Absorption of short chain fatty acids from the human jejunum.

Jejunal absorption of acetate, propionate, and butyrate--the three predominant short chain fatty acids (SCFA's) in small and large intestinal contents--was studied in 5 volunteer subjects. A triple-lumen perfusion technique was employed; the test solutions were isotonic and contained 0, 5, 10, 25, 40, or 50 mM of a SCFA as the sodium salt. Intermittent secretion of small amounts of acetate and butyrate occurred during 3 of 15 control perfusion periods, and the concentrations measured in intestinal samples exceeded those reported for circulating plasma. The three SCFA's were absorbed rapidly and at equal rates. Absorption rates rose in apparently linear fashion with the mean concentration in the study segment (up to 20 mM) but reached saturation at the higher concentrations present in the mixing segment. Water and sodium absorption increased slightly during butyrate absorption. The flow rate of fasting intestinal contents did not increase during SCFA perfusion. SCFA's are readily absorbed and do not exert a diarrheogenic effect in the normal human jejunum.

Major complications of coloscopy: bleeding and perforation.

The overall frequency and types of complications associated with diagnostic coloscopy and coloscopic polypectomy are unknown. A statewide survey of coloscopists was conducted to determine the morbidity and mortality associated with coloscopy. Twenty-eight physicians performed a total of 1,106 coloscopic procedures. 9 colonic perforations and 5 episodes of colonic bleeding resulted in a 1.3% complication rate. Explanations for several of the complications are identified and preventive measures proposed. 1 patient died of an unrecognized perforation of the sigmoid colon, resulting in a 0.09% mortality rate. Of 14 complications reported in this series, 12 occurred during the early experience (less that 40 procedures) of the coloscopist. Training programs in coloscopy need to be established in order to reduce the morbidity and mortality associated with a physician's early coloscopic experience.

Absorption of short-chain fatty acids from the human ileum.

Acetate, propionate, and n-butyrate are the major short-chain fatty acid (SCFA) anions in the gastrointestinal tract of animal and man, accounting for 90% of total SCFA in stool water. Their absorption from the human ileum was investigated in 8 volunteer subjects by the triple-lumen perfusion technique. Each test solution contained one of the SCFAs at a concentration of 0-100 mM; sodium, potassium, and bicarbonate concentrations were kept constant, as were pH and osmolality. Absorption of each SCFA was found to be rate-limited with an apparent K'm between 22 and 27 mM and a calculated Vmax between 0.54 and 0.82 mmol/hr cm. Water, sodium, and chloride transport were not affected by substantial rates of SCFA absorption. Rather, significant stimulation of calculated bicarbonate secretion and a rise in intraluminal pH were consistently observed. The results are compatible with either of two mechanisms for SCFA absorption: an anion exchange between bicarbonate (or hydroxyl) and SCFA ions, or protonation of the SCFA anion at the mucosal surface followed by simple diffusion of nonionized SCFA into the absorbing cell.

Alpha 1 antitrypsin deficiency: a study of the relationship between the Pi system and genetic markers.

Twenty-four members (4 generations) of a family with alpha 1 antitrypsin deficiency were studied in an attempt to determine the chromosomal location of the Pi system locus. Three alpha 1 antitrypsin alleles (PiM, PiI, and PiZ) and five phenotypes (MM, MZ, MI, IZ, and ZZ) were detected in family members. The quinacrine fluorescent banding technique was successfully utilized to reveal eight polymorphic chromosomal markers in family members. Eight red cell antigens and HL-A antigens were identified for each family member. No linkage between the Pi system and chromosomal markers, four polymorphic red cell antigens, and HL-A antigens was detected. On the basis of this family study, the Pi locus as defined by alpha 1 antitrypsin deficiency does not appear to be on chromosomes 2, 3, 13, 14, 21, or 22 within measurable distance of the markers used.

Watery diarrhea associated with pancreatic islet cell carcinoma.

A patient with severe watery diarrhea and a non-beta islet cell carcinoma of the pancreas producing five hormones (secretin, serotonin, enteroglucagon, vasoactive intestinal polypeptide, and pancreatic glucagon) is described. We have demonstrated massive pancreatic hypersecretion to be a major factor in this patient's diarrhea. Possible inter-relationships of the actions of five hormones present in excess in the patient are discussed.

Absorption of short-chain fatty acids by the colon.

Short-chain fatty acids (SCFAs) constitute the major solute fraction of normal stool water and are responsible for the diarrhea associated with carbohydrate (CHO) malabsorption. Although SCFA absorption from the human small bowel has been reported previously, the fate of SCFAs in the colon--their major site of production--was investigated in the present study. The colon of normal volunteers was perfused with neutral, isotonic solutions containing SCFA, 0-90 mM. Propionate was studied in detail with limited observations on acetate and n-butyrate. SCFA absorption was concentration-dependent; back diffusion of metabolic products, ketone bodies, was quantitatively insignificant. The transport process was accompanied by increased Na, K, and water absorption, by luminal alkalinization due to bicarbonate accumulation, and by a fall in lumen PCO2. The results are consistent with the existence of two mechanisms for colonic SCFA absorption: first, nonionic diffusion of protonated SCFA involving consumption of luminal CO2; this process accounts for about 60% of total SCFA absorption; and second, cellular uptake by ionic diffusion of the Na or K salt of the SCFA.

Optical limiting in solutions of diphenyl polyenes.

The optical-limiting behavior of a series of trans-alpha, omega-diphenyl polyene compounds was observed in solutions of chloroform. The influence of planarity, the substitution of donor and acceptor groups, and the extent of pi-electron delocalization on the nonlinear thresholds of the diphenyl polyenes in an optical-limiting geometry were examined. A saturation effect of optical-limiting nonlinear thresholds, consistent with the theoretical work, was observed at 10-11 pi-electron bonds. The temporal profiles of the transmitted laser pulses and the power dependence of the nonlinear thresholds as a function of spot size and wavelength were examined. These examinations led to the conclusion that the predominant nonlinear mechanism was quasi-steady-state self-focusing. Nonlinear thresholds an order of magnitude lower, and thus effective n(2) and X(3) values an order of magnitude higher, than the well-known self-focusing medium CS(2) were observed. Our studies demonstrate that this series of polyenes consists of efficient broadband nonresonant optical-limiting materials.