Safety evaluation of nuclear polyhedrosis virus replication in pigs

To evaluate the hygienic risk involved in using baculoviruses for insect pest control, safety studies are required. Pigs were chosen as representative test animals of commercial and agricultural importance. The tests were aimed at detecting virus propagation, immune reactions, and signs of acute infection (changes in body temperature and hematology profile, swelling of lymph nodes). Four of five animals inoculated with nuclear polyhedrosis virus showed a slight temperature rise at day 2 postinfection. After day 4 postinfection, no differences between infected animals and controls were observed. In the bioassay, virus activity could be recovered from fecal samples; however, no activity was found in organ extracts. The data did not indicate hygienic risks involved in the application of nuclear polyhedrosis virus, especially that from Mamestra brassicae, in biological pest control.     

Diphtheria toxin-receptor interaction: A polyphosphate-insensitive diphtheria toxin-binding domain

Inositol hexaphosphate, and other polyphosphates, inhibit diphtheria toxin-mediated cytotoxicity by binding to the toxin at a highly cationic site called the P site and preventing toxin binding to cell surface receptors. The binding of diphtheria toxin to a solubilized cell surface glycoprotein (150,000 daltons) is also inhibited by these polyphosphates. Treatment of this 150,000 dalton diphtheria toxin-binding cell surface glycoprotein with papain yielded an 88,000 dalton and a 74,000 dalton diphtheria toxin-binding glycoprotein whose binding to toxin was no longer inhibited by inositol hexaphosphate. This result suggests a model of diphtheria toxin-receptor interaction in which the toxin receptor possesses one binding site which interacts with the P site of the toxin in a $\text{polyphosphate-sensitive}$ fashion, and another binding site (located within the papain-derived 74,000–88,000 dalton glycoproteins) which can interact with the toxin at a site distinct from the P site (the X site) in a $\text{polyphosphate-insensitive}$ fashion. This X site-receptor interaction may be involved in the binding of CRM proteins that bind to the toxin receptor but that do not bind polyphosphates, or it may be involved in the entry process of the toxin.     

Ganglioside modulation of neural cell adhesion molecule and N-cadherin- dependent neurite outgrowth

We have used monolayers of control 3T3 cells and 3T3 cells expressing transfected human neural cell adhesion molecule (NCAM) or chick N-cadherin as a culture substrate for PC12 cells. NCAM and N-cadherin in the monolayer directly promote neurite outgrowth from PC12 cells via a G-protein-dependent activation of neuronal calcium channels. In the present study we show that ganglioside GM1 does not directly activate this pathway in PC12 cells. However, the presence of GM1 (12.5-100 micrograms/ml) in the co-culture was associated with a potentiation of NCAM and N-cadherin-dependent neurite outgrowth. Treatment of PC12 cells with GM1 (100 micrograms/ml) for 90 min led to trypsin-stable increases in both beta-cholera toxin binding to PC12 cells and an enhanced neurite outgrowth response to N-cadherin. The ganglioside response could be fully inhibited by treatment with pertussis toxin. These data are consistent with exogenous gangliosides enhancing neuritic growth by promoting cell adhesion molecule-induced calcium influx into neurons.     

Inactivation of coliphage MS-2 and poliovirus by copper, silver, and chlorine.

The efficacy of electrolytically generated copper and silver ions (400 and 40 micrograms/L, respectively) was evaluated separately and in combination with free chlorine (0.2 and 0.3 mg/L) for the inactivation of coliphage MS-2 and poliovirus type 1 in water at pH 7.3. The inactivation rate was calculated as log10 reduction/min: k = -(log10 Ct/C0)/t. The inactivation of both viruses was at least 100 times slower in water containing 400 and 40 micrograms/L copper and silver, respectively (k = 0.023 and 0.0006 for MS-2 and poliovirus, respectively), compared with water containing 0.3 mg/L free chlorine (k = 4.88 and 0.036). Significant increases in the inactivation rates of both viruses were observed in test systems containing 400 and 40 micrograms/L copper and silver, respectively, with 0.3 mg/L free chlorine when compared with the water systems containing either metals or free chlorine alone. Poliovirus was approximately 10 times more resistant to the disinfectants than coliphage MS-2. This observation suggests either a synergistic or an additive effect between the metals and chlorine for inactivation of enteric viruses. Use of copper and silver ions in water systems currently used in swimming pools and spas may provide an alternative to high levels of chlorination.     

Neuroethology of olfactory preference development

Young mammals come to approach the odor of their mother, a response that facilitates their survival during early life. Young rats induce a cascade of events in their mother to induce the emission of her odor. The pups increase circulating prolactin levels, which increases food intake and the emission of large quantities of cecotrophe containing the maternal odor. This odor is synthesized by the action of cecal microorganisms and changes with maternal diet. The diet-dependence of the odor requires the pups to acquire their attraction to the odor postnatally. The acquisition of this preference occurs when an odor is paired with the tactile stimulation that pups receive during maternal care. The action of the tactile stimulation appears to be mediated by noradrenaline. The development of this type of olfactory attraction is accompanied by changes in the regions of the olfactory bulb that are responsive to the attractive odor. Metabolic, anatomical, and neurophysiological changes in response to the attractive odor emerge in such regions of the bulb after early olfactory preference training. © 1992 John Wiley & Sons, Inc.     

A new concept of fibrin formation based upon the linear growth of interlacing and branching polymers and molecular alignment into interlocked single-stranded segments

In a previous electron microscopic study of early fibrin polymers processed by freeze drying and rotatory shadowing, a large proportion of loosely constructed, frequently branching linear molecular chains was observed; their structural organization was inconsistent with a half-staggered double-stranded model for fibrin polymerization. These conflicting results prompted us to investigate the structure of early fibrin polymers prepared according to a large variety of methods currently used for electron microscopy of macromolecules. By use of a systematic random sampling procedure, fibrin polymers were photographically recorded. They were classified according to their morphological form, and the frequency of occurrence of each configuration was determined. Half-staggered double-stranded forms accounted for less than 1% of all types encountered. Interpretation of the structural organization manifested in the diverse polymer forms observed necessitated the construction of a new interlocked single-strand model for fibrin polymerization. The fibrin polymerization process combines simultaneous propagation of linear growth, branching, and lateral interlocking (leading to lateral association), resulting in the rapid formation of a fibrin network. The structural pattern developing during growth of fibrin polymers appears to be determined principally by the enzymatic mechanism and not solely by the intrinsic molecular structure of fibrinogen. The validity of the interlocked single-strand model was tested by selective fibrinopeptide-B-releasing experiments. Under such activation conditions, the polymer forms predicted according to this and the half-staggered double-strand models should differ; the structures observed were indeed consistent with the interlocked single-strand hypothesis. The compatibility of existing data with this model is discussed.     

Cooperative interaction of reduced pyridine nucleotides with estrogen synthetase of human placental microsomes

The estrogen synthetase present in human placental microsomes appears to be dependent on the cooperative interaction of the reduced cofactors NADPH and NADH for optimal activity. Using steady-state concentrations of either cofactor, it was found that while the estrogen synthetase activity followed hyperbolic saturation kinetics with NADPH (K_mapp = 14 μM), the enzyme followed sigmoidal saturation kinetics when the cofactor was NADH, with the half-maximum velocity attained at a cofactor concentration of 1.1 mm. The maximum velocity obtained with NADPH as the cofactor was greater than with corresponding concentrations of NADH. Estrogen synthetase activity in the presence of NADH was not due to NADPH contamination. NADH, in the presence of small concentrations of NADPH (0.5 to 5 μm), stimulated significantly the rate of estrogen formation from androstenedione by placental microsomes and, in addition, the enzyme saturation kinetics changed from sigmoidal to hyperbolic, thus mimicking the effect of NADPH. Estrogen synthetase activity, measured in the presence of 1 mm NADH, was stimulated in a dose-dependent manner by NADPH (K_mapp = 0.4 μM NADPH) and, when the enzyme was measured in the presence of 5 μm NADPH, the activity was stimulated in a dose-dependent manner by NADH (K_mapp = 45 μM NADH). Estrogen synthetase activity measured in the presence of NADH, without and with NADPH (1 μm) remained linear both with time of incubation for approximately 15 min and with microsomal protein concentration up to 3 mg/ml. The apparent K_m of estrogen synthetase for androstenedione, when measured in the presence of NADH, was 1 μm. The synergistic interaction between NADH and NADPH in stimulating placental estrogen synthetase activity observed in vitro may, conceivably, take place in vivo in the intact placenta.     

Reduction in Brain Glucose Utilization Rate after Tryptophol (3-Indole Ethanol) Treatment

Abstract: 3-Indole ethanol has been recently identified as the hypnotic agent in trypanosomal sleeping sickness, and because it is formed in vivo after ethanol or disulfiram treatment, it is also associated with the study of alcoholism. When administered intraperitoneally to rats (250 mg/kg) tryptophol induced a sleep-like state that lasted less than an hour (no righting reflex was apparent 2 min after injection, but it returned at 11 min in bovine serum albumin solution, and 47 min in 40% ethanol solution). In ethanol solutions, tryptophol reduced brain cortical glucose utilization by 55% to the basal brain metabolic rate, and this effect lasted less than 1 h. Synergistic effects of tryptophol and ethanol were suggested by the observation that in albumin solution, tryptophol reduced brain glucose utilization by 35%, but a normal rate was not observed until 2 h postinjection.