Processing of the initiation methionine from proteins: properties of the Escherichia coli methionine aminopeptidase and its gene structure

Methionine aminopeptidase (MAP) catalyzes the removal of amino-terminal methionine from proteins. The Escherichia coli map gene encoding this enzyme was cloned; it consists of 264 codons and encodes a monomeric enzyme of 29,333 daltons. In vitro analyses with purified enzyme indicated that MAP is a metallo-oligopeptidase with absolute specificity for the amino-terminal methionine. The methionine residues from the amino-terminal end of the recombinant proteins interleukin-2 (Met-Ala-Pro-IL-2) and ricin A (Met-Ile-Phe-ricin A) could be removed either in vitro with purified MAP enzyme or in vivo in MAP-hyperproducing strains of E. coli. In vitro analyses of the substrate preference of the E. coli MAP indicated that the residues adjacent to the initiation methionine could significantly influence the methionine cleavage process. This conclusion is consistent, in general, with the deduced specificity of the enzyme based on the analysis of known amino-terminal sequences of intracellular proteins (S. Tsunasawa, J. W. Stewart, and F. Sherman, J. Biol. Chem. 260:5382-5391, 1985).

Molecular genetic analyses of the Tyrolean Ice Man

An approximately 5000-year-old mummified human body was recently found in the Tyrolean Alps. The DNA from tissue samples of this Late Neolithic individual, the so-called "Ice Man," has been extracted and analyzed. The number of DNA molecules surviving in the tissue was on the order of 10 genome equivalents per gram of tissue, which meant the only multi-copy sequences could be analyzed. The degradation of the DNA made the enzymatic amplification of mitochondrial DNA fragments of more than 100 to 200 base pairs difficult. One DNA sequence of a hypervariable segment of the mitochondrial control region was determined independently in two different laboratories from internal samples of the body. This sequence showed that the mitochondrial type of the Ice Man fits into the genetic variation of contemporary Europeans and that it was most closely related to mitochondrial types determined from central and northern European populations.

Arrangements of macro- and microchromosomes in chicken cells

Arrangements of chromosome territories in nuclei of chicken fibroblasts and neurons were analysed employing multicolour chromosome painting, laser confocal scanning microscopy and three-dimensional (3D) reconstruction. The chicken karyotype consists of 9 pairs of macrochromosomes and 30 pairs of microchromosomes. Although the latter represent only 23% of the chicken genome they containalmost 50% of its genes. We show that territories of microchromosomes in fibroblasts and neurons were clustered within the centre of the nucleus, while territories of the macrochromosomes were preferentially located towards the nuclear periphery. In contrast to these highly consistent radial arrangements, the relative arrangements of macrochromosome territories with respect to each other (side-by-side arrangements) were variable. A stringent radial arrangement of macro- and microchromosomes was found in mitotic cells. Replication labelling studies revealed a pattern of DNA replication similar to mammalian cell nuclei: gene dense, early replicating chromatin mostly represented by microchromosomes, was located within the nuclear interior, surrounded by a rim of late replicating chromatin. These results support the evolutionary conservation of several features of higher-order chromatin organization between mammals and birds despite the differences in their karyotypes.

Effects of method, duration, and sleep stage on rebounds from sleep deprivation in the rat

Total sleep deprivation (TSD) of rats for 24 hours or less by continually enforced locomotion has consistently produced subsequent rebounds of slow-wave or high-amplitude EEG activity in NREM sleep, which has contributed to the widely held view that this EEG activity reflects particularly "intense" or restorative sleep. These rebounds usually have been accompanied by substantial rebounds of REM sleep. In contrast, chronic TSD (2 weeks or longer) by the disk-over-water (DOW) method has produced only huge, long-lasting rebounds of REM sleep with no rebound of high-amplitude NREM sleep. To evaluate whether the different rebounds result from different methods or from different lengths of deprivation, rats were subjected to 24-hour TSD by the DOW method. Rebounds included increases in high-amplitude and slow-wave activity; i.e., the methods produced similar rebound patterns following short-term TSD. (Chronic TSD by continually enforced locomotion would be strategically difficult and severely confounded with motor fatigue.) Rats subjected to DOW-TSD for 4 days, well before the development of severe TSD symptoms, showed primarily REM sleep rebounds. Rats subjected to 1 day of selective REM sleep deprivation, but not their closely yoked control rats, showed large, significant REM sleep rebounds, which evidently were not induced by the stress of the deprivation method per se. The combined findings prompted reexamination of published evidence relevant to "sleep intensity," including "negative rebounds," rebounds in other species, the effects of stress and fatigue, depth of sleep indicators, and extended sleep. The review points out pitfalls in the designation of any specific pattern as intense sleep.

mtDNA analysis of Nile River Valley populations: A genetic corridor or a barrier to migration?

To assess the extent to which the Nile River Valley has been a corridor for human migrations between Egypt and sub-Saharan Africa, we analyzed mtDNA variation in 224 individuals from various locations along the river. Sequences of the first hypervariable segment (HV1) of the mtDNA control region and a polymorphic HpaI site at position 3592 allowed us to designate each mtDNA as being of "northern" or "southern" affiliation. Proportions of northern and southern mtDNA differed significantly between Egypt, Nubia, and the southern Sudan. At slowly evolving sites within HV1, northern-mtDNA diversity was highest in Egypt and lowest in the southern Sudan, and southern-mtDNA diversity was highest in the southern Sudan and lowest in Egypt, indicating that migrations had occurred bidirectionally along the Nile River Valley. Egypt and Nubia have low and similar amounts of divergence for both mtDNA types, which is consistent with historical evidence for long-term interactions between Egypt and Nubia. Spatial autocorrelation analysis demonstrates a smooth gradient of decreasing genetic similarity of mtDNA types as geographic distance between sampling localities increases, strongly suggesting gene flow along the Nile, with no evident barriers. We conclude that these migrations probably occurred within the past few hundred to few thousand years and that the migration from north to south was either earlier or lesser in the extent of gene flow than the migration from south to north.

Folliculostellate cell network: a route for long-distance communication in the anterior pituitary

All higher life forms critically depend on hormones being rhythmically released by the anterior pituitary. The proper functioning of this master gland is dynamically controlled by a complex set of regulatory mechanisms that ultimately determine the fine tuning of the excitable endocrine cells, all of them heterogeneously distributed throughout the gland. Here, we provide evidence for an intrapituitary communication system by which information is transferred via the network of nonendocrine folliculostellate (FS) cells. Local electrical stimulation of FS cells in acute pituitary slices triggered cytosolic calcium waves, which propagated to other FS cells by signaling through gap junctions. Calcium wave initiation was because of the membrane excitability of FS cells, hitherto classified as silent cells. FS cell coupling could relay information between opposite regions of the gland. Because FS cells respond to central and peripheral stimuli and dialogue with endocrine cells, the form of large-scale intrapituitary communication described here may provide an efficient mechanism that orchestrates anterior pituitary functioning in response to physiological needs.

A molecular analysis of ground sloth diet through the last glaciation

DNA was extracted from five coprolites, excavated in Gypsum Cave, Nevada and radiocarbon dated to approximately 11 000, 20 000 and 28 500 years BP. All coprolites contained mitochondrial DNA sequences identical to a DNA sequence determined from a bone of the extinct ground sloth Nothrotheriops shastensis. A 157-bp fragment of the chloroplast gene for the large subunit of the ribulosebisphosphate carboxylase (rbcL) was amplified from the boluses and several hundred clones were sequenced. In addition, the same DNA fragment was sequenced from 99 plant species that occur in the vicinity of Gypsum Cave today. When these were compared to the DNA sequences in GenBank, 69 were correctly (two incorrectly) assigned to taxonomic orders. The plant sequences from the five coprolites as well as from one previously studied coprolite were compared to rbcL sequences in GenBank and the contemporary plant species. Thirteen families or orders of plants that formed part of the diet of the Shasta ground sloth could be identified, showing that the ground sloth was feeding on trees as well as herbs and grasses. The plants in the boluses further indicate that the climate 11 000 years BP was dryer than 20 000 and 28 500 years BP. However, the sloths seem to have visited water sources more frequently at 11 000 BP than at earlier times.

The nucleoside analog GS-441524 strongly inhibits feline infectious peritonitis (FIP) virus in tissue culture and experimental cat infection studies

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GS-441524 inhibited replication of serotype II FIP virus (FIPV) in CRFK cell cultures at an EC50 of approximately 1 uM and no toxicity at 100 uM.

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GS-441524 inhibited wildtype FIPV replication in macrophage cultures from ascitic fluid of two cats with naturally occurring FIP.

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GS-441525 is triphosphorylated by CRFK cells in vitro and PBMC in vivo.

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Pharmacokinetic studies in laboratory cats demonstrated effective blood levels over 24 h after a single dose of 5 mg/kg SC or IV.

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Severe experimental effusive FIP was successfully treated with 2 or 5 mg/kg GS-441524 SC q24 h for two weeks.

Feline infectious peritonitis (FIP) is a common and highly lethal coronavirus disease of domestic cats. Recent studies of diseases caused by several RNA viruses in people and other species indicate that antiviral therapy may be effective against FIP in cats. The small molecule nucleoside analog GS-441524 is a molecular precursor to a pharmacologically active nucleoside triphosphate molecule. These analogs act as an alternative substrate and RNA-chain terminator of viral RNA dependent RNA polymerase. We determined that GS-441524 was non-toxic in feline cells at concentrations as high as 100 uM and effectively inhibited FIPV replication in cultured CRFK cells and in naturally infected feline peritoneal macrophages at concentrations as low as 1 uM. We determined the pharmacokinetics of GS-441524 in cats in vivo and established a dosage that would sustain effective blood levels for 24 h. In an experimental FIPV infection of cats, GS-441524 treatment caused a rapid reversal of disease signs and return to normality with as little as two weeks of treatment in 10/10 cats and with no apparent toxicity.

Paternal and maternal DNA lineages reveal a bottleneck in the founding of the Finnish population

An analysis of Y-chromosomal haplotypes in several European populations reveals an almost monomorphic pattern in the Finns, whereas Y-chromosomal diversity is significantly higher in other populations. Furthermore, analyses of nucleotide positions in the mitochondrial control region that evolve slowly show a decrease in genetic diversity in Finns. Thus, relatively few men and women have contributed the genetic lineages that today survive in the Finnish population. This is likely to have caused the so-called "Finnish disease heritage"-i.e., the occurrence of several genetic diseases in the Finnish population that are rare elsewhere. A preliminary analysis of the mitochondrial mutations that have accumulated subsequent to the bottleneck suggests that it occurred about 4000 years ago, presumably when populations using agriculture and animal husbandry arrived in Finland.

Body temperatures and oxygen consumption during skin-to-skin (kangaroo) care in stable preterm infants weighing less than 1500 grams

BACKGROUND

More and progressively smaller preterm infants are taken out of the incubator and placed skin to skin on their mother's chest to promote bonding, despite concerns that the infants are exposed to cold during this intervention.

OBJECTIVE

To test the hypothesis that skin-to-skin care is a cold stress for preterm infants weighing less than 1500 gm, with a decrease in rectal temperature, a decrease in peripheral skin temperature, or an increase in oxygen consumption compared with conditions monitored during incubator care.

STUDY DESIGN

We studied 22 stable, spontaneously breathing preterm infants weighing less than 1500 gm (appropriate in size for gestational age), who had their first skin-to-skin care in the first week of life. We continuously measured rectal temperature, peripheral skin temperature (foot), and oxygen consumption (indirect calorimetry) for 1 hour in a thermoneutral incubator, during 1 hour of skin-to-skin care, and for another hour in the incubator. Mean values for the three periods were compared by analysis of variance.

RESULTS

During skin-to-skin care the mean rectal temperature was 0.2 degree C (p < 0.01) and the peripheral skin temperature was 0.6 degree C (p < 0.01) higher than during the preceding hour in the incubator. Back in the incubator, body temperatures returned to values recorded before skin-to-skin care. Oxygen consumption during skin-to-skin care (6.1 +/- 0.9 ml/kg per minute) was not significantly higher than in the incubator (5.8 +/- 0.8 ml/kg per minute).

CONCLUSION

For stable preterm infants weighing less than 1500 gm and less than 1 week of age, 1 hour of skin-to-skin care is not a cold stress compared with care in a thermoneutral incubator.

Multilocular cystic renal cell carcinoma

Multilocular cystic renal cell carcinoma (MCRCC) appears to be a distinct subtype of renal cell carcinoma with characteristic gross and microscopic features. The authors' ten-year experience (1977-1987) included six cases of MCRCC that were followed for a minimum of two years, with neither recurrence nor metastasis observed in any of the cases. During this period, there were 855 urologic procedures for the upper urinary tract, with 256 neoplasms or cysts identified. These included 32 simple cysts, 41 transitional cell carcinomas, 133 renal cell carcinomas, 17 papillary renal cell carcinomas, and 33 miscellaneous tumors. Histologically, the MCRCCs were well-demarcated multicystic lesions containing variably sized aggregates of neoplastic clear cells showing grade 1 nuclear features and little or no mitotic activity. The cyst walls were densely fibrotic, and the lining was often devoid of epithelium. Flow-cytometric analysis performed in five of the six cases with the use of paraffin-embedded tissue showed the tumors to be diploid in all instances, with low proliferative activity. The authors believe that this tumor is a low-grade variant of renal cell carcinoma and should be studied further to determine appropriate therapy.

Specific detection of his-tagged proteins with recombinant anti-His tag scFv-phosphatase or scFv-phage fusions

Using a cell-bound immunogen, we have generated a monoclonal antibody, 3D5, that recognizes carboxy-terminal oligo-histidine tags (His tags) on a wide variety of proteins. From this monoclonal antibody, we have generated a single-chain fragment of the variable domains (scFv), a dimeric scFv-alkaline phosphatase fusion and an oligovalent scFv-display phage. The antibody in its various formats is an effective tool used in fluorescence-activated cell sorting analysis, the BIAcore method, Western blots and enzyme-linked immunosorbent assay (ELISA). Western blots and ELISAs can be developed directly by using crude extracts of E.coli cells that produce the scFv-alkaline phosphatase fusion, thus providing an inexhaustable and convenient supply of detection reagent. Alternatively, oligovalent scFv-displaying phage can be used directly from culture supernatants for this purpose. The dissociation constants, KD of the peptide KGGHHHHH (KD = 4 x 10(-7) M) and of imidazole (KD = 4 x 10(-4) M) were determined. Molecular modeling of the Fv fragment suggests the occurrence of two salt bridges between the protonated histidine side chains of the peptide and the acidic groups in the antibody, explaining why the antibody or the substrate may be eluted under mildly basic conditions.

Body composition, nutrition, and fluid balance during the first two weeks of life in preterm neonates weighing less than 1500 grams

To determine whether body weight during the first 2 weeks of life in preterm infants weighing less than 1500 gm reflects nutritional status or fluid balance, we studied total body water (TBW) (deuterium oxide dilution), extracellular volume (sucrose dilution), and plasma volume (Evans blue dilution), together with intake-output studies of nitrogen, fluid, and sodium on day 1 (median age 0.3 day), at a weight loss of 7.8% of birth weight (median age 3.4 days), and after birth weight was regained (median age 8.9 days) in eight clinically stable preterm infants (birth weight 810 to 1310 gm, gestational age 26 to 30 weeks) receiving ventilatory support. During the initial weight loss we found no evidence of catabolism. Body solids (weight--TBW) remained unchanged, there was nitrogen retention, and energy intake was sufficient to meet energy expenditure by day 2. However, we found evidence of fluid loss: TBW (mean +/- SD, -95 +/- 99 ml), extracellular volume (-98 +/- 63 ml), and interstitial volume (-102 +/- 75 ml) decreased significantly, indicating negative fluid and sodium balances. Blood volume and plasma volume remained unchanged. With the regaining of birth weight there was no increase in body solids despite a high degree of nitrogen retention, but there was a positive fluid balance although no significant increase in any body fluid compartment was found. We conclude that the observed postnatal weight changes reflect changes in interstitial volume.

Increased helper inducer and decreased suppressor inducer phenotypes in the rheumatoid joint

Cells isolated from the joints of patients with rheumatoid arthritis (RA) exhibit functional immune abnormalities, such as diminished suppressor activity, depressed response to mitogens, and enhanced immunoglobulin production. We sought to characterize the T lymphocyte subsets in the synovial fluid (SF) and peripheral blood (PB) of RA patients in an attempt to clarify the mechanism(s) responsible for these functional immune abnormalities. We used dual-immunofluorescence staining techniques with several combinations of monoclonal antibodies, including anti-4B4 and anti-2H4, which define, respectively, the helper inducer and suppressor inducer subsets of CD4+ (Leu-3+ and T4+) cells. Mononuclear cells from normal PB (n = 9), RA PB (n = 6), and RA SF (n = 9) were analyzed, after staining, by flow cytometry. We observed a significant increase (P less than 0.0002) in the number of cells bearing the helper inducer phenotype (CD4+, 4B4+), and a significant decrease (P less than 0.0002) in the number of cells bearing the suppressor inducer phenotype (CD4+, 2H4+), in RA SF compared with the levels in PB from RA patients or normal control subjects. We also observed that the CD8+, 2H4+ subset was significantly decreased (P less than 0.0001) in SF compared with that in PB. There was no significant difference in the lymphocyte subset levels in PB from RA patients and from normal subjects. These observations may account, in part, for the reduced suppressor activity, the poor response to mitogens, and the autologous mixed lymphocyte reaction, as well as the enhanced production of Ig and rheumatoid factor, that are observed in the rheumatoid joint.

The peptide transporter PepT2 is expressed in rat brain and mediates the accumulation of the fluorescent dipeptide derivative beta-Ala-Lys-Nepsilon-AMCA in astrocytes

We describe the synthesis of a fluorescent dipeptide derivative, beta-Ala-Lys-Nepsilon-AMCA, which could be used as an excellent reporter molecule for studying the oligopeptide transport system in brain cell cultures. Fluorescence microscopic and immunocytochemical studies revealed that the reporter peptide specifically accumulated in astrocytes (type I and II) and O-2A progenitor cells but not in neurons or differentiated oligodendrocytes. In astroglia-rich cell culture the dipeptide derivative is taken up in unmetabolized form by an energy dependent, saturable process with apparent kinetic constants of KM = 28 microM and Vmax = 6 nmol x h(-1) x mg protein(-1) at pH 7.2. Competition studies revealed that the accumulation of beta-Ala-Lys-Nepsilon-AMCA is strongly inhibited by dipeptides and pseudopeptides such as bestatin, arphamenine A and B. The biochemical data indicated that the properties of this high-affinity oligopeptide carrier closely resemble those of the renal peptide transport system PepT2 and Northern blot analysis demonstrated that PepT2 mRNAis expressed in glial but not in neuronal cell cultures. In situ hybridization histochemistry also revealed a non-neuronal localization of PepT2 transcripts and a diffuse, widespread distribution of PepT2 signals throughout the entire rat brain. The selective accumulation of the fluorescent reporter molecule by brain cells under viable conditions may provide a useful tool for studying peptide uptake systems and other aspects of astroglial physiology.

Starvation-induced changes in the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA and the hypothalamic release of proTRH-derived peptides: role of the adrenal gland

The purpose of this study was to investigate the mechanisms involved in the reduced thyroid function in starved, young female rats. Food deprivation for 3 days reduced the hypothalamic content of prothyrotrophin-releasing hormone (proTRH) mRNA, the amount of proTRH-derived peptides (TRH and proTRH160-169) in the paraventricular nucleus, the release of proTRH-derived peptides into hypophysial portal blood and the pituitary levels of TSH beta mRNA. Plasma TSH was either not affected or slightly reduced by starvation, but food deprivation induced marked increases in plasma corticosterone and decreases in plasma thyroid hormones. Refeeding after starvation normalized these parameters. Since the molar ratio of TRH and proTRH160-169 in hypophysial portal blood was not affected by food deprivation, it seems unlikely that proTRH processing is altered by starvation. The median eminence content of pGlu-His-Pro-Gly (TRH-Gly, a presumed immediate precursor of TRH), proTRH160-169 or TRH were not affected by food deprivation. Since median eminence TRH-Gly levels were very low compared with other proTRH-derived peptides it is unlikely that alpha-amidation is a rate-limiting step in hypothalamic TRH synthesis. Possible negative effects of the increased corticosterone levels during starvation on proTRH and TSH synthesis were studied in adrenalectomized rats which were treated with corticosterone in their drinking water (0.2 mg/ml). In this way, the starvation-induced increase in plasma corticosterone could be prevented. Although plasma levels of thyroid hormones remained reduced, food deprivation no longer had negative effects on hypothalamic proTRH mRNA, pituitary TSH beta mRNA and plasma TSH in starved adrenalectomized rats. Thus, high levels of corticosteroids seem to exert negative effects on the synthesis and release of proTRH and TSH. This conclusion is corroborated by the observation that TRH release into hypophysial portal blood became reduced after administration of the synthetic glucocorticosteroid dexamethasone. On the basis of these results, it is suggested that the reduced thyroid function during starvation is due to a reduced synthesis and release of TRH and TSH. Furthermore, the reduced TRH and TSH synthesis during food deprivation are probably caused by the starvation-induced enhanced adrenal secretion of corticosterone.

Connective tissue growth factor: a novel marker of layer VII neurons in the rat cerebral cortex

Connective tissue growth factor (CTGF) belongs to a family of secreted, extracellular matrix-associated proteins that are involved in the regulation of cellular functions such as adhesion, migration, mitogenesis, differentiation and survival. Recent studies have also suggested the up-regulation of CTGF in response to trauma, scar formation and excitotoxicity in the CNS. To further elucidate the localization and regulation of this molecule in the rat brain we performed in situ hybridization experiments and found a very strong and selective expression of CTGF messenger ribonucleic acid (mRNA) on the band of layer VII neurons throughout the adult cerebral cortex. Similarly strong neuronal expression was also present in the dorsal endopiriform nucleus, extending rostrally from the ventrocaudal cortical layer VII, and in the deep layers of the olfactory glomeruli and the accessory olfactory nucleus. Double in situ hybridization confirmed selective CTGF mRNA expression on a subpopulation (approximately 35%) of microtubule-associated protein 2 mRNA-positive neurons in the cortical layer VII and the dorsal endopiriform nucleus. The nucleus of lateral olfactory tract showed moderate signal intensity; other parts of the forebrain, mesencephalon and brain stem only revealed a very weak level of CTGF mRNA expression. Non-neuronal expression was rare, considerably weaker than on cortical layer VII neurons, and normally associated with blood vessels. Developmental analysis of CTGF mRNA expression in embryonic and postnatal mouse also showed a moderately late onset at embryonic day 16-18, and confirmed the presence of CTGF mRNA in cortical layer VII in a second rodent species. Interestingly, injury experiments using direct cerebral trauma or injection of excitotoxic kainic acid into rat brain failed to up-regulate CTGF mRNA after injury and during the ensuing period of neuronal cell death, gliosis and neural scar tissue formation. Altogether, the current data suggest a constitutive role of CTGF, particularly in the adult cerebral cortex. In view of the strong ascending projections of subplate neurons into cortical layer 1, this molecule may be involved in the modulation of synaptic input to apical dendrites of pyramidal neurons.

Postnatal body weight curves for infants below 1000 g birth weight receiving early enteral and parenteral nutrition

No body weight curves are available for preterm infants < 1000 g birth weight receiving early enteral and parenteral nutrition. Postnatal weight changes of 136 infants with a birth weight < 1000 g were analysed retrospectively. Body weight curves for the first 30 days of life were generated for five separate birth weight groups (430-599 g, 600-699 g, 700-799 g, 800-899 g, 900-999 g). All infants had received intravenous glucose and amino acids from day 1 and intravenous lipids from day 2. Enteral feeding was started on day 1. Thus caloric intake (+/-SD) was advanced to 384+/-46 kJ/kg per day (92+/-11 kcal/kg/day) in the 1st week of life. In 136 preterm infants mean postnatal weight loss was 10.1%+/-4.6% of birth weight, birth weight was regained at a mean postnatal age of 11+/-3.7 days, but significantly earlier (7.8+/-3.5 days) in the lowest compared to the highest weight group. Mean subsequent weight gain was 15.7+/-7.2 g/ kg per day. This was accomplished by exclusive enteral nutrition from day 20 (median).

CONCLUSION

Our body weight curves are more adequate to evaluate growth of preterm infants than older published reference values because they are based on infants treated according to current nutritional standards.

Associations of blood levels of PCB, HCHS, and HCB with numbers of lymphocyte subpopulations, in vitro lymphocyte response, plasma cytokine levels, and immunoglobulin autoantibodies

Pentachlorophenol (PCP), hexachlorocyclohexane-[alpha], -beta, and -[gamma] (HCH-[alpha], -beta, and -[gamma]), polychlorinated biphenyls (PCBs), and hexachlorobenzene (HCB) are widely distributed industrial chemicals. They are suspected to induce immunologic impairments in exposed individuals. We examined dose-response relationships of blood levels of these chemicals with cellular (numbers of lymphocyte subpopulations, in vitro lymphocyte response) or humoral (plasma cytokine levels, immunoglobulin autoantibodies) immunologic dysfunctions. We studied 146 patients who had been occupationally exposed primarily to PCBs for more than 6 months. Lymphocyte subpopulations, in vitro responses to mitogens and allogeneic stimulator cells, plasma neopterin, cytokines, soluble cytokine receptors, soluble adhesion molecules, anti-Ig autoantibodies, and liver transaminases were determined. Blood levels of the different compounds were strongly correlated with one another. There were only weak dose-response relationships between blood levels of PCBs with cellular immune parameters, and of HCHs and HCB with humoral immune parameters. An exception was the statistically significant negative association of HCB with interferon-[gamma] (IFN-[gamma]), indicating that HCB has a significant impact on Th1 lymphocytes. Patients with HCB blood levels above the mean of 1,109 ng/L more often had undetectable IFN-[gamma] blood levels than patients below the mean. Patients with increased PCB 138 (> 710 ng/L) had more frequently undetectable interleukin-4 blood levels than patients with PCB 138 below the mean, and patients with increased PCB 101 (> 31 ng/L) more often had low DR+ cell counts in the blood (< 190/microL) than patients with PCB 101 below the mean. To assess possible cumulative effects, we compared patients who had blood levels of all compounds below background with patients who had blood levels of all compounds above background. Patients with low or absent blood levels of the compounds studied had higher IFN-[gamma] plasma levels, providing some evidence for a cumulative effect of several weakly active compounds. In conclusion, exposure to PCBs, HCB, or HCHs is associated with weak immunologic abnormalities. These results contrast with those obtained in earlier studies of blood levels of PCP, which showed a strong dose-dependent relationship with immunologic impairments. Our data suggest that long-term exposure of patients to HCB suppresses IFN-[gamma] production.

Characterization of a nonchymotrypsin-like endopeptidase from anterior pituitary that hydrolyzes luteining hormone-releasing hormone at the tyrosyl-glycine and histidyl-tryptophan bonds

A neutral endopeptidase which degrades luteinizing hormone-releasing hormone (LH-RH, <GLu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-GLy-NH2) has been purified 900-fold from extracts of bovine anterior pituitary. This Ca2+-independent enzyme of 83 000 molecular weight (as estimated by gel filtration) cleaves LH-RH (KM = 180 microM) at the Tyr5-Gly6-His2-Trp3 bonds. Its activity is inhibited by the SH-reactive agents N-ethylmaleimide and p-(chloromercuri)benzoate but not by the OH-reactive agent diisopropyl fluorophosphate. Hydrolysis of the fluorogenic chymotrypsin substrate glutarkyl-Gly-Gly-Phe-beta-naphthylamide by this endopeptidase could not be detected. These properties differentiate the endopeptidase from chymotrypsin and from a glutaryl-Gly-Gly-Phe-beta-naphthylamide hydrolyzing activity of high molecular weight, which has been isolated from the same tissue and also hydrolyzes internal bonds of LH-RH.

Tandem immobilized metal-ion affinity chromatography/immunoaffinity purification of His-tagged proteins--evaluation of two anti-His-tag monoclonal antibodies

A tag comprising four to six histidines genetically fused to the protein of interest (His-tag) has been widely used to purify proteins by immobilized metal-ion affinity chromatography (IMAC). Here we report the utilization of the same tag twice in series, first for IMAC and subsequently for immunoaffinity purification. Both steps are based on completely different physical principles and can therefore remove different contaminants. Two anti-His-tag antibodies (3D5 and PentaHis) were characterized for their binding and elution properties using the BIAcore surface plasmon resonance biosensor. The dissociation constant of the PentaHis antibody was determined to be 1 x 10(-8) M and for the 3D5 antibody 3.4 x 10(-7) M at pH 7.4. Imidazole in the sample did interfere with binding, whereas chelating agents such as EDTA and high salt did not. The antibody 3D5 was coupled to a column matrix and used for a coupled two-step purification, in which the IMAC column is eluted with EDTA and the eluent is loaded directly on the immunoaffinity column. This method may constitute a very general procedure to purify proteins to near homogeneity without the need to tailor conditions individually, and it may thus be very attractive for high-throughput screening programs and for developing general protocols for clinical grade material.

Cloning of a cDNA encoding an ectoenzyme that degrades thyrotropin-releasing hormone

Thyrotropin-releasing hormone (TRH) is an important extracellular signal substance that acts as a hypothalamic-releasing factor, which stimulates the release of adenohypophyseal hormones and functions as a neurotransmitter/neuromodulator in the central and peripheral nervous system. The inactivation of TRH after its release is catalyzed by an ectoenzyme localized preferentially on neuronal cells in the brain and on lactotrophic pituitary cells. This enzyme exhibits a very high degree of substrate specificity as well as other unusual properties. The activity of the adenohypophyseal enzyme is stringently controlled by estradiol and thyroid hormones, indicating that this enzyme itself may serve regulatory functions. Fragments of the enzyme isolated from rat or pig brain were generated by enzymatic digestion or cyanogen bromide cleavage, purified by reverse-phase HPLC, and sequenced. PCR amplification and screening of cDNA libraries from rat brain and pituitary led to the identification and isolation of a cDNA that encodes a protein of 1025 amino acids. The analysis of the deduced amino acid sequence was consistent with the identification of the enzyme as a glycosylated, membrane-anchored Zn metallopeptidase. Furthermore, Northern blot analysis demonstrated that the mRNA levels paralleled the tissue distribution of the enzyme and that in pituitary tissue the transcript levels rapidly increased when the animals were treated with triiodothyronine. Finally, transient transfection of COS-7 cells with this cDNA led to the expression of an active ectopeptidase that displayed the characteristics of the TRH-degrading ectoenzyme.