A comparison of micropuncture and lithium clearance methods in the assessment of renal tubular function in rats with diabetes insipidus

The lithium clearance technique has been proposed as a non-invasive method whereby fluid delivery from the pars recta and pars convoluta of proximal tubules can be measured as C_Li and C_IN [0.78 C_Li/C_IN+0.22], respectively [12], C_Li being the clearance of lithium and C_IN that of inulin. In the present study, fluid delivery from proximal tubules was estimated simultaneously by micropuncture and lithium clearance techniques in anaesthetized Brattleboro rats with diabetes insipidus, under control conditions and following chronic treatment with hydrochlorothiazide. Absolute deliveries from the proximal convoluted tubules as determined by the micropuncture and lithium clearance methods were 437 and 427 μl/min, respectively, in untreated animals and 348 and 355 μl/min, respectively, in thiazide-treated animals. The individual results obtained by the two methods showed a high degree of correlation (r=0.85,P<0.001). In untreated Brattleboro rats, proximal fluid delivery as estimated by both the micropuncture and lithium clearance techniques showed significant (P<0.001) correlations with urine flow rate. These results provide further evidence for the acceptance of lithium clearance as a valid estimate of proximal tubular fluid delivery.     

Antibody to Mycoplasma pneumoniae in Nasal Secretions and Sputa of Experimentally Infected Human Volunteers

After experimental infection with Mycoplasma pneumoniae, 42% of 67 volunteers developed a threefold or greater rise in antibody in nasal secretions as measured by radioimmunoprecipitation. Development of an antibody increase in sputum was detected more often, i.e., in 73% of the volunteers. Each of the antibody increases involved immunoglobulin (Ig) A. Twelve rises in IgG antibody were detected in the specimens which exhibited a rise in IgA antibody. In almost every instance the rise in IgA antibody exceeded that seen with IgG antibody. Analysis of the response to experimental challenge with M. pneumoniae of volunteers with different levels of preexisting respiratory tract IgA antibody suggested that this secretory antibody was related to host resistance to M. pneumoniae disease. Further, respiratory tract IgA antibody appeared to be more directly related to host resistance than was antibody in serum.     

THE INTERACTION OF RESPONSES IN THE BRAIN TO SEMANTIC STIMULI

Long time-constant EEG recording during paired stimuli has led to the discovery of the contingent negative variation or expectancy wave (Walter, 1964). This effect is produced when a conditional stimulus signals that an imperative stimulus demanding action, decision, or attention will follow at a short, constant time interval. Symbolic and meaningful stimuli were presented to subjects tachistoscopically, and the evoked responses in the brain were electronically averaged. The cerebral evoked responses to such psychological stimuli are more complex than to flashes. A slow negative DC potential shift (CNV) was seen during the interval between an auditory ready signal and the visual exposure if recognition of the stimulus was required, or if it was interesting. Following the visual exposure, a slow positive DC shift occurred. The method has been developed to study the brain responses to psychological stimuli. The amplitude of the responses relates to the information content and subjective factors rather than to the physical strength of the stimulus.     

Placental pathologic changes in malaria. A histologic and ultrastructural study.

Placenta malarial changes (PMCs) related to maternal plasmodium infection were present in 33% (247 cases) of a series of 741 placentas collected from an unselected population living in an area of high malarial endemicity (Haut-Ogooué, Gabon, Africa). Plasmodia were found on material thick blood films taken at the time of delivery in 42% of the women with and 24% of women without associated PMCs. Plasmodium falciparum was the most frequent infecting organism. PMCs were more frequent and, in general, more marked in primiparas. The primiparas were significantly (P less than 0.001) more numerous in the group with PMCs than in the control group without such changes. The mean weight of term placentas with malarial changes was significantly (46 g; P less than 0.001) less than that of placentas without such changes. The morphologic changes were a combination of the following features: 1) presence of parasites in the intervillous spaces; 2) macrophage concentration in the intervillous spaces; 3) malarial pigment deposits; 4) excess of perivillous fibrinoid deposits; 5) syncytiotrophoblastic damage; and 6) trophoblastic basal lamina thickening. Plasmodia were found in placental intervillous spaces in 42% (105/247). Local parasitemia varied in magnitude; in a few cases, 30% or more of the maternal erythrocytes were infected. Macrophage concentration in the intervillous spaces was present in 29% (72/247) and was always associated with local parasitemia. Macrophages phagocytized red blood cells and malarial pigment, and their number varied inversely with that of the local parasites. It seems, therefore, that macrophages play an important role in local parasite clearance. Malarial brown pigment was observed in all cases from the series. It had characteristic ultrastructural features and occurred in perivillous deposits of fibrinoid, in macrophages, or free in intervillous spaces. Excessive perivillous fibrinoid deposits were a constant histologic finding and were usually associated with syncytiotrophoblastic necrosis or ultrastructural damage such as partial microvilli loss, filamentous material accumulation in intracytoplasmic vacuoles, and "podocytelike" cytoplasmic projections on the basal surface. At these sites the trophoblastic basal lamina was usually thickened. Previously reported morphologic data and our own findings suggest that the peculiar placental changes in malaria, restricted to intervillous spaces and to villous surfaces, may be related to an immunopathologic process.     

An efficient method to generate chromosomal rearrangements by targeted DNA double-strand breaks in Drosophila melanogaster

Homologous recombination (HR) is an indispensable tool to modify the genome of yeast and mammals. More recently HR is also being used for gene targeting in Drosophila. Here we show that HR can be used efficiently to engineer chromosomal rearrangements such as pericentric and paracentric inversions and translocations in Drosophila. Two chromosomal double-strand breaks (DSBs), introduced by the rare-cutting I-SceI endonuclease on two different mobile elements sharing homologous sequences, are sufficient to promote rearrangements at a frequency of 1% to 4%. Such rearrangements, once generated by HR, can be reverted by Cre recombinase. However, Cre-mediated recombination efficiency drops with increasing distance between recombination sites, unlike HR. We therefore speculate that physical constraints on chromosomal movement are modulated during DSB repair, to facilitate the homology search throughout the genome.     

Cyst-like cerebral lesions in tuberous sclerosis

Known brain manifestations of tuberous sclerosis (TSC) are cortical sclerotic tubera, giant cell astrocytomas, subependymal calcified nodules in the lateral walls of the lateral ventricles, and white matter heterotopias. In addition, small cyst-like lesions in the white matter have been described. We report on three TSC patients with hitherto undescribed large cyst-like cerebral lesions in subcortical and white matter locations. We emphasize that cystoid brain degeneration is a rare but typical cerebral manifestation of TSC and suggest that, in patients with such lesions, TSC should be taken into consideration.     

Enhanced responsiveness of human extravisual areas to photic stimulation in patients with severely reduced vision

Lesions in the primary visual cortex induce severe loss of visual perception. Depending on the size of the lesion, the visual field might be affected by small scotomas, hemianopia, or complete loss of vision (cortical blindness). In many cases, the whole visual field of the patient is affected by the lesion, but diffuse light-dark discrimination remains (residual rudimentary vision, RRV). In other cases, a sparing of a few degrees can be found (severely reduced vision, SRV).In a follow-up study, we mapped visually induced cerebral activation of three subjects with SRV using functional magnetic resonance imaging. We were especially interested in the visual areas that would be activated if subjects could perceive the stimulus consciously although information flow from V1 to higher visual areas was strongly reduced or virtually absent. Because subjects were only able to discriminate strong light from darkness, we used goggles flashing intense red light at a frequency of 3 Hz for full visual field stimulation. Besides reduced activation in V1, we found activation in the parietal cortex, the frontal eye fields (FEF), and the supplementary eye fields (SEF). In all patients, FEF activation was pronounced in the right hemisphere. These patterns were never seen in healthy volunteers. In a patient who recovered completely, we observed that extrastriate activation disappeared in parallel with the visual field restitution. This result suggests that damage to the primary visual cortex changes the responsiveness of parietal and extravisual frontal areas in patients with SRV. This unexpected result might be explained by increased stimulus-related activation of attention-related networks.     

Domains of simian virus 40 large T-antigen exposed on the cell surface

The orientation of SV40 large T on the surface of SV40-transformed mouse cells and of human cells infected with nondefective adenovirus 2 SV40 hybrid viruses has been studied. Using antibodies against a synthetic peptide corresponding to a region of 11 amino acids at the carboxyterminus of large T, the surface of formaldehyde-fixed SV40-transformed cells could be specifically stained by indirect immune fluorescence. Staining was inhibited by an excess of the peptide. These data suggest that the carboxyterminus of large T is exposed on the surface of formaldehyde-fixed cells. Antibodies against the carboxyterminus of large T also stained the surface of cells infected with the hybrid viruses Ad2⁺ND1, Ad2⁺ND2, and Ad2⁺ND4. Thus, the carboxytermini of the SV40-specific proteins synthesized in hybrid virus-infected cells are also exposed on the cell surface. When analyzed with an antiserum against purified denatured large T, which among many other determinants also recognizes the large T carboxyterminus, surface fluorescence was observed in cells infected by all three hybridviruses. The surface fluorescence of Ad2⁺ND1-infected cells, expressing an SV40-specific protein of 28 K, and Ad2⁺ND2-infected cells expressing SV40-specific proteins of 42 K and 56 K molecular weight, was completely inhibited by carboxyterminal peptide. However, the surface fluorescence of Ad2⁺ND4-infected cells, expressing SV40-specific proteins up to nearly full size large T, was unaffected by carboxyterminal peptide. Our data suggest that a major portion of large T, located between a region near the carboxyterminus and a region corresponding to the aminoterminus of the 56 K protein, is not exposed on the surface of hybridvirus-infected cells. However, some parts of the aminoterminal one-third of large T appear to be exposed again. We conclude that SV40 large T on the surface of SV40-transformed cells is oriented in a specific manner, suggesting that it is specifically associated with the plasma membrane.     

A Developmental Event-Related Potential Study of Picture Matching in Children, Adolescents, and Young Adults: A Replication and Extension

Event-related potentials were recorded in a developmental study of picture matching using an adaptation of Posner's (1978) letter-matching tasks. Subjects ranging in age from 6-39 were asked to decide whether two line drawings, presented sequentially, were the same or different on the basis of physical (physical identity), nominal (name identity), or categorical (category identity) criteria. The amplitude of a negativity at 400 ms (Neg400) increased as the number of dimensions on which the two line drawings differed increased. This effect held for all age groups, and was interpreted as reflecting the degree of semantic and/or physical relationship between the two pictures. However, one finding for Neg400 did suggest a qualitative difference in processing mode between the younger and older subjects. Both Neg400 and P3b latencies showed highly significant linear age trends, decreasing with increasing age. These age-related changes were interpreted as demonstrating quantitative speed of processing differences among age groups. The latencies of both Neg400 and P3b increased as the matching criteria became more complex. Moreover, P3b latency increased as the number of dimensions on which the two pictures differed increased, and this did not interact with age. Although both Neg400 and P3b showed age-related changes in scalp distribution, the fact that each was related to the experimental variables in similar fashion in all age groups suggested that they were homologous components across the age range studied. Taken as a whole, the data support continuity of information processing during these tasks across a wide age range.