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PubMed1987

Ultrastructural demonstration of exocytosis in intact and saponin-permeabilized cultured bovine chromaffin cells.

Exocytosis is the release of intracellular vesicular contents directly to the cell exterior after fusion of the vesicular and plasma membranes. It is generally accepted as the process by which transmitters and hormones are released from neurons and neurosecretory cells. There is overwhelming biochemical evidence that exocytosis is the mechanism by which catecholamines are released from adrenal chromaffin cells. With the exception of the hamster, however, there is little ultrastructural evidence to support such a mechanism. We have used a modified in vitro tannic-acid method to visualize exocytosis by transmission electron microscopy in intact and saponin-permeabilized bovine chromaffin cells. When cells are exposed to tannic-acid-containing medium, the content of vesicles involved in exocytosis is coagulated in situ as the vesicle opens to the exterior. Numerous exocytotic profiles were observed. The exposed vesicle contents appeared more granular than those of vesicles in the cell interior. Tannic acid also made the plasma membrane more distinct. Small holes were apparent in the plasma membrane of saponin-treated cells, with little disruption of underlying cytoplasmic structure. Furthermore, when these cells were stimulated with calcium, exocytosis was evident only at regions of intact plasma membrane, not at the holes. Parallel measurements of secretion showed no secretion in the presence of tannic acid. Pretreatment with tannic acid prevented subsequent secretion by intact cells and markedly reduced that of permeabilized cells, indicating a probable change in the nature of the plasma membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2002

Distribution and morphology of transgenic mouse oligodendroglial-lineage cells following transplantation into normal and myelin-deficient rat CNS.

Glial cells from neonatal MbetaP5 transgenic mice, which express bacterial beta-galactosidase (lacZ) under control of the myelin basic protein (MBP) promoter (Gow et al, 1992), were transplanted into the spinal cord or cerebral hemisphere of immunosuppressed normal and myelin-deficient (md) rats in order to assess the ability of the donor cells to survive, migrate, and differentiate within normal compared with myelin-deficient central nervous system (CNS). LacZ+ cells were detected as early as 6-7 days after transplantation into the low thoracic cord and by 10 days had spread rostrally to the brainstem and caudally to the sacral spinal cord. Initially, compact lacZ+ cells, lacking processes, were found associated with small blood vessels and with the glia limitans. Cells of this type persisted throughout the experiment. Later, lacZ+ cells with processes were seen along fiber tracts in the dorsal columns and, after intracerebral injection, subjacent to ventricular ependyma, as well as scattered in cerebral white and gray parenchyma. The extent of spread was comparable in md and normal rats, but in the md group, the success rate was higher, and more cells differentiated into process-bearing oligodendrocytes. Acceptance of xenografts in immunosuppressed recipients equaled that of allografts. The overall spread of grafted cells exceeded that of injected charcoal, indicating active migration. In contrast to earlier studies that identified oligodendrocytes based on morphology alone, this study has allowed us to identify and track oligodendrocytes based on myelin gene expression. We show some oligodendrocytes whose morphology is consistent with classical morphological descriptions, some that resemble astrocytes, and a class of compact perivascular oligodendrocyte-lineage cells that we suggest are migratory.

Animals↗
PubMed1996

Microglial ramification requires nondiffusible factors derived from astrocytes.

It is generally accepted that process-bearing microglial cells origina te from ameboid macrophage-like mesodermal cells. This transformation, often called ramification, accompanies down regulation of macrophage-like properties, but the mechanisms involved in ramification have not been clarified. We investigated factors to promote ramification in culture. Isolated ameboid microglial cells were seeded on living or paraformaldehyde-fixed astrocyte monolayers. About 80% of the cells ramified on the fixed astrocytes in astrocyte-conditioned medium as well as on the living astrocytes. In fresh culture medium, 50% of the cells on the fixed astrocytes ramified. On the other hand, ameboid cells rarely ramified on noncoated glass coverslips even in the conditioned medium. Ameboid cells cultured on extracellular matrices dervied from astrocytes ramified more than on those coated with plasma fibronectin or collagen type I. A synthetic peptide containing Arg-Gly-Asp sequence or a tyrosine kinase inhibitor genistein partially reversed the ramification induced on the fixed astrocyte monolayers. These results show that some nondiffusible factors derived from astrocytes are essential for microglial ramification. A part of the nondiffusible factors are present in the extracellular matrices, and the effects might be mediated by integrins. Some diffusible factors secreted by astrocytes seem to promote ramification, if the nondiffusible factors are present. The experiments using the fixed astrocyte monolayers may be useful to identify the diffusible factors responsibile for ramification.

Amino Acid Sequence↗
PubMed2000

Two nuclear localization signals in the HIV-1 matrix protein regulate nuclear import of the HIV-1 pre-integration complex.

Replication of HIV-1 in non-dividing and slowly proliferating cell populations depends on active import of the viral pre-integration complex (PIC) into the cell nucleus. While it is commonly accepted that this process is mediated by an interaction between the HIV-1 PIC and the cellular nuclear import machinery, controversial results have been reported concerning the mechanisms of this interaction. Here, we demonstrate that a recently identified nuclear localization signal within the HIV-1 matrix protein (MA), MA NLS-2, together with previously described MA NLS-1, mediates nuclear import of the HIV-1 PIC. Inactivation of both MA NLSs precluded nuclear translocation of MA and rendered the virus defective in nuclear import and replication in non-dividing macrophage cultures, even when functional Vpr and integrase (IN), two more viral proteins implicated in HIV-1 nuclear import, were present. Taken together, these results indicate that Vpr does not function as an independent nuclear import factor and demonstrate that HIV-1 MA, by virtue of its two nuclear localization signals, regulates HIV-1 nuclear import.

Amino Acid Sequence↗
PubMed2001

Guidelines for guidelines.

Clinical practice guidelines (CPGs) are suited tools for controlling and improving the effectiveness and efficiency of medical care. With the upcoming internet, the numbers of CPGs have increased rapidly, however, only few offer the attributes of good guidelines such as reliability/reproducibility, applicability, flexibility, clarity, multidisciplinary process, scheduled review and documentation of clinical and scientific evidence. Nearly identical criteria for appraisal of CPGs have been developed in many countries consisting of a checklist with questions concerning the quality of development, the content and format, and the applicability of the guideline. In the United States, guidelines which successfully passed the appraisal (or clearing) process, were stored in the National Guideline Clearinghouse, an internet-based database. A German counterpart is under construction, which will comprise clearing reports reviewing and appraising all existent guidelines covering a medical topic. Developing high-quality CPGs is a time consuming and expensive process. A widely accepted guideline for guideline development was published by the Scottish Intercollegiate Guideline Network. CPGs touching neurosurgical topics are rare and often developed without neurosurgical participation. Due to the potential medico-economic impact of CPGs in the future, national neurosurgical societies and their international associations should play a more active role in the development and implementation of CPGs.

Evidence-Based Medicine↗
PubMed1994

[Brain gangliosides and memory formation].

It is generally accepted that the process of molecular facilitation (= Bahnung) of neuronal circuits by means of stabilization of synaptic contacts represents the structural basis for memory formation. On the basis of physiological, electron microscopic, biochemical, and physicochemical data, a concept is presented speaking in favor of the idea that interactions between brain gangliosides (= amphiphilic sialic acid-containing glycosphingolipids with peculiar physicochemical properties), calcium, and functional membraneous proteins (ion channels, ion pumps, receptors, kinases) play a crucial modulatory role in the transmission and storage of information.

Animals↗
PubMedDate not supplied

Initiation and maintenance of patient behavioral change: what is the role of the physician?

If the physician is to help a patient adopt and maintain "preventive behaviors," the processes that influence and shape both patient and physician behaviors must be understood, the physician's role in the behavioral change process must be acceptable to both the patient and the physician, and an environment that both permits the physician to act and reinforces the physician for acting appropriately must be designed for the physician. A physician's role that is acceptable to both the patient and the physician can be seen as six obligations. The physician must 1) evaluate the medical literature on prevention to determine which services are indicated for which types of patients, 2) when seeing an individual patient, identify the services and behaviors needed by that patient, and 3) advise the patient of the need for action. As the patient responds positively to the physician's advice, the physician must 4) enable and assist the patient to have the indicated tests or procedures and accomplish the suggested behavioral changes, and 5) reinforce the patient's new and ongoing preventive behaviors. The sixth obligation of the physician is to establish, support, and maintain a system to facilitate tasks 2 through 5.

Attitude to Health↗
PubMed2006

[Dermatitis artefacta (factitial dermatitis)--an interdisciplinary diagnostic and therapeutic challenge].

Factitial cutaneous lesions result from self-inflicted injury leading to objectifiable clinically relevant damage to the skin. Triggering factors are frequently psychiatric disorders or specific stress situations. Clinical manifestations range from superficial erosions to deep wounds.The establishment of the diagnosis is often a time-consuming and complicated process that precedes acceptance of the underlying pathology by both the therapist and patient. If lasting therapeutic success is to be achieved, the possibility of such cutaneous lesions must be included in differential diagnostic considerations, and early interdisciplinary cooperation is necessary.

Adult↗
PubMed2000

Mechanisms of changes in lymphocyte numbers after psychological stress.

In the field of psychoneuroimmunology it has become obvious that the immune system is governed by multiple influences from the central nervous system. One approach to verify these interactions can be seen in stress research. While the phenomenon of stress-induced changes in immunological processes is widely accepted, more recent studies focus on possible moderators and mechanisms of these responses. Within this research strategy it became evident that catecholamine increases upon stress are of major importance for the frequently observed mild leukocytosis. The present study was conducted to investigate whether the often observed stress-induced increases in the number of peripheral lymphocyte subsets depends on the amount of epinephrine or norepinephrine release. Moreover, the question was addressed whether high or low catecholamine release is related to subjective ratings on discomfort. Using a "public speaking paradigm", we were able to replicate previous findings of high increases in the absolute number of CD8+ and CD56+ cells in peripheral blood. Moreover, when dividing subjects into high and low catecholamine responders, the amount of change was significantly larger in catecholamine responders irrespective of whether norepinephrine or epinephrine was used for grouping the subjects. However, high and low catecholamine responders did not differ with respect to subjective ratings on discomfort. The data are discussed with respect to underlying mechanisms in catecholamine-induced lymphocyte migration and possible reasons for the mismatch between objective and subjective indicators of stressor efficacy.

Adult↗
PubMed2000

Stochastic aspects and uncertainties in the prechemical and chemical stages of electron tracks in liquid water: a quantitative analysis based on Monte Carlo simulations.

A new physical module for the biophysical simulation code PARTRAC has recently been developed, based on newly derived electron inelastic-scattering cross-sections in liquid water. In the present work, two modules of PARTRAC describing the production, diffusion and interaction of chemical species were developed with the specific purpose of quantifying the role of the uncertainties in the parameters controlling the early stages of liquid water radiolysis. A set of values for such parameters was identified, and time-dependent yields and frequency distributions of chemical species produced by electrons of different energies were calculated. The calculated yields were in good agreement with available data and simulations, thus confirming the reliability of the code. As the primary-electron energy decreases down to 1 keV, the *OH decay kinetics were found to get faster, reflecting variations in the spatial distribution of the initial energy depositions. In agreement with analogous works, an opposite trend was found for energies of a few hundred eV, due to the very small number of species involved. The spreading effects shown at long times by *OH frequency distributions following 1 keV irradiation were found to be essentially due to stochastic aspects of the chemical stage, whereas for 1 MeV tracks the physical and pre-chemical stages also were found to play a significant role. Relevant differences in the calculated e(aq) -yields were found by coupling the physics of PARTRAC with descriptions of the pre-chemical and chemical stages adopted in different models. This indicates a strict interrelation of the various stages, and thus a strong dependence of the parameter values on the assumptions made for the preceding and subsequent stages of the process. Although equally acceptable results can be obtained starting from different assumptions, it is necessary to keep control of such uncertainties, since they can significantly influence the modeling of radical attack on DNA and, more generally, radiobiological damage estimation. This study confirms the need for new, independently derived data on specific steps of water radiolysis, to be included in comprehensive biophysical simulation codes.

Algorithms↗
PubMed2002

Two-quadrant semiclosed hemorrhoidectomy. A preliminary report.

Bleeding and delayed healing may affect the postoperative course following hemorrhoidectomy and cause discomfort to the patient. The present report deals with a modification of the Milligan-Morgan operation: the upper part of the surgical wound is covered with rectal mucosa and the distal edge is stitched with a running suture, with the aim of decreasing both the risk of bleeding and the healing time. The operation has been performed in 12 consecutive patients with two quadrant internal and external piles. The median operative time was 32 minutes (range, 21-30). The mean postoperative pain after 12 hours, measured from 1 to 10 on a visual analogue scale, was 4.4 (SEM, 1.4). All patients but three had their wounds healed within 3 weeks and none of them had postoperative bleeding requiring treatment. Acute urinary retention occurred in one case. All patients were discharged after 48 hours. None had anal incontinence or short-term recurrence. In conclusion, two-quadrant semiclosed hemorrhoidectomy provided good results in terms of both bleeding rate and healing process with an acceptable operative time and postoperative pain.

Adult↗
PubMed2005

How should we inform women at higher risk of breast cancer about tamoxifen? An approach with a decision guide.

BACKGROUND: Tamoxifen has been shown to reduce the incidence of invasive breast cancer in women at higher risk. Translating these research results to clinical practice is challenging. Our objective was to develop and evaluate a decision-making guide and process that can be used in clinical practice to inform eligible women of chemoprevention with tamoxifen. METHODS: A decision guide explaining the benefits and risks of tamoxifen was developed with input from health care professionals and two focus groups of women both with and without cancer. Following consent, 51 eligible women presenting to a multi-disciplinary diagnostic facility for breast problems were given the decision guide/questionnaire to read, fill out and return by mail. Women with further questions or wanting to take tamoxifen were encouraged to re-contact their physicians. RESULTS: Atypia was seen in 60% of subjects. Median 5-year Gail risk was 3.7 (range 1.7-9.4). Only 6 (11.8% 95% CI = 2.9, 20.6%) women reported they would like to take tamoxifen while 6 (11.8% 95% CI = 2.9, 20.6%) remained uncertain. CONCLUSION: We have developed a decision-making guide and process that is acceptable to providers and women to identify and inform women at higher risk of breast cancer with regard to chemoprevention with tamoxifen. Few women in this select group, when provided with a balanced decision guide, wished to pursue chemoprevention with tamoxifen.

Breast Neoplasms↗
PubMed1985

Infection and phagocytosis as possible mechanisms of rupture in premature rupture of the membranes.

The concept that premature rupture of the membranes is due to an infectious process is well accepted. However, no definitive data implicating a particular microorganism or a mechanism of action have been advanced. By the use of our recently developed experimental in vitro amnion-chorion reaction vessel model we have studied the effect of the peroxidase-hydrogen peroxide-halide antimicrobial system on these membranes. We have noted that amnion, chorion, decidua, and placental macrophages all possess peroxidase activity. Tissues collected from deliveries following labor (vaginal) are significantly higher in activity than those collected from deliveries with no labor (cesarean section). A mobilization of enzyme from macrophages to amnion appears to occur in the laboring patient. Increased protein hydrolysis is noted in membranes collected from patients without labor subjected to the peroxidase-hydrogen peroxide-halide cytotoxic system when compared with membranes from laboring patients. Bursting pressures of membranes collected from patients without labor are shown to be decreased when the membranes were incubated in the presence of lysolecithin or in the presence of amniotic fluid and phospholipase A2.

Amnion↗
PubMed1990

Myofibroblastoma of the tunica testis: evolving phase of so-called fibrous pseudotumor?

A collagen-rich stromal tumor attached to the testicular tunica albuginea of a 22-year-old male is reported. Immunocytochemical and ultrastructural characterization revealed a predominant population of myofibroblasts, an as yet unrecognized observation in tumors arising from testicular tunics. The possible relationship with so-called fibrous pseudotumor (nodular fibrous proliferation) is discussed. The myofibroblastic nature of the cell population would support the hypothesis of a reactive contractile process if one accepts this tumor as an evolving phase of fibrous pseudotumor.

Adult↗
PubMed1987

Fatigue properties of cast and heat treated Ti-6Al-4V alloy for anatomic hip prostheses.

The intricate shape of Ti-6Al-4V anatomic hip prostheses necessitates the use of casting as a fabrication method, since neither machining, nor forging or powder metallurgial processing are reasonably acceptable. Cast and hot isostatically pressed Ti-6Al-4V, however, has a relatively low ductility and reduced fatigue properties. Appropriate thermal treatments can improve these properties. Specifically, treatments comprising a beta-solutionizing and an aging step yield ductilities similar to the forged and annealed condition, and fatigue properties 11.5% above the non-treated condition. Such treatments produce small alpha-beta platelet colonies with a ragged, tortuous morphology. The reduction of scatter in fatigue strength is the result of the formation of this well controlled microstructure.

Alloys↗
PubMed1995

Brain gangliosides and memory formation.

It is generally accepted that the process of molecular facilitation of neuronal circuits by means of stabilization of synaptic contacts represents the structural basis for memory formation. At the distinct zone of synaptic contact the following basic events occur: alterations of the electrical field strength at the outer surface of synaptic membranes, conformational changes of membrane-bound functional proteins (ion channels, ion pumps, receptors) and activation of second messenger cascade. Finally a trophic feed-back between synaptic terminals and their cell bodies through retro- and anterograde neuronal transport exists, which guarantees a stabilization of the newly formed synaptic connection. As a controlled Ca(2+)-exchange between the extracellular space (mM Ca(2+)-concentration) and the synaptoplasm (microM Ca2+) is essential for all these events, the present research concentrates on Ca(2+)-mediated primary messenger systems at the outer leaflet of synaptic membranes and on Ca(2+)-mediated modulatory mechanisms. These enable an always efficient electroresponsiveness although the environmental temperature might have changed. In this regard gangliosides being amphiphilic sialic acid containing glycosphingolipids, which are highly accumulated in complex composition in synaptic membranes play an important role. According to specific physico-chemical properties, they are assumed to fulfill the task of neuromodulators in connection with calcium, and thus contribute to the transmission and storage of information. The outcome of a series of experiments derived from neurology, ecophysiology, behavioral sciences, electron microscopy, biochemistry and physical chemistry give strong circumstantial evidence for this concept.

Animals↗
PubMed1994

Interhemispheric transfer and the processing of foveally presented stimuli.

Two arguments are commonly given in favor of a nasotemporal overlap along the vertical meridian of the visual field: anatomical findings and the existence of macular sparing in hemianopia. A review of the literature, however, points to the weakness of the evidence. The anatomical indications are exclusively based on horseradish peroxidase studies, which can not give an unequivocal answer to the amount of overlap in central vision, and which were not supported by a recent study that made use of the more direct [14C]2-deoxy-D-glucose technique. The argument of macular sparing in hemianopia appears to be derived evidence that depends on the validity of the anatomical findings. In addition, behavioral studies consistently failed to find functional confirmation of the overlap. To further test the possibility of bilateral representation in central vision, a new paradigm is proposed. It is argued that if interhemispheric transfer is needed for the processing of foveally presented stimuli, the word-beginning superiority effect should be larger for subjects with left hemisphere dominance than for subjects with right hemisphere dominance. Results are in line with the hypothesis and point to the fact that interhemispheric transfer of visual information may be involved in more processing than usually accepted. It is also noted that transfer time seems to depend on the amount of information that must be transferred, and is significantly shorter than the estimates obtained in visual half field studies.

Adult↗
PubMed1990

The influence of the efferent system on acoustic overstimulation.

Since the first anatomical description by Rasmussen, the efferent innervation of the ear has been extensively investigated in order to establish its role in the hearing process. It is accepted that the olivocochlear bundle (OCB) influences the activity of the afferent fibers and through it, the peripheral ear is controlled by higher centers as well as connected to the other ear. Cody and Johnstone (1982) and Rajan and Johnstone (1983) concluded that the amount of ipsilateral temporary threshold shift (TTS) was reduced by simultaneous contralateral acoustic stimulation or by destroying the contralateral cochlea. They attributed the results to the efferent system. It was our aim to investigate whether, and under which conditions, the amount of TTS would be influenced by the efferent system. The efferent innervation was eliminated by cutting the superior vestibular nerve. Two factors influenced the magnitude of TTS; the integrity of the OCB and the functional condition of the contralateral ear.

Acoustic Stimulation↗