IMPDH forms the cytoophidium in zebrafish.

Inosine monophosphate dehydrogenase (IMPDH) catalyzes the rate-limiting step in de novo guanine nucleotide biosynthesis. Its activity is negatively regulated by the binding of GTP. IMPDH can form a membraneless subcellular structure termed the cytoophidium in response to certain changes in the metabolic status of the cell. The polymeric form of IMPDH, which is the subunit of the cytoophidium, has been shown to be more resistant to the inhibition by GTP at physiological concentrations, implying a functional correlation between cytoophidium formation and the upregulation of GTP biosynthesis. Herein we demonstrate that zebrafish IMPDH1b and IMPDH2 isoforms can assemble abundant cytoophidium in most of cultured cells under stimuli, while zebrafish IMPDH1a shows distinctive properties of forming the cytoophidium in different cell types. Point mutations that disrupt cytoophidium structure in mammalian models also prevent the aggregation of zebrafish IMPDHs. In addition, we discover the presence of the IMPDH cytoophidium in various tissues of larval and adult fish under normal growth conditions. Our results reveal that polymerization and cytoophidium assembly of IMPDH can be a regulatory machinery conserved among vertebrates, and with specific physiological purposes.

Sperm morphology of Muscidifurax uniraptor (Hymenoptera: Chalcidoidea: Pteromalidae).

Sperm morphology of the parasitoid Muscidifurax uniraptor was investigated under light and transmission electron microscopy. M. uniraptor sperm are filiform, spiraled, approximately 150 µm in length, with a distinctive head, hooded by an extracellular sheath and a flagellum. This extracellular layer, from which many filaments radiate, measures approximately 90 nm in thickness and covers a small acrosome and the anterior nuclear region. The acrosome is composed of an acrosomal vesicle and a perforatorium with its base inserted in the nuclear tip. The nucleus is filled with homogeneously compacted chromatin. The centriolar adjunct extends towards the anterior portion in a spiral around the nucleus for 3.5 µm in length. The two mitochondrial derivatives begin exactly at the centriole adjunct base and, in cross-section, have a circular shape with equal areas that are smaller than the axoneme diameter. It is coiled, with 9 + 9 + 2 microtubules and begins from the centriole, just below the nuclear base. The axoneme is connected to the mitochondrial derivatives by two small irregularly shaped masses. Between the derivatives and the axoneme, the 'center-flagellar material' is observed. Overall, these characteristics are recognized in other Chalcidoidea, especially in the eurytomids, but together they form a set of species-specific data.

Ultrastructural pathology of neuronal membranes in the oedematous human cerebral cortex.

Surgical biopsies of frontal, parietal and temporal regions of thirty two patients with clinical diagnosis of congenital hydrocephalus, brain trauma, tumours, and vascular anomalies were examined with the transmission electron microscope. The main goal was to study the submicroscopic alterations of somatodendritic, axonal, and synaptic plasma membranes, cytomembranes, and the cytoskeleton. In both, moderate and severe oedema, fragmentation of plasma membrane, enlargement and focal necrosis of rough endoplasmic cisterns and nuclear envelope, detachment of membrane-bound ribosomes and reduction of polysome were observed. The degenerated myelinated axons exhibited discontinuities of the axolemma, disorganisation of multiple myelin lamellae, myelin sheath vacuolization, and formation of myelin ovoids. In severe oedema, synaptic disassembly was frequently found characterized by separate pre- and postsynaptic endings and loss of perisynaptic glial ensheathment. Fragmented and intact microtubules and actin-like filaments also were distinguished. The alterations of plasma membranes and cytomembranes are related with the anoxic-ischaemic conditions of brain parenchyma. The role of free radical and lipid peroxidation, disturbed energy metabolism, altered metabolic cascades, excitotoxicity, protein aggregation, and presence of extracellular oedema fluid is discussed in relation with the derangement of neuronal membranes.

Characterization of larval haemocytes from the velvetbean caterpillar Anticarsia gemmatalis (Hübner) (Lepidoptera: Noctuidae).

Larval haemocytes of Anticarsia gemmatalis (Lepidoptera: Noctuidae) are presented and classified based on morphological characteristics. Haemolymph samples collected from 3rd to 6th instar larvae were observed using differential interference contrast microscopy as well as processed for transmission and scanning electron microscopy. Five general types of haemocytes were observed: prohaemocytes (Pr), plasmatocytes (Pl), granular haemocytes (GH), oenocytoids (Oe) and spherulocytes (SPh). Granular haemocytes were subdivided into two morphologically different subtypes (GH 1 and GH 2). Phenoloxidase activity was clearly observed in the Oe, and also less intensely in the Sph. The osmium/imidazole buffer technique revealed that GH 2 accumulated numerous, small lipid vesicles among their granules, while Pl contained larger but less numerous lipid inclusions. Total haemocyte counts varied between 12.3 and 20.9 x 10(3) haemocytes/microl. Pl, GH 1 and Sph were the cell types more frequently observed in all larval stages studied. GH 2 were rare in 3rd and 4th instars, becoming more numerous after the inception of the 5th instar. Populations of GH 1 and Sph maintained their proportions throughout larval development. Populations of Oe, Pl and Pr, however, presented more marked variations in their proportions. Ultrastructural studies were shown to be useful for the identification and classification of haemocytes, facilitating further analysis by light microscopy.

Pathology of rotavirus infection in suckling mice: A study by conventional histology, immunofluorescence, ultrathin sections, and scanning electron microscopy.

Pathologic changes induced in the small intestine of suckling mice by rotavirus infection were studied by conventional histology, immunofluorescence, scanning electron microscopy, and electron microscopy of ultrathin sections. Infection could be detected within 24 hours in a few mice, but after 2 days it was well established. Swollen, often vacuolated infected cells were found on the sides and tips of villi from which they rapidly became detached; microvilli showed variable irregularity. Immature enterocytes from crypts replaced lost infected cells. By the tenth day very few infected cells could still be found. Both tubular structures and spherical particles occurred in the infected cells. Only tubular structures were found in nuclei.