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Biomedical subjects

S Stephens

Publications and source records attributed to S Stephens.

At least 37 records · Page 2Linked to original sources
PubMed1988

Computerized real-time neuromuscular sonography: a new application, techniques and methods.

Diagnostic ultrasound has been extensively used for neurologic evaluation of cranial, vascular and spinal diseases. This study presents the techniques, methodology, and procedures for a new diagnostic application of ultrasound for evaluation of the neuromuscular system. In order to determine the optimum sonographic characterization of neuromuscular disease, normal anatomy has to be studied with ultrasound to develop a reproducible standardized methodology for routine use of ultrasound in neuromuscular imaging. To fulfill this objective, 30 subjects between the ages of 1 day and 59 years were studied with computerized real-time sonography. The results of this study are presented with illustration of the sonographic images of transverse and longitudinal planes of the upper and lower limbs. Computerization of optimum sonographic techniques, gradation of normal sonographic muscle anatomy by age, and elimination of operator variability were goals that were accomplished, thereby setting the stage for reliable, reproducible muscle imaging by ultrasound.

Adolescent↗
PubMed1988

Simultaneous therapy with high-dose cisplatin and radiation for unresectable squamous cell cancer of the head and neck: a phase I-II study.

Studies using simultaneous radiation therapy and conventional doses of cisplatin have suggested improvement in local control and patient survival. This study was undertaken to determine toxicity and patient tolerance to concomitant high-dose cisplatin (40 mg/m2 per day X 5) and radiation (60 Gy in 6 wk +/- 10-Gy boost to residual tumor). Seventeen patients with advanced, inoperable squamous cell cancer primary tumor in the head and neck were treated (15 males and 2 females; median age, 57 yr). Cisplatin was started on day 1 of radiation therapy and repeated every 28 days for three cycles. Normal saline infusion (250 ml/hr) was started 12 hours prior to the first dose and continued 12 hours after the fifth dose. The daily dose of cisplatin was dissolved in 250 ml of 3% NaCl and given over 30 minutes. The cisplatin dose for subsequent cycles was reduced 10 mg/m2 per day only for a nadir granulocyte count less than 500/mm3 or fever greater than 101 degrees F during leukopenia. Of the 17 patients who started therapy, 15 have completed therapy; 1 patient died after one cycle, and 1 died after two cycles. Eleven patients received three cycles of cisplatin, and 10 patients required one dose reduction (6 at course 2 and 4 at course 3). Seven possible infections were successfully treated. Grade 2 neuropathy occurred in 3 patients, and renal toxicity greater than grade 1 occurred in 1 patient. Additional toxic effects were median WBC count nadir of 1.8 X 10(3)/mm3, platelet count nadir of 128 X 10(3)/mm3, hemoglobin nadir of 9.8 g/dl, and median weight loss of 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

The pathogenesis of virus-associated encephalopathies: a prospective study of immunological mechanisms.

Thirty-two patients, including 29 children, presenting with acute unexplained encephalopathies were studied prospectively for evidence of virus infection, immunodeficiency, and immunologic involvement in the pathogenesis of their illnesses. Twenty-five of these patients had a clinical diagnosis of encephalitis. Twenty-two of these 25 had laboratory evidence of active virus infection, the majority with viruses usually associated with self-limiting illness outside the central nervous system. In patients with encephalitis, immune competence, as reflected by T-cell numbers and subsets in peripheral blood, in vitro interferon production, natural killer activity, and specific antiviral antibody production, was normal. Transudation of albumin into the cerebrospinal fluid (CSF), a measure of blood-brain barrier breakdown, was seen in 40% of patients. Intrathecal antibody synthesis was suggested by an elevated IgG index in 9/20 CSF/serum pairs but was confirmed by an elevated specific IgG ratio in only 3. The serum IgG1 and IgG3 subclass levels were significantly elevated at the time of the illness and remained elevated 8 months later; IgG2 and IgG4 levels were normal. IgE levels were elevated in 50% of patients. Serum levels of IgM antibodies against Escherichia coli measured 8 months after the neurological illness were also significantly higher in encephalitis patients than in age-matched healthy controls. Human myelin basic protein did not induce proliferation in peripheral blood lymphocytes in any patient. We conclude that most encephalopathies associated with viral infections are not due to an underlying generalized immunodeficiency, and probably result from an inappropriately vigorous immune response.

Adolescent↗
PubMed1986

Flow cytometry of DNA content using oxazine 750 or related laser dyes with 633 nm excitation.

The laser dyes oxazine 750 (OX750), LD700, and rhodamine 800 (R800) can be used in an instrument employing a low-power helium-neon laser source for flow cytometry of DNA content in ethanol-fixed or detergent-permeabilized cells. Cells in near-isotonic medium are stained with 10-30 microM dye, and fluorescence excited at 633 nm is measured at wavelengths above 665 nm. The dyes do not appear to stain RNA, and the intensity of DNA staining is not changed when 2 microM Hoechst 33342 is added to cells simultaneously with a red-excited dye. The effects on fluorescence of addition of DNA to LD700 or R800 in aqueous solution are strongly influenced by the base composition of the DNA; binding mechanisms remain to be determined.

Cell Line↗
PubMed1986

The contribution of large granular lymphocytes to B cell activation and differentiation after T-cell-depleted allogeneic bone marrow transplantation.

Immunoglobulin and specific antibody levels are well maintained in the recipients of T-cell-depleted allogeneic bone marrow transplants (BMT), even though up to 99% of mature T cells are removed from the donor graft. For 3-8 weeks after the procedure, natural killer (NK) cells with an activated pattern of target cell killing have been shown to circulate in the recipient. This study investigates whether these recipient NK cells spontaneously secrete lymphokines that modulate B cell function in a way analogous to that of in-vitro-activated NK cells from normal individuals. Large granular lymphocytes (LGLs) (which contain a high proportion of NK cells) have been prepared from the peripheral blood of 11 recipients of T-cell-depleted major-histocompatibility-complex-matched allografts. In the first 4-6 weeks after BMT these LGLs were found spontaneously to secrete interleukin 2, interferon gamma and B cell differentiation factor. While secretion of these factors declines by 20-24 weeks after BMT, the quantities are still greater than those seen from control donors. Patient LGLs are also able to activate autologous (donor) B cells, rendering them potentially responsive to the secreted factors. It appears likely that activated NK cells (or LGL) play a significant role in maintaining B cell function in vivo after T-cell-depleted BMT.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1986

Development of secretory immunity in breast fed and bottle fed infants.

Samples of saliva and nasal secretions were collected sequentially from 15 breast fed and 15 bottle fed infants on five occasions between 6 days and 9 months of age. Total immunoglobulin concentrations of G, M, and A classes, and class specific antibodies to tetanus toxoid and a pool of commensal strains of Escherichia coli were measured by solid phase radioimmunoassay and expressed per milligram of total protein. There were significant differences between feeding groups, which changed with age. Total IgM and IgA concentrations and IgA antibodies to E. coli were higher in the saliva and nasal secretions of breast fed infants at 6 days. There followed a rapid increase in IgM and IgA concentrations in secretions from all infants, and between 6 weeks and 9 months concentrations were higher in the saliva (but not in the nasal secretions) of the bottle fed group. There were no significant differences between the feeding groups for total IgG, specific G, M, and A antibodies to tetanus toxoid, and G and M antibodies to E. coli. These results suggest that breast feeding enhances secretory immunity in the early neonatal period only. By 6 weeks, local antigens are the main source of stimulation for production of immunoglobulin in the respiratory mucosa and thus may be obscuring any additional stimulation by growth factors in breast milk.

Aging↗
PubMed1986

The effect of breast-feeding on proliferation by infant lymphocytes in vitro.

The effect of breast-feeding on the development of lymphocyte responsiveness in infants has been studied. Peripheral blood mononuclear cells from 15 breast- and 15 bottle-fed infants were obtained sequentially between 6 days and 9 months of age. A number of agents were used to stimulate the cells in vitro and the resulting proliferative responses were compared between the two feeding groups. A hanging drop microculture system using serum-free medium, enabled spontaneous proliferation and proliferative responses to several stimuli (T and B cell mitogens, allogeneic lymphocytes, and antigen) to be studied at a range of cell concentrations and days of culture. Significant age-related differences were found between the responses of cells from the two feeding groups. Spontaneous proliferation and proliferative responses to the T cell mitogen phytohaemagglutinin and the antigen tetanus toxoid were significantly greater in the breast-fed group at the two earliest ages studied (6 days and 6 wk). Responses to mitogens which predominantly affect B cells, such as pokeweed mitogen and Staphylococcus aureus (Cowan), were similar in both feeding groups at this age. In contrast, from 3 to 9 months of age, responses of cells from bottle-fed infants were significantly greater to all stimuli than responses from breast-fed infants. One possible explanation for the higher level of proliferation by cells from newborn breast-fed infants, is that these infants may absorb the cell-growth factors and lymphokines known to be present in human colostrum and milk. These factors may stimulate T cells and/or their precursors in vivo.(ABSTRACT TRUNCATED AT 250 WORDS)

Breast Feeding↗
PubMed1986

A longitudinal study of gamma-interferon production by peripheral blood mononuclear cells from breast- and bottle-fed infants.

Production of gamma-interferon (gamma-IFN) in vitro by peripheral blood mononuclear cells (PBMC) from 15 breast-fed and 15 bottle-fed infants has been studied from birth to 9 months of age and compared with production by adult cells. Using a Terasaki plate microculture system with serum-free medium, PBMC were stimulated with staphylococcal enterotoxin A (SEA) and gamma-IFN production was assessed by an immunoradiometric assay. Cord blood mononuclear cells (CBMC) and PBMC from all infants secreted large quantities of gamma-IFN. The levels secreted did not change significantly with age over the 9 months of the study, nor did they differ from the levels secreted by adult cells. Cells from the bottle-fed infants secreted slightly more gamma-IFN than cells from breast-fed infants, but this difference was not significant. These results indicate that the potential for PBMC to secrete gamma-IFN in vitro is fully developed at birth in full-term infants and cannot therefore be further influenced by subsequent breast- or bottle-feeding. In addition, the greater susceptibility of infants than adults to certain bacterial and viral infections cannot be attributed to a deficiency in the potential of infant cells to secrete gamma-IFN in vitro.

Aging↗
PubMed1984

Development of a sensitive solid-phase radioimmunoassay technique for quantification of class-specific Escherichia coli antibodies.

A specific and sensitive, quantitative solid-phase radioimmunoassay (RIA) has been developed for the detection of Escherichia coli antibodies in serum and secretions. Preparation of affinity-purified anti-E. coli standards allows accurate quantification of G, M and A classes of antibody down to 10 ng/ml using only 20 microliters of sample. This technique has considerable advantages over indirect haemagglutination in sensitivity and accuracy of immunoglobulin class detection. RIA also compares favourably with ELISA in sensitivity and sample size required. Affinity-purified standards may also be used to quantify the ELISA test.

Adult↗
PubMed1984

In-vivo immune responses of breast- and bottle-fed infants to tetanus toxoid antigen and to normal gut flora.

The effects of breast- and bottle-feeding on serum immunoglobulin levels and specific antibody responses have been examined in 30 infants on five occasions from 6 days until 9 months of age. No significant differences were found on any sample occasion between the two feeding groups in total immunoglobulin levels of G, M and A classes or in class-specific antibody responses to tetanus toxoid vaccine. This suggests that the capacity of the two groups to make serum antibodies develops similarly. Concentrations of antibodies to commensal Escherichia coli 'O' lipopolysaccharide antigens, however, were significantly greater in the bottle-fed group, and it is suggested that this difference is due to an increase in the exposure of the systemic immune system to these gut antigens in the bottle-fed infants. There are several possible explanations for this increased exposure and the resulting effects on the infants' immune system. These experiments also illustrate a possible role of breast milk in stimulating the immune system.

Antibodies, Bacterial↗
PubMed1983

Antibodies to Escherichia coli O antigens and the in-vitro bacteriostatic properties of human milk and its IgA.

Only a very small part of the iron-reversed bacteriostatic activity of milk against Escherichia coli, demonstrable in vitro, is due to its anti-O antibody. Most of its growth-inhibitory activity is due to another lactoferrin-dependent, non-specific system. IgA prepared from milk is bacteriostatic for E. coli in the presence of lactoferrin, if it contains O-antibody for the indicator strain and if the strain is susceptible. Susceptibility depends to some extent on virulence, since those inhibited by IgA antibody to their own O-antigens were enteropathogenic or enterotoxigenic, whereas the growth of commensal strains was inhibited only slightly or not at all.

Antibodies, Bacterial↗
PubMed1980

Criteria and the PSRO program.

The Health Standards and Quality Bureau (HSQB) soon will issue two publications containing criteria that Professional Standards Review Organizations (PSROs) may use to assess the care delivered in short-stay hospitals. In this article, the authors anticipate and answer some of the questions that these documents may raise, and they discuss some of the problems that have been associated with the use of PSRO criteria in general.

Hospitals↗
PubMed1980

The effect of freezing and pasteurizing bovine milk on its ability to protect neonatal guinea-pigs against colonization of the small intestine by Escherichia coli.

The ability of frequent feeding of bovine milk diets to prevent the colonization of the small intestines of newborn guinea-pigs with orally inoculated Escherichia coli was tested. At 3--4 days small intestinal samples from suckled controls were frequently sterile or were colonized with only very low numbers of Esch. coli. No bovine milk diet exhibited a significant "protective" effect but the diets could, however, be ranged in order of effectiveness in decreasing colonization by Esch. coli. Raw, fresh bovine milk was best, followed by milk pasteurized at 56 degrees or 63 degrees, then boiled milk; frozen milk was the worst. Because of this last finding, neither the bacteriostatic lactoferrin-dependent activity nor the lactoperoxidase could be correlated with the ability to decrease the colonization of the small intestines by Esch. coli.

Animals↗
PubMed1980

Differences in inhibition of the growth of commensal and enteropathogenic strains of Escherichia coli by lactotransferrin and secretory immunoglobulin A isolated from human milk.

Immunoglobulins from bovine and human colostrum and milk and lactotransferrin (LTF) from human milk were investigated for bacteriostatic activity against Escherichia coli growing in a tissue culture medium. When tested separately, LTF or secretory immunoglobulin A (sIgA) from pooled human milk showed only slight bacteriostatic activity against human commensal or enteropathogenic strains of E. coli. Together, they had a considerable bacteriostatic effect, but only against strains of enteropathogenic serotype. This activity of the sIgA from pooled human milk was consistent for all enteropathogenic serotypes tested, but sIgA isolated from individual milk samples was inactive against some serotypes, and this specificity was associated with antibody to the O antigens. The activity of the sIgA was stable to heat at 56 degrees for 2 h but was lost progressively on heating at 65 degrees for 10 min or longer. Bovine colostral IgGl was without bacteriostatic effect alone. Together with LTF, it was active against a strain pathogenic to calves but not against human enteropathogenic strains. Tests on rabbit antisera raised against commensal enteropathogenic strains of E. coli showed that for the enteropathogens the bacteriostatic activity (in association with LTF) was high and was specific for the serotype of the eliciting strain, but bacteriostatic activity was low or absent in the antisera to commensal strains in spite of the presence of high titres of agglutinating antibodies to these strains.

Agglutinins↗
PubMed1979

The effect of in vitro antibacterial properties of bovine milk diets on the natural colonisation of newborn piglets with coliform bacteria.

The diets suitable for the hand rearing of piglets in incubators were examined. Diet A was based on cows' milk heated to 56 degrees C and had bacteriostatic and antiadhesive properties against Escherichia coli. Diet B was based on evaporated cows' milk and did not have these properties. The numbers of coliform bacteria naturally colonising the small intestines of newborn piglets fed entirely on these diets for one week did not differ significantly, however both were significantly higher than in control piglets suckled from birth. Faecal counts of coliforms were similar in all three groups. Examination of the bacteriostatic sensitivity of the isolated strains to sows' milk indicated a predominance of milk-sensitive strains colonising the suckled piglets and a predominance of milk-resistant strains in the piglets fed diet B. This diet-dependent colonisation could not be explained by the in vitro bacteriostatic properties of the diets alone.

Animals↗