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Biomedical subjects

P Niemi

Publications and source records attributed to P Niemi.

At least 19 recordsLinked to original sources
PubMed1991

Tissue relaxation enhancement after intravenous administration of (ITCB-DTPA)-gadolinum conjugated albumin, an intravascular magnetic resonance imaging contrast agent.

Gadolinium-isothiocyanato-benzyl-diethylenetriamine pentaacetic acid (ITCB-DTPA-Gd), a derivative of Gd-DTPA, was multiply conjugated to bovine serum albumin (BSA). In the synthesis of BSA-(ITCB-DTPA-Gd) conjugate, none of the five carboxylate groups of DTPA is functionalized for protein-chelate linkage. The rationale for this modification is to improve the affinity for Gd3+. We obtained a high-stability constant for the complex, comparable to unbound Gd-DTPA. Also, the complex had a T1 relaxivity as high as 30.3 seconds-1mmol-1 at 29 MHz (at 24 degrees C). At this field strength, and T1 of rat blood declined 91% after injection of 300 mg/kg of BSA-(ITCB-DTPA-Gd), corresponding to a Gd dose of 0.02 mmol/kg, while at 0.86 MHz it declined 64%. The shortening of T1 in vitro of blood, as well as spleen, lungs, and kidneys, persisted for 60 minutes. Better enhancement on post-contrast magnetic resonance images of rats was obtained at 1.0 T than at 0.04 T. Tissues with rich vascularization and large venous structures were well displayed at the higher field.

Animals↗
PubMed1991

Magnetic field dependence of longitudinal relaxation rates of solutions of various protein-gadolinium3+ chelate conjugates.

Bovine serum albumin (BSA) and porcine serum fibrinogen (FIB) were multiply labeled with gadolinium3+ by using three different ligands: DTPA dianhydride, isothio-cyanato-benzyl-DTPA (ITCB-DTPA), in which none of the five coordinating carboxylates is employed for macromolecular linkage, and isothiocyanatobenzyl-TRITA, a macrocyclic ligand. The nuclear magnetic resonance dispersion (NMRD) profiles of the protein-(Gd chelate) conjugates were characteristic to each chelate involved, possessing, as expected, greater longitudinal relaxivities than the corresponding Gd chelates alone and exhibiting prominent peaks at the proton Larmor frequency range of 10 to 40 MHz. Particularly favorable relaxation enhancement was measured in the solutions of BSA-(ITCB-DTPA-Gd) at this field range. When the number of chelates conjugated with protein increased, up to 163 Gd chelates per one fibrinogen, a progressive decrease in relaxivity was observed. This study demonstrates the relaxation properties of novel macromolecular contrast agents designed for magnetic resonance imaging.

Animals↗
PubMed1991

Chemical restraint-reversal with medetomidine and atipamezole in veterinary small animal practice: a survey on the opinions of the dog owners and veterinarians.

The opinions of animal owners and practising veterinarians concerning a new restraint-reversal medication (medetomidine-atipamezole) for dogs were obtained by two questionnaires in connection with a clinical study. Four alternative answers to each statement question scored as "completely agree", "somewhat agree", "somewhat disagree" and "completely disagree". The questionnaires were completed by 21 veterinarians and 245 dog owners. The overall response to the treatment was clearly positive. Both groups had a favourable attitude towards drug use with mean combined scores (from 1 to 4; 4 = most favourable) of 48.1 (max 56) for the dog owners and 39.2 (max 52) for the veterinarians. Only a little information was gained about the background of negative sentiments. Some pet owners (19%) opposed to medication on a priori grounds, some (26%) reacted strongly to the dizziness of their animals and some owners (21%) complained because of general anxiety before, during and after their pets were treated.

Adrenergic alpha-Agonists↗
PubMed1990

Proton relaxation enhancement of albumin, immunoglobulin G, and fibrinogen labeled with Gd-DTPA.

Bovine serum albumin, immunoglobulin G, and fibrinogen were labeled with Gd-DTPA using a bifunctional chelating agent DTPA anhydride. The protein-(Gd-DTPA) conjugates had 1.4- to 2.0-fold greater longitudinal relaxivities at 0.02 and 0.44 T than the relaxivity of plain Gd-DTPA. The increase of longitudinal relaxivity was not directly related to the size of carrier protein. Up to 50 Gd-DTPA chelates per protein, longitudinal relaxivity of the conjugates was proportional to the concentration of Gd and independent of the Gd/protein ratio.

Animals↗
PubMed1990

Eye movements during repeated reading of a text.

The facilitation of eye movements was studied in two experiments involving a repeated reading paradigm. A text was read three times. Initial reading was immediately followed by the first repetition; the second repetition took place one week later. Recall task instructions were used to encourage a detailed reading of the text. The data were analysed sentence by sentence from the 'first pass' readings not including returns to earlier test locations. A general facilitation for all eye movement parameters was found. Repetition decreased the summed fixation time, the average fixation duration, the number of progressive fixations, and the number of regressions. Additionally, repetition increased saccade lengths. Experiment 2 further qualified the general facilitory effect. The middle section of the text, being the most dense of information, was devoted the most visual attention by the readers. Moreover, it was also found to produce the largest degree of facilitation due to repetition. This was true with all other eye movement parameters except saccade length and average fixation duration. Average fixation durations were longer in the beginning of a text than in the end. This was true in all the three readings. Similarly, for each reading, highly important sentences received more visual attention than unimportant sentences.

Adult↗
PubMed1990

Semantic errors in a deep dyslexic.

A case of a Swedish-speaking deep dyslexic is reported whose semantic paralexias appeared to result mainly from a lexical retrieval failure in oral reading. He was able to draw correct pictures of the written words for which he had simultaneously produced a semantically erroneous oral reading response. Repeated attempts to correct paralexic responses were common, indicating that the patient was often aware of the errors. His lexical retrieval problems and semantic errors extended to naming as well, and the results support Nolan and Caramazza's (1982, Brain and Language, 16, 237-264), dual-deficit model of deep dyslexia.

Adult↗
PubMed1990

Superparamagnetic particles as gastrointestinal contrast agent in magnetic resonance imaging of lower abdomen.

Negative gastrointestinal contrast enhancement can be achieved by oral administration of superparamagnetic particles. Their feasibility for the MR imaging of the female pelvis and lower abdomen was evaluated in studies on 32 follow-up patients with treated gynaecologic cancer. All the applied doses (0.2-1.0 mg particles/ml given in a volume of 600-800 ml) of contrast medium decreased the intraluminal signal. However, there was unpredictable individual variation in segmental distribution, and in some cases only a limited contrast effect was obtained. Image distortion was detected when the applied particle concentration exceeded 0.5 mg/ml, especially of the sagittal sections.

Abdomen↗
PubMed1990

MR imaging of experimental intramuscular hemorrhage at 0.02 T. Contrast enhancement with Gd-DOTA.

Intramuscular hemorrhage was induced by injecting autologous blood into the paraspinal muscle of 8 rabbits. In order to evaluate the time-dependent changes of hemorrhage observed on MRI, the animals were imaged at different stages of blood resolution at 0.02 tesla (T), and control examined with ultrasound using a 7.5 MHz linear transducer. Six inversion recovery sequences (TR = 1,000 ms. TE = 30 ms, and TI = 18, 48, 148, 201, 302, and 398 ms) were used for the in vivo calculation of T1 relaxation times. IR 1,000 (398)/30 imaging was performed before and after the Gd-DOTA administration. The hemorrhage was evident on MR images throughout the study, especially on the T2 weighted (SE 1,000/100) images. MRI showed the healing lesion longer than ultrasound. The T1 relaxation time increased during the time of resolution. Lesions on days 4 to 7 enhanced in intensity after the injection of Gd-DOTA.

Animals↗
PubMed1989

Reading long words embedded in sentences: informativeness of word halves affects eye movements.

The possibility was explored that the informativeness of a specific region within a word can influence eye movements during reading. In Experiment 1, words containing identifying information either toward the beginning or toward the end were displayed asymmetrically around the point of fixation so that the reader was initially presented with either the informative or noninformative zone. Words were read with shorter summed initial fixation time when the reading was started from the informative zone. In Experiments 2 and 3, the target words were presented in sentences that were to be comprehended. More attention was given to the informative endings of words than to redundant endings. The latter were also skipped more often. The duration of the first fixation was not affected by information distribution within the word, whereas the second fixation duration was. The results of these experiments lend good support to the hypothesis of immediate lexical control over fixation behavior and to the notion of a convenient viewing position.

Adult↗
PubMed1988

Paramagnetic contrast enhancement at 0.02 T: an experimental study using Gd-DOTA in normal and hydronephrotic kidneys.

Both normal and experimentally hydronephrotic rabbits were imaged at 0.02 T using partial saturation (PS 160/30) and inversion recovery (IR 1000/200/40) sequences. The signal intensity of normal renal medulla and cortex markedly increased after the injection of 0.1 mmol/kg of Gd-DOTA. In the unilateral total hydronephrosis the dilated renal pelvis did not contrast enhance after 15 and 35 min of Gd-DOTA injection. The enhancement pattern was similar in 1- and 3-week-old hydronephrosis. The effect of Gd-DOTA on renal T1 times at 0.02 T was studied using rats. Fifteen minutes after the Gd-DOTA injection (0.1 mmol/kg) the T1 times of excised rat kidneys decreased from 311 to 90 ms. The authors conclude that the enhancement of the MR signal of the kidney by Gd-DOTA at an ultralow magnetic field (0.02 T) is similar to its enhancement at higher fields (greater than 0.15 T).

Animals↗
PubMed1988

Comparative pharmacokinetics of gadolinium DTPA and gadolinium chloride.

An intravenous injection of 153Gd-labeled gadolinium-DTPA or gadolinium chloride was given to 60 rats, which were killed either 15, 40, 120, 300, 900, or 3600 seconds later. Tissue concentrations of gadolinium in the blood, liver, spleen, stomach, pancreas, renal cortex, renal medulla, lungs, heart, adrenals, gluteal muscle, fat, skin, thymus, brain, thyroid, and parathyroids were measured. Five animals were killed at each time interval with gadolinium-DTPA, and at each of the latter four time intervals (15 and 40 seconds excluded) with gadolinium chloride. The pharmacokinetics of gadolinium-DTPA and chloride differ markedly in terms of tissue concentration, distribution volumes, and the time course of these parameters. Gadolinium, when injected as a chloride, evidently forms insoluble carbonate and phosphate precipitates in the blood, which are taken up by the reticuloendothelial system. The distribution of gadolinium-DTPA on dynamic MRI should closely parallel the distribution of iodinated contrast media on dynamic computed tomography.

Animals↗
PubMed1988

The utility of contrast media in MRI at 0.02 T. A preliminary report.

The effect of 0.1 mmol gadolinium-DTPA on ultralow field magnetic resonance (MR) images of intracranial neoplasms was studied on 20 patients. Tumors that characteristically were enhanced markedly on computed tomography (CT) (meningiomas, acoustic neuromas) demonstrated moderate to marked contrast enhancement with inversion recovery sequences and with saturation recovery sequences with a short repetition time. Standard spin-echo sequences failed to show any contrast effect. The enhancement of gliomas and metastases was weak and often absent. Contrast enhancement, when present, was helpful in delineating the tumor from surrounding edema but the differentiation of living from necrotic tumor was not successful because of low signal intensity. The low effect of gadolinium-DTPA at 0.02 T may be due to a relatively higher T2 weighting of available pulse sequences. The relaxing effect of macromolecules may also change the proportional effect of paramagnetic substances in an ultralow magnetic field.

Adult↗
PubMed1988

Differences in adjustment among university-educated men and women.

The present study forms a part of a thirteen-year longitudinal study of mental health and examines how university-educated men and women have adapted to an average environment. In basic cross-tabulations, 63 out of the total 356 psychological and sociological characteristics proved to be differently distributed for men and women. On the other hand, there were no quantitative differences in global mental health-illness indicators between the sexes. Fifteen central personality characteristics indicating good adaptation were kept constant. Different scales for men and women were needed for adjustment measures such as: "social position", "level of university degree", "ego strength", "control of anger", "general ability", "norm-dependence". On the contrary, "satisfaction with occupation", "self-actualization in love", "having children", "quality of social background" were distributed identically. Consequently, keeping these indicators constant did not decrease sex-differences. Hartmann's concept of adaptation to average environment proved to be rather difficult to apply in practice. Differences in how men and women adapted in Finnish society were examined in detail. The general adjustment was rather successful but there were signs indicating that the women's adaptation was less successful.

Adaptation, Psychological↗
PubMed1987

Event-related brain potentials and the perception of a phonetic continuum.

Competing predictions concerning phoneme discrimination were tested by means of event-related potentials. In research on speech perception, one tradition stems from the physiology of the auditory system whereas another emphasizes categorical perception which involves a marked psychological component. The stimuli were the end points of the Finnish (i)-(y) continuum together with the intermediate boundary sound. Two of these stimuli were presented in each block of trials. One (the 'standard') had a high probability while the other (the 'deviant') was rare. The so-called mismatch negativity (MMN) component of the ERP in response to deviant stimuli showed a large amplitude and short latency when these two stimuli were pure vowels (i) and (y). When the boundary stimulus and one of the pure vowels comprised the stimulus pair, a smaller and more delayed MMN occurred. This result may be taken as support that the discrimination occurs at a basic physiological level. On the other hand, cognitive perception was reflected in the different latencies of the P3 component to (i) and (y). In sum, the results lend support to multilevel hybrid models in the explanation of vowel perception.

Adult↗