Biomedical subjects

H Markus

Publications and source records attributed to H Markus.

51 records · Page 3Linked to original sources

PubMed1986

Splenic irradiation in treating warm autoimmune haemolytic anaemia.

An elderly man with severe congestive heart failure was noted to have a haemoglobin concentration of 87 g/l and a reticulocyte count of 13%. Direct Coombs test yielded a positive result and the serum contained a moderate amount of warm antibody (IgG class). Steroids were given, but to no avail, and the patient's condition precluded splenectomy. A course of splenic irradiation was therefore tried (midline dose 2000 cGy (rads)), and 60 days later the blood film showed similar appearances to those in patients treated successfully by splenectomy. Haemoglobin concentration subsequently rose to normal. Splenic irradiation may offer a simple treatment for resistant warm autoimmune haemolytic anaemia when splenectomy is contraindicated.

Aged↗

PubMed1986

Stability and malleability of the self-concept.

The self-concept literature is characterized by a continuing controversy over whether the self-concept is stable or malleable. In this article we suggest that it is both but that the stability observed for general descriptions of the self may mask significant local variation. In this study the social environment was varied by creating a situation in which subjects found themselves to be either very unique or very similar to others. Following this manipulation, subjects responded to a series of self-concept measures. Although the uniqueness and similarity subjects did not differ in the trait terms they used to describe themselves, they did differ systematically in their latency for these judgments, in positivity and negativity of their word associations, and in their judgments of similarity to reference groups. These findings imply that subjects made to feel unique recruited conceptions of themselves as similar to others, whereas subjects made to feel similar to others recruited conceptions of themselves as unique. The results suggest that very general self-descriptive measures are inadequate for revealing how the individual adjusts and calibrates the self-concept in response to challenges from the social environment.

Adult↗

PubMed1985

The nature of negative thoughts in depression.

We investigated the nature and content of the negative thoughts that accompany depression by examining thoughts about oneself and others during three cognitive tasks: imaging, recall, and inference. Mildly depressed and nondepressed subjects were asked to image, recall, and make inferences about a variety of events while thinking about themselves or another person. The events were sad or happy and either social or nonsocial in nature. The results suggest that the negativity in thought that accompanies depression is restricted to thoughts about oneself and does not extend to thoughts about others. The relation between negative thoughts and the depressive's view of self is discussed. It is proposed that depressives have a negative self-schema that makes the affective nature of their behavior particularly salient.

Adult↗

PubMed1984

Effect of applied electrical fields on sprouting of intact saphenous nerve in adult rat.

Saphenous nerve sprouting was measured behaviorally and histologically after chronic sciatic denervation in the adult rat. The effect of electrical stimulation (either weak DC fields, or stronger AC fields) on the rate of sprouting of the intact saphenous was studied. Sprouting was enhanced by DC fields (1 microA) if the cathode was placed distal to the growth tips, but was unaffected by anode stimulation. Sprouting was also enhanced by AC fields (1000 microA per pulse) given at 20 Hz and 0.1 ms duration. In the discussion we postulate that separate mechanisms might mediate the AC and DC results. The DC effects are the first demonstration in mammals of results previously observed in lower vertebrates.

Animals↗

PubMed1984

Spread of saphenous somatotopic projection map in spinal cord and hypersensitivity of the foot after chronic sciatic denervation in adult rat.

The left sciatic nerve was cut and ligated in adult rats (chronic denervation). Twenty-one days later the right sciatic nerve was cut and ligated (acute denervation). The somatotopic maps of the surviving intact saphenous nerves (left and right) were compared on day 21 by recording from single interneurons in the dorsal horn of the spinal cord. On the acute side saphenous mediated natural responses were observed only as far caudally as L3, while no natural responses were found in L4 and 5 (this silent zone in L4 and 5 had previously been sciatic territory). In contrast, after chronic sciatic denervation, L4 and L5 were not silent to natural stimulation as the saphenous natural responses had spread into the sciatic territory. Saphenous inputs always won the sciatic territory in L4 and L5 over competing thigh afferents after chronic sciatic denervation. Electrical stimulation of the saphenous nerve on the acute side produced unit responses all the way down to S1 (with no silent areas in L4 and 5). These electrically evoked unit responses in L4 to S1 of the acute side were called 'long range' pathways. There were no differences in 'long range' electrical responses in the acutely and chronically denervated cord. The caudal boundary for electrically evoked saphenous responses was S1 on both sides of the cord, and post stimulus histograms of unit responses were not statistically different on the two sides. Thus after chronic sciatic denervation natural responses mediated by saphenous spread caudally into sciatic territory, but electrically evoked responses did not change. Behaviorally, there was the expected spread of saphenous mediated responses from the medial toe and foot to more lateral regions after chronic sciatic denervation. Unexpectedly, there was an increase in sensitivity (hyperalgesia) of the medial toe and foot. We postulate that this increased sensitivity might be mediated by the spread of saphenous projections into L4 and L5 of the cord after chronic sciatic denervation. Perhaps post traumatic neuralgia in humans could be due to increased number of spinal cord cells responding to stimulation of the receptive field of the surviving nerve.

Animals↗

PubMed1984

[Aortic baroreceptor function in narcotized rabbits during alpha-adrenoceptor blockade with prazosin].

Since alpha-adrenoceptor blockade alters the mechanical vessel wall properties, the arterial baroreceptor function is to be changed also by this type of blockade. In 13 rabbits narcotized with chloralose and urethan, therefore, the aortic baroreceptor function was tested together with the baroreceptor heart reflex prior to and after intravenous administration of prazosin (0.005, 0.01, 0.05 mg per kg BW). By inflation and respective deflation of a balloon catheter lying with its tip in the thoracal aorta the arterial blood pressure level ahead was changed over a range as much as 30 to 50 mm Hg. The arterial blood pressure in the aortic arch, the heart rate and the electroneurogram from the peripheral stump of the left aortic nerve were registered. Intravenous administration of prazosin slowed down the arterial blood pressure in a dose related manner, and the heart rate remained similar. After having applied any doses of prazosin the baroreceptor heart reflex was completely abolished. The baroreceptor sensitivity was remarkably increased by prazosin. The characteristic curve describing the baroreceptor function was shifted to the left and was steeper. It was concluded that the baroreceptor heart reflex is directly blocked by the action of prazosin against the transmission in the parasympathetic pathway, and, mediated by the influence of prazosin on the vessel wall properties, the arterial baroreceptor becomes more sensitive.

Animals↗

PubMed1982

Neural control of the intestinal migrating myoelectric complex. A pharmacological analysis.

A pharmacological analysis of the participation of autonomic nerves in the control of the intestinal migrating myoelectric complex (MMC) was conducted on six conscious fasting dogs with implanted bipolar electrodes. All dogs exhibited regularly recurring MMC's. Hexamethonium (2-10 mg/kg i.v.) or atropine (25-100 micrograms/kg i.v.) immediately suppressed all spiking activity, stopped the progression of the ongoing complexes, and prevented the initiation of new complexes for 2.5 to 5 h. Phentolamine (2-4 mg/kg i.v.) and propranolol (2 mg/kg i.v.) given separately or in combination had no observable effect on any of the different phases of the complex, its progression, or its frequency. Phenylephrine (0.5-1 mg/kg) inhibited the spiking phases of the complex. Isopropylnoradrenaline had no effect on the complex at doses (up to 30 micrograms/kg) which produced maximal cardiac chronotropic effect. The effects of these agonists were totally blocked by the doses of respective adrenergic antagonists used. Phenoxybenzamine given in a dose of 10-15 mg/kg i.v. produced effects similar to atropine apparently owing to blockade of cholinergic muscarinic receptors. It is concluded that (a) the regular spiking phases of the migrating complex result from cyclical and sequential activation of preganglionic fibers forming nicotinic synapses on postganglionic cholinergic excitatory neurones; and (b) the function of adrenergic nerves is not normally required for the MMC.

Animals↗

PubMed1979

The birth order puzzle.

Studies relating intellectual performance to birth order report conflicting results, some finding intellectual scores to increase, others to decrease with birth order. In contrast, the relationship between intellectual performance and family size is stable and consistently replicable. Why do these two highly related variables generate such divergent results? This birth order puzzle is resolved by means of the confluence model that quantifies the influences upon intellectual growth arising within the family context. At the time of a new birth, two opposing influences act upon intellectual growth of the elder sibling: (a) his or her intellectual environment is "diluted" and (b) he or she loses the "last-born's handicap" and begins serving as an intellectual resource to the younger sibling. Since these opposite effects are not equal in magnitude, the differences in intellectual performance among birth ranks are shown to be age dependent. While elder children may surpass their younger siblings in intellectual performance at some ages, they may be overtaken by them at others. Thus when age is taken into consideration, the birth order literature loses its chaotic character and an orderly pattern of results emerges.

Adolescent↗

PubMed1976

The interaction of an anionic photoreactive probe with the anion transport system of the human red blood cell.

N-(4-azido-2-nitrophenyl)-2-aminoethyl[35S]sulfonate is employed as a photoreactive probe for the anion transport system in the human erythrocyte. In the dark and at 37 degrees C the probe penetrates the membrane via a pathway sensitive to specific inhibitors of anion permeability. It reversibly inhibits sulfate and chloride fluxes but the inhibition is reduced by higher concentrations of sulfate. Upon photolysis to produce a reactive nitrene (at 0 degrees C to minimize penetration), the probe inhibition of anion permeability. Under appropriate conditions the degree of inhibition after photoactivation (irreversible) is almost the same as that in the dark (reversible). The binding sites for the radioactive probe are largely found in proteins of 95 000 apparent molecular weight (band 3). After pronase treatment of the labelled cells, most of the probe is found in a 65 000 molecular weight segment derived from the 95 000 molecular weight protein. In this respect the photoreactive probe resembles another potent irreversible inhibitor of anion transport, 4, 4'-diisothiocyano-2, 2' stilbene disulfonate. In fact, most of the binding sites for each probe are common to both. Thus, in the dark, the azido derivative protects the anion system from inhibition by DIDS and substantially reduces the binding of DIDS to band 3 protein. Conversely, pretreatment with DIDS substantially reduces the binding of the photoreactive probe to the same protein. The fact that an apparent substrate for the anion permeation system competes for binding sites with a specific non-penetrating inhibitor of anion permeability suggests that the inhibitory and transport sites may be closely related and implicates the 95 000 molecular weight protein as the element of the anion transport system which contains the substrate binding site.

Biological Transport↗

PubMed1975

A comparison of intact human red blood cells and resealed and leaky ghosts with respect to their interactions with surface labelling agents and proteolytic enzymes.

Resealed ghosts and intact red blood cells were directly compared with respect to their interactions with surface proteins by 4.4'-diisothiocyano-2,2'-stilbene disulfonic acid (DIDS) and by pyridoxal phosphate-borohydride (as seen after sodium dodecylsulfate/acrylamide gel electrophoresis) was substantially the same in cells and resealed ghosts under conditions in which a relatively small change would be apparent. In each membrane system, DIDS labels a protein component of apparent molecular weight 95 000 and pyridoxal phosphate labels the same protein plus three glucoprotein components. The sensitivity of surface proteins and of DIDS and pyridoxal phosphate-labelled sites to pronase was also similar in the cells and resealed ghosts. The glycoproteins were digested, in each case, and the 95 000 (molecular weight) protein was largely split into two proteins of apparent molecular weights 65 000 and 35 000, with both portions containing DIDS and pyridoxal phosphate in the presence of hemoglobin was similar to the labelling of intact cells, provided that the pyridoxal phosphate was present on both the outside and inside of the cells. Virtually all of the major protein components visible by staining on acrylamide gels were labelled. It is concluded that none of the probes could detect any substantial differences in reactivity of proteins of the outer surface of the membrane protein conformation or arrangement occur as a consequence of lysis and resealing of ghosts, that are detectable by the reported procedures.

Blood Proteins↗

PubMed1973

Relationship between plasma and muscle concentrations of ketone bodies and free fatty acids in fed, starved and alloxan-diabetic states.

1. Concentrations of ketone bodies, free fatty acids and chloride in fed, 24-120h-starved and alloxan-diabetic rats were determined in plasma and striated muscle. Plasma glucose concentrations were also measured in these groups of animals. 2. Intracellular metabolite concentrations were calculated by using chloride as an endogenous marker of extracellular space. 3. The mean intracellular ketone-body concentrations (+/-s.e.m.) were 0.17+/-0.02, 0.76+/-0.11 and 2.82+/-0.50mumol/ml of water in fed, 48h-starved and alloxan-diabetic rats, respectively. Mean (intracellular water concentration)/(plasma water concentration) ratios were 0.47, 0.30 and 0.32 in fed, 48h-starved and alloxan-diabetic rats respectively. The relationship between ketone-body concentrations in the plasma and intracellular compartments appeared to follow an asymptotic pattern. 4. Only intracellular 3-hydroxybutyrate concentrations rose during starvation whereas concentrations of both 3-hydroxybutyrate and acetoacetate were elevated in the alloxan-diabetic state. 5. During starvation plasma glucose concentrations were lowest at 48h, and increased with further starvation. 6. There was no significant difference in the muscle intracellular free fatty acid concentrations of fed, starved and alloxan-diabetic rats. Mean free fatty acid intramuscular concentrations (+/-s.e.m.) were 0.81+/-0.08, 0.98+/-0.21 and 0.91+/-0.10mumol/ml in fed, 48h-starved and alloxan-diabetic states. 7. The intracellular ketosis of starvation and the stability of free fatty acid intracellular concentrations suggests that neither muscle membrane permeability nor concentrations of free fatty acids per se are major factors in limiting ketone-body oxidation in these states.

Journal Article↗

PubMed1973

Rapid intravenous sodium acetoacetate infusion in man. Metabolic and kinetic responses.

The metabolic and kinetic responses to rapidly intravenously administered sodium acetoacetate (1.0 mmol/kg body wt) was studied after an overnight fast in 12 male and female adults weighing between 88 and 215% of average body weight. Blood was obtained before, during, and after the infusion for determination of circulating concentrations of immunoreactive insulin, glucose, acetoacetate, beta-hydroxybutyrate and free fatty acids. In three obese subjects the studies were repeated after 3 and 24 days of total starvation. After the overnight fast acetoacetate rose rapidly reaching a peak concentration at the end of the infusion; beta-hydroxybutyrate concentrations also increased rapidly and exceeded those of acetoacetate 10 min postinfusion. Total ketone body concentration at the end of the infusion period was comparable to that found after prolonged starvation. After the initial mixing period, acetoacetate, beta-hydroxybutyrate and total ketone bodies rapidly declined in a parallel manner. There were no obvious differences between the subjects with regard to their blood concentrations of ketone bodies. The mean plasma free fatty acid concentration decreased significantly during the 20th to 90th min postinfusion period; for example the control concentration of 0.61 mmol/liter fell to 0.43 mmol/liter at 60 min. In the three obese subjects studied repeatedly, fasting plasma free fatty acids decreased with acetoacetate infusion from 0.92 to 0.46 mmol/liter after the 3 day fast and from 1.49 to 0.71 mmol/liter after the 24 day fast. Acetoacetate infusion caused no changes in blood glucose concentration after an overnight fast. However, in the three obese subjects restudied after 3- and 24-day fasts blood glucose decreased, respectively, from 3.49 to 3.22 mmol/liter and from 4.07 to 3.49 mmol/liter. The mean serum insulin concentration in all subjects significantly increased from 21 to 46 muU/ml at the completion of the infusion and rapidly declined. In the three obese subjects restudied after 3- and 24-day fasts an approximate two-fold increase of serum insulin was observed after each acetoacetate infusion. The mean fractional utilization rate of exogenously derived ketone bodies for all 12 subjects after an overnight fast was 2.9% min(-1). In the three obese subjects studied after an overnight, 3 and 24 day fast the mean fractional utilization rates were 2.1%, 1.5%, and 0.6% min(-1), respectively. Ketone body volumes of distribution in the overnight fasted subjected varied from about 18% to 31% of body wt, suggesting that ketone bodies are not homogenously distributed in the body water. In the three obese subjects restudied after 3- and 24-day fasts volumes of distribution remained approximately constant. When total ketone body concentrations in the blood were below 2.0 mmol/liter, there was a linear relationship between ketone body utilization rates and ketone body concentrations; no correlation was found when blood concentrations were higher.

Acetoacetates↗

PubMedDate not supplied

Transcranial cortical magnetic stimulation of lower-lip mimetic muscles: effect of coil position on motor evoked potentials.

The effect of the coil position along the interaural line on motor evoked potentials of lower-lip muscles to cortical transcranial magnetic stimulation was investigated in 17 healthy subjects. Using a figure-8-shaped coil, we observed ipsi- and contralateral middle-latency motor evoked potentials in all subjects, when the coil was centered within an area between 4 and 13 cm lateral to the vertex. Maximal responses (mean amplitude 1.4 +/- 0.8 mV contralateral, 0.7 +/- 0.5 mV ipsilateral) with shortest mean onset latencies (11.3 +/- 1.6 ms contralateral, 12.1 +/- 2.8 ms ipsilateral) were obtained at a stimulus position of 10 cm lateral to the vertex. Cortical maps of mean amplitude and mean response duration showed inverse U-shaped configuration. Furthermore, we observed an additional polyphasic and mostly bilateral response in 16 of the 17 subjects.

Adult↗

PubMedDate not supplied

Motor potentials of lower-lip mimetic muscles and distal arm muscles to cortical transcranial magnetic stimulation: the possibility of one-dimensional separation of two cortical representation areas.

The cortical representation of the abductor pollicis brevis muscle (APB) was investigated by transcranial magnetic stimulation (TMS) along the interaural line on the head surface in 17 healthy subjects. Comparing amplitudes of motor evoked potentials (MEPs) with those obtained by cortical TMS of lower-lip muscles, we found a considerable overlap between the areas from which reproducible MEPs of APB and lower-lip muscles could be elicited. However, there was a statistically significant separation of the two areas, the APB area being placed more medially. With regard to short examination procedures it can be concluded that a separation between distal arm and facial muscles is possible not only by two-dimensional cortical mapping procedures, but also by one-dimensional cortical TMS.

Adult↗

PubMedDate not supplied

Cortical transcranial magnetic stimulation of the frontalis muscle: characteristic features and details on motor-evoked potentials of the forehead.

The effect of coil position on the head surface along the interaural line on motor-evoked potentials (MEPs) of the frontalis muscle due to cortical transcranial magnetic stimulation was investigated in 16 healthy subjects. Bilateral reproducible responses could be observed in all subjects investigated at coil positions varying from 2 to 12 cm lateral to the vertex. MEP amplitudes of the frontalis muscle offered no significant side differences neither in amplitude nor in onset latency. Despite a considerable overlap, a statistically significant separation (p < 0.0001) of the two areas from which reproducible MEPs of upper and lower mimetic muscles could be elicited was evident for the calculated mediolateral center with the frontalis muscle area being placed more medially. Our findings are in accordance with anatomical studies indicating a predominance of corticonuclear descending fibers to lower but not to upper facial motoneurons.

Adult↗