Human insulin receptor beta-subunit transmembrane/cytoplasmic domain expressed in a baculovirus expression system: purification, characterization, and polylysine effects on the protein tyrosine kinase activity

We have expressed, purified, and characterized the insulin receptor protein tyrosine kinase (PTK) retaining the transmembrane and downstream domains. The proteins expressed in insect cells using a baculovirus expression system were identified as membrane-bound by immunofluorescence staining and biochemical characterization. One-step purification by immunoaffinity chromatography from Triton X-100 cell extracts resulted in a approximately 360-fold increase in the specific kinase activity with a yield of approximately 50%. An appMr = approximately 60,000 protein was the major component identified by both silver staining of the purified enzyme and immunostaining of the crude extracts after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Using nondenaturing conditions, the molecular weight was estimated to be approximately 250,000 and approximately 500,000 by glycerol gradient centrifugation and gel permeation chromatography, respectively, suggesting that oligomers of the beta-subunit domains such as tetramers and octamers are formed. The basal PTK activity of this enzyme was much higher than those of previously reported soluble-form insulin receptor PTKs expressed in insect cells or the native receptor. Km and Vmax for two substrates, src-related peptide and poly(Glu, Tyr) (4:1), were 2.4 mM and 2.5 mumol min-1 mg-1 and 0.26 mM and 1.2 mumol min-1 mg-1, respectively. Specific activities measured under two previously reported conditions using histone H2B as a substrate were 100 or 135 nmol min-1 mg-1, in contrast to those of soluble PTKs which were reported to be 20 or 70 nmol min-1 mg-1, respectively. The purified enzyme was autophosphorylated at Tyr residues. Autophosphorylation activated the enzyme approximately 3-fold.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequential combined tumorigenic effect of HPV-16 and chemical carcinogens

We immortalized oral keratinocytes by transfection with recombinant human papillomavirus type 16 (HPV-16) DNA and established two cell lines, human oral keratinocytes-16A (HOK-16A) and -16B (HOK-16B). These cell lines were morphologically different from the normal counterpart, contained HPV-16 DNA as integrated form and expressed numerous viral genes. However, these cells proliferated only in culture medium containing low calcium (0.15 mM) and are not tumorigenic in nude mice. To test the hypothesis that tumors can be developed by sequential combined effect of human papillomavirus and chemical carcinogens in the oral cavity, these immortalized cell lines were chemically transformed by exposure to either benzo[a]pyrene or methanesulfonic acid ethyl ester. Such transformants proliferated in medium containing physiological calcium levels (1.5 mM) and demonstrated enhanced growth potential in nude mice, whereas primary human oral keratinocytes treated with these chemical carcinogens failed to show any evidence of transformation. Chemically transformed cells contained integrated, intact HPV-16 sequences and transcribed significantly higher amount of HPV-16 E6/E7 messages and transforming growth factor-alpha (TGF-alpha) compared with the immortalized oral keratinocytes. Like the HPV-immortalized cell lines, the chemically transformed oral keratinocytes contained lower levels of newly synthesized, wild-type p53 proteins compared to normal cells, and expressed wild-type c-Ha-ras. These results indicate that this in vitro system is useful for investigating the mechanisms of multistep oral carcinogenesis.

In vitro and animal studies of the role of viruses in oral carcinogenesis

The linkage of herpes simplex virus (HSV) and human papillomavirus (HPV) to the development of oral cancer has been studied. In spite of the presence of viral nucleic acids in some human oral cancer specimens, HSV alone is not carcinogenic in animals: repeated viral inoculation to mouse or hamster oral mucosa fails to produce tumours or histopathological evidence of malignancy. However, HSV demonstrates co-carcinogenicity in vivo: viral inoculation significantly enhances the oncogenic capacity of chemical carcinogens in the oral cavity of mice and hamsters. Though the detailed mechanisms of HSV cocarcinogenicity are unknown, HSV promotes the chemical carcinogen-induced activation of certain cellular proto-oncogenes and inactivation of p53 tumour suppressor gene. Human papillomaviruses type 16 (HPV-16) and 18 (HPV-18) demonstrate oncogenicity by transforming normal human oral keratinocytes in vitro. While normal cells exhibit a limited life-span, cells transformed by these viruses show immortality and altered morphology in comparison with their normal counterparts. The HPV-immortalised cells contain multiple copies of intact viral genome integrated into cellular chromosomes. These cells also express several viral-specific mRNAs including viral E6/E7 mRNAs. Notably, these cells contain low levels of p53 protein and overexpressed cellular myc proto-oncogene compared to their normal counterpart; however, the immortilised cell lines are non-tumorigenic in nude mice.

Low p53 level in immortal, non-tumorigenic oral keratinocytes harboring HPV-16 DNA

The p53 protein level was determined in normal oral keratinocytes and two non-tumorigenic, immortal oral keratinocyte lines harboring human papillomavirus-16 (HPV-16)DNA. The p53 mRNA level in the immortal cells was higher than the normal counterpart, but the p53 protein level was notably lower in the immortalised cells. The half-life of p53 protein in the normal and immortal cells was < 1 h, and the p53 cDNA sequence of these cells showed no mutation. The immortal cells transcribed a high amount of E6/E7 mRNA encoded by HPV-16, but normal cells did not. These observations suggest that the immortal keratinocytes may translate normal level of wild-type p53 protein, and the low p53 level in these cells may be due to the enhanced degradation of the protein by HPV-16 E6 protein.

Long-term tolerance and efficacy of 3'-azidothymidine and 3'-fluorothymidine treatment of asymptomatic monkeys infected with simian immunodeficiency virus

Macaques chronically infected with simian immunodeficiency virus were treated with zidovudine (20 mg/kg of body weight per day for 9 weeks) or 3'-fluorothymidine (5 mg/kg of body weight per day for 9 weeks or three doses of 2 mg/kg per day for 24 days). Hematological changes in the treated animals included macrocytic anemia and leukopenia. Determination of antiviral effects in this model requires improved assay methods.

A monkey model for Epstein Barr virus-associated lymphomagenesis in human acquired immunodeficiency syndrome

High-grade malignant nonHodgkin's lymphomas--five lymphoblastic, three pleomorphic, and two immunoblastic--developed in 10/25 cynomolgus monkeys (Macaca fascicularis) followed for up to 746 d after infection with simian immunodeficiency virus, strain SIVsm. These lymphomas were shown to be associated with an Epstein-Barr (EB)-like cynomolgus B-lymphotropic herpesvirus (CBLV) by electron microscopy, by Southern blot hybridization with probes against human EBV, and by the expression of antigens corresponding to EBV-associated nuclear antigens (EBNAs) involved in human B cells transformation. Southern blot demonstration of immunoglobulin gene rearrangements and homogeneous EBV episomes indicated that all the lymphomas were CBLV-associated monoclonal B cell proliferations. Our findings suggest that these tumors correspond to the EBV-associated malignant lymphomas in acquired immunodeficiency syndrome with respect to clinical, morphological, phenotypic, and genotypic characteristics. The particular susceptibility of SIVsm immunodeficient cynomolgus monkeys for CBLV-associated lymphomagenesis appears therefore a useful model for EBV-associated lymphomas in humans.

Growth-stimulatory monoclonal antibodies against human insulin-like growth factor I receptor

Monoclonal antibodies (mAbs) against purified human placental insulin-like growth factor I (IGF-I) receptors were prepared and characterized. Three IgG mAbs were specific for the human IGF-I receptor and displayed negligible crossreactivity with the human insulin receptor. They stimulated 125I-labeled IGF-I (125I-IGF-I) or 125I-IGF-II binding to purified human placental IGF-I receptors and to IGF-I receptors expressed in NIH 3T3 cells in contrast to the well-studied mAb alpha IR-3, which inhibits 125I-IGF-I or 125I-IGF-II binding to both forms of IGF-I receptors. The mAbs introduced in this study stimulated DNA synthesis in NIH 3T3 cells expressing human IGF-I receptors approximately 1.5-fold above the basal level and the IGF-I- or IGF-II-stimulated level. In contrast, alpha IR-3 inhibited both basal and IGF-I or IGF-II-stimulated DNA synthesis by approximately 30%. Inhibition of IGF-II-stimulated DNA synthesis by alpha IR-3 was as potent as its inhibition of IGF-I-stimulated DNA synthesis, although IGF-II binding to the IGF-I receptors was not inhibited by IGF-II as potently as was IGF-I. With the purified IGF-I receptors, both inhibitory and stimulatory mAbs were shown to activate autophosphorylation of the IGF-I receptor beta subunit and to induce microaggregation of the receptors. These results suggest that conformational changes resulting from receptor dimerization in the presence of either type of mAb may affect the signal-transducing function of the IGF-I receptor differently. These additional mAbs and alpha IR-3 immunoprecipitated nearly 90% of IGF-I binding activity from Triton X-100-solubilized human placental membranes, indicating that IGF-I receptor reactive with these mAbs is the major form of the IGF-I receptor in human placenta.

Preliminary human trial of inactivated golden hamster kidney cell (GHKC) vaccine against haemorrhagic fever with renal syndrome (HFRS)

An inactivated golden hamster kidney cell culture (GHKC) vaccine against haemorrhagic fever with renal syndrome (HFRS) has been developed in recent years. A monovalent GHKC vaccine (lot 88-17) was prepared with L99 strain of the rat-type hantavirus, adapted in suckling mouse brain, cultivated in GHKC, and inactivated with 0.025% formalin, and a preliminary trial of the vaccine was carried out in a small number of human volunteers with the approval of the Ministry of Public Health, PRC, in order to identify safety and antibody response of the vaccine. Three inoculations were made on days 0, 7 and 28 respectively, by the intramuscular route with 1 ml vaccine each time for every volunteer. No obvious side effect was observed in vaccinees within 3 days after each inoculation. All 12 vaccinees (10 received three inoculations, and two received two inoculations of the vaccine) showed positive seroconversion of IgG antibody (by IFAT and ELISA) and neutralizing antibody (by enzyme focus reduction neutralization test, EFRNT), and 10 of them were still seropositive 180 and 360 days after the first inoculation. These results suggest that this vaccine would be safe for human use, and could effectively induce IgG and neutralizing antibody responses.

Role of thiol-disulfide exchange in insulin binding to its receptor

The effects of reduction by DTT, oxidation by DTNB and treatment with NEM on the thiol contents and insulin binding to its receptor in mice liver membranes were studied. Reduction with DTT leads to a parallel increase in the thiol content and the specific binding of insulin to the membrane. Scatchard analysis of the results shows little change in the number of binding sites but a twofold increase of the binding constant. Washing the membrane with bound insulin by a DTT containing buffer results in a more marked increase in the release of bound insulin than washing with buffer alone, suggesting that part of the insulin is bound to its receptor by covalent disulfide linkages through a thiol-disulfide exchange reaction and reduction with DTT leads to a marked increase in this "disulfide-linked" insulin. Treatment with DTNB or NEM of the DTT-reduced membrane seems to reverse the effect of DTT reduction, although the reaction of the untreated membrane with DTNB or NEM had little or no effect on the specific binding of insulin. It is suggested that initially, part of the thiols responsible for the exchange reaction may not be available for reaction with DTNB and reduction with DTT generates further thiols leading to increased specific binding in general and increased insulin binding to the receptor through covalent disulfide linkages in particular.

Effect of ibuprofen on the in vitro and in vivo reactivation of latent HSV-1

Prostaglandins have been suggested to play an important role in the reactivation of latent herpes simplex virus. To further understand the role of prostaglandins in the reactivation process, we investigated the effects of ibuprofen, a nonsteroidal anti-inflammatory drug with prostaglandin synthesis inhibitory activity, on the in vitro and in vivo reactivation of latent type 1 herpes simplex virus in mouse ganglia and rabbits, respectively. Ibuprofen, at a concentration of 50 or 100 microM, did not alter the titer of reactivated virus from explanted ganglia with latent virus, but, at a concentration of 200 or 500 microM, it significantly reduced the reactivated viral titer from the ganglia. Ibuprofen also directly inhibited the replication of herpes simplex virus in trigeminal ganglia and Vero cell monolayers, which indicates that the drug reduced the recovery of reactivated viral titers from explanted ganglia with latent virus by acting on the replication process rather than on the reactivation mechanism in vitro. The systemic administration of ibuprofen failed to demonstrate any significant effect on the ocular shedding of virus after attempted reactivation by 6-hydroxydopamine iontophoresis in rabbits with latent herpes simplex virus infection. This failure in vivo could be due to the short half-life and low concentration of ibuprofen at the site of reactivation and replication of latent virus. Alternatively, in the clinical setting, it is conceivable that ibuprofen may not have an effect on in vivo reactivation of latent herpes.

Malignant lymphoma associated with human AIDS and with SIV-induced immunodeficiency in macaques

Malignant lymphomas associated with human (HIV) and simian (SIV) immunodeficiency virus infections are reviewed and compared. Recent observation of a high frequency of lymphomas in a series of cynomolgus macaques, highly immunodeficient after infection with SIVsm(smm3) are described. In addition to the increased frequency in human and monkey AIDS, SIV and HIV lymphomas share several important features. Clinically and by histology they present as aggressive high-grade malignant tumors with a predilection for extranodal growth in viscera, skin, central nervous system, testis, and retroorbitally. Most malignant lymphomas are of B-cell origin. AIDS lymphomas in humans are heterogeneous with regard to Epstein-Barr virus (EBV) association. Similarly, most lymphomas in monkeys experimentally infected with SIV tested to date were shown to be associated with an EBV-like simian herpes virus. These observations point to the possibility of using SIV-immunodeficient macaques for study of EBV and other oncogenic and immunosuppressive factors in AIDS-associated lymphomagenesis.

Clinical features and predictive markers of disease progression in cynomolgus monkeys experimentally infected with simian immunodeficiency virus

OBJECTIVE

To study the pathogenicity of simian immunodeficiency virus (SIVsm) in cynomolgus monkeys in order to establish an animal model for human AIDS.

METHODS

Thirty-three cynomolgus monkeys were monitored for more than 2 years following experimental infection with SIVsm.

RESULTS

All the macaques became SIV-infected, as demonstrated by virus recovery from peripheral blood lymphocytes and by the appearance of viral antibodies. SIVsm was found to be pathogenic, killing 29 out of the 33 monkeys (88%) within 26 months. Clinically, infected monkeys developed lymphadenopathy, splenomegaly, diarrhoea, weight loss, neurological symptoms and a remarkably high incidence (39%) of malignant lymphomas. All lymphomas were high-grade malignant and of B-cell origin. Disease progression was associated with low CD4+ lymphocyte count, involution of initially hyperplastic follicular B-cell areas in lymph nodes, reappearance of viral antigen in serum, loss of anti-Gag antibodies and development of systemic giant cell disease in 55% of the monkeys.

CONCLUSIONS

There are many similarities between SIVsm-induced AIDS in cynomolgus monkeys and human AIDS with regard to clinical, virological, immunological and pathological manifestations.

Aggregation of IGF-I receptors or insulin receptors and activation of their kinase activity are simultaneously caused by the presence of polycations or K-ras basic peptides

Several groups including us reported that basic proteins and polycations activate the insulin receptor tyrosine-specific protein kinase (TPK) in vitro. However, some inconsistency has become obvious in the observations. The most intriguing was the brief description by Morrison et al. [(1989) J. Biol. Chem. 264, 9994-10001] that polylysine had no effect on the IGF-I receptor TPK despite its 84% identity to the insulin receptor TPK. In the present study, we used highly purified IGF-I and insulin receptor TPKs in an effort to solve the discrepancies noted in the recent publications and to reveal the mechanism by which polycations stimulate the receptor TPKs. We report that the IGF-I receptor TPK is stimulated by polycations and basic proteins in a manner similar to their effects on the insulin receptor TPK. When effects of polylysine and polyarginine on both receptor TPKs were closely compared, subtle qualitative differences were found: Polylysine stimulated autophosphorylation and exogenous substrate phosphorylation activities of both insulin receptor TPK and IGF-I receptor TPK similarly. In contrast, another polycation, polyarginine, affected both TPKs in a manner quite different from polylysine: Polyarginine stimulated insulin receptor autophosphorylation to a greater extent than polylysine did while it had a very small effect on the IGF-I receptor autophosphorylation as well as the exogenous substrate phosphorylation activities of the two receptor TPKs. We have further extended the studies to include the domains of natural proteins which contain a polylysine-like sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in the level of IL-2, T cell subsets and the function of T suppressor cells in patients with schistosomiasis japonica

The level of interleukin-2 (IL-2) produced by peripheral blood mononuclear cells in vitro, T cell subsets and the function of T suppressor cells (Ts) in patients with schistosomiasis japonica were investigated. It was found that the level of IL-2 induced by schistosomal antigens was significantly high and positively related to the percentage of CD4+ cells. In the groups of chronic and advanced schistosomiasis japonica, the level of IL-2 induced by schistosomal antigens was markedly lower than that in the group of acute schistosomiasis japonica, but significantly higher than that in the group of normal controls. The IL-2 level was negatively related to the percentage of CD8+ T cells and the ratio of CD4+/CD8+. The level of IL-2 induced by PHA was greatly reduced in the group of advanced schistosomiasis japonica. The changes in the level of IL-2 and its relationship with T cell subsets and the function of Ts are also discussed.

Immortalization of normal human oral keratinocytes with type 16 human papillomavirus

Primary human oral keratinocytes were transformed by transfection with recombinant human papillomavirus type 16 (HPV-16) DNA, and two transformed cell lines named human oral keratinocytes-16A and -16B (HOK-16A and HOK-16B) were established. While normal cells and cells transfected with vector only exhibited a limited lifespan, the HOK-16A and HOK-16B lines demonstrated immortality and altered morphology from their normal counterpart. The HOK-16A and HOK-16B lines contained approximately 40 and approximately 25 copies of intact HPV-16 DNA as integrated form per cell respectively, and both cell lines expressed several viral specific poly(A+) RNAs. Notably these cell lines also overexpressed cellular myc proto-oncogene in comparison with the normal counterpart. However, the immortalized cell lines were not able to produce tumors in nude mice, indicating that the cells are partially transformed. The HOK-16A and HOK-16B lines are, therefore, useful for investigating the multistep molecular events of oral carcinogenesis.

Patients treated with a monoclonal antibody (ab1) to the colorectal carcinoma antigen 17-1A develop a cellular response (DTH) to the "internal image of the antigen" (ab2)

The anti-tumor effector functions of unconjugated MAb in cancer therapy are not fully understood. Direct cytotoxic mechanisms have been demonstrated as well as induction of anti-idiotypic (ab2) and anti-anti-idiotypic (ab3) antibodies. If such a humoral response is induced, then an idiotypic cellular response would also be anticipated. Human monoclonal ab2s which mimic a tumor-associated antigen (TAA) (CO17-1A) of colorectal carcinoma (CRC) cells ("the internal image of the antigen") were produced. These ab2s were injected intradermally to patients with metastatic CRC who had been treated with the anti-colon carcinoma MAb 17-1A (ab1). Five out of 12 patients had a specific DTH (delayed-type hypersensitivity) reaction of the tuberculin type, which was proven by immunohistochemical analysis of skin biopsies. Serum ab3 was demonstrated in 4/4 tested DTH+ patients and also in 4 DTH patients. Control patients did not show any skin reactivity. Generation of an idiotypic response induced by the infused antibody (ab1) might be regarded as an active anti-tumor "vaccination". Induction of an idiotypic cellular and humoral cascade might be an important anti-tumor effector function of MAb and should be considered in future strategies for such therapy in cancer patients.

Monocyte/macrophage giant cell disease in SIV-infected cynomolgus monkeys

A non-opportunistic, generalized giant cell disease (GCD) was found in 12 out of 25 (48%) cynomologus monkeys infected with SIVsm. Most organs were affected notably the lymph nodes (LN), spleen, gut, liver, lungs and CNS. The multinucleated GC varied considerably in cell size and in the number and cytoplasmic distribution of the nuclei. Immunohistochemically most GC expressed SIV antigens and markers of mononuclear phagocytes (CD68), CD4 and also occasionally the T-cell markers CD45RO, CD43 and CD2. Monkeys with GCD had more pronounced immunosuppression with lower CD4-cell counts, more often demonstrable SIV antigen in the blood and LN and had been infected for a longer time period, as compared to monkeys without GCD. These findings show that SIV infection in cynomolgus monkeys is frequently associated with extensive formation of multinucleated GC of macrophage origin, which appears to be related to the pathogenesis of the infection and the degree of immunosuppression.

Synergism of herpes simplex virus and tobacco-specific N'-nitrosamines in cell transformation

Previous studies indicate that herpes simplex virus (HSV) enhances the carcinogenic activity of smokeless tobacco and tobacco-related chemical carcinogens in animals. Since tobacco-specific N'-nitrosamines (TSNAs) such as N'-nitrosonornicotine (NNN) and 4-(N-methyl-N'-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are major chemical carcinogens of smokeless tobacco and are known to be responsible for the development of oral cancers in smokeless tobacco users, the combined effects of TSNAs and HSV in cell transformation were investigated. Exposure of cells to NNN or NNK followed by virus infection resulted in a significant enhancement of transformation frequency when compared with that observed with chemical carcinogens or virus alone. This study suggests that TSNAs and HSV can interact together and show synergism in cell transformation.

Expression of MHC-class-I antigens in human carcinomas and sarcomas analyzed by isoelectric focusing

We analyzed the expression of class-I antigens in ex vivo human tumor cells by isoelectric focusing (IEF) the anti-class-I mAb W6/32 immunoprecipitates prepared from cell lysates. Out of 42 experiments, 27 were technically successful. The patient's blood lymphocytes were used as controls. In vitro exposure of the tumor cells to IFN gamma and TNF alpha elevated class-I antigen expression. In 11 cases, defects in MHC-class-I-antigen expression were observed. In 2 cases the antigens were detected only in the cytokine-treated tumor samples, probably due to a defect in the association between beta 2m and class-I heavy chains. Selective changes in the expression of alleles were seen in 10 cases and might involve HLA A, B and C antigens. Alterations in class-I expression as compared with the lymphocytes were observed in 9 of 13 cases in which the tumor cells were collected from metastases, and only in 2 of 14 primary tumors.

Functional characteristics of the intercellular adhesion molecule-1 (CD54) expressed on cytotoxic human blood lymphocytes

We have shown that intercellular adhesion molecule-1 (ICAM-1) (CD54) positive cells are mainly responsible for the natural cytotoxic function of human blood lymphocytes. The evidences were the inhibition of cytotoxicity by anti-ICAM-1 (LB-2) monoclonal antibodies (mAb) and the loss of lytic activity after removal of the ICAM-1+ cells. In addition, the cytotoxic potential of the separated ICAM-1- lymphocyte population after activation appeared in parallel with the expression of this molecule. The ICAM-1+ lymphocytes lysed both LFA-1 (CD11a/CD18 or Leu-CAMa) positive and negative cell lines, and pretreatment of the effectors with the LB-2 mAb also inhibited the lysis of LFA-1- targets. The results point to a yet unrecognized role of ICAM-1 on the lymphocytes. Kinetics experiments suggested that pretreatment of lymphocytes with alpha-ICAM-1 (LB-2) mAb did not inhibit the promptly established lytic interactions but influenced later events, recycling and/or recruitment of effectors. It is possible that the cytotoxic potential is regulated by contacts between the members of the lymphocyte population and that these events occur via their ICAM-1 and LFA-1. Exposure of lymphocytes to NK-sensitive targets for 16 hr elevated their cytotoxic potential. The function of activated lymphocytes was not inhibited by the LB-2 mAb.

Malignant lymphomas in cynomolgus monkeys infected with simian immunodeficiency virus

Malignant lymphomas were observed in 38% (9 of 24) of simian immunodeficiency virus (SIV)-infected cynomolgus monkeys (Macaca fascicularis) 5 to 15 months after inoculation with SIV strain SMM3. Lymphomagenesis in the SIV-infected monkeys was not related directly to the SIV-infectious dose given. All SIV-infected animals developed severe immunodeficiency. No significant difference in immunodeficiency was observed between tumor-bearing and non-tumor-bearing animals. In contrast, no lymphomas were observed in a comparable group of HIV-2-infected monkeys, which did not develop immunodeficiency; nor did the noninfected control monkeys. All 9 SIV-related tumors were high-grade B-cell lymphoblastic or pleomorphic lymphomas with extranodal, disseminated growth. Most tumors showed marked infiltration by monocytes and CD8+ T lymphocytes. Occasional tumor infiltrating cells showed immunohistochemical reaction for SIV. The cells of two tumors were established in vitro and shown to be of B-cell phenotype. The tumor cell cultures showed no reverse transcriptase activity and no evidence of virus infection by electron microscopy. Our observations indicate that SIV-induced immunodeficiency in cynomolgus monkeys also mimics HIV infection and AIDS in humans with regard to increased lymphomagenesis and type of lymphomas.

Molecular cloning and nucleotide sequence of the beta-lytic protease gene from Achromobacter lyticus

Two bacteriolytic enzymes secreted by Achromobacter lyticus M497-1 were purified and identified as being very similar (considering their amino acid composition and N-terminal sequence) to alpha- and beta-lytic proteases from Lysobacter enzymogenes. A 1.8-kb EcoRI fragment containing the structural gene for beta-lytic protease was cloned from A. lyticus chromosomal DNA. The protein sequence deduced from the nucleotide sequence was identical to the known sequence of beta-lytic protease, except for six residues. The nucleotide sequence revealed that the mature enzyme is composed of 179 amino acid residues with an additional 195 amino acids at the amino-terminal end of the enzyme, which includes the signal peptide, thus indicating that the enzyme is synthesized as a precursor protein.

Marfan syndrome in China: a collective review of 564 cases among 98 families

This is a collective review of 564 patients with Marfan syndrome among 98 pedigrees reported from 18 provinces and cities in China over a 37-year period from 1951 to 1987. A positive family history of Marfan syndrome was found in 74.3% of the patients: the mode of inheritance was dominant in 73.8% and recessive in 0.5%. Sporadic cases occurred in 25.7%. A screening of 29,067 children found five children with Marfan syndrome, giving a prevalence of 17.2 per 100,000 of the population, a gene frequency of 8.61 per 100,000 genes, and a penetrance of 71.69%. Pleiotropy was clear in these cases: arachnodactyly in 77%, ectopia lentis in 86.8%, and dilated aortic root in 80.1%. Chromosome examination showed no regular aberrations except in a family of five in whom a giant-satellited chromosome 14 was found in three afflicted members but not in the two unaffected relatives. The high prevalence of aortic root dilation in Marfan syndrome makes echocardiography the most useful and practical means of diagnosis. Close follow-up and regular echocardiographic evaluation are indicated not only in patients with Marfan syndrome but also in their families, for both diagnostic and therapeutic purposes.