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Biomedical subjects

M J Lane

Publications and source records attributed to M J Lane.

At least 19 recordsLinked to original sources
PubMed2000

Alternative or additional diagnoses on unenhanced helical computed tomography for suspected renal colic: experience with 1000 consecutive examinations.

OBJECTIVES: To determine the incidence and spectrum of significant alternative or additional diagnoses established or suggested on unenhanced helical computed tomography (CT) in a large series of patients with suspected renal colic. METHODS: One thousand consecutive unenhanced helical CT examinations were performed for suspected renal colic. All official CT reports were retrospectively reviewed, which was followed by review of all available relevant follow-up radiology reports. A selected image and chart review was also performed. RESULTS: Ureteral calculi were identified on 557 examinations, findings consistent with a recently passed stone were discovered on 67 examinations, and 275 CT examinations were unremarkable. An alternative or additional diagnosis was established or suggested on 101 examinations, including in 26 patients with concurrent ureteral calculi. There were 62 genitourinary and 39 nongenitourinary tract diagnoses. Eighty-seven of the diagnoses could be confirmed on retrospective image review combined with patient follow-up. There were two false-positive diagnoses for significant, alternative pathologic findings. CONCLUSIONS: A wide spectrum of significant, alternative, and additional genitourinary and nongenitourinary diagnoses can be reliably established or suggested on unenhanced helical CT performed for suspected renal colic. These abnormalities were identified in 10% of cases in this series of 1000 consecutive CT examinations.

Adult↗
PubMed1999

Melting studies of short DNA hairpins: influence of loop sequence and adjoining base pair identity on hairpin thermodynamic stability.

Spectroscopic and calorimetric melting studies of 28 DNA hairpins were performed. These hairpins form by intramolecular folding of 16 base self-complementary DNA oligomer sequences. Sequence design dictated that the hairpin structures have a six base pair duplex linked by a four base loop and that the first five base pairs in the stem are the same in every molecule. Only loop sequence and identity of the duplex base pair closing the loop vary for the set of hairpins. For these DNA samples, melting studies were carried out to investigate effects of the variables on hairpin stability. Stability of the 28 oligomers was ascertained from their temperature-induced melting transitions in buffered 115 mM Na(+) solvent, monitored by ultraviolet absorbance and differential scanning calorimetry (DSC). Experiments revealed the melting temperatures of these molecules range from 32.4 to 60.5 degrees C and are concentration independent over strand concentrations of 0.5 to 260 microM; thus, as expected for hairpins, the melting transitions are apparently unimolecular. Model independent thermodynamic transition parameters, DeltaH(cal), DeltaS(cal), and DeltaG(cal), were determined from DSC measurements. Model dependent transition parameters, DeltaH(vH), DeltaS(vH), and DeltaG(vH) were estimated from a van't Hoff (two-state) analysis of optical melting transitions. Results of these studies reveal a significant sequence dependence to DNA hairpin stability. Thermodynamic parameters evaluated by either procedure reveal the transition enthalpy, DeltaH(cal) (DeltaH(vH)) can differ by as much as 20 kcal/mol depending on sequence. Similarly, values of the transition entropy DeltaS(cal) (DeltaS(vH)) can differ by as much as 60 cal/Kmol (eu) for different molecules. Differences in free energies DeltaG(cal) (DeltaG(vH)) are as large as 4 kcal/mol for hairpins with different sequences. Comparisons between the model independent calorimetric values and the thermodynamic parameters evaluated assuming a two-state model reveal that 10 of the 28 hairpins display non-two-state melting behavior. The database of sequence-dependent melting free energies obtained for the hairpins was employed to extract a set of n-n (nearest-neighbor) sequence dependent loop parameters that were able to reproduce the input data within error (with only two exceptions). Surprisingly, this suggests that the thermodynamic stability of the DNA hairpins can in large part be reasonably represented in terms of sums of appropriate nearest-neighbor loop sequence parameters.

Base Sequence↗
PubMed1999

Thermodynamic, spectroscopic, and equilibrium binding studies of DNA sequence context effects in six 22-base pair deoxyoligonucleotides.

Effects of different end sequences on stability, circular dichroism spectra (CD), and enzyme binding properties were investigated for six 22-base pair, non-self-complementary duplex DNA oligomers. The center sequences of these deoxyoligonucleotides have 8-14 base pairs in common and are flanked on both sides by sequences differing in context and A-T content. Temperature-induced melting transitions monitored by differential scanning calorimetry (DSC) and ultraviolet absorbance were measured for the six duplexes in buffered 115 mM Na(+) solutions. Values of the melting transition enthalpy, DeltaH(cal), and entropy, DeltaS(cal), were obtained directly from DSC experiments. Melting transition parameters, DeltaH(vH) and DeltaS(vH), were also estimated from van't Hoff analysis of optical melting curves collected as a function of DNA concentration, assuming a two-state melting transition. Melting free energies (20 degrees C) of the six DNAs evaluated from DSC experiments ranged from -18.7 to -32.7 kcal/mol. van't Hoff estimates of the free energies ranged from -18.5 to -48.0 kcal/mol. With either method, the trends in free energy as a function of sequence were identical. Equilibrium binding by BamHI restriction endonuclease to the 22-base pair DNAs was also investigated. The central eight base pairs of all six molecules, 5'-A-GGATCC-A-3', contained a BamHI recognition sequence bounded by A-T base pairs. Magnesium free binding assays were performed by titering BamHI against a constant concentration of each of the deoxyoligonucleotide substrates and analyzing reaction products by gel retardation. Binding isotherms of the total amount of bound DNA versus protein concentration were constructed which provided semiquantitative estimates of the equilibrium dissociation constants for dissociation of BamHI from the six DNA oligomers. Dissociation constants ranged from 0.5 x 10(-)(9) to 12.0 x 10(-)(9) M with corresponding binding free energies of -12.5 to -10.6 (+/-0. 1) kcal/mol. An inverse relationship is found when binding and stability are compared.

Base Pairing↗
PubMed1999

Parathyroid localization with high-resolution ultrasound and technetium Tc 99m sestamibi.

HYPOTHESIS: High-resolution ultrasound and technetium Tc 99m sestamibi scanning can be used for preoperative localization of abnormal parathyroid glands in patients with hyperparathyroidism. DESIGN: Ultrasound and sestamibi scanning were performed in patients undergoing neck exploration for hyperparathyroidism. If the 2 scans agreed in identifying a single adenoma, and surgery confirmed the location of a single adenoma and an ipsilateral normal gland, a unilateral exploration was performed. SETTING: University tertiary care center. PATIENTS: Sixty-one consecutive patients undergoing surgery for hyperparathyroidism from September 1, 1994, through September 30, 1997. INTERVENTIONS: High-resolution ultrasound was performed in 59 patients and sestamibi scanning in 58 patients; all patients underwent neck exploration by a single surgeon. MAIN OUTCOME MEASURES: The results of preoperative ultrasound and sestamibi scanning were compared with operative and histological findings. RESULTS: All patients were cured of hypercalcemia. Specificity of ultrasound and sestamibi scanning was 98% and 99%, respectively; however, their sensitivity was only 57% and 54%, respectively. Both imaging modalities had lower sensitivities in the setting of multigland disease. If both imaging studies were considered as a single test, sensitivity for imaging in patients with primary hyperparathyroidism reached 78%. Our localization protocol allowed a unilateral approach in 43% of patients (23 of 53). CONCLUSIONS: These results confirm the value of preoperative localization in patients with hyperparathyroidism. A unilateral approach can be used with a high degree of success in cases when ultrasound and sestamibi scanning agree in the identification of a single adenoma confirmed by surgical exploration with the identification of a normal ipsilateral gland.

Adenoma↗
PubMed1999

Appendicitis and its mimickers.

Unenhanced helical CT is an accurate technique for the evaluation of patients with suspected acute appendicitis. This non-operator-dependent examination can be performed without the risk of intravenous contrast material or the delay associated with the use of oral and rectal contrast material. This article reviews the unenhanced helical CT findings of acute appendicitis and those entities that commonly mimic acute appendicitis clinically.

Acute Disease↗
PubMed1999

Unenhanced CT of abdominal and pelvic hemorrhage.

CT performed without oral or intravenous contrast is the initial imaging study of choice in many situations for the detection of hemorrhage anywhere in the abdomen and pelvis. The presence or absence of hemorrhage can be determined rapidly, and the amount and precise location of hemorrhage can also be evaluated. This article reviews the appearances and the common and unusual etiologies of abdominal and pelvic hemorrhage on unenhanced CT. The role of intravenous contrast-enhanced CT in patients with known or suspected abdominal and pelvic hemorrhage is also examined.

Abdomen↗
PubMed1999

The value of strength training for older adults.

Health in older adults can best be measured in terms of functional status. Skeletal muscle strength has been reported to be a determinant of functional status in older individuals. Two major contributors to the decline in muscle function as a person ages are disuse and physical inactivity. Declining muscle function through a loss of muscular strength may decrease functional independence and mobility and increase the risk for falls and injuries, physical frailty, and disability. Older individuals lacking an appropriate amount of muscular strength may not be able to perform various activities of daily living, which are important indicators of independence.

Activities of Daily Living↗
PubMed1999

Suspected acute appendicitis: nonenhanced helical CT in 300 consecutive patients.

PURPOSE: To determine the accuracy of helical computed tomography (CT) without the oral, intravenous, or rectal administration of contrast material in confirming suspected acute appendicitis. MATERIALS AND METHODS: Three hundred consecutive patients referred from the departments of surgery and emergency medicine were examined for suspected acute appendicitis by using thin-section nonenhanced helical CT. All transverse CT scans were obtained in a single breath hold from the upper abdomen (T12 vertebra) to the pubic symphysis with 5-mm collimation and a pitch of 1.6. All scans were obtained without oral, intravenous, or rectal contrast material. Criteria for diagnosis of acute appendicitis included an enlarged appendix (> 6 mm) and periappendiceal inflammation. CT diagnoses were recorded prospectively. Final diagnoses were established with the results of surgical or clinical follow-up or both. RESULTS: There were 110 true-positive diagnoses, 181 true-negative diagnoses (63 of which were an alternative diagnosis correctly established prospectively), five false-negative diagnoses, and four false-positive diagnoses, which yielded a sensitivity of 96%, a specificity of 99%, and an accuracy of 97%. CONCLUSION: Nonenhanced helical CT is a highly accurate technique for diagnosing or excluding acute appendicitis. Developing experience with the technique and understanding the subtleties of interpretation can further improve diagnostic accuracy.

Acute Disease↗
PubMed1998

Lipomas of the pancreas.

OBJECTIVE: The purpose of this study was to describe the CT findings of pancreatic lipomas in four patients. CONCLUSION: In all four cases, the lipoma was revealed incidentally on CT scans obtained for other reasons. CT scans were diagnostic, showing well-circumscribed masses within the pancreas composed almost entirely of fat, with a few scattered vessels or septa or both, which ranged in size from 1.4 x 2.0 cm to 4.5 x 5.3 cm in the axial plane. Pancreatic lipomas are rare, usually incidental tumors and, as with lipomas found elsewhere in the body, conservative management is often indicated.

Aged↗
PubMed1998

Use of color and power Doppler sonography to identify feeding arteries associated with parathyroid adenomas.

OBJECTIVE: The objective of our study was to determine the value of using color and power Doppler sonography to reveal extrathyroidal feeding arteries in the detection of abnormal parathyroid glands. SUBJECTS AND METHODS: Forty-four patients with primary hyperparathyroidism were imaged prospectively with high-resolution gray-scale, color flow, and power Doppler sonography. The presence of extrathyroidal arteries supplying the adenomas was noted. All patients underwent subsequent neck exploration. The locations of the abnormal glands were recorded. RESULTS: At surgery, 51 abnormal parathyroid glands were removed in the 44 patients. Sonography correctly revealed an adenoma in 40 of the 44 patients. Likewise, sonography revealed 42 of the 51 adenomas. Nine false-negative and two false-positive interpretations of the sonograms were made. Thus, overall sensitivity was 83%, specificity was 98%, and accuracy was 94%. Three of the false-negative interpretations were ectopic glands within the superior mediastinum. Excluding these three glands from analysis, the sensitivity for detection of adenomas within the neck was 88%, specificity was 98%, and accuracy was 95%. An extrathyroidal artery leading to a parathyroid adenoma was seen in 35 of the 42 adenomas revealed by sonography. The presence of an extrathyroidal artery leading to an adenoma was found to aid in the detection of an otherwise inconspicuous parathyroid gland in five patients, which improved sensitivity from 73% to 83%. CONCLUSION: Prominent vessels supplying parathyroid adenomas are frequently revealed by color flow and power Doppler sonography. These vessels can serve as "road maps" to abnormal parathyroid glands.

Adenoma↗
PubMed1997

The thermodynamic advantage of DNA oligonucleotide 'stacking hybridization' reactions: energetics of a DNA nick.

'Stacking hybridization reactions' wherein two or more short DNA oligomers hybridize in a contiguous tandem orientation onto a longer complementary DNA single strand have been employed to enhance a variety of analytical oligonucleotide hybridization schemes. If the short oligomers anneal in perfect head-to-tail register the resulting duplex contains a nick at every boundary between hybridized oligomers. Alternatively, if the short oligomers do not hybridize precisely in register, i.e. single strand regions on the longer strand are left unbound, gaps are formed between regions where short oligomers bind. The resulting gapped DNA duplexes are considerably less stable than their nicked duplex analogs. Formation of base pair stacking interactions between neighboring oligomers at the nicks that do not occur in gapped duplexes has been proposed as the source of the observed added stability. However, quantitative evidence supporting this hypothesis for DNA has not been reported. Until now, a direct comparison of the thermodynamics of DNA nicks versus DNA gaps has not been performed. In this communication we report such a comparison. Analysis of optical melting experiments in a well defined molecular context enabled quantitative evaluations of the relative thermodynamic difference between nicked and gapped DNA duplexes. Results of the analysis reveal that a nick may be energetically favored over a gap by at least 1.4 kcal/mol and perhaps as much as 2.4 kcal/mol. The presence of a 5'phosphate at a nick or gap fails to significantly affect their stabilities.

DNA↗
PubMed1997

Predicting sequence-dependent melting stability of short duplex DNA oligomers.

Many important applications of DNA sequence-dependent hybridization reactions have recently emerged. This has sparked a renewed interest in analytical calculations of sequence-dependent melting stability of duplex DNA. In particular, for many applications it is often desirable to accurately predict the transition temperature, or tm of short duplex DNA oligomers (approximately 20 base pairs or less) from their sequence and concentration. The thermodynamic analytical method underlying these predictive calculations is based on the nearest-neighbor model. At least 11 sets of nearest-neighbor sequence-dependent thermodynamic parameters for DNA have been published. These sets are compared. Use of the nearest-neighbor sets in predicting tm from the DNA sequence is demonstrated, and the ability of the nearest-neighbor parameters to provide accurate predictions of experimental tm's of short duplex DNA oligomers is assessed.

Base Sequence↗