Breaking Earth's shell into a global plate network.

The initiation mechanism of Earth's plate tectonic cooling system remains uncertain. A growing consensus suggests that multi-plate tectonics was preceded by cooling through a single-plate lithosphere, but models for how this lithosphere was first broken into plates have not converged on a mechanism or a typical early plate scale. A commonality among prior efforts is the use of continuum mechanics approximations to evaluate this solid mechanics problem. Here we use 3D spherical shell models to demonstrate a self-organized fracture mechanism analogous to thermal expansion-driven lithospheric uplift, in which globe-spanning rifting occurs as a consequence of horizontal extension. Resultant fracture spacing is a function of lithospheric thickness and rheology, wherein geometrically-regular, polygonal-shaped tessellation is an energetically favored solution because it minimizes total crack length. Therefore, warming of the early lithosphere itself-as anticipated by previous studies-should lead to failure, propagating fractures, and the conditions necessary for the onset of multi-plate tectonics.

Resolution of diplopia after repair of the deep orbit.

The degree of resolution of diplopia after repair of a blow-out fracture of the orbital floor varies and depends on many factors. We present six patients, each of whom had extensive fractures of the floor of the orbit that extended posteriorly to its anatomical limit. The mean (range) time for the resolution of diplopia after reconstruction was 4.4 (1-7) months. We think that its slow resolution in these patients may require preoperative counselling, and also the postoperative management of patients with extensive disruptions of the floor of the orbit posterior to the anterior limit of the inferior orbital fissure (within the deep orbit) must be carefully planned.

Post-traumatic orbital reconstruction: anatomical landmarks and the concept of the deep orbit.

Dissection deep within the orbit is a cause for concern to surgeons because of the perceived risks of injuring critical structures such as the contents of the superior orbital fissure and the optic nerve. Although "safe distances" (those distances within which it is considered safe to dissect within the orbit) have been described, these are of limited value if the orbit is severely disrupted or is congenitally shallow. In addition, traumatic defects in the orbital floor, in particular, often extend beyond these distances. Reliable landmarks based on the relations between anatomical structures within the orbit, rather than absolute distances, are described that permit safe dissection within the orbit. We present the concept of the deep orbit and describe its relevance to repair of injuries.

Behavioural analysis of the efficacy of treatments for injuries to the spinal cord in animals.

There have been very few clinical trials evaluating therapies for naturally occurring spinal cord injury in dogs and cats. This review describes the methods suitable for evaluating the behavioural recovery of animals with spinal cord injuries, in either a clinical or a laboratory setting. A list of commonly used methods for evaluating behavioural recovery in animals is provided, both in the clinical and laboratory setting; the tests, their limitations and benefits and specific recommendations for their use are also discussed in more depth.

The role of calcium in ABA-induced gene expression and stomatal movements.

There is much interest in the transduction pathways by which abscisic acid (ABA) regulates stomatal movements (ABA-turgor signalling) and by which this phytohormone regulates the pattern of gene expression in plant cells (ABA-nuclear signalling). A number of second messengers have been identified in both the ABA-turgor and ABA-nuclear signalling pathways. A major challenge is to understand the architecture of ABA-signalling pathways and to determine how the ABA signal is coupled to the appropriate response. We have investigated whether separate Ca2+-dependent and -independent ABA-signalling pathways are present in guard cells. Our data suggest that increases in [Ca2+]i are a common component of the guard cell ABA-turgor and ABA-nuclear signalling pathways. The effects of Ca2+ antagonists on ABA-induced stomatal closure and the ABA-responsive CDeT6-19 gene promoter suggest that Ca2+ is involved in both ABA-turgor signalling and ABA-nuclear signalling in guard cells. However, the sensitivity of these pathways to alterations in the external calcium concentration differ, suggesting that the ABA-nuclear and ABA-turgor signalling pathways are not completely convergent. Our data suggest that whilst Ca2+-independent signalling elements are present in the guard cell, they do not form a completely separate Ca2+-independent ABA-signalling pathway.

Audit of a multidisciplinary approach to the care of children with unilateral and bilateral cleft lip and palate.

Cleft lip and palate affects the child in many ways, particularly appearance, dental arch relationships, growth of the face, and speech development. The key to successful care is management in a multidisciplinary team adhering to a well-designed protocol, and careful audit of results. We present the intermediate outcome audit of 15 patients with complete bilateral and unilateral cleft lip and palate whose condition was managed in a multidisciplinary team according to a strict protocol. We give the results observations of operations of a single surgeon's functional primary surgery over a 6-year period in terms of dental arch relationships, cephalometric analyses, aesthetic assessments, and speech analysis. The results show good early facial growth, with dental arch relationships appropriate for the age and group; we found only minor speech discrepancies, with no patients requiring pharyngoplasty. The results show the importance of multidisciplinary management, the value of keeping to sound surgical protocols, and functional techniques in cleft lip and palate surgery. Our study includes the neglected group of children who have bilateral cleft lip and palate, and it conforms to the style of pan-European projects.

Surgical management of cutaneous squamous cell carcinoma of the head and neck.

A retrospective audit was made of histological records and hospital case notes of patients who had cutaneous squamous cell carcinomas excised from the head and neck region at the Maxillofacial Units at St Richard's Hospital, Chichester and Southlands Hospital, Shoreham-By-Sea, UK. A total of 227 lesions were excised from 183 patients over a 5-year period between 1990 and 1995. The local recurrence rate was 4% (9/227) and 12 (7%) of the patients presented with or developed regional nodal metastases. Of the 183 patients, 177 (97%) were cured. These rates compare favourably with those of other published series of cutaneous squamous cell carcinoma managed by surgical techniques that did not follow the micrographical technique of Mohs. Certain characteristics may aid in the prediction of those cancers that may be more aggressive. It is important to evaluate each case in terms of histological grade and site and to design management plans to deal with each lesion in the most appropriate way.

MR imaging findings in a dog with lumbar ganglion cysts.

Intraspinal cysts of the L6-L7 and L7-S1 articular process joints in a six-year-old neutered female German Shepherd Dog were diagnosed using magnetic resonance (MR) imaging. Histopathology provided a diagnosis of ganglion cysts. Clinical, laboratory, radiographic and MR imaging findings are described. Briefly, radiographic findings revealed lumbarization of the first sacral vertebra, and fusion of the first caudal vertebra to the sacrum. In addition, spondylosis and articular process osteoarthrosis occurred at L6-L7 and L7-S1. MR imaging revealed multiple, well encapsulated structures ranging in size from 3-10 mm in diameter which were found to arise from the L6-L7 and L7-S1 articular process joints. These cysts had signal intensities that varied from hyperintense to the cerebrospinal fluid (CSF) on T1 weighted images to isointense to CSF on T2 weighted images. Decompressive surgery in conjunction with arthrodesis of these joints resulted in resolution of clinical signs. The dog remained pain-free 1 1/2 years following surgical therapy.

Mini-review: assessment of behavioural recovery following spinal cord injury in rats.

Behavioural recovery is one of the primary goals of therapeutic intervention in animal models of disease. It is necessary, therefore, to have the means with which to quantify pertinent behavioural changes in experimental animals. Nevertheless, the number and diversity of behavioural measures which have been used to assess recovery after experimental interventions often makes it difficult to compare results between studies. The present review attempts to integrate and categorize the wide variety of behavioural assessments used to measure recovery in spinal-injured rats. These categories include endpoint measures, kinematic measures, kinetic measurements, and electrophysiological measurements. Within this categorization, we discuss the advantages and disadvantages of each type of measurement. Finally, we make some recommendations regarding the principles for a comprehensive behavioural analysis after experimental spinal cord injury in rats.

The blood-brain barrier and its role in inflammation.

The unique microenvironment within the central nervous system (CNS) relies upon the integrity of the blood-brain barrier (BBB). This selectively permeable barrier comprises interendothelial tight junctions located at the capillaries and postcapillary venules. Cells and structures in the local environment are required to maintain normal BBB function. When inflammation is present, the BBB itself plays an integral role in the inflammatory response by either producing or expressing a variety of cytokines, adhesion molecules, metalloproteinases, serine proteases, products of arachidonic acid metabolism, and nitric oxide. Understanding the role of the BBB during inflammation is essential when creating and employing a therapeutic regime for animals with CNS disease. This review focusses on recent discoveries about the BBB and its role in inflammation, and applies this knowledge to our current understanding of inflammatory CNS disease in dogs and cats.

ABI1 protein phosphatase 2C is a negative regulator of abscisic acid signaling.

The plant hormone abscisic acid (ABA) is a key regulator of seed maturation and germination and mediates adaptive responses to environmental stress. In Arabidopsis, the ABI1 gene encodes a member of the 2C class of protein serine/threonine phosphatases (PP2C), and the abi1-1 mutation markedly reduces ABA responsiveness in both seeds and vegetative tissues. However, this mutation is dominant and has been the only mutant allele available for the ABI1 gene. Hence, it remained unclear whether ABI1 contributes to ABA signaling, and in case ABI1 does regulate ABA responsiveness, whether it is a positive or negative regulator of ABA action. In this study, we isolated seven novel alleles of the ABI1 gene as intragenic revertants of the abi1-1 mutant. In contrast to the ABA-resistant abi1-1 mutant, these revertants were more sensitive than the wild type to the inhibition of seed germination and seedling root growth by applied ABA. They also displayed increases in seed dormancy and drought adaptive responses that are indicative of a higher responsiveness to endogenous ABA. The revertant alleles were recessive to the wild-type ABI1 allele in enhancing ABA sensitivity, indicating that this ABA-supersensitive phenotype results from a loss of function in ABI1. The seven suppressor mutations are missense mutations in conserved regions of the PP2C domain of ABI1, and each of the corresponding revertant alleles encodes an ABI1 protein that lacked any detectable PP2C activity in an in vitro enzymatic assay. These results indicate that a loss of ABI1 PP2C activity leads to an enhanced responsiveness to ABA. Thus, the wild-type ABI1 phosphatase is a negative regulator of ABA responses.

Intravenous regional anesthesia (Bier block) in a dog.

Intravenous regional anesthesia was used in an adult dog as part of a balanced approach to general anesthesia for amputation of the 4th digit of its right hind limb. It allowed the concentration of isoflurane to be reduced to 0.5%.

Skin care of the pediatric patient.

Several factors influence the chronically ill child's susceptibility for skin breakdown. Nurses are an integral part of the care team that has the responsibility for identification of these factors, as well as pressure ulcer prevention and early intervention. An important aspect of this responsibility is identification of individuals at risk. This article provides a guide for assessment and early intervention for skin breakdown in chronically ill children. A care plan and consultation recommendations are included.

Intradural spinal arachnoid cyst in a dog.

An 8-month-old, spayed female dog was presented with signs localizing a neurologic lesion between the 3rd thoracic and 3rd lumbar vertebrae. An arachnoid cyst was diagnosed by myelography, and a dorsal laminectomy with durotomy was performed. The dog continues to do well 1-1/2 year after surgery.

A descriptive study of missed appointments: families' perceptions of barriers to care.

INTRODUCTION: When clinic appointments are missed, families deprive their child of health care opportunities and contribute to rising health care costs. The purpose of this study was to determine families' perceptions of barriers to attending clinic appointments. METHOD: Two hundred participants with a history of missed appointments were randomly selected to participate in a telephone survey. Ninety-five of the families selected did not have telephones. Of the 105 families contacted by telephone, 101 consented to participate in a survey. For the group without phones (n = 95), demographic information was collected to use as comparison data with families that were reached. Patterns of missed appointments were also analyzed. RESULTS: The majority of families were headed by young single mothers. The families identified transportation problems, wait times, and not knowing the reason for the appointment as barriers. DISCUSSION: Clearly, many issues have an impact on decisions related to attending clinic appointments. In the interest of health, interventions to decrease barriers and increase attendance should be a priority for health care professionals. Further research of the effectiveness of these interventions will delineate the appropriate focus of health care professional's efforts.

Re-evaluation of i.m. ephedrine as prophylaxis against hypotension associated with spinal anaesthesia for Caesarean section.

PURPOSE: To assess the safety and efficacy of 37.5 mg ephedrine i.m. in preventing hypotension associated with spinal anaesthesia for Caesarean section. METHODS: In a double-blind randomised controlled study, 40 patients (20 in each group) were given either 37.5 mg ephedrine or placebo i.m. The following parameters were recorded: (i) blood pressure; (ii) heart rate; (iii) ephedrine i.v. supplementation; (iv) umbilical venous blood gases and neonatal Apgar scores. RESULTS: The incidence of hypertension in the study group was 30% compared with 20% for the control group (P:NS). There was no difference in mean highest blood pressure or mean highest heart rate between the groups. The incidence of hypotension was lower but not significantly lower in the study group (50%) than in the control group (80%) (P:NS). However, the incidence of delayed hypotension was only 10% in the study group patients compared with 50% in the control group patients (P < 0.05). CONCLUSION: Giving 37.5 mg ephedrine i.m. prior to spinal anaesthesia was not associated with reactive hypertension or tachycardia. Intramuscular ephedrine provided more sustained cardiovascular support than intravenous ephedrine.

The short-period mutant, toc1-1, alters circadian clock regulation of multiple outputs throughout development in Arabidopsis thaliana.

The coordination of developmental and physiological events with environmental signals is facilitated by the action of the circadian clock. Here we report a new set of circadian clock-controlled phenotypes for Arabidopsis thaliana. We use these markers together with the short-period mutant, toc1-1, and the clock-controlled cab2::luciferase reporter gene to assess the nature of the circadian clock throughout development and to suggest the position of TOC1 within the circadian clock system. In dark-grown seedlings, the toc1-1 lesion conferred a short period to the cycling of cab2::luciferase luminescence, as previously found in light-grown plants, indicating that the circadian clocks in these two divergent developmental states share at least one component. Stomatal conductance rhythms were similarly approximately 3 hours shorter than wild type in toc1-1, suggesting that a cell-autonomous clockwork may be active in guard cells in 5- to 6-week-old leaves. The effect of daylength on flowering time in the C24 ecotype was diminished by toc1-1, and was nearly eliminated in the Landsberg erecta background where the plants flowered equally early in both short and long days. Throughout a 500-fold range of red light intensities, both the wild type and the mutant showed an inverse log-linear relationship of fluence rate to period, with a 2-3 hour shorter period for the mutant at all intensities. These results indicate that TOC1 acts on or within the clock independently of light input. Temperature entrainment appears normal in toc1-1, and the period-shortening effects of the mutant remain unchanged over a 20 degrees C temperature range. Taken together our results are consistent with the likelihood that TOC1 codes for an oscillator component rather than for an element of an input signaling pathway. In addition, the pervasive effect of toc1-1 on a variety of clock-controlled processes throughout development suggests that a single circadian system is primarily responsible for controlling most, if not all, circadian rhythms in the plant.

Convergence of the abscisic acid, CO2, and extracellular calcium signal transduction pathways in stomatal guard cells.

We show that guard cells from Arabidopsis thaliana plants carrying the abscisic acid-insensitive mutations abi1 and abi2 fail to respond to CO2 and extracellular calcium. This demonstrates that the signal transduction pathways for all three stimuli converge on, or close to, the ABI1 and ABI2 gene products.