Exceptional preservation of mid-Cretaceous marine arthropods and the evolution of novel forms via heterochrony.

Evolutionary origins of novel forms are often obscure because early and transitional fossils tend to be rare, poorly preserved, or lack proper phylogenetic contexts. We describe a new, exceptionally preserved enigmatic crab from the mid-Cretaceous of Colombia and the United States, whose completeness illuminates the early disparity of the group and the origins of novel forms. Its large and unprotected compound eyes, small fusiform body, and leg-like mouthparts suggest larval trait retention into adulthood via heterochronic development (pedomorphosis), while its large oar-like legs represent the earliest known adaptations in crabs for active swimming. Our phylogenetic analyses, including representatives of all major lineages of fossil and extant crabs, challenge conventional views of their evolution by revealing multiple convergent losses of a typical "crab-like" body plan since the Early Cretaceous. These parallel morphological transformations may be associated with repeated invasions of novel environments, including the pelagic/necto-benthic zone in this pedomorphic chimera crab.

Biomineral ultrastructure, elemental constitution and genomic analysis of biomineralization-related proteins in hemichordates.

Here, we report the discovery and characterization of biominerals in the acorn worms Saccoglossus bromophenolosus and Ptychodera flava galapagos (Phylum: Hemichordata). Using electron microscopy, X-ray microprobe analyses and confocal Raman spectroscopy, we show that hemichordate biominerals are small CaCO(3) aragonitic elements restricted to specialized epidermal structures, and in S. bromophenolosus, are apparently secreted by sclerocytes. Investigation of urchin biomineralizing proteins in the translated genome and expressed sequence tag (EST) libraries of Saccoglossus kowalevskii indicates that three members of the urchin MSP-130 family, a carbonic anhydrase and a matrix metaloprotease are present and transcribed during the development of S. kowalevskii. The SM family of proteins is absent from the hemichordate genome. These results increase the number of phyla known to biomineralize and suggest that some of the gene-regulatory 'toolkit', if not mineralized tissue themselves, may have been present in the common ancestor to hemichordates and echinoderms.

Evolution of the chordate body plan: new insights from phylogenetic analyses of deuterostome phyla.

The deuterostome phyla include Echinodermata, Hemichordata, and Chordata. Chordata is composed of three subphyla, Vertebrata, Cephalochordata (Branchiostoma), and Urochordata (Tunicata). Careful analysis of a new 18S rDNA data set indicates that deuterostomes are composed of two major clades: chordates and echinoderms + hemichordates. This analysis strongly supports the monophyly of each of the four major deuterostome taxa: Vertebrata + Cephalochordata, Urochordata, Hemichordata, and Echinodermata. Hemichordates include two distinct classes, the enteropneust worms and the colonial pterobranchs. Most previous hypotheses of deuterostome origins have assumed that the morphology of extant colonial pterobranchs resembles the ancestral deuterostome. We present a molecular phylogenetic analysis of hemichordates that challenges this long-held view. We used 18S rRNA to infer evolutionary relationships of the hemichordate classes Pterobranchia and Enteropneusta. Our data show that pterobranchs may be derived within enteropneust worms rather than being a sister clade to the enteropneusts. The nesting of the pterobranchs within the enteropneusts dramatically alters our view of the evolution of the chordate body plan and suggests that the ancestral deuterostome more closely resembled a mobile worm-like enteropneust than a sessile colonial pterobranch.

Urochordates are monophyletic within the deuterostomes.

Understanding the phylogenetic relationships of the three major urochordate groups within the deuterostomes is central to understanding the evolution of the chordates. We have prepared a detailed phylogenetic analysis of urochordates based on comparisons of 10 new urochordate 18S ribosomal DNA sequences with other urochordate sequences in GenBank. Maximum parsimony, neighbor-joining, minimum evolution, and maximum likelihood analyses of this large urochordate data set are consistent with a topology in which the urochordates are monophyletic within the deuterostomes and there are four separate clades of urochordates. These four distinct clades--styelid + pyurid ascidians, molgulid ascidians, phlebobranch ascidians + thaliaceans, and larvaceans--are mostly consistent with traditional morphological hypotheses and classifications. However, we find that the ascidians may not be a monophyletic group (as they have been considered traditionally) but instead appear paraphyletic. Another disparity with traditional classification is that the thaliaceans do not form a separate urochordate clade but rather cluster with the phlebobranch ascidians. Larvaceans have long branch lengths, which can be problematic for molecular phylogenetic methods, and their position within the urochordates cannot be unequivocally determined with 18S rDNA. This is important because the tadpole morphology of larvacean and ascidian larvae is the key trait of interest that distinguishes urochordates as chordates. Nevertheless, the present data set resolves at least three clades of urochordates and suggests strongly that urochordates form a monophyletic clade within the deuterostomes.

Gonadotropin-releasing hormone in mulberry cells of Saccoglossus and Ptychodera (Hemichordata: Enteropneusta).

Mulberry cells are epidermal gland cells bearing a long basal process resembling a neurite and are tentatively regarded as neurosecretory cells. They occur scattered through the ectoderm of the proboscis, collar, and anterior trunk regions of the acorn worms Saccoglossus, usually in association with concentrations of nervous tissue. They contain secretion granules that appear from electron micrographs to be released to the exterior. The granules are immunoreactive with antisera raised against mammalian and salmon gonadotropin-releasing hormone (GnRH). Similar results were obtained with another enteropneust, Ptychodera bahamensis, using antisera raised against tunicate-1 and mammalian GnRH. Mulberry cells were not found in either Cephalodiscus or Rhabdopleura (Hemichordata: Pterobranchia). Extracts of tissues from 4200 Saccoglossus contain an area of immunoreactive GnRH that is detected by an antiserum raised against lamprey GnRH when characterized by high-performance liquid chromatography and radioimmunoassay. This is the first report of the occurrence of GnRH in hemichordates, probably the most primitive group clearly belonging to the chordate lineage. The physiological function of GnRH in enteropneusts is unknown, but an exocrine function appears more likely than an endocrine or neurotransmitter role.

Should you cancel the operation when a child has an upper respiratory tract infection?

Cancelling an operation when a child has an upper respiratory tract infection (URI) is not always feasible or practical. Yet we know very little about the additional risk posed by a URI occurring in a child undergoing anesthesia and surgery. Using a large prospectively collected pediatric anesthesia database, we studied 1283 children with a preoperative URI and 20,876 children without a URI. We found that children with a URI were two to seven times more likely to experience respiratory-related adverse events during the intraoperative, recovery room, and postoperative phases of their operative experience. Although these children also experienced significant disruptions in temperature regulation, they were not at risk for any other deleterious events. The elevation in risk after URI as compared with children without a URI was not explained by differences in age, physical status scores, surgical site, and emergency or elective status. However, if a child had a URI and had endotracheal anesthesia, the risk of a respiratory complication increased 11-fold (95% confidence intervals 6.8, 18.1). We conclude that the administration of general anesthesia to children with a URI is not benign and that these children require more observation/management in all perioperative phases of their surgical procedure.

Masseter muscle spasm in children: implications of continuing the triggering anesthetic.

This retrospective study was undertaken to examine the management and outcome of children who developed isolated masseter muscle spasm (MMS) after the administration of intravenous succinylcholine during anesthetic induction. The inhalation anesthetics used for induction were continued in all of these cases. The medical records of 68 patients (male/female ratio, 1.7:1), identified from approximately 42,000 anesthetics given during the period 1980-1989, were reviewed. Fifty-seven children (2.3-12 yr old) were diagnosed as having isolated MMS, i.e., MMS without spasm of other muscles; 11 experienced generalized rigidity in combination with MMS. Anesthetic and postoperative management of these two groups differed. The overall incidence of MMS was 0.3% of inhalation anesthetics during which succinylcholine was given. Intraoperative arrhythmias occurred in 33% of the patients who developed isolated MMS and more frequently in older children. Most children experienced some degree of hypercarbia and/or metabolic acidosis, but the significance of these abnormalities in the spontaneously ventilating, fasting child is unknown. Serum creatine kinase levels when measured 18-24 h postoperatively were elevated in all but one child (n = 45). There was no long-term morbidity and no mortality. We conclude that failure of the masseter muscles to relax after succinylcholine is not uncommon in children. Based on our experience, and accepting that MMS may be part of the clinical spectrum of malignant hyperthermia, we believe that anesthesia can be continued safely in cases of isolated MMS when careful monitoring accompanies diagnostic evaluation. This differs from the current practice of discontinuing the anesthetic or switching to a nontriggering anesthetic technique.

Perioperative management of patients with von Willebrand's disease.

This review focuses on the pathophysiology of the Factor VIII molecule as it relates to Von Willebrand's disease. Three major categories of Von Willebrand's disease are identified. The perioperative diagnosis and management of all categories are reviewed. 1-Deamino-8-D-arginine vasopressin (DDAVP) is presented as an alternative to the transfusion of blood and blood products for the management of a bleeding diathesis.

Pediatric anesthesia morbidity and mortality in the perioperative period.

One of the most frequent questions asked of a pediatric anesthesiologist is "What are the risks of anesthesia for my child?" Unfortunately, few studies have examined the consequences of general anesthesia in children. We used data from a large pediatric anesthesia follow-up program at Winnipeg Children's Hospital (1982-1987) to determine rates of perioperative adverse events among children of different ages. A check-off form was completed by a pediatric anesthesiologist for each case (n = 29,220) and a designated follow-up reviewer examined all anesthesia forms and hospital charts to ascertain adverse effects for children less than 1 mo, 1-12 mo, 1-5 yr, 6-10 yr, and 11-16 yr of age in the intraoperative, recovery room, and postoperative periods. The majority of the children were healthy, and 70% had no preoperative medical conditions. Infants less than 1 mo old were more likely to be undergoing major cardiac or vascular procedures, whereas the older children had mainly orthopedic or otolaryngologic procedures. Infants less than 1 mo old had the highest rate of adverse events both intraoperatively and in the recovery room. The main problem in this age group was related to the respiratory and cardiovascular systems. In children over 5 yr of age, postoperative nausea and vomiting was very frequent, with about one-third of the children experiencing this problem. When all events were considered (both major and minor), there was a risk of an adverse event in 35% of the pediatric cases. This contrasts with 17% for adults. This morbidity survey helps to focus on areas of intervention and for further study.

Injuries and deaths associated with off-road recreational vehicles among children in Manitoba.

Injuries and deaths associated with off-road recreational vehicles are of increasing concern in North America. We reviewed all hospital admissions and deaths attributed to these vehicles in Manitoba from April 1979 to April 1985 among children 16 years of age or younger. Of the 693 hospital admissions and deaths 480 were associated with motorbikes, snowmobiles or all-terrain vehicles (ATVs). The incidence of injuries resulting from snowmobile and dirtbike accidents remained stable over the study period; however, there was an almost exponential increase in the number of admissions because of ATV-related injuries. There were 21 deaths during the study period. Preventive measures through legislation are necessary to reduce the numbers of injuries and deaths; these include mandatory registration, licensing and enhanced safety regulations.

Cardiovascular effects of d-tubocurarine and pancuronium in newborn lambs during normoxia and hypoxia.

Nondepolarizing muscle relaxants are administered to hypoxic neonates (including those with severe cyanotic congenital heart disease) to reduce oxygen consumption. However, it is unknown whether paralysis actually reduces oxygen consumption or whether the drugs used affect the cardiovascular system of neonates. Therefore, we studied the effects of d-tubocurarine and pancuronium induced muscle paralysis on oxygen consumption, cardiac output, and tissue oxygen delivery in healthy normoxic and hypoxic 1- to 3-day-old lambs. We measured intravascular pressures, cardiac output and its distribution (microspheres), and blood gases and pH during: 1) spontaneous respiration with room air (control); 2) spontaneous respiration with a Pao2 of 27-33 mm Hg (hypoxia); 3) mechanical ventilation with room air; 4) mechanical ventilation with room air and paralysis with d-tubocurarine (0.3 mg/kg) or pancuronium (0.1 mg/kg); and 5) mechanical ventilation with hypoxia and paralysis. Mechanical ventilation, with or without muscle paralysis, had no effect on the oxygen delivery or oxygen consumption of normoxic animals. Hypoxia and spontaneous ventilation had no effect on oxygen consumption, but hypoxia, paralysis, and mechanical ventilation reduced it 35% (p less than 0.002 d-tubocurarine) and 50% (p less than 0.001 pancuronium). Cardiac output was unaffected by oxygenation, mechanical ventilation, or muscle paralysis. However, blood flow to the brain and heart increased during hypoxia, which maintained normal oxygen delivery to these organs. During hypoxia and spontaneous ventilation, mean pulmonary arterial pressures increased 34% (d-tubocurarine) and 54% (pancuronium) above control; during hypoxia, muscle paralysis, and mechanical ventilation, it increased 81%.(ABSTRACT TRUNCATED AT 250 WORDS)

Management of tracheobronchomalacia with continuous positive airway pressure.

Three infants presenting with respiratory distress required early ventilator support. With attempts at extubation recurrent airway obstruction occurred. The clinical course was marked by recurrent episodes of hyperinflation, atelectasis, and pneumonia. Bronchoscopy, bronchography, and chest fluoroscopy revealed extensive collapse of the trachea and main stem bronchi. Two of the infants had gastroesophageal reflux and recurrent aspiration. Treatment of tracheobronchomalacia (TBM) was carried out with a tracheostomy tube attached to a portable CPAP apparatus. Initially CPAP was maintained at 10 cm of water and subsequently weaning was achieved by gradual decreasing of both positive pressure and hours of treatment per day. Total treatment time ranged from 13 to 25 months. Feedings were carried out via gastrostomy. Two infants with severe gastroesophageal reflux underwent fundoplication. Each infant was successfully weaned from distending pressure and decanulated. The treatment of severe TBM with long-term CPAP appears to be a reasonable alternative or adjunct to surgical procedures such as tracheopexy, resection, external splinting and tracheobronchoplasty.

The cardiovascular and metabolic effects of halothane in normoxic and hypoxic newborn lambs.

Oxygen consumption, cardiac output, and tissue oxygen delivery were measured in normoxic and hypoxic 1-3-day-old lambs during the following six conditions: 1) (control) paralysis with pancuronium and controlled ventilation with room air; 2) paralysis, controlled ventilation and hypoxia (PaO2 = 30 +/- 3 mmHg, [SD]); 3) paralysis, controlled ventilation with room air and 0.5 MAC halothane; 4) paralysis, controlled ventilation, hypoxia, and 0.5 MAC halothane; 5) paralysis, controlled ventilation with room air, and 1 MAC halothane; and 6) paralysis, controlled ventilation, hypoxia, and 1 MAC halothane. During normoxia, 0.5 and 1 MAC halothane decreased total body oxygen consumption, cardiac output, and arterial blood pressure. One-half MAC halothane had no effect on blood flow to any organ except muscle, whose flow decreased 64%. One MAC halothane decreased blood flow to the brain, heart, kidney, muscle, and gut. Both concentrations of halothane decreased serum catecholamine levels below control values and prevented hypoxia from increasing catecholamine levels. Hypoxia decreased the oxygen consumption about 40% from the immediately previous normoxic value, whether the animals were anesthetized or not. Tissue oxygen delivery followed changes in blood flow. The cardiac output, arterial blood pressure, and heart rate of anesthetized, hypoxic animals were not different from those in the previous normoxic condition. Halothane did not prevent redistribution of blood flow to the heart and brain of hypoxic animals, nor did halothane prevent hypoxic pulmonary vasoconstriction.(ABSTRACT TRUNCATED AT 250 WORDS)

The minimum anesthetic concentration of isoflurane in children.

The minimum anesthetic concentration (MAC) of isoflurane was determined in five pediatric age groups. MAC was 1.6% in infants 0-1 month of age, 1.87% in those 1-6 months of age, 1.8% in those 6-12 months of age, 1.6% in those 1-3 yr of age, and 1.6% in children 3-5 yr of age. MAC in neonates was less than predicted.