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Biomedical subjects

M J Post

Publications and source records attributed to M J Post.

At least 73 records · Page 4Linked to original sources
PubMed1993

Cranial neuropathy heralding otherwise occult AIDS-related large cell lymphoma.

Three HIV-infected patients developed cranial neuropathy as the initial manifestation of an AIDS-related large cell lymphoma. All were homosexual men known to be HIV seropositive for 3 to 4.5 years. At the time of presentation for neurological disease, the CD4 T-lymphocyte count was < 400 cells/mm3 in each. Initial manifestations were retro-orbital headache and oculomotor nerve palsy in two and an abducens nerve palsy in the other. Repeatedly negative CSF cytologies and recovery of the cranial neuropathy obscured the diagnosis. These patients illustrate that cranial neuropathy with HIV infection may herald the presence of an occult large cell lymphoma. Spontaneous or corticosteroid-associated improvement of the cranial neuropathy, absence of abnormalities on brain imaging studies, and negative CSF cytologies do not exclude this diagnosis. We suggest that a diligent and repeated search for lymphoma be considered in HIV-infected patients presenting with cranial neuropathy, including repeated CSF examinations, MRI of brain and spine (T1 and T2) with and without gadolinium enhancement, chest and abdominal CT scans, and bone marrow biopsy.

Adult↗
PubMed1992

Acute traumatic central cord syndrome: MRI-pathological correlations.

The acute traumatic central cord syndrome (ATCCS) is commonly stated to result from an injury which affects primarily the center of the spinal cord and is frequently hemorrhagic. To test the validity of this widely disseminated hypothesis, the magnetic resonance images [MRI] of 11 consecutive cases of ATCCS caused by closed injury to the spine were analyzed and correlated with the gross pathological and histological features of 3 cervical spinal cords obtained at post mortem from patients with ATCCS, including 2 of patients studied by MRI. The MRI studies were performed acutely (18 h to 2 days after injury) in 7 patients and subacutely (3-10 days after injury) in 4. Ten of the 11 patients had pre-existing spondylosis and/or canal stenosis. The 11th suffered a cervical fracture. All patients exhibited hyperintense signal within the parenchyma of the cervical spinal cord on gradient echo MRI. None showed MRI features characteristic of hemorrhage on T1-weighted spin echo or T2-weighted gradient echo studies. Gross and histological examination of the necropsy specimens showed no evidence of blood or blood products within the cord parenchyma: the primary finding was diffuse disruption of axons, especially within the lateral columns of the cervical cord in the region occupied by the corticospinal tracts. The central gray matter was intact. In patients with ATCCS, the predominant loss of motor function in the distal muscles of the upper limbs may reflect the importance of the corticospinal tract for hand and finger function in the primate. In this study, the MRI and pathological observations indicate that ATCCS is predominantly a white matter injury and that intramedullary hemorrhage is not a necessary feature of the syndrome; indeed, it is probably an uncommon event in ATCCS. We suggest that the most common mechanism of injury in ATCCS may be direct compression of the cervical spinal cord by buckling of the ligamenta flava into an already narrowed cervical spinal canal; this would explain the predominance of axonal injury in the white matter of the lateral columns.

Adult↗
PubMed1992

Origin of arterial wall dissections induced by pulsed excimer and mid-infrared laser ablation in the pig.

To study adjacent tissue damage after delivery of holmium, thulium and excimer laser pulses, porcine thoracic aortas were irradiated in vivo. After 3 days, microscopic analysis of 67 craters produced by all three lasers demonstrated large dissections extending from the craters. The mean diameter of the dissections was smaller for excimer-induced craters (1.38 +/- 0.42 mm; n = 22) than for holmium-induced (2.7 +/- 0.87 mm; n = 22) and thulium-induced (2.37 +/- 0.42 mm; n = 14) craters (p less than 0.01 vs. mid-infrared dissections). In addition, microscopic analysis demonstrated necrosis adjacent to the crater. The lateral necrotic zones of the thulium-induced craters were smaller than the holmium- and excimer-induced necrotic zones (p less than 0.01). To identify the origin of the excessive tissue tearing, laser-saline and laser-tissue interaction were compared in vitro by time-resolved flash photography. In saline solution, the mid-infrared lasers showed bubble formation on a microsecond time scale. The excimer laser produced similar bubbles in the vicinity of tissue. For all three lasers, elevation of the tissue surface was shown during in vitro ablation. Dimension (diameter up to 4 mm) and time course (rise time of 100 to 300 microseconds) of bubble formation and tissue elevation were strikingly similar. Thus, tissue dissections are caused by the expansion of a vapor bubble within the target tissue. Coronary dissections after excimer and mid-infrared laser angioplasty might be related to the forceful bubble expansion.

Angioplasty, Laser↗
PubMed1992

MR imaging of tuberous sclerosis: pathogenesis of this phakomatosis, use of gadopentetate dimeglumine, and literature review.

Findings on cranial magnetic resonance (MR) images were correlated with known histopathologic findings in 42 patients with tuberous sclerosis (TS), 17 of whom received gadopentetate dimeglumine, to extend the range of signs on MR images. Four neuroradiologists recorded the number, sites, configurations, and relative signal intensities of intracranial abnormalities. White matter lesions, found in 39 patients (93%), showed four distinct patterns: (a) straight or curvilinear bands extending radially from the ventricle through the cerebral mantle toward the cortex, (b) wedge-shaped lesions, (c) nonspecific conglomerate foci, and (d) cerebellar radial bands. It is concluded that cortical tubers, white matter lesions, subependymal nodules, and sub-ependymal giant cell astrocytomas (SGCAs) may be enhanced after administration of gadopenetetate dimeglumine. Enhancement of a TS lesion does not indicate neoplastic transformation into SGCA. Imaging surveillance every 12 months appears indicated during the peak ages (8-18 years) of occurrence of SGCA. The appearance of white matter lesions supports the theory that the cerebral lesions of TS may be caused by disordered migration of dysgenetic cells.

Adolescent↗
PubMed1992

Syphilitic cerebral gumma with HIV infection.

We describe two human immunodeficiency virus (HIV)-infected patients with syphilitic cerebral gummas. Both patients presented with a seizure disorder associated with an isolated, peripherally located, contrast-enhancing lesion of the brain on CT. Cranial MRI performed on one patient revealed dural thickening in the region of the lesion. A brain biopsy in that patient revealed a lymphoplasmacytic infiltrate with extensive perivascular inflammation. Clinical manifestations, radiographic resolution of the lesions, and a decline in nontreponemal serologic tests for syphilis followed high-dose aqueous penicillin therapy in both patients. These patients illustrate that (1) cerebral mass lesions occurring with HIV infection may result from syphilis; (2) seizures may be the presenting manifestation of this form of neurosyphilis; and (3) high-dose, intravenous, aqueous penicillin is effective in treating these lesions.

Adult↗
PubMed1992

Mid-infrared pulsed laser ablation of the arterial wall. Mechanical origin of "acoustic" wall damage and its effect on wall healing.

Pulsed mid-infrared lasers are an alternative to excimer lasers for transluminal angioplasty. The mid-infrared lasers, however, were reported to produce "acoustic" wall damage that might impair the immediate and long-term results. To study the immediate and long-term effects on the arterial wall, 184 craters (1 mm diameter and 1 mm depth) were produced perpendicular to the intimal lining in the thoracic aortas of pigs. Three types of craters were evaluated: Ho-YSGG laser-induced (lambda = 2.09 microns, 2 pulses of 500 microseconds, 0.50 joule/pulse, 50 gm force), mechanically drilled, and "acoustic" craters. "Acoustic" craters were produced by two laser pulses delivered into a saline-filled metal fiber cap, which was placed in a mechanically drilled crater. The metal cap was provided with four outlets for water vapor and isolated "acoustic" from optical and thermal laser effects. The pigs survived 3, 14, and 28 days. Arterial wall damage, medial necrosis, and wall healing were assessed microscopically. At 3 days, laser and "acoustic" craters were accompanied by large tissue ruptures (2.7 +/- 0.9 mm and 2.9 +/- 0.8 mm, respectively, mean +/- standard deviation). These were attributed to large vapor bubbles expanding within the tissue. A zone of medial necrosis was observed adjacent to the laser craters (0.43 +/- 0.15 mm) and to the "acoustic" craters (0.17 +/- 0.14 mm). Neither ruptures nor necrosis was observed with the mechanical craters. At 2 and 4 weeks, the necrotic areas were repopulated with smooth muscle cells and all craters were adequately filled with smooth muscle cells, without any sign of an exaggerated proliferative response. We conclude that within the arterial wall, Ho-YSGG ablation was accompanied by the rapid expansion of a water vapor bubble. The formation of the relatively large vapor bubble is inherent to the use of a mid-infrared laser. The risk of creating dissections clinically, when delivering Ho-YSGG laser pulses, remains to be determined. The present study provided no indication that the arterial wall fissures might affect the restenosis rate unfavorably by promoting myointimal proliferation.

Angioplasty, Laser↗
PubMed1991

Functional characterization of the muscarinic receptor in rat lungs.

The effects of various muscarinic antagonists on antigen- and acetylcholine-induced bronchoconstriction were studied. In isolated and ventilated lungs of naive rats, the pA2 values with respect to acetylcholine-induced bronchoconstriction were 9.01 (atropine), 8.39 (ipratropium bromide), 7.39 (pirenzepine), 5.94 (AF-DX 116, a M2-selective muscarinic antagonist), 6.91 (UH-AH 37, a novel muscarinic antagonist) and 9.37 (4-DAMP: 4-diphenylacetoxy-N-methylpiperidine methobromide). Except for ipratropium bromide, the slopes of the Schild plots were not significantly different from unity. None of the drugs were potent or effective in inhibiting bronchoconstriction or histamine release evoked by antigen challenge in actively sensitized rats. However, in vivo, in anesthetized spontaneously breathing rats, vagotomy and atropine (1 mg/kg) did reduce antigen-induced bronchoconstriction. It is concluded that functional muscarinic receptors in isolated rat lungs are probably of the M3 receptor subtype. With respect to antigen-induced bronchoconstriction and mediator release in a denervated model such as the isolated lung, they are of little, if any, importance. In vivo, vagotomy and atropine reduced antigen-induced bronchoconstriction, probably by blockade of a vagal reflex which is thought to play a role in antigen-evoked bronchoconstriction.

Acetylcholine↗
PubMed1991

Imaging of post-mortem coronary arteries by 30 MHz intravascular ultrasound.

Intravascular ultrasound cross-sectional imaging of the atherosclerotic artery may be employed to guide plaque ablation by spark erosion, atherectomy, laser irradiation or other means. To assess whether in the coronary artery the echolucent zone of the three-layered ultrasound appearance of muscular arteries might be a reliable boundary to halt transluminal ablative angioplasty, epicardial coronary arteries were scanned under pressure over a distance of 4-8 cm at 1 mm intervals. A 5.2F catheter with a 30 MHz transducer rotating at 600 RPM was used. In 419 images from four post-mortem hearts, aged at death 22, 31, 56 and 82 years, the presence of a distinct echolucent zone was scored as percentage of the wall circumference. The median scores were 0%, 0%, 10% and 75%, respectively. In the three youngest hearts, the three-layered appearance was largely absent. In the 82 year old heart, in contrast, the three-layered appearance could generally be identified. Within subjects, the presence of an echolucent zone was variable in location. Qualitatively, neither abundant medial elastin tissue nor a reduced medial thickness could explain the absence of an echolucent zone when the ultrasound image was compared to the corresponding microscopic section. The results show that in the 82 year old heart, 30 MHz intravascular ultrasound discrimination of coronary wall layers would be adequate to guide transluminal plaque ablation. In the younger hearts, guided ablation would fail due to the limited presence of a distinct echolucent zone as an ultrasound landmark of the media. Whether the presence or absence of an echolucent zone is related to age remains to be determined.

Adult↗
PubMed1991

Percutaneous coronary and peripheral angioscopy with saline solution and carbon dioxide gas in porcine and canine arteries.

To obtain a clear view with angioscopy, blood must be displaced. Carbon dioxide (CO2) gas has proved to be a safe intraarterial contrast agent, and it may have advantages over saline solution as an infusion medium for angioscopy. This study compared the use of CO2 gas and saline solution in the femoral artery, in the presence and absence of a proximal occlusion, in nine pigs and six dogs. The applicability of CO2 gas in the coronary arteries was also evaluated. In total 185 angioscopy procedures were evaluated. With proximal occlusion, angioscopy with CO2 gas was successful in all 28 peripheral procedures, whereas with saline solution only 65% of the procedures resulted in a clear view (p less than 0.005). Without proximal occlusion, angioscopy was successful with CO2 gas and saline solution in 61% and 3% of procedures, respectively (p less than 0.0001). Cardiovascular parameters and blood gases showed minor changes after administration of CO2 gas. During coronary angioscopy with CO2 gas, mechanical heart failure occurred in all instances, which was lethal in 12 animals. None of the animals died as a result of saline angioscopy. In conclusion, CO2 gas is a safe medium for angioscopy in the peripheral arteries and in general offers a better view than saline solution. In contrast to saline solution, without proximal balloon occlusion CO2 gas provided a clear view in 61% of the peripheral procedures. In the coronary arteries, however, CO2 angioscopy was generally fatal in both animal models.

Animals↗
PubMed1991

Effects of milrinone, sulmazole and theophylline on adenosine enhancement of antigen-induced bronchoconstriction and mediator release in rat isolated lungs.

The effects of adenosine and some of its analogues on bronchoconstriction and mediator release were studied in isolated lungs of actively sensitized rats. The influence of two novel cardiotonic drugs, milrinone and sulmazole on these adenosine-induced effects was compared with that of theophylline, a well known adenosine antagonist. Adenosine (ADO) and its analogues N-ethyl-carboxamide-adenosine (NECA) and R-phenyl-isopropyladenosine (R-PIA), dose-dependently enhanced antigen-induced bronchoconstriction. The enhancement of anaphylactic bronchoconstriction by adenosine and its analogues was accompanied by a rise in histamine release. The rank order of potency for adenosine and analogues with respect to enhancement of anaphylactic bronchoconstriction, was NECA greater than or equal to R-PIA greater than ADO. An unequivocal classification of the adenosine receptor involved, was therefore not possible. Dipyridamole and S-(p-nitrobenzyl-6-thioinosine) (NBTI), both inhibitors of adenosine uptake, had no inhibitory influence on the adenosine-induced enhancement of anaphylactic bronchoconstriction, indicating that this enhancement is mediated by an extra-cellular receptor. Theophylline, milrinone and sulmazole inhibited the enhancement of anaphylactic bronchoconstriction, without affecting preformed mediator release. Theophylline and sulmazole were both more effective as inhibitors of adenosine-enhanced bronchoconstriction than as inhibitors of antigen-induced bronchoconstriction, suggesting adenosine antagonism. Milrinone was equi-effective as inhibitor of both types of bronchoconstriction. Since adenosine antagonism has been associated with the side effects of theophylline it will be interesting to further investigate the therapeutic merits of novel cyclic nucleotide phosphodiesterase inhibitors in the treatment of asthma.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1991

Asymptomatic and neurologically symptomatic HIV-seropositive individuals: prospective evaluation with cranial MR imaging.

As part of a prospective multidisciplinary study of individuals seropositive for the human immunodeficiency virus (HIV), cranial magnetic resonance (MR) imaging was performed on 119 HIV-seropositive subjects (95 asymptomatic, 24 symptomatic) and the results were correlated with clinical data. MR images regarded as positive included those showing atrophy and/or white matter lesions. On the basis of these criteria, 96 subjects had normal MR images and 23 had abnormal images. Results of chi 2 analysis revealed a statistically significant difference between the asymptomatic group (12 of 95 [13%] with abnormal scans) and the symptomatic group (11 of 24 [46%] with abnormal scans) (P = .001). In the asymptomatic group, positive MR images showed fewer, smaller, and/or less extensive abnormalities. The researchers conclude that (a) MR imaging can show indirect evidence of HIV infection early in the disease, but abnormalities will be minor and seen only in a small minority of neurologically asymptomatic subjects; (b) the appearance of clinically recognizable neurologic disease correlates with the MR imaging findings of increasingly severe brain atrophy and white matter lesions; and (c) in some HIV-seropositive subjects, despite neurologic disease, MR images can remain normal. Results indicate that routine screening with cranial MR imaging of neurologically asymptomatic HIV-seropositive individuals would likely result in a low yield of positive findings.

AIDS Dementia Complex↗
PubMed1991

Complications of epidural anesthesia: MR appearance of abnormalities.

Eight patients with acquired intradural arachnoid abnormalities caused by epidural anesthesia were evaluated with magnetic resonance (MR) imaging (eight patients) and intraoperative ultrasound imaging (four patients). Subarachnoid cysts were found in the lower cervical and thoracic spine in six patients. Irregularity of the surface of the cord was noted in seven cases. Associated intramedullary cysts and myelomalacia were seen in two patients. Arachnoiditis was unsuspected clinically in four patients; findings at MR imaging first suggested the cause of the patients' symptoms. The underlying mechanism for the intradural and cord abnormalities in seven of the eight patients was a chemically induced arachnoiditis produced by the administration of epidural anesthesia; in the eight case, an infection introduced at the time of the epidural injection was the cause of the abnormalities. The authors postulate that the preservative agents in the vials of anesthetic may have been the causative factor of this inflammation in the majority of the cases.

Adult↗
PubMed1991

Magnetic resonance imaging of spinal infection.

The findings on magnetic resonance imaging in various types of spinal infection are described, including disc space infection and osteomyelitis, epidural abscess, paraspinal abscesses, and meningitis. The characteristic appearance of spinal infection on both plain and gadolinium-enhanced magnetic resonance is contrasted with that of the normal spine.

Abscess↗
PubMed1990

Cine MR in the evaluation of normal and abnormal CSF flow: intracranial and intraspinal studies.

Evaluation of intracranial and intraspinal CSF flow was accomplished by the use of cardiac gated gradient echo magnetic resonance (MR) technique. Normal patterns of pulsatile flow within the ventricles, cisterns and cervical subarachnoid space were established by this technique and these observations were compared to prior description of CSF flow. With systole there is downward (caudal) flow of CSF in the aqueduct of Sylvius, the foramen of Magendie, the basal cisterns and the dorsal and ventral subarachnoid spaces while during diastole, upward (cranial) flow of CSF in these same structures is seen. The relationships between the cardiac cycle and the CSF pulsations are demonstrated on both magnitude reconstruction and phase reconstruction MR images. Calculations of actual fluid velocity within CSF containing spaces can be obtained from the phase reconstruction images and holds promise for a more accurate analysis of CSF flow. In conditions which result in alterations of flow, cine MR dramatically shows either obstruction or excessively turbulent flow within the CSF pathways. The site of obstructed flow whether in the third ventricle, aqueduct, fourth ventricle, or subarachnoid space can be appreciated by changes in or absence of the normal hypointense signal. Cystic cord lesions such as congenital syringohydromyelia and posttraumatic spinal cord cysts may show pulsatile flow of CSF, a fact which can relate to progressive enlargement of these cysts. The distinction between myelomalacia and cyst formation in the cord is facilitated by the technique. Although the use of cine MR for the analysis of CSF flow is in its infancy, our experience indicates that this technique is useful in a wide range of pathological conditions including, but not limited to, conditions resulting in hydrocephalus or cystic cord lesions.

Brain↗
PubMed1990

Adenosine enhances antigen-induced bronchoconstriction and histamine release in rat isolated lungs.

The effects of adenosine and some of its analogues on bronchoconstriction and mediator release were studied in isolated lungs of actively sensitized rats. Adenosine (ADO) and its analogues R-phenyl-iso-propyl-adenosine (R-PIA) and N-ethyl-carboxamide-adenosine (NECA), enhanced antigen-induced bronchoconstriction in a dose-dependent manner. The enhancement of anaphylactic bronchoconstriction by adenosine and its analogues was accompanied by a rise in histamine release. The observed rank order of potency for adenosine and analogues (NECA greater than or equal to R-PIA greater than ADO) did not permit an unequivocal classification of the adenosine receptor involved. Dipyridamole and S-(p-nitrobenzyl-6-thioinosine) (NBTI), both inhibitors of adenosine uptake, had no inhibitory influence on the adenosine-induced enhancement of anaphylactic bronchoconstriction. Therefore, this enhancement was likely to be mediated through an extra-cellular receptor. Theophylline inhibited the enhancement of anaphylactic bronchoconstriction by adenosine in a concentration-dependent manner, without affecting preformed mediator release.

Adenosine↗
PubMed1990

Modulation of histamine release by rat peritoneal mast cells in a superfusion set-up.

A new method is presented for studying mediator release in isolated peritoneal cells of the rat. Using a superfusion technique, cells can be maintained in a continuously cleared medium. Cells were stimulated with antigen, compound 48/80 or A23187 to characterize this preparation. In addition, inhibitory effects of theophylline, isoprenaline and cromoglycate on compound 48/80-induced histamine release were studied. We conclude that superfusion is a valid alternative to study mediator release from isolated peritoneal cells.

Animals↗
PubMed1990

Lumbar disk herniation and canal stenosis: value of intraoperative sonography in diagnosis and surgical management.

One hundred four patients with preoperative diagnoses of lumbar canal stenosis, disk herniation, or a combination of both were evaluated with intraoperative sonography with the intent of (1) describing the sonographic characteristics of herniated disks and distinguishing these from bulging anuli, epidural fat, scar tissue, and spondylolisthesis; (2) establishing criteria for adequate decompression of canal stenosis; and (3) determining the usefulness of sonography in monitoring disk removal. Disk material demonstrates medium echogenicity, different in its sonographic features from bone, epidural fat, scar tissue, and epidural veins. A sonographic diagnosis of disk herniation was made in 43 cases, 41 of which were confirmed during surgery. Sonography established the presence or absence of disk herniation (confirmed by surgery) in 14 of 19 patients who had equivocal preoperative findings. After routine diskectomy, residual disk material was found in 17 (41%) of 41 patients, which led to further surgery in 16 patients with removal of the additional disk fragments. In 84 patients undergoing decompressive surgery for canal stenosis, sonography detected residual canal compression in 19 (23%), which led to a widened decompression in 15 of these patients. Sonography can differentiate disk material from other normal or abnormal structures in the canal; therefore, sonographic monitoring helps to ensure adequate bony decompression and complete diskectomy. We conclude that intraoperative sonography is an important tool in the surgical management of lumbar disk disease and stenosis.

Adipose Tissue↗