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Biomedical subjects

M G Allen

Publications and source records attributed to M G Allen.

At least 19 recordsLinked to original sources
PubMed2000

Microfabricated microneedles for gene and drug delivery.

By incorporating techniques adapted from the microelectronics industry, the field of microfabrication has allowed the creation of microneedles, which have the potential to improve existing biological-laboratory and medical devices and to enable novel devices for gene and drug delivery. Dense arrays of microneedles have been used to deliver DNA into cells. Many cells are treated at once, which is much more efficient than current microinjection techniques. Microneedles have also been used to deliver drugs into local regions of tissue. Microfabricated neural probes have delivered drugs into neural tissue while simultaneously stimulating and recording neuronal activity, and microneedles have been inserted into arterial vessel walls to deliver anti-restenosis drugs. Finally, microhypodermic needles and microneedles for transdermal drug delivery have been developed to reduce needle insertion pain and tissue trauma and to provide controlled delivery across the skin. These needles have been shown to be robust enough to penetrate skin and dramatically increase skin permeability to macromolecules.

Animals↗
PubMed1998

Microfabricated microneedles: a novel approach to transdermal drug delivery.

Although modern biotechnology has produced extremely sophisticated and potent drugs, many of these compounds cannot be effectively delivered using current drug delivery techniques (e.g., pills and injections). Transdermal delivery is an attractive alternative, but it is limited by the extremely low permeability of skin. Because the primary barrier to transport is located in the upper 10-15 micron of skin and nerves are found only in deeper tissue, we used a reactive ion etching microfabrication technique to make arrays of microneedles long enough to cross the permeability barrier but not so long that they stimulate nerves, thereby potentially causing no pain. These microneedle arrays could be easily inserted into skin without breaking and were shown to increase permeability of human skin in vitro to a model drug, calcein, by up to 4 orders of magnitude. Limited tests on human subjects indicated that microneedles were reported as painless. This paper describes the first published study on the use of microfabricated microneedles to enhance drug delivery across skin.

Administration, Cutaneous↗
PubMed1998

Diode laser absorption sensors for gas-dynamic and combustion flows.

Recent advances in room-temperature, near-IR and visible diode laser sources for tele-communication, high-speed computer networks, and optical data storage applications are enabling a new generation of gas-dynamic and combustion-flow sensors based on laser absorption spectroscopy. In addition to conventional species concentration and density measurements, spectroscopic techniques for temperature, velocity, pressure and mass flux have been demonstrated in laboratory, industrial and technical flows. Combined with fibreoptic distribution networks and ultrasensitive detection strategies, compact and portable sensors are now appearing for a variety of applications. In many cases, the superior spectroscopic quality of the new laser sources compared with earlier cryogenic, mid-IR devices is allowing increased sensitivity of trace species measurements, high-precision spectroscopy of major gas constituents, and stable, autonomous measurement systems. The purpose of this article is to review recent progress in this field and suggest likely directions for future research and development. The various laser-source technologies are briefly reviewed as they relate to sensor applications. Basic theory for laser absorption measurements of gas-dynamic properties is reviewed and special detection strategies for the weak near-IR and visible absorption spectra are described. Typical sensor configurations are described and compared for various application scenarios, ranging from laboratory research to automated field and airborne packages. Recent applications of gas-dynamic sensors for air flows and fluxes of trace atmospheric species are presented. Applications of gas-dynamic and combustion sensors to research and development of high-speed flows aeropropulsion engines, and combustion emissions monitoring are presented in detail, along with emerging flow control systems based on these new sensors. Finally, technology in nonlinear frequency conversion, UV laser materials, room-temperature mid-IR materials and broadly tunable multisection devices is reviewed to suggest new sensor possibilities.

Absorption↗
PubMed1993

Utilization review of treatment for chemical dependence.

Utilization review of treatment for chemical dependence has become increasingly important as evidence accumulates that outpatient treatment can be effective in many cases. The authors discuss the basic questions that guide utilization review of treatment for chemical dependence, summarize research that has led to the increasing emphasis on outpatient and partial hospital treatment approaches, and review the American Psychiatric Association's guidelines for utilization review of chemical dependence treatment. Case examples illustrate issues in the treatment of adolescents, patients with dual diagnoses, and relapsing patients. The authors conclude that utilization review supports use of inpatient care only for patients who require intensive services, including those who are a danger to themselves or others, have serious physical or psychiatric disorders, or have not responded to an adequate trial of outpatient treatment.

Adolescent↗
PubMed1990

Psychophysiological correlates of posttraumatic stress disorder in Vietnam veterans.

We measured event-related brain potential (ERP) component amplitudes and heart rate (HR) to four intensities of randomly presented tones in two matched groups of drug-free male Vietnam veterans: 12 patients diagnosed with posttraumatic stress disorder (PTSD) and 6 normal combat veterans. Subjects were evaluated with structured diagnostic interviews and anxiety and depression rating scales. We found a significant group X intensity interaction for P2 peak amplitude at CZ. Subjects were classified as augmenters or reducers: positive P2 slopes as a function of stimulus intensity implying augmentation and negative slopes implying reduction. Nine of 12 PTSD subjects were reducers (sensitivity of 75%) and 5 of 6 normals were augmenters (specificity of 83.3%). By the third and fourth second following tone onset, the mean HR of PTSD subjects increased more than twice that of the normals. HR change scores were significantly responsive to the manipulation of stimulus intensity and to the difference between our two groups. P2 reduction differentiates Vietnam veterans with combat-related PTSD from combat veteran controls, and PTSD subjects are more autonomically arousable than their combat veteran peers.

Auditory Threshold↗
PubMed1980

Pathways between constitution and competence during the 1st 5 years of life.

A global measure of newborn constitutional adequacy was found to be positively related to competent functioning at the age of 5-6 years. In a sample of 15 boys and 5 girls, newborn constitutional adequacy was related to aspects of focused (versus unfocused) activity, outgoingness, cognitive and verbal ability, and motor skill at the early childhood follow-up. Additionally, some preschool data were available on most of the sample and continuity of competent functioning was traced across the 3 age periods. Also, hyperactive behaviors at the preschool period had negative implications for functioning in early childhood.

Child Development↗
PubMed1979

Peer review of group therapy: Washington, D.C., 1972-1977.

The author discusses the evolution of psychiatric peer review in Washington, D.C. In its first six years (1972-1977) the Washington Psychiatric Society Peer Review Committee evaluated 146 cases, 23 (16%) of which focused on group therapy. Eight of these cases (35%) were partially or fully denied. Most of the cases involved outpatients with neuroses or character disorders who were treated in combined group and individual therapy. The author presents specific cases illustrating group therapy issues and peer review decisions. He discusses the benefits and liabilities of peer review and emphasizes its importance as a flexible, clinically sensitive, confidential, and meaningful process.

District of Columbia↗
PubMed1977

A psychodynamically oriented group training program for early childhood care givers.

A training program for enhancing the care-giving qualities of child-care workers was developed and implemented through semistructured groups for family day-care mothers. The authors describe the theoretical orientation, program goals, and the outcome for trainees and trainers. Most impressive was the group process and content, which indicated the effectiveness of psychodynamically oriented program for care givers--people who ordinarly would not be expected to integrate such an experience successfully.

Adult↗
PubMed1976

Twin studies of affective illness.

In a summary of the major twin studies of affective illness, there are significant differences between monozygotic (MZ) and dizygotic (DZ) concordance rates for both unipolar and bipolar illness, indicating the importance of genetic factors in the etiology of affective illness. However, since 28% of MZ twins are discordant for bipolar illness and 60% of MZ twins are discordant for unipolar illness, environmental factors are important as well. In addition, there is a significant difference between unipolar and bipolar concordance for MZ twins (although not for DZ twins). This supports other evidence that unipolar and bipolar illness are separate entities, and it suggests the possibility that genetic factors are more important in the occurrence of bipolar illness than in unipolar illness.

Affective Symptoms↗