Dysferlin is a new marker for leaky brain blood vessels in multiple sclerosis

Dysferlin is a muscle protein involved in cell membrane repair and its deficiency is associated with muscular dystrophy. We describe that dysferlin is also expressed in leaky endothelial cells. In the normal central nervous system (CNS), dysferlin is only present in endothelial cells of circumventricular organs. In the inflamed CNS of patients with multiple sclerosis (MS) or in animals with experimental autoimmune encephalomyelitis, dysferlin reactivity is induced in endothelial cells and the expression is associated with vascular leakage of serum proteins. In MS, dysferlin expression in endothelial cells is not restricted to vessels with inflammatory cuffs but is also present in noninflamed vessels. In addition, many blood vessels with perivascular inflammatory infiltrates lack dysferlin expression in inactive lesions or in the normal-appearing white matter. In vitro, dysferlin can be induced in endothelial cells by stimulation with tumor necrosis factor-alpha. Hence, dysferlin is not only a marker for leaky brain vessels, but also reveals dissociation of perivascular inflammatory infiltrates and blood-brain barrier disturbance in multiple sclerosis.

Effect of diet on fat cell size and hormone-sensitive lipase activity

This study was designed to examine the relationship between diet-induced insulin resistance/hyperinsulinemia, fat cell hypertrophy, and hormone-sensitive lipase (HSL) to elucidate whether an attenuated HSL activity leads to obesity. Female Fischer 344 rats were fed either a low-fat, complex-carbohydrate diet or a high-fat, refined-sugar (HFS) diet for 2 wk, 2 mo, or 6 mo. Adipose tissue morphology and HSL activity as well as plasma free fatty acid and glycerol levels were determined at these times. No differences between groups were seen after 2 wk except the previously reported hyperinsulinemia in the HFS animals. At both 2 and 6 mo, the HFS animals demonstrated adipocyte hypertrophy. Basal and stimulated HSL activities and plasma glycerol were significantly elevated in the HFS group. There was a positive correlation between adipocyte size and HSL activity for both basal and stimulated states. These results demonstrate that an attenuated HSL activity is not observed with the onset of insulin resistance/hyperinsulinemia and therefore does not play a role in the development of obesity.

Diet-induced insulin resistance precedes other aspects of the metabolic syndrome

This study was designed to examine the effects of a high-fat refined-sugar (HFS) or a low-fat complex-carbohydrate (LFCC) diet on insulin-stimulated skeletal muscle glucose transport, plasma insulin, blood pressure, plasma triglycerides, plasma glycerol, body weight, and body fat in female Fischer rats. Insulin-stimulated glucose transport was significantly reduced in the HFS group at 2 wk, 2 mo, and 2 yr, whereas serum insulin was significantly elevated at all time points. Blood pressure was not significantly elevated in the HFS group until 12 mo, and all HFS animals were hypertensive by 18 mo. Glycerol, triglycerides, and abdominal fat cell size were not significantly different at 2 wk but were significantly elevated in the HFS rats at 2 and 6 mo. Body weight was similar in both groups until 20 wk on the diet, when the HFS rats started to gain more weight. These results demonstrate that insulin resistance and hyperinsulinemia occur before the other manifestations of the metabolic syndrome and that diet, not obesity, is the underlying cause.

Tuberculosis among foreign-born persons in New York City, 1992-1994: implications for tuberculosis control

OBJECTIVE

To study the pattern of transmission of tuberculosis (TB) among foreign-born persons living in New York City.

DESIGN

A retrospective multicenter study comparing 158 foreign-born patients to 231 US-born patients diagnosed with TB between 1992 and 1994. The patients were stratified according to their Mycobacterium tuberculosis isolate DNA fingerprint patterns.

RESULTS

Nineteen (16%) of 122 isolates from foreign-born TB patients and 75 (42%) of 180 isolates from US-born TB patients had DNA fingerprint patterns (cluster patterns) indicative of recent exogenous transmission (P < 0.001). All cluster pattern strains from foreign-born cases were identical to those found among US-born patients. The likelihood of infection with a cluster pattern strain among foreign-born persons increased with duration of residence in the US, and was significantly associated with being homeless (P < 0.05), or having multidrug-resistant TB (P = 0.00072).

CONCLUSION

Although most (84%) cases of TB among foreign-born persons in New York City appear to result from reactivation of infections they acquired abroad, the ones who acquire new infections become infected with strains that are already circulating among the US-born TB patients in New York City, and they have risk factors similar to those faced by US-born tuberculosis patients.

Tuberculosis among urban health care workers: a study using restriction fragment length polymorphism typing

Cases of tuberculosis identified during 1992-1994 through an active tuberculosis surveillance network among six hospitals that serve New York City (the TBNetwork) were analyzed according to the occupational status of the patients. Clinical data were obtained by review of medical records, and restriction fragment length polymorphism (RFLP) typing of Mycobacterium tuberculosis isolates was performed. No known nosocomial outbreaks of tuberculosis occurred at these hospitals in the study period. Occupational status was known for 142 of 201 patients whose isolates were available for strain typing. Patients infected by organisms with a clustered strain typing pattern, as determined by RFLP analysis, were presumed to have recently acquired disease. RFLP typing revealed that isolates from 13 (65%) of 20 health care workers and 50 (41%) of 122 non-health care workers had a clustered RFLP pattern. The strains infecting eight (89%) of nine health care workers seropositive for human immunodeficiency virus (HIV) had a clustered RFLP pattern. Multivariate analysis of 75 patients with known HIV and occupational status revealed that HIV status (P = .03) and health care worker status (P = .02; RR = 2.77) were independent risk factors for a clustered RFLP strain. These findings suggest that many of the apparently sporadic cases of tuberculosis among health care workers may be due to unrecognized occupational transmission.

Peptide YY augments postprandial small intestinal absorption in the conscious dog

Since feeding increases intestinal fluid and electrolyte losses in short bowel syndrome, an agent increasing postprandial small bowel absorption might have a therapeutic role. Peptide YY (PYY) has recently been shown to increase net small bowel absorption under basal conditions. The aim of this study was to determine whether PYY can also augment postprandial absorption. Exteriorized, neurovascularly intact jejunal and ileal segments (25 cm Thiry-Vella loops) were created in dogs (n = 6) and gastrointestinal continuity was restored. Luminal perfusion with [14C]polyethylene glycol was used to calculate the change in water (H2O) and sodium (Na+) and chlorine (Cl-) ion fluxes after an oral meal. Changes in fluxes were also determined after a 2-hour infusion of a physiological dose of PYY (100 pmol/kg per hour). In a third series of experiments, fluxes were measured after a meal, during PYY infusion. Feeding increased small bowel absorption of fluid and electrolytes independent of the luminal content. This effect persisted for 2 hours after the meal. PYY infusion significantly augmented this proabsorptive response in both jejunum and ileum. These results suggest that PYY-agonists may have a therapeutic role in conditions such as short bowel syndrome where postprandial absorption is reduced.

Indolent carcinoid tumor of the sigmoid colon

Carcinoid tumors of the colon are a rare cause of colonic malignant disease. A case of carcinoid tumor of the sigmoid colon is presented that illustrates the indolent course of this type of tumor. The case presented highlights the clinicopathologic features of carcinoid tumors of hindgut origin, including advanced local and widely metastatic disease at the time of diagnosis in the absence of symptoms of the carcinoid syndrome. The diagnosis and management of gastrointestinal carcinoid tumors are reviewed.

Peptide YY is a physiological regulator of water and electrolyte absorption in the canine small bowel in vivo

BACKGROUND

Peptide YY (PYY), a hormone released following a meal, is one potential mediator of intestinal absorption. Although PYY inhibits 5'-cyclic adenosine monophosphate (cAMP)-stimulated small intestinal secretion in vitro, its effects on fluid and electrolyte transport in vivo are unknown.

METHODS

This study examines the effects of physiological doses of PYY in dogs (n = 6) with jejunal and ileal exteriorized, neurovascularly intact intestinal loops (Thiry-Vella fistulas).

RESULTS

Plasma PYY levels increased after a meal from 155 +/- 15 to 324 +/- 26 pmol/L at 30 minutes and remained elevated for 2 hours. PYY infused intravenously in unfed animals at 25, 50, 100, and 200 pmol.kg-1.h-1, produced a dose-dependent increase in plasma PYY levels. At 100 pmol.kg-1.h-1, PYY plasma concentrations were similar to those of fed animals (317 +/- 39 pmol/L). PYY infusion resulted in a dose-dependent increase in water and electrolyte absorption at all doses in both the jejunum and ileum. Although the relative increase in absorption was similar, the magnitude was greater in the ileum.

CONCLUSIONS

Physiological concentrations of PYY produced an increase in small bowel absorption of water and electrolytes in vivo. The postprandial release of PYY may mediate the increase in absorption following a meal. Such a proabsorptive agent may have considerable potential for clinical use in malabsorptive states.

Effects of aging in vitro on intracellular proteolysis in cultured rabbit lens epithelial cells in the presence and absence of serum

Alterations in proteolytic capabilities have been associated with abnormalities in the aged eye lens, but in vivo tests of this hypothesis have been difficult to pursue. To simulate aging, we cultured cells from an 8-yr-old rabbit to early (population-doubling level 20 to 30) and late (population-doubling level greater than 125) passage. Long-lived (t1/2 greater than 10 h) and short-lived (t1/2 less than 10 h) intracellular proteins were labeled with [3H]leucine, and the ability of the cells to mount a proteolytic response to the stress of serum withdrawal was determined. For early passage cells, the average t1/2 of long-lived proteins in the presence and absence of serum was 62 and 39 h, respectively. For late-passage cells, the average t1/2 of long-lived proteins in the presence and absence of serum was 58 and 43 h, respectively. The net increase in intracellular proteolysis in the absence of serum was 59 and 35% for early and late-passage cells, respectively. Thus, in vitro-aged rabbit lens epithelial cells amount only 60% the proteolytic response to serum removal shown in "younger" cells. The enhanced ability of early passage cells to respond to serum removal seems to involve lower homeostatic levels of proteolysis in the presence of serum and greater enhancement of proteolysis in the absence of serum. Less than 2% of the protein is in the pool of short-lived proteins. Rates of proteolysis of short-lived proteins in the presence and absence of serum were indistinguishable. With respect to basal proteolytic rates in the presence of serum and ability to mount a proteolytic response upon serum withdrawal, these rabbit lens epithelial cells are similar to bovine lens epithelial cells and fibroblasts.

Intracellular protein degradation in cultured bovine lens epithelial cells

Although several proteases have been identified in homogenates of cultured epithelial cells of the eye lens and in lens tissues, there is little information regarding intracellular protein degradation in intact lens cells in vitro. Cultured lens cells may be useful in the study of intracellular protein degradation in the lens, a tissue with a wide range of protein half-lives. This is of interest because alterations in protein turnover in the lens have been implicated in cataract formation. This study examines intracellular protein degradation in cultured bovine lens epithelial cells (BLEC). Cell cultures were incubated with radiolabeled leucine to label intracellular proteins. Protein degradation was measured by monitoring the release of trichloroacetic-acid-soluble radioactivity into the culture medium. The average half-life of long-lived proteins (half-life greater than 50 h) was typically about 57 h in serum-supplemented medium. Average rates of degradation of long-lived proteins increased by up to 73% when fetal bovine serum was withdrawn from the culture medium. Serum had no effect on the degradation of short-lived proteins (half-life less than 10 h). Degradation of long-lived proteins in the presence and absence of serum was further studied in cultured BLEC from population doubling level (PDL) 2 to 43. Average half-life of proteins in serum-supplemented medium was 52 to 58 h and did not vary significantly as a function of PDL. Degradation rates in serum-free medium increased approximately twofold up to PDL 7, but returned by PDL 25 to original levels, which were maintained through PDL 43.

Protease activities in cultured beef lens epithelial cells peak and then decline upon progressive passage

Beef lens cells in culture are readily obtained and provide many opportunities to study phenomena related to cell differentiation and maturation, environmental stress, disease, and perhaps mechanisms of transformation. Although altered rates of proteolysis are known to accompany these phenomena, the proteolytic activities available in cultured beef lens epithelial cells have not been documented. In this work are documented the specific activities, based on protein and DNA content, of neutral exo- and endopeptidase, cathepsins B- and D-like enzymes and acid phosphatase in lens epithelial cortical and core tissue and in cultured epithelial cells at passages 1-43. Maximal activity of each protease occurs almost routinely at passage 5 or 9, reaching values of approx. 1400-, 0.77-, 4520-nmol min-1 per mg protein for neutral exopeptidase (passage 5), neutral endopeptidase (passage 5) and cathepsin B (passage 5) respectively, and 7.1 micrograms trichloroacetic acid soluble peptide min-1 per mg protein for cathepsin D (passage 15). On a microgram-1 DNA basis, the maximal specific activities for the same enzymes were 48 (passage 5), 0.03 (passage 5), 283 (passage 9), and 0.5 (passage 9) respectively. In subsequent passages, the specific activities declined to values which were similar to or lower than the specific activities observed for these proteases in lens epithelial tissue.

The use of frozen intravenous crystalloid solutions as the refrigerant for shipping blood

The authors studied whether cooled sterile intravenous crystalloid solutions could be used to refrigerate red cells during shipment. Six 1000-ml bags of 0.9 percent normal saline and lactated Ringers (RL) solutions were supercooled and tested separately at temperatures ranging from 1 to -78 degrees C, with either 5 or 30 units of packed red cells (PRBCs). The PRBCs were shipped in a standard military container that permitted separation of the supercooled solutions from the PRBCs. Cooling RL solutions to 6 degrees C and to -22 degrees C maintained acceptable storage temperatures of the PRBC for 36 and 50 hours, respectively, and did not cause visible damage to the units. No significant changes were observed in various biochemical measurements of the cells and plasma. Cooling the RL solution to -78 degrees C caused a significant (p less than 0.05) increase in plasma potassium concentration. The effectiveness of the crystalloid solutions in refrigerating blood varied with the ratio of the number of PRBCs to the volume of cooled solutions and with the ambient temperature surrounding the container. The results of this study suggest that cooled intravenous crystalloid solutions can be used as refrigerants for PRBCs during shipment.

Proteolysis in cultured cells during prolonged serum deprivation and replacement

Cells in culture show a series of changes in intracellular protein degradation in response to serum deprivation and replacement that are similar to alterations in degradation in tissues of starved and refed animals. Rates of intracellular protein degradation are increased in confluent cultures of IMR-90 human diploid fibroblasts when deprived of serum, but this enhanced proteolysis is transient. By 24-48 h, rates of protein degradation decline to values comparable to or below those for cells incubated in the presence of serum. Longer serum deprivation leads to further reductions in proteolysis. The reduced proteolysis after long-term deprivation cannot be explained by experimental artifacts or by gradual depletion of glucocorticoids or thyroid hormones from cells. Readdition of serum to deprived cells that are still in the enhanced phase of proteolysis restores degradation rates to values comparable to those in nondeprived cells. However, in cells deprived of serum for 24-48 h or longer, readdition of serum to the medium results in a marked reduction in proteolysis to rates below those observed in nondeprived cells. These responses of cultured cells to long-term serum deprivation and readdition may be of considerable physiological importance in that the proteolytic responses of tissues in starved and refed animals may be at least partially due to mechanisms operating at the cellular level.

Perioperative changes in blood pressure and heart rate

In order to evaluate the possible physiologic significance of intra- and postoperative hypotension, we monitored arterial blood pressure and heart rate continuously for 36 hr starting the night before and ending the morning after operation in 34 gynecologic patients. The lowest pressures that occurred during physiologic sleep were compared with the lowest arterial pressures that occurred during anesthesia without deliberate hypotension. Two values were calculated: a preoperative baseline pressure, i.e., the average value recorded during the second hour of monitoring on the night before surgery, and a preanesthetic standard pressure, i.e., the average value of 15 consecutive measurements made at 1-min intervals in the operating room before the induction of anesthesia. The results indicate that a systolic pressure 10% below the PAS during anesthesia does not constitute physiologically significant hypotension because this range resembles the range that occurs spontaneously during unmedicated sleep or sleep aided with a mild hypnotic. These physiologic nadirs in blood pressure are assumed to be tolerated well by the patient. Intraoperative pressures in elderly patients frequently drifted below sleep-associated levels of blood pressure and may, therefore, constitute physiologically significant hypotension.

Similar growth pattern of mouse mammary epithelium cultivated in collagen matrix in vivo and in vitro

Mouse mammary ductal cells cultured in type I collagen gels give rise to three-dimensional multicellular outgrowths consisting of thin spikes which are often branched, and which may have pointed or blunt ends. The significance of these spikes to normal ductal morphogenesis has been unclear, since identical structures are not known to occur in vivo; conversely, it has not been possible to maintain in gel culture the highly structured end buds which are characteristic of ductal elongation in the animal. In order to evaluate whether the pattern of radiating spikes observed in collagen gel cultures results from chemical or physical peculiarities of the culture environment, a small volume of unpolymerized type I collagen solution was injected into mammary gland-free fat pads of young adult mice. After the bubble of collagen had polymerized, an implant of mammary ductal epithelium was introduced into the center of the gel. Histological examination of the implants after 3 to 6 days of growth revealed numerous small epithelial spikes, similar to those observed in gel culture, extending into the fibrous matrix. The early stages of regeneration of mammary implants placed in gland-free fat pads were then examined without the addition of exogenous collagen. In cases where the epithelium happened to contact a fibrous region of the fatty stroma, spikes were also seen to form in these natural collagenous substrates. Whether or not exogenous collagen was used, normal end buds were formed only when epithelial spikes contacted adipocytes. It was concluded that the three-dimensional pattern of radiating tubules in collagen gels in vitro is not merely an artifact of culture, but has a counterpart in vivo whereever regenerating mammary epithelium is surrounded by fibrous stroma. A model is presented in which the pattern of epithelial outgrowth is determined by the physical characteristics of the surrounding stroma; in collagen matrix a comparatively primitive and unspecialized type of morphogenesis occurs which may not require the participation of stromal cells. In contrast, epithelial-adipocyte interactions appear to be necessary for the formation of end buds and subsequent morphogenesis of fully structured mammary ducts.

Stromal DNA synthesis is stimulated by young, but not serially aged, mouse mammary epithelium

Ductal elongation in young, proliferating mouse mammary gland is associated with a zone of DNA synthesis in stroma surrounding the end buds. In contrast, slowly growing, serially aged tissue fails to elicit a significant elevation of stromal DNA synthetic activity. Since fatty stroma is required for normal mammary growth and morphogenesis, this altered interaction may be a significant factor in the aging of mammary epithelium.

Diurnal rhythms in developing ducts of the mouse mammary gland

DNA synthesis (LI) and mitotic activity (MI) were studied at different times of the day in the developing mammary gland end bud of the postnatal mouse. Both LI and MI displayed a clear diurnal variation. Animals studied at the middle of the 12-hr dark cycle showed a LI 2.1-2.6 times that of the tissue from the middle of the 12-hr light cycle. Intermediate values were obtained in tissue sampled midway between these extremes. Mitotic activity was studied 4 hr after the peak and trough of LI and exhibited a corresponding variation. These diurnal vdle of the 12-hr dark cycle showed a LI 2.1-2.6 times that of the tissue from the middle of the 12-hr light cycle. Intermediate values were obtained in tissue sampled midway between these extremes. Mitotic activity was studied 4 hr after the peak and trough of LI and exhibited a corresponding variation. These diurnal vdle of the 12-hr dark cycle showed a LI 2.1-2.6 times that of the tissue from the middle of the 12-hr light cycle. Intermediate values were obtained in tissue sampled midway between these extremes. Mitotic activity was studied 4 hr after the peak and trough of LI and exhibited a corresponding variation. These diurnal variations may be related to cyclic changes in secretion of pituitary hormones or other peptide growth factors, but variation between individual end buds in the same animal is more likely a result of morphogenetic interactions at the tissue level.