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Biomedical subjects

B A Sampson

Publications and source records attributed to B A Sampson.

14 recordsLinked to original sources
PubMed2001

West Nile encephalitis: the neuropathology of four fatalities.

West Nile virus was identified by immunohistochemistry (IHC) and polymerase chain reaction (PCR) as the etiologic agent in four encephalitis fatalities in New York City in the late summer of 1999. Fever and profound muscle weakness were the predominant symptoms. Autopsy disclosed encephalitis in two instances and meningoencephalitis in the remaining two. The inflammation was mostly mononuclear and formed microglial nodules and perivascular clusters in the white and gray matter. The brain stem, particularly the medulla, was involved most extensively. In two brains, cranial nerve roots had endoneural mononuclear inflammtion. In addition, one person had acute pancreatitis. On the basis of our experience, we offer recommendations for the autopsy evaluation of suspected WNV fatalities.

Aged↗
PubMed2000

The pathology of human West Nile Virus infection.

West Nile Virus (WNV) was identified by immunohistochemistry (IHC) and polymerase chain reaction (PCR) as the etiologic agent in 4 encephalitis fatalities in New York City in the late summer of 1999. The fatalities occurred in persons with a mean age of 81.5 years, each of whom had underlying medical problems. Cardinal clinical manifestations included fever and profound muscle weakness. Autopsy disclosed encephalitis in 2 instances and meningoencephalitis in the remaining 2. The inflammation was mostly mononuclear and formed microglial nodules and perivascular clusters in the white and gray matter. The brainstem, particularly the medulla, was involved most extensively. In 2 brains, cranial nerve roots had endoneural mononuclear inflammation. In addition, 1 person had acute pancreatitis. Based on our experience, we offer recommendations for the autopsy evaluation of suspected WNV fatalities.

Aged↗
PubMed2000

The West Nile Virus outbreak of 1999 in New York: the Flushing Hospital experience.

West Nile Virus (WNV) is a mosquito-borne flavivirus, which has been known to cause human infection in Africa, the Middle East, and southwestern Asia. It has also been isolated in Australia and sporadically in Europe but never in the Americas. Clinical features include acute fever, severe myalgias, headache, conjunctivitis, lymphadenopathy, and a roseolar rash. Rarely is encephalitis or meningitis seen. During the month of August 1999, a cluster of 5 patients with fever, confusion, and weakness were admitted to the intensive care unit of the same hospital in New York City. Ultimately 4 of the 5 developed flaccid paralysis and required ventilatory support. Three patients with less-severe cases presented shortly thereafter. With the assistance of the New York City and New York State health departments and the Centers for Disease Control and Prevention, these were documented as the first cases of WNV infection on this continent.

Adult↗
PubMed1999

Pathologic detection of early myocardial infarction: a critical review of the evolution and usefulness of modern techniques.

The limitations of post mortem detection of early myocardial infarction by hematoxylin and eosin staining stimulated a search for the development of improved diagnostic methods based on biochemical and morphologic changes. Methods used and/or investigated included electron microscopic examination, gross and microscopic histochemical stains (tetrazolium salts, phosphotungstic acid-hematoxylin, trichrome, periodic acid-Schiff, hematoxylin-basic fuchsin-picric acid), fluorescence, immunohistochemical techniques, and chemical analysis of pericardial fluid. This practical review, designed for both forensic and hospital-based autopsy pathologists, examines the methods available for post mortem diagnosis of myocardial infarction for cases in which death might have occurred before the evolution of changes detectable by hematoxylin and eosin staining. The status and potential usefulness of each adjunct to classical morphologic examination is summarized. Recent developments are highlighted, including the possibility of using apoptosis as a marker for acute ischemic injury.

Apoptosis↗
PubMed1998

Human prostaglandin transporter gene (hPGT) is regulated by fluid mechanical stimuli in cultured endothelial cells and expressed in vascular endothelium in vivo.

BACKGROUND: biomechanical forces generated by blood flow within the cardiovascular system have been proposed as important modulators of regional endothelial phenotype and function. This process is thought to involve the regulation of vascular gene expression by physiological fluid mechanical stimuli such as fluid shear stresses. METHODS AND RESULTS: We demonstrate sustained upregulation of a recently identified gene encoding a human prostaglandin transporter (hPGT) in cultured human vascular endothelium exposed to a physiological fluid mechanical stimulus in vitro. This biomechanical induction is selective in that steady laminar shear stress is sufficient to upregulate the hPGT gene at the level of transcriptional activation, whereas a comparable level of turbulent shear stress (a nonphysiological stimulus) is not. Various biochemical stimuli, such as bacterial endotoxin and the inflammatory cytokines recombinant human interleukin 1beta cytokines (rhIL-1beta) and tumor necrosis factor-alpha (TNF-alpha), did not significantly induce hPGT. Using a specific antiserum to hPGT, we demonstrate endothelial expression within the arterial vasculature and the microcirculation of highly vascularized tissues such as the heart. CONCLUSIONS: Our results identify hPGT as an inducible gene in vascular endothelium and suggest that biomechanical stimuli generated by blood flow in vivo may be important determinants of hPGT expression. Furthermore, this demonstration of regulated endothelial expression of hPGT implicates this molecule in the regional metabolism of prostanoids within the cardiovascular system.

Antiporters↗
PubMed1998

Broncholithiasis and thoracoabdominal actinomycosis from dropped gallstones.

We report a case of successfully managed invasive, thoracoabdominal actinomycosis caused by the intraperitoneal spillage of gallstones during laparoscopic cholecystectomy. The infected gallstones traversed the diaphragm, migrated into the lung parenchyma, and obstructed a segmental bronchus, causing pneumonia. Treatment involved retrieval of the obstructing stone, debridement and drainage of the pleuroperitoneal phlegmon/abscess, and intravenous antibiotics. The case illustrates the need to remove gallstones at the time of cholecystectomy.

Abdominal Abscess↗
PubMed1998

Metastasizing mixed tumor of the parotid gland: a rare tumor with unusually rapid progression in a cardiac transplant recipient.

We report the case of a 69-year-old man who had a mixed tumor (pleomorphic adenoma) removed from his parotid gland 3 years after orthotopic heart transplantation. Two years later, he presented with widely metastatic mixed tumor, which resulted in his death within 6 months. Metastatic mixed tumor is histologically identical to a benign mixed tumor, but it inexplicably metastasizes. Such tumors are rare and have not been reported to date in a transplant recipient. This case illustrates the rapid and aggressive course that malignancies can follow in an immunosuppressed population. Mixed tumors are common salivary neoplasms, so transplant recipients should be carefully followed after resection for evidence of metastatic spread.

Adenoma, Pleomorphic↗
PubMed1997

Vascular MADs: two novel MAD-related genes selectively inducible by flow in human vascular endothelium.

Vascular endothelium is an important transducer and integrator of both humoral and biomechanical stimuli within the cardiovascular system. Utilizing a differential display approach, we have identified two genes, Smad6 and Smad7, encoding members of the MAD-related family of molecules, selectively induced in cultured human vascular endothelial cells by steady laminar shear stress, a physiologic fluid mechanical stimulus. MAD-related proteins are a recently identified family of intracellular proteins that are thought to be essential components in the signaling pathways of the serine/threonine kinase receptors of the transforming growth factor beta superfamily. Smad6 and Smad7 possess unique structural features (compared with previously described MADs), and they can physically interact with each other, and, in the case of Smad6, with other known human MAD species, in endothelial cells. Transient expression of Smad6 or Smad7 in vascular endothelial cells inhibits the activation of a transfected reporter gene in response to both TGF-beta and fluid mechanical stimulation. Both Smad6 and Smad7 exhibit a selective pattern of expression in human vascular endothelium in vivo as detected by immunohistochemistry and in situ hybridization. Thus, Smad6 and Smad7 constitute a novel class of MAD-related proteins, termed vascular MADs, that are induced by fluid mechanical forces and can modulate gene expression in response to both humoral and biomechanical stimulation in vascular endothelium.

Amino Acid Sequence↗
PubMed1992

Neisseria meningitidis encodes an FK506-inhibitable rotamase.

Eukaryotic peptidyl-prolyl cis-trans isomerases (rotamases) fall into two classes, the cyclophilins inhibited by cyclosporin A and the FK506-binding proteins inhibited by the macrolide antibiotic FK506. In prokaryotes homologs of cyclophilins have been identified and found to have rotamase activity. Sequence similarities have been noted between FK506-binding proteins and gene products in a number of bacterial species, but whether these bacterial proteins have rotamase activity is not known. Using the polymerase chain reaction, we have cloned and sequenced a homolog of an FK506-binding protein from Neisseria meningitidis and expressed the gene product as a fusion protein with maltose-binding protein. The fusion protein was purified by affinity chromatography. By measuring the rate of chymotrypsin cleavage of the substrate succinyl-Ala-Ala-Pro-Phe p-nitroanilide, we found that the fusion protein had rotamase activity comparable to that of human FK506-binding protein. This rotamase activity was inhibited by FK506.

Amino Acid Sequence↗
PubMed1992

Elimination of the vitamin B12 uptake or synthesis pathway does not diminish the virulence of Escherichia coli K1 or Salmonella typhimurium in three model systems.

The role of iron in infection is of great importance and is well understood. During infection, both the host and the pathogen go through many complicated changes to regulate iron levels. Iron and vitamin B12 share certain features. For example, Escherichia coli has similar transport systems for both nutrients, and binding proteins for both are located in gastric juice, liver, saliva, granulocytes, and milk. It is because of such parallels between iron and B12 that we have explored the role of B12 in virulence. A btuB::Tn10 insertion which disrupts the gene encoding the vitamin B12 receptor from E. coli K-12 was P1 transduced into a virulent E. coli K1 strain. In both an infant-rat model and a chicken embryo model, no difference in virulence between the wild-type and the mutant strains was found. Strains of Salmonella typhimurium with mutations in the cobalamin synthesis pathway (Cob) and in btuB were used in a mouse model of virulence. Mutation of the Cob locus or of btuB does not decrease virulence. Interestingly, the inability to synthesize vitamin B12 actually increases virulence compared with the wild type in the S. typhimurium model. This effect is independent of the B12 intake of the mice.

Animals↗
PubMed1989

Identification and characterization of a new gene of Escherichia coli K-12 involved in outer membrane permeability.

Using a genetic selection for mutations which allow large maltodextrins to cross the outer membrane of Escherichia coli in the absence of the LamB maltoporin, we have obtained and characterized two mutations that define a new locus of E. coli. We have designated this locus imp for increased membrane permeability. Mapping studies show that the imp gene resides at approximately 1.2 min on the E. coli chromosome. The mutations alter the permeability of the outer membrane resulting in increased sensitivity to detergents, antibiotics and dyes. The mutations are nonreverting and codominant. Genetic analysis of the mutations suggest that the imp gene is an essential gene. We describe a general cloning strategy that can be used to clone both dominant and recessive alleles. Using this technique, we have cloned the wild-type and mutant imp alleles onto a low copy number plasmid.

Alleles↗
PubMed1988

Mutations that alter the pore function of the OmpF porin of Escherichia coli K12.

We describe the isolation and characterization of mutations in ompF that alter the pore properties of the OmpF porin. The selection makes use of the fact that maltodextrins larger than maltotriose are too large to diffuse through the normal OmpF pore. By demanding growth on maltodextrins (Dex+) in the absence of the LamB protein, which is normally required for the uptake of these large sugars, we are able to obtain ompF mutations. These include transversions, transitions and small deletions. We obtained almost exclusively ompF mutations in spite of the fact that analogous alterations in ompC can result in similar phenotypes. Fifteen independent point mutations identify residues R42, R82, D113 and R132 of the mature peptide as important in pore function. The alterations result in uncharged amino acids being substituted for charged amino acids. Growth tests, antibiotic sensitivities and rates of [14C]maltose uptake suggest that the alterations result in an increased pore size. Small deletions of six to 15 amino acid residues in the region between A108 and V133 of mature OmpF dramatically alter outer membrane permeability to hydrophobic antibiotics and detergents as well as conferring a Dex+ phenotype. We suggest that these mutations affect both the pore function and interactions with other outer membrane components. A model of OmpF protein structure based on general rules for folding membrane proteins and these mutations is presented.

Anti-Bacterial Agents↗
PubMedDate not supplied

The negative autopsy: sudden cardiac death or other?

One of the most frustrating challenges faced by the forensic pathologist is the inability to determine the cause of death in a young person previously thought healthy. The four steps in the investigation of a sudden death include obtaining the history and scene information, performing a gross and microscopic autopsy, performing appropriate laboratory tests, and making the diagnosis. When examining the heart grossly it is important to preserve the anatomic landmarks, section the coronary arteries closely, and recognize lethal abnormalities such as anomalous origin of the coronary arteries. Specimens useful for toxicologic analysis include whole blood, serum, vitreous humor, gastric contents, bile, urine a purple top tube of blood, and frozen myocardium and spleen. Lethal cardiac diseases with minimal or no anatomic findings include Brugada and Garg's syndromes, the long QT syndrome, and Wolff-Parkinson-White (WPW) syndrome. Consultation with other experts, including cardiac pathologists, cardiologists, electrophysiologists, and molecular biologists, may be helpful in determining a cause of death.

Autopsy↗