Biomedical subjects
Publications and source records attributed to L Chen.
Two unique associations of disease with Escherichia coli O157:H7 are presented. These cases broaden the spectrum of disease associated with this organism which currently includes bloody and non-bloody diarrhoea, haemolytic-uraemic syndrome, and thrombotic thrombocytopenic purpura.
It has been postulated that a glucose transporter of beta cells (GLUT-2) may be important in glucose-stimulated insulin secretion. To determine whether this transporter is constitutively expressed or regulated, we subjected conscious unrestrained Wistar rats to perturbations in glucose homeostasis and quantitated beta-cell GLUT-2 mRNA by in situ hybridization. After 3 hr of hypoglycemia (glucose at 29 +/- 5 mg/dl), GLUT-2 and proinsulin mRNA signal densities were reduced by 25% of the level in control rats. After 4 days (blood glucose at 57 +/- 7 mg/dl vs. 120 +/- 10 mg/dl in saline-infused control rats), GLUT-2 and proinsulin mRNA densities were reduced by 85% and 65%, respectively (P = 0.001). After 12 days (glucose at 54 +/- 8 mg/dl), GLUT-2 mRNA signal density was undetectable whereas proinsulin mRNA was reduced by 51%. After 12 days of hypoglycemia, the Km for 3-O-methyl-D-glucose transport in isolated rat islets, normally 18-20 mM, was 2.5 mM. This provides functional evidence of a profound reduction of high Km glucose transporter in beta cells. In contrast, GLUT-2 was only slightly reduced by hypoglycemia in liver. To determine the effect of prolonged hyperglycemia, we also infused animals with 50% (wt/vol) glucose for 5 days (glucose at 200 +/- 50 mg/dl). Hyperglycemic clamping increased GLUT-2 mRNA by 46% (P = 0.001) whereas proinsulin mRNA doubled (P = 0.001). We conclude that GLUT-2 expression in beta cells, but not liver, is subject to regulation by certain perturbations in blood glucose homeostasis.
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The external ear of the rat is an excellent model for practicing microsurgical dissection and for the refinement of microvascular anastomoses, techniques that are crucial for microvascular en bloc tissue transfer and replantation. Preparation of the rat ear for replantation requires familiarity with the vascular anatomy and gentle tissue handling with atraumatic dissection of arterial and venous pedicles, steps similarly crucial in raising free flaps for microvascular transfer. The strategy of performing accurate reduction and stabilization of the tubal cartilage prior to vessel repairs, anastomosing the more deeply seated external carotid artery prior to the more superficial posterior facial vein, is as critical to rat ear replantation as for digital reattachment. In addition, the rat ear as compared to other animal models such as the rabbit ear or canine hindlimbs is much less expensive. Compared to the rat hindlimb model, rat ears are much easier to observe, which is a distinct advantage when used as a model for long-term study of replantation, revascularization, or transplantation.
The natural history of alloimmunization to the PlA1 platelet antigen is uncertain. We followed 50 PlA1-negative pregnant women during pregnancy and for 6 months post-partum in order to determine this natural history. The cohort of PlA1-negative women was obtained by PlA1 typing 5000 women. Three PlA1-negative women formed anti-PlA1 antibodies during this prospective study, two in pregnancy and one in the immediate post-partum period. All three PlA1 antibody producers were HLA-DR3 positive, a histocompatibility phenotype that is strongly associated with alloimmunization to the PlA1 antigen. One of the three infants delivered to these mothers was thrombocytopenic (platelet count 9 x 10(9)/l). The remaining two infants had normal platelet counts at birth (160 and 174 x 10(9)/l). The HLA-A1, -B8, -DR3 and -DRw52 phenotype frequencies in the group of PlA1-negative women who did not form PlA1 antibodies (n = 47) was similar to that found in their husbands, and that expected in a normal Caucasian population. From our data we estimate that alloimmunization to the PlA1 antigen occurs in approximately one out of every 1000 pregnancies in a Caucasian population. It is important to recognize that not all pregnancies in which a mother has formed PlA1 alloantibodies will result in the delivery of a thrombocytopenic infant. These findings are relevant to programs designed to either prevent alloimmunization to the PlA1 antigen (through passive administration of anti-PlA1 immunoglobulin to at-risk PlA1-negative mothers), or to identify women at risk of delivery of thrombocytopenic infants (by antenatal screening to detect women alloimmunized to the PlA1 antigen).
We examined the time course of changes in osmotic water permeability (Pf, micron/s), lumen-to-bath 22Na+ flux (Jl----b, pmol.min-1.mm-1), and transepithelial voltage (VT, mV) in response to arginine vasopressin (AVP) in isolated perfused rat and rabbit cortical collecting ducts (CCD). CCDs were isolated from "normal" (untreated) animals and animals 4-14 days after an intramuscular depot injection of deoxycorticosterone pivalate (DOC; 35 mg/rabbit, 5 mg/rat). In the normal rat CCD, 220 pM AVP added to the bathing solution increased Pf from approximately 0 to 981 +/- 120, Jl----b from 24 +/- 5 to 62 +/- 9, and VT from -0.7 +/- 0.6 to -4.0 +/- 0.6 (mean +/- SE; P less than 0.05). The effect of AVP on Pf in DOC-treated rats was not significantly different, but the effects on Jl----b and VT were greater. Jl----b rose from a control value of 78 +/- 16 to 192 +/- 14 with AVP, and VT hyperpolarized from -4.2 +/- 1.6 to -12.2 +/- 0.4. All of these effects of AVP in the normal and DOC-treated rat CCD persisted for greater than or equal to 90-150 min. In DOC-treated rabbit tubules, AVP caused a stable increase in Pf from 9 +/- 6 to 800 +/- 199, which was significantly greater than in normal tubules (379 +/- 32). In the normal rabbit CCD we confirmed previous observations that AVP produces only a transient increase in Na+ absorption and VT; Jl----b increased from 76 +/- 4 to 96 +/- 7 during the period 15-25 min after AVP addition but subsequently fell to 80 +/- 6; VT transiently hyperpolarized from -55 +/- 7 to -64 +/- 8 at 3-8 min after AVP and then fell to -54 +/- 9. In DOC-treated rabbit CCDs, AVP produced no change whatsoever in Jl----b, which was not significantly different from the control value of 99 +/- 7, nor in VT, which was -68 +/- 8 mV. These results indicate fundamental differences in the response of the rat and rabbit CCD to AVP and the presence or absence of synergistic interactions with mineralocorticoids, which may relate to their differing response to other autacoids.
The cellular events involved in generating the hypoxic pulmonary vasoconstriction response are not clearly understood, in part because of the multitude of factors that alter pulmonary vascular tone. The goal of the present studies was to determine if a cell culture preparation containing vascular smooth muscle (VSM) cells could be made to contract when exposed to a hypoxic atmosphere. Cultures containing only fetal bovine pulmonary artery VSM cells were assessed for contractile responses to hypoxic stimuli by two methods. In the first, tension forces generated by cells grown on a flexible growth surface (polymerized polydimethyl siloxane) were manifested as wrinkles and distortions of the surface under the cells. Wrinkling of the surface was noted to progressively increase with time as the culture medium bathing the cells was made hypoxic (PO2 approximately 25 mmHg). The changes were sometimes reversible upon return to normoxic conditions and appeared to be enhanced in cells already exhibiting evidence of some baseline tone. Repeated passage in culture did not diminish the hypoxic response. Evidence for contractile responses to hypoxia was also obtained from measurements of myosin light chain (MLC) phosphorylation. Conversion of MLC to the phosphorylated species is an early step in the activation of smooth muscle contraction. Lowering the PO2 in the culture medium to 59 mmHg caused a 45% increase in the proportion of MLC in the phosphorylated form as determined by two-dimensional gel electrophoresis. Similarly, cultures preincubated for 4 h with 32P and then exposed to normoxia or hypoxia for a 5-min experimental period showed more than twice as much of the label in MLCs of the hypoxic cells.(ABSTRACT TRUNCATED AT 250 WORDS)
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The effect of almitrine bismesylate on the hypoxic pulmonary vasoconstrictor response was studied in six closed-chest dogs anesthetized with pentobarbital and paralyzed with pancuronium. The right lung was ventilated continuously with 100% O2; the left lung was ventilated either with 100% O2 ("hyperoxia") or with an hypoxic gas mixture ("hypoxia": end-tidal oxygen tension = 60.3 +/- 0.6 mm Hg). On two consecutive days, each dog received either almitrine (Vectarion, Servier Lab) or malic acid. Consecutive almitrine doses of 0.003, 0.03, 0.3, and 3.0 micrograms.kg-1.min-1, or the equivalent volumes of malic acid without almitrine, were administered intravenously as a constant peripheral infusion for 15 min. Percent blood flow to each lung was calculated based on a variation of the traditional shunt equation. The change in percent left lung blood flow (delta %QL-VA) increased significantly between the hypoxia-no drug and the hypoxia-almitrine (3.0 micrograms.kg-1.min-1) phase. No significant changes occurred during the other almitrine doses or the respective malic acid control phases. The change in arterial oxygen tension (delta PaO2) also increased significantly between the hypoxia-no drug and the hypoxia-almitrine (3.0 micrograms.kg-1.min-1) phase. No significant changes occurred during the other almitrine doses or the respective malic acid control phases. It is concluded that in dogs low-dose almitrine enhances hypoxic pulmonary vasoconstriction and that this enhancement is dose-related.
This paper, contrary to skepticism about the human ability to perceive topological properties, addresses some commonly heard nontopological counterexplanations and provides evidence to rule out these apparent counterexamples against the topological hypothesis. Data from improved control conditions show that the reason why these counterexamples seem inconsistent with the topological hypothesis is that they fail to take due account of two factors: visibility, and organization other than physical connectedness.
The hemorheologic alterations were studied in experimental acute hemorrhagic necrotizing pancreatitis (AHNP) which was induced by injection of 5% sodium taurocholate into the main pancreatic duct. The results showed that during the early stage of AHNP, all of hemorheologic parameters were significantly elevated, and continually increased at the rest intervals. The authors suggested that the blood viscosity and hematocrit increase, red blood cells tend to aggregate, and erythrocyte deformation decrease are the causation of pancreatic microcirculatory disturbances and promoting pancreatic progressive necrosis. After using low molecular dextran and Salvia miltiorrhizae, the hemorheologic alterations in AHNP were recovered, and the histologic observation improved. Our data indicate the hemorheologic disturbances is one of the key factors in the pathogenesis of AHNP.
A 27-year-old male patient, a machinist, had median neuropathy after a minor contusion on his right wrist and underwent carpal tunnel release under the impression of carpal tunnel syndrome five years ago. However, symptoms persisted and a small palmar nodule was found one year later. This slow-growing palmar nodule was locking the flexor tendon and the carpal tunnel was re-explored. At the second operation, the nodule was found to be a pigmented villonodular synovitis of the flexor tendon sheath at the palm. After excision of the lesion, the patient became symptom free. After three years, no recurrence was noted. Exploration of the carpal tunnel is recommended when median neuropathy of the wrist responds poorly to conservative treatment or to previous surgical release of the transverse carpal ligament. Although carpal tunnel release is not a difficult procedure, the pathology has to be checked carefully, so that even a small nodule within or near the carpal tunnel is not neglected, as in this case.
Two cases of congenital spinal arachnoid cysts with paraparesis are presented. Case 1, a 16-year-old male patient, had a 2-year history of progressive weakness of the lower limbs. Postmyelographic axial computed tomography (CT) and myelography revealed a dorsally located extradural mass. The configuration of the mass was further assessed with magnetic resonance imaging (MRI). He underwent laminectomy from T8 to L1 with total excision of an extradural arachnoid cyst. A communication with the subarachnoid space found at the T8 level was surgically closed. The patient made an uneventful recovery. Case 2, a 9-year-old girl, developed paraparesis and the cauda equina syndrome two days prior to admission. Postmyelographic CT and myelography revealed an anteriorly located intradural mass. She underwent laminectomy from C6 to T2 and partial removal of an intradural arachnoid cyst. One week later, her neurological functions had recovered completely. The literature dealing with this rare spinal lesion is also reviewed.
Nineteen patients with carcinoma of the larynges and 1 patient with carcinoma of the pyriform sinus were studied by comparing preoperative CT scannings with corresponding postoperative pathological findings obtained by serial sectioning of the laryngeal specimens. The results indicated that CT could clearly show the mucosa and deep tissues of the larynx including paraglottic space, preepiglottic space and subglottic region. The determination of cartilage invasion larger than 5mm was very accurate and reliable. It also significantly enhanced preoperative T-staging accuracy of medium and large laryngeal carcinomas and provided an important basis for selection of laryngeal conservative surgery. Nevertheless, CT scanning of the larynx has certain limitations.
Six ingredients were isolated from the whole plant of Dactylicapnos torulosa (Hook. f. et Thomas.) Hutchins. Four of them were identified by UV, IR, 1HNMR and 13CNMR. One of them is a new compound named zijinlongine(I). The three others are 1-methoxyberberium chloride(II), triethylphenylammonium chloride (III) and isocorydine(IV). II and III were isolated from plants for the first time.
Analysis was made of the gluco, lipometabolic materials and trace elements in bile from patients. The specimens were collected in 11 cases with acute purulent cholangitis and 13 cases of selective biliary surgery at both inter-operational time, at which the bile were got by needling from the common bile duct, and post-operational time, at which the bile was obtained from T tube drainage bile before the extraction of the T tube or discharge from hospital. It was found that lactic acid and glucose markedly decreased and LDH activity increased in the cholangitis group at inter-operational time. Lifted hepatic glyconeogenesis and gluco-consumption and hepatic cellular damage were indicated. At the same time, most of the lipo-materials and lipase activity increased, as compared with the selective group, which showed that lipolysis was encouraged and that lipo-materials had flowed into the bile because of hepatic cellular damage. At the time of acute cholangitis, the Zn and Fe in bile markedly increased but the Cr in bile decreased, and the mechanism was not clear.
The authors report the results of penetrating keratoplasty combined with cataract extraction in 50 cases. The rate of transparent grafts was 62% after an average follow-up of 19 months. 60% of the patients restored their vision to 0.1 and better. The rate of transparent grafts and visual improvement did not correlate with the mode of cataract extraction; however, the extracapsular procedure had less vitreous during operation than the intracapsular modality did. The authors recommend that the combined operation be adopted for patients with corneal opacity and cataract, and preferably using the extracapsular mode.