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Biomedical subjects

A Weiss

Publications and source records attributed to A Weiss.

At least 415 records · Page 23Linked to original sources
PubMed1978

Platelet release reaction and intracellular cGMP.

Enchanced cAMP concentrations inhibit the aggregation and release reaction of isolated human platelets and platelet-rich plasma to all known inducing agents. An opposing role for cGMP in this phenomenon has been proposed by some but not by others, and the function of cGMP in this secretory process is unclear. To further elucidate the role of cGMP in the release reaction, the effect of increased concentrations of this cyclic nucleotide on 14C-serotonin release was evaluated utilizing isolated human platelets and highly purified human thrombin or commercially available bovine thrombin. Several recently described stimulators of guanylate cyclase, including sodium nitroprusside, sodium azide, nitrosoquanidines, and ascorbic acid, were found to markedly augment platelet cGMP levels. Enhanced platelet cGMP concentrations produced by these drugs or by the exogenous addition of cGMP and its analogues neither caused these cells to secrete nor modulated the thrombin-induced serotonin release reaction. The inhibition of serotonin release by increased cAMP concentrations was not counteracted by increased cGMP levels. Platelet cGMP concentrations were unaltered by thrombin. These data indicate that cGMP is not an obligatory signal or a modulator of the thrombin-induced platelet release reaction.

Ascorbic Acid↗
PubMed1978

Suppression of the plaque-forming cell response by macrophages present in the normal rat spleen.

Depletion of phagocytic and/or adherent cells from normal rat spleen cell preparations permitted the generation of PFC to SRBC in vitro. Suppressive activity was associated with the presence of macrophages in the normal rat spleen, since irradiated unfractionated or irradiated adherent cells suppressed the PFC response of macrophage-depleted cells. Whereas depletion of macrophages from normal rat spleen cells permitted the PFC response to SRBC to occur, comparable treatment of mouse spleen cells eliminated the PFC response. These results are discussed in relation to the requirement for macrophages in the generation of PFC with rat cells in vitro.

Animals↗
PubMed1978

[Aging changes of passive electrical and mechanical properties of human skin (author's transl)].

Mechanical and electrical properties of human skin are definable by a apparatus, developed by Pliquett and Rollius (1975). Using this method was determined a value, correlate to the product of the elasticity and the electrical conductance on 90 healthy persons. This value depends in a characteristically way on age, with a maximum near 25 and 55 years. The amount of the maximum depends on sex and profession of the probands.

Adolescent↗
PubMed1977

Effect of double-bonds on bimolecular films in membrane models.

The effect of unsaturation (especially by cis-bonds) is studied on bimolecular films of saturated and unsaturated alkylammonium ions and alkanols between silicate surfaces as model systems for lipid layers in membranes. Three types of structures are observed: all-trans-blocks, kink-blocks and gauche-blocks. The knowledge of the sequence of these phases and their thermal transitions provides detailed deductions about the role of double-bonds. cis-Unsaturated chains are taken up in bimolecular films as isomers with cis-trans-gauche conformation. This conformation makes the shape of the chain similar to that of kinked chains (chains with gauche-trans-gauche (--) conformation) and enables the incorporation into the film without greater sterical hindrance. The experimental results are in good agreement with X-ray measurements on biological membranes by Engelman (Engelman, D.M., J. Mol. Biol. 47, 115--117 (1970) and 58, 153--165 (1971)). Increasing the concentration of cis-chains decreases the transition temperature of the kink-blocks into gauche-blocks. The variation of the transition temperature with concentration of cis-unsaturated chains in the model system is similar to that observed for Escherichia coli membranes. It is suggested that phase changes in biomembranes are of the same nature: transition of kink-block analogues as ordered phases into gauche-block assemblies as less ordered phases.

Calcium↗
PubMed1977

Traumatic death in urban children.

Trauma has remained one of the leading causes of death in children in spite of improved medical care. A review of 911 pediatric trauma deaths which occurred over a 5 yr period in an urban setting revealed that almost 50% of these children died before receiving medical care. A significant improvement of the trauma mortality can thus only be accomplished by reducing the number of "DOAs". We therefore analyzed the cause and type of injury and its relationship to age, sex, race, seasonal occurrence, and sociological circumstances. The following four categories are merely part of the overall material developed in this review. Even with improved medical care of trauma patients the overall pediatric trauma mortality cannot be significantly reduced unless the number of DOAs is decreased through prevention. Educational and family assistance programs can be designed for specific problem areas to reach identified susceptible groups through existing channels such as day care centers, schools, or welfare agencies. Statistical data, such as presented here (but not previously available) are essential to analyze the particular problems of specific geographic and sociologic areas. Since the vast majority of pediatric trauma deaths fall within the interest sphere of the pediatric surgeon, our active participation in accident prevention is essential to achieve a significant reduction of pediatric trauma mortalities.

Accidents↗
PubMed1977

Macrophages suppress CTL generation in rat mixed leukocyte cultures.

The generation of CTL in rat MLC was actively suppressed by a cell population present in spleen cell preparations from normal rats. These suppressor cells were characterized by using a variety of cell fractionation techniques. Suppressor cells were removed by passage of spleen cells through nylon wool columns or by treatment with carbonyl iron. Suppressive activity was present in the mononuclear cell fraction of spleen cells obtained by Ficoll-Hypaque density gradient centrifugation. After velocity sedimentation at unit gravity, enrichment of suppressive activity was demonstrated in the fractions containing large cells as compared to the fractions containing small cells. Populations rich in macrophages were shown to have similar suppressive activity upon CTL induction in MLC. These studies suggest that macrophages present in normal rat spleen cell preparations account for the difficulty in generating CTL in MLC prepared with rat cells.

Animals↗
PubMed1977

Increased intraocular pressure following topical azide or nitroprusside.

In rabbits the topical administration of sodium azide (NaNs) or sodium nitroprusside (SNP) increased intraocular pressure in a dose-response manner. These agents, which activate guanylate cyclase, elevated cyclic GMP in the aqueous humor. Systemic blood pressure and pulse were not altered. Tonographic outflow facility was unchanged, suggesting an increase in aqueous humor flow as the mechanism for the elevation of intraocular pressure. Posterior chamber aqueous humor ascorbate concentration was decreased in the eye receiving the NaN3 or SNP. Systemic pretreatment with phenoxybenzamine, an alpha-adrenergic blocking agent, prevented the elevation of intraocular pressure observed following NaN3 and SNP. Pretreatment with systemic indomethacin, propranolol, or acetazolamide or the topical application of atropine or epinephrine failed to alter the elevation of intraocular pressure by either NaN3 or SNP.

Administration, Topical↗
PubMed1977

Isolated idiopathic chylopericardium.

The case history of a young asymptomatic patient with primary chylous pericardium is reported. On the basis of this case and those reported in the literature, we suggest that diagnosis should be established by echocardiograms, cardiac angiograms, and pericardiocentesis. Lymphangiograms are useful for the detection of the underlying abnormality of the lymph vessels. Pericardiectomy together with thoracic duct ligation are suggested as the preferred treatment. We propose that generalized lymphatic abnormality is the underlying mechanism of this entity. This lymphatic abnormality could be associated with impaired cellular immunity, although no such impairment was found in our patient.

Adolescent↗
PubMed1976

[The treatment of ptyalism in children with cerebral lesions (author's transl)].

The cytotoxic and alkylating substance, mustard gas, causes both acute poisoning and also damage to numerous organs following chronic exposure. Especially important is the carcinogenic effect, also confirmed in humans. 34 years after occupational exposure to mustard gas with many intoxication episodes, a former munition-worker died of a glioblastoma; two years before his death a neurofibroma was detected in the thorax and removed by operation. The causal connection between the mustard gas exposure and the development of two neurogenic tumors rests on the statistically significantly raised frequency of malignant tumors and the established psychic changes in former workers with mustard gas and especially on the production of malignant tumors of the central nervous system in experimental animals with alkylating nitrosamines.

Aged↗
PubMed1976

Metrizamide cisternography with hypocycloidal tomography: preliminary results.

Metrizamide (Amipaque), a nonionic water soluble contrast agent, has been shown to be safe and efficacious for lumbar myelography. Clinical trials of cervical, thoracic, and even intracranial examinations have produced good results. Despite an inherent neurotoxicity, significant complications have been quite rare, and patient tolerance in general is remarkably good. Preliminary results of metrizamide cisternograms using hypocycloidal tomography are presented to illustrate the anatomic detail which can be demonstrated using this technique.

Humans↗
PubMed1976

CSF enhancement for computerized tomography.

Metrizamide cisternography, combined with hypocycloidal tomography, has been performed in 12 patients with possible posterior fossa or parasellar mass lesions with finely detailed images of the basal cisterns resulting. Computed tomography was performed in nine of these patients and produced exceptional images of the cisternal anatomy. The technique of cerebrospinal fluid enhancement may be efficacious in identifying small basal masses not shown with conventional computed tomography, and thus may form an important complement to enhancement by intravenous injection of contrast medium.

Brain Neoplasms↗