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J Dworkin

Publications and source records attributed to J Dworkin.

At least 37 records · Page 2Linked to original sources
PubMed1995

Segmental conservation of sapA sequences in type B Campylobacter fetus cells.

Campylobacter fetus cells may exist as either of two defined serogroups (type A or B) based on their lipopolysaccharide (LPS) composition. Wild-type strains contain surface array proteins (S-layer proteins) that have partial antigenic cross-reactivity but bind exclusively to LPS from homologous (type A or B) cells. Type A cells possess 8 homologs of sapA, which encodes a 97-kDa S-layer protein; the gene products of these homologs have a conserved N terminus of 184 amino acids. To further explore the structural relationships between the C. fetus S-layer proteins and their encoding genes, we sought to clone and express an S-layer protein from type B strain 84-91. The cloned type B gene (sapB) was similar in structure to the previously cloned type A gene (sapA) and encoded a full-length 936-amino acid (97-kDa) S-layer protein. Sequence analysis of sapB indicated that the conserved N-terminal encoding region in sapA was absent but that the remainder of the ORF (encoding 751 amino acids) was identical to that of sapA in spite of the nonconserved nature of this region among sapA homologs. Noncoding sequences both 300 base pairs 5' and 1000 base pairs 3' to the sapB and sapA ORFs, including the sapA promoter and transcriptional terminator sequences, were essentially identical. Southern analyses revealed that the sapB N-terminal encoding region was conserved in multiple copies in type B strains but was absent in type A strains. Recombinant sapA and sapB products bound to a substantially greater degree to cells of the homologous LPS type compared with the heterologous LPS type, indicating that the conserved sapA- and sapB-encoded N termini are critical for LPS binding specificity. The parallel genetic organization and identity at the nucleotide level in both coding and noncoding regions for sap homologs in types A and B cells indicates the necessity of both homolog conservation and high fidelity DNA replication in the biology of sap diversity.

Amino Acid Sequence↗
PubMed1995

A lipopolysaccharide-binding domain of the Campylobacter fetus S-layer protein resides within the conserved N terminus of a family of silent and divergent homologs.

Campylobacter fetus cells can produce multiple S-layer proteins ranging from 97 to 149 kDa, with a single form predominating in cultured cells. We have cloned, sequenced, and expressed in Escherichia coli a sapA homolog, sapA2, which encodes a full-length 1,109-amino-acid (112-kDa) S-layer protein. Comparison with the two previously cloned sapA homologs has demonstrated two regions of identity, approximately 70 bp before the open reading frame (ORF) and proceeding 550 bp into the ORF and immediately downstream of the ORF. The entire genome contains eight copies of each of these conserved regions. Southern analyses has demonstrated that sapA2 existed as a complete copy within the genome in all strains examined, although Northern (RNA) analysis has demonstrated that sapA2 was not expressed in the C. fetus strain from which it was cloned. Further Southern analyses revealed increasing sapA diversity as probes increasingly 3' within the ORF were used. Pulsed-field gel electrophoresis and then Southern blotting with the conserved N-terminal region of the sapA homologs as a probe showed that these genes were tightly clustered on the chromosome. Deletion mutagenesis revealed that the S-layer protein bound serospecifically to the C. fetus lipopolysaccharide via its conserved N-terminal region. These data indicated that the S-layer proteins shared functional activity in the conserved N terminus but diverged in a semiconservative manner for the remainder of the molecule. Variation in S-layer protein expression may involve rearrangement of complete gene copies from a single large locus containing multiple sapA homologs.

Amino Acid Sequence↗
PubMed1991

Concern about AIDS among hospital physicians, nurses and social workers.

In this study, the authors examine the worry and discomfort experienced by direct care health professionals in treating AIDS patients and how their profession, attitudes, knowledge, experience and demographic characteristics influence their emotional reaction to those patients. The research focuses on experienced emotion as distinct from expressed emotion, as an important factor in explaining health behaviors among professionals. To address these issues 536 health care professionals comprising 132 physicians, 378 nurses and 26 social workers employed at a University teaching hospital in Chicago were surveyed. The findings suggest that health care workers' emotional reactions to HIV depend on the type of patient interaction. We found for all three professions, as the invasiveness of contact increased, the level of worry and amount of discomfort also increased. Nurses however, on the whole were the most adversely affected by their patient contacts. We conclude that emotional reactions in the workplace cannot be explained by cognitions, beliefs and attitudes alone. This study suggests that work roles, work assignments, and professional authority contribute to emotional reactions to patients with AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Contraction of neuronal branching volume: an anatomic correlate of Pavlovian conditioning.

Associative memory of the mollusc Hermissenda crassicornis, previously correlated with changes of specific K+ currents, protein phosphorylation, and increased synthesis of mRNA and specific proteins, is here shown to be accompanied by macroscopic alteration in the structure of a single identified neuron, the medial type B photoreceptor cell. Four to five days after training, terminal arborizations of B cells iontophoretically injected with Ni2+ ions and then treated with rubeanic acid were measured with charge-coupled device (CCD)-digitized pseudocolor images of optical sections under "blind" conditions. Boundary volumes enclosing medial-type B-cell arborizations from classically conditioned animals were unequivocally reduced compared with volumes for naive animals or those trained with unpaired stimuli. Branch volume magnitude was correlated with input resistance of the medial type B-cell soma. Such associative learning-induced structural changes may share function with "synapse elimination" described in developmental contexts.

Animals↗
PubMed1990

A preliminary study of unresolved grief in families of seriously mentally ill patients.

Investigations of the grief reactions experienced by families when a relative develops a serious mental illness have been hampered by the lack of an appropriate instrument to measure such reactions. The authors devised the Mental Illness Version of the Texas Inventory of Grief, adapted from the Texas Revised Inventory of Grief, to assess family members' initial and present feelings about their relative's loss of mental health. A test of the instrument with 58 family members of patients with schizophrenia or bipolar disorder revealed a surprisingly low level of initial grief but higher levels of present grief.

Adaptation, Psychological↗
PubMed1989

Certification of patients for involuntary hospitalization.

The author discusses the results of a study designed to determine the relationship of professional experience as a social worker with attitude toward serving as a qualified examiner. Findings indicated that workers with extensive experience had more positive attitudes toward the role.

Attitude of Health Personnel↗
PubMed1988

Transitional cells at the junction of seminiferous tubules with the rete testis of the rat: their fine structure, endocytic activity, and basement membrane.

Transitional cells line the intermediate region of rat seminiferous tubules situated between the rete testis and the seminiferous epithelium proper. These tall elongated cells orient themselves in a downstream direction and converge on one another distally in the lumen of the rete testis where they form a distinct papillalike structure through which a narrow patent lumen is apparent. In addition to widely dispersed Golgi apparatus and mitochondria, these cells contain an abundance of microtubules, cisternae of endoplasmic reticulum, and a distinct lobulated nucleus showing clumps of chromatin and a prominent nucleolus. The endocytic activity of these cells was examined by employing adsorptive (cationic ferritin, concanavalin A ferritin) and fluid-phase tracers (native ferritin, horseradish peroxidase-colloidal gold complex, and concanavalin A ferritin in presence of alpha methyl-D-mannoside). Such tracers were injected separately into the lumen of the rete testis, and the animals were killed at 2, 5, 15, and 30 min and 1, 2, and 6 hr after injection. At 2 min, both adsorptive and fluid-phase tracers were found within coated and uncoated pits of the apical plasma membrane of these cells as well as in large, subsurface, uncoated spherical, C-shaped, and tubular membranous elements. At 5 min the tracers were seen in endosomes of different sizes; while at 15 min and 30 min, pale and dense multivesicular bodies of small and large sizes, respectively, were labeled. At 1-hr and longer time intervals secondary lysosomes became labeled. While both fluid-phase and adsorptive tracers followed the same pathway and fate, binding to the apical and lateral plasma membranes of the transitional cells and to the membrane delimiting coated and uncoated pits was observed only with the adsorptive tracers. These results demonstrate that the transitional cells are actively involved in both fluid-phase and adsorptive endocytosis, which may play an important role in modifying the composition of the luminal fluid. The transitional cells of the distal zone of the intermediate region rest on an elaborate basement membrane (BM) complex which includes a thin BM immediately underlying these cells, a thick distal layer of BM, and strands of BM spanning the distance between the two in the form of a loose anastomotic network. Use of antisera against heparan sulfate proteoglycan, laminin, and type IV collagen revealed the presence of all three components within all areas of the BM complex. In the meshes of the anastomotic BM network, extracellular vesicles were observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

Role of epithelial clear cells of the rat epididymis in the disposal of the contents of cytoplasmic droplets detached from spermatozoa.

Upon release from the seminiferous epithelium, spermatoza show a small droplet of cytoplasm attached to the neck region. During transit of spermatozoa in the caput epididymidis, this cytoplasmic droplet migrates along the middle piece of the flagellum. In the corpus epididymidis, the droplet shows a lateral displacement, while in the cauda epididymidis it detaches from the spermatozoon. In the electron microscope, cytoplasmic droplets attached to spermatozoa were seen to contain numerous, short, straight or C-shaped, flattened membranous elements referred to as lamellae, small vesicles, and small particles (35-nm diameter) with a diffuse wall showing no apparent unit membrane. The lamellae were stacked closely on one another or arranged in a loose array. Structurally as well as cytochemically, with different cytochemical markers, the lamellae and vesicular elements failed to show any evidence of being components of the Golgi apparatus or elements of the endoplasmic reticulum. The lamellae, vesicular elements, and 35-nm particles were also seen free in the lumen of the corpus epididymidis but were especially prominent in the cauda epididymidis at a time when droplets were being released from spermatozoa. The lumen of the epididymis, as spermatozoa passed from the caput to the cauda epididymidis, was also noted to acquire progressively a flocculent background material. The epididymal epithelium is composed predominantly of principal and clear cells. The endocytic activity of clear cells was examined in rats at different time intervals after a single injection of cationic ferritin into the lumen of the cauda epididymidis. At 2 min the tracer was bound to the microvilli of these cells and was also observed within large coated and uncoated pits, subsurface coated vesicles, and numerous subsurface small uncoated vesicular membranous elements (150-200-nm diameter). At 5 min, in addition to the above structures, the tracer was present in endosomes, while at 15 and 30 min, pale and dense multivesicular bodies appeared labeled, respectively. At 1 and 2 hr, but more so at 6 hr large dense membrane-bound bodies identified cytochemically as secondary lysosomes became labeled. All of the above endocytic structures were also seen to contain the 35-nm particles, flattened or vesicular membranous profiles, and a fine flocculent background material reminiscent of those seen free in the lumen or found in cytoplasmic droplets attached to spermatozoa. (ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1988

To certify or not to certify: clinical social work decisions and involuntary hospitalization.

This research compares, on a variety of clinical and contextual factors, case episodes in which Clinical Social Workers decided to certify patients for involuntary hospitalization with those episodes where they decided not to certify them. A cross-sectional exploratory design was developed, and descriptive data was collected using a modified critical incident technique and a structured interview schedule. Among certified cases, the dangerousness of the patient was the major reason for certification, especially dangerousness to others. Lack of dangerousness to others and use of alternatives to involuntary hospitalization were major factors in the decision not to certify. Schizophrenic disorders were most frequently identified in certified patients; depressive and neurotic conditions in non-certified cases.

Commitment of Persons with Psychiatric Disorders↗
PubMed1987

Non-enzymatic synthesis of the coenzymes, uridine diphosphate glucose and cytidine diphosphate choline, and other phosphorylated metabolic intermediates.

The synthesis of uridine diphosphate glucose (UDPG), cytidine diphosphate choline (CDP-choline), glucose-1-phosphate (G1P) and glucose-6-phosphate (G6P) has been accomplished under simulated prebiotic conditions using urea and cyanamide, two condensing agents considered to have been present on the primitive Earth. The synthesis of UDPG was carried out by reacting G1P and UTP at 70 degrees C for 24 hours in the presence of the condensing agents in an aqueous medium. CDP-choline was obtained under the same conditions by reacting choline phosphate and CTP X G1P and G6P were synthesized from glucose and inorganic phosphate at 70 degrees C for 16 hours. Separation and identification of the reaction products have been performed by paper chromatography, thin layer chromatography, enzymatic analysis and ion pair reverse phase high performance liquid chromatography. These results suggest that metabolic intermediates could have been synthesized on the primitive Earth from simple precursors by means of prebiotic condensing agents.

Choline↗