Myosin autoantibodies detected by immunofluorescence.

Autoantibodies to striated and smooth muscles myosins were detected by indirect immunofluorescence and confirmed by absorption with purified contractile proteins extracted from human, rabbit and chicken muscle. Myosin antibodies were rare: of fifty-five sera examined from patients with various skeletal and cardiac muscle disorders, only one serum, from a case of Coxsackie viral pericarditis, had anti-myosin activity. It reacted with cardiac muscle and type 1 fibres of skeletal muscle, staining the 'A' band of the sarcomere only. The antibody was absorbed by skeletal myosin and by skeletal heavy meromyosin fragments, but not by smooth muscle myosin. Two types of smooth muscle myosin autoantibodies are described. One is restricted to smooth muscle myosin and examples were found in polyclonal and monoclonal SMA sera. The second type of smooth muscle myosin antibody cross-reacted with skeletal and cardiac muscle and with cytoplasmic myosin in liver, kidney and thyroid cells. It was completely absorbed using either smooth or skeletal myosin and by heavy meromyosin fragments. The different types of myosin autoantibodies reflect the variety of myosins found in mammalian tissues. Cross-reacting myosin antibodies indicate epitopes on the heavy meromyosin fragment which are common to several different tissue myosins.     

Mutations and impaired function of LKB1 in familial and non-familial Peutz-Jeghers syndrome and a sporadic testicular cancer

Germline mutations in LKB1 have been reported to underlie familial Peutz-Jeghers syndrome (PJS) with intestinal hamartomatous polyps and an elevated risk of various neoplasms. To investigate the prevalence of LKB1 germline mutations in PJS more generally, we studied samples from 33 unrelated PJS patients including eight non-familial sporadic patients, 20 familial patients and five patients with unknown family history. Nineteen germline mutations were identified, 12 (60%) in familial and four (50%) in sporadic cases. LKB1 mutations were not detected in 14 (42%) patients, indicating that the existence of additional minor PJS loci cannot be excluded. LKB1 is predicted to encode a serine/threonine kinase. To demonstrate the putative Lkb1 kinase function and to study the consequences of LKB1 mutations in PJS and sporadic tumors, we have analyzed the kinase activity of wild-type and mutant Lkb1 proteins. Interestingly, while most of the small deletions or missense mutations resulted in loss-of-function alleles, one missense mutation (G163D) previously identified in a sporadic testicular tumor demonstrated severely impaired but detectable kinase activity.      

Blood pressure reactivity to mental stress and aerobic fitness in normotensive young adult African–American males with parental history of hypertension

Hypertension (HT) is the leading health problem in the adult African–American (AA) community and is associated with risk factors of stress, physical inactivity, and family history. We examined the influences of aerobic fitness and parental history of HT on blood pressure (BP) reactivity to mental stress in 60 normotensive young adult AA males. A 5‐min mental arithmetic test was used as a provocative stress. Measurements of peak oxygen uptake (V̇O_2peak) were used to classify physically active and inactive subjects into groups of high and low aerobic fitness. A questionnaire was used to evaluate parental BP histories. Reactivity of BP was indexed by differences in values (delta) measured during baseline and stress testing periods. Subjects with a parental history of HT (PH⁺) had significantly higher baseline systolic BP and mean arterial BP (SBP, MABP) values than subjects with no parental history of HT (PH⁻). Among the group of PH⁺ subjects, BP reactivity to mental stress was as follows: the high aerobic fitness subgroup (V̇O_2peak=54.6±1.2 ml/kg/min) (n=15) exhibited a 7.3±2.0 mmHg rise in SBP and a 3.2±2.0 mmHg rise in MABP, and the low aerobic fitness subgroup (V̇O_2peak=37.1±0.7 ml/kg/min) (n=15) had a 15.8±2.0 mmHg rise in SBP and an 11.8±2.0 mmHg rise in MABP (p<0.05). Among the group of PH⁻ subjects with high and low aerobic fitness (n=30, 15/group), no differences in BP reactivity to mental stress were found. These results suggest that a lifestyle of physical activity associated with a high level of aerobic fitness may attenuate BP reactivity to mental stress and reduce the risk of HT in AA men. Copyright © 2000 John Wiley & Sons, Ltd.     

Transfusion-associated transmission of human T-lymphotropic virus types I and II: experience of a regional blood center

During a 22-month period, 78,000 blood donors were screened for human T- lymphotropic virus types I and II (HTLV-I/II) at Belle Bonfils Memorial Blood Center (Denver, Colorado). Positive donors and the living recipients of their previously donated blood components were evaluated for risk factors and symptoms related to HTLV-I infection, were screened by enzyme immunoassay, confirmed by Western blot for HTLV- I/II, and subsequently tested by polymerase chain reaction and peptide enzyme immunoassay to distinguish between HTLV-I and -II infection. Six seropositive blood donors (0.008%) were identified; four were typed as having HTLV-I infection and two as having HTLV-II. Of 18 living recipients of components from seropositive donors, none had risk factors for HTLV-I infection prior to transfusion and none had signs or symptoms of HTLV-I infection at follow-up. The mean time from transfusion to testing was 6.4 years. Seven recipients of HTLV-I- infected components were HTLV seropositive; all were typed as having HTLV-I. A possible case of posttransfusion HTLV-I-associated myelopathy was identified in one patient who died before complete evaluation. One possible case of transfusion-associated HTLV-II was identified. These data further support the continued screening of blood donors for HTLV- I/II.     

Supratentorial ependymoma: CT appearance

The computed tomographic appearances of 22 biopsy-proved supratentorial ependymomas were analyzed. Supratentorial ependymomas were usually intraparenchymal, larger than 4 cm, and cystic. Contrast enhancement was moderate to intense, with homogeneous or ring-enhancement patterns commonly seen. Intratumoral calcification was present in one-third of the cases, while hydrocephalus and peritumoral edema were seen in 50%. Intratumoral hemorrhage was not a characteristic of the lesion. In contrast to cellular ependymomas, malignant ependymomas and ependymoblastomas demonstrate higher attenuation prior to administration of contrast material, more intense enhancement, lower frequency of calcification within the tumor, and less distinct margination.     

Rapid effects of hypoxia on H+ homeostasis in articular chondrocytes

Articular chondrocytes experience low oxygen (O₂) levels compared with many other tissues, and values fall further in disease states. Chondrocyte intracellular pH (pH_i) is a powerful modulator of matrix synthesis and is principally regulated by Na⁺-H⁺ exchange (NHE). In equine chondrocytes, NHE is inhibited when cells are incubated for 3 h at low O₂, leading to intracellular acidosis. O₂-dependent changes in reactive oxygen species (ROS) levels appear to underlie this effect. The present study examines whether hypoxia can influence chondrocyte NHE activity and pH_i over shorter timescales using the pH-sensitive fluoroprobe BCECF in cells isolated not only from equine cartilage but also from bovine tissue. O₂ levels in initially oxygenated solutions gassed with N₂ fell to approximately 1% within 2 h. A progressive fall in pH_i and acid extrusion capacity was observed, with statistically significant effects (P?<?0.05) apparent within 3 h. For equine and bovine cell populations subjected to step change in O₂ by resuspension in hypoxic (1%) solutions, a decline in acid extrusion and pH_i was observed within 10 min and continued throughout the recording period. This effect represented inhibition of the NHE-mediated fraction of acid extrusion. Cells subjected to hypoxic solutions supplemented with CoCl₂ (100 μM) or antimycin A (100 µM) to raise levels of ROS did not acidify. The conserved nature and rapidity of the response to hypoxia has considerable implications for chondrocyte homeostasis and potentially for the maintenance of cartilage integrity.     

Patients’ preference for radiotherapy fractionation schedule in the palliation of symptomatic unresectable lung cancer†

The palliative radiotherapeutic management of unresectable non‐small‐cell lung cancer is controversial, with various fractionation (Fx) schedules available. We aimed to determine patient’s choice of Fx schedule after involvement in a decision‐making process using a decision board. A decision board outlining the various advantages and disadvantages apparent in the Medical Research Council study of Fx schedules (17 Gy in two fractions vs 39 Gy in 13 fractions) was discussed with patients who met Medical Research Council eligibility criteria. Patients were then asked to indicate their preferred Fx schedules, reasons and their level of satisfaction with being involved in the decision‐making process. Radiation oncologists (RO) could prescribe radiotherapy schedules irrespective of patients’ preferences. Of 92 patients enrolled, 55% chose the longer schedule. English‐speaking patients were significantly more likely to choose the longer schedule (P = 0.02, 95% confidence interval: 1.2–7.6). Longer Fx was chosen because of longer survival (90%) and better local control (12%). Shorter Fx was chosen for shorter overall treatment duration (80%), cost (61%) and better symptom control (20%). In all, 56% of patients choosing the shorter schedule had their treatment altered by the treating RO, whereas only 4% of patients choosing longer Fx had their treatment altered (P < 0.001). Despite this, all (100%) patients were satisfied with being involved in the decision‐making process. The decision board was useful in aiding decision‐making, with both Fx schedules being acceptable to patients. Interestingly, despite the longer average survival associated with longer Fx, nearly half of the patients believed that this was not as important as a shorter duration of treatment and lower cost. Despite patients’ preferences, there were significant alterations of preferred schedules because of RO’s own biases.