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Biomedical subjects

A Fröhlich

Publications and source records attributed to A Fröhlich.

At least 37 records · Page 2Linked to original sources
PubMed1988

Review of studies with plasminogen concentrates and proposals for further therapeutic strategies with plasminogen concentrates.

Since the introduction of thrombolytic treatment based on the activation of plasminogen (PLG) by streptokinase (SK) and urokinase (UK) the search for new and improved methods has been continuing. The pivotal issue is how to achieve clot-specific fibrinolysis without producing systemic fibrinogenolysis. One out of various approaches to enhance lysis rates has been the use of PLG either alone or in combination with UK or SK in the light of the fact that fibrinolytic treatment, particularly using SK, is associated with a consumption of PLG, and that thrombi contain relatively small amounts of native PLG, however, are capable of incorporating added PLG in vitro. PLG-concentrates from various manufactures have been administered intravenously for treatment of deep venous thrombosis, mainly in combination with SK, and of pulmonary embolism in combination with UK. Local intracoronary and intraarterial administration in combination with UK has been reported in patients with myocardial infarction, and peripheral arterial occlusions, respectively. Lysis rates obtained in these studies were in most cases superior to results obtained with SK or UK alone, without increasing the incidence of bleeding complications. In addition, excellent results in larger group of patients with cerebral thrombosis were obtained with PLG alone. The encouraging results of these studies may be explained by the fact that all of the preparations used contained partially activated forms of PLG (commonly designated lys-PLG) to a greater or lesser extent. Lys-PLG has a higher affinity for fibrin than the native glu-PLG and is activated by UK or SK by a manyfold faster. These properties allow for a rapid formation of plasmin which--bound to fibrin--is also protected from the attack of neutralizing antiplasmin. The design and results of previous studies with lys-PLG concentrates will be reviewed and approaches to further improve fibrinolytic regimens with lys-PLG-concentrates discussed.

Fibrinolysis↗
PubMed1987

Regulation of synaptic frequency: comparison of the effects of hypoinnervation with those of hyperinnervation in the fly's compound eye.

At the anterior rim of the first optic neuropile, or lamina, of the housefly's (Musca domestica) compound eye, the terminals of photoreceptors (R) innervate postsynaptic neurons in variable numbers to provide a continuous range of natural hypo- and hyperinnervations. Frequencies of photoreceptor synapses have been measured from quantitative electron microscopy on single sections of the lamina's unit synaptic modules, called cartridges. These are normally innervated by six photoreceptor terminals (6R cartridges). At the lamina's edge hypoinnervated cartridges (2R-5R) are found, whereas hyperinnervated cartridges (7R, 8R) are located at the equator between dorsal and ventral eye halves. In 2R cartridges each presynaptic terminal forms up to 1.5 times the normal, 6R cartridge number of synapses, thereby offsetting the reduced number of terminals and partially conserving the input upon the postsynaptic neurons. Thus the terminals have a reserve synaptogenic capacity never normally revealed. By comparison, terminals in 8R cartridges form about the same numbers of synapses as in "normal" eye regions, so that their postsynaptic neurons have a synaptic input increased by the extra number of terminals. The number of synapses formed between input terminals and target neurons is therefore not fixed but changes as a function of the total receptor terminal complement. The size of a photoreceptor terminal covaries to a certain extent with the number of its presynaptic sites; the spacing density of presynaptic sites over the terminals' surface in a 2R cartridge compared with an 8R cartridge increases far less (only 17%) than the increase in the number of sites (43%). The pair of postsynaptic cell interneurons in each 2R cartridge also shows a decrease in axonal diameter compared with those in 8R cartridges. Thus both the pre- and postsynaptic cells show size changes correlated with changes in their synaptic engagement.

Animals↗
PubMed1985

Freeze-fracture study of an invertebrate multiple-contact synapse: the fly photoreceptor tetrad.

Bow-shaped particle arrays on the P-faces of the photoreceptor terminals R1-R6 in the lamina ganglionaris of the house fly represent the presynaptic sites of chemically mediated multiple-contact synapses (Shaw and Stowe, '82, Saint Marie and Carlson, '82). A particle array consists of two polar patches of regularly arranged particles and a central patch of irregularly arranged ones. Corresponding to these P-face arrays, the receptor E-faces have lattices of pits opposite the polar patches, and pits and some particles at the center. The presynaptic particle array corresponds in its dimensions to the electron-dense bar found in thin sections. The center-to-center spacing of the regularly arranged particles agrees with the spacing of striations found in the bar overlying the two polar elements of the postsynaptic tetrad. The elements in the two medial postsynaptic positions are hyperpolarizing monopolar cells L1 and L2, which show a strip of P-face particles within an otherwise bare postsynaptic membrane enclosed by a ridge, and a bare E-face. Comparison with other invertebrate synapses reveals two types of organization of postsynaptic membranes. IMPs fracture with the postsynaptic P-face in GABAergic and/or inhibitory synapses and with the E-face in glutaminergic and/or excitatory synapses; the fly photoreceptor synapse thus fits in the former category.

Animals↗
PubMed1983

[Evaluation of results from the Landstuhl school experiment for the general development of severely handicapped children in schools for the physically handicapped].

The concept of integrated developmental intervention with profoundly disabled children has been evolved and tested in the school trial carried out at the Landstuhl Rehabilitation Centre Westpfalz. In its basic stage the intervention programme encompasses the availability of a good caring relationship between caregiver and child, with reliable satisfaction of needs and gentle child-centered care. This serves as a basis for systematic perceptual development by Basal Stimulation, movement development and initiation of communicative behaviour. The second stage in this developmental approach includes facilitation of continued growth of the children by experiencing concrete doing and meaning contexts. In line with the particular life situation of the parents and their children, parent involvement takes on a special dimension. Developmental intervention with profoundly disabled children presupposes the existence of an appropriate general framework.

Adolescent↗
PubMed1983

Quantitative features of synapse formation in the fly's visual system. I. The presynaptic photoreceptor terminal.

Photoreceptors of the adult fly's compound eye each form a population of stereotyped output synapses distributed over the surface of their terminal. The formation of this class of afferent synapses during development has been followed from serial electron microscopy of the same eye region in four pupal and several adult stages, all of female Musca domestica. These synapses, or tetrads, have an invariant postsynaptic composition of four members and so may provide a model for multiple-contact synapses in general. In the adult fly the four postsynaptic elements of each synapse are contributed by two interneurons, L1 and L2, and, usually, two alpha processes of an amacrine cell. These postsynaptic elements assemble at individual developing synapses by selective sequential addition. Assembly starts with L1 or L2, subsequent elements of the final tetrad adding in all conceivable permutations, at least as fast as one per 7 hr. They rarely (only once) incorporate incorrect or supernumerary elements, however. The synaptic population as a whole was also sampled during development to analyze the possible factors determining the normal precision of the size of the adult population. The number of synapses per terminal increases gradually until 74% pupal development. Thereafter it decreases so that the final number of synapses in each receptor's population is the consequence of a net loss. Synapses enlarge with age, chiefly by incorporating new elements, but the loss of synaptic sites is only partially offset by the increase in size of those that remain. Throughout all stages examined in pupal and adult life, total synaptic area is linearly proportional to the surface area of the axon terminal. Thus, from the 74% pupal development stage onward, a population of many small synapses closely spaced, on average, over the terminal's surface transforms into one characteristic of the adult with progressively fewer, larger, more widely spaced synapses.

Animals↗
PubMed1982

Synaptogenesis in the first optic neuropile of the fly's visual system.

The developmental transformation of the chief afferent class of fly photoreceptor synapse has been examined from serial electron micrographs of animals fixed at 74, 81, 94 and 100% pupal development (100% pupal development being defined by the time of normal adult eclosion). Animals were selected both by their age and the conformity of their eye coloration to standards for each stage. Two animals were analysed from each stage, one in greater detail than the other. For the first, the exact coordinates of the cartridges (the synaptic columns of the first optic neuropile) from which the analyses were made were mapped and selected to be within the same region of the eye field at all stages. From all animals a portion of one or two cartridges was analysed from series of up to 100 sections and the synapse populations (greater than 80) were analysed for their fine structure and postsynaptic composition. Adult synapses are confirmed as tetrads, with two of the four postsynaptic elements invariably from two monopolar interneurons L1 and L2, one from each. The two others are usually from alpha processes of the same amacrine cell. Synapses appear during the last half of pupal development, with no obvious asynchrony of ultrastructural maturation and in parallel with those of at least one of the other synaptic classes present (which were otherwise not studied). Many adult features of synaptic ultrastructure emerge late, only by 94% pupal development. These include adult numbers of synaptic vesicles, the complete form of the presynaptic ribbon with platform and the postsynaptic cisternae of L1/L2. Prior to 94% the synapses are smaller with postsynaptic elements having a less regular geometry and with postsynaptic densities which are subsequently lost (alpha processes) or replaced by cisternae (L1/L2). At the presynaptic sites of the younger animals (74%, 81%) dyads and triads of postsynaptic elements coexist with tetrads, those of older animals having, on average, more postsynaptic processes per synapse. It is suggested that individual synapses assemble piecemeal, element by element.

Afferent Pathways↗
PubMed1981

[Ménétrier's disease simulating pangastritis].

A case of giant hypertrophic gastritis observed at a male patient of age 38 is reported. The process clinically and radiographically simulated a tumour of the stomach, which has been totally removed. Histologically inflammatory changes of the gastric wall-pangastritis-were found with micro-abscesses in the submucosa. Problems of pathogenesis, diagnostics, differential diagnostics and pathology of the disease are dealt with. Possible ways of the therapy are also discussed.

Adult↗
PubMed1980

[Post-irradiation brain necrosis causing apoplexy and death 33 years after irradiation].

A case of post-irradiation brain-necrosis resulting in apoplexia of the cerebellum after 33 years of irradiation (19 984 r.) of a presumptive cerebellar tumour in childhood is reported. The pathohistologic study revealed symptoms of the "late" damage and vascular changes appeared to be the most prominent. Thickening of the vessel walls, hyperplasia of collagen fibres and deposition of calcium in the media, were the most characteristic lesions revealed. In some of the small vessels isolated calcification of the media was observed. It seems most probable, that in the development of apoplexia vascular alterations could play an important part. In the available literature author has not found report on a similarly long interval elapsing between the irradiation and death.

Adult↗
PubMed1979

[Immunofluorescent diagnosis of Entamoeba histolytica trophocoites in preserved stool specimens of patients (author's transl)].

A fixative and examination technique is described for identification of Entamoeba histolytica trophocoites in faeces with the aid of the indirect immunofluorescence technique. Magnaforms in bloody-dysenteric specimens and Minutaforms in spontaneous or saline purged specimens give equally good fluorescence. The specifity of the rabbit antiserum against axenically grown E. hist. is good: There is strong positive reaction only with trophocoites of E. hist. Weak crossreactions are encountered with trophocoites of E. coli, E. hartmanni and E. polecki. Negative reactions are encountered with trophocoites of Endolimax nana, Jodamoeba bāutschlii, and Dientamoeba fragilis. Amebic cysts, flagellates, leucocytes, epithelial cells and Blastocytis give negative reactions, too.

Animals↗