The sensitivity of carpal bone indices to rotational malpositioning

We investigated the dependence of 20 radiographic carpal measurements (carpal indices) on rotational positioning errors in posteroanterior and lateral radiographs. The measurements were made from "true perspective" digitally reconstructed radiographs created from computed tomography data. Most posteroanterior indices were not affected by rotation. Carpal height, carpal height ratio, revised carpal height ratio, capitate-radius distance, and carpal ulnar translocation were particularly robust. Lateral-view indices involving the scaphoid were the most sensitive to simulated malpositioning: radioscaphoid, scapholunate, and scaphocapitate angles were reduced from 58 degrees, 48 degrees, and 56 degrees at true lateral to 30 degrees, 24 degrees, and 34 degrees, respectively, at 20 degrees external rotation. Observers were unable to estimate the degree of malpositioning accurately in either view. Our results support use of the "scaphopisocapitate" criterion for assessing correct positioning in lateral plain radiographs.

Complementary signaling pathways regulate the unfolded protein response and are required for C. elegans development

The unfolded protein response (UPR) is a transcriptional and translational intracellular signaling pathway activated by the accumulation of unfolded proteins in the lumen of the endoplasmic reticulum (ER). We have used C. elegans as a genetic model system to dissect UPR signaling in a multicellular organism. C. elegans requires ire-1-mediated splicing of xbp-1 mRNA for UPR gene transcription and survival upon ER stress. In addition, ire-1/xbp-1 acts with pek-1, a protein kinase that mediates translation attenuation, in complementary pathways that are essential for worm development and survival. We propose that UPR transcriptional activation by ire-1 as well as translational attenuation by pek-1 maintain ER homeostasis. The results demonstrate that the UPR and ER homeostasis are essential for metazoan development.

The Caenorhabditis elegans homolog of FGD1, the human Cdc42 GEF gene responsible for faciogenital dysplasia, is critical for excretory cell morphogenesis

FGD1 mutations result in faciogenital dysplasia, an X-linked human disease that affects skeletogenesis. FGD1 encodes a guanine nucleotide exchange factor (GEF) that specifically activates the Rho GTPase Cdc42. To gain insight into the function of FGD1, we have isolated and characterized fgd-1, the Caenorhabditis elegans homolog of the human FGD1 gene. Comparative sequence analyses show that fgd-1 and FGD1 share a similar structural organization and a high degree of sequence identity throughout shared signaling domains. In nematodes, interference with fgd-1 expression results in excretory cell abnormalities and cystic dilation of the excretory cell canals. Molecular lesions associated with two exc-5 alleles affect the fgd-1 gene, and fgd-1 transgenic expression rescues the Exc-5 phenotype. Together, these data confirm that the fgd-1 transcript corresponds to the exc-5 gene. Transgenic expression studies show that fgd-1 has a limited pattern of expression that is confined to the excretory cell during development, a finding that suggests that the C.elegans FGD-1 protein might function in a cell autonomous manner. Serial observations indicate that fgd-1 mutations lead to developmental excretory cell abnormalities that cause cystic dilation and interfere with canal process extension. Based on these data, we conclude that fgd-1 is the C.elegans homolog of the human FGD1 gene, a new member of the FGD1-related family of RhoGEF genes, and that fgd-1 plays a critical role in excretory cell morphogenesis and cellular organization.

In Caenorhabditis elegans, the RNA-binding domains of the cytoplasmic polyadenylation element binding protein FOG-1 are needed to regulate germ cell fates

FOG-1 controls germ cell fates in the nematode Caenorhabditis elegans. Sequence analyses revealed that FOG-1 is a cytoplasmic polyadenylation element binding (CPEB) protein; similar proteins from other species have been shown to bind messenger RNAs and regulate their translation. Our analyses of fog-1 mutations indicate that each of the three RNA-binding domains of FOG-1 is essential for activity. In addition, biochemical tests show that FOG-1 is capable of binding RNA sequences in the 3'-untranslated region of its own message. Finally, genetic assays reveal that fog-1 functions zygotically, that the small fog-1 transcript has no detectable function, and that missense mutations in fog-1 cause a dominant negative phenotype. This last observation suggests that FOG-1 acts in a complex, or as a multimer, to regulate translation. On the basis of these data, we propose that FOG-1 binds RNA to regulate germ cell fates and that it does so by controlling the translation of its targets. One of these targets might be the fog-1 transcript itself.

A computational model of postoperative knee kinematics

A mathematical model for studying the passive kinematics of total knee prostheses can be useful in computer-aided planning and guidance of total joint replacement. If the insertion location and neutral length of knee ligaments is known, the passive kinematics of the knee can be calculated by minimizing the strain energy stored in the ligaments at any angular configuration of the knee. Insertions may be found intraoperatively, or may come from preoperative 3D medical images. The model considered here takes into consideration the geometry of the prosthesis and patient-specific information. This model can be used to study the kinematics of the knee joint of a patient after total joint replacement. The model may be useful in preoperative planning, computer-aided intraoperative guidance, and the design of new prosthetic joints.

Objective measures of dysphagia complexity in children related to suckle feeding histories, gestational ages, and classification of their cerebral palsy

Data collected during the routine assessment of 117 dysphagic children with cerebral palsy have been related to both suckle feeding histories and gestational ages and to the classification of cerebral palsy. In addition, a concurrent survey involving 281 children with cerebral palsy in special schools was undertaken which revealed that the sample of referred children appeared to be a true representation of a wider population of dysphagic children with cerebral palsy. A Feeding Difficulty Symptom Score (FDSS) describes the severity of swallowing symptoms reported. A numerical Dysphagia Complexity Index (DCI) quantifies numerically the neurological complexity of the swallowing difficulty. The FDSS correlates closely with the DCI. Twenty-seven percent of mothers of the children who were referred for advice on their present swallowing difficulties stated that they recalled no suckle feeding problems. However, there was no difference in the severity of present swallowing difficulties between those infants who suckle fed well and those who experienced severe difficulties. Those referred children with cerebral palsy born at term exhibited more complex later swallowing problems and were more likely to be classified as athetoid than those born preterm.

Specification of germ cell fates by FOG-3 has been conserved during nematode evolution

Rapid changes in sexual traits are ubiquitous in evolution. To analyze this phenomenon, we are studying species of the genus Caenorhabditis. These animals use one of two different mating systems-male/hermaphroditic, like the model organism Caenorhabditis elegans, or male/female, like C. remanei. Since hermaphrodites are essentially females that produce sperm for self-fertilization, elucidating the control of cell fate in the germ line in each species could provide the key to understanding how these mating systems evolved. In C. elegans, FOG-3 is required to specify that germ cells become sperm. Thus, we cloned its homologs from both C. remanei and C. briggsae. Each species produces a single homolog of FOG-3, and RNA-mediated interference indicates that FOG-3 functions in each species to specify that germ cells develop as sperm rather than as oocytes. What factors account for the different mating systems? Northern analyses and RT-PCR data reveal that the expression of fog-3 is always correlated with spermatogenesis. Since the promoters for all three fog-3 genes contain binding sites for the transcription factor TRA-1A and are capable of driving expression of fog-3 in C. elegans hermaphrodites, we propose that alterations in the upstream sex-determination pathway, perhaps acting through TRA-1A, allow spermatogenesis in C. elegans and C. briggsae XX larvae but not in C. remanei.

A cGMP-dependent protein kinase is implicated in wild-type motility in C. elegans

In mammals, cyclic GMP and cGMP-dependent protein kinases (cGKs) have been implicated in the regulation of many neuronal functions including long-term potentiation and long-term depression of synaptic efficacy. To develop Caenorhabditis elegans as a model system for studying the neuronal function of the cGKs, we cloned and characterized the cgk-1 gene. A combination of approaches showed that cgk-1 produces three transcripts, which differ in their first exon but are similar in length. Northern analysis of C. elegans RNA, performed with a probe designed to hybridize to all three transcripts, confirmed that a major 3.0 kb cgk-1 transcript is present at all stages of development. To determine if the CGK-1C protein was a cGMP-dependent protein kinase, CGK-1C was expressed in SF:9 cells and purified. CGK-1C shows a K(a) of 190 +/- 14 nM for cGMP and 18.4 +/- 2 microM for cAMP. Furthermore, CGK-1C undergoes autophosphorylation in a cGMP-dependent manner and is inhibited by the commonly used cGK inhibitor, KT5823. To determine which cells expressed CGK-1C, a 2.4-kb DNA fragment from the promoter of CGK-1C was used to drive GFP expression. The CGK-1C reporter construct is strongly expressed in the ventral nerve cord and in several other neurons as well as the marginal cells of the pharynx and intestine. Finally, RNA-mediated interference of CGK-1 resulted in movement defects in nematode larvae. These results provide the first demonstration that cGMP-dependent protein kinase is present in neurons of C. elegans and show that this kinase is required for normal motility.

Regulation of cell fate in Caenorhabditis elegans by a novel cytoplasmic polyadenylation element binding protein

The fog-1 gene of Caenorhabditis elegans specifies that germ cells differentiate as sperm rather than as oocytes. We cloned fog-1 through a combination of transformation rescue experiments, RNA-mediated inactivation, and mutant analyses. Our results show that fog-1 produces two transcripts, both of which are found in germ cells but not in the soma. Furthermore, two deletion mutants alter these transcripts and are likely to eliminate fog-1 activity. The larger transcript is expressed under the control of sex-determination genes, is necessary for fog-1 activity, and is sufficient to rescue a fog-1 mutant. This transcript encodes a novel member of the CPEB family of RNA-binding proteins. Because CPEB proteins in Xenopus and Drosophila regulate gene expression at the level of translation, we propose that FOG-1 controls germ cell fates by regulating the translation of specific messenger RNAs.

Fixation-based surgery: a new technique for distal radius osteotomy

OBJECTIVE

The objective was to develop a fixation-based three-dimensional presurgical planner and an intraoperative guidance system for distal radius osteotomy. Fixation-based surgery is a technique premised on using a fixation device, such as a fracture-fixation plate, during the alignment and distraction phases of an osteotomy.

MATERIALS AND METHODS

The planning system and guidance system were coded using OpenGL on UNIX workstations. In vitro tests were performed to compare the reproducibility of the computer-enhanced technique to that of the traditional technique, and an in vivo pilot study was initiated.

RESULTS

In vitro, the computer-enhanced technique produced a significant reduction by more than one half in both the maximum error of correction and the standard deviation of the correction error. Preliminary in vivo results on six patients suggest that similar error diminution will occur during regular clinical application of the technique.

CONCLUSIONS

Both studies showed that the computer system is simple to use. The planning system allowed the surgeon to perform multiple simulations of the surgical procedure preoperatively, which were used to optimize the plan and identify potential problems during realignment. The use of a fixation-based technique avoided the complexity of attempting to guide the surgeon to realign a bone fragment in six degrees of freedom of correction, and eliminated the use of X-ray fluoroscopy for achieving the alignment.

Feeding efficiency and respiratory integration in infants with acute viral bronchiolitis

OBJECTIVE

To examine the effects of bronchiolitis on feeding efficiency and respiratory integration.

STUDY DESIGN

We studied 21 infants with bronchiolitis and 21 bottle-fed healthy infants who formed a comparison group. Repeat evaluations of half the bronchiolitis group were performed during recovery. During each feeding study we measured the duration and frequency of sucking, the frequency of single and multiple swallows, the respiratory rate, the postswallow respiratory direction, and the suck and swallow volumes.

RESULTS

The infants with bronchiolitis devoted significantly less time to sucking than their healthy peers (P <.05), and the mean suck volume was reduced. Although the frequency of swallowing was slightly higher, the volume of milk consumed per swallow was almost half the amount consumed by the comparison group (P <.01). Coordination of breathing with swallowing was also less effective (P <.01).

CONCLUSION

Although most aspects of feeding are less efficient during periods of respiratory illness, others are preserved or recover rapidly. Coordination of breathing during feeding is also significantly impaired.

Non-invasive assessment of swallowing and respiration in Parkinson's disease

Oro-pharyngeal dysphagia is well recognised but often underestimated in people with Parkinson's disease. Asymptomatic patients may fail to receive timely advice or therapy, thus placing them at risk. The aim of this study was to determine whether subclinical abnormalities in swallowing and discrete changes in function such as those produced by prompting can be detected by non-invasive methods. We examined 12 people with idiopathic Parkinson's disease and 14 elderly comparison subjects. Five components of respiratory synchronisation and swallowing efficiency were monitored using the Exeter Dysphagia Assessment Technique. Ten feeding trials were administered under standard quiet conditions. The patients were then restudied using verbal prompts when the spoon was presented to the mouth. The duration of two oro-pharyngeal events and the frequency of respiratory variables were compared for unrelated and related samples. Results showed the oral and pharyngeal parts of the swallow to be significantly slower in those with Parkinson's disease. These patients required significantly more swallows to clear a 5-ml bolus, and fewer swallows were followed by expiration. When the patients were verbally prompted, there was a significant reduction in the duration of the oral part. This study demonstrates that non-invasive methods can be used to detect subclinical difficulties with swallowing amongst a group of asymptomatic patients with PD and that these methods are sensitive to small changes in function produced by a verbal cue.

Disruption of the CED-9.CED-4 complex by EGL-1 is a critical step for programmed cell death in Caenorhabditis elegans

In the nematode Caenorhabditis elegans, the apoptotic machinery is composed of four basic elements: the caspase CED-3, the Apaf-1 homologue CED-4, and the Bcl-2 family members CED-9 and EGL-1. The ced-9(n1950) gain-of-function mutation prevents most, if not all, somatic cell deaths in C. elegans. It encodes a CED-9 protein with a glycine-to-glutamate substitution at position 169, which is located within the highly conserved Bcl-2 homology 1 domain. We performed biochemical analyses with the CED-9G169E protein to gain insight into the mechanism of programmed cell death. We find that CED-9G169E retains the ability to bind both EGL-1 and CED-4, although its affinity for EGL-1 is reduced. In contrast to the behavior of wild-type CED-9, the interaction between CED-9G169E and CED-4 is not disrupted by expression of EGL-1. Furthermore, CED-4 and CED-9G169E co-localizes with EGL-1 to the mitochondria in mammalian cells, and expression of EGL-1 does not induce translocation of CED-4 to the cytosol. Finally, the ability of EGL-1 to promote apoptosis is impaired by the replacement of wild-type CED-9 with CED-9G169E, and this effect is correlated with the inability of EGL-1 to induce the displacement of CED-4 from the CED-9.CED-4 complex. These studies suggest that the release of CED-4 from the CED-9.CED-4 complex is a necessary step for induction of programmed cell death in C. elegans.

Non-invasive technique for assessment and management planning of oral-pharyngeal dysphagia in children with cerebral palsy

The non-invasive Exeter Dysphagia Assessment Technique (EDAT) was evaluated as a method of assessing the aetiology of dysphagia in children with cerebral palsy (CP). Data were collected from a group of 20 typically developing children (nine girls, 11 boys; age range 7 to 14 years) for comparison with 125 dysphagic children with CP (81 boys, 44 girls; age range 1 to 18 years). The swallowing mechanism has been separated into physiological phases: anticipatory, delivery, oral transit, and oral-pharyngeal. Normal or abnormal function in each phase was recorded and the common causes of any impaired phase were considered, starting with generalized possibilities before focusing on specific parts of swallowing physiology. Data from 125 dysphagic children with CP show marked differences from the data for the typically developing children. Interpreting individual results was valuable in assisting the assessment team to formulate management strategies; two examples are presented. The technique appears to provide a cost-effective, non-invasive, and valuable clinical tool.

TRA-1A regulates transcription of fog-3, which controls germ cell fate in C. elegans

In C. elegans, the zinc-finger protein TRA-1A is thought to be the final arbiter of somatic sexual identity. We show that fog-3, which is required for germ cells to become sperm rather than oocytes, is a target of TRA-1A. First, northern analyses and RT-PCR experiments indicate that expression of fog-3 is controlled by tra-1. Second, studies of double mutants show that this control could be direct. Third, the fog-3 promoter contains multiple sites that bind TRA-1A in gel shift assays, and mutations in these sites alter activity of fog-3 in vivo. These results establish fog-3 as one of the first known targets of transcriptional regulation by TRA-1A. Furthermore, they show that tra-1 controls a terminal regulator of sexual fate in germ cells, just as it is thought to do in the soma.

Air swallowing in Rett syndrome

The possible causes of excessive swallowing of air leading to bloating, which is common in Rett syndrome (RS), were investigated during feeding and at rest. Seven individuals with RS aged between 4 and 33 years (three with air bloat) underwent feeding videoflouroscopy and concurrent respiration monitoring. The results were compared with a randomly selected group of 11 individuals, aged between 2 and 16 years, with quadriplegic cerebral palsy and feeding problems, some of whom had mild air bloat. All individuals from both groups had isolated pharyngeal swallows and several mouth breathed; this may account for some air swallowing but not the severe air bloat characteristic of RS. Thirty-three individuals with RS aged between 3 and 44 years were monitored for nasal respiration, chest movements, swallowing, and vocal cord position at rest (between feeding). Twenty had air bloat, 17 of whom swallowed air during breath-holding in the same way, and three gulped air during hyperventilation. Of the 13 without air bloat, eight did not have recurrent breath-holding and five did, but without concurrent air swallowing. Several methods for reducing air swallowing in apnoea were investigated. The most successful was a dummy with an air leak, but this was poorly tolerated and could only be used for short periods of time. Apnoeas and air bloat are often worse when individuals are distressed and may in some individuals be reduced by anxiolytic medications.

A novel member of the tob family of proteins controls sexual fate in Caenorhabditis elegans germ cells

Although many cell fates differ between males and females, probably the most ancient type of sexual dimorphism is the decision of germ cells to develop as sperm or as oocytes. Genetic analyses of Caenorhabditis elegans suggest that fog-3 might directly control this decision. We used transformation rescue to clone the fog-3 gene and show that it produces a single major transcript of approximately 1150 nucleotides. This transcript is predicted to encode a protein of 263 amino acids. One mutation causes a frame shift at the sixth codon and is thus likely to define the null phenotype of fog-3. Although the carboxyl-terminus of FOG-3 is novel, the amino-terminal domain is similar to that of the Tob, BTG1, and BTG2 proteins from vertebrates, which might suppress proliferation or promote differentiation. This domain is essential for FOG-3 activity, since six of eight missense mutations map to this region. Furthermore, this domain of BTG1 and BTG2 interacts with a transcriptional regulatory complex that has been conserved in all eukaryotes. Thus, one possibility is that FOG-3 controls transcription of genes required for germ cells to initiate spermatogenesis rather than oogenesis. This model implies that FOG-3 is required throughout an animal's life for germ cells to initiate spermatogenesis. We used RNA-mediated interference to demonstrate that fog-3 is indeed required continuously, which is consistent with this model.

A surgical planning and guidance system for high tibial osteotomy

OBJECTIVE

To develop a three-dimensional pre-surgical planner and an intraoperative guidance system for high tibial osteotomy. The parameters that describe the placement and orientation of the osteotomy resection planes were to be transmitted to an accompanying guidance system that allowed the surgeon to reproducibly perform the planned procedure.

MATERIALS AND METHODS

The planning system and guidance system were coded using OpenGL on UNIX workstations. In vitro tests were performed to compare the reproducibility of the computer-enhanced technique to that of the traditional technique, and an in vivo pilot study was initiated.

RESULTS

In vitro, the computer-enhanced technique produced a significant reduction, by one half, in both the maximum error of correction and the standard deviation of the correction error. Preliminary in vivo results on six patients suggest that similar error diminution will occur during regular clinical application of the technique.

CONCLUSIONS

Both studies showed that the computer system is simple to use. The work suggests that three-dimensional planning and performance of high tibial osteotomy is essential for accurate correction of the alignment of the lower limb.

Dose dependency of dextromethorphan for cytochrome P450 2D6 (CYP2D6) phenotyping

Most dextromethorphan CYP2D6 phenotyping studies use a 30-mg dose, but data that show superiority of any particular dose are lacking. We compared metabolic ratios from six different dextromethorphan phenotyping doses to ascertain whether linearity existed over a dosage range. Forty subjects were enrolled in the study. Each subject received 0.05 mg/kg, 0.15 mg/kg, 0.3 mg/kg, 30 mg, 0.8 mg/kg, and 1.2 mg/kg dextromethorphan in a randomized crossover fashion. Urinary dextromethorphan to dextrorphan molar ratios were used to measure CYP2D6 activity. Single blood samples were obtained for CYP2D6 genotyping, which revealed one poor metabolizer and 39 extensive metabolizers. A statistical difference was found for the molar ratio between the 0.8 mg/kg and the 1.2 mg/kg dose compared with the other four doses. None of the 39 genotypic extensive metabolizers were incorrectly phenotyped with any of these doses. These data support the use of moderate doses of dextromethorphan for phenotyping to avoid dose dependency.

C. elegans MAC-1, an essential member of the AAA family of ATPases, can bind CED-4 and prevent cell death

In the nematode Caenorhabditis elegans, CED-4 plays a central role in the regulation of programmed cell death. To identify proteins with essential or pleiotropic activities that might also regulate cell death, we used the yeast two-hybrid system to screen for CED-4-binding proteins. We identified MAC-1, a member of the AAA family of ATPases that is similar to Smallminded of Drosophila. Immunoprecipitation studies confirm that MAC-1 interacts with CED-4, and also with Apaf-1, the mammalian homologue of CED-4. Furthermore, MAC-1 can form a multi-protein complex that also includes CED-3 or CED-9. A MAC-1 transgene under the control of a heat shock promoter prevents some natural cell deaths in C. elegans, and this protection is enhanced in a ced-9(n1950sd)/+ genetic background. We observe a similar effect in mammalian cells, where expression of MAC-1 can prevent CED-4 and CED-3 from inducing apoptosis. Finally, mac-1 is an essential gene, since inactivation by RNA-mediated interference causes worms to arrest early in larval development. This arrest is similar to that observed in Smallminded mutants, but is not related to the ability of MAC-1 to bind CED-4, since it still occurs in ced-3 or ced-4 null mutants. These results suggest that MAC-1 identifies a new class of proteins that are essential for development, and which might regulate cell death in specific circumstances.

Total knee arthroplasty kinematics. Computer simulation and intraoperative evaluation

The goal of this work was to develop computer simulations for intraoperative testing of the passive kinematics of knee prostheses. These are based on an anatomic model of the reconstructed joint, represented in the sagittal plane. A femoral component and a tibial component are linked by 3 springs that model the relevant ligaments, with the posterior cruciate providing the primary constraint. The components' behavior at each flexion angle is obtained by minimizing the total strain energy stored in the ligaments. Simulations were performed in vivo on 10 Interax implants (Howmedica International, Stain, UK) and showed good agreement with intraoperative observations, allowing monitoring of new parameters such as contact point motion, ligament strains, and the energetic state of the knee. This work contributes to the comprehension of individual knee kinematics after total knee arthroplasty, to improve long-term results and standardize the evaluation of the results of joint restoration.

Respiration patterns during feeding in Rett syndrome

Feeding problems are common in Rett syndrome in which there are characteristic oropharyngeal abnormalities. This study investigated the ways in which individuals regulated their respiration accordingly, and how this affected their overall feeding ability. Respiration during feeding was studied in 28 individuals, recording nasal airflow, chest and abdominal movements, and swallow sounds. Time to first swallow was defined as that between introduction of liquid/solid on a spoon and the first swallow. Six individuals also had videofluoroscopy with simultaneous respiration monitoring. Results indicated different respiratory patterns according to the time to first swallow and neurological status; the amount of time spent in apnoea was particularly important. Videofluoroscopy showed that apnoeas occurred most often when liquid was delayed in the pharynx, but this could be overcome in subjects with a lower level of disability. The carer's estimate of the time for feeding was significantly related to the time spent in apnoea with liquids.

Deglutition apnoea as indicator of maturation of suckle feeding in bottle-fed preterm infants

The maturation of deglutition apnoea time was investigated in 42 bottle-fed preterm infants, 28 to 37 weeks gestation, and in 29 normal term infants as a comparison group. Deglutition apnoea times reduced as infants matured, as did the number and length of episodes of multiple-swallow deglutition apnoea. The maturation appears related to developmental age (gestation) rather than feeding experience (postnatal age). Prolonged (> 4 seconds) episodes of deglutition apnoea remained significantly more frequent in preterm infants reaching term postconceptual age compared to term infants. However, multiple-swallow deglutition apnoeas also occurred in the term comparison group, showing that maturation of this aspect is not complete at term gestation. The establishment of normal data for maturation should be valuable in assessing infants with feeding difficulties as well as for evaluation of neurological maturity and functioning of ventilatory control during feeding.