Biomedical subjects

J N Collins

Publications and source records attributed to J N Collins.

8 recordsLinked to original sources

PubMed1999

Regional blood flow response to hypothermia in premature, newborn, and neonatal piglets.

BACKGROUND/PURPOSE: Hypothermia (HT) remains a significant stress to the newborn and has been implicated in the pathogenesis of necrotizing enterocolitis (NEC). The authors assessed the effect of transient HT (32 degrees C) on regional organ blood flow in anesthetized piglets at age 7 to 10 days preterm (PREM), 1 to 2 days (NB), and 1 to 2 weeks (NEO). METHODS: Radiolabeled microspheres were used to determine organ blood flows (mL/min/g) at baseline, 15, and 60 minutes after HT and 60 minutes after rewarming to baseline core temperature. RESULTS: Heart rate and cardiac output decreased significantly in all groups. Cardiac flow decreased significantly in the NEO group, and central nervous system (CNS) flow decreased significantly in the NB and NEO groups. Both returned to baseline levels after rewarming. The PREM group experienced decreased cardiac, CNS, and intestinal blood flows but not to significant levels. NB and NEO intestinal blood flow showed significant decreases, which remained so after rewarming (a response not seen in hypoxia or hypovolemia). Cardiac output did not return to baseline levels in any group. CONCLUSIONS: HT causes derangements in organ blood flows that differ from other deleterious stimuli such as hypoxia and hypovolemia. The prolonged intestinal ischemia supports HT as a factor in the development of NEC. This delay may offer opportunity to intervene in an attempt to lessen ischemia-reperfusion injury.

Age Factors↗

PubMed1996

Laparoscopic versus open appendectomy.

This prospective clinical study was done because our initial retrospective review suggested that laparoscopic appendectomy (LA) offers no significant advantages over open appendectomy (OA) yet is significantly more expensive. From July 1992 to August 1993, 57 patients were approached preoperatively for randomization to either LA (n = 19) or OA (n = 18). There were no statistically significant differences between the LA and OA groups in operative risk: mean age, 28 +/- 2 vs 26 +/- 2 years; percent female, 26% vs 22%; body mass index, 24 +/- 0.8 vs 26 +/- 1.2 kg/m2. All patients were either ASA class I or class II, 78% in each group being class II. The differences between the LA and OA groups in mean operating time required (93 +/- 12 vs 87 +/- 8 minutes), postoperative intramuscular narcotic analgesic usage (24 +/- 6 vs 26 +/- 6 hours), postoperative hospital stay (57 +/- 12 vs 66 +/- 10 hours), and return to normal activity (20 +/- 6 vs 14 +/- 3 days) were also not significant. However, LA was much more expensive because of higher operating room charges. The mean total hospital bill was $4,600 +/- $160 for the LA group and $1,700 +/- $70 for the OA group. This prospective study corroborated our previous analysis. Laparoscopic appendectomy is safe, effective, and expensive and overall has no greatly significant advantages over open appendectomy.

Adolescent↗

PubMed1995

Reduction of Aedes dorsalis by enhancing tidal action in a northern California marsh.

Full tidal action was restored to a 28-ha marshland in the brackish region of the San Francisco Bay Estuary to evaluate the impact of increased tidal circulation on Aedes dorsalis abundance. One year after project completion, mosquito abundance had decreased by 98.7%, from an average of 3.6 to 0.3 4th-instar larvae per dip. Larvicide applications have consequently been reduced from approximately 6 to zero per year. The effects on the marsh plant community and marsh elevation were assessed during the first 2.3 years since project completion. Total coverage by sedges, rushes, reeds, cattails, and brass buttons increased almost 80% at the expense of pickleweed (-65%) and peppergrass (-34%). Sedimentation on the marsh plain has averaged 1.2 cm/year, which is about 10 times greater than the average rate of sea level rise for the region. In general, the marsh ecosystem has begun to acquire characteristics that typify immature, highly productive, fully tidal brackish marshes of the region.

Aedes↗

PubMed1994

Effects of graded thermal injury on microvascular permeability at the site of injury.

To define whether capillary permeability traits at the site of a burn differ according to injury severity, a canine hind leg lymphatic was cannulated to measure macromolecular permeability in response to three different scalding solutions. Leg venous pressure was raised to approximately 40 mm Hg and maintained until a minimal lymph-to-plasma total protein ratio (CL/CP)min and steady-state lymph flow (QL; microliter/min/100 g) was attained. The protein reflection coefficient (1-CL/CP), fluid filtration coefficient (Kf; microliter/min/mm Hg/100 g), and QL were determined before and for 6 hr after a 5-sec hind paw immersion in either 100 degrees C (n = 7), 80 degrees C (n = 7), or 70 degrees C (n = 7) water. A group of five animals served as controls. In the absence of any systemic hemodynamic alterations, the 100 and 80 degrees C scald groups experienced significant (P < 0.05, ANOVA) increases in QL, CL/CP, and Kf as compared to respective preburn values and time-matched unburned control values. Most monitored parameters were significantly higher following 100 degrees C injury vs 80 degrees C injury. Parameters in the 70 degrees C group did change after scald, but were not significantly different from preburn values or from the control group. Alterations in capillary permeability to protein and fluid flux measured at the burn site are graded, not all or none phenomena, being dependent upon the severity of injury.

Analysis of Variance↗

PubMed1994

The effects of albumin administration on microvascular permeability at the site of burn injury.

In a canine hind leg model, lymph flow (QL), lymph (CL), and plasma (CP) total protein concentrations, the reflection coefficient for total proteins (sigma d), and the filtration coefficient (Kf) were determined before and for 6 hours after a 5-second 100 degrees C hind paw scald (3% total body surface area, TBSA). Before injury, hind leg venous pressure was elevated and maintained by outflow restriction until a minimal, steady-state CL/CP ratio was achieved. Albumin (5%) was infused 30 minutes after the scald at low (0.4 mL/kg/% TBSA) or high (2 mL/kg/% TBSA) doses. Scald uniformly increased QL, CL/CP, Kf, and paw weight gain (PWG). Whereas postburn infusion of low-dose albumin mildly attenuated increases in CL/CP and PWG noted in scald-alone animals, no differences were noted between the scald and scald/high-dose albumin groups.

Albumins↗

PubMed1994

Effects of pentafraction administration on microvascular permeability alterations induced by graded thermal injury.

BACKGROUND: Pentafraction is a pentastarch derivative hypothesized to limit burn edema by "sealing" damaged capillaries, restoring a barrier to fluid translocation and macromolecular (protein) flux. METHODS: Canine hind paw lymph flow (QL) and lymph (CL) and plasma (CP) protein concentrations were measured before and for 6 hours after (1) 5-second 100 degrees C (n = 6) or 80 degrees C (n = 6) foot paw scald, (2) 100 degrees C (n = 5) or 80 degrees C (n = 5) foot paw scald followed 30 minutes later by a 4 cc/kg bolus of 6% pentafraction, or (3) pentafraction infusion without scald (n = 5). Before scald or pentafraction infusion, hind paw venous pressure was elevated and maintained by outflow restriction until a steady state, minimal CL/CP was reached. The reflection coefficient, sigma d, was determined as 1-CL/CP, and the (fluid) filtration coefficient (Kf) was calculated. RESULTS: Scalding uniformly produced statistical (p < 0.05, ANOVA) increases in QL, CL/CP, sigma d, Kf, and paw weight gain. Postburn pentafraction infusion produced no enduring alterations in any measured parameter as compared with those of animals who received a matched severity scald without pentafraction. CONCLUSIONS: Pentafraction does not appreciably ameliorate the adverse microcirculatory consequences observed at the site of burn injury.

Animals↗

PubMed1993

Tumor necrosis factor-induced mortality is reversed with cyclooxygenase inhibition.

OBJECTIVE: The authors hypothesized that TNF would induce eicosanoid synthesis, and a cyclooxygenase inhibitor would attenuate both eicosanoid synthesis and improve survival in an LD90 TNF-induced (150 ng/kg/i.v./5 min) mortality model. SUMMARY BACKGROUND DATA: Tumor necrosis factor is a cardinal mediator in sepsis; however, little is known about its effects on arachidonate metabolism. METHODS: Conscious male rats with carotid arterial and jugular venous catheters were randomized for mortality: group I, TNF alone (150 kg/i.v./15 min, n = 30); group II, ibuprofen (30 mg/kg/i.v. at t = -20 and +240 min), plus TNF, (n = 28); and for hemodynamics, eicosanoid synthesis, blood gases: group III, TNF alone, (n = 8); group IV, ibuprofen + TNF (n = 8); group V, monoclonal antibody to TNF plus TNF (n = 8). Mortality was determined at 4-72 hr. Other parameters determined over 4 hours (0, 5, 60, 120, 240 min). RESULTS: TNF stimulated synthesis of (a) TXB2 (71 +/- 30 pg/ml, mean +/- SE at base vs. 117 +/- 18 at 4 hr, p < 0.02); (b) PGE2 (70 +/- 6 pg/ml at base vs. 231 +/- 68 at 4 hr, p < 0.02); (c) 6PGF (52 +/- 6 pg/ml at base vs. 250 +/- 80 at 4 hr, p < 0.02). Ibuprofen significantly (p < 0.05) inhibited eicosanoid synthesis from TNF. TNF-induced mortality (87%, 26/30) was dramatically decreased with ibuprofen (11%, 3/28), at 4, 24, and 72 hr (p < 0.01). Monoclonal antibody to TNF prevented all abnormalities and had 100% survival. Hemodynamic events were similar in both groups, but metabolic acidosis was attenuated with ibuprofen. CONCLUSIONS: TNF stimulates arachidonic acid metabolism in vivo. A cyclooxygenase inhibitor attenuates eicosanoid synthesis and dramatically improves survival. TNF appears to have different effect on tissues that synthesize certain eicosanoids. Hypotension from TNF is not mediated via the eicosanoids. TNF-induced mortality, like endotoxemia/sepsis may be mediated, in part, via arachidonic acid metabolites. These new findings support the notion that cyclooxygenase inhibitors may be used as adjunctive therapy in clinical sepsis.

6-Ketoprostaglandin F1 alpha↗

PubMedDate not supplied

Organ blood flow redistribution in response to hypoxemia in neonatal piglets.

This study was designed to determine the effects of severe hypoxemia on newborn piglet visceral blood flow. While the hemodynamic effects of a severe hypoxemic insult are well characterized in newborn animals, its impact on organ perfusion in premature infants is not well characterized. Cannulas were placed in the femoral vessels and left atrium of term (1-14 days old) and prematurely delivered (cesarean section at 90% of term gestation) piglets. After stabilization, some animals were subjected to 1 h of ventilator-controlled hypoxia (yielding PaO2 approximately = 30-40 torr) followed by 30 min of reoxygenation; the remaining animals served as unchallenged controls. Radiolabeled microspheres were injected in all animals at times 0 min (baseline), 5 and 60 min (hypoxia), and 90 min (reoxygenation). Blood flows (mL/min/g tissue) to organs were determined using reference organ techniques. Control animals displayed no alterations in any of the variables monitored. Throughout the experimental period, organ blood flows were almost uniformly lower (p<.05, ANOVA) in premature versus term animals. The trend toward increased cerebral and cardiac blood flows during hypoxia observed in the premature piglets was similar to that of term animals, but of lower magnitude. In term piglets, hypoxia produced an immediate and significant (*p<.05) decline in small-intestinal blood flow followed by autoregulatory escape (2.02+/-0.17 mL/min/g at time 0, 1.56+/-0.15 mL/min/g at 5 min hypoxia, 1.88+/-0.18 mL/min/g at 60 min hypoxia, 2.26+/-0.19 mL/min/g at 30 min reoxygenation), an effect not readily observed in the premature piglets (0.48+/-0.10 mL/min/g at time 0, 0.44+/-0.07 mL/min/g at 5 min hypoxia, 0.46+/-0.10 mL/min/g at 60 min hypoxia, 0.42+/-0.08 mL/min/g at 30 min reoxygenation). However, mucosal blood flows measured in these younger animals declined throughout the experimental period to almost 50% of baseline, compared to a complete restoration to baseline blood flow observed following reoxygenation of term piglets. Intestinal blood flow in premature infants is small when compared to term animals, and alterations in small intestinal blood mucosal flow induced by hypoxia appear less well tolerated by the premature animals. Taken together, this may in part account for the increased risk of developing intestinal ischemic diseases in premature infants who are even temporarily exposed to a severe hypoxic challenge.

Analysis of Variance↗