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Biomedical subjects

M Tan

Publications and source records attributed to M Tan.

At least 145 records · Page 8Linked to original sources
PubMed1996

Biofeedback therapy for excessive stool frequency and incontinence following anterior resection or total colectomy.

PURPOSE: Excessive stool frequency and incontinence after anterior resection (AR) or total colectomy (TC) can be refractory to expectancy and antidiarrheal agents. We prospectively assessed efficacy of anorectal biofeedback therapy (BF) in this clinical situation. METHODS: Thirteen patients (10 men and 3 women; mean age, 62.1 (standard error of the mean (SEM), 4.6) years) had more than six bowel movements per day and/or episodes of incontinence, which did not abate after antidiarrheal agents were given for at least six (mean, 27.9 (SEM, 6.3)) months after surgery. All underwent four sessions of outpatient BF. Assessment was by continence questionnaire and anorectal physiology tests, which were administered before and after BF. RESULTS: In seven AR patients, daily stool frequency was decreased (8.7 (SEM, 2.1) before and 4.6 (SEM, 1.2) after, P < 0.05), and daily incontinence episodes were reduced (2.7 (SEM, 0.9) before and 0.4 (SEM, 0.2) after, P < 0.05) after BF. Six TC patients also had decreased daily stool frequency (6.2 (SEM, 2.1) before, 3.3 (SEM, 1.6) after; P < 0.05) and incontinence episodes (2.4 (SEM, 0.9) before, 0.5 (SEM, 1) after; P < 0.05) after BF. There were no significant changes in anorectal physiology parameters after BF. At a mean follow-up of 10.6 (SEM, 2.5) months after BF, there were no regressions or complications. CONCLUSIONS: BF is a safe and effective option for refractory excessive stool frequency and/or incontinence following AR or TC.

Biofeedback, Psychology↗
PubMed1996

Clinical and physiologic effects of biofeedback in outlet obstruction constipation.

PURPOSE: We report the results of biofeedback (BF) on patients with outlet obstruction defecation (OOC), including those with and without measurable paradoxical puborectalis contractions (PP). Clinical and anorectal physiologic parameters (ARP) were assessed one week before and after a standardized course of BF. METHODS: Sixty-two consecutive patients (24 men, 38 women; mean age, 48 (standard error of the mean, 2.3) years) were recruited. All had persistent constipation despite six weeks of dietary fiber supplements. Colonic inertia was excluded by transit marker studies. Defecating proctography excluded anatomic abnormalities causing outlet obstruction. Patients underwent four outpatient sessions of biofeedback, each session lasting one hour. RESULTS: After BF, 56 patients (90.3 percent) were subjectively improved. Frequency of spontaneous bowel movements were significantly increased (P = 0.003). Frequency of laxative-induced (P = 0.004) and enema-induced (P = 0.005) stools were reduced. Anal resting (P = 0.04) and squeeze (P = 0.002) pressures were increased. Number of patients with PP was reduced from 40 to 31 (P = 0.004). Presence of PP did not affect response to BF. There were no differences in ARP between the 56 patients who improved and the 6 who did not. There were no side effects or clinical regressions after a mean follow-up of 14.9 (standard error of the means, 0.9) months. CONCLUSIONS: BF effectively treated OOC in 90.3 percent, regardless of PP. Anal pressures were increased, and PP was decreased.

Biofeedback, Psychology↗
PubMed1996

Concentration of rare earth elements, As, and Th in human brain and brain tumors, determined by neutron activation analysis.

Toxic elements As and Th, six rare-earth elemental profiles of brain tumor tissues from 16 patients of astrocytomas (grade I-III), and normal human brain tissues of 18 male, age-matched autopsies serving as controls have been studied by radiochemical neutron activation analysis. P-204 [di(2-ethylhexyl) phosphate] extraction chromatography column was used for group separation of rare-earth element (REE) by one step. Compared with the normal brain tissues, the analytical results showed that the concentrations of Th, La, Ce, Gd, and Lu were significantly higher in tumor tissues (P < 0.01 or 0.001). The possible effects of REE on tumor cell were discussed.

Adult↗
PubMed1996

Clinical neuroimmunology.

Clinical research has focused on autoimmune disease (AID) for a couple of decades. More sensitive and specific methods have been developed for neuroimmunological research. Gamma fraction bands (bands separated by electrophoresis and visualized by amino black staining) and IgG fraction bands (bands separated by iso-electric focusing and visualized by immunostaining) are used instead of oligoclonal bands. Myasthenia gravis (MG) mainly involves acetylcholine receptors of the postsynaptic membrane at the neuromuscular junction. Myasthenia gravis has been considered to be a generalized AID, because 7% of patients with myasthenia gravis associate with other AIDs and more than one autoimmune antibody is detected in 52.5% patients with myasthenia gravis. Pyramidal signs in myasthenia gravis patients are described; the possible mechanism may at least be partly due to the acetylcholine receptor antibody. P2 protein and its antibody are studied in patients with acute and chronic inflammatory demyelinating polyneuropathy.

Adolescent↗
PubMed1996

Subtle translocation (18;21) confirmed by FISH in a patient with Down syndrome.

The patient presented with the typical features of Down syndrome; hypotonia, brachycephaly, flattened occiput, bilateral prominent medical epicanthic folds, flat nasal bridge, protruding tongue, low-set dysplastic ears, short broad hands, bilateral clinodactyly and simian crease. The karyotype of this child was originally reported as normal. High-resolution chromosomes revealed extra material on the long arm of chromosome 18. The mother's karyotype showed a reciprocal translocation between the long arm of 18 and the long arm of 21 at band q23 and q22.1, respectively. FISH performed separately with two different 21q cosmid probes gave two signals on the mother's metaphases and three signals on the proband. These findings confirmed that the proband is trisomic for the long arm of chromosome 21 at loci D21S65 and D21S19.

Chromosomes, Human, Pair 18↗
PubMed1996

Identification of sequences necessary for transcription in vitro from the Chlamydia trachomatis rRNA P1 promoter.

Chlamydia trachomatis RNA polymerase was partially purified by heparin-agarose chromatography and used in conjunction with a plasmid-borne G-less cassette template to characterize the C. trachomatis rRNA P1 promoter in vitro. Stepwise mutational analysis revealed that sequences in the -10, -25, and -35 regions are necessary for promoter activity, but no sequence upstream of position -40 is required. Partially purified C. trachomatis RNA polymerase and purified Escherichia coli holoenzyme exhibited some differences in promoter specificity.

Base Composition↗
PubMed1996

Transcriptional organization and regulation of the dnaK and groE operons of Chlamydia trachomatis.

The transcriptional organization and regulation of the dnaK and groE heat shock operons of Chlamydia trachomatis were studied and found to resemble those of the cognate operons of Bacillus subtilis and Clostridium acetobutylicum. The gene order is conserved (hrcA-grpE-dnaK), but no dnaJ homolog could be identified in this region. The dnaK operon was transcribed as a low-abundance polycistronic mRNA whose levels did not increase upon exposure to heat shock. In contrast, a more abundant 2.3-kb mRNA encoding only the dnaK sequence was detectable, and its steady-state level increased upon heat shock. The transcription initiation sites of the dnaK and groE operons were found to be preceded by sequences that resemble an Escherichia coli sigma70 consensus promoter. Upstream of each putative promoter is an inverted repeat sequence which resembles a similar element (CIRCE [controlling inverted repeat of chaperone expression]) found upstream of the dnaK and groE operons in at least 27 eubacterial species. In vitro transcription studies utilizing partially purified C. trachomatis RNA polymerase demonstrated that the regions containing the putative promoter elements of the dnaK and groE operons are functional, although heat shock-regulated expression could not be demonstrated.

Amino Acid Sequence↗
PubMed1996

Random effects models in latent class analysis for evaluating accuracy of diagnostic tests.

When the results of a reference (or gold standard) test are missing or not error-free, the accuracy of diagnostic tests is often assessed through latent class models with two latent classes, representing diseased or nondiseased status. Such models, however, require that conditional on the true disease status, the tests are statistically independent, an assumption often violated in practice. Consequently, the model generally fits the data poorly. In this paper, we develop a general latent class model with random effects to model the conditional dependence among multiple diagnostic tests (or readers). We also develop a graphical method for checking whether or not the conditional dependence is of concern and for identifying the pattern of the correlation. Using the random-effects model and the graphical method, a simple adequate model that is easy to interpret can be obtained. The methods are illustrated with three examples from the biometric literature. The proposed methodology is also applicable when the true disease status is indeed known and conditional dependence could well be present.

AIDS Serodiagnosis↗
PubMed1995

Evolutionary conservation of both the hydrophilic and hydrophobic nature of transmembrane residues.

An algorithm (HRG), developed to allow the pairwise comparisons of the aligned residues of several members of large gene families of polytopic integral membrane proteins is described. Using hydrophobicity scales, application of this algorithm allows the number and size of the membrane-spanning domains of bacteriorhodopsin, a polytopic protein whose structure has been partially determined, to be predicted with a high degree of accuracy (sensitivity 94%, specificity 82% for predicting the membrane embedded or extramembranous location of residues). As opposed to previously reported structure-prediction algorithms, delineation of putative transmembrane segments from connecting loops is also more clearly evident with the application of the HRG algorithm, even with proteins from widely divergent species. This indicates strong evolutionary pressure for the conservation of both the hydrophobic and hydrophilic character of residues in membrane-embedded regions of polytopic proteins, such as those of the G-protein-coupled receptor superfamily. These and other structural and functional implications evident from the application of the HRG algorithm are considered.

Algorithms↗
PubMed1995

Thyrotropin with decreased biological activity, a delayed consequence of cranial irradiation for nasopharyngeal carcinoma.

Patients with TSH of decreased bioactivity have had previous surgery or no known cause (idiopathic). We describe eight patients with nasopharyngeal carcinoma treated with irradiation alone more than 5 yr ago. All had hypothalamic hypothyroidism with low FT4 and normal TSH. Iv TRH gave an exaggerated TSH response, with 60 min greater than 20 min values, without any FT4 or TT3 response at 24 h to the hypersecreted TSH. Radioiodine uptake in 2 patients before and after 3 days of bovine TSH increased from 13 to 31%, and 11 to 28%, respectively. Oral TRH given for 20 days to 5 patients showed a distinctive pattern in serum TSH, FT4 and TT3. Serum TSH rose markedly in the initial few days, dropped to moderate levels for a few days and finally dropped further towards normal values. In contrast, the FT4 and TT3 remained unchanged at hypothyroid levels in the first few days, despite the very elevated TSH; but increased to euthyroid levels and remained higher even while the serum TSH declined further. Direct measurement of TSH bioactivity in FRTL-5 cells in 3 patients showed low values of bioactivity to immunoactivity ratios: 0.4, < 0.2, and 0.35 (NR 0.6-2.1) which increased in 2 patients to 0.9 and 0.8 after 20 days TRH. Serum free alpha-subunit levels were low and unchanged (0.3 to 1.1 micrograms/L) with prolonged TRH. These observations suggest that cranial irradiation may cause hypothalamic hypothyroidism with TSH with decreased bioactivity, and that prolonged TRH administration may restore normal bioactivity.

Adult↗
PubMed1995

Ten-year experience with abdominal aortic aneurysm repair in octogenarians: early results and late outcome.

PURPOSE: This study was undertaken to determine the mortality and morbidity rates associated with abdominal aortic aneurysm (AAA) repair in octogenarians and to identify factors that may influence survival in this age group. METHODS: One hundred fourteen patients (mean age 83 years) were admitted consecutively with 106 infrarenal and eight juxtarenal AAAs from 1984 through 1993. Ninety-four AAAs were asymptomatic, whereas 20 patients with symptoms had 11 intact and nine ruptured AAAs. The mean AAA diameter was 6.7 cm. Repair consisted of aortic bifurcation grafts in 77 patients (67%), tube grafts in 35 (31%), and extraanatomic procedures in 2 (2%). A total of 29 patients (25%) had undergone previous coronary artery bypass (24 patients) or transluminal coronary angioplasty (five patients) either incidentally or as a preliminary procedure before resection of their AAAs. RESULTS: The 30-day mortality rate for the entire series was 14%, but it declined from 23% (11/48) during the first 5 years to 8% (5/66) during the second 5 years of the study period (p = 0.028). Fatal complications occurred in nine (9.6%) of the 94 patients with asymptomatic AAAs and in seven (35%) of the 20 patients who had symptomatic AAAs (p = 0.008). Considering only patients with asymptomatic AAAs, the early mortality rate in the second 5 years (4%) improved significantly (p = 0.038) in comparison to that (17%) for the first 5 years of the study period. The cumulative 5-year survival rate of 48% for 97 available operative survivors was not quite so good as that (59%) for the normal male population of the United States at the age of 80 years (p < 0.0001). Nevertheless, the 5-year survival rate was 80% for 27 operative survivors who received previous myocardial revascularization compared with 38% for 70 others who did not (p = 0.0077). Multiple Cox-regression analysis identified the perioperative homologous blood requirement (p = 0.03) and a history of previous myocardial revascularization (p = 0.03) as significant independent factors influencing late survival. CONCLUSIONS: Repair of AAAs in properly selected octogenarians is safe and durable. When otherwise indicated, it should not be withheld on the basis of advanced age alone. Prior treatment of severe coronary artery disease is associated with enhanced late survival, but patient selection probably is an important consideration in this respect.

Aged↗
PubMed1995

Progression of overt nephropathy in non-insulin-dependent diabetes.

The detection of overt albuminuria (> 300 mg/g creatinine) in the absence of azotemia was used to diagnose early nephropathy in 34 Pima Indians with NIDDM of 16 +/- 1 years duration. Differential solute clearances were performed serially to define the course of the glomerular injury over 48 months. At baseline, the GFR (107 +/- 5 ml/min), filtration fraction and sieving coefficients of relatively permeant dextrans (< 52 A) were all depressed below corresponding values in 20 normoalbuminuric Pima Indians with a similar duration of NIDDM. Over the ensuing 48 months the GFR (-34%) and filtration fraction (-13%) in the nephropathic patients declined further. The sieving coefficients of large, nearly impermeant dextrans (> 56 A radius) increased selectively and fractional clearances of albumin and IgG increased correspondingly by > 10-fold. Analysis of the findings with pore theory revealed: (1) a progressive decline in pore density and the ultrafiltration coefficient (Kf); and (2) broadening of glomerular pore-size distribution that resulted in greater prominence of large pores (> 70 A radius). We conclude that increasing loss of intrinsic ultrafiltration capacity is the predominant cause of the early and progressive decline in GFR that follows the development of nephropathy in NIDDM. We speculate that progressive impairment of barrier size-selectivity contributes to but does not fully account for the increasingly heavy proteinuria that is observed early in the course of this disorder.

Adolescent↗
PubMed1995

Del(3) (p25.3) without phenotypic effect.

A terminal deletion of chromosome 3 at p25.3 was observed during prenatal diagnosis. A similar deletion is also present in the phenotypically normal mother. The deletion was confirmed by FISH. The breakpoint is distal to the region responsible for the 3p- syndrome. A normal baby girl was born with no apparent phenotypic abnormalities.

Adult↗
PubMed1995

Magnetic resonance imaging of cystic meningiomas and its surgical implications.

Our purpose was to document the incidence and imaging features of cystic meningiomas, to correlate the imaging features of cystic meningiomas with the histopathological findings, and to analyze the surgical implications of the imaging features of cystic meningiomas. The imaging studies, clinical histories, operative findings, and histopathological findings of a total of 128 patients with meningiomas were reviewed retrospectively. The 15 cystic meningiomas in our series could be morphologically divided into three major types: cystic areas contained wholly within the tumor (6 meningiomas), cystic areas at the periphery of, but wholly within, the margins of the tumor (5 meningiomas), and cystic areas peripheral to the tumor, lying on the adjacent brain (4 meningiomas). A majority of cystic meningiomas were histopathologically diagnosed to be meningothelial (8 of 15 meningiomas). Cellular atypia was seen in many patients. Meningiomas may simulate astrocytomas or metastatic lesions on imaging studies. Magnetic resonance imaging had a diagnostic accuracy of 80% (12 of 15 patients), which was significantly better than the computed tomography diagnostic accuracy of 50% or less. Magnetic resonance imaging with contrast enhancement could distinguish Type 2 (cyst wall containing tumor cells) and Type 3 (cyst wall containing gliotic tissue without tumor invasion) cystic meningiomas. Cyst wall enhancement was seen in Type 2, but not in Type 3, cystic meningiomas. Cystic meningiomas represented approximately 10% of all meningiomas in our series. Histiologically, they were usually relatively aggressive, which probably partly explains why cystic changes may be secondary to tumor necrosis or hemorrhage. Recognition of the diagnostic features of cystic meningiomas is important, because they may mimic metastatic neoplasms or primary gliomas.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Possible lateralization of peripheral nerve conduction associated with gender.

Lateralization of peripheral nerve conduction velocity was studied in right-handed men (n = 40) and women (n = 48). Sensory and motor velocities were measured in ulnar and median nerves of the right and left hands. In women, the mean sensory velocity was significantly faster in the left than the right hand. There were no significant right-left differences in men. The mean sensory velocity from the right hand was significantly slower in women than men, creating an asymmetric organization of sensory conduction in women. Estradiol in women and testosterone in men were suggested as playing a role in asymmetric and symmetric nerve conductions, respectively.

Adult↗
PubMed1995

Pericentric inversion 9--incidence and clinical significance.

Pericentric inversion of the chromosome 9, inv(9)(p11q13), is such a common occurrence that some cytogeneticists would consider them as normal variants. The incidence is said to be about 1% to 1.65% in the general population. Despite being categorised as a minor chromosomal rearrangement which does not correlate with abnormal phenotypes, many reports in the literature raised conflicting views regarding the association with subfertility and recurrent abortions, abnormal clinical conditions, as well as chromosomal abnormalities arising as a result of having this inversion. We studied the incidence and clinical significance of inv(9)(p11q13) patients retrospectively from 2448 antenatal cytogenetic analysis and 1058 peripheral blood karyotype collected over a 3-year period. Thirty cases of inv(9)(p11q13) from 29 families were found from the antenatal group, which gave an incidence of 1.2% and 6 cases from the peripheral blood karyotype analysis (incidence of 0.6%). The parental origin of the inv(9)(p11q13) in the antenatal group was of equal proportion and there was also no sex predilection for the fetuses carrying the inversion. The babies with the inversion were born with no phenotypic abnormalities. The 6 cases picked up from the peripheral blood karyotype analysis were 2 cases of paediatric patients with associated chromosomal abnormalities (one Trisomy 21 and the other del 13(q22q32)) and 4 adult patients with obstetric and fertility problems. The incidence of subfertility (36%) appeared to be high amongst the adult patients with inv(9)(p11q13). This may represent a true reflection of subfertility in inv(9)(p11q13) patients or a selective bias towards the older subfertile women who conceive at a later age and thus utilising the antenatal diagnostic setup.

Abortion, Habitual↗