Myosin II heavy chain isoforms are phosphorylated in an EGF-dependent manner: involvement of protein kinase C.

To explore the involvement and regulation of the nonmuscle myosin II heavy chains isoforms, MHC-A and MHC-B in the chemotaxis of metastatic tumor cells, we analyzed the changes in phosphorylation and cellular localization of these isoforms upon stimulation of prostate tumor cells with epidermal growth factor (EGF). EGF stimulation of prostate tumor cells resulted in transient increases in MHC-A and MHC-B phosphorylation and subcellular localization with quite different kinetics. Furthermore, the kinetics of subcellular localization correlated with the in vivo kinetics of MHC-B phosphorylation but not of MHC-A phosphorylation, suggesting different modes of regulation for these myosin II isoforms. We further showed that protein kinase C (PKC) is involved in the EGF-dependent phosphorylation of MHC-A and MHC-B. To our knowledge, this is the first report demonstrating that MHC phosphorylation might regulate its subcellular localization and that the EGF signal is transmitted to MHC-A and MHC-B via PKC. The correlation between MHC-B phosphorylation and localization in response to EGF stimulation might suggest that MHC-B is the myosin II isoform that is involved in chemotaxis.

Acute onset of infantile spinal muscular atrophy.

Two patients with acute generalized weakness and areflexia are presented. The electrophysiologic studies in both revealed evidence of decreased conduction velocity and mixed axonal and demyelinating neuropathy, suggestive of the diagnosis of Guillain-Barré syndrome. The young ages of the patients and their failure to respond to immunoglobulin therapy were the major clues to the final diagnosis of spinal muscular atrophy type I. Blood for DNA study revealed homozygous deletion mutation in exons 7 and 8 of the survival motor neuron gene. This diagnosis should be considered in every child under 1 year of age who presents with acute weakness because Guillain-Barré syndrome in this age group is rare.

Acute necrotizing encephalopathy presenting as a basal ganglia syndrome.

Acute necrotizing encephalopathy is a relatively new disease. The characteristic clinical findings are of febrile illness followed by rapid deterioration in mental status and seizures. The hallmark of the disease is multifocal bilateral symmetric lesions affecting the thalamus, hypothalamus, brainstem tegmentum, cerebral white matter, and cerebellum. The etiology is unknown, but immune-mediated mechanism was suggested. We present a 12-year-old previously healthy girl who developed increased sleepiness progressing to stupor and coma. Magnetic resonance imaging (MRI) of the brain showed the characteristic findings previously described in acute necrotizing encephalopathy. Her mental status improved dramatically with steroid treatment, and the MRI findings resolved completely within 6 months. Following the acute illness, she developed a complex neuropsychiatric disorder consistent with basal ganglia syndrome.

Exercise performance-based outcomes of medically treated patients with coronary artery disease and profound ST segment depression.

OBJECTIVES: We sought to determine the relationship between exercise duration and cardiovascular outcomes in patients with profound (> or =2 mm) ST segment depression during exercise treadmill testing (ETT). BACKGROUND: Patients with stable symptoms but profound ST segment depression during ETT are often referred for a coronary intervention on the basis that presumed severe coronary artery disease (CAD) will lead to unfavorable cardiovascular outcomes, irrespective of symptomatic and functional status. We hypothesized that good exercise tolerance in such patients treated medically is associated with favorable long-term outcomes. METHODS: We prospectively followed 203 consecutive patients (181 men; mean age 73 years) with known stable CAD and > or =2 mm ST segment depression who are performing ETT according to the Bruce protocol for an average of 41 months. The primary end point was occurrence of myocardial infarction (MI) or death. RESULTS: Eight (20%) of 40 patients with an initial ETT exercise duration < or =6 min developed MI or died, as compared with five (6%) of 84 patients who exercised between 6 and 9 min and three (3.8%) of 79 patients who exercised > or =9 min (p = 0.01). Compared with patients who exercised < or =6 min, increased ETT duration was significantly associated with a reduced risk of MI/death (6 to 9 min: relative risk [RR] = 0.25, 95% confidence interval [CI] 0.08 to 0.76; >9 min: RR = 0.14, 95% CI 0.04 to 0.53). This protective effect persisted after adjustment for potentially confounding variables. We observed a 23% reduction in MI/death for each additional minute of exercise the patient was able to complete during the index ETT. CONCLUSIONS: Optimal medical management in stable patients with CAD with profound exercise-induced ST segment depression but good ETT duration is an appropriate alternative to coronary revascularization and is associated with low rates of MI and death.

Biphasic course of infant botulism.

The syndrome of infant botulism, characterized by constipation, poor feeding, hypotonia, poor head control, and bulbar involvement, is typically a monophasic disease. We describe a 7-month-old infant with a recurrence of illness 13 days after resolution of the presenting signs. The source of infection was unknown and the only potential risk factors were exclusive breastfeeding and decreased bowel movements, which by themselves cannot explain the recurrence. Although treatment with botulism immunoglobulin is now suggested for the acute phase of infantile botulism, its use for recurrence is controversial.

Melatonin improves sleep-wake patterns in psychomotor retarded children.

Five children with severe psychomotor retardation (mean age 8.2+/-3.6 years) and irregular sleep-wake patterns underwent 1 week of wrist actigraphic monitoring before and after treatment with 3 mg melatonin. Three underwent multiple measurements of urinary sulfatoxymelatonin levels. Urine sulfatoxymelatonin levels were abnormally low, without any significant day/night differences. Melatonin treatment increased nighttime sleep from 5.9+/-0.8 to 7.3+/-0.5 hours (paired t test, P<0.01) and sleep efficiency from 69.3%+/-6.2% to 88.3%+/-2.3% (P<0.01). Daytime sleep decreased from 3.2+/- 1.2 to 1.7+/-1.2 hours (P<0.05). Thus, no change in 24-hour total sleep time (9.1+/-1.5 vs. 9.0+/-1.6 hours) occurred. Administration of 3 mg melatonin to five severely psychomotor retarded children resulted in a significant improvement in their sleep-wake patterns.

Discrepancies in the use of medications: their extent and predictors in an outpatient practice.

BACKGROUND: Misuse of medications is a major cause of morbidity and mortality. Few studies have examined the frequency of, and factors associated with, discrepancies between what doctors prescribe and what patients take in actual practice. PATIENTS AND METHODS: Patients' medication bottles and their reported use of medications were compared with physicians' records of outpatients seen between November 1997 and February 1998 in a private practice affiliated with an academic medical center in Boston, Mass. Three hundred twelve patients from the practices of 5 cardiologists and 2 internists who were returning for their routine follow-up visits were included. MAIN OUTCOME MEASURE: The presence of discrepancies based on comparing medication bottles with medical records. RESULTS: Discrepancies were present in 239 patients (76%). The 545 discrepancies in these patients were the result of patients taking medications that were not recorded (n = 278 [51%]); patients not taking a recorded medication (n = 158 [29%]); and differences in dosage (n = 109 [20%]). Overall, discrepancies were randomly distributed among different drugs and discrepancy types with no discernible pattern. On multivariate analysis, patient age and number of recorded medications were the 2 most significant predictors of medication discrepancy. CONCLUSIONS: Discrepancies among recorded and reported medications were common and involved all classes of medications, including cardiac and prescription drugs. Older age and polypharmacy were the most significant correlates of discrepancy. The pervasiveness of discrepancies can have significant health care implications, and action is urgently needed to address their causes. Such action would likely have a positive impact on patient care.

Coma as an acute presentation of adrenoleukodystrophy.

X-linked adrenoleukodystrophy is a metabolic disorder with broad clinical variations. A 4-year-old male admitted to the hospital with fever, hypotension, and coma as the presenting signs of adrenoleukodystrophy is reported. The initial presentation followed by rapidly developing disseminated intravascular coagulopathy and multiorgan failure suggested an initial diagnosis of septic shock. However, bronze skin pigmentation and a cranial computed tomography scan demonstrating posterior demyelination consistent with adrenoleukodystrophy led to the final diagnosis. The diagnosis was confirmed by the findings of elevated very-long-chain fatty acid levels and an elevated C24/C16 ratio in plasma and fibroblast cultures. Atypical presentations of the disease require a high index of suspicion to initiate treatment before the appearance of irreversible sequelae.

Rapid recovery from transverse myelopathy in children treated with methylprednisolone.

Acute transverse myelopathy is an uncommon disease that manifests with gradually developing weakness of the lower extremities associated with bladder or bowel dysfunction, sensory deficits, and pain localized in the back, legs, or abdomen. There are controversies in the literature regarding the role of steroids in the treatment of acute transverse myelopathy. Recently, a pilot open study of five children with acute transverse myelopathy treated with high-dose methylprednisolone demonstrated significant shortening of motor recovery when compared with an historic control group receiving either no treatment or low-dose steroids. The authors add their experience of 10 children with acute transverse myelopathy treated with high-dose methylprednisolone as soon as the diagnosis was confirmed. The median time of motor recovery in the present series was 5.5 compared with 23 days in the other study. No significant side effects were observed after treatment. This study provides further support that this treatment modality is safe and efficient and should be suggested for all children with acute transverse myelopathy after establishing the diagnosis.

High incidence of hypoglycemic episodes with neurologic manifestations in children with insulin dependent diabetes mellitus.

UNLABELLED: Hypoglycemia is a serious frequent complication of insulin therapy in type 1 diabetes. PATIENTS AND METHODS: We surveyed 139 IDDM patients. RESULTS: Forty-four patients (32%) reported at least one severe hypoglycemic episode. All patients with severe hypoglycemia experienced neurological manifestations. Symptoms included confusion and abnormal behavior, convulsions, coma, transient hemiparesis and one case of permanent hemiparesis. Most episodes occurred at night or during morning hours. 44% of episodes were related to delayed meal or snack, 11% to excess insulin administration and 13% to extra physical activity. HbA1c was significantly lower in patients with severe hypoglycemia compared with diabetic controls (7.33 +/- 1.09% and 9.45 +/- 4.32%, respectively).

14-3-3 inhibits the Dictyostelium myosin II heavy-chain-specific protein kinase C activity by a direct interaction: identification of the 14-3-3 binding domain.

Myosin II heavy chain (MHC) specific protein kinase C (MHC-PKC), isolated from Dictyostelium discoideum, regulates myosin II assembly and localization in response to the chemoattractant cyclic AMP. Immunoprecipitation of MHC-PKC revealed that it resides as a complex with several proteins. We show herein that one of these proteins is a homologue of the 14-3-3 protein (Dd14-3-3). This protein has recently been implicated in the regulation of intracellular signaling pathways via its interaction with several signaling proteins, such as PKC and Raf-1 kinase. We demonstrate that the mammalian 14-3-3 zeta isoform inhibits the MHC-PKC activity in vitro and that this inhibition is carried out by a direct interaction between the two proteins. Furthermore, we found that the cytosolic MHC-PKC, which is inactive, formed a complex with Dd14-3-3 in the cytosol in a cyclic AMP-dependent manner, whereas the membrane-bound active MHC-PKC was not found in a complex with Dd14-3-3. This suggests that Dd14-3-3 inhibits the MHC-PKC in vivo. We further show that MHC-PKC binds Dd14-3-3 as well as 14-3-3 zeta through its C1 domain, and the interaction between these two proteins does not involve a peptide containing phosphoserine as was found for Raf-1 kinase. Our experiments thus show an in vivo function for a member of the 14-3-3 family and demonstrate that MHC-PKC interacts directly with Dd14-3-3 and 14-3-3 zeta through its C1 domain both in vitro and in vivo, resulting in the inhibition of the kinase.

[Hyponatremia due to prolonged excessive ingestion of water].

We report a 1.5-year-old boy admitted for restlessness and constipation. He was found to have hyponatremia caused by voluntary drinking of excessive amounts of water. Although unusual in children, intoxication by oral water is a recognized clinical syndrome in infants, 3-6 months old, fed with dilute formula. Water intoxication in older children is rare. The diagnosis was established by the water deprivation test.

Immune globulins are effective in severe pediatric Guillain-Barré syndrome.

The effect of high-dose intravenous immune globulins was evaluated in an open prospective multicenter study of 26 children with severe Guillain-Barré syndrome. They presented with mild to moderate flaccid weakness of extremities, with cranial nerve involvement (20) and sensory impairment (22). All children rapidly deteriorated in 2-16 days (mean 6) to become bedridden, and 2 children also developed respiratory failure requiring artificial ventilation (Disability Grading Scale 4-5). Immune globulins were then administered at a total dose of 2 gm/kg, on 2 consecutive days, without adverse effects requiring discontinuation of therapy. Marked and rapid improvement was noted in 25 children, who improved by 1 to 2 Disability Grade Scales < or = 2 weeks after the infusion. Twenty were able to walk independently by 1 week, and 1 could be weaned off a ventilator. Eighteen children recovered by 2 weeks. The rest recuperated in a period of four months, including a child who was artificially ventilated for 4 weeks. The uniform rapid improvement and recovery associated with immune globulins contrasts with the slow recovery course in severe natural cases. We conclude that immune globulins are effective and safe in severe childhood-onset Guillain-Barré syndrome and therefore may serve as the initial treatment of choice.

The effect of atrial fibrillation and the ventricular rate control on exercise capacity.

BACKGROUND: Atrial fibrillation (AF) is a common cardiac arrhythmia, affecting approximately 1.5 million patients in the United States. HYPOTHESIS: This study was designed to determine the effect of AF and the ventricular rate control during AF on cardiovascular performance as measured by exercise endurance on a standard Bruce protocol. METHODS: Sixty-three patients with AF who underwent exercise stress testing during both sinus rhythm and AF were analyzed. Heart rate, blood pressure, heart rate acceleration, exercise duration, and left ventricular (LV) systolic function were measured. RESULTS: Atrial fibrillation resulted in a small but statistically significant decrease in exercise endurance (426 +/- 180 vs. 402 +/- 168 s, p < 0.05). The drop in exercise tolerance was consistent regardless of the underlying heart condition or adequate ventricular rate control during AF. Heart rate in AF was consistently faster than in sinus rhythm, at rest, and at peak exercise (63 vs. 79 beats/min and 125 vs. 149 beats/min, respectively, p < 0.001). CONCLUSION: Our analyses indicated that (1) the loss of atrioventricular synchrony had minimal effect on cardiovascular performance in patients with preserved LV function, (2) the decrease in cardiovascular performance was related to loss of atrioventricular synchrony but not to underlying heart disease or ventricular rate control, and (3) compensation for the loss of the atrial contribution was provided by consistently faster heart rate during AF.

Autophosphorylation of Dictyostelium myosin II heavy chain-specific protein kinase C is required for its activation and membrane dissociation.

Myosin II heavy chain (MHC)-specific protein kinase C (MHC-PKC) isolated from the ameba, Dictyostelium discoideum, regulates myosin II assembly and localization in response to the chemoattractant cAMP. cAMP stimulation of Dictyostelium cells leads to translocation of MHC-PKC from the cytosol to the membrane fraction, as well as causing an increase in both MHC-PKC phosphorylation and its kinase activity. MHC-PKC undergoes autophosphorylation with each mole of kinase incorporating about 20 mol of phosphate. The MHC-PKC autophosphorylation sites are thought to be located within a domain at the COOH-terminal region of MHC-PKC that contains a cluster of 21 serine and threonine residues. Here we report that deletion of this domain abolished the ability of the enzyme to undergo autophosphorylation in vitro. Furthermore, after this deletion, cAMP-dependent autophosphorylation of MHC-PKC as well as cAMP-dependent increases in kinase activity and subcellular localization were also abolished. These results provide evidence for the role of autophosphorylation in the regulation of MHC-PKC and indicate that this MHC-PKC autophosphorylation is required for the kinase activation in response to cAMP and for subcellular localization.

[Juvenile myoclonic epilepsy--an underdiagnosed epileptic syndrome].

Clinical and electroencephalographic data and response to drug therapy of 3 boys and 3 girls aged 14-19 years, mean 16, with juvenile myoclonic epilepsy (JME) are described. All presented with violent myoclonic jerks upon awakening, prompted by sleep deprivation and precipitated by deliberate awakening. Following onset of myoclonic jerks, generalized tonic-clonic seizures (GCTS) and absences occurred after 6-18 months (mean 11). The EEG revealed normal background activity in all, along with generalized epileptiform activity in the form of 3-4 Hz polyspike/slow wave or spike/slow wave, commonly induced by hyperventilation. Valproic acid (VPA), 12 mg/kg/day (range 10-15), resulted in complete and rapid cessation of myoclonic jerks, of absences and recurrent GTCS. Discontinuation of VPA resulted in recurrence of myoclonic jerks and then GTCS, but were completely controlled by reinstitution of VPA. All have remained asymptomatic on VPA, with cognition preserved, during a follow-up of up to 6 years. JME is a unique, benign, epileptic syndrome easily and rapidly controlled by rather small doses of valproic acid given on a long-term basis. Myoclonic jerks may serve as a reliable indicator of JME and therefore should be screened for in any case of unprovoked generalized seizures. The smallness of the doses of the drug used suggests that the dose prescribed should be "syndrome" related rather than weight related, as is usually prescribed in children.

[Spontaneous pneumomediastinum in a child].

Spontaneous pneumomediastinum results from nontraumatic, mediastinal air leakage, without underlying lung disease. It is an uncommon, but important condition found in healthy young adults and children presenting with chest pain and shortness of breath. It should be considered in the differential diagnosis of chest pain. We present a 12-year-old boy who complained of chest pain and was found to have a spontaneous pneumomediastinum. We suggest that spontaneous pneumomediastinum is underdiagnosed in children.

Chemoattractant-mediated increases in cGMP induce changes in Dictyostelium myosin II heavy chain-specific protein kinase C activities.

Myosin II heavy chain (MHC)-specific protein kinase C (MHC-PKC) isolated from the ameba, Dictyostelium discoideum, regulates myosin II assembly and localization in response to the chemoattractant cAMP (Abu-Elneel et al. 1996. J. Biol. Chem. 271:977- 984). Recent studies have indicated that cAMP-induced cGMP accumulation plays a role in the regulation of myosin II phosphorylation and localization (Liu, G., and P. Newell. 1991. J. Cell. Sci. 98: 483-490). This report describes the roles of cAMP and cGMP in the regulation of MHC-PKC membrane association, phosphorylation, and activity (hereafter termed MHC-PKC activities). cAMP stimulation of Dictyostelium cells resulted in translocation of MHC-PKC from the cytosol to the membrane fraction, as well as increasing in MHC-PKC phosphorylation and in its kinase activity. We present evidence that MHC is phosphorylated by MHC-PKC in the cell cortex which leads to myosin II dissociation from the cytoskeleton. Use of Dictyostelium mutants that exhibit aberrant cAMP-induced increases in cGMP accumulation revealed that MHC-PKC activities are regulated by cGMP. Dictyostelium streamer F mutant (stmF), which produces a prolonged peak of cGMP accumulation upon cAMP stimulation, exhibits prolonged increases in MHC-PKC activities. In contrast, Dictyostelium KI-10 mutant that lacks the normal cAMP-induced cGMP response, or KI-4 mutant that shows nearly normal cAMP-induced cGMP response but has aberrant cGMP binding activity, show no changes in MHC-PKC activities. We provide evidence that cGMP may affect MHC-PKC activities via the activation of cGMP-dependent protein kinase which, in turn, phosphorylates MHC-PKC. The results presented here indicate that cAMP-induced cGMP accumulation regulates myosin II phosphorylation and localization via the regulation of MHC-PKC.