Zinc transporter 8 haploinsufficiency protects against beta cell dysfunction in type 1 diabetes by increasing mitochondrial respiration

OBJECTIVE

Zinc transporter 8 (ZnT8) is a major humoral target in human type 1 diabetes (T1D). Polymorphic variants of Slc30A8, which encodes ZnT8, are also associated with protection from type 2 diabetes (T2D). The current study examined whether ZnT8 might play a role beyond simply being a target of autoimmunity in the pathophysiology of T1D.

METHODS

The phenotypes of NOD mice with complete or partial global loss of ZnT8 were determined using a combination of disease incidence, histological, transcriptomic, and metabolic analyses.

RESULTS

Unexpectedly, while complete loss of ZnT8 accelerated spontaneous T1D, heterozygosity was partially protective. In vivo and in vitro studies of ZnT8 deficient NOD.SCID mice suggested that the accelerated disease was due to more rampant autoimmunity. Conversely, beta cells in heterozygous animals uniquely displayed increased mitochondrial fitness under mild proinflammatory conditions.

CONCLUSIONS

In pancreatic beta cells and immune cell populations, Zn2+ plays a key role as a regulator of redox signaling and as an independent secondary messenger. Importantly, Zn2+ also plays a major role in maintaining mitochondrial homeostasis. Our results suggest that regulating mitochondrial fitness by altering intra-islet zinc homeostasis may provide a novel mechanism to modulate T1D pathophysiology.

The physiological effects of deleting the mouse SLC30A8 gene encoding zinc transporter-8 are influenced by gender and genetic background

Objective

The SLC30A8 gene encodes the islet-specific transporter ZnT-8, which is hypothesized to provide zinc for insulin-crystal formation. A polymorphic variant in SLC30A8 is associated with altered susceptibility to type 2 diabetes. Several groups have examined the effect of global Slc30a8 gene deletion but the results have been highly variable, perhaps due to the mixed 129SvEv/C57BL/6J genetic background of the mice studied. We therefore sought to remove the conflicting effect of 129SvEv-specific modifier genes.

Methods

The impact of Slc30a8 deletion was examined in the context of the pure C57BL/6J genetic background.

Results

Male C57BL/6J Slc30a8 knockout (KO) mice had normal fasting insulin levels and no change in glucose-stimulated insulin secretion (GSIS) from isolated islets in marked contrast to the ∼50% and ∼35% decrease, respectively, in both parameters observed in male mixed genetic background Slc30a8 KO mice. This observation suggests that 129SvEv-specific modifier genes modulate the impact of Slc30a8 deletion. In contrast, female C57BL/6J Slc30a8 KO mice had reduced (∼20%) fasting insulin levels, though this was not associated with a change in fasting blood glucose (FBG), or GSIS from isolated islets. This observation indicates that gender also modulates the impact of Slc30a8 deletion, though the physiological explanation as to why impaired insulin secretion is not accompanied by elevated FBG is unclear. Neither male nor female C57BL/6J Slc30a8 KO mice showed impaired glucose tolerance.

Conclusions

Our data suggest that, despite a marked reduction in islet zinc content, the absence of ZnT-8 does not have a substantial impact on mouse physiology.

Expression and regulation of chemokines in murine and human type 1 diabetes

More than one-half of the ~50 human chemokines have been associated with or implicated in the pathogenesis of type 1 diabetes, yet their actual expression patterns in the islet environment of type 1 diabetic patients remain, at present, poorly defined. Here, we have integrated a human islet culture system, murine models of virus-induced and spontaneous type 1 diabetes, and the histopathological examination of pancreata from diabetic organ donors with the goal of providing a foundation for the informed selection of potential therapeutic targets within the chemokine/receptor family. Chemokine (C-C motif) ligand (CCL) 5 (CCL5), CCL8, CCL22, chemokine (C-X-C motif) ligand (CXCL) 9 (CXCL9), CXCL10, and chemokine (C-X3-C motif) ligand (CX3CL) 1 (CX3CL1) were the major chemokines transcribed (in an inducible nitric oxide synthase-dependent but not nuclear factor-κB-dependent fashion) and translated by human islet cells in response to in vitro inflammatory stimuli. CXCL10 was identified as the dominant chemokine expressed in vivo in the islet environment of prediabetic animals and type 1 diabetic patients, whereas CCL5, CCL8, CXCL9, and CX3CL1 proteins were present at lower levels in the islets of both species. Of importance, additional expression of the same chemokines in human acinar tissues emphasizes an underappreciated involvement of the exocrine pancreas in the natural course of type 1 diabetes that will require consideration for additional type 1 diabetes pathogenesis and immune intervention studies.

Regular treatment with long acting beta agonists versus daily regular treatment with short acting beta agonists in adults and children with stable asthma

BACKGROUND

Selective beta-adrenergic agonists for use in asthma are: short acting (2-6 hours) and long acting (>12 hours). There has been little controversy about using short acting beta-agonists intermittently, but long acting beta-agonists are used regularly, and their regular use has been controversial.

OBJECTIVES

To determine the benefit or detriment of treatment with regular short- or long acting inhaled beta-agonists in chronic asthma.

SEARCH STRATEGY

A search was carried out using the Cochrane Airways Group register. Bibliographies of identified RCTs were searched for additional relevant RCTs. Authors of identified RCTs were contacted for other published and unpublished studies.

SELECTION CRITERIA

All randomised studies of at least two weeks duration, comparing a long acting inhaled beta-agonist given twice daily with any short acting inhaled beta-agonist of equivalent bronchodilator effectiveness given regularly in chronic asthma.

DATA COLLECTION AND ANALYSIS

Two reviewers performed data extraction and study quality assessment independently. Authors of studies were contacted for missing data.

MAIN RESULTS

31 studies met the inclusion criteria, 24 of parallel group and 7 cross over design. Salmeterol xinafoate was used as long acting agent in 22 studies and formoterol fumarate in 9. Salbutamol was the short acting agent used in 27 studies and terbutaline in 5. The treatment period was over 2 weeks in 29 studies, and at least 12 weeks in 20. 25 studies permitted a variety of co-intervention treatments, usually inhaled corticosteroid or cromones. One study did not permit inhaled corticosteroid. Long acting beta-agonists were significantly better than short acting for a variety of lung function measurements including morning PEF (Weighted Mean Difference (WMD) 33 l/min 95% CI 25, 42) or evening PEF (WMD 26 l/min 95% CI 18, 33); and had significantly lower scores for day and night time asthma symptom scores and percentage of days and nights without symptoms. They were also associated with a significantly lower use of rescue medication both during the day and night. Risk of exacerbations was not different between the two types of agent, but most studies were of short duration which limits the power to test for such differences.

REVIEWER'S CONCLUSIONS

Long acting inhaled beta-agonists have advantages across a wide range of physiological and clinical outcomes for regular treatment.

Implementing and integrating computer-based activities into a problem-based gross anatomy curriculum

A problem-based learning curriculum in gross anatomy was begun for a limited number of students to address unsuccessful methodology inherent in a traditional instructional approach. To eliminate some concerns associated with the laboratory component, computer-based instruction and other computer- related activities were actively integrated into the total instructional process. Prosections, directions, quizzes, images, and grades were provided in lab at table-side computer workstations, in the library, and on the web. Results were assessed through questionnaires in which students rated their learning experience according to a Likert-type scale. Success was measured by quantitative improvements in student perception. In this three-year study, observations and measurements have suggested increasingly positive student attitudes toward educational technology, for networks as a faster and more effective method of student/faculty communication, and in the utilization of computer-based instruction for greater flexibility and efficiency in learning. This allowed a rethinking of the structure and content of the curriculum by the faculty, which permitted reduced laboratory time, more small-group activity, and less reliance on staff.

Constitutive activation of the prolactin receptor results in the induction of growth factor-independent proliferation and constitutive activation of signaling molecules

The ability to induce the oncogenic activation of the human prolactin receptor (PRLR) was examined by deleting 178 amino acids of the extracellular ligand-binding domain. Expression of this deletion mutant in the interleukin-3 (IL-3)-dependent murine myeloid cell line 32Dcl3 resulted in the induction of growth factor-independent proliferation. Parental 32Dcl3 cells proliferated only in the presence of exogenous murine IL-3 (mIL-3), while 32Dcl3 cells transfected with the long form of the human PRLR were able to proliferate in response to mIL-3, ovine prolactin, or human PRL. Cells expressing the Delta178 deletion mutant contained numerous phosphotyrosine-containing proteins in the absence of stimulation with either mIL-3 or ovine prolactin. Growth factor stimulation increased the number of proteins phosphorylated and the intensity of phosphorylation. These proteins included constitutively phosphorylated Janus kinase 2, signal transducer and activator of transcription 5, and SHC. Activated extracellular signal-regulated kinases 1 and 2 (ERK1 and ERK2) were observed in unstimulated 32Dcl3 cells expressing the Delta178 mutant. Likewise, transfection of Nb2 cells with the Delta178 deletion mutant induced growth factor-independent proliferation and constitutive activation of Janus kinase 2, ERK1, and ERK2. In addition to the induction of a growth factor-independent state, the expression of the Delta178 deletion mutant also suppressed the apoptosis that occurs when 32Dcl3 cells are cultured in the absence of growth factors such as IL-3. These data suggest that the constitutive activation of the PRLR can be achieved by deletion of the ligand binding domain and that this mutation leads to the oncogenic activation of the receptor as determined by the ability of the receptor to induce growth factor-independent proliferation of factor-dependent hematopoietic cells.

Effects of the protein kinase C stimulant bryostatin 1 on the proliferation and colony formation of irradiated human T-lymphocytes

The protein kinase C stimulant bryostatin 1 (Bryo) was used in examining human peripheral blood T-lymphocyte radiosensitivities in proliferation assays. Bryo was similar to PMA in inducing T-cell proliferation by the CD3, CD28 and CD69 pathways. No difference in radiosensitivities was observed in T-cells stimulated by the three independent surface antigen-mediated activation pathways. CD3 was chosen as the second signal for comparing the potencies of the three different first signals Bryo, phorbol 12-myristate, 13-acetate (PMA), and interleukin 2 (IL-2) in stimulating T-cell proliferation and in maintaining this response after radiation. Though there were radioresponse differences among various individuals, the irradiated lymphocytes consistently showed significantly greater proliferation when treated with Bryo or PMA than with IL-2 (p < 0.05- < 0.005). No difference in proliferative responses was observed in T-cells irradiated between 4 h before and 15 h after the addition of stimulants. Colony forming assays showed higher colony survival for irradiated T-cells stimulated with Bryo than with PMA. These results support the important role of protein kinase C in T-cell radiation responses, and suggest a potential role for Bryo in enhancing T-lymphocyte survival during radiation therapy.

Stimulation of interleukin-1 alpha and interleukin-1 beta production in human monocytes by protein phosphatase 1 and 2A inhibitors

Protein phosphatases 1 and 2A are important in regulating cellular functions by controlling the phosphorylation state of their substrates. In human monocytes, the inhibitors of these phosphatases, okadaic acid and calyculin A, were found to increase the mRNA accumulation and cytokine production of interleukin-1 beta and interleukin-1 alpha. The increased mRNA accumulation was found to be primarily because of the increase in the transcription rate of the interleukin-1 genes. Stimulation of interleukin-1 gene transcription may be caused by the stimulation of transcription factor activities, including those of AP-1, by these protein phosphatase inhibitors. Okadaic acid increased the synthesis of the interleukin-1 beta precursor and mature forms and their secretion. This increased processing and secretion correlated with the stimulation of IL-1 beta convertase mRNA accumulation. The stimulation of interleukin-1 alpha production by okadaic acid was more modest than that of interleukin-1 beta. However, the phosphorylation of the precursor interleukin-1 alpha cytokine was increased. These results show that protein phosphatase 1 and 2A inhibitors exert multiple effects on cytokine production in human monocytes and suggest that these two phosphatases play important roles in regulating interleukin-1 production.

Stimulation of tumor necrosis factor alpha production in human monocytes by inhibitors of protein phosphatase 1 and 2A

The protein phosphatase 1 and 2A inhibitor, okadaic acid, has been shown to stimulate many cellular functions by increasing the phosphorylation state of phosphoproteins. In human monocytes, okadaic acid by itself stimulates tumor necrosis factor alpha (TNF-alpha) mRNA accumulation and TNF-alpha synthesis. Calyculin A, a more potent inhibitor of phosphatase 1, has similar effects. TNF-alpha mRNA accumulation in okadaic acid-treated monocytes is due to increased TNF-alpha mRNA stability and transcription rate. The increase in TNF-alpha mRNA stability is more remarkable in okadaic acid-treated monocytes than the mRNA stability of other cytokines, such as interleukin 1 alpha (IL-1 alpha), IL-1 beta, and IL-6. Gel retardation studies show the stimulation of AP-1, AP-2, and NF-kappa B binding activities in okadaic acid-stimulated monocytes. This increase may correlate with the increase in TNF-alpha mRNA transcription rate. In addition to the stimulation of TNF-alpha secretion by monocytes, okadaic acid appears to modulate TNF-alpha precursor processing, as indicated by a marked increase in the cell-associated 26-kD precursor. These results suggest that active basal phosphorylation/dephosphorylation occurs in monocytes, and that protein phosphatase 1 or 2A is important in regulating TNF-alpha gene transcription, translation, and posttranslational modification.

Increased cyclic AMP levels enhance IL-1 alpha and IL-1 beta mRNA expression and protein production in human myelomonocytic cell lines and monocytes

The effects of increasing intracellular cAMP levels on IL-1 alpha and IL-1 beta mRNA expression and IL-1 production in human monocytes and nonlymphoid hematopoietic cell lines were examined. Peripheral monocytes and myelomonocytic cell lines could be stimulated by LPS or phorbol myristate acetate (PMA) to express IL-1 mRNA. Dibutyryl cAMP, 8-bromo-cAMP, forskolin, cholera toxin, PGE1, and PGE2 synergized with PMA or LPS to increase the accumulation in cell lines of IL-1 alpha mRNA by up to 50-fold and that of IL-1 beta mRNA by 10- to 20-fold compared to LPS or PMA alone. This increase in IL-1 alpha and IL-1 beta mRNA accumulation was more modest in monocytes. The synergistic stimulation was due to enhanced IL-1 gene transcription rate rather than increased IL-1 mRNA stability. Despite this marked increase in IL-1 mRNA accumulation, IL-1 protein synthesis in these cells was increased by only twofold. Thus, IL-1 synthesis in monocytes and myelomonocytic cell lines is under stringent translational control.

Tumor necrosis factor-alpha mRNA accumulation in human myelomonocytic cell lines. Role of transcriptional regulation by DNA sequence motifs and mRNA stabilization

The cytokine TNF mediates many of the pathologic signs of cachexia, inflammation, and sepsis. The current work describes the regulation of TNF in human myelomonocytic cell lines after PMA stimulation. The cell lines exhibit a low level of constitutive TNF mRNA expression. Within 2 to 4 h of PMA exposure, steady state levels of TNF mRNA are markedly elevated in all myelomonocytic cell lines studied. This rise is due to increased mRNA stability, which increased by almost twofold, and to an overall increase in transcription, which rises by more than sixfold. At the level of the genomic TNF gene, a DNase I hypersensitive site is detected within the TNF promoter between -200 to -100 bp relative to the transcription initiation site. Although absent in nonexpressing erythroleukemia cell lines, the DNase I site is present in uninduced myelomonocytic cell lines and is not changed after PMA induction. The PMA induction of c-fos mRNA correlated well with TNF gene induction; expression of genes encoding other proteins in the AP-1 complex (junB and junD) were also induced by PMA. The nuclear extracts from resting and induced ML-1 cells contain proteins binding specifically to the AP-1, AP-2, and NF kappa B sequence located within the TNF promoter. PMA induction increases the level of a number of specific binding complexes relative to the resting cells. The regulatory mechanisms of the human and murine TNF genes are discussed.

Tumor necrosis factor-alpha mRNA accumulation in human myelomonocytic cell lines. Role of transcriptional regulation by DNA sequence motifs and mRNA stabilization

The cytokine TNF mediates many of the pathologic signs of cachexia, inflammation, and sepsis. The current work describes the regulation of TNF in human myelomonocytic cell lines after PMA stimulation. The cell lines exhibit a low level of constitutive TNF mRNA expression. Within 2 to 4 h of PMA exposure, steady state levels of TNF mRNA are markedly elevated in all myelomonocytic cell lines studied. This rise is due to increased mRNA stability, which increased by almost twofold, and to an overall increase in transcription, which rises by more than sixfold. At the level of the genomic TNF gene, a DNase I hypersensitive site is detected within the TNF promoter between -200 to -100 bp relative to the transcription initiation site. Although absent in nonexpressing erythroleukemia cell lines, the DNase I site is present in uninduced myelomonocytic cell lines and is not changed after PMA induction. The PMA induction of c-fos mRNA correlated well with TNF gene induction; expression of genes encoding other proteins in the AP-1 complex (junB and junD) were also induced by PMA. The nuclear extracts from resting and induced ML-1 cells contain proteins binding specifically to the AP-1, AP-2, and NF kappa B sequence located within the TNF promoter. PMA induction increases the level of a number of specific binding complexes relative to the resting cells. The regulatory mechanisms of the human and murine TNF genes are discussed.

Characterization of a small cryptic plasmid isolated from a methicillin-resistant strain of Staphylococcus aureus

The nucleotide sequence of a small (1613 bp) plasmid, pOX2000, isolated from a methicillin-resistant strain of Staphylococcus aureus has been determined. The sequence contains only one large ORF and the predicted amino acid sequence shows homology to the REP proteins of some other small staphylococcal plasmids. In addition there are two palindromic sequences, palA and palJ, that are similar to but not identical with the palindromes known from other staphylococcal plasmids to be involved in lagging strand initiation and possibly leading strand termination, respectively. Preliminary functional analysis of pOX2000 has been carried out by assessing the effect of interrupting the sequence at three unique restriction endonuclease sites. The plasmid pOX2000, and its relationship to other small staphylococcal plasmids, is discussed.

Motivating and sustaining commitment to quality assurance

It is important to realize the dynamics of individual as well as group motivation when planning QA activities because measuring the quality of care should be important to all staff on the unit. The nursing manager, however, is a crucial individual to involve in QA activities in order to make unit QA activities a priority for the unit. By understanding the dynamics of motivation and change, the QA coordinator can successfully work with nursing managers and nursing staff to demonstrate the impact of QA activities on enhanced quality of care.

Effects of base sequence on the loop folding in DNA hairpins

High-resolution NMR and UV-melting experiments have been used to study the hairpin formation of partly self-complementary DNA fragments in an attempt to derive rules that describe the folding in these molecules. Earlier experiments on the hexadecanucleotide d(ATCCTA-TTTT-TAGGAT) had indicated that within the loop of four thymidines a wobble T-T pair is formed (Blommers et al., 1987). In the present paper it is shown that if the first and the last thymines of the intervening sequence are replaced by complementary bases, sometimes base pairs can be formed. Thus for the intervening sequences -CTTG- and -TTTA- with the pyrimidine in the 5'-position and the purine in the 3'-position, a base pair is formed leading to a loop consisting of two residues. For the intervening sequences -GTTC- and -ATTT- with the purine in the 5'-position and the pyrimidine in the 3'-position, this turns out not to be the case. It was found that it made no difference when the four-membered sequence was closed by a G-C base pair or an A-T base pair. Replacement of the two central thymidine residues by the more bulky adenine residues limits the hairpin to a four-membered loop scheme. Very surprisingly, it was found from 2D NOE experiments that the T-A base pair, formed in the loop consisting of the -TTTA- sequence, is a Hoogsteen pair. It is argued that the pairing of the bases in this scheme may facilitate the formation of a loop of two residues, since the distance of the C1' atoms in this base pair is 8.6 A instead of 10.4 A found in the canonical Watson-Crick base pair. Combination of the data obtained for the series of DNA fragments studied shows that the results can be explained by a simple, earlier proposed, loop folding principle which assumes that the folding of the four-membered loop is dictated by the stacking of the double-helical stem of the hairpin.

Production of lymphotoxin by isolated human tonsillar B lymphocytes and B lymphocyte cell lines

The expression of lymphotoxin (LT) mRNA and cytokine in human tonsillar B cells and B cell lines was examined by Northern blots and cytotoxicity assays, respectively. In tonsillar B cells, phorbol myristate acetate (PMA) or Staphylococcus aureus Cowan l (SAC) alone induced low levels of LT mRNA accumulation. However, SAC and anti-mu were strongly synergistic with PMA in this induction. Peak LT mRNA expression in tonsillar B cells stimulated by PMA plus SAC occurred between 48 and 72 h and was approximately half as much as that in PMA plus anti-CD3-stimulated T cells. Cyclosporine A was not effective in inhibiting LT mRNA accumulation by stimulated tonsillar B cells. A number of B cell lines could also be stimulated by PMA to express LT mRNA. Peak accumulation of LT mRNA in the cell line RPMI 1788 stimulated with PMA peaked about 8 h. A23187 in combination with PMA caused this accumulation to increase slightly and to peak earlier. The cytotoxic effects in the supernatants of stimulated B cells were contributed mostly by LT. The results indicate that tonsillar B cells are important in LT production and that there are important differences in the stimulation requirements for LT production and in LT mRNA expression kinetics between tonsillar B cells and B cell lines.

Identification and characterization of a hamster monoclonal antibody anti-2.28 directed against a 70-kilodalton activation antigen on human monocytes

Hamster mAb against activated human monocytes were examined for their reactivities against monocyte activation Ag. One mAb, anti-2.28, stained only monocytes activated with LPS plus IFN-gamma, but not unactivated peripheral blood monocytes, polymorphonuclear leukocytes, lymphocytes, RBC, and platelets. However, it stained peripheral blood T cells activated with PMA plus anti-CD3 and peripheral blood and tonsillar B cells activated with PMA plus anti-mu. Of the 35 cell lines of diverse origin examined for immunofluorescence staining by anti-2.28, only EBV-transformed cell lines showed strong staining by this mAb. One pre-B cell line, Nalm-12, could be induced by PMA to exhibit intermediate staining. Immunoprecipitation studies identified the 2.28 Ag as a 70- to 85-kDa monomer. Immunofluorescence staining, immunoprecipitation, and peptide mapping studies indicated that 2.28 was different from a number of monocyte and lymphocyte surface Ag including Mo3e, B-4 (CD19), B-5, CD39, and the G28-8 Ag Bgp 95. These studies suggest that 2.28 may be a novel hemopoietic non-lineage-specific activation Ag.

Identification and characterization of a hamster monoclonal antibody anti-2.28 directed against a 70-kilodalton activation antigen on human monocytes

Hamster mAb against activated human monocytes were examined for their reactivities against monocyte activation Ag. One mAb, anti-2.28, stained only monocytes activated with LPS plus IFN-gamma, but not unactivated peripheral blood monocytes, polymorphonuclear leukocytes, lymphocytes, RBC, and platelets. However, it stained peripheral blood T cells activated with PMA plus anti-CD3 and peripheral blood and tonsillar B cells activated with PMA plus anti-mu. Of the 35 cell lines of diverse origin examined for immunofluorescence staining by anti-2.28, only EBV-transformed cell lines showed strong staining by this mAb. One pre-B cell line, Nalm-12, could be induced by PMA to exhibit intermediate staining. Immunoprecipitation studies identified the 2.28 Ag as a 70- to 85-kDa monomer. Immunofluorescence staining, immunoprecipitation, and peptide mapping studies indicated that 2.28 was different from a number of monocyte and lymphocyte surface Ag including Mo3e, B-4 (CD19), B-5, CD39, and the G28-8 Ag Bgp 95. These studies suggest that 2.28 may be a novel hemopoietic non-lineage-specific activation Ag.

Production of tumor necrosis factor/cachectin by human B cell lines and tonsillar B cells

The production of TNF/cachectin by human B cell lines and tonsillar B cells was examined. Of the 15 B cell lines examined, 9 cell lines synthesize TNF mRNA constitutively. PMA stimulated most cell lines to accumulate increased amounts of TNF. SeD, 8866P, 32al, RPMI 1788, and four bone marrow-derived EBV-transformed cell lines accumulated high levels of TNF mRNA when stimulated by PMA. TNF production by these cell lines was examined. RPMI 1788 and WIH8 produced little TNF constitutively, but synthesized 5-7 ng/ml TNF when stimulated by PMA. A pre-B cell line, Nalm-6, did not synthesize any detectable amount of TNF mRNA, even with PMA stimulation. Tonsillar B cells could also be stimulated to produce TNF. PMA or Staphylococcus aureus Cowan I strain (SAC) alone stimulated some TNF mRNA accumulation, whereas B cell growth factor (BCGF) or anti-mu did not. This accumulation was synergistically elevated by the combinations of PMA and SAC, or PMA and anti-mu. BCGF increased PMA-, SAC-, PMA plus SAC-, or PMA plus anti-mu-induced TNF mRNA accumulations about twofold. The accumulation of TNF mRNA in tonsillar B cells stimulated by PMA plus SAC was between 32 and 48 h, the same peak interval as the accumulation of TNF and IL-2 mRNA in tonsillar T cells. This is in contrast to PMA or PMA plus A23187-stimulated RPMI 1788 cells in which TNF mRNA accumulation was maximal at 1-2 h. TNF activities found in tonsillar B cell supernatants correlated with the TNF mRNA levels in the cells. However, more TNF activity was found on the second-day than the third-day supernatants, indicating active TNF uptake by the B cells. Cyclosporin A (CsA) inhibited SAC and anti-mu responses in B cells in much the same way as the anti-CD3 responses in T cells. SAC-, PMA plus SAC-, and PMA plus anti-mu-stimulated, but not PMA-stimulated, increases in TNF mRNA accumulations in tonsillar B cells were inhibited by CsA. TNF production seems to increase in parallel with B cell proliferation, but the relationship of these two functions needs to be further examined.

Solution structure of the 3'-5' cyclic dinucleotide d(pApA). A combined NMR, UV melting, and molecular mechanics study

The 3'-5' cyclic dinucleotide d(pApA) was studied by means of 1H and 13C NMR experiments, UV-melting experiments, and molecular mechanics calculations. The 1H and 13C NMR spectra were analyzed by means of 2-dimensional NMR experiments. J-Coupling analysis of the 1D and 2D 1H and 13C spectra was used to determine the conformation of the ring systems in the molecule. It appeared that at low temperature (283 K) the deoxyribose sugars adopt a N-type conformation. The geometry is best described by an intermediate between the 3(2)T and 3E forms. In addition, we were able to derive all other torsion angles in the phosphate backbone ring system, i.e., alpha +, beta t, gamma +, delta (= 89 degrees), epsilon t, and zeta +. When the molecule is subjected to an energy minimization procedure (using the program AMBER), the sugar ring system retains, practically speaking, the torsion angles found from the NMR experiments, while the torsion angles around the glycosidic bond adopt a value of 175 degrees in the minimum energy conformation. UV-melting experiments indicate that two molecules can form a dimer in which the adenine bases are intercalated. The feasibility of this structure is indicated by molecular mechanics calculations. At higher temperatures the dimer is converted into separate monomers. In the monomer form the sugars exhibit S-pucker 20% of the time. Concomitantly with the conversion of the N- to the S-conformation, the torsion angles alpha and gamma change.

An innovative method of job interviewing

When the right candidate is hired for the right position, both the institution and the individual benefit. The individual has increased job satisfaction, is more likely to remain in the position longer, and is more productive. The author describes a method of job interviewing that objectively measures the abilities of candidates so that the best candidate for the position can be hired.

Study of the interaction between uncharged yeast tRNAPhe and elongation factor Tu from Bacillus stearothermophilis

Proton NMR studies are presented on the interaction of nonaminoacylated yeast tRNAPhe and elongation factor Tu X GTP from Bacillus stearothermophilis. From experiments in which transfer of magnetization is observed between proton spins of tRNA and the protein, it is concluded that complex formation takes place. Amino acid residues of the protein come into close contact with the base pair A5U68 and/or U52A62 of the acceptor T psi C limb of the tRNA molecule. From the line broadening of tRNA resonances, associated with complex formation, an association constant of 10(3)-10(4) M-1 is estimated. The NMR experiments do not monitor a significant conformational change of the tRNA molecule upon interaction with the protein. However, at times long after the onset of complex formation, spectral changes indicate that the upper part of the acceptor helix becomes distorted.

Membrane vesicles of cellular dimensions fit in two geometric series

Preparations of basal-lateral plasma membranes from rat intestinal epithelial cells were analyzed with the analytical centrifuge. In these preparations a number of well-defined membrane fractions were observed. The particle weights of these fractions appear to fit in two geometric series. Until now only relatively small vesicles up to a diameter of about 1 micron were observed. In our preparation we have observed vesicles up to a diameter of 7.5 microns. Therefore, even vesicles with the same size as the plasma membranes of intact cells fit in the two geometric series.

Influence of the polyamines spermine and spermidine on yeast tRNAPhe as revealed from its imino proton NMR spectrum

A comparison of imino proton NMR spectra of yeast tRNAPhe recorded at various solution conditions indicates, that polyamines have a limited effect on the structure of this tRNA molecule. Polyamines are found to catalyse the solvent exchange of several imino protons in yeast tRNAPhe not only of non hydrogen bonded imino protons, but also of imino protons of the GU and of some AU and tertiary base pairs. It is concluded that at low levels of catalysing components the exchange rates of the latter protons are not determined by the base pair lifetime. In the presence of high levels of spermidine the solvent exchange rates of imino protons of several base pairs in the molecule were assessed as a function of the temperature. Apparent activation energies derived from these rates were found to be less than 80 kJ/mol, which is indicative for (transient) independent opening of the corresponding base pairs. In the acceptor helix the GU base pair acts as a dynamic dislocation. The AU base pairs at one side of the GU base pair exhibit faster transient opening than the GC base pairs on the other side of this wobble pair. The base pairs m2GC10 and GC11 from the D stem and GC28 from the anticodon stem show relatively slow opening up to high temperatures. Model studies suggest that 1-methyladenosine, an element of tRNA itself, catalyses imino proton solvent exchange in a way similar to polyamines.

Interactions of some naturally occurring cations with phenylalanine and initiator tRNA from yeast as reflected by their thermal stability

The thermal unfolding of phenylalanine and initiator tRNA from yeast was investigated over a broad range of solution conditions by differential ultraviolet absorption at 260 nm. Under most conditions, the initiator tRNA exhibits two clearly separated transitions in its differential melting curve which were assigned to unfolding of tertiary and secondary structure elements, respectively. The tertiary transition of this tRNA and the overall transition observed for tRNAPhe do not show a maximum in a curve of Tm values plotted as a function of [Na+]. Such a maximum is usually observed for other nucleic acids at about 1 M Na+. In the presence of 5 mM of the divalent cation Mg2+ (or Ca2+), an overall destabilization of the tRNAs is observed when increasing the sodium concentration. The largest fall in Tm (approximately 15 degrees C) is observed for the tertiary transition of the initiator tRNA. Among various cations tested the following efficiency in the overall stabilization of tRNAPhe is observed: spermine greater than spermidine greater than putrescine greater than Na+ (approximately NH4+). Mg2+ is most efficient at concentrations above 5 mM, but below this concentration spermine and spermidine appear to be more efficient. The same hierarchy in stabilizing power of the polyamines and Na+ is observed for both transitions of the initiator tRNA. However, when compared with Mg2+, the polyamines are far less capable of stabilizing the tertiary structure. In contrast, spermine and spermidine are slightly better than Mg2+ in stabilizing the secondary structure. At increasing concentrations of the polyvalent cations (at fixed [Na+] ) the Tm values of the tRNAs attain a constant value.

Imino-proton resonances of yeast tRNAPhe studied by two-dimensional nuclear Overhauser enhancement spectroscopy

Application of two-dimensional nuclear Overhauser enhancement (NOE) spectroscopy to yeast tRNAPhe in H2O solution demonstrates that all imino-proton resonances, related to the secondary structure, and nearly all imino proton resonances, originating from the tertiary structure, can be assigned efficiently by this method. The results corroborate the assignments of the imino-proton resonances of this tRNA as established previously by one-dimensional NOE experiments (only the assignment of base pairs G1 X C72 and C2 X G71 should be reversed). The advantages of two-dimensional NOE spectroscopy over one-dimensional NOE spectroscopy for the assignments of imino-proton resonances and the structure elucidation of tRNA are illustrated and discussed. Furthermore, the use of non-exchangeable proton resonances as probes of the molecular structure is explored.

The solution structure of yeast tRNAPhe as studied by nuclear Overhauser effects in NMR

Recently, the imino proton spectrum of yeast tRNAPhe has been assigned by means of the application of the nuclear Overhauser effect (NOE). In the present paper it will be shown that even for tRNA (MW 28000) connectivities between the imino proton spins can be observed using two-dimensional NOE spectroscopy. In this way the imino proton resonances of the D-stem region are assigned. The results are discussed in relation to those obtained by the classical one-dimensional nuclear Overhauser effect. It turns out that in 2D-NOE experiments connectivities from overlapping resonances can be observed which cannot be determined by one-dimensional Overhauser experiments. Moreover, the total assignment of the imino proton spectrum of yeast tRNAPhe is used to relate the three-dimensional crystal structure of the tRNA to its solution structure. It is shown that the principle elements of the X-ray structure, i.e. the hydrogen bonding network and the stacking of the stems upon one another, are also found in solution. This is true for the presence as well as for the absence of magnesium ions. However, in absence of magnesium ions the tRNA structure appears to differ in details from that in the presence of magnesium ions. Finally, the influence of the elongation factor Tu from B.stearothermophilus on the tRNA structure is discussed.

Separation of basolateral plasma membranes from smooth endoplasmic reticulum of the rat enterocyte by zonal electrophoresis on density gradients

Basolateral plasma membranes of rat small intestinal epithelium were purified by density gradient centrifugation followed by zonal electrophoresis on density gradients. Crude basolateral membranes were obtained by centrifugation in which the marker enzyme, (Na+ + K+)-ATPase, was enriched 10-fold with respect to the initial homogenate. The major contaminant was a membrane fraction derived from smooth endoplasmic reticulum, rich in NADPH-cytochrome c reductase activity. The crude basolateral membrane preparation could be resolved into the two major components by subjecting it to zonal electrophoresis on density gradients. The result was that (Na+ + K+)-ATPase was purified 22-fold with respect to the initial homogenate. Purification with respect to mitochondria and brush border membranes was 35- and 42-fold, respectively. Resolution of (Na+ + K+)-ATPase from NADPH-cytochrome c reductase by electrophoresis was best with membrane material from adult rats between 180 and 250 g. No resolution between the two marker enzymes occurred with material from young rats of 125 to 140 g. These results demonstrate that zonal electrophoresis on density gradients, a simple and inexpensive technique, has a similar potential to free-flow electrophoresis.

On the binding of Mg2+ and Mn2+ to tRNA

In this paper previous binding studies of Mg2+ and Mn2+ ions to tRNA's are reconsidered. Binding data of some representative examples are interpreted including interactions between charges located on the macroion. Both curved and bell-shaped Scatchard plots can be accounted for quantitatively if corrections are made for electrostatic interactions and, if necessary, for the effect of conformational changes on these interactions. It appears that there is no need to invoke more than one class of binding sites on tRNA's, meaning that the experimental binding data can be described using the same intrinsic pK value for all phosphate groups.

D. Campbell Meyers, M.D., L.R.C.P., M.R.C.S. (Eng.) 1863-1927, pioneer of Canadian general hospital psychiatry

The paper describes the pioneering contributions of Dr. D. Campbell Meyers (1863--1927) to general hospital psychiatry during the first decade of this century at the Toronto General Hospital where, between 1906 - 1911, he operated the first public general hospital psychiatric unit in Canada. His conflict with Dr. C. K. Clarke who opposed his efforts is documented. To honour Meyers' contributions the Department of Psychiatry, Toronto General Hospital, has been named "The D. Campbell Meyers Memorial Department of Psychiatry".