Biomedical subjects

S R Shih

Publications and source records attributed to S R Shih.

34 records · Page 2Linked to original sources

PubMed1996

Characterization of the cardiac effects of acute subarachnoid hemorrhage in dogs.

BACKGROUND AND PURPOSE: We know that significant cardiac involvement can occur in patients with acute intracranial hemorrhage, particularly in those with subarachnoid hemorrhage. These patients may present with electrocardiographic abnormalities that were previously thought to be benign. However, many die of cardiovascular sequelae, which suggests more serious cardiac problems. To characterize the cardiac, rhythmic, and myocardial disturbances that occur 2 to 4 hours after subarachnoid hemorrhage, we conducted an experimental study using autologous blood (7.9+/-0.3 mL) injected into the right frontal lobe and subarachnoid space in canines. METHODS: Nine adult mongrel dogs were anesthetized with isoflurane and their rectal temperatures maintained at 37 degrees C. Electrocardiogram, heart rate, mean arterial pressure, mean pulmonary artery pressure, and intracranial pressure were continuously measured. Transesophageal echocardiography was performed to assess myocardial wall motion changes and aortic and pulmonary flow velocities before, immediately after, and 2 and 4 hours after intracranial hemorrhage. Blood samples were collected and analyzed for catecholamines and cardiac enzymes, and cardiac output was measured. Animals were killed at 2 to 4 hours after subarachnoid hemorrhage, and a piece of the myocardium was freeze-clamped for analysis of tissue catecholamines. Light and electron microscopy were used for histopathologic assessment. RESULTS: Subarachnoid hemorrhage produced significant increases in intracranial pressure, cardiac output, and aortic and pulmonary flow velocities. Also, significant changes in creatine kinase and catecholamines were observed. Electrocardiographic recordings showed changes of tachycardia, ST-segment depression, inverted T wave, and premature ventricular contractions in four animals at 1 to 5 minutes after injection, and echocardiographic changes were evident in all animals at 20 to 240 minutes. Microscopic examination of the heart showed evidence of myocardial changes in one animal with the use of light microscopy and in nine with the use of electron microscopy. CONCLUSIONS: This study demonstrates the high incidence of cardiac involvement, specifically wall motion abnormalities, that occur after subarachnoid hemorrhage and suggests the importance of continuous cardiac monitoring, particularly echocardiographic measurements, in those patients.

Acute Disease↗

PubMed1995

The choice of alternative 5' splice sites in influenza virus M1 mRNA is regulated by the viral polymerase complex.

The influenza virus M1 mRNA has two alternative 5' splice sites: a distal 5' splice site producing mRNA3 that has the coding potential for 9 amino acids and a proximal 5' splice site producing M2 mRNA encoding the essential M2 ion-channel protein. Only mRNA3 was made in uninfected cells transfected with DNA expressing M1 mRNA. Similarly, using nuclear extracts from uninfected cells, in vitro splicing of M1 mRNA yielded only mRNA3. Only when the mRNA3 5' splice site was inactivated by mutation was M2 mRNA made in uninfected cells and in uninfected cell extracts. In influenza virus-infected cells, M2 mRNA was made, but only after a delay, suggesting that newly synthesized viral gene product(s) were needed to activate the M2 5' splice site. We present strong evidence that these gene products are the complex of the three polymerase proteins, the same complex that functions in the transcription and replication of the viral genome. Gel shift experiments showed that the viral polymerase complex bound to the 5' end of the viral M1 mRNA in a sequence-specific and cap-dependent manner. During in vitro splicing catalyzed by uninfected cell extracts, the binding of the viral polymerase complex blocked the mRNA3 5' splice site, resulting in the switch to the M2 mRNA 5' splice site and the production of M2 mRNA.

Alternative Splicing↗

PubMed1995

A new solution for life without blood. Asanguineous low-flow perfusion of a whole-body perfusate during 3 hours of cardiac arrest and profound hypothermia.

BACKGROUND: The benefits of hypothermia for preventing ischemic injury are well known, but its application in surgery to protect the whole body during procedures requiring circulatory arrest is currently limited to < 1 hour at 15 degrees C using 50% hemodilution. In a significant departure from previous methods, we have developed a technique of asanguineous blood substitution with low-flow perfusion and cardiac arrest at < 10 degrees C in a canine model. Our approach has been to design a hypothermic blood substitute that would protect the brain and visceral organs during several hours of bloodless perfusion. Two different solutions have been designed to fulfill separate requirements in the procedure. METHODS AND RESULTS: With the use of extracorporeal cardiac bypass, 14 adult dogs were exsanguinated during cooling; 11 dogs were blood substituted using in combination the "purge" and "maintenance" solutions (group 1), and 3 dogs were perfused throughout with the "purge" solution alone as controls (group 2). After cardiac arrest, the solutions were continuously circulated for 3 1/2 hours by the extracorporeal pump (flow rate, 40 to 85 mL.kg-1.min-1; mean arterial blood pressure, 25 to 40 mm Hg). The temperature was maintained at < 10 degrees C (nadir, 6.6 +/- 0.1 degrees C) for 3 hours, and the hematocrit was kept at < 1% before controlled rewarming and autotransfusion. In the experimental group, the heart always started spontaneously in the temperature range of 11 degrees C to 27 degrees C, and 8 animals have survived long-term (current range, 14 to 110 weeks) without any detectable neurological deficit. In contrast, two control animals survived after extensive and aggressive cardiac resuscitation efforts; after surgery they exhibited transient motor and sensory deficits for approximately 1 week. Evaluation of biochemical and hematological parameters showed only a transient and inconsequential elevation in enzymes (eg, brain, liver, cardiac) in group 1 compared with the markedly greater elevations in group 2. For example, immediate postoperative values (mean +/- SEM) for lactate dehydrogenase were 114 +/- 10 for group 1 versus 490 +/- 210 for group 2 (P < .03); for SGOT, values were 93 +/- 18 for group 1 versus 734 +/- 540 for group 2 (P < .05). On day 1 for creatine kinase (CK), the group 1 value was 7841 +/- 2307 versus 71,550 +/- 2658 for group 2 (P = .03), and for CK-BB, the group 1 value was 108 +/- 22 versus 617 +/- 154 for group 2 (P = .03). Neurological evaluation using deficit scores (NDS) was based on a modification of the Glasgow Coma Scale score: 0, normal; 1, minimal abnormality; 2, weakness; 3, paralysis; 4, coma; and 5, death. At days 1 and 2 after surgery, NDS (mean +/- SEM) were 0 +/- 0 for the experimental group versus 1.5 +/- 0.5 for the control group. At days 3 and 7 after surgery, NDS were 0 +/- 0 for group 1 versus 1.0 +/- 1.0 for group 2. CONCLUSIONS: The faster neurological recovery of dogs treated with the "intracellular-type" maintenance solution supports the biochemical data showing the benefits of this type of blood substitute for extending the safe limits of hypothermic cardiac arrest procedures to > 3 hours.

Animals↗

PubMed1994

Molecular cloning of the common carp (Cyprinus carpio) rhodopsin cDNA.

A recombinant phage clone containing a 1584 nucleotides rhodopsin cDNA was screened from a carp retinal cDNA library. The inserted DNA consisting of a single open reading frame of 1062 nucleotides at positions 72 to 1133 encodes a 354 amino acid polypeptide. The deduced amino acid sequence of carp rhodopsin showed 95.7, 85.5 and 74.4% identity with that of goldfish, sand goby and lamprey, respectively. The sites of palmitoylation, glycosylation, disulfide bond formation and Schiff base formation in the putative rhodopsin are all conserved.

Amino Acid Sequence↗

PubMed1993

Stimulation of endothelin production in cultured human endothelial cells by fluorescent compounds associated with blackfoot disease.

The fluorescent compounds (FC) in humic substances isolated from the drinking water of endemic areas of blackfoot disease have been characterized as the causative factor of the disease. In this report we studied the effects of these fluorescent compounds on the synthesis and secretion of endothelin-1 by cultured human umbilical cord vein endothelial cells (HUVEC) in order to explore the possible pathological mechanism(s) of FC in the development of atherothrombotic vasculopathy in blackfoot disease. Incubation of confluent HUVEC with FC (100 micrograms/ml) enhanced endothelin mRNA expression. A sensitive ELISA method was developed to quantitate secreted endothelin antigen levels in conditioned medium. Incubation of confluent HUVEC cultures with different concentrations of FC (0-200 micrograms/ml) resulted in concentration-dependent enhanced production of endothelin. No significant changes in endothelin production were observed when subconfluent HUVEC cultures were incubated with FC. FC dose-dependently reduced the growth rate of subconfluent cultured HUVEC and exerted cytotoxic effects on the viability and integrity of confluent HUVEC monolayers. Since endothelin is one of the most potent vasoconstrictors affecting blood pressure and blood flow, and is mitogenic for smooth muscle cell proliferation, these results imply that the enhanced endothelin production and the reduced cell viability and growth rate induced by FC may contribute to the atherothrombotic vasculopathy observed in blackfoot disease.

Arterial Occlusive Diseases↗

PubMed1993

Rewarming, ultraprofound hypothermia and cardiopulmonary bypass.

Rewarming, a key event in resuscitation from accidental, experimental and clinical hypothermia, is sometimes followed by neurologic, cardiac, and respiratory sequelae and may lead to death. The rate of rewarming has been implicated but not quantified as etiologic in these sequelae. Under anesthesia fifteen dogs were cannulated and connected to an extracorporeal circuit for oxygenation, core cooling and rewarming. They were subjected to ultra-profound hypothermia with a core (esophageal) temperature as low as 1.3 degrees C, cardiac arrest, blood substitution, and continuous low flow perfusion. After 2-3 hours of cardiac arrest, rewarming began. Mechanical activity of the heart was seen between 10 degrees and 28 degrees C and respiration resumed at 29 degrees C. The rewarming rates of the 15 dogs were retrospectively studied. They were placed into three categories (G) based on the outcome. G-I (N=2):no neurological complications, G-II (N=8):transient neurological problems, and G-III (N=5):death, mainly from cardiovascular and respiratory complications confirmed at death by autopsy. Heat gain by each animal was recorded as a function of time for all experiments. The time it took each dog to reach 35 degrees C was determined and a mean was calculated (rewarming rate). Normal body temperature for a dog is 37.8 degrees C. Statistical analysis (ANOVA) was performed ex post facto to determine the relationship between rewarming rate and outcome. Our data contradicts the notion that slow core rewarming from nadir to normal temperature offers better outcome.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1992

Blood substitution: an experimental study.

Priming fluids for cardiopulmonary bypass have been extremely varied, with resultant hemodilution. Furthermore, major surgeries utilizing cardiopulmonary bypass require multiple postoperative transfusions of blood and blood products. The appeal of having a readily available blood substitute for major cardiovascular and neurosurgical operations could prove to be a life saver, while also eliminating the risk of diseases transmitted by transfusion. Blood substitutes could also lessen the reported complications resulting from blood damage due to prolonged circulation of the blood by the extracorporeal pump. A technique was examined in 15 dogs using hypothermia for maximum metabolic suppression, incorporating an aqueous blood substitute (Cryomedical Sciences, Inc., Rockville, MD). The anesthetized animals were cannulated for extracorporeal pump oxygenation. As temperature was lowered the dogs were exsanguinated and volume replaced with blood substitute to lower the hematocrit to less than 1%. After 3 hours of cardiac arrest and continuous perfusion at a core temperature less than 10 degrees C, rewarming began. When temperature reached greater than or equal to 10 degrees C, the blood substitute was drained and the animals were autotransfused. The heart was started at 15 degrees C and spontaneous respiration resumed at 29 degrees C. Using the first generation blood substitute the survival rate was maximal (100%) at 2.5 hrs under 10 degrees C and 3 hours of cardiac arrest. Research is underway on a new blood substitute, which is to serve as a universal hypothermic preservation solution (in situ organ preservation).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Ultraprofound hypothermia with complete blood substitution in a canine model.

The potential for hypothermia to prevent or ameliorate ischemic injury to the central nervous system is well known. To determine if a more prolonged period of metabolic suppression with blood substitution is possible, a method was developed to lower body temperature to near the freezing point. Eight adult mongrel dogs underwent closed-chest extracorporeal circulation with both external and internal body cooling. As they were cooled, progressive hemodilution was employed until complete exsanguination and blood substitution with an aqueous solution was accomplished. Continuous circulation and a core temperature at a mean of 1.7 degrees C were maintained from 2 1/2 to 3 hours. After rewarming to 20 degrees C, the animals were autotransfused and allowed to recover. Of the eight animals, two died due to technical factors related to cardiac defibrillation. Of the six surviving animals, five survived over a long period and one died on the 10th postoperative day with hepatorenal failure resulting from a presumed blood transfusion incompatability reaction. All six showed normal neurological function and kennel behavior, except one dog with mild weakness of a hindlimb. When the dogs were sacrificed 1 to 2 months postoperatively, all organs were histologically normal. Specifically, there was no gross or microscopic evidence of ischemic or hypoxic injury to any central nervous system structures. This pilot study demonstrates that it is possible to successfully achieve complete exsanguination, blood substitution, and ultraprofound body temperature, while continuous circulation of the blood substitute is maintained. With the capability of controlling and repeatedly performing washout of the extracellular environment and by reaching lower temperatures, it may be possible to attain greater cellular metabolic suppression. This perhaps will extend the allowable times for circulatory arrest procedures. In addition, "bloodless ischemia" may be beneficial in removing both blood substances and formed elements which may mediate organ ischemia. With replacement of blood at warm temperatures, coagulopathy is avoided. This preliminary evidence demonstrates potential in the combination of ultraprofound hypothermia and complete blood component substitution. However, further study is required to confirm the potential of achieving circulatory arrest of longer duration.

Animals↗

PubMed1990

The effect of fluorescent humic substances existing in the well water of Blackfoot disease endemic areas in Taiwan on prothrombin time and activated partial thromboplastin time in vitro.

Fluorescent humic substances (FHS) in well water of Blackfoot disease endemic areas were purified and fractionated by Sephadex G-25 column chromatography. Four fractions of the purified FHS were isolated. The purified FHS and their fractions were then added to normal human pool plasma in vitro separately to detect the abilities of the effects on prothrombin time (PT) and activated thromboplastin time (APTT). Results showed that all of the four fractions of the purified FHS prolonged both PT and APTT in the higher concentration ranges (10 mg/ml - 20 mg/ml), but shortened both PT and APTT in the lower concentration ranges (0.5 mg/ml - 5 mg/ml). Among the four fractions of the FHS, the fraction 1, the humic substance with the highest molecular weight among all the four FHS, showed the most obvious effects. Owing to the effects of the FHS on PT and APTT values, we supposed that there is a close relationship between the FHS and the cause of Blackfoot disease.

Arsenic↗

PubMed1990

CO2-laser radiation damage of the arterial wall.

This study describes the effects of CO2 laser radiation on the histology of the normal rabbit arterial wall, using models that simulate laser angioplasty and anastomosis. Rabbit arteries were exposed to laser treatments similar to those used clinically; 40, 0.5 sec pulses of 40-60 mW, CO2 continuous wavelength laser, or a 1/2-circumferential laser anastomosis with a 60-80 mW continuous pulse. Aneurysms developed in 8 of 22 femoral, 1 of 22 carotid, and no controls at 12 week. There were small breaks in the internal elastic lamina with atrophy, loss of muscularis, "packing" of the elastica, thinning of the muscularis at the damage site, and enlargement of the arterial diameter. Aneurysms developed in one femoral and no carotid anastomosed artery. Laser anastomoses demonstrated more muscle damage and loss, with extensive scarring and a wider area of elastic loss than the controls. The intima was reestablished with focal reduplication of the internal elastic lamina. There were no histologic differences between the arteries which developed aneurysms and those which did not in either series. These results suggest that low power laser damage of the arterial wall consists mainly of destruction of the muscularis propria, with minimal damage to the elastica.

Anastomosis, Surgical↗

PubMed1989

Splanchnic tissues are a major part of the rapid distribution spaces of inulin, urea and theophylline.

Distribution of kinetics of inulin, [14C]urea and theophylline were studied in five anesthetized dogs after splenectomy and gastrointestinal resection. Distribution was modeled with three-compartment mammillary systems in which the central compartment corresponds to intravascular space and the two peripheral compartments have different rates of transcapillary exchange. Compared with results in intact dogs, the surgical procedure removed between 41 and 55% of the rapidly equilibrating tissues and reduced the permeability coefficient-surface area products for the rapidly equilibrating inulin and urea compartments proportionately. This is consistent with the concept that splanchnic organs equilibrate rapidly with inulin and urea because they are supplied by fenestrated and discontinuous capillaries that are prominent in the splanchnic vascular bed. However, splanchnic organs probably do not contain all rapidly equilibrating tissues, and somatic tissues may contribute as much as 36 and 22%, respectively, of the rapidly equilibrating inulin and urea compartments. Cardiac output averaged 2.87 +/- 0.86 liters/min and was similar to the sum of compartmental blood flows estimated from the intercompartmental clearances of urea and inulin (2.74 +/- 0.96 liters/min) and to the sum of theophylline intercompartmental clearances (2.62 +/- 0.74 liters/min). Theophylline intercompartmental clearance to each peripheral compartment was similar to estimated compartmental blood flow.

Animals↗

PubMed1989

Pulmonary venous anastomosis in lung transplantation without donor left atrium. Experimental and clinical results.

Single lung transplantation now is a therapeutic option for some patients with end-stage lung disease. Cyclosporine immunosuppression and refinements in bronchial anastomosis have been responsible for recent successes. Since 1953, the usual pulmonary venous anastomosis, both in experimental animals and in humans, has been an atrium-to-atrium connection. This technique may limit the availability of usable donor lungs, since the donor heart, along with the atrium, is usually harvested for another recipient. Although techniques can be developed to allow both transplant teams to harvest atrial tissue, this study was undertaken to determine if, in fact, anastomosis with donor left atrium is necessary. Twenty-four dogs were anesthetized and a left thoracotomy performed. After heparinization (3 mg/kg), the pulmonary artery and left atrium were occluded. One of four different pulmonary venous anastomoses was performed at 3.5x magnification: superior pulmonary vein end to end (group I), inferior pulmonary vein end to end (group II), superior pulmonary vein implantation into left atrium (group III), and left atrium-to-left atrium anastomosis as control (group IV). Everting mattress sutures of 7-0 polypropylene were used in groups I, II, and III and 6-0 in group IV. Average crossclamp time for group I, group II, and group IV was 20 minutes. The average crossclamp time for group III was 10 minutes. All anastomoses were patent at the time of 1-week reevaluation. Gross and microscopic examination demonstrated establishment of an intimal lining; organized nonocclusive thrombus was present in only one anastomosis. We conclude that atrium-to-atrium anastomosis is not necessary for a successful single lung transplantation, and that transplantation of a single lobe is feasible. The best alternative is implantation of the pulmonary vein into the left atrium, which will easily allow use of the heart and both lungs from a single donor to different recipients. We have used this anastomosis in one patient without difficulty.

Anastomosis, Surgical↗

PubMed1987

Arterial aneurysm model using laser energy.

Continuous wavelength laser energy can be used to perform arterial anastomoses, but all experimental series report an incidence of anastomotic aneurysm formation. To elucidate the mechanism of aneurysm production, controlled injuries of the arterial wall were created with a pulsed CO2 laser beam (40-50 mW). One carotid and one femoral artery of 10 New Zealand rabbits were injured with laser and the contralateral vessel was exposed surgically as a sham operation. At reoperation 8 to 11 weeks later, all 40 arteries were patent. None of the carotid shams, one carotid laser, two femoral shams, and eight femoral laser vessels (80%) were aneurysmal. Histologic examination revealed extensive medial necrosis with fragmentation of the internal elastic lamina in the area of these aneurysms. Femoral vessels were significantly smaller than carotids (P less than 0.001) and the high incidence of aneurysm formation in the former may be due to the relatively greater area of injury. This new model of aneurysm formation after laser injury suggests a need for further study prior to clinical application of this technology, especially in vessels smaller than 2 mm in diameter.

Aneurysm↗

PubMedDate not supplied

Hypothermic blood substitution enables resuscitation after hemorrhagic shock and 2 hours of cardiac arrest.

Uncontrollable hemorrhage accounts for a large proportion of total mortality in both civilian (31%) and military (47%) trauma victims. Hypothermia is a relatively safe method that could provide total body protection during hypovolemic shock and facilitate surgical intervention as a potentially life-saving procedure. This study tested the hypothesis that profound hypothermia and complete blood replacement in an established canine model, would facilitate resuscitative therapy from exsanguinating hypovolemic shock. Adult dogs were prepared for extracorporeal bypass using closed-chest peripheral cannulation under general anesthesia. Controlled hypotensive, hemorrhagic shock (mean arterial blood pressure < 50 mmHg) was induced for 30 min at normal temperature followed by temporary resuscitation using crystalloid infusion for approximately 10 min. Using our established procedure, the dogs were then cooled externally to 27 degrees C before initiating blood substitution with Hypothermosol (Cryomedical Sciences, Inc. Rockville, MD) via the extracorporeal pump. The heart was arrested during further cooling to below 10 degrees C and Hypothermosol was recirculated for 2 hr, with (3 dogs) or without (5 dogs) 1 hr of circulatory arrest. During rewarming the animals were autotransfused, weaned from the pump, and allowed to recover. All dogs (n = 8) survived, all but one with complete neurologic recovery: blood chemistry samples examined immediately after the procedure showed significant differences (p < 0.05) in only a few parameters, including creatine kinase (CK-BB and CK-MB), compared with the previous group of control dogs. The consistent survival of dogs showing apparently normal neurologic, physiologic, and biochemical recovery supports the concept that profound hypothermia using a protective hypothermic blood substitute could provide time for therapeutic resuscitation of currently intractable trauma cases.

Animals↗

PubMedDate not supplied

A pilot investigation of poloxamer 407 for the prevention of leptomeningeal adhesions in the rabbit.

Leptomeningeal adhesion formation frequently complicates operations and diseases of the central nervous system. Chronic adhesive arachnoiditis may follow intraspinal surgery for disc, tumor, and closure of myelomeningocele, eventually producing pain and declining neurological status of the patient. Reoperation for scar removal is seldom successful as the arachnoidal adhesions reform. Poloxamer 407 (P407) has been shown to reduce postoperative peritoneal adhesion formation in rats and golden hamsters. In a rabbit model, we investigated the potential of P407 to prevent the production of arachnoidal adhesions and nerve root scarring following laminectomy and surgical meningeal injury. The lumbar spinal roots of 8 New Zealand white rabbits were surgically isolated under magnification. One root sleeve axilla was opened and immediately closed with 10-0 suture (control site) and a second root sleeve axilla was opened, P407 injected, and closed with 10-0 suture (treatment site). Five of 7 rabbits treated with P407 and followed for 7-42 days showed no arachnoidal adhesions at the level of the nerve root. Four New Zealand white rabbits had the lamina removed, and the dura over the spinal cord was opened at two sites separated by one to two lumbar segments. At one site P407 was inserted beneath the dura following durotomy, and the other site was opened in a similar fashion and immediately closed without the insertion of P407. There was a 50% reduction in leptomeningeal adhesion formation with the use of P407. P407 may be useful in neurosurgery for the prevention of arachnoidal adhesions.

Animals↗

PubMedDate not supplied

Ultraprofound cerebral hypothermia and blood substitution with an acellular synthetic solution maintains neuronal viability in rat hippocampus.

The acute effects of ultraprofound hypothermia and blood substitution (UHBS) on neuronal cell viability were examined in adult rat hippocampus, a brain region particularly vulnerable to ischemic cell death. UHBS was performed using either artificial cerebrospinal fluid (ACSF) or Hypothermosol, an "intracellular-type" hypothermic preservation solution. After the procedure, the hippocampus was sliced and tested for cellular viability using a combination of cellular fluorochromes that are markers for live cells (acridine orange) and dead cells (propidium iodide). UHBS with ACSF resulted in a variable degree of neuronal death within the hippocampal subfields CA1/CA3, and dentate granular layer and hilus (CA4). In contrast, UHBS with Hypothermosol consistently resulted in hippocampal slices with only mild neuronal death. Our results of preserved hippocampal neuronal viability with use of UHBS and Hypothermosol support the demonstrated central nervous system (CNS) protective effects of UHBS and Hypothermosol when used during prolonged cardiac arrest. The results of this study also suggest that UHBS and Hypothermosol may be useful in the preparation and maintenance of viable hippocampal tissue for physiological studies, especially those involving aged animals, which are particularly vulnerable to hypoxic-ischemic cellular injury

Animals↗