Complementing amino acid substitutions within loop 6 of the alpha/beta-barrel active site influence the CO2/O2 specificity of chloroplast ribulose-1,5-bisphosphate carboxylase/oxygenase

Photosynthesis-deficient mutant 45-3B of the green alga Chlamydomonas reinhardtii contains a chloroplast mutation that causes valine-331 to be replaced by alanine within the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. This amino acid substitution occurs in loop 6 of the alpha/beta-barrel active site, three residues distant from catalytic lysine-334. The mutation reduces the specific activity of the enzyme and also reduces its CO2/O2 specificity factor by 42%, but the amount of holoenzyme is unaffected. In a previous study, an intragenic-suppressor mutation, named S40-9D, was selected that causes threonine-342 to be replaced by isoleucine, thereby increasing the CO2/O2 specificity of the mutant enzyme by 36%. To determine which other residues might be able to complement the original mutation, nine additional genetically independent revertants have now been analyzed. Another intragenic suppressor, represented by mutation S61-2J, causes glycine-344 to be replaced by serine. This change increases the CO2/O2 specificity of the mutant enzyme by 25%. Of the revertants recovered and analyzed, the mutant enzyme was improved only due to true reversion or by intragenic suppression mediated by substitutions at residues 342 or 344. Changes in the physical properties of the two pairs of complementing substitutions indicate that steric effects within loop 6 are responsible for the observed changes in the CO2/O2 specificity of the enzyme.

Stimulation of proteinase and amidase activities in Porphyromonas (Bacteroides) gingivalis by amino acids and dipeptides

Proteolytic enzymes from the organism Porphyromonas gingivalis are believed to be involved in the development of periodontitis. Studies on both crude extracts and purified trypsinlike enzymes from this organism indicate that substantial stimulation of both amidase and proteinase activities can be obtained during incubation with glycine-containing compounds. We postulate that P. gingivalis may have developed this unusual property to take advantage of the glycine-rich environment which occurs during the periodontitis-associated degradation of gingival collagen. The finding of such a stimulation in crevicular fluids from discrete periodontal sites has been correlated with the presence of P. gingivalis and could be utilized for the early detection of infection by this organism during the onset of periodontitis.

[Expression of protooncogenes c-myb and c-myc during the hexamethylene bisacetamide (HMBA)-induced commitment to terminal differentiation of murine erythroleukemia cells]

Modulation of a number of protooncogene expression occurs during differentiation of eukaryotes. Changes in expression of c-myb and c-myc during the HMBA-induced terminal differentiation of murine erythroleukemia cells were characterized by an early decrease (within 4 hrs), followed by the recovery of c-myc mRNA by 10 hrs, and the retention of suppression of c-myb expression for the rest of the induction period. Two MELC variants were used to further define the relationship between the differentiation and the protooncogene expression. R1 was a MELC variant completely resistant to HMBA, and R1 (VCR), a vincristine resistant R1, became inducible by HMBA again. The cell differentiation and the c-myb and c-myc expression were determined on R1 or R1 (VCR) cultured with HMBA respectively. The results demonstrated that the c-myc mRNA increased and remained relatively high as the cells grew to a saturated density regardless of the induction of differentiation. The R1 (VCR) cultured with HMBA displayed an early decrease in c-myb mRNA and a subsequent suppression of its expression, while the R1 cultured with HMBA showed a stable level of c-myb mRNA. These results suggest that the c-myb expression, rather than c-myc expression, is closely related to the HMBA-induced terminal differentiation.

Suppressive effect of high energy shock waves on tumor cells

Suppressive effect on tumor cells of high energy shock waves (HESW) has aroused the interest of physicians in recent years. We assessed experimentally the cytotoxic effects of HESW on tumor cells both in vitro and in vivo and determined whether a Chinese domestic lithotriptor is capable of generating effective HESW, which has the potential to break tumor cells, reduce cell viability, retard cell growth, delay doubling time, impair cell attachment and cell clonogenicity. In nude rats, HESW was able to delay tumor growth and reduce tumor size without evidence of metastasis. The nature of HESW in the induction of cell damage and its clinical application need to be further investigated.

[Effect of colchicine on rat neuromuscular transmission]

The function of the microtubules (MTs) beneath the postsynaptic membrane was studied in the isolated non-uniform stretched muscle preparation of rat diaphragm with the use of colchicine. After exposure to this drug, the amplitude of miniature endplate potential (MEPP), the mean quantal contents and mean amplitude of endplate potentials (EPPs) elicited by 10 Hz and 50 Hz stimulation and the amplitude of acetylcholine potentials (AChP) were decreased significantly, but the frequency of MEPP, membrane potential and the time course of EPP and AChP remained unchanged. These results indicate that colchicine suppresses the responses of acetylcholine receptors (AChR). No such effects were observed with colchicine's isomer lumicolchicine. It is suggested that the MTs beneath the postsynaptic membrane may be involved in the responsive process of AChR.

[Retinoic acid and 12-0-tetradecanoylphorbol-13-acetate (TPA) inducing bipotent differentiation of cultured primary bone marrow cells from leukemia patients]

The in vitro differentiation of cultured primary bone marrow cells from patients with acute promyelocytic leukemia (M3) and chronic myelocytic leukemia (CML) induced by retinoic acid (RA) and TPA was studied. The results indicated that both the M3 and CML bone marrow cells bipotently differentiated into either myeloid or macrophage-monocytic lineage in response to the inducers. On M3 cells the effect of TPA was more potent than RA, and TPA could inhibit the phenotype of myeloid terminal differentiation induced by RA but not vice versa. However, RA could overcome the TPA-induced inhibition of myeloid terminal differentiation of CML cells. These experiments provide a useful model for studying the molecular mechanism of hematopoietic cell differentiation.

Antihypertensive effect of synthetic tetrandrine derivatives in SHR rats

1. Effects of oral administration of synthetic tetrandrine (TD) derivatives (20 mg/kg per day) for 9 weeks on blood pressure, heart rate, plasma renin concentration (PRC) and vascular reactivities to pressor substances were studied in spontaneously hypertensive (SHR) rats. 2. 7-O-Ethyl fangchinolin (7-O-EFC) and 7-O-isopropyl fangchinolin (7-O-IFC) produced a significant and sustained reduction in blood pressure from the first week of administration. 7-O-EFC reduced heart rate when determined under restraint conditions, but not under unanesthetized, freely moving conditions. 3. TD derivatives produced no effect on PRC. 4. Pressor response to phenylephrine was reduced significantly whereas the response to angiotensin II was enhanced after prolonged administration of 7-O-EFC and 7-O-IFC. 5. These results demonstrate that TD derivatives are potential antihypertensive drugs, and that attenuation of the pressor response to phenylephrine may contribute at least in part to its antihypertensive effect.

Nuclear mutation restores the reduced CO2/O2 specificity of ribulosebisphosphate carboxylase/oxygenase in a temperature-conditional chloroplast mutant of Chlamydomonas reinhardtii

The Chlamydomonas reinhardtii temperature-sensitive mutant 68-4PP results from a mutation within the chloroplast gene that encodes the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase. When grown at the permissive temperature (25 degrees C), the mutant has a reduced level of holoenzyme protein, and the purified enzyme has a lower CO2/O2 specificity than the wild-type enzyme. At the nonpermissive temperature (35 degrees C), the holoenzyme level is greatly reduced, and the mutant is unable to grow photosynthetically. When photosynthesis-competent revertants of 68-4PP were selected at 35 degrees C, a nuclear mutation was identified that suppresses the temperature-sensitive phenotype by enhancing both the activity and amount of the mutant enzyme. More significantly, the reduced CO2/O2 specificity of the 68-4PP enzyme is restored to the wild-type value. However, the nuclear suppressor mutation alone does not produce a phenotype different from wild type, and the CO2/O2 specificity of the suppressor strain's enzyme is normal. We have cloned and completely sequenced the two small-subunit genes from the suppressor strain, but no mutation has been found. These results suggest that some other nuclear-encoded protein is able to influence the structure of the holoenzyme, which in turn influences the CO2/O2 specificity factor.

Relationship between hormone profiles and the restoration of spermatogenesis in men treated with gossypol

Gossypol acetic acid was administered orally to 35 male volunteers at a dose of 20 mg once a day for 52-70 days in the loading phase and twice a week for 22 months in the maintenance phase. Sperm counts and the serum concentrations of LH, FSH, prolactin, testosterone and oestradiol were monitored regularly during treatment and for a follow-up period of 12 months. At around 90 days after treatment, all treated participants approached or attained azoospermia and remained at this level throughout the maintenance phase. By the end of the follow-up phase, eight treated men were still azoospermic, while sperm counts in the other 27 men were restored to normal levels. The only hormone that changed significantly during and after the treatment was FSH. From the 6th month of the treatment to the end of the follow-up phase, serum concentrations of FSH in the eight participants that reached irreversible azoospermia were significantly higher than in the other 27 men or in controls. It is suggested that monitoring of FSH levels might be of diagnostic use for identifying those participants with irreversible azoospermia during gossypol treatment.

Conversion of differentiation inducer resistance to differentiation inducer sensitivity in erythroleukemia cells

Hexamethylene bisacetamide (HMBA) is a potent inducer of differentiation of murine erythroleukemia cells (MELC). Commitment, the irreversible initiation of the program of terminal-cell differentiation, is first detected in HMBA-sensitive DS19-SC9 MELC in culture after 10 to 12 h of exposure to HMBA. Vincristine (VC)-resistant MELC derived from the DS19-SC9 MELC line display increased sensitivity to HMBA and become committed with little or no latent period. In the present study, we showed that the MELC line R1, which is resistant to HMBA-mediated differentiation, became sensitive to inducer if selected for a low level of VC resistance (less than 10 ng of VC per ml). Four independently derived VC-resistant cell lines from HMBA-resistant R1 cells, designated R1[VCR]a to R1[VCR]d, acquired sensitivity to HMBA and the accelerated kinetics of commitment that are characteristic of VC-resistant MELC derived from the parental DS19-SC9 cells. The calcium channel blocker verapamil suppresses the VC resistance of R1[VCR] cells but does not alter the accelerated response to HMBA. In R1[VCR] cells there was no detectable increase in the level of the 140-kilodalton P-glycoprotein. Transient inhibition of protein synthesis during the latent period delays inducer-mediated commitment of VC-sensitive DS19-SC9 MELC but does not alter the accelerated commitment kinetics of R1[VCR]a cells. Previously, we have reported evidence that protein kinase C beta (PKC beta) plays a role in HMBA-induced MELC differentiation and that compared with DS19-SC9 cells, R1 cells have a relatively low level and R1[VCR]a cells have a high level of PKC beta. These findings suggest that (i) acquisition of VC resistance overcomes the block acquired by R1 cells to HMBA-mediated differentiation; (ii) the accelerated kinetics of HMBA-induced commitment of VC-resistant MELC is not dependent on the verapamil-sensitive transport channel that is responsible, at least in part, for resistance to VC; (iii) in VC-resistant MELC, there is constitutive expression or accumulation of a protein required for HMBA-induced differentiation; and (iv) an elevated level of PKC beta activity may play a role in the altered response of R1[VCR] and other VC-resistant MELC to HMBA.

Structure and hypotensive activity relationships of tetrandrine derivatives in stroke-prone spontaneously hypertensive rats

1. Structure and hypotensive activity relationships of tetrandrine (TD), an alkaloid isolated from the Chinese herb Radix stephaniae tetrandrae and its derivatives were investigated in conscious stroke-prone spontaneously hypertensive rats (SHRSP). 2. Derivatives substituted at the 7-O position with various types of alkyl group produced varying degrees of hypotensive effect. 3. While the demethylated derivative, fangchinoline (FC), and its acetylated compound had no effect on blood pressure, 7-O-methyl FC (TD), and 7-O-ethyl and 7-O-isopropyl FC at oral doses of 25 and 50 mg/kg produced a gradual and sustained hypotensive effect without any significant effects on heart rate and plasma renin concentration. 4. Substitution at the 7-O position with longer side chains such as n-propyl, n-butyl and n-pentyl groups reduced both the degree and duration of hypotensive activity. 5. Substitution of N-methyl groups at the 2 and 2' positions with quaternary ammonium or N-oxide attenuated the hypotensive activity. 6. The results of this study suggest a possibility that 7-O-ethyl and 7-O-isopropyl derivatives as well as TD can be considered as potential antihypertensive drugs because of the gradual onset and long duration of their hypotensive action in SHRSP.

[A survey on Campylobacter jejuni high infection in a nursery]

An epidemiologic survey on Campylobacter jejuni infection in a nursery was made in April 1987. It was found that there was a spread of C. jejuni high infection. Two cooks affected by enteritis of C. jejuni were considered to be a reservoir of the infection. Stool cultures were positive for C. jejuni in 43 out of 187 children, with a positive rate of 23%. Eight of the 43 had diarrhea and the others were asymptomatic carriers (24.3%). Controls were set up in another nursery with 238 healthy children and 201 non-diarrheal outpatients; C. jejuni was positive for 11.4% and 7.5%, respectively. The difference was quite significant (P less than 0.005). Results of biotyping on the strains isolated from the two cooks and the children in the nursery showed that all were of C. jejuni biotype 1, except two (4.7%) of the strains from the children, which were E. coli. The authors have suggested that transmission of C. jejuni in the nursery may be caused by contaminated food or person-to-person contact.

[Effects of nebulized distilled water on tracheal reaction in asthmatic patients]

To investigate the mechanism of bronchial spasm induced by inhalation of ultrasonically nebulised distilled water (UNDW) ultrasonically nebulised solutions including hypoosmolar (distilled water, 0.3% NaCL) isoosmolar (0.9% NaCL) and hyperosmolar solutions (2.7% NaCL, 3.6% NaCL, 4.6% KCL 22.2% dextrose) were used for challenge test in 12 asthmatic patients and 10 healthy subjects as controls. The dose of solution required to induce a 20% reduction in FEV 1 (FD 20-FEV 1) was recorded. In another 10 asthmatic patients, a challenge with UNDW was conducted after pretreatment with sodium cromoglycate (SC), Ipratropine Bromide (IB) to investigate the protective effect of the two medicines. The results showed that distilled water and three hyperosmolar solutions which were of the same osmotic pressure (3.6% NaCL, 4.6% KCL and 22.2% dextrose) were most potent in inducing bronchoconstriction, and no significant difference in PD 20-FEV 1 was found among them 0.3% and 2.7% NaCL were next and 0.9% NaCL was the least potent. Normal subjects showed no response to the solutions. The SC gave significant protection to nine of the ten patients, and IB gave it to five of the ten. Our results indicate that a change in the osmolarity of the fluid lining the respiratory tract may be an important determinant of the airway response; sodium cromoglycate which inhibits the mediator release of mast cell can reduce the airway response to UNDW.

[Synovial chondromatosis]

24 cases of synovial chondromatosis were examined including 16 males and 8 females of 22-64 yrs of age. The lesions were located in the knee (16), hip (4) and elbow (4) joints. All cases were treated surgically. The number of cartilaginous nodules and joint mice removed from each joint ranged from 2 to 689. The authors emphasize that the diagnosis could not be definitely established unless multiple foci of cartilaginous metaplasia were found in biopsy of the synovial membrane and that complete removal of cartilaginous nodules and joint mice was essential for successful treatment. Since the disorder is self-limiting, local synovectomy is adequate in most cases and total or subtotal synovectomy is indicated only in cases with extensive synovial membrane involvement. If the synovial membrane is normal, simple removal of joint mice is enough.

Heterogenous response of primary cultured bone marrow cells of patients with different varieties of leukemia to differentiation inducers

The in vitro induced differentiation of a number of human leukemia cell lines by chemical inducers not only provides a valuable model system for the study on the mechanism of hematopoietic cell proliferation and differentiation at both cellular and molecular levels, but also reveals a new prospect in the treatment of leukemia. In order to find out the possibility of applying inducing agents to the patients with various types of leukemia, the bone marrow cells in primary culture from 50 patients with leukemia were tested for their inducibility in response to the inducers. Only M3 leukemia bone marrow cells can be markedly induced by retinoic acid to the myeloid terminal cells with positive NBT reduction while the cells of other types respond with uncertainty. TPA is able to cause a macrophage-like differentiation in bone marrow cells of all types of leukemia except M1. However, the leukemic cells of chronic myelogenous leukemia in lymphocytic blast crisis will lose response to TPA. The cultured bone marrow cells of acute lymphocytic leukemia respond neither to retinoic acid nor to TPA. Homoharringtonine, a chemotherapeutic drug used in the so-called HOAP regimen for acute nonlymphocytic leukemia, seems to possess the capability of inducing HL-60, the promyelocytic leukemia cell line, to NBT positive myeloid terminal cells, although the inducing effect is weaker than retinoic acid.

[Survey of Campylobacter jejuni/coli infection and risk factors in children]

From March to May 1987, 798 children under 7 years of the outpatients in Chengdu district were examined and their stool samples cultured for Campylobacter jejuni/coli. C. jejuni/coli was isolated from 31 (9.51%) of 326 children with diarrhea and 22 (4.66%) of 472 children with non-diarrhea. The difference was significant (P less than 0.05). This result indicated that C. jejuni/coli is an important pathogen of children diarrhea in Chengdu district. Meanwhile, by inquiry we investigated risk factors related with C. jejuni/coli infections. Case group was consisted of 53 children with C. jejuni/coli positive. For each case, 3 controls were chosen from 745 children with C. jejuni/coli negative and matched according to age (less than 6 month), sex, living place (city or countryside), way of feeding, and whether to have diarrhea or not. The results has shown that contact with animals a week before being ill and habit of intake of food with hands are risk factors of C. jejuni/coli infection of childhood in Chengdu, with an odd ratio of 2.97 and 2.71 respectively. This provides valuable information about the prevention of C. jejuni/coli infection.

Chloroplast intragenic suppression enhances the low CO2/O2 specificity of mutant ribulose-bisphosphate carboxylase/oxygenase

The competition between CO2 and O2 at the active site of ribulose-1,5-bisphosphate carboxylase/oxygenase limits net CO2 fixation in photosynthesis. In the green alga Chlamydomonas reinhardtii, a mutation in the chloroplast large-subunit gene reduces the CO2/O2 specificity of the enzyme by 37% and causes valine-331 to be replaced by alanine. Revertant selection identified an intragenic suppressor mutation that increases the CO2/O2 specificity of the mutant enzyme by 33%. This second-site mutation causes threonine-342 to be replaced by isoleucine. The complementing amino acid substitutions flank a catalytically essential lysyl residue at position 334. It thus appears that a number of amino acid residues can influence the CO2/O2 specificity of this bifunctional enzyme. The well defined chloroplast genetics of C. reinhardtii allows the interactions of these residues to be investigated.

Reduced CO2/O2 specificity of ribulose-bisphosphate carboxylase/oxygenase in a temperature-sensitive chloroplast mutant of Chlamydomonas

The Chlamydomonas reinhardtii chloroplast mutant 68-4PP is phenotypically indistinguishable from wild type at 25 degrees C but fails to grow photosynthetically at 35 degrees C. It had about 30% of the wild-type level of ribulose-1,5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39) holoenzyme and carboxylase activity when grown at 25 degrees C, but less than 15% when grown at 35 degrees C. Pulse-labeling with 35S showed that the decrease in enzyme level at the restrictive temperature was not a result of reduced synthesis of enzyme subunits. The CO2/O2 specificity factor (VCKO/VOKC, where VC and VO are Vmax values for carboxylation and oxygenation and KC and KO are Km values for CO2 and O2) of the mutant enzyme was found to be significantly less than that of the wild-type enzyme (54 +/- 2 and 62 +/- 1, respectively), and this alteration was accompanied by increases in KO and KC and a decrease in VC/VO. DNA sequencing revealed a single missense mutation in the 68-4PP chloroplast large-subunit gene. This mutation causes leucine to be replaced by phenylalanine at position 290 in the large-subunit polypeptide sequence. These results (i) support previous studies that implicated this region of the large subunit as an important structural component of the enzyme's function and (ii) demonstrate that chloroplast genetic modification of the CO2/O2 specificity factor of a plant-type carboxylase/oxygenase is feasible.

Metabolic products of microorganisms. 243. Pyridazomycin, a new antifungal antibiotic produced by Streptomyces violaceoniger

Pyridazomycin, a new antifungal antibiotic produced by Streptomyces violaceoniger sp. griseofuscus (strain Tü 2557), was detected in a selective screening against Mucor hiemalis (Tü 179/180). The amino acid side chain of 1 can be seen as L-ornithine, whose gamma-nitrogen atom is part of a pyridazine ring building a quaternary ammonium system. The structure of 1 was established by spectroscopic analysis of the parent compound and degradation products. The occurrence of a pyridazine ring in microbial secondary metabolites is unique.

[Treatment of male breast cancer]

From Mar. 1958 through 1985, 50 male patients with breast cancer were treated in our hospital. The ratio of male and female with primary breast cancer was 1:90 during the same period. All were proven by pathology except one case. Forty seven have been followed for more than 5 years. There were 12 stage I lesions, 19 stage II and 16 stage III. Radical mastectomy was performed in 22 patients, total mastectomy in 11 and lobectomy in 12, supplemented by radiotherapy, chemotherapy, hormonal therapy or their combination. Two were not indicated for surgery and were only given a combination combination therapy without operation. The irradiation after radical mastectomy was to deliver to the regional lymph nodes and for the rest, a dose of 5,000-6,000 cGy/5-6 weeks should be added to the chest wall. The chemotherapy, including Thio-TEPA, 5-fluorouracil, cyclophosphamide and methotrexate etc, in the form of single or multi-drug for 1-3 courses, was given. The overall 5 and 10 year survival rates were 51% and 22.5%. The 5 year survival rates of stage I, II and III patients were 83%, 53% and 25%. The 5 year survivals of radical mastectomy, total mastectomy and lobectomy combined with radiotherapy, chemotherapy and hormonal therapy were 59%, 27% and 67%. In those who failed, 50% developed local recurrence or regional metastasis or both and 60% had extensive dissemination. The results indicate that the combination therapy comprising radical mastectomy and lobectomy has a good prognosis. The authors believe that the male breast cancer is more hormone-dependent than the female breast cancer, orchiectomy plays an important role in the treatment of advanced lesions.

[Radioimmunodetection of human lung cancer xenografts by isotope labeling monoclonal antibody ALT-04 in nude mice]

Three nude mouse models bearing the human lung cancer were established from two fresh surgical specimens and one cell line. Tumor histological structure and cell morphology were similar before and after transplantation. The monoclonal antibody ALT-04 (McAb ALT-04) against human lung cancer was labeled by 125I, 131I and 201Tl. Radioimmunodetection study showed that all the three kinds of xenografts in nude mice were specifically located by McAb ALT-04. Imaging examination confirmed the ability of isotope labeling McAb ALT-04 to detect the presence of transplanted human lung cancer tissues without the aid of background subtraction manipulations. It is suggested that McAb ALT-04 have the possibility of locating in the tumor diagnosis and guiding in the treatment.