Chemical transformations in individual ultrasmall biomimetic containers.
Individual phospholipid vesicles, 1 to 5 micrometers in diameter, containing a single reagent or a complete reaction system, were immobilized with an infrared laser optical trap or by adhesion to modified borosilicate glass surfaces. Chemical transformations were initiated either by electroporation or by electrofusion, in each case through application of a short (10-microsecond), intense (20 to 50 kilovolts per centimeter) electric pulse delivered across ultramicroelectrodes. Product formation was monitored by far-field laser fluorescence microscopy. The ultrasmall characteristic of this reaction volume led to rapid diffusional mixing that permits the study of fast chemical kinetics. This technique is also well suited for the study of reaction dynamics of biological molecules within lipid-enclosed nanoenvironments that mimic cell membranes. (+info)
Nucleic acid detection technologies -- labels, strategies, and formats.
Currently, no consensus exists on assay formats, labels, or detection reactions for nucleic acid assays. New labels continue to be developed and tested, and recent candidates include acetate kinase, firefly luciferase, and genes for enzymes. An additional trend is toward nonamplification strategies (e.g., branched chain and dendrimer type assays) as alternatives to the popular PCR and related amplification strategies. The new wave of microanalytical devices (microchips, with nanoliter to microliter internal volumes), massively parallel simultaneous test arrays, and the desire to produce hand-held sensors present new challenges and requirements for nucleic acid detection methods (e.g., analysis of large arrays of micrometer-sized spots of nucleic acid with high resolution). Here I review selected developments and new directions in nucleic acid assays. (+info)
Versatile derivatisation of solid support media for covalent bonding on DNA-microchips.
A chemistry was developed that permits on DNA-arrays both the covalent immobilisation of pre-fabricated nucleic acids-such as oligonucleotides, PCR-products or peptide nucleic acid oligomers-and the in situ synthesis of such compounds on either glass or polypropylene surfaces. Bonding was found to be stable even after some 30 cycles of stripping. Due to a dendrimeric structure of the linker molecule, the loading can be modified in a controlled manner and increased beyond the capacity of glass without negative effects on hybridisation efficiency. Also, the chemistry warrants the modulation of other surface properties such as charge or hydrophobicity. Preferentially, attachment of nucleic acids takes place only via the terminal amino-group of amino-modified oligonucleotides or the terminal hydroxyl-group of unmodified molecules so that the entire molecule is accessible to probe hybridisation. This derivatisation represents a support chemistry versatile enough to serve nearly all current forms of DNA-arrays or microchips. (+info)
Laparoscopy-assisted intrapelvic sonography with a high-frequency, real-time miniature transducer for assessment of the Fallopian tube: a preliminary report.
Our purpose was to visualize normal and abnormal Fallopian tubes using laparoscopy-assisted intrapelvic sonography with a specially developed 20 MHz flexible catheter-based high-resolution, real-time miniature (2.4 mm outer diameter) ultrasound transducer in infertile women. A total of 21 women (20 infertile, one with unilateral hydrosalpinx, and one tubal pregnancy) were studied with pelvic saline effusion under laparoscopy. Fimbriae were clearly depicted with a cockscomb-like form in 95% of patients. All ampullae were visualized, and mucosal layers were clearly distinguished from muscle layers in 70% of patients. Scanty intratubal effusion was noted in 50% of patients, and tubal spastic findings were found in 10% of patients. In all, 60% of isthmuses were detected, and mucosal layers were distinguished from muscle layers in 30%. In the subject with hydrosalpinx, the tubal wall was thinner, and it was not possible to distinguish between muscle and mucosal layers. In the subject with a tubal pregnancy, the amniotic membrane and decidua were depicted more clearly than by transvaginal sonography. In conclusion, laparoscopy-assisted intrapelvic sonography with a high-frequency, real-time miniature transducer may be useful in the assessment of tubal texture and function in tubal disorders, possibly in infertility practice. (+info)
Can subretinal microphotodiodes successfully replace degenerated photoreceptors?
The idea of implanting microphotodiode arrays as visual prostheses has aroused controversy on its feasibility from the moment it appeared in print. We now present results which basically support the concept of replacing damaged photoreceptors with subretinally implanted stimulation devices. Network activity in degenerated rat retinae could be modulated through local electrical stimulation in vitro. We also investigated the long term stability and biocompatibility of the subretinal implants and their impact on retinal physiology in rats. Ganzfeld electroretinograms and histology showed no significant side effect of subretinal implants on retinal function or the architecture of the inner retina. (+info)
An in vivo comparison of a catheter mounted pressure transducer system with conventional balloon catheters.
In the assessment of respiratory muscle function balloon catheters have been widely used for pressure measurements. However, this type of investigation is poorly tolerated by acutely ill patients. This study assessed the performance of a possible alternative, a catheter-mounted miniature pressure transducer (CMT). The assessment consisted of a laboratory study of the linearity, frequency response, and stability of gain and baseline of the CMT system, and an in vivo study directly comparing the CMT and balloon catheter systems in seven normal subjects for a range of respiratory manoeuvres. These were: 1) maximal inspiratory and expiratory pressures against a closed airway, 2) twitch transdiaphragmatic pressure elicited by cervical magnetic phrenic nerve stimulation, and 3) tidal breathing, sniffs and coughs in five body positions. The agreement of the two systems was analysed for measurements of 1) absolute pressures, 2) magnitude of changes in pressure, and 3) rate of change of pressure (maximum relaxation rate after sniff manoeuvres). The CMT system was linear, with a high frequency response and stable gain, but showed baseline drift. The two systems agreed well for measurements of change and rate of change of pressure, but less well for measurements of absolute pressure. The CMT system tested is potentially useful for studies of acute changes in respiratory pressures, or studies of respiratory muscle strength, but would be less useful where accurate measurements of absolute pressures are required. (+info)
Early identification of diabetic foot ulcers that may require intervention using the micro lightguide spectrophotometer.
OBJECTIVE: Adequate tissue oxygenation is known to be essential for the healing of diabetic foot ulcers, but hypoxia has also been shown to be a potent stimulus for growth. There are no studies looking specifically at ulcer oxygen levels during the healing process. We measured the serial microvascular oxygen saturation (SaO2) of the foot ulcer, the ulcer margin, and a control site using the Erlangen micro lightguide spectrophotometer (EMPHO II; Bodenseewerk Geratetechnik, Erlangen, Germany) to study serial changes during healing. RESEARCH AND DESIGN METHODS: Studied over 9 months were 14 patients with neuropathy with a total of 24 foot ulcer sites. Of these patients, four (seven ulcers) had significant ischemia as determined by the ankle-brachial pressure index (ABPI) and transcutaneous oxygen tension. RESULTS: Of 21 ulcer sites with serial measurements, only 13 ulcers healed. In those ulcers, a significant reduction (P<0.05) in SaO2 occurred with healing. SaO2 dropped from 58% at initial presentation (mean area 2.6 cm2) to 47% at midsize (mean area 1.2 cm2 at 5.2 weeks) and finally reduced to 45% just before it healed. Similar trends were also seen around the margin of the ulcers (initial 49%, midsize 45%, and final 41%; P = 0.1). However, there were no such changes on the control sites (43, 40, and 40%; P = 0.5) or within the eight ulcers that did not heal (46, 42, and 53%; P = 0.2). CONCLUSIONS: Serial microvascular oxygen measurements may be used to identify at an early stage those ulcers that are unlikely to heal and, therefore, need surgical intervention. (+info)
Saline infusion contrast intrauterine sonographic assessment of the endometrium with high-frequency, real-time miniature transducer in normal menstrual cycle: a preliminary report.
Normal endometrial texture was visualized using saline infusion contrast intrauterine sonography with a specially developed 20 MHz flexible catheter-based high-resolution, real-time miniature (2.4 mm outer diameter) ultrasound transducer in primary infertile women (n = 15) with a normal menstrual cycle. All the women had <2 years infertility duration and were studied in proliferative, and early or mid-secretory phases. Before intrauterine sonography, transvaginal sonographic assessment of the endometrium was conducted. The overall image clarity was subjectively compared between intrauterine and transvaginal sonography. Most endometrial textures in both proliferative and secretory phases were viewed more easily with intrauterine rather than transvaginal sonography, and this was especially true with an intrauterine saline infusion technique. Moreover, it was possible to obtain finer image quality of very small endometrial interfacial and internal textures with intrauterine sonography. However, the depth of penetration of the ultrasound beam is only approximately 2 cm, therefore examination of larger pathological endometrial lesions is markedly limited because of the shallow scanning range of the high-frequency transducer. Intrauterine sonography may be a valuable tool in imaging endometrial texture in normal menstrual cycle, and possibly in infertility practice, complementing and not replacing transvaginal sonography. (+info)