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Biomedical subjects

S Cohen

Publications and source records attributed to S Cohen.

At least 739 records · Page 41Linked to original sources
PubMed1985

Extracellular matrix of the human thymus: immunofluorescence studies on frozen sections and cultured epithelial cells.

The immunohistochemical detection of elements of the human thymic extracellular matrix in situ and in vitro is described. In the normal thymus, the intracapsular and intraseptal fibers were strongly labeled by anti-type I collagen antiserum. Basement membranes bordering the capsule, septae, and perivascular spaces were intensely stained by anti-type IV collagen, anti-fibronectin, and anti-laminin sera. In hyperplastic myasthenia gravis thymuses, the major changes consisted of discontinuities of the basement membrane adjacent to clusters of epithelial (keratin-containing) cells, among which an unusual connective framework (densely labeled by all the antisera) was observed. In vitro, most epithelial cells were strongly labeled by antifibronectin serum and to a lesser extent by the anti-type IV collagen and anti-laminin sera. In addition, fibronectin, laminin, and type IV collagen were detected in the intercellular spaces bordering the epithelial cells in culture. Results show that thymic epithelial cells participate in the synthesis of extracellular matrix elements, which as a result of their localization and influence on epithelial cell growth, should be regarded as constitutive components of the thymic microenvironment.

Cells, Cultured↗
PubMed1985

Kinetic studies on ovarian C-17,20-lyase activity: effect of luteinizing hormone surge.

It has been shown that 3 h after the preovulatory gonadotropin surge, an abrupt decrease occurs in follicular C-17,20-lyase (lyase) activity which causes a decrease in C19-steroid production. To determine the reason for the reduced lyase activity, we used rats that were induced to ovulate by means of PMSG administration. In these rats, a 54% decrease in lyase activity occurred at the peak of the LH surge. When the gonadotropin surge and ovulation were blocked by pentobarbitone the decrease was prevented. Administration of LH to the pentobarbitone-blocked rats reduced lyase activity to well below the level reached after the endogenous gonadotropin surge. In cycling proestrous rats as well, human CG (hCG) decreased the lyase activity, as measured in isolated follicles 3 h after hCG administration. Out of three potential inhibitory steroids for lyase activity; progesterone, 3 alpha,17 alpha-dihydroxy-5 alpha-pregnen-20-one, and 17 alpha,20 alpha-dihydroxy-4-pregnen-3-one, only the last compound inhibited competitively ovarian lyase activity. The inhibition constant (Ki) value was 29 microM. In order to explore which of the two activities of the lyase complex is regulated by the gonadotropin, a double label double substrate experiment was conducted using [14C]progesterone with [3H]17 alpha-hydroxyprogesterone (17 alpha-OHP). With this assay procedure, we could determine in the same experiment the site of stimulation, the preferred substrate, and the amount of conversion. The conversion of progesterone to 17 alpha-OHP, as well as the conversion to androstenedione were significantly inhibited throughout the reaction by the gonadotropin. Thus, the changes in ovarian lyase after hCG mimic those of 17 alpha-hydroxylase. The labeling pattern of androstenedione showed that the ovarian lyase complex catalyzed the conversion preferentially from progesterone. Whereas the 3H/14C ratio in androstenedione varied between 0.29 to 0.76, the ratios in the 17 alpha-OHP were from 5 to 22. Thus, the exogenous 17 alpha-OHP did not equilibrate with the product formed from progesterone. The effect of the hCG was to decrease the preference of progesterone over 17 alpha-OHP as substrate. It is concluded that: the LH of the surge inhibits both the 17 alpha-hydroxylase and lyase activities. The ovarian lyase complex shows a preference for progesterone as a substrate rather than 17 alpha-OHP. 17 alpha-OHP is not an obligatory intermediate in androstenedione production in ovarian tissue. hCG affects the ovarian lyase complex by shifting the relative preference of substrates towards 17 alpha-OHP.

17-alpha-Hydroxyprogesterone↗
PubMed1985

Antibiotic susceptibilities of periodontal bacteria. In vitro susceptibilities to eight antimicrobial agents.

In vitro susceptibilities of 369 to 966 bacterial isolates from periodontal lesions to eight antibiotics were determined by agar dilution technique as a means of determining which antimicrobial agents were inhibitory for bacteria frequently associated with destructive periodontal diseases. Although most bacteria were relatively susceptible to the penicillins, greater activity was generally noted with amoxicillin than with either penicillin or ampicillin with the exception of Selenomonas sputigena and Peptostreptococcus. Antibacterial activities obtained with minocycline were significantly higher than with tetracycline for Actinobacillus actinomycetemcomitans and Streptococcus but comparable for most other taxa. Clindamycin and metronidazole both demonstrated excellent activity against the anaerobic Gram-negative rods but were less effective against some of the capnophilic and facultative organisms. Eikenella corrodens was exceptionally resistant to both of these drugs; and A. actinomycetemcomitans was generally resistant to clindamycin but relatively susceptible to metronidazole. Erythromycin was considerably less active than the other antibiotics against the majority of the periodontal bacteria. No single antibiotic, at concentrations equivalent to those achieved in body fluids, was uniformly effective in inhibiting all bacteria currently implicated or suspected as etiologic agents of periodontal diseases.

Actinobacillus↗
PubMed1985

Survival of pathogenic organisms in immunocompetent hosts.

Pathogens have evolved highly individual means of immune evasion. These involve their location within relatively shielded sites, the variability shedding or disguise of surface antigens and modifications of the host immune response. The latter include the use of proteases to split surface-bound antibodies, the production of compounds which consume complement, the avoidance of phagocytosis or the evasion of lysosomal systems of phagocytes and the excretion of products which inactivate effector functions of specific host cell populations. The continued study of immune evasion will enhance understanding of parasitism and promote the means for controlling organisms which are important pathogens of man and domestic animals.

Animals↗
PubMed1985

Antigen-mediated interleukin production by mononuclear cells from delayed hypersensitive mice.

Antigen-induced production of interleukins was examined using lymph node cells from BALB/c mice immunized with soluble protein antigens emulsified in complete Freund's adjuvant. We found both Interleukin 1 and Interleukin 2 activity in the antigen-stimulated culture supernatants of lymph node cells obtained from mice immunized with the corresponding antigen. The induction of interleukins correlated with in vivo (footpad response) and in vitro (lymphocyte proliferation) manifestations of delayed hypersensitivity. The kinetics of appearance of IL 1 and IL 2 in culture was similar. Stimulation with unrelated antigens could induce neither interleukins nor both types of cell-mediated immune responses. These results demonstrate that interleukins are inducible by stimulation with soluble proteins under conditions of immunization that lead to cell-mediated immunity.

Animals↗
PubMed1985

Adenosine-induced K+ current in Xenopus oocyte and the role of adenosine 3',5'-monophosphate.

Voltage clamp technique was used in Xenopus laevis oocytes in order to study and compare membrane currents evoked by extracellularly applied adenosine (0.1-10 microM) and intracellularly injected cyclic AMP (0.15-10 microM). The adenosine response is a late long-lasting outward K+ current ("H" current), mediated by the Ra purine receptor subtype. The H current amplitude is directly proportional to (occupancy)3; the KD for adenosine is 3.34 microM. The H current is inhibited by the intracellular injection of protein kinase inhibitors, types II and III (5-450 ng/oocyte) and is usually potentiated by intracellular injection of theophylline (100-300 microM), though extracellular application of theophylline (1-100 microM) reversibly blocks the receptor. Occasionally, the H current is contaminated by a small Cl- current. The cyclic AMP current is also a long-lasting K+ outward current which is potentiated by extracellular theophylline (2 mM). Injection of cyclic AMP inhibits the membrane response to subsequent application of adenosine. The converse inhibition of a cyclic AMP response by an earlier adenosine response is also observed but at very high concentrations of adenosine (greater than 0.6 mM). It was shown by radioimmunoassay that extracellular adenosine increases the level of the intracellular cAMP within a few seconds by about 30%. Intracellular injection of a comparable amount of cAMP was shown to evoke a measurable K+ current. It is proposed that the adenosine-evoked K+ outward current is mediated by a rise in intracellular cAMP.

Adenosine↗
PubMed1985

Cloning, expression and biological activity of a new variant of human interferon alpha identified in virus induced lymphoblastoid cells.

A synthetic oligonucleotide complementary to a highly conserved sequence in the IFN-alpha gene family, was used to screen a Namalva cDNA library. Among the cDNA clones having typical IFN-alpha traits, one was distinct from previously characterized IFN-alpha cDNAs. E. coli cells carrying this recombinant cDNA plasmid express an alpha-interferon activity. The sequence of this IFN-cDNA is extremely homologous (99.5%) to that of the IFN-alpha J gene and is designated IFN-alpha J1. Several E. coli trp expression plasmids were constructed for efficient transcription and translation of the mature IFN-alpha J1. The maximal level of expression (5 X 10(3) molecules/cells) was obtained from plasmid pJ1-4. A synthetic consensus translation initiation sequence coupled to the trp p/o region (in pJ1-5) proved to be 10 times less effective in promoting metIFN production in bacteria, than the in-vitro mutated trpL initiation sequence carried on pJ1-4. The bacterial IFN-alpha J1 was purified (to over 90% purity) to a specific activity of 1.3 X 10(8) units/mg. The antiviral activity of the purified IFN-alpha J1 was compared with other highly purified IFN-alpha species (bacterial IFN alpha A and alpha C, leukocyte IFN-alpha 1, leukocyte IFN mixture and Namalva IFN preparation) on a large panel of mammalian cell cultures. IFN-alpha J1 exhibits a distinct antiviral activity.

Amino Acid Sequence↗
PubMed1985

Detection of dihydroorotate dehydrogenase activity as a marker of de novo nucleic acid synthesis in germinal centers of spleens following antigen administration.

A histochemical technique, developed for the localization of DHO-D activity in tissue, has been utilized to study the distribution of this activity in rabbit spleen. This enzyme is involved in the de novo synthesis of pyrimidines of nucleic acids via orotic acid as an intermediate. The enzyme was found to be most active at the periphery of follicles in the resting spleen. Following antigenic challenge, enzyme activity became prominent for several days in macrophages within germinal centers, but not in the intensely pyroninophilic cells which are the dominant cell type of these structures. Antigenicity of the injected compound appeared to be necessary for the production of this effect. The pattern of localization of DHO-D is similar to the pattern of distribution of antigen within splenic tissue.

Animals↗
PubMed1985

Incidence of serious infection in infants under age two months with fever.

Infants less than eight weeks of age in a busy urban emergency department were prospectively reviewed during a six-month period, from October 1, 1981 to March 31, 1982. An axillary temperature of 37.8 degrees C or higher was arbitrarily defined as significantly elevated. A total of 1,655 young infants were seen during this time period, with 122 having temperatures of 37.8 degrees C or higher (7%). Four percent of the febrile patients were bacteremic. The degree of temperature elevation was not proportional to the severity of the illness. Total white blood cell count was less than 4,000/mm3 in two of the bacteremic patients. Cerebrospinal fluid pleocytosis was present in 13% of the patients undergoing lumbar puncture.

Bacterial Infections↗
PubMed1985

Role of interleukin 1 in experimental pulmonary granuloma in mice.

Pulmonary granulomas were induced in immunized BALB/c mice by the intratracheal injection of antigen-coated and plain agarose beads. Prominent lesions developed within 24 hr, reached peak intensity within 3 days, and gradually declined in size thereafter. The hypersensitivity granulomas induced in sensitized mice by antigen-coated beads were much larger than the lesions induced by plain beads. Minimal inflammation was produced in unsensitized mice injected with antigen-coated or plain beads. Aqueous extracts prepared from pulmonary granuloma lesions induced in sensitized mice by antigen-coated beads contained high levels of interleukin 1 (IL 1) and migration inhibition factor (MIF) activities. The kinetics of appearance of these mediators were similar. Lower but detectable activity of both mediators was detected in extracts prepared from sensitized mice injected with plain beads. Neither interleukin 2 (IL 2) nor IL 2 neutralizing activities were detected in the extracts. The presence of IL 1 and MIF in extracts prepared from early and peak pulmonary granulomatous lesions suggests that these soluble factors are produced by cells within the lesions, and that they are involved in mediating the expression and/or maintenance of the granulomas.

Animals↗
PubMed1985

Cloning of a bovine interferon-alpha gene subfamily and comparisons between genetically engineered and leukocyte bovine interferons.

Bovine peripheral leukocytes were virally induced for interferon production, and an acid stable, SDS stable, antiviral activity was detected in the preparation. This bovine interferon (BoIFN) was tested for its ability to induce an antiviral state in various mammalian cells and was found to be specific to cells from bovine origin. The BoIFN cross reacts with antibodies against human IFN-alpha but these antibodies do not neutralize the bovine IFN activity. Leukocyte BoIFN exhibits polymorphism upon Affi-Gel Blue chromatography and SDS-PAGE (16k and 24K). The virally induced leukocytes produce a 13S mRNA which upon translation in oocytes yields an active IFN molecule. Bovine genomic library was constructed and screened for BoIFN-alpha sequences, using human IFN-alpha probes. From the clones isolated, five were found to represent distinct genes. Sequence analysis indicate that these genes are closely related (94% homology). One of these genes was expressed in E. coli under the control of trp promoter operator. The physicochemical and biological properties of the bacterial BoIFN-alpha product resemble those of a subpopulation of natural BoIFN.

Animals↗