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Biomedical subjects

B J Sullivan

Publications and source records attributed to B J Sullivan.

At least 19 recordsLinked to original sources
PubMed1999

Profound hypothermia and circulatory arrest with skull base approaches for treatment of complex posterior circulation aneurysms.

OBJECTIVE: Cardiopulmonary bypass with profound hypothermia and circulatory arrest has seen a resurgence as an adjunct technique in neurological surgery. We report our experience with this technique in treating seven complex vertebro-basilar aneurysms. METHODS: Skull base approaches were used in all cases, providing excellent exposure and minimizing brain retraction. There were six basilar artery aneurysms and one giant fusiform vertebro-basilar artery aneurysm. All aneurysms but one had an apparent neck, which could be clipped. The fusiform vertebro-basilar artery aneurysm was trapped, partially resected, and the circulation was reestablished with a saphenous vein graft from the cervical internal carotid artery to the mid-basilar artery. RESULTS: Five patients had an excellent outcome and two had a good outcome at one year or at latest follow up. Two of the patients showed improvement of neurological deficits which were present before the surgical intervention. CONCLUSION: Applying very strict selection criteria in this small series of patients with posterior circulation aneurysms, excellent or good results were achieved using the profound hypothermic circulatory arrest technique.

Adolescent↗
PubMed1999

Structural and functional characterization of an epitope in the conserved C-terminal region of HIV-1 gp120.

Through an integrated study of the reactivity of a monoclonal antibody, 803-15.6, with synthetic peptides and native recombinant HIV-1 envelope glycoprotein gp120, we have obtained structure-functional information on a region of rgp120 not yet elucidated by X-ray crystallography. mAb 803-15.6 binds with high affinity and broad cross-clade specificity to the conserved C-terminal region (amino acids 502-516) of HIV-1 rgp120. Phage display selection from a random peptide library identified the core binding motif as AXXKXRH, homologous to residues 502-508. Using quantitative binding analyses, the affinity of mAb 803-15.6 for native, monomeric recombinant gp120HXB2 (rgp120) was found to be similar to that for the synthetic gp120 peptide (502-516). Circular dichroism studies indicate that the synthetic peptide largely has a random coil conformation in solution. The results therefore suggest that the 803-15.6 epitope is fully accessible on rgp120 and that this region of rgp120 is as flexible as the synthetic peptide. Residues 502-504 are on the edge of a putative gp41 binding site that has been postulated to change conformation on CD4 binding. However, the affinity of mAb 803-15.6 for rgp120 is not affected by binding of CD4 and vice-versa. These results suggest either that the 502-504 region does not change conformation upon CD4 binding, or that recombinant gp120 does not undergo the same changes as occur in the native viral gp120-gp41 oligomer. The detailed characterization of the 803-15.6 epitope may be useful for further study of the role of the C5 region of gp120 in the viral attachment and fusion process.

Amino Acid Sequence↗
PubMed1998

Effect of promoters and signal sequences on the production of secreted HIV-1 gp120 protein in the baculovirus system.

We compared insect cell production levels of secreted HIV-1 gp120 glycoprotein encoded by five different baculovirus expression constructs. Combinations consisting of one of two baculovirus promoters (very late or hybrid late/very late) and one of three different signal sequences [human tissue plasminogen activator (tpa), human placental alkaline phosphatase (pap), or baculovirus envelope glycoprotein (gp67)] were constructed. Production of secreted gp120 from these constructs was analyzed in two enzyme-linked immunosorbent assay formats, one detecting the total amount of secreted gp120 protein and the other measuring the level of "active" gp120 (as defined by the ability to bind to CD4). We found that for all of the constructs, approximately 50 to 90% of the secreted gp120 protein was active. Furthermore, our results indicated that expression from either promoter yielded comparable production of secreted protein, despite the fact that transcription from the hybrid promoter begins at an earlier time. By contrast, the signal sequence had a much greater effect on the levels of secreted gp120: the tpa leader yielded the highest level of secreted protein, followed by the gp67 and pap sequences. This result suggests that transcription is not a limiting factor in the production of secreted gp120, but rather that downstream processing of the protein is more critical. Furthermore, these results confirm the notion that the "optimal" signal sequence is protein dependent and that an insect-derived signal sequence is not optimal in all cases.

Alkaline Phosphatase↗
PubMed1997

Construction and characterization of a radio-iodinatable mutant of recombinant human CD4.

Recombinant soluble human CD4 (rsCD4) has been used in iodinated form to study the interaction of CD4 with its ligands. However, the utility of [125I]-rsCD4 is limited because rsCD4 is inefficiently iodinated and the iodinated protein is poorly active. The iodination properties of rsCD4 most likely reflect the poor accessibility of the tyrosine residues, apparent from the available X-ray structures. We have generated an iodinatable mutant of rsCD4 by substituting Tyr for Phe(179) in the flexible, solvent-exposed C-terminal region of rsCD4(183), a truncated form of CD4 that consists of the first 183 residues of CD4 and includes the binding sites for HIV-1 gp120 and MHC class II molecules. When F179Y rsCD4(183) is iodinated under trace-labeling conditions, the efficiency of 125I incorporation and the percentage of iodinated molecules that are active are much enhanced compared with WT rsCD4. Moreover, trace-labeled [125I]-F179Y rsCD4(183) has the same affinity for HIV-1 rgp120 as unlabeled WT rsCD4. The improved activity of trace-labeled [125I]-F179Y rsCD4(183) appears to be due to effective competition by Y179 for reactive iodine species that, in WT rsCD4, react with traces of denatured protein and/or with residues critical for activity or conformational integrity. The incorporation of accessible tyrosine residues may improve the iodinatibility of a protein both by introducing a readily iodinatable residue and by protecting sensitive proteins from adverse reactions.

Animals↗
PubMed1997

Cerebral vasospasm after tumor resection. A case report.

OBJECTIVE AND IMPORTANCE: Symptomatic cerebral vasospasm can occur after resection of tumors in or adjacent to the basal cisterns, causing delayed neurological deterioration. This potentially treatable condition may go unrecognized. Delay in its recognition will adversely affect the outcome of the patients. There has been a few cases of vasospasm after tumoral resection reported in the literature, mostly in adults. We report a case of vasospasm after resection of a third nerve schwannoma in a pediatric patient. This is the youngest patient reported to date with vasospasm after resection of a brain tumor. CLINICAL PRESENTATION: A six years old girl presented with sudden onset diplopia. Radiological work-up revealed a third nerve mass. She underwent a craniotomy for resection of her mass. Pathological findings were consistent with a third nerve schwannoma. One week postoperatively, her mental status deteriorated. A CT scan revealed a diffuse hypodense area involving the right frontal and temporal lobes in the middle cerebral artery distribution as well as the midbrain. The absence of these findings on the MRI imaging performed on the first postoperative day made us evoke a vascular etiology. A cerebral angiogram was performed and revealed vasospasm in the right internal carotid artery and in the right middle and posterior cerebral arteries. Hyperdynamic hypervolemic hemodilutional therapy was instituted. CONCLUSION: Delayed clinical deterioration from vasospasm is a potentially reversible condition, if recognized early. A high index of suspicion should be maintained in case delayed clinical deterioration occurs after surgery of tumors in the basal cisterns. Cerebral angiography will confirm the diagnosis. Early institution of hyperdynamic hypervolemic hemodilutional therapy and angioplasty may reverse the deficit and improve outcome.

Child↗
PubMed1991

Bacterial translocation induces procoagulant activity in tissue macrophages. A potential mechanism for end-organ dysfunction.

The ability of bacterial translocation to induce cell-associated procoagulant activity was examined in a rodent model. Intestinal decontamination with streptomycin sulfate and bacitracin followed by oral feeding with a streptomycin-resistant strain of Escherichia coli produced monoassociation of the gastrointestinal tract with this microorganism. Using this model, the rate of bacterial translocation at day 3 increased from 6% (1 of 17) to 90% (28 of 31). Cell-associated procoagulant activity was measured in the mononuclear cell population of mesenteric lymph nodes as well as portal and systemic blood and also in hepatic nonparenchymal cells. In monoassociated animals, the procoagulant activity of mesenteric lymph node mononuclear cells was significantly greater than in control animals at day 3 (210% +/- 28% vs 100% +/- 6%) but not at days 1 or 6. Procoagulant activity of hepatic nonparenchymal cells was elevated in monoassociated animals at days 3 and 6 compared with control animals. Both control and monoassociated animals remained well throughout the experiment. The histologic features of the gastrointestinal tract, mesenteric nodes, and liver did not differ between groups. These studies provide evidence that bacterial translocation, in the absence of external stimuli, is able to induce cell activation at sites remote from the gastrointestinal tract and may therefore contribute to the pathogenesis of multiple organ failure.

Animals↗
PubMed1991

Prospective comparison of the immune response of infants to three Haemophilus influenzae type b vaccines.

The antibody response to three Haemophilus influenzae type b vaccines was examined in 134 infants 17 to 22 months of age. Sera were collected from each subject before and 1 month after vaccination with either purified H. influenzae type b capsular polysaccharide (polyribosyl-ribitol phosphate (PRP] or one of two protein-conjugated vaccines (PRP-D or HbOC). Comparison of the two conjugate vaccines revealed that HbOC produced an antibody response greater than or equal to 1.0 micrograms/ml in 96% compared with 72% who were vaccinated with PRP-D (P less than 0.05). The isotype distribution of the antibodies produced by the two vaccines was similar. While all of the vaccines resulted in higher concentrations of anticapsular IgG1 than IgG2, the IgG1:IgG2 ratio was significantly higher in subjects immunized with HbOC. The IgG1:IgG2 ratio was similar in subjects immunized with PRP or PRP-D. The clinical significance of these observations remains to be determined.

Antibodies, Bacterial↗
PubMed1991

Diagnostic dilemma for the 1990s: Lyme disease versus rheumatic fever.

A 15-year-old boy developed an annular erythematous skin rash, fever, knee pain, syncope, and was found to be in complete heart block requiring temporary transvenous pacing. His recovery was complete following therapy with high dose steroids, aspirin, and IV ceftriaxone followed by oral penicillin. Serologic tests documented diagnostic levels of antibodies to Borrelia burgdorferi as well as to Group A streptococcal DNase B. Diagnoses of both Lyme disease and rheumatic fever are based on clinical presentation and serologic confirmation. Our patient had a clinical presentation compatible with either diagnosis and serologic test results suggestive of infection by both B burgdorferi and Group A streptococci. The patient's management was aimed at preventing complications of both diseases, since clinicians involved with the patient's case could not agree on the most likely diagnosis. We present this case to emphasize the following: both rheumatic fever and Lyme disease should be considered in patients presenting with annular skin rashes and complete heart block; serologic studies may be confusing in both Lyme disease and rheumatic fever since neither is entirely sensitive nor specific and efforts should be made to document the causative organism by appropriate cultures, biopsies, and stains when possible; and improved immunoserologic testing for Lyme disease, in particular, is highly needed.

Adolescent↗
PubMed1990

Isolation and characterization of a novel extracellular metalloprotease from Bacillus subtilis.

We have isolated and characterized two minor extracellular proteases from culture supernatants of a strain of Bacillus subtilis containing deletion mutations of the genes for the extracellular proteases subtilisin (apr) and neutral protease (npr) and a minor extracellular protease (epr) as well as intracellular serine protease-I (isp-1). Characterization studies have revealed that one of these enzymes is the previously described protease bacillopeptidase F. The second enzyme, the subject of this report, is a novel metalloprotease, which we designate Mpr. Mpr is a unique metalloprotease that has been purified to apparent homogeneity by using both conventional and high-performance liquid chromatography procedures. Mpr has a molecular mass of approximately 28 kilodaltons on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and a basic isoelectric point of 8.7. The enzyme showed maximal activity against azocoll at pH 7.5 and 50 degrees C. Mpr was inhibited by dithiothreitol and a combination of beta-mercaptoethanol and EDTA. Activity was moderately inhibited by beta-mercaptoethanol and EDTA alone as well as by cysteine and citrate and only marginally by phosphoramidon 1,10-phenanthroline and N-[N-(L-3-trans-carboxyoxiran-2-carbonyl)-L-leucyl]-agmatine. Mpr was not inhibited by phenylmethylsulfonyl fluoride. In addition, Mpr showed esterolytic but not collagenolytic activities. Our studies suggest that Mpr is a secreted metalloprotease containing cysteine residues that are required for maximal activity.

Bacillus subtilis↗
PubMed1990

Gene encoding a novel extracellular metalloprotease in Bacillus subtilis.

The gene for a novel extracellular metalloprotease was cloned, and its nucleotide sequence was determined. The gene (mpr) encodes a primary product of 313 amino acids that has little similarity to other known Bacillus proteases. The amino acid sequence of the mature protease was preceded by a signal sequence of approximately 34 amino acids and a pro sequence of 58 amino acids. Four cysteine residues were found in the deduced amino acid sequence of the mature protein, indicating the possible presence of disulfide bonds. The mpr gene mapped in the cysA-aroI region of the chromosome and was not required for growth or sporulation.

Amino Acid Sequence↗
PubMed1990

Bacillopeptidase F of Bacillus subtilis: purification of the protein and cloning of the gene.

We have purified a minor extracellular serine protease from Bacillus subtilis. Characterization of this enzyme indicated that it was most likely the previously reported enzyme bacillopeptidase F. The amino-terminal sequence of the purified protein was determined, and a "guess-mer" oligonucleotide hybridization probe was constructed on the basis of that sequence. This probe was used to identify and clone the structural gene (bpr) for bacillopeptidase F. The deduced amino acid sequence for the mature protein (496 amino acids) was preceded by a putative signal sequence of 30 residues and a putative propeptide region of 164 amino acids. The bpr gene mapped near pyrD on the chromosome and was not required for growth or sporulation.

Amino Acid Sequence↗
PubMed1990

Nutrition education and counseling: knowledge and skill levels expected by dietetic internship directors.

Development of nutrition education and counseling skills is important in the educational preparation of dietitians. A national survey of dietetic internship directors was conducted to determine competency levels expected of students at the start of an internship, internship training given, and further preparation students need in 32 knowledge/skills areas deemed essential for delivery of nutrition education and counseling services. Completed questionnaires were received from 66 of 102 (65%) internship directors surveyed. The majority of directors expected only basic preparation for group nutrition education and individual counseling knowledge/skills areas. Internship training in nutrition education competencies was "moderate" to "extensive," whereas preparation in nutrition counseling competencies was more likely to be "extensive." Directors perceived the internship to provide adequate preparation in all but the advanced practice skills, such as behavior modification and motivational strategies, for which further preparation was recommended. The majority of internship directors reported that more than 25% of the intern practice experience was in patient counseling, with less experience in group instruction. Implications for undergraduate dietetic education are discussed in relation to internship directors' expectations as well as to present and future trends in the dietetic profession.

Counseling↗
PubMed1989

Recurrent neonatal herpes presenting initially with hoarseness.

This report describes a newborn with recurrent herpes simplex meningoencephalitis despite vigorous antiviral therapy. The course is unusual in that the presenting symptom was hoarseness. Despite probable adequate acyclovir levels in the spinal fluid, a second episode or progression of herpetic encephalitis occurred, suggesting impairment of host defenses, particularly cellular immunity. This episode was treated with both acyclovir and vidarabine. Pharmacokinetics of the antiviral therapy and immune responses are discussed.

Acyclovir↗