Effects of posture, Valsalva maneuver and respiration on atrial flutter rate: an effect mediated through cardiac volume

The effects of passive upright tilting from 0 degrees to +60 degrees (n = 27), Valsalva maneuver (n = 16) and respiration (n = 10) on the rate of atrial flutter were studied in 27 patients. After tilting to +60 degrees, the atrial flutter cycle length shortened in all patients from 247.5 +/- 7 to 236.7 +/- 6.9 ms (range of shortening 1 to 21 ms, p less than 0.001). The Valsalva maneuver (strain of 40 mm Hg) shortened the flutter cycle length during the strain (phase 2) from 242.2 +/- 4.6 to 230.5 +/- 5 ms (range of shortening 2 to 19 ms, p less than 0.001). In 10 patients whose respiration was monitored, the flutter cycle length consistently prolonged during inspiration and shortened during expiration. Combined beta-adrenergic and muscarinic receptor blockade in six patients did not significantly alter the flutter cycle length at rest or the effects of the various maneuvers on the changes in flutter cycle length. This study revealed that the atrial flutter cycle length can be shortened by passive upright tilting, the strain phase of the Valsalva maneuver and expiration. Changes in flutter cycle length were independent of autonomic tone, implying that by decreasing cardiac volume, these maneuvers affect characteristics of the atrial flutter circuit, thereby producing dynamic changes in the rate of atrial flutter.

Tibial collateral ligament bursa: MR imaging

The bursa of the tibial collateral ligament (TCL) may be visualized at magnetic resonance (MR) imaging when it becomes distended with fluid. In the authors' experience, this finding signifies a pathologic condition either in the medial capsuloligamentous complex or in the bursa itself. Such a finding may indicate TCL bursitis. TCL bursitis can be suspected in the setting of isolated pain in the medial joint line in the absence of mechanical symptoms. Prolonged relief of symptoms after injection of steroid into the bursa is supportive of the diagnosis. Seven cases are presented in which a fluid-filled TCL bursa was identified at MR imaging. In five cases, TCL bursitis was suspected. The differential diagnosis for the MR findings is discussed.

Ex-vivo MR imaging of the cruciate ligaments

Eight pairs of cruciate ligaments were obtained at autopsy for ex-vivo MR imaging. Image analysis demonstrated no differences in intrinsic signal characteristics between the anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). Histologic examination showed no differences in ligament organization. These findings support the hypothesis that the normal signal intensity difference between the ACL and PCL noted on clinical images is due to a volume-averaging artifact.

The cytoplasmic domain of the CD8 alpha-chain is required for its interaction with p56lck

The CD8 glycoprotein expressed on the surface of CTLs is a heterodimer composed of alpha (Lyt-2) and beta (Lyt-3) chains. Recent studies have shown that CD4 and CD8 are physically associated with a T cell-specific protein-tyrosine kinase p56lck. Our previous experiments have suggested strongly that p56lck interacts directly with CD4 and CD8 molecules. The present report using cytoplasmic deletion mutants of the CD8 alpha-chain gene has extended our observations to demonstrate unequivocally that the cytoplasmic domain of the CD8 alpha chain is responsible for interaction with p56lck. The data has also confirmed the importance of the conserved twelve amino acid sequence motif of the CD8 alpha cytoplasmic domain in complex formation with p56lck.

Calcium-calmodulin binding in ischemic rat neurons after calcium channel blocker therapy

Calcium channel blockers such as nicardipine improve outcome after global cerebral ischemia and may attenuate ischemic neuronal injury by preventing calcium influx and binding to calmodulin. We followed the temporal and regional sequence of neuronal calcium-calmodulin binding in normal rats (n = 6), untreated ischemic rats (n = 15), and ischemic rats treated with 0.05 mg/kg/hr s.c. nicardipine (n = 13). After 30 minutes of four-vessel occlusion, 40-microns brain sections were incubated in an anti-calmodulin antibody specific for calmodulin not bound to calcium and brain protein. Light-microscopic sections were examined immediately after ischemia and after 2 and 24 hours of reperfusion. Extensive staining of unbound calmodulin was seen in all hippocampal regions and in the cortex in normal rats. In untreated ischemic control rats, staining was lost, indicating calcium-calmodulin binding immediately after ischemia in all regions. However, after 24 hours, staining returned to normal in the cortex and dentate, and minimal staining returned in CA1 and CA3. Nicardipine-treated animals had significantly less calcium-calmodulin binding in CA1 and in the dentate after 2 hours of reperfusion. This study demonstrates that in clinically relevant doses nicardipine has a limited effect on calcium-calmodulin binding in selectively vulnerable regions after severe ischemia.

Magnetic Resonance Imaging of Osseous Lesions of the Knee

In brief Although magnetic resonance imaging of the knee is performed primarily to assess meniscal and soft-tissue pathology, traumatic osseous lesions also may be detected with this method. These lesions include occult intraosseous fracture (a new diagnostic entity), stress fracture, and osteochondral fracture. The authors discuss specific features of magnetic resonance images that can help the physician make an accurate diagnosis.

Empyema of the gallbladder in a patient with AIDS-related complex

A case of staphylococcus aureus empyema of the gallbladder in a patient with AIDS-related complex is presented. The case is remarkable for the indolence of the clinical presentation and the magnitude of gallbladder dilatation noted at computed tomographic (CT) examination. Empyema of the gallbladder may constitute an unusual manifestation of bacterial disease in patients with AIDS or AIDS-related complex and cholelithiasis.

Magnetic Resonance Imaging of Major Ligamentous Knee Injuries

In brief: Magnetic resonance imaging (MRI) is useful for assessment of capsuloliga-mentous and other periarticular soft-tissue structures of the knee. It is especially valuable for its ability to accurately diagnose tears of the anterior cruciate ligament (ACL). MRI findings that indicate an ACL tear include frank disruption of the ligament, waviness to the anterior margin of the ligament, and areas of heterogeneous increased signal within the ligament on sagittal T2-weighted images.

Magnetic Resonance Imaging of Meniscal Tears

In brief: Magnetic resonance imaging (MRI) is highly accurate for diagnosing meniscal tears. It can be performed reliably even when the patient is in acute pain and when joint effusion and hemarthrosis are present. Though it is dependent on a machine and a protocol, MRI is essentially operator-independent, unlike arthrography and arthroscopy, which rely on operator skill. MRI has the potential to improve the accuracy of arthroscopy because it can localize pathology and prompt more thorough examination of difficult areas.

Occult intraosseous fracture: magnetic resonance appearance versus age of injury

Twenty-two cases of occult intraosseous fracture in the region of the knee are presented. Occult intraosseous fractures have been incidentally detected in the magnetic resonance (MR) evaluation of the knee in the setting of a recent physical injury and normal radiographic studies. There is no unique mechanism of injury, but occult intraosseous fracture presumably results from direct impaction or axial overloading. MR shows speckled or band-like areas of low signal in the intramedullary space of the epiphyses, and occasionally, the adjacent metaphyses. In most cases, T2-weighted images show high signal in corresponding regions of variable size. The relative extent of high signal findings is shown to vary significantly with the age of injury. Individual variability within groups, however, precludes the actual prediction of lesion age on the basis of the MR appearance. Our observations provide indirect evidence that the findings on T2-weighted images resolve earlier than the corresponding findings on T1-weighted proton density images. The primary differential diagnosis in cases of occult intraosseous fracture is stress fracture. The diagnosis of occult intraosseous fracture may be important in explaining persistent pain after injury in otherwise normal knees.

Rounded atelectasis associated with end-stage renal disease

Three cases of end-stage renal disease are presented where plain radiographs of the chest suggested the diagnosis of rounded atelectasis. The clinical setting and follow-up radiographs in each case served to corroborate this diagnosis. The recognition of this benign condition in patients with end-stage renal disease may be important in obviating further invasive procedures in this subset of high risk patients.

Avulsion of the posteromedial tibial plateau by the semimembranosus tendon: diagnosis with MR imaging

Two sports-related knee injuries resulted in small fractures at the posteromedial corner of the tibial plateau. Magnetic resonance imaging demonstrated findings consistent with an avulsion injury at the semimembranosus insertion, as well as a similar pattern of internal derangement in both cases.

Palmar dislocation of the trapezoid: case report

A case of palmar dislocation of the trapezoid, associated with radial subluxation of the trapezium, is presented. This rare injury was treated by internal fixation. A satisfactory clinical result is noted 4 years later.

Isoproterenol induction of vasodepressor-type reaction in vasodepressor-prone persons

The ability of isoproterenol to induce symptoms and laboratory findings of a vasodepressor reaction was tested in 48 patients, ages 17 to 74, divided into 4 groups according to the reason for their referral. Group 1 comprised 12 patients with vasodepressor syncope, group 2 had 8 patients with syncope of unknown origin, group 3 included 11 patients with syncope due to seizures in 2 and ventricular tachycardia in 9, group 4 had 17 patients with various arrhythmias not associated with syncope. Isoproterenol boluses were administered starting at 2 micrograms and increased in 2-micrograms steps to a maximum of 8 micrograms at 0 degree and +60 degrees. The responses at 0 degrees were all normal. At +60 degrees a vasodepressor reaction consisting of syncope or near syncope, hypotension and bradycardia was produced by isoproterenol (mean dose 6.0 +/- 0.26 micrograms) in 8 patients from group 1 (66.6%), 4 from group 2 (50%), 0 from group 3 and 4 from group 4 (23.5%). Three of the 4 patients in group 4 had a remote history of classic vasodepressor syncope. The overall sensitivity and specificity of the test were 73 and 85%, respectively, while the predictive accuracy of a test with positive or negative outcome were 69 and 89%, respectively. Muscarinic receptor blockade with atropine in 4 patients prevented isoproterenol-induced bradycardia but not hypotension or symptoms of fainting. Beta-adrenergic receptor blockade with propranolol inhibited all aspects of the isoproterenol-induced faint. Thus, the administration of isoproterenol during a passive upright tilt may identify persons who suffer from or are prone to a vasodepressor reaction.

Stress fractures: MR imaging

Five cases of stress fracture were studied with high-field-strength magnetic resonance (MR) imaging. In all cases, MR images showed bandlike areas of very low signal intensity in the intramedullary space, which were continuous with the cortex. These findings corresponded in location to the sites of fracture or new bone formation noted on radiographs. Surrounding areas of decreased signal intensity in the marrow space were also consistently seen on T1-weighted images. In three cases, prominent intramedullary areas of high signal intensity were noted on T2-weighted images obtained within 3 weeks of the onset of symptoms. Juxtacortical and/or subperiosteal areas of high signal intensity were also seen on T2-weighted images in two cases. Characteristic MR findings may distinguish stress fracture from occult intraosseous fracture.

Occult intraosseous fracture: detection with MR imaging

Magnetic resonance (MR) images were retrospectively evaluated in eight patients who had recent, symptomatic knee injuries and in whom plain radiographs showed no fractures. T2-weighted images revealed irregular, intraosseous areas of high signal intensity; T1-weighted and proton density images revealed speckled or linear regions of low signal intensity in corresponding areas. In the seven patients whose injuries did not result from direct contusion, abnormalities occurred in subchondral locations. Two patients underwent bone scintigraphy, which showed increased activity in locations corresponding to areas of abnormality noted on MR images. Two patients underwent follow-up MR imaging at 6 weeks and 3 months, which showed complete resolution of the abnormalities. The authors speculate that the MR imaging findings represent microscopic compression fracture of trabecular bone and discuss the related entity, stress fracture.

Anterior cruciate ligament tears: MR imaging compared with arthroscopy and clinical tests

Seventy-nine magnetic resonance (MR) studies of the knee were reviewed in an evaluation of the ability of MR imaging to demonstrate arthroscopically proved anterior cruciate ligament (ACL) tears. MR findings were also compared with the findings of two commonly applied clinical tests of ACL instability: the Lachman test and the anterior drawer test. The sensitivity of MR imaging was 94% (17 of 18), compared with 78% (14 of 18) for the anterior drawer test and 89% (16 of 18) for the Lachman test. The specificity was 100% for all three. Three MR criteria were applied: irregularity or a wavy contour of the anterior margin of the ligament, high-signal-intensity change within the substance of the ligament on T2-weighted images, and discontinuity of that substance. The sagittal T2-weighted image was especially helpful, producing an "arthrographic" effect, in which the anterior margin of the ACL is outlined by high-signal-intensity joint fluid. By demonstrating ACL and other extrameniscal lesions, MR imaging may help clarify the mechanisms of knee injury.

MR imaging of solitary osteochondromas: report of eight cases

MR imaging was performed in eight patients with osteochondromas, and the results were compared with the histologic findings in six of these cases. MR imaging effectively showed the essential anatomic features of lesions and was particularly useful in assessing the presence and thickness of the cartilage cap. The cartilage cap was clearly seen as a region of high signal intensity on T2-weighted images. A superficial zone of low signal intensity was seen covering the cartilage cap, corresponding to an intact perichondrium, in all of the five cases in which histologic examination confirmed the presence of an intact perichondrium. The results of MR in these cases suggest that MR is useful in the preoperative planning of cases in which excision of an osteochondroma is necessary. Optimal surgical resection of the lesion requires complete excision of an intact perichondrium to prevent possible recurrence of the tumor.

Multiple alleles and low variability of glycerol-3-phosphate dehydrogenase in Aedes albopictus (Diptera: Culicidae) from Peninsular Malaysia

1. A total of 8 samples from three natural populations and a laboratory strain of Aedes albopictus were analysed for glycerol-3-phosphate dehydrogenase phenotypes by means of horizontal starch-gel electrophoresis. 2. The electrophoretic phenotypes were governed by three codominant Gpd alleles. 3. There was low variability, with the heterozygosity in the variable samples ranging from 0.02 to 0.12. 4. The commonest allele in all the population samples was GpdB which encoded an electrophoretic band with intermediate mobility. 5. There was no temporal or spatial variation.

Digoxin metabolism in the elderly

Tritiated digoxin (0.5 mg) was given intravenously to five elderly men (mean age, 77 years) and nine young men (mean age, 27 years). The elderly were not in congestive heart failure. The serum creatinines of the old and young were not different. However, the creatinine clearance averaged 56 ml/min/1.73 m 2 in the old and 122 ml/min/1.73 m 2 in the young ( P <0.001). Digoxin clearance averaged 53 ml/min/1.73 m 2 in the old and 83 ml/min/1.73 m 2 in the young ( P <0.001). The blood concentrations of tritiated digoxin were significantly higher in the elderly throughout the study ( P <0.05). When blood digoxin concentrations were corrected for body surface area, there was no significant difference between the two groups during the first 24 hr, but thereafter the concentrations in the elderly were higher.

The same dose of digoxin resulted in higher blood concentrations and longer blood half-life in the elderly. This is due to the smaller body size and a diminished urinary excretion of digoxin in the elderly.