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Biomedical subjects

S Hoffman

Publications and source records attributed to S Hoffman.

At least 109 records · Page 6Linked to original sources
PubMed1991

Synthesis of wild type and mutant human hemoglobins in Saccharomyces cerevisiae.

We have expressed human alpha and beta-globin cDNA clones from separate, synthetic galactose-regulated hybrid promoters contained on a single plasmid in Saccharomyces cerevisiae. Co-expression of the alpha and beta-globin chains in S. cerevisiae results in the assembly of these proteins into soluble tetrameric hemoglobin that accumulates to 3-5 percent of the total cell protein. Endogenously produced heme is incorporated into the tetramer and the protein produced is functionally and structurally indistinguishable from human Ao hemoglobin. This expression system has been used to produce both wild type hemoglobin and a low O2-affinity hemoglobin mutant that has oxygen binding and dissociation characteristics similar to human whole blood. The yeast expression system we describe may be suitable for the production of a recombinant hemoglobin based blood substitute as well as for detailed structure-activity studies of human hemoglobin.

Amino Acid Sequence↗
PubMed1991

The erythrocytes in paroxysmal nocturnal haemoglobinuria of intermediate sensitivity to complement lysis.

The sensitivity to lysis by complement of the erythrocytes of 56 patients with paroxysmal nocturnal haemoglobinuria (PNH) was compared to the membrane expression of decay accelerating factor (DAF, CD55), membrane inhibitor of reactive lysis (MIRL, CD59) and acetylcholinesterase (AChE). Most patients (36/50 72% in whom the analysis could be made) appeared to have erythrocytes of intermediate sensitivity to complement in the blood. These cells appeared as a discrete population of cells (PNH II cells), as a 'tail' of cells slightly less sensitive than the predominant PNH III cells (previously called PNH IIIb cells), or as a continuous spectrum of cells sensitive to complement. The PNH III cells totally lacked all three proteins (DAF, MIRL, AChE) by flow cytometric analysis whereas PNH I cells appeared to have normal or nearly normal amounts of each. The cells of intermediate sensitivity (PNH II) had coordinately decreased expression of all three proteins; the level of expression of DAF and MIRL paralleled the sensitivity of the cells to the haemolytic action of complement.

Acetylcholinesterase↗
PubMed1991

Treating the latrogenically infantilized patient.

The treatment of an "iatrogenically infantilized" patient by cotherapists using a dialectical approach is described. By focusing on the adult part of the patient, the here and now and on behavioral change rather than on the past, catharsis and insight, the development of dependency and regression were discouraged, while growth and independence were encouraged. The practice of providing further treatment to patients with poor responses to past psychotherapeutic aid is questioned and an alternate approach is suggested.

Adolescent↗
PubMed1991

Gastroduodenal mucus gel thickness in patients with Helicobacter pylori: a method for assessment of biopsy specimens.

The gastroduodenal mucus layer is considered the primary mucosal protective barrier, especially important in the maintenance of a mucosal pH gradient. Thus, the measurement of the mucus layer thickness in various disease states could advance our understanding of gastroduodenal pathophysiology. We present a novel method for measuring the mucus layer in endoscopic biopsy material and compare layer thickness in Helicobacter pylori (HP)-negative and HP-positive specimens. Endoscopic biopsies were obtained from 17 patients with gastroduodenal mucosa harboring HP and from 15 patients without current HP colonization. The thickness of the mucus layer was measured in fresh specimens by the phase-contrast dark-field microscopy technique. In patients with confirmed HP infection, the thickness of the mucus layer (mean +/- SD) was 0.093 +/- 0.033 mm in duodenal, 0.085 +/- 0.027 mm in antral, and 0.105 +/- 0.033 mm in corporal mucosa. In patients without concomitant HP colonization, the thickness of the mucus gel was 0.162 +/- 0.045 mm, 0.175 +/- 0.067 mm, and 0.161 +/- 0.064 mm in duodenum, antrum, and corpus, respectively. The differences between the means were statistically significant (p less than 0.001 for the duodenal, p less than 0.001 for antral, and p less than 0.01 for corporal mucosa). This study suggests that colonization of the gastroduodenal mucosa by HP impairs the mucus layer covering the surface epithelium. This mucus layer impairment may lead to mucosal injury with subsequent development of inflammation and, possibly, peptic ulcer disease.

Adult↗
PubMed1990

Expression of adhesion molecules and the establishment of boundaries during embryonic and neural development.

Evidence is accumulating that molecules involved in cell-cell and cell-substratum interactions are important in the establishment and maintenance of borders between cell groups during development. In this report, we review evidence supporting this conclusion, particularly in regard to the role of adhesion molecules in the formation of cell collectives and in the modulation of cell and neurite movements.

Animals↗
PubMed1990

Indirect treatment of traumatic psychological experiences: the use of TAT cards.

An indirect therapeutic intervention using TAT cards in the treatment of a 13-year-old boy, who had accidentally killed a younger relative seven years ago, is described. Using a dialectical approach, the cotherapists presented contrasting TAT stories in an attempt to reflect the boy's inner conflicts, ambivalencies, and distorted perceptions. This approach provided the boy with alternate and more positive ways of perceiving and dealing with reality and enable him to relate to and cope with the taboo topic of the traumatic incident in a relatively short time. It is suggested that the use of this approach in highly sensitive situations, where considerable caution is warranted, should be explored with various age groups.

Adaptation, Psychological↗
PubMed1990

Evaluation of an in vitro assay aimed at measuring protective antibodies against sporozoites.

We have evaluated the in vitro biological activities of antibodies directed against sporozoites and compared them with their capacity to protect against challenge with both human and rodent malaria. The anti-Plasmodium falciparum antibodies evaluated with the test included monoclonal antibodies (MAbs) NFS1 and NFS2 as well as polyclonal antibodies contained in human hyperimmune sera directed against sporozoites of P. falciparum. The inhibitory effect of these antibodies was dependent on their concentration. However, total inhibition was not observed except occasionally with highly concentrated MAbs (10-100 micrograms/ml). Strong but also incomplete inhibition was observed with sera from humans living in hyperendemic areas. In the P. yoelii rodent system, we tested sera from mice immunized with subunit vaccines. None of these mice were protected in vivo against challenge with 40-200 sporozoites. In vitro only a sub-total inhibition was achieved (maximum 91% at 1:10 serum dilution). In contrast, we tested sera from mice that received NYS1, an IgG3 MAb, in passive transfer and were protected against challenge with 5000 sporozoites. At 1:10 dilution, 100% inhibition was achieved in vitro while IFA titres from these mice were similar to those of vaccinated mice. These data show a close correlation between in vivo and in vitro findings and thus suggest that the inhibition of liver-stage development assay (ILSDA) appears appropriate to evaluate the potential of antibodies.

Adult↗
PubMed1989

Correction of established capsular contractures with polyurethane implants.

Twelve patients with severe and recurrent capsular contractures following breast augmentation and reconstruction were improved with polyurethane-covered implants. It still has not been established whether these implants prevent or merely delay the onset of contractures, but some of these patients have been followed for over three years and all 12 were improved.

Adult↗
PubMed1989

Cytotactin and its proteoglycan ligand mark structural and functional boundaries in somatosensory cortex of the early postnatal mouse.

The expression of the extracellular matrix molecules cytotactin, which is synthesized by glia, and cytotactin-binding (CTB) proteoglycan, which is synthesized by neurons, was examined in the developing brain of the mouse, specifically in the cortical barrel field, using highly specific polyclonal antibodies to the purified molecules. Both molecules appeared early in the development of the cortex but were excluded from the centers of the developing barrels at the time of entry and arborization of thalamocortical axons. Of the two major forms of cytotactin (220 and 200 kDa), the larger form predominated during development of the mouse brain and also predominated in mixed neuron-glia cultures but not in pure glial cultures. Both cytotactin and CTB proteoglycan were recognized by various lectins that have been shown in other studies to demarcate the barrel field: both molecules were recognized by lentil lectin and concanavalin A and CTB proteoglycan was also recognized by peanut and wheat germ agglutinins. The HNK-1 carbohydrate antigen, present on cytotactin, CTB proteoglycan, and other adhesion molecules, was also found in the barrel walls and diminished in the barrel hollows. Cytotactin and CTB proteoglycan were preferentially expressed in barrel walls through P12. After this time, their expression became uniform even though the histological pattern of barrel walls and hollows was maintained. The fusion of a row of barrels which results from peripheral damage to a row of whiskers was accompanied by the loss of patterned expression of both molecules following electrocauterization of a row of whisker follicles at P1.5. We conclude that activity from the periphery is important not only to development of anatomical pattern but also of the molecular pattern and that the expression of both glial and neuronal proteins can respond to such activity. The results are consistent with previous studies showing that incoming thalamocortical axons play a primary role in barrel field formation. They also suggest that both the migration of cortical neurons on glia and the refinement of the mapping between the peripheral whisker field and its cortical representation may depend upon the distribution of substrate adhesion molecules.

Age Factors↗
PubMed1989

Topology of cell adhesion molecules.

The neural cell adhesion molecule (N-CAM) exists in two major forms [ld (large cytoplasmic domain) peptide and sd (small cytoplasmic domain) peptide] that contain transmembrane segments and different cytoplasmic domains and in a third form [ssd (small surface domain) peptide] that lacks transmembrane and cytoplasmic regions. All forms have the same extracellular region of more than 600 amino acid residues, a region also found in a fragment (Fr2) that can be released from cells by proteolysis. The liver cell adhesion molecule (L-CAM) is expressed as a single species that is distinct from N-CAM, but its extracellular region can also be obtained as a proteolytic fragment (Ft1). Examination of the various forms of N-CAM and the Ft1 fragment of L-CAM by electron microscopy of rotary shadowed molecules indicated that they all have rod-shaped structures that contain a hinge region which is apparently flexible. Both the ssd chain and the Fr2 fragment of N-CAM are single rods bent into arms approximately 18 and 10 nm long. The ld and sd chains are longer bent rods that form rosettes comprising two to six branches; detergent treatment disrupts these rosettes into single rods. Specific antibodies that block homophilic N-CAM binding labeled the distal ends of the branches of the ld/sd rosettes and the ends of the longer arm of both the ssd chain and the Fr2 fragment. Antibodies that bind to the sialic acid-rich region of N-CAM bound near the hinge. These data indicate that the N-CAM rosettes are formed by interaction between their transmembrane or cytoplasmic domains and not by interactions involving their homophilic binding sites. The L-CAM Ft1 fragment is also a bent rod with an apparently flexible hinge; like the ssd chain and the Fr2 fragment of N-CAM, it does not form aggregates. The similarities between L-CAM and N-CAM, despite their differences in amino acid sequence, suggest that their general configuration and the presence of a flexible hinge are important elements in assuring effective and specific cell-cell adhesion.

Antibodies↗
PubMed1989

A detailed structural model of cytotactin: protein homologies, alternative RNA splicing, and binding regions.

A combination of cDNA sequencing of the complete coding region, protein comparisons, binding site mapping, and electron microscopic imaging has permitted the formulation of a structural model of cytotactin. Cytotactin is a large extracellular matrix glycoprotein that displays a restricted tissue distribution during development. Although there appears to be a single cytotactin gene, multiple cytotactin polypeptides and mRNAs are detected in a variety of tissues. We report here the sequences and relationships of cDNAs that encode the complete amino acid sequences of two cytotactin polypeptides in chicken brain. The translated cDNA sequences agree with those obtained by direct analysis of cytotactin and fragments of the molecule. All regions of the polypeptides appear to be identical except for a 273 amino acid segment found in the larger but not in the smaller. At their amino termini, both polypeptides contain a cysteine-rich segment that probably includes those residues that link monomers into hexamers. This segment is followed by 13 epidermal growth factor-like (EGFL) repeats and then 8 consecutive segments that each resemble the type III repeats found in fibronectin. At their carboxyl termini, the polypeptides are similar to the beta and gamma chains of fibrinogen, including a calcium-binding segment. The additional sequence in the large polypeptide is inserted after the fifth type III repeat and includes three additional type III repeats. On RNA transfer blot analyses, cytotactin cDNA probes detected a 6.4-kilobase (kb) component in both brain and gizzard and larger mRNAs in both tissues, but those in gizzard were larger by about 1 kb than those in brain. A probe specific to the insert did not hybridize to the 6.4-kb mRNA in either tissue but detected the larger mRNAs in both tissues. At least a portion of the insert is thus present in both tissues, but there may be additional inserts in the gizzard mRNAs. The proposed model of cytotactin specifies the orientation of the polypeptides, the localization of interchain disulfide bonds, the structural elements constituting the thin and thick segments (EGFL repeats and type III repeats, respectively), the terminal fibrinogen-like nodular region, and the relative location of the cell-binding region.

Amino Acid Sequence↗