Biomedical subjects
Publications and source records attributed to H P Adams.
This report presents data from pilot studies of Org 10172 in the management of patients with acute ischemic stroke. The studies have established a potentially optimal dosage and treatment regimen and have provided information for the development of a large randomized trial. The trial of Org 10172 in acute stroke treatment is now underway in the United States.
We report a patient who sought treatment for an acute subarachnoid hemorrhage as a result of an intracranial aneurysm. Management included early surgical repair and intraoperative monitoring of evoked potentials. Pan-angiography revealed berry aneurysms of the communicating anterior artery and right middle cerebral artery. Surgery was uneventful, and the somatosensory evoked potential monitoring did not show any abnormalities. Nevertheless, the patient showed a neurological deficit due to a clip-related infarct in the right middle cerebral artery territory characterized by a right hemiparesis with no sensory deficit. This case report supports the possibility of false-negative results in single-mode intraoperative monitoring during aneurysm surgery.
Measures to prevent ischemic stroke after aneurysmal subarachnoid hemorrhage include management of fluids to avoid dehydration, use of calcium entry blocking drugs, and when necessary, therapy with drug-induced hypertension and hypervolemic hemodilution. Promising treatments that may also prove to be effective include 21-aminosteroids, intrathecal thrombolytic therapy, and transluminal angioplasty.
The sequence fibrinogen-A alpha-(148-160) can mimic part of the fibrin-induced rate enhancement of the activation of plasminogen by tissue-type plasminogen activator. Previously we have reported that the lysine residue at position A alpha-157 is crucial. During our further investigations on A alpha-157 we found that lysine at position A alpha-157 may be replaced by glutamic acid. This unexpected finding prompted us to re-investigate the requirements of this position. We prepared analogues of A alpha-(148-160) in which the lysine residue at position A alpha-157 was replaced by lysine derivatives (acetyl-lysine, benzyloxycarbonyl-lysine and methanesulphonylethyloxycarbonyl-lysine), acidic residues (aspartic acid and glutamic acid), basic residues (arginine and ornithine), polar residues (glutamine and methanesulphonylethyloxycarbonylornithine), apolar residues (alanine, valine, norleucine and glutamic acid 4-nitrobenzyl ester) and glycine. These analogues were tested for their stimulatory activity. When aspartic acid, glutamic acid 4-nitrobenzyl ester or norleucine is present at position A alpha-157 in A alpha-(148-160) virtually all stimulatory capacity is lost. With valine at position A alpha-157 the stimulatory activity is marginal. None of the other replacements at position A alpha-157 caused loss of rate-enhancing properties. From these results we conclude that for the rate-enhancing effect of A alpha-(148-160) the side chain of the amino acid residue at position A alpha-157 must fulfill certain requirements: there must be one (as in alanine) or no (as in glycine) carbon atom in the side chain, or at least two carbon atoms and a polar group (charged or uncharged) to which a rather bulky group (such as the benzyloxycarbonyl group) or a polar group (such as the methanesulphonylethyloxycarbonyl group) may be attached. The highest activity [even higher than native A alpha-(148-160)] was obtained with ornithine, methanesulphonylethyloxycarbonylornithine or methanesulphonylethyloxycarbonyl-lysine at position A alpha-157.
Fibrin accelerates the activation of plasminogen catalyzed by tissue-type plasminogen activator much stronger than fibrinogen. Detailed studies showed that (part of) this rate-enhancing effect of fibrin is brought about by two sites in the fibrin molecule: one in A alpha-(148-160) and one in the gamma-chain stretch 311-379 (also known as FCB-5). During the fibrinogen-to-fibrin conversion, A alpha-(148-160) appears to become accessible, because a monoclonal antibody against synthetic A alpha-(148-160) reacts with fibrin, but not with fibrinogen. Because a similar situation may exist for (at least parts of) FCB-5, we have prepared a monoclonal antibody against a part (ie, gamma-[312-324]) of FCB-5, and found that this is fibrin-specific and does not bind fibrinogen. We conclude that gamma-(312-324) is hidden in fibrinogen and is exposed by the formation of fibrin.
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The rate of activation of plasminogen by tissue-type plasminogen activator (t-PA) is greatly increased by fibrin, but much less by fibrinogen. Fibrin(ogen) fragments such as the fibrin(ogen) cyanogen bromide fragment FCB-2 and FCB-5, and a synthetic peptide with the sequence of fibrinogen A alpha-(148-160), a constituent of FCB-2, also have rate-enhancing properties. In order to find a possibly smaller, still stimulating site within A alpha-(148-160) we synthesized successive linear amino-terminally acylated hexapeptides [i.e. A alpha-(148-153), A alpha-(149-154)'d, .... A alpha-(155-160)] from the sequence A alpha-(148-160). The only hexapeptide within the sequence A alpha-(148-160) capable of enhancing the rate of plasminogen-to-plasmin conversion by t-PA appears to be the amino-terminally acylated peptide comprising the sequence A alpha-(154-159). This peptide enhances the plasminogen activation rate six-fold; half-maximal activation rate is reached at a peptide concentration of 56 microM.
The Mpc-group has a somewhat better stability than the Fmoc-group, resists catalytic hydrogenolysis, is highly stable in acidic media and its elimination product does not polymerize spontaneously. In a direct comparison of coupling efficiencies obtained in solid phase peptide syntheses using Mpc- or Fmoc-amino acids it is shown that the use of Mpc-amino acids leads to better coupling efficiencies and, consequently, a more homogeneous peptide. An improved synthesis of Mpc-ONSu and of Mpc-amino acid derivatives is presented.
We describe two adult patients who presented with acute cerebral infarction and were found to have a hypercoagulable state due to nephrotic syndrome. One patient had a deficiency of free protein-S. The other patient had a pulmonary embolus 4 months after the stroke. Our cases demonstrate that the hypercoagulable state associated with nephrotic syndrome can be associated with cerebral arterial thrombosis and infarction in adults. Examination of the urine remains an important part of the evaluation of patients with recent stroke. The presence of severe proteinuria and a low serum albumin content should prompt consideration of a hypercoagulable state. Our experience suggests that anticoagulant drugs may be required to reduce the risk of new thrombotic events.
We describe a pregnant young woman with branch retinal arteriolar occlusions, encephalopathy, and hearing loss in whom we demonstrated a patent foramen ovale. She improved while receiving anticoagulants and no immunosuppressive therapy. The microangiopathic syndrome of retinopathy, encephalopathy, and deafness may be due to a disturbance of coagulation and/or microembolism.
To determine the risk and time to cerebrovascular complications with idiopathic hypertrophic subaortic stenosis, we studied 119 patients (66 men and 53 women) with evidence of this disease based on strict echocardiographic criteria and followed them up for a mean +/- SEM of 6.5 +/- 0.6 years. Cerebral ischemic events occurred in 26 patients (22%), and in five patients stroke was the initial presenting event. Men had cardiac symptoms at a younger age than women, but there was no significant difference in age at the time of stroke. Cardioembolic cerebrovascular events were associated with atrial fibrillation and left atrial enlargement, whereas atheroembolic events were associated with hypertension. An increased risk of stroke was associated with female sex, mitral anulus calcification, hypertension, and atrioventricular conduction delay. Unlike most previous series, this study shows that patients with idiopathic hypertrophic subaortic stenosis may present with stroke.
We reviewed the one-month mortality among 213 patients aged fifteen to forty-five years (mean thirty-five) with acute cerebral infarction (CI) evaluated during the period July 1, 1977, to February 1, 1988. Atherosclerotic cerebral infarction (ACI) was diagnosed in 59 (27.7%) patients, 53 (24.9%) had non-atherosclerotic vasculopathies (NAV); 46 (21.6%) had cardioembolic infarcts (CEI). Hematologically related disorders were diagnosed in 30 (14.1%) patients; the cause of CI could not be established in 25 (11.7%) patients. Fourteen patients (9 men, 5 women, mean age 34.8 years), (6.6%) died within thirty days of their CI: 7 had CEI (7/46,15.2%); 4 had ACI (4/59, 6.7%); and 3 had NAV (3/53, 5.6%). Our data suggest that young patients with acute CI have a thirty-day mortality rate lower than older patients. Deaths were most common in patients with CEI. Brain edema and herniation accounted for 6 (43%) of the deaths.
Seventeen desert tortoises, Xerobates agassizii, with upper respiratory tract disease were examined; thirteen were euthanatized for necropsy. Four normal control desert tortoises from a clinically healthy population were similarly evaluated. Hemoglobin and phosphorus values were significantly (P less than or equal to 0.05) lower and serum sodium, urea, SGOT, and cholesterol values were significantly higher in ill tortoises compared to controls. No significant differences in concentrations of serum or liver vitamins A and E were found between the two groups. While no significant differences were found for concentrations of lead, copper, cadmium, and selenium, the livers of ill tortoises had higher concentrations of mercury and iron. Lesions were found consistently in the upper respiratory tract (URT) of ill tortoises. In all ill tortoises dense infiltrates of lymphocytes and histiocytes obscured the mucosal epithelium and underlying glands. The mucosal epithelium was variably dysplastic, hyperplastic, and occasionally ulcerated. Electron microscopic studies revealed small (350 to 900 nm), pleomorphic organisms resembling Mycoplasma sp., in close association with the surface epithelium of the URT of ill tortoises. Pasteurella testudinis was cultured from the nasal cavity of all ill tortoises and one of four control tortoises. A Mycoplasma sp. was cultured from the nasal passageways of four ill tortoises and was ultrastructurally similar to the pleomorphic organism present on the mucosa in tissue section.
Evoked potential monitoring has become a widely used procedure in the evaluation of stuporous patients on neurological intensive care units. Currently BAEP and SEP are preferentially employed. VEP monitoring is a relatively uncommon procedure, because late evoked potentials tend to be relatively unstable, varying in amplitude to a moderate extend from changes of temperature, drugs, attention and the level of consciousness. A valuable approach of VEP monitoring on intensive care units are structures of the visual system at risk in vascular disease of the vertebrobasilar system or during evaluated intracranial pressure (EIP). This study uses the data of 20 stuporous patients presenting with either intracranial mass lesions or vascular diseases of the vertebrobasilar system and 20 control persons. Light emitting diode (LED)-VEP are compared with checkerboard stimulation in control persons using the technique of cross-correlation. The comparison of the control group with patients using LED-VEP allows definition of limits for normal variation as a base for identification of significant changes. Despite methodical restrictions of LED-VEP, our results are in favour of serial studies in patients with EIP. There are no corresponding findings in LED-VEP and vascular lesions of the retrochiasmatic visual system.
Age is the most important risk factor for ischemic stroke. The most common cause of ischemic stroke in the elderly is atherosclerosis. Patients who have had a recent transient ischemic attack (TIA) are at high risk for subsequent stroke. Thus far only aspirin and ticlopidine have proven to be effective in preventing stroke. At present, all elderly patients who have had an atherothromboembolic TIA or stroke should receive therapy as well as either aspirin or ticlopidine for control of atherosclerotic risk factors.
To assess the impact of cigarette smoking on stroke in young adults (15 to 45 years old), we compared smoking data from 181 patients with cerebral infarction with that of 307 control subjects matched for age, gender, geographic location, and hospital admission dates. While controlling for these matching variables and hypertension, an analysis based on a conditional logistic regression model indicated that a smoker was 1.6 times more likely to have a cerebral infarction than a non-smoker (95% confidence interval, 1.07 to 2.42). There was a cumulative dose effect with each additional pack-year causing a greater risk of having a cerebral infarction. In fact, after adjusting for all other risk factors, there was a significant quadratic component to the dose-response relationships, with the result that individuals with a larger number of pack-years were invariably the stroke patients. There was no significant difference in smoking status among the various subtypes of cerebral infarction (atherosclerotic, nonatherosclerotic vasculopathy, cardioembolic, hematologic related, undetermined). These data indicate that cigarette smoking is an important risk factor for cerebral infarction in young adults. Risk factor modification through cessation of smoking may reduce the risk of ischemic stroke in young adults.
A circadian pattern for the onset of myocardial and cerebral infarction has been identified. To evaluate this phenomenon further, we analyzed prospectively collected data from 151 patients with acute ischemic stroke. The number of strokes per 6-hour period were the following: midnight to 6 AM, 20 (13%); 6 AM to noon, 86 (57%); noon to 6 PM, 21 (14%); and 6 PM to midnight, 24 (16%). This pattern was not affected by previous use of aspirin. The most frequent time of onset was 6 AM to noon for all subgroups of ischemic stroke: small artery, 71%; cardioembolic, 62%; large artery atherothrombotic, 57%; large artery atheroembolic, 46%; and "other" or unknown cause, 40%. We also investigated the time between awakening and stroke onset in 145 patients and found that 24% of ischemic strokes occurred within the first hour after awakening. Our data demonstrate that an early morning peak exists for all subtypes of stroke. Our data also suggest that the most critical period is the first hour after awakening.