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Biomedical subjects

B Stark

Publications and source records attributed to B Stark.

84 records · Page 5Linked to original sources
PubMed1982

Inhibition of Photosynthetic Energy Conversion by Cupric Ion : EVIDENCE FOR Cu-COUPLING FACTOR 1 INTERACTION.

This study describes a specific Cu(2+) and light-dependent inhibition of spinach (Spinacia oleracea L.) chloroplast reactions involving coupling factor 1 function. A primary effect is an inhibition of photophosphorylation induced by illumination of Class II chloroplasts with micromolar Cu(2+) and pyocyanine in the absence of ADP, Mg(2+), and HPO(4) (2-). The inhibition, which is dependent on free Cu(2+) as indicated by protection by ethylene diamine tetraacetic acid and dithiothreitol, requires illumination (electron flow) for establishment of the specific inhibition to be noted. Protection is also afforded by uncouplers and some partial protection is provided by micromolar concentrations of ADP and ATP. The data strongly suggest that Cu(2+) causes an O(2)-independent oxidation of sulfhydryl groups on coupling factor 1, which are essential to catalytic function. This conclusion is supported by the reduction of energy-dependent (3)H-N-ethylmaleimide labeling of the gamma subunit of coupling factor 1 by the Cu(2+)-light pretreatment.

Journal Article↗
PubMed1981

Nephrotic syndrome and renal insufficiency in association with amyloidosis: a correlation between structure and function.

The following results were obtained by correlating light and electron microscopic findings from 85 cases of glomerular renal amyloidosis with clinical parameters: 1. Amyloid masses deposited in the glomeruli do not represent an effective filtration barrier, i.e., the formation of primary urine is not significantly influenced even by extensive amyloid masses in the glomeruli; protein retention is first observed when the glomerular capillaries are almost totally obliterated. 2. Once the nephrotic syndrome has developed in association with glomerular renal amyloidosis, it shows no tendency for remittance, despite progressing renal insufficiency. 3. The reason for this persistance of the nephrotic syndrome, despite increasing renal insufficiency, is a progressive reduction in the capacity of the tubules for protein reabsorption in the presence of increasing interstitial fibrosis of the kidney. 4. Interstitial fibrosis of the kidney cortex leads to increasing impairment in the oxygen and energy supply to the tubule cells together with considerable functional deterioration which, in addition to other metabolic disturbances, also results in a reduced capacity for protein reabsorption.

Amyloidosis↗
PubMedDate not supplied

Decreased insulin-like growth factor-I receptor sites on circulating mononuclear cells from children with acute leukemia.

Insulin-like growth factor-I (IGF-I) is a known mitogen for various cell types, including those of the hematopoietic cell system. To study the role of IGF-I in the neoplastic process of leukemia in children, the authors have determined the number of IGF-I binding sites on circulating mononuclear cells of children with acute leukemia as compared to normal children, using binding assays. The IGF-I binding sites per cell on peripheral mononuclear cells of children with leukemia decreased compared to those of the control group (411 +/- 73 and 1334 +/- 227, respectively, p < .001), while their affinity increased (Kd = 0.14 +/- 0.04 and 0.43 +/- 0.16, respectively, p = .05). Furthermore, in the patients, the number of the IGF-I binding sites was significantly lower in the subgroup of the peripheral mononuclear cells, which included lymphocytes and monocytes, as compared to their number in the peripheral blast cells (254 +/- 43.6 and 536 +/- 98.6, respectively, p = .02). A significant reduction was found in serum GHBP levels in the patients as compared to the controls (28.21 +/- 1.93 and 35.83 +/- 2.90, respectively, p = .02), while serum IGF-I and growth hormone levels were similar in patient and control groups. These results suggest a possible involvement of IGF-I in childhood acute leukemia, but further studies are needed to establish whether IGF-I plays a role in this disease.

Adolescent↗
PubMedDate not supplied

Results after resection of intraoral cancer and reconstruction with the free radial forearm flap.

Between 1989 and 1996, 47 patients with an intraoral squamous cell carcinoma underwent tumor resection and reconstruction with a free volar forearm flap. Tumor resection and neck dissection were performed by a head and neck surgeon and the free tissue transfer by a plastic surgeon. Preoperative radiation therapy was given to 44 of 47 patients and postoperative radiation therapy to 2. One other patient was not irradiated. There were 15 females and 32 males, with a mean age of 61 years. The primary site of the cancer was the tongue in 15 cases, the floor of the mouth in 15, the tonsil in 10, the bucca in 3 and the retromolar trigone in 4 cases. The flap was harvested from the left forearm in 34 and from the right in 13 patients. The mean operation time was 10 h (range 6-20) and the mean intraoperative bleeding was 486 ml (250-2,500). Forty-four of 46 flaps healed completely. Twelve revisions on 9 free flaps were performed between 6 h and 6 days postoperatively. Overall revisional surgery was done in 9 of 47 cases (19%). Two flaps could not be saved (4%). Infections/fistulas in the neck occurred in 11 of 46 cases (24%). Complete healing of the donor site occurred at a mean of 2.5 months (1-5). Nine patients developed complications at the donor site, 3 hematomas and 6 superficial infections (19%). Twenty-seven of 47 patients are still alive (57%). The mean survival time was 49 months (16-71).

Adult↗
PubMedDate not supplied

Effects of atropine and propranolol on retinal vessel diameters during isometric exercise.

PURPOSE: There is controversy regarding the nervous control of retinal blood vessels in humans. Most in vitro studies indicate that the intraocular part of the central retinal artery lacks autonomic innervation. We investigated the response of retinal vessels to isometric exercise during blockade of beta-receptors (propranolol) or muscarinic receptors (atropine). METHODS: Twelve healthy subjects performed squatting for 6 min during infusion of either propranolol atropine or placebo. Blood pressure and pulse rate were measured non-invasively. Retinal vessel diameters were measured continuously using the Zeiss Retinal Vessel Analyser. RESULTS: Squatting induced a significant increase in blood pressure and pulse rate, which was paralleled by a decrease in retinal vein and artery diameters. Atropine did not change the retinal vessel response to isometric exercise. Propranolol significantly blunted the exercise-induced vasoconstriction in retinal arteries. CONCLUSION: This result likely indicates propranolol-evoked vasoconstriction in the extraocular parts of the central retinal artery during isometric exercise.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Childhood malignant thymoma: clinical, therapeutic, and immunohistochemical considerations.

Malignant thymomas are among the least common mediastinal tumors in the pediatric age group. Thymomas are considered malignant on the basis of macroscopic and microscopic invasiveness. As only 20 well-documented cases involving children have been reported in the literature, the pattern of responsiveness to therapy and the value of prognostic signs is obscure. Two cases of malignant pediatric thymomas are reported with pathognomonic histoimmunological features of aggressive thymoma. One was cured, with a follow-up of 70 months, and one died while on therapy. Analysis of the histological features and the immunoperoxidase staining displays the complexity of pediatric thymomas and the inability to prognosticate the outcome, respectively.

Adolescent↗
PubMedDate not supplied

Continuing education outcomes related to pain management practice.

BACKGROUND: Nursing practice outcomes of continuing education need to be measured and reported as one indicator of the value of nursing continuing education. This article makes the case that knowledge gain, the traditional measure of continuing education effectiveness, is not necessarily sufficient to assess changes in nursing practice. METHOD: A pretest/posttest design was used to measure nursing practice outcomes of a continuing education program about pain management. A total of 50 attendees returned both the pretests and posttests and 68 attendees returned the follow-up evaluation. RESULTS: Ninety-four percent of the respondents had improved scores on the posttest. Ninety-one percent of the follow-up evaluation respondents stated they had an opportunity to use the new information and 98% stated the use of this information has improved patient care. CONCLUSION: This study found that a continuing education program triggered practice changes. The results of this study correlate with previous research that supports the need for practice outcome measurements.

Education, Nursing, Continuing↗