The postnatal development of geniculocortical axon arbors in owl monkeys

To characterize the postnatal development of geniculocortical axon arbor morphology in owl monkeys at a series of ages from birth to adulthood, individual arbors were bulk-filled with HRP in brain slice preparations and were reconstructed from serial sections. At all ages, cortical layers and sublayers were obvious. Presumed M or magnocellular arbors were largely confined to layer IV alpha, but they also extended into layer IIIc (IVB of Brodmann, 1909); presumed P or parvocellular arbors were almost exclusively confined to layer IV beta. Other axons that may reflect feedback projections from MT terminated in layer IIIc. Overall, M axon arbors increased in size and complexity from birth to adulthood with mean surface-view arbor areas ranging from 0.08 +/- 0.01 mm2 in newborns to 0.24 +/- 0.02 mm2 in adults. The developing P arbor areas were, on average, as large or larger than adult (newborn = 0.07 +/- 0.01 mm2, adult = 0.047 +/- 0.01 mm2; n.s.) but the arbors were somewhat less complex. Since the brain and area 17 increase in size postnatally, the proportion of area 17 subserved by each P arbor would decrease in postnatal development. Terminal boutons with immature features were evident in both M and P populations at all developmental ages. The results indicate that, while both LGN axon types in monkeys undergo morphological changes postnatally, M arbors appear to mature by increasing arbor size and terminal branching complexity, whereas P arbors increase in complexity but not in size. These distinct programs of axon arbor development suggest that the periods of susceptibility of geniculocortical axon arbors to postnatal influences of the environment, and the types of plastic responses they potentially exhibit, are class-specific.     

Gallbladder wall thickening in dengue hemorrhagic fever: an ultrasonographic study

This study attempts to investigate whether gallbladder wall thickening (GBWT) measured by ultrasonography can be used in children as a reliable criterion to predict the onset of severe dengue hemorrhage fever (DHF). In this prospective study, we performed ultrasound examinations focusing on the gallbladder wall and the presence of intraperitoneal free fluid in 48 mild DHF cases (grades I-II) and 48 severe cases (grades III-IV). GBWT varied between 1 mm and 8 mm with a mean of 3.77 mm +/- 2.04 mm. The mean value of DHF grades I and II (2.39 mm +/- 1.48 mm) is significantly lower than that of grades III and IV (5.14 mm +/- 1.54 mm), p < 0.001. GBWT exceeded 3 mm in only 16 of 48 (33.3%) grade I-II patients and in 45 of 48 (93.8%) grade III-IV patients. A significant positive correlation was apparent between GBWT and the severity of illness, p < 0.001. Patients with ascites have significantly thicker gallbladder walls than those without, p < 0.01. In clinically confirmed DHF cases, the sonographic finding of GBWT > 3 mm to 5 mm, with 93.8% sensitivity, can be used as a criterion indicating the need for admission and monitoring. A GBWT of > or = 5 mm, with 91.7% specificity, is useful as a criterion for identifying DHF patients at high risk of developing hypovolemic shock.     

Determination of aflatoxin B1 in dried figs by visual screening, thin-layer chromatography and ELISA

Aflatoxin B1-contaminated fruits were sorted out from 250 kg dried figs (five Turkish and three Greek batches) by bright-greenish-yellow fluorescence under UV light. The aflatoxins of the fluorescent figs were extracted by simple soaking in methanol. Aflatoxin B1 was determined by thin-layer chromatography. Parallel to this, an extraction for the determination of aflatoxin B1 was developed by a competitive ELISA and the two methods were compared with each other. In a highly contaminated batch of Turkish figs, statistically there was one fig among 350 which had a high aflatoxin content (greater than 100 ng/g fig) and one fig amongst 140 fruits with an aflatoxin B1 content of greater than 10 ng B1/g fig.     

Acyclovir-resistant chronic cutaneous herpes simplex in Wiskott-Aldrich syndrome

A 28-year-old man with Wiskott-Aldrich syndrome presented with ulcerative-proliferative lesions on his face from which herpes simplex type 1 (HSV-1) was isolated. He was initially treated with 10 mg/kg of acyclovir (Zovirax) intravenously every 8 h, but his skin lesions worsened. Clinical resistance to acyclovir was suspected, and therapy with this drug was intensified. The dosage of acyclovir was increased to 45 mg/kg, administered by continuous infusion, and the lesions subsequently resolved. The strain of HSV recovered from the patient showed acyclovir-resistance in vitro, using the colorimetric method with neutral red. Herpes simplex virus resistance to acyclovir is rare. It is more common in immunocompromised patients if subtherapeutic doses are administered in the treatment of chronic persistent forms of infection. Whenever clinical resistance to acyclovir is suspected, the dosage should be increased to 2 mg/kg per h administered via an infusion pump. If no improvement is observed in the patient's condition with this regimen, a phosphorylated medication whose mechanism of action is not dependent on viral thymidine kinase, such as foscarnet (phosphonoformic acid), should be substituted.     

Pharmacokinetic-pharmacodynamic modelling of the anti-lipolytic and anti-ketotic effects of the adenosine A1-receptor agonist N6-(p-sulphophenyl)adenosine in rats

1. The purpose of this study was to develop and validate an integrated pharmacokinetic-pharmacodynamic model for the anti-lipolytic effects of the adenosine A1-receptor agonist N6-(p-sulphophenyl)adenosine (SPA). Tissue selectivity of SPA was investigated by quantification of haemodynamic and anti-lipolytic effects in individual animals. 2. After intravenous infusion of SPA to conscious normotensive Wistar rats, arterial blood samples were drawn for determination of blood SPA concentrations, plasma non-esterified fatty acid (NEFA) and beta-hydroxybutyrate levels. Blood pressure and heart rate were monitored continuously. 3. The relationship between the SPA concentrations and the NEFA lowering effect was described by the indirect suppression model. Administration of SPA at different rates and doses (60 microg kg[-1] in 5 min and 15 min, and 120 microg kg[-1] in 60 min) led to uniform pharmacodynamic parameter estimates. The averaged parameters (mean+/-s.e., n=19) were Emax: -80+/-2% (% change from baseline), EC50: 22+/-2 ng ml(-1), and Hill factor: 2.2+/-0.2. 4. In another group, given 400 microg kg(-1) SPA in 15 min, pharmacodynamic parameters for both heart rate and anti-lipolytic effect were derived within the same animal. The reduction in heart rate was directly related to blood concentration on the basis of the sigmoidal Emax model. SPA inhibited lipolysis at concentrations lower than those required for an effect on heart rate. The EC50 values (mean+/-s.e., n=6) were 131+/-31 ng ml(-1) and 20+/-3 ng ml(-1) for heart rate and NEFA lowering effect, respectively. 5. In conclusion, the relationship between blood SPA concentrations and anti-lipolytic effect was adequately described by the indirect suppression model. For SPA a 6 fold difference in potency was observed between the effects on heart rate and NEFAs, indicating some degree of tissue selectivity in vivo.     

Collinear stimuli regulate visual responses depending on cell's contrast threshold

Neurons in the primary visual cortex are selective for the size, orientation and direction of motion of patterns falling within a restricted region of visual space known as the receptive field. The response to stimuli presented within the receptive field can be facilitated or suppressed by other stimuli falling outside the receptive field which, when presented in isolation, fail to activate the cell. Whether this interaction is facilitative or suppressive depends on the relative orientation of pattern elements inside and outside the receptive field. Here we show that neuronal facilitation preferentially occurs when a near-threshold stimulus inside the receptive field is flanked by higher-contrast, collinear elements located in surrounding regions of visual space. Collinear flanks and orthogonally oriented flanks, however, both act to reduce the response to high-contrast stimuli presented within the receptive field. The observed pattern of facilitation and suppression may be the cellular basis for the observation in humans that the detectability of an oriented pattern is enhanced by collinear flanking elements. Modulation of neuronal responses by stimuli falling outside their receptive fields may thus represent an early neural mechanism for encoding objects and enhancing their perceptual saliency.