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Biomedical subjects

R M Hansen

Publications and source records attributed to R M Hansen.

At least 37 records · Page 2Linked to original sources
PubMed1994

Scotopic center surround organization in 10-week-old infants.

The large critical areas for complete spatial summation in infants may be due to immaturities of receptive field organization in both dark and light adapted scotopic conditions. Scotopic lateral excitatory/inhibitory interactions have been previously studied in adults using Westheimer's [(1965) Journal of Physiology, London, 181, 881-894] paradigm. We modified this paradigm to investigate scotopic receptive field organization in infants. Detection thresholds for probe flashes of constant diameter and duration presented on steady backgrounds of various diameters were determined for 10-week-old infants and adults. Infants' thresholds increased up to background diameters of 3 degrees to 3.5 degrees and then decreased at greater background diameters. Adults' thresholds increased for backgrounds up to about 0.75 degrees diameter and then decreased at greater background diameters. These results suggest that the excitatory, central receptive field size is larger in infants than adults, and that a balanced center-surround mechanism is operative.

Adult↗
PubMed1994

Scotopic optokinetic nystagmus thresholds in 10-week-old infants.

PURPOSE: To compare psychophysical and reflexive optokinetic nystagmus (OKN) estimates of dark-adapted scotopic thresholds mediated by the posterior retina in 10-week-old infants and adults. METHODS: A staircase procedure was used to determine the stimulus intensity needed to produce an OKN response to a moving 19 degrees x 19 degrees grating. In the same subjects, a two-alternative, forced-choice procedure was used to obtain thresholds for detecting 10 degrees diameter, 50 ms duration stimuli. RESULTS: Both OKN and psychophysical thresholds of infants are 0.9 log unit higher than those of adults. CONCLUSION: The infant-adult difference in thresholds mediated by retina at the posterior pole is greater than the infant-adult difference in thresholds for full-field stimuli. It is possible that delayed maturation of the posterior retina is the primary determinant of infants' high OKN and psychophysical thresholds.

Adolescent↗
PubMed1993

[Ambulatory labor--experience from the first 2 years].

A trial arrangement for mandatory early discharge for all normal multiparae in 1990 and 1991 was evaluated. 63.4 percent of 1661 multiparous women were discharged within 24 hours of giving birth. During the period the mean time to discharge rose from 6 1/2 to 10 1/2 hours. Only 2.6 per cent of the children were readmitted to hospital, as were 1.2 percent of the mothers. The purpose of the trial was to save money, but in the trial period no money was saved from the early discharged women, the savings came from deductions in the perinatal service to the non-early discharged women.

Adult↗
PubMed1993

[Long-term prognosis for women with chronic pelvic pain without laparoscopically demonstrable cause].

With the object of assessing the long-term prognosis and the frequencies of recurrence and remission in women chronic low abdominal pain without laparoscopically visible cause, questionnaire were sent in 1985 and 1991 to 55 women who had been submitted to laparoscopy in 1982-1984 for this reason. These women had been told that there was no demonstrable explanation of the pain experienced and were then discharged. 65% and 55% respectively had experienced and unfavourable course with considerable and continued symptoms. Only 22% stated in both investigations that they had experienced a favourable course and that they were, by and large, free from pain. 36% changed from an unfavourable to a favourable course or the reverse. The assessment made by the women was confirmed by a series of subordinate questions and this demonstrated a marked difference between the favourable and unfavourable courses of the condition. It is concluded that laparoscopy with exclusion of significant pathology is not, in itself, satisfactory as treatment of this patient group and that no improvement occurs in the course of time. The condition varies greatly with many recurrences and remissions and, for this reason, uncontrolled reports of the therapeutic effects are of no significance. When compared with the literature, it is suggested that this patient group should be referred early in the course of the condition to a therapist with specialist psychological/sexological insight and/or to a physiotherapist with interest in this patient group.

Abdominal Pain↗
PubMed1993

Natural course of visual functions in the Bardet-Biedl syndrome.

OBJECTIVE: To determine the course of visual functions in patients with Bardet-Biedl syndrome. PATIENTS AND METHODS: The 21 patients with Bardet-Biedl syndrome seen at Children's Hospital, Boston, Mass, had optotype and grating acuities and dark-adapted thresholds measured over time. Their ages at first visit ranged from 2 weeks to 23 years (median age, 6 years). The courses of the visual functions were analyzed with a random-effects model. RESULTS: Substantial declines in visual functions were found. On average, grating and optotype acuities declined 0.09 log units (roughly 1 line) per year, and thresholds increased about 0.19 log units per year. The rates at which these visual functions were lost and the predicted level of the visual functions at ages 11 to 12 years (the mean ages of measurement) varied among individuals. CONCLUSIONS: The visual prognosis for children with Bardet-Biedl syndrome is poor. The course of both central and peripheral visual functions is variable.

Adolescent↗
PubMed1993

A phase I trial of protracted 5-fluorouracil infusion and oral calcium leucovorin.

This phase I study of 36 patients was performed to identify the maximal tolerated dose of oral calcium leucovorin (CLV) that could be concomitantly administered with protracted 5-fluorouracil (5-FU) infusion (greater than 30 days). Administration of CLV in very small doses (5 mg p.o. q8h) with 5-FU, 200-300 mg/m2/day, resulted in excessive toxicity requiring treatment interruption in all patients. Subsequent reduction in the dose of 5-FU to 100 mg/m2/day with simultaneous administration of CLV, 5 mg p.o. q8h, decreased the toxicity and allowed for protracted administration of the combination. In subsequent patients the dose of oral CLV was increased to 22.5 mg p.o. q8h, which resulted in treatment-limiting toxicity in the majority of patients. Toxicity consisted almost exclusively of mucositis. No myelosuppression or significant organ toxicity was observed. We conclude that even low doses of oral CLV potentiate the biological effect of infusion 5-FU. If the combination is to be given on a protracted basis, 5-FU must be administered at a much smaller dosage than has been traditionally utilized.

Aged↗
PubMed1992

The effect of light adaptation on scotopic spatial summation in 10-week-old infants.

Psychophysical area-intensity functions of individual 10-week-old human infants and adults were obtained in the dark adapted state, and in the presence of a steady background that elevated threshold 1 log unit above the dark adapted level. For dark adapted infants, the mean diameter for complete spatial summation (4.42 degrees; SD: 1.67 degrees) was significantly larger than that of adults (2.32 degrees; SD: 0.09 degrees). The background reduced the mean critical diameter to 2.67 degrees for infants (SD: 0.64 degrees) and to 1.16 degrees for adults (SD: 0.08 degrees). Spatial probability summation has similar effects on infant and adult thresholds, and, therefore, does not appear to account for the developmental decrease in critical diameters. Rather, decreases in receptive field size are suspected.

Adaptation, Ocular↗
PubMed1992

Effects of halothane on children's electroretinograms.

BACKGROUND: At times, anesthesia is necessary to test children's electroretinographic (ERG) responses. Halothane, an anesthetic commonly used for pediatric patients, affects some aspects of ERG responses, but it is unknown if halothane affects ERG parameters evaluated by contemporary clinical protocols. METHODS: Scotopic and photopic ERG responses were recorded from children when awake and then under halothane. RESULTS: Halothane has no effect on scotopic b-wave stimulus/response parameters, including amplitude, sensitivity, and implicit time. Scotopic a-wave amplitudes, implicit times, model parameters, and ratio of a- to b-wave amplitudes are unaffected by halothane. The amplitudes and implicit times of photopic responses to red flashes and 30 Hz flickering white light are not altered by halothane. Halothane causes no significant change in amplitudes and implicit times of the oscillatory potential wavelets. CONCLUSION: These results suggest that significant departures of ERG responses (studied with the protocol described herein) from a laboratory's normal values cannot be attributed to halothane.

Adolescent↗
PubMed1992

Imaging of regional spread of breast cancer by internal mammary lymphoscintigraphy, CT, and MRI.

Forty women with breast cancer underwent imaging by internal mammary lymphoscintigraphy (IMLS), which was correlated with the results of CT and MRI of the chest. IMLS was performed and interpreted using the previously described methods of Ege. It identified 22 instances of ipsilateral internal mammary nodal involvement, none of which corresponded to cases of abnormally enlarged (diameter greater than 1.0 cm) internal mammary nodes on CT and/or MRI. Positive IMLS was associated with axillary nodal metastases in 15 out of 22 instances. The authors conclude that IMLS provides information on regional nodal spread of breast cancer that is not available with either CT/MRI imaging or axillary biopsy.

Antimony↗
PubMed1992

Periocular lymphoproliferative diseases: natural history, prognostic factors, and treatment.

A study was undertaken to assess the natural history of periocular lymphoproliferative diseases, identify key prognostic factors, and clarify the role of orbital irradiation. Thirty-four patients with periocular lymphoproliferative disease were treated with orbital irradiation between 1975 and 1990. Eight patients had atypical lymphoid infiltrate, and 26 had malignant lymphoma. Forty-three eyes were irradiated with en-face electrons or 6-MV photons. Five-year disease-free survival for all stages was 65%; it was not significantly affected by bilaterality or site. Stage, distinction between atypical lymphoid infiltrate and malignant lymphoma, and working formulation grade were important prognostic indicators. A complete response during irradiation was achieved in 24 of 43 (56%) eyes at a median dose of 2,400 cGy, and a partial response was achieved in 19 (44%), with resolution at a median of 2.8 months. Patients with periocular reactive lymphoid hyperplasia or atypical lymphoid infiltrate may have or are at significant risk of developing lymphoma and dissemination. Local treatment remains important; orbital irradiation achieves prompt local control with acceptable morbidity.

Adult↗
PubMed1992

The rod sensitivity of dark adapted human infants.

The determinants of infants' low scotopic visual sensitivity are controversial. Some interpret infants' scotopic vision as indicative of immature rod photoreceptor function while others attribute infantile sensitivities mainly to post receptoral immaturities. To date the rod photoreceptor sensitivity of human infants has not actually been measured. In the work reported herein, electroretinographic a-wave responses, which represent the rod photoresponse, were recorded from dark adapted 10-week old infants and adult control subjects. Rod isolated a-waves indicate that 10-week-old infants' rods are less sensitive than adults'. Thus, any explanation of infants' scotopic visual sensitivity must take into account this fundamental property of infants' rods, low sensitivity.

Adult↗
PubMed1992

Current status of interferons in the treatment of cancer.

Interferons produced by recombinant DNA technology began phase I trials little more than a decade ago. Today interferon alfa-2 is a mainstay in the treatment of hairy cell leukemia, and has demonstrated benefit in the more common chronic myelogenous leukemia. Interferon alfa-2 also has activity in other hematologic malignancies, including indolent non-Hodgkin's lymphomas, cutaneous T-cell lymphomas, T-cell lymphoma, and multiple myeloma, and in solid tumors such as disseminated melanoma, renal cell carcinoma, Kaposi's sarcoma, endocrine pancreatic tumors, and malignant carcinoid tumors. Interferon alfa, beta, and gamma remain under investigation to define potential roles in ovarian, breast, bladder, and cervical carcinomas and gliomas. The greatest value of the interferons will be in prolonging the disease-free interval when used in combination with other treatment modalities, including surgery, radiation, chemotherapy, and other biologic agents.

Combined Modality Therapy↗
PubMed1991

Twice-daily tapering dexamethasone treatment during cranial radiation for newly diagnosed brain metastases.

Twenty evaluable patients with newly diagnosed brain metastases underwent treatment with a novel dose/schedule of dexamethasone aimed at reducing steroid toxicity during palliative radiation therapy. All patients received twice daily dexamethasone starting at 8 mg bid for four days then 4 mg bid for four days then 2 mg bid until the last day of radiation therapy. The radiation prescriptions were not standardized varying from 2000 cGy/5 fractions to 5800 cGy/29 fractions. Fourteen patients received dexamethasone for a minimum of 24 hours before their first radiation treatment and 7 (50%) experienced improvement in neurologic symptoms/signs prior to starting radiation treatments. Fourteen patients completed the planned course of radiation and dexamethasone. Only 1 patient needed to restart dexamethasone within 30 days of finishing radiation because of steroid reversible neurologic deficits. Steroid toxicity was mild including hyperglycemia (1), candida esophagitis (1), steroid pseudorheumatism (2), peripheral edema (1) and steroid withdrawal syndrome (1). Only two toxic events were recorded in patients receiving steroids less than 21 days. Twice daily dexamethasone appears to provide good clinical results with minimal morbidity.

Administration, Oral↗
PubMed1991

Skeletal size and bone mineral content in Turner's syndrome: relation to karyotype, estrogen treatment, physical fitness, and bone turnover.

Bone mineral content (BMC), bone mineral density, and metacarpal dimensions were studied in 50 women with Turner's syndrome aged 21-45 years in relation to karyotype, estrogen treatment, physical fitness, and biochemical markers of bone turnover. No differences were found between the 25 women with karyotype 45.X and women with other karyotypes. Forty-six women had received estrogen. Significant partial correlations were found between bone mineral density of the forearm and duration of estrogen treatment and physical fitness. BMC of the lumbar spine corrected for vertebral height (BMC(C)spine) was directly correlated with duration of estrogen treatment and height, marginally correlated with physical fitness, and inversely correlated with age. Outer metacarpal width was positively correlated with duration of estrogen treatment, age at initiation of therapy, and body weight. The diameter of medullary space showed negative correlation with physical fitness and height, and positive correlation with age at initiation of estrogen treatment. Cortical thickness was positively correlated with duration of estrogen treatment, physical fitness, and height. No convincing effects of estrogen could be demonstrated in women below the age of 30. Above the age of 30, all bone mineral measurements were markedly elevated in women treated for longer than the average of this age group. BMC(C)spine was inversely correlated with biochemical markers of bone formation. Our results demonstrate that estrogen treatment and physical fitness are important determinants of bone mineral status in Turner's syndrome and add to the evidence that estrogen treatment increases BMC in Turner's syndrome.

Adult↗
PubMed1991

Dark adapted thresholds in young RCS rats.

The dark adapted thresholds of black-eyed RCS rats and cogenic controls were measured using a new psychophysical procedure that permits determination of thresholds at earlier ages than previously possible. Rats were tested longitudinally between about ages 1 and 3 months. At all ages, thresholds of RCS rats were higher than those of controls. Thresholds did not change systematically with age for either RCS rats or controls. At age 3 months, when the RCS rats' b-wave is no longer recordable, RCS thresholds are about 2.2 log units higher than those of controls.

Aging↗
PubMed1991

Temporal summation in dark-adapted 10-week old infants.

The effect of stimulus duration on the b-wave and psychophysical responses of dark-adapted 10-week-old infants and adult control subjects is reported. Both infant and adult b-wave sensitivities vary with stimulus duration, show summation for brief duration stimuli, critical durations estimated at 88-155 msec, and little variation in sensitivity for longer durations. There are however, substantial differences between the infant and adult psychophysical temporal summation functions. The infant function is described by a straight line, slope about -0.5, across all flash durations while adults show summation at durations less than 100 msec and critical durations of 136 to 151 msec. Adult, but not infant, b-wave integration times and b-wave rise and fall times show duration-dependent changes. Thus, both ERG and psychophysical measures demonstrate immaturities in the rod mediated function of the infant retina.

Adult↗
PubMed1991

Electroretinographic assessment of background adaptation in 10-week-old human infants.

Full field, scotopic b-wave stimulus/response functions of 10-week-old infants and adults were measured in the dark-adapted condition, and in the presence of steady backgrounds. Dark adapted b-wave sensitivity (log sigma) differed significantly between infants and adults; the median dark adapted sensitivity of infants was 0.50 log unit less than that of adults. The median eigengraus of infants (-1.32 log scot. td) and adults (-1.55 log scot. td) did not differ significantly. The median slope of the linear portion of the background adaptation function was about 0.9 for infants and adults. These results argue for post-receptoral immaturities, but do not rule out receptoral immaturities.

Adaptation, Ocular↗