The sporulation process in Thermomonospora fusca as revealed by scanning and transmission electron microscopy

The sporulation process in the thermophilic actinomycete Thermomonospora fusca was observed by scanning and transmission electron microscopy. As shown by scanning electron microscopy, spores were produced primarily on aerial hyphae and first appeared as bud-like enlargements at the tips of short multibranched sporophores. Young spores were oval to spherical in shape with a smooth surface. As they matured spores enlarged and developed a rough and globular covering, which was quite fragile and easily detached from the spore. This outer layer, as observed by transmission electron microscopy, was thought equivalent to the sheath of other Thermomonospora species. In cross section, mature spores exhibited a thick spore coat underneath the outer globular layer. This spore coat was usually observed as a single layer, but some spores produced a bilayered coat. No multilayered spore coat or spore cortex was observed in the heat-sensitive spores of T. fusca. They were, therefore, shown to be aleuriospores (microcondia), and not endospores.     

Muscular composition of the gastric groove in the golden hamster

The golden hamster possesses a forestomach and a glandular stomach. The gastric groove connects the cardia to the glandular stomach and is situated on the lesser curvature of the stomach. The constitution of the muscle fibers in the gastric groove was investigated. The gastric groove consisted of two lips and a groove floor. The muscle coat of the lips was composed of a mixture of smooth and striated muscle fibers. The smooth muscle fibers were components of the cardiac muscle loop. The striated muscle fibers were extensions from the esophageal inner circular muscle layer, and invaded about half the length of the lips. The muscle coat of the groove floor consisted of an inner circular muscle layer made up of smooth muscle fibers, and the outer longitudinal muscle layer of the striated muscle fibers extended from the esophageal outer longitudinal muscle layer. The present study revealed that the muscle coat of the gastric groove in the golden hamster was composed of smooth and striated muscle fibers, and that these striated muscle fibers were extensions of the esophageal muscle coat.     

Structural roles of the spore coat proteins in Dictyostelium discoideum

The integrity of spores formed by mutant strains of Dictyostelium discoideum lacking the major spore coat proteins, SP96, SP70, or SP60, was compared to that of wild-type strains. Single, double, and triple knock-out strains developed normally and produced spores which were indistinguishable from wild-type spores by light or electron microscopy. However, the mutant strains were susceptable to staining with the lectin, ricin A, which recognizes a galactose-rich polysaccharide that is normally hidden by overlying spore coat proteins. The intensity of staining with fluorescently labeled ricinA increased as the spore coat proteins were incrementally lost. While these results indicate that the major outer spore coat proteins are not essential for the construction of a multi-layered spore coat in Dictyostelium, they show that the spores are more porous which might make them at risk to predators before germination.     

Studies of asymmetric membrane assembly

The major capsid protein of M13 bacteriophage is incorporated at each stage of infection into the host plasma membrane with its amino terminus exposed on the outer surface. Purified M13 coat protein is incorporated with the same asymmetry into synthetic phosphatidylcholine vesicles formed near the Tm of the lipid by a cholate dilution technique. We now report that the lipid in the pre-dilution mixture exists as mixed micelles of uniform size. Prior to dilution, the coat protein is present in at least two states of aggregation, both of which behave similarly in the model membrane assembly reaction. No detectable lipid-protein interaction occurs prior to dilution. Upon dilution there is rapid production of small closed vesicles and coat protein is converted to a chymotrypsin-resistant form, presumably reflecting its incorporation into these vesicle bilayers. Formation of large (greater than 6000 A diameter) vesicles occurs slowly with preservation of coat protein asymmetry and internal volume. A model for this assembly reaction is proposed.     

Lipoprotein (a) and cholesterol in body builders using anabolic androgenic steroids

A 67-year-old Taiwanese woman with multilocular hydatid cysts of the liver presented with a 5-month history of intermittent right upper abdominal discomfort. Abdominal ultrasonography and computed tomography showed multiple cysts in both lobes of the liver. Subsequent selective celiac angiography revealed an avascular space-occupying lesion in the right lobe. She underwent a radical excision of the cyst by total closed (without opening the wall) cystopericystectomy over segments 4, 5 and 6. Histologic study of the lesions showed three structural components: 1) an outer acellular laminated membrane, 2) a thin nucleated germinal membrane and 3) several protoscolices with Echinococcus granulosus suckers. The patient has been well for 5 years since her discharge. Although hydatid cysts of the liver are extremely rare in Taiwan, they may cause life-threatening complications and mortality. Making a preoperative diagnosis is important and is only possible if this rare disease is kept in mind.     

Microstructural evolution of the nickel platinum-aluminide bond coat on electron-beam physical-vapor deposition thermal-barrier coatings during high-temperature service

The microstructural evolution of a (Ni,Pt)-aluminide bond coat underneath the ZrO₂-based thermal-barrier coating (TBC) topcoat system on a René N5 Ni-based superalloy turbine blade during prolonged high-temperature service has been characterized using transmission electron microscopy (TEM). The as-deposited bond coat has a spatially varying microstructure, which consists of an outer layer of single-phase β-(Ni,Pt)Al, a middle layer of a β-(Ni,Pt)Al matrix containing a high number density of μ-phase precipitates, and an inner layer containing a γ/γ′ matrix and numerous μ- and σ-phase precipitates. During service, microstructural changes in the hotter sections of the blade are more extensive than those in the cooler parts, as expected. As a result of interdiffusion, the inner layer grows into the γ/γ′ substrate, with the formation of some M₂₃C₆ precipitates, and the β matrix in the middle layer is transformed into a two-phase mixture of β and γ′. Corresponding changes occur in the morphologies and volume fractions of the various precipitate phases present in the bond coat. The single-phase β material in the outer layer retains its basic structure, except that the compositional changes due to diffusion between the bond coat and turbine blade cause a martensitic transformation to occur in the hottest sections during the final cooling of the blade. The distribution of various elements in the different layers has also been analyzed, as has growth of the thermally grown oxide (TGO) at the bond coat/TBC interface.     

A survey of Blastocystis in domestic chickens

The prevalence and morphology of Blastocystis in fresh faecal material from 227 domestic chickens was investigated. A very high prevalence of infection (approximately 95%) was found in chickens from four of the five commercial farms studied. Extremely high numbers of Blastocystis were found in the majority of samples. Blastocystis cells showed considerable variation in size, ranging from approx. 3 microm to approx. 120 microm in diameter. This size range is more extreme than those previously recognised for the organism from chickens. All chickens from one farm appeared free of Blastocystis infection. Most Blastocystis cells appeared to be the vacuolar form, although the shape of the cells and the appearance of the central vacuole contents varied considerably within and among faecal samples. Nuclei showed "spots" of electron-opaque material, generally arranged as a band within the nuclei. Multiple individual cysts within a single outer fibrillar layer were found in addition to single cysts without an encompassing fibrillar layer.     

Electron microscopic detection of spirochetes in dermatitis digitalis of cattle

In typical Dermatitis digitalis (D.d.) lesions, spirochaete-like bacteria with variations in spiralization were revealed by electron microscopy. While, in the early stages of the disease, these are found to be associated with fibrillar material of keratocytes, they occur massively in vacuoles at more advanced stages. The spirochaetes carry one pair of endoflagella, originating with a hook from the poles of the bacteria. These flagellae are composed of coiled flagellating fibrils in the pole region, merging towards the centre of the bacterium. A coat of fibrils was found in association with the cytoplasmatic membrane. The winding of this coat follows and may influence the coiling of the protoplast, and is probably involved in the rapid motility of this spirochaetes, together with the flagella. Immuno-electronmicroscopy revealed an antigenic relationship with Borrelia burgdorferi, at least with regard to the regions of flagella and undulating membrane. The paper discusses: 1. The possible classification of these spirochaetes with the genus Treponema; 2. The layer of peptidoglycan occurring on the outer membrane; and 3. The keratolytic activity of spirochaetes in D.d.     

含钨镀层研究的某些进展

介绍了镍钨镀层、镍钨硼(磷)镀层、含钨复合镀层和含钨电刷镀镀层等的研究与开发的近期进展。已有生产实践和研究工作表明 ,用含钨镀层代替传统对环境有危害的铬镀层等方面取得了很大进展。电沉积含钨镀层所用含钨原料主要是钨酸钠、碳化钨等 ,所得含钨镀层性能特色明显 ,其钨用量很少 ,发挥钨功能很大。因此 ,在钨的深加工与综合利用方面 ,应该进一步开展含钨镀层电镀技术的研究与开发。     

粉末冶金摩擦材料及对偶材料支承钢背镀层的研究

研究了粉末冶金摩擦材料及对偶材料支承钢背镀层的热疲劳行为。结果表明,在反复急冷急热后,烧结对偶材料,采用镀铜再镀镍的钢背,在镀层处产生穿透性裂纹;采用镀镍的钢背,在镀层处产生非穿透性裂纹,裂纹随镀层厚度的增加增减少。烧结摩擦材料,无论是采用镀镍还是镀铜再镀镍的钢背都没有镀层处发现热疲劳裂纹。     

Measurement of bubble characteristics in a molten iron bath at 1600 °C using an electroresistivity probe

A two-needle, electroresistivity probe was developed to measure bubble characteristics such as gas holdup, bubble frequency, and bubble rising velocity in a molten iron bath at 1600 °C. The probe’s electrode was made of a 0.5-mm platinum wire coated with ZrO₂ cement and an outer coat of alumina as insulator. The life of this probe at 1600 °C was 15 to 20 minutes, making it possible to systematically measure bubble characteristics. The measured values of the bubble characteristics were compared with their respective empirical correlations derived from cold model experiments. Good agreement between the measured values and the empirical correlations was seen for each bubble characteristic. This electroresistivity probe allows us to measure bubble characteristics in actual metallurgical reactors with gas injection at high bath temperatures.     

Hepatic hydatid cysts: sonographic follow-up after percutaneous sonographically guided aspiration

PURPOSE: We studied the sonographic appearances of hepatic hydatid cysts and used sonography to follow up these cysts after sonographically guided aspiration using the PAIR technique. METHODS: Included in this study were 362 patients with 558 hepatic hydatid cysts. Initial sonographic examination revealed 510 noncomposite cysts and 48 composite cysts (18 rosette and 30 honeycomb pattern). Noncomposite hydatid cysts (510 cysts) were aspirated and treated with scolicidal agents using the PAIR technique. Sonographic follow-up was done for up to 5 years after aspiration. RESULTS: There was immediate detachment of the germinal layer in all cysts during aspiration. There were no serious complications. Sonographic follow-up after 1 month and 1 year revealed complete cyst collapse in 326 cysts (64%) and 449 cysts (88%), respectively. Repeat ultrasound scanning showed a continued decrease in the sizes of all remaining cysts. Organized lesions (pseudosolid pattern) were detected in only 26 cases after up to 5 years of follow-up. CONCLUSIONS: The most common sonographic appearance of hepatic hydatid cysts among Egyptians is noncomposite, anechoic cysts. The PAIR technique is a safe, effective, and inexpensive therapeutic modality.     

Degradation of double-walled polymer microspheres of PLLA and P(CPP:SA)20:80. I. In vitro degradation

Double-walled (DW) polymer microspheres with a core of poly(1,3-bis-(p-carboxyphenoxy propane)-co-(sebacic anhydride)20:80 (P(CPP:SA)20:80) and an external coat of poly(L-lactic acid) (PLLA) were degraded for up to 6 months in vitro. The effects of hydrolytic degradation on the polymers were studied by Fourier-transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), gel permeation chromatography (GPC) and scanning electron microscopy (SEM). The inner core of the polyanhydride copolymer (P(CPP:SA)20:80) degraded first, breaking down into oligomers during the first week and then into monomers which were trapped by the outer shell of PLLA, crystallized, and remained in the core for the duration of the study. As expected, the PLLA coat degraded at a slower rate due to the ester bonds between lactic acid monomers being more hydrolytically resistant than the anhydride bonds. The PLLA in the DW microspheres decreased from its original molecular weight (Mw) of 24,000 g mol(-1) to approximately 5,000 g mol(-1) over the 6 month study. The melting temperature of the PLLA decreased more than 30 degrees C during the study, but no changes were observed in the FTIR spectra. The 6 month samples were very brittle, showing the concomitant drop in mechanical strength with the decrease in Mw.     

提高镀层粘附性能的研究

镀层的粘附性能是影响镀锌产品质量的关键，镀层的粘附性不良将导致镀层产生裂纹及脱落，直接影响镀锌产品的使用寿命。介绍了镀层粘附性机理，并结合实际研究了影响镀层粘陵性的各种因素。     

The uterine cervix on in vitro and in vivo MR images: a study of zonal anatomy and vascularity using an enveloping cervical coil

OBJECTIVE: The purpose of this study was to characterize the normal zonal anatomy and vascularity of the cervix on in vivo and in vitro MR images obtained with a receiver coil surrounding the cervix. These appearances provide a normal data base from which to interpret subtle changes in early neoplasia. SUBJECTS AND METHODS: Thirteen women of reproductive age with clinically and cytologically normal cervices were imaged with a ring-design solenoid receiver coil that was placed intravaginally and enveloped the cervix. T1- and T2-weighted axial images were obtained. Seven uterine specimens resected for benign disease were similarly studied, and imaging appearances were correlated with histologic findings. RESULTS: In the in vivo studies, the endocervical mucosa and two stromal zones surrounding the high-signal central canal were identified. Unlike the uterine body, they could be differentiated on both T1- and T2-weighted images, on which the inner ring had a low signal and the outer ring had an intermediate signal intensity. The outer zone was highly vascularized, with inflow effects from large vessels visible on single-slice scans. On administration of gadopentetate dimeglumine, the endocervical mucosa enhanced rapidly, whereas the outer stroma showed more gradual enhancement. The inner zone enhanced slowly relative to the outer zone. The parametrium was visualized up to 6 cm from the center of the coil, and adjacent colon, fat, and blood vessels were identified. Up to four lymph nodes less than 1 cm in diameter were seen in the parametrium of three subjects. In the in vitro studies, the endocervical mucosa was of high signal intensity. In the fibromuscular cervix, an inner low-signal ring correlated with a region of tightly packed stroma (fibroblasts and smooth muscle cells; cell count, 5900 +/- 2376 nuclei/mm2) and the intermediate-signal-intensity outer zone corresponded to a region of more loosely packed stroma (cell count, 2199 +/- 558 nuclei/mm2). Retention cysts were present in two multiparous cervices. CONCLUSION: These detailed appearances and enhancement patterns of the normal cervix need to be recognized so that subtle changes in locally invasive cervical neoplasia can be identified.     

Observations on two cases of apparent submandibular gland cysts in HIV positive patients: MR and CT findings

OBJECTIVE: To present two cases of probable lymphoepithelial cysts of the submandibular glands in patients who were human immunodeficiency virus (HIV) positive and who also had lymphoepithelial cysts of the parotid glands. MATERIALS AND METHODS: Computed tomography and MRI of two HIV positive patients with lymphoepithelial cysts of the parotid glands and cysts in the submandibular glands were correlated with the histories and the possible presence of other known causes of submandibular gland multiple cysts. RESULTS: Because of the present treatment philosophy regarding HIV positive patients with major salivary gland cysts, surgical resection of these glands was not performed. All other known causes of multiple submandibular gland cysts were excluded by either history or laboratory data. CONCLUSION: Computed tomography and MRI on two patients with known HIV infection and bilateral parotid lymphoepithelial cysts are presented. Both patients also had bilateral multiple submandibular gland cysts and no evidence of obstructive glandular disease, autoimmune disease, or other organ system cysts. These cases of presumed submandibular gland lymphoepithelial cysts are rare in the literature. They are presented in the hope that other radiologists will be stimulated to document the occurrence of this entity.     

Prepubertal ovarian cyst formation: 5 years' experience

OBJECTIVE: To document the frequency of ovarian cyst formation in the prepubertal female and to report on the clinical implications of these cysts. METHODS: We evaluated cases from a retrospective chart review of prepubertal females with ovarian cysts. RESULTS: Over a 5-year period, 1818 ultrasound studies were completed in prepubertal females, from which 99 patients were identified as having ovarian cysts. The majority (82 of 99, 83%) were small, unilocular cysts averaging 2-3 mm in diameter. The incidence of these small cysts ranged at 2-5% in females between birth and age 8. Large ovarian cysts (ie, greater than 2 cm in diameter) are rare in young girls over age 2, with most occurring within the first year of life. Of the 17 large ovarian cysts, two presented with torsion and both were complex on ultrasound examination. Five (29%) of the large ovarian cysts were treated conservatively and demonstrated regression on follow-up; these were unilocular cysts. Although functioning cysts resulting in precocious pseudopuberty are expected to be rare, we identified five cases (5%) in our series. CONCLUSIONS: Small, unilocular ovarian cysts less than 1 cm in diameter are found in prepubertal females with a frequency of 2-5% and are clinically insignificant. Ovarian cysts greater than 2 cm are rare. Unilocular ovarian cysts less than 5 cm may be followed conservatively with ultrasound surveillance until regression, without a major risk of torsion. Ovarian cysts associated with precocious pseudopuberty are generally larger than 2 cm and may be recurrent.