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Biomedical subjects

C Walther

Publications and source records attributed to C Walther.

At least 37 records · Page 2Linked to original sources
PubMed1999

Early clinical results after stentless mitral valve implantation and comparison with conventional valve repair or replacement.

BACKGROUND: A new quadricusp stentless mitral bioprosthetic valve (QMV) is evaluated and compared with current standards. METHODS AND RESULTS: Since August 1997, 67 patients were prospectively evaluated: 23 patients received a QMV, 23 had mitral valve repair (MVR), and 21 received conventional mitral valve replacement (MVP). Patient age was 69+/-8, 64+/-10, and 62+/-9 years for QMV, MVR, and MVP treatment, respectively. The underlying pathology was mitral stenosis, incompetence, and mixed disease in a corresponding 8, 9, and 6 patients for QMV, 1, 22, and 0 patients for MVR, and 2, 12, and 7 patients for MVP. The papillary muscles were sufficient in all QMV cases to suspend the valve. Cross-clamp time was 59+/-19 minutes for QMV implantation. In-hospital mortality for QMV, MVR, and MVP was 1, 0, and 0 patients, respectively, and thoracotomy had to be performed again in 1, 1, and 2 patients, respectively (these outcomes were not valve related). At baseline transthoracic echocardiography, respective maximum flow velocities were 1.6, 1.4, and 1.7 m/s, and valve orifice area was 2.6, 3.5, and 3.4 cm(2). Mild transvalvular reflux was seen in 8, 7, and 2 patients; moderate reflux, in 1, 1, and 1 patients. Left ventricular ejection fraction was 52%, 54%, and 51% in the respective treatment groups. At follow-up, hemodynamic parameters had further improved in all groups. CONCLUSIONS: One year after clinical implantation, the QMV appears to function well and has no additional risks compared with MVR or MVP. The subvalvular apparatus is preserved by suspending the QMV at the papillary muscles; this arrangement is hemodynamically advantageous. Echocardiography reveals an excellent valve performance that resembles native mitral valve morphology and hemodynamic function. The QMV is a promising alternative for biological mitral valve replacement.

Aged↗
PubMed1999

Stentless tricuspid valve replacement.

Stentless tricuspid valve replacement was performed in a 21-year-old patient with severe destructive tricuspid valve endocarditis resistant to medical therapy. Postoperative recovery was uneventful. Stentless atrioventricular valves are considered an additional treatment option besides stented valves or homograft implantations for severe right-sided endocarditis. Transvalvular hemodynamics are excellent, and right ventricular function can be preserved by suspending the valve at the papillary muscles.

Adult↗
PubMed1999

Quadrileaflet stentless mitral valve replacement.

BACKGROUND: The study evaluates clinical results and hemodynamic parameters one year after implantation of a stentless quadrileaflet mitral valve (QMV). METHODS: Since August 1997 28 patients received the QMV, patient age was 69 +/- 8 years; 13 had predominant mitral stenosis and 15 incompetence, preoperative NYHA functional class was III or IV and cardiac index 1.8 +/- 0.6 L/min/m2. RESULTS: Surgery was performed using a conventional (25) or a minimally invasive approach (3). 20 patients received a medium and 8 a large-size prosthesis, crossclamp time was 58 +/- 19 min. Additional procedures were myocardial revascularization in four, tricuspid repair in two, and left-atrial radiofrequency ablation to restore sinus rhythm in six patients. Perioperative mortality (1) was not valve-related. All other patients were discharged on time. At postoperative, 6-, and 12-months follow-up mean transvalvular pressure gradients were 4.2 +/- 1.5 / 4 +/- 0.9/ 3.8 +/- 1.4 mmHg and mitral valve orifice area index was 1.5 +/- 0.3 / 1.6 +/- 0.3 / 1.6 +/- 0.4, NYHA class was I or II. CONCLUSIONS: The QMV is well suited for mitral valve replacement. The anulo-ventricular continuity is preserved and the QMV function resembles native mitral valve function. If its performance is maintained in the long term the QMV may be the mitral prosthesis of choice.

Aged↗
PubMed1999

Stentless mitral valve replacement using the quattro valve.

This study analyzed early clinical results after stentless mitral valve (Quadrileaflet Mitral Valve (QMV)/Quattro) implantation. A total of 28 patients have received a Quattro valve since August 1997. Patient age was 69+/-8 years; the underlying disease was mitral incompetence (14) and stenosis (13). Preoperative New York Heart Association functional class was 3.2+/-0.4 and cardiac index was 1.8+/-0.6. Mean cross-clamp duration was 58+/-19 minutes. Twenty patients received a 28-mm prosthesis, and eight patients received a 30-mm prosthesis. Four patients had myocardial revascularization, two had tricuspid valve repair, and six had radiofrequency ablation therapy to restore sinus rhythm. Mortality (1) was nonvalve related. Reoperation was necessary in two patients for posterior paravalvular leakage (1) and for functional stenosis (1). Echocardiography showed satisfactory hemodynamic function. By stentless mitral valve implantation the annuloventricular continuity is preserved to stabilize left ventricular function. The Quattro valve resembles native mitral valve function and is well suited for mitral valve replacement.

Aged↗
PubMed1998

Resting membrane properties of locust muscle and their modulation I. Actions of the neuropeptides YGGFMRFamide and proctolin.

The resting K+ conductance (GK,r) of locust jumping muscle and its modulation by two neuropeptides, proctolin (Arg-Tyr-Leu-Pro-Thr) and YGGFMRFamide (Tyr-Gly-Gly-Phe-Met-Arg-Phe-NH2), were investigated using the two-electrode voltage clamp. At a physiological [K+]o of 10 mM, GK,r accounts for approximately 90% of the membrane resting conductance, and the resting membrane potential differs by </=1 mV from EK (mean: -74 mV). There is a K+ conductance that slowly activates on hyperpolarization (GK,H) and that seems to be largely located in the transverse tubules. Steady-state activation of GK,H was analyzed by tail current measurements. GK,H is activated partially at EK but accounts for probably </=50% of total resting K+ conductance. Raising [K+]o caused a large increase in GK,r and in maximal steady state GK,H without shifting the voltage sensitivity of GK,H. YGGFMRFamide and proctolin reduce GK,H, mainly affecting the maximal steady-state conductance. The voltage-insensitive component of the resting K+ conductance is also reduced. The conductance suppressed by the peptides exhibited an outwardly rectifying instantaneous current/voltage-characteristic that is quite similar to that of GK,H. The actions of the two peptides appeared to be identical, but proctolin was by some two orders of magnitude more potent than YGGFMRFamide. The effects of both peptides are mediated by G proteins. They are mimicked by phorbol esters but do not seem to be initiated by either branch of the phospholipase C-dependent intracellular pathways. The properties of the resting K+ conductance in locust muscle and other invertebrate muscles are compared. The biological significance of peptide-induced reduction in resting K+ conductance is discussed in view of the known property of proctolin to support tonic force as opposed to FMRFamide-peptides that support quick leg movements.

Animals↗
PubMed1998

Resting membrane properties of locust muscle and their modulation II. Actions of the biogenic amine octopamine.

Ionic currents in the resting membrane of locust jumping muscle and their modulation by the biogenic amine octopamine were investigated using the two-electrode voltage clamp. A Cl- conductance, GCl,H, which slowly activates on hyperpolarization, can be induced by raising the intracellular Cl- concentration via diffusion of Cl- ions from the recording electrode. The instantaneous I-V characteristic of the current, ICl,H, is linear and reverses at the same potential as the gamma-aminobutyric acid (GABA)-mediated Cl- current. Elevation of [Cl-]i increases the maximal steady state GCl,H (Gmax) and shifts the activation curve of GCl,H to more positive potentials. Octopamine enhances GCl,H, mainly by increasing Gmax. Octopamine also lowers the resting K+ conductance (GK,r). It reduces a hyperpolarization-activated component (GK,H) of GK,r, mainly by decreasing Gmax. Octopamine also transiently stimulates the Na+/K+ pump although this effect was not always seen. The effects of octopamine on the Cl- and K+ conductances are mimicked by membrane permeant cyclic nucleotides. The modulation of GK,r, but not that of GCl,H, seems to be mediated by protein kinase A (PKA). PKA seems to be constitutively activated as indicated by the pronounced increase in GK,r induced by a PKA inhibitor, H89. The properties of GCl,H and related Cl- conductances in invertebrate and vertebrate neurons are compared. GCl,H probably supports efflux of Cl- ions accumulating in the fibers during synaptic inhibition. Octopamine's multiple modulation at the level of the muscle cell membrane, in conjunction with previously established effects on synaptic transmission and excitation-contraction coupling, are suited to support strong and rapid muscle contractions.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Octopamine modulates ionic currents and spiking in dorsal unpaired median (DUM) neurons.

Modulatory effects of octopamine on ionic currents and spiking in isolated cockroach dorsal unpaired median neurons were investigated by means of the chopped voltage-/current-clamp and the patch-clamp technique. Octopamine increased the spiking frequency at concentrations < or = 10 microM and reduced it at > 10 microM. It enhanced a low voltage-activated Ca2+ current at 1 to 100 microM. At concentrations up to 10 microM two components of Ca2+-activated K+ current were potentiated. At > 10 microM octopamine in addition reduced a high voltage-activated Ca2+ current and the Ca2+-activated K+ current. A membrane permeant cAMP-analogue imitated the effects obtained at high octopamine concentration. Octopamine and cAMP in addition reduced a depolarizing resting current at both low and high concentration. Possible mechanisms and physiological significance are discussed for the opposite effects of octopamine observed at low versus high concentrations.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1996

Selective activity of a proctolin analogue reveals the existence of two receptor subtypes.

1. The neuropeptide proctolin (Arg-Tyr-Leu-Pro-Thr) both potentiates neurally evoked contractions and causes contractures of insect skeletal muscle. In the hindleg extensor tibiae muscle of the locust, Schistocerca gregaria, the proctolin analogue [Afb (p-NO2)2]-proctolin is also able to potentiate neurally evoked contractions but is approximately 1,000-fold less effective in evoking contractures. 2. Proctolin and [Afb (p-NO2)2]-proctolin are equipotent in their ability to elevate the second-messenger inositol trisphosphate in isolated extensor tibiae muscle fiber membranes. 3. [Afb (p-NO2)2]-proctolin is approximately 1,000-fold less effective than proctolin in reducing the resting potassium conductance (GK) in extensor tibiae fibers. 4. We conclude that the action of proctolin on the extensor tibiae muscle is mediated by at least two receptor subtypes and that [Afb (p-NO2)2]-proctolin acts selectively on the receptor that potentiates neurally evoked contractions.

Animals↗
PubMed1996

Forebrain patterning defects in Small eye mutant mice.

Pax6 is a member of the Pax gene family of transcriptional regulators that exhibits a restricted spatiotemporal expression in the developing central nervous system, eye and nose. Mutations in Pax6 are responsible for inherited malformations in man, rat and mouse. To evaluate the role of Pax6 in forebrain development, we studied in detail mouse Small eye/Pax6 mutant brains. This analysis revealed severe defects in forebrain regions where Pax6 is specifically expressed. The establishment of some expression boundaries along the dorsoventral axis of the secondary prosencephalon is distorted and the specification of several ventral structures and nuclei is abolished. Specifically, the development of the hypothalamo-telencephalic transition zone and the ventral thalamus is distorted. Our detailed analysis included a comparison of the expression of Pax6, Dlx1 and several other genes during embryonic mouse brain development in wild-type and in the mutant Small eye (Sey) brain. The results from the analysis of normal brain development show that the restricted expression of Pax6 and Dlx1 at E12.5 dpc respect domains within the forebrain, consistent with the implications of the prosomeric model for the organisation of the forebrain (L. Puelles and J. L. R. Rubenstein (1993) Trends Neurosci. 16, 472-479). Furthermore, we found an early restriction of Pax6 and Dlx1 expression into presumptive histogenetic fields that correlate with the formation of distinct forebrain structures and nuclei. Our results are discussed in light of changes in adhesive properties in the Sey brain that might control segregation, assembly and cell migration of progenitors of specific forebrain regions.

Animals↗
PubMed1996

[Classification of operative laparoscopy].

We are proposing a new approach in the classification of Operative Laparoscopy, divided in 3 areas: Area 1: Reproductive laparoscopy, that is exclusively to techniques of assisted reproduction, Area 2: Reconstructive laparoscopy that includes all the pathology of the female's inner organs its treatment in sterility and Area 3: Ablative laparoscopy related to the extraction of tissues and organs with gynecological pathology.

Female↗
PubMed1994

Neurohormone D induces ionic current changes in cockroach central neurones.

The octapeptide neurohormone D (NHD), a member of the family of adipokinetic hormones (AKH-peptides), increases the frequency of spontaneous activity in dorsal unpaired median (DUM) neurones isolated from the terminal ganglion of the cockroach Periplaneta americana. The increase in spike frequency is accompanied by changes in the shape and the amplitude of the single action potentials, e.g. a more pronounced afterhyperpolarization. Effects of NHD on membrane currents were investigated in these DUM cells with whole-cell voltage-clamp measurements. A voltage-independent Ca2+ current flowing at the resting potential (ICa,R) was found. NHD, at nanomolar concentrations, enhanced this ICa,R in a concentration-dependent manner. 0.1 mM Cd2+ markedly reduced ICa,R and in this case ICa,R was hardly potentiated by NHD. In the presence of NHD a fast activating Ca(2+)-dependent K+ current sensitive to charybdotoxin and to low concentrations of tetraethylammonium was augmented. The enhanced afterhyperpolarization of action potentials can be accounted for by the increase in the Ca(2+)-dependent K+ current. The changes of the membrane currents induced by NHD are discussed with respect to further effects on the spike pattern and in relation to the previously described mode of action of AKH-peptides in other preparations.

Animals↗
PubMed1992

The ubiquitous transactivator Zfp-38 is upregulated during spermatogenesis with differential transcription.

We describe the complete nucleotide sequence of a full length cDNA clone encoding a new mouse zinc finger protein gene, Zfp-38 and localize it on chromosome 5 by the interspecific backcross analysis. The N-terminal domain of the Zfp-38 protein (64 kDa) contains 358 amino acids and the C-terminal domain of 197 residues encodes 7 zinc fingers. We also present evidence that Zfp-38 is a strong transcriptional activator. The transactivation domain was localized in the non finger region and a fusion protein containing 112 amino acid residues from this region of the Zfp-38 and the DNA binding domain of the yeast Gal 4 protein, very efficiently transactivated the expression of a reporter CAT plasmid, harboring the Gal4 target site. By in situ hybridization and northern blotting technique, the Zfp-38 transcript can be detected at a highly elevated level during spermatogenesis. Its expression accompanies the progression from pachytene spermatocytes to round spermatids. The undifferentiated spermatogonia or the haploid elongated spermatid and the spermatozoa do not show any detectable level of the transcript. Interestingly, other tissues express low levels of a slightly shorter transcript with a different 5' end as determined by RNase protection. The presence of both a transcriptional activating domain and 7 DNA binding zinc fingers, coupled with the cell type(s) specific expression pattern, suggests that Zfp-38 has the potential to regulate transcription during spermatogenesis.

Amino Acid Sequence↗
PubMed1991

Identification of proteins resembling G-protein alpha subunits in locust muscle.

In locust skeletal muscle, FMRFamide-like peptides decrease a K+ conductance. Functional data suggest the involvement of G-proteins. For identification of G-protein alpha-subunits, membranes of locust skeletal muscle were probed with ADP-ribosylating bacterial toxins, the photoreactive GTP analog, [alpha-32P]GTP azidoanilide, and with antibodies against mammalian alpha-subunits. Multiple guanine nucleotide-binding proteins of approximately 24-95 kDa were detected. Pertussis toxin catalyzed the ADP-ribosylation of two proteins comigrating with the ADP-ribosylated alpha-subunits of the mammalian G-proteins Go and Gi. Cholera toxin promoted ADP-ribosylation of a protein comigrating with mammalian cholera toxin substrates (i.e., Gs alpha-subunits). An antibody against mammalian Go alpha-subunits detected a 54-kDa protein. Thus proteins with properties of mammalian G-protein subunits are present in insect muscle.

Adenosine Triphosphate↗
PubMed1991

Hyperpolarization slowly activates a potassium current in locust skeletal muscle.

An inward current activated by hyperpolarization, IK,H, was studied under voltage clamp in locust skeletal muscle. The dependence of its reversal potential on [K+]o and its insensitivity to changes in [Na+]o indicate that the underlying conductance is a K+ conductance. The instantaneous current-voltage (I-V)-relationship exhibits outward rectification. Activation and deactivation take seconds and have complex time courses. At 10 mM [K+]o activation seems to start at a voltage greater than or equal to 20 mV more positive than the resting potential (approximately -68 mV). Ba++ blocks IK,H strongly; so do Rb+ and Cs+, the latter in a voltage dependent manner. The slow inward current bears similarities to anomalous rectifiers as well as to mixed, hyperpolarization-activated K+/Na+ currents in other tissues.

Animals↗
PubMed1991

Pax: a murine multigene family of paired box-containing genes.

A murine multigene family has been identified that shares a conserved sequence motif, the paired box, with developmental control and tissue-specific genes of Drosophila. To date five murine paired box-containing genes (Pax genes) have been described and one, Pax-1, has been associated with the developmental mutant phenotype undulated. Here we describe the paired boxes of three novel Pax genes, Pax-4, Pax-5, and Pax-6. Comparison of the eight murine paired domains of the mouse, the five Drosophila paired domains, and the three human paired domains shows that they fall into six distinct classes: class I comprises Pox meso, Pax-1, and HuP48; class II paired, gooseberry-proximal, gooseberry-distal, Pax-3, Pax-7, HuP1, and HuP2; class III Pax-2, Pax-5, and Pax-8; class IV Pax-4; class V Pox neuro; and class VI Pax-6. Pax-1 and the human gene HuP48 have identical paired domains, as do Pax-3 and HuP2 as well as Pax-7 and HuP1, and are likely to represent homologous genes in mouse and man. Identical intron-exon structure and extensive sequence homology of their paired boxes suggest that several Pax genes represent paralogs. The chromosomal location of all novel Pax genes and of Pax-3 and Pax-7 has been determined and reveals that they are not clustered.

Amino Acid Sequence↗
PubMed1991

Pax-6, a murine paired box gene, is expressed in the developing CNS.

A multigene family of paired-box-containing genes (Pax genes) has been identified in the mouse. In this report, we describe the expression pattern of Pax-6 during embryogenesis and the isolation of cDNA clones spanning the entire coding region. The Pax-6 protein consists of 422 amino acids as deduced from the longest open reading frame and contains, in addition to the paired domain, a paired-type homeodomain. Beginning with day 8 of gestation, Pax-6 is expressed in discrete regions of the forebrain and the hindbrain. In the neural tube, expression is mainly confined to mitotic active cells in the ventral ventricular zone along the entire anteroposterior axis starting at day 8.5 of development. Pax-6 is also expressed in the developing eye, the pituitary and the nasal epithelium.

Amino Acid Sequence↗
PubMed1990

The murine paired box gene, Pax7, is expressed specifically during the development of the nervous and muscular system.

Eight murine paired box-containing (Pax) genes have been isolated so far. The gene described here, Pax7, contains not only a paired box, but also an octapeptide and a paired-type homeobox. As shown by Northern and in situ analysis, Pax7 is expressed from day 8 to 17 p.c. during embryogenesis. At early stages Pax7 transcripts are present in a subset of cells throughout the entire brain, but later in development expression is limited to the mesencephalon. In the developing neural tube Pax7 is restricted to the dorsal ventricular zone along the entire antero-posterior axis, suggesting a role for Pax7 in the formation of certain parts of the CNS. Additionally Pax7 expression can be followed during myogenesis from the dermamyotome of the somites to the skeletal muscle tissues.

Amino Acid Sequence↗