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Biomedical subjects

R Stock

Publications and source records attributed to R Stock.

At least 19 recordsLinked to original sources
PubMed2002

TOF-SIMS and XPS-investigations of ion implanted single crystal 1b-diamonds.

Near surface zones of (48)Ti- and (52)Cr-implanted single crystal diamonds (1b-MCD) were characterized by XPS, TOF-SIMS and white light interference microscopy (WLI). By the combination of WLI and TOF-SIMS it was possible to calibrate the depth scale of TOF-SIMS and XPS depth profiles quantitatively. The adjustment of TOF-SIMS and XPS elemental depth profiles in the implantation maximum increases the quantitative detection limit of the implanted elements by more than two orders of magnitude and enables the interpretation of results from wear simulation experiments. Peak fits of XPS C(1s)-photolines indicate the fraction and chemical nature of carbide-like structures in the implantation zone. Qualitative hints on carbide compounds are possibly included in the reconstructed TOF-SIMS spectra but this information can presently only be extracted with the aid of XPS analyses.

Journal Article↗
PubMed2001

Event-by-event fluctuations of the Kaon-to-Pion ratio in central Pb+Pb collisions at 158 GeV per nucleon.

We present the first measurement of fluctuations from event to event in the production of strange particles in collisions of heavy nuclei. The ratio of charged kaons to charged pions is determined for individual central Pb+Pb collisions. After accounting for the fluctuations due to detector resolution and finite number statistics we derive an upper limit on genuine nonstatistical fluctuations, which could be related to a first- or second-order QCD phase transition. Such fluctuations are shown to be very small.

Journal Article↗
PubMed2001

Maximal replacement of forage and concentrate with a new wet corn milling product for lactating dairy cows.

Three experiments were conducted to determine the maximal amount of concentrate and forage that could be replaced with a new wet corn milling product. The corn milling product contained 23.1% crude protein, 9.9% ruminally undegradable protein, 13.7% acid detergent fiber, 40.3% neutral detergent fiber, and 2.6% ether extract (% of dry matter; DM). In experiment 1, 16 Holstein cows were assigned to one of four diets in a replicated 4 x 4 Latin square design with 28-d periods. The four diets contained 54.3% forage (alfalfa:corn silages, 1:1 DM basis) with the wet corn milling product replacing 0, 50, 75, or 100% of the concentrate portion (corn and soybean meal) of the diet (DM basis). The diets containing wet corn milling product resulted in 7.8% lower DM intake, equivalent milk production (28.5 kg/d), and 13.6% greater efficiency of 4% fat-corrected milk (FCM) production than the control diet. There was no effect of diet on ruminal pH. In experiment 2, 16 Holstein cows were assigned to one of four diets in a replicated 4 x 4 Latin square design with 28-d periods. The 100% concentrate replacement diet from experiment 1 was used as control diet. For the test diets, forage was replaced with 15, 30, or 45% of the corn milling product (DM basis). Efficiency of FCM production (1.16) was not affected by diet. Rumination time was reduced for the 30 and 45% forage replacement diets, but ruminal pH was unaffected. In experiment 3, 30 Holstein cows were assigned at parturition to either a control diet (no corn milling product) or a diet containing 40% corn milling feed in place of both forage and concentrate (optimal levels from experiments 1 and 2) for 9 wk. The diet containing corn milling feed resulted in 21% greater efficiency of FCM production than the control diet. These results indicate that a new feed product based on wet corn milling ingredients has the potential to effectively replace all of the concentrate and up to 45% of the forage in the diet for lactating dairy cows.

Animal Feed↗
PubMed2001

The current status of Balint groups in US family practice residencies: A 10-year follow-up study, 1990-2000.

BACKGROUND AND OBJECTIVES: In 1990, the first and, to date, only objective study of Balint groups in US family practice residencies was conducted to measure their prevalence, composition, leadership, and function. The study reported here collected similar information about Balint groups. METHODS: Surveys were sent to all 464 US family practice residency program directors, with a 1-month follow-up to nonrespondents. The survey included questions about the existence, leadership, meeting frequency, and objectives of Balint training. RESULTS: A total of 298 (64%) residencies responded. Almost half (48%) of US responding residences reported conducting Balint groups, and 40% of those residencies have more than one group. The frequency of Balint group meetings has shifted in the past 10 years. In 1990, 55% of groups met weekly; in 2000, only 15% of groups met weekly. Sixty-five percent of residencies require Balint participation. One third of Balint groups are conducted without a coleader and the number of physicians leading groups is 22%, a decrease of 10% from 10 years ago. Forty-four percent of groups are led by psychologists, an increase of 19% from 10 years ago. Respondents indicated uncertainly about whether their groups were true Balint groups or simply resident support groups. CONCLUSIONS: About half of US family practice residencies operate groups described as Balint groups. They meet less frequently then 10 years ago and are less likely to have a physician involved in group leadership. Some of the groups may actually be support groups rather than Balint groups.

Clinical Competence↗
PubMed2000

The use of artificial intelligence technology to predict lymph node spread in men with clinically localized prostate carcinoma.

BACKGROUND: The current study assesses artificial intelligence methods to identify prostate carcinoma patients at low risk for lymph node spread. If patients can be assigned accurately to a low risk group, unnecessary lymph node dissections can be avoided, thereby reducing morbidity and costs. METHODS: A rule-derivation technology for simple decision-tree analysis was trained and validated using patient data from a large database (4,133 patients) to derive low risk cutoff values for Gleason sum and prostate specific antigen (PSA) level. An empiric analysis was used to derive a low risk cutoff value for clinical TNM stage. These cutoff values then were applied to 2 additional, smaller databases (227 and 330 patients, respectively) from separate institutions. RESULTS: The decision-tree protocol derived cutoff values of < or = 6 for Gleason sum and < or = 10.6 ng/mL for PSA. The empiric analysis yielded a clinical TNM stage low risk cutoff value of < or = T2a. When these cutoff values were applied to the larger database, 44% of patients were classified as being at low risk for lymph node metastases (0.8% false-negative rate). When the same cutoff values were applied to the smaller databases, between 11 and 43% of patients were classified as low risk with a false-negative rate of between 0.0 and 0.7%. CONCLUSIONS: The results of the current study indicate that a population of prostate carcinoma patients at low risk for lymph node metastases can be identified accurately using a simple decision algorithm that considers preoperative PSA, Gleason sum, and clinical TNM stage. The risk of lymph node metastases in these patients is < or = 1%; therefore, pelvic lymph node dissection may be avoided safely. The implications of these findings in surgical and nonsurgical treatment are significant.

Acid Phosphatase↗
PubMed2000

The American Brachytherapy Society recommendations for permanent prostate brachytherapy postimplant dosimetric analysis.

PURPOSE: The purpose of this report is to establish guidelines for postimplant dosimetric analysis of permanent prostate brachytherapy. METHODS: Members of the American Brachytherapy Society (ABS) with expertise in prostate dosimetry evaluation performed a literature review and supplemented with their clinical experience formulated guidelines for performing and analyzing postimplant dosimetry of permanent prostate brachytherapy. RESULTS: The ABS recommends that postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy for optimal patient care. At present, computed tomography (CT)-based dosimetry is recommended, based on availability cost and the ability to image the prostate as well as the seeds. Additional plane radiographs should be obtained to verify the seed count. Until the ideal postoperative interval for CT scanning has been determined, each center should perform dosimetric evaluation of prostate implants at a consistent postoperative interval. This interval should be reported. Isodose displays should be obtained at 50%, 80%, 90%, 100%, 150%, and 200% of the prescription dose and displayed on multiple cross-sectional images of the prostate. A dose-volume histogram (DVH) of the prostate should be performed and the D90 (dose to 90% of the prostate gland) reported by all centers. Additionally, the D80, D100, the fractional V80, V90, V100, V150 and V200 (i.e., the percentage of prostate volume receiving 80%, 90%, 100%, 150%, and 200% of the prescribed dose, respectively), the rectal, and urethral doses should be reported and ultimately correlated with clinical outcome in the research environment. On-line real-time dosimetry, the effects of dose heterogeneity, and the effects of tissue heterogeneity need further investigation. CONCLUSION: It is essential that postimplant dosimetry should be performed on all patients undergoing permanent prostate brachytherapy. Guidelines were established for the performance and analysis of such dosimetry.

Brachytherapy↗
PubMed1999

The effect of one injection of Depo-Provera on the human vaginal epithelium and cervical ectopy.

Two studies in rhesus monkeys have shown that progesterone implants, Depo-Provera and Norplant, were associated with vaginal thinning. Progesterone implants have also been associated with an increased risk of simian immunodeficiency virus (SIV) acquisition. This study in 16 women was done to assess vaginal epithelial thickness and number of cell layers from biopsies taken in the untreated follicular and luteal phases, and at 1 month and 3 months after administration of Depo-Provera. There was no significant change over time in either parameter from biopsies obtained in the luteal phase compared with those at either time after Depo-Provera administration. There was also no change in the mean number of Langerhans cells in vaginal wall specimens and no change in cervical ectopy. It appears that women do not respond to exogenous progestins with the dramatic vaginal thinning seen in rhesus monkeys.

Adult↗
PubMed1997

Prospective analysis of prostate-specific markers in pelvic lymph nodes of patients with high-risk prostate cancer.

BACKGROUND: Pathologic evidence of pelvic lymph node involvement is obtained in 12%-20% of patients with localized prostate cancer that exhibits high-risk features (defined on the basis of tumor size, serum prostate-specific antigen [PSA] level, or Gleason score). The rate of systemic failure (i.e., relapse) in patients with this type of prostate cancer and no pathologic evidence of regional lymph node involvement is 55%-92% within 5 years of definitive local therapy. Since reverse transcription-polymerase chain reaction (RT-PCR) methods are likely to be more sensitive than routine pathologic examination in detecting metastatic tumor cells, we compared the ability of the two approaches to detect prostate cells in the pelvic lymph nodes of patients with localized, high-risk disease. METHODS: Fifty-eight lymph node specimens isolated from 33 patients before definitive local therapy were examined. Expression of PSA and prostate-specific membrane antigen (PSM) messenger RNAs in the specimens was assessed by means of nested RT-PCR. RESULTS: Pathologic examination identified tumor cells in the lymph nodes of four (12%) of the 33 patients, and PSA and/ or PSM expression was positive in specimens from 27 (82%) of the patients (two-sided P<.0001). The four patients with positive pathologic findings also had positive RT-PCR results. Among the 29 patients with no pathologic evidence of lymph node involvement, 23 (79%) tested positive by means of RT-PCR. In these 23 patients, PSM expression was detected more frequently than PSA expression; however, in two patients, only PSA expression was detected. CONCLUSIONS: Expression of prostate-specific markers in the pelvic lymph nodes of patients with localized, high-risk prostate cancer may indicate the presence of metastatic tumor cells. Such cells may be responsible for the high rate of systemic failure seen in these patients. Additional studies are required to determine the prognostic relevance of our findings.

Antigens, Neoplasm↗
PubMed1997

Localized amyloidosis of the seminal vesicle. Possible association with hormonally treated prostatic adenocarcinoma.

OBJECTIVE: Localized seminal vesicle amyloidosis is an unusual finding in surgical pathology material. Previous studies have demonstrated that the amyloid is directly produced by the seminal vesicle epithelial cells. We investigated the possible association of seminal vesicle amyloid in patients hormonally treated for prostate carcinoma. METHODS: Cases were collected from over 200 prostate needle biopsies, seminal vesicle biopsies, and prostatectomy specimens from the surgical pathology files at The Mount Sinai Hospital, New York, NY. None of the patients with seminal vesicle amyloidosis had a chronic inflammatory disorder, serum or urine protein abnormalities, or other identifiable masses. RESULTS: Six cases of localized seminal vesicle amyloidosis were found in the surgical pathology material examined. Five of the six cases had prostatic carcinoma, and one case was seen in a biopsy for benign prostatic hyperplasia. Four of the five carcinoma cases had prior hormonal treatment (luteinizing hormone-releasing hormone agonist with an antiandrogen agent, and one patient, in addition, had received radiotherapy). The amyloid deposits were limited to the seminal vesicle lamina propria without involvement of vascular walls. The amyloid reacted with Congo red staining that was sensitive to potassium permanganate. Immunohistochemically, all cases were negative for AA amyloid, beta 2-microglobulin, and kappa and lambda light chains. CONCLUSION: We raise the possibility that in some instances, prior hormonal therapy may act as a seminal vesicle epithelial stimulant for the elaboration of this protein.

Adenocarcinoma↗
PubMed1995

Induction of an autoimmune response against syngeneic lymphoma cells by immunogenic 64-kDa protein isolated from normal blast cells of BALB/c mice.

Immunogenic proteins with identical molecular mass (64 kDa) were purified from a syngeneic spontaneous T cell leukaemia line, designated LB3, and lymphoblast extracts both derived from BALB/c mice. The 64-kDa protein was purified by a sequence of biochemical steps from cell extracts containing protease inhibitors. The following steps were included in the purification pathway: Sephadex G-100 gel filtration, anion-exchange chromatography, concanavalin A (ConA) affinity chromatography, and preparative gel electrophoresis. The immunogenic fraction isolated in each step was subjected to the next step along the purification pathway. The immunogenicity of the separated fractions was measured by a lymph-node proliferation assay, which is indicative of delayed-type hypersensitivity. The final 64-kDa isolated protein of blast cells induced in BALB/c mice an efficient lymph-node proliferation response, which was detected in the regional lymph node after challenge with the final isolated protein of LB3 cells and vice versa. In addition to their identical molecular mass, both proteins were eluted from an anion-exchange column with the same NaCl concentration (0.57 M) and both expressed affinity to the ConA-Sepharose column, suggesting that they are glycosylated. The specificity of the immunological responses induced or elicited with the various isolated proteins was also shown. The implications of these findings are discussed.

Animals↗
PubMed1995

Age estimation in biopsy specimens of dentin.

Determination of age at death on the basis of aspartic acid racemization in dentin is one of the most reproducible and accurate methods. In Germany, age estimation by this method has so far generally not been applied to living persons, since the extraction of a tooth exclusively for age estimation when it is not medically indicated is regarded as ethically and legally problematic. The development of a biopsy technique applicable to dentin took place against this background. Testing the technique and analysis of dentinal biopsy specimens revealed that the biopsy technique is a low-risk procedure that causes only minor discomfort to the affected person. It is readily practicable and facilitates standardized specimen removal. The relationship between the extent of aspartic acid racemization in dentinal biopsy specimens and age is very close, facilitating age estimation. A prerequisite for accurate results is the performance of biopsies under strictly standardized conditions. If this is guaranteed, age determination on the basis of aspartic acid racemization in dentinal biopsy specimens appears to be superior in precision to most other methods in living persons and can be used for all age groups.

Adolescent↗
PubMed1995

Identification of glucan-mannoprotein complexes in the cell wall of Candida albicans using a monoclonal antibody that reacts with a (1,6)-beta-glucan epitope.

The use of a novel monoclonal antibody (mAb) that reacts with (1,6)-beta-glucan has permitted the study of the different covalent linkages between glucan and mannoproteins in the cell wall of Candida albicans. The mAb JRR1 was originally raised by immunization with Zymolyase extracts from C. albicans cell walls, but it soon became apparent that it reacted with a (1,6)-beta-glucan epitope. By using this antibody, we show the existence of glucan-mannoprotein complexes between the (1,6)-beta-glucan epitope recognized by the antibody and cell wall mannoproteins. The topology of the (1,6)-beta-glucan in the cell wall of C. albicans has also been studied.

Antibodies, Monoclonal↗
PubMed1995

Laparoscopic pelvic lymph node dissection combined with real-time interactive transrectal ultrasound guided transperineal radioactive seed implantation of the prostate.

Laparoscopic pelvic lymph node dissection with real-time interactive transrectal ultrasound guided transperineal radioactive seed implantation is a new method of treatment for localized carcinoma of the prostate. A total of 58 patients with clinically confined prostate cancer and negative seminal vesicle biopsies underwent staging laparoscopic pelvic lymph node dissection immediately followed by prostate implantation: 50 had 125iodine and 8 had 103palladium implants. Mean operating time was 226 minutes (range 120 to 475), mean blood loss was 57 cc (range 5 to 400) and average hospital stay was 2.2 days (range 0.5 to 8). At a mean followup of 12 months (range 6 to 24), complications included proctitis in 1.7% of the cases, dysuria in 24%, nocturia in 21% and outlet obstruction in 17%. Erectile function remained unchanged. Prostate volume decreased to 58.9% of the pretreatment value by 12 months and to 44.3% by 24 months. Mean prostate specific antigen level was 18.4 +/- 26.3 ng./ml. before treatment, 3.4 +/- 3.9 ng./ml. at 6 months, 2.3 +/- 2.3 ng./ml. at 12 months and 4.9 +/- 6.0 ng./ml. at 24 months (1.2 +/- 1.0 ng./ml. for patients with no evidence of disease). Of the patients 15.8% had local failure at 18 to 24 months as determined by positive transrectal ultrasound guided biopsy. Five of 58 patients (8.6%) had persistently elevated prostate specific antigen levels, only 1 of whom had a positive biopsy. Laparoscopic pelvic lymph node dissection with transrectal ultrasound guided implantation is a safe and promising mode of therapy for patients with localized prostate cancer.

Aged↗
PubMed1995

Computerized interactive morphometry in the differential diagnosis of irradiated prostates.

Radiation therapy is becoming a treatment of choice for many patients with prostatic carcinoma. Distinguishing radiation change in prostate glands from carcinoma may be difficult. In this study we objectively assessed, by morphometric methods, the nuclear characteristics of benign and malignant prostates with a history of radiation treatment (125I implant with or without prior external beam radiation). This is part of our continuing efforts to achieve difficult differential diagnoses by analyzing perimeter, diameter and nuclear profile area of cells or interest and applying methods of statistical classification. Biopsies were performed 18-36 months following implant therapy. Eleven cases with residual prostate tumor constituted the malignant group. These were compared to 20 benign cases (benign glands in the 11 carcinoma cases plus 9 other cases with no residual carcinoma). Immunohistochemical staining with keratin 903 was performed on all cases. Differences in the nuclear parameters were most evident in the average nuclear profile areas (32.5 microns 2 for the malignant groups vs. 39.6 for the benign) and in the mean maximal cord length (diameter) (7.4 microns for the malignant group vs. 9.0 for the benign). Classification, however, is based on the size distribution plots of nuclear profile areas, which, in the malignant cases, had a sharper peak at lower value, while the benign cases had higher value and a broader peak with a trailing off into the larger values. This study emphasized the marked nuclear alterations that occur in irradiated prostates.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenocarcinoma↗
PubMed1992

Intrauterine intravascular transfusion for fetal haemolytic anaemia: the Western Australian experience.

OBJECTIVE: To report the first four years' clinical experience with fetal intravascular blood transfusion for the treatment of fetal haemolytic anaemia in Western Australia. SETTING: King Edward Memorial Hospital, Perth, which is the sole tertiary level perinatal centre in Western Australia with a referral base of approximately 25,000 pregnancies each year. METHODS: Transfusion was by injection of packed cells from Rh-negative donors into the fetal umbilical vein near the site of insertion into the placenta. Fetal haemoglobin levels were measured before and after each transfusion. In most cases, the fetus was paralysed by intramuscular tubocurarine. RESULTS: Sixty intravenous transfusions were performed in 20 pregnancies. At the time of the initial transfusion, the mean haemoglobin level was 5.8 g/dL (range, 2.5-8.5 g/dL) and six fetuses had signs of hydrops. The case survival rate was 80% and the procedure survival rate was 93%. Three of the deaths occurred in the first five cases. Caesarean section was performed during two of the procedures, one because of bleeding from the cord puncture site and one because of tamponade of the umbilical vessels. CONCLUSION: Fetal intravascular transfusion is a highly effective treatment for fetal alloimmunisation and allows pregnancies to continue to term and to be delivered vaginally. However, the procedure may be difficult and requires a team approach with ready access to fetal monitoring and emergency caesarean section. Our results suggest that increasing experience of the team is a major factor in improved outcome.

Adult↗