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Biomedical subjects

A Fox

Publications and source records attributed to A Fox.

At least 109 records · Page 6Linked to original sources
PubMed1993

Event-related potential indices of semantic processing in schizophrenia.

Event-related potentials (ERPs) were recorded while schizophrenic patients and healthy controls read congruous and incongruous sentences in anticipation of a memory test. The schizophrenic group performed more poorly in both recognition memory and cued recall tests. The two groups did not differ in the amplitude of the N400 component of the ERP but the difference between the ERPs to congruous and incongruous sentences persisted longer in the schizophrenic sample. The schizophrenic sample also showed reduced parietal positivity and a reduced effect of congruity on the late positive component that follows N400. Within the schizophrenic sample, measures of attentional impairment and positive thought disorder were correlated with mean amplitude of both the N400 and the subsequent positivity. The results imply that the structure and spread of activation within semantic memory is not impaired in schizophrenia. Rather, impairments appear to lie in processes required to integrate activated information with the current context.

Adolescent↗
PubMed1993

Activation of uterine intraepithelial gamma delta T cell receptor-positive lymphocytes during pregnancy.

Intraepithelial lymphocytes (IEL) of the uterus of non-pregnant sheep were analyzed by single- and two-color flow cytometry. Very few lymphocytes carrying classical B and T cell markers (CD5, surface immunoglobulin) were detected in the uterine epithelial cell suspensions and all IEL expressed the CD8 surface marker although with varying intensities. Three distinct subpopulations were identified including a major (46-56%) population of CD8+CD45R- gamma delta T cell receptor (TcR)-negative cells and approximately equal numbers of CD8+CD45R+ gamma delta TcR- and CD8+CD45R+ gamma delta TcR+ lymphocytes. The same three subpopulations were also present in the interplacentomal areas of the uterus of ewes at a late stage of pregnancy but there was a dramatic increase (60-70%) in the gamma delta TcR+ subpopulation. In addition, a pronounced increase in both size and granularity was observed in the IEL population of pregnant uteri and this was attributed to the gamma delta TcR+ cells. Light and electron microscopic examination of these gamma delta TcR+ IEL revealed an increase in metabolic activity and the formation of exceptionally large cytoplasmic granules and confirmed their restricted localization within the uterine epithelium close to the trophoblast. These results represent for the first time, a clear example of the activation of gamma delta TcR+ cells which is not associated with an ongoing disease process or infection. gamma delta TcR+ cells have recently been observed in the epithelium of the murine reproductive tract and were characterized by their unique homogeneous receptor structure. The present results indicate that these cells may play an important physiological role during pregnancy.

Animals↗
PubMed1993

Recurrent anterior uveitis induced by multiple systemic injections of muramyl dipeptide.

The development of new therapeutic modalities in the treatment of uveitis has been greatly aided by the availability of suitable animal models. The endotoxin model excellently mimics many features of acute anterior uveitis. A new model that exhibits many features of recurrent anterior uveitis is described here. Muramyl dipeptide, MDP, is a synthetic monomer of Gram positive and Gram negative bacterial cell walls. The molecule is highly inflammatory, but unlike endotoxin does not elicit an antibody response. After a single injection (4 hr post-injection), acute anterior segment changes include massive engorgement of peri-limbal blood vessels, anterior chamber flare, fibrin deposits and heterophil (neutrophil) infiltration which subside within 24-48 hr. There is also break-down of the blood-aqueous barrier. With multiple injections the exacerbations and remissions continue to be observed after each injection but the disease progresses to a recurrent form including the development of synechiae and a mononuclear infiltrate into the anterior segment. The ocular changes are paralleled by changes in the bloodstream with recurrent heterophilia. Thus MDP does not elicit ocular or systemic tolerance. This new model of anterior uveitis should allow study of many of the events that occur in recurrent uveitis in man.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1993

P300 indexes thought disorder in schizophrenics, but allusive thinking in normal subjects.

Loosening of thinking as assessed by the Object Sorting Test (OST) has been found in a percentage of normal subjects but in a higher percentage of schizophrenics, and is familially transmitted in both groups. Loosening of thinking in normal subjects is not associated with evidence of impaired function or increased psychopathology, and in recognition of this, it was termed allusive thinking rather than thought disorder. Both OST-assessed loosening and concreteness of thinking were found to be present independently in a high percentage of schizophrenics, so that both were considered to contribute to schizophrenic thought disorder. The presence of OST-assessed loosening in schizophrenics would, therefore, be predicted to correlate partially rather than totally with measures of schizophrenic thought disorder. It has been suggested that OST-assessed loosening in normal subjects is due to a genetically determined reduction in strength of an inhibitory process that limits the spread of activation of semantic associations and results in a predisposition to schizophrenia. The brain event-related potential P300, which is, in part, under genetic control, may index this inhibitory process. Therefore, it was predicted that in normal subjects, P300 would correlate with OST-assessed loosening of associations. If schizophrenic thought disorder is due to a further weakening of this inhibitory process, it can be predicted that P300 in schizophrenics correlates only weakly with OST-assessed loosening of thinking, but more strongly with schizophrenic thought disorder. In a study in which P300 was elicited using a difficult selective attention task with 15 unmedicated schizophrenics and 22 healthy subjects, all three predictions were supported.

Adult↗
PubMed1993

Dilated heart failure in transgenic mice expressing the Epstein-Barr virus nuclear antigen-leader protein.

The Epstein-Barr virus nuclear antigen-leader protein (EBNA-LP) is required for high efficiency B lymphocyte growth transformation by the virus. To test the potential contribution of EBNA-LP to tumorigenesis in vivo, we produced transgenic mice carrying an EBNA-LP cDNA construct, using the widely expressed metallothionein promoter. Expression of EBNA-LP was detected in liver, kidney, heart, lung and spleen. There were no apparent oncogenic consequences of EBNA-LP expression. Unexpectedly however, at ages ranging from about 4 months to over a year, transgenic mice developed symptoms of congestive heart failure, including left ventricular dilatation, right ventricular hypertrophy, left atrial thrombosis, pulmonary oedema and hydrothorax. Fibrillation was not apparent in the electrocardiograph; however a reduction in T-wave amplitude suggested that the development of an abnormality of ventricular repolarization may precede the manifestation of overt symptoms. The highly predictable development of dilated heart failure in these transgenic mice suggests they may be a useful model for the pathophysiological changes associated with human dilated cardiomyopathy.

Animals↗
PubMed1993

Investigation of the "hangover" effects of an acute dose of alcohol on psychomotor performance.

Performance on some complex and difficult tasks has been shown to be negatively affected for some time after an acute dose of alcohol has been cleared from the system. However, Dauncey reported impairment of a relatively simple reaction time task 3 hr after a dose of alcohol, when the blood alcohol concentration was at or near 0. This impairment was positively related to the subject's drinking history. A replication using the same task found a linear dose/impairment relationship during intoxication. A second simple reaction time task and a vigilance task showed a trend toward impairment, but only a divided attention task was significantly affected during intoxication. There was no significant effect of dose on any of these tests during a "morning after" session. The results are discussed in relation to the differences in method between Dauncey and this study.

Adult↗
PubMed1993

Monitoring of bacterial sugars and hydroxy Fatty acids in dust from air conditioners by gas chromatography-mass spectrometry.

Bacterial levels in dust collected from hospital air-conditioning filters were examined by chemical analysis (without prior culture). The dust was analyzed by gas chromatography-mass spectrometry after hydrolysis and derivatization. l-Glycero-d-mannoheptose and hydroxy fatty acids (3-OH 12:0 and 3-OH 14:0) (primarily found in lipopolysaccharide) and muramic acid (a chemical marker for bacterial peptidoglycan) were present at higher levels in dust collected from filters primarily contacting outdoor (as opposed to indoor) air. The ratio of l-glycero-d-mannoheptose to muramic acid in dust (compared with those of a group of gram-positive and gram-negative bacteria) suggested that both dust types contained appreciable numbers of gram-negative bacteria. There is potential for the chemical assessment of the microbial content of airborne dust.

Journal Article↗
PubMed1993

Role of beta-hemolytic group C streptococci in pharyngitis: incidence and biochemical characteristics of Streptococcus equisimilis and Streptococcus anginosus in patients and healthy controls.

The biochemical characteristics and the isolation rates of the two Lancefield group C streptococcal species (S. equisimilis and S. anginosus) from patients with pharyngitis and asymptomatic controls were compared. Some 239 strains of beta-hemolytic group C streptococci were isolated from 1,480 patients (209 strains) with pharyngitis and 227 controls (30 strains). A total of 44 strains displayed broad hemolysis, were Voges-Proskauer test negative, and produced glucuronidase. Some 72.7% of these strains also fermented ribose. A second group of 159 strains was Voges-Proskauer test positive and glucuronidase negative; 98.8% also displayed minute hemolysis and only 3.7% fermented ribose. These two groups represent typical large-colony S. equisimilis and small-colony S. anginosus, respectively. A small number of strains (36 in total) exhibited intermediate characteristics; morphologically, all 36 strains resembled S. anginosus, but 6 strains biochemically resembled S. equisimilis. No strains of S. equisimilis fermented sorbitol (unlike S. zooepidemicus) and all fermented trehalose (unlike S. equi). The structural carbohydrate profiles of S. equisimilis and S. anginosus both included galactosamine (consistent with their being group C organisms), but the profiles were not distinguishable. In total, 78.5% of strains from controls and 83.3% of strains from patients were determined to be the species S. anginosus. S. equisimilis was isolated from 3.0% of patients and 2.2% of controls, and S. anginosus was isolated from 11.1% of patients and 11.0% of controls. Thus, S. equisimilis and S. anginosus are both members of the normal flora of asymptomatic individuals. The incidence and biochemical characteristics of these two species are similar in patients who are healthy and those who have disease. However, a companion article provides clinical evidence associating S. equisimilis (but not s. anginosus) with pharyngitis.

Adult↗
PubMed1993

Role of group C beta-hemolytic streptococci in pharyngitis: epidemiologic study of clinical features associated with isolation of group C streptococci.

All Lancefield group C beta-hemolytic streptococci isolated over 12 months from college students with clinical pharyngitis and age-matched healthy controls were identified. Clinical features of upper respiratory tract infection and pyogenic pharyngitis as well as colony counts were tabulated for each patient according to throat culture results. Of 1,480 patients, Lancefield group C Streptococcus equisimilis was isolated from 45 (3%) patients and Streptococcus anginosus ("Streptococcus milleri") was isolated from 164 (11.1%) patients. Patients from whom S. equisimilis was isolated had clinical features more suggestive of pyogenic infection than did patients from whom S. anginosus was isolated. Colony counts on primary throat culture plates from patients from whom S. equisimilis and Streptococcus pyogenes were isolated were higher than those from patients from whom S. anginosus was isolated. This study presents epidemiologic evidence supporting a role for S. equisimilis in causing pharyngeal infection and for S. anginosus as representing part of the normal oropharyngeal flora.

Adult↗
PubMed1993

Determination of carbohydrate profiles of Bacillus anthracis and Bacillus cereus including identification of O-methyl methylpentoses by using gas chromatography-mass spectrometry.

Bacillus anthracis and Bacillus cereus are closely related pathogenic organisms that are difficult to differentiate phenotypically or genotypically. It is well known that vegetative and spore forms of bacilli are quite distinct both morphologically and chemically, but spore-specific chemical markers allowing these species to be distinguished have not been previously described. By using gas chromatography-mass spectrometry, vegetative cells and spores of the two species were shown to exhibit distinct carbohydrate profiles. Profiles of vegetative B. anthracis typically contained high levels of galactose but did not contain galactosamine, whereas B. cereus contained galactosamine and generally low levels of galactose. Spore cultures exhibited unique carbohydrate profiles compared with those of vegetative cultures. B. anthracis spore profiles contained rhamnose alone, whereas B. cereus spore profiles contained rhamnose and fucose. Additionally, two spore-specific O-methylated methylpentoses were discovered. Both B. anthracis and B. cereus spores contained 3-O-methyl rhamnose, whereas B. cereus spores also contained 2-O-methyl rhamnose. Carbohydrate profiling is demonstrated to be a powerful tool for differentiating the two closely related species. Differentiation does not depend on whether organisms are in the vegetative or spore stage of growth.

Bacillus anthracis↗
PubMed1993

Cytokines cause cultured retinal pigment epithelial cells to secrete metalloproteinases and to contract collagen gels.

PURPOSE: Because retinal pigment epithelial cells in epiretinal membranes remodel and contract their surrounding extracellular matrix, investigations were performed to determine if these cells can produce matrix metalloproteinases and contract collagen gels in vitro in the presence of serum or cytokines. METHODS: Cells were grown on collagen gels and their production of metalloproteinases was measured using zymography. RESULTS: Cells grown in a three-dimensional collagen gel culture system produce several latent metalloproteinases that are secreted into the gel and the surrounding medium. These include molecules of 49, 56, 66, and 100 kD. In addition, an enzyme that is probably the active form of the 66 kD enzyme is present. When interleukin 1 beta is added to the cultures, latent 49 kD and 100 kD gelatinase production is greatly stimulated and an active form of both enzymes is also observed in the medium. In contrast, transforming growth factor beta has no stimulatory effect. The cells contract the collagen gel but this is small without cytokines; however, contraction is greatly enhanced in the presence of serum or interleukin 1 beta plus transforming growth factor beta. Contraction is unlikely to be the result of metalloproteinase action on the underlying extracellular matrix because complete inhibition of these enzymes has little effect. CONCLUSIONS: These results show that cytokines can cause cultured retinal pigment epithelial cells to produce metalloproteinases that can, when activated, degrade most collagens and other structural molecules in extracellular matrix. In addition, they can stimulate the contraction of extracellular matrix constituents but there is not a simple causal relationship between matrix remodeling and contraction.

Adult↗
PubMed1992

Patterns of infection after pediatric liver transplantation.

OBJECTIVE: To characterize the patterns of infection that occur after orthotopic liver transplantation in children. DESIGN: Inception cohort, retrospective. SETTING: Referral center for liver transplantation, university hospital. PATIENTS: Thirty-six consecutive children who underwent orthotopic liver transplantation and who survived for at least 48 hours after transplantation. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Twenty-six (72%) of the children had at least one infection, and infection caused four deaths. More infections occurred when prophylactic antilymphocyte antibodies were given than when they were not given (2.9 vs 1.0 infections per transplant). The risk of infection was greatest during the first 2 weeks after orthotopic liver transplantation. Most infections were caused by bacteria (52 cases), followed by viruses (16 cases) and fungi (11 cases). Bacteria were the most common pathogens during all periods, except the third and fourth weeks, when viruses predominated. The most common primary sites of bacterial infection were abdomen (15 cases), bloodstream (15 cases), and surgical wound (10 cases); the most frequent isolates were aerobic gram-negative bacilli (48% of isolates) and enterococci (19%). Cytomegalovirus was the most common viral pathogen (seven cases), and Candida albicans caused all fungal infections. Fungal infections were significantly associated with systemic antibiotic therapy and abdominal complications. CONCLUSIONS: Characteristic patterns of infection occur after pediatric orthotopic liver transplantation, and knowledge of these patterns is likely to result in improved care for transplant recipients.

Age Factors↗
PubMed1992

The relationship between relative's Expressed Emotion and schizophrenic relapse: an Australian replication.

We report a predictive study, carried out in Sydney Australia, investigating the association between the Expressed Emotion (EE) status of the household to which the patient is discharged and schizophrenic relapse. Expressed Emotion was not related to illness severity either at admission or discharge, but was related to variables reflecting chronicity and employment history. There was a significant association between returning to a high EE household and both re-hospitalisation and relapse. The significant association between EE and relapse held only for: patients not on medication, males, and those patients in high contact with their relatives. A discriminant function analysis found that decline in occupational status and the number of critical comments expressed by the relative were the strongest predictors of relapse. The results presented here are consistent with the majority of published reports on EE and relapse and contradict the negative findings of a recently published but smaller study also carried out in Sydney.

Adult↗
PubMed1992

The Sydney intervention trial: a controlled trial of relatives' counselling to reduce schizophrenic relapse.

The result of a psychosocial intervention which aimed to reduce schizophrenic relapse through relatives' counselling is presented. Thirty-six schizophrenic patients living in high Expressed Emotion (EE) parental households were randomly allocated to an intervention or control group. The parents of patients allocated to the intervention were offered ten weekly sessions of counselling. The patient was not included in these sessions. Patients in both groups received standard after-care of medication and support. Relapses in the intervention group, although fewer, were not significantly different from the control group. Given the impressive evidence in favour of family interventions in reducing relapse rates in schizophrenic patients possible reasons for this result are discussed. Aspects of the intervention described here, exclusion of the patient, no control over the patients' medication or involvement with their management, short duration of intervention and lack of individual assessment, could explain this finding. This negative result is important in indicating what factors should be included in an effective psychosocial intervention.

Adult↗
PubMed1992

Polypeptide profiles of normal and inflamed rabbit aqueous humor: identification of catabolic products of immunoglobulin G in the normal eye.

The anterior segment of the eye is isolated from the bloodstream by anatomic barriers. These barriers break down during inflammation elicited by muramyl dipeptide (MDP), a component of the cell walls of bacteria. The protein composition of normal aqueous humor and inflamed aqueous were characterized using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. The presence of transferrin, albumin, IgG and IgM were demonstrated in normal and inflamed aqueous. Normal aqueous additionally contained seven polypeptides (35, 31, 29, 25, 22, 21 and 19 kDa, respectively) that were not observed in inflamed aqueous. Four of these peptides (31, 29, 25 and 19 kDa) were identified as fragments of IgG heavy chains based on their reactivity with anti-IgG antibodies and staphylococcal protein A. Immunoglobulin catabolism has been noted to occur in tissues diffusely throughout the body; this is the first report of it occurring in the eye. This phenomenon appears to be circumvented on breakdown of the blood-aqueous barrier. These observations may relate to the immunoprivilege of the eye and its modulation in inflammation.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1992

The impact of magnetic resonance imaging on the management of acute ischemic stroke.

Despite rapid advances in imaging technology, the etiology of stroke remains unestablished in 40% of patients. MRI improves localization in acute stroke. However, it is not known whether "accurate localization" results in better management. We reviewed the hospital records of all patients admitted with a diagnosis of acute ischemic stroke and who had had cranial CTs and MRI within 10 days of admission. Between January 1987 and June 1990, 116 patients (69 men, 47 women; mean age, 66 years) were identified. Compared with CT localization, infarcts were better localized in nine of 39 patients with cerebral cortical lesions, in 20 of 22 patients with brainstem and cerebellar lesions, and in three of three patients with isolated cerebellar lesions. In 22 patients (18.9%), MRI showed multiple infarcts in two or more vascular territories, suggesting embolic disease and leading to anticoagulation. MRI also showed arterial occlusions in 11 patients (9.5%). Based on the information obtained with MRI, the clinical diagnosis was changed in 19 patients (16.3%), resulting in changes in the management of most of those patients. Thus, we confirm earlier reports that MRI improves localization after acute cerebral infarction and show that such information alters patient management.

Acute Disease↗
PubMed1992

Hemangioma of the masseter muscle.

Intramuscular hemangiomas are rare benign tumors of vascular origin. The masseter is the muscle most commonly involved in the head and neck. A case of intramuscular masseter hemangioma is presented, the literature reviewed, and appropriate diagnostic modalities discussed.

Adult↗