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Biomedical subjects

S Hoffman

Publications and source records attributed to S Hoffman.

At least 127 records · Page 7Linked to original sources
PubMed1989

The dialectical approach in group therapy.

A dialectical therapeutic approach has been used in treating individuals and families. Its application in group therapy is described with the aid of several anecdotal examples.

Adult↗
PubMed1989

A silicone template to facilitate cartilage grafting in the nose.

Silicone sheeting that has the thickness and consistency of septal cartilage for use as a template has been developed to facilitate cartilage grafting in the nose. This technique makes it easier to determine whether or not a graft will correct the deformity and how much autogenous material will be needed before the donor site is harvested. It also allows for more accuracy in the sizing and positioning of the grafts.

Adult↗
PubMed1989

Quantitative muscle strength testing: a comparison of job strength requirements and actual worker strength among military technicians.

In this study the authors investigate the percentage of mismatch between job demands and worker physical capacity in Utah National Guard mechanics. This population had demonstrated a higher incidence of low back trouble than other job descriptions reviewed. The authors utilized onsite still and videotape photography and a computerized biomechanical strength prediction model to assess loads on the lumbosacral spine due to various job tasks. Job demands were then compared to the actual physical capacity of the individual workers based on static strength testing in job-related positions. A load cell on the testing apparatus entered the force generated into a computer which averaged the force of the last three seconds of a five-second lift. It was determined that as much as a 38% mismatch existed within this population for some job tasks which these workers were exposed to. Suggestions for preventing job-related low back cumulative trauma disorders are presented, including: engineering redesign, worker selection programs, work hardening, and others.

Back Pain↗
PubMed1988

Four exons encode a 93-base-pair insert in three neural cell adhesion molecule mRNAs specific for chicken heart and skeletal muscle.

The neural cell adhesion molecule (N-CAM) is detected in chicken brain as three polypeptides of 180 kDa, 140 kDa, and 120 kDa that arise from a single gene by alternative splicing. Heart tissue, however, contains components of 150 kDa, 140 kDa, and 130 kDa; neither the differences in molecular mass among these components nor the difference between neural and cardiac N-CAM could be accounted for by variations in glycosylation alone. A cDNA clone isolated from an embryonic chicken heart library, [lambda N101B, 1.8 kilobases (kb)] contained a 93-base-pair (bp) insert not found in neural N-CAM cDNAs. In the N-CAM gene this sequence mapped within a large region between exons 12 and 13 and was derived from four exons (12A-D) of 15, 33, 42, and 3 bp. Exons 12C and 12D together coded for 15 amino acids very similar to the second half of the muscle-specific insert (MSD1) found in N-CAM cDNA from human muscle cell cultures [Dickson, G., Gower, H. J., Barton, C. H., Prentice, H. M., Elsom, V. L., Moore, S. E., Cox, R. D., Quinn, C., Putt, W. & Walsh, F. S. (1987) Cell 50, 1119-1130]; the sequences of 12A and 12B, however, were much less similar to the corresponding region of the MSD1 sequence. Two oligonucleotides, one specific to exons 12A plus 12B and one specific to exon 12C both recognized mRNA species of 6.4 kb, 4.3 kb, and 3.0 kb in chicken cardiac and skeletal muscle and no mRNA species in smooth muscle or brain. The 3' end of clone lambda N101B contained a sequence coding for a potential phosphatidylinositol linkage signal as does the smallest form of brain N-CAM. In heart cell membranes only the 130-kDa N-CAM polypeptide was released by phospholipase C, suggesting that this form of N-CAM is encoded by clone lambda N101B. The other heart N-CAM species (150 kDa and 140 kDa) may be transmembrane forms that include the 12A-D (and possibly other) inserts. Tissue-specific forms of N-CAM can thus be formed by alternative use of multiple small exons that may alter the conformation of the extracellular region of the molecule. Differential use or switching of these small exons in conjunction with the differential expression of larger exons specifying regions associated with the cell membrane and cytoplasmic domains may signal key events in embryogenesis and histogenesis.

Animals↗
PubMed1988

A cDNA clone for cytotactin contains sequences similar to epidermal growth factor-like repeats and segments of fibronectin and fibrinogen.

Cytotactin is an extracellular glycoprotein that influences neuron-glia interactions. It has been shown to appear in multiple forms that are differentially expressed in neural and non-neural tissues during vertebrate development. We report here the isolation and characterization of a cytotactin cDNA clone (lambda C801) that encodes 933 amino acids, equivalent to about half of a cytotactin polypeptide. Clone lambda C801 is an authentic cytotactin cDNA: it encodes a polypeptide that reacts with a monoclonal anti-cytotactin antibody and its deduced amino acid sequence is identical for 15 amino acids to the directly determined sequence of a CNBr fragment that reacted with the same antibody. Southern blot analyses with fragments of lambda C801 suggested that there may be only one cytotactin gene, but RNA transfer blots detected multiple mRNAs ranging in size from 6.5 to 8.0 kilobases. An 8.0-kilobase message and a Mr 240,000 cytotactin polypeptide were present in embryonic gizzard but not brain, while a 7.2-kilobase message and a Mr 220,000 polypeptide were present in brain but not gizzard. These results indicate that differential splicing of primary transcripts of the cytotactin gene yields various site-specific polypeptides. Sequence analyses of lambda C801 indicated that it specifies a region with extensive similarities to other proteins: the sequence begins with four consecutive epidermal growth factor-like repeats that are followed by eight segments that closely resemble each other and the type III repeats in fibronectin, and it ends with a 66 amino acid sequence similar to part of the beta and gamma chains of fibrinogen. One fibronectin-like repeat contains a single Arg-Gly-Asp sequence. The similarities with all three of these apparently unrelated proteins are extensive, suggesting that cytotactin has an evolutionary and possibly a functional relationship to each.

Amino Acid Sequence↗
PubMed1988

Molecular forms, binding functions, and developmental expression patterns of cytotactin and cytotactin-binding proteoglycan, an interactive pair of extracellular matrix molecules.

Cytotactin is an extracellular matrix protein that is found in a restricted distribution and is related to developmental patterning at a number of neural and non-neural sites. It has been shown to bind specifically to other extracellular matrix components including a chondroitin sulfate proteoglycan (cytotactin-binding [CTB] proteoglycan) and fibronectin. Cell binding experiments have revealed that cytotactin interacts with neurons and fibroblasts. When isolated from brain, both cytotactin and CTB proteoglycan contain the HNK-1 carbohydrate epitope. Here, specific antibodies prepared against highly purified cytotactin and CTB proteoglycan were used to correlate the biochemical alterations and modes of binding of these proteins with their differential tissue expression as a function of time and place during chicken embryo development. It was found that, during neural development, both the levels of expression of cytotactin and CTB proteoglycan and of the molecular forms of each molecule varied, following different time courses. In addition, a novel Mr 250,000 form of cytotactin was detected that contained chondroitin sulfate. The intermolecular binding of cytotactin and CTB proteoglycan and the binding of cytotactin to fibroblasts were characterized further and found to be inhibited by EDTA, consistent with a dependence on divalent cations. Unlike the molecules from neural tissue, cytotactin and CTB proteoglycan isolated from non-neural tissues such as fibroblasts lacked the HNK-1 epitope. Nevertheless, the intermolecular and cellular binding activities of cytotactin isolated from fibroblast culture medium were comparable to those of the molecule isolated from brain, suggesting that the HNK-1 epitope is not directly involved in binding. Binding experiments involving enzymatically altered molecules that lack chondroitin sulfate suggested that this glycosaminoglycan is also not directly involved in binding. Although they clearly formed a binding couple, the spatial distributions of cytotactin and CTB proteoglycan in the embryo were not always coincident. They were similar in tissue sections from the cerebellum, gizzard, and vascular smooth muscle. In contrast, CTB proteoglycan was present in cardiac muscle where no cytotactin is present, and it was seen in cartilage throughout development unlike cytotactin, which was present only in immature chondrocytes. Cell culture experiments were consistent with the previous conclusion that cytotactin was specifically synthesized by glia, whereas CTB proteoglycan was specifically synthesized by neurons.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Functional mapping of cytotactin: proteolytic fragments active in cell-substrate adhesion.

Cytotactin is an extracellular matrix glycoprotein with a restricted distribution during development. In electron microscopic images, it appears as a hexabrachion with six arms extending from a central core. Cytotactin binds to other extracellular matrix proteins including a chondroitin sulfate proteoglycan (CTB proteoglycan) and fibronectin. Although cytotactin binds to a variety of cells including fibroblasts and neurons, in some cases it causes cells in culture to round up and it inhibits their migration. To relate these various effects of cytotactin on cell behavior to its binding regions, we have examined its ability to support cell-substrate adhesion and have mapped its cell-binding function onto its structure. In a cell-substrate adhesion assay, fibroblasts bound to cytotactin but remained round. In contrast, they both attached and spread on fibronectin. Neither neurons nor glia bound to cytotactin in this assay. In an assay in which cell-substrate contact was initiated by centrifugation, however, neurons and glia bound well to cytotactin; this binding was blocked by specific anti-cytotactin antibodies. The results suggest that neurons and glia can bind to cytotactin-coated substrates and that these cells, like fibroblasts, possess cell surface ligands for cytotactin. After applying methods of limited proteolysis and fractionation, these assays were used to map the binding functions of cytotactin onto its structure. Fragments produced by limited proteolysis were fractionated into two major pools: one (fraction I) contained disulfide-linked oligomers of a 100-kD fragment and two minor related fragments, and the second (fraction II) contained monomeric 90- and 65-kD fragments. The 90- and 65-kD fragments in fraction II were closely related to each other and were structurally and immunologically distinct from the fragments in fraction I. Only components in fraction I were recognized by mAb M1, which binds to an epitope located in the proximal portion of the arms of the hexabrachion and by a polyclonal antibody prepared against a 75-kD CNBr fragment of intact cytotactin. A mAb (1D8) and a polyclonal antibody prepared against a 35-kD CNBr fragment of cytotactin only recognized components present in fraction II. In cell-binding experiments, fibroblasts, neurons, and glia each adhered to substrates coated with fraction II, but did not adhere to substrates coated with fraction I. Fab fragments of the antibody to the 35-kD CNBr fragment strongly inhibited the binding of cells to cytotactin, supporting the conclusion that fraction II contains a cell-binding region. In addition, Fab fragments of this antibody inhibited the binding of cytotactin to CTB pr

Animals↗
PubMed1988

Merging facility and financial planning: a new approach.

This article seeks to help hospital administrators and boards (especially planning and finance committees) balance facility and financial aspects of a construction project by planning for each concurrently. It recommends that the process start with formal strategic plans, and that facility and capital plans be advanced interactively, thus maintaining flexibility to ensure that the hospital's objectives can be met within manageable financial limits. The authors suggest that the project thus delivered will be the most effective and efficient project possible within defined constraints. And, once planned, the project will be ready for implementation--false starts will be eliminated.

Capital Financing↗
PubMed1987

Ganciclovir hepatotoxicity.

A 33-year-old male with acquired immunodeficiency syndrome received ganciclovir for presumed cytomegalovirus retinitis. Although results of baseline liver function tests were abnormal, marked elevations of transaminases and alkaline phosphatase occurred when the drug was first instituted, as well as after rechallenge. These elevated laboratory values declined on each occasion that the drug was withdrawn. As no other toxic or infectious insults could clearly be incriminated in these acute, self-limited episodes of hepatic function abnormalities, ganciclovir was most likely responsible for the toxicity observed in this patient.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Reduction mammaplasty: a medicolegal hazard?

In spite of the potential for complications and poor results, reduction mammaplasty remains a procedure with a high degree of patient satisfaction. Although thousands of cases are done annually, only a small percentage of the patients are unhappy enough to consider a law suit. A questionnaire was sent to the members of the ASPRS. Thirty-eight percent of the members responded and 11% indicated that they had been sued at least once for this procedure. A review of the results of the questionnaire and suggestions for reducing the number of dissatisfied patients are presented.

Breast↗
PubMed1987

Asymmetric expression in somites of cytotactin and its proteoglycan ligand is correlated with neural crest cell distribution.

The development of the vertebrate neural crest presents a particularly challenging problem in pattern formation. Several studies have revealed that a population of neural crest cells penetrates the sclerotomal mesenchyme of the somite only in its rostral half. In a search for molecular correlates of this pattern, we have observed that cytotactin and a chondroitin sulfate proteoglycan, two interactive extracellular matrix molecules, show a specialized distribution within the sclerotome. Cytotactin was localized in the rostral half of the sclerotome at about the time of neural crest cell invasion. The proteoglycan was initially diffuse throughout the sclerotome but became restricted to the caudal half after the appearance of cytotactin and invasion of neural crest cells in the rostral half. These distributions were crest cell-independent; they occurred on the same schedule even when all crest cells were removed by surgical extirpation of the neural tube. Furthermore, in tissue culture, somite cells synthesized high levels of both molecules. In vitro, crest cells rounded up in the presence of these molecules and cell migration assays revealed that neither cytotactin nor proteoglycan alone was as good a substratum for crest cell migration as fibronectin. In combination with fibronectin, however, cytotactin or proteoglycan only restricted cell movement but did not prevent it. Taken together, these observations support the hypothesis that cytotactin and the chondroitin sulfate proteoglycan may contribute to pattern formation during embryogenesis by means of their site-restricted distribution, their ability to alter migration on other substrates such as fibronectin, and their ability to induce cell-surface modulation.

Animals↗
PubMed1987

A proteoglycan with HNK-1 antigenic determinants is a neuron-associated ligand for cytotactin.

Cytotactin is an extracellular matrix protein that is involved in neuron-glia adhesion and is found in both neural and nonneural sites. It is synthesized by glia but not by neurons. In this study, we have examined the binding of cytotactin to a variety of extracellular matrix components using uniform microscopic beads (Covaspheres) that could be labeled and then linked to purified molecules. Cytotactin-coated beads bound well to neurons, and this binding was strongly inhibited by anti-cytotactin antibodies but not by anti-neural cell adhesion molecule (anti-N-CAM) antibodies. In contrast, the binding of N-CAM-coated beads to neurons was inhibited by anti-N-CAM antibodies and not by anti-cytotactin antibodies. To identify a neuronal ligand for cytotactin, we tested several molecules for their ability to block the binding of cytotactin-coated beads to cells. A proteoglycan-containing fraction that copurified with cytotactin from brain extracts strongly inhibited binding, whereas neither a heparan sulfate proteoglycan from Engelbreth-Holm-Swarm tumor cells nor soluble cytotactin itself had a significant inhibitory effect. The neural proteoglycan also inhibited the binding of cytotactin-coated beads to fibroblasts. Digestion with chondroitinase, heparitinase, and hyaluronidase as well as immunological analyses suggested that the predominant species in the active fraction was a chondroitin sulfate proteoglycan with a Mr280,000 core protein bearing HNK-1 antigenic determinants and also indicated that hyaluronic acid was present in this fraction. In experiments on in vitro synthesis, it was found that the proteoglycan was synthesized in culture by embryonic chicken brain tissue but not by embryonic chicken glial cells. A series of binding experiments was performed on appropriately derivatized beads to confirm that the proteoglycan is a ligand for cytotactin and to check for the possibility that other extracellular matrix proteins might interact with one or the other member of this binding couple. Proteoglycan-coated beads and cytotactin-coated beads coaggregated readily. The aggregation was inhibitable by anti-cytotactin antibodies, soluble cytotactin, or soluble proteoglycan. Addition of laminin inhibited the binding of cytotactin-coated beads to proteoglycan-coated beads or to cells; this is consistent with data indicating that laminin interacts with a component of the proteoglycan-containing fraction. In contrast, fibronectin bound to cytotactin, but it did not bind to proteoglycan or interfere with the binding of cytotactin to proteoglycan. The results of this study are in accord with the idea that the functions of extracellular matrix components during neural and nonneural development may be modulated both by competition for shared cell surface receptors and by a network of molecular interactions among the matrix components themselves.

Animals↗