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Biomedical subjects

R Horn

Publications and source records attributed to R Horn.

At least 91 records · Page 5Linked to original sources
PubMed1993

Differentiation of multi-infarct and Alzheimer dementia by intracranial hemodynamic parameters.

BACKGROUND AND PURPOSE: The differentiation between the Alzheimer and multi-infarct types of dementia may still be equivocal considering clinical criteria, neuropsychological tests, and imaging techniques. Cerebral microangiopathic alterations underlying multi-infarct dementia should allow the characterization of dementia subgroups. METHODS: Patients with a diagnosis of multi-infarct dementia (n = 17; mean age, 69.1 +/- 8.5 years) or Alzheimer dementia (n = 24, mean age, 65.8 +/- 9.0 years) according to standard testing criteria, clinical findings, and neuroimaging techniques (computed tomography and magnetic resonance imaging) were investigated prospectively by transcranial Doppler sonography and compared with a normal reference group (n = 64; mean age, 61.0 +/- 11.1 years). Transcranial Doppler sonography allows an indirect evaluation of peripheral flow resistance in the microcirculatory bed by quantifying pulsatility characteristics, as reflected in the effective pulsatility range (time-averaged mean blood flow velocity minus the peak-systolic to end-diastolic amplitude, in centimeters per second). RESULTS: A total of 204 vessels were investigated in 105 subjects. Mean and diastolic blood flow velocities as well as the effective pulsatility range were significantly lower in the multi-infarct dementia group compared with the Alzheimer and the normal reference groups (p < 0.001). By using receiver operating characteristic analysis, a cutoff point for effective pulsatility range values of -5 cm/sec gives a side-dependent sensitivity of 90.48-95.24% and a specificity of 64.71-70.59% in diagnosing Alzheimer-type dementia; the corresponding sensitivity and specificity for a value of -2 cm/sec are 82.35-88.24% and 80.95-90.48%, respectively. CONCLUSIONS: Pulsatility changes as reflected by the effective pulsatility range are a noninvasive additional criterion in the differential diagnosis of dementia.

Aged↗
PubMed1993

Panning transfected cells for electrophysiological studies.

Panning was used to select co-transfected cells expressing plasmid-encoded ion channels. Adherent cells were cotransfected by the CaPO4 method with a plasmid encoding a cell surface marker (CD8) along with another plasmid encoding an ion channel. At 1-3 days post-transfection, the cells were suspended, treated with a biotinylated CD8-specific antibody and placed into streptavidin-coated bacterial petri dishes. After 2 h, these dishes were washed with a saline solution to remove cells that did not adhere to the streptavidin-coated dishes. By using molar ratios of > or = 8:1 of the ion channel encoding plasmid to the CD8 plasmid, we found that > or = 50% of the panned cells that adhered to coated dishes were positive for expression of the co-selected gene. Cells expressing plasmid-encoded channels (voltage-dependent sodium channels or cystic fibrosis transregulator chloride channels) were assayed using whole-cell recording, perforated-patch recording and single-channel recording. The method was tested on tsA201 and NIH3T3 cells, the latter of which transfected very poorly (usually < 4% efficiency) with our standard protocols. When the co-selected plasmid encoded the bacterial beta-galactosidase gene, it was possible to determine by histological assay the percentage of positively transfected cells (with and without panning). Panning in some cases increased the percentage of positively cotransfected cells by more than 20-fold. This technique is particularly useful when selecting co-transfected cells for electro-physiological recordings on individual cells.

3T3 Cells↗
PubMed1993

[HMPAO-SPECT in Alzheimer-type dementia and major depression with memory disorders].

The aim of the present study was to see whether HMPAO-SPECT may contribute to the differentiation between dementia of the Alzheimer type (DAT) and major depression (MD). The results in 77 patients with memory impairment were evaluated. 48 patients suffered from DAT and 29 from MD. Initially, the defects in SPECT imaging were attributed to a cerebral region and the degree of decrease was evaluated (-1/-2/-3). Thereafter, the results were classified by 7 categories. In some of these categories an accumulation of cases of either DAT or MD was found. 35% of the patients suffering from DAT had bilateral defects with distinct (> -1) parietal/parietotemporal hypoperfusions, but no patient with MD showed this perfusion pattern. 62% of the patients with MD had unilateral defects but only 31% of the patients with DAT. The present study demonstrates that only 35% of all patients suffering from DAT show a perfusion pattern, thought earlier as "pathognomonic" for this disease. This perfusion pattern--if it exists--may be used as a safe criterion to exclude MD. Beyond that no clearcut ("specific") perfusion pattern may be recognized but unilateral defects point to MD.

Aged↗
PubMed1993

[The "anxiety" ambulatory clinic: development and outlook].

The study herewith represents the conception of the Bonn "anxiety"-ambulance, which was established in the University of Bonn, Department of Psychiatry, in January 1991. Besides we report our experiences from the first four months after opening of our ambulance and present first results.

Agoraphobia↗
PubMed1992

Chimeric study of sodium channels from rat skeletal and cardiac muscle.

Two isoforms of voltage-dependent Na channels, cloned from rat skeletal muscle, were expressed in Xenopus oocytes. The currents of rSkM1 and rSkM2 differ functionally in 4 properties: (i) tetrodotoxin (TTX) sensitivity, (ii) mu-conotoxin (mu-CTX) sensitivity, (iii) amplitude of single channel currents, and (iv) rate of inactivation. rSkM1 is sensitive to both TTX and mu-CTX. rSkM2 is resistant to both toxins. Currents of rSkM1 have a higher single channel conductance and a slower rate of inactivation than those of rSkM2. We constructed (i) chimeras by interchanging domain 1 (D1) between the two isoforms, (ii) block mutations of 22 amino acids in length that interchanged parts of the loop between transmembrane segments S5 and S6 in both D1 and D4, and (iii) point mutations in the SS2 region of this loop in D1. The TTX sensitivity could be switched between the two isoforms by the exchange of a single amino acid, tyrosine-401 in rSkM1 and cysteine-374 in rSkM2 in SS2 of D1. By contrast most chimeras and point mutants had an intermediate sensitivity to mu-CTX when compared with the wild-type channels. The point mutant rSkM1 (Y401C) had an intermediate single-channel conductance between those of the wild-type isoforms, whereas rSkM2 (C374Y) had a slightly lower conductance than rSkM2. The rate of inactivation was found to be determined by multiple regions of the protein, since chimeras in which D1 was swapped had intermediate rates of inactivation compared with the wild-type isoforms.

Amino Acid Sequence↗
PubMed1992

Primary structure and functional expression of the human cardiac tetrodotoxin-insensitive voltage-dependent sodium channel.

The principal voltage-sensitive sodium channel from human heart has been cloned, sequenced, and functionally expressed. The cDNA, designated hH1, encodes a 2016-amino acid protein that is homologous to other members of the sodium channel multigene family and bears greater than 90% identity to the tetrodotoxin-insensitive sodium channel characteristic of rat heart and of immature and denervated rat skeletal muscle. Northern blot analysis demonstrates an approximately 9.0-kilobase transcript expressed in human atrial and ventricular cardiac muscle but not in adult skeletal muscle, brain, myometrium, liver, or spleen. When expressed in Xenopus oocytes, hH1 exhibits rapid activation and inactivation kinetics similar to native cardiac sodium channels. The single channel conductance of hH1 to sodium ions is about twice that of the homologous rat channel and hH1 is more resistant to block by tetrodotoxin (IC50 = 5.7 microM). hH1 is also resistant to mu-conotoxin but sensitive to block by therapeutic concentrations of lidocaine in a use-dependent manner.

Amino Acid Sequence↗
PubMed1992

Lidocaine block of human heart sodium channels expressed in Xenopus oocytes.

The tertiary amine lidocaine is used clinically for preventing cardiac arrhythmias, and has been widely studied on mammalian tissue. Xenopus oocytes were used as an expression system to study the effect of lidocaine on a sodium (Na) channel, derived from a full-length human heart (hH1) cDNA clone. The concentration dependence of the lidocaine block of hH1 Na current was consistent with a binding stoichiometry of 1:1. At low frequency stimulation, and at holding potentials < or = 100 mV, the IC50 was 226 microM, comparable to values found in mammalian cardiac cells. Lidocaine also shifted the steady-state inactivation of hH1 Na current to hyperpolarized potentials in a dose-dependent manner. Our experiments suggest that lidocaine block is state dependent, with high affinity for an inactivated state (KI = 11 microM) and low affinity for the resting state (KR = 3.9 mM). The quaternary amine derivative of lidocaine, QX-314, had no effect on Na current at an extracellular concentration of 1 mM.

Animals↗
PubMed1992

Gene expression of differentiation- and dedifferentiation markers in normal and malignant human thyroid tissues.

Steady state mRNA transcript levels of thyroid differentiation markers such as TSH receptor (TSHR), thyroglobulin (Tg) and thyroid peroxidase (TPO) as well as a potential marker of dedifferentiation, c-myc, marker were investigated in patients with thyroid tumors and in normal controls using Northern blot analysis. Blots were normalized by acridine orange staining whereas analysis of beta-actin mRNA levels revealed highly variable levels already in normal tissue suggesting regulation of this "constitutively" expressed gene. Determination of c-myc mRNA revealed increased steady state mRNA levels in anaplastic carcinomas (ATC) as compared to normal tissues. However, in some patients c-myc transcript levels were lower in the tumor than in the adjacent normal tissue reducing the significance of c-myc as a marker of dedifferentiation. High levels of TSH mRNA were found in control thyroids, whereas in ATC no normal TSHR mRNA was detected. In PTC and follicular thyroid carcinomas (FTC) the transcripts varied from increased to markedly reduced levels. In one patient with FTC 2 independent preparations of the tumor revealed different results, undetectable and clearly detectable TSHR mRNA levels. Xenotransplantation of this tissue on nude rats showed a variable expression pattern in the individual xenotransplantations suggesting heterogeneity of the tumor tissue. Tg and TPO mRNA were strongly expressed in normal tissues and completely lost in all ATC. In differentiated thyroid tumors the transcript levels of Tg and TPO varied from normal to complete loss of expression of either Tg or TPO, or both.(ABSTRACT TRUNCATED AT 250 WORDS)

Acridine Orange↗
PubMed1992

Susceptibilities of members of the Bacteroides fragilis group to 11 antimicrobial agents.

The susceptibilities of 200 clinical isolates of the Bacteroides fragilis group to 11 antimicrobial agents were determined by the broth microdilution method of the National Committee for Clinical Laboratory Standards. All isolates were susceptible to imipenem and ticarcillin-clavulanic acid. The rates of resistance to cefoxitin and clindamycin were low (4 and 6%, respectively), while those to ceftizoxime and cefotetan were higher (10.5 and 24%, respectively).

Anti-Bacterial Agents↗
PubMed1992

[Recurrent inguinal hernias: surgery with transversalis fascia repair].

Some authors recommend different prosthetic repairs for treatment of recurrent groin hernia. In our institution groin hernias are treated by a modified Shouldice-repair, which considers the transversalis fascia layer only. In this prospective study 240 consecutive patients with 298 groin hernias were operated on. 46 patients were treated for 53 recurrent hernias. It was possible to carry out the operative procedure of transversalis plasty in all recurrent cases. 90% of these patients were followed-up by personal examination after a median of 26 months after operation (range 12-36 months). 89% of the patients with primary operation have been checked 15 months postoperatively. 2 patients (4.5%) of the recurrent hernias had a recurrence. This compares well with the 3.2% recurrence rate (7 patients) in the patients with primary hernias. The difference is not significant (p greater than 0.5). The only observed difference between recurrent and primary hernias was in the rate of testicular atrophy (6.8% for recurrent and 0% for primary hernias). According to our experience large prosthetic repairs are not necessary for the common case of recurrent groin hernia, but may be useful in specially selected situations.

Adult↗
PubMed1992

[Anterior knee laxity in a healthy patient sample].

A prospective study investigates anterior knee laxity in 100 healthy subjects (mean age 24.5 years). Testing was performed by two examiners either clinically by Lachman test or by means of KT-1000 arthrometer. Mean anterior tibial translation was 4 mm for the right and 4.3 mm for the left knee when tested clinically. With use of KT-1000 at 89 Newton results were 4.6 mm and 4.0 mm, respectively. Clinical measurements revealed an inter-examiner difference of 0 to 1 mm in 77% of right and 80% of left knees. In the remainder difference was more than 1 mm. On apparative testing the two examiners obtained similar results at 67 Newton. Measurements differed increasingly, however, at 89 Newton and 134 Newton. In conclusion, the use of KT-1000 arthrometer in routine assessment of anterior knee laxity offers no advantage over clinical testing alone.

Adult↗
PubMed1991

[Cold-induced pathology at high altitude].

Cold injury is an objective danger in mountain climbing as well as in many outdoor and recreational sports such as skiing, fishing, etc. Symptoms are easily recognizable by the experienced, and prevention is mostly possible. Cold injury should be divided by pathological means in general hypothermia and local frostbite injuries. Life-threatening deep hypothermia with coma and insufficient circulation or cardiac arrest is reversible under the condition of sufficient core rewarming, for instance by CEC. Because of the big tolerance of hypothermic patients to hypoxia, clinical death is not like biological death and therefore reversible. Local frostbite is not life-threatening, but has often deleterious effects. Rapid rewarming in warm water of 37 to 42 degrees C is mandatory. After rewarming, the difference between superficial and deep frostbite can be established. Scintigraphy seems to be of great help in setting early prognosis. Daily sterile treatment of the injury, whirlpool bath and prevention of infections belong to standard treatment. There are little objective informations about the role of vasodilators, anticoagulants, antibiotics, sympathectomy and others. Early experience with Prostavasine seems to bee encouraging.

Adult↗
PubMed1991

Failure to elicit neuronal macroscopic mechanosensitive currents anticipated by single-channel studies.

Mechanosensitive channels can be observed in most cell types during single-channel recording and have been implicated in many cellular processes. Potassium-selective single-channel currents, both stretch-activated and stretch-inactivated, can be observed in growth cones and cell bodies of Lymnaea stagnalis neurons. Equivalent macroscopic mechanosensitive currents could not, however, be elicited while applying various mechanical stimuli. This discrepancy suggests that single-channel mechanosensitivity is an artifact of patch recording.

Animals↗
PubMed1991

A mitochondrial 16 kDa protein is associated with cytoplasmic male sterility in sunflower.

Cytoplasmic male-sterile lines CMS89 and CMSBaso of sunflower (Helianthus annuus) differ from the fertile lines HA89 and Baso in a mitochondrial DNA sequence in the vicinity of the atpA gene. In addition, the transcriptional pattern of the atpA gene is changed in male-sterile lines compared to fertile ones. Besides one main transcript in the fertile lines, the male-sterile lines additionally show larger transcripts. Investigation of Baso and CMSBaso revealed that the two fertility-restored lines of CMS89 have the same transcripts as CMSBaso or a combination of CMSBaso and CMS89. Comparing the mitochondrial in organello translation products we observed a unique 16 kDa protein, which is expressed in male-sterile lines carrying the H. petiolaris cytoplasm but is not detectable in fertile lines with H. annuus cytoplasm. The 16 kDa protein can also be observed in restored lines but not in H. petiolaris. As the expression of the 16 kDa polypeptide seems to be linked to the interspecific cross between H. petiolaris and H. annuus it may play a role in CMS. By different criteria such as molecular mass, isoelectric point and peptide fingerprinting the alpha subunit of the F1-ATPase of male-sterile and fertile lines is very similar if not identical.

Crosses, Genetic↗
PubMed1991

Cytoplasmic male sterility in sunflower is correlated with the co-transcription of a new open reading frame with the atpA gene.

The organization and expression of the mitochondrial (mt) genome of fertile, male-sterile and restored lines of Helianthus annuus and of H. petiolaris were compared to identify alterations which might lead to cytoplasmic male sterility (CMS). The mtDNAs of fertile and male-sterile lines differ by an 11 kb inversion and a 5 kb insertion. The rearrangements seem to be the result of recombination events within an inverted repeat of 261 bp. Detectable alterations in the transcript pattern of the rearranged mtDNA regions are restricted to the atpA locus. The male-sterile line CMSBaso shows three additional transcripts of the atpA locus of about 2500, 1200 and 250 nucleotides which are not detectable in Baso. However, the coding sequences of the atpA gene are entirely identical in the fertile line Baso and the male-sterile line CMSBaso. But a new open reading frame (orfH522) of 522 nucleotides is co-transcribed with the atpA gene as an additional larger transcript of about 2500 nucleotides in CMSBaso. orfH522 is also included in a second additional transcript of about 1200 nucleotides. The predicted translation product of orfH522 might play a role in CMS in sunflower.

Amino Acid Sequence↗