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Biomedical subjects

R Gonzalez

Publications and source records attributed to R Gonzalez.

At least 199 records · Page 11Linked to original sources
PubMed1992

Carbon catabolite regulation of gentamicin formation.

The effect of utilizable carbon sources on the production of gentamicin by Micromonospora purpurea has been studied. High D-glucose and D-xylose concentrations (40 mg/ml), exerted a strong and permanent negative action on antibiotic formation. On the other hand, similar concentrations of D-fructose, D-mannose, maltose and starch caused no effect. The glucose action is seen only if added during the logarithmic growth phase; moreover, the sugar needs to be metabolized to show its negative effect.

Carbohydrate Metabolism↗
PubMed1992

[Antibacterial resistance induced by injection of ascitic fluid (with IgM partially removed) and natural monoclonal antibodies of human origin in rainbow trout].

Human monoclonal immunoglobulins M from myeloma shown to have the typical polyspecificity of natural antibodies, were precipitated from the ascitic fluid that originally contained them. The IgM and their supernatant were injected in parallel, intraperitoneally into rainbow trout (Oncorhynchus mykiss) to test passive protection against experimental furunculosis. Protection was observed in both cases (significant protection at 2%). However, only trout treated with IgM were still protected against polybacterial cross-infections which occurred 10 days later (significant protection at 1%). These results confirm the passive mammalian protection conferred by biologic fluids injected in vivo in fish and provide further evidence for participation of natural antibodies in antibacterial defences.

Animals↗
PubMed1992

Pericytes as a supplementary source of osteoblasts in periosteal osteogenesis.

In the adult rat femur, lifting a periosteum strip with microscopic bone flakes on its deep surface, if performed without damaging the surrounding microcirculation, rapidly leads to new bone formation and angiogenesis. Using vascular labeling, the pericytes and endothelial cells (ECs) were labeled with monastral blue (MB) in the preformed, preexisting postcapillary venules of the periosteal microcirculation. MB was detectable by light and electron microscopy and it persisted in some of the daughter cells. Between one and 21 hours, the MB labeling was restricted to the pericytes and ECs of postcapillary venules. Immediately afterward, both pericytes and ECs of these vessels were activated and continued to show MB. The phenomenon of pericyte activation includes enlargement, disruption of their basal lamina, separation from the walls of the preformed vessels, and the presence of mitotic figures. At this stage, activated pericytes with MB in their cytoplasm, fibroblast-like cells, and transitional cell forms between them were seen in interstitial areas. After 27 hours, vascular buds appeared and MB was detected in some ECs and pericytes. Between three and six days, when bone-tissue development was observed, some osteoblasts were MB labeled. Previous findings support the hypothesis that when the periosteum is activated, the process of bone formation from cells already present in the periosteum is augmented by proliferation and differentiation of pericytes, which contribute a supplementary population of osteoprogenitor cells.

Animals↗
PubMed1991

Emergency intracardiac defibrillation for refractory ventricular fibrillation during routine electrophysiologic study.

Ventricular fibrillation refractory to cardiopulmonary resuscitation including multiple transthoracic defibrillations occurred in four patients during 1,215 consecutive ventricular tachycardia induction studies. A technique of emergency intracardiac defibrillation for management of refractory ventricular fibrillation is described. In four patients, stable monomorphic ventricular tachycardia (320 to 570 ms cycle length) was induced during the study and overdrive ventricular pacing resulted in ventricular fibrillation. These patients did not respond to prompt transthoracic defibrillations (5 to 15 attempts/patient) and cardiopulmonary resuscitation, including antiarrhythmic therapy. As a last resort, intracardiac defibrillation was performed with use of a previously inserted standard right ventricular quadripolar catheter as cathode and a posterior skin patch as anode. High energy intracardiac defibrillation pulses (100 to 500 J) delivered from a standard defibrillator successfully terminated each arrhythmia. Intracardiac defibrillation is technically simple and appears effective in terminating refractory ventricular fibrillation in the electrophysiology laboratory. However, further research is necessary to determine the safety and efficacy of this technique, as well as potential applications in other emergency settings.

Aged↗
PubMed1991

A pharmacokinetic model describing the removal of circulating radiolabeled antibody by extracorporeal immunoadsorption.

Extracorporeal immunoadsorption is a new technique for removal of circulating radiolabeled antibody from the peripheral blood (1) to reduce background activity for improved tumor imaging, and (2) to reduce whole-body and marrow toxicity when high doses of radiolabeled antibodies are used for antitumor therapy. A pharmacokinetic model was developed to describe plasma disappearance of 111In-KC-4G3 prior to, during, and after immunoadsorption in humans. The model is developed based on a two-compartment open model, and during immunoadsorption a third compartment is added for removed radioactivity by the immunoadsorption column. Goodness-of-fit statistics indicate a good fit of the model to the data. The resulting pharmacokinetic parameters for a selected patient are V1 = 2.64 L, VSS = 3.64 L, t 1/2 alpha = 3.77 hr, and t 1/2 beta = 48.5 hr. The immunoadsorption clearance (CLIA = 19.3 ml/min) was 21-fold greater than the patient's plasma clearance (CL10 = 0.899 ml/min), indicating a very effective immunoadsorption process. The model predicts an increase in plasma radioactivity upon termination of immunoadsorption, probably due to redistribution of radioactivity from the extravascular compartment to the plasma in response to the rapid decline in plasma radioactivity during immunoadsorption. Two series of simulations were performed to examine the influence of onset time and duration of immunoadsorption. In series one the onset time was varied and in series two immunoadsorption duration was varied. In series one, the predicted radioactivity amounts adsorbed by the immunoadsorption column ranged from 75% of the injected dose (4-hr onset) to 52% of the injected dose (24-hr onset). In series two, immunoadsorbed radioactivity ranged from 32% (2-hr duration) to 64% of the injected dose (12-hr duration). When instituted as early as 4 hr, the predictions suggest that earlier immunoadsorption onset improves the effectiveness of radioactivity removal, relating to higher early circulation concentrations, and longer immunoadsorption periods remove more radioactivity, but also result in larger predicted radioactivity redistribution form tissue to plasma. To employ the immunoadsorption procedure for tumor imaging and therapy optimally, the data and our predictions indicate that a compromise must be made that will balance immunoadsorption onset and duration against tumor radioactivity uptake and subsequent radioactivity redistribution from tissues back to plasma. Together with biologic considerations providing sufficient antigen-antibody interaction and dependent on the utilized radioisotope, these data support the utility of extracorporeal immunoadsorption during the radioimmunodetection of cancer and for future therapeutic applications.

Adsorption↗
PubMed1991

Syncope: etiology, prognosis, and relationship to age.

Syncope is a common and particularly troublesome problem in the elderly population. In a series of 146 patients admitted for syncope to an acute care hospital in Chile during a 4-year period, 2/3 (68%) were aged 65 years and older. A specific etiology could be established in 62%, and 3/4 of these were cardiovascular in origin. Diagnosis was established entirely on history, physical examination, resting ECG, and 24-hour cardiac monitoring in most cases but in some, more sophisticated measures (i.e., echocardiography, electrophysiologic studies, blood tests, EEG) were needed, and mostly to confirm clinically suspected problems. In-hospital mortality was 2.1% and mortality at the end of the approximately 2-year follow-up period was 18.1%. Mortality was higher for persons over age 65 than for younger persons (23.9% vs 2.3%), and for persons with cardiovascular syncope than for persons with other kinds of syncope (28.3% vs 8.9%). This study confirms the particular lethality of syncope in the elderly population and outlines a relatively simple strategy with which most syncope patients can be diagnosed without resorting to expensive procedures.

Adult↗
PubMed1991

Outcome of hydronephrosis diagnosed antenatally.

We evaluated 23 neonates with prenatally diagnosed dilatation of the renal pelvis involving 33 renal units. The dilatation was graded from 0 to 4 by ultrasonography. Diuresis renography was used to evaluate differential renal function. The patterns of the excretory curve following administration of furosemide were analyzed. Antegrade pyelography and pressure flow studies were done in selected patients. The mean follow-up was 34 weeks. The single most important prognostic indicator in this group of patients was the degree of dilatation on ultrasonography. Six of 7 renal units with grade I hydronephrosis improved and 1 remained stable on follow-up. Four of the 12 renal units with grade II hydronephrosis improved spontaneously; 1 remained stable. Three of 11 renal units with grade III hydronephrosis either improved or remained stable. The measurement of differential renal functions on DTPA renography did not correlate well with the degree of dilatation when renal size and parenchymal thickness were adequate. The excretory curves after lasix administration were not helpful to determine treatment in the neonatal period. Seventeen renal units (7 grade II, 9 grade III, 1 grade IV) were treated surgically due to persistent dilatation, evidence of obstruction on either DTPA renography or the Whitaker test, or because of impaired renal function. Sixteen of the 33 renal units diagnosed prenatally improved with observation. Of all the parameters studied only the degree of dilatation on ultrasonography correlated well with the prognosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1991

Hypospadias repair in an outpatient setting without proximal urinary diversion: experience with 113 urethroplasties.

A total of 113 consecutive patients underwent surgical repair of hypospadias. None had previously undergone a repair procedure. The median age of the patients at the time of surgery was 24 months (range, 5 months to 13 years). A meatal-based flap modified Mathieu technique was used in 48 children and a single- or double-faced transverse preputial island flap was used in 58 children. Urinary diversion was not performed. A 7F silicone rubber urethral stent with multiple perforations that drained freely was used in all cases. The stent was left indwelling for 7 days after meatal-based flap repairs and for 12 days preputial island flap repairs. Seventy-nine patients (70%) were discharged from the hospital the day of the operation. The results were cosmetically satisfactory in all cases. A total of 23 patients developed complications. Sixteen (14%) developed a urethrocutaneous fistula, 2 developed a stricture (1.7%), and 5 developed a urethral diverticulum (4.5%). There were no fistulas and only one stricture in the meatal based flap repairs. For 20 patients who suffered complications, a single outpatient surgical procedure corrected the problem. The remaining 3 patients required more than two surgical procedures. All complications were resolved within 12 months of the hypospadias repair.

Adolescent↗
PubMed1991

Prune belly syndrome in females: a triad of abdominal musculature deficiency and anomalies of the urinary and genital systems.

We describe seven female patients with deficient abdominal wall musculature and urinary tract and genital anomalies that represent the female equivalent of the prune belly syndrome. Urethral atresia, uterine duplication, and anorectal anomalies occurred frequently. The perinatal mortality rate was high; of the four surviving patients, renal failure developed in two and renal transplantation was required. The analysis of these cases suggests that urethral obstruction is an important factor contributing to the development of the prune belly syndrome in females.

Abdominal Muscles↗
PubMed1991

Seromuscular enterocystoplasty in rats.

Enterocystoplasty is commonly used in clinical practice. Many of its undesirable effects, that is infections, stones, mucus production, absorption of urinary components into the blood stream and risk of cancer, result from the intestinal mucosa lining the urinary tract. We report on the feasibility of creating an enterocytoplasty with a seromuscular colonic segment that acquires a transitional epithelial lining. Augmentation enterocystoplasty was performed in 51 male, 500 gm., Sprague-Dawley rats with a 1.82 cm.2 patch of left colon from which the mucosa had been stripped. The serosal surface was used as lining for the enterocystoplasty. The intestinal patch and the bladder capacity at known pressure were measured at operation and at sacrifice. The histology of the enterocystoplasty was studied in detail following sacrifice. Of the animals 40 survived without significant complications and were sacrificed at a mean postoperative time of 30 days (range 5 to 80 days). In the remaining 11 rats a bladder stone developed but it did not seem to affect the outcome of the experiment. The size of the patch could be measured in 22 rats: it was 1.82 cm.2 (standard deviation +/- 0.86) at operation and 2.30 cm.2 (standard deviation +/- 1.1) at sacrifice. In none of the rats did the patch decrease in size. The bladder capacity at a known pressure (mean 17 cm. water) could be measured in 26 animals: it was 2.35 ml. (standard deviation +/- 0.65) at operation and 5.18 ml. (standard deviation +/- 1.19) at sacrifice. Histological analysis was done in 40 rats. In all cases the serosal surface was lined with transitional epithelium, there was no fibrosis or inflammation and the structure of the muscular layer of the bowel remained intact. The earliest growth of uroepithelium in the serosal surface of the bowel was noted at 5 days. This model suggests that the seromuscular enterocystoplasty can be constructed successfully in the rat model. The seromuscular intestinal patch does not shrink. The bladder capacity increases and histology shows a uroepithelial lining of the augmentation.

Animals↗
PubMed1991

Preperitoneal approach for hernia repair: clinical application in pediatric urology.

The preperitoneal approach for inguinal hernia repair rarely is indicated in children. However, we report on its clinical usefulness for children in whom the perivesical space must be exposed, such as during surgical repair of bladder exstrophy, ureterocele and ureteral reimplantation. This approach allows for a true high ligation of the hernia sac, and the repair is safe, fast and effective.

Child↗
PubMed1991

Development of renal failure in children with the prune belly syndrome.

From 1970 to 1987, 32 male and female patients with the prune belly syndrome were evaluated. Of these patients 11 died as neonates or infants, and autopsy in 9 revealed 6 cases of diffuse and severe renal dysplasia. In the 10 surviving patients renal insufficiency developed and a total of 13 nephrectomies and renal biopsies were performed. Renal dysplasia was noted in 9 specimens, but unlike the infant kidneys, the dysplastic changes involved less than 25% of the parenchyma in most cases. Renal failure in these 10 patients was caused by pyelonephritis and obstruction. In our estimation perinatal renal failure in patients with the prune belly syndrome results from renal dysplasia caused by an in utero insult, while in older patients pyelonephritis and obstruction are the causes. Careful treatment of reflux, obstruction and urinary tract infections may decrease the incidence of renal failure in patients with the prune belly syndrome who survive infancy.

Adult↗
PubMed1991

Female effect in sheep. I. The effects of sexual receptivity of females and the sexual experience of rams.

When in contact with receptive or non-receptive ewes, the presence of females increased LH peak frequency both in experienced and inexperienced rams (P less than 0.05). The highest response was found in experienced rams stimulated by sexually receptive ewes. In this group only, the mean testosterone levels increased during stimulation (P less than 0.05). Sexual behavior did not differ between experienced and inexperienced males. The sexual receptivity of the females and the sexual experience of rams appear to interact and thus facilitate the rams' LH and testosterone responses to the presence of ewes.

Animals↗
PubMed1991

Female effect in sheep. II. Role of volatile substances from the sexually receptive female; implication of the sense of smell.

The importance of olfactory cues in inducing luteinizing hormone and testosterone secretion as a response to stimulation by sexually receptive ewes has been tested. In sexually experienced rams, olfactory stimulation with urine, wool and vaginal secretions from sexually receptive females placed in a mask did not induce an endocrine response. The female-induced secretion of LH and testosterone was similar in anosmic, sham-operated and in control rams. These results show that olfactory cues are not necessary in the mediation of interindividual stimulation of endocrine response in the sexually experienced ram.

Animals↗