Search PubMed⌕ Search

Biomedical subjects

J Mack

Publications and source records attributed to J Mack.

At least 37 records · Page 2Linked to original sources
PubMed1999

Optimization of tissue segmentation of brain MR images based on multispectral 3D feature maps.

The purpose of this work was to optimize and increase the accuracy of tissue segmentation of the brain magnetic resonance (MR) images based on multispectral 3D feature maps. We used three sets of MR images as input to the in-house developed semi-automated 3D tissue segmentation algorithm: proton density (PD) and T2-weighted fast spin echo and, T1-weighted spin echo. First, to eliminate the random noise, non-linear anisotropic diffusion type filtering was applied to all the images. Second, to reduce the nonuniformity of the images, we devised and applied a correction algorithm based on uniform phantoms. Following these steps, the qualified observer "seeded" (identified training points) the tissue of interest. To reduce the operator dependent errors, cluster optimization was also used; this clustering algorithm identifies the densest clusters pertaining to the tissues. Finally, the images were segmented using k-NN (k-Nearest Neighborhood) algorithm and a stack of color-coded segmented images were created along with the connectivity algorithm to generate the entire surface of the brain. The application of pre-processing optimization steps substantially improved the 3D tissue segmentation methodology.

Anisotropy↗
PubMed1998

Crystallization and preliminary X-ray studies of Pseudomonas putida histidine ammonium-lyase.

Histidine ammonium-lyase from P. putida was expressed in Escherichia coli, purified to homogeneity, and crystallized by the vapour-diffusion method using polyethylene glycol 3350 as the precipitant. The crystals, which diffract to at least 2.5 A resolution, exhibit the symmetry of space group P212121, with unit-cell parameters a = 89.7, b = 138.2 and c = 164.8 A. The asymmetric unit contains a tetramer, and the crystals have a Vm value of 2.41 A3 Da-1.

Bacterial Proteins↗
PubMed1998

Modification of glassy carbon surfaces with synthetic laminin-derived peptides for nerve cell attachment and neurite growth.

Interactions between cultured nerve cells and surfaces are of importance for the implantation of biocompatible electrode materials such as glassy carbon (GC). Since implants serve as recording sensors in prosthetic neuroscience, we investigated whether coating electrodes with certain laminin derivatives containing the peptide sequences SIKVAV, CDPGYIGSR, PDSGR, YFQRYLI, and RNIAEIIKDA influences neuronal adhesion and neurite outgrowth in vitro. The coating of GC was performed by electrochemical polymerization and, for comparison, by adsorption or covalent coupling. Electrochemical polymerization is suitable for the coupling of peptides to GC, as shown by amino acid analysis and sequencing. Embryonic chicken retinal ganglion cells and brain cells (days E7 or E17) were used for both attachment and growth studies. Surfaces made by electrochemical polymerization of peptides were more efficient than those made by adsorption or covalent coupling of peptides. Synthetic cyclic peptide derivatives of CDPGYIGSR and 18-mer SIKVAV were found to be more efficient than the linear peptides. Competitive effects that resulted in a decreased cell attachment could be found upon application of soluble peptides. Nevertheless, irrespective of the method of coating, peptides were less efficient compared with the whole laminin molecule, as expected from its multiple adhesion sites. When small GC pins were implanted into the brain of E17 chicken after coating with the 18-mer SIKVAV peptide, nerve cell attachment was observed in vivo. The results suggest that chronically implantable materials may exert a higher neurocompatibility when coated with synthetic peptides.

Amino Acid Sequence↗
PubMed1998

Managing care in an integrated delivery system via an Intranet.

The CareGroup Provider Service Network is a managed care contracting organization which provides central administrative services for over 1800 physicians and 200,000 managed care lives. Services include utilization management, disease management and credentialing for the entire network. The management model of the Provider Service Network empowers local physician groups with information and education. To meet the managed care information needs of the network, we implemented an intranet-based executive information system, PSNWeb, which retrieves data from a managed care data warehouse. The project required the integration of diverse technologies and development of a complex security/confidentiality infrastructure to deliver information to 8 major clinician groups, each with different information needs.

Computer Security↗
PubMed1997

Improved intracranial lesion characterization by tissue segmentation based on a 3D feature map.

Our aim was to develop an accurate multispectral tissue segmentation method based on 3D feature maps. We utilized proton density (PD), T2-weighted fast spin-echo (FSE), and T1-weighted spin-echo images as inputs for segmentation. Phantom constructs, cadaver brains, an animal brain tumor model and both normal human brains and those from patients with either multiple sclerosis (MS) or primary brain tumors were analyzed with this technique. Initially, misregistration, RF inhomogeneity and image noise problems were addressed. Next, a qualified observer identified samples representing the tissues of interest. Finally, k-nearest neighbor algorithm (k-NN) was utilized to create a stack of color-coded segmented images. The inclusion of T1 based images, as a third input, produced significant improvement in the delineation of tissues. In MS, our 3D technique was found to be far superior to that based on any combination of 2D feature maps (P < 0.001). We identified at least two distinctly different classes of lesions within the same MS plaque, representing different stages of the disease process. Further, we obtained the regional distribution of MS lesion burden and followed its changes over time. Neuropsychological aberrations were the clinical counterpart of the structural changes detected in segmentation. We could also delineate the margins of benign brain tumors. In malignant tumors, up to four abnormal tissues were identified: 1) a solid tumor core, 2) a cystic component, 3) edema in the white matter, and 4) areas of necrosis and hemorrhage. Subsequent neurosurgical exploration confirmed the distribution of tissues as predicted by this analysis.

Animals↗
PubMed1997

Conventional haemofiltration during routine coronary bypass surgery.

The use of conventional ultrafiltration during cardiopulmonary bypass (CPB) has been well recognized as an efficient modality of therapy to reverse the effects of deliberate haemodilution. Routine use of the haemofilter was prospectively studied on 60 patients undergoing coronary artery bypass surgery. Group A consisted of 30 patients on whom the ultrafiltrator was used and compared to group B who did not receive the ultrafiltration technique. The COBE 1200 ultrafiltration device was used. The results of the study demonstrated that, in group A, the mean total amount of ultrafiltrate collected during bypass was 2510 +/- 804 ml per patient. The mean 24-h postoperative blood loss was 440 +/- 192 ml in group A and 451 +/- 136 ml in group B. The average bank blood transfused was 0.6 +/- 1.3 units per patient in group A and 0.75 +/- 1.5 units per patient in group B. Postoperative weight gain in group A averaged 3.5 +/- 3.45 lb per patient, compared to 4.8 +/- 3.7 lb per patient in group B. Postoperative length of stay averaged 6.4 +/- 1.5 days per patient in group A and 6.4 +/- 2.1 days per patient in group B. Overall patient charges averaged $33,706 +/- 8348 per patient in group A and $33,041 +/- 7674 per patient in group B. It was concluded that routine use of ultrafiltration during routine coronary artery bypass surgery with CPB offers no improvement in the quality of care nor does it decrease the patient's overall charges.

Blood Cell Count↗
PubMed1996

Pregnancy following gastric bypass surgery for morbid obesity.

BACKGROUND: Surgical treatment for severe obesity is sometimes recommended. Many long-term risks, particularly to adolescents and to subsequent pregnancies, are still being determined. CASE: A 23-year-old woman, gravida 6, para 2, treated for morbid obesity during adolescence with gastric bypass surgery, presented at 6 weeks' gestation with severe microcytic anemia. Significant iron and cobalamin deficiencies were found. Although the vitamin B12 deficiency responded to parenteral treatment, the iron deficiency was refractory to oral supplementation because of malabsorption. By 30 weeks' gestation, the patient required blood transfusions to correct the progressive anemia. Subsequently, she delivered a healthy male infant at term. CONCLUSION: Severe iron deficiency anemia resulting from malabsorption can complicate pregnancy following gastric bypass surgery for morbid obesity. For women of childbearing age, this potential adverse effect must be considered.

Adult↗
PubMed1995

Scintigraphic imaging with 123I-metaiodobenzylguanidine as a marker of cardiac adrenergic neurotransmission in the rat.

This study was performed to determine if 123I-metaiodobenzylguanidine (123I-MIBG) could be used to create scintigraphic images of the rat heart and to determine if this method could be used to estimate cardiac norepinephrine turnover in the intact animal. Male F344 rats were injected i.v. with 200-350 muCi of 123I-MIBG. Beginning at 5 min after the injection, scintigraphic images were made every 30 min for 5 h. The half-life of 123I-MIBG retention within the heart during the 5 h of the experiment was determined by plotting the log of the counts for each image vs. time. The half-life of cardiac 123I-MIBG was 3.44 +/- 0.17 h with a rate constant of 0.21 +/- 0.01 (hr-1). In a separate experiment, methacholine, a parasympathomimetic agonist, was given after the injection of 123I-MIBG and increased 123I-MIBG efflux. Cardiac 123I-MIBG uptake was reduced by 65% in rats sympathetically denervated with 6 hydroxy dopamine indicating that 123I-MIBG is accumulating for the most part in adrenergic nerve terminals. We conclude that scintigraphic imaging with 123I-MIBG may be a useful procedure for estimating cardiac adrenergic nervous system activity in the intact animal.

3-Iodobenzylguanidine↗
PubMed1992

Improved indirect fluorescence immunocytochemical method using counterstains.

Immunocytochemistry in recent years has provided powerful tools for research in neurobiology. One of the more popular techniques is the indirect fluorescence technique in which fluorescein isothiocyanate (FITC) or tetrahodamine isothiocyanate (TRITC) is used. Although widely used, this technique has two disadvantages: (1) localization may be difficult in relation to background morphology, and (2) the fluorescence fades. The study reported here describes a modification of an indirect immunocytochemical technique using FITC, TRITC and 7-amino-4-methyl-coumarin-3-acetic acid (AMCA) which enhances localization and significantly prolongs fluorescence. Evans blue was used as a counterstain. The results show that FITC and AMCA stained cells are seen against a background of clearly distinguishable cells after counterstaining with Evans blue. However, Evans blue is not compatible with TRITC. In addition, the fluorescence life of the FITC is extended from several days to several weeks with Evans blue. These results clearly indicate that Evans blue can be used to improve indirect fluorescence immunocytochemical techniques.

Animals↗
PubMed1991

New model for analysis of mucosal immunity: intestinal secretion of specific monoclonal immunoglobulin A from hybridoma tumors protects against Vibrio cholerae infection.

Secretory immunoglobulin A (sIgA) plays a role in defense against Vibrio cholerae and other microorganisms that infect mucosal surfaces, but it is not established whether sIgA alone can prevent disease. We report here a strategy for identifying the antigen specificities of monoclonal sIgA antibodies that are capable of providing such protection. IgA hybridomas were generated from Peyer's patch lymphocytes after oral immunization with V. cholerae Ogawa 395. A clone was selected that produced dimeric monoclonal IgA antibodies directed against an Ogawa-specific lipopolysaccharide carbohydrate antigen exposed on the bacterial surface. Hybridoma cells were used to produce subcutaneous "backpack" tumors in syngeneic mice, resulting in secretion of monoclonal sIgA onto mucosal surfaces. Neonatal mice bearing anti-lipopolysaccharide hybridoma backpack tumors were specifically protected against oral challenge with 100 50% lethal doses of virulent Ogawa 395 organisms. Thus, the IgA hybridoma backpack tumor method identifies protective epitopes in the mucosal system and demonstrates that a single monoclonal sIgA can be sufficient to protect against intestinal disease.

Animals↗
PubMed1989

Support for GPs caring for drug misusers.

National policies encourage GPs to become involved in the care of drug misusers and the management of their dependence. A framework of support services is now in place to assist with this task. This article describes the roles of community drug teams and drug dependency units.

England↗
PubMed1987

Youth cancer education through a combined American Cancer Society-Boy Scouts of America pilot program.

A pilot cancer education program for Boy Scouts in grades six through nine was developed. Motivation to complete requirements was provided by awarding a "Cancer Awareness Patch." Content of the program included health issues related to smoking and tobacco use, diet, and sun exposure, plus education about the practice of testicular self-examination, and sunscreen usage. Retention of factual material was good up to 18 months post-program. Participants developed positive attitudes toward lifestyle development and volunteerism. The program is recommended for supplementation of school health promotion curricula.

Adolescent↗
PubMed1986

An antibody-toxin conjugate directed against a human mammary cancer antigen.

A conjugate has been constructed consisting of diphtheria toxin fragment A (DTA) linked to a monoclonal antibody, BLMRL-HMFG-Mc5 (MC5), directed against a mammary cancer antigen. The conjugate retains both binding and DTA enzymatic activity when tested against target MCF-7 cells, although the conjugate binds less well than the unconjugated antibody. The conjugate is toxic to MCF-7 cells. Toxicity is both dose- and time-dependent. Half-maximal toxicity is observed with 2-5 X 10(-8) M conjugate after 5 days of incubation. However, the conjugate need only be in contact with the cells for 1 day in order to effect complete killing by 5 days. The earliest that an effect can be seen on cell growth is 2 days. When tested against WRK-1 rat mammary tumor cells, the conjugate is inactive.

Antibodies↗