A missense mutation in the proteolipid protein gene responsible for Pelizaeus--Merzbacher disease in a Japanese family

We investigated the proteolipid protein (PLP) gene of two boysin a Japanese family with Pelizaeus—Merzbacher disease(PMD), an X-linked neurologic disorder characterized by dysmyelinationin the central nervous system (CNS). The patients showed similarclinical signs from birth and autopsy on the elder brother confirmeda connatal type of PMD. Direct sequencing of the PLP gene andPLP mRNAs from the brain of the PMD patient revealed a G toT transition in exon V of the PLP gene, which leads to a glycineto cystein substitution at residue 220. Allele-specific oligonucleotidehybridization revealed that this mutation was also present inhis brother, but was absent in 100 X chromosomes of normal Japaneseindividuals. Northern blot analysis showed that the mRNA levelsof PLP and myelin basic protein, two major myelin proteins producedby oligodendrocytes, were much reduced in the PMD brain, hence,there was a specific loss of oligodendrocytes. It seems likelythat the substitution is responsible for PMD (connatal type)in this particular family and causes oligodendrocytes deathin the CNS.     

Acute Trypanosoma cruzi infection differentially affects CD3 and Thy-1 mediated T cell activation.

Monoclonal antibodies directed against the Thy-1 molecule or the CD3 complex were used to analyze the activation of T cells from mice acutely infected with Trypanosoma cruzi. When stimulated with G7, a mitogenic anti-Thy-1 monoclonal antibody, spleen cells from infected mice showed a markedly reduced or absent response that could not be restored by varying the culture time or the antibody concentration. However, cells from acutely infected animals proliferated to 145-2C11, an anti-CD3 monoclonal antibody. Flow cytometric analysis showed that the impaired response to G7 could not be attributed to a lack of expression of Thy-1 or CD3. Indeed, G7 seemed to deliver a positive signal to the cells since the proliferative response was completely restored by the addition of PMA. Moreover, purified T cells from infected mice responded to G7 in the presence of accessory cells from uninfected animals. These results suggest that a defective co-stimulatory cell function could be involved in the immunosuppression. In addition, our data present evidence against a generalized T cell anergy in the acute phase of the disease, since CD3-mediated activation was normal.     

The mechanism of the force response to stretch in human skinned muscle fibres with different myosin isoforms

Force enhancement during lengthening of an active muscle, a condition that normally occurs during locomotion in vivo , is attributed to recruitment of myosin heads that exhibit fast attachment to and detachment from actin in a cycle that does not imply ATP splitting. We investigated the kinetic and mechanical features of this cycle in Ca²⁺ activated single skinned fibres from human skeletal muscles containing different myosin heavy chain (MHC) isoforms, identified with single-fibre gel electrophoresis. Fibres were activated by using a new set-up that allows development of most of the tension following a temperature jump from 0–1°C to the test temperature (∼12°C). In this way we could prevent the development of sarcomere non-uniformity and record sarcomere length changes with a striation follower in any phase of the mechanical protocol. We found that: (i) fibres with fast MHC isoforms develop 40–70% larger isometric forces than those with slow isoforms, as a result of both a larger fraction of force-generating myosin heads and a higher force per head; (ii) in both slow and fast fibres, force enhancement by stretch is due to recruitment of myosin head attachments, without increase in strain per head above the value generated by the isometric heads; and (iii) the extent of recruitment is larger in slow fibres than in fast fibres, so that the steady force and power output elicited by lengthening become similar, indicating that mechanical and kinetic properties of the actin–myosin interactions under stretch become independent of the MHC isoform.     

Acute respiratory infection by human metapneumovirus in children in southern Brazil.

BACKGROUND: Human metapneumovirus (hMPV) has been described as an etiologic agent of acute respiratory infections (ARI), mainly in pediatric patients. Viral isolation is difficult and has low sensitivity, and consequently RT-PCR assays are currently used for detection. OBJECTIVES: Detect hMPV in ARI in hospitalized children in Southern Brazil; standardize a RT-PCR for routine hMPV diagnosis; validate a positive control for molecular tests; and perform phylogenetics analyses. STUDY DESIGN: Nasopharyngeal aspirates (NPA) from 156 hospitalized children were studied. A conserved region of the nucleoprotein gene was cloned, characterized and used to standardize an RT-PCR assay. Phylogenetic analyses were performed. Clinical data were obtained from medical records. RESULTS: hMPV was detected in 6.4% of the samples. Dyspnea and wheezing were frequently reported symptoms and the most common diagnoses were bronchiolitis, acute respiratory insufficiency or laryngotracheobronchitis. Nucleotide sequence alignment revealed 97.7% identity with genotype A1 of hMPV. The detection limit of hMPV genomes by RT-PCR in clinical samples was 180 copies/microL. CONCLUSION: This is the first report of the detection and genetic characterization of hMPV infections in children with lower ARI in Southern Brazil.     

Dexamethasone suppression and multiple hormonal responses (TSH,prolactin and growth hormone) to TRH in some psychiatric disorders

Summary Baseline and TRH-induced changes of thyroid stimulating hormone (TSH), prolactin (PRL), and growth hormone (GH) were measured in 15 healthy control subjects and 63 psychiatric inpatients with DSM-III diagnoses of major depression (n = 19), schizophrenic disorder (n = 20), alcohol dependence (n = 10), and adjustment disorder (n = 14); baseline and postdexamethasone cortisol (CS) were also determined 3–6 days after the TRH-challenge. All patients and controls were women of similar mean age, weight, height, and they were free from interfering illness or drugs.Baseline TSH and PRL were lower in depression, TRH-induced TSH and PRL responses were lower in the whole patient group, but most markedly in depression and alcohol dependence. Postdexamethasone CS was significantly higher in depression, schizophrenia and alcohol dependence. Basal GH did not differentiate the subgroups; TRH-induced pathological GH responses were sometimes found in the patient groups. The differences were most marked quantitatively in major depression: a multivariate analysis of variance showed that TSH, postdexamethasone CS and PRL were the most important variables in separating patients from controls. A discriminant function derived from these variables classified all controls and 18 of 19 depressed patients correctly; however, 25 of the 44 other patients were also classified with depression.It was confirmed that psychiatric patients show significantly more endocrine disturbances than controls, and this was seen not only in major depression but also in at least three other conditions. Further work is needed to identify other neuroendocrine patterns more specific to depressive disorder.     

Post-traumatic diffuse brain swelling: isolated or associated with cerebral axonal injury

Eighteen children with severe head injuries and diffuse brain swelling were studied. They were separated into two groups based on the computed tomography (CT) findings. Seven patients had small ventricles in the normal location and small or absent cisterns. Eleven had these signs plus small deep-seated intraparenchymal hemorrhagic foci and/or intraventricular hemorrhage. Patients in the first group were in relatively good neurological condition; their intracranial pressure was easily controlled and all had a favourable outcome. On contrast, children in the second group had a more severe clinical presentation, frequently had uncontrollable intracranial hypertension, and more than 50% died.     

Effect of a rhodium complex on alterations of hepatic function in thioacetamide-induced hyperplastic noduligenesis in rats

An in vivo model of liver hyperplastic noduligenesis was inducedin rats by long-term administration of thioacetamide (TAM) (50mg/kg/day i.p.). Three doses of 50 mg/kg of an antitumoral Rh(III)complex were administered at 14, 9 and 5 days before the endof TAM treatment. Plasma and urine were obtained from eitherTAM or Rh(III) complex or TAM plus Rh(III) complex treated ratsto determine the interactions of both substances with the biochemicalparameters related to liver function. The rise in alkaline phosphatase(ALP), teucine aminopeptidase (LAP), -gtutamyl transferase (GGT)and the unchanged activities in the aspartate and alanine aminotransferases(AST, ALT) in plasma of TAM-treated rats indicated that thedisease induced by this substance can be considered as a chronicobstructive biliary disease with indices of cell proliferationand tumors. The increased concentration of bilirubin both inthe plasma and urine of TAM-treated rats suggested liver cholestasisand hepatobiliary obstruction. The very low values of creatinineclearance indicated that there was some degree of kidney failuredue to the effect of TAM. The increased concentration of ammoniaboth in plasma and urine were probably a consequence of thedecreased flux in the urea cycle in the liver. The Rh(III) complexalone did not produce significant changes in the plasma enzymeactivities. The only significant changes were found in the concentrationsof uric acid and ammonia in the urine. When the Rh(III) complexwas administered to TAM-treated rats, significant restorationof the following parameters were observed: plasma enzymaticactivities, blood bilirubin and ammonia, uric acid and creatininein the urine and the creatinine clearance. These results suggestthat the altered liver function induced by TAM can be restoredby Rh(III) complex. The mechanisms by which this complex actsto counteract the TAM-induced changes are not yet established.