The gene for a human microfibril-associated glycoprotein is commonly deleted in Smith-Magenis syndrome patients

Smith-Magenis syndrome (SMS) is a clinically recognizable multiple congenital anomaly/mental retardation syndrome associated with deletion of chromosome 17p11.2. Here we report the identification of a novel gene encoding a human microfibril-associated glycoprotein (MFAP4), which has been mapped to the SMS region. A full-length cDNA corresponding to this gene has been sequenced, and reveals a coding region of 255 amino acids. MFAP4 has a fibrinogen-like domain and shares a high level of sequence homology to a fragment of a bovine 36 kDa microfibril-associated glycoprotein. The N-terminus of the protein bears an Arg-Gly-Asp sequence that serves as the ligand motif for cell surface receptor integrin. These structural features of MFAP4 suggest that it is an extracellular matrix protein involved in cell adhesion or intercellular interactions. Deletion analysis has been conducted on 31 SMS patients by polymerase chain reaction and Southern analysis of somatic cell hybrids retaining the del(17)(p11.2) chromosome or by fluorescence in situ hybridization. The MFAP4 locus is deleted in 30 of 31 SMS patients. Thus, the function of this gene must be considered in the pathogenesis of SMS. Given our previous hypothesis that SMS is a contiguous gene syndrome, complete and exhaustive definition of the critical deletion interval and a thorough phenotype-genotype correlation is required to demonstrate the role and importance of the MFAP4 gene in SMS.

The oxidation of phenol by ferrate(VI) and ferrate(V). A pulse radiolysis and stopped-flow study

Potassium ferrate, K2FeO4, is found to oxidize phenol in aqueous solution (5.5 < or = pH < or = 10) by a process which is second order in both reactants; -d[FeVI]/dt=k1[FeVI][phenol], k1 = 10(7)M-1s-1. Product analysis by HPLC showed a mixture of hydroxylated products, principally paraquinone, and biphenols that indicate that oxidation of phenol occurs by both one-electron and two-electron pathways. The two-electron oxidant, producing both para- and ortho-hydroxylated phenols is considered to be ferrate(V) which is itself produced by the initial one-electron reduction of ferrate(VI). The rate of ferrate(V) reaction with phenol was determined by pre-mix stopped flow pulse-radiolysis and found to be k7 = (3.8 +/- 0.4) x 10(5)M-1s-1.

Unexpected inhibition of cholesterol 7 alpha-hydroxylase by cholesterol in New Zealand white and Watanabe heritable hyperlipidemic rabbits

We investigated the effect of cholesterol feeding on plasma cholesterol concentrations, hepatic activities and mRNA levels of HMG-CoA reductase and cholesterol 7 alpha-hydroxylase and hepatic LDL receptor function and mRNA levels in 23 New Zealand White (NZW) and 17 Watanabe heritable hyperlipidemic (WHHL) rabbits. Plasma cholesterol concentrations were 9.9 times greater in WHHL than NZW rabbits and rose significantly in both groups when cholesterol was fed. Baseline liver cholesterol levels were 50% higher but rose only 26% in WHHL as compared with 3.6-fold increase with the cholesterol diet in NZW rabbits. In both rabbit groups, hepatic total HMG-CoA reductase activity was similar and declined > 60% without changing enzyme mRNA levels after cholesterol was fed. In NZW rabbits, cholesterol feeding inhibited LDL receptor function but not mRNA levels. As expected, receptor-mediated LDL binding was reduced in WHHL rabbits. Hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels were 2.8 and 10.4 times greater in NZW than WHHL rabbits. Unexpectedly, cholesterol 7 alpha-hydroxylase activity was reduced 53% and mRNA levels were reduced 79% in NZW rabbits with 2% cholesterol feeding. These results demonstrate that WHHL as compared with NZW rabbits have markedly elevated plasma and higher liver cholesterol concentrations, less hepatic LDL receptor function, and very low hepatic cholesterol 7 alpha-hydroxylase activity and mRNA levels. Feeding cholesterol to NZW rabbits increased plasma and hepatic concentrations greatly, inhibited LDL receptor-mediated binding, and unexpectedly suppressed cholesterol 7 alpha-hydroxylase activity and mRNA to minimum levels similar to WHHL rabbits. Dietary cholesterol accumulates in the plasma of NZW rabbits, and WHHL rabbits are hypercholesterolemic because reduced LDL receptor function is combined with decreased catabolism of cholesterol to bile acids.

Serological survey of nasopharyngeal carcinoma in 21 cities of south China

This paper reports the results of serological survey of 318,912 persons for nasopharyngeal carcinoma (NPC) in 21 cities and counties of south China. There were 8,441 persons with positive VCA-IgA antibody (single item positive) of EB virus (EBV), with a rate of 2.65%. In these VCA-IgA positive persons, 287 persons also had positive EA-IgA (double items positive) of EBV. The overall positive rate was 0.09%. 100 cases of NPC were found and 87 of them (87.0%) were in early stage. NPC found in the group with single item positive accounts for 1.19%, but the rate in the group with double items positive was 19.16% (55 cases). In NPC patients with double items positive, 49 cases were in early stage (89.1%). In 100 cases of NPC found, 45 cases appeared with negative EA-IgA, only with positive VCA-IgA, which indicated that for diagnosis of NPC, sensitivity of EA-IgA was lower than that of VCA-IgA, but its specificity was higher. Therefore, both can increase the detecting rate and early diagnosis rate of NPC. The age of people checked varied with different antibody positive rate and NPC detecting rate. The three items showed a positive correlation. The results are compatible with those of the prospective study for NPC in Wuzhou City, Guangxi, China. The method for NPC serological diagnosis can be extended and applied to raise the NPC detecting rate and early diagnosis rate at secondary prevention. And, it is further proved that there is a close relationship between NPC and EBV.

Immunogenicity of dinitrocarboxyphenylated melittin: the influence of C-terminal chain shortening, N-terminal substitution and prolin insertion at positions 5 and 10

Peptides derived from the bee-venom melittin were fitted with the haptenic group dinitrocarboxyphenyl (Dncp) and tested in out-bred guinea pigs for immunogenicity by measuring the IgG anti-Dncp antibody response by ELISA. Dncp-conjugates comprising virtually the entire melittin proved to be strong immunogens producing antibody responses comparable to those of proteins. Weak responses were obtained with considerably shortened sequences. Conjugates with N-terminal Dncp gave markedly reduced antibody responses compared to peptides with C-terminal Dncp. An N-terminal biotinyl substituent abolished the immune response whereas N-terminal lauryl and caprylyl had little effect. Insertion of L-proline into a hexadecapeptide conjugate abolishing the possibility of helix formation gave an immunogen to which individual animals clearly responded on a low level. Oligomerisation, but not the cytolytic activity of melittin peptides, may contribute to the immunogenicities observed.

[Comprehensive evaluation of protective measures in electric welding]

Protective effects of safety masks, eyewear, work clothes, gloves, periodically physical examination system, and ventilation and barriers at workplace, were evaluated by one-way analysis for handtorch welding, carbon dioxide gas-protective welding, and argon-arc welding operations, etc. in township and village enterprises and state-owned enterprises by interviewing managers in the departments of technology and work safety and field investigating. Based on the results of one-way analysis of protective measures, comprehensive evaluations of various enterprises were made with a fussy mathematical model. Both enterprises in township and village level and of state-owned were graded as A on a basis of the evaluation, which will be helpful to the better management of occupational health in the future.

On-line capillary electrophoresis-electrospray ionization mass spectrometry of nucleotides

Capillary zone electrophoresis (CZE) and reversed anionic capillary isotachophoresis (CITP) conditions have been developed for the separation of mixtures comprised of monophosphate nucleosides, pyridine and flavin dinucleotides, and monophosphate dinucleosides. Results for the on-line coupling of CZE and CITP with electrospray ionization mass spectrometry (MS) are presented. CITP-tandem MS is utilized to provide both molecular weight and structural information of monophosphate dinucleotides. The fragmentation pattern of dinucleotides in the low collision energy range is described. The resulting mass spectra are readily interpreted in terms of dinucleotide structures. These results demonstrate the new capability for applications for the study of DNA and RNA.

Stimulation of tumor growth in vitro and in vivo by suramin on the VX2 model

Suramin is an antitrypanosomal compound with confirmed efficacy against several human malignancies. It is generally assumed that its mechanism of action includes the interaction with different growth factors, unlike most of the anticancer drugs. Its anticancer activity has not been tested in vivo against squamous cell carcinoma. The purpose of this study was to assess the efficacy and toxicity of suramin in vivo and in vitro on the VX2 tumor model at therapeutic monitored plasma concentrations. We determined the pharmacokinetics of suramin in rabbits, and modelized its administration in order to obtain plasma concentrations between 150 and 300 micrograms/ml throughout the treatment course of 3 weeks. Under these conditions, antitumor effects of suramin were evaluated in vivo by comparing liver tumor involvement in suramin-treated and control rabbits. Liver involvement was quantified by image analysis and in vitro effects were also determined at the same concentrations. In vivo, suramin promoted liver tumor growth significantly (p < 0.05), compared to untreated controls. In vitro, suramin significantly stimulated tumor cell growth at concentrations above 200 micrograms/ml (p < 0.01). Suramin may have stimulatory effects on tumor growth in squamous cell carcinoma at relevant plasma drug concentrations. Caution should be taken in further trials in patients with squamous cell carcinomas.

Machado Joseph disease maps to the same region of chromosome 14 as the spinocerebellar ataxia type 3 locus

Machado Joseph disease (MJD) is an autosomal dominantly inherited neuro-degenerative disorder primarily affecting the motor system. It can be divided into three phenotypes based on the variable combination of a range of clinical symptoms including pyramidal and extra-pyramidal features, cerebellar deficits, and distal muscle atrophy. MJD is thought to be caused by mutation of a single gene which has recently been mapped, using genetic linkage analysis, to a 29 cM region on chromosome 14q24.3-q32 in five Japanese families. A second disorder, spinocerebellar ataxia type 3 (SCA3), which has clinical symptoms similar to MJD, has also been linked to the same region of chromosome 14q in two French families. In order to narrow down the region of chromosome 14 which contains the MJD locus and to determine if this region overlaps with the predisposing locus for SCA3, we have performed genetic linkage analysis in seven MJD families, six of Portuguese/Azorean origin and one of Brazilian origin, using nine microsatellite markers mapped to 14q24.3-q32. Our results localise the MJD locus in these families to an 11 cM interval flanked by the markers D14S68 and AFM343vf1. In addition we show that this 11 cM interval maps within the 15 cM interval containing the SCA3 locus, suggesting that these diseases are allelic.

Reproducing abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome by inhibiting the conversion of 7-dehydrocholesterol to cholesterol in rats

The Smith-Lemli-Opitz syndrome is a recessive inherited disorder characterized by neurologic developmental defects and dysmorphic features in many organs. Recently, abnormal cholesterol biosynthesis with impaired conversion of 7-dehydrocholesterol to cholesterol has been discovered in homozygotes. To reproduce the biochemical abnormality, BM 15.766, a competitive inhibitor of 7-dehydrocholesterol-delta 7-reductase, the enzyme that catalyzes the conversion of 7-dehydrocholesterol into cholesterol was fed by gavage to rats. After 14 d, plasma cholesterol concentrations declined from 48 mg/dl to 16 mg/dl and 7-dehydro-cholesterol levels rose from trace to 17 mg/dl. Hepatocytes surrounding the central vein developed balloon necrosis. Stimulating cholesterol synthesis with cholestyramine followed by BM 15.766 produced an additional 40% decline (P < 0.05) in plasma cholesterol and 34% increase in 7-dehydrocholesterol levels compared to the inhibitor alone. Adding 2% cholesterol to the diet during the second week of BM 15.766 treatment increased plasma cholesterol threefold and decreased 7-dehydrocholesterol concentrations 55%. Hepatic 3-hydroxy-3-methylglutaryl co-enzyme A (HMG-CoA) reductase activity increased 73% with a 3.9-fold rise in mRNA levels but cholesterol 7 alpha-hydroxylase activity decreased slightly though mRNA levels increased 1.4 times with BM 15.766 treatment. These results demonstrate that BM 15.766 is a potent inhibitor of 7-dehydrocholesterol-delta 7-reductase. The model reproduces abnormal cholesterol biosynthesis as seen in the Smith-Lemli-Opitz syndrome and is useful to test different treatment strategies. Stimulating early steps of cholesterol synthesis worsens the biochemical abnormalities while feeding cholesterol inhibits abnormal synthesis, improves the biochemical abnormalities and prevents liver damage.

Pseudomonas aeruginosa infection of the cornea and asialo GM1

Extensive immunohistochemical and thin-layer chromatogram-immunostain analyses were carried out to establish whether asialo GM1, a glycolipid which contains binding sites for Pseudomonas aeruginosa, is present in corneal epithelium. The data suggest that rabbit corneal epithelium does not contain detectable levels of asialo GM1 even after corneas are scarified and incubated with trypsin, P. aeruginosa, or P. aeruginosa exoproducts to expose potential cryptic sites. Preliminary immunohistochemical analyses indicated that asialo GM1 is also not found in human corneas.

[A study on serologic markers for screening before hepatitis B vaccination]

Three serologic markers for screening before hepatitis B vaccination were HBsAg, anti-HBs and anti-HBc. The data of HB virus infection in eight cities were analysed in order to save test cost and to achieve similar immune effect. For routine screening, anti-HBc is the only one marker needed to be used. The neonates and children aged 0-3 years can be vaccinated directly without screening.

Insulin and glucagon modulate hepatic 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity by affecting immunoreactive protein levels

The question of whether the effects of insulin and glucagon on hepatic 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity are mediated largely by changes in the phosphorylation state of the enzyme or by changes in the quantity of enzyme protein was investigated by measuring enzyme protein and mRNA levels. If phosphorylation/dephosphorylation is responsible for the observed changes in HMG-CoA reductase activity, one would not expect to see changes in immunoreactive protein or mRNA levels in response to induction of diabetes, administration of insulin, or administration of insulin and glucagon. It was found that hepatic HMG-CoA reductase mRNA levels were decreased to 12% of control in diabetic rats. Immunoreactive protein was reduced to essentially undetectable levels. Administration of insulin restored both mRNA and immunoreactive protein levels. Glucagon blocked these effects. Enzyme activity changes were fully accounted for by changes in HMG-CoA reductase mRNA and immunoreactive protein. Fasting caused parallel falls in HMG-CoA reductase activity and immunoreactive protein levels with a lesser effect on mRNA levels. The insulin-mediated changes in HMG-CoA reductase gene expression correlated well with changes in blood glucose levels, indicating a physiological effect. Taken together, these results indicate that insulin and glucagon regulate HMG-CoA reductase gene expression largely at the level of enzyme protein through changes in mRNA concentrations.

Thyroid hormone rapidly induces hepatic LDL receptor mRNA levels in hypophysectomized rats

The effects of hypophysectomy and thyroid hormone treatment on the expression of the hepatic LDL receptor gene was studied in young male rats. Hypophysectomy lowered levels of LDL receptor mRNA and protein. It was found that increased levels of LDL receptor mRNA could be detected 30 min after giving hypophysectomized rats an intramuscular injection of 10 micrograms of L-triiodothyronine (T3) per 100 g of body weight. This dose of T3 also increased hepatic LDL receptor protein levels within 1 h. A T3 dose of only 0.25 microgram per 100 g increased LDL receptor mRNA levels more than threefold. The half-life of the hepatic LDL receptor mRNA was found to be about 30 min and was unaffected by T3. The data suggests that thyroid hormone acts physiologically to induce hepatic LDL receptor expression. This action may explain, in part, the hypocholesterolemic effect of the hormone.

Analysis of nucleotide pools in human lymphoma cells by capillary electrophoresis

Capillary electrophoresis is applied to determine nucleotide pool levels in human Burkitt lymphoma cells. The analysis was performed on a 65 cm x 50 microns I.D. Ucon-coated column with on-column UV detector. The method requires only nanoliters of sample and a simple sample preparation procedure. Over 12 nucleotides were separated and quantitated with high resolution and reproducibility. The whole capillary electrophoretic separation time was only 35 min. These results demonstrate that capillary electrophoresis provides a useful and easy way to analyze nucleotide pools in cells.

Thyroid hormone rapidly increases cholesterol 7 alpha-hydroxylase mRNA levels in hypophysectomized rats

The induction of hepatic cholesterol 7 alpha-hydroxylase mRNA by triiodothyronine was investigated in hypophysectomized rats. These rats exhibited markedly decreased levels of cholesterol 7 alpha-hydroxylase mRNA compared to normal controls. An increase in this mRNA could be detected within 30 min after giving triiodothyronine. A triiodothyronine dose of 0.25 microgram per 100 g of body weight, which produces 50% occupancy of hepatic nuclear thyroid hormone receptors, caused significant increases in hydroxylase mRNA levels. The half-life of cholesterol 7 alpha-hydroxylase mRNA was about 30 min and was not affected by thyroid hormone. Administration of the protein synthesis inhibitor, cycloheximide, after triiodothyronine caused superinduction. Hepatic HMG-CoA reductase mRNA levels, which are also low in livers from hypophysectomized rats, were unaffected by these doses of hormone within the 2 h time-frame examined in these studies. The results suggest that thyroid hormone may exert a primary affect on the expression of the hepatic cholesterol 7 alpha-hydroxylase gene. This could explain, in part, the hypocholesterolemic effect of thyroid hormone.

Capillary electrophoresis of nucleotides on ucon-coated fused silica columns

Ucon-coated columns have been used to isolate nucleotides, such as ribonucleotides, deoxyribonucleotides, and pyridine nucleotides, by capillary zone electrophoresis. This neutral, hydrophilic column coating (Ucon) significantly reduced macromolecule adsorption and electroosmotic flow, which provides the maximum resolution of the nucleotides separated under moderate buffer conditions (pH about 5-6). The relative standard deviations of the nucleotides were less than 1%. Low minimum detectable concentrations (about 2-8 microM) and quantities (about 70-360 fmol) of the ribonucleotides were obtained. A qualitative and quantitative analysis of the ribonucleotides in hybridoma cell extracts shows the applicability of the developed methodology for the determination of intracellular nucleotide pools under the desirable buffer conditions.

Effects of N-(4-hydroxyphenyl)-retinamide on the number and cytotoxicity of natural killer cells in vitamin-A-sufficient and -deficient rats

N-(4-hydroxyphenyl)retinamide (4-HPR), a synthetic retinoid with anticarcinogenic activity, has been shown to lower the plasma retinol level rapidly and significantly. We reported previously that vitamin A-deficient rats (plasma retinol < 0.175 mumol/l) have a low number of natural killer (NK) cells in peripheral blood. To investigate the effects of 4-HPR on NK cell number and activity, two studies were conducted. In study 1, vitamin-A-sufficient rats were fed a 'therapeutic' dose of 4-HPR (2 mmol/kg of diet) for 30 days. Despite a low plasma retinol concentration (approximately 0.1 mumol/l), the number of NK cells was not reduced. Moreover, the NK cytolytic activity per cell was significantly elevated. White blood cell and differential counts were normal. In study 2, the biological activity of 4-HPR was examined in vitamin-A-deficient rats. Rats depleted of vitamin A were fed a diet containing 4-HPR (54.7 micrograms/g of diet) for 11 days. Vitamin-A-dependent processes including growth, hematocrit, lymphocyte count and the number of NK cells were restored. For comparison, another group of vitamin-A-deficient rats were repleted with retinoic acid (RA; 4.2 micrograms/g diet); this treatment also effectively restored these vitamin-A-dependent processes. Therefore, despite the plasma-retinol-lowering property of 4-HPR, treatment with this retinoid did not impair NK cell number or function. Indeed, 4-HPR showed vitamin A activity similar to RA, and may stimulate NK cell cytotoxicity.

Effects of stimulated growth hormone secretion on age-related changes in plasma cholesterol and hepatic low density lipoprotein messenger RNA concentrations

Growth hormone (GH) secretion declines during aging. Since GH alters plasma cholesterol (PC) concentrations, it was of interest to determine how GH secretagogues affect age-related hypercholesterolemia. Fischer 344 rats (3 and 14 months old) were co-administered (s.c.) GH releasing hormone (3 micrograms/kg; GHRH) and GH releasing hexapeptide (100 micrograms/kg; GHRP) for 120 consecutive days. Aging was associated with a progressive increase in PC, which was reduced in rats administered GHRH and GHRP compared to those administered vehicle, i.e. changes in PC during the study were 26.5 +/- 1.2 mg/dl vs. 40.1 +/- 0.9 mg/dl (P < 0.05) in the younger rats and 17.6 +/- 2.3 mg/dl vs. 31.6 +/- 5.3 mg/dl (P < 0.05) in the older rats, respectively. The lower concentrations of PC in GH secretagogue-treated older rats were associated with higher mean concentrations of hepatic LDL receptor mRNA (1.27 +/- 0.4 vs. 0.4 +/- 0.1; P < 0.05) but not cholesterol 7-alpha hydroxylase mRNA. Although GH secretagogue treatment was also associated with lower plasma cholesterol in the younger rats, it was not accompanied by quantitative changes in mean group concentrations of hepatic LDL receptor mRNA. Instead, daily administration of GHRH and GHRP in the younger rats correlated with a significant reciprocal relationship (P < 0.05) between PC and hepatic LDL receptor mRNA for individual group members. The results of this study suggest that reduced GH secretion during aging contributes, at least in part, to a progressive increase in plasma cholesterol that can be partially prevented with GH secretagogues. Furthermore, the effects on PC may result from GH-mediated, qualitative and quantitative changes in hepatic LDL receptor mRNA that increase receptor-mediated cholesterol clearance.

Verapamil-reversing concentrations induce blood flow changes that could counteract in vivo the MDR-1-modulating effects

BACKGROUND

Intraarterial hepatic (IAH) administration of verapamil should achieve mdr-1-reversing concentrations with reduced cardiac toxicity. The authors have explored the tolerance of its IAH administration and its effects on doxorubicin pharmacodymamics.

METHODS

Verapamil was given to rabbits by intravenous or IAH administration, and its effects on heart rates were compared. Doxorubicin then was given intravenously either with IAH verapamil or with an IAH control perfusion, and tumor and liver drug concentrations were determined. Hepatic blood flow changes were studied by the administration of 99mTc-albumin macroaggregates (99mTc-MAA) under verapamil IAH perfusions.

RESULTS

Compared with the intravenous route, IAH administration of verapamil was not toxic, and cardiac effects were reduced significantly. Its effect on doxorubicin distribution was detrimental, because the tumor-liver doxorubicin concentration ratios were lower in the verapamil group (0.23 vs. 3.37; P < 0.05). Tumor doxorubicin concentrations were lower when verapamil was coinfused (43 vs. 573 ng/100 mg tissue; P < 0.05). In normal liver tissue, increased amounts of doxorubicin and metabolites were observed. The verapamil IAH perfusions with 99mTc-MAA confirmed a differential action on tumor and normal vessels; the distribution of radionuclide was diverted away from the tumor bed significantly when verapamil was administered (tumor-to-liver ratio of 25.3 control rabbits vs. 5.99 rabbits who received verapamil; P < 0.05).

CONCLUSIONS

Reversing the concentrations of verapamil provoked changes in the distribution of the liver blood flow. The hemodynamic effects of verapamil regional perfusions could counteract in vivo its potential mdr-1-reversing properties.

Altered pulmonary microvascular reactivity to norepinephrine in canine pacing-induced heart failure

Pulmonary hypertension in congestive heart failure causes medial hypertrophy in pulmonary vessels and thickening of the endothelial basement membrane. In this study, the functional consequences of such pulmonary vascular adaptations were evaluated. Heart failure was induced in dogs by rapid ventricular pacing (240 beats per minute) for 28 days, at which time left ventricular shortening fraction was decreased by 57% compared with that at baseline. Lung lobes from paced (n = 56) and control dogs (n = 68) were isolated and perfused with autologous blood. Total, arterial (Ra), and venous (Rv) vascular resistances were significantly increased and vascular capacitance decreased in lobes from paced animals compared with controls. Increments in Ra and Rv after intra-arterial boluses of norepinephrine were measured before and after sequential addition of the alpha 1- and alpha 2-receptor antagonists prazosin (16 mumol/L) and yohimbine (0.1 mumol/L) in the presence or absence of propranolol (5 mumol/L). Norepinephrine (1 to 40 micrograms) had little effect on Ra in the absence of propranolol, a pattern that persisted in control lobes after propranolol. However, when lobes from paced animals were pretreated with propranolol, norepinephrine increased Ra, Rv was increased after norepinephrine in control lobes, an effect that was enhanced in the paced group. In both groups, the increment in Rv was greater after propranolol. Irrespective of propranolol pretreatment, prazosin significantly attenuated, if not abolished, the response to norepinephrine. The enhancement in venous vascular reactivity in lobes from paced animals remained when venous pressure was elevated to 20 cm H2O. In control lobes under conditions of elevated tone or when endothelium-dependent relaxing factor was blocked, responses to norepinephrine did not mimic those observed in the paced group. Microvascular permeability, as measured by the capillary filtration coefficient, was not altered in the paced group. We conclude that the pulmonary adaptations to 4 weeks of rapid ventricular pacing include functional changes in pulmonary hemodynamics and vascular reactivity but not in microvascular permeability.

Phosphorylation and identification of a major tyrosine phosphorylation site in protein tyrosine phosphatase 1C

Protein tyrosine phosphatase 1C (PTP1C) was the first member of the protein tyrosine phosphatase family demonstrated to contain the src homology 2 (SH2) domain. This enzyme is believed to play a role in regulating downstream signaling in hematopoietic cells since it was predominantly expressed in these cells. However, recent studies have revealed that the protein is expressed in other tissues as well. This report describes both the phosphorylation of PTP1C in non-hematopoietic cells treated with growth factors (in vivo) and incubation of purified PTP1C with a variety of protein kinases (in vitro). PTP1C was transiently phosphorylated in A431 and 293 cells and also when the purified enzyme was incubated with receptor protein tyrosine kinases. In vitro, the tyrosine-phosphorylated PTP1C underwent rapid auto-dephosphorylation, an effect which could be blocked by the addition of sodium vanadate. On the other hand, cells containing a PTP1C in which the catalytic site had been inactivated through mutagenesis, stably phosphorylated the phosphatase. These results suggested that PTP1C was responsible for its own auto-dephosphorylation. The sites of tyrosine phosphorylation were characterized from purified enzyme following treatment with insulin receptor kinase and from PTP1C expressed in 293 cells which had been stimulated with platelet-derived growth factor. Through the techniques of peptide mapping and microsequencing, Tyr538 was determined to be the major phosphorylation site. This result was confirmed in vivo through site-specific mutagenesis of PTP1C expressed in 293 cells; changing Tyr538 to Phe538 completely abolished tyrosine phosphorylation of the molecule. In addition, Tyr538 lies within the sequence ESEYGNI which can be correlated with the consensus sequence pYXNX associated with GRB2 binding. These results suggest that PTP1C plays a prominent role in growth factor receptor-mediated signal transduction within both hematopoietic cells and tissues of non-lymphoid origin.

Exposure limits for ultra-short wave radiation in work environments

Exposure limit values for ultra-short wave radiation of humans were derived on the basis of epidemiological survey and experimental exposure of rabbits. Eighteen male rabbits were divided into 4 groups randomly. Three groups were irradiated with ultra-short waves (100 MHz) at 35, 1.5-3.5, and 0.07 mW/cm2 power density in an E-polarized TEM Cell at 24 +/- 4 degrees C ambient temperature. The last group in a sham chamber served as controls. Irradiation was performed 3 hours per day, 5 days per week for 24 weeks. Thermal effects occurred in the group irradiated at 35 mW/cm2. The thermal threshold limit value was set at 1.5 mW/cm2. An epidemiological survey was carried out on 136 factory workers and TV operators exposed over one year to ultra-short wave radiation at 0.2 mW/cm2. They were compared with 108 controls. The only complaint of the exposed group was neurosis. The exposure limit value (ELV) to short wave radiation was set at 0.2 mW/cm2 by using a 15- and 20-fold safety factor.