Clarifying dairy calf mortality phenotypes through postmortem analysis.

Health problems can be thought of as phenotypic expressions of the complex relationships between genes, environments, and phenomes as a whole. Detailed evaluations of phenotypic expressions of illness are required to characterize important biological outcomes. We hypothesized that classifying dairy calf mortality phenotypes via a systematic postmortem analysis would identify different cause-of-death diagnoses than those derived from treatments alone. This cross-sectional study was carried out on a dairy calf ranch in the northwestern United States from June to September 2017 and focused on calves ≤90 d of age. Comparisons were made between causes of death based on 3 levels of information: on-farm treatment records alone, necropsy-based postmortem analyses in addition to treatment records, and Washington Animal Disease Diagnostic Laboratory (WADDL) results in addition to all other information. A total of 210 dairy calves were necropsied during this study, of which 122 cases were submitted to WADDL. Necropsy- and WADDL-derived mortality phenotypes were in almost perfect agreement (Cohen's κ = 0.86) when broadly categorized as diarrhea, respiratory, diarrhea and respiratory combined, or other causes. The level of agreement between on-farm treatment records and postmortem-derived results was low and varied by the level of diagnostic detail provided. There was just fair agreement (κ = 0.22) between treatment-based and necropsy-based phenotypes without WADDL input and only slight agreement (κ = 0.13) between treatment-based and corresponding necropsy-based phenotypes with WADDL input. Even for those cases in which causes of death aligned along a comparable pathologic spectrum, the lack of detail inherent to standard treatment-based causes of death failed to identify meaningful target areas for intervention. This was especially apparent for numerous cases of necrotizing enteritis and typhlitis (cecal inflammation) that were variously categorized as diarrhea and pneumonia by treatment-based diagnoses. The specificity of these lesions stood in stark contrast to the otherwise generic cause of death diagnoses derived from treatments. The findings from this study supported the hypothesis and highlighted the value of on-farm necropsies and laboratory-based diagnostics to (1) detect antemortem disease misclassifications, (2) provide detail regarding disease processes and mortality phenotypes, and (3) direct disease mitigation strategies.

Adjunctive pregabalin for uncontrolled partial-onset seizures: findings from a prospective audit.

AIMS: Pregabalin (PGB) was licensed in Europe as an add-on antiepileptic drug (AED) for the treatment of partial-onset seizures in 2004. This audit assessed the response to adjunctive PGB in patients with uncontrolled seizures. METHODS: PGB was titrated in 135 patients [73 men; 62 women, aged 18-76 (median 44 years) until one of the following occurred: ≥ 6 months' seizure freedom, ≥ 50% or < 50% seizure reduction over 6 months; PGB withdrawal because of adverse effects, lack of efficacy or both. RESULTS: Of the 135 patients, 14 (10.4%) became seizure-free for ≥ 6 months (median PGB dose 300 mg/day; range 75-600 mg). A ≥ 50% seizure reduction occurred in 33 (24.4%) patients; 20 (14.8%) had < 50% reduction. PGB was withdrawn in 68 (50.4%) (40 adverse effects, seven lack of efficacy and 21 both). Commonest problems resulting in withdrawal were sedation (n = 18), weight gain (n = 14) and ataxia (n = 9). There was a positive correlation between increasing dose and weight gain (r = 0.42, P = 0.045). CONCLUSIONS: Add-on PGB benefited 50% of patients, but only 10% achieved 6 months' seizure freedom. Adverse effects, most commonly sedation, dose-related weight gain and ataxia, led to drug discontinuation by 45%. Prospective audits of novel AEDs are a useful adjunct to randomized, controlled trials in managing epilepsy.

Adrenal androgen excess and defective 11 beta-hydroxylation in women with idiopathic hirsutism.

We studied the simultaneous responses of four serum androgens (testosterone, androstenedione, dehydroepiandrosterone, and dehydroepiandrosterone sulfate) and five other steroids (deoxycorticosterone, corticosterone, 11-deoxycortisol, cortisol, and 17 alpha-hydroxyprogesterone) to the infusion of small amounts of cosyntropin in eight patients with idiopathic hirsutism and in six normal women. Serum testosterone and androstenedione concentrations were significantly higher in hirsute women after graded cosyntropin infusions than in controls, as were concentrations of plasma deoxycorticosterone and 11-deoxycortisol. Analysis of the substrate/product ratios 11-deoxycortisol/cortisol and deoxycorticosterone/corticosterone revealed defective 11 beta-hydroxylation in women with hirsutism. The presence of increased circulating androgen levels in response to physiologic amounts of adrenocorticotropic hormone thus appears to be a common response in women with idiopathic hirsutism, and, together with impaired adrenal 11 beta-hydroxylation, points to an adrenal defect as important components of this disorder.

Identification and characterization of metalloproteinase inhibitor activity in human ovarian follicular fluid.

Metalloproteinase inhibitors regulate collagenase activity in the extracellular matrix. To assess the role of metalloproteinase inhibitors in the ovulatory process, inhibitor activity was examined in human follicular fluid collected 2-4 h before ovulation. The relationship between inhibitor activity and steroid content was determined, and the inhibitors were partially purified and characterized. Inhibitory activity in follicular fluid (n = 25) correlated with both follicular estradiol (P less than 0.001) and progesterone (P less than 0.02) concentrations per follicle. Chromatographic separation of the follicular fluid on Sepharose 6B isolated two peaks of inhibitory activity. The inhibitor from the small mol wt (Mr) peak shared many of the properties of tissue inhibitors of metalloproteinase. It was stable in response to heat (60 C) and methylamine (200 mM), and was destroyed by reduction and alkylation, a procedure reported to destroy previously characterized inhibitors. Partial purification by affinity and ion exchange chromatography demonstrated the inhibitor to be a glycoprotein with an approximate Mr of 28-29K. The large Mr inhibitor had an approximate size of 700K and exhibited many of the characteristics of alpha 2-macroglobulin, a serum-derived metalloproteinase inhibitor. It was sensitive to heat, methylamine, and reduction and alkylation. Thus, follicular fluid contains metalloproteinase inhibitor activity that is steroid related and may be hormonally regulated. Ovarian metalloproteinase inhibitors may act to regulate connective tissue remodeling during follicular rupture.

Expression of plasminogen activator (PA) and a PA inhibitor in human granulosa cells from preovulatory follicles.

Studies with rat ovarian cells indicate that proteolytic enzymes, such as plasminogen activator (PA), play a role in the tissue remodeling that occurs before ovulation. In the rat, gonadotropins appear to increase granulosa cell tissue-type plasminogen activator (t-PA) content by increasing the cellular concentration of t-PA mRNA as well as by modulating the activity of a specific PA inhibitor (PAI). We obtained granulosa cells from preovulatory follicles of women undergoing either in vitro fertilization or gamete intra-fallopian tube transfer in order to evaluate the roles of PA and PAI in human ovulation. Samples of granulosa cell total RNA were hybridized with probes for t-PA, urokinase-type PA, PAI type 1 (PAI-1), or inhibin A-chain (as a control). Northern analyses revealed that the RNA of granulosa cells from preovulatory follicles contained little or no detectable PA mRNA. In contrast, two species of PAI mRNA were detected in relative abundance. The signal intensity produced by the PAI-1 probe varied by about 8-fold among patient samples, suggesting that PAI-1 may be useful as a marker of follicular maturation and differentiation. These results demonstrate that human granulosa cells collected immediately before ovulation contain PA inhibitor mRNA, yet have little or no PA mRNA.

Synaptic organization of serotonin-like immunoreactive amacrine cells in the larval tiger salamander retina.

Immunoelectron microscopy was used to investigate the ultrastructural features and synaptic relationships of serotonin-like immunoreactive amacrine cells in the larval tiger salamander retina. Serotonin-positive somas exhibited an evenly distributed peroxidase reaction product throughout their cytoplasm. Their nuclei were unstained and possessed indented nuclear membranes. Serotonin-immunoreactive processes were generally stained throughout with the exception of their mitochondria, whose morphology was often disrupted by the staining reaction. They were further characterized by an occasional dense-cored vesicle/s in addition to a generally homogeneous population of small, round, clear synaptic vesicles. Serotonin-immunoreactive amacrine cell processes formed conventional synapses that were characterized by symmetrical synaptic membrane densities. A total of 222 synaptic arrangements were observed that involved the immunostained processes of serotonin-amacrine cells. As presynaptic elements, they primarily contacted amacrine cells processes (37.8%). They also provided substantial synaptic input to processes that lacked synaptic vesicles (16.2%) and whose origin was unidentified. Serotonin-processes provided a far fewer number of synaptic contacts onto the processes of bipolar cells (1.4%) and the somas of cells in the amacrine cell layer (0.5%). As postsynaptic elements, they received synaptic inputs from amacrine cells (27.9%) and bipolar cells (16.2%). With the exception of their synapses onto bipolar cells and the somas of cells in the amacrine cell layer, each of the synaptic relationships of serotonin-amacrine cells was observed in each of sublayers 1-5 of the inner plexiform layer.

Alternate pathway of complement and bactericidal response of the channel catfish to Salmonella paratyphi.

Fresh channel catfish (Ictalurus punctatus) serum from unimmunized catfish exhibited 100% bactericidal activity against Salmonella paratyphi. Components responsible for bactericidal activity could be absorbed from the fresh catfish serum with S. paratyphi. The bactericidal system of the fresh catfish serum showed a need for magnesium rather than for calcium after EDTA treatment. The addition of salicylaldoxime or ammonium hydroxide to catfish serum indicated the alternate rather than the classical pathway of complement activation to be important in bactericidal activity against S. paratyphi. Bactericidal activity of catfish serum was labile when incubated at 47 degrees C for 30 min., stable for at least 4 mo. at -80 degrees C and could be absorbed with S. paratyphi at 25 degrees C. Very minimal bactericidal activity was present in the descending portion of the first 13.7S peak with most activity being found in the descending portion of the second 7.1S peak and throughout the entire 3.4S peak after Sephadex G-200 catfish serum fractionation.

Estradiol and progesterone binding in uterine leiomyomata and in normal uterine tissues.

To explain the sensitivity of uterine leiomyomata to endogenous and exogenous estrogens, specific cytosol receptor proteins for estradiol-17 beta and progesterone were found in tissue from uterine leiomyomata and compared with the concentrations of receptors in normal myometrium and endometrium from the same patient. The concentration of cytoplasmic estrogen receptors in leiomyomata (40.5 +/- 7.6 cytoplasmic estrogen receptors in leiomyomata (40.5 +/- 7.6 fmole/mg cytosol proteins, mean +/- SEM) was significantly greater than that found in myometrium (16.5 +/- 1.5) and significantly less than that found in endometrium (131 +/- 15.1). The concentration in leiomyomata of cytoplasmic progesterone receptors (104.4 +/- 41.2 fmole/mg cytosol protein, mean +/- SEM) was also greater than that found in myometrium (80.8 +/- 29.9) and less than that of endometrium (194.7 +/- 5.5); however, individual variation precluded statistical significance. The presence of cytoplasmic receptor proteins in myomatous tissues explains the sensitivity of the leiomyoma to endogenous or exogenous steroids and may provide information useful in the clinical management of this neoplastic disorder.

Determination of gestational age by serum concentrations of human chorionic gonadotropin.

To examine the accuracy and predictability of human chorionic gonadotropin concentrations in determining gestational age, serum concentrations of human chorionic gonadotropin (beta-subunit) were measured during the first 157 days after last menses. Using the regression curve generated, human chorionic gonadotropin concentrations obtained during the first 60 days accurately predicted the day of gestation. The difference (mean +/- SD) between the human chorionic gonadotropin-predicted estimated date of confinement and the estimated date of confinement established by known dates of last menses was 3.1 +/- 2.3 days. In patients followed to parturition, the difference between human chorionic gonadotropin-estimated gestational age and gestational age by physical assessment of the neonate was 8.1 +/- 7.1 days. After 60 days' gestation, human chorionic gonadotropin concentrations vary widely and are of little value in predicting gestational age. In addition to documenting conception, early human chorionic gonadotropin determinations accurately date the gestation and complement other clinical and biophysical methods for determining gestational age that are frequently used later in pregnancy.

Does technique or material used affect bladder tissue reactions when injecting teflon or silicone paste?

OBJECTIVES: Submucosal injections of polytetrafluoroethylene (PTFE) and polydimethylsiloxane (PDMS) paste continue to be used for the correction of vesicoureteral reflux and urinary incontinence. Potential distant particle migration and foreign body tissue reactions are thought to be significantly affected by the technique of injection and the paste material used. A study to determine if injection technique, paste material, or pretreatment of the injection site significantly affects local tissue reaction was performed on 44 New Zealand white rabbits. METHODS: Animals were randomly assigned to undergo four distinct injection treatments into the submucosa or bladder muscularis. Prior to injecting 0.1 cc of the PTFE or PDMS paste, some sites were pretreated with 0.1 cc saline to separate tissue planes, epinephrine to cause vasoconstriction, or doxycycline to provide sclerosis. Pretreatment controls were also performed without injecting PTFE or PDMS paste. Animals were killed, and quadrant bladder biopsies were performed at 1 hour (9), 1 day (9), 7 days (10), 1 month (8), and 6 months (8). A single pathologist, blinded to the injection treatments, performed a histologic evaluation to determine bleb location and the degree of inflammation, fibrosis, and epithelial necrosis. RESULTS: Seven of the 12 submucosal PTFE injection treatments were found on biopsy to be primarily within the muscularis, compared to 1 of 9 with PDMS paste. Three of the 24 PTFE injections could not be found at autopsy. Of these, two were injected into the muscularis, and all were discovered at least 1 month following injection. Particles were present in all 22 PDMS injection sites that were retrieved. Pretreatments, especially with doxycycline, resulted in significant epithelial necrosis at 1 and 7 days. At 1 and 6 months there were no differences in inflammation or fibrosis between PTFE and PDMS or any pretreatment combinations with saline or epinephrine. CONCLUSIONS: Correctly injected, silicone (PDMS) paste appears most likely to remain in the submucosal space. Pretreatment injections may cause early epithelial necrosis. PTFE and PDMS elicit similar foreign body reactions over time.

Evidence for centrally initiated genital vasocongestive engorgement in the female rat: findings from a new model of female sexual arousal response.

PURPOSE: In spite of rapidly growing interest, few research tools have been developed to study female sexual dysfunction. Using the D(1)/D(2) agonist, apomorphine (APO), our objective was to develop a new model of the sexual arousal response in female rats based on one previously established for the male condition. METHODS: APO (80 micro g/kg, s.c.) was given during proestrus (P), estrus (E), metestrus (M), early diestrus (DI) and late diestrus (DII), and in ovariectomized (OVX) female Wistar rats. APO-induced behavioral and genital responses were characterized (30 min) using video monitoring. RESULTS: APO-induced reproducible, periodic morphological changes in the external genitalia. The onset, timing and duration of these female APO responses were consistent with genital vasocongestive arousal (GVA) responses in males (ie erections). APO-induced GVAs occurred throughout the estrous cycle, peaking in E (1.4+/-1.21 overall; 0.9+/-0.64 in DII; 1.8+/-1.66 in E) and were markedly diminished by ovariectomy (OVX, 0.4+/-0.51). CONCLUSION: APO induced a reproducible sexual arousal response in female rats involving obvious genital vasocongestive engorgement. Further, the findings demonstrate that the APO-induced genital arousal responses are hormonally regulated.

Retrograde ejaculation: etiology and treatment via the use of a new noninvasive method.

Retrograde ejaculation (RE) is not a common infertility problem, but has increased in incidence recently due to surgical aggressiveness in pelvic and genital malignancies. However, RE is the most common cause of aspermia, or absence of ejaculate at orgasm. Meanwhile, surgical or drug therapy methods have not been very promising in regaining normal antegrade ejaculation. As yet, the standard procedures for treatment of RE involve the artificial insemination of either nonprocessed or processed (via centrifugation and resuspension) postcoital voided bladder contents. RE specimens in this study were collected after postcoital voiding into a TEST buffer and resuspended in TEST-yolk buffer. The urine effects on the voided spermatozoa were studied. The technique employed in this study assists in the recovery and reconstitution of RE fit for artificial insemination.

Studies on the surgical induction of endometriosis in the rat.

As a model to examine the pathophysiologic attributes of endometriosis, attempts were made to surgically induce the disease in the rat by autotransplanting endometrial or uterine tissue to the peritoneum. Rats (n = 46) were randomly assigned to one of four surgical techniques: (1) four uterine squares sutured to the peritoneal cavity; (2) uterine luminal lavages instilled into the peritoneal cavity; (3) endometrial scrapings flushed into the peritoneal cavity; and (4) sham-operated controls. Rats were examined at various days after surgery for the presence of endometrial implants. The autotransplantation of uterine squares to the peritoneal cavity was the only treatment that yielded healthy endometriotic implants. These implants grew into ellipsoidal cystic structures that were composed of both endometrial glands and stroma and were found to contain prostaglandin F (202 ng/mg) at concentrations similar to those measured in uterine tissue (205 ng/mg). To examine the effect of surgically induced endometriosis upon fecundity, rats (n = 40) were autotransplanted with uterine squares or were sham operated and mated. The presence of ectopic endometrial tissue reduced the number of pups at term by 48% and the number of day 14 embryos by 28% (P less than 0.05). Peritoneal adhesions were greater in rats with induced endometriosis than in sham-operated controls (P less than 0.05); however, in rats with induced endometriosis, no differences were noted in the severity of adhesions between pregnant and nonpregnant rats. Endometriotic implants underwent complete regression in the day 14 pregnant rat but had doubled in size in the nonpregnant rat. At term, the endometriotic implants were larger than in the day 14 pregnant rat (P less than 0.05) and similar to their original size. The successful growth and development of surgically transplanted endometrial tissue in the rat offers a research model that can be used to study those aspects of endometriosis that cannot be adequately investigated in women.

How does mild endometriosis cause infertility?

PIP: 30-40% of patients with endometriosis are infertile, and 6-15% of infertile women have endometriosis. Although the cause of the infertility observed in patients with mild endometriosis has not been established, several hypotheses have been proposed. Recent investigations have shown a link between endometriosis, altered prostaglandin (PG) secretion and metabolism, and infertility. Increased levels of PG metabolites have been found in the peritoneal fluid (PF) washings from patients with endometriosis; increased PF volume has also been noted. The increased PG concentration may alter ovarian function and tubal motility. Other studies have found endometriosis to coexist with anovulation. When both problems are treated, pregnancy rates improve. Many women with endometriosis may have a luteal phase defect. An autoimmune response to endometriosis has been considered as a cause of infertility as well. This response could produce rejection of the early implanted embryo or interfere with sperm transport. Endometriosis has also been regarded as a cause for some spontaneous abortion, but there may be a mediating mechanism, e.g., immune response or luteal phase defect. It is not known whether the various phenomena associated with endometriosis have a genetic basis or represent a secondary effect of endometriosis. A multivariate hypothesis, in which any or all of the factors noted in previous studies may be responsible for endometriosis-associated infertility and to varying degrees in different patients, is proposed. There may be genes that interfere with PG metabolism or lead to deficient immune status. If the multivariate causation theory is confirmed, patient evaluation may require performance of several diagnostic tests to determine the presence or absence of each factor and the extent to which that factor affects fertility. This approach will permit appropriate individualization of therapy.^ieng

Prolactin hyperstimulation in response to thyrotropin-releasing hormone in patients with endometriosis.

In order to clarify the role of hyperprolactinemia as a possible cause of infertility in patients with endometriosis, baseline serum prolactin (PRL) concentrations and the PRL response to thyrotropin-releasing hormone (TRH) stimulation were measured in 14 infertile women with endometriosis and in 13 normal, fertile women. Baseline PRL concentrations were 2-fold greater in the endometriosis group than in normal subjects, but the mean values did not differ significantly. Following TRH administration, a significant increase in peak PRL concentrations was observed in patients with endometriosis (211.5 +/- 34.9 ng/ml) when compared with corresponding values in control subjects (117.1 +/- 14.9 ng/ml, P less than 0.05). This hypersecretory state was selective for PRL because no significant differences between the baseline and TRH-stimulated thyroid-stimulating hormone (TSH) concentrations or total serum thyroxine concentrations were observed. In summary, some infertile women with endometriosis exhibit a greater capacity for PRL secretion than normal women. These results suggest that relative hyperprolactinemia may be responsible for the infertility associated with endometriosis, and that PRL suppression may be indicated in these patients.

Classification of endometriotic implants by morphologic appearance and capacity to synthesize prostaglandin F.

The severity of the symptoms of endometriosis has not always correlated well with the anatomic severity of the disease. This lack of correlation may be due to variations in the metabolic activity of the endometriotic implants present at different stages of the disease. Because prostaglandin F (PGF) has been implicated as a hormonal mediator of the clinical symptoms of endometriosis, PGF synthesis and content was measured in implants from 14 patients with mild, moderate, severe, or extensive disease. To assess whether PGF production was related to the status of implants, the authors classified implants, based on gross and histologic criteria, as petechial or reddish; intermediate or brown; or powder-burn or black. PGF production of implants from patients with mild or moderate disease was greater than that of implants from patients with severe or extensive disease (P less than 0.05), and PGF content was similar for all stages of endometriosis. Petechial implants produced twice the amount of PGF than intermediate implants (P less than 0.05), which in turn produced more PGF than powder-burn implants (P less than 0.05). Powder-burn implants did not have the in vitro capacity to produce PGF, and the amount of PGF contained in implants of all classes was similar. Therefore, endometriotic implant PGF production and possibly other biochemical activities are dependent on the physical status of the implant. The classification of implants by morphologic appearance may afford additional assistance in determining the prognosis of the disease and in the examination of the subtle effects of the disease on symptoms.

Rates of exponential increase of serum estradiol concentrations in normal and human menopausal gonadotropin-induced cycles.

Serum unconjugated estradiol concentrations were measured daily in patients who ovulated spontaneously and in patients whose ovulations were induced with human menopausal gonadotropins. When the logarithm of the estradiol concentration was plotted against time (semi-log plot) for each patient, the plots were essentially linear, and the rates of estradiol production were similar during spontaneous and induced cycles. Based on two or three estradiol determinations, subsequent estradiol concentrations can be determined as long as the established rates of estradiol production falls within reasonable confidence limits. The slope of serum unconjugated estradiol concentrations of a patient known to have a multiple gestation due to multiple ovulations did not differ significantly from the slopes of estradiol concentrations with single pregnancies, suggesting that the follicular phase estradiol concentrations do not reflect number of dominant follicles.

High dose gabapentin in refractory partial epilepsy: clinical observations in 50 patients.

Fifty patients with refractory partial seizures took part in a prospective, observational study of adjuvant gabapentin (GBP) in increasing doses. Thirty-three were started on 400 mg GBP daily with further weekly increments of 400 mg until seizures came under control for at least 6 months or to the limit of tolerability. A further 17 patients, not fully controlled on low dose GBP, followed the same regimen. All patients took the drug three times daily. Comparisons were made with seizure numbers during a 3-month baseline during which antiepileptic medication remained unchanged. Overall, 24 of the 50 patients documented a seizure reduction of 50% or more. Fifteen did so at or below 2400 mg GBP daily. Three of these patients became seizure-free. The remaining nine appeared to respond to higher daily doses of GBP (1:2800 mg; 3:3600 mg; 1:4000 mg; 1:4800 mg; 3:6000 mg), with two becoming seizure-free. Side-effects most commonly reported included tiredness, dizziness, headache and diplopia. On GBP doses exceeding 3600 mg daily, three patients developed flatulence and diarrhoea and two more had myoclonic jerks. Mean circulating GBP concentrations (mg/l) at each 1200 mg dose level were as follows: 1200 mg-4.1; 2400 mg-8.6; 3600 mg 13.2; 4800 mg 15.5; 6000 mg-17.2. In six patients, including three taking 6000 mg daily, GBP concentrations continued to rise linearly at each dosage increment. Although limited, our results do not support the suggestion that GBP absorption is saturable. High dose GBP may be effective in controlling seizures in patients with refractory partial epilepsy.

Revising appointment, promotion, and tenure procedures to incorporate an expanded definition of scholarship: the University of Kentucky College of Medicine experience.

Scholarly activity and scholarly productivity are key features of the academic health center (AHC) and the work of college of medicine faculty. Recent changes in the academic environment of the University of Kentucky (UK) College of Medicine led to an examination of its appointment, promotion, and tenure procedures. This, in turn, led to a re-examination of the college's definition of scholarship. This article describes three of UK's scholarship-related challenges, particularly those related to clinical departments. The authors describe some of the new procedures being implemented to address these challenges; these include new faculty designations, clearer articulation of promotion procedures, explicit recognition of multiple forms of scholarship, expectations for investment in junior faculty, and mandatory discussion of faculty success in chairs' annual reviews. Faculty reactions, positive and negative, to these changes in procedures are also presented.

Experimental microvascular polytetrafluoroethylene grafts: 6-month patency.

The efficacy of 1-mm internal-diameter polytetrafluoroethylene as a microvascular prosthesis is unclear. In this study, 8-mm-long segments of this material were implanted into the femoral arteries of 30 rats. Animals were examined every 2 weeks up to 6 months by Doppler ultrasound. Cumulative patency by the life-table method was 86.7 percent at 6 months. There were 26 patent grafts, 2 occlusions, and 2 deaths. Intimal hyperplasia adjacent to the anastomoses was seen in the native arteries. The pseudointima lining the grafts was cellular near the anastomoses but usually acellular in midgraft regions. It is concluded that if early failure does not occur, then good long-term patency is possible with 1-mm polytetrafluoroethylene in this setting and that patency is not dependent on development of a cellular pseudointima. Longer graft segments should be evaluated in future studies.