Time- and momentum-resolved photoemission studies using time-of-flight momentum microscopy at a free-electron laser

Time-resolved photoemission with ultrafast pump and probe pulses is an emerging technique with wide application potential. Real-time recording of nonequilibrium electronic processes, transient states in chemical reactions, or the interplay of electronic and structural dynamics offers fascinating opportunities for future research. Combining valence-band and core-level spectroscopy with photoelectron diffraction for electronic, chemical, and structural analyses requires few 10 fs soft X-ray pulses with some 10 meV spectral resolution, which are currently available at high repetition rate free-electron lasers. We have constructed and optimized a versatile setup commissioned at FLASH/PG2 that combines free-electron laser capabilities together with a multidimensional recording scheme for photoemission studies. We use a full-field imaging momentum microscope with time-of-flight energy recording as the detector for mapping of 3D band structures in (k_x, k_y, E) parameter space with unprecedented efficiency. Our instrument can image full surface Brillouin zones with up to 7 Å^-1 diameter in a binding-energy range of several eV, resolving about 2.5 × 10⁵ data voxels simultaneously. Using the ultrafast excited state dynamics in the van der Waals semiconductor WSe₂ measured at photon energies of 36.5 eV and 109.5 eV, we demonstrate an experimental energy resolution of 130 meV, a momentum resolution of 0.06 Å^-1, and a system response function of 150 fs.

Exclusive Activation of Caspase-3 in Mossy Fibers and Altered Dynamics of Autophagy Markers in the Mice Hippocampus upon Status Epilepticus Induced by Kainic Acid

Epileptic seizures are generally associated with pathological changes in the hippocampus such as astrogliosis, mossy fiber sprouting, and neuronal damage. However, more than 30% of temporal lobe epilepsy in humans shows neither neuronal damage nor mossy fiber sprouting despite chronic epileptic seizures. A similar situation exists in certain commonly used strains of mice, specifically C57BL/6 and BALB/c, which exhibit epileptic seizures, but no neuronal damage upon kainic acid administration. This suggests that intrinsic factors may influence the pathological manifestations of epilepsy. Mechanisms which are behind the resistance of hippocampal cells to KA-induced neuronal death are unknown. Autophagy seems to be involved in the pathogenesis of many brain insults and to have a dual nature in neuroprotection and cell death. This study addresses the role of autophagy upon status epilepticus (SE) that has been induced by kainic acid (KA) in the C57BL/6 strain which is classified as seizure resistant. We analyzed the dynamics in the expression of autophagic and cell death markers in the hippocampus upon SE. Immunofluorescence data show that KA did not induce neuronal death in the hippocampal CA1-CA3 subfields; however, it leads to an exclusive activation of caspase-3 in the mossy fibers. We also found alterations in the expression of core proteins of the autophagic machinery. Levels of MAP1LC3, phospho-mTOR/mTOR, and Beclin 1 were significantly increased after induction of seizures. However, levels of Atg3, Atg14, Atg5-Atg12, Atg7, BAG3, Hsp70, and LAMP1 showed no significant alterations compared to controls. Although KA did not induce neuronal death, this study provides morphological and biochemical evidence that status epilepticus induced by KA activates caspase-3 in mossy fibers and induces autophagy in the C57BL/6 hippocampus. These data indicate that autophagic factors may modulate the sensitivity of pyramidal cells to KA and that autophagy may constitute a part of an endogenous neuroprotective arsenal which might be behind the resistance of C57BL/6-hippocampal cells to KA-induced neuronal death.

Resonant metamaterial detectors based on THz quantum-cascade structures

We present the design, fabrication and characterisation of an intersubband detector employing a resonant metamaterial coupling structure. The semiconductor heterostructure relies on a conventional THz quantum-cascade laser design and is operated at zero bias for the detector operation. The same active region can be used to generate or detect light depending on the bias conditions and the vertical confinement. The metamaterial is processed directly into the top metal contact and is used to couple normal incidence radiation resonantly to the intersubband transitions. The device is capable of detecting light below and above the reststrahlenband of gallium-arsenide corresponding to the mid-infrared and THz spectral region.

Monolithic metallic nanocavities for strong light-matter interaction to quantum-well intersubband excitations

We present the design, realization and characterization of strong coupling between an intersubband transition and a monolithic metamaterial nanocavity in the mid-infrared spectral range. We use a ground plane in conjunction with a planar metamaterial resonator for full three-dimensional confinement of the optical mode. This reduces the mode volume by a factor of 1.9 compared to a conventional metamaterial resonator while maintaining the same Rabi frequency. The conductive ground plane is implemented using a highly doped n+ layer which allows us to integrate it monolithically into the device and simplify fabrication.

Small Cell Ovarian Carcinomas - Characterisation of Two Rare Tumor Entities

Objective: Small cell ovarian carcinomas (SCOC) are differentiated into two types: hypercalcaemic (SCOCHT) and pulmonary (SCOCPT). Unfortunately, little is known about pulmonary-type small cell ovarian carcinoma. Study Design: We carried out a systematic analysis of all available reports in the literature on individual cases of SCOCHT and SCOCPT. Results: We found that patients with SCOCPT were significantly older than those with SCOCHT. Vimentin and chromogranin detection by immunohistochemistry allow good differentiation between the two types. Interestingly, SCOCPT but not SCOCHT was found to be associated with other benign and malignant ovarian tumours in about 44 % of cases. Although the percentage of R0/R1 resections was high (~ 74 %), survival was poor; even in patients with disease limited to the ovaries (stage Ia and Ib) the recurrence rate was 40 %. Chemotherapy with etoposide or anthracyclines could be useful. Conclusion: Taking the limitations of our study such as its retrospective nature into account and based on the results from studies of small cell carcinomas originating from other tumour sites, we conclude that treatment of SCOCPT should be based on the therapies used to treat other small cell carcinomas. Surgery is appropriate, especially in very early stages of disease, but chemotherapy should not be omitted. Newer concepts such as treatment with somatostatin analogues could help to control symptoms and stabilise some slow-growing tumours.

Terahertz meta-atoms coupled to a quantum well intersubband transition

We present a method of coupling free-space terahertz radiation to intersubband transitions in semiconductor quantum wells using an array of meta-atoms. Owing to the resonant nature of the interaction between metamaterial and incident light and the field enhancement in the vicinity of the metal structure, the coupling efficiency of this method is very high and the energy conversion ratio from in-plane to z field reaches values on the order of 50%. To identify the role of different aspects of this coupling, we have used a custom-made finite-difference time-domain code. The simulation results are supplemented by transmission measurements on modulation-doped GaAs/AlGaAs parabolic quantum wells which demonstrate efficient strong light-matter coupling between meta-atoms and intersubband transitions for normal incident electromagnetic waves.

Electrically controllable photonic molecule laser

We have studied the coherent intercavity coupling of the evanescent fields of two microdisk terahertz quantum-cascade lasers. The electrically controllable optical coupling of the single-mode operating lasers has been observed for cavity spacings up to 30 mum. The strongest coupled photonic molecule with 2 mum intercavity spacing allows to conditionally switch the optical emission by the electrical modulation of only one microdisk. The lasing threshold characteristics demonstrate the linear dependence of the gain of a quantum-cascade laser on the applied electric field.

Active photonic crystal terahertz laser

We present the design and the realization of active photonic crystal (PhC) semiconductor lasers. The PhC consists of semiconductor nanostructure pillars which provide gain at a quantized transition energy. The vertical layer sequence is that of a terahertz quantum cascade laser. Thereby, the artificial crystal itself provides the optical gain and the lateral confinement. The cavities do not rely on a central defect, the lasing is observed in flat-band regions at high symmetry points. The experimental results are in excellent agreement with the finite-difference time-domain simulations. For the vertical confinement a double-metal waveguide is used. The lasers are showing a stable single-mode emission under all driving conditions. Varying the period of the PhC allows to tune the frequency by 400 GHz.

Terahertz photonic crystal resonators in double-metal waveguides

We present the design and the fabrication of photonic crystals with a complete bandgap for TM-modes used as a resonator for terahertz quantum-cascade lasers (QCL), which are lasing around 2.7 THz. The emission of the devices with and without a photonic crystal shows a shift in the emission from the gain maximum to the bandgap of the crystal. The devices are built up by a core, which provides the optical gain, and by a surrounding photonic crystal, which acts as a frequency selective mirror. The whole device is processed into a double-metal waveguide.

Expression of fructose sensitive glucose transporter in the brains of fructose-fed rats

Glucose transporters play a critical role in mammalian brain energy metabolism because glucose is the principal brain energy source and these transporters promote glucose movement into neural cells. When glucose is unavailable, fructose can serve as an alternative energy source. Using real-time polymerase chain reaction and actin as a reference mRNA, we investigated the impact of fructose feeding on rat brain and other tissue mRNA expression of glucose transporter 5 which has high affinity for fructose. Brain mRNA levels of glucose transporter 5 increased 1.5-fold in 35-day old rats after 7 days of fructose feeding compared with controls, whereas it increased 2.5-fold in jejunum. Semi-quantitative analysis of protein expression by immunofluorescence of glucose transporter 5 in rat hippocampi indicated a 2.4-fold increase. We demonstrated the specificity of fructose feeding on glucose transporter 5 expression by showing that the expression of the neuronal glucose transporter 3 and insulin-regulated glucose transporter 4 were unaffected. In addition, the expression of glucose transporter 5 increased in fructose fed older adult rats (8-months and 12-months old) when compared with controls. These results suggest that short-term fructose feeding increases the expression of glucose transporter 5 in both young and aging adult rats. Increased brain expression of glucose transporter 5 is likely to be important in the role of fructose as an alternative energy source.

Astrocytes exert a pro-apoptotic effect on neurons in postnatal hippocampal cultures

We investigated conditions that promote basal and activity-dependent neuronal apoptosis in postnatal rat hippocampal cultures. Low-density mixed cultures of astrocytes and neurons exhibited lower sensitivity than high-density cultures to basal neuronal death and activity-sensitive neuronal death, induced with glutamate receptor blockers, sodium channel blockers, or calcium channel blockers. Although elevations of [Ca(2+)](i) protect neurons from apoptosis, low-density microcultures and mass cultures exhibited only minor differences in resting [Ca(2+)](i) and Ca(2+) current density, suggesting that these variables are unlikely to explain differences in susceptibility. Astrocytes, rather than neurons, were implicated in the neuronal loss. Several candidate molecules implicated in other astrocyte-dependent neurotoxicity models were excluded, but heat inactivation experiments suggested that a heat-labile factor is critically involved. In sum, our results suggest the surprising result that astrocytes can be negative modulators of neuronal survival during development and when the immature nervous system is challenged with drugs that dampen electrical excitability.

Neuroprotective agent riluzole potentiates postsynaptic GABA(A) receptor function

The antiepileptic drug riluzole is a use-dependent blocker of voltage-gated Na(+) channels and selectively depresses action potential-driven glutamate over gamma-aminobutyric acid (GABA) release. Here we report that in addition to its presynaptic effect, riluzole at higher concentrations also strongly potentiates postsynaptic GABA(A) responses both in cultured hippocampal neurons and in Xenopus oocytes expressing recombinant receptors. Although peak inhibitory postsynaptic currents (IPSCs) of autaptic hippocampal neurons were inhibited, 20-100 microM riluzole significantly prolonged the decay of IPSCs, resulting in little change in total charge transfer. The effect was dose-dependent and reversible. Riluzole selectively increased miniature IPSC fast and slow decay time constants, without affecting their relative proportions. Miniature IPSC peak amplitude, rise time and frequency were unaffected, indicating a postsynaptic mechanism. In the Xenopus oocyte expression system, riluzole potentiated GABA responses by lowering the EC(50) for GABA activation. Riluzole directly gated a GABA(A) current that was partially blocked by bicuculline and gabazine. Pharmacological experiments suggest that the action of riluzole did not involve a benzodiazepine, barbiturate, or neurosteroid site. Instead, riluzole-induced potentiation was inhibited by the lactone antagonist alpha-isopropyl-alpha-methyl-gamma-butyrolatone (alpha-IMGBL). While most anticonvulsants either block voltage-gated Na(+) channels or potentiate GABA(A) receptors, our results suggest that riluzole may define an advantageous class of anticonvulsants with both effects.

Effects on gamma-aminobutyric acid (GABA)(A) receptors of a neuroactive steroid that negatively modulates glutamate neurotransmission and augments GABA neurotransmission

Neurosteroids positively and negatively modulate gamma-aminobutyric acid (GABA)(A) receptors and glutamate receptors, which underlie most fast inhibition and excitation in the central nervous system. We report the identification of a neuroactive steroid, (3 alpha,5 beta)-20-oxo-pregnane-3-carboxylic acid (3 alpha 5 beta PC), with unique cellular actions. 3 alpha 5 beta PC positively modulates GABA(A) receptor function and negatively modulates N-methyl-D-aspartate (NMDA) receptor function, a combination that may be of particular clinical benefit. 3 alpha 5 beta PC promotes net GABA(A) potentiation at low steroid concentrations (<10 microM) and at negative membrane potentials. At higher concentrations, the steroid also blocks GABA receptors. Because this block would presumably counteract the NMDA receptor blocking actions of 3 alpha 5 beta PC, we characterize the GABA receptor block in some detail. Agonist concentration, depolarization, and high extracellular pH increase the block. The apparent pK for both potentiation and block was 6.4 to 6.9, substantially higher than expected from carboxylated steroid in an aqueous environment. Block is not dependent on the stereochemistry of the carboxylic acid at carbon 3 and is relatively insensitive to placement of the carboxylic acid at the opposite end of the steroid (carbon 24). Potentiation is critically dependent on the stereochemistry of the carboxylic acid group at carbon 3. Consistent with the pH dependence of potentiation, effects of the amide derivative (3 alpha,5 beta)-20-oxo-pregnane-3-carboxamide, suggest that the un-ionized form of 3 alpha 5 beta PC is important for potentiation, whereas the ionized form is probably responsible for block. Further refinement of the neuroactive steroid to promote GABA potentiation and NMDA receptor block and diminish GABA receptor block may lead to a clinically useful neuroactive steroid.

Substrate turnover by transporters curtails synaptic glutamate transients

Although inhibitors of glutamate transport prolong synaptic currents at many glutamate synapses, the cause of the current prolongation is unclear. Transport inhibitors may prolong synaptic currents by simply interfering with synaptic glutamate binding to transporters, by inhibiting substrate translocation, or by promoting accumulation of ambient glutamate, which may act cooperatively at receptors with synaptic glutamate. We show that reversal of the membrane potential of astrocytes surrounding the synapse prolongs synaptic currents but does not decrease the apparent affinity of transporters or significantly alter glutamate-dependent kinetics of macroscopic transporter currents in excised membrane patches. Positive membrane potentials do not affect binding of a nontransported glutamate analog, nor do positive membrane potentials alter the number of transporters available to bind analog. We also test the hypothesis that glutamate accumulation during uptake inhibition by transporter substrates is the direct cause of synaptic current prolongations. Transporter substrates elevate ambient glutamate near synapses by fostering reverse transport of endogenous glutamate. However, increases in ambient glutamate cannot account for the prolongations of synaptic currents, because a nonsubstrate transport inhibitor does not foster reverse uptake yet it prolongs synaptic currents. Moreover, exogenous glutamate does not mimic synaptic current prolongations induced by substrate inhibitors. These results provide strong support for a major role of substrate translocation in determining the time course of the glutamate concentration transient at excitatory synapses.

Comparison of initial fixation strength between biodegradable and metallic interference screws and a press-fit fixation technique in a porcine model

The objective of this study was to evaluate the initial fixation strength of a biodegradable interference screw compared with press-fit fixation and a titanium interference screw in anterior cruciate ligament reconstruction using a bone-patellar tendon-bone graft. Porcine lower limbs were used. The specimens underwent 500 loading cycles between 60 and 250 N. This corresponds to loads in the graft during aggressive rehabilitation. Thereafter, intact specimens were loaded to failure. Failure mode was defined by visual analysis. Under cyclic loads none of the interference screw fixations failed. In the press-fit group (angle between load axis and tunnel axis 80 degrees), five specimens failed. The mean maximal load to failure was 945 N (+/- 87) for the titanium screw, 797 N (+/- 60) for the biodegradable screw, and 708 N (+/- 211) for the five press-fit specimens that did not fail during cyclic loading. With respect to primary fixation strength, biodegradable screws are a reasonable alternative to titanium interference screws. The press-fit fixation did not provide a secure fixation in all cases. Five press-fit specimens failed under cyclic loads comparable with those seen under conditions of accelerated rehabilitation.

Neuronal expression of the glutamate transporter GLT-1 in hippocampal microcultures

To address the question of the relative contributions of glial and neuronal glutamate transport in the vertebrate CNS, we studied the distribution of forebrain glutamate transporters in rat hippocampal microcultures, a preparation in which physiological functions of glutamate transporters have been well characterized. Two of the three transporters, GLAST (EAAT1) and EAAC1 (EAAT3), are localized to microculture glia and neurons, respectively, as expected. However, we find strong immunoreactivity for the third glutamate transporter GLT-1 (EAAT2), a putatively glial transporter, in microculture neurons and in a small subset of microculture glia. Indistinguishable immunohistochemical staining patterns for GLT-1 were obtained with antibodies directed against both the N terminal and C terminal of the GLT-1 protein. Double-labeling experiments suggest that neuronal GLT-1 protein is primarily localized to the dendrites of excitatory neurons. Neuronal electrogenic transport currents in response to D-aspartate applications were occluded by the selective GLT-1 inhibitor dihydrokainate. In contrast, glia exhibited a larger transporter current density than did neurons, and the glial transport current was less sensitive to dihydrokainate. Neuronal transport currents were potentiated less than were glial currents when the chaotropic anion thiocyanate was substituted for gluconate in the whole-cell recording pipette, consistent with the previously reported lower anion permeability of EAAC1 and GLT-1 compared with that of GLAST. After microculture glia were rendered nonviable, excitatory autaptic currents (EACs) were prolonged in the presence of dihydrokainate, suggesting that neuronal GLT-1 is capable of participating in the clearance of synaptically released glutamate. Our results suggest that the initially proposed characterization of GLT-1 as a purely glial transporter is too simplistic and that under certain conditions functional GLT-1 protein can be expressed in brain neurons. The study suggests that changes in GLT-1 levels that occur with pathology or experimental manipulations cannot be assumed to be glial.

Ventricular arrhythmias in dilated cardiomyopathy

Although prognosis of dilated cardiomyopathy (DCM) has improved due to advances in diagnosis and therapy, still too many sudden cardiac deaths occur in DCM. Spontaneous ventricular ectopy is a very common finding in patients with DCM, but the prognostic significance of Holter monitoring remains controversial. Other noninvasive methods, e.g., late potentials and QT dispersion, have not yet contributed to the evaluation of prognosis for arrhythmogenic events in DCM. Programmed ventricular stimulation has been repeatedly used to stratify long-term prognosis, yet satisfactory data are still missing as many deaths occur in patients without inducible arrhythmias. Several prognostic studies are still in progress, and preliminary data for the use of ICDs already appear to be promising. In patients with poor left ventricular function and ICDs in situ, prognosis is determined by progression of heart failure. Heart transplantation may be the ultimate therapeutic instrument for end-stage heart failure patients. For patients with advanced DCM and increased risk for malignant arrhythmias who are unsuitable for orthotopic heart transplantation, the combined therapy with an ICD and dynamic cardiomyoplasty may be an alternative treatment.

Components of glial responses to exogenous and synaptic glutamate in rat hippocampal microcultures

Although glia are known to be sensitive to exogenously applied neurotransmitter substances, little is known about how glia respond to neuronal activity on the millisecond time scale of individual synaptic events. We have explored the electrophysiological effects of excitatory neuronal signaling on glial cells in rat hippocampal microcultures. Exogenous applications of glutamate analogs to islands of glia revealed a large ionotropic AMPA receptor-mediated current and a smaller current mediated by electrogenic glutamate uptake. Glia demonstrated no evidence of NMDA or metabotropic receptor-mediated currents or membrane conductance changes. Despite the dominant contribution of AMPA receptors to exogenous glutamate applications in glia, AMPA receptor currents contributed only approximately 20% to the response of glia to endogenous glutamate release from solitary excitatory neurons. Electrogenic glutamate uptake contributed strongly to glial responses to neuronal stimulation. In addition, some glia exhibited a residual current is response to neuronal stimulation that was not attributable to calcium-dependent transmitter release or to neuronal potassium efflux. These results help provide a context for understanding the role of glial transporters and receptors in nervous system signaling.

Passive and synaptic properties of hippocampal neurons grown in microcultures and in mass cultures

1. We used whole cell recordings to compare passive membrane properties and synaptic properties of postnatal rat hippocampal neurons grown for 7-15 days in either conventional mass cultures or on physically restricted microisland cultures. Despite matching microisland and mass culture cell across several variables, there were significant differences between neurons in the two groups regarding passive membrane characteristics and synaptic properties. 2. Microisland neurons displayed significantly faster charging of the membrane capacitance than mass culture counterparts matched with microisland neurons for age, somal diameter, and transmitter phenotype. When we used a two-compartment equivalent circuit model to quantify this result, microisland neurons displayed approximately half the distal capacitance of mass culture neurons. These data suggest that microisland neurons elaborate less extensive neuritic arborizations than mass culture neurons. 3. Evoked synaptic responses were enhanced on microislands compared with mass cultures. Excitatory and inhibitory autaptic currents were more frequent and displayed larger amplitudes on single-neuron microislands than in matched mass culture neurons. 4. In recordings from pairs of neurons in the two environments, we observed a significantly higher probability of obtaining a monosynaptic response on two-neuron microislands than in matched mass culture pairs (85% vs. 42%). Evoked excitatory postsynaptic currents were also significantly larger in the microisland environment, with evoked excitatory synaptic currents from two-neuron microislands exhibiting a mean amplitude 20-fold larger than mass culture monosynaptic responses. 5. The differences in evoked synaptic responses were not reflected in differences in the amplitude or frequency of spontaneous miniature excitatory postsynaptic currents (mEPSCs). Analysis of mEPSC rise times, decay times, and peak amplitudes within individual cells suggests that electrotonic filtering is not an important contributor to the variability of peak amplitudes and decay times of synaptic currents in cells of either culture environment. However, composite data across neurons in both cultures reveal a significant correlation between mEPSC rise and decay times. 6. Out results suggest that the microisland preparation may be a useful tool for exploring factors that influence synapse formation and development. Additionally, the preparation is a particularly convenient model for the study of single-neuron-mediated synaptic events.

Expression of NK-associated surface-antigens cd-56 and cd-16 on aml-cells

Monoclonal antibodies Leu 11a (CD16) and Leu 19 (CD56) were tested for reactivity with cells from 36 patients with acute myelogenous leukemia (AML) using two-colour flow cytometry. Blast cells were identified by a broad panel of monoclonal antibodies. In 33% (12/36) the monoclonal antibody Leu 19, which has been demonstrated to bind to the 140 kD isoform of the human neural cellular adhesion molecule N-CAM, found on peripheral natural killer (NK)-cells, neuroectodermal cells, activated T-cells, and myeloma cells, was shown to bind strongly to the leukemic cells. The monoclonal antibody Leu 11a, which recognizes a surface differentiation antigen associated with the low affinity FcRIII for IgG, expressed on NK-cells, granulocytes and macrophages were found to bind to leukemic cells of four of the 12 Leu-19 positive cases. 50% (6/12) of Leu-19 positive patients were classified as having M4 according to the French-American-British (FAB) morphology criteria. The potential diagnostic and clinical importance of CD 56 and/or CD 16 expression in acute myelogenous leukemia is presently under investigation.

IgE and IgG4 levels in children with atopic dermatitis

Serum IgE and IgG4 concentrations were determined in 102 children with atopic dermatitis (AD) of varying severity and activity. Total as well as specific IgE levels, determined by the radioallergosorbent test (RAST), were correlated with disease severity and the coexistence of atopic respiratory diseases. The IgG 4 levels of children with only AD, even in severe cases, were within the normal ranges of healthy children. In contrast, the IgG4 levels of children with both cutaneous and respiratory atopic manifestations were elevated, suggesting that IgG4 are probably associated with respiratory diseases but do not play any role in the pathogenesis of the skin disorder.

[Hemophilia A: early detection of women carriers by Laurell's quantitative immunoelectrophoresis]

Using one-stage quantitative factor VIII assay and the quantitative immunoelectrophoretic method of LAURELL a good correlation has been found between factor VII activity and protein concentration. In 80% of the known hemophilia A carriers the protein concentration was about twice as high as in normals as compared to the factor VIII activity, whereas about 20% of the known carriers have the same ratio between factor VIII protein and factor VIII activity as normals. The reliability of the test and its usefulness for the detection of hemophilia A carriers are discussed.

Treatment of deep vein thrombosis with streptokinase

From September 1962 to May 1972 145 patients with acute or subacute deep vein thrombosis confirmed by phlebography were treated with streptokinase. During the same period 42 patients considered unfit for thrombolytic therapy were treated with herapin and oral anticoagulants. The results, assessed by repeat phlebography, in 93 of the patients treated with streptokinase were compared with those in 42 patients treated with heparin. The age, sex, and severity of occlusion were roughly similar in both groups. Streptokinase treatment was successful in 42 per cent, partially successful in 25 per cent, and unsuccessful in 32 per cent of the 93 patients compared with none, 10 per cent, and 88 percent respectively in the 42 patients treated with heparin. Streptokinase was more effective when the thrombus was in proximal rather than calf veins. Thrombi of more than six days old were readily lysed. Plasma fibrinogen levels were below 0-8 g/1 (80 mg/100 ml) in nearly all patients successfully treated. The incidence of pulmonary embolism was no greater with streptokinase than with heparin treatment. Only prolonged follow-up would show whether thrombolytic treatment would be effective in preventing late complications of deep vein thrombosis such as chronic venous insufficiency.