Abnormal liver function tests associated with severe rhabdomyolysis

Rhabdomyolysis is a syndrome of skeletal muscle injury with release of cellular constituents such as potassium,phosphate,urate and intracellular proteins such as myoglobin into the circulation,which may cause complications including acute kidney injury,electrolyte disturbance and cardiac instability.Abnormal liver function tests are frequently observed in cases of severe rhabdomyolysis.Typically,there is an increase in serum aminotransferases,namely aspartate aminotransferase and alanine aminotransferase.This raises the question of liver injury and often triggers a pathway of investigation which may lead to a liver biopsy.However,muscle can also be a source of the increased aminotransferase activity.This review discusses the dilemma of finding abnormal liver function tests in the setting of muscle injury and the potential implications of such an association.It delves into some of the clinical and experimental evidence for correlating muscle injury to raised aminotransferases,and discusses pathophysiological mechanisms such as oxidative stress which may cause actual liver injury.Serum aminotransferases lack tissue specificity to allow clinicians to distinguish primary liver injury from muscle injury.This review also explores potential approaches to improve the accuracy of our diagnostic tools,so that excessive or unnecessary liver investigations can be avoided.     

Responses of CDKs and p53 in Delayed Ischemic Neuronal Death

Stroke is a debilitating disease that affects millions each year.While in many cases cerebral ischemic in jury can be limited by effectivw resuscitation or thrombolytic treatment,the injured neurons wither in a process known as delayed neuronal death(DND).Mounting evidence indicates that DND is not simply necrosis played out in slow motion but apoptosis is triggered.Of particular interest are two groups of signal proteins that participate in apoptosis-cyclin dependent kinases(CDKs) and p53-among a myriad of signaling events after an ischemic insult.Recent investigations have shown that CDKs,a family of enzymes initially known for their role in cell cycle regulation,are activated in injured neurons in DND.As for p53,new reports suggest that its up-regulation may represent a failed attempt to rescue in jured neurons,although its up-regulation was previously considered an indication of apoptosis.These observations thus rekindle an old quest to identify new neuroprotective targets to minimize the stroke damage.In this review,the author will examine the evidence that indicates the participation of CDKs and p53 in DND and then introduce pre-clinical data to explore CDK inhibition as a potential neuroprotective target.Finally,using CDK inhibition as an example,this paper will discuss the pertinent criteria for a viable neuroprotective strategy for ischemic in jury.     

Cerebellar toxicity with high-dose cytosine arabinoside

CNS dysfunction, especially impaired cerebellar function, is the dose-limiting toxicity associated with high-dose cytosine arabinoside, which precludes doses of greater than 48 g/m2. Four hundred eighteen patients between the ages of 2 and 74 years with leukemia or lymphoma received 36 to 48 g/m2 cytosine arabinoside either alone or with anthracycline antibiotics, 4'-(9-acridinylamino) methane sulfon-m-anisidine (m-AMSA), or total body irradiation. In only 35 of 418 patients (8%) did severe cerebellar toxicity develop; it was irreversible or fatal in four (1%) patients. The age of the patient was a critical factor in the incidence of severe cerebellar toxicity. Patients greater than 50 years old had a statistically significant greater incidence of cerebellar toxicity compared with younger patients (26/137, 19%, v 9/281, 3%; P less than .0005, chi 2). Neither the diagnosis, disease status, sex, nor the regimen altered the incidence of severe cerebellar toxicity (when corrected for age). A second course of high-dose cytosine arabinoside, administered to 62 patients, did not increase the incidence of severe cerebellar toxicity, which occurred in five (8%) of these patients. Two of the five patients had severe toxicity with the initial course. Of the 60 patients with no antecedent cerebellar dysfunction, three (5%) had severe toxicity with the second course: one of 41 patients were less than 50 years old; two of 19 patients were greater than or equal to 50 years. Since the occurrence of severe cerebellar dysfunction is greatly affected by age, reduced doses of high-dose cytosine arabinoside should be given to patients greater than 50 years old, and methods for reducing the cerebellar toxicity should be investigated in these patients.     

Intravenous immunoglobulin may lessen all forms of infection in patients receiving allogeneic bone marrow transplantation for acute lymphoblastic leukemia: a pediatric oncology group study

Fifty patients with refractory acute lymphoblastic leukemia underwent allogeneic bone marrow transplantation after conditioning with high-dose cytosine arabinoside and fractionated total body irradiation. Twenty-nine received intravenous immunoglobulin (i.v.Ig) infusion, primarily to prevent cytomegalovirus infection, and 21 did not. The two groups were biologically comparable. Seven (24.5%) of the i.v.Ig-treated and 14 (66.7%) of the non-i.v.Ig-treated patients developed systemic viral, fungal or bacterial infections and/or interstitial pneumonitis (p less than 0.005), which were fatal in three and 12 cases respectively (p less than 0.001). Currently, 23 (79.3%) of the 29 i.v.Ig-treated and eight (38.1%) of the 21 non-i.v.Ig-treated patients are alive and well (p less than 0.01). We conclude that prophylactic i.v.Ig infusions may reduce the frequency of all forms of serious infection in patients with acute lymphoblastic leukemia undergoing allogeneic marrow transplantation, and thereby improve their survival expectation.     

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

Use of an automated multiple-locus, variable-number tandem repeat-based method for rapid and high-throughput genotyping of Staphylococcus aureus isolates

Fast and reliable genotyping methods that allow real-time epidemiological surveillance would be instrumental to monitoring of the spread of methicillin-resistant Staphylococcus aureus. We describe an automated variable-number tandem repeat-based method for the rapid genotyping of Staphylococcus aureus. Multiplex PCR amplifications with eight primer pairs that target gene regions with variable numbers of tandem repeats were resolved by microcapillary electrophoresis and automatically assessed by cluster analysis. This genotyping technique was evaluated for its discriminatory power and reproducibility with clinical isolates of various origins, including a panel of control strains previously characterized by several typing methods and collections from either long-term carriers or defined nosocomial outbreaks. All steps of this new procedure were developed to ensure a rapid turnaround time and moderate cost. The results obtained suggest that this rapid approach is a valuable tool for the genotyping of S. aureus isolates in real time.     

Dependence of force and immediate stiffness on sarcomere length and Ca2+ activation in frog skinned muscle fibres

1. Skinned fibres prepared from semitendinosus muscle of the frog (Rana temporaria) by a modified Natori's method were suspended in ATP-salt solution (pCa 5, pH 6.7, 3°C). Isometric tension was studied as a function of sarcomere length (determined by laser diffraction) and stiffness was measured by recording tension changes in response to quick changes in length performed within 0.5 ms during Ca²⁺ activated contractions.
2. There was a sigmoidal relationship between contractile tension or stiffness and pCa. The threshold Ca ion concentration was 5×10^?7 M at a sarcomere length of 2.2 μm and a little lower at larger sarcomere lengths (as also described by Endo 1972). At all sarcomere lengths peak tension was reached at about 10^?5 M Ca²⁺.
3. The skinned fibres produced maximum tension at sarcomere lengths of 2.0–2.3 μm. With a further increase in sarcomere length, contractile tension decreased. The relation between tension and sarcomere length was linear up to 3.2 μm above which value the relationship ‘tailed’.
4. Quick releases in the range of 0.1–0.5%L ₀ applied during Ca²⁺ activation produced an immediate elastic fall in tension in phase with the length change followed by a quick recovery phase completed within about 10 ms. Conversely, a quick stretch produced an elastic increase followed by a rapid tension decay completed within about 8–10 ms. When the extreme tensions obtained during the length step were plotted versus the size of the length step, a force-extension diagram was obtained corresponding to the T₁-curve of Huxley and Simmons (1973) which intercepted the length axis at about ?8 nm/half sarcomere at all sarcomere lengths investigated. The slope of the linear portion of the T₁-curve was taken to determine immediate stiffness which was proportional to tension when either sarcomere length or Ca²+ ion concentration were varied.
5. In conclusion tension and immediated stiffness are proportional to the extent of actin myosin filament overlap and hence to the number of possible crossbridges between thick and thin filaments.
6. At very low calcium ion concentrations (10^?7 M) skinned fibres develop tension and become stiff when the Mg-ATP concentration is lowered (at constant [ATP] total) to values below 10^?5 M. Under these conditions a quick release causes a drop in tension which is—as in the case of rigor—not followed by a fast recovery of tension. Again stiffness was independent of the direction and amplitude of quick length changes; but — as in the case of rigor — the stiffness to tension ratio was much higher than in Ca²⁺ activated contraction.