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Biomedical subjects

D E Goldberg

Publications and source records attributed to D E Goldberg.

13 recordsLinked to original sources

Components of sterol biosynthesis assembled on the oxygen-avid hemoglobin of Ascaris.

The parasitic nematode Ascaris infests a billion people worldwide. Much of its proliferative success is due to prodigious egg production, up to 10(6) sterol-replete eggs per day. Sterol synthesis requires molecular oxygen for squalene epoxidation, yet oxygen is scarce in the intestinal folds the worms inhabit. Ascaris has an oxygen-avid hemoglobin in the perienteric fluid that bathes its reproductive organs. Purified hemoglobin contained tightly bound squalene and functioned as an NADPH-dependent, ferrihemoprotein reductase. All components of the squalene epoxidation reaction--squalene, oxygen, NADPH, and NADPH-dependent reductase--are assembled on the hemoglobin. This molecule may thus function in sterol biosynthesis.

Animals

Ascaris hemoglobin gene: plant-like structure reflects the ancestral globin gene.

Animal globin genes have two introns at strictly conserved positions, while plant globin genes have both of these as well as an additional, central intron. It has been proposed that a common ancestor gene had three introns, one of which was subsequently lost from animal but not plant globin genes. We have elucidated the cDNA sequence and gene structure of a hemoglobin from the parasitic nematode Ascaris suum and found a plant-like central intron, providing strong evidence for a three-intron ancestor of modern globin genes.

Amino Acid Sequence

pS2 protein and steroid hormone receptors in invasive breast carcinomas.

We have used immunohistochemical and hormone-binding techniques to determine the presence of estrogen receptors, estrogen-receptor protein, progesterone receptors and pS2 protein in 97 invasive breast cancers. Our group of tumors displayed the same frequency of estrogen receptors and progesterone receptors as other comparable groups, but it contained more tumors containing pS2 protein. We also observed staining of morphologically normal cells in lobules adjacent to the tumors and in several fibroadenomas; both findings vary from some other reports. We attribute these variations to the use of a sensitive immunohistochemical method and choice of the lowest possible threshold to classify a tumor as pS2-positive. If we used a higher threshold, then about 95% of the tumors containing pS2 protein also contained estrogen receptor protein. Our results add further weight to the assertion that tumors containing pS2 protein also display estrogen receptors. The data also provide theoretical and indirect support to the clinical prediction that tumors containing pS2 protein are more likely to respond to hormonal therapy and may have a more indolent course than tumors lacking the molecule.

Adult

Plasmodial hemoglobin degradation: an ordered pathway in a specialized organelle.

During its intraerythrocytic development, the malarial parasite devours most of the hemoglobin in its host cell. This enormous catabolic process is achieved through an ordered, efficient degradative pathway that takes place in a specialized organelle, the digestive vacuole. The amino acids generated are used by the parasite for its growth and maturation; the heme released is polymerized into a crystalline matrix called hemozoin. We are beginning to understand the special enzymes that participate in this pathway. We do not yet fully understand the relative importance of exogenous versus catabolically generated amino acids, the function of hemozoin, the mechanism of action of quinoline drugs that concentrate in the digestive vacuole, or the mechanism of protection from malaria of variant hemoglobin gene carriers.

Animals

Hemoglobin degradation in the human malaria pathogen Plasmodium falciparum: a catabolic pathway initiated by a specific aspartic protease.

Hemoglobin is an important nutrient source for intraerythrocytic malaria organisms. Its catabolism occurs in an acidic digestive vacuole. Our previous studies suggested that an aspartic protease plays a key role in the degradative process. We have now isolated this enzyme and defined its role in the hemoglobinolytic pathway. Laser desorption mass spectrometry was used to analyze the proteolytic action of the purified protease. The enzyme has a remarkably stringent specificity towards native hemoglobin, making a single cleavage between alpha 33Phe and 34Leu. This scission is in the hemoglobin hinge region, unraveling the molecule and exposing other sites for proteolysis. The protease is inhibited by pepstatin and has NH2-terminal homology to mammalian aspartic proteases. Isolated digestive vacuoles make a pepstatin-inhibitable cleavage identical to that of the purified enzyme. The pivotal role of this aspartic hemoglobinase in initiating hemoglobin degradation in the malaria parasite digestive vacuoles is demonstrated.

Amino Acid Sequence

An iron-carboxylate bond links the heme units of malaria pigment.

The intraerythrocytic malaria parasite uses hemoglobin as a major nutrient source. Digestion of hemoglobin releases heme, which the parasite converts into an insoluble microcrystalline material called hemozoin or malaria pigment. We have purified hemozoin from the human malaria organism Plasmodium falciparum and have used infrared spectroscopy, x-ray absorption spectroscopy, and chemical synthesis to determine its structure. The molecule consists of an unusual polymer of hemes linked between the central ferric ion of one heme and a carboxylate side-group oxygen of another. The hemes are sequestered via this linkage into an insoluble product, providing a unique way for the malaria parasite to avoid the toxicity associated with soluble heme.

Animals

Estrogen receptors in skin appendage tumors and extramammary Paget's disease.

Determination of estrogen receptors (ER) in breast carcinoma is valuable in the management of patients. However, little is known about the presence of these receptors in other tumors. Normal skin appendages and their neoplasms, including extramammary Paget's disease (EPD), might be expected to express ER since the breast is histogenetically related to sweat glands. In this study, 41 cases of skin appendage tumors (SAT) and 11 cases of EPD were stained using the ER-ICA monoclonal kit (Abbott, Chicago, IL) with a modified technique for paraffin-embedded sections. Controls included 10 biopsies of primary breast carcinoma and 4 cases of metastatic breast carcinoma to skin, all positive for ER. None of the samples of SAT or EPD showed staining for ER. Normal skin appendages were also negative. Normal vaginal epithelium in one case of EPD showed positive nuclear staining for ER. ER determination using immunohistochemical technique in paraffin-embedded sections may be useful in the differential diagnosis between malignant SAT and metastatic breast carcinoma in the skin. The absence of ER in normal skin appendages suggests that its apparition is a feature of specialized differentiation of breast epithelium.

Adult

Computer-based program for identifying medication orders requiring dosage modification based on renal function.

A computer-based program that enables staff pharmacists to quickly review medication orders written for renally impaired patients is described. Medication orders requiring dosage modification based on the renal function of the patients for whom they were written were being identified by a medical staff-approved pharmacist intervention program. However, staff pharmacists were unable to assess the orders easily and rapidly because of a lack of readily available patient data. In response, a computer-based intervention program was developed. Specific dosage guidelines for renally eliminated drugs in patients with renal dysfunction were entered into the pharmacy computer. An interface with the laboratory computer enables the pharmacy computer to access creatinine concentration or clearance values, perform calculations if necessary, and alert pharmacists to specific drug orders that may require modification. Such medication orders are flagged by the pharmacy computer during order entry. When a staff pharmacist judges that intervention is needed, he or she telephones the ordering physician or sends a note to the patient's nursing station. Over a two-month period, 1485 orders were identified as being potentially inappropriate. Physicians were contacted about 191 of the flagged orders, and they accepted the pharmacist's recommendation for 141 (74%) of these orders. The interventions resulted in a drug acquisition cost saving of $7082 over the two-month period. A computer-based program enabled staff pharmacists to easily and rapidly identify orders for renally eliminated agents that required modification, reduced the risk of adverse reactions, trimmed costs, and promoted the clinical dimension of pharmacy practice.

Clinical Pharmacy Information Systems

Hemoglobin degradation in the malaria parasite Plasmodium falciparum: an ordered process in a unique organelle.

The malaria parasite Plasmodium falciparum uses host erythrocyte hemoglobin as a major nutrient source. We report the purification of P. falciparum digestive vacuoles and characterization of the degradative process therein. Vacuoles were isolated by a combination of differential centrifugation and density gradient separation. The pure vacuoles were capable of degrading hemoglobin to small fragments with a pH optimum of 5-5.5. Proteolysis in the vacuoles appears to be an ordered process, requiring an aspartic protease to clip intact hemoglobin before other proteolytic activities can function efficiently. The vacuoles do not contain other hydrolases commonly found in lysosomes and therefore appear to be unique proteolytic organelles designed specifically to degrade hemoglobin.

Animals

Pharmacy-coordinated process for evaluating physician drug prescribing.

A pharmacy-coordinated process is described in which the frequency and types of inappropriate drug prescribing are evaluated as part of the medical staff quality assurance and physician credentialing program. A pharmacist intervention program was implemented at an 838-bed private hospital to review all medication orders for appropriateness and to intervene with physicians and nurses when problems in drug prescribing or administration were identified. During a five-year period there were more than 6500 drug therapy interventions. Because of the recurrent problems identified, the medical staff asked the pharmacy department to develop a process for objectively evaluating the quality of prescribing practices that could be used in the medical staff quality assurance program and in physician credentialing. The drug-prescribing activities of physicians applying for clinical privileges are subjected to a "macro" review by using a computerized clinical financial information system to extract drug-use information from patients' bills. In a "micro" review, patient records are retrospectively analyzed by Pharm.D. clinical specialists; all medications prescribed by the physician for those patients being evaluated are scrutinized. Appropriate response scores are calculated by dividing the number of appropriate responses by the total responses. The pharmacy department in this hospital has assumed a more active role in patient care through its participation in a process for objectively evaluating the quality of prescribing practices.

Diagnosis-Related Groups

ColE1 hybrid plasmids for Escherichia coli genes of glycolysis and the hexose monophosphate shunt.

The Clarke-Carbon clone bank carrying ColE1-Escherichia coli DNA has been screened by conjugation for complementation of glycolysis and hexose monophosphate shunt mutations. Plasmids were identified for phosphofructokinase (pfkA), triose phosphate isomerase (tpi), phosphoglucose isomerase (pgi), glucose-6-phosphate dehydrogenase (zwf), gluconate-6-phosphate dehydrogenase (gnd), enolase (eno), phosphoglycerate kinase (pgk), and fructose-1,6-P2 aldolase (fda). Enzyme levels for the plasmid-carried gene ranged, for the various plasmids, from 4- to 25-fold the normal level.

Conjugation, Genetic