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Biomedical subjects

R Schmidt

Publications and source records attributed to R Schmidt.

At least 523 records · Page 29Linked to original sources
PubMed1990

[Mechanism of action of alloxan on pancreatic B-cells with special regard to the alloxan-metal-complex theory. II. Actions of alloxan, alloxanic acid, Zn2+ and ethyleneglycol-bis-(beta-aminoethylether)-N,N'tetraacetic acid (EGTA) on the assembly of microtubule proteins (MTP) into microtubules or MPT sheets in vitro].

Analyses of the cell structures in the islets of Langerhans revealed the presence of 2 predominant cations, calcium (beta-granules and saccules, mitochondria, sac membranes, and cell membranes) and zinc (secretory granules, encasing membraneous sacs) in association with organelles which involve directional secretion. Both elements are known to interact with microtubules influencing their structural and functional properties, e.g. movement of secretory granules. Influences of Zn2+ on microtubules are investigated with a view to interactions in vitro with and without diabetogenic substances. Turbidimetry and electron microscopic investigations showed that under the conditions mentioned above, alloxan of a concentration of 2 x 10(-5) mol/l (alloxan/tubulin 1:1) inhibits the formation of microtubules and increases the portion of microtubules stabilized of 4 degrees C. The Zn2(+)-induced formation of MTP sheets is not influenced by alloxan and the metal complex forming agent EGTA, if the molar concentrations of the substance and Zn2+ are equally high. With a molar proportion of 2:1 (EGTA:Zn2+), the formation of sheets does not longer occur and only microtubules are formed, whereas neither sheets nor microtubules were assembled by alloxan with this molar proportion. However, neither the assembly of microtubules nor the formation of Zn2(+)-induced sheets are influenced by alloxanic acid in both molar proportions. It is shown that the diabetogenic alloxan influences the formation of microtubules and that performed microtubules are destroyed. This result of alloxan corresponds to its antimitotic activity analogously to the wellknown effect of colchicine (s. Schmidt et al. 1990).(ABSTRACT TRUNCATED AT 250 WORDS)

Alloxan↗
PubMed1990

[The effects of incremental PEEP on atrial natriuretic peptide, right atrial pressure and the size of the right atrium in anesthetized patients].

8 ASA class II-III patients (50-67 years) undergoing traumatic-surgical procedures were studied. Since the release of atrial natriuretic peptide (ANP) is stimulated by volume loading and increased right atrial pressure (RAP), the effects of incremental positive end-expiratory pressure (PEEP) on ANP-concentration, RAP and right atrial dimensions were investigated. Anaesthesia was induced with intravenous etomidate and vecuronium and maintained after endotracheal intubation with 66% N2O in O2 and ethrane (0.4-0.6 Vol.-%). A catheter was inserted into the A. radialis for blood sampling and determination of mean arterial pressure (MAP). For determining endsystolic (RAESA) and end-diastolic (RAEDA) areas of the right atrium a 5 MHz transoesophageal echocardiographic (TEE)-probe was positioned at the level of the foramen ovale. Under TEE-control a catheter was placed into the right atrium for measurement of RAP. The method for ANP determination was based on a direct radioimmunoassay that is specific for human ANP (ANP-J125). PEEP was incrementally raised from 0 to 16 mbar in 4 mbar steps each for 5 min and thereafter reduced to 0 mbar. During the investigation no significant differences were detectable for MAP, heart rate, end-expiratory CO2 partial pressure and the arterial O2 saturation. However, 16 mbar PEEP ventilation increased plasma ANP concentrations (from 44.3 +/- 9.7 to 58.1 +/- 8.7 pg/ml) and RAP (from 4.4 +/- 0.9 to 10.7 +/- 0.9 mmHg) whereas the right atrial dimensions RAESA (from 9.4 +/- 1.0 to 4.6 +/- 0.6 cm2) and RAEDA (from 5.9 +/- 1.2 to 3.2 +/- 0.4 cm2) decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Results of fast neutron therapy of adenoidcystic carcinomas of the head and neck at the neutron facility Hamburg-Eppendorf.

Between July 1977 and March 1988, 31 patients with an adenoidcystic carcinoma were treated with fast neutrons of a 14 MeV-DT-generator at our department. Primary locations were: parotid gland eight cases, paranasal sinus five cases, submandibular gland five cases, trachea four cases and other locations nine cases. The median follow-up of our patients was 16 months. Most of the patients had advanced tumors. The calculated local control rate is 65% at two years.

Adult↗
PubMed1990

Status report of fast neutron therapy in the Department of Radiotherapy at the University Hospital Hamburg-Eppendorf.

Since 1976 710 patients were treated with fast neutrons at the University Hospital Hamburg-Eppendorf. Since January 1984 154 patients with soft tissue sarcomas (250 patients with soft tissue sarcomas since 1976), 20 patients with advanced and low grade tumors of the paranasal sinuses and 43 patients with adenoid cystic carcinomas were treated with fast neutrons. Our results and reports from several centers indicate a gain from fast neutron therapy for low grade soft tissue sarcomas, osteosarcomas (G1 and G2), for highly differentiated salivary gland tumors, and some other rare low grade tumors as malignant chordomas, chondrosarcomas, pencil gliomas or desmoid tumors.

Adult↗
PubMed1990

[Ergotism--a rare cause of acute ischemia of the extremities].

Clinical ergotism as seen today results almost exclusively from the excessive intake of ergotamine tartrate in the treatment of migraine headache. Vasospasm of peripheral arteries is the leading clinical picture. Beside formation of collaterals and secondary thrombosis, vasospasm is one of the specific findings in angiography. Early diagnosis and withdrawal of the medication makes complete restitution possible. In all other cases intraarterial or intravenous infusion of sodium nitroprusside or nitroglycerin has turned out to be the most effective therapy. Balloon dilatation or operative intervention are an alternative therapy in those cases, where amputation of the limb seems to be necessary.

Acute Disease↗
PubMed1990

Neutron dose planning with the MEVAPLAN system.

For treatment planning with fast neutrons the neutron and photon components have to be calculated separately. The data base and the source code of the MEVAPLAN system (Siemens) have been modified to fulfil these requirements. Major changes were made to enable the kerma-corrections for organs of different atomic compositions. Furthermore, the linear attenuation coefficients are used to calculate the transmission of neutrons through different organs. The data can be obtained indirectly from CT data, if the calibration of the CT data into density is known. The DT-neutron generators require a modified inverse square law for different SSD's. The corresponding coefficients are determined and are included in the data base of the system. A comparison between measured and calculated isodoses and treatment plans based on CTs is shown.

Energy Transfer↗
PubMed1989

Retinoic acid controls expression of epidermal transglutaminase at the pre-translational level.

Human epidermal keratinocytes were cultured until sub-confluence in low Ca2+ (0.15 mM) serum-free synthetic MCDB 153 medium. Raising the Ca2+ concentration to 1.15 mM caused an increase in envelope competence as well as plasma membrane associated transglutaminase (TGm) activity. This increase was not observed when the high Ca2+ medium contained retinoic acid. Immunofluorescence studies as well as immunoblotting with the TGm-specific monoclonal antibody B.C1 revealed that retinoic acid inhibits expression of TGm. Isolation and in vitro translation of mRNA with subsequent immunoprecipitation showed that retinoic acid inhibits TGm expression at the pretranslational level.

Antibodies, Monoclonal↗
PubMed1989

Massive pulmonary hemangiopericytoma. An innovative approach to evaluation and treatment.

The authors report the case of a 39-year-old woman with a massive malignant pulmonary hemangiopericytoma. The clinical presentation and histologic findings were typical of this rare entity, but workup and treatment were challenging because of the size and location of the tumor. Magnetic resonance imaging (MRI) proved to be critical in the preoperative evaluation because of its unique ability to delineate the precise anatomical extent of this highly vascular neoplasm. Previous treatment of this patient with exploratory thoracotomy and chemotherapy had been unsuccessful. The authors used an innovative approach to treatment which included complete surgical resection via combined median sternotomy and thoracotomy, along with intraoperative and postoperative radiotherapy. The patient is disease-free 28 months after surgery.

Adult↗
PubMed1989

Two isozymes of PKC found in HL-60 cells show a difference in activation by the phorbol ester TPA.

Cytosol from untreated cells and a detergent extract of the particulate fraction from TPA-treated HL-60 cells were analyzed for protein kinase C activity by consecutive column chromatography on Mono Q and hydroxyapatite. From both preparations two separate peaks of enzyme activity were obtained. The first peak, eluting at lower salt concentrations, is activated at lower TPA concentrations (3 X 10(-9) M) than the other (10(-7) M), which was eluted at higher salt concentrations.

Animals↗
PubMed1989

Significance of latent hyperthyroidism.

In euthyroidism the circadian rhythm and pulsatility of TSH is well known. With regard to hyperthyroidism only very preliminary data were described. In this study we investigated the secretion pattern of the pituitary-thyroid axis hormones during 24 h in latent and overt hyperthyroidism and in euthyroidism with regard to common and different properties. Blood was obtained for 24 h at 10-min intervals. In euthyroidism we found intraindividually three overlapping patterns of TSH, which are different in amplitude and frequency and can be found interindividually, too. These patterns are equal to the circadian rhythm, pulsatile secretion and lastly to the methodic rustle. The circadian rhythm in latent hyperthyroidism is distinctly suppressed and in overt hyperthyroidism totally. Whereas in latent hyperthyroidism pulsatile secretion is extant, in overt hyperthyroidism the TSH pulses are absent. To record the patients' TSH circadian rhythm with only three blood samples, we defined the TSH-Triplex. In young as well as in elderly healthy volunteers it demonstrated significantly higher TSH levels at midnight (at 24:00 h) than it did at 4 p.m. and 8 a.m. The present study shows a significantly different TSH pattern in latent hyperthyroidism compared to euthyroidism. It should be discussed whether latent hyperthyroidism could be defined as hyperthyroidism stage I. On the other hand, latent hyperthyroidism could be an illness with its own cause, different from hyperthyroidism. Our data suggest that the laboratory findings of latent hyperthyroidism in each age are non-physiological. However, the cause for this disorder is unclear until now; hence further investigations are necessary.

Adult↗
PubMed1989

Antidepressants in 'depressed' schizophrenic inpatients. A controlled trial.

Fifty-eight actively psychotic inpatients who initially met criteria for long-standing schizophrenia and subsequently met Research Diagnostic Criteria for a current episode of schizoaffective disorder (mainly schizophrenic) with a depressive syndrome, and who scored at least 30 (mean = 55, SEM = 1.6) on the Brief Psychiatric Rating Scale and 17 (mean = 23, SEM = 0.7) on the Hamilton Rating Scale for Depression, were treated for 5 weeks with haloperidol hydrochloride and benztropine. Haloperidol and benztropine treatment was continued, while those patients who consistently scored greater than 17 on the Hamilton Rating Scale for Depression were randomly assigned to the following double-blind treatment groups for 4 weeks: adjunctive amitriptyline hydrochloride, desipramine hydrochloride, or placebo. Adjunctive desipramine or amitriptyline showed no significant therapeutic advantage, when compared with haloperidol and placebo, on the Brief Psychiatric Rating Scale or the Hamilton Rating Scale for Depression. After 4 weeks of combine therapy, patients receiving adjunctive amitriptyline or desipramine, as compared with those receiving adjunctive placebo, tended to score higher on the Brief Psychiatric Rating Scale hallucinatory behavior item and on the thinking disturbance factor than patients receiving placebo. These results suggest that adjunctive antidepressants are not indicated for the treatment of depressive symptoms in actively psychotic schizophrenic inpatients. Adjunctive antidepressants may retard the rate of resolution of psychosis in this population.

Adolescent↗
PubMed1989

Sodium butyrate selectively antagonizes the inhibitory effect of retinoids on cornified envelope formation in cultured human keratinocytes.

Sodium butyrate affects cell differentiation in confluent epidermal keratinocyte cultures by considerably increasing the spontaneous formation of cross-linked envelopes in normal human keratinocytes (NHK). It also favors the development of envelope competence in the Simian virus-40 (SV-40)-transformed human foreskin keratinocyte line SV-K14. It completely abolishes the inhibitory effect of serum and retinoic acid on the expression of plasma membrane-associated transglutaminase. However, other markers of epidermal differentiation that are also under the control of retinoids such as keratins or the enzyme cholesterol sulfotransferase are not affected by butyrate. The level of the cellular retinoic acid binding protein (CRABP) is considerably increased in its presence. Butyrate does not interfere with the binding of retinoids to their cellular binding proteins. Our observations suggest that sodium butyrate stimulates cornified envelope formation via the induction of the plasma membrane-associated transglutaminase required for cornified envelope synthesis and, additionally, by abolishing the inhibitory effect of retinoids on the expression of this enzyme.

Butyrates↗
PubMed1989

The effects of demineralized bone matrix and direct current on an "in vivo" culture of bone marrow cells.

Bone marrow cells (BMCs) from rabbit femora and tibiae were grown in diffusion chambers implanted in rabbit muscle. At 42 days 80% of the BMC chambers exhibited cartilage formation within them. Demineralized bone matrix added to the marrow cell suspension in the chamber accelerated the appearance and increased the number of chambers with cartilage. Mineralization of the cartilage also occurred earlier in the chambers with bone matrix. In a second experiment, a 5-microA direct current cathode in the bone marrow chamber increased the number of chambers containing cartilage from 50 to 80% at day 25. Mineralization also occurred earlier in the chambers with direct current.

Animals↗
PubMed1989

Efficient transformation of Arabidopsis thaliana using direct gene transfer to protoplasts.

Direct gene transfer has proved to be an efficient transformation method for Arabidopsis thaliana, a member of the Brassicaceae. Transgenic Arabidopsis plants resistant to hygromycin B have been regenerated from mesophyll protoplasts treated with polyethylene glycol and plasmid DNA carrying the hygromycin phosphotransferase (HPT) gene under the control of the 35 S promoter of cauliflower mosaic virus. The transformation procedure reproducibly yields transformants at frequencies of approximately 1 x 10(-4) (based on the number of protoplasts treated) or 5% (based on the number of regenerating calli). DNA from plants regenerated from hygromycin resistant colonies was analysed by Southern blot hybridization demonstrating that the foreign gene is stably integrated into the plant chromosome. Genetic analysis of several hygromycin resistant plants showed that the HPT gene is transmitted to the progeny. Transformation experiments performed with a selectable and a non-selectable gene on separate plasmids resulted in a co-transformation rate of functionally active copies in about 25% of the transformants analysed. Hence this approach can be used to introduce non-selectable genes into the Arabidopsis genome.

Blotting, Southern↗
PubMed1989

Biological assays for irritant, tumor-initiating and tumor-promoting activities. II. Standardized initiation/promotion protocol and semiquantitative estimation of promoting (or initiating) potencies in skin of NMRI mice.

A versatile standardized protocol of initiation/promotion of skin is described using 7,12-dimethylbenz[a]anthracene as initiator and diterpene esters as promoters in 28 female NMRI mice per promoter (or initiator) dose group including appropriate positive and negative controls ("standardized initiation/promotion protocol 28" or "protocol 28"). To monitor the weekly tumor responses, the tumor rate Tr and the tumor yield Ty were recorded per dose group collectively as a measure of the tumor-promoting (or initiating) activity of individual compounds; similarly the general health status of the group was controlled twice weekly by collective weighing of the dose group and recorded daily by the survival rate Sr. Synoptic consideration of Tr, Ty and the promoter dose (or initiator dose) at a set time period of exposure was used for the semiquantitative estimation of the relative tumor-promoting (or initiating) potency, referring to a high-potency promoter (or initiator) as standard. The full scope of utilization of "protocol 28" to determine comparable individual promoting activities and -at 24 weeks of exposure--relative tumor-promoting potencies (rtpp24) is demonstrated in typical examples with 12-O-tetradecanoylphorbol 13-acetate (TPA) as well as various other phorbol esters as promoters. For estimation of promoting potencies TPA is rated a rtpp24 of + + + +. The other phorbol derivatives exhibit rtpp24 between 0 and + + + +. In this manner, "protocol 28" was verified in 1000 promoter dose groups (i.e. 28,000 mice) to determine tumor-promoting activities of individual diterpene esters and partly also their rtpp24. Grading of tumor-promoting potencies of diterpene esters in skin by rtpp24 proved useful for evaluating the relative environmental risk involved in exposure to various diterpene esters as well as in comparative mechanistic investigations including structure/activity relationships. As an example, the correlation of irritancy and tumor-promoting potency of certain diterpene esters in epithelial tissue, postulated previously from essentially qualitative data, is verified in semiquantitative terms by comparison--as a typical example--of the irritancy of phorbol esters on the ear and of the corresponding rtpp24 on the back skin of NMRI mice.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1989

Anesthetic management for surgical removal of renal carcinoma with caval or atrial tumor thrombus using deep hypothermic circulatory arrest.

Twenty cases of renal carcinoma with tumor thrombus extending into the vena cava or atrium, in which cardiopulmonary bypass (CPB) and deep hypothermic circulatory arrest (DHCA) were used, are reviewed. Arterial, central venous (n = 9), or pulmonary artery catheters (n = 11), ECG, and rectal or bladder and pharyngeal temperatures were used for monitoring. The anesthetic was a high-dose narcotic supplemented with a nondepolarizing relaxant and a volatile agent. The surgery consisted of mobilization of the kidney followed by CPB via atrial and aortic cannulae, cooling via CPB, exsanguination, and removal of thrombus during DHCA. Duration of cooling was 21 +/- 7 minutes to a pharyngeal temperature of 15.8 degrees +/- 2.6 degrees C with alpha-stat pH management; DHCA lasted 26 +/- 10 minutes, and rewarming was continued to a mean pelvic temperature of 36.2 degrees C. Duration of surgery was 8.1 +/- 1.6 hours. The mean initial hematocrit was 33.5%, mean lowest Hct during CPB was 16.9%, and mean Hct at the end of surgery was 30%. Intraoperatively, 9.0 +/- 6.4 units of blood were used, and most patients received component therapy. Average crystalloid use was 7 L, and albumin or hetastarch (1.3 +/- 0.9 L) was used in 13 patients. One patient with severe cardiac disease could not be weaned from CPB. In the 19 operative survivors, there were no neurological deficits. There was one late death from pulmonary complications. The use of thiopental (n = 13), dexamethasone (n = 11), or mannitol (n = 19) was not clearly related to outcome. Hypothermia, hemodilution, alpha-stat pH management, and normoglycemia are believed to be important aspects of perioperative care.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Splenopentin (DAc SP-5)-accelerated reconstitution of antibody formation after syngeneic bone marrow transplantation.

Sublethally irradiated AB/Bln, mice (800 c Gy) and supplemented with syngeneic bone marrow cells were treated with or without a splenopentin derivative (DAc SP-5) and compared for their capacity to produce antibodies. In bone marrow cell plus DAc SP-5 treated animals antibody forming cells were found earlier and in a higher frequency than in mice treated with bone marrow cells only. These findings demonstrate that DAc SP-5 is able to induce bone marrow cell maturation.

Animals↗