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Biomedical subjects

A Chung

Publications and source records attributed to A Chung.

At least 55 records · Page 3Linked to original sources
PubMed1993

A microplate system for ABO and Rh(D) blood grouping.

A microplate system for performing ABO and Rh(D) blood group determinations with a Kemble Kemtek 1000SP liquid handling processor, an Anthos 2001 microplate reader, an IBM Personal System 2 microcomputer, and Sanguin Forma software is described. The performance of this Kemble/Anthos/IBM/Sanguin microplate system for ABO and D grouping was evaluated by testing 10,042 routine blood donor samples in parallel with the forward-grouping channels of a Technicon AutoAnalyzer blood grouping system. Manual techniques were used to perform ABO reverse groupings and to resolve all ABO forward- and reverse-grouping discrepancies. D-negative test results were investigated and confirmed manually by the indirect antiglobulin test. Of the 10,042 samples tested, 97.3 percent were grouped correctly. There were 266 samples whose results were flagged as no type determined, of which 124 were ABO tests and 142 were Rh tests. In addition, 30 weak D samples missed by both automated systems were detected by manual indirect antiglobulin test. The system is flexible and easy to maintain and operate.

ABO Blood-Group System↗
PubMed1993

Comparative mapping of 9 human chromosome 22q loci in the laboratory mouse.

We present a comparative map of genes on human chromosome 22q and homologous loci in the mouse genome. Gene order in humans was established using a panel of somatic cell hybrids. Genetic maps spanning homologous segments on three mouse chromosomes were generated using an interspecific backcross. The conserved linkage between human chromosome 22 and mouse chromosome 16 includes two closely linked loci, Comt and IgI-1. The second conserved linkage involves human chromosome 22 and mouse chromosome 11 and contains two genetically and physically linked loci, Lif and Nfh. Finally, conserved synteny involving mouse chromosome 15 and human chromosome 22 spans 30 cM and contains five loci (Acr, Bzrp, Dia-1, Il2rb and Pdgfb). Loci within this conserved synteny have been sublocalized to different portions of human chromosome 22. The order of genes on mouse chromosome 15 and human chromosome 22 provides further evidence for chromosomal rearrangements within the conserved synteny that have occurred since the divergence of lineages leading to mice and humans.

Animals↗
PubMed1992

Postoperative haemodynamic and pharmacological responses in patients with positive technetium pyrophosphate single-photon emission computed tomography following CABG.

The aim of this prospective study was to evaluate the postoperative haemodynamic variables and medication requirements in patients with perioperative myocardial infarction (PMI), following elective coronary artery bypass graft (CABG) surgery, as documented by technetium pyrophosphate scintigraphy using single-photon emission computed tomography (TcPPi-SPECT). A high-dose fentanyl anaesthetic technique was applied. Twelve of 58 patients (21%) developed PMI with an infarcted myocardial mass of 35.7 +/- 3.9 g. Over the 48 hr postoperative period, patients with positive TcPPi-SPECT (n = 12) did not differ from those with negative TcPPi-SPECT (n = 46) in mean heart rate (below 100 bpm), systolic blood pressure (100-120 mmHg) or central venous pressure (8-16 mmHg). However, patients with positive TcPPi-SPECT had higher pulmonary artery diastolic pressures at 5-8 hr after surgery. No differences were found in the incidence and dosage requirements for postoperative sedative or vasoactive drugs (morphine, diazepam, propranolol, lidocaine, nitroglycerin and nitroprusside) between the two groups. There was no difference in the incidence of dopamine requirement between the groups (positive-scan: 16.7%, negative-scan: 13.0%). However, the dopamine dosage for inotropic support was higher in the positive TcPPi-SPECT group over 24 hr (318.5 +/- 125.2 mg vs 71.2 +/- 24.7 mg, P less than 0.05) and 48 hr (869.1 +/- 19.0 mg vs 142.3 +/- 49.4 mg, P less than 0.001) periods after surgery. We postulate that careful control of postoperative haemodynamic variables did not prevent but may limit the extent of PMI in elective CABG patients.

Coronary Artery Bypass↗
PubMed1992

Chronic pancreatitis in Jamaica.

Thirty-five patients with chronic pancreatitis (CP) treated over a 15-year-period were studied. There were 29 men and 6 women with a mean age of 47 years (range 21-67). Twenty-seven (77%) were chronic alcoholics, two (6%) had gallstones, one had stenosis of the Ampulla of Vater and in five (14%) no obvious cause was found. Thirty patients (86%) presented with abdominal pain. Chronic diarrhoea was present in 8 (23%), and steatorrhoea was documented in 6 of these. Fifteen (43%) had pancreatic calcifications. Five developed pseudocysts and 16 (46%) developed diabetes mellitus. Twelve patients required surgery. Three continue to have severe recurrent relapses of pain but the majority (91%) have had a relatively stable course with medical management.

Abdominal Pain↗
PubMed1991

Molecular basis for elliptocytosis associated with glycophorin C and D deficiency in the Leach phenotype.

Glycophorin C (GPC) and glycophorin D (GPD) are highly glycosylated integral membrane proteins of human erythrocytes encoded by the same gene and associated with expression of Gerbich blood group system antigens. GPC/D deficiency (the Leach phenotype) is a rare condition usually found after identification of Gerbich blood group system antibodies in persons undergoing prenatal or pretransfusion evaluation. In all cases, the Leach phenotype has been associated with elliptocytosis. Characterization of the molecular basis of this phenotype in three previously uninvestigated families has shown that the most common genetic basis of GPC/D deficiency is deletion of exons 3 and 4 of the GPC gene. However, in one family, the Leach phenotype appeared due to a deletion of one nucleotide in exon 3, causing a frameshift mutation in the messenger RNA and premature generation of a stop codon. The GPC and GPD protein sequences are therefore interrupted in the extracellular domain and probably intracellularly degraded.

Amino Acid Sequence↗
PubMed1991

Analgesic and pulmonary effects of continuous intercostal nerve block following thoracotomy.

This study examined the beneficial effects and potential systemic toxicity from continuous intercostal nerve block by repeated bolus injections of bupivacaine. In this double-blind, randomized study, 20 post-thoracotomy patients were assigned to receive four doses of either: 20 ml 0.5% bupivacaine with epinephrine 5 micrograms.ml-1 (bupivacaine group, n = 10), or 20 ml preservative-free saline (placebo group, n = 10) through two indwelling intercostal catheters every six hours. Patients receiving intercostal bupivacaine injections had greater decreases in visual analogue pain scores (VAS) (P less than 0.05) and lower 24 hr morphine requirements, 16.6 +/- 4.6 mg vs 35.8 +/- 7.2 mg, than patients in the placebo group (P less than 0.05). Higher post-injection values of forced expiratory volume in one second, forced vital capacity and peaked expiratory flow rate were also observed in the bupivacaine group (P less than 0.01). Repeated intercostal bupivacaine administration did lead to systemic accumulation, but the peak bupivacaine level after 400 mg was low at 1.2 +/- 0.2 microgram.ml-1. Thus, the technique of continuous intercostal nerve block described in this study is an effective treatment for the control of post-thoracotomy pain.

Adult↗
PubMed1990

The antithrombotic properties of human prothrombin fragment 1.2 in mice.

We have investigated the antithrombotic properties of prothrombin fragment 1.2 (F1.2) in this study. To do this, we established the minimum concentration of human placental tissue factor or human alpha-thrombin that was lethal in mice within 5 min after intravenous injection. Prothrombin F1.2 protected the mice from the lethal effect of tissue factor or alpha-thrombin in a dose dependent manner, with 500 micrograms (14 nmoles) of prothrombin F1.2 per mouse being the minimum amount required to protect all mice from the lethal effect of either thrombogenic stimulus. The minimum dose of heparin which protected mice from the lethal effect of thrombin or tissue factor was 6 units or approximately 3.3 nmoles. The observation that prothrombin F1.2 has antithrombotic properties suggests prothrombin F1.2 can modulate coagulation in vivo, as it has previously been shown to do in vitro.

Animals↗
PubMed1990

Suramin prevents binding of interleukin 2 to its cell surface receptor: a possible mechanism for immunosuppression.

Suramin, a polysulfonic naphthalene antihelminthic drug, inhibits proliferation of a variety of T-cell lines in vitro and induces immunosuppression in some human patients and thymic atrophy and splenic depletion in mice. Recent clinical trials indicate that suramin has activity against human tumors, indicating that it will be necessary to understand the mechanism by which suramin induces immunosuppression. The T-cell growth factor, interleukin 2 (IL2), is the major growth factor involved in regulating lymphoid differentiation and proliferation and thus regulates, to a major degree, the magnitude and duration of the immune response. We demonstrate herein that suramin induces a concentration-dependent decrease in binding of 125I-labeled IL2 to its receptor complex on human and murine T-lymphocytes. Binding of 125I-labeled IL2 to both Mr 75,000 and 55,000 IL2 binding molecules was inhibited by suramin. Similar concentrations of suramin were required to inhibit binding of 125I-labeled IL2, IL2-induced tyrosine phosphorylation, and IL2-induced proliferation, suggesting that these processes may be linked. With murine cells, suramin-induced growth inhibition could be overcome completely by increasing the concentration of IL2, suggesting that suramin inhibited growth by competing for the IL2 receptor. With human cells, growth inhibition by suramin could only be partially overcome by increasing the concentration of IL2, suggesting that an additional growth-inhibiting mechanism is present. The ability of suramin to prevent binding of IL2 to its receptor was used to confirm that prolonged interaction of IL2 with its receptor is required to induce cell proliferation. Since IL2 plays a role in lymphocyte proliferation and differentiation, the ability of suramin to inhibit binding of IL2 to its receptor may explain, in part, the in vivo immunosuppressive activities of suramin.

Animals↗
PubMed1990

Analysis of liver lymphoid cell subsets pre- and post-in vivo administration of human recombinant interleukin 2 in a C57BL/6 murine system.

The systemic administration of high dose recombinant interleukin 2 (RIL-2) can mediate significant reductions in the number of hepatic metastases in a murine system. This effect is sensitive to host irradiation. Both large granular (LGLs) and small (SLs) lymphocytes have been implicated as the cells mediating the antitumor effect. Utilizing selective Percoll fractionation of liver nonparenchymal lymphoid cells, we have attempted to determine the cell types involved in tumor immunotherapy of murine liver metastases during RIL-2 administration. At a RIL-2 dose of 25,000 units given i.p. three times a day, the total number of lymphoid cells seen in murine livers reached a peak on day 6 after the onset of RIL-2 therapy, lasting until day 10 and ranging from 25 to 29 times baseline values. Both LGLs and SLs were identified and SLs made up over one-half the cells present in murine livers. Phenotypic analysis of LGLs and SLs revealed that during exposure to RIL-2, bands 5 + 6 SLs expressed the Thy-1.2, Lyt-2, and Lyt-1 antigens to a greater degree than LGLs. LGLs exposed to RIL-2 demonstrated a decrease in the expression of the asialo GM1 antigen during exposure to RIL-2; however, the 49H.8 antigen normally expressed on natural killer cells and not on circulating T-cells was found only on LGLs. The role of murine liver LGLs and SLs needs to be further characterized.

Animals↗
PubMed1990

Age-related cognitive recovery after general anesthesia.

This study was designed to quantify the rate of mental recovery in elderly and young patients after general anesthesia for intraabdominal surgery (cholecystectomy). Forty patients (25-83 yr) were given four tests assessing neuropsychological function once preoperatively and on five occasions postoperatively. Two of the four neuropsychological tests showed impairment in scores in the elderly patients on the first postoperative day (Symbol Digit Modalities Test, P less than 0.004; The Trail Making Test, P less than 0.03). In addition, one of the tests (Symbol Digit Modalities Test) showed a deterioration in the younger patients (P less than 0.05). The changes that did occur in these tests on the first postoperative day reverted to baseline levels thereafter. There were no significant changes in the remaining two tests, the Mini Mental State Test or the Digit Span Test, at any time in either group. We conclude that postoperative mental deterioration is no greater in elderly than in young patients.

Adult↗
PubMed1989

Comparison of perioperative mental function after general anaesthesia and spinal anaesthesia with intravenous sedation.

This study compared the postoperative mental function in 44 elderly patients following general anaesthesia (GA) or spinal anaesthesia (SA) with sedation for transurethral resection of prostate. The Mini-Mental State (MMS) was done preoperatively and postoperatively at six hours, one day, three days, five days and one month. The geriatric mental status examination was performed preoperatively and one month after the anaesthetic. There was no significant intergroup difference in the MMS score in the preoperative, six hours, one day, three days, five days and 30 days postoperative scores between the GA and SA with sedation groups. A significant intragroup difference between preoperative and postoperative MMS score was detected in the GA group (P less than 0.02) and in the SA group with sedation (P less than 0.03). In the GA group, the significant decrease in MMS score occurred at 6 h postoperatively (P less than 0.002) whereas in the SA group with sedation, MMS score also decreased significantly at 6 h (P less than 0.005). In conclusion, there was no significant difference in perioperative mental function between the general and spinal anaesthetic groups when supplemental IV sedation was given. In both groups, perioperative mental function decreased significantly at 6 h postoperatively.

Aged↗
PubMed1989

The human ATP synthase beta subunit gene: sequence analysis, chromosome assignment, and differential expression.

In humans, the functional F0F1-ATP synthase beta subunit gene is located on chromosome 12 in the p13----qter region. Other partially homologous sequences have been detected on chromosomes 2 and 17. The bona fide beta subunit gene has 10 exons encoding a leader peptide of 49 amino acids and a mature protein of 480 amino acids. Thirteen Alu family DNA repeats are found upstream from the gene and in four introns. The gene has four "CCAAT" sequences upstream and in close proximity to the transcriptional initiation site. A 13-bp motif is found in the 5' nontranscribed region of both the beta subunit gene and an ADP/ATP translocator gene that is expressed in high levels in cardiac and skeletal muscle. Analysis of the beta subunit mRNA levels reveals marked differences among tissues. The highest levels are found in heart, lower levels in skeletal muscle, and the lowest levels in liver and kidney. These findings suggest that the tissue-specific levels of ATP synthase beta subunit mRNA may be generated through transcriptional control.

Amino Acid Sequence↗
PubMed1989

A novel human alloantibody in the Gerbich system.

A Gerbich-negative Leach phenotype individual was identified on the basis of distinct morphological, biochemical, and serological characteristics of her red blood cells. This individual has produced an antibody which was reactive with the various Gerbich phenotypes including Ge:-2,3 (Yus type) and Ge:-2,-3 (Ge type) cells; only her own and Leach phenotype cells were non-reactive. It is suggested that this antibody represents an example of a new specificity, one which defines the Leach phenotype, in the Gerbich system.

Blood Group Antigens↗
PubMed1989

Cognitive impairment after neuroleptanalgesia in cataract surgery.

This study was undertaken to evaluate the mental recovery of patients following cataract operations under neuroleptanalgesia. Mental function was assessed by Mini-Mental State (MMS) preoperatively and at 6 and 24 hours postoperatively. Preoperatively, 18.7% of the elderly had cognitive impairment of mental function while none in the younger group had any impairment (P less than 0.02). At six hours postoperatively, 29.7% of the elderly had cognitive impairment compared with 4% of the younger group (P less than 0.01). At 24 hours postoperatively, the percentage of elderly and younger patients with cognitive impairment had returned to preoperative levels. Baseline score and age were found to be significant predictors (P less than 0.004) of the 6-hour score and 24-hour score. In conclusion, cognitive impairment of mental function occurred in patients undergoing cataract operation with retrobulbar block and intravenous sedation at 6 hours postoperatively; MMS has the potential for use as a screening preoperative test for outpatients to identify those at risk for developing cognitive impairment.

Adult↗
PubMed1986

Synthetic inhibitors of carboxypeptidase N.

Further to explore the functions of carboxypeptidase N (CPN) in vivo, we undertook two studies to find CPN inhibitors of high potency and relatively long duration of action. In each study we examined for inhibition of hydrolysis of [3H]benzoyl-Ala-Arg using pure bovine serum CPN or human serum. In the first such study we synthesized a series of acyl amino acids and acyl di - and tripeptides containing arginine, lysine or both. All proved to be weak inhibitors (Ki = 10(-3) to 10(-4) M). N alpha-carbamoyl-Arg was the strongest: Ki = 3.5 X 10(-5) M. In the second study we prepared S-acyl (thio ester) derivatives of the highly potent CPN inhibitor 2-mercaptomethyl-3-guanidinoethylthiopropionic acid (2-MGP), as certain S-acyl groups markedly increase the duration of captopril, another mercapto-containing compound. Acetyl-, Boc-phenylalanyl-, phenylalanyl-, benzoyl-alanyl-, alanyl-, and Boc-alanyl-2-MGP retained the high potency of 2-MGP in vitro. Although Ala-2-MGP exerted maximum effects in vivo, like those of 2-MGP, the duration of action of Ala-2-MGP was slightly shorter than that of 2-MGP. These results indicate that the mercapto group of 2-MGP can be taken up in some forms of thioester linkage and still remain virtually the full potency of 2-MGP itself. Thus, it appears that a free mercapto function is not essential for the action of 2-MGP.

Amino Acids↗
PubMed1986

Toothbrushing and transient bacteremia in patients undergoing orthodontic treatment.

A study was made to determine the extent of bacteremia experienced by patients undergoing orthodontic treatment with fixed appliances during periods of routine oral hygiene--namely, brushing the teeth. Sixteen orthodontic patients made up the population--11 who practiced good oral hygiene and five who demonstrated poor oral hygiene. Blood was drawn aseptically from the median cubital vein of the subjects before and 15 minutes after brushing the teeth. An aliquot of each blood specimen was added to separate blood culture bottles and incubated at 37 degrees C for a period of up to 5 days. Blood was also used to determine the immune status of the subjects. Anaerobic bacteria were recovered from the blood of nine of the 16 patients studied; aerobic bacteria were not recovered. A negative blood culture before brushing and positive blood culture after brushing were expected but did not occur. Some subjects showed bacteremia before brushing and a negative blood culture after brushing. Others showed bacteremia before and after brushing. The unexpected results could be attributed to the patients eating and/or brushing before starting the test. The study showed the capacity of specific anaerobic bacteria to remain in the bloodstream for a 15-minute period. It also demonstrated a presence of bacteria in the bloodstream before the test began.

Adolescent↗
PubMed1986

A rapid, simple synthesis and purification of abscisic Acid glucose ester.

A simple and rapid technique was developed to synthesize abscisic acid glucose ester. The free acid of abscisic acid (ABA) was combined with CsHCO(3) to form the Cs salt of ABA. The Cs salt of ABA was then combined with acetobromo-alpha-d-glucose tetraacetate, and the tetraacetate derivative of abscisic acid glucose ester was formed. Acetate groups were selectively removed from the glucose moiety with a crude enzyme preparation derived from Helianthus annuus seeds. Abscisic acid glucose ester was purified via silica gel column chromatography and identified by micro NMR.

Journal Article↗