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Biomedical subjects

K Stahl

Publications and source records attributed to K Stahl.

17 recordsLinked to original sources
PubMed2000

Magnetic resonance imaging volumes of the hippocampus and the amygdala in women with borderline personality disorder and early traumatization.

BACKGROUND: Based on findings of stress-induced neural disturbances in animals and smaller hippocampal volumes in humans with posttraumatic stress disorder), we hypothesized that patients with borderline personality disorders (BPD), who often are victims of early traumatization, have smaller volumes of the hippocampus and the amygdala. We assumed that volumes of these brain regions are negatively correlated with traumatic experiences and with neuropsychological deficits. METHODS: We studied 21 female patients with BPD and a similar group of healthy controls. We performed clinical assessments, a modified version of the Childhood Trauma Questionnaire, and magnetic resonance imaging volumetric measurements of the hippocampus, amygdala, temporal lobes, and prosencephalon. Neuropsychological testing included scales on which disturbances in BPD were previously reported. RESULTS: The patients with BPD had nearly 16% smaller volumes of the hippocampus (P<.001) and 8% smaller volumes of the amygdala (P<.05) than the healthy controls. The results for both hemispheres were nearly identical and were controlled for the volume of the prosencephalon and for head tilts. The volumes of the hippocampus were negatively correlated with the extent and the duration of self-reported early traumatization only when BPD and control subjects were considered together. Levels of neuropsychological functioning were associated with the severity of depression but not with the volumes of the hippocampus. CONCLUSION: In female patients with BPD, we found reduction of the volumes of the hippocampus (and perhaps of the amygdala), but the association of volume reduction and traumatic experiences remains unclear. Arch Gen Psychiatry. 2000;57:1115-1122.

Adult↗
PubMed1998

[Recovery time after (S)-ketamine or ketamine racemate. Recovery time after short anesthesia in volunteers].

UNLABELLED: The anaesthetic potency of the (S)-ketamine isomer is approximately double that of racemic ketamine. The aim of this study was to compare the recovery of cerebral function after a bolus of 1.3 mg/kg racemic ketamine or 0.65 mg/kg (S)-ketamine followed by continuous application of 4 or 2 mg/kg x h over 15 minutes. METHODS: With their informed consent and approval of the local ethics committee 12 healthy volunteers were enrolled in a double-blind, cross-over study. All drugs were dissolved in identical volumes. On three dates with an interval of one week at least ketamine/NaCl, (S)-ketamine/physostigmine or (S)-ketamine/NaCl was administered (table 1). The sequence was randomized. In addition, the unspecific antagonistic potential of the centrally acting, cholinergic agonist physostigmine (0.012 mg/kg) after (S)-ketamine was tested against saline-placebo. Neuropsychological tests (tests 3-5 of the syndrome-short-test [Erzigkeit, see references]) were used to quantify cerebral function before and at 45, 75, 105, 135, 165 and 195 min after anaesthesia. All data are mean values and standard deviation. Comparisons over time and between drugs were carried out using two-dimensional analysis of variance (ANOVA). Wilcoxon-tests were used post-hoc. p < 0.05 was considered significant. RESULTS: After (S)-ketamine the subjects were able to carry out the tasks more rapidly than after racemic ketamine (p < 0.05). Mean time to reach preoperative test performance +10% was 117.5 min for (S)-ketamine/physostigmine, 121.3 min for (S)-ketamine/NaCl and 141.6 min for racemic ketamine (p < 0.05 between (S)-ketamine and racemic ketamine). No differences were found between physostigmine and placebo. The incidence of side effects (mainly nausea, vomiting) was not different. DISCUSSION: (S)-ketamine offers a shorter recovery time after short anaesthesia compared to racemic ketamine. The investigated dose of physostigmine was probably too low to produce antagonism of (S)-ketamine. An increased dosage of physostigmine has yet to be studied, but is likely to cause a higher rate of side effects such as nausea, vomiting, bradycardia and possibly even tonic-clonic seizures.

Adult↗
PubMed1997

[A new method of ex vivo whole blood perfusion of isolated mammalian organs, exemplified by the kidney of swine].

A new method for the ex vivo perfusion of organs from large mammals is described. Gas exchange and dialysis are carried out simultaneously with a low-flux polysulfon dialysis module. The dialysate (e.g. Tyrode solution) is aerated with a mixture of oxygen and carbon dioxide to ensure gas exchange with the blood. Dialysis is carried out in a closed thermostatically controlled system. Monitoring of ultrafiltration is maintained by continuously weighing the blood reservoir and adjusting an afferent and efferent blood pump. Initial results obtained with isolated pig kidneys demonstrate the suitability of the new method for use as a model for the replacement of animal experiments. Theoretically, clinical application in the area of in vivo regional organ perfusion may also be possible.

Animals↗
PubMed1996

Interaction of 11 beta-hydroxysteroid-oxido reductase in different organs of various mammalian species.

Distribution of 11 beta-HSOR activity in different organs has been measured using tissue slices, homogenates, and microsomes. The biological material was incubated in vitro with cortisol/ cortisone (human preparations) or corticosterone/11-dehydrocorticosterone, respectively (animal preparations). Metabolites formed were quantified using RP-HPLC and on-line detection of labeled compounds. The typical pattern of CS-metabolism as obtained with rat tissue slices revealed that testis, rectum and kidney are predominant oxidizers of active gluco-CS, while liver and lung mainly function as reducers. Human placenta preparations display an exclusive oxidase activity. To trace different types of 11 beta-HSOR homogenates and microsomes of various organs were incubated with different cosubstrates (NAD+/NADH or NADP+/ NADPH, respectively). In accordance with previous reports, this study found that isoenzymes with different cosubstrate preferences exist in individual organs. 11 beta-HS oxidase activity displays a NAD+ preference in the human placenta. There was no apparent difference in cosubstrate preference between human and guinea pig placenta homogenates. In mice there is also a detectable reductive activity, whereas the Sprague-Dawley rat and golden hamster do not show any detectable activities.

11-beta-Hydroxysteroid Dehydrogenases↗
PubMed1994

[Ketamine racemate versus S-(+)-ketamine with or without antagonism with physostigmine. A quantitative EEG study on volunteers].

The potency of S-(+)-ketamine is approximately double that of the racemic ketamine. This study was carried out to investigate the recovery of cerebral electrical function after a bolus of 1.3 mg/kg ketamine or 0.65 mg/kg S-(+)-ketamine and subsequent continuous application of 4 mg/kg h ketamine per h or 2 mg/kg S-(+)-ketamine, per h for 15 min. Furthermore, the centrally acting, cholinergic agonist physostigmine has been reported to antagonize ketamine and to shorten the recovery period. Therefore, after S-(+)-ketamine 0.012 mg/kg physostigmine was tested against saline placebo. METHODS. With their own informed consent and the approval of the ethics committee 12 healthy volunteers were enrolled in a double-blind cross-over study. All drugs were dissolved in identical volumes. On three dates with intervals of at least 1 week between, ketamine/NaCl, S-(+)-ketamine/physostigmine or S-(+)-ketamine/NaCl was administered (Table 1). The sequence was randomized. The EEG was recorded from 20 sites according to the 10/20 system and after Fast-Fourier transformation computed into amplitudes within the delta, theta, alpha, and beta bands and within the total spectrum. The median, the spectral edge frequency and the dominant frequency (dF) were also determined. Mean values of all electrodes before and at 10, 15, 30, 45 and 195 min after the bolus injection were compared using two-dimensional analysis of variance (ANOVA, significance level P < 0.05). RESULTS. The characteristic increase in theta-amplitude and decrease of alpha-amplitude were observed after ketamine and S-(+)-ketamine. Median and dF dropped from the alpha to the theta frequency range. Ketamine led to a greater increase in total, delta, theta and beta amplitude during anaesthesia. 3 hours after ketamine/S-(+)-ketamine anaesthesia a significant decrease in the median and dominant frequency and in total, delta, theta, alpha and beta amplitudes confirmed residual impairment of cerebral function after all study drugs. No differences were found between physostigmine and placebo. DISCUSSION. The EEG changes during ketamine/S-(+)-ketamine administration suggest a slightly deeper anaesthetic level after ketamine. The course of recovery was not different after ketamine and after S-(+)-ketamine. The spectral edge frequency did not differ between measurement points, and is therefore not suitable for assessment of the depth of anaesthesia reached with ketamine/S-(+)-ketamine. The dose of physostigmine tested was probably too low to produce antagonism of S-(+)-ketamine. An increased dosage of physostigmine has yet to be studied, but is likely to cause a higher rate of side effects, such as nausea, vomiting and bradycardia, and possibly even tonic-clonic seizures.

Adolescent↗
PubMed1991

Life cycle savings and consumption constraints: theory, empirical evidence, and fiscal implications.

"Recent tests of both the pure and the extended life cycle hypothesis have generated inconclusive results on the life cycle behavior of the elderly. We extend the life cycle model by introducing a constraint on the physical consumption opportunities of the elderly which, if binding, imposes a consumption trajectory declining in age. This explains much of the received evidence on the elderly's consumption and savings behavior, in particular declining consumption, and increasing savings and wealth with increasing age. Our analysis of [Federal Republic of Germany] data gives additional support to our theory. We finally draw the implications of the theory on the incidence of consumption and income (wealth) taxes, and on the recent (inconclusive) tests of intergenerational altruism."

Adult↗
PubMed1990

Emission of volatile sulfur compounds from spruce trees.

Spruce (Picea Abies L.) trees from the same clone were supplied with different, but low, amounts of plant available sulfate in the soil (9.7-18.1 milligrams per 100 grams of soil). Branches attached to the trees were enclosed in a dynamic gas exchange cuvette and analyzed for the emission of volatile sulfur compounds. Independent of the sulfate supply in the soil, H(2)S was the predominant reduced sulfur compound continuously emitted from the branches with high rates during the day and low rates in the night. In the light, as well as in the dark, the rates of H(2)S emission increased exponentially with increasing water vapor flux from the needles. Approximately 1 nanomole of H(2)S was found to be emitted per mole of water. When stomata were closed completely, only minute emission of H(2)S was observed. Apparently, H(2)S emission from the needles is highly dependent on stromatal aperture, and permeation through the cuticle is negligible. In several experiments, small amounts of dimethylsulfide and carbonylsulfide were also detected in a portion of the samples. However, SO(2) was the only sulfur compound consistently emitted from branches of spruce trees in addition to H(2)S. Emission of SO(2) mainly proceeded via an outburst starting before the beginning of the light period. The total amount of SO(2) emitted from the needles during this outburst was correlated with the plant available sulfate in the soil. The diurnal changes in sulfur metabolism that may result in an outburst of SO(2) are discussed.

Journal Article↗
PubMed1983

A note on the microeconomics of migration.

"The purpose of this note is to demonstrate in a simple model that an individual's migration from a small town to a large city may be rationalized purely by a consumption motive, rather than the motive of obtaining a higher income. More specifically, it is shown that in a large city an individual may derive a higher utility from spending a given amount of income than in a small town." A formal model is first developed that includes the principal forces at work and is then illustrated using a graphic example. The theoretical and empirical issues raised are considered in the concluding section.

Behavior↗
PubMed1979

Ultrastructural morphometric investigations on human platelets after long-term ingestion of oral contraceptives.

Platelets from healthy females, who were taking oral contraceptives over a long period of time, were investigated by ultrastructural morphometry. The size, shape, relative volumes, numerical and surface densities of the platelets and their organelles were measured. In 'long-term pill users' the platelets showed a significant increase in the area of section profile. Further changes as, for example, increased volume of platelet granules, reduced number of mitochondria, decreased volume and surface of the open canalicular system, and increased surface of the dense tubular system are to be noted.

Adolescent↗
PubMed1978

Ultrastructural morphometric investigations on normal human platelets.

Platelets from normal human volunteers were investigated by ultrastructural morphometry. Preparation of blood samples was done in two different ways in order to evaluate the possible influence of the preparative method on the size and shape of platelets and their organelles. No significant differences could be dmonstrated for any of the measured parameters. Relative volumes of specific granules, mitochondria and the open canalicular system were calculated according to the method of Weibel. Surface and numerical densities of some compartments were determined. Direct measurements of the long and short axes of the platelets were conducted to ascertain further information about their size and shape. Absolute data are in good agreement with the few reports in the literature.

Blood Platelets↗
PubMed1978

Ultrastructural morphometric investigations on normal human liver biopsies.

Normal liver biopsies of 14 volunteers were investigated ultrastructural morphometrically. Besides the determination of morphometric baseline data for comparative purposes particular emphasis was placed on the question, if morphometric evaluations of human livers yield reliable results in spite of the higher range of distribution than in experimental liver material. The results showed that the surface of the smooth endoplasmic reticulum of human liver is significantly greater than the surface of rough endoplasmic reticulum. Otherwise the morphometric data of the human liver tissue did not differ essentially to the values of the laboratory rat. The variance analytical consideration of the mean evaluated from the data of the 14 liver biopsies indicated that the standard error of nearly all proved parameters was less than 10% of the mean. The results suggest that ultrastructural morphometric evaluation of human liver biopsy samples yield reliable results provided the samples investigated are sufficiently extensive.

Animals↗
PubMed1977

[Ultrastructural-morphometric investigations on liver biopsies--the influence of oral contraceptives on the human liver (author's transl)].

Liver biopsies from 12 healthy women were investigated morphometrically--according to the methods of Weibel (1969). All women had taken an oral contraceptive agent during 2 til 76 months. The evaluated stereological datas were compared with base-line dates for normal human liver biopsies, which were elaborated in a previous investigation (Roessner et al., 1977). Statistical analysis was performed on an IBM 360/50 computer system, including F- and student's t-test. In the liver biopsy-specimen from the women, which were on oral contraceptives, the volume-density of lysosomes per ml hepatocytes shows a pronounced, significant (p less than 0.001) increase. A moderate increase of cytoplasm is combined with decrease of nuclei-volume. The surface-densities of the rough and smooth endoplasmatic reticulum do not differ significantly from the datas calculated from normal human liver biopsies. All other datas too demonstrate that there are no striking changes in the ultrastructure of human liver, caused by oral contraceptives. Functional alterations however can not be excluded.

Biopsy, Needle↗
PubMed1977

One pediatric burn unit's experience with sleepwear-related injuries.

Review of the records of 678 children with acute injuries referred during an eight-year period to this burn unit indicated that flame burns from a single ignition source (50%) outranked scalds (27%) or house fires (12%) as causes of injury. There was no temporal trend in the rank pattern. The majority of these single-source flame injuries were severe and involved ignition of the child's clothing. From 1969 through 1973, sleepwear was the clothing involved in 32% of the instances. Since that time and coincident with promulgation of strict federal and state standards for flammability of children's night clothing, a dramatic decline in the number of children, referred with injuries of this type has taken place. It is probable that the single factor most important to the decline, in our experience with these injuries, is lower fabric flammability but, because our data may not be representative, corroboration is needed before one can exclude factors such as altered garment design, fire safety-related practices at home, or changing patterns of hospital referral.

Age Factors↗