Monthly Archives: July 2023

Sprr1a knockdown in miR-150 KO mice largely corrects cardiac dysfunction mediated by miR-150 deletion

Sprr1a is a direct target of miR-150 in vitro, miR-150 acts as a gatekeeper of CM survival in part by inhibiting proapoptotic Sprr1a [13], and their correlative cardiac actions are shown [12, 13]; but an in vivo functional relationship between miR-150 and Sprr1a in the heart has not been established. To directly investigate their in vivo functional interaction in the heart, we generated a novel miR-150 KO;Sprr1ahypo/hypo mouse line by breeding miR-150 KO mice with Sprr1ahypo/hypo mice. We first conducted permanent ligation of the left anterior descending (LAD) artery in mice to induce MI. Consistent with a previous report [12], we observe that miR-150 KO mice exhibit normal cardiac function at baseline (Supplementary Table 1 and Fig. 1) but respond differently to MI. Cardiac function is significantly compromised in miR-150-null mice following MI. First, MI significantly worsens the cardiac function of miR-150 KO mice at 3 days as indicated by a decreased ejection fraction (EF), fractional shortening (FS), diastolic left ventricular anterior wall thickness (LVAW), and systolic left ventricular posterior wall thickness (LVPW) as well as an increase in end-systolic volume (ESV) and systolic left ventricular internal diameter (LVID) compared to those of WT controls (Supplementary Table 2 and Fig. 1). MiR-150 KO mice also display impaired cardiac function at 4 weeks post-MI, shown by a significant decrease in EF, FS, diastolic LVPW, and systolic LVPW as well as a significant increase in end-diastolic volume (EDV), ESV, diastolic LVID, and systolic LVID (Supplementary Table 3 and Fig. 1). MI also causes augmented cardiac dysfunction in miR-150 KO mice at 8 weeks as evidenced by a significant decrease in EF, FS, diastolic LVAW, diastolic LVPW, and systolic LVPW as well as a significant increase in EDV, ESV, diastolic LVID, and systolic LVID (Supplementary Table 4 and Fig. 1). In contrast, WT controls show less functional impairment at 4 weeks (Supplementary Table 3 and Fig. 1) and 8 weeks following MI (Supplementary Table 4 and Fig. 1).

We next show that miR-150 KO;Sprr1ahypo/hypo mouse hearts are functionally normal at baseline (Supplementary Table 1 and Fig. 1). However, a significant improvement in cardiac function at 3 days after MI is observed in miR-150 KO;Sprr1ahypo/hypo mice compared to miR-150 KO mice, indicated by an increase in cardiac output (CO), EF, FS, and diastolic LVAW as well as a decrease in EDV, ESV, diastolic LVID, and systolic LVID (Supplementary Table 2 and Fig. 1). MiR-150 KO;Sprr1ahypo/hypo mice also display enhanced cardiac function at 4 weeks post-MI as evidenced by a significant increase in EF, FS, diastolic LVAW, systolic LVAW, diastolic LVPW, and systolic LVPW as well as a significant decrease in EDV, ESV, diastolic LVID, and systolic LVID (Supplementary Table 3 and Fig. 1) compared to those of miR-150 KO mice. Last, we show improved cardiac function in miR-150 KO;Sprr1ahypo/hypo mice at 8 weeks post-MI compared to miR-150 KO mice as shown by a significant increase in CO, EF, FS, heart rate (HR), diastolic LVAW, systolic LVAW, and systolic LVPW as well as a significant decrease in EDV, ESV, diastolic LVID, and systolic LVID (Supplementary Table 4 and Fig. 1). Our morphometric data also show that miR-150 KO;Sprr1ahypo/hypo mice have a significant decrease in the ratio of heart weight/body weight (HW/BW) and the ratio of left ventricle weight/body weight (LVW/BW) at 8 weeks after MI compared to miR-150 KO controls (Supplementary Table 4). Notably, we do not observe any difference in post-MI mortality between groups (Supplementary Tables 1, 3, and 4: see n for animal numbers per each group at week 0, week 4, and week 8 after MI).

We previously reported that miR-150 KO mice display excessive maladaptive post-MI remodeling, such as cardiac damage, inflammation, and apoptosis [12]. To determine whether repression of Sprr1a mediates the major functions of miR-150 in vivo, we employed miR-150 KO;Sprr1ahypo/hypo mice and assessed post-MI remodeling compared to that of miR-150 KO controls. We find that miR-150 KO;Sprr1ahypo/hypo hearts exhibit a decrease in the loss of normal architecture and cellular integrity (Fig. 2A) as well as decreased mRNA levels of fetal Nppa (Fig. 2B) after 8 weeks of MI compared to miR-150 KO hearts. We next examined whether an improved cardiac inflammatory cell (CI) response contributes to the decreased disorganized structure in miR-150 KO;Sprr1ahypo/hypo hearts post-MI. Notably, inflammatory Il-6, Tnf-, and Ptprc are also downregulated in miR-150 KO;Sprr1ahypo/hypo hearts (Fig. 2C, D and Supplementary Fig. 1) compared to miR-150 KO hearts post-MI. Finally, we find that miR-150 KO;Sprr1ahypo/hypo hearts contain significantly lower numbers of cleaved caspase-3-positive cells (Fig. 3A, B), indicating decreased apoptosis in miR-150 KO;Sprr1ahypo/hypo hearts. Our data further show that miR-150 KO;Sprr1ahypo/hypo hearts have decreased mRNA levels of apoptotic P53, Bak1, and Bax (Fig. 3CE) compared to levels in miR-150 KO hearts. Altogether, our data suggest that sustained Sprr1a downregulation ameliorates adverse post-MI remodeling caused by miR-150 deletion and that miR-150 is a functionally important upstream negative regulator of Sprr1a in the heart.

A Representative hematoxylin and eosin (H&E) staining of heart sections of the peri-ischemic border area from the 6 experimental groups at 8 weeks post-MI shows a decrease in the loss of normal architecture and cellular integrity as well as in disorganized structure in miR-150 KO;Sprr1ahypo/hypo hearts compared to miR-150 KO controls. Scale bars: 100m. B qRT-PCR analysis of Nppa expression representing cardiac damage in ischemic areas from WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo mouse hearts at 8 weeks post-MI. qRT-PCR analysis of inflammatory Il6 (C) and Tnf-a (D) expression in ischemic areas from WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo mouse hearts at 8 weeks post-MI. N=56 per group. qRT-PCR data (BD) are shown as the fold induction of gene expression normalized to Gapdh. Two-way ANOVA with Tukeys multiple comparison test. *P<0.05 or **P<0.01 vs. sham for each genotype; #P<0.05, ##P<0.01, or ###P<0.001 vs. WT or miR-150 KO. Data are presented as the meanSEM.

Representative cleaved caspase-3 staining images in heart sections of the peri-ischemic border area in WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo hearts at 8 weeks post-MI (A) and quantification of apoptosis in six 40X fields (B). Scale bars: 100 m. qRT-PCR analysis of proapoptotic p53 (C), Bak1 (D), or Bax (E) expression in the ischemic areas from WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo mouse hearts at 8 weeks post-MI. Data are shown as the fold induction of gene expression normalized to Gapdh. N=6 per group. Two-way ANOVA with Tukeys multiple comparison test. *P<0.05 or ***P<0.001 vs. sham for each genotype; #P<0.05, ##P<0.01, or ###P<0.001 vs. WT or miR-150 KO. Data are presented as the meanSEM.

To further determine the response of miR-150 KO;Sprr1ahypo/hypo mice to MI, we assessed the degree of fibrosis using Massons trichrome staining and picrosirius red staining of the hearts at 8 weeks post-MI. We find larger regions of fibrosis in miR-150 KO hearts than in WT MI controls, as reported previously [12]. We next observe reduced fibrosis post-MI in miR-150 KO;Sprr1ahypo/hypo hearts compared to miR-150 KO hearts (Figs. 4, 5A, B, and Supplementary Fig. 2). MiR-150 KO MI hearts also exhibit increased expression of fibrotic Col5a1, Col6a1, Col1a1, Col3a1, and Ctgf (Figs. 5C, D, and 6AC) compared to expression in WT controls, but miR-150 KO;Sprr1ahypo/hypo MI hearts exhibit decreased expression of these profibrotic genes (Figs. 5C, D, and 6AC) compared to miR-150 KO controls. Next, our in vivo protein analysis reveals significantly elevated levels of VIMENTIN and -SMA in miR-150 KO MI mouse hearts compared to WT controls and significantly decreased levels of VIMENTIN and -SMA in miR-150 KO;Sprr1ahypo/hypo hearts at 8 weeks post-MI compared to miR-150 KO controls (Fig. 6D, E, and Supplementary Fig. 3); this is consistent with the mRNA data for the profibrotic genes (Figs. 5C, D, and 6AC). Collectively, these results demonstrate for the first time that genetic knockdown of Sprr1a significantly attenuates adverse postinfarct remodeling mediated by miR-150 deletion.

Representative Massons trichrome staining (A, B) in heart sections of the peri-ischemic border area in the 6 experimental groups at 8 weeks post-MI and fibrosis quantification (C) in whole left ventricles (LVs). Fibrosis histology images from whole heart longitudinal sections (A: Scale bars: 1mm) and zoomed in images of the peri-ischemic border area (B: Scale bars: 100m). N=6 per group. Two-way ANOVA with Tukeys multiple comparison test. ***P<0.001 vs. sham for each genotype; #P<0.05 or ##P<0.01 vs. WT or miR-150 KO. Data are presented as the meanSEM.

Representative picrosirius red staining (A) from heart sections in the 6 experimental groups at 8 weeks post-MI and fibrosis quantification (B) in whole left ventricles (LVs). Fibrosis histology images from whole heart longitudinal sections (A: Scale bars: 1mm) are shown. N=6 per group. Two-way ANOVA with Tukeys multiple comparison test. ***P<0.001 vs. sham for each genotype; #P<0.05 or ###P<0.001 vs. WT or miR-150 KO. Data are presented as the meanSEM. qRT-PCR analysis of profibrotic Col5a1 (C) or Col6a1 (D) expression in ischemic areas from WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo mouse hearts at 8 weeks post-MI. Data are shown as the fold change of gene expression normalized to Gapdh. N=6 per group. Two-way ANOVA with Tukeys multiple comparison test. **P<0.01 or ***P<0.001 vs. sham for each genotype; #P<0.05, ##P<0.01, or ###P<0.001 vs. WT or miR-150 KO. Data are presented as the meanSEM.

qRT-PCR analysis of profibrotic Col1a1 (A), Col3a1 (B), or Ctgf (C) expression in ischemic areas from WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo mouse hearts at 8 weeks post-MI. Data are shown as the fold induction of gene expression normalized to Gapdh. N=46 per group. Two-way ANOVA with Tukeys multiple comparison test. *P<0.05 or ***P<0.001 vs. sham for each genotype; #P<0.05, ##P<0.01, or ###P<0.001 vs. WT or miR-150 KO. Data are presented as the meanSEM. D, E VIMENTIN protein levels were measured in ischemic areas from WT, miR-150 KO, and miR-150 KO;Sprr1ahypo/hypo mouse hearts at 8 weeks post-MI. N=56 per group. Two-way ANOVA with Tukeys multiple comparison test. *P<0.05 or **P<0.01 vs. sham for each genotype; #P<0.05 vs. WT or miR-150 KO. Data are presented as the meanSEM.

Because of the cardiac upregulation of miR-150 by Carv [11] concurrent with the downregulation of Sprr1a [13], and the downregulation of miR-150 in CFs isolated from TAC mice [15] concurrent with the upregulation of Sprr1a in CFs during MI [13], we next studied primary adult human CFs (HCFs) to test whether miR-150 and SPRR1A are inversely regulated in HCFs treated with Carv as well as HCFs subjected to H/R conditions. Indeed, SPRR1A is downregulated in HCFs subjected to H/R conditions after Carv treatment (Supplementary Fig. 4) concurrent with the upregulation of miR-150 [28]. We also observe that SPRR1A is increased in HCFs after H/R (Supplementary Fig. 4), consistent with our in vivo results in post-MI hearts and isolated CFs from ischemic myocardium [13]. Notably, we previously reported that miR-150 is downregulated in HCFs after H/R [28]. Together with other previous reports on miR-150 downregulation in H/R and MI [12] as well as I/R [29, 30], our results indicate that Sprr1a is a critical functional target of miR-150 in CFs.

Because Sprr1a expression is upregulated in CFs isolated from ischemic mouse hearts [13] concurrent with the downregulation of miR-150 in CFs isolated from TAC mice [15], and miR-150 negatively regulates mouse CF activation in vitro [15], we first confirmed whether a direct target of miR-150, SPRR1A is repressed by miR-150 in HCFs. Our loss-of-function studies indeed show that SPRR1A is increased after miR-150 inhibition in HCFs (Fig. 7A, B). We next investigated whether SPRR1A regulates HCF activation. We first observe that SPRR1A knockdown in HCFs decreases the expression of profibrotic ACTA2 and CTGF (Fig. 7C and Supplementary Fig. 5), and miR-150 knockdown increases the expression of ACTA2, CTGF, and POSTN (Supplementary Fig. 6).

HCFs were transfected with antimiR control or antimiR-150 (A, B) and with control scramble siRNA (si-control) or SPRR1A siRNA (si-SPRR1A) (C). qRT-PCR analyses for miR-150 (A) or SPRR1A (B, C) were then performed to check their expression after the indicated transfection. Data were normalized to U6 SNRNA (A) or GAPDH (B, C) and are expressed relative to controls. N=6 per group. Unpaired 2-tailed t-test. RNA interference with SPRR1A protects HCFs from the increased proliferation mediated by antimiR-150. HCFs were transfected as indicated and subjected to normoxia or hypoxia/reoxygenation (H/R). Bromodeoxyuridine (BrdU) assays were then performed under both normoxic (D, F) and H/R (E, F) conditions. The percentage of proliferating nuclei (green) was calculated by normalizing to the total nuclei (blue). N=6 per group. One-way ANOVA with Tukeys multiple comparison test. *P<0.05 or **P<0.01 vs. control: either si-control or antimiR control. #P<0.05 vs. anti-miR-150. Data are presented as the meanSEM.

To further assess the effects of SPRR1A knockdown, we examined HCF proliferation using bromodeoxyuridine assay. We find that compared to controls, SPRR1A knockdown decreased HCF proliferation (Fig. 7DF) under both normoxic and H/R conditions. This is consistent with our gene expression data, showing that HCFs with SPRR1A knockdown have decreased mRNA levels of S-phase marker PCNA, mitosis (M) marker AURKB, and G2/M-phase marker CCNB1 compared with controls (Supplementary Fig. 7). Moreover, our wound migration studies reveal that compared to controls, SPRR1A knockdown decreased HCF migration (Fig. 8AC) under both normoxic and H/R conditions. This is consistent with our gene expression data, showing that SPRR1A knockdown in HCFs subjected to H/R decreases mRNA levels of cell migration markers, CTHRC1 and TNC compared with controls (Supplementary Fig. 8). SPRR1A knockdown in HCFs also suppresses mRNA levels of CF differentiation markers, COL4A1, COL8A1, and SRF (Supplementary Fig. 9), as well as the protein levels of profibrotic -SMA and FIBRONECTION (Supplementary Fig. 10). Because TGF-1/SMAD signaling pathway plays a key role in CF activation, we next investigated the role of SPRR1A in the regulation of TGF-1 and SMADs. We observe that SPRR1A knockdown in HCFs subjected to H/R decreases mRNA levels of TGFB1, SMAD2, and SMAD3 compared with controls (Supplementary Fig. 11). This is consistent with our in vivo data, showing that Sprr1a knockdown in mice decreases Smad3 expression as well as mRNA and protein levels of TGF-1 compared with controls (Supplementary Figs. 12, 13). Our data thus suggest that SPRR1A is sufficient to increase HCF activation in part by activating TGF-1/SMAD signaling pathway.

AC HCFs were transfected and subjected to normoxia or hypoxia/reoxygenation (H/R) as indicated in Fig. 7DF. Scratch migration assays were then performed. RNA interference with SPRR1A protects HCFs from the increased migration mediated by antimiR-150. N=6 per group. Two-way repeated-measures ANOVA with Bonferroni post hoc test. One-way ANOVA with Tukeys multiple comparison test. *P<0.05, **P<0.01, or ***P<0.001 vs. control: either si-control or anti-miR control. #P<0.05 or ##P<0.01 vs. anti-miR-150. Data are presented as the meanSEM.

Finally, to establish the functional relationship between miR-150 and SPRR1A in HCF activation, we applied an antimiR/siRNA-based rescue strategy to validate the functional relevance of the direct miR-150 target SPRR1A. MiR-150 knockdown increases HCF proliferation (Fig. 7DF and Supplementary Fig. 7) and migration (Fig. 8AC and Supplementary Fig. 8), which are attenuated by siRNA against SPRR1A (Figs. 7DF, 8AC, Supplementary Figs. 7, 8). We also show that miR-150 knockdown increases the expression of profibrotic TGFB1, SMAD2, SMAD3, COL1A1, COL3A1, COL4A1, COL8A1, and SRF under normoxic and/or H/R conditions, which are attenuated by SPRR1A knockdown (Supplementary Figs. 9, 11, 14). Taken together, our data indicate that profibrotic SPRR1A is a key direct and functional target of miR-150 in HCFs and whole mouse hearts.

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Even for me as a nest researcher, these are the craziest bird nests Ive ever seen, says biologist Auke-Florian Hiemstra in a Twitter thread outlining examples of how birds have reused, repurposed or ripped out anti-bird infrastructure. Some birds are just done with our stupid spikes. (Alexander Schippers/Naturalis Biodiversity Center)

Crows and magpies are building nests with the metal spikes meant to deter them from perching or nesting. Carrion crows (Corvus corone) and Eurasian magpies (Pica pica) in The Netherlands, Belgium and Scotland were observed to have plucked the sharp metal pins off buildings to use in their nests. The magpies even put most of the spikes on top of their nests, perhaps in an anti-bird effort of their own (crows eat magpies eggs).

The Guardian | 5 min read

Reference: Deinsea paper

Last week, we explored the pros and cons of efforts to turn animal cells into meat in the lab.

When we asked readers whether they would eat cultured meat if price wasnt an issue the majority said yes, including a small percentage of people who dont currently eat meat. If the cell-cultured meat could be made in a way that it didnt exploit the animals from which the cells were derived, didnt cause an outsize environmental footprint, was reasonably healthy and the jobs produced from the product were well-paid/ethical, then sure Id like to have it on occasion, says environmental scientist Sarah Hines, who is vegan.

Among those who said they wouldnt eat it, there were concerns about safety and nutrition. Many readers said that they would rather switch to one of the many meat substitutes, limit their meat intake to only local, extensively (rather than intensively) farmed products or simply stick to vegetables.

On the whole, readers wanted to withhold judgement until more is known about the environmental impact of lab-grown meat. Bioreactors would almost certainly use less land and water than livestock farming does, but would consume large amounts of energy. Overall, cultured meats carbon footprint, assuming it is produced using renewable energy, could be about the same as or less than that of poultry farming, and one-tenth that of rearing beef cattle.

Experimentalists should think of collaborations with data scientists as partnerships, rather than as transactions, say three experienced data wranglers. They offer 14 tips for non-data scientists who want to ensure productive and rewarding interdisciplinary projects that integrate data science.

Nature | 6 min read

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A black hole helps two post-human consciousnesses find a transcendent connection in the latest short story for Natures Futures series.

Nature | 6 min read

This week, the hosts of the Nature Podcast discuss some of the most compelling stories from this Briefing, including how scientists wrote a research paper from scratch in just one hour using ChatGPT. They also dig into a record-breaking series of global average temperatures and look at how an anti-ageing protein called klotho boosted cognition in old monkeys.

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Environmental scientist Erle Ellis, who has resigned from the Anthropocene Working Group, explains why some scientists question the wisdom of a proposal to define the period on the basis of radioactive plutonium fallout from nuclear-bomb testing. (Personal blog | 3 min read)

Read more: A sediment core from an unusual lake in Canada could become the golden spike the official marker for the Anthropocene, the geological epoch in which humanity has profoundly affected Earth. (Nature | 6 min read)

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Daily briefing: Birds build nests from anti-bird spikes - Nature.com

A Windsor man connected to an active missing persons case has been charged.

Donald Paul Britton, 51, Cody Wooten and Thomas Guinn were arrested , July 18, and charged with destruction, desecration or removal of human remains, according to jail records.

John Belote's daughter told deputies she last spoke with her father on June 28 after an argument between Britton and Belote, according to an incident report from the Aiken County Sheriffs Office.

When she spoke to Belote, he was going to see family, friends and a girlfriend, or going to confront Britton in the Windsor area, the report said.

The daughter told police she had been unable to contact her father since she last spoke with him.

Capt. Eric Abdullah with the Aiken County Sheriffs Office said Belote is still listed as a missing person.

Britton is listed as an inmate at the Aiken County detention center and has no bond.

Wooten has posted bond and Guinn has a $15,000 bond.

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Windsor man connected to active missing person case faces ... - Charleston Post Courier

Updated July 13, 2023 at 5:38 p.m. EDT|Published July 13, 2023 at 4:22 p.m. EDT

Landscaper Eduardo Rios can feel those moments when the familiar in Phoenix morphs into the treacherous, as the skin under his straw hat starts peeling off his forehead, the heat radiating up through his steel-toe boots.

Adrienne Kane tries to hike five days a week, even in summer, but she doubles her water and wears gardening gloves so the metal railings on Camelback Mountain dont burn her palms during times like this week. Dale Dean, who is homeless, sometimes settles into the seat of his black wheelchair and it feels like hes sitting down on hot coals.

Phoenix is in the middle of a record-breaking run of feverish days and suffocating nights, and human skin is a meager barrier against the scorching and scalding that comes at these temperatures. The city has already smashed records for the highest low temperatures for this time of year, when nights never dropped below the 90s, and it has already had 13 consecutive days with Thursday expected to be the 14th at or above 110 degrees Fahrenheit. The record for that is 18, set in 1974, according to the National Weather Service. And the worst of the heat is coming this weekend.

The city and a network of aid organizations mobilize on a large scale during these periods with cooling centers and programs to distribute water and ice to vulnerable residents. Earlier this year, the city painted its 100th mile of pavement with a light gray coating that is cooler than typical streets. Billboards around the city broadcast temperatures; some hiking trails are closed during midday; tons of snow gets dumped at the zoo to keep animals cool.

Were concerned about the severity of the temperatures to begin with, but the consecutive nature of them adds to the public health risk, said David Hondula, director of Phoenixs office of heat response and mitigation. This is a time for maximum vigilance in the community.

On these extremely hot days, even tiny mistakes can have grave consequences.

Cameron had just stepped into the laundry room to feed his dog and his wife was in the bathroom when their 18-month-old son, Mason, slipped through the pet door and stepped onto their concrete patio. He was screaming within seconds.

It was so fast, recalled Cameron, who asked that he and his family only be identified by first names to avoid shaming from other parents. It was immediately blistered on one foot. I knew it was bad.

Overnight low temperatures in Phoenix are not dropping below 90 degrees, and the unhoused are struggling with no relief from the heat. (Video: Erin Patrick O'Connor/The Washington Post)

Mason suffered second-degree burns on the soles of his feet that day in May, when Phoenix temperatures were only in the 90s, but the concrete had gotten hot enough to be dangerous. When the family reached the Arizona Burn Center at Valleywise Health Medical Center, they met another toddler with burned feet.

It was the exact same thing at the exact same time: 2 p.m., kid walked out onto the balcony, Cameron said. As a citizen of Phoenix I wonder, is it just going to keep getting hotter? How much hotter is it going to get?

The citys hospitals and firefighters this week have been trying to help people who are seared by pavement that can register 160 degrees or hotter. They are treating patients whose temperatures are running as much as 10 degrees above normal by injecting them with frigid IV fluids, blasting them with evaporative cooling fans, and placing them in what look like small inflatable kayaks filled with ice.

Doctors at the burn center this week said they had 10 patients with contact burns serious enough to require hospitalization. The number of burn admissions has grown over the past decade, as temperatures have risen and days with extreme heat have become more common. In 2015, the hospital admitted 43 people during the summer months with burns. Last summer, that number rose to 85, and seven of the people died.

The most common cases, doctors here said, are elderly people who fall or those who are under the influence of fentanyl or other drugs and spend minutes or hours splayed on the pavement. Homeless people are particularly vulnerable.

But other cases involve freakish missteps people burned by their seat belts or mailboxes. Swimmers attempting to walk across not-so-cool cool decks. The hospital has seen truckers who drive barefoot, step down onto a parking lot surface and end up badly blistered. On the hottest days, patients have been scalded by the water coming out of their garden hoses.

That first burst of water out of there, its practically boiling, said Kevin Foster, a physician and the director of the burn center.

One current patient was celebrating his day off with a cocktail, fell and burned 20 percent of his body, requiring surgery and skin grafting, Foster said.

He was not a drinker. It was just enough. He went down and couldnt get up, he said. All it took was that one little thing.

Phoenix is the hottest city in the country, and its 1.6 million people are accustomed to summer in the desert. But a warming climate and the sprawl of development, with more pavement radiating heat, has made life increasingly perilous during the hottest stretches of the year. Maricopa County recorded 425 heat-related deaths last year, up 25 percent over the prior year, figures that have been rising steadily over the past decade.

One-third of those deaths, over the past five years, have happened on days when the Weather Service issues an excessive heat warning. Doctors in Phoenix say they typically see a spike in patients when temperatures hit triple digits.

Thats sort of the magic number, 100 degrees, Foster said. We didnt see many of these patients coming in, and as soon as we hit triple digits, they started coming in.

In the Valleywise emergency room, patients with heat exhaustion dizziness, fatigue, nausea, vomiting, muscle breakdown called rhabdomyolysis are common during a Phoenix summer, said Frank LoVecchio, an emergency medicine physician. They usually recover well with cooling and fluids.

But more serious cases of burns and heatstroke, when people have been on the ground for minutes or hours, can be extremely debilitating. They can involve organ failure or brain damage and require weeks or months of hospitalization for those who survive. About half of the current patients in this condition at the hospital are intubated and in drug-induced comas, doctors said.

These people are down and were breathing for them, were dialyzing them, were doing the work of their kidneys for them, said Louis Ferrari, another burn surgeon.

A rule of thumb, he said, is that a burn encompassing 40 percent of a persons body can put a patient in the hospital for 40 days. The people who come in with these extreme burns and heatstroke, he said, are some of the sickest patients Ive ever encountered.

On Wednesday, firefighters encountered a man sprawled in the street in north Phoenix. The emergency responders found drug paraphernalia around the man, and witnesses said he had been acting erratically, slamming his head into the side of a truck.

When firefighters arrived, the man was unconscious. There were burns all over his body. His skin was coming off and his internal temperature was 107 degrees, they said. They delivered him to the emergency room.

Basically, his brain was fried, said firefighter Brandon Kanae, who responded to the scene.

During such extreme temperatures, fire officials estimate 10 to 15 percent of the calls are for people in heat-related distress.

The same things are going to happen again. Its unrelenting. Its coming back tomorrow, Capt. Tim Russell said. If youre in the sun, youre in trouble fast.

Such extreme heat acts like an invisible natural disaster that first responders and medical personnel say causes so much damage it should receive additional federal help, as would a tornado or a hurricane somewhere else.

The risks to public health increase exponentially at the upper extremes, said Hondula, the heat office director.

I cant tell people what to do, LoVecchio, the emergency room physician, said, but I would suggest anything nonessential, outdoors dont do right now.

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How bad is a Phoenix heat wave? The perils of burning pavements ... - The Washington Post