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N Kahn

Publications and source records attributed to N Kahn.

At least 19 recordsLinked to original sources
PubMed2002

Complexity analysis of placental blood flow in normal and high-risk pregnancies.

Various strategems of complexity analysis of microvascular blood flow were carried out in several fields of medicine in the past, as such as angiology, ophthalmology and neurology. The introduction of colour-angio-mode, a special form of colour coded Doppler sonography, now makes possible to perform complexity analysis of the placental blood displacement even in the absence of information about hydrodynamic details such as directionality, velocity profile and number of displaced blood cells. Algorithms were developed which allows to extract information concerning the time averaged power of phonon-erythrocytes collision events (from the square of the frequencies of back scattered ultrasound recorded during 166 ms) in 20,000 to 40,000 regions of interest. The obtained values are being displayed as false coloured pixels on a video-screen, we succeeded to obtain quantitative data about displacement rates.In cross-sectional and longitudinal studies we generated typical diagrams displaying the "occurrence rate" of various powers of displacement over time. By this mode of display contour plots can be generated, showing a large amount of low intensity pixels and a small amount of high intensity pixels representing the parenchymatous blood flow inside the placenta. As was to be expected, interdependencies between the placental blood flow and the maternal and fetal heart rates as well as the maternal breathing can be found. While there was only limited influence of maternal and fetal heart rate on the placental blood flow, maternal breathing showed striking influence. Surprisingly, during expiration the power of placental blood movement was decreased, and there was a marked increase during inspiration. In cases of severe intrauterine growth retardation, colour pixel intensities were seen to transiently vanish during end-expiration. The power of placental blood displacement was marked increased subsequent to reducing maternal hematocrit during hemodilution therapy by infusion of artificial colloids. These interdependencies could be confirmed by ex vivo examinations perfusing and percolating the placenta after birth in a hemodynamic model. Additionally, we found interdependencies between fetal and maternal blood displacement inside the placenta. By modelling the decrease of fetal inotropic power in the ex vivo examinations, increase in the power of maternal blood displacement in the intervillous space. The two types of placental blood flow are known to be determined by many factors. While it is currently impossible to measure all these parameters determining an parenchymatous blood flow, it is possible to obtain useful informations about the physiologic and pathophysiologic changes of placental blood flow using colour-angio-mode as a tool of complexity analysis based on the distribution of local blood displacement. This new knowledge can help to understand clinically relevant changes in the individual patient as well their underlying causes.

Female↗
PubMed2001

Impaired platelet prostacyclin receptor activity: a monozygotic twin study discordant for spinal cord injury.

Coronary artery disease (CAD) has been reported to occur prematurely in individuals with spinal cord injury (SCI). Although persons with SCI have metabolic abnormalities that may predispose them to CAD, other potential aetiologies may also be operative. Increased platelet aggregation, among other factors, initiates thrombus formation at the site of the vessel injury, which may acutely obstruct arterial blood flow. Prostacyclin is known to have a beneficial effect to inhibit platelet aggregation and prevent thrombus formation. Platelets were studied from 12 pairs of monozygotic twins, one co-twin with SCI. Each twin pair had similar patterns of platelet aggregation with adenosine diphosphate (ADP), thrombin or collagen, as well as inhibition of platelet aggregation by prostacyclin (PGE1/I2) and synthesis of cyclic adenosine mono phosphate (AMP) by the prostanoid. However, the twin pairs differed in their response to PGE1/I2 inhibition of platelet-stimulated thrombin generation that was completely inhibited in non-SCI platelets but not in SCI platelets. Scatchard analysis of the binding of 3H-prostaglandin E1, a stable prostacyclin receptor probe, showed the presence of one high-affinity (Kd1=8.1 +/- 2.8 nM; nl=168 +/- 35 sites per platelet) and one low-affinity (Kd2=1.1 +/- 0.22 microM; n2=1772 +/- 220 sites per cell) prostacyclin receptor in normal platelets, whereas in SCI platelets there was a significant loss (P<0.00l) of high-affinity receptor sites (Kd1=6.34 +/- 1.80 nM; n1=42 +/- 11 sites per platelet) with no significant change in the low-affinity receptor sites (Kd2=1.2 +/- 0.23 microM; n2=1860 +/- 412 sites per cell). These discordant platelet findings in identical twin pairs raises the possibility of an environmental aetiology for accelerated CAD in those with SCI. The loss of inhibitory effect of PGI2 on thrombin generation in the twin with SCI appears to be because of loss of platelet high-affinity prostanoid receptors, which may contribute to atherogenesis in individuals with SCI.

Alprostadil↗
PubMed2001

The Interdisciplinary Generalist Curriculum (IGC) project: an overview of its experience and outcomes.

The Interdisciplinary Generalist Curriculum (IGC) Project was a competitive, seven-year demonstration project funded by the Health Resources and Services Administration (HRSA). It was established to determine whether specific interdisciplinary innovations in preclinical medical school curricula could affect students' selection of careers in family medicine, general internal medicine, or general pediatrics. Through collaboration among the three generalist disciplines, the IGC innovation exposed all preclinical students in ten demonstration schools to a new or significantly enhanced preclinical curriculum that included a direct supervised clinical experience with a generalist physician preceptor. The project was managed by an interdisciplinary executive committee that was codirected by one representative each from family medicine, general internal medicine, and general pediatrics. A national advisory committee with representation from the academic and professional organizations of family medicine, internal medicine, pediatrics, and osteopathy provided input to the executive committee in guiding the project. The project was externally evaluated. Major outcomes of the IGC Project include sustained curricular changes in ten institutions, prompted by relatively few dollars and demonstration of models for collaboration at institutional and national levels. This supplement describes the IGC Project's experience and outcomes so that others may draw pertinent information to apply to their own efforts in medical education.

Curriculum↗
PubMed2001

Implementation of the Interdisciplinary Generalist Curriculum Project: considerations of structure, funding, and design.

Implementation of the Interdisciplinary Generalist Curriculum (IGC) Project involved complex processes that reflect structural, funding, and intervention design considerations. Among structural considerations, the IGC Project benefited from a national structure above the level of the demonstration schools. Governance by committee was highly effective because it harnessed and balanced power. At the national level, governance by committee was enhanced by strong central coordination, and it had a role-modeling effect for governance at the school level. The IGC experience over the seven-year course of the project suggests that it is important to revisit the role of a national advisory committee over time and to revise that role as warranted. Funding considerations, including the importance of funding evaluation for a period of time long enough to measure intended impacts and the length and amount of funding to demonstration schools, are discussed. Prescription of the IGC intervention and the focus on years one and two of medical education are critical design considerations. The authors conclude that the IGC Project used relatively few federal dollars to demonstrate a highly prescribed intervention in a limited number of medical schools toward a clear and limited goal. IGC lessons apply to programs specifically targeting primary care education, but also to other medical school curricular innovations, and perhaps, to a larger framework of multi-site educational interventions.

Curriculum↗
PubMed2001

Curricular change: recommendations from a national perspective.

Recommendations on future directions, funding, and organizational and curricular issues have emerged from the complexity of the Interdisciplinary Generalist Curriculum (IGC) Project. For example, future demonstration projects aimed at innovations in medical education that are funded through the contracting mechanism are recommended, and funding intended to serve as institutional leverage for demonstrating desired curricular innovations in medical education is encouraged. Funding provided to entities that can maximize influence within the institutions is recommended. Also, the period of time over which funds are provided needs to take into consideration the breadth of the impact of the funded program on the larger curriculum and the length of time needed to measure desired outcomes. Organizational findings are that multi-site projects with administrative oversight bodies should be governed by representatives of concerned disciplines who have stakes in the demonstration of the innovations in medical education, and roles of the executive and advisory committees involved in the effort need to be made explicit at the onset and revisited over time. Similarly, the role of the funder needs to be explicit. Curricular recommendations are that medical schools are encouraged to develop longitudinal generalist preceptorship experiences early in medical education for all students, regardless of their eventual career choices. Schools should anticipate that curricular innovations in the preclinical years may require modifications of the educational process in the clinical years.

Curriculum↗
PubMed2001

Entry of US medical school graduates into family practice residencies: 2000-2001 and 3-year summary.

This is the 20th report prepared by the American Academy of Family Physicians (AAFP) on the percentage of each US medical school's graduates entering family practice residency programs. Approximately 12.8% of the 15,825 graduates of US medical schools between July 1999 and June 2000 were first-year family practice residents in 2000, compared with 13.4% in 1999 and 15.4% in 1998. Medical school graduates from publicly funded medical schools were almost twice as likely to be first-year family practice residents in October 2000 than were residents from privately funded schools, 15.6% compared with 8.7%. The West North Central region reported the highest percentage of medical school graduates who were first-year residents in family practice programs in October 2000 at 18.2%; the Middle Atlantic and New England regions reported the lowest percentages at 8.3% and 6.8%, respectively. Nearly half of the medical school graduates (47.0%) entering a family practice residency program as first-year residents in October 2000 entered a program in the same state where they graduated from medical school. The percentages for each medical school have varied substantially from year to year since the AAFP began reporting this information. This article reports the average percentage for each medical school for the last 3 years. Also reported are the number and percentage of graduates from colleges of osteopathic medicine who entered Accreditation Council for Graduate Medical Education-accredited family practice residency programs, based on estimates provided by the American Association of Colleges of Osteopathic Medicine.

Career Choice↗
PubMed2000

Analysis of the inter- and intravillous placental blood circulation in high-risk pregnancies before and after the hemodilution therapy using the colour-angio-mode.

OBJECTIVE: The aim of the study was to examine the efficiency of a hemodilution (HD) therapy on the inter- and intravillous placental blood circulation in high-risk pregnancies by applying the colour-angio-mode (CAM). PATIENTS AND METHODS: 24 patients were examined who had fetal growth retardation and/or pathological Doppler results. In all cases the hematocrit was >36%. The patients were given 500 ml Ringer solution and 500 ml HAES 10% intravenously per day; maternal heart rate and blood pressure were measured continuously. Prior to and after the therapy the same area of the placenta was examined using CAM; histograms demonstrating the distribution of the intensity values and summation values of the color pixels were calculated. RESULTS: In 14 patients the fetal outcome was good. The histograms showed in 11/14 cases an increase of low intensity values indicating an improvement of the placental circulation. The summation value of the color pixels as measured by CAM was significantly increased after the therapy in these cases (p = 0.022). In 10 patients the fetal outcome was unfavorable. The histograms showed a decrease of the intensity values in 6/10 cases. There was no significant change in the summation values of the color pixels after the therapy (p = 0.139). CONCLUSIONS: CAM sonography demonstrated for the first time a local effect of the HD therapy within the placenta. In the positive case the placental blood circulation will improve and the pregnancy develops favourably (responder). In the negative case there is no change of the placental blood circulation and pregnancy must be terminated due to a pathological fetal heart rate tracing, fetal growth failure or hypertensive disorders (nonresponder).

Adolescent↗
PubMed1999

[The role of genetic factors in the development of gastric cancer].

In general, a genetic predisposition to a tumour disease such as gastric cancer is postulated in patients with cancer at an unusually early age or when several relatives are affected. A clear definition of hereditary gastric cancer is lacking. Two types of families may be distinguished: kindreds with gastric cancer only (site-specific), and kindreds with gastric as well as colorectal cancer, representing the hereditary non-polyposis colon cancer (HNPCC) syndrome. A genetic predisposition is presumed in young patients with a diffuse type of gastric cancer, in contrast to the intestinal type which is associated with atrophic gastritis and older age. A variety of genetic abnormalities in tumour tissue have been described, e.g. mutations in genes involved in DNA repair. Helicobacter pylori plays an important role in the aetiology, but the interaction with genetic factors is unknown.

Adult↗
PubMed1994

The generalist health care workforce: issues and goals.

The generalist health care workforce in the United States is best characterized as those practitioners who deliver primary care services. These include most family physicians, general internists, general pediatricians, nurse practitioners, osteopathic family physicians, and physician assistants. Based on a variety of factors, including health care needs, managed care/HMO hiring practices, international comparisons, and health care costs, the case for increasing the amount and proportion of generalist providers is compelling. Projections strongly suggest a worsening shortfall of generalists if no change is made. Changing the career choices of medical students to promote generalism, even significantly, will take 20 years or more to have a meaningful impact. Therefore, retraining specialist physicians in oversupply to practice as generalists is an important option to consider. To best meet the nation's health care needs, three issues need to be addressed in the context of health care reform: the creation of a "system" of generalist care that integrates into a coherent and collaborative framework the scopes of practice of the various generalist disciplines; the pursuit of a workable short-term model to convert specialist physicians into generalist physicians, led jointly by family medicine, general internal medicine, and general pediatrics, and a significant change in the medical education process to produce an ample supply of well-trained generalists.

Delivery of Health Care↗
PubMed1990

Nucleoside inhibitors of rhodopsin kinase.

The specificity of the ATP-binding site of rhodopsin kinase was studied with adenosine analogues that are competitive inhibitors. Systematic changes in the ribose ring (position 5') and the purine ring (positions 2, 6, 7, 8, and 9) and determination of the inhibitory properties of these analogues lead to the following conclusions: (1) The N6 nitrogen in the purine ring is essential for binding at the active site, which may explain the marked preference for ATP rather than GTP as substrate. (2) The configuration of the sugar moiety is critical for the binding. (3) Positions 2, 3, and 8 of the purine ring, as well as the polyphosphate chain, play a minor role in substrate recognition by rhodopsin kinase. (4) ATP gamma S is a good substrate for rhodopsin kinase (thus rhodopsin phosphorothioate, a phosphatase-resistant product, can be formed in order to study the role of phosphorylation in rod outer segments). Pyrrolopyrimidine derivatives are very potent inhibitors of rhodopsin kinase. The Ki of one of these, sangivamycin, is 180 nM. Sangivamycin in solution assumes the anti conformation, as determined by nuclear Overhauser measurement. These measurements show that the most potent inhibitors of rhodopsin kinase, sangivamycin and toyocamycin, occur in solution preferentially in the anti conformation. Many nucleotides and nucleosides tested that are not inhibitors are syn, and many that are inhibitors form a mixture of syn and anti. The hypothesis that inhibitors may have a conformation intermediate between syn and anti was strengthened by testing a cyclic nucleoside locked in an anti conformation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1990

Behavioral and pharmacologic management of patients with Alzheimer's disease.

While as yet there are no proven effective primary treatments for Alzheimer's disease, physicians play a critical role in the evaluation and long-term supportive care of these patients and their families. The physician also plays a pivotal role in helping the patient make management decisions regarding their loved one such as organizing the process of nursing home placement in the more advanced phases of the illness. In addition, physicians provide a focal point for triage community support resources, such as the Alzheimer's Association. When necessary, the judicious and conservative use of psychopharmacologic agents can serve to partially diminish the pervasive behavioral complications of this illness.

Aged↗
PubMed1987

Hazards of 'deleading' homes of children with lead poisoning.

"Deleading" the homes of children with lead poisoning is a necessary step to terminate the child's exposure to lead. Lead poisoning as a result of lead exposure during the process of deleading has occurred in deleading workers but has not been well documented among children whose homes are deleaded. We treated four children with classes I through III lead poisoning (range of blood lead [Pb-B] level, 1.6 to 2.75 mumol/L [33 to 57 micrograms/dL]) who had significant elevation of their Pb-B levels (range, peak 4.34 to 6.27 mumol/L [90 to 130 micrograms/dL]) following deleading of their homes. The methods used for deleading included scraping, sanding, and burning of the paint. Symptoms included irritability (n = 3) and vomiting (n = 1). The elevation of the Pb-B levels was detected early, allowing prompt chelation therapy. Because exacerbation of lead poisoning may occur in children following deleading of their homes, safer approaches of deleading should be determined.

Chelating Agents↗
PubMed1987

Postpartum psychosis induced by bromocriptine.

Two multigravida patients with no prior psychiatric history were seen with postpartum psychosis, having received bromocriptine for inhibition of lactation. Bromocriptine given in high doses has been associated with psychosis in patients receiving the drug for Parkinson's disease. These cases demonstrate that bromocriptine may cause psychosis even when given in low doses.

Adult↗