Biomedical subjects
Publications and source records attributed to D Lee.
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Subcutaneous protein C concentrate (Immuno, Vienna) was used to treat a child with homozygous protein C deficiency who was formerly treated with intravenous protein C concentrate. After 3000 units subcutaneous protein C concentrate (250 iu/kg), protective protein C levels were maintained for 48 h after infusion, with peak levels at 12 h. Subcutaneous protein C concentrate is given every third day and is well tolerated by the patient. No thrombotic events have occurred. We conclude that subcutaneous administration of protein C concentrate is a valuable therapeutic option in the long-term management of homozygous protein C deficiency and avoids the potential hazards of long-term central venous lines.
Thiopurine methyltransferase (TPMT) catalyzes the S-methylation of thiopurine drugs. Individual variation in the toxicity and therapeutic efficacy of these drugs is associated with a common genetic polymorphism that controls levels of TPMT activity and immunoreactive protein in human tissues. Because of the clinical significance of the "pharmacogenetic" regulation of this enzyme, it would be important to clone the gene for TPMT in humans and to study the molecular basis for the genetic polymorphism. As a first step toward cloning the gene for TPMT, we used the rapid amplification of genomic DNA ends to obtain a TPMT-specific intron sequence. That DNA sequence was used to design primers for the polymerase chain reaction (PCR), which made it possible to determine that the active gene for TPMT is located on human chromosome 6. A TPMT-positive cosmid clone was then isolated from a human chromosome 6-specific genomic DNA library, and the gene was sublocalized to chromosome band 6p22.3 by fluorescence in situ hybridization. The gene for TPMT was found to be approximately 34 kb in length and consisted of 10 exons and 9 introns. On the basis of the results of 5'-rapid amplification of cDNA ends, transcription initiation occurred at or near a point 89 nucleotides upstream from the translation initiation codon of previously reported TPMT cDNAs. Once the structure of the TPMT gene had been determined, it was possible to perform the PCR with primers complementary to the sequences of introns flanking each exon that encodes enzyme protein with template DNA obtained from subjects with known phenotypes for the TPMT genetic polymorphism. This DNA was isolated from blood samples from 4 unrelated subjects with genetically low TPMT activity and 4 unrelated subjects with high TPMT activity. All subjects with low TPMT activity were homozygous for two point mutations--a G-->A transition at nucleotide 460 in exon 7 and an A-->G transition at nucleotide 719 in exon 10. Both mutations resulted in alterations in amino acid sequence, with Ala-154-->Thr and Tyr-240-->Cys, respectively. All DNA samples isolated from the blood of subjects with high TPMT activity contained "wild-type" sequence. Results obtained with these blood samples were confirmed when DNA from four human liver samples with high TPMT activity were found to have wild-type sequence at nucleotides 460 and 719, while three liver samples with intermediate enzyme activity (i.e., samples presumed to be heterozygous for the polymorphism) were heterozygous for the exon 7 and exon 10 mutations present in the blood samples of homozygous low subjects. Transient expression in COS-1 cells of TPMT expression constructs that contained both of the mutations in exons 7 and 10, as well as each independently, demonstrated that each mutation, as well as both together, resulted in decreased expression of TPMT enzymatic activity and immunoreactive protein. Molecular cloning and structural characterization of the TPMT gene as well as elucidation of the molecular basis for a common TPMT genetic polymorphism will help make it possible to develop DNA-based diagnostic tests for the polymorphism and to determine the mechanism by which it results in decreased expression of this important drug-metabolizing enzyme.
Conventional radiofrequency (RF) ablative techniques have shown promise for the treatment of symptomatic benign prostatic hyperplasia (BPH); however, present RF technology is limited by the small lesion size, necessitating several probe placements and heating cycles to achieve sizable lesions. This limitation is attributable primarily to a rapid increase in electrical impedance secondary to tissue desiccation and charring at the electrode tip. We devised a hollow screw-tip needle electrode that permits fixation to tissue, recording of temperature and impedance, infusion of fluid, and delivery of RF energy. Infusion of electrolyte solution (i.e., saline) into tissue prevents impedance rise by conducting RF energy away from the metal electrode and permits the creation of large lesions. By varying the conductivity of the perfusate (concentration and temperature), lesions of large diameter can be created in a controlled manner. To determine the long-term tissue effects, we applied this new modified RF technique to the prostates of five mongrel dogs in a chronic (0.5 to 8-week) study. The screw-tip electrode was serially embedded into each lobe of the perineally exposed glands with 1-minute infusion of 0.9% saline (2 mL/min) followed by application of RF energy (500 KHz, 50 W, 2-18 minutes) along with continuous saline infusion. Thermocouples were embedded 5 mm below and at the gland capsule, and RF application was discontinued when the temperature reached 50 degrees C at the periphery. Postoperatively, the animals were examined daily for clinical status and weekly for glandular changes using transrectal ultrasonography. At predetermined intervals, the animals were sacrificed and the prostates excised, measured, sectioned, and examined for histologic changes. Ablative tissue temperatures of 50 to 100 degrees C were produced while impedance remained stable. Four animals required a single catheterization for relief of urinary retention between days 2 and 3; otherwise, all animals demonstrated a quick and uneventful recovery with no edema detectable on day 7 ultrasound examination. The outside dimensions of the gland remained relatively constant throughout the study (+ or - 0.39 cm L + W + H). Histologic examination revealed coagulation necrosis (ablation) in both lobes of all prostates (69.94% + or - 16.62% of the gland) with tissueless cavities forming from the ablation area (28.71% + or - 8.24% of the gland) contained within the capsule surrounded by healthy tissue at the periphery. Intraprostatic lesions were obtained without any gross damage to surrounding tissue, including the bladder and rectal wall. Utilizing a liquid conductor in prostate tissue allows a single electrode-placement heating cycle for controlled ablation for the potential treatment of BPH. This new technique produces more extensive and uniform lesions than conventional RF procedures, and lesion size is limited only by the duration of RF energy application.
Approximately 500 million years ago, the Paleozoic era heralded an evolutionary marvel: the skeleton. Unique to this evolutionary development was the capacity for regeneration: the physiologic renewal of embryologically derived tissue. Many of the cellular and molecular components for bone regeneration have been identified (bone morphogenetic proteins), and their therapeutic manipulation will become common clinical practice. Moreover, synthetic materials produced in the laboratory and novel bone derivatives will be used to exploit the skeleton's capacity to regenerate and repair. The concept of repair may be viewed as the restoration of form and function to deficient osseous tissue. Materials that provoke repair can be categorized broadly as bone substitutes. In this review, bone substitutes are grouped into 2 categories, polymers and ceramics, and each is subclassified as biodegradable or nonbiodegradable. Examples of these materials are provided as well as some of their liabilities and virtues.
The alarming increase in human immunodeficiency virus (HIV) infection, expected to reach 40 million cases worldwide by the year 2000, has enormous impact on the otolaryngologist, since up to 70% of HIV-positive patients present with head and neck symptoms. Parenteral and nonparenteral acquisition of HIV has been documented with seroconversion from needle sticks estimated at 1 for every 200 exposures. The rate of compliance with universal precautions is found to be reported as low as 16%. In 1993, over 1400 patients with HIV were admitted to Kings County Hospital Center. There were 165 reported cases of sharp injuries of which 4 were scalpel related and 17 were suture needle related. We surveyed HIV safety experiences at five hospitals emphasizing operating room procedures, including instrument handling, gloving, elimination of excess equipment and personnel, utilization of nonsharp instruments, and team discipline. Preventive measures are recommended to help minimize inadvertent sharp injuries.
Over 90% of all cutaneous malignancies occur in the head and neck. Malignancies involving the external auditory meatus, auricle, and periauricular region are notoriously difficult to control. The morbidity and mortality associated with extension of these malignancies underscore the importance of complete initial removal. We present 14 patients who underwent excision of periauricular lesions. All lesions were less than 2 cm in diameter and previously excised with negative margins. These patients were subsequently referred for regional disease. Twenty-nine percent of the patients failed definitive surgical therapy. We examine the indications for regional lymphadenectomy in the treatment of auricular and periauricular cutaneous malignancies.
Several cDNA clones encoding 4-coumarate:coenzyme A ligase (4CL) were isolated from a tobacco (Nicotiana tabacum) cDNA library and grouped into two classes. Sequencing of one cDNA from each class showed that the clones were similar to other 4CL genes and about 80% identical with each other. Genomic Southern blots using DNA from Nicotiana sylvestris, Nicotiana tomentosiformis, and N. tabacum demonstrated the presence of both classes of 4CL sequences (4CL1 and 4CL2) in the progenitor species and in tobacco. Northern blots indicated that 4CL mRNA transcripts are highest in old stems and higher in the unpigmented corolla tubes than in the pigmented limbs of tobacco flowers. The 4CL genes are developmentally regulated and are wound and methyl jasmonate inducible. The relative abilities of recombinant 4CL1 and 4CL2 proteins to utilize 4-coumarate, ferulate, and caffeate as substrates were similar and comparable with that of 4CL in tobacco stem extracts. Surprisingly, both recombinant 4CL proteins utilized cinnamate as a substrate, an activity not observed in stem extracts. This activity was inhibited by a heat-labile, high-molecular-weight factor found in tobacco stem extracts, suggesting that the substrate specificity of 4CL is, in part, determined by the activity of proteinaceous cellular components.
In order to compare the anaesthetic staffing and facilities provided for patients undergoing electroconvulsive therapy with those provided for patients undergoing elective cystoscopy, a confidential telephone enquiry was conducted. An anaesthetist in each of the 40 hospitals where electroconvulsive therapy is performed in three Health Regions chosen at random was questioned. The results show that a high standard of care is provided for patients undergoing elective cystoscopy in terms of pre-operative assessment, anaesthetic assistance, intra-operative monitoring and postoperative recovery facilities. The standards of care and of facilities for patients undergoing electroconvulsive therapy are substantially inferior and commonly fall short of accepted national guidelines.
Recent studies have suggested the secretion of Atrial Natriuretic Peptide (ANP) is regulated by receptor mediated activation of protein kinase C, which causes the autocrine release of prostaglandins. Prostaglandins stimulate ANP secretion via the adenylate cyclase second messenger system. This report examined the response of right and left atrial ANP secreting cells to the three endothelin isopeptides and to cyclooxygenase inhibition. Our results show that right atrial ANP secretion is stimulated by endothelin 1 and 2 but not 3. In addition, right atrial ANP secretion is reduced by inhibition of cyclooxygenase. In contrast, left atrial ANP secretion is stimulated by endothelin 2 and 3 but not 1. Inhibition of cyclooxygenase did not affect left atrial ANP secretion. These results show the regulation of ANP secretion is different between the two atrial chambers. Right atrial cells appear to contain the prostaglandin-mediated response to protein-kinase C activation, whereas left atrial cells regulate ANP secretion differently.
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The data presented in this manuscript describes the binding characteristics of [3H]SB 209670, a potent nonpeptide tritium-labeled endothelin (ET) receptor antagonist. The binding of this antagonist to cloned human ETA and ETB receptors was specific, saturable and of high affinity. The apparent dissociation constants were 0.20 and 1.0 nM for ETA and ETB receptors, respectively. The maximum binding was 4.7 and 22.5 pmol/mg protein for ETA and ETB receptors, respectively. Unlike [125]ET-1, the binding of [3H]SB 209670 was reversible. The half-times (T1/2) for dissociation of this ligand from ETA and ETB receptors were approximately 60 and 10 min, respectively. Competition binding studies using [3H]SB 209670 and unlabeled agonists ET-1, ET-3 and S6c indicated that these agonists displayed similar affinities for human ETB receptors, whereas with ETA receptors, ET-1 was approximately 50-fold and 1500-fold more potent than ET-3 and S6c, respectively. Of the peptide antagonists tested, BQ123 (ETA-selective peptide antagonist), displayed Ki values of 40 and > 2300 nM for ETA and ETB, whereas RES701 (ETB-selective antagonist) displayed Ki values of > 1600 and 81 nM for ETA and ETB receptors, respectively. The nonselective peptide antagonist, PD 142893, was approximately 2-fold more potent for ETA compared with ETB receptors. Similar observations were made with nonselective nonpeptide antagonists, Bosentan, (+/-) SB 209670, SB 209670, and (-) SB 209670. All these compounds were 2 to 10 times more potent for ETA than ETB receptors.
Inflammation often is considered a contributing factor to both thrombosis and disseminated intravascular coagulation. The molecular mechanisms that dictate which of these clinical manifestations will result from the inflammatory stimulus remain obscure. Bacterial infection and certain tumors are common initiators of the disseminated intravascular coagulant response. Complement activation resulting from bacterial infection shares with selected tumors the capacity to generate or release membrane particles that lack functional adhesion receptors and hence could circulate to amplify a disseminated intravascular coagulant response. We developed a model of venous thrombosis that resulted in localized thrombus formation without disseminated intravascular coagulation. The model involves infusion of tumor necrosis factor, blockade of protein C and a partial decrease in venous flow caused by ligation of the superficial femoral vein without obstruction of the deep formal vein. Infusion of phospholipid vesicles into this model resulted in amplification of a localized thrombotic response into a consumptive response. Seven different groups of animals were studied. The first three groups established the conditions necessary to produce deep vein thrombosis. The second four groups established the conditions necessary to produce disseminated intravascular coagulation. The infusion of phospholipid vesicles plus tumor necrosis factor and anti-protein C antibody resulted in consumption of fibrinogen, the production of thrombin/antithrombin complexes, a fall in platelet count, and venous thrombosis. Without ligation and catheterization phospholipid vesicles failed to produce the consumptive response. We conclude, therefore, that phospholipid vesicles can amplify a local thrombotic response into a consumptive response, and that vesiculation accompanying inflammation is one means by which localized coagulant activity may be amplified to produce disseminated intravascular coagulation.
Carbon monoxide intoxication usually disturbs the normal human biochemical respiratory chain cascade from which high affinity of carboxyhemoglobin to oxygen causes ischemic insult to the human tissues and cells. Ubiquitous injuries to human cells have already been well documented for a long period of time. Here we reported a 42-year-old female who was sent to the medical emergent unit under the suspicion of carbon monoxide exposure mainly with neurologic deficits. Serum carboxyhemoglobin level was found to be 18%. Serial revolutional changes of serum CK level and ECG were noted. The echocardiogram showed hypokinesia of left ventricular apical lateral wall. Normal coronary arteriogram was found in later admission date. The patient received hyperbaric oxygen therapy and was discharged with residual psychotic symptoms. This report presented normal coronary arteriogram with serial EKG and biochemical changes in a victim of CO intoxication with evidence of myocardial infarction. Impaired oxygen delivery and disturbed intracellular mitochondrial metabolism were considered to be responsible for the ischemic insult associated with carbon monoxide exposure. The role of hyperbaric oxygen therapy was also discussed in this report; however, more experiences in application are needed to determine it's benefits for patients.
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BACKGROUND: Any hypertensive patient may be found to have associated lung disease. The response of high blood pressure to specific antihypertensive agents in this category is still unknown. Thus, a group of 76 consecutive patients with mild-to-moderate hypertension and chronic obstructive pulmonary disease (COPD) were selected to participate in a clinical antihypertensive trial to define the roles of lisinopril, nifedipine and conventional therapy, and their impact on the renin-antiotensin system (RAS). METHODS: After a two-week placebo period, patients were randomly assigned to a regimen of one of three main treatment strategies: (A) lisinopril with or without diuretics; (B) nifedipine with or without diuretics; or (C) diuretics with or without conventional vasodilators (sorbitrate and hydralazine) or selective beta-blockers. The drug doses were titrated to a goal of less than 90 mmHg for maximal diastolic pressure, and the patients continued to receive therapy for at least one year. RESULTS: After one year of follow-up, only 66 patients had completed the study. All high blood pressure was significantly reduced by the three regimens (p < 0.005), but no significant difference in blood pressure control by any individual regimen was noted. Double product also showed the similar trend. Therapy A achieved the best reduction of double product among three regimens, but statis tieally insignificant. Furthermore therapy A suppressed the RAS, whereas therapies B and C might activate this system. Concomitantly, therapy A also had significant favorable effects on metabolic responses in contrast to therapy C. Therapy B revealed a neutral effect on such responses. CONCLUSIONS: These data indicated that these three main strategies could provide significant antihypertensive efficacy for blood pressure control in patients with hypertension and COPD. For preventive strategy, therapy A may provide more advantageous effects than therapy C. A long-term double-blind trial including more subjects is warranted to identify the true advantages of therapy A in reduction or major cardiovascular and respiratory events.
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