Biomedical subjects

M J Miller

Publications and source records attributed to M J Miller.

At least 235 records · Page 13Linked to original sources

PubMed1994

Arginine 41 of subunit c of Escherichia coli H(+)-ATP synthase is essential in binding and coupling of F1 to F0.

Two substitutions were made for Arg41 in the polar loop of subunit c of the Escherichia coli F1F0 H(+)-transporting ATP synthase. The R41K and R41H mutants were initially studied by use of a plasmid carrying the complete c R41K or c R41H unc (F1F0) operon in a chromosomal strain deleted for the unc operon. The extent of F0 incorporation into membranes of these cells was quite variable, and the system was concluded to be unsuitable for biochemical characterization. Ultimately, the mutant genes were recombined into the chromosome using a novel method for the unc system. The biochemical phenotype of the chromosomally expressed mutants proved to be reproducible. The c R41H mutation causes a specific defect in assembly of F0, i.e. subunit a was not incorporated into the membrane despite near normal incorporation of subunits b and c. On the other hand, c R41K mutant F0 assembled normally in one of two background strains studied. (In the second genetic background, subunit a was inefficiently incorporated into the c R41K membrane.) In membranes prepared from a c R41K strain assembling a complete F0, R41K F0 was found to bind F1 with near normal affinity and to transport H+ at near normal rates. Although R41K F0 binds F1, F1-ATPase activity and H+ transport remained uncoupled. The uncoupling was indicated by a lack of ATP-driven H+ translocation and by the high proton permeability of membranes with F1 bound to F0. The uncoupled phenotype of the R41K mutant closely resembles that previously reported for the c Q42E mutant.

Adenosine Triphosphate↗

PubMed1994

Maturation of the cholinergic response of tracheal smooth muscle in the piglet.

Maturational changes of the contractile properties of airway smooth muscle have been suggested to occur during the late prenatal and early postnatal period in the piglet. However, the timing and mechanisms involved remain elusive. Therefore, we studied isometric contraction of tracheal smooth muscle (TSM) to evaluate the effects of maturation on 1) the response of TSM to the muscarinic agonist acetylcholine (Ach); and 2) the regulatory activity of acetylcholinesterase (AChE) during the early postnatal period in the piglet. Studies were performed in 1-5-day-old (n = 6) and 14-22-day-old (n = 8) anesthetized, mechanically ventilated piglets. Changes in tracheal tension were measured in vivo from an open tracheal segment and normalized for both longitudinal length of the tracheal segment and cross-sectional area. Dose-response curves to locally applied Ach were obtained before and after the intravenous administration of the AChE inhibitor physostigmine (Phys). Ach-induced changes in tracheal tension significantly increased with maturation during the first 3 weeks of life (P < 0.01), regardless of normalization method. The addition of Phys significantly increased the cholinergic responses of TSM in both age groups (P < 0.02). However, this increase was comparable between age groups. There was also no difference in AChE activity measured in tracheal smooth muscle homogenates between the 1-5 and 14-22-day-old animals. These data indicate that maturation significantly enhances the cholinergic responses of tracheal smooth muscle in the early postnatal period in the piglet.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗

PubMed1994

Complexation of iron cation by sodium urate crystals and gouty inflammation.

Gouty inflammation can be suppressed by an iron chelator. We therefore hypothesized that arthritis associated with sodium urate crystal deposition could follow the incomplete complexation of iron cation with subsequent oxidant generation as the metal cycles through reduced and oxidized states. Urate crystals adsorbed Fe3+ in vitro and crystals collected from a human tophus had significant concentrations of ionizable iron. Urate crystals oxidized deoxyribose to a thiobarbituric acid (TBA)-reactive product, augmented luminol chemiluminescence by neutrophils, released leukotriene B4 from neutrophils, activated complement, and promoted neutrophil chemotaxis. All of these events increased with the concentration of complexed iron and were suppressed by the iron chelator deferoxamine or the .OH scavenger dimethylthiourea. These results suggest that some portion of gouty inflammation after urate crystal deposition could result from the incomplete complexation of iron with subsequent catalytic generation of reactive oxygen species.

Chemotaxis, Leukocyte↗

PubMed1994

Inhibition of calcium-dependent nitric oxide synthase causes ileitis and leukocytosis in guinea pigs.

As nitric oxide reduces gut epithelial permeability, we designed a study to determine if chronic nitric oxide synthase inhibition predisposes the gut to inflammation. Nitric oxide synthase (NOS) inhibitors were administered in the drinking water ad libitum, for seven days: aminoguanidine (10 micrograms/ml), a selective inhibitor of the inducible form of nitric oxide synthase; and NG-nitro-L-arginine methyl ester (L-NAME, 1, 10, and 100 micrograms/ml), which inhibits both the constitutive and inducible forms. Control animals drank tap water only or water with D-NAME, the inactive enantiomer. After one week, circulating leukocyte count and tissue myeloperoxidase activity were measured. L-NAME (100 micrograms/ml), but not D-NAME or aminoguanidine, caused a twofold increase in a circulating leukocyte numbers. This increase in leukocyte numbers was time- and dose-dependent, but the differential count was unaltered. Tissue myeloperoxidase (MPO) activity as an index of granulocyte infiltration was comparable in all groups in the stomach, jejunum, colon, liver, lung, kidney, heart, and skeletal muscle. However, ileal MPO activity was elevated threefold in the L-NAME-(100 micrograms/ml) treated group (P < 0.05). Results in the D-NAME and aminoguanidine groups were similar to controls. L-NAME administration resulted in a reduction in NOS activity ([14C]citrulline formation) in the ileum but not jejunum, whereas cGMP levels were elevated in both ileum and jejunum. We conclude that chronic inhibition of the constitutive form of nitric oxide synthase predisposes the ileum to inflammation and leads to a progressive leukocytosis.

Amino Acid Oxidoreductases↗

PubMed1994

Immediate versus delayed free-tissue transfer salvage of the lower extremity in soft tissue sarcoma patients.

BACKGROUND: Free tissue transfer (FTT) can extend the limits of limb salvage in patients with soft tissue sarcoma (STS), but few data exist on the efficacy and morbidity in this patient population. METHODS: We prospectively examined 19 patients who underwent resection of STS and an immediate or a delayed FTT reconstruction between November 1989 and May 1992. RESULTS: There were 11 immediate and eight delayed FTT reconstructions (mean age 52 years). All delayed patients presented with complications resulting from previous STS treatment. Defects involved the leg (n = 7), knee (n = 2), and thigh (n = 10) and had a mean size of 129 cm2, 154 cm2, and 283 cm2, respectively. Preoperative radiatiotherapy had been administered to 74% of patients in the series (mean dose 53 Gy). FTT success rate was 95% (one failure in the delayed group). Limb salvage and postreconstruction ambulatory rates were both 95%. The overall complication rate was 47%, with the trend of a higher rate (63%) in the delayed group compared with the immediate group (36%). The immediate reconstruction group required no additional operative procedures before FTT and had a shorter hospital stay (13 days) compared with that of the delayed reconstruction group (40.6 days). Mean follow-up was 11.9 months (range 2-30). CONCLUSIONS: FTT is a reliable and versatile adjunctive treatment for lower extremity salvage of patients with STS. Immediate reconstruction appears to carry a lower complication rate and a faster rehabilitation for the patient.

Female↗

PubMed1994

Rationale for elective contralateral mastectomy with immediate bilateral reconstruction.

BACKGROUND: Women with breast cancer treated by mastectomy with immediate breast reconstruction can get exceptionally good results if the reconstruction is performed with autogenous tissue using the transverse rectus abdominis myocutaneous (TRAM) flap. Bilateral reconstruction with TRAM flaps is also possible, but only if both breasts are reconstructed at the same time. To avoid the possibility of subsequently developing contralateral malignancy and having to undergo assymetrical reconstruction with a different technique, some patients have chosen the alternative of bilateral mastectomy with bilateral immediate reconstruction. This is only reasonable if the incidence of failure in bilateral breast reconstruction is very low. METHODS: We prospectively studied reconstructive outcomes in 100 patients who had breast cancer and who underwent bilateral mastectomy and reconstruction (using implants as well as TRAM flaps). We also reviewed the histologic findings in 88 prophylactically removed high-risk breasts. RESULTS: Successful outcomes were initially achieved in 95 patients; of the 5 failures, two were successfully reconstructed with alternative techniques for an overall success rate of 97%. Of the 63 patients reconstructed with bilateral TRAM flaps, all but one (98%) were successful on the first try. TRAM flap reconstructions were significantly more likely to be successful than were those based on implants (p = 0.05). Previously unsuspected invasive cancer was found in 3 patients (3.4%), whereas carcinoma in situ was found in 5 patients (5.7%) and in another 18 patients (20%) cellular atypia was present. CONCLUSIONS: Bilateral breast reconstruction has a low incidence of failure, particularly if TRAM flaps are used. For selected patients, elective contralateral mastectomy with immediate bilateral reconstruction is a reasonable treatment alternative provided that the necessary expertise is available and the patients clearly understand the risks.

Adult↗

PubMed1994

Comparison of charges related to radiotherapy for soft-tissue sarcomas treated by preoperative external-beam irradiation versus interstitial implantation.

BACKGROUND: We compared treatment-related charges associated with external beam irradiation and interstitial implantation for soft-tissue sarcoma of the extremity. METHODS: Charges related to radiotherapy in 35 patients with soft-tissue sarcoma of the extremity were reviewed. Preoperative external beam irradiation (EB) delivering 50 Gy in 25 fractions with 6 MV photons was administered to 12 of the patients evaluated. The remaining 23 patients were treated with interstitial implantation (IR) as the only radiotherapeutic intervention. The anatomic distribution of the sarcomas treated by IR included 14 lower-extremity (LE) and nine upper-extremity (UE) lesions. The average length of iridium wire used for IR was 78 cm. Because LE lesions tend to be larger, the average length equaled 109.5 cm as compared with the 47 cm for UE implants. RESULTS: The radiotherapeutic approach represented the only difference in treatment-related charges because the operative procedure of wide local excision was performed in each group. No difference in perioperative complications was observed between the two treatment approaches. Charges were stratified according to hospital-based and professional services. Radiotherapy-based hospital charges for the administration of EB averaged $6,515 compared with $4,050 for IR (p < 0.0001). Professional services also were significantly different, totaling $4,390 for EB and $3,240 for IR (p < 0.0001). The total of these charges for radiotherapy procedures and professional fees equaled $10,905 for EB compared with $7,290 for IR (p < 0.0001). Incorporating the necessary operating-room time for implant placement ($750) and five additional hospital days ($1,800), the costs associated with IR totaled $9,840; using chi-square analysis, the cost for IR remained significantly (p < 0.0001) less expensive than the $10,905 associated with EB. Because a large component of the radiotherapy cost for IR is related to the length of iridium 192 wire required, charges were stratified according to the location of the tumor. The total charge for IR of the UE equaled $9,345 compared with $10,335 for LE implants. Chi-square comparison for both UE and LE implants continued to show significant differences (p < 0.0001) when related to EB therapy. CONCLUSION: Cost-analysis comparison of brachytherapy versus external beam irradiation found lower charges for patients undergoing adjuvant irradiation with brachytherapy for soft-tissue sarcoma. To optimize the cost-benefit ratio, prospective studies are necessary to define the application of these radiotherapeutic approaches based on clinical criteria.

Arm↗

PubMed1994

Nitric oxide inhibition causes intrauterine growth retardation and hind-limb disruptions in rats.

OBJECTIVE: Our purpose was to determine the effects of nitric oxide synthase inhibition on maternal and fetal health in the last third of pregnancy. STUDY DESIGN: Pregnant rats were treated from gestational day 13 to day 19 or 20 with the nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester, which was administered in the drinking water ad libitum. Control animals received the inactive enantiomer NG-nitro-D-arginine methyl ester or no treatment. Maternal blood pressure, blood chemistry studies, and placenta and pup size were determined. A separate group of rats received nitroprusside sodium in conjunction with NG-nitro-L-arginine methyl ester. RESULTS: NG-nitro-L-arginine methyl ester caused a dose-dependent reduction in placenta and pup size. Amniotic fluid levels of cyclic guanosine monophosphate were significantly reduced at 0.1 mg/ml but not at higher doses. Hemorrhagic necrosis of fetal hind limbs occurred only with treatment with NG-nitro-L-arginine methyl ester and was prevented by coadministration of nitroprusside sodium. Maternal blood pressure and blood and urine chemistry studies were unaffected by NG-nitro-L-arginine methyl ester. CONCLUSION: Chronic reductions of nitric oxide production in the last third of pregnancy result in significant intrauterine growth retardation and hemorrhagic disruptions of hind limbs. Maternal complications were minimal and did not mimic preeclampsia.

Amniotic Fluid↗

PubMed1994

Plasma proteins as early biomarkers of exposure to carcinogenic aromatic amines.

Two-dimensional gel electrophoresis (2DG) has been used to study the changes induced in dog plasma polypeptides by the known urinary bladder carcinogens, 4-aminobiphenyl (4-ABP) and 2-naphthylamine (2-NA). Treatment with 3-aminobiphenyl (3-ABP) and 1-naphthylamine (1-NA), both considered to be non-carcinogenic, were used as controls. The purpose of this study was: (1) to determine whether or not changes that occurred in the plasma protein patterns were specific to 4-ABP and/or other related carcinogenic arylamines; (2) to measure the time course in the changes of the major polypeptides during dosing and their resynthesis during a recovery period; and (3) to determine, by microsequencing, the biochemical identity of the affected proteins. The results indicate that only the most potent carcinogen, 4-ABP, had the effect of suppressing the expression of some proteins, while the other aromatic amines caused no discernible change in the 2DG patterns during a 12-week dosing period. The 4-ABP caused dramatic suppression of two sets of proteins. One set of three spots had an apparent molecular weight of 32.5 kDa, and a pI of 5.8-6.0. The major component in this group was identified as the beta-chain of haptoglobin. Expression of this protein decreased markedly during the first 2 weeks of treatment and recovered slowly after dosing stopped. Since haptoglobin functions to bind with free hemoglobin and facilitates its elimination from the blood stream, these results can be rationalized as a consequence of 4-ABP binding to hemoglobin in the erythrocyte, resulting in cell death and hemolysis. The 4-ABP modified hemoglobin then binds to haptoglobin and this tertiary complex is purged from the blood stream, resulting in the disappearance of free haptoglobin. A second set of spots (mol. wt., 65 kDa; pI, 6.5-6.6) disappeared much faster than the haptoglobin, and recovered more quickly. The major protein is about one-fifth the intensity of haptoglobin and appeared to be N-terminally blocked. Internal microsequencing of four fragments obtained from tryptic cleavage of the major spot of this group showed significant similarity to the serum albumin sequence of several species. This spot group is not the major serum albumin spot, however, since the latter is readily identified as the most abundant spot on the plasma map. During the course of this study, several other polypeptides in the 2DG map of dog plasma were identified and are presented here.

2-Naphthylamine↗

PubMed1994

Hypoglossal and phrenic responses to central respiratory inhibition in piglets.

Neonatal apnea is characterized by decreased neural output to the ventilatory muscles, and frequently associated with upper airway obstruction. We sought to characterize: (1) the role of central chemosensitive structures at the ventral medullary surface (VMS) in modulating hypoglossal and phrenic neural output, and (2) the recovery of hypoglossal and phrenic neural output during simulated central apnea. We studied 14 anesthetized, paralyzed, ventilated piglets aged 14-21 days and performed VMS cooling to inhibit central neural pathways mediating CO2 sensitivity. Phrenic and hypoglossal ENGs and end-tidal CO2 were continuously recorded. During CO2 rebreathing, hypoglossal activity was always more sensitive than phrenic activity to the inhibitory effects of VMS cooling. When phrenic apnea was induced by VMS cooling, and followed by discontinuation of ventilation for 60 sec in order to induce simultaneous hypercapnia and hypoxia, reappearance of hypoglossal ENG was delayed and recovery was significantly suppressed when compared to phrenic ENG. Therefore, attenuated central chemosensitivity during early postnatal life appears to preferentially inhibit neural output responsible for upper airway patency, and may predispose to upper airway obstruction during recovery from neonatal apnea.

Animals↗

PubMed1994

A nurse-managed inpatient program for patients with chronic mental disorders.

The deinstitutionalization movement has left a legacy of need for appropriate care for inpatients with chronic refractory mental illness. This article describes a nurse managed program for such patients based on the principles of a therapeutic milieu. The program was formally defined for a 6-month period with an effort to include outcome measures for program evaluation. Multidisciplinary treatment team planning with a psychiatric nursing clinical specialist as team leader provided a format for putting therapeutic concepts into practice. The nurse clinical specialist and two nurse practitioners served as case managers as well as primary care providers. Program evaluation showed that cost-effective quality care could be achieved with a reduction in polypharmacy and overall neuroleptic usage. The notion of a restraint appropriate environment, with the goal of minimizing restraint use, was introduced and put into practice.

Adult↗

PubMed1994

The use of hypodermoclysis for rehydration in terminally ill cancer patients.

The need to treat dehydration in terminally ill patients to minimize symptom distress remains a controversial issue. Hypodermoclysis (HDC) is a simple technique for rehydration that offers many advantages over the intravenous route. In this prospective open study of 100 consecutive patients who died on a palliative care unit, we recorded our indications for, and use of, HDC. Of the 100 patients, 69 received HDC for an average of 14 +/- 18 days during an average admission of 35 +/- 41 days. The 31 patients who did not receive HDC had an average admission of 22 +/- 24 days, and appeared to have different characteristics than the HDC group. HDC was well tolerated in most patients at an average volume of 1203 +/- 505 mL/day. These results confirm that HDC for dehydration is a safe and effective technique and suggest the need for further research to clarify the role of rehydration in assisting symptom control.

Aged↗

PubMed1994

The radial forearm free flap for head and neck reconstruction: a review.

BACKGROUND: The radial forearm free flap has become a workhorse flap in head and neck reconstruction. Its lack of bulk, ease of dissection, vascularity, and malleability are among its many advantages. PATIENTS AND METHODS: A review of 157 radial forearm free flaps performed in 155 patients between March 1988 and June 1994 at The University of Texas M.D. Anderson Cancer Center was undertaken to determine outcome. Patient age ranged from 22 to 80 years (mean 56). There were 79 men and 76 women. Follow-up ranged from 2 to 75 months. The most prevalent neoplasm was squamous cell carcinoma (n = 129). RESULTS: The most frequent tumor staging was T3, N0, M0. Various defects were observed; however, those requiring floor-of-mouth coverage were most common (n = 95). Partial or segmental mandibular resection was seen in 42. An osseous component was included in the radial forearm flap in 9 patients, and 64 patients had undergone some form of previous tumor resection. Fifty-seven patients received preoperative irradiation and 52, postoperative. The internal jugular vein (n = 131) and the external carotid artery (n = 134) were the most frequent recipient sites for microvascular anastomosis. Vein grafts were needed in 4 cases, and end-to-side anastomoses were most commonly performed. Total flap loss occurred in 7 cases (4.5%) and partial flap loss in 1 (0.6%). For total flap loss, salvage was accomplished by a second radial forearm free flap in 2 cases and alternative rotational flaps in 5. Other complications (infection, hematoma, fistula formation, etc.) were seen in 34%. Donor-site difficulties were seen in 21 cases. CONCLUSION: The radial forearm free flap offers a variety of reconstructive options for the head and neck. Its low flap loss and complication rates offer the best choice for oral lining restoration if bulk is not required.

Adult↗

PubMed1994

Functionalized 3,5-dihydroxybenzoates as potent novel inhibitors of EPSP synthase.

Aromatic analogues of the EPSP synthase enzyme substrate (S3P), reaction intermediate (1), and product (EPSP) were synthesized from 3,5-dihydroxybenzoic acid and were evaluated as inhibitors of E. coli EPSP synthase. These simple, synthetically accessible aromatic analogues are highly effective competitive inhibitors versus S3P with an apparent Ki for the tetrahedral intermediate analogue 4 of 160 +/- 40 nM. This demonstrates that a simple benzene ring is a quite suitable substitute for the complex shikimate ring in the design of EPSP synthase inhibitors.

3-Phosphoshikimate 1-Carboxyvinyltransferase↗

PubMed1994

Use of interposition vein grafts in head and microsurgery.

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Head↗

PubMed1994

Morbidity associated with free-tissue transfer after radiotherapy and chemotherapy in elderly cancer patients.

Because of their ages and associated medical problems, many elderly cancer patients are treated with radiotherapy and/or chemotherapy to avoid the increased morbidity perceived to occur with prolonged surgical procedures such as tumor resection and reconstruction with free tissue transfer (FTT). The failure of such therapy still often requires tumor resection and reconstruction in irradiated tissue, which may add to the morbidity of surgery. To determine the validity of these concerns, 66 elderly cancer patients who underwent tumor resection and FTT after previous radiotherapy and/or chemotherapy (PT) were compared to a similar group of 64 elderly patients who had not received such previous therapy (NPT). Despite the two groups having similar patient traits, reconstructive-site characteristics, types of flaps used, medical risk factors, and time variables, there were no statistically significant differences between groups for FTT failure (PT3 percent, NPT 6 percent), medical complication rate (PT 16 percent, NPT 27 percent), surgical complication rate (PT 41 percent, NPT 49 percent), or wound-healing problems. The perioperative mortality rate was 2 percent. The authors conclude, that when medical problems are appropriately corrected before surgery, FTT may be safely performed in elderly patients with a high degree of success, acceptable morbidity, and low mortality. Previous cancer treatment does not appear to predispose elderly patients to a higher rate of FTT failure or wound-healing problems after FTT reconstruction.

Aged↗

PubMed1994

A quantitative comparison of DNA sequence assembly programs.

We have compared 11 sequence assembly programs for the accuracy and reproducibility with which they assemble DNA fragments into a completed sequence. To test the assemblers under controlled conditions, the rat multidrug resistance (RATMDRM) gene sequence was randomly divided into overlapping 200- to 400-base fragments. Various degrees of error, in the form of miss-identified bases, missed bases, and duplicated bases, were randomly added to these fragments. The probability of an error, and the type of error, was modified using an error distribution template that was developed by comparing the original fragments used to sequence RATMDRM with the final, edited sequence stored in GenBank. From 0 to 15% error was then added to independent sets of fragments, and assemblage was attempted. The quality of the assemblages was evaluated by comparing the number of differences between the assembled sequence and the original sequence. Tests were also done to determine if the order in which fragments were added to a project affected the final sequence and if the quality of assemblage was sequence dependent. Similar results were also obtained using other, unrelated sequences. The programs could be roughly divided into three groups based on the accuracy and reproducibility of assembly. Three (GCG, FAB, and AutoAssembler) consistently produced consensus sequences of low error and high reproducibility. Intermediate results were obtained with five other programs (Sequencher, AssemblyLIGN, XBAP, SeqMan, and AutoAssembler in a mode that made use of an external special processor). Less satisfactory results were obtained with the remaining three programs (GeneWorks, GENeration, and PC/Gene). The ability of the programs to edit the assembled sequence was also compared. Five of the programs were able to display and edit automatic sequencer trace files. The Sequencher program had a particularly well-designed sequence editor that allowed rapid examination and correction of assembly errors.

Animals↗

PubMed1994

Dietary nucleotides: effects on the gastrointestinal system in swine.

Nucleotides in the intestinal lumen may decrease the inflammatory response to ischemia-reperfusion. In a newborn-swine model, we showed that perfusion of the intestinal lumen with nucleotides in concentrations similar to those in human milk induced hyperemia. The levels of hypoxanthine (and xanthine) were not increased in the presence of nucleotides during ischemia-reperfusion, and the number of leukocytes accumulated in the intestine was reduced in the presence of nucleotides. Furthermore, nucleotides may have decreased protein leak and the production of nitric oxide during ischemia. These effects are not changed significantly in the presence of an adenosine antagonist. We interpreted our results to indicate that the protective effects of nucleotides in the intestinal lumen are not due to adenosine alone.

Adenosine↗