Biomedical subjects

I Mena

Publications and source records attributed to I Mena.

At least 73 records · Page 4Linked to original sources

PubMed1990

Long-term effects of prepubertal testicular vessel ligation on testicular function in the rat.

To determine the effects of unilateral testicular vein and artery ligation in the immature rat on the function and final location of the testis at adulthood, 10-day-old male rats underwent either a sham operation or unilateral ligation of these vessels of the still undescended testis. Testicular location, blood flow, size and histology as well as ventral prostate weights were measured 50 days later at adulthood. At age 60 days, it was determined that all testes were descended into the scrotum, and there were no differences in testis and ventral prostate weights, intratesticular sperm counts and mean seminiferous tubular area between the control and sham operated animals. However, there was an 18% reduction in testicular blood flow (ml. per 100 gm. per minute +/- standard error of mean) in the operated animals when compared to the sham (20.43 +/- 1.10 versus 16.69 +/- 0.74, p less than 0.02). These data indicate that although there is a slight but significant reduction in testicular blood flow at adulthood when the testicular artery and vein are ligated early in life, this diminution is not sufficient to alter the ultimate location, testicular weight and spermatogenic function of the testis. This would suggest that after ligation of the main testicular vessels to the immature testis, the collateral blood supply is able to compensate with time to allow normal growth and development of the testis. These experimental observations provide additional support for the 2-staged approach to the high undescended testis whereby the testicular vessels are initially ligated and a subsequent procedure is performed to place the undescended testis into the scrotum.

Animals↗

PubMed1990

Simultaneous assessment of left ventricular wall motion and myocardial perfusion with technetium-99m-methoxy isobutyl isonitrile at stress and rest in patients with angina: comparison with thallium-201 SPECT.

The newly developed technetium-99m (99mTc) isonitriles can be used for the simultaneous evaluation of ventricular function and myocardial perfusion. We compared technetium-99m hexakis-2-methoxy isobutyl isonitrile [( 99mTc] MIBI) derived first-pass left ventricular wall motion at stress and rest with simultaneous myocardial perfusion defined by [99mTc]MIBI SPECT. These results were then compared with 201TI SPECT. We examined 28 patients with coronary artery disease; 25 had a previous myocardial infarction. We found concordance between segmental wall motion and myocardial perfusion imaging in defining normal, ischemic, and infarcted myocardium in 68% and 69% of segments using [99mTc]MIBI and 201TI respectively. The best agreement between wall motion and myocardial perfusion was seen in the inferior wall, while most of the discrepancies were found at the apex. Agreement between [99mTc]MIBI and 201TI SPECT myocardial perfusion was seen in 93% of segments. Technetium-99m-MIBI appears to be an ideal radiopharmaceutical for the simultaneous evaluation of ventricular function and myocardial perfusion during stress and at rest.

Angina Pectoris↗

PubMed1990

Lacrimal gland dosimetry for the brain imaging agent technetium-99m-HMPAO.

We calculated lacrimal gland dosimetry for the brain imaging agent 99mTc-HMPAO. One hundred thirty-eight patients were studied using a dedicated brain imaging device. Only 11% of the patients showed lacrimal gland uptake. For a 740-MBq (20 mCi) injected dose of 99mTc-HMPAO, the radiation exposure to the lacrimal glands is 10.2 mGy (1.02 rad), or 0.0138 mGy/MBq (0.051 rad/mCi). These values are five times lower than the ones reported by the manufacturer of HMPAO. As the dosimetry calculation is only for subjects showing 99mTc-HMPAO uptake in the lacrimal gland, the average radiation dose to all subjects is considerably lower, 1/10 of the estimated value.

Brain↗

PubMed1989

The effect of beta blockade on single photon emission computed tomographic (SPECT) thallium-201 images in patients with coronary disease.

We evaluated the effect of beta blockers on thallium-201 (Tl-201) single photon emission computed tomographic (SPECT) imaging in 12 patients with coronary disease using an automated computer algorithm. Maximal exercise heart rate and blood pressure were reduced and exercise time was increased with beta blockers. Estimated stress defect size decreased from 47 +/- 36.3 gm during placebo treatment to 32 +/- 27.1 gm during beta blocker therapy (-32%; p less than 0.01). The placebo treatment redistribution defect was estimated to be 28 +/- 29.8 gm. It fell to 15 +/- 23.3 gm with beta blockade (-46%; p less than 0.005). All patients had a stress Tl-201 defect during placebo treatment and eight had redistribution defects consistent with residual scar. During beta blocker therapy, 2 of 12 patients had normal stress-redistribution studies and only five patients had redistribution defects. Beta blockade can reduce exercise and redistribution Tl-201 SPECT defect size significantly while simultaneously increasing exercise time and reducing angina. Beta blockers may unmask or may eliminate evidence of redistribution. Tl-201 SPECT imaging may be useful in defining the reduction in ischemia produced by cardiac drugs.

Adrenergic beta-Agonists↗

PubMed1989

Association between postprandial changes in colonic intraluminal pressure and transit.

The aim of this study was to correlate the movement of colonic luminal contents with the changes in intraluminal pressure. Studies were performed in 9 healthy volunteers. Intraluminal pressure was measured with perfused catheter ports in the transverse, splenic flexure, descending, and sigmoid colon. Movement of the luminal contents was measured by following the movement of technetium 99m-ethylenetriamine-pentaacetic acid that was instilled as a bolus in the splenic flexure. During fasting there was very little change in pressure or in the movement of intraluminal contents. After eating a 1000-kcal meal, the tracer moved from the splenic flexure into the transverse colon and the sigmoid colon. Nonpropagating colonic motor activity increased in all colonic segments immediately after eating the meal (p less than 0.05). The increase in motility was significantly greater in the descending colon than in the transverse and sigmoid colon (p less than 0.05). In one-half of the subjects propagating contractions occurred postprandially. The movement of the intraluminal tracer occurred during both types of motility. The nonpropagating contractions were associated with a gradual movement of the luminal contents. The direction of the movement of the contents was determined by the differences in pressure in the different segments of the colon. The propagating contractions were associated with a rapid movement of intraluminal contents. These studies suggest that (a) colonic motility and transit are quiescent during fasting and (b) the transverse colon acts as a mixing and storage area, as retrograde transit into the transverse colon is the characteristic postprandial pattern.

Adult↗

PubMed1989

Recovery of testicular blood flow following ligation of testicular vessels.

To determine whether initial ligation of the testicular vessels of the high undescended testis followed by a delayed secondary orchiopexy is a viable alternative to the classical Fowler-Stephens procedure, a series of preliminary experiments were conducted in the rat in which testicular blood flow was measured by the 133xenon washout technique before, and 1 hour and 30 days after ligation of the vessels. In addition, testicular histology, and testis and sex-accessory tissue weights were measured in 6 control, 6 sham operated and 6 testicular vessel ligated rats 54 days after vessel ligation. The data demonstrate that ligation and division of the testicular blood vessels produce an 80 per cent decrease in testicular blood flow 1 hour after ligation of the vessels. However, 30 days later testis blood flow returns to the control and pre-treatment value. There were no significant changes in testis or sex-accessory tissue weights 54 days after vessel ligation. Histologically, 4 of the surgically operated testes demonstrated necrosis of less than 25 per cent of the seminiferous tubules while 1 testis demonstrated more than 75 per cent necrosis. The rest of the tubules in all 6 testes demonstrated normal spermatogenesis. From this study we conclude that initial testicular vessel ligation produces an immediate decrease in testicular blood flow but with time the collateral vessels are able to compensate and return the testis blood flow to its normal pre-treatment value. These preliminary observations lend support for the concept that initial ligation of the testicular vessels followed by a delayed secondary orchiopexy in patients with a high undescended testis may be a possible alternative to the classical Fowler-Stephens approach.

Animals↗

PubMed1989

Abnormalities in the duodenal transit and motility in duodenal ulcer patients: studies with a new isotopic technique.

Abnormalities of duodenal motility have been described in patients with duodenal ulcer and in experimental ulcers in rats and it has been postulated that they could be pathogenic in peptic ulcer disease. We have investigated with an isotopic technique whether duodenal bulb clearance or duodenal transit are abnormal in duodenal ulcer. Six patients with inactive and six with active duodenal ulcers, all men, and six healthy male controls were studied. Motility of the duodenum was simultaneously monitored. A bolus of 99mTcDTPA was injected into the duodenum while water or acid were perfused on different occasions. Duodenal bulb clearance and transit to the ligament of Treitz were calculated. Duodenal transit in duodenal ulcer patients 108.8 (23) sec was faster than in controls, 194.9 (5.1) sec (p less than 0.05) during the quiescent period of the motility cycle. The frequency of duodenal bulb contractions during acid perfusion was higher in duodenal ulcer patients 1.7 (0.4) cont/min, than in controls 0.8 (0.1) cont/min (p less than 0.05). No other significant differences were observed between ulcer patients and controls. These data suggest that patients with duodenal ulcers do not have major abnormalities of duodenal bulb clearance, nor of duodenal transit and that duodenal motility does not play a primary role in the pathogenesis of the ulcer.

Adolescent↗

PubMed1989

Technetium-99m ECD: a new brain imaging agent: in vivo kinetics and biodistribution studies in normal human subjects.

Lipophilic neutral 99mTc complexes of diaminedithiol (DADT) ligands cross the brain-blood barrier. A new derivative of DADT family, 99mTc ethyl cysteinate dimer (ECD) showed high brain uptake in nonhuman primates. We report here the in vivo kinetics and biodistribution results in 16 normal human subjects. Dynamic images of brain obtained for 10 min following an i.v. administration of [99mTc]ECD showed that the maximum 99mTc brain activity reached within 1 min and remained near that level for the next 10 min. The blood clearance of the tracer was very rapid and the activity remaining in blood after 5 min was less than 10%. Within 2 hr 50% of 99mTc activity was excreted in urine. Anterior and posterior total-body images were obtained at 5, 30, 60 min, 2, 4, 24, and 48 hr using a moving table at 20 cm/min. Percent injected dose was calculated for different organs and tissues. The brain uptake was 6.5 +/- 1.9% at 5 min postinjection and remained relatively constant over several hours. Two-compartment analysis of brain time-activity curve showed that 40% of brain activity washed out faster (T 1/2 = 1.3 hr) while the remaining 60% had a slower clearance rate (T 1/2 = 42.3 hr). Some of the tracer was excreted through the hepatobiliary system. Lung uptake and retention of [99mTc]ECD was negligible. Radiation dosimetry is favorable for the administration of up to 20-40 mCi of [99mTc]ECD. These results show that [99mTc]ECD is rapidly extracted and retained by the brain providing favorable conditions for single photon emission computed tomography imaging.

Adult↗

PubMed1988

Effect of nifedipine on gastric emptying and gastrointestinal motility in man.

Nifedipine, a calcium-blocking agent, inhibits smooth muscle contractions in various organs including gastric muscle in vitro. Despite this, nifedipine has been found to have no effect on gastric emptying in man. We have investigated the effect of nifedipine on gastric emptying of liquids and solids and on gastrointestinal motility in six healthy subjects. For this, isotopic techniques and manometric methods were used. We confirm that nifedipine 30 mg per os does not modify gastric emptying of liquids or solids. By contrast, antral motility was significantly inhibited (P less than 0.05) and duodenal motility increased. These results could be interpreted as (1) gastroduodenal motility changes are not severe enough to alter emptying or (2) isotopic techniques are not sensitive enough to detect subtle changes in gastric emptying.

Adult↗

PubMed1988

Conventional and right precordial ECGs, creatine kinase, and radionuclide angiography in post-traumatic ventricular dysfunction.

Right ventricular infarction due to ischemic heart disease can be diagnosed by a right precordial electrogram or by first-pass radionuclide angiography (FPRNA). Prior FPRNA studies have shown that cardiac dysfunction after blunt chest trauma (myocardial contusion) is most often due to right ventricular dysfunction. We hypothesized that right ventricular dysfunction due to ischemic heart disease and myocardial contusion should produce similar ECG changes due to myocyte disruption. The purpose of our study was to evaluate the diagnostic value of the right precordial electrogram in suspected cardiac contusion. Thirty-five patients with suspected myocardial contusion based on mechanism of injury/clinical findings and no history of clinical heart disease were enrolled prospectively. All patients had conventional ECG, right precordial electrogram, and FPRNA studies. Twenty patients had normal cardiac scans (group 1); percentage of myocardial creatine kinase (CK-MB) was measured in 12 of these patients and was less than 5% in 11. Fifteen patients had abnormal cardiac scans (wall motion abnormality and/or decreased right ventricular ejection fraction) (mean, 34% +/- 7% [SD]; normal, greater than 40%) (group 2); percentage of CK-MB was measured in 13 of 15 patients and was less than 5% in all 13. Conventional ECGs and right precordial electrograms in all patients were analyzed for differences in heart rate, PR interval, QRS duration, corrected QT interval, and the axis of the frontal and horizontal plane QRS complex and ST segment. There were no significant differences between group 1 and group 2 patients. No patient with myocardial contusion diagnosed by FPRNA had elevated ST segments in V4R through V6R or a percentage CK-MB of more than 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

Evaluation of valvular regurgitation by factor analysis of first-pass angiography.

We have evaluated left ventricular regurgitation by means of factor analysis of 99mTc first-pass radionuclide angiography (FPRNA) and time-activity curve deconvolution. The FPRNA regurgitant fraction (RF) was computed in 26 individuals: 13 patients (eight mitral, three aortic, and two mitral-aortic) and 13 controls. The reference method was contrast ventriculography (CV) performed within 1 hr after FPRNA. In 19 patients, CV was preceded by the determination of cardiac output, using indocyanine green dye (n = 16) or thermodilution technique (n = 3), to determine a catheterization regurgitant fraction (CATH-RF). Lung and left ventricular (LV) time-activity curves were gathered by factor analysis and the FPRNA regurgitant fraction assessed by a lagged normal deconvolution of these curves. In valvular regurgitation, the LV deconvolved curve demonstrates the appearance of a long transit time component that is amenable to quantification. The presence of regurgitation was determined by contrast ventriculography. With a 10% RF as an acceptable upper limit of normal for nonregurgitant patients, FPRNA yielded one false-negative and no false-positive studies (n = 26), while CATH-RF yielded two false-negative and four false-positive determinations (n = 19). The following are results of quantitative determination of RF (mean +/- s.d.): FPRNA 0.39 +/- 0.19 (n = 13 Valvular), 0.01 +/- 0.03 (n = 13 Controls); CATH 0.34 +/- 0.24 (n = 11 Valvular), 0.13 +/- 0.12 (n = eight controls). FPRNA was able to differentiate (p less than 0.001) between control patients (CV grading 0) and mild/moderate regurgitation (CV grading 1+ or 2+) and severe regurgitation (3+ or 4+) (p less than 0.025).

Adult↗

PubMed1987

Thallium-201 single-photon emission computed tomographic estimates of left ventricular mass in patients with and without ischemic heart disease.

A new automated edge detection program has been developed to estimate left ventricular mass from single-photon emission computed tomographic (SPECT) thallium-201 images of patients. Left ventricular (LV) mass was measured from contrast angiograms in 21 patients and was compared with LV mass estimated from thallium-201 tomographic studies. A comparison of angiographic mass to mass estimated from stress studies yielded an r = 0.97 (SEE = 21.6 gm) and a comparison of angiographic mass to mass determined from the redistribution images yielded r = 0.96 (SEE = 23.0 gm). Values of mass from stress and redistribution studies varied 7.3% +/- 6.7 and 8.8% +/- 9.2, respectively, when compared with values obtained by cineangiography. LV mass derived from the stress and redistribution studies were highly correlated (r = 0.97; SEE = 21.9 gm). Linear regression analysis revealed a slope of 1.06 (stress ventricular mass = 1.06 X redistribution mass - 14.9 gm). Thirteen patients had two thallium-201 SPECT studies performed approximately 1 month apart. Estimated LV mass was highly correlated when the two studies were compared (r = 0.94; SEE = 21.7 gm comparing the two stress studies; and r = 0.93, SEE = 19.4 gm for the two redistribution studies). We conclude that SPECT thallium-201 imaging can define LV mass accurately and reproducibly in normal, ischemic, or infarcted tissue.

Coronary Disease↗

PubMed1987

Effect of pectin on gastric emptying and gastroduodenal motility in normal subjects.

The effects of pectin ingestion on gastric emptying, gastroduodenal motility, and plasma levels of glucose, insulin, and glucagon were studied. Initial studies demonstrated that 15 g of pectin was the optimal dose. Subsequently 6 healthy male volunteers were studied on 4 separate days at random. On day 1, gastric emptying of a liquid and a solid meal was assessed by radioisotope technique using 99mTc-dithiopropylthiomine. On day 2, the gastric emptying study was repeated with the addition of pectin to each meal. Plasma levels of glucose, insulin, and glucagon also were determined during these 2 days. On day 3, the effects of liquid and solid meals on gastroduodenal motility were assessed by means of a perfused catheter system. On day 4, the motility study was repeated with the addition of pectin to each meal. Pectin supplementation caused a significant prolongation of gastric emptying half-time of both liquid and solid meals (p less than 0.05). The addition of pectin, however, did not have any significant effect on gastroduodenal motility other than increasing the duodenal motility index 10 min after the liquid meal. The addition of pectin to the liquid meal lowered plasma levels of insulin at 15, 30, and 45 min, and glucagon levels 15 min after the meal. No effect was noted on blood sugar levels. On the other hand, the addition of pectin to the solid meal had no effect on plasma levels of glucose, insulin, and glucagon. We conclude that pectin supplementation delays gastric emptying of both liquid and solid meals in normal human subjects without causing notable changes in gastroduodenal motility or significant variations in pancreatic hormone plasma levels. The pectin effect on gastric emptying may be caused solely by increasing the viscosity of the meals.

Adult↗

PubMed1987

Intraventricular somatostatin-14, arginine vasopressin, and oxytocin: analgesic effect in a patient with intractable cancer pain.

The analgesic effect of intraventricular somatostatin-14 (SOM-14), arginine vasopressin (AVP), and oxytocin (OT) were tested in one terminally ill cancer patient with a diffuse mesothelioma suffering intractable continuous and incapacitating thoracic pain. SOM-14 reduced pain by 90% for 48 min; AVP reduced pain by 95% for 75 min, and OT reduced pain by 88% for 77 min. The only notable side effects were seen after the administration of AVP, which induced anesthesia and flaccid paralysis of the lower limbs, from which the patient fully recovered after 20 h.

Arginine Vasopressin↗

PubMed1987

Accelerated solute clearance in Pneumocystis carinii pneumonia.

A radioaerosol clearance test was used to detect lung injury in 12 patients with acquired immune deficiency syndrome (AIDS) and Pneumocystis carinii pneumonia documented by bronchoscopy. The clearance of 99mTc-DTPA was elevated over most regions of interest in all of these patients. In each of 7 subjects who responded to trimethoprim-sulfamethoxazole therapy, clearance returned toward normal. Average clearances were either normal or very slightly above the 95% expected upper limit of normal in each of 6 patients with either AIDS or AIDS-related complex without clinical evidence of Pneumocystis infection. The radioaerosol diffusion test may prove useful for determining whether patients who are predisposed to this infection require bronchoscopy and may provide information concerning their response to therapy.

Acquired Immunodeficiency Syndrome↗

PubMed1987

Estimation of left ventricular mass in normal and infarcted canine hearts using thallium-201 SPECT.

A new automated edge detection program has been developed to estimate left ventricular mass from single photon emission computed tomographic (SPECT) 201Tl images and 14 dogs were studied. Six of the 14 dogs underwent imaging before and 5 hr after coronary artery occlusion with a closed-chest technique. True left ventricular mass was determined at time of killing within 1 hr of the last 201Tl study. Left ventricular mass determined by tomography correlated well with autopsy left ventricular mass (r = 0.94; p less than 0.001, s.e.e. = 5.9 g) over a range of 62-156 g. The intraobserver variation between repeated measurements of the same SPECT study yielded an r = 0.99; p less than 0.0001; s.e.e. = 2.3 g. The reproducibility of the mass determination was assessed in four animals with two studies performed 10-14 days apart. The estimate of left ventricular mass from the two studies were highly correlated (r = 0.98; p less than 0.001) with a mean absolute difference of 4 g (3.3%). In the six dogs with a control and postinfarct study the mean total left ventricular mass by 201Tl tomography varied by less than 3.8% (r = 0.89; p less than 0.001). In conclusion, tomographic imaging with 201Tl can define left ventricular mass accurately and reproducibly in the dog model. The ability of this 201Tl tomographic left ventricular mass program to measure both normal and infarcted tissue accurately suggests the possibility of documenting interventions designed to alter left ventricular mass and of sizing acute infarcts and assessing interventions that may alter acute infarct size.

Animals↗

PubMed1986

Myocardial contusion diagnosed by first-pass radionuclide angiography.

Myocardial contusion, (traumatic myocardial dysfunction) is a relatively common complication of blunt trauma. The diagnosis is often elusive. Studies using clinical and laboratory parameters often fail to detect patients with significant myocardial injury. No constellation of clinical signs, electrocardiographic findings, or cardiac enzymes has been sensitive or specific enough to evaluate such patients accurately. Recently, radionuclide angiography was found to be a sensitive indicator of myocardial dysfunction. The authors studied ten patients with blunt thoracic or multisystem trauma who had myocardial dysfunction documented by first-pass radionuclide angiography. Follow-up study within five weeks demonstrated normalization or improvement in ejection fraction and wall motion abnormalities in all patients. Radionuclide angiography is cost effective, can be performed in the emergency department, and can assist in the management of patients with blunt thoracic or multisystem trauma.

Adult↗

PubMed1986

Diagnosis and quantitation of pulmonary arteriovenous malformations by factor analysis.

The diagnosis of a pulmonary arteriovenous malformation (AVM) was made by performing a computer-assisted first-pass cardiopulmonary imaging procedure using Tc-99m pertechnetate and processing the image information using factor analysis. This analytical technique is capable of separating partially overlapping structures by automatically extracting factors with different temporal behavior (time-activity curves) which correspond to functional areas without anatomic constraint. This procedure was accomplished successfully despite the presence of four-chamber enlargement, mitral stenosis and regurgitation, tricuspid regurgitation, chronic obstructive pulmonary disease and pulmonary hypertension. The magnitude of the right-to-left shunt resulting from the AVM was quantitated using both the factor analysis data and an independent Tc-99m MAA computer-assisted imaging procedure. Both methods gave comparable values.

Arteriovenous Malformations↗