[The molecular mechanism of visual transduction]. / Mecanismul molecular al transductiei vizuale.

Light absorbtion by the visual pigment rhodopsin triggers, through Gt-protein (transducin) coupling, a cascade of events--in the outer segment of the rod cell of the retina--that results in membrane hyperpolarization and nerve excitation. Activated rhodopsin is removed from the cascade of reactions by rhodopsin kinase and arrestin that stop the visual transduction pathway. Thus, when light stimulation ceases, the transduction system is restored to its resting state.

Scintigraphic findings mimicking focal nodular hyperplasia in a case of hepatoblastoma.

Hepatoblastoma is a primary liver neoplasm in which prompt diagnosis and resection are critical to long-term survival. Liver scintigraphy using Tc-99m sulfur colloid and Tc-99m iminodiacetic acid (IDA) derivatives has been used in the evaluation of hepatic masses. Most space-occupying lesions of the liver appear as photopenic regions following either Tc-99m SC or IDA agents. Two exceptions have been reported. Focal nodular hyperplasia (FNH) has been shown to have variable colloid uptake, which is dependent upon the number of Kupffer cells per given volume. Many patients with FNH will demonstrate activity within the FNH to be greater or equal to the normal liver. In addition, two cases of hepatoblastoma have been reported to show colloid activity within the tumor, and in one patient slight uptake of Tc-99m IDA was noted in the tumor 15 minutes postinjection. The current case demonstrates a hepatoblastoma in which the scintigraphic findings with Tc-99m SC and Tc-99m IDA were similar to those reported, with retention of IDA far greater than the previously reported case.

[A study on periodontal implications of the therapy for dento-maxillary anomalies]. / Studiu privind implicatiile parodontale ale terapiei anomaliilor dentomaxilare.

Dento-maxillary anomalies are the results of a deviation of growth processes, or of the development of the dento-maxillary apparatus. From the viewpoint of their frequencies the dento-maxillary anomalies hold the third place in the list of stomatological affections. The great variety of clinical manifestations of dento-maxillary anomalies has determined definition of therapeutical attitudes, in the frame of which therapy with orthodontal devices has an important place. This type of therapy exerts its effects also by implicating the parodontium, and this by at least two different mechanisms:-the induction of changes in the structures of the dento-maxillary apparatus by a direct parodontal mechanisms; as an element in the overall regulation of the growth of the dento-maxillary apparatus. The treatment with orthodontial devices should be conceived in such a way that it will protect the parodontium from the deleterious effects of these devices. The data presented further were obtained from 2 groups of patients and concern the improvement of the efficiency of treatments with orthodontal devices, and the protection of the parodontium during treatment. The first group was investigated in 1988, and criteria for the selection of participants in the second group were established. In the first group a total of 109 subjects were included, aged between 5 and 20 years, in whom stomatologic procedures were started in January 1988. These subjects were followed until the month of November of the same year. The most frequently encountered anomaly was maxillary compression (endalvellia) in 70 subjects. With regard to the condition of the marginal parodontium clinical exploration showed that 57 subjects had not underwent changes.(ABSTRACT TRUNCATED AT 250 WORDS)

[The clinical and technological particularities of using Gaudent "S" and Gaudor alloys in the conjoint treatment of extensive edentation]. / Studiul particularitatilor clinice si tehnologice ale utilizarii aliajelor Gaudent S si Gaudor în terapia conjuncta a edentatiilor întinse.

The present paper forms part of a longitudinal study on prostheses restaurations with Romanian non-noble alloys for establishing the clinical, technological and biological implications of their utilization in mass assistance. The large contact surface with biological structures and the buccal medium of total conjoint restaurations permitted chacking of previous data regarding the biological behaviour of these alloys. In the group of 58 patients with total bridges followed up for 2 to 5 years there were no adverse reactions in which the alloy used could be incriminated. The iatrogenic aspects observed consequent to the application of prostheses were common to the use of any other metal alloy. The surface colour changes in a reduced number of cases depended upon the technologic preparation of the alloys and particularly upon the patient's limited ability to keep the plate under bacterial control. The study demonstrated that casting of a total Gaudent S bridge under present conditions does not give correct adaptation of the cervical limits which means more accurate compliance with the technology and homologation of the specific of this alloy.

[Contribution of immediate orthopedic-orthodontic treatment in maxillo-palatine-labial clefts]. / Aportul tratamentului asociate ortopedico-ortodontic în despicaturile labio-maxilo-palatine.

Labio-maxillo-palatine clefts are pathological conditions accompanied by severe handicaps, congenital malformations of particular interest for medical assistance because of several reasons, including the following: they are the most frequent congenital malformations of the bucco-maxillo-facil region: in certain cases there are other teratologic conditions in other parts of the organism that are associated to these clefts; there are no disturbances from the intellectual viewpoint; there are efficient possibilities for therapy as a result of a multidisciplinary approach, and the progress achieved in each of the fields involved may contribute to continuous improvement of the therapeutical prognosis; because of the therapeutical problems that these pathological conditions may raise, and because of the long duration of the treatment, the pathology involved in labio-maxillo-palatine clefts has a special social character which renders necessary the support of extra-medical factors (special schooling, special conditions for work, etc.). All these aspects explain the world-wide interest for this type of pathology, as it is also reflected in the large number of scientific manifestations dedicated exclusively, or in association to this problem, aimed at achieving a permanent therapeutic progress in this field. In the period between 1986 and 1987 the authors have selected 60 patients out of those hospitalized for this defect in the Clinic. The patients were aged between 2 and 43 years. Orthodontal therapy is the type of therapy which takes the longest time in these patients. This is achieved by the successive application of orthodontal devices, which necessitate a long-term therapeutic strategy. In the course of this therapy a permanent cooperation is necessary between the specialist in orthodontics and the maxillofacial surgeon. A common approach is beneficial for both specialties. The number of specialists in orthodontics involved in the orthodontal therapy of labio-maxillo-palatine clefts is alarmingly low, and thus there is no possibility to evolve a special program for their further special education. Another difficulty is the fact that patients from all over the country demand the services of the same specialist, and a series of aspects evolve from this situation, as follows: the patients (usually accompanied by one of the parents) have to perform long trips, which are also expensive; when incidents occur, in relation with the use of a orthodontal device these patients cannot require immediately the assistance of specialized services, and, as a result, the number of recidives is alarmingly high.(ABSTRACT TRUNCATED AT 400 WORDS)

False-positive iodine-131 body scan caused by a large renal cyst.

Focal I-131 accumulation is generally a reliable indicator of functioning thyroid tissue or a differentiated thyroid cancer metastasis. Normal accumulation of activity may be seen in areas such as the intestinal tract, liver, and salivary glands. This report describes a patient with significant accumulation of I-131 in the right upper quadrant of the abdomen. The abnormality, first thought to represent metastatic thyroid carcinoma, was subsequently proven to be accumulation within a large renal cyst.

Comparison of magnetic resonance imaging and radionuclide imaging in the evaluation of renal transplant failure.

Magnetic resonance imaging (MRI) was compared with radionuclide scintigraphy (RNS) in 16 patients with renal transplants undergoing renal failure to determine which modality could best discriminate between rejection, acute tubular necrosis (ATN), and cyclosporin nephrotoxicity (CN). Although all rejecting transplants had reduced corticomedullary differentiation (CMD) on T1-weighted MR images, four of five cases of ATN had appearances that could not be distinguished from rejection. A normal CMD suggests nonrejection, but diminished CMD is nonspecific. Tc-99m DTPA/I-131 hippuran RNS was superior to MRI in differentiating rejection from ATN. Although ATN and CN have similar RNS patterns, this distinction can usually be made based on the clinical time course. Other potential uses of MRI in the evaluation of the renal transplants are discussed.

Failure of episodic high-dose oral verapamil therapy to convert supraventricular tachycardia: a study of plasma verapamil levels and gastric motility.

The practicality of administering large oral doses of verapamil tablets to terminate supraventricular tachycardia (SVT) was investigated in 10 patients. A pilot study in four patients showed that unexpectedly low plasma levels (less than 40 ng/ml) were obtained 60 minutes after administering 160 mg or 240 mg of verapamil during SVT. Nuclear studies in the six other patients showed that fractional liquid gastric emptying times (T) were significantly prolonged in SVT compared to sinus rhythm (SR), p less than 0.05 from T 1/3 onward. Further verapamil absorption studies (200 to 360 mg) performed during SVT and SR in five of six patients showed that peak verapamil levels in four patients in SVT were 23% to 71% lower than in sinus rhythm, where they had peaked at greater than 250 ng/ml 60 minutes post verapamil ingestion, and areas under the plasma concentration time curves were 26% to 100% (mean 67%) less in SVT than in SR for all five patients. SVT was terminated by verapamil in one patient after 40 minutes and the rate of SVT was slowed after 90 minutes in two other patients. Thus plasma verapamil levels are considerably reduced during SVT as compared to SR, and changes in gastric emptying are likely a contributing cause. Since SVT was converted to sinus rhythm in only 1 of 10 patients within 1 hour, large oral doses of verapamil tablets appear unsatisfactory for the episodic treatment of SVT.

Regional comparison of technetium-99m DTPA aerosol and radioactive gas ventilation (xenon and krypton) studies in patients with suspected pulmonary embolism.

The regional distribution of [99mTc]DTPA aerosol was compared with that of 133Xe (n = 30) and krypton (n = 24) in a group of patients with suspected pulmonary embolism. All patients had an aerosol study using a recently available commercial generator system, a ventilation study with one of the gases, and perfusion imaging. Regional information was assessed visually on xenon, krypton, and aerosol studies independently by considering each lung as three equal-sized zones. In addition, gas ventilation findings peripheral to regions of aerosol turbulence ("hot spots") were evaluated. Only 64% of the zones were in complete agreement on xenon and aerosol. Most of the discordance between xenon and aerosol was accounted for by minor degrees of 133Xe washout retention in zones that appeared normal in the aerosol study. An agreement rate of 85% was noted between 81mKr and aerosol regionally. The regions of discordance between aerosol and gas studies, however, usually were associated with unimpressive perfusion defects that did not change the scintigraphic probability for pulmonary embolism in any patient. Regarding zones of aerosol hyperdeposition, 76% had associated washout abnormalities on xenon; however, there was no correlation between the presence of these abnormalities or perfusion abnormalities. The results confirm the high sensitivity of 133Xe washout imaging, but suggest that radioaerosol imaging will detect most parenchymal abnormalities associated with perfusion defects of significance.

Evaluation of low-dose radioiodine ablation therapy in postsurgical thyroid cancer patients.

Nineteen patients with differentiated thyroid carcinoma were given low dose (30 mCi) radioiodine therapy for the ablation of residual thyroid tissue following total thyroidectomy. Using 5- to 10-mCi diagnostic I-131 scans, ablation was achieved in two of 19 patients following the first low dose and three of 12 patients following the second low-dose therapy. The ablation response was 53% (ten of 19) following one large dose (100 mCi) in another concurrent group of 19 patients. The ablation response following the first low dose when compared with the first high-dose therapy was significantly lower (P = 0.015). The combined ablation response following first and second low doses (five of 14) when compared to a single large dose was not significantly different (P = 0.534). The use of low-dose-I-131 therapy, although not as effective as large dose therapy, may be warranted in patients resistant to entering the hospital for therapy. However, ablation as defined by a five- to ten-mCi I-131 scan can be expected to occur in only one third of the patients after two attempts at ablation, while a single 100-mCi regimen can be successful in achieving ablation in over one half of the patients after the first attempt.

Treatment rationale in thyroid carcinoma. Effect of scan dose.

The authors have previously shown that the definition of ablation of thyroid tissue in patients treated with thyroidectomy and radioiodine (I-131) for thyroid carcinoma depends upon the dose of I-131 used to scan the patient. The therapeutic response to I-131 therapy was evaluated in a group of ten differentiated thyroid cancer patients who had a negative 2-mCi (-2 mCi) diagnostic study, but had a positive 10-mCi (+10 mCi) diagnostic study (group 1) during their follow-up evaluation. These results were compared to another group of ten differentiated thyroid cancer patients who received I-131 ablation therapy based on a positive 2-mCi (+2 mCi) I-131 scan (group 2). Six patients in group 1 and eight in group 2 had improvement or ablation of residual tissue based on the 10-mCi scan following therapy. The difference in response between the two groups was not statistically significant (P = 0.63) by two-tailed Fisher's exact test, indicating that even patients with -2-mCi, but +10-mCi scans may respond to I-131 therapy. Whether the large dose therapy makes any impact on the clinical outcome has not been answered by this study.

Correlation of thyroglobulin measurements and radioiodine scans in the follow-up of patients with differentiated thyroid cancer.

Correlation of radioiodine (131I) scans and serum thyroglobulin (Tg) concentrations were performed in the follow-up of 85 differentiated thyroid cancer patients who had undergone total thyroidectomy. Tg results were also compared with the control group of 33 thyroidectomized patients with no evidence of thyroid carcinoma and normal values for Tg established. Excellent correlation between Tg and scans was noted in patients with scan evidence of metastasis distant from the neck. Poor correlation was present in patients with scan evidence of local neck metastasis only, thyroid bed activity, and those with mediastinal activity. In addition, in 8% of the patients, the Tg assay could not be performed because of interfering antibodies. The conclusion is that elevated Tg concentration is a good indicator of metastasis outside of the neck as detected by 131I scans. Caution should be used when Tg alone is used in evaluating local neck metastasis demonstrated on scans. The significance of mediastinal activity warrants further investigation.

Scintigraphy of gastrointestinal hemorrhage: superiority of 99mTc red blood cells over 99mTc sulfur colloid.

The relative efficacy of 99mTc sulfur colloid and in vitro-labeled 99mTc red blood cells in detecting and localizing gastrointestinal hemorrhage was evaluated in a prospective tandem study of 100 patients referred for suspicion of gastrointestinal tract hemorrhage. Thirty-eight true-positive scintigrams were obtained with 99mTc red blood cells, whereas 99mTc sulfur colloid detected only five sites of hemorrhage. Scintigraphic findings were corroborated by clinical, endoscopic, arteriographic, and surgical findings. 99mTc red blood cells were clearly superior, with a sensitivity of 93%, specificity of 95%, and overall accuracy of 94% in detecting and localizing gastrointestinal hemorrhage.

Cholescintigraphy in acute acalculous cholecystitis.

Acute acalculous cholecystitis is a relatively rare but potentially lethal condition if not treated promptly. Since stones are not present, diagnostic procedures such as ultrasound or other radiological procedures are frequently not helpful. Tc-99m iminodiacetic acid scan results were analyzed in 11 proven cases of acute acalculous cholecystitis. All had positive tests with nonvisualization of the gallbladder giving a sensitivity of 100%. Tc-99m iminodiacetic acid cholescintigraphy is a highly reliable test and is easily performed even in acutely ill patients and should be the test of choice in all patients predisposed to and suspected of acute acalculous cholecystitis.

Gallium scintigraphy in bronchogenic carcinoma. The effect of tumor location on sensitivity and specificity.

Fifty-one patients with primary lung cancer were evaluated using 67Ga citrate scintigraphy with respect to detection of peripheral primary, hilar metastasis, and mediastinal metastasis. The results demonstrated the necessity for an understanding of the criteria used in considering the gallium scintigram as either positive or negative, as well as the instrumentation employed in performing the test before any meaningful sensitivity and specificity figures can be derived within a given institution. Only with this understanding can actual strategy for instituting invasive procedures be achieved.

Acute gangrenous cholecystitis: radionuclide diagnosis.

Radionuclide hepatobiliary imaging is a useful procedure for the diagnosis of acute cholecystitis. Visualization of the gallbladder essentially rules out acute cholecystitis. Nonvisualization suggests acute cholecystitis but may also be associated with chronic gallbladder disease or other conditions. We recently observed five patients in whom a rim of increased parenchymal liver activity was seen adjacent to the gallbladder fossa. All five patients had acute gangrenous cholecystitis. The rim of increased activity appears to be a useful secondary sign of acute cholecystitis.