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Biomedical subjects

G Hirsch

Publications and source records attributed to G Hirsch.

At least 19 recordsLinked to original sources
PubMed2001

Growth influences knee laxity after anterior tibial spine fracture: a study on rabbits.

An anterior tibial spine (ATS) fracture, with or without displacement, was created in the right knee of 8-week and 22-23-week-old rabbits. After 4 weeks of cast immobilization and 8 weeks of free cage activities, the animals were killed. A method to measure anterior knee laxity in rabbits was developed using a material testing machine. The laxity of the right knee was compared to the unoperated left knee in each rabbit. The difference was found to have increased in the adult rabbits after the healing of a displaced ATS fracture (median 0.5 mm, range 0.3-0.9), but not in the young rabbits (median 0.2 mm, range 0.0 -0.4). The ultimate load of the anterior cruciate ligament (ACL) was reduced after healing of the ATS fracture. The results support the theory that further growth may compensate for the functional elongation of the ACL caused by healing of a displaced ATS fracture. The study also indicates that an ATS fracture may affect the mechanical properties of the ACL.

Animals↗
PubMed2001

Specific or superfluous? Doubtful clinical value of granulocyte scintigraphy in osteomyelitis in children.

To study the clinical usefulness of granulocyte scintigraphy, eight children with clinical, laboratory and/or radiologic findings strongly suggestive of osteomyelitis were prospectively evaluated. Comparison was made with bone scintigraphy and magnetic resonance imaging. In adults, granulocyte scintigraphy is highly infection specific, although nonspecific findings (i.e. photopenic lesions) may also occur. Granulocyte scintigraphy was positive in one patient, false-negative in two and demonstrated nonspecific photopenic lesions in five children (62%). In conclusion, there appears to be little place for granulocyte scintigraphy in routine investigation of suspected ostoemyelitis in children.

Antibodies, Monoclonal↗
PubMed2001

Myocardial scintigraphy correlates poorly with coronary angiography in the screening of transplant arteriosclerosis.

BACKGROUND: Coronary angiography remains an important screening tool for transplant coronary arteriosclerosis (TxCAD) after heart transplantation despite criticism that it underestimates the incidence of TxCAD. In an effort to improve TxCAD incidence estimation, several methods of screening have been proposed. In the present study, the incidence of TxCAD assessed by both yearly coronary angiography and stress myocardial scintigraphy imaging was reviewed. PATIENTS AND METHODS: Ninety-nine consecutive primary heart transplantations were performed from 1988 to 1999. The standard immunosuppression protocol consisted of the introduction of antilymphocyte globulin and steroids, while maintenance therapy was with cyclosporine, imuran and steroids. Coronary angiography and a stress 2-methoxyisobutyl-isonitrile perfusion scan were performed yearly. TxCAD was defined by angiographic evidence of luminal abnormality by catheterization, or a perfusion abnormality at rest or after stress on myocardial scintigraphy. RESULTS: The mean recipient age was 49+/-12 years and the mean donor age was 33+/-13 years. The etiology of heart failure was ischemic cardiomyopathy (50%), dilated cardiomyopathy (41%) and congenital heart disease (9%). The freedom from angiographic TxCAD was 92% at one year, 64% at five years and 35% at eight years. The freedom from nuclear imaging TxCAD was 92% at one year, 69% at five years and 44% at eight years. However, a diagnosis of TxCAD by angiography only correlated with a diagnosis of TxCAD by nuclear imaging 52.8% of the time in the same patient, with a median time between studies of one month. CONCLUSION: The overall incidence of TxCAD diagnosed by angiography and nuclear imaging appears similar but correlates poorly in patients, casting doubt on the routine use of myocardial scintigraphy for screening TxCAD.

Adolescent↗
PubMed2000

Type and position of promoter elements in retroviral vectors have substantial effects on the expression level of an enhanced green fluorescent protein reporter gene.

PURPOSE: Although gene transfer with retroviral vectors has already been applied to patients as part of clinical protocols, low expression of transgenes in target cells still remains a problem. Therefore, we compared various retroviral vectors using different promoters and backbones for expression of the enhanced green fluorescent protein (EGFP) reporter gene in fibroblasts and CD34+ cells. METHODS: The N2A retroviral vector was used to test expression from the herpes simplex virus thymidine kinase promoter (vector N2A-TK-EGFP), a human phosphoglycerate kinase promoter (vector N2A-PGK-EGFP), and the SV40 promoter (vector N2A-SV-EGFP). Additional constructs used the spleen focus-forming virus (SFFV) long terminal repeat (LTR) as promoter and expressed EGFP alone (vector SFbeta1-EGFP) or EGFP and a downstream (vector SFbeta1-EGFP-IRES) or upstream (vector SFbeta1-IRES-EGFP) internal ribosomal entry site. RESULTS: For NIH 3T3 cells the fluorescence-activated cell sorting analysis revealed that the most active internal promoter was the SV40 promoter in the vector N2A-SV-EGFP (mean fluorescence intensity, MFI, 66.7 +/- 0.4), followed by N2A-PGK-EGFP (26.3 +/- 1.8 MFI), and N2A-TK-EGFP (4.8 +/- 0.1 MFI). Expression from the SFbeta1-EGFP vector (82.6 +/- 6.7 MFI) and the SFbeta1-EGFP-IRES vector (102.8 +/- 6.2 MFI) was higher than from SFbeta1-IRES-EGFP vector (15.5 +/- 1.8 MFI). In human CD34-positive cells, the EGFP expression from all vectors was considerably lower than in fibroblasts with the SFbeta1-EGFP vector still being four- to fivefold more active than the internal promoters tested. CONCLUSION: The SFFV LTR seems to allow a high expression of transgenes, as long as the transgene is not expressed downstream of an internal ribosomal entry site. Internal promoters may be useful for targeted gene expression in specific cell types, but the reduced level of expression from some internal promoters has to be taken into consideration.

3T3 Cells↗
PubMed2000

CD8+ T lymphocytes mediate destruction of the vascular media in a model of chronic rejection.

Allograft arteriosclerosis is an important characteristic of chronic graft rejection. In allograft arteriosclerosis there is a striking loss of medial smooth muscle cells (SMCs) before the development of a concentric intimal proliferative response. In this study we evaluated the role of CD8+ T lymphocytes in this medial SMC loss. Brown Norway aortic segments were transplanted into Lewis animals for 60 days (long allo-exposure) or 20 days (short allo-exposure). After 20 days allogeneic exposure aortic segments were transplanted back into syngeneic (Brown Norway) animals for 40 days. Experimental animals were treated with mAb to CD8. Apoptosis was measured by terminal dUTP nick-end labeling at 20 days and morphometry analyzed at 60 days to evaluate medial and intimal changes. Anti-CD8 treatment significantly lowered CD8+ T cell counts in peripheral blood, reduced medial SMC apoptosis at 20 days, and increased medial SMC counts at 60 days. Both short- and long-allogeneic exposure groups confirmed these findings and demonstrated that medial SMC loss is proportional to the length of allogeneic exposure. Antibody depletion of CD8+ T cells results in reduced medial SMC apoptosis and better medial SMC preservation. This supports the hypothesis that medial SMC loss occurs by apoptotic death and is driven by CD8+ T lymphocytes.

Animals↗
PubMed1999

A Theoretical Investigation of the Renner Interactions and Magnetic Dipole Transitions in the Ã-&Xtilde; Electronic Band System of HO(2).

The Ã(2)A' --> &Xtilde;(2)A" electronic band system of HO(2) has been simulated in emission using an extended version of the program RENNER (P. Jensen, M. Brumm, W. P. Kraemer, and P. R. Bunker, J. Mol. Spectrosc. 171, 31-57 (1995)). The two electronic states involved in this transition have strongly bent equilibrium geometries but they correlate together to form a (2)Pi state at linearity. As a result the energy level pattern in the states is affected by electronic angular momentum effects (i.e., the Renner effect and spin-orbit coupling). To simulate the spectrum, we have calculated ab initio the potential energy surfaces, electric dipole moment surfaces, magnetic dipole moment surfaces, spin-orbit coupling parameter, and the electronic angular momentum matrix elements. Some of the forbidden DeltaK(a) = 0 transitions occurring in the spectrum are induced by the magnetic dipole transition moment, and the others are electric dipole transitions that gain intensity because of the Renner interaction, spin-orbit coupling, or because of rotation-vibration interaction. All of these effects are allowed for in our calculation. The electric dipole transition moment is very small (0.017 D at the ground state equilibrium geometry) and because of this the magnetic dipole transitions are quite visible; the strongest magnetic dipole transitions are calculated to be about 10 times weaker than the strongest electric dipole transitions. In this way previous experimental assignments (E. H. Fink and D. A. Ramsay, J. Mol. Spectrosc. 185, 304-324 (1997)) are confirmed theoretically. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Ten-year heart transplantation experience at the MARITIME HEART CENTER: does volume affect results?

OBJECTIVE: To evaluate the experience of a small volume Canadian heart transplantation centre. DESIGN: Ninety-four consecutive primary heart transplants were performed from 1988 to 1998 at the Maritime Heart Center, Halifax, Nova Scotia, with 100% follow-up. Kaplan-Meier survival analysis was used. RESULTS: The mean recipient age was 48.5+/-12.3 years and donor age 33+/-13.2 years. Eighty per cent of recipients were men. The prevalence of elevated pulmonary vascular resistance (4 or more Wood units) was 20.2%. Etiology of heart failure was ischemic cardiomyopathy (50%), dilated cardiomyopathy (40.9%) and congenital heart disease (9.1%). Survival was 85.9% at one year (n=71), 75.3% at five years (n=33) and 60.5% at eight years (n=8). There was a trend toward survival benefit with human leukocyte antigen (HLA) -DR matching, body mass index ratio of donor to recipient greater than 0.8, ischemic time less than 90 mins and male donors. There was no effect on survival with donor or recipient age, recipient sex, diabetes, hypertension, hypercholesterolemia, elevated pulmonary vascular resistance and HLA-A/B mismatch. CONCLUSIONS: Excellent survival at one and five years following heart transplantation is reported that compares favourably with results published by the International Society for Heart and Lung Transplantation.

Adolescent↗
PubMed1998

Clinical value of imaging techniques in childhood osteomyelitis.

PURPOSE: The traditional approach to investigating suspected osteomyelitis in children includes conventional radiography and bone scintigraphy. The roles of US, CT and MR imaging are controversial. Our objective was to determine whether the additional use of these modalities would yield information likely to lead to treatment modification. MATERIAL AND METHODS: Sixty-five children with clinically suspected osteomyelitis took part in a prospective study. All patients underwent conventional radiography and bone scintigraphy. In addition to this, US, CT and MR imaging were all performed in 33 patients; the remaining 32 patients were examined with various combinations of these three modalities. The value of the additional information obtained was estimated retrospectively by a pediatric orthopedic surgeon in terms of possible modification of treatment. RESULTS: MR imaging was the modality with the highest sensitivity and specificity for detecting osteomyelitis. MR yielded information likely to influence treatment in the greatest proportion of patients (45%) followed by US (30%). CONCLUSION: The standard investigation protocol with the addition of US (because of its ability to detect subperiosteal abscesses early and simply) is adequate in uncomplicated cases. When additional imaging is required to outline a lesion, or in complicated cases, and when bone scintigraphy is inconclusive, MR imaging should also be performed. CT should be considered when MR investigation is not available or when anesthesia is required but cannot be provided.

Adolescent↗
PubMed1997

Ab initio Relativistic CI Calculations of the Spectroscopic Constants and Transition Probabilities for the Low-Lying States of the BiOH/HBiO Isomers

Spin-orbit MRD-CI calculations have been carried out for the potential energy surfaces of the seven lowest-lying electronic states of the BiOH molecule by employing relativistic effective core potentials. The HBiO isomer is found to be 4020 cm-1 less stable because of its inability to form multiple Bi-O bands. A bent 3A" BiOH ground state is predicted, which is split into all three of its components by spin-orbit coupling. The calculated X2A"-X1A' splitting is computed to be 5217 cm-1, but the corresponding X3-X2 value is only 29 cm-1. Fink et al. have observed spectral bands which appear with a Te value of 6200 cm-1 which are likely caused by BiOH. Since calculations at the same level for BiF underestimate the observed X2-X1 spin-orbit splitting by 650 cm-1, it appears that the present calculations are consistent with this experimental assignment. A vibrational progression with a 500 cm-1 frequency is also observed and this result fits in well with the computed Bi-O stretch omegae value of 527 cm-1. The calculations also find a relatively large 1Delta splitting (600 cm-1) because of the bent BiOH geometry, with comparatively strong transitions to the X1A' ground state, and it is suggested that the experimental BiOH assignment can be confirmed on this basis. Much stronger transitions to the 1Delta component should also be observed in emission in the 10 000 cm-1 range. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Intraaortic balloon pumping for cardiac support: trends in practice and outcome, 1968 to 1995.

OBJECTIVES: A total of 4756 cases of intraaortic balloon pump support have been recorded at the Massachusetts General Hospital since the first clinical insertion for cardiogenic shock in 1968. This report describes the patterns of intraaortic balloon use and associated outcomes over this time period. METHODS: A retrospective record review was conducted. RESULTS: Balloon use has increased to more than 300 cases a year at present. The practice of balloon placement for control of ischemia (2453 cases, 11.9% mortality) has become more frequent, whereas support for hemodynamic decompensation (congestive heart failure, hypotension, cardiogenic shock) has been relatively constant (1760 cases, 38.2% mortality). Mean patient age has increased from 54 to 66 years, and mortality has fallen from 41% to 20%. Sixty-five percent (3097/4756) of the total patient population receiving balloon support underwent cardiac surgery. Placement before the operation (2038 patients) was associated with a lower mortality (13.6%) than intraoperative (771 patients, 35.7% mortality) or postoperative use (276 patients, 35.9% mortality). Independent predictors of death with balloon pump support were insertion in the operating room or intensive care unit, transthoracic insertion, age, procedure other than angioplasty or coronary artery bypass, and insertion for cardiogenic shock. Independent predictors of death with intraoperative balloon insertion were age, mitral valve replacement, prolonged cardiopulmonary bypass, urgent or emergency operation, preoperative renal dysfunction, complex ventricular ectopy, right ventricular failure, and emergency reinstitution of cardiopulmonary bypass. CONCLUSIONS: Balloons are being used more frequently for control of ischemia in more patients who are elderly with lower mortality. An institutional bias toward preoperative use of the balloon pump appears to be associated with improved outcomes.

Age Distribution↗
PubMed1997

Safety and pharmacokinetics of hyperimmune anti-human immunodeficiency virus (HIV) immunoglobulin administered to HIV-infected pregnant women and their newborns. Pediatric AIDS Clinical Trials Group Protocol 185 Pharmacokinetic Study Group.

The pharmacokinetics and safety of hyperimmune anti-human immunodeficiency virus (HIV) intravenous immunoglobulin (HIVIG) were evaluated in the first 28 maternal-infant pairs enrolled in a randomized, intravenous immunoglobulin (IVIG)-controlled trial of HIVIG maternal-infant HIV transmission prophylaxis. Using 200 mg/kg, mean half-life and volume of distribution (Vd) in women were 15 days and 72 mL/kg, respectively, after one and 32 days and 154 mL/kg after three monthly infusions, with stable 4 mL/kg/day clearance. Transplacental passage occurred. Newborn single-dose half-life, Vd, and clearance were 30 days, 143 mL/kg, and 4 mL/kg/day, respectively. HIVIG rapidly cleared maternal serum immune complex-dissociated p24 antigen, and plasma HIV-1 RNA levels were stable. Mild to moderate adverse clinical effects occurred in 2 of 103 maternal and 2 of 25 infant infusions. No adverse hematologic, blood chemistry, or immunologic effects were seen. HIVIG is well-tolerated in HIV-infected pregnant women and their newborns, clears antigenemia, crosses the placenta, and exhibits pharmacokinetics similar to those of other immunoglobulin preparations.

Adolescent↗
PubMed1996

Tardive dyskinesia and pregnancy and delivery complications.

Twelve children and adolescents with movements suggestive of tardive dyskinesia (TD) were compared to 49 non-TD patients while receiving neuroleptic treatment. A multiple regression analysis revealed the diagnosis of TD to be significantly associated with a history of pregnancy and delivery complications (PDCs), suggesting that these events may increase the risk of the development of treatment emergent TD.

Adolescent↗