High Altitude Physiology

Ranges of high altitude and what happens in high altitude

• high altitude 1500-3500m

• Very high altitude = 3500-5500m

• Extreme altitude = above 5500

as altitude rises - air pressure drops and O2 lowers

What effect does latitude have on altitude?

different zones occur at different altitudes depending on the latitude

Massenerhebung effect

If the mountain is in a mountain range then there will be differing climates on either side of the mountain due to heat retention and wind shadow

• regions of same elevation and latitude can have much warmer or colder climates depending on surrounding mountain ranges

The treeline will also vary depending on mountain size and latitude

• Generally, mountains surrounded by large ranges tend to have higher treelines than isolated mountains

Nival zone

permanent ice/snow most of year

glaciers

very limited vegetation

alpine

above treelines to snowline

analogous to tundras

subalpine

treeless alpine meadows with occasional shrubs

below alpine layer

montane zone

mid elevation forests upward to treeline

ecosystem analogous to taiga in temperate latitudes or temperate forests in tropical latitudes

Biological aspects of the Scaleless Carp in the Qinghair lake

• Teleost

• 48cm length

• Diet: mixed invertebrates, algae, zooplankton

• Endemic and only fish in lake

• endure high altitude, strong radiation, low water temperatures

• IUCN red list

• 7-10 years to reach reproductive size

• march-July lake adults population migrate 40-50km to nearby freshwater streams to spawn and physiology changes due to migration to freshwater they then return to lake after spawning so readapt to salinity

Importance of ammonia and how its excreted

main excretory substance resulting from the catabolism of proteins and amino acids

excreted through gills via diffusion and possibly transporters

What techniques were used in Wang et al.’s study on the physiology of scale-less carp?

pH and O2 probes

refractometer for salinity

colorimetry to determine concentration of Cl-, Na+, Mg2+, Ca2+, K+ in lake and river water

What happened to the lake scaleless carp when exposed to 0.4nmol per l of ammonia

all died within 8hrs

what happened to the river scaleless carp when exposed to 1 nmol per l of ammonia

all survived until 24hrs

how was water urea measured on the scale-less carp

using a modified diacetyl-monoxime thiosemicarbizide colorimetric assay

how was water ammonia measured on the scale less carp

indophenol blue method with spectrophotometry

how was tissue ammonia measured on the scale less carp

homoginized tissue neutralized with saturated Tris buffer then

sigma NAD/glutamate dehydrogenase kits: a quantitative enzymatic distribution of ammonia

Results of Ammonia N levels and urea concentrations in plasma, liver, and muscle of scale less carp

Ammonia N levels significantly higher in liver, muscle, and brain tissue of lake fish

no significant differences between river and lak fishes urea concentrations

Differences and similarites between the ammonia excretions of the river and lake scale less carp

both are ammonotelic

excrete NH3 ammonia as main nitrogenous waste product

significantly lower ammonia excretion rates in lake fish

• due to inhibition of ammonia excretion in alkaline water as high pH impedes the ammonia diffusion gradient in the gills

• this causes increased unionized ammonia passing into cell membranes

GDH

links amino acid metabolism and TCA cycle activity in brain and other tissues

GSase

protects neurons against excitotoxicity by taking up excess ammonia and glutamate and converting it ot glutamine via the enzyme GS

Differences and similarities of GDH adn GSase between river scale less carp, lake scale less carp, and other teleosts and what these differences mean

GDH and GSase were not different between lake fish and river fish

GDH levels higher in lake and river fish compared to other teleosts in conditions inhibiting ammonia excretion

GDH and GSase convert ammonia to amino acids which allows amino acid accumulation

what is dangerous about the scale less carp not having a stomach and their inability to partition intestinal water absorption from food digestion

allows ammonia buildup and absorption of excess ions and electrolytes

Results of whether scale less carp feed during the day and drink at night

they feed during the day and drink at night

Results of gene expression at different times of the day for scale less carp

NKA-a mRNA expressed higher at 4 adn 2200

SLC26A6 mRNA expressed higher at 2200

SLC4A4 mRNA expressed higher at 4 adn 2200

Eastern deer mouse biological traits

Distribution: alpine habitats, northern boreal forests, desert, grassland, brushland, agricultural fields, southern montane woodland, and arid upper tropical habitats

lives 12-30 months

nests high in hollow trees in constructed spherical or cup-shaped nests of shredded plant fibres, fur, and feathers as well as under logs, stumps, or rocks in abandoned dens of other mammals

Diet: omnivorous on fungi, seeds, arthropods

nocturnal

High metabolic rate in high altitude deer mice thus have short lifespan

disease reservoires of lyme and hantavirus

reproduction of eastern deer mice

seasonally polyoestrous with cycly of approx 5 days

gestation 21-37 days

litter of 5-6 that are naked and blind

What is alveoli septation

saccules partition into alveoli

can happen post or pre natally

effects of hypoxia on alveoli septation

hypoxia during early post-natal alveoli septation impedes development

hypoxia during later post-natal alveoli septation can enhance lung volume and alveolar surface area

when do high altitude taxa undergo alveolarization

early post natal life

results of 3 different hypoxic levels on the lung histology of high altitude and low altitude mice with a comparison to white footed mice kept at normoxia conditions

body mass and lung volume higher in white footed mouse

Results of developmental hypoxia in high altitude mice when high altitude mice are bred under normoxia until 6th generation when the litter is born and raised either under normoxia or hypoxic conditions

developmental hypoxia increased lung volume without impeding alveolarization such that hypoxia led to an associated increase in alveolar surface area

lung volume increased in hypoxic offspring when measured at 7, 14, and 30 days old

alveolar surface area increased in hypoxic offspring at 30 days

pial arterial vessels

found in dura mater

they are intracranial vessels on the surface of the brain within the pia-arachnoid

consists of smaller distal arteries and arterioles that cover the entire cerebral cortical surface

connects the branches of the anterior, middle, and posterior cerebral arteries of the cerebrum

circle of willis

located at the base of the brain near several cranial nerves and optic chiasm

ring of vessels connecting the anterior and posterior circulations of the brain

provides collateral blood flow between anterior and posterior circualtions of the brain

protecting against ischemia in teh event of vessel disease or damae in one or more areas

native collaterals

provides support

forms in embryogenesis

anastomose between brances of the 3 major cerebral arteries

optimizes O2 delivery to brain to meet oxygen demand when oxygen availability is limited

flow in collaterals is near 0 due to pressure in main branches unless:

• there is an increase in activity/metabolism where local vasodilation occurs which causes a drop in local pressure that increases flow

Neurovascular coupling

when brain activation is accompanied by cellular, metabolic, and vascular processes and then coupled together to create brain function

What genes are increasingly expressed within the collaterogenesis pathway in deer mice during hypoxia

Hif2a

Vegfa

Rabep2

Angpt2

Tie2

Cxcr4

Hif2a

makes a protein called hyoxia-inducer factor 2-alpha (HIF-2a)

critical role in the bodys ability to adapt to changing oxygen levels

controls several important genes involved in cell division, formation of new blood vessels

increases production of red blood cells

major regulator of a hormone called erythropoietin (controls red blood cell production)

Usage of Angiography in research of collateral abundance in helping protect against tissue injury after cerebral, coronary, and peripheral artery occlusion

Maximal vasodilation using nitroprusside as vassodilation needed for viewing arteries during xray

Microfil used to fill and opacify microvascular structures in euthanised animals when under physiological pressure

results of research of collateral abundance in helping protect against tissue injury after cerebral, coronary, and peripheral artery occlusion in guinea pigs, deer mice, and rats

high altitude evolved guinea pigs have higher number of pial arteries and higher density of pial collaterals compared to lowlander mice

lowlander mice have abundant collaterals in C57BL/6 and sparse collaterals in BALB/cBy

high altitude evolved guinea pigs and deer mice have a greater number of pial collaterals compared to lowland rats and deer mice

Rats and deer mice have a greater density of ITA than guinea pigs in a defined area of MCA tree

watershed areas or zones

areas perfused by both the anterior and middle cerebral arteries

border-zones in the brain

regions supplied by the major cerebral arteries but where blood supply is decreased

impacts of permanent middle or anterior cerebral artery occlusion in rats, guinea pigs, and deer mice

In guinea pigs at high altitude: 0% cerebral infarction so collateral worked will and no tissues affected

in deer mice: 0.7% infarction so very small amount

in lowland species: 2.7% so much more infarction

so highland species had collaterals that worked better

How were guinea pigs affected when the left anterior descending coronary artery (the widow maker) was ligated

guinea pigs have many collaterals they were protected from a heart attack

Laser doppler imaging

imaging method that uses a laser beam to scan live tissue

when the laser light reaches the tissue, the moving blood cells generate doppler components in the reflected light

How were high altitude guinea pigs and deer mice affected when the femoral artery was ligated

massive collateral flow once femoral artery ligated so even in ligation blood flow was continued all the way to feet

Qinghai Tibetan plateau terrestrial habitat

large glaciers, alpine grassland, wetlands, permafrost - mix of alpine and arid environment

permafrost

ground that remians at or below 0c for at least 2yrs and is primarily a consequence of climate

seasonally thawed active layer underlain by perrenially frozen ground

effects of climate change on Qinghai Tibetan plateau

between 1957-2019:

• air temp increased 0.031-0.039c/yr

• precipitation increasing but seasonally

between 1999-2019:

• active layer of permafrost increasing by 1m with 4.6cm/yr

• permafrost table increasing at mean of 0.03c/yr

• permafrost temps at 15m depth increasing 0.01-0.02c/yr

aspects affecting Distribution of lizards at high altitude

ectotherms so temperature is important for metabolic/biological processes but it varies spatially and temporally

variation constrains species distribution

thermal adaptations lead to evolutionary changes in physiology, behaviour, life history, morphology

what type of gestation do high altitude lizards favour?

viviparity

where embryos complete development within maternal reproductive tract

lecithotrophic

retained eggs where embryos derive all nutrition from yolk

matrotrophic

embryo source of nourishment is not limited to yolk so supplemented by nourishment derived from mother

Advantages of viviparity

-            Permits maternal thermoregulation of embryos and optimal mean and stable temperatures

-            Permits maternal oxygen supply to embryos at high altitudes and microenvironments with low oxygen tensions

-            Protects eggs from environmental hazards & allows use of a range of environments

-            Allows resorption of eggs - recycling of nutrients from abortive eggs

-            Allows extra-vitelline nutrient provision by the female as nutrient supplementation

Disadvantages of viviparity

-            Maternal Metabolic costs

-            Abdominal space constraints

-            Decreased foraging ability & inability to replenish lipid stores

-            Decreased maternal locomotor performance due to burden

-            Increased exposure to predators due to thermoregulatory needs

two ways that foetal blood has a higher affinity for O2 then maternal blood in squamates

• Through specialized foetal haemoglobin

• through altered maternal nucleoside triphosphate levels

set of function required to maintain pregnancy in squamates

reduction in shell gland activity, increased uterine vascularity

Progesterone and corpus luteum (hormone released after egg released) suggested to influence changes in uterine cavity

Varieties of nutrient supply in viviparous squamates

•        In certain scincid lizards nearly all nutrients are supplied by placenta

•        In other reptiles, it is the yolk & then at limb bud stage a placenta

3 tissues placentae are derived from in squamates

•         the uterus of the mother

•        the embryo’s chorioallantoic

•        yolk sac membranes

Reproductive cycle of P. vlangalii and variables with it

- Reproductive cycle is largely dependent on abiotic factors

o   E.g., precipitation, temperature and photoperiod

-  Central Mexico montane region many viviparous lizards are asynchronous in reproduction

o   Mating occurs several months prior to ovulation, and parturition (favourable conditions)

-   Cycle of P. vlangalii

o   Exit hibernation burrow in early April-May

o   Courtship and mating behaviors occur in May and June

o   Parturition in August synchronous between females

o   Hibernation begins late October

annual gonadal cycle of P. vlangalii males and females

Males,  Snout Vent Length = 53.09 ± 1.48 mm

•        Testis size and diameter of seminiferous tubules decreased sharply from April to June

•        Above caused by peak of spermiogenesis occurring in October

•        Spermiation in May – Synchronous with ovulation of females

Females, SVL = 51.11 ± 1.31 mm

•        Follicle maturation max size (matured) Nov – Mar – right before out of hibernation

•        Vitellogenesis - late Aug – Dec

•        All females in same reproductive state

•        Liver mass decreased gradually from June to August

•        Liver mass increased sharply from August to October

Histology

-            Spermatogonia appeared in June (Stage I)

-            Spermatocytes appeared in August (Stage II)

-            Spermatids and sperm appeared in September

-            Sperms became abundant in October/ November (Stage IV)

-            Abundant sperm before spermiation in May of the following year (Stage V).

Neonate survival over winter of P. vlangalii and overall health and aspects of mothers

•        Litter size ranged from 1 – 4

•        Mean SVL of neonates was 26.12 ± 0.99 mm

•        Neonate mean mass was 0.90 ± 0.10 g

•        Large adult females produced higher mass & longer SVL neonates

•        Adult Female SVL did not determine litter size

From 96 neonates, 81 were recaptured after winter hibernation and there was an 84% survival!!

Problems with viviparity during Hypoxia, thermal regulation and reproduction

•        Reduced capacity for optimal ventilation & supply of oxygen

•        Increased oxygen consumption by embryos

•        Near parturition (due to embryo occupation) maternal food intake reduced so metabolism constant or increased in female

Do pregnant female P. vlangalii lower their body temp in response to hypoxia?

no significant difference in female body tempratures whilst pregnant

Will the P. vlangalii offspring be affected by having smaller size and lower locomotion speeds in hypoxia?

no changes