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Biomedical subjects

D A Potter

Publications and source records attributed to D A Potter.

At least 37 records · Page 2Linked to original sources
PubMed1991

Bringing social structure back into clinical decision making.

Although research in the past twenty years has resulted in an increasingly sophisticated understanding of clinical decision making processes, the dominant approach in this area of inquiry remains limited. Most studies emphasize normative models of how decisions ought to be made, others attempt to describe physicians' thinking, but few take the social context of decision making systematically into account. Research models typically assume that physicians are autonomous professionals practicing in socially insular clinical settings--an approach that is consistent with classic formulations of the social structure of medical practice, but they ignore 30 years of sociological research on research on patient-physician relationships and major historical changes in the structure of medical practice. Eisenberg's still timely advice to students of clinical decision making--that they need to describe decision making in the context of 'sociologic influences' (including patient, physician and practice setting characteristics)--is expanded in the present discussion. Recent studies are reviewed, highlighting important dimensions of social structure impinging on physicians' decision making. Findings indicate that the process of clinical decision making is likely influenced by patients' age, gender, socioeconomic status, and race, physicians' professional training and experience, as well as by larger structural features of organized clinical settings. Our review of these studies on the social context of clinical decision making, however, reveals major methodological limitations including those inherently imposed by secondary data analysis, normative approaches, written case vignettes, small, non-random samples and the inadequate control of confounding influences. We present a feasible, alternative research strategy, built on a factorial experimental design. Illustrative findings indicate how complex social structural influence on clinical decision making may be disentangled in an unconfounded manner.

Age Factors↗
PubMed1986

High-grade soft tissue sarcomas of the extremities.

From July 1975 to December 1982, 358 patients were referred to the Surgery Branch of the National Cancer Institute (NCI) with the diagnosis of soft tissue sarcoma of the extremities. Two hundred eleven of these patients presented with resectable, localized high-grade soft-tissue sarcomas and have been included in the present analysis of the management and outcome of patients with high-grade soft tissue sarcomas of the extremity treated at the NCI. One hundred forty-seven of these 211 patients have been included in randomized prospective trials. The remaining 64 patients in this analysis have been followed at the NCI, but were not included in randomized trials because of patient refusal or ineligibility. Tumor size was identified as a highly significant prognostic variable for disease-free and overall survival (P2 = 0.00001 and 0.0081, respectively). Tumor site, histologic type, and microscopic margins of resection were not significant prognostic variables. There was no difference between patients undergoing amputation compared to those undergoing limb-sparing procedures plus postoperative radiotherapy in disease-free or overall survival for all 211 patients in this study (P2 = 0.068 and 0.131, respectively). A significantly greater frequency of local failure among patients treated by local excision was noted compared to patients undergoing amputation (12/128 versus 0/83, P2 = 0.004), but this did not result in decreased overall survival in patients undergoing combined modality limb-sparing procedures. Adjuvant chemotherapy significantly prolonged disease-free survival (P2 = 0.005) for the 124/211 patients treated with adjuvant chemotherapy, although analysis of overall survival did not reveal a significant increase (P2 = 0.10). In a subset of 65 patients included in a prospective randomized trial evaluating the efficacy of adjuvant chemotherapy, a significant improvement in both disease-free (P2 = 0.033) and overall (P2 = 0.055) survival was seen in patients receiving chemotherapy. Sixty-five patients developed recurrent disease (65/211, 31%) and 42 of these patients were rendered disease-free surgically. Survival from the time of first recurrence was significantly prolonged among the 42 patients who were rendered disease-free (median survival, 31 months) compared to those who were not (median survival, 9 months, P2 less than 0.001).

Actuarial Analysis↗
PubMed1986

Structure of the murine serum amyloid A gene family. Gene conversion.

Serum amyloid A (SAA) is an apolipoprotein produced by the liver in response to inflammation; the levels of SAA mRNA and SAA protein increase at least 500-fold within 24 h. We have obtained clones of all three genes and pseudogene that make up the murine SAA gene family. Two of the genes have 96% sequence homology over their entire length, including introns and flanking sequences 288 base pairs (bp) 5' and 443 bp 3' to the genes: an overall length of 3215 bp. The sharp boundaries between homologous and nonhomologous sequences and the absence of interspersed repeated sequences there suggest that conversion has occurred between these two genes. The homologous regions are bounded by short inverted repeats containing alternating purine and pyrimidine residues, as described for other gene conversion units. The third SAA gene has evolved separately, although all are closely linked on chromosome 7. Comparison of the upstream regions of the SAA genes with those of the rat fibrinogen genes, whose expression is also induced by inflammation, reveals sequences common to all six genes which are very improbable on a random basis.

Amyloid↗
PubMed1985

Liposome uptake by melanoma: in vitro comparison with hepatocytes.

Liposomes are artificially generated vesicles entrapping aqueous solutions within lipid bilayer membranes. A major potential use of liposomes is for the delivery of antineoplastic agents to malignant tissue. However, liposome-cell interactions with both normal and neoplastic cells must be characterized in vitro to identify neoplastic tissues for which this approach may be most applicable in vivo. In this study, mouse melanoma-liposome interactions were examined in vitro. Small, unilamellar vesicle liposomes of three different phospholipid-cholesterol compositions were synthesized incorporating an aqueous phase fluorescent marker. Mouse melanoma had a significantly greater affinity for phosphotidylcholine-cholesterol liposomes than did mouse hepatocytes, as determined by comparing quantities of free intracellular 6-carboxyfluorescein in cells after a 15-min incubation with each of the three different liposome preparations (P less than 0.001). In addition, the efficiency of liposome internalization, calculated as the percentage of total cell-associated 6-carboxyfluorescein present as free, intracellular 6-carboxyfluorescein, was significantly greater for melanoma than for hepatocytes with all three liposome preparations (P less than 0.05). Therefore, in vitro liposome uptake by melanoma depends on lipid characteristics of the liposome preparation. Because melanoma uptake of liposomes appears to be a very efficient process in vitro, liposomes may be a useful vesicle for delivery of antineoplastic agents to melanoma in vivo.

Animals↗
PubMed1985

Insect feeding deterrents in endophyte-infected tall fescue.

The presence of an endophytic fungus, Acremonium coenophialum, in tall fescue (Festuca arundinacea) deterred aphid feeding by Rhopalosiphum padi and Schizaphis graminum. Both species of aphid were unable to survive when confined to endophyte-infected tall fescue plants. Feeding deterrents and toxic factors to R. padi and Oncopeltus fasciatus, large milkweed bug, were primarily associated with a methanol extract obtained when endophyte-infected tall fescue seed was serially extracted with hexane, ethyl acetate, and methanol. The concentrations of pyrrolizidine alkaloids were determined to be 30 to 100 times greater in the methanol extract than in the hexane and ethyl acetate extracts.

Journal Article↗
PubMed1985

Patterns of recurrence in patients with high-grade soft-tissue sarcomas.

From July 1975 to December 1982, 563 patients were referred to the Surgery Branch of the National Cancer Institute with the diagnosis of soft-tissue sarcoma. Three hundred and seven of these patients had fully resectable, localized high-grade soft-tissue sarcomas and were treated at the National Cancer Institute using standard protocols with surgery alone, or in combination with chemotherapy and/or radiotherapy. An aggressive surgical approach was undertaken in the management of patients who subsequently developed recurrent disease. These 307 cases have been reviewed, with a median duration of follow-up of 30 months, to determine the frequency of recurrent disease, the patterns of recurrence, and the impact of surgery on the survival of patients who developed recurrent disease. Disease recurred in one hundred seven patients (107/307, 35%), with a median disease-free interval of 18 months (range, 0.5 to 72.0 months). The frequency of recurrence by site of primary sarcoma was extremity, 31% (65/211); head and neck, 33% (4/12); trunk, 40% (17/42); retroperitoneum, 47% (17/36); and breast, 67% (4/6). Isolated pulmonary metastatic disease was the most common pattern of initial recurrence (56/107, 52%) followed by isolated local recurrence (21/107, 20%). Single other sites of recurrence and multiple concurrent sites of recurrence each accounted for 14% (15/107) of all initial recurrences. The relative frequency of each of these four patterns of recurrence varied with the site of the primary sarcoma. The outcome for patients with recurrent disease depended on the site of recurrence, rather than on the site of the primary sarcoma. Sixty-six patients (66/107, 62%) with recurrent disease were rendered surgically disease-free with the first recurrence, including 40 (40/56, 72%) patients with isolated pulmonary metastases, 20 patients (20/21, 96%) with isolated local recurrences, five patients (5/15, 33%), with isolated other sites of recurrence and one patient (1/15, 7%) with multiple sites of initial recurrence. Following surgical resection, the actuarial three-year survival for the 66 patients rendered disease-free was 51%. The median survival for the 41 patients not rendered surgically disease-free with the first recurrence was only 7.4 months. Thirty of the sixty-six patients (30/66, 45%) rendered disease-free with the first recurrence remained disease-free at follow-up, with a median follow-up of 28 months from the time of resection of the first recurrence. The remaining 36 patients (36/66, 55%) subsequently recurred, with a median disease-free interval of 7.3 months.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1984

Evaluation of abdominal pain in the AIDS patient.

Acquired immune deficiency syndrome (AIDS) is a recently recognized entity characterized by a deficiency in cell mediated immune response. The syndrome is manifested by the development of otherwise rare malignant neoplasms and severe life-threatening opportunistic infections. Case histories of five AIDS patients evaluated for abdominal pain are presented to demonstrate the unusual spectrum of intra-abdominal pathology that may be encountered in the AIDS patient. As the number of patients with AIDS continues to escalate, surgical evaluation and intervention will be required more frequently. An understanding of this syndrome and its complications is mandatory for the surgeon to adequately evaluate AIDS patients with abdominal pain.

Abdomen↗
PubMed1984

Thoracic manifestations of the acquired immune deficiency syndrome.

The acquired immune deficiency syndrome is characterized by the development of multiple recurrent opportunistic infections or unusual neoplasms in individuals with no prior history of immune suppression. This report summarizes the thoracic diseases encountered in such patients before after death and the role of diagnostic techniques currently used in the evaluation of thoracic disease in 15 patients with this syndrome. Efficacy of treatment was determined by correlation with postmortem findings in all patients. Pulmonary disease was present in all 15 patients and necessitated 23 transbronchial biopsies in 11 patients. Pneumocystis carinii pneumonia and cytomegalovirus pneumonia were the most common findings. Nine open lung biopsies in eight patients disclosed either Pneumocystis carinii pneumonia or Kaposi's sarcoma. Esophageal disease was present in four patients, and endoscopic evaluation demonstrated Candida esophagitis (two), esophageal Kaposi's sarcoma (one), and cytomegalovirus esophagitis and Kaposi's sarcoma (one). Mean time to death from diagnosis of acquired immune deficiency syndrome was 7.7 months, with respiratory insufficiency being the most common cause of death (9/15, 60%). Pneumocystis carinii pneumonia was successfully eradicated in 70% of the patients. Candida esophagitis was ameliorated in both patients with the disease. Unsuspected pulmonary Kaposi's sarcoma, cytomegalovirus pneumonitis, and other infectious pathogens were documented at autopsy. These data reveal that Pneumocystis carinii pneumonia and Candida esophagitis can be managed successfully in patients with acquired immune deficiency syndrome if appropriately diagnosed. The major cause of death in this series was pulmonary insufficiency, often the result of severe cytomegalovirus infection. Thoracic surgeons must continue to play an aggressive and important role in the early diagnosis and management of potentially treatable pulmonary and esophageal disease in these patients.

Acquired Immunodeficiency Syndrome↗
PubMed1981

Induction of hepatic synthesis of serum amyloid A protein and actin.

Major changes in the mRNA population of murine liver occur after administration of bacterial lipopolysaccharide, an agent that causes increases in the concentrations of acute-phase serum proteins. The mRNA for one of these, serum amyloid A, is increased at least 500-fold compared to the normal level. It becomes one of the most abundant hepatic mRNAs, and serum amyloid A synthesis comprises about 2.5% of total hepatic protein synthesis in the acute-phase response. Its synthesis is tissue-specific in that amyloid A mRNA was not detected in the kidney, an important site of amyloid fibril accumulation. The protein synthesized in largest amount by acute-phase liver tissue in culture is cytoplasmic actin. Its relative rate of synthesis is increased about 5-fold compared to the normal tissue; that of serum albumin is decreased to about one-third of its normal rate. The concentration of mRNA for serum albumin is decreased by a similar amount. Starting with induced liver RNA, we have constructed a recombinant plasmid containing most of the DNA sequence encoding the serum amyloid A polypeptide.

Actins↗
PubMed1981

Total mastectomy with complete axillary dissection.

A technique for total mastectomy with complete axillary dissection, which uses division of the insertion of the sternal portion of the pectoralis major muscle, preservation of its innervation, reconstruction after completion of the dissection and resection of the pectoralis minor muscle has been evaluated for 115 consecutive procedures. This modification facilitates a thorough axillary dissection, while preserving the cosmetic and functional benefits of the Patey operation.

Adult↗
PubMed1980

Rhythmic variations of valine and leucine decarboxylation in rat diaphragm.

Daily rhythmic variations of valine and leucine decarboxylation in the rat diaphragm were measured. Both valine and leucine decarboxylation increased during the hours of darkness and decreased during hours of light. Hypophysectomy eliminated the daily variation of decarboxylation. When food is available ad lib. to normal rats, the time of most active feeding coincides with the hours of darkness. Therefore, the period of darkness and maximum feeding coincides with the maximum oxidation of these two essential amino acids, valine and leucine, by diaphragm, and an active pituitary appears to be necessary to maintain this relationship. This model can be used to study interrelationships to behavioral, neurohumoral, and metabolic rhythms.

Animals↗
PubMed1980

DNA-protein interactions in the Drosophila melanogaster mitochondrial genome as deduced from trimethylpsoralen crosslinking patterns.

The location of proteins on the mitochondrial DNA (mtDNA) of Drosophila melanogaster was investigated by trimethylpsoralen photoreaction of embryos disrupted by gentle homogenization. After photoreaction, the mtDNA was isolated and the pattern of DNA crosslinking was determined by electron microscopy of the DNA under totally denaturing conditions. In contrast to nuclear DNA, which showed periodic crosslinks indicative of a nucleosome structure, most of each mtDNA molecule exhibited uniformly heavy crosslinking. A 10% region of the mtDNA was, however, protected from psoralen crosslinking in a distinctive manner: five uncrosslinked segments were closely clustered in the mtDNA. Four were 394 +/- 13 (SD) base pairs in size, while the fifth measured about 200 base pairs. These protected segments mapped within the A+T-rich region of the mtDNA, extending from the end of the A+T-rich region near the Bg1 II cleavage site to the center of the A+T-rich region. Protection of this part of the mtDNA from crosslinking was interpreted to be the result of association with proteins in the mitochondrion because mtDNA that was deproteinized before the photoreaction was uniformly crosslinked over its entire length. The origin of replication of the mtDNA is also located at the center of the A+T-rich region, which suggests that the protection from the psoralen photoreaction may be due to proteins involved in membrane attachment or replication.

Animals↗
PubMed1977

Substrate specificities of base-level and induced forms of oncofetal alkaline phosphatase in HeLa cells.

HeLa65 cells contain an oncofetal form of alkaline phosphatase that exhibits an increase in catalytic activity when cultures are grown in medium containing adrenal glucocorticoid hormones such as hydrocortisone or its analogue prednisolone. The increase in alkaline phosphatase specific activity in cells grown with hormone is apparently the result of a reduced phosphate content of the enzyme which alters the transition state of the enzyme-substrate complex with an increase in catlytic efficiency. Fourteen different substrates possessing aliphatic, aromatic and heterocyclic configurations were studied with respect to the initial velocities of hydrolysis catalyzed by the base-level and induced forms of the enzyme. The magnitude of increase in catalytic activity was not substantially influenced by the structure of the nonphosphoryl moiety of substrates.

Alkaline Phosphatase↗
PubMedDate not supplied

Low-dose follicular-phase cocaine administration disrupts menstrual and ovarian cyclicity in rhesus monkeys.

OBJECTIVE: To evaluate the effects of daily low-dose follicular-phase cocaine administration on menstrual cyclicity, ovulation rates, corpus luteum function, and hormone levels in rhesus monkeys. METHOD: Normally cycling, drug-naive, adult rhesus monkeys were randomized to receive either 1 mg/kg of cocaine (n = 7), 2 mg/kg of cocaine (n = 7), or normal saline (n = 7) daily on cycle days 2 to 14. Daily blood samples were obtained through indwelling catheters for measurement of serum gonadotropins and ovarian steroids. Daily vaginal swabs were obtained to determine onset of menses. Laparoscopy was performed 2 days after the midcycle estrogen peak to document ovulation. Daily caloric intakes as well as pretreatment and posttreatment weights were recorded. RESULTS: Two of seven monkeys receiving 1 mg/kg per day and two of seven monkeys receiving 2 mg/kg per day of cocaine had timely ovulation and normal menstrual cycle lengths. One monkey receiving the 2-mg/kg dose ovulated on cycle day 24 and had a short luteal phase (7 days) with a mean progesterone level of 2.4 ng/mL. All seven saline-treated control monkeys ovulated normally; the mean cycle length was 29 days and all had adequate luteal phases. The difference in ovulation rates between cocaine-treated and control monkeys was statistically significant (P = .003). There were no differences in basal levels of LH or FSH between treatment groups. There were no significant differences in weight change or caloric intake among groups. One third of the subsequent menstrual cycles in cocaine-treated monkeys were of abnormal duration. CONCLUSION: Daily low-dose follicular-phase cocaine administration disrupts menstrual cyclicity and folliculogenesis. This effect is independent of weight loss, caloric intake, and basal gonadotropin levels. Cocaine exposure may have a persistent effect on menstrual and ovarian cyclicity in some monkeys.

Animals↗