Modifications in the B10 and B26-30 regions of the B chain of human insulin alter affinity for the human IGF-I receptor more than for the insulin receptor

Inversion of the natural sequence of the B chain of human insulin (HI) from ProB28LysB29 to LysB28ProB29 generates an insulin analogue with reduced tendency to self-associate. Since this substitution increases the homology of insulin to insulin-like growth factor-I (IGF-I), we have examined the affinity of a series of insulin analogues with the general modified structure XaaB28ProB29 HI for binding to both human placental insulin and IGF-I receptors. The XaaB28ProB29 HI series is approximately equipotent to HI in binding to the insulin receptor with the exception of when Xaa = Phe, Trp, Leu, Ile, and Gly (40-60% relative to HI). Substitution with basic residues in the B28 position increased the relative affinity to the IGF-I receptor approximately 1.5-2-fold (ArgB28ProB29 > OrnB28ProB29 = LysB28ProB29). Substitution with acidic residues reduced relative affinity for the IGF-I receptor approximately 2-fold (CyaB28ProB29 = GluB28ProB29 > AspB28ProB29). Combination of AspB10 substitution in conjunction with a modification in the B28-29 position (e.g. AspB10LysB28ProB29 HI) showed an additional 2-fold selective increase in affinity for the IGF-I receptor, suggesting that these two effects are additive. Addition of Arg residues at B31-32, on the backbone of either HI or AspB10 HI, increased affinity for the IGF-I receptor 10 and 28 fold, respectively, compared to HI, confirming the significance of enhanced positive charge at the C-terminal end of the insulin B-chain in increasing selectivity for the IGF-I receptor. This relative increase in IGF-I receptor affinity correlated largely, but not completely, with enhanced growth promoting activity in human mammary epithelial cells. In the case of LysB28ProB29 HI, growth activity correlated with dissociation kinetics from the insulin receptor which were shown to be identical with those of human insulin.

Caveolin and MAL, two protein components of internal detergent-insoluble membranes, are in distinct lipid microenvironments in MDCK cells

The MAL proteolipid and caveolin have been identified as components of internal detergent-insoluble membrane microdomains enriched in glycolipids and cholesterol. We have addressed the study of the glycolipid-enriched membranes in cells expressing endogenously only either MAL (Jurkat T cells) or caveolin (epithelial A498 cells) and in polarized MDCK cells which express both proteins simultaneously. Subcellular fractionation by centrifugation to equilibrium in sucrose gradients of Triton X-100 cell extracts from Jurkat and A498 cells revealed that MAL and caveolin are incorporated in detergent-insoluble buoyant membranes independently of the expression of each other and indicated the existence in these cells of insoluble membrane microdomains with either MAL or caveolin. Immunofluorescence analysis in MDCK cells indicated that both MAL and caveolin were located in the Golgi region, whereas caveolin was found in addition at the cell surface. Biochemical analysis in these cells revealed the existence of distinct membrane microenvironments differentially susceptible to detergent solubilization containing either internal MAL or internal plus surface caveolin. The observed heterogeneity within the internal glycolipid-enriched membrane fraction suggests the existence of distinct specialized lipid microenvironments in MDCK cells.

Determination of Deuterium Incorporation into RNA and Protein Components of the Escherichia Coli Ribosome at Biosynthetic Deuteration by Small-Angle Neutron Scattering

A simple method for the determination of deuterium incorporation into nonexchangeable (C-bonded) positions of RNA and protein components of the Escherichia coli ribosome at biosynthetic deuteration has been proposed using small-angle neutron scattering. The theory of the method is based on the joint use of two measurements: one of them is the dependence of neutron scattering intensity at zero angle on the contrast; the second is the dependence of the radius of gyration on the contrast. The main advantage of the method over the standard procedure is that it requires neither separation of the ribosome into RNA and protein components nor a subsequent time-consuming analysis of the hydrolysis products by nuclear magnetic resonance or mass spectrometry.

[Association of pregnancy induced hypertension with human leucocyte antigen system]

OBJECTIVE

To examine whether pregnancy induced hypertension (PIH) is correlated with a polymorphism of human leucocyte antigen (HLA)-DRB1 in the Shanghai population.

METHODS

We determined the HLA-DRB1 types of 17 PIH families and 14 normotension families by DNA typing utilizing the polymerase chain reaction (PCR) and hybridization of Dig-labeled sequence specific oligonucleotide (PCR-SSO).

RESULTS

The antigens frequency and feto-material sharing of HLA-DR4 in PIH were increased and relative to that of the controls, and furthermore the 0405 allele occurred more often in PLH patients.

CONCLUSION

These results suggest that a PIH susceptibility gene is associated with HLA-DRB1 0405. We therefore propose the following working hypothesis; 0405 allele is presumably due to linkage disequilibrium or the possibility that it acts directly as an immune response gene; PIH is correlated with DR4 compatibility between PIH mother and fetus which leads to failure of the mother's nonresponsiveness to fetal antigen. Lack of blocking factor increases the risk for PIH.

The MAL proteolipid is a component of the detergent-insoluble membrane subdomains of human T-lymphocytes

The human mal gene, identified during a search for cDNAs selectively expressed during T-cell development, encodes a highly hydrophobic protein belonging to a group of proteins, termed proteolipids, characterized by their unusual property of being soluble in organic solvents used to extract cell lipids. To study the localization of the MAL protein we have prepared stable transfectants expressing the MAL protein tagged with a c-myc epitope (MAL/c-myc) using human epithelial A-498 cells. Immunofluorescence analysis suggested that MAL/c-myc is localized mainly to cholesterol-enriched structures with a post-Golgi location and, at low levels, in early endosomes. Moreover, extraction of A-498 cell membranes with Triton X-100 (TX100) and fractionation by centrifugation to equilibrium in sucrose gradients demonstrated the presence of MAL/c-myc in the detergent-insoluble buoyant fraction, known to be enriched in glycolipids and cholesterol. To compare the behaviour of MAL in T-cells with that in epithelial A-498 cells, we prepared stably transfected cells expressing MAL/c-myc using human Jurkat T-cells. When TX100 extracts from Jurkat cells were subjected to centrifugation to equilibrium in sucrose gradients we found MAL exclusively in the floating fractions, together with molecules characteristic of the T-cell insoluble complexes, such as the tyrosine kinase p56lck, the glycosylphosphatidylinositol-anchored protein CD59 and the ganglioside GM1. These results, taken together, indicate that the MAL proteolipid is a component of the detergent-resistant membrane microdomains present in T-lymphocytes, and suggest that MAL might play a role in modulating the function of these microdomains during T-cell differentiation.

Association of human papillomavirus type 11 DNA with squamous cell carcinoma of the tongue

A 47-year-old man with a history of a benign papilloma of the tongue 5 years earlier was treated for a squamous cell carcinoma of the tongue with surgical resection. An analysis of the tumor DNA using several methods showed the presence of human papillomavirus (HPV) type 11 sequences that migrated with the high molecular weight cellular DNA, suggesting integration of viral DNA into the cellular genome. A segment of the HPV DNA was cloned from the lesion and shown to be similar to prototype HPV 11 DNA, except for some variability in the viral long control region. The proviral DNA contained part of the L1 region, all of the viral long control region, the entire E6 and E7 open-reading frames, and at least a portion of the E1 region; the E4 region appeared to be deleted. The integration sites of the HPV DNA could not be specifically identified. An analysis of the p53 tumor suppressor gene region of the tumor DNA showed no evidence of mutation. These results suggest that the HPV 11 DNA may have had a role in the origin of the cancer in this patient.

Activation of metabotropic glutamate receptor subtype mGluR1 contributes to post-traumatic neuronal injury

The role of phospholipase C-coupled (group I) metabotropic glutamate receptors (mGluR1 and mGluR5) in post-traumatic neuronal injury was examined using rat in vivo and in vitro models. Traumatic injury to mixed neuronal/glial cultures induced phosphoinositide hydrolysis and caused neuronal death. Pharmacological blockade of group I receptors significantly reduced these effects in vitro and decreased neurological deficits as well as neuronal loss produced by traumatic brain injury in vivo. In contrast, activation of group I receptors by a specific agonist in vitro exacerbated post-traumatic neuronal death in a dose-dependent manner. Antisense oligodeoxynucleotide directed to mGluR1, but not to mGluR5, was neuroprotective in vitro, although each oligodeoxynucleotide reduced the respective receptor-stimulated accumulation of inositol phosphates to a similar degree. Together, these findings suggest that activation of mGluR1 contributes to post-traumatic neuronal injury and that mGluR1 antagonists may have therapeutic potential in brain injury.

Theoretical Study of Ethylene Oligomerization by an Organometallic Nickel Catalyst

The mechanism for ethylene oligomerization by (acac)NiH has been studied using density functional theory (DFT). The transition states for chain propagation and chain termination were optimized and the related reaction barriers calculated. Several possible mechanisms were considered for the chain termination step. Chain termination by beta-hydrogen elimination was found to be energetically unfavorable, and is not likely to be important. Instead, beta-hydrogen transfer to the incoming ethylene unit seems to be operative. The most favorable beta-hydrogen transfer pathway has two transition states. The first leads from a weak pi-complex between an incoming ethylene unit and (acac)NiCH(2)CH(2)R to an intermediate in which the two olefins C(2)H(4) and H(2)CCHR both are strongly pi-complexed to the nickel hydride (acac)NiH. The second barrier takes the intermediate to another weak pi-complex between (acac)NiCH(2)CH(3) and H(2)C=CHR from which the oligomer H(2)C=CHR can be released and the catalyst (acac)NiCH(2)CH(3) regenerated. Due to the mechanism of chain termination, the actual catalyst is proposed to be (acac)NiCH(2)CH(3) whereas (acac)NiH serves as a precursor or precatalyst.

Enhanced natriuretic response to intrarenal infusion of atrial natriuretic factor during ovine pregnancy

Volume-loading and intravenous infusion studies have suggested that the natriuretic response of atrial natriuretic factor (ANF) is blunted or unaltered during pregnancy, but these findings may be influenced by changes in peripheral metabolism or clearance. To better define the direct renal actions of ANF, three doses (0.3, 1.5, and 3.0 pmol.kg-1.min-1) of ANF were infused directly into the renal artery of nonpregnant (n = 7) and 115- to 135-day pregnant (n = 6) unilaterally nephrectomized conscious sheep. Each dose was administered on a separate day according to a protocol that consisted of two 20-min control periods, two 20-min ANF infusions, and three 30-min recovery periods. The levels of basal mean arterial pressure averaged 86 +/- 25 mmHg and were similar and constant throughout all protocols in nonpregnant and pregnant ewes. Glomerular filtration rate (GFR) and renal blood flow (RBF) were increased during pregnancy, but GFR, RBF, and fractional proximal tubular reabsorption were not significantly altered by infusion of ANF. Nonpregnant sheep exhibited a selective renal response that was limited to an increase in urinary sodium excretion (UNaV). Pregnant sheep exhibited a selective renal response that included increases in UNaV and urine flow rate produced by suppression of distal sodium and, presumably, fluid reabsorption. The natriuretic and diuretic response of pregnant sheep was much greater than that of nonpregnant sheep despite a smaller proportional increment in intrarenal ANF concentration. These data suggest that the ovine renal response to ANF is limited to actions on the distal tubule that are enhanced during pregnancy.

Experimental brain injury induces differential expression of tumor necrosis factor-alpha mRNA in the CNS

In the present study, we examined the expression of tumor necrosis factor-alpha (TNF-alpha) mRNA i specific brain regions following experimental lateral fluid percussion traumatic brain injury (TBI) in rats. Adult Sprague-Dawley rats (n = 42) were anesthetized with sodium pentobarbital (60 mg/kg, i.p.) and subjected to lateral fluid percussion brain injury of moderate severity (2.4 atm.) centered over the left temporoparietal cortex, or 'sham' treatment (anesthesia and surgery without injury). Animals were killed by decapitation at 1, 6 or 24 h post injury, brains removed, and tissue samples of left (injured) parietal cortex (LC), right parietal cortex (RC), left adjacent cortex (LA), right adjacent cortex (RA), left hippocampus (LH) and right hippocampus (RH) were prepared. Total RNA was isolated and Northern blot hybridization was performed. TNF-alpha mRNA is expressed as the percent relative radioactivity of macrophage (positive control) RNA. In sham or naive animals, no consistent changes in expression of TNF-alpha mRNA were observed in any of the six brain areas at any times (less than 5%). A marked increase of TNF-alpha mRNA expression was observed in LH (104 +/- 17, P < 0.05 compared with sham), LC (105 +/- 21, P < 0.05) and LA (69 +/- 8, P < 0.01) in the traumatized hemisphere 1 h following injury. An increased TNF-alpha mRNA expression was also observed in LH (46 +/- 8, P < 0.05), LC(30 +/- 3, P < 0.01) and LA(32 +/- 3, P < 0.01) at 6 h which resolved by 24 h following injury. In the contralateral hemisphere, expression of TNF-alpha mRNA was increased in RH (46 +/- 2, P < 0.01) at 1 h and in RA (26 +/- 6%, P < 0.05) at 6 h. These results indicate that following parasagittal fluid percussion brain injury, the temporal expression of TNF-alpha mRNA is altered in specific brain regions, including those of the non-traumatized hemisphere. Post-traumatic alteration in gene expression of TNF-alpha might play an important role in both the acute and regenerative response to CNS trauma.

[An experimental study of regional spontaneous portasystemic shunt in cirrhotic rats]

CCl4 induced splenic portasystemic shunt (SPSS) was measured in 11 CCl4-induced cirrhotic rats and 10 controls, and mesenteric shunt (MPSS) was measured in 11 controls. 125I labeled albumin microspheres was used as nuclear markers for measurement of shunting rate. It was found that, portal resistance, free portal pressure, wedged hepatic venous pressure, portahepatic venous pressure gradient were all elevated markedly in cirrhotic rats, while the volume of portal flow had no significant difference between the two groups. SPSS and MPSS were higher remarkably those that in the normal controls, and SPSS was greater than MPSS significantly. It suggested that splenogastric venous bed is the main area for compensatory shunt and also the dangerous site of bleeding. Portaazygous disconnection is the operation of choice for control of bleeding. However it could impair the mechanism of spontaneous shunting compensation seriously. Disconnection operation combined with splenorenal shunt seems to be a reseasonable consideration.

The Dai minority population of southwest China: heterogeneity of DR2-associated HLA-DRB1,DRB5,DQA1, and DQB1 haplotypes

HLA-DR2 is the most common DR specificity (60.3%) identified in the Dai minority population of Xishuangbanna, Yunna Province, China. We characterized the DRB1, DRB5, DQA1, and DQB1 alleles of 44 unrelated DR2-positive individuals, 11 of whom (15%) were DR2 homozygous. Four DRB1 and four DRB5 alleles encoding DR2 were identified in this population. The most frequent DR2-associated DRB1 alleles were *1602 (gf = 0.164) and *1502 (gf = 0.151). DRB1*1501 (gf = 0.048) and a new allele designated DRB1*1504 (gf = 0.014) were also detected, but *1601 and *1503 were absent. The most frequent DR2-associated DRB5 alleles were *0101 (gf = 0.233) and *0102 (gf = 0.110). Nine different DR2-associated DR/DQ haplotypes were identified. The two most common DR2 haplotypes were DRB1*1602, DRB5*0101, DQA1*0102, DQB1*0502 (hf = 0.142) and DRB1*1502, DRB5*0102, DQA1*0101, DQB1*0501 (hf = 0.075). The new DRB1*1504 allele was found on a single haplotype: DRB1*1504, DRB5*0101, DQA1*0102, DQB1*0502 (hf = 0.017). The Dw2, Dw12, Dw21, and Dw22 haplotypes, present in many other Asian and Mongoloid populations, were not identified in this unique group. However, the Dai minority population is characterized by a relatively large number of diverse DR2 haplotypes and a new DRB1 allele encoding DR2.

Differentiation between emboli and artefacts using dual-gated transcranial Doppler ultrasound

It is well documented that transcranial Doppler ultrasound has the ability to detect cerebral emboli. During intraoperative patient monitoring studies, many signals due to artefact (probe motion, patient movement or surgical manipulation) are also detected and can be difficult to distinguish from genuine embolic events. We have constructed a Doppler system that can simultaneously range-gate at two separate depths, in order to test the hypothesis that it should be possible to distinguish between emboli and artefact by comparing the signal from the two separate regions within the vessel. The classification algorithm is based on the principle that emboli propagate with blood motion (whereas artefacts do not) and thus will be detected sequentially at different depths along the insonated cerebral artery. One hundred thirty-eight (presumed) embolic and 170 artefact signals were analysed. The median (interquartile range) gate separation was 10.01 mm (7.41-10.78 mm). The time delay between detection of embolic signals in the two channels was 11.04 ms (6.24-16.41 ms, but was only 0.08 ms (-0.48(-)+0.64 ms) for artefact (p < 0.0001). Dual-gated Doppler ultrasound is a conclusive and independent method that differentiates emboli from artefact. Incorporation of this system for long-term monitoring may eliminate the need for an experienced observer to be present.

Heat shock response of Trichinella spiralis and T. pseudospiralis

Heat shock proteins (HSPs) were documented for the first time in both somatic extracts and excretory/secretory (ES) products of the infective-stage larvae of Trichinella spiralis and T. pseudospiralis. Larvae recovered from muscles of infected mice were heat shocked at 37, 40, 43 and 45 degrees C in RPMI 1640 medium containing L(-)[35S]methionine. Somatic extracts and ES products of heat-shocked worms were then analysed by SDS-PAGE, autoradiography and laser densitometry. Prominent bands of HSPs were observed at 43 degrees C which is the optimal heat shock temperature. The major HSPs in somatic extracts of T. spiralis were 20, 47, 50, 70, 80 and 86 kDa. When the temperature was increased from 37 to 43 degrees C, the greatest increase in absorbance was observed in HSPs 70 and 86. In vitro translation of mRNA in a nuclease-treated rabbit reticulocyte lysate system showed an increase in the synthesis of the 80 kDa protein. This suggests that the production of HSP 80 is regulated at the transcriptional level. The major HSPs in the ES products were 11, 45, 53 and 64 kDa. In T. pseudospiralis, the major HSPs in the somatic extracts were 20, 26, 31, 50, 53, 70, 80 and 86 kDa, and in the ES products, 11, 35, 37, 41 and 64 kDa.

Interpretation of embolic phenomena during carotid endarterectomy

BACKGROUND AND PURPOSE

Air and particulate emboli are a major source of morbidity during carotid endarterectomy (CEA); however, amplitude overload and poor time resolution have restricted the ability of transcranial Doppler ultrasound to differentiate between the two.

METHODS

We have now overcome these two limitations by (1) rerouting embolic signals away from the audio frequency amplifier to avoid amplitude overload and (2) substituting the Wigner distribution function for the fast Fourier transform to improve time and frequency resolution. Thus, we can now accurately determine embolic duration and embolic velocity, the product of which is the sample volume length (SVL). This measurement represents the physical distance over which an embolic signal can be detected. The underlying hypothesis was that air reflected more ultrasound and would therefore be detected over a greater SVL.

RESULTS

The median SVL (interquartile range) for 75 in vitro air emboli was 1.97 cm (range, 1.70 to 2.35) compared with 0.27 cm (range, 0.16 to 0.43) for 185 particulate emboli detected during the dissection phase of CEA. Off-line analysis on an additional 560 embolic signals detected during different phases of CEA suggested that 46 of 143 (32%) of emboli immediately after shunt insertion were particulate, as were 19 of 33 (58%) occurring during shunting, 28 of 78 (36%) after restoration of flow in the external carotid artery, 23 of 251 (9%) after restoration of flow in the internal carotid artery, and 55 of 55 (100%) of those emboli detected during the early recovery phase.

CONCLUSIONS

This development provides objective physical criteria upon which embolus characterization (particulate/air) can be based. This could have major implications for future patient monitoring with respect to modification of surgical technique and pharmacological intervention.

Control of atrial natriuretic factor by right and left atrial distension in pregnant sheep

Previous studies of the atrial stretch-atrial natriuretic factor (ANF) relationship during pregnancy have employed volume expansion and measured only right atrial pressure (RAP). Consequently, we studied nonpregnant (n = 7) and 115- to 125-day pregnant (n = 7) sheep and assessed the ANF response to changes of RAP and left atrial pressure (LAP) induced by graded balloon inflation. Ewes prepared with vascular catheters and atrial balloons were studied after recovery from preparatory surgical procedures. The basal levels of mean arterial pressure (MAP, 83 +/- 3 mmHg), RAP (2.1 +/- 0.7 mmHg), LAP (4.7 +/- 0.9 mmHg), and heart rate (HR, 102 +/- 6 beats/min) were similar in nonpregnant and pregnant sheep. Pregnancy also resulted in elevation of ANF concentration from 25 +/- 6 to 57 +/- 4 fmol/ml. With right atrial distension, the RAP-ANF relationships were similar in both nonpregnant and pregnant sheep, with a 10-mmHg increase in RAP increasing ANF by an average of 95 +/- 9 fmol/ml. In nonpregnant sheep, the LAP-ANF relationship was more responsive than RAP-ANF because a 10-mmHg increase in LAP resulted in a 193 +/- 10 fmol/ml increase in ANF. Moreover, during pregnancy, the LAP-ANF relationship was significantly more sensitive because a 10-mmHg increase in LAP resulted in a 433 +/- 15 fmol/ml elevation of ANF. These data demonstrate that plasma ANF levels are more responsive to distension of the left atria than to the right. More importantly, the ANF response to left, but not right, atrial distension is enhanced by pregnancy.

Effects of angiotensin II on plasma atrial natriuretic factor in nonpregnant and pregnant ewes

The release of atrial natriuretic factor (ANF) is primarily determined by atrial stretch, but may also be modulated by circulating angiotensin II (AngII). During pregnancy, the circulating concentrations of both ANF and AngII are increased. To further define possible effects of AngII on ANF release, four doses of AngII (0.5, 5, 20, 40 ng.kg-1.min-1) were intravenously infused into five nonpregnant and five pregnant (105-140 days of gestation) ewes alone and during the simultaneous infusion of sodium nitroprusside at doses sufficient to abolish the pressor effects of AngII. Mean arterial pressure (MAP) was increased from 80 +/- 2 to a maximum of 121 +/- 5 mmHg (1 mmHg = 133.3 Pa) in nonpregnant ewes (p < 0.01) and from 79 +/- 2 to 116 +/- 4 mmHg in pregnant ewes (p < 0.01) over the range of AngII infusion. MAP was unaltered during AngII plus nitroprusside infusion, averaging 78 +/- 3 mmHg in nonpregnant ewes and 80 +/- 2 mmHg in pregnant ewes. Basal ANF was higher (p < 0.01) in pregnant sheep than in nonpregnant sheep. With AngII infusion alone, plasma ANF was increased from 13 +/- 2 to 42 +/- 4 fmol/microL in nonpregnant ewes (p < 0.01) and from 23 +/- 5 to 72 +/- 16 fmol/microL in pregnant ewes (p < 0.01). However, during AngII plus nitroprusside infusion, the increases in plasma ANF observed were completely abolished in both nonpregnant and pregnant ewes.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental brain injury induces expression of interleukin-1 beta mRNA in the rat brain

Cytokines have been shown to be induced following a variety of central nervous system (CNS) insults, and may play a role in the pathophysiological sequelae of CNS injury. In the present study, we characterized the regional expression of interleukin-1 beta (IL-1 beta) mRNA in specific brain regions following experimental lateral fluid-percussion traumatic brain injury (TBI) in rats. Adult Sprague-Dawley rats (n = 42) were anesthetized with sodium pentobarbital (60 mg/kg, i.p.) and subjected to lateral fluid-percussion brain injury of moderate severity (2.4 atm.) centered over the left parietal cortex, or 'sham' treatment (anesthesia and surgery without injury). Animals were sacrificed at 1, 6 and 24 h post injury, brains were removed, and tissue samples of left (injured) parietal cortex (LC), corresponding area in the contralateral right cortex (RC), cortex adjacent to injured parietal cortex (LA), corresponding adjacent area in the right cortex (RA), left hippocampus (LH) and right hippocampus (RH) were prepared. Total RNA was isolated and Northern blot hybridization was performed and the quantity of brain tissue IL-1 beta mRNA is presented as percent relative radioactivity of IL-1 beta positive macrophage RNA which was loaded on same gel.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytotoxicity, DNA adduct formation and DNA repair induced by 2-hydroxyamino-3-methylimidazo[4,5-f]quinoline and 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine in cultured human mammary epithelial cells

2-Amino-3-methylimidazo[4,5-f]quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) are heterocyclic amines (HAs) found in cooked meats. Both compounds are mammary gland carcinogens in rats. The initiation of carcinogenesis by the HAs is believed to be associated with their DNA adduct formation that occurs after metabolic activation of the parent amines via cytochrome P-450-mediated N-hydroxylation and esterification. To assess the capacity of the human mammary epithelium to metabolically activate the HAs, we used the 32P-postlabeling method to measure the levels of DNA adducts in a culture of human mammary epithelial cells exposed to IQ, PhIP or their N-hydroxylamine metabolites. Whereas 50 microM parent amines did not form detectable levels of DNA adducts in cultured human mammary epithelial cells after 24 h incubations, concentrations as low as 1 microM N-hydroxylamines produced detectable levels of adducts after 2 h incubations. N-Hydroxy-PhIP formed higher adduct levels than N-hydroxy-IQ at all concentrations tested. For example, following a 2 h incubation at 50 microM, adduct levels (per 10(7) nucleotides) were 674 and 16 for N-hydroxy-PhIP and N-hydroxy-IQ, respectively. At similar initial adduct levels (10-11/10(7) nucleotides), 60-80% of IQ- and PhIP-DNA adducts were removed after 24 h, indicating that the mammary epithelial cell culture showed efficient repair of HA adducts. Whereas neither IQ nor PhIP was cytotoxic, both N-hydroxy-IQ and N-hydroxy-PhIP were cytotoxic as assessed by a dose-dependent inhibition of colony formation. After exposure to 0.1, 1, 10 or 50 microM N-hydroxy-PhIP (or N-hydroxy-IQ), colony formation was 103 (94), 84 (74), 37 (29) and 3 (2)% of the control values, respectively. Only N-hydroxy-PhIP (at 10 and 50 microM), however, was cytotoxic as assessed by the MTT cell survival assay (which measures the capacity of mitochondria to metabolize a tetrazolium salt). The ability of the N-hydroxylamines to form DNA adducts and to be cytotoxic in a culture of human mammary epithelial cells may implicate these metabolites as proximate carcinogenic forms of IQ and PhIP in the human mammary gland. However, whether there are inter-individual differences in N-hydroxylamine metabolism, adduct formation and repair in human mammary epithelial cells requires further study. The results from this study support the usefulness of cultured human mammary epithelial cells for studies on the genotoxicity and metabolism of the N-hydroxylamines of HA food mutagens.

An appraisal of equilibrium and disequilibrium models of population migration

"This article [discusses] the basic assumptions of the equilibrium and disequilibrium models and their pertinent discussion. In addition, the article examines the conditions under which the two types of models apply in different socioeconomic situations, while paying special attention to the assumptions selected for research of migration in developing countries especially at a time when they begin to move toward a market economy."

Characterization of DNA polymerase-alpha/primase complex from developing embryonic chicken brains

DNA polymerase-alpha and primase activities present in a complex, have been isolated, partially purified, and characterized from embryonic chicken brain. DNA polymerase-alpha activity, characterized by its sensitivity to N-ethyl-maleimide, high sedimentation coefficient (11.3 S), and acidic isoelectric point (5-5.5) was found in all embryonic ages. Primase activity, the enzyme responsible for the initiation of DNA synthesis, co-sedimented with DNA polymerase-alpha activity on a continuous glycerol velocity gradient. A complex containing both DNA polymerase-alpha and primase activities was isolated by DE-23 cellulose column chromatography of cell-free extracts of different embryonic ages of chicken brain. In addition to the primase complexed with DNA polymerase-alpha, a free primase activity was isolated by DE-23 cellulose column chromatography of an ammonium sulfate (0-45%; w/v) precipitated fraction of embryonic chicken brain cell-free extract. DNA polymerase-alpha activity from developing chicken brains in the embryonic stage was purified by immuno-affinity column chromatography. Of all the single-stranded DNA templates tested, primase activity was found to be maximally active with poly dC. Primase activity was not inhibited by a high concentration of alpha-amanitin. The results obtained may provide insight into further understanding of regulation of chromosomal DNA replication in developing tissues.