A role for the basal ganglia in nicotinic modulation of the blink reflex

Summary In humans and rats we found that nicotine transiently modifies the blink reflex. For blinks elicited by stimulation of the supraorbital branch of the trigeminal nerve, nicotine decreased the magnitude of the orbicularis oculi electromyogram (OOemg) and increased the latency of only the long-latency (R2) component. For blinks elicited by electrical stimulation of the cornea, nicotine decreased the magnitude and increased the latency of the single component of OOemg response. Since nicotine modified only one component of the supraorbitally elicited blink reflex, nicotine must act primarily on the central nervous system rather than at the muscle. The effects of nicotine could be caused by direct action on lower brainstem interneurons or indirectly by modulating descending systems impinging on blink interneurons. Since precollicular decerebration eliminated nicotine's effects on the blink reflex, nicotine must act through descending systems. Three lines of evidence suggest that nicotine affects the blink reflex through the basal ganglia by causing dopamine release in the striatum. First, stimulation of the substantia nigra mimicked the effects of nicotine on the blink reflex. Second, haloperidol, a dopamine (D₂) receptor antagonist, blocked the effect of nicotine on the blink reflex. Third, apomorphine, a D₂ receptor agonist, mimicked the effects of nicotine on the blink reflex.     

A new graphical method for determining the affinity constants of monoclonal antibodies to enzymes

A new graphical method is presented for determining the affinity constants of antibodies to enzymes. The method does not require purification of reactants or separation steps at equilibrium. The plot 1/v versus [AT]/V - v) ([AT] = total concentration of antibody binding sites, V = enzyme activity measured in the absence, and v = activity measured in the presence, of antibodies) yields straight lines in the case of simple antibody-enzyme interactions. More complex interaction models show different curve shapes, which can be used for model discrimination as shown by computer simulation studies. The applicability of the method was demonstrated by the determination of the affinity constant of the monoclonal antibody IB 10B8 to alkaline phosphatase of calf intestine. This antibody inhibits enzymic activity completely.     

Bacteremia and urinary tract infection associated with CDC group Vd biovar 2.

A case of urinary tract infection and bacteremia caused by CDC group Vd biovar 2 in a 23-year-old woman with Hodgkin's disease is described. This is the first report of CDC group Vd biovar 2 isolated from a clinical specimen and considered as a pathogen. Detailed antimicrobial susceptibility data are presented.     

Intratympanic injection of sodium arsanilate (atoxyl) solution results in postural changes consistent with changes described for labyrinthectomized rats

Intratympanic injections of sodium arsanilate (atoxyl) have been shown to produce vestibular dysfunction in the rat. Unilateral and bilateral dysfunction can be distinguished by changes in the animals' postures. These changes are consistent with changes described for unilateral or bilateral labyrinthectomized rats. The intratympanic injection technique offers a simple yet effective alternative to labyrinthectomy.     

Sharing neuroimaging studies of human cognition

After more than a decade of collecting large neuroimaging datasets, neuroscientists are now working to archive these studies in publicly accessible databases. In particular, the fMRI Data Center (fMRIDC), a high-performance computing center managed by computer and brain scientists, seeks to catalogue and openly disseminate the data from published fMRI studies to the community. This repository enables experimental validation and allows researchers to combine and examine patterns of brain activity beyond that of any single study. As with some biological databases, early scientific, technical and sociological concerns hindered initial acceptance of the fMRIDC. However, with the continued growth of this and other neuroscience archives, researchers are recognizing the potential of such resources for identifying new knowledge about cognitive and neural activity. Thus, the field of neuroimaging is following the lead of biology and chemistry, mining its accumulating body of knowledge and moving toward a 'discovery science' of brain function.     

Computer-assisted work station timing analysis of instrument labor efficiency

Labor use ratings assigned to instruments by the Workload Recording Method (WRM) do not change with batch size or walk-away time use. The authors evaluated the effect of both on the labor use of the analyzers Paramax B6100 (Baxter Paramax, Irvine, CA) and Ektachem 700 (Eastman Kodak, Rochester, NY) by timing all worked and walk-away intervals on both instruments. Extrapolation of the data to a workload of slightly more than 1.1 million tests showed that reapportionment of tests to various batch sizes caused Paramax-Ektachem labor cost differences to fluctuate between $37,254 and $34,995. When the minimum usable walk-away interval length was varied from 1 to 20 minutes, Ektachem savings over Paramax increased from $8,700 to $61,400. The WRM predicted a constant $29,050 labor cost advantage for Ektachem over Paramax. If other instruments show similar labor use characteristics with respect to batch size and walk-away utility, laboratory managers who do not consider these factors may fail to select the most cost-effective instruments for their laboratories.     

The expression and activity of renal nitric oxide synthase and circulating nitric oxide in polycystic kidney disease rats

Nitric oxide (NO) influences tubular fluid and electrolyte transport, and hence possibly also fluid accumulation in renal cysts. The expression and activity of intrarenal constitutive NO synthase (cNOS) [neuronal NOS, nNOS and endothelial NOS, eNOS] and inducible NOS (iNOS) and plasma nitrite/nitrate (PNOx) concentration were assessed in homozygous Han:SPRD polycystic kidney disease (PKD) rats (cy/cy), heterozygous Han:SPRD PKD rats (cy/+), homozygous normal Han:SPRD littermates (+/+) and Sprague Dawley rats (sd). The results showed: 1) nNOS expression was decreased in proximal tubules and thick ascending limbs of the loop of Henle in cy/cy and cy/+ rats compared to +/+ and sd rats (p<0.05). nNOS was weakly expressed in the epithelium of small cysts and unexpressed in epithelium of large cysts. 2) iNOS expression was increased in proximal tubular epithelial cells in cy/+ rats compared to +/+ rats and sd rats (p<0.01). iNOS expression in cyst epithelium was decreased in cy/+ rats (p<0.05) and absent in cy/cy rats. 3) eNOS expression was similar in the endothelium of intrarenal arteries in all groups. 4) The activity of renal cNOS was decreased in cy/cy and cy/+ rats; the activity of iNOS was decreased only in cy/cy rats, with no significant difference among the other three groups. 5) PNOx concentration was higher in cy/cy rats than in the other three groups, and correlated positively with plasma creatinine and urea. In conclusion, NOS expression and activity decreased as cysts developed, suggesting that NO downregulation is involved in the pathogenesis of PKD.     

Serratia plymuthica sepsis associated with infection of central venous catheter.

Serratia plymuthica was isolated from the blood and from a central venous catheter tip in a 54-year-old man with alcoholic cirrhosis and clinical signs of sepsis. This was the seventh reported isolate of S. plymuthica from a clinical specimen and the first in which the organism was clearly a significant pathogen.