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Biomedical subjects

Robert Greenberg

Publications and source records attributed to Robert Greenberg.

10 recordsLinked to original sources
PubMed2006

In vitro and in vivo evaluation of ultrananocrystalline diamond for coating of implantable retinal microchips.

In this work, ultrananocrystalline diamond (UNCD) thin films were evaluated for use as hermetic and bioinert coatings for a retinal microchip. These films were deposited on highly conductive Si substrates at different temperatures (from 400 to 800 degrees C), using microwave plasma enhanced chemical vapor deposition with argon-rich Ar/CH4 gas mixtures and different relative amounts of hydrogen (0-20%). Scanning electron microscopy studies showed that all the films are dense and continuous. Results of cyclic voltammetry test revealed that when there was <2% of hydrogen in the plasma, the film obtained renders the surface electrochemically inactive, with very low leakage currents ( approximately 4 x 10(-7) A/cm2 at +/-5 V). In addition, in vivo tests of the UNCD-coated Si samples were performed by implanting them in the eyes of rabbits for 4-6 months within the eye physiological environment. According to all these results, it was concluded that UNCD is a promising candidate for use as the encapsulating coatings for implantable retinal microelectronic devices.

Animals↗
PubMed2005

Nanopowder molding method for creating implantable high-aspect-ratio electrodes on thin flexible substrates.

Metal nanoparticles and a nanopowder molding process were used to fabricate 2D and 3D patternable structures having a height-to-width ratio of up to 10:1. By means of this process, an entire neural stimulation circuit, including stimulating electrode, connection trace, and contact pad, can be fused into one continuous, integrated structure where different sections can have different heights, widths, and shapes. The technique is suitable for mass production, and the fabricated electrode is robust and very flexible. More importantly for biomedical applications, the entire fabricated structure can be packed at room temperature onto a biocompatible flexible substrate, such as polydimethylsiloxane, parylene, and polyimide as well as other temperature-sensitive or vacuum-sensitive materials. The electrodes and wires have about the same electrical resistivities as bulk materials and desirable electrochemical properties, including low impedance.

Electric Capacitance↗
PubMed2005

Long-term stimulation by active epiretinal implants in normal and RCD1 dogs.

An epiretinal prosthesis, consisting of an extraocular microelectronic stimulator and an intraocular electrode array, was implanted in one eye of three blind and three sighted dogs. Three dogs (2 blind, 1 normal) were stimulated for 120 days, and two dogs (both normal) for 60 and 103 days respectively for 8-10 h/day at levels of 0.1 mC cm(-2) and 0.05 mC cm(-2), with each stimulus level presented to half of the array. One blind dog was kept as an inactive implant control. During the study period, electroretinograms (ERG) and fundus photographs were recorded. At the end of the study period, the dogs were sacrificed and histological and morphometric evaluation was made of the retina. No inflammatory reaction, neovascularization or hemorrhage was observed during the follow-up examinations. ERGs were unchanged. Stimulus levels used were of sufficient amplitude to elicit cortical evoked potentials. Histological evaluation showed no inflammatory infiltrates or changes in retina morphometry related to electrical stimulation when compared to the unstimulated control eye. Morphometric analysis revealed no consistent differences relating to electrical stimulation. In summary, chronic electrical stimulation of the dog retina at up to 0.1 mC cm(-2) with an epiretinal prosthesis does not appear to adversely affect the retina.

Animals↗
PubMed2005

Inhibition of insulin-like growth factor-I receptor (IGF-IR) signaling and tumor cell growth by a fully human neutralizing anti-IGF-IR antibody.

Insulin-like growth factor-I receptor (IGF-IR) plays an important role in tumor cell growth and survival. On ligand stimulation, IGF-IR, a receptor tyrosine kinase, phosphorylates tyrosine residues on two major substrates, IRS-1 and Shc, which subsequently signal through the Ras/mitogen-activated protein kinase and phosphatidylinositol 3-kinase/AKT pathways. Here, we describe the characterization of a fully human anti-IGF-IR monoclonal antibody 19D12 that inhibits IGF binding and autophosphorylation of both IGF-IR/IGF-IR homodimers and IGF-IR/insulin receptor heterodimers. 19D12 does not recognize insulin receptor homodimers. In addition to inhibiting IGF-IR autophosphorylation, 19D12 also inhibits IRS-1 phosphorylation and activation of the major downstream signaling molecules AKT and extracellular signal-regulated kinase 1/2. Furthermore, the antibody down-regulates the total IGF-IR protein level and can exhibit antibody-dependent cellular cytotoxicity activity against a non-small cell adenocarcinoma cell line in vitro in the presence of isolated human natural killer cells. 19D12 binds tightly to the receptor, with an affinity of 3.8 pmol/L as measured by KinExA. In cell culture, 19D12 inhibits proliferation and soft agar growth of various tumor cell lines. In vivo, 19D12 inhibits the tumor growth of a very aggressive human ovarian tumor xenograft model A2780. These data support the development of this anti-IGF-IR monoclonal antibody as a promising anticancer agent.

Animals↗
PubMed2003

Visual perception in a blind subject with a chronic microelectronic retinal prosthesis.

A retinal prosthesis was permanently implanted in the eye of a completely blind test subject. This report details the results from the first 10 weeks of testing with the implant subject. The implanted device included an extraocular case to hold electronics, an intraocular electrode array (platinum disks, 4 x 4 arrangement) designed to interface with the retina, and a cable to connect the electronics case to the electrode array. The subject was able to see perceptions of light (spots) on all 16 electrodes of the array. In addition, the subject was able to use a camera to detect the presence or absence of ambient light, to detect motion, and to recognize simple shapes.

Aged↗
PubMed2003

The value of preoperative tests in the selection of blind patients for a permanent microelectronic implant.

PURPOSE: To determine the best candidates (ie, those requiring lowest current levels delivered to the retina to elicit visual perceptions) for long-term implantation of a microelectronic retinal implant through a series of preoperative visual, psychophysical, and electrophysiological tests. METHODS: This study protocol was granted an investigational device exemption by the Food and Drug Administration and was approved by the institutional review board at the University of Southern California. After informed consent was obtained, all subjects underwent the following preoperative tests: dark-adapted bright flash and 30-Hz flicker electroretinograms, electrical evoked responses (EERs) using a Burian-Allen corneal electrode to stimulate the globe, and psychophysical tests to evaluate the light and electrically elicited visual perceptions. Intraocular stimulation (IOS) of the retina was performed by an array of electrodes positioned on the internal limiting lamina. RESULTS: Lower vision correlated with less sensitive psychophysical responses (P<.0001). Lower vision and less sensitive psychophysical tests correlated with higher EER values for stimulus pulse widths of 2 ms (P<.0008) and 4 ms (P<.0002). Lower IOS currents correlated with more sensitive psychophysical responses (P<.02) and lower EER values at 4 ms (P<.04). CONCLUSIONS: Preoperative testing, especially psychophysical and electrophysiological tests to assess light and electrically driven visual responses, can help in evaluating patients for suitability for receiving a permanent microelectronic retinal implant. Further study is warranted.

Blindness↗
PubMed2002

The health of Latino children: urgent priorities, unanswered questions, and a research agenda.

Latinos recently became the largest racial/ethnic minority group of US children. The Latino Consortium of the American Academy of Pediatrics Center for Child Health Research, consisting of 13 expert panelists, identified the most important urgent priorities and unanswered questions in Latino child health. Conclusions were drawn when consensus was reached among members, with refinement through multiple iterations. A consensus statement with supporting references was drafted and revised. This article summarizes the key issues, including lack of validated research instruments, frequent unjustified exclusion from studies, and failure to analyze data by pertinent subgroups. Latino children are at high risk for behavioral and developmental disorders, and there are many unanswered questions about their mental health needs and use of services. The prevalence of dental caries is disproportionately higher for Latino children, but the reasons for this disparity are unclear. Culture and language can profoundly affect Latino children's health, but not enough cultural competency training of health care professionals and provision of linguistically appropriate care occur. Latinos are underrepresented at every level of the health care professions. Latino children are at high risk for school dropout, environmental hazards, obesity, diabetes mellitus, asthma, lack of health insurance, nonfinancial barriers to health care access, and impaired quality of care, but many key questions in these areas remain unanswered. This article suggests areas in which more research is needed and ways to improve research and care of Latino children.

Asthma↗
PubMed2002

Post-Traumatic Stress Disorder in subjects with schizophrenia and bipolar disorder.

The purpose of this study was to identify subjects with Post-traumatic Stress Disorder (PTSD) consequent to hallucinations and delusions and the experiences related to psychosis in schizophrenic and bipolar subjects. Schizophrenic and bipolar subjects were given questionnaires in order to evaluate PTSD incidence and symptoms. Subjects with classical types of trauma were excluded. Depression and stress scales were also answered. About one-third of schizophrenic subjects and one-half of bipolar subjects met PTSD criteria on the Penn PTSD Inventory. Hallucinations and delusions were identified as traumatic events in 60% of subjects with schizophrenia, but in only 15% of the subjects with bipolar disorder. Also, childhood abuse and various present stressors may contribute to the current PTSD symptomatology. Increases in PTSD scale scores were paralleled by increases in Beck depression scale scores. This study underscores the need for mental health clinicians to be sensitive to patients' illness experiences and to be aware of the therapeutic implications in treating PTSD in subjects with schizophrenia and bipolar illnesses.

Adult↗
PubMed1985

Clinic turmoil and staff transitions.

The effects of the July academic rotation on the course of patient treatment in an outpatient clinic were studied. The rotation time was found to be associated with substantial changes in clinic patients' behavior in treatment. The transfer of recent clinic admissions to new therapists was associated with a high rate of dropping out of treatment.

Adolescent↗