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Biomedical subjects

S Morgan

Publications and source records attributed to S Morgan.

At least 127 records · Page 7Linked to original sources
PubMed1990

The basal ganglia-orofacial system: studies on neurobehavioral plasticity and sensory-motor tuning.

We have employed the unilateral removal of the vibrissae as a tool to examine ensuing behavioral changes in relation to concomitant changes in the central nervous system. In this paper we review a series of studies showing that unilateral removal of the vibrissae leads to behavioral asymmetries (e.g., in thigmotactic scanning) from which rats recover over time. Time-related to these behavioral changes we found neuronal alterations in striatal afferents, that is, in uncrossed and crossed projections from the substantia nigra and the tuberomammillary nucleus. The involvement of dopaminergic mechanisms was indicated by results showing that dopaminergic agonists can induce asymmetries in thigmotactic scanning and turning; the direction of these asymmetries was also dependent on time after vibrissae removal. Furthermore, it was shown that endogenous preferential use of one vibrissae side in thigmotactic scanning interacts with the expression of spontaneous and drug-induced behavioral asymmetries exhibited after unilateral vibrissae removal. Neurochemical studies indicated that both unilateral vibrissae removal and unilateral perioral stimulation can have lateralized effects on biogenic amines in the brain. Finally, using electrical stimulation of the substantia nigra, evidence was found for a lateralized and bidirectional interaction between basal ganglia and the orofacial systems, indicating an involvement in mechanisms of motivation and particular stimulation. These results are important from several perspectives. One, they indicate functional links between the orofacial systems and the basal ganglia. Two, they raise the possibility that unilateral removal of the vibrissae can serve as a model (a) to investigate the dynamics of recovery of function after CNS insults, in general, and specifically, (b) to study neuronal plasticity in the nigrostriatal and tuberomammillary-striatal pathways, and (c) to investigate the neuropharmacology of catecholamine systems in the brain.

Animals↗
PubMed1990

Antilymphocyte globulin therapy enhances impaired function of natural killer cells and lymphokine activated killer cells in aplastic anaemia.

MHC-unrestricted cytotoxic lymphocytes, namely natural killer (NK) and lymphokine activated killer (LAK) cells, have been implicated in the regulation of haemopoiesis. To investigate the possible role of these lymphocytes in the pathogenesis of aplastic anaemia (AA), we studied their functions in the peripheral blood mononuclear cells (PBMC) and bone marrow mononuclear cells (BMMC) of patients with AA treated with antilymphocyte globulin (ALG). Before treatment, both NK and LAK activities in the PBMC of 25 patients were low (NK = 1.9 +/- 2.1 x 10(3) LU/l) LAK = 4.7 +/- 3.6 x 10(3) LU/l) compared to normal (NK = 6.0 +/- 3.0 x 10(3) LU/l, LAK = 10.0 +/- 3.5 x 10(3) LU/l) or multiply transfused (NK = 7.8 +/- 6.6 x 10(3) LU/l, LAK = 25.2 +/- 13.6 x 10(3) LU/l) controls. The NK and LAK activities in the BMMC in AA patients were not significantly different from those in PBMC. In all patients with low LAK and NK activities pre ALG there was an increase in activity 2-24 weeks after therapy which eventually reached normal levels and which was maintained for up to 2 years. Analysis of lymphocyte phenotypes in AA patients before treatment showed both significantly low mean proportion and absolute numbers of CD16+ cells compared to normals, which increased after therapy. Changes in MHC-unrestricted cytotoxicity and lymphocyte phenotypes post therapy were not correlated with haemopoietic recovery. These data suggest that ALG treatment can enhance the functions of MHC-unrestricted lymphocytes independently from haemopoiesis. It is unlikely that these cells play a role in the pathogenesis of AA.

Adolescent↗
PubMed1990

Muramic acid is not detectable in Chlamydia psittaci or Chlamydia trachomatis by gas chromatography-mass spectrometry.

By using the powerful separation technique of capillary gas chromatography combined with the selectivity of mass spectrometric detection, muramic acid was not detectable in purified elementary bodies of Chlamydia psittaci Cal 10 (less than or equal to 0.006%) or C. trachomatis serovar E (less than or equal to 0.02%). This confirms previous reports which suggested the absence of a typical peptidoglycan in Chlamydia spp.

Chlamydia trachomatis↗
PubMed1990

Trisomy/tetrasomy 13 in seven cases of acute leukemia.

We report the clinical presentation and the morphologic, histochemical, and immunophenotypic characteristics of seven patients with acute leukemia who had trisomy/tetrasomy 13 as the sole cytogenetic abnormality in their leukemia. Five patients had trisomy 13 at diagnosis of acute leukemia. All five of these patients had undifferentiated leukemias. The sixth patient, who had French-American-British (FAB) type M2 acute nonlymphocytic leukemia (ANLL), and the seventh patient with biphenotypic acute leukemia developed the trisomic clone as a new abnormality late in the course of their disease. A review of the literature revealed 28 previously reported hematologic malignancies with trisomy 13 or tetrasomy 13q as a solitary cytogenetic abnormality. Trisomy 13 appears to represent another rare but nonrandom cytogenetic abnormality in acute leukemia. In our series trisomy 13 is largely associated with acute leukemia with little myeloid or lymphoid differentiation.

Acute Disease↗
PubMed1989

Etiologic heterogeneity in dyskeratosis congenita.

Most patients with dyskeratosis congenita [DC or Zinsser-Cole-Engman syndrome] are males hemizygous for an X-linked recessive mutation. However, one or more autosomal form(s) of DC may exist. We have studied a 6-year-old black girl with the characteristic triad of nail dystrophy, cutaneous and mucosal pigmentary changes, and bone marrow failure. Severe microcephaly, mental retardation, cerebellar hypoplasia, and purple discoloration of the tongue were other manifestations not usually seen in DC. Comparison of our patient's phenotype with that of 5 other sporadic and 10 familial cases of DC in females showed that the autosomal and X-linked phenotypes are not distinguishable in the absence of a suggestive pedigree pattern. Additional cases of DC need to be studied to better elucidate the apparent causal heterogeneity in this syndrome.

Bone Marrow Diseases↗
PubMed1989

Asymmetries in crossed and uncrossed nigrostriatal projections dependent on duration of unilateral removal of vibrissae in rats.

The influence of unilateral removal of vibrissae on the crossed and uncrossed nigrostriatal projections was examined with the horseradish peroxidase tract tracing technique. Hemivibrissotomy mainly affected the projections arising from the rostral part of the substantia nigra. One to three days after clipping the vibrissae, rats were found to have more labeled neurons in the crossed projection to the caudate-putamen (CPU) on the same side as vibrissae removal than in the crossed projection to the CPU opposite to vibrissae removal. A reversed asymmetry was seen in rats examined 4-20 days after vibrissae removal. These animals had more labeled cells in the crossed and uncrossed projections terminating in the CPU opposite to the shaved side, i.e. in the hemisphere deprived of vibrissal sensory input. This time-course of neural alterations is similar to that of the recovery from behavioral asymmetries seen after hemivibrissotomy. Similar time-dependent alterations in the nigrostriatal projection had been found after unilateral injection of 6-OHDA into the substantia nigra.

Animals↗
PubMed1989

Preliminary results of coloanal anastomosis.

Coloanal anastomosis after resection of the rectum is the ultimate procedure to preserve the patient's sphincter and avoid a permanent colostomy. Carcinoma of the midrectum, and sometimes of the lower third of the rectum, may not require excision of the pelvic floor and anus for cure. A colonal anastomosis was achieved in 38 patients in whom the indications for surgery were carcinoma in 29, recurrent or extensive adenomas in four, radiation proctitis in two, rectal fistula following radical cystectomy in one, secondary low Hartmann reconstruction after a failed attempt in one, and stenosis of a very low colorectal anastomosis in one. Twenty-six patients were men and 12 women, with a mean age of 62. Dukes' staging for carcinoma were A: 9, B: 7, C: 11, and two had a palliative resection. The mean distance from the anus was 6.0 cm. All had a temporary defunctioning colostomy. There were no postoperative deaths and 17 (45 percent) had postoperative complications, major in 7 (18 percent), minor in 10 (26 percent). Mean follow-up is now 40 months (range, 12 to 64 months). Among patients who underwent curative resection, three have had pelvic recurrences. Two of these patients died of widespread distant disease and one underwent abdominoperineal resection and is now free of disease. All others are alive with no evidence of disease. The colostomy was closed in all but six (16 percent). Two (palliative) died within the colostomy and the other four are awaiting closure. Anastomotic stricture was the most common long-term problem, occurring in 16 and requiring more than one dilatation in eight. Six months after closing the colostomy, the mean daily number of bowel movements is 3.8. Twenty-six (87 percent) are continent to solid stools, two are incontinent to solid stools, and 16 have to wear a pad to prevent soiling. All but one prefer their present status to having their colostomy. In selected cases of rectal carcinoma with little or no extramural spread, the authors estimate that resection and colonal anastomosis is a good alternative with acceptable function and a low rate of recurrent disease, which is comparable to complete rectal excision but avoids a permanent colostomy. However, it should not be a substitute for standard abdominoperineal resection for extensive lower rectal carcinoma or for a colorectal anastomosis when the latter is technically feasible.

Adult↗
PubMed1989

Developmental and individual differences in performance on phonological synthesis tasks.

This study was conducted in order to examine the role of individual differences in working memory and lexical access in accounting for age and reading skill related differences in performance on phonological synthesis tasks. The performance of 28 kindergarten, first-, and second-grade children with normal reading skills, as well as that of 28 reading-disabled second graders, was compared under four testing conditions. The testing conditions were formed by completely crossing rate of presentation of phoneme strings with type of stimulus to be blended (real or nonword). Both independent variables affected performance on the blending tasks, with better performance obtained at faster presentation rates and with real words. There was a developmental discontinuity in overall performance, with the kindergarten children obtaining substantially lower scores than the first or second graders. In the comparison of second-grade good and poor readers, there was a significant interaction between groups, presentation rates, and type of stimulus. The findings are discussed in terms of their implications for a general model of performance on the sound blending task, as well as their value for interpreting individual differences on the task.

Awareness↗
PubMed1989

The effects of varying cigarette deprivation duration on cognitive and performance tasks.

The effects of varying times of cigarette deprivation on cognitive and performance tasks were examined. This study employed a between-subjects design in which five groups of smokers (9-10 subjects in each group) were compared on a vigilance task and cognitive measures as a function of length of deprivation (0, 2, 4, 8, or 24 hours). Each subject was tested during baseline ad-lib smoking and at one of the deprivation durations. Difference scores were compared between the 0-hour group and the 2-, 4-, 8-, and 24-hour groups. The results showed that there were no significant withdrawal effects on the measures at 2, 4, and 8 hours after cigarette deprivation with the exception of poorer performance on the Trail Making Test (B) at 4 hours, However, there were significant withdrawal effects at 24-hours deprivation. These included increased mean reaction time, increased variability in reaction time, and increased errors of commission on the vigilance task. There were near significant changes at 24-hours deprivation on the Trail Making Test (B) and Symbol Digits Modalities.

Adolescent↗
PubMed1988

Clinical, clinicopathologic, pathologic, and toxicologic alterations associated with gossypol toxicosis in feeder lambs.

The toxicity of gossypol was studied in 20, 8-week-old feeder lambs that weighed approximately 16 kg. The lambs were allotted to 4 groups (A, B, C, D) and given (orally for 30 days) a daily dosage of gossypol (0, 45, 136, or 409 mg, respectively). Lambs were observed twice daily until they died or were euthanatized on the day the last dose was given. Clinical, electrocardiographic, clinicopathologic, pathologic, and toxicologic findings were recorded. All lambs given 409 mg of gossypol (group D) died before the end of the 30-day study. In this group, clinical signs included sudden death and/or chronic dyspnea syndromes. One group-B lamb had chronic dyspnea, but did not die. Electrocardiographic abnormalities observed in gossypol-treated lambs included increased amplitude of the T wave and decreased duration of the ST segment. Clinicopathologic alterations in group-D lambs included high serum total lactate dehydrogenase and lactate dehydrogenase liver-specific isoenzyme activities. Serum total creatine kinase activity decreased markedly in lambs of all groups treated with gossypol. Hemoglobinuria was detected in 2 group-D lambs. The average daily weight gain was remarkably consistent in lambs of all groups, except in 1 lamb each of groups D and B. Lambs were necropsied when they died or on day 30 of the study. The heart of gossypol-treated lambs weighted more than did that of untreated (control group A) lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1988

[Malignant colonic polyps: is polypectomy adequate treatment?].

The management of patients with endoscopically removed malignant intestinal polyps is controversial. The risk of residual disease should be assessed against the risk of a surgical operation. The authors report 35 cases of malignant polyps (5.5% of 641 colonoscopically removed adenomas). Sixteen patients had carcinoma in situ and received no further treatment and 19 had invasive carcinoma (sessile in 6, pedunculated in 13). Of these 19, 7 did not undergo surgery--because of old age in 2, minimal invasion in 3, a low rectal location in 1 and refusal in 1. Twelve patients (3 with sessile, 9 with pedunculated polyps) underwent a surgical resection, and residual disease was present in 3 (25%), 1 with positive nodes. Reported criteria of increased risk of residual disease--cancer in lymphatics or veins, incomplete excision, tumour at resection margin, sessile and villous tumours--were present in nine. All three patients with residual disease had microscopically involved margins of resection. The authors believe that the increased risk of recurrence justifies the risk associated with subsequent surgical resection unless the patient is otherwise a poor operative risk.

Adenoma↗
PubMed1987

The role of apheresis in the support of life-threatening ITP relapse.

A 14-year-old girl with chronic idiopathic thrombocytopenic purpura (ITP) presented in relapse with a platelet count of 1,000/microL and a high-level serum antiplatelet IgG antibody. She previously had been unresponsive to courses of therapy with steroids, vincristine, and splenectomy. When treatment with danazol and purified immunoglobulins was unsuccessful in controlling her rapidly progressive course, an 8-day plasma exchange procedure was initiated in combination with platelet transfusion therapy and immunosuppression with cyclophosphamide and vincristine. Within 2 days, her clinical state improved markedly, correlating with a drop in her serum antiplatelet antibody level. She continued to improve and was discharged on a regimen of cyclophosphamide and danazol. Her antiplatelet antibody level had fallen to within the normal range, despite a typical platelet count of 5,000/microL during the 8-day period. Two weeks later her platelet count rose to 65,000/microL. This case suggests that a course of therapeutic plasma exchange may have a temporizing role in the acute management of life-threatening chronic ITP relapse, generating time for the more definitive therapy of immunosuppression to take effect.

Adolescent↗
PubMed1987

Should cholecystectomy be done en passant for asymptomatic cholelithiasis?

The management of asymptomatic gallstones discovered during abdominal surgery is controversial. Should cholecystectomy be performed en passant? The authors report a 4-year survey of 109 patients with asymptomatic cholelithiasis who underwent surgery for other abdominal conditions: colorectal (31), gastric (24), vascular (20), gynecologic (21) and miscellaneous (13). Cholelithiasis was established preoperatively by ultrasonography in 52 of 55 examinations (95%). In the other 54, the gallstones were discovered at operation. Cholecystectomy was performed in 78 patients and in 31 the gallbladder was left in place. In the former group, 11 (14%) had complications, 2 being attributable to the cholecystectomy. Intraoperative cholangiograms were obtained in 43 and led to common-bile-duct explorations in 8. Common-bile-duct stones were found in seven. In the non-cholecystectomized group, three died postoperatively and three were lost to follow-up. Twelve of the remaining 25 are still asymptomatic and 13 have had symptoms: 7 underwent cholecystectomy (4 for acute cholecystitis) between 2 weeks and 11 months after the initial laparotomy. Because of the low morbidity and the relatively high number of cholecystectomies that were subsequently necessary, the authors recommend cholecystectomy en passant unless there is a specific contraindication. They also recommend ultrasonography before major gastrointestinal or vascular surgery in order to plan for cholecystectomy.

Adult↗
PubMed1987

Is preoperative colonoscopy in carcinoma a realistic and valuable proposition?

Colonoscopy was performed preoperatively in 100 consecutive patients as a prospective study to establish the feasibility of the procedure and its value, which was considered "adequate" when the colon remaining after surgical resection had also been examined preoperatively. Colonoscopy was adequate in 35 of 46 patients (76%) with malignant tumour located in the cecum and ascending and transverse colon, but in only 15 of 54 patients (28%) who had a tumour in the left colon or rectum. Synchronous malignant tumours were present in 2 patients, and 54 additional adenomas were discovered in 29 patients. These adenomas could be removed endoscopically in 13 patients and were included in the standard resection in 12. Extension of the planned operation was necessary in only four patients with synchronous adenomas. Routine preoperative colonoscopy to assess the presence of synchronous colonic tumours is more likely to be adequate in proximal or right-sided large-bowel tumours than in left-sided tumours because of the annular configuration of the latter. Because of the high rate (46%) of synchronous adenomas in adequate examinations, inadequate preoperative colonoscopy should be complemented by a repeat examination 3 to 6 months postoperatively in every patient with a malignant tumour of the large bowel.

Adenoma↗