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Biomedical subjects

M Gold

Publications and source records attributed to M Gold.

At least 19 recordsLinked to original sources
PubMed1992

THR246 mutations decrease substrate inhibition in lactate dehydrogenase.

Threonine 246 in Bacillus stearothermophilus L-lactate dehydrogenase has been changed to valine, serine, and alanine by site-directed mutagenesis. Kinetic analyses show a decrease in substrate inhibition for pyruvate reduction with the T246S mutant and virtual elimination of substrate inhibition for the T246A and T246V mutants. The results indicate that the absence of substrate inhibition in the 246A/V-catalyzed reactions is due to the elimination of a key hydrogen bond between the hydroxyl group of threonine and pyruvate in the wild-type complex that is an important contributor in the formation of the abortive enzyme-NAD(+)-pyruvate complex responsible for substrate inhibition.

Escherichia coli↗
PubMed1992

Crystallization and preliminary X-ray diffraction studies of two mutants of lactate dehydrogenase from Bacillus stearothermophilus.

Bacillus stearothermophilus lactate dehydrogenase, one of the most thermostable bacterial enzymes known, has had its three-dimensional structure solved, the gene coding for it has been cloned, and the protein can be readily overexpressed. Two mutants of the enzyme have been prepared. In one, Arg171 was changed to Trp (R171W) and Gln102 was changed to Arg (Q102R). In the other, the mutation Q102R was maintained, but Arg171 was changed to Tyr (R171Y). In addition, an inadvertent C97G mutant was present. Both mutants have been crystallized by the hanging drop vapor diffusion method at room temperature. Bipyrimidal crystals have been obtained against (NH4)2SO4 in 50 mM piperazine HCl buffer. The crystals belong to space group P6(2)22 (P6(4)22) (whereas the native enzyme, the structure of which has been solved by Piontek et al., Proteins 7:74-92, 1990) crystallized in the space group P6(1)) with a = 102.3 A, c = 168.6 A for the R171W, Q102R, C97G triple mutant, and a = 98.2 A; c = 162.1 A for the R171Y, Q102R, C97G mutant. These crystal forms appear to contain one-quarter of a tetramer (M(r) 135,000) in the asymmetric unit and have VM values of 3.8 and 3.3 A3/dalton, respectively). The R171W mutant diffracts to 2.5 A and the R171 Y mutant to approximately 3.5 A.

Bacterial Proteins↗
PubMed1992

Mutations abolishing the endonuclease activity of bacteriophage lambda terminase lie in two distinct regions of the A gene, one of which may encode a "leucine zipper" DNA-binding domain.

Bacteriophage lambda terminase is a multifunctional enzyme composed of two subunits which are the products of the phage-encoded Nu1 and A genes. The enzyme catalyzes the endonucleolytic cleavage of lambda DNA at a site known as cosN and mediates packaging of the phage DNA into empty heads. This work describes the characterization of mutations within the A gene which lead to the loss of terminase endonuclease activity without affecting the ability of the enzyme to package monomeric mature (cut) lambda DNA. The residues changed by these mutations lie in two distinct regions within the carboxy half of the A protein. One of these regions has sequence homology with a conserved region of DNA polymerases. The other region resembles the "leucine zipper" DNA binding domain (bZIP) found in eukaryotic transcription factors in that both a basic region and leucine heptad-repeat are present. This terminase domain may be involved in the recognition and/or cleavage of cosN.

Amino Acid Sequence↗
PubMed1992

Renal autotransplantation in the loin pain-hematuria syndrome: a cautionary note.

The current literature suggests that renal autotransplantation is nearly uniformly effective in controlling the severe and debilitating pain of the loin pain-hematuria syndrome (LPHS). However, we report two patients thought to have this syndrome in whom renal autotransplantation did not result in long-term control of pain. In case 1, autotransplantation resulted in immediate cessation of pain; however, the flank pain recurred 7 1/2 months later. The recurrent pain was also severe and debilitating, requiring narcotic medications for control. In case 2, autotransplantation of the left kidney resulted in chronic pain in the left pelvic area, the site of the autotransplanted kidney. In addition, the patient continued to experience chronic discomfort in the left flank and along the flank incision. One year after autotransplantation, the patient still requires multiple daily doses of narcotic medications for pain control. Our two patients represent the 13th and 14th reported patients subjected to renal autotransplantation for management of LPHS. They represent only the third and fourth reported patients with recurrence of pain after renal autotransplantation. Because studies with negative results are less likely to be reported in the literature than studies with positive results, it is possible that the literature overestimates the effectiveness of renal autotransplantation in the LPHS. To assess the true effectiveness of renal autotransplantation in LPHS, a survey of patients with LPHS who have undergone renal autotransplantation needs to be performed.

Adult↗
PubMed1992

Single amino acid substitutions can further increase the stability of a thermophilic L-lactate dehydrogenase.

Lactate dehydrogenases are of considerable interest as stereospecific catalysts in the chemical preparation of enantiomerically pure alpha-hydroxyacid synthons. For such applications in synthetic organic chemistry it would be desirable to have enzymes which tolerate elevated temperatures for prolonged reaction times, to increase productivity and to extend their applicability to poor substrates. Here, two examples are reported of significant thermostabilizations, induced by site-directed mutagenesis, of an already thermostable protein, the L-lactate dehydrogenase (EC 1.1.1.27, 35 kDa per monomer subunit) from Bacillus stearothermophilus. Thermal inactivation of this enzyme is accompanied by irreversible unfolding of the native protein structure. The replacement of Arg171 by Tyr stabilizes the enzyme against thermal inactivation and unfolding. This stabilizing effect appears to be based on improved interactions between the subunits in the core of the active dimeric or tetrameric forms of the enzyme. The thermal stability of L-lactate dehydrogenase variants with an active site Arg residue, either in the 171 (wild-type) or in the 102 position, is further increased by sulfate ions. The two stabilizing effects are additive, as found for the Arg171Tyr/Gln102Arg double mutant, for which the stability of the protein in 100 mM sulfate solution reaches that of L-lactate dehydrogenases from extreme thermophiles. All mutant proteins retain significant catalytic activity, both in the presence and absence of stabilizing salts, and are viable catalysts in preparative scale reactions.

Calorimetry↗
PubMed1991

Recombinant granulocyte-macrophage colony-stimulating factor after autologous bone marrow transplantation for lymphoid cancer.

BACKGROUND: The period of neutropenia after autologous bone marrow transplantation results in substantial morbidity and mortality. The results of previous phase I-II clinical trials suggest that recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) may accelerate neutrophil recovery and thereby reduce complications in patients after autologous bone marrow transplantation. METHODS: We conducted a randomized, double-blind, placebo-controlled trial at three institutions. The study design and treatment schedules were identical, and the results were pooled for analysis. One hundred twenty-eight patients were enrolled. Sixty-five patients received rhGM-CSF in a two-hour intravenous infusion daily for 21 days, starting within four hours of the marrow infusion, and 63 patients received placebo. RESULTS: No toxic effects specifically ascribed to rhGM-CSF were observed. The patients given rhGM-CSF had a recovery of the neutrophil count to 500 x 10(6) per liter 7 days earlier than the patients who received placebo (19 vs. 26 days, P less than 0.001), had fewer infections, required 3 fewer days of antibiotic administration (24 vs. 27 days, P = 0.009), and required 6 fewer days of initial hospitalization (median, 27 vs. 33 days; P = 0.01). There was no difference in the survival rate at day 100. CONCLUSIONS: In patients undergoing autologous bone marrow transplantation for lymphoid neoplasia, rhGM-CSF significantly lessens morbidity. Further studies will be required to establish its optimal dosage and schedule of administration.

Adolescent↗
PubMed1991

Excitatory amino acid antagonists (kynurenic acid and MK-801) attenuate the development of morphine tolerance in the rat.

To investigate the possible role of excitatory amino acids (EAAs) in the mechanisms of morphine tolerance, rats were treated either with the wide-spectrum EAA antagonist, kynurenic acid (150 mg/kg), or the specific N-methyl-D-aspartic acid (NMDA) receptor antagonist. MK-801 (0.05 mg/kg), during a four-day induction period of morphine tolerance. Morphine was given once daily at a dose of 15 mg kg. On the fifth day rats were injected only with morphine (15 mg/kg), and analgesia was assessed using the hot-plate test. Morphine tolerance was significantly reduced by both EAA antagonists. Control experiments showed that at the same doses neither acute nor chronic administration of these antagonists affected morphine analgesia itself in a manner that can explain these findings. The possible involvement of EAAs in the mechanisms of morphine tolerance is discussed.

Analgesia↗
PubMed1991

Intraoperative anaphylaxis: an association with latex sensitivity.

Latex products have recently been identified as the cause of severe intraoperative anaphylactic reactions. We have identified a group of pediatric patients who appear to be at increased risk for such reactions. Fifteen patients with either spina bifida or congenital urologic abnormalities experienced 19 intraoperative anaphylactic reactions. All patients had frequent previous exposures to rubber materials since infancy as part of their management and/or investigative procedures. Seven of 15 patients had a previous history of local skin reactions to rubber. Only four patients were atopic. All patients had undergone multiple (two of 26) operative procedures before their reactions, the onset of which ranged from 40 to 290 minutes after induction of anesthesia. The reactions varied in intensity from urticaria to severe cardiorespiratory collapse. All these patients subsequently had positive allergy skin tests and positive RAST to latex antigen. We conclude that this group is at risk when they are exposed to latex intraoperatively as a result of frequent past exposure to these materials. Allergic evaluation for latex allergy may assist in the preoperative evaluation of similar patients. In sensitized patients, appropriate prophylactic measures, particularly the avoidance of latex, is required.

Adolescent↗
PubMed1991

Granulocytic sarcoma presenting as an epidural mass with acute paraparesis in an aleukemic patient.

Granulocytic sarcomas are rare tumors composed of granulocytic precursor cells. They are most commonly encountered in patients with acute myelogenous leukemias and myeloproliferative disorders in blast crisis. Rarely, patients presenting with granulocytic sarcoma show no evidence of acute leukemia. The authors report an aleukemic patient with acute paraparesis from an epidural granulocytic sarcoma. Only five such cases have been reported previously. Immunoperoxidase stain for lysozyme and chloroacetate esterase stain were used to prove the myeloid origin of the tumor cells.

Aged↗
PubMed1991

Determinants of health insurance status among young adults.

This study evaluates the determinants of insurance coverage in the 18-24-year-old population using the National Medical Care Utilization and Expenditure Survey. Three specific issues are addressed: 1) the characteristics of the insured versus uninsured, 2) the reason given by the uninsured for not having coverage, and 3) the role of employment status and other variables in determining insurance status. An important consideration is whether age or usual activity is more important in its effect on insurance status. The results show that employment is the strongest predictor of insurance status in all age and usual activity subgroups. Generally, permanent/full-time workers are most likely to be insured. An exception to this trend is found for those attending school who are also permanent/part-time workers. These individuals are more likely to be insured than permanent full-time workers who are in school. Furthermore, young adults with lower incomes, less education, rural residence, not married, hispanic ethnicity, and Western geography are the least likely to be insured. The findings of this analysis can be used by policymakers to identify the mechanisms that can best enhance insurance coverage among young adults.

Adult↗
PubMed1991

Isolation and characterization of mutations in the bacteriophage lambda terminase genes.

The terminase enzyme of bacteriophage lambda is a hetero-oligomeric protein which catalyzes the site-specific endonucleolytic cleavage of lambda DNA and its packaging into phage proheads; it is composed of the products of the lambda Nul and A genes. We have developed a simple method to select mutations in the terminase genes carried on a high-copy-number plasmid, based on the ability of wild-type terminase to kill recA strains of Escherichia coli. Sixty-three different spontaneous mutations and 13 linker insertion mutations were isolated by this method and analyzed. Extracts of cells transformed by mutant plasmids displayed variable degrees of reduction in the activity of one or both terminase subunits as assayed by in vitro lambda DNA packaging. A method of genetically mapping plasmid-borne mutations in the A gene by measuring their ability to rescue various lambda Aam phages showed that the A mutations were fairly evenly distributed across the gene. Mutant A genes were also subcloned into overproducing plasmid constructs, and it was determined that more than half of them directed the synthesis of normal amounts of full-length A protein. Three of the A gene mutants displayed dramatically reduced in vitro packaging activity only when immature (uncut) lambda DNA was used as the substrate; therefore, these mutations may lie in the endonuclease domain of terminase. Interestingly, the putative endonuclease mutations mapped in two distinct locations in the A gene separated by a least 400 bp.

Bacteriophage lambda↗
PubMed1991

Role of sinusitis in asthma.

Chronic sinusitis has been suggested to play a causal role in creating recalcitrant asthma. However, this hypothesis has never been confirmed in a blind placebo-controlled study. Several studies have documented an association between abnormal sinus X-rays and asthma in 30-70% of patients, depending on criteria chosen for evaluation of the radiologic changes. Asthma is associated with inflammation in the lower airways, and the same inflammation might involve the sinuses in a parallel fashion. It is now felt that early therapy of this inflammation can modify the course of asthma resulting in its amelioration. Conversely, delay in institution of this therapy might result in the inflammation entrenching airway reactivity. It must be clearly proven in a controlled fashion that antibiotic or other therapy of sinusitis will improve the course of asthma since such therapy could delay the aggressive management of inflammation.

Asthma↗
PubMed1991

Health maintenance organizations: structure, performance, and current issues for employee health benefits design.

After summarizing the origins and key principles of HMOs, including the current characteristics of the HMO industry, this article reviews the evidence of HMO performance in the areas of benefits design, utilization and cost effectiveness, quality of care and consumer satisfaction, and selection and overall employer satisfaction. Outstanding issues and concerns, from the perspective of employee health benefits design, include issues such as assuring a fair price for HMO benefits, employer contribution methods, HMO diversification, and cost escalation and the search for value. Results of research studies have been generally positive about HMO performance on benefits, cost effectiveness, quality, and consumer satisfaction, and more mixed on employer satisfaction. As employers address concerns, some changes are likely in the methods used to integrate HMOs into a health benefits strategy. Because the issues involved in these changes are numerous and complex, careful consideration and design are desirable to assure that the net impact of any change is positive and consistent with overall goals.

Consumer Behavior↗
PubMed1990

Intraoperative anaphylaxis to latex.

This case report describes intraoperative anaphylaxis occurring in a fourteen-year-old female with spina bifida in which latex surgical gloves were incriminated as the aetiologic agent. The patient was non-atopic but since eight years of age she had developed localized angioedema and urticarial skin reactions on exposure to rubber. She had previously undergone several uneventful surgical procedures. Forty-five minutes following induction of anaesthesia and during laparotomy for elective cholecystectomy she experienced sudden onset of increased airway pressure, oxygen desaturation, tachycardia, profound hypotension and erythema consistent with an anaphylactic reaction. Resuscitation with manual ventilation and oxygen, intravenous fluids and an epinephrine infusion was successful. Subsequent investigations for allergies demonstrated a strongly positive skin prick test and RAST to latex antigen, with negative results to anaesthetic agents, antibiotics and inhalant allergens. During two later operations prophylaxis consisting of diphenhydramine, ranitidine and hydrocortisone appeared to prevent further reactions. Latex should be considered as a cause of life-threatening intraoperative allergic reactions in patients with a history of rubber allergy or frequent exposure to latex products.

Adolescent↗
PubMed1990

Comparison between the prevalence and treatment of wheezing and coughing in Brampton and Mississauga children.

An analysis of hospital discharge data showed that Brampton children 4 years and under had higher rates of hospital admissions for asthma, bronchitis and upper respiratory infections than children in the same age group living in Mississauga and other Ontario municipalities. The present study was done to compare the prevalence and treatment of wheezing and coughing between Brampton and Mississauga children 4 and 5 years of age. The study showed that increased use of pediatricians on the part of Mississauga children in comparison to Brampton children resulted in a higher proportion being placed on anti-asthmatic medications even though the underlying prevalence rate of wheezing and coughing was the same in the two samples. Further study is required to determine whether differences in primary care between the two samples can explain a two-fold increase in hospital admission rates for lower respiratory illness among Brampton preschool children in comparison to their counterparts in Mississauga.

Child, Preschool↗
PubMed1990

Anorexia and bulimia.

Anorexia nervosa and bulimia nervosa are eating disorders with distinct clinical presentations. Reduced caloric intake, a hallmark of both disorders, is manifested by self-induced starvation in anorexia and by binge eating and gastrointestinal purging in bulimia. Treatment includes nutritional intervention, psychotherapy and pharmacotherapy in either the ambulatory or the hospital setting.

Adolescent↗