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Biomedical subjects

A R Mayer

Publications and source records attributed to A R Mayer.

At least 19 recordsLinked to original sources
PubMed2001

Somatotopic organization of the medial wall of the cerebral hemispheres: a 3 Tesla fMRI study.

Somatotopic organization of the human medial wall of the cerebral hemispheres was studied using functional MRI conducted at high field strength (3 T) with fine spatial resolution ( approximately 2 mm). Healthy subjects performed paced, repetitive movements of the fingers and toes. Within the supplementary motor area (SMA), two regions were identified: finger movements activated a region rostral and superior to that for toe movements. Two activation foci were also identified in the cingulate motor area: toe movements activated a region rostral and ventral to that activated by finger movements. All foci were located between the anterior and posterior commissures. Our results confirm previous human and non-human primate studies regarding the rostral-caudal organization of the SMA and CMA. The dorsal-ventral organization of the CMA, however, appears to be divergent from results derived from cortical stimulation studies conducted in non-human primates.

Adult↗
PubMed2001

Can medial temporal lobe regions distinguish true from false? An event-related functional MRI study of veridical and illusory recognition memory.

To investigate the types of memory traces recovered by the medial temporal lobe (MTL), neural activity during veridical and illusory recognition was measured with the use of functional MRI (fMRI). Twelve healthy young adults watched a videotape segment in which two speakers alternatively presented lists of associated words, and then the subjects performed a recognition test including words presented in the study lists (True items), new words closely related to studied words (False items), and new unrelated words (New items). The main finding was a dissociation between two MTL regions: whereas the hippocampus was similarly activated for True and False items, suggesting the recovery of semantic information, the parahippocampal gyrus was more activated for True than for False items, suggesting the recovery of perceptual information. The study also yielded a dissociation between two prefrontal cortex (PFC) regions: whereas bilateral dorsolateral PFC was more activated for True and False items than for New items, possibly reflecting monitoring of retrieved information, left ventrolateral PFC was more activated for New than for True and False items, possibly reflecting semantic processing. Precuneus and lateral parietal regions were more activated for True and False than for New items. Orbitofrontal cortex and cerebellar regions were more activated for False than for True items. In conclusion, the results suggest that activity in anterior MTL regions does not distinguish True from False, whereas activity in posterior MTL regions does.

Behavior↗
PubMed2001

Paclitaxel, an active agent in nonsquamous carcinomas of the uterine cervix: a Gynecologic Oncology Group Study.

PURPOSE: A phase II trial of paclitaxel was initiated in advanced nonsquamous carcinoma of the cervix to determine its activity in patients who had failed standard chemotherapy. PATIENTS AND METHODS: Eligible patients had at least one measurable lesion. The starting dose of paclitaxel was 170 mg/m(2) (135 mg/m(2) for patients with prior pelvic radiation) given as a 24-hour continuous intravenous infusion with courses repeated every 3 weeks. Dose escalation to 200 mg/m(2) and de-escalation to 110 mg/m(2) were allowed based on adverse effects. RESULTS: In this trial, 42 assessable patients were initially entered onto the study, and 13 responses were seen; four patients had a complete response, and nine patients had a partial response. The overall response rate was 31%. The primary and dose-limiting toxicity was neutropenia. CONCLUSION: The response rate to paclitaxel exceeds the rates reported using other single agents in nonsquamous carcinoma of the cervix.

Adult↗
PubMed2001

The evolution of brain activation during temporal processing.

Timing is crucial to many aspects of human performance. To better understand its neural underpinnings, we used event-related fMRI to examine the time course of activation associated with different components of a time perception task. We distinguished systems associated with encoding time intervals from those related to comparing intervals and implementing a response. Activation in the basal ganglia occurred early, and was uniquely associated with encoding time intervals, whereas cerebellar activation unfolded late, suggesting an involvement in processes other than explicit timing. Early cortical activation associated with encoding of time intervals was observed in the right inferior parietal cortex and bilateral premotor cortex, implicating these systems in attention and temporary maintenance of intervals. Late activation in the right dorsolateral prefrontal cortex emerged during comparison of time intervals. Our results illustrate a dynamic network of cortical-subcortical activation associated with different components of temporal information processing.

Adult↗
PubMed2000

Neural systems underlying the recognition of familiar and newly learned faces.

Memory for famous faces can be used to examine the neural systems underlying retrieval from long-term memory. To date, there have been a limited number of functional neuroimaging investigations examining famous face recognition. In this study, we compared recognition of famous faces to recognition of newly learned faces. Whole-brain, event-related functional magnetic resonance imaging was used to image regional changes in neural activity in 11 subjects during the encoding of unfamiliar faces and during familiarity judgments for: (1) newly learned faces, (2) unfamiliar face distractors, and (3) famous faces. Image analyses were restricted to correct recognition trials. Recognition accuracy and response time to famous and recently learned faces were equivalent. Recognition of famous faces was associated with a widespread network of bilateral brain activations involving the prefrontal, lateral temporal, and mesial temporal (hippocampal and parahippocampal regions) regions compared to recognition of recently encoded faces or unfamiliar faces seen for the first time. Findings are discussed in relation to current proposals concerning the neural regions thought to participate in long-term memory retrieval and, more specifically, in relation to retrieval of information from the person identity semantic system.

Adult↗
PubMed2000

Specialized neural systems underlying representations of sequential movements.

The ease by which movements are combined into skilled actions depends on many factors, including the complexity of movement sequences. Complexity can be defined by the surface structure of a sequence, including motoric properties such as the types of effectors, and by the abstract or sequence-specific structure, which is apparent in the relations amongst movements, such as repetitions. It is not known whether different neural systems support the cognitive and the sensorimotor processes underlying different structural properties of sequential actions. We investigated this question using whole-brain functional magnetic resonance imaging (fMRI) in healthy adults as they performed sequences of five key presses involving up to three fingers. The structure of sequences was defined by two factors that independently lengthen the time to plan sequences before movement: the number of different fingers (1-3; surface structure) and the number of finger transitions (0-4; sequence-specific structure). The results showed that systems involved in visual processing (extrastriate cortex) and the preparation of sensory aspects of movement (rostral inferior parietal and ventral premotor cortex (PMv)) correlated with both properties of sequence structure. The number of different fingers positively correlated with activation intensity in the cerebellum and superior parietal cortex (anterior), systems associated with sensorimotor, and kinematic representations of movement, respectively. The number of finger transitions correlated with activation in systems previously associated with sequence-specific processing, including the inferior parietal and the dorsal premotor cortex (PMd), and in interconnecting superior temporal-middle frontal gyrus networks. Different patterns of activation in the left and right inferior parietal cortex were associated with different sequences, consistent with the speculation that sequences are encoded using different mnemonics, depending on the sequence-specific structure. In contrast, PMd activation correlated positively with increases in the number of transitions, consistent with the role of this area in the retrieval or preparation of abstract action plans. These findings suggest that the surface and the sequence-specific structure of sequential movements can be distinguished by distinct distributed systems that support their underlying mental operations.

Adolescent↗
PubMed2000

Neural mechanisms of visual attention: object-based selection of a region in space.

Objects play an important role in guiding spatial attention through a cluttered visual environment. We used event-related functional magnetic resonance imaging (ER-fMRI) to measure brain activity during cued discrimination tasks requiring subjects to orient attention either to a region bounded by an object (object-based spatial attention) or to an unbounded region of space (location-based spatial attention) in anticipation of an upcoming target. Comparison between the two tasks revealed greater activation when attention selected a region bounded by an object. This activation was strongly lateralized to the left hemisphere and formed a widely distributed network including (a) attentional structures in parietal and temporal cortex and thalamus, (b) ventral-stream object processing structures in occipital, inferior-temporal, and parahippocampal cortex, and (c) control structures in medial- and dorsolateral-prefrontal cortex. These results suggest that object-based spatial selection is achieved by imposing additional constraints over and above those processes already operating to achieve selection of an unbounded region. In addition, ER-fMRI methodology allowed a comparison of validly versus invalidly cued trials, thereby delineating brain structures involved in the reorientation of attention after its initial deployment proved incorrect. All areas of activation that differentiated between these two trial types resulted from greater activity during the invalid trials. This outcome suggests that all brain areas involved in attentional orienting and task performance in response to valid cues are also involved on invalid trials. During invalid trials, additional brain regions are recruited when a perceiver recovers from invalid cueing and reorients attention to a target appearing at an uncued location. Activated brain areas specific to attentional reorientation were strongly right-lateralized and included posterior temporal and inferior parietal regions previously implicated in visual attention processes, as well as prefrontal regions that likely subserve control processes, particularly related to inhibition of inappropriate responding.

Adult↗
PubMed2000

Handedness and psychopathy.

OBJECTIVES: The current study investigated whether psychopathic persons exhibit a pattern of motor dominance that differs from the left-hemisphere dominance that characterizes the majority of the population. BACKGROUND: Research with cognitive tasks suggests that psychopathy may be associated with an atypical pattern of cerebral organization characterized by either left-hemisphere dysfunction or decreased hemispheric asymmetry. However, studies that evaluate motor dominance in psychopathy have provided mixed results. METHOD: The handedness of 420 adult male inmates at a county jail was assessed using a scale developed by Chapman and Chapman as part of their participation in ongoing research. RESULTS: Psychopaths reported reduced right-hand dominance, which cannot be accounted for by differences in age, intelligence, or race. CONCLUSIONS: Psychopathy is associated with an increased proportion of mixed-handedness relative to that seen in nonpsychopathic persons. This finding is consistent with theory and research suggesting anomalous cerebral asymmetry in psychopathic offenders.

Adolescent↗
PubMed1999

Chemical analysis of adnexal cyst fluid.

OBJECTIVE: The purpose of the study was to determine if adnexal cyst fluid glucose, protein, and lactate dehydrogenase (LDH) levels can discriminate between cancerous and noncancerous adnexal masses. METHODS: Intracystic fluid was aspirated from adnexal masses immediately after operative excision. Patient age and menopausal status, mass size, and cyst fluid specific gravity were recorded. Cyst fluid and intraoperative serum glucose, protein, and LDH levels were measured. Masses were grouped by histopathologic diagnosis. Cyst fluid chemical levels and cyst fluid/serum ratios were compared among and between the groups. RESULTS: Fifty-eight adnexal masses were analyzed: 15 nonneoplastic (group 1), 23 benign neoplastic (group 2), and 20 malignant (group 3). There were no significant differences among the groups with regard to patient age, menopausal status, or cyst fluid specific gravity. Cyst size (cm2) was significantly different among the three groups (P < 0.01), with the largest mean size found in the cancer group. No significant differences in cyst chemistries or cyst fluid/serum ratios were found between groups 1 and 2. Comparing groups 1 and 3, all values were significantly different (P < 0.05), with the greatest level of significance attained by comparison of cyst fluid LDH levels (P < 0.001). Groups 2 and 3 statistically differed in cyst fluid levels and cyst fluid/serum ratios of both protein and LDH, with the highest levels of significance achieved by comparisons of cyst fluid levels and ratios of LDH (P = 0.001 and P < 0.001, respectively). The cyst fluid LDH level was found to be the best single chemistry for distinguishing noncancerous (groups 1 and 2) from cancerous (group 3) adnexal masses. A cyst fluid LDH level of >/=451 U/L imparted a 90% sensitivity and 71% specificity for detecting malignancy. CONCLUSIONS: Evaluation of adnexal cyst fluid LDH may help to distinguish benign from malignant adnexal masses. More cases are needed to adequately assess the predictive value and clinical utility of this approach.

Adnexal Diseases↗
PubMed1998

Prolonged oral etoposide as second-line therapy for platinum-resistant and platinum-sensitive ovarian carcinoma: a Gynecologic Oncology Group study.

PURPOSE: A phase II trial was conducted to determine the activity of prolonged oral etoposide in platinum-resistant and platinum-sensitive ovarian carcinoma. PATIENTS AND METHODS: Platinum-resistant disease was defined as progression on platinum-based chemotherapy or recurrence within 6 months of completing therapy. The starting dose was 50 mg/m2/d (30 mg/m2/d for prior radiotherapy) for 21 days, every 28 days. A dose escalation to a maximum dose of 60 mg/m2/d was prescribed. RESULTS: Of 99 patients entered, 97 were assessable for toxicity and 82 were assessable for response. Among 41 platinum-resistant patients a 26.8% response rate (7.3% complete response [CR] and 19.5% partial response [PR] rate) occurred. The median response duration was 4.3 months (range, 1.3 to 8.7), median progression-free interval (PFI) was 5.7 months (range, 0.8 to 30.8+), and median survival time was 10.8 months (range, 1.9 to 45.8). Twenty-five of 41 platinum-resistant patients had also previously received paclitaxel; of which eight (32%) responded. Among 41 platinum-sensitive patients, a 34.1% response rate (14.6% CR and 19.5% PR rate) occurred. The median response duration was 7.5 months (range, 1.9 to 15.2+), median PFI was 6.3+ months (range, 0.9 to 20.4), and median survival time was 16.5+ months (range, 0.9 to 34.8). Of 97 patients assessable for toxicity, grade 3 or 4 hematologic toxicity was common, with leukopenia occurring in 41.2% (grade 3, 29%; grade 4, 12%), neutropenia in 45.4% (grade 3, 20%; grade 4, 25%), thrombocytopenia in 9% (grade 3, 5%; grade 4, 4%), and anemia in 13.4%. Three treatment-related deaths occurred: two from neutropenic sepsis and one from thrombocytopenic bleeding after an overdose. One patient developed leukemia. CONCLUSION: This regimen is active in platinum-resistant and platinum-sensitive ovarian carcinoma. Additionally, the regimen is active in paclitaxel-resistant ovarian carcinoma.

Adenocarcinoma↗
PubMed1997

Alpha-1 acid glycoprotein is an immunosuppressive factor found in ascites from ovaria carcinoma.

BACKGROUND: Although the ascites of patients with ovarian carcinoma has been reported to contain immunosuppressive factors, the identity and source of this activity has not been fully elucidated. The objective of this study was to describe the purification of a single immunosuppressive protein, alpha-1 acid glycoprotein, from ovarian carcinoma ascites, identify its site of production, and describe a possible mechanism by which it inhibits lymphocytes. METHODS: Ascites from proteins from five patients with epithelial ovarian carcinoma first were differentially precipitated by size with different concentrations of polyethylene glycol and then separated on the basis of isoelectric focusing. The protein factions then were placed in a lymphocyte proliferation assay to determine immunosuppressive activity. Western blot analysis was used to identify alpha-1 acid glycoprotein as an immunosuppressive protein in ascites. Total RNA was extracted from ovarian and hepatic cell lines as well as primary and recurrent ovarian tumor samples. Reverse-transcriptase polymerase chain reaction then was utilized to identify the site of production of this protein. Purified alpha-1 acid glycoprotein was placed in lymphocyte culture and its effects on lymphocyte interleukin-2 (IL-2) production were measured by enzyme-linked immunoadsorbent assay. RESULTS: Addition of purified alpha-1 acid glycoprotein to the lymphocyte assay resulted in a 60% decrease in lymphocyte proliferation (P < 0.05). Alpha-1 acid glycoprotein transcript was not identified in ovarian tumor cells. The addition of purified alpha-1 acid glycoprotein to the lymphocyte culture resulted in a 65% decrease in IL-2 secretion into the media (P < 0.05). CONCLUSIONS: Alpha-1 acid glycoprotein is an immunosuppressive protein purified from ovarian carcinoma ascites. It is not expressed primarily by ovarian carcinoma cells. It appears to inhibit IL-2 secretion by lymphocytes.

Ascites↗
PubMed1997

Chemoprophylaxis with ciprofloxacin in ovarian cancer patients receiving paclitaxel: a randomized trial.

The objective of this study was to evaluate the efficacy of oral ciprofloxacin in preventing febrile morbidity superimposed on the neutropenia induced from a paclitaxel regimen in ovarian cancer patients. Eligible patients received paclitaxel at doses of 135 to 175 mg/m2 alone or in combination with a platinum agent. They were randomized to either an observation (control) group or a ciprofloxacin prophylaxis group. Patients in the ciprofloxacin group received 500 mg ciprofloxacin orally twice a day once the absolute neutrophil count (ANC) was less than 500/mm3 and continued until the ANC was greater than 1000/mm3. Ninety patients were enrolled between the control (n = 45) and ciprofloxacin (n = 45) groups. They received 371 cycles of a paclitaxel-based regimen with 177 and 194 cycles in the control and ciprofloxacin groups, respectively. Ciprofloxacin prophylaxis was prescribed for 138 (71%) of the cycles in the ciprofloxacin group and was given for a mean duration of 7.7 days per cycle. The groups were similar in disease status and risk factors for neutropenia. Fifteen patients in the control group developed febrile neutropenia versus 12 of those in the ciprofloxacin group (P = 0.69). The mean ANC and mean length of hospital stay for neutropenic fever were also similar between groups. There was a greater frequency of an ANC < 100 associated with those prophylaxed with ciprofloxacin (P = 0.01). Only 44% of the febrile episodes were associated with a positive culture. Staphylococcus aureus was the most frequently reported organism isolated. Considering these results, it does not appear that febrile neutropenia is reduced by ciprofloxacin during grade IV neutropenia.

Administration, Oral↗
PubMed1995

Accuracy and intraobserver variability of simulated cervical dilatation measurements.

OBJECTIVE: Our purpose was to assess the accuracy and intraobserver variability of clinical cervical diameter measurements among obstetric health care providers. STUDY DESIGN: Polyvinyl chloride pipes 1 to 10 cm in diameter were mounted in cardboard boxes and used to simulate cervical examinations. The boxes were designed so that the examiner had to rely solely on proprioception to determine the inner diameter. RESULTS: A total of 1574 simulated cervical diameter measurements were obtained from 102 different examiners in a two-part study. The overall accuracy for determining the exact diameter was 56.3%, which improved to 89.5% when an error of +/- 1 cm was allowed. Intraobserver variability for a given diameter measurement was 52.1%, which decreased to 10.5% when an error of +/- 1 cm was allowed. CONCLUSIONS: Cervical diameter measurements obtained by digital examination are precise when an error of +/- 1 cm is allowed for. Intraobserver variability is > 50% and is an important consideration when evaluating dysfunctional labor.

Cervix Uteri↗
PubMed1994

Experience with the intravenous totally implanted port in patients with gynecologic malignancies.

The purpose of this paper was to assess the intraoperative and long-term complications associated with intravenous totally implanted devices in women with pelvic cancers. Retrospective review of medical records was performed for 67 consecutive women with pelvic cancers who underwent port insertion. Seventy catheters were successfully placed in 67 patients. Pneumothorax occurred in three cases (4.3%), none requiring chest tube placement. Malposition of the catheter occurred in four patients (5.7%). Two infected ports (2.9%) were removed after a failed trial of antibiotics. Venous thrombosis developed in one woman, requiring removal of the system. In conclusion, semipermanent central venous catheters facilitate delivery of chemotherapy, parenteral nutrition, blood products, antibiotics, and hydration in cancer patients. This is the first report detailing the experience with a totally implanted subcutaneous port in patients with gynecologic malignancies. We demonstrate that such devices may be inserted and utilized with a low incidence of complications in this patient population.

Adolescent↗
PubMed1994

Cervical cone margins as a predictor for residual dysplasia in post-cone hysterectomy specimens.

OBJECTIVE: To determine the relation between dysplasia at cervical cone margins and the presence or absence of residual dysplasia in post-cone hysterectomy specimens. METHODS: We performed a 6-year retrospective, multicenter study and reviewed 250 cases in which the patient had a cold-knife cervical cone biopsy followed by a hysterectomy within 6 months. Pathology reports from 23 institutions described the margins in conization specimens and the subsequent status of residual dysplasia in the hysterectomy specimens. RESULTS: There was a statistically significant difference in the prevalence of residual dysplasia in hysterectomy specimens between patients with positive margins on cone biopsy (47%) and those with negative margins (23%) (P < .01). The positive predictive value for residual dysplasia given positive cone margins was 47%, and the negative predictive value was 77%. The grade of post-cone residual dysplasia increased commensurately with the grade of dysplasia in the conization specimen. CONCLUSIONS: The presence of dysplasia at the cervical cone margin relates significantly with the presence of residual dysplasia in the post-cone hysterectomy specimen. The grade of residual dysplasia in the post-cone hysterectomy specimen increased as the grade of dysplasia in the conization specimen increased. Free margins on a cone biopsy specimen with dysplasia offer reassurance that invasive cancer is not present in the remaining uterus.

Analysis of Variance↗
PubMed1992

Ovarian cancer staging: does it require a gynecologic oncologist?

Forty-seven patients with presumed Stages I-II invasive ovarian epithelial carcinoma were treated with intravenous 50 mg/m2 cis-platinum, for 2-18 cycles (median, 9), 50 mg/m2 doxorubicin for 2-14 cycles (median, 9), and/or 600 mg/m2 cyclophosphamide for 2-14 cycles (median, 6) after surgical staging by a gynecologic oncologist or a nononcologic surgeon. Mean follow-up is 6.8 years. Cumulative 5-year actuarial survival is 73 +/- 6%; 75 +/- 12% for Stage I and 71 +/- 8% for Stage II disease. When screened for poor prognosticators, only the specialty of the operating surgeon was identified (P < 0.05). Five-year actuarial survival and disease-free survival, respectively, for Stages I-II patients surgically staged by a gynecologic oncologist were 83 +/- 7% and 76 +/- 8%, compared to 59 +/- 11% (P < 0.05) and 39 +/- 11% (P < 0.03) for the group operated upon by a nononcologist.

Actuarial Analysis↗
PubMed1991

Vulvar reconstruction using a pedicle flap based on the superficial external pudendal artery.

We present a new method for vulvar reconstruction based on recently described vasculature of the lower abdominal skin and subcutaneous tissue. The superficial external pudendal artery supplies the region encompassing the suprapubic and infraumbilical skin. Thus, a pedicled skin flap based on the superficial external pudendal artery is designed in the suprapubic area and rotated into place for vulvar reconstruction. Because of the thickness and pliability of the flap as well as the inconspicuous donor scar, we believe this method of reconstruction to be superior to skin grafts or bulkier (ie, musculo- and fasciocutaneous) tissue flaps.

Adult↗