Analysis of postinspiratory activity of phrenic motoneurons with chemical and vagal reflexes

We examined the effects of chemical and reflex drives on the postinspiratory inspiratory activity (PIIA) of phrenic motoneurons using a single-fiber technique. Action potentials from "single" fibers were recorded from the C5 phrenic root together with contralateral mass phrenic activity (also from C5) in anesthetized, paralyzed, and artificially ventilated cats with intact vagus and carotid sinus nerves. Nerve fibers were classified as "early" or "late" based on their onset of discharge in relation to mass phrenic activity during hyperoxic ventilation. Only the early fibers displayed PIIA but not the late fibers, even when their activity began earlier in inspiration with increased chemical drives. Isocapnic hypoxia increased, whereas hyperoxic hypercapnia shortened the duration of PIIA. Pulmonary stretch and "irritant" receptors inhibited PIIA. Hypercapnia and stimulation of peripheral chemoreceptors by lobeline excited both early and late units to the same extent, but hypoxic ventilation had a less marked excitatory effect on late fiber activity. Irritant receptor activation increased the activity of early more than late fibers. Hyperoxic hyperventilation eliminated late phrenic fiber activity, whereas early fibers became tonically active. Bilateral vagotomy abolished this sustained discharge in eight of nine early units, suggesting the importance of vagal afferents in producing tonic firing during hyperventilation. These results suggest that early and late phrenic fibers have different responses to chemical stimuli and to vagally mediated reflexes; late units do not discharge in postinspiratory period, whereas early fibers do; the PIIA is not affected in the same way by various chemical and vagal inputs; and early units that exhibit PIIA display tonic activity with hyperoxic hypocapnia.     

Role of mixed-function amine oxidase in N-hydroxylation of 2-acetamidofluorene by hamster liver microsomal preparations (Short Communication)

Pretreatment of hamsters with 3-methylcholanthrene (100mg/kg body wt.) 24h before death did not appreciably change the extent of N-oxide formation when hepatic microsomal preparations were incubated with NN-dimethylaniline as substrate. In contrast, the N-hydroxylation of 2-acetamidofluorene was increased severalfold in hepatic microsomal preparations from pretreated animals. Under these conditions there were no appreciable changes in cytochrome P-450 content and NADPH-cytochrome c reductase activity. On the basis of these comparative data, it is suggested that amine oxidase is not involved in N-hydroxylation of 2-acetamidofluorene.     

Ripening tomatoes: Ethylene,oxygen, and light treatments

Tomato fruit (Lycopersicon esculentum Mill. var. V. R. Moscow) harvested at the mature green stage were ripened by treatments with ethylene, oxygen, and oxygen plus ethylene. Treatments were made under dark and light conditions. Ethylene increased the ripening and respiration rates of the tomatoes. The fruit treated with ethylene had a general increase in beta carotene and lycopene when compared with untreated controls. The per cent acid was variable from year to year in the fruit treated with ethylene. The fruit ripened in ethylene had higher concentrations of citric acid than did the untreated controls. Treatments with oxygen decreased the reducing sugars and at the high concentrations used, had no effect on the rate of lycopene synthesis. Light treatments increased the per cent acid, reducing sugars, and color of the ripened fruit. The increase in color was related to an increase in both beta carotene and lycopene. Light treatment seemed to decrease the respiration rate of the fruit not treated with ethylene. Studies usingC¹⁴O₂ showed that this may be due to utilization of CO₂ evolved from respiration by the green fruit in photosynthesis.     

Conformational changes in pennisetin using intrinsic fluorescence spectroscopy

Fluorescence spectra of native pennisetin resulted in a single emission peak at 335 nm at excitation wavelength of 274 and 295 nm with quantum yield values for tyrosine and tryptophan as 0.086 and 0.097, respectively. These results indicate the presence of tryptophan residues in a polar environment and quenching of tyrosine residues in the native state of pennisetin. In the presence of an increasing concentration of guanidine hydrochloride (Gdn · HCl), changes such as red shift in emission peak from 335 to 344 nm, decrease in relative fluorescence intensity and increase in quantum yield value were observed, suggesting unfolding of the pennisetin molecule during denaturation. The quenching of tryptophanyl fluorescence by acrylamide and iodide further showed the presence of a single kind of tryptophanyl residue and its polar environment in pennisetin molecule.     

Role of substance P in hypercapnic excitation of carotid chemoreceptors

Experiments were performed on 17 anesthetized, paralyzed, and artificially ventilated cats to evaluate the importance of substance P-like peptide (SP) on the carotid body responses to CO2. Single or paucifiber carotid chemoreceptor activity was recorded from the peripheral end of the cut carotid sinus nerve. In eight of the cats the influence of SP on hyperoxic hypercapnic responses was studied. While the animals breathed 100% O2, intracarotid infusion of SP (1 microgram.kg-1.min-1, 3 min) increased chemoreceptor activity by +4.8 +/- 0.3 impulses/s. After SP infusion, inhalation of CO2 in O2 caused a rapid increase in activity that reached a peak and then adapted to a lower level, whereas similar levels of CO2 before SP caused only a gradual increase in carotid body discharge rate without any overshoot in response. Furthermore SP significantly increased the magnitude and slope of the CO2 response. In the other nine cats the effect of intracarotid infusion of an SP antagonist, [D-Pro2,D-Trp7,9] SP (10-15 micrograms.kg-1.min-1), on carotid body responses to 1) hyperoxic hypercapnia (7% CO2-93% O2), 2) isocapnic hypoxia (11% O2-89% N2), and 3) hypoxic hypercapnia (11% O2-7% CO2-82% N2) was examined. SP antagonist had no effect on carotid body response to hyperoxic hypercapnia but significantly attenuated the chemoreceptor excitation caused by isocapnic hypoxia and hypoxic hypercapnia. These results suggest that 1) SP may play an important role in carotid body responses to hypoxia but not to CO2, and 2) the mechanisms of stimulation of the carotid body by hypercapnia and by hypoxia differ.     

Epstein-Barr virus-transformed lymphocytes produce monoclonal autoantibodies that react with antigens in multiple organs.

Peripheral blood lymphocytes from normal individuals and patients with autoimmune abnormalities such as insulin-dependent diabetes mellitus and thyroiditis were infected with Epstein-Barr virus, and the culture supernatants were tested for autoantibodies that reacted with normal tissues. Between 58 and 86% of Epstein-Barr virus-transformed cultures produced immunoglobulin M antibodies, and between 9 and 24% of the transformed cultures produced immunoglobulin G antibodies that reacted with normal tissues. Ten Epstein-Barr virus-transformed clones secreting human immunoglobulin M monoclonal autoantibodies were isolated. Four of these monoclonal autoantibodies were studied in depth and found to react with antigens in multiple organs, including thyroid, pancreas, stomach, smooth muscle, and nerves. It is concluded that Epstein-Barr virus can trigger the production of autoantibodies without infecting the target cells to which the autoantibodies are directed.     

Revision of Gangesia (Cestoda: Proteocephalidea) in the Indomalayan Region: Morphology,Molecules and Surface Ultrastructure

Tapeworms of Gangesia Woodland, 1924 (Cestoda: Proteocephalidea) parasitic in freshwater fishes in the Indomalayan Region were critically reviewed. Evaluation of type specimens and newly collected materials from Bangladesh, Cambodia and India, as well as critical examination of extensive literature have shown that only the following four species, instead of 48 nominal species of Gangesia and Silurotaenia Nybelin, 1942 reported from this region (36 new synonymies proposed), are valid: Gangesia bengalensis (Southwell, 1913), type-species of the genus and most common parasite of Wallago attu (Siluridae), G. macrones Woodland, 1924 typical of Sperata seenghala (Bagridae), both species characterized by the possession of two circles of hooks on the rostellum-like organ and several rows of hooklets on the anterior margins of suckers; G. agraensis Verma, 1928 from W. attu (typical host), which has the scolex with only one circle of hooks and 1–3 incomplete rows of tiny hooklets on the suckers; and G. vachai (Gupta and Parmar, 1988) n. comb. from several catfishes, which possesses 4–6 circles of hooks and 5–11 rows of hooklets on the anterior half of suckers. Scolex morphology, including surface ultrastructure (microtriches), of all but one species (G. vachai) is described for the first time using scanning electron microscopy. A phylogenetic analysis based on the partial sequences encoding the large nuclear ribosomal subunit RNA gene has shown that three Indomalayan species, namely G. bengalensis, G. macrones and G. vachai, form a monophyletic group within Gangesia, whereas G. agraensis tends to form a clade with the Palaearctic species of the genus. A table with differential characters of all species from the Indomalayan Region is also provided together with a key to identification of genera of the subfamily Gangesiinae. The present study demonstrates that species of Silurotaenia do not occur in the Indomalayan region.     

EFFECTS OF S-TRIAZINES ON PROTEIN AND FINE STRUCTURE OF COTYLEDONS OF BUSH BEANS

A significant increase in protein content of bean cotyledons resulted by applications of 0.5 ppm of atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine), simazine [2-chloro-4,6-bis(ethylamino)-s-triazine], terbutryn (2-methylmercapto-4-ethylamino-6-isobutylamino-.s-triazine), or GS-14254 (2-methoxy-4-isopropylamino-6-butylamino-s-triazine) to the foliage of 5-6 week old bean plants grown in a controlled environment or field conditions. Aen electron microscopic study indicated that in the cotyledonary cells s-triazines inducd a 2-fold increase in the number of cisternae of rough endoplasmic reticulum. These treatments also increased the number of vesicles, which apparently contain protein, and the amount of cytoplasmic ribosomes.