Biomedical subjects
M Chan
Publications and source records attributed to M Chan.
Aids to the diagnosis of acute appendicitis.
Explore the source record for details and available documents.
Adhesive strength of single muscle cells to basement membrane at myotendinous junctions.
Whole muscles loaded to failure frequently fail at or near myotendinous junctions. The present investigation was directed toward determining the breaking stress and failure site of intact and injured myotendinous junction preparations consisting of muscle cells dissected free from surrounding parallel structures but still attached to tendon collagen fibers. These tests show that the breaking stress for intact myotendinous units is 2.7 x 10(5) N/m2, expressed relative to cell cross-sectional area. Failure occurs immediately external to the junction membrane between the cell membrane and lamina densa of the basement membrane. Site and stress at failure are independent of strain and strain rate over a biologically relevant range. Breaking stress in the plane of the membrane, corrected for membrane folding, is 1.2 X 10(4) N/m2. This value is not significantly greater than stress at maximum isometric tension for these cells at these sarcomere lengths. After compression injury, cells fail within the compression site at significantly lower stress (1.9 X 10(5) N/m2). These findings suggest that, in muscle strain injuries that occur under conditions simulated here, failure occurs at myotendinous junctions unless the muscle has suffered previous compression injury leading to failure within the muscle.
Respiratory control: its contribution to the treatment of panic attacks. A controlled study.
Patients who experienced panic attacks, with or without avoidance, were treated for two weeks with either training in controlled breathing or a placebo treatment. Subsequently, both groups received a limited period of conventional anxiety treatments, most commonly in vivo exposure. Patients were subdivided into 'hyperventilators' and 'non-hyperventilators' on the basis of the conventional provocation test. Observer ratings of anxiety showed a greater improvement for the group that received breathing training, but there was no evidence that 'hyperventilators' benefited more from respiratory training than 'non-hyperventilators'. Self-report measures of anxiety, avoidance, and depression/dysphoria showed no difference between treatments. These findings suggest that training in controlled breathing is not of specific benefit for those identified as 'hyperventilators' by the provocation test, but that it may have a non-specific effect in the treatment of patients with panic attacks.
Comparative use of amino acids by three auxotypes of Neisseria gonorrhoeae.
Auxotypes of Neisseria gonorrhoeae are usually distinguishable by their particular requirements for growth; these requirements often include amino acids. It is possible that strains needing particular substrates to grow can be distinguished not merely by their growth requirements but also by their metabolism of these particular substrates. In this work amino acid utilization and oxidation studies were performed enabling prototype, pro- and thia-strains to be distinguished. The metabolism study also underlined the importance of proline as an energy source and pointed to the probability of distinct relationships with the metabolism of the key amino acids, glutamic and aspartic acids, for the three auxotypes. It is proposed that the specific amino acid required by the naturally occurring auxotype serves as an energy source at the site of infection and has important implications with respect to particular auxotypes at various sites.
Endometrial carcinoma in a young woman.
We present an unusual case of endometrial carcinoma which developed in a 22-year-old woman shortly after pregnancy.
Scale-up of the recovery and reactivation of recombinant proteins.
Explore the source record for details and available documents.
Aspiration cytology in the management of breast lesions.
In a group of patients with breast lumps, diagnosis made by pre-operative aspiration cytology was compared with that obtained by histological section of excised specimens. Results showed that aspiration cytology correctly diagnosed 89% of malignant lesions and 92.6% of benign lesions based upon histological diagnosis. Cytological diagnosis of benign disease had a false negative rate of 6% while cytological diagnosis of malignant disease had a 2.7% false positive rate. Only 3.5% of cytologies returned an inadequate diagnosis. This study shows that aspiration cytology should be useful in allowing a better psychological preparation of patients before surgery as well as better utilization of operation theatre facilities.
Ca2+ Mg2+ ATPase in the distal tubule.
Explore the source record for details and available documents.
Treatment of residual and recurrent cervical metastasis from nasopharyngeal carcinoma.
Eleven patients with cervical metastases from nasopharyngeal carcinoma were studied. Even after adequate radiotherapy treatment, viable tumour cells were detected in all patients. Nine patients underwent radical neck dissection and the histological study of the specimens confirmed the operative findings. The extent of the disease was far greater than the clinical assessment suggesting that simple lymphadenectomy is an inadequate form of treatment.
The human and murine influenza-specific B cell repertoires share a common idiotope.
We have dissected the human influenza-specific B cell repertoire by performing Epstein-Barr virus (EBV) limiting dilution analysis of lymphocytes obtained from donors before and after immunization with a commercially available influenza vaccine. In addition to an analysis of precursor frequency and light chain diversity, we studied sera and culture supernatants containing human anti-influenza antibodies with a panel of murine monoclonal antibodies specific for idiotopes identified on murine anti-PR8 and anti-X-31 antibodies. An idiotypic specificity present on the X-31-specific murine monoclonal PY206 has previously been shown to be shared by murine antibodies specific for PR8, X-31, and other influenza viruses. We observed little correlation among the following parameters: anti-viral titer, serum idiotope content, precursor frequency and immune status. More interestingly, there was a striking predominance of human influenza-specific antibodies that utilized lambda light chains. In addition, 12 of 26 human anti-influenza monoclonals strongly inhibited the binding of one of the murine anti-idiotopes to the labeled murine antibody, PY206. This is the same idiotope that is shared among murine antiinfluenza antibodies and all six individuals studied contained clones reactive with this anti-idiotope. Seven of these 12 idiotope-positive human antibodies gave partial cross-reactivity in a second anti-idiotypic system. These observations imply that a significant level of homology exists between the binding sites of human and murine influenza-specific antibodies and suggest that idiotypic manipulation of the human immune response to influenza virus may have important therapeutic implications.
Differences in diazepam pharmacokinetics in Chinese and white Caucasians--relation to body lipid stores.
We have compared diazepam pharmacokinetics in 16 Chinese and 18 white Caucasian healthy male volunteers, resident in Hong Kong and have correlated them with physical attributes. Serum concentrations of diazepam and desmethyldiazepam were measured in venous blood by an enzyme-linked immunoassay (0-3 h samples) and HPLC (3-72 h samples). Pharmacokinetic parameters were derived assuming a two compartment model, distribution phase less than 6 h, and 100% oral systemic availability. Compared with the Chinese the white Caucasians were older, heavier, taller, and fatter, as judged by skin fold thickness (SFT) and total body weight to 'Ideal' body weight (TBW/IBW) ratio; respective mean differences being 16%, 27%, 4%, 26%, and 15% (p less than 0.05). Mean diazepam apparent volume of distribution (V) and V/IBW were larger in the white Caucasians (52% & 39% respectively, p = 0.002). SFT and TBW/IBW ratio yielded the best correlations with V, V/TBW and V/IBW (0.50-0.75, p less than 0.05). Obesity indices contributed most to the overall regressions (R2 up to 0.52), and for V there was a further small effect (2%, partial F test) due to ethnic group, possibly reflecting stature. Mean peak diazepam concentration (Cmax) was similar in both ethnic groups. Time to Cmax (tmax) was more often prolonged in the Chinese (chi 2 test, p = 0.01). Body fat and stature may thus account for these inter-ethnic differences in the apparent volume of distribution of diazepam, a highly lipid-soluble drug.
High affinity Ca2+ -Mg2+ ATPase in the distal tubule of the mouse kidney.
The purpose of this study was to investigate whether Ca2+ -Mg2+ ATPase in the distal tubule (where calcium transport is active, against a gradient, and hormone dependent) presents some characteristics different from those observed in the proximal tubule, and whether these characteristics are likely to shed light on the respective roles of this enzyme at the two sites of the nephron. The Ca2+ - and Mg2+-dependent ATP hydrolysis was measured in microdissected segments of the distal nephron, the kinetic parameters were determined, and the influence of magnesium upon the sensitivity to calcium was examined. Results were compared with those obtained in the proximal tubule, and in purified membranes as reported by others. In the distal tubule, low concentrations of Mg2+ (less than 10(-7) M) did not influence ATP hydrolysis. At concentrations above 10(-7) M, Mg2+ increased ATP hydrolysis according to Michaelis kinetics (apparent Km = 11.3 +/- 2.4 microM, Vmax = 219 +/- 26 pmol.mm-1.20 min-1). The addition of 1 microM Ca2+ decreased the apparent Km for Mg2+ and the Vmax for Mg2+. Similar results were obtained in the proximal tubule. At low Mg2+ concentrations, Ca2+ also stimulated ATP hydrolysis according to Michaelis kinetics with an apparent Km value for Ca2+ of 0.18 +/- 0.06 and 0.10 +/- 0.03 microM Ca2+ (ns) and a Vmax of 101 +/- 12 and 89 +/- 9 pmol.mm-1.20 min-1 (ns) in the distal and proximal tubules, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Idiotypic analysis of the influenza virus-specific human B cell repertoire.
Explore the source record for details and available documents.
Computer aided diagnosis of acute abdominal pain: a multicentre study.
A multicentre study of computer aided diagnosis for patients with acute abdominal pain was performed in eight centres with over 250 participating doctors and 16,737 patients. Performance in diagnosis and decision making was compared over two periods: a test period (when a small computer system was provided to aid diagnosis) and a baseline period (before the system was installed). The two periods were well matched for type of case and rate of accrual. The system proved reliable and was used in 75.1% of possible cases. User reaction was broadly favourable. During the test period improvements were noted in diagnosis, decision making, and patient outcome. Initial diagnostic accuracy rose from 45.6% to 65.3%. The negative laparotomy rate fell by almost half, as did the perforation rate among patients with appendicitis (from 23.7% to 11.5%). The bad management error rate fell from 0.9% to 0.2%, and the observed mortality fell by 22.0%. The savings made were estimated as amounting to 278 laparotomies and 8,516 bed nights during the trial period--equivalent throughout the National Health Service to annual savings in resources worth over 20m pounds and direct cost savings of over 5m pounds. Computer aided diagnosis is a useful system for improving diagnosis and encouraging better clinical practice.
Computer aided diagnosis of acute abdominal pain at Middlesbrough General Hospital.
This presentation reports the experience of the surgical house staff and registrars at Middlesbrough General Hospital who used a desk-top computer system to support their clinical diagnosis of acute abdominal pain. The results cover a two year period and are compared with a baseline period of one year. Substantial benefits followed the introduction of the computer-aided diagnostic support system; increased diagnostic accuracy of the whole surgical team, reduction in negative laparotomy rates, earlier surgical intervention for acute appendicitis, reduction in the number of cases of perforated appendicitis and more efficient use of resources. The reasons for these improvements include more thorough collection of data, use of common terminology and an educational element provided by detailed feedback from the computer system.
The acute abdomen: management with microcomputer aid.
This paper describes the management consequences of the use of a microcomputer as a special investigation in patients with an acute abdomen. Results in 812 patients seen by 42 junior doctors are compared six monthly and with baseline data from 295 cases from the preceding 2 years. Improvement in diagnostic ability from 48.5% to 71.8% (X2 = 25.8, P less than 0.001) resulted in a fall in negative appendicectomy from 37.5% to 9.71% (X2 = 16.2, P = less than 0.001). Bad management errors were also reduced from 22% to 10% (P = less than 0.01). The number of emergency investigation fell from 4 to 2 and inpatient stay of patients with non-surgical abdominal pain was reduced from 3 to 2 days. These results demonstrate that the use of microcomputers as investigative tools improves the surgical management of patients with acute abdominal pain.
Measurement of cerebral circulation time in man.
A simple, inexpensive method for measuring the cerebral circulation time (CCT) was developed. The CCT was considered to be equal to the time that an intravenously injected bolus of sodium pertechnetate Tc 99m took to go from the subclavian artery to the posterior venous confluence. The dilution curves were externally recorded at these two vessels. Particular attention was given to the curve treatment. The computer programmes were specially conceived in order to detect and, if possible, correct the experimental curve defects. Several reliability criteria were also defined in order to test the validity of each measurement. From a physiological point of view, the CCT is equal to the ratio of the global cerebral blood volume to the global cerebral blood flow. Thus, it can be widely applied in clinical research. For example, in a study of the relationship between CCT and age, sex and light cerebrovascular impairment, the technique was sensitive enough to discriminate between healthy subjects and patients suffering from-transient ischemic attack, or regressive stroke, and to show the action of a drug on the cerebral circulation in such patients.