Heat-induced alterations in embryonic cytoskeletal and stress proteins precede somite malformations in rat embryos

Previous work from this laboratory has demonstrated that heat exposure on gestation day 10 (GD10) resulted in disrupted somite development 24 hr after exposure and subsequent thoracic skeletal malformations in neonates. The purpose of the present study was to examine the effects of in vitro heat shock on de novo protein synthesis and on cytoskeletal protein levels in developing rat embryos. Explanted GD10 embryos were exposed to temperatures of 42-42.5 degrees C for 15 min. At various times postexposure (0-27 hr). embryos were labeled with 35S-methionine and processed for sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) separation. Transient enhanced de novo synthesis of 70- and 90-kD proteins was observed 1-8 hr after exposure. The 70-kD protein was identified as a eukaryotic stress protein and the presence of this protein was detected between 2 and 27 hr posttreatment. Western blot analysis was used to detect quantitative changes in total actin (microfilaments), tubulin (microtubules), and vimentin (intermediate filaments). Immediately following exposure, a reduction of total vimentin to minimal detectable levels was observed in heat-treated embryos. Levels of total vimentin remained depressed for more than 2 hr and gradually returned to control levels 4-8 hr postexposure. No change in total actin or tubulin was detected in treated embryos. The data demonstrate that heat-induced alterations in proteins comprising intermediate filaments occur concomitantly with the induction of stress proteins and precede aberrant somite morphology. These alterations in embryonic proteins may help elucidate the mechanism(s) by which skeletal malformations are produced.     

Extemporaneous prescribing module 3

Australian Family Physician is pleased to be able to present a home course in extemporaneous prescribing, an interesting area that is poorly understood by many practitioners, especially recent graduates. Dr Bernard Kelly has been teaching this discipline to Family Medicine Trainees in New South Wales for many years and has written a series of modules to be placed in the journal during 1993. A question is included at the end of each module.     

A computational model of cholinergic disruption of septohippocampal activity in classical eyeblink conditioning

Aspartate-like immunoreactivity was visualized in the neostriatum of rats using indirect immunofluorescence techniques and antibodies raised against aspartate conjugated to keyhole limpet hemocyanine. In normal rats only a few aspartate-positive cell bodies with limited processes were observed. A moderate increase was seen after treatment with (+)methamphetamine and haloperidol. A dramatic increase in the number and fluorescence intensity was observed in the unilaterally 6-hydroxy-dopamine lesioned rats after multiple injections of the D1-dopamine receptor agonist SKF 38393. In these rats strongly fluorescent processes as well as extensive terminal varicose fibre networks were observed. This increase could partly be blocked by the D1-dopamine receptor antagonist SCH 23390. Using a modified technique the aspartate-positive cell bodies and processes were observed even when the antiserum was diluted 1:80,000. Positive cell bodies and fibres were also seen on the ipsilateral side outside the neostriatum, for example in the islet of Calleja and in the piriform cortex. The aspartate-positive cells were negative for dopamine- and cyclic AMP-regulated phosphoprotein-32, a marker for neurons bearing dopamine D1-receptor subtype. A proportion of the aspartate-positive neurons (20%) contained neuropeptide tyrosine-like immunoreactivity. On adjacent sections there was a marked up-regulation of preprodynorphin-like immunoreactivity. The up-regulation of dynorphin and aspartate was only observed when there was an almost complete denervation of the neostriatum as visualized with antiserum to tyrosine hydroxylase, a marker for dopamine fibres. The present results raise the possibility that aspartate may act as a neurotransmitter released from interneurons in the neostriatum.     

Localization of a gene for a glutamate binding subunit of a NMDA receptor (GRINA) to 8q24

De novo acute leukaemia presenting with a mixed lymphoid and myeloid leukaemic population has rarely been described. We have used the consensus Ig heavy chain primers and DNA isolated from these two distinct populations of cells in polymerase chain reactions. We demonstrated that both populations of cells exhibited Ig heavy chain gene rearrangements. Cloning and subsequent DNA sequencing of the amplified products showed a common V-D-J junctional nucleotide sequence. This work therefore provides the first evidence that the leukaemic cells in de novo acute leukaemia with a mixed lymphoid and myeloid population are derived from a common progenitor clone and may offer an explanation for the poor prognosis in these patients.     

Randomized event-related experimental designs allow for extremely rapid presentation rates using functional MRI

Previous studies have shown that hemodynamic response overlap severely limits the maximum presentation rate with event-related functional MRI (fMRI) using fixed intertrial experimental designs. Here we demonstrate that the use of randomized experimental designs can largely overcome this limitation, thereby allowing for event-related fMRI experiments with extremely rapid presentation rates. In the first experiment, fMRI time courses were simulated using a fixed intertrial interval design with intervals of 16, 3, and 1 s, and using a randomized design having the same mean intertrial intervals. We found that using fixed intertrial interval designs the transient information decreased with decreasing intertrial intervals, whereas using randomized designs the transient information increased with decreasing mean intertrial intervals. In a second experiment, fMRI data were collected from two subjects using a randomized paradigm with visual hemifield stimuli presented randomly every 500 ms. Robust event-related activation maps and hemodynamic response estimates were obtained. These results demonstrate the feasibility of performing event-related fMRI experiments with rapid, randomized paradigms identical to those used in electrophysiological and behavioral studies, thereby expanding the applicability of event-related fMRI to a whole new range of cognitive neurosciences questions and paradigms.     

Comparison of two devices for wound measurement

Sixty leg ulcers were measured with two techniques, a common paper tape measure and a new technique, a plastic grid device. The plastic grid proved to be a reliable, valid, and feasible method to quickly assess wounds in a busy outpatient setting. The grid was superior to the tape measure in assessing large and/or irregular ulcers.     

Transdermal nitroglycerin patch therapy improves left ventricular function and prevents remodeling after acute myocardial infarction: results of a multicenter prospective randomized, double-blind, placebo-controlled trial

BACKGROUND: Nitrates are widely used in the treatment of angina in patients with acute myocardial infarction (AMI). Short-term administration prevents left ventricular (LV) dilation and infarct expansion. However, little information is available regarding their long-term effects on LV remodeling in patients surviving Q-wave AMI. METHODS AND RESULTS: This was a randomized, double-blind, placebo-controlled trial designed to investigate the long-term (6-month) efficacy of intermittent transdermal nitroglycerin (NTG) patches on LV remodeling in 291 survivors of AMI. Patients meeting entry criteria had baseline gated radionuclide angiography (RNA) followed by randomization to placebo or active NTG patches delivering 0.4-, 0.8-, or 1.6-mg/h. RNA was repeated at 6 months and 6.5 days after withdrawal of double-blind medication. The primary study end point was the change in end-systolic volume index (ESVI). Both ESVI and end-diastolic volume index (EDVI) were significantly reduced with 0.4-mg/h NTG patches (-11.4 and -11.6 mL/m2, respectively, P<.03). This beneficial effect was observed primarily in patients with a baseline LV ejection fraction < or =40% (deltaESVI, -31 mL/m2; deltaEDVI, -33 mL/m2; both P<.05) and only at the 0.4-mg/h dose. After NTG patch withdrawal, ESVI significantly increased but did not reach pretreatment values. CONCLUSIONS: Transdermal NTG patches prevent LV dilation in patients surviving AMI. The beneficial effects are limited to patients with depressed LV function and only at the lowest (0.4-mg/h) dose. Continued administration is necessary to maintain efficacy. Whether these remodeling effects confer a clinical or survival advantage will need to be addressed in an adequately powered cardiac event trial.     

Infectious ocular complications in orthotopic liver transplant patients

We report the frequency and type of infectious ocular complications following orthotopic liver transplantation (OLT) and review diagnostic and therapeutic strategies. During the period September 1988 through November 1994, 684 patients underwent OLT at Mount Sinai Hospital (New York). Nine orthotopic liver transplant patients (1.3%) developed ocular infections: Candida albicans endophthalmitis (2), Aspergillus fumigatus endophthalmitis (1), cytomegalovirus retinitis (4), herpes simplex virus keratitis (1), and varicella-zoster virus panophthalmitis (1). The mean time from OLT to ocular symptoms was 42 days for patients with fungal infections and 128 days for patients with viral infections. Blurred vision was the commonest symptom (five of nine cases). The mean duration of follow-up was 2 years (range, 33 days to 5 years). Permanent loss of vision occurred in three patients, five had improvement in visual acuity, and one died of disseminated aspergillosis 33 days after OLT. Infectious ocular complications following OLT may occur as isolated events or with disseminated disease. Fungal infections occur earlier (mean, 42 days after OLT) than viral infections (mean, 4 months after OLT). The clinical presentation may be atypical; aggressive vitreoretinal procedures and serial examinations may be required to establish the diagnosis. Cytomegalovirus retinitis in orthotopic liver transplant patients may not require life-long maintenance therapy with antiviral agents.