Increasing control over biomineralization in conodont evolution.

Vertebrates use the phosphate mineral apatite in their skeletons, which allowed them to develop tissues such as enamel, characterized by an outstanding combination of hardness and elasticity. It has been hypothesized that the evolution of the earliest vertebrate skeletal tissues, found in the teeth of the extinct group of conodonts, was driven by adaptation to dental function. We test this hypothesis quantitatively and demonstrate that the crystallographic order increased throughout the early evolution of conodont teeth in parallel with morphological adaptation to food processing. With the c-axes of apatite crystals oriented perpendicular to the functional feeding surfaces, the strongest resistance to uniaxial compressional stress is conferred along the long axes of denticles. Our results support increasing control over biomineralization in the first skeletonized vertebrates and allow us to test models of functional morphology and material properties across conodont dental diversity.

A new interpretation of Pikaia reveals the origins of the chordate body plan.

Our understanding of the evolutionary origin of Chordata, one of the most disparate and ecologically significant animal phyla, is hindered by a lack of unambiguous stem-group relatives. Problematic Cambrian fossils that have been considered as candidate chordates include vetulicolians,1Yunnanozoon,2 and the iconic Pikaia.3 However, their phylogenetic placement has remained poorly constrained, impeding reconstructions of character evolution along the chordate stem lineage. Here we reinterpret the morphology of Pikaia, providing evidence for a gut canal and, crucially, a dorsal nerve cord-a robust chordate synapomorphy. The identification of these structures underpins a new anatomical model of Pikaia that shows that this fossil was previously interpreted upside down. We reveal a myomere configuration intermediate between amphioxus and vertebrates and establish morphological links between Yunnanozoon, Pikaia, and uncontroversial chordates. In this light, we perform a new phylogenetic analysis, using a revised, comprehensive deuterostome dataset, and establish a chordate stem lineage. We resolve vetulicolians as a paraphyletic group comprising the earliest diverging stem chordates, subtending a grade of more derived stem-group chordates comprising Yunnanozoon and Pikaia. Our phylogenetic results reveal the stepwise acquisition of characters diagnostic of the chordate crown group. In addition, they chart a phase in early chordate evolution defined by the gradual integration of the pharyngeal region with a segmented axial musculature, supporting classical evolutionary-developmental hypotheses of chordate origins4 and revealing a "lost chapter" in the history of the phylum.

Cambrian stem-group ambulacrarians and the nature of the ancestral deuterostome.

Deuterostomes are characterized by some of the most widely divergent body plans in the animal kingdom. These striking morphological differences have hindered efforts to predict ancestral characters, with the origin and earliest evolution of the group remaining ambiguous. Several iconic Cambrian fossils have been suggested to be early deuterostomes and hence could help elucidate ancestral character states. However, their phylogenetic relationships are controversial. Here, we describe new, exceptionally preserved specimens of the discoidal metazoan Rotadiscus grandis from the early Cambrian Chengjiang biota of China. These reveal a previously unknown double spiral structure, which we interpret as a chordate-like covering to a coelomopore, located adjacent to a horseshoe-shaped tentacle complex. The tentacles differ in key aspects from those seen in lophophorates and are instead more similar to the tentacular systems of extant pterobranchs and echinoderms. Thus, Rotadiscus exhibits a chimeric combination of ambulacrarian and chordate characters. Phylogenetic analyses recover Rotadiscus and closely related fossil taxa as stem ambulacrarians, filling a significant morphological gap in the deuterostome tree of life. These results allow us to reconstruct the ancestral body plans of major clades of deuterostomes, revealing that key traits of extant forms, such as a post-anal region, gill bars, and a U-shaped gut, evolved through convergence.

Trends and outcomes of open, laparoscopic, and robotic inguinal hernia repair in the veterans affairs system.

PURPOSE: Robotic inguinal hernia repair (RHR) is an evolving technique but is comparatively expensive and has yet to show superior outcomes versus open (OHR) or laparoscopic (LHR) approaches. The utilization and clinical outcomes of RHR have not been reported within the veterans affairs (VA) system. This study analyzes trends in utilization and 30-day post-operative outcomes between OHR, LHR, and RHR in veterans. METHODS: This is a retrospective review of patients that underwent inguinal herniorrhaphy using the Veterans Affairs Quality Improvement Program database. Multivariable analysis of outcomes was performed adjusting for pre-operative confounding covariates between OHR, LHR, and RHR. Trends in utilization, complication rates, and operative times were also reported. RESULTS: From 2008-2019, 124,978 cases of inguinal herniorrhaphy were identified: 100,880 (80.7%) OHR, 18,035 (14.4%) LHR, and 6063 (4.9%) RHR. Compared to LHR, RHR was associated with 4.94 times higher odds of complications, 100 min longer mean operative time, and 1.5 days longer median length of stay (LOS). Compared to OHR, RHR was associated with 5.92 times higher odds of complications, 57 min longer mean operative time, and 1.1 days longer median LOS. Utilization of RHR and LHR significantly increased over time. RHR complication rates decreased over time (2008: 20.8% to 2019: 3.2%) along with mean operative times (2008: 4.9 h to 2019: 2.8 h; p < 0.05). CONCLUSION: While this study demonstrated inferior outcomes after RHR, the temporal trends are encouraging. This may be due to increased surgeon experience with robotics. Further prospective data will elucidate the role of RHR as this technique increases.

Growth and feeding ecology of coniform conodonts.

Conodonts were the first vertebrates to develop mineralized dental tools, known as elements. Recent research suggests that conodonts were macrophagous predators and/or scavengers but we do not know how this feeding habit emerged in the earliest coniform conodonts, since most studies focus on the derived, 'complex' conodonts. Previous modelling of element position and mechanical properties indicate they were capable of food processing. A direct test would be provided through evidence of in vivo element crown tissue damage or through in vivo incorporated chemical proxies for a shift in their trophic position during ontogeny. Here we focus on coniform elements from two conodont taxa, the phylogenetically primitive Proconodontus muelleri Miller, 1969 from the late Cambrian and the more derived Panderodus equicostatus Rhodes, 1954 from the Silurian. Proposing that this extremely small sample is, however, representative for these taxa, we aim to describe in detail the growth of an element from each of these taxa in order to the test the following hypotheses: (1) Panderodus and Proconodontus processed hard food, which led to damage of their elements consistent with prey capture function; and (2) both genera shifted towards higher trophic levels during ontogeny. We employed backscatter electron (BSE) imaging, energy-dispersive X-ray spectroscopy (EDX) and synchrotron radiation X-ray tomographic microscopy (SRXTM) to identify growth increments, wear and damage surfaces, and the Sr/Ca ratio in bioapatite as a proxy for the trophic position. Using these data, we can identify whether they exhibit determinate or indeterminate growth and whether both species followed linear or allometric growth dynamics. Growth increments (27 in Pa. equicostatus and 58 in Pr. muelleri) were formed in bundles of 4-7 increments in Pa. equicostatus and 7-9 in Pr. muelleri. We interpret the bundles as analogous to Retzius periodicity in vertebrate teeth. Based on applied optimal resource allocation models, internal periodicity might explain indeterminate growth in both species. They also allow us to interpret the almost linear growth of both individuals as an indicator that there was no size-dependent increase in mortality in the ecosystems where they lived e.g., as would be the case in the presence of larger predators. Our findings show that periodic growth was present in early conodonts and preceded tissue repair in response to wear and damage. We found no microwear and the Sr/Ca ratio, and therefore the trophic position, did not change substantially during the lifetimes of either individual. Trophic ecology of coniform conodonts differed from the predatory and/or scavenger lifestyle documented for "complex" conodonts. We propose that conodonts adapted their life histories to top-down controlled ecosystems during the Nekton Revolution.

The 'biomineralization toolkit' and the origin of animal skeletons.

Biomineralized skeletons are widespread in animals, and their origins can be traced to the latest Ediacaran or early Cambrian fossil record, in virtually all animal groups. The origin of animal skeletons is inextricably linked with the diversification of animal body plans and the dramatic changes in ecology and geosphere-biosphere interactions across the Ediacaran-Cambrian transition. This apparent independent acquisition of skeletons across diverse animal clades has been proposed to have been driven by co-option of a conserved ancestral genetic toolkit in different lineages at the same time. This 'biomineralization toolkit' hypothesis makes predictions of the early evolution of the skeleton, predictions tested herein through a critical review of the evidence from both the fossil record and development of skeletons in extant organisms. Furthermore, the distribution of skeletons is here plotted against a time-calibrated animal phylogeny, and the nature of the deep ancestors of biomineralizing animals interpolated using ancestral state reconstruction. All these lines of evidence point towards multiple instances of the evolution of biomineralization through the co-option of an inherited organic skeleton and genetic toolkit followed by the stepwise acquisition of more complex skeletal tissues under tighter biological control. This not only supports the 'biomineralization toolkit' hypothesis but also provides a model for describing the evolution of complex biological systems across the Ediacaran-Cambrian transition.

The impact of taphonomic data on phylogenetic resolution: Helenodora inopinata (Carboniferous, Mazon Creek Lagerstätte) and the onychophoran stem lineage.

BACKGROUND: The origin of the body plan of modern velvet worms (Onychophora) lies in the extinct lobopodians of the Palaeozoic. Helenodora inopinata, from the Mazon Creek Lagerstätte of Illinois (Francis Creek Shale, Carbondale Formation, Middle Pennsylvanian), has been proposed as an intermediate between the "weird wonders" of the Cambrian seas and modern terrestrial predatory onychophorans. The type material of H. inopinata, however, leaves much of the crucial anatomy unknown. RESULTS: Here we present a redescription of this taxon based on more complete material, including new details of the head and posterior portion of the trunk, informed by the results of experimental decay of extant onychophorans. H. inopinata is indeed best resolved as a stem-onychophoran, but lacks several key features of modern velvet worms including, crucially, those that would suggest a terrestrial mode of life. CONCLUSIONS: The presence of H. inopinata in the Carboniferous demonstrates the survival of a Cambrian marine morphotype, and a likely post-Carboniferous origin of crown-Onychophora. Our analysis also demonstrates that taphonomically informed tests of character interpretations have the potential to improve phylogenetic resolution.

Functional adaptation underpinned the evolutionary assembly of the earliest vertebrate skeleton.

Conodonts are the first vertebrates to bear a mineralized skeleton, restricted to an array of tooth-like feeding elements. The functional implications for the development of tooth-like elements differentiated into two tissues is tested using 2D finite element modeling, mapping the patterns of stress and strain that elements with differing material properties exhibited during function. Addition of a stiff crown does not change the patterns of stress, rather it reduces the deformation of the element under the same force regime, and distributes stress more evenly across the element. The euconodont crown, like vertebrate dental enamel, serves to stiffen the element and protect the underlying dentine. Stiffness of the crown may be a contributing factor to the subsequent diversity of euconodont form, and logically function, by allowing a greater range of feeding strategies to be employed. The euconodont crown also serves as an analogue to enamel and enameloid, demonstrating that enamel-like tissues have evolved multiple times in independent vertebrate lineages, likely as a response to similar selective pressures. Conodonts can, therefore, serve as an independent test on hypotheses of the effect of ecology on the development of the vertebrate skeleton.

Evaluating scenarios for the evolutionary assembly of the brachiopod body plan.

The fossil faunas of the Cambrian provide the only direct insight into the assembly of animal body plans. However, for many animal groups, their early fossil record is linked to disarticulated remains, interpretation of which is problematic since they possess few characters from which their affinity to phyla can be established and, indeed, few characters at all. One such group is the tommotiids, which has been interpreted, on the basis of skeletal anatomy, as a paraphyletic assemblage uniting brachiopods and phoronids, through the acquisition and subsequent modification, or loss, of an imbricated set of dorsal phosphatic sclerites. Here we present a reexamination of the fossil evidence uniting the tommotiids and brachiopods, supplemented with new anatomical data from synchrotron radiation X-ray tomographic microscopy of key tommotiid taxa. The characters used to support the complex hypothesis of character evolution in the brachiopod stem lineage relies on scleritome reconstructions and inferred mode of life which themselves rely on brachiopods being chosen as the interpretative model. We advocate a more conservative interpretation of the affinity of these fossils, based a priori on their intrinsic properties, rather than the modern analogue in whose light they have been interpreted.

The origin of conodonts and of vertebrate mineralized skeletons.

Conodonts are an extinct group of jawless vertebrates whose tooth-like elements are the earliest instance of a mineralized skeleton in the vertebrate lineage, inspiring the 'inside-out' hypothesis that teeth evolved independently of the vertebrate dermal skeleton and before the origin of jaws. However, these propositions have been based on evidence from derived euconodonts. Here we test hypotheses of a paraconodont ancestry of euconodonts using synchrotron radiation X-ray tomographic microscopy to characterize and compare the microstructure of morphologically similar euconodont and paraconodont elements. Paraconodonts exhibit a range of grades of structural differentiation, including tissues and a pattern of growth common to euconodont basal bodies. The different grades of structural differentiation exhibited by paraconodonts demonstrate the stepwise acquisition of euconodont characters, resolving debate over the relationship between these two groups. By implication, the putative homology of euconodont crown tissue and vertebrate enamel must be rejected as these tissues have evolved independently and convergently. Thus, the precise ontogenetic, structural and topological similarities between conodont elements and vertebrate odontodes appear to be a remarkable instance of convergence. The last common ancestor of conodonts and jawed vertebrates probably lacked mineralized skeletal tissues. The hypothesis that teeth evolved before jaws and the inside-out hypothesis of dental evolution must be rejected; teeth seem to have evolved through the extension of odontogenic competence from the external dermis to internal epithelium soon after the origin of jaws.

Cutting the first 'teeth': a new approach to functional analysis of conodont elements.

The morphological disparity of conodont elements rivals the dentition of all other vertebrates, yet relatively little is known about their functional diversity. Nevertheless, conodonts are an invaluable resource for testing the generality of functional principles derived from vertebrate teeth, and for exploring convergence in a range of food-processing structures. In a few derived conodont taxa, occlusal patterns have been used to derive functional models. However, conodont elements commonly and primitively exhibit comparatively simple coniform morphologies, functional analysis of which has not progressed much beyond speculation based on analogy. We have generated high-resolution tomographic data for each morphotype of the coniform conodont Panderodus acostatus. Using virtual cross sections, it has been possible to characterize changes in physical properties associated with individual element morphology. Subtle changes in cross-sectional profile have profound implications for the functional performance of individual elements and the apparatus as a whole. This study has implications beyond the ecology of a single conodont taxon. It provides a basis for reinterpreting coniform conodont taxonomy (which is based heavily on cross-sectional profiles), in terms of functional performance and ecology, shedding new light on the conodont fossil record. This technique can also be applied to more derived conodont morphologies, as well as analogous dentitions in other vertebrates and invertebrates.

Evolutionary origins of animal skeletal biomineralization.

The evolutionary history of biomineralization in animals is crucial to our understanding of modern mineralized tissues. Traditional methods of unravelling this history have aimed to derive a theory of the development of biomineralization through evolution by the comparison of mineralized systems in model organisms. This has led to the recognition of the 'biomineralization toolkit' and raised the question of the homology of mineralized tissues versus convergent or parallel evolution. The 'new animal phylogeny' reveals that many of the groups known to biomineralize sit among close relatives that do not, and it favours an interpretation of convergent or parallel evolution for biomineralization in animals. In addition, the fossil record of the earliest mineralized skeletons presents a rapid proliferation of biomineralization across a range of animal phyla with fossil representatives of many modern biomineralizing phyla. A synthesis of molecular, developmental, phylogenetic and fossil evidence demonstrates the convergent or parallel evolution of biomineralization in animals at the phylum level. The fossil record of the Cambrian explosion not only provides vital evidence for the evolution of animal mineralized tissues but also suggests a mechanism for its rapid and synchronous convergent origin.

Endotoxin regulates corticotropin-releasing hormone receptor 2 in heart and skeletal muscle.

We tested the effect of endotoxin on the peripheral corticotropin-releasing hormone receptor (CRH-R2), which is highly expressed in the heart. Systemic injection of LPS markedly downregulated CRH-R2 mRNA levels in the heart in a dose and time dependent manner. In contrast, CRH-R2 levels in skeletal muscle increased following exposure to endotoxin. These results suggest that CRH-R2 may be differentially regulated in cardiac tissue and skeletal muscle. Finding that CRH-R2 expression in the heart is modulated by endotoxin, a potent inducer of cardiovascular dysregulation, suggests a possible link between CRH and the cardiovascular response to stress.

Pulmonary surfactant inhibits cationic liposome-mediated gene delivery to respiratory epithelial cells in vitro.

Cationic lipid-mediated transfection of the alveolar epithelium in vivo will require exposure of plasmid DNA and cationic lipids to endogenous surfactant lipids and proteins in the alveolar space. Effects of pulmonary surfactant and of surfactant constituents on transfection in vitro of two respiratory epithelial cell lines (MLE-15 and H441) with a plasmid encoding the luciferase reporter gene were studied using two cationic lipid formulations: 1,2-dimyristyloxypropyl-3-dimethyl-hydroxyethyl ammonium bromide/cholesterol (DMRIE/C) and 1,2-dioleoyl-3-trimethylammonium propane/dioleoyl phosphatidylethanolamine (DOTAP/DOPE). Gene expression, as assessed by luciferase activity, decreased as increasing concentrations of natural surfactant were added to cationic lipid-DNA complexes. Incorporation of phospholipids DOPC/DOPG or surfactant proteins SP-B or SP-C in the cationic lipid formulation inhibited transfection. A fluorescent lipid mixing assay was used to determine the effects of surfactant proteins SP-B and SP-C on mixing between cationic lipid-DNA complexes and surfactant lipid vesicles. Mixing between DOPC/DOPG vesicles and cationic lipid-DNA complexes in the absence of added proteins amounted to 10-20%. Addition of SP-B or SP-C increased the mixing of DOPC/DOPG vesicles with DOTAP/DOPE-DNA complexes, but not DMRIEC-DNA complexes. These results demonstrate that pulmonary surfactant lipids and proteins inhibit transfection with cationic lipid-DNA complexes in vitro, and may therefore represent a barrier to gene transfer in the lung.

Behavioral effects of 3 alpha-androstanediol. II: Hypothalamic and preoptic area actions via a GABAergic mechanism.

We investigated whether 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-androstanediol; 3 alpha-Diol), a neurosteroid whose effects are primarily inhibitory to sexual behavior, may act through interactions with gamma-aminobutyric acid (GABA) receptor complexes (GBRs) in the medial basal hypothalamus (MBH) and the preoptic area (POA). In Experiment (Exp.) 1, ovariectomized (ovx) rats were implanted with bilateral guide cannulae aimed above the MBH and were later treated with 17 beta-estradiol (E2, 2 injections of 1 microgram/0.2 ml in 10% ethanol) and either 3 alpha-Diol (3.0 mg/kg, s.c.) or vehicle. Progesterone (0.5 mg, s.c.) was given 24 h after the first E2 injection and a pre-test for lordosis responsiveness was carried out 4 h later. The GABAA agonist, muscimol (50 ng), then was infused into the MBH and rats were tested 10, 30 and 60 min later. Muscimol infusion facilitated lordosis behavior in vehicle-treated controls, but 3 alpha-Diol-treated animals failed to show this facilitation. To ascertain whether 3 alpha-Diol would also prevent muscimol's action in the POA, a site in which muscimol inhibits, rather than facilitates, sexual receptivity, ovx animals in Exp.2 were implanted with bilateral guide cannulae aimed above the POA and were treated with E2, 3 alpha-Diol, and P and infused and tested as in Exp. 1. Muscimol and 3 alpha-Diol each significantly inhibited receptivity; when they were combined, the inhibition was more pronounced. In Exp. 3, POA infusions of the GABAA antagonist, bicuculline, counteracted muscimol's and 3 alpha-Diol's inhibition of sexual behavior. In Exp. 4, in vitro treatment of POA and MBH membrane fractions with 3 alpha-Diol (30 microM) enhanced maximal [3H]muscimol binding without altering the affinity of the binding sites for the agonist. These data suggest that 3 alpha-Diol inhibits E2 and progestin-induced lordosis behavior via actions at the GBR in both the MBH and POA.

Susceptibility of exogenous surfactant to phospholipase A2 degradation.

The inhibition of surfactant biophysical activity in vivo is potentially mediated by many factors, including serum proteins, particularly enzymatic proteins such as phospholipases. In the present study, we investigated the susceptibility of the phosphatidylcholine component of two exogenous surfactants, Exosurf and Survanta, to secretory-type phospholipase A2 (PLA2) deacylation in vitro. Lyophilized Exosurf and Survanta preparations were incubated at 37 degrees C for 120 min in the presence of bovine pancreatic PLA2, and the production of lysophosphatidylcholine was determined as a measure of the magnitude of phosphatidylcholine deacylation. The phosphatidylcholine component of Survanta was readily deacylated by PLA2, whereas the dipalmitoylphosphatidycholine (DPPC) component of Exosurf was resistant over the entire duration of the assay. To further evaluate this observed resistance the individual and combined effects of tyloxapol and hexadecanol, components of Exosurf, upon PLA2 deacylation of Survanta and DPPC were investigated. In both Survanta and DPPC preparations, PLA2-mediated deacylation was significantly inhibited in the presence of tyloxapol. We conclude that the presence of tyloxapol in the Exosurf preparation inhibits secretory type PLA2 mediated DPPC deacylation. This unique feature of Exosurf may be of clinical significance when this preparation is utilized in the treatment of surfactant-deficient infants.

Estradiol benzoate potentiates neuroactive steroids' effects on pain sensitivity.

Progesterone (P), its metabolites, and other neuroactive steroids alter pain thresholds consistent with their efficacies at modulating gamma-aminobutyric acid (GABAA) receptor complexes. We investigated whether estradiol benzoate (EB) potentiates low dosages of neuroactive steroids' effects on pain. Subcutaneous EB (10 micrograms) or sesame oil vehicle was administered to ovariectomized Long-Evans rats (n = 40) 48 h before intracerebroventricular (ICV) infusion of a neuroactive steroid (0.0, 0.1, 0.3, or 0.5 micrograms) in cyclodextrin vehicle. Neuroactive steroids (listed from greatest to least efficacious at GABAA receptor complexes) were THP [5 alpha-pregnan-3 alpha-ol-20-one], THDOC [5 alpha-pregnan-3 alpha, 21-diol-20-one], DHP [5 alpha-pregnan-3,20-dione], P [4-pregnen-3,20-dione], and DHEAS [5-androsten-3 beta-ol-17-one sulfate]. Pain sensitivity was assessed using the radiant heat tail-flick method before and 20 and 60 min following infusion. Estradiol benzoate interacted with the neuroactive steroids to alter tail-flick latencies. In particular, EB potentiated the antinociceptive effect of THP and DHP by significantly increasing tail-flick latencies above those of non-EB-treated animals. A similar pattern of increased tail-flick latencies occurred in EB-primed animals that received THDOC. Estradiol benzoate less consistently altered the pain threshold of animals administered P, which is less effective at modulating GABAergic activity. Conversely, EB increased the nociceptive effect of the neurosteroid DHEAS, an allosteric antagonist of GABAA receptor complexes, by significantly decreasing tail-flick latencies of EB-compared to vehicle-primed rats. Thus, EB priming potentiated neuroactive steroids' effects on pain threshold.

Progesterone metabolites, effective at the GABAA receptor complex, attenuate pain sensitivity in rats.

To investigate whether progesterone metabolites' antinociceptive effects correlate with their previously established binding efficacies at the GABA receptor complex (GBR), seven progestin metabolites were administered to ovariectomized Long-Evans rats s.c. (Expt. 1), via i.c.v. implantation (Expt. 2) and then i.c.v. infusion (Expt. 3). Progestins, listed from most to least efficacious at the GBR, were THP [5 alpha-pregnan-3 alpha-ol-20-one], THDOC [5 alpha-pregnan-3 alpha,21-diol-20-one], P [4-pregnen-3,20-dione], DHP [5 alpha-pregnan-3,20-dione],17-OH-P [17-hydroxyprogesterone], DHEAS [5-androsten-3 beta-ol-17-one sulfate] and PS [5-pregnen-3 beta-ol-20-one sulfate]. Pain sensitivity was measured via the radiant heat tailflick method 0, 5, 20, 40, 60, 80, 100 and 120 min after weekly progestin administration. Peripheral administration of 0.0, 0.1, 0.4, 1.6, 3.2 or 6.4 mg/kg of potent to moderate agonists of the GBR (THP, THDOC, P and DHP) tended to elevate tailflick latencies above baseline, whereas administration of the non-5 alpha-reduced metabolite (17-OH-P) and GBR antagonists (DHEAS and PS) did not. Intracerebroventricular implantation and infusion (0.0, 0.5, 1.0, 2.0 micrograms/rat) of THP, THDOC, P and DHP all significantly increased tailflick latencies above baseline and vehicle control, consistent with their GBR efficacies. Central 17-OH-P, DHEAS and PS did not elevate tailflick latencies. These rapid differences were unlikely confounded by stress given that corticosterone levels were not elevated (Expt. 4). As pain sensitivity was attenuated rapidly (0-5 min post-i.c.v.) and consistent with GBR efficacies, this suggests that progestins' modulation of pain may occur via GBR action.

Severe proliferative vitreoretinopathy and retinal detachment. I. Initial clinical findings.

We studied 716 eyes of 697 patients with retinal detachment associated with the more advanced stages of proliferative vitreoretinopathy (PVR). The factors that influenced the severity of PVR and our criteria for surgical treatment were analyzed using statistical methods. The more severe cases of PVR showed a higher prevalence of cases with (1) retinal detachment exceeding 12 months' duration, (2) no retinal breaks observed, (3) the largest retinal break of a size equal to or exceeding one clock hour, and (4) poor initial visual acuity. Compared with the unoperated group, the eyes on which we subsequently operated were characterized by a greater prevalence of (1) patients with bilateral retinal detachment complicated by PVR, (2) cases with relatively recent onset of retinal detachment, (3) phakic eyes, (4) eyes without vitreous hemorrhage, (5) eyes with one or more visible retinal breaks and with smaller breaks, (6) relatively better initial visual acuity, and (7) less severe degrees of PVR.