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Biomedical subjects

A Cohen

Publications and source records attributed to A Cohen.

At least 433 records · Page 24Linked to original sources

Effect of partial outlet obstruction on choline acetyltransferase activity in the rat and rabbit.

Partial outlet obstruction of the rabbit bladder induces a rapid and significant increase in bladder mass. This increase in mass is associated with a variety of specific contractile dysfunctions, characterized by a marked decrease in the response to field stimulation (acting through the release of neurogenic transmitters). There is histological evidence indicating that the decrease in the contractile response of isolated strips of rabbit urinary bladder to field stimulation is associated with a degeneration of synaptic membranes within the bladder detrusor (neuropathy). In the current experiments, the effect of partial outlet obstruction in rabbit and rat urinary bladders on choline acetyltransferase activity (ChAT) were determined and correlated with both the level of bladder hypertrophy (increase in mass) and the contractile response to field stimulation. The results can be summarized as follows: In the rabbit, partial outlet obstruction induced a rapid 5-fold increase in bladder mass over the 7 day period of study. This increase in mass was associated with a decrease in the contractile response of isolated strips of bladder body and base to field stimulation and a decrease in ChAT activity. Interestingly, the rabbit bladder base showed a significantly higher ChAT activity than the bladder body, although the contractile response to muscarinic stimulation was significantly greater in the bladder body than in the base. In the rat, partial outlet obstruction induced a mild 2-fold increase in bladder mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Presence of telomeric and subtelomeric sequences at the fusion points of ring chromosomes indicates that the ring syndrome is caused by ring instability.

In situ hybridization of a telomeric (TTA-GGG)n sequence to metaphases from three cases of ring chromosome, involving respectively chromosomes 4, 16, and 20, showed the presence of the cognate sequences in all three rings. To investigate whether these ring chromosomes originated by telomere-telomere fusion, we determined, by in situ hybridization, whether telomere-associated sequences and/or specific distal sequences were still present in the ring chromosomes. The finding that these sequences were preserved in all the ring chromosomes strongly indicates that they originated by telomere-telomere fusion. All three subjects carrying the ring chromosomes are affected by the so-called ring syndrome, with failure to thrive, minor dysmorphic signs and no major anomalies. The r(4) patient has the ring in mosaic form with a normal cell line and has normal intelligence. The r(16) and the r(20) patients have moderate mental retardation and suffer from seizures. We conclude that the ring syndrome, even in its more severe manifestation, is caused by ring chromosome instability.

Adolescent↗

The effectiveness and safety of the simultaneous administration of quinidine and amiodarone in the conversion of chronic atrial fibrillation.

The effectiveness and safety of quinidine in the conversion of chronic atrial fibrillation after administration of amiodarone was assessed in 15 patients. A total quinidine dosage of 1097 +/- 408 mg was administered up the point of conversion or for a total of 48 hours. Nine of 15 patients (60%) converted to sinus rhythm. No clinical variable such as the duration of atrial fibrillation, left atrial size, left ventricular fractional shortening, amiodarone duration, or maintenance dose of amiodarone was able to discriminate between converters and nonconverters when patients were treated with the combination of amiodarone and quinidine. The mean QT interval with amiodarone was 414 +/- 44 msec and slightly increased to 434 +/- 40 msec (p = 0.01) when quinidine was added. The amiodarone-quinidine combination was well tolerated, and no side effects or proarrhythmias were recorded.

Aged↗

Transient forebrain ischemia alters acutely endothelin receptor density and immunoreactivity in gerbil brain.

Pharmacologic studies suggest that endothelin (ET) plays an important role in the pathophysiology of hemorrhagic and ischemic stroke. In the gerbil, transient forebrain ischemia (10 min) resulted in profound motor deficits and a 15% reduction in ET receptor density in the hippocampus at 60 min post-reperfusion. A significant 2-fold increase in forebrain immunoreactive ET accompanied the maximum post-ischemic decrease in ET receptor density. These results suggest that the synthesis and availability of ET are increased acutely in the forebrain following transient cerebral ischemia.

Analysis of Variance↗

Asymmetries in visual search for conjunctive targets.

Asymmetry is demonstrated between conjunctive targets in visual search with no detectable asymmetries between the individual features that compose these targets. Experiment 1 demonstrated this phenomenon for targets composed of color and shape. Experiment 2 and 4 demonstrate this asymmetry for targets composed of size and orientation and for targets composed of contrast level and orientation, respectively. Experiment 3 demonstrates that search rate of individual features cannot predict search rate for conjunctive targets. These results demonstrate the need for 2 levels of representations: one of features and one of conjunction of features. A model related to the modified feature integration theory is proposed to account for these results. The proposed model and other models of visual search are discussed.

Adult↗

Heteroduplex strand-specificity in restriction-stimulated recombination by the RecE pathway of Escherichia coli.

The RecE recombination pathway is active in Escherichia coli recB recC sbcA mutants. To isolate and characterize products and intermediates of RecE-mediated, break-induced, intramolecular recombination, we infected recB recC sbcA mutants, expressing EcoRI endonuclease, with chimeric lambda phages that allow EcoRI-mediated release of cloned linear recombination substrates. Substrates with direct terminal repeats recombined to yield a circular product with one copy of the repeated sequence. Some recombinants were heteroallelic for the recombining markers. Markers distant to the break were recovered in the circular product at a higher frequency than markers close to the break. To examine the heteroduplex structures that may have yielded the heteroallelic recombinants, nonreplicative substrates were employed. Some of the nonreplicative recombination products contained heteroduplexes, with a strong bias for paired strands ending 3' at the break. This strand bias in heteroduplex formation is consistent with recombination models that postulate homologous pairing of protruding 3' single-stranded ends.

Base Sequence↗

Left ventricular function in patients with acute myocardial infarction, acute pulmonary edema, and mechanical ventilation: relationship to prognosis.

OBJECTIVES: To evaluate the relationship between left ventricular function and prognosis in patients treated with mechanical ventilation for severe, persistent pulmonary edema as a consequence of acute myocardial infarction. DESIGN: A prospective study. SETTING: A nine-bed coronary care unit in a 900-bed teaching hospital. PATIENTS: Sixty-nine successive patients. INTERVENTIONS: All patients had acute pulmonary edema not responding to classical treatment and were treated with mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: The inhospital mortality rate was 67%. Thirteen of 23 patients surviving hospitalization died during follow-up, a mean of 5.8 +/- 7.7 months after infarction. Six of ten long-term survivors are in functional capacity class 1 or 2 (New York Heart Association) and four survivors are in class 3. Echocardiographic examination indicated that severe left ventricular dysfunction was present in most patients during the time of mechanical ventilation. Repeat echocardiographic examination performed 14.2 +/- 8.1 months after infarction showed a remarkable improvement in left ventricular function among the survivors. Multivariate analysis indicated that the small group of patients with a good long-term prognosis could not be separated prospectively from the larger group dying during or after hospitalization using variables obtained at the time of mechanical ventilation. CONCLUSIONS: The mortality rate is high in this group of patients. Left ventricular function of survivors is severely diminished at the time of infarction but improves markedly during follow-up. The small subgroup of patients with a good long-term prognosis cannot be identified prospectively when evaluated during the acute stage of infarction and the provision of mechanical ventilation.

Acute Disease↗

Effects of exercise on total and segmental colon transit.

To investigate the effect of aerobic exercise on total gastrointestinal and segmental colon transit, 16 male health care workers with a sedentary life-style were studied during 1 week of rest and 1 week of exercise. The exercise phase consisted of walking 4.5 km on a level treadmill for 1 h on each of 3 days. Total gastrointestinal and segmental colon transit times were measured using radiopaque markers ingested on each of 3 consecutive days with an abdominal radiograph obtained on the fourth day. With exercise, total gastrointestinal transit time decreased in 5, increased in 6, and did not change in 5 subjects. Using a paired t test, total transit did not show a significant change from rest (24.5 +/- 21.8 h) to exercise (20.9 +/- 16.8 h), p = 0.50. These observations support our previous findings that physical activity to the extent that average people consider routine exercise does not necessarily improve gastrointestinal transit. Therefore, the role of such exercise in the management of chronic constipation can be seriously questioned.

Adult↗

ECG compression using long-term prediction.

A new algorithm for ECG signal compression is introduced. The compression system is based on the subautoregression (SAR) model, known also as the long-term prediction (LTP) model. The "periodicity" of the ECG signal is employed in order to further reduce redundancy, thus yielding high compression ratios. The suggested algorithm was evaluated using an in-house database. Very low bit rates on the order of 70 b/s are achieved with a relatively low reconstruction error (percent rms difference-PRD) of less than 10%. The algorithm was compared, using the same database, with the conventional linear prediction (short-term prediction--STP) method, and was found superior at any bit rate. The suggested algorithm can be considered a generalization of the recently published average beat subtraction method.

Algorithms↗

A review of 2000 consecutive ICU admissions.

The working practices and outcomes from UK intensive care units are poorly documented to date. We have reviewed 2000 consecutive admissions to one intensive care unit in a tertiary referral centre with initially six, then eight beds. The study was a retrospective review of contemporaneous data collection within the period 1986-1990. Demographic details, referral source, admission time, admission diagnosis, APACHE II score, therapeutic interventions, and outcome were recorded. A high overall mortality in the intensive care unit (23%), proportional to APACHE II scoring on admission, was demonstrated. This reflects the referral of many patients who have, or who develop, multiple organ failure. Mortality was significantly higher in patients over the age of 40 years. A total of 69.5% of patients were admitted outside the hours 0800-1800 h on Monday to Friday and admissions peaked between 1200 and 2100 h, demonstrating the need for senior out-of-hours cover. These figures may be used to compare future mortality and work practices in this and other units. The report illustrates some of the advantages and disadvantages of one method of data collection. As it represents one unit only, care must be taken in extrapolating results to others. The timing of admissions suggests that a review of medical staffing practices would be useful.

Adolescent↗

Leukemoid reaction induced by prenatal administration of betamethasone.

A case of leukemoid reaction in a premature baby whose mother was antenatally treated by betamethasone is reported. The neonatal and maternal factors which might lead to leukocytosis or leukemoid reaction were excluded. The presented case is the last in a series of eight previously reported cases of leukemoid reaction, in which the common denominator was the antenatal administration of betamethasone.

Betamethasone↗

Genetic and molecular analyses of the C-terminal region of the recE gene from the Rac prophage of Escherichia coli K-12 reveal the recT gene.

The nucleotide sequence of the C-terminal region of the recE gene of the Rac prophage of Escherichia coli K-12 reveals the presence of a partially overlapping reading frame we call recT. Deletion mutations show that recT is required for the RecE pathway of conjugational recombination. By cloning recT with a plasmid vector compatible with pBR322, we showed by cis-trans tests that the portion of the recE gene encoding ExoVIII DNA nuclease activity is also required for RecE pathway conjugational recombination. The recT gene can replace the redB gene of lambda for recA-independent plasmid recombination. A Tn10 insertion mutation previously thought to be in recE is located in recT and is renamed recT101::Tn10. Discrepancies between the molecular mass estimates of wild-type ExoVIII protein determined from mobility in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and calculated from the predicted amino acid sequence are discussed. The hypothesis that wild-type ExoVIII protein results from fusion of RecE and RecT proteins is disproved genetically, thus supporting a previous hypothesis that the discrepancies are due to abnormal protein mobility in SDS-PAGE. A computer-performed scan of the bacteriophage nucleotide sequence data base of GenBank revealed substantial similarity between most of recE and a 2.5-kb portion of the b2 region of lambda. This suggests interesting speculations concerning the evolutionary relationship of lambda and Rac prophages.

Amino Acid Sequence↗

Patent foramen ovale: is stroke due to paradoxical embolism?

BACKGROUND AND PURPOSE: A patent foramen ovale has been reported to be significantly more frequent in young stroke patients than in matched control subjects, and paradoxical embolism has been suggested as the main mechanism of stroke in this situation. The present study was designed to test this hypothesis. METHODS: Sixty-eight consecutive patients under 55 years of age presenting with an ischemic stroke had an extensive workup, including transesophageal echocardiography with contrast. We compared the prevalence of criteria for the diagnosis of paradoxical embolism in patients with and without a patent foramen ovale. RESULTS: A patent foramen ovale was found in 32 patients (47%). A Valsalva-provoking activity was present at stroke onset in six patients with a patent foramen ovale and in eight patients with no patent foramen ovale (chi 2 = 0.1, nonsignificant). Clinical/radiological features suggestive of an embolic mechanism were not more frequent in patients with a patent foramen ovale. Clinical evidence of deep vein thrombosis was present in one patient with a patent foramen ovale and in none of the others. No occult venous thrombosis was found in a subgroup of patients with a patent foramen ovale and no definite cause for stroke who underwent venography (n = 13). CONCLUSIONS: Our results do not support the hypothesis that paradoxical embolism is the primary mechanism of stroke in patients with a patent foramen ovale.

Adult↗

Atrial septal aneurysm and patent foramen ovale as risk factors for cryptogenic stroke in patients less than 55 years of age. A study using transesophageal echocardiography.

BACKGROUND AND PURPOSE: An association between atrial septal aneurysm and embolic events has been suggested. Atrial septal aneurysm has been shown to be associated with patent foramen ovale and, in some reports, with mitral valve prolapse. These two latter cardiac disorders have been identified as potential risk factors for ischemic stroke. The aim of this prospective study was to assess the role of atrial septal aneurysm as an independent risk factor for stroke, especially for cryptogenic stroke. METHODS: We studied the prevalence of atrial septal aneurysm, patent foramen ovale, and mitral valve prolapse in 100 consecutive patients < 55 years of age with ischemic stroke who underwent extensive etiological investigations. We compared these results with those in a control group of 50 consecutive patients. The diagnosis of atrial septal aneurysm and patent foramen ovale relied on transesophageal echocardiography with a contrast study and that of mitral valve prolapse, on two-dimensional transthoracic echocardiography. RESULTS: Stepwise logistic regression analysis showed that atrial septal aneurysm (odds ratio, 4.3; 95% confidence interval, 1.3 to 14.6; P = .01) and patent foramen ovale (odds ratio, 3.9; 95% confidence interval, 1.5 to 10; P = .003) but not mitral valve prolapse were significantly associated with the diagnosis of cryptogenic stroke. The stroke odds of a patient with both atrial septal aneurysm and patent foramen ovale were 33.3 times (95% confidence interval, 4.1 to 270) the stroke odds of a patient with neither of these cardiac disorders. For a patient with atrial septal aneurysm of > 10-mm excursion, the stroke odds were approximately 8 times the stroke odds of a patient with atrial septal aneurysm of < 10 mm. CONCLUSIONS: This study shows that atrial septal aneurysm and patent foramen ovale are both significantly associated with cryptogenic stroke and that their association has a marked synergistic effect. Atrial septal aneurysms of > 10-mm excursion are associated with a higher risk of stroke.

Adolescent↗

Cerebral infarction due to painless thoracic aortic and common carotid artery dissections.

BACKGROUND: Aortic arch dissection is usually lethal unless emergency surgery is performed. The dissection rarely may have a benign outcome or may occur without pain and be revealed by cerebral infarction. It is then likely to be seen primarily by a neurologist. In such cases, the value of new noninvasive diagnostic testing has not been reported. CASE DESCRIPTION: A 51-year-old man had a sudden left-sided hemiplegia due to hemorrhagic capsular and caudate infarcts on the right side. Cervical ultrasound examination with color flow imaging showed a bilateral common carotid artery dissection extending up to the bifurcation. Transesophageal echocardiography showed an aortic arch dissection, involving the innominate and left common carotid artery origins, which was confirmed by magnetic resonance imaging and aortography. The patient spontaneously fully recovered and is still alive 24 months after the stroke onset. CONCLUSIONS: This case emphasizes the usefulness of new noninvasive techniques such as transesophageal echocardiography and color-coded Doppler echocardiography in the diagnosis and follow-up of painless dissection of aortic and common carotid arteries. This cause of stroke may be underestimated.

Aortic Dissection↗

Recombinant human insulin-like growth factor-I accelerates recovery and reduces catabolism in rats with ischemic acute renal failure.

This study evaluated whether recombinant human insulin-like growth factor-I (rhIGF-I) enhances recovery of renal function and reduces catabolism in rats with ischemic acute renal failure (ARF). ARF and sham rats received subcutaneous injections of either rhIGF-I or vehicle three times daily starting 5 h after surgery. Serum creatinine and urea, which initially rose similarly in the ARF+vehicle and ARF+rhIGF-I rats, increased more slowly after commencing the rhIGF-I injections. 72 h after surgery, the ARF+rhIGF-I rats, in comparison with ARF+vehicle animals, showed significantly greater renal plasma flow and filtration fraction, a fivefold higher glomerular filtration rate, greater renal cortical IGF-I levels, increased proliferating cell nuclear antigen expression in proximal tubule nuclei and enhanced DNA synthesis in the renal cortex, corticomedullary junction, glomeruli, and tubules as demonstrated by [3H]thymidine incorporation and in corticomedullary junction tubules as determined by autoradiography. Estimated total nitrogen output (ETNO) was greater in ARF+vehicle than in ARF+rhIGF-I or sham rats throughout the study. ETNO in ARF+rhIGF-I rats returned to sham values by the second day after surgery. 72 h after surgery, protein degradation was increased and protein synthesis reduced in the epitrochlearis muscle of ARF+vehicle as compared with ARF+rhIGF-I or sham+vehicle rats. Thus, treatment with rhIGF-I starting 5 h after inducing ischemic ARF in rats increases recovery of renal function, enhances formation of new renal tubular cells, lowers protein degradation, and increases protein synthesis in skeletal muscle and reduces net catabolism.

Acute Kidney Injury↗

Randomized trial of hepatic arterial floxuridine, mitomycin, and carmustine versus floxuridine alone in previously treated patients with liver metastases from colorectal cancer.

PURPOSE: This study was designed to determine if hepatic arterial therapy with floxuridine (F), mitomycin, and carmustine (BCNU) (FMB) is superior to hepatic arterial therapy with F alone in previously treated patients with hepatic metastases from colorectal cancer. PATIENTS AND METHODS: Ninety-five patients were randomized to intrahepatic FMB versus intrahepatic F. All patients had tumor progression after systemic chemotherapy (either therapeutic or adjuvant). RESULTS: There was no significant difference in response rate (47% FMB v 33% F; P = .17). Median survival was similar in the two groups, 19.1 months for the FMB group compared with 14.0 months for the F group (P = .23). The overall median survival was 16.8 months. In patients who received prior adjuvant therapy, there was no difference between the two groups, but response rate was high in both (50% FMB v 62% F). The response rate for all patients who had received only prior adjuvant therapy versus all those who had received prior therapy for metastatic disease was 57% and 35%, respectively (P = .066). In the subset of patients whose disease had progressed with prior systemic chemotherapy, the response rate to FMB was greater than that to F (47% v 23%; P = .035). CONCLUSION: The overall partial response rate of 39% and the overall survival of 16.8 months from initiation of intrahepatitis therapy show that hepatic arterial therapy is a reasonable treatment option for patients whose tumor does not respond to systemic therapy or whose disease progresses after adjuvant therapy for colorectal cancer.

Adult↗