Infections of the nervous system: an update on recent developments

The past decade has seen major changes in the field of infectious diseases. In particular, many new infections of the nervous system have been recognised, including the lethal infections of Enterovirus 71, and the Nipah and West Nile viruses. Increased interest in prion diseases has occurred, following the recognition of animal-to-human transmission in Europe. Familiar bacteria such as the pneumococcus continue to cause problems due to increasing resistance to multiple antibiotics. Furthermore, human immunodeficiency virus-infected and other immunocompromised patients are under the constant threat of opportunistic infections, many of which are targeted towards the brain and spinal cord. This paper reviews the changing world of nervous system infections, highlighting some of the most significant recent developments.

Point dose variations with time during traditional brachytherapy for cervical carcinoma

In traditional brachytherapy for carcinoma of the cervix, doses are often prescribed to specifically chosen points (A and B) and the normal tissue tolerance calculated at specific reference points in the bladder and rectum. These tolerance doses are often used to modify the brachytherapy treatment plan. It is inherently assumed that the position of the brachytherapy applicator does not change in relation to the relevant anatomical structures over the time-course of an implant. To assess the accuracy of this assumption, 2 sets of localization films were obtained for each implant in 28 patients, 1 prior to loading and another after the removal of the radioactive sources. Significant applicator movement and, consequently, significant dose variations were ob: served. Therefore, isolated one-time dose measurements to normal critical structures should not be used as the sole basis for making therapeutic decisions. The magnitude of dose variations and their clinical significant are discussed.

Bacterial Polysaccharides as Vaccines — Immunity and Chemical Characterization

Studies on protective immunity and biochemical characterization of bacterial capsular polysaccharides have led to significant contributions to understanding of the mechanisms of infectious diseases and development of effective vaccines. Immunity to encapsulated bacteria is related to antibody response to polysaccharide (PS) antigen, interactions with T- and B-lymphocytes, and host defense mechanisms. Meningococcal, pneumococcal and Salmonella vi PSs and Haemophilus type b PS-protein conjugate vaccines have been licensed and provided effective immunity for prevention of these bacterial infections. Capsular PSs are cell-surface polymers consisting of oligosaccharide repeating units. Many PSs are highly polar and hydrophilic and interfere with cell-to-cell interactions with phagocytes. Most pneumococcal PSs are negatively charged and possess acidic components such as D-glucuronic acid and phosphate in phosphodiester bonds. Extensive immunologic cross-reactivity has been observed among bacterial capsular PSs. In infants the antibody responses to most capsular PSs are generally poor. Enhanced immunogenicity of PS antigens can be achieved through PS-protein conjugate vaccines, immunization during a critical period of perinatal development and effective antigen delivery system.

Preincubation with endothelial cell monolayers increases gene transfer efficiency into human bone marrow CD34(+)CD38(-) progenitor cells

Retroviral gene transfer studies targeting bone marrow CD34(+)CD38(-) stem cells have been disappointing because of the rarity of these cells, their G(0) cell cycle status, and their low or absent expression of surface retroviral receptors. In this study, we examined whether preincubation of bone marrow CD34(+)CD38(-) stem cells with a hematopoietically supportive porcine microvascular endothelial cell line (PMVECs) could impact the cell cycle status and expression of retroviral receptors in pluripotent CD34+CD38- cells and the efficiency of gene transfer into these primitive target cells. PMVEC coculture supplemented with GM-CSF + IL-3 + IL-6 + SCF + Flt-3 ligand induced >93% of the CD34(+)CD38(-) population to enter the G(1) or G(2)/S/M phase while increasing this population from 1.4% on day 0 to 6.5% of the total population by day 5. Liquid cultures supplemented with the identical cytokines induced 73% of the CD34(+)CD38(-) population into cell cycle but did not maintain cells with the CD34(+)CD38(-) phenotype over time. We found no significant increase in the levels of AmphoR or GaLVR mRNA in PMVEC-expanded CD34(+)CD38(-) cells after coculture. Despite this, the efficiency of gene transfer using either amphotropic vector (PA317) or GaLV vector (PG13) was significantly greater in PMVEC-expanded CD34(+)CD38(-) cells (11.4 +/- 5.6 and 10.9 +/- 5.2%, respectively) than in either steady state bone marrow CD34(+)CD38(-) cells (0.6 +/- 1.7 and 0.2 +/- 0.6%, respectively; p < 0.01 and p < 0.01) or liquid culture-expanded CD34(+)CD38(-) cells (1.4 +/- 3.5 and 0.0%, respectively; p < 0.01 and p < 0.01). Since PMVEC coculture induces a high level of cell cycling in human bone marrow CD34(+)CD38(-) cells and expands hematopoietic cells capable of in vivo repopulation, this system offers potential advantages for application in clinical gene therapy protocols.

Protective effect of topically applied olive oil against photocarcinogenesis following UVB exposure of mice

Reactive oxygen species have been shown to play a role in ultraviolet light (UV)-induced skin carcinogenesis. Vitamin E and green tea polyphenols reduce experimental skin cancers in mice mainly because of their antioxidant properties. Since olive oil has also been reported to be a potent antioxidant, we examined its effect on UVB-induced skin carcinogenesis in hairless mice. Extra-virgin olive oil was applied topically before or after repeated exposure of mice to UVB. The onset of UVB-induced skin tumors was delayed in mice painted with olive oil compared with UVB control mice. However, with increasing numbers of UVB exposures, differences in the mean number of tumors between UVB control mice and mice pretreated with olive oil before UVB exposure (pre-UVB group) were lost. In contrast, mice that received olive oil after UVB exposure (post-UVB group) showed significantly lower numbers of tumors per mouse than those in the UVB control group throughout the experimental period. The mean number of tumors per mouse in the UVB control, pre-UVB and post-UVB groups was 7.33, 6.69 and 2.64, respectively, in the first experiment, and 8.53, 9.53 and 3.36 in the second experiment. Camellia oil was also applied, using the same experimental protocol, but did not have a suppressive effect. Immunohistochemical analysis of DNA damage in the form of cyclobutane pyrimidine dimers (CPD), (6-4) photoproducts and 8-hydroxy-2'-deoxyguanosine (8-OHdG) in samples taken 30 min after a single exposure of UVB showed no significant difference between UVB-irradiated control mice and the pre-UVB group. In the post-UVB group, there were lower levels of 8-OHdG in epidermal nuclei, but the formation of CPD and (6-4) photoproducts did not differ. Exposure of olive oil to UVB before application abrogated the protective effect on 8-OHdG formation. These results indicate that olive oil topically applied after UVB exposure can effectively reduce UVB-induced murine skin tumors, possibly via its antioxidant effects in reducing DNA damage by reactive oxygen species, and that the effective component may be labile to UVB.

Helicobacter pylori sero-prevalence in asthma

Asthma is a very common respiratory disease which is characterized by the presence of cytokine-mediated airway inflammation leading to smooth muscle contraction, oedema and progressive airway damage in some cases. In light of our recent finding of an increased sero-prevalence of Helicobacter pylori in bronchiectasis, we have determined serum levels of H. pylori-specific IgG in asthmatic and control subjects. Altogether 90 consecutive asthmatic [mean age +/- SD 42.6+/-16 years and 52 female (F)] and 97 healthy control subjects (mean age +/- SD 43.2+/-13.3 years and 51 female (F); P = 0.78 and 0.39 respectively) were recruited prospectively. H. pylori sero-prevalence was not significantly different between asthmatic and control subjects (P>0.05). Serum H. pylori IgG levels did not correlate with FEV1 % predicted, FVC % predicted or duration of asthma (P>0.05). Similar to the results of previously published sero-epidemiological studies, there was a weak correlation between serum H. pylori IgG with increasing age (r = 0.43, P = 0.004). Despite the sero-epidemiological association of H. pylori infection with many inflammatory conditions, our data showed no such association for middle age asthmatic patients with mild intermittent asthma in our locality.

Status epilepticus-induced neuronal loss in humans without systemic complications or epilepsy

PURPOSE

To determine the regional distribution of neuronal damage caused strictly by status epilepticus (SE) without systemic complications, underlying brain pathology, or a history of preexisting epilepsy.

METHODS

The medical records and electroencephalograms (EEGs) of three deceased patients who developed SE in the hospital were reviewed. Their brains were formalin-fixed, and 17 brain regions were selected, embedded in paraffin, and sectioned. Alternate sections were stained with either hematoxylin and eosin and cresyl violet to determine the extent of neuronal loss and gliosis or glial fibrillary astrocytic protein to confirm the extent of astrocytic proliferation.

RESULTS

The three patients died 11 to 27 days after the onset of focal motor SE; none had hypotension, hypoxemia, hypoglycemia, or significant hyperthermia. Two patients had no prior seizures and no underlying brain pathology. The third patient, who had leptomeningeal carcinomatosis, had one seizure 2 months before the onset of SE. The duration of SE was 8.8 hours to 3 days. EEGs showed unilateral temporal lobe sharp-wave discharges in one patient and independent temporal lobe sharp-wave discharges bilaterally in the other two patients. In addition to widespread neuronal loss and reactive gliosis in the hippocampus, amygdala, dorsomedial thalamic nucleus, and Purkinje cell layer of the cerebellum, we report for the first time periamygdaloid (piriform) and entorhinal cortical damage occurring acutely after SE in humans.

CONCLUSIONS

In the absence of systemic complications or preexisting epilepsy, SE produces neuronal loss in a distribution similar to that from domoic acid-induced SE in humans and from kainic acid- and pilocarpine-induced SE in rats.

A new power law for determination of total (125)I seed activity for ultrasound-guided prostate implants: clinical evaluations

PURPOSE

The intraoperative planning with peripheral loading approach is an important technique for ultrasound-guided transperineal prostate implant. In this paper a sphero-cylindrical dose model is described to generate a new power law or a look-up table for determination of the total (125)I activity required to deliver a prescription dose to a given prostate volume.

METHODS AND MATERIALS

Dose calculations were based on the new standards for (125)I seeds (model 6711) implemented by the National Institute of Standards and Technology (NIST) in 1999. Using the sphero-cylindrical dose model with peripheral loading approach, a new power law for calculating total activity of radioactive iodine required to deliver a prescribed dose for the target volume was developed. Accounting for random variation of the seed positioning in the prostate and the current air-kerma strength standard of (125)I seeds, this new power law is formulated as follows: A (mCi) = 2.15 d (cm)(2.00) where A is apparent activity in mCi, or A (U) = 1. 69 d (cm)(2.00) where A is air-kerma strength in U, required to deliver a cumulative dose of 145 Gy to a prostate gland with an average dimension, d, in centimeters.

RESULTS

The efficacy of using the new power law in prostate implants was demonstrated. For clinical evaluations of this new power law, 40 patients were chosen in 1998. The average D(90) of these 40 patients was 172.0 Gy (SD +/- 29 Gy). This means that on the average, 90% of the target volume received was 172.0 Gy. The average coverage index (CI) in this study was 94.7 (SD +/- 4.7). As a result, 94.7% of the target volume received the prescription dose. The dose homogeneity index (HI) which measured the degree of the dose inhomogeneity was 0.38 (SD +/- 0.21).

CONCLUSION

This new and simple power law or a new mCi-volume look-up table for (125)I seed prostate implantation has been developed and formulated for clinical use. Clinical evaluations expressed in quantitative parameters such as D(90), CI, and HI in prostate implants have been thoroughly analyzed and clearly demonstrated the efficacy of this approach.

Conformal prostate treatment planning using a low-energy (6-MV) beam

A 4-field noncoplanar technique for treatment of prostate cancer developed at the University of Michigan was modified for use with low-energy (6 MV) beams. These modifications include the use of wedges on the 2 anterior inferior-superior oblique fields and adjusting the weights of the oblique and lateral fields appropriately. A margin of 1.5 cm around the physician-defined target region was used to define the blocks on each beam's-eye view. Dose distributions produced using this technique with 6-MV and 24-MV beams were compared visually on several dose planes (transverse and sagittal) and quantitatively by dose volume histograms (target, rectum, and bladder). These comparisons showed insignificant differences between the high-energy and low-energy treatment plans. Much larger differences were observed in comparisons of 2 types of coplanar plans with the noncoplanar setup for the 6-MV photon machine. Rectal doses measured in situ were used to help validate the dose distribution predicted by the treatment planning system for the 6-MV noncoplanar technique.

[A comprehensive evaluation on intervention measures for injuries in primary and middle school students]

OBJECTIVE

To explore the intervention measures for prevention and control of injuries and evaluation for their effectiveness in students of middle and primary schools.

METHODS

Effectiveness of intervention was evaluated by comparison of incidence of injury before and after intervention in 3,896 students of nine middle and primary schools and comparison with a non-intervention group in 651 students of four primary schools in Jiangmen City, Guangdong Province during January to December, 1999.

RESULTS

Incidence of injury dropped to 11.78% after intervention from 50.55% before intervention in the intervention group, with 76.70% of reduction. Proportion of severe injury dropped to 0.65% after intervention from 7.84% before intervention. Incidence of multiple injuries dropped to 3.15% from 19.16%, with 83.56% of reduction. But, in the control group, incidence of injury dropped to 49.00% from 52.67%, with 6.97% of reduction only, with a ratio of reduction of intervention to control of 11.02% and a ratio of cost to benefit of 1:13.9.

CONCLUSION

Intervention measures focusing on health promotion can prevent and control the occurrence of injury in students of middle and primary schools cost-effectively.

Responses of trembling aspen and hazelnut to vapor pressure deficit in a boreal deciduous forest

The branch bag method was used to monitor photosynthesis and transpiration of trembling aspen (Populus tremuloides Michx.) and hazelnut (Corylus cornuta Marsh.) over a 42-day midsummer period in 1996, as part of the Boreal Ecosystem-Atmosphere Study (BOREAS). During the same period, daytime measurements of stomatal conductance (g(s)) and leaf water potential (Psi(leaf)) were made on these species, and sap flow was monitored in aspen stems by the heat pulse method. Weather conditions during the study period were similar to the long-term average. Despite moist soils, both species showed an inverse relationship between daytime g(s) and vapor pressure deficit (D) when D was > 0.5 kPa. Daytime Psi(leaf) was below -2 MPa in aspen and near -1.5 MPa in hazelnut, except on rainy days. These results are consistent with the hypothesis that stomatal responses are constrained by hydraulic resistance from root to leaf, and by the need to maintain Psi(leaf) above a minimum threshold value. Reductions in g(s) on sunny afternoons with elevated ambient D (maximum 2.3 kPa) were associated with a significant decrease in photosynthetic rates. However, day-to-day variation in mean carbon assimilation rate was small in both species, and appeared to be governed more by solar radiation than D. These results may be generally applicable to healthy aspen stands under normal midsummer conditions in the southern boreal forest. However, strong reductions in carbon uptake may be expected at the more extreme values of D (> 4 kPa) that occur during periods of regional drought, even if soil water is not locally limiting.

Urinary morbidity with a modified peripheral loading technique of transperineal (125)i prostate implantation

PURPOSE

Analysis of urinary morbidity within the first 12 months following a modified peripheral loading technique for permanent transperineal transrectal ultrasound (TRUS) guided (125)I prostate implantation and comparison of urinary morbidity with various clinical and implant parameters.

MATERIALS AND METHODS

Between October 1, 1996, and March 11, 1998, 87 patients with favorable, early stage prostate cancer were treated with permanent transperineal TRUS guided (125)I prostate implantation. A peripheral loading technique was utilized for source placement with 75-80% source distribution in the periphery and 20-25% source distribution centrally. A mean total activity of 38 mCi of (125)I was implanted (range, 19-66 mCi). The mean source activity was 0.43 mCi/source (range, 0.26-0.61 mCi/source) and the mean number of sources implanted was 88 (range, 56-134). The minimum prescribed dose to the prostate was 145 Gy. The median D(90), V(100), and V(150) were 152 Gy (range, 104-211 Gy), 92% (range, 71-99%), and 61% (range, 11-89%), respectively. The median follow-up time was 19 months (range, 12-29 months). Urinary morbidity was scored at 3 weeks and then at 3-month intervals for the first 2 years using a modified Radiation Therapy Oncology Group (RTOG) grading system (scale 0-5).

RESULTS

Most patients developed at least minor urinary symptoms with frequency or nocturia being the most common. Overall, 79% (69/87) of patients experienced urinary morbidity with 21% (18/87) reporting no symptoms. The incidence of overall Grade 1 urinary morbidity was 37% (32/87); Grade 2 morbidity was 37% (32/87); and Grade 3 morbidity was 6% (5/87). There was no Grade 4 or 5 morbidity. The incidence of Grade 0 frequency/nocturia was 36% (31/87); Grade 1 was 33% (29/87); Grade 2 was 30% (26/87); and Grade 3 was 1% (1/87). Grade 0 dysuria was seen in 56% (49/87) of patients; 32% (28/87) had Grade 1; 10% (9/87) Grade 2; and 1% (1/87) Grade 3 dysuria. Most urinary symptoms started a few weeks after implantation and began to subside by 6 months. At 12 months, 22% (19/87) of patients had persistent urinary symptoms (78% Grade 0, 15% Grade 1, 3% Grade 2, and 3% Grade 3). The mean urethral point dose was 174 Gy (range, 99-315 Gy). The mean number of sources implanted correlated significantly with the likelihood of developing acute urinary morbidity (p = 0.03). The total activity implanted also correlated with the morbidity outcome dysuria (p = 0.01) with a threshold seen at 37 mCi. Urethral point dose, source activity, intraoperative TRUS prostate volume, D(90), V(100), V(150), patient age, pretreatment PSA, Gleason score, and T stage did not correlate with morbidity.

CONCLUSIONS

Permanent transperineal TRUS guided (125)I prostate implantation using a modified peripheral loading technique is associated with mild urinary morbidity that resolves in 78% of patients by 12 months. Grade 3 urinary morbidity was encountered in only 6% (5/87) of patients. Urinary morbidity may be related to the total number of sources implanted and/or the total activity implanted. Overall urinary morbidity was not correlated with urethral point dose, source activity, intraoperative TRUS prostate volume, D(90), V(100), V(150), patient age, pretreatment PSA, Gleason score, and T stage. The low incidence of urinary morbidity may be a consequence of our modified peripheral loading technique and/or the selection of patients with good-to-excellent preimplant urological parameters. Longer follow-up is necessary to assess biochemical control rates and long-term morbidity.

Deltamethrin induces altered expression of P53, Bax and Bcl-2 in rat brain

In this study we investigated the effects of deltamethrin on the expression of P53, Bax and Bcl-2 in rat brain. Immunohistochemical analysis demonstrated that the immunoreactivity for P53 was markedly increased in the cerebral cortex and hippocampus at 5 h after deltamethrin treatment, and maintained at an increased level at 24 and 48 h, whereas little immunoreactivity for P53 was seen in the same brain regions of control rats. The immunostaining for Bax was also elevated in the same brain regions, showing the same time course of P53 expression after deltamethrin treatment. However, the immunolabeling for Bcl-2 was markedly decreased at 24 h after a transient increase at 5 h following deltamethrin treatment. These results indicate that deltamethrin leads to the persistent increase of P53 and Bax expression and transient elevation of Bcl-2 expression, resulting in an increased ratio of Bax to Bcl-2, which may contribute to apoptotic cell death in rat brain following deltamethrin treatment.

Deltamethrin induces delayed apoptosis and altered expression of p53 and bax in rat brain

Our previous work indicates that deltamethrin induces degeneration and apoptosis in rat brain at 24 and 48 h after treatment. To determine whether molecular characteristics of apoptosis is involved in neurodegeneration in rat brain after deltamethrin treatment, we investigated the effects of deltamethrin on the mRNA expression of p53 and bax and their correlation with deltamethrin-induced apoptotic cell death in rat brain. Hematoxylin-eosin and cresyl violet staining revealed numerous degenerative cells in cortex and hippocampus at 5 and 24 h after deltamethrin treatment. Apoptotic cells were detected in cortex and hippocampus of treated rats at 24 h by in situ end labeling, whereas no apoptotic cells were observed in the same brain regions at 5 h after treatment. By using in situ hybridization, it was demonstrated that the increase of p53 and bax mRNA levels appeared at 5 and also at 24 h after treatment. The alterations in mRNA expression of p53 and bax preceded the occurrence of delayed apoptotic cell death in the same brain regions after deltamethrin treatment. These results indicate that (1) deltamethrin induces delayed apoptotic cell death, which may play an important role in deltamethrin-elicited neurodegeneration; (2) deltamethrin leads to the persistent increase of p53 and bax mRNA levels, which may contribute to delayed apoptosis in rat brain following deltamethrin treatment.

Preventive effect of antioxidant on ultraviolet-induced skin cancer in mice

Reactive oxygen species (ROS) have been shown to be responsible for inducing DNA damage after ultraviolet radiation (UV). Antioxidant, vitamin E and epigallocatechin gallate extracted from green tea, applied topically to the skin, delayed the onset of UV-induced skin cancer in mice. Since olive oil is reported to have a potent antioxidative effect in in vitro system, we asked whether, topical use of olive oil reduces the number and delays the onset of UV-induced skin cancer in mice. We found that super virgin olive oil painted immediately after UVB radiation significantly delayed the onset and reduced the number of skin cancer, but pretreatment of super virgin olive oil and pre- and/or post treatment by regular olive oil neither retarded nor reduced skin cancer formation in UV-irradiated mice. Further, 8-hydroxy-deoxyguanosine (8-OHdG) formation in mice epidermis was apparently reduced by super virgin olive oil painted immediately after UV radiation, although cyclobutane pyrimidine dimers and (6-4) photoproducts were not reduced by olive oil treatment. Our results suggest that daily topical use of super virgin olive oil after sun bathing may delay and reduce UV-induced skin cancer development in human skin, possibly by decreasing ROS-induced 8-OHdG which is responsible for gene mutation.

Apoptotic cell death in rat brain following deltamethrin treatment

In the present study we identified the degeneration and apoptotic cell death in rat brain after deltamethrin treatment. By hematoxylin-eosin (H&E) staining, a large number of degenerative cells (pyknosis of nuclei, disruption of eosinophilic cytoplasm) were seen in the hippocampus and cortex at 24 and 48 h after deltamethrin treatment at a dose of 12.5 mg/kg (i.p.) in corn oil. The similar morphological changes of degenerative cells were observed by cresyl violet staining. Numerous apoptotic cells were detected by in situ end labeling (ISEL) and flow cytometric analysis in the hippocampus and cortex at 24 and 48 h following deltamethrin treatment at the same dose, whereas no ISEL-positive cells were seen in the same brain regions of control rats. Moreover, using DNA gel electrophoresis, it was demonstrated that DNA fragmentation was markedly induced in the hippocampus and cortex at 24, 48 and 72 h after treatment. In addition, the protein synthesis inhibitor cycloheximide inhibited the DNA fragmentation elicited by deltamethrin in rat brain. These results indicate that deltamethrin induces degeneration and apoptotic cell death in rat brain, suggesting an important role played by apoptosis in neurotoxicity of deltamethrin.

Effects of deltamethrin on nitric oxide synthase and poly(ADP-ribose) polymerase in rat brain

The effects of deltamethrin on the activities of nitric oxide synthase (NOS) and poly(ADP-ribose) polymerase (PARP) and the protein expression of neuronal NOS (nNOS) and PARP in rat brain were investigated in the present study. The activity of NOS was significantly increased in cortex and hippocampus at 5 h after deltamethrin treatment, and maintained at an increased level at 24 h. The activity of PARP was also elevated at the same time points in the same brain regions of treated rats. By immunohistochemical analysis, it was demonstrated that the nNOS-immunoreactive cells were markedly increased at 24 h after treatment in the cortex and hippocampus, whereas few nNOS-immunoreactive cells were observed in the same brain regions of control and treated rats at 5 h after treatment. The immunoreactivity for PARP was also increased in the same brain regions, showing the similar time course of the induction of nNOS by deltamethrin. These results indicate that deltamethrin increases the activities of NOS and PARP and initiates the protein expression of nNOS and PARP, suggesting that NOS and PARP might play important roles in neurotoxicity of deltamethrin.

Systemic antitumor immunity in experimental brain tumor therapy using a multimutated, replication-competent herpes simplex virus

Replication-competent, attenuated herpes simplex virus (HSV) vectors have been developed for viral oncolytic therapy of primary and metastatic malignant brain tumors. However, the role of the host immune responses in the brain has not been elucidated. N18 neuroblastoma cells were used as a tumor model in syngeneic A/J mice to test the therapeutic efficacy of G207, a conditionally replicating HSV vector, in an immunocompetent condition. G207 inoculated intraneoplastically exhibited a prominent oncolytic antitumor effect in mice harboring N18 tumors in the brain or subcutaneously, and, in addition, elicited a systemic antitumor immune response. Subcutaneous tumor therapy with G207 caused regression of a remote, established tumor in the brain or in the periphery, which was potentially mediated by the systemic antitumor immune response, and provided persistent tumor-specific protection against N18 tumor rechallenge in the brain as well as in the periphery. Antitumor immunity was associated with an elevation of specific CTL activity against N18 tumor cells that persisted for at least 13 months. The results suggest that the oncolytic antitumor action of replication-competent HSV may be augmented by induction of specific and systemic antitumor immunity effective both in the periphery and in the brain.

Correlation of the expression of human telomerase subunits with telomerase activity in normal skin and skin tumors

BACKGROUND

Telomerase activation is thought to be crucial for the continued growth or progression of cancer cells. Three major subunits of human telomerase, human telomerase RNA (hTR), telomerase-associated protein (TP1), and human telomerase catalytic subunit (hTERT) have been identified recently. In the current study, the expression of these telomerase subunits was examined in various human skin tumors and in normal skin samples, and the correlation of their expression with telomerase activity was evaluated.

METHODS

Forty-five skin tumors, including benign, premalignant, and malignant tumors, and 19 samples of normal skin were analyzed by reverse transcriptase-polymerase chain reaction for the expression of telomerase subunits and by telomeric repeat amplification protocol assay for telomerase activity.

RESULTS

TP1 expression was found in 43 of 45 skin tumors (95.6%) and in all normal skin samples analyzed. hTR expression was found in 42 of 45 skin tumors (93.3%) and in 18 of 19 normal skin samples (94.7%). In contrast, hTERT expression was detected in 33 of 45 skin tumors (73.3%) and in only 3 of 19 normal skin samples (15.8%). Telomerase activity was positive in 33 of 45 skin tumors (73.3%) and in 3 of 19 normal skin samples (15.8%). All together, 53 of 64 cases (82.8%) were concordant for both results (P < 0.001), i.e., telomerase activity positive and hTERT positive, or telomerase activity negative and hTERT negative.

CONCLUSIONS

Activation of telomerase activity in skin tumors is strongly correlated with hTERT expression.

Permanent prostate seed implant brachytherapy: report of the American Association of Physicists in Medicine Task Group No. 64

There is now considerable evidence to suggest that technical innovations, 3D image-based planning, template guidance, computerized dosimetry analysis and improved quality assurance practice have converged in synergy in modern prostate brachytherapy, which promise to lead to increased tumor control and decreased toxicity. A substantial part of the medical physicist's contribution to this multi-disciplinary modality has a direct impact on the factors that may singly or jointly determine the treatment outcome. It is therefore of paramount importance for the medical physics community to establish a uniform standard of practice for prostate brachytherapy physics, so that the therapeutic potential of the modality can be maximally and consistently realized in the wider healthcare community. A recent survey in the U.S. for prostate brachytherapy revealed alarming variance in the pattern of practice in physics and dosimetry, particularly in regard to dose calculation, seed assay and time/method of postimplant imaging. Because of the large number of start-up programs at this time, it is essential that the roles and responsibilities of the medical physicist be clearly defined, consistent with the pivotal nature of the clinical physics component in assuring the ultimate success of prostate brachytherapy. It was against this background that the Radiation Therapy Committee of the American Association of Physicists in Medicine formed Task Group No. 64, which was charged (1) to review the current techniques in prostate seed implant brachytherapy, (2) to summarize the present knowledge in treatment planning, dose specification and reporting, (3) to recommend practical guidelines for the clinical medical physicist, and (4) to identify issues for future investigation.