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B Shapiro

Publications and source records attributed to B Shapiro.

At least 37 records · Page 2Linked to original sources
PubMed1990

Speeding up the dynamic algorithm for planar RNA folding.

The simplest dynamic algorithm for planar RNA folding searches for the maximum number of base pairs. The algorithm uses O(n3) steps. The more general case, where different weights (energies) are assigned to stacked base pairs and to the various types of single-stranded region topologies, requires a considerably longer computation time because of the partial backtracking involved. Limiting the loop size reduces the running time back to O(n3). Reduction in the number of steps in the calculations of the various RNA topologies has recently been suggested, thereby improving the time behavior. Here we show how a "jumping" procedure can be used to speed up the computation, not only for the maximal number of base pairs algorithm, but for the minimal energy algorithm as well.

Algorithms↗
PubMed1990

A computational procedure for assessing the significance of RNA secondary structure.

In our recent series of papers, we have used the structures of statistical significance from Monte Carlo simulations to improve the predictions of secondary structure of RNA and to analyze the possible role of locally significant structures in the life cycle of human immunodeficiency virus. Because of intensive computational requirements for Monte Carlo simulation, it becomes impractical even using a supercomputer to assess the significance of a structure with a window size greater than 200 along an RNA sequence of 1000 bases or more. In this paper, we have developed a new procedure that drastically reduces the time needed to assess the significance of structures. In fact, the efficiency of this new method allows us to assess structures on the VAX as well as the CRAY.

Biometry↗
PubMed1990

Late presentation of metastatic pheochromocytoma: a problem case solved by I-131 MIBG scintigraphy.

A patient presented with recurrent pheochromocytoma 10 years following the apparently successful surgical cure of a right adrenal pheochromocytoma. Conventional medical imaging techniques, (chest radiograph, abdominal ultrasound, and abdominal CT) suggested local recurrence for which surgery was planned. I-131 MIBG scintigraphy revealed disseminated metastatic disease that rendered attempts at surgical cure futile. The patient was treated with three therapeutic doses of I-131 MIBG with good symptomatic palliation and improvement of some biochemical parameters.

3-Iodobenzylguanidine↗
PubMed1990

Scintigraphic endocrine mimicry.

The control of hormone secretion and substrate uptake by the thyroid and inner adrenal cortex is similar because both glands undergo hypothalamic-pituitary trophic hormone modulation and negative feedback by their respective major secretory products: thyroid hormone and cortisol, respectively. As a result of these parallel mechanisms of endocrine function, thyroidal accumulation of radioiodine or Tc-99m pertechnetate and adrenal cortical accumulation of I-131-6 beta-iodomethylnorcholesterol (NP-59) and other radiocholesterol analogs are strikingly similar. The patterns of imaging of these glands are thus functional maps of the process(es) of substrate accumulation and depict the endocrine pathophysiology of these glands in a variety of dysfunctional states. The well-recognized patterns of thyroid imaging can be shown analogous to those of the adrenal cortex.

Adosterol↗
PubMed1990

Morphine-augmented hepatobiliary scintigraphy in the severely ill: caution is in order.

Morphine augmentation in hepatobiliary scintigraphy has been reported as a useful tool to shorten imaging time. The technique has not been extensively evaluated in patients who are severely ill and receiving total parenteral nutrition, although the study of these patients with non-morphine-augmented hepatobiliary scintigraphy is problematic. The authors retrospectively analyzed 51 morphine-augmented hepatobiliary studies performed in a tertiary referral center on a population with a high proportion of severe intercurrent illness (18 patients, 14 of whom were receiving total parenteral nutrition) and hepatocellular dysfunction (eight patients). The overall sensitivity was 94%, specificity was 69%, and the false-positive rate was 40% for the diagnosis of acute cholecystitis. The majority of the false-positive cases occurred in the severely ill subgroup (false-positive rate, 60%). Morphine-augmented hepatobiliary studies may be advantageous because of shortened imaging time. However, patients who have severe intercurrent illness, whether or not they are receiving total parenteral nutrition, have a higher frequency of false-positive morphine-augmented hepatobiliary studies, and positive findings at scintigraphy in this patient group should be interpreted with caution.

Acute Disease↗
PubMed1990

The role of imaging tests in the diagnosis of thyroid carcinoma.

Many noninvasive high-quality imaging tests are widely available to assist in the evaluation of thyroid nodules. These include thyroid scans, computed tomography, ultrasonography, and magnetic resonance imaging. These procedures and other less commonly performed tests are reviewed. Their routine role in the diagnosis of thyroid carcinoma, however, has been, for the most part, obviated by the convenience and accuracy of fine needle aspiration cytology. Special situations in which imaging tests are most useful are discussed.

3-Iodobenzylguanidine↗
PubMed1990

Adrenal cortical adenoma causing Cushing's syndrome: correct localization by functional scintigraphy despite nonlocalizing morphological imaging studies.

A 60-year-old woman with Cushing's syndrome in whom high-dose dexamethasone failed to suppress glucocorticoids was studied by ultrasound and CT. Neither of these morphological studies was interpreted as revealing any adrenal abnormality. Functional imaging with NP-59 (131-I-beta-iodomethylnorcholesterol) revealed unequivocal, intense, unilateral uptake in the left adrenal gland and subsequent surgery removed a 2.5 cm adrenocortical adenoma from this site. Following surgery the patient was temporarily adrenocortically insufficient but later returned to normal. It is unusual for adrenocortical adenomas causing Cushing's syndrome not to be correctly located by CT. NP-59 scintigraphy in addition to being highly accurate in the location of adrenocortical adenomas also has the advantage of correctly depicting bilateral cortical nodular hyperplasia in which CT will frequently reveal only the largest nodule, which may be incorrectly designated a unilateral adenoma. Furthermore, scintigraphy provides evidence of suppression of the contralateral, normal adrenal cortical tissue in Cushing's syndrome caused by an adrenal adenoma and predicts the vulnerability of such patients to postoperative adrenocortical insufficiency.

Adenoma↗
PubMed1990

Diagnostic accuracy and pitfalls of [iodine-131]6-beta-iodomethyl-19-norcholesterol (NP-59) imaging.

NP-59 concentrates in steroid hormone synthesizing tissues, enabling scintigraphic localization and characterization of endocrine dysfunction in the adrenal cortex and ovary. Studying 108 consecutive cases from 1982 to 1985 and using clinical, biochemical, radiographic, and pathologic data, we performed a rigorous assessment of the accuracy and pitfalls of NP-59 scintigraphy. The evaluation was divided into categories of abnormal hormone secretion: Cushing's syndrome, primary aldosteronism, and hyperandrogenism. Additional categories included euadrenal tumors (without detectable hormone dysfunction) and sites of residual adrenal cortical tissue. The accuracy of NP-59 scintigraphy ranged from 71% in primary aldosteronism and 75% in euadrenal tumors, to 100% for Cushing's syndrome and hyperandrogenism. However, more than in most nuclear medicine studies, NP-59 imaging requires well-defined indications to be met for it to be efficacious, including the fulfillment of clear clinical, biochemical, and radiographic criteria. The high reproducibility of NP-59 scintigraphic interpretation was demonstrated when 40 random cases underwent interinstitutional exchange and through interobserver evaluation at the University of Michigan. Responses of 85/126 medical centers to questionnaires revealed the high level of NP-59 safety.

Adosterol↗
PubMed1979

Ultracentrifugation evidence for a somatostatin-binding protein in serum.

Using a technique of high speed centrifugation of serum and a well validated immunoassay for the measurement of serum somatostatin-like immunoreactivity, we have demonstrated that somatostatin, unlike other peptide hormones, appears to sediment with large molecular weight proteins. When synthetic somatostatin of increasing concentration was incubated with serum prior to ultracentrifugation, a linear plot of concentration of somatostatin added against concentration sedimenting (or apparently bound to protein) revealed an association curve. These data provide further evidence for the existence of a serum-binding protein for somatostatin.

Adult↗
PubMed1979

Palmitoyl coenzyme A synthetase activation by uncomplexed ATP.

Uncomplexed ATP, ADP, alpha, beta-methylene ATP and adenosinetetraphosphate were shown to activate long chain fatty acyl-coenzyme A synthetase. The presence of uncomplexed nucleotides was shown: (1) to induce the palmitoyl-AMP-dependent palmitoyl-coenzyme A formation, (2) to activate the MgATP-dependent overall reaction and (3) to stabilize the synthetase against ageing denaturation. In all three cases the observed nucleotide activation was shown to be eliminated upon metal chelation.

Adenine Nucleotides↗
PubMed1979

Growth hormone release inhibitory hormone-like immunoreactivity in pancreas and gut in streptozotocin diabetes in the rat and response to insulin administration.

In streptozotocin diabetes in the rat, growth hormone release-inhibitory hormone-like immunoreactivity (GHRIH-LI) content of pancreas, gastric antrum and colon was increased. Insulin therapy significantly lowered the increased pancreatic GHRIH-LI content but did not affect that of the gastric antrum and colon at the dosage used. The relevance of these findings in relation to pancreatic and gastrointestinal function in diabetes awaits clarification.

Animals↗