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Biomedical subjects

K Cohn

Publications and source records attributed to K Cohn.

At least 19 recordsLinked to original sources
PubMed2003

Transient optical elements: application to near-field microscopy.

We report methods of near-field infrared microscopy with transient optically induced probes. The first technique - a transient aperture (TA) - uses photoinduced reflectivity in semiconductors to generate a relatively large transient mirror (TM) with a small aperture at its centre. We report the optical properties of the TM and TA and experiments performed on near-field imaging with the TA. The second technique is based on solid immersion microscopy, in which high resolution is achieved when light is focused inside a solid with a high refractive index. By creating a transient Fresnel lens on the surface of a semiconductor wafer via photoinduction, we were able to form a solid immersion lens (SIL) for use as a near-field probe. The use of transient probes eliminates the need for mechanical scanning of the lens or sample, and thus provides a much faster scanning rate and the possibility to work with soft and liquid objects.

Journal Article↗
PubMed1997

The expression of acylphosphatase is associated with the metastatic phenotype in human colorectal tumors.

We have performed differential display comparing gene expression from cell lines derived from human colorectal tumors. The cell lines were selected for study based on their ability to form metastases following injection into athymic mice. One gene which was expressed exclusively by the metastatic lines was identified as human acylphosphatase (e.c. 3.6.1.7, acylphosphate phosphohydrolase). The expression of this gene was confirmed by RT-PCR using gene-specific primers. This gene product catalyzes the hydrolysis of phosphorylated intermediates of Na+/K(+)-ATPase and of Ca(2+)-ATPases of mammalian cells. Changes in the activity of the Na+/K(+)-ATPase pump, regulated by acylphosphatase, have been previously reported in chemically-induced colonic tumors. The differential expression of this gene in the human metastatic colorectal lines suggests it may be involved in the metastatic phenotype.

Acid Anhydride Hydrolases↗
PubMed1986

Adrenocortical carcinoma.

From 1962 to 1985, 47 patients with carcinoma of the adrenal cortex were treated at Memorial Sloan-Kettering Cancer Institute. There were 21 men and 26 women. Seventy-two percent of the tumors were functional and 28% were nonfunctional. Despite the advent of ultrasonography and computerized tomography, these tumors were infrequently diagnosed until they infiltrated adjacent organs or metastasized to distant sites. Only 30% of patients had tumors confined to the adrenal gland; their mean duration of survival was 5.0 years. Seventy percent of the patients had invasion of the kidney, lymph nodes, liver, diaphragm, and/or pancreas at the initial operation; their mean duration of survival was 2.3 years. Eight patients had reoperation for abdominal recurrences; three of the patients with abdominal recurrence and one additional patient underwent thoracotomy to resect localized lung metastases. The mean duration of survival of these nine patients was 3.5 years, not significantly different from the mean overall survival of 3.1 years. The duration of survival of all patients was not significantly correlated with age, sex, adjuvant therapy, or production of hormones by the tumor. Only two patients were deemed unresectable. Wide en-bloc dissection of the primary tumor, resection of contiguous organs for local invasion, and excision of resectable metastases in the liver and lungs remain the basis of therapy.

Adrenal Cortex Neoplasms↗
PubMed1985

Comparison of nuclear DNA content in primary and metastatic papillary thyroid carcinoma.

Nuclear DNA values were determined in 40 primary papillary thyroid carcinomas, as well as in 52 corresponding local recurrences and metastases were observed either at the time of diagnosis or up to 20 years later. The patient population consisted of 34 survivors and 6 nonsurvivors. In survivors, both the primary tumors and their recurrences and metastases exhibited a majority of cells with DNA values within the normal diploid region, whereas nonsurvivors showed increased and scattered DNA values. In all cases, the primary tumors and the corresponding recurrences and metastases showed similar DNA distribution patterns even if many years had passed between the detection of the primary tumor and the metastases. The results indicate that in papillary thyroid carcinomas, the DNA distribution patterns in the primary tumor and the corresponding recurrences or metastases are generally similar throughout the entire period of disease.

Adult↗
PubMed1985

Parathyroid carcinoma: the Lahey Clinic experience.

From 1942 to 1984, 301 operations were performed for hyperparathyroidism; nine patients (3%) had carcinoma. The mean serum calcium level of the patients with carcinoma was 14.0 mg/dl, whereas the mean serum calcium level of patients with benign hyperparathyroidism was 12.0 mg/dl. With follow-up ranging from 2 to 16 years, there has been one death 9 years after the initial operation caused by primary lung cancer. At autopsy the patient also had a recurrence of parathyroid carcinoma in the neck. There were no additional recurrences or deaths. Prognosis was not correlated with any laboratory or pathologic findings. The importance of intraoperative recognition at the time of the initial operation is stressed. En bloc resection is recommended, including ipsilateral thyroid lobectomy and dissection of the tracheoesophageal groove. Radical neck dissection is performed only for extensive cervical node metastases or for reoperations where scarring prevents accurate delineation of the extent of the tumor.

Adult↗
PubMed1984

Determinants of prognosis of patients with aortic regurgitation who undergo aortic valve replacement.

Insidious and potentially irreversible left ventricular dysfunction may develop in patients with aortic regurgitation. To determine whether preoperative variables can predict postoperative outcome, 113 consecutive patients with aortic regurgitation who underwent surgical correction between 1962 and 1977 were studied and survivors were followed up for 4.6 +/- 3.3 years. Clinical and hemodynamic examinations were made in all patients before the operation. Echocardiograms were performed in 44 patients preoperatively and in 36 patients postoperatively. Perioperative or postoperative death due to congestive heart failure occurred in only eight patients (19%). No statistically significant predictors of total mortality or death due to cardiac failure were found based on preoperative clinical, hemodynamic or echocardiographic findings. Survivors of the operation showed significant functional improvement: preoperatively, 77% of all patients were in functional class III or IV; postoperatively, 84% of patients were in class I or II (p less than 0.0001). A weak statistical correlation of functional improvement was found with a preoperative presence of increased cardiac diameter on the chest radiograph (p less than 0.05) and the severity of left ventricular hypertrophy (p less than 0.05). Improvement of left ventricular function was also consistently found in survivors and correlated best with the degree of preoperative preservation of left ventricular function. Patients with an echocardiographic preoperative fractional shortening of the minor diameter greater than 26%, end-systolic dimension less than 55 mm and end-diastolic dimension less than 80 mm were most likely to have normal function after the operation. It is concluded that operative mortality and survival after surgical correction of aortic regurgitation cannot be accurately predicted from preoperative findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

The effect of thyroid hormone administration upon survival in patients with differentiated thyroid carcinoma.

Seven hundred sixty-one patients with operable differentiated thyroid carcinoma were treated between 1931 and 1970. Median follow-up time was 18 years and ranged from 5 to 40 years. Sixty-three percent of the patients were followed more than 15 years, and 46% were followed more than 20 years. Because resections usually spared sufficient thyroid tissue for homeostasis, thyroid hormone was not routinely prescribed after operations performed before 1960. Altogether 244 patients with papillary carcinoma and 76 patients with follicular carcinoma received thyroid hormone, while 296 patients with papillary carcinoma and 45 patients with follicular carcinoma did not receive thyroid hormone after operation. With papillary carcinoma, 14% of men greater than 40 and women greater than 50 years of age (high risk) but only 2% of men less than or equal to 40 years of age and women less than or equal to 50 years of age (low risk) died of disease (P 0.0001). Twenty-six percent of high-risk but only 4% of patients with low-risk follicular cancer died (P 0.0001). However, there was no statistically significant improvement in survival times with use of thyroid hormone when patients were categorized by risk group and pathology. These data support the importance of age and sex in previously described risk groups; these factors supersede the effects of adjuvant treatment. This absence of effect on survival times calls into question current recommendations for routine use of thyroid hormone after surgical therapy. Conceptually, such absence of adjunctive hormone effect on survival time after operation is similar to hormonal effects in other endocrine cancers, which may nevertheless provide good palliation in some cases.

Adenocarcinoma↗
PubMed1981

The influence of ectopic beats and tachyarrhythmias on stroke volume and cardiac output.

The potentially adverse influence of premature ectopic beats or tachyarrhythmias on cardiac performance was studied by assessing the echocardiographic left ventricular stroke volume in 21 patients with cardiac rhythm disturbances. The beat to beat stroke volume correlated closely with end-diastolic volume in each patient (average R = .9). Premature ventricular contractions decreased stroke volume by an average of 48 +/- 8 ml (-71%) compared with sinus beats; whereas the postextrasystolic beats, although preceded by a pause and higher end-diastolic volume, increased stroke volume by only 16 +/- 7 ml (18%) over the sinus beats. Those postextrasystolic beats with equivalent timing and end-diastolic volume to the sinus beats had a mean stroke volume only 8 ml higher, suggesting that postextrasystolic potentiation plays only a minor role in augmenting stroke volume. Transient aberrant ventricular conduction of intermittent left bundle branch block, ectopic beats or atrial fibrillation failed to alter stroke volume. Ventricular bigeminy, trigeminy and quadrigeminy lowered cardiac output by 1.3, .9 and .7 l/min. The onset of tachyarrhythmias was oftentimes associated with a continuously changing end-diastolic volume and stroke volume, with either alternation or progressive increment of these variables. It is apparent that premature contractions decrease stroke volume by virtue of their infringement on diastolic filing, the principle beat to be determinant of stroke volume in arrhythmias being left ventricular end-diastolic volume. Since premature beats decrease stroke volume to an extent greater than postextrasystolic beats increase it, they may reduce cardiac output by a substantial degree, depending on their frequency of occurrence and degree of prematurity.

Arrhythmias, Cardiac↗
PubMed1979

Pharmacokinetics of furosemide in patients with congestive heart failure.

Since patients vary in their response to furosemide, a pharmacokinetic study of this drug was undertaken in 7 patients with severe congestive heart failure. The extent of oral availability, determined by the ratio of areas under the oral to intravenous plasma concentration-time curve, averaged 61%, but varied widely from patient to patient, from 34 to 80%. Absorption of the drug was often delayed, with a lag time before appearance in the plasma averaging 28 +/- (SD) 15 min. The volume of distribution of furosemide (averaging 114 ml/kg) was not diminished in the presence of congestive failure; likewise, drug clearance and elimination half-lives are similar to values reported in normal subjects. Urinary flow rates 1--2 h following dosing were significantly less after oral than intravenous dosing, but flow rates over 4, 8 or 24 h after dosing were similar for both routes of administration.

Absorption↗
PubMed1979

Use of treadmill score to quantify ischemic response and predict extent of coronary disease.

In this study we assessed whether various responses to exercise testing could be quantified in order to derive the probabilities of presence of coronary disease, and if present, to assess its severity. A treadmill score based on the exercise response was determined in 405 patients who had both treadmill tests and coronary angiograms. The score was derived using discriminant function analysis, by weighting and combining depth and configuration of ST depression (downsloping, horizontal or slowly upsloping), timing onset and duration of ischemia, grading ventricular arrhythmias, heart rate and blood pressure change, coexistence of exercise-induced chest pain and sex. The treadmill score was effective in detecting coronary disease (lesions with an greater than or equal to 50% narrowing), with a predictive accuracy (PA) (probability that a subject manifesting a positive test has disease) of 87%, a true negative rate (TNR) (probability of a subject with a negative test having no disease) of 80%, and sensitivity of 94%. The treadmill score also detected severe disease (triple-vessel, main left and/or greater than 90% proximal occlusion of the left anterior descending artery), with a PA of 73%, TNR of 79% and sensitivity of 82%. We conclude that the exercise response, expressed numerically as a treadmill score, permits analysis of most of the relevant data from exercise testing, increases test accuracy by 10-15% compared with standard criteria for treatmill test interpretation, and enables the derivation of probability statements for presence and severity of coronary disease. The validity of any prediction on the basis of exercise performance may thus be quantitatively judged.

Analysis of Variance↗
PubMed1978

On the interpretation of the exercise test.

The widespread popularization of stress testing and the extensive application of its results in a variety of clinical settings make it imperative that a better method than the presently used simplistic "positive" or "negative" interpretation be devised. As a step toward a comprehensive diagnostic and prognostic index based on stress tests, a simple grading system of electrocardiographic changes, together with recognition of clinical modifiers, is suggested.

Electrocardiography↗