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Biomedical subjects

K Gross

Publications and source records attributed to K Gross.

At least 55 records · Page 3Linked to original sources
PubMed1988

Electrophysiology and metallosis: support for an oxidative (free radical) mechanism in the human eye.

Nine cases of metal intraocular foreign body are presented. This study investigates the use of electrodiagnostic techniques in the diagnosis of metallosis and as a prognostic indicator. The electro-oculogram (EOG) and the electoretinogram (ERG) indicate that there are two mechanisms of metallosis, one of which involves cytotoxic damage by siderosomes, and the other lipid peroxidation of photoreceptor outer segments and retinal pigment epithelium. The evidence suggests that the location of the foreign body in the eye determines whether either or both of these mechanisms occur. We propose that these tests can help the ophthalmologist decide when a foreign body has to be removed and give information as to the mechanism of the pathological process.

Biomechanical Phenomena↗
PubMed1985

Bacterial clearance in the intact and regenerating liver.

The Kupffer cells in the liver play an important role in reticuloendothelial system (RES) function by clearing particulate matter and bacteria from the blood stream. While hepatocyte regeneration and function have been extensively studied following partial hepatectomy, little information is available concerning RES function in the regenerating liver. This study investigates hepatic RES function by evaluating bacterial clearance (live E. coli) in the intact and regenerating liver. Thirty-four young male Sprague Dawley rats were studied. Twenty-two animals underwent a standard 70% partial hepatectomy using ligature technique and 12 had a sham operation. Both groups of rats received 10(9) organism of S35 labeled E coli, intravenously at 24 hours, 72 hours, 2 1/2 weeks, and 6 weeks postoperatively. Rats were killed 10 minutes following injection and liver, lung, spleen, and kidney harvested, fixed, and radioactivity was determined using a scintillation spectrometer interfaced with a micro-computer counting the S35 radiolabel. The total organ count of trapped bacteria in liver in partially hepatectomized rats was lower than intact controls at 24 hours (22.0% v 46.4%, P less than .01), but was similar at 72 hours, 2 1/2 weeks, and 6 weeks. Partial hepatectomy increased the amount of bacterial trapping in the lung at 24 hours (11.3% v 1.7%, P less than .01) and 72 hours (10.1% v 1.7%, P less than .05) and returned to normal at 2 1/2 weeks and 6 weeks. Splenic activity was increased following hepatectomy at 2 1/2 weeks. Renal clearance was increased at 72 hours and 2 1/2 weeks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Intra-abdominal complications of cystic fibrosis.

In recent years patients with cystic fibrosis (CF) have experienced longterm survival and have demonstrated a number of intra-abdominal complications. This report evaluates the intra-abdominal complications seen in 69 of 189 children with cystic fibrosis from 1972 to 1983. Forty-one patients were boys and twenty-eight girls. Complications occurred in 36 neonates, with meconium ileus (MI) noted in 33 and giant cystic meconium peritonitis (GCMP) in 3. Meconium ileus equivalent occurred in seven older children presenting with bowel obstruction. In addition, rectal prolapse occurred in 12, inguinal hernia in 10, intussusception in 3, cholelithiasis in 3, GE reflux in 4, stress ulcer in 1 and appendicitis in 1. Three infants with GCMP survived resection and enterostomy. Infants with MI were divided into simple (15) or complicated (18) cases. Nonoperative therapy using gastrografin enema was successful in three of eight with simple MI. Operative enterotomy and irrigation was successful in three cases while resection and enterostomy was done in nine. MI was complicated by atresia, volvulus and/or perforation in 18 cases requiring resection and anastomosis or enterostomy. Survival for MI was 86% compared to 36% in 25 MI patients treated in the previous two decades. Meconium ileus equivalent was successfully managed using gastrografin enema in five of seven children. Only 3 of 12 children with rectal prolapse required repair. Two cases of intussusception were reduced while one required resection. Three of 10 children had hernia recurrence due to chronic pulmonary problems.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdomen↗
PubMed1984

Effects of unequal alternating monocular exposure on the sizes of cells in the cat's lateral geniculate nucleus.

In unequal alternating monocular exposure, each eye receives normal patterned input, but on alternate days and for unequal periods. This imbalance in stimulation produces a behavioral deficit for the less-experienced eye and alters the ability of that eye to activate cortical cells. To determine whether unequal alternating exposure also affects the sizes of cells in the lateral geniculate nucleus (LGN), we measured the cross-sectional areas of geniculate neurons in seven normally reared cats, 14 cats reared with equal alternating exposure, and 17 cats reared with unequal alternating exposure. We found that, in the LGNs of cats reared with unequal alternating monocular exposure, cells in layers that received their input from the less-experienced eye were smaller than those in layers that received their input from the more-experienced eye. This effect was restricted to the binocular segments of the nucleus, and the difference in cell size was a function of the imbalanced exposure, rather than the length of exposure per se. In control groups given balanced alternating exposure, cell size was not correlated with the length of daily exposure. In cats reared with unequal exposure, the change in cell size was greater in the nucleus ipsilateral to the less-experienced eye. Further, the size of the effect was correlated with the size of the imbalance imposed during rearing: Cats reared with a moderate imbalance (8 hours/day vs. 4 hours/day) showed less change in cell size than cats reared with a large imbalance (8 hours/day vs. 1 hour/day). These results are consistent with those of behavorial and physiological studies and strongly suggest (1) that unequal alternating monocular exposure affects the sizes of cells in the LGN by altering the normal competitive balance between the retinogeniculocortical pathways from the left and right eyes, and (2) that the contralateral pathway has some inherent advantage in this competition. We also found a slight shrinkage of cells in the LGNs of cats reared with equal alternating monocular exposure. Since this effect was restricted to the binocular segments of the nucleus, and was not related to the length of exposure given, it was probably caused by the imbalanced binocular competition that occurred during each day's monocular exposure.

Animals↗
PubMed1984

Bupropion does not antagonize cardiovascular actions of clonidine in normal subjects and spontaneously hypertensive rats.

Tricyclic antidepressants (TADs) are known to antagonize the hypotensive and sedative actions of clonidine. We compared the effects of bupropion and imipramine pretreatment on the acute hypotensive and sedative actions of clonidine in eight normotensive male subjects in a randomized, double-blind crossover study. Pretreatment with bupropion, 100 mg by mouth three times a day for 9 days, had no effect on baseline supine blood pressure (BP) and heart rate (HR) and did not modify the hypotensive, bradycardic, and sedative actions of clonidine. Imipramine, 25 mg by mouth three times a day for 9 days, increased supine and standing HR and decreased standing systolic BP. In half the subjects the hypotensive action of clonidine was reduced 40% to 50% by imipramine. The specific binding of 3H-yohimbine to alpha 2-receptors of platelet membranes was not affected by pretreatment with either antidepressant. In spontaneously hypertensive rats, 16 days of bupropion, 25 mg/kg subcutaneously, had no effect on baseline BP and HR and did not antagonize the hypotensive and bradycardic effects of clonidine, 5 mg/kg iv. Pretreatment with desipramine, 5 mg/kg subcutaneously for 16 days, accelerated baseline HR and reduced cardiovascular actions of clonidine. These observations suggest that not all antidepressants antagonize the effects of clonidine. If the negative interaction between TADs and clonidine is a result of sensitivity of alpha 2-receptors, these receptor changes are not the common denominator of antidepressant activity and may only be seen with TADs.

Adult↗
PubMed1984

Impaired bacterial clearance and trapping in obstructive jaundice.

Sepsis is a major cause of mortality in patients with common bile duct obstruction. To define possible contributing factors to this phenomenon, this study evaluates the effect of biliary obstruction on the intravascular clearance and organ trapping of viable Escherichia coli using a rat model. Adult male Sprague-Dawley rats were placed in three groups: Group I controls had sham operation, Group II had division and ligation of common bile duct (CDL), and Group III underwent splenectomy. At 21 days following operation 10(9) radiolabeled E. coli were injected intravenously. At varying intervals after infusion, blood samples were obtained for clearance study. At 10 minutes, bacterial distribution in the liver, spleen, kidneys, and lungs was determined (expressed as the mean percentage of injected viable E. coli). Intravascular clearance was similar in all groups. There was a significant decrease in the trapping of bacteria by the liver of CDL rats 14.5% +/- 4.95 (vs. control = 70.0% +/- 13.3) (p less than 0.005). A significant increase of bacterial trapping by the lung was observed in the CDL animals: 63.1% +/- 7.06 (vs. controls 1.4% +/- 0.82) (p less than 0.005). There was no significant change in bacterial localization in splenectomized rats. These data suggest that biliary obstruction decreases hepatic phagocytosis and increases pulmonary localization of viable E. coli. As the Kupffer cells of the liver are usually effective in removal of blood borne bacteria, this phagocytic dysfunction may contribute to the increased susceptibility to infection noted in instances of biliary obstruction.

Animals↗
PubMed1983

Mitral valve E point to ventricular septal separation in infants and children.

This investigation establishes heretofore unavailable norms that permit clinical application of mitral valve E point to ventricular septal separation (EPSS) as an ejection phase index in infants and children. The study consisted of 105 normal subjects (1 day through 15 years of age, mean 7.4 years) and 67 patients of comparable age. Fifty-seven patients had increased left ventricular (LV) volume with normal function (ventricular septal defect or patent ductus arteriosus) and 10 patients had increased LV volume with depressed function (dilated cardiomyopathy). In normal subjects, EPSS was 2.5 +/- 1.7 mm and "normalized" EPSS, that is, the ratio of EPSS to end-diastolic dimension (EPSS/EDD), was 0.08 +/- 0.06 (mean +/- standard deviation); there was no correlation between either of these indexes and age, body surface area, height or weight. In patients with ventricular septal defect or patent ductus arteriosus, or both, the EPSS and EPSS/EDD were similar to those of normal subjects (3.2 +/- 2.3 mm and 0.09 +/- 0.06 mm, respectively). In patients with dilated cardiomyopathy, these indexes were significantly increased (p greater than 0.05) (EPSS 16.5 +/- 5.1 mm; EPSS/EDD 0.39 +/- 0.09). The data provide normal values for EPSS and EPSS/EDD in infants and children and show that these indexes are independent of age, body surface area, height or weight. Mitral valve EPSS and EPSS/EDD can now be used in pediatric echocardiography as a simple, practical and accurate means of separating normal from abnormal LV function.

Adolescent↗
PubMed1983

Comparative effects of indomethacin, prostaglandin E1, and ibuprofen on bowel ischemia.

This study evaluates the effects of Indomethacin (IND), Prostaglandin E1 (PGE1), and Ibuprofen (IBP) in a bowel ischemia model. Laparotomy was performed in 80-gram rats (n = 260). Transient ischemia was induced by a one minute occlusion of the superior mesenteric artery. Animals were placed in five experimental groups: (I) ischemic controls (n = 80), (II) PGE1, 80 micrograms/kg IV (n = 20), (III) IBP, 12.5 mg/kg IV (n = 60), (IV) IND 15 mg/kg IV (n = 80) and (V) PGE1 + IND (n = 20). All medications were given just prior to laparotomy. Animals were evaluated for survival, length of survival and the presence of bowel necrosis and/or perforation at seven days. Survival was 18% in controls and was reduced to 5% by IND (p less than .005). Improved survival was observed with PGE1 (35%), TBP (31%) and PGE1 + IND (35%). IND resulted in early death, while PGE1, IBP, and PGE1 + IND all increased the length of survival (p less than .05). IND-treated rats had a high incidence of bowel perforation (greater than 40%). PGE1 reversed this effect when given concomitantly with IND. IBP had a significantly lower incidence of intestinal necrosis. These data suggest that infants treated with IND who are at risk for NEC should be carefully monitored for evidence of bowel necrosis. PGE1 and IBP may have a cytoprotective role in subjects at risk for bowel ischemia.

Alprostadil↗
PubMed1983

Characterization of mutants of herpes simplex viruses, types 1 and 2, that produce fragments of the thymidine kinase polypeptide.

Seven tk- mutants of herpes simplex virus, type 2 (HSV-2), and three tk- mutants of herpes simplex virus, type 1 (HSV-1), were isolated which did not produce the thymidine kinase (TK) polypeptides but formed smaller polypeptides not seen in wild-type infected cells. Positive TK mRNA selection by hybridization to the cloned tk genes followed by in vitro translation identified the TK polypeptides. Comparisons of the products of partial proteolysis of the polypeptides of four HSV-2 and two HSV-1 tk- mutants to those of the parental TK polypeptides indicated that, in each case, the novel polypeptide was a fragment of the TK polypeptide, showing that these mutants have defects in the structural gene for tk. HSV-2 mutants of this sort have not been previously described. They and the HSV-1 mutants are similar to HSV-1 mutants reported previously. In addition, it was found that TK mRNA was present early in infection but was absent late in infection, suggesting that the shutoff of TK synthesis is due to message degradation. Also, HSV-2 TK mRNA did not hybridize to the cloned HSV-1 tk gene indicating that these genes have extensively diverged.

Chymotrypsin↗
PubMed1981

Adjustment of weanling and adolescent rats to a reward condition requiring slow responding.

The effects of a schedule of discontinuously negatively correlated reinforcement (DNC), in which only approach responses that take 5 sec or longer are reinforced, were studied in weanling rats that began training at 18 days of age and adolescents that began training at 60 days. Yoked partially reinforced subjects (PRF) received rewards on the same trials as corresponding DNC subjects of the same age, whereas continuously reinforced subjects (CRF) were rewarded on all trials. At the end of DNC training (210 trials), the older but not the younger DNC subjects were running slower than their yoked-PRF controls. The results are consistent with development of inhibition and suppression related to the developing brain, particularly the hippocampus.

Adaptation, Psychological↗
PubMed1980

Specific oculomotor deficit after acute methadone. I. Saccadic eye movements.

Changes in saccadic eye movements before and after up to 10 mg oral methadone were measured electrooculographically in nontolerant nondependent humans. Undershoot of initial saccades increased with increasing size of horizontal target displacement (to 36 degrees) from a central viewing position. Dosage as low as 5 mg caused significant increase in saccade undershoot especially to target displacements greater than 10-15 degrees. Latency from target displacement to onset of initial saccade also increased after methadone. These results, in combination with the lack of significant drug effect on latency between initial saccade and corrective saccade, and on initial saccade duration, maximum velocity, and time to maximum velocity indicate methadone action on specific sensory, rather than motor, components of saccadic response. The similarity of alteration of saccadic response after methadone and after lesion of the upper layers of the superior colliculus in primates, as reported in the literature, suggests that opiate binding sites in the upper layers of the superior colliculus may be physiologically active.

Adult↗
PubMed1980

Specific oculomotor deficit after acute methadone. II. Smooth pursuit eye movements.

Changes in smooth pursuit eye tracking of targets moving sinusoidally in horizontal and vertical planes before and after up to 10 mg oral methadone were measured electrooculographically in nontolerant nondependent humans. Methadone depressed the gain of horizontal tracking movements at most frequencies tested (0.2 - 1.6 Hz) without changing target-eye phase relationships. Lack of change in target-eye cross-correlation functions after methadone and examination of individual records indicate that gain reduction was due to the eye failing to follow the target to the full extent of target excusion (+5 degrees from eyes straight ahead view). Possible mechanisms and the practical consequences of methadone action on smooth pursuit were discussed.

Adult↗
PubMed1980

Naloxone and shuttlebox self-stimulation in the rat.

Rats self timed electrical brain stimulation on and off periods in a shuttlebox. Electrodes for self-stimulation were located either in the lateral hypothalamic area (LHA) or the periaqueductal gray (PAG). Doses of the narcotic antagonist, naloxone, were administered intraperitoneally immediately prior to self-stimulation testing. Doses of 1.0, 5.0, 10.0 or 50.0 mg/kg failed to alter shuttlebox self-stimulation behavior. These results are inconsistent with one lever-press self-stimulation study employing PAG electrodes [3], but agree with other studies using LHA electrodes [9, 15, 21, 24). Possible reasons for the discrepancy are suggested.

Animals↗