Nucleotide base sequence of the mitochondrial COIII gene of Schizophyllum commune

The cytochrome oxidase subunit III gene (COIII) of the Badidiomycete S. commune has been identified, cloned, and sequenced. The gene contains no introns, is AT-rich (69%) and exhibits a high degree of similarity to sequences from Ascomycetes. While most mitochondrial genes use both TGA and TGG to specify tryptophan, the COIII gene of Schizophyllum uses TGG exclusively. Translation requires no deviation from the universal code.

Canthaxanthine-induced retinal pigment epithelial changes in the cat

Canthaxanthine retinopathy in humans is a retinal crystalline deposition associated with ingestion of canthaxanthine, an over-the-counter oral tanning agent. In this study cats were fed doses of canthaxanthine varying from 2 mg/kg/day (an equivalent standard human dose) to 16 mg/kg/day for up to six months. Indirect opthalmoscopy showed progressive development of an orange sheen in the retina overlying the tapetum lucidum without evidence of crystal formation. Electroretinograms performed at one and two months showed no significant change from baseline examination. On light and transmission electron microscopic examination, the retinal pigment epithelium of the experimental animals showed an increase in cell height and a regional vacuolization due to an enlargement and disruption of some phagolysosomes and the development of cytoplasmic spaces. These observations suggest that further studies should be conducted on humans who ingest canthaxanthine to assess structural and functional alterations, especially in the pigment epithelium.

Perisilicone proliferation after vitrectomy for proliferative vitreoretinopathy

From 1983 to 1986, silicone oil injections were used to treat 31 patients with retinal detachment (RD) and advanced proliferative vitreoretinopathy (PVR). In 19 eyes (61%), perisilicone proliferation (PSP) developed causing recurrent RDs in 15 eyes (49%). At an average of 5 weeks after surgery, PSP occurred and was characterized by extensive transparent preretinal membranes with denser focal areas. Microscopic examination of five preretinal membranes showed droplets of silicone oil and necrotic cells on the silicone side and glial or retinal pigment epithelial cells, or both, on the retinal side, often in layers separated by extracellular matrix. Silicone oil was present in periretinal membranes removed several months after the intraocular silicone had been evacuated indicating that silicone within cells may persist despite the removal of silicone. The use of silicone oil to provide tamponade in eyes with recurrent PVR is associated with a high incidence of periretinal proliferation that frequently leads to recurrent RD and visual failure.

Acute sensory neuropathy-neuronopathy from pyridoxine overdose

We report two patients who developed an acute, profound, and permanent sensory deficit after treatment with massive doses of parenteral pyridoxine. Aside from rapid onset, their clinical picture resembles that described in chronic pyridoxine neurotoxicity. It also is consonant with experimental models of acute pyridoxine intoxication and is probably secondary to a sensory ganglion neuronopathy. These patients also had transient autonomic dysfunction, mild weakness, nystagmus, lethargy, and respiratory depression. These previously undocumented features may be attributable to either the preservative used in the parenteral pyridoxine preparation or to the exceptionally high doses of pyridoxine these patients received.

Site-directed mutagenesis of core sequence elements 9R', 9L, 9R, and 2 in self-splicing Tetrahymena pre-rRNA

The intron within the Tetrahymena thermophila nuclear large rRNA precursor is the best studied example of group I self-splicing introns. In this paper, we examine the structural and functional roles of four internal sequence elements which are characteristic of group I introns in the RNA-catalyzed processing reactions. Oligonucleotide-directed mutagenesis was used to generate mutations in sequence elements 9R', 9L, 9R and 2 of the Tetrahymena intervening sequence. Self-splicing activities of variant precursor RNAs were characterized by in vitro splicing following transcription with T7 or SP6 RNA polymerase. First, we confirm the proposed base pairing of sequence elements 9R and 9R' by construction and analysis of compensatory mutations. Mutations in elements 9R (G272A C274G) and 9R' (G100C C102U) each disrupt the pairing and eliminate self-splicing activity. A compensatory 9R/9R' mutation (G100C C102U G272A C274G) restores pairing and normal splicing activity. We conclude that 9R X 9R' pairing is a requirement for self-splicing. Second, we show that self-splicing activity is very sensitive to both nucleotide sequence and RNA secondary structure in the pairing segments of elements 9L and 2. Mutations within these regions at positions 266, 268, 307, and 309 can increase as well as decrease activity relative to wild type. Third, a mutation in the highly conserved nonpairing segment of element 9L (U259A A261C) increases KM for GTP from 29 to 120 microM, but does not otherwise affect splicing activity. The primary consequence of this mutation is a decrease in GTP binding energy of approximately 0.9 kcal/mol. Last, we show that a mutation in the highly conserved nonpairing segment of element 2 (A301C A302G G303C) eliminates transesterification activity, but does not affect 3' splice site hydrolysis.

Structural conventions for group I introns

Conventions for nomenclature of structural elements and a standard secondary structure representation for group I introns have been established by workers in the field. These conventions are designed to facilitate effective communication of information concerning the structure and function of these self-splicing introns.

Effect of silicone oil on experimental traction retinal detachment

The use of silicone oil as a retinal tamponade in the treatment of proliferative vitreoretinopathy is often complicated by membrane reproliferation. We studied the development of traction retinal detachments following the intravitreal injection of 15,000 retinal pigment epithelial cells in silicone-, perfluoropropane-, and fluid-filled rabbit eyes. By 28 days a higher proportion of silicone-filled eyes (83%) had severe proliferative vitreoretinopathy than either the perfluoropropane-filled (30%) or fluid-filled (10%) eyes. An in vitro proliferation assay using the vitreous samples showed that the silicone-filled vitreous had increased mitogenic activity for retinal pigment epithelial cells compared with the gas-filled or fluid-filled vitreous. Silicone oil appears to increase proliferation by stimulating the release of more or different mitogenic factors as well as by concentrating active factors into a smaller volume near the retina.

Vitreous macrophage elicitation: generation of stimulants for pigment epithelium in vitro

Vitreous and macrophage samples were tested for the ability to stimulate proliferation and cell migration in cultured rabbit retinal pigment epithelium (RPE). A macrophage invasion was elicited by the intravitreal injection of latex particles in rabbits and after 3 days the vitreal macrophages were collected. The macrophages themselves, macrophage-conditioned culture medium, and macrophage-incubated vitreous had modest effects on RPE proliferation, but significantly stimulated RPE migration. A portion of the migration activity may be due to macrophage-derived proteases acting on normal vitreous. Mitogenic and additional migration-stimulating activity may also arise from adjacent tissues or from a breakdown of the blood-vitreous barrier that accompanies a macrophage invasion. A macrophage ingress into the vitreous may provide part of the stimulation for the migration and proliferation of RPE in conditions such as proliferative vitreoretinopathy.

Titanium retinal tacks with pneumatic insertion. Histologic evaluation in rabbits

Titanium retinal tacks were implanted through the formed vitreous into the posterior retinas of rabbits and evaluated by electroretinographic testing and by light microscopy at intervals after implantation. Tritiated thymidine autoradiography was used to evaluate the proliferation of ocular tissues in response to tack insertion. Within one month after implantation, the retinal tacks were surrounded by scar tissue produced by the proliferation of retinal glial cells and choroidal and scleral connective tissue cells. The tissue response was focal and there was no excessive fibrous tissue or vascular proliferation or any indication of iris neovascularization for six months. The observations of firm retinal adherence and low tissue reactivity suggest that titanium tacks can be used to secure the retina during retinal attachment surgery and can remain permanently in the eye.

Development of traction retinal detachments following intravitreal injections of retinal Muller and pigment epithelial cells

We injected varying numbers of retinal Muller glia into the rabbit vitreous in an established model of traction retinal detachment. We used indirect ophthalmoscopy to observe the changes elicited during the following 1 month. Although the severity of the tractional changes increased with increasing numbers of the glial cells, the pathology produced stabilized within the 1st week of injury. Muller glia were less effective at eliciting retinal detachments than retinal pigment epithelial cells (RPE) or mixtures of glia and RPE. Intravitreal tissue membranes derived from the glia differed morphologically from those derived from RPE. The glial membranes had fewer fibroblast-like cells, synthesized less extracellular matrix, and showed lower intravitreal cell proliferation, as determined by 3H-thymidine radioautography. Our findings indicate that membranes composed only of Muller glial cells promote less severe retinal pathology than those membranes composed of RPE or mixed cell types.

Role of conserved sequence elements 9L and 2 in self-splicing of the Tetrahymena ribosomal RNA precursor

Oligonucleotide-directed mutagenesis has been used to alter highly conserved sequences within the intervening sequence (IVS) of the Tetrahymena large ribosomal RNA precursor. Mutations within either sequence element 9L or element 2 eliminate splicing activity under standard in vitro splicing conditions. A double mutant with compensatory base changes in elements 9L and 2 has accurate splicing activity restored. Thus, the targeted nucleotides of elements 9L and 2 base-pair with one another in the IVS RNA, and pairing is important for self-splicing. Mutant splicing activities are restored by increased magnesium ion concentrations, supporting the conclusion that the role of the targeted bases in splicing is primarily structural. Based on the temperature dependence, we propose that a conformational switch involving pairing and unpairing of elements 9L and 2 is required for splicing.

The nonexpansile, equilibrated concentration of perfluoropropane gas in the eye

Bubbles of 100% perfluoropropane (0.4 ml) were injected into the vitreous cavities of 31 New Zealand White rabbits. Gas bubbles were aspirated from eyes at six and 12 hours and at one, two, three, four, five, seven, nine, and 14 days, and were analyzed by gas chromatography. The nonexpansile concentration of perfluoropropane (found at maximum expansion of the gas bubble at four days) was approximately 12%. The gas bubble concentration equilibrated at seven days with a perfluoropropane concentration of approximately 10% with little change through 14 days. Using a similar protocol, we injected 0.56-ml bubbles of 100% perfluoropropane into the vitreous cavities of three owl monkeys. When sampled on day 4 for analysis by gas chromatography, results were comparable to the rabbit data. A 12% concentration of perfluoropropane should approximate the ideal composition of a gas mixture for a total fluid-gas exchange. This would achieve complete retinal tamponade without later compromise of intraocular pressure by further expansion.

Clinicopathologic results of vitreous surgery for epiretinal membranes in patients with combined retinal and retinal pigment epithelial hamartomas

Two patients (a 44-year-old woman and a 26-year-old man) with progressive visual loss associated with macular combined retinal-retinal pigment epithelial hamartomas underwent pars plana vitrectomies with peeling of macular epiretinal membranes. Histopathologic findings for one of the membranes were similar to those in idiopathic or other secondary epiretinal membranes. Although the epiretinal membranes were satisfactorily removed, visual acuity improved in neither eye. Fluorescein angiography showed persistence of vascular tortuosity and leakage and cystoid macular edema after surgery in both cases. One eye developed a late postoperative operculated retinal tear which was successfully treated with cryopexy. The role of vitrectomy and membrane removal in cases of macular combined retinal-retinal pigment epithelial hamartomas appears to be limited.

Plasma cortisol and corticosterone concentrations in the golden hamster, (Mesocricetus auratus)

Because some recent studies of hamster adrenocortical function have depended on older studies that may have been inadequate or misinterpreted, the present study re-examined plasma corticosterone and cortisol concentrations in hamsters under several conditions to determine which plasma glucocorticoid predominated in this animal. Sensitive radioimmunoassays were used to measure separately the two glucocorticoids in the basal condition, after adrenocorticotropin (ACTH) treatment, after acute stress, and after chronic stress. In the basal condition, corticosterone concentrations were 3-4 times higher than those of cortisol. After stimulation, this difference disappeared, but rarely were any hamster's cortisol levels higher than their corticosterone levels. Both ACTH and acute stress elevated plasma corticosterone and cortisol concentrations, but only plasma cortisol concentrations were elevated following chronic stress. The dissociation between cortisol and corticosterone concentrations after chronic stress suggests that the two glucocorticoid hormones in the hamster may be regulated independently. The data also indicate that both corticosterone and cortisol should be measured when assessing adrenocortical function in the hamster.

Synthesis of (+/-)-ariensin

Ariensin, a lignan occurring in the exudate of the bark of BURSERA ARIENSIS has been synthesized by a short stereospecific pathway. Dihydrocubebin which occurs in CLEISTANTHUS COLLINUS and PIPER GUINEENSE was also obtained as an intermediate in the reaction sequence.

Neurosyphilis in the antibiotic era

Among 30 patients with neurosyphilis diagnosed between 1970 and 1981, 43% had symptoms attributable to neurosyphilis, 43% had unrelated symptoms, and 14% were asymptomatic. Serum VDRL was positive in 86%, and the CSF VDRL was positive in 53%. Meningovascular and vascular syphilis were relatively more common than in the prepenicillin era; tabes dorsalis and general paresis were unchanged in relative frequency.

Induction of DNA synthesis by co-culture of retinal glia and pigment epithelium

Retinal glia (RG) and retinal pigment epithelial cells (RPE) have been previously identified in intravitreal cellular membranes of patients with proliferative vitreoretinopathy (PVR). This study was undertaken to determine if the co-presence of both cell types might lead to increased membrane growth due to some heterotypic cell interactions that enhance cell proliferation. Cell proliferation in co-cultures of RPE plus RG, RPE plus dermal fibroblasts (DF), or RG plus DF was evaluated by quantitation of labeled nuclei in radioautographs prepared from monolayer co-cultures exposed to 3H-thymidine. In each co-culture, one cell type was premarked by phagocytosis of latex particles so that the cells could be identified and the labeling rates in each cell type could be assessed. In co-cultures of RPE and RG, both cell types exhibited a higher labeling rate. In RG-DF co-cultures, DF-labeling was increased, but RG-labeling was unaffected or suppressed. Co-culture of RPE and DF did not affect labeling in either cell type. Studies of conditioned media suggested that RG stimulate RPE and DF by means of a product secreted into the culture medium by the RG. Further, cell-cell contact might modulate the growth response at least for RG. The interaction of RPE and RG in co-culture differed from the interaction of either cell type with DF in that the co-culture of RPE and RG resulted in a higher apparent proliferation rate for both cell types. If similar interactions occur in vivo, the presence of both types of retinal cells in intravitreal membranes of PVR might result in greater growth than in lesions derived from a single retinal cell population.

Corneal stromal fibroblasts from adult rabbits retain the capacity to deposit an orthogonal matrix

Stromal fibroblasts from the adult rabbit cornea were propagated in vitro, then injected into the vitreous compartment of normal rabbit eyes. In this environment the stromal cells deposited a matrix of imperfect orthogonal collagenous lamellae resembling normal corneal stroma. Extracellular matrices were also secreted by other ocular and nonocular cell types intravitreally, but no orthogonal regions were observed. The vitreous appears to provide some of the physical and humoral factors required to permit adult corneal fibroblasts to secrete a stroma-like matrix in the absence of embryonic tissue influences.

Culture of adult rabbit retinal glial cells: methods and cellular origin of explant outgrowth

Culture methods to propagate glial cells from the avascular adult rabbit neural retina are described. To determine the site(s) in the retina from which the cells originated, retina fragments were retrieved from culture at intervals after explanation and processed for light microscopy to localize surviving cells. Tritiated-thymidine radioautography was used to determine the time of onset and the localization of proliferating cells in the isolated retina and in the early culture outgrowth. Although some glial cells located just subjacent to the inner limiting membrane and at the interface between the ganglion cell and inner plexiform layers were activated to DNA synthesis in three to five days after explanation of the retina, the dominant cell type in the cultures derived from the retina appeared to be the Muller cell. Regionally, in isolated retina fragments, Muller cells became hyperplastic and formed tissue masses of proliferating cells surrounding photoreceptor remnants. These proliferating clusters could be retrieved from the culture medium after about 10 days in vitro and replated whereupon they attached to the culture substrate and gave rise to cellular outgrowths. The cells in the early explant outgrowth were heteromorphic, but passaged cultures contained a relatively homogeneous population of cells that exhibited a low maximal growth rate and senesced quickly in vitro.

Cytochrome b gene of Neurospora crassa mitochondria. Partial sequence and location of introns at sites different from those in Saccharomyces cerevisiae and Aspergillus nidulans

We have sequenced a 2614-base pair fragment of the Neurospora crassa mitochondrial DNA which contains part of the structural gene for apocytochrome b. This gene is split by at least two introns. The sequence reported here begins within one intron, extends through the next exon, another intron 1276 base pairs long, and the last exon which encodes the COOH terminus of cytochrome b. Within the 254 amino acids encoded by the two exons, there is a high degree of sequence conservation, 81%, with cytochrome b of Aspergillus nidulans. Surprisingly, both introns in the N. crassa cytochrome b gene are located at positions different from introns in the corresponding genes in Saccharomyces cerevisiae or A. nidulans. The upstream intron is located 22 nucleotides before the first intron in the long form of the S. cerevisiae cytochrome b gene. The downstream intron is located 16 nucleotides before the third intron in the long form of the S. cerevisiae gene and the only intron in the A. nidulans cytochrome b gene. The 1276-base pair downstream intron contains a 314 amino acid long open reading frame, which is in-phase with the preceding exon. The protein product of this reading frame has some resemblance to intron-encoded proteins, known as "mRNA maturases," which are thought to participate in RNA splicing in the mitochondria of S. cerevisiae. Another feature shared by the downstream intron and most other mitochondrial introns is the presence of the Box 9 and Box 2 consensus sequences, which may also be important for RNA splicing.

Angiographic findings in a young man with recurrent stroke and positive fluorescent treponemal antibody (FTA)

A young man with a history of two strokes was found to have serologic evidence of a prior syphilitic infection, abnormal spinal fluid, and angiographic evidence of diffuse intracranial and extracranial angiopathy which we believe was due to tertiary syphilis, although his use of oral amphetamines cannot be ruled out as a contributing factor. This is the first reported case in which angiography has demonstrated both intracranial and extracranial disease arterial disease due to neurosyphilis. Since syphilis can produce diffuse cerebral arterial changes, this diagnosis should be considered in young patients with stroke even when non-treponemal serologic tests are negative.

Cell-cell contact promotes DNA synthesis in retinal glia but not in fibroblasts

Contact among retinal glial cells in monolayer cultures of intermediate density stimulated DNA synthesis. The stimulation occurred in passaged cultures lacking neuronal elements and is, therefore, the first demonstration of growth promotion by contact among cells of the same apparent type. In contrast, low levels of association among dermal fibroblasts in cultures of similar density had no stimulatory effect. However, as few as three cellular contacts depressed fibroblast DNA synthesis. This latter observation suggests that the density dependent suppression of fibroblast proliferation observed in confluent cultures begins to be expressed at subconfluent cell densities.

Intron within the large rRNA gene of N. crassa mitochondria: a long open reading frame and a consensus sequence possibly important in splicing

We describe the sequence of the 2295 nucleotide long intron and 245 nucleotides of the flanking exon sequences within the large (24S) rRNA gene of Neurospora crassa mitochondria. The intron contains a long open reading frame, which could correspond to ribosomal protein S5. Comparison with the corresponding intron of the large rRNA gene of yeast mitochondria reveals a single highly homologous 57 nucleotide long sequence, including the sequence (formula; see text), which is present in virtually all the sequenced introns of yeast, Aspergillus nidulans and Zea mays mitochondrial genes, and which may be important for their processing. Sequences closely related to this consensus sequence are also present within all four of the introns of nuclear rRNA genes which have been sequenced. The intron is located within a highly conserved region of the large rRNA sequence and at exactly the same site as in the corresponding introns in yeast mitochondria and also in Physarum polycephalum nuclei.

Injured vitreous stimulates DNA synthesis in retinal pigment epithelial cells in culture and within the vitreous

Cultures of rabbit retinal pigment epithelium (RPE) were exposed to normal vitreous and to vitreous injured by intravitreal injection of foreign particles. Counts of labeled RPE nuclei after incubation with 3H-thymidine in vitro indicated an increase in DNA synthesis with exposure to normal vitreous and an even greater increase with exposure to injured vitreous. Fractionation of injured vitreous demonstrated that the apparent proliferation stimulus resided in the cell-free supernate. The data suggest that normal vitreous contains a humoral factor that stimulates RPE proliferation and that levels of an active agent increase after vitreal injury. RPE injected into the vitreous also responds by increased DNA synthesis to subsequent vitreal injury. This observation implies that foreign substances in the vitreous, as after vitreal hemorrhage, promote development of extraretinopathies involving RPE by stimulating intravitreal proliferation of invasive RPE cells.

Ultrastructural demonstration of transretinal migration by vitreal macrophages marked with latex particles

The injection of 1.1-micrometer latex particles into the rabbit vitreous elicits an intravitral invasion of macrophages. The particle-filled macrophages are initially restricted to the vitreous, are later found at the vitreoretinal interface, and by 6 weeks are distributed throughout the inner layers of the retina. The phagocytes appear to lyse in the outer retinal layers, and the released particles are found between and within the cells of the photoreceptor region. The observations indicate that latex-marked macrophages from the vitreous can penetrate and migrate within the retina.

Retinal proliferation in response to vitreous hemoglobin or iron

To examine the effects of blood components within the vitreous on proliferation by cells in the retina, homologous hemoglobin or FeSO4 was injected into the rabbit vitreous. Cells undergoing DNA synthesis were labeled by 3H-thymidine injected into the vitreous or into the circulation. Both hemoglobin and FeSO4 stimulate proliferation in cells throughout the retina. There are two periods of increased retinal labeling. The first occurs 3 to 4 days after first contact with the introduced agents, and the second occurs after 2 to 4 weeks. Analysis of movement of cells after hemoglobin injection suggests that many labeled cells seen in the retina in the early period of labeling migrate from the outer layers toward the vitreous. Other data indicate that many of these cells are of hematogenous origin. Labeled cells also enter the vitreous from the region of the ciliary processes at this time. During the second period of retinal labeling, many proliferating cells may pass in the opposite direction through the retina toward the choroid. The accumulated data imply that the rabbit retina does not act as barrier to transmigrating cells after vitreous injury. Intravitreal hemoglobin also promotes cell multiplication in cells of the pigmented epithelium and possibly in some populations of retinal glial cells. Since these cells have been identified within the vitreous in some pathologic conditions, their suggested ability to respond by proliferation to a hemoglobin stimulus implies that vitreous hemorrhage may aggravate these pathologies in part by promoting multiplication of invasive cells.

Cell proliferation in response to vitreous hemoglobin

Rabbits were examined at intervals to 90 days after receiving two or three intravitreal injections, on consecutive days, of homologous hemoglobin or saline. Cell proliferation in the vitreous was assessed by scintillation counting and radioautography after intravitreal administration of 3H-thymidine 4 hr prior to sacrifice. Two populations of vitreous cells phagocytize the vitreous hemoglobin and are stimulated to DNA synthesis. Cells that migrate into the vitreous in response to hemoglobin also contribute to total 3H-thymidine uptake. Tritiated thymidine incorporation peaks between 5 to 10 days and again between 22 to 30 days after the first administration of hemoglobin. By 45 to 60 days after two injections and 90 days after three injections the vitreous cell proliferative activity has returned to normal. It is concluded that a bleeding event which leads to the release of hemoglobin in the vitreous stimulates a minor, transient vitreous cell proliferation and a more significant, but also transient, migration of cells into the vitreous. Aside from contributing by phagocytosis to vitreal clearing, no other functions have been ascribed to these cells.

Vitreal superoxide and superoxide dismutase after hemorrhagic injury: the role of invasive cells

It was previously reported that injection of whole blood or hemoglobin into the rabbit vitreous is followed by two periods of immigration of phagocytic cells. The first period occurs within the first few days, and the second at round 3 weeks after experimental injury. In this report, invasive cells from these two periods after intravitreal hemoglobin injection were tested for their ability to release superoxide anion (O2). Levels of vitreal superoxide dismutase activity were also measured. The data indicate that cells of the second but not the first period of influx release excess O2. The cell-generated free radicals may contribute to vitreal liquefaction, although substantial liquefaction precedes the invasion of the second cell population. Since these cells can traverse adjacent tissues like the retina, they may also contribute by free radical production to the retinal injury that follows hemorrhage.

Phagocytes that invade the vitreous after injury stimulate DNA synthesis in neural retina in vitro

Phagocytes that invade the rabbit vitreous after intravitreal injection were co-cultured with cells from the rabbit neural retina. Counts of labeled nuclei after exposure to 3H-thymidine indicate an increase in DNA synthesis by retinal cells exposed to the phagocytes. In contrast, using the same procedures, vitreal phagocytes do not promote DNA synthesis by rabbit dermal fibroblasts in vitro. The apparent proliferation stimulus due to vitreal phagocytes may be functionally related to other macrophage-dependent proliferation-stimulating activities. Since blood components promote vitreal phagocyte invasion, ocular hemorrhage may aggravate some extraretinopathies in part by a phagocyte-mediated stimulation of retinal cell proliferation.

An analysis of rabbit vitreous collagen

Where similar techniques are employed, the properties of collagen peptides extracted from rabbit vitreous by pepsin treatment resemble those described in published reports of bovine vitreous. Further, rabbit vitreous also contains minor components that migrate on polyacrylamide gel electrophoresis more slowly than the minor 1 alpha and 2 alpha chains of rabbit cartilage. Properties of the major vitreous components suggest a mixture of the closely-related cartilage collagen chains alpha 1(II) and 3 alpha.

Defective F pili and other characteristics of Flac and Hfr Escherichia coli mutants resistant to bacteriophage R17

Mutants resistant to the donor-specific bacteriophage R17 were isolated from Hfr and Flac-containing strains of Escherichia coli K-12. Thirty-five mutants were examined for the presence of F pili by electron microscopy. The pilus morphology was studied, as were the abilities of the cells to retract their pili and to synthesize new pili. Measurements were made of the efficiency of the conjugal deoxyribonucleic acid transfer and of M13 and R17 phage infection. All mutants had noticeable defects in pilus production, structure, or function. Mutants were found which produced unusually long pili, displayed wide variations in the number of pili per cell, and were deficient in pilus retraction and synthesis. Evidence is presented that there may be two pathways of pilus retraction.

Synthesis of types I and III procollagen and collagen by monkey aortic smooth muscle cells in vitro

Analysis of pepsin-resistant proteins produced in culture by monkey aortic smooth muscle cells (SMC) indicates the synthesis of types I and III collagen. As determined by carboxymethylcellulose chromatography and disc gel electrophoresis, SMC cultures synthesize more type III collagen than monkey skin fibroblast cultures; aortic adventitial cell cultures (a mixture of SMC and fibroblasts) synthesize an intermediate amount of type III collagen. Both types I and III procollagens can also be isolated from the culture medium of SMC and skin fibroblasts. The procollagens were separated by diethylaminoethylcellulose (DEAE-cellulose) chromatography in identified by electrophoresis and after cleavage with pepsin and cyanogen bromide. Quantitation of the procollagen by DEAE-cellulose chromatography suggests that 68% of the SMC procollagens and less than 10% of the skin fibroblast procollagens are type III. On the other hand, estimation of the proportions of collagen types secreted by cells, employing pepsin digestion of cell culture medium at 15 degrees C, leads to an underestimation of the amount of type III collagen relative to type I. SMC and fibroblasts may differ in their ability to convert type I procollagen to collagen ad indicated by the observation that skin fibroblast culture medium contains both pN and pC collagen intermediates after 24 h, while cultures of SMC essentially lack the pC collagen intermediates.

A radioautographic study of collagen synthesis by earthworm epidermis

Secreation by the epidermis of two oligochaetes (Eisenia and Enchytraeus) was investigated radioautographically following administration of 3H-proline, 3H-tryptophan or Na2(35)SO4. Regionally epidermal columnar cells of Enchytraeus synthesize the overlying, probably collagenous, cuticle. Eisenia epidermis does not recordably synthesize the cuticle until after wounding (first eight segments removed). By two days postoperative the epidermal columnar cells of Eisenia synthesize the collagenous cuticle and, later in regeneration, the epidermis may simultaneously synthesize the different collagen of the underlying basement lamella. The epidermis of Enchytraeus, but not of Eisenia, synthesizes some sulfated material associated with the cuticle surface.