Structural basis of SARM1 activation, substrate recognition, and inhibition by small molecules

The NADase SARM1 (sterile alpha and TIR motif containing 1) is a key executioner of axon degeneration and a therapeutic target for several neurodegenerative conditions. We show that a potent SARM1 inhibitor undergoes base exchange with the nicotinamide moiety of nicotinamide adenine dinucleotide (NAD⁺) to produce the bona fide inhibitor 1AD. We report structures of SARM1 in complex with 1AD, NAD⁺ mimetics and the allosteric activator nicotinamide mononucleotide (NMN). NMN binding triggers reorientation of the armadillo repeat (ARM) domains, which disrupts ARM:TIR interactions and leads to formation of a two-stranded TIR domain assembly. The active site spans two molecules in these assemblies, explaining the requirement of TIR domain self-association for NADase activity and axon degeneration. Our results reveal the mechanisms of SARM1 activation and substrate binding, providing rational avenues for the design of new therapeutics targeting SARM1.

Enhancing human-machine teaming for medical prognosis through neural ordinary differential equations (NODEs)

Machine learning (ML) has recently been demonstrated to rival expert-level human accuracy in prediction and detection tasks in a variety of domains, including medicine. Despite these impressive findings, however, a key barrier to the full realization of ML’s potential in medical prognoses is technology acceptance. Recent efforts to produce explainable AI (XAI) have made progress in improving the interpretability of some ML models, but these efforts suffer from limitations intrinsic to their design: they work best at identifying why a system fails, but do poorly at explaining when and why a model’s prediction is correct. We posit that the acceptability of ML predictions in expert domains is limited by two key factors: the machine’s horizon of prediction that extends beyond human capability, and the inability for machine predictions to incorporate human intuition into their models. We propose the use of a novel ML architecture, Neural Ordinary Differential Equations (NODEs) to enhance human understanding and encourage acceptability. Our approach prioritizes human cognitive intuition at the center of the algorithm design, and offers a distribution of predictions rather than single outputs. We explain how this approach may significantly improve human-machine collaboration in prediction tasks in expert domains such as medical prognoses. We propose a model and demonstrate, by expanding a concrete example from the literature, how our model advances the vision of future hybrid human-AI systems.

[Impact of functional mass lesions in professional female singers : Biomechanics of vocal fold oscillation in the register transition regions]

BACKGROUND

The influence of functional mass lesions on vocal fold oscillation patterns in vocally challenging tasks is not yet understood in detail.

MATERIALS UND METHODS

Glissandi on the vowel [a:] from 220 to 440 Hz and 440 to 880 Hz were analyzed in three groups of four professional female singers: without a mass lesion or dysphony (group A), with a functional mass lesion (swellings without a great impact on oscillation patterns during stroboscopy; group B), and with organic dysphony (group C). High-speed digital imaging (HSDI; 20,000 fps), and acoustic and electroglottographic (EGG) signals were used for analysis. Based on the EGG sample entropy, time windows for analysis of register transition phenomena were constructed. The voice signals (glottal area waveform, GAW; acoustic and EGG signals) were perceptually rated in terms of the noticeability of registration events.

RESULTS

The absolute sample entropy revealed maxima in fundamental frequency regions where register transitions typically occur. Groups A and B could be distinguished neither by perceptual rating nor based on sample entropy values. In comparison to the other two groups, the absolute sample entropy values of group C were greater in the lower glissando. However, the larger vocal fold oscillatory irregularities were observable for the upper glissando in this group.

CONCLUSION

Functional mass lesions do not influence biomechanics adversely in vocally challenging tasks such as register transitions. The use of sample entropy as a criterion for detection of register transitions is promising, but needs further validation.

The effect of education plus access on perceived fruit and vegetable consumption in a rural African American community intervention

African Americans have an increased risk of cardiovascular disease partly due to low fruit and vegetable consumption. This article reports the results of an intervention to provide nutrition education and access to fruits and vegetables through community gardens to change dietary behaviors among African Americans in rural Missouri. Cross-sectional surveys evaluated the intervention effect on blood pressure, body mass index (BMI), and perceived fruit and vegetable consumption in this quasi-experimental study with a comparison group. Hypertension (OR = 0.52, 95% CI: 0.38-0.71) and BMI (OR = 0.73, 95% CI: 0.52-1.02) were lower in the intervention county at mid-intervention. Participation in nutrition education (OR = 2.67, 95% CI: 1.63-4.40) and access to fruits and vegetables from a community garden (OR = 1.95, 95% CI: 1.20-3.15) were independently associated with perceived fruit and vegetable consumption. The strongest effect on perceived fruit and vegetable consumption occurred with high participation in nutrition education and access to community gardens (OR = 2.18, 95% CI: 1.24-3.81). Those with access but without education had a reduced likelihood of consuming recommended servings of fruits and vegetables (OR = 0.57, 95% CI: 0.34-0.95). Education plus access interventions may be best at increasing consumption of fruits and vegetables in a rural African American population.

Three-dimensional mesoporous structures fabricated by independent stacking of self-assembled films on suspended membranes

We report an original iterative method for fabricating three-dimensional mesoporous structures by independently stacking multiple self-assembled block copolymer films supported by Si membranes. A first layer is formed on the substrate by a self-assembled PS-b-PMMA (polystyrene-block-poly(methyl methacrylate)) film. A porous, permeable Si membrane deposited on top of the first block copolymer film provides mechanical support, preventing pattern collapse during the wet developing used to selectively remove the PMMA component of the PS-b-PMMA film. A second, dense Si membrane is deposited to seal the porous membrane, resulting in an impermeable coating suspended atop the self-assembled mesoporous polystyrene structures. The process can then be iterated using the sealed membrane as the new substrate to support a subsequent self-assembled block copolymer film. This multilayer approach provides a flexible three-dimensional fabrication technique where, in each layer, pattern morphology, domain orientation and degree of ordering can be designed independently. Furthermore, the process is compatible with electron-beam directed assembly, used to achieve regular patterns with feature density multiplication at any level in the stack.

Chronic intestinal giardiasis with isolated levothyroxine malabsorption as reason for severe hypothyroidism--implications for localization of thyroid hormone absorption in the gut

We report a case of isolated levothyroxine malabsorption in the course of chronic intestinal giardiasis, leading to severe hypothyroidism. Infection with Giardia lamblia was proved histologically by jejunal biopsy. Treatment with metronidazole resulted in complete elimination of parasites and recovery of regular intestinal thyroid hormone absorption. Stable euthyroidism was accomplished with common replacement doses of orally administered levothyroxine.

Intravenous injection of siRNA directed against hypoxia-inducible factors prolongs survival in a Lewis lung carcinoma cancer model

Different routes for the in vivo administration of synthetic siRNA complexes targeting lung tumors were compared, and siRNA complexes were administered for the inhibition of hypoxia-inducible factor (HIF-1alpha and HIF-2alpha). Intravenous jugular vein injection of siRNA proved to be the most effective means of targeting lung tumor tissue in the Lewis lung carcinoma (LLC1) model. In comparison, intraperitoneal injection of siRNA was not suitable for targeting of lung tumor and intratracheal administration of siRNA exclusively targeted macrophages. Inhibition of HIF-1alpha and HIF-2alpha by siRNA injected intravenously was validated by immunohistofluorescent analysis for glucose-transporter-1 (GLUT-1), a well-established HIF target protein. The GLUT-1 signal was strongly attenuated in the lung tumors of mice treated with siRNA-targeting HIF-1alpha and HIF-2alpha, compared with mice treated with control siRNA. Interestingly, injection of siRNA directed against HIF-1alpha and HIF-2alpha into LLC1 lung tumor-bearing mice resulted in prolonged survival. Immunohistological analysis of the lung tumors from mice treated with siRNA directed against HIF-1alpha and HIF-2alpha displayed reduced proliferation, angiogenesis and apoptosis, cellular responses, which are known to be affected by HIF. In conclusion, intravenous jugular vein injection of siRNA strongly targets the lung tumor and is effective in gene inhibition as demonstrated for HIF-1alpha and HIF-2alpha.

Real-time observation of FIB-created dots and ripples on GaAs

We report a phenomenological study of Ga dots and ripples created by a focused ion beam (FIB) on the GaAs(001) surface. Real-time observation of dot diffusion and ripple formation was made possible by recording FIB movies. In the case of FIB irradiation with a 40 nA current of Ga(+) ions accelerated under 40 kV with an incidence angle of θ = 30°, increasing ion dose gives rise to three different regimes. In Regime 1, dots with lateral sizes in the range 50-460 nm are formed. Dots diffuse under continuous sputtering. In Regime 2, dots self-assemble into Bradley and Harper (BH) type ripples with a pseudo-period of λ = 1150 ± 25 nm. In Regime 3, ripples are eroded and the surface topology evolves into microplanes. In the case of normal incidence, FIB sputtering leads only to the formation of dots, without surface rippling.

Cellular adaptations to hypoxia and acidosis during somatic evolution of breast cancer

Conceptual models of carcinogenesis typically consist of an evolutionary sequence of heritable changes in genes controlling proliferation, apoptosis, and senescence. We propose that these steps are necessary but not sufficient to produce invasive breast cancer because intraductal tumour growth is also constrained by hypoxia and acidosis that develop as cells proliferate into the lumen and away from the underlying vessels. This requires evolution of glycolytic and acid-resistant phenotypes that, we hypothesise, is critical for emergence of invasive cancer. Mathematical models demonstrate severe hypoxia and acidosis in regions of intraductal tumours more than 100 μm from the basement membrane. Subsequent evolution of glycolytic and acid-resistant phenotypes leads to invasive proliferation. Multicellular spheroids recapitulating ductal carcinoma in situ (DCIS) microenvironmental conditions demonstrate upregulated glucose transporter 1 (GLUT1) as adaptation to hypoxia followed by growth into normoxic regions in qualitative agreement with model predictions. Clinical specimens of DCIS exhibit periluminal distribution of GLUT-1 and Na⁺/H⁺ exchanger (NHE) indicating transcriptional activation by hypoxia and clusters of the same phenotype in the peripheral, presumably normoxic regions similar to the pattern predicted by the models and observed in spheroids. Upregulated GLUT-1 and NHE-1 were observed in microinvasive foci and adjacent intraductal cells. Adaptation to hypoxia and acidosis may represent key events in transition from in situ to invasive cancer.

Hypoxia-inducible-factor 2 alpha mediates cisplatin resistance in the lung adenocarcinoma cell line A549

10573

Background: Hypoxia in solid tumors is associated with cancer progression, metastasis and resistance to chemotherapy. The hypoxia inducible factors (HIF-1a and HIF-2a) are key players in the response to hypoxia affecting angiogenesis, proliferation and apoptosis. Here we investigated the role of HIF-1a and HIF-2a in cellular resistance to cisplatin in non small lung cancer cells (A549). Results: Hypoxia reduced the efficiency of cisplatin treatment on A549 cells via enhancement of drug efflux activity. In addition, hypoxia induced the hypoxia-responsive-element (HRE) reporter gene assay, demonstrating the transcriptional activity of HIF-1a and HIF-2a. Administration of cisplatin further increased the reporter activity under both normoxic and hypoxic conditions. This correlated with the induction of HIF-2a protein expression upon cisplatin treatment in normoxia and hypoxia, whereas HIF-1a was suppressed. Additionally, cisplatin induced nuclear accumulation of HIF-2a. Suppression of HIF-2a by RNA interference potentiated the sensitivity to cisplatin treatment in hypoxic A549 cells. In vivo growth delay assay gave analogues results for subcutaneous A549 tumors treated with cisplatin and suppression of HIF-2a. In comparison, other cytostatic drugs such as doxorubicin and gemcitabine differed with respect to HIF signalling. Doxorubicin induced both HIF-1a and HIF- 2a. Cellular sensitivity to doxorubicin was increased via suppression of HIF-1a and HIF-2a. Gemcitabine appeared to act independent of HIF. The underlying mechanism of hypoxia-induced resistance was due to increased mRNA expression of drug resistance proteins such as MDR1, MRP1 and LRP. These were found to be HIF-2a but not HIF-1a dependent. Conclusion: This data identified HIF-2a as a key player in the hypoxia induced cisplatin resistance and show on the molecular level that HIF-2a is a credible target for therapeutic strategies.

No significant financial relationships to disclose.

Effect of mycophenolate mofetil on rat kidney grafts with prolonged cold preservation

The impact of mycophenolate mofetil (MMF) on initial renal transplant function is not well characterized. We tested how MMF may modulate graft function and survival in a syngeneic rat kidney transplantation model after prolonged cold preservation. Donor kidneys were preserved in University of Wisconsin for either 24 or 39 h prior to transplantation into nephrectomized rats. Recipients received MMF (20 mg/kg/day) or vehicle. Mycophenolic acid (MPA) blood concentrations were measured by high-performance liquid chromatography. The inflammatory response, tubular epithelial proliferation, and histologic damage 3 days post-transplantation were assessed microscopically. In the 24 h cold storage (c.s.) group serum-creatinine was measured. In the 39 h c.s. group 1-week recipient survival was determined. After 24 h of c.s., recipient survival was 100%. The number of T-cell infiltrates was low and not influenced by MMF, whereas renal ED1+ cell infiltration was significantly suppressed by MMF. Tubular cell proliferation was enhanced by MMF. Serum-creatinine levels and renal histology were comparable between MMF and vehicle-treated animals. In the 39 h c.s. group, recipient survival was 20% in MMF-treated vs 90% in vehicle-treated animals (P=0.001). MMF effectively suppressed inflammatory cell infiltration and inhibited tubular cell proliferation. MMF-induced structural damage was most striking in the renal papilla. In rat kidney grafts with moderate preservation injury (24 h c.s.), MMF, given at an immunosuppressive dose, showed predominantly antiinflammatory effects without compromising graft function. In grafts with severe preservation injury (39 h c.s.), MMF caused irreversible structural damage and inhibited tubular cell regeneration resulting in renal failure.

RELMb is a hypoxic induced mitogenic factor in human adenocarcinoma A549 celline

20072

Background: RELMb (resistin-like molecule) represents the closest related human homologue of mouse RELMa, also known as hypoxic-induced-mitogenic-factor (HIMF). However, no orthologous gene of mouse HIMF exists in human. Results and Methods: In this study, we cloned human RELMb cDNA from lung and performed regulatory and functional expression studies in adenocarcinoma A549 cell line. RELMb mRNA was found to be strongly upregulated in hypoxia in these cells. Upon transfection of a RELMb encoding expression plasmid, we observed significant induction of proliferation in A549 cells, which could be blocked by phosphatidyl-inositol 3-kinase (PI3K) inhibitors LY294002 and wortmannin. Conclusions: The results suggest that human RELMb may contribute to hypoxic-induced proliferative responses in adenocarcinoma cells via PI3K dependent signal transduction.

No significant financial relationships to disclose.

Zardaverine and aerosolised iloprost in a model of acute respiratory failure

In this study, the impact of aerosolised prostacyclin (PGI2) and iloprost in the absence or presence of subthreshold intravascular doses of the dual-selective phosphodiesterase-3/4 inhibitor zardaverine was investigated in an experimental model of acute respiratory failure. In perfused rabbit lungs, continuous infusion of the thromboxane-A2-mimetic U46619 provoked pulmonary hypertension, accompanied by progressive lung oedema formation and severe ventilation-perfusion mismatch with predominance of shunt flow (increasing from approximately 2 to 58%, as assessed by the multiple inert gas elimination technique). Aerosolisation of PGI2 (in total 1.05 microg x kg(-1) for 15 min caused a decrease in pulmonary artery pressure (Ppa) and a limitation of maximum shunt flow to approximately 37%. When nebulised PGI2 was combined with subthreshold intravascular zardaverine, which did not affect pulmonary haemodynamics per se, the duration of the PGI2 effect was increased. Aerosolisation of 3 microg x kg(-1) PGI2 resulted in a transient decrease in Ppa and a reduction in shunt flow. In the presence of subthreshold zardaverine, the effects of this PGI2 dose were only marginally increased. Aerosolisation of iloprost (in total 0.7 microg x kg(-1)) for 15 min caused a more sustained decrease in Ppa, some enhanced reduction of oedema formation as compared with PGI2 and a decrease in shunt flow to approximately 32%. Most impressively, when combined with subthreshold zardaverine, iloprost suppressed oedema formation to <15% and shunt flow to approximately 8%. In conclusion, combined use of aerosolised iloprost and subthreshold systemic phosphodiesterase-3/4 inhibitor may result in selective intrapulmonary vasodilation, a reduction in oedema formation and an improvement in ventilation-perfusion matching in acute respiratory failure.

(E)-2(R)-[1(S)-(Hydroxycarbamoyl)-4-phenyl-3-butenyl]-2'-isobutyl-2'-(methanesulfonyl)-4-methylvalerohydrazide (Ro 32-7315), a selective and orally active inhibitor of tumor necrosis factor-alpha convertase

Tumor necrosis factor-alpha (TNF-alpha), a cytokine secreted by inflammatory cells, has been implicated in several inflammatory disease states. (E)-2(R)-[1(S)-(Hydroxycarbamoyl)-4-phenyl-3-butenyl]-2'-isobutyl-2'-(methanesulfonyl)-4-methylvalerohydrazide (Ro 32-7315), is a potent, orally active inhibitor of the TNF-alpha convertase (TACE), an enzyme responsible for proteolytic cleavage of the membrane bound precursor, pro-TNF-alpha. Ro 32-7315 inhibited a recombinant form of TACE (IC(50) = 5.2 nM) with selectivity over related matrix metalloproteinases. In a cellular assay system, THP-1 cell line, and in human and rat whole blood, Ro 32-7315 significantly reduced lipopolysaccharide (LPS)-induced TNF-alpha release with IC(50) values of 350 +/- 14 nM (n = 5), 2.4 +/- 0.5 microM (n = 5), and 110 +/- 18 nM (n = 5), respectively. Oral administration of Ro 32-7315 to Wistar rats caused a dose-dependent inhibition of LPS-induced release of systemic TNF-alpha with an ED(50) of 25 mg/kg. Treatment (days 0-14) of Allen and Hamburys hooded rats with Ro 32-7315 (2.5, 5, 10, and 20 mg/kg, i.p., twice daily) significantly reduced adjuvant-induced secondary paw swelling (42, 71, 83, and 93%, respectively) as compared with the vehicle group. In the Ro 32-7315-treated group, the reduced paw swelling was associated with improved lesion score and joint mobility. Furthermore, in a placebo-controlled, single-dose study, Ro 32-7315 given orally (450 mg) significantly suppressed ex vivo, LPS-induced TNF-alpha release in the whole-blood samples taken from healthy male and female volunteers (mean inhibition of 42% over a 4-h duration, n = 6). These data collectively support the potential use of such a compound for the oral treatment of inflammatory disorders.

Lung cGMP release subsequent to NO inhalation in pulmonary hypertension: responders versus nonresponders

Inhalation of nitric oxide (NO) is widely employed for the assessment of pulmonary vasoresponsiveness in pulmonary hypertension (PH). However, the reasons for the huge differences in vascular reactivity to NO between patients are unknown, and the role of NO-induced cyclic guanosine monophosphate (cGMP) is unclear. Twenty patients with severe precapillary PH were investigated. Thirty-six Swan-Ganz catheter investigations were performed and the study subjects were tested for responses to NO inhalation. This included an assessment of pulmonary and systemic arterial plasma cGMP and atrial natriuretic peptide (ANP) levels. A significant NO response (pulmonary vascular resistance (PVR) decrease >20%) was noted in nine of 20 patients (45%) during the first catheterization. A highly significant correlation between baseline plasma cGMP and ANP levels with PVR was observed (r=0.62 and r=0.66, respectively; p<0.0001). In response to NO, systemic and mixed venous cGMP levels increased from 13.9 +/- 1.28 nM and 12.75 +/- 0.99 nM to 79.23 +/- 4.99 nM and 55.25 +/- 4.41 nM (p<0.001), respectively, accompanied by the appearance of a marked transpulmonary cGMP gradient. Although in the responder group ANP levels were significantly reduced after NO inhalation, no significant correlation was observed to the extent of PVR reduction. The magnitude of the NO-elicited cGMP response did not discriminate between haemodynamic responders and nonresponders. This study concludes that plasma cyclic guanosine monophosphate levels are significantly correlated with the severity of disease in pulmonary arterial hypertension. Nitric oxide inhalation provokes a prompt increase in cyclic guanosine monophosphate secretion, but the magnitude of this release is not linked with a decrease in pulmonary vascular resistance.

Cellular pathophysiology and therapy of pulmonary hypertension

The identification of several mutations of the bone morphogenetic protein receptor 2 (BMPR2) gene, a member of the transforming growth factor beta receptor family, gives hope for new insights into the pathophysiology of pulmonary hypertension. Genetic predisposition might dictate the responses of pulmonary artery fibroblasts, smooth muscle cells, and endothelial cells, as well as platelets and leukocytes, or their specific interactions with different extrinsic factors. These cells possess distinct subtypes and interact with each other. Pulmonary hypertension is associated with vasoconstriction, remodeling, and in situ thrombosis of the pulmonary arteries, but the initial events and their relationship to the genetic background are presently unknown. Current therapeutic approaches are based on our knowledge of the physiologic regulation of pulmonary artery tone, pathophysiologic changes, and our clinical experience with different treatment strategies. Beyond diuretics and anticoagulants, prostaglandins are generally accepted therapeutic agents for primary pulmonary hypertension and related diseases, whereas high-dose calcium-channel blockers are reserved for a small subset of patients, those who respond favorably to vasodilators in an acute test. Long-term intravenous prostacyclin infusion has become the most important specific therapy for primary pulmonary hypertension and associated diseases. However, this therapy is hampered by catheter complications and systemic side effects. Alternative application routes of prostacyclin or its stable analogs may avoid these problems. Inhaled application of the prostacyclin analog iloprost results in predominant pulmonary vasodilation with few systemic side effects and may possess clinical efficacy similar to that of intravenous prostacyclin. Inhaled nitric oxide is widely accepted as a screening agent for active responders to vasodilators and has a similar hemodynamic profile as inhaled iloprost, although the percentage of responders is considerably lower. However, there are unsolved toxicologic questions and practical difficulties concerning the safe long-term application of nitric oxide. Combining inhaled vasodilators with phosphodiesterase inhibitors may prolong the duration of the effects and improve the convenience of inhaled therapy for pulmonary hypertension. Therapeutic approaches in the future may aim at the transforming growth factor beta pathway and at the identification of early stages of the disease to prevent further disease progression.

Coaerosolization of phosphodiesterase inhibitors markedly enhances the pulmonary vasodilatory response to inhaled iloprost in experimental pulmonary hypertension. Maintenance of lung selectivity

Inhalation of aerosolized iloprost, a stable prostacyclin analog, has been suggested for treatment of primary and secondary pulmonary hypertension, but demands multiple daily inhalation maneuvers because of the short-term effect of this approach. In intact rabbits, pulmonary hypertension was induced by continuous infusion of the stable thromboxane mimetic U46619. Thereafter, the influence of aerosolized iloprost on pulmonary and systemic hemodynamics and gas exchange was investigated in the presence and absence of phosphodiesterase (PDE) inhibitors for stabilization of the second-messenger cAMP. First, dose-effect curves for pulmonary artery pressure (Ppa) decline were established for the nonspecific PDE inhibitors pentoxifylline and dipyridamole and for the dual-selective PDE3/4 inhibitor tolafentrine when being applied as sole agent, either via the intravenous or the inhalative route. Subthreshold doses for each agent and each route of administration were then combined with a standardized iloprost aerosolization maneuver, which resulted in a substantial prolongation, but not augmentation, of the lung vasodilatory response for the prostanoid. Next, higher doses of each PDE inhibitor were employed for nebulization, causing per se some pulmonary vasodilative effect, in the absence of arterial pressure decrease or impairment of gas exchange. Coaerosolization of these PDE inhibitor doses with standardized iloprost caused approximate doubling of the immediate pulmonary vasodilator response, marked prolongation of the pressure relief overtime, and a 2- to 4-fold increase in the area under the curve of pulmonary vasodilation (efficacy tolafentrine > dipyridamole > pentoxifylline). Still, systemic arterial pressure was not suppressed and gas exchange was fully maintained. We conclude that coadministration of PDE inhibitors with inhaled iloprost markedly enhances the prostanoid-induced pulmonary artery pressure decrease while maintaining the lung selectivity of the vasodilatory response, and that coaerosolization is a particularly suitable route of administration. Even nonselective clinically approved PDE inhibitors may be employed for this purpose.

Myoclonus secondary to the concurrent use of trazodone and fluoxetine

A 39-y-o male with a history of human immunodeficiency virus infection and depression was admitted for diagnosis and treatment of tuberculosis and pneumocystis carinii pneumonia infections. Prior to admission, he was on 50 mg trazodone every evening for 2 mo for depression. He was admitted with a 2-w history of fever chills and fatigue and on admission had hand tremors which disappeared at rest. Four days post-admission the trazodone dose was increased to 100 mg and 20 mg fluoxetine was initiated. He became increasingly anxious and his hand tremor worsened 3 d after initiation of the regimen. To rule out drug induced tremor, both trazodone and fluoxetine were discontinued and symptoms resolved in 7 d. Clinicians should be aware of the potential for excessive seratonergic activities secondary to trazodone + fluoxetine interactions causing a worsening myoclonus adverse event.