Distribution kinetics of solutes in the isolated in-situ perfused rat head using the multiple indicator dilution technique and a physiological two-barrier model

The purpose of this study was to determine the pharmacokinetics of [C-14]diclofenac, [C-14]salicylate and [H-3]clonidine using a single pass rat head perfusion preparation. The head was perfused with 3-[N-morpholino] propane-sulfonic acid-buffered Ringer's solution. Tc-99m-red blood cells and a drug were injected in a bolus into the internal carotid artery and collected from the posterior facial vein over 28 min. A two-barrier stochastic organ model was used to estimate the statistical moments of the solutes. Plasma, interstitial and cellular distribution volumes for the solutes ranged from 1.0 mL (diclofenac) to 1.6 mL (salicylate), 2.0 mL (diclofenac) to 4.2 mL (water) and 3.9 mL (salicylate) to 20.9 mL (diclofenac), respectively. A comparison of these volumes to water indicated some exclusion of the drugs from the interstitial space and salicylate from the cellular space. Permeability-surface area (PS) products calculated from plasma to interstitial fluid permeation clearances (CLPI) (range 0.02-0.40 mL s(-1)) and fractions of solute unbound in the perfusate were in the order: diclofenac>salicylate >clonidine>sucrose (from 41.8 to 0.10 mL s(-1)). The slow efflux of diclofenac, compared with clonidine and salicylate, may be related to its low average unbound fraction in the cells. This work accounts for the tail of disposition curves in describing pharmacokinetics in the head.

Patterning of the vertebrate ventral spinal cord

We review investigations that have lead to a model of how the ventral spinal cord of higher vertebrate embryos is patterned during development. Central to this model is the secreted morphogen protein, Sonic hedgehog. There is now considerable evidence that this molecule acts in a concentration-dependent manner to direct the development of the spinal cord. Recent studies have suggested that two classes of homeodomain proteins are induced by threshold concentrations of Sonic hedgehog. Reciprocal inhibition between the two classes acts to convert the continuous gradient of Sonic hedgehog into defined domains of transcription factor expression. However, a number of aspects of ventral spinal cord patterning remain to be elucidated. Some issues currently under investigation involve temporal aspects of Shh-signalling, the role of other signals in ventral patterning and the characterisation of ventral interneurons. In this review, we discuss the current state of knowledge of these issues and present some preliminary studies aimed at furthering understanding of these processes in spinal cord patterning.

Physiological profiles of restricted endemic plants and their widespread congenors in the North Queensland wet tropics, Australia

Little is known about causes of endemic rarity in plants. This study pioneered an approach that determined environmental variables in the rainforest habitat and generated physiological profiles for light, water, and nutrient relations for three endemically restricted versus widespread congeneric species' pairs. We found no overall consistent differences in the physiological variables between the group of restricted species and the group of widespread species, and congeneric species pairs were therefore examined individually. Availability of soil nutrients did not differ between restricted-widespread species sites suggesting that species grow under comparable nutrient conditions. Under ambient and manipulated higher light conditions, widespread Gardenia ovularis had a greater photosynthetic activity than restricted Gardenia actinocarpa suggesting that the two species differ in their photosynthetic abilities. Differences between Xanthostemon species included lower photosynthetic activity, higher transpiration rate, and a higher foliar manganese concentration in restricted Xanthostemon formosus compared to widespread Xanthostemon chrysanthus. It is suggested that X. formosus is restricted by its high water use to its current rainforest creek edge habitat, while X. chrysanthus grows in a range of environments, although naturally found in riparian rainforest. Restricted Archidendron kanisii had higher electron transport rates, greater dissipative capacity for removal of excess light, and more efficient investment of nitrogen into photosynthetic components, than its widespread relative Archidendron whitei. These observations and previous research suggest that restricted Archidendron kanisii is in the process of expanding its range. Physiological profiles suggest a different cause of rarity for each species. This has implications for the conservation strategies required for each species. (C) 2002 Elsevier Science Ltd. All rights reserved.

Preservation of three-dimensional capillary structure in frog muscle during aestivation

In mammals, prolonged immobilization of the limbs can result in a loss of capillary tortuosity, resulting in skeletal muscle haemorrhaging if rapid remobilization is permitted. In this study, we examined the effect of 4 months' immobilization on semimembranosus capillary structure in the Green-striped burrowing frog, Cyclorana alboguttata. C alboguttata routinely aestivates as part of a physiological strategy to avoid desiccation in semi-arid environments and, in this capacity, the hindlimbs of C alboguttata are immobilized in a cocoon for months at a time. We found that 4 months' aestivation had no effect on three-dimensional capillary structure in the semimembranosus muscle and that capillary tortuosity is preserved in immobilized C. alboguttata. The preservation of capillary structure in the hindlimb muscles of C alboguttata in part accounts for their remarkable ability to emerge with a fully competent locomotor system after prolonged immobilization.

Development of motor system dysfunction following whiplash injury

Dysfunction in the motor system is a feature of persistent whiplash associated disorders. Little is known about motor dysfunction in the early stages following injury and of its progress in those persons who recover and those who develop persistent symptoms. This study measured prospectively, motor system function (cervical range of movement (ROM), joint position error (JPE) and activity of the superficial neck flexors (EMG) during a test of cranio-cervical flexion) as well as a measure of fear of re-injury (TAMPA) in 66 whiplash subjects within 1 month of injury and then 2 and 3 months post injury. Subjects were classified at 3 months post injury using scores on the neck disability index: recovered (30). Motor system function was also measured in 20 control subjects. All whiplash groups demonstrated decreased ROM and increased EMG (compared to controls) at 1 month post injury. This deficit persisted in the group with moderate/severe symptoms but returned to within normal limits in those who had recovered or reported persistent mild pain at 3 months. Increased EMG persisted for 3 months in all whiplash groups. Only the moderate/severe group showed greater JPE, within 1 month of injury, which remained unchanged at 3 months. TAMPA scores of the moderate/severe group were higher than those of the other two groups. The differences in TAMPA did not impact on ROM, EMG or JPE. This study identifies, for the first time, deficits in the motor system, as early as 1 month post whiplash injury, that persisted not only in those reporting moderate/severe symptoms at 3 months but also in subjects who recovered and those with persistent mild symptoms. (C) 2002 International Association for the Study of Pain. Published by Elsevier Science B.V. All rights reserved.

Motor and functional skills of children with developmental coordination disorder: A pilot investigation of measurement issues

This paper reports on the motor and functional outcomes of 20 children with developmental coordination disorder (DCD) aged 4-8 years consecutively referred to a pediatric physiotherapy service. Children with a Movement ABC (M-ABC) score less than the 15th percentile, and with no concurrent medical, sensory, physical, intellectual or neurological impairments, were recruited. The Motor Assessment Outcomes Model (MAOM) [Coster and Haley, Infants and Young Children 4 (1992) 11] provided the theoretical base for measurement selection, and preliminary findings at the activities and participation levels of the model are reported in this article. Children with DCD performed at the lower end of the normal range on the Pea-body Developmental Motor Scales (fine motor total score) (M = 85.65, SD = 12.23). Performance on the Visual Motor Integration Test (VMI) standard scores was within the average range (M = 96.15, SD = 10.69). Videotaped observations of the children's writing and cutting indicated that 29% were left-handed and that a large proportion of all children (31%) utilized unusual pencil grasp patterns and immature prehension of scissors. Measurement at the participation level involved use of the Pictorial Scale of Perceived Competence and Social Acceptance (PCSA) and Pediatric Evaluation of Disability Inventory (PEDI). Overall, these young children rated themselves towards the more competent and accepted end of the PCSA over the dimensions of physical and cognitive competence and peer and maternal acceptance. The PEDI revealed generally average performance on social (M = 49.98, SD = 16.62) and mobility function (M = 54.71, SD = 3.99), however, self-care function was below the average range for age (M = 38.01, SD = 12.19). The utility of the MAOM as a framework for comprehensive measurement of functional and motor outcomes of DCD in young children is discussed. (C) 2003 Elsevier B.V. All rights reserved.

Effect of organic amendments and solarisation on Fusarium wilt in susceptible banana plantlets, transplanted into naturally infested soil

Despite extensive research since pathogenicity was first established in 1919, no cultural or chemical control strategy has proven effective against Fusarium wilt of bananas. The efficacy of cultural control is attributed to the suppression of pathogen activity. Yet, amending naturally infested soil with aged chicken manure has been shown to enhance disease severity, without any change in the activity of the pathogen Fusarium oxysporum f. sp. cubense (Foc) in the soil. In this study, the effect of amending soil with composted sawdust, and of solarising soil, was compared with the effect of amending soil with chicken manure. Bioassays comparing the activity of Foc in the soil with the extent of invasion of banana pseudostem tissue by Foc were used to investigate why strategies targetting pathogen survival have not proven successful in controlling this disease. The enhancement of Foc invasion of the banana plantlets was reproduced with the addition of chicken manure to the naturally infested soil. However, changes in the activity of Foc in the soil were not associated with changes in the frequency of invasion of the plantlets. Invasion of banana pseudostems in the sawdust and solarisation treatments was not significantly different from invasion in the respective control treatments, despite a reduction in the activity of Foc in the sawdust-amended soil and an enhancement in the solarised soil. Moreover, the increase in Foc activity in the solarised soil recorded during the bioassays occurred despite the effectiveness of solarisation in reducing the survival of Foc in pre-colonised banana root tips buried in the soil. Changes in the frequency of invasion were associated with changes in the availability of mineral nitrogen, particularly ammonium N. These results suggest that the physiological response of banana cultivars to ammonium N may be associated with their susceptibility to Fusarium wilt. Accordingly, cultural strategies for controlling Panama disease will only be effective if they enhance the ability of the host to resist invasion.

Adult onset Krabbe disease may mimic motor neurone disease

Krabbe's disease (galactocerebrosidase deficiency) rarely presents in adults, usually with predominantly upper motor neurone clinical features. We report a case in whom the clinical features were similar to motor neurone disease. Nerve conduction studies and neuroimaging were important in leading to the correct diagnosis. Differences in adult-onset presentations are described. (C) 2003 Elsevier Science Ltd. All rights reserved.

Effect of changing data collection parameters on statistical motor unit number estimates

The effect of number of samples and selection of data for analysis on the calculation of surface motor unit potential (SMUP) size in the statistical method of motor unit number estimates (MUNE) was determined in 10 normal subjects and 10 with amyotrophic lateral sclerosis (ALS). We recorded 500 sequential compound muscle action potentials (CMAPs) at three different stable stimulus intensities (10–50% of maximal CMAP). Estimated mean SMUP sizes were calculated using Poisson statistical assumptions from the variance of 500 sequential CMAP obtained at each stimulus intensity. The results with the 500 data points were compared with smaller subsets from the same data set. The results using a range of 50–80% of the 500 data points were compared with the full 500. The effect of restricting analysis to data between 5–20% of the CMAP and to standard deviation limits was also assessed. No differences in mean SMUP size were found with stimulus intensity or use of different ranges of data. Consistency was improved with a greater sample number. Data within 5% of CMAP size gave both increased consistency and reduced mean SMUP size in many subjects, but excluded valid responses present at that stimulus intensity. These changes were more prominent in ALS patients in whom the presence of isolated SMUP responses was a striking difference from normal subjects. Noise, spurious data, and large SMUP limited the Poisson assumptions. When these factors are considered, consistent statistical MUNE can be calculated from a continuous sequence of data points. A 2 to 2.5 SD or 10% window are reasonable methods of limiting data for analysis. Muscle Nerve 27: 320–331, 2003

Chk1 regulates the S phase checkpoint by coupling the physiological turnover and ionizing radiation-induced accelerated proteolysis of Cdc25A

Chk1 kinase coordinates cell cycle progression and preserves genome integrity. Here, we show that chemical or genetic ablation of human Chk1 triggered supraphysiological accumulation of the S phase-promoting Cdc25A phosphatase, prevented ionizing radiation (IR)-induced degradation of Cdc25A, and caused radioresistant DNA synthesis (RDS). The basal turnover of Cdc25A operating in unperturbed S phase required Chk1-dependent phosphorylation of serines 123, 178, 278, and 292. IR-induced acceleration of Cdc25A proteolysis correlated with increased phosphate incorporation into these residues generated by a combined action of Chk1 and Chk2 kinases. Finally, phosphorylation of Chk1 by ATM was required to fully accelerate the IR-induced degradation of Cdc25A. Our results provide evidence that the mammalian S phase checkpoint functions via amplification of physiologically operating, Chk1-dependent mechanisms.

Nerve growth factor overexpression and autocrine loop in breast cancer cells

We show here that nerve growth factor (NGF), the canonical neurotrophic factor, is synthesized and released by breast cancer cells. High levels of NGF transcript and protein were detected in breast cancer cells by reverse transcription-PCR, Western blotting, ELISA assay and immunohistochemistry. Conversely, NGF production could not be detected in normal breast epithelial cells at either the transcriptional or protein level. Confocal analysis indicated the presence of NGF within classical secretion vesicles. Breast cancer cell-produced NGF was biologically active, as demonstrated by its ability to induce the neuronal differentiation of embryonic neural precursor cells. Importantly, the constitutive growth of breast cancer cells was strongly inhibited by either NGF-neutralizing antibodies or K-252a, a pharmacological inhibitor of NGF receptor TrkA, indicating the existence of an NGF autocrine loop. Together, our data demonstrate the physiological relevance of NGF in breast cancer and its potential interest as a marker and therapeutic target.