Recent parallel speciation in Antirrhinum involved complex haplotypes and multiple adaptive characters

A role of ecological adaptation in speciation can be obscured by stochastic processes and differences that species accumulate after genetic isolation. One way to identify adaptive characters and their underlying genes is to study cases of speciation involving parallel adaptations. Recently resolved phylogenies reveal that alpine morphology has evolved in parallel in the genus Antirrhinum (snapdragons): first in an early split of an alpine from a lowland lineage and, more recently, from within the lowland lineage to produce closely related sympatric species with contrasting alpine and lowland forms. Here, we find that two of these later diverged sympatric species are differentiated by only around 2% of nuclear loci. Though showing evidence of recent gene flow, the species remain distinct for a suite of morphological characters typical of earlier-diverged alpine or lowland lineages and their morphologies correlate with features of the local landscape, as expected of ecological adaptations. Morphological differences between the two species involve multiple, unlinked genes so that parental character combinations are readily broken up by recombination in hybrids. We detect little evidence for post-pollination barriers to gene flow or recombination, suggesting that genetic isolation related to ecological adaptation is important in maintaining character combinations and might have contributed to parallel speciation. We also find evidence that genes involved in the earlier alpine-lowland split were reused in parallel evolution of alpine species, consistent with introgressive hybridisation, and speculate that many non-ecological barriers to gene flow might have been purged during the process.

A phylogeny of Antirrhinum reveals parallel evolution of alpine morphology

Parallel evolution of similar morphologies in closely related lineages provides insight into the repeatability and predictability of evolution. In the genus Antirrhinum (snapdragons), as in other plants, a suite of morphological characters are associated with adaptation to alpine environments. We tested for parallel trait evolution in Antirrhinum by investigating phylogenetic relationships using restriction-site associated DNA (RAD) sequencing. We then associated phenotypic information to our phylogeny to reconstruct the patterns of morphological evolution and related this to evidence for hybridisation between emergent lineages. Phylogenetic analyses showed that the alpine character syndrome is present in multiple groups, suggesting that Antirrhinum has repeatedly colonised alpine habitats. Dispersal to novel environments happened in the presence of intraspecific and interspecific gene flow. We found support for a model of parallel evolution in Antirrhinum. Hybridisation in natural populations, and a complex genetic architecture underlying the alpine morphology syndrome, support an important role of natural selection in maintaining species divergence in the face of gene flow.

The β-Secretase Substrate Seizure 6-Like Protein (SEZ6L) Controls Motor Functions in Mice

The membrane protein seizure 6-like (SEZ6L) is a neuronal substrate of the Alzheimer's disease protease BACE1, and little is known about its physiological function in the nervous system. Here, we show that SEZ6L constitutive knockout mice display motor phenotypes in adulthood, including changes in gait and decreased motor coordination. Additionally, SEZ6L knockout mice displayed increased anxiety-like behaviour, although spatial learning and memory in the Morris water maze were normal. Analysis of the gross anatomy and proteome of the adult SEZ6L knockout cerebellum did not reveal any major differences compared to wild type, indicating that lack of SEZ6L in other regions of the nervous system may contribute to the phenotypes observed. In summary, our study establishes physiological functions for SEZ6L in regulating motor coordination and curbing anxiety-related behaviour, indicating that aberrant SEZ6L function in the human nervous system may contribute to movement disorders and neuropsychiatric diseases.

The malleable brain: plasticity of neural circuits and behavior - a review from students to students

One of the most intriguing features of the brain is its ability to be malleable, allowing it to adapt continually to changes in the environment. Specific neuronal activity patterns drive long-lasting increases or decreases in the strength of synaptic connections, referred to as long-term potentiation and long-term depression, respectively. Such phenomena have been described in a variety of model organisms, which are used to study molecular, structural, and functional aspects of synaptic plasticity. This review originated from the first International Society for Neurochemistry (ISN) and Journal of Neurochemistry (JNC) Flagship School held in Alpbach, Austria (Sep 2016), and will use its curriculum and discussions as a framework to review some of the current knowledge in the field of synaptic plasticity. First, we describe the role of plasticity during development and the persistent changes of neural circuitry occurring when sensory input is altered during critical developmental stages. We then outline the signaling cascades resulting in the synthesis of new plasticity-related proteins, which ultimately enable sustained changes in synaptic strength. Going beyond the traditional understanding of synaptic plasticity conceptualized by long-term potentiation and long-term depression, we discuss system-wide modifications and recently unveiled homeostatic mechanisms, such as synaptic scaling. Finally, we describe the neural circuits and synaptic plasticity mechanisms driving associative memory and motor learning. Evidence summarized in this review provides a current view of synaptic plasticity in its various forms, offers new insights into the underlying mechanisms and behavioral relevance, and provides directions for future research in the field of synaptic plasticity. Read the Editorial Highlight for this article on page 788. Cover Image for this issue: doi: 10.1111/jnc.13815.

Should early amputation impact initial fluid therapy algorithms in burns resuscitation? A retrospective analysis using 3D modelling

AIMS

While the epidemiology of amputations in patients with burns has been investigated previously, the effect of an amputation on burn size and its impact on fluid management have not been considered in the literature. Fluid resuscitation volumes are based on the percentage of the total body surface area (%TBSA) burned calculated during the primary survey. There is currently no consensus as to whether the fluid volumes should be recalculated after an amputation to compensate for the new body surface area. The aim of this study was to model the impact of an amputation on burn size and predicted fluid requirement.

METHODS

A retrospective search was performed of the database at the Queen Elizabeth Hospital Birmingham Regional Burns Centre to identify all patients who had required an early amputation as a result of their burn injury. The search identified 10 patients over a 3-year period. Burn injuries were then mapped using 3D modelling software. BurnCase3D is a computer program that allows accurate plotting of burn injuries on a digital mannequin adjusted for height and weight. Theoretical fluid requirements were then calculated using the Parkland formula for the first 24 h, and Herndon formula for the second 24 h, taking into consideration the effects of the amputation on residual burn size.

RESULTS AND CONCLUSIONS

This study demonstrated that amputation can have an unpredictable effect on burn size that results in a significant deviation from predicted fluid resuscitation volumes. This discrepancy in fluid estimation may cause iatrogenic complications due to over-resuscitation in burn-injured casualties. Combining a more accurate estimation of postamputation burn size with goal-directed fluid therapy during the resuscitation phase should enable burn care teams to optimise patient outcomes.

Parental authority to refuse acute burn treatment versus the protection our children deserve

Our society has empowered parents to care for their children and take legally binding decisions on their behalf. One of the areas where such decision making is required is in medical care when a child's health is at stake. Three cases of child abuse and neglect were identified and reported. Literature searches were done to identify cases of child abuse in Kuwait using Medline and PubMed. News of child abuse was searched for using search engines (bbc.co.uk, cnn.com, and foxnews.com). The British Child Protection Act and the Kuwaiti Criminal Prosecution Code were studied. Child abuse and neglect exist in Kuwait and are probably underreported. The laws in Kuwait are designed to punish child abuse once it has occurred rather than aiming at preventing it. It is reported that 75% of those responsible for child abuse are the parents. They retain full authority to restrict medical access. Medical staff are offered very limited support and are restricted as to what they can achieve due to the Kuwaiti legal infrastructure, which should be amended so as to protect children rather than prosecute offenders. A local authority has to be established and empowered to investigate, report, and act when suspicions of child abuse arise.

The genetic basis for natural variation in heteroblasty in Antirrhinum

Heteroblasty refers to the changes in leaf shape and size (allometry) along stems. Although evolutionary changes involving heteroblasty might contribute to leaf diversity, little is known of the extent to which heteroblasty differs between species or how it might relate to other aspects of allometry or other developmental transitions. Here, we develop a computational model that can quantify differences in leaf allometry between Antirrhinum (snapdragon) species, including variation in heteroblasty. It allows the underlying genes to be mapped in inter-species hybrids, and their effects to be studied in similar genetic backgrounds. Heteroblasty correlates with overall variation in leaf allometry, so species with smaller, rounder leaves produce their largest leaves earlier in development. This involves genes that affect both characters together and is exaggerated by additional genes with multiplicative effects on leaf size. A further heteroblasty gene also alters leaf spacing, but none affect other developmental transitions, including flowering. We suggest that differences in heteroblasty have co-evolved with overall leaf shape and size in Antirrhinum because these characters are constrained by common underlying genes. By contrast, heteroblasty is not correlated with other developmental transitions, with the exception of internode length, suggesting independent genetic control and evolution.

The evolutionary history of Antirrhinum suggests that ancestral phenotype combinations survived repeated hybridizations

The model species Antirrhinum majus (the garden snapdragon) has over 20 close wild relatives that are morphologically diverse and adapted to different Mediterranean environments. Hybrids between Antirrhinum species have been used successfully to identify genes underlying their phenotypic differences, and to infer how selection acts on them. To better understand the genetic basis for this diversity, we have examined the evolutionary relationships between Antirrhinum species and how these relate to geography and patterns of phenotypic variation in the genus as a whole. Large population samples and both plastid and multilocus nuclear genotypes resolved the relationships between many species and provided some support for the traditional taxonomic division of the genus into morphological subsections. Morphometric analysis of plants grown in controlled conditions supported the phenotypic distinction of the two largest subsections, and the involvement of multiple underlying genes. Incongruence between nuclear and plastid genotypes further suggested that several species have arisen after hybridization between subsections, and that some species continue to hybridize. However, all potential hybrids appear to have retained a phenotype similar to one of their ancestors, suggesting that ancestral combinations of characters are maintained by selection at many different loci.

End of life decisions and care of the adult burn patient

INTRODUCTION

Despite advancements in the provision of burn care, there is still a significant cohort of patients who fail to respond to therapy or for whom treatment is deemed futile. The decision to withdraw support from, or to implement a Do-Not-Resuscitate (DNAR) order in, such patients can be challenging. Our aims were to review the withdrawal of life-sustaining treatment, issuing of DNAR orders and end of life care in burn patient deaths.

METHODS

A retrospective case notes review was undertaken, for all burn in-patient deaths from 1st April 2001 to 31st December 2007.

RESULTS

Following exclusions, 63 patients were included in our study, with a median age of 56 years (21-94). End of life decisions in younger patients (under 65 years) were more often due to burn severity. In those over 65 years, reasons were due to co-morbidities, and these decisions were made late in the patient's admission. In 34% of patients, end of life care was not comprehensively documented.

CONCLUSION

A coherent, decisive approach should be adopted and adhered to by all members of the multi-disciplinary team, with clear, standardised documentation in place.

Evolution of allometry in antirrhinum

Correlated variation in shape and size (allometry) is a major component of natural diversity. We examined the evolutionary and genetic basis for allometry using leaves and flower petals of snapdragon species (Antirrhinum). A computational method was developed to capture shape and size variation in both types of organ within the Antirrhinum species group. The results show that the major component of variation between species involves positively correlated changes in leaf and petal size. The correlation was maintained in an F2 population derived from crossing two species with organs of different sizes, suggesting that developmental constraints were involved. Identification of the underlying genes as quantitative trait loci revealed that the larger species carried alleles that increased organ size at all loci. Although this was initially taken as evidence that directional selection has driven diversity in both leaf and petal size, simulations revealed that evolution without consistent directional selection, an undirected walk, could also account for the parental distribution of organ size alleles.

A brightness-area-product-based protocol for the quantitative assessment of antigen abundance in fluorescent immunohistochemistry

A problem frequently facing researchers examining abundance of expression of a given antigen is measurement. When the antigen is confined to the nucleus, absolute numbers of nuclei or a percentage of nuclei expressing the antigen in a given region can be estimated. When the antigen is localized to cytoplasm, cytoplasmic organelles or processes or membranes, the assessment becomes more difficult. In these settings, an observer/experimenter may assign a density score but intra- and inter-observer agreement using a three-tiered system, and finer resolution than this, is unlikely to be reproducible. Digital image analysis provides an opportunity to minimize observer bias in quantification of immunohistochemical staining. Previously, reported digital methods have mostly employed chromogen-staining methods and often report mean image brightness. We report a method for quantitatively assessing and expressing abundance of expression of an antigen in neural tissue stained with immunofluorescent methods by determining the brightness-area-product (BAP). The described protocol utilizes simple to use commercially available software and calculates BAP rather than mean brightness as a measure more representative of antigen abundance and visual interpretation. Accordingly, we propose this protocol as a useful adjunct to observer interpretation of fluorescent immunohistochemistry and its application to assessment of antigen abundance for varying patterns of antigen localization.

Fos-tau-LacZ mice expose light-activated pathways in the visual system

We have employed fos-tau-LacZ (FTL) transgenic mice to examine functional activation in the visual areas of the nervous system. The FTL mice express the marker gene lacZ in neurons and their processes following many different stimuli, and allow the imaging of activation from the level of the entire brain surface through individual neurons and their projections. Analysis of FTL expression in the retinas of mice following diurnal exposure to light shows that bipolar cells, specific classes of amacrine cells, ganglion cells, and a dense network of processes in the inner plexiform layer are functionally activated. In animals deprived of light, there is almost no activity in the retina. In the lateral geniculate nucleus (LGN), light exposure appears responsible for FTL expression in dorsal nuclei, but not for expression in the ventral nuclei or the intergeniculate leaflet. In the superficial layers of the superior colliculus, FTL expression is highly dependent on light exposure. Similarly, light exposure is required for FTL expression in primary visual cortex (area 17), but some expression remains in area 18 of dark-adapted animals. Finally, using mice with one or both eyes missing, we have determined which parts of the visual system are dependent on the presence of a functional connectivity from the eye. These data demonstrate the usefulness of the FTL mice to map functional activation within the entire visual system. Furthermore, we can capture visual activation in a conscious animal. Our findings give an insight into the architecture of activity within the retina and throughout the visual system.

A spontaneous compartment syndrome in a patient with diabetes

A compartment syndrome is an orthopaedic emergency which can result from a variety of causes, the most common being trauma. Rarely, it can develop spontaneously and several aetiologies for spontaneous compartment syndrome have been described. We describe a patient with diabetes who developed a spontaneous compartment syndrome. The diagnosis was delayed because of the atypical presentation.

Skin grafts for the salvage of degloved below-knee amputation stumps

We present a series of six patients in whom a traumatic below-knee amputation was associated with significant degloving, such that there was inadequate local skin to achieve primary stump closure. In each case, skin grafts were used to cover the stump muscle flaps. The patients ranged in age from 21 years to 73 years; the mean hospital stay was 72 days and the mean follow-up was 48 months. Despite an average of five procedures to achieve stump healing and an average of 118 days to first limb fitting, all patients have achieved independent mobility with their prosthesis. All have had minor stump problems necessitating periods of time off their prosthesis. Three patients have required minor stump-revision surgery. The advantages of a below-knee amputation over an above-knee amputation compensate for these problems. The forgiving nature of modern prostheses has contributed to acceptable results in these patients, who had what may previously have been considered insufficiently durable stump cover.

Visualization of functionally activated circuitry in the brain

We have used a transgenic approach to visualize functionally activated neurons and their projections. The transgenic mice contain a tau-lacZ fusion gene regulated by the promoter for c-fos, an immediate early gene that is rapidly induced in neurons after functional stimulation. Constitutive expression of beta-galactosidase (beta-gal), the lacZ product, was low and in accord with previous reports of c-fos expression. However, expression of beta-gal in positive neurons was clearly in cell bodies, axons, and dendrites. Treatment of the mice with kainic acid, a strong inducer of c-fos expression, resulted in high induction of beta-gal. beta-gal was induced in the same defined populations of neurons in the brain as those that express c-fos after kainic acid induction. Furthermore, the pattern of beta-gal expression within the neurons changed over time after kainic acid treatment. Early after kainate treatment, beta-gal was found mainly in cell bodies; at later times, expression extended further along the neuronal processes. This expression pattern is consistent with induction and anterograde transport of the Fos-Tau-beta-gal protein in the neurons. To test whether a functionally activated pathway could be visualized, transgenic mice were deprived of water, which activates nuclei involved in body fluid homeostasis. beta-gal induction was traced in neurons and their processes in the lamina terminalis, in magnocellular neurons of the supraoptic and paraventricular nuclei, and in their projections to the posterior pituitary gland. This strategy allowed the mapping of an activated osmoregulatory pathway. This transgenic approach may have general application in the mapping of functionally activated circuitry in the brain.

Long-term sequelae of fasciotomy wounds

A retrospective study of patients admitted to an Orthopaedic Trauma Unit over an 8-year period requiring fasciotomies, of either upper or lower limb, to reduce the risk of compartment syndrome was performed. Sixty patients were studied, of which 49 had an underlying fracture. The long-term morbidity of the wounds was studied. Ongoing symptoms such as pain related to the wound occurred in six patients (10%) and altered sensation within the margins of the wound occurred in 46 patients (77%). Examination revealed 24 patients (40%) with dry scaly skin, 20 patients (33%) with pruritus, 18 patients (30%) with discoloured wounds, 15 patients (25%) with swollen limbs, 16 patients (26%) with tethered scars, eight patients (13%) with recurrent ulceration, eight patients (13%) with muscle herniation and four patients (7%) with tethered tendons. The appearance of the scars affected patients such that 14 (23%) kept the wound covered, 17 (28%) changed hobbies and seven (12%) changed occupation. This study reveals a significant morbidity associated with fasciotomy wounds. In light of these findings, further consideration should be given to techniques that reduce both the symptoms and examination findings mentioned above and the aesthetic insult to the affected limb.

Unilateral asymptomatic carotid disease does not require surgery

BACKGROUND AND PURPOSE

The efficacy of carotid endarterectomy (CEA) in symptomatic patients with > 70% stenosis is accepted. The stroke risk of asymptomatic patients may not justify surgical intervention. The aim of this study is to use natural history data from a single unit to identify asymptomatic patients who would benefit from CEA.

METHODS

Five hundred and sixty-four patients attending for duplex ultrasound assessment of the internal carotid artery between 1986 and 1993 were retrospectively identified as focally asymptomatic with > 40% ipsilateral stenosis. Patients were traced using hospital records, family practitioner databases and the Office of Population of Census and Surveys. The number of strokes, transient ischaemic attacks and cause of death were determined. Exclusions were 15 (2.7%) asymptomatic occlusions and 49 patients (8.7%) who underwent surgery for asymptomatic disease.

RESULTS

Thirteen patients (2.6%) were not traced, leaving 487 study patients. The average follow-up was 41 months (range, 1-120 months). Mean presentation age was 69 years (S.D. 8.9), and the male to female ratio was 3:2. One hundred and fifty-six (32%) patients died. Forty-three patients suffered strokes, of whom two had bilateral strokes. In total there were 16 (i/p) strokes, 25 (c/l) strokes and four strokes undetermined. The average yearly stroke rate was 2.74 per 100 person years and the (i/p) rate 1.02 per hundred person years. There was no effect of age, sex or degree of stenosis on stroke. The presence of bilateral disease did increase the risk of stroke (rel risk 2.35, p = 0.029) but not ipsilateral stroke (rel risk 1.6, p = 0.39). Patients with unilateral asymptomatic carotid disease had an all stroke rate of less than 5% in the first year after presentation and this was unaffected by degree of stenosis. In patients with bilateral disease the stroke rate in the first year after presentation increased with degree of stenosis to a stroke rate of 9.6 per 100 person years in patients with > 90% contralateral stenosis.

CONCLUSIONS

This data suggests that CEA will not benefit patients with unilateral asymptomatic disease. Patients with bilateral disease warrant inclusion in clinical trials.

Mode of vascularization of control and basic fibroblast growth factor-stimulated prefabricated skin flaps

This study, using 62 rabbits, examines the rate and pattern of vascular outgrowth from a subcutaneously implanted vascular pedicle, how the newly formed vessels connect to preexisting skin vessels, and whether local application of basic fibroblast growth factor can accelerate the angiogenic process. When the femoral artery and vein of rabbits are implanted beneath the skin, angiogenesis from both the pedicle and small blood vessels within the adjacent skin begins within 3 days. Perfusion with India ink reveals connections between the pedicle and dermal vessels as early as 5 days after implantation of the pedicle. Provided the pedicle does not thrombose, skin flaps based on it may survive completely when elevated as early as 2 weeks after implantation. Flap survival depends on the development of a small number of vascular connections between vessels arising from the pedicle and preexisting dermal vessels. If elevation is delayed until 4 weeks after implantation a flap may survive even if its pedicle has thrombosed. Prolonged release of basic fibroblast growth factor adjacent to the pedicle significantly increases the survival of flaps elevated 1 week after implantation but does not alter the survival of flaps elevated at 2 and 4 weeks.

Detection of an elusive osteoid osteoma using a registration bone scan

A case of osteoid osteoma in a young man is presented which evaded diagnosis for 9 years, and was eventually localized to the palmar aspect of the third carpometacarpal joint using the technique of registration bone scan to provide accurate localization. The lesion was removed with complete relief of pain.

Voltage dependent calcium and potassium currents in Y-1 adrenocortical cells are unresponsive to ACTH

In this report we use both whole cell and perforated patch clamp recording techniques to characterize calcium and potassium channels in Y-1 adrenocortical cells in order to assess their responsiveness to ACTH. Both transient and long-lasting components of an inward calcium current were identified which were similar to T and L-type Ca2+ currents. With Ba2+ as the charge carrier, the transient current activated at voltages more hyperpolarized than -50 mV with V1/2 for activation at -78.1 mV, and for steady state inactivation at -52.3 mV. The L-type current activated at -20 mV, with a V1/2 for activation at -29.9 mV and steady state inactivation at -44.2 mV. Under perforated patch conditions the response was shifted to more depolarized voltages. Both currents were responsive to agents which usually affect T- or L-type Ca2+ currents. The transient current was completely blocked by 50 microM lanthanum or 200 microM nickel and partially blocked by 300 mM amiloride. Cadmium (100 microM) and nifedipine (300 nM) completely blocked the long-lasting current while omega-conotoxin GVIA (1992 nM) inhibited the current by only 20-25%. The agonist, Bay K 8644 was stimulatory at 50 nM. Both transient and sustained outward potassium currents similar to A-type and delayed rectifier currents, respectively, were present. The transient current demonstrated fast activation at voltages more positive than -10 mV, inactivation with continued depolarization and steady state inactivation at V1/2 = -50 mV. The sustained current activated rapidly and had minimal inactivation with continued depolarization. The transient current was blocked by 5 mM 4AP and the sustained by 25 mM TEA. While Y-1 cells contain both calcium and potassium currents similar to those found in other adrenocortical cells, none of the currents were affected by ACTH or AII, secretagogues which stimulate steroidogenesis. These data, combined with the inability of both Ca2+ and K+ channel blockers to alter ACTH-induced steroidogenesis as reported earlier, suggests that neither calcium nor potassium currents are responsive to ACTH in Y-1 cells.

Investigation of the presence and role of calmodulin and other mitogens in human burn blister fluid

It is unclear whether burn blister fluid is beneficial or deleterious to the healing of the underlying wound. We investigated the calcium binding protein calmodulin in human burn blister fluid and its role in the mitogenicity of this fluid in the culture of human keratinocytes, fibroblasts, and mouse 3T3 fibroblasts. Calmodulin levels in blister fluid were three times greater than in serum (p < 0.005), whereas epidermal growth factor and platelet-derived growth factor concentrations were significantly lower (p < 0.001). Calmodulin in blister fluid was biochemically identified after affinity chromatography, Western blotting, and immunostaining with a monoclonal antibody. Inhibiting calmodulin with either an antagonist or antibody to calmodulin reduced the mitogenic activity of blister fluid in three cell types by 26% to 80%. These in vitro studies suggest that burn blister fluid may promote wound healing, and locally released calmodulin contributes to this effect. In appropriate cases it may be beneficial to leave burn blisters intact.

Immunocytochemistry in the assessment of pS2 protein expression in fine needle aspiration cytology from breast carcinoma

pS2 protein is a cysteine-rich polypeptide, of unknown function, the expression of which is induced in the human cancer cell line MCF-7 by oestrogen. The availability of a murine monoclonal antibody to human pS2 protein has prompted us to evaluate its expression in 47 cases of primary breast carcinoma. Using a double indirect immunoperoxidase technique, we compared the expression of pS2 protein in fine needle aspiration (FNA) cytology smears with that in formalin-fixed, paraffin-embedded sections from subsequently excised tumours from the same patients. We also compared the expression of pS2 protein and oestrogen receptor (ER) status using immunocytochemical assay (ER-ICA) in formalin-fixed, paraffin-embedded sections from 22 primary breast carcinomas. We found the application of immunocytochemistry in the assessment of pS2 protein expression in FNA cytology to be a reliable and cost-effective technique, having a sensitivity of 84% and a specificity of 100%. There was also a good correlation between the expression of pS2 protein and ER status.

Scalds related to bleeding domestic heating radiators

While scalds are the commonest burns within the home, scalds resulting from bleeding domestic central heating radiators have not previously been reported. We have encountered two examples of significant burns to the hands received in this way. The incidence of these injuries in the UK is unknown but several similar cases have been identified by the Consumer Safety Unit of the Department of Trade and Industry. The mechanism of injury is described and recommendations made for safely bleeding domestic central heating radiators.

V-Y advancement of the entire volar soft tissue of the thumb in distal reconstruction

The commonly used variant of Moberg's advancement flap for thumb reconstruction requires a skin graft to reconstruct the proximal thumb defect after advancing the flap. A modification has been described previously which allows direct closure of this proximal defect by incorporation of the V to Y principle into the design of the proximal part of the flap. A variant of the V-Y Moberg flap is presented and its advantages discussed.

Potent DNA chain termination activity and selective inhibition of human immunodeficiency virus reverse transcriptase by 2',3'-dideoxyuridine-5'-triphosphate

2',3'-Dideoxyuridine (ddUrd) exhibits poor if any anti-human immunodeficiency virus (HIV) activity in ATH8 and MT-4 cells. This is in agreement with the failure of ddUrd to be efficiently anabolized intracellularly to its 5'-triphosphate metabolite. However, 2',3'-dideoxyuridine-5'-triphosphate (ddUTP) proved to be a potent and selective inhibitor of the reverse transcriptase of HIV (Ki, 0.05 microM) and avian myeloblastosis virus (Ki, 1.0 microM). Bacterial DNA polymerase I, mammalian DNA polymerase alpha, terminal deoxyribonucleotidyl transferase, and Moloney murine leukemia virus reverse transcriptase were resistant to ddUTP. ddUTP is incorporated into the growing DNA chain principally at dTTP sites and inhibits further elongation. The potential of ddUTP as an anti-HIV therapeutic agent merits further investigation. However, to achieve this goal, it will be necessary to resort to techniques capable of delivering preformed phosphorylated ddUrd to the susceptible cells.

A morphologic and histochemical study of metaplastic polyps of the colorectum

A combined morphologic and histochemical study of metaplastic polyps of the colorectum was undertaken. With increasing size, these lesions showed alterations in architecture and differentiation, increased secretion of carcinoembryonic antigen and a reduced secretion of O-acylated sialomucin. These functional changes are also observed in colorectal cancers, but not in tubular adenomas showing low-grade dysplasia. Since there is little clinical evidence for a metaplastic polyp-carcinoma sequence, it is suggested that the sets of factors which lead to adenoma and metaplastic polyp formation in the colorectum are both required to induce malignant transformation.

A straightforward radiometric technique for measuring IMP dehydrogenase

[2-3H]Inosinic acid ([2-3H]IMP) has been biosynthesized in good yield from [2-3H]hypoxanthine and PRPP via the action of a partially purified preparation of hypoxanthine/guanine phosphoribosyl transferase from mouse brain. The product was purified in one step by ascending paper chromatography, and used to assess the activity of IMP dehydrogenase. To conduct the assay, tritiated substrate is admixed with enzyme in a final volume of 10 microliters; NAD is present to serve as cofactor for the reaction, and allopurinol to inhibit the oxidation of any hypoxanthine generated as a consequence of side reactions. After an appropriate period of incubation, the 3H2O arising from the oxidation of tritiated IMP via [3H]NAD is isolated by quantitative microdistillation. Performed as described, the assay is facile, sensitive, and accurate, with the capability of detecting the dehydrogenation of as little as 1 pmol of [3H]IMP. Using it, measurements have been made of IMP dehydrogenase in a comprehensive array of mouse organs. Of these, pancreas contained the enzyme at the highest specific activity.