Biomedical subjects
Publications and source records attributed to J Pasternak.
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We describe a study of 11-year-old twin sisters who are physically identical in appearance but who have considerably different conscious experiences. One twin appears to be a synaesthete in that she states that she has specific colour experiences (i.e. photisms) whenever she views, hears or thinks of digits. The other twin does not report such conscious experiences when viewing, hearing or thinking about digits. A genotypic analysis using eight microsatellite loci plus the gender of the twins and their parents confirmed that the twins are monozygotic. A phenotypic analysis using a modification of the Stroop task confirmed that only one twin is a synaesthete. We suggest that the discordance in synaesthesia may be due to either an epigenetic event, X chromosome inactivation, or a mutation of a synaesthesia gene.
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S-crystallins are the predominant soluble proteins of the squid lens. Of these, S-III crystallin is the major component and S-I and S-II crystallin are the minor lens components. The lens has a posterior and anterior segment, each derived from separate groups of ectodermal cells referred to as lentigenic cells. In the present study, the appearance of S-crystallins during the development of the lens of Loligo opalescens was followed by immuno-cytochemistry. S-crystallins of the lens and lentigenic cells were first observed at day 17 (Arnold stage 27) of embryogenesis. S-crystallins were not confined to a single region, but were present in the middle group (group 2) of lentigenic cells, the posterior lens primordium, and the processes connecting the lentigenic cells and the posterior lens primordium. Two days later (Arnold stage 28), the S-crystallins were also observed in the anterior group (group 1) of lentigenic cells, the anterior lens primordium, and the processes connecting the cells with the anterior lens primordium. Thus, during development, S-crystallins accumulate first in the posterior lens primordium and subsequently in the anterior lens primordium and their respective lentigenic cells and connecting lentigenic processes. Incubated sections of the adult lens and lentigenic cells also show specific immuno-peroxidase staining when compared with controls. This evidence in combination with a recent investigation (West [1993] Ph.D. dissertation), which indicates that the cephalopod lens continues to grow throughout adulthood, suggests that squid lens crystallins are synthesized during adulthood.
Scabies epidemics are not unusual, and the recommended way of stopping them is by simultaneous treatment of everybody in the facility; this has been known since the last century, when Norwegian scabies was a problem in Norway. When this is not done, scabies epidemics can smolder for months. Scabies should not spread with good infection control measures, but we learned that a good infection control service is not enough. Efforts have to be done to educate everybody in the hospital, including laundry workers, and to improve work conditions.
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The membrane protein CD4 is commonly found on mature T cells specific for antigen in association with class II major histocompatibility complex (MHC; Ia) proteins. This correlation has led to the suggestion that CD4 binds to a monomorphic region of the Ia molecule on the antigen-presenting cell (APC) and functions either by enhancing interaction between the T cell and the APC, or conversely, by transducing negative signals to the T cell. To address this hypothesis, we have made use of sublines from an unusual T hybrid that is class I MHC restricted but also CD4+. By incorporating purified MHC proteins into a planar membrane system, we show that different Ia molecules can greatly enhance the ability of a CD4+ but not a CD4- variant of this class I-restricted T hybrid to respond to isolated class I molecules. T-cell responses can be strongly augmented by the concurrent expression of CD4 on the T cell and any of four different Ia proteins on planar membranes, thus supporting the idea that CD4 binds to a monomorphic region of the Ia molecule and increases the avidity with which the T cell can interact with its target.
Binding of ligand to B-cell membrane immunoglobulin (mIg) can lead to activation of a number of distinct biologic responses, including altered expression of genes encoding c-fos, c-myc, and Ia, as well as proliferation and immunologic tolerance. Tolerance could reflect a functional uncoupling of receptors from systems that generate intracellular second messengers (i.e., receptor desensitization). To better understand the molecular basis of immune regulation, we examined the ability of mIg to function as a signal transducer after the cell's initial contact with mIg-binding ligand. The results show that ligand binding to as little as 2-10% of mIgM or mIgD renders the cell unresponsive to ligand binding to the reciprocal isotype as judged by Ca2+ mobilization and protein kinase C translocation responses. This heterologous receptor desensitization lasts longer than 24 hr and does not reflect loss of receptor from the cell surface. Studies with the calcium ionophore ionomycin, 1,2-dioctanoyl-sn-glycerol, and the protein kinase inhibitor staurosporine indicate that both protein kinase C-dependent and protein kinase C-independent (staurosporine-insensitive) mechanisms mediate heterologous desensitization after mIg crosslinking.
Myopia, as characterized by a large refractive error (e.g. -10.7 +/- 0.4 D), was induced in post-hatch chicks by a 14 day application of a goggle that was designed to blur the retinal image. In comparison to untreated eyes, the treated eye showed significant changes in wet eye weight and both axial and equatorial lengths. However, the lenses of myopic and non-myopic eyes were not significantly different in focal characteristics, light transmittance or total soluble protein content. Thus the lens neither contributes to, nor compensates for the large refractive error observed in experimentally induced myopia.
The proteins of the cuticle of adult Ascaris lumbricoides suum were characterized with respect to heterogeneity, glycosylation, and susceptibility to collagenase. Pepsin digestion of intact cuticles was used to determine the extent of stable triple-helical structures of the cuticular components. With sodium dodecyl sulfate-poly-acrylamide gel electrophoresis, it was shown that treatment of purified cuticles with beta-mercaptoethanol released three components (99, 90, and 68 kDa) which comprise 95% of the total solubilized material. The remaining fraction consists of at least four components (16, 28, 154, and 173 kDa). Periodic acid-Schiff staining showed that the only glycoprotein was the 173-kDa component. All cuticular components, except the 173-kDa protein, were degraded by bacterial collagenase. Pepsin digestion of intact cuticles for 24 hr at 4 C produced, after reduction, a 95-kDa fragment; by 96 hr, four fragments (95, 90, 83, and 77 kDa) were evident. When the 96-hr pepsin digest was treated with fresh pepsin, the 77-kDa fragment became the major constituent. With agarose gel electrophoresis, analysis of non-reduced, pepsin-released material revealed intact aggregates that were greater than 2 X 10(3) kDa. The enzyme digestion studies indicate that, with the exception of the 173-kDa component, each cuticular protein contains collagenous domains and that, within the cuticle, the longest contiguous collagen chain in a triple-helical conformation has a uniform molecular size of 77 kDa.
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The pharmacokinetics of aztreonam were studied in 25 adult patients with hematological malignancies. Two groups of nine patients each received aztreonam (1 or 2 g every 8 h) prophylactically, and seven infected patients received a therapeutic regimen of aztreonam (1.5 g every 4 h). The mean peak serum concentration after a 1-g dose of aztreonam (given over 0.5 h on day 1) was 75.5 micrograms/ml; after a 2-g dose it was 177.2 micrograms/ml. The mean peak serum concentration after a 1.5-g dose of aztreonam (given over 2 h on day 1) was 68.5 micrograms/ml. The serum half-life ranged between 1.7 and 2.0 h for all regimens studied. The urinary concentration of the metabolite of aztreonam, SQ 26,992, increased during 1 week of administration of the drug; however, serum levels of the metabolite were barely detectable.
Bacteremia caused by newly described Campylobacter-like organisms occurred in two immunosuppressed homosexual patients with tuberculosis. Although these organisms grow well in aerobic bottles using a radiometric blood culture system, they are not readily seen in gram-stained smears and are easily missed if routine subculture methods are used. Microscopic examination of wet preparations and subculture to brucella agar base supplemented with 10% sheep blood and incubated in microaerophilic conditions are useful for identification and isolation. The recovery of Campylobacter-like organisms from the blood suggests that these organisms, formerly known only to be associated with proctocolitis or asymptomatic rectal infection in homosexual men, can also cause systemic infection in these patients.
While devising a protocol for the isolation of chick crypt cells infected with Eimeria necatrix, it was observed that infected cells were readily lysed by 0.25% trypsin. Time-course studies at 17 C with 5.5 x 10(5) cells at 96 hr postinfection revealed that 0.001% trypsin effectively lysed greater than 90% of infected cells within 10 min. Uninfected crypt cells were not lysed under these conditions. To determine the site of action of trypsin, the plasma membrane proteins from trypsin-treated and untreated infected cells were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. While the major proteins were unaffected by the trypsin treatment, some minor changes were noted: (1) three components (congruent to 60, congruent to 52, and congruent to 20 KDa) were trypsin sensitive and (2) a new band (congruent to 42 KDa) appeared in the membrane of trypsin-treated infected cells. Previously, it was found that the plasma membrane of infected cells, in contrast to uninfected cells, accumulated gel-phase lipid (J. E. Thompson, M. A. Fernando, and J. Pasternak, Biochimica et Biophysica Acta 555, 472-487, 1979). Here, it was examined whether trypsin would perturb the physical state of the plasma membrane of infected cells. Both X-ray diffraction patterns and transition temperature studies revealed no difference between membranes from untreated and trypsin-treated infected cells. Thus, "trypsin sensitivity" may be a secondary phenomenon that is due primarily to the cellular leakiness that accompanies the accumulation of gel-phase lipid in the plasma membrane of infected cells. The uptake of trypsin may stimulate the release of catabolic enzymes that, consequently, lyse an infected cell.
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