Two new limonoids from the seeds of Microula sikkimensis

Two new limonoids, cis-p-hydroxycinnamoylrutaevin and trans-p-hydroxycinnamoylrutaevin were isolated along with three known limonoids. Their structures were deduced on the basis of their spectral data. This is the first report on the isolation of limonoids from seeds of Microula sikkimensis Hemsl.

Changes in ovarian expression of tissue-type plasminogen activator and plasminogen activator inhibitor type-1 messenger ribonucleic acids during ovulation in rat

We investigated the time course and localization of ovarian tissue-type plasminogen activator (tPA) and plasminogen activator inhibitor type-1 (PAI-1) expression during the ovulatory period in rat by RNase protection assay and in situ hybridization. Immature female Wistar rats were injected with 25 IU pregnant mare serum gonadotropin (PMSG), followed 50 h later by 25 IU human chorionic gonadotropin (hCG). Levels of tPA mRNA were low before hormone treatment and after PMSG treatment. After hCG treatment, tPA mRNA levels increased rapidly, the first peak at 4 h after hCG treatment and reached a maximum just prior to ovulation, 12 h later, before declining again. PAI-1 mRNA was barely detectable before hormone treatment but was transiently induced by hCG treatment, reaching peak levels after 4 h. Subsequently, PAI-1 mRNA levels decreased until early luteinization. The expression of tPA mRNA 4 h after hCG treatment occurred mainly in the follicular thecal-interstitial cells, but was barely detectable in the granulosa cells, whereas 12 h after hCG treatment it was maximal in the granulosa cells of the large follicles destined to ovulate. PAI-1 mRNA was expressed mainly in ovarian stromal tissue and in the thecal external interstitial cells encapsulating the follicles at 4 h after hCG treatment. These results suggest that the temporal regulation of tPA biosynthesis after hCG induction depends on the cell types and size classes in the various ovarian compartments. PAI-1 may be produced by the stormal tissue and the thecal external interstitial cells and is perhaps implicated in structural changes during follicular growth, ovulation and luteinization.

[Observation of changes of cardiovascular function during 2.5h HDT (-15 degrees) with sphygmogram method]

To understand the changes of cardiovascular functions in the initial stage of space flight, the changes in 19 healthy young men during 2.5h head down tilt (HDT) (15 degrees) were observed with CF-II cardiovascular function detecting and diagnosing equipment. The blood pressure and sphygmogram of left radial arterial were recorded in sedentary condition and at 10th, 30th, 60th, 90th, 120th and 140th minute of HDT. The results showed that changes of cardiovascular indices during HDT can be divided into acute regulation stage (< 1h) and the regulation stage (1-2.5 h); circulatory blood volume, stroke volume and cardiac output were increased, while heart rate, pre and after load of the heart, CVP, coronary circulatory function, blood pressure and systemic vascular resistance were decreased; the vagus feedback index increased and the regulation function of vasscule decreased. Most of the changes of cardiovascular indices as reflected in the sphygmogram are in consistent with the reported result in space flight or simulated micro-G, so the sphygmogram method might be applied to space medical research.

Detection of human herpesvirus 6(HHV-6) DNA in salivary glands by the polymerase chain reaction

To assess the presence of HHV-6-Specific DNA in human salivary glands, eighteen specimens of salivary gland tissue were investigated using the polymerase chain reaction. Eight of nine parotid glands, five of seven submandibular glands and one of two sublingual glands were found to have amplification of the HHV-6-specific sequence. The findings suggest that salivary gland tissue is one of the potential sites for HHV-6 persistence following primary infection and that saliva is a vehicle for transmission of the virus.

Species-specific tRNA recognition in relation to tRNA synthetase contact residues

In spite of variations in the sequences of tRNAs, the genetic code (anticodon trinucleotides) is conserved in evolution. However, non-anticodon nucleotides which are species specific are known to prevent a given tRNA from functioning in all organisms. Conversely, species-specific tRNA contact residues in synthetases should also prevent cross-species acylation in a predictable way. To address this question, we investigated the relatively small tyrosine tRNA synthetase where contacts of Escherichia coli tRNA(Tyr) with the alpha2 dimeric protein have been localized by others to four specific sequence clusters on the three-dimensional structure of the Bacillus stearothermophilus enzyme. We used specific functional tests with a previously not-sequenced and not-characterized Mycobacterium tuberculosis enzyme and showed that it demonstrates species-specific aminoacylation in vivo and in vitro. The specificity observed fits exactly with the presence of the clusters characteristic of those established as important for recognition of E. coli tRNA. Conversely, we noted that a recent analysis of the tyrosine enzyme from the eukaryote pathogen Pneumocystis carinii showed just the opposite species specificity of tRNA recognition. According to our alignments, the sequences of the clusters diverge substantially from those seen with the M. tuberculosis, B. stearothermophilus and other enzymes. Thus, the presence or absence of species-specific residues in tRNA synthetases correlates in both directions with cross-species aminoacylation phenotypes, without reference to the associated tRNA sequences. We suggest that this kind of analysis can identify those synthetase-tRNA covariations which are needed to preserve the genetic code. These co-variations might be exploited to develop novel antibiotics against pathogens such as M. tuberculosis and P. carinii.

E2F4-RB and E2F4-p107 complexes suppress gene expression by transforming growth factor beta through E2F binding sites

Transforming growth factor beta (TGF-beta) causes growth arrest in most cell types. TGF-beta induces hypophosphorylation of retinoblastoma susceptibility gene 1 product (RB), which sequesters E2F factors needed for progression into S phase of the cell cycle, thereby leading to cell cycle arrest at G1. It is possible, however, that the E2F-RB complex induced by TGF-beta may bind to E2F sites and suppress expression of specific genes whose promoters contain E2F binding sites. We show here that TGF-beta treatment of HaCaT cells induced the formation of E2F4-RB and E2F4-p107 complexes, which are capable of binding to E2F sites. Disruption of their binding to DNA with mutation in the E2F sites did not change the expression from promoters of E2F1, B-myb, or HsORC1 genes in cycling HaCaT cells. However, the same mutation stimulated 5- to 6-fold higher expression from all three promoters in cells treated with TGF-beta. These results suggest that E2F binding sites play an essential role in the transcription repression of these genes under TGF-beta treatment. Consistent with their repression of TGF-beta-induced gene expression, introduction of E2F sites into the promoter of cyclin-dependent kinase inhibitor p15(INK4B) gene effectively inhibited its induction by TGF-beta. Experiments utilizing Gal4-RB and Gal4-p107 chimeric constructs demonstrated that either RB or p107 could directly repress TGF-beta induction of p15(INK4B) gene when tethered to p15(INK4B) promoter through Gal4 DNA binding sites. Therefore, E2F functions to bring RB and p107 to E2F sites and represses gene expression by TGF-beta. These results define a specific function for E2F4-RB and E2F4-p107 complexes in gene repression under TGF-beta treatment, which may constitute an integral part of the TGF-beta-induced growth arrest program.

Quantification of latent tissue reservoirs and total body viral load in HIV-1 infection

The capacity of HIV-1 to establish latent infection of CD4+ T cells may allow viral persistence despite immune responses and antiretroviral therapy. Measurements of infectious virus and viral RNA in plasma and of infectious virus, viral DNA and viral messenger RNA species in infected cells all suggest that HIV-1 replication continues throughout the course of infection. Uncertainty remains over what fraction of CD4+ T cells are infected and whether there are latent reservoirs for the virus. We show here that during the asymptomatic phase of infection there is an extremely low total body load of latently infected resting CD4+ T cells with replication-competent integrated provirus (<10(7) cells). The most prevalent form of HIV-1 DNA in resting and activated CD4+ T cells is a full-length, linear, unintegrated form that is not replication competent. The infection progresses even though at any given time in the lymphoid tissues integrated HIV-1 DNA is present in only a minute fraction of the susceptible populations, including resting and activated CD4+ T cells and macrophages.

Chemical composition and microstructure of uroliths and urinary sediment crystals associated with the feeding of high-level cottonseed meal diet to water buffalo calves

The chemical composition and microstructure of seven uroliths and four urinary sediment samples associated with the feeding of high-level cottonseed meal diet to buffalo calves were examined by chemical qualitative analyses, scanning electron microscopy (SEM), X-ray diffraction, and X-ray energy dispersive spectrometry (EDS). Struvite was a major component of kidney stones and of some bladder stones. The kidney stone sample appeared cracked under low power under SEM, aggregated into tiny balls under high power, and as a blade-like structure under even higher power. The bladder stone samples appeared finely granular or granular with various forms of prismatic crystals. The urinary sediments were prismatic crystals, with granules. The newly found prismatic crystals, which were rich in potassium and similar to struvite in crystal structure, were identified as potassium magnesium phosphate (KMgPO4.6H2O) in some bladder stones and urinary sediments. However, crystals which contained Mg and P only, which had been used for struvite identification, were not found by EDS examination in urinary sediments from fresh urine samples of buffalo calves fed the high-level cottonseed meal diet.

Integrated regulation in response to simulated weightlessness

To investigate physiological effects of tail suspension, Ca2+ concentration, immune factors, erythrocyte rheological properties, and growth hormone were determined in rats suspended for 15 and 30 d. The results showed that inhibitory changes of both local factors (proteins secreted by bone cell, Ca(2+)-ATPase in sarcoplasmic reticium) and integrated regulative factors (immune factor, growth hormone) were observed simultaneously with the decrease of bone mineral content, calcium transportation in skeletal muscles as well as erythrocyte deformability. It suggests that both local and integrated regulative processes are functioning in response to the effects of weightlessness.

[Lead exposure level in umbilical cord blood and its related factors]

Six hundred and five specimens of umbilical cord blood were collected from Yangpu District, Shanghai, and blood lead levels were determined with graphite stove atom absorption spectrophotometry in 348 of them to study fetal exposure to lead and its related factors in the people of Shanghai. Survey on household social and environmental health status was conducted in families with the babies whose umbilical cord blood lead were above the 70th percentile and below the 30th percentile with a face-to-face questionnaire. Data were analyzed with multiple regression for the factors which affected the lead level in umbilical cord blood significantly. Results showed that blood lead levels in 348 cases were normally distributed, with a range of 0.08 to 0.84 mumol/L, a mean of 0.44 mumol/L and a standard deviation of 0.15 mumol/L. Specimens with cord blood lead level exceeding the safety criteria of 0.48 mumol/L accounted for 40.8 percent of the total. The study also found that passive smoking during pregnancy, exposure to lead in family members, one's living room adjacent to the major traffic roads, pollution by coal-burning smoke in the environment of one's residence, use of coal as domestic fuel, and eating preserved eggs during pregnancy all were risk factors for lead exposure. Multiple logistic regression analysis revealed that contribution of passive smoking to cord blood lead level was still statistically significant after adjusting other confounding factors. It concluded that environmental lead pollution could cause ad-verse effects on fetal development.

Greater airway narrowing in immature than in mature rabbits during methacholine challenge

It has been demonstrated that methacholine (MCh) challenge produces a greater increase in lung resistance in immature than in mature rabbits (R. S. Tepper, X. Shen, E. Bakan, and S. J. Gunst. J. Appl. Physiol. 79: 1190-1198, 1995). To determine whether this maturational difference in the response to MCh was primarily related to changes in airway resistance (Raw) or changes in tissue resistance, we assessed airway narrowing in 1-, 2-, and 6-mo-old rabbits during intravenous MCh challenge (0.01-5.0 mg/kg). Airway narrowing was determined from measurements of Raw in vivo and from morphometric measurements on lung sections obtained after rapidly freezing the lung after the MCh challenge. The fold increase in Raw was significantly greater for 1- and 2-mo-old animals than for 6-mo-old animals. Similarly, the degree of airway narrowing assessed morphometrically was significantly greater for 1- and 2-mo-old animals than for 6-mo-old animals. The fold increase in Raw was highly correlated with the degree of airway narrowing assessed morphometrically (r2 = 0.82, P < 0.001). We conclude that the maturational difference in the effect of MCh on lung resistance is primarily caused by greater airway narrowing in the immature rabbits.

Mechanism of interferon action sequence of the human interferon-inducible RNA-dependent protein kinase (PKR) deduced from genomic clones

The pkr gene encoding the interferon-inducible, RNA-dependent protein kinase was isolated as lambda phage and P1 phage clones from human genomic DNA and characterized by restriction mapping, Southern blot analysis, and nucleotide sequencing. The genomic nucleotide sequence, when compared to that of previously determined cDNA sequences, revealed 17 exons encoding the 551-amino-acid PKR protein. We report herein the sequence of the human PKR protein kinase deduced from genomic clones.

[Repair of acute thumb avulsion with the bi-lobed island flap of the second web]

The authors designed a bi-lobed island flap of the second web pedicled with the first and the second dorsal metacarpal arteries. Since 1993, five cases of acute thumb avulsion have been repaired using this flap. The size of the flaps ranged from 3 cm x 6 cm to 6 cm x 7 cm. All flaps survived with primary healing of the incisions. Three to nine months' follow-up showed that the flaps were thin and had sensation. The function and appearance of the reconstructed thumb were satisfactory. The bi-lobed island flap of the second web is a valuable method for the repair of thumb avulsion.

Structural organization of the human gene (PKR) encoding an interferon-inducible RNA-dependent protein kinase (PKR) and differences from its mouse homolog

The gene encoding the interferon-inducible, RNA-dependent protein kinase (PKR) was isolated as lambda phage and P1 phage clones from human genomic DNA libraries and characterized by Southern blot and nucleotide sequence analyses. Southern blot analyses were consistent with a single PKR gene, and genomic clones colocalized by fluorescence in situ hybridization to human chromosome 2p. Sequence analysis demonstrated that the human PKR gene consists of 17 exons and spans about 50 kb. The AUG translation initiation site for the 551-amino-acid PKR protein was located in exon 3; exon 17 was the largest exon and included the UAG translation termination site, AUUAAA polyadenylation signal, and putative C(A) 3' cleavage site. Two RNA-binding motifs, RI and RII, were present in exons 4 and 6, respectively, and the codon phasing of these exon junctions was conserved between them. The organization of the regulatory and catalytic subdomains of the PKR protein was remarkably preserved between the human and the mouse PKR genes; the amino acid junction positions for 13 of the 15 protein coding exons were exactly conserved.

Linker histone H1 regulates specific gene expression but not global transcription in vivo

In a linker histone H1 knockout strain (delta H1) of Tetrahymena thermophila, the number of mature RNAs produced by genes transcribed by pol I and pol III and of most genes transcribed by pol II remains unchanged. However, H1 is required for the normal basal repression of a gene (ngoA) in growing cells but is not required for its activated expression in starved cells. Surprisingly, H1 is required for the activated expression of another gene (CyP) in starved cells but not for its repression in growing cells. Thus, H1 does not have a major effect on global transcription but can act as either a positive or negative gene-specific regulator of transcription in vivo.

[Comparison between Cistanche deserticola Y. C. Ma and C, tubulosa (Shenk) Wight on some pharmacological actions]

The weights of seminal vesicle and prostate gland of castrated young rats were significantly increased by administration of alcohol soluble extract from the decoction of Cintanche deserticola, C. tubulosa and soaked C. deserticola. The phagocytic function of intra-abdominal macrophage in mice was activated by the decoction of C. deserticola and C. tubulosa.

Peptides corresponding to CD4-interacting regions of murine MHC class II molecules modulate immune responses of CD4+ T lymphocytes in vitro and in vivo

Immune responses mediated by CD4+ T cells depend on Ag-specific alpha beta TCRs that recognize the specific antigenic peptide presented by MHC class II molecules. Interactions between CD4 coreceptors and monomorphic regions of MHC class II molecules contribute to these responses. To examine whether immune reactions could be modulated by specifically interfering with CD4-MHC class II interactions, we have used, in various in vitro and in vivo assays, peptides that correspond to a region of MHC class II molecules previously shown to control interaction with CD4. Depending on the chemical nature and concentration of these peptides, they modulated Ag-specific responses of CD4+ T cells. At high concentrations, these peptides inhibited T cell responses in vitro. However, under conditions that can cause Ag-induced unresponsiveness, the peptides enhanced T cell responses. Also, primary in vivo immune responses to systemically administered soluble protein Ag, keyhole limpet hemocyanin, were enhanced when mice were treated with peptides corresponding to the CD4-interacting region of MHC class II molecules but not when treated with control peptides. Lymphokine profiles suggested that the peptides may favor the differentiation of Th1 cells, because lymphocytes from peptide-treated mice secreted more IL-2 and IFN-gamma than lymphocytes from nontreated or control-peptide-treated mice upon restimulation with Ag in vitro. These results demonstrate that MHC class II-derived peptides can directly interfere with interactions with CD4 and modulate T cell responses in vitro and in vivo.

Peptides corresponding to CD4-interacting regions of murine MHC class II molecules modulate immune responses of CD4+ T lymphocytes in vitro and in vivo

Immune responses mediated by CD4+ T cells depend on Ag-specific alpha beta TCRs that recognize the specific antigenic peptide presented by MHC class II molecules. Interactions between CD4 coreceptors and monomorphic regions of MHC class II molecules contribute to these responses. To examine whether immune reactions could be modulated by specifically interfering with CD4-MHC class II interactions, we have used, in various in vitro and in vivo assays, peptides that correspond to a region of MHC class II molecules previously shown to control interaction with CD4. Depending on the chemical nature and concentration of these peptides, they modulated Ag-specific responses of CD4+ T cells. At high concentrations, these peptides inhibited T cell responses in vitro. However, under conditions that can cause Ag-induced unresponsiveness, the peptides enhanced T cell responses. Also, primary in vivo immune responses to systemically administered soluble protein Ag, keyhole limpet hemocyanin, were enhanced when mice were treated with peptides corresponding to the CD4-interacting region of MHC class II molecules but not when treated with control peptides. Lymphokine profiles suggested that the peptides may favor the differentiation of Th1 cells, because lymphocytes from peptide-treated mice secreted more IL-2 and IFN-gamma than lymphocytes from nontreated or control-peptide-treated mice upon restimulation with Ag in vitro. These results demonstrate that MHC class II-derived peptides can directly interfere with interactions with CD4 and modulate T cell responses in vitro and in vivo.

The regulation by gender, strain, dose, and feeding status of the induction of multiple forms of cytochrome P450 isozymes in rat hepatic microsomes by 2,4,5,2',4',5'-hexachlorobiphenyl

2,4,5,2',4',5'-hexachlorobiphenyl (HCB) induces hepatic microsomal cytochromes P450 with a similar selectivity for responsive genes to phenobarbital (PB). CYP2Bl, CYP2B2, CYP2C6, CYP3Al, and CYP2Al each showed large strain differences in induction by HCB Fisher F344 >> Wistar Furth (WF) that were much more evident in female rats, paralleling previous observations with PB. These five P450s and epoxide hydrolase were, however, induced more effectively by HCB than by PB and strain differences were even larger. With HCB, strain differences in male rats were much more apparent than with PB. This change was not due to the greater HCB induction since a 2-fold lower induction was maintained even with a 10-fold lower dose of HCB. The sex and strain differences were seen both by immunoblot analysis and by form-selective enzyme activity assays. induction of CYP2B1, CYP2B2, and CYP3A1 by HCB was decreased 3-fold when starvation during the final 24 hr was replaced by continuous feeding. This effect was similar in each strain and therefore independent of the regulatory processes associated with the differential suppression of induction in WF rats. This modulation of induction by feeding was also seen with PB which caused only a 30% lowering of induction in continuously fed F344 rats. A 52-kDa microsomal protein (p52) was prominently induced by both HCB and PB after starvation, while minor induction of a 50-kDa microsomal protein (p50) also occurred after the same treatment. Furthermore, a 100-kDa microsomal protein (p100) was induced by HCB but not by PB and only in rats that were continuously fed. These results suggest that the induction of multiple forms of P450 following HCB treatment functions through the same PB-stimulated pathway that shows a strain-dependent endocrine (GH/T3/testosterone)-sensitive suppression mechanism. The induction of p5O, p52, and plOO by HCB suggests the presence of at least two additional hepatic response mechanisms for HCB.

Is the CvaA protein, encoded within the colicin V export gene cvaA, required for colicin V transport?

The antibacterial peptide toxin colicin V is exported from Escherichia coli cells by a signal sequence-independent, ABC export system. Export requires at least three proteins-membrane fusion protein CvaA, ABC export protein CvaB, and outer membrane protein TolC. The cvaA gene also encodes a second protein, CvaA, initiated from an in-frame translational re-start within the cvaA coding sequence. To determine whether the internally encoded CvaA protein also functions in the export pathway, the putative start codons for CvaA were mutagenized, while maintaining CvaA function. Elimination of CvaA translation caused no change in colicin V export levels, indicating that the CvaA protein is not required in the secretion pathway.

Acute bacterial meningitis in children in Hefei, China 1990-1992

OBJECTIVE

To obtain etiologic and epidemiologic information about bacterial meningitis, especially the H influenza type B (Hib), from a medium-sized city, Hefei, China.

METHODS

Data were collected prospectively over 3 years, from 1990 to 1992 by a well-organized group including 13 hospitals. All children with a clinical diagnosis of acute bacterial meningitis were enrolled and the specimens were taken for the etiologic studies. CSF and blood were tested by standard bacteriologic technique. CSF, blood and concentrated urine were tested directly for detection of antigen by countercurrent immuno-electrophoresis (CIE). Data were analyzed by epidemiologic methods.

RESULTS

Bacterial culture and CSF Gram's staining were positive only in 13.3% and 11.7%, respectively. Bacterial antigen detection was positive in up to 90% by CIE which was more sensitive than bacterial culture (chi 2 = 67.7, P < 0.005). The annual incidence of acute bacterial meningitis in the city is calculated as 9.3 cases/100,000 children from 1 month to 15 years of age and 19.2 cases/100,000 children from 1 month to 5 years of age. Hib meningitis accounted for 51.7%, N. meningitis (Nm) for 38.3%, and S. pneumoniae (Sp) for 8.3%. There was no significant seasonal variation. Of the patients, 76.7% were children under 5 years of age, and 51.7% under 1 year of age. The case fatality rate was 11.7% for all bacterial meningitis, 9.7% for Hib, 17.4% for Nm and 20% for Sp. A total of 22.6% of survivors suffered from neurological or psychological problems.

CONCLUSIONS

Using antigen detection combined with bacterial culture, we could make an etiologic diagnosis in up to 90% of the patients in this group. Hib, Nm and Sp were the predominant pathogens, which was similar to the findings in other countries. Hib was the most common cause of bacterial meningitis, but the incidence was much lower than in most parts of the world.

Childhood lead poisoning in China

In China, comprehensive epidemiological data relating to the prevalence of childhood lead poisoning are not available. However, existing data suggest that this disease may be widely pervasive as a result of rapid industrialization and the use of leaded gasoline. Seventeen publications have reported elevated blood lead levels in children from different areas of the country. Children residing in industrial and busy traffic areas had average blood lead levels(BPb) of 21.8-67.9 mu g/dl. The percentages of BPb values above 10 mu g/dl, which is the definition of lead poisoning in children, ranged from 64.9% to 99.5%. Even for 'unexposed' children, about 50% of them had BPb values above 10 mu g/dl. Furthermore, several retrospective pilot studies were conducted in Shanghai, Shenyang, Fuzhou and Beijing to evaluate the health effects of lead at current degree of exposure. The link between low-level lead exposure and deficits in IQ, neurobehavioral development and physical growth is remarkably consistent without exception. In summary, the harmful health effects of childhood lead poisoning in limited studies of exposed and 'unexposed' children demonstrate that this totally preventable disease warrants considerable public health attention in China.

[Relationship between lead content in umbilical blood and neurobehavioral development in infants]

One hundred and thirty-two babies were selected and their umbilical blood lead level were determined as a marker to reflect their exposure, to study the diagnostic criteria for lead poisoning in young children. And, mental development index (MDI) and psychomotor development index (PDI) of three-month babies in Bayley scales of infant development were used as effective indicators to study levels of lead on their development. Results indicated that both MDI and PDI in infants with blood lead levels of greater than or equal to 0.48 mumol/L were obviously lower than those with less than 0.48 mumol/L. All children were divided into two groups (high-blood-lead and low-blood-lead) according to the cut-off values for blood lead of 0.72, 0.48, and 0.24 mumol/L, respectively, and the difference in MDI and PDI between the two groups decreased gradually with the cut-off value shifted down, and there was no difference in them between the two groups when the cut-off point lowering down to 0.24 mumol/L. Therefore, the authors recommended that a level of 0.48 mumol/L of blood lead be used as diagnostic criteria for lead poisoning in young children.

[Metabolism and utilization of calcium derived from hydrolysed oyster shell in rats]

Experimental rats modeled on calcium deficiency were fed with calcium derived from hydrolysed oyster shell, calcium carbonate and calcium chloride respectively, equivalent to 45 mg a day, for four weeks to study their bioavailability. Calcium contents in the blood, urine, feces and bone of rats were determined with atomic absorption spectrometry and EDTA complex titration, and their bone density was measured with densitometry. Results showed proportions of calcium absorption and retention were 67.3% +/- 16.7% and 64.6% +/- 17.5%, respectively, in rats fed with calcium from hydrolysed oyster, and their femur calcium content and bone density (BMC/BW) 131.2 +/- 1.48 mg/g and 0.318 +/- 0.034 g/cm2, respectively, significantly higher than those in the rats fed with calcium carbonate. There were no significant difference in blood calcium contents, weight gains and feed intake between those three groups of rats. It suggests that calcium derived from hydrolysed oyster shell may be absorbed and utilized more easily than calcium carbonate.

Cytochromes CYP1A1 and CYP1B1 in the rat mammary gland: cell-specific expression and regulation by polycyclic aromatic hydrocarbons and hormones

Cultured rat mammary cells express both CYP1A1 and CYP1B1 in response to polycyclic aromatic hydrocarbons (PAH) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in a cell type-specific manner. The expression of each P450 was determined functionally (regioselective PAH metabolism), as apoprotein (immunoblots) and as mRNA (Northern hybridization). The epithelial rat mammary cells (RMEC) expressed CYP1A1, however only after PAH or TCDD treatment. CYP1B1 protein was scarcely detected in these induced RMEC but was surprisingly active as a participant in 7,12-dimethylbenz[a]anthracene (DMBA) metabolism shown through selective antibody inhibition (40% of total activity). CYP1B1 was selectively expressed in the stromal fibroblast population of rat mammary cells to the exclusion of CYP1A1. In the rat mammary fibroblasts (RMF), CYP1B1 protein and associated activity were each present at low levels constitutively and were highly induced by benz[a]anthracene (BA) to a greater extent than by TCDD (12- versus 6-fold). However, BA (10 microM) and TCDD (10 nM) stimulated the 5.2-kb CYP1B1-specific mRNA equally. These increases are consistent with the involvement of the aryl hydrocarbon (Ah) receptor in the transcription of the CYP1B1 gene and with the additional stabilization of CYP1B1 protein by BA, previously observed in embryo fibroblasts. Exactly this regulation of CYP1B1-dependent activity was seen in RMEC suggesting that this arises from exceptionally active CYP1B1 in a small proportion (5%) of residual RMF. The constitutive expression and PAH inducibility of CYP1B1 and CYP1A1 proteins in RMF and RMEC, respectively, were each substantially decreased (approximately 75%) by a hormonal mixture (17 beta-estradiol (0.2 microM) progesterone (1.5 microM) cortisol (1.5 microM) and prolactin (5 micrograms/ml)). Progesterone and cortisol, added singly to RMF suppressed CYP1B1 protein expression (approximately 80%) in both untreated and BA-induced cells, while cortisol also suppressed the 5.2-kb CYP1B1 mRNA. In contrast, 17 beta-estradiol stimulated constitutive expression of CYP1B1 protein (50-75%) and mRNA level (2- to 3-fold), but did not affect CYP1B1 expression in BA-treated RMF. The expression of CYP1A1 and CYP1B1 is therefore highly cell specific even though each is regulated through the Ah receptor. Each P450 exhibits a surprisingly similar pattern of hormonal regulation even though expressed in different cell types.

Topology analysis of the colicin V export protein CvaA in Escherichia coli

The antibacterial protein toxin colicin V is secreted from Escherichia coli cells by a dedicated export system that is a member of the multicomponent ATP-binding cassette (ABC) transporter family. At least three proteins, CvaA, CvaB, and TolC, are required for secretion via this signal sequence-independent pathway. In this study, the subcellular location and transmembrane organization of membrane fusion protein CvaA were investigated. First, a series of CvaA-alkaline phosphatase (AP) protein fusions was constructed. Inner and outer membrane fractionations of cells bearing these fusions indicated that CvaA is inner membrane associated. To localize the fusion junctions, the relative activities of the fusion proteins, i.e., the amounts of phosphatase activity normalized to the rate of synthesis of each protein, as well as the stability of each fusion, were determined. These results indicated that all of the fusion junctions occur on the same side of the inner membrane. In addition, the relative activities were compared with that of native AP, and the protease accessibility of the AP moieties in spheroplasts and whole cells was analyzed. The results of these experiments suggested that the fusion junctions occur within periplasmic regions of CvA. We conclude that CvaA is an inner membrane protein with a single transmembrane domain near its N terminus; the large C-terminal region extends into the periplasm. This study demonstrates the application of AP fusion analysis to elucidate the topology of a membrane-associated protein having only a single transmembrane domain.

Maximal airway response in mature and immature rabbits during tidal ventilation

Airway closure during maximal methacholine (MCh) challenge was evaluated using alveolar capsules in eight immature and eight mature anesthetized rabbits in vivo during imposed tidal ventilation. Changes in airway opening and alveolar pressures (delta PA) and pulmonary resistance (RL) were measured during MCh challenge at a positive end-expiratory pressure of 5 cmH2O. In immature rabbits, delta PA remained > 3 cmH2O in all animals, indicating no detectable airway closure. This contrasts to our previous study of isolated immature rabbit lungs under static conditions in which delta PA was < 0.1 cmH2O during maximal MCh challenge, findings consistent with airway closure. Airway closure also did not occur in mature animals during tidal ventilation in vivo; however, the frequency of closure in isolated lungs under static conditions was very low. With increasing MCh, end-expiratory PA increased in immature but not in mature rabbits. RL did not reach a plateau in immature rabbits during MCh, whereas a plateau was reached in mature rabbits. Immature rabbits also had greater increases in RL. These results suggest that tidal ventilation can limit bronchoconstriction in immature rabbits and prevent airway closure during maximal MCh challenge. Tidal ventilation may limit bronchoconstriction by inhibitory effects of stretch on airway smooth muscle contraction and also by causing hyperinflation and thereby increasing transpulmonary pressure.

Involvement of both major histocompatibility complex class II alpha and beta chains in CD4 function indicates a role for ordered oligomerization in T cell activation

CD4 is a membrane glycoprotein on T lymphocytes that binds to the same peptide:major histocompatibility complex (MHC) class II molecule recognized by the antigen-specific receptor (TCR), thereby stabilizing interactions between the TCR and peptide;MHC class II complexes and promoting the localization of the src family tyrosine kinase p56lck into the receptor complex. Previous studies identified a solvent-exposed loop on the class II beta 2 domain necessary for binding to CD4 and for eliciting CD4 coreceptor activity. Here, we demonstrate that a second surface-exposed segment of class II is also critical for CD4 function. This site is in the alpha 2 domain, positioned in single class II heterodimers in such a way that it cannot simultaneously interact with the same CD4 molecule as the beta 2 site. The ability of mutations at either site to diminish CD4 function therefore indicates that specifically organized CD4 and/or MHC class II oligomers play a critical role in coreceptor-dependent T cell activation.

Linker histones are not essential and affect chromatin condensation in vivo

We have (separately) disrupted all of the expressed macronuclear copies of the HHO gene encoding macronuclear histone H1 and of the micronuclear linker histone (MLH) gene encoding the protein MicLH in Tetrahymena thermophila. These disruptions are shown to eliminate completely the expression of each protein. Strains without either linker histone grow at normal rates and reach near-normal cell densities, demonstrating that linker histones are not essential for cell survival. Histone H1 knockout (delta H1) cells have enlarged DAPI-stained macronuclei and normal-sized micronuclei, while MicLH knockout (delta MicLH) cells have enlarged micronuclei and normal-sized macronuclei. delta MicLH cells undergo mitosis normally. However, the micronuclear mitotic chromosome structure is less condensed. These studies provide evidence that linker histones are nonessential and are involved in chromatin packaging and condensation in vivo.

[Experimental studies of protective effects of ischemic myocardium preconditioning and its mechanism]

Recent research has shown that repeated brief myocardial ischemia (RBMI) can increase the tolerance of myocardium to a subsequent sustained ischemia and have protective effects on myocardial cells. With the isolated rat heart Langendorff model, we investigated the effects of RBMI on myocardial morphology, systolic function, coronary flow rates (CFR), myocardial membrane phospholipid (PL) content and its marker enzyme's activity (5'-AMPase). The results showed: After ischemia-reflow, the HR, LVP and CFR in control and experimental groups had no significant difference (P > 0.05). But the PL content and specific activity of 5'-AMPase were significantly higher in the experimental group than that in control group (P < 0.01, P < 0.05). And the observations of ultrastructure suggested that the myocardium of the experimental group was preserved better than that in control group. It was also shown that RBMI had protective effects on myocardial membrane structure, and however effective had no relation to CFR.

Effect of transpulmonary pressure on airway closure in immature and mature rabbits

The transpulmonary pressures (Ptp values) at which airway closure occurred during maximal stimulation with methacholine were compared in 10 mature and 9 immature rabbit lungs by using an alveolar capsule technique to assess airway closure. After maximal constriction, airway opening and alveolar capsule pressures were recorded during small volume oscillations as Ptp was lowered from 12 to 4 cmH2O. At each Ptp, the proportion of alveolar capsules indicating airway closure was greater for the immature than for the mature lungs (P < 0.025). At Ptp of 4 cmH2O, only 20% of alveolar capsules indicated airway closure in the mature lungs in contrast to 85% indicating closure in the immature lungs (P < 0.001). The in vitro sensitivity of tracheal smooth muscle to acetylcholine and histamine was greater in tissues from immature than from mature rabbits. We conclude that the more frequent airway closure observed in immature rabbits could reflect maturational differences in the structure of the bronchi or lung parenchyma or differences in the coupling between the parenchyma and the airways.

[Effects of lyophilized royal jelly on experimental hyperlipidemia and thrombosis]

Rat models with experimental hyperlipidemia were fed with lyophilized royal jelly 700 mg/kg body weight daily for six weeks. Results showed lyophilized royal jelly can reduce serum cholesterol level (P < 0.01) and increase high-density lipoprotein-cholesterol level (P < 0.05). Lyophilized royal jelly can also increase the red cell deformability (RCD) and decrease plasma fibrinogen level. Thrombus was formed less in trial animals than in controls with a statistical significance. It suggested lyophilized royal jelly can be used in preventing and treatment of hyperlipidemia, and improving highly-coagulant status of blood.

Activation of neutrophils by a chemically separated but optically coupled neutrophil population undergoing respiratory burst

Neutrophils from pig blood were used as a model system to investigate the optical communication between cells. It was found that neutrophils stimulated to undergo respiratory burst can activate a second, chemically separated, but optically coupled population of neutrophils. The response of the latter was visualized as a temporary rising of their low-level chemiluminescence and an enhanced generation of superoxide radicals detected by both the reduction of ferricytochrome c and spin trapping. The results provide evidence that a long-range optical coupling of biological significance between living cells exists.

Alteration of lysophosphatidylcholine content in low density lipoprotein after oxidative modification: relationship to endothelium dependent relaxation

OBJECTIVE

The aim was to examine the formation of lipid peroxidation products and the alteration in phospholipid content in low density lipoprotein (LDL) after oxidative modification by CuSO4, and subsequently, to determine the ability of the modified LDL to impair endothelium dependent relaxation in rat aortic rings.

METHODS

Blood samples were obtained from normal human volunteers. LDL was prepared by sequential ultracentrifugation and it was oxidatively modified in the presence of 5 microM CuSO4. Lipid peroxidation products (thiobarbituric acid reactive substances, TBARS), and alterations in electrophoretic mobility and phospholipid content were determined in normal (native) and oxidised LDL. Endothelium dependent relaxation was produced by acetylcholine (10(-8)-10(-5) M) in phenylephrine precontracted rat aortic rings.

RESULTS

LDL incubated for 24 h with 5 microM CuSO4 at 20 degrees C and 37 degrees C with constant agitation displayed higher amounts of TBARS than the respective native LDL. While the amounts of TBARS in LDL modified at 20 degrees C and 37 degrees C were similar, the former condition resulted in statistically smaller changes of phospholipid contents. LDL with higher lysophosphatidylcholine content showed greater impairment of endothelium dependent relaxation in rat aortic rings than LDL with lower lysophosphatidylcholine content.

CONCLUSIONS

The raised lysophosphatidylcholine level in oxidatively modified LDL was related to the ability of the LDL to impair endothelium dependent relaxation. However, lipid peroxidation products assessed by TBARS did not relate to the phospholipid changes in LDL and therefore cannot be used to predict the vascular effects of LDL after oxidative modification.

[Effect of nifedipine on T wave in ischemic myocardium]

Calcium antagonists are generally considered to have no substantial effect on repolarization of the myocardium, so they have no direct effect on T wave, either. But in a pig model of myocardial ischemia, intracoronary nifedipine was found to reverse the inverted T wave induced by ischemia to upright promptly. Ten pigs were anesthetized with the chest opened, anterior interrentricular branch of left coronary artery (LAD) was narrowed to 4.67 kPa of LAD pressure, and then adenosine or nifedipine was infused into the coronary respectively. During the 9-minute ischemia, intracoronary adenosine or intracoronary nifedipine got the similar HR, LVEDP, LVDP, CAP, CAQ, and the intracoronary adenosine even got higher CAQ than the intracoronary nifedipine did. However, the T wave was retained inverted during the adenosine infused, but during the intracoronary nifedipine, the inverted T wave was promptly turned upright. The relevant factors and mechanisms are discussed.

[Effects of endotoxin on coronary circulation]

To investigate the effects of endotoxin (ETX) on coronary circulation, we infused endotoxin (4ng/ml) intravenously in a small dose (0.3ng/kg.min-1) which did not reduce the blood pressure, nor did it disturb the coronary autoregulation, and the flow kept constant during the ETX infusion. But when the left coronary artery descending branch (LAD) was narrowed and the LAD pressure was reduced to 4.67kPa, the ETX showed a vasodilator effect on the LAD (pre-ETX 65.2 +/- 29.2 ml/min, post-ETX 89.5 +/- 32.7 ml/min, P < 0.05). This effect suggested that the ETX in a small dose had a vasodilator effect on a narrowed coronary artery, even when it did not disturb the hemodynamics. The possible mechanisms were surveyed preliminarily.

[Comparative study of ischemia-induced and reperfusion-induced ventricular fibrillation in pigs]

To have a better understanding of reperfusion-induced ventricular fibrillation (VF), we studied the relevant morbidity in pigs and compared it with that of the ischemia-induced VF. In 10 hearts of anesthetized chest-open pigs, a total of 127 cycles of various degrees and varied duration of ischemia and reperfusion were completed. VF occurred 13 times (10.2%). Of these, 11 were ischemia-induced VF, while only 2 were reperfusion-induced VF. In two cases of ischemia-induced VF, electric defibrillation failed before the reestablishment of left anterior interventricular branch of coronary artery flow, but after adequate reflowing, all VF turned out to be sinus-rhythm by electric defibrillation. The results suggest that ventricular fibrillation be mainly induced by ischemia but less induced by reperfusion.

Cycloversion and cyclovergence: the effects of the area and position of the visual display

Rotation of a display in the frontal plane evokes a conjugate nystagmic rotation of the eyes (cycloversion) about the visual axes, with slow phases in the direction of stimulus motion--a response known as torsional optokinetic nystagmus (TOKN). Antiphase rotation of large dichoptic displays evokes a disconjugate rotation of the eyes about the visual axes, a response known as cyclovergence. Using the scleral-coil technique for monitoring eye movements we recorded TOKN evoked by black-and-white sectored displays rotating about the visual axis at an angular velocity of 30 degrees/s. The display was confined to central areas with diameters ranging from 5 degrees to full field or with the central 5 degrees to 75 degrees occluded. A 5 degrees central display evoked TOKN with 40% of the gain for the full-field display and gain increased as a function of the size of the display. The gain of TOKN decreased with increasing size of a central occluder. These characteristics of TOKN are similar to those of horizontal OKN. Cyclovergence was virtually absent with a 5 degrees display but was immune to occlusion of the central 40 degrees. Cyclovergence therefore differs from cycloversion in showing no preference for centrally placed stimuli. These effects are free from the influence of stationary edges, since these were concentric with the stimulus motion. The effects are also free from the influence of voluntary pursuit, since humans do not normally have voluntary control over torsional eye movements.

[Effect of hemorheological factors on coronary flow during myocardial ischemia]

Intracoronary infusion of some drugs may induce superimposed coronary vasodilation upon endogenous vasodilation during myocardial ischemia, which was suggested as coronary vasodilator reserve. For an investigation of this phenomenon, 8 pigs were anesthetized, chest-opened, LAD (left anterior descending coronary artery)-dissected and instrumented. The LAD pressure was reduced to 4.67 kPa (35mmHg), and then intracoronary infusion of adenosine, saline, or anisodamine (at the same rate of 2ml/min) was started and maintained for 9 minutes. The three solutions all produced a significant increase in the coronary flow, including the saline (compared with the control, P < 0.05). The hemorheological examination of the distal coronary blood revealed a reduced hematocrit, plasma viscosity and whole blood viscosity during the saline and anisodamine infusion periods (P < 0.05), but in the adenosine infusion, the statistical analysis on hemorheological data revealed no significance compared with the control (P > 0.05). The results showed that the coronary vasodilator reserve induced by intracoronary drugs during myocardial ischemia might be partly accounted by regional hemodilution in the LAD bed. The study suggested that a decrease in blood viscosity might play an important role in the improvement of the narrowed coronary circulation, even more important than vasodilator drugs.

Experimental healing of distraction osteogenesis comparing metaphyseal with diaphyseal sites

Distraction osteogenesis was performed on 32 adult dogs to compare bone healing at metaphyseal and diaphyseal sites. Sixteen dogs underwent proximal metaphyseal corticotomy and 16 dogs underwent middiaphyseal corticotomy of the left tibiae for gradual lengthening. Each major group was then divided into four subgroups of four dogs each on the basis of zero-, seven-, 14- and 21-day latency periods. The standard radiograph, quantitative computer tomography density, and bone-healing index were used to evaluate new bone formation and consolidation. A distraction rate of 1 mm per day for four weeks created an average elongation of 23.9 +/- 3.7 mm in the metaphyseal groups and 23.8 +/- 2.0 mm in the diaphyseal groups, excluding nine premature consolidations. In the 16 metaphyseal lengthenings, there were six premature consolidations (37.5%): four with a 21-day latency, two with a 14-day latency, and one nonunion (6.2%). In the 16 diaphyseal lengthenings, three fused prematurely (18.7%), two with a 21-day latency and one incomplete corticotomy with a seven-day latency. Three lengthenings of the diaphyseal group resulted in nonunion (18.7%). All animals, metaphyseal and diaphyseal, successfully bridged the distraction gap after a zero-day latency. The bone-healing index showed that new bone consolidation was best with a zero-day latency in metaphyseal (22 +/- 7.6 days/cm) and diaphyseal lengthening (26.5 +/- 6.5 days/cm). Comparing the minimum quantitative computer tomography density ratio of the experimental side with the contralateral side indicated a significant difference at the end of distraction (p = 0.001), at fixator removal (p = 0.001), and when the dogs were killed (p = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of electromagnetic stimulation with different waveforms on cultured chick tendon fibroblasts

An energy efficient electromagnetic stimulator device for fracture healing was compared to a commercially available device in stimulating cell growth in tissue cultures. The energy efficient device, which conserves energy by using a bidirectional time-dependent magnetic wave form, and the commercially available stimulator, which uses a unidirectional time-dependent magnetic wave form, were tested on chick tendon fibroblasts in primary culture. Comparing non-stimulated control and cells electromagnetically stimulated with unidirectional and bidirectional waveforms showed that at the growth phase between days 2 and 3, both electrical stimulation techniques increased cell division as measured by DNA synthesis. When cells were dividing rapidly, collagen synthesis was reduced. When the cells reached the confluence there was no difference among the groups (control, unidirectionally stimulated, and bidirectionally stimulated) in terms of number of cells or collagen produced.

Identification and chromosomal mapping of a receptor tyrosine kinase with a putative phospholipid binding sequence in its ectodomain

We have cloned a novel receptor tyrosine kinase that has an unusual ectodomain. The extracellular sequence consists of 416 amino acids and has none of the structural motifs that have been found in other receptor tyrosine kinases. The 150 amino acids in the amino terminus of the receptor is homologous to a putative phospholipid-binding sequence that is found also in other cell adhesion molecules such as the neuronal A5 antigen and coagulation factors V and VIII. The kinase domain has a short cytoplasmic tail and contains a short insert between subdomains I and II. The structure of this receptor kinase suggests that it belongs to a new family of receptors involved in cell-cell interactions. The cell adhesion kinase (Cak) is expressed at low levels in most adult tissues and expression is highest in the brain and lung. Using fluorescence in situ hybridization and interspecific backcross mapping, the Cak gene was localized to human chromosome 6 and mouse chromosome 17.