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Biomedical subjects

H Medina

Publications and source records attributed to H Medina.

18 recordsLinked to original sources
PubMed2001

Effect of an electric field on the motility of Entamoeba histolytica examined by multiple-beam interference microscopy.

A recently developed multiple-beam interference microscopic technique has been used to visualize submicroscopic structures of Entamoeba histolytica and their movements in applied external electric fields. The movements were videorecorded and it was found that at low current (120 microA) pseudopods are filled with hyaline ectoplasm. At slightly higher current (about 150 microA), the amoeba stops extending the pseudopods and loosens its attachment to the surface. At higher currents (200 microA), it forms a cyst and remains immobile for a time. Before this stage is reached a narrow ring is formed around the nucleus due to alterations in the proteins to protect it.

Animals↗
PubMed2001

Determination of the ultrastructural pathology of human sperm by atomic force microscopy.

OBJECTIVE: To investigate ultrastructural changes, particularly at the surface, that occur in pathological spermatozoa by using atomic force microscopy (AFM) and to examine the morphological alterations responsible for infertile sperm. DESIGN: Normal fertile and pathological spermatozoa were examined by using a conventional AFM in a noncontact mode. SETTING: Andrology clinic at Los Andes University Hospital. PATIENT(S): Sperm of patients with oligoasthenoteratozoospermia (OAT) and asthenozoospermia were obtained from the Los Andes University Hospital, Mérida, Venezuela. INTERVENTION(S) MAIN OUTCOME MEASURE(S): Morphological details, topological information, and three-dimensional images of the head, neck, and flagellum are presented for both normal and pathological sperm. RESULT(S): The obtained images clearly show dramatic alterations in the morphology of the head, neck, and flagellum of pathological sperm. Even the ultrastructure at the top of the flagellum and the region of the acrosome cap are clearly distinguishable. CONCLUSION(S): This study has significant importance not only for identifying spermatozoa alterations but also for understanding morphological defects and their effects on infertility. If properly exploited, this technique could be an important research tool.

Humans↗
PubMed2001

Morphological investigation of Toxoplasma gondii in vivo by a multiple beam interference microscope.

A recently developed technique, namely multiple beam interference microscopy, has been applied to investigate the morphology of the parasite Toxoplasma gondii for the first time. The interference pattern obtained from the multiple internal reflection of a T. gondii, sandwiched between a glass plate and a cover plate, was focused on the objective of a conventional microscope. Because of the enhance contrast, several details of sub cellular structure and separating compartments are clearly visible. Details reveal the presence of a nucleus, lipid body, dense granule, rhoptry and amylopectin. The wall thickness of the membrane of the lipid body and the amylopectin is of the order of 0.02 microm and can be clearly distinguished with the help of the present technique. The same parasite has also been examined with the help of atomic force microscopy, and because of its thick membrane, the inner structural details were not observed at all. Sub cellular details of T. gondii observed with the present technique have been reported earlier only by low amplification transmission electron microscopy and not by any optical microscopic technique.

Animals↗
PubMed2000

Multiple Beam Interference Confocal Microscopy: Tool for Morphological Investigation of a Living Spermatozoon.

The interference pattern obtained from a multiple internal reflection of a spermatozoon, sandwiched between the glass plate and the cover plate, was focused on the objective of a scanning confocal microscope. According to optical path differences, morphological details were revealed. The combined features, namely improved resolution in z axis, originating from the interference pattern and the optical sectioning of the confocal scanning system, enhanced the resolution and contrast in an impressive manner. These features permitted unprecedented images of the spermatozoon to be obtained at 0.1 µm optical sectioning and reconstruction of three-dimensional (3-D) images. With the help of optical sectioning, it was possible to estimate the thickness and the morphological details of the spermatozoon.

Journal Article↗
PubMed2000

Toxic pseudomembranous colitis in a patient with ulcerative colitis.

UNLABELLED: Toxic colitis is a severe disease that may be caused by several inflammatory and/or infectious diseases. Ulcerative colitis is one of the most frequent causes of toxic colitis in the United States. Toxic megacolon complicating Clostridium difficile colitis is a rare occurrence with significant morbidity and mortality. CASE REPORT: A 52-year-old male presented with rectal bleeding and tenesmus. He had been treated for amebiasis with metronidazole, and had improved. Two weeks later, symptoms recurred, and he was referred to our hospital. A sigmoidoscopy and biopsies demonstrated mucosal ulcerative colitis. He underwent treatment with systemic prednisone, mesalamine, and hydrocortisone enemas with adequate response. He was asymptomatic for 2 months, but later presented with a tender abdomen and rectal bleeding. Plain abdominal and thorax films showed colonic distention and free intraperitoneal air. Emergency laparotomy was performed, and an inflamed and distended colon, with free inflammatory liquid in the peritoneum, was found. A total abdominal colectomy with temporary ileostomy and Hartmann's pouch was performed. The histopathology analysis demonstrated a Clostridium difficile pseudomembranous colitis. CONCLUSION: The presence of toxic megacolon due to Clostridium difficile in patients with ulcerative colitis is a rare complication that may be suspected in patients with initial relapse who are on antibiotics.

Abdominal Pain↗
PubMed1999

Parenteral infusions bacterial contamination in a multi-institutional survey in Mexico: considerations for nosocomial mortality.

BACKGROUND: Parenteral infusions can be contaminated during administration (extrinsic contamination). A previous survey found that extrinsic contamination was not uncommon in a hospital in Mexico with lapses in aseptic techniques. To determine whether this problem exists in other similar institutions, we undertook a multi-institutional study. METHODS: We surveyed 6 hospitals (A to F) lacking an infection control committee to determine the level of extrinsic contamination. We visited each hospital and obtained samples of all the parenteral infusions in use, drawing 0.5-1 mL from the tubing injection port. Quantitative and qualitative bacterial cultures were performed. Chlorine levels of the tap water were measured. Visits were repeated until the survey was completed. RESULTS: A total of 751 infusions were cultured, of which 16 (2.13%) were contaminated. Hospital contamination rates varied from zero to 5.56%. Klebsiella pneumoniae was the most common isolate (10 cases). During the first sampling day in hospital C, the 7 infusions from the pediatric ward were found to be contaminated with a similar K pneumoniae strain. In-service education was started in this hospital. Infusion contamination was eliminated followed by a reduction in mortality rate. Overall, a higher risk for infusion contamination was noted for pediatric patients (P =.01, odds ratio = 3.28, 95% CI, 1.10-9.91) and in wards with inadequate water chlorine levels (P =. 02, odds ratio = 3.64, 95% CI, 1.08-13.51). CONCLUSIONS: If the hospitals surveyed are representative of others in developing countries, an endemic level of parenteral infusion contamination could exist in many hospitals throughout the world.

Adult↗
PubMed1999

[Control of pediatric nosocomial bacteremia by a program based on culturing of parenteral solutions in use].

OBJECTIVE: As Klebsiella, Enterobacter and Serratia are capable of growth in i.v. fluids and these bacteria are commonly implicated in nosocomial bacteremia, a control strategy through microbiological surveillance of in-use parenteral solutions is proposed. MATERIAL AND METHODS: A second level general teaching hospital, serving low-income patients. Through four consecutive strategies, a continuous surveillance program of i.v. fluids sterility in pediatric wards was stablished in 1992. During the first stage all of the in-use solutions were cultured. During the second stage randomly selected samples were studied. Third stage was designed as a case-control study. The last stage included samples drawn in convenience. Positive cultures point out eventual infusion mishandling, as well as high-risk areas and patients. RESULTS: After culturing 1940 parenteral solutions, infusion contamination rates decreased from 29.6% in 1992 to 12.9% in 1997 (p < 0.001). The proportion of Gram-negative rods isolated from blood cultures went from 72.7% to 40.85% (p < 0.0001), and the nosocomial bacteremia rate dropped from 3.12 to 1.54 per 100 discharges. CONCLUSIONS: The program has enabled us to: 1) Detect and control eventual bacteremia outbreaks; 2) Assess the endemic infusion contamination rate; 3) Arouse healthcare workers awareness about infusion line precautions; 4) Have a suitable surveillance strategy according to our laboratory's workload.

Bacteremia↗
PubMedDate not supplied

Ultrastructural investigation of human sperm using atomic force microscopy.

Ultrastructural investigation of human sperm in its natural environment (without fixation, dehydration, embedding, sectioning, etc.) was carried out by using atomic force microscope (AFM) in its tapping mode. This technique permits the examination of fine structural details of undamaged sperm and its topography with precision. Moreover, it allows 3D reconstruction of images and enhances the contrast to resolve details such as mitochondria that surround the axoneme at the sperm middle piece. An organized structure has been found in the flageller axoneme region. Ultrastructure also reveals folding and details of the depression of the membrane that cannot be examined with conventional techniques.

Humans↗
PubMedDate not supplied

Ultrastructural pathology of varicocele spermatozoa by using atomic force microscopy (AFM).

Ultrastructural investigation of pathological spermatozoa of patients having varicocele (grades I and III) in its natural environment (without fixation, dehydration, embedding, sectioning, etc.) was carried out by using Atomic Force Microscope (AFM) in tapping mode. This is a unique technique to examine the topographical structure with precision and to obtain 3-D images. It revealed structural alterations caused by the presence of varicocele. Not only neckpieces and flagella were defective, but also the head; particularly, dimensions and heights are altered.

Case-Control Studies↗
PubMedDate not supplied

An ectopic adrenocorticotropic hormone syndrome caused by a sacrococcygeal chordoma: report of a case with a slow progression.

OBJECTIVE: To report the first case of an ectopic adrenocorticotropic hormone (ACTH) syndrome caused by a sacrococcygeal chordoma. METHODS: We present a case report with clinical, laboratory, and histologic details. RESULTS: A 76-year-old man was admitted to the hospital because of urinary obstruction. Five years previously, a urethral mass had been detected, and transurethral prostatectomy had been performed. Annual computed tomographic (CT) scans showed no change in size of the mass. In 1995, skin hyperpigmentation, central obesity, and bilateral edema were noted. The patient was admitted to the hospital in July 1996. A CT scan of the abdomen revealed a large mass close to the sacrum and compressing the bladder and rectum. Cortisol measurements (AM and PM) were 309 and 271 ng/mL, respectively. The plasma ACTH concentration was extremely elevated (3,125 pg/mL). Although resection of the mass was attempted, complete resection was not possible because the tumor had infiltrated the sacrum. Plasma cortisol concentrations in samples obtained 7 and 8 days postoperatively were normal. Plasma ACTH was substantially decreased (180 pg/mL) but remained above normal. The histologic features of the tumor were compatible with a chordoma. Neoplastic cells stained positively for ACTH. CONCLUSION: This report describes the first case of an ectopic ACTH syndrome caused by a sacrococcygeal chordoma. A slow progression of symptoms in an ectopic ACTH syndrome had been described only for carcinoid tumors. These data add a new entry to the list of neoplasms capable of causing this syndrome.

Journal Article↗
PubMedDate not supplied

Parenteral infusions as culture media from a viewpoint of nosocomial bacteremia.

OBJECTIVE: To assess the growth patterns of selected organisms in common parenteral solutions, in order to ascertain implications for nosocomial bacteremia. DESIGN: A microbial suspension of approximately 300 CFU/mL was sequentially inoculated into common parenteral infusions from three different manufacturers and incubated at room temperature. Initially, 11 bacterial isolates and one Candida species from clinical specimens were studied. Eight gram-negative rods (GNR) were tested at varying pH's. Species variability was examined by testing an additional 39 isolates. RESULTS: The eight GNR grew in Ringer's lactate (RL) from two manufacturers and only two grew in dextrose 5% in water (D5/W) (Klebsiella pneumoniae and Serratia marcescens). No organism grew in saline or dextrose 5% in saline. The gram-positive cocci and Candida did not grow in any solution. No significant changes in growth were found after modifying the pH of solutions. Significant inter- and intra-species growth variability was noted. CONCLUSIONS: RL is a good culture media for GNR and D5/W is a poor culture media with the exception of some bacteria of the Tribe Klebsielleae. We recommend to follow high standards of nursing practice for administering intravenous infusions and to avoid nutrient-containing solutions for prolonged parenteral use, when possible.

Bacteremia↗
PubMedDate not supplied

Recurrent transient paresis in a turkey flock.

Recurring episodes of extreme leg weakness and associated mortality were documented in a turkey flock at 8 to 15 weeks of age. Flock mortality attributed to posterior paresis was approximately 12%, or 4800 of 40,000 turkeys. Four of six open-confinement units were affected. Gross and histological examinations revealed no significant lesions. Immunology and virology were uninformative. There were no significant differences in serum chemistry between clinically affected and normal turkeys. Testing of feed, water, soil, and tissues revealed no common toxicants. Isolation and supportive care for affected turkeys, both in the laboratory and in the field, frequently resulted in full recovery. Injection of a test group of affected turkeys with Type C botulism antitoxin appeared to enhance recovery. However, repeated attempts to detect botulism toxin in serum, liver, or cecal contents using mouse bioassay procedures were unsuccessful.

Animals↗
PubMedDate not supplied

Use of atomic force microscopy to reveal sperm ultrastructure in HIV-patients on highly active antiretroviral therapy.

Atomic force microscopy (AFM) has been employed to examine morphological and topographical changes caused by human immunodeficiency virus (HIV) and the effects of highly active antiretroviral therapy (HAART) on spermatozoon of HIV infected patients. This powerful technique has allowed us to visualize morphological alterations present in the spermatozoa of patients either with or without treatment. In addition to this, even the minute details, such as viral particles, located on the membrane of the spermatozoa, and the merging of such particles on the surface of the spermatozoa were detected with precision. The most important aspect is that AFM, unlike electron microscopy, permits to image virions in their nearly natural environment. Excess of damage of spermatozoon is due to the chemicals involved in HAART rather than the damage made by virus.

Antiretroviral Therapy, Highly Active↗
PubMedDate not supplied

[Perioperative management of the diabetic patient in cardiac surgery with extracorporeal circulation].

The hyperglycemia usually observed in patients undergoing heart surgery with extracorporeal circulation (EC) represents a difficult therapeutic problem. We studied the effects of several regimens of insulin therapy on serum glucose (SG) in 24 noninsulin dependent diabetic patients (NIDDs). The patients were randomly divided in five groups; group A received on IV bolus of 10.0-50.0 U/h according to glycosuria; groups B, C, D and E were given a continuous iv insulin infusion of 2.5, 5.0, 7.5 and 10.0 U/h respectively. In 10 non-diabetic patients (NDP) SG levels were also measured, but insulin was not given. A mean of 5.0 l/m2 of body surface of fluids containing 300 g of glucose were administered to all patients during surgery. At the operations SG levels rose progressively soon after the anesthesia was started, reached the highest values during the period of EC, and decreased slowly in blood samples taken after the EC phase and by 24h. This patterns was shown by all groups studied statistically significant lower SG levels, however, were observed in patients of group C, whose values were similar to those seen in the NDP group. Groups D and E had slightly higher SG levels than those of group C. An additional NIDDM patient with advanced chronic renal failure (CRF), had a tendency to hypoglycemia even during the EC period in response to relatively low doses of insulin (2.5 U/h), given by a continuous iv infusion and, although the insulin administration was stopped, his SG levels remained well below the mean values of the other patients for the rest of the operation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

[Metastatic disease of the liver: surgical perspective].

Approximately half of patients with colorectal cancer will develop hepatic metastases and it is estimated that up to 10% of that group will have resectable liver disease. Surgical resection remains the first line treatment option of metastatic liver tumors and has yielded a 20 to 40% five year survival rate. Selection of appropriate patients for resection is critical to a successful outcome. The best results are obtained in patients with isolated metastases. Factors that are associated with a poorer results are the presence of four or more lesions or a surgical margin less than 1 cm. Endocrine metastases can be resected in a palliative fashion but each case has to be individualized. This is also true for non colorectal-nonendocrine metastases. For this tumors the experience is anecdotal and confined to limited reported series. Adjuvant treatment (infusional chemotherapy and chemoembolization) can also have a role in treatment as well as cryotherapy.

Antimetabolites, Antineoplastic↗