rg=0.28 [P=2.99 × 10-3]), SCZ (rg=0.34 [P=4.37 × 10-5]) and MDD (rg=0.57 [P=1.04 × 10-3]). We believe our study is the first to demonstrate that BOR overlaps with BIP, MDD and SCZ on the genetic level. Whether this is confined to transdiagnostic clinical symptoms should be examined in future studies.

Common polygenic risk for autism spectrum disorder (ASD) is associated with cognitive ability in the general population

Cognitive impairment is common among individuals diagnosed with autism spectrum disorder (ASD) and attention-deficit hyperactivity disorder (ADHD). It has been suggested that some aspects of intelligence are preserved or even superior in people with ASD compared with controls, but consistent evidence is lacking. Few studies have examined the genetic overlap between cognitive ability and ASD/ADHD. The aim of this study was to examine the polygenic overlap between ASD/ADHD and cognitive ability in individuals from the general population. Polygenic risk for ADHD and ASD was calculated from genome-wide association studies of ASD and ADHD conducted by the Psychiatric Genetics Consortium. Risk scores were created in three independent cohorts: Generation Scotland Scottish Family Health Study (GS:SFHS) (n=9863), the Lothian Birth Cohorts 1936 and 1921 (n=1522), and the Brisbane Adolescent Twin Sample (BATS) (n=921). We report that polygenic risk for ASD is positively correlated with general cognitive ability (beta=0.07, P=6 × 10(-7), r(2)=0.003), logical memory and verbal intelligence in GS:SFHS. This was replicated in BATS as a positive association with full-scale intelligent quotient (IQ) (beta=0.07, P=0.03, r(2)=0.005). We did not find consistent evidence that polygenic risk for ADHD was associated with cognitive function; however, a negative correlation with IQ at age 11 years (beta=-0.08, Z=-3.3, P=0.001) was observed in the Lothian Birth Cohorts. These findings are in individuals from the general population, suggesting that the relationship between genetic risk for ASD and intelligence is partly independent of clinical state. These data suggest that common genetic variation relevant for ASD influences general cognitive ability.

The Borrelia burgdorferi RelA/SpoT Homolog and Stringent Response Regulate Survival in the Tick Vector and Global Gene Expression during Starvation

As the Lyme disease bacterium Borrelia burgdorferi traverses its enzootic cycle, alternating between a tick vector and a vertebrate host, the spirochete must adapt and persist in the tick midgut under prolonged nutrient stress between blood meals. In this study, we examined the role of the stringent response in tick persistence and in regulation of gene expression during nutrient limitation. Nutritionally starving B. burgdorferi in vitro increased the levels of guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), collectively referred to as (p)ppGpp, products of the bifunctional synthetase/hydrolase RelBbu (RelA/SpoT homolog). Conversely, returning B. burgdorferi to a nutrient-rich medium decreased (p)ppGpp levels. B. burgdorferi survival in ticks between the larval and nymph blood meals, and during starvation in vitro, was dependent on RelBbu. Furthermore, normal morphological conversion from a flat-wave shape to a condensed round body (RB) form during starvation was dependent on RelBbu; relBbu mutants more frequently formed RBs, but their membranes were compromised. By differential RNA sequencing analyses, we found that RelBbu regulates an extensive transcriptome, both dependent and independent of nutrient stress. The RelBbu regulon includes the glp operon, which is important for glycerol utilization and persistence in the tick, virulence factors and the late phage operon of the 32-kb circular plasmid (cp32) family. In summary, our data suggest that RelBbu globally modulates transcription in response to nutrient stress by increasing (p)ppGpp levels to facilitate B. burgdorferi persistence in the tick.

Indoleamine 2,3 dioxygenase contributes to transferable tolerance in rat red blood cell inducible model of experimental autoimmune haemolytic anaemia

Autoimmune haemolytic anaemia (AIHA) is caused by autoantibodies against red blood cell (RBC) surface antigens that render RBC susceptible to Fc-mediated phagocytosis and complement-mediated lysis. Experimental AIHA can be induced by injection of rat RBC to naive mice, but a lymphocyte-mediated regulatory mechanism eventually suppresses the production of autoantibodies specific for mouse RBC. Critically, this tolerogenic response can be transferred to naive mice by splenocytes from the rat RBC-immunized mouse. Here we investigate whether indoleamine 2,3 dioxygenase (IDO) or the initiators of IDO cascade, including the cytotoxic T lymphocyte antigen (CTLA)-4 receptor and its soluble isoform, contribute to this tolerogenic mechanism. Splenocytes from experimental AIHA mice were transferred adoptively to naive mice under the cover of anti-CTLA-4, anti-soluble CTLA-4 antibodies or IDO inhibitor 1-methyl tryptophan (1-MT). Recipient mice were immunized with rat RBC and levels of antibody against self-RBC and rat-RBC were monitored. Our results indicate that transfer of tolerance to naive recipients is dependent upon IDO-mediated immunosuppression, as mice receiving previously tolerized splenocytes under the cover of 1-MT were refractory to tolerance and developed haemolytic disease upon further challenge with rat RBC. Initiators of IDO activity, CTLA-4 or soluble CTLA-4 did not mediate this tolerogenic process but, on their blockade, boosted antigen-specific effector immune responses.

An inverted repeat in the ospC operator is required for induction in Borrelia burgdorferi

Borrelia burgdorferi, the spirochete that causes Lyme disease, differentially regulates synthesis of the outer membrane lipoprotein OspC to infect its host. OspC is required to establish infection but then repressed in the mammal to avoid clearance by the adaptive immune response. Inverted repeats (IR) upstream of the promoter have been implicated as an operator to regulate ospC expression. We molecularly dissected the distal inverted repeat (dIR) of the ospC operator by site-directed mutagenesis at its endogenous location on the circular plasmid cp26. We found that disrupting the dIR but maintaining the proximal IR prevented induction of OspC synthesis by DNA supercoiling, temperature, and pH. Moreover, the base-pairing potential of the two halves of the dIR was more important than the nucleotide sequence in controlling OspC levels. These results describe a cis-acting element essential for the expression of the virulence factor OspC.

Multicenter evaluation of a Candida albicans peptide nucleic acid fluorescent in situ hybridization probe for characterization of yeast isolates from blood cultures

We evaluated aliquots from 244 clinical blood culture bottles that demonstrated yeasts on Gram stain using a Candida albicans peptide nucleic acid (PNA) fluorescent in situ hybridization (FISH) probe. The sensitivity, specificity, positive predictive value, and negative predictive value of the C. albicans PNA FISH test in this study were 99%, 100%, 100%, and 99.3%, respectively.

Identification of further DLA-DRB1 and DQA1 alleles in the dog

Three novel DLA-DRB1 alleles and one novel DQA1 allele have been identified in a panel of 367 dogs. These were suggested by unusual reaction patterns found in sequence specific oligonucleotide probing (SSOP) data. Four new alleles were confirmed using DNA cloning and sequencing.

Visual outcomes in children with bilateral retinoblastoma

BACKGROUND

Retinoblastoma is the most common primary intraocular tumor of childhood. Although studies have explored trends in retinoblastoma management and prognosis, few have addressed visual outcome.

METHODS

A retrospective chart review was performed on children in whom bilateral retinoblastoma was diagnosed at New York Hospital-Cornell Medical College. A total of 74 children were included in the study. All children underwent radiation to the eyes that were studied. Fundus drawings done at the time of diagnosis were evaluated to determine the location of tumors on presentation and the Reese-Ellsworth classification. Visual outcome was classified into 3 groups: group 1 represented visual acuity of 20/20 to 20/40; group 2, 20/50 to 20/400, and group 3, <20/400.

RESULTS

A total of 74 children were studied. Forty-six (62%) underwent enucleation of 1 eye. The visual acuity of the remaining 102 eyes was divided into groups 1, 2, and 3. Fifty-eight percent of these eyes were in group 1, 31% in group 2, and 9% in group 3. Two percent underwent subsequent enucleation after treatment. The tumors were analyzed on the basis of Reese-Ellsworth classification, location, size, and distance from the macula. Excluding Reese-Ellsworth group VB, there was no correlation between Reese-Ellsworth classification and final visual outcome. Tumors involving the macula were in 7 (78%) of 9 eyes with poor visual outcome (group 3), and 16 (33%) of 48 eyes with excellent vision (group 1) had macular tumors. Paradoxically, 2 (22%) of 9 eyes in group 3 did not have tumors involving the macula.

CONCLUSIONS

Children with retinoblastoma now have an excellent prognosis for life. Although correlated with tumor location, visual outcome is not always easily predicted on the basis of the initial presentation. Final acuity is excellent in most cases but may be influenced by multiple factors that must be considered when caring for these children and families.

Early development and embryology of the platypus

Information on the pre-hatching development of the platypus, Ornithorhynchus anatinus, is reliant on a small number of specimens, whose precise age is unknown. Material collected for J. P. Hill and now housed in the Hubrecht International Embryological Laboratory, Utrecht, contributes a major source of specimens. This paper presents new observations on developmental stages from the Hill collection, which allow for a more complete description of pre-hatching development. A feature of the pre-embryonic development of the platypus is the incomplete meroblastic cleavage. A column of fine yolk spheres extends from beneath the embryonic blastodisc towards the centre of a yolky vitellus, as seen in birds. The major expansion of extra-embryonic membranes occurs after the formation of the primitive streak. The primitive streak develops within an embryonal area as part of the superficial wall of the yolk-sac, a feature also shared with marsupials, birds and reptiles. The full-term, subspheroidal, intrauterine egg of the platypus has a major axis of about 17 mm and contains a flat, 19-20 somite, neurula-stage embryo which has prominent trigeminal ganglion primordia. The embryo at this stage is in a period of rapid modelling of the major early organ primordia of the nervous system, cardiovascular system, excretory system, and somite-derived components of the body wall. Soon after laying, five primary brain vesicles are present, the trigeminal ganglia CN5 as well as CN7, CN8, CN9, CN10, CN11 and CN12 are well developed. The alimentary system has an expanded stomach, pancreatic primordia and a gall bladder. Mesonephric tubules are associated with patent mesonephric ducts, which empty laterally into the cloaca. Extra-embryonic membranes at this stage show an extensive chorioamniotic connection that extends through the greater part of the caudal half of fused amniotic folds. The vascularized yolk-sac consists of a superficial yolk-sac omphalopleura and a deep yolk-sac splanchnopleure. The non-vascularized yolk-sac comprises one-quarter of the ahembryonal pole. Some distinctive monotreme features have developed by the mid-incubation period. The head is bent at an acute angle to the main body axis. The blunt upturned snout marks the site of the future oscaruncle and on the maxilla there is a median primordial papilla representing the egg tooth. The eye is open with a partly pigmented retinal ring. The forelimbs have partly separated digits, and the hindfeet are paddles. Just before hatching the upturned snout contains an oscaruncle and a sharp recurved median egg tooth. Forelimbs are pronated with separate digits possessing claw primordia. Portions of the highly vascularized extra-embryonic membranes are attached to the umbilical region and the flattened vesicular allantois has a distal region fused with the chorion. Prominent features of the hatchling are the presence of a bluntly conical oscaruncle and a translucent, horn-like egg tooth. These structures are though to enable the hatchling to extricate itself from the egg shell. At hatching, the forelimbs exhibit clawed digits and are capable of digitopalmar prehension. Hindlimbs are still paddles with digital rays. A prominent yolk-sac navel is present. The newly hatched platypus has an external form similar to that of a new-born marsupial. The early development of the platypus has many major differences to the developmental sequence for humans, which has been categorized by the use of Carnegie Stages. The rate of somitogenesis of the platypus is faster in relation to the central nervous system morphogenesis than seen in humans, and the size of the early platypus embryonal area is massive in relation to that of humans. The unique morphology and function of extra-embryonic membranes in the platypus defies comparative staging with human development. Structures adapted for altricial survival of the platypus hatchling require the acquisition of functional competence at an earlier stage of organogenesis than seen in eutherians, although they are reminiscent of those found in new-born marsupials.

The development of the external features of the platypus (Ornithorhynchus anatinus)

The present study describes the post-hatching development of the external features of the platypus. Specimens range in age from the day of hatching through to 6 months old, and provide the first comprehensive view of the developmental sequence of these features. Various features, those specific to the platypus, those specific to monotremes and those shared with marsupials and eutherians, are described. Features specific to the platypus, including the bill and webbing of the forefeet, are seen to develop precociously. Many features show similarities to marsupials, although marsupials show differential development both in timing and in morphology. The developmental progression is related to the age, in days, although the exact age of the specimens is unclear, and relies on ages given to the specimens at the time of collection, sometimes as long as 70 years ago. Despite this, the progression of development of these features suggests that the ageing given is relatively accurate.

Varicella-zoster virus retrobulbar optic neuritis in a patient with human immunodeficiency virus

PURPOSE

To determine the cause of bilateral retrobulbar optic neuritis followed by progressive outer retinal necrosis in a patient with human immunodeficiency virus (HIV).

METHODS

Extensive ophthalmologic, neurologic, infectious disease, rheumatologic, and radiologic examinations were performed.

RESULTS

Cerebrospinal fluid samples taken after the onset of bilateral retrobulbar optic neuritis and before the development of clinical progressive outer retinal necrosis disclosed varicella-zoster virus from polymerase chain reaction and viral culture.

CONCLUSION

Ophthalmologists and neurologists should consider varicella-zoster virus optic neuritis as a potential precursor of progressive outer retinal necrosis and as a cause of retrobulbar optic neuritis in patients infected with HIV.

Cloning, sequence analysis and expression pattern of mouse desmocollin 2 (DSC2), a cadherin-like adhesion molecule

Desmocollins are cadherin-like adhesion molecules of desmosomes. We have determined the full cDNA sequence of a murine desmocollin, the homologue of human and bovine type 2 desmocollins (DSC2), and studied its tissue distribution and expression in stratified epithelia. An 8.5 day mouse embryo cDNA library was screened yielding overlapping clones which encoded the mouse DSC2. This gene has an open reading frame of 2710 base pairs (bp) encoding a polypeptide of 902 amino acids (aa). The polypeptide comprises a signal peptide, a precursor peptide, and a mature protein of 766 aa having an extracellular domain of 549 aa, a single transmembrane domain and a cytoplasmic domain of 184 aa. Like other desmocollins, murine DSC2 has two products, Dsc2a and Dsc2b, produced by alternative splicing of a 46 bp exon which encodes 11 COOH-terminal aa followed by an in-frame stop codon. Inclusion of this exon forms Dsc2b which is 54 aa shorter than Dsc2a. Mouse Dsc2a shows 75.7% amino acid identity to human and 63.3% identity to bovine Dsc2a. The mouse desmocollin is also homologous to the cadherins; 32.2% to the most closely related typical cadherin, human N-cadherin. DSC2 is ubiquitously expressed in epithelial tissues and the heart of adult mice and from the blastocyst stage of development. In situ hybridization shows that the gene is most strongly expressed suprabasally in stratified epithelia, similar to the expression of bovine DSC2.

Histological Observations on the Wing of the Grey-Headed Flying-Fox (Pteropus-Poliocephalus) (Chiroptera, Pteropodidae)

The histological features of the wing membrane of Pteropus poliocephalus are described at both the light and electron microscope level. A method is described for the processing of bat wing tissue for both light and electron microscopy. The flight membrane of P. poliocephalus had a dorsal and ventral layer of epidermis with a common dermis in between. There was no hypodermis and all layers were greatly reduced in comparison with the skin of other mammals. The epidermis consisted of three layers of active keratinocytes, covered by 7-10 layers of cornified cells. Melanocytes were generally confined to the basal layer and were more numerous in the dorsal epidermis. Prominent droplets of a lipid-like substance were found in the epidermal keratinocytes and these coalesced towards the superficial layers. It is postulated that the substance contained in these droplets is a waterproofing agent. The dermis consisted mainly of collagen bundles with a network of elastin bands. An array of hair-dome complexes were found on the wing membrane surface. These receptors are similar to those described in several microchiropterans, where it is thought they provide information on airflow patterns over the wing.

Sexual Dimorphism in the Pelvic Girdle of Australian Flying Foxes

Sexual dimorphism was observed in the pelvic girdle of all individuals and age classes of Pteropus alecto, P. poliocephalus and P. scapulatus. In females the pelvic girdle is open (V-shaped) whereas it is closed (O-shaped) in males. This striking dimorphism enabled the sex of any individual, including skeletal material alone, to be determined with 100% accuracy. In females the interpubic distance (i.e. the distance between the two pubic bones) is correlated with forearm length. The first comparative photographs of the dimorphic pelvis are presented and the usefulness of this new diagnostic character explored.

Breast self examination: use of a visual reminder to increase practice

1. Breast cancer, the most common type of cancer affecting women and the second leading cause of cancer death in women, will affect more than 10% of the female population of this country. 2. Breast self examination (BSE), known to be an effective component of a three part breast health program which includes physical examination and mammography, is not practiced consistently by American women. 3. A convenient memory aid serving as a visual stimulus, combined with appropriate educational materials, is effective in increasing both the knowledge of breast health and the frequency of BSE practice.

Phylogenetic relations between microbats, megabats and primates (Mammalia: Chiroptera and Primates)

We examine the paraphylectic hypothesis of bat origins, both in the light of previous discussions, and in the light of new evidence from our analyses of neurological traits and wing morphology. Megabats share with primates a variety of complex details in the organization of neural pathways that have not been found in any other mammalian group, particularly not in microbats. The features previously used to link microbats and megabats have been examined and found to be questionable bases for support of a monophyletic origin. In particular, morphological analyses of the musculoskeletal adaptations associated with the flight apparatus are consistent with two separate origins of the mammalian wing. Taken together, these analyses suggest that megabats evolved from an early branch of the primate lineage. This branch was comprised of moderate-sized, phytophagous gliders, of which the other living descendants are the dermopterans. Microbats, in contrast, probably evolved much earlier from small, agile insectivores whose forelimbs had long metacarpals in relation to their phalanges.

The embryological development and cytodifferentiation of the anterior pituitary in the marsupial, Isoodon macrourus

Light and electron microscopy were used to study the development of the anterior pituitary gland from fetal stages to the end of pouch life in the marsupial I. macrourus. The early morphological development of the anterior pituitary in I. macrourus follows a similar pattern of events to that described for eutherians. Rathke's and Seessel's pouches were present in 10 1/2 day old embryos. At birth these pouches had formed a multi-chambered vesicle which was still connected to the stomodeum by a thin cord of tissue. A small number of granules (200-400 nm dia.) were found in cells at birth. These cells could not be classified on ultrastructural features but alcian blue-periodic acid Schiffs-orange G staining suggested one cell type was possibly a presumptive thyrotroph. There were no capillaries in the pars distalis at birth. The cords connecting Rathke's and Seessel's pouches to the stomodeum were located at the site of the periosteal bud of the developing basisphenoid which commenced to ossify at 7 days. At this stage presumptive thyrotrophs, gonadotrophs, and somatotrophs could be distinguished using alcian blue-periodic acid Schiffs-orange G staining. However, five cell types could be categorised at the same age using ultrastructural characteristics alone. Precise names for these cells are unavailable but two closely resemble presumptive mammotrophs and thyrotrophs described for another marsupial M. eugenii. By 13 days after birth the anterior pituitary of I. macrourus had become vascular and acidophils were concentrated in a posterior zone. There was little gross morphological change from 13 to 66 days after birth by which the time weaning has occurred. Cilia were seen in cells of the anterior pituitary and mitosis of granulated cells was observed from birth onwards. There is a considerable range of variation in pituitary cytogenesis amongst marsupials, and its functional significance awaits further investigation.

The Morphology of the Gastrointestinal Tract and Food Transit Time in the Fruit Bats Pteropus Alecto and P. Poliocephalus (Megachiroptera)

The gastrointestinal tract of the fruit bats Pteropus alecto and P. poliocephalus was investigated by dissection and by light and electron microscopy. Food transit time was recorded for cultivated fruits and roentgenograms were obtained from bats given barium-labelled food. Minimum food transit time varied from 12 to 34 min for cultivated fruits but this was extended to 44 min by the addition of Ba. There was little variation between the gastrointestinal tracts of the two species. The stomach has an elongated terminal part, and expanded cardiac and fundic regions which display a relatively thick gastric mucosa and abundant parietal cells. A caecum and appendix are absent. Well developed villi of the small intestine feature absorptive cells with relatively large microvilli (less than or equal to 5.7 mu m tall). The intestinal mucosa displays more goblet cells in P. poliocephalus than in P. alecto. The large intestine is short and features prominent longitudinal folds; the mucosa undergoes a gradual transition, with number and size of villi decreasing in the distal part of the intestine. Although a distinct rectum cannot be distinguished, the colonic mucosa is restricted to a short segment, slightly shorter in P. poliocephalus than in P. alecto. The study highlights several anatomical features of the gastrointestinal tract, which probably allow fruit bats to process large quantities of food rapidly. The advantage of this to a flying mammal is a reduction in bulk carried in the digestive tract, enabling it to reduce the energy expenditure associated with foraging flights.

Observations on Body Weights and Breeding of the Northern Brown Bandicoot, Isoodon macrourus, Trapped in South-East Queensland

Information on body weight, measurements and breeding is recorded for 96 female and 42 male Isoodon macrourus, trapped in the vicinity of Brisbane. Data are also given on sex ratio, nipple attachment site and mortality for 128 pouch young from 44 litters. I. macrourus is the heaviest peramelid, with a mean body weight of 1046 ( � 263)g for females and 1496 ( � 359)g for males. Seasonal effects on body weight are evident in females but absent in males. Females with pouch young were significantly heavier than those without young for most months of the year. Unlike most other peramelids, I. macrourus has no defined breeding season in south-eastern Queensland. Females produce litters in all months of the year, with a peak in August and a low in June. Litter size averaged 2.9, which is the lowest recorded for the species. Female body weight had a positive linear relationship with litter size (y= 0.001297x + 1.444). Sex ratio of adults was 1:1, but that of pouch young favoured males 1:0.8. Of the eight pouch teats available, young favoured the four anterior nipples (72 v.56) and males outnumbered females on the left-side nipples. Survival rate of pouch young, as indicated by litter size from 0 to 50 days, showed no variation but there appears to be a high mortality for young after they leave the pouch and before they reach a body weight of 500 g.

Plasminogen activator from human embryonic kidney cell cultures. Evidence for a proactivator

The nature of the trypsin-activatable plasminogen activator produced by kidney cell cultures (Bernik, M.B (1973), J. Clin. Invest. 52, 823-834) was investigated using human embryonic kidney (HEK) cell cultures in serum-free medium. Plaminogen activator activity ratios (trypsin-activated/ untreated controls) in HEK cell-conditioned media were maximal (up to 3) during the first week of culture and remained nearly constant at approximatley 2 for the next 3-5 weeks, while the total plasminogen activator titer increased in a nearly linear manner. Therefore, coincident with progressive cell degeneration and death, the ratios decreased to near unity due to "spontaneous" activation of the enzyme, which was inhibited in cell-free conditioned media by the pancreatic trypsin inhibitor Kunitz and benzamidine. Since the activator is not inhibited by the trypsin inhibitor, it is concluded that a protease other than the plasminogen activator is responsible for the activation. Increases in the plasminogen activator titers (about 2-fold) were similarly obtained by culturing the cells in medium containing low concentrations (0.05-0.10 mug/ml) of trypsin for up to about 6 weeks. The presence of the trypsin inhibitor in HEK cells cultures decreased the rate of activation, resulting in higher activity ratios (up to 6), and the total plasminogen activator activity was reduced only minimally (less than 20%), if at all, by the highest concentration of the trypsin inhibitor (100 mug/ml) tested. Affinity chromatography of conditioned media with activity ratios of 1.6--2 separated the plasminogen activator into an active fraction and a fraction which was activated a minimum of 200-fold by trypsin and contained no measurable activity prior to activation. Gel filtration of crude conditioned media or partially purified activator separated the plasminogen activator into two peaks; both were trypsin-activatable, and their relative proportions varied with the isolated conditions. The results indicate the occurrence of a proenzyme form of the plasminogen activator in the culture media.

Stomach Contents of Forty-Two Species of Bats From the Australasian Region

Bats were killed between 1963 and 1973 during surveys in Australia, Papua New Guinea and Bougainville Island. Results are given as number of stomachs containing particular food items, or as number of items in a stomach. Insect remains on the floor of bat caves were examined also. There were 42 species of bat examined, of 16 genera; stomachs of 36 species had Lepidoptera, 29 had Coleoptera, 27 had Hymenoptera and 23 had Hemiphera. Twelve bat species ate wingless insects and 7 ate aquatic insects, though those may be found away from water. Results are discussed in relation to foraging behaviour of bats.

Reproducibility, efficacy and methodology of mitogen-induced lymphocyte transformations by the whole blood assay

For the past few years, the whole blood culture method has been scrutinized for its usefulness and reproducibility in evaluating the immunologic status of patients. This method, used in our laboratory mainly screening specimens for evidence of immunodeficiencies, has been systematically evaluated for reproducibility, and factors affecting normal response through testing specimens from over 70 normal persons. Three mitogens (phytohemagglutinin, Concanavalin A, and pokeweed) were studied; peak time responses occurred later than in the separated cell culture method, and they were different for each mitogen. The dose response curves also depended on the mitogen tested, with pokeweed giving a sharp curve and the others a broad plateau. The harvesting procedure was studied by varying reagents and was optimized for speed and efficiency. The mononuclear cell count of the specimen had little effect on the results as long as it remained less than 3.5 X 10(6)/ml. The results for all mitogens followed a similar distribution curve irrespective of whether the results were expressed as cpm or cpm divided by the mononuclear cell count. The use of the stimulation ratio method to express results was less satisfactory. The mean coefficient of variation for all triplicate samples remained 20% or less and for all conditions tested. In evaluating the immunodeficient patient, the whole blood culture method was found to be equally as informative and easier to perform than the separated cell method.

The Distribution of Rabbit Warrens at Mitchell, Queensland, in relation to Soil and Vegetation Characteristics

In a 42,750-ha survey area in subtropical Queensland, rabbit warrens are confined mainly to sandy soils. Within these favoured areas the population is distributed unevenly, and there is further selection for preferred habitats. Detailed studies on a 246-ha area of sandhill showed that the open woodland and grassy open woodland associations contain most warrens per unit area, and also the largest warrens. The quality of habitat for rabbits appears to be determined by availability of food, type of soil, and vegetation cover providing protection from predators. In some vegetation associations, use of burrows varies only slightly, in others there are significant changes. There is a significant correlation between the estimated numbers of rabbits in the population, the total number of rabbits seen on spotlight transect counts in the evening, the numbers of rabbits seen on warrens during late afternoon watches, and the total number of active burrow entrances present in the study area. A list of plant species present and a description of the 23 vegetation associations in the study area is presented.