PubMed Health⌕ Search

Biomedical subjects

M L Walker

Publications and source records attributed to M L Walker.

At least 19 recordsLinked to original sources
PubMed1992

The history of ventriculoscopy: where do we go from here?

With the availability of better endoscopes, improved lighting and increased instrumentation, the use of ventriculoscopy and ventriculostomy in the management of hydrocephalus is becoming increasingly more common. Neurosurgeons recognized the potential for endoscopic surgery early in this century, but were frustrated in many of their attempts at treatment due to the poor quality of the instruments available. Nevertheless, much progress has been made, and the stage was set for better results with modern instrument design. This paper reviews the history of endoscopes in neurosurgery and ponders the direction these instruments will take us in the near future.

Cerebral Ventricles↗
PubMed1992

On healing.

Explore the source record for details and available documents.

Culture↗
PubMed1992

The operative approach to pancreatic injury.

Major pancreatic trauma is uncommon and often challenging even for the most experienced trauma surgeon. An organized, well-rehearsed operative approach to these injuries represents the surgeon's best defense. This article highlights operative decision-making. Operative assessment is reliable. The integrity of the main pancreatic duct is the major discriminating variable in the management of pancreatic injury. Pancreaticoduodenectomy can be done safely for devitalizing injuries to the head of the pancreas associated with major duodenal and common bile duct injury. For selected cases, distal pancreatectomy with splenic preservation is realistic. The surgeon must have a wide array of procedures from which to select for major complicated pancreatic trauma.

Abdominal Injuries↗
PubMed1991

Trauma-adult respiratory distress syndrome.

Sixteen trauma victims with adult respiratory distress syndrome were retrospectively examined. High injury severity score (mean: 44), massive transfusion requirements, and prolonged ventilator days characterize this group. Persistent intra-abdominal infection accounted for two of three deaths in this series. Most of these patients were managed without paralysis using intermittent mandatory ventilation and positive-end expiratory pressure (PEEP). High frequency jet ventilation was necessary in one subject. Two patients exhibited early ARDS reversal, ie, clinical improvement, better chest x-ray and decreased shunt (within 72 hours) when an intra-abdominal septic focus was eradicated. Principles of critical care for these patients remain: an FiO2 less than .40, limiting barotrauma, using PEEP for alveolar recruitment and close monitoring of O2 transport.

Adolescent↗
PubMed1990

Chronic encephalitis, epilepsy, and cerebrovascular immune complex deposits.

Refractory epilepsy, electroencephalographic abnormalities, progressive hemiplegia, and contralateral hemicerebral atrophy developed in a previously healthy 3-year, 9-month-old girl. Extensive laboratory testing showed elevated serum antinuclear antibody titers, cerebrospinal fluid oligoclonal bands, and elevated immunoglobulin G (IgG): albumin ratio, IgG index, and IgG synthesis rate. Pathological study of a subtotal hemispherectomy specimen revealed widespread cerebral vasculitis with immunofluorescence staining for IgG, IgM, IgA, C3, and Clq, and ultrastructural evidence of vascular injury in addition to severe cortical atrophy with marked neuronal loss. Cerebrospinal fluid abnormalities in other reported patients suggest that immunological abnormalities may not be unique to this girl. These data suggest possible immunopathogenetic mechanisms in these patients.

Antibodies, Antinuclear↗
PubMed1990

Intrauterine growing skull fracture.

Growing skull fractures with development of leptomeningeal cysts are rare complications of head injuries and have not been described in the perinatal period. The case history of a newborn with bilateral parietal fractures and the formation of a leptomeningeal cyst on one side detected at birth is presented. The importance of radiographic evaluation, including skull films, computered tomography, and magnetic resonance imaging, as well as the associated subarachnoid cyst and the age of presentation are discussed.

Arachnoid Cysts↗
PubMed1990

Relationship between performance of selected scapular muscles and scapular abduction in standing subjects.

The purpose of this study was to examine the relationship between muscular forces generated by the middle trapezius and pectoralis minor muscles and the position of the scapula in relaxed standing. The muscular forces of 60 subjects were measured in standard manual muscle testing positions with a hand-held dynamometer. Scapular abduction in standing was measured with a tape measure. Each measurement was taken twice, and the measurements were shown to be reliable. The correlation between scapular abduction and middle trapezius muscle force was .20. The correlation between scapular abduction and pectoralis minor muscle force was .14. The correlation between scapular abduction and a ratio of middle trapezius muscle force to pectoralis minor muscle force was .01. The results indicate that no relationship exists between the position of the scapula in standing subjects and the muscular force produced by the middle trapezius and pectoralis minor muscles. Clinical practices based on an assumed relationship between these variables (eg, the practice of using middle trapezius muscle strengthening exercises to correct a forward shoulder position) should be reexamined in light of these findings.

Adult↗
PubMed1990

Modulation of adrenocorticotropin-stimulated baboon fetal adrenal dehydroepiandrosterone formation in vitro by estrogen at mid- and late gestation.

We have reported that ACTH stimulation of dehydroepiandrosterone (DHA) formation by the baboon fetal adrenal at midgestation was suppressed by estrogen. Because fetal adrenal regulation changes with advancing gestation, the action of estrogen on fetal adrenal steroidogenesis may also be dependent on the degree of fetal adrenal maturation. We examined this possibility in the present study by determining the effects of ACTH and estrogen on DHA formation by adrenal cells of fetuses obtained from baboons at mid- and late gestation and from animals administered the antiestrogen MER-25 throughout late gestation. Because low density lipoprotein (LDL) provides substrate for the fetal adrenal, we also determined whether the effect of estrogen was mediated by LDL uptake. Adrenals were removed from baboon fetuses on day 100 (midgestation; n = 7) and day 170 (late gestation; n = 6; term, day 184) of gestation from untreated animals and on day 170 from fetuses whose mothers were treated with MER-25 on days 140-170 (25 mg/kg BW.day; n = 7). Cells were dispersed with 0.2% collagenase and incubated at 37 C for 3 h in 4 ml medium 199 with 10 nM ACTH, 10(-6) M estradiol and/or 500 micrograms LDL. The secretion of DHA into medium was determined by RIA. At midgestation, mean (+/- SE) basal DHA formation (nanograms per 10(5) cells/3 h) was 5.8 +/- 2.1, and DHA was increased (P less than 0.01) by ACTH to 20.0 +/- 5.9. Although estradiol alone had no effect, estradiol prevented the increase in DHA obtained with ACTH. Basal DHA production by adrenals of late gestation (0.7 +/- 0.3 ng/10(5) cells) was lower (P less than 0.01) than at midgestation. ACTH increased (P less than 0.01) DHA in a comparable manner near term in the presence (2.0 +/- 0.4) or absence (1.7 +/- 0.4) of estradiol. Thus, in contrast to day 100, estrogen did not attenuate the action of ACTH on adrenal cells on day 170. In fetal adrenal cells obtained on day 170 from MER-25-treated baboons, DHA formation (1.4 +/- 0.6 ng/10(5) cells) was comparably increased (P less than 0.05) to 2.4 +/- 0.2 and 3.0 +/- 0.5 ng/10(5) cells by ACTH in the absence or presence of estradiol. Thus, ACTH remained effective in enhancing DHA by adrenal cells of fetuses exposed in utero to antiestrogen. DHA formation by adrenals of midgestation was increased (P less than 0.05) to 15.4 +/- 4.8 and 27.4 +/- 7.5 ng/10(5) cells, respectively, by LDL and ACTH plus LDL.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenal Glands↗
PubMed1990

Principles of management of shotgun wounds.

As an instrument of close range combat, the shotgun has no parallel. At short distances, its destructive capacity parallels that seen from high velocity missile injury. In this study, the history of the shotgun, wound ballistics, principles of initial therapy and special management problems related to shotgun wounds of specific sites are reviewed. An analysis of pooled data on abdominal shotgun wounds is presented. A subset of patients who do not require abdominal exploration exists. Specific problems encountered in defining this subset are enumerated. Three algorithms are presented that summarize our current management approach to shotgun wounds of the torso and extremities.

Abdominal Injuries↗
PubMed1989

Light scattering and photocrosslinking in the calf lens crystallins gamma-II, III and IV.

The calf lens proteins gamma-II, -III and -IV crystallin have been photolyzed in pH 7.5 phosphate buffer solution at 25 degrees C. The photolysis light source was either a xenon arc lamp/monochromator system set to pass 290 +/- 5 nm or a nitrogen laser operating at 337.1 nm. Photolysis experiments at 337.1 nm were done both in the presence and absence of added 1.0 x 10(-4) M N-formylkynurenine (NFK). In addition, 1 x 10(-5) M riboflavin was added as a photosensitizer in a few of the experiments. All solutions were 1.0 mg ml-1 protein, and 1.0 ml of solution was irradiated for periods ranging from 10 min to 3 hr. During the 337.1 nm irradiations, the turbidity of the protein solutions was continuously monitored using a He-Ne laser at 632.8 nm. Progress of the 290 nm irradiations was monitored by observing the loss of tryptophan fluorescence for each of the gamma crystallin proteins. The rate of growth of light scattering, upon 337.1 nm irradiation, was greatest for gamma-IV. Addition of NFK caused the rates of growth of UV-induced light scattering of all three gamma crystallins to increase significantly. These rates were in the order: gamma-IV much greater than gamma-III greater than gamma-II. Following UV exposure, the protein solutions were analyzed using UV-visible absorption spectroscopy and SDS-PAGE. Irradiated gamma crystallin solutions showed increased optical density throughout the visible region, resulting from solution turbidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

UV laser photodamage to whole lenses.

Lenses from rat or calf were exposed in vitro to UV radiation from a nitrogen laser operated at 337.1 nm or from an excimer laser operated at 3.8 nm. Visible light transmission was monitored during calf lens irradiations at 308 nm and found to decrease. Proteins were extracted from the irradiated rat or calf lenses, separated into water soluble and insoluble fractions, and analysed using SDS-PAGE. Comparison of these gels with dark controls showed that, following photolysis, there was loss of polypeptide material in the 20-30 kDa region and concomitant formation of polymers at 40 and 60 kDa, and at greater than 100 kDa in calf lens (308 nm irradiation) and rat lenses (337.1 nm irradiation) in vitro. In addition, there was evidence for formation of lower molecular weight polypeptides at 10 kDa in the protein from irradiated rat lenses. The rat SDS-PAGE gels were challenged against anti-calf gamma crystallin serum. There was clear evidence that the polymeric material, in the water insoluble protein fraction from the 337.1 nm photolyzed rat lenses was derived in part from gamma crystallin. The macromolecular changes detected in these photolyzed rat and calf lens proteins were similar to those previously reported to accompany aging in the human lens. Biochemical changes of the type observed in UV irradiated rat and calf lenses may be responsible for the loss of visible light transmission seen in calf lenses.

Animals↗
PubMed1989

Intrasession and intersession reliability of hand-held dynamometer measurements taken on brain-damaged patients.

Recent reports have characterized force measurements obtained with hand-held dynamometers from brain-damaged patients as being highly reliable. The purposes of this two-part study were to replicate essential parts of those studies and to further examine the reliability of these measurements in a clinical context. Repeated force measurements were taken from the nonparetic and paretic limbs of brain-damaged patients during the same testing session (Part 1) and during two testing sessions separated by two days (Part 2). The intratester intraclass correlation coefficients (ICCs) for all measurements taken during a single session ranged from .88 to .98. The ICCs for repeated measurements taken two days apart from the paretic limbs ranged from .90 to .98. The ICCs for repeated measurements taken two days apart from the nonparetic limbs ranged from .31 to .93. The ICCs for repeated measurements taken two days apart from the combined data for all limbs ranged from .79 to .97. Hand-held dynamometer measurements taken on brain-damaged patients appear to be highly reliable when taken during the same testing session. When repeated measurements are separated by a longer time interval, the measurements taken from the paretic limbs continue to be highly reliable, whereas most measurements taken on the nonparetic limbs exhibit poor reliability.

Adult↗
PubMed1989

Stereotactic surgery in children.

Stereotactic biopsy has been popularized over the last decade since the advent of newer, more sophisticated instrumentation and technology. However, less than 300 cases of pediatric stereotaxy are recorded in the literature and few reports emphasize the necessary modifications required in children. Sixty-six stereotaxic procedures were performed on 62 children using the Brown-Roberts-Well (BRW) apparatus at our institutions. The mean age was 9.0 years (range 5 months to 18 years). The indication for the technique was diagnostic in 36 cases and therapeutic in 9 cases; location was a factor in 21 children with the lesion involving a 'deficit-prone' area of the brain. The BRW technique was applicable in 61 procedures (93%). Inability to enter cysts or biopsy of necrotic tissue and tumor capsule occurred in 5 cases. One patient had a transient increase in cerebral edema, for an overall complication rate of 2%. It appears that the BRW stereotactic technique is equally effective in children and adults and will no doubt play an ever increasing role in the future of pediatric neurosurgery.

Adolescent↗
PubMed1989

Management of posthemorrhagic hydrocephalus in the low-birth-weight preterm neonate.

Over a period of 34 months from 1987 to 1990 we inserted ventricular catheter reservoirs (VCR) into 20 premature low-birth-weight infants who had developed progressive, symptomatic posthemorrhagic hydrocephalus following grade III or IV intraventricular hemorrhages. The mean estimated gestational age was 27.7 +/- 5.3 weeks and mean birth weight was 1,041 +/- 699 g. The ventricular catheter reservoirs were placed on day of life 30.7 +/- 29.7 and tapped for a total of 3-34 days at varying frequencies and for varying volumes. Of the 20 patients, 4 died on days of life 25, 76, 88, and 187. There were two reservoir infections, both occurring in infants who eventually died. The 16 survivors have been followed from 2 to 24 months (adjusted age). Four (25%) remain shunt-free and 3 have undergone VCR removal. There have been two shunt infections in the 12 shunted patients; ten shunt revisions have been performed overall. At the time of last follow-up, 14 patients were old enough to undergo neurodevelopmental evaluation. Five patients (36%) were 'normal' on gross neurological screening examination, 5 (36%) had 'mild developmental delay' and 4 (28%) had 'significant developmental delay'. We feel these data support the continued use of ventricular catheter reservoirs in the management of posthemorrhagic hydrocephalus and offer hope that some of these patients might remain shunt-free and most will have a normal or mildly delayed neurodevelopmental outcome.

Brain Damage, Chronic↗
PubMed1988

Dietary influences on growth and sexual maturation in premenarchial rhesus monkeys.

The effect of a high-fat diet on growth, sexual maturation, and developmental changes in serum levels of estradiol (E2), growth hormone (GH), somatomedin-C (Sm-C), and insulin were examined in outdoor-housed premenarchial rhesus monkeys. From 16 to 32 months of age, females were fed either a high-fat diet (HFD, N = 5) with 31% calories from fat or a control diet (commercial laboratory chow, N = 10) with 12% of the calories from fat. Maintenance on a HFD did not accelerate physical growth, as all animals exhibited similar increments in body weight, crown-rump length, and weight/height ratios. In contrast, the HFD group exhibited an earlier onset of perineal swelling and menarche despite lower body weights during that time. Moreover, 80% of the HFD animals exhibited an early first ovulation (31-32 months of age) compared with 40% of control animals. These reproductive changes were associated with significant differences in the endocrine profiles of HFD animals. Fasting serum levels of insulin were significantly elevated within 2 months of diet treatment and remained elevated throughout the study period. Levels of Sm-C were elevated relative to those of controls after 3 months of diet treatment, but not thereafter. Serum GH increased after 6 months on the HFD and, overall, concentrations were higher in HFD animals. A significant rise in E2 was observed after only 45 days on the HFD treatment. These concentrations did not differ from 18 to 21 months of age but again were elevated at 27 months in the HFD females. Since these endocrine and physical changes associated with reproductive physiology occurred in the absence of enhanced growth, these data suggest that a high-fat diet may influence the rate of sexual maturation through changes in certain metabolic factors which may act on the developing neuroendocrine system.

Animals↗