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Biomedical subjects

M P Patel

Publications and source records attributed to M P Patel.

At least 37 records · Page 2Linked to original sources
PubMed1994

Evaluation of three methods for the rapid identification of Staphylococcus aureus in blood cultures.

A total of 445 blood cultures containing Gram-positive cocci in clusters were tested for the presence of Staphylococcus aureus with the Accuprobe, heat-stable thermonuclease, and latex agglutination using Staphaurex. The results show that the Accuprobe, thermonuclease, and Staphaurex correctly identified 95, 96, and 62 of the 100 specimens containing S. aureus. The corresponding specificity for the methods was 99.1%, 100%, and 98.5%, respectively.

Bacteremia↗
PubMed1994

Mechanisms of unresponsiveness associated with pretransplant blood transfusion-cyclosporine-induced mixed lymphocyte chimerism.

Multiple pretransplant blood transfusions while under limited daily cyclosporine cover (PTBT-CsA) induce extensive rat renal allograft survival and antigen-specific non-responsiveness. The underlying mechanisms of this extensive allograft survival are not yet fully understood. We hypothesized that one of the potential contributing mechanisms to tolerance induction in PTBT-CsA-treated kidney recipients is the development of stable mixed chimerism, putatively due to the proliferation of stem cells capable of haematopoiesis in the transfused blood. BN rats served as whole blood and kidney donors. LEW rats served as recipients of the PTBT-CsA protocol and BN kidney transplants. Three weekly transfusions were given under concomitant limited CsA cover. Following these multiple primary sensitizations, antigen-specific splenic cellular responsiveness in vivo was normal in comparison with naive animals. However, these experimental splenocytes were non-specifically suppressed against third-party allodeterminants. At 100 days post-transplantation (T100) following tolerance induction to kidney allografts (secondary challenge), in vivo adoptive transfer experiments demonstrated the existence of potent splenic suppressor cells. In vitro suppressor cell assays confirmed that these cells were non-specific suppressor cells. However, following chimerism stabilization at T130, splenic antigen-specific suppressor cells became exclusively expressed in the tolerant animals, replacing the non-specific suppressor cells. At this time, splenic microchimerism was at peak levels and remained stable from T100 to T130. In conclusion, these findings demonstrate that sequential mechanisms of suppressor cell network expression are induced within a chimeric environment by blood-CsA immune modulation. Stable mixed lymphocyte chimerism and related immunomodulatory mechanisms may, therefore, play an important tolerogenic role in blood-CsA-induced non-responsiveness and in the beneficial effect of blood transfusion.

Animals↗
PubMed1992

Refractive index and molar refraction of methacrylate monomers and polymers.

The refractive indices of a number of methacrylate monomers have been measured and corresponding molar refraction data calculated. Similar determinations were made on a number of methacrylate polymers. The molar refraction values determined were in excellent agreement with the values calculated from the published molar refraction values of the chemical groups involved. There was little difference between the molar refraction values of monomers and that of the repeat unit in the corresponding polymers, in marked contrast to the molar volumes. The ratio of refractive index to molar volume was reasonably consistent for all methacrylates studied (0.25-0.30 approximately).

Chemical Phenomena↗
PubMed1991

Heterocyclic methacrylates for clinical applications. I. Mechanical properties.

The mechanical properties of a number of heterocyclic and one cyclic methacrylate have been studied for their potential in low polymerization shrinkage systems. This study included both homopolymers and room temperature polymerizing systems using poly(ethyl methacrylate) powder with a heterocyclic methacrylate monomer. The one cyclic methacrylate studied, isobornyl methacrylate, gave an extremely brittle polymer; furthermore, it would not form a dough with poly(ethyl methacrylate). The homopolymers gave Young's moduli in the range 1.38-2.19 GN/m2, i.e. lower than poly(methyl methacrylate). The moduli of poly(ethyl methacrylate)/monomer systems are theoretically predictable from the moduli of the homopolymers involved. The above materials were generally ductile and the mechanical properties indicated a useful class of materials for clinical use.

Biocompatible Materials↗
PubMed1991

Heterocyclic methacrylates for clinical applications. II. Room temperature polymerizing systems for potential clinical use.

A number of useful room temperature polymerizing resins were formulated, based on poly(ethyl methacrylate) powder and a range of low shrinkage heterocyclic methacrylate monomers. N,N-dimethyl-p-toluidine or p-tolyl diethanolamine were used as activating amines, but the latter material is less active and some care is necessary with respect to the source of the monomer. Isobornyl methacrylate is a useful diluent monomer to reduce the exotherm.

Biocompatible Materials↗
PubMed1991

Heterocyclic methacrylates for clinical applications. III. Water absorption characteristics.

The water absorption and desorption behaviour of poly(isobornyl methacrylate) and poly(tetrahydropyran-2-ylmethyl methacrylate) obeyed diffusion laws on repeated absorption/desorption cycles. However, the polymers of 2,3-epoxypropyl, tetrahydrofurfuryl and tetrahydropyranyl methacrylates did not obey diffusion laws, did not equilibrate after 2 yr immersion in water and exhibited very high uptake values (30-90%). For 2,3-epoxypropyl methacrylate, the sample disintegrated. A clearly detailed structure of the heterocyclic ring is critical. The use of these monomers in room temperature polymerizing poly(ethyl methacrylate)/monomer systems generally reflected the behaviour of the related homopolymers.

Absorption↗
PubMed1991

Developmental anomalies associated with hypospadias.

Hundred and thirty patients with hypospadias were studied between 1983 and 1990, with an aim of analysing the associated anomalies in these patients. Urogenital anomalies were observed in 30% and extra-urogenital anomalies were noted in 16%. Undescended testis was the most frequently seen anomaly, having been noted in 6.9% of 130 cases. Vesico-ureteral reflux was present in 5.4% and inguinal hernia in 3.8%. The incidence of these anomalies increased in proportion to the severity of penile deformity. The present article emphasizes the need for systemic urological and endocrinal examination, especially in severe cases of hypospadias.

Abnormalities, Multiple↗
PubMed1991

Mechanisms of prior blood transfusion-cyclosporine-induced tolerance: a potential role for immune-cellular chimerism.

Skin allografts were not enhanced by prior conditioning of blood and CyA (5 or 10 mg/kg/d). However, when BM-CyA pretreatment was used, SA survival was significantly prolonged (CyA, 5 or 10 mg/kg/d). In examining differences between the BT-CyA and BM-CyA protocols, equivocal levels of donor microchimerism (1.5%) were found in the spleens of BT-CyA conditioned recipients at the time of transplantation (day 0). In contrast, highly significant levels of splenic donor chimerism (17.2%) developed at day 0 for the BM-CyA pretransplant recipients. Skin-allograft prolongation under the BM-CyA protocol implied that the effect may be linked to the existence of a donor-specific stem-cell population in the recipient animal.

Animals↗
PubMed1991

Vascularized bone marrow transplantation (VBMT): induction of stable mixed T-cell chimerism and transplantation tolerance in unmodified recipients.

In this preliminary report, our model of VBMT across a semiallogeneic barrier consistently brings about antigen-specific host tolerance with absence of GVHD in the majority of recipients. No immunologic or radiologic intervention was utilized. These results emphasized a potentially important mechanism for low-level stable mixed lymphoid chimerism (SMLC) in tolerance induction, independent of immune suppressive effects due to irradiation or immunopharmacologic intervention.

Animals↗
PubMed1990

Development of stable mixed T cell chimerism and transplantation tolerance without immune modulation in recipients of vascularized bone marrow allografts.

A consistent majority (62.5%) of immunologically unmodified rat recipients transplanted with vascularized hind-limb bone marrow allografts across a semiallogeneic transplant barrier developed tolerance with absence of graft-versus-host disease. A minority of recipients (37.5%) demonstrated lethal GVHD. Transplantation tolerance in the majority was associated with the induction of stable low-level mixed T cell chimerism, including donor CD5+, CD4+, and CD8+ lymphocytes. Chimeras were specifically immune nonresponsive to host alloantigenic determinants. These results emphasized a potentially important mechanism for low-level stable mixed lymphoid chimerism (SMLC) in tolerance induction, independent of immune suppressive effects due to irradiation or immunopharmacologic intervention. These vascularized bone marrow transplantation (VBMT) results may establish the experimental foundation for a novel approach to stem cell transfer and bone marrow transplantation.

Animals↗
PubMed1990

Site-specific suppression of cell-mediated immunity by cyclosporine.

In this study, it was demonstrated that site-specific suppression of T-cell-mediated immune responsiveness could indeed be achieved by topical application of cyclosporine. Evidence for site-specific immune suppression was obtained from a dual skin allograft model in rats. These animals were given an initial 10-d systemic treatment of CsA. Subsequently, one allograft was treated with topical CsA and the other was treated with the vehicle alone. Anti-inflammatory efficacy and prolonged skin allograft survival were observed both grossly and histopathologically in the presence of topically administered CsA, while contralateral vehicle-treated control grafts underwent vigorous rejection. Systemic lymphocyte DNA synthesis following Con-A and PHA stimulation was normal to elevated. Therefore, systemic T-cell-mediated immunity appeared unaffected or possibly activated even with concomitant topical CsA treatment. CsA levels were low systemically, and showed relative site-specificity in terms of tissue concentration. In conclusion, this study indicates that topical CsA is capable of locally suppressing a strong T-cell-mediated immune response after an initial short-term systemic dose of CsA. Furthermore, certain putative autoimmune and inflammatory diseases of the skin, such as psoriasis and eczematous dermatitis, which may share common mechanisms of action compared to skin allograft rejection should likewise benefit from topical CsA treatment.

Animals↗
PubMed1989

Evaluation of five commercial systems for identification of coagulase-negative staphylococci to species level.

Five commercially available systems for identification of coagulase-negative staphylococci to the species level were evaluated using 163 clinical staphylococcal isolates. The conventional method of Kloos and Schleifer served as reference method. The API20GP system showed the highest rate of agreement with the reference method, correctly identifying 98.8% of the isolates. The Microscan system had an overall rate of agreement of 96.3%, and Staph-Trac, Sceptor and Staph-Ident rates of 88.8%, 87.6% and 84.% respectively.

Bacterial Typing Techniques↗
PubMed1989

Cross-linking and ring opening during polymerization of heterocyclic methacrylates and acrylates.

Heterocyclic methacrylates have been shown to have low polymerization shrinkage. In this paper, the extent of ring opening has been assessed by the degree of consequent cross-linking. In polymers of tetrahydrofurfuryl methacrylate and acrylate, tetrahydropyranyl and tetrahydropyran-2-ylmethyl methacrylate, fewer than 1% monomer units were involved in cross-linking and hence ring-opening reactions. 2-epoxypropyl methacrylate, when polymerized, was very extensively cross-linked indicating prolific ring opening. However, the polymerization shrinkage of this material was the highest of the heterocyclic methacrylates studied and was that predicted from the known molar volume change of methacrylate esters. Ring opening does not, therefore, appear to be a significant factor in the polymerization shrinkage of heterocyclic methacrylates.

Acrylates↗
PubMed1989

Spontaneous spinal epidural hematoma in a 7-year-old girl. Diagnostic value of magnetic resonance imaging.

The authors report a 7-year-old girl who developed neck pain and stiffness over a four-day period. There was no fever, trauma, systemic illness or headache. Physical examination demonstrated subtle neurologic deficits indicative of cervical cord compression. CAT scan and subsequent Magnetic Resonance Imaging (MRI) of the cervical spine demonstrated a spinal epidural hematoma, which was evacuated surgically. Post-operative angiography failed to demonstrate a vascular abnormality. The child recovered without neurologic deficit. MRI proved to be a sensitive tool in identifying the nature and extent of this lesion, and may be considered in lieu of myelography.

Child↗
PubMed1989

A simple method of identifying loosening or infection of hip prostheses in nuclear medicine.

Joint replacement is now established as a reliable orthopaedic procedure for the relief of many painful degenerative conditions of the hip. When successful it enhances hip movement and relieves pain with a concomitant improvement in function and well being for the patient. When unsuccessful the persistence of pain usually signifies loosening or infection. Loosening may result from mechanical failure or infection. Accurate distinction between septic and aseptic loosening is important for planning and executing surgical intervention. The experience of the Department of Nuclear Medicine in Coventry assessing pathology in painful hip prostheses was retrospectively reviewed in 47 patients. These patients were imaged from 1985 to 1987 and all had good clinical follow-up enabling the diagnosis of loosening, infection or normal to be made with confidence. All patients had three phase bone imaging and some had additional gallium imaging. The images were reviewed with particular emphasis on the pattern of uptake in the late bone image and congruence of abnormal uptake in the early bone image and gallium image. It is concluded that for the majority of patients simple three phase bone imaging will provide the required diagnostic information.

Aged↗
PubMed1987

Polymerization shrinkage of methacrylate esters.

The polymerization shrinkage of a range of poly(n-alkyl methacrylates) in the range C1 to C16, some of their isomers and the polymers of cyclic and heterocyclic methacrylates have been measured using densitometry. The percentage volume shrinkage decreases with the size of the substituent side group. This proved to reflect the fact that the change in molar volume on polymerizing a methacrylate ester is reasonably constant at 22 cc/mol irrespective of the geometry of the substituent group. However, the glass transition temperature of the polymer depends very critically on the geometry of the side group. Hence one method for the development of low shrinkage glassy polymers is to investigate methacrylate esters of large molar volume, but with side group geometry that results in a high glass transition temperature. Polymerization shrinkage can be used to determine the degree of conversion of a polymer, using the value of 22 cc/mol as the change in molar volume.

Acrylates↗