Malignant hyperthermia--still a current and dangerous problem

Malignant hyperthermia is a potentially fatal condition inducible by volatile anaesthetics and/or suxamethonium in genetically susceptible individuals. A disturbed calcium homeostasis in skeletal muscle (possibly in the ryanodin receptor) results in elevated myoplasmatic calcium. The latter causes muscle contraction and a hypermetabolic state, clinically observed as rigidity, fever, hypercarbia, metabolic acidosis and hyperkalemia. Arythmia ensues. Dantrolene inhibits the release of calcium and can halt the process if the diagnosis is made early. A fatal incident of probable malignant hyperthermia in a 13 year old boy is described and evaluated according to a multifactorial clinical grading scale. The value of the in vitro contracture test to diagnose malignant hyperthermia is discussed. Suggestions concerning the treatment of masseterspasm rigidity, an acute episode of malignant hyperthermia, and safe anaesthesia for susceptible patients are presented.     

Adenylyl cyclase activation underlies intracellular cyclic AMP accumulation, cyclic AMP transport, and extracellular adenosine accumulation evoked by beta-adrenergic receptor stimulation in mixed cultures of neurons and astrocytes derived from rat cerebral cortex

We have previously shown that stimulation of cortical cultures containing both neurons and astrocytes with the beta-adrenergic agonist isoproterenol (ISO) results in transport of cAMP from astrocytes followed by extracellular hydrolysis to adenosine [Rosenberg et al. J. Neurosci. 14 (1994) 2953-2965]. In this study we found that the endogenous catecholamines epinephrine (EPI) and norepinephrine (NE), but not dopamine, serotonin, or histamine, all at 10 microM, significantly stimulated intracellular cAMP accumulation, cAMP transport, and extracellular adenosine accumulation in cortical cultures. Detailed dose-response experiments were performed for NE and EPI, as well as ISO. For each catecholamine, the potencies in evoking intracellular cAMP accumulation, cAMP transport, and extracellular adenosine accumulation were similar. These data provide additional evidence that a single common mechanism, namely beta-adrenergic mediated activation of adenylyl cyclase, underlies intracellular cAMP accumulation, cAMP transport, and extracellular adenosine accumulation. It appears that regulation of extracellular adenosine levels via cAMP transport and extracellular hydrolysis to adenosine may be a final common pathway of neuromodulation in cerebral cortex for catecholamines, and, indeed, any substance whose receptors are coupled to adenylyl cyclase.     

Unilateral injury of posterior parietal cortex and spatial learning in hooded rats

The influences of bilateral or unilateral injuries within the posterior parietal cortex (PPC) upon spatial learning in a water maze were examined in three experiments. Place-learning and response-learning were investigated in a four-alley 'Greek-cross' shaped water maze with extra-maze visual cues available. No differences were detected on any of several measures sensitive to learning between the lesion groups on the place-learning task. Microanalysis of behavior within trials revealed that animals with either bilateral or right unilateral PPC injuries committed significantly more total errors, initial alley entrance ('reference memory') errors, and re-entry ('working memory') errors in the response-learning paradigm than did either the control or left PPC-injured rats. No differences were detected between the latter two groups on these measures. Unilateral lesions resulted in asymmetrical placing responses ipsilateral to the injury 10 days after surgery whereas bilateral injuries resulted in asymmetrical placing with mixed directionality. The acquisition of the response-learning problem in the absence of visual cues was studied on animals prepared with unilateral lesions and housed post-operatively either in isolation or in a 'complex environment.' In the absence of visual cues both right and left PPC-injured rats committed more errors than sham controls, and differential post-surgical housing did not attenuate these impairments. These same animals were trained on the landmark navigation task. Although no differences appeared between the lesion groups, a generalized but transient facilitation of learning was observed in animals housed in the 'complex' environment. Unilateral injuries placed in sham controls failed to disturb retention of the landmark navigation strategy. Because none of the PPC-injured animals were deficient in the landmark task, a result which is contrary to observations in other laboratories, the influence of post-surgical recovery interval upon acquisition of the landmark navigation strategy was explored. Animals were prepared with right PPC injuries and trained following either a 5 or 35 day recovery interval. Only those animals limited to the short recovery interval proved to have a spatial deficit in the landmark task. It is concluded that injuries in the PPC of either hemisphere disturb egocentric spatial functions. However, animals with left PPC injuries are able to compensate by using allocentric visual cues if they are available. It is due to the special role played by the right PPC in complex visuospatial functions that animals with this injury are unable to compensate.     

Mitochondrial antigen/antibody systems in primary biliary cirrhosis: revisited

Methods for the evaluation of the four antimitochondrial antibody subtypes in primary biliary cirrhosis - anti-M2, -M4, -M8, -M9 - are described. The importance of the application of different preparations for the demonstration of complement fixing antibodies and the detection of antibodies by ELISA or Western blotting is emphasized. Complement fixing antigens can be prepared by discontinuous isopynic sucrose density gradient centrifugation using mitochondrial subfractions derived with from beef heart (M2), rat liver (M4), or pig kidney (M8). Anti-M9 antibodies do not fix complement. For ELISA, the pyruvate dehydrogenase or the ATPase-associated antigen fraction (M2), the sulfite oxidase fraction (M4), and the chromatographically purified M8-fraction should be used. The same antigen fractions are suitable for Western blotting, but anti-M4 and anti-M8 by ELISA and Western blotting a purified fraction prepared from rat liver has to be applied. Correlating antimitochondrial antibody-subtypes with clinical condition and the natural course, there is convincing evidence that especially the presence of complement fixing antibodies against the subtypes M2, M4, and M8 is a reliable indicator for a more active course. Patients expressing only anti-M9 (without anti-M2) have biochemically all the typical features also found in classical anti-M2 positive primary biliary cirrhosis patients, but seem not to advance to late stages. Since these antimitochondrial antibody-subtypes are present even in very early stages stages without changing their pattern during the course, antimitochondrial antibody-profiles can also be taken as early prognostic parameters. The evaluation of the immunological activity by antimitochondrial antibody-subtype testing may further facilitate the decision whether therapy with ursodeoxycholic acid should be combined with steroids and/or immunosuppressive agents. The role of mitochondrial autoantigens in the induction of this chronic destructive bile duct process is also discussed. The concept is put forward that not bile ducts but naive(?) B-cells expose the different mitochondrial antigens, thereby stimulating autoreactive T-cells to provide a second signal for antibody production. The degree of breakage of tolerance to the different mitochondrial epitopes may be one crucial factor which determines the diversity of antimitochondrial antibody-subtypes in patients with primary biliary cirrhosis.     

E. coli D-glyceraldehyde-3-phosphate dehydrogenase modified by 2,3-butanedione: manifestation of a pairwise of non-equivalence of active centers

Chemical modification of E. coli d-glyceraldehyde-3-phosphate dehydrogenase by an arginine-specific reagent, 2,3-butanedione, stabilized the tetrametric enzyme in an asymmetric state, with only two of the four active centers able to catalyze oxidative phosphorylation of D-glyceraldehyde-3-phosphate. The catalytically incompetent active centers retain the capacity of binding NAD+, forming charge transfer complex, and be alkylated by iodoacetamide. Analogous results have been previously obtained with the rabbit muscle D-glyceraldehyde dehydrogenase modified at a single arginine residue per subunit (Kuzminskaya, E.V., Asryants, R.A., and Nagradova, N.K. (1991) Biochim. Biophys. Acta 1075, 123-130), the only differences being inaccessibility of the catalytically incompetent pair of active centers to the alkylating reagent, on one hand, and lower residual activity exhibited by the functioning active centers (3-4%), on the other. In the case of E. coli enzyme, activity loss upon arginine modification never exceeded 80-82%. These results are consistent with the idea that the two enzymes share common principles of the protein design, but differ in the peculiarities of their active centers conformations. An improved method for D-glyceraldehyde-3-phosphate dehydrogenase purification from a wild type E. coli strain is described.     

Patterning of the neural ectoderm of Xenopus laevis by the amino-terminal product of hedgehog autoproteolytic cleavage

The patterns of embryonic expression and the activities of Xenopus members of the hedgehog gene family are suggestive of role in neural induction and patterning. We report that these hedgehog polypeptides undergo autoproteolytic cleavage. Injection into embryos of mRNAs encoding Xenopus banded-hedgehog (X-bhh) or the amino-terminal domain (N) demonstrates that the direct inductive activities of X-bhh are encoded by N. In addition, both N and X-bhh pattern neural tissue by elevating expression of anterior neural genes. Unexpectedly, an internal deletion of X-bhh (delta N-C) was found to block the activity of X-bhh and N in explants and to reduce dorsoanterior structures in embryos. As elevated hedgehog activity increases the expression of anterior neural genes, and as delta N-C reduces dorsoanterior structures, these complementary data support a role for hedgehog in neural induction and anteroposterior patterning.     

Paraoesophageal hiatus hernia: an important complication of laparoscopic Nissen fundoplication

Postoperative paraoesophageal hiatus hernia occurred in 17 of 253 patients who underwent laparoscopic fundoplication at five different hospitals. Ten patients have undergone subsequent surgical revision, eight by an open technique and two by laparoscopy. This complication may have important implications for the technique of laparoscopic fundoplication, as it is possible that routine posterior repair of the diaphragmatic hiatus may greatly reduce the risk. Early postoperative contrast radiology may also achieve earlier diagnosis, enabling correction to be undertaken by laparoscopy.     

TAP1-independent loading of class I molecules by exogenous viral proteins

Presentation of peptides derived from endogenous proteins on class I molecules needs functional TAP peptide transporters. To reveal whether class I-associated presentation of exogenous proteins also required the presence of TAP transporters, we assessed in vitro the ability of spleen cells and macrophages from TAP1-deficient mice (TAP1-/-) to present peptides derived from exogenous recombinant viral proteins on their class I molecules. We found that recombinant glyco- and nucleoprotein from lymphocytic choriomeningitis virus and nucleoprotein of vesicular stomatitis virus were presented as efficiently by TAP1-/- cells as by control cells. Peptide regurgitation was not involved. Since particulate, non-replicating antigens can efficiently prime anti-viral cytotoxic T cells in vivo, this new, TAP-independent pathway of class I-associated antigen presentation may be applicable for vaccine strategies.     

The use of objective measures of asthma severity in primary care: a report from ASPN

This study compared the use of 2 1/2-hour multimedia workshop with distribution of an algorithm on the ability of fourth-year medical students to present a stop-smoking plan to a simulated patient. Results showed that students who participated in the workshop performed statistically significantly better on the skill areas of providing information, eliciting and responding to feeling and on content areas of past experience with quitting, resources available for change and negotiating a plan. There were no significant differences in the skill area of eliciting information and the content areas of motivation to stop smoking, factors that inhibit change and problems affecting the plan. Neither of the groups performed very well. The highest number of available points obtained by both groups was in eliciting information (53% in the algorithm group and 64% in the formal training group); however, most of the values were in the range of 10%-25% of possible points. Suggested reasons for the low values may be due to the specific items rated, the teaching methods or the time needed to assimilate new skills.     

Evidence for two tumour suppressor loci on chromosomal bands 1p35-36 involved in neuroblastoma: one probably imprinted, another associated with N-myc amplification

Previous reports on possible genomic imprinting of the neuroblastoma tumour suppressor gene on chromosome 1p36 have been conflicting. Here we report on the parental origin of 1p36 alleles lost in 47 neuroblastomas and on a detailed Southern blot analysis of the extent of the 1p deletions in 38 cases. The results are remarkably different for tumours with and without N-myc amplification. In the N-myc single copy tumours we show that the lost 1p36 alleles are of preferential maternal origin (16 of 17 cases) and that the commonly deleted region maps to 1p36.2-3. In contrast, all N-myc amplified neuroblastomas have larger 1p deletions, extending from the telomere to at least 1p35-36.1. These deletions are of random parental origin (18 of 30 maternal LOH). This strongly suggests that different suppressor genes on 1p are inactivated in these two types of neuroblastoma. Deletion of a more proximal suppressor gene is associated with N-myc amplification, while a distal, probably imprinted, suppressor can be deleted in N-myc single copy cases.