Binocular processing in the cat's dorsal lateral geniculate nucleus. III. Spatial frequency, orientation, and direction sensitivity of nondominant-eye influences

The present experiments examined the extent to which binocular processing in the cat's dorsal lateral geniculate nucleus (LGN) depends upon the spatial frequency, orientation, and direction of movement of stimuli presented to the nondominant eye. In Experiment 1, we tested the effects of varying these stimulus parameters on the responses of LGN cells to nondominant-eye stimulation. Sixteen of 34 cells tested had statistically significant responses to the nondominant eye and, in agreement with a previous study (Guido et al. 1989), the responsive cells were spatial-frequency sensitive. However, there was little evidence for orientation or direction sensitivity in responses to the nondominant eye: changes in discharge with changes in stimulus orientation and direction were small and were statistically significant in only nine of the cells. In Experiment 2, we tested the effects of varying spatial frequency, orientation, and direction of movement of stimuli presented to the nondominant eye on its ability to influence responses to the dominant eye (i.e., on binocular interactions). The dominant eye was stimulated with the optimal spatial frequency for the cell being tested. For 22 of 45 cells tested, nondominant-eye stimulation had a statistically significant effect on the response to the dominant eye. Fourteen of these cells showed band-pass spatial-frequency sensitivity in the nondominant-eye influence, and eight showed low-pass spatial-frequency sensitivity. However, only 11 of the cells had statistically significant variations in their binocular interactions that depended on the orientation or direction of stimuli presented to the nondominant eye. Furthermore, even for those cells, the effect of varying orientation and direction was only about half as strong as the effect of varying spatial frequency. We conclude that binocular processing in the LGN, including responses to the nondominant eye and nondominant-eye influences on responses to the dominant eye, are affected significantly by the spatial frequency of the nondominant-eye stimulus and relatively little by stimulus orientation or direction of movement. The significance of these findings for understanding the functions of LGN binocular processing is discussed.

Effect of duodenal switch procedure on gastric acid production, intragastric pH, gastric emptying, and gastrointestinal hormones

The duodenal switch operation preserves the pylorus and the proximal 3 to 7 cm of duodenum in continuity with the stomach while diverting pancreaticobiliary secretions. We compared it with the Roux-en-Y without vagotomy or antrectomy in 12 dogs with innervated gastric pouches. Acid secretion was inhibited between tests using ranitidine in the Roux-en-Y group only, but two of the six dogs still developed stomal ulcers and the remainder showed stomal hyperemia. This may be due to a significant increase in gastric acid output after Roux-en-Y, but gastric emptying and plasma gastrin, cholecystokinin, secretin, gastric inhibitory polypeptide, peptide YY, and neurotensin were similar after both procedures. In 12 patients and a further 6 dogs, the duodenal switch caused no significant change in the intragastric pH environment as assessed by intragastric pH monitoring. The duodenal switch is a suitable procedure for pancreaticobiliary diversion.

Isolation and structural characterization of a molecular variant of dog pancreatic secretory trypsin inhibitor

A rapid two-step method has been developed for the purification of pancreatic secretory trypsin inhibitor (PSTI) from pancreatic juice obtained from dogs, stimulated with secretin and the octapeptide of cholecystokinin. The PSTI was isolated in two biologically active molecular forms. Determination of amino acid compositions and NH2-terminal amino acid sequences demonstrated that the major form represented the intact 57-amino-acid residue peptide, and the minor form (comprising 5-10% of the total activity) represented des[Asn1 Asn2 Met3] PSTI. The metabolite arises from cleavage of a Met-Leu bond, and its formation may be a consequence of incomplete inhibition of chymotrypsinogen activation in the juice.

The cause of dysphagia in uncomplicated sliding hiatal hernia and its relief by hiatal herniorrhaphy. A roentgenographic, manometric, and clinical study

Patients with an uncomplicated sliding hiatal hernia frequently experience dysphagia. The present study shows, using video barium contrast esophagograms, that the cause of dysphagia in 60% of these patients is an obstruction to the passage of the swallowed bolus by diaphragmatic impingement on the herniated stomach. Manometrically this was reflected by a double-hump high pressure zone (HPZ) at the gastroesophageal junction, and specifically to the length and amplitude of the distal HPZ and the length of the intervening segment between the two HPZs. The former represents the degree of the diaphragmatic impingement on the herniated stomach and the latter the size of the supradiaphragmatic herniated stomach. Surgical reduction of the hernia resulted in relief of dysphagia in 91% of the patients.

Effects of oral administration of tin and zinc protoporphyrin on neonatal and adult rat tissue heme oxygenase activity

The purpose of this study was to investigate if oral metalloporphyrin treatment could suppress intestinal heme oxygenase (HO) activity and thus prevent HO-mediated heme degradation in this organ. Six hours after a single 40 mumol/kg oral dose of tin protoporphyrin (TP), zinc protoporphyrin (ZP), or heme to adult rats, no significant difference in the HO activity of the intestine was observed relative to control tissues. Moreover, the activity was not inhibited by in vitro exposure to 40 microM TP or ZP. Liver and spleen HO activity was also not significantly inhibited in vivo after oral administration of metalloporphyrins; however, in vitro exposure to TP or ZP decreased the HO activity of preparations from these organs significantly. Like adults, the intestinal HO activity of neonates was not inhibited effectively by oral administration of either metalloporphyrin. The results of subsequent in vitro exposure of control neonatal tissue preparations to ZP or TP was similar to those using adult tissue preparations. Even at 100 microM, only ZP seemed to have some in vitro inhibitory effect on the intestinal HO of suckling rats. We conclude that intestinal HO is less inhibitable by TP or ZP reaching the intestine via the stomach in concentrations at least 30-fold greater than those achieved after parenteral 40 mumol/kg doses, which cause significant hepatic and splenic HO inhibition. Intestinal absorption and enterohepatic circulation of heme, TP, and ZP do not seem to occur in amounts sufficient to consistently and significantly affect HO activity in liver or spleen.

Lack of inhibition of intestinal heme oxygenase by antibiotics and tin-protoporphyrin

We assessed the in vivo and in vitro effects of antibiotics and tin-protoporphyrin (TP) on intestinal heme oxygenase (HO) activity using a gas chromatographic assay. This method measures the carbon monoxide produced from heme in the presence of NADPH. After in vivo administration of kanamycin (10 mg/kg body weight), ampicillin (200 mg/kg body weight) or neomycin (60 mg/kg body weight) with or without TP (65 mumol/kg body weight) to suckling rats, no significant difference in HO activity along the small intestine was observed. In vitro exposure of adult rat intestinal preparations to the antibiotics showed no significant decrease in HO activity between control and experimental tissue preparations. A concentration-dependent stimulatory effect of neomycin was observed. Subcutaneous administration of TP (25 mumol/kg body weight) to adult male Wistar rats revealed no significant inhibition of the intestine. However, in vitro addition of TP (12.5 microM) to the control tissue preparations of adult Wistar rats revealed highly significant inhibition in liver and spleen when compared to the unexposed control tissues. In contrast, when TP was added to control intestinal preparations no inhibition was observed. These findings suggest that suckling rat intestinal heme oxygenase is not inhibited by in vivo treatment with high concentrations of kanamycin, ampicillin, or neomycin. Furthermore, these antibiotics are not in vitro inhibitors of adult rat intestinal HO. Finally, adult rat intestinal HO is not inhibited either in vivo or in vitro by a concentration of TP that significantly inhibits liver and spleen activity.

In vitro carbon monoxide production by the small intestine of suckling and adult Wistar rats: effect of parenteral tin-protoporphyrin

Single subcutaneous doses (25 mumol/kg body weight) of tin-protoporphyrin (TP), a potent competitive inhibitor or heme oxygenase (HO), were administered to both suckling and adult Wistar rats. The effect of TP on the carbon monoxide excretion rate (VeCO), an index of total bilirubin formation, and on in vitro carbon monoxide (CO) production by the small intestine were evaluated. Whereas the VeCO of the adult group was decreased (p less than 0.0005) after TP, that of the suckling rat was unchanged. Gradients of CO production along the small intestine were observed in sucklings as well as adults; however, these gradients were in opposite directions. Intestinal CO production was greatest in the adult duodenum, decreasing distally; conversely, the CO production was greatest in the suckling ileum, decreasing proximally. No significant difference in CO production between control and TP-treated adult intestinal mucosa was observed. In sucklings, a significant reduction of intestinal CO production in the TP-treated rats was detected in the duodenum only (p less than 0.05). The results suggest that suckling rats differ from adults in terms of the capacity to produce CO and the direction of the gradient of CO production along the intestine. We conclude that (1) TP may not substantially decrease the in vivo production of CO by the small intestine at a dose which inhibits hepatic and splenic heme oxygenase, and (2) because after a heme load, heme is excreted into the intestine after TP administration, heme-degrading, CO-producing processes in the intestine may contribute to an animal's VeCO under such conditions.

Tin protoporphyrin inhibits carbon monoxide production in suckling mice

The carbon monoxide excretion rate (VeCO) of groups of 1-day-old mice was measured after administration of two separate doses of 50 nmol of tin protoporphyrin (TP) per gram of body weight. The mean VeCO of the saline-treated control groups over the study period was 1.50 +/- 0.26 nmol/g/h, and that of the TP-treated groups was 1.35 +/- 0.29 nmol/g/h. Tin protoporphyrin treatment reduced the CO excretion by approximately 14% in 2-day-old mice over 24-48 h.

Syndrome of growth resistance, obesity, and intellectual impairment with precocious puberty

A syndrome of growth resistance, obesity, and intellectual impairment with precocious puberty is described. Two girls presenting with many of the manifestations of the Prader-Willi syndrome, including growth resistance, obesity, and intellectual impairment, also exhibited precocious sexual maturation. It is suggested that this syndrome represents a hypothalamic disturbance closely related to the Prader-Willi syndrome and should be considered one of its variants.