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Biomedical subjects

M A Machado

Publications and source records attributed to M A Machado.

At least 55 records · Page 3Linked to original sources
PubMed1992

Characterization of a type II collagen gene (COL2A1) mutation identified in cultured chondrocytes from human hypochondrogenesis.

A subtle mutation in the type II collagen gene COL2A1 was detected in a case of human hypochondrogenesis by using a chondrocyte culture system and PCR-cDNA scanning analysis. Chondrocytes obtained from cartilage biopsies were dedifferentiated and expanded in monolayer culture and then redifferentiated by culture over agarose. Single-strand conformation polymorphism and direct sequencing analysis identified a G----A transition, resulting in a glycine substitution at amino acid 574 of the pro alpha 1(II) collagen triple-helical domain. Morphologic assessment of cartilage-like structures produced in culture and electrophoretic analysis of collagens synthesized by the cultured chondrocytes suggested that the glycine substitution interferes with conversion of type II procollagen to collagen, impairs intracellular transport and secretion of the molecule, and disrupts collagen fibril assembly. This experimental approach has broad implications for the investigation of human chondrodysplasias as well as human chondrocyte biology.

Alleles↗
PubMed1989

Tissue and cell studies of the growth plate in the chondrodysplasias.

As the morphologic expression of the chondrocytic differentiation pathway responsible for bone development and growth, the growth plate has been investigated extensively in the chondrodysplasias. Unique morphologic abnormalities identified in many disorders have provided insight into pathogenetic mechanisms and have been useful diagnostically and nosologically. Biochemical studies have detected evidence of type II collagen defects in patients having disorders in the achondrogenesis type II-spondyloepiphyseal dysplasias (SED) congenita family of chondrodysplasias. Most promising may be the cell culture systems now being developed for human chondrocytes. Preliminary results suggest that they will allow the cellular and molecular biology of the dysplastic growth plate to be directly analyzed.

Cartilage↗
PubMed1989

Type II collagen screening in the human chondrodysplasias.

Abnormalities of type II collagen have been considered strong candidates for causing human condrodysplasias. We have employed peptide mapping to screen for several types of type II colagen abnormalities in cartilage samples from 66 patients with 20 separate disorders. Except for achondrogenesis type II (Langer-Saldino) and spondyloepiphyseal dysplasia (SED) congenita in which abnormalities have been described and diastrophic dysplasia in which the changes were probably secondary, no abnormalities were detected. Within the limitations of the screening technique, the results combined with other data from the literature suggest that abnormalities of this molecule are not common causes of chondrodysplasias outside of the achondrogenesis type II-SED congenita family of disorders.

Adolescent↗
PubMed1989

Expression of the human chondrocyte phenotype in vitro.

We report a culture scheme in which human epiphyseal chondrocytes lose their differentiated phenotype in monolayer and subsequently reexpress the phenotype in an agarose gel. The scheme is based on a method using rabbit chondrocytes. Culture in monolayer allowed small quantities of cells to be amplified and provided a starting point to study expression of the differentiated human chondrocyte phenotype. The cells cultured in monolayer produced type I procollagen, fibronectin, and small noncartilaginous proteoglycans. Subsequent culture in agarose was associated with the acquisition of typical chondrocyte ultrastructural features and the synthesis of type II collagen and cartilage-specific proteoglycans. The switch from the nonchondrocyte to the differentiated chondrocyte phenotype occurred under these conditions between 1 and 2 wk of agarose culture and was not necessarily homogeneous throughout a culture. This culture technique will facilitate direct investigation of human disorders of cartilage that have been addressed in the past by alternative approaches.

Cell Differentiation↗
PubMed1988

Abnormal ossification in thanatophoric dysplasia.

Thanatophoric dysplasia (TD) is a lethal human bone dysplasia characterized by severe dwarfism. It pathogenesis is thought to involve an abnormal ossifying fibrous tissue that disrupts the skeletal growth plate. We employed a combined morphologic, immunohistochemical and biochemical approach to better define the nature of this tissue in growth plate cartilage from 15 TD fetuses and infants in whom the abnormality was observed. The tissue was organized into tufts comprised of a cap of interstitial connective tissue, a transition region containing preosteoblastic cells near the cap and osteoblastic cells near the base, and a mineralized base which formed the subchondral bone trabeculae. The morphology of the cells and the presence of type I collagen in all regions of the tufts suggested that they were foci of membraneous ossification. However, elements of cartilage matrix (type II collagen, proteoglycan, link protein) were identified in the pericellular matrix of the osteoblastic cells and adjacent osteocytic cells. These observations suggest that a peculiar form of ossification occurs in the TD growth plate and may be involved in the pathogenesis of the disorder.

Collagen↗
PubMed1987

Bovine achondrogenesis: evidence for defective chondrocyte differentiation.

A survey study of growth cartilage abnormalities in bovine bone dysplasias revealed that a disorder in Holstein cattle called bulldog calf closely resembles human achondrogenesis Type II. Substantial amounts of Type I collagen and other non Type II collagens were detected in the bulldog cartilage which was comprised primarily of extensive vascular canals and cells having the characteristics of hypertrophic and degenerative chondrocytes normally found in the growth plate. It is proposed that chondrocytes throughout the bulldog growth cartilage prematurely differentiate into hypertrophic cells that degenerate and predispose the cartilage to vascular invasion and the formation of cartilage canals. The presence of these canals probably accounts for most of the observed collagen abnormalities.

Animals↗
PubMed1987

Achondrogenesis type II, abnormalities of extracellular matrix.

Immune and lectin histochemical and microchemical methods were employed to study growth cartilage from seven cases of achondrogenesis type II (Langer-Saldino). The normal architecture of the epiphyseal and growth plate cartilage was replaced by a morphologically heterogeneous tissue. Some areas were comprised of vascular canals surrounded by extensive fibrous tissue and enlarged cells that had the appearance and histochemical characteristics of hypertrophic chondrocytes. Other areas contained a mixture of cells ranging from small to the enlarged chondrocytes. The extracellular matrix in the latter areas was more abundant and had characteristics of both precartilage mesenchymal matrix and typical cartilage matrix; it contained types I and II collagen, cartilage proteoglycan, fibronectin, and peanut agglutinin binding glycoconjugate(s). Peptide mapping of cyanogen bromide cartilage collagen peptides revealed the presence of types I and II collagen. These observations could be explained by a defect in the biosynthesis of type II collagen or in chondrocyte differentiation.

Bone Diseases, Developmental↗
PubMed1986

[Tethered spinal cord syndrome: report of 2 cases].

The tethered spinal cord syndrome is a disease that is part of the group of spinal dysraphisms, that was recently recognized as an individualized nosological entity, yet not frequently diagnosed among us. It is characterized by shortening and thickening of the filum terminale which prevents the ascent of the spinal cord into spinal canal, the conus medularis abnormally remaining in a low place. It is associated in all cases with spina bifida. The diagnosis is simple, once the disease is suspected. It is manifested by progressive motor or sensory deficit in the legs, urinary incontinence, scoliosis and leg or back pain, specially in young children. The plain lumbosacral RX always shows spina bifida. Myelography makes the diagnostic. It shows, basically, the negative image of the thickened filum terminale and the low placed conus medularis. Other exams which can help are the computerized tomography and the ultra-sound of the spinal cord. The surgical treatment is very simple and heals without sequels if done in due time. It consists in a sectioning of the filum terminale through laminectomy. Two cases diagnosed and treated at Hospital da Baleia, from Fundação Benjamin Guimarãcs, Belo Horizonte, are reported in this paper.

Abnormalities, Multiple↗
PubMed1985

Cartilage collagen analysis in the chondrodystrophies.

A simple and reproducible method for analyzing small samples of cartilage collagens was developed. Following extraction with guanidine HCl, the cartilage specimens were digested directly with CNBr and the resultant peptides separated by gel-permeation high-performance liquid chromatography. Resting cartilage collagen CNBr peptide maps differed from normal in two inherited chondrodystrophies, achondrogenesis II and spondyloepiphyseal dysplasia congenita.

Bone Diseases, Developmental↗
PubMedDate not supplied

[Laparoscopic treatment of common bile duct lithiasis].

With the advances of videolaparoscopic surgery, this approach had become the treatment of choice for cholelithiasis. However, about 5% to 10% may present common bile duct lithiasis. Most surgeons have still difficulties to deal with this situation and do prefer resolve with open surgery or with further endoscopic approach. We present a case of a 60-year-old man, with 18 months history of right upper quadrant pain, weight loss and jaundice. He was referred with diagnostic of pancreatic cancer. Laboratory investigation showed increased bilirubin (10 mg/dL), alkaline phosphatase and GGT. Abdominal ultrasound showed atrophic gallbladder with dilated intra and extrahepatic biliary tree. Computerized tomography scan disclosed enlarged biliary tree with 3 cm stone in the distal common bile duct. The patient underwent a laparoscopic cholecystectomy followed by choledochotomy and retrieval of the large stone. A latero-lateral choledochoduodenum anastomosis was then performed to decompress the biliary tree. The patient had an uneventful recovery being discharged at the 6th postoperative day. Laparoscopic management of choledocholithiasis is feasible in many patients, specially those with dilated biliary tree. The retrieval of stones may be followed by biliary drainage with T-tube. In some elderly patients with chronically dilated common bile duct, as in the present case, a choledochoduodenal anastomosis is the procedure of choice.

Anastomosis, Surgical↗
PubMedDate not supplied

[Surgical treatment of insulinoma: study of 59 cases].

UNLABELLED: After establishing the diagnosis of an insulinoma the next step is its localization in order to perform the most suitable management approach. PURPOSE: To evaluate the methods used for the diagnosis of insulinoma and the localization of its site as well as the results of the surgical treatment. METHODS: Fifty nine consecutive patients with pancreatic insulinomas were studied. The discriminative power of the preoperative investigations in the localization of insulinomas was analysed. Special attention was focused to the intra operative methods of tumor localizations. The early and late results of the surgical treatment were also investigated. RESULTS: There were 55 benign cases and 4 malignant tumors. Preoperative localization was attempted by using ultrasonography (positive in 28.1%) CT imaging (positive in 25%), selective arteriography (positive in 54.1%), endoscopic ultrasonography (positive in 27.2%) and assay of portal plasma insulin levels (positive in 94.4%). In 54/55 cases (98.2%) the tumors were identified intraoperatively by palpation. By addition of intraoperative ultrasonography all lesions were identified and successfully removed without mortality. Five patients had multiple endocrine neoplasias all with multiple lesions in the pancreas. In patients with benign lesions 29 enucleations and 32 resections were performed. Pancreatic fistulas were the most common complication (29/59). Excluding the patients with malignant lesions the recovery rate was 98.1%. Three patients who underwent corporo caudal pancreactectomy developed diabetes. CONCLUSIONS: The preoperative localization is not necessary, since a combination of palpation and intraoperative ultrasonography can deal with most cases. Enucleation when possible is the best choice for benign lesions.

Adolescent↗
PubMedDate not supplied

Extrahepatic bile ducts injury: a report on 14 cases.

Traumatic injuries of the extrahepatic biliary tract are infrequent, occurring in approximately 0.5% of all patients with blunt and penetrating abdominal trauma. The incidence of this injury due to blunt abdominal trauma is rare. This study reviewed patients with injuries of the extrahepatic biliary tract due to abdominal trauma over a 6-year period to determine the incidence, trauma scores, associated injuries, surgical treatment performed, complications and mortality rate. We report our experience with 14 patients with extrahepatic biliary tract trauma. A review of the literature and the discussion about the management are presented.

Abdominal Injuries↗
PubMedDate not supplied

Carcinoid tumor of the gallbladder.

The carcinoid tumor is a relatively rare type of endocrine tumor, which arises mainly in the gastrointestinal tract. Primary gallbladder and biliary duct system carcinoids comprise less than 1% of all carcinoid tumors arising from any tissue or organ in the body. We describe a case of carcinoid tumor of the gallbladder in a 39-year-old man. There have been only 32 cases described in the literature.

Adult↗
PubMedDate not supplied

[Contribution to the study of devascularization of esophagogastric transition in the treatment of esophageal bleeding varices].

The usual techniques of esophagogastric desvascularization associated with splenectomy are reviewed and a new one is presented. It is a variant of EGDS technique described by Espíndula (1978) with the following modifications: A) In order to get a possible reduction of the transudation at the dissected area, on reperitonize: 1) the lesser curvature of stomach, naked during proximal gastric vagotomy (PGV). Fig. 1a and 1b; 2) the area of peritoneum concerning splenic hilum and tail of pancreas; 3) the dissected area of distal esophagus, performing a fundoplication (Lind, 1965) that also serves to obtain a good anti-reflux procedure. The EGDS was complemented with endoscopic sclerosis of varices, three to six months after operation. On consider that endoscopic sclerosis substitutes the surgical suture of the varices and reduces the surgical time and morbidity. From 1987 to 1989, eight patients with esophageal varices and gastrointestinal bleeding secondary to mansonic schistosomiasis were operated upon. Based on Child classification, two of these patients (25%) were graded B, six (75%) were graded A. None of the patients had post-operative esophageal bleeding or reflux esophagitis. There were no mortality. Two patients had postoperative ascitis that disappeared with clinic measures. The patients were followed during a period of six months to two years.

Adult↗
PubMedDate not supplied

[The use of peripheral blood progenitor cells as an autologous hematopoietic support in high-dose chemotherapy. I. The rationale and results].

We review the rationale for PBPC transplantation and the results reported in the literature. In order to prolong complete remissions and increase cure rates, high-dose chemotherapy is frequently used in the treatment of selected neoplasias. Hematological toxicity can be overcome by the infusion of autologous hemopoietic progenitors. Recently, peripheral blood is being used as the preferred source for hemopoietic progenitors, since it allows faster hematopoietic recoveries when compared to progenitors harvested from bone marrow. An adequate graft is defined by its content in clonogenic progenitors (mainly CFU-GM) and CD34 positive cells; these two parameters need to be accurately determined by specific laboratory methods. PBPC grafts are harvested using cell separators during leukaphereses; to increase efficiency, hemopoietic progenitors are first mobilized into the circulation with growth factors and or chemotherapy. PBSC transplantation may have procedure-associated toxicity related to the mobilization, harvest or reinfusion of the graft.

Antineoplastic Agents↗
PubMedDate not supplied

[The use of peripheral blood progenitor cells as an autologous hematopoietic support in high-dose chemotherapy. II. The experience of the Hematological Intensive Care Unit of the IPOFG. Franciso Gentil Portuguese Institute of Oncology].

We report the results of PBPC collection by large-volume leukaphereses and the hematologic recovery after high-dose chemotherapy supported by autologous PBPC reinfusion in a series of cancer patients treated at the Hematological Intensive Care Unit (UCHI) (Portuguese Institute of Oncology, Lisbon). Large volume leukaphereses were used to increase the efficacy of the PBPC collection. This modification of the standard apheresis technique allowed the harvesting, in only one session, of enough progenitors to proceed to transplantation in nearly 2/3 of patients and without significant toxicity. From December 1993 until September 1997, 95 autologous PBSC transplants were performed at the UCHI; 45% were performed in solid tumor patients and 55% in patients with hematologic malignancies. Hematologic recovery was similar to that published in the literature and related to the number of CD34+ cells infused. Patients supported with bone marrow in addition to PBPC showed delayed hematopoietic recovery, probably because the bone marrow harvest was only performed when an insufficient number of PBPC had been collected (2 x 10(6) CD34+ cells/Kg). The speed of hematological recovery differed per diagnosis, being higher in multiple myeloma and solid tumor patients and lower in Hodgkin's disease patients.

Adolescent↗