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Biomedical subjects

R Miller

Publications and source records attributed to R Miller.

At least 919 records · Page 51Linked to original sources
PubMedDate not supplied

Short TE proton MRS and neurofibromatosis type 1 intracranial lesions.

PURPOSE: The intracranial lesions of neurofibromatosis type 1(NF-1) have variable pathology and growth based on molecular genetics. Because of this variable pathology and growth, the lesions are followed by sequential MRI. Our hypothesis was that MR spectroscopy (MRS) could provide a noninvasive neurochemical biopsy of NF-1 lesions, thereby distinguishing the different lesions, monitoring their variable growth, and having added value when compared with MRI. METHOD: Nineteen patients fulfilling the National Institutes of Health criteria for NF-1 were followed with sequential MRI and short TE proton MRS. MRI monitored the lesions by observing the area of prolonged T2, mass effect, and degree of enhancement. MRS monitored the lesions by following the level of neurons, cellularity, and a by-product of the inositol signaling pathway. A comparison was made between the MRI and MRS findings to determine if MRS provided added value. Sixty-nine spectra were obtained in 24 resions. RESULTS: MRI was able to identify hamartomas, gliomas, and indeterminate lesions. MRS was able to distinguish three distinct spectra when compared with the cellularity of normal deep white matter (DWM): a hamartoma spectrum with a choline/creatine (CHO/CRE) ratio below 1.5, a transitional spectrum with a CHO/CRE ratio above 1.5 and below 2.0, and a glioma spectrum with a CHO/CRE ratio above 2.0. On comparing MRS and MRI, MRS provided added value by identifying changes in cellularity while MR images were stable, identifying spectra that could distinguish hamartomas from gliomas, and identifying a transitional spectrum that could progress or regress into glioma or hamartoma spectrum. CONCLUSION: MRS was able to identify three distinct spectra in NF-1 lesions when compared with the cellularity of normal DWM, thereby providing a neurochemical means to characterize lesions.

Adolescent↗
PubMedDate not supplied

Extreme elevation of maternal serum alpha-fetoprotein associated with mosaic trisomy 8 in a liveborn.

Constitutional mosaic trisomy 8 has been associated with syndromic dysmorphology, corneal opacities, leukemias, and trophoblastic disease. However, abnormal maternal serum alpha-fetoprotein (MSAFP) has not been reported in association with mosaic trisomy 8. Our case first presented for evaluation of an extremely elevated MSAFP with mild elevation of MShCG in an otherwise normal pregnancy: MSAFP 13.89 MoM, MShCG 3.57 MoM, and MSuE3 1.04 MoM. Fetal dysmorphism was limited to bilateral pyelectasis and a prominent third ventricle. Spontaneous labor at 38 weeks resulted in the birth of a 3,570-gram AGA male with APGARs 7(1)/8(5). The neonate had facial asymmetry, 5th finger clinodactyly, 2-3 toe syndactyly, undescended testicle, abnormal prepuce, and mild pyelectasis. CT scan revealed hypoplasia of the corpus callosum, while echocardiography demonstrated bicuspid aortic valve, and the neonatal karyotype (blood) returned 46,XY/47,XY+8. Evaluation at 3 months revealed more prominent facial asymmetry, plagiocephaly, plantar creases, descent of the testis, and mild developmental delay. Review of the literature does not include any previously reported maternal serum alpha-fetoprotein aberrations in mosaic trisomy 8.

Adult↗
PubMedDate not supplied

Adjunctive measures for successful laryngotracheal reconstruction.

The field of reconstructive surgery of the laryngotracheal complex has been the object of considerable enthusiasm in recent years. New surgical techniques, better surgical tools, and improved diagnostic skills all have contributed to a more confident approach to severe laryngotracheal stenosis. Just as the surgeon's judgment is crucial for a successful primary laryngotracheal reconstruction, so are his or her skill and judgment vitally important in managing the various problems that frequently are found following reconstructive surgery of the larynx and trachea. These problems, although seemingly minor, may prevent successful decannulation if not managed appropriately. This paper discusses the various problems that have been encountered while achieving decannulation following laryngotracheal reconstruction. An approach to such frustrating problems as suprastomal collapse, granulation tissue, and the inability to decannulate are presented.

Catheterization↗
PubMedDate not supplied

Medial collateral ligament knee sprains in college football. Brace wear preferences and injury risk.

In this prospective, multiinstitutional analysis of medial collateral ligament sprains in college football players, we categorized 987 previously uninjured study subjects according to frequency of wearing preventive knee braces, studied the patterns by which 47 of 100 injuries occurred to unbraced knees, and identified several extrinsic, sport-specific risk factors shared for both braced and unbraced knees. The attendance, brace wear choice, position, string, and session of each participant were recorded daily; medial collateral ligament sprains were reported whenever tissue damage was confirmed. Both the likelihood of wearing braces and risk of injury without them was highly dependent on session (games/practices), position group (line, linebacker/tight end, skill), and string group (players/nonplayers). Subjects wearing braces often faced a high injury risk to their unbraced knees, a finding compatible with the opinion that braces were a necessary evil, best worn when concern over danger of injury outweighed desire for speed and agility. It is concluded that to avoid misinterpretations due to the confounding influence of brace wear selection bias, accurate investigation of daily brace wear patterns is required. Then, before considing the impact of preventive knee braces, a repartitioning of the data base is essential to assure that only similar groups will be compared.

Athletic Injuries↗
PubMedDate not supplied

Medial collateral ligament knee sprains in college football. Effectiveness of preventive braces.

This is the second of 2 articles on a 3-year investigation of medial collateral ligament sprains of the knee to assess the effectiveness of prophylactic knee braces in NCAA Division I college football players. Position, string, type of session, and daily brace wear were recorded. The injury rates for braced and unbraced knees were used to create an incidence density ratio. The data were stratified and simultaneously controlled for position, string, and session and evaluated for their statistical significance. The 987 Big Ten players generated 155,772 knee exposures over the study period (50% braced). Noticeable differences existed in the rates of injury for the braced and unbraced knees in almost every position during practices, depending on player or nonplayer status. When the influential factors of position, string, and session are considered, there is a consistent but not statistically significant tendency for the players wearing preventive knee braces to experience a lower injury rate than for their unbraced counterparts. For starters and substitutes in the line positions, as well as the linebackers and tight ends, there was a consistent trend toward a lower injury rate in both practices and games. The braced players in the skill positions (backs/kickers), at least during games, exhibited a higher injury rate.

Athletic Injuries↗
PubMedDate not supplied

Increasing workload of an HIV/AIDS counselling service in a London teaching hospital, 1990-91.

The number of new patients referred to the HIV/AIDS Counselling Unit at the Royal Free Hospital, London, increased from 926 in 1989-90 to 1450 in 1990-91. Follow-up contacts nearly doubled during the same period of time. Growing demand for HIV testing as well as the shift to the treatment of HIV as a chronic condition increased the workload of the HIV/AIDS counsellors.

AIDS Serodiagnosis↗
PubMedDate not supplied

Studies on the placental transfer of cell-free human immunodeficiency virus and p24 antigen in an ex vivo human placental model.

OBJECTIVE: We studied whether the human placenta has the structural integrity to impede transplacental passage of cell-free human immunodeficiency virus (HIV)-1 or p24 antigen from the maternal to the fetal circulation. METHODS: Nine term human placentas from uncomplicated vaginal or cesarean section deliveries were studied ex vivo with a placental perfusion apparatus to determine whether cell-free HIV-1 at 200-2000 tissue culture infectious dose (TCID50/mL) would pass to the fetal circulation. Passage of virus or p24 was assessed by infectivity titration and/or p24 antigen capture enzyme immunoassay. RESULTS: Infectious HIV-1 was not detected in any of the fetal perfusate samples taken periodically during experiments. Low concentrations of HIV-1 p24 antigen, however, were detected in fetal perfusate samples from three placentas. CONCLUSIONS: The term human placenta effectively impedes passage of cell-free HIV-1 from the maternal to the fetal circulation. However, it may be permeable to passage of p24 antigen.

Cell-Free System↗
PubMedDate not supplied

The effect of repeated doses of succinylcholine on serum potsssium in patients with renal failure.

The effect of 1 mg/kg of succinylcholine IV in repeated doses on serum potassium (K+) was studied in 11 patients with renal failure. Increases in K+ did not differ from those seen in patients with normal kidney function, the largest increase being 0.6 mEq/L. The authors conclude that succinylcholine administered repeatedly at this dosage is not contraindicated in patients with renal failure.

Adolescent↗
PubMedDate not supplied

Maintenance of body temperature by heated humidification.

Though difficult to prove conclusively, humidification of anesthetic gases during prolonged surgery appears beneficial. Even slight falls in body temperature are detrimental, causing significant increases in O2 consumption in the immediate postoperative period. A new heated humidifier which supplies gases at 100% relative humidity at 35 degrees C at the patient inlet has been used both to supply humidity and to prevent a fall in interoperative temperature. This was successfully employed in 19/25 prolonged procedures. The warmed humidified gases contributed significantly to the maintenance of homeostasis during anesthesia.

Adolescent↗
PubMedDate not supplied

Enumeration of waterborne Escherichia coli with petrifilm plates: comparison to standard methods.

Escherichia coli is often monitored in environmental waters as an indicator of the possible presence of human pathogens associated with feces. Petrifilm E. coli/coliform count plates (3M, Minneapolis, MN), previously validated for enumerating E. coli in food, were tested for monitoring E. coli in environmental water. Escherichia coli counts in environmental water samples enumerated with Petrifilm were significantly correlated (R > 0.9; slope = 0.9-1.0; p < 0.001) with counts obtained with three commonly used methods, mTEC (Becton Dickinson, Sparks, MD), m-ColiBlue (Hach, Loveland, CO), and Colilert-18/IDEXX Quanti-Tray 2000 (IDEXX, Westbrook, ME). Blue colonies on Petrifilm plates were most reliably identified as E. coli when accompanied by gas formation, as determined by characterization of the colonies on MacConkey agar plates (PML Microbiologicals, Mississauga, ON, Canada) and by polymerase chair reaction (PCR) with E. coli-specific primers. The main disadvantage of Petrifilm plates for environmental water testing is the small volume (1 mL per sample) that can be tested; however, the plates appear to be suitable for screening and locating sites that exceed criteria for total body and partial body contact. Simplicity of use and storage, reliability, and relatively low cost make Petrifilm plates suitable for volunteer-based and educational water quality monitoring applications, particularly when used as a preliminary screening method to identify problem sites.

DNA, Bacterial↗
PubMedDate not supplied

Cytotoxic effect of 1,3 bis (2-chloroethyl)-N-nitrosourea at elevated temperatures: Arrhenius plot analysis and tumour response.

The effect of hyperthermia on the cytotoxicity of 1,3-bis-(2-chloroethyl)-N-nitrosourea (BCNU) was investigated in vitro and in vivo. Tumour cells were early-generation isotransplants of a spontaneous C3Hf/Sed mouse fibrosarcoma, FSa-II. For in vitro studies, single cell suspensions containing 1.0 x 10(6) cells/ml were treated in a water bath where a desired temperature was maintained by a constant-temperature circulator. Cell survival was determined by lung colony assay immediately thereafter. For in vivo studies the tumour cell suspensions were transplanted into the dorsal site of the C3Hf/Sed mouse foot. Tumours were treated by immersing animal feet into a constant-temperature water bath when tumours reached an average diameter of 4 mm (35 mm3). The tumour growth (TG) time or the time for one-half of the treated tumours to reach 1000 mm3 from initial treatment day was used as an endpoint. BCNU dose-cell survival curve at 37 degrees C was exponential with a D0 of 1.1 microgram/ml. Dose-cell survival curves at 37-43 degrees C were determined as a function of treatment time at pH 6.7 and 7.4. BCNU of 1 microgram/ml was added immediately before treatment. The slope of the survival curve became steeper with increasing temperature, indicating that the cytotoxic effect of BCNU was enhanced by hyperthermia. The Arrhenius plot analysis showed that activation energies at pH 6.7 and 7.4 were 53 and 51 kcal/M, respectively (no significant difference). Of interest in this analysis was that the Arrhenius plot did not show a breaking point which has been observed for other agents. Further investigation demonstrated that the decomposition of BCNU, which has been reported to be essential for production of reactive intermediates, occurred in aqueous medium at elevated temperatures. The magnitude of this decomposition depended on treatment temperature. As a result, preheated BCNU became less cytotoxic with an increase in preheating temperatures. The activation energy for this decomposition was about one-half of the activation energy for BCNU cytotoxicity. Studies in vivo indicated that the effect of BCNU was enhanced with increasing temperatures, and the enhancement was greatest when BCNU was administered i.p. immediately before hyperthermia. A glucose dose of 5 g/kg administered i.p. 60 min before hyperthermia further enhanced the antitumour effect of BCNU.

Animals↗
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New techniques for the treatment and disruption of renal calculi.

Kidney stones are a major cause of morbidity and affect 3 to 4% of Western Europeans. Two new techniques have been developed in the last five years which reduce the morbidity, hospital stay and convalescent period of patients compared with those undergoing conventional renal surgery. These methods, percutaneous nephrolithotomy and extracorporeal stone disintegration, are examined with particular reference to the equipment necessary for stone disintegration. There is little doubt that these techniques will supersede conventional surgical procedures in the near future.

Humans↗