Primary ductal adenocarcinoma of the lacrimal gland with sarcomatoid differentiation: case report and genomic analysis.

We describe a case of primary ductal adenocarcinoma of the lacrimal gland with novel histopathological characteristics corresponding to a biphasic growth course and provide a comprehensive genomic profile of this malignancy. A 39-year-old male with a history of slowly progressive unilateral proptosis and hypoglobus presented after 1 month of hyperacute exacerbation. Orbital imaging revealed a superior mass with osseous erosion. The patient underwent orbital exploration and excisional biopsy via lateral orbitotomy. Histopathology demonstrated high-grade adenocarcinoma with a well-differentiated glandular component alongside a poorly differentiated sarcomatoid region. The glandular section was immunopositive for Her-2, CK7, GATA3, and androgen receptor. Tumor recurrence necessitated en-bloc exenteration with dural resection alongside adjuvant radiotherapy and chemotherapy. This represents the first report of sarcomatoid differentiation in primary ductal adenocarcinoma of the lacrimal gland, which may incite hyperacute progression. Conversely, GATA3 immunopositivity may correlate with indolent growth. Genomic variants such as SEMA3C represent potential therapeutic targets for this condition.

Bilateral Cerebral Mucormycosis in an Immunocompetent Female.

Background: Mucormycosis is a serious angioinvasive fungal infection. Immunocompromised patients are more likely to be susceptible to mucormycosis than immunocompetent individuals. Cerebral mucormycosis has been reported, but cases have primarily been unilateral. We report a case of bilateral cerebral mucormycosis in an immunocompetent patient. Case Report: A 37-year-old female with no significant medical history was transferred to our tertiary center after cerebrospinal fluid profile following a lumbar puncture at an outside hospital suggested bacterial meningitis. Computed tomography of the head revealed hypodensity and cerebral edema in the left basal ganglia, and magnetic resonance imaging (MRI) brain showed increased T2 signal and mass-like configuration centered in the left basal ganglia. During her hospital stay, she had neurologic decompensation with respiratory failure. She was intubated and placed on mechanical ventilation. Repeat MRI brain revealed evolving cerebral edema signal and interval development of progression across the midline involving the right basal ganglia. Because of the aggressive nature of the lesion and cerebral edema, she underwent a biopsy with placement of an external ventricular drain. Despite medical and surgical interventions, she neurologically worsened and died. Histopathologic evaluation of the biopsied lesion revealed numerous fungal hyphae consistent with mucormycosis. Conclusion: Our patient was not immunocompromised, and this case highlights the clinical challenges in initiating immunosuppressive therapy in a patient with rapidly progressive central nervous system disease.

Extra Precautions while Caring for a Suspected COVID-19 Patient in an ICU beyond PPE and Hand Hygiene.

Since the diagnosis of the first case of COVID-19 in December 2019, there have been reports of several healthcare workers infected with COVID-19. It has changed the infection control practices of most ICUs all over the world. Prevention is better than cure is definitely proven true as there is no definite cure for COVID-19 yet. Personal protective equipment and hand hygiene are a must while handling any suspected COVID-19 patient. Apart from that, there are several other things, which should be followed in ICU and specifically while caring for a patient on ventilator. There are a large number of interventions done while treating any critically ill patient in ICU, which can generate aerosols and exaggerate spread of COVID-19, which include high-flow nasal cannula, NIV, nebulization, suctioning, bag and mask ventilation, endotracheal intubation, and bronchoscopy. We will be reviewing those things beyond PPE and hand hygiene along with the rationale of each of them, which can help to minimize the risk of exposure to healthcare workers and other patients in the surrounding. It will help not only to prevent COVID-19 transmission but also to reduce overall nosocomial infection rate. As per our knowledge, this will be the first paper reviewing innovative ideas to minimize the risk of infection in a comprehensive manner. How to cite this article: Shah V, Tyagi N, Trivedi D. Extra Precautions while Caring for a Suspected COVID-19 Patient in an ICU beyond PPE and Hand Hygiene. Indian J Crit Care Med 2021;25(3):331-336.

To lie or not to lie: Super-relaxing with myosins.

Since the discovery of muscle in the 19th century, myosins as molecular motors have been extensively studied. However, in the last decade, a new functional super-relaxed (SRX) state of myosin has been discovered, which has a 10-fold slower ATP turnover rate than the already-known non-actin-bound, disordered relaxed (DRX) state. These two states are in dynamic equilibrium under resting muscle conditions and are thought to be significant contributors to adaptive thermogenesis in skeletal muscle and can act as a reserve pool that may be recruited when there is a sustained demand for increased cardiac muscle power. This report provides an evolutionary perspective of how striated muscle contraction is regulated by modulating this myosin DRX↔SRX state equilibrium. We further discuss this equilibrium with respect to different physiological and pathophysiological perturbations, including insults causing hypertrophic cardiomyopathy, and small-molecule effectors that modulate muscle contractility in diseased pathology.

Single Residue Variation in Skeletal Muscle Myosin Enables Direct and Selective Drug Targeting for Spasticity and Muscle Stiffness.

Muscle spasticity after nervous system injuries and painful low back spasm affect more than 10% of global population. Current medications are of limited efficacy and cause neurological and cardiovascular side effects because they target upstream regulators of muscle contraction. Direct myosin inhibition could provide optimal muscle relaxation; however, targeting skeletal myosin is particularly challenging because of its similarity to the cardiac isoform. We identified a key residue difference between these myosin isoforms, located in the communication center of the functional regions, which allowed us to design a selective inhibitor, MPH-220. Mutagenic analysis and the atomic structure of MPH-220-bound skeletal muscle myosin confirmed the mechanism of specificity. Targeting skeletal muscle myosin by MPH-220 enabled muscle relaxation, in human and model systems, without cardiovascular side effects and improved spastic gait disorders after brain injury in a disease model. MPH-220 provides a potential nervous-system-independent option to treat spasticity and muscle stiffness.

Posttreatment Maturation of Medulloblastoma into Gangliocytoma: Report of 2 Cases.

INTRODUCTION: We report 2 cases of medulloblastoma maturing into gangliocytoma after receiving multimodal therapy. Here we present 2 cases of diagnosed medulloblastoma which on re-resection were noted to be gangliocytoma without heterogeneity, which is an extremely rare occurrence. CASE PRESENTATION: The first patient, an 11-year-old boy diagnosed with high-risk (non-WNT, non-SHH) medulloblastoma, was treated with near-total surgical resection followed by craniospinal radiation therapy with weekly vincristine. He then received maintenance chemotherapy with vincristine, cyclophosphamide, and cisplatin. On surveillance MR imaging studies residual tumor in the lateral aspect of the tumor bed was noted to be slowly growing, eliciting gross-total resection of the residual tumor. Histopathology showed benign gangliocytoma without residual medulloblastoma. The second patient, a 3-year-old girl, was diagnosed with medulloblastoma, desmoplastic nodular variant. She was initially treated with gross total resection and chemotherapy with etoposide, carboplatin, and high-dose methotrexate. At 4 months off therapy, she was noted to have local recurrence along the resection cavity. Second-line therapy was started with irinotecan and temozolomide, but MRI assessment during treatment showed further disease progression. She then received craniospinal radiation. Eleven months off therapy, further radiographic progression was noted, and the patient underwent second-look surgery, with pathology showing gangliocytoma and treatment-related gliosis. DISCUSSION/CONCLUSION: The maturation of medulloblastoma into a ganglion cell-rich lesion is very rare, with few well-characterized previous reports. Given the rare nature of this entity, it would be of great value to understand the process of posttreatment maturation and the genetic and treatment factors which contribute to this phenomenon.

The hypertrophic cardiomyopathy mutations R403Q and R663H increase the number of myosin heads available to interact with actin.

Hypertrophic cardiomyopathy (HCM) mutations in ß-cardiac myosin and myosin binding protein-C (MyBP-C) lead to hypercontractility of the heart, an early hallmark of HCM. We show that hypercontractility caused by the HCM-causing mutation R663H cannot be explained by changes in fundamental myosin contractile parameters, much like the HCM-causing mutation R403Q. Using enzymatic assays with purified human ß-cardiac myosin, we provide evidence that both mutations cause hypercontractility by increasing the number of functionally accessible myosin heads. We also demonstrate that the myosin mutation R403Q, but not R663H, ablates the binding of myosin with the C0-C7 fragment of MyBP-C. Furthermore, addition of C0-C7 decreases the wild-type myosin basal ATPase single turnover rate, while the mutants do not show a similar reduction. These data suggest that a primary mechanism of action for these mutations is to increase the number of myosin heads functionally available for interaction with actin, which could contribute to hypercontractility.

The Myosin Family of Mechanoenzymes: From Mechanisms to Therapeutic Approaches.

Myosins are among the most fascinating enzymes in biology. As extremely allosteric chemomechanical molecular machines, myosins are involved in myriad pivotal cellular functions and are frequently sites of mutations leading to disease phenotypes. Human ß-cardiac myosin has proved to be an excellent target for small-molecule therapeutics for heart muscle diseases, and, as we describe here, other myosin family members are likely to be potentially unique targets for treating other diseases as well. The first part of this review focuses on how myosins convert the chemical energy of ATP hydrolysis into mechanical movement, followed by a description of existing therapeutic approaches to target human ß-cardiac myosin. The next section focuses on the possibility of targeting nonmuscle members of the human myosin family for several diseases. We end the review by describing the roles of myosin in parasites and the therapeutic potential of targeting them to block parasitic invasion of their hosts.

Atypical presentations of intracranial dysgerminoma mimicking central nervous system inflammatory or demyelinating disease.

OBJECTIVES: The aim of this study is to report a case series of atypical presentations of intracranial dysgerminoma in which the diagnosis was delayed due to clinical and radiographic findings initially suggestive of CNS inflammatory or demyelinating diseases, such as MS. METHODS: This study is a case series detailing the history, clinical presentations, radiographic and laboratory results, and management of three patients with biopsy-proven intracranial dysgerminoma. RESULTS: All three patients demonstrated hyperintense lesions on MRI that were more suggestive of demyelinating or inflammatory diseases, including lesions involving the midbrain and corpus callosum. All three patients were serum positive for oligoclonal bands and negative for both AFP and beta-hCG (these two markers are commonly seen in dysgerminoma cases). One case involved a steroid-responsive tumor whereas the other two cases either did not respond to steroids or steroids were withheld due to uncertainty of etiology. Following biopsy, all three results were consistent with dysgerminoma. CONCLUSION: Clinicians should be aware that dysgerminoma may mimic the clinical and radiographic presentations of demyelinating diseases such as MS. These lesions can cause acute visual loss or diplopia, have MRI and CSF findings that might mimic MS, and have been shown to respond to steroids. Atypical clinical (e.g., headache, dorsal midbrain syndrome, bilateral optic neuropathy) or atypical radiographic features (e.g., mass effect, hydrocephalus) should prompt consideration for repeat imaging and possible biopsy even if serum or CSF tumor markers (beta-hCG and AFP) are negative for dysgerminoma.

ß-Cardiac myosin hypertrophic cardiomyopathy mutations release sequestered heads and increase enzymatic activity.

Hypertrophic cardiomyopathy (HCM) affects 1 in 500 people and leads to hyper-contractility of the heart. Nearly 40 percent of HCM-causing mutations are found in human ß-cardiac myosin. Previous studies looking at the effect of HCM mutations on the force, velocity and ATPase activity of the catalytic domain of human ß-cardiac myosin have not shown clear trends leading to hypercontractility at the molecular scale. Here we present functional data showing that four separate HCM mutations located at the myosin head-tail (R249Q, H251N) and head-head (D382Y, R719W) interfaces of a folded-back sequestered state referred to as the interacting heads motif (IHM) lead to a significant increase in the number of heads functionally accessible for interaction with actin. These results provide evidence that HCM mutations can modulate myosin activity by disrupting intramolecular interactions within the proposed sequestered state, which could lead to hypercontractility at the molecular level.

SETD3 is an actin histidine methyltransferase that prevents primary dystocia.

For more than 50 years, the methylation of mammalian actin at histidine 73 has been known to occur1. Despite the pervasiveness of His73 methylation, which we find is conserved in several model animals and plants, its function remains unclear and the enzyme that generates this modification is unknown. Here we identify SET domain protein 3 (SETD3) as the physiological actin His73 methyltransferase. Structural studies reveal that an extensive network of interactions clamps the actin peptide onto the surface of SETD3 to orient His73 correctly within the catalytic pocket and to facilitate methyl transfer. His73 methylation reduces the nucleotide-exchange rate on actin monomers and modestly accelerates the assembly of actin filaments. Mice that lack SETD3 show complete loss of actin His73 methylation in several tissues, and quantitative proteomics analysis shows that actin His73 methylation is the only detectable physiological substrate of SETD3. SETD3-deficient female mice have severely decreased litter sizes owing to primary maternal dystocia that is refractory to ecbolic induction agents. Furthermore, depletion of SETD3 impairs signal-induced contraction in primary human uterine smooth muscle cells. Together, our results identify a mammalian histidine methyltransferase and uncover a pivotal role for SETD3 and actin His73 methylation in the regulation of smooth muscle contractility. Our data also support the broader hypothesis that protein histidine methylation acts as a common regulatory mechanism.

Converter domain mutations in myosin alter structural kinetics and motor function.

Myosins are molecular motors that use a conserved ATPase cycle to generate force. We investigated two mutations in the converter domain of myosin V (R712G and F750L) to examine how altering specific structural transitions in the motor ATPase cycle can impair myosin mechanochemistry. The corresponding mutations in the human ß-cardiac myosin gene are associated with hypertrophic and dilated cardiomyopathy, respectively. Despite similar steady-state actin-activated ATPase and unloaded in vitro motility-sliding velocities, both R712G and F750L were less able to overcome frictional loads measured in the loaded motility assay. Transient kinetic analysis and stopped-flow FRET demonstrated that the R712G mutation slowed the maximum ATP hydrolysis and recovery-stroke rate constants, whereas the F750L mutation enhanced these steps. In both mutants, the fast and slow power-stroke as well as actin-activated phosphate release rate constants were not significantly different from WT. Time-resolved FRET experiments revealed that R712G and F750L populate the pre- and post-power-stroke states with similar FRET distance and distance distribution profiles. The R712G mutant increased the mole fraction in the post-power-stroke conformation in the strong actin-binding states, whereas the F750L decreased this population in the actomyosin ADP state. We conclude that mutations in key allosteric pathways can shift the equilibrium and/or alter the activation energy associated with key structural transitions without altering the overall conformation of the pre- and post-power-stroke states. Thus, therapies designed to alter the transition between structural states may be able to rescue the impaired motor function induced by disease mutations.

Deciphering the super relaxed state of human ß-cardiac myosin and the mode of action of mavacamten from myosin molecules to muscle fibers.

Mutations in ß-cardiac myosin, the predominant motor protein for human heart contraction, can alter power output and cause cardiomyopathy. However, measurements of the intrinsic force, velocity, and ATPase activity of myosin have not provided a consistent mechanism to link mutations to muscle pathology. An alternative model posits that mutations in myosin affect the stability of a sequestered, super relaxed state (SRX) of the protein with very slow ATP hydrolysis and thereby change the number of myosin heads accessible to actin. Here we show that purified human ß-cardiac myosin exists partly in an SRX and may in part correspond to a folded-back conformation of myosin heads observed in muscle fibers around the thick filament backbone. Mutations that cause hypertrophic cardiomyopathy destabilize this state, while the small molecule mavacamten promotes it. These findings provide a biochemical and structural link between the genetics and physiology of cardiomyopathy with implications for therapeutic strategies.

Increased (pro)renin receptor expression in the subfornical organ of hypertensive humans.

The central nervous system plays an important role in essential hypertension in humans and in animal models of hypertension through modulation of sympathetic activity and Na+ and body fluid homeostasis. Data from animal models of hypertension suggest that the renin-angiotensin system in the subfornical organ (SFO) of the brain is critical for hypertension development. We recently reported that the brain (pro)renin receptor (PRR) is a novel component of the brain renin-angiotensin system and could be a key initiator of the pathogenesis of hypertension. Here, we examined the expression level and cellular distribution of PRR in the SFO of postmortem human brains to assess its association with the pathogenesis of human hypertension. Postmortem SFO tissues were collected from hypertensive and normotensive human subjects. Immunolabeling for the PRR and a retrospective analysis of clinical data were performed. We found that human PRR was prominently expressed in most neurons and microglia, but not in astrocytes, in the SFO. Importantly, PRR levels in the SFO were elevated in hypertensive subjects. Moreover, PRR immunoreactivity was significantly correlated with systolic blood pressure but not body weight, age, or diastolic blood pressure. Interestingly, this correlation was independent of antihypertensive drug therapy. Our data indicate that PRR in the SFO may be a key molecular player in the pathogenesis of human hypertension and, as such, could be an important focus of efforts to understand the neurogenic origin of hypertension. NEW & NOTEWORTHY This study provides evidence that, in the subfornical organ of the human brain, the (pro)renin receptor is expressed in neurons and microglia cells but not in astrocytes. More importantly, (pro)renin receptor immunoreactivity in the subfornical organ is increased in hypertensive humans and is significantly correlated with systolic blood pressure.

Hypertrophic cardiomyopathy and the myosin mesa: viewing an old disease in a new light.

The sarcomere is an exquisitely designed apparatus that is capable of generating force, which in the case of the heart results in the pumping of blood throughout the body. At the molecular level, an ATP-dependent interaction of myosin with actin drives the contraction and force generation of the sarcomere. Over the past six decades, work on muscle has yielded tremendous insights into the workings of the sarcomeric system. We now stand on the cusp where the acquired knowledge of how the sarcomere contracts and how that contraction is regulated can be extended to an understanding of the molecular mechanisms of sarcomeric diseases, such as hypertrophic cardiomyopathy (HCM). In this review we present a picture that combines current knowledge of the myosin mesa, the sequestered state of myosin heads on the thick filament, known as the interacting-heads motif (IHM), their possible interaction with myosin binding protein C (MyBP-C) and how these interactions can be abrogated leading to hyper-contractility, a key clinical manifestation of HCM. We discuss the structural and functional basis of the IHM state of the myosin heads and identify HCM-causing mutations that can directly impact the equilibrium between the 'on state' of the myosin heads (the open state) and the IHM 'off state'. We also hypothesize a role of MyBP-C in helping to maintain myosin heads in the IHM state on the thick filament, allowing release in a graded manner upon adrenergic stimulation. By viewing clinical hyper-contractility as the result of the destabilization of the IHM state, our aim is to view an old disease in a new light.

Granulomatous Thyroiditis: A Case Report and Literature Review.

BACKGROUND: Granulomatous disease in the thyroid gland has been linked to viral, bacterial and autoimmune etiologies. The most common granulomatous disease of the thyroid is subacute granulomatous thyroiditis, which is presumed to have a viral or post-viral inflammatory cause. Bacterial etiologies include tuberculosis, actinomycosis, and nocardiosis, but are extremely rare. Disseminated actinomycosis and nocardiosis more commonly affect organ-transplant patients with the highest susceptibility within the first year after transplant surgery. CASE: A 45-year-old African American male, who received his third kidney transplant for renal failure secondary to Alport Syndrome, presented with numerous subcutaneous nodules and diffuse muscle pain in the neck. Further workup revealed bilateral nodularity of the thyroid. Fine needle aspiration of these nodules demonstrated suppurative granulomatous thyroiditis. Subsequent right thyroid lobectomy showed granulomatous thyroiditis with filamentous micro-organisms, morphologically resembling Nocardia or Actinomyces. CONCLUSION: Disseminated granulomatous disease presenting in the thyroid is very rare, and typically afflicts immune-compromised patients. The overall clinical, cytologic and histologic picture of this patient strongly points to an infectious etiology, likely Nocardia, in the setting of recent organ transplantation within the last year.

Anaplastic myxopapillary ependymoma in an infant: Case report and literature review.

A 7-month-old boy presented with gastrointestinal disturbance, mild neurologic deficit of the left lower extremity and levo-scoliosis of the thoracic spine. Magnetic resonance imaging demonstrated a large intramedullary lesion involving the thoracic spine, from level T1 to T11. Histologic analysis showed a glial tumor with fibrillary processes arranged in radial pattern around mucoid fibrovascular cores with a high proliferative index (focally up to 80%) and prominent vascular endothelial hyperplasia. These findings were consistent with an anaplastic myxopapillary ependymoma. Subtotal resection was performed via a T3-T10 laminoplasty. A ventricular shunt was placed, and the patient subsequently received chemoradiation therapy. To date, this is the second case of a myxopapillary ependymoma with high-grade anaplastic features and the first case in an infant reported in the literature.

The myosin mesa and the basis of hypercontractility caused by hypertrophic cardiomyopathy mutations.

Hypertrophic cardiomyopathy (HCM) is primarily caused by mutations in ß-cardiac myosin and myosin-binding protein-C (MyBP-C). Changes in the contractile parameters of myosin measured so far do not explain the clinical hypercontractility caused by such mutations. We propose that hypercontractility is due to an increase in the number of myosin heads (S1) that are accessible for force production. In support of this hypothesis, we demonstrate myosin tail (S2)-dependent functional regulation of actin-activated human ß-cardiac myosin ATPase. In addition, we show that both S2 and MyBP-C bind to S1 and that phosphorylation of either S1 or MyBP-C weakens these interactions. Importantly, the S1-S2 interaction is also weakened by four myosin HCM-causing mutations but not by two other mutations. To explain these experimental results, we propose a working structural model involving multiple interactions, including those with myosin's own S2 and MyBP-C, that hold myosin in a sequestered state.

Effects of hypertrophic and dilated cardiomyopathy mutations on power output by human ß-cardiac myosin.

Hypertrophic cardiomyopathy is the most frequently occurring inherited cardiovascular disease, with a prevalence of more than one in 500 individuals worldwide. Genetically acquired dilated cardiomyopathy is a related disease that is less prevalent. Both are caused by mutations in the genes encoding the fundamental force-generating protein machinery of the cardiac muscle sarcomere, including human ß-cardiac myosin, the motor protein that powers ventricular contraction. Despite numerous studies, most performed with non-human or non-cardiac myosin, there is no clear consensus about the mechanism of action of these mutations on the function of human ß-cardiac myosin. We are using a recombinantly expressed human ß-cardiac myosin motor domain along with conventional and new methodologies to characterize the forces and velocities of the mutant myosins compared with wild type. Our studies are extending beyond myosin interactions with pure actin filaments to include the interaction of myosin with regulated actin filaments containing tropomyosin and troponin, the roles of regulatory light chain phosphorylation on the functions of the system, and the possible roles of myosin binding protein-C and titin, important regulatory components of both cardiac and skeletal muscles.