Prolonged presence of replication-competent SARS-CoV-2 in mildly symptomatic individuals: A report of two cases.

It has been estimated that individuals with COVID-19 can shed replication-competent virus up to a maximum of 20 days after initiation of symptoms. The majority of studies that addressed this situation involved hospitalized individuals and those with severe disease. Studies to address the possible presence of SARS-CoV-2 during the different phases of COVID-19 disease in mildly infected individuals, and utilization of viral culture techniques to identify replication-competent viruses, have been limited. This report describes two patients with mild forms of the disease who shed replication-competent virus for 24 and 37 days, respectively, after symptom onset.

Nanoarchitecture and dynamics of the mouse enteric glycocalyx examined by freeze-etching electron tomography and intravital microscopy.

The glycocalyx is a highly hydrated, glycoprotein-rich coat shrouding many eukaryotic and prokaryotic cells. The intestinal epithelial glycocalyx, comprising glycosylated transmembrane mucins, is part of the primary host-microbe interface and is essential for nutrient absorption. Its disruption has been implicated in numerous gastrointestinal diseases. Yet, due to challenges in preserving and visualizing its native organization, glycocalyx structure-function relationships remain unclear. Here, we characterize the nanoarchitecture of the murine enteric glycocalyx using freeze-etching and electron tomography. Micrometer-long mucin filaments emerge from microvillar-tips and, through zigzagged lateral interactions form a three-dimensional columnar network with a 30 nm mesh. Filament-termini converge into globular structures ~30 nm apart that are liquid-crystalline packed within a single plane. Finally, we assess glycocalyx deformability and porosity using intravital microscopy. We argue that the columnar network architecture and the liquid-crystalline packing of the filament termini allow the glycocalyx to function as a deformable size-exclusion filter of luminal contents.

Bacteria arise at the border of mycoplasma-infected HeLa cells, containing cytoplasm with either malformed cytosol, mitochondria and endoplasmic reticulum or tightly adjoined smooth vacuoles.

A study with transmission electron microscopy of mycoplasma-contaminated HeLa cells using five cell donors referred to as donors A, B, C, D and E, observations are herein presented. Experiments performed with cells from donors B, C and D, revealed the presence of Mycoplasma hyorhinis after PCR and sequencing experiments. Bacteria probably originated from a cytoplasm with compacted tiny granular particles replacing the normal cytosol territories, or from the contact with the cytoplasm through a clear semi-solid material. The compact granularity (CG) of the cytoplasm was crossed by stripes of smooth and rough endoplasmic reticulum cisternae. Among apparently normal mitochondria, it was noted, in variable proportions, mitochondria with crista-delimited lucent central regions that expand to and occupied the interior of a crista-less organelle, which can undergo fission. Other components of the scenarios of mycoplasma-induced cell demolition are villus-like structures with associated 80-200 nm vesicles and a clear, flexible semi-solid, process-sensitive substance that we named jam-like material. This material coated the cytoplasmic surface, its recesses, irregular protrusions and detached cytoplasmic fragments. It also cushioned forming bacteria. Cyst-like structures were often present in the cytoplasm. Cells, mainly apoptotic, exhibiting ample cytoplasmic sectors with characteristic net-like profile due to adjoined vacuoles, as well as ovoid or elongated profiles, consistently appeared in all cells from the last four cell donors. These cells were named "modified host cells" because bacteria arose in the vacuoles. The possibility that, in some samples, there was infection and/or coinfection of the host cell by another organism(s) cannot be ruled out.

Bacteria arise at the border of mycoplasma-infected HeLa cells, containing cytoplasm with either malformed cytosol, mitochondria and endoplasmic reticulum or tightly adjoined smooth vacuoles

A study with transmission electron microscopy of mycoplasma-contaminated HeLa cells using five cell donors referred to as donors A, B, C, D and E, observations are herein presented. Experiments performed with cells from donors B, C and D, revealed the presence of Mycoplasma hyorhinis after PCR and sequencing experiments. Bacteria probably originated from a cytoplasm with compacted tiny granular particles replacing the normal cytosol territories, or from the contact with the cytoplasm through a clear semi-solid material. The compact granularity (CG) of the cytoplasm was crossed by stripes of smooth and rough endoplasmic reticulum cisternae. Among apparently normal mitochondria, it was noted, in variable proportions, mitochondria with crista-delimited lucent central regions that expand to and occupied the interior of a crista-less organelle, which can undergo fission. Other components of the scenarios of mycoplasma-induced cell demolition are villus-like structures with associated 80-200 nm vesicles and a clear, flexible semi-solid, process-sensitive substance that we named jam-like material. This material coated the cytoplasmic surface, its recesses, irregular protrusions and detached cytoplasmic fragments. It also cushioned forming bacteria. Cyst-like structures were often present in the cytoplasm. Cells, mainly apoptotic, exhibiting ample cytoplasmic sectors with characteristic net-like profile due to adjoined vacuoles, as well as ovoid or elongated profiles, consistently appeared in all cells from the last four cell donors. These cells were named "modified host cells" because bacteria arose in the vacuoles. The possibility that, in some samples, there was infection and/or coinfection of the host cell by another organism(s) cannot be ruled out.

Viperid venom glands with defective venom production. Morphological study.

The venom of viperid snakes is collected monthly at Butantan Institute for research purposes and production of antivenoms. Here we describe histological and ultrastructural changes on Crotalus durissus terrificus and Bothrops sp. venom glands with defective venom production. Secretory tubules commonly showed partial or total obliteration of their lumina by masses of necrotic cells and cellular debris. Secretory cells showed varying degrees of degenerative and/or metaplastic alterations seriously affecting the structures responsible for the synthesis and secretion of venom. The intertubular connective tissue presented fibroblast hyperplasia, inflammatory cells infiltration, vacuolated cells and blood vessels alterations. In two venom glands out of nineteen snakes examined, virus-like particles were found. The alterations observed in most of the glands could have been caused by excessive manual pressure, during venom extraction routine, causing disruption of the secretory tubules and leakage of venom to the intertubular connective tissue.

TGF-beta and mesenchymal hepatic involvement after visceral leishmaniasis.

The liver involvement in the human visceral leishmaniasis (VL) has been related to parasitism and activated Kupffer cells with further occasional fibrotic alterations, especially after long-term disease without treatment. However, fibrotic alterations have been reported after therapy, whose clinical finding is the persistence of hepatomegaly. Fibrotic involvement of the liver after therapy was never well understood, and the aim of this study was to evaluate this finding through ultrastructural and morphometric analysis. A case-control study was performed with 20 patients (15 cases and five controls). Cases included patients with persistent hepatomegaly (residual) after treatment of VL submitted to liver biopsy to exclude other causes of liver enlargement, including serum tests of viral hepatitis. The material was evaluated by electron microscopy allowing ultrastructural with morphometric analysis of medium portion of hepatic lobule. Narrow sinusoidal lumen and prominent Kupffer cells were found with insignificant alterations of hepatocytes, pit, and endothelial cells. On ultrastructural analysis, the enlargement of the space of Disse was due to fibrous collagen, increase of number of Ito cells, and nonfibrous extracellular matrix that were associated with Kupffer cells enlargement. Immunohistochemistry showed an intense expression of TGF-beta in patients with VL. These findings suggest a production of TGF-beta by Kupffer cells that resulted in the characteristic fibrotic involvement of the liver. Residual hepatomegaly in visceral leishmaniasis could result from sustained Kupffer cell activation with perihepatocytic fibrosis.

Morphometric analysis of the fate of secretory epithelial cells in the ventral lobe of the rat prostate during massive apoptosis

Orchiectomy causes marked, rapid involution of the prostatic secretory epithelium. Concurrently, macrophages, which in normal glands are small and rarely occur at the base of the secretory epithelium, increase in size and number. Apoptotic cells are engulfed by companion epithelial cells and also by macrophages. In secretory cells and macrophages, dense bodies progressively increase in number and store membranes derived from dead cells of the secretory epithelium. In this work, we examined the contributions of the various routes of disposal of demised secretory epithelial cells of the rat prostate, induced to enter in apoptosis by retrieval of androgen. Specifi cally, we sought to determine how much membrane surface area derived from apoptotic cells of the secretory epithelium could be stored in dense bodies, and how these data compared with the disposal of dead cells via the glandular lumen. Glands from unoperated controls (day 0) and from rats examined 12 h and 1, 2, 3, 4, 5, 6, 7, 8, and 9 days after orchiectomy were studied morphometrically. The total membrane surface area of rough and smooth endoplasmic reticulum, Golgi apparatus, mitochondria and vesicles declined from 6.75 x 103 ìm2 in non-castrated rats to 1.12 x 103 ìm2 nine days after castration. Similarly, the total surface area of the secretory epithelium decreased from 10.6 x 1011 ìm2 in non-castrated rats to 0.204 x 1011 ìm2 nine days after castration. Geometrical models revealed that 1 ìm3 of dense body accommodated at least 142 ìm2 of myelin-like membrane surface area. Three to four days after castration, the total volume of intramacrophage dense bodies peaked (~5 x 106 ìm3) and represented 1-2% of the volume of intraepithelial dense bodies (~4 x 108 ìm3). The minimum membrane surface area that could be stored in dense bodies of the secretory epithelium on post-castration days 0, 1, 2, 3, 4 and 9 was 1.4%, 9%, 16%, 23%, 28% and 44%, respectively, of the total membrane surface area of the...

Influence of a cholesterol-rich emulsion and BCNU on the apoptotic indices of myeloma cells induced in BALB/C mice

Proliferating malignant cells express low-density lipoprotein (LDL) receptors, and a cholesterol-rich microemulsion (LDE) resembling the lipid portion of LDL can be bound to lipophilic drugs such as 1,3-bis (2-chloroethyl)-1-nitrosourea (BCNU) to increase the drug´s capture and decrease the drug-associated toxicity. In this work, we studied the effect of BCNU and BCNU+LDE on apoptosis in plasmacytoma-related cells obtained from BALB/c mice with myeloma. Four groups of mice (n=4 each) were treated with LDE, BCNU, BCNU in LDE or vehicle solution (control group). Morphological methods (histology and transmission electron microscopy) and immunohistochemistry (TUNEL procedure) were used to evaluate the occurrence of apoptosis. The drugs were injected intraperitoneally in the 14th month after induction of the myeloma and the mice in all groups were sacrificed six hours after this injection. The apoptotic indices of the plasmacytoma mesenteric cells evaluated in the four experimental groups revealed that the LDE emulsion significantly (p<0.05) increased the percentage of tumoral cells dying by apoptosis. All the groups with LDE, alone or in combination with BCNU showed significantly higher apoptotic indices than the controls. This enhanced cytotoxicity suggests a potential use for LDE in improving the efficacy of chemotherapeutic agents.

Molecular mechanisms of mitochondrial apoptogenic factor release through pores and megachannels

Mitochondrial membrane permeabilization is a biochemically well-defined phenomenon that occurs in response to numerous physiological and pathological processes that regulate cell survival. In many situations, mitochondrial membrane permeabilization is triggered by an excess of reactive oxygen species (ROS), Ca2+ overload, and the interference of BH3-only proteins of the BCL-2 family, as well as by activated caspases that can act on components of the inner or outer membrane to cause the opening, assembly and/or activation of membrane mitochondrial permeability transition pores. These pores permit the release of apoptogenic factors such as cytochrome c, apoptosis-inducing factor, Smac/Diablo, HtrA2/Omi and endonuclease G from the intermembrane space to the cytosol where they mediate many of the biochemical and morphological features of apoptosis and necrosis. In this review, we discuss the pharmacological, genetic and biochemical evidence that proteins, protein complexes and membrane structures can form pores through which apoptogenic factors can be released from mitochondria.

Pitfalls in the use of electron microscopy to study the mitochondrial membrane permeability transition in apoptotic cells and pellets: where do we stand in relation to the incidence of mitochondrial swelling in apoptosis?

The importance of apoptosis as a form of programmed cell death was recognized in the 1980s, whereas the central role of mitochondria in controlling this process was identifi ed in the mid-1990s. An important event in apoptosis is the collapse of the mitochondrial transmembrane potential (ÃØm), with the ensuing loss of the selective permeability of the inner membrane resulting in swelling of the hyperosmolar mitochondrial matrix. This event is known as the mitochondrial permeability transition (MPT). After swelling of the intermembrane space, the outer membrane ruptures, exposing the permeable inner membrane. An increasingly swollen matrix covered by the inner membrane eventually herniates into the cytoplasm through the breach formed in the outer membrane (OM). The increase in surface area of the inner mitochondrial membrane (IMM) involves the unfolding of membrane stored in the cristae. This membrane movement is osmotically driven since the cytoplasm has a lower osmolality. The proteins partly embedded in the inner membrane are thus exposed to the cytoplasm. In nine out of ten electron microscopy studies of isolated mitochondria expressing the permeability transition, the existing ruptures of the OMM were overlooked. The MPT can also be recognized in individual mitochondria by using fl uorescent probes that are not retained in these organelles once the ÃØm is lost. In cases in which there is no rupture of the OMM, cytochrome c must be released from mitochondria with impermeable inner membranes. Examination of several hundred of the more than 61,000 published papers on programmed cell death revealed that the key signaling events of apoptosis, such as the onset of the MPT, mitochondrial swelling and cytochrome c release to the cytoplasm, are infl uenced by factors such as the cell type and presence of apoptogenic agents...

Morphology of mitochondrial permeability transition: morphometric volumetry in apoptotic cells.

Here we report on the mitochondrial permeability transition (MPT), which refers to the morphology of mitochondria whose inner membrane has lost its selective permeability. In all types of apoptotic cells so far examined, we found outer mitochondrial membranes that had been ruptured. These mitochondria present a swollen matrix covered by an inner membrane herniating into the cytoplasm through the breached outer membrane. Similarly ruptured outer mitochondrial membranes have been reported in studies on mitochondrial fractions induced to undergo MPT, carried out by others. Our observations were made on five types of rat tissue cells and six different cultured cell lines in the early stages of apoptosis. Samples from the cell lines HL-60, HeLa, WEHI-164, and a special batch of PC-12 cells were subjected to various apoptogenic agents and analyzed morphometrically. Nonapoptotic companion cells with unaltered nuclear structure (CUNS) were also analyzed. The mitochondrial volume in microm(3) and the volume fraction of the cytoplasm occupied by mitochondria in cells with typical nuclear signs of apoptosis and also in CUNS were evaluated. The volume of the mitochondria with ruptured membrane represents at least 69% (47-89%) of the total mitochondrial volume of the apoptotic cells. Thus, a considerable fraction of the cellular mitochondrial mass is or was in the state of permeability transition and probably involved in enhancement of the apoptotic program. In all samples, a fraction of the cells with normal nuclei possessed mitochondria with breached outer membranes as described above. In these cells, MPT occurred before the appearance of the typical nuclear phenotype of the apoptotic cells.

Participação da apoptose na rejeição aguda do transplante intestinal em ratos / Apoptosis participation in the acute rejection of intestinal transplantation in rats

RACIONAL: O transplante de intestino delgado é procedimento cirúrgico em estudo visando sua aplicação no tratamento dos pacientes portadores da síndrome do intestino curto, com vistas à reabilitação oral. A grande barreira, porém, se deve à rejeição pela grande quantidade de tecido linfóide presente no intestino delgado. OBJETIVO: Estudo da apoptose em alotransplante heterotópico intestinal. MATERIAL E MÉTODOS: Realizaram-se 24 alotransplantes intestinais em ratos da raça Brown-Norway (doador) para Lewis (receptor), sendo subdivididos em três subgrupos de oito animais, sacrificados respectivamente no terceiro dia de pós-operatório (Tx(3)), no quinto dia de pós-operatório (Tx(5)) e no sétimo dia de pós-operatório (Tx(7)) para coleta das biopsias dos enxertos intestinais. Compararam-se os resultados com o grupo isotransplante (C) que envolveu oito animais da raça Lewis (doador) para Lewis (receptor), porém neste grupo realizaram-se biopsias seriadas no mesmo animal, sendo subdivididos em três momentos: biopsia no terceiro dia de pós-operatório (C(3)), no quinto dia de pós-operatório (C(5)) e sacrificados no sétimo dia de pós-operatório (C(7)) para coleta da biopsia. Realizou-se, inicialmente, análise intragrupo entre os momentos C(3), C(5) e C(7) para todos os parâmetros de rejeição citados anteriormente, como também para os três subgrupos Tx(3), Tx(5) e Tx(7). Posteriormente, realizou-se a análise intergrupo de forma transversal e pareada comparando-se o grupo isotransplante com o grupo alotransplante. (C(3) com Tx(3); C(5) com Tx(5) e C(7) com Tx(7)). No grupo isotransplante não houve expressão estatística quanto aos marcadores analisados. Porém, no grupo alotransplante observou-se que alterações da apoptose foram marcantes a partir do terceiro dia de pós-operatório.

[Apoptosis participation in the acute rejection of intestinal transplantation in rats]. / Participação da apoptose na rejeição aguda do transplante intestinal em ratos.

BACKGROUND: Intestinal transplantation is a possible treatment for patients with short bowel syndrome, aiming the reintroduction of oral diet. However, the major obstacle in this procedure is the strong rejection. Delay in rejection diagnosis may be irreversible and lethal. AIM: To define method for early diagnosis of rejection based on the apoptosis from intestinal allograft. MATERIAL AND METHODS: Isogenic rats Brown-Norway (BN) and Lewis (LEW) were submitted to intestinal heterotopic allotransplantation and divided in two groups: LEW donor to LEW recipient isograft group C and BN donor to LEW recipient allograft group (Tx). According to the day of sacrifice, Tx group were subdivided in three subgroups with eight animals each as follow: Tx3-- sacrificed at third postoperative day (POD), Tx5 -- sacrificed at fifth POD and Tx7 -- sacrificed at seventh POD. Eight animals from control group were subdivided in three moments according to the time of biopsy from the graft as follow: C3 -- biopsy at third POD; C5 -- biopsy at fifth POD and C7 -- biopsy at seventh POD. All animals from control group were sacrificed at seventh POD. Rejection parameters were compared between the control groups (C3 vs C5, C3 vs C7 and C5 vs C7, and allograft group (Tx3 vs Tx5, Tx3 vs Tx7 and Tx5 vs Tx7). The same parameters were analyzed between the control group and allograft groups ( C3 vs Tx3, C5 vs Tx5 and C7 vs Tx7). In C group no statistical significant difference regarding the expression of the apoptotic cells were detected, while in Tx group, the presence of apoptotic cells were remarkable since the third postoperative day.

Ultrastructure of the rat sublingual gland during period of high proliferative activity in postnatal development

The postnatal development of the rat sublingual gland was studied using autoradiography and electron microscopy. The lebeling indices of parenchymal and stromal cells were determined in autoradiographs from rats injected with H-thymidine. The lebeling index of parenchymal cells remained high from the second to the twentieth day after birth, but declined significantly thereafter. Ultrastructural analysis showed that during the period of high proliferative activity the secretory cells had an ultrastructure that was qualitatively similar to that of cells show large amounts of rough endoplasmic reticulum and secretory granules that reached the adult pattern 30 days after birth. Maturation of the myoepithelial cells occurred during the same period.

Immunolocalization of venom metalloproteases in venom glands of adult and of newborn snakes of Bothrops jararaca.

Using immunoelectronmicroscopy we analyzed qualitative and quantitatively the intracellular distribution of bothropasin, hemorrhagic factor 2 (HF2) and hemorrhagic factor 3 (HF3) in the venom secretory cells from adult snakes in the active (7 days after venom extraction) and in the resting (without venom extraction for 40 days) stages of protein synthesis. Glands from the newborn Bothrops jararaca were also studied. The results lead to the conclusion that all the secretory cells and the secretory pathway in the cells are qualitatively alike in regard to their content of the three metalloproteases. Secretory cells from the resting glands, unlike the active ones and the newborn glands, did not present immunolabeling in the narrow intracisternal spaces of the rough endoplasmic reticulum (RER). The label intensity for bothropasin was greater than that for the other proteins in the adults. HF3 and HF2 labeling densities in the newborn were higher than in the adults and HF3 labeling was not different from that of bothropasin. Co-localization of the three metalloproteases was detected in the RER cisternae of the active gland secretory cells, implying that mixing of the proteases before co-packaging into secretory vesicles occurs at the beginning of protein synthesis in the RER cisternae.

Enhanced glomerular permeability to macromolecules in the Nagase analbuminemic rat.

Plasma albumin restricts capillary water filtration. Accordingly, the glomerular ultrafiltration coefficient is higher in Nagase analbuminemic rats (NAR) than in Sprague-Dawley controls. We investigated whether the glomerular permeability to macromolecules is also enhanced in NAR. SDS-PAGE fractionation of urine proteins showed several bands with molecular masses between 60 and 90 kDa in NAR only. Acute administration of BSA to NAR led to nearly complete disappearance of these proteins from urine, an effect partially reversed when most of the exogenous albumin was cleared from circulation. The fractional clearance of 70-kDa dextran was increased in NAR, indicating a size defect. Binding of cationized ferritin to the glomerular basement membrane was decreased in NAR, suggesting associated depletion of fixed anions. The magnitude of cationic ferritin binding correlated negatively with the fractional clearance of 70-kDa dextran, suggesting that the two abnormalities may share a common pathogenic mechanism. Collectively, these results suggest enhanced glomerular permeability to macromolecules in NAR. Albumin may be necessary to maintain the normal glomerular permselectivity properties.

Avaliaçäo da homogeneidade da amostra em morfometria / Evaluation of the sample homogeneity in morphometry

Os autores apresentam com intuito de divulgaçäo, um método para se verificar a homogeneidade da amostra na avaliaçäo morfométrica do número de células, da densidade de volume e da densidade de superfície. O esquema apresentado permitirá ao pesquisador na fase de planejamento do trabalho, determinar à partir de contagens preliminares, o tamanho mínimo da amostra (número de campos ou de eletromicrografias) necessário para a obtençäo de resultados cientificamente consistentes, o que permitirá uma grande economia no consumo de tempo

Grau de precisäo na avaliaçäo morfométrica do número de células / Precision degree in the morphometric cell number evaluation

Os autores apresentam com o intuito de divulgaçäo, um método para se estimar o grau de precisäo na avaliaçäo morfométrica do número absoluto de células em um orgäo. Este método permitirá ao pesquisador durante a fase de planejamento do projeto de pesquisa, calcular à partir de contagens iniciais, o tamanho da amostra (número total de campos histológicos) necessário para se trabalhar com um nível pré-estabelecido de erro nas avaliaçöes. Este fato é muito importante porque, às vezes, dependendo do objetivo do trabalho, um grau muito alto de precisäo pode näo ser necessário, nesse caso, estabelecendo-se um coeficiente de variaçäo aceitável, ocorrerá um enorme ganho no consumo de tempo