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PubMed1986

Studies on glutamine synthetase from Streptomyces hygroscopicus var. jinggangensis.

Streptomyces hygroscopicus var. jinggangensis produces validamycin, an important antibiotic used in agriculture. It was found that there was a positive correlation between the specific activity of mycelial glutamine synthetase (GS) and validamycin biosynthesis in our laboratory. So, in this paper, the purification, characteristics and regulatory properties of GS are reported. The native enzyme had a molecular weight of approximately 530,000 and was composed of 12 identical subunits, each 43,000. Electronic microscopic examination of preparations negatively stained disclosed that the subunits were arranged in two hexagonal rings that lay one on top of the other in a face-to-face fashion. Mg2+ or Mn2+ was absolutely needed as cofactor for GS activity. The enzyme activity was regulated by feedback inhibition and cumulative feedback inhibition. In addition, it was also regulated through a covalent modification, adenylylation and deadenylylation, suggesting that the covalent modification of GS exists not only in Gram-negative bacteria but also in some Gram-positive bacteria.

Chromatography, High Pressure Liquid↗
PubMed1993

Cauliflower mosaic virus gene I product (P1) forms tubular structures which extend from the surface of infected protoplasts.

Immunofluorescent staining of Chinese cabbage protoplasts infected with cauliflower mosaic virus (CaMV) showed different patterns of staining when antibodies raised against virus particles or antibodies specific for the CaMV movement protein (P1) were used. Anti-virion serum showed that particles accumulated as small discrete aggregates within the cytoplasm of infected protoplasts. In contrast, anti-P1 serum identified long thread-like structures extending from the protoplast surface. The same structures were seen when protoplasts were isolated from infected plants and held in culture. Electron microscopical examination after immunogold labeling and negative staining of protoplasts revealed some extracellular tubular structures which labeled with anti-P1 and which contained virus particles. Western blot analysis of isolated tubules showed them to be composed of the full-length P1 but not the smaller P1 products detected in infected tissues or protoplasts. The time course of P1 accumulation in infected protoplasts paralleled the accumulation of virus coat protein, as measured by immunofluorescence microscopy, and did not indicate that P1 was an early gene product as has been suggested for other virus movement proteins.

Blotting, Western↗
PubMed1991

[Pathological study of carbohydrate antigens in human lung cancer with monoclonal antibodies].

The expressions of carbohydrate antigens were examined with panel of specific anti-carbohydrate monoclonal antibodies (MAbs) on human lung cancer tissues. The MAbs used were SH1, SH2, SNH3, AH6, CA3F4, TKH2, TKH6 and TKH5 which define Lex, dimeric Lex, sialosyl Lex, Ley, Lea, sialosyl Tn, Tn and fucosyl GM1, respectively. Paraffin-embedded tissue sections (30 squamous cell carcinomas, 30 adenocarcinomas and 27 small cell carcinomas) were tested by immunohistological staining. Evaluation of stained specimens was performed by taking mean value of scores evaluated by three independent examiners. In squamous cell carcinoma, expression of Ley, sialosyl Tn, sialosyl Lex and Lea was significantly higher than other antigens. Lex was also expressed especially in keratinized tissues. In adenocarcinoma, Lea was expressed most remarkably. Sialosyl Lex, Ley, sialosyl Tn were also highly expressed in malignant cells. There was no significant difference in staining patterns between well and poorly differentiated adenocarcinomas. Sialosyl Tn and sialosyl Lex were positive in morphologically normal mucous glands adjacent to tumors. In small cell carcinomas, Ley was expressed more than other types of tumors, whereas Lex and sialosyl Tn were less than others. Tn antigen was observed throughout adenocarcinomas, squamous and small cell carcinomas in a relatively weak manner. Dimeric Lex and fucosyl GM1 antigens were not detected. Most of normal lung sections showed negative staining with those MAbs. These findings indicate that there are differential expressions of certain carbohydrate antigens in different types of human lung cancers based on their origins.

Adenocarcinoma↗
PubMed2001

Paramyxovirus infection in caiman lizards (Draecena guianensis).

Three separate epidemics occurred in caiman lizards (Dracaena guianensis) that were imported into the USA from Peru in late 1998 and early 1999. Histologic evaluation of tissues from necropsied lizards demonstrated a proliferative pneumonia. Electron microscopic examination of lung tissue revealed a virus that was consistent with members of the family Paramyxoviridae. Using a rabbit polyclonal antibody against an isolate of ophidian (snake) paramyxovirus, an immunoperoxidase staining technique demonstrated immunoreactivity within pulmonary epithelial cells of 1 lizard. Homogenates of lung, brain, liver, or kidney from affected lizards were placed in flasks containing monolayers of either terrapene heart cells or viper heart cells. Five to 10 days later, syncytial cells formed. When Vero cells were inoculated with supernatant of infected terrapene heart cells, similar syncytial cells developed. Electron microscopic evaluation of infected terrapene heart cells revealed intracytoplasmic inclusions consisting of nucleocapsid strands. Using negative-staining electron microscopy, abundant filamentous nucleocapsid material with a herringbone structure typical of the Paramyxoviridae was observed in culture medium of infected viper heart cells. Seven months following the initial epizootic, blood samples were collected from surviving group 1 lizards, and a hemagglutination inhibition assay was performed to determine presence of specific antibody against the caiman lizard isolate. Of the 17 lizards sampled, 7 had titers of < or =1:20 and 10 had titers of >1:20 and < or =1:80. This report is only the second of a paramyxovirus identified in a lizard and is the first to snow the relationship between histologic and ultrastructural findings and virus isolation.

Animals↗
PubMedDate not supplied

[Effect of formaldehyde on the ribonucleoprotein structure of Sendai virus].

The effect of formaldehyde on the conformation of Sendai virus ribonucleoprotein (RNP) was studied by electron microscopy and a spectrophotometric method. The effect of formaldehyde on RNP conformation was found to depend strongly on the ionic strength of the solution. Under conditions of a low ionic strength in the presence of 1.5% formaldehyde the tightly coiled rods of RNP stained with uranyl acetate become loosely coiled or almost completely extended. At the same time, formaldehyde reaction with RNP results in a decrease in extinction of the RNP suspension in the 250 to 290 spectral region. However, RNP incubation with formaldehyde in the presence of 0.5M NaCl caused no changes in the morphology and spectral properties of the RNP under study. The results indicate that formaldehyde cannot be used for fixation of Sendai virus nucleocapsids before negative staining for electron microscopy examinations.

Formaldehyde↗
PubMed2004

Co-downregulation of PTEN, KAI-1, and nm23-H1 tumor/metastasis suppressor proteins in non-small cell lung cancer.

The multistep process of carcinogenesis implies the accumulation of multiple molecular defects. Alteration of tumor suppressor and metastasis suppressor genes are the important steps. Increasing experimental evidence indicates that decreased expression of tumor-metastasis/suppressor genes and gene products are involved in the progression of a variety of human malignancies. In the present study, we have extended this analysis to non-small cell lung carcinomas (NSCLC). The expression and prognostic significance of the tumor suppressor gene PTEN and metastasis suppressor genes nm23-H1 and KAI-1 was evaluated in NSCLCs. Immunohistochemical staining was performed on formalin-fixed, paraffin-embedded tissues from 53 bronchogenic adenocarcinomas and 51 squamous cell carcinomas using monoclonal antibodies against PTEN, nm23H-1, and KAI-1 proteins. Immunohistochemical results were correlated with tumor stage, grade, lymph nodes positivity, metastasis, and patient survival. Significant co-expression of PTEN, nm23-H1 and KAI-1 was observed in NSCLC (P<.001 to .002). The immunohistochemical expression of these proteins was significantly higher in stages 1 and 2 compared with stages 3 and 4 (P=.04 for PTEN and KAI-1, P=.039 for nm23-H1). When all stages were considered together, loss of immunoreactivity for PTEN, nm23-H1 and KAI-1 was found in advanced NCSCLs (P=.015 for PTEN, P=.001 for KAI-1, P=.004 for nm23-H1), which is suggestive of co-downregulation of these proteins in the process of tumor progression. On multivariate analysis, negative staining for PTEN (P=.014), KAI-1 (P=.034), and nm23-H1 (a trend toward association for nm23-H1 reached near significance P=.08) correlated with disease-related death. Positive lymph node status was associated with negative immunostaining for PTEN (P=.007) but no correlation was observed for nm23-H1 and KAI-1. Loss of expression was linked to distant metastasis (P=.006 for PTEN, P=.002 for nm23H1, P=.001 for KAI-1). On multivariate analysis, co-downregulation of PTEN (P=.009), KAI-1 (P=.02), and nm23-H1 (P=.011) independently predicted shortened survival in NSCLC. Although NSCLC exhibits strong co-expression of PTEN, nm23-H1 and KAI-1, there is a loss of these proteins in high-stage tumors. Co-downregulation of PTEN, KAI-1, and nm23-H1 significantly correlates with distant metastasis and predicts shortened survival. Our study supports a role of these tumor suppressor and metastasis suppressor genes in the evolution and progression of NSCLC.

Adult↗
PubMed1993

Fusion of dioleoylphosphatidylcholine vesicles induced by an amphiphilic cationic peptide and oligophosphates at neutral pH.

Peptide E5 is an analogue of the fusion peptide of influenza virus hemagglutinin and K5 is a cationic peptide which has an arrangement of electric charges complementary to that of E5. We reported that a stoichiometric mixture of E5 and K5 caused fusion of large unilamellar vesicles (LUV) of neutral phospholipids (Murata, M., Kagiwada, S., Takahashi, S. and Ohnishi, S. (1991) J. Biol. Chem. 266, 14353-14358). K5 caused fusion of LUV composed of dioleoylphosphatidylcholine (DOPC) at pH > 10, but not at neutral pH. In the presence of oligophosphates, such as 1 mM ATP, GTP, or polyphosphate, K5 caused rapid and efficient fusion of DOPC LUV at neutral pH without hydrolysis of oligophosphate groups, but another anions such as citrate, acetate, AMP, phosphate, or EDTA were ineffective. The peptide/oligophosphate-induced fusion behaviors have been investigated by a fluorescence resonance energy transfer assay for lipid mixing of LUV and negative staining electron microscopy. At higher ionic strengths ( > 0.3 M KCl) or in the presence of 5.0 mM MgCl2, the fusion was inhibited. Even at the inhibitory conditions, the association of K5 with lipid vesicles at neutral pH was directly confirmed by the Ficoll gradient assay method and by blue shifts of the tryptophan fluorescence of the peptide. A nonhydrolyzable GTP analogue, GTP gamma S, also induced fusion. These observations suggested that the electrostatic interactions between the positive and negative charges of K5 and oligophosphate, respectively, induced complex formation, triggering membrane fusion.

Adenosine Triphosphate↗
PubMed1990

Choice of reference assay for the detection of rotavirus in fecal specimens: electron microscopy versus enzyme immunoassay.

Two previously demonstrated sensitive and specific enzyme immunoassays (EIAs) for rotavirus, one using polyclonal and monoclonal antisera (TestPack Rotavirus [TPK]; Abbott Laboratories) and the other using only monoclonal anti-rotavirus antibodies (Rotaclone [RTC]; Cambridge BioScience Corporation), were evaluated as potential reference assays for rotavirus testing in comparison with direct negative-staining electron microscopy (EM), the current laboratory standard. Two hundred and seven stool samples collected consecutively during the winter of 1989 from children with acute diarrhea admitted to a ward for infants from 0 to 2 years of age were tested by the EIAs and by EM. TPK specimens were read visually; RTC results were read spectrophotometrically. Specimens with discordant EIA and EM results were further evaluated by a fluorescent focus assay. Specimens positive by EM and those negative by EM but positive by fluorescent focus assay were considered to be positive for rotavirus. Of the 207 stools tested, 35 (17%) were positive for rotavirus by these criteria. EM had a sensitivity of only 80%. Specificities were 100% for RTC and EM and 89% for TPK. These findings indicate that EM, although very specific, is relatively insensitive compared with a highly sensitive monoclonal antibody-based EIA. An EIA with high sensitivity and specificity, such as RTC, is a more appropriate reference standard for rotavirus testing.

Acute Disease↗
PubMed1992

Correlation of expression of H/Le(y)/Le(b) antigens with survival in patients with carcinoma of the lung.

BACKGROUND: The level of expression of H/Le(y)/Le(b) antigens is high in various histologic types of lung cancer, a feature that may be related to deletion of A and B blood-group antigens. We evaluated the possibility that expression of this antigen, which can be defined by the monoclonal antibody MIA-15-5, might be of prognostic value, as suggested by our previous observation that MIA-15-5 inhibits tumor-cell motility and metastasis. METHODS: We used MIA-15-5 to stain tissue sections from 149 patients with primary lung cancer whose clinico-pathological histories were well documented. The survival curves for patients whose tumors stained positively were compared with the curves for those whose tumors stained negatively. Multivariate analyses were performed with a Cox proportional-hazards regression model. RESULTS: Among the 149 patients studied, five-year survival in the 91 patients with MIA-positive tumors was significantly lower than survival in the 58 with MIA-negative tumors (20.9 percent vs. 58.6 percent, P less than 0.001). Among the 67 patients with squamous-cell carcinoma, the rates also differed significantly (10.5 percent vs. 62.1 percent, P less than 0.001). The difference in survival between patients with MIA-positive tumors and those with MIA-negative tumors was significant among patients with blood groups A and AB (P less than 0.001), but not among those with blood group B or O (P = 0.071 and 0.068, respectively). Multivariate analysis with the Cox regression model indicated that positivity best correlated with five-year mortality, followed by lymph-node status (N stage) and tumor size status (T stage), whereas sex, age, and blood group did not correlate with mortality. CONCLUSIONS: Positivity for MIA (i.e., immunohistologic staining by MIA-15-5, which defines H/Le(y)/Le(b) antigens) is inversely correlated with survival among patients with primary lung cancer and may be of prognostic value.

ABO Blood-Group System↗
PubMed2000

Molecular detection of Mycobacterium tuberculosis in tissues showing granulomatous inflammation without demonstrable acid-fast bacilli.

Early diagnosis of tuberculosis (TB) is important for early medical intervention and prevention of spread of the bacteria. It is not uncommon to observe granulomatous inflammation but without demonstrable acid-fast bacilli (AFB) on Ziehl-Neelsen (ZN) staining in tissues sent for histologic examination, and the definitive diagnosis of TB cannot be made because no concurrent tissue is sent for TB culture. In this study, the authors explored the feasibility of using polymerase chain reaction (PCR) for early detection of Mycobacterium tuberculosis (Mtb) in formalin-fixed, paraffin-embedded tissues where a definite diagnosis of TB cannot be made. One hundred fifteen patients (131 paraffin blocks of biopsy specimens) with granulomatous inflammation but ZN-negative for AFB were studied. DNA was extracted from paraffin sections and amplified by PCR with the IS6110 primers (specific for the Mtb complex) and the specific 122-base pairs (bp) PCR product was detected by agarose gel electrophoresis. Sixty-eight of the 115 (59%) patients were TB-PCR positive, thus enabling definite diagnosis of TB in significant numbers of these patients in 3 days. The authors conclude that molecular diagnosis by PCR is useful for early detection of TB in histologic material where morphologic features are suggestive but not confirmatory because of negative staining for AFB.

Adolescent↗
PubMed1986

Influence of phospholipids on the formation and stability of vimentin-type intermediate filaments.

The interaction of vesicles produced from individual phospholipids and mixtures thereof with preformed vimentin filaments as well as the influence of these vesicles on filament assembly were investigated employing negative stain electron microscopy and sucrose density gradient equilibrium centrifugation. Liposomes with a phospholipid composition characteristic of Ehrlich ascites tumor cells were able to bind efficiently to vimentin filaments without significantly affecting their morphology at higher concentrations. However, in sucrose density gradient centrifugation partial disintegration of the filaments was observed. In addition, larger quantities of phospholipid mixture totally blocked intermediate filament (IF) formation. Using vesicles of individual phospholipids, these effects could be shown to be due to the presence of negatively charged lipid species in the phospholipid mixture. While these were highly active in preventing filament assembly and in dissociating preformed filaments, electrically uncharged phospholipids were virtually inactive. The highest efficiency was shown by phosphatidylinositol-4,5-diphosphate. These results demonstrate that a negative surface charge of liposomes is an essential prerequisite for their successful and tight association with vimentin filaments. However, the high susceptibility of these filaments to photoaffinity labeling with the membrane-penetrating reagent 1-azidopyrene in the presence of phospholipid vesicles, points to additional interactions between hydrophobic regions of both reactants. Finally, the data also suggest a direct relationship between IFs and the lipid bilayer as the active principle underlying the association of IFs with natural membranes as observed by electron and immunofluorescence microscopy.

Animals↗
PubMed2000

Jejunal adenocarcinoma presenting as a primary ovarian carcinoma.

OBJECTIVE: The aim of this case report was to evaluate the impact of immunohistochemical markers in diagnosing the primary site of adenocarcinoma in the abdominopelvic region. METHODS: Surgicopathologic data were obtained from laparotomy and necropsy. Paraffin-embedded tissue from the ovary and jejunum was stained with hematoxylin and eosin, as well as with immunohistochemical stains for cytokeratin 20 and cytokeratin 7. RESULTS: A 53-year-old African American woman underwent an emergency laparotomy due to small bowel obstruction. During the operation, in addition to a complex adnexal mass as the cause of obstruction, a small solid jejunal tumor was also identified. Pathologic evaluation of the two sites demonstrated an infiltrating moderately to poorly differentiated adenocarcinoma with mucinous features. The malignant cells from both intestinal and ovarian sites showed immunoreactivity for cytokeratin 20 and revealed negative staining for cytokeratin 7. These results confirmed the diagnosis of intestinal primary with ovarian metastasis, which was initially misdiagnosed as an ovarian primary. CONCLUSION: Given the potential difficulty in determining the primary site of these tumors, immunohistochemistry proved to be a useful tool in reaching the correct diagnosis.

Adenocarcinoma↗
PubMed1986

Ultrastructure and chemical composition of lipopolysaccharide extracted from Leptospira interrogans serovar copenhageni.

Lipopolysaccharide (LPS) from Leptospira interrogans serovar copenhageni was prepared from the aqueous phase of a phenol/water extract. Electron microscopic examination of negatively stained LPS showed a mixture of ribbon-like, round and ring structures. Carbohydrate analysis of the preparations revealed pentoses, hexoses, heptoses, hexosamines, and a 2-keto-3-deoxyonic acid which was chromatographically different from authentic 2-keto-3-deoxyoctonic acid (KDO). The major fatty acids of the LPS were hydroxylauric, palmitic and oleic acids. Although the leptospiral LPS preparations did not contain KDO or hydroxymyristic acid, they were otherwise morphologically and chemically similar to the LPS of other Gram-negative bacteria.

Chemical Phenomena↗
PubMed2006

HLA class I expression in metastatic melanoma correlates with tumor development during autologous vaccination.

Our knowledge of the mechanisms underlying tumor-specific immune response and tumor escape has considerably increased. HLA class I antigen defects remain an important tumor escape mechanism since they influence the interactions between tumor cells and specific T and NK cells in the course of malignant disease. We have studied here HLA class I expression in six subcutaneous metastases obtained from a melanoma patient immunized with an autologous melanoma cell vaccine (M-VAX). We report in this paper that HLA class I antigen expression on these metastatic lesions strongly correlated with the course of the disease. The three metastases that were partially regressing at the time of their excision showed a strong HLA class I expression, whereas the progressing ones showed a very weak or negative staining with most of the anti-HLA class I mAbs used. Real-time quantitative PCR of the samples obtained from microdissected tumor tissue revealed a significant difference in the mRNA levels of HLA-ABC heavy chain and beta2m between the two types of metastases, i.e., lower levels in progressing metastases and high levels in regressing ones, confirming the immunohistological findings. This is, to our knowledge, the first report where the clinical outcome of different HLA class I positive and negative melanoma metastases can be clearly correlated with the regression and progression of the disease, respectively.

Cancer Vaccines↗
PubMed1988

Ruthenium red staining reveals surface fibrils and a layer external to the cell wall in Streptococcus salivarius HB and adhesion deficient mutants.

Ruthenium red staining revealed both the long and short classes of cell surface fibril in thin sections of Streptococcus salivarius HB, indicating that the fibrils contained polyanionic polymers, probably polysaccharides. Also visible was a 16.2 +/- 2.2 nm thick ruthenium red staining layer (RRL) outside the 16.7 +/- 2.2 nm thick cell wall. The fibrils could not be seen after conventional glutaraldehyde and osmium fixation. The RRL was protease resistant and was not involved in septum formation. Loss of the fibrils after protease treatment coincided with a decrease of 54% in cell surface hydrophobicity, indicating that cell surface hydrophobicity was due partly to fibrils and partly to the RRL. There was no correlation between the lengths of fibrils as measured on whole cells after negative staining and on thin sections of ruthenium red stained cells. The thickness of the RRL was the same in three adhesion deficient mutants--strains HB-7, HB-V5 and HB-V51--with various fibril lengths. However, a completely bald mutant, HB-B, had a significantly thicker RRL than S. salivarius HB, although it was unable to adhere to buccal epithelial cells, and it could not co-aggregate with Veillonella parvula V1. The RRL therefore did not contain adhesins.

Bacterial Adhesion↗
PubMed2007

Sentinel lymph node biopsy improves staging in early cervical cancer.

OBJECTIVES: The main study objective was to describe the distribution of sentinel lymph nodes (SLNs) and the prevalence of SLN micrometastases in patients with early cervical cancer. The secondary objective was to confirm the SLN detection rate and negative predictive value found in our preliminary study. PATIENTS AND METHODS: We prospectively included 25 patients with early cervical cancer, each of whom received an injection of 120 MBq of technetium-99m for preoperative lymphoscintigraphy and intraoperative node detection using an endoscopic gamma probe. Patent blue dye was injected intraoperatively. SLNs were sought in the pelvic and para-aortic drainage areas. Radical iliac dissection was performed routinely at the end of the procedure. SLNs were examined after hematoxylin-eosin-saffron staining; negative specimens were assessed using immunohistochemistry. RESULTS: Most (85%) of the SLNs were in the inter-iliac territory. Para-aortic or parametrial SLNs were found respectively in 2 patients and common iliac SLNs in 5 patients. Thus 9/25 patients had additional information due to SLN detection. One metastasis and one micrometastasis were detected in SLNs. No patients had positive non-sentinel nodes with negative SLNs. CONCLUSION: SLN detection ensures the identification of SLNs in unusual locations in 36% of patients. SLN disease was found in 8% of our patients. Thus, SLN biopsy improves staging in patients with early cervical cancer. Studies in larger patient populations are needed to evaluate the clinical impact of SLN biopsy.

Adenocarcinoma↗
PubMed1984

Polyhistidine mediates an acid-dependent fusion of negatively charged liposomes.

Polyhistidine facilities the fusion of negatively charged liposomes prepared by sonication. Liposome fusion was demonstrated by (a) negative-stain electron microscopy, (b) gel filtration, and (c) resonance energy transfer of the fluorescent phospholipids. Liposome fusion required the presence of polyhistidine, whereas histidine at equivalent concentrations had no effect. Little or no liposome fusion was detectable at pH 7.4, but it was greatly enhanced when the pH of the medium was reduced below 6.5. Although acidic phospholipid is necessary for fusion, liposomes made of acidic lipids alone showed only low levels of fusion activity. Liposomes composed of mixtures (1:1) of a negatively charged phospholipid and a neutral phospholipid such as phosphatidylcholine and phosphatidylethanolamine (PE), but not sphingomyelin, showed high levels (about 80%) of fusion competency. For liposomes made of PE/phosphatidylserine (PS) (1:1), fusion at pH 5.2 and 2.5 micrograms/mL polyhistidine resulted in an increase in the average liposome diameter from 296 to 2400 A, indicating multiple rounds of fusion had occurred. Liposome fusion was not very leaky as revealed by the lack of release of encapsulated calcein. For PE/PS (1:1) liposomes, about 10% of dye leakage was observed for up to about 30% liposome fusion and about 45% leakage at 80% liposome fusion. Since polyhistidine becomes a strong polycation at acidic pH, liposome fusion may be a direct result of the bilayer phase separation induced by the binding of polyhistidine with the negatively charged phospholipids. Therefore, this phenomenon is similar to the liposome fusion induced by other polycations such as polylysine at neutral pH.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy Transfer↗
PubMed1981

High-resolution electron microscopy of glycoproteins: the crystalline cell wall of Lobomonas.

Lobomonas piriformis is a member of an order of green algae (Volvocales) that have crystalline glycoprotein cell walls. As part of a program of investigation of these glycoproteins and their architecture we have studied the cell wall of Lobomonas by a variety of chemical, electron-microscopical and image-analysis techniques. Lobomonas and Vitreochlamys incisa show a very similar structure in their cell walls and represent I of the 4 classes into which all the structures of the wall of these algae that we have so far examined fall. The 2 classes that we have previously studied in detail, represented by Chlamydomonas reinhardii and chlorogonium elongatum, have a crystalline component of the wall that is a more or less smooth continuous surface overlying an amorphous inner wall layer. Although Lobomonas also has this 2-layer structure, the crystalline layer consists of distinct plates, each of which is built around a single, very coherent crystal lattice. The polar nature of the architecture of the cell wall is shown by sectioning and by examination of the cell-wall surface by metal-shadowing of carbon replicas, both of intact cells and of isolated cell-wall plates. There are great similarities in chemical composition between the glycoproteins of the cell wall of C. reinhardii and those of Lobomonas. Both has a large content of hydroxyproline in their amino acid composition and a sugar/hydroxyproline ratio of about 6.0, and both contain sugar sulphates. Lobomonas however has a large glucose content, whereas Chlamydamonas has almost none. Electron micrographs of walls stained with methylamine tungstate and shadowed specimens show that the Lobomonas crystal structure is entirely different from that of C. Reinhardii, and that there is a distinctly different structure in the centre of the plates from that at their edges, although the transition between the 2 areas occurs with no distortion of the crystal lattice. Computer image analysis has been used to calculate reconstructed images of the 2 areas, and by using minimal-dose techniques has yielded 2-dimensional maps of the negatively stained structure at a resolution of I.8 nm. The 2-sided plane group of both areas of the crystal is P2, and the centre area contains 2 distinct structural units, both centered on dyad axes, together with other more complex features. In the edge structure, one of the structural units appears unchanged, but the other unit has a considerably different appearance. The most likely interpretation of this is as a conformational or positional change in one of the subunits. However, because the underlying lattice is so accurately maintained across this transition, it seems probable that the basic structural arrangement that defines the lattice is common to the 2 areas. Some of the computational and mathematical techniques used in the image analysis have not been previously published and are described in detail and compared with published techniques in an Appendix.

Cell Wall↗