Pharmacokinetics of baquiloprim and sulphadimidine in pigs after intramuscular administration

Baquiloprim, a novel 5-substituted 2, 4-diaminopyrimidine, has been developed specifically for veterinary use. It has been formulated as an injectable preparation and combined with sulphadimidine to exploit the synergistic activity of the two antibacterial agents. The formulation was given by deep intramuscular injection to pigs at doses of 10 mg kg-1 and 30 mg kg-1 and the pharmacokinetic properties were investigated. The in vitro activity of the two components was also determined against a range of porcine pathogens. Both components were rapidly absorbed and the maximum concentrations of 0.55 microgram ml-1 baquiloprim and 15.6 micrograms ml-1 sulphadimidine observed after the administration of the lower dose were well in excess of the minimum inhibitory concentration (MIC) values against susceptible pathogens, the highest combined MIC90 being 0.06 microgram ml-1 baquiloprim + 6.25 micrograms ml-1 sulphadimidine. Concentrations above the MIC values of most pathogens were maintained for more than 24 and 48 hours after the administration of the lower and higher doses, respectively. The volumes of distribution of 2.41 litre kg-1 observed after the lower dose and 4.60 litre kg-1 after the higher dose indicated that baquiloprim was well distributed and concentrated in tissues. These findings suggest that the formulation should be effective in the treatment of bacterial infections in pigs.

Localization of nerve growth factor (NGF) and low-affinity NGF receptors in touch domes and quantification of NGF mRNA in keratinocytes of adult rats

Touch domes are clearly delineated mechanoreceptors that are visible on the depilated skin of mammals. These structures consist of a sharply circumscribed disk of thickened epithelium surmounting a group of Merkel cells that are innervated by type I sensory neurons. These characteristic cutaneous structures provide an ideal opportunity for investigating whether the localization of nerve growth factor (NGF) in the skin is related to sites of sensory axon termination. For these reasons, we have used immunocytochemistry to study the distribution of NGF and the low-affinity NGF receptor (p75NGFR) in the touch domes of adult rat skin. Intense NGF-like immunoreactivity was sharply restricted to keratinocytes (excluding the stratum corneum) of the thickened epidermis of touch domes. The epidermis immediately surrounding touch domes and the epidermis of the tylotrich hair follicle associated with touch domes were not stained by anti-NGF antiserum. Merkel cells of the basal epidermis of touch domes were immunonegative for NGF but were immunopositive for p75NGFR as were the type I nerve endings innervating these cells. Quantitative Northern blotting revealed that the level of NGF mRNA was substantially higher in keratinocytes isolated from the stratum granulosum and stratum spinosum than in keratinocytes isolated from the stratum germinativum. These findings indicate that NGF synthesis in mature skin has a highly restricted regional distribution that is primarily associated with the innervation of a specialized touch receptor.

The survival of NGF-dependent but not BDNF-dependent cranial sensory neurons is promoted by several different neurotrophins early in their development

Recent work has shown that the survival of the nerve growth factor (NGF)-dependent trigeminal ganglion neurons of the mouse embryo is promoted by brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) during the early stages of target field innervation (Buchman and Davies, (1993) Development, 118, 989–1001). The present study was undertaken to ascertain if responsiveness to multiple neurotrophins is a universal feature of the early stages of neuronal development or is restricted to only certain kinds of neurons. To address this issue, we took advantage of the accessibility, from an early developmental stage, of several populations of cranial sensory neurons in the chicken embryo that depend for survival on just one or two known neurotrophins during the phase of naturally occurring cell death. During the mid-embryonic period (E10 to E12) when the number of sensory neurons is declining due to naturally occurring neuronal death, the neurons of the jugular ganglion and the dorsomedial part of the trigeminal ganglion (DMTG) were supported by NGF, the neurons of the ventrolateral part of the trigeminal ganglion (VLTG) were supported by BDNF and the nodose ganglion contained a major subset of neurons supported by BDNF and a minor subset supported by NT-3. Earlier in development (E6), the survival of DMTG and jugular neurons was additionally promoted by BDNF and NT-3. In contrast, E6 VLTG neurons did not exhibit a survival response to either NGF or NT-3, and E6 nodose neurons did not exhibit a survival response to NGF.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of transforming growth factor-beta isoforms in regulating the expression of nerve growth factor and neurotrophin-3 mRNA levels in embryonic cutaneous cells at different stages of development

We have investigated if transforming growth factor-beta (TGF-beta) isoforms influence the level of expression of nerve growth factor (NGF) mRNA and neurotrophin-3 (NT-3) mRNA in embryonic tissues innervated by neurons that depend on NGF and NT-3 for survival. Presumptive dermal and epidermal cells from the maxillary territory of the embryonic mouse trigeminal ganglion were cultured in defined medium during the early stages of innervation when trigeminal neurons switch their survival dependence from NT-3 to NGF. In E11 and E12 cultures, when the in vivo levels of NGF mRNA and NT-3 mRNA are increasing, TGF-beta 1, TGF-beta 2 and TGF-beta 3 each increased the level of NGF mRNA but had no effect on NT-3 mRNA. In E13 cultures, when the in vivo levels of NGF mRNA and NT-3 mRNA reach a peak (relative to actin mRNA) prior to a marked fall in the level of NT-3 mRNA and a gradual decrease in the level of NGF mRNA, TGF-beta s promoted further increases in the level of NGF mRNA but caused a decrease in the level of NT-3 mRNA. All three TGF-beta mRNAs were detected in the maxillary territory in vivo before the arrival of the earliest axons and their levels rose throughout the period in which sensory axons reach this territory.(ABSTRACT TRUNCATED AT 250 WORDS)

Parasymphyseal insufficiency fracture

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Intrinsic programmes of growth and survival in developing vertebrate neurons

Neurons become dependent on a supply of target-derived neurotrophins for survival when their axons reach their targets in development. Because the distance axons have to grow varies from one population of neurons to another, the timing of dependence on neurotrophins likewise varies. Although it would be expected that the simplest way of getting the timing right would be for the target to provide a suitable signal to the arriving axons, detailed studies on developing cranial sensory neurons suggest that these neurons are programmed, before differentiation, to acquire dependence at the correct time independently of external signals. Neurons not only partly compensate for different target distances by extending axons more rapidly the further they have to grow, but possess an intrinsic clock that switches on dependence at the right time in accordance with the time it normally takes their axons to reach their targets. Here the experimental evidence for these intrinsic programmes of growth and survival is reviewed, the rationale that might have favoured their evolution is discussed, and parallels are drawn with other developing neuronal systems.

Magnetic resonance imaging appearances of fatigue fractures of the long bones of the lower limb

Fatigue fractures may be confused with malignant bone lesions on radiography and hence are periodically referred for further imaging assessment with computed tomography (CT) and magnetic resonance imaging (MRI). The appearances on MRI are characteristic although not pathognomonic. Typical findings include: intramedullary bands of low signal intensity, continuous at some point with the cortex, indicative of a fracture line; intramedullary areas of high signal on both T2-weighted and short-tau inversion recovery (STIR) images representing marrow oedema or haemorrhage, together with evidence of periosteal oedema. We present seven cases of fatigue fractures of the long bones of the lower limb and discuss the MRI findings and compare CT and MRI in imaging these lesions.

Computed tomographic arthrography in the assessment of osteochondritis dissecans of the elbow

Eleven cases of osteochondritis dissecans of the elbow are reviewed. Computed tomography (CT) accurately identified the abnormality, its extent and its precise location. Computed tomographic arthrography (CTA) allowed accurate delineation of the overlying cartilage in all cases, identifying cartilage defects in four patients, fissuring in two and cartilage thinning in a further two. In those patients who had plain CT, four were shown to have loose bodies, one of which was obscured by contrast medium at subsequent CTA. Two further patients with loose bodies were identified using CTA alone. The possible relevance of these findings to management is discussed.

p75-deficient embryonic dorsal root sensory and neonatal sympathetic neurons display a decreased sensitivity to NGF

To understand the role of low-affinity neurotrophin receptor p75 in neural development, we previously generated mice carrying a null mutation in the p75 locus (Lee, K. F., Li, E., Huber, L. J., Landis, S. C., Sharpe, A. H., Chao, M. V. and Jaenisch, R. (1992) Cell 69, 737–749). To elucidate the mechanisms leading to deficits in the peripheral nervous system in p75 mutant mice, we have employed dissociated cultures to examine the responses of p75-deficient dorsal root ganglion (DRG) and superior cervical ganglion (SCG) neurons to different neurotrophins. We found that p75-deficient DRG and SCG neurons displayed a 2- to 3-fold decreased sensitivity to NGF at embryonic day 15 (E15) and postnatal day 3 (P3), respectively, ages that coincide with the peak of naturally occurring cell death. Furthermore, while p75-deficient E15 DRG neurons did not change their response specificity to BDNF, NT-3, and NT-4/5, P3 SCG neurons became more responsive to NT-3 at higher concentrations (nanomolar ranges). These results may help explain the deficits in the peripheral nervous system in p75 mutant mice and provide evidence that p75 can modulate neurotrophin sensitivity in some neurons.

Neurotrophic factors. Switching neurotrophin dependence

Recent studies have revealed an unexpected switch in the survival requirements of neurons, from one set of neurotrophins to another, during the early stages of target-field innervation.

The value of computed tomographic measurements in osteosarcoma as a predictor of response to adjuvant chemotherapy

The response to pre-operative adjuvant chemotherapy was assessed with computed tomography (CT) in 41 osteosarcomas of the long bones of the lower limb. Measurements were made of cross-sectional tumour areas and volumes on both the pre- and post-chemotherapy CT examinations. Changes in these measurements were compared with the percentage necrosis determined from examination of the tumour histology from the excised specimen in 39 cases. An increase in the relative size of the tumour (expressed as a ratio of the pretreatment volume) showed a statistically significant correlation with a poor tumour response as judged by the degree of tumour necrosis. Further analysis of the results showed that quantitative assessment of tumour response by CT is able to identify cases with poor response to therapy (negative predictive value = 0.9). This is, however, only achieved with a low specificity (0.5-0.6). These findings are in agreement with other studies of tumour volume changes using MR imaging.

The role of neurotrophins during successive stages of sensory neuron development

Neurotrophins comprise a family of basic homodimeric proteins. The isolation of the first two neurotrophins, nerve growth factor and brain-derived neurotrophic factor, was based on the ability of these proteins to promote the survival of embryonic neurons. However, the identification of additional neurotrophins by homology screening together with recent work on these proteins has shown that neurotrophins do more than just regulate neuronal survival. Neurotrophins influence the proliferation and differentiation of neuron progenitor cells and regulate the expression of several differentiated traits of neurons throughout life. Moreover, the influence of neurotrophins on survival is more complex than originally thought; some neurons switch their survival requirements from one set of neurotrophins to another during development and several neurotrophins may be involved in regulating the survival of a population of neurons at any one time. Most of what is known of the developmental physiology of neurotrophins has come from studying neurons of the peripheral nervous system. Quite apart from the accessibility of these neurons and their progenitor cell populations, investigation of the actions of neurotrophins on several well-characterised populations of sensory neurons has permitted the age-related changes in the effects of neurotrophins to be interpreted in the appropriate developmental context. In this review I provide a chronological account of the action of neurotrophins in neuronal development with special reference to sensory neurons.

Ectopic trkA expression mediates a NGF survival response in NGF-independent sensory neurons but not in parasympathetic neurons

We have investigated the role of trkA, the tyrosine kinase NGF receptor, in mediating the survival response of embryonic neurons to NGF. Embryonic trigeminal mesencephalic (TMN) neurons, which normally survive in the presence of brain-derived neurotrophic factor (BDNF) but not NGF, become NGF-responsive when microinjected with an expression vector containing trkA cDNA. In contrast, microinjection of ciliary neurotrophic factor (CNTF)-dependent embryonic ciliary neurons with the same construct does not result in the acquisition of NGF responsiveness by these neurons despite de novo expression of trkA mRNA and protein. The failure of trkA to result in an NGF-promoted survival response in ciliary neurons is not due to absence of the low-affinity NGF receptor, p75, in these neurons. Quantitative RT/PCR and immunocytochemistry showed that TMN and ciliary neurons both express p75 mRNA and protein. These findings not only provide the first direct experimental demonstration of trkA mediating a physiological response in an appropriate cell type, namely NGF-promoted survival of embryonic neurons, but indicate that not all neurons are able to respond to a trkA-mediated signal transduction event.

Age-related effects of nerve growth factor on the morphology of embryonic sensory neurons in vitro

Studies of neonatal and adult mammals have shown that neuronal morphology is regulated in part by the availability of target-derived neurotrophic factor. To test whether the same is true for embryonic neurons, which are dependent on target-derived neurotrophic factors for survival, we grew neural crest-derived sensory neurons from the trigeminal ganglion of avian embryos of different ages in vitro in different concentrations of nerve growth factor (NGF) and measured the number of branch points and total length of the resulting arborizations. Although the size and complexity of arborizations increased with embryonic age up to embryonic day (E)14, neuronal morphology for embryos younger than E14 was unaffected by the concentration of NGF in the culture medium. However, beginning at E14, the stage at which trigeminal neurons start to lose their absolute requirement for NGF for survival, the neurons had significantly more branch points and larger arborizations in higher concentrations of NGF. Thus, it appears that the extent of neurite outgrowth in young embryos is independent of neurotrophic factor concentration; each neuron that receives enough neurotrophic factor to survive elaborates approximately the same size arbor. As trigeminal neurons mature and become less dependent on neurotrophic factor for survival, they acquire the ability to respond to neurotrophic factor with increased neurite growth and branching, as in neonates and adults.

Regulation of expression of mRNAs encoding the nerve growth factor receptors p75 and trkA in developing sensory neurons

We have used a quantitative reverse transcription/polymerase chain reaction amplification technique to study the regulation of p75 mRNA and trkA mRNA expression in developing NGF-dependent trigeminal neurons. Before becoming NGF dependent, these neurons express low levels of p75 and trkA mRNAs in vivo. At this stage in vitro, the level of p75 mRNA is maintained and up-regulated by BDNF, whereas the level of trkA mRNA is sustained independently of neurotrophins and is down-regulated by BDNF. With the acquisition of NGF dependence, p75 and trkA mRNA levels increase markedly in vivo. At this stage in vitro, the level of p75 mRNA is up-regulated by NGF, but this response is lost at later stages. The level of trkA mRNA is sustained in neurons grown with NGF but is not up-regulated by concentrations of NGF above those required to support survival. At no stage during the early development of trigeminal neurons do depolarising levels of potassium ions affect the expression of either p75 mRNA or trkA mRNA. These findings suggest that the expression of p75 and trkA mRNAs are differentially regulated by BDNF and NGF at successive early stages of neuronal development.

Neurotrophin-4/5 is a mammalian-specific survival factor for distinct populations of sensory neurons

We have studied the effect of human recombinant neurotrophin-4/5 (NT-4/5) on the survival of developing PNS neurons from embryonic mice and chickens. NT-4/5 transiently supported mouse NGF-dependent trigeminal and jugular neurons at early stages of target field innervation and mouse brain-derived neurotrophic factor (BDNF)-dependent no-dose neurons during the phase of naturally occurring cell death. NT-4/5 was as potent as BDNF in supporting the survival of these neuronal populations. Surprisingly, NT-4/5 was 3 orders of magnitude less potent than BDNF as a survival factor for early chick dorsomedial trigeminal sensory neurons and did not support the survival of chick BDNF-dependent trigeminal mesencephalic or ventrolateral trigeminal sensory neurons at any of the developmental stages tested. Thus, NT-4/5 is a survival factor for certain embryonic mouse cranial sensory neurons. It is the first species-specific neurotrophin to be identified and it can discriminate at high concentrations between different BDNF-responsive chick neurons.

p75-deficient trigeminal sensory neurons have an altered response to NGF but not to other neurotrophins

The role of the common low affinity neurotrophin receptor, p75, is controversial. Studies using cell lines suggest that p75 is either essential or dispensable for neurotrophin responsiveness. To resolve this issue, we studied the survival response of developing neurons obtained from normal mouse embryos and embryos with a null mutation in the p75 gene. Embryonic cranial sensory and sympathetic neurons from mutant embryos responded normally to NGF, BDNF, NT-3, and NT-4/5 at saturating concentrations. Dose responses of sympathetic and visceral sensory neurons from mutant embryos were also normal. In contrast, embryonic cutaneous sensory trigeminal neurons isolated from mutant embryos displayed a consistent displacement in the NGF dose response. Compared with wild-type neurons, the concentration of NGF that promoted half-maximal survival was 3- to 4-fold higher for neurons from homozygous embryos and was 2-fold higher for neurons from heterozygous embryos. These findings indicate that p75 enhances the sensitivity of NGF-dependent cutaneous sensory neurons to NGF and may explain, at least in part, the cutaneous sensory abnormalities of mice homozygous for the p75 mutation.

Heterotopic transplantation of presumptive placodal ectoderm changes the fate of sensory neuron precursors

The placode-derived cranial sensory neurons of the vestibular and nodose ganglia in avian embryos exhibit differences in neurite growth rate and the duration of neurotrophin-independent survival in vitro that arise prior to gangliogenesis and target contact (Davies, A. M. (1989) Nature 337, 553–555; Vogel, K. S. and Davies, A. M. (1991) Neuron 7, 819–830). To ascertain the state of commitment of presumptive placodal ectoderm to differentiate into neurons of the vestibular or nodose type, we performed heterotopic transplantation of labelled presumptive placodal ectoderm at E1.5 in the chicken embryo. We then assayed transplant-derived neurons for hindbrain innervation patterns, neurite growth and survival at E3.5. We show that presumptive placodal ectoderm is not determined to give rise to neurons of the vestibular or nodose phenotype at E1.5. Explantation of presumptive placodal ectoderm at E1.5 showed that this ectoderm is also not specified to differentiate into neurons at this stage. In addition, we demonstrate that non-neurogenic ectoderm from the trunk can give rise to nodose-type neurons when transplanted heterotopically to the nodose region.

Different neurotrophins are expressed and act in a developmental sequence to promote the survival of embryonic sensory neurons

To investigate if different neurotrophins regulate the survival of neurons at successive developmental stages, we studied the effect of nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) on the survival of mouse trigeminal neurons at closely staged intervals in development. We show that during the earliest stages of target field innervation trigeminal neurons display a transitory survival response to BDNF and NT-3. This response is lost as the neurons become NGF-dependent shortly before neuronal death begins in the trigeminal ganglion. BDNF and NT-3 mRNAs are expressed in the peripheral trigeminal target field before the arrival of the earliest axons and the onset of NGF mRNA expression. The levels of BDNF and NT-3 mRNAs peak during the early stages of target field innervation and decline shortly after the loss of neuronal responsiveness to BDNF and NT-3. Our study provides the first clear evidence that different target-derived neurotrophins can act sequentially to promote the survival of developing neurons.

Redesign of the interior hydrophilic region of mitochondrial cytochrome c by site-directed mutagenesis

Heme propionate-7 in cytochrome c is an ionizable group located in a region of the protein that is inaccessible to bulk solvent. Electrostatic stabilization of this functional group appears to be achieved through interaction of heme propionate-7 with several amino acid residues that occur within hydrogen-bonding distance of it. To investigate the functional and spectroscopic roles of the amino acid residues that contribute to the immediate environment of heme propionate-7, the following variant forms of yeast (Saccharomyces cerevisiae) cytochrome c have been prepared and characterized by electrochemical and spectrochemical analyses: Arg38Ala, Tyr48Phe, Ala38Phe, Tyr48Phe/Trp59Phe, and Arg38Ala/Tyr48Phe/Trp59Phe. For each protein, the dependence of midpoint reduction potential and NMR spectrum on pH was determined, and the UV (250-450 nm) circular dichroic (CD) spectrum was measured. All of the variant proteins exhibited decreased reduction potentials with the greatest difference (-65 to -70 mV) exhibited by the multiply mutated proteins. The electrostatic properties of the variant proteins as reflected by the oxidation-state dependence of the His-39 pKa value were similar to those of the wild-type protein. Previous indirect assignments of minima in the CD spectrum of cytochrome c at 282 and 289 nm to Trp-59 are confirmed by spectra of the variant cytochromes in which this residue is replaced by Phe. The present results establish that the electrochemical effects of eliminating hydrogen-bonding interactions with heme propionate-7 are not additive and that the functional modulation of cytochrome c through regulation of the heme propionate-7 dielectric environment involves a complex combination of solvation effects and electrostatic or hydrogen-bonding interactions.

The proto-oncogene bcl-2 can selectively rescue neurotrophic factor-dependent neurons from apoptosis

Apoptosis plays an important role in regulating cell numbers in a wide variety of tissues during development. The product of the bcl-2 gene inhibits apoptosis in certain cells of the myeloid and lymphoid lineages and is expressed in many cells that have an extended life span. To assess the role of bcl-2 in neuronal apoptosis, we microinjected a bcl-2 expression vector into neurotrophic factor-deprived embryonic neurons. Sensory neurons that depend for survival on one or more members of the nerve growth factor family of neurotrophic factors (nerve growth factor, brain-derived neurotrophic factor, and neurotrophin-3) were rescued by bcl-2, whereas ciliary neurotrophic factor (CNTF)-dependent ciliary neurons were not. Sensory neurons, however, became refractory to bcl-2 after exposure to CNTF. These findings indicate that at least two death pathways operate in neurons that are distinguished by their susceptibility to bcl-2. Neurons may die by either pathway, depending on the factors to which they have been exposed.

Fenfluramine-induced place aversion in a three-choice apparatus

The hedonic properties of the anorectic agent fenfluramine (0.25, 1.0, 2.5, 5.0, and 10.0 mg/kg) were assessed in two experiments in a place conditioning paradigm. After four conditioning trials, rats were tested for their preference for a drug-paired chamber, saline-paired chamber, and a novel chamber. Fenfluramine produced a place aversion at doses of 2.5-10 mg/kg.

Transforming growth factor-betas inhibit mitogen-stimulated proliferation of astrocytes

We have studied the influence of three members of the transforming growth factor-beta (TGF-beta) family of multifunctional growth factors on the proliferation of cultured astrocytes isolated from newborn mouse cerebral cortex. Although TGF-beta s 1, 2, and 3 cause only a small reduction in the low level of astrocyte proliferation occurring in chemically defined medium, they each inhibit the effects of five astrocyte mitogens (bFGF, EGF, PDGF, IL-1 alpha, and IL-2). Inhibition is observed when astrocytes are exposed to mitogen and TGF-beta at the same time and when they are exposed to TGF-beta prior to, and separately from, mitogen. This latter effect appears to be due to the binding of TGF-beta s to astrocyte-secreted extracellular matrix. These findings raise the possibility that TGF-beta may co-operate with other growth factors to control astrocyte proliferation in vivo.

Fatigue fracture of the sacrum in a child

Fatigue fractures involving the sacrum are extremely rare, and to our knowledge no occurrence of such a fracture in a child has been reported in the English-language literature. These fractures may mimic primary bone tumours or infection, and it is important to make an accurate diagnosis so that unnecessary biopsy can be avoided. We report a fatigue fracture of the sacrum in an 11-year-old child following prolonged aerobic exercise.

Detection of significant abnormalities on lumbar spine radiographs

The purpose of this study was to determine the proportion of significant abnormalities detected on anteroposterior (AP) and lateral radiographs of the lumbar spine when viewed separately, in a series of cases where the prevalence of abnormalities had been artificially increased. Five radiologists of varying experience were required to report separately on the AP and lateral films of 300 cases in which randomly included were 30 cases with metastatic disease, a disc infection or an inflammatory spondylitis. At a later date, unaware of their initial observations, the radiologists repeated the exercise reviewing all the films together. As might be expected the false positive rate was relatively high, particularly in the least experienced radiologists' responses. Nevertheless the overall results indicate that the majority of early inflammatory spondylitis cases will be missed on a solitary lateral film as will many of the metastases. Conversely, fractionally more of the disc infections were observed on the lateral film than on the AP. Further analyses in terms of sensitivity, specificity, positive and negative predictive values are presented. The authors conclude that it is preferable to reduce the overall number of lumbar spine examinations performed, by adherence to accepted guidelines, than to prejudice the detection of significant, albeit rare, abnormalities by restricting the routine series of radiographs.

Computed tomographic appearances of the pelvis following hindquarter amputation

Bilateral and midline symmetry of the normal pelvic anatomy is an aid to the interpretation of computed tomographic (CT) examinations. Following hindquarter amputation (HQA) or partial hemipelvectomy (PHP) the normal anatomical relationships are disturbed. The CT examinations of 15 patients who had undergone either an HQA or a PHP for an advanced musculoskeletal malignancy are reviewed. The new "normal" anatomy revealed displacement of the bladder and small bowel to the side of surgery in one third of patients, more commonly in the PHP cases. There were varying degrees of wasting of the ipsilateral musculature, gluteus maximus muscle flap, erector spinae and psoas muscles, etc., because of partial denervation and disruption of their origin or insertion. Recurrent tumour was identified in eight of 10 cases in which it was clinically suspected prior to the CT examination. Invariably the recurrence arose within the muscle flap at the resection margin. Bone involvement by direct tumour spread was present in three cases. Pitfalls in differentiating recurrent tumour from scar tissue are discussed.

Intracellular calcium regulates the survival of early sensory neurons before they become dependent on neurotrophic factors

To investigate the role of intracellular Ca2+ in the survival of developing neurons before they become neurotrophic factor dependent, we have studied chick embryo nodose neurons, which have a particularly protracted period of neuorophic factor independence. Pharmacological reduction of intracellular free Ca2+ or depletion of either Ca(2+)-regulated or inositol trisphosphate-regulated intracellular Ca2+ stores kills early neurotrophic factor-independent neurons, but has a negligible effect on older neurons growing in the presence of brain-derived neutrotrophic factor. Shortly before they become dependent on brain-derived neurotrophic factor, nodose neurons express L-type Ca2+ channels and their survival can be enhanced by depolarization-induced Ca2+ influx. We conclude that intracellular Ca2+ plays a role in regulating neuronal survival both prior to and after the onset of neurotrophic factor dependence, but does not mediate the survival-promoting effects of neurotrophic factors.

Neurotrophic factors promote the maturation of developing sensory neurons before they become dependent on these factors for survival

We have studied the early development of chicken embryo sensory neurons in culture before they become dependent on neurotrophic factors for survival. During this period, they undergo a distinct change in morphology:initially they have small, spindle-shaped, phase-dark cell bodies, which become spherical and phase bright and extend long neurites. Although this maturational change occurs in isolated cells grown in chemically defined medium, it is accelerated by brain-derived neurotrophic factor (BDNF) or neurotrophin-3 and is retarded by antisense oligonucleotides that inhibit expression of the common, low affinity neurotrophic factor receptor (gp75NGFR) and by antisense BDNF oligonucleotides. We conclude that neurotrophic factors play a role in the earliest stages of sensory neuron development and suggest that they operate by an autocrine mechanism at this time.

The incidence and significance of fluid-fluid levels on computed tomography of osseous lesions

The demonstration of a fluid-fluid level (FFL) within an osseous lesion on computed tomography (CT) has been reported as suggestive of an aneurysmal bone cyst (ABC) although FFLS have also been rarely found in association with other lesions. This study was conducted to determine the frequency of FFLS on CT in a group of ABCs and a series of patients presenting to a major tertiary referral centre for the treatment of bone tumours. An FFL was present on CT in 21 (84%) of the 25 ABCs and in 17 was multiple. FFLs are typical of the mid ("blow-out") or late phase of development of an ABC and not the incipient ("permeative") stage or where the internal architecture of the tumour has been disrupted by biopsy or previous surgery. In a 3-year period, 16 ABCs were found in 491 bone lesions referred to a bone tumour treatment centre. CT of the ABCs revealed FFLs in 14 (87.5%) cases. Within the same period, 728 CTs of these and other bone lesions were performed and FFLs were identified in two further cases: a massive telangiectatic osteosarcoma and a conventional osteosarcoma following chemotherapy. The diagnostic significance of an FFL on CT for ABC is: sensitivity = 87.5%, specificity = 99.7%, positive predictive value = 87.5%, negative predictive value = 99.7%, accuracy = 99.4%. An FFL within a bone lesion on CT remains strongly suggestive of an ABC although the radiologist should be wary of a rare telangiectatic osteosarcoma.

Computed tomographic assessment of soft tissue abnormalities following calcaneal fractures

Computed tomographic (CT) examinations of 50 acute calcaneal fractures were compared with a further series of 77 fractures in which the date of injury preceded the CT by 6 months or more. 42 (84%) of the fractures in the acute group and 55 (71%) in the chronic group were classified as intra-articular and they form the basis of this study. The alteration in the position of the peroneal tendons in the two groups was similar, with a 5% or less difference in each category. In the acute group the peroneal tendons were normally located in 40.4% of the cases, entrapped by bone in 11.9%, subluxed in 33.3% and dislocated in 14.2%. Structural abnormalities of the peroneal tendons and surrounding soft tissues were identified in 52.4% of the acute group and in 61.1% of the chronic group. The incidence of partial rupture of the peroneal tendons in the chronic group was approximately one third that in the acute group, but the low incidence of complete tendon rupture remained unchanged. The inference from these observations is that, in the majority of cases, partial peroneal tendon rupture is reversible, whereas complete rupture is not. Seven fractures were common to both series and from this limited group the identification of haemorrhage around the peroneal tendons in the acute phase was shown not to be related to the subsequent development of chronic stenosing tenosynovitis. Various abnormalities of the medial tendons of the hindfoot were identified in 17% of the acute group and in 18% of the chronic group. Following calcaneal fracture, CT in both the immediate post-fracture period and in the late phase can be used to detect and classify the soft tissue changes. The limitations of comparing the two groups in this study are discussed.

NMR study of the structural characteristics of variants of yeast iso-1-cytochrome c in which unvaried aromatic residues have been substituted

The structures of variants of yeast iso-1-cytochrome c, in which the previously unchanged Tyr48 and Tyr48 + Trp59 have been replaced by Phe, have been characterised by NMR. The NMR data indicated that the structures of the variant cytochromes c are very similar to the wild-type protein. In particular, the heme environment and interactions of the heme macrocycle were shown to be preserved. The observation of chemical shift differences have allowed for the assessment of conformational changes. The substitution of Trp59 by Phe may have caused a small conformational change, a manifestation of which is the observed chemical shift differences at His39, Val57 and Tyr74. The structural basis for the reduction in redox potential accompanying the amino acid substitutions is discussed and the proposal made that the changes in potential are a direct consequence of the side chain properties and do not result primarily from conformational changes.

Chronic stress injuries of the elbow in young gymnasts

The radiological changes of chronic stress injuries of the elbow in 19 adolescent elite gymnasts are reported. The principal abnormalities were avascular necrosis of the capitellar epiphysis (Panner's disease) (one patient), post-traumatic subarticular necrosis (osteochondritis dissecans) of the capitellum (six patients) and the medial articular eminence of the distal humerus (one patient). Flattening and anterior depression of the radial head epiphysis with an underlying metaphyseal notch associated with an epiphyseal cleft (three patients), which, in one patient who continued training, developed into a chronic Salter Type IV stress fracture. A further patient, post-epiphyseal fusion, showed osteochondritis dissecans of the anterior aspect of the radial head. Seven patients exhibited a spectrum of olecranon changes from fragmentation of the epiphysis to chronic Salter Type I stress fractures of the growth plate. A follow-up survey found that, of those who responded to a questionnaire, nearly all the patients with articular surface damage failed to continue with competitive gymnastics whereas those with olecranon abnormalities were able to continue gymnastics at the same level. The mechanism of injury and the pathological changes are discussed.

The duration of neurotrophic factor independence in early sensory neurons is matched to the time course of target field innervation

To investigate how the onset of neurotrophic factor dependence in neurons is coordinated with the arrival of their axons in the target field, we have studied the survival of four populations of cranial sensory neurons whose axons reach their common central target field, the hindbrain, at different times. We show that neurons whose axons reach the hindbrain first survive for a short time in culture before responding to brain-derived neurotrophic factor (BDNF). Neurons whose axons reach the hindbrain later survive longer before responding to BDNF. These differences in survival, which arise prior to gangliogenesis, may play a role in coordinating trophic interactions for cranial sensory neurons.

Real-time digital contrast enhancement and magnification in the assessment of acute elbow injuries

The elbow is a common site of injury and missed fractures may lead to disability and litigation. An assessment was made of a commercially available desk-top digital contrast enhancement and magnification unit (DETECT system) in a series of 320 patients with an acute elbow injury. Five radiologists of varying experience independently viewed elbow radiographs on a conventional light-box, and subsequently using the digitizer, indicating the presence or absence of a fracture. The overall results demonstrated no difference in performance when using the unit, though small improvements in the confidence with which a definite diagnosis was made were observed. Assessment of soft tissues with the digitizer was less reliable.

Change in charge of an unvaried heme contact residue does not cause a major change of conformation in cytochrome c

The structure of the Ala38 variant of yeast iso-1-cytochrome c, in which the previously unchanged Arg38 has been replaced, has been characterised by NMR. The NMR data indicate that the structure of the Ala38 variant is very similar to that of the wild type protein. In particular, the heme environment and interactions of the heme macrocycle are shown to be preserved. Analysis of the chemical shift perturbations to the resonances of Ile35 is shown to be consistent with the change in charge at position 38. The only significant area of conformational change detected was at residues 39 and 58, close to the site of modification. Therefore the redox potential change accompanying the modification [1988, Biochemistry 28, 3188-3197] appears to be a direct consequence of the altered side-chain of residue 38 and not a result of secondary conformational changes induced by the modification.

Glenoid hypoplasia: assessment by computed tomographic arthrography

Four cases of an uncommon congenital skeletal anomaly, isolated bilateral glenoid hypoplasia, are presented with discussion of the possible pathogenesis and clinical significance. Bilateral computed tomographic arthrography of the shoulder demonstrated thickening of the inferior glenoid cartilage in two cases. The technique was of value in the symptomatic shoulder revealing the location of a contrast medium filled cleft within the posterior cartilage in one case and the true configuration of the glenohumeral joint in the second case, when the degree of deformity had rendered plain radiographs and conventional arthrography uninterpretable.

Iliac insufficiency fractures

Twenty-five post-menopausal women with one or more insufficiency fractures of the pelvic ring are reported. In 80% of cases the fractures were multiple and a total of 79 insufficiency fractures was identified. Twelve iliac insufficiency fractures were present in 11 patients located at one of three sites: above and parallel to the acetabular roof ("supra-acetabular"), extending diagonally across the iliac ala from the greater sciatic notch ("oblique iliac"), and adjacent to the sacro-iliac joint ("superomedial iliac"). The plain radiographic appearances of these iliac fractures were typically subtle with ill defined medullary sclerosis, due to trabecular compression, the cardinal sign. Scintigraphy revealed the fractures as foci of increased activity which, in the presence of multiple pelvic insufficiency fractures, may be mistaken for metastatic disease. Computed tomography can be helpful in confirming the presence of suspected fractures, revealing further occult fractures and also excluding the likelihood of malignancy.

Developmental programmes of growth and survival in early sensory neurons

In the developing vertebrate nervous system the survival of neurons becomes dependent on the supply of a neurotrophic factor from their targets when their axons reach these targets. To determine how the onset of neurotrophic factor dependency is coordinated with the arrival of axons in the target field, we have studied the growth and survival of four populations of cranial sensory neurons whose axons have markedly different distances to grow to reach their targets. Axonal growth rate both in vivo and in vitro is related to target distance; neurons with more distant targets grow faster. The onset trophic factor dependency in culture is also related to target distance; neurons with more distant targets survive longer before becoming trophic factor dependent. These data suggest that programmes of growth and survival in early neurons play an important role in coordinating the timing of trophic interactions in the developing nervous system.

Coordination of trophic interactions by separate developmental programs in sensory neurons and their target fields

In the developing vertebrate nervous system the survival of sensory neurons becomes dependent on neurotrophic factors when their axons reach their target fields, and the synthesis of nerve growth factor (NGF) by target field cells commences with the arrival of the earliest axons. The timing of NGF synthesis and the onset of neurotrophic factor dependence are not, however, reliant on innervation. NGF synthesis occurs on time in developing target fields in which innervation is prevented, and sensory neurons cultured before innervating their targets become dependent on neurotrophic factors for survival after a certain length of time in culture. The length of time neurons survive in culture before becoming neurotrophic factor-dependent is related to the time they would normally contact their targets in vivo: populations of neurons that have nearby targets which are innervated early respond to neurotrophic factors before neurons that have more distant targets which are innervated later. The timing of target field innervation is governed not only by the distance axons have to grow but by the rate at which they grow. Axonal growth rate is also regulated in accordance with target distance: neurons with distant targets extend axons faster than neurons with nearby targets. In addition to reviewing evidence for separate developmental programs that control the timing of neurotrophic factor synthesis in the target field and the onset of neurotrophic factor dependence in early sensory neurons, we will consider the mechanisms that might play a role in regulating the survival of neurons during the phase of neurotrophic factor independence.

Real-time digital contrast enhancement and magnification in the assessment of scaphoid and other wrist injuries

A study on the value of a commercially available desk-top digital magnifier-contrast enhancer (DETECT System) was made in a series of 550 patients presenting with an acute wrist injury. Four radiologists, of varying experience, independently reviewed the radiographs on a conventional lightbox and later with the digitizer. In the scaphoid series (350 cases), the performance of the two more experienced radiologists was marginally better with the digitizer, whereas the less experienced radiologists performed slightly worse. Overall the digitizer improved the confidence of the radiologists in diagnosing correctly the presence of a scaphoid fracture but, for the less experienced radiologists, this was at the expense of identifying normality. In the wrist series (200 cases), the use of the digitizer resulted in a minor increase in the true positive and decrease in the false negative observations, but this was offset by a concomitant minor increase in the false positive and decrease in the true negative categories. Evaluation of the soft-tissue planes around the wrist joint showed a limited value in the identification of a scaphoid fracture with an overall positive predictive value of 0.26. Correlation of soft-tissue changes and the presence or absence of a scaphoid fracture was slightly worse with the digitizer. Possible causes for the apparently poorer performance of the digitizer are discussed, as well as the relative merits and potential value of the unit.

Computed tomographic assessment of old calcaneal fractures

Prolonged pain and disability are common complications of calcaneal fractures. A prospective study was conducted on the value of computed tomography (CT) in 63 patients with 73 calcaneal fractures sustained more than 6 months before. The fractures were classified from the initial plain radiographs, and the patients' current clinical condition assessed in terms of a "disability score". The mean disability scores (MDS) associated with the different types of fracture were correlated with the CT findings. The highest MDS was found in the intra-articular fracture group which comprised 71% of the series. In this group the MDS was increased in the presence of post-traumatic osteoarthrosis of the subtalar joint (61% of cases), involvement of the calcaneocuboid joint (39% of cases) and subluxation/dislocation of the peroneal tendons (47% of cases). Structural abnormalities of the peroneal tendons were associated with a higher MDS including chronic tenosynovitis (eight cases), chronic partial tendon rupture (eight cases), complete peroneus brevis tendon rupture (two cases) and scarring indicating stenosing tenosynovitis (14 cases). A similar spectrum of appearances affecting the medial tendons of the hindfoot was identified in eight cases. Direct CT measurements of the degree of comminution did not correlate well with the patients' MDS. In the patient with persistent symptoms, CT is of value in the later assessment of long-term complications by revealing abnormalities of the subtalar joints and adjacent tendons.

Coordination of breathing, sucking, and swallowing during bottle feedings in human infants

Incoordination of sucking, swallowing, and breathing might lead to the decreased ventilation that accompanies bottle feeding in infants, but the precise temporal relationship between these events has not been established. Therefore, we studied the coordination of sucks, swallows, and breaths in healthy infants (8 full-term and 5 preterm). Respiratory movements and airflow were recorded as were sucks and swallows (intraoral and intrapharyngeal pressure). Sucks did not interrupt breathing or decrease minute ventilation during nonnutritive sucking. Minute ventilation during bottle feedings was inversely related to swallow frequency, with elimination of ventilation as the swallowing frequency approached 1.4/s. Swallows were associated with a 600-ms period of decreased respiratory initiation and with a period of airway closure lasting 530 +/- 9.8 (SE) ms. Occasional periods of prolonged airway closure were observed in all infants during feedings. Respiratory efforts during airway closure (obstructed breaths) were common. The present findings indicate that the decreased ventilation observed during bottle feedings is primarily a consequence of airway closure associated with the act of swallowing, whereas the decreased ventilatory efforts result from respiratory inhibition during swallows.

NGF mRNA expression in developing cutaneous epithelium related to innervation density

To determine if the initial level of NGF mRNA in developing cutaneous epithelium is correlated with its final innervation density, we measured the concentration of NGF mRNA in the epithelia of the maxillary, mandibular and ophthalmic territories of trigeminal ganglion in the embryonic mouse. At the onset of neuronal death in the ganglion there were marked differences in the concentration of NGF mRNA in these epithelia: the level was highest in the epithelium of the densely innervated maxillary territory, it was lower in the epithelium of the moderately innervated mandibular territory and was lowest in the epithelium of the sparsely innervated ophthalmic territory. These regional differences in the level of NGF mRNA during the early stages of target field innervation suggest that the level of NGF production in target field cells, rather than regional differences in the access of innervating neurons to NGF, governs the number of neurons that survive. Because the same percentage cell death occurs in each of the subsets of trigeminal neurons that innervate the maxillary, mandibular and ophthalmic territories, regional differences in NGF synthesis are not responsible for establishing differences in innervation density, rather they maintain differences that arise earlier in development.

Inhibition of protein synthesis prevents cell death in sensory and parasympathetic neurons deprived of neurotrophic factor in vitro

Shortly after neurons begin to innervate their targets in the developing vertebrate nervous system they become dependent on the supply of a neurotrophic factor, such as nerve growth factor (NGF) for survival. Recently, Martin et al. (1988) have shown that inhibiting protein synthesis prevents the death of NGF-deprived sympathetic neurons, suggesting that NGF promotes neuronal survival by suppressing an active cell death program. To determine if other neurotrophic factors may regulate neuronal survival by a similar mechanism we examined the effects of inhibiting protein and RNA synthesis in other populations of embryonic neurons that require different neurotrophic factors, namely: 1) trigeminal mesencephalic neurons, a population of proprioceptive neurons that are supported by brain-derived neurotrophic factor; 2) dorsomedial trigeminal ganglion neurons, a population of cutaneous sensory neurons that are supported by NGF; 3) and ciliary ganglion neurons, a population of parasympathetic neurons that are supported by ciliary neuronotrophic factor. Blocking either protein or RNA synthesis rescued all three populations of neurons from cell death induced by neurotrophic factor deprivation in vitro. Thus, at least three different neurotrophic factors appear to promote survival by a similar mechanism that may involve the suppression of an endogenous cell death program.