Evaluation of a technique for identification of Shiga-like toxin-producing Escherichia coli by using polymerase chain reaction and digoxigenin-labeled probes

A polymerase chain reaction (PCR) technique for the identification of Shiga-like toxin (SLT)-producing Escherichia coli was assessed by using 95 strains of SLT-producing E. coli and 5 Shigella dysenteriae type 1 strains. PCR was used for the amplification of slt gene sequences from whole bacterial colonies. A digoxigenin-labeled DNA probe was used for identification of the PCR products in a spot blot hybridization assay. Modifications were made to adapt this technique for the proper identification of 10 SLT-producing isolates which were refractory to the heat lysis step that was used to liberate whole-cell DNA for PCR and 6 isolates which gave nonspecific amplification products. The sensitivity and specificity of this assay were each 99% when compared with toxin neutralization results by using SLT-specific monoclonal antibodies. These values indicate that this detection technique could be suitable for use in a clinical laboratory.     

Isolation of porcine circovirus-like viruses from pigs with a wasting disease in the USA and Europe

Sinus pericranii is an anomalous extracranial vascular malformation that is in continuity with the intracranial dural venous sinuses. Five case reports, three congenital and two traumatic, are described. Clinical management, including evaluation, diagnosis, and treatment, is discussed. Awareness of this entity by plastic surgeons will allow for earlier diagnosis and appropriate surgical management, resulting in decreased risk of complications.     

The organization and postnatal development of the commissural projection of the rat somatic sensory cortex

Anterograde and retrograde tracing experiments have been used to demonstrate the origin and terminal distribution of commissural fibers in the first somatosensory cortex (SI) of the rat. The commissural fibers originate from pyramidal cells of all layers, but predominantly from layers III and V. The fibers terminate in a series of approximately vertical bands. In each of these there are concentrations of terminals extending from the inner portion of the molecular layer to the deep portion of layer III as well as in the superficial part of layer V, and in layer VI. Discrete vertical bands of cortex are reciprocally connected across the midline to give both the origin and terminal regions of the projection a patchy or "columnar" appearance. The commissural fibers arise from and terminate in areas of the cortex that lie between and alongside the aggregations of granule cells that distinguish SI of the rat. No commissural fibers terminate within the aggregations of layer IV cells themselves but the more superficial terminal ramifications may come to overlie these aggregations. A heterotopic projection to the contralateral second somatosensory cortex has been observed and is similar in form to the homotopic projection to SI. Many commissural fibers have crossed the midline in the corpus callosum by the day of birth but lie in the underlying white matter and do not enter the cortical plate until at least the third postnatal day. During the first postnatal week these fibers grow somewhat diffusely into the maturing cortex and their topographic and laminar pattern of distribution attains its adult characteristics by the end of the first week. Commissural axons, thus, arise from immature cells but the maturation of cell form seems to precede the ingrowth of these axons and the acquisition of commissural synapses.     

Interim report on the radiosurgical treatment of cerebral arteriovenous malformations. The influence of size, dose, time, and technical factors on obliteration rate

During the authors' initial 4-year experience with radiosurgery using the Leksell cobalt-60 gamma unit, they treated 121 patients with cerebral arteriovenous malformations (AVMs). The radiosurgical dose to the margin of the nidus was 20 Gy for lesions less than 2.0 cm in diameter (volume < or = 4.2 cm3); 18 Gy for malformations 2.1 to 3.0 cm in diameter (volume 4.2-14.1 cm3); and 16 Gy for malformations greater than 3.0 cm (volume > 14.1 cm3). Fifty-one patients underwent follow-up angiography between 1 and 3 years after treatment, and complete obliteration of the nidus was confirmed in 38 (74.5%) of these patients. Thirty-two (74.4%) of 43 AVMs with volumes of 10 cm3 or less and six (75%) of eight larger AVMs (volume 11-30 cm3) showed complete obliteration. Analysis of the time course of AVM nidus shrinkage and obliteration showed that most of the radiosurgically induced effect had occurred by 36 months after treatment. Retrospective analysis of the dose plans for 10 AVMs that were not obliterated by 36 months after gamma knife radiosurgery at the authors' institution (eight cases) or elsewhere (two cases) revealed that six AVMs had not been covered completely by the prescribed isodose. Six (5%) of the 121 patients developed neurological deficits as a direct result of radiosurgical treatment. The authors infer from these data that malformations up to 30 cm3 in volume (approximately 4.0 cm in average diameter) can be treated effectively with an acceptably low complication rate using a radiosurgical dose of 16 Gy to the margin of the nidus. The obliteration rate for the larger malformations that were treated with a dose of 16 to 18 Gy appears to be similar to that for smaller ones treated with 18 to 20 Gy. As more experience accrues using radiosurgery to treat AVMs, patient selection criteria and the variables associated with successful obliteration of the nidus should become more clearly defined.     

The CD40-CD154 system in anti-infective host defense

Research in the past few years has documented significant advances in our understanding of the CD40-CD40 ligand (CD154) system in diverse immune functions. This system influences many T cell mediated inflammatory immune responses and effector functions, unmasking a previously unexpected role for CD40-CD154 in cell mediated immunity. Manipulation of CD154 in animal models of infection by the use of CD154-deficient mice or anti-CD154 antibodies has shown the importance of this system in the initiation of the inflammatory response, in the activation of antigen-presenting cells and in resistance to infections.     

Genetic marking shows that Ph+ cells present in autologous transplants of chronic myelogenous leukemia (CML) contribute to relapse after autologous bone marrow in CML

Relapse after autologous bone marrow transplantation for chronic myelogenous leukemia (CML) can be due either to the persistence of leukemia cells in systemic tissues following preparative therapy, or due to the persistence of leukemia cells in the autologous marrow used to restore marrow function after intensive therapy. To help distinguish between these two possible causes of relapse, we used safety-modified retroviruses, which contain the bacterial resistance gene NEO, to mark autologous marrow cells that had been collected from patients early in the phase of hematopoietic recovery after in vivo chemotherapy. The cells were then subjected to ex vivo CD34 selection following collection and 30% of the bone marrow were exposed to a safety-modified virus. This marrow was infused after delivery of systemic therapy, which consisted of total body irradiation (1,020 cGy), cyclophosphamide (120 mg/kg), and VP-16 (750 mg/m2). RT PCR assays specific for the bacterial NEO mRNA, which was coded for by the virus, and the bcr-abl mRNA showed that in two evaluable CML patients transplanted with marked cells, sufficient numbers of leukemia cells remained in the infused marrow to contribute to systemic relapse. In addition, both normal and leukemic cells positive for the retroviral transgenome persisted in the systemic circulation of the patients for at least 280 days posttransplant showing that the infused marrow was responsible for the return of hematopoiesis following the preparative therapy. This observation shows that it is possible to use a replication-incompetent safety-modified retrovirus in order to introduce DNA sequences into the hematopoietic cells of patients undergoing autologous bone marrow transplantation. Moreover, this data suggested that additional fractionation procedures will be necessary to reduce the probability of relapse after bone marrow transplantation in at least the advanced stages of the disease in CML patients undergoing autologous bone marrow transplantation procedures.     

Multifactorial analysis of lung cancer dose-response relationships for workers at the Mayak nuclear enterprise

Dose-response relationships for alpha-radiation-induced lung cancers (adenocarcinoma, squamous carcinoma and small cell carcinoma) were developed by multifactorial analysis using data for Mayak nuclear enterprise workers chronically exposed by inhalation to 239Pu. The three most important lung cancer risk factors (smoking, plutonium incorporation, and external gamma irradiation), out of six factors previously identified, were used. Relative risks (odds ratios) were determined for 500 nuclear enterprise workers (162 cancer cases, 338 control) for different dose levels using a case-control study design and logistic regression. A threshold at about 3.7 kBq or 0.80 Gy was discovered for incorporated plutonium, which is satisfactorily described by linear-quadratic and quadratic models. Excess relative risk was 0.020 kBq(-2) and 0.97 Gy(-2). This quadratic function was mainly due to adenocarcinoma. A trend for decreasing risk was noted for the lowest levels of plutonium incorporation, near permissible level. No clear-cut dose-response relationship for lung cancer induction by chronic external gamma irradiation was obtained. Lung cancer induction by cigarette smoking had a linear dependence: smoking of one pack of papiroses (a type of Russian cigarette) per day for 5 y increases the lung cancer risk twofold. The effect was most clearly manifested for squamous-cell carcinoma.