Comparison of a quadratic response surface model and a square root model for predicting the growth rate of Yersinia enterocolitic

Polynomial equations, relating the growth rate of Yersinia enterocolitica to temperature (0–25°C) and pH (4.5–6-5) in a liquid medium were constructed for four different acidulants. The logarithm of the time for a 100-fold increase in bacterial numbers could be represented by a quadratic response surface function of pH and temperature. The interactions between pH and temperature on growth rate were found to be additive. Values for a 2 log cycle increase in growth derived from the model were in good agreement with experimental values. Predictions from the quadratic model and from a square root model were compared with experimental values in laboratory media and UHT milk. The mean square error (MSE) for the quadratic response surface model was smaller than that for the square root model in 81% of cases. In UHT milk the square root model increasingly underestimated growth rate, as the temperature decreased and would 'fail dangerous' if used for predictive purposes. This indicated that the response surface model is more reliable for predicting the growth of Y. enterocolitica under conditions of sub-optimal temperature and pH.     

Effect of diisopropylfluorophosphate on muscarinic and gamma-aminobutyric acid receptors in visual cortex of cats.

Administration of diisopropylfluorophosphate (DFP), an organophosphorus (OP) compound, irreversibly inhibits acetylcholinesterase (AChE) and results in cholinergic hyperactivity. This study investigated muscarinic and gamma-aminobutyric acid (GABA) receptor changes in visual cortex of cats following an acute exposure to DFP. A single acute administration of DFP (4 mg/kg) decreased the number of muscarinic receptors at 2, 10, and 20 hours after treatment. GABA receptors were elevated at 2 and 10 hours but returned to within control levels at 20 hours. No significant alteration in muscarinic or GABA receptor affinity was noted. In all cases cortical AChE activity was inhibited 60-90%. These findings show a down regulation of muscarinic receptors after DFP associated with low AChE activity. GABA receptors also are altered, and may be part of a compensatory mechanism to counteract excess cholinergic stimulation.     

Stereoselective effect of morphine on antinociception and endogenous opioid peptide levels in plasma but not cerebrospinal fluid of dogs.

Morphine releases endogenous opioids into the circulation of dogs. To test the stereospecificity of this effect, as well as to determine whether morphine also releases endogenous opioids centrally, which might be involved in its antinociceptive action, the effects of (-)-morphine sulfate (10 mg/kg, sc) or (+)-morphine hydrobromide on antinociception in a dog tail-flick test, on semi-quantified morphine-induced signs of salivation, emesis, defecation and ataxia, and on the plasma and cerebrospinal fluid (CSF) levels of endogenous opioid peptides were studied. Plasma and CSF levels of immunoreactive beta-endorphin (i-BE), met-enkephalin (i-ME), leu-enkephalin (i-LE), and dynorphin (i-DY) were quantified by radioimmunoassay in octadecylsilyl-silica cartridge extracts. Immunoreactive morphine (i-M) levels were measured in unextracted samples. (-)-Morphine treatment significantly increased antinociception, morphine-induced signs, i-M levels in plasma and CSF, and i-BE, i-ME, and i-LE levels in plasma, but not CSF. Levels of i-DY remained constant in plasma and CSF. (+)-Morphine treatment did not alter any of these parameters, indicating that the effects of morphine on nociception, behavioral signs, and plasma endogenous opioids in dogs were stereoselective. It is concluded that morphine does not cause an increase in immunoreactive endogenous opioid peptides in the CSF at the time of its peak antinociceptive effect.     

Induction of high-titer neutralizing antibodies, using hybrid human immunodeficiency virus V3-Ty viruslike particles in a clinically relevant adjuvant.

The localization of neutralization determinants within the envelope glycoproteins of human immunodeficiency virus (HIV) has been largely achieved by immunizing small animals in conjunction with Freund's adjuvant. However, for eventual use in humans, candidate HIV vaccine components must also be efficacious in a nontoxic formulation. We describe here the production of hybrid Ty viruslike particles carrying the major neutralizing domain of HIV and demonstrate the induction of high-titer virus-neutralizing antibodies and an HIV-specific T-cell proliferative response after immunization in conjunction with aluminum hydroxide. As aluminum hydroxide and aluminum phosphate are the only adjuvants currently licensed for use in humans, these observations have implications for the development of an effective vaccine against HIV.     

The influence of adrenal medullectomy on the development of ethanol-induced cardiac hypertrophy

Cardiac hypertrophy was assessed in adrenal medullectomized and sham control rats given ethanol in a liquid diet mixture, intragastrically, in severely intoxicating doses at 8-h intervals for 48 and 96 h. The ethanol treatments produced increases of some 20% in wet and dry proportional heart weights in the control animals, but this rapid development of hypertrophy was less apparent in the medullectomized rats. Hearts of the medullectomized animals given ethanol were heavier than those of pair-matched controls given isocaloric maltose-dextrin in the diet mix. These increases were not statistically significant. The ethanol treatments produced, in addition, equivalent increases in the weight of the adrenal glands of both medullectomized and control animals. Medullectomy was evaluated by analysis of adrenal glands and urine samples for catecholamines. The majority of adrenals from the demedullated group had nondetectable amounts of catecholamines and minimal quantities were found in the remainder. Adrenaline was not detected generally in urine samples from this group. The adrenaline contents of adrenals from sham controls given ethanol were markedly reduced by the ethanol treatments, whereas the quantities in urine were many times greater than those from rats given maltose-dextrin. Urinary noradrenaline levels were increased in both control and medullectomized rats given ethanol. The results of this study identify that adrenal medullary catecholamines participate in the rapid development of cardiac hypertrophy that results from severe, continuing ethanol intoxication in the rat.     

Biochemical differentiation among karyotypic forms of Australian Rattus

Isozyme electrophoresis of up to 55 loci, and microcomplement fixation of albumin were used to assess the extent of structural gene divergence among karyotypic forms of Australian Rattus. The results show that the Australian Rattus are monophyletic with respect to R. rattus or R. norvegicus. Within the Australian Rattus, rates of chromosomal evolution have varied enormously, the highest rates being found among members of the R. sordidus group, where extensive chromosomal repatterning has occurred with little or no structural gene divergence.     

Transitional epithelial zone of the bovine nasal mucosa

To determine the extent and ultrastructure of epithelium lining the transitional nasal mucosa of the neonate, gnotobiotic calf tissues were prepared for scanning and transmission electron microscopy. Stratified cuboid epithelium of the rostral 40% of the nasal cavity contained few ciliated cells; the next caudal 10-15%, although ciliated, had extensive nonciliated areas. The predominant type of surface cell was nonciliated, had short microvilli, and contained a multilobate nucleus and numerous pinocytotic vesicles. In some areas the surface of these cells presented a cobblestone appearance. Basal cells contained numerous bundles of filaments, ribosomes, and basal vesicles. Caudally, nonciliated columnar cells included a cell type similar to the more rostral cuboid cell, as well as brush cells and immature secretory and ciliated cells. Goblet cells were infrequently observed. Intraepithelial nerve terminals were abundant. Other intraepithelial cells, often difficult to identify owing to varying characteristics, included lymphocytes. Based upon comparisons of this neonatal epithelium with mature epithelium, observed in earlier studies of other mammalian species, the transitional mucosa is believed normally to occupy an extensive area of the nasal cavity.     

1-Methyl-4-phenylpyridine (MPP+) induces oxidative stress in the rodent

MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) produces an irreversible parkinsonism in primates. Recent evidence suggests metabolism of MPTP to 1-methyl-4-phenylpyridine (MPP+) is required for toxicity. We have proposed that MPP+ may play a central role in the toxicity of MPTP, but direct assessment of the effects of MPP+ in brain is difficult. Therefore, we have sought to define the mechanism of peripheral MPP+ toxicity in the rat and mouse. Systemically administered MPP+ produced its major pathology in the lung and was typified by perivascular edema. An increase in plasma glutathione disulfide concentrations also resulted, suggesting that MPP+ in analogy to paraquat produces oxidative stress. In addition, the lethality of MPP+ in the mouse was increased by dietary selenium deficiency. These results define in both pathological and chemical terms the potent systemic toxicity of MPP+ and suggest that MPP+, because of its high concentration in primate brain, has the potential to play an important role in the CNS toxicity of MPTP.     

Interferon-gamma modulates protein kinase C activity in murine peritoneal macrophages

The content of Ca2+-, phospholipid-dependent protein kinase activity (protein kinase C) in murine peritoneal macrophages treated with recombinant interferon-gamma (IFN-gamma) has been investigated. Protein kinase C activity was solubilized by nonionic detergent extraction of sonicated cells and separated by high performance liquid chromatography on a TSK 4000 SW gel filtration column. The enzyme eluted from the column in a molecular weight range of 60-80 X 10(3) and was identified by virtue of Ca2+ and phospholipid requirements. Macrophages treated with recombinant IFN-gamma exhibited a substantial increase in total protein kinase activity which could be accounted for entirely by increased protein kinase C activity. This activity was enhanced as much as 5-fold over that seen in untreated macrophages and was specific for IFN-gamma in that other agents known to signal changes in macrophage function had no effect. The time required for the elevation of kinase activity was identical to that required for induction of other functions by IFN-gamma in macrophages. These observations suggest that protein kinase C may be a focus of regulatory action in IFN-gamma-mediated macrophage activation.