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V Smith

Publications and source records attributed to V Smith.

173 records · Page 10Linked to original sources
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Liquid chromatographic determination of urea in water-soluble urea-formaldehyde fertilizer products and in aqueous urea solutions: collaborative study.

Water soluble urea-formaldehyde (UF) fertilizers, manufactured by complex reaction of urea and formaldehyde, typically contain varying amounts of unreacted urea. A liquid chromatography method for the analysis of urea in these products, and in aqueous urea solutions, was collaboratively studied. An amine chromatography column was used to separate the unreacted urea from numerous UF reaction products present in these liquid fertilizers. Unreacted urea was determined by using external urea standards with UV detection at 195 nm. The standards and test samples were prepared in the mobile phase of 85% (v/v) acetonitrile in water. Ten laboratories analyzed 5 different UF-based commercial products containing unreacted urea in the range of 6 to 17% by weight, and 5 different concentrations of urea in water equivalent to commercial products of that nature. The aqueous urea solutions contained 2-20% urea (w/w). The range of s(R) values for the 5 UF-based commercial fertilizers was 0.49-1.02 and the %RSD(R) was 1.94-6.14. The s(R) range for the 5 urea solutions was 0.10 to 0.79 and the %RSD(R) range was 2.54 to 4.88. The average recovery of urea from the aqueous urea solutions was 96-103%. Therefore, this method is capable of monitoring urea nitrogen manufacturers' label claims and total nitrogen claims in those cases where urea is the sole source of plant food nitrogen. Based on the collaborative study data, the authors recommend this method be approved for AOAC Official First Action status.

Chromatography, Liquid↗
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Hormone-sensitive gene expression in breast tumours.

The expression of genes specifically induced by estrogens (pS2), prolactin (PIP) or progestins (Pg8) was measured in primary breast tumours. A highly augmented pS2 gene expression was evident in 55% of estrogen receptor (ER)+, progesterone receptor (PR)+ tumours but was absent in ER- PR- tumours. There was no clear cut correlation between augmented levels of PIP and Pg8 mRNAs in tumours and ER and PR status. Tumours from premenopausal patients were more likely to contain high levels of Pg8 mRNA (P less than 0.038), whereas tumours from postmenopausal patients tended to have augmented levels of PIP mRNA (P less than 0.053).

Adult↗
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Hybrid formation within the genus Leishmania?

Leishmanial organisms isolated from a desert rodent (Psammomys obesus) and a feral dog (Canis familiaris) in the Eastern Province of Saudi Arabia were isoenzymically distinct from Leishmania major and L. arabica, organisms usually associated with human and wild animal cutaneous leishmaniasis in this area. Further examination of isoenzyme banding patterns of cloned populations of these organisms, together with karyotyping using orthogonal field alternation gel electrophoresis and the use of highly specific kinetoplast DNA probes, has produced evidence suggesting that these organisms isolated from the dog and the rodent are hybrids of L. major and L. arabica.

Animals↗
PubMedDate not supplied

Evaluating child protective services training: the participant action plan approach.

As part of protective services training, participants developed action plans-lists of practice behaviors or organizational changes they planned to carry out as a result of the training. A three-month follow-up indicated that a number of action items were successfully implemented, particularly in the areas of risk assessment and therapeutic interventions.

Child↗
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Just another day.

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Humans↗
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Factors influencing survival after gamma knife radiosurgery for patients with single and multiple brain metastases.

PURPOSE: Radiosurgery has been reported to yield high local control rates for brain metastases. However, further work is needed to define which subgroups of patients may benefit from this treatment modality. PATIENTS AND METHODS: We reviewed 116 patients who underwent stereotactic radiosurgery for initial management or recurrence of solitary or multiple brain metastases from September 1991 through December 1994 at the University of California, San Francisco. Survival time and time to local-regional failure were calculated using the Kaplan-Meier method. Univariate and multivariate analyses were performed using the Cox proportional hazards model. RESULTS: Median survival was 40 weeks from radiosurgery. In multivariate analysis, smaller total tumor volume, absence of extracranial metastases, higher Karnofsky score, and age < or = 70 had a positive effect on survival. In patients initially managed for brain metastases, the addition of whole brain radiotherapy to radiosurgery had no significant effect on survival. Although the presence of multiple metastases was associated with a significantly worse survival rate in patients initially managed with radiosurgery in univariate analysis, it was not as a significant factor in multivariate analysis. An analysis of patients within this series treated with radiosurgery who would have been eligible for Patchell's study on the role of surgery in the treatment of solitary brain metastasis revealed a favorable median survival of 70 weeks. CONCLUSIONS: We conclude that radiosurgical treatment of brain metastases results in survival times that compare favorably with the historic experience in patients treated with whole brain radiotherapy alone or with surgical resection. In patients presenting initially with brain metastases, radiosurgery alone may yield survival results equivalent to radiosurgery with whole brain radiotherapy, but intracranial control and quality of life also need to be evaluated. Also, the presence of multiple brain metastases should not be a contraindication for the use of radiosurgery given the good survival achieved with such patients in this series. Each such case should therefore be evaluated based on other factors such as patient's age, Karnofsky score and systemic disease.

Adolescent↗
PubMedDate not supplied

Determination of water in forages and animal feeds by Karl Fischer titration.

Oven methods for determining moisture (volatiles) in forages and other animal feeds are empirical. The moisture concentration obtained depends upon the time and temperature the sample was dried and is influenced by the presence of other volatiles than water. A validated reference method to measure water in forages and animal feeds could be used to evaluate the appropriateness of oven methods for various types of animal feeds and forages. Karl Fischer titration is a well-established method for determining water. However, thorough extraction of water from forages and feeds is a challenge because they often contain cellular structures that release water slowly. Water was successfully extracted into methanol-formamide (50 + 50) by high-speed homogenization and then titrated directly at 50 degrees C with a one-component Karl Fischer reagent based on imidazole. The method is described in detail, results of day-to-day repeatability and laboratory-to-laboratory reproducibility are reported, and preliminary comparison data between oven methods are provided.

Analysis of Variance↗
PubMedDate not supplied

Gamma knife radiosurgery for malignant melanoma brain metastases.

PURPOSE: To evaluate the efficacy and toxicity of gamma knife radiosurgery in the treatment of melanoma metastases to the brain. PATIENTS AND METHODS: We retrospectively reviewed 55 patients with single or multiple intracranial melanoma metastases treated at the University of California, San Francisco, with gamma knife radiosurgery from 1991 through 1995. Sixteen patients were treated with gamma knife radiosurgery for recurrence following previous radiation therapy, 11 received radiosurgery as a boost to whole-brain radiation therapy, and 28 had radiosurgery alone for initial management of brain metastases. The median minimum radiosurgery tumor dose for 140 treated lesions was 19 Gy (range, 10-22 Gy) prescribed at the 35% to 90% isodose contour (median, 50%). The median total target volume per patient was 6.1 cc (range, 0.25-28.3 cc). RESULTS: With a median follow-up of 75 weeks in living patients, the median survival times were 35 weeks overall: 35 weeks for patients with solitary metastases versus 33 weeks for those with multiple metastases. A factor that was significant in univariate analysis of survival was total target volume treated. This parameter remained significant on multivariate analysis. The actuarial median freedom from progression analyzed by lesion for 113 lesions in 46 patients with imaging follow-up was 89 weeks with 6-month and 1-year actuarial freedom from progression rates of 89% (95% confidence interval, 80%-95%) and 77% (95% confidence interval, 62%-87%). In univariate analysis, improved freedom from progression was associated with smaller target volume treated, smaller maximum diameter, or higher prescribed dose. Four patients (7%) developed acute Radiation Therapy Oncology Group grade > or = 2 morbidity, and five patients (9%) developed late grade > or = 2 morbidity. DISCUSSION: Median survival and freedom from progression in patients treated with radiosurgery for melanoma metastatic to the brain are comparable to results in published radiosurgery series of grouped histologies. For melanoma patients, total intracranial tumor volume appears to be of greater prognostic significance than the absolute number of metastases treated. We conclude that gamma knife radiosurgery is effective and should be considered among various management strategies.

Adolescent↗