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Biomedical subjects

K Lehmann

Publications and source records attributed to K Lehmann.

At least 109 records · Page 6Linked to original sources
PubMed1989

Exercise-induced ST segment depression in the diagnosis of multivessel coronary disease: a meta analysis.

To evaluate the variability in the reported accuracy of the exercise electrocardiogram (ECG) for predicting severe coronary disease, meta analysis was applied to 60 consecutively published reports comparing exercise-induced ST depression with coronary angiographic findings. The 60 reports included 62 distinct study groups comprising 12,030 patients who underwent both tests. Both technical and methodologic factors were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity 81% [range 40% to 100%, SD 12%]; mean specificity 66% [range 17% to 100%, SD 16%]). All three variables found to be significantly and independently related to sensitivity were methodologic (the exclusion of patients with right bundle branch block, the comparison with another exercise test thought to be superior in accuracy and the exclusion of patients taking digitalis). Exclusion of patients with right bundle branch block and comparison with a "better" exercise test were both significantly associated with sensitivity for the prediction of triple vessel or left main coronary artery disease. Adjustment of exercise-induced ECG changes for changes in heart rate was strongly associated with the specificity for critical disease (partial R2 = 0.436, p = 0.0001).

Coronary Angiography↗
PubMed1989

Deleterious effects of shock in internal mammary artery anastomoses.

Internal mammary arteries (IMAs) are increasingly used for coronary artery revascularization. However, spastic reactions after IMA-coronary artery anastomoses have been reported. Internal mammary artery flow and the effects of sudden hypovolemia, gradual hypovolemia, papaverine hydrochloride, nitrates, and epinephrine were evaluated in a canine model (n = 10) (body weight, 19 +/- 5 kg) without interference from coronary artery resistance by dissecting the IMA as a pedicle, calibrating the flowmeter during free IMA flow, and anastomosing the IMA to the right atrium. Sudden hypovolemia (withdrawal of 20% of circulating blood volume over 90 seconds) caused significant modifications (p less than 0.01) of the following hemodynamic variables: heart rate (+12%), right atrial pressure (-17%), pulmonary artery pressure (-20%), wedge pressure (-30%), aortic pressure (-49%), cardiac output (-33%), distal IMA pressure (-54%), and IMA flow (-85%). During hypovolemia, IMA flow could not be increased with topical application of papaverine, but baseline values were achieved after retransfusion of the withdrawn blood volume. Gradual hypovolemia and application of large doses of nitrates showed less dramatic effects, and injection of an epinephrine bolus under normovolemic conditions increased aortic pressure and IMA flow. Under sever hypovolemia, however, administration of an epinephrine bolus provoked only a minimal increase in aortic pressure and a contrasting decrease in IMA flow. We conclude that sudden, severe hypovolemia can lead to disproportionate IMA flow reduction and that pharmacological interventions are delicate under these circumstances.

Animals↗
PubMed1989

Retrograde internal mammary to coronary artery anastomoses.

In an effort to expand the utilization of the internal mammary artery (IMA) for revascularization of the distal coronary artery branches, distally pedicled retrograde internal mammary arteries (retro-IMA) were evaluated in 10 mongrel dogs with a mean weight of 38 +/- 13 kg. One IMA was transected at it's origin (retro-IMA) and compared to the contralateral IMA which was transected at the level of the 5th intercostal space. At a mean systemic pressure of 68 +/- 15 mmHg the mean pressure measured at the tip of the IMAs with antegrade flow was 63 +/- 14 mmHg in the retro-IMAs with retrograde flow (p less than 0.05; pressure ratio 0.8). With the same mean systemic pressure, mean antegrade free flow of the IMAs was assessed 97 +/- 43 ml/min versus 48 +/- 13 ml/min in the retro-IMAs with retrograde flow (p less than 0.005; flow ratio 0.5). Left retro-IMA to coronary artery anastomosis was performed in 6 animals to the distal left anterior descending (LAD) coronary artery and in 2 animals to the distal left obtuse marginal branch. Right retro-IMA to coronary artery anastomosis to the right posterior descending coronary artery was performed in 2 animals. The LAD coronary artery was ligated proximally to the retro-IMA to coronary artery anastomosis while the retro-IMA remained crossclamped. After documentation of significant ischemia (EKG, left atrial pressure), the crossclamp of the retro-IMA graft was removed. Subsequent normalisation of EKG and left atrial pressure occurred in all animals. We conclude that the canine retro-IMA delivers significant retrograde flow and discuss a possible use in humans.

Anastomosis, Surgical↗
PubMed1989

Exercise-induced ST depression in the diagnosis of coronary artery disease. A meta-analysis.

To evaluate the variability in the reported diagnostic accuracy of the exercise electrocardiogram, we applied meta-analysis to 147 consecutively published reports comparing exercise-induced ST depression with coronary angiography. These reports involved 24,074 patients who underwent both tests. Population characteristics and technical and methodologic factors, including publication year, number of electrocardiographic leads, exercise protocol, use of hyperventilation, definition of an abnormal ST response, exclusion of certain subgroups, and blinding of test interpretation were analyzed. Wide variability in sensitivity and specificity was found (mean sensitivity, 68%; range, 23-100%; SD, 16%; and mean specificity, 77%; range, 17-100%; SD, 17%). The four study characteristics found to be significantly and independently related to sensitivity were the treatment of equivocal test results, comparison with a "better" test such as thallium scintigraphy, exclusion of patients on digitalis, and publication year. The four variables found to be significantly and independently related to specificity were the treatment of upsloping ST depressions, the exclusion of subjects with prior infarction or left bundle branch block, and the use of preexercise hyperventilation. Stepwise linear regression explained less than 35% of the variance in sensitivities and specificities reported in the 147 publications. There is wide variability in the reported accuracy of the exercise electrocardiogram. This variability is not explained by information reported in the medical literature.

Coronary Disease↗
PubMed1989

[Development of a small-lumen vascular prosthesis coated with autologous endothelial cells].

A new compliant prosthesis with a monolayer of autologous endothelial cells (ENC) has been developed. It consists of a porous polyurethane-siloxane-copolymer reinforced by a polyester network to prevent excessive dilatation. On the inner surface an ENC monolayer is established before implantation by a cell culture procedure. The prosthesis displays compliance (13.2 +/- 3.0 x 10(-4) mmHg-1) comparable to native arteries. It is non-kinkable (minimal radius of curvature less than 5 mm). Burst resistance, remaining deformation, cut out force and tensile strength are superior to standard values. ENC-coverage in excess of 95% of the inner surface was produced in vitro using a lining procedure. The monolayer of confluent cells was demonstrated to consist of endothelial cells by their characteristic cobblestone morphology, the expression of factor VIII related antigen and the specific uptake of Dil-Ac-LDL. The unstimulated prostacyclin production was similar both in native veins as well as in lined prostheses. Antithrombogenicity of the endothelial cell lining was demonstrated in 24 h animal implants.

Animals↗
PubMed1988

Difference between endothelium-dependent relaxation in arterial and in venous coronary bypass grafts.

Both the internal mammary artery and the saphenous vein are used to construct coronary-artery bypass grafts. We hypothesized that the release or production of endothelium-derived relaxing factor, which regulates blood flow and inhibits platelet function, may differ in venous and arterial grafts. We therefore studied endothelium-dependent relaxation in internal mammary arteries, internal mammary veins, and saphenous veins obtained from 58 patients undergoing coronary bypass surgery. Vascular rings with and without endothelium were suspended in organ chambers, and isometric tension was recorded. Acetylcholine (10(-8) to 10(-4) M), thrombin (1 U per milliliter), and adenosine diphosphate (10(-7) to 10(-4) M) evoked potent endothelium-dependent relaxation in the mammary artery but weak response in the saphenous vein (P less than 0.005; n = 6 to 27). In the mammary artery, relaxation was greatest in response to acetylcholine (86 +/- 4 percent reduction in norepinephrine-induced tension), followed by thrombin (44 +/- 7 percent) and adenosine diphosphate (39 +/- 8 percent). In the saphenous and mammary veins, relaxation was less than 25 percent. Relaxation was unaffected by indomethacin but was inhibited by methylene blue and hemoglobin (P less than 0.005 and 0.01, respectively), which suggests that endothelium-derived relaxing factor was the mediator. Endothelium-independent relaxation in response to sodium nitroprusside was similar in arteries and veins. We conclude that endothelium-dependent relaxation is greater in the mammary artery than in the saphenous vein. The possibility that this contributes to the higher patency rate among arterial grafts than among venous grafts will require further study.

Acetylcholine↗
PubMed1987

[Developmental status and goals in occupational therapy. The "Guidelines for Occupational Therapy in Psychiatric Hospitals"].

Work therapy, or ergotherapy, is a recognised and permanent part of psychiatric treatment and medical rehabilitation. It is also an essential part of psychiatric diagnosis and therapy; furthermore, it enables the patient to develop and stabilise a realistic image of himself and contributes to the prevention and reduction of damage caused by hospitalism. The present status of work therapy was checked in 74 psychiatric hospitals throughout the Federal Republic of Germany, resulting in the need for further development of present practical procedures. A working group was created by the Federal Ministry of Labour and National Welfare within the framework of the model programme for psychiatry, at the suggestion of a Federal Working Group of the organisations running public mental hospitals in the FRG. The aim of this working group was to develop a specialised concept of work therapy. The group consisted of experts from clinical practice as well as from the Federal German Labour Office Institution, psychiatric consultants of the Federal Government and the Land Governments, as well as from the Land Government sponsors of state social welfare services. The "Guidelines for Work Therapy in Psychiatric Hospitals and Departments of Psychiatry" are officially considered to be a suitable basis for further development work in the field of ergotherapy.

Germany, West↗
PubMed1986

Position of Igl-1, md, and Bst loci on chromosome 16 of the mouse.

The experiments described here delineate the position of the chromosome 16 markers Igl-1 (immunoglobulin lambda 1, light chain), md (mahoganoid), and Bst (belly spot and tail), and suggest their location relative to the endogenous proviral locus Akv-2, which is linked within 5.9 centimorgans to Igl-1 (Epstein et al. 1984). The data from an intercross and a three-point backcross detailed herein show the order of these three genes and distances between them to be: centromere-md-10.4 +/- 1.6-Igl-1-15.6 +/- 2.6-Bst. Using a recombinant chromosome recovered in the intercross, we have constructed a stock homozygous for md and Igl-1b (KpnI-), that will aid in mapping other genes on chromosome 16.

AKR murine leukemia virus↗
PubMed1985

A monoclonal lambda 1-bearing anti-dextran antibody from a lambda-defective mouse strain.

A hybridoma from the lambda-defective mouse strain SJA has been established. It produces a lambda 1-bearing IgG2b, dextran B 1355-binding antibody. The DNA sequence of the VJ and C gene segment was in complete accordance with the published germ-line sequence. The rate of secretion and the steady state level of cytoplasmic RNA of this line was comparable to that of cell lines from normal mice. The idiotype was closely related to that of MOPC 104E indicating that the lambda 1 light chain is associated with the same VH region and in a similar fashion as in BALB/c mice. This antibody should be useful for further experiments on the lambda defect of SJL or SJA mice.

Animals↗
PubMed1985

Morphologic alterations of blood cells in the impedance aggregometer.

The scanning (SEM) and transmission (TEM) electron microscopic appearance of blood cells was studied in correlation with the aggregometer tracing recorded after activation of whole blood samples by collagen or ADP. Early morphologic alterations of platelets characterized by the formation of marginal pseudopods and bulbous protrusions were not indicated by the aggregometer. The initial increase in impedance was caused by the attachment of platelets displaying typical shape change morphology at the surface of the electrode wires joint with collagenous fibrils in collagen activated specimens. During further increase in impedance, aggregates were detectable in the blood suspension and at the electrode, the number and size of which increased up to the maximal extension of the aggregometer tracing. Using low doses of ADP (2-3 microM), dissociation of aggregates in the blood suspension was detectable by SEM, which was not recorded by the aggregometer tracing indicating further limitation of the impedance aggregometer. In collagen activated samples, platelet aggregates were covered by PMN and monocytes that in TEM displayed distinct phagocytosis of platelet fragments and fibrin masses. In ADP specimens, activation of leukocytes was only rarely detectable. The detection of mixed aggregates may be important for further employment of the impedance aggregometer in the diagnosis of hematologic diseases.

Adenosine Diphosphate↗
PubMed1984

Linkage of the Igl-1 structural and regulatory genes to Akv-2 on chromosome 16.

Evidence is presented here for a close linkage between Akv-2, an ecotropic provirus found uniquely on chromosome 16 of AKR/N mice, and the immunoglobulin lambda 1 light chain locus, Igl-1. No recombinants between the Igl-1 locus and Akv-2 were found by Southern blot analysis of DNA obtained from progeny of the backcross of (AKR/N X SJL/J)F1 to SJL/J, indicating that these genes map within 5.9 cM of each other. A probe specific for the flanking sequence of Akv-2 was used to detect the provirus, while one specific for the Igl-1 constant region was used to determine which allele of the structural gene was expressed in the backcross mice. The constant region of Igl-1 differs between AKR/N and SJL/J with respect to a site for the restriction endonuclease KpnI. This backcross was also used to seek recombinants between the regulatory, Igl-1r, and structural, Igl-1, loci of the immunoglobulin light chain locus, since the existence of such recombinants would prove that these loci are distinct. Since only parental types were recovered in the offspring, the structural and regulatory loci are no more than 2.3 cM apart, and the implications of this finding are discussed.

Animals↗
PubMed1984

Mice completely suppressed for the expression of immunoglobulin kappa light chain.

Complete suppression of expression of immunoglobulin kappa light chain was achieved by injecting female mice from birth with a mixture of antisera against the mu heavy chain and kappa light chain (anti-mu and anti-kappa). Then their offspring were injected with anti-kappa from birth. This resulted in stable suppression as long as anti-kappa injections were continued. kappa light chain was not detectable either in serum or at the cellular level. The number of B cells in spleen and the concentration of immunoglobulin classes and subclasses in serum were normal. The normal levels were achieved by a compensating enhancement of lambda light chain expression. Analysis of the light chains of immunoglobulins secreted by spleen cells from suppressed mice after liposaccharide stimulation by two-dimensional gels showed lambda chain to have a limited heterogeneity. Primary responses to dinitrophenol, influenza strain A, and keyhole limpet hemocyanin were drastically affected, whereas secondary responses appeared to be quite normal, suggesting a surprisingly large potential repertoire.

Animals↗
PubMed1983

Induction of lambda 1-immunoglobulin is determined by a regulatory gene (r lambda 1) linked (or identical) to the structural (c lambda 1) gene.

The cis-acting gene regulating specifically the inducibility of lambda 1-bearing B cells has been mapped within 2.9 cM of the structural gene. If the lambda 1lo-phenotype is due to the gly leads to val interchange in C lambda 1, then an argument can be made that (a) the lambda 1lo-phenotype is due to inefficient induction of lambda 1lo-bearing B cells and (b) B cell triggering is dependent upon a conformational change in the Ig receptor upon interaction with antigen. If the lambda 1lo-phenotype is due to a regulatory sequence linked to the structural C lambda 1-gene, then it must control the expression of the lambda 1-locus during development into adulthood, e.g., by an effect on methylation.

Animals↗
PubMed1983

Monoclonal antibodies to murine immunoglobulin isotypes.

We have obtained cell lines producing monoclonal antibodies against mu, alpha, lambda, and lambda 1 by fusing the mouse myeloma P3X63Ag8.653 with spleen cells from Lewis rats immunized with several lambda 1 bearing myeloma proteins. The anti-lambda 1 antibody is particularly useful. It was shown to be suitable for radioimmunoassays, for ELISAs when coupled to alkaline phosphatase, and for indirect fluorescence staining of the membrane as well as the cytoplasm.

Animals↗