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Biomedical subjects

A Schaefer

Publications and source records attributed to A Schaefer.

At least 91 records · Page 5Linked to original sources
PubMed1987

Plasma amino-acids analysis: effects of delayed samples preparation and of storage.

This paper describes changes occurring in plasma amino-acid concentrations of: samples which are not prepared for analysis immediately after blood collection and samples stored for 5 to 6 months in the form of either plasma, or of deproteinized plasma, or of deproteinized and at pH 2.2 buffered plasma. Results showed that in order to avoid these changes, plasma should be deproteinized and buffered as soon as possible after blood collection. When analysis could not be performed immediately, storage of samples in a freezer at -18 degrees C in the form of deproteinized and at pH 2.2 buffered plasma showed after 5 to 6 months the best recovery of the initial concentrations, but did not exclude all changes.

Amino Acids↗
PubMed1987

[Indications for coronary angiography in patients with acquired heart valve diseases with reference to risk factors].

The aims of the study were to examine the frequency of coronary artery disease (CAD) in patients with acquired valvular heart disease and to investigate the parameters by which significant coronary artery stenosis can be identified without invasive measures in these patients. For this reason 266 consecutive patients with acquired valvular heart disease (aortic, mitral or combined lesions) were examined retrospectively. In 24 patients (9%) a significant (50% or more reduction of the diameter) coronary artery stenosis was found. The prevalence of CAD increased with age: only one patient younger than 50 years, but 23 patients (13%) older than 50 years revealed significant CAD (19% men, 7% women). Increased levels of cholesterol and/or triglycerides were found more frequently in patients with CAD (33% and 29%, respectively) than in those without (6% and 12%, respectively). No differences were found in patients with aortic and mitral valve disease. Patients with typical chest pain revealed CAD in 30% of cases, whereas only 5% of the patients without angina pectoris (or 4% with atypical chest pain) showed a significant coronary artery stenosis. A high percentage (62%) of patients with typical chest pain and mitral valve disease revealed CAD. None of the 77 female patients without typical angina pectoris had significant coronary artery stenosis, whereas 11% of the male patients showed significant CAD even without typical symptoms. In 51 patients without typical angina pectoris and with no risk factors, no CAD was observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Influence of medium amino acids on the ouabain sensitive and insensitive 86Rb+-fluxes in HeLa cells.

Components of the 86Rb+-influx in HeLa cells were investigated in Joklik minimal essential medium, or in Earle's balanced salt solution with and without medium amino acids. The presence of amino acids led to the stimulation of the ouabain sensitive 86Rb+-uptake and inhibition of the diuretic-sensitive and residual 86Rb+-fluxes. These results show that the presence of amino acids is an important regulator of the K+/Rb+-fluxes under normal conditions in growth medium.

Amino Acids↗
PubMed1986

Mefenorex (Rondimen).

Mefenorex, N-(3-chloropropyl)-alpha-methylphenethylamine, (RONDIMEN), is included in the list of centrally acting stimulants and/or hallucinogens or related compounds to be considered by a World Health Organization (WHO) Expert Committee in 1985 for possible scheduling under the Convention on Psychotropic Substances, 1971. The therapeutic efficacy of mefenorex as an adjunctive support in the treatment of obesity for limited periods of time, as well as its ability to be well tolerated, has been amply demonstrated. There have been no reports of actual abuse. There have been no reports of illicit trafficking, falsification of packages or materials, or clandestine laboratories manufacturing the compound. Data from preclinical and clinical studies do not suggest a potential for abuse similar to that of amphetamine or related compounds. Moreover, the lack of pulmonary hypertension with mefenorex has been demonstrated in both preclinical and clinical studies. There have been no reports of any public health or social problems associated with mefenorex use. The compound is a well-tolerated anorectic agent with little central stimulant activity.

Adult↗
PubMed1986

Fenetylline: therapeutic use, misuse and/or abuse.

Fenetylline (CAPTAGON) is included in a list of compounds to be considered by a World Health Organization (WHO) Expert Committee in April 1985 for possible international scheduling under the Convention on Psychotropic Substances, 1971. For over 23 years, this central stimulant has been used therapeutically in hyperkinetic children and other indications in place of amphetamines and other central stimulants with higher risk levels. In good correspondence with recent animal data fenetylline also shows significant qualitative and quantitative differences compared to amphetamine in man. It has few adverse side effects, a lower abuse potential and little actual abuse compared to amphetamine. Thus its benefit/risk assessment is substantially more favourable than that of other central stimulants. For proper therapeutic use of the substance, prescription status is or should be required by national authorities.

Aged↗
PubMed1986

Erythroid differentiation and the Na+,K+-pump in ouabain-sensitive and ouabain-resistant Friend erythroleukemia cell lines.

The selection and biochemical characterization of ouabain-resistant erythroleukemia cell lines are described. Treatment of ouabain-resistant Friend erythroleukemia cell (FLC) lines with 1 mM ouabain demonstrated a reduced ouabain-sensitive 86Rb+-uptake after Na+-preloading in comparison with ouabain-sensitive cells. The ouabain- and diuretic (piretanide)-insensitive component of the 86Rb+-uptake (residual influx) was significantly enhanced in the ouabain-resistant FLC clones. Measurements of the Na+,K+-ATPase activity (E.C. 3.6.1.3) in plasma membrane preparations of the ouabain-resistant FLC clone B6/2 indicated that a ouabain-resistant Na+,K+-ATPase activity of about 20% of the total enzyme activity existed in the presence of 1 mM ouabain. Further experiments showed that the Na+,K+-ion-gradient in ouabain-resistant B6/2 cells was unaffected by ouabain exposure whereas the gradient collapsed in wild type 12 N cells. Another property of the ouabain-resistant cell lines was a decrease of the 86Rb+-uptake due to the Na+,K+, 2Cl(-)-cotransport system measured as piretanide-sensitive 86Rb+-uptake. The data on ion transport mechanisms in QuaR and QuaS FLC are discussed with respect to mutagen-induced and spontaneous cellular ouabain resistance. In addition, the role of altered ion transport mechanisms is considered for induced erythroid differentiation.

Animals↗
PubMed1984

Alterations of 86Rb+ fluxes in poliovirus-infected HeLa cells and their dependence on virus replication.

Components of the 86Rb+ influx were investigated subsequent to poliovirus infection in the presence and absence of guanidine-HCl, both under normal steady-state conditions and after Na+ preloading of the cells. Measurements of the ouabain-sensitive 86Rb+ uptake indicated a biphasic change in the activity of the Na+, K+ pump in the course of virus infection: a transient increase in the second hour postinfection, that was detectable only after Na+ preloading and inhibition after 3 hr. The enhanced activity of the Na+, K+ pump was not affected, while the decrease later was fully prevented by the antiviral agent guanidine-HCl. The piretanide-sensitive 86Rb+ uptake due to the Na+, K+, 2 Cl- cotransport system also became strongly inhibited beginning in the second hour postinfection. The inhibition of this transport system was partially antagonized by guanidine-HCl. The remaining 86Rb+ influx in the presence of ouabain and piretanide increased in the third hour postinfection. The latter change in 86Rb+ influx, indicating an increased permeability to monovalent cations was completely abolished by guanidine-HCl.

Biological Transport, Active↗
PubMed1984

Cryosurgical treatment of the eyelids and lacrimal drainage ducts of the rhesus monkey. Course of injury and repair.

Freezing injuries were produced on the eyelids and lacrimal drainage systems in ten rhesus monkeys. The instrumentation produced both single and double freezing cycles at tissue temperatures of -30 and -60 degrees C. The extent of injury and the course of repair were evaluated by clinical observation and by histologic examination of tissue specimens removed at intervals up to three months after freezing. Both cryosurgical techniques produced necrosis of the tissues, but injury was less with single freezing cycles at -30 degrees C. The course of repair was favorable. Even at the three-month observation period, when healing was complete, there was minimal-clinical or histologic evidence of canalicular obstruction or other periocular complications.

Animals↗
PubMed1984

A reduction in the activity of the Na+, K+-pump in dimethylsulfoxide-treated Friend erythroleukemia cells is not due to partial inactivation of the Na+, K+-ATPase.

Treatment of Friend-erythroleukemia cells with 1.5% dimethylsulfoxide (DMSO) caused a decrease in ouabain sensitive 86Rb+-uptake beginning six to seven hours after DMSO addition indicating a reduced function of the Na+, K+-pump. However, analysis of the ouabain sensitive 86Rb+-uptake after Na+-preloading of the cells as well as measurements on the Na+, K+-ATPase activity in isolated membrane fragments revealed that no inhibition of the Na+, K+-ATPase occurred during the first 12 hours. On the contrary the Na+, K+-ATPase activity was initially enhanced and then returned to control levels during the early phase of induction by DMSO. On the other hand, 22Na+-transport into DMSO-treated cells was reduced similar to the ouabain sensitive 86Rb+ uptake in cells without Na+ preloading. The piretanide sensitive 86Rb+-uptake, due to the Na+, K+, 2Cl - cotransport system was inhibited after seven hours exposure to DMSO. Some three hours after DMSO addition the incorporation of 35S-methionine into proteins began to decrease, which was accompanied with or followed by a reduction in the methionine uptake of DMSO treated cells. Membrane-potential-dependent tetraphenylphosphonium cation uptake was not altered relative to the controls in the first 12 hours following DMSO addition. These results suggest that the reduced activity of the Na+, K+-pump in Friend cells after DMSO exposure is not due to inhibition of the Na+, K+-ATPase, but most probably due to a smaller Na+-influx, which results from inhibition of Na+-cotransport processes (amino acid uptake, Na+, K+, 2Cl - cotransport system).

Animals↗
PubMed1984

Factors influencing the accumulation of tetraphenylphosphonium cation in HeLa cells.

Exposure of HeLa cells to tetraphenylphosphonium cation (TPP+) results in a rapid accumulation intracellularly, and a steady-state level is reached within 10 min. Accumulation of [3H]TPP+ in HeLa cells is reduced under the following conditions: (i) after preincubation of cells in buffered saline or in medium containing two- to fourfold higher concentrations of amino acids, (ii) exposure to the alkylating agent L-1-tosylamido-2-phenyl-ethylchloromethyl ketone, (iii) ouabain-mediated inhibition of the Na+, K+ ATPase, and (iv) high external K+ concentrations. In contrast, addition of serum increases the uptake of TPP+. In synchronized cells, intracellular levels of TPP+ differ at various stages of cell cycle and are lowest in mitosis.

Biological Transport, Active↗
PubMed1983

Relationship of cerebral intraventricular hemorrhage and early childhood neurologic handicaps.

The outcome in 198 surviving very-low-birth-weight (less than 1501 gm) infants with and without cerebral intraventricular hemorrhage was compared to determine whether CVH is associated with early childhood developmental or neuromotor handicaps. Major handicaps were noted in 10% of the infants without and 28% of the infants with CVH. Among the infants with CVH, a major handicap was present in 9% with grade 1, 11% with grade 2, 36% with grade 3, and 76% with grade 4 CVH. Infants with posthemorrhagic hydrocephalus had the same incidence of major handicaps (59%) as did comparable infants with no hydrocephalus (57%). Our data indicate that grades 1 and 2 CVH do not increase an infant's risk for major handicaps, and there is a direct relationship of grades 3 and 4 CVH and major handicaps.

Cerebral Hemorrhage↗
PubMed1983

[Passive mechanical characteristics of the eyeball joint system during rabbit ontogenesis].

The postnatal development of vestibulo-ocular reactions is among other factor probably caused by changes of the passivee mechanical properties of the bulb joint system. Therefore, curarized rabbits from the newborn up to the adult age were studied in respect of the passiv deviation of the ocular bulb. The required force of stepwise traction (5 degrees each) of the bulb between the primary position and a 20 degrees deviation was measured. A linear enhancement of the force with increasing deviation angles was found in all age groups. Force relief resulted in a hysteresis in each case, the bulb did not reach the primary position. There were no differences of the force between newborns and adult animals, but 16 to 20 d old rabbits exhibited a statistical significant decrease of the required force in all deviation steps, except in 5 degrees.

Age Factors↗
PubMed1982

Interferon-induced alterations in membrane functions and the growth of Daudi lymphoma and Friend leukemia cells.

The Friend murine erythroleukemia cell system and the Daudi Burkitt's lymphoma cell system were used to study the effect of growth-inhibitory concentrations of interferon on membrane functions. Experiments with Friend-cell clones sensitive and resistant to interferon indicated that a number of changes in membrane transport occur rapidly after the addition of interferon to sensitive cells. While no change was observed in the activity of the (Na+/K+) ATPase in Friend cells sensitive or resistant to interferon, a piretanide-inhibitable Na+,K+, 2Cl- co-transport system was specifically inhibited after interferon treatment of sensitive cells. In contrast, treatment of Daudi cells with purified molecularly cloned or standard preparations of human leukocyte interferon gave rise to no early changes in the transport of amino acids, 32Pi, sugars, or 86Rb+. The major change observed in Daudi cells was a marked reduction in the uptake and incorporation of thymidine, which begins to decrease after 8-10 h of exposure to interferon.

Animals↗
PubMed1982

Alterations in plasma-membrane functions after poliovirus infection.

After exposure of HeLa cells to poliovirus there is a rapid decline (within minutes) in fluorescence polarization of DPH (1,6-diphenyl-1,3,5-hexatriene). Within one hour after infection the (Na+/K+)ATPase activity of an isolated plasma-membrane-rich fraction is enhanced, the cell volume decreases, and the intracellular concentration of a potent low-molecular-weight inhibitor of host protein synthesis increases.

Cell Membrane↗
PubMed1982

On the mechanism of the involvement of monoamine oxidase in catecholamine-stimulated prostaglandin biosynthesis in particulate fraction of rat brain homogenates: role of hydrogen peroxide.

The mechanism of involvement of monoamine oxidase (MAO) in catecholamine-stimulated prostaglandin (PG) biosynthesis was studied in the particulate fraction of rat brain homogenates. High concentrations of either noradrenaline (NA) or dopamine (DA) stimulated effectively PGF2 alpha formation. The same amount of 2-phenylethylamine (PEA) acted similarly, provided that it was administered together with a catecholamine analogue or metabolite possessing the 3,4-dihydroxyphenyl nucleus--3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylacetic acid (DOPAC), 3,4-dihydroxyphenylglycol (DOPEG), 3,4-dihydroxyphenylacetaldehyde (DOPAL), or alpha-methylnoradrenaline (alpha-met-NA)--or with SnCl2. In the absence of PEA, these compounds were ineffective with regard to stimulation of PGF2 alpha formation. Catalase, pargyline, or indomethacin abolished completely PGF2 alpha formation elicited either by catecholamines or by PEA plus a 3,4-dihydroxyphenyl compound or SnCl2. With regard to the stimulation of PGF2 alpha formation in the presence of alpha-met-NA, PEA could be replaced by H2O2 generated by the glucose oxidase(GOD)-glucose system. The effect of H2O2 was inhibited by indomethacin or catalase, but pargyline was ineffective. It is assumed that catecholamines play a dual role in the activation of PG biosynthesis in brain tissue. During the enzymatic decomposition of catecholamines MAO produces H2O2, which stimulates endoperoxide synthesis. Simultaneously, catecholamines as hydrogen donors promote the nonenzymatic transformation of endoperoxides into PGF2 alpha. The possible physiological importance of these findings is discussed.

Animals↗