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Biomedical subjects

M M Solis

Publications and source records attributed to M M Solis.

At least 19 recordsLinked to original sources
PubMed2001

Accurate deployment of vena cava filters: comparison of intravascular ultrasound and contrast venography.

BACKGROUND: The increasing use of vena cava filters by trauma surgeons has led to reports of filter placement using intravascular ultrasound (IVUS). Although attractive because of its ease of use and elimination of contrast and radiation, no studies have examined the accuracy of filter placement by IVUS as compared with contrast venography (CV). The purpose of this study was to compare the anatomic information obtained by both techniques during filter placement. METHODS: Twenty-one patients meeting trauma service criteria for filter placement were studied (11 women and 10 men; mean age, 46.8 years). All procedures were performed in the operating room by trauma surgeons. Vascular access was obtained by percutaneous placement of an 8 French sheath in the right femoral vein. CV, IVUS, and bilateral selective renal venography were performed before deployment of a Greenfield filter. Localization and diameter measurements were made in reference to a radiopaque ruler placed on the patient's abdomen. We chose the "best location" for filter deployment as 1 cm below the junction of the lowest renal vein and the vena cava. Measurements by CV and IVUS were compared with the "gold standard" of selective renal venography. RESULTS: As compared with selective renal venography, the difference between best location by CV and IVUS was 16.3 +/- 13.8 mm and 3.7 +/- 5.6 mm, respectively (p = 0.001). In four cases (19%) the CV missed best location by 3 cm or more. CV overestimated the diameter of the vena cava in all cases. Average vena cava diameter was 26.4 +/- 3.3 mm by venography and 20.6 +/- 3.1 mm by IVUS (p < 0.0001). CV incorrectly identified four patients as having vena cava diameters too large (>2.8 cm) for the placement of a Greenfield filter. The two renal vein anomalies (one double left renal vein and one absent left renal vein) were correctly diagnosed by IVUS. CONCLUSION: IVUS is a more accurate method of localizing the renal veins and measuring vena cava diameter for placement of vena cava filters than contrast venography.

Female↗
PubMed2000

Song selectivity and sensorimotor signals in vocal learning and production.

Bird song, like human speech, is a learned vocal behavior that requires auditory feedback. Both as juveniles, while they learn to sing, and as adults, songbirds use auditory feedback to compare their own vocalizations with an internal model of a target song. Here we describe experiments that explore a role for the songbird anterior forebrain pathway (AFP), a basal ganglia-forebrain circuit, in evaluating song feedback and modifying vocal output. First, neural recordings in anesthetized, juvenile birds show that single AFP neurons are specialized to process the song stimuli that are compared during sensorimotor learning. AFP neurons are tuned to both the bird's own song and the tutor song, even when these stimuli are manipulated to be very different from each other. Second, behavioral experiments in adult birds demonstrate that lesions to the AFP block the deterioration of song that normally follows deafening. This observation suggests that deafening results in an instructive signal, indicating a mismatch between feedback and the internal song model, and that the AFP is involved in generating or transmitting this instructive signal. Finally, neural recordings from behaving birds reveal robust singing-related activity in the AFP. This activity is likely to originate from premotor areas and could be modulated by auditory feedback of the bird's own voice. One possibility is that this activity represents an efference copy, predicting the sensory consequences of motor commands. Overall, these studies illustrate that sensory and motor processes are highly interrelated in this circuit devoted to vocal learning, as is true for brain areas involved in speech.

Animal Communication↗
PubMed2000

Compromised neural selectivity for song in birds with impaired sensorimotor learning.

Anterior forebrain (AF) neurons become selective for song as songbirds learn to produce a copy of a memorized tutor song. We report that development of selectivity is compromised when birds are prevented from matching their output to the tutor song. Finches with denervated vocal organs developed stable song, but it usually did not resemble the tutor song. In those birds, numerous neurons in Area X responded selectively to both tutor and bird's own song (BOS), indicating the importance of both in shaping AF responses. The degree of selectivity for BOS was less, however, than that of normal adults. In contrast, neurons in denervated birds that successfully mimicked tutor song exhibited normal adult selectivity for BOS. Thus, during sensorimotor learning, selectivity for complex stimuli may be influenced by how well motor output matches internal sensory models.

Acoustic Stimulation↗
PubMed2000

Schwannoma of the cervical sympathetic chain: it's not a carotid body tumor.

Schwannoma of the cervical sympathetic chain is a rare nerve tumor with fewer than 40 confirmed cases in the English literature. These lesions typically present as an asymptomatic neck mass and are easily mistaken for a carotid body tumor during the initial workup. We report a case of schwannoma of the cervical sympathetic chain in a 35-year-old man followed by a review of the current literature.

Adult↗
PubMed2000

Tuberculous enteritis: a case report.

Tuberculous enteritis is an unusual diagnosis in the United States. Because this entity is rare and the symptoms are not specific, the physician must have a high index of suspicion. We report the case of a young man with tuberculous involvement of the gastrointestinal tract who required surgical intervention for small bowel obstruction.

Adult↗
PubMed1999

Contributions of tutor and bird's own song experience to neural selectivity in the songbird anterior forebrain.

Auditory neurons of the anterior forebrain (AF) of zebra finches become selective for song during song learning. In adults, these neurons respond more to the bird's own song (BOS) than to the songs of other zebra finches (conspecifics) or BOS played in reverse. In contrast, AF neurons from young birds (30 d) respond equally well to all song stimuli. AF selectivity develops rapidly during song learning, appearing in 60-d-old birds. At this age, many neurons also respond equally well to BOS and tutor song. These similar neural responses to BOS and tutor song might reflect contributions from both song experiences to selectivity, because auditory experiences of both BOS and tutor song are essential for normal song learning. Alternatively, they may simply result from acoustic similarities between BOS and tutor song. Understanding which experience shapes selectivity could elucidate the function of song-selective AF neurons. To minimize acoustic similarity between BOS and tutor song, we induced juvenile birds to produce abnormal song by denervating the syrinx, the avian vocal organ, before song onset. We recorded single neurons extracellularly in the AF at 60 d, after birds had had substantial experience of both the abnormal BOS (tsBOS) and tutor song. Some neurons preferred the unique tsBOS over the tutor song, clearly indicating a role for BOS experience in shaping neural selectivity. In addition, a sizable proportion of neurons responded equally well to tsBOS and tutor song, despite their acoustic dissimilarity. These neurons were not simply immature, because they were selective for tsBOS and tutor song relative to conspecific and reverse song. Furthermore, their similar responses to tsBOS and tutor song could not be attributed to residual acoustic similarities between the two stimuli, as measured by several song analyses. The neural sensitivity to two very different songs suggests that single AF neurons may be shaped by both BOS and tutor song experience.

Acoustic Stimulation↗
PubMed1999

Improved antibody responses to delayed pneumococcal vaccination in splenectomized rats.

Pneumococcal vaccination following splenectomy is widely used as prophylaxis against overwhelming postsplenectomy infection. There remains controversy however, over the timing of vaccination. We hypothesized that delaying vaccination would increase the antibody response. Pneumococcal vaccinations were given at designated intervals to rats that had undergone either a sham abdominal surgery or splenectomy. Sixty male Sprague-Dawley rats, 250 to 400 g, were divided into three groups for vaccination: I, 1 day postoperatively; II, 7 days postoperatively; and III, 28 days postsplenectomy/sham. Serum antibody levels were then determined by enzyme-linked immunosorbent assay at 5 and 21 days after vaccination. Immunoglobulin (Ig) levels after delayed vaccination at 1 week postoperatively and 1 month postoperatively were significantly higher than levels from rats vaccinated 1 day postoperatively. IgM levels after vaccinations 1 week and 1 month postoperatively were also significantly higher than levels of rats vaccinated 1 day postoperatively (P < 0.05 for both IgG and IgM). On the basis of these results, we conclude that delaying vaccination after splenectomy enhances antibody responses.

Animals↗
PubMed1997

Acoustic and neural bases for innate recognition of song.

In behavior reminiscent of the responsiveness of human infants to speech, young songbirds innately recognize and prefer to learn the songs of their own species. The acoustic and physiological bases for innate recognition were investigated in fledgling white-crowned sparrows lacking song experience. A behavioral test revealed that the complete conspecific song was not essential for innate recognition: songs composed of single white-crowned sparrow phrases and songs played in reverse elicited vocal responses as strongly as did normal song. In all cases, these responses surpassed those to other species' songs. Although auditory neurons in the song nucleus HVc and the underlying neostriatum of fledglings did not prefer conspecific song over foreign song, some neurons responded strongly to particular phrase types characteristic of white-crowned sparrows and, thus, could contribute to innate song recognition.

Animals↗
PubMed1997

Anterior forebrain neurons develop selectivity by an intermediate stage of birdsong learning.

Auditory neurons of the anterior forebrain (AF) in adult zebra finches are highly selective for the bird's own song (BOS): they respond more to BOS than to songs of other zebra finches (conspecifics) and to BOS played in reverse. In contrast, juvenile AF neurons are not selective at 30 d of age, responding equally well to all song stimuli. Both BOS and tutor song experience are required by juveniles for normal song learning and may produce the selective properties of adult neurons. Because such selectivity could subserve song learning, it is important to determine when it arises. Birds were therefore studied at an intermediate stage of learning, after substantial experience of both tutor song and their own developing (plastic) song. Extracellular single neuron recordings in 60-d-old zebra finches revealed that AF neurons had significant song and order selectivity for both tutor song and BOS (the bird's plastic song). The degree of BOS selectivity was less than that found in adults, as indicated in part by 60 d neurons that were sensitive to the local order within syllables but not yet to the global order of syllables within a song. When responses to BOS and tutor song were compared, most neurons preferred BOS, some preferred tutor song, and others responded equally to both stimuli. The latter type of neuron was not simply immature, because many of these neurons responded significantly more to BOS and tutor song than to conspecific and reverse songs. The selectivity of AF neurons at 60 d is markedly different from the unselective properties of neurons at 30 d and may function in vocal learning at this stage. Moreover, the selectivity for both BOS and tutor song raises the possibility that both aspects of the birds' sensory experience during learning are reflected in properties of AF neurons.

Acoustic Stimulation↗
PubMed1997

Song- and order-selective neurons develop in the songbird anterior forebrain during vocal learning.

The anterior forebrain (AF) pathway of songbirds has an essential but poorly understood function during song learning, a process requiring auditory experience. Consistent with a role in processing auditory information, two nuclei of the AF, the lateral magnocellular nucleus of the anterior neostriatum (IMAN) and Area X (X), contain some of the most complex auditory neurons known. In adult zebra finches, these neurons are strongly selective for both spectral and temporal properties of song: They respond more robustly to the bird's own song (BOS) than to songs of conspecific individuals, and they respond less well to BOS if it is played in reverse. IMAN and X neurons of young finches early in the process of song learning (30-45 days of age) are also song responsive, but lack the song and order selectivity present in adult birds. By an intermediate stage of learning (60 days), when birds have experience of both tutor song and their own developing (plastic) song, AF neurons have significant song and order selectivity for both tutor song and BOS (in this case, plastic song). The degree of BOS selectivity is still less than that found in adults, however. In addition, neurons at 60 days are heterogenous in their preference for BOS versus tutor song: Most prefer BOS, some prefer tutor song, and others respond equally to both songs. The selectivity of adult AF auditory neurons therefore arises rapidly during development in neurons that are initially unselective. These neurons are one of the clearest examples of experience-dependent acquisition of complex stimulus selectivity. Moreover, the neural selectivity for both BOS and tutor song at 60 days raises the possibility that experience of both songs during learning contributes to the properties of individual AF neurons.

Aging↗
PubMed1996

A technique for the creation of long autogenous tissue arterial patches.

An endarterectomized segment of an occluded artery (e.g. superficial femoral artery), is an alternative autogenous material for patch angioplasty which preserves the continuity of the saphenous vein. A technique of incising endarterectomized segments of superficial femoral artery in a spiraled manner is presented which allows for the creation of long autogenous tissue patches. A spiral is drawn on the exterior of a harvested arterial segment which is either 1 cm, 7 mm or 5 mm in width. When incised along the spiral, the length of the resulting elliptical patch will be two, three, or four times, respectively, the length of the original artery segment. The authors have used the technique to close extended profundoplasty in three patients and for construction of a patched distal anastomosis in two patients undergoing prosthetic femoropopliteal bypass grafting. There have been no early complications.

Bioprosthesis↗
PubMed1996

Surgical clerkship performance of traditional and nontraditional students in a problem-based learning environment.

BACKGROUND: To determine whether nontraditional students perform better than traditional students during surgical clerkships as reflected on the surgical clerkship final examination. METHODS: Retrospective review of medical student records from the classes of 1986 through 1993. Students admitted soon after completing undergraduate training were identified as "traditional," and those having prior careers as "nontraditional." RESULTS: There were 150 traditional and 72 nontraditional students. The ratio of men to women and admission MCAT scores were not significantly different. Traditional students were significantly younger and had higher admission grade point averages (GPAs). Nontraditional students were more likely to be married and have children. Final examination scores of traditional and nontraditional students were not significantly different. MCAT scores and college GPAs were the best predictors of final examination performance. Married students performed significantly better than single students. CONCLUSIONS: There was no significant difference between nontraditional and traditional student performance on the surgical clerkship final examination.

Adult↗
PubMed1996

Major vascular injury from high-pressure water jet.

High-pressure water jets are used in industry as a cleaning and cutting tool. Penetrating injuries by these devices can produce minimal external evidence of extensive internal damage. We report a literature review and the case of a limb-threatening injury to the lower extremity caused by such a device.

Accidents, Occupational↗
PubMed1996

Mesenteric lymphangioma causing bowel obstruction in a child.

Mesenteric lymphangioma was manifested as a bowel obstruction in a child with cerebral palsy. Diagnosis was not confirmed until the time of laparotomy. Mesenteric lymphangioma is rare but should be considered in a child with bowel obstruction and no other known abdominal disease.

Cerebral Palsy↗
PubMed1995

Surgery in nonagenarians: morbidity, mortality, and functional outcome.

BACKGROUND: There are few studies that document the outcomes experienced by very old patients who undergo major surgery. METHODS: This is a case series and 7-year follow-up of 116 consecutive patients who were aged 90 years or older and underwent major surgery at a large university-affiliated community hospital. We describe the functional status, short- and long-term mortality, and predictors of mortality in this group of frail elders. RESULTS: The 116 nonagenarians in this study underwent 134 major operations. Sixty-three patients were admitted to the hospital from a nursing home. The most common surgical procedures were for hip fracture, lower extremity amputation, and abdominal problems. Nineteen patients died in the hospital following surgery, and 23 patients died within 30 days of operation. Follow-up at 7 years revealed that all but three patients had died. Survival was worse for patients admitted from nursing homes, those who were nonambulatory before surgery, and those with major or complete functional impairment. CONCLUSIONS: Major surgery in nonagenarians is associated with a 20% perioperative mortality. Functional status and ambulatory ability are maintained in most patients. Whether to operate on these frail elders is a complex decision.

Aged↗
PubMed1994

Recombinant soluble human thrombomodulin: a randomized, blinded assessment of prevention of venous thrombosis and effects on hemostatic parameters in a rat model.

UNLABELLED: Thrombomodulin is an endothelial surface receptor that binds thrombin and accelerates the activation of protein C. We compared the effects of a recombinant thrombomodulin analog (TME), recombinant hirudin (r-HIR), heparin sodium (HEP), and normal saline (Control) on thrombus formation, activated partial thromboplastin time (APTT), thrombin time (TT), platelet aggregation and tail transection bleeding time (BT) in a rat model of vena cava thrombosis. RESULTS: TME, r-HIR and HEP prevented venous thrombosis in this model in a dose-dependent manner. At the dose required to reduce vena cava thrombosis by 50% (ED50), TME did not prolong the APTT or TT as did HEP and r-HIR. Platelet aggregation in response to thrombin was not effected by TME but was inhibited by both r-HIR and HEP. BT did not differentiate the agents tested. CONCLUSION: TME inhibited venous thrombosis in a rat vena cava model with less effect on hemostatic variables than HEP or r-HIR.

Animals↗
PubMed1994

Isolated symptomatic midcervical stenosis of the internal carotid artery.

All carotid arteriograms performed between January 1, 1986 and December 31, 1991 were reviewed for instances of midcervical carotid stenosis. Sixteen cases were identified. A stenosis related to the hypoglossal nerve was specifically identified in three operative reports in the retrospective review. Pathologic examinations of the specimens confirmed the presence of atherosclerotic plaque or fibrous dysplasia. In another case, relief of intermittent neurologic symptoms (TIAs) was obtained by division of the stylohyoid ligament. Prospective observation of five cases confirmed a stenosis immediately distal to a transverse neurofascial band formed by the hypoglossal nerve, which arose with the vagus nerve in three patients, and a large cervical contribution to the ansa hypoglossi in two. Presumably the lesion was caused by the turbulent flow in the internal carotid artery distal to the band. Isolated stenosis of the midcervical internal carotid artery unrelated to bifurcation disease may be the result of turbulence induced by tethering neural or myofascial bands.

Aged↗