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Biomedical subjects

D M Cohen

Publications and source records attributed to D M Cohen.

At least 109 records · Page 6Linked to original sources
PubMed1988

Dosimetric calculations and measurements of gold plaque ophthalmic irradiators using iridium-192 and iodine-125 seeds.

The dosimetry of ophthalmic plaques designed to hold iridium-192 or iodine-125 seeds is investigated experimentally and by means of a computer model. A phantom for thermoluminescent dosimetry (TLD) which permits measurements to within 2 mm of the plaque surface is described. TLD data are compared with model calculations that take into account the active length of the seeds, anisotropy of dose distribution from single seeds, and scatter within the phantom. An isotropic point source calculational model is accurate for clinical calculations, particularly at depths greater than 5 mm. Relative central axis dose measurements for 125I in a gold plaque are also in agreement with the model. Comparisons of 192Ir, 125I and 60Co plaques are presented. The relative advantages of using these isotopes in eye plaques are discussed.

Brachytherapy↗
PubMed1988

Histological characteristics associated with suppurating periodontal pockets.

The purpose of this study was to characterize histologically the gingival lesion associated with suppuration in advanced periodontitis. Thirty-three bleeding, suppurating (S) and 23 bleeding, nonsuppurating (NS) interproximal biopsies were obtained from nine patients and processed for light microscopy. Pocket depths (mean +/- SD) were 6.7 +/- 1.6 mm (S) and 5.4 +/- 2.2 mm (NS). Six-micron serial sections were stained with (1) hematoxylin/eosin and (2) van Gieson. Quantitative cell types were determined by a grid intersection counting technique at x 1000. Volumetric analysis of collagen-poor (inflammation) areas was conducted using a computer biometric system that revealed three histologic patterns: Type I sites showed mild to moderate inflammation (less than 50% infiltrate, S = 15, NS = 20); Type II sites showed intense inflammation (greater than 50% infiltrate, S = 17, NS = 3); and only one (S) site had a large connective tissue abscess (Type III). The mean percentage of collagen-poor area was significantly larger in suppurating (42.1 +/- 25.5%) versus nonsuppurating (27.7 +/- 20.4%) sites (P = 0.02). In both S and NS sites, plasma cells (means = 66%) and lymphocytes (means = 27%) predominated in the inflammatory infiltrates. Histologically, suppuration appeared to be associated with increased gingival inflammation and a slight increase in connective tissue neutrophils.

Adult↗
PubMed1987

Acrocephalopolysyndactyly type II--Carpenter syndrome: clinical spectrum and an attempt at unification with Goodman and Summit syndromes.

Carpenter syndrome (ACPS type II) was first described by Carpenter in 1901. The syndrome consists of acrocephaly, soft tissue syndactyly, brachy- or agenesis mesophalangy of the hands and feet, preaxial polydactyly, congenital heart disease, mental retardation, hypogenitalism, obesity, and umbilical hernia. Here we review the literature on Carpenter syndrome and add 2 affected sibs with marked intrafamilial variability. This review showed that 2 reported variations of Carpenter syndrome, Goodman and Summitt syndromes, actually fall within the clinical spectrum of this disorder. This confirms earlier suggestions of Gorlin (personal communication 1982) and Hall et al [Am J Med Genet 5:423-434, 1980].

Acrocephalosyndactylia↗
PubMed1987

Mylohyoid herniation: gross and histologic evaluation with clinical correlation.

The purpose of this study was to further document the presence of a mass herniating inferiorly through the mylohyoid muscle into the submandibular area, to identify the mass histologically, and to discuss its importance in a differential diagnosis of masses in this area. A mass that perforated the mylohyoid muscle was found in 45 of the 100 cadavers studied. These 45 cadavers contained a total of 63 herniations. Of the 60 male cadavers, 26 (43.33%) showed herniation, and 19 (47.50%) of the 40 female cadavers showed herniation. Histologic evaluation of the 63 biopsy specimens revealed the following: 30 herniating masses (47.61%) were of the sublingual gland; 28 (44.44%) were of the submandibular gland; 4 (6.34%) were composed of pure adipose tissue, and 1 (1.58%) was a cholesteatoma. Inflammation was found in 46 (73.00%) of the biopsy specimens, consisting of sclerosing sialoadenitis in 30 specimens (47.61%) and a mild chronic inflammatory infiltrate in 16 specimens (25.39%).

Diagnosis, Differential↗
PubMed1987

Management of a common oral lesion of the elderly.

Lichen planus of the oral cavity produces significant functional and symptomatic problems for elderly patients. Oral lesions often occur in the absence of concomitant skin lesions. Unlike cutaneous lesions, oral lesions of lichen planus may become a chronic, recurring problem that is difficult to control. The diagnostic features of lichen planus of the oral cavity are reviewed and treatment strategies presented. Periodic follow-up is recommended to monitor the disease process and to observe for the development of early squamous cell carcinoma.

Administration, Topical↗
PubMed1986

Synthesis of novel angiotensin converting enzyme inhibitor quinapril and related compounds. A divergence of structure-activity relationships for non-sulfhydryl and sulfhydryl types.

The synthesis and angiotensin converting enzyme (ACE) inhibiting activities of quinapril (CI-906, 22), its active diacid (CI-928, 33), and its dimethoxy analogue (CI-925, 25) are reported. These tetrahydro-3-isoquinolinecarboxylic acid derivatives possess equivalent in vitro potency and in vivo efficacy to enalapril. Sulfhydryl analogues with the same structural variation are also highly potent. In contrast, tetrahydro-1-isoquinolinecarboxylic acid and homologous isoindoline-1-carboxylic acid analogues show a striking divergence in potency between the two types, sulfhydryl analogues being essentially inactive, while non-sulfhydryl analogues are equipotent with the proline prototype. This is the first evidence suggesting that alternate binding modes may exist for the two major structural classes of small molecule ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1986

CI-926 (3-[4-[4-(3-methylphenyl)-1-piperazinyl]butyl]-2,4-imidazolinedione): antihypertensive profile and pharmacology.

CI-926 (10(-7)-10(-6) M) selectively antagonized the contraction of isolated rabbit aortae to phenylephrine and displaced the alpha-1 adrenoceptor ligand WB4101 (IC50: 82 nM) in rat brain. In the spontaneously hypertensive rat, single oral doses of either CI-926 (0.3-10 mg/kg) or prazosin (0.3-100 mg/kg) caused dose-related reductions in blood pressure; however, CI-926 was more efficacious. The maximal antihypertensive response to CI-926 was unchanged with three consecutive days of oral dosing in the spontaneously hypertensive rat, whereas a first dose effect was noted with prazosin. In two-kidney, one-clip, renal hypertensive rats, CI-926 and prazosin (1-10 mg/kg) lowered blood pressure; however, prazosin was more efficacious. In perinephritic hypertensive dogs, CI-926 (10 mg/kg) lowered blood pressure 20%. In anesthetized dogs, CI-926 in the presence of supermaximal blood pressure-lowering doses of prazosin caused an additional reduction in pressure. With equivalent alpha-1 blockade in anesthetized rats, CI-926 tended to have greater hypotensive activity than prazosin. These results demonstrate that CI-926 is a potent, orally active antihypertensive agent in renin-dependent and -independent hypertension. The profile of CI-926 suggests that it lowers blood pressure in part by interacting with peripheral alpha-1 adrenoceptors and in part via an additional mechanism(s). Although weak relative to its affinity for alpha-1 adrenoceptors, CI-926 was found in preliminary experiments to interact with alpha-2 adrenoceptors, serotonergic receptors and dopaminergic receptors. The importance of these interactions to the blood pressure response of CI-926 remains to be elucidated.

Adrenergic alpha-Antagonists↗
PubMed1985

Laser catheter-induced atrioventricular nodal delays and atrioventricular block in dogs: acute and chronic observations.

Selective modification of atrioventricular (AV) nodal conduction, that is, induction of varying degrees of AV nodal delays or block (second or third degree), or both, was achieved with a pervenous laser catheter technique. In six adult mongrel dogs anesthetized with pentobarbital (Nembutal), 5F leads were placed through femoral and external jugular veins and placed into the right atrium and His bundle region. Through another femoral vein, a 200 micron optical fiber was inserted by way of a 7F catheter with a preformed curved tip. Guided by fluoroscopy and His bundle electrograms, the fiber's tip was positioned in the AV nodal region. After autonomic blockade was achieved with intravenous propranolol (5 mg) and atropine (1 mg), AV conduction was analyzed. An argon laser delivered 3 to 4 watts into the fiber in bursts of 10 seconds' duration until the desired degree of AV nodal delay or block (second or third degree) was manifested. Monitoring of His bundle electrograms was continued for 2 hours. Four weekly serial electrocardiograms were recorded, after which electrophysiologic studies were repeated. Acute post-lasing studies showed that: in all six dogs, the mean PR interval was prolonged from 116 ms (range 100 to 135) to 153 ms (range 120 to 185), with the prolongation being caused exclusively by AH lengthening from 68 ms (range 50 to 90) to 105 ms (range 65 to 140); the mean effective refractory period of the AV node increased from less than 185 ms (range less than 150 to less than 200) to 215 ms (range 190 to 280); and the mean atrial pacing cycle length, at which second degree AV nodal block was manifested, increased from 210 ms (range 160 to 260) to 261 ms (range 205 to 320).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1985

Laser recanalization of occluded atherosclerotic arteries in vivo and in vitro.

Controlled laser irradiation was used to recanalize atherosclerotic stenoses in vivo and in vitro. In 15 rabbits with atherosclerotic arteries a catheter was positioned in the distal aorta for angiographic examination and as a guide for a small silica optical fiber. Both Nd-YAG and argon lasers were used for recanalization with varying power and duration. As determined by angiographic studies the severity of iliofemoral stenoses in eight 15 arteries decreased from 78 +/- 18% to 32 +/- 11% (mean +/- SD). In one additional artery the stenosis improved from 45% to 25%, but this was associated with perforation. The other six arteries were perforated (two after fiber manipulation, four after laser discharge) without obvious improvement in severity of stenosis. No angiographic loss of distal circulation was noted. To better define tissue- laser interactions in the live-rabbits, lasing of 15 totally occluded atherosclerotic rabbit arterial segments in vitro was done while the optical fiber was advanced or fixed. When the fiber was fixed, serial sections showed that the new lumen was flame shaped. The width and depth of the lumen increased with increasing laser energy. When the fiber was advanced, histologic examination showed a smooth cylindrical vascular channel with limited lateral tissue damage. This study demonstrated that lasers can recanalize atherosclerotic stenoses in a live animal preparation; however, arterial perforation remains a problem.

Animals↗
PubMed1985

The effects of myocardial ischemia followed by reperfusion on perfused coronary capillarity.

To determine the effects of ischemia and reperfusion on myocardial perfused capillary density, rat hearts were excised, kept ischemic for thirty minutes then reperfused with blood from a support animal. Control hearts were isolated and perfused for either 10 or 60 minutes before injection of a vascular marker (Monastral Blue-blood mixture, 30 sec at 100 mmHg). The ischemic hearts were perfused with Blue after 10 minutes of reperfusion. The perfused capillary density (theta) and capillary/fiber ratio (C/F) were measured from frozen transverse sections of the left ventricle. For 10- and 60-minute control hearts, the epicardial theta values were 2324 +/- 476 caps/mm2 and 2378 +/- 330 SD. The endo/epi theta ratio was not significantly less than unity for either control group. For the ischemic group, theta was significantly decreased both in the epicardium (707 +/- 515 caps/mm2) and endocardium (130 +/- 30 caps/mm2) (p less than 0.05). The endo/epi theta ratio was significantly less than unity for the ischemic group (P less than 0.05). The C/F ratio analysis yielded the same results. The decrease in both theta and CF ratio indicate that 30 minutes of ischemia followed by 10 minutes of reperfusion caused a marked "No-reflow" phenomena in isolated, supported hearts. The No-reflow was most pronounced in the endocardium.

Animals↗
PubMed1984

Selective effects of secretagogues on insulin secretion: a mathematical model.

A mathematical model of the secretion of insulin from pancreatic islets of Langerhans is proposed. Previously proposed mathematical models of insulin secretion have dealt solely with glucose-stimulated release, and not with the more complex patterns of secretion (such as "off-responses") in response to other secretagogues or combinations of secretagogues. We conclude that an off-response is consistent with a compartmental model; and the facilitating effect of a constant concentration of glucose on leucine-stimulated insulin secretion is consistent with a selective effect of glucose on a single compartment of the model.

Animals↗
PubMed1984

C-peptide and insulin secretion. Relationship between peripheral concentrations of C-peptide and insulin and their secretion rates in the dog.

Estimation of the insulin secretory rate from peripheral C-peptide concentrations depends upon the following characteristics of C-peptide kinetics: (a) equimolar secretion of insulin and C-peptide by pancreatic beta cells; (b) negligible hepatic extraction of C-peptide; (c) constant metabolic clearance rate (MCR) of C-peptide over a physiological and pathophysiological range of plasma levels; and (d) proportional changes in the secretion rate of C-peptide and its peripheral concentrations under varying physiological conditions. In the present experiments, the relationship between a variable intraportal infusion of C-peptide and its concentration in the femoral artery was explored in 12 pancreatectomized dogs. As the infusion of C-peptide was rapidly increased, the magnitude of its peripheral concentration initially increased less than the infusion rate by 20-30%. After an equilibration period of approximately 30 min, however, further increases and decreases in the intraportal infusion were accompanied by nearly proportional changes in its peripheral concentration. Estimates of the amount of C-peptide infused during the experiment based on the steady state C-peptide MCR and its peripheral concentration were within 20% of the amount of C-peptide actually infused. These experiments demonstrate that the portal delivery rate of C-peptide can be calculated from its MCR and peripheral concentration in the dog. They also provide a basis for testing the validity of more complicated models of insulin secretion based on peripheral C-peptide concentrations in the dog as well as other species, including man. Finally, we have shown that the hepatic extraction of endogenously secreted C-peptide is negligible in the basal state (3.1 +/- 6.1%), and does not change after oral glucose ingestion. The MCR of exogenous dog C-peptide was similar whether measured by constant peripheral intravenous infusion (12.3 +/- 0.7 ml/kg per min), constant intraportal infusion (13.4 +/- 0.6 ml/kg per min), or analysis of the decay curve after a bolus injection (13.5 +/- 0.7 ml/kg per min).

Animals↗