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Biomedical subjects

G Lindner

Publications and source records attributed to G Lindner.

At least 37 records · Page 2Linked to original sources
PubMed1990

Shielding requirements on-site loading and acceptance testing on the Leksell gamma knife.

On August 14, 1987, the first stereotactic radiosurgical procedure using the gamma knife was performed in North America. Located in a self-contained radiosurgical suite in the basement of Presbyterian-University Hospital in Pittsburgh, Pennsylvania. This device uses 201 highly focused beams 60Co for the single-treatment closed-skull irradiation of brain lesions localized by stereotactic techniques (radiosurgery). One hundred and fifty-two patients with intracranial arteriovenous malformations or brain tumors were treated in the first year of operation. The Presbyterian University Hospital of Pittsburgh gamma knife is the first such unit in which the 60Co sources were loaded on-site. This effort required us to solve some difficult and unusual problems encountered during site preparation, delivery, and loading of the unit in a busy hospital setting. The solutions developed enabled installation and use of the gamma knife with minimal disruption of hospital activities while maintaining acceptable levels of exposure to radiation. Environmental surveys performed during the loading of the 201 radioactive sources (total, 219 TBq) confirmed that on-site loading is possible and practical. Our experience in the design, construction, and implementation of the first North American gamma knife supports the practicality and safety of on-site loading and may be of value in the planning and development of future gamma knife installations.

Brain Neoplasms↗
PubMed1990

Physics of gamma knife approach on convergent beams in stereotactic radiosurgery.

The Presbyterian-University Hospital of Pittsburgh installed the first clinically designated Leksell gamma knife in the U.S. in August 1987. Gamma knife radiosurgery involves stereotactic target localization with the Leksell frame and subsequent closed-skull single-treatment session irradiation of a lesion with multiple highly focused gamma ray beams produced from 60Co sources. The hemispherical array of sources, the large number of small-diameter beams, and the steep dose gradients surrounding a targeted lesion make physical characterization of the radiation field complex. This paper describes the physical features and the operation of the gamma knife as well as the calibration procedures of the very small, well-collimated beams. The results of studies using in-phantom ion chamber, diode, film, and lithium fluoride thermoluminescent dosimetry were all in close agreement. Both single-beam and multiple-beam dose profiles were measured and reported for the interchangeable helmets, which have 4-, 8-, 14-, and 18-mm-diameter collimators. We also describe the dose calculation and treatment planning algorithm in the treatment planning system. Measurements of the accuracy of mechanical and radiation alignment are also performed and discussed.

Brain Diseases↗
PubMed1990

Intradialytic changes of the oxyhaemoglobin dissociation curve during acetate and bicarbonate haemodialysis. Possible interactions with haemodialysis-associated hypoxaemia.

In nine chronic haemodialysis patients, treated alternately with acetate and bicarbonate, the main critical factors in oxygen supply to the tissues were evaluated: Hb values, blood gas parameters, red cell 2-3 diphosphoglycerate (2-3 DPG), phosphataemia and P50 in vivo. Predialytic P50 was higher than in normal controls. During dialysis, arterial pO2 and pCO2 significantly decreased in acetate dialysis, whereas they were stable in bicarbonate dialysis. Rising alkalinisation was accompanied, both in acetate dialysis and in bicarbonate dialysis, by reduction of P50, while 2-3 DPG did not change. The acute increase in Hb-O2 affinity adversely affected peripheral oxygen release. In acetate dialysis this mechanism might magnify the effects of dialysis-induced hypoxaemia, affecting the clinical tolerance.

2,3-Diphosphoglycerate↗
PubMed1989

Postnatal treatment of rats with beta-adrenergic agonists or antagonists influences differentiation of sexual brain functions.

Sexual differentiation of the brain seems to be influenced by postnatal interaction of gonadal steroids with neurotransmitter systems, in particular the adrenergic system. Stimulation or inhibition of alpha-adrenergic receptors during early postnatal development had previously been shown to influence steroid-induced sexual differentiation of brain functions. In the present study newborn male and female rats were treated either with salbutamol, a selective beta 2-adrenergic receptor agonist, isoprenaline, a general beta-adrenergic receptor agonist, or with alprenolol, a general beta-adrenergic receptor antagonist. In adulthood the female animals were ovariectomized and were tested for the capacity to show an LH-surge response and female sexual behaviour after priming with estradiol benzoate (EB) and progesterone (P). Male animals were tested for expression of male sexual behavior and, after gonadectomy and priming with EB + P, for the capacity to show female lordosis behavior. In summary, our results suggest that activation or inhibition of beta-adrenergic receptors during postnatal development permanently impairs the responsiveness of the center for cyclic gonadotropin release to gonadal steroids in female rats and impairs the expression of ejaculatory behavior in male rats. A slight stimulatory effect on the expression of female lordosis behavior was observed in male and female rats after postnatal activation of beta-adrenergic receptors.

Albuterol↗
PubMed1989

Stereotactic radiosurgery of the brain using the first United States 201 cobalt-60 source gamma knife.

The first United States 201 cobalt-60 source gamma knife for stereotactic radiosurgery of brain tumors and arteriovenous malformations became operational at the University of Pittsburgh on August 14, 1987. Four and one-half years of intensive planning, regulatory agency review, and analysis of published results preceded the first radiosurgical procedure. Installation of this 18,000-kg device and loading of the 201 cobalt-60 sources posed major challenges in engineering, architecture, and radiophysics. In the first 4 months of operation, we treated 52 patients (29 with arteriovenous malformations, 19 with extra-axial neoplasms of the skull base, and 4 with intra-axial malignant tumors). Most patients either had lesions considered "inoperable" or had residual lesions after attempted surgical resection. Neither surgical mortality nor significant morbidity was associated with gamma knife radiosurgery. As compared with treatment by conventional intracranial surgery (craniotomy), the average length of stay for radiosurgery was reduced by 4 to 14 days, and hospital charges were reduced by as much as 65%. Based on both the previously published results of treatment of more than 2,000 patients worldwide and on our initial clinical experience, we believe that gamma knife stereotactic radiosurgery is a therapeutically effective and economically sound alternative to more conventional neurosurgical procedures, in selected cases.

Adult↗
PubMed1989

[Effects of different buffers, ethanol and hydrogen peroxide on the morphology of cultured brain cells].

Effects of different buffers: N-2-Hydroxyethylpiperazine-N-2-ethanesulfonic acid (HEPES), Ethanolamine (2-Aminoethanol), sodium bicarbonate (NaHCO3) in the presence of 0.003% H2O2 or 0.5% ethanol were investigated on cell cultures from brain (chick embryo 5 1/2 or 9 day in ovo). Morphological parameters: density of cells, reaggregation, size of cell aggregates were used. H2O2 in the presence of NaHCO3 led to a decrease of isolated cells and an increase of reaggregation with degeneration in the great clusters. When H2O2 and 5 mM HEPES were present together in the absence of NaHCO3, the aggregation was less than with HEPES alone. By use of a chemical defined medium DME/F-12 supplemented with Insulin, Transferrin, sodium selenite, bovine serum albumin and 15 mM HEPES both the number and the diameter of cell aggregates increased. Addition of 0.5% ethanol in the presence of NaHCO3 stimulated in cultures of the ganglion trigeminale and telencephalon (9 day chick embryos) the regeneration of neurites and the proliferation and migration of non-neural cells. No growth of neurites was observed on the same condition in brain cultures from 6 day chick embryo. The number of large aggregates increased significantly in the presence of NaHCO3 and in the chemical defined and supplemented medium DME/F-12. Bologa et al. (1987) demonstrated that the buffers TREA (Triethanolamine) and HEPES enhance the expression of properties related to post-mitotic differentiated cellular states in both neurons and glia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

[The effect of methionine enkephalin, leucine enkephalin and the hexapeptide, dalargin on the morphology of cultured neurons].

Cell cultures derived from brain, ganglion trigeminale or retina of 5- and 9-day-old chick embryos and from brain stem or hippocampus of 16-18 day-old fetal rats were treated with Met5-, Leu5-enkephalin, or Dalargin--a synthetic hexapeptide structurally related to Leu5-enkephalin--and evaluated morphologically. The treatment of the nervous tissue cultures with the peptides markedly affected their growth pattern. Aggregates of glial and neuronal cells were surrounded by flat cells forming monolayer network structures. In cultures of brain from 5 day-old chick embryos the proliferation of the cells was significantly stimulated. No growth of neurites was observed. It is discussed that the tested Enkephalins and in the same way the Dalargin may play an important role in the early neuronal development. Their activity in phase 0 and phase 1 of the life history of nerve cells indicates aspects of temporary peptide influences. Excess of glial cells caused by the tested peptides did not enhance neuronal differentiation. The transdifferentiation of developing receptor cells into ependymal cells during the adaptation process in retina cultures as a special effect of Dalargin is discussed. The present findings suggest that the influence of (opioid) peptides in vitro may be detected morphologically and that nervous tissue culture is a valuable tool for differentiating neuronotrophic neurite-promoting and neurotoxic drug effects.

Animals↗
PubMed1988

Scanning electron microscopical observations on telencephalon explants cultivated in vitro.

Telencephalon explants from 10 or 12 days old chicken embryos were cultivated 2 days in vitro and investigated by SEM. Already at that day, nerve fibres forming thick fasciculi were observed in the outgrowth region of the explant. Neuritic growth cones of the filiforme, or lamellipodiale type were demonstrated as well as button-like dendritic growth cones. The cell somata of bipolar or multipolar neuroblasts and pyramidal neurons could be distinguished from those of astrocytes. Some nerve fibres establish axosomatic or axodendritic contacts, basket-like arrangements of axon terminals around small neuroblasts were found.

Animals↗
PubMed1987

First United States 201 source cobalt-60 gamma unit for radiosurgery.

Installation of the first United States 201-source 60Co gamma unit for stereotactic radiosurgery was completed at the University of Pittsburgh in May, 1987. Despite a very favorable 19-year experience in Stockholm, introduction of this technology into the US proved to be a formidable task. Extensive internal and government regulatory review by the Health Systems Agency, the Food and Drug Administration and the Nuclear Regulatory Commission ultimately resulted in approval of marketing and use of the gamma unit. Clinical use and radiobiological research has begun.

Cobalt Radioisotopes↗
PubMed1987

[Effects of cyclic adenosine-3',5'-monophosphate and cyclo(Lys-Pro).HCl neuronotrophic factors in tissue culture].

Explants and cell cultures of embryonic chick ganglia trigeminalia, telencephalon and retina or hippocampus from fetal rats were incubated in maximow chambers in the presence of cyclic AMP and the dipeptide cyclo(Lys-Pro).HCL under various conditions. Maintenance of nerve cells and growth of nerve fibers were observed by morphometrical methods. 1. Cyclo(Lys-Pro).HCL promoted the maintenance of neuroblasts and the growth of nerve fibres in explants of the ganglion trigeminal and retinal cell cultures. The effect depended on the presence of serum in the medium by use of poly-I-lysine substrate. 2. Extern applicated cyclic AMP and the dipeptide SP3-4 = cyclo(Lys-Pro).HCL facilitated neurite growth in PNS cultures. In the presence of the drugs the length of nerve fibers increased for a short term. On CNS explants substance P (SP1-11) and SP3-4 were without effect. Cyclic AMP stimulated the growth of nerve fibers in CNS explants and cell cultures in number and length. 3. Discussed is the effect of SP1-11 and cyclo(Lys-Pro).HCL for competence of nerve fibre regeneration in vitro in relation to increasing cAMP levels, which may then act as an initial second messenger. It is suggested that explants and cell cultures of nervous tissues will be useful as a tool for the further characterisation of factors with neuronotrophic activities.

Animals↗
PubMed1987

Scanning electron microscopical observations on retina cells in culture.

In cell cultures of the retina from 10 days old chicken embryo photoreceptors, bipolar neurons, synaptic contacts, and supporting cells of Müller were demonstrated by scanning electron microscopy. It was found that the longer the cells survive in culture media they form constantly growing cell aggregates. After 12 days in vitro large multilayered cell complexes covered by an epithelioid cell layer had developed. Merely at the border of such aggregates typical retinal cells could be observed. The occurrence of a dense epithelioid cell layer covering the aggregate of neuronal cells is interpreted as a general adaptational reaction of the cells to the long lasting survival under in vitro conditions.

Animals↗
PubMed1986

[Effect of derivatives of substance P dipeptide on nerve fiber growth in tissue culture].

Explants and cells from the peripheral (PNS) and central nervous system (CNS) were cultivated in MAXIMOW chambers. The following four derivatives of Substances P (SP) dipeptide were tested for their effects in concentrations between 10(-4) and 10(-8) mol/l: Lys-Pro X 2HBr, Lys(Z)-Pro X HCl, Lys[Z(NO2)]-Pro X HCl and cyclo(Lys-Pro) X HCl. The results suggest that SP and SP derivatives may modulate nerve fibre outgrowth in vitro. In ganglion trigeminale explants Lys(Z)-Pro X HCl stimulated the growth of nerve fibres. The explant covered areas increased significantly. In telencephalon explants and cell cultures the tested derivatives did not essentially promote neurite outgrowth. In retinal cell cultures incubated with cyclo(Lys-Pro) X HCl and Lys[Z(NO2)]-Pro X HCl the neurite outgrowth index was stimulated in a different way. The neurite length was affected and stimulated in the presence of Lys(Z)-Pro X HCl and cyclo(Lys-Pro) X HCl. Both for survival and differentiation PNS neurons depend on specific biofactors. In sensory ganglia explants SP and especially SP derivatives were shown to improve neuronal survival provided that serum or embryonic extract was simultaneously present in the medium. Even if the dipeptides need other biofactors for their full function the may be discussed as neuronotrophic factors because they ensure survival and general growth capability of the responsive neuroblasts.

Animals↗