Comparison of some antineoplastic drugs on inhibiting thrombin catalizing fibrinogen clotting in vitro

OBJECTIVE

To classify the effect of thrombin, the key enzyme which enables fibrinogen to form fibrin (fibrinogen clotting) on the formation of metastasis by comparing the inhibition of some antineoplastic drugs on fibrinogen clotting in vitro.

METHODS

Time intervals of different drugs to reach a maximum OD (340 nm) data in fibrinogen solution added with thrombin were used in this work.

RESULTS

It was found that L-4-oxalysine (8-40 micrograms/ml) and arabinosyl cytosine (10-50 micrograms/ml) could inhibit the effect of thrombin by extending the fibrinogen clotting time to 100%-150% (P < 0.001) and 61%-100% (P < 0.001) while the other antimetastatic drugs razoxane, probimane, adriamycin, harringtonine homoharringtonine and alpha-anordrin at the treatment concentrations showed no such activity. The positive rate of drugs to thrombin activity was approximately 25%.

CONCLUSION

It suggests that L-4-oxalysine and arabinosyl cytosine may even exhibit antimetastatic effect through thrombin-fibrinogen pathway, and thrombin might operate in tumor metastasis for only limited step but crucial to fibrin formation in tumor nodules.

[Efficacy of Chinese recipes of replenishing kidney and activating blood circulation in female rats with osteoporosis induced by ovariectomy]

OBJECTIVE

To investigate the efficacy of Chinese recipe of replenishing Kidney and activating blood circulation (RKABC) in female rats with osteoporosis induced by ovariectomy.

METHODS

Fifty female SD rats at 12 months of age were chosen, and were divided into 5 groups; control, model, model plus nylestriol, RKABC (high dose) and RKABC (low dose). The model of osteoporosis was established by ovariectomy in rats for 12 weeks, and then was given different kinds of liquid and administered approximately for 12 weeks. General bone mineral density (GBMD), femur bending strength (FBS), serum-BGP and urine-Hyp/Cr were measured.

RESULTS

GMBD, FBS in 3 treatment groups were significantly higher than those in the model group (P < 0.05), but lower than those in the normal control group (P < 0.05); GBMD, FBS in 2 RKABC groups were slightly higher than those in nylestriol's group (P > 0.05). Compared with model group, levels of serum BGP in 2 RKABC groups increased (P < 0.05) and in RKABC (H) treatment group increased almost the same as those in the control group (P > 0.05). In comparison with model group, levels of U-Hyp/Cr in 3 treatment groups decreased (P < 0.05, P < 0.01) but 2 RKABC treatment groups still significantly higher than those in the normal control group (P < 0.05).

CONCLUSION

It indicated that RKABC could control osteoporosis in female rats induced by ovariectomy and seems to promote bone formation.

Altered expression of CD44 and variant isoforms in human adenocarcinoma of the endocervix during progression

OBJECTIVE

Altered expression of the CD44 family of cell adhesion molecules has been associated with tumor progression and metastasis. The aim of this study was to investigate the expression of the gene products of CD44 standard (CD44s) and several alternatively spliced variants (CD44v4, v6, v7, and v9) in adenocarcinoma of the endocervix and to correlate the degree of their expression with disease progression.

METHODS

Immunohistochemical staining for CD44s and CD44v4, v6, v7, and v9 was performed on formalin-fixed, paraffin-embedded endocervical specimens. Seventeen cases of adenocarcinoma in situ (AIS) and 22 cases of invasive adenocarcinoma of the endocervix were included in this study, and the immunoreactivity was compared with that of normal endocervical epithelium.

RESULTS

(1) In the normal endocervical mucosa, immunoreactivity for CD44s and the splice variants was lacking or was confined to only the basal portion of the glandular epithelium along the basement membrane; (2) CD44s was diffusely expressed along the entire cytoplasmic membrane, including the luminal surface of the tumorous glands in 94% of AIS and 95% of invasive adenocarcinomas; (3) a significantly stronger expression of CD44s was observed in invasive adenocarcinomas than in AIS; (4) in contrast to all other splice variants, CD44v9 demonstrated an increased expression in nearly all in situ and invasive lesions compared to the normal tissue; (5) CD44v4 and v6 were expressed only in a small proportion of invasive adenocarcinomas and were near totally absent in the in situ lesions; and (6) CD44 v7 was totally absent in all normal, in situ, and invasive lesions studied.

CONCLUSIONS

It appears that neoplastic transformation of endocervical epithelium is associated with qualitative and quantitative changes in the expression of CD44 standard molecule and some CD44 splice variants.

[Linkage analysis of chromosome 5 and asthma in a Chinese population]

OBJECTIVE

To investigate the linkage between asthma and 5q31-33 in a Chinese population.

METHODS

The linkage between microsatellite markers in 5q and asthma and allergy was tested by lod score analysis.

RESULTS

The linkage between asthma and 5q31-33 was not confirmed.

CONCLUSION

The genes at 5q31-33 are not likely to contribute to inheritance of asthma in this Chinese population.

Crystal structure of enteropeptidase light chain complexed with an analog of the trypsinogen activation peptide

Enteropeptidase is a membrane-bound serine protease that initiates the activation of pancreatic hydrolases by cleaving and activating trypsinogen. The enzyme is remarkably specific and cleaves after lysine residues of peptidyl substrates that resemble trypsinogen activation peptides such as Val-(Asp)4-Lys. To characterize the determinants of substrate specificity, we solved the crystal structure of the bovine enteropeptidase catalytic domain to 2.3 A resolution in complex with the inhibitor Val-(Asp)4-Lys-chloromethane. The catalytic mechanism and contacts with lysine at substrate position P1 are conserved with other trypsin-like serine proteases. However, the aspartyl residues at positions P2-P4 of the inhibitor interact with the enzyme surface mainly through salt bridges with the Nzeta atom of Lys99. Mutation of Lys99 to Ala, or acetylation with acetic anhydride, specifically prevented the cleavage of trypsinogen or Gly-(Asp)4-Lys-beta-naphthylamide and reduced the rate of inhibition by Val-(Asp)4-Lys-chloromethane 22 to 90-fold. For these reactions, Lys99 was calculated to account for 1.8 to 2.5 kcal mol(-1) of the free energy of transition state binding. Thus, a unique basic exosite on the enteropeptidase surface has evolved to facilitate the cleavage of its physiological substrate, trypsinogen.

[Effect of running granule on repairing capacity of neuro-endocrine-immunity and DNA in treating mastoplasia]

OBJECTIVE

To explore the clinical effect and therapeutic mechanism of Runing Granule (RNG) in treating mastoplasia to elucidate its pathogenesis.

METHODS

One hundred and eighty-seven patients suffering from mastoplasia were randomly divided into the RNG treated group (treated group, 147 cases), and the tabellae tamoxifen control group (control group, 40 cases). The follow-up underwent for 3 months. Before and after treatment, changes of levels of plasma neurotransmitters, serum endocrine hormone, peripheral lymphocyte unscheduled DNA synthesis, the count of T lymphocyte subsets in the luteal phase during the menstrual cycle of 104 cases were measured, their clinical effects were also observed.

RESULTS

Before treatment, these cases showed disturbances in the secretion of 5-hydroxytryptamine (5-HT), epinephrine (E), estradiol (E2), follicle stimulating hormone (FSH), luteinizing hormone (LH), and the levels of norepinephrine (NE), prolactin (PRL), inducer-helper T lymphocytes (OKT4+), suppressor T lymphocytes (OKT3+), were significantly increased, progesterone (P), testosterone (T), total T cells (OKT3+), OKT4+/OKT8+ ratio, unscheduled DNA synthesis (UDS) were obviously reduced (P < 0.05, P < 0.01) in mastoplasia patients. After treatment, RNG showed regulation on disturbances of these parameters, the curative rate of the treated group was higher than that of the control group; the metabolic disturbances of 5-HT/NE, E2/P, T, OKT3+ in the treated group were improved more significantly than those in the control group (P < 0.05). During the period of clinical observation, no obvious side effect and toxicity of RNG were found.

CONCLUSIONS

Mastoplasia is caused by the interactions among multi-factors in which the neuro-endocrine-immune network plays a key role in the pathogenesis of mastoplasia. RGN was effective in treating mastoplasia, the mechanism probably lays on the regulation of comprehensive coordination from the multi-layers, multi-links and multiple pathways in the neuro-endocrine-immunity network and elevation of internal environment-stabilizing capacity of the body.

Bcr: a negative regulator of the Bcr-Abl oncoprotein

Chronic myelogenous leukemia is typically characterized by the presence of the Philadelphia chromosome (Ph) in which 5' portions of the BCR gene are fused to a large portion of the ABL gene. Our studies and those of others indicate that Bcr sequences within the Bcr-Abl oncoprotein are critically involved in activating the Abl tyrosine kinase and actively participate in the oncogenic response, which is generated by the Bcr-Abl oncoprotein. We investigated the role of the Bcr protein in the oncogenic effects of Bcr-Abl. Reduction of the level of the Bcr protein by incubating cells with a 3' BCR anti-sense oligodeoxynucleotide increased the growth rate and survival of hematopoietic cell lines expressing Bcr-Abl. Also, enforced expression of Bcr in Bcr-Abl cell lines strongly reduced transformation efficiency. Induction of Bcr expression drastically reduced the phosphotyrosine content of Bcr-Abl in Rat-1 fibroblasts transformed by P185 BCR-ABL and in hematopoietic cells expressing P210 Bcr-Abl within days following induction of Bcr. Rat-1/P185 cells maintained for three weeks after Bcr induction had dramatically reduced amounts of phosphotyrosine proteins compared to cells in which Bcr expression was repressed by the addition of Tet. In contrast Bcr expression did not decrease the phosphotyrosine content of either v-Src or activated Neu tyrosine kinase. Importantly, the phosphotyrosine content of total P160 BCR (induced plus endogenous) was strongly reduced by inducing expression of Bcr, indicating that the induced Bcr protein was not a target of the tyrosine kinase activity of Bcr-Abl but instead functioned as an inhibitor of Bcr-Abl. These results show that the Bcr protein can function as a negative regulator of Bcr-Abl, but that the inhibitory effects of Bcr are dependent on achieving an elevated level of Bcr expression relative to Bcr-Abl.

Novel conformationally restricted tetracyclic analogs of delta8-tetrahydrocannabinol

Novel analogs of (-)-delta8-tetrahydrocannabinol (delta8-THC) in which the conformation of the side chain was restricted by incorporating the first one or two carbons into a six membered ring fused with the aromatic phenolic A ring were synthesized. The affinities of the novel ligands for CB1 and CB2 indicated that the "southbound" chain conformer retained the highest affinity for both receptors.

[Prophylaxis and treatment of cytomegalovirus infection in allogeneic bone marrow transplantation]

OBJECTIVE

To assess the efficacy and safety of Cymevene (ganciclovir) in the prophylaxis and treatment of cytomegalovirus (CMV) infection after allogeneic bone marrow transplantation (allo-BMT).

METHODS

Sixty patients with leukemia undergoing allo-BMT were observed. Cymevene was given prophylactically to 20 patients at a dose of 5 mg/kg twice daily from day -9 to day -2 and restarted when the ANC > or = 1.0 x 10(9)/L and BPC > or = 30 x 10(9)/L at a daily dose of 5 mg/kg for 5 days every week until day +100. In diagnosed symptomatic CMV infections, the dose of Cymevene was 5 mg/kg twice daily for 2-3 weeks followed by 5 mg/kg twice a day for 5 days every week for an additional 2-3 weeks.

RESULTS

The incidence of active CMV infection was 0 in the prophylaxis-treated patients and 25% in the controls (P < 0.05). In diagnosed CMV diseases, marked improvement was noted in 17 of 20 patients (85%) treated with Cymevene. The most common adverse events of Cymevene were leukopenia and thrombocytopenia, but were reversible.

CONCLUSION

Cymevene is effective and safe for the prophylaxis and treatment of CMV infections after allo-BMT.

[A study of mitoxantrone with other chemical agents in treating 126 cases of adult acute myeloid leukemia]

OBJECTIVE

To estimate the effect of mitoxantrone with other chemical agents in treating adult acute myeloid leukemia.

METHODS

126 inpatients diagnosed as acute myeloid leukemia between January 1993 to December 1997 were treated with mitoxantrone with other chemical agents. 85 had not been treated previously, (untreated) while 51 were relapsing or resistant to previous treatment.

RESULTS

The complete response rate among untreated and the relapsing/resistant groups were 44.7% and 27.5%; while the partial response rate were 20.0%, 9.8% respectively. 4 patients were in the untreated group died early. The main side-effect of mitoxantrone is bone marrow depression which led to fever and bleeding with rates of 40.4%, 24.3%. The non-bone marrow side-effects were tolerable. Damage to the liver was a prominent occurrence 31.8%.

CONCLUSION

mitoxantrone was effective as the first line anti-tumor drug with other chemical agents in treating adult acute myeloid leukemia, its side-effects were mild.

[Determination of selenium in human hair with graphite furnace atomic absorption spectrometry]

Determination of selenium in human hair by GFAAS has been described in this paper, Hairs from 120 middle school teachers were determined. The results are 0.15-1.00 mg/kg and the median is 0.43 mg/kg. The sensitivity of this method is 2.96 ng/mL and the relative standard deviation is 2.4%-6.7%.

[A clinico-pathological study of granulomatous amoebic encephalitis]

OBJECTIVE

To study the clinico-pathological characteristics and differential diagnosis of granulomatous meningioencephalitis caused by acanthamoeba.

METHODS

The clinical features, CT scan findings and post mortem pathological changes of 3 patients afflicted with granulomatous amoebic encephalitis (GAE) were analysed.

RESULTS

GAE is a chronic clinical entity. Clinical manifestations include headache, low fever, seizures, hemiparesis and coma leading to death. CSF: pressure slightly elevated with presence of lymphocytes and plasma cells, glucose usually low with moderately high protein levels. CT scans were non specific. Clinical course insidious and may mimic bacterial meningitis or tuberculous meningitis. Post mortem pathological examinations showed that acanthamoeba produced a chronic or subacute granulomatous meningioencephalitis. Acanthamoebic trophoziotes and cysts were found within the hemorrhagic necrotic cerebral tissues. In some cases there is severe angitis and fibrinoid necrosis of the vascular wall with perivascular cuffing by lymphocytes and plasma cells. Trophozoites and cysts were found within the perivascular space.

CONCLUSIONS

Acanthamoeba is an opportunistic pathogenic free living amoeba which can produce fatal GAE.

[Determination of mercury in food by microwave oven digestion-hydride generation atomic absorption spectrometry]

Mercury in food was determined by microwave oven digestion-hydride generation atomic absorption spectrometry. The best condition of digestion was also studied. Furthermore, the way of doing digestion was compared to standard method with satisfactory results. The method is rapid and simple, and of good precision and high accuracy. The sensitivity is 0.43 microg/L. The detection limit is 0.35 microg/L. The relative standard deviation is 2.8% and the recovery is 93.5%-103.0%.

Nucleolin, defective for MPF phosphorylation, localizes normally during mitosis and nucleologenesis

To determine what effect maturation promoting factor (MPF, p34(cdc2) kinase/cyclin B) phosphorylation has on nucleolin's distribution during mitotic nucleolar disassembly and reassembly, we altered Chinese hamster ovary (CHO) nucleolin (the N protein) such that it cannot be phosphorylated by p34(cdc2). As expected, the transiently expressed epitope-tagged N protein showed no apparent defect in nucleolar localization in interphase CHO cells, even after hypotonic shock and recovery to quickly disassemble and then reassemble interphase nucleoli. In mitotic CHO cells, the N protein localized to the perichromosomal sheath and the cytoplasm, as is typical for nucleolin. Similar to epitope-tagged wild-type nucleolin, the N protein also maintained its association with persistent nucleoli characteristic of mitotic Chinese hamster lung (Dede) cells. In synchronized HeLa cells, the N protein again localized to the perichromosomal sheath and the cytoplasm as nucleoli disassembled during prophase. In HeLa cell telophase, the N protein localized normally to nucleolus-derived foci within the cytoplasm and prenucleolar bodies within reforming nuclei. The observations indicate that MPF phosphorylation is not essential for nucleolin's localizations to the perichromosomal sheath and the cytoplasm during prophase and metaphase, and that functional MPF phosphorylation sites are not essential for nucleolin's localizations during nucleologenesis.

Evidence for production of a new lantibiotic (butyrivibriocin OR79A) by the ruminal anaerobe Butyrivibrio fibrisolvens OR79: characterization of the structural gene encoding butyrivibriocin OR79A

The ruminal anaerobe Butyrivibrio fibrisolvens OR79 produces a bacteriocin-like activity demonstrating a very broad spectrum of activity. An inhibitor was isolated from spent culture fluid by a combination of ammonium sulfate and acidic precipitations, reverse-phase chromatography, and high-resolution gel filtration. N-terminal analysis of the isolated inhibitor yielded a 15-amino-acid sequence (G-N/Q-G/P-V-I-L-X-I-X-H-E-X-S-M-N). Two different amino acid residues were detected in the second and third positions from the N terminus, indicating the presence of two distinct peptides. A gene with significant homology to one combination of the determined N-terminal sequence was cloned, and expression of the gene was confirmed by Northern blotting. The gene (bvi79A) encoded a prepeptide of 47 amino acids and a mature peptide, butyrivibriocin OR79A, of 25 amino acids. Significant sequence homology was found between this peptide and previously reported lantibiotics containing the double-glycine leader peptidase processing site. Immediately downstream of bvi79A was a second, partial open reading frame encoding a peptide with significant homology to proteins which are believed to be involved in the synthesis of lanthionine residues. These findings indicate that the isolated inhibitory peptides represent new lantibiotics. Results from both total and N-terminal amino acid sequencing indicated that the second peptide was identical to butyrivibriocin OR79A except for amino acid substitutions in positions 2 and 3 of the mature lantibiotic. Only a single coding region was detected when restriction enzyme digests of total DNA were probed either with an oligonucleotide based on the 5' region of bvi79A or with degenerate oligonucleotides based on the predicted sequence of the second peptide.

[HLA-DQA1 genes involved in the genetic susceptibility to duodenal ulcer in Wuhan Hans]

OBJECTIVE

To study the genetic susceptibility of HLA-DQA1 alleles to duodenal ulcer in Chinese Hans from Wuhan and its nearby regions.

METHODS

Seventy patients with duodenal ulcer and fifty healthy controls were examined for HLA-DQA1 genotypes. HLA-DQA1 typing was carried out by digesting the locus specific polymerase chain reaction amplified products with alleles specific restriction enzymes (PCR-RFLP), Apal I, Basj I, Hph I, Fok I, Mbo II and Mnl I.

RESULTS

The allele frequency of DQA1 0301 in patients with duodenal ulcer (64.3%) was significantly higher than that in healthy controls (36%). In contrast, the allele frequency of DQA1 0102 in patients with duodenal ulcer (8.6%) was significantly lower than that in healthy controls (26%).

CONCLUSION

These findings suggest that DQA1 0301 is a susceptible gene for duodenal ulcer in Wuhan Hans while DQA1 0102 is its resistant gene, and there are immunogenetic differences in HLA-DQA1 locus between duodenal ulcer patients and healthy controls.

[The examination of SIgE in perennial allergic rhinitis with mast allergy test system]

OBJECTIVE

To explore the relation between serum specificity immunoglobulin E (SIgE) and skin test (intracutaneous test) as well as nasal provocation in Perennial allergy rhinitis (PAR) by Mast Allergy Test System.

METHOD

Serum allergen-specific IgE (SIgE) were examined by Mast Allergy Test System in 57 case of PAR patients.

RESULT

The SIgE positive rate of fannae and pteronvssinus are highest (52.6%), the sensitive rate of intracutaneous test is 88.4% and nasal provocation is 88.9%. The SIgE positive rates of cludosporium, penicillum and altemana are 26.3%, 24.6% and 21.0%, respectively. The SIgE positive rates of fannae, cockroach, shrimp, crab, egg and milk is direct proportion with intracutaneous test (P < 0.01). Pteronvssiaus and pigweek mix have no relationship with intracutaneous test (P > 0.05). In addition, the positive rate of ragweed mix SIgE is 22.8%, but there is non of this plant in South China. It is worthy of paying attention in clinic.

CONCLUSION

It indicate that Mast Allergy Test System is one of the better examination for PAR allergens.

Transduction of primitive human marrow and cord blood-derived hematopoietic progenitor cells with adeno-associated virus vectors

We evaluated the capacity of adeno-associated virus (AAV) vectors to transduce primitive human myeloid progenitor cells derived from marrow and cord blood in long-term cultures and long-term culture-initiating cell (LTC-IC) assays. Single-colony analyses showed that AAV vectors transduced CD34(+) and CD34(+)38(-) clonogenic cells in long-term culture. Gene transfer was readily observed in LTC-ICs derived from 5-, 8-, and 10-week cultures. Recombinant AAV (rAAV) transduction was observed in every donor analyzed, although a wide range of gene transfer frequencies (5% to 100%) was noted. AAV transduction of LTC-ICs was stable, with week-8 and -10 LTC-ICs showing comparable or better transduction relative to week-5 LTC-ICs. Fluorescence in situ hybridization (FISH) analyses performed to determine the fate of AAV vectors in transduced cells showed that 9% to 28% of CD34(+) and CD34(+)38(-) cells showed stable vector integration as evidenced by chromosome-associated signals in metaphase spreads. Comparisons of interphase and metaphase FISH suggested that a fraction of cells also contained episomal vector at early time points after transduction. Despite the apparent loss of the episomal forms with continued culture, the number of metaphases containing integrated vector genomes remained stable long term. Transgene transcription and placental alkaline phosphatase (PLAP) expression was observed in CD34(+), CD34(+)38(-) LTC-ICs in the absence of selective pressure. These results suggest that primitive myeloid progenitors are amenable to genetic modification with AAV vectors.

Inhibition of vascular endothelial growth factor induced mitogenesis of human endothelial cells by a chimeric anti-kinase insert domain-containing receptor antibody

The kinase insert domain-containing receptor (KDR) is the human vascular endothelial growth factor (VEGF) receptor responsible for the mitogenic and angiogenic effects of VEGF. There is much experimental evidence to suggest that the VEGF/KDR pathway plays an important role in tumor angiogenesis, a process essential for tumor growth and metastasis. Here we produced a chimeric anti-KDR antibody (IgG1), c-p1C11, from a single chain (scFv) antibody isolated from a phage display library. C-p1C11 binds specifically to the extracellular domain of soluble as well as cell-surface expressed KDR. It effectively blocks VEGF-KDR interaction and inhibits VEGF-stimulated activation of KDR and MAP kinases p44/p42 of human endothelial cells. Furthermore, c-p1C11 efficiently neutralizes VEGF-induced mitogenesis of human endothelial cells. Our results suggest that antibodies against KDR have potential clinical applications in the treatment of cancer and other diseases where pathological angiogenesis is involved.

[Study on the pathogenesis of acquired pure amegakaryocytic thrombocytopenic purpura]

OBJECTIVE

To investigate the possible pathogenesis of acquired pure amegakaryocytic thrombocytopenic purpura(APATP).

METHODS

Twenty eight patients with APATP were studied. Bone marrow mononuclear cells(MNCs) from these patients were plated into methyl cellulose cultures for CFU-GM, CFU-E and CFU-MK assay. The influence of depleting T cells or adherent cells from patients' marrow cells on CFU-MK growth was observed. The humoral inhibitory effect on CFU-MK was determined by co-incubation of patients' sera or IgG with normal or autologous MNCs prior to cultures. The serum MK-CSA was also assessed.

RESULTS

Fifteen cases (53.6%) of APATP was resulted from intrinsic defect of CFU-MK. The megakaryocyte colony formation was augmented significantly in 3 T lymphocytes-depleted and 2 mono-macrophages depleted patients. Sera from 6 patients(21.4%) were inhibitor to CFU-MK. The inhibitor originated from IgG and selectively directed against the megakaryocyte. In the remaining 2 cases, the pathogenesis was not ascertained.

CONCLUSION

The intrinsic defect of megakaryocyte progenitor cell is considered to be a primary pathogenesis of APATP. In some patients the disease can result from abnormal immune mechanisms. The decompensation of MK-CSA production could also be an important cause for APATP.

Apical sorting of bovine enteropeptidase does not involve detergent-resistant association with sphingolipid-cholesterol rafts

Enteropeptidase is a heterodimeric type II membrane protein of the brush border of duodenal enterocytes. In this location, enteropeptidase cleaves and activates trypsinogen, thereby initiating the activation of other intestinal digestive enzymes. Recombinant bovine enteropeptidase was sorted directly to the apical surface of polarized Madin-Darby canine kidney cells. Replacement of the cytoplasmic and signal anchor domains with a cleavable signal peptide (mutant proenteropeptidase lacking the amino-terminal signal anchor domain (dSA-BEK)) caused apical secretion. The additional amino-terminal deletion of a mucin-like domain (HL-BEK) resulted in secretion both apically and basolaterally. Further deletion of the noncatalytic heavy chain (L-BEK) resulted in apical secretion. Thus enteropeptidase appears to have at least three distinct sorting signals as follows: the light chain (L-BEK) directs apical sorting, addition of most of the heavy chain (HL-BEK) inhibits apical sorting, and addition of the mucin-like domain (dSA-BEK) restores apical sorting. Inhibition of N-linked glycosylation with tunicamycin or disruption of microtubules with colchicine caused L-BEK to be secreted equally into apical and basolateral compartments, whereas brefeldin A caused basolateral secretion of L-BEK. Full-length BEK was not found in detergent-resistant raft domains of Madin-Darby canine kidney cells or baby hamster kidney cells. These results suggest apical sorting of enteropeptidase depends on N-linked glycosylation of the serine protease domain and an amino-terminal segment that includes an O-glycosylated mucin-like domain and three potential N-glycosylation sites. In contrast to many apically targeted proteins, enteropeptidase does not form detergent-resistant associations with sphingolipid-cholesterol rafts.

A mutation in the insulin 2 gene induces diabetes with severe pancreatic beta-cell dysfunction in the Mody mouse

The mouse autosomal dominant mutation Mody develops hyperglycemia with notable pancreatic beta-cell dysfunction. This study demonstrates that one of the alleles of the gene for insulin 2 in Mody mice encodes a protein product that substitutes tyrosine for cysteine at the seventh amino acid of the A chain in its mature form. This mutation disrupts a disulfide bond between the A and B chains and can induce a drastic conformational change of this molecule. Although there was no gross defect in the transcription from the wild-type insulin 2 allele or two alleles of insulin 1, levels of proinsulin and insulin were profoundly diminished in the beta cells of Mody mice, suggesting that the number of wild-type (pro)insulin molecules was also decreased. Electron microscopy revealed a dramatic reduction of secretory granules and a remarkably enlarged lumen of the endoplasmic reticulum. Little proinsulin was processed to insulin, but high molecular weight forms of proinsulin existed with concomitant overexpression of BiP, a molecular chaperone in the endoplasmic reticulum. Furthermore, mutant proinsulin expressed in Chinese hamster ovary cells was inefficiently secreted, and its intracellular fraction formed complexes with BiP and was eventually degraded. These findings indicate that mutant proinsulin was trapped and accumulated in the endoplasmic reticulum, which could induce beta-cell dysfunction and account for the dominant phenotype of this mutation.

Molecular and pharmacological characterization of dominant black coat color in sheep

Dominant black coat color in sheep is predicted to be caused by an allele ED at the extension locus. Recent studies have shown that this gene encodes the melanocyte stimulating hormone receptor (MC1-R). In mouse and fox, naturally occurring mutations in the coding region of MC1-R produce a constitutively activated receptor that switches the synthesis from phaeomelanin to eumelanin within the melanocyte, explaining the black coat color observed phenotypically. In the sheep, we have identified a Met-->Lys mutation in position 73 (M73K) together with a Asp --> Asn change at position 121 (D121N) showing complete cosegregation with dominant black coat color in a family lineage. Only the M73K mutation showed constitutive activation when introduced into the corresponding mouse receptor (mMC1-R) for pharmacological analysis; however, the position corresponding to D121 in the mouse receptor is required for high affinity ligand binding. The pharmacological profile of the M73K change is unique compared to the constitutively active E92K mutation in the sombre mouse and C123R mutation in the Alaska silver fox, indicating that the M73K change activates the receptor via a mechanism distinct from these previously characterized mutations.