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Biomedical subjects

S Chan

Publications and source records attributed to S Chan.

At least 109 records · Page 6Linked to original sources
PubMed1998

The role of bladder neck biopsy in men undergoing radical retropubic prostatectomy with preservation of the bladder neck.

PURPOSE: Radical retropubic prostatectomy is often performed with preservation of the bladder neck. We examine the incidence of benign and malignant prostatic tissue at the bladder neck margin in men undergoing radical retropubic prostatectomy with preservation of the bladder neck for clinically localized prostate cancer. MATERIALS AND METHODS: The study included 100 cases of radical retropubic prostatectomy with preservation of the bladder neck performed by a single surgeon (H. L.). A 2 mm. thick circumferential specimen was excised from the bladder neck, divided into 4 quadrants (anterior, posterior, right and left) and submitted for frozen section examination. The permanent sections from these bladder neck biopsies and the entire surgical specimens were analyzed by a single pathologist (J. M.). RESULTS: The frozen section diagnosis from the bladder neck biopsies were adenocarcinoma, benign prostatic tissue and no prostatic tissue in 3, 38 and 59 cases, respectively. The permanent section diagnosis of the bladder neck biopsies was adenocarcinoma, benign prostatic tissue and no prostatic tissue in 4, 57 and 39 cases, respectively. The sensitivity specificity, and positive and negative predictive values for examination of the surgical specimen to identify benign prostatic tissue was 67, 90, 90 and 65%, respectively. The bladder neck was re-biopsied because of the findings of adenocarcinoma and benign prostatic tissue in 3 and 8 cases, respectively. The initial bladder neck biopsy resulted in pathological down staging to pT2c in only 1 case. Repeat resection of the bladder neck in all cases with 10% or less benign prostatic tissue showed no prostatic tissue, whereas 50% of the cases with more than 10% benign prostatic tissue demonstrated residual benign prostatic tissue. Serum prostate specific antigen was undetectable immediately after radical retropubic prostatectomy in all cases with benign prostatic tissue only. CONCLUSIONS: Preservation of the bladder neck during radical retropubic prostatectomy does not significantly compromise total extirpation of the malignant process. Benign prostatic tissue at the bladder neck margin is relatively common. Examination of the surgical specimen has limited sensitivity, and negative and positive predictive values for the presence of benign prostatic tissue at the bladder neck margin. The impact of benign prostatic tissue as it relates to future malignant transformation is unknown. Submitting frozen section specimens from the bladder neck is reasonable for the younger man who may be at risk from benign prostatic tissue at the bladder neck margin.

Adenocarcinoma↗
PubMed1998

Medium-chain triglyceride and n-3 polyunsaturated fatty acid-containing emulsions in intravenous nutrition.

Medium-chain triglycerides and n-3 polyunsaturated fatty acid emulsions as a physical mixture have attracted increasing interest for use in parenteral nutrition and may play an important role in the development of structured triglycerides in a future generation of new lipids. Over the past two decades, the clinical use of intravenous emulsion for the nutritional support of hospitalized patients has relied exclusively on long-chain triglycerides providing both a safe, calorically dense alternative to dextrose and a source of essential fatty acids needed for biological membranes and maintenance of the immune function. During the past decade, the development of new triglycerides (medium- and long-chain triglyceride emulsions and structured triglyceride emulsions) for parenteral use have provided useful advances and opportunities to enhance nutritional and metabolic support. Medium-chain triglycerides and n-3 polyunsaturated fatty acid emulsions possess unique physical, chemical, and metabolic properties that make them theoretically advantageous over the conventional long-chain triglycerides. The physical mixture of medium- and long-chain triglycerides have been used clinically in patients with critical illness, liver disease, immunosuppression, pulmonary disease, and in premature infants, with good tolerance and the avoidance of some of the problems encountered with long-chain triglycerides alone.

Animals↗
PubMed1998

CD4/CD8 lineage commitment: matching fate with competence.

The outcome of positive selection of T lymphocytes is that there is a close match between the lineage adopted by a particular cell (CD4+ or CD8+) and the specificity of the T-cell receptor for the class of Major Histocompatibility Complex molecule recognized. How this match is obtained has been a matter of debate. We review the evidence, from recent and older experiments, that indicates that the process follows a selective logic, rather than an instructive one.

Animals↗
PubMed1998

CADASIL in a North American family: clinical, pathologic, and radiologic findings.

OBJECTIVE: To expand the reported phenotypic range of cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). BACKGROUND: Despite numerous patient reports, our knowledge of the phenotypic range of CADASIL remains incomplete. METHOD: We performed clinical, pathologic, and radiologic examinations on members of a family with CADASIL. RESULTS: The proband is a 61-year-old man with a history of migraine and depression who has experienced multiple subcortical infarctions resulting in a stepwise decline. Neuropsychological testing documented a dementia syndrome with frontal lobe features and neurologic examination noted a left hemiparesis and a right-sided palmomental reflex. Brain biopsy with light microscopy revealed a nonatherosclerotic small-vessel angiopathy with periodic acid-Schiff positive granular changes in the media and white matter gliosis, with unremarkable cortex. Genetic testing confirmed a Notch3 mutation. The proband's first cousin has a history of depression, one seizure possibly resulting from an acute stroke, and a learning disorder. Neuropsychological testing demonstrated deficits in executive function and neurologic examination noted persistent extraneous adventitial movements, poor coordination, and primitive reflexes. Skin biopsy with electron microscopy demonstrated granular osmiophilic material within the basement membrane of vascular smooth muscle cells, which is considered to be pathognomonic of CADASIL. The proband's older son and younger son have histories of migraine and depression, respectively, and both also had learning disorders. MRI revealed diffuse white matter disease extending into the temporal lobes, and lacunar infarctions in these four nonhypertensive patients. Other family members have experienced migraine, recurrent stroke, dementia, and depression. CONCLUSIONS: CADASIL is a genetic basis for vascular dementia that may be manifest earlier in life than previously reported.

Adult↗
PubMed1998

Emergency defibrillation performed by coronary nursing staff: A pilot report.

The time taken to initiate defibrillation is a key factor in determining survival after cardiac arrest; all first-responding medical or paramedical personnel are thus recommended to receive training in defibrillation skills. We have recently established a working programme that allows trained coronary care nurses to defibrillate in emergencies. Prospective data collected from 1 October 1996 to 31 January 1997 showed that a total of 11 witnessed episodes of ventricular fibrillation or pulseless ventricular tachycardia occurred in nine patients, and were defibrillated by nurses. All the defibrillations were started within 1 minute of cardiac arrest. In five patients, defibrillation was commenced before the arrival of the crash team of doctors; three of the five patients survived. There were no violations of the resuscitation protocol or complications relating to defibrillation. Through programmed training in advanced cardiac life-support, coronary care nurses are capable of providing safe and prompt defibrillation. The importance of training and re-certification is also stressed.

Journal Article↗
PubMed1998

Effects of combined endurance and strength training on left ventricular morphology in male and female rowers.

The effects of 10 weeks of combined endurance and strength training on left ventricular (LV) morphology, muscular strength, maximal oxygen consumption (VO2max) and rowing performance were assessed. Twenty-five subjects (eight males, mean age 23.0 +/- 6.1 years, and 17 females, 22.7 +/- 5.0 years) were tested at baseline and after five and 10 weeks of training. Combined training was associated with significant improvements in VO2max, rowing performance and muscular strength after 10 weeks of training. A significant increase in LV diastolic dimension was found in males after 10 weeks of training; however, no significant alteration was found for any other measured echocardiographic variable. Therefore, with the exception of LV diastolic dimension in males, 10 weeks of combined endurance and strength training appears to be an insufficient stimulus to elicit significant alterations in LV morphology despite changes in VO2max, muscular strength or rowing performance.

Female↗
PubMed1998

Somatic gene therapy. Present situation and future perspective.

The ultimate goal in the management of inherited as well as acquired diseases is a rational therapy with the aim to eliminate the underlying biochemical defects, rather than a symptomatic treatment. Among other approaches somatic gene therapy is a promising candidate to meet these objectives and appears to have the potential to revolutionize modern medicine. Gene therapy is characterized by the transfer of genetic information to a patient through the use of recombinant DNA technology. Several strategies for the treatment of monogenetic disorders as well as chronical diseases like cancer and AIDS have been used in various somatic gene therapy projects. So far, 329 clinical studies (phases I, I/II and II) with over 2500 patients have been initiated worldwide since 1989. No significant toxicity and adverse side effects have been observed. To allow efficient transfer of the therapeutic genes, a variety of gene delivery techniques have been developed based on viral and non-viral vector systems. For the success of this technology it is vital to achieve regulated and sustained expression of foreign genes in specific target tissues. This will be crucial for the widespread application of somatic gene therapy. So far none for the gene delivery systems is able to meet the requirements of safety, efficiency and specificity demonstrating that vector research will be an important focus in the development of optimized transfer methods. From a regulatory point of view pharmaceutical DNA-products can be regarded as drugs and are therefore subject to the same regulations. Human gene therapy must, however, be limited to manipulations affecting somatic, differentiated cells to prevent the transferred gene from being transmitted to the individual's descendants. Applications for the purpose of 'enhancement' and not for the treatment of diseases are also not acceptable. Under these prerequisites, somatic gene therapy does not raise any new ethical concerns and can be interpreted as a special form of an organ transplantation. A comparison of the different regulatory situations of gene therapy in Europe and the United States demonstrates that for the European countries a uniform regulation is desired. Today somatic gene therapy is still in its infancy. It will continue to be scientifically and technically challenging until simple and effective procedures will have been developed. Demonstration of its clinical efficacy especially in the long term will have to be the next step. Looking at the history of biotechnology and the success of the biotechnology industry that is now providing safe and efficient products from recombinant DNA-technology there is little doubt that gene therapy will become a successful treatment for various indications in the next decade. The purpose of this article is to review the current status of the development in somatic gene therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Technical and clinical aspects of spectrometric analysis of trace elements in clinical samples.

The capabilities of ICP-MS far exceed the slow, single-element analysis of GFAAS for determination of multiple trace elements. Additionally, its sensitivity is superior to that of DCP, ICP, and FAAS. The analytic procedure for ICP-MS is relatively straightforward and bypasses the need for digestion in many cases. It enables the physician to identify the target trace element(s) in intoxication cases, nutritional deficiency, or disease, thus eliminating the treatment delays experienced with sequential testing methods. This technology has its limitations as well. The ICP-MS cannot be used in the positive ion mode to analyze with sufficient sensitivity highly electronegative elements such as fluorine, because F+ is unstable and forms only by very high ionization energy. The ICP mass spectrometers used in most commercial laboratories utilize the quadrupole mass selector, which is limited by low resolution and, thus, by the various interferences previously discussed. For example, when an argon plasma is used, selenium (m/e 80) and chromium (m/e 52) in serum, plasma, and blood specimens are subject to polyatomic and molecular ion interferences. Low-resolution ICP mass spectrometers can therefore be used to analyze many trace elements, but they are not universal analyzers. High-resolution ICP-MS can resolve these interferences, but with greater expense. With the advent of more research and development of new techniques, some of these difficulties may be overcome, making this technique even more versatile. Contamination during sample collection and analysis causes falsely elevated results. Attention and care must be given to avoid contamination. Proper collection devices containing negligible amounts of trace elements should be used. Labware, preferably plastic and not glass, must be decontaminated prior to use by acid-washing and rinsed with [table: see text] de-ionized water. A complete description of sample collection and contamination has been written by Aitio and Jarvisalo as well as by Chan and Gerson. Lutz et al observed the ranges in blood shown in Table 4. We have adopted the ranges listed in Table 5 in urines of healthy, ambulatory, and community-dwelling individuals through a limited in-house study and review of literature. In conclusion, differentiation of trace element abnormalities (primary intoxication or disease versus secondary underlying disease) can be made only by utilizing results from trace element analyses in clinical specimens, medical history, and careful observation of symptoms. Repeat analysis on a second specimen collection is recommended when contamination is suspected.

Body Fluids↗
PubMed1998

The role of copper, molybdenum, selenium, and zinc in nutrition and health.

Copper, zinc, selenium, and molybdenum are involved in many biochemical processes supporting life. The most important of these processes are cellular respiration, cellular utilization of oxygen, DNA and RNA reproduction, maintenance of cell membrane integrity, and sequestration of free radicals. Copper, zinc, and selenium are involved in destruction of free radicals through cascading enzyme systems. Superoxide radicals are reduced to hydrogen peroxide by superoxide dismutases in the presence of copper and zinc cofactors. Hydrogen peroxide is then reduced to water by the selenium-glutathione peroxidase couple. Efficient removal of these superoxide free radicals maintains the integrity of membranes, reduces the risk of cancer, and slows the aging process. On the other hand, excess intake of these trace elements leads to disease and toxicity; therefore, a fine balance is essential for health. Trace element--deficient patients usually present with common symptoms such as malaise, loss of appetite, anemia, infection, skin lesions, and low-grade neuropathy, thus complicating the diagnosis. Symptoms for intoxication by trace elements are general, for example, flu-like and CNS symptoms, fever, coughing, nausea, vomiting, diarrhea, anemia, and neuropathy. A combination of observation, medical and dietary history, and analyses for multiple trace elements is needed to pinpoint the trace element(s) involved. Serum, plasma, and erythrocytes may be used for the evaluation of copper and zinc status, whereas only serum or plasma is recommended for selenium. Whole blood is preferred for molybdenum. When trace element levels are inconsistent with medical evaluations, a test for activity of the suspected enzyme(s) would support the differential diagnosis. Furthermore, it is important to differentiate whether trace element deficiency or toxicity is the primary cause of the disorder, or is secondary to other underlying diseases. Only successful treatment of the primary disorder will lead to complete recovery. In the event of sample contamination during collection or analysis, the physician may be misled by falsely elevated results. Royal blue top evacuated tubes containing negligibly low concentrations of the trace element or acid-washed plastic sterilized syringes should be used for blood, serum, or plasma collection. Powdered gloves must be avoided. When possible, mineral supplements are not to be administered to the patient for a minimum of 3 days prior to sample collection. Serum and plasma specimens are to be transported in acid-washed polypropylene and polyethylene tubes. Analysis is performed in a controlled environment to minimize or eliminate contamination. During analysis, all laboratory wares should be acid-washed for decontamination. A detailed description of these precautions may be found in reviews by Aitio and Jarvisalo and by Chan and Gerson. Copper and zinc analysis on serum and plasma are commonly performed by flame atomic absorption spectrometry, inductively coupled plasma-atomic emission spectrometry, and inductively coupled plasma-mass spectrometry. Serum and plasma selenium levels are determined by graphite furnace atomic absorption with Zeeman background correction and neutron activation analysis. Molybdenum levels are best determined by neutron activation and highly sensitive inductively coupled plasma-mass spectrometry. The reader is referred to reviews by Tsalev and Jarvis.

Adolescent↗
PubMed1997

Early tracheal extubation after liver transplantation.

OBJECTIVE: To assess the value and safety of tracheal extubation in the operating room at the end of liver transplantation. DESIGN: Retrospective chart review. SETTING: University Medical Center. PARTICIPANTS: Eighteen adult patients extubated in the operating room at the end of liver transplantation (study patients) compared with 17 patients who were not extubated and had < or = 3 U of blood transfused during liver transplantation (control patients). INTERVENTIONS: Data collected include severity of preoperative liver disease, anesthetic technique, use of venovenous bypass, surgical time, intraoperative blood replacement, core temperature and arterial blood gases on admission to the intensive care unit (ICU), times to discharge from ICU and the hospital. MEASUREMENTS AND MAIN RESULTS: Except for age (43.9 +/- 2.7 in study patients v 52.4 +/- 2.5 years; p = 0.03), patients were similar with regard to preoperative Child's-Pugh class and liver function tests. Study patients received more crystalloid in the OR (5,306 +/- 561 v 3,771 +/- 454 mL; p = 0.04), were warmer (36.6 degrees C +/- 0.2 degree C v 35.6 degrees C +/- 0.3 degree C; p = 0.01), had a lower arterial pH (7.29 +/- 0.01 v 7.36 +/- 0.02; p = 0.003) and higher arterial carbon dioxide tension (45 +/- 1 v 35 +/- 2 mmHg; p < 0.001) on admission to ICU than controls. There were no significant differences between groups with regard to discharge times from the ICU (50.6 +/- 2.7 hours in the study group v 61.2 +/- 4.7 in control group; p = 0.06), or discharge from the hospital (14.8 +/- 1.6 in the study group v 21.3 +/- 3 days in control group; p = 0.06). CONCLUSIONS: Tracheal extubation of selected patients at the end of liver transplant surgery in the operating room is safe but did not result in decreased ICU or hospital stay.

Adult↗
PubMed1997

The predictive value of intraoperative electrocorticography in resections for limbic epilepsy associated with mesial temporal sclerosis.

OBJECTIVE: Prior studies on the predictive value of intraoperative electrocorticography (ECoG) have been performed on heterogeneous groups of patients with both temporal and extratemporal interictal spikes, lesional and nonlesional pathological findings, and variably extensive resections by different surgeons. METHODS: We performed both pre- and postresection intraoperative ECoG on 29 consecutive patients with medial temporal lobe epilepsy (17 left-sided) who underwent standard nontailored resections by one surgeon (RRG). All patients had only temporal interictal spikes (six bitemporal) and mesial temporal sclerosis diagnosed by preoperative magnetic resonance imaging and confirmed by pathological examination of resected tissue. RESULTS: After a mean follow-up of 24.8 months, there were 15 (52%) patients who were seizure-free, 6 (21%) who were seizure-free except for auras, and 8 (28%) who had any seizure after the 1st postoperative month. Fourteen patients (48%) had active interictal discharges outside the area of planned resection revealed by preresection ECoG. Neither the presence of these spikes nor their mean frequency correlated with seizure outcome. Eleven patients (38%) had residual spike discharges after resection, and 18 patients (62%) had new spikes revealed by the postresection ECoG. Neither of these findings nor the mean spike frequency of residual or new spikes related to seizure outcome. Persistent spikes increased in frequency after resection in all outcome groups. CONCLUSIONS: Electrocorticographic monitoring of interictal epileptiform activity intraoperatively is not useful in the surgical treatment of patients undergoing standard resection for medial temporal lobe epilepsy with magnetic resonance imaging evidence of mesial temporal sclerosis.

Adolescent↗
PubMed1997

Effects of renal denervation on cardiovascular and renal responses to ACE inhibition in conscious lambs.

Effects of renal denervation on cardiovascular and renal responses to ACE inhibition in conscious lambs. J. Appl. Physiol. 83(2): 414-419, 1997.-Cardiovascular and renal effects of either the angiotensin-converting enzyme inhibitor captopril or vehicle were measured in chronically instrumented lambs in the presence (intact; n = 6) and absence of renal sympathetic nerves (denervated; n = 5) to determine whether there was an interaction between the renin-angiotensin system and renal sympathetic nerves early in life. Captopril caused a similar decrease in mean arterial pressure (P < 0. 001) in intact and denervated lambs, predominantly through a decrease in diastolic pressure. Heart rate was increased from 177 +/- 34 to 213 +/- 22 (SD) beats/min during captopril compared with vehicle infusion in intact lambs. In denervated lambs, basal heart rates were elevated to 218 +/- 33 beats/min; there was no further increase in heart rate during captopril compared with vehicle infusion. Captopril infusion caused a decrease in renal vascular resistance but only in the absence of renal nerves. These findings provide evidence to suggest that early in life there is an interaction between renal sympathetic nerves and the renin-angiotensin system in regulating renal hemodynamics and the baroreflex control of the heart.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1997

Docetaxel vs doxorubicin in metastatic breast cancer resistant to alkylating chemotherapy.

Single-agent docetaxel (Taxotere) has been shown to be highly active in metastatic breast cancer, with an overall response rate of 47%, median time to progression of 4 months, and survival of 10 months when administered as second-line therapy. These data compare favorably with those reported for doxorubicin (Adriamycin), which has been considered the most active single agent in this setting. This nonblinded, multicenter, randomized phase III study compared the median time to progression, response rate, quality of life, toxicity, and survival after treatment with docetaxel or doxorubicin in patients with metastatic breast cancer in whom previous alkylating chemotherapy failed. Patients were randomized to receive an intravenous infusion of either docetaxel, 100 mg/m2, for 1 hour once every 3 weeks or doxorubicin, 75 mg/m2, for 15 to 20 minutes once every 3 weeks. This preliminary analysis presents data on 200 of 326 patients recruited. It was performed after the completion of patient accrual. The median time to progression was greater in the docetaxel group than in the doxorubicin group (29 vs 21 weeks, respectively; P = not significant). Overall response rates were higher with docetaxel (47% vs 27%), and fewer patients in the docetaxel group had progressive disease as their best overall response (10% vs 22%). Both regimens caused the same incidence and severity of neutropenia, yet patients treated with doxorubicin had a higher incidence of infection and febrile neutropenia. In addition, doxorubicin produced a higher incidence of grade 3 to 4 thrombocytopenia. Cardiac toxicity led to discontinuation in 7 patients and death in 2 patients in the doxorubicin group; fluid retention led to discontinuation in 1 patient in the docetaxel group. Based on this preliminary analysis, docetaxel was more active and safer than doxorubicin in patients with metastatic breast cancer in whom previous alkylating chemotherapy failed.

Adolescent↗
PubMed1997

Pharmaceutical treatment of obesity.

The prevalence of obesity in America has increased steadily in the past 7 decades, especially in the last decade. Health factors that lead to obesity are discussed. This article focuses on the treatment of obesity and potential results.

Anti-Obesity Agents↗