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Biomedical subjects

F Medina

Publications and source records attributed to F Medina.

At least 55 records · Page 3Linked to original sources
PubMed1987

Injuries associated with downhill sledding.

During the winter season of 1985 to 1986, 30 children presented to the emergency department with injuries related to downhill sledding. All of the patients were seen and treated during December 1985, which was an unusually cold and snowy month. The age range of the patients was six to 16 years. Six patients required admission, and all were related to head and/or abdominal trauma. The special characteristics of the sled, the environment, and the rider work in concert to produce injuries. The injury is most likely to occur under cold, icy conditions. After analysis of this series of patients, it is concluded that downhill sledding injuries can be minimized. The factors that make this activity dangerous are defined, and safety precautions are suggested.

Adolescent↗
PubMed1987

Safety aspects of long-term antihypertensive therapy (10 years) with clonidine.

We have treated 128 patients aged 40 +/- 9 years (60 males and 68 females), all with essential hypertension (W.H.O. I and II), over a period of 10 yr. The treatment was performed with clonidine at a dose that ranged from 0.150 to 1,200 mg (twice daily). Forty-two patients also received a diuretic (HCTZ 25 mg daily). Mean blood pressure decreased significantly from 169 +/- 10 mm Hg systolic, 107 +/- 3 diastolic to 145 +/- 6 mm Hg (p less than 0.001) 90 +/- 3 mm Hg diastolic (p less than 0.001). Side effects occurred during the first month. These were drowsiness 28%, dry mouth 35%, constipation 13%, dizziness 9%, postural hypotension 2%, and male impotence 3.3% (2/60). Side effects still present after 120 months of treatment were drowsiness 11.7%, dry mouth 26.6%, constipation 14.1%, dizziness 4.7%, and male impotence 1.7% (1/59). The number of patients who discontinued treatment resulting from side effects were 3.34%, all of them within the first 6 months. There were no changes in renal or liver function or in serum electrolytes or lipids. Retinopathy improved in most patients. Electrocardiogram (ECG) improved in 45 patients with LVH. It is concluded that clonidine provided sustained blood pressure control with minimum side effects during 10-year therapy for hypertension.

Adult↗
PubMed1986

Toxicity of human hemoglobin solution infused into rabbits.

Aqueous human hemoglobin is being considered as an oxygen-transporting resuscitation solution. However, there are some indications that such solutions may be toxic. We report here that at a clinically significant dose (20% to 30% of the estimated blood volume) of hemoglobin solution (10 gm/dl), toxicity similar to that reported in humans is produced in rabbits. This toxicity is characterized by cardiac rhythm disturbances (25%) and coagulation abnormalities, manifested as intravascular thrombi. Hypoxia, tissue necrosis (brain 29%, liver 25%), and death (22%) were seen. Hypoxia appears to be the cause of death, because the arterial PO2 of rabbits that died was significantly lower (43 +/- 8 mm Hg) than that of rabbits that lived (80 +/- 12 mm Hg). We also report the effect of the method of preparation or degree of purity on the observed toxicity. Stroma-free red blood cell hemolysate, stroma-free hemoglobin, zinc-precipitated hemoglobin, and chromatographically purified hemoglobin were infused. Purification of these solutions ranged from removal of stroma to removal of all detectable nonhemoglobin protein components. In addition, the nonhemoglobin proteins were concentrated and infused into rabbits to compare their effects. All of these hemoglobin solutions induced similar toxicity for rabbits infused with stroma-free hemoglobin. The nonhemoglobin proteins, as well as human serum albumin, exhibited no toxicity. These results demonstrate that, at the clinically relevant dose, hemoglobin or something inherently associated with hemoglobin is toxic.

Animals↗
PubMed1985

The buffering capacity of crystalloid and colloid resuscitation solutions.

The buffering capacities of common colloid and crystalloid resuscitation solutions were compared in vitro. An equal volume of each resuscitation solution was titrated above and below its initial pH with 0.14 N sodium hydroxide or 0.11 N hydrochloric acid. The volume (+/- S.D.) of titration solution necessary to lower the pH one unit (7.1-6.1) in these solutions was less than 0.5 ml for normal saline, less than 0.5 ml for Ringer's lactate, 1.9 +/- 0.1 ml for Plasmalyte-A, 2.0 +/- 0.23 ml for Plasmalyte-R, 8.8 +/- 0.17 ml for human serum albumin (HSA), 45 +/- 2.2 ml for human fresh frozen plasma (FFP), and 50 +/- 6.6 ml for swine FFP. With the method of this in vitro study, human fresh frozen plasma was 25-50 times better as an acid buffer than the crystalloid solutions and approx. 5 times better than human serum albumin (HSA). On an equal volume basis, it was the superior resuscitation solution as a buffer, probably because of combined bicarbonate and protein content.

Animals↗
PubMed1984

Pathogenic and free-living protozoa cultured from the nasopharyngeal and oral regions of dental patients.

Protozoa of nose, mouth, and pharynx of 30 randomly chosen female caries patients at an odontological clinic of the National Autonomous University of Mexico, were surveyed by culture from swabs. Culture tubes of swabs from each patient were observed every other day during 5 weeks. Pathogenic protozoa found included Entamoeba histolytica Schaudinn, 1903; Naegleria fowleri Carter, 1970; Acanthamoeba castelanii Douglas, 1930; Acanthamoeba culbertsoni Singh & Das, 1970; and Balantidium coli (Malmsten, 1857) Stein, 1862. This isolation of pathogens suggests that healthy patients may be healthy carriers of cysts of protozoa, mainly amoebae, responsible for several diseases, including primary amoebic meningoencephalitis. Small pathogenic free-living amoebae have not been isolated before from females in Mexico. Many species of free-living protozoa were also cultured from swabs from the patients.

Adult↗
PubMed1983

A survey of pathogenic and free-living amoebae inhabiting swimming pool water in Mexico City.

A survey of pathogenic and free-living amoebae in swimming pool waters of Mexico City was performed. Among the organisms isolated those which have public health importance were Naegleria fowleri Carter and Acanthamoeba castellanii Douglas. Amoebae of the genera Acanthamoeba, Naegleria, and Vahlkampfia were recovered in their cystic stage while those specimens of the genera Amoeba, Entamoeba, Thecamoeba, and Vanella were recovered only in their trophic stage during this study. Amoebae were concentrated through filtration procedures and subsequently cultured in different culture media. Nonpathogenic amoebae also isolated by culture included: Amoeba proteus (Pallas) Leidy, Amoeba striata Penard, Paratetramitus jugosus Page, Acanthamoeba astronyxis Ray and Hayes, Vahlkampfia avara Page, Vahlkampfia inornata Page, Thecamoeba verrucosa Ehrenberg, and Vanella mira Schaeffer. Trophozoites of Entamoeba gingivalis Gros, were also recovered, both directly and by culture. Most commonly found were amoebae of the species Naegleria gruberi Schardinger (59.02%), N. fowleri (16.77%), and A. castellanii (7.64%). Least-frequently found amoebae belonged to the species Thecamoeba verrucosa (0.12%). All isolated strains of N. fowleri and A. castellanii were thermophilic at 45 and 40 degrees C, respectively, and also pathogenic when inoculated into white mice. More populated by amoebae were those swimming pools of the indoor type with an inner side garden. It was also shown that the free residual chloride values of 0.50 to 1.5 mg/liter, ordinarily used in pool waters, are not adequate for elimination of amoebae.

Amoeba↗
PubMed1983

Modification of hemoglobin - tetrameric stabilization.

Advantage has been taken of the unique affinity of DBBF for hemoglobin to stabilize the T state and crosslink tetrameric hemoglobin. The oxygen affinity has been further decreased by using PLP to produce a chemically unique molecule with a P50 of 32 under physiologic conditions. Furthermore, the modification is specific, requires only reagents that are commercially available or easily synthesized, and can be prepared in large quantities with up to 80% yield. The unique modified hemoglobin was purified by HPLC and the crosslink was found between the beta chains. This derivative, pyridoxalated-fumarate hemoglobin, sustained life in five rats that were 95% exchanged-transfused with the solution. Preliminary in vivo tests support this derivative as a desirable oxygen-transporting resuscitation fluid.

Aspirin↗
PubMed1982

The value of a portal study in determining the etiology of hepatic masses in the adult.

The intrahepatic portal system was studied by superior mesenteric angiography in 80 patients with hepatic masses. The portal study helped to identify the highly significant portal signs of malignancy (amputations, irregular stenosis, portal hypertension), and, among the malignant tumors, the specific signs of hepatoma (portal trunk amputation, ill-defined hepatographic lacunae, association of portal hypertension with proximal portal amputation). It is concluded that the intrahepatic portal study is essential in pretherapeutic staging. It is better than superselective hepatic arteriography in assessing the involvement of one hepatic lobe when a hypervascular tumor involves the other lobe, and it is indispensable if embolization is planned.

Adolescent↗
PubMed1981

Glycoprotein changes in fresh vs. room temperature-stored platelets and their buoyant density cohorts.

Membranes from platelets obtained from normal human volunteers were isolated for evaluation of their glycoproteins. Values were measured in fresh and stored platelet concentrates at 72 and 96 hr (22 degrees +/- 2 degrees C). Polyacrylamide gels were used to separate the membrane glycoproteins. These were identified as GPI, GPII, GPIII, GPIV, GP77, and GP44. The relative amount of GPI (155,000 daltons) was about 30% less after 72 hr storage than in fresh platelets regardless of the change in the pH of the platelet concentrate. At 96 hr, only an additional 5% loss was seen. The 72 hr value for soluble glycoprotein, glycocalicin, was only 64% of the initial value. GP77 (77,000 daltons) and GP44 (44,000 daltons) became apparent or more prominent with storage. A correlation with pH of the platelet concentrate could be demonstrated for GPI but only with those units in which the pH rose during storage. Density-separated populations of fresh and stored platelets also were studied. They were separated on arabinogalactan (Stractan II) gradients for comparative studies of membrane proteins that might be affected, since platelets become less dense with storage. There was an equal loss of GPI in all populations. However, the change was most striking in the least dense (lightest) fraction because these cells started with 20% less GPI when fresh than did heavier cells. The smallest glycoprotein, GP44, was always present in the lightest platelets after storage, whereas only 40% of the concentrates showed GP77, in small amounts, associated with heavy platelets. Alterations in the membranes of platelets stored as platelet concentrates could result in their functional impairment and loss viability.

Blood Platelets↗
PubMed1975

[Effects of thymectomy on the natural bactericidal power of thymectomized mice].

T and B-dependent systems are correlated between themselves and with the macrophage system in eliciting the immune humoral response. Not all immunogens require T-B interactions to elicit the antibody response: consequently, the problem of the limits of T-dependence, with regard to different immunogen stimulations, remains open. The comparative study of the serum antibody response in mice, thymectomized at birth and in the normal ones, inferred from the values of bactericidal activity (b.a.), detected versus E. coli, S. typhi and S. albus strains did point out evident variation. Thymectomy has impaired b.a. against E. coli; it seems to have no consequence on b.a. against S. typhi; is not possible to the results of our investigation, it seems that the response to the immunogens, responsible for the so-called natural antibodies does require T-B cooperation only for some bacterial species and not for others. A higher bactericidal capacity of normal serum with regard to Gram positive as compared with Gram negative bacteria, is confirmed.

Animals↗