Neuroendocrine protein 7B2 is essential for proteolytic conversion and activation of proprotein convertase 2 in vivo

The 7B2 protein is widely distributed in neural and endocrine tissues. Its biological function was found to be related to the processing enzyme proprotein convertase 2 (PC2), a mammalian subtilisin/kexin-like endoproteinase that cleaves at specific single or multiple basic amino-acid residues. In order to examine the proposed function of 7B2 on PC2 in in vivo models, we first compared the distribution of 7B2 and PC2 mRNAs in the rat brain. Expression of 7B2 mRNA was found to be pan-neuronal, but additionally, we observed 7B2 mRNA in ependymal cells and in the subcommissural organ. Although the expression of PC2 mRNA was exclusively neuronal, it was more restricted, sparing some regions expressing high levels of 7B2. This finding suggests that 7B2 has an additional function in non-PC2-expressing cells. No evidence of PC2-positive/7B2-negative cells could be obtained in the adult rat brain. However, in the developing rat brain (E17), such regions were easily observed, showing higher levels of pro-PC2 (75 kD). Similarly, in the animal model of insulin-induced hypoglycemic shock, where adrenomedullary 7B2 expression is decreased, the ratio of pro-PC2 to mature PC2 (75 kD:68 kD) was observed to be increased. Finally, the human neuroepithelioma SK-N-MCIXC expresses PC2 but not 7B2. Accordingly, only inactive pro-PC2 forms were observed: 75-kD intracellular and 71-kD extracellular. After stable transfection of SK-N-MCIXC cells with 27-kD pro-7B2, mature and active (68-kD) PC2 was secreted into the medium. Our data demonstrate a critical role of 7B2 in the proteolytic conversion and activation of PC2 in vivo.

Guanylyltransferase activity of the LEF-4 subunit of baculovirus RNA polymerase

The baculovirus Autographa californica nuclear polyhedrosis virus encodes a DNA-dependent RNA polymerase that transcribes viral late genes. This polymerase is composed of four equimolar subunits, LEF-4, LEF-8, LEF-9, and p47. Here we present data indicating that the LEF-4 subunit of RNA polymerase is a guanylyltransferase. Incubation of RNA polymerase in the presence of divalent cation and radiolabeled GTP resulted in the formation of a covalent enzyme-guanylate complex that comigrated with the LEF-4 subunit. The label transfer assay showed an absolute requirement for divalent cation which could be satisfied by either manganese or magnesium. The reaction was specific for guanine nucleotides, and GTP was more effective than dGTP in the formation of enzyme-guanylate complex. To demonstrate that LEF-4 was the guanylyltransferase, the single subunit was overexpressed in baculovirus-infected cells. The overexpressed protein was primarily cytosolic, indicating that other proteins in the RNA polymerase complex were responsible for nuclear targeting of LEF-4. LEF-4 alone was able to covalently bind GMP, although less efficiently than viral RNA polymerase.

Gender differences in accessing cardiac surgery across England: a cross-sectional analysis of the health survey for England

OBJECTIVE

To examine gender differences in access to cardiac surgery in a nationally representative sample.

DESIGN

Nationwide cross sectional household based survey (Health Survey for England).

SETTING

Private households in England around 1993 and 1994.

SUBJECTS

1708 subjects reporting a history of either doctor diagnosed angina or heart attack from a stratified random sample of 32 378 people aged 16 and above.

OUTCOME MEASURE

The proportion reporting having had cardiac surgery or on a waiting list.

RESULTS

13.5% reported previous (n = 206) or pending (n = 25) cardiac surgery. Men were more likely than women to have had or to be waiting for cardiac surgery (19.1% of men versus 6.8% of women, chi2 54.7, P<0.001). This finding was consistent regardless of age group and across three regional areas. The unadjusted odds ratio for cardiac surgery for men versus women was 3.3 (95% Cl 2.3, 4.5, P<0.001) and was only slightly attenuated to 2.8 (95% CI 1.9, 4.0. P<0.001), after adjustment for other factors. The gender difference remained even when analysis was restricted to subjects reporting a previous heart attack, and after statistical adjustment for disease severity.

CONCLUSION

Women are less likely than men to receive cardiac surgery across all age groups and regional areas. These results include private operations and adjust for individual behavioural data. Neither disease severity or co-morbidity explains these discrepancies. Further studies are required to determine why this inequality occurs and how it can be addressed.

[Study on effect of Erigeron injection in prevention and treatment of cerebral ischemic injury]

OBJECTIVE

To study the effect of Erigeron injection (EI) on cerebral ischemic injury.

METHODS

Animal model of brain ischemic/reperfusion was established in male Wistar rats and the effect of EI on proteinkinase C (PKC) activity, intraneuronal free calcium and regional cortex blood flow (rCBF) were observed.

RESULTS

EI could prevent the activation of PKC, calcium overload and decrease of RCBF induced by cerebral ischemia/reperfusion.

CONCLUSION

EI could prevent neuronal ischemic injury by inhibiting activation of PKC.

Identification of mouse CPX-2, a novel member of the metallocarboxypeptidase gene family: cDNA cloning, mRNA distribution, and protein expression and characterization

A novel member of the metallocarboxypeptidase gene family was identified from its homology with carboxypeptidase E and has been designated CPX-2. The cDNA of 2500 nucleotides encodes a protein of 764 amino acids that contains an N-terminal signal peptide-like sequence, a 158-residue discoidin domain, and a 400-residue carboxypeptidase domain. The 400-residue metallocarboxypeptidase domain has 59% amino acid identity with a protein designated AEBP-1; 44% to 46% identity with carboxypeptidases E, N, and Z; and lower homology with other members of the metallocarboxypeptidase gene family. The discoidin domain of CPX-2 has 22% amino acid identity with the carbohydrate-binding domain of discoideum-I, 29% to 34% identity with the phospholipid-binding domain of human factors V and VIII, and 59% identity with the discoidin-like domain on AEBP-1. CPX-2 is missing several of the predicted active-site residues that are conserved in most other members of the metallocarboxypeptidase gene family and which are thought to be required for enzyme activity. Expression of CPX-2 using the baculovirus system produced several forms of protein, from 80 to 105 kDa, but no detectable activity toward a variety of carboxypeptidase substrates. A shorter 50-kDa form of CPX-2, which contains the carboxypeptidase domain but not the discoidin domain, was also inactive when expressed in the baculovirus system. CPX-2 is able to bind to Sepharose-Arg; this binding is blocked by 10 mM Arg. Northern blot analysis showed CPX-2 mRNA in mouse brain, liver, kidney, and lung. In situ hybridization analysis of brain revealed a broad distribution. Areas that are enriched in CPX-2 include the hippocampus, cerebral cortex, median eminence, and choroid plexus. Taken together, these data suggest a widespread function for CPX-2, possibly as a binding protein rather than an active carboxypeptidase.

A virus-encoded RNA polymerase purified from baculovirus-infected cells

A DNA-dependent RNA polymerase was purified to homogeneity, starting from insect cells infected with the baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV). The purified polymerase supported accurate and specific transcription from late and very late promoters but was not active on viral early promoters. Thus, promoter recognition is an integral function of the purified enzyme. The purified RNA polymerase was composed of only four equimolar subunits, which makes it the simplest DNA-directed RNA polymerase from a eukaryotic source described so far. Amino-terminal protein sequencing, peptide fingerprinting, and immunochemical analyses were used to identify the four subunits, all of which are virus encoded. Overexpression of the four viral proteins (LEF-8, LEF-4, LEF-9, and p47) in baculovirus-infected cells resulted in a significant increase in the levels of RNA polymerase produced in the infected cells. Thus, the overexpression data are consistent with our identification of the RNA polymerase subunits.

Altered alveolar macrophage function in calorie-restricted rats

Alveolar macrophage functions associated with clearance of bacteria from the lung were assessed in male Fischer 344 rats maintained on a 25% calorie-restricted diet. Calorie-restricted and ad libitum-fed (control) rats were exposed to concentrations of ozone known to compromise phagocytic function of alveolar macrophages. Ozone suppressed alveolar macrophage phagocytosis of latex beads in vitro in ad libitum-fed rats, but not in calorie-restricted rats. In fact, caloric restriction enhanced phagocytic function in both control and ozone-exposed animals. Ad libitum-fed rats exposed to ozone and challenged with Streptococcus zooepidemicus experienced a prolonged infection and influx of polymorphonuclear leukocytes (PMN), whereas calorie-restricted rats exposed to ozone cleared the bacteria in 24 h without an inflammatory response. Bacterial endotoxin-stimulated in vitro production of nitric oxide and tumor necrosis factor (TNF)-alpha as well as expression of TNF-alpha and interleukin-6 messenger RNAs were all lower in alveolar macrophages isolated from calorie-restricted rats. Together, the data suggest that caloric restriction enhances resistance to gram-positive bacteria, while lowering the production of proinflammatory mediators elicited by endotoxin, a component of gram-negative bacteria. Although increased bacterial resistance is considered beneficial, reduction in the lung's ability to induce inflammatory mediators can have both positive and pathophysiologic consequences.

Toxic metals stimulate inflammatory cytokines in hepatocytes through oxidative stress mechanisms

Hepatocytes, as well as nonparenchymal cells, secrete proinflammatory cytokines and chemokines that are involved in the pathology of many liver diseases. In particular, tumor necrosis factor-alpha (TNFalpha), as well as members of the CXC family of chemokines, including interleukin (IL)-8 in humans and macrophage inflammatory protein (MIP)-2 in rodents, have been implicated in both damage and repair processes associated with various hepatotoxins. In the liver, cytokine secretion is usually associated with nonparenchymal cells, particularly Kupffer cells. In the present studies, cytokine gene expression and secretion were investigated in hepatocytes treated with cadmium chloride (CdCl2) or vanadium pentoxide (V2O5). Using human Hep G2 cells and freshly isolated rodent hepatocytes, it was demonstrated that metals increase gene expression and secretion of CXC chemokines and TNFalpha. IL-8 and MIP-2 secretion induced either by the metals or H2O2 were inhibited by antioxidants such as tetramethyl-thiourea and N-acetyl-cysteine. In vitro neutralization experiments with TNFalpha and in vivo studies with TNFalpha receptor knockout mice indicated that the metals directly stimulate CXC chemokine secretion without the need for TNFalpha. Taken together these studies indicate that, in addition to other inflammatory mediators and acute phase proteins, cytokines and chemokines are produced by hepatocytes, which may participate in hepatotoxic responses. The events responsible for their expression involve cellular redox changes.

Cytokine expression in hepatocytes: role of oxidant stress

Inflammatory mediators, including cytokines and chemokines, are associated with the pathology of chronic liver disease. Interleukin-8 (IL-8) in humans and macrophage inflammatory protein-2 (MIP-2) in rodents, both members of the C-X-C family of chemokines, are particularly potent neutrophil attractants and have been implicated in chronic liver diseases. In the liver, cytokine secretion is usually associated with non-parenchymal cells, particularly Kupffer cells. In the present studies, chemokine gene expression and secretion were investigated in hepatocytes treated with various stimulators. Using human Hep G2 cells, it was demonstrated that, in contrast to lipopolysaccharides (LPS), both tumor necrosis factor-alpha (TNF-beta) and H2O2 are potent inducers of IL-8, presumably acting via protein kinase C (PKC)-dependent pathways. MIP-2 expression occurred in freshly isolated rat hepatocytes following treatment with TNF-alpha, LPS, and to a lesser degree, H2O2. Both IL-8 and MIP-2 secretion were inhibited, although to varying degrees, by such antioxidants as TMTU, DMSO, catalase, and N-acetylcysteine. Furthermore, in vitro TNF-alpha neutralization experiments and transfection of Hep G2 cells with an IL-8 construct confirmed that TNF-alpha and H2O2 directly stimulate IL-8 secretion. RT-PCR analyses indicated that chemokine secretion induced by these agents operates via increased gene expression. Furthermore, a variety of cytokine genes were found to be expressed by hepatocytes, including MCP-1, cytokine-induced neutrophil chemoattractant (CINC), and IL-6. Taken together, these studies indicate that hepatocytes respond to biologically relevant levels of common activators, including H2O2, to produce cytokines and chemokines that contribute to pathophysiologic and repair processes in the liver.

Enhanced allergic responses to house dust mite by oral exposure to carbaryl in rats

Epidemiological studies have demonstrated an association between use of carbamate insecticides, including carbaryl, and increased incidence of allergic asthma in farmers. In this study the effect of oral carbaryl exposure on the development of allergic responses to house dust mite (HDM) was examined in female Brown Norway rats. Rats were gavaged for 2 weeks with 0, 2, 10, or 50 mg/kg/day of carbaryl. They were sensitized with a subcutaneous injection of HDM in aluminum hydroxide adjuvant 3 days after the beginning of carbaryl exposure and challenged with antigen via the trachea 1 day after the final carbaryl ingestion. Two days after challenge, antigen-specific cell proliferation in pulmonary lymph nodes was significantly higher in the 50 mg/kg group than in controls, while antigen-specific splenocyte proliferation was decreased in groups dosed with 2, 10, and 50 mg/kg carbaryl. Total protein and lymphocyte number in bronchoalveolar lavage (BAL) fluid were also increased in the 50 mg/kg group. By 7 days after challenge, immune-mediated pulmonary inflammation (eosinophils), antigen-specific immunoglobulin (Ig) E level in serum, and antigen-specific IgE and IgA levels in BAL fluid were significantly elevated in the 50 mg/kg group. No apparent change was observed for lactate dehydrogenase and eosinophil peroxidase in BAL fluid, while the number of BAL macrophages were decreased in groups dosed with 10 and 50 mg/kg carbaryl. The results suggest that carbaryl may cause systemic immune suppression, while enhancing pulmonary allergic responses to house dust mite antigen.

Blood pressure screening, management and control in England: results from the health survey for England 1994

OBJECTIVE

To assess the current levels of awareness, treatment and control of hypertension in England and to determine the number and type of drugs prescribed.

DESIGN

A cross-sectional household-based survey of English adults.

SUBJECTS

A random sample from the adult English population of 12,116 adults who participated in the 1994 Health Survey for England.

MAIN OUTCOME MEASURES

Prevalences of treatment hypertension, awareness and control.

RESULTS

Using a definition of hypertension as a systolic blood pressure > or = 160 mmHg or a diastolic blood pressure > or = 95 mmHg, or a patient's being administered antihypertensive treatment, the prevalence of awareness of hypertension was 63%. Among hypertensives, 50% were receiving treatment and 30% had their hypertension controlled (< 160 mmHg/95 mmHg). Awareness, treatment and control rates are considerably lower than the most recently reported rates from the USA. Diuretics and beta-blockers remain the most common antihypertensive agents used in England.

CONCLUSION

There is considerable scope for improving the treatment and control of hypertension in the English adult population.

[Image and quantity analysis of prostaglandin in rats' blood plasma and Na(+)-K(+)-ATPase in their cerebellum during the prevention of motion sickness by cinnarizine]

To study the mechanism of cinnarizine in preventing motion sickness, TXB2, 6-Keto-PGF1 alpha in rats' blood plasma and Na(+)-K(+)-ATPase activity in the endothelial cells of their cerebellar capillary were measured and analysed by a radioactive immunity analyser and a computer image system. The results showed that TXB2 and 6-Keto-PGF1 alpha in rats' blood plasma in the cinnarizine preventing group (CPG) decreased remarkably, compared with those in the motion sickness group(MSG) (p < 0.05). The activity of Na(+)-K(+)-ATPase in the endothelial cells of rats' cerebellar capillary in CPG was higher than that in MSG (p < 0.01). The authors suggest that the lower concentration of TXB2 and 6-Keto-PGF1 alpha in rats' blood plasma in CPG is closely related to cinnarizine which prevents Ca2+ from entering into the platelets and into the endothelial cells of blood vessels. The higher activity of Na(+)-K(+)-ATPase in the cerebellum may be caused by cinnarizene which dilates the blood vessels in the brain, increases the blood flow therein, and hinders Ca2+ from getting into the cerebellum cells. These change are believed to be the important mechanism of how cinnarizine prevents motion sickness.

Cloning, sequence analysis, and distribution of rat metallocarboxypeptidase Z

A cDNA encoding human carboxypeptidase Z (CPZ), a novel metallocarboxypeptidase, was recently cloned (Song and Fricker, J. Biol. Chem., 272, 1054, 1997). In the present study, a cDNA encoding the rat homolog of CPZ was identified. As with the human form, rat CPZ contains an N-terminal domain of 120 amino acids that has 20% to 30% amino acid identity with the "frizzled" domain found on proteins that interact with Wnt, a protein involved in tissue polarity in early embryogenesis. Sequence analysis showed rat and human CPZ to be highly conserved within the frizzled domain (77% amino acid identity), the carboxypeptidase domain (91%), and the C-terminal 28 residues (78%). The entire rat CPZ protein has high sequence similarity with human CPZ (81% amino acid identity), moderate sequence similarity to human carboxypeptidase N (45%), human carboxypeptidase E (41%), and human carboxypeptidase M (33%), and less sequence similarity with other metallocarboxypeptidases. Northern blot analysis showed rat CPZ mRNA to be abundant in the placenta, with low to moderate levels in the brain, lung, thymus, and kidney. The BRL3A rat liver cell line and the PC12 rat adrenal cell line express high levels of CPZ mRNA. In situ hybridization analysis indicated that CPZ is expressed only in specific cell types. For example, in the brain, CPZ mRNA is present in leptomeningeal cells, but not in the majority of other cell types. This distribution in leptomeningeal cells is shared by AEBP1, a recently reported member of the metallocarboxypeptidase gene family. However, the distribution of CPZ and AEBP1 differ in pituitary and thyroid. Taken together, these studies suggest that CPZ functions in a range of cell types.

[Experimental studies on antitumor activity of new recombinant human tumour necrosis factor in nude mice bearing nasopharyngeal carcinoma]

OBJECTIVE

Nude mice model bearing nasopharyngeal carcinoma were established using nasopharyngeal squamous carcinoma cell line (CNE-2).

METHODS

New recombinant human tumor necrosis factor (NrhTNF-alpha) and carboplatin were administered locally or systemically, single or in combination. The microstructural and ultra-micro-structural changes of carcinoma after administration of NrhTNF-alpha were observed under light and electron microscopes.

RESULTS AND CONCLUSION

1. After treatment, the tumor showed hemorrhage, necrosis, regression, the survival time was prolonged. 2. Locally administered NrhTNF-alpha had more significant antitumor effect than intravenously administered of NrhTNF-alpha. 3. There is a notable synergistic antitumor effect by the combination use of NrhTNF-alpha and carboplatin. 4. Microscopy showed that cell changes mostly took place in plasma especially in mitochondria and endoplosmic reticula. The mitochondria were highly bloated. Besides, some nuclei were condensed and fragmented, resulted in cell death. These studies provide experimental basis for biological treatment of nasopharyngeal carcinoma.

Prodynorphin processing by proprotein convertase 2. Cleavage at single basic residues and enhanced processing in the presence of carboxypeptidase activity

Endoproteolytic processing of the 26-kDa protein precursor prodynorphin (proDyn) at paired and single basic residues is most likely carried out by the proprotein convertases (PCs); however, the role of PCs at single basic residues is unclear. In previous studies we showed that limited proDyn processing by PC1/PC3 at both paired and single basic residues resulted in the formation of 8- and 10-kDa intermediates. Because PC2 is colocalized with proDyn, we examined the potential role of this convertase in cleaving proDyn. PC2 cleaved proDyn to produce dynorphin (Dyn) A 1-17, Dyn B 1-13, and alpha-neo-endorphin, without a previous requirement for PC1/PC3. PC2 also cleaved at single basic residues, resulting in the formation of the C-peptide and Dyn A 1-8. Only PC2, but not furin or PC1/PC3, could cleave the Arg-Pro bond to yield Dyn 1-8. Structure-activity studies with Dyn A 1-17 showed that a P4 Arg residue is important for single basic cleavage by PC2 and that the P1' Pro residue impedes processing. Conversion of Dyn A 1-17 or Dyn B 1-13 into leucine-enkephalin (Leu-Enk) by PC2 was never observed; however, Dyn AB 1-32 cleavage yielded small amounts of Leu-Enk, suggesting that Leu-Enk can be generated from the proDyn precursor only through a specific pathway. Finally, PC2 cleavages at single and paired basic residues were enhanced when carried out in the presence of carboxypeptidase (CP) E. Enhancement was blocked by GEMSA, a specific inhibitor of CPE activity, and could be duplicated by other carboxypeptidases, including CPD, CPB, or CPM. Our data suggest that carboxypeptidase activity enhances PC2 processing by the elimination of product inhibition caused by basic residue-extended peptides.

Superinduction of IL-2 gene expression by vomitoxin (deoxynivalenol) involves increased mRNA stability

To better understand molecular mechanisms by which the trichothecene vomitoxin (VT) superinduces cytokine gene expression, we studied the posttranscriptional effects of this mycotoxin on interleukin-2 (IL-2) gene expression in murine EL-4 thymoma cells stimulated with phorbol 12-myristate 13-acetate and ionomycin (PMA + ION). Northern analysis revealed that doses of 50 to 500 ng/ml VT superinduced IL-2 mRNA expression in a dose- and time-dependent manner in a synchronous model where VT was added at onset of PMA + ION stimulation. In accordance with the mRNA levels, IL-2 production was significantly elevated in the presence of 50 to 250 ng/ml VT. Superinduction of IL-2 mRNA was also observed in a delayed synchronous model (VT added 20 hr after PMA + ION stimulation) and an asynchronous model (VT added 20 hr after PMA + ION stimulation and removal). To assess the effects of VT (500 ng/ml) on IL-2 mRNA half-life, three transcriptional inhibitors were used in the delayed synchronous model. Actinomycin D (ActD) had a pronounced stabilizing effect on IL-2 mRNA but not on mRNA for the housekeeping gene GAPDH. VT did not affect IL-2 mRNA levels in ActD-treated cells. Although 5,6-dichloro-beta-D-ribofuranosyl-benzimidazole (DRB) also had a stabilizing effect on IL-2 mRNA, IL-2 mRNA half-life t1/2 in VT-treated cells was three times that of control. In contrast, inclusion of cyclosporin A (CsA) into the cultures specifically arrested IL-2 transcription in EL-4 cells without any stabilizing effect. VT exposure in the presence of CsA markedly prolonged the half-life of IL-2 mRNA in a dose-dependent manner. The t1/2 for IL-2 mRNA in the control culture was 2.1 hr, whereas t1/2 was 3.1, 3.4, 4.2, and 10.5 hr in cultures containing 50, 100, 250, and 500 ng/ml VT, respectively. These results suggest that VT can superinduce IL-2 at both the mRNA and the protein level and that this superinduction can be explained, in part, by posttranscriptional mechanisms such as enhanced mRNA stability.

Blood pressure in women using oral contraceptives: results from the Health Survey for England 1994

OBJECTIVE

To assess whether the blood pressure is higher among women who take oral contraceptives than it is among those who do not.

DESIGN

A cross-sectional survey of a stratified random sample of English adults (aged > or = 16 years).

SETTING

Non-institutionalized households in England during 1994.

PARTICIPANTS

From this sociodemographically representative sample of English adults, 3545 premenopausal women, of whom 892 were current users of oral contraceptives, were evaluated.

INTERVENTIONS

An interviewer-administered questionnaire determined details of menopausal status, use of oral contraceptives and antihypertensive agents and other sociodemographic variables. Measurements of the weight, height and blood pressure (the mean of the last two of three readings taken with a Dinamap 8100 device) were recorded.

MAIN OUTCOME MEASURES

Systolic and diastolic blood pressures adjusted for potential confounders by oral-contraceptive-user status.

RESULTS

Mean blood pressures adjusted for age were significantly higher among oral contraceptive users (125/70 mmHg) than they were among non-users (123/68 mmHg, P < 0.001 both for systolic and for diastolic blood pressures). These results remained unchanged after further adjustment for the body mass index, alcohol intake, physical activity and hypertension treatment. Blood pressure differences tended to be larger among older oral contraceptive users. Oral contraceptives containing progestogen only were not associated with higher blood pressures.

CONCLUSIONS

Despite the fact that most combined oral contraceptives in current use in England contain low doses of oestrogen, slightly but significantly higher blood pressures were observed among oral contraceptive users. Blood pressures should be screened before oral contraceptives are supplied and should be monitored regularly during oral contraceptive use.

Synthesis of Uniform Ferric Oxide Particles from Deionized Colloids

A modified method was employed to prepare monodispersed colloidal particles of ferric (hydrous) oxide. The method contains three steps: (i) preparation of uniform nuclei of ferric hydrous oxide via a so-called instantaneous nucleation method; (ii) purification of the nuclei suspension via dialysis; (iii) aging of the purified nuclei suspension in a reflux reactor at certain pH. Cubic and pseudocubic alpha-Fe2O3 monodisperse particles which are much smaller than the cubic alpha-Fe2O3 particles obtained from the same reactant through a usual method were produced by aging needle like nuclei at a lower pH. A close-packed three-dimensional QDs (quantum dots) superlattice structure 40 nm in edge length with cubic geometry was formed by self-aggregation between spherical amorphous ferric hydrous oxide nuclei 3-5 nm in diameter. The growth processes of the two kind particles were also illustrated. This study showed an approach to prepare smaller particles from aqueous metal salt solutions in relatively higher concentration, and ordered QDs superlattice structure by controlled self-aggregation of QDs in hydrosol.

Cloning and sequence analysis of cDNA encoding rat carboxypeptidase D

Carboxypeptidase D (CPD) is a recently described 180-kD enzyme with carboxypeptidase E-like enzymatic properties. CPD has been proposed to be present in the secretory pathway and to contribute to peptide hormone processing in the Cpe(fat)/Cpe(fat) mouse, which lacks functional CPE. Sequence analysis of cDNA clones encoding rat CPD show the protein to contain an amino-terminal signal peptide, three carboxypeptidase-like domains, a putative transmembrane domain, and a 60-amino-acid cytoplasmic tail. Whereas active site, substrate-binding, and metal-binding residues of other metallocarboxypeptidases are conserved in the first two domains of CPD, several of the critical residues are not conserved in the third domain; this third domain is not predicted to form an active carboxypeptidase. The overall homology between rat CPD and the duck homolog gp180 is high, with 75% amino acid identity. The three carboxypeptidase domains show 66%, 83%, and 82% amino acid identity between rat CPD and duck gp180. Homology is also high in the transmembrane domain (86%) and in the cytoplasmic tail (97%). The mouse Cpd gene maps to the medial portion of chromosome 11, approximately 45.5 cM distal to the centromere. Northern blot analysis of CPD mRNA shows major bands of approximately 8 and 4 kb in many rat tissues, and additional species ranging from 1.4 to 5 kb that are expressed in some tissues or cell lines. CPD mRNA is detectable in most tissues examined, and is most abundant in hippocampus, spinal cord, atrium of the heart, colon, testis, and ovaries. In situ hybridization of CPD mRNA shows a distribution in many cells in rat brain and other tissues, with high levels in hippocampus, olfactory bulb, and the intermediate pituitary. The broad distribution is consistent with a role for CPD in the processing of many peptides and proteins that transit the secretory pathway.

[Clinical strategies for development of intracoronary stents]

Intracoronary stenting is an effective measure to prevent PTCA-associated complications in clinical practice, appearing to be superior to all other interventional techniques. However, the intrinsic thrombogenicity and permanent stimulation to injured vessel wall tissue of all the current available metallic stents may result in inhospital events such as thrombosis, (sub)acute coronary closure, emergency bypass surgery, hemorrhagic complications, pseudoaneurysm, or even vessel perforation), and restenosis. In order to settle the above-mentioned problems, the authors point out that intravascular stenting in combination with target drug delivery, or ionic radiation, or gene therapy (direct gene transfer, antisense oligodeoxynucleotides, etc); seeding of genetically reformed endothelial cells on metallic stents; study and development of new materials for biodegradable stents, controlled drug release system; temporary metallic stents; and locally site-specific drug delivery system take facilitated new clinical strategies for the development of intracoronary stents.

Arsenic can mediate skin neoplasia by chronic stimulation of keratinocyte-derived growth factors

Although numerous epidemiological studies have shown that inorganic arsenicals are human skin carcinogens, there is currently no accepted mechanism for its action or an established animal model for its study. We observed increased mRNA transcripts and secretion of keratinocyte growth factors, including granulocyte macrophage-colony stimulating factor (GM-CSF) and transforming growth factor-alpha (TGF-alpha) and the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in primary human epidermal keratinocytes cultured in the presence of low micromolar concentrations of sodium arsenite. Total cell numbers, as well as c-myc expression and incorporation of [3H]thymidine, both indicators of cell proliferation, were also elevated in keratinocyte cultures treated with sodium arsenite. As an in vivo model, the influence of arsenic on mouse skin tumor development was studied in transgenic TG.AC mice which carry the v-Ha-ras oncogene, and can serve as a genetically initiated model for skin carcinogenesis. Following low-dose application of 12-O-tetradecanoyl phorbol-13-acetate (TPA), a marked increase in the number of skin papillomas occurred in transgenic mice receiving arsenic in the drinking water as compared to control drinking water. Papillomas did not develop in arsenic-treated transgenic mice that had not received TPA or arsenic-treated wild-type FVB/N mice, suggesting that arsenic is neither a tumor initiator or promoter but rather an enhancer. Injection of anti-GM-CSF antibodies following application of TPA in transgenic mice reduced the number of papillomas. Consistent with that observed in human keratinocyte cultures, increases in GM-CSF and TGF-alpha mRNA transcripts were found within the epidermis of arsenic-treated mice when compared to controls within 6 weeks of treatment. These results suggest that arsenic enhances papilloma development via the chronic stimulation of keratinocyte-derived growth factors and represents the first example of a chemical carcinogen that acts in this manner. These studies suggest that in vitro studies with human keratinocyte cultures examined in conjunction with TG.AC transgenic mice can provide a useful model for examining the tumor enhancing properties of environmental chemicals.

Prohormone convertases in mouse submandibular gland: co-localization of furin and nerve growth factor

Nerve growth factor (NGF) in mouse submandibular glands (SGs) is generated from a 35-kD precursor by proteolytic enzymes that have yet to be identified. Prohormone convertases (PCs) cleave the NGF precursor in vitro, and in this study we questioned whether PCs could process salivary NGF in vivo. mRNA coding for PC2 (but not PC1) was detected on Northern blots of SG mRNA and also by in situ hybridization within parasympathetic neurons of intralobular ganglia. Northern blot and in situ hybridization analyses also detect mRNA coding for furin. In SGs of male mice, furin mRNA levels are high at birth and remain high throughout development. In glands from female mice, levels decline during postnatal development and are lower in adults than in newborns. Immunocytochemistry detects furin immunoreactivity in pro-acinar and ductal cells of glands from newborn and pubescent mice. In glands of adults, furin immunoreactivity is detectable in acinar cells but highest levels are present in NGF-containing granular convoluted tubule cells. These data, taken together with those from previous studies, suggest that furin is a candidate processing enzyme for NGF in mouse submandibular glands.

[Effects of increasing perilymph calcium levels on various cochlear potentials]

In the present study, we examined the effects of increasing perilymph calcium (12.20 mmol/L) on guinea pig cochlear functions. The results demonstrated that high calcium perilymphs suppressed the magnitude of compound action potential of auditory nerves (CAP) with a prolongation of N1-peak delay at a constant intensity (90 dB SPL), but not of cochlear microphonics (CM). High calcium perilymph didn't change general endocholear potential (G-EP), while reduced the rapid change of EP at on and off set of 115dB SPL white noise exposure. Furthermore the value of negative potential (N-EP) induced by anoxia was decreased because of high calcium perfusions. Machanisms of these effects were discussed.

[Total hip replacement in patients with steroid-induced femoral head necrosis]

In order to evaluate the long-term effect of total hip replacement (THR) in patients with steroid-induced femoral head necrosis, 40 cases of 50 hips received THR patients were followed up for an average of 8.5 years after operation. Evaluation was carried act according to Harris score system. In these cases, average score was seventy-five points. Revision rate among them was 2% after four years and 18% after five to eight and a half years, with as overall rate of 20%. It was found that the main reason for revision was looseness of the prosthesis. In this follow-up, it showed that besides foreigen body reaction, abnormal osseous remodelling was the main factor in long-term failure of this arthroplasty. It was also proved that it was a good selection to perform cemented total hip replacement in younger patients, which could improve living quality.

Ecological analysis of collectivity of alcohol consumption in England: importance of average drinker

OBJECTIVE

To assess whether the average consumption of alcohol is associated with the prevalence of heavy drinking, problem drinking, and abstention in England.

DESIGN

Ecological analysis using data from a cross sectional household based survey of English adults.

SUBJECTS

Random sample of 32,333 adults from the English population who participated in the 1993 and 1994 health surveys for England.

MAIN OUTCOME MEASURES

Association, expressed as the correlation coefficient, between the regional mean and median alcohol consumption and the regional prevalence of heavy drinking, problem drinking, and abstention.

RESULTS

Mean consumption of alcohol in light to moderate drinkers was strongly positively associated with the prevalence of heavy drinking (r = 0.75 in men and r = 0.62 in women for drinking more than 21 and 14 units per week respectively). A similar association was found between median consumption and prevalence of heavy drinking. Abstention was not significantly associated with mean consumption in drinkers (r = 0.08 for men and r = -0.29 for women). Both the median and mean consumption in drinkers were positively associated with the prevalence of problem drinking as defined by the CAGE questionnaire on alcohol use (r = 0.53 for men and r = 0.42 for women for the association with mean consumption).

CONCLUSION

Factors that increase the average consumption of alcohol in the population may result in an increase in the prevalence of heavy drinking and related problems.

TGFbeta1 regulates gene expression of its own converting enzyme furin

TGFbeta1 is known for its potent and diverse biological effects, including immune regulation, and cell growth and differentiation. We have recently shown that TGFbeta1 precursor is processed by human furin COOH-terminal to the R-H-R-R278 cleavage site to generate authentic mature TGFbeta1. In the present study, we demonstrate that steady-state furin mRNA levels are increased in rat synovial cells by 2 and 20 ng/ml TGFbeta1. Stimulation with TGFbeta1 results in a significant increase in furin mRNA levels, starting at 3 h with the peak effect observed at 12 h (2.5-fold increase +/-0.4). TGFbeta1 did not increase furin mRNA stability, and treatment of synovial cells with actinomycin D, before TGFbeta1 addition prevented the increase in fur gene expression, suggesting that the observed regulation occurs at the level of gene transcription. Treatment of synovial and NRK-49F fibroblastic cells with exogenous TGFbeta1 (5 ng/ml) or TGFbeta2 (10 ng/ml) translates into an increase in pro-TGFbeta1 processing as evidenced by the appearance of a 40-kD immunoreactive band corresponding to the TGFbeta1 NH2-terminal pro-region. Furin processing activity stimulated by TGFbeta2 correlates with significant increase in extracellular mature and heat-activable TGFbeta1 as determined by an isoform-specific ELISA assay. Taken together, these results demonstrate for the first time that TGFbeta1 upregulates gene expression of its own converting enzyme, and that this expression is translated into augmented processing of the TGFbeta1 precursor form. Such adaptive responsiveness of the TGFbeta1 convertase may represent an important aspect of TGFbeta1 bioavailibility in TGFbeta1-related processes and pathological conditions.

Cellular localization of the prohormone convertases in the hypothalamic paraventricular and supraoptic nuclei: selective regulation of PC1 in corticotrophin-releasing hormone parvocellular neurons mediated by glucocorticoids

The prohormone convertases (PCs) are processing enzymes that activate proproteins via cleavage at specific single or pairs of basic residues. The hypothalamic paraventricular nucleus (PVN) and supraoptic nucleus (SON) are primary sites of biosynthesis of several neuroendocrine hormone precursors, including provasopressin (pro-AVP), pro-oxytocin (pro-OT), and procorticotrophin-releasing hormone (pro-CRH), which require post-translational processing to yield active products. Using in situ hybridization, we observed PC1 and PC5 mRNAs in PVN and SON magnocellular neurons, while PC2 mRNA was observed in both magnocellular and parvocellular PVN neurons as well as magnocellular SON neurons. Similar to furin, PC7 mRNA was expressed throughout the PVN and SON, whereas PACE4 mRNA levels were undetectable. Both immunohistochemical and Western blot studies were performed to demonstrate the presence of PC proteins and forms in the PVN and SON. Using double-labeling in situ hybridization, we examined the cellular colocalization of each PC mRNA with pro-AVP, pro-OT, and pro-CRH mRNAs in PVN and SON. PC1 mRNA was colocalized with both AVP and OT mRNA in PVN and SON magnocellular neurons. All AVP, OT, and CRH neurons expressed PC2. In contrast, PC5 mRNA was colocalized only with OT mRNA. We examined the effects of adrenalectomy (ADX) on PVN PC mRNA levels. PC1 mRNA levels were increased selectively within CRH/AVP parvocellular neurons but were unchanged in PVN magnocellular AVP or OT neurons. These results established the anatomical organization of each convertase and proneuropeptide substrates in the PVN and SON and suggested potential roles for each enzyme under resting and stimulated conditions.

Lattice fringe continuity in the absence of crystal continuity in enamel

Since high-resolution transmission electron microscopy (HRTEM) provides information on a nearly atomic level, the confidence level with this method is very high. Thus, when lattice fringe continuity is found between two enamel crystals in proximity, such continuity has been taken as evidence of crystal fusion (Daculsi and Kerebel, 1977). Similarly, selected-area dark-field (SADF) electron microscopic imaging has been used to study the axial and spatial orientation of crystals. These studies have shown that there is apparent continuity between enamel and dentin crystals (Arsenault and Robinson, 1989). This observation supported the hypothesis that enamel crystallites are initiated by crystallites in dentin. We have used both HRTEM and SADF methods to identify instances of spatial relationship between crystallites in sections of rat incisor enamel and shark enameloid. In each instance of apparent continuity, goniometric tilting was used to examine the continuous interface. All instances where two crystallites seemed to come into contact, and where HRTEM imaging showed the lattice fringes to be directly continuous, were separated into individual crystallites when the specimen was tilted a few degrees. Thus, adjacent crystallites can show lattice fringe continuity in the absence of real crystallite contact. When instances of overlapping crystallites were examined by SADF imaging, the overlapping crystallites gave a single bright image. Goniometric tilting revealed separate crystallites. Thus, neither lattice fringe continuity nor image continuity under SADF can be used as evidence of crystal continuity unless goniometric rotation and tilting are applied when spatial relationships are suspected.

Arsenic induces overexpression of growth factors in human keratinocytes

Although epidemiological studies have shown that inorganic arsenicals are human skin carcinogens and induce hyperproliferation and hyperkeratosis, there is currently no known mechanism for their action or an established animal model for its study. We observed increased mRNA transcripts and secretion of keratinocyte growth factors, including granulocyte macrophage-colony stimulating factor (GM-CSF) and transforming growth factor-alpha (TGF alpha) and the proinflammatory cytokine tumor necrosis factor-alpha in primary human epidermal keratinocytes cultured in the presence of low micromolar concentrations of sodium arsenite. Treatment with sodium arsenite resulted in a significant increase in cell proliferation, as indicated by increases in cell numbers, c-myc gene expression, and incorporation of [3H]thymidine into cellular DNA. Studies of transcriptional regulation indicate that the rate of GM-CSF mRNA transcription is increased, while the elevated TGF alpha is likely the results of message stabilization. While a number of cytokine regulatory networks exist in the skin, studies utilizing neutralizing antibodies against the growth factors of interest indicate that inhibition of the arsenic-induced increase in TGF alpha results in a corresponding decrease in the gene expression and secretion of GM-CSF. The present studies demonstrate that growth-promoting cytokines and growth factors are induced in keratinocytes following treatment with arsenic and could play a significant role in arsenic-induced skin cancer.

[Factors influencing long-term survival in patients with nonoperable lung cancer: an analysis by Cox model]

This paper reports a prospective survey of 173 patients with nonoperable lung cancer between January. 1, 1983 to March. 1, 1985. The follow-up rate was 97.7% over five years. Fourteen factors including sex, age, course of disease before treatment, clinical stage, performance status, size of mass, metastatic status, hemoglobin before treatment, short-term response to treatment and so on which might influence long term survival were studied by univariate analysis (Kruskal-Wallis test for Kaplan-Meier survival curve) and by multivariate analysis (Cox's proportional hazad model and audio-visual chart test for goodness of fit). Multivariate analysis using Cox's model revealed 6 significant prognostic factors: performance status, short-term response to treatment, clinical stage, hemoglobin before treatment, smoking index and method of treatment. The survival prediction equation was chi 2 = 72.14, nu = 6, P < 0.0001. The results indicate that the performance status and the CR rate of the initial treatment, among other things, is the major factors affecting prognosis.

Role of endotoxin in tumor necrosis factor alpha expression from alveolar macrophages treated with urban air particles

The effects of urban air and diesel particles on inflammatory cytokine gene expression, tumor necrosis factor alpha (TNF-alpha) in particular, were studied in rat alveolar macrophages. TNF-alpha, interleukin (IL)-1, IL-6, cytokine-induced neutrophil chemoattractant (CINC), and macrophage inflammatory protein (MIP)-2 gene expression and TNF-alpha secretion were increased in cells treated with 50 to 200 micrograms/mL of urban air particles in a concentration-related manner. There was no cytokine induction by diesel particles at any of the concentrations tested. Cytokine expression was not related to reactive oxygen species since antioxidants, such as catalase, TMTU, or DMSO, had no effect on TNF-alpha secretion. However, cytokine induction by urban air particles was completely prevented by polymyxin B, an antibiotic capable of neutralizing bacterial lipopolysaccharide (LPS) activities. Furthermore, LPS was detected on the urban air particles, but not on diesel particle. These results suggest that activation of cytokine gene expression and secretion in rat alveolar macrophages by urban air particles is due to the presence of endotoxin on the particles.

Effects of mycotoxins on cytokine production and proliferation in EL-4 thymoma cells

The thymoma cell line EL4.IL-2 (EL-4) was used as a T-cell model to assess the immunotoxic effects of several mycotoxins produced by the Aspergillus-Penicillium and the Fusarium groups. EL-4 cells were stimulated with phorbol 12-myristate 12-acetate (PMA) in the presence of mycotoxins at various concentrations for 5 d and culture supernatants were analyzed for interleukins (IL) IL-2 and IL-5 by enzyme-linked immunosorbent assay (ELISA). The cytokine effects were further related to proliferation and cell viability using the MTT [3-(4,5-dimethylthiazol-2-yl) 2,5-diphenyltetrazolium bromide] assay with absorbance at 570 nm (A570) as the endpoint indicator. IL-2 and IL-5 levels were dramatically increased by cyclopiazonic acid at 50-1000 ng/ml, whereas IL-2 was significantly decreased at 10 microgram/ml. Proliferation was slightly increased at 100-1000 ng/ml cyclopiazonic acid but markedly depressed at 5 and 10 microgram/ml. When EL-4 cells were exposed to 5 and 10 microgram/ml of ochratoxin A, IL-2 production was markedly increased while IL-5 production was significantly decreased. The A570 was significantly decreased by ochratoxin A at 10 microgram/ml. IL-2 and Il-5 production was almost totally suppressed by patulin at concentrations > or = 500 ng/ml and by T-2 toxin at > or = 5 ng/ml. These effects occurred concurrently with marked depression of A570 in the MTT assay. Although A570 was unaffected by either zearalenone or alpha-zearalenol exposure, both IL-2 and IL-5 levels were significantly elevated by these toxins at 5 or 10 microgram/ml. IL-2 and IL-5 production were not affected in EL-4 cells cultured with either the Aspergillus-Penicillium toxins aflatoxin B1 and secalonic acid or the Fusarium toxins wortmannin, fumonisin B1, or fusaric acid at concentrations up to 10 microgram/ml. In total, the EL-4 culture studies indicated that cyclopiazonic acid, ochratoxin A, zearalenone, and alpha-zearalenol could stimulate cytokine production whereas patulin and T-2 toxin were inhibitory. Cytokine dysregulation was not always related directly to perturbations in proliferation. The results suggest that the EL-4 thymoma cell line could be a simple and effective in vitro model for evaluating immunotoxicity of various classes of environmental chemicals.

cDNA structure, tissue distribution, and chromosomal localization of rat PC7, a novel mammalian proprotein convertase closest to yeast kexin-like proteinases

By using reverse transcription-coupled PCR on rat anterior pituitary RNA, we isolated a 285-bp cDNA coding for a novel subtilisin/kexin-like protein convertase (PC), called rat (r) PC7. By screening rat spleen and PC12 cell lambda gt11 cDNA libraries, we obtained a composite 3.5-kb full-length cDNA sequence of rPC7. The open reading frame codes for a prepro-PC with a 36-amino acid signal peptide, a 104-amino acid prosegment ending with a cleavable RAKR sequence, and a 747-amino acid type I membrane-bound glycoprotein, representing the mature form of this serine proteinase. Phylogenetic analysis suggests that PC7 represents the most divergent enzyme of the mammalian convertase family and that it is the closest member to the yeast convertases krp and kexin. Northern blot analyses demonstrated a widespread expression with the richest source of rPC7 mRNA being the colon and lymphoid-associated tissues. In situ hybridization revealed a distinctive tissue distribution that sometimes overlaps with that of furin, suggesting that PC7 has widespread proteolytic functions. The gene for PC7 (Pcsk7) was mapped to mouse chromosome 9 by linkage analysis of an interspecific backcross DNA panel.

Molecular basis of alpha-methyltryptophan resistance in amt-1, a mutant of Arabidopsis thaliana with altered tryptophan metabolism

A mutant of Arabidopsis thaliana, amt-1, was previously selected for resistance to growth inhibition by the tryptophan analog alpha-methyltryptophan. This mutant had elevated tryptophan levels and exhibited higher anthranilate synthase (AS) activity that showed increased resistance to feedback inhibition by tryptophan. In this study, extracts of the mutant callus exhibited higher AS activity than wild-type callus when assayed with either glutamine or ammonium sulfate as amino donor, thus suggesting that elevated AS activity in the mutant was due to an alteration in the alpha subunit of the enzyme. The mutant also showed cross-resistance to 5-methylanthranilate and 6-methylanthranilate and mapped to chromosome V at or close to ASA1 (a gene encoding the AS alpha subunit). ASA1 mRNA and protein levels were similar in mutant and wild-type leaf extracts. Levels of ASA1 mRNA and protein were also similar in callus cultures of mutant and wild type, although the levels in callus were higher than in leaf tissue. Sequencing of the ASA1 gene from amt-1 revealed a G to A transition relative to the wild-type gene that would result in the substitution of an asparagine residue in place of aspartic acid at position 341 in the predicted amino acid sequence of the ASA1 protein. The mutant allele in strain amt-1 has been renamed trp5-1.

Evaluation of isofagomine and its derivatives as potent glycosidase inhibitors

A pseudo-aza-monosaccharide and several pseudo-aza-disaccharide compounds were constructed based on replacement of the anomeric carbon with a nitrogen and the ring oxygen with a carbon. The inhibition constants of these compounds toward five different glycosidases, alpha-glucosidase, beta-glucosidase, isomaltase, alpha-mannosidase, and glucoamylase, were obtained. Isofagomine, the pseudo-aza-monosaccharide, shows a broad spectrum of strong inhibition against glycosidases. It is the most potent inhibitor of beta-glucosidase from sweet almonds reported to date and also a strong inhibitor of glucoamylase, isomaltase, and alpha-glucosidase. Isofagomine inhibits beta-glucosidase, glucoamylase, and isomaltase more strongly than 1-deoxynojirimycin where the ring oxygen has been replaced with a nitrogen. The alpha-1,6- linked pseudo-disaccharide showed very strong inhibition toward glucoamylase, being nearly as potent an inhibitor as acarbose. Pseudo-disaccharides in which the anomeric nitrogen was methylated to favor formation of either the alpha or beta substrate linkage generally had weakened inhibition for the glycosidases studied most likely due to steric interference with the various active sites. These results indicate that the presence of a basic group at the anomeric center is important for carbohydrase inhibition. The presence of a charged carboxylate group near the anomeric carbon which interacts with the basic nitrogen is suggested for these enzymes, particularly for beta-glucosidase. The presence of a second alpha-linked glucosyl residue is also critical for strong inhibition of glucoamylase.

Kinetic studies of calcium binding to the regulatory site of troponin C from cardiac muscle

We have studied the kinetics of the structural transitions induced by calcium binding to the single, regulatory site of cardiac troponin C by measuring the rates of calcium-mediated fluorescence changes with a monocysteine mutant of the protein (C35S) specifically labeled at Cys-84 with the fluorescent probe 2(-)[4'-(iodoacetamido)anilino]naphthalene-6-sulfonic acid. At 4 degrees C, the binding kinetics determined in the presence of Mg2+ was resolved into two phases with positive amplitude, which were completed in less than 100 ms. The rate of the fast phase increased linearly with [Ca2+] reaching a maximum of approximately 590 s-1, and that of the slow phase was approximately 100 s-1 and did not depend on Ca2+ concentration. Dissociation of bound Ca2+ from the regulatory site occurred with a rate of 102 s-1, whereas the dissociation from the two high affinity sites was about two orders of magnitude slower. These results are consistent with the following scheme for the binding of Ca2+ to the regulatory site: [formula: see text] where the asterisks denote states with enhanced fluorescence. The apparent second-order rate constant for calcium binding is Kok1 = 1.4 x 10(8) M 1 s-1. The two first-order transitions occur with observed rates of k1 + kappa-1 approximately 590 s-1 and kappa 2 + kappa-2 approximately 100 s-1, and the binding of Ca2+ to the regulatory site is not a simple diffusion-controlled reaction. These transitions provide the first information on the rates of Ca(2+)-induced conformational changes involving helix movements in the regulatory domain.

Expression of mRNA for somatostatin receptor (sstr) types 2 and 5 in individual rat pituitary cells. A double labeling in situ hybridization analysis

To characterize cell specific expression of sstr subtypes in the pituitary we have analyzed mRNA for sstr1-5 in rat pituitary somatotrophs by reverse transcriptase polymerase chain reaction and determined the pattern and level of expression of mRNA for sstr subtypes 2 and 5 in individual pituitary cell subpopulations by double label in situ hybridization. Purified somatotrophs expressed mRNA for all 5 sstrs. In situ hybridization analysis revealed sstr5 mRNA in 70% of somatotrophs, 57% of thyrotrophs, 38% of corticotrophs, 33% of lactotrophs, and 21% of gonadotrophs. mRNA for sstr2 occurred in 40% of somatotrophs, 36% of thyrotrophs, 26% of lactotrophs, 3% of corticotrophs, and 8% of gonadotrophs. Not only were more cells positive for sstr5 mRNA but the average number of autoradiographic grains/cell was also higher for sstr5 than sstr2. These results show expression of multiple sstr genes in individual pituitary cells. mRNA for sstr2 and 5 occur in each of the 5 major pituitary cell subsets, sstr5 mRNA being more widely and more abundantly expressed than sstr2.

[Motoneuronal death following prevention of reinnervation during postnatal development]

The hypothesis that survival of motoneurons depends on targets postnatally was tested in Wistar rats of known age. Under ether anesthesia, the cut distal end of a medial gastrocnemius (MG) nerve was anchored to the lateral gastrocnemius (LG) muscle to prevent reinnervation. The compound action potential (CAP) in response to stimulation of the MG nerve was recorded from L4 and L5 ventral roots to evaluate the degree of motoneuronal death in the nerve. CAPs of MG nerves were greatly reduced 1 to 8 months after the operation in the rats operated on at 6 or 9 days of age, which indicates that the majority of MG motoneurons died after the operation. In contrast, the CAPs in the animals which were operated on at older than 12 days were similar to normal animals. However, the number of motor units that remained in the implanted MG nerve was 1.3 on the average in the rats operated on at 12-days-old. In normal rats, it was 87. Thus, the results indicate that in the rats operated on at 12 days of age, a majority of MG motoneurons survived without making functional synapses. We conclude that there is a sharp critical period, between 9 and 12 days after birth, during which motoneuronal target dependency changes.

Mortality study of construction workers in the UK

BACKGROUND

Construction is one of the most dangerous industries in the world. However, there has been little literature on occupational epidemiology in this field. A study of the mortality experience over a 13-year period among construction workers in the UK was carried out.

METHOD

This was based on 15,007 death certificates of members of the Building and Civil Engineering Holiday and Benefit Scheme, who had died during 1975 to 1987 aged 20-64 years. Proportional mortality ratio (PMR) and mortality odds ratio techniques were used.

RESULTS

Significantly elevated PMR were found for deaths from all cancers, including cancer of the lung and stomach, and for accidental deaths. Associations were demonstrated between several job categories and an increased risk of cancer mortality. Occupational exposures to hazardous substances may have contributed to the elevated cancer mortality, although the study findings should be interpreted with caution. Inadequate supervision of safety procedures, together with a high proportion of young and inexperienced workers, may be associated with the high number of accidental deaths.

CONCLUSIONS

The results support the hypothesis that working in the construction industry is associated with a high risk for accidental death and probably also for malignant diseases including lung, mesothelium and stomach cancers. Further epidemiological studies among construction workers are needed to support policies aimed at improving occupational health, including the prevention of accidents.

c-KIT expression enhances the leukemogenic potential of 32D cells

The growth of human leukemic cells in culture and in vivo is dependent upon the presence of hematopoietic growth factors. Most populations of human leukemic acute myeloblastic leukemia (AML) cells express c-Kit on their surface and respond to Kit ligand (KL) in culture. To determine if this interaction was of potential significance in vivo we used a mouse model system. 32D cells, a murine IL-3-dependent myeloid cell line, were rendered KL responsive by transfection of the murine c-Kit. After injection of 32D or 32D-Kit cells into syngeneic hosts, animals bearing 32D-Kit cells, but not 32D cells, became moribund and were killed. These animals had circulating leukemic blast cells, infiltration of bone marrow, spleen, brain, liver, lung, and kidney. Cells recovered from some of the animals continued to be dependent upon IL-3 or KL for growth while in other cases the cells were factor independent. This model illustrates that the constitutive expression of c-Kit enhances the leukemic potential of 32D cells. The model will be useful for studying the progression of leukemia in vivo and testing whether interruption of the interaction of Kit and KL can affect the growth of leukemic cells.

Matrix protein synthesis by glomerular mesangial cells in culture: effects of transforming growth factor beta (TGF beta) and platelet-derived growth factor (PDGF) on fibronectin and collagen type IV mRNA

The pathogenesis of glomerular scarring is multifactional; recent evidence suggests that transforming growth factor beta (TGF beta), a pleiotropic cicatricial mediator, may promote mesangial sclerosis by enhancing the production of extracellular matrix proteins. We studied the effect of TGF beta 1 and TFG beta 2 on collagen type IV and fibronectin (FN) synthesis in human glomerular mesangial cells in culture (GMC). Two hours after addition of TGF beta, an up to twofold increase in abundance of collagen type IV mRNA was found, which further increased up to fivefold within 24 h. Addition of cycloheximide did not inhibit the TGF beta effect, but caused by itself an up to twofold increase in the abundance of collagen type IV mRNA after 2 h. Together with collagen mRNA, the mRNA for FN and for platelet-derived growth factor (PDGF) was also enhanced. PDGF was found to enhance abundance of the collagen type IV and fibronectin mRNA in GMC. A neutralizing antibody to PDGF or a PDGF-antisense oligonucleotide partly inhibited the TGF beta-induced increase of collagen type IV mRNA, suggesting that TGF beta can affect the collagen type IV synthesis not only directly but also indirectly via the synthesis of PDGF.

The lef-3 gene of Autographa californica nuclear polyhedrosis virus encodes a single-stranded DNA-binding protein

The Autographa californica nuclear polyhedrosis virus (AcNPV) replicates in the nuclei of infected cells and encodes several proteins required for viral DNA replication. As a first step in the functional characterization of viral replication proteins, we purified a single-stranded DNA-binding protein (SSB) from AcNPV-infected insect cells. Nuclear extracts were chromatographed on single-stranded DNA agarose columns. An abundant protein with an apparent molecular weight of 43,000 was eluted from the columns at 0.9 to 1.0 M NaCl. This protein was not evident in extracts prepared from control cells, suggesting that the SSB was encoded by the virus. SSB bound to single-stranded DNA in solution, and binding was nonspecific with respect to base sequence, as single-stranded vector DNA competed as efficiently as single-stranded DNA containing the AcNPV origin of DNA replication. Competition binding experiments indicated that SSB showed a preference for single-stranded DNA over double-stranded DNA. To determine whether SSB was encoded by the lef-3 gene of AcNPV, the lef-3 open reading frame was cloned under the control of the bacteriophage T7 promoter. Immunochemical analyses indicated that LEF-3 produced in bacteria or in rabbit reticulocyte lysates specifically reacted with antiserum produced by immunization with purified SSB. Immunoblot analyses of infected cell extracts revealed that SSB/LEF-3 was detected by 4 h postinfection and accumulated through 48 h postinfection.

Failure to demonstrate a protein coat on enamel crystallites by morphological means

Phosphotungstic acid (PTA) treatment of section of Epon-embedded enamel dissolves the crystallites and stains material postulated to be crystal-bound proteins. Alternative, capillarity forces within the channels left after crystallite removal may draw in PTA. This prediction was tested on three systems. (1) Protein free synthetic hydroxyapatite was embedded in Epon; treatment of thin sections with PTA removed most crystals, leaving empty holes outlined by stain that could not represent protein. (2) Sections of rat incisor enamel were treated with PTA and then re-embedded in Epon and sectioned at 90 degrees to the original plane. In these sections-of-section the cut ends of dissolved crystallite profiles were coated with stain. To determine if stained protein coats can be detected in the absence of the crystallite profiles, Epon sections were partially demineralized with formic acid, re-embedded in Epon and sections-of section were PTA treated. Previously extracted crystallites left no stained coats, and only the crystallites that were not removed by formic acid left PTA-stained outlines. (3) PTA-treated sections of dogfish shark enameloid were flooded with 5-nm colloidal gold particles and sections-of-section were prepared. The presence of gold particles on the section surface and in holes previously occupied by crystallites suggested that PTA solution could also be sucked into similar holes. It is concluded that PTA outlines are not crystal-bound proteins but artefacts caused by stain lining holes left in the section when the crystallites have been extracted.