Detachment Phase Research Articles

Korrelation zwischen sonographischen und klinischen Befunden in der Plazentarperiode - Lösungszeiten, Lösungszeichen und Lösungsmodus

Objective: We analyzed the duration and phases of the third stage of labor with gray-scale and color Doppler sonography. We also compared ultrasound findings with the clinical signs of placental separation and the mode of placental delivery. Methods: The third stage of labor was recorded by color Doppler sonography in 57 patients after vaginal delivery. Results: The third stage of labor can be broken down into three distinct phases. The latent phase consists of the interval between delivery of the newborn and beginning placental separation (median duration 141 sec, range 5 - 790 sec). The beginning of this phase was marked by cessation of blood flow between the myometrium and the placenta. The detachment phase is characterized by shearing off of the placenta from the myometrium (median duration 50 sec, range 15-100 sec). The expulsion phase begins with completed separation and ends with the vaginal delivery of the placenta (median 80.5 sec, range 2-385 sec). Kustner's sign (absent umbilical cord retraction on suprapubic pressure) was positive and Schroder's sign (fundal elevation) in 98% of women with sonographically separated placentae. Clinically, placental separation by the Schultze mechanism was present in 45 cases (79%). In contrast, sonography showed that placental separation began from the inferior pole of the placenta without retroplacental hematoma in all cases. Conclusion: The third stage of labor consists of three distinct phases. The duration of the third stage is determined mainly by the latent phase, in which blood flow between the myometrium and the placenta ceases. Clinical and sonographic signs of placental separation correlate closely. The lower part of the placenta usually separates first, so that the mechanism described by Schultze is only of theoretical interest.

Inherited neurodegenerative diseases: the one-hit model of neurodegeneration.

The clinical manifestations of inherited neurodegenerative diseases are often delayed for periods from years to decades. This observation has led to the idea that, in these disorders, neurons die from cumulative damage. A critical prediction of the cumulative damage hypothesis is that the probability of neuronal death increases with age. However, we recently demonstrated, in 17 examples of neurodegeneration, that the kinetics of neuronal death appear to be exponential. These examples include both monogenic disorders, such as photoreceptor degenerations, as well as others that are partly or entirely acquired (such as the clinical phase of parkinsonism and retinal detachment). Exponential kinetics indicate that (i) the risk of death is constant, (ii) death occurs randomly in time and (iii) the death of each neuron is independent of other neurons. We use the term 'one-hit model' to refer to the single catastrophic intracellular biochemical event, analogous to radioactive decay, which leads to neuronal death in the diseases we analyzed. Here, we examine the major features and implications of the one-hit model and provide preliminary evidence that amyotrophic lateral sclerosis also appears to fit this model. We also discuss a testable biochemical hypothesis, the mutant steady-state hypothesis, that we proposed to account for the one-hit model. Finally, we explore six unresolved issues that appear to challenge this model. The one-hit model appears to capture a novel principle underlying many neurodegenerations. Our findings suggest that any consideration of the biochemical basis of neurodegeneration must include a meticulous examination of the kinetics of cell death.

Platelet-Derived Growth Factor Stimulates the Formation of Versican–Hyaluronan Aggregates and Pericellular Matrix Expansion in Arterial Smooth Muscle Cells

Hyaluronan and versican-rich pericellular matrices form around arterial smooth muscle cells (ASMC) preferentially during the detachment phase of proliferation and migration. PDGF is a potent mitogen and chemotactic agent for ASMC and also stimulates the production of extracellular matrix molecules which may regulate the proliferative and migratory capacity of the cells. We have examined the effect of PDGF on the formation of hyaluronan-dependent pericellular matrices, and on the synthesis and interaction of several major pericellular coat constituents. As demonstrated using a particle exclusion assay, PDGF stimulated the formation of pericellular matrices and was seen both in an increased proportion of cells with a coat and a greater coat size. This increase was accompanied by a transient increase in hyaluronan synthase 2 (HAS2) expression and an increase in hyaluronan synthesis and polymer length. PDGF also increased the synthesis of versican and link protein as measured at the mRNA and protein levels. The amount of native versican-hyaluronan aggregates and link-stabilized aggregate was also increased following PDGF treatment. Time lapse imaging showed that pericellular matrix formation occurred around trailing cell processes prior to their detachment. These data suggest that PDGF modulates the synthesis and organization of ASMC pericellular coat-forming molecules such as versican, hyaluronan, and link protein, which leads to extracellular matrix expansion and alterations in ASMC phenotype.

Simulation of the 1992 Tessina landslide by a cellular automata model and future hazard scenarios

Cellular Automata are a powerful tool for modelling natural and artificial systems, which can be described in terms of local interactions of their constituent parts. Some types of landslides, such as debris/mud flows, match these requirements. The 1992 Tessina landslide has characteristics (slow mud flows) which make it appropriate for modelling by means of Cellular Automata, except for the initial phase of detachment, which is caused by a rotational movement that has no effect on the mud flow path. This paper presents the Cellular Automata approach for modelling slow mud/debris flows, the results of simulation of the 1992 Tessina landslide and future hazard scenarios based on the volumes of masses that could be mobilised in the future. They were obtained by adapting the Cellular Automata Model called SCIDDICA, which has been validated for very fast landslides. SCIDDICA was applied by modifying the general model to the peculiarities of the Tessina landslide. The simulations obtained by this initial model were satisfactory for forecasting the surface covered by mud. Calibration of the model, which was obtained from simulation of the 1992 event, was used for forecasting flow expansion during possible future reactivation. For this purpose two simulations concerning the collapse of about 1 million m3 of material were tested. In one of these, the presence of a containment wall built in 1992 for the protection of the Tarcogna hamlet was inserted. The results obtained identified the conditions of high risk affecting the villages of Funes and Lamosano and show that this Cellular Automata approach can have a wide range of applications for different types of mud/debris flows.

Cytotoxic effects of an oxidative stress on neuronal-like pheochromocytoma cells (PC12)

Although the generation of oxygen derivatives during ischemia and reperfusion is generally held as a major event in the process leading to neuronal death, the biochemical mechanisms responsible for cell degeneration remain poorly understood. To better understand the toxicity induced by oxidative stress in neural tissue, we have tested the effect of an exogenous hydroperoxide, cumene hydroperoxide (CHP), on the metabolism and viability of PC12 cells. Addition of CHP in the culture medium leads to significant cell death that becomes perceptible at concentrations above 1 μM and reaches a maximum (80–90% toxicity) at 100 μM. A time-course study shows that Trypan blue uptake is preceded by a rapid phase of cell rounding and detachment from the substratum (within 30 min) followed by a progressive uptake of the dye (60–120 min). During this 2-hr period, we failed to observe any major signs of membrane lipoperoxidation (such as MDA production or fatty acid release). On the other hand, we observed that cell death is preceded by a striking decrease in cellular ATP content and in the retention of rhodamine 123 (within 15–30 min of treatment); thus, suggesting that the mitochondria may be the primary target of hydroperoxide action.

The influence of ionic strength upon relaxation from rigor induced by flash photolysis of caged-ATP in skinned murine skeletal muscle fibres

The influence of ionic strength upon relaxation kinetics from rigor in skinned murine extensor digitorum longus (EDL) skeletal muscle fibres was examined using photolysis of caged-ATP at low Ca2+. The ionic strength was adjusted with either KMeSO3 or ethylene glycolbis-(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid, dipotassium salt (K2EGTA) in the range of tau /2 = 65-215mM, or I.E. 49-194mM, where I.E. denotes ionic equivalent. Following rigor development at a tau /2 of 165-215mM (I.E. 144-194mM), the liberation of approximately 0.5mM ATP resulted in an initial 6-to 10-ms detachment phase with a decline in force of approximately 10-20% followed by a 10-to 30-ms reattachment with up to a 60% increase compared to the corresponding rigor level and a final detachment leading to complete relaxation. Interestingly, when similar ATP concentrations were liberated at lower ionic strengths between a tau /2 of 65mM and 110mM (I.E. 60-100mM), the initial detachment phase was shortened and force decreased by only approximately 5-10%, while the following reattachment phase was lengthened and led to an increased steady-state force of approximately 20-80% without final relaxation. ATP-induced detachment and subsequent reattachment were mainly determined by the currently present ionic strength and were relatively independent of the preceding rigor state which had been developed at higher or lower ionic strengths. The effects of phosphate and apyrase on the force transient suggest that reattachment of ADP- binding crossbridges may contribute to the increase in tension at high and even more at low ionic strengths. The study shows that the kinetics of initial fast relaxation and subsequent redevelopment of force following flash photolysis of similar ATP concentrations are markedly modified by the ionic strength in the narrow range of between 65mM and 215mM.

Changes in uterine artery Doppler flow velocity waveforms during the third stage of labor.

Transabdominal Doppler velocity waveform measurements of the uterine arteries during the third stage of labor were performed upon 25 patients with uncomplicated vaginal deliveries and 5 with prolonged third stage in order to further assess third-stage mechanisms. Based on Doppler flow measurements, three phases of the third stage of labor were observed: (1) a latent phase with a systolic/diastolic ratio (S/D) and a pulsatility index (PI) of 2.14 +/- 0.49 and 0.89 +/- 0.17, respectively; (2) a contraction and detachment phase with an S/D and PI of 2.53 +/- 0.53 and 1.28 +/- 0.37, respectively, and (3) an expulsion phase with an S/D and PI of 2.20 +/- 0.34 and 0.91 +/- 0.20, respectively (p < 0.05). During the third stage of labor, it was shown that uterine contractions squeezed the uterine vessels as they traversed the myometrium, leading to an increase in the extrinsic resistance, which was reflected by high resistance flow. Following placental separation and changes in the placental-site wall, there was slight uterine relaxation resulting in decreased uterine vessel resistance. This observation encourages the authors to continue investigating the contribution of ultrasound and Doppler flow for studies of the postpartum period.

Finite-element analyses of thrust tectonics: Computer simulation of detachment phase and development of thrust faults

The mechanics of thrust fault formation in rectangular and wedge-shaped, homogeneous thrust blocks are examined using finite-element techniques incorporating elasto-plastic material behaviour. Compression is simulated by applying an incremental end displacement parallel to the top of the horizontal or inclined basement. Shear zones (or faults) can form where the material experiences plastic strain softening. These models simulate that thrusts initiate in sequences that are “pushed from behind”, by some tectonic force, over a decollement horizon. In all models, the formation of thrusts is preceded by the formation of a basal slip plane near the base of the block or in a weak substratum. The front of this slip plane does not control the location of thrusts formed subsequently. In the rectangular block, a thrust forms at the pushed end. In the tapered wedge, drained as well as undrained, a fault system composed of a thrust and a backthrust forms. It is argued that the geometry of the block is the main controlling feature for the formation of thrusts within the tapered wedge. The shape of reverse faults depends on the magnitude of shear stresses acting along the basal slip plane. The higher the shear stress, the more pronounced the curvature. In the drained tapered wedge, the intersection of the backthrust with the basal slip plane appears to control the location of the thrust. Under undrained conditions, the backthrust forms subsequent to the thrust and acts only as an accommodation feature.

Dynamic ultrasonographic imaging of the third stage of labor: New perspectives into third-stage mechanisms

Dynamic ultrasonographic imaging of the third stage of labor was performed to document ultrasonographic findings and to present new perspectives into third-stage mechanisms. Twenty-five normal deliveries and five with prolonged third-stage labor were studied. Normal third-stage labor could be divided into four phases: (1) latent phase, characterized by thick, placenta-free wall and thin, placenta-site wall; (2) contraction phase, with thickening of placenta-site wall (from < 1 cm to > 2 cm); (3) detachment phase, in which the placenta completes its separation and detaches; and (4) expulsion phase, with a sliding movement of the placenta. Although oxytocic agents were routinely used, they do not seem to influence the findings. In five cases with retained placenta the placenta-site wall was initially thin. In four of them it became thick, and the placenta was removed by traction of the cord, whereas in the fifth case the placenta-site wall remained thin and the placenta had to be removed manually. Shearing forces seem to tear the decidual septae and thereby separate the placenta. This process is completed only when the placenta-site wall attains full thickness. In cases of prolonged third-stage labor, traction of the cord should be applied only when this phase is completed and the actual sliding movement of the placenta is observed.

Surgical management of exudative maculopathies: preliminary report.

A new surgical approach to the management of exudative maculopathies has been developed including the transvitreal route. As a result of surgery the subretinal spaces are drained and their viscous content removed. A special tool was designed for this operation. The method has been clinically tested on 32 patients (32 eyes) with different forms of age-related macular degeneration in the phase of complicated pigment epithelium detachment and on six patients (six eyes) with myopic exudative maculopathy. The follow-up ranged from 6 to 32 months. No fluid reappeared in the macular zone in patients with age-related macular degeneration, except one; visual function improved in 26 out of 32 cases (81.3%). Similar results were obtained in all six patients with myopic exudative maculopathy.

Synchronised secretory organelle docking in Paramecium saltatory movement along microtubules transiently formed from ciliary basal bodies and selective exclusion of microinjected heterologous organelles

ABSTRACT Ln certain strains (nd) of Paramecium tetraurelia all secretory organelles (trichocysts) can be detached from the cell surface and then reattached synchronously. To account for the lability of microtubules involved in trichocyst docking during the preparation procedures we analysed this process by combining video microscopy, analogue contrast enhancement microscopy, laser scanning fluorescence microscopy (both after fast freezing, freeze-substitution and anti-tubulin antibody fluorescence labelling), and electron microscopy after cryoflxation. We found that synchronous trichocyst docking is saltatory, occurring along transiently formed microtubules (not normally recognised in these cells), which emanate from ciliary basal bodies, acting as organising centres. Hence, trichocyst transport proceeds from the plus to the minus end of microtubules (in contrast to gland cells), with the ‘correct’ polarity (trichocyst tips pointing to the cell surface). We then injected chromaffin granules (isolated from bovine adrenal medullae) during the trichocyst detachment phase and analysed cells by electron microscopy during and after synchronised redocking of trichocysts. We used a chromate reaction for chromaffin granule identification on semithin sections by X-ray microanalysis (scanning transmission EM). While chromaffin granules remained intact (as judged by morphology and Cr signals) and although cell function was unimpaired (as judged by complete trichocyst attachment), we determined that heterologous organelle transport was not detectable, probably because of inverse microtubule polarity.

FMC46, a cell protrusion-associated leukocyte adhesion molecule-1 epitope on human lymphocytes and thymocytes.

In this report, we describe a 76-kDa glycoprotein recognized by mAb FMC46 that, by virtue of its concentration on cell protrusions involved in motility, may be important in lymphoid cell locomotion. FMC46 detects an epitope of the leukocyte adhesion molecule-1 (LAM-1), a member of the selecting family (LAM-1, Endothelial Leukocyte Adhesion Molecular-1 (ELAM-1), and Granule Membrane Protein-140 (GMP-140), that is expressed on LAM-1-transfected cell lines, is a glycosylation epitope based on its loss after culture in tunicamycin, and is closely related to the LAM-1.2 epitope. FMC46 is expressed at high density on the majority of CD45RA+ and CD45RO+ peripheral blood T cells (60 to 70%) and on a subset of thymocytes that includes the multinegative CD3- CD4- CD8- progenitor cells (100% FMC46hi) and the CD45R0- presumptive thymic generative lineage (70% FMC46hi). It appears at reduced density and frequency on CD45RA- thymocytes (50% FMC46lo), comprised mainly of death-committed thymocytes. Among thymic subsets defined by expression of CD4 and/or CD8, FMC46 is expressed at high density predominantly on a subset of single-positive cells and not on double-positive cells. These results suggest a fundamental role for LAM-1 in thymic development, with a high density preferentially expressed on cells involved in thymic generative processes and a low density on cells progressing to intrathymic death. A major subset of peripheral blood B cells and thymic B cells also express FMC46. Immunohistochemistry on frozen sections indicated strong staining in splenic follicles and around blood vessels, staining of the thymic medulla and subcapsular areas, and staining of the mantle zone of germinal centers of the lymph node. FMC46+ lymphocytes accumulated along high endothelial venules in the lymph node. On locomoting multinegative thymocytes, FMC46 is concentrated on the leading tip of extended processes, on pseudopods, and on ruffles, unlike the distribution of either CD44 or TQ1 (LAM 1.2), suggesting a role in locomotion. On dividing multinegative thymocytes, FMC46 was found almost exclusively along the cleavage furrow, implicating it in detachment processes. We conclude that the properties of the LAM-1 molecule recognized by FMC46 are consistent with a role in detachment phases of motility and of cell interactions.

Kinetics and Modelling of Aerobic and Anaerobic Film Growth

Our fundamental studies of the kinetics of growth and substrate removal by aerobic and anaerobic biofilms have shown that the process comprises six phases : the latent, dynamic, linear, decrease, stabilization and detachment phases. During these experiments we also observed:-steady state functioning in the liquid bulk from the end of the dynamic phase. At this point a very thin pseudo-thickness of biofilm was observed (50 µm maximum).-steady state functioning relative to the observed biofilm mass, reached in the stabilization phase, the corresponding thickness being generally several hundred microns. To explain this phenomenon we suggest a new biofilm modelling hypothesis, based on physiological aspects, which consists of defining two types of bacteria : active bacteria (Ma) responsible for substrate removal and characterized by a specific growth rate (µo), and inert or deactivated bacteria (Md) which play no role in the removal process but are responsible for the observed accumulation of biofilm. Using this hypothesis, it is possible to modelize the dynamic and linear phases of growth of total biofilm dry matter (Mb) and carbon substrate removal kinetics. This model enables the exponential growth rate (µo), the accumulation rate (K) and the maximum quantity of active bacteria (Ma)max to be calculated. In another series of experiments, we studied the influence on these parameters of several factors which affect growth, such as the carbon substrate concentration provided by the feed (So) and the dissolved oxygen for the aerobic biofilms. The results demonstrate that the biological constants are strongly dependent on (So). The same is true for the volumetric substrate removal rate(kov), which shows that the process always depends on the reaction. Thus we have established that the substrate metabolization reaction occurs at the biofilm-liquid interface, and that it is preferable to use thin biofilms for an attached culture industrial process. This has been done by optimizing the surface and volume properties of new granular materials called OSBG (Optimized Support for Biological Growth). Initial results, notably for three-phase fluidized bed carbon removal, show that it is possible to eliminate very high carbon loading (10 to 15 kg TOD.m3.day−1) under very stable conditions with a very small quantity of active biomass (0.5 D.W. m). In addition, excess sludge production is relatively low and respirometric studies performed in situ with a gas phase mass spectrometer confirm the very high catabolic activity of thin biofilm.

Effect of critical surface tension on retention of oral microorganisms.

The effect of critical surface tension on the initial retention of microorganisms from unstimulated human saliva was tested in a flow cell system. Prior to each experiment the total numbers and the morphotypes of microorganisms present in saliva were recorded. The test surfaces were prepared to display known increasing critical surface tensions, as verified and standardized by contact angle measurements. Surfaces of initially low (20-22 mN/m), medium (35-38 mN/m) and high (greater than 50 mN/m) critical surface tension were exposed to saliva at a flow rate of 1 ml/min. Microbiota and biofilm material associated with the test surface after 15 min of salivary exposure, were then subjected to standard detachment forces, by introducing a cell-free rinsing fluid at two different shear rates. Both the attachment and the detachment phases were executed at room temperature or 37 degrees C. The retained population was counted in three different zones of the test surfaces with a light microscope and statistically tested for correlation to the main variables (critical surface tension, flow rate and temperature) and interactions. Retention success was significantly dependent on the initial critical surface tension and the flow rate. Surfaces of medium critical surface tension, representative of human tooth surfaces and most restorative dental materials, retained the highest numbers of microorganisms in comparison with the other surfaces tested, with no statistically verified selectivity in proportions of retained coccoid and rodshaped microorganisms for any surface. A 30-fold increase of the flow rate resulted in a 70-80% reduction of the retention success, with a higher relative number of cocci present on all the test surfaces. These results demonstrate that initial retention of microorganisms to surfaces is non-specific with regard to morphotypes, but is strongly related both to the mechanical removal forces and the surface energetic state of the solid surface exposed. Retention of microbial populations at interfaces might, therefore, be controllable by advance selection of the critical surface tensions and predicted if shear forces at given sites are known.

The reaction-limited kinetics of membrane-to-surface adhesion and detachment.

Biological adhesion is frequently mediated by specific membrane proteins (adhesion molecules). Starting with the notion of adhesion molecules, we present a simple model of the physics of membrane-to-surface attachment and detachment. This model consists of coupling the equations for deformation of an elastic membrane with equations for the chemical kinetics of the adhesion molecules. We propose a set of constitutive laws relating bond stress to bond strain and also relating the chemical rate constants of the adhesion molecules to bond strain. We derive an exact formula for the critical tension. We also describe a fast and accurate finite difference algorithm for generating numerical solutions of our model. Using this algorithm, we are able to compute the transient behaviour during the initial phases of adhesion and detachment as well as the steady-state geometry of adhesion and the velocity of the contact. An unexpected consequence of our model is the predicted occurrence of states in which adhesion cannot be reversed by application of tension. Such states occur only if the adhesion molecules have certain constitutive properties (catch-bonds). We discuss the rational for such catch-bonds and their possible biological significance. Finally, by analysis of numerical solutions, we derive an accurate and general expression for the steady-state velocity of attachment and detachment. As applications of the theory, we discuss data on the rolling velocity of granulocytes in post-capillary venules and data on lectin-mediated adhesion of red cells.

A novel form of sperm detachment from eggs of Urechis caupo

Urechis sperm bind to the egg's extracellular envelope via acrosomally derived adhesive material. Sperm initially adhere tightly, but within minutes they loosen from the egg envelope. Using transmission electron microscopy, we have determined that the sperm's binding material disperses during the detachment phase. Dispersion appears to be caused by the egg and to be necessary for sperm detachment, because sperm bound to glutaraldehyde-fixed eggs do not detach, nor does their binding material disperse. The binding material also fails to disperse when sperm are artificially acrosome reacted in the absence of eggs, using an ionophore. Our results suggest a form of sperm detachment not previously described: an egg-induced removal of the binding material.

Sperm Bind but Do not Unbind from the Fixed Sea Urchin Egg: (sperm binding kinetics/fixed eggs).

In S. purpuratus sperm remained bound to aldehyde-fixed eggs and did not exhibit a detachment phase. Sperm bound in high numbers and the binding curve was similar to that for unfixed homologous gametes. Binding kinetics were analyzed using sequential still photographs of slightly flattened, fixed eggs under supported coverslips. In this way, a single egg could be observed. Alternatively, sperm remaining in the supernatant over settled eggs were counted at successive time points postmixing using spectrophotometry (340 nm) and hemocytometry. Additionally, aliquots of mixed gametes were fixed at successive time points and the numbers of bound sperm determined microscopically on egg perimeters. The maximum number of sperm bound by 2 min; this number remained at or near maximum for as long as 10 min when the experiments were terminated. When sperm were jelly-reacted before addition to eggs, fewer sperm bound, although binding curves were similar to the above experiments. It appears that the binding efficiency of sperm decreases with time after initiation of the acrosome reaction: (1) fewer prereacted sperm bound; and, (2) sperm did not continue to bind after 2 min even though the egg surface was not saturated. Whether these effects are related to motility or other factors is unclear. Furthermore, the above results indicate the importance of the cortical reaction to sperm unbinding. Such studies enable one to observe sperm behavior while precluding the effects of egg secretion during the initial stages of fertilization.

Effects of brief separation from mother on rhesus monkeys.

To summarize, data on the course of development of mother-infant relations in rhesus monkeys have been presented; a method for teasing apart the relative roles of mother and infant in causing changes or differences in the interaction described; and the complexity of the social nexus, within which the relationship is set, stressed. When the mother is removed for a few days, the infant calls a great deal at first and then shows depressed locomotor and play activity. These symptoms may last for a month after the mother's return. Simple tests given 6 months and even 2 years later strongly suggest that the differences (between infants that have had such a separation experience and infants that have not) are persistent. Are these data relevant to the human case? The rhesus monkey has no verbal language and a much less complex social development than man. Furthermore, its social environment is quite different from that found in any human culture. Parallels between monkey and man must therefore be scrutinized carefully before being used as a basis for generalization. But the facts show that a brief separation experience produces in rhesus monkey infants symptoms that are very similar (except for the apparent absence of a "phase of detachment" on reunion) to those in human infants (25). While age of separation, within the rather narrow limits used here, was a variable of minor importance, the effects of the separation varied, as in the human case, with the length of the separation experience and the sex of the infant. Differences in the techniques of experimenters, as well as differences in the species, prevent precise comparisons of the roles of the mother-infant relationships; nevertheless, the nature of the relationship appears to be an important variable in both monkey and man. There would seem, therefore, to be strong reasons for thinking that we are dealing with comparable phenomena. If that is the case, the fact that monkeys function at a simpler conceptual level than man limits the complexity of the explanatory hypotheses necessary in the human case. In addition, the finding that such a brief separation experience, involving removal of the mother but no exposure to a strange environment, can produce effects lasting for months or years in rhesus monkeys strengthens the evidence that long-term effects may occur also in man. Finally, this analysis provides bases for attempts to predict individual differences in the effects of a period of separation on rhesus infants, and the parallels with man suggest that examination of the same variables in the human case would be worthwhile.

Surgery of retinal detachment; the old versus the new.

In October, 1951, at the annual session of the American Academy of Ophthalmology and Otolaryngology, a symposium on retinal detachment was presented. This symposium was of particular note because of the concise but complete coverage of such a broad subject, the renowned status of the speakers, and the large audience that attended the presentation. One of the speakers who participated in this symposium is now the president of this section, Dr. Dohrmann K. Pischel. Because of Dr. Pischel's particular interest in retinal detachment, the panel discussion of this subject today is very timely. I thought it appropriate, therefore, to reevaluate Dr. Pischel's remarks of 1951 in light of the developments that have occurred in the past six and one-half years and compare the clinical results obtained with the older technics and with the newer ones. In the symposium of 1951 Dr. Pischel¹discussed the treatment phase of retinal detachment

PROGRESS IN MEDICAL AND IN SURGICAL TREATMENT IN OPHTHALMOLOGY 1929-1930

The observations offered here are meant to be an orderly arrangement of topic material gleaned from literature that has appeared in English, originally or by abstracts, during the last twelve months. DETACHMENT OF THE RETINA Knapp¹stated that the remarkable results in retinal detachment obtained by Gonin would lead to a renewed interest and study of the whole subject. Of the titles considered for this report, 42 per cent pertained to some phase of detachment of the retina. Gonin's operation is not readily comprehensible without a methodical presentation of the subject for which it was devised. Detachment of the retina is considered to be spontaneous or traumatic in origin. Spontaneous cases occur without known injury. Traumatic cases arise from mechanical factors such as progressive myopia,²perforating wounds or contusions of the globe, blows on the head, concussion of the body and physical strain.³When