Microinsemination by sperm transfer.
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Female↗
Biomedical subjects
P Leung
Publications and source records attributed to P Leung.
Antagonism of the lethal effects of cyanide with resealed erythrocytes containing rhodanese and thiosulfate.
A new concept has been presented for the antagonism of cyanide and possibly other chemical toxicants. Until now, only a half dozen truly specific "antidotes" were known. There are many other "antidotes" which merely prevent the absorption or enhance the elimination of a toxic compound rather than specifically destroying the substance to prevent its toxic effect. This new approach has considerable conceptual significance in toxicology, as it suggests the encapsulating other enzymes to degrade various other chemical toxicants. There are many chemical toxicants for which there are no specific antidotes, and the conceptual approach of employing erythrocyte-encapsulated enzyme provides an innovative, specific approach to antagonize the toxic and lethal effects of these chemicals.
Animals↗
Patterns of recurrence of malignant astrocytoma following stereotactic interstitial brachytherapy with iodine-125 implants.
The pattern of tumor recurrence was studied in a series of 68 patients who were treated with interstitial brachytherapy for malignant astrocytoma. Thirty-six patients had newly diagnosed tumors and were treated following surgery and external beam therapy, while 32 were treated for recurrent tumors. Recurrence pattern was determined using computed tomography at the time of clinical deterioration. Thirty-eight percent of tumor recurrence occurred within the original tumor margin and 50% occurred at the original site but extended beyond the initial margin. In all, 88.0% recurred at the initial tumor site, 71.4% being confined to within 2 cm of the pretreatment tumor borders while 6.0% recurred intracranially outside of the initial tumor margin. One patient recurred with spinal metastasis while two patients developed systemic metastases. The significance of these findings is discussed.
Adolescent↗
Molecular biology of the 2-oxo-acid dehydrogenase complexes and anti-mitochondrial antibodies.
The confluence of molecular biology and clinical medicine has provided new and valuable insights in PBC. Our understanding of the immunobiology of PBC has changed dramatically using this new technology. It is now possible to explicitly define mitochondrial autoantigens and examine recognition sites, by using autoantibodies, at the primary sequence level. In addition, cloned antigens have been developed to reliably assay for presence of autoantibodies; the use of cloned recombinant antigens should replace that of traditional immunofluorescence for AMA assay. It is also now possible to begin the task of defining the role of T cells in the immunopathology of PBC and exploring the issue of whether immunotherapy is possible. Finally, there is increasing evidence that PDC-E2 is located on the cell membrane of biliary epithelial cells. The mechanism for this expression remains to be studied. The explosion of data in PBC is an example of the serendipity and synergy brought about by application of new techniques to investigate old problems.
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
M4 and M9 antibodies in the overlap syndrome of primary biliary cirrhosis and chronic active hepatitis: epitopes or epiphenomena?
Before the identification of the major mitochondrial antigens of primary biliary cirrhosis as components of the 2-oxo-acid dehydrogenase enzyme family, mitochondrial autoantigens were believed to be extremely heterogeneous and were divided into nine subtypes termed M1 to M9. This classification was based on the data derived from the relatively nonspecific biochemical and immunological techniques that were available. After the cloning and definition of the major autoantigens, more than 95% of the sera of patients with primary biliary cirrhosis were found to react with components of the 2-oxo-dehydrogenase enzymes; these enzymes correspond to the old M2 classification. Two other "M" species, dubbed M4 and M9, have attracted significant attention because they have been postulated to be prognostic indicators and more recently have been tentatively identified respectively as sulfite oxidase (EC 1.8.3.1) and glycogen phosphorylase (EC 2.4.1.1). Indeed, patients with the "overlap syndrome" are reported to have antibodies to M4 and a poor prognosis, whereas patients with antibodies to M9 have a favorable prognosis. To address the significance and definition of M4 and M9, we performed in-depth studies of sera from 11 patients with the overlap syndrome, 75 patients with primary biliary cirrhosis, 19 chronic active hepatitis patients, 13 patients with primary sclerosing cholangitis, 10 patients with cholangiocarcinoma, 20 patients with systemic lupus erythematosus, 20 patients with alcoholic cirrhosis, 17 patients with scleroderma and 30 normal individuals, using techniques of ELISA, complement fixation, immunoblotting and enzyme inhibition. We report herein that we were unable to show any disease-specific reactivity toward the proposed M4 and M9 antigens.(ABSTRACT TRUNCATED AT 250 WORDS)
Adenoma, Bile Duct↗
Antagonism of the lethal effects of cyanide with rhodanese containing murine carrier erythrocytes.
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Animals↗
In vivo studies on rhodanese encapsulation in mouse carrier erythrocytes.
Resealed erythrocytes containing sodium thiosulfate and rhodanese (CRBC) are being employed as a new approach in the antagonism of cyanide intoxication. In earlier in vitro studies, the behavior of red blood cells containing rhodanese and sodium thiosulfate was investigated with regard to their properties and their capability of metabolizing cyanide to thiocyanate. The present studies are concerned with the properties of these rhodanese-containing carrier erythrocytes in the intact animal. These carrier erythrocytes were administered intravenously and the survival of the encapsulated enzyme was compared with the administration (iv) of free exogenous enzyme. Also, the amount of leakage of the encapsulated rhodanese from the red blood cell was determined. The survival of the carrier red blood cell. prepared by hypotonic dialysis, was found to be characterized by a biphasic curve. There was an initial rapid loss of approximately 40 to 50% of the carrier cells with a t1/2 = 2.5 hr. Subsequently the remaining resealed annealed carrier erythrocytes persisted in the vascular system with a t1/2 = 8.5 days. When free exogenous rhodanese was administered directly into the vascular system, it was rapidly eliminated with a t1/2 = 53 min. Red blood cells containing sodium thiosulfate and rhodanese apparently are effective in vivo in the biotransformation of cyanide. In animals pretreated with encapsulated rhodanese and sodium thiosulfate, blood cyanide concentrations are appreciably decreased with a concomitant increase in thiocyanate ion, a metabolite of cyanide. When erythrocytes, which contained no rhodanese or sodium thiosulfate, were subjected to hypotonic dialysis, cyanide was not metabolized to any appreciable extent. Furthermore, carrier erythrocytes containing rhodanese and sodium thiosulfate were found to increase the protection against the lethal effects of cyanide by approximately twofold. The ability of these carrier erythrocytes alone to metabolize cyanide and to antagonize the lethal effects of cyanide reflects the potential of this new antidotal approach in the antagonism of chemical toxicants.
Animals↗
Rhodanese and sodium thiosulfate encapsulated in mouse carrier erythrocytes. II. In vivo survivability and alterations in physiologic and morphologic characteristics.
Biodegradable drug carrier mechanisms were employed in drug antagonism studies. Prior studies indicated that erythrocytes containing encapsulated rhodanese and sodium thiosulfate metabolized cyanide to thiocyanate in vitro. Studies were conducted to investigate the properties of these sulfurtransferase-loaded red blood cells in vivo by administering the carrier red blood cells intravenously. Approximately 40 to 50% of the cells were eliminated within the first few hours while the remaining loaded erythrocytes persisted in the circulation. The present studies were initiated to investigate the characteristics of the disposition of the loaded erythrocytes and to examine differences in the properties between carrier and noncarrier erythrocytes. Also, the disposition and viability of the erythrocytes in vivo were studied with relation to various biochemical, physiological, and morphological properties. These studies indicated that the carrier erythrocytes had a smaller cell volume and were more susceptible to hemolysis than normal erythrocytes. Morphologic studies by electron microscopy indicated that extensive morphologic changes occurred during the procedures after hypotonic dialysis, isotonicity adjustment, and resealing were completed. Differences were noted between those cells that were only resealed and those cells that were also subjected to annealing. The morphologic characteristics of most of the cells were restored to the "normal" morphologic appearance only after annealing. Annealed erythrocytes' in vivo survivability was correlated with the physical properties of these cells.
Animals↗
Interstitial brachytherapy for malignant brain tumors: preliminary results.
The authors report their experience with interstitial brachytherapy in 46 patients with malignant brain tumors. Twenty-three patients received implants after external radiation for newly diagnosed malignant astrocytoma, as part of a randomized study (Group I). Eighteen patients received implants for recurrent malignant astrocytoma (Group II) and 3 for recurrent solitary cerebral metastasis from adenocarcinoma of the lung (Group III). Two additional patients received implants as part of their initial therapy for a radiation-induced malignant astrocytoma and a malignant fibrous histiocytoma. In all patients high-activity iodine-125 sources were implanted temporarily by a stereotactic technique. To date 50 patients have been entered in the randomized study with a maximum follow-up of 31 months. The small numbers and short follow-up preclude any conclusions regarding the efficacy of brachytherapy used as part of initial therapy. The median survival to date in the 23 patients in this group who received implants is 60 weeks. The median survival to date for the 18 patients who received implants for recurrent malignant astrocytoma is 44 weeks postimplant. Two of the three patients who received implants for recurrent solitary metastasis are alive at 41 and 49 weeks postimplant; a third died at 39 weeks postimplant. Significant complications attributable to interstitial brachytherapy have been observed in 10 of 46 patients (21.7%). A second operation for clinical and radiological deterioration was performed in 12 patients (26.1%) 8 to 105 weeks after brachytherapy. The authors conclude that interstitial brachytherapy is beneficial for selected patients with recurrent malignant astrocytoma and solitary recurrent metastasis.(ABSTRACT TRUNCATED AT 250 WORDS)
Adolescent↗
Aminoglycoside dosing regimen and pharmacokinetic parameters in the guinea pig.
To complement a study on aminoglycoside dosing regimen and ototoxicity in the guinea pig, we designed an experiment to examine: (1) the effect of dosing regimen on guinea pig pharmacokinetic parameters, and (2) possible differential accumulation after repeated intramuscular administrations of netilmicin and amikacin (150 mg/kg/day) for 7 days by 1 or 3 daily injections. The area under the curve (AUC infinity) and the maximum plasma concentration (Cmax) were dose-dependent. Within each regimen, no significant difference was observed between days 1 and 7. Little or no accumulation was observed after 21 days of treatment. The results show a good dose-dependence of AUC infinity and Cmax and are in accordance with data from human studies. Moreover, the fact that no accumulation occurred in the guinea pig suggests that it is a suitable animal model to evaluate the relation between aminoglycoside ototoxicity and dosing regimen.
Amikacin↗
Sjögren's syndrome and primary biliary cirrhosis: presence of autoantibodies to purified mitochondrial 2-OXO acid dehydrogenases.
Sjögren's syndrome is well known for the presence of antibodies directed at specific nuclear antigens. However, the presence of antibodies reacting with a variety of other self antigens, including antimitochondrial antibodies, has often been reported although their significance is unknown. Moreover, patients with Sjögren's syndrome have been occasionally reported to be concordant with primary biliary cirrhosis. To address this issue we studied in a group of 96 patients with Sjögren's syndrome the presence of autoantibodies to the dihydrolipoamide acetyltransferases of both pyruvate dehydrogenase and branch chain ketoacid dehydrogenase and to alpha-ketoglutarate dehydrogenase; these latter enzymes are the mitochondrial target antigens of primary biliary cirrhosis. We report that 7 of the 96 patients reacted with the mitochondrial antigens that are prominent in primary biliary cirrhosis. Moreover, in those patients showing reactivity with mitochondrial antigens, the autoantibodies were directed at the same immunodominant epitopes that have been previously characterized in primary biliary cirrhosis. One of the 7 positive patients was known to have primary biliary cirrhosis. We hypothesize that the remaining 6 patients are at clinical risk for the development of primary biliary cirrhosis and/or that abnormalities would be found on liver biopsy.
3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
Influence of food on the absorption of albuterol Repetabs.
A study was conducted in 12 healthy, nonsmoking male volunteers to examine the effect of food intake on the absorption profile of albuterol repeat-action tablets. This randomized crossover study consisted of two phases separated by a 1-week washout period. All subjects fasted 10 hours preceding drug administration. Each subject received two 4 mg albuterol repeat-action tablets with and without a high fat content breakfast. Plasma albuterol concentrations were determined by a gas chromatographic/mass spectrophotometric assay. Relative bioavailability was assessed by comparing areas under the plasma-albuterol concentration time curves as well as peak concentrations and time to peak concentration. No significant differences were noted between the two treatment phases in the area under the curve or peak plasma concentrations. The areas under the curve were 100 and 105 hr.ng/ml when the drug was administered with and without food, respectively. The corresponding peak plasma concentration values were 9.4 and 10.4 ng/ml, respectively. The only significant difference observed was in the maximum time to reach peak plasma concentrations, which was delayed by about 1 hour when the drug was administered with food. Therefore, food has minimal effect on the absorption of albuterol from repeat-action tablets.
Adult↗
Clonidine in Cambodian patients with posttraumatic stress disorder.
Some symptoms of posttraumatic stress disorder (PTSD) are related to central nervous system adrenergic hyperarousal. It has been suggested that an adrenergic receptor-blocker could be used to diminish, if not alleviate, the target symptoms of PTSD. Severely traumatized Cambodian refugee patients (N = 68) who suffered from chronic PTSD and major depression improved symptomatically when treated with a combination of clonidine and imipramine. A prospective pilot study of nine patients using this combination of an alpha-2 adrenergic agonist and a tricyclic antidepressant resulted in improved symptoms of depression in six patients, five to the point that DSM-III-R diagnoses were no longer met. The average decrease in the Hamilton Rating Scale for Depression score was 16. PTSD global symptoms improved in six patients but only in two to the point that DSM-III-R diagnoses were not met. There was no further sleep disorder in five and the frequency of nightmares lessened in seven patients. Startle reaction improved only in four patients; avoidance behavior showed little improvement in any of the nine. The imipramine-clonidine combination was well tolerated and presents a promising treatment for severely depressed and traumatized patients, although further studies are needed.
Adult↗
Metoclopramide-associated parkinsonism mimicking functional psychiatric illness.
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Aged↗
Autoantibodies of primary biliary cirrhosis recognize dihydrolipoamide acetyltransferase and inhibit enzyme function.
Autoantibodies against mitochondria occur in the sera of patients with primary biliary cirrhosis (PBC) with characteristic reactivity to an inner membrane protein of approximately 74 kDa. To precisely define these autoantigens, we recently cloned and sequenced a rat liver cDNA (pRMIT) that encodes for all of the epitopes recognized by Ig to the 74-kDa autoantigen. In the present study we have used this recombinant probe as a tool, in addition to purified enzymes, to demonstrate by immunoblotting that the 74-kDa mitochondrial autoantigen is dihydrolipoamide acetyltransferase (EC 2.3.1.12), the core protein of the pyruvate dehydrogenase complex. Furthermore, and of particular interest, inhibition of pyruvate dehydrogenase enzyme activity was demonstrated after incubation with sera from patients with PBC but not from normal volunteers or patients with chronic active hepatitis. Such inhibition was abrogated by absorption of the PBC sera with an expressing subclone of pRMIT, designated pRMIT-603. Identification of dihydrolipoamide acetyltransferase as the target of autoimmunity in PBC provides a reagent that can be used to determine mechanisms by which this molecule is recognized. It will allow study of whether autoimmune reactivity, at the humoral or T cell level, is the basis for the pathogenesis of PBC. Additionally, such data present evidence of functional inhibition of a critical metabolic enzyme. Dihydrolipoamide acetyltransferase is well-known to mitochondrial biochemistry and, similar to identified autoantigens in other autoimmune diseases, is highly conserved in evolution.
Autoantibodies↗
The autoepitope of the 74-kD mitochondrial autoantigen of primary biliary cirrhosis corresponds to the functional site of dihydrolipoamide acetyltransferase.
Autoantibodies to mitochondrial antigens are characteristic of the autoimmune liver disease primary biliary cirrhosis (PBC), but the precise antigenic determinants recognized by these antibodies have not been defined. Recently, our laboratory identified a 1,370-bp rat liver cDNA clone that coded for a polypeptide recognized specifically by sera from patients with PBC but not by sera from patients with other forms of liver disease. This recombinant protein was identified as the 74-kD M2 mitochondrial inner membrane autoantigen, now known to be dihydrolipoamide acetyltransferase. In the present study, we have identified a 603-bp fragment that codes for a polypeptide containing all of the autoreactivity of the original clone. In addition, based on hydrophobicity/hydrophilicity plots of the amino acid sequence of this polypeptide segment, several peptides were synthesized and tested for reactivity by an inhibition assay using sera from patients with PBC. One peptide, defined by the amino acids AEIETDKATIGFEVQEEGYL, absorbed serum reactivity to the protein product of the original clone. Of particular interest was the finding that this peptide contains the lipoic acid binding site KATIGF of the dihydrolipoamide acetyltransferase found in the inner mitochondrial membrane. Thus, it appears that for this autoantigen, the target of the autoantibodies corresponds to a functional site of the dihydrolipoamide acetyltransferase.
Acetyltransferases↗
The mechanism of cyanide intoxication and its antagonism.
The mechanism of cyanide intoxication has been attributed to the inhibition of cytochrome oxidase, thereby decreasing the tissue utilization of oxygen. One mechanism of cyanide antagonism is by sequestering cyanide with methaemoglobin to form cyanmethaemoglobin and another mechanism is detoxifying with a sulphur donor to thiocyanate. Questions have been raised with regard to these classical mechanisms. Oxygen with nitrite-thiosulphate antagonizes the lethal effects of cyanide. Theoretically, increased oxygen should serve no useful purpose, as it is the tissue utilization of oxygen which is inhibited. In the nitrite-thiosulphate antidotal combination, the proposal is made that the predominate antidotal action of nitrite is a vasogenic action, rather than methaemoglobin formation, because when methaemoglobin formation is inhibited by methylene blue the protective action of sodium nitrite persists. This suggests that methaemoglobin formation plays only a small part, if any, in the therapeutic antagonism of the lethal effects of cyanide. The roles and implications of sodium thiosulphate and non-rhodanese substrates in the detoxification mechanism are compared. Lastly, a new approach to cyanide antagonism has been initiated which involves the erythrocyte encapsulation of thiosulphate and sulphurtransferase as an antidote and prophylaxis against cyanide.
Animals↗
Group therapy with Southeast Asian refugees.
This report describes a one-year experience with a new program of group therapy for Southeast Asians who were treated in a psychiatric program for Indochinese refugees. Cultural factors involving communication styles, respect for authority, and traditional social relationships greatly influence the group process. Socialization experiences which encouraged traditional activities and practical information were the most acceptable medium by all the groups. Psychological issues of losses, cultural conflicts, and persistent discussion of somatic symptoms were voiced throughout the activities. Formal group psychotherapy was periodically useful in some groups. Flexibility, meeting concrete needs, keeping a bicultural focus, and maintaining the individual therapy sessions contributed to the acceptance by the patient.
Acculturation↗