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Biomedical subjects

A Peters

Publications and source records attributed to A Peters.

At least 397 records · Page 22Linked to original sources
PubMedDate not supplied

[Validation of the North American Spine Society Instrument for assessment of health status in patients with chronic backache].

BACKGROUND: Pain and functional limitations are the chief symptoms in patients with back pain. However, standardized assessment of these domains are still not commonplace in clinical practice. The objective of this study was the cultural adaptation and validation of the North American Spine Society (NASS) Lumbar Spine Outcome Assessment Instrument for German speaking patients with back pain. METHODS: Translation and backtranslation of the NASS instrument was performed according to international recommendations. 56 consecutive inpatients with a confirmed diagnosis of dorsopathia completed a German version of the NASS instrument, the SF-36 and an established German instrument for back patients (FFbH-R). All patients completed the questionnaires 48 hours apart to assess test-retest reliability. Validity was assessed through correlation with corresponding subscales of the SF-36, the FFbH-R and a 0-10 pain numeric rating scale. Internal consistency and item-to-scale correlation served as statistics of reliability. RESULTS: The two subscales of the NASS Instrument for cervical and lumbar problems correlate significantly with the corresponding subscales of the FFbH-R and the SF-36 (r = 0.28-0.83, p < 0.05) and 0.39-0.68 (p < 0.05) with a pain numeric rating scale. Test-retest reliability demonstrated intraclass correlation coefficients between 0.82 to 0.89. CONCLUSION: The German version of the NASS Cervical and Lumbar Spine Outcome Assessment Instrument allows the standardized assessment of pain, functional limitations and neurogenic symptoms in patients with back pain and the international comparison of health states and therapeutic outcomes.

Activities of Daily Living↗
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["Lumbar intervertebral disk-induced sciatica" diagnostic error in extensive extra- and intrapelvic lipoma].

PURPOSE: The aim of this study is to demonstrate the importance of the differential diagnosis of sciatica. Radiculopathy in the lower extremity of an adult usually originates from a herniated nucleus pulposus. In this paper an extraspinal cause of sciatica due to a pelvic tumor is reported, which is initially often not recognized. METHODS AND RESULTS: A 67-year old woman suffered from sciatica. After one year of unsuccessful conservative treatment and beginning weakness of hip flexion a computed tomography of the pelvis revealed a giant lipoma with compression of the lumbosacral plexus. CONCLUSIONS: The results of this case illustrate the problem of over-rating CT-findings of the lumbar intervertebral disks in patients with sciatica. Extraspinal tumorous causes of radiculopathy are rare, but should be considered if the therapeutical measures are resistant to treatment. Computed tomography and magnetic resonance imaging are most useful in confirming a retroperitoneal tumor causing lumbosacral radiculopathy.

Adult↗
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Blinding laser weapons.

At its October 1995 Review Conference, the Convention on Conventional Weapons added a protocol banning the use and transfer of blinding laser weapons. The background to, and significance and limitations of this ban are discussed.

Blindness↗
PubMedDate not supplied

Layer IVA of rhesus monkey primary visual cortex.

Layer IVA of rhesus monkey striate cortex contains pyramidal cells arranged in distinct groups. Their cell bodies are in a configuration of flat cones, each with an average diameter of 60 microns, and their apical dendrites aggregate into bundles that ascend toward the pial surface. Nissl-stained sections suggest that these pyramidal cell cones have their bases in layer IVB, with their tops extending into layer IVA. The neurons in the cones are readily apparent in MAP2 antibody-stained material, and in cytochrome oxidase-reacted tissue it is evident that the pyramidal cell cones occupy the pale spaces that are surrounded by the darkly reactive honeycomb lattice. This lattice of neuropil around the cones contains some axons and boutons that are immunoreactive for parvalbumin, and it is within the lattice that other investigators have shown afferents from the parvocellular (P)-layers of the dLGN to terminate. Because of this input, it is likely that the pyramidal cell cones of layer IVA are involved with color and form perception. The relationship between the layer IVA cones of neurons and the underlying system of previously described pyramidal cell modules (Peters and Sethares, 1991) is discussed, as well as the possibility that the pyramidal cell cones might represent aggregations of neurons, which receive input from basic sets of P-like afferents originating from color-responsive ganglion cells of the retina, as described by Schein and de Monasterio (1987).

Animals↗
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Neuronal organization in area 17 of cat visual cortex.

An antibody to microtubule-associated protein 2 (MAP2) has been used to examine the arrangements of neurons in striate cortex of the cat. It is found that the apical dendrites of medium-sized and large pyramidal cells in layer V group together to form clusters that have a center-to-center spacing of about 56 microns. As these clusters ascend, the apical dendrites of pyramidal cells in layer II/III are added to them. The thinner apical dendrites of the smaller pyramidal cells in layer VIa also form groups that are referred to as bundles. These bundles ascend into layer IV independent of the clusters, and their arrangement suggests that the bundles are formed so that the apical dendrites of the layer VIa pyramids can pass between the groups of cell bodies of the layer V neurons. It is proposed that the clusters formed from the apical dendrites of the layer V and layer II/III pyramidal cells represent the axes of vertical modules of pyramidal cells, which represent the basic neuronal aggregates within area 17 of cat visual cortex. And it is suggested that these modules can be recruited in various combinations, most obviously by the excitation provided by the thalamic inputs, to form the functional columns, such as the ones that are concerned with eye preference and orientation. Based upon the distribution of the dendritic clusters, the pyramidal cell modules would have diameters of 56 microns, and since they are considered to extend through the depth of the cortex, each one would contain some 203 neurons. The striate cortex of one hemisphere contains 160,000 of these modules, which is about the same as the number of X-cells projecting to one hemisphere from the dorsal lateral geniculate nucleus and twice the number of X- or beta-ganglion cells in the retina. The form of the pyramidal cell modules in cat striate cortex is compared to those present in monkey striate cortex, in which the similar modules are about 10 times more numerous, but only 31 microns in diameter (Peters and Sethares, 1991a).

Animals↗
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Numerical relationships between geniculocortical afferents and pyramidal cell modules in cat primary visual cortex.

An analysis has been made of the quantitative data available on the number of pyramidal cell modules of layer IV neurons, and of geniculocortical axons and their synapses in cat striate cortex. It is found that the convergence of geniculocortical afferents upon any one pyramidal cell module is enormous, since in any one location there is overlap between 360-540 X-axons and 300-540 Y-axons. In total, the X- and Y-axonal arbors provide some 1640 x 10(6) synapses to area 17, which is equivalent to a ratio of 160-200 synapses per layer IV neuron. These values assume that geniculocortical terminals synapse only with the spiny stellate cells of layer IV. The values are reduced to 100-125 per spiny stellate cell when account is taken of the synapses that involve the dendrites that enter layer IV from neurons with cell bodies in other layers. Since each layer IV neuron receives some 2500 asymmetric synapses, this means that only 5% of the total excitatory input to a layer IV neuron seems to be provided by the geniculocortical afferents. Further, if the boutons in the geniculocortical axonal arbors are distributed homogeneously across layer IV, each axon could only provide one synapse to about one in four of the layer IV neurons encompassed by its plexus. It may be, however, that instead of being spread evenly, boutons in individual arbors converge upon individual neurons to supply a number of synapses to them. But even so, it seems unlikely that any individual geniculate axon could dominate the activity of a particular cortical neuron.

Animals↗
PubMedDate not supplied

A numerical analysis of the geniculocortical input to striate cortex in the monkey.

Using data that are available in various publications, a quantitative analysis has been made of the geniculocortical input to layer IVC of the macaque striate cortex. The data suggest that only 1.3-1.9% of the excitatory, or asymmetric synapses in layer IVC alpha of striate cortex are provided by the neurons of the magnocellular layers of the LGN. This amounts to only 18-40 of the 1000-2100 asymmetric synapses that the average layer IVC alpha neuron receives. The parvicellular afferents to layer IVC beta, on the other hand, provide 3.7-8.7% of the asymmetric synapses formed by the average layer IVC beta neuron, or 37-191 synapses to each neuron. If it is assumed that the boutons in the geniculocortical axonal plexuses are evenly spread, it can be calculated that the input to an individual layer IVC neuron is provided by some 24 axonal plexuses. This is regardless of whether the neuron lies in layer IVC alpha or in IVC beta. This calculation suggests that a single axonal plexus provides not more than one or two of the excitatory synapses received by an individual layer IVC alpha neuron, and between one and eight excitatory synapses for a layer IVC beta neuron. Consequently, it is unlikely that the response properties of a particular cortical neuron are dominated by its input from a single geniculate neuron. Since the geniculocortical input essentially determines the response properties of neurons in layer IV of macaque striate cortex, it is surprising that this input amounts to such a small number of synapses to an individual neuron, although we obtained a somewhat similar result in our earlier quantitative analysis of the geniculate input to the striate cortex of the cat (Peters and Payne, 1993). But it has to be questioned whether the low values obtained are correct. Interestingly, the geniculocortical input to cortex has been largely neglected in favor of analyses of intracortical circuitry, but in view of the basic importance of this afferent input, it is suggested that more quantitative data about it should be generated, so that a better assessment can be made of its extent.

Afferent Pathways↗
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The effects of aging on area 46 of the frontal cortex of the rhesus monkey.

An examination of cortex of area 46 in the floor of the principal sulcus in the frontal lobe of the rhesus monkey has been carried out using three young (4-6 years of age), one middle-aged (12 years of age), and five old (25-32 years of age) rhesus monkeys. Light microscopic examination revealed no age-related change in the thickness of the cortex, and no changes in the frequency of profiles of neurons displaying nuclei and contained in 250-micron-wide strips of 1-micron-thick sections. Since the diameters of the nuclei of the neurons were found to be the same in the young and old monkeys, it was concluded that there was no change in the numbers of neurons beneath similar areas of cortical surface of area 46 with age. This conclusion was reinforced by an electron microscopic examination, since there was no suggestion of degeneration of the cell bodies of the neurons, which accumulated but little lipofuscin in the old monkeys. However, there were signs of degeneration in some of the dendrites in the upper layers of the cortex in the old monkeys, especially in layer 1, in which many of the dendrites had lost organelles from their cytoplasm. The other notable change was a degeneration of myelinated axons in the deep layers and white matter in some of the old monkeys. In contrast to the neurons, the effects of aging on the neuroglial cells and pericytes were very obvious, since in the old monkeys each type of neuroglial cell accumulated large inclusions within its cytoplasm. Prior to fixation, these monkeys had been behaviorally tested using a series of spatial and visual recognition tasks, which revealed that relative to the young monkeys, the old monkeys as a group displayed memory impairment. On one task, the extent of the impairment for each old monkey correlated well with the extent of degeneration of myelinated fibers in the cortex and white matter. Consequently, it is suggested that age-related cognitive changes are unlikely to be a result of a loss of neurons, but might be due to an alteration in connections between the cortex and other brain structures.

Aging↗
PubMedDate not supplied

The organization of pyramidal cells in area 18 of the rhesus monkey.

The aim of this study was to investigate the vertical organization of axons and pyramidal cells in area 18, and to compare it with that in area 17. In area 18 there are regularly spaced vertical bundles of myelinated axons that have an average center-to-center spacing of 21 microns. This arrangement of axons resembles that in area 17. Pyramidal cells in area 18 and their apical dendrites are less regularly arranged. The apical dendrites of the pyramidal cells of layer 6A aggregate with those from layer 5 pyramids to form swathes of apical dendrites that pass into layer 4. There they are joined by the apical dendrites of the small layer 4 pyramids, so that much of the neuropil of layer 4 is occupied by apical dendrites. Most of these apical dendrites form their terminal tufts in layer 3. Very few of them reach layer 1, which is dominated by the apical dendrites of layer 2/3 pyramids. Thus, there are two tiers of apical dendrites and their apical tufts, a deep one formed by the layer 4, 5 and 6 apical dendrites that terminate in layer 3, and a second one formed by the apical dendrites of layer 2/3 pyramids that terminate in layer 1. In contrast, in area 17 the apical dendrites of layer 5 pyramids form discrete clusters that have a center-to-center spacing of 23 microns. These clusters are joined by the apical dendrites of the layer 2/3 pyramids and all of these apical dendrites form their apical tufts in layer 1. Based upon the dispositions of the apical dendrites of the pyramidal cells in area 17 and 18, we speculate that the influences of, and the interactions between, the feed-forward and feed-back signals in the two areas are quite different, because in the two areas different postsynaptic targets are available to these afferents.

Animals↗
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Sperm antibodies after intraperitoneal insemination of sperm: a preliminary report.

To test the hypothesis that intraperitoneal insemination of sperm induces the expression of anti-sperm antibodies a prospective study was designed. Fifteen women undergoing intraperitoneal insemination (with or without oocyte transfer) were studied with 11 women having evaluation of anti-sperm antibodies. Sperm antibodies were detected by the immunobead test prior to intraperitoneal insemination and after each treatment cycle. Two criteria were used to assess positivity: the first based upon negative controls and the second based upon the evaluation of 20 fertile control couples. Using the first criteria, of 11 of the women undergoing IPI for the first time, 7 were initially negative and 4 were initially positive for at least 1 isotype. After treatment, 3 additional patients were positive (for a total of 7) and 4 patients remained negative. This alteration in sperm antibody frequency was not different (P = .4) as determined by the Fisher's Exact Test. Four of the 11 patients underwent a second cycle of IPI. All 4 patients were negative prior to the first treatment and 3 were negative prior to the second treatment. Subsequent to the second exposure, all 4 of these women were positive for at least 1 isotype. This shift in frequency distribution after 2 cycles was significant (P = .01). The frequency of antisperm antibodies for the same 11 patients was evaluated by using fertile control values as the basis of positivity. Two patients (18%) were positive for anti-sperm antibodies prior to intraperitoneal insemination. There was no change in the frequency of positivity after 1 cycle of IPI.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
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Radiofrequency ablation of liver tumors: how to enlarge the necrotic zones?

In an attempt to increase necrotic zones in liver tissue by radiofrequency ablation fresh bovine liver was coagulated by means of a needle electrode continuously perfused with NaCl solution. Power output (60 W) and application time (15 min) were kept constant while the perfusion was varied in terms of saline concentration (0.9, 5.85 and 10%) and perfusion rate (40 or 80 ml/h). Our results showed that the use of higher osmolar saline solutions in radiofrequency ablation with perfused needle electrodes did not lead to significantly larger coagulation volumes. By contrast, increasing the perfusion rate produced significantly larger necrotic zones. Doubling the perfusion rate made it possible to reach higher temperatures (>60 degrees C) within significantly shorter time.

Animals↗
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Radiofrequency ablation using perfused needle electrodes - study of intermittent and continuous triple needle application ex vivo.

To increase necrotic zones, bovine livers were treated by means of three parallel-oriented radiofrequency ablation (RFA) needles spaced at 3 cm using a puncture guide. The triple application was varied as a continuous and intermittent energy application compared to a single needle applicator. In all three study arms the applied energy (60 W) and the perfusion rate (240 ml/h) were kept constant. After treatment the smallest necrosis diameter was determined. In addition, temperature and the device's power output were monitored. Our study shows that synchronous use of three RFA application needles achieves significantly larger necrosis zones ex vivo than does single needle application. Intermittent energy application heats up the necrosis faster and more evenly with highest average temperature than continuous energy application.

Animals↗
PubMedDate not supplied

[Analytic design and clinical application of an intelligent control system for pharmacotherapy with insulin--1].

To determine whether insulin dosage recommendations provided by a computer system are as effective as those given by human experts, we developed an intelligent control system and prospectively studied its use in 42 type-1 diabetics attending a diabetes education center. Control algorithms were based on blood glucose self-monitoring and included parameter estimations to determine glucose metabolism. The algorithms were implemented in a vest pocket-sized system. Over a period of 32 days, 21 patients used the computer to determine the necessary dose of insulin, while a second group of 21 patients followed the recommendations of the diabetes specialists. Baseline HbA1 levels (9.8 +/- 1.6 vs 9.9 +/- 1.6%) were identical in the two groups. The mean serum glucose over the last two weeks of the study was lower in the computer group (151.3 +/- 25.2 vs 165.7 +/- 36.0 mg/dl; p < 0.01) although the rates of hypoglycaemic episodes were equal (1.7 vs 2.3%). Metabolic control, measured by the day-to-day standard deviation of the serum glucose (46.8 +/- 14.4 vs 50.4 +/- 16.2 mg/dl; p < 0.01), was more stable in the computer group. We conclude that metabolic control and safety were comparable in the two groups, and suggest that such an intelligent control system may be of benefit for use at home, when the help of doctors or diabetes educators is not available.

Artificial Intelligence↗
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Hysteroscopic endometrial destruction, optimum method for preoperative endometrial preparation: a prospective, randomized, multicenter evaluation.

OBJECTIVE: To compare the outcome and cost-effectiveness of various forms of preoperative endometrial preparation prior to hysteroscopic endometrial destruction for abnormal uterine bleeding. METHODS: This was a multicenter, prospective, comparative, randomized study conducted in a tertiary care hospital in Cairo, Egypt and 2 academic tertiary care teaching hospitals in the United States. One hundred thirty-one premenopausal women, who had completed childbearing, mean age of 45.7 years, with abnormal uterine bleeding refractory to medical management without histologic evidence of endometrial neoplasia were studied. The 131 patients were randomized for preoperative preparation for hysteroscopic endometrial destruction into 1 of 5 groups as follows: Group I, dilation and curettage (D & C) (39); Group II, gonadotropin-releasing hormone analogue (GnRHa) for 1 month (23); Group III, GnRHa for 3 months (26); Group IV, danazol for 3 months (26); and Group V, medroxyprogesterone acetate (MPA) 15 mg for 3 months (27). The choice of endometrial ablation or endometrial resection was left to the surgeon. RESULTS: Improvement in bleeding patterns, amenorrhea, operative times, complications, and relative cost were the measured outcomes. The mean follow-up time was 1 year from the time of the procedure. Overall, in Group I, 39/39 (100%) improved and 7/39 (18.0%) experienced amenorrhea; in Group II, 21/23 (91.3%) improved and 9/23 (39.1%) experienced amenorrhea; in Group III, 24/26 (92.3%) improved and 10/26 (38.5%) experienced amenorrhea; in Group IV, 24/26 (92.3%) improved and 9/26 (34.6%) experienced amenorrhea; and in Group V, 23/27 (85.1%) improved and 7/27 (25.9%) experienced amenorrhea. CONCLUSION: Endometrial destruction whether by the ablation or resection technique, regardless of the type of surgical pretreatment is a safe and effective surgical approach for treating abnormal uterine bleeding. D & C or MPA appear to be the most cost-effective pretreatment regimens. MPA pretreatment may confer the added advantage of decreasing blood flow and allowing better hysteroscopic visualization than D & C pretreatment.

Cost-Benefit Analysis↗
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[Malignant melanomas of the head and neck area].

Today's treatment methods have less effect on the prognosis of malignant melanomas in the primary tumor stage, irrespective of their localization, than certain prognostically important factors related to the tumor and the tumor patient. In a validation study the dominating prognostic value of tumor thickness after Breslow (1975) and the patient's gender as two independent factors is confirmed. The retrospective comparative treatment studies on the effects of elective lymph node dissection (ELND) and the extent of excision on prognosis are based on the separate evaluation of male and female patients grouped according to tumor thickness classes (0.76 to 1.5, 1.51 to 3.0 and greater than 3.0 mm). The results confirm what was to be expected according to more recent views on the pathology of melanomas (Balch et al. 1987), i.e. that regionally preventive radical measures, particularly elective lymph node dissection, have a positive effect only in a limited intermediate stage of development. Thus, it was only in a small patient group of men with melanomas of the tumor thickness class 1.5 to 3.0 mm that there was, both in relation to the total number of patients (n = 123) and to the group of head and neck melanomas (n = 30), a prognostic difference of 26% or, respectively, 44% to the favor of lymph node dissection. All other male patients as well as the female patient group exhibited better survival rates after removal of the primary tumor without subsequent elective lymph node dissection. Based on own studies and the critical consideration of published treatment studies, a number of recommendations for differentiated treatment according to acknowledged prognostic criteria (stage-specific therapy!) are given.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗