Lewis B. Coons

Induction of hepatic mixed function oxidases by the insecticide, mirex

Abstract the effect of mirex (dodecachlorooctahydro-1,3,4-metheno-2 H -cyclobuta-[c,d]pentalene) on hepatic cytochrome P-450 and O -demethylase activity has been tested in rats and mice by both injection and feeding studies. Intraperitoneal injection of mirex at a dose rate of 10 mg/kg or higher, increased the hepatic microsomal cytochrome P-450 level in mice. Under the same conditions 25 mg/kg were necessary to elicit the same response in the rat. The O -demethylase activity was also increased. Dietary mirex caused induction of cytochrome P-450 in the rat at all levels tested (1–250 ppm for 14 days). Examination of type I and type II substrate difference spectra indicate that induction at higher levels (100–250 ppm for 14 days) was not only greater but that the cytochrome induced was qualitatively different from that induced at lower levels. Ultrastructural examination of the liver tissue after mirex feeding revealed a proliferation of the smooth endoplasmic reticulum.

The occurrence of multiple forms of cytochrome P-450 in hepatic microsomes from untreated rats and mice☆☆☆

The hepatic microsomes of rat and mice were subfractionated by the procedure of Dallner. When a 1.3 M sucrose lower layer was used for the two-step discontinuous gradient, no differences in spectral characteristics were noted between subfractions, though the smooth fractions (SER) had higher oxidative activity towards the substrates tested. When lower layers of 1.05, 1.1 or 1.15 M sucrose were used, and the SER isolated contained cytochdrome P-450 with significantly different spectral characteristics from that of the rough fraction (RER). The SER cytochrome P-450 had a wavelength maximum in the carbon-monoxide reduced difference spectrum that was significantly lower (ca. 1.0 nm) than that in the RER. In addition, the type I:CO-reduced spectral ratio of these fractions is significantly elevated. These data indicate that liver microsomes from untreated rats and mice contain more than one cytochrome P-450 and that of these cytochromes may be located in different parts of the endoplasmic reticulum.

Low speed preparation of microsomes: a comparative study.

Abstract Microsomal fractions were isolated from hepatic tissue, housefly abdomen and southern armyworm midgut, either by centrifugation of post-mitochondrial supernatant for 1 h at 105 000× g or by calcium sedimentation and low speed centrifugation. A comparison of the two methods of isolation were made on the basis of: NADPH oxidase activity, O -demethylation of p -nitroanisole, spectral parameters of cytochrome P-450, and integrity of ultrastructural constituents. The method of isolation did not effect these parameters appreciably for microsomes isolated from hepatic tissue. Calcium sedimentation of insect microsomes resulted in a reduction of enzyme activity and an apparent decrease in cytochrome P-450. Ultrastructural integrity did not appear to be influenced by the method of sedimentation.

The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 23. Fine structure of the salivary glands of unfed A. (P.) Arboreus Kaiser, Hoogstraal, and Kohls.

Salivary glands of the unfed adult Argas (Persicargas) arboreus (family Argasidae) contain 2 types of alveoli, one nongranular and one granule-secreting. The fine structure of the nongranular alveolus is similar to that of the family Ixodidae. In the granule-secreting alveolus, the presence of 3 types of secretory cells, each with morphologically distinct granular inclusions, confirms histological and histochemical observations on argasid salivary glands. Epithelial cells with numerous membranous infoldings, mitochondria, microtubules, and a complex canalicular system probably concerned with fluid regulation and secretion are located between granule-secreting cells and form caps over their basal regions. The luminal border of both secretory and epithelial cells is microvillate. The alveolar lumen leads into the chitinous alveolar duct which lacks the complex valvular structure of ixodid alveoli. Axons containing neurosecretory material occur in both nongranular and granule-secreting alveoli and probably control salivary secretion.

Cellular organization in the synganglion of the mite Macrocheles muscaedomesticae (Acarina: Macrochelidae)

SummaryThe synganglion is bounded by an extracellular sheath and is divided into the cortex and the neuropile. The cortex contains two glial layers, each of which is composed of a distinctive type of glial cell, and three types of neurons. Type I is the least common and most electron dense, type II is most common, and type III represents neurosecretory cells with a larger volume of cytoplasm than in types I and II. Substantial areas of the neuron cell bodies are unsheathed. A third type of glial cell is found in the neuropile.The first glial layer of the cortex, the perineurium, lies beneath the extracellular sheath and overlies the neuron cell bodies contributing to their ensheathment. In areas lacking neuron cells bodies, the perineurium overlies a second glial layer, the subpermeurium, which is inflected inwards where a group of neuron cell bodies is encountered. The subperineurium contributes to the ensheathment of both the cell bodies of neurons and the nerve fibers. It is confluent with glial cells which arise within the neuropile. The neuropile contains nerve fibers and glial cells and is perforated by the esophageal canal, which is lined by the perineurium and subperineurium. Unsheathed nerve fibers contact each other in three ways: end-knob, longitudinal, and cross contacts.ZusammenfassungDas Synganglion wird von einer extrazellulären Scheide umkleidet und ist in Cortex und Neuropil gegliedert. Der Cortex enthält zwei Gliazellschichten (die jeweils durch einen bestimmten Zelltyp charakterisiert sind) und drei Typen von Neuronenzellkörpern. Neuronenzellkörper vom Typ I sind sehr elektronendicht und nur selten anzutreffen; Typ II ist am häufigsten vertreten; Typ III wird durch neurosekretorische Zellen repräsentiert, die zudem ein relativ größeres Plasmavolumen als Typ I und Typ II besitzen. Ausgedehnte Bereiche der Neuronenzellkörper sind nicht umhüllt. Außerdem wurde ein dritter Gliazelltyp im Neuropil gefunden.Die äußere corticale Gliaschicht, Perineurium genannt, liegt unter der extrazellulären Scheide und überdeckt die Neuronen teilweise. In Gebieten, in denen Neuronenzellkörper fehlen, überlagert das Perineurium eine zweite Gliazellschicht, das Subperineurium. Diese Schicht kann sich ins Innere des Ganglions erstrecken, falls sie auf eine Neuronenzellkörpergruppe stößt. Das Subperineurium trägt sowohl zur Umhüllung der Neuronenzellkörper, als auch der Nervenfasern bei. Es steht in direktem Zusammenhang mit Gliazellen aus dem Inneren des Neuropils.Das Neuropil umfaßt Nervenfasern und Gliazellen und umgibt den ösophagealen Kanal, welcher vom Perineurium und Subperineurium gebildet wird. Hüllenlose Nervenfasern treten in drei Arten miteinander in Verbindung, durch Endknöpfe, Längs- und Querkontakte.

Sensory Receptors in Ticks and Mites

Sensory receptors in Acari are poorly known although extensive research has been reported on other Arthropoda, particularly Insecta. Our investigations of the setae on the first tarsus of the hard ticks, Amblyomma americanum (L.) and Haemaphysalis (Alloceraea) inermis Birula revealed the presence of chemo- and mechanoreceptors, judging from ultrastructural characteristics. A consistent pattern of distribution of tarsal sensilla in the region of Haller’s organ was observed, by scanning electron microscopy (SEM), in the different species and life stages. Presumably chemoreceptive sensilla, resembling one type in the ticks, were found on the first tarsus of the mesostigmatid mite, Macrocbeles muscaedomesticae (Scopoli).

Ultrastructure of the excretory tubes of the mite Macrocheles muscaedomesticae (Mesostigmata, Macrochelidae) with notes on altered mitochondria

The fine structure of the excretory tubes of the mesostigmatid mite Macrocheles muscaedomesticae were investigated. These paired tubes are partially ensheathed by fat body and invested throughout by a branching system of visceral muscles. The fine structure of the cells of the excretory tube is in general similar with only minor differences found throughout its length. The basal region of each epithelial cell of the excretory tube borders the hemocoel and is divided into many compartments by the extensive infolding of the plasma membrane. Mitochondria and vacuolar inclusions are often closely associated with these compartments. More than one morphological type of mitochondria was found distributed throughout the cells of the excretory tubes. The most commonly encountered type had well developed cristae and an electron dense matrix. Less commonly, mitochondria with somewhat poorly developed cristae and a translucent matrix often containing myelin‐like figures of varying complexity were observed. It is suggested that they represent part of a normal process of mitochondrial degeneration. The apical region of the cell has a border composed of plate‐like folds of the plasma membrane termed microlamellae. The lumen contains abundant granules of the excretory product.