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Biomedical subjects

R Lozano

Publications and source records attributed to R Lozano.

At least 73 records · Page 4Linked to original sources
PubMed1994

The healing of grafts combining freeze-dried and demineralized allogeneic bone in rabbits.

The adjunctive role of demineralized bone matrix (DBM) in enhancing the incorporation of segmental freeze dried (FD)-allogeneic bone grafts has been studied in the rabbit ulna and fibula. The studies compared the healing patterns of fresh segmental autografts, FD-allografts, DBM-allografts, and FD-allografts supplemented at the graft-host junctions with FD- or DBM-allografts as particulates (ulna) or as segmental struts (fibula). The outcome was evaluated at five and ten weeks by a radiologic score, by biomechanical properties (breaking strength, energy to failure, stiffness), and histology. The ulnar autografts healed most rapidly (ten weeks = 100%), followed by DBM allografts (60%). By all criteria, FD-allografts were poorly incorporated (20-40%), and the process was not improved by supplements of FD- or DBM-particulate/strut bone. Histologically, the DBM component of composite fibular strut grafts was osteoinductive and united with host tissues within 35 days. The contiguous FD-allograft struts were not incorporated, showing fibrocartilaginous nonunions and resorptive foci. While the addition of DBM does not protect FD-allograft integrity in the rabbit, segmental mineralized FD-allografts could provide mechanical support for some intervals until, in such composite grafts, osteoinductive processes produced biomechanically competent new bone.

Animals↗
PubMed1993

Periosteal attachment fibers in the rat calvarium.

The anatomical relationships between the fiber tracts and bone lining cells within the rat calvarial periosteum have been studied by electron microscopy. Classical Sharpey's fibers were not observed in this location. Rather, thin unmineralized fibers originating from the periosteum traversed the cambial layer and passed to the bone surface between individual osteoblasts or groups of osteoblasts. The organizational relationship suggests that the osteogenic calvarial cell populations are compartmentalized into domains that might be particularly sensitive and responsive to the biomechanical forces of masticatory muscles.

Animals↗
PubMed1991

Low peptic ulcer and high gastric cancer prevalence in a developing country with a high prevalence of infection by Helicobacter pylori.

We compared the prevalence rates of peptic ulcer (duodenal and gastric) and gastric cancer in 1,796 dyspeptic Peruvian patients with those reported in 2,883 similar patients from developed countries. The prevalence of total peptic ulcer was significantly lower, and that of gastric cancer significantly higher, in the Peruvian patients. The prevalence of gastric ulcer was lower but not significantly so. We deduced that the significantly lower prevalence of total peptic ulcer was directly related to the low prevalence rate of duodenal ulcer. We hypothesize that the reason for these differences was probably a higher prevalence of Helicobacter pylori-associated chronic atrophic gastritis with hypochlorhydria in the Peruvian patients. Hypochlorhydria decreases the predisposition to peptic ulcer (especially duodenal ulcer), and chronic atrophic gastritis may predispose an individual to gastric cancer.

Adult↗
PubMed1991

Epidemiologic study and control of Taenia solium infections with praziquantel in a rural village of Mexico.

This study reports the results of an epidemiologic survey for the detection of Taenia solium in a rural village of 559 inhabitants in Sinaloa, Mexico, as well as a large scale treatment of the population with praziquantel. The study was carried out in two stages. In stage 1, serial stool analysis of 392 persons detected a cluster of three T. solium tapeworms. A fourth T. solium tapeworm was detected through a household census, giving a 1.32% prevalence rate for this helminth. Over 70% of the population over five years of age was treated with a 10 mg/kg dose of praziquantel, and no additional tapeworms were found. Environmental studies for the detection of Taenia sp. eggs in soil, water, and and objects from the houses of tapeworm-infected individuals showed only one soil sample containing eggs compatible with Taenia sp. A total of 72 domestic pigs were examined for the presence of cysticerci under the tongue. One animal had cysts, and belonged to a household that had two T. solium tapeworm infections. Stage 2 of the study was carried out one year after large scale antihelminthic treatment (LSAT), and no infections with Taenia sp. eggs were found. No cysticercus-infected pigs were detected. Intestinal parasitosis decreased from 69.2% to 37.5%. It is concluded that LSAT with praziquantel is efficient in decreasing endemic foci of T. solium. Seropositivity to T. solium bladder fluid antigens was tested by enzyme-linked immunosorbent assay and found to be 11% before LSAT and 7% one year later. In family members living with T. solium tapeworm carriers, the number of seropositive individuals was 28%. The relative risk ratio of seropositivity for persons living in the same household with a T. solium tapeworm carrier was 2.95. Positive response was significantly higher in the 30-39-year-old age group, in which 30% were seropositive in stage 1, compared with 7% one year after LSAT. High seropositivity rates were significantly associated with tapeworm clusters as well as with individuals with a clinical history of seizures.

Adolescent↗
PubMed1991

Elements for a theory of the health transition.

This article presents the basic elements for developing a theory of the health transition. Such elements include the definition of concepts, the specification of a framework on the determinants of health status, the analysis of the mechanisms through which health change occurs in populations, the characterization of the attributes that allow us to identify different transition models, and the enumeration of the possible consequences of the transition. The propositions are presented with a sufficient level of generality as to make them applicable to different contexts; at the same time, an attempt is made to provide them with the necessary specificity to account for different national experiences, thus opening a space for future comparative research efforts. Through the systematization exercise presented in this article, we hope to contribute to the progress of a topic that has grown in importance during recent years. Such importance is due to the enormous potential that health transition theory has for understanding and transforming the growing complexity of our times.

Demography↗
PubMed1991

[The epidemiologic transition in Latin America].

The concept of health transition is considered to include two interrelated processes: transition of health care and epidemiological transition. The latter encompasses three basic processes: (a) replacement of the common infectious diseases by noncommunicable diseases and injuries as the leading causes of death; (b) a shift in peak morbidity and mortality from the young to the elderly; and (c) change from a situation in which mortality predominates in the epidemiological panorama to one in which morbidity is dominant. Latin America is characterized by a heterogeneous health profile in which different countries are in various stages of epidemiological transition. However, in most of them, the transition experience is unlike that of the developed countries and is distinguished by: (a) a simultaneous high incidence of diseases from both the pre- and post-transitional stages; (b) a resurgence of some infectious diseases that had previously been under control; (c) a lack of resolution of the transition process, so that the countries appear to be caught in a state of mixed morbidity; (d) a peculiar epidemiological polarization, not only between countries but also in the different geographical areas and between the various social classes of a single country. This experience is called a "prolonged polarized model."

Adolescent↗
PubMed1990

Cornstarch ingestion after oral glucose loading: effect on glucose concentrations, hormone response, and symptoms in patients with postprandial hypoglycemic syndrome.

In susceptible individuals ingestion of glucose can lead to clinical symptoms of hypoglycemia as well as a reflex rise of counterregulatory hormones. We hypothesized that cornstarch, a slowly absorbed starch, might prevent hypoglycemic-symptom episodes. Eight patients who had characteristic signs, symptoms, and reflex hormonal responses of hypoglycemia at the glucose nadir after ingesting 75 g glucose (OGTT) participated. Patients ingested 75 g glucose followed by 75 g raw cornstarch (OGTT + CS). None of the patients reported symptoms or had signs of hypoglycemia in response to OGTT + CS. The glucose nadir concentration during OGTT + CS (3.8 +/- 0.6 mmol/L) was significantly higher than during OGTT (3.2 +/- 0.6; P less than 0.03). The responses of cortisol (331 +/- 166 nmol) and epinephrine (491 +/- 589 pmol/L) at the glucose nadir during OGTT + CS were significantly lower than the responses of cortisol (524 +/- 193 nmol/L; P less than 0.003) and epinephrine 1834 +/- 1135 pmol/L (P less than 0.0005) during OGTT. A slowly absorbed starch such as cornstarch may be an effective component in dietary management of this disorder.

Administration, Oral↗
PubMed1990

Anesthesia and immunosuppression in an experimental model.

The purpose of the present work was to study: (1) if anesthesia induces changes in the helper/cytotoxic/suppressor T cell ratio in the rat spleen, and (2) if there is any difference between two anesthetic methods usually employed in rat experimentation. 50 Fisher 344 rats were allotted into 5 groups. In group A (control), a splenectomy was performed in an average time of 3 min under ether anesthesia. In groups B1 and B2, the rats anesthetized for 1 h with ether (group B1) or with one single dose of ketamine + atropine + diazepam (group B2) and then underwent splenectomy. Groups C1 and C2 were similar to groups B1 and B2 but splenectomy was performed 24 h later, under ether anesthesia during 3 min. T helper (Th) and T cytotoxic-suppressor (Ts-c) cells were identified in periarterial and follicular spleen tissue by means of an immunohistologic analysis using an immunoperoxidase technique with monoclonal antibodies. In periarterial tissue the Th/Ts-c ratio (mean +/- SE) was: group A, 1.61 +/- 0.11; group B1, 1.10 +/- 0.1; group B2, 1.28 +/- 0.11; group C1, 0.85 +/- 0.08, and group C2, 1.23 +/- 0.12. The differences between groups A and B1, C1 and C2 were statistically significant (t = 2.2833) as well as the difference between groups C1 and C2 (t = 2.5223). The Th/Ts-c ratio was also compared when equal to 1 or less than 1. The difference between groups A and C1 was statistically significant (p less than 0.05) as well. In follicular tissue the ratio was 1 in all the groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia↗
PubMed1990

The influence of nicardipine in patients with high risk of stroke.

Blood pressure and clinical status of 1,736 patients with cerebrovascular disease were observed during 12 months of treatment with nicardipine. The most common diagnoses were chronic cerebral ischemia (53.2%), transient ischemic attacks (TIA; 25.1%), and cerebral infarct (8.7%); 50.1% of patients were classed as hypertensive [systolic blood pressure (SBP) > or = 160 mm Hg or diastolic blood pressure (DBP) > or = 90 mm Hg]. Most patients (91.2%) received a daily dose of 60 mg nicardipine. Additional treatments included diuretics (37%), beta-blockers (11.5%), other antihypertensive drugs (15.8%), platelet antiaggregants (25.1%), and cardiotonic drugs (15.1%). A total of 282 patients (16.2%) were lost to follow-up, 21 (1.2%) patients withdrew due to side effects, 32 (1.8%) died, and 9 (0.5%) patients had treatment interrupted due to concomitant illness. In the hypertensive subgroup, blood pressure (SBP/DBP) was reduced from a mean baseline value of 175 +/- 22/97 +/- 14 mm Hg to 152 +/- 17/85 +/- 11 mm Hg at 3 months and 149 +/- 23/81 +/- 11 mm Hg after 12 months of treatment. The incidence of TIA or stroke among these patients was reduced from 29 cases (3.5%) during the first 3 months to 11 cases (1.54%) during months 4-12 (p < 0.01). In normotensive patients there were 18 (2.15%) cases during months 1-3 and 13 (1.55%) cases during months 4-12 (difference not significant). In the 280 patients treated with nicardipine alone, the most frequent side effects during the first month were facial flushing (6.8%), gastrointestinal problems (5%), dizziness (3.2%), headache (3.2%), drowsiness (3.2%), and hypotension (1.1%). Most of these side effects were transient.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Calcitonin: chronotherapeutic effect on osteopenia in the ovariectomized rat.

This chronotherapeutic study has revealed no clear evidence to support the concept that calcitonin promotes bone formation in intact or OVX'd rats. Rather, the efficacy of CT-impaired bone resorption appeared to be optimal in OVX'd rats treated during the daytime, and least effective during the first half of the environmental dark span. These findings indicate a benefit for calcitonin chronotherapy in this animal model where the cellular kinetics resemble those documented in early development of postmenopausal osteoporosis.

Animals↗