Biomedical subjects

C Haun

Publications and source records attributed to C Haun.

12 recordsLinked to original sources

PubMed2006

A musculo-skeletal model of rat ankle motion and its experimental test on rat.

A biomechanical musculo-skeletal model of functional electrical stimulation (FES)-induced rat ankle motion was implemented and tested in rat experiments. The muscle model is a new Hill-based model which includes established physiological relations of force-velocity and force-length-frequency. However, the series-elastic component and the activation component of previous Hill-based models are replaced by a new component which accounts for dynamic time delays and recruitment that occur in real muscle force generation during limb movements. The skeletal model includes gravity and dynamic forces that occur in real rat ankle motions. In computer simulations, various FES patterns were applied to the tibialis anterior (TA) and soleus (SO) model muscles to produce walk-like ankle motions. In lab experiments, the same stimulation patterns were applied by epimysial electrodes implanted in the TA and SO muscles of live rats cordotomized at level T7. The resulting rat motions were recorded by video camera. Video data was converted to ankle angle-vs-time files for comparison with corresponding model angle-vs-time files. Over a physiologically significant range of ankle motions, model parameters were adjustable to yield model motions that agreed with rat motions to within 2 degrees (root mean square differences of rat and model ankle angles). This is shown in plots of model and rat motions presented here for representative cases of FES. The accuracy of our model in reproducing real ankle motions supports the hypothesis that our new muscle model generates correct muscle forces over a useful range of limb motions. It suggests that the model may be useful in the design of FES neural prostheses.

Animals↗

PubMed2002

Biventricular repair of double outlet right ventricle with non-committed ventricular septal defect (VSD) by VSD rerouting to the pulmonary artery and arterial switch.

OBJECTIVES: Biventricular repair of double outlet right ventricle non-committed ventricular septal defect (DORVncVSD) is usually achieved by a VSD rerouting to the aorta. This technique can be limited by the presence of tricuspid chordae and by the pulmonary artery to tricuspid valve distance. Furthermore, there is an important risk of late subaortic obstruction related to the long patch required that creates a potential akinetic septal area. Presented here is another technique; by VSD rerouting to the pulmonary infundibulum and arterial switch. METHODS: Ten patients, with DORVncVSD, underwent a VSD rerouting to the pulmonary infundibulum followed by arterial switch. Seven had a previous pulmonary artery banding and one a moderate infundibular stenosis. The median age at surgery was 16 months (range 3 weeks to 4.5 years). All patients had a bilateral infundibulum, with a large persistent subaortic conus, D malposition of the aorta, side-by-side vessels and double loop coronary patterns. The VSD was perimembranous with inlet or trabecular extension. Subaortic obstruction was constant. The VSD was severely distant from both the aortic and the pulmonary annulus. The operation was conducted through a combined approach. The VSD was constantly enlarged superiorly. The almost permanent subaortic obstruction was released. The VSD was always found quite close to the pulmonary infundibular ostium. The arterial switch technique was adapted to the complex coronary anatomy. RESULTS: There was one non-cardiac death. At a mean follow-up of 20 months, all nine survivors are in NYHA class I, in sinus rhythm, and have no subaortic gradient greater than 15 mm. CONCLUSION: This technique of VSD rerouting to the pulmonary artery and arterial switch limits greatly the size of the rerouting patch, respects the tricuspid chordae and is independent of the pulmonary artery-tricuspid valve distance. In this early series of biventricular repair of DORVncVSD, the VSDs were always found close to the pulmonary artery, allowing this new type of repair.

Cardiac Surgical Procedures↗

PubMed2001

The Caenorhabditis elegans peb-1 gene encodes a novel DNA-binding protein involved in morphogenesis of the pharynx, vulva, and hindgut.

Gene expression in the Caenorhabditis elegans pharynx is regulated in part by organ-specific signals, which in the myo-2 gene target a regulatory sequence called the C sub-element. C sub-element activity requires the organ specification factor PHA-4, a winged-helix transcription factor expressed in all pharyngeal cells. To identify additional factors involved in pharyngeal organogenesis, we performed a yeast one-hybrid screen for C sub-element binding proteins. Here we describe the novel factor PEB-1, which is coexpressed with PHA-4 in many pharyngeal cell types, including muscles, epithelial cells, marginal cells, and glands, but is undetectable in the pharyngeal nervous system. PEB-1 is also detected outside the pharynx in cells surrounding the rectum and vulva, as well as in the germ line. Reduction of peb-1 function using RNAi results in morphological defects in the somatic tissues in which peb-1 is expressed. We have mapped the PEB-1 DNA-binding domain to a 158-residue region, which is unrelated to known DNA-binding proteins but shares some sequence similarity to the Drosophila Mod(mdg4) proteins. PEB-1 specifically recognizes a site in the C subelement that partially overlaps the PHA-4 binding site. Both the PEB-1 and the PHA-4 binding sites are necessary for strong C sub-element enhancer activity in some cells in which these factors are coexpressed. In contrast the PEB-1 site is dispensable for C sub-element activity in pharyngeal neurons. We propose that PEB-1 functions with PHA-4 to activate target gene expression in cells in which they are coexpressed.

Amino Acid Sequence↗

PubMed2000

Nosocomial outbreak of vancomycin-resistant Enterococcus faecium at a German university pediatric hospital.

Nosocomial Infections caused by vancomycin-resistant enterococci (VRE) are an emerging threat to critically ill patients. At the University Hospital Eppendorf, VRE were isolated from 38 patients between August 1993 and April 1997, of whom 32 were hospitalized at the Department of Pediatrics. Pulsed-field gel electrophoresis revealed that 26 Enterococcus faecium isolates from patients of the Department of Pediatrics were identical or closely related, and that isolates from three additional patients of the same department were possibly related. All of these isolates were of vanA genotype. They were resistant to glycopeptides, ampicillin, ciprofloxacin, clindamycin, and erythromycin. Most isolates displayed high-level resistance to gentamicin, but all remained susceptible to quinupristin/dalfopristin. Implementation of stringent hand disinfection and environmental disinfection policies, as well as measures for patient isolation contained this first outbreak of VRE at a German Children's hospital, which emphasizes the importance of hygienic measures for the control of nosocomial spread of these organisms.

Child, Preschool↗

PubMed1999

The DAF-3 Smad binds DNA and represses gene expression in the Caenorhabditis elegans pharynx.

Gene expression in the pharyngeal muscles of Caenorhabditis elegans is controlled in part by organ-specific signals, which in the myo-2 gene target a short DNA sequence termed the C subelement. To identify genes contributing to these signals, we performed a yeast one-hybrid screen for cDNAs encoding factors that bind the C subelement. One clone recovered was from daf-3, which encodes a Smad most closely related to vertebrate Smad4. We demonstrated that DAF-3 binds C subelement DNA directly and specifically using gel mobility shift and DNase1 protection assays. Mutation of any base in the sequence GTCTG interfered with binding in the gel mobility shift assay, demonstrating that this pentanucleotide is a core recognition sequence for DAF-3 binding. daf-3 is known to promote formation of dauer larvae and this activity is negatively regulated by TGFbeta-like signaling. To determine how daf-3 affects C subelement enhancer activity in vivo, we examined expression a gfp reporter controlled by a concatenated C subelement oligonucleotide in daf-3 mutants and other mutants affecting the TGFbeta-like signaling pathway controlling dauer formation. Our results demonstrate that wild-type daf-3 can repress C subelement enhancer activity during larval development and, like its dauer-promoting activity, daf-3's repressor activity is negatively regulated by TGFbeta-like signaling. We have examined expression of this gfp reporter in dauer larvae and have observed no daf-3-dependent repression of C activity. These results suggest daf-3 directly regulates pharyngeal gene expression during non-dauer development.

Animals↗

PubMed1998

Rescue of Caenorhabditis elegans pharyngeal development by a vertebrate heart specification gene.

Development of pharyngeal muscle in nematodes and cardiac muscle in vertebrates and insects involves the related homeobox genes ceh-22, nkx2.5, and tinman, respectively. To determine whether the nematode and vertebrate genes perform similar functions, we examined activity of the zebrafish nkx2.5 gene in transgenic Caenorhabditis elegans. Here, we report that ectopic expression of nkx2.5 in C. elegans body wall muscle can directly activate expression of both the endogenous myo-2 gene, a ceh-22 target normally expressed only in pharyngeal muscle, and a synthetic reporter construct controlled by a multimerized CEH-22 binding site. nkx2.5 also efficiently rescues a ceh-22 mutant when expressed in pharyngeal muscle. Together, these results indicate that nkx2.5 and ceh-22 provide a single conserved molecular function. Further, they suggest that an evolutionarily conserved mechanism underlies heart development in vertebrates and insects and pharyngeal development in nematodes.

Amino Acid Sequence↗

PubMed1997

The Caenorhabditis elegans NK-2 homeobox gene ceh-22 activates pharyngeal muscle gene expression in combination with pha-1 and is required for normal pharyngeal development.

Pharyngeal muscle development in the nematode Caenorhabditis elegans appears to share similarities with cardiac muscle development in other species. We have previously described CEH-22, an NK-2 class homeodomain transcription factor similar to Drosophila tinman and vertebrate Nkx2-5, which is expressed exclusively in the pharyngeal muscles. In vitro, CEH-22 binds the enhancer from myo-2, a pharyngeal muscle-specific myosin heavy chain gene. In this paper, we examine the role CEH-22 plays in pharyngeal muscle development and gene activation by (a) ectopically expressing ceh-22 in transgenic C. elegans and (b) examining the phenotype of a ceh-22 loss-of-function mutant. These experiments indicate that CEH-22 is an activator of myo-2 expression and that it is required for normal pharyngeal muscle development. However, ceh-22 is necessary for neither formation of the pharyngeal muscles, nor for myo-2 expression. Our data suggest parallel and potentially compensating pathways contribute to pharyngeal muscle differentiation. We also examine the relationship between ceh-22 and the pharyngeal organ-specific differentiation gene pha-1. Mutations in ceh-22 and pha-1 have strongly synergistic effects on pharyngeal muscle gene expression; in addition, a pha-1 mutation enhances the lethal phenotype caused by a mutation in ceh-22. Wild-type pha-1 is not required for the onset of ceh-22 expression but it appears necessary for maintained expression of ceh-22.

Animals↗

PubMed1981

Comparison of the barium test meal and the gamma camera scanning technic in measuring gastric emptying.

In 21 patients with nonresected stomachs and symptoms of delayed gastric emptying, obstruction was excluded by upper gastrointestinal series and upper endoscopy; all had abnormal results of barium test meal (BTM) study. Each had repeat BTM after the administration of 10 mg of metoclopramide. Each patient also had two gamma camera studies after a technetium Tc 99m sulfur colloid labeled meal; normal saline or metoclopramide was administered before each test in a blinded and random manner. Half-time (T1/2) and percentage of isotope remaining at six hours (GC6) were recorded. Ten asymptomatic controls had a gamma camera scanning study, and seven of these had a BTM. Nine of 19 patients had a T1/2 in the normal range, and in 12 of 19 patients the GC6 was in the normal range. The magnitude of retention of barium at six hours on the BTM did not correlate with the T1/2 (r = 0.076) or the GC6 (r= 0.296). Thus, these tests were not comparable in this study. By regression analysis, a significant reduction was shown in the amount of retained food and barium (P less than .01), the T1/2 (P less than .01), and the GC6 (P less than .01) after intramuscular administration of metoclopramide, indicating that both tests were able to evaluate the effects of this drug.

Adult↗

PubMed1980

Laser therapy of rheumatoid arthritis.

Thirty people with classical or definite rheumatoid arthritis received laser exposure to a Q-switch neodymium laser that operated at 1.06 micrometer with an output of 15 joules/cm2 for 30 nsec. One hand was lased at the proximal interphalangeal (PIP) and metacarpal phalangeal (MCP) joints, whereas the other hand was sham lased. The patient, physician, and occupational therapy evaluators did not know which hand was being lased. Twenty-one patients noted improvement of both their MCP and PIP joints of both hands during laser therapy. Twenty-seven noted improvement of their PIP joints and 26 noted improvement of the MCP joints during therapy. Heat, erythema, pain, swelling, and tenderness all improved with time in both hands, but the lased hand had more significant improvement in erythema and pain. There was also significant improvement in grasp and tip pressure on the lased side. The level of circulating immune complexes as measured by platelet aggregation decreased during lasing. The improvement may be related to laser exposure. The exact role that laser radiation has upon rheumatoid arthritis and its mechanism of action remain to be elucidated.

Adult↗

PubMed1980

Acute calcific quadriceps tendinitis.

Acute calcific quadriceps tendinitis can be the cause of acute periarthritis of the knee. Physical examination can detect cellulitis and a tender tendon sheath. Lateral roentgenograms of soft tissues show thickening of the tendon and sometimes small flecks of amorphous calcification within the body of the tendon near the attachment. Although hyperostosis of the patella near the tendon attachment is often present, it is well defined ossification and not associated with the acute symptoms. The amorphous calcium deposits quickly disappear during the acute tendinitis and are not detected on follow-up radiologic examination.

Acute Disease↗

PubMed1980

Developmental defects of the distal femoral metaphysis.

The posteromedial aspect of the distal end of the femur in the area of insertion of the adductor magnus is the site of occurrence of a developmental defect that may have the roentgenographic characteristics of a malignant bone tumor. As it is asymptomatic, this common defect is almost always an incidental finding, but it has been confused with osteosarcoma. The lesion is thought to be due to trauma or the avulsion of small bits of bone at the site of insertion of the adductor magnus muscle. Histologically the lesion has been mistaken for osteosarcoma because of the immature reactive bone and fibrous tissue presnet. It is usually possible to identify these defects roentgenographically and avoid biopsy.

Adolescent↗

PubMedDate not supplied

Utility of N-terminal brain natriuretic peptide plasma concentrations in comparison to lactate and troponin in children with congenital heart disease following open-heart surgery.

We conducted a prospective study in a pediatric cardiac intensive care unit in order to determine the diagnostic value of N-terminal brain natriuretic peptide (N-BNP) plasma concentration in the perioperative care of children with congenital heart disease (CHD). N-BNP plasma concentrations were determined by using a validated enzyme immunoassay. We measured N-BNP the day before surgery and up to 15 days postoperatively in 23 children (age range, 0.25-11 years) undergoing cardiac surgery due to various CHDs. Supply and duration of catecholamines, vasodilators, and respiratory therapy were determined and correlated to N-BNP. In addition, troponin T (TnT) and arterial Lactat (aL) concentrations were measured simultaneously. We found a significant correlation between preoperative and maximal N-BNP levels and dosage of vasodilators (r = 0.41, p < 0.02 and r = 0.83, p < 0.01, respectively). Maximal TnT and aL levels were not correlated to dosage of vasodilators. The dosage and duration of catecholamines, the duration of respiratory therapy, and the plasma concentration of TnT and aL were not correlated to pre- or perioperative N-BNP. Maximal TnT and aL levels were correlated to duration (r = 0.53, p < 0.01 and r = 0.48, p < 0.02) and dosage (r = 0.52, p < 0.02 and r = 0.60, p < 0.01) of catecholamines and duration of respiratory therapy (r = 0.57, p < 0.01 and r = 0.50, p < 0.02). As recent studies show, N-BNP appears to be a powerful neurohumoral indicator of ventricular function and prognosis for guiding therapy in the outpatient department or for discriminating cardiac from noncardiac symptoms. In contrast, the value of N-BNP for guiding perioperative therapy in pediatric cardiac intensive care units is limited.

Child↗