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.

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.

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.

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.

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.

Surgical treatment of pleomorphic carcinoma of the pancreas.

Pleomorphic carcinoma of the pancreas is a rare malignancy that carries a poor prognosis. This case describes a patient with a pleomorphic carcinoma of the head of the pancreas, cured by a pylorus sparing pancreaticoduodenectomy. The literature is reviewed with emphasis on the surgical cures reported. The giant cell variety of pleomorphic carcinoma may carry a better prognosis. Pleomorphic histology of pancreatic neoplasms is not a contraindication for surgical resection.

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.

Thru-knee amputation: the operation of choice for non-ambulatory patients.

Between 1983 and 1990, 32 consecutive patients had 35 thru-knee amputations for ischemia causing infection or gangrene of the lower leg. Twenty-seven patients were nonambulatory, five had limited mobility, and none were considered to be candidates for rehabilitation with a prosthesis after surgery. The average age was 73 years. Thirty-day hospital mortality was 3 per cent. The incidence of complications was low, and healing was achieved in 97 per cent of survivors. One patients required revision to an above-knee amputation. Average postoperative hospital stay was 8.7 days. It is concluded from this study that thru-knee amputation is the treatment of choice in patients with nonsalvageable ischemic legs and in whom ambulation is not planned after operation.

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.

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.

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.

Drug resistance in Mexico: results from the National Survey on Drug-Resistant Tuberculosis.

OBJECTIVE: To present estimations obtained from a population-level survey conducted in Mexico of prevalence rates of mono-, poly- and multidrug-resistant strains among newly diagnosed cases of pulmonary tuberculosis (TB), as well as the main factors associated with multidrug resistance (combined resistance to isoniazid and rifampicin). DESIGN: Study data came from the National Survey on TB Drug Resistance (ENTB-2008), a nationally representative survey conducted during 2008-2009 in nine states with a stratified cluster sampling design. Samples were obtained for all newly diagnosed cases of pulmonary TB in selected sites. Drug susceptibility testing (DST) was performed for anti-tuberculosis drugs. RESULTS: DST results were obtained for 75% of the cases. Of these, 82.2% (95%CI 79.5-84.7) were susceptible to all drugs. The prevalence of multidrug-resistant TB (MDR-TB) was estimated at 2.8% (95%CI 1.9-4.0). MDR-TB was associated with previous treatment (OR 3.3, 95%CI 1.1-9.4). CONCLUSIONS: The prevalence of drug resistance is relatively low in Mexico. ENTB-2008 can be used as a baseline for future follow-up of drug resistance.

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.

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.

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 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.

Results of venous thrombectomy in the treatment of deep vein thrombosis.

Despite the infrequent use in the United States, venous thrombectomy seems to have a beneficial effect in carefully selected patients with acute iliofemoral thrombosis. The final decision to proceed with venous thrombectomy should be based on a balanced analysis of two factors--the characteristics of the thrombus and the characteristics of the patient. First, the diagnosis of acute deep vein thrombosis must be unequivocally established preoperatively. Accurate anatomic localization is usually achieved with venography, but duplex Doppler examination may be sufficient in selected instances. Second, the distribution of thromboses should be determined. Venous thrombectomy should be considered only in instances of deep vein thrombosis involving the iliofemoral venous segment. Thrombectomy for venous thrombosis below the inguinal ligament has not been consistently beneficial. Third, the age of the thrombus should be estimated. This can usually be accomplished though a careful analysis of the clinical history, but may be corroborated by duplex Doppler or venographic features of the thrombus. Venous thrombectomy should rarely be attempted if the age of the thrombus is thought to be greater than 72 hours. Unfortunately, in many instances the clinical history substantially underestimates the actual age of the underlying thrombus. Fourth, patient characteristics must be assessed preoperatively. While venous thrombectomy can usually be accomplished using local anesthesia, substantial shifts in fluid and acid base balance may be poorly tolerated by elderly, frail patients. In the setting of widespread metastatic disease, rethrombosis rates may be too high to justify thrombectomy in some patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Surgical treatment of superior mesenteric artery dissecting aneurysm and simultaneous celiac artery compression.

Spontaneous dissections of visceral arteries are rare, but when they do occur, they most commonly involve the superior mesenteric artery (SMA). We present a case of intestinal ischemia caused by a spontaneous dissection of the SMA in a patient with simultaneous celiac artery occlusion. The patient was a 45-year-old woman who presented with intestinal angina of sudden onset. Arteriography revealed the classic findings of SMA dissection and occlusion of the celiac artery. The patient underwent repair of both visceral vessels and made a full recovery. The 18 previously reported cases of isolated, spontaneous dissection of the SMA are reviewed. No previous case has been associated with celiac compression syndrome. The reported experience with symptomatic dissections of the SMA would suggest that prompt surgical repair is indicated and yields excellent results.